Printing unit and method for printing a substrate

Abstract

The invention relates to a printing unit (1) and a method for printing on a substrate (12). The printing unit (1) for printing on a substrate (12) comprises two print heads (2a, 2b) arranged one behind the other in the direction of travel of the substrate (12) and two pinning units (3a, 3b), wherein each print head (2a, 2b) has one or more print chips (4), each with two rows of nozzles (5a, 5b, 5e, 5f) arranged transversely to the direction of travel of the substrate (12), wherein each row of nozzles (5a, 5b, 5e, 5f) has two or more nozzles (6).The two rows of nozzles (5a, 5b, 5e, 5f) in each of the two print heads (2a, 2b) have a first color in a first of the two rows of nozzles (5a, 5e) and a second color, different from the first color, in a second of the two rows of nozzles (5b, 5f), and either the color sequence of the first and second colors in the two rows of nozzles (5a, 5b, 5e, 5f) between the two print heads (2a, 2b) is identical and the two print heads (2a, 2b) further have a mechanical offset (7) from one another which corresponds to half the distance between two adjacent nozzles (6) of the two or more nozzles (6), or the color sequence of the first and second colors in the two rows of nozzles (5a, 5b, 5e, 5f) between the two print heads (2a, 2b) is reversed.

Description

[0001] The invention relates to a printing unit and a method for printing a substrate.

[0002] When printing in color with corresponding printing units, it is common practice to print only a single color using a print head due to the head architecture. To achieve the maximum resolution of, for example, 600 dpi per color, each row of nozzles is filled with the same color with a physical resolution of 300 dpi, so that the maximum resolution of 600 dpi per color is achieved. It is also known to dry the printed ink using pinning units, whereby drying can generally take place after each or several of the print heads mentioned above. The so-called single-pass and multi-pass, such as the dual-pass process, are known as printing processes. In the single-pass process, each color is printed in one print pass, for example, all the yellow components of an image at once. In the multi-pass process, such as the dual-pass process, the image is printed in two separate passes, i.e.For example, the yellow components of the image are not divided all at once, but rather into two passes, with the division typically occurring stochastically. A disadvantage of known printing devices, which particularly implement the above-mentioned processes, is that they cannot achieve satisfactory print results for all desired applications, which are characterized by a homogeneous print result, high print quality, good edge sharpness, as well as high printing speed and correspondingly short cycle times.

[0003] A homogeneous print result is understood here in particular to mean a homogeneous color impression of the printed areas. High print quality is understood here in particular to mean achieving the desired print resolution, attractive multi-color printing and / or strong, preferably not pale, colors. Disadvantages of the single-pass process are often a lack of edge definition and a pale-appearing surface print that lacks satisfactory homogeneity. Disadvantages of the multi-pass process are long cycle times due to the back and forth movement of the print head and the mechanical offset of the print head by approximately 1 mm to eliminate systematic errors, such as two adjacent nozzles firing at an angle.Furthermore, this technology can only be used in direct printing applications where the substrate to be printed can be moved under the print head at least twice or more, so that a corresponding technical effort is also required here.

[0004] The invention is based on the object of providing an improved printing unit and an improved method for printing on a substrate, by means of which, in particular, the disadvantages of the prior art are avoided. In particular, the invention is therefore based on the object of providing a compact printing unit that delivers a homogeneous print result with high print quality and good edge sharpness.

[0005] This object is achieved by a printing unit, in particular for printing a substrate, comprising two print heads arranged one behind the other in the running direction of the substrate and two pinning units, wherein each print head has one or more print chips, each with two rows of nozzles arranged transversely to the running direction of the substrate, wherein each row of nozzles has two or more nozzles, and in particular wherein the two rows of nozzles are offset from one another by half a distance between two adjacent nozzles of the two or more nozzles, and wherein the two rows of nozzles in each of the two print heads have a first color in a first of the two rows of nozzles and a second color, different from the first color, in a second of the two rows of nozzles,and that either the color sequence of the first and second colors in the two nozzle rows between the two print heads is identical and the two print heads have a mechanical offset from each other that corresponds to half the distance between two adjacent nozzles of the two or more nozzles, and / or that the color sequence of the first and second colors in the two nozzle rows between the two print heads is reversed or swapped.

[0006] This object is further achieved by a method for printing a substrate comprising the following steps, which are carried out in particular in the following order: - providing a printing unit according to the invention, in particular according to one of claims 1 to 15; - feeding the substrate to the printing unit; - printing the substrate by means of the printing unit, in particular in two or more colors and / or with a resolution of 600 x 600 dpi.

[0007] The printing unit according to the invention and the method according to the invention for printing on a substrate combine the advantages of single-pass methods and multi-pass methods, such as the dual-pass method. In other words, the printing unit according to the invention simulates a dual-pass method, i.e. the printing of each color component of the image in two passes. Because the color sequence of the colors in the nozzle rows is reversed, or because the printing heads have a mechanical offset from one another when the color sequence in the nozzle rows is the same, the desired or maximum resolution of the print heads used is still achieved overall despite the use of two different colors per print head, because the second print head always prints into the spaces between the first print head, particularly in the printed area on the substrate.By using two print heads in combination with two colors in the nozzle rows, two-color printing is realized which achieves the maximum resolution of the print heads used and also achieves short cycle times, since the print heads simulate two passes, although physically or mechanically only one pass is carried out. Furthermore, this makes it possible to utilize the high print quality, good edge sharpness, high registration accuracy and the homogeneous print result of multi-pass processes, in particular the dual-pass process, in just a single pass. Thus, using the printing unit according to the invention, applications that were usually carried out using the single-pass process with printing units according to the prior art and therefore also have the associated disadvantages can now be produced with high print quality.This avoids the disadvantages previously associated with the known single-pass processes using conventional printing units. Such printing applications, which were usually carried out using the single-pass process, include, among others: roll-to-roll applications, such as the printing of labels, or sheet-fed applications or the printing of workpieces. In these applications, the advantages described here can now be achieved with the help of the printing unit according to the invention. The two pinning units contribute to the drying and thus the simulation of the two passes by means of appropriate intermediate drying. This thus provides a compact printing unit that produces a homogeneous print result with high print quality and good edge sharpness and high registration accuracy, while at the same time enabling short cycle times.

[0008] Register or registration, or register accuracy or registration precision, is the positioning accuracy of two or more elements and / or layers relative to one another. The register accuracy should be within a specified tolerance and as low as possible. At the same time, the register accuracy of several elements and / or layers with one another is an important feature for increasing process reliability. Accurate positioning can be achieved in particular using sensor-based, preferably optically detectable, registration marks or register marks. These registration marks or register marks can either represent special, separate elements, areas or layers, or they can themselves be part of the elements, areas or layers to be positioned. Ideally, the registration accuracy should be “0” or as low as possible.The registration accuracy is preferably less than 32 µm, preferably less than 16 µm, particularly preferably less than 8 µm.

[0009] In other words, it is possible to provide a printing unit, in particular for printing on a substrate, comprising a first and a second print head in the direction of travel of a substrate, wherein the first and second print heads are arranged one behind the other in the direction of travel of the substrate. Further preferably, each print head has one or more printing chips, each with two rows of nozzles arranged transversely to the direction of travel of the substrate, in particular wherein each row of nozzles has two or more nozzles, and wherein the two rows of nozzles are preferably offset from one another by half the distance between two adjacent nozzles.

[0010] Preferably, the two nozzle rows in the first and second print heads have a first color in a first of the two nozzle rows and a second color, different from the first color, in a second of the two nozzle rows, in particular wherein the color sequence of the first and second colors in the two nozzle rows is identical between the first and second print heads, and the first and second print heads have a mechanical offset from one another that preferably corresponds to half the distance between two adjacent nozzles of the two or more nozzles. Alternatively or additionally, it is preferred that the color sequence of the first and second colors in the two nozzle rows is reversed between the first and second print heads.

[0011] It's possible for the first and second print heads to have the first and second colors, respectively. It's also possible for the two print heads to have a first and second color.

[0012] It is also possible for the two print heads, or the first and second print heads, to each have a first and second row of nozzles, with the first row of nozzles having or containing the first color and the second row of nozzles having or containing the second color, or vice versa. In this context, "vice versa" means, in particular, that the first row of nozzles has or contains the second color and the second row of nozzles has or contains the first color.

[0013] In this case, it is possible for the color sequence in the nozzle rows of the two print heads, or of the first and second print heads, to be identical or reversed. If the color sequence is identical, it is particularly preferred for the first and second print heads to have a mechanical offset from one another, which preferably corresponds to half the distance between two adjacent nozzles of the two or more nozzles.

[0014] Thus, it is preferred that the two print heads, in particular the first and the second print head, are arranged offset from one another, preferably mechanically offset from one another, in such a way that the second of the two print heads, in particular the second print head, or the nozzles of the second print head print into the spaces between the nozzles, in particular into the gaps, of the first of the two print heads, in particular the first print head.

[0015] The at least two print heads are arranged in the direction of travel of the substrate. The distance between the first and second print heads is preferably one print head width. Similarly, the distance between the second and third, as well as the third and fourth, print heads is preferably one print head width.

[0016] The term "nozzle" is also used here to describe pixels, especially since a nozzle creates a dot or pixel on the substrate as a print or printed image. In other words, a row of adjacent pixels forms a pixel row or nozzle row. The spacing between the nozzles thus corresponds to the spacing of the pixels printed by the corresponding nozzles on the substrate.

[0017] In addition to the two rows of nozzles, a printing chip preferably also comprises actuators, in particular TFP actuators, and ink channels.

[0018] Furthermore, it is advantageous if the printing unit has at least two print heads arranged one behind the other in the direction of travel of the substrate and correspondingly at least two pinning units.

[0019] In other words, it is therefore possible for the printing unit according to the invention for printing a substrate to comprise at least two print heads arranged one behind the other in the running direction of the substrate and at least two pinning units.

[0020] In this regard, reference is also made to the explanations below, which describe a printing unit with two additional print heads and two additional pinning units.

[0021] It is also possible for the number of at least two print heads arranged one behind the other in the direction of travel of the substrate and accordingly the number of at least two pinning units to be selected depending on the colors to be printed or depending on the desired print and / or its color design. For example, it is possible for the number of print heads and pinning units to be four when selecting the CMYK model (cyan, magenta, yellow, key / black) or for the number of print heads and pinning units to be three when selecting the RGB model (red, green, blue). The CMYK model is the preferred color model and the color model commonly used in the printing industry, which is also preferably used in the present invention. Furthermore, it is also conceivable that in addition to the CMYK model, further special colors can be provided and printed.These can be colors, for example, individually or in multiples selected from: white, colors shaded with white, pastel colors, skin color, metallic color, neon colors. Thus, the number of print heads and / or pinning units can be, for example, two, three, four, five, six, seven, eight, or more, with two being preferred and four being particularly preferred. The design of the print heads and / or pinning units preferably corresponds to the design of the two print heads or the two additional print heads and / or the two pinning units or the two additional pinning units.

[0022] It is also possible to combine the printing unit according to the invention with two print heads, for example with one print head and / or one printing unit, wherein this print head and / or this printing unit is operated conventionally and, for example, has the same color in all nozzle rows. This means that the printing unit according to the invention can be combined with conventional printing units, in particular depending on the requirements for the print result. For example, it is conceivable that two colors with good edge sharpness, high registration accuracy, a homogeneous print result, and good print quality can be printed using the printing unit according to the invention, while other colors need not have such stringent requirements in a specific printing project and can therefore be printed using conventional printing units.

[0023] Colors here preferably refer to printing inks, especially printing inks. For example, a wide variety of colors and ink types, particularly those used industrially, are suitable. It is possible to use water-based inks, UV-curing inks, eco-solvent inks, oil-based inks, and / or solvent inks. Furthermore, special fluids, particularly those primarily found in digital and production printing, can also be used. Colors from the CMYK color model are preferably used for printing. However, it is also possible to use colors from other color spaces or color models, such as the RGB color model.

[0024] The drying of the ink, especially printing ink, takes place using pinning units, which intermediately dry or partially dry the ink and thus fix it. Drying here refers in particular to ultraviolet (UV) curing, i.e., polymerization or crosslinking of a UV-curable ink. Drying can also mean only partial crosslinking, i.e., gelling and / or increasing the viscosity. The pinning unit can also be referred to as a drying unit or intermediate drying unit.

[0025] Furthermore, the use of a printing unit according to the invention, in particular according to one of claims 1 to 15, in a printing device is expedient, preferably wherein the printing device comprises a substrate table, in particular for transporting the substrate.

[0026] The term printing device or printing system is understood here to mean a system that comprises a printing unit, in particular according to the invention, and further components such as a substrate table, a conveyor belt, a drying unit and / or a smoothing unit.

[0027] This makes it possible for the substrate, in particular the printing unit, to be fed via a substrate table.

[0028] It is also useful to use a printing unit according to the invention, in particular according to one of claims 1 to 15, for printing a substrate and / or in a method for printing a substrate.

[0029] Furthermore, the use of, in particular at least, two print heads, which are arranged one behind the other in particular in the running direction of the substrate, and wherein each print head has one or more print chips each with two rows of nozzles, which are arranged in particular transversely to the running direction of the substrate, preferably in a printing device, is also conceivable.

[0030] Here too, each row of nozzles preferably has two or more nozzles, and more preferably the two rows of nozzles are offset from one another by half a distance between two adjacent nozzles of the two or more nozzles.

[0031] Here too, the two rows of nozzles in each of the, in particular at least, two print heads expediently have a first color in a first of the two rows of nozzles and a second color, different from the first color, in a second of the two rows of nozzles, wherein either the color sequence of the first and second colors in the two rows of nozzles between the two print heads is identical and the two print heads have a mechanical offset from one another which corresponds in particular to half the distance between two adjacent nozzles of the two or more nozzles, and / or that the color sequence of the first and second colors in the two rows of nozzles between the two print heads is reversed.

[0032] Furthermore, the use of, in particular at least, two pinning units is advantageous in one printing device, preferably with one pinning unit being arranged downstream of each print head along the running direction of the substrate.

[0033] Further advantageous embodiments of the invention are described in the subclaims.

[0034] In the following, further preferred embodiments of the printing unit are described, among others: It is therefore possible for the first and second colours to be selected from cyan, black, yellow or magenta. In particular, if the first colour is cyan, the second colour is black, or vice versa, or if the first colour is yellow, the second colour is magenta, or vice versa. Conversely, in this context, means that if the first colour is black, the second colour is cyan, or if the first colour is magenta, the second colour is yellow. It is preferable to print the darker colours black and magenta first, followed by the lighter colours cyan and yellow. This enables two-colour printing, which already covers a broad spectrum of colours due to the CMYK colour model used.

[0035] However, it is also possible to use colors according to other color spaces or color models, such as the RGB color model.

[0036] It is advantageous if the printing unit has two additional print heads arranged one behind the other in the direction of travel of the substrate, as well as two additional pinning units, in particular where the two print heads and the two additional print heads are also arranged one behind the other in the direction of travel of the substrate. This makes it possible to print four colors, for example, the entire color spectrum of the CMYK model, using the printing unit, whereby the advantages outlined above are also achieved here.

[0037] Here too, it is expedient if each print head has one or more print chips, each with two, in particular further, rows of nozzles arranged transversely to the running direction of the substrate, wherein each, in particular further, row of nozzles has two or more nozzles, and wherein more preferably the two, in particular further, rows of nozzles are arranged offset from one another by half a distance between two adjacent nozzles of the two or more nozzles.

[0038] Preferably, the two, in particular further, rows of nozzles in each of the further two print heads have a third color, different from the first and second color, in a first of the two, in particular further, rows of nozzles and a fourth color, different from the first, second and third color, in a second of the two, in particular further, rows of nozzles.

[0039] In other words, it is possible for the printing unit to further comprise a third and fourth print head in the running direction of the substrate, wherein the third and fourth print heads are preferably arranged one behind the other in the running direction of the substrate.

[0040] It makes sense if the two print heads have a first and a second print head and / or the two other print heads have a third and a fourth print head.

[0041] Furthermore, it is also advisable for the two print heads, the other two print heads, the first, second, third, and / or fourth print head to be a PrecisionCore print head from Epson, Suwa, Japan. However, it is also possible to use other print heads that have one or more print chips with two rows of nozzles each, such as those from Konica Minolta, Tokyo, Japan, or Ricoh Company Ltd., Tokyo, Japan.

[0042] Preferably, the printheads are compatible with a variety of inks and ink types, particularly those used industrially. This makes it possible to use water-based inks, UV-curing inks, eco-solvent inks, oil-based inks, and / or solvent inks with the printheads.

[0043] Special fluids, especially those primarily found in digital and production printing, can also be used. However, the print heads are preferably used to print inks with the CMYK color model, as explained above and below.

[0044] It's possible for the third and fourth print heads to have the third and fourth colors, respectively. It's also possible for the two other print heads to have a third and fourth color.

[0045] It is also possible for the two further print heads or the third and fourth print heads to each have a further first and a further second row of nozzles, wherein the further first row of nozzles has or contains the third color and the further second row of nozzles has or contains the fourth color or vice versa.

[0046] It is advantageous that if the first print head has or contains the first and second colors, then the second print head also has or contains the first and second colors. It is also advantageous that if the third print head has or contains the third and fourth colors, then the fourth print head also has or contains the third and fourth colors.

[0047] It is advantageous if the print heads that print the same colors, in particular the two print heads and / or the additional print heads, or the first and second print heads and / or the third and fourth print heads, follow one another. Thus, print heads that print the same colors are preferably located close to one another.

[0048] What is meant by "sequential" here is that after a print head with one color combination, such as yellow / magenta, the next print head, which has the same color combination, for example yellow / magenta again, is arranged. However, it is possible for a pinning unit to be arranged between these print heads, but in particular no print head with a different color combination. This significantly reduces register variations or inaccuracies between the same colors. Although this does make the register accuracy between the other colors, for example from yellow / magenta to cyan / black, the human eye does not perceive register variations from one color to another color as strongly because in this case colored areas are either not occupied and so, for example, white areas orAreas can be represented in the color of the unprinted substrate, or color areas can be covered with two colors, thus creating mixed colors, for example. Registration variations within a color, however, are perceived by the human eye as, for example, unclean edges and / or poor edge sharpness. Therefore, it is preferable for print heads that print the same colors to be located close to each other, so that, for example, the two print heads and, accordingly, the two other print heads follow one another and are only separated by an intermediate pinning unit.

[0049] As explained above, it is possible for the color sequence in the nozzle rows of the print heads to be identical or reversed. For example, if the first color is present in the first nozzle row of the first print head and the second color is present in the second nozzle row of the first print head, then either the first or the second color can be present in the first nozzle row of the second print head. The same applies to the second nozzle row of the second print head. For example, if the third color is present in the first nozzle row of the third print head and the fourth color is present in the second nozzle row of the third print head, then either the third or the fourth color can be present in the first nozzle row of the fourth print head. The same applies to the second nozzle row of the fourth print head.

[0050] It is preferred if the color sequence in the print heads is identical and there is a mechanical offset between the print heads. For example, if the first color is present in the first nozzle row of the first print head and the second color is present in the second nozzle row of the first print head, then the first color is also present in the first nozzle row of the second print head and the second color is also present in the second nozzle row of the second print head, with the first and second print heads exhibiting the mechanical offset as described above.Furthermore, it is preferred, for example, if the third color is present in the first row of nozzles of the third print head and the fourth color is present in the second row of nozzles of the third print head, then the third color is also present in the first row of nozzles of the fourth print head and the fourth color is also present in the second row of nozzles of the fourth print head, wherein the third and the fourth print head have the mechanical offset, as already explained above and also below.

[0051] The printing inks can be printed using different printing approaches. The printing inks are preferably printed in the following order: cyan, magenta, yellow, black. The printing inks are particularly preferably printed from light to dark, in the following order: yellow, magenta, cyan, black. The “light to dark” approach has been established for inkjet printers. Regardless of the printing approach chosen, it is preferably provided that black is printed last; when four printing inks are used, as the fourth color; when six printing inks are used, as the sixth printing color, etc. It is expedient here if the first, second, third and fourth colors are selected from cyan, black, yellow, magenta; preferably, if the first color is cyan, the second color is magenta, or if the first color is magenta, the second color is cyan.Alternatively, it is also conceivable that if the first color is yellow, the second color is magenta, or that if the first color is magenta, the second color is yellow. Alternatively, it is also conceivable that if the first color is yellow, the second color is cyan, or that if the first color is cyan, the second color is yellow. This makes it possible to print the entire color spectrum of the CMYK model using the printing unit, while also achieving the advantages outlined above.

[0052] It is also advantageous that the color sequence of the third and fourth colors in the two, in particular further, rows of nozzles between the two further print heads is preferably identical and the two further print heads have a mechanical offset from one another which corresponds to half the distance between two adjacent nozzles of the two or more nozzles, or alternatively or additionally preferably that the color sequence of the third and fourth colors in the two rows of nozzles between the two further print heads is reversed.

[0053] Thus, it is preferred that the two further print heads, in particular the third and the fourth print head, are arranged offset from one another, preferably mechanically offset from one another, in such a way that the second of the two further print heads, in particular the fourth print head, or the nozzles of the fourth print head print into the spaces between the nozzles, in particular into the gaps, of the first of the two further print heads, in particular the third print head.

[0054] This also achieves the maximum resolution of each print head, since the second print head with the same color combination is forced to print into the gaps of the first print head, either due to mechanical offset or due to the reversal of the color sequence in the two nozzle rows. Furthermore, by reversing the color sequence in the two nozzle rows, all print heads can be arranged in a row directly behind one another, which shortens the mechanical alignment work.

[0055] It is also conceivable to arrange multiple print heads perpendicular to the substrate's direction of travel to increase the print image size accordingly. In this case, a distance of one print head length would be necessary between the individual print heads, especially those of the same color.

[0056] Advantageously, the distance between two adjacent nozzles of the two or more nozzles is between 10 µm and 100 µm, preferably between 20 µm and 80 µm, particularly preferably between 30 µm and 50 µm.

[0057] Advantageously, all distances between the two or more nozzles are equidistant. Preferably, the distances between the two or more nozzles are equidistant along a direction transverse to the direction of travel of the substrate and / or the distances between the two or more nozzles having the same color, in particular the first, second, third, and / or fourth color, are equidistant.

[0058] Preferably, the distance between the two rows of nozzles and / or the two further rows of nozzles or the first and second row of nozzles and / or the further first and the further second row of nozzles is between 500 µm and 5000 µm, preferably between 1000 µm and 3000 µm.

[0059] Preferably, the mechanical offset between the two print heads and / or between the two further print heads arranged transversely to the running direction of the substrate is between 20 µm and 60 µm, preferably between 30 µm and 50 µm, more preferably 40 µm.

[0060] It is therefore useful if the mechanical offset between the two print heads and / or between the two further print heads or between the first and second print heads and / or between the third and fourth print heads corresponds to half the distance between two adjacent nozzles of the two or more nozzles or corresponds to half a pixel.

[0061] It is also useful if the mechanical offset is between the two print heads and / or the other two print heads or between the first, second, third and fourth print heads, which each have the same colors or color combinations, such as the first and second and / or third and fourth colors.

[0062] It is thus possible for the two print heads and / or the two further print heads to have the mechanical offset from one another. It is also possible for the first and second print heads and / or the third and fourth print heads to have the mechanical offset from one another. Furthermore, it is expedient for the first and fourth and / or the second and third print heads to have the mechanical offset from one another. Preferably, the first and third or the second and fourth print heads are not offset from one another. It is thus expedient if the first and third or the second and fourth print heads are arranged directly behind one another and / or are aligned along an imaginary line.

[0063] It is further advantageous if the distance between the two print heads and / or between the two further print heads, in particular between the first, second, third and fourth print heads, is between 20 mm and 80 mm, preferably between 30 mm and 50 mm.

[0064] Advantageously, the printing unit has a resolution of 600 x 600 dpi. However, it is also possible for the printing unit to have a resolution of 1200 x 1200 dpi, or a resolution of 600 x 1200 dpi, or 1200 x 600 dpi. As explained above, a resolution of 600 x 600 dpi per color is typically achieved with print heads by filling each nozzle row with the same color, each with a physical resolution of 300 dpi, thus achieving a maximum resolution of 600 dpi per color.According to the printing unit according to the invention, the resolution of 600 x 600 dpi is achieved by using two print heads, each with two rows of nozzles, wherein each two rows of nozzles, as explained above, have the first color in the first row of nozzles and the second color in the second row of nozzles, and wherein the color sequence is either swapped between the two print heads or, with the same color sequence, the second print head is offset by half a pixel. As a result, the second print head always prints in the spaces between the first print head, so that the print resolution of 600 dpi is achieved. If the print heads used have other maximum resolutions, such as 1200 dpi, these resolutions can also be achieved accordingly using the printing unit described here.

[0065] In the following, further preferred embodiments of the pinning units are described, among others: It is further advantageous that a pinning unit is arranged downstream of each print head along the direction of travel of the substrate, in particular that one of the two pinning units is arranged downstream of each of the two print heads along the direction of travel of the substrate and / or that one of the two further pinning units is arranged downstream of each of the two further print heads along the direction of travel of the substrate. By carrying out the intermediate drying after each color or each print, high print quality and high edge sharpness are achieved. Furthermore, the intermediate drying after each print head ensures that, as explained above, two passes per color are simulated, although physically only one pass takes place.

[0066] Advantageously, the two pinning units and / or the two further pinning units have an irradiance between 0 W / cm 2 up to 10 W / cm 2 , preferably between 0.5 W / cm 2up to 7.5 W / cm 2 , more preferably between 2 W / cm 2 up to 5 W / cm 2 This ensures sufficient fixation of the print, thus achieving high print quality.

[0067] Furthermore, it is advantageous that the two pinning units and / or the two further pinning units have a circuit board with one or more light-emitting diodes (LEDs), in particular UV LEDs.

[0068] Preferably, the two pinning units and / or the two further pinning units have one or more LEDs, preferably UV LEDs, in particular which generate light from the wavelength range between 100 nm and 420 nm, preferably between 280 nm and 405 nm, more preferably between 350 nm and 400 nm, even more preferably between 365 nm and 395 nm.

[0069] It is advantageous if the two pinning units have a first and a second pinning unit and / or if the other two pinning units have a third and fourth pinning unit.

[0070] Preferably, each print head is followed by a pinning unit, particularly in the direction of travel of the substrate. Thus, it is preferred if a first pinning unit is arranged after the first print head, a second pinning unit after the second print head, a third pinning unit after the third print head, and a fourth pinning unit after the fourth print head, particularly in the direction of travel of the substrate.

[0071] Furthermore, it is expedient that the two print heads and / or the two further print heads and that the two pinning units and / or the two further pinning units are constructed identically, in particular structurally identical.

[0072] Furthermore, it is possible that the distance between each print head and the pinning unit arranged after the print head is between 10 mm and 80 mm, preferably between 30 mm and 50 mm.

[0073] It is expedient to select the distance between each print head and the pinning unit arranged downstream of the print head depending on at least one of the following parameters: distance and / or properties and / or type of substrate to be printed, the electrical power of the pinning unit, the irradiance of the pinning unit, the printing ink used, the cooling capacity of the water cooling system, the application volume of the ink used and the resolution of the printing unit.

[0074] In the following, further preferred embodiments of a printing unit with a base plate are described, among others: Advantageously, the printing unit further comprises a base plate, wherein the two pinning units and / or the two further pinning units or the first, second, third or fourth pinning unit are at least partially integrated into the base plate.

[0075] The base plate is advantageously made of aluminum, steel, or magnesium and / or has dimensions of between 200 mm and 1000 mm, preferably between 400 mm and 600 mm, in the running direction of the substrate. A dimension transverse to the running direction of the substrate (substrate width) varies greatly and depends in particular on the substrate used and its dimensions transverse to the running direction of the substrate, the printing application, and the number of printing inks used. However, larger dimensions are also conceivable, particularly depending on the print heads used, the substrate to be printed, and / or the printing system used. It is also possible for the printing unit to further comprise a base plate, in particular wherein the two pinning units and / or the two further pinning units are integrated into the base plate and / or at least partially integrated or built into the base plate.

[0076] It is possible that the circuit board with one or more light-emitting diodes (LEDs), in particular UV LEDs, the two pinning units and / or the two further pinning units is installed or integrated in the base plate.

[0077] It is therefore expedient if at least a portion of the two pinning units and / or the two additional pinning units are arranged below the surface of the base plate. Preferably, less than 75%, preferably less than 50%, and more preferably less than 25% of the maximum height of the pinning unit is below the surface of the base plate.

[0078] This makes it possible to further reduce the space required by the pinning units, as the installation height of the pinning units is significantly reduced. This creates more space, especially above the pinning units, which can be used for the ink supply tubes to the print heads.

[0079] It is also expedient for the base plate to comprise two parts, with a first part of the two parts comprising the two print heads and the two pinning units, and a second part of the two parts comprising the two additional print heads and the two additional pinning units. It is also possible for the two parts to be designed to be inclined or tiltable relative to the horizontal, as explained in particular below.

[0080] The base plate is preferably V-shaped; in particular, the base plate comprises two parts that are inclined relative to the horizontal, preferably between 0 degrees and 25 degrees, more preferably between 0 degrees and 15 degrees, and even more preferably between 0 degrees and 10 degrees. In other words, a base plate shaped in this way forms an upside-down V-shape. This reduces the problem of the web edge, particularly in roll-to-roll printing machines, undesirably raising up as the substrate is fed to the printing unit. The raising of the web edge is achieved, in particular despite the compactness of the printing unit, by this shape of the base plate, so that the advantage of compactness is retained and, at the same time, raising of the web edge is avoided.

[0081] For example, it is possible for the base plate to be designed in such a way that it can be switched back and forth between a flat position and a V-shaped configuration. This is possible, for example, using an adjustment device such as an eccentric, so that the base plate is positioned flat for sheet-fed applications and V-shaped, as described above, for roll-to-roll applications. This ensures that the printing unit can be used in a variety of ways.

[0082] Furthermore, it is advantageous for the two pinning units and / or the two additional pinning units to be water-cooled. This ensures effective cooling and, in contrast to air-cooled systems, prevents air currents that transport tiny ink drops into the printer's interior, causing contamination and negatively impacting print quality. Furthermore, water cooling, especially compared to air cooling, enables a compact design and thus contributes to the compactness of the printing unit, while advantageously maintaining or even improving cooling performance.

[0083] Preferably, the water cooling system has a volume flow or flow rate between 50 liters / h and 1000 liters / h, more preferably between 100 liters / h and 550 liters / h, and / or the water cooling system has a cooling capacity between 400 watts and 1600 watts. This ensures efficient and sufficient cooling.

[0084] It is also expedient to select the dimensions of the two pinning units and / or the dimensions of the two additional pinning units according to the dimensions along the substrate's running direction (substrate length) and / or across the substrate's running direction (substrate width). These compact dimensions ensure that the space requirements of the pinning units are as small as possible.

[0085] As explained above, it is also possible for the substrate to be fed to the printing unit via a substrate table. It is advantageous in this case for the substrate table to be raised in the center such that, preferably when using a V-shaped base plate, in particular according to a V-shaped base plate as described above, the distance between the substrate and / or the two print heads and the two other print heads is essentially identical.

[0086] Furthermore, it is possible for final drying to take place, particularly after printing the substrate using the printing unit according to the invention, with the inks, particularly the first, second, third, and / or fourth inks. In this case, it is also possible for the final drying to be carried out using a final drying unit. Furthermore, it is also possible for the final drying to be delayed, particularly with a time delay, so that the inks are given more time to blend. This allows the colored areas to appear more homogeneous.

[0087] Preferably, the distance between the substrate and the two print heads and / or the two further print heads is between 0.5 mm and 5 mm, more preferably between 1 mm and 2 mm, even more preferably between 0.8 mm and 1.5 mm.

[0088] The features, effects, and advantages described in connection with the printing unit can also be applied analogously to the method for printing a substrate and are therefore considered to be disclosed. The same applies in reverse: Features, effects, and advantages described in connection with the method for printing a substrate can also be applied to the printing unit and are considered to be disclosed.

[0089] In the following, embodiments of the invention are explained by way of example with the aid of the enclosed figures, which are not to scale. Fig. 1 shows a schematic of a print head Fig. 2a to 2d show schematic pressure units Fig. 3a and Fig. 3b shows schematic pressure units Fig. 4a and Fig. 4b show schematic pressure units Fig. 5a shows schematically a printing unit in side view Fig. 5b shows a section of Fig. 5a Fig. 6 shows schematically a printing device in side view

[0090] Fig. 1 shows a schematic diagram of a print head 2.

[0091] As in Fig. As shown in Figure 1, the print head 2 has four print chips 4, each with two rows of nozzles 5a, 5b, 5c, 5d. The rows of nozzles 5a, 5b, 5c, 5d are preferably arranged transversely to the direction of travel of a substrate. The print chips 4 are Fig. The print head 2 shown in Figure 1 is arranged in two rows one behind the other, with the two rows being slightly offset from one another. However, it is also possible for the print head 2 to have, for example, only one print chip 4 with two rows of nozzles 5a, 5b. Furthermore, other arrangements of the print chips 4 and a different number of print chips 4 are also possible.

[0092] In the Fig. The print head 2 shown in Figure 1 is a PrecisionCore print head from Epson, Suwa, Japan. However, as explained above, it is also possible to use other print heads 2 that have one or more print chips 4, each with two rows of nozzles 5a, 5b, 5c, and / or 5d, such as those from Konica Minolta, Tokyo, Japan, or Ricoh Company Ltd., Tokyo, Japan.

[0093] The Fig. The print head 2 shown in Figure 1 is compatible with a wide variety of inks and ink types, particularly those used industrially. Thus, it is possible to use water-based inks, UV-curing inks, eco-solvent inks, oil-based inks, and / or solvent inks with the print head 2. Furthermore, special fluids, particularly those primarily found in digital and production printing, can also be used. However, inks with the colors of the CMYK color model are preferably printed with the print head 2.

[0094] The distance between the printing chips 4 is Fig. For example, the print head 2 shown in Figure 1 is 20 mm. Furthermore, the two rows of print chips 4 are spaced 15 mm apart, and the two rows of print chips 4 are offset by 30 mm.

[0095] As already explained, due to the head architecture, most print heads only allow a single color to be printed. For example, with conventional print heads, both nozzle rows 5a, 5b or 5c, 5d are occupied with the same color, with, for example, a nozzle row 5a, 5b, 5c, or 5d each having a physical resolution of 300 dpi. This results in a physical resolution of 600 dpi per color.

[0096] In the print heads 2 of the printing unit 1 according to the invention, however, the two nozzle rows 5a and 5b and 5c and 5d are provided with two different colors, so that in the upper nozzle rows, for example the nozzle rows 5a and 5c, a first color is present and in the lower nozzle rows, for example the nozzle rows 5b and 5d, a second color different from the first color is present or is printed by the corresponding nozzle rows.

[0097] It is advantageous if the first and second colors are selected from cyan, black, yellow, or magenta. In particular, if the first color is cyan, the second color is black, or vice versa, or if the first color is yellow, the second color is magenta, or vice versa. The colors used therefore preferably reflect the colors of the CMYK color model. However, it is also possible, in principle, to use colors according to other color spaces or color models, such as the RGB color model.

[0098] Fig. 2a to 2d show schematically printing units 1.

[0099] The Fig. The printing unit 1 shown in Figure 2a comprises the two print heads 2a and 2b, which are arranged as shown in Fig. 2a indicated by the dashed arrow in the direction of travel of a substrate which is Fig. 2a shown printing unit 1. The Fig. The printing unit 1 shown in Figure 2a therefore comprises a first print head 2a and a second print head 2b. The print heads 2a, 2b have, as shown in Fig. 1, printhead 2, print chips 4 each with two rows of nozzles, such as 5e and 5f. The two rows of nozzles 5e and 5f each have two or more nozzles 6, as shown below in Fig. 3a, b and Fig. 4a, b. Here, as is usual with most print heads, the two nozzle rows 5e and 5f are advantageously arranged offset from each other by half the distance between two adjacent nozzles 6. As the Fig. 2a and further illustrated by the different hatching of the nozzle rows 5e and 5f, in the two nozzle rows 5e and 5f in each of the two print heads 2a and 2b, a first color is present in the nozzle row 5e of the print heads 2a, b and a second color is present in the nozzle row 5f of the print heads 2a, b, wherein the second color differs from the first color. Furthermore, the two print heads 2a and 2b, as shown in Fig. 2a by the dotted lines 20a, an offset 7, in particular a mechanical offset 7, to each other, which corresponds to half the distance between two adjacent nozzles 6.

[0100] In the Fig. For example, the different colors shown in Figure 2a in the two nozzle rows 5e and 5f are two colors from the CMYK color model. Thus, it is possible that the first color is cyan and the second color is black, or vice versa, or that the first color is yellow and the second color is magenta, or vice versa.

[0101] At the Fig. The printing unit 1 shown in Figure 2a uses black as the first color and cyan as the second color. Furthermore, the Fig. The printing unit 1 shown in Figure 2a has a resolution of 600 x 600 dpi.

[0102] Again Fig. 2a can be further removed, the printing unit 1 further comprises two pinning units 3a and 3b. The pinning units 3a and 3b are arranged such that each print head 2a, 2b is assigned a pinning unit 3a, 3b. As the Fig. 2a, a pinning unit 3a is arranged after each of the print heads 2a and 2b along the direction of travel of the substrate, which is indicated by the dashed line. The distance between the print heads 2a and 2b and the pinning units 3a and 3b arranged thereafter is Fig. For example, the distance between the print heads 2a and 2b and the pinning units 3a and 3b arranged downstream thereof typically depends on parameters such as the distance and / or properties and / or type of substrate to be printed, the electrical power of the pinning unit, the irradiance or light intensity of the pinning unit, the printing ink used, the cooling capacity of the water cooling system, the application volume of the ink used, and the resolution of the printing unit.

[0103] The Fig. 2b shown printing unit 1 corresponds to the one in Fig. 2a with the difference that the printing unit 1 of the Fig. 2b has two further print heads 2c and 2d and two further pinning units 3c and 3d. As in Fig. 2b, all print heads 2a, 2b, 2c and 2d are arranged one behind the other in the direction of travel of the substrate. Just as in Fig. 2a, each print head 2a, 2b, 2c and 2d is followed by a pinning unit 3a, 3b, 3c and 3d. Furthermore, as in Fig. 1 and Fig. 2a each print head 2a, 2b, 2c and 2d has a print chip 4 with two nozzle rows 5e, 5f, 5g, 5h, which are also arranged as in Fig. 2a are arranged transversely to the direction of travel of the substrate, which is indicated by the dashed arrow. The nozzle rows 5g, 5h of the print heads 2c and 2d also have, as in Fig. 3a, b and Fig. 4a, b, nozzles 6. Preferably, these nozzle rows 5g, 5h are also offset by half a distance between two adjacently arranged nozzles 6, particularly depending on the print head used.

[0104] As in Fig. As shown in Figure 2b by the different hatching, two different colors are also present in the other two print heads 2c and 2d, in the form of a third and fourth color. All colors are different from each other. Thus, the first, second, third, and fourth colors are different from each other. Fig. 2b the first 2a and the second 2b printheads print the first and second colors and the third 2c and the fourth 2d printheads print the third and fourth colors. As in Fig. As shown in Figure 2b, the two print heads 2a and 2b also have the same color sequence of the first and second colors, and the two other print heads 2c and 2d have the same color sequence of the third and fourth colors.

[0105] At the Fig. For example, the different colors shown in Figure 2b in the two nozzle rows 5e and 5f, as well as 5g and 5h, are four colors from the CMYK color model. Thus, it is possible that the first color is cyan and the second color is black, or vice versa, or that the first color is yellow and the second color is magenta, or vice versa. Fig. In the printing unit 1 shown in Figure 2b, black is used as the first color, cyan as the second color, magenta as the third color, and yellow as the fourth color. However, it is also expedient to use, for example, yellow as the first color, magenta as the second color, black as the third color, and cyan as the fourth color. In principle, the colors of the CMYK color model can be distributed arbitrarily between the nozzle rows 5e and 5f, as well as 5g and 5h, as long as each color is arranged in two nozzle rows and, in this case, in the same color sequence in the print heads 2a and 2b, as well as 2c and 2d.

[0106] In accordance with the Fig. The printing unit 1 shown in Figure 2a also has the Fig. 2b, the printing unit 1 has an identical color sequence of the first and second colors in the two print heads 2a and 2b. The color sequence of the third and fourth colors in the print heads 2c and 2d is also identical. Furthermore, just like the print heads 2a and 2b, the print heads 2c and 2d are mechanically offset from one another in such a way that the offset 7, as indicated by the dotted line 20a, corresponds to half the distance between two adjacent nozzles 6 and, as also indicated in the context of Fig. 4a, b is explained again. The Fig. The printing unit 1 shown in Figure 2b, like the one in Fig. The printing unit 1 shown in Figure 2a has a resolution of 600 x 600 dpi, but unlike the one shown in Fig. However, the printing unit 1 shown in Figure 2a can print all colors from the CMYK model, as it has all four basic colors of the color model.

[0107] The Fig. 2c pressure unit 1 corresponds to the one in Fig. 2b, with the difference that the print heads 2a and 2b and 2c and 2d do not have the same colors, but the print heads 2a and 2c and 2b and 2d have the same colors. The mechanical offset 7 indicated by the dotted line 20a is adjusted here such that the print heads 2a and 2c and 2b and 2d, which have the same colors, each have the mechanical offset described above. Here, the print heads 2a and 2c are offset from each other and, accordingly, the print heads 2b and 2d. As already explained above, the print heads 2a and 2c and 2b and 2d are located in the Fig. 2c, however, are relatively far apart, so that here, in comparison to the embodiment shown in Fig. The risk of register variations is higher in the embodiment shown in Figure 2b. Therefore, reference is made to the above comments in this regard.

[0108] The Fig. The printing unit 1 shown in Figure 2d also essentially corresponds to the one shown in Fig. 2b, but has the following differences. First, the printing unit shown in Fig. 2d, the printing unit 1 has print heads 2a, 2b, 2c and 2d, which, like the one shown in Fig. 1 may comprise a plurality of print chips 4. Here, too, the print heads 2a and 2b have a first and a second color, and the print heads 2c and 2d have a third and fourth color. In contrast to the Fig. 2b shown printing unit 1 and also to the one in Fig. However, in the printing unit 1 shown in Figure 2c, the color sequence in the nozzle rows 5i, 5j and 5k, 5l as well as 5m, 5n and 5o, 5p is reversed or swapped. Thus, the color sequence of the first and second colors in the nozzle rows 5i, 5j, 5k, 5l between the print heads 2a and 2b is reversed or swapped. Likewise, the color sequence of the third and fourth colors in the nozzle rows 5m, 5n, 5o, 5p between the print heads 2c and 2d is reversed or swapped. This is shown in Figure 2c. Fig. 2d by the corresponding shading. As explained above, by reversing the color sequence in the nozzle rows in the two print heads, which have the same colors, as well as by the Fig. 2a, Fig. 2b and Fig. 2c alternatively presented mechanical offset 7 with the same color sequence in the nozzle rows, achieves that the physical resolution of the print head used is realized, since the respective second print head, which has the same colors as a first print head, then prints into the gaps of the first print head. As shown in Fig. 2d shown all print heads 2a, 2b, 2c and 2d are arranged in series, ie arranged directly one after the other, thus aligned along an imaginary line, then this is only, as in Fig. 2d, by reversing the color sequence in the respective second print head 2b and 2d, which has the same colors as the respective first print head 2a and 2c.

[0109] This reversal of the color sequence in the print heads 2a and 2b or 2c and 2d is explained below using the Fig. 3a and Fig. 3b, which also schematically shows printing units 1.

[0110] The Fig. The printing unit 1 shown in Figure 3a corresponds to the one shown in Fig. 2a, with the difference that the color sequence of the first and second colors in the two nozzle rows 5q, 5r, 5s, 5t between the two print heads 2a and 2b is reversed or swapped.

[0111] For example, the Fig. 3a, the printing unit 1 comprises two print heads 2a and 2b, i.e. a first print head 2a and a second print head 2b. The print heads 2a, 2b have print chips 4 each with two nozzle rows 5q, 5r and 5s and 5t, wherein the two nozzle rows 5q, 5r and 5s and 5t, as shown in Fig. 3a, two or more nozzles 6, wherein the nozzle rows 5q and 5r of the print head 2a are offset from each other by half the distance between two adjacent nozzles 6. The same applies to the nozzle rows 5s and 5t of the print head 2b. The distance between two adjacent nozzles 6 in Fig. 3a, for example, is 80 µm, so half the distance here is 40 µm. As the Fig. As can be further seen from Figure 3a, in the two nozzle rows 5q, 5r and 5s, 5t in each of the two print heads 2a and 2b, there is a first color in the nozzle row 5q and 5t of the print heads 2a, b, and a second color in the nozzle row 5r and 5s of the print heads 2a, b, with the second color being different from the first color. The color sequence of the first and second colors in the two nozzle rows 5q, 5r, 5s, 5t is therefore reversed or swapped between the two print heads 2a and 2b. Because the nozzle rows 5q and 5r of the print head 2a and the nozzle rows 5s and 5t of the print head 2b are arranged offset from one another by half the distance between two adjacent nozzles 6, the reversal of the color sequence between the first print head 2a and the second print head 2b ensures that the second print head 2b inevitably prints into the gaps of the first print head 2a and thus achieves the maximum or minimum ink jet density.The specified resolution of the print head 2a, b used is achieved. This is further indicated by the dotted line 20a in . Fig. 3a, which shows that a nozzle of the first print head 2a is located in the middle between two nozzles of the second print head or prints between them. Here, as in Fig. 3a, advantageously all distances between the two or more nozzles 6 are equidistant, in particular along a direction transverse to the running direction of the substrate. In other words, the nozzles having the same color are at the same distance from one another along the direction transverse to the running direction of the substrate, preferably in at least one row or in all rows. The running direction of a substrate is in Fig. 3a as already shown above by a dashed arrow.

[0112] Again Fig. 3a, the printing unit 1 also has two pinning units 3a and 3b. The pinning units 3a and 3b are, as in the Fig. 2a, Fig. 2b, Fig. 2c and Fig. 2d are arranged such that each print head 2a, 2b is assigned a pinning unit 3a, 3b. In this regard, reference is also made to the above explanations.

[0113] The Fig. 3b shown printing unit 1 corresponds to the one shown in Fig. 3a, with the difference that the pressure unit of the Fig. 3b also has the additional print heads 2c and 2d and two additional pinning units 3c and 3d. As with print heads 2a and 2b, the color sequence between print heads 2c and 2d is swapped or reversed. Thus, just as in Fig. 3a, the print head 2a in the nozzle row 5q has the color yellow and in the nozzle row 5r has the color magenta. The print head 2b has the same Fig. 3a prints magenta in nozzle row 5s and yellow in nozzle row 5t. The other two print heads 2c and 2d, i.e., the third 2c and fourth 2d print heads, print black in nozzle rows 5u and 5x and cyan in nozzle rows 5v and 5x. Regarding the effect of reversing the color sequence, please refer to the above explanations.

[0114] As already explained above, it is also possible, with the same color sequence in the print heads 2a, 2b as well as 2c and 2d, to achieve a mechanical offset 7 of the two print heads 2a and 2b as well as 2c and 2d, which have the same colors, to each other as well as by means of the color reversal in the print heads, as in the context of Fig. 3a, b, to achieve the maximum or specified physical performance of the print heads used. This is demonstrated below using the Fig. 4a and Fig. 4b, which also schematically shows printing units 1.

[0115] The Fig. The printing unit 1 shown in Figure 4a corresponds to the one shown in Fig. 2a shown printing unit 1, wherein in Fig. 4a the individual nozzles are shown. Also in Fig. 4a, the direction of travel of a substrate to be printed is indicated by a dashed arrow. Regarding the shapes of the printing chips 4, including the arrangement of the nozzles, reference is made to the above explanations, in particular those relating to the Fig. 3a. In contrast to the Fig. However, in the printing unit 1 shown in Figure 3a, the color sequence between the first print head 2a and the second print head 2b is not reversed. Rather, the color sequence is identical. Thus, the nozzle rows 5q and 5r of the print head 2a and the nozzle rows 5s and 5t of the print head 2b have the same colors and also the same color sequence in the nozzle rows 5q, 5r and 5s, 5t. Thus, the color yellow is present in the nozzle rows 5q and 5s, and the color magenta is present in the nozzle rows 5r and 5t. However, since the color sequence is identical here, the two print heads 2a and 2b are offset from one another in such a way that the second print head 2b prints in the gaps of the first print head 2a. This is generated by a mechanical offset 7 of the second print head 2b relative to the first print head 2a, which corresponds to half the distance between two adjacent nozzles 6.The first print head 2a can also be offset from the second print head 2b. In other words, the two print heads 2a and 2b have an offset 7 from each other that corresponds to half the distance between two adjacent nozzles 6.

[0116] The Fig. 4b shown printing unit 1 corresponds to the one in Fig. 4a, with the difference that the pressure unit of the Fig. 4b also has the additional print heads 2c and 2d and two additional pinning units 3c and 3d. As with print heads 2a and 2b, the color sequence between print heads 2c and 2d is now identical. Thus, just as in Fig. 4a, the print head 2a has the color yellow in the nozzle row 5q and the color magenta in the nozzle row 5r. The print head 2b has the same Fig. 4a prints yellow in nozzle row 5s and magenta in nozzle row 5t. The other two print heads 2c and 2d, i.e., the third 2c and fourth 2d print heads, print cyan in nozzle rows 5u and 5w and black in nozzle rows 5v and 5x. Regarding the effect of reversing the color sequence, please refer to the above explanations.

[0117] Fig. Figure 5a schematically shows a side view of a printing unit 1. The printing unit 1 comprises the print heads 2a, 2b, 2c and 2d as well as a pinning unit 3a, 3b, 3c and 3d associated with the respective print head 2a, 2b, 2c and 2d. Furthermore, the printing unit 1 comprises a base plate 8, which, like the Fig. 5a, which includes parts 8a and 8b. Fig. The base plate 8 shown in Figure 5a is made of aluminum and measures 500 cm by 440 cm. The base plate 8, or rather the parts 8a and 8b, are as shown in the Fig. 5a, inclined relative to the horizontal in such a way that the base plate forms an upside-down V. It is advantageous if the base plate 8 is designed such that it can be switched back and forth between a flat position and a V-shaped configuration, particularly an upside-down configuration. This is possible, for example, by means of an adjustment means 9, such as an eccentric, so that the base plate is positioned flat for sheet-fed applications, for example, and formed in a V-shape, as explained above, for roll-to-roll applications.

[0118] Furthermore, the Fig. 5a, the printing unit 1 shown has four pinning units 3a, 3b, 3c, 3d, wherein, as explained above, each print head 2a, 2b, 2c, and 2d is assigned a pinning unit 3a, 3b, 3c, and 3d, and therefore a pinning unit 3a, 3b, 3c, or 3d is arranged directly following the respective print head 2a, 2b, 2c, or 2d. The distance between each print head 2a, 2b, 2c, and 2d and the pinning unit 3a, 3b, 3c, and 3d arranged after the print head 2a, 2b, 2c, and 2d is, for example, between 30 mm and 50 mm. The pinning units 3a, 3b, 3c, and 3d are in Fig. 5b according to section 20b of Fig. 5a is shown enlarged. As in Fig. 5a and Fig. As shown in Figure 5b, the pinning units 3a, 3b, 3c and 3d are at least partially integrated into the base plate. Fig. 5b, the circuit board with the LED 10b is installed in the base plate 8 and not, as is usual, as a component with its own housing. For example, it is possible that at least a portion of the pinning units 3a, 3b, 3c, and 3d is arranged below the surface of the base plate 8. Preferably, less than 75%, preferably less than 50%, more preferably less than 25%, of the maximum height of the pinning units 3a, 3b, 3c, and 3d is below the surface of the base plate 8. The LED here is a UV LED, which for the pinning units 3a, 3b, 3c, and 3d, for example, has an irradiance between 0 W / cm 2 up to 10 W / cm 2generated. Furthermore, the pinning units 3a, 3b, 3c, 3d have a water cooling system 10e, which is arranged within the frame 10d. The pinning units 3a, 3b, 3c, and 3d each have a base plate 10a of the pinning units 3a, 3b, 3c, and 3d in order to be able to attach them to the base plate 8 for the print heads 2a, 2b, 2c, and 2d. Furthermore, the pinning units, such as the Fig. 5b, a quartz glass rod 10c can be removed, which in particular focuses the UV light in such a way that it dries and thus fixes the ink printed on the substrate.

[0119] Fig. Figure 6 schematically shows a side view of a printing system or a printing device 13. The printing device 13 comprises a printing unit 1 and a substrate table 11, which feeds the substrate 12 to the printing unit 1 for printing. Regarding the design of the printing unit 1, reference is made to the above explanations, in particular in the context of Fig. 5a and Fig. 5b. As in Fig. 6, the substrate table 11 is raised centrally such that, particularly when using a V-shaped base plate 8, as explained above, the distance between the substrate 12 and the print heads 2a, 2b, 2c and 2d is substantially identical. List of reference symbols 1 printing unit 2, 2a-d printheads 3a-d pinning units 4 print chip 5a-x nozzle rows 6 nozzles 7 Offset 8 Base plate 8a, 8b Parts of the base plate 9 Adjustment tools 10a Base plate pinning unit 10b board with LED 10c quartz glass rod 10d frame 10e water cooling 11 Substrate table 12 Substrat 13 Printing device 20a line(s) 20b Excerpt

Claims

[1] Printing unit (1) for printing on a substrate (12) comprising two print heads (2a, 2b) arranged one behind the other in the direction of travel of the substrate (12) and two pinning units (3a, 3b), wherein each print head (2a, 2b) has one or more print chips (4) each with two rows of nozzles (5a, 5b, 5e, 5f) arranged transversely to the direction of travel of the substrate (12), wherein each row of nozzles (5a, 5b, 5e, 5f) has two or more nozzles (6), and in particular wherein the two rows of nozzles (5a, 5b, 5e, 5f) are arranged offset from one another by half a distance between two adjacent nozzles (6) of the two or more nozzles (6), characterized bythat the two rows of nozzles (5a, 5b, 5e, 5f) in each of the two print heads (2a, 2b) have a first color in a first of the two rows of nozzles (5a, 5e) and a second color, different from the first color, in a second of the two rows of nozzles (5b, 5f), and that either the color sequence of the first and second colors in the two rows of nozzles (5a, 5b, 5e, 5f) between the two print heads (2a, 2b) is identical and the two print heads (2a, 2b) have a mechanical offset (7) from one another which corresponds to half the distance between two adjacent nozzles (6) of the two or more nozzles (6), or that the color sequence of the first and second colors in the two rows of nozzles (5a, 5b, 5e, 5f) between the two print heads (2a, 2b) is reversed. [2] Printing unit (1) according to claim 1, characterized bythat the first and second color are selected from cyan, black, yellow and magenta, in particular that if the first color is cyan, the second color is black or vice versa or that if the first color is yellow, the second color is magenta or vice versa. [3] Printing unit (1) according to one of claims 1 or 2, characterized by that the printing unit (1) has two further print heads (2c, 2d) arranged one behind the other in the running direction of the substrate (12) and two further pinning units (3c, 3d), in particular wherein the two print heads (2a, 2b) and the two further print heads (2c, 2d) are arranged one behind the other in the running direction of the substrate (12). [4] Printing unit (1) according to claim 3, characterized byin that each print head (2a, 2b, 2c, 2d) has one or more print chips (4) each having two rows of nozzles (5a-5x) arranged transversely to the running direction of the substrate (12), wherein each row of nozzles (5a-5x) has two or more nozzles (6), and in particular wherein the two rows of nozzles (5a-5x) are arranged offset from one another by half a distance between two adjacent nozzles (6) of the two or more nozzles (6). [5] Printing unit (1) according to claim 4, characterized by that the two rows of nozzles (5g, 5h, 5m, 5n, 5o, 5u, 5v, 5w, 5x) in each of the further two print heads (2c, 2d) have a third color, different from the first and second color, in a first of the two rows of nozzles (5g, 5m, 5o, 5u, 5w) and a fourth color, different from the first, second and third color, in a second of the two rows of nozzles (5h, 5n, 5p, 5v, 5x). [6] Printing unit (1) according to claim 5, characterized bythat the first, second, third and fourth colors are selected from cyan, black, yellow and magenta, preferably that if the first color is cyan, the second color is black or vice versa or that if the first color is yellow, the second color is magenta or vice versa and further preferably that if the third color is cyan, the fourth color is black or vice versa or that if the third color is yellow, the fourth color is magenta or vice versa. [7] Printing unit (1) according to one of claims 5 or 6, characterized by that the first and second color is selected from cyan and black and the third and fourth color is selected from yellow and magenta or vice versa. [8] Printing unit (1) according to one of claims 5 to 7, characterized bythat either the colour sequence of the third and fourth colours in the two rows of nozzles (5g, 5h, 5m, 5n, 5o, 5u, 5v, 5w, 5x) between the two further print heads (2c, 2d) is identical and the two further print heads (2c, 2d) have a mechanical offset (7) to one another which corresponds to half the distance between two adjacent nozzles (6) of the two or more nozzles (6), or that the colour sequence of the third and fourth colours in the two rows of nozzles (5g, 5h, 5m, 5n, 5o, 5u, 5v, 5w, 5x) between the two further print heads (2c, 2d) is reversed. [9] Printing unit (1) according to one of the preceding claims, characterized by that the mechanical offset (7) between the two print heads (2a, 2b) and / or between the two further print heads (2c, 2d) arranged transversely to the running direction of the substrate is between 20 µm and 60 µm, preferably between 30 µm and 50 µm, more preferably 40 µm. [10] Printing unit (1) according to one of the preceding claims, characterized by that the printing unit (1) has a resolution of 600 x 600 dpi. [11] Printing unit (1) according to one of the preceding claims, characterized by that a pinning unit (3a, 3b, 3c, 3d) is arranged downstream of each print head (2a, 2b, 2c, 2d) along the running direction of the substrate (12), in particular that one of the two pinning units (3a, 3b) is arranged downstream of each of the two print heads (2a, 2b) along the running direction of the substrate (12) and / or that one of the two further pinning units (3c, 3d) is arranged downstream of each of the two further print heads (2c, 2d) along the running direction of the substrate (12). [12] Printing unit (1) according to claim 11, characterized by that the distance between each print head (2a, 2b, 2c, 2d) and the pinning unit (3a, 3b, 3c, 3d) arranged after the print head (2a, 2b, 2c, 2d) is between 10 mm and 80 mm, preferably between 30 mm and 50 mm. [13] Printing unit (1) according to one of the preceding claims, characterized by that the printing unit (1) further comprises a base plate (8), wherein the two pinning units (3a, 3b) and / or the two further pinning units (3c, 3d) are at least partially integrated into the base plate (8). [14] Printing unit (1) according to claim 13, characterized by that the base plate (8) is V-shaped, in particular that the base plate (8) comprises two parts (8a, 8b) which are inclined towards the horizontal, preferably between 0 degrees and 25 degrees, more preferably between 0 degrees and 15 degrees, even more preferably between 0 degrees and 10 degrees. [15] Printing unit (1) according to one of the preceding claims, characterized by that the two pinning units (3a, 3b) and / or the two further pinning units (3c, 3d) have a circuit board with one or more light-emitting diodes (10b) and / or a water cooling system (10e). [16] Method for printing a substrate (12) comprising the following steps, which are carried out in particular in the following order: - Providing a printing unit (1) according to one of claims 1 to 15 - Feeding the substrate (12) to the printing unit (1) - Printing the substrate (12) by means of the printing unit (1), in particular in two or more colors and / or with a resolution of 600 x 600 dpi. [17] Method according to claim 16, characterized by that the substrate (12) is fed to the printing unit (1) via a substrate table (11), in particular wherein the substrate table (11) is raised centrally in such a way that, preferably when using a V-shaped base plate (8), further preferably according to the printing unit (1) according to claim 14, the distance between the substrate (12) and the two print heads (2a, 2b) and / or the two further print heads (2c, 3d) is substantially identical.

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