U.S. patent application number 10/120488 was filed with the patent office on 2002-08-15 for apparatus for bonding an optical disk substrate.
Invention is credited to Higaki, Norihide, Kanashima, Keinosuke, Matsunaga, Koji.
Application Number | 20020108715 10/120488 |
Document ID | / |
Family ID | 17049953 |
Filed Date | 2002-08-15 |
United States Patent
Application |
20020108715 |
Kind Code |
A1 |
Higaki, Norihide ; et
al. |
August 15, 2002 |
Apparatus for bonding an optical disk substrate
Abstract
A method and an apparatus for bonding optical disk substrates,
includes placing a pair of optical disk substrates on a stage while
securing a height difference at an upper face of the stage loading
the substrates between an upper face at a side of a center of the
substrates and an upper face at a side of an outer circumference of
the substrates. The method and the apparatus also includes
photosetting the adhesive layer on the stage by irradiating a
setting light to the substrate pair, thereby photosetting the
adhesive layer and bonding the substrates.
Inventors: |
Higaki, Norihide;
(Ibaraki-shi, JP) ; Matsunaga, Koji; (Katano-shi,
JP) ; Kanashima, Keinosuke; (Osaka-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
17049953 |
Appl. No.: |
10/120488 |
Filed: |
April 12, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10120488 |
Apr 12, 2002 |
|
|
|
09382831 |
Aug 25, 1999 |
|
|
|
Current U.S.
Class: |
156/379.6 ;
156/273.7; G9B/7.194 |
Current CPC
Class: |
B29C 35/08 20130101;
B29C 66/73921 20130101; B32B 37/12 20130101; B29C 65/521 20130101;
B29C 65/4845 20130101; B29C 66/9141 20130101; B29C 66/91411
20130101; B29K 2101/10 20130101; G11B 7/26 20130101; B29C 65/1406
20130101; B29C 65/1435 20130101; B29C 66/452 20130101; B29C
66/91216 20130101; B29C 2035/0827 20130101; B29C 66/934 20130101;
B29C 66/91641 20130101; B29C 66/71 20130101; B29C 66/91221
20130101; B29C 66/8322 20130101; B29C 66/72321 20130101; B29C
66/9532 20130101; B29K 2105/0097 20130101; B29C 66/9534 20130101;
B32B 37/0023 20130101; B32B 2038/0076 20130101; B29C 66/961
20130101; B29C 65/1496 20130101; B29C 66/1122 20130101; B29K
2995/0027 20130101; B32B 2429/02 20130101; B29C 66/91431 20130101;
B29L 2017/005 20130101; B29C 65/1483 20130101; B29C 65/7847
20130101; B29C 66/71 20130101; B29K 2069/00 20130101 |
Class at
Publication: |
156/379.6 ;
156/273.7 |
International
Class: |
B32B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 1998 |
JP |
10-239792 |
Claims
What is claimed is:
1. A method for bonding optical disk substrates, comprising:
placing a pair of optical disk substrates on a stage while securing
a height difference at an upper face of the stage loading the
substrates between an upper face at a side of a center of the
substrates and an upper face at a side of an outer circumference of
the substrates; and photosetting the adhesive layer on the stage by
irradiating a setting light to the substrate pair, thereby
photosetting the adhesive layer and bonding the substrates.
2. A method for bonding optical disk substrates according to claim
1, wherein in the photosetting, warp deforimation caused when the
substrate pair finishes photosetting operation is offset by
deforming the substrate pair tracing the height difference at the
upper face of the stage because of a weight of the substrate
pair.
3. A method for bonding optical disk substrates according to claim
1, wherein the height difference of the stage is realized by a step
whereby the substrates are made higher at the center than at the
outer circumference.
4. A method for bonding optical disk substrates according to claim
1, wherein the height difference of the stage is realized by a
taper whereby the substrates are lowered from the center to the
outer circumference.
5. A method for bonding optical disk substrates according to claim
1, further comprising: controlling temperature of at least a front
surface side one of the substrates thereby reducing a temperature
difference between both faces of the substrate pair when the
adhesive layer is photoset.
6. A method for bonding optical disk substrates according to claim
1, further comprising: uniforming a temperature distribution of the
substrates in a plane direction through controlling of temperature
of the substrates when the adhesive layer is photoset.
7. A method for bonding optical disk substrates according to claim
1, wherein in the photosetting, the setting light is irradiated in
a step of temporarily setting the adhesive layer with a less
quantity of light than required for completely setting the adhesive
layer and a succeeding step of practically setting the adhesive
layer with the required quantity of light for completely setting
the adhesive layer.
8. A method for bonding optical disk substrates according to claim
1, further comprising: controlling a humidity of the substrate pair
when the adhesive layer is photoset.
9. An apparatus for bonding optical disk substrates, said apparatus
comprising: a stage having a front face on which a substrate pair
comprising optical disk substrates in a pair with a photosetting
adhesive layer located in between is placed when the photosetting
adhesive layer is to be photoset, said stage being structured to
secure a height difference between a center of the substrate pair
and an outer circumference of the substrate pair so as to correct a
warp deformation of the substrate pair by tracing the height
difference at said front face of said stage due to a weight of the
substrate pair; and a light source operable to irradiate a setting
light to the substrate pair, thereby to photoset the photosetting
adhesive layer and to bond the pair of optical disk substrates,
wherein said front face is gradually tapered such that a center of
said front face is higher than an outer circumference of said front
face.
10. An apparatus for bonding optical disk substrates according to
claim 9, further comprising a spacer detachably disposed to said
stage at a center of said front face and projecting from said front
face of said stage.
11. An apparatus for bonding optical disk substrates according to
claim 10, wherein a projection amount of said spacer from said
front face of said stage is adjustable.
12. An apparatus for bonding optical disk substrates, said
apparatus comprising: a stage having a front face on which a
substrate pair comprising optical disk substrates in a pair with a
photosetting adhesive layer located in between is placed when the
photosetting adhesive layer is to be photoset, said stage being
structured to secure a height difference between a center of the
substrate pair and an outer circumference of the substrate pair so
as to correct a warp deformation of the substrate pair by tracing
the height difference at said front face of said stage due to a
weight of the substrate pair; and a light source operable to
irradiate a setting light to the substrate pair, thereby to
photoset the photosetting adhesive layer and to bond the pair of
optical disk substrates, wherein said light source initially
irradiates a lower quantity of the setting light then is required
to completely set the photosetting adhesive layer, and then
irradiates a required quantity of the setting light for completely
setting the photosetting adhesive layer.
13. An apparatus for bonding optical disk substrates according to
claim 12, further comprising a shutter part located to be between
the substrate pair and said light source, said shutter part being
operable to control passage of the setting light so as to initially
irradiate the lower quantity of the setting light than is required
to completely set the photosetting adhesive layer, thereby
temporarily setting the photosetting adhesive layer, and then
irradiating the required quantity of setting light, thereby
completely setting the photosetting adhesive layer.
Description
[0001] This application is a continuation of Ser. No. 09/382,831,
filed on Aug. 25, 1999.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method and an apparatus
for bonding optical disk substrates, and more particularly, a
method and an apparatus for bonding substrates in pairs to be
optical disks by setting with light via a photosetting type
adhesive, thereby manufacturing bond type optical disks utilized
for DVDs (Digital Versatile Disks), etc.
[0003] Techniques are known whereby a plurality of substrates
having recording layers are bonded each other thereby constituting
optical disks for DVDs, so that multilayer recording is
achieved.
[0004] The Applicant already proposed techniques related to the
bond method and apparatus as disclosed in Japanese Patent
Application Nos. 8-73536 and 8-89243.
[0005] Specifically, according to the proposal, an adhesive of a
type set with ultraviolet rays or the like type is injected to a
gap of a pair of substrates facing each other via the relatively
small gap. The adhesive is spread to the entirety of the gap,
whereby a layered body comprising the pair of substrates and the
intermediate adhesive layer is obtained. With the projection of
ultraviolet rays to the layered body or by the like manner, the
adhesive is set and the substrates are bonded to each other.
[0006] In order to read stored data on or write data to an optical
disk, a laser light is used. The laser light is projected from
outside of the optical disk while the optical disk rotates at high
speed. The laser light passing through the transparent substrate of
the optical disk is irradiated onto a recording layer. At this
time, the laser light is required to be correctly shed onto a
predetermined position of the recording layer because the optical
disk has a considerably high recording density. Meanwhile, it is
impossible to focus the laser light correctly on the predetermined
position of the recording layer if the recording layer and the
whole optical disk show a poor degree of flatness. Thus,
information errors can easily occur.
[0007] Under the circumstances, a high degree of flatness with no
warp or distortion is required to be maintained in the manufacture
process of the optical disk.
[0008] However, optical disks of the aforementioned bond type, more
strictly, disk substrates tend to warp, thereby decreasing the
degree of flatness when the adhesive is being set with light.
[0009] The reason is the heat generated by an ultraviolet
projection lamp used in setting the adhesive. A material of the
optical disk is expanded by the heat at the projection of light,
then shrunken and returned to an initial state subsequent to
cooling, upon completion of the photosetting process. The expansion
and shrinkage by the heating and cooling takes place in an
unbalanced state between the material at the side close to the lamp
and the material at the side away from the lamp, thereby causing
the optical disk to warp. The substrate of the optical disk close
to the ultraviolet projection lamp has a larger quantity of heat
generated thereon because of a larger quantity of light projected
thereto and therefore expands greatly, whereas the substrate
opposite to the above substrate via the adhesive has a smaller
quantity of heat generated thereon and expands less. When the
adhesive is completely set in this state with a difference in
expansion amount between the substrates, the cooling makes the
substrate close to the projection lamp which has expanded more
shrink more than the other substrate and consequently the optical
disk is deformed to warp towards the projection lamp due to a
shrinkage stress.
[0010] The deformation to the optical disk is caused by reasons
other than the above. For instance, the optical disk is deformed
through the expansion and shrinkage process at the time of setting
the adhesive, which practically originates from thermal
deformation, etc. and an imbalance in material structure brought
about in the photosetting process or production process prior to
the photosetting process. The deformation presents not only a
uniform warp from the center to the outer circumference, but can
also cause local unevenness or swell in radial and circumferential
directions within a plane.
[0011] Temperatures of base materials and apparatuses handling the
substrates change with time in a production line where optical
disks are produced continuously, sometimes causing an influence on
temperature, and the expansion and shrinkage of substrates.
Moreover, changes in temperature, and expansion and shrinkage of
the substrates are influential to a deformation amount of the
optical disk. Particularly for a while when the production line
starts to operate after a pause, a temperature condition within the
production apparatus is not stable and therefore, the deformation
amount of the optical disk is apt to vary.
[0012] Environmental conditions where the optical disk is handled
also influences the generation of the deformation. For example, a
change in humidity influences the expansion and shrinkage. The
influence is large when a humidity-absorbing synthetic resin is
used as the substrate material.
[0013] The object of the present invention is therefore to provide
a method and an apparatus for bonding optical disk substrates
capable of obtaining optical disks with a good degree of flatness
by preventing the optical disks from being deformed, for example,
warped, when manufactured through bonding disk substrates.
SUMMARY OF THE INVENTION
[0014] In order to achieve the aforementioned objective, the
present invention provides a method and an apparatus for bonding
optical disk substrates, whereby a setting light is projected to a
pair of optical disk substrates having a photosetting adhesive
layer interposed therebetween, thereby photosetting the adhesive
layer and bonding the substrates. According to the present
invention, a device is arranged for preventing optical disk
substrates from being deformed when the adhesive layer is set with
light.
[0015] In accomplishing these and other aspects, according to a
first aspect of the present invention, there is provided a method
for bonding optical disk substrates. The method comprises placing a
pair of optical disk substrates on a stage while securing a height
difference at an upper face of the stage loading the substrates
between an upper face at a side of a center of the substrates and
an upper face at a side of an outer circumference of the
substrates, and photosetting the adhesive layer on the stage by
irradiating a setting light to the substrate pair, thereby
photosetting the adhesive layer and bonding the substrates.
[0016] According to a second aspect of the present invention, there
is provided a method for bonding optical disk substrates according
to the first aspect, wherein in the photosetting, warp deformation
caused when the substrate pair finishes the photosetting operation
is offset by deforming the substrate pair tracing the height
difference at the upper face of the stage because of a weight of
the substrate pair.
[0017] According to a third aspect of the present invention, there
is provided a method for bonding optical disk substrates according
to the first aspect, wherein the height difference of the stage is
realized by a step whereby the substrates are made higher at the
center than at the outer circumference.
[0018] According to a fourth aspect of the present invention, there
is provided a method for bonding optical disk substrates according
to the first aspect, wherein the height difference of the stage is
realized by a taper, whereby the substrates are lowered from the
center to the outer circumference.
[0019] According to a fifth aspect of the present invention, there
is provided a method for bonding optical disk substrates according
to the first aspect, the method further comprising controlling
temperature of at least a front surface side one of the substrates
thereby reducing a temperature difference between both faces of the
substrate pair when the adhesive layer is photoset.
[0020] According to a sixth aspect of the present invention, there
is provided a method for bonding optical disk substrates according
to the first aspect, the method further comprising making a
temperature distribution of the substrates uniform in a plane
direction through controlling temperature of the substrates when
the adhesive layer is photoset.
[0021] According to a seventh aspect of the present invention,
there is provided a method for bonding optical disk substrates
according to the first aspect, wherein in the photosetting, the
setting light is irradiated in a step of temporarily setting the
adhesive layer with a lower quantity of light than required for
completely setting the adhesive layer and a succeeding step of
practically setting the adhesive layer with the required quantity
of light for completely setting the adhesive layer.
[0022] According to an eighth aspect of the present invention,
there is provided a method for bonding optical disk substrates
according to the first aspect, the method further comprising
controlling a humidity of the substrate pair when the adhesive
layer is photoset.
[0023] According to a ninth aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates, the
apparatus comprising a stage on which a substrate pair comprising
optical disk substrates in a pair with a photosetting adhesive
layer placed in between, when the adhesive layer is to be photoset,
the stage securing a height difference at an upper face of the
stage loading the substrates between an upper face at a side of a
center of the substrates and an upper face at a side of an outer
circumference of the substrates, and a light source for irradiating
a setting light to the substrate pair, thereby photosetting the
adhesive layer and bonding the substrates.
[0024] According to a 10th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates,
according to the ninth aspect, wherein the stage comprises a spacer
disposed detachably to the stage at a side of a center of the
substrate pair and projecting from a front face of the stage.
[0025] According to an 11th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the 10th aspect, wherein a projection amount of the
spacer from the front face of the stage is adjustable.
[0026] According to a 12th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the ninth aspect, wherein the stage comprises a front
face thereof which is tapered to be gradually lower from the center
of the front face to an outer circumference of the front face.
[0027] According to a 13th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the 9th aspect, the apparatus further comprising a
temperature control device for adjusting a surface temperature of
the stage.
[0028] According to a 14th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the 13th aspect, wherein the temperature control
device comprises a temperature control medium passage built in the
stage, and a medium feed device for feeding a temperature control
medium to the passage.
[0029] According to a 15th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the ninth aspect, the apparatus further comprising a
shutter part set between the substrate pair and a light source for
irradiating the setting light to the substrate pair, for
controlling the passing of the setting light.
[0030] According to a 16th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the 15th aspect, wherein the shutter part comprises a
shielding member for shielding the setting light so as to not pass,
a light-passing space set at part of the shielding member to permit
the setting light to pass, and a shielding member driving device
for selectively arranging the light-passing space at a position
corresponding to the substrate pair and a position shifted from the
substrate pair.
[0031] According to a 17th aspect of the present invention, there
is provided an apparatus for bonding optical disk substrates
according to the 16th aspect, wherein the shielding member is
constituted of a pair of shielding members each having the
light-passing space opened at one side end opposite to the
counterpart shielding member, and the shielding member driving
device has an interlocking reciprocation device for reciprocating
the pair of shielding members interlockingly in opposite directions
to each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] These and other aspects and features of the present
invention will become clear from the following description taken in
conjunction with the preferred embodiments thereof with reference
to the accompanying drawings, in which:
[0033] FIG. 1 is a schematic perspective view showing a total
structure of a bonding apparatus according to a first embodiment of
the present invention;
[0034] FIGS. 2A, 2B, 2C, and 2D are diagrams showing step by step a
bonding process of a bonding method according to the first
embodiment of the present invention;
[0035] FIG. 3 is a half sectional view of a photosetting process
using a stage with a spacer in the apparatus and method of the
first embodiment;
[0036] FIG. 4 is a half sectional view of another photosetting
process using a stage with a tapered face in a bonding apparatus
and method according to a second embodiment of the present
invention;
[0037] FIG. 5A is a partial sectional view of a still another
photosetting process using a height variable spacer in a bonding
apparatus and method according to a third embodiment of the present
invention;
[0038] FIG. 5B is a partially enlarged view of FIG. 5A;
[0039] FIG. 6A is a half sectional view of a stage with a
temperature control device in a bonding apparatus and method
according to a fourth embodiment of the present invention;
[0040] FIG. 6B is a horizontal sectional view of the stage of FIG.
6A;
[0041] FIGS. 7A and 7B are graphs of measurement results of a
deformation amount of an optical disk;
[0042] FIG. 8 is a half sectional view of a photosetting process
using a stage in a bonding apparatus and method according to a
fifth embodiment of the present invention
[0043] FIG. 9 is a half sectional view of a photosetting process
using a stage in a bonding apparatus and method according to a
sixth embodiment of the present invention
[0044] FIG. 10 is a graph showing one example of a relation between
a tilt angle and a distance in radial direction;
[0045] FIG. 11 is a graph showing another example of a relation
between a tilt angle and a distance in radial direction;
[0046] FIG. 12 is a graph showing a regulated relation between a
tilt angle and a distance in radial direction;
[0047] FIG. 13 is a schematic plan view of showing a total
structure of a bonding apparatus a bonding apparatus and method
according to a seventh embodiment of the present invention;
[0048] FIGS. 14A and 14B are step-by-step schematic diagrams of the
photosetting process using a shutter part in a bonding apparatus
and method according to an eighth embodiment of the present
invention;
[0049] FIG. 15 is a plan view of the shutter part of FIG. 14;
[0050] FIGS. 16A, 16B, and 16C are step-by-step schematic diagrams
of a photosetting process in a bonding apparatus and method
according to a ninth embodiment of the present invention;
[0051] FIGS. 17A and 17B are step-by-step schematic diagrams of a
photosetting process in a bonding apparatus and method according to
a tenth embodiment of the present invention;
[0052] FIG. 18 is a plan view of the shutter part of FIGS. 17A and
17B;
[0053] FIG. 19 is a diagram of a driving mechanism for the shutter
part of FIGS. 17A and 17B;
[0054] FIG. 20 is a block diagram of a control unit of the bonding
apparatus of the seventh embodiment; and
[0055] FIG. 21 is a plan view of a stage switching arm of a
modification of the seventh embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0056] Before the description of the present invention proceeds, it
is to be noted that like parts are designated by like reference
numerals throughout the accompanying drawings.
[0057] Before methods and apparatuses for bonding optical disk
substrates according to embodiments of the present invention are
specifically described with respect to the drawings, the schematic
features of the embodiments of the present invention is firstly
described below.
OPTICAL DISK
[0058] The present invention is applied to various optical disks
such as DVDs, CDs, PDs (Phase change rewritable optical Disks),
LDs, etc., that is, bond type optical disks each comprising a
plurality of substrates bonded to one another. The bond type
optical disks are classified into two types, one that has a single
recording layer and the other that has a plurality of recording
layers.
SUBSTRATE
[0059] In conformity with use purposes, substrates, e.g. single
sheets or plates for DVDs, are formed of a suitable combination of
synthetic resin, metallic thin films, and other materials. The DVD
has a disk main body of transparent resin such as polycarbonate
resin or the like, and a recording layer having a metallic thin
film or the like on which is disposed projections and recesses for
recording on one face of the disk main body. A protecting film is
sometimes formed on a front face of the recording layer. Generally
the face where the recording layer is arranged is made a bond
face.
[0060] Substrates to be bonded can be formed of the same material
in the same structure or of different materials or in different
structures. A pair of substrates to be bonded are generally
different in structure at least at recording layers. For example,
upper substrates may be formed of polycarbonate resin with gold
thin film and lower substrates may be formed of polycarbonate resin
with aluminum thin film. The recording layer may be eliminated from
either one of the pair. The substrate is a thin disk-shaped sheet
or plate in the DVD, but may be a different shape other than the
circular sheet depending on the usage. The shape of the substrates
may be processed after the bonding.
[0061] A set condition for a means for preventing the deformation,
for example, a stage height, a temperature control condition to
substrates, etc. to be described later, may be changed in
accordance with the material and structure of the substrates.
ADHESIVE
[0062] Various kinds of photosetting adhesives may be used to match
the material and usage of the substrates to be bonded. Although a
transparent adhesive capable of being set with ultraviolet rays is
preferred for the DVD, an adhesive capable of being set with light
of a wavelength other than a wavelength of the ultraviolet rays is
also utilizable in the present invention. That is, the photosetting
adhesive according to the present invention includes adhesives
capable of being set with lights of various wavelengths including
ultraviolet rays and radioactive rays.
PRODUCTION OF SUBSTRATE PAIR
[0063] A general production technique for bond type optical disks
is applicable to a method and an apparatus for producing pairs of
substrates wherein each of the substrate pairs is produced by
interposing an adhesive layer between a pair of substrates.
[0064] For instance, the following method is applied.
[0065] While a pair of substrates are held facing each other with a
relatively narrow gap in between, an adhesive injection nozzle is
inserted into the gap and the adhesive is discharged from the
injection nozzle. At this time, the pair of substrates are rotated
in a plane direction, that is, in a direction around a rotary axis
of the substrates, so that the adhesive is discharged in a loop in
the gap on the substrates. Thereafter, the gap between the
substrates is narrowed by relatively moving one or both of the
substrates and at the same time rotating the substrates, whereby
the looped adhesive spreads in a radial direction and fills the
small gap between the substrates. The technique is disclosed
concretely in a detailed manner in Japanese Patent Application Nos.
8-73536, 8-89243 referred to earlier, and others.
[0066] Since the adhesive is not yet set at this point in time, the
pair of substrates are required to not shift from each other, nor
to allow the adhesive to protrude from the edge when the substrates
are sent to a succeeding photosetting process. Preferably, the
substrates, in pairs, are held in a state in which the substrates
maintain a horizontal attitude and are handled in this state, i.e.
horizontally, while only one substrate at the bottom side is held
generally. When a supporting member is inserted into a center hole
of the DVD penetrating the center of the substrate pair, the
substrates are prevented from shifting from each other.
PHOTOSETTING
[0067] A general production technique for optical disks is
substantially satisfactorily applied as a method and an apparatus
for setting the adhesive layer with light so long as a setting
light necessary for setting the adhesive layer is obtained.
[0068] Generally, a light projection lamp is arranged above the
pair of substrates placed horizontally on a flat stage. A light
projected from the light projection lamp is passed through the
transparent upper substrate to reach the adhesive layer, whereby
the adhesive is set.
DEFORMATION PREVENTION MEANS OR DEVICE: MEMBER FOR PROVIDING HEIGHT
DIFFERENCE TO STAGE
[0069] As a first example of the deformation prevention means or
device, a member for providing a height difference is placed on the
stage so as to form a height difference which is provided between
the center and the outer circumference of an upper face of the
stage loading the substrate pair thereon.
[0070] When placed on the stage having the height difference, the
substrate pair is deformed, tracing from a higher part to a lower
part of the stage because of its weight so as to correct the warp
deformation of the substrates. This correction deformation of the
substrate pair is designed to counteract the warp deformation
caused in the substrate pair, thus offsetting the warp deformation
when the substrate pair, namely, the optical disk finishes the
photosetting process. Accordingly, an optical disk with a high
degree of flatness and with reduced deformation is obtained.
[0071] The height difference of the stage is preferably set so that
the center is high and the outer circumference is low. As described
before, the warp deformation in the photosetting process generally
takes place in a direction towards the ultraviolet projection lamp
disposed at the opposite side to the stage with respect to the
substrate pair, and therefore the correction deformation is
preferably directed in the direction opposite to the warp
deformation.
[0072] For providing the height difference to the stage, a front
face of the stage is tapered, generally preferably tapered in a
circular cone which is gradually lowered in a radial direction from
the center to the outer circumference. An inverse taper gradually
lowered from the outer circumference to the center may be formed
depending on a state of the warp deformation of the optical disk.
The taper is formed at the whole face of the stage in touch with
the substrate pair or only partly where the correction deformation
is required, and also, an angle of the taper may be changed at each
point.
[0073] The taper may be preferably set to a specific amount by
detecting the amount of the warp deformation of the optical disk
from experiments or trial. In the DVD, for example, a height
difference of 0.1-0.35 mm is allowable between a position
corresponding to an inner circumferential edge and a position
corresponding to an outer circumferential edge.
[0074] As another way to provide the height difference to the
stage, a step may be set at the front face of the stage. Similar to
the taper, the step is generally preferably formed to make the
center of the substrate pair higher than the outer circumference.
The amount of the step is set in a similar manner to the taper
amount. The step may be a single step or may comprise a plurality
of steps.
[0075] The step may be formed by processing the front face of the
stage. Alternatively, a spacer can be arranged to obtain the
step.
[0076] The spacer is a doughnut-shaped sheet, adjusting the step
amount by a thickness thereof. The spacer when detachably set to
the stage is exchangeable with another spacer of a different height
upon necessity. The spacer is simply placed on the stage or fixed
by bolts and metal fittings. Or, a disk-like spacer may be fitted
to a center shaft of the stage to make the center of the stage
higher, thereby constituting the step. The spacer may be set on the
flat stage. Instead of setting the spacer on the flat stage, a
groove can be formed at part of the stage and the spacer can be
fitted in the groove to partly project up from the front face of
the stage.
[0077] A projection amount of the spacer from the front face of the
stage is made adjustable. More specifically, the projection amount
of the spacer set to the stage is adjusted with the use of a
position adjustment mechanism of screws, cams, etc. An adjustment
range of the projection amount is kept in the aforementioned
preferable range of the step amount or taper amount.
DEFORMATION PREVENTION MEANS OR DEVICE: CONTROLLING FRONT-REAR FACE
TEMPERATURE DIFFERENCE
[0078] As a second example of the deformation prevention means or
device, a temperature of at least the front face-side substrate of
the substrate pair is controlled, thereby decreasing a temperature
difference between both faces of the substrate pair.
[0079] As described earlier, the warp deformation of the optical
disk results from a difference of thermal expansion amounts between
the front and rear faces of the substrate pair. The difference of
the thermal expansion amounts is lessened if the temperature
difference between the front and rear faces of the substrate pair
is reduced, so that the warp deformation is restricted.
[0080] The substrate at the side where the photosetting light is
irradiated in the substrate pair is heated more by the lamp and
increased in temperature, and the opposite side is relatively low
in temperature. Therefore, the temperature difference can be
reduced by cooling the side when the photosetting light is
irradiated or heating the opposite side.
[0081] A device for blowing a cold wind is utilizable to cool the
side where the photosetting light is irradiated. A hot wind is
blown or a heating member may be brought in touch to heat the
opposite side. In the case where the photosetting light is
projected to the substrate pair on the stage from the rear side of
the stage, the front face of the stage is heated or cooled, whereby
a contact face of the substrate pair to the stage is heated or
cooled.
[0082] A temperature control medium passage may be installed in the
stage as a device for controlling the temperature and, a medium
feed device for feeding a temperature control medium to the passage
is provided.
[0083] The temperature control medium is a fluid that can be heated
and cooled, for example, the air, water, oil, etc., and fed or
circulated by a pump, blower, or the like to the temperature
control medium passage constituted of an internal conduit or a
space inside the stage.
[0084] Depending on the reason for the deformation of the optical
disk, the substrate at the side where the photosetting light is
irradiated may be heated or the opposite side may be cooled.
DEFORMATION PREVENTION MEANS OR DEVICE: UNIFORMING TEMPERATURE
DISTRIBUTION
[0085] As a third example of the deformation prevention means, a
method of controlling the temperature of the substrate pair thereby
uniforming a temperature distribution in the plane direction of the
substrate pair is adoptable. An unequal temperature distribution in
the plane direction of the substrate pair leads to distortion
deformation totally or locally in the plane direction. Therefore,
making the temperature distribution uniform can prevent the above
deformation.
[0086] When the above-described temperature control device for
lessening the temperature difference of both faces of the substrate
pair also performs a function of making the temperature
distribution uniform in the plane direction, this temperature
control device can be used for both purposes.
[0087] Meanwhile, when the temperature control medium passage of
the temperature control device utilizing the temperature control
medium is installed properly, the temperature distribution at the
front face of the stage is efficiently uniform. In the event that
the conduction of heat from outside, namely, supply of heat happens
to cause temperature imbalance at points of the substrate pair, it
is effective to cool the substrate pair thereby getting rid of the
heat corresponding to the heat conducted from out-side.
[0088] Either one of a plurality of methods is employed to make the
temperature distribution uniform, i.e. a method of heating the
substrate pair to set the whole substrate pair at a constant
temperature, or a method of cooling the substrate pair thereby
setting the whole substrate pair at a constant temperature.
[0089] A heat uniforming body may be arranged at the front face of
the stage in touch with the substrate pair so as to make the
temperature distribution uniform. The heat uniforming body is
formed of material with a high conductivity in the plane direction,
for example, carbon graphite, etc.
DEFORMATION PREVENTION MEANS OR DEVICE: CONTROLLING HUMIDITY
[0090] As a fourth example of the deformation prevention means or
device, a humidity of the substrate pair can be controlled when the
adhesive layer is set with light. This arrangement is effective to
prevent generation and dispersion of the deformation as a result of
humidity absorption or humidity change of the substrate pair.
[0091] To control the humidity, the whole ambience in which the
photosetting process is carried out is maintained in a constant
humidity condition range with the use of an apparatus capable of
controlling a humidity environment, for instance, an air
conditioner, etc.
[0092] The humidity condition is preferably set to keep a humidity
close to that when the substrates are molded. More specifically,
the humidity is not larger than 60%, preferably not larger than
40%. A humidity change with time is preferred to be lessened.
DEFORMATION PREVENTION MEANS OR DEVICE: PHOTOSETTING IN PLURALITY
OF STAGES
[0093] As a fifth example of the deformation prevention means or
device, the setting light can be projected in a plurality of steps.
Specifically, the projection is conducted including a temporary
setting step of projecting a smaller quantity of light than that
required for completely setting the adhesive layer, thereby
temporarily setting the adhesive layer, and a succeeding step of
projecting the required quantity of light for completely setting
the adhesive layer, thereby completely setting the adhesive
layer.
[0094] The adhesive layer is set in the temporary setting step with
a level of flexibility or deformability ensured, so that the
adhesive layer does not move or is not deformed unexpectedly, but
the thermal deformation of the substrate pair subsequent to the
projection of the setting light can be absorbed in the cooling
process. That is, the warp deformation of the substrates are
determined by the temporary setting step. Thus, the division of the
temporary setting step and the complete setting step allows the
warp deformation of the substrates to be reduced, as compared with
a case where only one setting step is carried out.
[0095] The pair of substrates after finishing the temporary setting
step shrinks in the cooling process and is returned to the original
flat state.
[0096] In the complete setting step, the adhesive layer is
perfectly set thereby bonding the substrates at both sides. Since
the adhesive layer is set to a certain degree in the temporary
setting step, a relatively slight quantity of light or a short-time
projection of light is enough to perfectly set the adhesive layer.
Accordingly, the substrate pair receives less heat in the complete
setting step and the deformation subsequent to the expansion and
shrinkage is restricted.
[0097] The temporary setting step can be further divided to a
plurality of steps.
[0098] In order to control the quantity of the setting light
projected to the substrate pair in the temporary and complete
setting steps, timing for turning on and off the light source
opposed to the substrate pair are controlled. However, the
ultraviolet projection lamp or the like light source is hard to
turn on and off in a time period shorter than several seconds to
one second which is necessary to distinguish the temporary setting
step and the complete setting step from each other.
[0099] As such, instead of controlling the timing, the substrate
pair may be adapted to traverse at high speed a projection range of
the light source kept on at all times at a constant position,
whereby the quantity of the setting light is controlled. The
quantity of light projected to the pair of substrates is adjustable
by controlling a traverse speed of the substrates.
SHUTTER PART
[0100] A shutter part is employable as a different way to control
the quantity of light.
[0101] The shutter part is arranged between the light source for
emitting the setting light and the substrate pair to control a
passing time of the setting light.
[0102] Concretely, the shutter part is constituted in the same
structure as a shutter mechanism of various optical apparatuses
used for controlling the quantity of light.
[0103] For example, the shutter part comprises a shielding member
for hindering the setting light from passing through, a
light-passing space provided at a part of the shielding member to
let the setting light pass through, and a shielding member driving
device for selectively positioning the light-passing space at a
position corresponding to the substrate pair and at a position
separated from the substrate pair.
[0104] The light-passing space can be provided to correspond to a
shape of the substrate pair to which the light is projected. That
is, a circular light-passing space is adopted when the substrates
are disk-shaped.
[0105] A driving mechanism used in various mechanical apparatuses
is applied as an example of the shielding member driving device,
which is constituted of a combination of a cylinder mechanism, a
cam mechanism, a rack mechanism, a ball-screw mechanism, a link
mechanism, etc.
[0106] As mentioned earlier, the passing time of the setting light
in the temporary and complete setting steps is required to be
correctly controlled to be, for example, smaller than one second.
Therefore, the shielding member driving device is preferably
constituted of a mechanism capable of operating quickly and
correctly.
[0107] In order to fulfill the function of controlling the passing
time of the setting light correctly and quickly, the shielding
member can include a pair of shielding members which form a
light-passing space for passing the setting light at respective
ends with one side of the space opened, and the shielding member
driving device may be provided with a reciprocation interlocking
device for reciprocating the pair of shielding members in opposite
directions interlockingly.
[0108] At one end of reciprocation of the pair of shielding
members, the shielding members form a light-passing space which
shape corresponds to the substrate pair by the light-passing spaces
of the pair of shielding members at respective ends. For example,
the pairing shielding members each having a semicircular space
present a circular light-passing space when combined with each
other. At the other end of the reciprocation, the light-passing
spaces of the shielding members are shifted from the substrate pair
and the shielding members shut out the light and prevent it from
passing through. As compared with a single shielding member, the
pair of shielding members can shorten a reciprocation distance,
thus achieving quick action with ease.
[0109] An interlocking mechanism used in general mechanical
apparatuses, for example, a gear mechanism, a cam mechanism, etc.
is employed to interlock the reciprocation of the pair of shielding
members.
COMBINATION OF DEFORMATION PREVENTION MEANS OR DEVICES
[0110] Although the aimed function is achieved with the use of the
single deformation prevention means or device described
hereinabove, superior prevention efficiency is achieved if two or
more means or devices are used together.
[0111] For instance, forming the stepped portion with the spacer
and dividing the photosetting process into the plurality of steps
can be carried out in combination. Further, making the temperature
distribution uniform or controlling the humidity may be added to
the above.
WHOLE STRUCTURE OF BONDING APPARATUS
[0112] A bonding apparatus according to a first embodiment of the
present invention shown in FIG. 1 is used to manufacture DVDs. The
apparatus can carry out a bonding method of the first embodiment.
Substrates Da and substrates Db are used to constitute optical
disks. Both substrates Da, Db are formed of transparent
polycarbonate resin fundamentally in a common shape, while
recording layers are formed of different materials in different
structures.
[0113] The bonding apparatus has a substrate pile part 10 where the
substrates Da, Db are piled, an alignment transfer part 20 for
aligning and transferring the substrates Da, Db, bond parts 40 for
respectively bonding the substrates Da, Db with an adhesive, for
example, an acrylic adhesive, a photosetting part 60 for setting
the adhesive with ultraviolet rays, an inspection part 70 for
inspecting manufactured optical disks, and an optical disk
collection part 80 where optical disks are piled.
[0114] The substrates Da, Db piled on turntables 14, 12 at the
substrate pile part 10 are alternately taken out by a crossed
turning arm 18 and sent to the alignment transfer part 20 in a
state in which the substrates are aligned. At this time, the arm 18
is reciprocally rotated by 90 degrees. The substrates Da, Db are
alternately taken out by a turning arm 32 at an end part of the
alignment transfer part 20 and sent to each of the bond parts 40 in
a state while the substrates Da, Db face each other. At the bond
part 40, an adhesive is supplied to between the substrates Da and
Db in a pair, whereby a substrate pair Dx composed of the
substrates Da, Db and the adhesive layer interposed therebetween is
obtained.
[0115] The substrate pair Dx is transferred to an elliptical
conveyor 64 of the photosetting part 60 and sent to an ultraviolet
irradiation part 62.
[0116] When ultraviolet rays are projected at the ultraviolet
irradiation part 62 thereby photosetting the adhesive, an optical
disk D is completed. After finishing a product inspection at the
inspection part 70, the optical disks are sequentially transferred
by transfer arms 77 and piled on a turntable 82 of the optical disk
collection part 80.
BONDING PROCESS
[0117] Bonding is carried out in processes (A)-(D) in FIGS.
2A-2D.
[0118] PROCESS (A)
[0119] As shown in FIG. 2A, at the bond part 40, the substrates Da,
Db are vacuum-sucked and held at upper and lower rotary holding
panels 42 faced to each other.
[0120] A discharge nozzle 45 proceeds in a direction from the outer
circumference to the center of the substrates Da, Db. An adhesive g
is discharged from a leading end of the discharge nozzle 45.
[0121] PROCESS (B)
[0122] As shown in FIG. 2B, while the adhesive g is discharged from
the discharge nozzle 45, the substrates Da, Db are rotated together
with the rotary holding panels 42. As a result, the adhesive g is
expanded in a circumferential direction and forms a loop.
[0123] PROCESS (C)
[0124] As shown in FIG. 2C, the discharge nozzle 45 retreats and
the rotary holding panels 42, 42 move close to each other, thereby
narrowing a gap between the substrates Da and Db. In this state,
the substrates Da, Db are rotated along with the rotary holding
panels 42, whereby the adhesive g is spread all over the
confronting faces of the substrates Da, Db, forming an adhesive
layer g of a constant thickness. The substrate pair Dx is thus
constituted.
[0125] PROCESS (D)
[0126] As shown in FIG. 2D, the substrate pair Dx is taken out of
each of the bond parts 40 and sent to the photosetting part 60.
[0127] The substrate pair Dx is loaded on a stage 100 at the
photosetting part 62. A center hole of the substrate pair Dx is
fitted in a core shaft 102 projecting from the center of the stage
100, so that the substrate pair is positioned in a horizontal
direction.
[0128] The ultraviolet projection lamp, namely, a light source 66
installed above the stage 100 projects light to set the adhesive g
of the substrate pair Dx. The upper and lower substrates Da, Db are
bonded accordingly.
SPACER
[0129] In the bonding apparatus of the first embodiment, as shown
in FIG. 3, a spacer 110 is set at a flat surface of the stage
100A.
[0130] The spacer 110 is a doughnut-shaped circular plate
detachably fitted at the center shaft 102 at the center of the
stage 100A. A height of the spacer 110 is set in a range of
0.1-0.35 mm, for example, 0.25 mm in the first embodiment.
[0131] The substrate pair Dx placed on the stage 100A maintains a
shape as when loaded on the spacer 110. That is, an outer
circumferential part of the substrate pair Dx not supported by the
spacer 110 hangs down because of its weight, and therefore the
substrate pair Dx slopes downwards from a central part to the outer
circumferential part of the substrate pair Dx.
[0132] When the light source 66 projects light, the substrate pair
Dx is heated, raised in temperature, and thermally expanded in a
direction towards the outer circumference of the substrate pair Dx.
Since the front (upper) substrate of the substrate pair Dx at the
side close to the light source 66 is heated more intensively, the
front substrate expands larger than the rear (lower) substrate
close to the stage 100. Because of the presence of the spacer 110,
the thermally expanded substrate pair Dx is still kept higher at
the center with its height reduced towards the outer
circumference.
[0133] The adhesive g is set in this state, whereby the substrates
Da, Db are bonded.
[0134] The substrate pair Dx is cooled when the emission from the
light source 66 is stopped upon completion of the photosetting
process. The front substrate which had expanded to a greater extent
than the rear substrate, shrinks more at this time and tends to
warp upward. The substrate pair Dx which is inclined from the
center to the outer circumference, i.e., is higher at the center
and lower towards the outer circumference when expanded is apt to
warp upwards when cooled and shrunken. In consequence, the
substrate Dx is brought to a horizontal attitude after the cooling.
The spacer 110 enables the warp of the substrate pair Dx to be
offset by the slope. That is, the warp deformation of the substrate
pair Dx can be cancelled by the inclination formed by the spacer
110 and the stage 100A.
[0135] Since the upward warp in the photosetting process is
perfectly eliminated or reduced greatly as discussed above, an
optical disk D of high flatness can be obtained.
TAPER FACE
[0136] As a second embodiment of the present invention, an upper
face 104 of a stage 100B is tapered as shown in FIG. 4.
[0137] More specifically, the upper face 104 stands high at a
position of the core shaft 102 and gradually uniformly decreases
its height towards the outer circumference of the upper face 104,
in other words, the upper face 104 is shaped in a flat circular
cone.
[0138] The photosetting process is carried out in the same manner
as described hereinabove.
[0139] The substrate pair Dx is deformed through irradiation of
light and then turned to a flat circular cone following the tapered
face 104 of the stage 100B. When the substrate pair Dx is cooled
after the irradiation is completed, the upward warp is offset with
the correction deformation by the tapered face 104, so that the
obtained substrate pair Dx is in a horizontal state.
HEIGHT VARIABLE SPACER
[0140] As a third embodiment of the present invention, a spacer 112
employed in FIGS. 5A and 5B is a height-variable one.
[0141] As illustrated in an enlarged view of FIG. 5B, a male screw
102a is provided in the outer circumference of the core shaft 102
located at the center of the stage 100C. The spacer 112 of a hollow
disk is arranged at the outer circumference of the core shaft 102
between the male screw 102a and the stage 100C. The spacer 112 has
an upper end projecting from the stage 100C. A female screw 112a
formed at an inner circumferential face of the spacer 112 is
screwed in the male screw 102a of the core shaft 102. When a
position of the spacer 112 screwed to the core shaft 102, that is,
a heightwise position of the spacer 112 is changed by turning the
spacer 112, a projection length of the spacer 112 from the stage
100C is adjusted.
[0142] A supporting body 106 for supporting the stage 100C and the
core shaft 102 has a ball plunger 114 contacting a bottom face of
the spacer 112. The ball plunger 114 is a mechanism element having
a ball at a leading end urged upward by a spring at the back. The
ball plunger 114 is contacted the bottom face of the spacer 112 and
urged upward, whereby the female screw 112a of the spacer 112 is
pressed in touch with the male screw 102a of the core shaft 102 at
all times, thereby preventing a shift of the position where the
spacer 112 is screwed to the core shaft 102 due to vibrations,
shocks, etc. Since the spacer 112 and the ball plunger 114 slide
smoothly in rolling contact therebetween when the spacer 112 is
turned in order to adjust the screw position, the screw position of
the spacer 112 can be adjusted easily.
[0143] According to the height variable spacer 112 of the above
structure, the projection length from the surface of the stage 100C
is adjusted on the basis of an estimated value of the warp of the
substrate pair Dx which is obtained beforehand from experiments or
data analyses.
[0144] The photosetting process afterwards is equally conducted to
that in the case using the fixed spacer 110.
[0145] In the third embodiment of FIGS. 5A and 5B, the spacer 112
can be adjusted in height properly and easily to conform to
operation conditions, and therefore the trouble of preparing many
spacers of different thicknesses is eliminated.
TEMPERATURE CONTROL DEVICE
[0146] As a fourth embodiment of the present invention, the stage
100 is provided with a temperature control device of FIGS. 6A and
6B.
[0147] As shown in FIG. 6A, the stage 100 has a temperature control
medium passage 120 grooved from its rear face, and a back plate 122
for shutting the passage 120 from the rear face.
[0148] In FIG. 6B, the temperature control medium passage 120 is
connected to a feed piping 124 and a return piping 126 for a
temperature control medium at the outer circumference of the flat
disk-shaped stage 100. The passage 120 starts from the feed piping
124 towards the center of the stage 100 in a radial direction, runs
one round in a circumferential direction in a locus of the letter
"C" from the central part of the stage 100, then returns another
round in an opposite direction at an outer circumference than the
above locus of the letter "C". The passage 120 running in this way
is connected to the return piping 126 at the outer circumference of
the stage 100.
[0149] The temperature control medium such as the air, water, oil,
or the like which is regulated in temperature is supplied to the
feed piping 124, passing through the passage 120 thereby regulating
the entire stage 100 at a constant temperature. The temperature
control medium is finally collected from the return piping 126. The
feed piping 124 and the return piping 126 are coupled to a
temperature control apparatus 330. In the apparatus 330, the
temperature control medium collected at the return piping 126 is
adjusted again to a predetermined temperature and then fed back to
the feed piping 124 to be recycled.
[0150] The temperature control device enables heating or cooling to
a surface of the rear substrate of the substrate pair Dx closer to
the stage 100, and therefore a temperature difference of the
surface to a surface of the front substrate heated by the projected
light from the light source 66 is adjusted properly.
[0151] Moreover, since a temperature of the total surface of the
stage 100 is uniform, irregularities in expansion and shrinkage of
the substrate pair Dx in the plane direction are reduced, local
swell or warp in the plane direction is prevented, and eventually
the whole substrate pair Dx is improved in its degree of
flatness.
[0152] Even if temperature of the stage 100 or temperature in the
surrounding environment of the stage 100 is changed with time by
heat generated inside the bonding apparatus after the bonding
apparatus starts operating, the surface of the stage 100 or the
surface of the substrate pair Dx can be maintained under a proper
temperature condition by the above temperature control device.
Accordingly, a variation in amount of the deformation for every
optical disk is eliminated, thus realizing optical disks of stable
quality.
[0153] A non-contact type temperature sensor 301 that can detect
the temperature of the surface of the stage 100 or the substrate
pair Dx may be installed above the stage 100 or at a passage where
the stages 100 are moved. A feed temperature or feed amount of the
temperature control medium can be controlled on the basis of
temperature information detected by the sensor 301.
TEMPORARY SETTING AND COMPLETE SETTING
[0154] The photosetting process is specifically described
hereinbelow. The photosetting process is executed in a plurality of
divided stages, namely, temporary setting and complete setting,
with the use of the stages 100 having the spacers 110 shown in FIG.
3.
[0155] The substrate pair Dx for a DVD is subjected to a
photosetting process. Doughnut-shaped circular plates of different
thicknesses and outer diameters of 20-30 mm are used as the spacer
110. The stage 100 has an outer diameter of 115 mm. The light
source 66 is an ultraviolet projection lamp. A shutter part for
controlling a projection timing of light is arranged between the
light source 66 and the substrate pair Dx. Then, the substrate
pairs Dx are continuously supplied and bonded.
TEMPORARY SETTING PROCESS
[0156] The light source 66 is set at 30% (220 mW/cm.sup.2) of
power. An irradiation time is set to be 0.3 sec by controlling the
shutter part.
COMPLETE SETTING PROCESS
[0157] The light source 66 is set at 65% (1050 mW/cm.sup.2) of
power and the irradiation time is set to be 1.2 sec.
[0158] The amount of the warp of the optical disk bonded in the
photosetting process in two steps is evaluated. Specifically, an
angle of the warp in the radial direction at a position of the
outermost circumference of the disk to a position of the innermost
circumference of the disk is measured as a tilt angle, and a
maximum value (MAX) and a minimum value (MIN) of the tilt angles
measured in the circumferential direction of the optical disk are
obtained. FIGS. 7A and 7B are graphs showing results of the
measurements obtained with various thicknesses of the spacer
110.
[0159] The graphs of FIGS. 7A and 7B indicate that it possible to
keep the warp amount of the optical disk within a fixed ranged if
the thickness of the spacer 110 is set properly. The warp
deformation is minimized when the spacer has the thickness of
approximately 0.25 mm in FIGS. 7A and 7B.
[0160] A tolerance of the tilt angle is .+-.0.80.degree. in general
DVDs, and the tolerance at the production time of the disks is set
to be approximately .+-.0.5.degree.. Even when the spacer 110 has 0
mm thickness, that is, even when no spacer 110 is used, the
tolerance may be nearly satisfied by a simple combination of the
temporary setting and complete setting. However, the additional use
of the spacer 110 of a suitable thickness can achieve higher
flatness of the optical disk.
[0161] FIG. 8 is a half sectional view of a photosetting process
using a stage in a bonding apparatus and method according to a
fifth embodiment of the present invention. The fifth embodiment is
constituted by combining the first embodiment and the fourth
embodiment. That is, as shown in FIG. 8, a spacer 110D is fixedly
and integrally set at a flat surface of a stage 100D. That is, the
spacer 110D is a doughnut-shaped circular plate portion
mechanically processed around the center shaft 102 at the center of
the stage 100D. As examples, there may be prepared the stages 100D
having the spacers 110D of diameters of 60 mm, 70 mm, 80 mm, 90 mm
etc. A suitable one of the spacers 110D is selected from the
spacers 110D in correspondence with the dimension of the warp
deformation of the substrate pair Dx. The stage 100D has the
temperature control medium passage 120 grooved from its rear face
and flowing the temperature control medium such as the air, and the
back plate 122 for shutting the passage 120 from the rear face. The
temperature control medium passage 120 may have the same shape of
FIG. 6B.
[0162] FIG. 9 is a half sectional view of a photosetting process
using a stage in a bonding apparatus and method according to a
sixth embodiment of the present invention. The sixth embodiment is
constituted by combining the second embodiment and the fourth
embodiment. That is, as shown in FIG. 9, an upper face 104 of a
stage 100E is tapered. More specifically, the upper face 104 stands
high at a position of the core shaft 102 and gradually uniformly
decreases its height towards the outer circumference of the upper
face 104, in other words, the upper face 104 is shaped in a flat
circular cone. As one example, a height of the upper face 104 of
the stage 100E is set in a range of 22 mm-120 mm in diameter and a
tilt angle .theta. of 0.1-0.34 degrees [obtained from an equation:
tan .theta.={(0.1-0.35 mm)/60 mm}] which means an angle of the warp
in the radial direction at a position of the outermost
circumference of the upper face 104 to a position of the innermost
circumference of the upper face 104 when each of the substrates has
a diameter of 120 mm. The stage 100E has the temperature control
medium passage 120 grooved from its rear face and flowing the
temperature control medium such as the air, and the back plate 122
for shutting the passage 120 from the rear face. The temperature
control medium passage 120 may have the same shape of FIG. 6B. As
examples, there may be prepared the spacers 100E have heights H of
0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mmm, 0.35 mm etc., that is,
tilt angles .theta. obtained by substituting the heights H of 0.1
mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm into an equation:
.theta.=tan.sup.-1 (H/60 mm). A suitable one of the spacers 100E is
selected from the spacers 100E in correspondence with the
inclination of the warp deformation of the substrate pair Dx.
[0163] The selection of the spacers 100A, 100B, 100D, and 100E is
carried out as follows. For easy understanding, the selection of
the spacers 100D and 100E of FIGS. 8 and 9 are exemplified. The
selection of the spacers 100A and 100B is almost the same as that
of the spacers 100D and 100E.
[0164] First, a plurality of optical disks, as samples, are
manufactured by the bonding apparatus and the tilt angles of the
disks D are measured by the inspection part 70. Then, the maximum
data and the minimum data are extracted from the measured results
to make a graph showing relation between the tilt angle and the
distance in radial direction of the disk. Instead of the samples,
the actually manufactured optical disks may be inspected and
measured to obtain the above data.
[0165] When the found graph is the graph of FIG. 10, it is found
that there is a recess at a position in the radial direction of the
disk. In such a case, the spacer 100A or 100D of FIG. 3 or FIG. 8
is used. When a plurality of spaces 100A or 100D having different
diameters are prepared, one of the spaces 100A or 100D is
preferably selected depending on the position of the recess, so as
to make lines of the maximum data and the minimum data parallel to
the abscissa axis as shown in FIG. 12.
[0166] When the found graph is the graph of FIG. 11, it is found
that there is a slope in the radial direction of the disk. In such
a case, the spacer 100B or 100E of FIG. 4 or FIG. 9 is used. When a
plurality of spaces 100B or 100E having different inclinations are
prepared, one of the spaces 100B or 100E is preferably selected
depending on the inclination of the slope, so as to make lines of
the maximum data and the minimum data parallel to the abscissa axis
as shown in FIG. 12.
[0167] When the spacer 100D or 100E is selected, the temperature of
the spacer 100D or 100E is adjusted. That is, a distance between
the zero point of the graph of FIG. 10 or FIG. 11 in the ordinate
axis of the tilt angle and a position where the center line of the
found graph crosses the ordinate axis is calculated. Based on the
found distance and the temperature of the spacer detected by the
temperature sensor 301, the temperature of the air as one example
of the temperature control medium for flowing in and cooling or
heating the spacer 100D or 100E is controlled so as to reduce the
distance between the zero point and the position as shown in FIG.
12. In most cases, since the spacer is heated by the ultraviolet
irradiation part 62, the spacer is cooled with the air. In general,
when the temperature of the spacer is increased, the found graph is
relatively moved downward, i.e. in the minus direction. When the
temperature of the spacer is decreased, the found graph is
relatively moved upward, i.e. in the plus direction. As a result,
the optimum selection and the temperature adjustment of the spacer
allows optical disks D with a higher degree of flatness to be
surely obtained.
[0168] In one example, two or three stages 100D of FIG. 8 and one
stage 100E of FIG. 9 are prepared, and when it is difficult to use
the stages 100D, the stage 100E is used.
[0169] The material of the stage preferably has good thermal
conductivity so as to make it easy to control the temperature of
the stage.
[0170] FIG. 13 is a schematic plan view showing a total structure
of a bonding apparatus and method according to a seventh embodiment
of the present invention.
[0171] The bonding apparatus is different from the bonding
apparatus in FIG. 1 in structure. The bonding apparatus has two
substrate pile parts 10 where the substrates Da, Db are piled on
turntables 14, 12 at the substrate pile parts 10. A crossed turning
arm 18 reciprocally and intermittently rotates by 90 degrees by an
arm driving device 400. As a result, the substrates Da, Db are
alternatively transferred from the substrate pile parts 10 to a
second turning arm 201 so as to supply the substrates in order of
Da, Db, Da, Db. The second turning arm 201 has four chucks 202 for
holding the substrates and is clockwisely and intermittently
rotated by a first transfer device 401. The second turning arm 201
is reciprocally moved within a specified range by a second transfer
device 205 and transfers the substrates Da, Db received from the
crossed turning arm 18 to one of third transfer arms while the two
substrates are held by a chuck 206 of the third transfer arm. A
substrate inversion device 203 inverts one of the substrates Da or
Db so that the recording layers of the substrates Da and Db are
faced to each other.
[0172] Each of the third transfer arms receives the substrates Da
and Db with the recording layers of the substrates Da and Db faced
to each other, and transfers the faced substrates Da and Db to an
adhesive application device 204 to inject the adhesive into the gap
g between the faced substrates Da and Db. And then each of the
third transfer arms transfers the substrates Da and Db with the
adhesive injected into the gap g to the bond part 40. At the bond
part 40, the gap g is narrowed by moving one of the substrates Da,
Db against the other of the substrates. Then, each of the third
transfer arms transfers the substrates Da and Db to a stage
movement arm 200, and then, the substrates Da and Db, i.e.
substrate pair Dx is placed on one of the stages 100 spaced 180
degrees.
[0173] The stage movement arm 200 has the two stages 100 and is
rotated by 180 degrees by a stage driving device 302 while each of
the stages 100 passes through a ultraviolet irradiation part 62 in
a photosetting part 60. The photosetting part 60 sets the adhesive
with ultraviolet rays.
[0174] After the substrate pair Dx passes through the ultraviolet
irradiation part 62 and the adhesive in the gap g between the
substrates is photoset to obtain a optical disk D as a product, the
substrate pair Dx is transferred from the stage movement arm 200 to
a product transfer arm 207. The product transfer arm 207 has a
plurality of arm elements for holding the optical disks D to
sequentially transfer them and pile them on a turntable 82 of an
optical disk collection part 80. An inspection part 70 is located
in a way from the stage movement arm 200 to the turntable 82 of the
optical disk collection part 80. The inspection part 70 inspects
manufactured optical disks D. If an unfavorable product is found by
the inspection part 70, the unfavorable product is removed so as
not to pile it on the turntable 82.
[0175] FIG. 20 is a block diagram of control unit of the bonding
apparatus of the seventh embodiment. A controller 300 is connected
to the arm driving device 400, the first transfer device 401, the
second transfer devices 205, the adhesive application devices 204,
the substrate inversion device 203, the bond parts 40, the stage
driving device 302, and a stage switching controller 500 so as to
control the operations of the above devices or members. The stage
switching controller 500 for controlling stage switching operation
is connected to the temperature sensor 301, a stage switching
device 303, a kind selection section 310, a calculating section
320, and the temperature control apparatus 330 so as to control the
operations of the above devices or sections.
[0176] FIG. 21 is a plan view of a stage switching arm of a
modification of the seventh embodiment. That is, instead of the
stage movement arm 200, a stage switching arm 350 is provided. The
stage switching arm 350 has two kinds of spacers 100D, 100E with
the same kind of spacers spaced 180 degrees. The stage switching
arm 350 is normally rotated by 180 degrees by a stage driving
device 302. When the kind of spacer is changed, the stage switching
device 303 controls the stage driving device 302 so as to rotate
the stage switching arm 350 by 90 degrees to switch the spacers
100D with the another kind of spacer 100E or vice versa.
[0177] In this modification, the switching of the kinds of the
stages can be automatically carried out by using the inspection
part 70, the temperature sensor 301, the stage switching device
303, the kind selection section 310, the calculating section 320,
and the temperature control apparatus 330 under control operation
of the stage switching controller 500. That is, the tilt angles of
the optical disks D are detected by the inspection part 70. The
kind selection section 310 selects the suitable kind of spacer
based on the detected results. Then, it is decided whether or not
the selected kind of stage is used, if yes, the stage switching
operation is unnecessary. If no, the stage switching operation is
carried out. That is, based on the selection of the kind selection
section 310, the stage switching device 303 is driven to drive the
stage driving device 302 so as to rotate the stage switching arm
350 by 90 degrees. Thus, the kind of spacer is switched with
another kind of spacer. Then, the calculating section 320
calculates the distance between the zero point of the graph of FIG.
10 or FIG. 11 in the ordinate axis of the tilt angle and a position
where the center line of the found graph crosses the ordinate axis.
Based on the calculated results and the temperature of the selected
spacer detected by the temperature sensor 301, the temperature of
the air as one example of the temperature control medium for
flowing in and cooling or heating the spacer 100D or 100E is
controlled by the temperature control apparatus 330 so as to reduce
the distance between the zero point and the position as shown in
FIG. 12. As a result, the optimum selection and the temperature
adjustment of the spacer allows the optical disks D with a higher
degree of flatness to be surely obtained.
SHUTTER PART
[0178] In an eighth embodiment of the present invention, as shown
in FIGS. 14A, 14B, and 15, both the temporary setting and the
complete setting are carried out, the shutter part is constructed
to precisely control the irradiation time of the setting light.
[0179] A rectangular plate-shaped shielding member 130 movable in a
horizontal direction is arranged between the light source 66 and
the substrate pair Dx. As is clear from FIG. 15, a circular
light-passing space 134 penetrates one side of the shielding member
130. The shielding member 130 supported by a rodless cylinder 138
slidable along a guide rod 139 reciprocates linearly.
[0180] As shown in FIG. 14A, a fixed shielding plate 132 is set
between the shielding member 130 and the stage 100. A circular
through hole 136 of almost the same size as the outer diameter of
the substrate pair Dx is formed at a position of the fixed
shielding plate 132 corresponding to the stage 100. The shutter
part operates as follows.
[0181] Referring to FIG. 14A, when the light-passing space 134 of
the shielding member 130 is present at a position shifted from the
through hole 136 of the fixed shielding plate 132, the light from
the light source 66 is blocked by the shielding member 130 and does
not reach the substrate pair Dx.
[0182] On the other hand, in FIG. 14B, when the shielding member
130 moves horizontally to bring the light-passing space 134 to a
position where the light-passing space 134 aligns with the through
hole 136 of the fixed shielding plate 132, the light from the light
source 66 reaches the substrate pair Dx through the light-passing
space 134 and the through hole 136.
[0183] A necessary quantity of light is fed to the substrate pair
Dx in the above state of FIG. 14B for a fixed time, and then the
shielding member 130 is moved horizontally to an original position,
namely, in a state of FIG. 14A, whereby the light is not shed onto
the substrate pair Dx.
[0184] A time for the light to be shed onto the substrate pair Dx
is correctly controlled when the action of the shielding member 130
is controlled. The shielding member 130 is relatively simple in
structure and operation and therefore, can operate correctly and
stably.
[0185] In the above eighth embodiment, the light-passing space 134
of the shielding member 130 can be constituted of many slits in a
row. The light-passing space 134 constituted of the slits is
effective to control the quantity of light projected to the
substrate pair Dx, or ease a difference in intensity of light
between the center and the periphery of the light source 66, etc.
The slits are also replaceable with many fine openings.
SHUTTER PART IN DIFFERENT EMBODIMENT
[0186] As a ninth embodiment of the present invention, a shielding
member 130 of a shutter part in FIGS. 16A-16C operates in a
different manner from the eighth embodiment.
[0187] A light-passing space 134 is formed in the vicinity of the
center of the shielding member 130 in a longitudinal direction
thereof, as shown in FIG. 16A. A fixed shielding plate 132 and a
through hole 136 are in the same constitution as in the eighth
embodiment.
[0188] When the shielding member 130 moves rightward from a
position of FIG. 16A to a position of FIG. 16B, the light-passing
space 134 aligns with the through hole 136, so that the light of
the light source 66 is projected to the substrate pair Dx.
[0189] In FIG. 16C, the shielding member 130 moves horizontally
rightward from the state of FIG. 16B and the light-passing space
134 is displaced from the position corresponding to the through
hole 136, whereby the light of the light source 66 is shut by the
shielding member 130.
[0190] According to the ninth embodiment, one irradiation of light
to the substrate pair Dx is completed while the shielding member
130 moves once from left to right, In comparing the ninth
embodiment with the eighth embodiment of FIGS. 14A, 14B, and 15
wherein the shielding member 130 reciprocates to return to the
original position, the irradiation time is shortened and can be
controlled precisely.
[0191] The irradiation of light for the next time is accomplished
while the shielding member 30 moves from right to left once.
SHUTTER PART IN A FURTHER DIFFERENT EMBODIMENT
[0192] As a tenth embodiment of the present invention, a pair of
shielding members are employed as shown in FIGS. 17A, 17B, 18, and
19.
[0193] As shown in FIG. 18, the pair of shielding members 140a,
140b are rectangular plate-shaped ones. A light-passing space 142
of a semicircle is formed at one side (left side of FIG. 17A) of
the shielding member 140a, and a light-passing space 142 of the
same shape is formed at one side (right side of FIG. 17A) of the
shielding member 140b opposite to the above light-passing space 142
of the shielding member 140a. The light-passing spaces 142, 142 of
the shielding members 140a, 140b when arranged side by side produce
a circular light-passing space.
[0194] In FIG. 17A, the pair of shielding members 104a, 140b are
arranged to nearly overlap in an up-down direction between the
light source 66 and the stage 100.
[0195] Since each light-passing space 142 is shut by the
counterpart shielding member 140a, 140b, the light from the light
source 66 does not reach the substrate pair Dx.
[0196] In FIG. 17B, the shielding members 140a, 140b move in
opposite directions horizontally. As a result, as is indicated in
FIG. 18 alike, the light-passing spaces 142, 142 of the shielding
members 140a, 140b are aligned side by side, enabling the light of
the light source 66 to pass therethrough to reach the substrate
pair Dx.
[0197] After the irradiation of light to the substrate pair Dx is
finished, the shielding members 140a, 140b move and return to the
state of FIG. 17A, shutting the light from the light source 66.
[0198] FIG. 19 shows a mechanism for reciprocating the shielding
members 140a, 140b in opposite directions interlockingly.
[0199] Gears 146, 146 in pairs are meshed with each other. When one
gear 146 is rotated by a motor or the like, the meshed gears 146,
146 rotate in opposite directions.
[0200] The pair of shielding members 140a, 140b are coupled to the
gears 146, 146 via respective links 144, 144. Coupling points at
both ends of each link 144 are rendered rotatable. The shielding
members 140a, 140b are supported by a guide structure such as a
guide rail or the like (not shown) to be movable horizontally.
[0201] When the pair of gears 146, 146 are rotated in opposite
directions, the shielding members 140a, 140b coupled via the links
144, 144 move horizontally in opposite directions by a fixed
distance and then return horizontally to the original positions.
The rotation of the gears 146, 146 thus makes the shielding members
140a, 140b reciprocate in opposite directions. When a rotational
speed of the gears 146, 146 is changed, a reciprocation speed of
the shielding members 140a, 140b is changed, whereby the
irradiation time of the light to the substrate pair Dx is
controlled.
[0202] According to the method and apparatus for bonding optical
disk substrates of the present invention, when a pair of substrates
are to be bonded in the photosetting process to the adhesive layer,
the deformation prevention means or devices efficiently prevents
the warp or the like deformation of the substrates subsequent to
the photosetting, thereby realizing an optical disk with a high
degree of flatness.
[0203] In one aspect of the present invention, in the photosetting,
warp deformation caused when the substrate pair finishes the
photosetting operation can be offset by deforming the substrate
pair tracing the height difference at the upper face of the stage
because of a weight of the substrate pair, thereby realizing an
optical disk with a high degree of flatness.
[0204] In an aspect of the present invention, the adhesive layer is
set in the temporary setting step with a level of flexibility or
deformability ensured, so that the adhesive layer does not move or
is not deformed unexpectedly, but the thermal deformation of the
substrate pair subsequent to the projection of the setting light
can be absorbed in the cooling process. That is, the warp
deformation of the substrates are determined by the temporary
setting step. Thus, the division of the temporary setting step and
the complete setting step allows the warp deformation of the
substrates to be reduced, as compared with a case where only one
setting step is carried out.
[0205] In an aspect of the present invention, a temperature of at
least the front face-side substrate of the substrate pair is
controlled thereby decreasing a temperature difference of both
faces of the substrate pair. Thus, the difference of the thermal
expansion amounts is lessened, so that the warp deformation is
restricted.
[0206] Although the present invention has been fully described in
connection with the preferred embodiments thereof with reference to
the accompanying drawings, it is to be noted that various changes
and modifications are apparent to those skilled in the art. Such
changes and modifications are to be understood as included within
the scope of the present invention as defined by the appended
claims unless they depart therefrom.
* * * * *