Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1999-08-30
2002-08-27
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044280, C369S112080, C369S112240
Reexamination Certificate
active
06442110
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-249880 filed Sep. 3, 1998 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a beam irradiation apparatus, an optical apparatus having a beam irradiation apparatus for an information recording medium, a method for manufacturing an original disk for an information recording medium, and a method for manufacturing an information recording medium.
2. Description of the Related Art
As information recording media, there are CD-ROMs (Compact Disk—Read Only Memories), so-called CD-Rs, and recordable disks such as magneto optical disks.
FIG. 8
shows a perspective view of such a recording medium. Each of
FIGS. 9A and 9B
is a schematic oblique view of a principal part showing sections of a part of an optical disk. On a signal recording region
2
formed on a disk substrate
1
, minute concaves and convexes
18
are formed as shown in
FIGS. 9A and B
. The minute concaves and convexes
18
are formed by, for example, continuous grooves
3
as shown in FIGS.
9
A. Alternatively, a sequence of pits
4
are spirally formed on each of tracks having a predetermined track pitch, for example, in the range of 1 &mgr;m to 2 &mgr;m.
On a signal recording surface having the minute concaves and convexes formed thereon, a light reflection film or a protection film is formed, in the case of, for example, CD-ROMS. In the case of recordable optical disks of phase change type, magneto optical recording type or the like, a recording layer using a phase change film or a magnetic film is formed on the signal recording surface having the minute concaves and convexes formed thereon, and a light reflection film and a protection film are formed thereon.
For example, in the above described recordable optical disks, the so-called lands interposed between the grooves
3
are typically used as a recording section, and the grooves
3
are used as a light reflection section for tracking.
Reproduction from such an information recording medium such as an optical disk and optical recording onto a recordable optical disk are conducted by irradiating a laser light typically from a rear surface of the substrate
1
opposite to the recording surface while rotating the disk.
For example, in the CD-ROM used exclusively for reproduction, information readout and tracking are conducted by detecting a reflected light or diffracted light coming from the pit
4
.
In the recordable optical disk, information is optically written (recorded) on the recording layer located, for example, on the land portion by irradiation a laser light. By using a reflected light, readout (reproduction) of the recorded information is conducted. In order to irradiate a laser light for recording or reproduction always onto a predetermined track, a reflected light from, for example, the groove
3
is detected and tracking is effected.
As for the formation of the above described minute concaves and convexes, they are molded simultaneously with the molding of the disk substrate
1
by, for example, the injection molding. Alternatively, for example, an ultraviolet ray setting resin layer is formed on the disk substrate
1
by coating, and minute concaves and convexes are formed thereon. The latter method is the so-called 2P method (Photo Polymerization method) or the like.
In either of the injection molding method and the 2P method, a stamper having minute concaves and convexes inverted in pattern as compared with the minute concaves and convexes formed on the disk substrate
1
is used. For example, in the case of the injection molding, the stamper having the above described inverted pattern is disposed in a cavity of a molding die, and a disk substrate having concaves and convexes transferred from the stamper is molded by the injection molding of resin. In the case of the 2P method, there are included the steps of pressing the stamper against, for example, an ultraviolet ray setting resin layer coated onto the disk substrate, forming thereby minute concaves and convexes, then conducting cure using irradiation of ultraviolet rays, and thus forming a disk having minute concaves and convexes transferred from the stamper.
A method for fabricating such a stamper having minute concaves and convexes formed thereon will now be described by referring to perspective views in respective steps shown in
FIG. 10A
to FIG.
10
C. In this case, an original disk is first fabricated. As for the fabrication of this original disk, a disklike substrate
11
, such as a glass substrate, serving as a substrate of the original disk and having a smoothed mirror surface is prepared as shown in FIG.
10
A.
Onto the smooth mirror surface of this substrate
11
, a photoresist layer
12
containing, for example, positive photoresist is coated by using the rotation coating method or the like so as to have a required thickness, such as a thickness of 0.1 &mgr;m as shown in FIG.
10
B.
Then, this photoresist layer
12
is objected to a required pattern exposure. In other words, while the substrate
11
is being rotated around its center axis as shown in
FIG. 10C
, a laser beam
20
is focused onto the photoresist layer
12
by a focusing lens
21
, and irradiated while it is relatively moved in the radial direction of the substrate
11
. A latent image of minute concaves and convexes, i.e., a latent image
22
of a groove or pit is formed along a spiral line.
The photoresist layer
12
thus objected to the pattern exposure is developed. By doing so, there is obtained an information recording medium having minute concaves and convexes
13
each comprised of a groove or a pit formed by removing the photoresist layer
12
according to a predetermined exposure pattern. In this example, an original disk
14
for manufacturing optical disks is obtained.
FIG. 11A
or B shows a partial perspective view thereof.
By using the original disk
14
thus formed, a stamper is fabricated. As for the fabrication of the stamper, a metal layer
15
is formed on the surface of the original disk
14
having minute concaves and convexes
13
formed thereon by using a Ni plating as shown in FIG.
12
A. The metal layer
15
is exfoliated from the original disk
14
. By doing so, a stamper
17
comprised of the metal layer
15
having minute concaves and convexes
16
formed by inverting in pattern the minute concaves and convexes
13
of the original disk
14
is formed as shown in FIG.
12
B.
By using the stamper
17
thus formed, it is possible as shown in
FIGS. 13A and 13B
to obtain an optical disk, i.e., an information recording medium
19
, having minute concaves and convexes
18
inverted in pattern as compared with the minute concaves and convexes
16
of the stamper
17
, i.e., having grooves
3
and pits
4
shown in FIG.
9
A and
FIG. 9B
, by using the above described injection molding or 2P method.
In this case, the stamper
17
has been formed from the original disk
14
by the Ni plating. An alternative method includes the steps of fabricating a so-called master from the original disk
14
by the Ni plating, fabricating a so-called mother by transferring the master, and fabricating a stamper by transfer from the mother.
An exposure apparatus, i.e., a beam irradiation apparatus, used in the exposure process for the photoresist layer
12
has a schematic configuration as shown in FIG.
14
. There is provided a beam generation source
31
for generating a laser light, to which the photoresist layer
12
is exposed. The laser light emitted from the beam generation source
31
is focused and irradiated on the photoresist layer
12
of the substrate
11
to be exposed, via a mirror
32
, a condenser lens
33
, a modulator
34
, a collimator lens
35
, mirrors
36
and
37
, and an objective lens, i.e., a focusing lens
21
.
With respect to the irradiation object, the beam irradiation apparatus conducts a light intensity modulation of the beam, or concretely turns on and off the beam,
Imanishi Shingo
Kashiwagi Toshiyuki
Yamamoto Masanobu
Edun Muhammad
Sonnenschein Nath & Rosenthal
Sony Corporation
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