| 摘要 |
PROBLEM TO BE SOLVED: To realize a high C/N by changing a state of a recording film through projection of a laser light and also a state of grooves on a substrate, and making the change of amounts of reflected light in the same direction. SOLUTION: A recording film 2 is a phase transition type. When a laser light 3 is projected to a groove 15 thereby to crystallize, record information, a reflectance is increased because of the phase transition of the recording film 2, and the amount of reflected light at the reproduction time is increased. The groove 15 is melted and deformed by the laser light 3 to a groove 16, and a diffraction efficiency is increased. Owing to the increased diffraction efficiency in addition to the increased reflectance, the amount of reflected light is increased at the reproduction time, so that a level of information signals becomes high. When the laser light is projected to a flat face 17 thereby to perform amorphous recording, the reflectance of the recording film 2 is decreased because of the phase transition, and the amount of reflected light at the reproduction time is reduced. The face 17 is melted and deformed to a groove 18, the diffraction efficiency is lowered and the amount of reflected light is decreased. Since the information is recorded in a direction changed to a direction in which the amount of reflected light is decreased because of the deformation of the substrate 1 and change of the reflectance of the recording film 2, a higher signal level is obtained than when the information is recorded only by the change of the reflectance of the film 2. |
