Patent ID: 7595273
Filing Date: 2009-09-29
Classification: C03C,G11B

Abstract:
1. A glass substrate for an information recording medium, which is formed of a glass comprising SiO 2 , Al 2 O 3 , ZrO 2 , CaO, BaO, Li 2 O and Na 2 O as essential components and comprising, by mol %, 50 to 70% of SiO 1 to 10% of Al over 0% but not more than 12% of ZrO 2 to 24% of CaO, over 0% but not more than 15% of BaO, 0 to 2% of MgO, 0 to 15% of SrO, provided that the content of CaO+BaO+MgO+SrO is over 10% but less than 25%, over 0% but not more than 6% of Li over 0% but not more than 10% of Na 0 to 5% of K 0 to 10% of TiO wherein the glass has a glass transition temperature of 560° C. or higher.