Coating glass

Abstract

A process for the production of a heat-treatable low emissivity coated glass that comprises the steps of depositing an underlayer onto a glass substrate and subsequently depositing a reflective metal layer by a vacuum deposition process, wherein the underlayer is deposited by a pyrolytic deposition process. Preferably an anti-reflection layer is deposited by a vacuum deposition process on to the coated glass after deposition of the reflective metal layer. The underlayer may comprise a silicon oxide, the reflective metal layer may comprise silver and the anti-reflection layer may comprise a metal oxide, especially tin oxide or zinc oxide. The coated glass preferably has an emissivity of below 0.2 after heat treatment in an oxidizing atmosphere.

1 . A process for the production of a heat-treatable low emissivity coated glass that comprises the steps of: 
 a) depositing an underlayer onto a glass substrate by a pyrolytic deposition process; and    b) subsequently depositing a reflective metal layer by a vacuum deposition method, directly on the underlayer, wherein the underlayer comprises a silicon oxide.    
   
   
       2 . A process according to  claim 1  wherein the pyrolytic deposition of the underlayer comprises contacting the glass substrate with a fluid mixture containing a silicon source, an oxygen source and a carbon source under conditions such that a silicon oxide layer is deposited.  
   
   
       3 . A process according to  claim 2  wherein the fluid mixture is a vapor mixture.  
   
   
       4 . A process according to  claim 1  wherein the underlayer is deposited on the glass substrate when the glass substrate is at a temperature in the range 450° C. to 800° C.  
   
   
       5 . A process according to  claim 1  wherein the underlayer is deposited on to a glass ribbon during the float glass production process at substantially atmospheric pressure.  
   
   
       6 . A process according to  claim 1  wherein the reflective metal layer comprises silver or aluminum.  
   
   
       7 . A process according to  claim 1  wherein an anti-reflection layer is deposited by a vacuum deposition process on to the coated glass after deposition of the reflective metal layer.  
   
   
       8 . A process according to  claim 7  wherein the anti-reflection layer comprises a metal oxide.  
   
   
       9 . A process according to  claim 8  wherein the anti-reflection layer comprises zinc oxide or tin oxide.  
   
   
       10 . A process according to  claim 7  wherein a second reflective metal layer and a second anti-reflection layer are sequentially deposited by a vacuum deposition process after deposition of the first anti-reflection layer.  
   
   
       11 . A process according to  claim 1  additionally comprising a heat treatment step wherein the heat-treatable low emissivity coated glass is subjected to a temperature in the range 400 to 750° C. in an oxidizing atmosphere.  
   
   
       12 . A process according to  claim 11  wherein the visible transmission of the coated glass is increased by the heat-treatment step.  
   
   
       13 . A coated glass produced by a process according to  claim 1 .  
   
   
       14 . A heat-treatable low emissivity coated glass comprising a glass substrate having a multilayer coating on one surface, said multilayer coating comprising a pyrolytically deposited underlayer which comprises a silicon oxide and is deposited directly on the glass, a vacuum deposited reflective metal layer that is deposited directly on the underlayer, and a vacuum deposited anti-reflection layer.  
   
   
       15 . A coated glass according to  claim 14  wherein the underlayer has a refractive index in the range 1.5 to 3 and a thickness in the range 30 to 100 nm.  
   
   
       16 . A coated glass according to  claim 14  wherein the reflective metal layer has a thickness in the range 5 to 30 nm.  
   
   
       17 . A coated glass according to  claim 14  wherein the anti-reflection layer has a thickness in the range 30 nm to 90 nm.  
   
   
       18 . A coated glass according to  claim 14  wherein the coated glass has a normal emissivity of below 0.2.  
   
   
       19 . A heat-treatable low emissivity coated glass comprising a glass substrate having a multilayer coating on one surface, said multilayer coating comprising an oxygen scavenging underlayer comprising a silicon oxide, a vacuum deposited reflective metal layer that is deposited directly on the underlayer, and a vacuum deposited anti-reflection layer.  
   
   
       20 . A multiple glazing unit comprising a first glazing pane of a coated glass according to  claim 19  and a second glazing pane.