Chemically strengthened glass, substrate for information recording medium and information recording medium

Abstract

A glass for use in chemical reinforcement for use in a substrate of an information recording medium, having a composition comprising, denoted as mol %: SiO2 47 to 70% Al2O3 1 to 10% (where the total of SiO2 and Al2O3 is 57 to 80%) CaO 2 to 25% BaO 1 to 15% Na2O 1 to 10% K2O 0 to 15% (where the total of Na2O and K2O is 3 to 16%) ZrO2 1 to 12% MgO 0 to 10% SrO 0 to 15% (where the ratio of the content of CaO to the total of MgO, CaO, SrO, and BaO is greater than or equal to 0.5) ZnO 0 to 10% (where the total of MgO, CaO, SrO, BaO, and ZnO is 3 to 30%) TiO2 0 to 10% and the total content of the above-stated components is greater than or equal to 95%. A glass for use in chemical reinforcement for use in the substrate of an information recording medium employed in a perpendicular magnetic recording system, in which the glass exhibits the glass transition temperature is greater than or equal to 600° C. A substrate for use in an information recording medium consisting of the above glass and being chemically reinforced. A substrate for an information recording medium consisting of a chemically reinforced glass having a glass transition temperature of greater than or equal to 600° C. and exhibiting a bending strength following heating for two hours at 570° C. of greater than or equal to 15 kgf/mm2. An information recording medium comprising an information recording layer on the above substrate for an information recording medium. The present invention provides glass having both high thermal resistance and high strength, a substrate for use in information recording media comprised of this glass, and an information recording medium employing such a substrate.

Dependencies are inferred from the claim text.