| 摘要 |
According to one embodiment, there is provided An optical disk including a first information layer (R1) having first guide grooves consisting of a first protrusive flat portion having a first width (X 1 ) formed close to the light incidence side and a first recessed flat portion having a second width (Y 1 ) having a first height difference (Z 1 ) from the first protrusive flat portion and formed close to the opposite side of the light incidence side, the first information layer being formed on the transparent substrate layer, a second information layer (R2) having second guide grooves consisting of a second protrusive flat portion having a third width (Y 2 ) formed close to the light incidence side and a second recessed flat portion having a fourth width (X 2 ) having a second height difference (Z 2 ) from the second protrusive flat portion and formed close to the opposite side of the light incidence side, the second information layer being formed on the adhesive layer, wherein a cycle P (µm) of the first and second guide grooves has a value ranging from 0.35 µm to 0.8 µm and has a relationship of Q 1 = 2Z 1 /(P - X 1 - Y 1 ), Q 2 = 2Z 2 /(P - X 2 - Y 2 ), 0.9 < Q 2 /Q 1 < 1.5, and 1 < X 1 /Y 1 < 4, 0.25 < X 2 /Y 2 < 1 is satisfied.
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