Nec Corporation

Nippon Electric Co., Ltd.

Masaki Itoh

Akio Morimoto

Mitsuya Okada

Sotaro Esho

Eizoh Fukami

Shuichi Ohkubo

Hiroshi Gokan

Mitsuru Sakai

Katsuji Nakagawa

Yoshitake Ohnishi

Kenji Mizuno

Masaru Matsuoka

Syu-Ichi Ohkubo

There is disclosed an optical information recording medium having phase-change recording films whose the transmittance can be made substantially uniform irrespective of the presence or absence of recording. There are also disclosed methods for recording, reading, and erasing information well at a high density on such a medium. Each of the phase-change recording films other than the top one has a phase-change recording film for recording and erasing information by a phase change caused by illumination of laser light. A transparent upper protective film is formed on the phase-change recording film to protect the phase-change recording film mainly against thermal deformation during recording and erasing of information. A transparent lower protective film is formed under the phase-change recording film to protect the phase-change recording film mainly against thermal deformation during recording and erasing of information. A foundation interference film is formed under the transparent lower protective film to adjust the transmittance of the phase-change recording film for the laser light.

Optical information recording medium and methods for recording, reading, and erasing information thereupon

An optical data recording medium utilizing reversible inter-crystalline-amorphous phase changes for recording, reproducing and erasing data as phase changes of a recording film caused by laser beam irradiation. The medium is formed by a lamination of a transparent substrate having tracking guide grooves for laser beam tracking, a base film formed on the substrate, a first protective film formed on the base film, a phase change type recording film formed on the first protective film, a second protective film formed on the recording film, and a reflecting film formed on the second protective film. Thus formed, the medium improves the over-writing characteristics of phase change type optical discs and permits high density recording.

Optical recording media

A method and apparatus for preventing generation of third generation data of an original data recorded on a read-only region of a partial read-only memory (ROM) optical disk includes an operation for copying source data from the partial read-only memory to a read-write medium by first attempting to write check data on a read-write region of the partial ROM optical disk. If the check data cannot be written, the copy operation terminates. If the check data can be written, the source data is overwritten. Then, the source data is copied from the partial ROM optical disk to the read-write medium.

Method for protecting data recorded on a partial read-only memory (ROM)

A magnetooptical recording medium having a higher recording density, improved bit error rate and superior weather resistance and a recording and playback method for the same are provided. The magnetooptical recording medium has a first magnetooptical layer having a high Curie temperature a second perpendicularly magnetizable magnetooptical layer having a low Curie temperature and a third perpendicularly magnetizable magnetooptical layer having an intermediate Curie temperature set between the Curie temperatures of the first and second magnetooptical layers, laminated in this order on a substrate. The first, second and third magnetooptical layers are formed respectively of amorphous alloys containing GdFeCo, TbFeTi and TbFeCoTi as the main component thereof. The first, second and third magnetooptical layers are exchange-coupled at 10.degree. C. to 90.degree. C., and the first and third magnetooptical layers are not magnetostatically coupled in the external magnetic field for reading use at the temperature at which the magnetization of the second magnetooptical layer is diminished.

Magneto-optical recording medium, recording and playback method and

A magnetooptical recording medium having a higher recording density, improved bit error rate and superior weather resistance and a recording and playback method for the same are provided. The magnetooptical recording medium has a first magnetooptical layer having a high Curie temperature, a second perpendicularly magnetizable magnetooptical layer having a low Curie temperature and a third perpendicularly magnetizable magnetooptical layer having an intermediate Curie temperature set between the Curie temperatures of the first and second magnetooptical layers, laminated in this order on a substrate. The first, second and third magnetooptical layers are formed respectively of amorphous alloys containing GdFeCo, TbFeTi and TbFeCoTi as the main component thereof. The first, second and third magnetooptical layers are exchange-coupled at 10.degree. C. to 90.degree. C., and the first and third magnetooptical layers are not magnetostatically coupled in the external magnetic field for reading use at the temperature at which the magnetization of the second magnetooptical layer is diminished.

Magneto-optical recording medium with amorphous alloy film layers

For use in recording information by an irradiation of a laser beam, an optical information recording medium comprises a substrate transparent for the laser beam and a first and a second magneto-optical layer which are made of GdFeTi and TbFeCo, respectively. The first magneto-optical layer is between the substrate and the second magneto-optical layer and thermally coupled to the second magneto-optical layer. For carrying out a recording operation, the laser beam is irradiated to the substrate to heat the first magneto-optical layer. A temperature of the first magneto-optical layer is transferred to the second magneto-optical layer. In this condition, the second magneto-optical layer is subjected to a magnetic field representative of information. As a result, the information is recorded as recorded information to the second magneto-optical layer. The recorded information is transferred from the second magneto-optical layer to the first magneto-optical layer with decreasing of the temperature of the first magneto-optical layer. The recorded information can be read from the first magneto-optical layer in the manner known in the art.

Optical information recording medium comprising two magneto-optical

In an optical information recording medium comprising a substrate (11) of polycarbonate, a recording layer, and a reflecting layer (14) covering the reflecting layer and containing Al, an alloy layer (17) of a Ni-Cr alloy is deposited on the reflecting layer to sufficiently protect transmission of moisture into the reflecting layer. A covering layer (18) of ultraviolet curable resin may be deposited on the alloy layer. The recording layer is formed on the substrate and includes a magneto-optical layer (13) sandwiched between first and second interference layers (15, 16). For protecting transmission of moisture into the substrate, it is preferable that an additional layer (21) of SiO.sub.2 is deposited on the substrate opposite to the recording layer.

Optical information recording medium in which a protective layer

An optical information recording medium according to the present invention is featured by its recording layer which contains a compound of tellurium (Te), selenium (Se) and nitrogen (N). The thickness of the recording layer 2 favorably ranges from about 100 angstroms (.ANG.) to about 1000 .ANG. and more favorably from 180 .ANG. to 400 .ANG.. The content of Se in the recording layer 2 favorably lies within a range from 2 to 40 atomic percent, more favorably from 10 to 30 atomic percent. The content of N is favorably to be from 2 to 20 atomic percent, and more favorably from 2 to 10 atomic percent.

Optical information recording medium

An optical information storage medium comprising a transparent substrate and an information carrying layer positioned on one side of the substrate, wherein the information carrying layer contains at least 30 per cent by volume of tin and at least 15 per cent by volume of cobalt oxide. The information carrying layer may be formed directly on one surface of the substrate.

Optical information storage medium

An optical information storage medium comprising a transparent substrate and an information carrying layer positioned on one side of the substrate, wherein the information carrying layer contains at least 30 percent by volume of tin and at least 20 percent by volume of nickel oxide. The information carrying layer may be formed directly on one surface of the substrate. Alternatively, the information storage medium may further comprise a first spacer layer formed on one surface of the substrate and a second spacer layer which intervenes between the first spacer layer and the information carrying layer, wherein the first spacer layer is substantially transparent to a radiation with a predetermined wavelength and is larger in refractive index than the substrate at the aforesaid wavelength and the second spacer layer is substantially transparent to the aforesaid radiation and is smaller in refractive index than the first spacer layer at the aforesaid wavelength.

An optical recording medium such as an optical disc memory, with which data can be stored and reproduced by means of laser beam with a high sensibility is disclosed. The optical recording medium comprises:

Optical recording medium

An optical recording medium is disclosed which allows information to be recorded thereinto and read thereoutof by means of semiconductor laser light. The recording medium comprises at least a substrate and a recording layer formed on one or both sides of the substrate. Information is recorded into and read from the recording layer by laser light. The recording layer comprises an organic film of a naphthoquinonoid dye corresponding to the following molecular formula or an organic film whose major component is the naphthoquinonoid dye: ##STR1## where R is a first auxochrome and R' a second auxochrome. The first auxochrome is a hydroxyl group, an amino group, or an alkyl substituted amino group, while the second auxochrome is a hydroxyl group, an amino group, an alkyl substituted amino group or ##STR2## where X' is a hydrogen atom, an alkyl group, an amino group, a substituted amino group or an alkoxyl group.

Optical information recording medium for semiconductor laser

A lithographic resist for use in microfabrication comprising a negative-type resist containing a radical scavenger capable of preventing post-irradiation reaction.

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Tokyo, Japan

Masaki Itoh