Multi-layer CD disc

Application Number: 00108297
Application Date: 2000.02.04
Publication Number: 1268743
Publication Date: 2000.10.04
Priority Information: 1999/2/12 JP 035086/1999
International: G11B7/24
Applicant(s) Name: Sony Corp.
Inventor(s) Name: Yasuda Koichi;Kurokawa Kotaro
Patent Agency Code: 11038
Patent Agent: wang yonggang
Abstract A multi-layered optical disc having its recording unit comprised of plural information recording layers, with the interposition of a transparent layer, to form a recording unit, a light transmitting protective layer is formed on the recording unit. 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<1> and an extinction coefficient kc<1> in the crystallized state and a refractive index na<1> and an extinction coefficient ka1 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 (nc1/na1)<=12, (kc1/ka1)<=12 and (kc1/ka1)<=5 , (nc1/na1) where the cases of kc1/ka1<=1 and nc1/na1<=1 are excluded.