Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
2000-07-25
2004-06-22
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S112230
Reexamination Certificate
active
06754161
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a manufacturing method for an optical information recording medium and a manufacturing device for an optical information recording medium, and is for instance applicable to light exposure devices for base disks. The present invention regulates the temperature of the semiconductor laser by compensating for chromatic aberrations or compensating for fluctuations in the wavelength so that with a laser beam from a laser-pumped semiconductor laser, a base disk can be exposed at high precision.
2. Description of the Related Art
In the process of the related art for manufacturing a base disk, after exposing the disk in the exposure device, an optical disk is manufactured by a stamper. The stamper further produces the base disk in mass quantities and an optical disk is produced after forming a protective film on the base disk.
A perspective view of the optical disk is shown in FIG.
8
. After an information recording surface
3
is formed on the base disk
2
, a protective film
4
is formed to produce an optical disk
1
.
The base disk
2
is disk-shaped member of transparent plastic. Tiny irregularities (convex and concave shapes) are formed on the information recording surface side of this base disk
2
. These tiny irregularities are set as various shapes according to the manufacture of the optical disk. In an optical disk for record and reproduction such as the initial minidisk, groove shapes are formed by a laser beam to constitute the guide grooves shown by arrow A in the enlarged view in FIG.
8
. In an optical disk solely for reproduction such as a compact disc, concave shapes are formed to constitute the pits shown by arrow B in the enlarged view of FIG.
8
. In initial MO (magnetic optical) disks made to ISO standards, both pits and grooves are formed.
Among the optical disks
1
capable of recording/reproducing, phase-change optical disks have an information recording surface formed of laminations of phase-change layers and reflective layers on the surface of the base disk
2
formed with these tiny irregularities. On optical magnetic disks, the information recording surface is formed of laminations of magnetic layers and reflective layers. On an optical disk
1
solely for reproduction (playback), an information recording surface is formed of a reflective layer on the surface of the disk substrate
2
.
A diagrammatic sketch of the manufacturing process for the optical disk for producing the disk substrate
2
is shown in
FIGS. 9A
to
9
F. In the manufacturing process for this optical disk, the surface of a glass substrate
5
is ground (polished) flat, the glass substrate
5
washed (FIG.
9
A), and a photoresist
6
applied by spin coating (
FIG. 9B
) to the surface of the glass substrate
5
. The photoresist
6
here is applied in a thickness of approximately 100 nm, using a material that is alkali-soluble when exposed to light. The manufacturing method for the optical disk in this way produces a base disk
7
from this glass substrate
5
.
Next, in the optical disk manufacturing process, the disk base
7
is set in the exposure device and the disk base
7
driven to rotate at a specific speed (FIG.
9
C). While in this state, a laser beam L
1
as the exposure light, is focused by means of an objective lens
6
on the photoresist
6
on the disk base
7
, and along with modulating the exposure laser beam L
1
by means of a modulating signal, the beam position of the exposure laser beam L
1
is shifted sequentially to the outer circumference. The scanning track of the exposure laser beam L
1
is in this way formed in a spiral shape in the optical disk manufacturing process, and a latent image formed according to the modulation signal in this scanning track.
The latent image formed on the base disk
7
in this way in the optical disk manufacturing process is developed (
FIG. 9D
) and the portions of the photoresist
6
exposed to light are dissolved away by the developer fluid. In this way, the tiny irregularities are formed on the surface of the base disk
7
. The example in
FIG. 9D
shows that the base disk
7
is formed with the tiny irregularities corresponding to the grooves and lands.
In the next step (
FIG. 9E
) of the process for manufacturing the optical disk, after a nickel plating layer
8
is formed by nickel (Ni) plating on the side formed with the tiny irregularities, this nickel plating layer
8
is then peeled away from the base disk
7
. In this way, in the optical disk manufacturing process, the tiny irregularities of the base disk
7
are transferred to the nickel plating layer, and a frame made by the nickel plating layer
8
then set in a metal mold to make a stamper
9
.
Next, in the process for manufacturing the optical disk, the disk substrate
2
is made by the plastic injection molding or the so-called 2P method (photo polymerization) using the stamper
9
(FIG.
9
F). The tiny irregularities of the base disk
7
transferred to the stamper
9
are now transferred to the disk substrate
2
. The latent image of the tiny irregularities described using
FIG. 8
is in this way formed on this disk substrate
2
by exposure of the base disk
7
to light in the exposure device.
A flat view showing the exposure device used in light exposure of the base disk
7
is shown in
FIG. 10. A
diagrammatic sketch for describing the optical system of an exposure device
11
is shown in FIG.
11
. The exposure device
11
contains a base disk
7
on a turntable
12
, driven to rotate in a specific direction shown by the arrow A. The exposure device
11
drives an optical drive table
13
radially across the base disk
7
as shown by the arrow B. In this way, the exposure device
11
makes an exposure laser beam (LR) scanning track in a spiral shape on the base disk
7
by means of the optical system contained in the optical drive table
13
, and makes a latent image consisting of arrays of pits in the scanning track.
A laser light source
14
in the exposure device
11
is a gas laser comprising Ar, Kr, He—Cd, etc. An (exposure) laser beam LR is beamed within a wavelength of 500 nm and quantity of light of 50 mW to expose the photoresist on the base disk
7
to light. When the laser light source
14
is for a Kr laser, the (exposure) laser beam LR is beamed at a wavelength within 413 nm.
An electro-optical crystal element
15
and an optical detector element
16
compensate (offset) fluctuations of the luminous energy in the (exposure) laser beam LR and emit the beam. In other words, the electro-optical crystal element
15
changes the polarized plane of the (exposure) laser beam LR emitted by the laser light source
14
according to a drive signal and the optical detector element
16
selectively permeates the specified polarized surface components. Next, a beam splitter
17
separates the (exposure) laser beam LR into two beams and outputs these beams and the optical receive element
18
receives the (exposure) laser beam LR on the side permeated by the beam splitter
17
and outputs the detected quantity of light (luminous energy).
A recording optical power control circuit
19
(
FIG. 11
) generates a drive signal so that the signal level with the light quantity detection results from the optical receive element
18
match a reference voltage REF and drives the electro-optical crystal element
15
. The electro-optical crystal element
15
thus forms a feedback loop along with the optical detector element
16
, the beam splitter
17
, the optical receive element
18
, and the optical receive element
18
and maintain the luminous energy (hereafter, quantity of light) of the (exposure) laser beam LR at a fixed luminous energy level.
The electro-optical crystal element
15
along with a feedback loop having a frequency response with an upper limit of 1 [MHz], reduces the noise of the (exposure) laser beam LR.
A lens
21
(
FIG. 10
) converts the side of the exposure laser beam LR reflected by the beam splitter
17
into a concentrated light beam and outputs it to an AOM (aco
Aki Yuichi
Masuhara Shin
Yamamoto Kenji
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sony Corporation
Tran Thang V.
LandOfFree
Manufacturing method for optical recording medium and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manufacturing method for optical recording medium and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacturing method for optical recording medium and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3364994