DUAL STAGE ION EXCHANGE FOR CHEMICAL STRENGTHENING OF GLASS

• US 20100028607A1
• Filed: 07/28/2009
• Published: 02/04/2010
• Est. Priority Date: 07/29/2008
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Mann, Lawrence George, Yan, Yongsheng, Quintal, Jose Mario, Lee, Christopher Morton
• Granted Patent: US 8,312,739 B2
• Time in Patent Office: Days
• US Class Current: 428/156
• CPC Class Codes: C03C 21/002 to perform ion-exchange between alkali ions C03C21/005 takes precedence
• CPC Class Codes: C03C 21/005 to introduce in the glass such metals or metallic ions as Ag, Cu
• CPC Class Codes: C03C 3/093 containing zinc or zirconium
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

A method of chemically strengthening a glass. The method includes ion exchange of the glass in a first bath, followed by immersion in the second bath. The first bath is diluted with an effluent ion. The second bath has a smaller concentration of the effluent ion than the first bath. The method provides a compressive stress at the surface of the glass that is sufficient to arrest flaws introduced by contact forces at the surface of the glass while having sufficiently deep compressive depth-of-layer for high reliability.

Claims

1. A method of strengthening a glass, the method comprising:

creating a compressive stress in an outer region of the glass, the region extending from a surface of the glass to a depth-of-layer, the compressive stress being sufficient to arrest flaws within the glass and to arrest flaws at the surface introduced by contact forces at the surface, and wherein the compressive stress is created by;

a. providing a glass, the glass having a plurality of first metal ions within the outer region;

b. ion exchanging a first portion of the plurality of first metal ions in the glass with a plurality of second metal ions in a first salt bath, wherein the first salt bath is diluted with a first concentration of the first metal ions; and

c. ion exchanging a second portion of the plurality of the first metal ions in the glass with a plurality of the second metal ions in a second salt bath, wherein the second salt bath has a second concentration of the first metal that is less than the first concentration.

2. The method of claim 1, wherein at least one of the first metal and the second metal is an alkali metal.

3. The method of claim 2, wherein the first metal is one of lithium, sodium, potassium, and cesium and wherein the second metal is one of sodium, potassium, cesium, and rubidium.

4. The method of claim 1, wherein the glass is an alkali aluminosilicate glass.

5. The method of claim 4, 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 %.

6. The method of claim 4, 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 %.

7. The method of claim 5, wherein the glass has a liquidus viscosity of at least 130 kilopoise.

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

9. The method of claim 7, wherein the glass is one of a cover plate and a display window in an electronic device.

10. The method of claim 7, wherein the glass has a thickness in a range from about 0.5 mm up to about 5 mm.

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

m.

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

14. The method of claim 12, wherein at least one of the first metal and the second metal is an alkali metal.

16. The method of claim 12, wherein the glass is an alkali aluminosilicate glass.

18. The method of claim 16, wherein at least one of the first metal and the second metal is an alkali metal.

20. The method of claim 16, wherein the glass is an alkali aluminosilicate glass.

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

a. providing a glass, the glass comprising a plurality of ions of a first metal, each of the ions having a first ionic radius;

b. immersing the glass in a first ion exchange bath, the first ion exchange bath comprising a plurality of ions of a second metal and a first concentration of ions of the first metal, wherein each of the ions of the second metal has a second ionic radius, the second ionic radius being greater than the first ionic radius; and

c. immersing the glass in a second ion exchange bath after immersing the glass in the first ion exchange bath, the second ion exchange bath comprising a plurality of ions of the second metal and a second concentration of ions of the first metal, wherein the second concentration is less than the first concentration, wherein a portion of the plurality of ions of the first metal in the glass are replaced by ions of the second metal to create a compressive stress in a surface region of the glass.

15. The method of claim 13, wherein the first metal is one of lithium, sodium, potassium, and cesium, and wherein the second metal is one of sodium, potassium, cesium, and rubidium.

17. A method of reducing variability of compressive stress in chemically strengthened glass articles;

the method comprising the steps of;

a. providing a glass article, the glass comprising a plurality of ions of a first metal, each of the ions having a first ionic radius;

b. immersing the glass article in a first ion exchange bath, the first ion exchange bath comprising a plurality of ions of a second metal and a first concentration of ions of the first metal, wherein each of the ions of the second metal has a second ionic radius, the second ionic radius being greater than the first ionic radius; and

c. immersing the glass article in a second ion exchange bath after immersing the glass in the first ion exchange bath, the second ion exchange bath comprising a plurality of ions of the second metal and a second concentration of ions of the first metal, wherein the second concentration is less than the first concentration, wherein a portion of the plurality of ions of the first metal in the glass are replaced by ions of the second metal to create a compressive stress in a surface region of the glass, wherein the compressive stress is greater than a predetermined value of compressive stress.

19. The method of claim 17, wherein the first metal is one of lithium, sodium, potassium, and cesium, and wherein the second metal is one of sodium, potassium, cesium, and rubidium.