Method for making strengthened glass
There is a method for making. The method includes providing an untreated alkali aluminosilicate glass having an annealing point temperature that is at least about 580° C. The method also includes providing a mixed potassium and sodium salt bath having greater than about 50 mole % potassium salt and less than about 50 mole % sodium salt. The method also includes immersing the untreated glass in the mixed salt bath and maintaining the mixed salt bath with the immersed untreated glass within a temperature range from about 450° C. to less than the annealing point temperature of the untreated glass for a period greater than about 2 hours to produce a strengthened glass. The produced strengthened glass has a surface compression of at least about 100,000 psi and a compression case depth of at least about 600 microns.
1. A method comprising:
providing an untreated alkali aluminosilicate glass having an annealing point temperature of at least about 580° C.;
providing a potassium and sodium salt composition including greater than about 50 mole % potassium salt and less than about 50 mole % sodium salt;
exposing the untreated glass to the salt composition; and
maintaining the salt composition together with the untreated glass within a temperature range from about 450° C. to less than the annealing point temperature of the untreated glass for a period to produce a strengthened alkali aluminosilicate glass,
wherein the strengthened glass has a surface compression of at least about 100,000 psi and a compression case depth of at least about 600 microns.
2. The method of claim 1 wherein the untreated glass includes Li 2 O, Al 2 O 3 and SiO 2 .
3. The method of claim 1 , wherein the untreated glass includes at least one of Na 2 O and K 2 O.
4. The method of claim 1 , wherein the untreated glass includes less than about 3% by weight of Na 2 O, K 2 O, or a combination thereof.
5. The method of claim 1 , wherein the salt composition includes greater than about 80 mole % potassium salt and less than about 20 mole % sodium salt.
6. The method of claim 1 , wherein the salt composition includes greater than about 90 mole % potassium salt and less than about 10 mole % sodium salt.
7. The method of claim 1 , wherein the salt composition is maintained together with the untreated glass at a temperature from about 450° C. to less than about 25° C. below the annealing point temperature of the untreated glass.
8. The method of claim 1 , wherein the salt composition is maintained with the untreated glass at a temperature from about 475° C. to less than the annealing point temperature of the untreated glass.
9. The method of claim 1 , wherein the salt composition includes nitrate salts of potassium and sodium.
10. The method of claim 1 , wherein the salt composition includes at least one of chloride, sulfate and phosphate salts of potassium and sodium.
11. The method of claim 1 , wherein the period is about 2 hours to 1 week.
12. The method of claim 1 , wherein the period is about 2 hours to 96 hours.
13. The method of claim 1 , wherein the period is about 2 hours to 24 hours.
14. The method of claim 1 , wherein the period is about 2 hours to 4 hours.
15. The method of claim 1 , wherein the strengthened glass has a compression of at least about 30,000 psi at a depth of about 50 microns.
16. The method of claim 1 , wherein the strengthened glass has a compression case depth of at least about 1,000 microns.
17. The method of claim 1 , wherein the untreated glass includes less than about 2% by weight of Na 2 O, K 2 O, or a combination thereof.
18. The method of claim 1 , wherein the untreated glass includes about 3-9% by weight of Li 2 O.
19. The method of claim 1 , wherein the strengthened glass includes about 7-30% by weight of Al 2 O 3 .
20. The method of claim 1 , wherein the strengthened glass has a Weibull modulus of greater than about 4.5.
21. The method of claim 1 , wherein the strengthened glass has a Weibull modulus of from about 9 to 18.
22. The method of claim 1 , wherein the strengthened glass has a surface compression of from about 100,000 to 145,000 psi.
23. The method of claim 1 , wherein the strengthened glass has a compression case depth of from about 600 to 1,000 microns.