| 摘要 |
PURPOSE:To obtain a stable mark length by providing the information recording medium with a recording layer which is changed in optical characteristics by irradiation of this layer with a light beam for recording and a reflection layer thereon and setting the reflectivity after recording higher than the reflectivity before recording. CONSTITUTION:A translucent metallic layer 11 is formed on a transparent substrate 10. A first protective layer 12, the recording layer 13, a second protective layer 14 and the reflection layer 15 are laminated on this metallic layer 11. Since the incident light from the substrate 10 side generates multiple reflections at the boundaries between the respective layers, the way of changing of the reflectivity varies with the thickness of the film 12. The reflectivity at the time of recording increases if the thickness of the layer 12 is 1000 to 1700 angstrom or 2800 to 3600 angstrom. The change rate of the reflectivity attains 22% which is max. if the thickness of the layer 12 is particularly 1500 angstrom or 3400 angstrom in such a case. Since the reflectivity in unrecorded parts is 20% at this time, the reflectivity of after recording eventually increases. Stable focusing is thereby made possible. |
