CHEMICALLY STRENGTHENED GLASS, AND GLASS FOR CHEMICAL STRENGTHENING
A glass for chemical strengthening contains, in mole percentage on an oxide basis, 58 to 80% of SiO 2 , 13 to 18% of Al 2 O 3 , 0 to 5% of B 2 O 3 , 0.5 to 4% of P 2 O 5 , 4 to 10% of Li 2 O, 5 to 14% of Na 2 O, 0 to 2% of K 2 O, 0 to 11% of MgO, 0 to 5% of CaO, 0 to 20% of SrO, 0 to 15% of BaO, 0 to 10% of ZnO, 0 to 1% of TiO 2 , and 0 to 2% of ZrO 2 . A value of X is 30000 or more. The value of X is calculated based on the formula, X=SiO 2 ×329+Al 2 O 3 ×786+B 2 O 3 ×627+P 2 O 5 ×(− 941 )+Li 2 O×927+Na 2 O×47.5+K 2 O×(−371)+MgO×1230+CaO×1154+SrO×733+ZrO 2 ×51.8, by using the contents in mole percentage on an oxide basis of components.
1 - 7 . (canceled)
8 . A chemically strengthened glass sheet, comprising a glass which comprises, in mole percentage on an oxide basis, 58 to 72% of SiO 2 , 13 to 18% of Al 2 O 3 , 0 to 5% of B 2 O 3 , 0.5 to 4% of P 2 O 5 , 4 to 13% of Li 2 O, 7 to 14% of Na 2 O, 0 to 2% of K 2 O, 0 to 11% of MgO, 0 to 14% of CaO, 0 to 12% of SrO, 0 to 15% of BaO, 0 to 10% of ZnO, 0 to 1% of TiO 2 , and 0 to 2% of ZrO 2 , wherein:
the chemically strengthened glass sheet has a surface compressive stress (CS) of 450 MPa or more;
a compressive stress value (CS 90 ) in a portion at a depth of 90 μm from a surface of the chemically strengthened glass sheet is 25 MPa or more, or a compressive stress value (CS 100 ) in a portion at a depth of 100 μm from the surface is 15 MPa or more;
a depth d h of a portion at which a magnitude of an internal compressive stress of the chemically strengthened glass sheet reaches ½ of a surface compressive stress (CS) of the chemically strengthened glass sheet is 30 μm or less; and
a value of X is 30000 or more, the value of X being calculated based on the following formula by using contents in mole percentage on an oxide basis of components of SiO 2 , Al 2 O 3 , B 2 O 3 , P 2 O 5 , Li 2 O, Na 2 O, K 2 O, MgO, CaO, SrO, BaO, and ZrO 2 :
X=SiO 2 ×329+Al 2 O 3 ×786+B 2 O 3 ×627+P 2 O 5 ×(−941)+Li 2 O×927+Na 2 O×47.5+K 2 O×(−371)+MgO×1230+CaO×1154+SrO×733+ZrO 2 ×51.8.
9 . The chemically strengthened glass sheet according to claim 8 , wherein the chemically strengthened glass sheet has a thickness of 2 mm or less.
10 . The chemically strengthened glass sheet according to claim 8 , wherein a product (CS 100 ×t 2 ) of a compressive stress value CS 100 (MPa) in a portion at a depth of 100 μm from the surface and a square of a thickness t (mm) of the chemically strengthened glass sheet is 5 MPa·mm 2 or more.
11 . The chemically strengthened glass sheet according to claim 8 , wherein an area Sc (MPa-μm) of a compressive stress layer of the chemically strengthened glass sheet is 30000 MPa·μm or more.
12 . The chemically strengthened glass sheet according to claim 8 , wherein the depth d h is 8 μm or more.
13 . The chemically strengthened glass sheet according to claim 8 , wherein a depth of a compressive stress layer (DOL) of the chemically strengthened glass sheet is 110 μm or more.