Abstract: When glass substrate is polished by using a polishing carrier, this invention provides a production method of a magnetic disk substrate that can be applied irrespective of shape, material and hardness of a polishing carrier and can prevent the occurrence of scratches on an outer end face of the glass substrate, a magnetic disk glass substrate obtained by such a method and having excellent characteristics, a production method of a magnetic disk characterized in that a magnetic recording layer is formed on such a magnetic disk glass substrate, and a magnetic disk. When glass of the glass substrate contains alkali metals, the invention can prevent the occurrence of protrusions that may result from the movement of sodium ions and lithium ions, on a magnetic film, a protective film, and so forth.

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: A manufacturing method for silicon substrates for a magnetic recording medium has the steps of forming a stack body of a number of silicon substrates which are stacked via spacers therebetween, wherein each silicon substrate has a circular hole at a center of the substrate; immersing the stack body of the silicon substrates in a polishing liquid in which grains are suspended; and polishing inner peripheral end faces of the circular holes of the silicon substrates, wherein in polishing, a polishing brush contacts the end faces while performing a relative rotation between the end faces and the polishing brush, and the stack body of the silicon substrates is inverted during polishing. The step of polishing the inner peripheral end faces may be performed before inner and outer peripheries of the silicon substrate are subjected to chamfering. Preferably, the polishing brush is made of polyamide resin.

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 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 object of the invention is to provide a method of polishing the inner peripheral end surfaces of substrates while maintaining a sufficiently high working precision at the time of polishing the inner peripheral end surfaces of a plurality of disk-like substrates for a recording medium.

Abstract: The invention can provides a production method of a magnetic disk substrate capable of controlling surface roughness and can reduce surface defects using only a polishing step, and a production method of a magnetic disk. When a glass substrate is polished, the glass substrate polished is with abrasive slurry containing abrasives. Next, the glass substrate is further polished with an aqueous rinse solution not containing the abrasives so that the surface roughness Ra of the glass substrate is 4 to 8 ?.

Abstract: The invention provides a production method for a magnetic disk substrate capable of reducing the number of scratches occurring on the surface of a glass substrate and improving the yield of the glass substrate. When a surface of a magnetic disk substrate is polished by using polishing plates each having a pad, an amorphous or crystallized glass substrate is polished by setting a processing rate to 0.15 ?m/min or below and a pad groove width to 2 to 4 mm. Furthermore, a chemical tempered glass substrate is polished by setting the processing rate to 0.15 ?m/min or below.

Abstract: A polishing method without dispersion in the amount of working at the time of polishing the inner peripheral end surfaces of a plurality of disk-like substrates for a recording medium is provided.

Abstract: To reduce a head floating height on a magnetic disk, the invention provides a production method for a magnetic disk substrate capable of efficiently polishing the glass substrate until the degree of flatness (TIR value) of the glass substrate becomes 5 ?m or below. The invention relates to a production method, for a magnetic disk substrate, by polishing a glass substrate by lapping by using a lap plate, characterized in that plate accuracy is set to 180 ?m or below and polishing is carried out until a degree of flatness (TIR value) of the glass substrate becomes 5 ?m or below. A magnetic disk is obtained by forming a magnetic recording layer on this magnetic disk 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: A silicon substrate for magnetic recording medium is provided, which, even though it is a silicon substrate of a fragile material, is not prone to chip on the substrate edge faces or cracks on the substrate, and which prevents debris from being produced from the substrate edge faces, and which prevents debris from being produced by rubbing against a process cassette. Therefore, in a silicon substrate for a magnetic recording medium, in which there is provided a chamfer section between a main surface of the substrate and an edge face, the edge face and chamfer section of the substrate are of mirror finish, and a curved surface with a radius of greater than or equal to 0.01 mm and less than 0.3 mm is interposed between the main surface of the substrate and the chamfer section.