EP3221149B1 - Process and apparatus for printing a surface with a fluid - Google Patents

Description

The invention relates to a method of printing a surface with a fluid containing an organic semiconductor material, wherein the fluid from a reservoir is conveyed through a feed line to a surface-traveling printhead and imprinted onto the surface by the printhead.

In recent years, numerous applications and uses for organic semiconductor materials have been developed in a variety of applications. In organic electronics or in molecular electronics, organic semiconductor materials are combined with electronic components in order to be able to utilize the advantageous properties of the organic semiconductor material in the electronic components. With suitable organic semiconductor materials, for example, organic light-emitting diodes (OLEDs) and large-area displays can be produced from organic light-emitting diode arrangements.

Organic semiconductor materials also have advantageous properties and uses in processing capabilities and in the fabrication of electronic devices with organic semiconductor materials. Thus, it is known from practice that organic semiconductor materials can be dissolved in a fluid and processed by printing technology, wherein in particular with suitably modified inkjet systems dissolved in a fluid organic semiconductor material can be applied without contact on a large area to be printed surface.

In order to produce as homogeneous as possible layers of the organic semiconductor material without error, it is necessary that the organic semiconductor material has a very high degree of purity and contains as few disturbing foreign particles or air pockets. In addition, it has been found that most organic semiconductor materials which have advantageous properties and are used for the production of products, are extremely sensitive to contact with oxygen and air. In order to avoid contamination of the organic semiconductor material as possible or to keep as low as possible, the organic semiconductor material is often filled under high-purity environmental conditions in storage, then placed in gas-tight storage containers to the place of use and there shielded as possible from contaminating particles or gases and in particular processed by oxygen.

When changing between different storage containers, which are connected and emptied successively with the respective pressure systems used, it is often necessary to flush the supply line from the reservoir to the outlet opening of the printing system, so that a required for the flushing fluid amount is no longer for printing can be used. In addition, when changing between different fluids, expensive cleaning of the printing system is regularly required, so that additional fluid losses are unavoidable.

By long transport routes between the place of manufacture of the fluid and the filling of a reservoir and the location of the use of the fluid for printing a surface with a printing system and by a long storage time to exhaustion of the amount of fluid in a reservoir contamination with the fluid Impurities, for example, by particles dissolved from a reservoir wall particles, by filling and emptying openings penetrating particles and by diffusion of gases and in particular oxygen favors. For this reason, often Reservoir used with a small effective volume, arranged spatially as close to an outlet nozzle of the printing system during a printing operation and used up as quickly as possible. Despite a considerable expense, unwanted contamination of the fluid is usually unavoidable.

It is considered to be an object of the present invention to provide a method for printing a surface with a fluid containing an organic semiconductor material in such a way that the highest possible purity of the fluid used for printing the surface is made possible with the lowest possible loss amounts of the fluid.

This object is achieved in that at least a portion of the fluid which is conveyed through the supply line to the print head, is fed back via a return line into the reservoir, wherein a fluid circuit is formed, and that the fluid in the fluid circuit a cleaning device flows through, with which the fluid is purified. The formation of the fluid circuit, which comprises a cleaning device, makes it possible for the fluid in the reservoir to flow through the cleaning device several times, if necessary, and thereby to be cleaned.

This cleaning of the fluid can be carried out immediately before the use of the fluid or before the beginning of a printing operation. It is no longer necessary to clean the fluid before filling into the reservoir with considerable effort and additionally to ensure that during transport of the reservoir from the place of manufacture to the intended use any re-contamination of the fluid is avoided or kept as low as possible , The printing apparatus with which the printing operation is performed may lower the purity of the components involved and the shielding of the fluid before and during the printing process Requests are made so far, as required and possibly multiple or even continuously provided for the printing process fluid can be promoted by device and thereby cleaned.

In addition, during the execution of a printing operation, a cleaning of a quantity of fluid circulated in the fluid circuit can take place continuously or at intervals in order to reduce contamination of the fluid. It is therefore not necessary to use up the amount of fluid in the reservoir as quickly as possible.

According to a particularly advantageous embodiment of the inventive concept, it is provided that the fluid conveyed back to the reservoir flows around at least sections of the fluid conveyed in the supply line to the print head. Many organic semiconductor materials that are suitable, for example, for the production of large-area displays can be accidentally rapidly contaminated with oxygen, which is absorbed by the environment or penetrates into the fluid. For this purpose, many components of the printing device are designed and made of suitable materials such as stainless steel that a penetration or a diffusion process of oxygen into the fluid as possible prevented and kept as low as possible. The undesired penetration of oxygen into the fluid, which is conveyed through the supply line to the print head, can thereby be made more difficult and possibly largely avoided, that the fluid pumped back to the reservoir completely surrounds the supply line at least in sections, so that from the environment into the Fluid lines penetrating oxygen substantially only in the return line and thus can penetrate into the back to the reservoir again conveyed fluid. The return line, which is the supply line surrounds, forms an additional shield and the function lock for the supply line surrounding the return line. The fluid returned back through the recycle line may be precautionary or, if necessary, cleaned prior to refeeding to the printhead to reduce any contamination.

It is further contemplated that during a printing operation, the reservoir is fixedly disposed at a distance from the surface and the printhead connected via a flexible supply line and a flexible return line to the reservoir is moved to print on the surface. Due to the possibility of circulating the fluid in a fluid circuit and thereby having it cleaned with the cleaning device integrated in the fluid circuit, a large distance between the reservoir and the printhead is made possible because any contamination within the pressure device or in the fluid circuit during the printing process can be reduced with the help of the cleaning device. It is not necessary to place the reservoir directly on or on the printhead and to move it over the surface during the printing process together with the printhead. The reservoir can be arranged stationarily at a distance to the surface to be printed. The connection of the reservoir to the print head is made possible via a flexible supply line and a flexible return line. With the return line surrounding the feed line, the flexible feed line is additionally shielded. If necessary, a contamination of the fluid which may be favored by a longer residence time in the supply line can be reduced again by conveying the fluid through the return line and through the cleaning device.

By the arrangement of the reservoir at a distance from the surface and in particular at a distance from the printhead and through the Connection by means of a flexible supply line and a flexible return line enables cost-effective production of efficient and fast printing devices. The spaced and stationary storage containers may have a much larger capacity than reservoir, which are arranged on or on a movable print head. A single print job can be done and completed much faster. With large-volume storage containers, in each case a large number of printing operations can be performed before an exchange of the storage container is required.

In order to enable the most efficient and effective cleaning of the fluid, it is provided that the fluid in the cleaning device is conveyed through a degassing device and through a particle filter device. The degassing device can be used to reduce unwanted gas contamination and, in particular, oxygen contamination that is detrimental to the organic semiconductor materials. With the particulate filter device, particles can be filtered out of the fluid which, for example, detach from the reservoir or components of the pressure device during transport or during a prolonged storage and contaminate the fluid. The particle filter device may in turn be designed in multiple stages or have a plurality of different filter components in order to detect increasingly finer particles and to be able to filter them out of the fluid flow. It is also conceivable that, for example, with low demands on the purity of the applied with the print head fluid or cost reasons, the fluid is conveyed only by a degassing or only by a particle filter before the fluid supplied to the print head and the print head to be printed Surface is printed.

In order to be able to ensure that only sufficiently pure fluid is used during a printing operation and is printed by the print head on the surface to be printed, the invention provides that the fluid in the fluid circuit is conveyed through an analysis device and an analysis of the fluid is performed. With the analysis device suitable parameters for the fluid can be determined and, for example, the purity of the fluid that is conveyed by the analysis device can be determined. The analysis device is expediently arranged in the flow direction downstream of the cleaning device, so that the analyzes carried out with the analysis device describe the fluid after the cleaning and immediately before the feed to the print head.

The analysis device can be connected to a storage device in order to record and store, for example, the results of the analyzes carried out before the start of a printing operation or continuously during a printing operation. In this way it is also possible to carry out a subsequent evaluation of the analyzes carried out before or during the printing process.

It is advantageously provided that, depending on a result of the analysis, a use of the print head for printing on the surface is enabled or disabled. For example, should the result of the analysis indicate that the fluid is not sufficiently pure to ensure good printing results, the printhead may be disabled for printing and the fluid conveyed through the fluid circuit to effect cleaning of the fluid in the purifier. The analyzes can be continued and the cleaning of the fluid already effected with the cleaning device can be checked before the print head is released again for printing on the surface.

The invention also relates to a device for printing a surface with a fluid containing an organic semiconductor material, the device having a reservoir for the fluid, a print head movable over the surface to be printed for printing the surface with the fluid and a supply line which the fluid from the reservoir to the print head can be promoted.

According to the invention, the device has a return line, with which at least a portion of the fluid conveyed to the print head can be conveyed back into the storage container, wherein a fluid circuit can be formed with the return line together with the supply line, and that the device has a cleaning device for the fluid, which is arranged in the fluid circuit and can be flowed through by the fluid.

According to an advantageous embodiment of the inventive concept it is provided that the return line completely surrounds at least a portion of the supply line in the circumferential direction. The return line can be at least partially hollow cylindrical and surrounding the concentrically arranged in an interior of the hollow cylinder feed line. It is also conceivable that the return line runs around the supply line wound. The return line thereby forms a shield for the supply line from the environment and a contamination of the fluid in the supply line. The return line may surround and shield the supply line substantially completely the entire length of the supply line. It is also conceivable that the return line surrounds the supply line only along a section or in particularly exposed areas.

In order to enable a cost-effective application of the movable print head to a spaced apart from the print head reservoir, the invention provides that the supply line and the return line are at least partially flexible and are arranged between the stationary storage container and the movable print head. The reservoir can be separated and shielded, for example, by a housing wall or by a room wall of the movable print head and the surface to be printed, so that a replacement of the reservoir is possible without affecting the ambient conditions in the immediate vicinity of the surface to be printed. The volume of the reservoir spaced from the printhead may be several liters or more. The stationary arranged reservoir can be provided with suitable quick-release connections and replaced quickly. It is also conceivable that a plurality of storage containers are provided, which can be put into operation alternately. After the complete emptying of a first reservoir can be switched and a second reservoir can be used, so that a printing process can be continued quickly. The first reservoir can be refilled or replaced with a refilled reservoir. In this way, a large number of printing operations can be performed almost uninterrupted.

The cleaning device expediently has a degassing device and a particle filter device. The optionally multi-stage or different components comprehensive degassing and particle filter device can be arranged outside of the reservoir. It is also conceivable that the degassing device and the particle filter device are integrated into the reservoir and exchanged together with the reservoir and can be regenerated, for example, in a refilling of the reservoir.

In individual cases, for cost reasons, for example, it may be advantageous for the cleaning device to have only one degassing device or only one particle filter device if degassing or filtering of the fluid is considered to be unnecessary or disproportionately cost-intensive. It is likewise possible for the degassing device or the particle filter device not to be a permanent component of the cleaning device and to be integrated into the circuit or into the reservoir for the fluid only when required.

The apparatus may further comprise an analyzer for analyzing the fluid. With a control device which is signal-transmittingly connected to a printhead release device, the printhead can be released for an imminent printing process or blocked, if the requirements required for a printing process should not be met. By connecting the analysis device to the control device, analysis results can be transmitted to the control device and, depending on the analysis results, the print head can be released with the control device or blocked.

Both the analysis device and the control device can be arranged in the reservoir or integrated into it. In this case, the reservoir only needs to have connections for connection to the supply line and the return line in order to connect to the printhead. Once the reservoir is connected to the supply line and the return line, the fluid in the reservoir can be conveyed through the fluid circuit and analyzed. If the analyzes indicate that the fluid is not of the required purity, printhead release be denied to first perform an additional cleaning of the fluid. Once the required purity is detected with the analyzer, the printhead can be released and pending printing started.

The cleaning and control of a printing process can be carried out in this way self-sufficient with the help of a suitably designed reservoir. A complex adaptation of the installed on-site printing device is not required.

The provision of the fluid with an organic semiconductor material usually takes place organisationally and spatially separate from the operation of the printing device and the intended use of the fluid with the organic semiconductor material for printing on surfaces. With the help of a storage of analysis results, which are continuously detected and detected during operation of the printing device and an increasing emptying of the reservoir, characteristics for the purity of the fluid during its use and removal from the reservoir can be documented. In this way, causes and the responsibility for any errors occurring during operation can be more easily detected and assigned.

It is also possible, with an integrated arrangement of the cleaning device in the reservoir, to circulate and clean the fluid therein in the interior of the reservoir, without the reservoir being connected to a pressure device or to a supply line and to a return line. In this case, for example, even during storage of the filled storage container prior to its use with a pressure device, a cleaning of it fluid located in order to reduce at intervals a possibly intermittent contamination of the fluid.

• Fig. 1 eine schematische Darstellung einer Vorrichtung zum Bedrucken einer Oberfläche, bei welcher ein Vorratsbehälter beabstandet zu einem über eine Oberfläche verfahrbaren Druckkopf angeordnet und mit einer flexiblen Zuführungsleitung und einer flexiblen Rückführungsleitung mit dem verfahrbaren Druckkopf verbunden ist,
• Fig. 2 eine schematische Darstellung einer Ausgestaltung der flexiblen Zuführungsleitung und der die Zuführungsleitung umgebenden flexiblen Rückführungsleitung,
• Fig. 3 eine schematische Darstellung eines Vorratsbehälters, in dem eine Reinigungseinrichtung und eine Analyseeinrichtung integriert sind und
• Fig. 4 eine schematische Darstellung eines Teilbereichs der Druckvorrichtung, bei der zwei Vorratsbehälter über ein Dreiwegeventil wahlweise mit der Zuführungsleitung und der Rückführungsleitung verbunden werden können.

Various embodiments of the inventive concept will be explained in more detail, which are illustrated in the drawing. It shows:

• Fig. 1 a schematic representation of an apparatus for printing a surface, in which a reservoir arranged spaced from a movable over a surface printhead and connected to a flexible supply line and a flexible return line to the movable printhead,
• Fig. 2 a schematic representation of an embodiment of the flexible supply line and the supply line surrounding the flexible return line,
• Fig. 3 a schematic representation of a storage container in which a cleaning device and an analysis device are integrated and
• Fig. 4 a schematic representation of a portion of the printing device, in which two reservoirs can be connected via a three-way valve optionally with the supply line and the return line.

An in Fig. 1 schematically illustrated device 1 for printing a surface 2 has a movable over the surface 2 printhead 3. From a pressure nozzle 4 of the print head 3, a fluid can be sprayed onto the surface 2 and thereby printed on the surface 2.

The print head 3 is connected via a flexible supply line 5 and a likewise flexible return line 6 with a spaced from the surface 2 arranged reservoir 7 is connected. The reservoir 7 is arranged stationary. The flexibly configured supply line 5 and the also flexibly configured return line 6 allow a connection of the movable print head 3 to the stationary arranged / /ratsbehälter. 7

In the print head 3, a control valve 8 is arranged, with which the supplied via the supply line 5 the print head 3 fluid can either be sprayed through the pressure nozzle 4 on the surface 2, or the fluid is fed into the return line 6 to back in the reservoir 7 to be promoted. The supply line 5 and the return line 6 form a Fluidkrelislauf.

In the supply line 5, a pump 9 is arranged, with which the fluid from the reservoir 7 can be conveyed to the print head 3 out. When the control valve 8 blocks the pressure nozzle 4 and the fluid conveyed via the supply line 5 into the print head 3 leads into the return line 6, the pump 9 generates a circulation of the fluid in the fluid circuit.

In the supply line 5, a degassing device 10 and a particle filter device 11 are further arranged, with which the funded through the supply line 5 fluid would be cleaned. Both particles are filtered out and an undesirable gas contamination of the fluid is reduced.

In Fig. 2 schematically an advantageous embodiment of the supply line 5 and the return line 6 is shown. The return line 6 is configured as a hollow cylinder and surrounds the feed line 5 arranged concentrically in an interior of the hollow cylinder. The arrows show exemplary flow directions of the fluid in the feed line 5 and in the return line 6 indicated. Within a wide area, in Fig. 1 is indicated by dashed lines, the return line 6 surrounds the supply line 5 completely in the circumferential direction and forms a shield of the supply line 5 with respect to the environment. A contamination, which is almost unavoidable in particular when flexible conduit materials are used, of the fluid in the supply line 5 or in the return line 6 is thereby largely concentrated and limited to contamination of the fluid in the return line 6, which is conveyed back into the storage container 7 and before a renewed one Feeding to the print head 3 by the degassing device 10 and the particle filter device 11 is cleaned again. The degassing device 10 and the particle filter device 11 may each be designed in multiple stages or each having a plurality of components. The degassing device 10 and the particle filter device 11 form a cleaning device 12 for the fluid flowing through.

In Fig. 3 is merely an example of a differently configured configuration of the reservoir 7 and the cleaning device 12 shown. The degassing device 10 and the particle filter device 11 of the cleaning device 12 are arranged in an inner space 13 of the reservoir 7. Furthermore, an analysis device 14 with a control device 15 in the interior 13 of the reservoir 7 is arranged. The pumped with the pump 9 in the supply line 5 and to the print head 3 fluid is conveyed from the interior 13 of the reservoir 7 first by the cleaning device 12 and then by the analyzer 14 before it get into the feed line 5 and to the print head 3 can. In this case, an analysis with the analysis device 14 is carried out after the cleaning of the fluid. The result of the analysis can be transmitted by means of the control device 15 to the control valve 8 of the print head 3 to the printhead 3 for a printing operation to release or to block in order to direct the conveyed through the supply line 5 to the printhead 3 fluid in the return line 6 and again supply the reservoir 7 for a new cleaning.

In Fig. 4 is schematically shown a portion of a deviating variant of the device 1. The supply line 5 and the return line 6 are connected via a three-way valve 16 optionally with one of two storage containers 7. While one of the two storage container 7 is connected to the print head 3 for carrying out printing operations, the other storage container 7 can be exchanged and replaced by a reservoir 7 filled with new fluid. Once the fluid from the currently used reservoir 7 is running low, can be switched with the three-way valve 16 and filled with new fluid other reservoir 7 continue to be used. In this way, the downtime during operation of the device 1 can be significantly reduced.

The cleaning device 12 and the analysis device 14 are arranged externally in this embodiment and not integrated into the reservoir 7. The control device 15 connected to the analysis device 14 can wirelessly transmit control information to the control valve 8 in the print head 3.

It is also possible that, independently of a variant of the device 1 described in the exemplary embodiments, the pump 9 can be arranged at any point within the fluid circuit. Thus, the pump 9 can also be arranged in the flow direction before the cleaning device 12 or, if appropriate, between the cleaning device 12 and the analysis device 14. It is also possible to arrange the cleaning device 12 and possibly also the analysis device 14 in the return line 6.

Claims (10)

1. Process for printing a surface (2) with a fluid which comprises an organic semiconductor material, where the fluid is conveyed from a storage container (7) through a supply line (5) to a print head (3) which can be moved over the surface (2) and is printed onto the surface (2) by the print head (3), characterised in that at least some of the fluid conveyed through the supply line (5) to the print head (3) is conveyed back into the storage container (7) via a return line (6), with a fluid circuit being formed, and in that the fluid in the fluid circuit flows through a cleaning device (12), by means of which the fluid is cleaned, and in that the fluid conveyed back to the storage container (7) flows, at least in a section, around the fluid conveyed to the print head (3) in the supply line (5).
2. Process according to Claim 1, characterised in that, during a printing operation, the storage container (7) is arranged in a fixed location at a distance from the surface (2) and the print head (3), which is connected to the storage container (7) via a flexible supply line (5) and via a flexible return line (6), is moved over the surface (2) for printing.
3. Process according to Claim 1 or 2, characterised in that the fluid in the cleaning device (12) is conveyed through a degassing device (10) or through a particle filter device (11) or through a degassing device (10) and a particle filter device (11).
4. Process according to one or more of the preceding claims, characterised in that the fluid in the fluid circuit is conveyed through an analysis device (14) and an analysis is carried out.
5. Process according to Claim 4, characterised in that a use of the print head (3) for printing the surface (2) is allowed or blocked depending on the result of the analysis.
6. Device (1) for printing a surface (2) with a fluid which comprises an organic semiconductor material, where the device (1) has a storage container (7) for the fluid, a print head (3), which can be moved over the surface (2) to be printed, for printing the surface (2) with the fluid, and a supply line (5), by means of which the fluid can be conveyed from the storage container (7) to the print head (3), characterised in that the device (1) has a return line (6), by means of which at least some of the fluid conveyed to the print head (3) can be conveyed back into the storage container (7), where a fluid circuit can be formed with the return line (6) together with the supply line (5), and in that the device (1) has a cleaning device (12) for the fluid, which is arranged in the fluid circuit and through which the fluid can flow, and in that the return line (6) surrounds at least a section of the supply line (5) in the circumferential direction.
7. Device (1) according to Claim 6, characterised in that the supply line (5) and the return line (6) are flexible, at least in a section, and are arranged between the storage container (7), which is arranged in a fixed location, and the movable print head (3).
8. Device (1) according to Claim 6 or 7, characterised in that the cleaning device (12) has a degassing device (10) or a particle filter device (11) or a degassing device (10) and a particle filter device (11).
9. Device (1) according to one or more of the preceding Claims 6 to 8, characterised in that the device (1) has an analysis device (14) for analysis of the fluid.
10. Device (1) according to one or more of Claims 6 to 9, characterised in that the device (1) has a control device (15) with a print head release device.

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