Dynamic information storage or retrieval – Storage medium structure – Layered
Reexamination Certificate
1999-09-09
2002-09-24
Ometz, David L. (Department: 2652)
Dynamic information storage or retrieval
Storage medium structure
Layered
Reexamination Certificate
active
06456586
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese application No. HEI 10(1998)-256253 filed on Sep. 10, 1998, whose priority is claimed under 35 USC §119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magneto-optical recording medium on which information is recorded and from which information is reproduced with irradiation of light.
2. Description of Related Art
Magneto-optical recording media have been in actual use as rewritable optical recording media. With such a magneto-optical recording medium, there is found a defect that reproducing characteristics deteriorate as the size of a recording bit, which is a unit magnetic area for recording, and the interval between recording bits become smaller than the diameter of a spot of a light beam which is emitted from a semiconductor laser and converged onto the magneto-optical recording medium.
The cause for this defect is that recording bits adjoining a targeted recording bit fall within the spot of the light beam converged on the targeted recording bit and therefore individual recording bits cannot be separately reproduced.
In order to eliminate the above-described defect, Japanese Unexamined Patent Publication No. HEI 6(1994)-150418 proposes a magneto-optical recording medium constructed to have a reproducing layer which is in an in-plane magnetization state at room temperature and changes into a perpendicular magnetization state as temperature rises, a recording layer and a non-magnetic intermediate layer provided between the reproducing layer and the recording layer to couple the reproducing layer and the recording layer magnetostatically. In this recording medium, by utilizing a heat distribution in the light beam spot, information transferred from the recording layer to the reproducing layer is reproduced only in a recording bit at a temperature higher than a threshold temperature. With this constitution, if adjoining recording bits are within the spot of the converged light beam, information in the targeted recording bit can be separately reproduced.
Japanese Unexamined Patent Publication No. HEI 9(1997)-231631 proposes a construction wherein a layer of a metal film or a layer of a dielectric film and a metal film is provided between the reproducing layer and the recording layer. With this constitution, it is possible to control a leakage magnetic field generated from magnetization present in the reproducing layer and also to utilize light reflected by the metal film positively. Therefore, favorable reproducing characteristics can be obtained.
However, the above-described Japanese Unexamined Patent Publications Nos. HEI 6(1994)-150418 and HEI 9(1997)-231631 cannot provide good recording and reproducing characteristics when smaller-sized recording bits and smaller intervals between recording bits are adopted. Accordingly, there is a problem that it is impossible to realize a higher-density recording and reproducing than now and therefore a larger memory capacity cannot be expected.
SUMMARY OF THE INVENTION
Under these circumstances, an object of the present invention is to provide a magneto-optical recording medium permitting improvement in the quality of reproducing signals and in recording an reproducing characteristics and allowing a higher-density recording and reproduction, as well as a production process for such a medium.
The present invention provides a magneto-optical recording medium provided with a reproducing magnetic layer having a magnetic layer which is in an in-plane magnetization state at room temperature but shifts to a perpendicular magnetization state as temperature rises; a dielectric layer; and a recording magnetic layer having a magnetic layer which exhibits a perpendicular magnetization, sequentially from a photo-receptive side, the recording medium being characterized by further comprising a metal layer between the reproducing magnetic layer and the dielectric layer.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred examples of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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patent: 9-231631 (1997-09-01), None
Iketani Naoyasu
Murakami Yoshiteru
Suzuki Ippei
Takahashi Akira
Altman Franklin D.
Nixon & Vanderhye P.C.
Ometz David L.
Sharp Kabushiki Kaisha
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