| 摘要 |
This invention provides an optical disk whose recorded information cannot be easily copied to other recording media, with practically no degradation of strength. The optical disk of this invention has a ring-shaped signal layer made of radiation curable resin on a transparent substrate, a reflective layer formed on this signal layer, and a protective layer formed on this reflective layer; moreover, the above mentioned signal layer has a peel strength against the above mentioned transparent substrate in the range of about 20/100 to about 80/100 according to the JIS-K5400 test method; and if the outer and inner diameters of the mentioned signal layer are represented by Os and Is respectively, the outer and inner diameters of the mentioned reflective layer are represented by Or and Ir respectively, and the outer and inner diameters of the mentioned protective layer are represented by Op and Ip respectively, these diameters satisfy the relationships, Os<Or<Op and Ip<Ir<Is.
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