| 摘要 |
PURPOSE:To satisfy the standard of block error rate specified by the compact disk (CD) standard by specifying the pencil hardness, coefft. of thermal expansion and shrinkage rate of a protective layer. CONSTITUTION:The optical information recording medium 1 has a light- transmitting substrate 2, light-absorbing layer 3 formed on the substrate 2, light-reflecting layer 4 deformed on the light-absorbing layer 3, and a protective layer 5 formed on the light-reflecting layer 4. The coefft. of thermal expansion alphaof the protective layer 5 is specified to 1.5 X 10<-5> <= alpha <= 9.0 X 10<-5> (1/ deg.C) in the use environment temp. range of -15 deg.C to 70 deg.C, so that the protective layer 5 shows same thermal changes in volume as that of the substrate 2. Thereby, the optical information recording medium 1 as a whole has little warpage when heated. Thereby, reproduction signals which satisfy the CD standard can be obtained. |
