Showa Denko K.k.

Kabushiki Kaisha Toshiba

Showa Denko Kabushiki Kaisha

Yukihisa Matsumura

Masato Fukushima

Ryuji Sakaguchi

Katsuaki Aida

Junya Kato

Yoshihito Sueoka

Koji Sonoda

Koji Yukimatsu

Junichi Kishimoto

A substrate for a magnetic recording medium having a disc shape with a central hole is provided in which the surface roughness of the principal surface of the substrate is 1 angstrom or less in terms of root mean square roughness (Rq) when a space period (L) of an undulation in the circumferential direction is in the range 10 to 1,000 &#x3bc;m, and in which when a component in the vertical axis direction of a line segment Z connecting a point A with the space period (L) of 10 &#x3bc;m and a point B with the space period (L) of 1,000 &#x3bc;m in a curve S marked on a double logarithmic graph which is obtained by analyzing the surface roughness using a spectrum and in which the horizontal axis is set to the space period (L) (&#x3bc;m) and the vertical axis is set to the power spectrum density (PSD) (k&#xb7;angstrom&#xb7;&#x3bc;m) (where k is a constant) is defined as H and a displacement at which the component in the vertical axis direction of the curve S is the maximum with respect to the line segment Z is defined as &#x394;H, a value (P) expressed by (&#x394;H/H)&#xd7;100 (%) is 15% or less.

Substrate for magnetic recording medium, magnetic recording medium, method of manufacturing magnetic recording medium, and method of inspecting surface

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

A texture processing for imparting a magnetic orientation in the circumferential direction is applied to a substrate so as to impart a magnetic anisotropy to the magnetic disk in the circumferential direction. An underlying film, a magnetic recording film, a protective film, and a lubricating film are laminated one upon the other on the surface of the substrate. The surface of the magnetic disk has a value of the contact ratio [BH 1.0 nm] falling within a range of 7% to 15% in a region having a height not smaller than 1.0 nm, based on the height at which the contact ratio in the bearing curve of a surface roughness is 50%.

Magnetic disk with specified contact ratio [BH 1.0 nm] and circumferential texturing and magnetic disk apparatus equipped with magnetic disk

A process for producing a magnetic recording medium, which process comprises a texturing step for forming texture grooves having a line density of 7,500 lines/mm or more on the surface of a non-metallic substrate, and a step for forming an orientation-determining film, a non-magnetic undercoat layer, and a magnetic layer on the non-metallic substrate.

Magnetic recording medium, process for producing the same, and magnetic recording and reproducing apparatus

A magnetic recording medium exhibiting excellent read-write conversion characteristics, including a non-metallic substrate including, on its surface, texture grooves having a line density of 7,500 lines/mm or more; an orientation-determining film; a non-magnetic undercoat layer; and a magnetic layer in order is disclosed. A production process for the medium; and a magnetic recording and reproducing apparatus are also disclosed.

Growing community of inventors

Ichihara, Japan

Yukihisa Matsumura