Ion exchangeable glass with high crack initiation threshold
Alkali aluminosilicate glasses that are resistant to damage due to sharp impact and capable of fast ion exchange are provided. The glasses comprise at least 4 mol % P 2 O 5 and, when ion exchanged, have a Vickers indentation crack initiation load of at least about 7 kgf.
1. An alkali aluminosilicate glass comprising:
from 40 mol % to 70 mol % SiO 2 ;
from 11 mol % to 25 mol % Al 2 O 3 ;
from 4 mol % to 15 mol % P 2 O 5 ;
from 13 mol % to 20 mol % Na 2 O;
Li 2 O; and
less than or equal to 4 mol % B 2 O 3 ,
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 a sum of monovalent cation oxides present in the alkali aluminosilicate glass.
2. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprises from 55 mol % to 65 mol % SiO 2 .
3. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprises from 14 mol % to 20 mol % Al 2 O 3 .
4. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprises from 5 mol % to 15 mol % P 2 O 5 .
5. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprises less than 1 mol % K 2 O.
6. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass is free of K 2 O.
7. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass comprise less than 1 mol % B 2 O 3 .
8. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass is free of B 2 O 3 .
9. The alkali aluminosilicate glass of claim 1 , wherein 1.5<[(P 2 O 5 +R 2 O)/M 2 O 3 ]≤2.0.
10. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass has a potassium/sodium interdiffusion coefficient of at least 2.4×10 −10 cm 2 /s at 410° C.
11. The alkali aluminosilicate glass of claim 10 , wherein the potassium/sodium interdiffusion coefficient is in a range from 2.4×10 −10 cm 2 /s up to 1.5×10 −9 cm 2 /s at 410° C.
12. The alkali aluminosilicate glass of claim 1 , wherein the alkali aluminosilicate glass is ion exchanged to a depth of layer of at least 10 μm.
13. The alkali aluminosilicate glass of claim 12 , wherein the depth of layer is at least 30 μm.
14. The alkali aluminosilicate glass of claim 12 , wherein the alkali aluminosilicate glass has a compressive layer extending from a surface of the alkali aluminosilicate glass to the depth of layer, and wherein the compressive layer is under a compressive stress of at least 300 MPa.
15. The alkali aluminosilicate glass of claim 14 , wherein the compressive stress is at least 500 MPa.
16. The alkali aluminosilicate glass of claim 12 , wherein the alkali aluminosilicate glass has a Vickers indentation crack initiation load of at least 7 kgf.
17. The alkali aluminosilicate glass of claim 16 , wherein the Vickers indentation crack initiation load is at least 12 kgf.
18. A method of forming an ion-exchanged alkali aluminosilicate glass, the method comprising:
a. providing a non-ion exchanged alkali aluminosilicate precursor glass comprising:
from 40 mol % to 70 mol % SiO 2 ;
from 11 mol % to 25 mol % Al 2 O 3 ;
from 4 mol % to 15 mol % P 2 O 5 ;
from 13 mol % to 20 mol % Na 2 O;
Li 2 O; and
less than or equal to 4 mol % B 2 O 3 ,
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 a sum of monovalent cation oxides present in the non-ion exchanged alkali aluminosilicate precursor glass; and
b. immersing the non-ion exchanged alkali aluminosilicate precursor glass in an ion exchange bath for a time period of up to 24 hours to form a compressive layer extending from a surface of the ion-exchanged alkali aluminosilicate glass to a depth of layer of at least 10 μm.
19. The method of claim 18 , wherein the non-ion exchanged alkali aluminosilicate precursor glass comprises:
from 55 mol % to 65 mol % SiO 2 ; and
from 5 mol % to 15 mol % P 2 O 5 .
20. The method of claim 18 , wherein the compressive layer is under a compressive stress of at least 300 MPa, and the ion-exchanged alkali aluminosilicate glass has a Vickers indentation crack initiation load of at least 7 kgf.