Fuji Electric Device Technology Co., Ltd.

Matsushita Electric Industrial Co., Ltd.

Fuji Electric Co., Ltd.

Kengo Kainuma

Kunio Hibino

Tatsumi Kawata

Hidenao Kataoka

Kazuo Nimura

Hiroyuki Uwazumi

Tomokazu Tokunaga

Hajime Kurihara

Youichi Tei

Akira Iso

Michiru Fujita

Masaki Sakuma

Tatsuo Take

Kazuhito Higuchi

Hideaki Tadano

A disk substrate for a perpendicular magnetic recording medium is, disclosed. The substrate exhibits sufficient productivity, serves the function of a soft magnetic backing layer of the perpendicular magnetic recording medium, and scarcely generates noise. A perpendicular magnetic recording medium using such a substrate also is disclosed. The disk substrate comprises at least a soft magnetic underlayer formed on a nonmagnetic base plate by means of an electroless plating method. The thermal expansion coefficient of the soft magnetic underlayer is larger than a thermal expansion coefficient of the nonmagnetic disk-shaped base plate. A saturation magnetostriction constant &#x3bb;s satisfies a relation &#x3bb;s&#x2267;&#x2212;1&#xd7;10.

Disk substrate for a perpendicular magnetic recording medium and a perpendicular magnetic recording medium using the substrate

A press die and a molding process can form a disk member having a shaft shaped portion at a center with satisfactory circularity and flatness in a disk portion, dimensional precision in the shaft shaped portion, and concentricity between the disk portion and the shaft shaped portion at the center. The press die is designed for press molding of a glass substrate of a disk member with a shaft shaped portion at a center thereof. The press die includes an upper die forming an upper surface of the disk member, an intermediate die having a shaft forming hole portion for forming a shaft shaped portion projecting from a disk portion of the disk member, a lower die for forming a lower surface of the shaft shaped portion and a guide member for guiding the upper die, the intermediate die and the lower die.

Press die of disk with shaft shaped portion

A method of manufacturing a glass substrate for a storage medium by pressing a glass material between an upper and a lower dies. The method includes a heating step of heating the glass material arranged between the upper and lower dies, a pressing step of pressing the heated glass material via the upper and lower dies, and a cooling step of having, after the pressing step, a cooling member contact the upper and lower dies to cool them together with the molded glass material arranged between the upper and lower dies. During the heating step and the pressing step, a vacuum atmosphere is maintained in a space containing the dies and the glass material. When the pressing step has completed, an inert gas is filled in the space to set a pressure in the space equal to an ambient pressure.

Method and apparatus for manufacturing glass substrate for storage medium

Molding process of disk with shaft shaped portion

A cooling water conduit extending through a segment of a crucible is curved inward in the portion around a molten metal tapping hole.

Levitation melting furnace

Growing community of inventors

Nagano, Japan

Kengo Kainuma