| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and a device for reducing the contraction of the clamp part of an optical disk, wherein a distortion is reduced and efficient production is carried out. SOLUTION: The improved optical disk has a substantially transparent substrate, and includes an optical data structure constituted of a pit and a land in the outside of the clamp area of a disk on its one surface. In the clamp area, a protruded part structure is provided to protrude from a first surface, and accordingly a thickness for a clamp is provided, which is thicker than the thickness of the other part of the disk. Only a part of the clamp area is covered with the protruded part, thereby ensuring a thickness equivalent to that of a disk having thick clamp area. To reduce distortion generated by the contraction of a material, the amount of a material used for forming the protruded part is set less than 5% of the amount of a material used for forming the other clamp area. |
