OPTICAL DISK, METHOD FOR RECORDING AND REPRODUCING WRITE-ONCE INFORMATION ON AND FROM OPTICAL DISK, OPTICAL DISK REPRODUCING DEVICE, OPTICAL DISK RECORDING AND REPRODUCING DEVICE, DEVICE FOR RECORDING WRITE-ONCE INFORMATION ON OPTICAL DISK, AND OPTICAL DISK RECORDING DEVICE

摘要

An optical disk storing write-once information usable for protecting the copyright of the software by preventing the duplication, unauthorized use, etc., of the software. In the optical disk, a recording layer (213) is formed on a disk substrate (211) with a dielectric layer (212) inbetween. Then, an intermediate dielectric layer (214) and a reflecting layer (215) are successively laminated upon the recording layer (213), and an overcoat layer (216) is formed on the surface of the reflecting layer (215). A plurality of BCA (one of write-once identification information systems) sections (220a and 220b) are recorded in the circumferential direction of the disk on the recording layer (213). The sections (220a and 220b) are recorded by lowering the vertical magnetic anisotropy of the recording layer (213). At the time or reproduction, the write-once information is detected from differential signals.