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 printheads (2a, 2b) arranged one behind the other in the direction of travel of the substrate (12) and two pinning units (3a, 3b), wherein each printhead (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 nozzle rows (5a, 5b, 5e, 5f) in each of the two printheads (2a, 2b) have a first color in one of the two nozzle rows (5a, 5e) and a second color, different from the first color, in a second of the two nozzle rows (5b, 5f), and either the color sequence of the first and second color in the two nozzle rows (5a, 5b, 5e, 5f) between the two printheads (2a, 2b) is identical and the two printheads (2a, 2b) further have a mechanical offset (7) from each other 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 color in the two nozzle rows (5a, 5b, 5e, 5f) between the two printheads (2a, 2b) is reversed.

Description

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

[0002] When printing ink with appropriate printing units, it is common practice to print only a single color per printhead, due to the printhead architecture. To achieve a maximum resolution of, for example, 600 dpi per color, each nozzle row, with a physical resolution of 300 dpi, is filled with the same color, thus achieving the maximum resolution of 600 dpi per color. Furthermore, it is known to dry the printed ink using pinning units, whereby drying can occur after each or more of the aforementioned printheads. Printing methods include single-pass and multi-pass processes, such as the dual-pass method. In the single-pass method, each color is printed in one pass, for example, all the yellow components of an image at once. In the multi-pass method, such as the dual-pass method, the image is printed in two separate passes.For example, the yellow components of the image are not printed all at once, but rather divided into two passes, with the division typically occurring stochastically. However, a disadvantage of known printing devices, particularly those employing the aforementioned methods, is that they cannot achieve satisfactory printing results for all desired applications, results characterized by a homogeneous print, high print quality, good edge sharpness, high printing speed, and correspondingly short cycle times.

[0003] A homogeneous print result, in this context, refers specifically to a uniform color appearance across the printed areas. High print quality, in this context, refers specifically to achieving the desired print resolution, appealing multicolor printing, and / or vibrant, preferably not washed-out, colors. Disadvantages of the single-pass process often include a lack of edge sharpness and a washed-out print surface that lacks satisfactory homogeneity. Disadvantages of the multi-pass process include long cycle times due to the back-and-forth movement of the printhead, as well as the mechanical offset of the printhead by approximately 1 mm to eliminate systematic errors, such as two adjacent nozzles firing at an angle.Furthermore, this technique can only be used in direct printing applications where the substrate to be printed can be moved under the printhead at least twice or more, resulting in a corresponding technical effort.

[0004] The invention is based on the objective 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. Specifically, the invention aims to provide a compact printing unit that delivers a homogeneous printing result with high print quality and good edge sharpness.

[0005] This problem is solved by a printing unit, in particular for printing on a substrate, comprising two printheads arranged one behind the other in the direction of travel of the substrate and two pinning units, wherein each printhead has one or more print chips, each with two rows of nozzles arranged transversely to the direction of travel 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 each other 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 printheads 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 color in the two rows of nozzles between the two printheads is identical and the two printheads have a mechanical offset from each other,which 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 printheads is reversed or swapped.

[0006] This problem is further solved 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 using 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, as well as the inventive method for printing a substrate, combines the advantages of single-pass and multi-pass methods, such as dual-pass methods. In other words, the printing unit according to the invention simulates a dual-pass method, i.e., printing each color component of the image in two passes. Because the color sequence in the nozzle rows is reversed, or because the printheads have a mechanical offset relative to each other when the color sequence in the nozzle rows is the same, the desired or maximum resolution of the printheads used is still achieved despite the use of two different colors per printhead, since the second printhead always prints into the spaces between the first printhead, particularly in the printed area on the substrate.By using two printheads in combination with two colors in the nozzle arrays, two-color printing is achieved, which utilizes the maximum resolution of the printheads and also achieves short cycle times, since the printheads simulate two passes, although only one pass is physically or mechanically performed. Furthermore, this makes it possible to utilize the high print quality, good edge sharpness, high registration accuracy, and homogeneous print results of multi-pass processes, especially dual-pass processes, in just one pass. Thus, with the printing unit according to the invention, applications that were typically carried out using single-pass processes with prior art printing units, and therefore also exhibited the associated disadvantages, can now be produced with high print quality.This avoids the disadvantages previously associated with known single-pass processes using conventional printing units. Such printing applications, typically performed using the single-pass method, include roll-to-roll applications, such as label printing, as well as sheet-fed applications or the printing of workpieces. In these applications, the advantages described here can now be achieved with the printing unit according to the invention. The two pinning units contribute to drying and thus simulate the two passes by performing targeted intermediate drying. This results in a compact printing unit that produces a homogeneous print result with high print quality, good edge sharpness, and high registration accuracy, while simultaneously enabling short cycle times.

[0008] Register accuracy refers to the positional accuracy of two or more elements and / or layers relative to each other. The register accuracy should fall within a predefined tolerance and be as low as possible. At the same time, the register accuracy of multiple elements and / or layers relative to each other is an important characteristic for increasing process reliability. Precise positioning can be achieved, in particular, using sensory, preferably optically detectable, register marks. These register marks can either represent specific separate elements, areas, or layers, or they can themselves be part of the elements, areas, or layers being positioned. Ideally, the register accuracy should be zero or as low as possible.The fit accuracy is preferably less than 32 µm, preferably less than 16 µm, and particularly preferably less than 8 µm.

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

[0010] Preferably, the two nozzle rows in the first and second printheads have a first color in the first of the two nozzle rows and a second color, different from the first color, in the second of the two nozzle rows, particularly wherein the color sequence of the first and second colors in the two nozzle rows between the first and second printheads is identical, and the first and second printheads have a mechanical offset from each other, preferably corresponding 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 between the first and second printheads is reversed.

[0011] It is possible that the first and second printheads each have the first and second colors, respectively. It is also possible that the two printheads each have one first and one second color.

[0012] It is also possible that the two printheads, or the first and second printheads, each have a first and second row of nozzles, with the first row of nozzles containing the first color and the second row containing the second color, or vice versa. In this context, "conversely" specifically means that the first row of nozzles contains the second color and the second row of nozzles contains the first color.

[0013] It is possible that the color sequence in the nozzle rows of the two printheads, or of the first and second printhead, is identical or reversed. If the color sequence is identical, it is particularly preferred that the first and second printheads have a mechanical offset from each other, preferably corresponding to half the distance between two adjacent nozzles of the two or more nozzles.

[0014] It is therefore preferred that the two printheads, in particular the first and the second printhead, are arranged offset from each other, preferably mechanically offset from each other, such that the second of the two printheads, in particular the second printhead, or the nozzles of the second printhead print into the spaces between the nozzles, in particular into the gaps, of the first of the two printheads, in particular the first printhead.

[0015] The at least two printheads are therefore arranged in the direction of substrate movement. The distance between the first and second printhead is preferably one printhead width. Similarly, the distance between the second and third, as well as the third and fourth printheads, is preferably one printhead width.

[0016] The term nozzle is also used here to refer to pixels, especially since a nozzle creates a point or pixel on the substrate as a print or printed image. In In other words, a row of adjacent pixels forms a pixel row or nozzle row. The spaces between the nozzles thus correspond to the spaces between the pixels printed by the respective nozzles on the substrate.

[0017] Preferably, in addition to the two rows of nozzles, a print chip also includes actuators, in particular TFP actuators, and ink channels.

[0018] Furthermore, it is advantageous if the printing unit has at least two printheads 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 that the printing unit according to the invention for printing a substrate comprises at least two printheads arranged one behind the other in the direction of travel 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 printheads and two additional pinning units.

[0021] It is also possible to select the number of printheads (at least two arranged one behind the other in the direction of substrate movement) and, correspondingly, the number of pinning units (at least two) depending on the colors to be printed or the desired print and / or its color scheme. For example, the number of printheads and pinning units could be four when selecting the CMYK model (cyan, magenta, yellow, key / black), or three when selecting the RGB model (red, green, blue). The CMYK model is the preferred color model and the standard color model in the printing industry, and it is also the preferred model used in the present invention. Furthermore, it is conceivable that additional spot colors could be provided and printed alongside the CMYK model.These can be, for example, colors, selected individually or in multiples from: white, colors tinted with white, pastel colors, skin tone, metallic colors, neon colors. Thus, the number of printheads 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 printheads and / or the pinning units preferably corresponds to the design of the two printheads or the two additional printheads 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 printheads, for example, with a single printhead and / or a printing unit, wherein this printhead and / or printing unit is operated conventionally and, for example, has the same color in all nozzle rows. That is, the printing unit according to the invention can be combined with conventional printing units, particularly depending on the requirements for the print result. For example, it is conceivable that two colors with good edge sharpness, high registration accuracy, homogeneous print result, and good print quality can be printed using the printing unit according to the invention, while other colors have less stringent requirements in a specific printing project and can therefore be printed with conventional printing units.

[0023] The term "colors" here primarily refers to printing inks, particularly printing inks. A wide variety of inks, especially those used in industrial applications, are suitable. These include water-based, UV-curing, eco-solvent, oil-based, and solvent-based inks. Special fluids, particularly those commonly used in digital and production printing, can also be employed. CMYK color models are preferred for printing. However, other color spaces and models, such as RGB, are also possible.

[0024] The drying of the ink, especially printing ink, is achieved by means of pinning units, which partially dry or partially dry the ink and thus fix it. Drying here refers specifically to ultraviolet (UV) curing, i.e., polymerization or cross-linking of a UV-curable ink. Drying can also mean only partial cross-linking, i.e., gelling and / or an increase in viscosity. The pinning unit can also be referred to as a drying unit or intermediate drying unit.

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

[0026] The term printing device or printing system here refers to a system that includes 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, especially to 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 on a substrate and / or in a method for printing on a substrate.

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

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

[0031] Advantageously, here too, the two nozzle rows in each of the, in particular at least, two printheads 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, wherein either the color sequence of the first and second color in the two nozzle rows between the two printheads is identical and the two printheads have a mechanical offset from each other, which in particular 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 color in the two nozzle rows between the two printheads is reversed.

[0032] Furthermore, the use of, in particular at least, two pinning units is advantageous in a printing device, preferably wherein one pinning unit is arranged along the direction of travel of the substrate after a print head.

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

[0034] The following are some particularly preferred embodiments of the printing unit: For example, the first and second colors may be selected from cyan, black, yellow, and magenta; specifically, 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. "Conversely" in this context means that if the first color is black, the second color is cyan, or if the first color is magenta, the second color is yellow. Preferably, the darker colors black and magenta are printed first, followed by the lighter colors cyan and yellow. This enables two-color printing, which, due to the CMYK color model used, already covers a broad spectrum of colors.

[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 printheads arranged one behind the other in the direction of the substrate's travel, and two additional pinning units, particularly if the two printheads and the two additional printheads are also arranged one behind the other in the direction of the substrate's travel. This makes it possible to print four colors, and thus, for example, the entire color spectrum of the CMYK model, using the printing unit, thereby achieving the advantages outlined above.

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

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

[0039] In other words, it is possible that the printing unit further comprises a third and fourth printhead in the direction of travel of the substrate, preferably with the third and fourth printheads being arranged one behind the other in the direction of travel of the substrate.

[0040] It is therefore useful if the two printheads have a first and a second printhead and / or the two further printheads have a third and a fourth printhead.

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

[0042] The printheads are preferably compatible with a wide variety of colors and ink types, especially those used in industrial applications. This makes it possible to use water-based inks, UV-curing inks, eco-solvent inks, oil-based inks, and / or solvent-based inks with these printheads.

[0043] Furthermore, special fluids, particularly those primarily found in digital and production printing, can also be used. However, preferably, inks with the colors of the CMYK color model are printed using the printheads, as already explained above and below.

[0044] It is possible that the third and fourth printheads display the third and fourth colors. It is also possible that the two remaining printheads display a third and a fourth color.

[0045] It is also possible that the two additional printheads, or the third and fourth printheads, each have an additional first and a further second row of nozzles, with the further first row of nozzles having or containing the third color and the further second row of nozzles having or containing the fourth color, or vice versa.

[0046] It is therefore advantageous that if the first printhead has or includes the first and second colors, then the second printhead also has or includes the first and second colors. Furthermore, it is advantageous that if the third printhead has or includes the third and fourth colors, then the fourth printhead also has or includes the third and fourth colors.

[0047] It is therefore advantageous if the printheads that print the same colors, in particular the two printheads and / or the subsequent printheads, or the first and second printheads and / or the third and fourth printheads, are located consecutively. This ensures that printheads printing the same colors are preferably positioned close together.

[0048] The term "sequential printing" here refers to the arrangement of printheads with the same color combination, such as yellow / magenta, after each printhead with the same combination, for example, yellow / magenta again. A pinning unit may be positioned between these printheads, but not a printhead with a different color combination. This significantly reduces registration variations or inaccuracies between the same colors. While this does reduce the registration accuracy between subsequent colors, such as from yellow / magenta to cyan / black, the human eye is less likely to perceive registration variations from one color to another because areas of color are either unprinted, resulting in, for example, white areas or...Areas can be printed in the color of the unprinted substrate, or color areas can be printed with two colors, resulting in mixed colors, for example. However, registration variations within a single color are perceived by the human eye as, for example, unclean edges and / or poor edge sharpness. Therefore, it is preferable for printheads printing the same colors to be located close together, so that, for example, the two printheads and the two subsequent printheads follow one another and are separated only by an intervening pinning unit.

[0049] As explained above, the color sequence in the nozzle rows of the printheads can be identical or reversed. For example, if the first color is present in the first nozzle row of the first printhead and the second color is present in the second nozzle row of the first printhead, then the first nozzle row of the second printhead can contain either the first or the second color. The same applies to the second nozzle row of the second printhead. Similarly, if the third color is present in the first nozzle row of the third printhead and the fourth color is present in the second nozzle row of the third printhead, then the first nozzle row of the fourth printhead can contain either the third or the fourth color. The same applies to the second nozzle row of the fourth printhead.

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

[0051] The printing inks can be applied according to different printing approaches. Preferably, the printing inks are printed in the following order: cyan, magenta, yellow, black. Particularly preferred is printing from light to dark, in the following order: yellow, magenta, cyan, black. The "light to dark" approach has become established for inkjet printers. Regardless of the chosen printing approach, it is preferably provided that black is printed last; therefore, as the fourth color when using four printing inks, as the sixth color when using six printing inks, and so on. It is advantageous if the first, second, third, and fourth colors are selected from cyan, black, yellow, and 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 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 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, thereby 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, nozzle rows between the two further printheads is preferably identical and that the two further printheads have a mechanical offset from each other 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 nozzle rows between the two further printheads is reversed.

[0053] It is therefore preferred that the two further printheads, in particular the third and the fourth printhead, are arranged offset from each other, preferably mechanically offset from each other, such that the second of the two further printheads, in particular the fourth printhead, or the nozzles of the fourth printhead, print into the spaces between the nozzles, in particular into the gaps, of the first of the two further printheads, in particular the third printhead.

[0054] This also ensures the maximum resolution of each printhead, since the second printhead, using the same color combination, is forced to print into the gaps of the first printhead, either due to mechanical offset or the reversal of the color sequence in the two nozzle rows. Furthermore, reversing the color sequence in the two nozzle rows allows all printheads to be arranged directly behind one another in a row, thus reducing the mechanical alignment work.

[0055] It is also conceivable to arrange several printheads perpendicular to the substrate's direction of travel in order to widen the print image size accordingly. In this case, a distance of one printhead length would be necessary between the individual printheads, 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 that have the same color, in particular the first, second, third and / or fourth color, are equidistant.

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

[0059] Preferably, the mechanical offset between the two printheads and / or between the two further printheads, which are arranged transversely to the direction of travel 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 advantageous if the mechanical offset between the two printheads and / or between the two further printheads or between the first and second printhead and / or between the third and fourth printhead corresponds to half the distance between two adjacent nozzles of the two or more nozzles or to half a pixel.

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

[0062] It is possible that the two printheads and / or the two subsequent printheads have a mechanical offset relative to each other. It is also possible that the first and second printheads and / or the third and fourth printheads have a mechanical offset relative to each other. Furthermore, it is advantageous for the first and fourth and / or the second and third printheads to have a mechanical offset relative to each other. Preferably, the first and third or the second and fourth printheads are not arranged with an offset relative to each other. It is therefore advantageous if the first and third or the second and fourth printheads are arranged directly behind one another and / or aligned along an imaginary line.

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

[0064] The print unit preferably has a resolution of 600 x 600 dpi. However, it is also possible for the print 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 in printheads by assigning each row of nozzles, with a physical resolution of 300 dpi each, to the same color, thus achieving the maximum resolution of 600 dpi per color.According to the printing unit according to the invention, a resolution of 600 x 600 dpi is achieved by using two printheads, each with two rows of nozzles. As described above, each pair of nozzle rows has the first color in the first row and the second color in the second row. The color sequence is either reversed between the two printheads or, if the color sequence is the same, the second printhead is offset by half a pixel. This ensures that the second printhead always prints in the spaces between the first printhead, thus achieving the 600 dpi print resolution. If the printheads used have other maximum resolutions, such as 1200 dpi, these resolutions can also be achieved using the printing unit described here.

[0065] The following describes, among other things, further preferred embodiments of the pinning units: It is further advantageous that a pinning unit is arranged along the substrate's direction of travel after each printhead, in particular that one of the two pinning units is arranged along the substrate's direction of travel after each of the two printheads, and / or that one of the two further pinning units is arranged along the substrate's direction of travel after each of the two subsequent printheads. By performing intermediate drying after each color or each print, high print quality and high edge tangibility are achieved. Furthermore, intermediate drying after each printhead ensures that, as explained above, two passes per color are simulated, although only one pass physically takes place.

[0066] Advantageously, the two pinning units and / or the two additional pinning units have an irradiance between 0 W / cm² and 10 W / cm², preferably between 0.5 W / cm² and 7.5 W / cm², and more preferably between 2 W / cm² and 5 W / cm². This ensures sufficient fixation of the print, resulting in high print quality.

[0067] Furthermore, it is advantageous that the two pinning units and / or the two additional 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 those that 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, and even more preferably between 365 nm and 395 nm.

[0069] It is therefore 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 printhead is followed by a pinning unit, particularly in the direction of substrate movement. It is thus preferred that a first pinning unit is arranged after the first printhead, a second pinning unit after the second printhead, a third pinning unit after the third printhead, and a fourth pinning unit after the fourth printhead, particularly in the direction of substrate movement.

[0071] Furthermore, it is advantageous that the two printheads and / or the two additional printheads and that the two pinning units and / or the two additional pinning units are identical in design, in particular identical in construction.

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

[0073] It is advisable to select the distance between each printhead and the pinning unit arranged after the printhead depending on at least one of the following parameters: distance and / or properties and / or type of the 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] The following describes, among other things, further preferred embodiments of a printing unit with a base plate: 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] Advantageously, the base plate is made of aluminum, steel, or magnesium and / or has a dimension between 200 mm and 1000 mm, preferably between 400 mm and 600 mm, in the direction of the substrate's travel. The dimension perpendicular to the substrate's travel (substrate width) varies considerably and depends in particular on the substrate used and its dimensions perpendicular to the substrate's travel, the printing application, and the number of printing inks used. However, larger dimensions are also conceivable, especially depending on the printheads used, the substrate to be printed, and / or the printing system used. It is also possible for the printing unit to have a base plate, in particular where the two pinning units and / or the two additional pinning units are integrated into the base plate and / or at least partially integrated or mounted in it.

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

[0077] It is therefore advantageous if at least part 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%, more preferably less than 50%, and further preferably less than 25% of the maximum height of the pinning unit lies below the surface of the base plate.

[0078] This makes it possible to further reduce the space required for the pinning units, as their height is significantly reduced. This frees up more space, particularly above the pinning units, which can be used for the ink supply lines to the printheads.

[0079] It is also advantageous for the base plate to comprise two parts, with the first part comprising the two printheads and the two pinning units, and the second part comprising the two additional printheads and the two additional pinning units. Furthermore, it is possible for the two parts to be inclined or tiltable relative to the horizontal, as will be explained in detail below.

[0080] Preferably, the base plate is V-shaped; in particular, the base plate comprises two parts that are inclined to the horizontal, preferably between 0 and 25 degrees, more preferably between 0 and 15 degrees, and even more preferably between 0 and 10 degrees. In other words, a base plate shaped in this way forms an inverted V-shape. This reduces the problem of the web edge of the substrate being fed to the printing unit, especially in roll-to-roll printing presses, unintentionally curling up. This shape of the base plate prevents the web edge from curling up, especially despite the compactness of the printing unit, thus preserving the advantage of compactness while simultaneously preventing the web edge from curling up.

[0081] The base plate can be designed to switch between a flat position and a V-shaped configuration. This can be achieved, for example, using an adjustment mechanism such as an eccentric cam, allowing the base plate to be positioned flat for sheet-fed applications and V-shaped for roll-to-roll applications, as described above. This design ensures the printing unit can be used in a variety of applications.

[0082] Furthermore, it is advantageous that the two pinning units and / or the two additional pinning units have water cooling. This ensures effective cooling and, compared to air-cooled systems, prevents air currents that carry minute ink droplets into the printer's interior, causing contamination and negatively impacting print quality. Additionally, water cooling, especially compared to air cooling, allows for a compact design, thus contributing to the overall compactness of the printing unit, while advantageously maintaining or even improving cooling performance.

[0083] Preferably, the water cooling system has a volume flow rate between 50 liters / hour and 1000 liters / hour, more preferably between 100 liters / hour and 550 liters / hour, 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 further advantageous if the dimensions of the two pinning units and / or the dimensions of the two additional pinning units are selected according to the dimensions along the direction of travel of the substrate (substrate length) and / or perpendicular to the direction of travel of the substrate (substrate width). These compact dimensions ensure that the space required by the pinning units is kept to a minimum.

[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 here that the substrate table is raised in the center such that, preferably when using a V-shaped base plate, particularly according to the V-shaped base plate described above, the distance between the substrate and / or the two printheads and the two other printheads is essentially identical.

[0086] Furthermore, it is possible that final drying takes place, particularly after the substrate has been printed using the printing unit according to the invention, specifically after the first, second, third, and / or fourth color has been printed. It is also possible that this final drying is carried out using a dedicated drying unit. Additionally, it is possible that the final drying is delayed, particularly by a specific time interval, to allow the colors more time to spread. This can result in more homogeneous color areas.

[0087] Preferably, the distance between the substrate and the two printheads and / or the two additional printheads is between 0.5 mm and 5 mm, more preferably between 1 mm and 2 mm, and 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 on a substrate and are therefore considered to be disclosed. The same applies in the reverse direction: features, effects, and advantages described in connection with the method for printing on a substrate are also transferable to the printing unit and are considered to be disclosed.

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

[0090] Fig. 1 schematically shows a printhead 2.

[0091] As in Fig. 1 As shown, the printhead 2 has four print chips 4, each with two nozzle rows 5a, 5b, 5c, 5d. The nozzle rows 5a, 5b, 5c, 5d are preferably arranged transversely to the direction of travel of a substrate. The print chips 4 are in the Fig. 1 The printhead 2 shown is arranged in two rows, one behind the other, with the two rows slightly offset from each other. However, it is also possible that the printhead 2 has, 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] At the in Fig. 1 The printhead 2 shown is a PrecisionCore printhead from Epson, Suwa, Japan. However, as explained above, it is also possible to use other printheads 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 in Fig. 1 The printhead 2 shown is compatible with a wide variety of inks, particularly those used in industrial applications. This allows the use of water-based inks, UV-curing inks, eco-solvent inks, oil-based inks, and / or solvent-based inks with printhead 2. Furthermore, special fluids, especially those primarily found in digital and production printing, can also be used. However, printhead 2 is preferably used with inks using the CMYK color model.

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

[0095] As previously explained, most printheads, due to their design, can only print a single color. In conventional printheads, both nozzle rows (5a, 5b or 5c, 5d), each with a physical resolution of 300 dpi, are printed with the same color. This results in a physical resolution of, for example, 600 dpi per color.

[0096] In contrast, in the printheads 2 of the printing unit 1 according to the invention, the two nozzle rows 5a and 5b and 5c and 5d are provided with two different colors, so that in the upper nozzle rows, i.e. for example the nozzle rows 5a and 5c, a first color is present and in the lower nozzle rows, i.e. 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, and magenta, specifically that 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 bis 2d schematically show pressure units 1.

[0099] The in Fig. 2a The print unit 1 shown comprises the two printheads 2a and 2b, which are arranged as shown in Fig. 2a indicated by the dashed arrow in the direction of flow of a substrate, which is conveyed by means of the in Fig. 2a The printing unit 1 shown can be printed on and is arranged as follows: Fig. 2a The print unit 1 shown therefore comprises a first printhead 2a and a second printhead 2b. The printheads 2a and 2b have, as shown in Fig. 1 The printhead 2 shown, print chips 4 each with two nozzle rows, such as 5e and 5f, are shown. The two nozzle rows 5e and 5f each have two or more nozzles 6, as shown below. Fig. 3a , b and Fig. 4a, b shown. Advantageously, as is common with most printheads, the two nozzle rows 5e and 5f are arranged offset from each other by half the distance between two adjacent nozzles 6. As the Fig. 2a As can be further seen and is also shown by the different hatching of nozzle rows 5e and 5f, in each of the two printheads 2a and 2b, there is a first color in nozzle row 5e of printheads 2a and b and a second color in nozzle row 5f of printheads 2a and b, the second color being different from the first color. Furthermore, the two printheads 2a and 2b, as shown in Fig. 2a represented 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. 2a The different colors shown in the two nozzle rows 5e and 5f, for example, represent 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 in Fig. 2a The printing unit 1 shown uses black as the first color and cyan as the second color. Furthermore, the Fig. 2a The print unit shown (unit 1) has a resolution of 600 x 600 dpi.

[0102] Again Fig. 2a The print unit 1 further comprises two pinning units 3a and 3b. The pinning units 3a and 3b are arranged such that each printhead 2a, 2b is assigned one pinning unit 3a, 3b. As the Fig. 2a To allow for the removal of material, a pinning unit 3a is arranged after each of the printheads 2a and 2b along the substrate's direction of travel, indicated by the dashed line. The distance between the printheads 2a and 2b and the pinning units 3a and 3b arranged downstream is, according to the diagram... Fig. 2a The printing unit shown, for example, has a distance of 80 mm. However, it should be noted that the distance between the printheads 2a and 2b and the pinning units 3a and 3b arranged downstream of them usually depends on parameters such as distance and / or properties and / or type of the 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 in Fig. 2b The pressure unit 1 shown corresponds to the one in Fig. 2a shown pressure unit 1 with the difference that pressure unit 1 of the Fig. 2b It features two additional printheads, 2c and 2d, and two additional pinning units, 3c and 3d. As shown in Fig. 2b As indicated by the dashed arrow, all printheads 2a, 2b, 2c and 2d are arranged one behind the other in the direction of substrate movement. Just as in Fig. 2a Each printhead 2a, 2b, 2c and 2d is followed by a pinning unit 3a, 3b, 3c and 3d. Furthermore, as in Fig. 1 und 2a Each printhead 2a, 2b, 2c and 2d has a print chip 4 with two rows of nozzles 5e, 5f, 5g, 5h, which are also arranged as in Fig. 2a are arranged perpendicular to the substrate's direction of travel, as indicated by the dashed arrow. The nozzle rows 5g and 5h of printheads 2c and 2d also exhibit, as shown in Fig. 3a, b and Fig. 4a, b The nozzles 6 are shown. Preferably, these nozzle rows 5g, 5h are also offset by half a distance between two adjacent nozzles 6, particularly depending on the printhead used.

[0104] As in Fig. 2b As indicated by the different hatching, the two other printheads, 2c and 2d, also contain two different colors in the form of a third and fourth color. All colors are distinct from one another. Thus, the first, second, third, and fourth colors differ from each other. This is evident in Fig. 2b The first 2a and the second 2b printhead print the first and second colors, and the third 2c and the fourth 2d printhead print the third and fourth colors. As shown in Fig. 2b As shown, the two printheads 2a and 2b also have the same color sequence for the first and second colors, and the two other printheads 2c and 2d have the same color sequence for the third and fourth colors.

[0105] At the in Fig. 2b The different colors shown in the two nozzle rows 5e and 5f, as well as 5g and 5h, represent, for example, 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. In the Fig. 2b The print unit 1 shown uses black as the first color, cyan as the second, magenta as the third, and yellow as the fourth. However, it is also practical to use, for example, yellow as the first color, magenta as the second, black as the third, and cyan as the fourth. In principle, the colors of the CMYK color model can be distributed arbitrarily between nozzle rows 5e and 5f, as well as 5g and 5h, as long as each color is represented in two nozzle rows and, in this case, with the same color sequence, in printheads 2a and 2b, as well as 2c and 2d.

[0106] In accordance with the Fig. 2a The pressure unit 1 shown also exhibits the in Fig. 2b The printing unit 1 shown in the two printheads 2a and 2b displays an identical color sequence for the first and second colors. The color sequence for the third and fourth colors in printheads 2c and 2d is likewise identical. Furthermore, printheads 2c and 2d, like printheads 2a and 2b, are mechanically offset from each other such that the offset 7, as indicated by the dotted line 20a, corresponds to half the distance between two adjacent nozzles 6, and as also shown in the Fig. 4a, b This will be explained again. Fig. 2b The pressure unit 1 shown, like the one in Fig. 2a The printing unit shown (unit 1) has a resolution of 600 x 600 dpi, unlike the one in Fig. 2a However, the printing unit 1 shown can print all colors from the CMYK model, as it has all four basic colors of the color model.

[0107] The in Fig. 2c The pressure unit 1 corresponds to the one in Fig. 2b The printing unit 1 shown differs in that printheads 2a and 2b, as well as 2c and 2d, do not display the same colors, but rather printheads 2a and 2c, as well as 2b and 2d, display the same colors. The mechanical offset 7, indicated by the dotted line 20a, is adjusted here such that printheads 2a and 2c, as well as 2b and 2d, which display the same colors, each exhibit the mechanical offset from each other as described above. Thus, printheads 2a and 2c are offset from each other, and printheads 2b and 2d are offset accordingly. As already explained above, printheads 2a and 2c, as well as 2b and 2d, are located in the Fig. 2c However, the embodiment shown is relatively far apart, so that here, compared to the one in Fig. 2b In the embodiment shown, the risk of passivity fluctuations is higher. Therefore, please refer to the explanations above.

[0108] The in Fig. 2d The pressure unit 1 shown essentially corresponds to the one in Fig. 2b The pressure unit 1 shown, however, exhibits the differences explained below. First, the one shown in Fig. 2d The printing unit shown has printheads 2a, 2b, 2c and 2d, which, like the one in Fig. 1 The printhead shown comprises several print chips 4. Here too, printheads 2a and 2b have a first and a second color, and printheads 2c and 2d have a third and fourth color. Im Difference to in Fig. 2b shown pressure unit 1 and also to the one in Fig. 2c However, in the printing unit 1 shown, the color sequence in nozzle rows 5i, 5j and 5k, 5l as well as 5m, 5n and 5o, 5p is reversed or swapped. Specifically, the color sequence of the first and second colors in nozzle rows 5i, 5j, 5k, 5l between printheads 2a and 2b is reversed or swapped. Likewise, the color sequence of the third and fourth colors in nozzle rows 5m, 5n, 5o, 5p between printheads 2c and 2d is reversed or swapped. This is shown in the Fig. 2d This is also clarified by the corresponding shading. As explained above, the reversal of the color sequence in the nozzle rows in the two printheads that display the same colors, as well as the in Fig. 2a, 2b and 2cThe alternative mechanical offset 7, with the same color sequence in the nozzle rows, ensures that the physical resolution of the printhead used is achieved, since the respective second printhead, which has the same colors as a first printhead, is then forced to print in the gaps of the first printhead. As in Fig. 2d If all printheads 2a, 2b, 2c and 2d are shown arranged in a row, i.e. directly behind one another, thus aligned along an imaginary line, then this is only as shown in Fig. 2d also shown, this is feasible by reversing the color sequence in the respective second printhead 2b and 2d, which has the same colors as the respective first printhead 2a and 2c.

[0109] This reversal of the color sequence in printheads 2a and 2b or 2c and 2d is explained below using the following: Fig. 3a und 3b further clarified, which also schematically show pressure units 1.

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

[0111] Thus, the in Fig. 3a The printing unit 1 shown comprises two printheads 2a and 2b, i.e., a first printhead 2a and a second printhead 2b. The printheads 2a and 2b have print chips 4, each with two rows of nozzles 5q, 5r, 5s, and 5t, as shown in Fig. 3a shown, having two or more nozzles 6, wherein the nozzle rows 5q and 5r of the printhead 2a are arranged 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 printhead 2b. The distance between two adjacent nozzles 6 in Fig. 3a For example, the distance here is 80 µm, so half the distance is 40 µm. As the Fig. 3a As can be further determined, in the two nozzle rows 5q, 5r and 5s, 5t in each of the two printheads 2a and 2b, there is a first color in nozzle row 5q and 5t of printheads 2a and b, and a second color in nozzle row 5r and 5s of printheads 2a and b, whereby the second color differs 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 printheads 2a and 2b. By arranging the nozzle rows 5q and 5r of printhead 2a and the nozzle rows 5s and 5t of printhead 2b offset from each other by half the distance between two adjacent nozzles 6, the reversal of the color sequence between the first printhead 2a and the second printhead 2b ensures that the second printhead 2b inevitably prints into the gaps of the first printhead 2a, thus achieving the maximum orThe specified resolution of the printhead used 2a, b is achieved. This is further indicated by the dotted line 20a in . Fig. 3a This clarifies that a nozzle of the first printhead 2a is located in the middle between two nozzles of the second printhead, or prints between them. As shown in Fig. 3a shown, advantageously all distances between the two or more nozzles 6 are equidistant, in particular along a direction transverse to the direction of travel of the substrate. In In other words, the nozzles, which are of the same color, have the same spacing from each other along the direction perpendicular to the direction of travel of the substrate, preferably in at least one row or in all rows. The direction of travel of a substrate is in Fig. 3a as already shown above by a dashed arrow.

[0112] Again Fig. 3a The printing unit 1, which can be further removed, also has two pinning units 3a and 3b. The pinning units 3a and 3b are, as in the Fig. 2a, 2b , 2c und 2d arranged such that each printhead 2a, 2b is assigned a pinning unit 3a, 3b. Reference is therefore also made to the above explanations.

[0113] The in Fig. 3b The pressure unit 1 shown corresponds to the one in Fig. 3a shown pressure unit, with the difference that the pressure unit of the Fig. 3b It also has the additional printheads 2c and 2d and two further pinning units 3c and 3d. In the two additional printheads 2c and 2d, as with printheads 2a and 2b, the color sequence between printheads 2c and 2d is reversed. Thus, just as in Fig. 3a Printhead 2a prints yellow in nozzle row 5q and magenta in nozzle row 5r. Printhead 2b, like in Fig. 3a In nozzle row 5s, the color magenta is printed, and in nozzle row 5t, the color yellow. The other two printheads, 2c and 2d (i.e., the third 2c and fourth 2d printheads), have black in nozzle rows 5u and 5x, and cyan in nozzle rows 5v and 5x. For information regarding the effect of reversing the color sequence, please refer to the explanations above.

[0114] As explained above, it is also possible, with the same color sequence in printheads 2a, 2b and 2c and 2d, to achieve this by mechanically offsetting the two printheads 2a and 2b and 2c and 2d, which display the same colors, from each other, as well as by means of color inversion in the printheads, as in the context of the Fig. 3a, b described, to achieve the maximum or specified physical output of the printheads used. This will be shown below using the Fig. 4a und Fig. 4b further clarified, which also schematically show pressure units 1.

[0115] The in Fig. 4a The pressure unit 1 shown corresponds to the one in Fig. 2a shown pressure 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 here to the above explanations, in particular those relating to the Fig. 3a , referred to. Unlike in Fig. 3a In the print unit 1 shown, the color sequence between the first printhead 2a and the second printhead 2b is not reversed. Rather, the color sequence is identical. Nozzle rows 5q and 5r of printhead 2a and nozzle rows 5s and 5t of printhead 2b display the same colors and the same color sequence in nozzle rows 5q, 5r and 5s, 5t. Specifically, yellow is present in nozzle rows 5q and 5s, and magenta is present in nozzle rows 5r and 5t. Since the color sequence is identical, printheads 2a and 2b are offset from each other in such a way that the second printhead 2b prints in the gaps left by the first printhead 2a. This is achieved by a mechanical offset 7 of the second printhead 2b relative to the first printhead 2a, which corresponds to half the distance between two adjacent nozzles 6.The first printhead 2a can also be offset relative to the second printhead 2b. In other words, the two printheads 2a and 2b have an offset 7 from each other, which corresponds to half the distance between two adjacent nozzles 6.

[0116] The in Fig. 4b The pressure unit 1 shown corresponds to the one in Fig. 4a shown pressure unit, with the difference that the pressure unit of the Fig. 4b It also has the additional printheads 2c and 2d and two further pinning units 3c and 3d. The color sequence between printheads 2c and 2d is now identical, just as it is between printheads 2a and 2b. Thus, just as in Fig. 4a Printhead 2a prints yellow in nozzle row 5q and magenta in nozzle row 5r. Printhead 2b, like in Fig. 4a In nozzle row 5s, the color yellow is printed, and in nozzle row 5t, the color magenta is printed. The other two printheads, 2c and 2d (i.e., the third 2c and fourth 2d printheads), have cyan in nozzle rows 5u and 5w, and black in nozzle rows 5v and 5x. For information regarding the effect of reversing the color sequence, please refer to the explanations above.

[0117] Fig. 5a Figure 1 schematically shows a printing unit 1 in side view. The printing unit 1 comprises the printheads 2a, 2b, 2c, and 2d, as well as a corresponding pinning unit 3a, 3b, 3c, and 3d assigned to each printhead 2a, 2b, 2c, and 2d. The printing unit 1 also includes a base plate 8, which, like the Fig. 5a which can be extracted, comprising parts 8a and 8b. The in Fig. 5a The base plate 8 shown is made of aluminum and has dimensions of 500 cm by 440 cm. The base plate 8, or parts 8a and 8b, are as shown in the Fig. 5a As shown, the base plate is inclined to the horizontal such that it forms an inverted V. It is advantageous if the base plate 8 is designed to allow switching between a flat position and a V-shaped configuration, particularly an inverted one. This can be achieved, for example, by means of an adjustment device 9, such as an eccentric, so that the base plate can be positioned flat for sheet applications and V-shaped for roll-to-roll applications, as described above.

[0118] Furthermore, the in Fig. 5a The print unit 1 shown comprises four pinning units 3a, 3b, 3c, 3d, wherein, as explained above, each printhead 2a, 2b, 2c, and 2d is assigned one pinning unit 3a, 3b, 3c, and 3d, and therefore a pinning unit 3a, 3b, 3c, or 3d is arranged directly following the respective printhead 2a, 2b, 2c, or 2d. The distance between each printhead 2a, 2b, 2c, and 2d and the pinning unit 3a, 3b, 3c, and 3d arranged after the printhead 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 excerpt 20b from Fig. 5a Shown enlarged. As in Fig. 5a und Fig. 5b As shown, the pinning units 3a, 3b, 3c and 3d are at least partially integrated into the base plate. As the Fig. 5b The circuit board with the LED 10b is integrated into the base plate 8 and is not, as is usual, a separate component with its own housing. For example, at least part of the pinning units 3a, 3b, 3c, and 3d is located below the surface of the base plate 8. Preferably, less than 75%, more preferably less than 50%, and more preferably less than 25% of the maximum height of the pinning units 3a, 3b, 3c, and 3d lies below the surface of the base plate 8. The LED is a UV LED, which, for example, generates an irradiance of between 0 W / cm²< and 10 W / cm²< for the pinning units 3a, 3b, 3c, and 3d. Furthermore, the pinning units 3a, 3b, 3c, and 3d have a water cooling system 10e, which is located within the frame 10d.The pinning units 3a, 3b, 3c, and 3d each have a base plate 10a for mounting them on the base plate 8 for the printheads 2a, 2b, 2c, and 2d. Furthermore, the pinning units, like the... Fig. 5b Each can be removed to take out a quartz glass rod 10c, which focuses the UV light in such a way that it dries and thus fixes the ink printed on the substrate.

[0119] Fig. 6 Figure 13 schematically shows a printing system or printing device 13 in side view. 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 descriptions, particularly within the context of the Fig. 5a und Fig. 5b referred to. As in Fig. 6As shown, the substrate table 11 is raised in the middle 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 essentially identical. Reference symbol list

[0120] 1 Print unit 2, 2a-d Print heads 3a-d Pinning units 4 Print chip 5a-x Nozzle rows 6 Nozzles 7 Offset 8 Base plate 8a, 8b Base plate parts 9 Adjustment means 10a Base plate Pinning unit 10b Circuit board with LED 10c Quartz glass rod 10d Frame 10e Water cooling 11 Substrate table 12 Substrate 13 Printing setup 20a Line(s) 20b Cutout

Claims

1. Printing unit (1) for printing a substrate (12) comprising two printheads (2a, 2b) arranged one behind the other in the direction of travel of the substrate (12) and two pinning units (3a, 3b), wherein each printhead (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 offset from each other by half the distance between two adjacent nozzles (6) of the two or more nozzles (6), characterized by thatthe two nozzle rows (5a, 5b, 5e, 5f) in each of the two printheads (2a, 2b) have a first color in a first of the two nozzle rows (5a, 5e) and a second color, different from the first color, in a second of the two nozzle rows (5b, 5f), and that either the color sequence of the first and second color in the two nozzle rows (5a, 5b, 5e, 5f) between the two printheads (2a, 2b) is identical and the two printheads (2a, 2b) have a mechanical offset (7) from each other 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 color in the two nozzle rows (5a, 5b, 5e, 5f) between the two printheads (2a, 2b) is reversed.

2. Pressure unit (1) according to claim 1, characterized by thatThe first and second colors are selected from cyan, black, yellow and magenta, in particular that if the first color is cyan, the second color is then black or vice versa, or that if the first color is yellow, the second color is then magenta or vice versa.

3. Pressure unit (1) according to one of claims 1 or 2, characterized by that the printing unit (1) has two further printheads (2c, 2d) arranged one behind the other in the direction of travel of the substrate (12) and two further pinning units (3c, 3d), in particular wherein the two printheads (2a, 2b) and the two further printheads (2c, 2d) are arranged one behind the other in the direction of travel of the substrate (12).

4. Pressure unit (1) according to claim 3, characterized by thatEach printhead (2a, 2b, 2c, 2d) has one or more print chips (4) each with two rows of nozzles (5a-5x) arranged transversely to the direction of travel 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 offset from each other by half the distance between two adjacent nozzles (6) of the two or more nozzles (6).

5. Pressure unit (1) according to claim 4, characterized by that the two nozzle rows (5g, 5h, 5m, 5n, 5o, 5u, 5v, 5w, 5x) in each of the further two printheads (2c, 2d) have a third color, different from the first and second colors, in one of the first two nozzle rows (5g, 5m, 5o, 5u, 5w) and a fourth color, different from the first, second and third colors, in one of the second two nozzle rows (5h, 5n, 5p, 5v, 5x).

6. Pressure unit (1) according to claim 5, characterized by thatThe 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 then black, or vice versa, or that if the first color is yellow, the second color is then magenta, or vice versa, and further preferably that if the third color is cyan, the fourth color is then black, or vice versa, or that if the third color is yellow, the fourth color is then magenta, or vice versa.

7. Pressure unit (1) according to one of claims 5 or 6, characterized by that The first and second colors selected are from cyan and black, and the third and fourth colors selected are from yellow and magenta, or vice versa.

8. Pressure unit (1) according to one of claims 5 to 7, characterized by thateither the color sequence of the third and fourth colors in the two nozzle rows (5g, 5h, 5m, 5n, 5o, 5u, 5v, 5w, 5x) between the two further printheads (2c, 2d) is identical and the two further printheads (2c, 2d) have a mechanical offset (7) to each other 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 third and fourth colors in the two nozzle rows (5g, 5h, 5m, 5n, 5o, 5u, 5v, 5w, 5x) between the two further printheads (2c, 2d) is reversed.

9. Pressure unit (1) according to any one of the preceding claims, characterized by that the mechanical offset (7) between the two printheads (2a, 2b) and / or between the two further printheads (2c, 2d) which are arranged transversely to the direction of travel of the substrate, is between 20 µm and 60 µm, preferably between 30 µm and 50 µm, more preferably 40 µm.

10. Pressure unit (1) according to any one of the preceding claims, characterized by that the printing unit (1) has a resolution of 600 x 600 dpi.

11. Pressure unit (1) according to any one of the preceding claims, characterized by that along the direction of travel of the substrate (12) after each printhead (2a, 2b, 2c, 2d) a pinning unit (3a, 3b, 3c, 3d) is arranged, in particular that along the direction of travel of the substrate (12) after each of the two printheads (2a, 2b) one of the two pinning units (3a, 3b) is arranged and / or that along the direction of travel of the substrate (12) after each of the two further printheads (2c, 2d) one of the two further pinning units (3c, 3d) is arranged.

12. Pressure unit (1) according to claim 11, characterized by thatthe distance between each printhead (2a, 2b, 2c, 2d) and the pinning unit (3a, 3b, 3c, 3d) arranged after the printhead (2a, 2b, 2c, 2d) is between 10 mm and 80 mm, preferably between 30 mm and 50 mm.

13. Pressure 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. Pressure 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 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.

15. Pressure unit (1) according to any one of the preceding claims, characterized by thatthe 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) using 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 thatthe substrate (12) of the printing unit (1) is supplied via a substrate table (11), in particular wherein the substrate table (11) is raised in the middle such that, preferably when using a V-shaped base plate (8), further preferably according to the printing unit (1) of claim 14, the distance between the substrate (12) and the two printheads (2a, 2b) and / or the two further printheads (2c, 3d) is essentially identical.

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