| 摘要 |
PURPOSE:To contrive a single-plate structure with a smaller thickness while maintaining high sensitivity and high C/N by causing a light-reflecting layer to comprise a coloring matter film having a peak of light reflectance in the vicinity of the wavelengths of recording and reproducing lights, and specifying the film thickness of the light-reflecting layer at a value at which the film thickness-dependent reflectance at the wavelengths of recording and reproducing lights is maximized. CONSTITUTION:Upon irradiation with laser light, heat is generated more strongly, and mixing or dissolution of materials occurs at the interface between a light-absorbing layer 6 and a light-reflecting layer (coloring matter film) 3, whereby the clear interface is lost, snd an interference structure is broken. This causes a partial lowering in reflectance, resulting in recording. The light-reflecting layer, which reflects the laser light and is capable of recording information therein through some optical change effected by intense irradiation with laser light, comprises a croconium-type dye or the like as a main constituent. The film thickness of the light-reflecting layer is set at such a value that the reflectance of the layer is maximized at the wavelength of the light used. The value is determined depending on the birefringence of the light-reflecting layer, and is not determined unconditionally, but is preferably about 100Angstrom to 10mum. The light-absorbing layer is provided by use of a material which is of substantially the same kind as the material for the light-reflecting layer but which is superior to the material for the light-reflecting layer in light-absorbing capability at the wavelength of a recording light. |
