| 摘要 |
An optical disk including first information layer having first guide grooves consisting of first protrusive flat portion having first width and first recessed flat portion having a second width having first height difference from the first protrusive flat portion, the first information layer being formed on the transparent substrate layer, second information layer having second guide grooves consisting of second protrusive flat portion having third width formed on second recessed flat portion having fourth width having second height difference, the second information layer, wherein cycle P (mum) of the first and second guide grooves has value ranging from 0.35 mum to 0.8 mum and has relationship of Q<SUB>1</SUB>=2Z<SUB>1</SUB>/(P-X<SUB>1</SUB>-Y<SUB>1</SUB>), Q<SUB>2</SUB>=2Z<SUB>2</SUB>/(P-X<SUB>2</SUB>-Y<SUB>2</SUB>), 0.9<Q<SUB>2</SUB>/Q<SUB>1</SUB><1.5, AND 1<X<SUB>1</SUB>/Y<SUB>1</SUB><4, 0.25<X<SUB>2</SUB>/Y<SUB>2</SUB><1 is satisfied.
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