Sharp Kabushiki Kaisha Corporation

Toshikazu Nagaura

Kenji Ohta

Tetsuya Inui

Hirotoshi Takemori

Michinobu Mieda

Akira Takahashi

Yoshiteru Murakami

Kazuo Van

Hirotaka Toki

Shinji Yamagami

Masayasu Futagawa

Hiroyuki Ikenaga

Zenjiro Yamashita

Hiroo Yoshidome

Kazuhiko Arikawa

An optical disc having a recording film formed on one surface of a plastics substrate transparent to light, a first protection film formed on the recording film, a moisture proof film formed on the other surface of the substrate, and a second protection film formed on the moisture proof film.

Optical disc

It can be selected whether to form a both-side wobble groove whose both side walls wobble by irradiating two light beams while oscillating the same along the radius of a magneto-optical master disk, or to form a one-side wobble groove one of whose side walls alone wobbles by irradiating two light beams while fixing one of the same and oscillating the other along the radius of the magneto-optical master disk. Then, either a single one-side or both-side groove for tracking-use is formed by irradiating both the two light beams on a photo-resist applied on a glass substrate in accordance with address data. As a result, grooves of different types, both-side and one-side grooves, can be formed continuously in the exposing process.

Manufacturing method of magneto-optical master disk

A cartridge provided with a case for housing an optical disk so that it can be driven and rotated. A recessed section is formed around the peripheral edge of the center hole of the optical disk. A hub, which is used for clamping the optical disk by the use of a magnetic force, is formed into a hat-shape, and it is placed at the recessed section. The height of the hub is set to be greater than the gap between the optical disk and the cartridge case. Without the necessity of fixing the hub to the disk, this arrangement makes it possible to prevent the hub from coming off from the recessed section. Thus, the arrangement eliminates the fixing process between the hub and the optical disk as well as maintaining the clamping function of the hub, thereby making it possible to reduce the manufacturing cost.

Cartridge used for a disc-shaped recording medium

An optical disk for use in an optical memory device having guide grooves and pits on one surface thereof, wherein the depth of the guide grooves is different from that of the pits and the distance from the bottom face of each of the guide grooves to the other surface of the optical disk opposite to the one surface of the optical disk on which the guide grooves and pits are disposed is the same as the distance from the bottom face of each of the pits to the other surface of the optical disk opposite to the one surface of the optical disk on which the guide grooves and pits are disposed, and a method for the production of optical memory master plates that are used for the production of the above-mentioned optical disk.

Optical disk with grooves and pits of different depths

An optical disk including a transparent plastic substrate, a recording film formed on an one side surface of said substrate, a first protective film covering said recording film, and a moisture-impermeable film formed on the other side surface of said substrate via or not via an intermediate film.

Optical disk

An optical disc includes a recording film formed on one surface of a disc-shaped plastics substrate having light transmission properties, and a coating film formed on the other surface of the substrate to which an optical beam is applied, in which the plastics substrate is made by injection molding and a barrier, such as a U-shaped annular groove or ridge, is circumferentially formed on the other surface, at a radial distance which is the distance from a center position to a joint position of an injection mold, and a method for manufacturing the same.

Optical disc with surface coating and manufacturing method therefor

Optical disk for use in optical memory devices

An optical disc comprises an antistatic film of light transmission properties which is formed of a synthetic resin, includes a tin oxide with a phosphorous as electro-conductive filler and is provided on another side of a plastics substrate of the optical disc where an optical beam is applied.

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Nara, Japan

Toshikazu Nagaura