| 摘要 |
PURPOSE:To prolong the life of a disk and to make stable and excellent reproduction possible by preventing the surfce of the disk from getting uneven in rotation of the disk by increasing its thickness in a recording area gradually from the circumferential part to the center part. CONSTITUTION:Disk D has group guard B (B') coming into airtight contact with the top surface of the outer circumferential support part of the turntable (not shown in the figure) at the outermost circumferential part and group guide A (A') coming into contact with tight contact with the top of the inner circumferential support part of the turntable in the center, and disk D is absorbed into the back room constituted between it and the turntable. To compensate the extent of depression in disk D in this case, the thickness of disk D in recording area 1 (including recorded part 2 and unrecorded part 3) is increased gradually from circumferetial part t1 to center part t2. When the extent of projection is t2-t1/2, the sliding contact of the reproducing stylus with disk D is excellent at any position in the recorded area and the reproduction of disk D can be stabilized. |
