Hoya Corporation

Takemi Miyamoto

Hiroshi Tomiyasu

Kouji Takahashi

Tomotaka Yokoyama

Takeshi Kojima

Genshichi Hata

Kouichi Takahashi

Hideki Isono

Masao Takano

There are disclosed a polishing method and a polishing device in which cleaning of a glass substrate surface can be achieved to a high level. A glass substrate (MD substrate) in the shape of a circular disc having a circular hole in a center portion is polished with an abrasive liquidcontaining free abrasive grains being supplied, and an inner peripheral end surface of the glass substrate is polished using the abrasive liquid containing the free abrasive grains by rotating a rotary brushor a polishing pad in contact with the inner peripheral end surface.

Polishing method, polishing device, glass substrate for magnetic recording medium, and magnetic recording medium

On a principal surface of a glass disk substrate, a texture comprising a combination of an isotropic texture for stabilizing a flight of a magnetic head flying and traveling over a magnetic disk and an anisotropic texture for imparting a magnetic anisotropy to a magnetic layer of the magnetic disk is formed.

Glass substrate for a magnetic disk, magnetic disk, and methods of producing the glass substrate and the magnetic disk

A substrate for an information recording medium has a microwaviness average height Ra' not greater than 0.05 microinch as measured by a contactless laser interference technique for measurement points within a measurement region of 50 &#x3bc;m&#x25a1;-4 mm&#x25a1; on a surface of the substrate. The microwaviness average height Ra&#x2032; is given by:where xi represents a measurement point value of each measurement point, {overscore (x)} representing an average value of the measurement point values, n representing the number of said measurement points. Alternatively, the substrate has a waviness period between 300 &#x3bc;m and 5 mm and a waviness average height Wa of 1.0 nm or less as measured by the contactless laser interference technique for measurement points in a measurement region surrounded by two concentric circles which is spaced from a center of a surface of the substrate by a predetermined distance. The waviness average height Wa is given by:where Xi represents a measurement point value of each measurement point, {overscore (X)} representing an average value of the measurement point values, n representing the number of said measurement points.

Substrate for an information recording medium, information recording medium using the substrate, and method of producing the substrate

A substrate for an information recording medium, wherein the period of microwaviness is 2 &mgr;m to 4 mm, and if we let wa be the maximum height of this microwaviness and Rmax be the maximum height measured by atomic force microscope, the main surface of the substrate has a wa of no more than 5 nm and an Rmax of no more than 12 nm, provided that wa is the difference between the highest and lowest points on a measurement curve of all measured points in a measurement area.

Substrate for information recording medium, information recording medium, and method for controlling surface of substrate for information recording medium

There are disclosed a polishing method and a polishing device in which cleaning of a glass substrate surface can be achieved to a high level. A glass substrate (MD substrate ) in the shape of a circular disc having a circular hole in a center portion is immersed in an abrasive liquid containing free abrasive grains, and an inner peripheral end surface of the glass substrate is polished using the abrasive liquid containing the free abrasive grains by rotating a rotary brush or a polishing pad in contact with the inner peripheral end surface.

In a method of manufacturing a chemical reinforced glass substrate, consideration is previously made about a relationship between conditions of chemical reinforcement for a glass substrate and deformation caused by the chemical reinforcement at an edge portion of the glass substrate. The glass substrate is chemically reinforced on the basis of the relationship so that an edge profile is shaped into a desirable edge profile during the chemical reinforcement. The resultant chemical reinforced glass substrate is flat and smooth in a wide area and effective to improve a recording density and to avoid head crashes.

Chemical reinforced glass substrate having desirable edge profile and method of manufacturing the same

Substrate for an information recording medium, information recording medium using the substrate and method of producing the substrate

In a method of manufacturing a glass substrate for a magnetic recording medium for forming a predetermined roughness, a principal surface of the glass substrate is precisely polished by the use of polishing material containing free abrasive grain. Remaining stress distribution for a portion of a polishing trace due to the free abrasive grain is generated on the surface of the glass substrate. A surface process is performed for at least the principal surface of the glass substrate by the use of hydrosilicofluoric acid. A portion having relatively high remaining distortion in the generated remaining stress distribution is decided as an island portion. The glass substrate is heated after precisely polishing before performing the surface process by the use of the hydrosilicofluoric acid.

Glass substrate for magnetic recording medium, magnetic recording medium, and method of manufacturing the same

There are disclosed a polishing method and a polishing device in which cleaning of a glass substrate surface can be achieved to a high level. A glass substrate (MD substrate,) in the shape of a circular disc having a circular hole in a center portion is immersed in an abrasive liquid,containing free abrasive grains, and an inner peripheral end surface of the glass substrate is polished using the abrasive liquid containing the free abrasive grains by rotating a rotary brush,or a polishing pad in contact with the inner peripheral end surface.

In a glass substrate for use in a magnetic recording medium, the glass substrate has a pair of principal surfaces opposite to each other and a peripheral side area contiguous to the principal surfaces. The peripheral side area has a side end wall and intermediate regions between the side end wall and the principal surfaces. In this case, at least one of the intermediate regions and the side end wall is formed by a mirror finished surface which has a surface roughness Ra not greater than 1 &mgr;m or a surface roughness Rmax not greater than 4 &mgr;m. With this structure, no particles are generated from the peripheral side area because the side end surface of the glass substrate is mirror finished. Consequently, reproduction is performed without reproduction errors because of no generation of a thermal asperity and a head crash can be sufficiently avoided because of no projections which might result from the particles.

Glass substrate, magnetic recording medium and method of manufacturing the magnetic recording medium

In a glass substrate for use in a magnetic recording medium, the glass substrate has a pair of principal surfaces opposite to each other and a peripheral side area contiguous to the principal surfaces. The peripheral side area has a side end wall and intermediate regions between the side end wall and the principal surfaces. In this case, at least one of the intermediate regions and the side end wall is formed by a mirror finished surface which has a surface roughness Ra not greater than 1 .mu.m or a surface roughness Rmax not greater than 4 .mu.m. With this structure, no particles are generated from the peripheral side area because the side end surface of the glass substrate is mirror finished. Consequently, reproduction is performed without reproduction errors because of no generation of a thermal asperity and a head crash can be sufficiently avoided because of no projections which might result from the particles.

Growing community of inventors

Yamanashi-ken, Japan

Takemi Miyamoto