Low-maintenance coatings

Abstract

The invention provides a substrate bearing a low-maintenance coating. The coating includes at least two films: a base film optionally comprising silica (e.g., silicon dioxide) and a film comprising titania (e.g., titanium dioxide). The invention also provides methods of depositing such coatings.

What is claimed is: 
     
       1. A low-maintenance coating on a substrate, the coating comprising a base film positioned directly over a first major surface of the substrate and a film comprising titania positioned directly over the base film, wherein the base film has a thickness of less than about 100 angstroms, and wherein the film comprising titania has a thickness of less than 50 angstroms. 
     
     
       2. The low-maintenance coating of  claim 1  wherein the film comprising titania includes titanium dioxide or substoichiometric titanium oxide. 
     
     
       3. The low-maintenance coating of  claim 1  wherein the base film comprises silica. 
     
     
       4. The low-maintenance coating of  claim 3  wherein the base film consists essentially of silicon dioxide. 
     
     
       5. The low-maintenance coating of  claim 1  wherein the film comprising titania has a thickness of less than 35 angstroms. 
     
     
       6. The low-maintenance coating of  claim 1  wherein the film comprising titania has a thickness of between about 5 angstroms and about 30 angstroms. 
     
     
       7. The low-maintenance coating of  claim 1  wherein the substrate 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 base film and film comprising titania are both sputtered films. 
     
     
       9. A low-maintenance coating on a glass sheet, the coating comprising a base film positioned over a first major surface of the glass sheet and a film comprising titania positioned directly over the base film, wherein the base film comprises silica and has a thickness of less than 100 angstroms, and wherein the film comprising titania has a thickness of less than 100 angstroms. 
     
     
       10. The low-maintenance coating of  claim 9  wherein the film comprising titania comprises titanium dioxide or substoichiometric titanium oxide. 
     
     
       11. The low-maintenance coating of  claim 9  wherein the base film consists essentially of silicon dioxide. 
     
     
       12. The low-maintenance coating of  claim 9  wherein the film comprising titania has a thickness of less than 50 angstroms 
     
     
       13. The low-maintenance coating of  claim 9  wherein the film comprising titania has a thickness of less than 35 angstroms. 
     
     
       14. The low-maintenance coating of  claim 9  wherein the film comprising titania has a thickness of between about 5 angstroms and about 30 angstroms. 
     
     
       15. The low-maintenance coating of  claim 9  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. 
     
     
       16. The low-maintenance coating of  claim 9  wherein the silica base film and film comprising titania are both sputtered films. 
     
     
       17. An insulating glass unit comprising two spaced-apart panes bounding a between-pane space, wherein at least one of the panes has a desired major surface bearing a low-maintenance coating, wherein said desired major surface is an exterior surface of the unit and faces away from the between-pane space, the coating comprising a base film positioned directly over said desired major surface and a film comprising titania positioned directly over the base film, wherein the base film comprises silica has a thickness of less than 100 angstroms and the film comprising titania has a thickness of less than 50 angstroms. 
     
     
       18. The low-maintenance coating of claim 3 wherein the base film further comprises an oxidized electrically conductive material. 
     
     
       19. The low-maintenance coating of claim 18 wherein the electrically conductive material is aluminum. 
     
     
       20. The low-maintenance coating of claim 1 wherein the film comprising titania further comprises a material selected from the group consisting of oxides of iron, silver, copper, tungsten, aluminum, zinc, strontium, palladium, gold, platinum, nickel, and cobalt. 
     
     
       21. The low-maintenance coating of claim 1 wherein the film comprising titania is an outermost film of the coating. 
     
     
       22. The low-maintenance coating of claim 9 wherein the film comprising titania is an outermost film of the coating. 
     
     
       23. The low-maintenance coating of claim 17 wherein the film comprising titania is an outermost film of the coating. 
     
     
       24. A low-maintenance coating on a glass sheet, the coating comprising a base film extending directly from a first major surface of the glass sheet to a thickness of less than about 100 angstroms, and a film comprising titania extending directly from a surface of the base film to a thickness of less than 50 angstroms. 
     
     
       25. The low-maintenance coating of claim 24 wherein the film comprising titania includes titanium dioxide or substoichiometric titanium oxide. 
     
     
       26. The low-maintenance coating of claim 24 wherein the base film comprises silica. 
     
     
       27. The low-maintenance coating of claim 26 wherein the base film consists essentially of silicon dioxide. 
     
     
       28. The low-maintenance coating of claim 24 wherein the film comprising titania has a thickness of less than 35 angstroms. 
     
     
       29. The low-maintenance coating of claim 24 wherein the film comprising titania has a thickness of between about 5 angstroms and about 30 angstroms. 
     
     
       30. The low-maintenance coating of claim 24 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. 
     
     
       31. The low-maintenance coating of claim 24 wherein the base film and film comprising titania are both sputtered films. 
     
     
       32. A low-maintenance coating on a glass sheet, the coating comprising a base film deposited directly over a first major surface of the glass sheet and having a thickness of less than 100 angstroms but greater than about 30 angstroms, and a film comprising titania deposited directly over the base film and having a thickness of less 100 angstroms but greater than about 30 angstroms. 
     
     
       33. The low-maintenance coating of claim 32 wherein the base film comprises silica that includes an electrically conductive material present in an oxidized form. 
     
     
       34. The low-maintenance coating of claim 33 wherein the base film consists essentially of silicon dioxide. 
     
     
       35. The low-maintenance coating of claim 32 wherein the base film is a silica film containing aluminum oxide. 
     
     
       36. The low-maintenance coating of claim 32 wherein the film comprising titania includes titanium dioxide or substoichiometric titanium oxide. 
     
     
       37. The low-maintenance coating of claim 32 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. 
     
     
       38. The low-maintenance coating of claim 32 wherein the base film and film comprising titania are both sputtered films. 
     
     
       39. The low-maintenance coating of claim 32 wherein the glass sheet is soda-lime glass. 
     
     
       40. The low-maintenance coating of claim 32 wherein the glass sheet is part of an insulating glass unit.