| 摘要 |
PROBLEM TO BE SOLVED: To provide a disk substrate for an information recording medium having sufficiently high Young's modulus compared to aluminum without impairing surface flatness and an information recording medium using the disk substrate. SOLUTION: The glass substrate for an information recording medium has a composition of (expressed by mol.%) 0-25% SiO2 , 20-60% B2 O3 , 0-30% Al2 O3 , 0-35% CaO+MgO+ZnO, 0.5-30% at least one kind of rare earth oxide and 0-15% ZrO2 +TiO2 . The information recording medium has the glass substrate and a recording layer formed on the glass substrate and a magnetic disk has the glass substrate and the magnetic recording layer formed on the glass substrate. |
