Aluminosilicate glasses for ion exchange
Glass compositions that may be used to produce chemically strengthened glass sheets by ion exchange. The glass compositions are chosen to promote simultaneously high compressive stress and deep depth of layer or, alternatively, to reduce the time needed to ion exchange the glass to produce a predetermined compressive stress and depth of layer.
1. An alkali aluminosilicate glass, the alkali aluminosilicate glass having a liquidus viscosity in a range from at least 20 kiloPoise to 64 kiloPoise and comprising at least 59 mol % to about 76 mol % SiO 2 ; from 16 mol % to about 20 mol % Al 2 O 3 , 0 mol % B 2 O 3 , from 0 mol % to about 20 mol % Li 2 O; from 12.3 mol % to about 20 mol % Na 2 O; from 0 mol % to about 8 mol % K 2 O; from 0 mol % to about 10 mol % MgO; and from 0 mol % to about 10 mol % ZnO, wherein Al 2 O 3 (mol %)−Na 2 O (mol %)≧−4 mol %, wherein Al 2 O 3 is present in a tetrahedral configuration, and wherein the alkali aluminosilicate glass, when ion exchanged, has a compressive layer extending from a surface of the alkali aluminosilicate glass into the alkali aluminosilicate glass to a depth of layer, wherein the compressive layer is under a compressive stress of at least 1.1 GPa.
2. The alkali aluminosilicate glass of claim 1 , wherein 12.3 mol %≦Li 2 O+Na 2 O+K 2 O≦20 mol %.
3. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprises at least one of MgO, CaO, SrO, BaO, and ZnO.
4. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass is free of divalent metal oxides.
5. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass is ion exchanged and has a compressive layer extending from a surface of the alkali aluminosilicate glass into the alkali aluminosilicate glass to a depth of layer.
6. The alkali aluminosilicate glass of claim 5 , wherein the compressive layer is under a compressive stress of at least 1.1 GPa.
7. The alkali aluminosilicate glass of claim 5 , wherein the alkali aluminosilicate glass has a nanohardness of at least 7 GPa.
8. The alkali aluminosilicate glass of claim 1 , further comprising at least one fining agent.
9. The alkali aluminosilicate glass of claim 8 , wherein the fining agent comprises at least one of SnO 2 , As 2 O 3 , and Sb 2 O 3 .
10. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass is free of divalent metal oxides other than MgO and ZnO.
11. An alkali aluminosilicate glass, the alkali aluminosilicate glass being free of TiO 2 and comprising at least 59 mol % to about 76 mol % SiO 2 ; from 16 mol % to about 20 mol % Al 2 O 3 ; 0 mol % B 2 O 3 ; from 0 mol % to about 20 mol % Li 2 O; from 12.3 mol % to about 20 mol % Na 2 O; from 0 mol % to about 8 mol % K 2 O; from 0 mol % to about 10 mol % MgO; and from 0 mol % to about 10 mol % ZnO, wherein Al 2 O 3 (mol %)−Na 2 O (mol %)≧−4 mol %, wherein the alkali aluminosilicate glass has a liquidus viscosity in a range from at least 20 kiloPoise to 64 kiloPoise, and wherein the alkali aluminosilicate glass is ion exchanged and has a compressive layer extending from a surface of the alkali aluminosilicate glass into the alkali aluminosilicate glass to a depth of layer, the compressive layer being under a compressive stress of at least 1.1 GPa.
12. The alkali aluminosilicate glass of claim 11 , wherein 12.3 mol %≦Li 2 O+Na 2 O+K 2 O≦20 mol %.
13. The alkali aluminosilicate glass of claim 11 , wherein the alkali aluminosilicate glass comprises at least one of MgO, CaO, SrO, BaO, and ZnO.
14. The alkali aluminosilicate glass of claim 11 , wherein the alkali aluminosilicate glass is free of divalent metal oxides.
15. The alkali aluminosilicate glass of claim 11 , wherein the alkali aluminosilicate glass is free of divalent metal oxides other than MgO and ZnO.