Glass for magnetic recording media substrates, magnetic recording media substrates, magnetic recording media and method for preparation thereof

摘要

A glass for a magnetic recording medium substrate permitting the realization of a magnetic recording medium substrate affording good chemical durability and having an extremely flat surface, a magnetic recording medium substrate comprised of this glass, a magnetic recording medium equipped with this substrate, and methods of manufacturing the same. The glass is an oxide glass not including As or F.

主权项

1. A method for manufacturing a glass for a magnetic recording medium substrate comprised of an oxide glass, characterized by:
preparing a glass starting material to which Sn and Ce are added, comprising, as converted based on the oxide, denoted as molar percentages: SiO2 60 to 75 percent, Al2O3 1 to 15 percent, Li2O 5 to 10 percent, Na2O 8 to 15 percent, P2O5 0 percent, and K2O 0 to 5 percent, (wherein one or more of MgO, CaO, SrO and BaO is present and the total amount of MgO, CaO, SrO and BaO is in a range of 0.1 to 5% and a total content of Li2O, Na2O, and K2O is 25 percent or lower); so as to permit obtaining a glass containing a total quantity of Sn oxide and Ce oxide of 0.5 mass percent to 1.5 mass percent based on the total amount of the glass components, wherein the ratio of the content of Sn oxide to the total content Sn oxide and Ce oxide (content of Sn oxide/(content of Sn oxide+content of Ce oxide)) is 0.45 to 0.85, having an Sb oxide content of 0 to 0.1 percent, and comprising no As or F; melting the glass starting material; clarifying the resulting glass melt; and molding the resulting glass melt, wherein the molded glass contains 2 pieces/kg or less of residual bubbles.