Patent ID: 8697592
Filing Date: 2014-04-15
Classification: B24B,C03C,G11B

Abstract:
1. A glass substrate for an information recording medium comprising, by mol %, greater than 65%, as a total, of SiO 2 and optionally B 2 O 3 and 2 to 20% Al 2 O 3 , 5 to 20% of RO in which R is at least one member selected from the group consisting of Mg, Ca, Zn, Sr and Ba, 0 to 28% of R′ 2 O in which R′ is at least one member selected from the group consisting of Li, Na and K, 0 to 10% of TiO 2 , 0 to 10% of ZrO 2 , 0 to 2% of Li 2 O and 0 to 2% K 2 O, the total content of said components being at least 95 mol %, the substrate having a fragility index value, measured in water, of 12 μm −1/2 or less and a chemically strengthened layer.