Patent ID: 7263055
Filing Date: 2007-08-28
Classification: G11B

Abstract:
1. A phase-change optical recording medium comprising a recording layer which comprises a phase-changeable recording material capable of being subjected to a phase-change by irradiation of an electromagnetic wave for recording and/or rewriting information, said medium is recorded by a recording method, said recording method comprising: modulating an input signal and conducting pulse width modulation recording; varying a recording linear velocity for said medium so as to perform multi-speed recording or CAV (constant angular velocity) recording, wherein (A) a recording pulse string for recording and rewriting information in the medium, corresponding to a zero (0) signal with a signal width nT, in which n is a positive integer, and T is a clock unit time, after the modulation of said input signal, is a continuous electromagnetic wave with a power level e, and (B) a recording pulse string for recording and rewriting information in the medium, corresponding to a one (1) signal with a signal width nT, in which n is a positive integer, and T is a clock unit time, after the modulation of said input signal, is an electromagnetic wave pulse string having: a front-pulse portion fp with a power level a and a pulse duration period x, a multi-pulse portion mp comprising a low-level pulse with a power level b and a high-level pulse with a power level c, with a duty ratio y, alternatively and an off-pulse portion op with a power level d and a pulse duration period z, in which x, y and z respectively satisfy 0.5T≦x≦2.0T, 0.125≦y≦0.875, and 0.125T≦z≦1.0T, and (a and c)≧e≧(b and d), wherein said duty ratio y is decreased as a recording linear velocity for said phase-change optical recording medium is increased, whereby multi-speed recording or CAV recording is carried out; and wherein said recording linear velocity, when said duty ratio y is a given ratio, is set in a range of more than (V H +V L )/2 to V H or less, that is, (V H +V L )/2< said recording linear velocity (when y=said given ratio)≦V H , wherein V H is a maximum recordable linear velocity and V L is a minimum recordable linear velocity.