| 摘要 |
PURPOSE: An optical disk combining high density/low density recording surfaces is provided to form a 0.6t high density signal recording surface in thickness on an outer circumference of one disk, and to form a 1.2t low density signal recording surface in thickness on an inner side of the disk, to perform a low density test on a central part, then to perform a high density test on the outer circumference. CONSTITUTION: An upper plate(31) mastering a low density signal and a lower plate(32) mastering a high density signal are bonded on the basis of a disk center. A low density signal recording surface(31a) is formed on an inner circumference of the upper plate(31). A high density signal recording surface(32a) is formed on an outer circumference of the lower plate(32). The upper plate(31) has a 1.2t low density disk structure in thickness on a central part, to be manufactured having a 0.6t high density disk structure in thickness on the outer circumference. The lower plate(32) is manufactured having a 0.6t high density disk structure in thickness.
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