Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
1999-06-07
2001-11-27
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C428S064400
Reexamination Certificate
active
06324156
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an information-recording medium that uses light to recording information and to play back or erase recorded information, to a method for manufacturing such an information recording medium, to a method for recording and playing back information and to a method for erasing information, and more specifically it relates to an information-recording medium that is capable of recording high-density information and a method for manufacturing such an information-recording medium.
2. Description of the Related Art
Magneto-optical discs and DVD-RAMs are known as information-recording media which use light to recording information and to play back or erase recorded information. In information-recording media of the past, the medium was formed by recording regions (land parts) that record information and separating region (groove parts) that separate adjacently arranged recording regions from each other, and a protective film, a recording film, a protective film and a reflective film being laminated in that order along the pattern of a convex-concave configuration reflecting the land parts and the groove parts which are formed on a surface of a transparent substrate.
A laser beam is used for the recording, playback, and erasing of information, recording marks being applied to a part of the recording film corresponding to the recording region. By reducing the spacing between the land and groove parts for the purpose of recording more information, the density of the information recording is increased.
In an information-recording medium of the past, however, if the spacing between the land and groove parts is reduced in an attempt to record more information, the recording marks of recorded information spill over from the land parts to the groove parts.
When the recording marks spill over from the land parts to the groove parts, in an information erasing operation, incomplete erasure can occur, the result being that information from neighboring land parts are read simultaneously in the next play backing operation, this phenomenon being generally call crosstalk.
The information-recording medium that is disclosed in the Japanese Unexamined Patent Publication (KOKAI) No. 9-190649 reduces the crosstalk from the header region by displacing the pre-pit portion that is formed in a region placed in front of the recording region (the header region) in towards the direction of the inner circumference with respect to a center portion of the land part.
The occurrence of crosstalk in an information-recording medium of the past was an unavoidable problem when recording information at a high density.
With the information-recording medium that is disclosed in the Japanese Unexamined Patent Application publication H9-190649, although the crosstalk from the header region is reduced, crosstalk from the recording region was not reduced.
Accordingly, it is an object of the present invention to improve over the drawbacks as noted above in the prior art, by providing an information-recording medium, a method for manufacturing such an information-recording medium, a method for recording and playbacking information and a method for erasing information, so that the crosstalk generated when the play backing operation can be reduced and the recording information with high-density can be realized.
SUMMARY OF THE INVENTION
In order to achieve the above-noted object, the present invention adopts the following basic technical constitution.
Specifically, the first aspect of the present invention relates to an information-recording medium which has a recording film that records information, a reflective film, which is formed on the recording film, and which reflects light so as to record information on the recording film, play back information therefrom, or erase information and a protective film that is formed between the recording film and the reflective film, and which has a configuration so that the reflectivity of a part corresponding to the recording region of the information-recording medium will differ from each other depending upon whether or not the recording film of the recording region has information recorded thereon, while the reflectivity of a part corresponding to the separating region of the information-recording medium separating adjacently arranged recording regions from each other, is substantially uniform to each other whether or not the recording film of the separating region has information recorded thereon.
According to the present invention, the protective film is configured so that a clear distinction is made in the recording region between the condition in which information is recorded on a recording track and the condition in which information is not recorded on a recording track, while in the separating region, the distinction between the condition in which information is recorded and the condition in which information, is not recorded is not made.
The result is that it is possible to greatly reduce cross talk whereby information of adjacent recording tracks is simultaneously read, and contributing to improve density of recording information.
In accordance with the present invention, the protective film may have a thickness so that in the recording region, the reflectivity of a part corresponding to the recording region of the information-recording medium will differ from each other depending upon whether or not the recording film of the recording region has information recorded thereon, while the reflectivity of a part corresponding to the separating region of the information-recording medium is substantially uniform to each other whether or not the recording film of the separating region has information recorded thereon.
The protective film of the present invention may have a convex-concave configuration corresponding to the recording region and the separating region, respectively.
Further, in the present invention, a surface of the recording film is preferably flat, and further the reflective film may have a convex-concave configuration that is substantially the same as that of the protective film.
The recording film of the present invention, may have a convex-concave configuration that is substantially the same as that of the protective film and the protective film may fill this pattern of surface unevenness of the recording film and have a flat surface, further the surface of the reflective film may be flat.
On the other hand, a thickness of the protective film is established in accordance with at least one parameter of the group consisting of the wavelength of the light used for play back information, the material of the recording film, the material of the protective film, and the material of the reflective film.
Further, in the present invention, the protective film may have a thickness so that in a case of a light having a first wavelength being used, the reflectivity of a concaved part of the convex-concave configuration will be uniform whether or not the recording film has information recorded thereon, while the reflectivity of a convexed part thereof will differ from each other, depending upon whether or not the recording film has information recorded thereon, further in a case of a light having a second wavelength being used, the reflectivity of a convexed part of the convex-concave configuration will be uniform whether or not the recording film has information recorded thereon, while the reflectivity of a concaved part thereof will differ from each other, depending upon whether or not the recording film has information recorded thereon.
The second aspect of an information-recording medium according to the present invention can record information onto circular tracks, the medium comprises a plurality of first tracks eccentrically arranged to each other and a plurality of second tracks each being eccentrically arranged to each other and between the first tracks adjacently arranged, wherein the first tracks has different reflectivities from each other corresponding to the fact that whether or not a par
Dinh Tan
Hayes Soloway Hennessey Grossman & Hage PC
NEC Corporation
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