GLASS SUBSTRATE FOR MAGNETIC DISK AND MANUFACTURING METHOD OF THE SAME

摘要

A glass substrate for a magnetic disk of the invention is a disk-shaped glass substrate for a magnetic disk where the substrate has a main surface and end face and is subjected to chemical reinforcement treatment, and is characterized in that the penetration length in the uppermost-portion stress layer on the main surface is 49.1μm or less, and that assuming that an angle between the main surface and compressive stress in the stress profile by a Babinet compensator method isθ, a value y of {12·t·ln(tanθ)+(49.1/t)} is the penetration length in the uppermost-portion stress layer or less.