Stock material or miscellaneous articles – Circular sheet or circular blank
Reexamination Certificate
2000-12-14
2002-07-16
Evans, Elizabeth (Department: 1774)
Stock material or miscellaneous articles
Circular sheet or circular blank
C428S064400, C428S064800, C204S192120
Reexamination Certificate
active
06420007
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording medium having a recording layer for capable of recording information and a light reflecting layer which are disposed on a substrate and a method of manufacturing such a recording medium, and more particularly to a recording medium having such a light reflecting layer formed by sputtering and a method of manufacturing such a recording medium.
2. Description of the Related Art
Usually, a light reflecting layer of a recording medium which has a recording layer capable of recording information is formed by sputtering.
FIG. 15
of the accompanying drawings shows a sputtering mechanism
1
for performing such a sputtering process. As shown in
FIG. 15
, the sputtering mechanism
1
has a target
3
(light reflecting layer material) disposed above a substrate
2
in confronting relationship thereto and supporting a permanent magnet
4
on its upper surface. An atmospheric gas, e.g., an Ar gas, is introduced into a space between the substrate
2
and the target
3
, and a certain voltage is applied between the substrate
2
and the target
3
to generate a plasma
7
therebetween. The plasma
7
causes Ar ions
5
to impinge upon the target
3
, which then discharges atoms
6
that are deposited on the substrate
2
.
However, since the intensity and distribution of a magnetic field produced by the permanent magnet
4
are constant, the sputtering process performed by the sputtering mechanism
1
is disadvantageous in that Ar ions
5
tend to concentrate on and hit a certain area of the target
3
.
As a result, atoms
6
discharged from the target
3
are liable to be deposited unevenly on the substrate
2
, forming a light reflecting layer of irregular film thickness on a recording layer on the substrate
2
. The irregular film thickness of the light reflecting layer changes the manner in which heat is transferred depending on the position accessed by a laser beam, so that the size of pits tends to vary from accessed position to accessed position. Such varying pit sizes are liable to increase jitter in recorded information. In addition, the localized impingement of the Ar ions
5
upon the target
3
is apt to shorten the service life of the target
3
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a recording medium which has a light reflecting layer formed substantially uniformly on a substrate for reduced jitter, and a method of manufacturing such a recording medium using a target whose service life is prolonged.
According to an aspect of the present invention, there is provided a recording medium comprising a substrate, a recording layer disposed on the substrate for recording information, and a light reflecting layer disposed on the substrate, the light reflecting layer being formed on the recording layer by a sputtering mechanism having a permanent magnet, an electromagnet, and a target while the intensity and distribution of a magnetic field generated by the permanent magnet and the electromagnet is being controlled by a controller.
According to another aspect of the present invention, there is also provided a method of manufacturing a recording medium having a substrate, a recording layer disposed on the substrate for recording information, and a light reflecting layer disposed on the substrate, comprising the step of forming the light reflecting layer on the recording layer with a sputtering mechanism having a permanent magnet, an electromagnet, and a target while the intensity and distribution of a magnetic field generated by the permanent magnet and the electromagnet is being controlled by a controller.
According to still another aspect of the present invention, there is also provided a method of manufacturing a recording medium having a substrate, a recording layer disposed on the substrate for recording information, and a light reflecting layer disposed on the substrate, comprising the step of forming the light reflecting layer on the recording layer with a sputtering mechanism having a permanent magnet and a target while the intensity and distribution of a magnetic field generated by the permanent magnet is being changed by displacing the permanent magnet parallel to the substrate.
According to yet another aspect of the present invention, there is also provided a method of manufacturing a recording medium having a substrate, a recording layer disposed on the substrate for recording information, and a light reflecting layer disposed on the substrate, comprising the step of forming the light reflecting layer on the recording layer with a sputtering mechanism having an electromagnet and a target while the intensity and distribution of a magnetic field generated by the electromagnet is being controlled by a controller.
With the above arrangement, the light reflecting layer may be formed substantially uniformly on the substrate for reduced jitter, and the target may be of an increased service life.
A direct current may flow through the electromagnet. The permanent magnet may be of a coaxial cylindrical shape or a bar shape. The permanent magnet may comprise an annular array of bar-shaped permanent magnets.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example.
REFERENCES:
patent: 5512150 (1996-04-01), Bourez
patent: 5589040 (1996-12-01), Nishimura
patent: 5693199 (1997-12-01), Bourez
patent: 6093290 (2000-07-01), Tamura
patent: 2-300288 (1990-12-01), None
patent: 3-224793 (1991-10-01), None
patent: 4-146189 (1992-05-01), None
Japanese Abstract No. 08236062, dated Sep. 13, 1996.
Japanese Abstract No. 10088341, dated Apr. 7, 1998.
Japanese Abstract No. 08081769, dated Mar. 26, 1996
Japanese Abstract No. 62017174, dated Jan. 26, 1987.
Japanese Abstract No. 07262633, dated Oct. 13, 1995.
Japanese Abstract No. 09125247, dated May 13, 1997.
Japanese Abstract No. 06025845, dated Feb. 1, 1994.
Japanese Abstract No. 11144338, dated May 28, 1999.
Patent Abstract of Japan 04146189 A, May 20, 1992.
Patent Abstract of Japan 02300288 A, Dec. 12, 1990.
Patent Abstract of Japan 03224793 A, Oct. 3, 1991.
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