AU701991B2 - Process and device for lacquering or coating a substrate - Google Patents

Abstract

The appts. includes a container (10) from which a substrate (29) is covered with liq. (11) through a capillary tube (13) ending in a nozzle (40). A coating (31) is typically formed up to 5 to 50 microns thick in the wet condition. The structure (12) enclosing the capillary is mounted on a vertical rod (15) movable within a bellows (17) by e.g. a hydraulic or pneumatic jack (44). Upon completion of a coating, the tube is lowered through the aperture (48) in the top of the container, until the nozzle is below the surface of the liquid. The aperture is closed (46) by translation of a cover plate (19).

Description

S CD/98175003.1 1 PROCESS AND DEVICE FOR LACQUERING OR COATING A

SUBSTRATE

BACKGROUND OF THE INVENTION The invention relates to a method and a device for lacquering or coating a substrate by means of a capillary channel. In this specification, the terms "lacquering" and "lacquering processes", are also intended to respectively include coating and coating processes with appropriate fluids, ie. with appropriate lacquers or appropriate coating fluids. The term "fluid" is intended to include lacquer or coating liquid.

In the field of thin layer technology, especially in the production of LCD monitors, of masks for semi-conductor production, semi-conductor substrates or ceramic substrates etc. a problem often encountered is to provide rectangular or round plates with a uniform layer of lacquer or other initially liquid media, for example, with colour filters, photo lacquers, or with special protective layers. In accordance with current engineering practices for lacquering, the plates are horizontally attached to a turntable. To the center point of the plate a certain quantity of lacquer is dripped from above by means of a nozzle. Then the turntable is rotated. Due to centrifugal forces the lacquer is distributed on the substrate during rotation ("spin coating"). By this technique, a large portion of the lacquer is spun across the rim of the substrate. The achievable uniformity of the layer thickness depends on the magnitude of the rotation acceleration, the rotation speed, as well as on the viscosity of the lacquer.

9 9 *o* .oeO 25 9 9 9 9 99 99 9 9 Difficulties with respect to the uniformity of the lacquer thickness on rectangular, plate-shaped substrates are encountered with this known process, especially in the area of the rims of the substrate. In these areas, strips of greater lacquer thickness, ie., so-called lacquer bulges, are commonly observed. This causes a substantial reduction in the uniformity of the lacquer thickness.

In order to collect the lacquer which is spun across the rim of the substrate, such lacquering turntables are commonly mounted within a kind of container.

CD/98175003.1 2 During the lacquering process spun-off lacquer may splash back onto the surfaces of the substrate. This is disadvantageous for the further processing of the substrate. Moreover, with this known method up to more than 90% of the applied lacquer quantity is spun over the rim of the substrate; this excess lacquer can only be reused at very high expenditure/technical resources. The size of the plates that can be lacquered or coated, has an upper limit. Furthermore, small particles may get ground off and released from the rotating parts of such devices, deposit on the surfaces of the plates, and interfere with the subsequent processes.

Moreover, during the spinning operation, lacquer hits the edge of the substrate and this can lead to problems in subsequent processes. Furthermore, the entire construction and the drive of such a turntable are complicated and expensive.

An improvement in lacquering and coating processes was achieved by a device for lacquering and coating plates (WO 94/25177) with which the lacquering or coating liquid is applied to the downwardly facing surface of the substrate from below by means of an open channel that is narrowed down to a capillary slot. The substrate is guided across the channel at a constant speed. The channel is formed in such a way that it acts as a capillary tube and thus supplies the lacquer automatically and at a particularly constant speed. The capillary action is achieved by the channel being only, for example, less than 0.5 mm wide. As a result of the capillary action the fluid automatically and at a constant speed rises within the capillary slot, against the force of gravity, and flows out at its outlet opening. Above the slot the lacquer stream contacts the surface that is to be coated in a narrow line and is deposited on this surface as a uniform layer while the substrate is moved relative to the outlet opening.

25 Thus, the lacquering or coating process is carried out by combined use of capillary action and adhesive action. Within this device the uniformity of the thickness of the lacquer layers, particularly on rectangular substrates, can be improved, and the required lacquer quantity decreases. It can have a disadvantageous effect on the operation of the device that the fluid, in longer 30 intervals between the single lacquering or coating processes, begins to dry or o dries out in the area of the outlet opening of the capillary slot. This can have a -CD/98175003.1 3 very disadvantageous effect on the subsequent lacquering or coating process.

Furthermore, it can also be disadvantageous that, due to the adhesive action at the end edge of the substrate that is to be lacquered or coated, an undesired bulge of lacquering or coating material is created.

An object of the present invention is to provide a new device and a new method for lacquering and coating of substrates.

According to the invention this object is resolved with a device for lacquering or coating a substrate with a component having a capillary slot with an outlet opening, the device having a container filled in use of the device with a lacquer or coating liquid, the component being at least in part disposed within the container such that the capillary slot communicates with the lacquer or coating liquid whereby, the lacquer or coating liquid can be supplied to the capillary slot and thereby to said outlet opening, said device further having means for varying the vertical position of the outlet opening of the capillary slot relative to the S: 15 container.

S° It is particularly advantageous that the outlet opening of the capillary slot can be completely immersed into the fluid by said variation of the vertical position of the outlet opening relative to the container. By this measure the outlet opening of the capillary channel can, during the intervals of lacquering processes, be completely immersed in the fluid. This prevents possible remnants of the fluid, which remain at or on top of the capillary channel, from the beginning of the process, to dry and prevents particles from depositing thereon from the outside.

Either of these can lead to interference during a later lacquering process.

In a further, extremely advantageous development of the invention a closing mechanism for the container is provided in order to substantially close it off from the atmosphere when not in use. By this measure any drying process of the entire fluid quantity is prevented for which purpose the closing mechanism is preferably designed to be air-tight.

It has also proven very advantageous to provide a filter device and a pump CD/98 17ho3.1 4 for filtering the recirculating fluid inside the container. Thus it is possible to filter the fluid by means of a micro particle filter (recirculation filtration), to keep it clean and in a condition that is appropriate for lacquering purposes. The filtration is advantageously interrupted during a coating or lacquering process.

Particularly for the prevention of lacquer bulges at the end edge of a lacquered or coated substrate there are advantageously provided means for rapidly lowering the level of the fluid in the container, especially at the end of a lacquering or coating process. By this lowering of the level, the fluid is rapidly sucked back into the capillary slot so that the formation of a bulge at a rim of the substrate can be reduced or prevented.

Such a sucking back of the fluid can be achieved particularly advantageously by providing a device which is adjustable in its volume and is positioned in the fluid inside the container. When this volume is reduced, the liquid level in the container is lowered. This creates a low pressure in the capillary 15 slot that sucks back the fluid contained therein.

The invention also provides a method for lacquering or coating the underside of a substrate by capillary action with liquid from a container, using a :component having a capillary slot and an outlet opening thereof, including the following steps: 20 advancing, from below, the outlet opening of the capillary slot closely to the underside of the substrate at the beginning of a coating or lacquering o*o process so that the liquid at the outlet opening comes into contact with said underside; subsequently increasing the distance between said outlet opening and the underside of the substrate to a distance sufficient for lacquering or coating.

Preferably, the method further includes, subsequent to step a step (c) of moving the substrate across the outlet opening of the capillary slot, or vice versa and, subsequent to step a step of rapidly lowering the level of liquid in the container in order to interrupt the lacquering or coating process.

CD/98175003.1 Due to the rapid lowering of the fluid level, the fluid in the capillary channel is sucked back and by this the lacquering is interrupted without the formation of a bulge at the rim of the substrate.

By this, the beginning of a lacquering and the beginning of the fluid transport process within the capillary channel are secured in a simple way.

Further details and advantageous developments of the invention are presented in the exemplified embodiments that are described in the following and are illustrated in the drawings and in no way are to be understood as a limitation of the invention. It is illustrated in: Fig. 1 a cross-section through a device according to an embodiment of the invention in which the member that forms a capillary slot is positioned in an immersed state; Fig. 2 a cross-section through the device of Fig. 1 in which the component that forms the capillary slot has emerged from the fluid in the container during a lacquering process, viewed along line I-11 of Fig. 3; Fig. 3 a longitudinal section through a part of a device according to the invention with an emerged capillary slot component, during a lacquering process; 20 Fig. 4 a perspective view, partly in cross section, of a preferred

S

exemplified embodiment of a device; Fig. 5 a detail of Fig. 4, also in perspective view; S- *Fig. 6 a cross-section, viewed along line VI-VI of Fig. 8, in an enlarged scale in respect to Fig. 6; Fig. 7 a perspective view of the detail VII of Fig. 6; CD/98175003.1 6 Fig. 8 a longitudinal section through the device, illustrated in Fig. 4; Fig. 9 a perspective view of the device illustrated in Fig. 4, with the capillary slot in operating position, shown from above; and Fig. 10 a perspective view, analogous to Fig. 9, but shown from underneath.

DESCRIPTION OF PREFERRED EMBODIMENTS First, the basic principle of the present invention is explained with the aid of the schematic illustrations of Figs. 1 to 3. Then, with the aid of Figs. 4 to 10, a practical exemplified embodiment of the invention is illustrated which operates in accordance with this basic principle.

Fig. 1 shows a cross section through a container 10, the hollow interior of which is mostly filled with the lacquer or coating material 11, in the following called "fluid". The container 10 has the shape of an elongated channel or of an elongated trough. Within the container 10, an elongated component 12 is provided which includes a capillary slot 13 that is necessary for the lacquering process. This slot commonly has a width in the range of 0.1 to 0.8 mm and is formed by a vertically extending gap within the component 12 and enlarges downwardly at 13a in order to allow unhindered flow of the fluid 11 toward the capillary slot 13.

At the upper end of the component 12, the capillary slot 13 has an outlet 20 opening 40, or nozzle, which will be explained in detail in the following with the aid of Fig. 7. Depending on the width of a substrate 29 (Fig. 2 and 3) that is to be coated, this outlet opening 40 can have a length in the range of, for example, to 75 cm, whereby, of course, longer or shorter lengths are not excluded.

The component 12 is basically shaped in cross section as an approximately o.

rectangular base body which is limited, toward the top, by two sloping, rooflike surfaces 41,42, and in the center of which two knife-like extensions 43, 44 project upwardly, each of which has a width of approximately only 0.1-0.5 mm in the area ~t~4,upwardly, each of which has a width of approximately only 0.1-0.5 mm in the area CD/98175003.1 7 of the nozzle 40. These extensions 43, 44 are tapered toward the top where they become extremely narrow.

The component 12 is, at its bottom surface, connected to a rod 15. This rod is vertically slidable in the direction of arrow 16 by device 44 that is schematically illustrated. Through this the component 12 can be moved in the vertical direction. The hollow interior 10 Oa of the container 1 is sealed relative to the rod 15 passing through its bottom by a bellows 17 which in the cross section is illustrated to the right and to the left of the rod 15. The device 44 may be a hydraulic or pneumatic working cylinder for example.

The hollow interior 10a of the container 10 is closed by a fixedly mounted plate 18 on the upper right (Figs. 1 and 2) and by a slidable angular member 19 on the upper left. The plate 18 is directly mounted on the right side wall of the container 10. The angular member 19 is laterally slidable in the direction of arrow (Fig. 1) by means of a linear driving means 46 which is illustrated schematically. For example, the guidance of this sliding movement can, as is illustrated, be effected by a guide bolt 21 which is mounted at the left side wall of the container.

The hollow interior 10a is sealed off by two elastomeric members 22 and 23. The member 22 is inserted in an appropriate groove in the end face of the plate 18 and is pressed by the end face of the angular member 19 into the groove as is illustrated in Fig. 1. The sealing member 23 is inserted in an appropriate *9 :.o:groove in the left sidewall of the container 10 and is pressed by a vertically extended side 19' of the angular member 19 into the groove. Contact pressure is applied by the means 46 which slides the angular member 19. Alternatively, the .9o* 25 plate 18 and the angular member 19 can be coated with an appropriate solvent- S9 resistant synthetic of a thickness of e.g. 0.5 mm, which, in the closed position, provides the sealing functions.

9 component 12 with its capillary slot 13 is illustrated in Fig. 1 as completely immersed below the level 24 of the fluid 11. This corresponds to a 0 state in which no lacquering takes place, the outlet opening 40 of the CD/98175003.1 8 component 12 is positioned below the level 24 of the fluid 11.

Fig. 2 illustrates the same cross-section of the container 10 with all components, as illustrated in Fig. 1, but during a lacquering process. The closing apparatus of the hollow interior 10a which comprises the plate 18 and the angular member 19 is open since the angular member 19 is, in comparison to the illustration of Fig. 1, slid to the left in the direction of arrow 20. The component 12 with its capillary slot 13 has been moved upwards in the direction of arrow 28 by a vertical movement of the rod 15. Accordingly, the knife-like extensions or parts 43, 44 now project past the level 24 of the fluid in the container 10 and also through a narrow opening 48 between plate 18 and angular member 19. The narrow shape of the knife-like extensions 43, 44 allows the opening 48 to be very narrow thereby reducing the risk of contaminants entering the fluid 11 through the opening 48.

Furthermore, vaporisation of the fluid 11 is reduced by this measure.

In Fig. 2 a substrate 29 (in the shape of a plate) is illustrated during a lacquering process. This substrate 29 is guided across the outlet opening 40 of the capillary slot 13 at a constant speed in the direction of arrow 30 at a very small distance 0.2-0.5 mm). By this a very uniform lacquer layer 31 is deposited at the bottom surface 50 of the substrate 29 through capillary action and adhesion.

In the wet state the thickness of the lacquer layer 31 typically ranges from 5 to 50 pm.

In Fig. 3 is illustrated a longitudinal section through a part of the container 10 and the component 12 during a lacquering process. The component 12, as in the illustration of Fig. 2, has been upwardly displaced in the direction of arrow 28.

At the bottom surface 50 of the substrate 29 to be lacquered, a uniform lacquer 25 layer 31 is deposited. The thickness of this layer 31 is, for illustration purposes, g o drawn in extreme dimensions.

The partial longitudinal section of Fig. 3 shows the left section 52 of the So. container 10 and of the component 12 as well as the rod 15 as the vertical drive.

o Symmetrical to this, at the other end of the container 10, a corresponding second rod 15 is provided, not illustrated in Fig. 3. The plane of symmetry is symbolically CD/98175003.1 9 illustrated at 54. As has already been explained, the complete length of the component 12 can range, for example, between 50 and 75 cm, whereby the outer rim areas, as illustrated in Fig. 3, are not to be used for the lacquering process.

Parallel reciprocating movements of the rod 15 ensure that the outlet opening (nozzle) 40 of the capillary slot 13 constantly remains in the required, exactly horizontal position.

In Fig. 3, an overflow pipe 32 is illustrated in section. After turning on a pump 34, the fluid 11 in the hollow interior 10Oa increases. As soon as the filling level of the fluid 11 in the hollow interior 10a reaches the upper rim of this overflow pipe 32 fluid begins to flow out at that rim. Through the overflow pipe 32 it is guided into an expansion tank 33, for example a supply container or bottle which, for example, contains 2.5 L of the fluid 11. The pump 34 is linked via a tube 34' to the container 33 and sucks fluid 11 therefrom. The fluid 11 is returned into the hollow interior 10a through a filtering device in the form of micro filter 35 and a tube 35a. The pump 34 and the filter 35 are commercially available components and are therefore only schematically illustrated.

The fluid 11 is cleaned by recirculating by pumping between the lacquering processes, and its filling level 24 inside the container 10 is constantly held at a defined level. Both of these actions are important for the quality of the lacquering or coating process. During the lacquering process, the fluid 11 is not pumped through the filter 35 since the flow inside the container 10 may have a negative impact on the lacquering result. During the lacquering process of a substrate 29, 99 between 1 and 3 ml of the fluid 11 are commonly used which causes the fluid 9*go surface 24 to drop only very little, e.g. by 0.1 to 0.4 mm, which does not interfere o° 25 with the lacquering process.

*999 Furthermore, within the hollow interior 10a, a bellows 25 is provided. Its upper stop plate 56 is linked, by a rod 57 that penetrates the bottom of the container 10, to a piston 58 of a working cylinder 60 which can be actuated by S means of a schematically illustrated device 62.

9: 9 °o When the piston 58, is pushed downward by actuating the device 62 (which CD/98175003.1 is commonly actuated by a central control by means of a micro processor which is not illustrated), the upper stop plate 56 of the bellows 25 moves downward and the volume of the bellows 25 is reduced, whereby air can escape downwardly through an opening 65 in the bottom of the container 10. This causes the fluid level 24 inside the container 10 to drop rapidly. In reverse, when the upper stop plate 56 is moved upwards by means of the working cylinder 60, the fluid level 24 rises to a maximum value which is defined by the overflow pipe 32.

Therefore the fluid level 24 inside the container 10 can, by means of control of the device 62, be changed rapidly as required.

METHOD OF OPERATION When a substrate 29 to be lacquered is positioned for starting a lacquering process, the cover of the container 10 is opened by sliding the angular member 19 to the left by means of the device 46. Then the knife-like extensions 43, 44 of the component 12 are advanced to position below the front edge of the substrate 29 that is to be lacquered so as to be spaced at a very small distance of e.g. 0.05 mm. Since the pump 34 is turned off during this step, the fluid level 24 slightly drops, e.g. by 0.1 to 0.5 mm, which does not interfere with the coating process.

The slight drop of fluid level is a result of the small and thus very advantageous volume of the knife-like extensions 43, 44 which emerge from fluid 11. By the movement of the component 12 contact is made between the small fluid bulge which due to immersion has remained on top of the outlet opening 40 of the

O.

oio capillary channel 13, and with the front bottom edge of the substrate 29. After :contact is made, the distance between the outlet opening 40 of the component 12 and the substrate 29 that is to be lacquered, is increased a little, e.g. to 0.2 to 25 mm. By this the capillary action is started which transports the fluid 11, against S" the force of gravity, through the capillary slot 13 at a constant speed. Now, the substrate 29 is guided horizontally in the direction of the arrow 30 at a constant see: speed. During this operation, a uniform, thin fluid layer 31 is deposited on the bottom surface of the substrate 29 via the capillary channel 13.

9 When the end edge (which is not illustrated) of the substrate 29 that is to be *D/98175003.1 11 lacquered is reached, the bellows 25 is rapidly, e.g. within a second, reduced in size in the way that has already been described. Accordingly, the fluid surface 24 within the hollow interior 10a rapidly drops. (During this step the pump 34 is turned off). As a result a low pressure is created within the capillary slot 13 which sucks the fluid 11 that is inside the capillary slot 13 down. The fluid deposition at the bottom surface of the plate 29 is thereby suddenly terminated and the undesired forming of a bulge at the (not illustrated) end edge of the substrate 29 is reliably prevented. By means of the extremely narrow design of the knife-like extensions 43, 44 in the area of the nozzle 40 it is ensured that no lacquer bulges or the like form at the end edge of the substrate 29.

The component 12 is then again lowered downward into the container and the cover consisting of plate 18 and angular member 19, is again closed in order to seal the interior of the container 10 hermetically towards the outside thereby preventing evaporation of the fluid 11.

9.

After the cover is closed (by sliding the angular member 19 to the right), the *.pump 34 is turned on. As a result of this the fluid 11 that has been exhausted °o during the lacquering process is replenished within the hollow interior 10a. As soon as the required filling level of the fluid 11 is reached, the fluid 11 again begins to flow into the expansion tank 33 through the overflow pipe 32. The fluid 20 11 is being filtered during recirculation. Typically the pump 34 operates for only a .f :few seconds. If contamination of the fluid 11 is detected, the pump can be operated for a longer time period in order to clean the fluid with the filter 35. The expansion tank 33 has to be replaced from time to time when the fluid inside is spent. A great advantage of the invention is the very economic usage of fluid, e.g.

only approximately 1 to 3 ml per plate 29 to be coated. The bottle in which the fluid 11 is delivered by the manufacturer may be used as an expansion tank.

Naturally, many variations and modifications are possible. For example, the component 12 could also be brought into its submerged position, from the position according to Fig 2 by a rotation about its longitudinal axis. However, a vertical movement of the component 12 is presently preferred in order to prevent undesired, unsymmetrical flow processes of the fluid during the lacquering zprocess.

CD/98175003.1 12 The device according to the invention may be a part of a larger lacquering apparatus as it is illustrated, e.g. in W094/25177. To avoid a lengthy description, reference is expressively made to the contents of the aforementioned international application.

Figs. 4 to 10 illustrate a preferred embodiment of an inventive device 100.

Similar references numerals are used to indicate like parts.

Fig. 4 illustrates the device 100 in a longitudinal section and in a perspective view.

This device has an elongated, trough-like container 110 the bottom of which is labelled as 110'. Its hollow interior 110 a is, as illustrated in Fig. 8, filled with fluid 111 up to the level of an overflow pipe 132. In Fig. 8 the fluid surface is labelled as 124.

Inside the container an elongated component 112 is provided which, as shown in Fig. 5, is assembled from two symmetrical halves 112a, 112b which are separated from each other by a capillary slot 113. This capillary slot 113 has a width dl, as shown in Fig. 7, which depending on the applied fluid 111 ranges between approximately 0.1 to 0.8 mm. The capillary slot 113 widens, in its lower area, into an enlargement 113a which in cross section is funnel-shaped and is illustrated in Figs. 4, 5, and 6. It facilitates the flow of the fluid 11 into the capillary 9•!.9 20 slot 113.

9 As is particularly well illustrated in Figs. 4, 5, 6, and 8, the symmetrical halves 112a, 112b are designed wider in their centre area in vertical direction in order to prevent sagging. At its two ends they are of reduced height, and there they are fixedly mounted in an appropriate way, e.g. by (not illustrated) screws on installation plates 170, 171 which are also fixedly linked to a cylindrical rod 115, 9."9115'. These rods penetrate the bottom 110' of the container 110 and, at their .9 lower ends, are linked by a cross link 172 which is slidable in a vertical direction by means of a device 144 by which the component 112 can be lifted and lowered as SrAi has already been described in connection with Fig. 1 and 2 for the component 12.

CD/98175003.1 13 The device 144 can be any linear drive, e.g. a pneumatic cylinder or an electrical linear drive.

The rods 115, 115' are sealed by means of bellows 117, 117' in the illustrated way, again, as it has already been explained in detail with the bellows 17inFigs. 1to3.

As is particularly well illustrated in Figs. 5 and 6, the halves 112a, 112b of the elongated component 112, at their upper ends are respectively provided with knife-like extensions 143, 144 which basically project vertically upwardly. Each of these extensions 143, 144 at their upper end terminate in a narrow, surface 177, 178 (Fig. 7) that is horizontal during operation and in which the capillary channel 113 ends as an opening 140. This opening 140 and its surrounding surfaces 177, 178 can also be called a nozzle.

The surface 177 has, according to Fig. 7, a width d2 which ranges between 0.1 and 0.5 mm and preferably is 0.3 mm. The surface 178 has a width d3 (Fig 7) which ranges between 0.1 and 0.5 mm and preferably is 0.3 mm. The advantage of these narrow surfaces 177, 178 is that they largely prevent the creation of a fluid bulge at the back edge of a substrate 129 that is to be coated. Such a substrate is illustrated in Fig. 8. Its width W is smaller than the length of the component 12, i.e. for a uniform coating only the central longitudinal portion W of S: 20 the component 112 is utilised. At the rim areas discontinuities of the fluid layer (31 in Figs. 1 to 3) may occur.

As Fig. 9 illustrates the largest part of the top side of the container 110 is covered by a cover/sealing plate (118). This plate has a rectangular cutout 118' S: and a slidable angular plate 119 is inserted into it which is horizontally slidable in 25 the direction of arrow 120. When, in Fig. 9, it is slid towards the front, it forms an opening 119' through which the knife-like extensions 143, 144 can be slid upwards for the lacquering process. When the angular plate in Fig. 9 is slid towards the back it closes the opening 119' completely and seals it off. For this purpose both plates 118 and 119 can be coated with a synthetic (not illustrated) which is Z 3 0 solvent-resistant that, for example has a thickness of 0.5 mm and which creates CD/981 7 5003.1 14 the desired sealing at the rims.

For sliding the angular plate 119 horizontally two linear driving devices 146, 146' (Fig. 10) are provided which are operated in synchronism in order to achieve a uniform sliding of the angular plate 119.

Inside the hollow interior 110a of the container 110 a bellows 125 is also provided, the volume of which can be changed by means of an actuating means 160. When the volume is changed by moving an actuating rod of the bellows 125 downwards, a rapid lowering of the fluid level 124 inside the container 110 results by which the fluid inside the capillary slot 113 is sucked down and the lacquering process is terminated. When the rod 157 is moved upwards, the fluid level 124 rises rapidly.

To the overflow pipe 132 a pipe 180 is linked which leads down and, through a lid 133', into the interior of an extension tank 133 for the fluid 111. A suction tube 182 leads from this tank 133, again through the lid 133' to a pump 134 which can only be operated when no lacquering process is taking place. This pump 134 transports fluid in the direction of arrow 183 (Fig. 8) to a microfilter 135 and from there through a tubing 135a into the interior 11 0a of the container 110.

When the angular plate 119 is in its (not illustrated) closed state, in which it hermetically seals off the top of the container 10, the pump 134 can be actuated.

20 It then pumps fluid 111 from the expansion tank 133 through a microfilter 135 into the hollow interior 110Oa of the container 110 and fills it up to the level of the overflow pipe 132 (Fig. (During a lacquering process the fluid level 124 dips slightly since a small quantity of fluid is used for the lacquering process).

METHOD OF OPERATION 25 When a substrate 129 to be lacquered is positioned for starting a lacquering process, the cover of the container 110 is opened by sliding the angular plate 119 in the opening direction by the two devices 146, 146'. Then the knife-like extensions 143, 144 of the component 112 are advanced to a position CD/98175003.1 below the front edge of the substrate 129 that is to be lacquered at a very short distance of, e.g. 0.05mm, by means of a drive 144. Accordingly, contact is made between the small fluid bulge which remained on top of the outlet opening 140 of the capillary channel 113 as a remains of the fluid 111 that is inside the container 110, and with the front bottom edge of the substrate 129 that is to be lacquered.

After this contact is made the distance between the outlet opening 140 of the component 112 and the substrate 129 that is to be lacquered, is increased a little, e.g. to 0.2 to 0.5mm. This begins the capillary action which transports the fluid 111 from the container 110, against the force of gravity, through the capillary channel 113 upwards at a constant speed. Now the substrate 129 is horizontally guided at a constant speed as is described in detail in Fig. 2. During this operation, a uniform, thin fluid layer is deposited on the bottom surface of the substrate 129 via the capillary channel 113. This layer commonly has a thickness, in the wet state, of between 5 and When the end edge (which is not illustrated) of the substrate 129 has reached the capillary slot the bellows 125 is rapidly, e.g. within a second, reduced in size in the way that has already been described. Through this the fluid surface 124 within the hollow interior 110Oa drops rapidly. (During this the pump 134 is turned off). As a result a low pressure is created within the capillary slot 113 20 which sucks down the fluid 11 which is inside the capillary slot. The fluid deposition at the bottom surface of the plate 129 is thereby suddenly terminated and the undesired forming of a bulge at the (not illustrated) end edge of the substrate 129 is reliably prevented. By means of the extremely narrow design of the knife-like extensions 143, 144 in the area of the opening 140 it is ensured that no lacquer bulges or the like form at the end edge of the substrate 129.

Then the component 112 is again returned into the container 110 where it S-is completely immersed into the fluid 111 and the opening 119' again is hermetically closed up by the angular plate 119 in order to seal the interior of the container 110 towards the outside and thus prevent evaporation of the fluid 111.

After the cover is closed, the pump 134 is turned on, and as a result the fluid 111 that has been exhausted during the lacquering process is replenished CD/98175003.1 16 within the hollow interior 11 Oa. As soon as the required filling level is reached, the fluid 111 again begins to flow into the supply and expansion tank 133 through the overflow pipe 132. During recirculation the fluid 111 is being filtered by the microfilter 135. Typically the pump operates for only a few seconds but can also be operated for a longer time period in order to clean the fluid 111. The expansion tank is replaced by a new tank when the fluid within is used up. For this purpose a new tank 133 is screwed from the bottom against the fixedly mounted lid. A great advantage of the invention is the very economic usage of fluid 111 and the elimination of the necessity to dispose of fluid remains.

Naturally, within the scope of the invention, many variations and modifications are possible. For example, the closing apparatus of the container 110 can be designed in various ways, e.g. by placing a lid from above. Also, alternatively, the substrate 129 can be guided towards the opening 140 of the component 112 from above instead of reversely guiding the opening 140 towards the bottom side of the substrate 129.

Also, instead of the bellows 125, a pump could be provided which rapidly sucks fluid 111 from inside the container 110 in order to rapidly lower the fluid surface 124 in which case this pump can very simply be in the form of a hollow ";interior of a working cylinder. This would be analogous to the process of sucking, 20 before an injection, the liquid that is to be injected, into a syringe. In both cases (pump or cylinder) the fluid can subsequently again be pumped back into the container 110, eg by reversing the transporting direction of the pump (not e illustrated).

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