| 摘要 |
PURPOSE:To improve the flatness and also to decrease the weight inertial moment, by constituting a disk so that its thickness is made gradually thinner toward the outside circumference. CONSTITUTION:Thickness of magnetic recording disks 20, 30 and 40 is made gradually thinner toward the outside circumference linearly or curvedly, for instance, so that a doughnut-like disk having 168mm. inside diameter and 356mm. ouside diameter is formed, and thickness of the inside circumference and that of the outside circumference become 4mm. and 1.3mm. respectively. In this regard, external curves of the disk are shown in 21, 31 and 41. |
