STRENGTHENED GLASS ARTICLES AND METHODS OF MAKING

• US 20100035038A1
• Filed: 08/07/2009
• Published: 02/11/2010
• Est. Priority Date: 08/08/2008
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Barefoot, Kristen L., Stewart, Ronald Leroy, Price, James Joseph, Quintal, Jose Mario
• Granted Patent: US 8,075,999 B2
• Time in Patent Office: Days
• US Class Current: 428/220
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 2204/00 Glasses, glazes or enamels with special properties
• CPC Class Codes: C03C 3/064 containing boron
• CPC Class Codes: C03C 3/078 containing an oxide of a divalent metal, e.g. an oxide of zinc
• CPC Class Codes: C03C 3/083 containing aluminium oxide or an iron compound
• CPC Class Codes: C03C 3/085 containing an oxide of a divalent metal
• CPC Class Codes: C03C 3/087 containing calcium oxide, e.g. common sheet or container glass
• CPC Class Codes: C03C 3/091 containing aluminium
• CPC Class Codes: C03C 3/093 containing zinc or zirconium
• CPC Class Codes: C03C 3/095 containing rare earths
• CPC Class Codes: C03C 4/18 for ion-sensitive glass
• CPC Class Codes: Y10T 428/31 Surface property or characteristic of web, sheet or block
• CPC Class Codes: Y10T 428/315 Surface modified glass [e.g., tempered, strengthened, etc.]

Abstract

A strengthened glass article having a central tension that is below a threshold value above which the glass exhibits frangible behavior. The central tension varies non-linearly with the thickness of the glass. The glass article may be used as cover plates or windows for portable or mobile electronic devices such as cellular phones, music players, information terminal (IT) devices, including laptop computers, and the like.

Claims

1. A strengthened glass article, the strengthened glass article having a thickness t and comprising:

a. an outer region, the outer region extending from a surface of the article to a depth of layer DOL within the article, wherein the outer region is under a compressive stress CS; and

b. an inner region, wherein the inner region is under a central tension CT, and wherein −

15.7 t+52.5<

CT≦

−

38.7 ln(t)+48.2, wherein CT is expressed in megaPascals (MPa) and t is expressed in millimeters (mm).

2. The strengthened glass article of claim 1, wherein the strengthened glass article is substantially non-frangible behavior when subjected to a point impact sufficient to break the strengthened glass article.

3. The strengthened glass article of claim 1, wherein the strengthened glass article, when subjected to a point impact sufficient to break the strengthened glass article, has a frangibility index of less than 3.

4. The strengthened glass article of claim 1, wherein the strengthened glass article is a sheet and the thickness t is in a range from about 0.2 mm up to about 2 mm.

5. The strengthened glass article of claim 4, wherein the thickness is in a range from about 0.5 mm up to about 0.75 mm.

6. The strengthened glass article of claim 4, wherein the thickness is in a range from about 0.9 mm up to about 2 mm.

7. The strengthened glass article of claim 1, wherein the strengthened glass article comprises an alkali aluminosilicate glass.

8. The strengthened glass article according to claim 7, wherein the alkali aluminosilicate glass comprises:

60-70 mol % SiO₂;

6-14 mol % Al₂O₃;

0-15 mol % B₂O₃;

0-15 mol % Li₂O;

0-20 mol % Na₂O;

0-10 mol % K₂O;

0-8 mol % MgO;

0-10 mol % CaO;

0-5 mol % ZrO₂;

0-1 mol % SnO₂;

0-1 mol % CeO₂;

less than 50 ppm As₂O₃; and

less than 50 ppm Sb₂O₃;

wherein 12 mol %≦

Li₂O+Na₂O+K₂O≦

20 mol % and 0 mol %≦

MgO+CaO≦

10 mol %.

9. The strengthened glass article according to claim 7, wherein the alkali aluminosilicate glass comprises:

5-50 wt % SiO₂;

2-20 wt % Al₂O₃;

0-15 wt % B₂O₃;

1-20 wt % Na₂O;

0-10 wt % Li₂O;

0-10 wt % K₂O; and

0-5 wt % (MgO+CaO+SrO+BaO);

0-3 wt % (SrO+BaO); and

0-5 wt % (ZrO₂+TiO₂), wherein 0≦

(Li₂O+K₂O)/Na₂O≦

0.5.

10. The strengthened glass article of claim 7, wherein the alkali aluminosilicate glass has a liquidus viscosity of at least 130 kpoise.

11. The strengthened glass article of claim 7, wherein the alkali aluminosilicate glass is substantially free of lithium.

12. The strengthened glass article of claim 1, wherein the outer region has a depth of at least 30 μ

m.

13. The strengthened glass article of claim 1, wherein the compressive stress is at least about 600 MPa.

14. The strengthened glass article of claim 1, wherein the strengthened glass article is a cover plate or a window for one of a portable electronic device, an information terminal device, and a display for a computer.

15. The strengthened glass article of claim 1, wherein the outer region is strengthened by ion exchange.

16. The strengthened glass article of claim 1, wherein CT=(CS·

DOL)/(t−

2 DOL), and wherein CS is expressed in MPa and DOL is expressed in mm.

17. A strengthened glass article, the strengthened glass article having a thickness t of less than about 2 mm and comprising:

a. an outer region; and

b. an inner region under a central tension CT, wherein CT{tilde over (>

)}15.7 t+52.5, wherein the central tension CT is expressed in megaPascals (MPa), and wherein the strengthened glass article is substantially non-frangible when subjected to a point impact that is sufficient to break the strengthened glass article.

18. The strengthened glass article of claim 17, wherein the strengthened glass article, when subjected to a point impact sufficient to break the strengthened glass article, has a frangibility index of less than 3.

19. The strengthened glass article of claim 17, wherein the strengthened glass article is a sheet the thickness t is in a range from about 0.2 mm up to about 2 mm.

20. The strengthened glass article of claim 19, wherein the thickness is in a range from about 0.5 mm up to about 0.75 mm.

21. The strengthened glass article of claim 19, wherein the thickness is in a range from about 0.9 mm up to about 2 mm.

22. The strengthened glass article of claim 17, wherein the strengthened glass article comprises an alkali aluminosilicate glass.

23. The strengthened glass article of claim 17, wherein the strengthened glass article is a cover plate or a window for one of a portable electronic device, an information terminal device, and a display for a computer.

24. The strengthened glass article of claim 17, wherein the outer region is strengthened by ion exchange.

25. A method of making a strengthened glass article, the strengthened glass article being substantially non-frangible, the method comprising the steps of:

a. providing a glass article, the glass article having a thickness t; and

b. creating a compressive stress CS to a depth of layer DOL in an outer region of the glass article to form the strengthened glass article, the compressive stress being sufficient to generate a central tension CT in a central region of the strengthened glass article such that CT≦

−

38.7 ln(t)+48.2, wherein CT is expressed in megaPascals (MPa) and t is expressed in millimeters (mm), and wherein the strengthened glass article is substantially non-frangible.

26. The method of claim 25, wherein the step of creating the compressive stress CS in the outer region comprises exchanging a plurality of first metal ions in the outer region with a plurality of second metal ions so that the outer region comprises the plurality of the second metal ions, wherein each of the first metal ions has a first ionic radius and each of the second metal ions has a second ionic radius, the second ionic radius being greater than the first ionic radius, and wherein the presence of the second metal ions creates the compressive stress in the outer region.

27. The method of claim 26, wherein at least one of the plurality of first metal ions and the plurality of second metal ions comprises alkali metal ions.

28. The method of claim 26, wherein the plurality of first alkali metal ions comprises at least one of lithium ions, sodium ions, potassium ions, and rubidium ions, and wherein the plurality of second alkali metal ions comprises at least one of sodium ions, potassium ions, cesium ions, and rubidium ions.

29. The method of claim 26, wherein the step of exchanging a plurality of first metal ions in the outer region with a plurality of second metal ions so that the outer region comprises the plurality of the second metal ions comprises immersing the glass article in a molten salt bath, the molten salt bath comprising the second metal ions.

30. The method of claim 26, wherein the strengthened glass article comprises an alkali aluminosilicate glass.

31. The method of claim 25, wherein CT=(CS·

DOL )/(t−

2 DOL), and wherein CS is expressed in MPa and DOL is expressed in mm.

32. The method of claim 25, wherein −

15.7 t+52.5<

CT≦

−

38.7 ln(t)+48.2, wherein CS is expressed in MPa.

33. The method of claim 25, wherein the strengthened glass article has a frangibility index of less than 3.

34. The method of claim 25, wherein the strengthened glass article is a sheet and the thickness t is in a range from about 0.2 mm up to about 2 mm.