PROTECTIVE FILM FOR OPTICAL DISK, AND SPUTTERING TARGET FOR FORMING PROTECTIVE FILM

摘要

PROBLEM TO BE SOLVED: To provide a material for a protective film which does not contain S, has the refractive index and transmittance of light equal to those of a material of ZnS-20 mol% SiO2and is suitably used for an optical disk dealing with high recording density by allowing to have a comparatively high sputtering rate.

SOLUTION: The protective film for the optical disk containing In, Ce and O by elemental analysis and having an atomic ratio of In to Ce of 1:0.08 to 0.35 is obtained by using a sputtering target for forming the protective film containing 10 to 40 mass% CeO2and the balance In2O3. By using a sputtering target further containing 0.1 to 5 mass% at least one of TiO2and SnO2, the protective film for the optical disk containing In, Ce and at least one of Ti and Sn and having the atomic ratio of In to Ce of 1: 0.08 to 0.35 and an atomic ratio of In to the sum total of Ti and Sn of 1:0.001 to 0.09 is obtained.

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