Patent ID: 7482109

Claim:
A phase change optical recording medium for implementing at least recording and readout steps on information data by electromagnetic radiation, utilizing a change in reflectivity, R=R (v), of said recording medium during said readout steps, said recording medium and an optical unit moving relative to each other during said recording steps at a relative velocity, v, ranging from minimum to maximum relative velocities warranted for said recording medium, v WL and v WH , respectively, wherein said recording medium comprises a substrate and at least one recording layer, wherein said at least one recording layer has a thickness in a range of 13 nm to 17 nm, wherein v WH ≧10.0 m/s, wherein said at least one recording layer includes at least a recording material essentially consisting of Ag, In, Sb, Te and an additive selected from a group consisting of B, N, C, O, Si, Ga, Ge, S, Se, Al, Fe, Co, Ni, Cu, Zn, Sn, Pd, Pt and Au, with a proportion in atomic percent of α(Ag): β(In): γ(Sb): δ(Te): ε(additive), with 0.1≦α≦3.0, 5.0≦β≦12.0, 60.0≦γ≦72.0, and 22.0≦δ≦30.0, provided that α+β+γ+δ≧97, wherein said recording medium is operable for recording at a velocity of 12.0 m/s, wherein, when said optical unit is operated under conditions of record/readout wavelength of 789 nm and numerical aperture of 0.49, a critical relative velocity of phase change, v 0 , which is defined by a value of v, at which a differential coefficient, −dR(v)/dv, reaches a maximum, satisfies a relation v 0 ≧0.7 v WH , where the reflectivity, R(v), of said recording medium is measured by said optical unit during a DC mode irradiation of electromagnetic radiation at a power P E =0.75 P OH and at said relative velocity, v WH , with P OH being an optimum recording power at said maximum relative velocity V WH , said reflectivity, R(v), changing with v from one saturated value at a low v region, R A , to another saturated value at a high v region, R B , and wherein a normal recording velocity is 1.2 m/sec (CD 1×).