GLASS AND CHEMICALLY STRENGTHENED GLASS
A glass includes, as represented by mole percentage based on oxides, from 60% to 68% of SiO 2 , from 8 to 12% of Al 2 O 3 , from 12 to 20% of Na 2 O, from 0.1 to 6% of K 2 O, from 6.4 to 12.5% of MgO, and from 0.001 to 4% of ZrO 2 . In the glass, a total content of B 2 O 3 , P 2 O 5 , CaO, SrO, and BaO is from 0% to 1%. The glass satisfies 2×Al 2 O 3 /SiO 2 ≦0.4 and 0<K 2 O/Na 2 O≦0.3.
1 . A glass comprising, as represented by mole percentage based on oxides, from 60 to 68% of SiO 2 , from 8 to 12% of Al 2 O 3 , from 12 to 20% of Na 2 O, from 0.1 to 6% of K 2 O, from 6.4 to 12.5% of MgO, and from 0.001 to 4% of ZrO 2 , wherein a total content of B 2 O 3 , P 2 O 5 , CaO, SrO, and BaO is from 0 to 1%, and the glass satisfying 2×Al 2 O 3 /SiO 2 ≦0.4 and 0<K 2 O/Na 2 O≦0.3.
2 . The glass according to claim 1 , wherein Li 2 O is substantially not contained.
3 . The glass according to claim 1 , wherein a total content of B 2 O 3 and P 2 O 5 is equal to or less than 0.2%.
4 . The glass according to claim 1 , wherein a total content of SiO 2 , Al 2 O 3 , MgO, CaO, ZrO 2 , Na 2 O, and K 2 O is equal to or more than 98.5%.
5 . The glass according to claim 1 , wherein SnO 2 is substantially not contained.
6 . The glass according to claim 1 , wherein Sb 2 Os 3 and As 2 O 3 are substantially not contained.
7 . The glass according to claim 1 , wherein the glass is produced through annealing in which an average cooling rate is from 20° C./min to 200° C./min.
8 . The glass according to claim 1 , wherein a temperature (T2) at which a viscosity is 10 2 dPa·s is equal to or lower than 1,700° C.
9 . The glass according to claim 1 , wherein a coefficient of thermal expansion in a temperature range of from 50 to 350° C. is equal to or less than 100×10 −7 ° C. −1 .
10 . The glass according to claim 1 , wherein the glass is a glass sheet having a sheet thickness of 1.5 mm or less.
11 . The glass according to claim 1 , wherein when a surface compressive stress of a chemically strengthened glass obtained by performing an ion exchange treatment on a glass sheet having a sheet thickness of 0.7 mm at 425° C. for 6 hours using a molten salt which includes 100 mass % of potassium nitrate is set as CS 1 , and a surface compressive stress of a chemically strengthened glass obtained by performing an ion exchange treatment on a glass sheet having a sheet thickness of 0.7 mm at 425° C. for 6 hours using a molten salt which includes 5 mass % of sodium nitrate and 95 mass % of potassium nitrate is set as CS 2 , a ratio CS 2 /CS 1 of CS 2 to CS 1 is equal to or more than 0.65.
12 . The glass according to claim 1 , to which a chemical strengthening treatment is applicable.
13 . A chemically strengthened glass which is obtained by chemically strengthening the glass according to claim 12 .
14 . The chemically strengthened glass according to claim 13 , wherein a thickness of a compressive stress layer formed in a surface of the chemically strengthened glass is equal to or more than 10 and a surface compressive stress is equal to or more than 200 MPa.