Optical information recording medium of phase change type having variably grooved tracks depending on their radial locations

摘要

In an optical information recording medium such that a recording layer undergoing an optically detectable phase change by absorbing a laser beam is formed on a transparent substrate having geometrically concavo-convex groove tracks concentrically or spirally formed on its surface, the shapes of the groove tracks are variably determined continuously or stepwise depending on the material of the substrate, the structure of the recording layer, and the radial locations of the tracks so that the thermal diffusivity of heat generated in the recording layer becomes larger in an inner part than in an outer part whereby the differences of recording characteristics between in an inner part and in an outer part are suppressed, and the effective recording area is enlarged. There is also disclosed an optical information recording medium having outer zone in which the groove width decreases monotonically or stepwise as recording radius decreases and inner zone in which the land width increases monotonically or stepwise as recording radius increases.