| 摘要 |
PROBLEM TO BE SOLVED: To provide a two-layered optical disk by sticking two sheets of disk substrates to each other dealing with medium density recording and higher density recording. SOLUTION: This optical disk is provided with first, second disk like disk substrates 31, 32 consisting of transparent synthetic resin, information recording layers consisting of translucent reflection films 34, 35 formed on one surfaces of respective disk substrates and transparent adhesive layer 32 sticking respective disk substrates to each other. The information recording layer of the first disk substrate 31 is higher density than the information recording layer of the other side second disk substrate 32, and the information recording layer 34 (high density recording layer) of the first disk substrate 31 is recorded and/or reproduced by optical parameters of λ<=460 nm, and N.A >=0.6, and the information recording layer 35 (medium density recording layer) of the second disk substrate 32 is recorded/reproduced at the optical parameters of 615 nm<=λ<=655 nm, and N.A.=0.6±0.05. |
