Low temperature chemical strengthening process for glass

Abstract

A method of chemically strengthening a glass. The method includes heating an ion exchange solution to a temperature less than about 360° C., and contacting the glass and the strengthening solution at the temperature for a duration from about 0.5 hours to about 24 hours. The ion exchange solution includes a primary nitrate and at least one monovalent or divalent cation nitrate component in an amount from about 1 wt. % to about 10 wt. %.

1 . A method of chemically strengthening a glass, the method comprising:
 heating an ion exchange solution to a temperature less than about 360° C.; and   contacting the glass and the ion exchange solution at the temperature for a duration from about 0.5 hours to about 24 hours,   wherein the ion exchange solution comprises KNO 3  in an amount from about 90 wt. % to about 99 wt. % and at least one monovalent or divalent cation nitrate component selected from the group consisting of Ca(NO 3 ) 2 . Mg(NO 3 ) 2 , and Sr(NO 3 ) 2  in an amount from about 1 wt. % to about 10 wt. %.   
     
     
         2 . The method according to  claim 1 , wherein the ion exchange solution is heated to a temperature from about 310° C. to about 350° C. 
     
     
         3 . (canceled) 
     
     
         4 . The method according to  claim 1 , wherein the at least one monovalent or divalent cation nitrate component is Ca(NO 3 ) 2 . 
     
     
         5 . (canceled) 
     
     
         6 . The method according to  claim 1 , wherein the ion exchange solution comprises the at least one monovalent or divalent cation nitrate component in an amount from about 3 wt. % to about 6 wt. %. 
     
     
         7 . The method according to  claim 1 , wherein the duration is from about 1 hour to about 4 hours. 
     
     
         8 . The method according to  claim 1 , wherein the duration is greater than about 8 hours. 
     
     
         9 . The method according to  claim 1 , wherein contacting the glass and the ion exchange solution forms a compressive stress layer on a surface of the glass, and
 the compressive stress layer has a surface compressive stress greater than about 850 MPa.   
     
     
         10 . The method according to  claim 9 , wherein the compressive stress layer has a compressive stress from about 850 MPa to about 1200 MPa. 
     
     
         11 . The method according to  claim 9 , wherein a depth of the compressive stress layer is greater than about 40 μm. 
     
     
         12 . The method according to  claim 1 , wherein the glass is a glass sheet having a thickness less than about 1 mm. 
     
     
         13 . The method according to  claim 12 , wherein contacting the glass and the ion exchange solution forms a compressive stress layer on a surface of the glass, and the compressive stress layer has a surface compressive stress from about 250 MPa to about 850 MPa. 
     
     
         14 . The method according to  claim 13 , wherein a depth of the compressive stress layer is less than about 30 μm. 
     
     
         15 - 25 . (canceled) 
     
     
         16 . The method according to  claim 1 , wherein the ion exchange solution comprises the at least one monovalent or divalent cation nitrate component in an amount from about 1 wt. % to 4 wt. %. 
     
     
         17 . The method according to  claim 1 , wherein prior to the contacting the glass comprises a compressive stress layer on the surface of the glass.