Ion exchangeable glass with high crack initiation threshold

1. An alkali aluminosilicate glass comprising at least about 4 mol % P 2 O 5 and from 0 mol % to about 4 mol % B 2 O 3 , wherein the alkali aluminosilicate glass is lithium-free and ion exchanged to a depth of layer of at least about 10 μm, and wherein:

i. 1.3<[(P 2 O 5 +R 2 O)/M 2 O 3 ]≦2.3;

where M 2 O 3 =Al 2 O 3 +B 2 O 3 , and R 2 O is the sum of monovalent cation oxides present in the alkali aluminosilicate glass.

2. The alkali aluminosilicate glass of claim 1 , wherein the glass satisfies:

1.5<[(P 2 O 5 +R 2 O)/M 2 O 3 ]≦2.0.

3. The alkali aluminosilicate glass of claim 1 , wherein the glass comprises less than 1 mol % K 2 O.

4. The alkali aluminosilicate glass of claim 1 , wherein the glass comprises less than 1 mol % B 2 O 3 .

5. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass has a potassium/sodium interdiffusion coefficient of at least about 2.4×10 −10 cm 2 /s at 410° C.

6. The alkali aluminosilicate glass of claim 4 , wherein the potassium/sodium interdiffusion coefficient is in a range from about 2.4×10 −10 cm 2 /s up to about 1.5×10 −9 cm 2 /s at 410° C.

7. The alkali aluminosilicate glass of claim 1 , wherein the glass has a compressive layer extending from a surface of the glass to the depth of layer, and wherein the compressive layer is under a compressive stress of at least about 300 MPa.

8. The alkali aluminosilicate glass of claim 1 , wherein the ion exchanged glass has a Vickers indentation crack initiation load of at least about 7 kgf.

9. The alkali aluminosilicate glass of claim 8 , wherein the ion exchanged glass has a Vickers indentation crack initiation load of at least about 12 kgf.

10. The alkali aluminosilicate glass of claim 1 , wherein the monovalent and divalent cation oxides are selected from the group consisting of Na 2 O, K 2 O, Rb 2 O, Cs 2 O, MgO, CaO, SrO, BaO, and ZnO.

11. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprises from about 40 mol % to about 70 mol % SiO 2 ; from about 11 mol % to about 25 mol % Al 2 O 3 ; from about 4 mol % to about 15 mol % P 2 O 5 ; and from about 13 mol % to about 25 mol % Na 2 O.

12. The alkali aluminosilicate glass of claim 11 , wherein the alkali aluminosilicate glass comprises from about 50 mol % to about 65 mol % SiO 2 ; from about 14 mol % to about 20 mol % Al 2 O 3 ; from about 4 mol % to about 10 mol % P 2 O 5 ; and from about 14 mol % to about 20 mol % Na 2 O.

13. The alkali aluminosilicate glass of claim 11 , wherein the alkali aluminosilicate glass wherein the glass comprises less than 1 mol % K 2 O.

14. The alkali aluminosilicate glass of claim 11 , wherein the alkali aluminosilicate glass wherein the glass comprises less than 1 mol % B 2 O 3 .

15. The alkali aluminosilicate glass of claim 11 , wherein the potassium/sodium interdiffusion coefficient is in a range from about 2.4×10 −10 cm 2 /s up to about 1.5×10 −9 cm 2 /s at 410° C.

16. A method of forming an ion-exchanged alkali aluminosilicate glass, the method comprising:

a. providing a non-ion exchanged alkali aluminosilicate precursor glass comprising at least about 4 mol % P 2 O 5 and from 0 mol % to about 4 mol % B 2 O 3 , wherein the precursor glass is lithium-free and wherein 1.3<[P 2 O 5 +R 2 O)/M 2 O 3 ]≦2.3, where M 2 O 3 =Al 2 O 3 +B 2 O 3 , and R 2 O is the sum of monovalent cation oxides present in the precursor glass, and

b. immersing the precursor glass in an ion exchange bath for a time period of up to about 24 hours to form an ion-exchanged alkali aluminosilicate glass having a compressive layer extending from a surface of the ion-exchanged alkali aluminosilicate glass to a depth of layer of at least 10 μm.

17. The method of claim 16 , wherein the precursor glass satisfies,

1.5<[(P 2 O 5 +R 2 O)/M 2 O 3 ]≦2.0.

18. The method of claim 16 , wherein the ion-exchanged alkali aluminosilicate glass comprises less than 1 mol % K 2 O.

19. The method of claim 16 , wherein the ion-exchanged alkali aluminosilicate glass comprises less than 1 mol % B 2 O 3 .

20. The method of claim 16 , wherein the compressive layer is under a compressive stress of at least about 300 MPa.

21. The method of claim 16 , wherein the ion exchanged alkali aluminosilicate glass has a Vickers indentation crack initiation load of at least about 7 kgf.

22. The method of claim 21 , wherein the ion exchanged alkali aluminosilicate glass has a Vickers indentation crack initiation load of at least about 12 kgf.

23. An alkali aluminosilicate glass consisting essentially of from about 40 mol % to about 70 mol % SiO 2 ; from about 11 mol % to about 25 mol % Al 2 O 3 ; from about 4 mol % to about 15 mol % P 2 O 5 ; from about 13 mol % to about 25 mol % Na 2 O; from about 13 to about 30 mol % R x O; from about 11 to about 30 mol % M 2 O 3 ; from 0 mol % to about 1 mol % K 2 O; from 0 mol % to about 4 mol % B 2 O 3 , and 3 mol % or less of one or more of TiO 2 , MnO, Nb 2 O s , MoO 3 , Ta 2 O 5 , WO 3 , ZrO 2 , Y 2 O 3 , La 2 O 3 , HfO 2 , CdO, SnO 2 , Fe 2 O 3 , CeO 2 , As 2 O 3 , Sb 2 O 3 , Cl, and Br; wherein

i. R x O is the sum of the alkali metal oxides, alkaline earth metal oxides, and transition metal monoxides present in the glass,

ii. the glass is lithium-free;

iii. the glass is ion exchanged to a depth of layer of at least about 10 μm, and

iv. 1.3<[(P 2 O 5 +R 2 O)/M 2 O 3 ]≦2.3;

where M 2 O 3 =Al 2 O 3 +B 2 O 3 , and R 2 O is the sum of monovalent cation oxides present in the glass.

24. The alkali aluminosilicate glass of claim 23 , wherein the glass comprises from about 50 mol % to about 65 mol % SiO 2 ; from about 14 mol % to about 20 mol % Al 2 O 3 ; from about 4 mol % to about 10 mol % P 2 O 5 ; and from about 14 mol % to about 20 mol % Na 2 O.

25. The alkali aluminosilicate glass of claim 24 , wherein the glass wherein the glass comprises less than 1 mol % B 2 O 3 .

26. The alkali aluminosilicate glass of claim 23 , wherein the potassium/sodium interdiffusion coefficient is in a range from about 2.4×10 −10 cm 2 /s up to about 1.5×10 −9 cm 2 /s at 410° C.