GLASS SUBSTRATE FOR MAGNETIC RECORDING MEDIUM AND METHOD OF MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a glass substrate for magnetic recording medium which is capable of preventing the failure of a magnetic disk and a method of manufacturing the same. SOLUTION: The glass substrate 100 for the magnetic recording medium of a doughnut shape has a chamfered surface 104a for connecting a main surface 101a and an outer peripheral surface 102. The chamfered surface 104a consists of an annular curved surface part 104a' and a conical surface part 104a" connected to each other. The percentage ratio of the length d1 of the external form line of the annular curved surface part 104a' to the length L of the external form line 200 of the chamfered surface 104a at the section of the glass substrate 100 inclusive of a central line 106 of the glass substrate 100 is >=20%. The radius R of curvature of the annular curved surface part 104a' is 0.10 to 0.50 mm. The angleθformed by the main surface 101a and the conical surface part 104a" is 136 to 165 deg..