Abstract: There is provided a method of polishing the inner peripheral end surfaces of disk-like substrates for a recording medium using a brush comprising, providing a plurality of pieces of disk-like substrates having circular holes at the central portion thereof; bringing a polishing material slurry containing a polishing material into contact with the object to be polished; inserting a polishing brush into the circular hole of the object from a first side of the object to be polished, and rotating the polishing brush with the shaft as a center to polish the inner peripheral end surfaces of the substrates; and inserting the polishing brush into the circular hole of the object to be polished from a second side opposite to the first side and rotating the polishing brush with the shaft as a center axis to polish the inner peripheral end surfaces of the substrates.

Abstract: The present invention provides a low-cost polishing slurry having excellent effect with respect to defects and smoothness of the surface to be polished. The polishing slurry comprises a silica abrasive and a ceria abrasive, wherein the silica abrasive content is less than 3 mass % and the ceria abrasive content is less than 1 mass %, based on the entire polishing slurry. Further, the present invention provides a method for producing a crystallized glass substrate for an information recording medium, wherein the method use a polishing slurry of the present invention. Furthermore, the present invention provides a method for producing an information recording medium, comprising forming a recording layer on a crystallized glass substrate for an information recording medium obtained by the present method.

Abstract: The present invention relates to a magnetic disk substrate, in which an amplitude Wa of a waviness on a surface measured by using an interferometer for a versatile disk at a measuring wave-length of 5.0 mm is within the range of 0.1 nm to 0.5 nm, an average amplitude Wb of a microwaviness generated on the waviness measured by using a microscopy for three-dimensional surface-structural analysis at a measuring wave-length of 30 ?m to 200 ?m is 0.3 nm or less, and a value calculated by dividing the average amplitude Wb of the microwaviness by the amplitude Wa of the waviness is 0.6 or more.

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 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: 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 present invention relates to a magnetic disk substrate, in which an amplitude Wa of a waviness on a surface measured by using an interferometer for a versatile disk at a measuring wave-length of 5.0 mm is within the range of 0.1 nm to 0.5 nm, an average amplitude Wb of a microwaviness generated on the waviness measured by using a microscopy for three-dimensional surface-structural analysis at a measuring wave-length of 30 ?m to 200 ?m is 0.3 nm or less, and a value calculated by dividing the average amplitude Wb of the microwaviness by the amplitude Wa of the waviness is 0.6 or more.

Abstract: A glass substrate for a magnetic recording medium, having a chamfer face between the surface of the substrate for forming thereon a film comprising a magnetic layer, and the outer peripheral end face (straight face) of the substrate, wherein an R face having a curvature of 0.013 to 0.080 mm is provided between the data face and the chamfer face of the glass substrate.

Abstract: A silicon substrate for a magnetic recording medium in which the substrate has a chamfered surface between its data-carrying surface (surface) having layers including a magnetic layer and its outer peripheral end surface (straight surface) is provided. The silicon substrate is characterized in that a dub-off value at an outer peripheral side of the data-carrying surface is not more than 120 ? wherein when a first position (A) is a point on the data-carrying surface radially and inwardly positioned at 1 mm from the outer peripheral end surface of the substrate, a second position (B) is a point on the data-carrying surface radially and inwardly positioned further at 1.

Abstract: The invention can provide a production method for a magnetic disk substrate capable of reducing the number of surface defects of a glass substrate. When a magnetic disk is produced by using the resulting magnetic disk substrate, the yield and, furthermore, the reliability can be improved. When a surface of a magnetic disk substrate is washed after it is polished, the glass substrate is dipped into a washing solution while the surface of the glass substrate polished is held under a wet condition. The wet condition of the surface of the glass substrate includes a condition in which the glass substrate is dipped into water that may contain a surfactant, and a condition in which a liquid film is formed substantially on the entire surface.

Abstract: The object of present invention is to provide a magnetic disk substrate which uses a silicon substrate, in which chamfered surfaces are provided between the main surfaces of the silicon substrate and the outer circumferential surface; a ski-jump value H0 where H0?0 ?m, representing the distance from the basal level to point A3; a roll-off value H1 where H1??0.2 ?m and H1?0.0 ?m, representing the distance from the basal level to point A1; a tag-off value H2 where H2?0 ?m and H2?0.012 ?m, representing the maximum displacement of the border line of the main surface with respect to the line A1 to A2; curved surfaces are provided between the main surfaces and the chamfered surfaces; and the curvature radius R of the curved surface where R?0.013 mm and R?0.080 mm.

Abstract: An object is to provide a polishing carrier that can prevent scratches from occurring on the edge face of a substrate, and prevent debris from being produced from the edge face, while a single crystal silicon substrate, which is fragile, and has a high cleavage strength, is polished, and to make it difficult for debris to be produced due to rubbing against a cassette when it is stored in a cassette in subsequent processing, and prevent the substrate from being broken. Therefore a part of the internal circumference of a substrate holding hole in a polishing carrier, that makes contact with the silicon substrate is formed from a cushion whose hardness is less than that of the silicon substrate. For the cushion, any type selected from for example suede, polyamide resin, polypropylene resin, or epoxy resin may be used. Especially, the use of epoxy resin is desirable.

Abstract: A glass substrate for a magnetic recording medium, having a chamfer face between the surface (data face) of the substrate for forming thereon a film comprising a magnetic layer, and the outer peripheral end face (straight face) of the substrate, wherein the outer peripheral chamfer face has a dub-off of 120 ? or less in the radial direction.

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: In a silicon substrate for a magnetic recording medium, a curved surface having a radius from 0.01 mm to 0.05 mm is provided at an edge portion between a main surface and an end face of the substrate. The curved surface may be provided at an outer periphery or an inner periphery of the substrate. Preferably, the maximum heights for surface roughness for the end face and the main surface are respectively 1 ?m or less and 10 nm or less. A manufacturing method for a silicon substrate includes forming a circular hole at a center of the silicon substrate; immersing the substrate in a polishing liquid in which grains are suspended; and respectively polishing outer and inner peripheral end faces of the substrate. In polishing of each end face, a polishing brush contacts the end face while performing a relative rotation between the end face and the polishing brush.

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: A process for manufacturing a glass substrate for a magnetic recording medium, comprising polishing a glass substrate is polished using abrasive grains and then washing the substrate using a 0.02-0.3% aqueous hydrofluoric acid solution, and a glass substrate for a magnetic recording medium which is manufactured by the process. A polished glass substrate for a magnetic recording medium is manufactured, whereby during washing after polishing of the glass substrate, manifestation of substrate surface defects and overall waviness of the substrate can be minimized, and whereby texture formation in the subsequent texturing step can be accomplished in a uniform manner without creating variation between substrates.