Patent ID: 8124315

Claim:
An optical recording medium comprising: a transparent substrate, a first protective layer disposed on the transparent substrate, a recording layer disposed on the first protective layer, a second protective layer disposed on the recording layer, and a reflective layer disposed on the second protective layer, wherein the recording layer is composed of a phase-change recording material comprising Ga, Sb, Sn and Ge, and where the transfer linear velocity is 20 m/s to 30 m/s, wherein when the wavelength of a recording and reproducing light is within the range of 650 nm to 665 nm and the recording linear velocity is 20 m/s to 28 m/s, the refractive index Nc and the extinction coefficient Kc in a crystalline state and the refractive index Na and the extinction coefficient Ka in an amorphous state in the recording layer respectively satisfy the following numerical expressions: 2.0≦Nc≦3.0, 4.0≦Kc≦5.0, 4.0≦Na≦5.0, and 2.5≦Ka≦3.1, and wherein information is recordable at the range of 20 m/s to 28 m/s of recording linear velocity, wherein the optical recording medium further comprises a sulfidation prevention layer between the second protective layer and the reflective layer, and wherein the optical recording medium further comprises an additional layer containing a mixture of ZrO 2 , Y 2 O 3 , and TiO 2 with 2 nm to 8 nm of film thickness between the second protective layer and the sulfidation prevention layer.