| 摘要 |
PROBLEM TO BE SOLVED: To keep rotation stable without the occurrence of a tracking error or a write/read error and also rotate at high speed by constituting a hub by means of a material with a heat conductive rate being more than a specified value, constituting a substrate by means of the material with the heat conductive rate being within a specified range and also permitting the relation of a hub diameter with a substrate diameter to be the specified one. SOLUTION: The hub consists of the material with the heat conductive rate being more than 0.05 cal/ deg.C.cm.s, the substrate comprises material with the heat conductive rate being 10-4-10-6 cal/ deg.C.cm.s and relation between the hub diameter Y and the substrate diameter X is Y/X>=0.28 in a magneto-optical disk. It is favorable that the hub consists of Fe, Ni, Co or the metal magnetic material of an alloy including them in quality, the thickness of the substrate is equal to below 0.7 mm and the number of rotation in the case of recording/ reproducing is more than 720 rpm, more favorably 2400 rpm. It is also favorable that the relation of a contact area Y1 between the hub and the substrate with the projection area X1 of the substrate is Y1/X1>=0.30.
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