Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making named article
Reexamination Certificate
1999-11-03
2002-02-12
Angebranndt, Martin (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making named article
C430S320000, C430S945000, C369S084000
Reexamination Certificate
active
06346367
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk and a method for manufacturing the same, and more particularly, to an optical disk with an improved information pit structure and a method for manufacturing the same.
2. Description of the Related Art
An optical disk such as a compact disk (CD) or a digital versatile disk (DVD) used as a medium for recording and/or reproducing audio or video information, as shown in
FIGS. 1 and 2
, includes information pits
2
recessed from a reference surface
1
a
, and the information is written based upon the information pits
2
. The reference surface
1
a
corresponds to the upper surface of a land on an optical disk
1
or that of a groove. The information written on the optical disk
1
can be reproduced by an optical pickup (not shown) of a recording/reproducing apparatus, as is well known. To reproduce the information of the optical disk
1
, the optical pickup irradiates a laser beam LB onto the reference surface
1
a
of the optical disk
1
and detects the amount of the laser beam reflected from the optical disk
1
. Since the irradiated laser beam LB is scattered at the portion corresponding to the information pit
2
, the amount of the laser beam reflected toward the optical pickup is reduced. The reduction in the amount of the laser beam LB occurs in all the information pits
2
, and the information of the optical disk
1
can be reproduced by detecting the change in the reflected light amount in the information pit
2
. Thus, the less the amount of the laser beam reflected from the information pit
2
, the better the information reproduction characteristics. It is generally known that the amount of the light reflected from the information pit
2
becomes a minimum when the depth (d) of a bottom surface
2
a
of the information pit
2
is set to &lgr;/4n (&lgr;: the wavelength of the laser beam and n: refractive index of the optical disk).
In the conventional optical disk, to adjust the depth of the information pit appropriately, when manufacturing a master board for manufacturing the optical disk, the thickness of a photoresist layer must be consistently controlled. Also, even if the appropriate depth of the information pit is adjusted correctly, the laser beam reflected from the bottom surface of the information pit may be detected by an optical pickup, which has an adverse effect on the information reproduction characteristics of the optical disk.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an optical disk with an improved information pit, by which a laser beam irradiated onto an information pit is suppressed from being reflected toward an optical pickup.
It is another object of the present invention to provide a method of manufacturing an to optical disk, by which a laser beam irradiated onto an information pit is suppressed from being reflected toward an optical pickup.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, to achieve the first object of the present invention, there is provided qn optical disk including a plurality of information pits for recording predetermined information; and a plurality of projection [respectfully] respectively projecting form bottom surfaces of the plurality of information pits to scatter the laser beam irradicated onto each information pit.
To achieve the second object of the present invention, there is provided a method of manufacturing an optical disk having predetermined information recorded by a plurality of information pits, including the steps of preparing a master board having a photoresist layer in its one plane; exposing portions of the photoresist layer where the plurality of information pits are to be formed, to at least a pair of laser beams partly overlapping with each other; forming concavities of a same pattern as the information pits of the optical disk by etching the exposed portions; and forming the optical disk using the master board having the concavities.
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Keizer, E.O., “VideoDisc Mastering”, RCA Review, vol. 39(1), pp. 60-86, Mar. 1978.*
Japanese Abstract for JP 63-149846, published Jun. 22, 1988.
Ahn Young-man
Suh Hae-jung
Angebranndt Martin
Staas & Halsey , LLP
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