PURPOSE: To enhance reflectability and to improve durability by including a protective overcoating, a reflection layer of a silver-palladium alloy, a recording layer in proximity to this reflection layer and a plastic substrate in proximity to this recording layer into a compact disk and memory medium.

CONSTITUTION: This compact disk and memory medium have the plastic substrate 11, the recording layer 12, the reflection layer 13 and the protective overcoating 24. The reflection layer contains the silver-palladium alloy, silver- copper alloy or silver-palladiumcopper alloy. In this case, the palladium component in the alloy is maintained at <15at.% and the copper component at <30at.%, the reflectivity of the reflection layer is made equal to the reflectivity of the curvilinear gold reflection layer and simultaneously jitters and NORP level may be lowered with respect to the illumination output level higher than the output ordinarily used for writing of the recording layer.