| 摘要 |
PROBLEM TO BE SOLVED: To improve an erasure ratio by providing a multiple interference film adjacent to a recording film for utilizing a phase change on a substrate, allowing a function indicating the relationship between the power of laser beams being applied to the recording film and the reflection factor of an irradiation part where reproduction laser beams are applied to have an extreme value, and applying laser beams with a power where the reflection factor becomes the extreme value and crystallizing the recording film. SOLUTION: In an optical disk 20, an AIN film, an INSbTe phase change film, an Au film, and the AIN film are formed as a first interference film 6', a recording film 7, a reflection film 8, and a protection film 9, respectively, on a transparent glass substrate 5 by sputtering. A recording laser power operating point is set to 14mW. When an erasure laser power is set to 8-10mW where a reproduction laser beam reflection factor becomes an extreme value, the reproduction laser beam reflection factor does not change even if the degree of crystallization on erasure slightly changes, thus suppressing unerasure (a slight change in the degree of crystallization) on overwriting and improving an erasure ratio. |
