Hoya Corporation

Nobuyuki Eto

Shinji Eda

Kazuhiko Maeda

Hiroshi Tomiyasu

Tomotaka Yokoyama

Koji Takahashi

Masatomo Shibui

Jun Ozawa

Kinobu Osakabe

Hideki Isono

Katsutoshi Ono

Naohiro Kamiya

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

There are disclosed an information recording medium substrate having a surface roughness of Rmax 15 nm or less, and an information recording medium, particularly an information recording medium substrate and information recording medium in which for surfaces of the substrate and medium, a bearing area value (offset bearing area value) in a depth of 0.5 to 5 nm (predetermined slice level) from a bearing height (real peak height) corresponding to the bearing area value of 0.2% to 1.0% is 90% or less, and a manufacture method of the substrate and medium.

Management technique of friction coefficient based on surface roughness, substrate for information recording medium, information recording medium and manufacture method thereof

On manufacturing a glass substrate for an information recording medium, after a principal surface of the glass substrate is polished, sulfuric acid-cleaning of the principal surface is carried out so that the glass substrate has surface roughnesses Ra and Rmax satisfying Ra&equals;0.1-0.7 nm and Rmax/Ra<20 as measured by an inter-atomic force microscope (AFM), where Ra is representative of a center-line-mean roughness and where Rmax is defined as a maximum height representative of a difference between a highest point and a lowest point.

Method of manufacturing a glass substrate for an information recording medium, and method of manufacturing an information recording medium

The surface of a glass substrate withdrawn from a chemically strengthening treatment liquid is processed with a heated acid (for example, a thermal concentrated sulphuric acid at a temperature of over 100.degree. C., or a water soluble organic solvent such as glycerol or polyethylene glycol). Consequently, precipitated fused salt can be effectively removed without damaging the glass substrate and the change in quality of the glass surface can be also prevented at a high level.

Method of fabricating glass substrate for magnetic disk and method of

An object of the present invention is to prevent the dhesion of particles such as fine iron powders onto a glass substrate upon the production of a glass substrate for an information recording medium. To attain the above object, any one of the following means is adopted: (1) at least one of the production, inspection, packing and filling steps of the glass substrate for an information recording medium is carried out under a clean atmosphere which does not permit the adhesion of particles; (2) at least a wall surface of a chemical reinforcement tank containing a chemical reinforcement liquid therein and/or said retaining means which is contact with the chemical reinforcement liquid is formed of a stainless alloy having corrosion resistance in a high-temperature region as high as the heating temperature of the chemical reinforcement liquid; (3) a means for trapping fine particles existing in the chemical reinforcement liquid used in the chemical reinforcement step is provided; and (4) the glass substrate is washed with hydrochloric acid.

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Tokyo, Japan

Nobuyuki Eto