GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM, METHOD FOR MANUFACTURING GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM, AND INFORMATION RECORDING MEDIUM

摘要

Provided are a glass substrate for an information recording medium, which has both high strength and high flatness and can be manufactured at low cost, a method for manufacturing such glass substrate and an information recording medium using such glass substrate. The glass substrate for the information recording medium satisfies inequalities of 0.1=(W1-W3)/W2=5, where, W1 is an ion concentration at the center portion in the thickness direction of the glass substrate in a chemically reinforced region at the outer circumference end surface and the inner circumference end surface of the glass substrate and is the maximum value of K<SUP>+</SUP> ion concentration, W2 is a Na<SUP>+</SUP> ion concentration at a position where the K<SUP>+</SUP> ion concentration is maximum, and W3 is a K<SUP>+</SUP> ion concentration in a glass substrate region not chemically reinforced.