| 摘要 |
PURPOSE:To decrease the burden on the optical disk device by using materials which is changed in crystallization time by compsn. as a recording film and changing the compsn. thereof radially, thereby forming the optical disk. CONSTITUTION:The compsn. of the information recording film of the phase change type optical disk is radially changed. The optical disk which is varied in the crystallization rate in the radial direction by changing the compsn. of the recording in the radial direction is obtd. if the material which is changed in the crystallization rate by the compsn. is used. The difference in cooling conditions occurring in irradiation with a laser at the time of rotation of the disk at a specified rotating speed is controlled by changing the compsn. of the recording film in the radial direction in such a manner. The need for controlling erasing conditions with high accuracy at every recording radius as with the conventional disks is, therefore, eliminated and the good erasing is executed under the specified conditions regardless of the radial position. |
