METHOD OF MANUFACTURE OF GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM, METHOD OF MANUFACTURE OF MAGNETIC RECORDING DISK, AND MAGNETIC RECORDING DISK

摘要

A method of manufacture of a glass substrate for a magnetic recording medium, which has both high substrate strength and low alkaline elution, includes an etching process of etching the inner-edge face of a donut-shaped glass substrate having an aluminosilicate composition, formed by removing the center portion of a die-molded disc-shaped glass substrate, and an alkali sealing process of performing alkali sealing treatment by proton substitution of alkali ions in the surface layer of the etched donut-shaped glass substrate. The process is used to manufacture a magnetic recording medium incorporating a glass substrate having a total alkaline elution amount of less than 3.1 mug/disk, wherein the magnetic recording medium has a transverse rupture strength greater than 132 N.