| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a glass substrate of a magnetic disk capable of improving fluttering of the magnetic disk at high speed rotation, and a magnetic disk thereof.SOLUTION: The glass substrate of a magnetic disk has a circular hole (inner hole) 2 at the center, a pair of main surfaces, and a side wall surface perpendicular to the main surfaces. A circularity of the circular hole is 1.5μm or less, and a difference between the largest value and the smallest value of radiuses of three inscription circles obtained with contour lines in circumferential directions at three positions A to C on the side wall surface of the circular hole which are apart from each other by 200μm in the substrate thickness direction is 3.5μm or less.</p> |
