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