Chemically strengthened lithium aluminosilicate glass having high strength effective to resist fracture upon flexing

• US 8,304,078 B2
• Filed: 08/30/2006
• Issued: 11/06/2012
• Est. Priority Date: 09/12/2005
• Status: Active Grant

• Current Assignee: Saxon Glass Technologies, Inc.
• Original Assignee: Saxon Glass Technologies, Inc.
• Inventors: Varshneya, Arun K.
• Primary Examiner(s): GROUP, KARL E
• Application Number:
  US11/468,470
• Publication Number:
  US 20070060465A1
• Time in Patent Office: 2,260 Days
• Field of Search: 428/426, 428/410, 501/68, 501/69
• US Class Current: 428/410
• CPC Class Codes: B32B 17/10761 containing vinyl acetal
• CPC Class Codes: B32B 2605/18 Aircraft blades, propellers B32B2603/00
• 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 3/087 containing calcium oxide, e.g. common sheet or container glass
• CPC Class Codes: C03C 3/112 containing fluorine
• CPC Class Codes: F41H 5/0407 Transparent bullet-proof laminatesinformative reference: layered products essentially comprising glass in general B32B17/06, e.g. B32B17/10009; manufacture or composition of glass, e.g. joining glass to glass C03; permanent multiple-glazing windows, e.g. with spacing therebetween, E06B3/66
• CPC Class Codes: Y10T 428/315 Surface modified glass [e.g., tempered, strengthened, etc.]

Abstract

Chemically strengthened lithium aluminosilicate glass is characterized by a surface compression of at least 100,000 psi and a compression case depth of at least 600 microns. The glass also may be characterized by a compression at 50 microns below a surface of the glass that is at least 30,000 psi. A method of making this glass includes providing a lithium aluminosilicate glass having a composition comprising (in weight %): Li₂O in an amount ranging from 3 to 9%, Na₂O+K₂O in an amount not greater than 3%, and Al₂O₃ in an amount ranging from 7 to 30%. The composition provides the glass with an annealing point temperature of at least 580° C. A mixed potassium and sodium salt bath is provided comprising predominantly potassium salt. A ratio of moles of sodium salt to moles of potassium salt in the mixed salt bath can range from 1:10 to 1:2. The temperature of the salt bath is maintained in a range of 450° C. up to an annealing point temperature of the glass. The glass is immersed in the salt bath for a period ranging from 2 to 96 hours. The inventive strengthened glass has high strength effective to resist fracture upon flexing and includes: bullet-resistant glass, blast-resistant glass, glass for armored defense vehicles, windows for government buildings, windows for monuments, windows for vehicles, train transparencies, aircraft transparencies, hurricane-resistant windows, earthquake-resistant windows, bank teller windows, display cases, and ATM touch panels.

Claims

1. Chemically strengthened lithium aluminosilicate glass having high strength effective to resist fracture upon flexing, the glass having a composition comprising:

SiO₂ and Al₂O₃,

wherein the glass is characterized by having a surface compression of at least about 100,000 psi and a compression case depth of at least about 600 microns,

wherein the glass is formed by chemically strengthening an untreated glass having a composition including Li₂O in an amount ranging from about 3 to 9 weight % and Al₂O₃ in an amount ranging from about 7 to 30 weight % and SiO₂, and an annealing point temperature of at least about 580°

C. prior to chemical strengthening, and

wherein the glass is formed by a method comprising immersion of the untreated glass in a mixed potassium and sodium salt bath, containing greater than about 50 mole % potassium salt and less than about 50 mole % sodium salt, at a temperature ranging from about 450°

C. to below the annealing point temperature of the untreated glass.

2. The glass of claim 1, having a compression that is at least about 30,000 psi at about 50 microns below a surface of the glass.

3. The glass of claim 1, wherein the glass is characterized by having a compression case depth of at least about 1000 microns.

4. The glass of claim 1, wherein the glass is formed by a method comprising immersion of the untreated glass having a composition further comprising Na₂O+K₂O in an amount less than about 3.5 weight %.

5. The glass of claim 4, wherein the Na₂O+K₂O ranges from about 0 to 3 weight % and the Al₂O₃ ranges from about 18 to 28 weight %.

6. The glass of claim 4, wherein a ratio of moles of sodium salt to moles of potassium salt in the mixed sodium and potassium salt bath ranges from about 1:

10 to about 1;

2.

7. The glass of claim 6, wherein the ratio of moles of sodium salt to moles of potassium salt in the mixed sodium and potassium salt bath is about 1:

4.

8. An article comprising the glass of claim 1, wherein the article is a member selected from the group consisting of:

bullet-resistant glass, blast-resistant glass, glass for armored defense vehicles, windows for government buildings, windows for monuments, windows for vehicles, train transparencies, aircraft transparencies, hurricane-resistant windows, earthquake-resistant windows, bank teller windows, display cases, and ATM touch panels.

11. The glass of claim 1, wherein the untreated glass has a glass transition temperature of at least about 620°

C. prior to chemical strengthening.

12. The glass of claim 1, wherein the untreated glass has a glass transition temperature of at least about 630°

C. prior to chemical strengthening.

14. The glass of claim 1, wherein the mixed potassium and sodium salt bath contains less than about 40 mole % sodium salt.

15. The glass of claim 1, wherein the mixed potassium and sodium salt bath contains less than about 33 mole % sodium salt.

9. Chemically strengthened lithium aluminosilicate glass, the glass having a composition comprising:

SiO₂ and Al₂O₃, wherein the glass is characterized by having a surface compression of at least about 100,000 psi and a compression case depth of at least about 600 microns,

wherein the glass is formed by chemically strengthening an untreated glass having a composition including Li₂O in an amount ranging from about 3 to 9 weight % and Al₂O₃ in an amount ranging from about 7 to 30 weight % and SiO₂, the untreated glass having an annealing point temperature of at least about 580°

C. prior to chemical strengthening, and

wherein the glass is formed by a method comprising immersion of the untreated glass in a mixed potassium and sodium salt bath, containing less than 50 mole % sodium salt, at a temperature ranging from about 450°

C. to below the annealing point temperature of the untreated glass.

10. The glass of claim 9 wherein the glass is characterized by having a compression case depth of at least about 1000 microns.

13. The glass of claim 9, wherein the glass is characterized by having a compression at about 50 microns below a surface of the glass that is at least about 30,000 psi.

16. The glass of claim 9, wherein the length of time is up to about 1 day.

17. The glass of claim 9, wherein the length of time is up to about 4 hours.