| 摘要 |
PROBLEM TO BE SOLVED: To enable the supply of a test disk which satisfies the standard of mass and has stable characteristics decreased in physical or electrical fluctuations even if the disk is formed by using material which is standardized in the mass relatively lighter with respect to the overall size like the disk of a DVD and has the specific gravity failing to satisfy the standard with respect to the overall size. SOLUTION: Glass is used as a substrate 11 of the information disk 1 and the side opposite to the side of the substrate 11 where light is made incident, i.e., a protective layer 13 side is provided with a spacer 2 for making the clamping thickness in the clamping region C of the information disk 1 larger than the thickness of the information disk 1. As a result, the standard of the mass may be satisfied even if the material which cannot satisfy the standard of the mass with respect to the overall size of the disk is used for the substrate. |
