Coated substrates having undercoating layers that exhibit improved photocatalytic activity

Abstract

A coated substrate is disclosed. The coated substrate includes a substrate; an undercoating layer comprising at least one layer selected from a mixture of silica and zirconia; a mixture of silica and alumina; or a mixture of silica, alumina and titania overlaying at least a portion of the substrate; and a functional coating overlaying at least a portion of the undercoating. The coated substrates of the invention exhibit improved properties such as increased durability, photocatalytic activity, etc. as a result of the undercoating layer.

1 . A method of coating a substrate, comprising the steps of:
 providing at least one undercoating layer consisting essentially of a mixture of silica and alumina or a mixture of silica and zirconia over at least a portion of a substrate, wherein the undercoating layer is selected from the group consisting of:
 (a) a mixture of silica and alumina having a molar ratio of about 4 moles of silica to about 1 mole of alumina; and 
 (b) a mixture of silica and zirconia having a molar ratio of about 8 to about 20 moles of silica to about 1 mole of zirconia; and 
   providing a photocatalytic functional coating over at least a portion of the undercoating layer, wherein the photocatalytic functional coating comprises Mania, and wherein the coated substrate with the undercoating layer has a higher photocatalytic activity than without the undercoating layer.   
     
     
         2 . The method of  claim 1 , wherein the undercoating layer has a thickness ranging from 1 nm to 300 nm. 
     
     
         3 . The method of  claim 1 , wherein the undercoating layer consists essentially of the mixture of silica and alumina. 
     
     
         4 . The method of  claim 1 , wherein the substrate is a glass ribbon. 
     
     
         5 . The method of  claim 1 , wherein the coated substrate exhibits the following reflected color coordinates according to the CIE 1967 as measured from the coated side: a* ranging from −20 to 20; b* ranging from −20 to 20; and L* ranging from 40 to 60. 
     
     
         6 . The method of  claim 1 , wherein the undercoating layer has a thickness of about 20 nm to about 73 nm. 
     
     
         7 . The method of  claim 1 , wherein the undercoating layer has a thickness of about 104 nm to about 337 nm. 
     
     
         8 . The method of  claim 1 , wherein the undercoating layer consists essentially of the mixture of silica and zirconia. 
     
     
         9 . A method of coating a substrate, comprising the steps of:
 providing a first undercoating layer over at least a portion of a substrate, the first undercoating layer comprising a first mixture of about 54.8 to about 70.6 volume % of silica and about 29.4 to about 45.2 volume % of zirconia;   providing a second undercoating layer over at least a portion of the first undercoating layer, the second undercoating layer comprising a second mixture of about 10.3 to about 20.0 volume % of silica and about 80.0 to about 89.7 volume % of zirconia; and   providing a photocatalytic functional coating over at least a portion of the undercoating layer, wherein the photocatalytic functional coating comprises titania.   
     
     
         10 . The method of  claim 9 , wherein the first undercoating layer has a thickness of about 23.76 nm to about 36.93 nm. 
     
     
         11 . The method of  claim 9 , wherein the second undercoating layer has a thickness of about 40.29 nm to about 56.61 nm. 
     
     
         12 . The method of  claim 9 , wherein the photocatalytic functional coating has a thickness of about 76 nm to about 118 nm, 
     
     
         13 . The method of  claim 9 , wherein the substrate is a glass ribbon. 
     
     
         14 . The method of  claim 9 , wherein the coated substrate exhibits the following reflected color coordinates according to the CIE 1967 as measured from the coated side: a* ranging from −20 to 20; b* ranging from −20 to 20; and L* ranging from 40 to 60.