Strengthened glass articles and methods of making
A strengthened glass article having a central tension that is below a threshold value above which the glass exhibits frangible behavior. The central tension varies non-linearly with the thickness of the glass. The glass article may be used as cover plates or windows for portable or mobile electronic devices such as cellular phones, music players, information terminal (IT) devices, including laptop computers, and the like.
1. A strengthened glass article, the strengthened glass article having a thickness t<0.5 mm and comprising:
an outer region having a depth of layer of at least 30 μm and a compressive stress of at least 600 MPa,
an inner region, wherein the inner region is under a central tension CT, and wherein CT(MPa)>15.7 (MPa/mm)·t(mm)+52.5 (MPa) and wherein the strengthened glass article has a frangibility index of less than 3.
2. The strengthened glass article of claim 1 , wherein the strengthened glass article has a thickness t<0.5 mm.
3. The strengthened glass article of claim 2 , wherein when the strengthened glass article is broken by the point impact, the strengthened glass article exhibits at least one of fragment size n 1 (%≦1 mm) of 0%≦n 1 ≦5%, fragment density n 2 (fragments/cm 2 ) of 0 fragments/cm 2 ≦n 2 ≦3 fragments/cm 2 , crack branching n 3 of 0≦n 3 ≦5 and ejection n 4 (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof.
4. The strengthened glass article of claim 2 , wherein the strengthened glass article is substantially non-frangible when subjected to a point impact that is sufficient to break the strengthened glass article.
5. The strengthened glass article according to claim 2 , wherein the strengthened glass article is an alkali aluminosilicate glass comprising: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol % Li 2 O +Na 2 O+K 2 O≦20 mol %.
6. The strengthened glass article of claim 5 , wherein the alkali aluminosilicate glass further comprises 0 mol %≦MgO+CaO≦10 mol %.
7. The strengthened glass article of claim 6 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO.
8. The strengthened glass article of claim 1 , wherein t is between 0.3 mm and 0.5 and CT is between about 75.0 and about 94.8 MPa.
9. The strengthened glass article of claim 2 , wherein the thickness of the strengthened glass article is 0.3≦t<0.5 mm.
10. The strengthened glass article of claim 9 , wherein when the strengthened glass article is broken by the point impact, the strengthened glass article exhibits at least one of fragment size n 1 (%≦1 mm) of 0%≦n 1 ≦5%, fragment density n 2 (fragments/cm 2 ) of 0 fragments/cm 2 ≦n 2 ≦3 fragments/cm 2 , crack branching n 3 of 0≦n 3 ≦5 and ejection n 4 (%≧5 cm) of 0%≦n 4 ≦2%, or combinations thereof.
11. The strengthened glass article of claim 9 , wherein the strengthened glass article is substantially non-frangible when subjected to a point impact that is sufficient to break the strengthened glass article.
12. The strengthened glass article according to claim 9 , wherein the strengthened glass article is an alkali aluminosilicate glass comprising: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol %≦Li 2 O+Na 2 O+K 2 O ≦20 mol %.
13. The strengthened glass article of claim 12 , wherein the alkali aluminosilicate glass further comprises 0 mol %≦MgO+CaO≦10 mol %.
14. The strengthened glass article of claim 13 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO.
15. A strengthened glass article, the strengthened glass article having a thickness t≦0.5 mm and comprising:
an outer region having a depth of layer of at least 30 μm and a compressive stress of at least 600 MPa; and
an inner region under a central tension CT, wherein CT (MPa)>15.7 (MPa/mm)·t(mm)+52.5 (MPa),
wherein the strengthened glass article is substantially non-frangible when subjected to a point impact that is sufficient to break the strengthened glass article, and wherein the strengthened glass article has a frangibility index of less than 3, and wherein when the strengthened glass article is broken by the point impact, the strengthened glass article exhibits at least one of fragment size n 1 (%≦1 mm) of 0%≦n 1 ≦5%, fragment density n 2 (fragments/cm 2 ) of 0 fragments/cm 2 ≦n 2 ≦3 fragments/cm 2 , crack branching n 3 of 0≦n 3 ≦5 and ejection n 4 (%≧5 cm) of 0%≦n 4 2%, or combinations thereof.
16. The strengthened glass article of claim 15 , wherein the strengthened glass article having a thickness t≦0.5 mm.
17. The strengthened glass article according to claim 16 , wherein the strengthened glass article is an alkali aluminosilicate glass comprising: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol % Li 2 O+Na 2 O+K 2 O≦20 mol %.
18. The strengthened glass article of claim 17 , wherein the alkali aluminosilicate glass further comprises 0 mol % MgO+CaO−10 mol %.
19. The strengthened glass article of claim 16 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO.
20. The strengthened glass article of claim 16 , wherein the thickness of the strengthened glass article is 0.3≦t≦0.5 mm.
21. The strengthened glass article according to claim 20 , wherein the strengthened glass article is an alkali aluminosilicate glass comprising: 60-70 mol % SiO 2 ; 6-14 mol % Al 2 O 3 ; 0-15 mol % B 2 O 3 ; 0-15 mol % Li 2 O; 0-20 mol % Na 2 O; 0-10 mol % K 2 O; 0-10 mol % CaO; 0-5 mol % ZrO 2 ; 0-1 mol % SnO 2 ; 0-1 mol % CeO 2 ; less than 50 ppm As 2 O 3 ; and less than 50 ppm Sb 2 O 3 ; wherein 12 mol % Li 2 O+Na 2 O+K 2 O≦20 mol %.
22. The strengthened glass article of claim 21 , wherein the alkali aluminosilicate glass further comprises 0 mol %≦MgO+CaO≦10 mol %.
23. The strengthened glass article of claim 22 , wherein the alkali aluminosilicate glass further comprises up to 8 mol % MgO.
24. The strengthened glass article of claim 15 , wherein t is between 0.3 mm and 0.5 and CT is between about 75.0 and about 94.8 MPa.