| 摘要 |
PROBLEM TO BE SOLVED: To permit making a signal in the lowest layer of a disk the maximum and to increase stored quantity of information by making almost same transmissivity of a half mirror layer in each information recording layer of continuously laminated N layers out of information recording layers other than information recording layers being apart from an incident plane the most almost, and setting it to a specific relation with absorptivity. SOLUTION: Transmissibity of a half mirror layer in each information recording layer of N layers continuously laminated is made t=(2N-2)×(1-a)/ (2N-1) assuming that absorptivity in each half mirror layer is (a). Thus, the smallest signal quantity out of signals obtained from each layer can be made the maximum by heightening reflectance of a lower layer of a multi-layer disk more than that of an upper layer. A surface border plane 11 of a transparent disk, a first information recording plane 12 in which polycarbonate resin is placed from a border plane, a first half mirror plane 13 deposited on the first information recording plane a second information recording plane 14, a second half mirror plane 15, and the like are successively formed, and the disk is constituted. |
