Sony Corporation

Kawasaki Steel Corporation

Tdk Corporation

Jfe Steel Corporation

Koichi Yasuda

Kotaro Kurokawa

Osamu Kawakubo

Atsushi Fukumoto

Toshiyuki Kashiwagi

Masahiko Kaneko

Noboru Nishiyama

Yutaka Kasami

Akira Yasuda

Takeshi Yamasaki

Takatoshi Okabe

Yuji Kuroda

Motohiro Furuki

Tomomi Yukumoto

Hiroyuki Sumi

Koji Yamato

Kenji Oi

Yasushi Kitani

Shigeki Takagawa

Mitsuo Naito

Satoru Kitahara

Toshio Izu

Tadao Komatsu

Shuichi Sakaguchi

Shosaburo Nakano

Tadashi Nakajima

Tokihiko Kataoka

Takaro Matsumoto

Katsuaki Nakatsuji

Hideo Koumura

Syozaburo Nakano

An optical recording medium includes a substratewith a concave and convex shape for dividing a track area formed on its surface, an optical recording layerhaving a compound consisting of at least tin (Sn), nitrogen (N) and oxygen (O) formed on the surface in which the concave and convex shape is formed and a light transmission layerformed on this optical recording layer Then, a compound composition SnNOof tin (Sn) nitrogen (N) and oxygen (O) comprising the optical recording layeris selected so as to satisfy 30&#x3c;x&#x3c;70 (atomic %), 1&#x3c;y&#x3c;20 (atomic %) and 20&#x3c;z&#x3c;60 (atomic %). According to this arrangement, the optical recording medium can improve jitter caused when Sn is used as a recording material.

Optical recording medium

The present invention is a multilayer optical disc formed of a plurality of information recording sections having a phase change recording layer. A first information recording section provided at a laser-incident side uses, as a recording material, a phase change recording material which uses Sb and Te as major components and satisfies their ratio of 2.3&#x3c;Sb/Te&#x2266;4.0 according to the atomic ratio. Since this phase change recording material provides a fast crystallization speed, it is possible to stably record, reproduce, and rewrite an information signal at a high transfer rate.

Multilayer phase-change type optical disc capable of recording and reproducing information at high transfer rate

A steel wire for MAG welding in DC-electrode negative contains about 0.20% by mass or less of C, about 0.25% to about 2.5% by mass of Si, about 0.45% to about 3.5% by mass of Mn, about 0.005% to about 0.040% by mass of rare-earth elements, about 0.05% by mass or less of P, about 0.05% by mass or less of S, and the balance being Fe and incidental impurities. A method for MAG welding in DC-electrode negative for welding steel sheets having a thickness of about 0.2 to about 4.5 mm using the steel wire is also disclosed.

Steel wire for MAG welding and MAG welding method using the same

Initialization nonuniformity due to interference of light which occurs during an initialization process is reduced without causing degradation in the characteristic of signals recorded/reproduced on/from respective recording layers. A multilayer optical disk comprising at least a first information recording layer and a second information recording layer formed, on a substrate, into a multilayer structure with an intermediate layer disposed therebetween is illuminated with initializing light from the side of the first information recording layer to initialize the first information recording layer formed of a phase-change material serving as a recording material. The illumination with the initializing light is performed such that the numerical aperture NA of an objective lens used for illumination with the illuminating light, the longitudinal length L of the beam size of the initializing light, the thickness D of the intermediate layer, and the ratio R1 of the amount of light striking the first information recording layer after passing through the first information recording layer and being reflected by the second information recording layer to the amount of light incident on the first information recording layer satisfy the following relation for a wavelength &lgr;i of the initializing light: L&times;R1 &lE;25&lsqb;1&minus;exp(&minus;0.0004&times; &times;D )&rsqb;.

Multilayer optical disk and method of initializing the same

A multi-layered optical disc having its recording unit comprised of plural information recording layers, in which two or more information recording layers are layered on a substrate 0.3 to 1.2 mm in thickness, with the interposition of a transparent layer, to from a recording unit, a light transmitting protective layer is formed on the recording unit to a thickness of 10 to 177 &mgr;m, and in which the light is illuminated from the side of the light transmitting protective layer to effect recording and/or reproduction of information signals. At least one of the information recording layers except the information recording layer formed at a remotest position from the light transmitting protective layer has a phase change material as a recording material. A refractive index nc and an extinction coefficient kc in the crystallized state and a refractive index na and an extinction coefficient ka in the amorphous state of the phase change material constituting the first information recording layer as counted from the light transmitting protective layer satisfy the relationship of (nc /na )&lE;12, (kc /ka )&lE;12 and (kc /ka )&lE;5 (nc /na ), where the cases of kc /ka <1 and nc /na <1 are excluded.

Multi-layered optical disc

An optical disc on or from which information signals are recorded/reproduced by irradiation of a laser light beam is disclosed. The optical disc has a plurality of top surfaces, a plurality of bottom surfaces, and a plurality of portions formed on a major surface of a disc substrate of the optical disc. The portions separate the top and bottom surfaces from each other. A recording track is constituted by each top surface and each bottom surface. Each bottom surface and each top surface have a first width, while each portion has a second width. The recording track has a track pitch P defined by the sum of the first width and said second pitch. The pitch is related with the second width and the spot diameter of the playback light &phgr; by a formula and P<&phgr;/2 and 0.1 &mgr;m<second width &lE;&phgr;/2.5.

Optical disc having narrow recording track relative to light spot diameter

Reduced thickness of a light transmissive layer for a high density optical disc

A multi-layered optical disc having superior recording/reproducing characteristics, in which the recording density in three-dimensional direction can be increased to increase the recording capacity, and its manufacturing method. A multi-layered optical disc,has a light reflecting layer,a second information recording layer,a transparent layer,a first information recording layer,and a light-transmitting layer,sequentially formed on a major surface,of its substrate,The laser light is illuminated from the light-transmitting layer,of the multi-layered optical disc,to record and/or reproduce information signals.

Multi-layer optical disc and recording/reproducing apparatus

An optical recording medium is provided which achieves a higher recording capacity. This optical recording medium includes a base formed of thermoplastic resin which has a thickness ranging from between approximately 0.3 to 1.2 nm, a guide groove formed on the base, at least a reflective film and a phase-change recording layer successively formed on the guide groove, arid a light transmissive layer having a thickness ranging from between approximately 3 to 177 .mu.m. In this optical recording medium, the unevenness .DELTA.t of the thickness of the light transmission layer is set within the range of:

Optical recording medium and optical disk apparatus

An optical recording medium having a phase-changing material layer served as a recording layer is composed to excellently repeat the rewrite of bits independently of the line speed of the writing light. The amount of the additive to be added to the phase-changing material layer is regulated in relation to the line speed for the write. The additive is added for suppressing the crystallization.

Phase-change optical recording medium having an additive related to the

Method of fabricating high strength and high toughness large-diameter

A multiple-recording-layer optical recording medium has a plurality of recording layers to be initialized by exposure to light, with a transparent layer interposed between the recording layers. Light is applied simultaneously to the to the recording layers to initialize the recording layers simultaneously.

Method of and apparatus for initializing multi-layer optical recording

An optical disc comprising transparent substrate, a phase-changing material layer disposed on the transparent substrate and made of a material which is phase-changeable by radiation of a light beam, a reflecting film layer disposed on the phase-changing material layer, and a cooling layer disposed between the phase-changing material layer and the reflecting layer, wherein the cooling layer has a heat conductivity ranging from 0.25 J/cmKs to 20.00 J/cmKs. The optical disc of the present invention has such a structure that a crystal phase portion of the phase-changing material layer shows a higher light absorptivity than that of the amorphous phase portion and exhibits a high carrier to noise ratio (C/N ratio) irrespective of a line speed upon rotational driving of the optical disc.

Optical disc

A galvannealed steel sheet having a superior spot weldability characteristic in which the steel sheet has a base steel sheet cold-rolled from a material containing 0.005 wt % or less of C, 0.005 to 0.05 wt % of Ti, 0.01 to 0.1 wt % of Al, 0.005 to 0.015 wt % of Nb and 0.0002 to 0.002 wt % of B. In the process for making, the hot-dip plating layer applied after the alloying heat treatment has an Fe content of from 9 wt % to 12 wt %.

Galvannealed steel sheet having improved spot-weldability

Growing community of inventors

Tokyo, Japan

Koichi Yasuda