The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 28, 2003
Filed:
Feb. 04, 2000
Koichi Yasuda, Tokyo, JP;
Kotaro Kurokawa, Kanagawa, JP;
Sony Corporation, Tokyo, JP;
Abstract
A multi-layered optical disc having its recording unit comprised of plural information recording layers, in which two or more information recording layers are layered on a substrate 0.3 to 1.2 mm in thickness, with the interposition of a transparent layer, to from a recording unit, a light transmitting protective layer is formed on the recording unit to a thickness of 10 to 177 &mgr;m, and in which the light is illuminated from the side of the light transmitting protective layer to effect recording and/or reproduction of information signals. At least one of the information recording layers except the information recording layer formed at a remotest position from the light transmitting protective layer has a phase change material as a recording material. A refractive index nc and an extinction coefficient kc in the crystallized state and a refractive index na and an extinction coefficient ka in the amorphous state of the phase change material constituting the first information recording layer as counted from the light transmitting protective layer satisfy the relationship of (nc /na )≦12, (kc /ka )≦12 and (kc /ka )≦5 (nc /na ), where the cases of kc /ka <1 and nc /na <1 are excluded.