WO2015071270A1

WO2015071270A1 - Print head, printing device and method for applying a printing medium to a substrate, in particular a photovoltaic solar cell

Info

Publication number: WO2015071270A1
Application number: PCT/EP2014/074288
Authority: WO
Inventors: Maximilian Pospischil; Harald Gentischer; Martin KUCHLER; Markus KLAWITTER; Florian Clement; Daniel Biro; Jan Specht
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.
Priority date: 2013-11-14
Filing date: 2014-11-11
Publication date: 2015-05-21
Also published as: EP3068626A1; EP3068626B1; DE102013223250A1

Abstract

The invention relates to a print head for applying a printing medium to a substrate, in particular a semiconductor structure such as a photovoltaic solar cell, having a print head housing and a valve element, wherein the print head housing has at least one feed opening for feeding in printing medium and a plurality of outlet openings for discharging the printing medium, wherein the valve element is mounted rotatably in the print head housing, in order to switch between a first printing operating state, in which the feed opening is connected in a fluid-conducting manner to the outlet openings, and a second shut-off operating state, in which there is no fluid-conducting connection between the feed opening and the outlet openings. The invention is characterized in that the print head has at least one flushing medium connector and the valve element is configured and mounted rotatably in the print head housing in such a way that, in a third flushing operating state, the flushing medium connector is connected in a fluid-conducting manner to the outlet openings and, in the first and second operating state, there is no fluid-conducting connection between the flushing medium connector and the outlet openings.

Description

Printhead, printing device and method for applying a printing medium to a substrate, in particular a photovoltaic solar cell

description

The invention relates to a print head, a printing device and a method for applying a printing medium to a substrate, in particular a semiconductor structure such as a photovoltaic solar cell, according to the preambles of claims 1, 9 and 11.

In industrial printing operations, particularly in the manufacture of semiconductor structures, it is often desirable to apply a print medium to the substrate. Such a printing medium may be a printing paste, which in particular contains a dopant for doping one or more regions of the semiconductor structure, which serves for forming a mask for subsequent process steps and / or which contains metal particles for forming a metallic contact structure.

The substrate may be a semiconductor structure in the manufacturing process, for example for producing a photovoltaic solar cell or an LED structure such as an OLED structure or an inorganic LED structure.

It is known to apply printing paste by means of screen printing on a semiconductor structure. Likewise, US Pat. No. 5,151,377 discloses the use of a dispenser for applying a paste containing metal particles. From EP 2 196 316 a printing device with a print head is known, which print head has a multiplicity of outlet openings which can be closed by means of a valve element arranged in the print head.

It is an object of the present invention to provide the prior art printhead, the printing apparatus comprising the printhead, and the method of ren to improve the printing paste to the effect that increased precision and reliability is achieved.

This object is achieved by a print head according to claim 1, a printing device comprising such a print head according to claim 9 and a method according to claim 12, preferably embodiments of the print head are in claims 2 to 8, the printing device in claims 10 to 1 1 and the method in claims 13 to 16. Hereby, the wording of all claims is explicitly incorporated by reference into the description.

The inventive method is preferably designed for implementation by means of the print head according to the invention and / or the printing device according to the invention, in particular a preferred embodiment of the print head and / or the printing device. The printhead according to the invention and the printing device according to the invention are preferably designed to be carried out by means of the method according to the invention, in particular a preferred embodiment thereof. The printhead according to the invention is designed for applying a printing medium to a substrate, in particular for application to a semiconductor structure such as, for example, a photovoltaic solar cell during its production.

The printhead has a printhead housing and a valve element. The printhead housing includes at least one supply port for supplying the print medium and a plurality of discharge ports for discharging the print medium.

The valve element is rotatably supported in the printhead housing to control between a first pressure operating condition in which the supply port is fluidly connected to the exhaust ports and a second reverse operation state in which there is no fluid communication between the supply port and the exhaust ports. It is essential that the print head has at least one rinsing medium connection and the valve element is designed and rotatable in the pressure chamber. W is mounted head housing, is fiuidleitend connected to the Ausiassöffnungen and in the first and second operating state no connection, in particular no fluitleitende connection between Spülmediumanschluss and the outlet openings.

The invention is based on the knowledge that, for the precise dispensing of the pressure medium at the plurality of outlet openings, in particular when using highly viscous pressure media having flow limits, the flow path between valve and outlet opening is advantageously made short. Furthermore, experiments have shown that a precise control of the pressure medium flow at several parallel outlet openings through a central valve arranged in a common feed channel is not possible with sufficient precision. By contrast, if a separate separate valve is arranged for each outlet opening, the influence of elasticities in the system is reduced, and the formation of pressure gradients between the outlet opening during startup and shutdown processes is also prevented. Therefore, the print head according to the invention has a rotatably mounted in the print head housing valve element, wherein by rotating the valve element, the pressure medium output at the outlet openings can be allowed or prevented.

A further advantage of the device according to the invention is a self-reinforcing effect wherein the overpressure of the pressure medium in conjunction with the characteristic shaping of the closure shaft causes a force directed in the direction of the outlet openings, whereby the tightness of the valve increases with increasing pressure.

However, the investigations further revealed that high throughput and high precision are impeded by contaminants in the flow paths, in particular between the valve element and the outlet ports. In order to enable a high throughput and to prevent a reduction in the precision of the pressure medium output, it is therefore necessary to clean the printhead, in particular the flow paths between the valve element and the outlet openings. The printhead according to the invention enables quick cleaning by turning over the valve element in the purge operating state via the Spüimeöiumanschluss flushing medium can be guided to the plurality of outlet openings in a simple manner, so that rinsing takes place, in particular the flow paths immediately in front of the outlet openings. The change between the individual operating states takes place in a simple manner by turning the valve element, so that in rapid succession, a cleaning of the print head z. B. between two Druckmediumaufbringvorgängen can take place,

As a result, in particular an industrial application with a high throughput rate and a low risk of failure is achieved.

Preferably, a flushing medium line is formed in the print head, with a flushing medium connection and at least one flushing medium outlet, so that in the flushing operating state the flushing medium outlet of the valve element is arranged in the region of at least one outlet opening and fluidically connected to it. As a result, the supply of flushing medium to the outlet opening is ensured in a simple manner.

In particular, it is advantageous that, in the scavenging operating state, the scavenging medium outlet of the valve element is arranged in the region of the plurality of outlet openings and connected in a fluid-conducting manner to the latter. In this preferred embodiment, the flushing medium outlet thus covers a larger area, so that in the flushing operating state, the plurality of outlet openings are fluid-conductively connected to the flushing medium outlet of the flushing medium line.

In a further preferred embodiment, the flushing medium line has a flushing medium outlet for each of the plurality of outlet openings, so that in the flushing operating state each flushing medium outlet is arranged in the region of a respective outlet opening and is connected to the latter in a fluid-conducting manner. As a result, a defined supply of flushing medium is achieved at each outlet opening.

Preferably, the purge line is at least partially formed in the valve element. This ensures reliable separation of the flow paths between the pressure medium on the one hand and the flushing medium on the other hand. A particularly advantageous embodiment results here, by the purge line at least partially formed as an axial line, in particular as an axial bore in the valve element. In this preferred embodiment, the rinsing agent can be supplied in a simple manner in the valve element via the axial bore. Furthermore, starting from the axial bore, an approximately radially arranged recesses, in particular radial bores, are preferably provided, which connect the axial bore in the flushing operating state in each case to an outlet opening in a fluid-conducting manner. This results in the advantage that the flushing medium line can be formed in a simple manner by an axial and for each outlet opening in each case a radial bore in the valve element. In a further preferred embodiment, the flushing medium line between an inner wall of the pressure head housing facing the valve and the valve element is formed, preferably by a trench-like recess of the valve element. Preferably, the flushing medium line is at least partially formed as a partial hollow cylinder between the printhead housing and Ventiiele- ment, in particular by a partially hollow cylindrical recess of the valve element. This results in the advantage that no axial bore has to take place in the valve element, which can simplify the production process, in particular with long valve elements.

In this case, the flushing medium connection is preferably formed in the print head housing and arranged such that in the flushing operating state, the flushing medium connection is fluid-conductively connected to the flushing agent line.

Preferably, all of the plurality of outlet openings, in particular all outlet openings, are turned off simultaneously, i. a switching between the operating states B and C for all outlet openings takes place simultaneously. In some applications, it is desirable that one or more of the discharge openings be selectively disconnected separately from the remaining outlet openings.

In this preferred embodiment, therefore, some outlet openings are preferably switched off in time with respect to others; in particular, switching between the operating states B and C takes place for a partial amount of the outlet openings (4) offset in time to the remaining outlet openings.

For example, when using the printhead for applying a printing paste to a semiconductor structure, it is desirable for non-rectangular semiconductor structures such as semiconductor structures on so-called pseudo-square wafers to separately connect and disconnect marginal outlet openings so that a pressure medium output of only the marginal outlet openings is avoided these are not yet above the semiconductor substrate.

The valve element is therefore preferably designed such that in a fourth partial pressure operating state, the feed opening is fluid-conductively connected only to a subset of the plurality of outlet openings, in particular that peripheral outlet openings are not contained in the subset. Sn this advantageous embodiment can thus also be achieved by turning the valve element in a simple manner, an output of the pressure medium only at the subset of the plurality of outlet openings. It is within the scope of the invention to provide additional partial pressure operating states in further advantageous embodiments in which different subsets of the plurality of outlet openings are fluid-conductively connected to the feed opening, whereas the outlet openings not belonging to the respective subset are not fluid-conductively connected to the feed opening are. This can be achieved by a plurality of partial pressure

Operating conditions an adaptation to the desired shape of the substrate, in particular the semiconductor structure can be achieved, in particular, for example, an order of printing medium lines on round or polygonal substrates possible,

In a further advantageous embodiment, a common fluidization is formed between the feed opening and a plurality of outlet openings. This results in the advantage that there is a higher pressure medium throughput and thus a lower risk of contamination or blockages in the common Fluidieitung. When the valve element is designed with partial pressure operating states as described above, it is in particular teühaft, such outlet openings, which are connected in fluidieitend in all pressure operating conditions with the supply port to connect via a common fluid line with the supply port. Preferably, therefore, the common fluid line between the feed opening and the subset of the plurality of outlet openings is formed, in particular for the not contained in the subset outlet preferably a further fluid line, in particular preferably each formed a further fluid line.

In order to avoid a negative influence on the pressure medium, in particular of highly viscous printing pastes, a fluid line with a constant cross-section and preferably the same channel geometry between the feed opening and the outlet opening is preferably formed for each outlet opening.

Preferably, therefore, a pressure medium channel is formed for each outlet opening, which is connected fluidieitend with the supply port in the pressure-operating state and each pressure medium channel preferably has at least between the valve element and outlet a constant cross-section. In particular, in a preferred embodiment, in which each pressure medium channel is at least partially formed as a recess of the valve element, preferably for each pressure medium channel formed by the valve member portion of the pressure medium channel and the portion of the pressure medium channel between the valve element and outlet a constant cross-section.

The object underlying the invention is further achieved by a printing device according to claim 10. The printing device according to the invention for applying a printing medium to a substrate, in particular to a semiconductor structure, such as a photovoltaic solar cell, has a pressure medium reservoir and a Druckmediumpumpmittel and a printhead according to the invention, in particular a preferred embodiment thereof on. The pressure medium pumping means is fluidly connected to the pressure medium reservoir and the supply port of the printhead to supply pressure medium to the printhead. Preferably, the printing device comprises an actuating center! for the valve element. This actuating means is preferably designed for rotating the valve element relative to the printhead housing. In order to allow a precise change of the operating conditions, the actuating means is preferably designed to rotate the valve element at a peripheral speed in the range of 10 mm / s to 10 m / s and / or switching times between the operating conditions in the range 150 ps -. 1 50 ms to allow. It is within the scope of the invention to provide per se übiiche control means, in particular a control unit such as a microprocessor and / or a computer to control the printing process and in this case in particular by means of control signals to rotate the valve member by means of the actuating means to the respective to set the desired operating state.

The object underlying the invention is further achieved by a method for applying a printing medium to a substrate according to claim 13.

The method according to the invention for applying a printing medium to a substrate, in particular to a semiconductor structure such as a solar photovoltaic line, is effected by means of a printhead according to the invention, in particular an advantageous embodiment thereof.

The method comprises the following method steps:

In a method step A, the printhead is set up in the printing operating state.

In a method step B, the printing medium is fed to the print head and the print medium is discharged from the outlet openings onto the substrate. In a method step C, the printhead is set in the blocking operating state and the supply of printing medium to the printhead is ended. It is essential that, in a method step D, the printhead is set into the rinsing operating state and a supply or removal of rinsing medium to the rinsing medium connection occurs, so that the rinsing medium flows through the printhead and exits at the outlet openings, and thus a rinsing process takes place.

The flushing medium is preferably supplied via the flushing medium connection, so that the flushing medium connection acts as flushing medium inlet for the print head and the flushing medium is discharged at the outlet openings. It is likewise within the scope of the invention to remove the flushing medium via the flushing medium connection, in particular to suck it off, so that the flushing medium is supplied via the outlet openings and removed via the flushing medium connection (as sink indium outlet).

Preferably, compressed air is used as flushing medium. The compressed air can be supplied via the flushing medium connection, so that it is likewise within the scope of the invention to use a solvent, in particular acetone, isopropyl alcohol and / or terpineol, as the flushing medium.

In particular, when using compressed air as the flushing medium, it is advantageous to suck the compressed air through the flushing medium connection. Because this allows the ambient air to be used for rinsing in a simple manner and the impurities are not output from the outlet openings, but discharged via the flushing medium connection. The printhead according to the invention, the printing device according to the invention and the method according to the invention can be used for coating any desired substrates, for example silicon wafers, in particular in the production of various types of semiconductor structures. In particular, a use in the production of large-area semiconductor structures, such as LED, OLED or photovoltaic solar cells is advantageous because here often line-like structures should be generated by applying pressure medium, in particular a printing paste.

In particular, use for producing metallic contacting structures, preferably by using a printing paste containing metal particles, is advantageous. Such metallic contact structures are used in particular in photovoltaic solar cells. Typically, a metal contacting grid for discharging the charge carriers is arranged on the side facing the incident radiation when the solar line is used. The grid typically has a plurality of line-like, parallel contacting fingers. In particular for the production of these contacting fingers, the print head according to the invention, the printing device according to the invention and the method according to the invention are particularly suitable.

The print head is preferably designed such that no further line for the print medium is arranged between the outlet openings and the semiconductor substrate, i. H. that the pressure medium is applied directly to the semiconductor substrate after exiting the outlet openings.

Preferably, the print head is designed such that the flow path between the valve element and Ausiassöffnung in each of the plurality of outlet openings each smaller than 5 cm, preferably less than 1 cm, particularly preferably less than 0.3 cm.

The printing process can be carried out in a manner known per se, in particular as described in EP 2 196 316 B1. Thus, typically, the printhead is moved relative to the semiconductor substrate and, more particularly, moved perpendicularly to a longitudinal extent of the printhead during the printing operation to achieve application of a plurality of parallel, fin-like print media strands on the semiconductor substrate.

The execution openings are preferably arranged along a straight line.

Further preferred features and embodiments are explained below with reference to the figures and embodiments. Showing: Figures 1 a to 1 c, a first embodiment of a print head according to the invention;

Figures 2a to 2c, a second embodiment of an inventive

Printhead and

Figure 3 is a perspective view of an application example of a third embodiment of a printhead according to the invention.

In the figures, like reference numerals designate like or equivalent elements.

A first embodiment of a printhead according to the invention is shown schematically in FIGS.

Figures 1 a and 1 b and 2a and 2b show radial sectional views; Figure c and 2c each show an axial sectional view.

The printhead according to the first embodiment has a printhead housing 1 which has a cylindrical recess. In the cylindrical recess, a valve element 2 is rotatably mounted. The rotation can take place in FIGS. 1 a and 1 b in clockwise or counterclockwise direction about a pivot point D shown in FIG. 1 a. Accordingly, the axis of rotation D of the valve element 2 is shown in Figure 1 c.

The printhead housing 1 has a feed opening 3 for supplying pressure medium. Furthermore, the printhead housing 1 has a plurality of outlet openings 4 for discharging the pressure medium. By way of example, in FIG. 1c, the peripheral outlet openings 4a and 4b and two central outlet openings 4 are identified.

As already described, the valve element 2 is rotatably mounted in the housing 1 Druckkopfge. Figure 1 a shows here the rotational position of a printing operating state: In this rotational position, a pressure medium as example, a printing paste via the supply port 3 are fed (flow path indicated by arrows), the pressure medium passes through a conduit path which is formed between the valve element 2 and an inner wall of the printhead housing 1 and finally exits at the outlet openings 4.

As can be seen in FIG. 1, the feed opening 3 in the axial direction covers the entire pressure-active width of the print head. The valve element 2, in contrast, has for each outlet opening 4 in each case a part-ring-like recess (in the form of a hollow part cylinder with a rectangular cross-section), see for example the reference numerals 2a and 2b for the marginal teüringartigen recesses of the valve element 2 in Figure 1 c). The pressure medium is thus supplied by means of a feed opening 3 and fed through the part-ring-like recesses 2 a, 2 b in each case an outlet opening 4.

In a second blocking operating state, the valve element 2 is rotated relative to the printhead housing 1, so that the region of the valve element 2 labeled S in FIG. 1 a covers the outlet openings 4 and thus the pressure medium output is interrupted.

Finally, FIG. 1 b shows a third rinse operating state:

The valve element 2 has a flushing medium connection 5, which in the exemplary embodiment according to FIG. 1 is designed as an axial bore of the valve element 2. Furthermore, the valve element 2 has in each case a radial flushing medium line 6 designed as a radial bore for each outlet opening 4.

As can be seen in FIG. 1 b, the valve element 2 is rotated in the flushing operating state such that the radial flushing medium line 6 is in each case fluid-conductively connected to the associated outlet opening 4. In this operating state, rinsing agent can thus be supplied via the flushing medium connection 5, which passes through the axial rinsing agent line and reaches the outlet openings 4 via the respective radial rinsing agent lines 4, so that rinsing of the printing head takes place.

The printhead according to FIG. 1 thus enables an output of printing medium as well as a precise shutdown and a flushing only depending on the rotational pitch of the valve element 2 relative to the printhead housing 1. For the use of highly viscous pastes as a pressure medium, it is advantageous that the distance A between the valve element 2 and the outlet openings 4 is low. In the embodiment shown in Figure 1, the distance A is 0.5 mm.

The dashed line 7 according to FIG. 1 a describes a preferably modification of the first exemplary embodiment with edge shutoff. In this exemplary embodiment, the part-ring-like recesses 2 a, 2 b of the valve element 2 are designed differently from the remaining part-ring-like recesses. The marginal part-ring-like recesses overlap a smaller angular range compared to FIGS remaining part-ring-like recesses. As can be seen in FIG. 1A, the part-ring-like recess not shown in dashed lines overlaps an angular range over 200 °, whereas the partial ring-like recess 2b, which ends at the dashed line 7, covers an angle range smaller than 200 °.

In the rotational division of the valve element 2 shown in FIG. 1a, a partial pressure operating state is thus represented: the marginal outlet openings 4a and 4b are closed by the valve element (there is no fluid-conducting connection between the feed opening 3 and the outlet openings 4a and 4b, as in FIG 1 a, the flow path of the printing paste ends at the dashed line 7,

In this partial-pressure operating state, therefore, there is no pressure medium output at the outlet openings 4a and 4b, but only at the remaining outlet openings 4. In this way, for example, the formation of metallic contacting fingers and pseudo-square-wafers with correspondingly shorter fingers in the edge regions of the wafer is possible.

If, on the other hand, the valve element 2 is rotated further in the clockwise direction according to FIG. 1a, so that the area marked with the dashed line 7 is arranged on the left edge of the outlet opening 4, then pressure medium can be dispensed from all the outlet openings 4. FIG. 2 shows a second exemplary embodiment of a printhead according to the invention. To avoid repetition, only the essential differences from the first exemplary embodiment will be discussed below:

In the second embodiment of a printhead according to the invention, the flushing medium line is partially formed between the valve element 2 and the inner wall of the printhead housing 1. Accordingly, the flushing medium connection 5 is formed in the print head housing, so that in the flushing operating position according to FIG. 2 b there is a fluid-conducting connection between flushing medium connection 5 and outlet opening 4. The flow path between the feed opening 3 and outlet opening 4 is blocked accordingly in this operating state.

Conversely, in the pressure operating state illustrated in FIG. 2a, the flow path between flushing medium connection 5 and outlet opening 4 is blocked, as is the flow path between supply opening 3 and flushing medium connection 5, whereas a fluid-conducting connection exists between supply opening 3 and outlet opening 4. Finally, an application example is shown schematically and perspectively in FIG. 3 for explaining an exemplary embodiment of a printing device according to the invention and of a method according to the invention:

To produce a photovoltaic solar cell, printing paste containing metal particles on a pseudo-squared wafer W is applied in a plurality of parallel lines in order to form metallic contacting fingers.

For this purpose, the wafer W is moved through under the print head housing 1 in the dispensing direction indicated by an arrow. The print head can be designed according to FIG. 1 or FIG.

The print head is part of a printing device according to the invention, which further comprises a pressure medium reservoir 7 with integrated pressure medium pumping means, so that pressure medium of the feed opening 3 of the print head housing 1 can be fed via a line. Here, by turning the Ventä lelementes 2 by means of a designed as an electric motor Betätigungsm ittels 8 first set a partial pressure operating state, so that at the marginal Ausiassöffn kei n pressure medium is output. In the area of the beveled corners (two of the four beveled corners are marked by dashed circles) of the pseudo-square-wave wafer, no printing medium is initially applied.

Once the wafer W is arranged in full width under the print head, by turning the Ventiliements 2, the printing operating state is set in which over all Auslassöffn openings 4 pressure medium is output. As soon as the opposite chamfered corners of the pseudo square wafer reach the area under the print head, the partial pressure operating state is again set by turning the valve element 2, so that pressure medium is emitted solely via the non-edge outlet openings. Finally, if the entire wafer is printed, the blocking operating state is again set by turning the valve element 2 so that no pressure medium escapes from the outlet openings.

The actuating means can also be designed as a magnetic switch or pneumatic cylinder. Preferably, the actuating means is formed around

Switching times between the operating states in the range 1 50 ps to 1 50 ms to allow.

After passing through the wafer a Spülmediu m drip tray is driven under the print head and you rch turning the valve element 2, the purge mode is established by means of a compressed air source 9 compressed air is passed to a flushing medium connection 5 of the printhead, which on the

Rinse medium line is passed to all Ausiassöffnungen 4, so that a cleaning of the print head and in particular all Ausiassöffnungen 4 follows.

Subsequently, by turning the valve element 2, the partial pressure operating state is set again and the next wafer can be printed.

Claims

claims

A printhead for applying a printing medium to a substrate, in particular a semiconductor structure such as a photovoltaic solar cell, comprising a printhead housing (1) and a valve element (2), the printhead housing having at least one supply port (3) for supplying pressurized medium and a plurality of exhaust ports (4) for discharging the pressure medium,

wherein the valve member is rotatably supported in the printhead housing (1) to switch between a first pressurized operating condition in which the supply port is fluidly connected to the outlet ports (4) and a second disengaged operating condition in which no fluid communication between supply port (3 ) and the outlet openings consists of controlling

characterized,

the printhead has at least one flushing medium connection (5) and the valve element (2) is designed and rotatably mounted in the print head housing (1) such that in a third flushing operating state the flushing medium connection is fluid-conductively connected to the outlet openings (4) and in which first and second operating state there is no fluid-conducting connection between flushing medium connection (5) and the outlet openings (4).

2. Printhead according to claim 1,

characterized,

in that a flushing medium line is formed in the print head, with a flushing medium connection (5) and at least one flushing medium outlet, so that in the flushing operating state the flushing medium outlet of the valve element is arranged and fluidically connected to at least one outlet opening (4), preferably,

in the flushing operating state, the flushing medium outlet of the valve element is arranged in the region of the plurality of outlet openings (4) and is connected in a fluid-conducting manner to the latter and / or

that the flushing medium line for each outlet opening in each case one Has Spülmediumausgang and that each flushing medium outlet in the region each having an outlet opening is arranged in the purge operating state and fluidly connected thereto.

3. Printhead according to claim 2,

characterized,

the flushing medium line is formed at least partially in the valve element (2), in particular as an axial line, preferably an axial bore in the valve element (2).

4. Printhead according to claim 2,

characterized,

the flushing medium line is formed between an inner wall of the print head housing facing the valve element (2) and the valve element (2), in particular by a trench-like recess of the valve element,

5. Printhead according to claim 4,

characterized,

the flushing medium connection (5) is formed in the print head housing (1) and arranged such that in the flushing operating state the flushing medium connection (5) is fluid-conductively connected to the flushing agent line.

6. Printhead according to one of the preceding claims,

characterized,

that in a fourth partial pressure Beträebszustand the supply port (3) is fluidly connected only to a subset of the plurality of outlet openings (4), in particular that marginal outlet openings (4) are not included in the subset.

7. Printhead according to one of the preceding claims,

characterized,

a common fluid line is formed between the feed opening (3) and a plurality of outlet openings (4).

8. Printhead according to claim 6 and claim 7,

characterized,

in that the common fluid line is formed between the feed opening (3) and the subset of the plurality of discharge openings (4), in particular that at least one further fluid line is formed for the outlet openings (4) not contained in the subset, preferably that for each not the subset contained outlet opening in each case a further fluid line is formed.

9. Printing device for applying a printing medium to a substrate, in particular a semiconductor structure such as a photovoltaic solar cell,

with a pressure medium reservoir (7) and a pressure medium pumping means and a print head according to one of the preceding claims,

wherein the pressure medium pumping means is fluidly connected to the pressure medium reservoir (7) and the supply port (3) of the print head for supplying print medium to the print head.

10. Printing device according to claim 9,

characterized,

in that the pressure device comprises an actuating means for the valve element (2), in particular that the actuating means is designed to rotate the valve element relative to the printhead housing (1).

1 1. Printing device according to claim 10,

characterized,

that the printing device comprises a control unit, which is designed to cooperate with the actuating means such that by means of the control unit for each operating state, a rotational position of the valve element relative to the printhead housing (1) can be predetermined.

12. Method for applying a printing medium to a substrate, in particular a semiconductor structure such as a photovoltaic solar cell, Mitteis a printhead according to one of claims 1 to 9, comprising the following method steps:

A setting up the printhead in the printing mode;

B supplying the print medium to the printhead and discharging the print medium from the exhaust ports (4) onto the substrate;

C, setting up the printhead in the lock-up mode and terminating the supply of print medium to the printhead; characterized,

in a method step D, the printhead is set up in the scavenging operating state and the scavenging medium is supplied to the scavenging medium connection (5).

13. The method according to claim 12,

characterized,

that a switching between the operating states B and C for all outlet openings (4) takes place simultaneously.

14. The method according to claim 12,

characterized,

a switchover between the operating states B and C takes place for a subset of the outlet openings (4) offset in time from the remaining outlet openings.

15. The method according to any one of claims 12 to 14,

characterized,

that as flushing medium one or more of the group

- gases, in particular air,

Solvent, in particular acetone and / or terpineol

Thinner, in particular a substance already contained in the printing medium

is used.

16. The method according to any one of claims 12 to 1 5,

characterized,

that in process step D at the flushing medium connection (5) sucking the flushing medium takes place.