Abstract: A magnetic-disk glass substrate according to the present invention is a doughnut-shaped magnetic-disk glass substrate having a circular hole provided in the center, a pair of main surfaces, and an outer circumferential end surface and an inner circumferential end surface each including a side wall surface and a chamfered surface that is formed between each main surface and the side wall surface. A measurement point is provided on the outer circumferential end surface every 30 degrees in the circumferential direction with reference to a center of the glass substrate, and when a curvature radius of a shape of a portion between the side wall surface and the chamfered surface is determined at each measurement point, the difference in the curvature radius between neighboring measurement points is 0.01 mm or less.

Abstract: A magnetic disk substrate highly reliable to prevent the occurrence of crash failure even if a magnetic disk is rotated at high speed, and suitable for a hard disk that starts and stops by the load/unload method, and a magnetic disk using such a substrate. The representative structure of the magnetic disk substrate is a disk-shaped glass substrate 10 having a generally flat main surface 11, an end face 12, a chamfered face 13 formed between the main surface 11 and the end face 12, and an offset portion, at the periphery of the main surface 11, raised or lowered with respect to a flat surface, other than the periphery, of the main surface 11, and characterized in that the magnitude of the offset portion is approximately uniform over the entire circumference of the glass substrate 10.

Abstract: It is an object to provide a magnetic disk substrate highly reliable to prevent the occurrence of crash failure even if a magnetic disk is rotated at high speed, and suitable for a hard disk that starts and stops by the load/unload method, and a magnetic disk using such a substrate. The representative structure of a magnetic disk substrate is a disk-shaped glass substrate 10 having a generally flat main surface 11, an end face 12, a chamfered face 13 formed between the main surface 11 and the end face 12, and an offset portion, at the periphery of the main surface 11, raised or lowered with respect to a flat surface, other than the periphery, of the main surface 11, and characterized in that the magnitude of the offset portion is approximately uniform over the entire circumference of the glass substrate 10.

Abstract: A method for forming a glass substrate comprises the steps of forming a glass blank with opposing substantially planar surfaces and at least one edge, coating the glass blank in silica-alumina nanoparticles, the silica-alumina nanoparticles comprising an inner core of silica with an outer shell of alumina, annealing the coated glass blank to form a conformal coating of silica-alumina around the glass blank, and polishing the coated glass blank to remove the conformal coating of silica-alumina from the opposing substantially planar surfaces thereof.

Abstract: It is an object to provide a magnetic disk substrate highly reliable to prevent the occurrence of crash failure even if a magnetic disk is rotated at high speed, and suitable for a hard disk that starts and stops by the load/unload method, and a magnetic disk using such a substrate. The representative structure of a magnetic disk substrate according to this invention is a disk-shaped glass substrate 10 having a generally flat main surface 11, an end face 12, a chamfered face 13 formed between the main surface 11 and the end face 12, and an offset portion, at the periphery of the main surface 11, raised or lowered with respect to a flat surface, other than the periphery, of the main surface 11, and characterized in that the magnitude of the offset portion is approximately uniform over the entire circumference of the glass substrate 10.

Abstract: An information medium substrate is formed as a flat plate and includes a first convex part formed on one surface of the information medium substrate in a region between a rim part of a center hole and an inner circumferential edge of an information region and a second convex part formed on another surface of the information medium substrate at a position that overlaps a protruding end part of the first convex part in a thickness direction of the information medium substrate.

Abstract: A main surface of a glass substrate for a magnetic disk is disk-shaped and has a ski jump on an outer peripheral end portion of the main surface opposing a magnetic head slider to be loaded. A rate of change of angles of tangents to a slope of the ski jump in a radial direction in a range between an inner circumferential side and a transition point on the slope is equal to or less than 10/W ?rad/mm where W is a width of the magnetic head slider.

Abstract: In a magnetic disk substrate having first and second chamfered faces respectively connecting between first and second main surfaces opposite to each other and an edge face located between the first and second main surfaces, the ranges of the first and second chamfered faces are specified. Specifically, the distance a from a first boundary portion being a boundary between the first main surface and the first chamfered face to a point of intersection between the first main surface and an extended line of the edge face and the distance b from a second boundary portion being a boundary between the second main surface and the second chamfered face to a point of intersection between the second main surface and an extended line of the edge face are set to satisfy a/b?1.6.

Abstract: The invention provides a magnetic recording medium substrate product which enables enhancement of contact strength between a substrate end surface and a soft magnetic layer, as well as suppression of occurrence of corrosion, a magnetic recording medium including the substrate product, which exhibits no deterioration of electromagnetic conversion characteristics and has excellent durability and a magnetic recording and reproducing apparatus including the magnetic recording medium. The magnetic recording medium substrate product includes a disk-shaped non-magnetic substrate having a circular hole in a center portion thereof, and having a chamfer formed at least one of a portion between a main surface on which a magnetic layer is to be formed and an outer end surface and a portion between the main surface and an inner end surface defining the circular hole, wherein the chamfer has a surface roughness (Ra) falling within a range of 4.0 ??Ra?100 ?, preferably 4.0 ??Ra?50 ?, as measured by means of an AFM.

Abstract: The invention provides a magnetic disk glass substrate capable of preventing the occurrence of dust and adhesion of particles to the magnetic disk surface during a magnetic disk production process, a production method and a magnetic disk. A glass substrate for a magnetic disk has a construction in which an outer peripheral edge shape formed around a peripheral edge portion of a main surface has, with another flat portion of the main surface being the reference: an outer peripheral edge portion ski jump value of not greater than 0 ?m; an outer peripheral edge portion roll-off value of ?0.2 to 0.0 ?m; and an outer peripheral edge portion dub-off value of 0 to 120 ?; and the glass substrate has a chamfer surface between the main surface (data surface) and the outer peripheral edge surface (straight surface), and has an R surface having a radius of curvature of 0.013 to 0.080 mm between the data surface and the chamfer surface of the glass substrate.

Abstract: The present invention is a magnetic recording medium substrate made of amorphous glass of B2O3—Al2O3—SiO2—Li2O type, wherein a chamfer is formed between an edge face at an outer circumference side or an inner circumference side of the substrate and a principal plane of the substrate, and a content of sodium and potassium at a surface area of the inner or outer circumference side edge face and a surface area of the chamfer is greater than a mean content of sodium and potassium of the magnetic recording medium substrate. With the present invention, it is possible to prevent generation of projections on a magnetic film, a protective film or the like due to movement of lithium ions in a magnetic recording medium substrate made of amorphous glass which includes lithium.

Abstract: To provide a substrate which is not substantially chipped or cracked on the substrate end faces even when the substrate is a silicon substrate made of a brittle material, and provide a substrate which prevents dust raising from the substrate end faces and prevents dust raising due to rubbing with a processing cassette. A silicon substrate for a magnetic recording medium is formed by setting the lengths L of chamfered portions between the main surfaces of the substrate and the outer circumferential side end face to 0.1±0.03 mm and setting the angles ? between the main surfaces and the chamfered portions between the main surfaces and the outer circumferential side end face to 45 degrees ±5 degrees. It is also possible for a curved portion with a radius of 0.01 mm or more and less than 0.3 mm is interposed between the main surfaces and the outer circumferential side chamfered portions of the substrate.

Abstract: A method for producing a glass substrate for a magnetic disk by polishing a circular glass plate, which comprises a step of polishing the principal plane of the circular glass plate by using a slurry containing at least one water-soluble polymer selected from the group consisting of a water-soluble organic polymer having amino groups, a water-soluble organic polymer having amine salt groups and a water-soluble organic polymer having quaternary ammonium salt groups, and colloidal silica.

Abstract: Preventing a molded disc substrate from generating a separation pattern. To this end, a molding die 1 includes a pair of stationary die 6 and movable die 7, and an outer circumference ring 16 for molding an outer circumference end of the disc substrate 2. The outer circumference ring 16 is so mounted as to be movable along forward and backward directions in parallel with a moving direction of the movable die 7 toward the stationary die 6, and has a retaining surface 39 for retaining the outer circumference of the molded disc substrate 2.

Abstract: A storage media comprises: a substrate comprising a plastic resin portion, wherein to plastic resin portion comprises poly(arylene ether) and a styrene material selected from the group consisting of polystyrene, styrenic copolymer(s), and reaction products and combinations comprising at least one of the foregoing styrene material(s), and a data layer on the substrate. The data layer can be at least partly read from, written to, or a combination thereof by an energy field. Additionally, when the energy field contacts the storage media, the energy field is incident upon the data layer before it could be incident upon the substrate.

Abstract: A magnetic tape comprising: a coating layer containing ferromagnetic powder and a binder; a support; and a back layer, in this order, which satisfies the following conditions (1) to (3): (1) on a cut plane of the tape, an apex of a biggest convexity of the support does not protrude from a line connecting an apex of a biggest convexity of the coating layer and an apex of a biggest convexity of the back layer; (2) a Young's modulus in a thickness direction of a surface of the magnetic layer is from 1,000 to 2,500 kg/mm2 (from 9.8 to 24.5 GPa); and (3) a Young's modulus in a thickness direction of a surface of the back layer is from 600 to 2,000 kg/mm2 (from 5.9 to 19.6 GPa).