Showa Denko K.k.

Katsuaki Aida

Hiroyuki Machida

Kazuyuki Haneda

Masato Fukushima

Kenji Shimizu

Yukihisa Matsumura

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.

Method of polishing the inner peripheral end surfaces of substrates for a recording medium using a brush

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.

Polishing slurry, production method of glass substrate for information recording medium and production method of information recording medium

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 &#x3bc;m to 200 &#x3bc;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.

Magnetic disk substrate and magnetic recording medium thereof

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 &#x212b;&#x2266;Ra&#x2266;100 &#x212b;, preferably 4.0 &#x212b;&#x2266;Ra&#x2266;50 &#x212b;, as measured by means of an AFM.

Substrate for magnetic recording medium, magnetic recording medium, and magnetic recording and reproducing apparatus

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.

Process for manufacturing glass substrate for magnetic recording medium, glass substrate for magnetic recording medium obtained by the process, and magnetic recording medium obtained using the substrate

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:

Magnetic disk substrate and production method of magnetic disk

The present invention is a magnetic recording medium substrate made of amorphous glass of BO&#x2014;AlO&#x2014;SiO&#x2014;LiO 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.

Magnetic recording medium substrate and manufacturing method therefor, magnetic recording medium, and magnetic recording and reproducing device

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&#xb1;0.03 mm and setting the angles &#x3b1; between the main surfaces and the chamfered portions between the main surfaces and the outer circumferential side end face to 45 degrees &#xb1;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.

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Ichihara, Japan

Katsuaki Aida