| 摘要 |
PROBLEM TO BE SOLVED: To secure reliability in the outer and inner edge part of a disk susceptible to stripping, by making the external size of a light transmitting cover layer, which is stuck together with a substrate, smaller than that of the substrate. SOLUTION: Since the outer diameter of a light transmitting cover layer 2 is formed smaller than that of a substrate 1, the part stuck together is not exposed to the outer peripheral end face of a disk. As a result, a shock imparted to the disk end face is not directly transmitted to the stuck part. Consequently, this structure increases strip resistivity of the cover layer 2 against a shock imparted to the disk end face. Further, since the inner diameter of the cover layer 2 is formed larger than that of the substrate 1, the stuck part is not exposed to the inner peripheral end face of the disk. As a result, the cover layer 2 is less susceptible to stripping due to a possible contact in chucking the disk. In this case, the inner edge part is provided with an area where the substrate is exposed; therefore, chucking with this area enables highly accurate chucking. |
