Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1998-10-19
2001-06-05
Neyzari, Ali (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
C369S059100, C369S124010
Reexamination Certificate
active
06243326
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to magneto-optic recording media and recording and reproduction devices therefor, and more specifically to a magneto-optic recording medium capable of recording information by optical super-resolution and a recording and reproduction device therefor.
BACKGROUND ART
Magneto-optic disks have been noted as a medium which is rewritable, has large recording capacity and is highly reliable, and they have been put to use as memories for computers and the like. However, as the amount of information is increased and devices are miniaturized, a recording/reproduction technology with higher density is increasingly demanded.
High-density recording/reproduction technology is constituted by device techniques and medium techniques. The former techniques include optical super-resolution for obtaining a condensation spot exceeding the diffraction limit of laser light, reduction in laser beam wavelength, and the like. The latter techniques include reduction of medium pitch, improvement of reproduction resolution by means of magnetic multilayered film, and the like. The technique for improvement of reproduction resolution by means of magnetic multilayered film employs the fact that the temperature within a laser spot is maximized around its center or presents a Gaussian distribution to selectively transfer the state of a recording layer to a reproduction layer and read the state of the reproduction layer, and at present there are three main techniques, i.e. FAD, RAD and CAD (Center Aperture Detection). According to these techniques, the front or rear side or the center of a laser spot can be masked to provide a substantial reproduction area that is smaller than the diameter of the laser spot. This results in an improved reproduction density.
Conventionally, a magneto-optic disk employed in optical super-resolution includes a substrate, a base layer formed on the substrate, a reproduction layer formed on the base layer, a recording layer formed on the reproduction layer, and a protection layer formed on the recording layer. A magneto-optic disk with such a structure typically has a recording capacity of approximately 5 Gbytes.
The FAD, RAD and CAD systems described above cannot provide a magneto-optic disk with sufficiently large recording capacity, since the laser beams radiated for recording cause enlargement of the recording area that exceeds the Curie temperature. The laser beams radiated for reproduction also result in enlargement of the reproduction area exceeding the Curie temperature and hence low carrier-noise (CN) ratio in reproduction.
DISCLOSURE OF THE INVENTION
A main object of the present invention is to provide a large-capacity magneto-optic recording medium capable of recording/reproduction, and a recording/reproduction device therefor.
According to one aspect of the present invention, a magneto-optic recording medium has a recording capacity of 5 to 20 Gbytes, preferably 8 to 20 Gbytes, or 6 to 10 Gbytes.
According to another aspect of the present invention, a magneto-optic recording medium includes a substrate, a base layer formed on the substrate, a reproduction layer formed on the base layer, a recording layer formed on the reproduction layer, a first protection layer formed on the recording layer, a heat emitting layer formed on the first protection layer, and a second protection layer formed on the heat emitting layer. Preferably the magneto-optic recording medium also includes an intermediate layer formed between the reproduction layer and the recording layer.
In the magneto-optic recording medium, the heat generated within the recording layer by laser beams can rapidly be diffused via the heat emitting layer to reduce enlargement of the area exceeding the Curie temperature. Thus, information can be recorded at higher density.
According to still another aspect of the present invention, a recording/reproduction device for a magneto-optic recording medium includes a magnetic unit which supplies magnetic field to the magneto-optic recording medium in response to a recording signal indicative of information to be recorded, an optical unit which radiates a laser beam to the magneto-optic recording medium, and a pulsing circuit which pulses a laser beam. Preferably the recording/reproduction device also includes a blocking unit which blocks the center of a laser beam in reproduction.
In the recording/reproduction device, a laser beam to be radiated to the magneto-optic recording medium can be pulsed and the center of the laser beam can preferably be blocked to magnetize a recording area of the magneto-optic recording medium before diffusion of the heat generated by the laser beam in the magneto-optic recording medium and thus reduce enlargement of a recording area exceeding the Curie temperature. Thus, information can be recorded at higher density.
The above and other objects, features, aspects and advantages of the present invention become more apparent from the following detailed description of the present invention with reference to the accompanying drawings.
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Proceedings of Magneto-Optical Recording International Symposium '94, J. Magn Soc. Jpn., vol. 19, Supplemnet No. S1 (1995), pp. 273-278, 1994 by The Magnetics Society of Japan.
Proc.Int. Symp. on Optical Memory, 1989; Japanese Journal of Applied Physics, vol. 28 (1989) Supplement 28-3, pp. 197-200.
Murata Seiji
Sumi Satoshi
Suzuki Yoshihisa
Tanase Kenji
Torazawa Kenji
Armstrong Westerman Hattori McCleland & Naughton, LLP
Neyzari Ali
Sanyo Electric Co,. Ltd.
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