Glass with high surface strength
Embodiments of alkali aluminosilicate glass articles that may be chemically strengthened to achieve a maximum surface compressive stress that exceeds compressive stresses that have been achieved in similar glasses are disclosed. In one or more embodiments, the fictive temperature of these glass articles may be equal to the 10 11 poise (P) viscosity temperature of the glass article. In some embodiments, the strengthened alkali aluminosilicate glass articles described herein may exhibit a maximum compressive stress of at least about 400 MPa, 800 MPa, 930 MPa or 1050 MPa. In some embodiments, the strengthened alkali aluminosilicate glass articles described herein may exhibit a compressive stress layer extending to a depth of layer of at least about 40 μm (in samples having a thickness of 1 mm). In still other embodiments, these strengthened alkali aluminosilicate glass articles exhibit a parabolic or near-parabolic tensile stress profile in the central region of the glass articles.
1. An alkali aluminosilicate glass article comprising: a thickness t, a compressive stress layer extending from a surface of the alkali aluminosilicate glass to a depth of layer (DOL), and a central region comprising a maximum tensile stress, wherein the central region extends from the DOL, and wherein the alkali aluminosilicate glass is free of B 2 O 3 and comprises at least about 58 mol % SiO 2 , from about 0.5 mol % to about 3 mol % P 2 O 5 , from 15 mol % to 20 mol % Al 2 O 3 , from 6 mol % to 18 mol % Na 2 O, and from 0.1 mol % to 10 mol % Li 2 O, wherein the ratio of the amount of Li 2 O (mol %) to Na 2 O (mol %) (Li 2 O/Na 2 O) is less than 1.0, wherein the DOL is less than or equal to 0.25*t, and wherein the maximum tensile stress is about 35 MPa or greater.
2. The alkali aluminosilicate glass article according to claim 1 , wherein the glass article further comprises a tensile stress profile in the central region, wherein the tensile stress profile is substantially parabolic.
3. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises a fictive temperature T f that is equal to a temperature at which the alkali aluminosilicate glass article has a viscosity of 10 11 Poise.
4. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises a zircon breakdown viscosity of less than about 35 kPoise.
5. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises a liquidus viscosity of at least 200 kPoise.
6. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises a ratio R 2 O (mol %)/Al 2 O 3 (mol %) that is less than 2, where R 2 O═Li 2 O+Na 2 O.
7. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises a total amount of SiO 2 and P 2 O 5 that is greater than 65 mol % and less than 67 mol % (65 mol %<SiO 2 (mol %)+P 2 O 5 (mol %)<67 mol %).
8. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises a relationship R 2 O (mol %)+WO (mol %)−Al 2 O 3 (mol %)+P 2 O 5 (mol %) that is greater than about −3 mol %, wherein R 2 O=the total amount of Li 2 O and Na 2 O present in the alkali aluminosilicate glass article and WO is a total amount of divalent metal oxides present in the alkali aluminosilicate glass article.
9. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises from about 58 mol % to about 65 mol % SiO 2 ; from 0 mol % to about 6 mol % MgO; and from 0 mol % to about 6 mol % ZnO.
10. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article comprises P 2 O 5 in an amount in a range from about 0.5 mol % to about 2.8 mol %.
11. The alkali aluminosilicate glass article according to claim 1 , wherein the alkali aluminosilicate glass article is free of K 2 O.