| 摘要 |
PURPOSE:To improve the accuracy of an optical disk provided with a recording layer on a transparent substrate and to increase the lifetime thereof by specifying the heat conductivity and thermal deformation temp. of the substrate stock of the above-mentioned optical disk. CONSTITUTION:The transparent substrate 1 is formed by using 3 kinds of resins which are different in the heat conductivity and thermal deformation temp. and providing U-shaped tracking guide grooves thereto. The optical disk is formed by laminating a dielectric layer 22 consisting of the same stock as for the stock of the substrate 1, a recording carriage layer 21 and a protective layer 3 on said substrate. Such optical disk is subjected to the cycle withstand test to repeat recording, reproducing and erasing of signals at a specific linear speed and frequency and the change in the C/N thereof is measured after the specific number of cycles. As a result, the deterioration in the characteristics is low with the optical disk 1 for which the substrate 1 having >=105 deg.C thermal deformation temp. and <=4.6X10<-4>cal.cm<-1>.sec<-1>.K<-1> heat conductivity is used. The improved accuracy and the increased lifetime are, therefore, obtd. by using the stock having the high thermal deformation temp. and the low heat conductivity. |
