| 摘要 |
PROBLEM TO BE SOLVED: To obtain a glass substrate for a recording medium in improved productivity and in enhanced reliability without requiring an examination for measuring the flatness of the glass substrate after an ion exchange treatment by measuring the elongation of the glass substrate in its flat surface direction after the ion exchange treatment. SOLUTION: This method for producing a glass substrate for a recording medium comprises a process for molding a glass raw material to obtain a disk-like substrate and then polishing the glass substrate, a process for measuring the flatness of the polished glass substrate and then selecting the glass substrate having a prescribed flatness range, a process for subjecting the selected glass substrate to an ion exchange treatment, and subsequently a process for measuring the elongation of the ion- exchanged glass substrate to the defined dimension of the ion-nonexchanged glass substrate and then selecting the glass substrate having a prescribed elongation range on the basis of the relation of the flatness to the elongation and the strength. It is preferable that the selection range of the elongation of the ion-exchanged glass substrate to the defined dimension of the ion-nonexchanged glass substrate is 0.01-0.18%. The glass substrate preferably has an outer diameter of 10-95 mm and a thickness of 0.3-1.1 mm.
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