| 摘要 |
PROBLEM TO BE SOLVED: To enable recording and erasure with laser light having a relatively large spot diameter by regulating the ratio of the thickness of a recording layer to the spot diameter of laser light to a specified value or below. SOLUTION: A 1st interference film 2, a recording film 3, a 2nd interference film 4, a reflecting film 5 and an org. protective film 6 are successively formed on a glass substrate 1. The thickness (d) of the recording film 3 is regulated to 3/100 of 1μ spot diameter (ϕ) of laser light, that is, 30nm. When the resultant optical disk 8 is irradiated with laser light, in accordance with the increase of the ratio (d/ϕ) of the thickness (d) to the spot diameter (ϕ), the film 3 becomes less liable to conversion into an amorphous film and the ratio in variation of reflectance before and after the irradiation is reduced. It is necessary to regulate the ratio (d/ϕ) to <=0.1 because >=35% ratio in variation of reflectance necessary for practical use is not attained in the case of >0.1. In the case of 0.03, the area of the heated part of the film 3 in the plane direction is larger than that in the thickness direction, the heat radiating effect of the film 3 between the films 2, 4 is enhanced in spite of the low heat conductivity of the film 3 and the film 3 can be converted into an amorphous film to attain a high signal level. |
