High density disc with protruding portion in succession area.

摘要

An optical disc (20, 21, 22) for storing data having first and second surfaces, the second surface being an entrance surface with respect to a light beam for recording or reproduction and being parallel to the first surface; an area fastener including first and second clamping surfaces; a first side having the first surface and the first clamping surface; a second side having the second surface and the second clamping surface; a center plane (c) which is located in the middle between the first surface and the second surface; a central hole having a predetermined diameter; and a recording layer which is located between the center plane (c) and the second surface, wherein the clamping area has a protruding portion on the first clamping surface, wherein the clamping area of ​​the projecting portion has a first and second thicknesses (P1, P2) measured from the center plane of the disk (20, 21, 22), the first thickness (P1) measured in a direction extending from the center plane (c) of the disk (20, 21, 22) toward the first clamping surface of the clamping area and the second thickness (P2) measured in a direction toward the second clamping surface, wherein the first thickness (P1) is greater than the second thickness (P2) and in which the recording layer is located about 0.1 mm from the second surface.