Patent ID: 7482049
Filing Date: 2009-01-27
Classification: G11B,Y10T

Abstract:
1. An optical disc comprising: a disc-like support base; and at least one disc-like information-retrieval layer having an almost same size as the support base and formed over the support base, the information-retrieval layer being thinner than the support base and made of a sheet cut out from a roll of a sheet material and cut into a disc-like sheet before formed over the support base so that the disc-like sheets exhibits a two-cycle variation in birefringence within ±20 nmpp (nano meter peak to peak) under double-pass measurements during one disc rotation, wherein the information-retrieval layer at least having a hard-coat layer, and variation in reproduced output of 15% or lower obtained by dividing a difference between maximum and minimum outputs by the minimum output.