Patent ID: 7820234
Filing Date: 2010-10-26
Classification: G11B

Abstract:
1. A method of manufacturing an optical information recording medium to/from which signals can optically be recorded and reproduced, the recording medium comprising a signal substrate, a signal recording layer on one principal surface of the signal substrate, and a transparent cover layer, the transparent cover layer including a first transparent layer formed on the signal recording layer and a second transparent layer that is formed on the first transparent layer and is harder than the first transparent layer, signals being recorded and reproduced to and from the recording medium by a light transmitted to the signal recording layer through the transparent cover layer, the method comprising: forming the first transparent layer so that at least one part of the first transparent layer has a first distribution of thickness which has a thickness gradient in a radial direction; and forming the second transparent layer so that variations in thickness of the transparent cover layer are within ±3 μm wherein the second transparent layer has a thickness of T′