| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical disk wherein deterioration of recording and reproducing characteristics is prevented to be highly maintained and damage on the surface of the disk can be prevented. <P>SOLUTION: A first disk substrate 12 having a first recording layer 12A having a first recording density and a second disk substrate 14 having a second recording layer 14A having a recording density higher than the first recording density are stuck to each other to form the optical disk D. When a region from a center axis of the first and the second disks to a prescribed radius position is defined as a first region and a region from the prescribed radius position to the outer peripheral end is defined as a second region, the first region of the second disk substrate is specified to be an information recording region IA wherein its thickness is in the range of the specification in the recording system of the second recording density, the second region of the second disk substrate is specified to be a blank region WA wherein its thickness is out of the range of the specification and thinner than the thickness of the first region and information is not recorded and sum total thickness of the first and the second disk substrates is made to be a uniform value of ≤1.5 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
