Hitachi, Ltd.

Keizo Kato

Seiji Yonezawa

Shinkichi Horigome

Kazuo Shigematsu

Masaru Ito

Yoshinori Miyamura

Harukazu Miyamoto

Takeshi Maeda

Motoyasu Terao

Ryo Suzuki

Hirofumi Sukeda

Norio Ohta

Tsuneo Terasawa

Yumiko Anzai

Kimio Tatsuno

Keiji Kataoka

Masahiro Ojima

Hiroshi Shiraishi

Masuo Umemoto

Yoshio Taniguchi

Teruichi Tomura

Fumiyuki Inose

Hajime Fukke

Toshimitsu Miyauchi

Akira Fukuhara

Klaus Kinstatter

According to the present invention, etching is used to form a concave and convex pattern corresponding to information on an embossing metal mold comprising a conductive layer and a layer which includes an Ni electric-plating layer, or an Ni electric-plating layer, so that the surface of the embossing metal mold will not be contaminated even if processing conditions are somewhat changed, and that the mold will have less defects. Thus, optical disk substrates of high quality can be produced. Besides, time required for manufacturing a stamper can be shortened.

Embossing metal hold

In a process for producing optical disks comprising the steps of subjecting the photoresist layer on a substrate formed of silicon, quartz, glass or a metal to light exposure, developing and etching treatments to obtain a stamper and then duplicating an information pattern for an optical disk from the stamper obtained above to a transparent substrate by using a UV curable resin to prepare a replicated substrate of an optical disk, a large number of stampers can be prepared in a short time by conducting the light exposure either by contacting the mask side surface of a substrate provided with a photomask having an information pattern for an optical disk to the photoresist side surface of said substrate having the photoresist layer or by noncontact projection, and a rapid replication of large quantities of replicated substrates becomes possible by using a large number of stampers thus prepared.

Process for producing optical disks

The present invention uses a magnetic recording medium equipped with those magnetically readable recording servo pits which are preformed on a magnetic recording medium and have different magnetic characteristics from those of a recording magnetic film, detects magnetically a tracking signal or preformat signals such as sync signals, address signals, and the like, from the magnetic flux distribution (leakage magnetic field) occurring at edges of each of the servo pits using a magnetic head, makes servo control of the position of the magnetic head by the detected tracking signal and records or reads magnetically the data along the center of a track. In the magnetic recording medium of the present invention, magnetically readable, wobbled servo pits or sync pits, track address pits and data pits are preformed on the magnetic recording medium, these pit portions have locally different magnetic characteristics from those of the recording magnetic film and have a magnetic film structure wherein saturated magnetization is smaller than at other portions or the magnetic film is removed locally. These preformed pits can be read magnetically by detecting the local magnetic field (leakage magnetic field) generated at their edges by the magnetic head.

Method of magnetically recording and reading data, magnetic recording

A magneto-optic recording medium in which a vertically magnetized film on which magnetized domains are recorded by applying a light beam and an outer magnetic field is provided along a recording track and structure bands which do not contribute to read out of the magnetized domains are provided on both sides of the recording track so that the magnetization state of the magnetized domains recorded on the vertically magnetized film is read from an area limited by the width of the recording track. By scanning the magneto-optic recording medium along the recording track with a light beam having a diameter larger than the width of the recording track so as to heat an area larger than the width of the recording track to a temperature exceeding the curie temperature of the vertically magnetized film and also by applying a magnetic field in a predetermined direction to the area irradiated with the light beam, the magnetized domains are recorded in accordance with the direction of the applied magnetic field, and the magnetization state of the magnetized domains is read out only from the area limited by the width of the recording track through the magneto-optic effect.

Magneto-optic recording/reproducing method and device and magneto-optic

A recording member having a predetermined substrate, and a thin film which is formed on the substrate and which is formed with recesses or pits for recording information when irradiated with a working beam, characterized in that said thin film is formed of an inorganic material which contains at least arsenic, selenium and tellurium, and that a distribution of either of said Se and said Te decreases from a part near the surface of said thin film towards a central part thereof, while a distribution of said As increases from a part near the surface towards said central part, is disclosed. This recording member can afford a high signal-to-noise ratio and a long lifetime. It is preferable that the distribution of said Se decreases so as to be at least 50 atomic-% in terms of the content of said Se in a part being the closest to the surface of said thin film and to be at most 40 atomic-% in terms of the average content of said Se over the whole thin film, and that the distribution of said As increases so as to be at most 15 atomic-% in terms of the content of said As in the closest part and to be 5 to 35 atomic-% in terms of the average content of said As in said whole thin film. The Se-Te-As-based material may well be doped with at least one element selected from the group consisting of Ge, S, Tl, Sn, Pb, In and Ta, within a range of 2 to 15 atomic-%.

Recording member

An optical information recording and reproducing apparatus is disclosed in which a predetermined signal is recorded on a track of a rotating recording medium by a recording light beam and the recorded information is reproduced by a reproducing light beam. The information recorded on the last record track is reproduced by the recording beam and the reproducing beam and radiating position of the recording beam on the recording medium is displaced by a predetermined distance from the last record track.

Optical information recording apparatus

In order to record information spirally on a disk and to reproduce the recorded information accurately without any contact, at the recording, an information signal and a predetermined signal for synchronous detection are added together, the resultant signal is subjected to frequency modulation and, while a laser beam intensity-modulated by the frequency-modulated signal is minutely swung in the radial direction of the rotating disk at the same frequency as that of the synchronous detection signal, it is caused to impinge on the disk to thereby record the information spirally on a recording medium of the disk without any contact. During the reproduction, as the disk is being rotated, a light spot is caused to impinge along an information groove formed on the disk, and reflected light or transmitted light from the disk is detected in the form of an electric signal. A synchronous detection signal is derived from the electric signal and an envelope signal of the electric signal is synchronously rectified by the use of the snychronous detection signal to thus detect the offset between the light spot and the information groove and, as the offset is being corrected, the information signal is reproduced.

Method and apparatus for recording and reproducing a video-disc with an

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Hachioji, Japan

Keizo Kato