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.