Patent ID: 6232036
Filing Date: 2001-05-15
Classification: G11B,Y10S

Abstract:
An optical disk for use at a recording/reproducing wavelength between 500 nm and 700 nm, comprising: a transparent substrate having a guide groove having a groove depth between 100 nm and 200 nm, a groove width between 0.2 .mu.m and 0.3 .mu.m and arranged with a pitch between 0.7 .mu.m and 1.0 .mu.m, defining a groove area and a land area; and a recording film, a metallic reflective film and a protective film consecutively formed on said transparent substrate, said recording film containing an organic pigment selected from the group of materials defined bv the following expressions: ##STR31##wherein X.sup.2 is a hydrogen atom, an alkyl group having 1 to 7 carbons or a cycloalkyl group having 3 to 7 carbons, and each of R.sup.1 and R.sup.2 is an alkyl group having 1 to 6 of carbons, methoxymethyl group, ethoxyethyl and M.sup.2+ represents a divalent ion of nickel, cobalt or copper, Y.sup.2 is hydroxyl group, carboxyl group, SO.sub.3 or (NSO.sub.2 Y.sup.3).sup.-, wherein Y.sup.3 is an alkyl group having 1 to 6 carbons which may have a substituent; and ##STR32##wherein Z.sub.2 and Z.sub.3 are electron-withdrawing groups, R.sup.1, R.sup.2, X.sup.3, Y.sup.2 and M.sup.2+ are same as described above, said optical disk satisfying one of the following requirements (a) and (b);(a) that the film thickness of said recording film at said groove area corresponds to a first interference mound of a disk reflectance, said recording film having an extinction coefficient between 0.03 and 0.09, and said recording film having an absorbance A1 at a wavelength between .+-.3 nm from the recording/reproducing wavelength and an absorbance A0 of a maximum absorbance or step absorbance most adjacent to A1, such that the ratio of A1/A0 is between 0.07 and 0.18 and A0 resides in a range between 0.5 and 0.7; andthat said recording film exhibits, in a thermogravimetric analysis, substantially no weight reduction at temperatures below the starting temperature of the main weight reduction, exhibits a reduction rate of 2%/.degree. C. or more and exhibits a total weight reduction of 35% of more in the main weight reduction, and exhibits, in a differential thermal analysis, an exothermic calorie peak between -10 .mu.V/mg and +10 .mu.V/mg and a peak width of 20.degree. C. or less at exothermic calorie peak;(b) that said optical disk exhibits a distorted angle .theta. of 15.degree. or less in a reproduced signal reproduced at a linear speed of 4.9 m/s or above from 10T or larger mark recorded at a linear speed of 4.9 m/s or above.