ION EXCHANGEABLE GLASS WITH ADVANTAGED STRESS PROFILE

• US 20140227524A1
• Filed: 02/06/2014
• Published: 08/14/2014
• Est. Priority Date: 02/08/2013
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Ellison, Adam James, Hanson, Benjamin Zain, Roussev, Rostislav Vatchev
• Granted Patent: US 9,714,192 B2
• Time in Patent Office: Days
• US Class Current: 428/410
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 3/091 containing aluminium
• CPC Class Codes: Y10T 428/315 Surface modified glass [e.g., tempered, strengthened, etc.]

Abstract

Ion exchangeable glass compositions that develop concentration profiles and stress profiles that have higher magnitudes of concentration and compressive stress profiles than those provided by the error function (erfc)-shaped compressive stress profile for similar surface concentrations of stress-inducing components such as K⁺ or K₂O and stresses. The advantaged stress profile is the result of a glass composition that is low in K₂O (or potassium) in the base glass prior to ion exchange. A glass comprising lower amounts of K⁺ or K₂O has a stronger dependence of diffusivity on concentration, leading to a non-erfc-shaped concentration profile. Several glass compositions that contain low amounts of K⁺ or K₂O exhibit this beneficial effect, whereas other glasses containing higher amounts of K⁺ or K₂O do not exhibit this effect.

Claims

1. An alkali aluminosilicate glass having a layer under a compressive stress CS(d) that varies as a function of depth d from the surface to a depth of layer DOL, wherein CS(d)>

CS_erfc(d) at 0<

d≦

DOL, where CS_erfc(d) is a compressive stress at depth d determined from an error function erfc.

2. The alkali aluminosilicate glass of claim 1, wherein the glass comprises from 0 mol % to about 2.5 mol % K₂O.

3. The alkali aluminosilicate glass of claim 2, wherein the glass comprises from 0 mol % to about 1 mol % K₂O.

4. The alkali aluminosilicate glass of claim 1, wherein the glass comprises alkali metal oxides, and wherein K₂O comprises less than about 7% of the total alkali metal oxide concentration.

5. The alkali aluminosilicate glass of claim 1, wherein the glass comprises alkali metal oxides, and wherein K₂O comprises less than about 3% of the total alkali metal oxide concentration.

6. The alkali aluminosilicate glass of claim 1, wherein the glass comprises at least about 50 mol % SiO₂;

at least about 10 mol % R₂O, wherein R₂O comprises Na₂O;

Al₂O₃; and

B₂O₃, and wherein B₂O₃—

(R₂O—

Al₂O₃)≧

3 mol %.

7. The alkali aluminosilicate glass of claim 6, wherein the glass has a Vickers crack initiation threshold of at least about 10 kgf.

8. The alkali aluminosilicate glass of claim 6, wherein the glass comprises:

at least about 50 mol % SiO₂, from about 9 mol % to about 22 mol % Al₂O₃;

from about 3 mol % to about 10 mol % B₂O₃;

from about 9 mol % to about 20 mol % Na₂O;

from 0 mol % to about 5 mol % K₂O;

at least about 0.1 mol % MgO, ZnO, or combinations thereof, wherein 0≦

MgO≦

6 and 0≦

ZnO≦

6 mol %; and

, optionally, at least one of CaO, BaO, and SrO, wherein 0 mol %≦

CaO+SrO+BaO≦

2 mol %.

9. The alkali aluminosilicate glass of claim 1, wherein the compressive stress CS(0) at d=0 is at least about 900 MPa and the depth of layer DOL is at least about 30 μ

m, and wherein the glass article comprises at least about 50 mol % SiO₂ and at least about 11 mol % Na₂O.

10. The alkali aluminosilicate glass of claim 9, wherein the glass further comprises Al₂O₃ and at least one of B₂O₃, K₂O, MgO and ZnO, and wherein −

340+27.1.Al₂O₃−

28.7.B₂O₃+15.6.Na₂O−

61.4.K₂O+8.1.(MgO+ZnO)≧

0 mol %.

11. The alkali aluminosilicate glass of claim 9, wherein the glass comprises:

from about 7 mol % to about 26 mol % Al₂O₃;

from 0 mol % to about 9 mol % B₂O₃;

from about 11 mol % to about 25 mol % Na₂O;

from 0 mol % to about 2.5 mol % K₂O;

from 0 mol % to about 8.5 mol % MgO; and

from 0 mol % to about 1.5 mol % CaO.

12. The alkali aluminosilicate glass of claim 1, wherein 0.4·

DOL≦

d≦

0.6·

DOL.

13. The alkali aluminosilicate glass of claim 1, wherein the alkali aluminosilicate glass comprises at least 14 mol % Na₂O.

14. The alkali aluminosilicate glass of claim 13, wherein Na₂O+K₂O=15 mol %.

15. An ion exchanged glass comprising a first alkali metal cation and a second alkali metal cation, wherein the first alkali metal cation is larger than the second alkali metal cation, and wherein the compressive stress σ

(d) at a depth d is given by the equation σ

(d)=(BE/1-v)(C_avg−

C(d), where B is the lattice dilation coefficient, E is Young'"'"'s modulus, v is the Poisson ratio, C(d) is the concentration of the larger ion, and C_avg is the average concentration.

16. The ion exchanged glass of claim 15, wherein the ion exchanged glass has a layer under a compressive stress, the layer extending from a surface of the ion exchanged glass to a depth of layer DOL, and wherein 0.4·

DOL≦

d≦

0.6·

DOL.

17. The ion exchanged glass of claim 15, wherein CS(d)>

CS_erfc(d) at 0<

d≦

DOL, where CS_erfc(d) is a compressive stress at depth d determined from an error function erfc.

18. The ion exchanged glass of claim 15, wherein the first cation is potassium and the second cation is sodium.

19. The ion exchanged glass of claim 18, wherein the glass comprises from 0 mol % to about 2.5 mol % K₂O.

20. The ion exchanged glass of claim 18, wherein the glass comprises from 0 mol % to about 1 mol % K₂O.

21. The ion exchanged glass of claim 18, wherein the glass comprises alkali metal oxides and wherein K₂O comprises less than about 7% of the total alkali metal oxide concentration.

22. The ion exchanged glass of claim 21, wherein the glass comprises alkali metal oxides and wherein K₂O comprises less than about 3% of the total alkali metal oxide concentration.

23. The ion exchanged glass of claim 18, wherein the glass comprises at least 14 mol % Na₂O.

24. The ion exchanged glass of claim 23, wherein Na₂O+K₂O=15 mol %.

25. The ion exchanged glass of claim 15, wherein the glass comprises at least about 50 mol % SiO₂;

at least about 10 mol % R₂O, wherein R₂O comprises Na₂O;

Al₂O₃; and

B₂O₃, and wherein B₂O₃−

(R₂O−

Al₂O₃)≧

3 mol %.

26. The ion exchanged glass of claim 25, wherein the glass has a Vickers crack initiation threshold of at least about 10 kgf.

27. The ion exchanged glass of claim 25, wherein the glass comprises:

at least about 50 mol % SiO₂, from about 9 mol % to about 22 mol % Al₂O₃;

from about 3 mol % to about 10 mol % B₂O₃;

from about 9 mol % to about 20 mol % Na₂O;

from 0 mol % to about 5 mol % K₂O;

at least about 0.1 mol % MgO, ZnO, or combinations thereof, wherein 0≦

MgO≦

6 and 0≦

ZnO≦

6 mol %; and

, optionally, at least one of CaO, BaO, and SrO, wherein 0 mol %≦

CaO+SrO+BaO≦

2 mol %.

28. The ion exchanged glass of claim 15, wherein the compressive stress CS(0) at d=0 is at least about 900 MPa and the depth of layer DOL is at least about 30 um, and wherein the glass article comprises at least about 50 mol % SiO₂ and at least about 11 mol % Na₂O.

29. The ion exchanged glass of claim 28, wherein the glass further comprises Al₂O₃ and at least one of B₂O₃, K₂O, MgO and ZnO, and wherein −

340+27.1.Al₂O₃−

28.7.B₂O₃+15.6.Na₂O−

61.4.K₂O+8.1.(MgO+ZnO)≧

0 mol %.

30. The ion exchanged glass of claim 28, wherein the glass comprises:

from about 7 mol % to about 26 mol % Al₂O₃;

from 0 mol % to about 9 mol % B₂O₃;

from about 11 mol % to about 25 mol % Na₂O;

from 0 mol % to about 2.5 mol % K₂O;

from 0 mol % to about 8.5 mol % MgO; and

from 0 mol % to about 1.5 mol % CaO.

31. A method of ion exchanging a glass, the method comprising:

ion exchanging an alkali aluminosilicate glass in a single ion exchange bath, wherein the alkali aluminosilicate glass comprises at least 14 mol % Na₂O and from 0 mol % to about 2.5 mol % K₂O; and

wherein the ion exchanged glass has a layer under a compressive stress CS(d) that varies as a function of depth d from the surface to a depth of layer DOL, wherein CS(d)>

CS_erfc(d) at 0<

d≦

DOL, where CS_erfc(d) is a compressive stress at depth d determined from an error function erfc.

32. The method of claim 31, wherein the glass comprises from 0 mol % to about 1 mol % K₂O.

33. The method of claim 31, wherein the glass comprises alkali metal oxides and wherein K₂O comprises less than about 7% of the total alkali metal oxide concentration.

34. The method of claim 31, wherein the glass comprises at least 14 mol % Na₂O.

35. The method of claim 31, wherein the ion exchange bath comprises at least about 90 wt % of at least one potassium salt.

36. The method of claim 31, wherein 0.4·

DOL≦

d≦

0.6·

DOL.