WO2024125843A1 - Printed image correction - Google Patents

Abstract

A method for printing a carrier material (21) using a digital printing device (120) is disclosed, wherein the carrier material (21) experiences a change in size during the printing operation, and wherein the method comprises the following steps: - carrying out a first print of the carrier material (21); - providing printing data for at least one further print of the carrier material (21); - adapting the printing data for the at least one further print to the change in size of the carrier material (21); - carrying out the at least one further print of the carrier material (21) in accordance with the adapted printing data for the at least one further print. Further disclosed are a digital printing device (120) and a computer program product.

Description

Print image correction

Description

The present invention relates to a method for printing a carrier material with a digital printing device, in particular a digital printing device with single-pass technology, wherein the carrier material undergoes a change in size during the printing process. The invention further relates to a digital printing device for carrying out the method and a computer program product.

When printing on substrates with a digital printing device, in particular with a single-pass digital printing device, where the substrates change in size as a result of printing, there is the problem that the change in size of the substrate causes a relative shift of the substrate surface to be printed on compared to the digital printing device. If the relative shift is large enough to exceed the dimensions of a pixel, a corresponding pixel stored in print data in front of the digital printing device will no longer be printed in the intended position on the substrate surface, since this position is no longer in the intended location under the substrate due to the relative shift relative to a printing medium of the digital printing device. As a result, the corresponding pixel is printed in the wrong place. If the substrate is enlarged transversely to a feed direction, the corresponding pixel is printed too far inward on the substrate surface, and if the substrate is reduced in size transversely to a feed direction, the corresponding pixel is printed too far outward on the substrate surface. The change in size of the carrier material can have different causes. This can be due to the swelling of the carrier material, which absorbs moisture from printed material such as ink and therefore experiences a change in size, particularly in width but also in length. If the carrier material is elastic, tension caused by the transport of the carrier material during the printing process can also lead to a change in size. If, for example, a carrier material is printed in the form of a web that is guided over an arrangement of deflection rollers, the carrier material is under tension in the feed direction and can experience elongation in the feed direction, while at the same time shrinking transversely to the feed direction. Temperature differences or other environmental and/or machine influences such as air humidity, changes in air humidity and the like can also cause the carrier material to shrink or enlarge. Furthermore, the application of a pre-coating, e.g. a printing primer, can have the same effect. These so-called printing primers are often applied to improve the subsequently created print image, for example to positively influence the adhesion of the ink, the flow properties of the ink, the sharpness of the print image, the homogeneous color transition, and other properties of the print image.

Especially when multiple prints are made on the surface of the carrier material, which is particularly the case with digital multi-color printing, and especially with single-pass digital printing, where each individual color CMYK (cyan, magenta, yellow and black) is printed with a separate printing medium, blurring of the printed image occurs when pixels of colors applied later cannot be printed correctly relative to the colors printed first due to the change in size.

Figure 4 shows a corresponding print result in view 4.1. It shows a printed image of a wooden surface that was printed on a carrier material. The feed direction of the carrier material (here, for example, paper) was oriented vertically in view 4.1. Due to the printing, the carrier material has a size change in a direction transverse to the feed direction, ie in view 4.1 in horizontal direction. This resulted in pixels that were printed in the edge areas (arrows) no longer being able to be placed precisely in line with previously printed pixels, as the carrier material had grown across the feed direction. As a result, the printed image becomes blurred the further away from the center of the image it is. This is a registration error.

To make matters worse, the width growth of the carrier material can vary depending on the amount of printing material applied. The width growth depends on factors such as tensile stress, paper type, ambient temperature, ambient humidity, paper moisture, ink, ink formulation and ink quantity. This makes it almost impossible to plan a correction in advance when generating the print data (RIP process). Compensation in the RIP process is possible, but very time-consuming. A RIP is an image file with one or more colors in which a bitmap color separation in a specified resolution is calculated from another graphics format, e.g. a vector graphic, using so-called RIP software. In other words, a RIP file consists of one or more bitmap files, with a bitmap file of the specified resolution assigned to each color.

A quick and easy adjustment of the print data is not possible with the RIP process. In particular, this is not possible “on the fly” during the printing process.

It is therefore an object of the present invention to show a possibility how this problem can be solved and the printing result can be improved with little effort despite a change in the size of the carrier material.

This problem is solved by the subject matter of the independent claims. Advantageous further developments are the subject matter of the subclaims.

According to the invention, a method for printing a carrier material with a digital printing device is provided, wherein the carrier material during the undergoes a change in size during the printing process, the method comprising the following steps:

- Carrying out a first printing of the carrier material;

- Providing print data for at least one further printing of the carrier material;

- Adapting the print data for at least one further print to the change in size of the carrier material;

- Carrying out at least one further printing of the carrier material according to the adapted print data for the at least one further printing.

Preferably, the adaptation of the print data for the at least one further print to the change in size of the carrier material is carried out by adding and/or removing individual pixels.

Preferably, the addition and/or removal of individual pixels is carried out for at least one color and/or for at least one digital printing medium and at the same time is not carried out for at least one color and/or for at least one digital printing medium.

Preferably, the adjustment of the print data takes place within color separations previously generated and used for further printing, so that no further generation of a color separation is carried out for the at least one further printing.

The carrier material can comprise any material, whereby the method is particularly suitable for carrier materials that experience a change in size during the printing process. In particular, absorbent carrier materials such as paper but also corresponding wood materials that, as a result of printing with a printing material such as ink, draw moisture from the printing material and thus change their size.

The carrier material can be in the form of a web, which is, for example, rolled up on a supply roll, for the first and at least one further Printing is unrolled and then rolled back onto a supply roll.

However, it is also possible for the carrier material to be available as a single product, particularly in plate or sheet form. In this case, individual workpieces are printed. If the carrier material is available as a single product, the first printing can be carried out in such a way that printing material is printed on the same workpiece during the first printing and the at least one further printing. Alternatively, the first printing can relate to a first workpiece and the at least one further printing can relate to at least one further workpiece. In this case, the same motif or structure is preferably printed on each workpiece with the corresponding printing.

Printing is preferably carried out using a digital printing device. This is characterized by the fact that it has at least one digital printing medium. The digital printing medium can be a digital print head or a digital nozzle bar or can comprise one or more digital print head(s) or one or more digital print bars. The digital printing medium applies printing material to the carrier material, the area to be printed on which is divided into pixels. This is done according to the printing data provided, which in particular includes information about the amount of printing material applied per pixel and/or information about the spatial position of each pixel.

The printing material used in the first or at least one further printing can be an ink that is in particular water-based. The printing material can in particular contain a water content of at least 50%. In particular, the printing material can be colored ink, in which case color printing is preferably carried out on the carrier material, in which, for example, the individual colors CMYK (Cyan Magenta Yellow and Black) are each printed on the carrier material using a separate digital printing medium. Alternatively, fewer colors, e.g. two or three colors, or more colors, e.g. eight, nine or ten colors, can be printed on the carrier material. The colors can alternatively also be RBYK (Red Blue Yellow Black), which is often used in decorative printing. Alternatively or additionally, the printing material released during the first or at least one subsequent printing process can be a structuring material. This can be used to build a three-dimensional structure on the carrier material. This structure is characterized by elevations and/or depressions. This type of structure construction corresponds to an additive structuring process in which printing material is applied to the carrier material in different positions and in different quantities so that a structure is built up upwards, i.e. away from the surface of the carrier material. Here, too, the carrier material can absorb moisture from the printing material and thus experience a change in size.

The printing material can in particular have radiation-curing properties, whereby radiation drying of the printing material printed on the carrier material is preferably provided. Alternatively or additionally, the printing material can be dried by physical drying. This can be, for example, a water-based or solvent-based ink which is dried by heating, infrared radiation and/or swirling air from a fan.

Changes in the size of the carrier material due to mechanical stress, such as tensile stresses caused by the transport of the carrier material, are always possible with the appropriate carrier material.

Adapting the print data by adding and/or removing individual pixels is a relatively simple process. In this way, the area that the at least one digital printing medium prints can be changed. If the carrier material has increased in size, for example, the area that the at least one digital printing medium covers and can therefore print on is increased by adding pixels. If the carrier material has decreased in size, for example, the area that the at least one digital printing medium covers is reduced by removing pixels. The adjustment of the print data can be carried out in an automated manner. This has the advantage that such print data can be adjusted in a relatively short time and a digital printing device that prints the carrier material only needs to be stopped briefly in order to adjust the print data in the working memory (digital printing device idle time approx. 5 to 15 seconds). If the digital printing device is sufficiently powerful, it is not even necessary to stop the digital printing device, as adjustments can be made during operation.

The first print here can be printing with a single printing color. The at least one further print can then comprise printing with another single printing color.

Preferably, the change in size of the carrier material is recorded. In this way, the change in size can be measured and prepared for further processing, in particular for adapting the print data for the at least one further printing. Preferably, a change in size is recorded as a result of at least one of the printing operations carried out. However, it can also be provided that a change in size is recorded that occurs due to the mechanical stress on the carrier material or due to environmental conditions.

Preferably, the change in size is detected using a detection means. The detection means can in particular be optically based and have a camera. Furthermore, the detection means can have an image recognition system with which the image data captured by the camera is evaluated in order to determine the change in size. The image recognition system can in particular be provided in a data processing means which, for example, comprises a separate computer. The detection means can alternatively or additionally also have other sensors, such as laser sensors for measuring width, capacitive and/or inductive sensors which can, for example, carry out a width measurement on one or both sides at the edge of the carrier material. The size change itself can be recorded by recording the printed printing material by comparing an expected target position with an actually printed position on the surface of the carrier material. If the target position and the actually printed position do not coincide, there is a change in the size of the carrier material. The target position can be obtained, for example, from the print data according to which a previous digital printing medium has printed. If it is then recorded that the printing material is not in the target position, a size change can be assumed. A subsequent digital printing medium can then use adjusted print data to print in the correct position relative to the already printed printing material. Alternatively or additionally, the edge or width of the carrier material can also be recorded. If the actual width of the carrier material is known, a change in the size of the carrier material can be recorded by measuring the carrier material from one edge to the opposite edge. This is also possible with a length of the carrier material, provided it is a plate or web-shaped material with opposite edges in the feed direction. Alternatively or additionally, detection of marks on the carrier material can also be provided. A change in size is detected by determining the distance between at least two marks. The marks can already be present on the carrier material or can have been applied by individual printing. For example, the first printing can apply two marks whose distance is known. If these marks are then detected and it is determined that their distance has changed, the size of the carrier material has changed. The marks can be printed in an area of the carrier material that is later removed before the carrier material is made into a final product. On the other hand, individual or multiple printed pixels or structural elements that also remain on the final product can also function as marks.

Preferably, the change in size of the carrier material is recorded after the first printing. If the change in size is recorded after the first printing, the print data can be adjusted accordingly for the subsequent printing. Alternatively or additionally, the Recording the size change after at least one further print. If the recording is carried out after the first print and each further print, it is possible to adjust the print data for each print individually. In this way, each individual size change that occurs after each individual print can be responded to with appropriately adjusted print data. Alternatively or additionally, the size change of the carrier material is recorded after the last print. This is also possible and particularly advantageous if the number of recording devices is to be reduced. For example, the size change due to each previous print can be determined from a completely printed motif (this can be the case if no further printing material needs to be printed to complete the motif), with the adjustment of the print data then leading to an improvement in the next printed motif. Alternatively, the recording can also be carried out after each individual color when printing with several colors in order to determine the size change before printing the next color and to directly correct individual colors and their print width. However, it is also possible to carry out the recording not after each individual print, but after every second print. Generally speaking, it is possible to carry out the recording only after certain individual prints. In this way, an optimum can be found between the necessary recordings on the one hand and the print quality on the other. If recording devices are used for the recordings, it can be checked, particularly from an economic point of view, how many recording devices are actually needed so that the print quality meets the requirements.

Preferably, the change in size of the carrier material as a result of printing is recorded by a user. This has the advantage that a recording device can be dispensed with. For example, the user can measure the carrier material or the distances between opposite edges of the carrier material after printing and thus determine a change in size. In addition, it is possible for the user to use the above-mentioned marks or the The printer generally compares the printed image with a target image in order to determine the change in size. In particular, it can create a test print for this purpose.

Alternatively, the change in size of the carrier material as a result of printing is detected by a detection device, in particular as described above.

Preferably, the first printing process involves printing on printing material with a different color than the at least one further printing process. The printing material used can be ink and/or structuring material.

Alternatively, during the first printing of the carrier material, a printing process is carried out with exactly one printing ink and during the at least one further printing of the carrier material, a printing process is also carried out with exactly one printing ink, whereby this printing ink is either identical to the printing ink printed during the first printing or is different from it.

Preferably, the adjustment of the print data for at least one print is carried out by a user. The user can, for example, access the print data via a user interface such as a computer and adjust it pixel-precisely. He can either use the recorded size change from the recording or adjust the print data without this information. The effect of the adjustment can then be checked, particularly on the result of further prints.

Alternatively, the adjustment of the print data for the at least one print is carried out by a data processing means. This can preferably be done automatically by the data processing means processing the change in size of the carrier material and by the data processing means determining a pixel-accurate adjustment of the print data therefrom.

Preferably, the carrier material is moved in a feed direction for printing. In particular, this can be a continuous printing process, in which the at least one digital printing medium remains stationary relative to the surface of the carrier material and the carrier material is moved relative to it. Preferably, the printing is carried out completely in one pass (so-called single-pass printing process). Preferably, web-shaped carrier material is printed on, which is first unrolled from a supply roll and then fed to the at least one digital printing medium via a roller system. After printing, the web-shaped carrier material is preferably rolled back onto another supply roll. Alternatively, sheet-shaped or plate-shaped carrier materials can also be printed here, which are fed to the at least one digital printing medium as individual workpieces.

Alternatively, the at least one digital printing medium is moved in a feed direction for printing.

Preferably, the at least one digital printing medium used for printing is arranged such that it can print the entire width of the carrier material in the feed direction. This means that preferably the at least one digital printing medium, which can be a digital print head or a digital nozzle bar or can comprise a digital print head or a digital print bar, is arranged over the entire width of the carrier material. This means that the at least one digital printing medium preferably extends over the entire extension direction of the carrier material transversely to the feed direction.

Preferably, the adjustment of the print data is carried out by adding and/or removing individual pixels transverse to the feed direction and/or in the feed direction. The at least one digital printing medium carries out the printing according to the print data. The print data comprises information that describes the surface of the carrier material to be printed, divided into pixels, with the printing taking place according to a pixel row transverse to the feed direction. If the carrier material is moved further in the feed direction by one pixel row or alternatively the digital printing medium is moved further in relation to the carrier material by one pixel position, the printing takes place according to a subsequent pixel row transverse to the feed direction, etc. An adjustment of the print data by adding and/or Removing individual pixels in the print data results in the area on which the at least one digital printing medium prints on the carrier material being changed. If pixels are added, the area increases; if pixels are removed, the area is reduced.

If a row of pixels is adjusted in this way across the feed direction, it is possible to react in particular to the change in size of the carrier material across the feed direction, i.e. to a change in the width of the carrier material. Adding pixels widens the area to be printed, removing them narrows the area to be printed. A change in size of the carrier material in the feed direction can be reacted to by adding and/or removing pixels in the feed direction. Adding pixels lengthens the area to be printed, removing them shortens the area to be printed.

Preferably, individual pixels are added by duplicating at least one pixel. This means that no pixels with any printing information are inserted, but rather existing pixels are duplicated. Preferably, no additional printing information is added, but rather one or more pixels are inserted whose printing information is already available. This is a simple way of stretching or compressing the print image in the previously created RIP separation, without having to calculate, load and then print a new RIP separation.

Particularly preferably, pixels are duplicated whose printing information is identical to the printing information of a neighboring pixel. For example, it can be provided that the printing information of a pixel contains the delivery of a certain amount of printing material and a pixel with the same printing information is adjacent to this pixel, i.e. directly adjacent (for example directly adjacent in the feed direction or transverse to the feed direction). The duplication of such a pixel leads to the fact that now there are no longer just at least two pixels with the same printing information next to each other, but at least three. This means that the area printed by these pixels is enlarged accordingly. However, since this affects an area that has a uniform optical appearance due to the same printing information of the pixels, this enlargement of the area is not perceptible to a viewer.

Preferably, the same principle is used when pixels are removed. This means that if there are two adjacent pixels that have the same printing information, one of the two pixels can be removed so that the total area on the carrier material printed by the corresponding digital printing medium is reduced. Alternatively, one or more random pixels can be removed when compressing the printed image. Preferably, the pixels to be removed or added are not removed/added directly next to each other, but distributed across the printing width.

Preferably, the addition and/or removal of the at least one pixel is carried out in such a way that a pixel is added and/or removed that has no printing information. This means that such a pixel has printing information according to which no printing with printing material should take place at the corresponding position on the carrier material. Here too, the addition and/or removal of the pixels can be carried out in such a way that pixels that are adjacent to identical pixels are duplicated and/or removed.

Preferably, print data are also provided for the first printing, wherein the first printing is carried out according to the print data for the first printing.

Preferably, the print data for the first printing is adapted to the change in size of the carrier material by adding and/or removing individual pixels. If it is already known from previous printing how a change in size of the carrier material occurs, this can be reacted to during the first printing by adapting the print data accordingly. It is also possible to react to changes in size of the carrier material that occur, for example, purely as a result of the transport process of the carrier material. This can, for example, be an elongation of the carrier material due to a tension in the feed direction caused by the transport of the carrier material.

Alternatively or additionally, this may also cause shrinkage of the carrier material transverse to the feed direction.

However, it can also be provided that the print data for the first print and/or for at least one further print are not adjusted. This means that individual pixels are not added and/or removed. This means that adjustment of print data can be deliberately omitted if it can be assumed that the size of the carrier material will not change. This can be the case, for example, when providing the print data for the first print, since the carrier material has not yet been printed at this point.

Preferably, the printing of the carrier material takes place in a continuous process, in particular as described above, with the adjustment of the print data for the at least one further print being carried out in the working memory of the digital printing device, so that no interruption of the printing process is necessary. The image data for the individual printing colors are preferably loaded into the working memory and adjusted at pixel level.

The method described above allows the adjustment of the print data to the change in size of the carrier material in a simple manner, namely simply by adding and/or removing individual pixels in the individual print data for individual digital printing media. This can reduce a registration error that occurs when printing with a digital printing medium followed by at least one further printing with a digital printing medium.

A particular advantage here is that the actual cause of the change in size of the carrier material does not necessarily have to be known. If, for example, the ambient temperature, humidity, mechanical load on the carrier material as a result of mechanical tension, etc. are also to be taken into account in a conventional setting of a printing process, this can be neglected here. as the only response to a registration error is the adjustment of the print data as described above.

Further aspects of the invention, namely a digital printing device and a computer program product, are described below. It is clear to a person skilled in the art that features mentioned above in the description of the method can be transferred analogously to the digital printing device and the computer program product. The above description of the method is therefore always to be understood as a description of aspects of the device according to the invention or the computer program product according to the invention.

According to the invention, a digital printing device is provided which is particularly suitable for carrying out the method described above. The digital printing device has the following elements:

- a digital printing medium for a first print;

- at least one further digital printing medium for at least one further printing;

- a data processing means which is designed to adapt print data for at least one printing to the change in size of the carrier material, in particular by adding and/or removing individual pixels, and/or a second user interface via which a user can provide adapted print data; and

- a control means which is designed to control the printing device for the first and for the at least one further printing according to provided print data.

The digital printing medium for the first printing and the at least one further digital printing medium for the at least one further printing can be identical or different from one another. With identical digital printing media, printing in a single pass is not possible, since the carrier material must be fed back to the same digital printing medium. In order to implement a single-pass process, all digital printing media must be fed in a sequence in the feed direction. position. Alternatively, the digital printing means can also be provided in a movable manner, whereby a single digital printing means can be provided for the individual prints, which is moved several times over the carrier material in order to carry out the individual prints. Alternatively, it can also be provided that several movable digital printing means are provided.

The data processing means, which is designed to adapt print data for at least one print to the change in size of the carrier material by adding and/or removing individual pixels, can be automated. This means that the adaptation takes place automatically according to a certain predetermined pattern, in particular according to a computer program. Alternatively or additionally, the data processing means comprises a user interface via which a user can provide adapted print data or adapt print data. It is thus possible for pixels to be added and/or removed manually, for example on a computer, and then for the adapted print data to be provided. The user interface can thus comprise in particular input means, such as a keyboard or a separate computer. It can also comprise a data interface via which the input can be made. The data processing means is preferably designed as an electronic control unit.

The control means, which is designed to control the printing device for the first and for the at least one further printing according to the provided printing data, preferably also comprises an electronic control unit. The control means, preferably the electronic control unit, can be identical to the data processing means, preferably to the electronic control unit of the data processing means, or at least designed as a structural unit.

The digital printing device preferably has a transport means which is designed to transport the carrier material to the digital printing means. In the case of a carrier material in the form of a single product, this can be a belt transport. In the case of a web-shaped carrier material, the transport means can comprise corresponding rollers or deflection rollers. The digital printing device preferably has a drying unit which is designed to dry and/or harden the printing material which has been printed onto the carrier material. For this purpose, it can comprise a heating element and/or a radiation source, in particular a UV or IR radiation source.

The digital printing device preferably has a detection means for detecting the change in size of the carrier material as a result of the printing. The detection means can, as described above, be designed in particular to be optically based and preferably comprise a camera. Furthermore, the detection means can have an image recognition with which the image data captured by the camera is evaluated in order to determine the change in size. The image recognition can in particular be provided in a data processing means which, for example, comprises a separate computer, or the data processing means mentioned above. The detection means can alternatively or additionally comprise a user interface via which a user can enter the change in size as a result of the printing after he has carried out the corresponding detection himself. The detection means itself can be designed to determine the change in size from an image recognition. The user interface via which a user can enter the change in size as a result of the printing can comprise input means such as a keyboard or a separate computer. It can also comprise a data interface via which the input can be made. The detection means is preferably designed as an electronic control unit.

According to the invention, a computer program product with code means is further provided.

The code means are preferably designed to allow a detection means to detect the change in size of the carrier material as a result of the printing. Alternatively or additionally, the code means are designed to allow a data processing means to adapt print data for at least one printing to the change in size of the carrier material, in particular by Adding and/or removing individual pixels. Alternatively or additionally, the code means are designed to cause a control means to control a digital printing device for a first and for the at least one further printing according to provided printing data.

The invention is explained in more detail below with reference to the accompanying drawings.

Show it

Figure 1a shows an embodiment of a digital

Printing device for carrying out the process;

Figure 1b shows a further development of the digital printing device from Figure 1a;

Figure 1c shows a further embodiment of a digital

Printing device for carrying out the process;

Figure 1d shows a further development of the printing device according to the invention for

Carrying out the method according to the invention, in which a detection means is positioned behind each individual digital printing medium;

Figure 2 shows a typical arrangement of several digital printing media in a digital printing device;

Figure 3 shows an example of adjustment of print data according to the

Principle of the invention; and

Figure 4 shows a comparison of a print result with and without the inventive adaptation of the print data. Figure 1a shows a digital printing device 120 according to the present invention, which is designed for printing according to the single-pass method. The digital printing device 120 is equipped with a carrier material 21 in the form of a web, which can be a decorative paper, a normal paper or also a film, such as a plastic film. The carrier material 21 is unwound from a supply roll 22 and fed via deflection rollers 30 to a printing area with digital printing means 40, 50, 60, 70, which are designed here as fixed printing bars that extend perpendicular to the drawing plane and thus transversely to the feed direction of the carrier material 21, wherein the feed direction under the digital printing means 40, 50, 60, 70 runs from left to right. The digital printing means 40, 50, 60, 70 are designed to deliver printing material to the surface of the carrier material 21 facing the digital printing means 40, 50, 60, 70.

After passing through the printing area, i.e. after the last printing medium 70, the carrier material 21 is guided further over deflection rollers 31, 32, where it is dried by means of a drying unit 105 and then wound up again on a supply roll 95. The drying unit 105 can comprise a radiation source, such as a UV or IR light source, or a heat source, such as a heating element. Alternatively or additionally, the drying unit 105 can also apply preheated air. The drying unit 105 serves in particular to dry the printed printing material so that it can be wound up on the supply roll 95 without destroying the printing material or the decoration formed by the printing material on the carrier material 21 (i.e. a two-dimensional motif or a three-dimensional structure). The drying unit 105 can also be present multiple times (not shown in Figure 1a), and can be positioned once or multiple times directly behind the digital printing means 40, 50, 60, 70.

Furthermore, a data processing means 110 is shown, which is designed here as a computer. The data processing means has a data connection to each of the digital printing means 40, 50, 60, 70, as shown by the arrow connections. The data processing means 110 is designed to adapt print data for printing to the change in size of the carrier material 21 by adding and/or removing individual pixels in the print data. This can be done automatically within the data processing means 110, for example by a suitably designed computer program and/or by a user who uses the data processing means 110 as a user interface to adapt the print data. It is thus possible to adapt the print data according to which the digital printing means 40, 50, 60, 70 print in order to be able to react to changes in the size of the carrier material 21.

In the digital printing device 120 shown here, it is possible for a user to detect the change in size of the carrier material 21, for example, by detecting and analyzing a print result on the carrier material 21. He can then make the corresponding changes in the print data via the data processing means 110.

The digital printing device 120 further comprises a control means 115 which controls the digital printing device 120. In particular, this refers to the control of the digital printing means 40, 50, 60, 70. The data processing means 110 and the control means 115 are advantageously implemented in the same device, such as a computer, using computer programs.

Figure 1b shows a further development of the digital printing device 120 from Figure 1a. Identical elements are provided with the same reference numerals. For their description, reference is made to the description of Figure 1a. The differences from the embodiment of Figure 1a are discussed below.

Following the printing process, ie after the last printing means 70, the printed carrier material 21 is detected with a detection means 100 arranged here and the change in size of the carrier material 21 is determined. The detection means 100 can have a camera for this purpose. To detect the change in size, the detection means 100 can have image recognition software that determines the change in size from the image data. The detection is carried out in such a way that, for example, the print width of the printing material printed by each digital printing medium 40, 50, 60, 70 is checked to see how much the individual printed pixels were shifted by the change in size of the carrier material 21.

The detection means 100 is in contact with the data processing means 110 via a data connection. The change in size of the printed carrier material 21 is transmitted via this to the data processing means 110. In the data processing means 110, the print data is then adjusted based on the change in size of the printed carrier material 21 and transmitted to the digital printing means 40, 50, 60, 70. Additionally or alternatively, a user can also use the data processing means 110 to make a corresponding adjustment to the print data based on the change in size of the printed carrier material 21. Instead of changing the size of the printed carrier material 21, it can also be provided that only image data from the detection by the detection means 100 is transmitted to the data processing means 110. Here, the change in size is then determined based on the image data as part of the detection. In this case, the detection means 100 is also partially implemented by the data processing means 110, which is designed by the corresponding software to determine the change in size.

The positioning of the detection means 110 shown here allows the size change of the printed carrier material 21 to be detected only after the entire printing by all digital printing means 40, 50, 60, 70. This has the advantage that only a single detection means 100 is required. However, it is also only possible to react to a registration error when all digital printing means 40, 50, 60, 70 have printed the carrier material 21.

One way to react more quickly to a registration error is to provide additional detection means. For example, after each digital printing medium 40, 50, 60, 70, a corresponding detection means can be provided in order to detect a change in the size of the carrier material 21 due to printing by a digital printing medium 40, 50, 60 and to immediately Data processing means 110 to make a corresponding adjustment of the print data for the following digital printing medium 50, 60, 70 so that a registration error is avoided as far as possible.

Figure 1c shows a further embodiment of a digital printing device according to the invention for carrying out the method. The elements that are the same as those in Figures 1a and 1b described above are provided with the same reference numerals. For their description, reference is made to the description of Figures 1a and 1b. The corresponding differences are discussed below.

The digital printing device 120 shown here comprises, in addition to the digital printing means

40, 50, 60, 70 additional digital printing media 80, 90. Each digital printing media 40, 50,

60, 70, 80, 90, a drying unit 41, 51, 61, 71, 81, 91 is arranged downstream so that the printing material printed by the corresponding digital printing medium 40, 50, 60, 70, 80 can be dried before printing by the following digital printing medium 50, 60, 70, 80, 90. In this way, the printed printing material can also be fixed immediately to the carrier material 21.

The drying units 41, 51, 61, 71, 81, 91 can be designed like the drying unit 105. In particular, it can be provided that the drying units

41, 51, 61, 71, 81, 91 ensure intermediate drying of the printing material on the carrier material and final hardening or drying is carried out by the drying unit 105.

The embodiment shown here can also have a data processing means 110 as shown in Figure 1b, which is connected to the detection means 100. Furthermore, a comparable control means 115 can also be present in order to control the digital printing means 40, 50, 60, 70, 80, 90 and possibly also the drying units 41, 51,

61, 71, 81, 91. The data processing means 110 can adapt the print data for the individual digital printing means 40, 50, 60, 70, 80, 90. It is also possible that one or more further detection means 100 are provided, which adapt the size change of the carrier material 21 to different positions of the printing area. In particular, it can be provided that the change in size of the carrier material 21 is recorded after each digital printing medium 40, 50, 60, 70, 80, 90 in order to be able to react immediately to registration errors.

Figure 1d shows a further developed digital printing device 120, which is based on the printing device from Figure 1b. Here, instead of one detection means 100, several detection means 100a, 100b, 100c and 100d are arranged directly behind one of the digital printing means 40, 50, 60, 70. As a result, the print image can be adjusted directly behind each color without interrupting the printing process by means of the data processing means and the control means 110, 115.

Figure 2 shows a typical arrangement of several digital printing media in a digital printing device.

A top view of a digital printing device is shown, through which a carrier material 21 is conveyed from left to right. The side of the carrier material 21 to be printed is facing the viewer. In the configuration shown, the carrier material 21 is in the form of a web. For example, after printing, the carrier material 21 is rolled up again, e.g. using a supply roll (not shown), after it was first unrolled from a supply roll (not shown) for printing.

A number of digital printing means 40, 50, 60, 70 are arranged above the carrier material 21. These are designed here as printing bars with individual digital printing heads and are positioned in such a way that they print on the surface of the carrier material 21 to be printed when the carrier material 21 is moved under the digital printing means 40, 50, 60, 70 in the feed direction from left to right. The digital printing means 40, 50, 60, 70 can, for example, be designed to print the carrier material 21 in color. Each digital printing means 40, 50, 60, 70 can therefore be assigned a color CMYK (cyan magenta yellow and black), but other configurations are also conceivable in principle. The printing material used here therefore corresponds to that of a printing ink. Alternatively or In addition, printing material can also be printed using the digital printing media 40, 50, 60, 70, which serves to structure the surface as described above.

It can be seen in this drawing that the carrier material 21 undergoes a change in size as a result of printing by the digital printing means 40, 50, 60, 70. This can be due, for example, to the fact that the carrier element 20 is absorbent and liquid from the printing material printed by means of the digital printing means 40, 50, 60, 70 is drawn into the carrier material 21, causing it to swell on the one hand and/or become more stretchable on the other, so that a change in size can also occur as a result of the tensile stress caused by the conveyance of the carrier material 21 from left to right.

In the illustration shown, the carrier material 21 gradually widens transversely to the feed direction due to the printing and in particular due to moisture absorption from the printing material. With a different carrier material 21, however, shrinkage is also conceivable. It is also conceivable that the change in size of the carrier material 21 does not occur evenly. Rather, it depends on many factors. First and foremost, the amount of printing material actually printed by one of the digital printing media 40, 50, 60, 70 must be mentioned here. In other words, the more printing material is printed onto the carrier material 21, the greater the change in size. If shrinkage of the carrier material 21 is to be expected as a result of the printing, the more shrinkage is usually the greater the amount of printing material is printed onto the carrier material 21.

It can also be seen in the drawing that the digital printing means 40, 50, 60, 70 are dimensioned such that they can cover the entire width of the carrier material 21 at any time, i.e. even when it is widened. This is easily recognizable for the digital printing means 40, 50, 60. The digital printing means 70 indicated by dashed lines is also wide enough to cover the entire width of the now widened carrier material 21, which leaves the digital printing means 60 to the right, and thus to be able to print on it. As can also be seen, the carrier material 21 widens further due to the printing by the digital printing medium 70, so that it grows to such an extent that it exceeds the width of the digital printing medium 40, 50, 60, 70 and thus can no longer be completely covered and printed by another digital printing medium that would be arranged downstream of the digital printing medium 70. The maximum possible change in the width of the carrier material 21 due to the printing therefore represents a design criterion when designing the digital printing device shown. If the digital printing medium 70 is the last printing medium in the arrangement shown, it is ensured that printing of the full width of the carrier material 21 is possible by each digital printing medium 40, 50, 60, 70.

Figure 3 shows an exemplary adaptation of print data according to the principle of the invention.

In the upper area, which is headed "Original print image", a series of two pixel rows is shown, with the lower pixel row corresponding to the color magenta and the upper pixel row corresponding to the color cyan. Transferred to the embodiment shown in Figure 2, it could be provided, for example, that the lower row (magenta) is made available to the digital printing means 40 and the upper row to the digital printing means 50 (cyan) as control data.

The individual pixels of the pixel rows are numbered from left to right with consecutive numbers from 1 to 20, whereby pixel 1 contains the printing information (amount of printing material to be applied) that is to be applied to the carrier material 21 at the left edge of the printing area and pixel 20 contains the printing information that is to be applied to the carrier material 21 at the right edge of the printing area. Pixels 1 to 20 of each printing row are arranged in such a way that pixels arranged one above the other correspond to the same printing position on the carrier material 21. This means that magenta printing according to the printing information of pixel 1 and cyan printing according to the printing information of pixel 1 should take place on the carrier material 21 at the same location. If one compares this in Figure 2 with the carrier material 21 that was printed by digital printing medium 40 (magenta) and is still in front of the digital printing medium 50 (cyan), it becomes clear that the Resizing or widening of the carrier material 21 Pixel 1 of the digital printing medium 50 can no longer be printed on the carrier material 21 congruently with the previously printed pixel 1 of the digital printing medium 40, since the printed pixel 1 of the digital printing medium 40 is now located further out (it has experienced a shift transversely to the feed direction or to the left in the feed direction due to the resizing of the carrier material 21).

In the lower area of Figure 3, which is entitled "Corrected print image", an adjustment of the pixel rows according to the invention has now been made in order to take account of the change in size of the carrier material 21.

Here, pixels 6 and 14 (marked with arrows) have been doubled, so that the upper pixel row (cyan) has now been widened by a total of two pixels. If, for data processing reasons, the number of pixels in each pixel row has to remain the same, pixels in other pixel rows can be filled or supplemented accordingly. In this case, the lower pixel row (magenta) has been supplemented by two pixels, each of which is located at the very outside (to the left of pixel 1 and to the right of pixel 20) and is symbolized by empty fields. These pixels do not contain any printing information or the printing information that no printing material should be delivered at this point.

The doubling of the pixels 6 and 14 is chosen here only as an example.

Of course, other pixels can also be duplicated. Doubling pixels 6 and 14 means that the outer pixels (here pixels 1, 2, 3, 4, 5 and 15, 16, 17, 18, 19, 20) of the upper pixel row (cyan) are pushed outwards. This brings them closer to the areas that have moved outwards due to the change in size of the carrier material 21 and can also be made to coincide with them again.

It should be noted that this is an example explanation of the method according to the invention. In reality, a further adjustment of the print data, ie a further duplication of individual pixels or even the removal of pixels at another location, may be necessary. In this case, pixels that have the same printing information as a neighboring pixel can advantageously be duplicated or removed. Such pixels are ideally assigned to an area that has the same printing information across several pixels, so that only this area is changed by adjusting the pixels. Alternatively or additionally, it can be provided that pixels that do not contain any printing information are added and/or removed. This means that these pixels do not result in any printing material being released.

Figure 4 shows a comparison of print results according to the state of the art (view 4.1) and after adjusting the print data, as described for example in Figure 3 (view 4.2). Each figure shows a print result for the same wood decor.

The blurred representation of the edge areas (arrows) of the printed wood decor in Figure 4.1 was already discussed at the beginning. The result is a registration error that has arisen due to the change in size of the carrier material when printing with the individual digital printing media.

If you now compare this with the corresponding edge areas (arrows) in view 4.2, it becomes clear that the sharpness of the wood decor has improved, because the fine wood grains are no longer blurred but clearly visible.

This is achieved by adapting the print data, as described above for Figure 3. By duplicating pixels such as pixels 6 and 14, it is ensured that pixels located in the middle of the print area, i.e. pixels 7, 8, 9, 10, 11, 12, 13, do not change their position. Here, the change in size of the carrier material is not as serious as in the edge areas. However, the outer pixels are each pushed outwards by one pixel due to the duplication, which means that in the outer area of the print area, i.e. pixels 1, 2, 3, 4, 5 and 15, 16, 17, 18, 19, 20, which are printed with the digital printing medium 50 printed, a better coverage is achieved with the pixels previously printed by the digital printing medium 40. The print data of the other digital printing media 60, 70 were adjusted in a similar way.

In this way, a significant improvement in the print result can be achieved with a relatively simple adjustment of the print data, as Figure 4 shows.

Finally, three specific embodiments of the invention are described with reference to Figures 1b and 1c. Each of the details described is to be viewed as a separate feature that can be used separately for a digital printing device.

Example 1 (Figure 1 b):

A digital single-pass printing device 120 is equipped with a carrier material 21, designed as decorative paper with a width of 1400 millimeters and a paper grammage of 70 grams per square meter. The decorative paper is unwound from a supply roll 22, which comprises 5000 linear meters, and fed via deflection rollers 30 to the actual printing area with the digital printing means 40, 50, 60, 70 designed as printing bars. In this case, the carrier material 21 is printed in color. Each digital printing means 40, 50, 60, 70 prints a single color CMYK (color separation). When printing the individual color separation, an ink quantity of 1.5 grams per square meter is released for each color. The printing material, in this case the ink, is a pigmented, aqueous ink with a water content of more than 50%. Following the printing process, the carrier material 21 is inspected via an optical control at the edge of the web on the left and right sides with a detection device 100.

The data on the print width of the respective printed color separations are forwarded to a data processing device 110, which is designed as a central computer. The carrier material 21 is passed through the fixed digital printing devices 40, 50, 60, 70 at a speed of 70 meters per minute. The distance between the carrier material 21 and the digital printing devices 40, 50, 60, 70 is two millimeters. Following the optical inspection, the Carrier material 21 is dried via a drying unit 105 and then rewound onto the supply roll 95.

Example 2 (Figure 1 b):

A carrier material 21, which is designed as decorative paper with a width of 2100 millimeters, is unwound from the supply roll 22. The carrier material 21 has a grammage of 100 grams per square meter and is fed to the individual digital printing media 40, 50, 60, 70 via deflection rollers 30 at a speed of 120 meters per minute. The carrier material 21 is printed with an ink quantity of 2.5 grams per square meter for each digital printing medium 40, 50, 60, 70. Each digital printing medium 40, 50, 60, 70 prints a single color CMYK (color separation). Following the printing process, the carrier material 21 is dried in a drying device 105 with an infrared radiator (near infrared NIR). The surface temperature of the carrier material 21 briefly increases to over 200 degrees Celsius. Before drying, the entire surface of the carrier material 21 is recorded with an optical detection device 100 and the width and length changes of the printed image are measured and fed to a central data processing device 110. The data processing device 110 compares the actual width and length measurements for each color with the original individual color separations and calculates an individual correction for each color. During the printing process, the separation is widened or narrowed at pixel level only for each color. The files are not completely recalculated. The printed and dried carrier material 21 is then wound up on a supply roll 95.

Implementation example 3 (Fig. 1c):

A carrier material 21 consisting essentially of plastic (preferably a PVC material) is fed from a supply roll 22 via deflection rollers 30 to a digital printing device 120 with a total of eight colors and the associated digital printing means 40, 50, 60, 70, 80, 90 (other digital printing means are not shown in Figure 1c). The carrier material 21 is printed with a solvent-based printing ink by the digital printing means 40, 50, 60, 70, 80, 90. A Drying unit 41, 51, 61, 71, 81, 91 (other drying units are not shown in Figure 1c). Following the printing process, the print image width for each color is recorded using an optical detection device 100 in order to record the change in size of the carrier material 21. The print data for the digital printing means 40, 50, 60, 70, 80, 90 are adjusted pixel by pixel, for example, using a data processing device 110 in order to reduce registration errors. The printed carrier material 21 is then rewound onto a supply roll 95.

Example 4 (Figure 1 d):

A plate-shaped carrier material 21 consisting of a plastic composition with a PVC content of more than 60% is fed with a UV-curing ink in a single-pass process to a printing device with a total of eight colors and the associated digital printing means 40, 50, 60, 70 (other digital printing means are not shown in Figure 1d). Detection means 100a, 100b, 100c and 100d are positioned behind the respective digital printing means 40, 50, 60, 70 (other detection means behind the digital printing means for other colors, which are also not shown, are also not shown). UV radiation means are provided between the digital printing means and the detection means (also not shown in Figure 1d). This means that a UV radiation means is positioned after the digital printing means 40 and before the detection means 100a, etc. These UV radiation means are designed as UV LEDs. In an alternative embodiment, these UV radiation means can also be designed as UV tubes. They can also be positioned in the direction of production behind the detection means 100a, 100b, 100c and 100d. The UV radiation emitted by the UV radiation means causes a partial or complete curing of the UV ink used here (in the color of the respective digital printing medium). The carrier material 21 is printed with a UV-curing printing ink by the digital printing means 40, 50, 60, 70 (and others not shown). The detection means 100a, 100b, 100c and 100d (and others not shown) record the print image width for each color after the printing process in order to record the change in size of the carrier material 21. The print data for the digital printing media 40, 50, 60, 70 (and others not shown) are adjusted pixel by pixel via the data processing means 110 in order to reduce registration errors. The printed plate-shaped carrier material 21 is transported for further processing. It can then be rolled up again on the supply roll 95.

Reference symbols

1 to 20 pixels

21 Carrier material (especially roll or plate-shaped)

22 Supply roll

30 pulleys

31 pulley

32 pulley

40 Digital printing media

41 Drying unit

50 Digital printing media

51 Drying unit

60 Digital printing media

61 Drying unit

70 Digital printing media

71 Drying unit

80 Digital printing media

81 Drying unit

90 Digital printing media

91 Drying unit

95 supply roll

100 recording devices

100a-d Recording equipment

105 Drying unit

110 Data processing equipment

115 Tax funds

120 digital printing device

Claims

Expectations 1. A method for printing a carrier material (21) with a digital printing device (120), wherein the carrier material (21) undergoes a change in size during the printing process and wherein the method comprises the following steps: - carrying out a first printing of the carrier material (21); - Providing print data for at least one further printing of the carrier material (21); - adapting the print data for the at least one further print to the change in size of the carrier material (21); - carrying out the at least one further printing of the carrier material (21) according to the adapted printing data for the at least one further printing. 2. Method according to claim 1, wherein the adaptation of the print data for the at least one further printing to the change in size of the carrier material (21) is carried out by adding and/or removing individual pixels. 3. Method according to claim 2, wherein the addition and/or removal of individual pixels is carried out for at least one color and/or for at least one digital printing medium and at the same time is not carried out for at least one color and/or for at least one digital printing medium. 4. Method according to one of the above claims, wherein the adjustment of the print data takes place within color separations previously generated and used for the further printing, so that no further generation of a color separation is carried out for the at least one further printing. 5. Method according to one of the above claims, wherein a detection of the change in size of the carrier material (21) is carried out as a result of at least one of the printing operations carried out, and/or wherein the detection of the change in size of the carrier material (21) is carried out after the first printing operation and/or after the at least one further printing operation, and/or wherein the detection of the change in size of the carrier material (21) is carried out after the last printing operation. 6. The method according to claim 5, wherein the detection of the change in size of the carrier material (21) as a result of the printing is carried out by a user, or wherein the detection of the change in size of the carrier material (21) as a result of the printing is carried out by a detection means (100). 7. Method according to one of the preceding claims, wherein during the first printing, printing material is printed with a different color than during the at least one further printing, or wherein during the first printing of the carrier material (21) a printing process is carried out with exactly one printing color and during the at least one further printing of the carrier material (21) a printing process is also carried out with exactly one printing color, wherein this printing color is either identical to the printing color printed during the first printing or is different from this. 8. Method according to one of the preceding claims, wherein the adaptation of the print data for the at least one printing is carried out by a user, or wherein the adaptation of the print data for the at least one printing is carried out by a data processing means (110). 9. Method according to one of the preceding claims, wherein the carrier material (21) is moved in a feed direction for printing or wherein digital printing means (40, 50, 60, 70) are moved in a feed direction for printing. 10. The method according to claim 9, wherein the adjustment of the print data is carried out by adding and/or removing individual pixels transversely to the feed direction and/or in the feed direction, wherein preferably the addition of individual pixels is carried out by duplicating at least one pixel. 11. Method according to one of claims 2 to 10, wherein the addition and/or removal of the at least one pixel is carried out such that a pixel is added and/or removed which has no printing information or which has printing information identical to an adjacent pixel. 12. Method according to one of the preceding claims, wherein Print data for the first printing are provided, wherein the first printing is carried out according to the print data for the first printing, wherein preferably an adaptation of the print data for the first printing to the change in size of the carrier material (21) is carried out by adding and/or removing individual pixels, or wherein preferably the print data for the first printing and/or for at least one further printing are not adapted by adding and/or removing individual pixels. 13. Method according to one of the preceding claims, wherein the printing of the carrier material (21) takes place in a continuous process and the adaptation of the print data for the at least one further printing takes place in the working memory of the digital printing device (120), so that no interruption of the printing process is necessary. 14. Digital printing device (120) for carrying out the method according to one of claims 1 to 13, comprising: - a digital printing means (40) for a first printing; - a digital printing medium (50, 60, 70) for at least one further printing; - a data processing means (110) which is designed to adapt print data for at least one printing to the change in size of the carrier material (21), in particular by adding and/or removing individual pixels; and - a control means (115) which is designed to control the printing device (120) for the first and for the at least one further printing according to provided printing data. 15. Computer program product with code means which are designed to allow a detection means (100) to detect the change in size of the carrier material (21) as a result of the printing, and/or which are designed to allow a data processing means (110) to adapt print data for at least one printing to the change in size of the carrier material (21), in particular by adding and/or removing individual pixels, and/or which are designed to cause a control means (115) to control a digital printing device (120) for a first and for the at least one further printing according to provided print data.