| 摘要 |
PURPOSE:To uniformize the recording sensitivity over the entire surface of a disk and reproduction C/N by decreasing the film thickness of a transparent interference layer from the inside peripheral side to the outside peripheral side along the radial direction of the disk. CONSTITUTION:An SiN film is provided as a transparent interference layer 2 on a polycarbonate substrate formed by providing spiral guide grooves at 2mum pitch on a disk-shaped transparent resin substrate 1 and a recording layer 3 consisting of an RE-TM film and TbCo film having 30nm film thickness is formed thereon. Further, the 2nd interference layer 4 consisting of an SiN film having 100nm film thickness and a light reflective layer 5 consisting of an Al film having 50nm film thickness are successively laminated thereon. The transparent interference layer 2 has the film thickness in the recording area decreased uniformly from the inside peripheral side toward the outside peripheral side in the radial direction of the disk. The threshold temp. of recording is thereby relatively decreased on the outside peripheral side where the supply energy density is relatively small. The recording density and reproduction C/N are thus uniformized.
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