GLASS WITH COMPRESSIVE SURFACE FOR CONSUMER APPLICATIONS

• US 20100009154A1
• Filed: 07/10/2009
• Published: 01/14/2010
• Est. Priority Date: 07/11/2008
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Allan, Douglas Clippinger, Ellison, Adam James, Gomez, Sinue
• Granted Patent: US 8,561,429 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 3/085 containing an oxide of a divalent metal
• CPC Class Codes: C03C 3/093 containing zinc or zirconium

Abstract

A strengthened glass that does not exhibit frangible behavior when subjected to impact or contact forces, and a method of strengthening a glass. The glass may be strengthened by subjecting it to multiple, successive, ion exchange treatments. The multiple ion exchange treatments provide a local compressive stress maximum at a depth of the strengthened layer and a second local maximum at or near (e.g., within 10 μm) the surface of the glass.

Claims

1. A glass, the glass being strengthened and having an outer region under a compressive stress, the outer region extending from a surface of the glass to a depth of layer, and a central tensile region, the central tensile region being under an integrated central tension of less than or equal to a value in a range from about 2.8 MPa·

cm up to about 3.2 MPa·

cm.

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

3. The glass of claim 2, wherein the glass, when subjected to a point impact sufficient to break the glass, breaks with less than five multiple cracks branching from an initial crack with pieces ejected less than two inches from their original location.

4. The glass of claim 1, wherein the outer region has a depth of layer of at least 50 μ

m.

5. The glass of claim 1, wherein the compressive stress is at least about 200 MPa.

6. The glass of claim 1, wherein the glass in an alkali aluminosilicate glass.

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

64 mol %≦

SiO₂≦

68 mol %;

12 mol %≦

Na₂O≦

16 mol %;

8 mol %≦

Al₂O₃≦

12 mol %;

0 mol %≦

B₂O₃≦

3 mol %;

2 mol %≦

K₂O≦

5 mol %;

4 mol %≦

MgO≦

6 mol %; and

0 mol %≦

CaO≦

5 mol %, and wherein;

66 mol %≦

SiO₂+B₂O₃+CaO≦

69 mol %;

Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>

10 mol %;

5 mol %≦

MgO+CaO+SrO≦

8 mol %;

(Na₂O+B₂O₃)—

Al₂O₃≦

2 mol %;

2 mol %≦

Na₂O—

Al₂O₃≦

6 mol %; and

4 mol %≦

(Na₂O+K₂O)—

Al₂O₃≦

10 mol %.

8. The glass of claim 6, 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 glass of claim 6, wherein the glass has a liquidus viscosity of at least 130 kilopoise.

10. The glass of claim 1, wherein the glass is one of a planar sheet and a three-dimensional curved sheet.

11. The glass of claim 10, wherein the glass is one of a cover plate and a display window in an electronic device.

12. The glass of claim 10, wherein the glass has a thickness in a range from about 0.5 mm up to about 5 mm.

13. The glass of claim 1, wherein the glass is chemically strengthened by successive immersion in a plurality of ion exchange baths.

14. The glass of claim 1, wherein the surface region comprises a plurality of ions of a first alkali metal ion and a plurality of ions of a second alkali metal, wherein each of the ions of the first alkali metal has a first ionic radius and each of the ions of the second alkali metal has a second ionic radius, wherein the first alkali metal is different from the second alkali metal, and wherein the second ionic radius is greater than the first ionic radius.

15. The glass of claim 14, wherein the surface region has been ion exchanged.

16. The glass of claim 1, wherein the glass has a compressive stress within 10 μ

m of the surface.

17. A method of strengthening a glass, the method comprising the steps of:

a. providing the glass, the glass having a surface;

b. creating a compressive stress in an outer region to strengthen the glass, the outer region extending from the surface to a depth of layer, wherein the compressive stress creates an integrated central tension of less than or equal to a value in a range from about 2.8 MPa·

cm up to about 3.2 MPa·

cm in a central tensile region of the glass.

18. The method of claim 17, wherein the step of creating a compressive stress in the surface region comprises successively immersing at least a portion of the glass in a plurality of ion exchange baths.

19. The method of claim 18, wherein the successive ion exchange baths have compositions that are different from each other.

20. The method of claim 18, further comprising annealing the glass between successive immersions of the glass in the plurality of ion exchange baths.

21. The method of claim 18, wherein the step of immersing at least a portion of the glass in a plurality of ion exchange baths comprises immersing the glass in a first ion exchange bath comprising a salt of a first metal followed by immersing the glass in a second ion exchange bath comprising a salt of a second metal, wherein the first metal is different from the second metal.

22. The method of claim 21, wherein the first metal and second metal are alkali metals.

23. The method of claim 18, wherein each of the plurality of ion exchange baths comprises at least one alkali metal salt.

24. The method of claim 17, wherein the glass is an alkali aluminosilicate glass.

25. The method of claim 17, wherein the glass, when strengthened, is substantially free of frangible behavior.