| 摘要 |
PURPOSE:To obtain an optical disk which has a RAM part and ROM part and excels in reliability and mass productivity by forming the same information recording medium to the RAM part and ROM part and putting only the ROM part recorded with fixed information in the recording state. CONSTITUTION:Rugged parts 20 are provided on a PMMA substrate 10 and the fixed information by pits is preliminarily formed in the rugged parts 20 in the ROM part. Guide grooves for making tracking in the recording state and address pits which are address information are preliminarily formed in the rugged parts 20 in the RAM part. A mask 21 imposed on the optical disk 24 and a xenon lamp 19 is made to emit light. The information recording layer in the ROM part of the disk 24 is put into the recording state by the irradiation rays 20 thereof. The optical disk in which the RAM part and ROM part co-exist is thus easily obtd. and an expansion in the system for applying the optical disk is made possible.
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