Chemically strengthened glass and manufacturing method thereof
The present invention relates to a chemically strengthened glass having a thickness t (mm), in which a first-order derivative CS x ′ of a stress value CS x (MPa) is −4.7 or larger in a range of CS x ≥0 in a profile of the stress value CS x (MPa), in which the stress value CS x (MPa) is a function of depth×(μm) from a glass surface, and in which the stress value CS x (MPa) is measured by a scattered light photoelastic stress meter, and a manufacturing method thereof.
1. A chemically strengthened glass having a thickness t in mm, wherein a first-order derivative CS x ′ of a stress value CS x in MPa is −4.7 or larger in a range of CS x ≥ 0 in a profile of the stress value CS x in MPa,
wherein the stress value CS x in MPa is a function of a depth x in μm from a glass surface,
wherein the stress value CS x in MPa is measured by a scattered light photoelastic stress meter,
wherein a base composition of the chemically strengthened glass comprises, as represented by mol % based on oxides,
from 52 mol % to 75 mol % of SiO 2 ;
from 8 mol % to 20 mol % of Al 2 O 3 ;
5 mol % to 16 mol % of Li 2 O; and
8 mol % or less of Na 2 O, and
wherein a maximum stress value CS 90 at a depth 90 μm from a glass surface satisfies the following inequality:
CS 90 /{CT 2 ×( t− 2×DOL/1,000)}/ t≥ 1.62,
wherein t is the thickness in mm, CT 2 is a tensile stress in MPa and DOL is a compressive stress layer depth in μm.
2. The chemically strengthened glass according to claim 1 , wherein in the profile of the stress value CS x , a second-order derivative CS x ″ of the stress value CS x satisfies CS x ″≤0.050.
3. The chemically strengthened glass according to claim 1 , wherein a second-order derivative CS x ″ of the stress value CS x is greater than 0.
4. The chemically strengthened glass according to claim 1 , wherein the first-order derivative CS x ′ of the stress value CS x is 0 or smaller.
5. The chemically strengthened glass according to claim 1 , wherein in the profile of the stress value CS x in MPa, a stress value CS 0 at a glass outermost surface is 300 MPa or smaller.
6. The chemically strengthened glass according to claim 1 , wherein a maximum tensile stress CT 2 in MPa satisfies the following inequality:
CT 2 ≤19.5/( t/ 2−DOL/1,000),
wherein t is the thickness in mm and DOL is a compressive stress layer depth in μm.
7. The chemically strengthened glass according to claim 1 , wherein:
the chemically strengthened glass is a chemically strengthened glass obtained by a chemical strengthening of at least two steps; and
a maximum tensile stress CT 2 in MPa of the chemically strengthened glass is from 50% to 99% of a maximum tensile stress CT 1 in MPa of a chemically strengthened glass obtained after a first-stage chemical strengthening of the chemical strengthening of the at least two steps.