U.S. patent application number 11/183515 was filed with the patent office on 2005-11-10 for optical disk, method for producing the same, and apparatus for producing the same.
This patent application is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Hayashi, Kazuhiro, Hisada, Kazuya, Inoue, Kazuo, Ohno, Eiji.
Application Number | 20050249104 11/183515 |
Document ID | / |
Family ID | 26590749 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050249104 |
Kind Code |
A1 |
Hisada, Kazuya ; et
al. |
November 10, 2005 |
Optical disk, method for producing the same, and apparatus for
producing the same
Abstract
An optical disk of the present invention includes a first
substrate having a signal area on a principal plane and a central
hole, and a second substrate that is transparent and attached to
the first substrate. The second substrate is thinner than the first
substrate, and has a central hole whose diameter is larger than
that of the first substrate. The first substrate and the second
substrate are attached to each other with radiation curable resin
(adhesive member) disposed therebetween so as to extend at least
from an inner peripheral edge of the second substrate to an outer
peripheral edge thereof.
Inventors: |
Hisada, Kazuya; (Osaka-shi,
JP) ; Hayashi, Kazuhiro; (Neyagawa-shi, JP) ;
Inoue, Kazuo; (Osaka-shi, JP) ; Ohno, Eiji;
(Hirakata-shi, JP) |
Correspondence
Address: |
HAMRE, SCHUMANN, MUELLER & LARSON P.C.
P.O. BOX 2902
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Matsushita Electric Industrial Co.,
Ltd.
Kadoma-shi
JP
|
Family ID: |
26590749 |
Appl. No.: |
11/183515 |
Filed: |
July 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11183515 |
Jul 18, 2005 |
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10639924 |
Aug 13, 2003 |
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10639924 |
Aug 13, 2003 |
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09843273 |
Apr 25, 2001 |
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6743527 |
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Current U.S.
Class: |
369/272.1 ;
369/275.1; 369/283; G9B/7.194 |
Current CPC
Class: |
B29C 65/7802 20130101;
B29C 65/524 20130101; B29C 65/521 20130101; B29C 65/1435 20130101;
B29C 66/452 20130101; G11B 7/26 20130101; G11B 7/24 20130101; B29C
2035/0827 20130101; B29L 2017/005 20130101; B29C 65/7847 20130101;
B29C 65/1403 20130101; B29C 65/78 20130101; B29C 65/1483 20130101;
B29C 66/723 20130101; B29C 65/7811 20130101; B29C 66/1122 20130101;
G11B 7/265 20130101; B29C 65/7852 20130101; B29C 65/1406 20130101;
B29C 2035/0877 20130101; B29C 65/4845 20130101; B29C 65/527
20130101; B29C 66/71 20130101; G11B 7/266 20130101; B29C 65/78
20130101; B29C 65/00 20130101; B29C 66/71 20130101; B29K 2031/00
20130101; B29C 66/71 20130101; B29K 2033/08 20130101; B29C 66/71
20130101; B29K 2033/12 20130101; B29C 66/71 20130101; B29K 2067/00
20130101; B29C 66/71 20130101; B29K 2069/00 20130101 |
Class at
Publication: |
369/272.1 ;
369/275.1; 369/283 |
International
Class: |
G11B 007/26; G11B
007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2000 |
JP |
2000-124220 |
Oct 5, 2000 |
JP |
2000-305816 |
Claims
1-40. (canceled)
41. An optical disk comprising a first substrate having a signal
area on a principal plane and a second substrate that is
transparent and attached to the first substrate, wherein the first
substrate and the second substrate are attached to each other with
an adhesive member disposed therebetween, and the first substrate
has a convex portion formed on the principal plane side, the height
of the convex portion being larger than the sum of thickness of the
second substrate and the thickness of the adhesive member:
42. The optical disk according the claim 41, wherein the height of
the convex portion in a range from 0.05 mm to 0.5 mm.
43. The optical disk according to claim 41, wherein the first
substrate has a central hole A, and the convex portion is formed in
a circular shape so as to surround the central hole A.
44. The optical disk according to claim 43, wherein the second
substrate has a central hole B whose diameter is larger than that
of the central hole A, the adhesive member is disposed so as to
extend at least from an inner peripheral edge of the second
substrate to an outer peripheral edge thereof, and an outer
diameter of the convex portion is equal to or smaller than a
diameter of the central hole B.
45. The optical disk according to claim 41, wherein a thickness of
the second substrate is in a range of 0.03 mm to 0.3 mm.
46. The optical disk according to claim 41, wherein the signal area
of the first substrate is provided with a plurality of signal
recording layers.
47. The optical disk according to claim 41, wherein the adhesive
member is radiation curable resin.
48. The optical disk according to claim 44, wherein the central
hole B is larger than a clamp area of the optical disk.
49. The optical disk according to claim 48, wherein the adhesive
member is disposed on an outer peripheral side of a clamp area or
disposed so as to cover the entire clamp area.
50. The optical disk according to claim 48, wherein a thickness of
a clamp area portion of the first substrate is in a range of 1.1 mm
to 1.3 mm.
51. The optical disk according to claim 41, wherein an average
thickness of the adhesive member is in a range of 0.5 .mu.m to 30
.mu.m.
52. The optical disk according to claim 41, wherein the optical
disk is adapted for reproduction of information by application of a
laser having a wavelength of 450 nm or less.
53. An optical disk comprising: a substrate having a signal area on
a principal plane and a central hole; a transplant layer provided
in a first region of the principal plane, the first region
including the signal area; and a convex portion provided at a
second region of the principal plane so as to surround the central
hole, the second region being located between a peripheral edge of
the center hole and an inner peripheral edge of the first region;
wherein the top of the convex portion projects from the surface of
the transplant layer.
54. The optical disk according to claim 53, wherein the transparent
layer is constructed with a second substrate and an adhesive member
for attaching the both substrate to each other.
55. The optical disk according to claim 53, wherein a height of the
convex portion from the principal plane is larger than the
thickness of the transplant layer.
56. The optical disk according to claim 53, wherein the convex
portion is formed integrally with the substrate.
57. The optical disk according to claim 56, wherein the substrate
and the convex portion are made from the same material.
58. The optical disk according to claim 53, wherein the second
region is distant from the inner edge of the first region.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical disk and a
method for producing the same. In particular, the present invention
relates to an optical disk in which a substrate on an incident side
of laser light is thinner, and a method for producing the same.
[0003] 2. Description of the Related Art
[0004] In recent years, various studies have been conducted on the
recording of optical information in the field of information
recording. Recording of optical information can be conducted at
higher density, and optical information can be recorded/reproduced
in a non-contact manner; therefore, as a method for realizing the
recording/reproducing of optical information at a low cost,
applications for use in a wide range are being realized. Examples
of current optical disks include those having a structure in which
an information layer is provided on a transparent resin substrate
with a thickness of 1.2 mm and protected by an overcoat or those
having a structure in which an information layer is provided on one
side or both sides of a transparent resin substrate with a
thickness of 0.6 mm, and two substrates are attached to each
other.
[0005] Recently, in order to increase the recording density of an
optical disk, a method for increasing a numerical aperture (NA) of
an objective lens, a method for shortening a wavelength of the
laser to be used, and the like have been considered. As the
thickness of a recording/reproducing side substrate (i.e.,
substrate on an incident side of laser light) becomes smaller, the
influence of aberration on a laser spot can be decreased, and an
allowable value of a tilt of a disk can be increased. Because of
this, it is proposed that the thickness of a recording/reproducing
side substrate, a NA, and a laser wavelength are prescribed to be
about 0.1 mm, about 0.85, and about 400 nm, respectively.
[0006] In a current DVD (digital versatile disk), mainly, a method
is used in which two transparent resin substrates (thickness: 0.6
mm), on which film formation and the like are conducted, are
attached, with radiation curable resin. Even when the thickness of
a recording/reproducing side substrate becomes about 0.1 mm for the
purpose of achieving high density, it is desirable to attach
substrates to each other by the same method using the same facility
as those currently used.
[0007] However, with an optical disk in which two substrates are
attached to each other, it is necessary to enhance durability.
Furthermore, when the centers of two substrates are shifted from
each other, deflections occur when the optical disk is rotated.
Therefore, it is required to align the centers of two substrates
with each other with high precision. There also is a demand for a
method for easily producing such optical disks.
SUMMARY OF THE INVENTION
[0008] Therefore, with the foregoing in mind, it is an object of
the present invention to provide an optical disk that is recordable
at high density by attaching two substrates to each other, and a
method for producing the same.
[0009] In order to achieve the above-mentioned object, an optical
disk of the present invention includes a first substrate having a
signal area on a principal plane and a central hole A and a second
substrate that is transparent and attached to the first substrate,
wherein the second substrate is thinner than the first substrate
and has a central hole B whose diameter is larger than that of the
central hole A, and the first substrate and the second substrate
are attached to each other with an adhesive member disposed
therebetween so as to extend at least from an inner peripheral edge
of the second substrate to an outer peripheral edge thereof.
[0010] According to the above-mentioned configuration, an
easy-to-handle optical disk is obtained that is capable of
conducting high-density recording. Because of this, when a disk is
handled, cracking or peeling of a contact portion can be prevented.
The term "radiation" used herein includes a particle wave such as
an electron beam and ultraviolet-rays and an electromagnetic
wave.
[0011] In the above-mentioned optical disk, the adhesive member may
be radiation curable resin. According to this configuration, an
optical disk can be produced easily.
[0012] In the above-mentioned optical disk, a thickness of the
second substrate may be in a range of 0.03 mm to 0.3 mm. According
to this configuration, in particular, an optical disk that is
recordable at high density can be obtained.
[0013] In the above-mentioned optical disk, the central hole B may
be larger than a clamp area of the optical disk. According to this
configuration, an optical disk can be fixed stably. Furthermore,
when an optical disk is clamped, the second substrate can be
prevented from peeling.
[0014] In the above-mentioned optical disk, the adhesive member may
be disposed on an outer peripheral side of a clamp area or disposed
so as to cover the entire clamp area. According to this
configuration, since a thickness of the clamp area can be rendered
uniform, a tilt is prevented from occurring during
recording/reproduction.
[0015] In the above-mentioned optical disk, a thickness of a clamp
area of the first substrate may be in a range of 1.1 mm to 1.3
mm.
[0016] In the above-mentioned optical disk, the first substrate
includes, on the principal plane, at least one selected from the
group consisting of a convex portion formed in a circular shape so
as to surround the central hole A and having an outer diameter
equal to or smaller than a diameter of the central hole B, and a
concave portion formed in a circular shape so as to surround the
central hole A and having a diameter equal to or smaller than the
diameter of the central hole B.
[0017] In the above-mentioned optical disk, a height of the convex
portion may be larger than a sum of a thickness of the second
substrate and a thickness of the adhesive member.
[0018] In the above-mentioned optical disk, an average thickness of
the adhesive member may be in a range of 0.5 .mu.m to 30 .mu.m.
[0019] In the above-mentioned optical disk, the optical disk is
adapted for reproduction of information by application of a laser
having a wavelength of 450 nm or less. According to this
configuration, in particular, information can be recorded at high
density.
[0020] Furthermore, a first method for producing an optical disk of
the present invention including a first substrate having a central
hole A and a second substrate that is transparent and has a central
hole B whose diameter is larger than that of the central hole A
includes the processes of: (a) bringing the first substrate having
a signal area on a principal plane and the second substrate that is
thinner than the first substrate into contact with each other with
radiation curable resin interposed therebetween so that the
principal plane faces inside; and (b) irradiating the radiation
curable resin with radiation to cure the radiation curable resin,
thereby attaching the first substrate to the second substrate,
wherein, in the process (a), the radiation curable resin is
disposed so as to extend at least from an inner peripheral edge of
the second substrate to an outer peripheral edge thereof.
[0021] According to the first production method, an easy-to-handle
optical disk that is recordable at high-density can be produced
easily.
[0022] In the first production method, a thickness of the second
substrate may be in a range of 0.03 mm to 0.3 mm.
[0023] In the first production method, the process (a) may include
interposing the radiation curable resin between the first and
second substrates, and rotating the first and second substrates to
draw the radiation curable resin. According to this configuration,
the thickness of resin easily can be rendered uniform.
[0024] In the first production method, the process (a) may include
pouring the radiation curable resin onto the first substrate,
rotating the first substrate to coat the first substrate with the
radiation curable resin, and bringing the first substrate and the
second substrate into contact with each other with the radiation
curable resin interposed therebetween.
[0025] In the first production method, in the process (a), the
first substrate and the second substrate are brought into contact
with each other in a vacuum atmosphere. According to this
configuration, air bubbles can be prevented from entering between
the first substrate and the second substrate. The term "vacuum
atmosphere" as used here refers to an atmosphere with a reduced
pressure (e.g., an atmosphere of 1000 Pa or less).
[0026] In the first production method, the first substrate may
include, on the principal plane, at least one selected from the
group consisting of a convex portion formed in a circular shape so
as to surround the central hole A and having an outer diameter
equal to or smaller than a diameter of the central hole B, and a
concave portion formed in a circular shape so as to surround the
central hole A and having a diameter equal to or smaller than that
of the central hole B.
[0027] In the first production method, a height of the convex
portion may be larger than a sum of a thickness of the second
substrate and a thickness of the radiation curable resin.
[0028] Furthermore, a second method for producing an optical disk
of the present invention includes the processes of: (A) bringing a
first substrate having a signal area on a principal plane and a
central hole A and a second substrate that is transparent and
thinner than the first substrate into contact with each other with
radiation curable resin interposed therebetween so that the
principal plane faces inside; (B) irradiating the radiation curable
resin with radiation to cure the radiation curable resin, thereby
attaching the first substrate to the second substrate; and (C)
removing a part of the second substrate to form a central hole B
whose diameter is larger than that of the central hole A in the
second substrate, wherein, in the process (A), the radiation
curable resin is disposed so as to extend at least from an outer
periphery of a position where the central hole B is formed to an
outer peripheral edge of the second substrate.
[0029] According to the second production method, an easy-to-handle
optical disk that is recordable at high density can be
produced.
[0030] In the second production method, a thickness of the second
substrate may be in a range of 0.03 mm to 0.3 mm.
[0031] In the second production method, the process (A) may include
interposing the radiation curable resin between the first and
second substrates, and rotating the first and second substrates to
draw the radiation curable resin.
[0032] In the second production method, the process (A) may include
pouring the radiation curable resin onto the first substrate,
rotating the first substrate to coat the first substrate with the
radiation curable resin, and bringing the first substrate and the
second substrate into contact with each other with the radiation
curable resin interposed therebetween.
[0033] In the second production method, in the process (A), the
first substrate and the second substrate are brought into contact
with each other in a vacuum atmosphere.
[0034] Furthermore, a third method for producing an optical disk of
the present invention includes the processes of. (i) opposing a
first substrate in which a central hole A with a diameter dA is
formed to a second substrate in which a central hole B with a
diameter dB is formed with radiation curable resin interposed
therebetween so that a center of the first substrate is aligned
with a center of the second substrate; and (ii) irradiating the
radiation curable resin with radiation to cure the radiation
curable resin, wherein dA<dB, and a thickness of the second
substrate is in a range of 0.03 mm to 0.3 mm.
[0035] According to the above-mentioned configuration, an optical
disk that is recordable at high density can be produced with good
precision.
[0036] In the third production method, in the process (i), the
center of the first substrate is aligned with the center of the
second substrate by using a pin that fits in the first and second
central holes A and B. According to this configuration, it is easy
to align the center of the first substrate with the center of the
second substrate. As a result, an optical disk can be obtained in
which deflections are unlikely to occur even when the optical disk
is rotated at a high speed during recording/reproduction.
[0037] In the third production method, the process (i) may include
the processes of: (i-1) fixing the second substrate on a table in
which the pin is disposed so that the pin is inserted into the
central hole B; (i-2) pouring the radiation curable resin onto the
second substrate; (i-3) moving the first substrate so that the pin
is inserted into the central hole A, thereby opposing the first
substrate to the second substrate with the radiation curable resin
interposed therebetween; and (i-4) rotating the first and second
substrates to draw the radiation curable resin. According to this
configuration, the thickness of the radiation curable resin can be
rendered uniform. Therefore, an optical disk with good productivity
and reliability can be produced.
[0038] In the third production method, the pin may include a first
pin that fits in the central hole A and a second pin that fits in
the central hole B, in the process (i-1), the second substrate may
be fixed with the second pin, and in the process (i-3), the first
substrate may be fixed with the first pin.
[0039] The third production method may include, after the process
(i-1) and before the process (i-2), lowering an upper surface of
the second pin below an upper surface of the second substrate.
[0040] In the third production method, the second pin may have a
cylindrical shape, and the first pin may be inserted into the
second pin.
[0041] Furthermore, a fourth method for producing an optical disk
of the present invention is a method for producing an optical disk
including a first substrate in which a central hole A with a
diameter dA is formed and a second substrate in which a central
hole B with a diameter dB is formed, including the processes of:
(I) coating at least one substrate selected from the group
consisting of the first substrate and the second substrate with
radiation curable resin; (II) opposing the first substrate to the
second substrate with the radiation curable resin interposed
therebetween in a vacuum atmosphere so that a center of the first
substrate is aligned with a center of the second substrate; and
(III) irradiating the radiation curable resin with radiation to
cure the radiation curable resin, wherein dA<dB, and a thickness
of the second substrate is in a range of 0.03 mm to 0.3 mm.
[0042] According to the fourth production method, an optical disk
that is recordable at high density can be produced. Furthermore,
the first substrate and the second substrate are opposed to each
other in vacuum, so that air bubbles can be prevented from entering
therebetween.
[0043] In the fourth production method, in the process (II), the
center of the first substrate is aligned with the center of the
second substrate by using a pin that fits in the first and second
central holes A and B. According to this configuration, it is easy
to align the center of the first substrate with the center of the
second substrate.
[0044] In the fourth production method, the process (II) may
include the processes of (II-1) fixing the second substrate on a
table in which the pin is disposed so that the pin is inserted into
the central hole B; and (I1-2) in a vacuum atmosphere, moving the
first substrate so that the pin is inserted into the central hole
A, thereby opposing the first substrate to the second substrate
with the radiation curable resin interposed therebetween. According
to this configuration, by fixing a second thin substrate on a
table, the surface of the second substrate can be rendered flat; as
a result, the thickness of the radiation curable resin can be
rendered uniform. Furthermore, according to this configuration, air
bubbles can be prevented from entering between the first substrate
and the second substrate.
[0045] In the fourth production method, the pin may include a first
pin that fits in the central hole A and a second pin that fits in
the central hole B, in the process (II-1), the second substrate may
be fixed with the second pin, and in the process (II-2), the first
substrate may be fixed with the first pin.
[0046] The fourth production method further may include, after the
process (II-1) and before the process (II-2), lowering an upper
surface of the second pin below an upper surface of the second
substrate.
[0047] In the fourth production method, the second pin may have a
cylindrical shape, and the first pin may be inserted into the
second pin.
[0048] Furthermore, a production apparatus of the present invention
is an apparatus for producing an optical disk including a first
substrate in which a central hole A is formed and a second
substrate in which a central hole B is formed, including: a coating
member for coating at least one substrate selected from the group
consisting of the first substrate and the second substrate with
radiation curable resin; a disposing member for disposing the first
substrate and the second substrate so that a center of the first
substrate is aligned with a center of the second substrate; and an
irradiating member for irradiating the radiation curable resin with
radiation.
[0049] According to the above-mentioned apparatus for producing an
optical disk, the third and fourth production methods of the
present invention can be conducted easily.
[0050] In the above-mentioned production apparatus, the disposing
member may include a pin that fits in the first and second central
holes A and B.
[0051] In the above-mentioned production apparatus, the pin may
include a first pin that fits in the central hole A and a second
pin that fits in the central hole B.
[0052] In the above-mentioned production apparatus, the second pin
may have a cylindrical shape, and the first pin may be inserted
into the second pin.
[0053] In the above-mentioned production apparatus, the disposing
member may include a table for fixing the at least one
substrate.
[0054] In the above-mentioned production apparatus, the disposing
member further may include a container surrounding the table and an
exhaust member for exhausting the container.
[0055] These and other advantages of the present invention will
become apparent to those skilled in the art upon reading and
understanding the following detailed description with reference to
the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] FIGS. 1A and 1B are a plan view and a cross-sectional view
showing an example of an optical disk of the present invention.
[0057] FIGS. 2A and 2B are a plan view and a cross-sectional view
showing another example of an optical disk of the present
invention.
[0058] FIGS. 3A and 3B are a plan view and a cross-sectional view
showing still another example of an optical disk of the present
invention.
[0059] FIGS. 4 A and 4B are a plan view and a cross-sectional view
showing still another example of an optical disk of the present
invention.
[0060] FIG. 5A is a cross-sectional view showing an example of a
substrate used in an optical disk of the present invention, and
FIG. 5B is a cross-sectional view showing another example of a
substrate used in an optical disk of the present invention.
[0061] FIGS. 6A and 6B are cross-sectional views showing an example
of the processes of a method for producing an optical disk of the
present invention.
[0062] FIGS. 7A to 7D are cross-sectional views showing a part of
the processes of a method for producing an optical disk of the
present invention.
[0063] FIGS. 8A to 8C are cross-sectional views showing a part of
the processes of a method for producing an optical disk of the
present invention.
[0064] FIG. 9 is a cross-sectional view showing a part of the
processes of a method for producing an optical disk of the present
invention.
[0065] FIGS. 10A to 10C are cross-sectional views showing another
example of the processes of a method for producing an optical disk
of the present invention.
[0066] FIG. 11 is a plan view showing an example of a substrate
used in a method for producing an optical disk of the present
invention.
[0067] FIGS. 12A and 12B are cross-sectional views showing another
example of the processes of a method for producing an optical disk
of the present invention.
[0068] FIGS. 13A to 13E are cross-sectional views showing a part of
the processes of a method for producing an optical disk of the
present invention.
[0069] FIGS. 14A and 14B are cross-sectional views showing a part
of the processes of a method for producing an optical disk of the
present invention.
[0070] FIGS. 15A and 15B are cross-sectional views showing a part
of the processes of a method for producing an optical disk of the
present invention.
[0071] FIGS. 16A and 16B are cross-sectional views showing a part
of the processes of a method for producing an optical disk of the
present invention.
[0072] FIGS. 17A to 17C are cross-sectional views showing a part of
the processes of a method for producing an optical disk of the
present invention.
[0073] FIG. 18 is a cross-sectional view showing a part of the
processes of a method for producing an optical disk of the present
invention.
[0074] FIGS. 19A to 19C are cross-sectional views showing a part of
the processes of a method for producing an optical disk of the
present invention.
[0075] FIG. 20 is a cross-sectional view showing a part of the
processes of a method for producing an optical disk of the present
invention.
[0076] FIGS. 21A and 21B are cross-sectional views showing a part
of the processes of a method for producing an optical disk of the
present invention.
[0077] FIG. 22 is a perspective view schematically showing an
example of an apparatus for producing an optical disk of the
present invention.
[0078] FIG. 23 is a perspective view schematically showing a part
of an exemplary apparatus for producing an optical disk of the
present invention.
[0079] FIG. 24 is a perspective view schematically showing a part
of another exemplary apparatus for producing an optical disk of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0080] Hereinafter, the present invention will be described by way
of illustrative embodiments with reference to the drawings. Like
components are denoted with like reference numerals. The repeated
description of the components may be omitted.
Embodiment 1
[0081] In Embodiment 1, the present invention will be described by
way of an example of an optical disk. FIGS. 1A and 1B are a plan
view and a cross-sectional view of an optical disk 10 of Embodiment
1, respectively.
[0082] Referring to FIGS. 1A and 1B, the optical disk 10 includes a
first substrate 11 (hatching is omitted; hereinafter, hatching of
the first substrate similarly may be omitted), and a second
substrate 12 attached to the first substrate 11. The first
substrate 11 and the second substrate 12 are attached to each other
with radiation curable resin (adhesive member) 13 disposed
therebetween.
[0083] The first substrate 11 has a signal area SA on a principal
plane 11a. A signal recording layer 14 is formed in the signal area
SA. The structure of the signal area SA is varied depending upon
the use of an optical disk. In the case where the optical disk 10
is a read-only disk, for example, pits with unevenness are formed
in the signal area SA on the principal plane 11a, and a film made
of Al or the like is formed on the pits as a signal recording
layer. Furthermore, in the case where the optical disk 10 is a
recording/reproducing disk, a recording film composed of a
phase-change material, a colorant, and the like is formed in the
signal area SA so that recording/reproduction can be conducted.
[0084] The first substrate 11 has a circular central hole A with a
diameter dA (e.g., 15 mm) at its center. The thickness of the first
substrate 11 is not particularly limited. However, it is preferable
that the sum of thickness of the first and second substrates 11 and
12 is in a range of 0.5 mm to 0.7 mm or 1.1 mm to 1.3 mm. The outer
diameter of the first substrate 11 is not particularly limited, and
it may be, for example, 120 mm. The first substrate 11 is made of,
for example, thermoplastic resin such as polycarbonate resin and
acrylic resin, or thermosetting resin such as vinylester resin and
polyester resin.
[0085] The second substrate 12 is thinner than the first substrate
11 and transparent. The thickness of the second substrate 12 is in
a range of preferably 0.03 mm to 0.3 mm, more preferably 0.03 mm to
0.12 mm. More specifically, the thickness of the second substrate
12 is, for example, 0.05 mm or 0.1 mm. By prescribing the sum of
thickness of the first substrate 11 and the second substrate 12 in
a range of 1.1 mm to 1.3 mm, the compatibility with respect to
existing optical disks can be ensured. Furthermore, by prescribing
the sum of thickness in a range of 0.5 mm to 0.7 mm or 1.1 mm to
1.3 mm, a conventional apparatus for producing an optical disk can
be used.
[0086] The second substrate 12 is exposed to laser light
(wavelength: preferably 450 nm or less) for recording/reproducing a
signal, and is made of transparent material. More specifically, the
second substrate 12 is made of thermoplastic resin such as
polycarbonate resin and acrylic resin, or thermosetting resin such
as vinylester resin and polyester resin. The second substrate 12
has a circular central hole B with a diameter dB. As shown in FIG.
1A, the central hole B preferably is larger than a clamp area
C.
[0087] Herein, the clamp area C is held when the optical disk 10 is
transported or rotated for the purpose of recording/reproduction.
It is preferable that the thickness of the clamp area C of the
first substrate 11 is in a range of 1.1 mm to 1.3 mm.
[0088] The radiation curable resin 13 that is an adhesive member is
disposed so as to extend at least from an inner peripheral edge 12s
of the second substrate 12 to an outer peripheral edge 12t thereof.
More specifically, the radiation curable resin 13 extends at least
over the entire surface of the principal plane of the second
substrate 12 on the first substrate 11 side. The radiation curable
resin 13 may extend up to the inner peripheral edge 11s of the
first substrate 11. The radiation curable resin 13 is cured with
radiation. As the radiation curable resin 13, for example,
UV-curable resin that is cured with ultraviolet radiation, resin
that is cured with an electron beam, and the like can be used. It
is preferable that the radiation curable resin 13 is disposed on an
outer side of the clamp area C, as shown in FIG. 1A, or disposed so
as to cover the entire clamp area C. It is preferable that the
average thickness of the radiation curable resin 13 is in a range
of 0.5 .mu.m to 30 .mu.m. An adhesive member such as a double-faced
tape may be used in place of the radiation curable resin 13.
[0089] In the optical disk 10 of Embodiment 1, since the second
substrate 12 on a light incident side is thinner, high-density
recording can be conducted. Furthermore, the diameter of the
central hole B of the second substrate 12 is larger than that of
the central hole A of the first substrate 11. Therefore, peeling
and cracking of the second substrate 12 are unlikely to occur, and
an optical disk thus obtained can be handled easily. Furthermore,
since the radiation curable resin 13 extends up to the inner
peripheral edge 12s of the second substrate 12, peeling and
cracking of the second substrate 12 are unlikely to occur, and an
optical disk thus obtained can be handled easily.
[0090] It is preferable that the first substrate 11 has, on the
principal plane 11a side, at least one selected from a convex
portion formed in a circular shape so as to surround the central
hole A and having an outer diameter equal to or smaller than a
diameter of the central hole B, and a concave portion formed in a
circular shape so as to surround the central hole A and having a
diameter equal to or smaller than a diameter of the central hole
B.
[0091] FIGS. 2A and 2B respectively show a plan view and a
cross-sectional view of an optical disk 20 in the case where a
first substrate 21 has a convex portion in a circular shape. FIGS.
3A and 3B respectively show a plan view and a cross-sectional view
of an optical disk 30 in the case where a first substrate 31 has a
convex portion in another shape. FIGS. 4A and 4B respectively show
a plan view and a cross-sectional view of an optical disk 40 in the
case where a first substrate 41 has a concave portion in a circular
shape. FIG. 5A is a cross-sectional view of a first substrate 51 in
the case where a convex portion and a concave portion in a circular
shape are provided, and FIG. 5B is a cross-sectional view of a
first substrate 56 in the case where a convex portion and a concave
portion in a circular shape are provided. The first substrates 21,
31, 41, 51, and 56 are similar to the first substrate 11 in the
portions other than the convex and concave portions. More
specifically, principal planes 21a, 31a, 41a, 51a, and 56a
correspond to the principal plane 11a. Furthermore, the optical
disks 20, 30, and 40 are similar to the optical disk 10 except for
the first substrates 21, 31, and 41. Therefore, the repeated
description thereof will be omitted here.
[0092] As shown in FIGS. 2A and 2B, the first substrate 21 of the
optical disk 20 has a convex portion 22 formed in a circular shape
so as to surround the central hole A and having an outer diameter
L1 equal to a diameter dB of the central hole B, on the principal
plane 21a with a signal area SA formed thereon. Because of the
convex portion 22, an optical disk can be produced easily as
described in the following embodiments. Furthermore, it is
preferable that the height of the convex portion 22 (i.e., height
from the principal plane 21a) is 0.05 mm to 0.5 mm. Furthermore,
the height of the convex portion 22 preferably is larger than the
sum of thickness of the second substrate 12 and the radiation
curable resin 13 (this also applies to the convex portion described
below). Because of this, when the optical disk 20 is held/stored by
being stacked on another optical disk, the reproduction surface
does not come into contact with another optical disk, whereby the
reproduction surface will not be damaged. Furthermore, as shown in
FIG. 2B, it is preferable that the convex portion 22 is formed so
as to come into contact with the inner peripheral edge of the
second substrate 12 (the outer diameter L1 of the convex portion 22
is prescribed to be equal to the diameter dB of the central hole B)
(this also applies to the following convex portion). Because of
this, eccentricity between the first substrate 11 and the second
substrate 12 can be suppressed. Furthermore, a center cone table or
a motor turn table of a clamp does not come into contact with the
second substrate 12 during recording/reproduction; therefore, a
decrease in strength caused by prescribing the second substrate 12
to be thinner can be prevented, and an increase in a tilt also can
be prevented.
[0093] As shown in FIGS. 3A and 3B, the first substrate 31 of the
optical disk 30 has a convex portion (step difference) 32 formed in
a circular shape so as to surround the central hole A and having
the outer diameter L1 equal to the diameter dB of the central hole
B, on the principal plane 31a with a signal area 31 SA formed
thereon. In this case, the convex portion 32 extends up to the
inner peripheral edge of the first substrate 31.
[0094] As shown in FIGS. 4A and 4B, the first substrate 41 of the
optical disk 40 has a concave portion 42 formed in a circular shape
so as to surround the central hole A and having the diameter L2
equal to or smaller than the diameter dB of the central hole B, on
the principal plane 41a with a signal area SA formed thereon. It is
preferable that the depth of the concave portion 42 (i.e., depth
from the principal plane 41a) is in a range of 0.01 mm to 0.2 mm.
Because of the concave portion 42, an optical disk can be produced
easily as described in the following embodiments.
[0095] As shown in FIG. 5A, the first substrate 51 has a convex
portion 22 and a concave portion 42 on the principal plane 51 a
with a signal area SA formed thereon. The convex portion 22 is
formed in a circular shape so as to surround the central hole A and
has an outer diameter equal to or smaller than the diameter of the
central hole B. The concave portion 42 is formed in a circular
shape so as to surround the convex portion 22. Because of this, the
above-mentioned effects of the convex portion and the concave
portion are obtained.
[0096] As shown in FIG. 5B, the first substrate 56 has a convex
portion 32 and a concave portion 42 on the principal plane 56 a
with the signal area SA formed thereon. The convex portion 32 is
formed in a circular shape so as to surround the central hole A and
has an outer diameter equal to or smaller than that of the central
hole B. The concave portion 42 is formed in a circular shape so as
to surround the convex portion 32. Because of this, the
above-mentioned effects of the convex portion and the concave
portion are obtained.
[0097] It is appreciated that the above-mentioned optical disks 20,
30, and 40 also have the same effects as those of the optical disk
10.
[0098] In Embodiment 1, an optical disk in which a signal recording
layer is formed only on a first substrate has been described.
However, in the optical disk and the method for producing the same
according to the present invention, a signal recording layer may be
formed on a second substrate (this also applies to the following
embodiments). For example, in the optical disk and the method for
producing the same according to the present invention, a
semi-transparent signal recording layer also may be formed on the
second substrate so that both the first and second substrates have
a signal recording layer. Furthermore, a plurality of signal
recording layers may be formed on the first substrate (this also
applies to the following embodiments). Because of these
configurations, an optical disk with a double-layered structure can
be obtained. In this case, information recorded on both the signal
recording layers can be reproduced with laser light incident
through the second substrate.
Embodiment 2
[0099] In Embodiment 2, the present invention will be described by
way of an example of a method for producing an optical disk. FIGS.
6A and 6B show the processes of producing the optical disk 10
according to the production method of Embodiment 2.
[0100] According to the production method of Embodiment 2, as shown
in FIG. 6A, the first substrate 11 having the signal area SA on the
principal plane 11a and the second substrate 12 that is thinner
than the first substrate 11 are brought into contact with each
other with uncured radiation curable resin 13a interposed
therebetween so that the principal plane 11a faces inside (Process
(a)). The first substrate 11 has the central hole A, and the second
substrate is transparent and has the central hole B larger in
diameter than the central hole A. At this time, the radiation
curable resin 13a is disposed at least from the inner peripheral
edge 12s of the second substrate 12 to the outer peripheral edge
12t thereof. The radiation curable resin 13 a may be disposed up to
the inner peripheral edge 11s of the first substrate 11. However,
it is preferable that the radiation curable resin 13a is disposed
so as not to cover the clamp area C.
[0101] The signal area SA of the first substrate 11 can be
obtained, for example, by molding resin by injection molding or
photopolymerization to form uneven pits, and forming a reactive
film (signal recording layer 14 ) made of Al having a thickness of,
for example, 50 nm by sputtering. Furthermore, in the case where
the signal area SA is formed of a phase-change film or a colorant
film, sputtering or vapor deposition can be utilized. The first
substrate 11 is the same as that described in Embodiment 1, which
is, for example, a polyearbonate substrate with a thickness of 1.1
mm, a diameter of 120 mm, and a central hole diameter of 15 mm.
[0102] The second substrate 12 is the same as that described in
Embodiment 1, which is, for example, a polycarbonate or acrylic
substrate with a thickness of 90 .mu.m, an outer diameter of 120
mm, and a central hole diameter of 40 mm. The second substrate 12
can be formed by injection molding or casting. The thickness of the
second substrate 12 is in a range of 0.03 mm to 0.3 mm.
[0103] Thereafter, as shown in FIG. 6B, the radiation curable resin
13a is irradiated with radiation (ultraviolet rays or an electron
beam), whereby the radiation curable resin 13a is cured to obtain
radiation-cured resin 13, and the first substrate 11 and the second
substrate 12 are attached to each other (Process (b)). Radiation
may be applied continuously or as a pulse (this also applies to the
following embodiments). In this manner, the optical disk 10 can be
produced.
[0104] Hereinafter, two methods for bringing the first substrate
into contact with the second substrate 12 with the radiation
curable resin 13a interposed therebetween in the above-mentioned
first process will be described.
[0105] According to the first method, the first substrate 11 is
integrated with the second substrate 12 with the radiation curable
resin 13a interposed therebetween, and the first and second
substrates 11 and 12 thus integrated are rotated, whereby the
radiation curable resin 13a is drawn. FIGS. 7A to 7D show an
example of the processes of this method. As shown in FIG. 7A,
first, the first substrate 11 is coated with the radiation curable
resin 13a in a circular shape with a nozzle 71. At this time, the
first substrate 11 or the nozzle 71 is rotated at a low speed (20
rpm to 120 rpm). Furthermore, in order to exactly bring the first
substrate 11 into contact with the second substrate 12 up to the
inner peripheral edge 12s, the radiation curable resin 13a is
coated at a position (for example, a position with a radius of 20
mm to 25 mm) on the first substrate. 11 where the inner peripheral
edge 12s is disposed.
[0106] Next, as shown in FIG. 7B, the first substrate 11 and the
second substrate 12 are opposed and stacked so that they are
positioned concentrically. If the radiation curable resin 13 a
adheres to the clamp area C, a tilt will be influenced
substantially. Therefore, as shown in FIG. 7C, it is preferable to
irradiate an outer peripheral side of the clamp area C with
radiation 72 such as UV-rays in a circular shape, thereby
preventing the radiation curable resin 13a from entering the clamp
region C. More specifically, Process (a) may include the process of
curing at least a part of the radiation curable resin 13a disposed
on an inner side of the signal area SA, before rotating the first
substrate 11 (this also applies to the second method). The second
substrate 12 may be coated with the radiation curable resin
13a.
[0107] Thereafter, as shown in FIG. 7D, the first substrate 11 and
the second substrate 12 are rotated at a high speed (1000 rpm to
10000 rpm) under the condition that they are stacked adjacent each
other, whereby the radiation curable resin 13a is dispersed to an
outer peripheral portion. Because of this, air bubbles become
unlikely to enter the contact portion, and excessive radiation
curable resin 13 a is shaken off to be discharged from between the
first and second substrates 11 and 12. Thus, Process (a) can be
conducted.
[0108] In the above-mentioned process, m order to render the
thickness of the radiation curable resin 13a uniform, it is
preferable to select the viscosity of the radiation curable resin
13a in accordance with the rotation number/rotation time of
substrates for dispersion of resin, and the thickness of the
radiation curable resin 13a. In general, according to the
above-mentioned method, the thickness of the radiation curable
resin 13a is likely to become thinner on an inner peripheral side
and thicker on an outer peripheral side. In order to conduct
recording/reproduction under the conditions of a laser with a
wavelength of 400 nm and an NA of an objective lens of 0.85
considered for achieving the high density of an optical disk, it is
required that the variation in film thickness of the
radiation-cured resin 13 is in a range of about .+-.3 .mu.m with
respect to the central value (sum of the thickness of the second
substrate 12 and the thickness of the radiation-cured resin 13,
e.g., 0.1 mm).
[0109] Table 1 shows a relationship between the viscosity of the
radiation curable resin 13a and the in-plane variation of the
radiation-cured resin 13 in the above-mentioned first method.
1TABLE 1 Vis- cosity (mPa .multidot. s) 5000 3000 1500 1000 600 300
150 50 10 5 In-plane 11.1 8.1 5.5 4.7 4.3 4.1 4.1 4.3 4.7 6.1 vari-
ation (.mu.m)
[0110] As is apparent from Table 1, by prescribing the viscosity of
the radiation curable resin 13a in a range of 10 to 1500 mPa.s, the
variation in film thickness of the radiation curable resin 13 can
be set at 6 .mu.m or less (i.e., .+-.3 .mu.m or less).
[0111] Furthermore, Table 2 shows a relationship between the
viscosity of the radiation curable resin 13a and the cycle time in
the above-mentioned first method.
2TABLE 2 Vis- cosity (mPa .multidot. s) 5000 3000 1500 1000 600 300
150 50 10 5 Cycle 90 60 27 18 10 3.3 1.5 0.7 0.3 0.3 time
(Sec.)
[0112] As is apparent from Table 2, in order to shorten a cycle
time, it is preferable to set the viscosity of the radiation
curable resin 13a in a range of 10 to 600 mPa.s.
[0113] Next, the second method for conducting the first process
will be described. According to the second method, the radiation
curable resin 13 a is poured onto the first substrate 11, and the
first substrate 11 is rotated, whereby the first substrate 11 is
coated with the radiation curable resin 13 a; then, the first
substrate 11 and the second substrate 12 are brought into contact
with each other with the radiation curable resin 13a interposed
therebetween. FIG. 8 shows an example-of the processes of this
method. According to the second method, as shown in FIG. 8A, first,
the first substrate 11 is coated with the radiation curable resin
13a in a circular shape with a nozzle 71. This process is the same
as that described with reference to FIG. 7A.
[0114] Next, as shown in FIG. 8B, the first substrate 11 is rotated
at a high speed (1000 to 10000 rpm), whereby the radiation curable
resin 13a is drawn to the outer peripheral portion. At this time,
as described in the process shown in FIG. 7C, laser light may be
applied to the radiation curable resin 13 a on an outer peripheral
side of the clamp area C in a circular shape.
[0115] Thereafter, as shown in FIG. 8C, the first substrate 11 and
the second substrate 12 are stacked so that they are disposed
concentrically and brought into contact with each other. In this
manner, the above-mentioned Process (a) can be conducted. An
appropriate pressure is applied uniformly during stacking, the
distribution of the radiation curable resin 13a can be rendered
further uniform. At this time, it is required to take care so that
air bubbles do not enter between the first and second substrates 11
and 12. In order to prevent air bubbles from entering therebetween,
as shown in FIG. 9, it is preferable to conduct the process of
bringing the substrates into contact with each other in a vacuum
chamber 90 (i.e., in a vacuum atmosphere).
[0116] Table 3 shows a relationship between the viscosity of the
radiation curable resin 13a and the in-plane variation of the
radiation-cured resin 13 in the above-mentioned second method.
3TABLE 3 Viscosity (mPa .multidot. s) 20000 15000 5000 3000 1500
1000 600 300 150 50 10 5 In-plane 7 5.4 3.2 2.8 2.6 2.5 2.4 2.4 2.5
2.7 3.5 6.2 variation (.mu.m)
[0117] As is apparent from Table 3, by prescribing the viscosity of
the radiation curable resin 13a in a range of 10 to 15000 mPa.s,
the variation in film thickness of the radiation-cured resin 13 can
be set at 6 .mu.m or less (.+-.3 .mu.m or less).
[0118] Furthermore, Table 4 shows a relationship between the
viscosity of the radiation curable resin 13a and the cycle time in
the above-mentioned first method.
4TABLE 4 Viscosity (mPa .multidot. s) 20000 15000 5000 3000 1500
1000 600 300 150 50 10 5 Cycle time 100 80 35 25 15 10 4 1.5 0.5
0.3 0.3 0.2 (Sec.)
[0119] As is apparent from Table 4, in order to shorten the cycle
time, it is preferable to set the viscosity of the radiation
curable resin 13a in a range of 10 to 1000 mPa.s.
[0120] As described above, according to the method for producing an
optical disk of Embodiment 2, an optical disk described in
Embodiment 1 can be produced easily.
[0121] According to the production method of Embodiment 2, the
first substrates 21, 31, 41, 51, or 56 described in Embodiment 1
may be used in place of the first substrate 11. By using these
substrates, an inner peripheral side of a circular convex portion
or concave portion can be prevented from being coated with the
radiation curable resin 13a. In this case, the process of
irradiation in a circular shape is not required, so that production
becomes easy Furthermore, by prescribing the outer diameter L1 of
the convex portion to be equal to the diameter dB of the second
substrate 12, eccentricity can be prevented from occurring in the
course of attachment of the first substrate to the second
substrate.
Embodiment 3
[0122] In Embodiment 3, the present invention will be described by
way of another example of a method for producing an optical disk.
Regarding the components described in the above-mentioned
embodiments, the repeated description may be omitted here.
[0123] FIGS. 10A to 10C show the processes of a production method
of Embodiment 3. According to the production method of Embodiment
3, as shown in FIG. 10A, first, the first substrate 11 having the
signal area SA on the principal plane 11a and the central hole A
and a second substrate 102 that is transparent and thinner than the
first substrate 11 are brought into contact with each other with
the radiation curable resin 13a interposed therebetween so that the
principal plane 11a faces inside (Process (A)). The first substrate
11 is the same as that described in Embodiment 1. The second
substrate 102 is different from the second substrate 12 described
in Embodiment 1, only in that the second substrate 102 does not
have a central hole, and an incision 102a in a dotted line shape is
formed at a portion where the central hole B will be formed in the
following process. The second substrate 102 may have both an
incision and a central hole. In this case, it is preferable that
the second substrate 102 has a central hole with the same size as
that of the central hole A. When the second substrate 102 has a
central hole with the same size as that of the central hole A of
the first substrate 11, eccentricity in the course of attachment of
the substrates can be prevented easily.
[0124] FIG. 11 is a plan view of the second substrate 102. The
second substrate 102 includes the incision 102a at an outer
peripheral portion (that corresponds to the inner peripheral edge
12s of the second substrate 12 ) of a position where the central
hole B will be formed in the following process.
[0125] In Process (A), the radiation curable resin 13a is disposed
at least from the portion of the incision 102a (outer peripheral
portion of a position where the central hole B will be formed) to
the outer peripheral edge 102t of the second substrate 102.
[0126] Thereafter, as shown in FIG. 10B, the radiation curable
resin 13a is irradiated with radiation for curing to obtain
radiation-cured resin 13, whereby the first substrate 11 is
attached to the second substrate 120 (Process (B)). This process is
the same as that in FIG. 6B described in Embodiment 2, and two
methods (see FIGS. 7A-7D and 8A-8C) described in Embodiment 2 can
be used.
[0127] Then, as shown in FIG. 10C, a part 102b of the second
substrate 102 is removed to form the second substrate 102 having
the central hole B with a diameter larger than that of the central
hole A. At this time, because of the incision 102a, the central
hole B can be formed easily. The second substrate 12 is the same as
that described in Embodiment 1.
[0128] Thus, the optical disk described in Embodiment 1 can be
produced easily. According to the production method of Embodiment
3, an easy-to-handle optical disk that is recordable at high
density can be produced easily.
[0129] It is appreciated that the first substrate 41 described in
Embodiment 1 may be used in place of the first substrate 11.
Embodiment 4
[0130] In Embodiment 4, the present invention will be described by
way of still another example of a method for producing an optical
disk. FIG. 12 shows a cross-sectional view showing the processes of
a production method of Embodiment 4.
[0131] As shown in FIG. 12A, first, the first substrate 11 and the
second substrate 12 are opposed to each other with uncured
radiation curable resin 121 interposed therebetween so that the
center of the first substrate 11 is aligned with that of the second
substrate 12 (Process (i)). At this time, the first substrate 11
and the second substrate 12 are opposed to each other so that the
principal plane 11a on which the signal area SA is formed faces
inside. Process (i) will be described later in more detail. As the
radiation curable resin 121, the resin similar to the radiation
curable resin 13a can be used. As described in Embodiment 1, the
first substrate 11 and the second substrate 12 have the central
hole A with the diameter dA and the central hole B with the
diameter dB, where dA<dB. The thickness of the second substrate
12 is in a range of 0.03 mm to 0.3 mm.
[0132] Next, as shown in FIG. 12B, the radiation curable resin 121
is irradiated with radiation 122 such as an electron beam and
UV-rays, whereby the radiation curable resin 121 is cured (Process
(ii)). Thus, an optical disk can be produced.
[0133] FIG. 12B shows the case where the radiation 122 is applied
through the second substrate 12. However, an irradiation direction
of the radiation 122 is selected depending upon the structure of an
optical disk. More specifically, the irradiation direction of the
radiation 122 is selected so that the radiation 122 easily reaches
the radiation curable resin 121. For example, in the case where the
signal recording layer 14 is formed only on the second substrate 12
side, the radiation 122 is applied through the first substrate 11.
Furthermore, in the case of an optical disk with a double-layered
structure in which the signal recording layer 14 is formed on both
the first substrate 11 and the second substrate 12, the radiation
122 is applied through the second substrate 12.
[0134] Next, a method for conducting Process (i) by using a pin
that fits in the central hole A and the central hole B will be
described with reference to FIGS. 13A to 13E. According to this
method, a pin 131 with a first pin 131a that fits in the central
hole A and a second pin 131b that fits in the central hole B is
used. The second pin 131b has a cylindrical shape. The outer
diameter of the first pin 131a substantially is equal to the inner
diameter of the second pin 131b. The first pin 131a is inserted
into the second pin 131b so that they are disposed concentrically.
The outer diameter of the first pin 131a substantially is equal to
dA, and the outer diameter of the second pin 131b substantially is
equal to dB.
[0135] First, as shown in FIG. 13A, the second substrate 12 is
fixed on a table 132 in which the pin 131 is disposed in such a
manner that the second pin 131b is inserted into the central hole B
(Process (i-1)). The pin 131 is disposed at the center of the table
132. It is preferable that the second pin 131b is disposed so that
its upper surface is positioned higher than a principal plane 12a
of the second substrate 12. Because of this, the second substrate
12 can be fixed securely. The table 132 is rotatable. Furthermore,
the table 132 is provided with an exhaust port 132a for fixing the
second substrate 12. Due to the exhaust through the exhaust port
132a, the second substrate 12 is fixed on the table 132. The second
substrate 12 may be fixed by using static electricity or adhesive
material in place of the exhaust port 132a.
[0136] Next, as shown in FIG. 13B, the radiation curable resin 121
is poured onto the second substrate 12 (Process (i-2)). By rotating
the table 132 while pouring resin through a dispenser 133, the
radiation curable resin 121 can be disposed in a circular shape.
Furthermore, by moving the dispenser 133 simultaneously with the
rotation of the table 132, the radiation curable resin 121 can be
disposed in a spiral shape.
[0137] Next, as shown in FIG. 13C, the first substrate 11 is moved
so that the first pin 131a is inserted into the central hole A, and
the first substrate 11 and the second substrate 12 are opposed to
each other with the radiation curable resin 121 interposed
therebetween (Process (i-3)). In FIGS. 13A to 13E, although the
signal recording layer 14 is not shown (this also applies to the
following drawings), the first substrate 11 is disposed so that the
signal recording layer 14 faces inside. It is preferable that
Process (i-3) is conducted after the second pin 131b is moved so
that the upper surface of the second pin 131b is positioned below
the upper surface of the second substrate 12. The second pin 131b
can be moved at any time after Process (i-1) and before Process
(i-3). Even when the movement of the second pin 131b causes the
radiation curable resin 121 to penetrate the inside of the central
hole B of the second substrate 12, the resin can be prevented from
adhering to the second pin 131b. As a result, an optical disk can
be produced with good productivity.
[0138] In Process (i-3), the first pin 131a is aligned with the
second pin 131b. Therefore, the first substrate 11 is disposed so
that the center of the first substrate 11 is aligned with the
center of the second substrate 12. Furthermore, since the second
substrate 12 is fixed on the flat table 132, the surface of the
second substrate 12 is kept flat. As a result, the radiation
curable resin 121 comes into contact with the first substrate 11
uniformly, and air bubbles can be prevented from being mixed with
the resin. Furthermore, the thickness of the radiation curable
resin 121 can be rendered uniform. By rendering the thickness of
the radiation curable resin 121 uniform, an optical disk can be
produced, in which focus servo control and tracking servo control
are conducted easily (i.e., in which recording/reproduction can be
conducted stably).
[0139] Next, as shown in FIG. 13D, by rotating the first substrate
11 and the second substrate 12, the radiation curable resin 121 is
drawn (Process (i-4)). Thus, Process (i) can be conducted.
[0140] Finally, as shown in FIG. 13E, the radiation curable resin
121 is cured with radiation 134. In this manner, an optical disk
can be produced. In the case where radiation is applied through the
second substrate 12, radiation should be applied through the table
132 that transmits radiation. Furthermore, light may be applied
through the second substrate 12 by inverting the first substrate 11
and the second substrate 12 while they are opposed to each
other.
[0141] A pin in another shape may be used in place of the pin 131.
FIGS. 14A-14B, 15A-15B, and 16A-16B illustrate the case where
various pins are used. A pin 141 shown in FIG. 14A has a first pin
141a and a second pin 141b. The second pin 141b is provided with a
concave portion in which the first pin 141a fits. In the case of
using the pin 141, as shown in FIG. 14A, the second substrate 12 is
fixed under the condition that the first pin 141a is covered with
the second pin 141b. Furthermore, the first substrate 11 is fixed
under the condition that the second pin 141b is removed, as shown
in FIG. 14B.
[0142] A pin 151 shown in FIG. 15A includes a first pin 151a and a
second pin 151b integrated with each other. In the case of using
the pin 151, as shown in FIG. 15A, the second substrate 12 is fixed
with the second pin 151b. Furthermore, the first substrate 11 is
fixed under the condition that the second pin 151b is lowered, as
shown in FIG. 15B.
[0143] A pin 161 shown in FIG. 16A includes a first pin 161a and a
second pin 161b integrated with each other. Furthermore, a step
difference 161s is formed between the first pin 161 a and the
second pint 161b. The outer diameter dS of the step difference 161s
is larger than dA and smaller than dB. In the case of using the pin
161, as shown in FIG. 16A, the second substrate 12 is fixed with
the second pin 161b. Furthermore, the first substrate 11 is fixed
under the condition that the second pin 161b is lowered, as shown
in FIG. 16B. At this time, the interval between the first substrate
11 and the second substrate 12 can be controlled by the step
difference 161s. In the pins 151 and 161 in which the first pin and
the second pin are integrated with each other, the first pin can be
rendered concentric with the second pin with good precision.
[0144] FIGS. 14A-14B to 16A-16B show the case where the outer
diameters of the first pin and the second pin are constant.
However, these outer diameters may not be constant. For example, a
pin that is widened toward the table 132 so as to fit in the
central holes A and B may be used. Furthermore, in the pin 141, the
outer diameter of the first-pin 141a and the concave portion of the
second pin 141b may be tapered.
Embodiment 5
[0145] In Embodiment 5, the present invention will be described by
way of still another example of a method for producing an optical
disk. FIG. 17 -is a cross-sectional view showing the processes of a
production method of Embodiment 5.
[0146] Embodiment 5 is directed to a method for producing an
optical disk having the first substrate 11 in which the central
hole A with a diameter dA is formed and the second substrate 12 in
which the central hole B with a diameter dB is formed. The first
substrate 11 and the second substrate 12 are the same as those
described in Embodiment 1.
[0147] First, at least one substrate selected from the first
substrate 11 and the second substrate 12 is coated with radiation
curable resin (Process (I)). For example, as shown in FIG. 17A, the
second substrate 12 is coated with radiation curable resin 171. In
the following description, the case where the second substrate 12
is coated with the radiation curable resin 171 will be described.
The radiation curable resin 171 can be coated as shown in FIG. 18.
More specifically, first, the second substrate 12 is fixed on a
table 181 in which an exhaust port 181a is formed. Thereafter, the
radiation curable resin 171 is poured from a dispenser 182 while
the table 181 is rotated, whereby the radiation curable resin 171
is disposed in a circular or spiral shape. Thereafter, by rotating
the table 181 at a high speed, the second substrate 12 can be
coated with the radiation curable resin 171. Furthermore, the
second substrate 12 may be coated with the radiation curable resin
171 by screen printing, using the apparatus shown in FIG. 23.
[0148] Next, as shown in FIG. 17B, the first substrate 11 and the
second substrate 12 are opposed to each other with the radiation
curable resin 171 interposed therebetween in a vacuum atmosphere,
so that the center of the first substrate 11 is aligned with the
center of the second substrate 12 (Process (II)). Process (II) will
be described later in more detail.
[0149] Next, as shown in FIG. 17C, the radiation curable resin 171
is irradiated with radiation 172 such as an electron beam and
UV-rays to be cured (Process (III)). Thus, an optical disk can be
produced.
[0150] Hereinafter, the case where Process (II) is conducted using
the pin similar to that in Embodiment 4 will be described. First,
as shown in FIG. 19A, the second substrate 12 is fixed on a table
191 in which the pin 131 is disposed so that the second pin 131b is
inserted into the central hole B (Process (II-1)). The pin 131 is
the same as that described in Embodiment 4.
[0151] The table 191 includes a fixing member 192 for fixing the
substrate. As the fixing member 192, for example, an apparatus for
fixing a substrate with static electricity or an adhesive sheet can
be used. The pin 131 is disposed at the center of the table 132. It
is preferable that the second pin 131b is disposed so that its
upper surface is positioned higher than the upper surface of the
second substrate 12. Because of this, the second substrate 12 can
be fixed securely.
[0152] Next, as shown in FIG. 19B, the first substrate 11 is moved
so that the first pin 131a is inserted into the first central hole
A in a vacuum atmosphere, and the first substrate 11 and the second
substrate 12 are opposed to each other with the radiation curable
resin 171 interposed therebetween (Process (II-2)). More
specifically, after the first substrate 11 and the second substrate
12 are disposed in a container 193, and the container 193 is
exhausted through a vacuum pump, the first substrate 11 and the
second substrate 12 should be stacked adjacent each other. By
fixing the second substrate 12, the second substrate 12 can be
prevented from moving during the exhaust step. Furthermore, when
the first substrate 11 and the second substrate 12 are stacked
adjacent each other, it is preferable that the second pin 131b is
moved so that the upper surface thereof is lowered below that of
the second substrate 12. The second pin 131b may be moved at any
time after Process (II-1) and before Process (II-2). By moving the
second pin 131b, even when the radiation curable resin 171
penetrates the inside of the central hole B of the second substrate
12, the resin can be prevented from adhering to the second pin
131b. As a result, an optical disk can be produced with good
productivity.
[0153] Next, as shown in FIG. 19C, the radiation curable resin 171
is irradiated with radiation 194 such as an electron beam and
UV-rays to be cured. Thus, an optical disk can be produced.
According to the method shown in FIGS. 19A to 19 C, two substrates
are attached to each other in a vacuum atmosphere, so that air
bubbles can be prevented from entering therebetween. Pin 141, 151,
or 161 may be used in place of the pin 131.
[0154] Next, an example of a method for conducting Process (II)
without using a pin will be described. According to this method,
the centers of the first and second substrates 11 and 12 are
calculated based on the respective outer peripheries, and they are
aligned with each other. For example, as shown in FIG. 20, a center
CA of the first substrate 11 is obtained from at least three
coordinates (PA1, PA2, PA3) on an outer periphery of the first
substrate 11. Similarly, a center CB of the second substrate 12 is
obtained from at least three coordinates (PB1, PB2, PB3) on an
outer periphery of the second substrate 12. Then, the first
substrate 11 or the second substrate 12 is moved so that the center
CA is aligned with the center CB, whereby the first and second
substrates 11 and 12 are attached to each other. The centers CA and
CB may be obtained from three coordinates on an inner periphery of
the central holes A and B.
[0155] According to the method in FIG. 20, more specifically, as
shown in FIG. 21A, image processing of the first substrate 11 and
the second substrate 12 is conducted by using two cameras 211 and
212, and the centers CA and CB are obtained. Then, as shown in FIG.
21B, the center CA is aligned with the center CB. Thus, Process
(II) can be conducted.
Embodiment 6
[0156] In Embodiment 6, the present invention will be described by
way of an example of an apparatus for producing an optical disk.
FIG. 22 is a schematic perspective view of a production apparatus
220 of Embodiment 6. In FIG. 22, driving members are not shown.
[0157] Referring to FIG. 22, the production apparatus 220 includes
transport arms 221 to 224, a table 225, a table 227 at the center
of which a pin 226 is disposed, a resin curing portion 228, and a
nozzle 229. The transport arms 221 to 224 and the nozzle 229
respectively are rotated and raised by driving members.
Furthermore, the tables 225 and 227 are rotated and moved by
driving members. The pin 226 can be moved upwards/downwards by
driving members. The driving member can be formed by combining at
least one selected from a motor, an air cylinder, and a hydraulic
cylinder.
[0158] In the production apparatus 220, the second substrate 232 is
transported from a substrate holder 230 to the table 227 by the
transport arm 221. At this time, the second substrate 232 is
disposed so that the pin 226 is inserted into the central hole B.
The table 227 fixes the second substrate 232 by vacuum, static
electricity, or an adhesive member.
[0159] Radiation curable resin is poured from the nozzle 229 to the
second substrate 232 disposed on the table 227. The nozzle 229
functions to coat the second substrate 232 with the radiation
curable resin. By rotating the table 227 while the resin is poured,
the radiation curable resin can be disposed in a circular or spiral
shape on the second substrate 232. FIG. 23 is an enlarged view of
the table 227. The table 227 is rotated by a driving member 237.
The driving member 237 is moved by a driving member 238.
[0160] After the resin is poured, the table 227 on which the second
substrate 232 is disposed is moved to a stacking portion 233
together with the pin 226 by a driving member. In the stacking
member 233, the first substrate 231 is transported onto the second
substrate 232 by the transport arm 222. The first substrate 231 is
disposed so that the pin 226 is inserted into the central hole A.
Thus, the pin 226 functions to dispose the first substrate 231 and
the second substrate 232 so that the center of the first substrate
231 is aligned with that of the second substrate 232. As the pin
226, the pins 131, 141, 151, and 161 described in Embodiment 4 can
be used.
[0161] Thereafter, by rotating the table 227, the first substrate
231 and the second substrate 232 are rotated, whereby the radiation
curable resin is drawn. In this manner, the first substrate 231 and
the second substrate 232 are stacked with the resin interposed
therebetween. The transport arm 223 moves a stacked substrate 234
to the table 225. The substrate 234 disposed on the table 225 is
moved to the resin curing portion 228. The resin curing portion 228
is used for curing the radiation curable resin. The resin curing
portion 228 includes an irradiation member for applying radiation
such as an electron beam and UV-rays. More specifically, the resin
curing portion 228 includes an electron beam source, a metal halide
lamp, a mercury lamp, or a rare gas lamp such as a xenon lamp. By
irradiating the radiation curable resin with an electron beam or
UV-rays in the resin curing part 228, the radiation curable resin
is cured, and the first substrate 231 and the second substrate 232
are attached to each other. Thus, an optical disk 235 is formed.
The optical disk 235 thus formed can be transported to a substrate
holder 236 by the transport arm 224.
[0162] In the production apparatus 220, the first substrate 231 may
be exchanged with the second substrate 232. In the production
apparatus 220, the case has been described in which a coating
member for coating at least one substrate selected from the first
substrate 231 and the second substrate 232 with radiation curable
resin includes the nozzle 229. However, the coating member may be
an apparatus as shown in FIG. 24.
[0163] The apparatus shown in FIG. 24 includes a driving member
241, a spatula 242, and a screen 243. The screen 243 is provided
with a pattern for coating of resin. On the screen 243, radiation
curable resin 244 (hatched portion) is disposed. In this apparatus,
the screen 243 is disposed on the second substrate 232, and
thereafter, the spatula 242 is moved by the driving member 241,
whereby the second substrate 232 is coated with resin. In the case
where the second substrate 232 disposed on the table 227 is coated
with resin, the second substrate 232 is fixed before being coated
with the resin, and the pin 226 is moved from a coating surface. In
the case of using the coating apparatus shown in FIG. 24, it is
preferable that the resin curing portion 228 includes a
pressure-reducible container, and the first substrate 231 and the
second substrate 232 are stacked in the container. The
pressure-reducible container may be disposed before the resin
curing portion 228 on production lines.
[0164] Furthermore, FIG. 22 shows the apparatus in which the
disposing member for disposing the first substrate 231 and the
second substrate 232 in a concentric manner includes the pin 226.
However, in the production apparatus of the present invention, two
substrates may be disposed by image processing, as described with
reference to FIGS. 21A and 21B. In this case, the production
apparatus includes a camera, a processing apparatus for calculation
processing of an image captured by the camera, and a movement
apparatus for moving a substrate.
[0165] By using the production apparatus of Embodiment 6, the
production method described in Embodiments 4 and 5 can be conducted
easily.
[0166] The invention may be embodied in other forms without
departing from the spirit or essential characteristics thereof The
embodiments disclosed in this application are to be considered in
all respects as illustrative and not limiting. The scope of the
invention is indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
* * * * *