Taiyo Yuden Co., Ltd.

Ryou Negishi

Toru Fujii

Emiko Hamada

Toshiaki Tajima

Yuji Tomizawa

Masahiko Hirano

An optical information medium made up of a transparent substrate capable of allowing a recording laser beam to penetrate therethrough; a recording layer formed on the transparent substrate; and a reflective layer formed on the recording layer and reflecting a reproducing laser beam thereupon. A numerical aperture of an objective lens of an optical pickup for irradiating the recording laser beam on the recording layer is approximately 0.65, and the numerical aperture of an objective lens of the optical pickup for irradiating the recording laser beam on the reflection layer is approximately 0.60. An inclination angle &thgr; at both edges of the groove for tracking, being formed spirally on the surface of the transparent substrate on which the recording layer is formed, with respect to the main surface of the transparent substrate, is selected to be from 55&deg; to 75&deg;. An index &prop;, expressed by 1&minus;Dr/Ds when assuming that the depth of the groove on the transparent substrate is Ds and the depth of the recording layer at the position of said groove is Dr, is selected to be from 0.2 to 0.4. Further, the full width at half maximum of the groove on the transparent substrate is selected to be from one-third (&frac13;) to a half (&frac12;) of the pitch p of the groove. With this optical information medium, it is possible to record high density signals as signals that are readable optically, as well as to record them with stability.

Optical information medium and recording method therefor

An optical information recording medium enables accurate tracking servo throughout the recording area including inner and outer peripheral region by way of reducing the differences between the amplitudes of the push-pull signals from those regions. The medium comprises a light transmitting substrate, a tracking groove formed on a surface of the light transmitting substrate, a recording layer formed on the surface of the substrate having the groove, and a reflective layer, formed on the recording layer, for reflecting recording and reproducing laser beams. The width of the groove at the outer peripheral region is made smaller than that at the inner peripheral region. Specifically, the ratio of the width at the outer peripheral region to that at the inner peripheral region is set to be greater than or equal to 0.8.

High-density optical information recording medium and a substrate and a stamper for the manufacture thereof

An optical information recording medium provides a high reflectance of a laser beam and thus enables an accurate tracking servo. The optical information recording medium, for recording optically readable signals thereon through the use of a recording laser beam, includes a light transmitting substrate, a tracking groove formed on a surface of the light transmitting substrate, a land formed between two neighboring tracks of the tracking groove, a recording layer formed on a surface of the light transmitting substrate on which the tracking groove and the land are provided, and a reflective layer formed on the recording layer for reflecting the recording laser beam. A top width D of the land is arranged to be within the range of about 0.30&lE;D&lE;0.45 &mgr;m.

Optical information recording medium for recording optically reproducible signals thereon through the use of a recording laser beam and method for recording optical information thereon

An optical information medium is made up of a transparent substrate for a reproducing laser beam to penetrate therethrough, a recording layer formed on the transparent substrate and a reflective layer for reflecting the reproducing laser beam thereupon, thereby enabling the recording of optically readable signals by a recording laser beam incident upon the transparent substrate. This optical information medium has a spiral-like tracking guide on a side surface of the transparent substrate, on which the recording layer is formed, and on lands defined between the spiral-like tracking guide are formed land pre pits indicative of the sector information, including the address and so on, wherein the length of the land pre pits is selected to be from 50% to 83% of the length of the minimum pit and to be from 1.5 to 2.5 times the length of the channel clock. Also, the film thickness of the recording layer in the area of the land pre pits is selected to differ from the film thickness of the recording layer in the area of the tracking guide.

Optical information medium

A method and an apparatus capable of recording optical information at high density are disclosed. A recording pulse which includes a top pulse followed by a multiple pulse set is generated to form a pit, wherein, based on the distance from the top pulse, either pulse widths of pulses within the multiple pulse set are set to be sequentially smaller or pulse intervals of pulses within the multiple pulse set are set to be sequentially larger.

Method and apparatus for recording optical information by varying recording pulse width

An optical information medium, comprising: a transparent substrate for penetrating a recording laser beam therethrough; a recording layer being formed on the transparent substrate; and a reflective layer being formed on the recording layer and for reflecting reproducing laser beam thereupon. A numerical aperture of an objective lens of an optical pickup for irradiating the recording laser beam on the recording layer is approximately 0.65, and the numerical aperture of an objective lens of the optical pickup for irradiating the recording laser beam on the reflection layer is approximately 0.60. An inclination angle &thgr; at both edges of the groove for tracking, being formed spiral-like on the surface of the transparent substrate on which the recording layer is formed, with respect to the main surface of the transparent substrate is selected from 55&deg; to 75&deg;. An index &agr;, being expressed by 1&minus;Dr/Ds when assuming that depth of the groove on the transparent substrate is Ds and depth of the recording layer at position of said groove is Dr, is selected from 0.2 to 0.4. Further, full width at half maximum of the groove on the transparent substrate is selected to be from one-third (&frac13;) to a half (&frac12;) of the pitch p of the groove. With this optical information medium, it is possible to record high density signals as signals being readable optically, as well as to record them with stability.

An optical information medium comprises a first disc forming information recording layer on a main surface thereof, a second disc being bonded to the first disc at the surface where the information recording layer is formed by way of an adhesive. A hydrophilic resin film is formed on the surface of the disc at the inner peripheral side extending from the center hole to the information non-recording area. The hydrophilic resin film is damp and is rough compared with the other portion formed of non-hydrophilic resin, and it is elastic. The characters, patterns or designs can be printed on the optical information medium using water-base ink, etc. after manufacturing the optical information medium. Further, the hydrophilic resin film is formed on the disc at the portion outside the information recording area. Further, when the hydrophilic resin film is formed, the surface of the inner and outer peripheral portions of the optical information medium protuberates slightly thicker than other portion so that the fats of the fingers is hardly stuck to the recording surface of the optical information medium even if the inner and outer peripheral portions of the disc is grasped by hand.

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Tokyo, Japan

Ryou Negishi