Abstract: To provide a glass for an information recording media substrate, which is excellent in weather resistance. A glass for an information recording media substrate, which comprises, as represented by mol % based on oxide, from 61 to 66% of SiO2, from 11.5 to 17% of Al2O3, from 8 to 16% of Li2O, from 2 to 8% of Na2O, from 2.5 to 8% of K2O, from 0 to 6% of MgO, from 0 to 4% of TiO2 and from 0 to 3% of ZrO2, provided that Al2O3+MgO+TiO2 is at least 12%, and Li2O+Na2O+K2O is from 16 to 23%, wherein in a case of where B2O3 is contained, its content is less than 1%. The above glass for an information recording media substrate, wherein when the glass is left under steam atmosphere at 120° C. at 0.2 MPa for 20 hours, and the amount of Li, the amount of Na and the amount of K, which precipitate on a surface of the glass are represented as CLi, CNa and CK respectively, CNa is at most 0.7 nmol/cm2, and CLi+CNa+CK is at most 3.5 nmol/cm2.

Abstract: To provide a substrate glass for data storage medium which is excellent in weather resistance even when no additional treatment such as chemical reinforcement treatment is applied and less susceptible to a whitening phenomenon and which has a glass transition temperature of at least 680° C. and is excellent in acid resistance. A substrate glass for data storage medium, which comprises, as represented by mass %, from 47 to 60% of SiO2, from 8 to 20% of Al2O3, from 0 to 8% of MgO, from 0 to 6% of CaO, from 1 to 18% of SrO, from 0 to 13% of BaO, from 1 to 6% of TiO2, from 1 to 5% of ZrO2, from 2 to 8% of Na2O and from 1 to 15% of K2O and which has a glass transition temperature of at least 680° C.

Abstract: A method for manufacturing a magnetic recording medium disk substrate is provided for achieving a magnetic disk having a suitable surface roughness, a high in-plane magnetic anisotropy and a high S/N. The manufacturing method has a texturing process wherein the magnetic recording medium disk substrate is rotated in the circumferential direction while a polishing tape is pressed against the rotating substrate. The polishing tape includes polyester fiber having a fiber diameter of 400 nm to 950 nm, on the surface coming into contact with the substrate. All the while, slurry including abrasive grains including a cluster diamond is supplied to the surfaces of the substrate. The present invention relates to a magnetic recording medium disk substrate produced by the manufacturing method; and a magnetic recording medium at least comprising a magnetic layer on the magnetic recording medium disk substrate and manufacturing method of the magnetic recording medium.

Abstract: The present invention provides a base material for disk rolls which is a platy molded article for obtaining ring-shaped disks for use in a disk roll comprising a rotating shaft and ring-shaped disks fitted thereon by insertion, whereby the peripheral surface of the disks serves as a conveying surface, the base material comprising inorganic fibers having a crystallization temperature of 800-900° C., a filler, and a clay. Also disclosed is a disk roll which comprises disks cut out of the base material.

Abstract: To provide glass for a data storage medium substrate, whereby high heat resistance can be obtained. Glass for a data storage medium substrate, which comprises, as represented by mol percentage based on the following oxides, from 55 to 70% of SiO2, from 2.5 to 9% of Al2O3, from 0 to 10% of MgO, from 0 to 7% of CaO, from 0.5 to 10% of SrO, from 0 to 12.5% of BaO, from 0 to 2.5% of TiO2, from 0.5 to 3.7% of ZrO2, from 0 to 2.5% of Li2O, from 0 to 8% of Na2O, from 2 to 8% of K2O and from 0.5 to 5% of La2O3, provided that the total content of Al2O3and ZrO2(Al2O3+ZrO2) is at most 12%, and the total content of Li2O, Na2O and K2O (R2O) is at most 12%.

Abstract: Provided is a textured silicon substrate for a magnetic disk, comprising a magnetic film in which magnetic anisotropy can be attained and high recording density can be achieved, while ensuring the flying stability of a head by controlling the surface roughness of the substrate through texturing. Especially, provided is a surface-treated silicon substrate for a magnetic disk, comprising a texture formed on a surface of a silicon substrate comprising an oxide film of 0 to 2 nm thickness, and a magnetic recording medium comprising the surface-treated silicon substrate. Also provided is a method for manufacturing a surface-treated silicon substrate for a magnetic disk, comprising steps of: removing or reducing an oxide film on a surface of a silicon substrate; and forming a texture on the surface of the silicon substrate having the oxide film removed or reduced using a free abrasive-containing slurry and a tape; and a magnetic recording medium comprising the silicon substrate.

Abstract: A substrate for use as a disk substrate in a hard disk drive or the like, an information recording medium such as a magnetic disk, and a starting material glass plate which is a starting material of the substrate for information recording media. The forming conditions of the starting material glass plate are controlled such that the starting material glass plate has a long-wavelength waviness of not more than 6 nm. This starting material glass plate is polished so as to have a long-wavelength waviness of not more than 6 nm using CeO2 abrasive grains having a mean grain diameter of not less than 0.01 ?m and a 90% diameter of the volume grain size distribution of not less than 0.02 ?m. The resulting substrate for an information recording medium has an excellent planarity, can be obtained in a short time and with a low polishing amount, and the resulting information recording medium is able to cope with increased data zone recording density.

Abstract: A method for producing a recording medium provides good throughput for mass production and reduces cost. The method facilitates the control of the shape or dimensions of a pattern obtained by microfabrication, allows an accurate pattern transfer, and provides superior uniformity. A magnetic layer is formed on a substrate. A nano-particle film 16 is formed on a desired portion on the magnetic layer. Using the nano-particle film as a mask, the magnetic layer is cut. A micropattern with concavities and convexities is formed on the magnetic layer by removing the nano-particle film.

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: A process for manufacturing a glass substrate for a magnetic recording medium comprising polishing a crystallized glass substrate using abrasive grains, and then washing the substrate using an aqueous organic carboxylic acid solution; a glass substrate for a magnetic recording medium which is manufactured by the process; and a magnetic recording medium obtained using the substrate. A glass substrate for a magnetic recording medium is manufactured, whereby the surface roughness is low and the surface defects are minimal for washing after polishing of a crystallized glass substrate, and wherein the Read-Write performance are not impaired when a recording layer including a magnetic film is formed on the magnetic recording medium substrate for manufacturing a magnetic recording medium.

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 object of the invention is to provide a method of polishing the end surfaces of a substrate for a recording medium, which is capable of efficiently polishing the inner peripheral end surface and/or the outer peripheral end surface of the substrate preventing the reliability of performance of the recording medium from being impaired by the adhesion of the residual polishing material. According to the invention, there is provided a method of polishing end surfaces of a substrate for a recording medium wherein an inner peripheral end surface or an outer peripheral end surface of a substrate for a disk-like recording medium having a circular hole at the central portion thereof is brought into contact with a polishing medium obtained by dispersing polishing grains in a viscoelastic resin carrier and the polishing medium flows, thereby to polish the inner peripheral end surface or the outer peripheral end surface.

Abstract: The invention uses an adhesion layer of an amorphous alloy of aluminum. A first aluminum titanium embodiment of the amorphous adhesion layer preferably contains approximately equal amounts of aluminum and titanium (+/?5 at. %). A second embodiment of the amorphous adhesion layer preferably contains approximately equal amounts of aluminum and titanium (+/?5 at. %) and up to 10 at. % Zr with 5 at. % Zr being preferred. A third embodiment is aluminum tantalum preferably including from 15 to 25 at. % tantalum with 20 at. % being preferred. The most preferred compositions are Al50Ti50, Al47.5Ti47.5Zr5 or Al80 Ta20. The adhesion layer is deposited onto the substrate. The substrate can be glass or a metal such as NiP-plated AlMg. The preferred embodiment of media according to the invention is for perpendicular recording and includes a magnetically soft underlayer deposited above the adhesion layer.

Abstract: An electromagnetic noise suppressor including a ferrite film is formed by regularly arranging constituents such as magnetized grains or one analogous to that. In the ferrite film, the constituents have at least one of the uniaxial anisotropy and the multiaxial anisotropy. The ferrite film has the magnetic anisotropy or the magnetic isotropy. The ferrite film is formed by a plating method in the presence of a magnetic field.

Abstract: According to one embodiment, a substrate for a magnetic recording media has circumferential protrusions corresponding to recording tracks and circumferential recesses corresponding to grooves between the recording tracks, in which the substrate satisfying at least one of conditions of (a) a surface of the recess has a surface energy smaller than that of the protrusion, (b) the surface of the recess is modified with a thermally decomposable or deformable substance, (c) the surface of the recess has surface roughness smaller than that of the protrusion, (d) crystal orientation is more disturbed on the surface of the recess than on the protrusion, (e) the surface of the recess is modified with a substance that causes reaction with a magnetic material or that diffuses into the magnetic material, and (f) the surface of the recess is modified with a substance soluble in a solvent or with a deformable substance.

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 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 ?s satisfies a relation ?s??1×10?5.

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: A perpendicular magnetic recording medium has a granular magnetic layer and a nonmagnetic underlayer of a metal or an alloy having a hexagonal close packed (hcp) crystal structure. A seed layer of a metal or an alloy of a face-centered cubic (fcc) crystal structure is provided under the nonmagnetic underlayer. Such a perpendicular magnetic recording medium exhibits excellent magnetic characteristics even when the thickness of the underlayer or the total thickness of the underlayer and the seed layer is very thin. Excellent magnetic characteristics can be obtained even when of the substrate is not preheated. Accordingly, a nonmagnetic substrate, such as a plastic resin can be employed to reduce the manufacturing cost.