PURPOSE: To decrease the interference of a servocontrol signal and a recording and reproducing signal by specifying the reflectivity of laser light irradiated to an optical disk, which is formed by providing a light absorptive thin film onto the rugged grooves of a substrate provided with the rugged grooves and providing a protective film on said film, from the substrate side of the disk and reflected from the film plane within a specific range.
CONSTITUTION: Rugged grooves 2 and rugged pits are formed on a resin substrate 3 made of polymethyl methacrylate (PMMA), etc. and a light absorptive thin film 1 of which the thermal state changes when irradiated with laser light is provided thereon and thereafter a protective layer film 4 is tightly formed over the entire surface thereof, by which an optical disk 5 having a center hole 5 is obtd. The reflectivity of light reflected from the film plane of the rugged grooves provided to such optical disk is so set as to attain 8W14%. A lower oxide of Te contg. ≥1 element among Ge, Sn, Se, S, In, Bi, Al, Cu and Sb is used for the film 1. The disk of which the fluctuation is smaller than the output control range 30% of a servocontrol system before and after recording and with which the recording and reproducing as well as tracking servocontrol are stable is thus obtd.
NAKAMURA TATSUSHI
TANIGAWA YASUHIKO
| JPS5862842A | 1983-04-14 |