LASER BEAM OPTICAL RECORDING MEDIUM OF SUCH TYPE AS HAVING PLURALITY OF READING/WRITING ACCESS LEVELS

摘要

PROBLEM TO BE SOLVED: To provide a material to be used best-suitably for a first access level near a laser beam, in an optical recording medium having a plurality of access levels. SOLUTION: The laser beam optical recording medium has a plurality of reading/writing access levels which are a first access level and one or more second access levels, each access level having a phase changing material layer. In addition, a phase changing material is a metal alloy of such a composition as [(GeyTe1-y)a(SbzTe1-z)1-a]1-b(In1-xTex)b. The reflection coefficient of the first access level is 10 to 30% and its permeability coefficient is at least 45%. Further, the writing power of the first access level is less than 23 mW and the erasing power is less than 10 mW.