Glass substrate for information recording medium and magnetic information recording medium to which the glass substrate is applied

摘要: Disclosed are a glass substrate for an information recording medium, having excellent scratch resistance and light weight high fracture toughness, the fragility index value, measured in water, of 12 μm−1/2 or less atmosphere dew point −5° C. lower, 7 less, comprising, by mol %, 40 to 75% SiO2, 2 45% B2O3 and/or Al2O3 0 40% R′2O which R′ is at least one member selected from group consisting Li, Na K), wherein total content B2O3, 90 magnetic medium comprising layer formed on substrate.