| 摘要 |
PURPOSE:To prevent the deterioration in disk characteristics and to extend the life of the disk by specifying the bending modulus as the property of a substrate of the optical disk provided with a recording layer on a transparent substrate to a specific value or above and specifying the coefft. of linear expansion to a specific value or below. CONSTITUTION:The transparent substrate 1 is formed by using a polycarbonate resin and polymethyl methacrylate resin which are different in the bending modulus and coefft. of linear expansion and providing U-shaped tracking guide grooves thereto. The optical disk is formed by laminating a dielectric layer 22 consisting of nitride, a recording carrier layer 21 consisting of an amorphous film and a protective film 3 consisting of a UV curing resin on the substrate 1. These disks are exposed to specific force deterioration conditions and the change in the C/N thereof is measured after the specific number of date. As a result, the deterioration is hardly admitted with the disks for which the substrate 1 having >=2.4X10<4>kg/cm<2> bending modulus and <=6.5X10<-5>cm/cm.K coefft. of linear expansion is used. The deterioration in the characteristics of the disk is prevented and the life thereof is extended if the properties of the substrate are specified in the above-mentioned values. |
