| 摘要 |
PURPOSE:To prevent generation of the cracks occurring in a change in external environment by specifying the film thickness of recording layers to a specific thickness or below to provide a gradient in the film thickness between the inside circumference and outside circumference and tightly sticking substrates to each other by means of an adhesive agent having a UV curing or anaerobic curing property. CONSTITUTION:A protective layer of ceramics, recording layer, and protective layer of ceramics, respectively having 800Angstrom film thicknesses are successively laminated on the light transmittable substrate 1 consisting of polycarbonate and a thin film 2 is formed thereon. The gradient is provided to the film thickness from the position of about 2mm from the outside circumference of the substrate 1 to about 2.4mm. Such substrates are then tightly stuck to each other by a UV curing resin 3. The stress exerted to the thin films 2 is relieved by the gradient provided to the thin films 2 at the time of curing by the irradiation of UV rays at this time, by which the generation of the cracks in the recording layers is prevented. |
