| 摘要 |
PROBLEM TO BE SOLVED: To control the cooling speed of a recording layer and to improve margins for recording linear velocity and recording power by defining the volume resistivity of a reflection layer of a phase transition medium within a specified range. SOLUTION: A lower part protection layer 2, a phase transition type recording layer 3, an upper part protection layer 4 and the reflection layer 5 whose film thickness is >=40 nm and <=300 nm, and the volume resistivity is >=20 nΩ.m and <=150 nΩ.m are provided on a substrate 1 in this order. The thickness of the recording layer and the protection layers are selected also considering an optical interference effect accompanying to multilayer constitution. At this time, by using the reflection layer of a low volume resistivity, the linear speed margin and the recording power margin are improved. Particularly, when the upper part protection layer 4 is made relatively thick such as >=30 nm, a remarkable effect is obtained. Then, in recording/reproducing, etc., in a low linear speed, by combining the reflection layer 5 of the remarkably low volume resistivity with the thickened upper part protection layer 4, a phase difference by a phase transition can be used effectively, and recording sensitivity and linear speed dependency can be improved. |
