Note: Descriptions are shown in the official language in which they were submitted.
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CA 02157033 2002-05-17
DEVICE FOR LACQUERING OR COATING
OF PLATES OR DISKS
The present invention relates to a device for lacquering or
coating of thin elements, particularly plates or disks with
an open channel and in particular with an open channel that
is narrowed to a capillary, especially for coating glass
plates for LCD production.
In the field of thin layer technology, especially for the
production of LCD monitors, masks for semi-conductor
manufacture, semi-conductor or ceramic substrates etc., the
following problem is often encountered: Rectangular or
round plates must be provided with a uniform layer of
lacquer or other initially liquid media such as color
filters or special protective layers.
It is therefore an object of the present invention to
improve the known lacquering and coating devices and
methods and to simplify their constructive design.
According to one aspect of the present invention, there is
provided a device for lacquering or coating a thin flat
part, comprising:
- an upwardly facing capillary gap for coating a
downwardly facing surface of the thin flat part with a
coating of a liquid coating medium contained in said
capillary gap; and
- a linear transport device for placing said thin flat
part above said capillary gap in such a way that said thin
flat part is at a predetermined distance of less than
0,2 mm above said capillary gap to prevent contact between
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CA 02157033 2002-05-17
mechanical parts of said capillary gap and said thin flat
part during coating process, and for advancing said
downwardly facing surface above said capillary gap and at
said predetermined distance such that a thin layer of said
liquid coating medium is deposited on said downwardly
facing surface by capillary and adhesion effects.
According to another aspect of the present invention, there
is provided a method for lacquering or coating a thin
element with a coating medium, comprising step of:
- providing a capillary gap having an upper end and a
lower end,
- supplying said lower end with said coating medium,
- attaching an uncoated thin element to a holding device
with the surface to be coated facing downwardly;
- linearly advancing said surface to be coated across
the upper end of said capillary gap in order to deposit a
thin layer of said coating medium on said surface by
capillary and adhesion effects, without allowing said thin
element to come into physical contact with the upper end of
said capillary gap, a distance of less than 0,2 mm being
maintained during a coating process between the upper end
of said capillary gap and said surface to be coated.
By the expression "placing" or "means for placing" one
should understand the fact that either the holding device
supporting the thin element is displaceable towards the
capillary slot or the holding device is stationary and it
is the capillary slot which is displaced towards and under
the surface to be coated of the thin element.
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CA 02157033 2002-05-17
According to another aspect of the present invention, there
is also a method for lacquering or coating a thin plate,
said method comprising the steps of:
a) providing a channel and filling said channel with a
liquid coating medium;
b) arranging in said channel two elements at a distance
from each other for forming therebetween a predetermined
gap so that said predetermined gap can be supplied with
said liquid coating medium from said channel;
c) advancing said plate towards said predetermined gap
with a surface to be coated facing downwardly;
d) decreasing said distance between said two elements to
reduce said predetermined gap into a capillary gap and to
press an amount of the liquid coating medium out of said
capillary gap;
e) linearly moving said plate across the capillary gap
for depositing a film of the liquid coating medium on the
plate by a capillary effect and by adhesion;
f) enlarging said distance between said two elements to
increase said capillary gap into said predetermined gap in
order to cancel the capillary effect and preserve the
liquid coating medium; and
g) repeating the steps c) through f).
In a preferred embodiment, it is possible to place the
surface to be coated accross the upper end of said
capillory slot by maintaining the holding device and
therefore the thin element stationary and displacing the
capillary slot under it. In such situation, the means for
placing the thin element above said capillary slot
comprises means for displacing said capillary slot below
said thin element which is maintained stationary.
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CA 02157033 2002-05-17
According to the present invention, there is also provided
use of the devices and the methods of the present invention
in the manufacture of LCD monitors, of masks for semi-
conductors and semi-conductor substrates and ceramic
substrates.
The preferred embodiments are explained below in general
terms.
The thin element, for example a plate, with the surface to
be lacquered facing downwardly is guided across the channel
that is designed such that it acts as a capillary and thus
supplies
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2157Q~~
the liquid coating medium or lacquer automatically and with an
especially uniform velocity. The capillary effect is achieved
by providing a narrow slot which preferably is less than
0.5 mm wide. Due to -the capillary effect, the lacquer or other
liquid coating medium advances automatically upwardly with a
constant velocity ag<~inst the force of gravity in the slot and
exits at the channel surface. Above the slot the stream of
lacquer contacts as a narrow line the plate surface to be
coated and is deposited thereon.
It is advantageous to generate the capillary by providing two
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vertically extending ithin plates that are immersed in the open
channel filled with a liquid coating medium, whereby the
distance between them can be adjusted in an infinitely variable
manner. Thus, between the two plates over the entire length of
the channel a slot with a width that corresponds mast suitably
to the desired capillary effect can be formed. Accordingly, the
capillary geometry can be adjusted to the various types of
plates to be coated.
It is especially advantageous to guide the plate to be
lacquered or coated with a uniform and low velocity at a very
small distance, for e:~ample, less than 0.2 mm, across the upper
end of the capillary slot. Accordingly, the lacquer, after
exiting from the upper end of the capillary contacts directly
the plate surface. Due to an adhesion effect, the lacquer is
attached to the plane surface and is carried away from the
channel surface with the plate. The result is that the
following lacquer, in addition to its upward movement due to
the capillary effect, is pulled from the channel and, as a
function of the velocity of the plate, is deposited in a
defined layer thickness on the plate. Due to the adhesion
effect of the lacquer at the plate surface there is also no
risk that the lacquE~r after exiting from the capillary slot
could flow laterally, resulting in a decrease of the
uniformness of the layer thickness.
It is expedient and advantageous to open the capillary slot
between the plates after each lacquering process to between
2 mm and 3 mm. This prevents the automatic upward movement of
the lacquer, which is. undesirable between lacquering processes.
It has been shown that during longer residence within the
capillary slot the lacquer changes its properties. Such changes
are disadvantageous for the lacquering process. However, when
the capillary slot :is widened to between 2 mm and 3 mm, the
lacquer remains unchanged.
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Expediently and advantageously, the slot between the plates is
narrowed directly before starting the lacquering process to
reach the capillary width. Accordingly, the lacquer located
between the plates :is in a first step pressed mechanically
upwardly until it exits from the channel and contacts the plate
surface waiting to 1'oe coated. Thus, the coating process is
started, which is sulbsequently commenced due to the capillary
effect within the slot that is now of a capillary width, the
movement of the plate, and the adhesion effect, as described
to above.
According to another preferred embodiment of the present
invention, it is no longer necessary to feed the plates with a
leading corner and at a small upward angle to the horizontal
across the lacquering channel. Furthermore, it is no longer
required that a liquid meniscus forms above the channel so that
a lacquer supply via a compensation tank becomes obsolete.
Further details and advantageous embodiments of the invention
20 may be taken from examples presented in the following and
represented in the drawings, which examples are not to be
understood as a limiitation of the invention. In the drawings:
Fig. 1 shows a side view of the inventive design of a
lacquering and coating device; and
Fig. 2 shows a cross-section of the channel with capillary
slot according to Fig. 1 at the beginning of a coating
process.
30 Fig. 1 shows a first embodiment of an inventive coating device
10. A channel 12 as well as supports 13 and 14 for a linear
transport device 15 are connected to a frame 11. The movable
portion of the linear transport device 15 is facing
downwardly: To it a rotatable holding device 16 for a plate 17
to be coated is connected. The plate 17 is, for example, a
glass plate to be coated with lacquer for manufacturing
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subsequently a mask or an LCD monitor. The plate 17 is
attached to the holding device 16, for example, by a vacuum
suction effect. For this purpose, the holding device 16 is
provided with corresponding non-represented vacuum bores.
Within the context of the invention it is also possible to use
other holding devices that are known to a person skilled in the
art.
The channel 12 is shown in cross-section in Fig. 1 and in an
enlarged view in Fig. 2. The cavity 18 of the open channel 12
is partially filled with lacquer. Two thin plates 19 and 20 are
immersed from above in the lacquer filling. The plate 19 is
fixedly connected at the location 33 to the upper edge of the
channel 12. It is not displaceable. On the ather hand, the
plate 20 is connected to a linear displacement unit 22 by means
of a suitable device. Via this displacement unit 22, the plate
2o can be moved back and forth in the direction of the arrow
23. Accordingly, the width of the slot 24 between the plates 19
and 20 can be adjusted in an infinitely variable manner
especially to a spacing between the plates that results in a
slot 24 with capillary action that is less than 0.5 mm wide.
For achieving optimal lacquering or coating results, the
corresponding liquid coating medium sho~.ild preferably have a
certain temperature and should preferably be very clean.
Accordingly, it is supplied from a supply tank 28 via a
temperature control unit 29 and a filter 30 to the channel 12.
Conveying can be achieved by generating a pressure (gas
cushion) within the ;supply tank 28 or by providing a suitable
arrangement of the supply tank 28 so that the liquid is
conveyed by the geodetical height difference to the channel 12.
However, other suitable solutions for liquid conveyance are
known to a person sk:i.lled in the art.
For a fully automatE~d version of the coating device, at the
location indicated at 31 an automated loading device and at the
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location 32 an automated unloading devic,~ are provided. The
loading device 31 rf~moves a plate l7 to be coated fram a
magazine connected at a certain location and conveys the plate
to the plate holding dlevice 16. The unloading device 32 removes
the plate 17 from the holding device 16 and loads it into
another magazine connected at a certain location.
Mode of opefation of the lacquering and coating device l0
l0 In a first step, the plate 17 is automatically or manually
connected to the holding device 16. By rotating the holding
device 16, its position can still be corrected. The holding
device 16, at this time, is located at the location indicated
at 31 in Fig. 1. After the plate 17 has been correctly
positioned at the holding device 16, the linear transport
device 15 is set in motion in the direction of arrow 26; i.e.,
in direction toward the open channel 12.
Plate 17 is thus advanced from one side to the upper edge of
20 the slot 24. As soon as the leading edge 25 of the plate l7 is
positioned directly above the slot 24, the~plate 20 within the
channel 12 is advanced toward the plate 19 such that a suitable
capillary width is provided between the plates. Due to the
narrowing of the capi:Llary slot 24, a small amount of liquid is I
forced out at the upper side of the capillary slot 24 against
the leading edge of t:he surface to be coated of the plate 17.
Thus, the coating process has begun. The plate 17 is now
advanced further at a uniform velocity by the linear transport
device 15 in the direction of arrow 26. Due to adhesion, a thin
30 liquid layer is deposited on the plate surface. The required
liquid flow is supplied by the capillary action of the
capillary slot 24. ~'
It is possible to support the plate on a balding device 16, and
to move the capillary slot 24 relative to the holding device so
that the step of coating is performed with said holding device
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being stationary and the capillary slot being moved across the
plate.
The coating process .i.s terminated as soon as the rear edge 27
of the plate 17 has passed the capillary slot 24. The two
plates 19 and 20 are now moved apart to a distance of 2 to 3 mm
for the aforementioned reasons until the next coating process
is to be performed. The coated plate 17 is advanced to the
location indicated at 32 where it may be automatically or
l0 manually removed from the holding device 16.
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