U.S. patent application number 10/622357 was filed with the patent office on 2004-07-15 for method and apparatus for curing adhesive between substrates, and disc substrate bonding apparatus.
Invention is credited to Kobayashi, Hideo, Nishimura, Hironobu, Shinohara, Shinichi, Utsunomiya, Yukio.
Application Number | 20040134603 10/622357 |
Document ID | / |
Family ID | 32719336 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040134603 |
Kind Code |
A1 |
Kobayashi, Hideo ; et
al. |
July 15, 2004 |
Method and apparatus for curing adhesive between substrates, and
disc substrate bonding apparatus
Abstract
An apparatus for bonding disc substrates is provided with a
spinner which spreads adhesive placed between a first substrate and
second substrate, and a curing device which radiates ultraviolet
light onto the adhesive through the substrate to cure it. The
curing device includes; a support mechanism which supports the
first substrate and second substrate after the adhesive is spread
by the spinner, a semiconductor light emitting apparatus having a
plurality of light emitting semiconductor elements arranged facing
a region where the adhesive is cured, and a positioning mechanism
which positions the semiconductor light emitting apparatus such
that the light emitting semiconductor elements are a predetermined
distance away from the adhesive. The adhesive is cured or
semi-cured by ultraviolet light emitted from the plurality of light
emitting semiconductor elements.
Inventors: |
Kobayashi, Hideo; (Tokyo,
JP) ; Shinohara, Shinichi; (Tokyo, JP) ;
Nishimura, Hironobu; (Tokorozawa-shi, JP) ;
Utsunomiya, Yukio; (Tokyo, JP) |
Correspondence
Address: |
KOLISCH HARTWELL, P.C.
520 S.W. YAMHILL STREET
SUITE 200
PORTLAND
OR
97204
US
|
Family ID: |
32719336 |
Appl. No.: |
10/622357 |
Filed: |
July 17, 2003 |
Current U.S.
Class: |
156/272.8 ;
156/275.7; 156/360; 156/379.6; 156/539; 156/64; 156/74 |
Current CPC
Class: |
B29C 65/4845 20130101;
B29K 2069/00 20130101; B29C 65/1454 20130101; B29C 65/1483
20130101; B29C 66/954 20130101; B29C 66/8322 20130101; B29C 66/71
20130101; B29C 66/952 20130101; C09J 5/00 20130101; B29C 65/1435
20130101; B29C 66/723 20130101; B29K 2995/0027 20130101; B29C 65/16
20130101; B29L 2017/005 20130101; B29C 65/1467 20130101; B29C
66/452 20130101; B32B 2429/02 20130101; B29C 65/1406 20130101; B29C
66/1122 20130101; B32B 37/12 20130101; B29C 66/71 20130101; B29K
2069/00 20130101; B29C 2035/0827 20130101; B29C 65/1409 20130101;
B29C 66/00141 20130101; B29C 66/73521 20130101; Y10T 156/1702
20150115 |
Class at
Publication: |
156/272.8 ;
156/275.7; 156/074; 156/064; 156/379.6; 156/539; 156/360 |
International
Class: |
G11B 007/26; B29C
035/08; B29C 065/54; B32B 031/16; B32B 031/28 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2002 |
JP |
2002-209897 |
Oct 22, 2002 |
JP |
2002-307283 |
Oct 22, 2002 |
JP |
2002-307385 |
Jun 30, 2003 |
JP |
2003-188734 |
Claims
What is claimed is:
1. A method of curing adhesive between substrates, comprising the
steps of: emitting ultraviolet light using a light emitting
semiconductor element or a gas laser, and radiating said
ultraviolet light onto adhesive spread between first and second
substrates through at least one of said first substrate and said
second substrate to cure or semi-cure said adhesive.
2. A method of curing adhesive between substrates according to
claim 1, wherein said ultraviolet light has wavelengths in a range
where a transmissivity of said adhesive before curing is lower than
the transmissivity of said adhesive after curing.
3. A method of curing adhesive between substrates according to
claim 1, wherein the wavelength of said ultraviolet light is mainly
in a range of 280 to 450 nm.
4. A method of curing adhesive between substrates according to
claim 1, wherein distance between an emission surface of
ultraviolet light from said light emitting semiconductor element or
said gas laser and an irradiated surface of said substrate is 10 mm
or less.
5. A method of curing adhesive between substrates according to
claim 1, wherein during irradiation by said ultraviolet light, said
ultraviolet light and said adhesive are moved relative to each
other.
6. A method of curing adhesive between substrates according to
claim 1, wherein a recording layer is formed on at least one of
said first substrate and second substrate, and the ultraviolet
light that said light emitting semiconductor element or said gas
laser emits is radiated from the circumference side of said first
or second substrates onto said adhesive.
7. A method of curing adhesive between substrates according to
claim 1, further comprising a step wherein after said adhesive is
semi-cured or cured by irradiation of said ultraviolet light, said
substrate is transferred to a next process, and said adhesive is
cured by irradiation by ultraviolet light.
8. A method of curing adhesive between substrates according to
claim 1, further comprising the step of: rotating said first and
second substrates at high speed to spread said adhesive applied
between said first and second substrates; and on completion of said
high speed rotation, radiating said ultraviolet light progressively
from the internal circumference of said first substrate or said
second substrate to the external circumference, while said
substrate is rotated slowly, or stopped.
9. A method of curing adhesive between substrates according to
claim 1, further comprising the step of: radiating said ultraviolet
light onto said adhesive protruding from between said first
substrate and said second substrate in an atmosphere where an
oxygen concentration is lower than in air.
10. A method of curing adhesive between substrates according to
claim 1, wherein a thickness of an adhesive layer between said
first and second substrates is detected, and said ultraviolet light
is radiated when said thickness reduces to a preset thickness with
said high speed rotation.
11. An apparatus for curing adhesive between substrates which
radiates ultraviolet light onto an adhesive spread between first
and second substrates through at least one of said first substrate
and second substrate for curing, comprising: a support mechanism
which supports said first substrate and second substrate; a
semiconductor light emitting apparatus having a plurality of light
emitting semiconductor elements arranged facing a region where said
adhesive is cured; and a positioning mechanism which positions said
semiconductor light emitting apparatus such that said light
emitting semiconductor elements are a predetermined distance away
from said adhesive, wherein said adhesive is cured or semi-cured by
ultraviolet light emitted from said plurality of light emitting
semiconductor elements.
12. An apparatus for curing adhesive between substrates according
to claim 11, wherein said positioning mechanism positions said
semiconductor light emitting apparatus so that a distance between
said light emitting semiconductor elements and said adhesive is
within 10 mm.
13. An apparatus for curing adhesive between substrates according
to claim 11, wherein said light emitting semiconductor elements
emit ultraviolet light having a wavelength in a range where a
transmissivity of said adhesive before curing is lower than the
transmissivity of said adhesive after curing.
14. An apparatus for curing adhesive between substrates according
to claim 11, wherein said light emitting semiconductor elements are
light emitting diodes which mainly emit light with a wavelength
within a wavelength range of 280 to 450 nm.
15. An apparatus for bonding disc substrates, comprising: a spinner
which spreads adhesive placed between a first substrate and second
substrate, and a curing device which radiates ultraviolet light
onto said adhesive through said substrate to cure it, wherein said
curing device comprises; a support mechanism which supports said
first substrate and second substrate after said adhesive is spread
by said spinner, a semiconductor light emitting apparatus having a
plurality of light emitting semiconductor elements arranged facing
a region where said adhesive is cured, and a positioning mechanism
which positions said semiconductor light emitting apparatus such
that said light emitting semiconductor elements are a predetermined
distance away from said adhesive, and said adhesive is cured or
semi-cured by ultraviolet light emitted from said plurality of
light emitting semiconductor elements.
16. An apparatus for bonding disc substrates according to claim 15,
wherein said light emitting semiconductor elements of said curing
apparatus are arranged in one row or a plurality of rows so as to
extend from the internal circumference to the external
circumference of said substrate, and at least one of said support
mechanism and said positioning mechanism rotates said semiconductor
light emitting apparatus and said first and second substrates
relative to each other.
17. An apparatus for bonding disc substrates according to claim 15,
wherein said light emitting semiconductor elements are fixed onto a
printed substrate, and connected to a conductive pattern formed on
said printed substrate.
18. An apparatus for bonding disc substrates according to claim 15,
wherein said light emitting semiconductor elements are light
emitting diodes which mainly emit light within a wavelength range
of 280 to 450 nm.
19. An apparatus for bonding disc substrates according to claim 15,
wherein said support mechanism is the turntable of said spinner,
and after the adhesive between said first substrate and second
substrate is spread by high speed rotation of said turntable, said
ultraviolet light is radiated onto said adhesive from above said
turntable.
20. An apparatus for bonding disc substrates according to claim 19,
wherein when said ultraviolet light is radiated onto said adhesive,
said turntable is rotated.
21. An apparatus for bonding disc substrates according to claim 15,
further comprising an emitting device which radiates light onto
said adhesive spread by said spinner to semi-cure or cure it for
tacking said first substrate and second substrate, and a disc
transfer mechanism which transfers the tacked first substrate and
second substrate to said curing device.
22. An apparatus for bonding disc substrates according to claim 21,
wherein said emitting device radiates ultraviolet light onto said
adhesive located in a non-recording region of the internal
circumference of said substrate to semi-cure or cure it for
tacking.
23. An apparatus for bonding disc substrates which bonds disc
substrates via an adhesive, comprising: a spinner that rotates said
disc substrates stacked via said adhesive at high speed to spread
said adhesive between said disc substrates; a tacking mechanism
that radiates light through said disc substrates and starts to cure
said adhesive spread between said disc substrates to tack said disc
substrates together; a transfer mechanism which moves the tacked
disc substrates to another location; and a curing device which
cures said adhesive.
24. An apparatus for bonding disc substrates according to claim 23,
wherein said tacking mechanism radiates light onto said disc
substrates mounted on a disc pedestal of said spinner, for
tacking.
25. An apparatus for bonding disc substrates according to claim 24,
wherein while said disc substrates are rotating at high speed in
said spinner, said tacking mechanism radiates light onto said
adhesive in a non-recording region of said disc substrates, to
stabilize an internal circumference of said adhesive layer.
26. An apparatus for bonding disc substrates according to claim 23,
further comprising: a transfer mechanism which transfers the bonded
disc substrates to a centering location; a centering mechanism,
which is positioned at said centering location and has a centering
member that is inserted into a center hole of said bonded disc
substrates to align the internal circumferences thereof; and a
transfer mechanism which transfers the tacked disc substrates to
said curing device, wherein said tacking mechanism radiates light
through said centered disc substrates and starts to cure said
adhesive between said disc substrates to tack said disc substrates
together, said transfer mechanism transfers the tacked disc
substrates to a curing location, and said curing device cures said
adhesive layer between said disc substrates.
27. An apparatus for bonding disc substrates according to claim 23,
wherein said tacking mechanism semi-cures or cures said adhesive in
a non-recording region, which is a region on said disc substrates
where no information is recorded.
28. An apparatus for bonding disc substrates according to claim 23,
wherein said tacking mechanism semi-cures or cures said adhesive in
an information recording region of said optical disc
substrates.
29. An apparatus for bonding disc substrates according to claim 23,
wherein said tacking mechanism emits said light while it is rotated
relative to said disc substrates.
30. An apparatus for bonding disc substrates according to claim 23,
wherein said tacking mechanism is provided with light emitting
diodes, a semiconductor laser, or a gas laser, which generates said
light.
31. An apparatus for bonding disc substrates according to claim 23,
wherein said tacking mechanism comprises; a tacking emission
mechanism which generates light to start curing said adhesive; an
arm member at the end of which said tacking emission mechanism is
installed; a vertical direction drive unit which supports said arm
member and moves it up and down; and a horizontal direction drive
mechanism that can support said vertical direction drive mechanism
and move it in the horizontal direction.
32. An apparatus for bonding disc substrates according to claim 26,
wherein said tacking mechanism radiates light onto said disc
substrates mounted on said centering mechanism, for tacking.
33. An apparatus for bonding disc substrates, comprising: a spinner
which rotates a first and second disc substrate stacked via an
adhesive at a high speed to spread said adhesive between said disc
substrates; a disc mounting stage which is provided with a
centering mechanism that is inserted into a center hole of the disc
substrates for which said adhesive has been spread, to align the
internal circumferences of said first and second disc substrates;
and a disc substrate transfer mechanism which transfers said disc
substrates from said spinner to said disc mounting stage, wherein
said disc mounting stage is provided with an emission mechanism
which radiates light onto the disc substrates whose internal
circumferences are aligned to start curing the adhesive layer
between said disc substrates.
34. An apparatus for bonding disc substrates according to claim 33,
wherein said emission mechanism semi-cures or cures said adhesive
on the whole surface or a partial region of said disc
substrates.
35. An apparatus for bonding disc substrates according to claim 33,
wherein said emission mechanism semi-cures or cures said adhesive
in a non-recording region of said disc substrates.
36. An apparatus for bonding disc substrates according to claim 33,
wherein said emission mechanism has a plurality of light emitting
diodes that generates said light.
37. An apparatus for bonding disc substrates according to claim 33,
wherein said emission mechanism has an annular ultraviolet light
radiating lamp surrounding said centering mechanism.
38. An apparatus for bonding disc substrates according to claim 33,
wherein said disc mounting stage has a cooling medium distribution
path for cooling said emission mechanism.
39. An apparatus for bonding disc substrates according to claim 33,
wherein said centering mechanism comprises; a shaft which moves up
and down inside the center hole of said disc substrates, a drive
mechanism which is connected to said shaft, and an elastic body
surrounding said shaft, which is put under pressure from above when
said drive mechanism lowers said shaft, and expands in a radial
direction of said disc substrates, and when said elastic body
expands, the elastic force presses against the internal
circumferences of said center holes of said first and second disc
substrates.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method and an apparatus
for curing adhesive, which are suitable for curing adhesive applied
between substrates such as those for optical discs and the like,
and an apparatus for bonding disc substrates.
[0003] 2. Description of Related Art
[0004] In general, an optical disc such as a DVD or the like has a
structure in which two transparent substrates are bonded together
by adhesive. Some of them have a recording layer including a
reflective layer or a semi-reflective layer formed on only one of
the substrates, and some have recording layers formed on both
substrates. In the case where a recording layer is formed on only
one substrate, the thickness of the two substrates may be the same,
or the substrate on which no recording layer is formed may be
formed with a thin, transparent sheet. Some have a structure in
which two pairs of substrates are bonded together in a laminate of
four substrates. Furthermore, in some cases a plurality of sheets
of transparent glass or lenses are bonded to each other via
intermediate adhesive.
[0005] When manufacturing such an optical disc, after two
substrates have been stacked via intermediate adhesive, the
adhesive is spread evenly over the substrates by high speed
rotation, and excess adhesive is removed. Afterwards, ultraviolet
light is normally radiated onto one or both sides of the substrate
to cure the adhesive quickly. Regarding the ultraviolet light
radiation, ultraviolet light is radiated continuously for a
prescribed time using a UV lamp, or pulsed ultraviolet light is
radiated using a xenon lamp.
[0006] However, the method of curing using these lamps has the
following problems.
[0007] (1) Since ultraviolet light emitting lamps have low luminous
efficiency, and generate significant heat, there is a possibility
of the heat distorting the substrates. Furthermore, since a
suitable heat dissipation mechanism is required, the size of the
apparatus increases, and the cost is high.
[0008] (2) Since ultraviolet light emitting lamps are expensive,
and their lifetime is short, the running costs are high. Those with
a short lifetime must be changed after several tens of hours, which
has a detrimental effect on productivity.
[0009] (3) In the case of radiating pulsed ultraviolet light, there
is an advantage in regard to heat compared with continuous
radiation. However, the shock during irradiation is great, so there
is a possibility in that vibration during that time may damage the
objects to be bonded, such as glass, or have a detrimental effect
on adhesiveness. Furthermore, the sound caused by the shocks during
irradiation increases the ambient noise level and is not desirable
environmentally. In order to solve these problems, conventionally a
damping mechanism or a noise control mechanism has been installed.
However, this invites a further increase in the size of the
apparatus and increases costs.
[0010] (4) In the case of lamps, power loss is considerable, so
there are disadvantages from both environmental and cost
standpoints.
[0011] Examples of a conventional DVD manufacturing apparatus and
its manufacturing method are described in Japanese Unexamined
Patent Application, First Publication No. 2002-245692 (pages 6 to
8, FIG. 1), and Japanese Unexamined Patent Application, First
Publication No. 09-231625 (pages 3 to 5, FIG. 1).
[0012] In the apparatus described in the references above, adhesive
is placed between two disc substrates, the adhesive is spread by a
spinner, and the disc substrates are transferred to a pedestal by a
transfer mechanism. During this transfer process the adhesive is
not cured, and hence there is a possibility in that disc substrates
newly bonded together may move. If this happens, they will cure in
this state, which causes a drop in quality. Furthermore, there is
also a concern that the area around the center hole of the stacked
disc substrates may be pulled apart and contaminated by bubbles
when the center holes of the disc substrates are mounted on the
center pin of a mounting stage in an ultraviolet light irradiating
apparatus. Consequently, the uniformity in the tilt and thickness
of the completed optical disc is affected, and there is a problem
that the quality of the optical disc and the production efficiency
deteriorate.
[0013] Especially, the uniformity of the tilt and thickness is a
major problem for Blu-Ray Disc, which have a very thin, 0.1 mm
thick light transmission layer formed from an adhesive layer and a
protective sheet, or large capacity optical discs called AOD
(Advanced Optical Disc) in which two disc substrates with a
thickness of 0.6 mm, which is the same as a DVD, are bonded
together, and which require a sufficiently tight tolerance on the
thickness of the adhesive film.
[0014] In order to solve the above problems, Japanese Unexamined
Patent Application, First Publication No. 10-97740 discloses a
technique in which disc substrates are transferred after high speed
rotation, and the stack of disc substrates is centered, and then
cured from above by an emission mechanism moved from a different
location, for tacking.
[0015] However, this method requires a process in which disc
substrates are mounted on a mounting stage for centering, and then
a retracted emission mechanism is moved over the disc substrates.
Accordingly, operating the apparatus at high speed is difficult,
and requires appropriate mechanisms. Furthermore, the inside
diameters of the center holes of the disc substrates vary, and
hence there is a concern that the inside diameters do not match
when the two disc substrates are laminated. Conventionally, when
the diameter of a metal member formed from a plurality of blocks is
expanded, and applies a pressure to the internal circumferences of
the center holes of the disc substrates to center them, a high load
is applied to disc substrates with a small inside diameter, which
affects the tilt of the disc substrates. Therefore, fine pressure
adjustment is difficult.
SUMMARY OF THE INVENTION
[0016] A method of curing adhesive between substrates according to
the present invention comprises a step for emitting ultraviolet
light using a light emitting semiconductor element or a gas laser,
and a step for radiating the ultraviolet light onto adhesive spread
between first and second substrates through at least one of the
first substrate and the second substrate to cure or semi-cure the
adhesive.
[0017] According to this method, since a light emitting
semiconductor element or a gas laser is used, heat generation can
be lower than from a conventional lamp, and hence the influence of
heat on the substrates can be reduced. Since the lifetime is
significantly longer than a lamp, running costs can be reduced.
Furthermore, the electrical energy used for the emission is small,
so that influences on the environment can be reduced.
[0018] The ultraviolet light may have wavelengths in a range where
a transmissivity of the adhesive before curing is lower than the
transmissivity of the adhesive after curing. In this case, since
the transmissivity of the ultraviolet light improves as the
adhesive cures, it is possible to cure the adhesive more
effectively.
[0019] The wavelength of the ultraviolet light may be mainly in a
range of 280 to 450 nm. In this case, the influence of heat on the
substrates can be reduced, and the transmissivity of the
ultraviolet light improves as the adhesive cures. Therefore, it is
possible to cure the adhesive more effectively.
[0020] A distance between an emission surface of ultraviolet light
from the light emitting semiconductor element or the gas laser and
an irradiated surface of the substrate may be 10 mm or less. In
this case, the influence of heat on the optical disc can be
reduced, and the adhesive can be cured more efficiently. More
preferably, it is 7 mm or less.
[0021] During irradiation by the ultraviolet light, the ultraviolet
light and the adhesive may be moved relative to each other. In this
case, it is possible to cure the adhesive more uniformly.
[0022] A recording layer may be formed on at least one of the first
substrate and second substrate, and the ultraviolet light that the
light emitting semiconductor element or the gas laser emits may be
radiated from the circumference side of the first or second
substrates onto the adhesive. In this case, it is possible to cure
the adhesive to a more desirable state, and to do it uniformly.
[0023] After the adhesive is semi-cured or cured, the substrate may
be transferred to a next process, and the adhesive may be cured by
irradiation by ultraviolet light. In this case, it is possible to
cure the adhesive to a more desirable state. After the adhesive is
semi-cured, since the amount of ultraviolet light required to cure
the adhesive is small, it is possible to cure the adhesive
sufficiently by suitable weak ultraviolet light.
[0024] After spreading the adhesive applied between the first and
second substrates by high speed rotation, ultraviolet light may be
radiated onto it progressively from the internal circumference of
the first substrate and the second substrate to the external
circumference, while the substrate is rotated slowly, or while the
substrate is stopped. In this case, it is possible to cure the
adhesive more efficiently, and hence enable quality to be
improved.
[0025] Either one of the first substrate and the second substrate
or both may be polycarbonate. In this case, ultraviolet light of a
longer wavelength than the wavelength at which the transmissivity
of light saturates for polycarbonate may be radiated. In this case,
it is possible to cure the adhesive more efficiently, and hence
enable the influence of heat on the substrate to be reduced.
[0026] The ultraviolet light may be radiated onto the adhesive
protruding from between the first substrate and the second
substrate in an atmosphere where an oxygen concentration is lower
than in air. In this case, it is possible to cure the adhesive
protruding from between the substrates more efficiently and more
effectively.
[0027] A thickness of an adhesive layer between the first and
second substrates may be detected, and the ultraviolet light
radiated when the thickness reduces to a preset thickness with the
high speed rotation. In this case, it is possible to cure the
adhesive more efficiently.
[0028] The thickness of the adhesive layer between the first and
second substrates may be detected, and the ultraviolet light
radiated progressively from an area whose thickness is reduced to a
preset thickness with the high speed rotation.
[0029] A curing apparatus of the present invention radiates
ultraviolet light onto an adhesive spread between first and second
substrates through at least one of the first substrate and second
substrate for curing. This apparatus comprises a support mechanism
which supports the first substrate and second substrate, a
semiconductor light emitting apparatus having a plurality of light
emitting semiconductor elements arranged facing a region where the
adhesive is cured, and a positioning mechanism which positions the
semiconductor light emitting apparatus such that the light emitting
semiconductor elements are a predetermined distance away from the
adhesive, and the adhesive is cured or semi-cured by ultraviolet
light emitted from the plurality of light emitting semiconductor
elements.
[0030] According to this apparatus, heat generation is far less
than from a conventional lamp, so the influence of heat on the
substrates can be reduced. Furthermore, since the lifetime is
significantly longer than an ultraviolet light lamp, running costs
are reduced, and the electrical energy used for emission is
low.
[0031] The plurality of light emitting semiconductor elements may
be arranged along any of a helical, concentric circular, or
polygonal pattern. Furthermore, the plurality of light emitting
semiconductor elements may be arranged at random.
[0032] The plurality of light emitting semiconductor elements may
be arranged in a helical pattern, and the light emitting
semiconductor elements may irradiate ultraviolet light from the
inside to the outside progressively with time. In this case, it is
possible to cure the adhesive more effectively. Furthermore, it is
possible to release the stress occurring in the adhesive layer by
curing from the internal circumference to the external
circumference, and hence the quality of the bonded substrates is
improved.
[0033] The plurality of light emitting semiconductor elements may
be arranged in a concentric circular pattern, and the light
emitting semiconductor elements in the concentric circular pattern,
which are adjacent in the radial direction, may radiate ultraviolet
light onto the adhesive from the inside toward the outside
progressively with time.
[0034] The light emitting semiconductor elements may be connected
in parallel. Alternatively, a predetermined number of them may be
connected in series, and then those groups of series connections
may be connected in parallel. In this case, it is possible to use a
low voltage power supply, and hence the reliability is also
improved.
[0035] The time duration may be almost the same as the curing time
of the adhesive, or it may be longer.
[0036] The semiconductor light emitting devices are preferably
within 10 mm from the adhesive, and more preferably within 7
mm.
[0037] The light emitting semiconductor elements of the curing
apparatus may be arranged in one row or a plurality of rows so as
to extend from the internal circumference to the external
circumference of the substrate, and at least one of the support
mechanism and the positioning mechanism may rotate the
semiconductor light emitting apparatus and the first and second
substrates relative to each other.
[0038] The curing apparatus may be provided with a gas blowing
mechanism for blowing an inert gas such as nitrogen gas or the like
onto the surface of the adhesive where ultraviolet light is
radiated.
[0039] The light emitting semiconductor elements may be fixed onto
a printed substrate, and connected to a conductive pattern formed
on the printed substrate.
[0040] An apparatus for bonding disc substrates of the present
invention is provided with a spinner which spreads adhesive placed
between a first substrate and second substrate, and a curing device
which radiates ultraviolet light onto the adhesive through the
substrate to cure it, wherein the curing device comprises; a
support mechanism which supports the first substrate and second
substrate after the adhesive is spread by the spinner, a
semiconductor light emitting apparatus having a plurality of light
emitting semiconductor elements arranged facing a region where the
adhesive is cured, and a positioning mechanism which positions the
semiconductor light emitting apparatus such that the light emitting
semiconductor elements are a predetermined distance away from the
adhesive, and the adhesive is cured or semi-cured by ultraviolet
light emitted from the plurality of light emitting semiconductor
elements.
[0041] After the adhesive between the first substrate and second
substrate is spread by high speed rotation of the spinner
turntable, the ultraviolet light may be radiated onto the adhesive
from above the turntable.
[0042] When the ultraviolet light is radiated onto the adhesive,
the turntable may be rotated.
[0043] When the ultraviolet light is radiated onto the adhesive,
the turntable may be located above a partition of the spinner.
[0044] The curing device may further comprise an emitting device
which radiates light onto the adhesive spread by the spinner to
semi-cure or cure it for tacking the first substrate and second
substrate, and a disc transfer mechanism which transfers the tacked
first substrate and second substrate to the curing device.
[0045] Tacking may be performed while the spinner is rotating.
Tacking may be performed by semi-curing or curing the adhesive in a
non-recording region where no recording layer is formed in the
internal circumference of the optical disc substrate.
[0046] An apparatus for bonding disc substrates of another aspect
of the present invention comprises: a spinner that rotates the disc
substrates stacked via an adhesive at high speed to spread the
adhesive between the disc substrates; a tacking mechanism that
radiates light through the disc substrates and starts to cure the
adhesive spread between the disc substrates to tack the disc
substrates together; a transfer mechanism which moves the tacked
disc substrates to another location; and a curing device which
cures the adhesive. This apparatus enables high quality discs to be
obtained.
[0047] The tacking mechanism may radiate light onto the disc
substrates mounted on a disc pedestal of the spinner, for
tacking.
[0048] While the disc substrates are rotating at high speed in the
spinner, the tacking mechanism may radiate light onto the adhesive
in the non-recording region, which is a region on the disc
substrates where no information is recorded, to stabilize an
internal circumference of the adhesive layer.
[0049] Another aspect of an apparatus for bonding disc substrates
comprises: a spinner which rotates the disc substrates stacked via
intermediate adhesive at high speed to spread the adhesive between
the disc substrates; a transfer mechanism which transfers the
bonded disc substrates to a centering location; a centering
mechanism, which is positioned at the centering location and has a
centering member that is inserted into a center hole of the bonded
disc substrates to align the internal circumferences thereof; a
tacking mechanism for tacking the disc substrates by radiating
light through the centered disc substrates to start curing the
adhesive layer between the disc substrates; a transfer mechanism
which transfers the tacked disc substrates to a curing location;
and a curing device, which is positioned at the curing location and
cures the adhesive layer between the disc substrates.
[0050] The tacking mechanism may semi-cure or cure the adhesive in
a non-recording region, which is a region on the disc substrates
where no information is recorded.
[0051] The tacking mechanism may semi-cure or cure the adhesive in
an information recording region of the optical disc substrates.
[0052] The tacking mechanism may emit the light while it is rotated
relative to the disc substrates.
[0053] The tacking mechanism may be provided with light emitting
diodes, a semiconductor laser, or a gas laser, which generates the
light.
[0054] The tacking mechanism may have a tacking emission mechanism
which generates light to start curing the adhesive; an arm member
at the end of which the tacking emission mechanism is installed; a
vertical direction drive unit which supports this arm member and
moves it up and down; and a horizontal direction drive mechanism
that can support this vertical direction drive mechanism and move
it in the horizontal direction.
[0055] The tacking mechanism may radiate light onto the disc
substrates mounted on the centering mechanism, for tacking.
[0056] An apparatus for bonding disc substrates according to
another aspect of the present invention comprises: a spinner which
rotates a first and second disc substrate stacked via an adhesive
at a high speed to spread the adhesive between the disc substrates;
a disc mounting stage which is provided with a centering mechanism
that is inserted into a center hole of the disc substrates for
which the adhesive has been spread, to align the internal
circumferences of the first and second disc substrates; and a disc
substrate transfer mechanism which transfers the disc substrates
from the spinner to the disc mounting stage, and the disc mounting
stage is provided with an emission mechanism which radiates light
onto the disc substrates whose internal circumferences are aligned
to start curing the adhesive layer between the disc substrates.
[0057] Using this apparatus, by providing a disc mounting stage,
which has both a centering mechanism and an adhesive curing
mechanism, at a separate location from the spinner, it is possible
to realize accurate centering after a uniform adhesive layer is
created by the spinner rotating at high speed, and to improve the
production efficiency, thus enabling high quality optical discs to
be obtained. Moreover, it is possible to start curing the adhesive
almost at the same time as the accurate centering, so that it is
possible to improve the quality and efficiency of producing the
optical disc substrates.
[0058] The emission mechanism may semi-cure or cure the adhesive on
the whole surface or a partial region of the disc substrates. In
this case, it is possible to bond or tack the disc substrates
efficiently.
[0059] The emission mechanism may semi-cure or cure the adhesive in
a non-recording region of the disc substrates. By curing the
adhesive in the non-recording region in the internal circumference
of the disc substrates, it is possible to maintain the partially
tacked and centered state. Furthermore, it is possible to adjust
the spread of the adhesive in the internal circumference of the
disc substrates, thus preventing adhesive from protruding from the
internal circumference of the center hole of the disc
substrates.
[0060] The emission mechanism may have a plurality of light
emitting diodes that generates the light. In this case, it is
possible to miniaturize the emission mechanism, and reduce power
consumption. Furthermore, the lifetime of the emission mechanism is
long, and reliability is improved.
[0061] The emission mechanism may have an annular ultraviolet light
radiating lamp surrounding the centering mechanism. In this case,
it is possible to complete the adhesive curing during centering,
and a high quality optical disc can be obtained, and at the same
time the production efficiency can be improved.
[0062] The disc mounting stage may have a cooling medium
distribution path for cooling the emission mechanism. In this case,
it is possible to prevent the conduction of heat generated by the
emission mechanism from affecting the disc substrates. Furthermore,
it is possible to prevent the light emitting elements from being
damaged.
[0063] The centering mechanism may have a shaft which moves up and
down inside the center hole of the disc substrates, a drive
mechanism which is connected to the shaft, and an elastic body
surrounding the shaft, which is put under pressure from above when
the drive mechanism lowers the shaft, and expands in a radial
direction of the disc substrates, and when the elastic body
expands, the elastic force presses against the internal
circumferences of the center holes of the first and second disc
substrates. In this case, it is possible to apply optimal pressure
to the internal circumferences of the center holes of both the
first and second disc substrates for accurate centering.
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] FIG. 1 is a front view showing an embodiment of an apparatus
for bonding disc substrates according to the present invention.
[0065] FIG. 2 and FIG. 3 are graphs showing the wavelength and
transmissivity of ultraviolet light.
[0066] FIG. 4 is a graph showing the emission characteristic of a
light emitting diode for ultraviolet light emission.
[0067] FIG. 5 is a front view, partially cut away, showing an
apparatus for bonding disc substrates according to another
aspect.
[0068] FIG. 6A and FIG. 6B are a plan view and a front view of a
semiconductor light emitting unit.
[0069] FIG. 7A and FIG. 7B are a plan view and a front view of
another example of a semiconductor light emitting unit.
[0070] FIG. 8 to FIG. 13 are front views to explain the operation
of an apparatus for bonding disc substrates of another
embodiment.
[0071] FIG. 14A and FIG. 14B are a plan view and a sectional view
of a tacking mechanism.
[0072] FIG. 15 is a sectional view to explain the function of the
tacking mechanism.
[0073] FIG. 16 is a graph showing the thickness of an adhesive
layer.
[0074] FIG. 17A and FIG. 17B are plan views of examples of
centering members.
[0075] FIG. 18 is a sectional view showing another embodiment of an
apparatus for bonding disc substrates of the present invention.
[0076] FIG. 19 is an enlarged sectional view of a disc mounting
stage.
[0077] FIG. 20 is a plan view of an emission mechanism.
[0078] FIG. 21 and FIG. 22 are sectional views showing the
operation of a centering mechanism.
[0079] FIG. 23 is a sectional view of the centering mechanism.
[0080] FIG. 24A to FIG. 24D are sectional views to explain an
embodiment of a bonding method of the present invention.
[0081] FIG. 25 is a sectional view to explain another example of a
curing mechanism.
DETAILED DESCRIPTION OF THE INVENTION
[0082] Hereunder is a description of a plurality of embodiments of
the present invention. However, the present invention is not
limited to these embodiments and the structures of parts of the
embodiments may be replaced with other known structures, and also
the structures of the embodiments may be interchanged. Furthermore,
the following embodiments use the present invention for bonding
disc substrates. However, the present invention is not limited to
this, and it can be used for any other application provided the
application is to bond a pair of substrates with adhesive.
[0083] [Embodiment 1]
[0084] FIG. 1 to FIG. 3 illustrate embodiment 1 of the present
invention. In FIG. 1, reference symbols 1 and 2 denote disc shaped
substrates such as disc substrates formed from polycarbonate, and
an adhesive layer 3 (uncured state) spread by high speed rotation
is formed between the substrates 1 and 2. In this example, no
recording layer is formed on the substrate 1, and a recording layer
including a reflective layer is formed only on the substrate 2.
However, recording layers may be formed on both the substrates 1
and 2. In this case, a recording layer including a semi-reflective
layer is formed on the substrate 1, and a recording layer including
a reflective layer is formed on the substrate 2.
[0085] The substrates 1 and 2 are mounted on a flat, disc-shaped
pedestal 4, and the pedestal 4 is connected to an elevator unit 6
via an ascending and descending shaft 5. A locating pin 4a is
provided in the center of the pedestal 4 for locating the
substrates 1 and 2. When the substrates 1 and 2 are mounted, the
locating pin 4a is inserted into the center holes of the substrates
1 and 2.
[0086] A semiconductor light emitting unit 7 is placed above the
uppermost substrate 1 coaxially. The semiconductor light emitting
unit 7 has a slightly larger outside diameter than the substrate 1.
The semiconductor light emitting unit 7 has a large number of light
emitting diodes 7a as light emitting semiconductor elements, and a
support 7b for supporting the light emitting diodes 7a. The large
number of light emitting diodes 7a is arranged over the whole of
the underside of the support 7b, and emission faces X of the large
number of light emitting diodes 7a are all on the same plane.
[0087] The light emitting diodes 7a may be arranged closely at
random. However, it is preferable to arrange them in multiple
concentric circles having the same center as the substrate 1. A
certain space may be made between adjacent light emitting diodes
7a, or they may touch each other. The light emitting diodes 7a are
all connected in parallel, and a resistor is connected in series
with each of the light emitting diodes 7a for protection. During
physical assembly, surface mount type light emitting diodes and
resistors may be surface mounted on a disc shaped printed substrate
serving as the support 7b or part of it. Hence it is possible to
assemble them easily even if there are about 350 to 450 of
each.
[0088] One reason why the light emitting diodes 7a are connected in
parallel rather than in series is that failure of a light emitting
diode 7a may be of a short circuit type or an open circuit type,
and if connected in series, emission of the semiconductor light
emitting unit 7 may be disrupted if the failure is an open circuit
type. An other reason is that since the voltage drop of each light
emitting diode is several volts, if 350 to 450 diodes are connected
in series, a high voltage of over 1000V is required.
[0089] The cathode side of each of the light emitting diodes is
connected to the negative terminal of a DC power supply 8, and the
anode side thereof is connected to the positive terminal via a
protective resistor 9 and a switching device 10. The most simple
switching device 10 opens and closes the circuit for a fixed
period. The switching device 10 may be equipped with a simple
sequencer or a CPU in order to turn a prescribed number of light
emitting diodes 7a on and off sequentially. For greater efficiency,
each emission surface X of the light emitting diodes 7a is
positioned so as to not touch the top surface of the uppermost
substrate 1, and the spacing from the surface of the uppermost
substrate 1 is as small as possible. This is because light
diminishes in proportion to the inverse square of the distance.
Preferably the spacing between the emission surface X and the
surface of the uppermost substrate 1 is 10 mm or less, and more
preferably 1 to 7 mm.
[0090] Preferred characteristics of the light emitting diodes 7a
used for this invention are described using FIG. 2 to FIG. 4. In
FIG. 2 and FIG. 3, the horizontal axis represents light wavelength,
and the vertical axis transmissivity. Curve A shows the
transmissivity of a polycarbonate substrate, curve B the
transmissivity of adhesive before being irradiated by ultraviolet
light, and curve C the transmissivity of adhesive after curing by
irradiation by ultraviolet light. Polycarbonate material is used
for current optical disc substrates, and the transmissivity of a
substrate formed from polycarbonate material increases rapidly when
the wavelength is longer than approximately 280 nm. In this
embodiment, since ultraviolet light is radiated onto the adhesive 3
through the substrate 1 or 2 of the optical disc to cure it,
ultraviolet light whose wavelength is shorter than 280 nm is
difficult to use because the transmissivity is low, and hence
ultraviolet light with a wavelength of 280 nm or greater,
preferably 300 nm or greater, is used, whose transmissivity is
high.
[0091] As shown in FIG. 2 and FIG. 3, there is a wavelength region
where the transmissivity of ultraviolet light through the adhesive
is lower before irradiation than after being cured by irradiation.
The wavelength region where the transmissivity before irradiation
by ultraviolet light from the light emitting diodes is lower than
after irradiation is approximately 280 nm to 450 nm, and in this
region the transmissivity of the adhesive increases as the adhesive
cures by light irradiation. Considering absorption by the adhesive,
wavelengths where the absorption rate of ultraviolet light is high
are effective for accelerating curing. However, it has been found
that even if the adhesive has a high ultraviolet light absorption
rate, if the ultraviolet light transmissivity of a substrate made
of polycarbonate is too low, the substrate deteriorates. The light
wavelength at this time was below 280 nm. Furthermore, it was also
found that when sufficient light of wavelengths over 600 nm was
radiated for a sufficient time to cure the adhesive, problems
occurred such as deterioration or damage to the organic dye film of
the optical disc recording layer.
[0092] Since the wavelengths when problems occur in the optical
disc itself are 280 nm or less, or 600 nm or more, a wavelength
region of 280 nm to 600 nm was selected. The results of radiation
of light with a range of wavelengths in this wavelength region onto
adhesive through a substrate made of polycarbonate confirmed that a
photopolymerization reaction of the adhesive occurred when the
light wavelength emitted by the light emitting diodes was between
280 nm and 450 nm. Especially when the wavelength of light emitted
by the light emitting diodes was between 300 nm and 420 nm, the
photopolymerization reaction of the adhesive occurred successfully,
and it was also confirmed that there was no detrimental effect on
the substrates, the recording layers and the like. The wavelength
region of 280 to 450 nm is almost the same as the wavelength region
where the transmissivity of ultraviolet light before curing
adhesive is lower than the transmissivity of ultraviolet light
after curing it.
[0093] FIG. 4 shows the characteristics of a commercial ultraviolet
light emitting semiconductor element, wherein the horizontal axis
represents wavelength, and the vertical axis relative emission
intensity. As shown in FIG. 4, the ultraviolet light emitting
semiconductor element emits light within a narrow wavelength width,
approximately 360 nm to 420 nm, and the peak is at approximately
380 nm. This ultraviolet light at a wavelength of approximately 380
nm is within the desirable wavelength range of 300 nm to 420 nm, so
it is clear that this commercial ultraviolet light emitting
semiconductor element is suitable as a source of ultraviolet light
emission. Accordingly, as a light source for emitting ultraviolet
light, it is desirable to use ultraviolet light emitting diodes
that emit ultraviolet light with wavelengths as shown in FIG. 4.
Almost all light emitted from ultraviolet light emitting diodes
that emit ultraviolet light with wavelengths as shown in FIG. 4 can
be used for curing the adhesive layer between substrates.
[0094] The operation of the apparatus will be described. After the
substrates 1 and 2 are joined together via the intermediate
adhesive layer 3, the adhesive is spread uniformly by high speed
rotation using a typical spinner, which is not shown in the figure.
The substrates 1 and 2 are mounted on a substrate pedestal 4 using
a typical substrate transfer mechanism, which is not shown in the
figure. At the same time, the elevator unit 6 raises an elevator
shaft 5, and when the surface of the uppermost substrate comes
within a distance of 1 mm to 10 mm, preferably 7 mm, of the
emission surface X of the semiconductor light emitting unit 7, the
elevator unit 6 is stopped. At the same time as this stops, in
other words at the point of time that the surface of the uppermost
substrate 1 approaches the predetermined distance within 10 mm of
the emission surface X of the semiconductor light emitting unit 7,
the switching device 10 operates, current flows from a DC power
supply 8 through a switching element, which is not shown in the
figure, the protective resistor 9, and all of the light emitting
diodes 7a of the semiconductor light emitting unit 7. Thus all of
the light emitting diodes 7a emit ultraviolet light mainly in a
wavelength range of 280 to 450 nm. The ultraviolet light is
radiated onto the adhesive layer 3 through the uppermost substrate
1 to cure the adhesive layer 3. This may be semi-cured. Afterwards,
the elevator unit 6 operates again, and lowers the elevator shaft
5, and the substrates 1 and 2 on the substrate pedestal 4 are then
removed by the typical substrate transfer mechanism.
[0095] Although the light emitted by the light emitting diodes 7a
is not strong, the light emitting diodes 7a generate smaller heat,
and have less thermal effect on substrates than an ultraviolet
light emitting lamp such as a typical xenon lamp. Accordingly, it
is possible to reduce the distance between the emission surface X
of the semiconductor light emitting unit 7 and the uppermost
substrate 1 significantly as described above, compared with the
case of using a lamp. Accordingly, it is possible for light from
the light emitting diodes of the semiconductor light emitting unit
7 to cure adhesive in approximately the same time as in the case of
the conventional lamp.
[0096] Furthermore, in this embodiment, the light emitting diodes
are arranged closely, so that light from adjacent, surrounding
light emitting diodes overlaps. Accordingly, even if one of the
adjacent light emitting diodes is damaged, it is possible to reduce
the effects to a minimum, and there is no physical, detrimental
effect on curing the adhesive.
[0097] Furthermore, since the semiconductor light emitting unit 7
is larger than the outer circumferences of the substrates 1 and 2
by one light emitting diode, it is also possible to cure adhesive
protruding between the outer edges of the substrates 1 and 2.
[0098] In order to cure the adhesive protruding between the
substrates 1 and 2 in a short time efficiently, one or a plurality
of light emitting diodes, which is not shown in the figure, may be
arranged at a location 1 mm to 10 mm away from the circumferences
of the substrates 1 and 2 with identical spacing, and light from
the light emitting diodes may be radiated onto the adhesive
protruding between the substrates 1 and 2 effectively. In this
case, it is desirable to rotate the substrates 1 and 2 and the
light emitting diodes relative to each other. Normally, the
substrates 1 and 2 are rotated. Since the speed for curing the
adhesive slows in the presence of oxygen, a gas blowing nozzle for
blowing an inexpensive, inert gas such as nitrogen gas may be
provided in the location where the light emitting diodes, which are
not shown in the figure, radiate, to surround the adhesive to be
irradiated with nitrogen gas. In this case, curing of the adhesive
in contact with the gas is promoted, and the curing time is
reduced.
[0099] In this embodiment, the distance between the emission
surface X of the semiconductor light emitting unit 7 and the
substrates 1 and 2 is narrowed or widened by raising or lowering
the pedestal 4a. However, the arrangement may be such that the
substrates 1 and 2 are mounted conventionally on a substrate
pedestal on a turntable, which is not shown in the figure, and the
turntable is rotated in the horizontal direction intermittently or
continuously, so that the substrates 1 and 2 pass through a
location a predetermined distance below the emission surface X of
the semiconductor light emitting unit 7.
[0100] In another embodiment of the present invention, ultraviolet
light from the semiconductor light emitting unit is radiated onto
the adhesive while the substrates 1 and 2 are rotated by a spinner.
This embodiment will be described using FIG. 5. However,
beforehand, a typical optical disc manufacturing process will be
described. In a manufacturing process of an optical disc such as a
DVD, adhesive is typically applied to the internal circumference of
one substrate in an annular pattern, then the other substrate is
stacked on top of it. Afterwards, the stacked substrates are
transferred to the spinner by a substrate transfer mechanism, which
is not shown in the figure. In the stacking process, a voltage may
be applied between the substrates as required to deform the
adhesive into a tapered form with the attractive force of the
electric field.
[0101] The outline of the spinner is as shown in FIG. 5, and has a
turntable 11, which supports a pair of substrates 10 stacked via
intermediate adhesive and rotates them, a shaft 13 connecting the
turntable 11 with a rotation drive unit 12 such as a motor, and a
partition 14 surrounding the area around the substrates 10 on the
turntable 11, excluding the above. The spinner generally rotates
the substrates 10 at a high rotation speed of 2000 to 6000
revolutions per minute for a predetermined time, thus removing
excess adhesive from between the substrates by its centrifugal
force, and forms an adhesive layer of a uniform desired thickness.
After it stops rotating, the substrates 10 are removed from the
spinner by a substrate transfer mechanism, which is not shown in
the figure, transferred to an ultraviolet light irradiation
mechanism, which is not shown in the figure, and irradiated by
ultraviolet light to cure the adhesive between the substrates.
[0102] In this embodiment, while the spinner is operating, the
semiconductor light emitting unit 7 is placed above the substrates
10. The semiconductor light emitting unit 7 may be the same as in
the embodiment described previously. The excess adhesive between
the substrates 10 is removed, and when the substrates 10 stop
rotating, or at the point of time when the rotation speed slows
before rotation stops, the semiconductor light emitting unit 7 is
lowered by a vertical motion drive unit 15 and a vertical motion
shaft mechanism 16 such that the emission surface X arrives at a
location 1 to 10 mm, or preferably 1 to 5 mm, from the surface of
the substrates 10. When the emission surface X arrives at the
location 1 to 5 mm from the surface of the substrates 10, the
semiconductor light emitting unit 7 radiates ultraviolet light with
a wavelength range of 280 to 450 nm onto the substrates 10 to cure
the adhesive between the substrates. The substrates 10, in which
the substrates 1 and 2 are bonded together completely in this
manner, are removed from the spinner by the substrate transfer
mechanism, which is not shown in the figure.
[0103] Ultraviolet light may be radiated onto the substrates 10
while the substrates are stopped. However, in order to achieve
uniformity of the amount of ultraviolet light irradiation, it is
preferable to radiate ultraviolet light while rotating the
substrates 10 at low speed. While the substrates 10 are rotating,
ultraviolet light is radiated, and the substrates 10 may stop
during irradiation.
[0104] In this embodiment, some ultraviolet light may leak from the
semiconductor light emitting unit 7 and cure part of the adhesive
attached to the inside of the partition 14 of the spinner. In order
to avoid this, the semiconductor light emitting unit 7 is fixed
above the spinner, and the substrates 10 may be lifted from the
spinner to radiate ultraviolet light onto the substrates 10 from
outside the spinner.
[0105] In this case, an elevator unit, which moves the shaft 13 and
the turntable 11 up and down, is provided in addition to the
rotation drive unit 12. In this case, the elevator unit 15 and the
elevator shaft 16 are not required to drive the semiconductor light
emitting unit 7 up and down. The semiconductor light emitting unit
7 is fixed above the partition 14 of the spinner. In the spinner,
when high speed rotation stops, the elevator unit raises the
rotation drive unit 12, the shaft 13, the turntable 11 and the
substrates 10, and stops them in the vicinity of the semiconductor
light emitting unit 7. The semiconductor light emitting unit 7 then
radiates ultraviolet light in the aforementioned region onto the
substrates 10 to cure the adhesive between the substrates when the
surface of the substrates 10 arrives at the location 1 to 7 mm from
the emission surface X. By so doing, the adhesive inside the
partition 14 is not cured by ultraviolet light. Before the adhesive
layer between the substrates cures, if the substrate transfer
mechanism, which is not shown in the figure, attracts and holds the
surface of the substrates to remove them from the spinner, there is
a possibility of detrimental effects occurring such as a slight
shift of the substrates, distortion and the like. However, in this
embodiment, since the substrates are removed from the spinner after
the adhesive layer between them is cured, such detrimental effects
do not occur.
[0106] An example of the semiconductor light emitting unit 7 will
be described using FIG. 6A and FIG. 6B. FIG. 6A shows an example of
an arrangement of light emitting semiconductor elements 7a, wherein
the lines a, b, c to n are arranged in concentric circles in the
disc shaped support 7b. Line a represents the innermost circle,
line b represents the second circle from the inside, and similarly,
line n represents the outermost circle. In this embodiment, the
support 7b is a disc shaped, printed substrate. Regarding the
concentric circular lines a, b, c to n, the light emitting diodes
on each of the lines a, b, c to n are all connected in parallel by
a conductive pattern P. The innermost line a is connected to line b
in series by connecting a light emitting diode a1 to a light
emitting diode b1 of line b, which is the next line out, by a
conductive pattern P1. Line b and line c, which is the third line
from the inside, are connected in series by connecting a light
emitting diode b1 and a light emitting diode c1 of line c by a
conductive pattern P2. Line c and the fourth line d are connected
in series by connecting a light emitting diode c1 and a light
emitting diode d1 of line d by a conductive pattern P3. The other
adjacent lines are similarly connected in series by conductive
patterns. T1 and T2 are input terminals, and when a predetermined
voltage is applied to the input terminals T1 and T2, the light
emitting diodes of each of the lines a, b, c to n all emit at the
same time.
[0107] By all of the light emitting diodes of the lines a, b, c to
n emitting at the same time, ultraviolet light is radiated onto the
whole surface of substrate 1 at the same time, and the whole
surface of the adhesive layer 3 is cured at the same time. However,
since the adhesive layer 3 is cured by a photopolymerization
reaction, a considerable amount of heat occurs at the time of
polymerization, and the temperature of the substrates 1 and 2
rises, which may cause distortion. It was found that in order to
reduce distortion of the substrates 1 and 2 by reducing heat
generation during curing, it is effective for the light emitting
diodes to emit in the order of the lines a, b, c to n from the
internal circumference side towards the external circumference
side.
[0108] In order for the lines a, b, c to n to emit in order, a
switching element such as a MOSFET is provided between adjacent
lines. In this case, switching elements 20a, 20b, to 20n may be
installed between the light emitting diodes a1 and b1, between b2
and c2, and so on to between n-1 and n, respectively, such that
they connect between them in series. As shown in FIG. 6B, a drive
unit 21 may be installed at the back of the disc shaped, printed
substrate 7b to switch the switching elements 20a, 20b, to 20n on
and off sequentially. The switching element 20a is installed
between the light emitting diode a1 and the light emitting diode
b1, one end of the switching element 20a is connected to the light
emitting diode a1 via a through hole BH formed on the printed
substrate 7b, and the other end of the switching element 20a is
connected to the light emitting diode b1 via another through hole
BH formed on the printed substrate 7b. Similarly, the switching
element 20b is provided between the light emitting diode b2 and the
light emitting diode c2, and one end of the switching element 20b
is connected to the light emitting diode a2 via a through hole BH
formed on the printed substrate 7b, and the other end of the
switching element 20b is connected to the light emitting diode c2
via another through hole BH formed on the printed substrate 7b.
Switching elements connected between the other predetermined light
emitting diodes are located behind the switching elements 20a and
20b in FIG. 6B.
[0109] The drive unit 21 switches the switching elements 20a, 20b
etc. on for a certain time at fixed intervals. Accordingly, all of
the light emitting diodes on line a emit first, and after a
predetermined time, 20 ms for example, the switching element 20a is
turned on, so that all of the light emitting diodes on line b also
emit. Similarly, by switching the switching elements on, lines a,
b, c to n emit in sequence. When a predetermined on time has
elapsed, the switches are turned off in sequence every 20 ms from
the switching element 20a, and the light emitting diodes on line n
stop emitting last. If a fixed sequential delay time is determined
in advance, and the on time is also predetermined in this manner,
it is also possible to use a delay circuit comprising a capacitor
and a resistor for example, instead of switching elements.
[0110] For example, by measuring in advance which regions of the
adhesive layer are difficult to cure, and which are easy to cure,
and by storing in advance the length of the on time of each
switching element 20, the timing of the on time, the order of on,
and the like in memory, the emission time of the light emitting
diodes corresponding to the regions which are difficult to cure is
made longer than that of the light emitting diodes corresponding to
the regions which are easy cure, and it is also possible to cure
uniformly in the shortest photo-irradiation time. In the
embodiment, lines a, b, c to n are connected in series via the
switching elements 20. However, since the light emitting diodes are
connected in parallel in each of lines a, b, c to n, the voltage
from a commercial power supply is sufficient. Lines a, b, c to n
may be connected in parallel via each of the switching elements
20.
[0111] Furthermore, a photo-irradiation mechanism in which lines a,
b, c to n are connected in parallel via switching elements, and a
spinner as shown in FIG. 5, may be combined, and also a sensor may
be installed that can measure the thickness of the adhesive layer
from the innermost circle to the adhesive on the outermost circle.
In this case, when rotated at high speed in order to spread the
adhesive applied between the substrates 10, the thickness of the
adhesive layer is measured from the innermost circle to the
outermost circle, the measured value is compared with the set value
stored in the CPU, and by switching on the switching elements of a
line corresponding to a region where the thickness has reached the
set value, firstly the light emitting diodes on this line are
turned on, then the switching element corresponding to a region
where the thickness of the adhesive layer next reaches the set
value is turned on. Thus it is possible to radiate ultraviolet
light in sequence from the region where the thickness first reaches
the set value. By so doing, it is possible to obtain an adhesive
layer of which all parts are closer to the set value, and thus it
is possible to obtain an optical disc with higher quality.
[0112] As another embodiment, the arrangement may be such that
lines of light emitting diodes connected in series, or connected in
parallel, or a predetermined plurality of them connected in series
and then connected in parallel, are arranged in a spiral pattern.
Preferably, the diameter of the innermost side of the spiral
pattern arrangement is smaller than the inner diameter of the
adhesive layer between substrates, and the diameter on the
outermost side is larger than the outer diameter of the adhesive
layer between the substrates. This is adequate in itself, but delay
elements, which generate a delay for a predetermined time, or
switching elements, may be connected between the light emitting
diodes connected in series or connected in parallel, or the
switching elements or the delay elements may be connected at
intervals of a plurality of light emitting diodes, for example,
every 10 light emitting diodes. By switching the delay elements or
the switching elements on sequentially, it is possible for the
light emitting diodes arranged in a spiral pattern to emit one at a
time, or a plurality of them at a time, from the internal
circumference side towards the external circumference side. This
enables an optical disc with higher quality to be obtained.
[0113] In the above embodiment, in order for the emission surface
to be equal to or slightly larger than the surface of the adhesive
layer to be cured, a large number of light emitting diodes is
arranged in a concentric circular pattern or a spiral pattern.
However, the light emitting diodes may be arranged at random and
close to each other, in a hexagonal pattern such that the spacing
between adjacent light emitting diodes is a fixed distance, in a
concentric circular pattern, a spiral pattern or the like. Instead
of arranging a large number of light emitting diodes so as to
create an emission surface equal to or slightly larger than the
surface of the adhesive layer to be cured, the light emitting
diodes may be arranged such that the emission surface is made to be
a part of the surface of the adhesive layer to be cured.
[0114] This embodiment will be described with reference to FIG. 7.
The support 7b of the semiconductor light emitting unit 7 has a
fan-shaped printed substrate 7b. A plurality of light emitting
diodes 7a is arranged at high density on this printed substrate 7b,
and they are all connected in parallel by a conductive pattern (not
shown in the figure) formed on the printed substrate 7b.
Accordingly, all of the light emitting diodes 7a are turned on and
off at the same time. Their emission surface X is at a
predetermined distance of 10 mm or less from the surface of the
substrate 10. In this embodiment, the semiconductor light emitting
unit 7 and the substrate 10 are rotated at a certain rotation speed
relative to each other. A rotation drive mechanism is required to
rotate the substrate 10. However, if a spinner is used also as
mentioned previously, no specific rotation drive mechanism is
required. Since the support 7b is fan shaped, the number of light
emitting diodes 7a arranged on the external outer arc is larger
than that on the inner arc in proportion to the radius. Therefore,
the irradiation time can be equal although the circumferential
speeds are different between the inner arc and the outer arc. This
semiconductor light emitting unit 7 can reduce the number of light
emitting diodes required significantly compared with the
aforementioned embodiment, and can reduce the cost. However, if
light emitting diodes with the same characteristics are used, the
time to cure the adhesive layer is longer. However, by blowing
cooling air onto the region of the substrate where there is no
semiconductor light emitting unit 7, it is possible to reduce the
influence of the heat from the photo-polymerization reaction, so
that it is possible for the emission surface X to approach closer
to the substrate 10.
[0115] In the above embodiment, the light emitting diodes emit
light continuously, but they may emit light in a pulse pattern,
that is intermittently. In this case, compared with the case of
emitting continuously, it is possible for a high peak current to
flow into the light emitting diodes to generate ultraviolet light
of high luminous intensity. By having a higher peak current than
when emitting continuously, flowing sequentially from the light
emitting diodes on the inner circumference to the light emitting
diodes on the outer circumference, a curing adhesive of higher
quality may be expected. Furthermore, by controlling the width and
peak value of the current pulse supplied to each of the light
emitting diodes, or the width of the dead time between current
pulses, as required, it is possible to cure the adhesive more
uniformly and with higher quality.
[0116] Adhesive suitable for the present invention will be
described. At present, commercial ultraviolet light curing type
adhesive usually contains photoinitiator which reduces the
sensitivity to ultraviolet light so that curing does not start
during handling. However, since a light emitting diode has a lower
luminous intensity of ultraviolet light than a flash lamp, it is
preferable to increase the amount of photoinitiator which enhances
the sensitivity to ultraviolet light. Furthermore, if the
photoinitiator added to the adhesive is increased to enhance the
sensitivity to ultraviolet light, it is not possible to handle the
adhesive in a conventional environment, and hence red light
emitting diodes are used, preferably, for the environment lighting
in this case. These red light emitting diodes emit ultraviolet
light with a wavelength of tens of nm centered at 645 nm, and do
not contain wavelengths in a wavelength range of 300 to 420 nm, so
that adhesive with high sensitivity can be used in an environment
lit by red light emitting diodes similarly to the conventional
method. Furthermore, since yellow light emitting diodes emitting a
yellow light with a wavelength of around 590 nm, and green light
emitting diodes emitting a green light with a wavelength of around
520 nm do not contain wavelengths in a wavelength range of 300 to
420 nm fundamentally, it is possible to use them for lighting. In
this manner, by using ultraviolet light emitting diodes in an
apparatus for curing adhesive whose sensitivity to ultraviolet
light is increased, and by using light emitting semiconductor
elements that do not contain wavelengths in a wavelength range of
280 to 450 nm, such as red light emitting diodes, yellow light
emitting diodes, or the like for the lighting of areas where the
adhesive is handled, it is possible to reduce power usage costs
significantly, it is very desirable environmentally, and the costs
also can be reduced.
[0117] In the case where ultraviolet light emitting diodes are used
in an apparatus for curing adhesive whose sensitivity to
ultraviolet light is increased, and light emitting semiconductor
elements, which have no wavelength in the wavelength range of 300
to 420 nm, are used for the lighting of areas where the adhesive is
used, the process for applying the high sensitivity adhesive onto
the substrates and the processes for stacking the substrates with
the adhesive in-between, and bonding them together by spinning, are
performed under the lighting generated by the light emitting
semiconductor elements.
[0118] The description in the above embodiment uses optical disc
substrates for the substrates. However, the substrates may be other
transparent sheet type materials, such as glass, lenses, and the
like, whose light transmissivity is high, and it is possible to
bond them by curing similarly to the above.
[0119] Furthermore, in the above embodiment, an example is
described in which a semiconductor light emitting unit comprises
light emitting diodes. However, solid-state lasers, such as
semiconductor lasers, which generate visible light laser beams with
similar wavelengths may also be used. In this case, solid-state
lasers are arranged such that the light focus of the solid-state
lasers is soft, and the spacing between the semiconductor light
emitting unit and the irradiation surface is large, so that a
uniform light is radiated onto the irradiation surface. Moreover,
it is also possible to use an argon gas laser which generates a
laser beam with a wavelength of primarily 488.5 nm, a gas laser
such as a helium/neon gas laser, which generates a laser beam with
a wavelength of 632.8 nm, a dye laser of an appropriate color, or
the like, as a light source.
[0120] Before removing the disc substrates from the spinner used
for spreading the adhesive, a part or the whole of the adhesive may
be semi-cured or cured by radiating ultraviolet light with a peak
wavelength in the range of 280 to 450 nm for tacking purposes. In
this case, it is preferable to perform the tacking while the
spinner is rotating, because the tacking can be performed
uniformly, and no extra time for tacking is required. Especially in
order not to affect the optical discs, it is preferable to perform
the tacking by radiating ultraviolet light with a peak wavelength
in the range of 280 to 450 nm onto the adhesive in only a
non-recording region on the internal circumference side of the disc
substrates to semi-cure or cure them. In this case, since there is
hardly any detrimental effect on the other areas by ultraviolet
light irradiation, it is possible to perform the tacking by
ultraviolet light irradiation in the spinner. In this manner, if
the optical disc substrates are removed from the spinner after
tacking by a typical transfer mechanism, which is not shown in the
figure, and transferred to the next process, there is no shift
between an optical transmission layer and the disc substrates, or
between the disc substrates themselves, and hence it is possible to
obtain an optical disc with high quality.
[0121] In the above embodiment an example is described in which
light emitting diodes are used as light emitting semiconductor
elements. However, a semiconductor laser with a wavelength peak in
a wavelength range of 280 to 450 nm, for example a bluish purple
laser, which generates a laser beam with a wavelength of 405 nm may
be used. Furthermore, a gas laser, such as a YAG laser doped with
neodymium (Nd), which generates a laser beam with a wavelength
whose third harmonic is 355 nm, an Ar laser (diatomic ion) with a
wavelength of about 351 nm or 364 nm, or the like may be used. It
is also possible to perform tacking efficiently by using a gas
laser, and radiating a laser beam onto the adhesive in only a
non-recording region on the internal circumference side of the
optical disc substrates while rotating the optical substrates to
semi-cure or cure them.
[0122] Furthermore, a lamp such as a fluorescent lamp may be
combined with a bandpass filter that blocks wavelengths of and
around 405 nm. In this case, the bandpass filter irradiates onto
the optical disc substrates, visible light of wavelengths longer
than 405 nm, being the wavelength of light emitted by a bluish
purple laser that records on the recording film of the optical
disc, and neighboring wavelengths, and preferably only visible
light of wavelengths 430 nm or greater. At least light equal to or
shorter than the wavelengths of and around 405 nm are blocked, and
are not radiated onto the optical disc substrates.
[0123] In this embodiment, similarly to the embodiment described
previously, it is possible to cure an optical transmission layer,
or an adhesive of a visible light curing type composition without
damaging the recording film of an optical disc to be recorded on
and played back by bluish purple laser beams. Furthermore, it is
possible to provide an optical disc which employs a visible light
curing type composition, which has high transmissivity of light
with wavelengths of and around 405 nm, even after curing.
[0124] [Embodiment 2]
[0125] Next is a description of embodiment 2 of the present
invention. In FIG. 8 through FIG. 15, a spinner 31 rotates two disc
substrates 32 stacked via intermediate adhesive at high speed to
spread the adhesive between the two disc substrates and remove
excess adhesive. The spinner 31 has a disc pedestal 31a, which
receives the two disc substrates 32 from a transfer mechanism 33
and attracts and holds them, a rotation drive unit 31b such as an
electric motor for rotating the disc pedestal 31 at high speed, a
cylindrical outer wall 31c for preventing removed adhesive from
splashing, and a center pin 31d.
[0126] The transfer mechanism 33 transfers the two disc substrates
stacked via intermediate adhesive from another place to the disc
pedestal 31a, mounts them, and transfers the bonded disc substrates
32 to a different place. The transfer mechanism 33 has an
attraction head section 33a for attracting or releasing the disc
substrates, a handling section 33b for moving the attraction head
section 33a in the vertical direction and horizontal direction, and
a drive section (omitted in the figure) for driving the handling
section 33b.
[0127] The tacking mechanism 34 is an essential element in this
embodiment. The tacking mechanism 34 has a horizontal direction
drive unit 34a, such as a cylinder fixed on a base 35, a vertical
direction drive unit 34b, such as a cylinder installed on the
horizontal direction drive unit 34a, an arm section 34c fixed on
the moving part of the vertical direction drive unit 34b, and a
tacking emission mechanism 34d fitted at the end of the arm section
34c.
[0128] FIG. 14A and FIG. 14B show an example of a tacking emission
mechanism 34d. This tacking emission mechanism 34d has a support
member A3, which is fixed at the end of the arm 34c, and a
plurality of light emitting diodes B3, which are arranged in an
annular pattern on the support member A3, and that are connected
electrically in series or in parallel. The light emitting diodes B3
are mounted on a ring shaped printed circuit board C3 on which
conductive patterns connected in parallel or series are formed. An
input cable D3 is installed for supplying direct current to the
light emitting diodes. The disc substrates 32 have center holes,
and have an internal circumference region of a predetermined width
centered on the center holes, widely known as a non-recording
region (for example, L shown in FIG. 15), where no information is
recorded. Information is stored in the area outside the
non-recording region L, which is an information recording region to
be recorded on later. The light emitting diodes B3 arranged in an
annular pattern are arranged on an imaginary circle facing the
non-recording region of the disc substrates 32. One layer of light
emitting diodes B3 is fitted in the figure. However, since light
such as ultraviolet light may be radiated onto the adhesive in the
non-recording region of the disc substrates 32, two or more rows of
light emitting diodes B3 may be fitted.
[0129] Next, an example of a tacking method will be described using
FIG. 8 through FIG. 14A and FIG. 14B. Firstly, the transfer
mechanism 33 attracts the disc substrates 32 stacked via
intermediate adhesive applied in a doughnut shape, using the
attraction head section 33a to move the substrates 32 directly
above the disc pedestal 31a of the spinner 31. Next, the handling
section 33b is lowered, and the handling section 33b stops
immediately before the disc substrates 32 touch the disc pedestal
31a. At the same time, the attraction head section 33a stops
attraction, and the disc substrates 32 are mounted on the disc
pedestal 31a. At this time, the disc substrates 32 are centered by
the centering member 31d located in the center of the disc pedestal
31a.
[0130] Next, as shown in FIG. 9, the handling section 33b of the
transfer mechanism 33 starts to ascend, and at the same time the
rotation drive unit 31b rotates the disc pedestal 31a at high speed
while the disc substrates 32 are attracted to the disc pedestal 31a
of the spinner 31. In this manner, the disc substrates 32 are
rotated at high speed to spread adhesive between the disc
substrates, and remove excess adhesive. In this process, the
horizontal direction drive unit 34a of the tacking mechanism 34
operates, and moves the vertical direction drive unit 34b and the
arm section 34c fixed thereon in the direction of the arrow, that
is to say towards the left in the figure, moves the tacking
emission mechanism 34d at the end to a predetermined location, and
then the horizontal direction drive unit 34a stops operation.
[0131] The vertical direction drive unit 34b starts to descend,
moves the arm section 34c down vertically as shown in FIG. 10, and
stops at a location where it does not touch the disc substrates 32,
for example at a location 0.4 mm or more from the top surface of
the disc substrates. The tacking emission mechanism 34d starts
emission after the adhesive layer is spread between the disc
substrates by high speed rotation, and radiates ultraviolet light
onto only an adhesive layer formed in the non-recording region of
the disc substrates 32 to semi-cure or cure the adhesive layer. The
disc substrates 32 are preferably rotated at high speed at this
time, which enables the adhesive layer to be semi-cured or cured
uniformly. Although it depends on how long is required for tacking,
in the case where a longer time is required for tacking than the
time of high speed rotation, an appropriate low speed rotation time
may be provided after the high speed rotation finishes.
[0132] When the adhesive layer is semi-cured or cured, and tacking
finishes, the tacking emission mechanism 34d stops emitting
ultraviolet light, and the vertical direction drive unit 34b raises
the arm section 34c vertically upwards slightly as shown in FIG.
11. Next, the horizontal direction drive unit 34a operates to move
the arm section 34c to the initial position in the direction of the
arrow, that is towards the right in the figure, and stops. At this
time, as shown in FIG. 13, the transfer mechanism 33 attracts and
holds the tacked disc substrates 32 by the attraction head section
33a, and lifts it to transfer it to the next location, for example
a location for curing by ultraviolet light irradiation, which is
not shown in the figure, and cures the adhesive sufficiently.
Afterwards the same operations are repeated.
[0133] As described above, in this embodiment, after adhesive is
spread between the disc substrates 32 by high speed rotation using
the spinner 31, ultraviolet light is immediately radiated only onto
an adhesive layer formed in the non-recording region of the disc
substrates 32 to semi-cure or cure it for tacking purposes, and
they are then transferred to the next location. Accordingly, there
is no detrimental effect on the information recording region, and
no shift occurs between the disc substrates 32 during transfer.
Furthermore, since tacking is performed in a condition where the
two disc substrates 32 are substantially centered by high speed
rotation, it is possible to obtain a disc with higher quality than
conventionally.
[0134] Another embodiment will be described. The tacking emission
mechanism 34d as shown in FIG. 15 starts emitting ultraviolet light
when a predetermined time has elapsed after the spinner 31 starts
rotating at high speed. The predetermined time cannot be set to an
absolute value since it is affected by characteristics such as the
viscosity of adhesive, temperature, humidity of the environment,
and the like, but is determined by the conditions at the time using
experimental data obtained and stored in advance in a CPU. The
predetermined time can also be set according to the characteristics
of the adhesive to be used, by maintaining the environment at a
constant temperature, humidity and the like. In this manner, when
detecting that the predetermined time has elapsed using a timer,
which is not shown in the figure, after the spinner 31 starts
rotating at high speed, current is supplied from the input cable
D3, and the tacking light emitting mechanism 34d emits light. Thus
it is possible to cure the adhesive 32c in the non-recording region
between the disc substrates 32a and 32b before it flows from the
center hole of the disc substrates 32a and 32b. Accordingly, by
further controlling the point of time when the tacking light
emitting mechanism 34d starts emitting light, it is possible to
control the spread of adhesive toward the internal circumference
side. Thus it is also possible to spread it to locations closer to
the edge of the internal circumference than that shown in FIG.
15.
[0135] In general, as shown by the chain lines in FIG. 16, if
adhesive is rotated at high speed to spread it between the disc
substrates, there is a tendency for the thickness of the adhesive
layer to be thinner toward the inside than toward the outside due
to centrifugal force, as shown by curve x. However, as mentioned
previously, while the disc substrates are rotating at high speed,
for example from when half of the high speed rotation time has
elapsed to when four fifths has elapsed, if ultraviolet light
emitted by the tacking light emitting mechanism 34d is radiated
onto only the adhesive layer formed in the non-recording region of
the disc substrates to semi-cure or cure it for tacking purposes,
spreading toward the internal circumference is limited. As a
result, it is possible to thicken the adhesive layer spreading
toward the internal circumference as shown by curve y. That is to
say, it is possible to control the thickness of the adhesive on the
internal circumference side of the disc substrates.
[0136] In the above embodiments, light emitting diodes are used for
the tacking light emitting mechanism 34d of the tacking mechanism
34. However, semiconductor lasers or gas lasers may be used. In the
case of semiconductor lasers, the arrangement may be such that one
semiconductor laser, or a plurality of them arranged at equal
spacing or in a zigzag, replaces the light emitting diodes. In the
case of gas lasers, since greater power can be obtained than from
semiconductor lasers, using one gas laser, the gas laser may be
arranged such that the laser beam is radiated onto the
non-recording region of the disc substrates, and the disc
substrates may be rotated. However, the disc substrates are not
necessarily rotated, and it is also possible to rotate the tacking
light emitting mechanism 34d of the tacking mechanism 34.
[0137] The tacking power can be improved without using a laser beam
by forming the disc pedestal 31a from a transparent material such
as glass, arranging another tacking light emitting mechanism 34d
below the disc pedestal 31a, and radiating ultraviolet light onto
the adhesive layer from both sides of the disc substrates 32, which
enables the tacking to be performed in a shorter time.
[0138] In the case of radiating only from the top side, if an
ultraviolet light reflecting film is formed in the ultraviolet
light irradiation region on the surface of the disc pedestal 31a,
tacking can be performed efficiently by the reflected ultraviolet
light.
[0139] In the above embodiment, the adhesive layer of the disc
substrates on the disc pedestal of the spinner is tacked. However,
as shown in FIG. 15, in the case where the centering member is pin
shaped, the diameter of the centering member must be sufficiently
smaller than the center hole of the disc substrates 32. As a
result, it is not possible to center the two disc substrates 32a
and 32b with high accuracy. Therefore, in this embodiment, the
construction is such that a centering mechanism is provided at a
location where the substrates are mounted temporarily, and the
diameter of the centering member 31d of a pedestal, which is not
shown in the figure, can be expanded and contracted.
[0140] The centering member 31d has a structure consisting of three
120.degree. segments around its center, and it expands and
contracts the fan shaped centering pieces 1d1, 1d2 and 1d3 using a
drive unit, which is not shown in the figure. In a normal state, as
shown in FIG. 17A, the diameter of the centering pieces 1d1, 1d2
and 1d3 is contracted, so the outline of the centering member 31d
is small. The disc substrates 32 are mounted on the pedestal, which
is not shown in the figure, while the diameter is contracted, so
that the centering member 31d is inserted into the center hole H3
of the disc substrates 32. Next, when the drive unit, which is not
shown in the figure, expands the diameter of the centering member
31d, the diameter of the centering pieces 1d1, 1d2 and 1d3 expands
outward radially as shown in FIG. 17B, and the arc sections press
outwards against the internal circumference of the disc substrates
32 radially. This pressure enables the disc substrates 32 to be
centered with considerable accuracy.
[0141] In this highly accurate centered state, the tacking light
emitting mechanism 34d of the tacking mechanism is arranged as
shown in FIG. 15, and ultraviolet light is radiated onto the
adhesive layer in the non-recording region for tacking. Thus there
is no shift observed at all between the disc substrates even when
they are transferred to a curing apparatus, which is not shown in
the figure, by a transfer mechanism, which is not shown in the
figure. Therefore, it is possible to obtain a DVD with highly
accurate centering. The centering member 31d is not limited to the
structures shown in FIG. 17A and FIG. 17B provided that it expands
and contracts its diameter. The embodiments of FIG. 17A and FIG.
17B show constructions in which the diameter of the centering
member 31d of the pedestal, which is not shown in the figure, being
a temporary mounting location, can be expanded and contracted.
However, the construction may be such that the diameter of the
centering member of the spinner can be expanded and contracted.
[0142] In the above embodiment, since the adhesive layer in the
non-recording region on the inner side of the disc substrates is
semi-cured or cured, it has no effect on curing the adhesive layer
later, compared with the case where the adhesive layer in the
non-recording region on the outer side is semi-cured or cured. At
the time of tacking, the disc substrates 32 and the tacking light
emitting mechanism 34d do not always rotate relative to each other,
and the tacking light emitting mechanism 34d may touch the surface
of the non-recording region of the disc substrates 32. Furthermore,
it is also possible to obtain the desired effect of the present
invention by the tacking light emitting mechanism 34d radiating
ultraviolet light onto the whole surface or part of the
non-recording region and the information recording region of the
disc substrates 32 to semi-cure or cure the adhesive layer between
the disc substrates corresponding to the non-recording region and
the information recording region of the disc substrates. Each of
the disc substrates may consist of two disc substrates bonded
together. One disc substrate may be a thin film, which will become
a cover layer of a next generation DVD. In the above embodiment, an
attraction head is described. However, other types such as those
that hold mechanically may also be used instead of the attraction
type.
[0143] [Embodiment 3]
[0144] FIG. 18 shows a disc mounting stage used in a third
embodiment of a disc substrate bonding apparatus. The disc mounting
stage basically comprises a mounting stage 43 for supporting disc
substrates 41a and 41b stacked via intermediate adhesive, and a
centering mechanism 44, which is inserted into the center holes of
the disc substrates 41a and 41b, and an emission mechanism 45,
which encircles it and is fitted on the mounting stage 43.
[0145] As shown in FIG. 19 and FIG. 20, the emission mechanism 45
comprises a plurality of light emitting diodes 46 arranged in an
annular pattern, and the light emitting diodes 46 are mounted on an
annular shaped printed circuit board 47 on which a conductive
pattern is formed. The light emitting diodes 46 arranged in an
annular pattern are arranged inside the mounting stage 43 facing
toward a non-recording region (for example, L as shown in FIG. 19)
of a predetermined width centered on the center holes of the disc
substrates 41 and 41b. The light wavelength region in which the
light emitting diodes emit light is preferably from 280 nm to 450
nm, considering the wavelength characteristics of the disc
substrates, the wavelength region where the photopolymerization
reaction of adhesive occurs, and the like.
[0146] When the light emitting diodes 46 are mounted at high
density, the amount of heat generated cannot be ignored.
Accordingly, in this embodiment, a thin heat sink made of aluminum,
which is not shown in the figure, is provided at the back of the
printed circuit board 47 where the light emitting diodes 46 are
mounted. Furthermore, the printed circuit board 47 where the light
emitting diodes 46 are mounted is held in an annular shaped support
member 48. In order to cool the aluminum heat sink, which is not
shown in the figure, a cooling medium distribution path 410 through
which air is passed is provided under the heat sink. Cooling air
which is supplied from a supply port 411a, cools the heat sink
while passing through the annular shaped cooling medium
distribution path 410, and is then exhausted from an exhaust vent
411b.
[0147] Heat generated by the light emitting diodes 46 is dissipated
by the aluminum heat sink. Furthermore, since the surface of the
heat sink is cooled, the cooling efficiency is high, so that it is
possible to prevent the disc substrates from being affected by heat
conduction and the light emitting diodes 46 from being damaged by
the heat generated.
[0148] The emission mechanism 45 where the light emitting diodes 46
are mounted on the support member 48 can be handled as a single
component. Accordingly, in the case where the light emitting diodes
46 are damaged, the whole emission mechanism can be changed, which
makes maintenance easy. Numeral 49 shown in FIG. 18 denotes a
cylinder having a cylinder rod 49a, operating as an up-and-down
drive unit.
[0149] As shown in FIG. 18, the centering mechanism 44 comprises a
shaft 412, which is moved up and down, and an elastic body 413. The
shaft 412 is column shaped, and has an umbrella section 412a on the
top, which expands radially from the shaft 412 like an umbrella.
The bottom of the shaft 412 is connected to the cylinder rod 49a of
the cylinder 49, being a drive mechanism that moves the shaft 412
up and down.
[0150] The elastic body 413 is made of a resin having an
appropriate elasticity and hardness, such as silicon rubber for
example. As shown in FIG. 18, the elastic body 413 is installed
around the shaft 412, and the top of the elastic body 413 is
pressed down by the bottom of the umbrella section 412a. The
elastic body 413 has an appropriate thickness, and there is a gap
415 between the elastic body 413 and the side face of the shaft
412.
[0151] When the shaft 412 is lowered by backward movement of the
cylinder rod 49a of the cylinder 49, the elastic body 413 is
pressed by the umbrella section 412a of the shaft 412, and
contracts in the central axis direction of the center holes of the
disc substrates 41a and 41b, and the silicon rubber elastic body
413 expands in the radial direction of the disc substrates 41a and
41b.
[0152] As shown in FIG. 21 and FIG. 22, the silicon rubber elastic
body 413, inserted into the center holes of the two disc substrates
41a and 41b stacked via intermediate adhesive 42, expands radially,
thus pressing the internal circumference side faces 416a and 416b
of the disc substrates 41a and 41b to correct any shift.
[0153] When the elastic body 413 expands radially, since there is a
gap 415 between the elastic body 413 and the side face of the shaft
412, then as the elastic body 413 is put under load from the
internal circumference side faces 416a and 416b of the center holes
of the disc substrates 41a and 41b, the elastic body 413 can
release the pressure towards the gap 415. As a result, no more
stress than necessary is applied to the internal circumference side
faces 416a and 416b.
[0154] Afterwards, when the shaft 412 is raised by forward movement
of the cylinder rod 49a of the cylinder 49, the silicon rubber
elastic body 413 returns to its original shape due to its
elasticity, and pressure is released from the internal
circumference side faces 416a and 416b of the center holes of the
disc substrates 41a and 41b.
[0155] In order to correct the shift between the disc substrates
41a and 41b, it is necessary to add appropriate pressure to the
internal circumference side faces 416a and 416b of the center holes
of the two disc substrates. However, as mentioned above, the inside
diameters of the center holes of the disc substrates to be molded
vary, and they do not always match. As shown in FIG. 23, when the
silicon rubber elastic body 413 expands in the radial direction of
the disc substrates, the elastic body 413 is distorted flexibly
along the internal circumference side faces 416a and 416b of the
center holes of two disc substrates whose inner diameters are
different, and by applying pressure along the whole length of the
two internal circumference side faces 416a and 416b, it is possible
to correct the shift and center them accurately without loading
one, or part of one, side face. As a result, there is no
detrimental effect on the tilt of the disc substrates 41a and
41b.
[0156] When the silicon rubber elastic body 413 is expanded in the
radial direction, it is preferable that the arc of the side face of
the elastic body 413 is large, and the closer it is to flat, the
better. In the case of a small arc, since optimal pressure cannot
be applied to the internal circumference side faces 416a and 416b
of the center holes of the stacked disc substrates 41a and 41b,
there is a possibility in that force applied to the stacked disc
substrates pulls them apart. Therefore, the elastic body 413 needs
to be a certain height, so the elastic body 413 of the present
embodiment has a height of around 10 mm from the surface of the
disc substrate 41a mounted on the mounting stage 43.
[0157] An example of a method for bonding disc substrates will be
described using FIG. 24A to FIG. 24D. As shown in FIG. 24A, the two
disc substrates 41a and 41b stacked via intermediate adhesive 42
are mounted on the mounting stage 17 of the spinner for high speed
rotation to spread the adhesive 42 between the disc substrates
uniformly, and remove excess adhesive.
[0158] Next, as shown in FIG. 24B, after the adhesive 42 is spread
between the disc substrates uniformly by high speed rotation, the
disc substrates are mounted on the disc mounting stage 43 of the
present invention by a transfer mechanism, which is not shown in
the figure, and the center holes of the disc substrates are
inserted into a centering mechanism 44. The disc mounting stage 43
is located between the spinner of a bonding apparatus and an
ultraviolet light irradiation apparatus.
[0159] Next, as shown in FIG. 24C, when the disc substrates are
mounted, a cylinder rod 49a of a cylinder 49 operates to lower a
shaft 412, so that the elastic body 413 is pressed down from the
top, and expands in the radial direction of the disc substrates. As
a result, the shift between the disc substrates is corrected for
accurate centering with no detrimental effect on the tilt.
[0160] After centering, a plurality of light emitting diodes 46 of
an emission mechanism 45 installed in the periphery of the
centering mechanism 44 of the disc mounting stage 43 starts
emitting light to cure the adhesive layer in the non-recording
region of the disc substrates.
[0161] By curing the adhesive layer in the non-recording region, as
well as maintaining centering, there is also an effect of
preventing the adhesive 42 from leaking from the internal
circumference side faces 416a and 416b of the center holes of the
disc substrates 41a and 41b. Furthermore, by controlling the point
of time at which the light emitting diodes 46 start emitting light,
it is possible to prevent the adhesive 42 from spreading toward the
internal circumference. As a result, it is possible to enhance the
adhesive strength in the internal circumference of the disc
substrates, thus enabling an optical disc with an excellent visual
appearance to be obtained.
[0162] It is preferable to ventilate cooling air into the cooling
medium distribution path 410 installed below the light emitting
diodes 46 so that the temperature of the disc substrates does not
increase due to the heat generated by the emission from the light
emitting diodes 46.
[0163] Afterwards, as shown in FIG. 24D, the centered and tacked
disc substrates are transferred to a mounting stage 418 of an
ultraviolet light curing apparatus at another location, and
irradiated by ultraviolet light from an ultraviolet light radiating
lamp 419, so that the adhesive 42 of the whole area between the
substrates is completely cured.
[0164] In this embodiment, after the adhesive 42 is spread by high
speed rotation, and before curing the adhesive 42 of the whole area
between the stacked disc substrates, the stacked disc substrates
are centered accurately on the disc mounting stage 43 of the
present invention. Thus it is possible to partially cure the
adhesive between the substrates for tacking, without reducing the
production efficiency.
[0165] The centering mechanism 44 is not limited to this
embodiment. For example, it is possible to use an elastic body made
of resin that expands in the radial direction of the disc
substrates when supplied with a fluid such as air or liquid.
[0166] In the above embodiment, an emission mechanism 45 is
described in which light emitting diodes are arranged in a location
corresponding to the internal circumference of the disc substrates.
However, the emission mechanism 45 may have light emitting diodes
arranged over a surface area corresponding to the whole surface of
the disc substrates, light emitting diodes arranged in an annular
pattern in the center, light emitting diodes arranged radially in
one or more rows at 90.degree. spacing or at 120.degree. spacing,
or the like. In any case, the emission mechanism 45 is installed in
the disc mounting stage 43. The disc mounting stage 43 may move up
and down as required.
[0167] The emission mechanism 45 is not limited to light emitting
diodes. Semiconductor lasers, or an ultraviolet light radiating
lamp such as a xenon lamp, a metal halide lamp, or the like may be
used. In the case of semiconductor lasers, a plurality of
semiconductor lasers arranged at equal spacing may be used instead
of light emitting diodes. In the case of an ultraviolet light
radiating lamp, a small sized, annular shaped one may be
utilized.
[0168] As another embodiment, an embodiment is shown in FIG. 25 in
which ultraviolet light is radiated onto the whole surface of
adhesive spread between disc substrates to cure it at the same time
as centering is performed. In this case, as shown in FIG. 25, one
or more annular shaped ultraviolet light radiating lamps 420, which
are smaller than conventional ones, are provided inside a disc
mounting stage 43, and the whole surface of adhesive 42 spread
between the disc substrates is cured by irradiation from the
ultraviolet light radiating lamps 420.
[0169] The ultraviolet light radiating lamps 420 are inside the
disc mounting stage 43, whose inner diameter is almost the same as
the outer diameter of the disc substrates 41a and 41b, the surface
of the disc mounting stage 43 facing the disc substrates is open,
or covered by heat-resistant glass, and its other surface is in a
condition close to a mirror finished surface. As a result,
ultraviolet light is radiated onto the disc substrates
efficiently.
[0170] In order to shield against heat generated by the ultraviolet
light radiating lamps 420, it is preferable to cool the disc
mounting stage 43 and the ultraviolet light radiating lamps 420 by
providing a cooling medium distribution path to supply air into the
disc mounting stage 43.
[0171] In this embodiment, in order to cure the whole surface of
the adhesive spread between the disc substrates at the same time as
centering is performed, in a case where a process is required to
cure the whole surface of the adhesive completely in a later
process, since curing of the adhesive has started it is possible to
cure it completely in a short time. Furthermore, miniaturization of
an ultraviolet light curing apparatus can be achieved.
[0172] In this apparatus, since small sized, ultraviolet light
radiating lamps are used, the amount of ultraviolet light radiation
is smaller than that in a curing apparatus (for example, an
ultraviolet light curing apparatus as shown in FIG. 24D) using
normal ultraviolet light radiation. Accordingly, in order to cure
the adhesive almost completely instead of only tacking, the
arrangement may be such that a plurality of ultraviolet light
irradiation mechanisms with a structure as shown in FIG. 25 is
installed in a rotating transfer mechanism such as a turntable, so
that the whole surface of the adhesive can be cured completely
during a process of transferring to a predetermined location.
Needless to say, the arrangement may also be such that a plurality
of disc mounting stages is installed in which light emitting diodes
are arranged on a surface area corresponding to the whole surface
of the disc substrates, so that the whole surface of the adhesive
can be cured completely.
[0173] Regarding disc substrates to be bonded, the effects of the
present invention can be obtained even in a case where disc
substrates have different thicknesses, for example, one disc
substrate is a thin film.
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