PROCESS FOR PRODUCING GLASS SUBSTRATE FOR MAGNETIC DISK, AND PROCESS FOR PRODUCING MAGNETIC DISK

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PROBLEM TO BE SOLVED : To provide a process for producing a glass substrate for a magnetic disk, which is particularly useful in the production of the magnetic disk for levitating and flying a magnetic head at a low levitation level of not more than 10 nm, and a process for producing the magnetic disk utilizing the glass substrate. SOLUTION : The process for producing the glass substrate for the magnetic disk comprises mirror polishing and washing of the glass substrate. A polishing agent composed mainly of a rare earth oxide and having a fluorine content of not more than 5% by weight is supplied onto the glass substrate. An abrasive cloth and the glass substrate are moved relatively to mirror-polish the end face of the glass substrate. Then, the glass substrate is brought into contact with a washing liquid containing ascorbic acid and a fluorine ion and not less than 3% by weight of sulfuric acid to dissolve and remove the polishing agent. The concentration of the ascorbic acid contained in the washing liquid is brought to not less than 0.1% by weight, and the content of the fluorine ion is brought to not less than 1 ppm and not more than 40 ppm. At least a magnetic layer is formed on the glass substrate for the magnetic disk to prepare the magnetic disk. COPYRIGHT : (C)2010, JPO&INPIT