MEDIUM FOR OPTICAL DISK, MANUFACTURING METHOD OF MEDIUM FOR OPTICAL DISK AND SHIFTED GRAVITY CENTER ANGLE MEASUREMENT DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a medium for an optical disk having high line productivity while following changes of a direction and an amount of imbalance of a substrate in a molding step and holding rotation stability even when being rotated at high speed as the optical disk.

SOLUTION: In the medium for the optical disk having front and rear both surfaces, wherein a front substrate 1 and a rear substrate 2 have reference marks 4 formed by molding of signal recording original plate, shifted gravity center angles from the reference marks 4 are respectively measured and the front substrate 1 and the rear substrate 2 are stuck to each other so that the shifted gravity center angle θAof the front substrate 1 and the shifted gravity center angle θBof the rear substrate 2 are nearly reversed.

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