Phase change optical disk medium

A phase change optical disk medium including a disk-like substrate and a recording layer constituted of a plurality of lamination-thin films having a phase change film to record information marks with an amorphous phase and crystal phase changed, and having tracks formed concave-convex like grooves on said recording layer with lands and grooves arranged to record said information marks wherein,

• a reproduced signal amplitude of a shortest information mark recorded on said recording layer has a ratio equal to or greater than 17% of a reproduced signal amount by an optical reflectance of said recording layer with none-information mark recorded, and wherein
• a length of said shortest information mark is in a range of 0.39 μm to 0.46 μm.

A phase change optical disk medium including a recording layer having an upper interference layer, a lower interference layer, and a phase change film disposed between said upper interference layer and lower interference layer to record information marks with a crystal phase and amorphous phase changed, wherein

• the thickness of said upper interference layer, said lower interference layer and phase change film is of a thickness of becoming that a reproduced signal amplitude of a shortest information mark recorded on said recording layer with the phase change film stated in the crystal phase has a ratio equal to or greater than 17% of a reproduced signal amount by an optical reflectance of said recording layer with the phase change film stated in the crystal phase, and wherein
• a length of said shortest information mark is in a range of 0.39 μm to 0.46 μm.

A phase change optical disk medium including a recording layer having an upper interference layer, a lower interference layer, and a phase change film disposed between said upper interference layer and lower interference layer to record information marks with a crystal phase and amorphous phase changed, wherein

• a reproduced signal amplitude obtained at a state in recording a shortest information mark recorded on said phase change film has a ratio equal to or greater than 17% of a reproduced signal amount obtained at a state with none-information mark recorded, and wherein
• a length of said shortest information mark is in a range of 0.39 μm to 0.46 μm.

A phase change optical disk medium including a recording layer having a reflecting layer, an upper interference layer, a phase change film recorded information marks with a crystal phase and amorphous phase changed and a lower interference layer, which are laminated in the order, wherein

• the thickness of said upper interference layer, said lower interference layer and phase change film is of a thickness of becoming that a reproduced signal amplitude of a shortest information mark recorded on said recording layer with the phase change film stated in the crystal phase has a ratio equal to or greater than 17% of a reproduced signal amount by an optical reflectance of said recording layer with the phase change film stated in the crystal phase, and wherein
• a length of said shortest information mark is in a range of 0.39 μm to 0.46 μm.

A phase change optical disk medium including a recording layer having a reflecting layer, an upper interference layer, a phase change film recording information marks with a crystal phase and amorphous phase changed and a lower interference layer, which are laminated in the order, wherein

• a reproduced signal amplitude obtained at a state in recording a shortest information mark recorded on said phase change film has a ratio equal to or greater than 17% of a reproduced signal amount obtained at a state with none-information mark recorded, and wherein
• a length of said shortest information mark is in a range of 0.39 μm to 0.46 μm.