US2012052271A1PendingUtilityA1

Two-step method for strengthening glass

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Assignee: GOMEZ SINUEPriority: Aug 26, 2010Filed: Aug 17, 2011Published: Mar 1, 2012
Est. expiryAug 26, 2030(~4.1 yrs left)· nominal 20-yr term from priority
Inventors:Sinue GomezLisa Ann LambersonRobert Michael Morena
Y10T428/315Y10T428/2495C03C 21/002C03C 21/00C03C 3/097C03C 3/095C03C 3/091C03C 2204/00C03C 4/18
49
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Claims

Abstract

A method of strengthening an alkali aluminoborosilicate glass. A compressive layer extending from a surface of the glass to a depth of layer is formed by exchanging larger metal cations for smaller metal cations present in the glass. In a second step, metal cations in the glass are exchanged for larger metal cations to a second depth in the glass that is less than the depth of layer and increase the compressive stress of the compressive layer. Formation of the compressive layer and replacement of cations with larger cations can be achieved by a two-step ion exchange process. An alkali aluminoborosilicate glass having a compressive layer and a crack indentation threshold of at least 3000 gf is also provided.

Claims

exact text as granted — not AI-modified
1 . A method of strengthening an alkali aluminoborosilicate glass, the method comprising the steps of:
 a. providing the alkali aluminoborosilicate glass, the glass comprising alkali metal cations;   b. forming a compressive layer extending from a surface of the glass to a depth of layer, wherein the compressive layer is under a compressive stress; and   c. replacing at least a portion of the alkali metal cations in the compressive layer with a larger alkali metal cation to a second depth that is less than the depth of layer, wherein replacing the alkali metal cations in the compressive layer with the larger alkali metal cation increases the compressive stress.   
     
     
         2 . The method of  claim 1 , wherein the step of forming the compressive layer comprises replacing lithium cations with sodium cations to the depth of layer of the glass. 
     
     
         3 . The method of  claim 2 , wherein the step of forming the compressive layer comprises immersing the glass in a first ion exchange bath comprising a sodium salt. 
     
     
         4 . The method of  claim 3 , wherein the first ion exchange bath further comprises a potassium salt. 
     
     
         5 . The method of  claim 1 , wherein the step of replacing the alkali metal cations in the compressive layer with the larger alkali metal cation comprises replacing at least one of sodium cations and lithium cations with potassium cations within the second depth. 
     
     
         6 . The method of  claim 5 , wherein the step of replacing the alkali metal cations in the compressive layer with the larger alkali metal cation comprises immersing the glass in a second ion exchange bath comprising a potassium salt. 
     
     
         7 . The method of  claim 1 , wherein the step of providing the alkali aluminoborosilicate glass comprises providing an alkali aluminoborosilicate glass comprising: 50-70 mol % SiO 2 ; 5-15 mol % Al 2 O 3 ; 5-20 mol % B 2 O 3 ; 2-15 mol % Li 2 O; 0-20 mol % Na 2 O; and 0-10 mol % K 2 O. 
     
     
         8 . The method of  claim 7 , wherein the alkali aluminoborosilicate glass further comprises at least one of: 0-10 mol % P 2 O 5 ; 0-5 mol % MgO; 0-1 mol % CeO 2 ; and 0-1 mol % SnO 2 . 
     
     
         9 . The method of  claim 1 , wherein the step of providing the alkali aluminoborosilicate glass comprises providing an alkali aluminoborosilicate glass having a crack initiation threshold of at least 1000 gf upon indentation with a Vickers indenter. 
     
     
         10 . The method of  claim 1 , wherein, after replacing the alkali metal cations in the compressive layer with the larger alkali metal cation, the surface of the glass has a crack initiation layer threshold of at least 3000 gf upon indentation with a Vickers indenter. 
     
     
         11 . The method of  claim 1 , wherein, after replacing alkali metal cations in the compressive layer with the larger alkali metal cation, the compressive stress is at least 500 MPa and the depth of layer is at least 50 μm. 
     
     
         12 . The method of  claim 1 , wherein the depth of layer is in a range from 70 μm up to 290 μm. 
     
     
         13 . The method of  claim 1 , wherein the second depth is in a range from 5 μm up to 20 μm. 
     
     
         14 . The method of  claim 1 , wherein the step of providing the alkali aluminoborosilicate glass comprises providing an alkali aluminoborosilicate glass sheet having a thickness of less than 2 mm. 
     
     
         15 . A method of strengthening an alkali aluminoborosilicate glass, the method comprising the steps of:
 a. providing the alkali aluminoborosilicate glass, the glass comprising lithium cations and sodium cations;   b. replacing lithium cations with sodium cations to form a compressive layer extending from a surface of the glass to a depth of layer, wherein the compressive layer is under a compressive stress; and   c. replacing sodium cations and lithium cations with potassium cations to a second depth that is less than the depth of layer, and wherein replacing the lithium cations and the sodium cations in the compressive layer with the potassium cations increases the compressive stress.   
     
     
         16 . The method of  claim 15 , wherein the step of replacing the lithium cations with the sodium cations comprises immersing the glass in a first ion exchange bath, the first ion exchange bath comprising a sodium salt. 
     
     
         17 . The method of  claim 16 , wherein the first ion exchange bath further comprises a potassium salt. 
     
     
         18 . The method of  claim 15 , wherein the step of replacing sodium cations and optionally lithium cations with potassium cations comprises immersing the glass in a second ion exchange bath, the second ion exchange bath comprising a potassium salt. 
     
     
         19 . The method of  claim 15 , wherein the step of providing the alkali aluminoborosilicate glass comprises providing an alkali aluminoborosilicate glass comprising: 50-70 mol % SiO 2 ; 5-15 mol % Al 2 O 3 ; 5-20 mol % B 2 O 3 ; 2-15 mol % Li 2 O; 0-20 mol % Na 2 O; and 0-10 mol % K 2 O. 
     
     
         20 . The method of  claim 19 , wherein the alkali aluminoborosilicate glass further comprises at least one of: 0-10 mol % P 2 O 5 ; 0-5 mol % MgO; 0-1 mol % CeO 2 ; and 0-1 mol % SnO 2 . 
     
     
         21 . The method of  claim 15 , wherein the step of providing the alkali aluminoborosilicate glass comprises providing an alkali aluminoborosilicate glass having a crack initiation threshold of at least 1000 gf upon indentation with a Vickers indenter. 
     
     
         22 . The method of  claim 15 , wherein, after replacing sodium cations and optionally lithium cations with potassium cations, the surface of the glass has a crack initiation layer threshold of at least 3000 gf upon indentation with a Vickers indenter. 
     
     
         23 . The method of  claim 15 , wherein, after replacing sodium cations and optionally lithium cations with potassium cations, the compressive stress is at least 500 MPa and the depth of layer is at least 50 μm. 
     
     
         24 . The method of  claim 15 , wherein the depth of layer is in a range from 70 μm up to 290 μm. 
     
     
         25 . The method of  claim 15 , wherein the second depth is in a range from 5 μm up to 20 μm. 
     
     
         26 . The method of  claim 15 , wherein the step of providing the alkali aluminoborosilicate glass comprises providing an alkali aluminoborosilicate glass sheet having a thickness of less than 2 mm. 
     
     
         27 . An alkali aluminoborosilicate glass comprising lithium cations, sodium cations, and potassium cations, wherein the glass has a surface having a compressive layer extending from the surface to a depth of layer and is enriched in potassium cations to a second depth that is less than the depth of layer, and wherein the surface of the glass has a crack initiation layer threshold of at least 3000 gf upon indentation with a Vickers indenter. 
     
     
         28 . The glass of  claim 27 , wherein the surface has a compressive stress of at least 500 MPa, and wherein the depth of layer is at least 50 μm. 
     
     
         29 . The glass of  claim 27 , wherein the depth of layer is in a range from 70 μm up to 290 μm. 
     
     
         30 . The glass of  claim 27 , wherein the second depth is in a range from 5 μm up to 20 μm. 
     
     
         31 . The glass of  claim 27 , wherein the alkali aluminoborosilicate glass comprises: 50-70 mol % SiO 2 ; 5-15 mol % Al 2 O 3 ; 5-20 mol % B 2 O 3 ; 2-15 mol % Li 2 O; 0-20 mol % Na 2 O; and 0-10 mol % K 2 O. 
     
     
         32 . The glass of  claim 31 , wherein the alkali aluminoborosilicate glass further comprises at least one of: 0-10 mol % P 2 O 5 ; 0-5 mol % MgO; 0-1 mol % CeO 2 ; and 0-1 mol % SnO 2 . 
     
     
         33 . The glass of  claim 27 , wherein the glass is a glass sheet having a thickness of up to 2 mm.

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