DE102019135208B4 - Printing unit, printing device and method for parallel extrusion of printing medium onto a substrate - Google Patents

Abstract

Printing unit for the parallel extrusion of print medium, in particular for the production of conductor tracks, with a plurality of output openings (2), for the simultaneous output of print medium from the output openings (2), characterized in that the printing unit has at least one central print head (1) and at least two edge print heads , wherein the central print head (1) and each edge print head (3a, 3b) each have a plurality of output openings (2) for the simultaneous output of print medium from the output openings (2) and on two opposite sides of the central print head one of the two edge print heads on the central print head is pivotally arranged.

Description

The invention relates to a printing unit, a printing device and a method for parallel extrusion of printing medium onto a substrate according to claims 1, 8 and 11.

In industrial printing operations, particularly in the manufacture of semiconductor structures such as photovoltaic solar cells, it is often desirable to apply a printing medium to a substrate in a plurality of parallel swaths. Such a print medium can be a print paste which contains in particular a dopant for doping one or more regions of the semiconductor structure, which is used to form a mask for subsequent process steps and/or which contains metal particles for forming a metallic contact structure.

Typical printing devices for applying parallel swaths of print medium to a substrate to be printed have a plurality of dispensing orifices arranged in a straight line. These discharge orifices are typically formed as holes in a metallic nozzle bar.

Out U.S. 10,026,617 B2 and US 2012/0 193 655 A1 are known printing devices with which several webs of printing medium can be applied to a substrate to be printed. Said printing devices each comprise a plurality of printing units that can be adjusted in relation to one another.

Out US 2013/0 206 220 A1 a printing unit with several dispenser openings is known. The positions of the dispenser openings are adapted to the contour geometry of the substrate to be printed.

In the case of large-area semiconductor components, in particular in the case of photovoltaic solar cells, so-called pseudo-square wafers are frequently used. These have a shape determined by the manufacturing process, which is basically rectangular, mostly square, but has beveled corners. In order to nevertheless achieve high efficiencies in photovoltaic solar cells, it is necessary for the parallel lines to begin and end at a small, specified distance from the edge of the substrate. Edge parallel lines in the area of the beveled corners are thus of a shorter length compared to the lines of print medium in the central area of the substrate.

In known screen printing methods for producing contacting grids in photovoltaic solar cells, excess printing medium is collected in the area of the beveled corners using templates. However, this print medium cannot be reused and thus increases the overall costs, on the one hand due to the amount of print medium to be disposed of and on the other hand due to the technical complexity of catching the print medium that is not required in the area of the beveled corners. Print heads are also known which have separate valves for the print medium at least for the output openings on the wall, so that the output of print medium at the output openings on the edges can be started later and ended earlier in order to apply the shorter lines of print medium on the edges. However, such valve elements have a significant technical complexity and also increase the risk of uneven delivery of pressure medium or clogging of the valve elements.

The object of the present invention is therefore to provide a printing unit, a printing device and a method for parallel extrusion of printing medium which offers an alternative to printing on non-rectangular substrates, in particular pseudo-square wafers.

This object is achieved by a printing unit according to claim 1, a printing device according to claim 8 and a method according to claim 11. Advantageous refinements can be found in the dependent subclaims. The printing unit and the printing device are preferably designed to carry out the method according to the invention, in particular a preferred embodiment thereof. The method is preferably designed to be carried out using the printing unit according to the invention and/or the printing device according to the invention, particularly preferred embodiments thereof.

The printing unit for parallel extrusion of printing medium according to the invention has a plurality of discharge openings for simultaneously discharging printing medium from the discharge openings.

It is essential that the printing unit has at least one central print head and at least two edge print heads, with the central print head and each edge print head each having a plurality of output openings for the simultaneous output of print medium from the output openings and one of the two edge print heads on the central print head on two opposite sides of the central print head is pivotally arranged.

The printing unit according to the invention thus has the advantage that the pivoting of the edge print heads makes it possible to adapt to the geometry of the substrate to be printed. The pivoting can take place in a technically uncomplicated manner by a drive element, in particular by one or more motorized means, so that there is a structurally less complex structure compared to previously known devices using templates or valve elements in individual dispensing openings of the print head.

The object mentioned at the outset is also achieved by a printing device according to claim 8. The printing device according to the invention for the parallel extrusion of printing medium onto a substrate has a printing unit according to the invention, in particular a preferred embodiment thereof. Furthermore, the printing device preferably has at least one drive element, in particular at least one motorized means for pivoting the edge print heads, in particular one or more electrical actuating means.

As a result, the advantages listed above in the description of the printing unit according to the invention are achieved in a structurally simple manner.

Furthermore, the object mentioned at the outset is achieved by a method according to claim 11 . In the method according to the invention for the parallel extrusion of print medium onto a substrate, print medium is simultaneously discharged from a plurality of discharge openings of a print unit while the print unit and substrate are moved relative to one another in a print direction. It is essential that during the printing process, using a central print head of the printing unit and at least two edge print heads arranged on opposite edge sides of the central print head, print medium is applied to the substrate from a plurality of output openings and that the edge print heads are pivoted relative to the central print head during the printing process.

This achieves the advantages mentioned above in the description of the printing unit according to the invention.

In an advantageous embodiment of the printing unit according to the invention, the edge print heads are arranged so as to be pivotable about pivot axes which are parallel to one another. This results in the advantage that both edge print heads carry out a similar pivoting movement.

In typical uses of a printing unit for parallel extrusion of printing medium onto a substrate, the substrate has a planar surface and the printing unit and substrate are moved relative to each other according to a printing direction which is parallel to the surface of the substrate. The printing device is therefore advantageously designed to move the printing unit and a substrate to be printed on in a rectilinear printing direction relative to one another, and the pivot axes of the edge print heads are perpendicular to the printing direction. In particular, the pivot axes are preferably perpendicular to the surface of the substrate to be printed during the printing process. Typical prior art printheads for extruding print media have dispensing orifices with central axes parallel to one another. The dispensing openings are thus aligned in the same direction. In particular, dispensing openings are preferably designed to be rotationally symmetrical, in particular cylindrical and/or truncated with parallel cylinder/cone axes.

In an advantageous embodiment, the output openings of the central print head have central axes that are parallel to one another and the pivot axes of the edge print heads are parallel to the central axes of the output openings of the central print head. In particular, it is advantageous that the output openings of the central print head and the edge print heads have central axes that are parallel to one another. Due to the pivot axes being parallel to the central axes, this parallel alignment of all output openings to one another is retained even when the edge print heads are pivoted.

Advantageously, each edge print head has a plurality of output elements, each with at least one, preferably exactly one, output opening, the output elements being arranged to be displaceable along a displacement direction relative to the edge print head, so that the distance between the output elements can be changed.

This advantageous embodiment has the advantage that the distance between the output openings of the edge print heads can also be changed when the edge print heads are pivoted. It is thus particularly possible with this advantageous embodiment to apply equidistant, parallel print medium lines even when the edge print heads are pivoted, in that any change in the distance between the output openings perpendicular to the printing direction is compensated for by shifting the output elements.

Therefore, the distance between the output openings of the edge print heads is advantageously changed during the pivoting of the edge print heads. Especially advantageously modified in such a way that parallel lines of print medium are applied to the substrate to be printed.

• In einer vorteilhaften Ausführungsform sind die Randdruckköpfe gegenüber dem Zentraldruckkopf zu Beginn des Druckvorgangs in Druckrichtung verschwenkt und während des Druckvorgangs werden die Randdruckköpfe derart geschwenkt, dass die Randdruckköpfe am Ende des Druckvorgangs gegenüber dem Zentraldruckkopf entgegen der Druckrichtung verschwenkt sind.

This allows pseudo-square wafers to be printed with parallel lines, and yet avoids wastage of print media without the use of a stencil or valving for edge dispensers, as explained below:

• In an advantageous embodiment, the edge print heads are pivoted relative to the central print head at the beginning of the printing process in the printing direction, and during the printing process the edge print heads are pivoted in such a way that the edge print heads are pivoted relative to the central print head counter to the printing direction at the end of the printing process.

This advantageous configuration takes account of the slanted corners of a pseudo-square wafer, particularly preferably in such a way that the printing unit with the central print head and the two pivotable edge print heads has approximately the shape of the Substrate edge simulates with the beveled corners. By pivoting the edge print heads, the edge profile of the substrate with the beveled corners is thus reproduced in an advantageous manner.

Advantageously, the edge print heads therefore have a length that corresponds to the beveled corners of the substrate to be printed. In particular, the central print head preferably has a width which corresponds approximately to the edge width of the substrate minus the beveled corners.

Because the edge print heads are pivoted in the printing direction at the beginning of the printing process, the course of the edge with the beveled corners is reproduced, so that print medium can be output from all output openings at the same time and print medium is nevertheless applied to the substrate from all output openings, so that in particular a stencil , as known from the prior art, is not necessary. Because the edge print heads continue to be pivoted during the printing process in such a way that the edge print heads are pivoted at the end of the printing process relative to the central print head in the opposite direction to the printing direction, the edge of the substrate that is opposite the edge of the substrate at the beginning of the printing process is also at the end of the printing process , simulated by the printing unit, so that the output of print medium from all output openings of the printing unit can be ended at the same time, and yet all lines end at approximately the same, predetermined distance from the edge of the printing substrate.

The edge print heads are thus preferably pivoted in opposite directions during the printing process.

When the edge print heads are pivoted during the printing process, the lines applied by the edge print heads thus have arc-like shapes, provided no compensation takes place.

In order to also achieve rectilinear print medium lines in the case of the lines applied by means of the edge print heads, it is therefore advantageous, as described above, to design the edge print heads with output elements which can be displaced in relation to one another.

In particular, it is advantageous that elastic elements are arranged between the output elements of the edge print heads. In this way, a uniform change in the distance between adjacent output elements can be achieved in a simple manner, for example by shifting an edge output element. In particular, it is advantageous that the elastic elements between the output elements have approximately the same restoring force, in particular have approximately the same spring constant.

In an advantageous embodiment, the printing unit has at least one actuator, preferably an electric actuator, in order to displace the output element of at least one edge print head, particularly preferably both output elements of both edge print heads.

Advantageously, each edge print head has at least one actuator, preferably an electric actuator, which is designed to interact with at least one output element, preferably an edge output element, in order to displace the output element in the displacement direction.

In particular in combination with the previously described advantageous elastic elements between the output elements, a change in the distance between the output elements of the edge print heads can be achieved in a structurally simple manner.

Another way to avoid curved lines of print media due to pivoting of the edge print heads is to create an electrical potential between line electrodes and the print media. This alignment of the print medium by an electrical potential can be used alternatively or preferably in addition to the displaceable output elements previously described. The use of an electrical potential to align print media per se is in DE 10 2019 122 131 A1 described.

The printing device therefore advantageously has a voltage source and a plurality of line electrodes, the printing device having a carrier unit for receiving a substrate to be printed and the carrier unit and line electrodes being arranged in such a way that a substrate to be printed can be arranged between the print heads and the line electrodes, the line electrodes are arranged in the area of the edge printheads and the voltage source is connected to the edge printheads and the line electrodes to generate an electrical potential between print medium which is output from the edge printheads and the line electrodes.

The line electrodes are thus preferably located beneath the substrate along lines which correspond to the desired lines of print media output by the edge printheads. In particular, the line electrodes are thus preferably arranged parallel to one another and more preferably parallel to the printing direction.

In the method, an electrical potential is thus preferably generated during the printing process between the print medium and electrodes, particularly preferably line electrodes, which are arranged on the side of the substrate to be printed opposite the printing unit, in order to achieve the aforementioned advantageous alignment.

• 1 ein erstes Ausführungsbeispiel einer erfindungsgemäßen Druckeinheit;
• 2 Detailansichten eines zweiten Ausführungsbeispiels einer erfindungsgemäßen Druckeinheit und
• 3 ein Anwendungsbeispiel für das erste Ausführungsbeispiel.

Further preferred features and embodiments are explained below using exemplary embodiments and the figures. It shows:

• 1 a first embodiment of a printing unit according to the invention;
• 2 Detailed views of a second embodiment of a printing unit according to the invention and
• 3 an application example for the first embodiment.

The figures represent schematic views that are not true to scale. The same reference numbers in the figures denote the same elements or elements that function in the same way.

1 shows a first exemplary embodiment of a printing unit according to the invention for the parallel extrusion of printing media, in this case for the production of conductor tracks for forming a contacting structure of a photovoltaic solar cell.

The printing unit has a central print head 1 with a plurality of output openings 2. The output openings are each shown as unfilled circles. For reasons of graphical representation, here and in the following for each element with dispensing openings, only one such circle is marked with the reference number 2.

In 1 a plan view from below is shown so that the dispensing openings 2 can be seen. The central print head 1 has the functionality of previously known print heads for parallel extrusion in that the print head is on the top and therefore in 1 not visible has a print medium input, which is connected to all output openings 2 in order to output 1 print media simultaneously from all output openings 2 of the central print head.

The printing unit also has two edge print heads 3a and 3b. Each edge print head also has a plurality of output openings 2 and one in the 1 on the opposite upper side lying and therefore not visible print medium input, so that with each of the edge print heads 3a and 3b print medium can be output from all output openings at the same time.

One of the two edge print heads 3a and 3b is pivotably arranged on two opposite sides of the central print head. Edge print head 3a is arranged on the central print head 1 about a pivot axis 4a and edge print head 3b about a pivot axis 4b. The pivot axes 4a and 4b are in 1 perpendicular to the plane of the drawing and are thus arranged parallel to one another.

For parallel extrusion of printing medium onto a substrate, for example, the printing unit can be moved along the printing direction D relative to the substrate and/or the substrate can be moved relative to the printing unit in the opposite direction. This creates parallel conductor tracks with a total print width B.

Simplified views are shown in the figures. In the present case, the print head has a total of 70 to 200, in the present case 100, output openings with a spacing of in the present case 1.556 mm between the output openings. The edge printheads each have 6 orifices with a spacing of 1.556mm between orifices.

As in the in 1 As can be seen from the angled arrangement of the edge print heads 3a and 3b in relation to the central print head 1 shown, a substrate, in particular a semiconductor wafer with beveled corners, for example a so-called pseudo-square wafer, can be printed, with print medium only being applied to the substrate and no print medium at the beginning or at the end in the area of the beveled corners next to or outside the substrate. If, during the printing process, the printing unit leaves the area of the substrate with beveled corners, the edge print heads 3a and 3b are pivoted relative to the central print head, according to the illustration 1 pivoted upwards, so that the central print head and edge print heads 3a and 3b have approximately parallel longitudinal extensions and the output openings of all print heads lie approximately on a straight line or at least on straight lines that are parallel to one another.

In a final stage of the printing process, when the print head reaches the beveled corners of the substrate at the opposite edge region, the edge print heads 3a and 3b are further pivoted, as shown in FIG 1 pivoted further upwards until there is a configuration which corresponds to the representation in 1 is mirrored about a horizontal mirror plane that is perpendicular to the plane of the drawing.

• Auf einer Solarzelle 5, welche aus einem Pseudo-Square-Siliziumwafer mit den Maßen (12,5 cm × 12,5 cm) hergestellt wird, werden zur Kontaktierung der bei Benutzung dem Lichteinfall zugewandten Vorderseite parallele Leiterbahnen zur Ausbildung einer metallischen Kontaktierungsstruktur aufgebracht. Hierzu wird die Druckeinheit mit Zentraldruckkopf 1 und den Randdruckköpfen 3a und 3b zunächst in der in 3 links gezeigten Konfiguration angeordnet und anschließend in Richtung der Druckrichtung D über die Solarzelle 5 bewegt. Sobald sich die Ausgabeöffnungen 2 über der Solarzelle 5 befinden und einen vorgegebenen Randabstand für die Leiterbahnen zum Rand der Solarzelle überschritten haben, erfolgt gleichzeitig aus allen Ausgabeöffnungen 2 sowohl des Zentraldruckkopfes 1, als auch der Randdruckköpfe 3a und 3b die Ausgabe von Druckmedium, vorliegend einer an sich bekannten Druckpaste, welche Metallpartikel und Glasfritte enthält.

The print result is shown schematically in 3 shown:

• On a solar cell 5, which is made from a pseudo-square silicon wafer with the dimensions (12.5 cm×12.5 cm), parallel conductor tracks are applied to form a metallic contacting structure for contacting the front side facing the incidence of light when in use. For this purpose, the printing unit with the central print head 1 and the edge print heads 3a and 3b is first positioned in 3 The configuration shown on the left is arranged and then moved over the solar cell 5 in the printing direction D. As soon as the output openings 2 are located above the solar cell 5 and have exceeded a predetermined edge distance for the conductor tracks to the edge of the solar cell, print medium is output simultaneously from all output openings 2 of both the central print head 1 and the edge print heads 3a and 3b, in this case one at known printing paste, which contains metal particles and glass frit.

Because of the links in 3 In the illustrated configuration of the printing unit with angled edge print heads 3a and 3b relative to the central print head 1, the arrangement of the output openings 2 roughly reflects the shape of the left edge of the solar cell 5 with the beveled corners, so that print medium can only be output onto the solar cell 5, also in the areas of the beveled corners.

When the printing unit reaches position Pi one, edge print head 3a is pivoted clockwise and edge print head 3b is pivoted counterclockwise to a position in which the longitudinal extension of edge print heads 3a and 3b is as shown in FIG 3 is vertical, ie parallel to the longitudinal extension of the central print head 1st In 3b the arrangement of the edge print head 3a is shown on the left when printing the left area of the solar cell 5 in the area of the beveled corners and in the middle the arrangement of the edge print head 3a when printing the middle area of the solar cell 5, which has no beveled corners. If the printing unit now reaches position P2, at which the beveled corners begin in the opposite edge area of the solar cell 5, the edge print head 3a is pivoted clockwise and the edge head 4b counterclockwise, so that the output openings 2 of Central print head and the edge print heads 3a and 3Bb reproduce approximately the edge shape of the solar cell 5 with beveled corners.

A particularly simple embodiment of the method results in that the prescribed pivoting of the edge print heads takes place continuously and particularly preferably at a constant rotational speed. In particular, it is advantageous to carry out continuous pivoting from the start of the printing process to its end. As a result, the printing process can be carried out in a simple manner and without a change in speed being necessary when pivoting the print heads.

In 3 the solid lines show the printing result with such a continuous pivoting of the edge print head 3A clockwise and the pivot axis 4a and of the edge print head 3b counterclockwise about the pivot axis 4b during the movement of the printing unit along the printing direction D over the solar cell 5. In a central area, which is delimited upwards and downwards by the start of the beveled corners, parallel, rectilinear conductor tracks are generated by the central print head 1. In an upper and lower edge area, the edge print heads 3a and 3b generates conductor tracks which run parallel to one another but have an arc shape. This arc shape is also in accordance with the explanatory view 3b shown.

The printing unit according to the first exemplary embodiment thus enables conductor tracks to be extruded in parallel onto a solar cell 5 with little structural effort, the printing medium being output only onto the solar cell 5 .

The edge print heads 3a and 3b are pivoted about the pivot axes 4a and 4b by means of motorized means, in the present case by means of an electric motor in each case.

• 2 zeigt in den Teildarstellungen a) und b) jeweils eine Schnittdarstellung des Randdruckkopfes 3a entlang einer Schnittebene S, welche gemäß der Darstellung in 1 senkrecht zur Zeichenebene steht. Die Schnittebene S durchdringt somit die Ausgabeöffnungen 2 des Randdruckkopfes 3a in der Abwandlung gemäß des zweiten Ausführungsbeispiels. Der Randdruckkopf 3b gemäß dem zweiten Ausführungsbeispiel ist in gleicher Weise aufgebaut.

In 2 In a modification of the first embodiment, a partial view of a second embodiment of a printing unit is shown, which also enables the formation of parallel, straight print medium lines in the edge areas with beveled corners:

• 2 shows in the partial illustrations a) and b) a sectional illustration of the edge print head 3a along a sectional plane S, which according to the illustration in 1 is perpendicular to the plane of the drawing. The sectional plane S thus penetrates the discharge openings 2 of the edge print head 3a in the modification according to the second embodiment. The edge print head 3b according to the second embodiment is constructed in the same way.

According to the second exemplary embodiment, each of the edge print heads 3a and 3b has a linear actuator, in this case an electrically operated linear actuator. In 2 a linear actuator 6 is shown schematically in sub-images a and b.

The linear actuator 6 is designed to interact with the edge print head 3a in such a way that the width of the edge print head 3a can be changed by means of the linear actuator 6, for example from a larger width B1 according to FIG 2a to a comparatively smaller width B2 according to 2 B .

The discharge openings 2 of the edge head 3a are each formed in discharge elements shown in black. These output elements are shown in accordance with 2 arranged so that it can be moved horizontally. Elastic elements 7 are arranged between the dispensing elements shown in black, each of which has a dispensing opening 2 . These elastic elements are marked by horizontal, parallel lines.

All elastic elements 7 have approximately the same properties in terms of expansion and compressibility, so that when the overall width is reduced, for example from a width B1 according to FIG 2a to a smaller width B2 according to 2 B by means of the linear actuator 6, the distance between the dispensing elements and thus also the dispensing openings 2 is reduced uniformly.

This makes it possible to change the distance between the output openings 2 of the edge print heads 3a and 3b while pivoting the edge print heads 3a and 3b relative to the central print head 1 in such a way that the total print width B according to 1 does not change despite the pivoting of the edge print heads 3a and 3b.

As a result, in the edge areas, the in 3 printed image indicated by dashed lines can be achieved, ie parallel, straight print medium lines are also generated in the edge areas, the length of which is, however, adapted to the beveled corners, ie according to the representation in 3 In the edge areas, the print media lines have a length that increases from top to bottom in the upper edge area and from bottom to top in the lower edge area.

Reference List

1

central printhead

2

dispensing openings

3a, 3b

edge printhead

4a, 4b

pivot axis

5

solar cell

6

linear actuator

7

elastic element

B

total print width

D

pressure direction

Claims (15)

Printing unit for the parallel extrusion of print medium, in particular for the production of conductor tracks, with a plurality of output openings (2), for the simultaneous output of print medium from the output openings (2), characterized in that the printing unit has at least one central print head (1) and at least two edge print heads , wherein the central print head (1) and each edge print head (3a, 3b) each have a plurality of output openings (2) for the simultaneous output of print medium from the output openings (2) and on two opposite sides of the central print head one of the two Edge print heads is pivotally mounted on the central print head. pressure unit claim 1 , characterized in that the edge print heads are pivotable about mutually parallel pivot axes. Printing unit according to one of the preceding claims, characterized in that the output openings (2) of the central print head have central axes parallel to one another and the pivot axes of the edge print heads are parallel to the central axes of the output openings (2) of the central print head. Printing unit according to one of the preceding claims, characterized in that each edge print head (3a, 3b) has a plurality of output elements, each with at least one, preferably exactly one, output opening, the output elements being arranged to be displaceable along a displacement direction, so that the distance between the Output elements can be changed. pressure unit claim 4 , characterized in that elastic elements (7) are arranged between the output elements of the edge print heads. Pressure unit according to one of Claims 4 until 5 , characterized in that the printing unit has at least one actuator (6) in order to displace the output element of at least one edge print head, in particular both output elements of both edge print heads, in particular that each edge print head (3a, 3b) has at least one actuator, preferably an electric actuator, which is designed to interact with at least one output element, preferably a peripheral output element, in order to displace the output element in the displacement direction. Printing unit according to one of the preceding claims, characterized in that the output openings (2) of the central print head and the edge print heads are each arranged along a straight line and the edge print heads are arranged pivotably on the central print head (1) such that in a middle position the output openings (2 ) of the edge print heads and the center print head lie on a common straight line. Printing device for parallel extrusion of print medium onto a substrate, with a printing unit according to one of the preceding claims, characterized in that the printing unit has at least one drive element, in particular at least one motorized means for pivoting the edge print heads, in particular one or more electrical actuating means. Printing device according to one of the preceding claims, characterized in that the printing device is designed to move the printing unit and a substrate to be printed in a rectilinear printing direction (D) relative to one another and in that the pivot axes of the edge print heads are perpendicular to the printing direction (D). Printing device according to one of the preceding claims, characterized in that the printing device has a voltage source and a plurality of line electrodes, the printing device having a carrier unit for receiving a substrate to be printed and the carrier unit and line electrodes being arranged in such a way that a substrate to be printed between the print heads and the Line electrodes can be arranged, the line electrodes being arranged in the area of the edge print heads and the voltage source being connected to the edge print heads and the line electrodes in order to generate an electrical potential between the print medium which is output by the edge print heads and the line electrodes. Method for the parallel extrusion of print medium onto a substrate, wherein print medium is simultaneously discharged from a plurality of discharge openings (2) of a printing unit, while the printing unit and substrate are moved relative to one another in a printing direction (D), characterized in that during the printing process by means of a central print head the printing unit and at least two edge print heads arranged on opposite edge sides of the central print head, print medium is applied to the substrate from a plurality of output openings (2), and that the edge print heads are pivoted relative to the central print head (1) during the printing process. procedure after claim 11 , characterized in that the edge print heads are pivoted relative to the central print head (1) at the beginning of the printing process in the printing direction (D) and are pivoted during the printing process in such a way that at the end of the printing process the edge print heads are pivoted relative to the central print head (1) against the printing direction (D ) are pivoted. Procedure according to one of Claims 11 until 12 , characterized in that the edge print heads are pivoted in opposite directions during the printing process. Procedure according to one of Claims 11 until 13 , characterized in that during the printing process an electrical potential is generated between the printing medium and electrodes which are arranged on the opposite side of the printing unit of the substrate to be printed. Procedure according to one of Claims 11 until 14 , characterized in that during the pivoting of the edge print heads the distance between the output openings (2) of the edge print heads is changed, in particular is changed in such a way that parallel lines of print medium are applied to the substrate to be printed.

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