Photo-induced hydrophilic article and method of making same

Abstract

Methods and articles are disclosed in which a substrate is provided with a photo-induced hydrophilic surface by forming a photo-induced hydrophilic coating on the substrate by spray pyrolysis, chemical vapor deposition, or magnetron sputter vacuum deposition. The coating can have a thickness of 50 Å to 500 Å, a root mean square roughness of less than 5, preferably less than 2, and photocatalytic activity of less than 3.0×10 −3 cm −1 min −1 ±2.0×10 −3 cm −1 min −1 . The substrate includes glass substrates, including glass sheets and continuous float glass ribbons.

We claim:  
     
         1 . An article, comprising: 
 a substrate having at least one surface; and    a photo-induced hydrophilic coating deposited over at least a portion of the at least one surface, wherein an outer surface of the photo-induced hydrophilic coating has a root mean square roughness of less than or equal to 2 nm; and    wherein the photo-induced hydrophilic coating is deposited by a process selected from chemical vapor deposition, magnetron sputtered vacuum deposition, and spray pyrolysis.    
     
     
         2 . The article as claimed in  claim 1 , wherein a contact angle of a water droplet on the article is less than 15° after exposure of the coating to UVA340 radiation at 24 W/m 2  for 60 mins.  
     
     
         3 . The article as claimed in  claim 1 , wherein a contact angle of a water droplet on the article is less than 10° after exposure of the coating to UVA340 radiation at 24 W/m 2  for 60 mins.  
     
     
         4 . The article as claimed in  claim 1 , wherein a contact angle of a water droplet on the article is less than 5° after exposure of the coating to UVA340 radiation at 24 W/m 2  for 60 mins.  
     
     
         5 . The article as claimed in  claim 1 , wherein the contact angle of a water droplet on the article is less than or equal to 1°.  
     
     
         6 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating has a thickness of less than or equal to 500 Å.  
     
     
         7 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating has a thickness of less than or equal to 400 Å.  
     
     
         8 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating has a thickness of less than or equal to 300 Å.  
     
     
         9 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating has a thickness of less than or equal to 200 Å.  
     
     
         10 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating has a thickness in the range of 50 Å to 500 Å.  
     
     
         11 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating includes at least one metal oxide and/or metal alloy oxide selected from titanium oxides, silicon oxides, aluminum oxides, iron oxides, silver oxides, copper oxides, tungsten oxides, zinc/tin alloy oxides, zinc stannates, molybdenum oxides, zinc oxides, strontium titanate, cobalt oxides, chromium oxides, and mixtures or combinations thereof.  
     
     
         12 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating comprises titanium dioxide.  
     
     
         13 . The article as claimed in  claim 12 , wherein the titanium dioxide is selected from the group consisting of anatase, rutile, brookite, amorphous, and mixtures or combinations thereof.  
     
     
         14 . The article as claimed in  claim 1 , wherein the photo-induced hydrophilic coating is substantially non-porous.  
     
     
         15 . The article as claimed in  claim 1 , wherein the outer surface of the coating has a root mean square roughness of less than or equal to 1 nm.  
     
     
         16 . The article as claimed in  claim 1 , wherein the outer surface of the coating has a root mean square roughness in the range of 0.2 nm to 0.7 nm.  
     
     
         17 . The article as claimed in  claim 1 , wherein the coating has a photocatalytic activity of less than or equal to 5×10 −3  cm −1  min −1 .  
     
     
         18 . The article as claimed in  claim 1 , wherein the coating has a photocatalytic activity of less than or equal to 3×10 −3  cm −1  min −1 .  
     
     
         19 . The article as claimed in  claim 1 , wherein the coating has a photocatalytic activity of less than or equal to 2×10 −3  cm −1  min −1 ±2×10 −3  cm −1  min −1 .  
     
     
         20 . The article as claimed in  claim 1 , wherein the article has a visible light reflectance in the range of 15% to 25%.  
     
     
         21 . The article as claimed in  claim 1 , including at least one additional coating located between the photo-induced hydrophilic coating and the substrate.  
     
     
         22 . The article as claimed in  claim 21 , wherein the additional coating is a functional coating selected from the group consisting of a sodium ion diffusion barrier, a solar control coating, and an antireflective coating.  
     
     
         23 . The article as claimed in  claim 1 , wherein the substrate includes a first surface and a second surface, with the coating deposited over at least a portion of the first surface and with the second surface having tin diffused therein.  
     
     
         24 . The article as claimed in  claim 1 , wherein the substrate is a float glass ribbon and the process is selected from chemical vapor deposition and spray pyrolysis.  
     
     
         25 . The article as claimed in  claim 24 , wherein the float glass ribbon is located in a molten metal bath and the process is chemical vapor deposition.  
     
     
         26 . The article as claimed in  claim 1 , wherein the article is a monolithic or laminated window unit having an inner surface and an outer surface with the photo-induced hydrophilic coating deposited on the outer surface.  
     
     
         27 . The article as claimed in  claim 1 , wherein the article is an insulating glass unit having number 1, 2, 3, and 4 surfaces and the photo-induced hydrophilic coating is located on at least one of the number 1 or number 4 surfaces.  
     
     
         28 . The article as claimed in  claim 27 , including a functional coating located on at least one of the number 2, number 3, or number 4 surfaces.  
     
     
         29 . The article as claimed in  claim 1 , wherein the article is an automotive transparency.  
     
     
         30 . The article as claimed in  claim 1 , wherein the article is an architectural window.  
     
     
         31 . The article as claimed in  claim 1 , wherein the article is an automotive transparency having an inner surface and the coating is deposited on the inner surface.  
     
     
         32 . The article as claimed in  claim 1 , wherein the coating comprises titanium dioxide having a thickness in the range of 200 Å to 300 Å, a root mean square smoothness of less than or equal to 1 nm, and a photocatalytic activity of less than or equal to 3×10 −3  cm −1  min −1 .  
     
     
         33 . The article as claimed in  claim 1 , wherein the substrate includes a functional coating deposited over at least a portion of the substrate.  
     
     
         34 . The article as claimed in  claim 33 , wherein the functional coating is a solar control coating.  
     
     
         35 . The article as claimed in  claim 1 , wherein the substrate includes a first surface and a second surface, with the photo-induced hydrophilic coating deposited over at least a portion of the first surface and with a functional coating deposited over at least a portion of the second surface.  
     
     
         36 . An article, comprising: 
 a float glass ribbon having at least one surface; and    a photo-induced hydrophilic coating deposited directly on at least a portion of the at least one surface,    wherein the photo-induced hydrophilic coating is deposited directly on the float glass ribbon in a molten metal bath.    
     
     
         37 . An article, comprising: 
 a substrate having at least one surface; and    a photo-induced hydrophilic coating deposited over at least a portion of the at least one surface,    wherein the photo-induced hydrophilic coating has a photocatalytic activity of less than or equal to 3×10 −3  cm −1  min −1 .    
     
     
         38 . An article, comprising: 
 a substrate having at least one surface;    a photo-induced hydrophilic coating deposited over at least a portion of the at least one surface,    wherein the substrate is a float glass ribbon located in a molten metal bath,    wherein the photo-induced hydrophilic coating has a thickness of 500 Å or less, and    wherein the photo-induced hydrophilic coating is deposited over the at least one surface in a molten metal bath by chemical vapor deposition.    
     
     
         39 . An article, comprising: 
 a substrate having at least one surface; and    a photo-induced hydrophilic coating deposited over at least a portion of the at least one surface,    wherein the photo-induced hydrophilic coating is deposited by chemical vapor deposition at a temperature in the range of 500° C. to 1200° C., and wherein the photo-induced hydrophilic coating has a thickness of 500 Å or less.    
     
     
         40 . A method of forming a photo-induced hydrophilic coating over at least a portion of a substrate, comprising the steps of: 
 providing a substrate having a first surface and a second surface, with at least one of the surfaces having tin diffused therein;    depositing a metal oxide precursor from a coating device onto at least one of the surfaces by a process selected from chemical vapor deposition, spray pyrolysis, and magnetron sputtered vacuum deposition; and    heating the substrate to a temperature sufficient to decompose the metal oxide precursor to form the photo-induced hydrophilic coating having a root mean square roughness of 2 nm or less.    
     
     
         41 . The method as claimed in  claim 40 , wherein the coating device is a chemical vapor deposition coater, and the metal oxide precursor is selected from titanium tetrachloride, titanium tetraisopropoxide, titanium tetraethoxide, titanium tetrabutoxide, and mixtures thereof.  
     
     
         42 . The method as claimed in  claim 40 , wherein the photo-induced hydrophilic coating comprises titanium dioxide.  
     
     
         43 . The method as claimed in  claim 40 , wherein the photo-induced hydrophilic coating has a thickness such that a contact angle of a water droplet on the coated substrate is less than 15° after exposure of the coating to UV radiation of 340 nm at an intensity of 24 W/m 2  for 60 mins.  
     
     
         44 . The method as claimed in  claim 40 , wherein the photo-induced hydrophilic coating has a thickness of less than or equal to 300 Å.  
     
     
         45 . The method as claimed in  claim 40 , wherein the photo-induced hydrophilic hydrophilic coating has a thickness of 50 Å to 250 Å.  
     
     
         46 . The method as claimed in  claim 40 , wherein the coating device is a pyrolytic coater and the method includes directing a suspension of the metal oxide precursor from the pyrolytic coater onto the first surface.  
     
     
         47 . The method as claimed in  claim 40 , wherein the metal oxide precursor is deposited directly onto the surface of the substrate.  
     
     
         48 . The method as claimed in  claim 40 , wherein the coating has a photocatalytic activity of less than or equal to 3×10 −3  cm −1  min −1 .  
     
     
         49 . The method as claimed in  claim 40 , wherein the coating has a thickness in the range of 200 Å to 300 Å, a root mean square roughness of 0.2 nm to 1.5 nm, and a photocatalytic activity of less than or equal to 3×10 −3  cm −1  min −1 .  
     
     
         50 . A method of forming a photo-induced hydrophilic coating over at least a portion of a substrate, comprising the steps of: 
 providing a float glass ribbon in a molten metal bath;    depositing a metal oxide precursor material from a coating device directly onto a top surface of the glass ribbon by chemical vapor deposition; and    heating the glass ribbon to a temperature sufficient to decompose the metal oxide precursor material to form the photo-induced hydrophilic coating.    
     
     
         51 . The method according to claim  50 , including depositing the metal oxide precursor material to provide a photo-induced hydrophilic coating having a thickness of 500 Å or less.  
     
     
         52 . A method of forming a photo-induced hydrophilic coating over at least a portion of a substrate, comprising the steps of: 
 providing a substrate having at least one surface;    depositing a metal oxide precursor material from a CVD coating device over at least a portion of the at least one surface;    heating the substrate to a temperature in the range of 400° C. to 1200° C. to decompose the metal oxide precursor material to form the photo-induced hydrophilic coating; and    providing sufficient precursor material such that the photo-induced hydrophilic coating has a thickness of 500 Å or less.    
     
     
         53 . A product formed by the process of claim  40 .