Optical disk with a uniform film thickness by having different angles of inclination for the side surfaces of grooves

摘要

An optical disk including a substrate having a circular shape and a recording film on which information is recorded formed on the substrate. The substrate includes grooves formed in a concentric circular shape or spiral shape, the grooves including a first groove having a specific radially positioned circumference on the substrate, second grooves formed circumferentially inside the first groove, and third grooves formed circumferentially outside the first groove. At least an outer circumferential side surface of the second grooves have a taper with an angle of inclination of the outer circumferential side surface being smaller than the angle of inclination of an inner circumferential side surface of the second grooves. At least an inner circumferential side surface of the third grooves have a taper with an angle of inclination of the inner circumferential side surface being smaller than an angle of inclination of an outer circumferential side surface of the third grooves, and the recording film covers the grooves. The optical disk provides land portions and groove portions having equal film thickness of the recording film.