Optical disk, method for recording and reproducing write-once information on and from optical disk, otpical 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 ( 220 a and 220 b) are recorded by lowering the vertical magnetic anisotropy of the recording layer ( 213 ). At the time of reproduction, the write-once information is detected from differential signals.