| 摘要 |
PROBLEM TO BE SOLVED: To prevent deformation in a substrate such as warpage and shrinkage, to ensure satisfactory rotating performance and to attain satisfactory adaptation to the increase of recording density by laminating two or more 1st and 2nd resin layers which transmit incident light and comprise different materials different from each other in physical and/or mechanical characteristics to form the substrate. SOLUTION: A signal recording layer 3, a light reflecting layer 4 and a protective coat 5 are successively laminated on a substrate 2 to obtain the objective optical disk. The substrate 2 has a sandwich structure obtained by forming 1st and 2nd skin layers 6a, 6b on both principal faces of a core layer 7. The skin layers 6 are formed with a material having a lower water absorption than the core layer 7 so as to inhibit the warpage of the optical disk. The core layer 7 is formed with a material having a higher glass transition temperature and a larger mechanical internal loss than the skin layers 6 so as to inhibit the warpage of the optical disk even at a high temperature and to prevent the resonance phenomenon of the optical disk in rotation. |
