Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A substrate for a perpendicular magnetic recording medium and a perpendicular magnetic recording medium using such a substrate are disclosed. The substrate exhibits sufficient productivity and functions as a soft magnetic backing layer of a perpendicular magnetic recording medium based on the substrate, ensuring surface hardness. The substrate comprises a nonmagnetic base plate composed of an aluminum alloy, an adhesion layer formed on the nonmagnetic base plate and composed of a material containing at least nickel, and a soft magnetic underlayer formed on the adhesion layer by means of an electroless plating method. The soft magnetic underlayer contains phosphorus in a range of 3 at % to 20 at %, and at least 25 at % of cobalt in proportion to the number of atoms of cobalt and nickel excluding the phosphorus (Co/(Co+Ni)). Thickness of the adhesion layer is at least 0.1 ?m. Thickness of the soft magnetic underlayer is at least 0.

Abstract: 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.

Abstract: 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.