PURPOSE: To suppress the deformation of protective layers due to heat recording, erasing, etc., so as to improve recording and erasing characteristics and to stabilize the repetitive characteristics of recording and erasing by using a material formed by adding a small amt. of TiO2, to SiO2 as the protective layers.
CONSTITUTION: The 1st protective layer 2 consisting of a mixture composed of the SiO2 and the TiO2 a recording thin-film layer 3 consisting of Te-Ge-Sb, the 2nd protective layer 4 consisting of the same material as the material of the layer 2, and a reflection layer 5 consisting of an Al alloy are formed on a disk substrate 1 formed with grooves. A protective plate 7 is adhered by an adhesive 6. The thin films formed by mixing the TiO2 with the SiO2 are nearly zero in the coefft. of linear expansion and deformation is not generated by the repetition of recording and erasing. The movement of the recording film is not admitted.
OTA TAKEO
KAWAHARA KATSUMI
ISOMURA HIDEKI
