U.S. patent application number 09/984193 was filed with the patent office on 2002-02-28 for method for glueing together disc elements.
This patent application is currently assigned to OTB Group, B.V.. Invention is credited to Ohman, Ove.
Application Number | 20020023703 09/984193 |
Document ID | / |
Family ID | 26662567 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023703 |
Kind Code |
A1 |
Ohman, Ove |
February 28, 2002 |
METHOD FOR GLUEING TOGETHER DISC ELEMENTS
Abstract
A method and a device for glueing together two disc elements.
The two disc elements are brought together coaxially against each
other to form a gap between the disc elements. In an inner area of
the gap a liquid adhesive is applied so that it comes essentially
simultaneously into contact with facing sides of the two disc
elements. The two disc elements are then brought towards each other
to achieve a uniform adhesive layer between the disc elements. The
disc comprises lower and upper holders for respective disc elements
and a unit for applying liquid adhesive in an inner area of the
gap.
Inventors: |
Ohman, Ove; (Uppsala,
SE) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON
VA
22202
|
Assignee: |
OTB Group, B.V.
Eindhoven
NL
|
Family ID: |
26662567 |
Appl. No.: |
09/984193 |
Filed: |
October 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09984193 |
Oct 29, 2001 |
|
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09504434 |
Feb 15, 2000 |
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Current U.S.
Class: |
156/74 ;
156/290 |
Current CPC
Class: |
B29C 65/546 20130101;
B29C 66/342 20130101; B29C 65/548 20130101; B29C 65/521 20130101;
B29C 66/452 20130101; B29K 2069/00 20130101; B29C 65/542 20130101;
B29D 17/005 20130101; Y10T 156/1798 20150115; B29L 2017/005
20130101; G11B 7/26 20130101; B29C 66/723 20130101; B29C 65/7847
20130101; B29C 66/1122 20130101; B32B 37/0007 20130101; B29C 66/71
20130101; B29C 66/71 20130101 |
Class at
Publication: |
156/74 ;
156/290 |
International
Class: |
B32B 031/16 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 1996 |
SE |
9601263-8 |
Claims
What is claimed is:
1. Method of glueing together two disc elements, for digital audio,
video or computer discs, which comprises the steps of: a) bringing
the two disc elements together coaxially with each other in such a
manner that a gap is left between the disc elements; b) applying in
an inner area of the gap, while rotating the disc elements, a
liquid adhesive in the shape of a ring in such manner that the
adhesive will essentially come into contact simultaneously with
facing sides of the two disc elements; c) rotating the disc
elements relative to each other to even out the adhesive ring by
shearing action; and d) bringing the disc elements towards each
other to achieve a well-defined, uniform filling out of adhesive
between the disc elements.
2. Method according to claim 1, wherein the disc elements are each
rotated at least one half rotation in opposite directions.
3. Method according to claim 1, wherein the disc elements are each
rotated between one half to one complete rotation in opposite
directions.
4. Method according to claim 1, wherein at least one adhesive
injection nozzle is inserted into the gap prior to the application
of adhesive.
5. Method according to claim 4, wherein the nozzle is inserted into
the gap radially from the outside.
6. Method according to claim 1, wherein the disc elements are kept
in parallel relationship to each other during the application of
adhesive.
7. Method of glueing together two disc elements, for digital audio,
video or computer discs, which comprises the steps of: a) bringing
the two disc elements together coaxially with each other; b)
holding at least one of the disc elements in a convexly curved
shape relative to the other disc element to form a radially
outwardly diverging gap between at least a radially outer section
of the disc elements; c) applying, in an inner area of the
diverging gap, while rotating the disc elements, a liquid adhesive
in the shape of a ring in such manner that the adhesive will
essentially come into contact simultaneously with facing sides of
the two disc elements; and d) bringing the disc elements towards
each other to achieve a well-defined, uniform filling out of
adhesive between the disc elements.
8. Method according to claim 7, wherein at least one injection
nozzle is inserted into the diverging gap prior to adhesive
application.
9. Method according to claim 7, wherein the injection nozzle is
inserted into the diverging gap radially from outside the outer
section of the disc elements.
10. Method according to claim 7, wherein at least one of the disc
elements is curved against a respective profiled holder by creation
of a subatmospheric pressure on the side of the disc element facing
the holder.
11. Method according to claim 7, wherein the disc elements, after
the application of adhesive, are rotated relative to each other to
even out the adhesive ring by shearing action.
12. Method according to claim 7, wherein the disc elements are each
rotated at least one half rotation in opposite directions.
13. Method according to claim 7, wherein the disc elements are each
rotated between one half to one complete rotation in opposite
directions.
Description
[0001] The present invention relates to a method of glueing
together two disc elements, especially substrates for digital
audio, video or computer discs, such as digital video discs
(DVDs).
[0002] When manufacturing certain types of data storage discs, such
as so-called DVDs, with one or more information layers, two
substrate discs of polycarbonate of a thickness of 0.6 mm are
normally glued together, with the information layer(s) adjacent to
the adhesive layer joining the discs.
[0003] In one proposed method of glueing the adhesive is applied to
one of the discs by means of a printing process, for example screen
printing, whereafter the discs are joined together. This method
does not waste adhesive and the application can be done very
rapidly. However, there is some risk of air enclosures when the
discs are put together and some risk that the printing system will
break down should the screen printing blanket rupture.
[0004] A method using double adhesive tape for joining the two disc
elements has also been suggested, but this method causes air
enclosures and provides a joint of unreliable strength and thermal
stability. Nor can this method be used for DVDs of the type "SD9",
i.e. where both of the discs elements have information layers and
where these layers are to be read by laser light which must pass,
with the correct defraction, through the joint layer between the
disc elements.
[0005] One purpose of the present invention is to suggest a glueing
method which prevents the occurrence of air enclosures in the
adhesive layer between the discs.
[0006] For this purpose, the method according to the invention is
characterized by the steps of:
[0007] a) bringing the two disc elements together coaxially with
each other in such a manner that a gap is left between the disc
elements:
[0008] b) applying, in an inner area of the gap, a liquid adhesive
in such manner that the adhesive will essentially come into contact
simultaneously with facing sides of the two disc elements, and
[0009] c) bringing the disc elements towards each other to achieve
a well defined uniform filling out of adhesive between the disc
elements.
[0010] It has been found that a simultaneous or essentially
simultaneous wetting of the opposing gap surfaces with an easily
flowing adhesive with good capillary filling properties is an
essential precondition in order for the applied adhesive to flow
out and be evenly distributed over the entire surface between the
outer and inner peripheral limiting edges of the disc elements
without forming air enclosures, since the disc elements are brought
towards each other with only the aid of gravity and "are sucked
together" by the capillary forces of the adhesive. In this way a
very uniform, homogeneous adhesive layer without air enclosures can
be obtained without forceably pressing the discs together.
[0011] The disc elements can be kept plane-parallel to each other
during the application of adhesive, or they can be held relative to
each other in such a way during the application of adhesive that a
radially outwardly diverging gap is formed between at least one
radially outer section of the disc elements.
[0012] The diverging gap can be obtained by curving one or both of
the disc elements convexly from each other, preferably by creating
a subatmospheric pressure on the side of the disc element facing
away from the gap.
[0013] The adhesive is applied preferably by injection via a nozzle
insertable into the gap during simultaneous rotation of the disc
elements, whereupon a coherent annular adhesive string can be laid
out in the gap between the disc elements.
[0014] After application of the adhesive string, the nozzle is
retracted and the two disc elements are rotated individually in
opposite directions, each at least half a rotation, preferably
about one half to one rotation, so that any uneveness in the
circumferential distribution of the adhesive string can be evened
out by the disc elements producing a shearing effect in the
adhesive. The result will be a homogeneous and uniform ring of
adhesive, which is an essential precondition for even distribution
over the entire disc surface of the adhesive in a subsequent
step.
[0015] The present invention also relates to a device for glueing
together disc elements of the above mentioned type, said device
comprising a lower holder for carrying one disc element, an upper
holder for carrying the other disc element in a coaxial relation to
the lower disc element to form a gap between the disc elements, and
a means for applying a liquid adhesive in an inner area of the
gap.
[0016] In order to create a diverging gap to facilitate insertion
of the adhesive application means between the disc elements, there
is one holder that can have an essentially convex surface facing
the disc element. This convex surface is intended to define,
together with the disc element and sealing elements a space which
can be subjected to vacuum. Alternatively, the holders can be
disposed to hold the disc elements plane-parallel.
[0017] The means for applying adhesive can comprise a nozzle which
is disposed to direct, either radially from outside or inside, a
stream of adhesive into the gap in such a way that the stream of
adhesive strikes facing surfaces of the disc elements essentially
simultaneously. The nozzle can be insertable into and extractable
from the gap so that its opening comes close to the facing cap
surfaces in an inner portion of the gap.
[0018] In order to provide a continuous annular string of adhesive
in the gap, the holders are rotatable.
[0019] For the case when only one of the holders is arranged to
curve an associated disc element to create the adhesive
introduction gap, it is suitable to make the lower holder with a
planar disc-carrying surface.
[0020] The invention will be described in more detail below with
reference to the accompanying drawings, in which:
[0021] FIG. 1 shows a schematic cross-section of an enlarged
section of a so-called DVD of "SD9" type to illustrate its
construction;
[0022] FIG. 2 shows a schematic cross-sectional view of a device
according to the invention for glueing together DVDs substrates,
where both disc substrates are curved to form an adhesive
introduction gap;
[0023] FIG. 3 shows the device in FIG. 2 in a step after injection
of adhesive, when the disc elements are flattened out and the
homogeneous layer of adhesive has been formed therebetween;
[0024] FIG. 4 shows an alternative embodiment of the device
according to the invention, where only one holder curves its
associated disc element to form an adhesive introduction gap;
[0025] FIG. 5 shows the device in FIG. 4 when the disc elements
have been joined together by gravity and the capillary forces of
the adhesive;
[0026] FIG. 6 shows an additional embodiment of the device
according to the invention, where the disc elements are kept in
separated plane-parallel relation during adhesive application,
whereby the adhesive is introduced by means of an adhesive
introduction nozzle insertable radially from within into the cap
between the disc elements; and
[0027] FIG. 7 shows the device in FIG. 6 in a step after the
introduction of adhesive, when the upper disc element has been
released from its holder after having been joined to the lower disc
element to form a homogeneous adhesive layer between the disc
elements.
[0028] FIG. 1 shows schematically a digital data storing disc of CD
format, namely a so-called digital video disc 10 of the type called
"SD9". Such a disc 10 comprises two disc substrates 12, 14, each
having a thickness of 0.6 mm and a diameter of ca 120 mm and made
of a transparent plastic material such as polycarbonate. Each disc
substrate 12, 14 respectively has an information layer 16, 18
respectively on facing sides containing short 20 and long 22
depressions with a depth of about 0.1 .mu.m. The information layer
16 on the lower disc substrate 12 is coated with a layer of for
example Al, Au or SiN which is semi-reflecting for laser light,
while the information layer 18 on the upper disc substrate 14 is
made completely reflecting. The two disc substrates 12, 14 are
joined together by means of a thin adhesive layer 24 (cirka 14-70
.mu.m), the index of refraction of which should be complementary to
the index of reflection of the substrates (polycarbonate) in order
to avoid any refractive error when the laser light is to read the
upper information layer 18. In FIG. 1, a light beam 26 is shown
which is focused on the lower, semi-reflecting layer 16.
[0029] For DVDs 10 with double information layers, as shown in FIG.
1, it is of the greatest importance that the adhesive layer 24 be
homogeneous and completely free of air enclosures in order to
provide undisturbed focusing of the laser light on the information
layer 18. This problem is, however, not critical in a single layer
DVD ("SD5"), where the upper disc substrate can be a blank
information free disc, i.e. where only a single lower completely
reflecting layer is read.
[0030] FIG. 2 shows schematically a device 28 according to the
invention for glueing together two disc substrates 12, 14. The
device 28 comprises a lower substrate holder 30 and an upper
substrate holder 32, which are rotatable about a central shaft 34.
The holders 30, 32, which can be essentially identical, each have
an outer and inner sealing ring 36 and 38 respectively and are
formed with a thicker hub portion 40 and a thinner peripheral
portion 42 in order to create between the holders 30, 32 a radially
outwardly diverging space 44 (FIG. 3) in order to make it possible
to hold the disc substrates 12, 14 in a convexly curved state for
the application of adhesive, as shown in FIG. 2.
[0031] For the purpose of holding securely the respective disc
elements 12, 14 in a convexly curved state to form an intermediate
radially outwardly diverging gap 46 for the introduction of
adhesive, each of the holders 30, 32 have a surface section between
its outer and inner sealing rings 36, 38, forming therebetween and
with a disc element a space 48 which is in communication with a
vacuum source (not shown). After placing a disc substrate 12, 14 on
each holder 30, 32 and connecting a vacuum source (not shown), the
substrates can be made to curve to the shape shown in FIG. 2 or
similar thereto, thus making it possible to insert an adhesive
dispensing nozzle 50 into the outer broadest portion of the gap 46
in order to dispense a carefully measured amount of a flowable
adhesive towards a narrow portion of the gap so that the adhesive
essentially comes into contact simultaneously with the facing
surfaces of the substrates. By rotating the two holders 30, 32 one
rotation at the same time as adhesive is injected, an annular
string of adhesive 52 is created around the substrate gap. After
application of the adhesive string 52, the nozzle 50 is retracted
from the gap 46. In order to eliminate any uneveness in the
distribution of adhesive in the peripheral adhesive string, the two
holders are also rotatable relative to each other, so that the
adhesive string can be subjected to a shearing effect and thus be
made more even before the disc substrates are brought together. The
relative rotation is performed suitably by causing the two holders
to rotate approximately one half to one complete rotation in
opposite directions. The vacuum in the space 48 is then equalized
so that the disc substrates 12, 14 are released from their
respective holders and spring back to a normal flat state, as shown
in FIG. 3, whereupon the adhesive in the string 52, due to the
bringing together of the disc substrates and the capillary forces
of the adhesive, will be distributed uniformly in the space between
the disc substrates 12, 14. Any air present between the disc
substrates will thus be expelled from the intermediate space, both
radially inwards and radially outwards so that a thin even adhesive
layer is formed which is free from air enclosures.
[0032] FIG. 4 shows an alternative simplified embodiment of a disc
glueing device according to the present invention, which differs
from the device described above only in that the lower holder 30'
is made flat and lacks means for bending the associated disc
substrate. Instead, only the upper holder 32' is arranged to
achieve an adhesive introduction gap 46 and for this purpose it
must bend its associated disc substrate 14 somewhat more than in
the embodiment according to FIGS. 2 and 3 to permit insertion of
the adhesive application nozzle 50.
[0033] FIG. 5 shows the disc elements 12, 14 in their flat state
after adhesive application in the embodiment shown in FIG. 4, after
the adhesive has spread out and filled the gap between the disc
elements 12, 14 to the required extent.
[0034] An additional conceivable embodiment of the device according
to the invention is shown in FIG. 6, where the disc elements 12, 14
at glue application are kept essentially in a plane-parallel spaced
state by a planar lower holder 30", and a planar upper holder 32".
The adhesive is inserted into the gap 46 between the disc elements
of means of an adhesive injection nozzle 50', which can be inserted
into the gap radially from within. After application of a circular
string 52 of adhesive by rotation of the holders 30", 32" one
rotation during adhesive dispensing, the nozzle 50' is then
retracted, and after a relative rotation of the holders for even
spreading of the adhesive string the upper disc element 14 is
released from its holder 32", as shown in FIG. 7, and the disc
elements 12, 14 are brought together by the effect of gravity on
the upper disc element and the effect of capillary forces in the
adhesive, striving to pull the two disc elements 12, 14 towards
each other as the adhesive spreads out and fills the space between
the disc elements forming a uniform adhesive layer free from air
enclosures.
[0035] Within the scope of the invention it is also conceivable to
apply the adhesive by injecting it into the gap via one or more
fixed nozzles, which do not need to be inserted into the gap. It
would thus be sufficient to have such a fixed nozzle which ejects a
well-defined stream of adhesive towards a preferably tapered
portion of the gap 46, making contact at the same time with the two
facing surfaces of the substrates.
[0036] It is also conceivable to make the device in such a manner
that the disc elements form a radially inwardly diverging gap when
an adhesive introduction nozzle of the type shown in FIGS. 6 and 7
is used.
[0037] It is also conceivable within the scope of the invention to
make the substrate holders in such a manner that, after adhesive
application, they also exert a pressure on the disc substrates 12,
14 to accelerate the filling out of the gap with adhesive.
* * * * *