Application device for applying an application material to a substrate and printing device for printing on a substrate which has such an application device

Abstract

The invention relates to an application device (30) for applying a hydrophobic coating material to a substrate and a printing device (10) for printing on a substrate (11, 47). The printing device (10) has an application device (30) that is arranged at the edge of the substrate in the region of a cut edge (44). The application device (30) applies the hydrophobic coating material only to a narrow edge strip (32) with a width (33) of approximately 0.5 mm to 5 mm from the cut edge (44) on the substrate. In a printing device (10), the application device (30) is arranged at the edge, downstream of a dryer (16) when viewed in the transport direction (23) of the substrate.

Description

[0001] The invention relates to an application device for applying an application material to a substrate and a printing device for printing on a substrate, wherein the printing device comprises such an application device.

[0002] In papermaking and paper printing, it is common to use a web-like substrate (hereinafter referred to as a substrate web), for example made of paper, which is wound onto a roll and is thus available as roll material for printing or cutting into individual sheets. Fig. Figure 1a shows an example of such a roll 40. After the paper is manufactured, a finished paper web is wound into a roll 40. This makes it easier to transport the roll 40 to a printing plant for printing. There, the substrate web 11 can be easily fed into the printing device and printed at high speed.

[0003] Both in papermaking, where the paper is dried under heat at the end of the production process, and in printing, where the substrate with the printed image on it (i.e., after the application of printing ink) is also dried, the paper becomes very dry and brittle after heat treatment. It should be remoistened to prevent it from breaking during subsequent processing steps. To remoisten the paper, a water-based liquid can be applied liberally to make it supple again.

[0004] In the printing industry, paper is typically coated (coated paper, etc.) to achieve a high-quality print image. The coating material is typically applied to one or both sides of the paper, covering as much of the surface as possible on the top and / or bottom. This also protects the paper from moisture. However, the outermost edges of the paper, such as the cut edges, are not coated.

[0005] If rewetting with an aqueous solution takes place, water / moisture can be drawn into the paper in the area of ​​the cut edges by capillary action, since the fibers are cut and therefore "open" there, causing the paper to swell in this edge area along the cut edges. Such swelling 45 is in Fig. 1b is shown exaggeratedly large (see the area of ​​the printing web 11 within the dashed circle at the cut edges 44). A deformation / raised area is clearly visible at the edge of the roll 40. This swelling at the cut edges 44 is due to absorption of moisture, primarily via the cut surface 46 (cf. Fig. 1c) due to the open area there (since it is cut there; see dotted area in Fig. 1c) Fiber structure of the paper and caused by the capillary effect. Due to capillary forces, moisture penetrates much more easily at the "open" cut surface 46 of the paper, for example into narrow cavities between the paper fibers or along the fibers, causing the paper to swell there.

[0006] In Fig. Figure 1c shows a single sheet 47, its dimensions greatly distorted for clarity. The single sheet 47 is cut along its four edges, thus exhibiting four lateral cut surfaces 46 and eight cut edges 44. The cut fibers are exposed in the cut surfaces 46 and are therefore easily accessible to moisture or water. Moisture can then penetrate the paper relatively easily via the cut surface 46.

[0007] During further processing of the paper, for example for printing or cutting a web into individual sheets, problems can arise with precise positioning or exact cuts due to curling at the edges. This is because only the edges at the cut edges 44 are swollen, and thus the paper is longer there than, for example, in the middle of the web 11 between the two cut edges 44. Precise transport of the web 11 is therefore not guaranteed. A largely uniform / precise transport is a prerequisite for high positioning accuracy of the substrate. Otherwise, the print image could be degraded, or straight cuts of the substrate could no longer be possible.

[0008] Digital printing devices, such as inkjet printers, can be used for printing in one or more colors on a substrate web 11. The design of such inkjet printers is well known. In particular, high-speed digital inkjet printers are known in which ink droplets are ejected from nozzles of a printhead onto a rapidly moving substrate web to create a printed image.

[0009] During the printing process, the substrate, such as paper, is dried / fixed at high temperature to dry / fix the printing ink. However, this also dries out the paper. Therefore, to ensure smooth and precise paper transport, it is preferably re-moistened across its entire surface with an aqueous solution to make the web more supple again. This can, however, lead to swelling at the cut edges, which is undesirable.

[0010] The problem has previously been solved by reducing the amount of ink applied, as described, for example, in patent DE 10 2010 060 409 B4. By using a humidification system after the printing process, the dried substrate web can be re-moistened with a predefined amount of liquid (adjustable for both sides), thus compensating for moisture differences between the printed surfaces. However, the problem of swelling at the edges of the substrate web still remains.

[0011] In the past, this problem was addressed by adding water-repellent substances to the coating materials used on the top and bottom sides of the paper. This made the coating water-repellent, thereby reducing or even eliminating warping or swelling at the edges of the paper. However, this requires a significantly larger quantity of water-repellent substances, which are not only very expensive because they are applied over a large area, but would also hinder the penetration of aqueous ink into the paper during the actual printing process.

[0012] The invention addresses the problem of creating an application device that prevents or at least significantly reduces swelling of a substrate in the area of ​​cut edges. Furthermore, the invention aims to create a printing device for a substrate that reduces swelling of the substrate in edge areas at cut edges / surfaces due to high liquid application after drying.

[0013] This problem is solved by an application device for applying a coating material to a substrate, having the features of claim 1. The application device is arranged in at least one edge region with respect to a cut edge of the substrate. It is designed to apply a hydrophobic coating material to the substrate only in the edge region, in a narrow strip with a width of between 0.5 mm and 5 mm, extending inwards from the cut edge towards the center of the substrate, onto the top and / or bottom surface of the substrate.

[0014] This problem is also solved by a printing device for printing on a substrate with the features of claim 6. The printing device includes a transport unit for conveying the substrate through the printing device. A printing unit prints the substrate with printing inks. A dryer dries the printing inks under the influence of heat. An application device according to claim 1 is arranged downstream of the dryer in the transport direction to apply a hydrophobic coating in a narrow border strip to the top and / or bottom of the substrate. The application device is arranged in the region of a cut edge of the substrate such that the hydrophobic coating is applied to the top and / or bottom of the substrate with a border strip width of approximately 0.5 mm to 5 mm from the cut edge.

[0015] A central control unit is connected to all parts of the printing device to be controlled, such as the transport device, the printing unit, the dryer and the application device, in order to synchronize the transport, printing, drying, application of coating material or, if applicable, re-moistening.

[0016] This solution has the advantage that the hydrophobic coating is applied selectively only in a narrow strip along the cut edge of the substrate, which does not affect the current print image or hinder subsequent printing. Furthermore, only a very small amount of the hydrophobic coating is required. The coating thus acts precisely where it is needed and most effectively, namely against swelling of the substrate in the cut area.

[0017] Advantageous embodiments of the invention are characterized by the dependent claims. For example, it is advantageous if the width with which the coating material is applied to the top and / or bottom surface in the edge strip of the substrate is 1 mm.

[0018] A separate application device can be positioned either above or below the substrate in the area of ​​the cut edge to apply the coating material to the top, bottom, or both sides simultaneously, as needed. This is particularly advantageous when the substrate is relatively thick and a coating applied to only one side cannot penetrate deeply enough due to its thickness. In such cases, the coating material can also be applied to the other side.

[0019] It is also advantageous to design the application device in such a way that the hydrophobic coating material is applied to the substrate in contact, either as a solid or liquid. Through this contact and the resulting friction with the substrate, the coating material is better incorporated into the substrate.

[0020] It is also advantageous to design the application device in such a way that a liquid coating material is applied to the substrate without contact, for example by spraying. This prevents the substrate from being mechanically damaged by contact during the application of the coating material.

[0021] In a printing press, the application device is located near the substrate exiting the press, but before any humidification unit that may be present. Advantageously, the application device is also positioned away from the dryer. This allows the substrate to cool down further before the coating material is applied. However, the application device must also be positioned far enough from the humidification unit to allow the coating material sufficient time to penetrate the substrate and thus develop its hydrophobic properties at the cut edge. It is beneficial for the coating material to have a relatively low viscosity to enable it to penetrate the substrate as quickly as possible.

[0022] Exemplary embodiments of the invention are explained in more detail below with reference to schematic drawings. The individual figures are not to scale, but are intended to better illustrate the technical concept through appropriate "exaggerations," i.e., partly local changes in scale. They show: Fig. 1a a view of a roll of printing material, Fig. 1b a partial view of the roll in the area of ​​a cut edge of the substrate, Fig. 1c a view of a single sheet as printing material, Fig. 2 a view of an inkjet printer used for printing on a web-shaped substrate, Fig. 3 A view of two inkjet printers arranged one behind the other for printing on the front and back of a web-shaped substrate, Fig. 4 a view of a web-shaped printing material, at whose two cut edges application devices are arranged, and Fig. 5 a view of a single sheet, at whose four cut edges application devices are arranged.

[0023] The invention of an application device for applying a hydrophobic coating material to a substrate is explained below by way of example, using an embodiment and its use in a printing device. The printing device shown is an inkjet printer, preferably using aqueous ink as the printing ink. The substrate can be a web-shaped substrate (hereinafter referred to as the substrate web) or a sheet- or sheet-shaped substrate (hereinafter referred to as a single sheet).

[0024] Of course, other printing devices or printing machines can also be used, which operate with different printing processes or use different printing inks. What all these printing devices have in common is that the printing ink is dried under the influence of heat after printing, resulting in a relatively dry substrate.

[0025] Furthermore, the application device can also be used independently of a printing device, for example in paper manufacturing as a standalone device for applying a hydrophobic coating material to the substrate.

[0026] In the following figures, functionally identical or equivalent elements are marked with the same reference symbols.

[0027] In Fig. Figure 2 shows an inkjet printer for printing on a web-like substrate as an example of a printing device 10. The substrate web 11 is transported through the printing device 10 at high speed and printed on one or both sides. The substrate web 11 is fed into the printing device 10 via a feeder 12 in the transport direction 23 (see also arrows in the substrate web 11). A rotating frame 13 controls the lateral alignment of the substrate web 11 during transport. A printing unit 14 with multiple inkjet printheads 15 prints the substrate web 11 on the top side (which can also be referred to as the front). In a subsequent drying unit (hereinafter referred to as a dryer 16), the printed ink, and thus the printed image, is dried under heat and therefore fixed to the substrate.The printing web 11 is guided out of the printing device 10 via a dispensing device 17.

[0028] The substrate web 11 can then be turned over by a turning device 18 so that the underside (or back) of the substrate can be printed in a further printing device 10 (as is the case in Fig. 3 is shown in more detail). The printed material can also be fed, as required, to a post-processing device (not shown) where it is further processed, for example by cutting, folding, etc., or simply placed on a rewinder 19 after exiting (as shown in Fig. 3 after the second printing device 10 is shown) is wound up for further use.

[0029] For multicolor printing, the printing unit 14 contains separate printheads 15, each capable of printing a different color (such as the primary colors Y, M, C, and K) or printing fluid / functional fluid. The printheads 15 are arranged transversely to the transport direction 23 across the entire width of the substrate web 11 and print the substrate web 11 line by line during transport. Typically, the edge of the substrate web 11 remains unprinted (i.e., no image is printed in this area), as this area may contain transport rollers for advancing the substrate web 11 or printed positioning marks for precise paper feed control. The width of this unprinted area is typically 10–20 mm to minimize waste of the substrate.

[0030] In the dryer 16 following the printing unit 14, the ink applied to the substrate is dried. Heat is applied to the substrate either by contact via rollers or heating elements on the side opposite the printed image, or non-contact by means of radiation or hot air flow.

[0031] Drying with heat can make the substrate very dry and brittle, which could have a detrimental effect on further processing (such as cutting, folding, transporting, winding, etc.) of the substrate, as an excessively dry substrate could break and also be transported inaccurately. Therefore, a separate re-moistening device 22 should be arranged along the further transport path of the substrate web 11 (e.g., near the exit of the printing device 10), with which a transparent, aqueous re-moistening fluid (such as water or ink) can preferably be applied to the substrate (top and / or bottom) largely over its entire surface. This fluid is preferably applied without contact by spraying, usually onto the side that is not currently being printed (in the Fig. 2. the underside) applied as evenly as possible.

[0032] All elements of the printing unit 10 are controlled by a control unit 25 (device control or controller). This unit controls the transport of the substrate with all transport elements, such as the feeder 12, the output tray 17, the rotating frame 13, etc. Position data and the transport speed of the substrate are also supplied to the printing unit 14, the dryer 16, the rewetting unit 22, etc., so that all parts of the inkjet printer are synchronized with respect to the longitudinal position of the printed image. The print data itself is fed to the printing unit 10 via a print data stream, processed in a data controller (not shown), and synchronized with the line positions so that the printed image can be printed in the correct position. Therefore, it is very important that the substrate is transported securely and accurately so that the printed image is printed precisely with all colors.This ensures correct registration and precise alignment of individual colors in multicolor printing. In other words, all pixels of the printing colors are printed in their calculated positions.

[0033] In Fig. Figure 3 shows an embodiment with two printing units 10 arranged one behind the other, in which the substrate web 11 is fed by a unwinder 26 to the first printing unit 10, where the front side of the substrate is printed. The substrate web 11 is then turned over by the turning device 18 and fed to the second printing unit 10, so that the reverse side of the substrate can be printed there. The substrate web 11 is then wound onto a rewinder 19 to form a roll 40.

[0034] In this embodiment of Fig. 3 Each printing device 10 is equipped with a re-humidification device 22 for applying a transparent moistening liquid in order to make the substrate, which is too dry and therefore very brittle, “supple” again after the respective dryer 16.

[0035] A rehumidification device 22 can also be located outside the printer 10 near the outlet.

[0036] However, the large-area application of aqueous liquid means that, due to the cut and therefore open fibers, liquid can easily penetrate the substrate at the cut surfaces 46 (between the two cut edges 44) of the substrate web 11, causing the edge of the substrate to swell along the cut edges 44. Without countermeasures, this would lead to swelling / deformation of the substrate in the area of ​​the cut edges 44 (see also Fig. 1b), which would lead to less precise transport and thus less precise positioning of the substrate web 11, resulting in impairments in the printed image, as the individual pixels of the printed image would not necessarily be in the desired position. At the output of the second printing unit 10, deformation of the cut edge 44 would also cause problems for further transport by a subsequent (not shown) post-processing device or – as in Fig. 3 shown - during the winding of the printed material web 11 onto the rewinder 19 to form a roll 40.

[0037] The moisture content of the substrate depends on the one hand on the substrate material, particularly its absorbency. On the other hand, it also depends on the amount of aqueous liquid applied to the substrate per unit area. Moisture always results in at least some of the liquid penetrating (being absorbed) into the substrate web 11. Particularly at the cut edges 46, the liquid can penetrate the substrate to a greater or lesser extent via capillary action. Consequently, the fibers of the substrate can swell in the area of ​​the cut edges 44.

[0038] To minimize the penetration of applied aqueous liquid or ambient moisture into the edge region along the cutting edge 44, one or more application devices 30 are arranged in each printing unit 10 downstream of the dryer 16, but upstream of any rehumidification device 22. Each application device 30 applies a hydrophobic coating material only in a narrow edge strip 32, i.e., in the area along the cutting edge 44 at the outermost edge of the substrate. The coating material is applied to the top and / or bottom surface of the substrate only on this narrow edge strip 32, extending from the cutting edge 44 to a small width 33. The coating material can be applied with a width 33 of approximately 0.5 mm to 10 mm along the edge strip 32. When the substrate web 11 is transported, this results in a narrow edge strip 32 coated with coating material, extending along the cutting edge 44.The width of 33 can depend on the quantity and properties of the application material and the amount of moisture / water expected to subsequently act on the substrate.

[0039] Preferably, only a narrow edge strip 32, approximately 1 mm wide 33, is coated with the coating material. This ensures that no coating material is applied to the printing area containing the printed image, thus preventing any degradation of the image. The coating material makes the substrate water-repellent in this area. If the coating material were applied to a much wider edge strip 32 (e.g., significantly more than 10 to 20 mm), aqueous ink would have difficulty penetrating the substrate, resulting in a considerable deterioration of the printed image. Furthermore, this narrow edge strip 32 requires only a small amount of coating material to prevent or at least significantly reduce unwanted swelling 45 or deformation in the area of ​​the cut edge 44.

[0040] The application device 30 can be designed such that it is arranged above and / or below the substrate web 11 in the area of ​​the cut edge 44 of the substrate in order to apply a narrow edge strip 32 with application material to the top and / or the bottom of the substrate.

[0041] Therefore, at least one single application device 30 or two opposing application devices 30 can be present in the area of ​​each of the cut surfaces 46 of the substrate.

[0042] The application device 30 is also controlled by the control unit 25 so that, at the respective transport speed of the printing material, the desired amount of application material is applied to the edge strip 32 per area.

[0043] The application device 30 is a technical device with which a hydrophobic coating material is applied only to the narrow edge strip 32 along a cut edge 44 of a substrate, in time before the targeted application of an aqueous solution to re-moisten the substrate or before high ambient humidity can penetrate the substrate. Typically, the coating material is applied to the edge strips 32 after the substrate has dried during production or after the substrate has dried / fixed in a printing unit 10 after printing. This is because the substrate is relatively dry after drying, so it should usually be re-moistened afterward to prevent it from cracking in subsequent printing process steps.The applied coating material also provides protection against ambient moisture, which could easily penetrate the substrate through the cut surfaces 46 after drying. Therefore, the application device 30 should not be positioned too far from the dryer 16 so that the cut edges 44 are protected from water / moisture penetration from an early stage. Depending on the properties of the coating material, it may penetrate a warm substrate more quickly, allowing the application device 30 to be positioned closer to the dryer.

[0044] The substrate can be used in this process - as in Fig. Figure 4 shows a web-shaped substrate (substrate web 11) that is unwound from a roll 40 for printing purposes. During the production of the substrate, it is usually manufactured in web form and then wound onto a roll 40 to facilitate transport to its point of use, such as a printing plant.

[0045] The substrate can also be a sheet- or sheet-shaped substrate, as used in the Fig. Figure 5 is shown as an example. Such a printing material is referred to below as a single sheet 47. The single sheet 47 is cut on four sides (cutting edges 44) and thus has four cut surfaces 46, as is the case, for example, in Fig. Figure 1c illustrates this. For this purpose, the web-shaped substrate is cut into individual sheets 47 in such a way as to maximize the usable area and thus produce the maximum number of individual sheets 47 of the desired size. For individual sheets 47, the roll 40 can be cut directly after the substrate has been produced, and stacks of individual sheets 47 are then supplied to the corresponding printing equipment.

[0046] Regardless of its shape, whether web-like or sheet-like, the substrate always has lateral cut surfaces 46 between two cut edges 44. One or more application devices 30 are arranged at the edge, preferably in the area of ​​each cut surface 46. The application devices 30 apply a hydrophobic coating material to a narrow edge strip 32 along the cut edges 44. The coating material penetrates the substrate and thus protects the edge area, including the cut surfaces 46, from the ingress of moisture or water.

[0047] The hydrophobic coating material can be in liquid or solid form. In the case of a solid material, the coating material can be applied to the substrate by contact, either by pressure or friction, along the cut edge 44 on the edge strip 32. To apply a solid coating material, such as wax, the material is preferably heated until it begins to melt. This allows the coating material to be readily absorbed by the substrate. Heating can be achieved actively using a heating element or through friction between the solid wax and the substrate. As the coating material penetrates the substrate, it acquires hydrophobic properties in the edge region, thus becoming water-repellent. Consequently, little or no water or moisture can penetrate the substrate through the cut surface 46.

[0048] To apply the coating material, the coating device 30 can be moved relative to the substrate, or the substrate can be moved relative to a stationary coating device 30. The coating device 30 can also be designed to extend lengthwise along a cutting edge 44, such that it covers the entire length of the substrate (as is exemplified by the right-hand coating device 30 at the right-hand cutting edge 44 in Figure 1). Fig. 5 is shown). The prerequisite for this is that the application material is applied to the edge of the substrate up to the cutting edge 44 only with the very narrow width 33 of the edge strip 32.

[0049] If the substrate is already being moved in the transport direction 23, the coating material can be applied in this direction by a stationary coating device 30. In the transverse direction, the coating device 30 must either move transversely or be long enough transversely to allow the entire length to be coated with coating material at once.

[0050] In papermaking, the application device can be used, for example, at the end of the production process after a newly produced web of substrate has dried, to apply the hydrophobic coating material as a narrow strip (hereinafter referred to as the edge strip) along the cut edges. If a wide web of substrate is later to be cut lengthwise into narrower strips, the new cut edges can also be coated with the coating material in a narrow edge strip at each cut edge.

[0051] The coating material should definitely be applied if the substrate has been significantly heated beforehand (for example, by drying during manufacturing or drying of the printed image during the printing process). This is because significant heating makes the substrate brittle and prone to cracking. Re-moistening with an aqueous solution restores the substrate's suppleness.

[0052] The coating material should be applied to the edge strip 32 of the cut edges 44 with an application device 30 with sufficient time before any re-moistening, so that the coating material has enough time to be absorbed into the substrate. The necessary time depends on the properties of the substrate and the coating material.

[0053] The coating material should be applied soon after drying to prevent or minimize the penetration of ambient moisture into the substrate via the cut surfaces 46. If coating material was additionally applied to the edge strips 32 of the cut edges 44 before printing, care should be taken to ensure that the coating material does not lose its effectiveness or evaporate due to printing or drying caused by high heat.

[0054] If the coating material remains effective for a longer period despite high heat exposure, for example during drying, it can be applied days, weeks, or even longer before the next drying cycle. This protects the substrate from moisture penetration through the cut surfaces 46, even during extended storage. However, during the production of the substrate, a coating material should always be applied to the edges to minimize moisture penetration into the open cut surfaces 46 of a substrate stored on a roll 40, even during subsequent, potentially prolonged storage.

[0055] In Fig. Figure 4 shows a web-shaped substrate (substrate web 11) with an application device 30 arranged at each of its two cut edges 44. With such an application device 30, both the top and bottom surfaces of the substrate can be coated with the coating material in the narrow edge strip 32. Since the substrate is usually transported during printing (as is the case in Fig. 4. In this case, where the substrate web 11 is transported from right to left, as indicated by the arrow for the transport direction 23, the application device 30 itself does not need to be moved. The application device 30 can then be stationary at a predetermined position in the area of ​​the cutting edge 44 (i.e., the longitudinal edge in the direction of transport).

[0056] As a result of the transport of the substrate and the continuous application of the coating material, a narrow edge strip 32 is provided with the coating material (see the two dotted edge strips 32 in Fig. 4) The application material is supplied to the application devices 30 via liquid lines from application material reservoirs (not shown) via liquid supply lines 34.

[0057] Such an arrangement of the application devices 30 also corresponds to the arrangement in the production of the printing material, which is also present there as a web of printing material and is only provided with application material in its narrow edge area with a width 33.

[0058] In Fig. Figure 5 shows a substrate in the form of a single sheet 47, which has four cut edges 44 all around. The aim is that, after drying (e.g., of the printed image), the single sheet 47 is preferably coated with an application material at each of the four cut edges 44 in a narrow strip 32 extending from the respective cut edge 44. The application device 30 is described in Fig. Five different design options are shown schematically and not to scale for better understanding. The right-hand application device 30, located at the right-hand cutting edge 44, is positioned only above the substrate and applies the substrate to a narrow edge strip 32 parallel to the right-hand cutting edge 44 on the front side.

[0059] At the upper cut edge 44, an application device 30 is arranged both above and below the substrate, which applies the application material in strips to the top and / or bottom (or front / back) of the substrate in the respective edge area.

[0060] A dispensing device 30, representing a dispensing roller, is shown schematically at the left cut edge 44. Using a dispensing roller with a predetermined roller width, the liquid dispensing material can be applied in contact to the edge strip 32. For this purpose, the roller can be rolled along the cut edge 44.

[0061] At the lower cutting edge 44, an application device 30 is shown, which encompasses the edge of the substrate at cutting edges 44 and simultaneously applies the coating material to the edge strip 32 without contact both below and above.

[0062] When a liquid coating material is used, the coating devices have 30 liquid feeds 34 (in Fig. 5 (schematically represented by the angled arrows), through which the application material is supplied to the application device 30. Pipes or hoses can be used for this purpose, delivering the application material from a storage container to the respective application device 30.

[0063] For a single sheet 47 (sheet- or sheet-shaped substrate), the application devices 30 can be moved along the cutting edges 44. If the substrate is in the transport direction 23 = longitudinal direction (see arrow direction in Fig.5) If the substrate is moved, it is sufficient if the application devices 30, which apply the coating material to the edge strips 32 of the longitudinal edges (i.e., in the transport direction 23), are stationary. As a result, coating material is applied to the entire length of the edge strips 32 in the transport direction 23 when the substrate is moving / transported.

[0064] For the cutting edges 44 perpendicular to the transport direction 23, the application devices 30 must either be moved themselves or extend along the edge region of the cutting edges 44 over the entire length of the cutting edge 44 perpendicular to the transport direction 23. In the latter case, the application devices 30 can be designed as elongated strips, in which case they can simultaneously apply the material to the entire length of the edge region along the cutting edge 44. Devices for moving the application devices 30 (such as drive motors including gearboxes, etc.) are not shown here for the sake of clarity. Such devices are well known and therefore do not need to be explained in detail here.

[0065] Preferably, the hydrophobic coating material is applied in strips to the edge area along the cut edge 44. The coating material should definitely be applied after drying and certainly before any aqueous (re-)humidifying agent is applied, so that little or no moisture can penetrate the substrate through the cut surface 46. The coating material should also be applied as soon as possible after drying to minimize deformation due to ambient humidity.

[0066] The duration of this process should be long enough to ensure that a high concentration of hydrophobic coating material has already penetrated the substrate at the edges before moisture / water can penetrate the substrate (e.g., through re-wetting). This is because when the substrate at the cut surface 46 is coated with the hydrophobic coating material, it becomes water-repellent there, and the edges swell considerably less.

[0067] Examples of hydrophobic coating materials include organic solutions, oils, or fats (natural fats, mineral oils, synthetic oils, waxes, etc.). Depending on its hydrophobic properties, the coating material can be applied well in advance of rewetting to prevent or at least significantly reduce moisture penetration through the cut surface 46, even during prolonged storage of the substrate.

[0068] However, the optimal time interval between the application of a hydrophobic coating and any subsequent rewetting depends on many factors, such as the viscosity and surface energy of the hydrophobic liquid. It also depends on the surface energy and capillary structure of the substrate, as well as many other chemical and physical parameters / properties of both the coating and the substrate. High ambient humidity can also be a decisive factor in applying the coating to the edges early on. Similarly, the time interval between drying the substrate and applying the hydrophobic coating depends on the ambient humidity and the substrate's capacity to absorb the hydrophobic coating.

[0069] Many different application methods can be used for the application device 30. Both contact and non-contact methods can be employed. Contact application involves applying a more or less solid or liquid material using one or more brushes or rollers that come into direct contact with the substrate. The brushes or rollers can be made of suitable materials and have different surface finishes designed to apply the material as homogeneously and precisely as possible to the edge strip 32 of the substrate. The roller surfaces can also be made of different materials, such as metal, polymers, fur, etc. Soft or textured roller surfaces are also possible. A solid material can also be applied directly to the substrate by contact (e.g., by friction).

[0070] Preferably, non-contact applications are preferred to ensure that the substrate or any printed image already present on it cannot be damaged by contact. In these non-contact applications, a more or less liquid application material with a low viscosity suitable for the substrate is used. The application material can be sprayed onto the substrate using suitable nozzles, atomizers, inkjet printheads, or similar devices, or ejected in another suitable manner. The application material is then applied precisely in a narrowly defined area (narrow edge strip 32) along the edge of each cut edge 44. The nozzles can have protective devices to prevent spraying outside the substrate next to the cut edge 44 or spraying too far towards the center of the substrate.The nozzle openings can be small round openings or narrow slit-shaped openings through which the applied material is sprayed.

[0071] Extraction devices can also be provided to quickly extract any unwanted mist of application material generated by the nozzles, so that the mist does not settle in unwanted places.

[0072] Small spheres or a hydrophobic coating material can also be applied via slot nozzles to the edge strip 32. The nozzles can emit one or more spray cones, spray bands, or spray jets to apply the coating material. Other technical spraying devices are also possible, with which the liquid coating material is applied to the substrate from the cut edge 44 onwards, with a precisely defined width 33 of the edge strip 32.

[0073] When the substrate is moving and the application device 30 is stationary, the amount of substrate ejected or applied per unit area must be coordinated / synchronized with the substrate's transport speed via the control unit 25 to prevent the application of too much or too little substrate. For this purpose, the application device 30 is controlled accordingly by the control unit 25 (the communication links between the control unit 25 and the application device 30, the transport unit, the printing unit 14, or the dryer 16 are not shown in the figures for clarity).

[0074] Only after a hydrophobic precursor has been applied to the substrate in a border strip 32 can an aqueous solution be subsequently applied as re-moistening over the entire surface of the substrate (usually paper in the printing industry) without the substrate swelling at the cut edges 44. Since the border strip 32 is very narrow and the aqueous moistening agent is applied to the entire surface of the substrate, causing only very slight but homogeneous swelling, the substrate's transport behavior under tensile stress is hardly affected. In the area of ​​the border strip 32, the precursor prevents swelling. However, because the precursor is only applied in a narrow border area, this does not affect the transport behavior of the substrate or the printed image in any way.

[0075] Thus, the substrate, which is typically transported by means of rollers, can also be transported with the application material in the edge area exactly and with very high positional accuracy by a printing device 10 or by a post-processing device in order to be printed or processed accordingly.

[0076] Conventionally, an area of ​​approximately 2-10 millimeters at the edge of a substrate remains untreated; that is, this area is not coated or varnished (nor is it printed). Therefore, it is perfectly possible to apply the hydrophobic coating to an edge strip 32 starting at the cut edge 44 without affecting the printed image or the substrate itself. On the contrary, the coating prevents swelling 45 in the edge area, resulting in significantly more precise and reliable / predictable substrate transport.

[0077] This untreated edge area is usually removed (cut away) from the final printed product anyway and therefore represents waste. Therefore, the application of the coating material does not cause any problems.

[0078] Since the edge strip 32 coated with the applied material is very narrow, only a small amount of hydrophobic coating material is required. This results in a significant reduction in resources with regard to sustainability, as the substrate can be used for printing across almost its entire width, and only a very small amount of coating material is used.

[0079] Therefore, any substance is suitable as a coating material, provided it has a low viscosity and is also hydrophobic / water-repellent. For example, vegetable oil, mineral oil, wax, paraffin, synthetic oils such as silicone oil, and similar hydrophobic substances can be used as coating materials. Preferably, the viscosity of the liquid coating material should be a maximum of approximately 350 Pa*s; ideally, the viscosity should be around 100 Pa*s or even less. The required viscosity depends on the absorption properties of the substrate. The coating material should penetrate the substrate quickly enough to rapidly exert its hydrophobic properties across the entire thickness of the substrate.

[0080] The term "coating material" refers to a substance (or material) that possesses at least hydrophobic (water-repellent) properties and low viscosity, enabling it to penetrate the substrate effectively. The coating material can be in a solid or liquid state (or somewhere in between). It is a hydrophobic substance, meaning it is insoluble in water or polar solvents. The term "hydrophobic substances" therefore encompasses nonpolar substances such as fats, waxes, alkanes, and alkenes, which are well-known examples. Generally, hydrophobic substances are characterized by their immiscibility with water.

[0081] Lipids or lipoids are also generally suitable as application materials, as they are water-insoluble (hydrophobic) natural substances that dissolve very well in hydrophobic (or lipophilic) solvents such as chloroform or methanol due to their low polarity.

[0082] Waxes and natural waxes are also well-suited as coating materials and are a mixture of various hydrocarbons that melt at around 40 °C, forming a low-viscosity liquid. Waxes are practically insoluble in water. Their chemical composition and origin can vary considerably, and therefore, depending on their composition, they are well-suited as coating materials because they can penetrate the substrate relatively well in their liquid state.

[0083] The term "printing substrate" refers to the base material onto which printing takes place. The printing substrate can consist of paper, plastics (polymers), or other suitable materials or mixtures. Paper is often mentioned here, as it is the most common printing substrate. Of course, this also includes other types of printing substrate that are not made of paper. Paper is typically made from fibrous materials (such as pulp, wood pulp, and recycled paper pulp), which are primarily derived from wood. In addition to the fibrous material or a mixture of fibrous materials, paper can also contain fillers and other additives.

[0084] The substrate can be in web form (referred to here as substrate web 11) or in sheet or sheet form (referred to here as individual sheet 47). A substrate web 11 is frequently used in high-performance printing equipment. In this case, the substrate is supplied to a printing device 10 as a roll of material (roll 40), fed into the printing device, and transported through the printing device 10 at high speed for printing. The substrate web 11 is then cut according to the desired page formats.

[0085] Individual sheets are often available in DIN A3 or DIN A4 sizes. Preferably, individual sheets are coated with the substrate before printing (i.e., during production). Printed sheets are typically around 1000 x 750 mm. These can also be coated with substrate in the edge areas 32 during production. Substrate webs 11 can be available in a wide range of widths. Typically, these webs can have a width between 200 mm and 1000 mm. Thus, the width 33, at only a few millimeters, is very small compared to the width of the substrate web 11 and is therefore hardly significant, but is, however, immensely important for preventing swelling 45 if a substrate has been applied in the edge area 32.

[0086] In the production of the substrate, it is often manufactured in the form of a web 11, which is then cut into individual webs of the appropriate width. These webs are then wound onto a roll and supplied to a printing device 10, where the substrate is printed. If individual sheets 47 are to be printed, the web 11 is fed to a cutting device after its production, where it is cut into individual sheets 47 of the desired size. If individual sheets 47 or so-called sheets are already manufactured as such (e.g., cardboard, paperboard, etc.), these individual sheets 47 can be supplied to a printing device 10 and printed there.

[0087] The term "application device 30" describes a device with which a hydrophobic coating material is applied to one or more narrow edge strips 32 on the top and / or bottom surface of the substrate. The application device 30 is used when the substrate has been previously heated to a high temperature and has therefore become very dry and brittle. A coating material should always be applied to the substrate before re-moistening. Applying a coating material is also very helpful if the substrate is stored for an extended period after application and is kept in a more or less humid environment. The coating material effectively "seals" the cut surfaces 46 to moisture / water.

[0088] Each application device 30 can be positioned directly after the production of a substrate web 11 at the two cut edges 44 for applying the substrate. If the produced web is cut again into several narrower webs, the new cut edges 44 should also be coated with the substrate.

[0089] Advantageously, at least one application device 30 is provided in the area of ​​each cut surface 46 of a substrate in the edge region of a cut edge 44. Thus, each cut surface 46 of the substrate is separately protected from moisture penetration by the application material.

[0090] Dryers are well known. The substrate web 11 can be dried by supplying energy (hot air, direct heat contact, high-energy radiation, etc.). As a result of drying with heat (also during the production of the substrate), the substrate dries out.

[0091] The term "re-humidification device 22" describes a device with which a transparent, aqueous liquid (humidification fluid) is applied to the entire top and / or bottom surface of the substrate to compensate for an excessively dry substrate. Through re-humidification, moisture penetrates the substrate to a greater or lesser extent across the entire surface.

[0092] The application device 30 according to the invention is arranged in a printing device 10 downstream of the dryer 16 and upstream of any re-moistening device 22. The exact position depends on the properties of the application material, such as its viscosity (i.e., how quickly it penetrates the substrate), or the transport speed of the substrate, which determines the position of the application device 30 downstream of the dryer and upstream of any re-moistening device. This ensures that the application material has already penetrated the substrate well, so that significantly less moisture can subsequently penetrate the cut edges 44 of the substrate and thus prevent deformation.

[0093] However, for the invention, it is irrelevant which printing process is used to apply the printing ink to the substrate. Many printing processes have in common that, after the printing ink is applied, it is usually dried by heat and thus fixed to the substrate. This undesirably leads to the substrate becoming very dry and brittle.

[0094] In papermaking or the production of the substrate, an application device 30 can also be used after a substrate web 11 has dried. This device applies the coating material to a narrow edge strip 32 along the edges and cut edges 44 of the freshly produced substrate. The coating material should be applied as soon as possible after drying. Therefore, the application device 30 can also be located in the production plant shortly after the dryer 16. Of course, the application device 30 can also be located shortly before the substrate is wound onto a roll. The application device 30 is controlled by a control unit 25, depending on the transport speed during the production of the substrate, such that the desired or required amount of coating material is applied to the edge strip 32.

[0095] This results in a substrate that can be stored for extended periods as roll material or as a stack of sheets without moisture causing significant deformation of the edges at the cut edges 44. Furthermore, this results in a substrate that exhibits uniform tensile stress characteristics across its entire width during transport of the web 11, thus enabling precise and well-defined transport and positioning for printing or winding. Reference symbol list 10 Printing device 11 Printing material web 12 Move-in 13 rotating frames 14 printing units 15 Printhead 16 dryers 17 deduction 18 Turning device 19 winders 22 Rehumidification device 23 Direction of transport (arrow) 25 Control unit 26 liquidators 30 Ordering device 32 edge strips 33 Width of the edge strip 34 Liquid supply 40 rolls 44 Cutting edge 45 swelling 46 Cut surface 47 single sheets C Cyan K Black M Magenta Y Yellow

Claims

[1] Application device (30) for applying a hydrophobic coating material to a substrate, which is arranged at the edge of the substrate in the area of ​​a cutting edge (44), wherein the application device (30) is designed to apply a hydrophobic coating material only to a narrow edge strip (32) with a width (33) of about 0.5 mm to 5 mm from the cutting edge (44) on the substrate. [2] Application device (30) according to claim 1, characterized by , that the width (33) of the edge strip (32) onto which the application material is applied is approximately 1 mm. [3] Ordering device (30) according to any of the preceding claims, characterized by , that it is arranged above and / or below the substrate in the area of ​​the cutting edge (44) of the substrate in order to apply the coating material to the top and / or bottom of the substrate. [4] Application device (30) according to any of the preceding claims, characterized by , that it is designed in such a way that the hydrophobic coating material is applied to the substrate in contact as a solid coating material or as a liquid coating material. [5] Ordering device (30) according to any one of claims 1 to 3, characterized by , that it is designed in such a way that the hydrophobic coating material is applied to the substrate as a liquid coating material without contact. [6] Printing device (10) for printing on a substrate (11, 47) comprising: - a transport device (12, 13, 17) for transporting the printing material (11, 47) through the printing device (10), - a printing unit (14) for printing the substrate (11, 47) with printing inks according to available print data, - a dryer (16) for drying the printing inks by means of heat, - an application device (30) according to claim 1, which is arranged in the transport direction (23) after the dryer (16) in the area of ​​a cut edge (44) of the substrate (11, 47), wherein the application device (30) applies a hydrophobic coating material with a width (33) of an edge strip (32) of about 0.5 mm to 5 mm from the cut edge (44) onto the top and / or bottom of the substrate (11, 47), and - a control unit (25) connected to the transport device (12, 13, 17), the printing unit (14), the dryer (16) and the application device (30) to control the transport, printing, drying and application of the coating material depending on a transport speed. [7] Pressure device (10) according to claim 6, characterized by, that the application device (30) is arranged near the exit of the substrate (11, 47) from the printing device (10), but after the dryer (16) in order to apply the application material to the slightly cooled substrate (11, 47). [8] Printing device (10) according to claim 6, characterized by , that the application device (30) is arranged above and / or below the substrate (11, 47) in the edge area at a cut edge (44) such that it applies the hydrophobic application material to the edge strip (32) with a width (33) of about 1 mm on the top and / or bottom of the substrate (11, 47). [9] Pressure device (10) according to claim 6, characterized by , that at least one application device (30) is provided for each cutting surface (46) in the edge area of ​​a cutting edge (44) of the substrate (11).

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