CHEMICALLY STRENGTHENED LITHIUM ALUMINOSILICATE GLASS HAVING HIGH STRENGTH EFFECTIVE TO RESIST FRACTURE UPON FLEXING FROM IMPACT OF HIGH VELOCITY PROJECTILES

• US 20070060465A1
• Filed: 08/30/2006
• Published: 03/15/2007
• Est. Priority Date: 09/12/2005
• Status: Active Grant

• Current Assignee: Saxon Glass Technologies, Inc.
• Original Assignee: Saxon Glass Technologies, Inc.
• Inventors: Spinelli, Ian, Varshneya, Arun
• Granted Patent: US 8,304,078 B2
• Time in Patent Office: Days
• US Class Current: 501/68
• 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 glass has high strength effective to resist fracture upon flexing from impact of high velocity projectiles 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 from impact of high velocity projectiles, wherein said glass is characterized by a surface compression of at least 100,000 psi and a compression case depth of at least 600 microns.

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

3. The glass of claim 1 wherein a composition of said glass provides said glass with an annealing point temperature of at least 580°

C.

4. The glass of claim 1 wherein said compression case depth is at least 1000 microns.

5. The glass of claim 1 formed by a method comprising immersion of glass having a composition comprising (in weight %):

Li₂O in an amount ranging from 3 to 9%, Na₂O+K₂O in an amount less than about 3.5%, and Al₂O₃ in an amount ranging from 7 to 30%, in a mixed potassium and sodium salt bath containing predominantly potassium salt at a temperature ranging from 450°

C. to below said annealing point temperature for a period up to 96 hours.

6. The glass of claim 5 wherein Na₂O+K₂O ranges from 0 to 3% and Al₂O₃ ranges from 18-28%.

7. The glass of claim 5 wherein a ratio of moles of sodium salt to moles of potassium salt in said mixed salt bath ranges from 1:

10 to 1;

2.

8. The glass of claim 7 wherein a ratio of moles of sodium salt to moles of potassium salt in said mixed salt bath is about 1:

4.

9. The glass of claim 1 characterized by a Weibull modulus ranging from 9 to 18.

10. An article comprising the glass of claim 1 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. Chemically strengthened lithium aluminosilicate glass, wherein said glass is characterized by a surface compression of at least 100,000 psi, a compression case depth of at least 600 microns and a compression at 50 microns below a surface of said glass that is at least 30,000 psi.

12. The glass of claim 11 wherein said compression case depth is at least 1000 microns.

13. A method of chemically strengthening lithium aluminosilicate glass to achieve high strength effective to resist fracture upon flexing from impact of high velocity projectiles, comprising:

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%;

providing a mixed salt bath comprising a mixture of sodium salt and potassium salt, wherein a ratio of moles of sodium salt to moles of potassium salt in said mixed salt bath ranges from 1;

10 to 1;

2;

maintaining a temperature of said mixed salt bath in a range of 450°

C. up to an annealing point temperature of said glass; and

immersing said glass in said mixed salt bath for a period ranging from 2 to 96 hours.

14. The method of claim 13 wherein the amount of Na₂O+K₂O is not greater than 2%.

15. The method of claim 13 wherein said composition provides said glass with an annealing point temperature of at least 580°

C.

16. The method of claim 13 wherein said composition consists essentially of (in weight %):

Li₂O in an amount ranging from 3 to 9%, Na₂O+K₂O in an amount less than about 3.5%, Al₂O₃ in an amount ranging from 7 to 30%, up to about 4% each of ZrO₂, TiO₂, MgO, ZnO totaling no more than 10%, with the balance being SiO₂ and unavoidable impurities.

17. The method of claim 13 comprising immersing said glass in said salt bath at a temperature and for a period effective to provide said glass with a surface compression of at least 100,000 psi and a compression case depth of at least 600 microns.

18. The method of claim 17 comprising immersing said glass in said salt bath at a temperature and for a period effective to provide said glass with a compression at 50 microns below a surface of said glass that is at least 30,000 psi.

19. The method of claim 17 comprising immersing said glass in said salt bath effective to provide said glass with a compression case depth of at least 1000 microns.

20. The method of claim 19 wherein said period of immersion is not greater than 24 hours.

21. A method of chemically strengthening lithium aluminosilicate glass to achieve high strength effective to resist fracture upon flexing from impact of high velocity projectiles, comprising:

providing a lithium aluminosilicate glass having a composition consisting essentially of (in weight %);

Li₂O in an amount ranging from 3 to 9%, Na₂O+K₂O in an amount less than about 3.5%, Al₂O₃ in an amount ranging from 7 to 30%, up to about 4% each of ZrO₂, TiO₂, MgO, ZnO totaling no more than 10%, with the balance being SiO₂ and unavoidable impurities, wherein said composition provides said glass with an annealing point temperature of at least 580°

C.;

providing a mixed salt bath comprising a mixture of sodium salt and potassium salt, wherein a ratio of moles of sodium salt to moles of potassium salt in said mixed salt bath ranges from 1;

10 to 1;

2;

maintaining a temperature of said mixed salt bath in a range of 450°

C. up to an annealing point temperature of said glass; and

immersing said glass in said salt bath for said temperature and a period ranging from 2 to 96 hours effective to provide said glass with a surface compression of at least 100,000 psi, a compression case depth of at least 600 microns and a compression at 50 microns below a surface of said glass that is at least 30,000 psi.

22. The method of claim 21 comprising immersing said glass in said salt bath for a temperature and period effective to provide said glass with a compression case depth of at least 1000 microns.

23. The method of claim 22 wherein said period of immersion is not greater than 24 hours.