Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-05-04
2001-05-08
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S295000, C156S556000
Reexamination Certificate
active
06228203
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to technique of fabricating disks such as optical disks, and more specifically to technique for bonding a plurality of disk together into multi-layer disks.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide disk bonding method and system advantageous for excluding air bubbles from adhesive layers.
FIGS.
11
~
14
show a disk bonding system of related art. In an optical disk fabricating system
50
shown in
FIG. 11
, lower disks DL are placed one by one on a first turntable
51
at a position Q
1
by a lower disk supplying section (not shown). At the position Q
1
, a lower disk DL is in a state in which its joint surface faces upwards. The lower disk is then conveyed by the turntable from the position Q
1
through a position Q
2
to a position Q
3
. At the position Q
2
, a nozzle N
3
discharges adhesive so as to form an annular adhesive layer on the upwardly facing joint surface of the lower disk DL.
Upper disks DU are placed one by one on a second turntable
52
at a position Q
4
in a state having a joint surface facing upwards by a second disk supplying mechanism (not shown), and conveyed through a position Q
5
to a position Q
6
by the turntable
52
. At the position Q
5
, a nozzle N
4
discharges the adhesive so as to form an annular adhesive layer on the upwardly facing joint surface of the upper disk DU. An inverting arm mechanism
53
picks up the upper disk DU from the position Q
6
and places the upper disk DU at a position Q
7
in an inverted state with the joint surface facing downwards.
A transfer arm
54
transfers the lower disk DL from the position Q
3
to a spinner SP
1
at a position Q
8
. Then, a transfer arm
55
transfers the upper disk DU from the position Q
7
to the spinner SP
1
and places the upper disk DU on the lower disk DL.
In the spinner SP
1
, the upper and lower disks in the overlapped state are spun to spread the adhesive by the centrifugal force between the upper and lower disks. By this spin coating operation, the upper and lower disks are brought into a laminated disk DD with a uniform thin adhesive layer tightly sandwiched between the upper and lower disks. The laminated disk DD is not readily separable.
Thereafter, a transfer arm
56
transfers the laminated disk DD from the spinner SPY onto a turntable
57
at a position Q
9
, and the turntable
57
conveys the laminated disk DD from the position Q
9
through a position Q
10
to a position Q
11
. At the position Q
10
, an ultraviolet irradiating apparatus
58
irradiates ultraviolet rays to the laminate disk DD, and cures the intervening adhesive layer to complete a bonded disk DB. The turntable
57
is covered with a shield cover
59
. Thus-completed bonded disks DB are discharged or unloaded one by one from the position Q
11
by an unloading mechanism (not shown).
FIG. 12
illustrates an overlapping operation for placing the upper disk DU held by the transfer arm
55
, on the lower disk DL resting on the spinner SP
1
. Annular adhesive layers
60
and
61
are brought into contact with each other.
However, the disk bonding system of the related art is unable to prevent bubbles completely.
First, the annular adhesive layers
60
and
61
are microscopically irregular in shape. Therefore, contact regions or contact interface between the two adhesive layers
60
and
61
are distributed and spread irregularly, so that a considerable possibility arises that air is involved and bubbles are formed in the adhesive layers.
Second, the annular adhesive layers
60
and
61
are brought into contact with each other in substantially flat top regions. The substantially flat surfaces tend to trap air and form bubbles when the confronting flat surfaces come into contact with each other.
According to the knowledge the inventors of the present application have acquired, bubbles formed at the instant of contact between the adhesive layers are mostly minute in the range of 0.05 mm to 0.1 mm in diameter. The wettable surfaces of the adhesive layers function as the cause, presumably. Minute bubbles are troublesome because of the difficulty to expel minute bubbles in the spin coating operation.
FIGS. 13A and 13B
illustrate forces acting on a large air bubble
63
in the spin coating operation while
FIG. 14
illustrates forces acting on a small bubble
65
.
In
FIGS. 13A and 13B
, a centrifugal force is directed in the rightward direction due to the rotation. As shown in
FIG. 13A
, the large air bubble
63
exists in a liquid adhesive layer
62
. The large air bubble
63
receives a centrifugal force f whereas a centrifugal force F acts on a fictitious liquid ball
64
assumed to have the same size and the same position. The large bubble
63
and the imaginary liquid ball
64
should coincide with each other although
FIG. 13A
shows as if they were at two separate positions, to avoid confusion.
FIG. 13B
shows a relation among forces acting on the large bubble
63
when the liquid adhesive flows by the centrifugal force. In this field of flow, the large bubble
63
receives a force having a magnitude of F−f and a direction opposite to the centrifugal direction as the result of the centrifugal forces. A centrifugal force acting on a rotating object is proportional to the mass of the object, and the mass of air is smaller than the mass of the liquid adhesive of an equal volume. Therefore, the air bubble
63
receives a centrifugal force of a smaller magnitude than the surroundings. Namely, the air bubble
63
has an inherent tendency to lag behind the liquid adhesive flowing due to the centrifugal force.
The air bubble
63
further receives a friction force R caused by the viscosity of the liquid adhesive. The frictional force R acts in the centrifugal direction as shown in FIG.
13
B. Consequently, whether the air bubble
63
is expelled together with the flowing adhesive is determined by the magnitude of the resulting force R+f−F acting in the centrifugal direction, or the magnitude of the frictional force R due to the viscosity. In the example of
FIGS. 13A and 13B
, the bubble
63
having a large projected area A
1
with respect to the flow receives a large friction force R due to the viscosity of the liquid adhesive. The resulting strong force in the radial outward direction acts to expel the large bubble
63
from the adhesive layer
62
.
The small bubble
65
shown in
FIG. 14
receives a force F′−f due to the centrifugal force, and a force R′ due to the viscosity of the adhesive, like the large bubble
63
. In the case of the small bubble
65
, however, a small projected area A
2
relative to the flow reduces the frictional force R′, and the resulting force acting to expel the small bubble
65
is weak and insufficient for the removal of the bubble.
The present invention offers methods and systems for effectively excluding bubbles.
According to the present invention, a disk bonding method or system for forming bonded disks by bonding disks together with adhesive comprises the following elements.
A first element is designed to form a first adhesive layer on a joint surface of a first disk by supplying the adhesive. The first adhesive layer is an annular adhesive layer.
A second element is designed to form a second adhesive layer on a joint surface of a second disk. The second adhesive layer is a dotted adhesive layer in a form of a plurality of dots arranged in a ring.
A third element is designed to overlap the first and second disks by decreasing a spacing between the first and second disks in a confronting state in which the joint surfaces of the first and second disks confront each other, and by bringing the first and second adhesive layers into contact with each other.
According to another aspect of the invention, a disk bonding system for forming multi-layer disks by bonding constituent disks together, comprises:
a first adhesive supplying section which forms an annular adhesive layer on a joint surface of a first constituent disk around a center of the first disk;
a
Kobayashi Hideo
Kotoyori Masahiko
Nakamura Masahiro
Nishimura Hironobu
Shinohara Shinichi
Ball Michael W.
Haran John T.
McDermott & Will & Emery
Origin Electric Company Limited
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