| 摘要 |
PROBLEM TO BE SOLVED: To obtain a glass substrate capable of forming with small warpage by a float glass method and having the eluted quantity below a specific value under a specific condition in a pure water by using a composition specified in the content of structural oxides and containing substantially no ZrO2 . SOLUTION: The chemically reinforced glass substrate for magnetic recording medium having <=1μg/cm<2> total eluted quantity at the time of holding at 60 deg.C for 120 hr in pure water contains by wt.% SiO2 of 61-70, Al2 O3 of 9-18, Li2 O of 2-3.9, Na2 O of 6-13, K2 O of 0-5, R2 O of 10-16 (R2 O=Li2 O+Na2 O+K2 O), MgO of 0-3.5, CaO of 1-7, SrO of 0-2, BaO of 0-2, RO of 2-10 (RO=MgO+CaO+SrO+ BaO), TiO2 of 0-2, CeO2 of 0-2, Fe2 O3 of 0-2, MnO of 0-1 and TiO2 +CeO2 +Fe2 O3 +MnO=0.01-3 and substantially no ZrO2 . The chemical reinforcement is carried out by ion-exchanging with the dipping in a fused salt as KNO3 .
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