U.S. patent application number 11/248723 was filed with the patent office on 2006-02-09 for device for vacuum-pressing of dvd substrates.
This patent application is currently assigned to KRAUSS-MAFFEI KUNSTSTOFFTECHNIK GMBH. Invention is credited to Martin Eichlseder.
Application Number | 20060027330 11/248723 |
Document ID | / |
Family ID | 7631877 |
Filed Date | 2006-02-09 |
United States Patent
Application |
20060027330 |
Kind Code |
A1 |
Eichlseder; Martin |
February 9, 2006 |
Device for vacuum-pressing of DVD substrates
Abstract
The invention relates to a device for vacuum-pressing of
disk-shaped substrates, in particular DVD substrates into a
finished DVD, wherein the device has a vacuum chamber with two
substrate holders and an intermediate element that can be displaced
inside the vacuum chamber; and wherein the intermediate element
divides the vacuum chamber into a first low-pressure chamber and a
second chamber that can be alternatingly connected to vacuum or to
an overpressure, which makes the device particularly suited for use
with a hot-melt thermoplastic adhesive.
Inventors: |
Eichlseder; Martin;
(Tettenweis, DE) |
Correspondence
Address: |
HENRY M FEIEREISEN, LLC
350 FIFTH AVENUE
SUITE 4714
NEW YORK
NY
10118
US
|
Assignee: |
KRAUSS-MAFFEI KUNSTSTOFFTECHNIK
GMBH
|
Family ID: |
7631877 |
Appl. No.: |
11/248723 |
Filed: |
October 12, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10226095 |
Aug 22, 2002 |
6971428 |
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11248723 |
Oct 12, 2005 |
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PCT/EP01/01979 |
Feb 21, 2001 |
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10226095 |
Aug 22, 2002 |
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Current U.S.
Class: |
156/382 ;
156/556; 156/580 |
Current CPC
Class: |
B29L 2017/005 20130101;
B29C 65/1496 20130101; B29C 65/1406 20130101; B29C 65/4815
20130101; G11B 7/26 20130101; B29C 66/452 20130101; B29C 66/001
20130101; B29C 66/1122 20130101; B29C 65/7847 20130101; Y10T
156/1744 20150115; Y10T 156/1702 20150115; B29C 66/342 20130101;
B29C 65/4845 20130101 |
Class at
Publication: |
156/382 ;
156/556; 156/580 |
International
Class: |
B32B 37/00 20060101
B32B037/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2000 |
DE |
100 08 111.8 |
Claims
1. A device for vacuum-pressing of disk-shaped substrates, in
particular of DVD substrates, comprising: a vacuum chamber; a first
substrate holder for a first substrate housed in the vacuum chamber
and formed as an intermediate element dividing the vacuum chamber
into a first low-pressure chamber connected to a vacuum pump and a
second chamber that can be alternatingly connected to the vacuum
pump and a compressed gas source, said intermediate element
displaceable in the vacuum chamber and being equipped with a
peripheral seal; and a second substrate holder for a second
substrate housed in the vacuum chamber, wherein the intermediate
element on a side facing the first chamber is formed as a first
substrate support for the first substrate, and wherein the second
substrate holder has a second substrate support for the second
substrate disposed in the vacuum chamber opposite the first
substrate support.
2. The device according to claim 1, wherein the vacuum chamber
comprises separate connections for connecting the second chamber
alternatingly to the vacuum pump and the compressed gas source.
3. The device according to claim 1, wherein the vacuum chamber
comprises a single connection from which a connecting line branches
off, for connecting the second chamber alternatingly to the vacuum
pump and the compressed gas source.
4. The device according to claim 1, wherein the intermediate
element is formed as a piston having at least two spaced annular
grooves and the peripheral seal comprises at least two spaced apart
sealing rings inserted in the corresponding annular grooves.
5. The device according to claim 1, wherein the intermediate
element includes a plurality of sections, wherein at least two
sections are provided with a peripheral seal, with the section,
which seals against the first low-pressure chamber, formed as the
first substrate holder; and a plurality of rods disposed between
the plurality of sections.
6. The device according to claim 1, the intermediate element
further comprising circumferentially arranged sliding or roller
bearings enabling displacement of the intermediate element in the
vacuum chamber.
7. The device according to claim 1, wherein the seal further
includes at least one sealing lip.
8. The device according to claim 1, wherein the first low-pressure
chamber includes a cover section being hingedly secured on the
vacuum chamber to enable opening and closing the cover section.
9. The device according to claim 8, wherein the cover section
further includes an axially displaceable centering pin for
centering the second substrate, with the centering pin being
insertable through the second substrate into a center hole provided
in the first substrate when the first substrate is disposed on the
first substrate holder.
10. The device according to claim 1, wherein at least one of the
first and second substrate holders is implemented as a vacuum
plate.
11. The device according to claim 1, wherein at least one of the
first and second substrate holders includes vacuum channels for
holding the first and second substrates by vacuum-suction.
12. The device according to claim 11, wherein the vacuum channels
disposed in the first substrate holder and the second substrate
holder can be operated separately from each other.
13. The device according to claim 11, wherein the vacuum channels
disposed proximate to a center hole of the first and second
substrates have a larger cross section than the vacuum channels
disposed in a peripheral region of the first and second substrate
holders.
14. The device according to claim 11, wherein at least one of the
first and second substrates includes an O-ring surrounding the
substrate.
15. The device according to claim 11, wherein the vacuum channels
can be connected to a compressed gas source, with a compressed gas
being blown through the vacuum channels when the vacuum-suction is
switched off.
16. The device according to claim 15, wherein the compressed gas
blows at least one of the first and second substrates off a
corresponding substrate holder from a center of the substrate
towards the periphery of the substrate.
17. The device according to claim 11, wherein the vacuum channels
disposed near a center of the at least one of the first and second
substrate holders can be operated separately from the vacuum
channels disposed near a periphery of the substrate holder.
18. A device for vacuum-pressing of disk-shaped substrates, in
particular of DVD substrates, comprising: a vacuum chamber; a first
substrate holder for a first substrate housed in the vacuum chamber
and formed as an intermediate element dividing the vacuum chamber
into a first chamber connected to a vacuum pump and a second
chamber connected to a compressed gas source, said intermediate
element displaceable in the vacuum chamber and being equipped with
a peripheral seal; and a second substrate holder for a second
substrate housed in the vacuum chamber, wherein the intermediate
element on a side facing the first chamber is formed as a first
substrate support for the first substrate, and wherein the second
substrate holder has a second substrate support for the second
substrate disposed in the vacuum chamber opposite the first
substrate support, wherein at least one of the first and second
substrate holders includes vacuum channels for holding the first
and second substrates by vacuum-suction, wherein a first plurality
of vacuum channels are disposed proximate to a center hole of the
first and second substrates and have a cross section which is
greater than a cross section of a second plurality of vacuum
channels which are disposed in a peripheral region of the first and
second substrate holders.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a division of prior filed copending U.S.
application Ser. No. 10/226,095, filed Aug. 22, 2002, which is a
continuation of prior filed copending PCT International application
no. PCT/EP01/01979, filed Feb. 21, 2001 and which claims the
priority of German Patent Application Serial No. 100 08 111.8,
filed Feb. 22, 2000, pursuant to 35 U.S.C. 119(a)-(d).
FIELD OF THE INVENTION
[0002] The invention relates to a device for vacuum pressing of
disk-shaped substrates, in particular DVD substrates into a
finished DVD, and more particularly to a device that uses a
hot-melt thermoplastic adhesive.
BACKGROUND OF THE INVENTION
[0003] Various conventional machines apply vacuum and pressure to
join disk-shaped substrates, such as DVD substrates, by using both
hot-melt adhesives and UV-curable varnishes. UV-curable varnish
requires a smaller pressure than hot-melt adhesive. Also, with
UV-curable varnish, the superpositioned substrates still float on
top of each other as long as the UV varnish is not cured by
exposing it to UV radiation. Conversely, with a hot-melt adhesive,
the position of the substrates is immediately fixed in upon contact
and can no longer be adjusted.
[0004] DE 197 15 779 A1 describes a method for joining two DVD
substrates with a UV varnish by inserting one of the substrates in
the cover section and the other substrate in the bottom section of
a vacuum chamber and fixing them in a centered position, and by
placing the cover section on the bottom section with the adhesive
layers opposing one another. After the vacuum chamber is evacuated
and the pressure has decreased below a predetermined pressure, a
centering/clamping device disposed in the cover section is released
and the upper substrate falls onto the lower substrate, whereby the
falling motion is reinforced by several weights which are arranged
in the cover section around the central hole of the substrate and
provided with axial guide rods. Springs and the like can be
provided instead of weights. When the two adhesive layers of the
substrates are then positioned on top of each other with the
adhesive layers still wet, the vacuum chamber is vented to air,
whereby the atmospheric pressure causes those areas between the
adhesive and the two substrates that have not yet made contact to
be pressed against each other. This arrangement is not suitable for
gluing substrates with an applied hot melt adhesive, because the
weights and the atmospheric pressure cannot generate the pressing
force required for precisely joining the substrates. In addition,
the contact pressing force produced by the weights is not
distributed uniformly across the entire substrate surface.
[0005] JP 1-204727 A suggests producing optical data carriers by
coating two substrates with an adhesive of the hot-melt type and
subsequently joining the two substrates in a vacuum chamber,
whereby certain upper limit values for pressure, temperature and
pressing force are preset. A wall in the vacuum chamber has
openings for piston rods which can be used to press the pressure
plates against each other, with the substrates placed between the
pressure plates.
[0006] EP 0 735 530 A1 describes a system where the DVD substrates
have initially an adhesive of the hot melt type (thermoplastic
adhesive) spread across their surfaces. Subsequently, a UV-curable
liquid adhesive is filled in a recess provided proximate to the
central hole in one substrate. The substrate that has only hot melt
adhesive applied, is then rotated by a handling system by
180.degree., so that the sides of the substrates having the applied
adhesive face one another, and placed on the lower substrate. In
this joined state, the two substrates and/or the DVD are placed
onto a lower pressure plate which has in its center a quartz glass
window for admitting UV radiation, and which also forms the bottom
plate of a vacuum chamber. The cover section of the vacuum chamber
is moved from the top position downwardly, until the edge of the
cover contacts the bottom plate, thereby forming a chamber, which
can be evacuated through a connection disposed in the bottom plate.
The piston rod of a piston-cylinder unit passes through the cover.
Another pressure plate is located on the lower end of the piston
rod. When the pressure in the vacuum chamber drops below a
predetermined pressure, the pressure is applied to the upper piston
rod which moves the piston rod downwardly and presses the
superpositioned substrates together between the upper pressure
plate and the bottom plate. At the same time, UV light is
introduced through the quartz glass window into the vacuum chamber
to cure the UV adhesive. After a time that can be preset, the
vacuum chamber is vented to air, the piston is moved downwardly and
the UV irradiation is tuned off. This concludes the process step of
joining the substrates and the completed DVD can be removed.
[0007] These conventional systems for joining DVD substrates have
the disadvantage that the vacuum chamber, on one hand, and the
pressing device, on the other hand, are implemented as separate
units and are operated independent of each other. As a result, the
pressure plates which press the substrates against each other are
always restrictively guided, so that a small tilt in the position
of the substrates cannot be easily compensated. When such small
tilt in the position of the substrate occurs, a very high pressing
force is applied at one location and a rather lower pressing force
is applied at another location. This impairs the parallel alignment
of the DVD.
[0008] The German utility model DE 299 04 325 U1 describes a device
for joining DVD substrates by applying a vacuum. This reference
provides a collapsible chamber, whereby one substrate is inserted
in the cover section and the other substrate in the bottom section
of the vacuum chamber. The substrate holder which is located in the
bottom portion is movably supported. In addition, a lifting plate
is provided, from which several guide shafts extend upwardly
through the bottom portion of the vacuum chamber. The guide shafts
are operatively connected with the lower substrate holder so as to
enable an additional mechanical displacement of the lower substrate
holder for increasing the pressing force. When a low-pressure is
applied between the substrates, in a first step, the lower moveable
substrate holder moves upwardly and the substrates are glued
together with a first value of the pressing force. In a second
step, the lifting plate is moved upwardly and mechanically
displaces via the a guide shafts the lower substrate holder,
thereby increasing the pressing force to a second value. However,
the guide shafts have to be disadvantageously guided vacuum-tight
through the bottom portion of the vacuum chamber, which requires
complex sealing measures. Moreover, at least the lifting plate and
the guide shafts must disadvantageously be moved downwardly by the
joining vacuum due to the mechanical connection with the lower
substrate holder. Consequently, the drive means for the lifting
plate have to be mechanically decoupled from this lifting plate, or
the drive means has to also be moved downwardly by the joining
vacuum. This system also restrictedly guides the substrates due to
the guide shafts and the lifting plate. This device therefore has
the same disadvantages as the conventional devices described
above.
[0009] It is desirable to provide a device for vacuum pressing of
DVD substrates, which allows for relative alignment of the
substrates to be glued. The device should preferably have a
relatively simple construction and the pressing force employed for
joining and pressing the DVD substrates should preferably be
continuously adjustable across a wide range.
SUMMARY OF THE INVENTION
[0010] According to one aspect of the invention, a device for
vacuum-pressing of disk-shaped substrates, in particular of DVD
substrates, includes a vacuum chamber; a first substrate holder for
a first substrate housed in the vacuum chamber and formed as an
intermediate element dividing the vacuum chamber into a first
low-pressure chamber and a second overpressure chamber. The
intermediate element can be displaced in the vacuum chamber and is
equipped with a peripheral seal. The device further includes a
second substrate holder for a second substrate housed in the vacuum
chamber. The intermediate element, on a side facing the
low-pressure chamber, is formed as a first substrate support for
the first substrate. The second substrate holder has a second
substrate support for the second substrate that is disposed in the
vacuum chamber opposite the first substrate support.
[0011] The process flow during vacuum pressing can thereby be
optimized by controllably adjusting, on one hand, the low-pressure
and, on the other hand, the overpressure, whereby the intermediate
element is pulled in when the vacuum is applied, causing a decrease
in volume of the low-pressure chamber, which pulls the substrates
against each other. The process flow can be further optimized by
building up additional pressure in the overpressure chamber at an
appropriate time, whereby the intermediate element and thereby also
one of the substrates are pressed sufficiently strongly against the
other substrate. Since the intermediate element is supported only
by the seal(s) and is therefore floating to some extent, the
intermediate element can perform a small tilting motion, allowing
the substrate holder of the intermediate element to conform within
certain limits to the position of the other substrate. It should be
noted that the molded substrates do not have exactly the same
thickness across their surface area, so that regions are formed
that are subjected to a high pressing force, where the other
regions are subjected to a lower pressing force.
[0012] According to another aspect of the invention, a device for
vacuum-pressing of disk-shaped substrates, in particular of DVD
substrates, includes a vacuum chamber and a first substrate holder
for a first substrate housed in the vacuum chamber and formed as an
intermediate element dividing the vacuum chamber into a first
low-pressure chamber connected to a vacuum pump and a second
chamber that can be alternatingly connected to the vacuum pump and
a compressed gas source. The intermediate element can be displaced
in the vacuum chamber and is equipped with a peripheral seal. A
second substrate holder for a second substrate is also housed in
the vacuum chamber. The intermediate element on a side facing the
first chamber is formed as a first substrate support for the first
substrate. The second substrate holder has a second substrate
support for the second substrate disposed in the vacuum chamber
opposite the first substrate support.
[0013] By connecting the lower chamber selectively and
alternatingly to a compressed air source and a vacuum pump, a
vacuum can be produced on both sides of the intermediate element.
When the same vacuum pressure is applied on both sides, then there
is a force equilibrium and the intermediate element initially
remains in its initial position. When a certain value of the
low-pressure is reached, the pressure in the lower chamber is
raised to ambient pressure, which causes the intermediate element
to move upwardly and the substrates to contact each other.
Subsequently, the system is switched over to an overpressure to
enable a reliable pressing operation. The joining speed of the
process can be optimized by adjusting the rate at which the
pressure in the lower chamber is raised. Depending on the joining
speed, the joining process can be adjusted to be rather hard or
rather soft, which is important for brittle or sensitive layers,
such as DVD 18, DVD-R and DVD-RW.
[0014] Advantageous embodiments of the invention may include one or
more of the following features. The device can include pressure
generating means for generating a pressure on at least one of the
first and second substrate holders, such as a vacuum pump and a
compressed gas source. The intermediate element can be formed as a
piston having at least two spaced annular grooves, with the
peripheral seal having at least two spaced apart sealing rings
inserted in the corresponding annular grooves.
[0015] The intermediate element further can be made of several
sections, wherein at least two sections are provided with a
peripheral seal. The seal can include one or more sealing lips. The
section forming a boundary between the first low-pressure chamber
and the second chamber is formed as the first substrate holder.
Several rods can be disposed between the sections.
[0016] The intermediate element can further include
circumferentially arranged sliding or roller bearings, enabling the
intermediate element to move in the vacuum chamber. The first
low-pressure chamber can include a cover section being secured on
the vacuum chamber by a hinge, to enable opening and closing the
cover section. The cover section may further include an axially
displaceable centering pin for centering the second substrate,
wherein the centering pin can be inserted through the second
substrate into a center hole provided in the first substrate when
the first substrate is positioned on the first substrate
holder.
[0017] Advantageously, at least one of the substrate holders can be
implemented as a vacuum plate which can include vacuum channels for
holding the substrates by vacuum-suction. The vacuum channels can
be operated separately of each other. The cross sectional area of
the vacuum channels disposed near the center of the substrate
holders is greater than the cross sectional area of the vacuum
channels near the peripheral region of the substrate holders. The
vacuum channels can also be connected to a compressed gas source,
wherein the compressed gas can blow at least one of the substrates
off a corresponding substrate holder from a center of the substrate
towards the periphery of the substrate. The vacuum channels located
near the center of the substrate holders can be operated separately
from the vacuum channels located near the periphery of the
substrate holder. An O-ring can surround either substrate for
providing a seal.
[0018] The vacuum chamber, in particular the second chamber, can
have either separate connections or a single connection from which
a connecting line branches off, for alternatingly connecting the
second chamber to the vacuum pump and the compressed gas
source.
[0019] Further features and advantages of the present invention
will be apparent from the following description of preferred
embodiments and from the claims.
BRIEF DESCRIPTION OF THE DRAWING
[0020] The following figures depict certain illustrative
embodiments of the invention in which like reference numerals refer
to like elements. These depicted embodiments are to be understood
as illustrative of the invention and not as limiting in any
way.
[0021] FIG. 1(a)-FIG. 1(m) show schematically an exemplary device
for vacuum pressing of substrates at various stages of the
process;
[0022] FIG. 2 is an enlarged view of the device for vacuum pressing
of substrates at the process stage depicted in FIG. 1(i);
[0023] FIG. 3 is a first embodiment of the exemplary device for
vacuum pressing in an open position;
[0024] FIG. 4 is a top view of the device of FIG. 3; and
[0025] FIG. 5 is a second embodiment of the exemplary device for
vacuum pressing in an open position.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0026] The invention is directed to a device for vacuum-pressing of
substrates, in particular DVD substrates.
[0027] Referring first to FIG. 1, a vacuum chamber 1 includes a
bottom section 2 for receiving a first (A) substrate 3 and a cover
section 4 for receiving a second (B) substrate 5. The vacuum
chamber can be closed by rotating the cover section 4 about an axis
6 that is perpendicular to the plane of the drawing sheet. First,
the DVD substrates 3 and 5, to which an adhesive has been applied,
are inserted in the cover section and the bottom section (FIG. 1a),
with the surface having the adhesive pointing upwardly. The
substrates are positioned in the bottom section and the cover
section on vacuum plates and are fixed in their position by the
vacuum (holding vacuum). In the next step of the process (FIG. 1b),
the holding vacuum on the A-substrate 3 and the holding vacuum on
the B-substrate 5 are switched off, the centering pins 7 and 8 are
extended so as to pass through the corresponding center hole of the
substrates. Thereafter, the holding vacuum on the B-substrate 5 is
turned on again (FIG. 1c), the B-centering pin 8 is retracted (FIG.
1d), the cover section 4 is rotated about the axis 6 and the vacuum
chamber 1 is closed (FIG. 1e). To prevent the substrates from being
pulled against each other due to electrostatic charges, the holding
vacuum on the A-substrate 3 is turned on again when the vacuum
chamber is closed. After the vacuum chamber is closed, the
B-centering pin 8 is extended, passing through the center opening
of the A-substrate 3, whereby the A-centering pin 7 is
simultaneously pushed back (FIG. 1f). Both DVD substrates A and B
are now centered together on the B-centering pin 8. The joining
vacuum is now applied, i.e., the vacuum chamber 1 is evacuated with
the vacuum pump, causing the joining plate A, i.e., substrate
holder 9, to be pulled upwardly by the vacuum (FIG. 1g). To provide
support, compressed air is applied to the substrate holder 9 from
below (FIG. 1h). When the lower substrate holder 9 with the
A-substrate 3 has come within a certain distance of the B-substrate
5, the holding vacuum is switched off on both substrates A and B,
and air is admitted to the substrates A and B through the vacuum
channels in the substrate holders. Both substrates A and B are then
blown off the substrate holders (FIG. 1i), which will be described
in more detail below with reference to FIG. 2. Since neither
substrate A and B is connected to the vacuum plates shortly before
contact between the adhesive surfaces is established, the
substrates can once more be precisely centered via the common
centering pin. When the substrates are blown off, they are bent in
the middle from the inside to the outside (see also FIG. 2), so
that the adhesive surfaces establish contact from the inside
towards the outside, whereby the joining vacuum between the
substrates A and B also removes the residual air between the
substrates. The substrates A and B are now joined; the substrate
holder 9 (see FIG. 3) which is formed as a piston reaches a stop,
and the desired pressure (FIG. 1j) can build up under the piston.
When the pressing force has been applied for a sufficiently long
time, the B-centering pin 8 is retracted, the holding vacuum A is
switched on and the joining vacuum is switched off (FIG. 1k). As
soon as the pressure is switched off, the piston can retract, the
blow-off at B is switched on and the A-centering pin is extended
(FIG. 11). Finally, the cover section 4 is rotated in the open
position and the holding vacuum A is switched off. The completed
DVD is centered on the substrate holder 9 (the plate A) and can now
be removed.
[0028] FIG. 2 is an enlarged view of the process step 1i. Vacuum
channels 11 to 13 are disposed in both substrate holders 9 and 10,
with the main channels 11 which are each connected to a vacuum pump
extending horizontally in the substrate holders 9 and 10. Channels
12 branch off the main channels 11 proximate to the center hole,
whereas channels 13 branch off the main channels 11 in the
peripheral region and terminate in the surface of the substrate
holders. The channels 12 have a larger diameter that the channels
13. This system of channels helps form the holding vacuum in the
process steps depicted in FIG. 1. By switching from vacuum to
blow-off, air is also admitted via this channels system in the
process step depicted in FIG. 1i for blowing off the substrates A
and B in the center. The substrates are centered by the B-centering
pin 8, which passes through both center holes. The lower substrate
holder 9 has a sufficiently large opening for the B-centering pin
8. By blowing off the substrates A and B, the substrates are
released from the surface of the substrate holders and can be
centered exactly once more before the adhesive-coated surfaces make
contact with each other. The substrates are preferably released and
blown off first on the inside due to the larger vacuum bore 12 on
the inside. Releasing and blowing off the substrate from the inside
outside significantly reduces the risk of air inclusions between
the substrates A and B. Alternatively, the inner and outer channels
12 and 13, respectively, can be separated, as shown in the example
of FIG. 5, so that the vacuum on the outside can be switched off
with a delay by a separate valve and can be switched over with a
delay for blowing off the substrates. When the vacuum channels 12
and 13 are operated separately (see FIG. 5), then the vacuum
channels 12 and 13 can have the same diameter. Holdings the
substrates at the marginal regions can be supported by using upper
and lower O-rings. By separately forming and controlling the vacuum
channels in the upper substrate holder 10 and in the lower
substrate holder 9, different blow-off pressures P1 and P2 can be
set, whereby a different dishing can be defined to counteract or
compensate for existing dishing effects.
[0029] FIG. 3 shows the vacuum chamber 1 in an open position, with
substrates A and B (reference numerals 3 and 5) inserted in the
bottom section 2 and the cover section 4, as well as with the
centering pins 7 and 8. Also seen in the bottom section and the
cover section are the vacuum channels 11, 12 and 13 for the holding
vacuum and the blow-off feature. It can also be seen that the lower
substrate holder 9 is formed as a piston, which is floatingly, but
sealingly, supported by an upper sealing lip 14 and a lower sealing
lip 15 for displacement in the bottom section 2. The guide means 25
can be provided in the region of the upper sealing lip. Otherwise,
the piston 9 is spaced apart from the interior wall of bottom
section. In this way, the floating piston 9 can optimally adapt to
the stationary cover. When the vacuum chamber is closed and sealed
with a sealing ring 18, a two-chamber system is formed whereby
above the piston 9 a low-pressure chamber 20 is formed having a
forming vacuum and below the piston 9 an overpressure chamber 19 is
formed which is operatively connected with a compressed air source
21 (not shown). The lower substrate holder 9 is drawn in by the
forming vacuum in the low-pressure chamber 20 and suctioned against
the upper substrate holder 10. In the process steps depicted in
FIGS. 1h to k, air is introduced into the overpressure chamber 19
and the lower substrate holder 9 is moved upwards by this
compressed air. A mechanical misalignment during the pressing
operation is eliminated by guiding the piston 9 only in its upper
range and otherwise connecting the piston 9 with the interior wall
only by the sealing lips 14 and 15. When the lower substrate holder
or piston 9 reaches a stop, the required pressure can be applied to
the piston 9 via the overpressure chamber 19, so as to complete the
joining process with a pressing step.
[0030] FIG. 4 shows a top view of the vacuum chamber 1 in an open
position. Identical reference numerals describe identical
elements.
[0031] Since the adhesive of the hot melt type is free of solvents
and melts and becomes tacky at high temperatures, the substrate
holder 9 and/or 10 as well as the cover section and/or the bottom
section of the vacuum chamber can be heated to shorten the time
between the joining operation and the cooling step.
[0032] In the second embodiment of the joining station according to
the invention illustrated in FIG. 5, the lower chamber 19 is
connected to both a compressed air source 21 and a vacuum pump 24
and can alternatingly be filled with compressed air or evacuated.
For reducing the amount of air entrained between the substrates as
much as possible before joining, a high vacuum is required in the
joining space 20 between the substrates. A high joining vacuum
reduces air inclusions between the adhesive-covered surfaces of the
substrates. This improves the quality of the glued surface as well
at the adhesion, which results in an improved stability and
flatness of the bonded disk. For achieving a high joining vacuum of
approximately 50 mbar and below, the lower chamber 19 is initially
also connected to a vacuum pump 24 and also evacuated. In other
words, an identical vacuum pressure is applied to both sides of the
piston 9. The low-pressure chamber 20 (=joining vacuum chamber) and
the lower chamber 19 have the same diameter. Accordingly, the
forces are balanced and the piston 9 initially remains in its
initial position. When the desired vacuum is reached on both sides
of the piston 9, the pressure in the lower chamber 19 is raised to
ambient pressure, allowing the piston to move upwardly due to the
pressure difference. Subsequently, the system is switched over to
the compressed air source 21 and the substrates are pressed
together as shown in the example of FIG. 3. The joining speed,
i.e., the speed at which the piston 9 moves upwardly, can be
optimized for the process by adjusting the speed at which the
pressure is raised from vacuum to ambient pressure. The joining
process can be adjusted to be rather hard or rather soft by
adjusting the joining speed, which is important for brittle or
delicate layers, such as DVD 18, DVD-R, and in DVD-RW. In all other
aspects, the construction and the functionality are identical to
those of the embodiment of FIG. 3. Identical reference numerals
describe identical elements.
[0033] To facilitate joining of the two substrates from the inside
to the outside, the upper substrate 5 is initially slightly curved
with the help of the upper centering pin 8, which has for this
purpose a suitable shoulder. Then the vacuum on the inner vacuum
channels 12 is switched off. Thereafter, the vacuum on the outer
vacuum channels 13 is switched off. Optionally, additional vacuum
channels 26 can be provided in the center region of the substrate,
which can preferably be connected with the inner vacuum connection.
A soft support for the substrates, for example PAI, facilitates
joining from the inside to the outside. After the inner vacuum is
switched off, the system can optionally be switched over to
blow-off.
[0034] Positioning and orientation of the substrates A and B
relative to one another can be improved by mechanically
interlocking the cover section 4 with the bottom section 2 after
the joining station is closed.
[0035] While the invention has been disclosed in connection with
the preferred embodiments shown and described in detail, various
modifications and improvements thereon will become readily apparent
to those skilled in the art. Accordingly, the spirit and scope of
the present invention is to be limited only by the following
claims. What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims and their
equivalents:
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