Mitsubishi Chemical Corporation

Mitsubishi Kagaku Media Co., Ltd.

Natsuko Nobukuni

Michikazu Horie

Takashi Ohno

Masae Kubo

Haruo Kunitomo

Masao Komatsu

Masaaki Mizuno

Ken'Ichi Takada

Ken' Ichi Takada

An optical recording method for recording mark length-modulated information on a recording medium by using a plurality of recording mark lengths. The optical recording method comprises the steps of:

Optical recording method and optical recording medium

In a rewritable compact disc having a wobble groove on a substrate, crystal and amorphous states of a phase-change recording layer are an unrecorded/erased state and a recorded state, respectively. When the recording layer is exposed to recording light, amorphous marks assuming the recorded state are formed. At any of 2-, 4- and 8-times velocities with respect to a reference velocity (1-times velocity) whose linear velocity is 1.2-1.4 m/s, modulation mof a recorded signal when the recording light of approximately 780 nm in wavelength irradiates the recording layer via an optical system with NA=0.5 or 0.55 is 60-80%. A topmost level Rof reflectivity of the eye pattern of the recorded signal during retrieving at the 1-times velocity is 15-25%, and a jitter of the individual length of marks and inter-mark spaces during retrieving at 1-times velocity is 35 ns or less. Recording at 8-times or higher velocities is thereby realized without any risk of impairing the read-compatibility with the conventional CD-RW specifications at least at 4-times velocity.

Rewritable optical recording medium, recording method on the same, and optical disc recording/retrieving apparatus

In a rewritable compact disc having a wobble groove on a substrate, crystal and amorphous states of a phase-change recording layer are an unrecorded/erased state and a recorded state, respectively. When the recording layer is exposed to recording light, amorphous marks assuming the recorded state are formed. At any of 2-, 4- and 8-times velocities with respect to a reference velocity (1-times velocity) whose linear velocity is 1.2&#x2013;1.4 m/s, modulation mof a recorded signal when the recording light of approximately 780 nm in wavelength irradiates the recording layer via an optical system with NA=0.5 or 0.55 is 60&#x2013;80%. A topmost level Rof reflectivity of the eye pattern of the recorded signal during retrieving at the 1-times velocity is 15&#x2013;25%, and a jitter of the individual length of marks and inter-mark spaces during retrieving at 1-times velocity is 35 ns or less. Recording at 8-times or higher velocities is thereby realized without any risk of impairing the read-compatibility with the conventional CD-RW specifications at least at 4-times velocity.

Rewritable optical recording medium recording method on the same and optical disc recording/retrieving apparatus

Recording and retrieving method on rewritable optical recording medium

An optical information recording medium comprising a substrate, a recording layer, a protective layer containing a sulfur atom, an intermediate layer in contact with the protective layer and a reflective layer containing silver as the main component in contact with the intermediate layer, wherein the intermediate layer comprises an element which does not form a compound with silver, the element contained in the intermediate layer having a solid solubility of at most 5 atomic % to silver and silver having a solid solubility of at most 5 atomic % to the element contained in the intermediate layer, on the side in contact with the reflective layer, and the intermediate layer comprises an element less reactive to sulfur or its sulfide comprises chemically stable elements, on the side in contact with the protective layer.

Optical information recording medium

An optical information recording medium for recording, retrieving and erasing mark length-modulated amorphous marks, which comprises a substrate, and a lower protective layer, a phase-change recording layer, an upper protective layer and a reflective layer having a thickness of from 40 to 300 nm and a volume resistivity of from 20 to 150 n.OMEGA..multidot.m, formed in this sequence on the substrate.

An optical recording process for recording data on a recording medium of phase-change type employs laser power modulation scheme for mark-length modulation recording. The process selects one of pulse division schemes for modulating the laser power in accordance with a linear velocity on the disc. The recording laser includes m pulses for nT mark having a power level Pw and a duration of .alpha..sub.i T, with m intervals .beta..sub.i T sandwiched therebetween, wherein on condition that m=n-k and .SIGMA..alpha..sub.i +.SIGMA..beta..sub.i =n-j, .alpha..sub.i or bias power Pb.sub.i is changed in accordance with the linear velocity, Pb.sub.i being a bias power level for modulation, k and j being an integer and a real number, respectively, both selected between 0 and 2. A large range of the linear velocity margin can be obtained for the disc without changing either the composition of the phase-change material or multi layer structure on the disc.

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Kanagawa, Japan

Natsuko Nobukuni