Composition for preparing water-repellent coatings on optical substrates

Abstract

Composition for preparing water-repellent coatings on optical substrates, comprising a porous, electrically conductive molding and an organosilicon compound, obtainable by mixing an electrically conductive or semiconductive support material with a binder and subjecting the mixture to compression molding to form a compression molding, sintering the compression molding at preferably 1100 to 1500° C. in air to form a porous molding, impregnating the molding with the organosilicon compound, and ageing the impregnated molding by storage in air for at least 3 days.

We claim:  
     
         1 . A composition for preparing a water-repellant coating on an optical substrate, comprising a porous, electrically conductive molding and an organosilicon compound, wherein said composition is obtained by 
 a) mixing an electrically conductive or semiconductive support material with a binder and subjecting the resulting mixture to compression to form a compression molding,    b) sintering said compression molding at 1100 to 1500° C. in air to form a porous molding,    c) impregnating said porous molding with said organosilicon compound, and    d) ageing said impregnated molding.    
     
     
         2 . A composition for preparing a water-repellant coating on an optical substrate, wherein said composition comprises: 
 a porous, electrically conductive molding and an organosilicon compound,    wherein said composition is obtained by ageing a sintered compression molding which is impregnated with an organosilicon compound,    and wherein said electrically conductive molding comprises carbon;    a conductive metal oxide, carbide, nitride or silicide; a metal powder and a non-conductive material; or a mixture thereof.    
     
     
         3 . The composition of    claim 2   , wherein said ageing is performed for a time sufficient to cleave said organosilicon compound.  
     
     
         4 . A composition for preparing a water-repellant coating on an optical substrate, comprising an organosilicon compound and a porous, electrically conductive molding, wherein said electrically conductive molding comprises 
 a) an electrically conductive metal oxide, carbide, nitride or silicide,    b) carbon,    c) a metal powder and a non-conductive material, or    d) a mixture thereof.    
     
     
         5 . The composition according to    claim 2   , wherein said organosilicon compound is of formula I  
       C n F 2n+1 —(CH 2 ) m —Si(R 1 R 2 R 3 )  (I)  wherein    R 1  is an alkoxy of 1 to 3 a carbon atoms or C n F 2n+1 —(CH 2 ) m —Si(R 2 R 3 )—O—,    R 2  and R 3  are each independently alkyl or alkoxy of 1 to 3 carbon atoms,    n is 1 to 12 and    m is 1 to 6.    
     
     
         6 . The composition according to    claim 2   , wherein said conductive metal oxide is indium oxide or tin dioxide which is optionally doped with antimony, fluorine, phosphorus, niobium or tantalum.  
     
     
         7 . The composition according to    claim 2   , wherein said metal carbide is titanium carbide, chromium carbide or tungsten carbide.  
     
     
         8 . The composition according to    claim 2   , wherein said metal nitride is chromium nitride or tungsten nitride.  
     
     
         9 . The composition according to    claim 2   , wherein said metal silicide is molybdenum silicide, titanium silicide, or chromium silicide.  
     
     
         10 . The composition according to    claim 2   , wherein said metal powder is titanium, zirconium, silicon, chromium, nickel or iron.  
     
     
         11 . The composition according to    claim 2   , wherein said non-conductive material is silicon oxide, aluminum oxide, zirconium oxide, aluminum silicate or a mixture thereof.  
     
     
         12 . The composition according to    claim 2   , wherein said organosilicon is triethoxy (3,3,4,4,5,5,6,6,7,7,7-undecafluoroheptyl)silane.  
     
     
         13 . The composition according to    claim 2   , wherein said organosilicon is triethoxy (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane.  
     
     
         14 . The composition according to    claim 2   , wherein said organosilicon is triethoxy (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)silane.  
     
     
         15 . The composition according to    claim 2   , wherein said organosilicon is diethoxymethyl (3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)silane.  
     
     
         16 . The composition according to    claim 2   , wherein said organosilicon is bis[ethoxymethyl(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl) silyl ether.  
     
     
         17 . The composition according to    claim 2   , wherein said electrically conductive molding comprises 50 to 90% by weight of an electrically non-conductive material and 10 to 50% by weight of a metal powder.  
     
     
         18 . The composition according to    claim 2   , wherein said electrically conductive molding comprises 40 to 60% by weight of aluminum silicate and 20 to 60% by weight of silicon powder.  
     
     
         19 . A method of making a composition for preparing a water-repellant coating on an optical substrate, comprising 
 a) mixing an electrically conductive or semiconductive support material with a binder and subjecting the resulting mixture to compression to form a compression molding,    b) sintering said compression molding at 1100 to 1500° C. in air to form a porous molding,    c) impregnating said molding with said organosilicon compound, and    d) ageing the impregnated molding.    
     
     
         20 . A method of making a composition for preparing a water-repellant coating on an optical substrate, comprising ageing a sintered compression molding of carbon, or a conductive metal oxide, carbide, nitride or silicide, or a metal powder and a non-conductive material, or a mixture thereof, which is impregnated with an organosilicon compound.  
     
     
         21 . The method according to    claim 19   , wherein said binder is polyvinyl alcohol, glycerol, methylcellulose, dextrin or a wax, and the concentration of said binder in said compression molding is 1-20% by weight.  
     
     
         22 . The method according to    claim 20   , wherein said compression molding is in the form of a tablet which has a diameter of 10-15 mm and a height of 5-10 mm, or in the form of a granule which has a particle size of 1-4 mm, and/or wherein said porous molding has a porosity of 40-60%.  
     
     
         23 . The method according to    claim 19   , further comprising heating said compression molding in air at 400-600° C. before sintering it at 1100-1500° C.  
     
     
         24 . A method for coating an optical substrate with a water-repellant coating, comprising subjecting a composition of    claim 2    to a vacuum 10 −5 -10 −3  mbar and a temperature of 300-500° C., thereby vaporizing said organosilicon compound from such composition, and depositing said vaporized organosilicon compound on said substrate by vapor deposition.  
     
     
         25 . The composition according to    claim 4   , wherein said organosilicon compound is of formula I  
       C n F 2n+1 —(CH 2 ) m —Si(R 1 R 2 R 3 )  (I)  wherein    R 1  is an alkoxy of 1 to 3 a carbon atoms or C n F 2n+1 —(CH 2 ) m —Si(R 2 R 3 )—O—,    R 2  and R 3  are each independently alkyl or alkoxy of 1 to 3 carbon atoms,    n is 1 to 12 and    m is 1 to 6.    
     
     
         26 . The composition according to    claim 4   , wherein said metal powder is titanium, zirconium, silicon, chromium, nickel or iron.  
     
     
         27 . The composition according to    claim 4   , wherein said non-conductive material is silicon oxide, aluminum oxide, zirconium oxide, aluminum silicate or a mixture thereof.  
     
     
         28 . The composition according to    claim 5   , wherein said electrically conductive molding comprises 50 to 90% by weight of an electrically non-conductive material and 10 to 50% by weight of a metal powder.  
     
     
         29 . The composition according to    claim 4   , wherein said electrically conductive molding comprises 40 to 60% by weight of aluminum silicate and 20 to 60% by weight of silicon powder.  
     
     
         30 . The composition according to    claim 1   , wherein said electrically conductive molding comprises an electrically conductive material with the exception of a metal, or a mixture of an electrically conductive material and an electrically non-conductive material.