| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass substrate which has high mechanical strength without strengthening chemically and which is easily handled and also improves the magnetic recording/reproducing characteristics of a magnetic disk when the glass is used as substrate of magnetic disk, and to provide a magnetic disk by using the glass substrate. SOLUTION: The glass substrate contains rare earth oxides of Pr, Nd, Sm, Eu, and has such properties that the transmittance of the glass substrate for visible rays at 300 nm to 700 nm wavelength is >=50% and <=85%, the coefficient of thermal expansion measured in the temperature range from 30 deg.C to 380 deg.C ranges from 75 to 120×10-7/ deg.C and the magnetization of the glass substrate when a 1 A/m magnetic field is applied is <=1×10-4 emu/cc.
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