Patent ID: 6580678
Filing Date: 2003-06-17
Classification: G11B

Abstract:
A rewritable compact disk having at least a phase-change recording layer (52) on a substrate (50), characterized in thata recordable, erasable and retrievable RAM area (105) and a ROM area (104) available only for retrieving are provided on the same disk surface, said phase-change recording layer is formed in each of said RAM area and said ROM area, a groove (61) having a wobble is made in said RAM area, and a crystalline portion of said phase-change recording layer is made as a non-recorded state/erased state while an amorphous portion thereof is made as a recorded state, with irradiation being carried out with recording light so that an amorphous mark is formed in said groove to record EFM information, in said ROM area, EFM information is recorded in the form of a pre-pit string (60), and when measured using a wavelength of 770 to 790 nm and an optical pickup whose objective lens numerical aperture is 0.49 to 0.51, a ratio |I1âˆ’I2|/|I1âˆ’I2|a of values of push pull signals before and after recording of an EFM signal in said RAM area is in a range from 1.05 to 2.0.