| 摘要 |
PROBLEM TO BE SOLVED: To provide a glass substrate with improved quality of an information recording disk. SOLUTION: The glass substrate comprises SiO2 of 50 wt.% to 70 wt.%, Al2 O3 of 10 wt.% to 25 wt.%, Ln2 O3 of 1 wt.% to 8 wt.% (wherein Ln represents Pr, Nd, Sm or Eu), B2 O3 of 5 wt.% to 15 wt.% and R2 O of 10 wt.% to 13 wt.% (wherein R represents an alkaline metal element). By this, the visibility of the glass substrate is improved, the occurrence of defects such as a flaw, a chip and the like is reduced in its processing, and the defects of the glass substrate are easily detected in a quality inspection. Further, it is possible to reduce the influence of the glass substrate on magnetization characteristics when it is processed into a magnetic or magneto-optical disk, and, in addition, it is possible to prevent a layer and a film formed on the surface of the glass substrate from peeling off. That is, the quality of the glass substrate can be improved.
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