| 摘要 |
An optical disc of this invention is configured to be capable of dealing with both information in HD DVD and information in DVD. The optical disc is basically specified by the following items (1) to (7): (1) the optical disc is a single-sided dual layer optical disc where a light transmission layer, a first recording layer accessed with a first laser beam, an space layer, and a second recording layer accessed with a second laser beam are arranged in that order in the direction in which the laser beam enters, (2) the areal recoding density of the second recording layer is three times or more as high as that of the first recording layer, (3) identifying information which indicates that the first recording layer has been formed is formed in the second recording layer, (4) the distance in the light transmission layer from the incidence plane to the first recording layer is 550 mum or more, (5) the distance in the light transmission layer from the incidence plane to the second recording layer is 622 mum or less, (6) the reflectivity of the first recording layer with respect to the first laser beam is 45% to 65%, and (7) the reflectivity of the second recording layer with respect to the second laser beam is 15% to 29%.
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