| 摘要 |
PROBLEM TO BE SOLVED: To obtain a large-capacity medium by specifying the intervals of the tracks of the phase transition optical disk medium formed with the groove parts of a recording layer and the tracks for recording information in the inter-groove parts by groove- like rugged shapes to a specific range and specifying the ratio of the optical reflectivity of the recording layer when the recording layer is the crystal phase of a phase transition film and when the layer changes to an amorphous phase to a specific value or below. SOLUTION: When the intervals of the tracks of the optical disk medium are specified to 0.54 to 0.64 μm and the optical reflectivity of the recording layer when the phase transition film is the crystal phase is defined as 1, the ratio of the optical reflectivity of the recording layer when the phase transition film changes to the amorphous phase is specified to <=0.35. The recording layer 3 comprises a lower interference layer 4 of a dielectric substance, etc., the phase transition film 5 for recording the information marks by the phase transition between the crystalline phase and the amorphous phase, an upper interference layer 6, such as dielectrics and a reflection layer 7 essentially consisting of aluminum, etc. The inter-groove parts and groove widths shown by the radial section 1a of the optical disk are previously formed at the substrate 2, by which a land-and-groove structure is formed. |
