GLASS FOR CHEMICAL STRENGTHENING AND CHEMICALLY STRENGTHENED GLASS
A glass for chemical strengthening contains, in terms of mol percentage based on oxides, SiO 2 : 60 to 67%, Al 2 O 3 : 9 to 13.5%, Na 2 O: 13.5 to 18.5%, K 2 O: 0.1 to 3%, MgO: 6 to 10.5%, and TiO 2 : more than 0% and 5% or less. The glass has a main surface and a back surface opposing the main surface. A tin content in the back surface is larger than a tin content in the main surface. A hydrogen concentration in a depth of 1 to 2 μm in a sheet thickness direction from a surface of the main surface is gradually decreased in a depth direction.
1 . A glass for chemical strengthening comprising, in terms of mol percentage based on oxides:
SiO 2 : 60 to 67%,
Al 2 O 3 : 9 to 13.5%,
Na 2 O: 13.5 to 18.5%,
K 2 O: 0.1 to 3%,
MgO: 6 to 10.5%, and
TiO 2 : more than 0% and 5% or less,
wherein the glass has a main surface and a back surface opposing the main surface, a tin content in the back surface is larger than a tin content in the main surface, and a hydrogen concentration in a depth of 1 to 2 μm in a sheet thickness direction from a surface of the main surface is gradually decreased in a depth direction.
2 . The glass for chemical strengthening according to claim 1 , wherein a hydrogen concentration in a depth of 1 to 2 μm in a sheet thickness direction from a surface of the back surface is gradually decreased in a depth direction.
3 . The glass for chemical strengthening according to claim 1 , wherein a hydrogen concentration in a depth of 1 to 10 μm in a sheet thickness direction from the surface of the main surface is lower than a hydrogen concentration in a depth of 1 to 10 μm in a sheet thickness direction from a surface of the back surface.
4 . The glass for chemical strengthening according to claim 1 , wherein a temperature T4 at which a viscosity of the glass reaches 10 4 dPa·s is 1255° C. or lower.
5 . The glass for chemical strengthening according to claim 1 , further comprising ZrO 2 in an amount of more than 0.11% and 4.0% or less in terms of mol percentage based on oxide.
6 . A chemically strengthened glass obtained by chemically strengthening the glass for chemical strengthening according to claim 1 .
7 . The chemically strengthened glass according to claim 6 , having a surface compressive stress (CS) of 900 MPa or more.
8 . The chemically strengthened glass according to claim 7 , having a depth of a compressive stress layer (DOL) of 30 μm or more.