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AssigneeMitsubishi Chemical Corporation
InventorsMichikazu Horie, Takashi Ohno, Hideyuki Kubo, Masae Kubo, Hironobu Mizuno, Masaaki Mizuno, Haruo Kunitomo, Ken-Ichi Takada
Estimating the term…
An optical phase-change disc comprises a substrate having thereon a spiral groove or concentric grooves for guiding a focused light beam, and a layer structure including a recording layer and protective layers sandwiching therebetween the recording layer. The groove has wobble for recording ATIP (absolute time information) or ADIP (address information). The following relationship between the groove width GW, beam diameter R.sub.0 and wobble amplitude a.sub.w : 0.25.ltoreq.GW/R.sub.0 .ltoreq.0.45 or 0.65.ltoreq.GW/R.sub.0 ; and 0.03.ltoreq.a.sub.w /GW.ltoreq.0.08 hold for preventing distortion of the groove caused by repeated overwriting operation to improve reliability of the optical disc.
An optical disc comprising a substrate having thereon a spiral groove or concentric grooves for guiding a focused light beam and a land between each adjacent turns of said groove or between adjacent said grooves, at least a part of said groove or grooves having a wobble in accordance with a modulation signal and having a depth between 25 nm and 200 nm, and at least three layers including a lower protective layer having a thickness between 70 nm and 200 nm, a rewritable recording layer of phase-change type, and an upper protective layer having a thickness between 10 nm and 60 nm, wherein said wobble provides a wobble signal having a ratio of C/N which is not lower than 25 dB, and wherein parameters of said optical disc and the focused light beam satisfy the following relationship:
Dependencies are inferred from the claim text.