| 摘要 |
PURPOSE: A light record medium is provided to improve a characteristic while stabilizing a record and a reproduce by counterbalancing a difference of a wave length according to a variation of a thickness of a light transmission layer. CONSTITUTION: In the light record medium, a light transmission layer(12) is formed on an information record plane(11a) on which an information record pit is formed. The light record medium has a signal record region in which information is read by irradiating a laser beam from the light transmission layer through a lens system. The laser beam has a wave length(lambda) of lambda is greater than or equal 380nm and less than or equal 450nm, and a numerical aperture(N.A.) of the lens system is over 0.76. In the signal record region, a thickness(t) of the light transmission layer is set to 3 to 182 micrometer, a thickness irregularity(delta t) is set in a range of plus and minus; λ/(N.A.)¬4. A track pit(TP) of the information record plane is set in a range of 0.27 to 0.40 micrometer, a minimum pit length(Pmin) thereof is set in a range of 0.13 to 0.219 micrometer, a record line density(LD) is set to a pit string below about 0.146 micrometer/bit. A depth(D) of the information record pit is set in a range of 31 to 75 micrometer.
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