| 摘要 |
PURPOSE:To suppress the deterioration of a recording layer due to a reproducing light by providing a recording layer by using as a main constituent in organic coloring matter having a peak of spectral reflectance in the vicinity of the wavelengths of recording and reproducing lights, and providing a protective layer by use of a coloring material having an absorption peak in the vicinity of the wavelengths of the recording and reproducing lights and a heat-softenable resin. CONSTITUTION:A recording layer, in which information can be recorded by causing some optical change by irradiation with laser light, comprises a croconium-type dye or the like as a main constituent. The film thickness of the recording layer is set at such a value that reflectance of the layer is maximized at the wavelength used. The value is determined depending on the birefringence of the recording layer, and is not determined unconditionally, but is about 100Angstrom to 10mum. A coloring material (a dye, a pigment, a metal, a metallic compound or the like) having an absorption peak in the vicinity of the wavelengths of lasers used and a heat-softenable resin, e.g., polymethyl carbonate or polycarbonate, for maintaining or enhancing sensitivity and C/N are desirably used in a protective layer. The mixing ratio of the coloring material to the heat-softenable resin in the protective layer is preferably from 5/95 to 70/30 (by weight). |
