Patent attributes
A single disc is configured to deal with both HD DVD information and DVD information. This invention has the following basic elements (1) 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 a laser beam enters, (2) the areal recoding density of the second recording layer is three times or more that of the first recording layer, (3) information indicating that the second recording layer has been formed is formed in the first recording layer, and (4) information indicating that the first recording layer has been formed is formed in the second recording layer.
