US2002016250A1PendingUtilityA1
Method for photocatalytically rendering a surface of a substrate superhydrophilic, a substrate with a superhydrophilic photocatalytic surface, and method of making thereof

Priority: Mar 20, 1995Filed: Aug 14, 2001Published: Feb 7, 2002
Est. expiryMar 20, 2015(expired)· nominal 20-yr term from priority
Inventors:Makoto Hayakawa Eiichi Kojima Keiichiro Norimoto Mitsuyoshi Machida Atsushi Kitamura Toshiya Watanabe Makoto Chikuni Akira Fujishima Kazuhito Hashimoto
G02B 1/18C03C 2218/32C09K 3/18C03C 2217/23C03C 17/256C03C 2217/71C03C 2218/113C03C 2218/151C03C 2217/212C03C 17/23C03C 17/2456C03C 2217/229
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References
Claims
Abstract

The surface of a substrate is coated with an abrasion-resistant photocatalytic coating comprised of a semiconductor photocatalyst. Upon irradiation by a light having a wavelength of an energy higher than the bandgap energy of the photocatalyst, water is chemisorbed onto the surface in the form of hydroxyl groups (OH − ) whereby the surface of the photocatalytic coating is rendered highly hydrophilic. In certain embodiments, the surface of a mirror, lens, or windowpane is coated with the photocatalytic coating to exhibit a high degree of antifogging function. In another embodiment, an article or product coated with the photocatalytic coating is disposed outdoors and the highly hydrophilic surface thereof is self-cleaned as it is subjected to rainfall. In a still another embodiment, an article is coated with the photocatalytic coating and, when the article is soaked in, rinsed by or wetted with water, fatty dirt and contaminants are readily released without resort to a detergent.
Claims

exact text as granted — not AI-modified
1 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 preparing a substrate coated with a photocatalytic layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby cause molecules of water to be physically adsorbed onto the surface of said photocatalytic layer under the photocatalytic action of the photocatalyst whereby the surface of the substrate is rendered hydrophilic.    
     
     
         2 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface;    a photocatalytic layer comprised of a photocatalyst, said layer being bonded to the surface of said substrate; and,    molecules of water physically adsorbed onto the surface of said photocatalytic layer upon photoexcitation of the photocatalyst.    
     
     
         3 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising a photocatalyst operable upon photoexcitation thereof to cause molecules of water to be physically adsorbed onto the surface of said coating under the photocatalytic action of the photocatalyst to thereby render the surface hydrophilic.  
     
     
         4 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic layer comprised of a photocatalyst, said layer being bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 5° in terms of the contact angle with water.    
     
     
         5 . An antifogging transparent sheet member comprising: 
 a transparent substrate having a surface; and,    a substantially transparent photocatalytic layer comprised of a photocatalyst, said photocatalytic layer being bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic on the order of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         6 . An antifogging mirror comprising: 
 a substrate having a surface and a reflective coating; and,    a substantially transparent photocatalytic layer comprised of a photocatalyst, said photocatalytic layer being bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic on the order of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         7 . An antifogging lens comprising: 
 a transparent lens-forming body having a surface; and,    a substantially transparent photocatalytic layer comprised of a photocatalyst, said photocatalytic layer being bonded to the surface of said lens-forming body;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic on the order of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the lens-forming body from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         8 . A composite according to  claim 4 , wherein said photocatalytic layer is resistant to adhesion by deposits and contaminants when contacted with an aqueous substance.  
     
     
         9 . A composite according to  claim 8 , wherein, for self-cleaning of the composite, said photocatalytic layer operates to permit adherent deposits and/or contaminants to be washed away by rainwater as said composite is subjected to rainfall.  
     
     
         10 . A composite according to  claim 8 , wherein said photocatalytic layer operates to prevent contaminants from adhering to the surface thereof as contaminant-laden rainwater flows therealong.  
     
     
         11 . A composite according to  claim 8 , wherein, to facilitate cleansing of the composite with water, said photocatalytic layer operates to release adherent deposits and/or contaminants when soaked in or wetted with water.  
     
     
         12 . A composite according to  claim 4 , wherein said photocatalytic layer is resistant to the formation of water droplets on the surface of said layer.  
     
     
         13 . A composite according to  claim 12 , wherein, for prevention of growth of water droplets, said photocatalytic layer operates to cause adherent moisture condensate and/or water droplets to spread over the surface of said layer.  
     
     
         14 . A composite according to  claim 12 , wherein, to promote drying of the substrate after wetted with water, said photocatalytic layer operates to cause adherent water droplets to spread over the surface of said layer.  
     
     
         15 . A composite according to  claim 4 , wherein the surface of said layer is further coated with a hydrophilic protective layer.  
     
     
         16 . A composite according to  claim 4 , wherein the surface of said layer is further coated with a photocatalytic protective layer which is adapted to be rendered hydrophilic upon photoexcitation.  
     
     
         17 . A composite according to  claim 4 , wherein said photocatalyst comprises an oxide selected from the group consisting of TiO 2 , ZnO, SnO 2 , SrTiO 3 , WO 3 , Bi 2 O 3  and Fe 2 O 3 .  
     
     
         18 . A composite according to  claim 4 , wherein said photocatalyst comprises the anatase form of titania.  
     
     
         19 . A composite according to  claim 4 , wherein said photocatalyst comprises the rutile form of titania.  
     
     
         20 . A composite according to  claim 4 , wherein said photocatalytic layer further comprises SiO 2  or SnO 2 .  
     
     
         21 . A composite according to  claim 4 , wherein said photocatalytic layer comprises a coating in which particles of said photocatalyst are uniformly dispersed.  
     
     
         22 . A composite according to  claim 4 , wherein said photocatalytic layer is comprised of silicone having organic groups bonded to silicon atoms of silicone molecules, and wherein the surface of said photocatalytic layer is formed of a derivative of silicone in which the organic groups bonded to the silicon atoms of the silicone molecules have been substituted upon photoexcitation at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst.  
     
     
         23 . A composite according to  claim 4 , further comprising an intermediate layer of a non-decomposable material interleaved between said substrate and said photocatalytic layer.  
     
     
         24 . A composite according to  claim 4 , wherein said substrate contains alkaline metal ions or alkaline-earth metal ions and wherein a thin film for preventing said ions from diffusing from said substrate into said photocatalytic layer is interleaved between said substrate and said photocatalytic layer.  
     
     
         25 . A composite according to  claim 24 , wherein said thin film comprises silica.  
     
     
         26 . A composite according to  claim 4 , wherein the thickness of said photocatalytic layer is less than about 0.2 micrometers.  
     
     
         27 . A composite according to  claim 4 , wherein said photocatalytic layer further comprises a metal selected from the group consisting of Ag, Cu and Zn.  
     
     
         28 . A composite according to  claim 4 , wherein said photocatalytic layer further comprises a metal selected from the group consisting of Pt, Pd, Rh, Ru, Os and Ir.  
     
     
         29 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water.    
     
     
         30 . An antifogging method for preventing a transparent sheet member from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a transparent sheet member coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         31 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a mirror coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         32 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a lens coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         33 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    disposing said substrate outdoors;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    subjecting said substrate to rainfall whereby deposits and/or contaminants adhering on the surface of said layer are washed away by rainwater.    
     
     
         34 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    rinsing said substrate with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom and washed away by water.    
     
     
         35 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    causing said substrate soaked in or wetted with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom.    
     
     
         36 . A method for maintaining a surface of a substrate disposed outdoors clean, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    disposing said substrate outdoors; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby contaminants are prevented from adhering to the surface of said substrate as contaminant-laden rainwater flows therealong.    
     
     
         37 . A method for preventing growth of water droplets adhering on a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    causing adherent moisture condensate and/or water droplets to spread over the surface of said layer.    
     
     
         38 . A method according to one of claims  29 - 37 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with the sunlight.  
     
     
         39 . A method according to one of claims  29 - 37 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with an electric lamp selected from the group consisting of fluorescent lamp, incandescent lamp, metal halide lamp, and mercury lamp.  
     
     
         40 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 coating the surface of the substrate with a layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water.    
     
     
         41 . An antifogging method for preventing a transparent sheet member from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a transparent sheet member;    coating the surface of said transparent sheet member with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         42 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a mirror;    coating the surface of said mirror with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         43 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a lens;    coating the surface of said lens with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         44 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    disposing said substrate outdoors;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    subjecting said substrate to rainfall whereby deposits and/or contaminants adhering on the surface of said layer are washed away by rainwater.    
     
     
         45 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    rinsing said substrate with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom and washed away by water.    
     
     
         46 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    causing said substrate soaked in or wetted with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom.    
     
     
         47 . A method for maintaining a surface of a substrate disposed outdoors clean, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    disposing said substrate outdoors; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water whereby contaminants are prevented from adhering to the surface of said substrate as contaminant-laden rainwater flows therealong.    
     
     
         48 . A method for preventing growth of water droplets adhering on a substrate, comprising the steps of: 
 preparing a substrate having a surface;    coating the surface of said substrate with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 5° in terms of the contact angle with water; and,    causing adherent moisture condensate and/or water droplets to spread over the surface of said layer.    
     
     
         49 . A method according to one of claims  40 - 48 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with the sunlight.  
     
     
         50 . A method according to one of claims  40 - 48 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with an electric lamp selected from the group consisting of fluorescent lamp, incandescent lamp, metal halide lamp, and mercury lamp.  
     
     
         51 . A method of manufacturing a composite with a hydrophilic surface, comprising the steps of: 
 preparing a substrate having a surface; and,    coating the surface of said substrate with a photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 5° in terms of the contact angle with water.    
     
     
         52 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface; and,    coating the surface of said substrate with a substantially transparent photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 5° in terms of the contact angle with water.    
     
     
         53 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface; and,    coating the surface of said substrate with a photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 5° in terms of the contact angle with water.    
     
     
         54 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    coating the surface of said substrate with a substantially transparent photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 5° in terms of the contact angle with water; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of coating.    
     
     
         55 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface; and,    coating the surface of said body with a substantially transparent photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 5° in terms of the contact angle with water.    
     
     
         56 . A method according to one of claims  51 - 55 , wherein said step of coating comprises the substeps of: 
 (a) coating the surface with a thin film of amorphous titania; and,    (b) heating said thin film at a temperature less than the softening point of the substrate to transform amorphous titania into crystalline titania.    
     
     
         57 . A method according to  claim 56 , wherein prior to said substep (a) the substrate is coated with a thin film of silica to prevent alkaline network-modifier ions from diffusing from the substrate into said photocatalytic layer.  
     
     
         58 . A method according to  claim 56 , wherein said substep (a) is carried out by applying onto the surface a solution of an organic compound of titanium, followed by subjecting said compound to hydrolysis and dehydration polymerization to form said thin film of amorphous titania over the surface.  
     
     
         59 . A method according to  claim 58 , wherein said organic compound of titanium is selected from the group consisting of an alkoxide of titanium, a chelate of titanium and an acetate of titanium.  
     
     
         60 . A method according to  claim 56 , wherein said step (a) is carried out by applying onto the surface a solution of an inorganic compound of titanium, followed by subjecting said compound to hydrolysis and dehydration polymerization to form said thin film of amorphous titania over the surface.  
     
     
         61 . A method according to  claim 60 , wherein said inorganic compound of titanium is TiCl 4  or Ti(SO 4 ) 2 .  
     
     
         62 . A method according to  claim 56 , wherein said step (a) is carried out by sputtering.  
     
     
         63 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising a photocatalyst operable upon photoexcitation thereof to render the surface of said coating hydrophilic on the order of less than about 5° in terms of the contact angle with water.  
     
     
         64 . A coating composition according to  claim 63 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.  
     
     
         65 . A coating composition according to  claim 63 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent deposits and/or contaminants to be washed away by rainwater as the substrate is subjected to rainfall whereby the surface is self-cleaned.  
     
     
         66 . A coating composition according to  claim 63 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to prevent contaminants from adhering to the surface as contaminant-laden rainwater flows therealong.  
     
     
         67 . A coating composition according to  claim 63 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to release adherent deposits and/or contaminants when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.  
     
     
         68 . A coating composition according to  claim 63 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby prevent growth of water droplets.  
     
     
         69 . A coating composition according to  claim 63 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby promote drying of the substrate after wetted with water.  
     
     
         70 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 5° in terms of the contact angle with water.    
     
     
         71 . An antifogging transparent sheet member comprising: 
 a transparent substrate; and,    a substantially transparent photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface of said layer presents a water wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         72 . An antifogging mirror comprising: 
 a substrate with a reflective coating; and,    a substantially transparent photocatalytic layer bonded to the front surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface of said layer presents a water wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         73 . An antifogging lens comprising: 
 a transparent lens-forming body; and,    a substantially transparent photocatalytic layer bonded to the surface of said lens-forming body and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface of said layer presents a water wettability of less than about 5° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the lens-forming body from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         74 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating in which particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby adherent deposits and/or contaminants are washed away by rainwater to self-clean the composite as it is subjected to rainfall.    
     
     
         75 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby contaminants are prevented from adhering to the surface of the composite as contaminant-laden rainwater flows therealong.    
     
     
         76 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the composite with water.    
     
     
         77 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent growth of water droplets.    
     
     
         78 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby adherent water droplets are caused to spread over the surface of said layer to thereby promote drying of the composite after wetted with water.    
     
     
         79 . A composite with a hydrophilic surface, comprising: 
 a substrate;    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed; and,    a hydrophilic protective layer covering said photocatalytic layer;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         80 . A composite with a hydrophilic surface, comprising: 
 a substrate;    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed; and,    a protective layer covering said photocatalytic layer, said protective layer being adapted to be rendered hydrophilic upon photoexcitation;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         81 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed, said photocatalyst comprising an oxide selected from the group consisting of TiO 2 , ZnO, SnO 2 , SrTiO 3 , WO 3 , Bi 2 O 3  and Fe 2 O 3 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         82 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst comprising the anatase form of titania are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         83 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst comprising the rutile form of titania are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         84 . A composite with a hydrophilic surface, comprising: 
 a substrate;    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst comprising the rutile form of titania are uniformly dispersed, said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic; and,    an intermediate layer of a non-decomposable material interleaved between said substrate and said photocatalytic layer.    
     
     
         85 . A composite with a hydrophilic surface, comprising: 
 a substrate, said substrate containing alkaline metal ions and/or alkaline-earth metal ions;    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst comprising the rutile form of titania are uniformly dispersed, said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic; and,    a diffusion prevention thin film interleaved between said substrate and said photocatalytic layer to prevent said ions from diffusing from said substrate into said photocatalytic layer.    
     
     
         86 . A composite according to  claim 85 , wherein said thin film is comprised of silica.  
     
     
         87 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalytic layer having a thickness of less than about 0.2 micrometers;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         88 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalytic layer further comprising a metal selected from the group consisting of Ag, Cu and Zn;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         89 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalytic layer further comprising a metal selected from the group consisting of Pt, Pd, Rh, Ru, Os and Ir;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         90 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a coating wherein particles of a photocatalyst are uniformly dispersed;    said photocatalyst operating upon photoexcitation thereof to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water.    
     
     
         91 . A composite according to  claim 90 , wherein upon photoexcitation the surface of said composite presents a water wettability of less than about 5° in terms of the contact angle with water.  
     
     
         92 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic layer bonded to the surface of said substrate, said photocatalytic layer comprising a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic.    
     
     
         93 . An antifogging transparent sheet member comprising: 
 a transparent substrate; and,    a substantially transparent photocatalytic layer bonded to the surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         94 . An antifogging mirror comprising: 
 a substrate with a reflective coating; and,    a substantially transparent photocatalytic layer bonded to the front surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         95 . An antifogging lens comprising: 
 a transparent lens-forming body; and,    a substantially transparent photocatalytic layer bonded to the surface of said lens-forming body and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the lens-forming body from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         96 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby adherent deposits and/or contaminants are washed away by rainwater to self-clean the composite as it is subjected to rainfall.    
     
     
         97 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby contaminants are prevented from adhering to the surface of the composite as contaminant-laden rainwater flows therealong.    
     
     
         98 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the composite with water.    
     
     
         99 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent growth of water droplets.    
     
     
         100 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a photocatalytic layer bonded to the surface of said substrate and comprised of a photocatalyst and SiO 2  or SnO 2 ;    said photocatalyst operating upon photoexcitation thereof to render the surface of the composite hydrophilic whereby adherent water droplets are caused to spread over the surface of said layer to thereby promote drying of the composite after wetted with water.    
     
     
         101 . A composite according to one of claims  92 - 100 , wherein upon photoexcitation the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water.  
     
     
         102 . A composite according to  claim 101 , wherein upon photoexcitation the surface of said composite presents a water wettability of less than about 5° in terms of the contact angle with water.  
     
     
         103 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the composite hydrophilic.    
     
     
         104 . An antifogging transparent sheet member comprising: 
 a transparent substrate having a surface; and,    a substantially transparent photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the sheet member hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         105 . An antifogging mirror comprising: 
 a substrate having a surface and a reflective coating; and,    a substantially transparent photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the mirror hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         106 . An antifogging lens comprising: 
 a transparent lens-forming body having a surface; and,    a substantially transparent photocatalytic coating bonded to the surface of said lens-forming body and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the lens hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the body from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         107 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the composite hydrophilic whereby adherent deposits and/or contaminants are washed away by rainwater to self-clean the composite as it is subjected to rainfall.    
     
     
         108 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the composite hydrophilic whereby contaminants are prevented from adhering to the surface of the composite as contaminant-laden rainwater flows therealong.    
     
     
         109 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the composite hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the composite with water.    
     
     
         110 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the composite hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         111 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein due to photoexcitation of said photocatalyst said organic group at the surface of said photocatalytic coating are substituted at least in part with hydroxyl groups under the photocatalytic action of the photocatalyst thereby rendering the surface of the composite hydrophilic whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the composite after wetted with water.    
     
     
         112 . A composite according to one of claims  103 - 111 , wherein upon photoexcitation the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water.  
     
     
         113 . A composite according to  claim 112 , wherein upon photoexcitation the surface of said composite presents a water wettability of less than about 5° in terms of the contact angle with water.  
     
     
         114 . An antifogging sheet glass adapted to prevent moisture condensate and/or water droplets adhering on the surface thereof from fogging or blurring the sheet glass, said sheet glass comprising: 
 a transparent substrate having a surface; and,    a substantially transparent coating of silicone which is bonded to the surface of said substrate and in which particles of a photocatalyst are uniformly dispersed, said silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups whereby the surface of said substrate is rendered highly hydrophilic.    
     
     
         115 . An antifogging mirror adapted to prevent moisture condensate and/or water droplets adhering on the surface thereof from fogging or blurring the mirror, said mirror comprising: 
 a substrate having a surface and a reflective coating; and,    a substantially transparent coating of silicone which is bonded to the surface of said substrate and in which particles of a photocatalyst are uniformly dispersed, said silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups whereby the surface of said substrate is rendered highly hydrophilic.    
     
     
         116 . An antifogging lens adapted to prevent moisture condensate and/or water droplets adhering on the surface thereof from fogging or blurring the lens, said lens comprising: 
 a transparent lens-forming body having a surface; and,    a substantially transparent coating of silicone which is bonded to the surface of said body and in which particles of a photocatalyst are uniformly dispersed, said silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups whereby the surface of said substrate is rendered highly hydrophilic.    
     
     
         117 . A composite with a hydrophilifiable surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water.    
     
     
         118 . A composite with a hydrophilifiable surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water whereby adherent deposits and/or contaminants are washed away by rainwater to self-clean the composite as it is subjected to rainfall.    
     
     
         119 . A composite with a hydrophilifiable surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water whereby contaminants are prevented from adhering to the surface of the composite as contaminant-laden rainwater flows therealong.    
     
     
         120 . A composite with a hydrophilifiable surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the composite with water.    
     
     
         121 . A composite with a hydrophilifiable surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         122 . A composite with a hydrophilifiable surface, comprising: 
 a substrate having a surface; and,    a photocatalytic coating bonded to the surface of said substrate and comprised of a photocatalyst and silicone having organic groups bonded to silicon atoms of silicone molecules;    wherein said organic groups at the surface of said coating are capable of being substituted, upon photoexcitation of said photocatalyst, at least in part with hydroxyl groups to render the surface of said composite hydrophilic such that the surface of said composite presents a water wettability of less than about 10° in terms of the contact angle with water whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the composite after wetted with water.    
     
     
         123 . A method of manufacturing a composite with a hydrophilifiable surface, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising crystalline titania particles dispersed in a precursor of amorphous silica; and,    subjecting said precursor to hydrolysis where necessary and to dehydration polymerization to thereby form on said surface a photo-reactive layer of titania particles bound by amorphous silica.    
     
     
         124 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    applying onto the surface of the substrate a suspension comprising crystalline titania particles dispersed in a precursor of amorphous silica; and,    subjecting said precursor to hydrolysis where necessary and to dehydration polymerization to thereby form on said surface a substantially transparent photo-reactive layer of titania particles bound by amorphous silica.    
     
     
         125 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising crystalline titania particles dispersed in a precursor of amorphous silica; and,    subjecting said precursor to hydrolysis where necessary and to dehydration polymerization to thereby form on said surface a photo-reactive layer of titania particles bound by amorphous silica.    
     
     
         126 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    applying onto the surface of the substrate a suspension comprising crystalline titania particles dispersed in a precursor of amorphous silica;    subjecting said precursor to hydrolysis where necessary and to dehydration polymerization to thereby form on said surface a substantially transparent photo-reactive layer of titania particles bound by amorphous silica; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of applying a suspension.    
     
     
         127 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    applying onto the surface of the substrate a suspension comprising crystalline titania particles dispersed in a precursor of amorphous silica; and,    subjecting said precursor to hydrolysis where necessary and to dehydration polymerization to thereby form on said surface a substantially transparent photo-reactive layer of titania particles bound by amorphous silica.    
     
     
         128 . A method according to one of claims  123 - 127 , wherein said precursor is tetraalkoxysilane, silanol, polysiloxane having an average molecular weight of less than 3000, or a mixture thereof.  
     
     
         129 . A method of manufacturing a composite with a hydrophilifiable surface, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of silica dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to form a thin film of amorphous titania in which particles of silica are dispersed; and,    heating said film at a temperature less than the softening point of the substrate to transform amorphous titania into crystalline titania to thereby form a photo-reactive coating of photocatalytic titania in which particles of silica are dispersed.    
     
     
         130 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of silica dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to form a thin film of amorphous titania in which particles of silica are dispersed; and,    heating said film at a temperature less than the softening point of the substrate to transform amorphous titania into crystalline titania to thereby form a substantially transparent photo-reactive coating of photocatalytic titania in which particles of silica are dispersed.    
     
     
         131 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of silica dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to form a thin film of amorphous titania in which particles of silica are dispersed; and,    heating said film at a temperature less than the softening point of the substrate to transform amorphous titania into crystalline titania to thereby form a photo-reactive coating of photocatalytic titania in which particles of silica are dispersed.    
     
     
         132 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of silica dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to form a thin film of amorphous titania in which particles of silica are dispersed;    heating said film at a temperature less than the softening point of the substrate to transform amorphous titania into crystalline titania to thereby form a substantially transparent photo-reactive coating of photocatalytic titania in which particles of silica are dispersed; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of applying a suspension.    
     
     
         133 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    applying onto the surface of the body a suspension comprising particles of silica dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to form a thin film of amorphous titania in which particles of silica are dispersed; and,    heating said film at a temperature less than the softening point of the body to transform amorphous titania into crystalline titania to thereby form a substantially transparent photo-reactive coating of photocatalytic titania in which particles of silica are dispersed.    
     
     
         134 . A method according to one of claims  129 - 133 , wherein said organic compound of titanium is selected from the group consisting of an alkoxide of titanium, a chelate of titanium and an acetate of titanium.  
     
     
         135 . A method of manufacturing a composite with a hydrophilifiable surface, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of crystalline titania and particles of silica; and,    heating said substrate at a temperature less than the softening point thereof to bond particles to said substrate and to sinter particles with each other to thereby form a photo-reactive coating comprised of sintered particles of titania and silica.    
     
     
         136 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of crystalline titania and particles of silica; and,    heating said substrate at a temperature less than the softening point thereof to bond particles to said substrate and to sinter particles with each other to thereby form a substantially transparent photo-reactive coating comprised of sintered particles of titania and silica.    
     
     
         137 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of crystalline titania and particles of silica; and,    heating said substrate at a temperature less than the softening point thereof to bond particles to said substrate and to sinter particles with each other to thereby form a photo-reactive coating comprised of sintered particles of titania and silica.    
     
     
         138 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of crystalline titania and particles of silica;    heating said substrate at a temperature less than the softening point thereof to bond particles to said substrate and to sinter particles with each other to thereby form a substantially transparent photo-reactive coating comprised of sintered particles of titania and silica; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of applying a suspension.    
     
     
         139 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    applying onto the surface of the body a suspension comprising particles of crystalline titania and particles of silica; and,    heating said body at a temperature less than the softening point thereof to bond particles to said substrate and to sinter particles with each other to thereby form a substantially transparent photo-reactive coating comprised of sintered particles of titania and silica.    
     
     
         140 . A method of manufacturing a composite with a hydrophilifiable surface, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of the anatase form of titania and particles of tin oxide; and,    heating said substrate at a temperature of less than 900° C. to bond particles to said substrate and to sinter particles with each other to thereby form a photo-reactive coating comprised of sintered particles of titania and tin oxide.    
     
     
         141 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of the anatase form of titania and particles of tin oxide; and,    heating said substrate at a temperature of less than 900° C. to bond particles to said substrate and to sinter particles with each other to thereby form a substantially transparent photo-reactive coating comprised of sintered particles of titania and tin oxide.    
     
     
         142 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of the anatase form of titania and particles of tin oxide; and,    heating said substrate at a temperature of less than 900° C. to bond particles to said substrate and to sinter particles with each other to thereby form a photo-reactive coating comprised of sintered particles of titania and tin oxide.    
     
     
         143 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of the anatase form of titania and particles of tin oxide;    heating said substrate at a temperature of less than 900° C. to bond particles to said substrate and to sinter particles with each other to thereby form a substantially transparent photo-reactive coating comprised of sintered particles of titania and tin oxide; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of applying a suspension.    
     
     
         144 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    applying onto the surface of the substrate a suspension comprising particles of the anatase form of titania and particles of tin oxide;    heating said body at a temperature of less than 900° C. to bond particles to said substrate and to sinter particles with each other to thereby form a substantially transparent photo-reactive coating comprised of sintered particles of titania and tin oxide.    
     
     
         145 . A method of manufacturing a composite with a hydrophilifiable surface, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of tin oxide dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to thereby form a thin film of amorphous titania in which particles of tin oxide are dispersed; and,    heating said thin film at a temperature of less than 900° C. to transform amorphous titania into crystalline titania to thereby form a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed.    
     
     
         146 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of tin oxide dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to thereby form a thin film of amorphous titania in which particles of tin oxide are dispersed; and,    heating said thin film at a temperature of less than 900° C. to transform amorphous titania into crystalline titania to thereby form a substantially transparent photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed.    
     
     
         147 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of tin oxide dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to thereby form a thin film of amorphous titania in which particles of tin oxide are dispersed; and,    heating said thin film at a temperature of less than 900° C. to transform amorphous titania into crystalline titania to thereby form a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed.    
     
     
         148 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    applying onto the surface of the substrate a suspension comprising particles of tin oxide dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to thereby form a thin film of amorphous titania in which particles of tin oxide are dispersed;    heating said thin film at a temperature of less than 900° C. to transform amorphous titania into crystalline titania to thereby form a substantially transparent photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of applying a suspension.    
     
     
         149 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    applying onto the surface of the body a suspension comprising particles of tin oxide dispersed in a solution of an organic compound of titanium;    subjecting said compound to hydrolysis and dehydration polymerization to thereby form a thin film of amorphous titania in which particles of tin oxide are dispersed; and,    heating said thin film at a temperature of less than 900° C. to transform amorphous titania into crystalline titania to thereby form a substantially transparent photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed.    
     
     
         150 . A method of manufacturing a composite with a hydrophilic surface, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a coating composition comprising particles of a photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed, said silicone coating having organic groups bonded to silicon atoms of silicone molecules; and,    subjecting the photocatalyst to photoexcitation so that said organic groups at the surface of the coating are substituted at least in part with hydroxyl groups.    
     
     
         151 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    applying onto the surface of the substrate a coating composition comprising particles of a photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    curing said film-forming element to form a substantially transparent silicone coating in which particles of the photocatalyst are uniformly dispersed, said silicone coating having organic groups bonded to silicon atoms of silicone molecules; and,    subjecting the photocatalyst to photoexcitation so that said organic groups at the surface of the coating are substituted at least in part with hydroxyl groups.    
     
     
         152 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    applying onto the surface of the substrate a coating composition comprising particles of a photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed, said silicone coating having organic groups bonded to silicon atoms of silicone molecules; and,    subjecting the photocatalyst to photoexcitation so that said organic groups at the surface of the coating are substituted at least in part with hydroxyl groups.    
     
     
         153 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    applying onto the surface of the substrate a coating composition comprising particles of a photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    curing said film-forming element to form a substantially transparent silicone coating in which particles of the photocatalyst are uniformly dispersed, said silicone coating having organic groups bonded to silicon atoms of silicone molecules;    subjecting the photocatalyst to photoexcitation so that said organic groups at the surface of the coating are substituted at least in part with hydroxyl groups; and,    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of applying a coating composition.    
     
     
         154 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    applying onto the surface of the body a coating composition comprising particles of a photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    curing said film-forming element to form a substantially transparent silicone coating in which particles of the photocatalyst are uniformly dispersed, said silicone coating having organic groups bonded to silicon atoms of silicone molecules; and,    subjecting the photocatalyst to photoexcitation so that said organic groups at the surface of the coating are substituted at least in part with hydroxyl groups.    
     
     
         155 . A method according to one of claims  150 - 154 , wherein said step of subjecting the photocatalyst to photoexcitation is carried out until the water wettability of the surface of said coating becomes less than about 10° in terms of the contact angle with water.  
     
     
         156 . A method according to  claim 155 , wherein said step of subjecting the photocatalyst to photoexcitation is carried out until the water wettability of the surface of said coating becomes less than about 5° in terms of the contact angle with water.  
     
     
         157 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.    
     
     
         158 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic;    said coating having the surface thus rendered hydrophilic being operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         159 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic;    said coating having the surface thus rendered hydrophilic being operable to permit adherent deposits and/or contaminants to be washed away by rainwater as said substrate is subjected to rainfall to thereby permit self-cleaning of the substrate.    
     
     
         160 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic;    said coating having the surface thus rendered hydrophilic being operable to prevent contaminants from adhering to the surface thereof as contaminant-laden rainwater flows therealong.    
     
     
         161 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic;    said coating having the surface thus rendered hydrophilic being operable to release adherent deposits and/or contaminants when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         162 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic;    said coating having the surface thus rendered hydrophilic being operable to cause adherent moisture condensate and/or water droplets to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         163 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic;    said coating having the surface thus rendered hydrophilic being operable to cause adherent water droplets to spread over the surface of the coating to thereby promote drying of the substrate after wetted with water.    
     
     
         164 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous silica and capable of forming a coating of amorphous silica when cured, said precursor being tetraalkoxysilane, silanol, polysiloxane having an average molecular weight of less than 3000, or a mixture thereof; and,    particles of photocatalytic titania dispersed in said film-forming element for rendering upon photoexcitation the surface of said coating hydrophilic.    
     
     
         165 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.    
     
     
         166 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         167 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent deposits and/or contaminants are away by rainwater as said substrate is subjected to rainfall to thereby permit self-cleaning of the substrate.    
     
     
         168 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby contaminants are prevented from adhering to the surface of the substrate as contaminant-laden rainwater flows therealong.    
     
     
         169 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         170 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         171 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the substrate after wetted with water.    
     
     
         172 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination, said precursor being selected from the group consisting of an alkoxide of titanium, a chelate of titanium and an acetate of titanium; and,    particles of silica dispersed in said film-forming element;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic.    
     
     
         173 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.    
     
     
         174 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         175 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent deposits and/or contaminants are away by rainwater as said substrate is subjected to rainfall to thereby permit self-cleaning of the substrate.    
     
     
         176 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby contaminants are prevented from adhering to the surface of the substrate as contaminant-laden rainwater flows therealong.    
     
     
         177 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         178 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         179 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of silica;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and silica upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the substrate after wetted with water.    
     
     
         180 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.    
     
     
         181 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         182 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent deposits and/or contaminants are away by rainwater as said substrate is subjected to rainfall to thereby permit self-cleaning of the substrate.    
     
     
         183 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby contaminants are prevented from adhering to the surface of the substrate as contaminant-laden rainwater flows therealong.    
     
     
         184 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         185 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         186 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a suspension comprising particles of photocatalytic titania and particles of tin oxide;    said coating composition being capable of forming a photo-reactive coating comprised of sintered particles of photocatalytic titania and tin oxide upon application on the substrate followed by sintering;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the substrate after wetted with water.    
     
     
         187 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.    
     
     
         188 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         189 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent deposits and/or contaminants are away by rainwater as said substrate is subjected to rainfall to thereby permit self-cleaning of the substrate.    
     
     
         190 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby contaminants are prevented from adhering to the surface of the substrate as contaminant-laden rainwater flows therealong.    
     
     
         191 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         192 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         193 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising a precursor of amorphous titania and capable of forming a coating of photocatalytic titania upon curing and calcination; and,    particles of tin oxide dispersed in said film-forming element;    upon application on the substrate followed by calcination said coating composition being capable of forming a photo-reactive coating of photocatalytic titania in which particles of tin oxide are dispersed;    said photocatalytic titania rendering upon photoexcitation the surface of said coating hydrophilic whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the substrate after wetted with water.    
     
     
         194 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.    
     
     
         195 . A coating composition according to  claim 194 , wherein said particles of photocatalytic titania are operable upon photoexcitation to render the surface of said coating hydrophilic on the order of less than about 5° in terms of the contact angle with water.  
     
     
         196 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said coating to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         197 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic whereby adherent deposits and/or contaminants are away by rainwater as said substrate is subjected to rainfall to thereby permit self-cleaning of the substrate.    
     
     
         198 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic whereby contaminants are prevented from adhering to the surface of the substrate as contaminant-laden rainwater flows therealong.    
     
     
         199 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic whereby deposits and/or contaminants adhering to the surface are released therefrom when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         200 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating to thereby prevent growth of water droplets.    
     
     
         201 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising: 
 a film-forming element comprising uncured or partially cured silicone or a precursor thereof and capable of forming a coating of silicone when cured; and,    particles of photocatalytic titania dispersed in said film-forming element for causing upon photoexcitation the organic groups bonded to the silicon atoms of the silicone molecules at the surface of the coating to be substituted at least in part with hydroxyl groups in the presence of water under the photocatalytic action to thereby render the surface of said coating hydrophilic whereby adherent water droplets are caused to spread over the surface of the coating to thereby promote drying of the substrate after wetted with water.    
     
     
         202 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of said layer hydrophilic.    
     
     
         203 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water.    
     
     
         204 . An antifogging method for preventing a transparent sheet member from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 (a) preparing a transparent sheet member coated with a substantially transparent layer of silicone in which particles of a photocatalyst are uniformly dispersed; and,    (b) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         205 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 (a) preparing a lens coated with a substantially transparent layer of silicone in which particles of a photocatalyst are uniformly dispersed; and,    (b) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         206 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 (a) preparing a mirror coated with a substantially transparent layer of silicone in which particles of a photocatalyst are uniformly dispersed; and,    (b) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         207 . A method for cleaning a substrate, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) disposing said substrate outdoors;    (c) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst whereby the surface of said layer is rendered hydrophilic; and,    (d) subjecting said substrate to rainfall whereby deposits and/or contaminants adhering on the surface of said layer are washed away by rainwater.    
     
     
         208 . A method for cleaning a substrate, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst whereby the surface of said layer is rendered hydrophilic; and,    (c) rinsing said substrate with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom and washed away by water.    
     
     
         209 . A method for cleaning a substrate, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst whereby the surface of said layer is rendered hydrophilic; and,    (c) causing said substrate soaked in or wetted with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom.    
     
     
         210 . A method for maintaining a surface of a substrate disposed outdoors clean, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) disposing said substrate outdoors; and,    (c) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of said layer hydrophilic whereby contaminants are prevented from adhering to the surface of said substrate as contaminant-laden rainwater flows therealong.    
     
     
         211 . A method for preventing growth of water droplets adhering on a substrate, comprising the steps of: 
 (a) preparing a substrate coated with a layer of silicone in which particles of a photocatalyst are uniformly dispersed;    (b) subjecting said photocatalyst of said layer to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said layer are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst whereby the surface of said layer is rendered hydrophilic; and,    (c) causing adherent moisture condensate and/or water droplets to spread over the surface of said layer.    
     
     
         212 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 (a) applying onto the surface of said substrate a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (b) curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed; and,    (c) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic.    
     
     
         213 . A method according to  claim 212 , wherein said photocatalyst is photoexcited until the surface of said coating presents a water-wettability of less than about 10° in terms of the contact angle with water.  
     
     
         214 . An antifogging method for preventing a transparent sheet member from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 (a) preparing a transparent sheet member;    (b) applying onto the surface of said sheet member a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a substantially transparent silicone coating in which particles of the photocatalyst are uniformly dispersed; and,    (d) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating.    
     
     
         215 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 (a) preparing a lens;    (b) applying onto the surface of the lens a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a substantially transparent silicone coating in which particles of the photocatalyst are uniformly dispersed; and,    (d) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating.    
     
     
         216 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 (a) preparing a mirror;    (b) applying onto the surface of the mirror a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a substantially transparent silicone coating in which particles of the photocatalyst are uniformly dispersed; and,    (d) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of the coating.    
     
     
         217 . A method for cleaning a substrate, comprising the steps of: 
 (a) preparing a substrate;    (b) applying onto the surface of the substrate a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed;    (d) disposing said substrate outdoors;    (e) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic; and,    (f) subjecting said substrate to rainfall to thereby permit deposits and/or contaminants adhering on the surface of said layer to be washed away by rainwater.    
     
     
         218 . A method for cleaning a substrate, comprising the steps of: 
 (a) preparing a substrate;    (b) applying onto the surface of said substrate a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed;    (d) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic; and,    (e) rinsing said substrate with water to thereby permit organic deposits and/or contaminants adhering on the surface of said coating to be released therefrom and washed away by water.    
     
     
         219 . A method for cleaning a substrate, comprising the steps of: 
 (a) preparing a substrate;    (b) applying onto the surface of said substrate a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed;    (d) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic; and,    (e) causing said substrate soaked in or wetted with water to thereby permit organic deposits and/or contaminants adhering on the surface of the coating to be released therefrom.    
     
     
         220 . A method for maintaining a surface of a substrate disposed outdoors clean, comprising the steps of: 
 (a) preparing a substrate;    (b) applying onto the surface of the substrate a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed;    (d) disposing said substrate outdoors; and,    (e) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic whereby contaminants are prevented from adhering to the surface of said substrate as contaminant-laden rainwater flows therealong.    
     
     
         221 . A method for preventing growth of water droplets adhering on a substrate, comprising the steps of: 
 (a) preparing a substrate;    (b) applying onto the surface of said substrate a coating composition comprising particles of photocatalyst and a film-forming element of uncured or partially cured silicone or a precursor thereof;    (c) curing said film-forming element to form a silicone coating in which particles of the photocatalyst are uniformly dispersed;    (d) subjecting said photocatalyst to photoexcitation so that the organic groups bonded to the silicon atoms of the silicone molecules at the surface of said coating are substituted at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst to thereby render the surface of the coating hydrophilic; and,    (e) causing adherent moisture condensate and/or water droplets to spread over the surface of said coating.    
     
     
         222 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic layer comprised of a photocatalyst, said photocatalytic layer being bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface presents a water wettability of less than about 10° in terms of the contact angle with water.    
     
     
         223 . An antifogging transparent sheet member comprising: 
 a transparent substrate; and,    a substantially transparent layer comprised of a photocatalyst and bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         224 . An antifogging mirror comprising: 
 a substrate with a reflective coating; and,    a substantially transparent layer comprised of a photocatalyst and bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         225 . An antifogging lens comprising: 
 a transparent lens-forming body; and,    a substantially transparent layer comprised of a photocatalyst and bonded to the surface of said lens-forming body;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic such that the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the lens-forming body from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         226 . A composite according to  claim 222 , wherein, for self-cleaning of the composite, said layer operates to permit adherent deposits and/or contaminants to be washed away by rainwater as said composite is subjected to rainfall.  
     
     
         227 . A composite according to  claim 222 , wherein said layer operates to prevent contaminants from adhering to the surface thereof as contaminant-laden rainwater flows therealong.  
     
     
         228 . A composite according to  claim 222 , wherein, to facilitate cleansing of the composite with water, said layer operates to release adherent deposits and/or contaminants when soaked in or wetted with water.  
     
     
         229 . A composite according to  claim 222 , wherein, for prevention of growth of water droplets, said layer operates to cause adherent moisture condensate and/or water droplets to spread over the surface of said layer.  
     
     
         230 . A composite according to  claim 222 , wherein, to promote drying of the substrate after wetted with water, said layer operates to cause adherent water droplets to spread over the surface of said layer.  
     
     
         231 . A composite according to  claim 222 , wherein the surface of said layer is further coated with a hydrophilic protective layer which is operable to present upon photoexcitation a water-wettability of less than about 10° in terms of the contact angle with water.  
     
     
         232 . A composite according to  claim 222 , wherein the surface of said layer is further coated with a hydrophilifiable protective layer which is operable to present upon photoexcitation a water-wettability of less than about 10° in terms of the contact angle with water.  
     
     
         233 . A composite according to  claim 222 , wherein said photocatalyst comprises an oxide selected from the group consisting of TiO 2 , ZnO, SnO 2 , SrTiO 3 , WO 3 , Bi 2 O 3  and Fe 2 O 3 .  
     
     
         234 . A composite according to  claim 222 , wherein said photocatalyst comprises the anatase form of titania.  
     
     
         235 . A composite according to  claim 222 , wherein said photocatalyst comprises the rutile form of titania.  
     
     
         236 . A composite according to  claim 222 , wherein said layer further comprises SiO 2  or SnO 2 .  
     
     
         237 . A composite according to  claim 222 , wherein said layer comprises a coating wherein particles of said photocatalyst are uniformly dispersed.  
     
     
         238 . A composite according to  claim 222 , wherein said layer is made of a coating containing silicone and wherein the surface of said coating is formed of a derivative of silicone in which the organic groups bonded to the silicon atoms of the silicone molecules have been substituted upon photoexcitation at least in part with hydroxyl groups under the photocatalytic action of said photocatalyst.  
     
     
         239 . A composite according to  claim 222 , further comprising an intermediate layer of a non-decomposable material interleaved between said substrate and said layer of photocatalyst.  
     
     
         240 . A composite according to  claim 222 , wherein said substrate contains alkaline metal ions and/or alkaline-earth metal ions and wherein a thin film for preventing said ions from diffusing from said substrate into said layer is interleaved between said substrate and said layer.  
     
     
         241 . A composite according to  claim 240 , wherein said thin film comprises a thin film of silica.  
     
     
         242 . A composite according to  claim 222 , wherein the thickness of said layer is less than about 0.2 micrometers.  
     
     
         243 . A composite according to  claim 222 , wherein said layer further comprises a metal selected from the group consisting of Ag, Cu and Zn.  
     
     
         244 . A composite according to  claim 222 , wherein said layer further comprises a metal selected from the group consisting of Pt, Pd, Rh, Ru, Os and Ir.  
     
     
         245 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water.    
     
     
         246 . An antifogging method for preventing a transparent sheet member from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a transparent sheet member coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         247 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a mirror coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         248 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a lens coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         249 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    disposing said substrate outdoors;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water; and,    subjecting said substrate to rainfall whereby deposits and/or contaminants adhering on the surface of said layer are washed away by rainwater.    
     
     
         250 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water; and,    rinsing said substrate with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom and washed away by water.    
     
     
         251 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water; and,    causing said substrate soaked in or wetted with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom.    
     
     
         252 . A method for maintaining a surface of a substrate disposed outdoors clean, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    disposing said substrate outdoors; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10 in terms of the contact angle with water whereby contaminants are prevented from adhering to the surface of said substrate as contaminant-laden rainwater flows therealong.    
     
     
         253 . A method for preventing growth of water droplets adhering on a substrate, comprising the steps of: 
 preparing a substrate coated with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water; and,    causing adherent moisture condensate and/or water droplets to spread over the surface of said layer.    
     
     
         254 . A method according to one of claims  245 - 253 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with the sunlight.  
     
     
         255 . A method according to one of claims  245 - 253 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with an electric lamp selected from the group consisting of fluorescent lamp, incandescent lamp, metal halide lamp, and mercury lamp.  
     
     
         256 . A method for rendering a surface of a substrate hydrophilic, comprising the steps of: 
 coating the surface of the substrate with a layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water.    
     
     
         257 . An antifogging method for preventing a transparent sheet member from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a transparent sheet member;    coating the surface of said transparent sheet member with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         258 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a mirror;    coating the surface of said mirror with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         259 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a lens;    coating the surface of said lens with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         260 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    disposing said substrate outdoors;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water; and,    subjecting said substrate to rainfall whereby deposits and/or contaminants adhering on the surface of said layer are washed away by rainwater.    
     
     
         261 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water; and,    rinsing said substrate with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom and washed away by water.    
     
     
         262 . A method for cleaning a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water; and,    causing said substrate soaked in or wetted with water whereby organic deposits and/or contaminants adhering on the surface of said layer are released therefrom.    
     
     
         263 . A method for maintaining a surface of a substrate disposed outdoors clean, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    disposing said substrate outdoors; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water whereby contaminants are prevented from adhering to the surface of said substrate as contaminant-laden rainwater flows therealong.    
     
     
         264 . A method for preventing growth of water droplets adhering on a substrate, comprising the steps of: 
 preparing a substrate;    coating the surface of said substrate with a layer comprised of a photocatalyst;    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic until the surface of said layer presents a water-wettability of less than about 10° in terms of the contact angle with water; and,    causing adherent moisture condensate and/or water droplets to spread over the surface of said layer.    
     
     
         265 . A method according to one of claims  256 - 264 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with the sunlight.  
     
     
         266 . A method according to one of claims  256 - 264 , wherein the step of subjecting said photocatalyst to photoexcitation is carried out with an electric lamp selected from the group consisting of fluorescent lamp, incandescent lamp, metal halide lamp, and mercury lamp.  
     
     
         267 . A method of manufacturing a composite with a hydrophilic surface, comprising the steps of: 
 preparing a substrate having a surface;    coating the surface of said substrate with a photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 10° in terms of the contact angle with water; and,    subjecting said photocatalyst to photoexcitation until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water.    
     
     
         268 . A method of manufacturing an antifogging transparent sheet member, comprising the steps of: 
 preparing a transparent substrate having a surface;    coating the surface of said substrate with a substantially transparent photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 10° in terms of the contact angle with water; and,    subjecting said photocatalyst to photoexcitation until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water.    
     
     
         269 . A method of manufacturing a self-cleaning composite, comprising the steps of: 
 preparing a substrate having a surface;    coating the surface of said substrate with a photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 10° in terms of the contact angle with water; and,    subjecting said photocatalyst to photoexcitation until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water.    
     
     
         270 . A method of manufacturing an antifogging mirror, comprising the steps of: 
 preparing a substrate with or without a reflective coating, said substrate having a surface;    coating the surface of said substrate with a substantially transparent photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 10° in terms of the contact angle with water;    forming where necessary a reflective coating on the opposite surface of said substrate prior to or subsequent to or during the course of said step of coating; and,    subjecting said photocatalyst to photoexcitation until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water.    
     
     
         271 . A method of manufacturing an antifogging lens, comprising the steps of: 
 preparing a lens-forming body having a surface;    coating the surface of said body with a substantially transparent photo-reactive layer comprised of a photocatalyst and operable to present upon photoexcitation a water wettability of less than about 10° in terms of the contact angle with water; and,    subjecting said photocatalyst to photoexcitation until the water wettability of said layer becomes less than about 10° in terms of the contact angle with water.    
     
     
         272 . A method according to one of claims  267 - 271 , wherein said step of coating comprises the substeps of: 
 (a) coating the surface with a thin film of amorphous titania; and,    (b) heating said thin film at a temperature less than the softening point of the substrate to transform amorphous titania into crystalline titania.    
     
     
         273 . A method according to  claim 272 , wherein prior to said step of coating the substrate is coated with a thin film of silica to prevent alkaline network-modifier ions from diffusing from the substrate into said photo-reactive layer.  
     
     
         274 . A method according to  claim 272 , wherein said step (a) is carried out by applying onto the surface a solution of an organic compound of titanium, followed by subjecting said compound to hydrolysis and dehydration polymerization to form said thin film of amorphous titania over the surface.  
     
     
         275 . A method according to  claim 274 , wherein said organic compound of titanium is selected from the group consisting of an alkoxide of titanium, a chelate of titanium and an acetate of titanium.  
     
     
         276 . A method according to  claim 272 , wherein said step (a) is carried out by applying onto the surface a solution of an inorganic compound of titanium, followed by subjecting said compound to hydrolysis and dehydration polymerization to form said thin film of amorphous titania over the surface.  
     
     
         277 . A method according to  claim 276 , wherein said inorganic compound of titanium is TiCl 4  or Ti(SO 4 ) 2 .  
     
     
         278 . A method according to  claim 272 , wherein said step (a) is carried out by sputtering.  
     
     
         279 . A coating composition for use in forming a photocatalytically hydrophilifiable coating on a substrate, said coating composition comprising a photocatalyst operable upon photoexcitation thereof to render the surface of said coating hydrophilic on the order of less than about 10° in terms of the contact angle with water.  
     
     
         280 . A coating composition according to  claim 279 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.  
     
     
         281 . A coating composition according to  claim 279 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent deposits and/or contaminants to be washed away by rainwater as the substrate is subjected to rainfall whereby the surface is self-cleaned.  
     
     
         282 . A coating composition according to  claim 279 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to prevent contaminants from adhering to the surface as contaminant-laden rainwater flows therealong.  
     
     
         283 . A coating composition according to  claim 279 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to release adherent deposits and/or contaminants when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.  
     
     
         284 . A coating composition according to  claim 279 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby prevent growth of water droplets.  
     
     
         285 . A coating composition according to  claim 279 , wherein the surface of said coating thus rendered hydrophilic upon photoexcitation is operable to permit adherent moisture condensate and/or water droplets to spread thereover to thereby promote drying of the substrate after wetted with water.  
     
     
         286 . An antifogging transparent sheet member comprising: 
 a transparent substrate; and,    a substantially transparent layer comprised of a photocatalyst and bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         287 . An antifogging mirror comprising: 
 a substrate with a reflective coating; and,    a substantially transparent layer comprised of a photocatalytic semiconductor material and bonded to the surface of said substrate;    said photocatalytic material operating upon photoexcitation thereof to render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the substrate from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         288 . An antifogging mirror according to  claim 287 , wherein said mirror is a rearview mirror for a vehicle.  
     
     
         289 . An antifogging lens comprising: 
 a transparent lens-forming body; and,    a substantially transparent layer comprised of a photocatalyst and bonded to the surface of said lens-forming body;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer to thereby prevent the lens-forming body from being fogged or blurred with adherent moisture condensate and/or water droplets.    
     
     
         290 . An antifogging method for preventing a mirror from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a mirror coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         291 . An antifogging method for preventing a lens from being fogged or blurred with adherent moisture condensate and/or water droplets, said method comprising the steps of: 
 preparing a lens coated with a substantially transparent layer comprised of a photocatalyst; and,    subjecting said photocatalyst to photoexcitation to thereby render the surface of said layer hydrophilic whereby adherent moisture condensate and/or water droplets are caused to spread over the surface of said layer.    
     
     
         292 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic layer comprised of a photocatalyst, said photocatalytic layer being bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic to permit adherent deposits and/or contaminants to be washed away by rainwater to thereby self-clean the composite as said composite is subjected to rainfall.    
     
     
         293 . A composite with a hydrophilic surface, comprising: 
 a substrate having a surface; and,    a photocatalytic layer comprised of a photocatalyst, said photocatalytic layer being bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic to thereby prevent contaminants from adhering to the surface thereof as contaminant-laden rainwater flows therealong.    
     
     
         294 . A composite according to  claim 292  or 293, wherein said substrate is a building material.  
     
     
         295 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a layer comprised of a photocatalyst and bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic to permit adherent deposits and/or contaminants to be released when soaked in or wetted with water to thereby facilitate cleansing of the substrate with water.    
     
     
         296 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a layer comprised of a photocatalyst and bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic to permit adherent moisture condensate and/or water droplets to spread thereover to thereby prevent growth of water droplets.    
     
     
         297 . A composite according to  claim 296 , wherein said substrate is a radiator fin for a heat exchanger and wherein said layer permits adherent moisture condensate and/or water droplets to spread into water film to thereby increase the efficiency of the heat exchanger.  
     
     
         298 . A composite with a hydrophilic surface, comprising: 
 a substrate; and,    a layer comprised of a photocatalyst and bonded to the surface of said substrate;    said photocatalyst operating upon photoexcitation thereof to render the surface of said layer hydrophilic to permit adherent moisture condensate and/or water droplets to spread thereover to thereby promote drying of the substrate after wetted with water.    
     
     
         299 . A composite according to  claim 298 , wherein said substrate is a surface of an article selected from the group consisting of mirror, lens, sheet glass, and windshield.  
     
     
         300 . A composite according to  claim 298 , wherein said substrate is a surface of a pavement.
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