Optical recording medium having bca of write-once information

Abstract

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 () is formed on a disk substrate () with a dielectric layer () inbetween. Then, an intermediate dielectric layer () and a reflecting layer () are successively laminated upon the recording layer (), and an overcoat layer () is formed on the surface of the reflecting layer (). A plurality of BCA (one of write-once identification information systems) sections (and) are recorded by lowering the vertical magnetic anisotropy of the recording layer (). At the time of reproduction, the write-once information is detected from differential signals.