Patent ID: 6269070
Filing Date: 2001-07-31
Classification: G11B

Abstract:
A phase change type optical disc comprising a recording layer having a land and a groove to/from which an information signal is recorded/reproduced by a light having a wavelength .lambda. in .mu.m in an optical system having a numerical aperature NA,wherein the relationship 0.997.ltoreq..lambda./NA.ltoreq.1.250 is satisfied andwherein said groove has a bottom width W1 and an opening width W2, and a groove average width X in .mu.m expressed as follows:X=(W1+W2)/2wherein said groove has a depth Y in nm, X and Y satisfy the following relationships:Y.gtoreq.4736X.sup.2 -4764X+1239X.ltoreq.-0.000127Y.sup.2 +0.018624Y-0.075043X>0.40wherein the track pitch is in a range of about 0.8.+-.0.01 .mu.mand wherein said optical disc has a push-pull signal greater than or equal to 0.6 and a cross track signal greater than or equal to 0.1.