Fuji Photo Film Company, Limited

Fujifilm Corporation

Takako Ozawa

Toshio Ishida

Takeshi Kakuta

Hiroaki Doushita

Shinji Saito

Masakazu Nishikawa

Akira Mizuta

Kouichi Masaki

Takeshi Harasawa

An optical information recording medium including a substrate having successively disposed thereon a recording layer, an interlayer, a pressure sensitive adhesive layer and a cover film in which information is recordable and reproducible by irradiating laser light and the pressure sensitive adhesive layer contains a polymer having a glass transition temperature Tg of 0&#xb0; C. or lower, as well as a method for producing an optical information recording medium including adhering a cover layer to a surface of a recording layer so that a pressure sensitive adhesive layer is abutted on the surface of the recording layer, and an optical information recording medium produced by the method.

Optical information recording medium

The present invention provides an optical information recording medium that includes a substrate including a groove with a track pitch of 200 to 400 nm and a groove depth of 20 to 150 nm and having successively disposed thereon a light reflecting layer, a recording layer containing a dye in which information is recorded by irradiation with a laser beam having a wavelength of no greater than 450 nm, an adhesive layer, and a cover layer with a thickness of 0.01 to 0.5 mm. A surface of the optical information recording medium on a side disposed with the cover layer has a center surface average roughness (SRa) of no greater than 3.0 nm when measured over a large surface area and a center surface average roughness (SRa) of no greater than 3.0 nm when measured over a minute surface area.

A master information carrier has on its surface an irregularity pattern representing information to be magnetically transferred to a magnetic recording medium held in contact with the surface of the master information carrier. The parts of the surface of the master information carrier which is brought into contact with the magnetic recording medium are in the range of 0.3 nm to 10.0 nm in center plane mean surface roughness SRa.

Master information carrier for magnetic transfer

The invention provides a method for manufacturing an optical information recording medium having a track pitch of 200 to 400 nm and a groove depth of 20 to 150 nm, and being capable of recording and reproducing using a light with a wavelength of 450 nm or less, the method at least including: a metal reflective layer forming step for forming a metal reflective layer on a substrate; a recording layer forming step for forming a recording layer of an organic dye type on said metal reflective layer; and a cover layer forming step for forming a cover layer on said recording layer; in this order.

Method for producing an optical information recording medium

The present invention provides an optical information recording medium including a substrate having a groove that has a track pitch of 200 to 400 nm and a depth of 20 to 150 nm, the substrate having successively disposed thereon a light-reflective layer, a recording layer on which information is recordable by a laser beam having a wavelength of 450 nm or less, an adhesive layer containing an adhesive, and a cover layer having a thickness of 0.01 to 0.5 mm, wherein a surface of the light-reflective layer at a side thereof at which the recording layer is disposed has a ten-point average roughness Rz of 70 nm or less, a central surface average roughness SRa of 30 nm or less, and an average projection diameter Dv, at a height of 15 nm from a reference plane, of 75 nm or less.

A magnetic recording medium comprising: a support; and at least a magnetic layer comprising a hexagonal ferrite powder and a binder, wherein the hexagonal ferrite powder is of magnetoplumbite type and has an average diameter of 15 to 35 nm and an alkaline earth element to iron ratio of 0.10 to 0.15 in terms of peak intensity ratio analyzed by electron spectroscopy for chemical analysis.

Magnetic recording medium

Provided is a magnetic recording medium having improved electromagnetic characteristics, particularly, in which the C/N ratio in the high-density recording region is markedly improved. The magnetic recording medium comprises a nonmagnetic layer comprising a nonmagnetic powder and a binder and a magnetic layer comprising a ferromagnetic hexagonal ferrite powder and a binder in this order on a support. The number of magnetic aggregates present in the magnetic layer that are equal to or higher than 0.5 &mgr;m in size and have a magnetic intensity equal to or greater than 20 times the average value of magnetization turbulence obtained from a magnetic force image measured by a magnetic force microscope is equal to or less than 100/2,000 &mgr;m .

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Kanagawa, Japan

Takako Ozawa