Strengthened glass articles having improved survivability

1. A strengthened glass article comprising:

a thickness t≤1 mm,

an inner region under a central tension CT, and

at least one compressive stress layer adjacent the inner region and extending within the strengthened glass article from a surface of the strengthened glass article to a depth of layer DOL, wherein the DOL is greater than or equal to 70 μm,

wherein the strengthened glass article is under a compressive stress at the surface CSs,

wherein the strengthened glass article is an alkali aluminosilicate glass article comprising 0 mol % Li2O, and at least 3 mol % Al2O3, and

wherein the strengthened glass article has a stress profile such that a compressive stress CSD at an intermediate critical depth of 50 μm below the surface of the strengthened glass article is at least 10% of CSs.

2. The strengthened glass article of claim 1 , wherein the CSs>300 MPa.

3. The strengthened glass article of claim 1 , wherein the strengthened glass article comprises 0-5 mol % K2O.

4. The strengthened glass article of claim 1 , wherein the thickness t≤0.9 mm.

5. The strengthened glass article of claim 1 , wherein CSD is at least 50 MPa.

6. The strengthened glass article of claim 1 , wherein the strengthened glass article comprises from 5 mol % to 20 mol % Na2O.

7. The strengthened glass article of claim 1 , wherein the strengthened glass article comprises from 0 mol % to 10 mol % MgO.

8. The strengthened glass article of claim 1 , wherein the CSs/DOL ratio is in a range from 8 MPa/μm to 10 MPa/μm.

9. The strengthened glass article of claim 1 , wherein the DOL is in a range from 0.1t to 0.2t.

10. The strengthened glass article of claim 1 , wherein the DOL is in a range from 70 to 120 μm.

11. The strengthened glass article of claim 1 , wherein the CSs is in a range from 700 to 1200 MPa.

12. The strengthened glass article of claim 1 , wherein the thickness t is in a range from about 0.4 mm to about 0.8 mm.

13. The strengthened glass article of claim 1 , wherein the CT is less than or equal to 150 MPa.

14. The strengthened glass article of claim 1 , wherein the CSs/DOL ratio is in a range from 3 MPa/μm to 12 MPa/μm.

15. The strengthened glass article of claim 14 , wherein the CSs/DOL ratio is in a range from 3 MPa/μm to 5 MPa/μm.

16. The strengthened glass article of claim 1 , wherein the strengthened glass article has a stress profile defined by a first compressive stress zone which extends from the surface of the strengthened glass article to a distance x below the surface, and a second compressive stress zone extending from the distance x to the DOL, and

wherein the first compressive stress zone defines a rate r1 of decrease of compressive stress from the surface to the distance x below the surface, the second compressive stress zone defines a rate r2 of decrease of compressive stress from the distance x to the DOL, and wherein r1≥2r2.

17. The strengthened glass article of claim 1 , wherein the CSs≥350 MPa.

18. The strengthened glass article of claim 1 , wherein the strengthened glass has at least a 60% survival rate when dropped in a drop test from a height of at least 100 cm onto a drop surface comprising 180 grip alumina sandpaper utilizing a uniform drop rate procedure, wherein the survival rate is based on testing at least 5 samples.

19. The strengthened glass of claim 18 , wherein the strengthened glass is incorporated into an electronic device.

20. The strengthened glass article of claim 1 , wherein CSs/DOL≥2.5 MPa/μm.

21. A method of producing the strengthened glass article according to claim 1 , having a thickness t≤1 mm and at least one compressive stress layer extending from a surface of the strengthened glass article to a depth of layer DOL which is great than or equal 70 μm, the method comprising:

conducting a first ion exchange step by immersing an alkali aluminosilicate glass article in a first ion exchange bath at a temperature of greater than 400° C. for a time sufficient such that the compressive stress layer has a depth of at least 70 μm after the first ion exchange step; and

conducting a second ion exchange step by immersing the alkali aluminosilicate glass article in a second ion exchange bath different from the first ion exchange bath at a temperature of at least 350° C. for a time sufficient to produce the compressive stress layer having DOL, wherein the strengthened glass article has a stress profile such that a compressive stress CS D at an intermediate critical depth of 50 μm below the surface of the strengthened glass article is at least 10% of a compressive stress at the surface CSs, and wherein the strengthened glass article comprises 0 mol % Li 2 O.

22. The method of claim 21 , wherein the first ion exchange step is conducted for a time of at least 8 hours.

23. The method of claim 21 , wherein the first ion exchange bath comprises at least about 30% by weight of a sodium composition that delivers sodium ions to the alkali aluminosilicate glass article.

24. The method of claim 23 , wherein the first ion exchange bath comprises from about 30% to about 60% by weight of the sodium composition.

25. The method of claim 21 , wherein the temperature of the first ion exchange step is 435° C. or greater.

26. The method of claim 21 , wherein the strengthened glass article has a compressive stress of at least 150 MPa after the first ion exchange step.

27. The method of claim 26 , wherein the strengthened glass article has a compressive stress of about 200 to about 400 MPa after the first ion exchange step.

28. The method of claim 21 , wherein the second ion exchange step is conducted for a time of 75 minutes or less.

29. The method of claim 28 , wherein the second ion exchange step is conducted for a time of about 10 to about 20 minutes.

30. The method of claim 21 , wherein the second ion exchange bath comprises at least about 95% by weight of a potassium composition that delivers potassium ions to the alkali aluminosilicate glass article.

31. The method of claim 30 , wherein the second ion exchange bath comprises from about 98% to about 99.5% by weight of the potassium composition.

32. The method of claim 30 , wherein the second ion exchange bath comprises 0-2% by weight of a sodium composition.

33. The method of claim 21 , wherein the temperature of the second ion exchange step is 360° C. or greater.

34. The method of claim 21 , wherein the strengthened glass article has a compressive stress of at least 700 MPa after the second ion exchange step.

35. The method of claim 34 , wherein the strengthened glass article has a compressive stress of 700 to about 1000 MPa after the second ion exchange step.

36. The method of claim 21 , wherein the compressive stress layer has a depth of 70 μm to 85 μm after the first ion exchange step.

37. The method of claim 21 , wherein the DOL is in a range from 70 μm to 100 μm after the second ion exchange step.

38. A strengthened glass article comprising:

a thickness t≤1 mm,

an inner region under a central tension CT, and

at least one compressive stress layer adjacent the inner region and extending within the strengthened glass article from a surface of the strengthened glass article to a depth of layer DOL, wherein the DOL is greater than or equal to 70 μm,

wherein strengthened glass article is under a compressive stress at the surface CSs,

wherein the strengthened glass article is an alkali aluminosilicate glass article comprising 0mol % Li2O, at least 3 mol % Al2O3, and at least 5 mol % Na2O,

and

wherein the strengthened glass article has a stress profile such that a compressive stress CSD at an intermediate critical depth of 50 μm below the surface of the strengthened glass article is at least 10% of a compressive stress at the surface CSs, and the CT≤150 MPa.

39. The strengthened glass article of claim 38 , wherein the CSs>300 MPa.

40. The strengthened glass article of claim 38 , wherein the CSs/DOL ratio is in a range from 3 MPa/μm to 12 MPa/μm.

41. The strengthened glass article of claim 38 , wherein the CSs≥350 MPa.

42. The strengthened glass article of claim 38 , wherein the thickness t≤0.9 mm.

43. The strengthened glass article of claim 38 , wherein the DOL is in a range from 0.1t to 0.3t, where DOL is expressed in mm.

44. The strengthened glass article of claim 38 , wherein the strengthened glass has at least a 60% survival rate when dropped in a drop test from a height of at least 100 cm onto a drop surface comprising 180 grit alumina sandpaper utilizing a uniform drop rate procedure, wherein the survival rate is based on testing at least 5 samples.

45. The strengthened glass of claim 44 , wherein the strengthened glass is incorporated into an electronic device.

46. The strengthened glass article of claim 45 , wherein CSD is at least 50 MPa.

47. A strengthened glass, the strengthened glass comprising:

a thickness t≤1 mm,

an inner region under a central tension CT, and

at least one compressive stress layer under a compressive stress CS, the compressive stress layer extending from a surface of the glass to a depth of compression, p 1 wherein the strengthened glass article has a stress profile such that a compressive stress CSD at an intermediate critical depth of 50 μm below the surface of the strengthened glass article is at least 10% of a compressive stress at the surface CSs,

wherein the strengthened glass comprises 0 mol % Li2O, and

wherein the strengthened glass has at least a 60% survival rate when dropped in a drop test from a height of at least 100 cm onto a drop surface comprising 180 grit alumina sandpaper utilizing a uniform drop rate procedure, wherein the survival rate is based on testing at least 5 samples.

48. The strengthened glass of claim 47 , wherein the strengthened glass is incorporated into an electronic device.

49. The strengthened glass of claim 47 , wherein the strengthened glass a 60% probability of withstanding fracture when the strengthened glass contacts the drop surface at a flat angle, at a non-flat angle, or both.

50. The strengthened glass of claim 49 , wherein the non-flat angle is 30° relative to the drop surface.