Low-maintenance coatings

Abstract

The invention provides a substrate bearing a low-maintenance coating. The coating includes two films: a first film comprising silica (e.g., silicon dioxide) and a second film comprising titania (e.g., titanium dioxide). Preferably, both films are provided within particular thickness ranges. The invention also provides methods of depositing such coatings.

1. A low-maintenance coating on a glass sheet, the coating comprising a first base film positioned directly over a first major surface of the glass sheet and a second photocatalytic film positioned directly over the first base film, wherein the first base film includes a base film and has a thickness of less than about 100 angstroms, and wherein the second film includes a photocatalytic film and has a thickness of less than about 100 angstroms. 
     
     
       2. The low-maintenance coating of  claim 1  wherein the base film is silica. 
     
     
       3. The low-maintenance coating of  claim 2  wherein the coated first major surface is in periodic contact with rain. 
     
     
       4. The low-maintenance coating of  claim 1  wherein the photocatalytic film is titania. 
     
     
       5. The low-maintenance coating of  claim 1  wherein the thickness of the first base film is between about 70 angstroms and about 100 angstroms. 
     
     
       6. The low-maintenance coating of  claim 1  wherein the thickness of the second photocatalytic film is between about 30 angstroms and about 120 100 angstroms. 
     
     
       7. The low-maintenance coating of  claim 1  wherein the glass sheet is a window pane mounted in a window frame, and wherein the coated first major surface is exposed to an outdoor environment. 
     
     
       8. The low-maintenance coating of  claim 1  wherein the first base film consists essentially of silica and the second photocatalytic film consists essentially of titania. 
     
     
       9. The low-maintenance coating of  claim 8  wherein the silica is silicon dioxide, and the titania is titanium dioxide or substoichiometric titanium oxide. 
     
     
       10. The low-maintenance coating of  claim 1  wherein the first base and second photocatalytic films are both sputtered films. 
     
     
       11. A low-maintenance coating on a glass sheet, the coating comprising a first film positioned directly over a first major surface of the glass sheet and a second film positioned directly over the first film, wherein the first film consists essentially of silica and has a thickness of between about 30 angstroms and about 100 angstroms, and wherein the second film consists essentially of titania and has a thickness of less than 100 angstroms but greater than about 30 angstroms. 
     
     
       12. The low-maintenance coating of  claim 11  wherein the second film has a thickness of less than about 80 angstroms. 
     
     
       13. The low-maintenance coating of claim 11 wherein the silica of the first film contains aluminum oxide. 
     
     
       14. The low-maintenance coating of claim 11 wherein the silica of the first film includes an electrically conductive material present in oxidized form. 
     
     
       15. The low-maintenance coating of claim 14 wherein the second film is an outermost film of the coating. 
     
     
       16. The low-maintenance coating of claim 2 wherein the base film further comprises an oxidized electrically conductive material. 
     
     
       17. The low-maintenance coating of claim 16 wherein the electrically conductive material is aluminum. 
     
     
       18. The low-maintenance coating of claim 8 wherein the base film has a thickness of between about 70 angstroms and about 100 angstroms, and the photocatalytic film has a thickness of between about 30 angstroms and about 100 angstroms. 
     
     
       19. A low-maintenance coating on a substrate, the coating comprising a base film extending directly from a first major surface of the substrate to a thickness of less than about 100 angstroms, and a photocatalytic film extending directly from a surface of the base film to a thickness of less than about 100 angstroms. 
     
     
       20. The low-maintenance coating of claim 19 wherein the base film consists essentially of silica and the photocatalytic film consists essentially of titania. 
     
     
       21. The low-maintenance coating of claim 19 wherein the base and photocatalytic films are both sputtered films. 
     
     
       22. The low-maintenance coating of claim 19 wherein the base film extends directly from the first major surface of the substrate to a thickness of between about 70 angstroms and about 100 angstroms, and the photocatalytic film extends directly from the surface of the base film to a thickness of between about 30 angstroms and about 100 angstroms.