Hoya Corporation

Naohiro Kamiya

Hideki Isono

Kazuhiko Maeda

Shinji Eda

Nobuyuki Eto

A magnetic disk glass substrate manufacturing method includes a step of polishing a surface of a glass substrate to a mirror surface, a gas heating process step of causing a heated atmosphere and the glass substrate to contact each other so as to heat the glass substrate at a temperature T, a step of causing a chemically strengthening salt melted exceeding a freezing temperature Tand the glass substrate to contact each other so as to chemically strengthen the glass substrate at a temperature T, a gas cooling process step of causing a gas coolant and the glass substrate to contact each other so as to cool the glass substrate to a temperature T, and a liquid cooling process step of causing a liquid coolant and the glass substrate to contact each other so as to cool the glass substrate to a temperature T, the above-mentioned steps being included in this order, wherein the temperature Tis set to a temperature less than the freezing temperature Tof the chemical strengthening salt in a gas cooling process.

Magnetic disk glass substrate manufacturing method

Chemical strengthening treatment is performed by first providing a granular chemical strengthening salt so as to prevent spread in atmosphere at the time of introduction of chemical strengthening salt in a treating vessel, introducing the chemical strengthening salt in a treating vessel, melting the chemical strengthening salt into molten chemical strengthening salt and bringing a glass disc into contact with the molten chemical strengthening salt. The granular chemical strengthening salt is, for example, one obtained by forming of a powdery chemical strengthening salt material into grains. A chemically strengthened glass substrate for magnetic disk can be obtained through the process of carrying out chemical strengthening treatment of magnetic disk glass substrates. A magnetic disk can be obtained by forming at least a magnetic layer on the chemically strengthened glass substrate for magnetic disk.

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Tokyo, Japan

Naohiro Kamiya