| 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 49.1 μm or less, and that assuming that an angle between the main surface and compressive stress in the stress profile by a Babinet compensator method is &thetas;, a value y of {12·t·ln(tan &thetas;)+(49.1/t)} is the penetration length in the uppermost-portion stress layer or less.
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