Printing device

Abstract

The invention relates to a printing device (1) comprising: - at least one inking unit (2) for supplying an ink (3), to which an intermediate element (4) is connected, wherein the intermediate element (4) is supplied with the ink (3) by its associated inking unit (2); - at least one printing plate (5) with image areas arranged therein, which is configured to receive the ink (3) directly or indirectly from the intermediate element (4); - and at least one doctor blade (7) configured to wipe off excess supplied ink (3) from the printing plate (5) and / or from the intermediate element (4), wherein the intermediate element (4) has recesses in at least one area associated with the image areas in an ink-receiving surface, the recesses preferably being arranged in a grid pattern.

Description

[0001] The invention relates to a printing device comprising at least one inking unit for providing an ink, downstream of which is arranged at least one intermediate element that is supplied with the ink from its associated inking unit. Furthermore, the device comprises at least one printing plate with image areas arranged therein, which is designed to receive the ink from the intermediate element, and at least one doctor blade designed to wipe off excess applied ink from the printing plate.

[0002] The elements of the printing device described above relate specifically to the field of intaglio printing for sheet-fed or web-fed printing of securities, especially banknotes. Intaglio printing inherently offers protection against counterfeiting, as its effort and associated costs represent a first barrier to reworking securities. Furthermore, securities are equipped with certain security features. For example, different colors or highly specialized inks that are difficult to obtain on the market are incorporated to further complicate reworking. However, the production of securities is not limited to the intaglio printing process. Using the example of a euro banknote, the offset printing process is used in combination with the intaglio printing process for its background and main motifs. Various holograms and numbers with color changes in the banknotes are produced using screen printing.

[0003] A conventional intaglio printing machine for producing security documents according to the prior art is disclosed in DE 698 01 184 T2. This intaglio printing machine has a plate cylinder, around the circumference of which at least one printing plate, preferably several printing plates regularly distributed around its circumference, is / are clamped. An ink collection cylinder is impinged with ink by ink selection rollers arranged side by side around a portion of the circumference of the ink collection cylinder and having reliefs corresponding to the inked zones to be printed in different colors and in contact with the circumference of the ink collection cylinder. The ink collection cylinder transfers the inks applied to its surface to the printing plate(s) of the plate cylinder.On the circumference of the plate cylinder, a wiping cylinder is provided as a doctor blade, which is located behind the ink collecting cylinder, as seen in the direction of rotation of the plate cylinder, and removes or removes ink from the surface of the engraved printing plates outside the engraving pits.

[0004] A major problem with this well-known intaglio printing press, and other similar printing machines, is that a significant amount of ink is lost during the doctoring process. This is particularly disadvantageous in the field of securities production, since highly specialized and correspondingly expensive inks are sometimes used in the production of these securities, and the printed motifs are sometimes only individual lines and dots, which cause particularly high ink loss.

[0005] Another generic printing device is disclosed in US 5282417 A. The printing device shown comprises three assemblies I, II, III. Assembly II comprises an inking unit and a stencil roller, while assembly I comprises a printing cylinder, a plate cylinder, and a wiping cylinder serving as a doctor blade. In between is assembly III, which has an ink collecting cylinder and can be removed if necessary, so that assembly I connects directly to assembly II. The stencil rollers have a relief structure that is coordinated with the areas of the gravure plates of the plate cylinder to be printed. The relief structure, onto which ink is applied, is a zone that is raised compared to the surrounding areas of the stencil rollers. The relief structure is formed by cutting away the areas of the stencil roller material surrounding the relief structure, starting from the outline of the relief structure.

[0006] With wet offset printing, which is also used to produce certain sections of securities, there is the problem that a lot of ink and sheets are wasted when adjusting the press until the ratio of ink to water produces usable print results. Furthermore, the print resolution is limited, which is why this offset printing process is used almost exclusively for printing flat background patterns.

[0007] It is therefore the object of the present invention to provide a printing device which overcomes or at least mitigates the problems of the prior art explained above, and in particular reduces the excess ink consumption in intaglio printing machines and reduces the waste in the setting of wet offset printing machines.

[0008] According to the invention, the present object is achieved by providing a device having the features of claim 1. Advantageous embodiments of the invention are set forth in the dependent claims, the description, and the drawings.

[0009] The printing device according to the invention comprises at least one inking unit for providing an ink, which is followed by at least one intermediate element, the intermediate element being supplied with the ink by the inking unit; at least one printing plate with image areas arranged therein, which is designed to receive the ink from the intermediate element; and at least one doctor blade designed to wipe off excess applied ink from the printing plate. The intermediate element has depressions in an ink-receiving ink surface in at least one region associated with the image areas, the depressions preferably being arranged in a raster pattern.

[0010] The printing plate can be mounted on a plate cylinder. Multiple printing plates can also be arranged evenly distributed around the circumference of a plate cylinder. The intermediate elements are preferably designed as stencil cylinders. The doctor blade is preferably designed as a wiping cylinder.

[0011] The invention offers the advantage of these depressions in the intermediate elements that the depressions absorb more ink than the surrounding ink surface without depressions. When the ink is transferred from the intermediate element to the printing plate, the ink from the depressions is transferred to the area of ​​the respective image areas on the printing plate. However, ink applied to the surrounding ink surface without depressions is also transferred to the printing plate. To ensure that the printing plate only has ink in the image areas, the doctor blade is provided to wipe off the excess ink in order to doctor the non-image areas, i.e. the non-depressed areas, free of ink. The ink that is wiped off in this way cannot usually be returned to the inking unit, which results in ink loss.

[0012] In existing processes, the intermediate element without indentations must absorb sufficient ink to fill all image areas, regardless of how deep or high these image areas are. If the printing plate has a particularly deep image area in only a small area, the entire printing plate must be coated with the same amount of ink, tailored to this single image area, which results in a particularly large amount of ink being wiped off non-image areas during doctoring.

[0013] By providing the inventive recesses in the intermediate elements, more ink can be absorbed for these image areas in precisely these recesses, which correspond to image areas on the printing plate. This eliminates the need to coat the entire intermediate element with more ink, as is necessary with known devices. Reducing ink loss can thus be achieved by requiring less ink to be wiped off the printing plate with the doctor blade, since the recesses of the intermediate element transfer the additional ink required for the deeper image areas.

[0014] The image quality remains unaffected, whereby according to the invention a printing device is obtained which can print without loss of quality but with lower ink consumption compared to a device without depressions in ink selection rollers.

[0015] With known ink selection rollers without indentations, i.e., with a smooth surface or raised areas, up to 70% of the transferred ink is wiped off by the doctor blade and thus lost. The invention thus represents a significant economic and resource-saving advantage, especially for large print runs, such as banknotes.

[0016] The printing plate can be supplied with ink by the intermediate elements indirectly by interposing an ink collecting cylinder between the at least one intermediate element and the printing plate, which cylinder is supplied with ink by the intermediate element, the ink collecting cylinder supplying the printing plate with the ink picked up by the intermediate element.

[0017] Preferably, the surface of the ink collecting cylinder can be covered with a rubber blanket which has depressions arranged in a grid pattern in an ink-receiving ink surface in at least one area assigned to the image areas of the printing plate. This embodiment with the depressions provided in the rubber blanket of the ink collecting cylinder offers the same advantages as those described above with regard to the depressions in the intermediate elements. The depressions in the rubber blanket of the ink collecting cylinder can be formed in addition to the depressions in the intermediate element. In another embodiment of the device, the depressions in the ink surface of the rubber blanket assigned to the image areas of the printing plate are provided as an alternative to the depressions in the at least one intermediate element. The advantage of reduced ink consumption is thereby also retained.

[0018] The printing plate can be exposed to ink directly by the intermediate elements, in that at least one intermediate element is in direct contact with the printing plate and exposes the printing plate to ink.

[0019] In one embodiment of the invention, at least one of the recesses between a low point and the paint surface is provided with a single-stage or multi-stage chamfer and / or a rounded edge. This provides the advantage of reducing paint adhesion in the recesses.

[0020] In a further embodiment, the depth of the at least one depression in the paint surface can be dependent on the width of the depression. Preferably, the depth is: for a width of 20 µm to 620 µm the depth is 21 µm to 30 µm, for a width of 620 µm to 640 µm the depth is 30 µm to 50 µm, for a width of 640 µm to 660 µm the depth is 50 µm to 65 µm, for a width of 660 µm to 670 µm the depth is 65 µm to 75 µm, and for a width of 670 µm to 680 µm the depth is more than 75 µm.

[0021] This provides the advantage that the ink can be completely removed from the depression(s), reducing the risk of ink sticking to the depression.

[0022] Preferably, the depressions in the ink surface of the preferred screen pattern can be surrounded by a border. This provides the advantage of separating several adjacent areas with different screen patterns and / or depressions from one another. This can improve the quality of the printed motif.

[0023] Conventional ink selection rollers or stencil cylinders are made of a polymer. However, this material has proven unsuitable for the present invention, primarily because the indentations cannot be produced with the required precision, especially when formed using a laser.

[0024] Instead, the invention proposes that at least the surface of the intermediate element and / or, if applicable, the rubber blanket of the ink collecting cylinder be made of an elastomer or rubber. This provides the advantage of enabling precise ink transfer to the printing plate or to another downstream element.

[0025] In a preferred embodiment of the invention, at least the surface of the intermediate element and / or optionally of the rubber blanket of the ink collecting cylinder is provided from ethylene propylene diene (monomer) rubber (EPDM) or from acrylonitrile butadiene rubber, because this allows precisely dimensioned depressions to be produced which retain their shape even during prolonged use.

[0026] It has also been shown that it is particularly advantageous if the surface of the intermediate element and / or, if applicable, the rubber blanket of the ink collecting cylinder is colored black, because this provides significantly more accurate results when the depressions are formed by a laser.

[0027] In a further embodiment, the depressions in the ink surface of the intermediate element and / or, if applicable, the rubber blanket of the ink collecting cylinder can be formed by lasering and / or plasma bombardment of the intermediate element. Particularly when the intermediate element is made of the aforementioned elastomers or rubber, lasering is expedient for forming defined and repeatable depressions.

[0028] Preferably, the printing plate can be a gravure printing plate, with the image areas of the plate positioned deeper than the non-image areas. The deeper image areas prevent significant ink loss when the plate is doctored off.

[0029] In a particular embodiment of the gravure printing process, the image areas can have an engraving depth and an engraving width, wherein the depth of the at least one depression depends on the engraving depth and the engraving width. Preferably, the depth is: with an engraving depth of 21 µm to 30 µm and preferably an engraving width of 610 µm to 630 µm, the depth is 10 µm to 40 µm; with an engraving depth of greater than 30 µm and less than or equal to 50 µm and preferably an engraving width of greater than 630 µm and less than or equal to 650 µm, the depth is 40 µm to 60 µm; with an engraving depth of greater than 50 µm and less than or equal to 65 µm and preferably an engraving width of greater than 650 µm and less than or equal to 665 µm, the depth is 60 µm to 75 µm; For an engraving depth greater than 65 µm and less than or equal to 74 µm and preferably an engraving width greater than 665 µm and less than or equal to 675 µm, the depth is 75 µm to 90 µm; and for an engraving depth greater than 74 µm and preferably an engraving width greater than 675 µm and less than or equal to 685 µm, the depth is 90 µm to 110 µm.

[0030] The interaction of these values ​​allows particularly defined halftone values ​​to be created on a print motif, whereby the adhesion of ink in the depressions and the engraving or in the image areas of the printing plate of the gravure printing process is minimized.

[0031] Furthermore, it is preferred that the width of the at least one recess is between 500 µm and 1100 µm.

[0032] In a further embodiment, the intermediate element can be that of a flexographic printing process, wherein the intermediate element is positioned upstream of an anilox roller, and wherein the doctor blade wipes off excess applied ink from the intermediate element and / or from the anilox roller. This in turn reduces ink loss. However, the anilox roller should not be confused with the printing plate of a gravure printing process. Although the anilox roller also has so-called cells, these cells do not form image areas like the printing plate of a gravure printing process. The anilox roller of the flexographic printing process is a so-called upstream roller, which indirectly transfers the ink from an inking unit to a printing plate. In the context of this document, the printing plate can also be understood as a printing plate. In the context of the flexographic printing process, the printing plate is usually made of rubber and can also be called a flexographic printing plate, which defines this indirect printing process.

[0033] In a further embodiment of the printing device according to the invention, the intermediate element is that of an offset printing process, and the printing plate is a letterpress printing plate. This embodiment replaces a conventional offset printing process using mixtures of ink and water. The disadvantage of the conventional offset printing process is that a lot of waste is initially produced when setting up the machine until a usable mixture of ink and water is found. The use of letterpress printing plates also achieves a significantly higher print resolution, which enables the printing of finer, tighter, and more isolated motifs, especially line patterns, than before.

[0034] Advantageous and non-limiting embodiments of the invention are explained in more detail below with reference to the drawings. Fig. 1a shows a device according to the invention for reducing color loss. Fig. 1b shows a section of the device of the Fig. 1 . Fig. 2a shows the step of doctoring from the Fig. 1 . Fig. 2b shows a further section of a device according to the invention similar to the Fig. 1 . Fig. 2c shows an enlarged section of one of the recesses from Fig. 2 . Fig. 3a shows a section of the Fig. 3b , showing a top view of a regular grid pattern with depressions. Fig. 3b shows a print motif. Fig. 4a bis Fig. 4e show single-stage and multi-stage chamfered embodiments of recesses according to the invention. Fig. 5a bis Fig. 5e show embodiments of recesses with roundings according to the invention. Fig. 6a shows a surface of an ink collecting cylinder with rubber blanket. Fig. 6b shows an embodiment of the printing device according to the invention with alternative recesses. Fig. 7a shows a grid pattern with irregularly arranged depressions according to an embodiment of the invention. Fig. 7b shows a grid pattern with irregularly arranged depressions according to another embodiment of the invention.

[0035] Fig. 1a shows a printing device 1 according to the invention for carrying out a gravure printing process T with two inking units 2 for providing an ink 3 and an intermediate element arranged downstream of each of the two inking units 2, wherein each intermediate element 4 is supplied with the ink 3 from its associated inking unit 2. Inking unit 2 is understood to be a collection of components for the automatic provision of ink for transfer to the printing plate 5. Such an inking unit 2 can comprise several rollers, an immersion tank with ink 3, or ink pumps, and other ink dosing devices. Inking unit 2 can also be understood to mean inkjet printers. The number of inking units 2 in the device is not limited; rather, one is provided for each of the colors to be printed in inking unit 2.

[0036] Furthermore, the device 1 comprises a printing plate 5 with image areas 6 arranged therein, which is designed to receive the ink 3 from the intermediate element 4. The printing plate 5 is arranged on the surface of a plate cylinder, whereby several printing plates 5 can also be arranged regularly around the circumference of the plate cylinder. The intermediate elements 4 are designed as stencil cylinders. The intermediate elements 4 have depressions 9 arranged in a grid pattern 10 in an ink surface 8 receiving the ink 3 in at least one area B, which is assigned to the image areas 6 of the printing plate 5 (see Fig. 1b In this embodiment of the printing device 1, the intermediate elements 4 do not transfer the inks 3 directly to the printing plate 5, but rather an ink collecting cylinder OL is interposed between the intermediate element 4 and the printing plate 5. In this embodiment, the ink collecting cylinder OL is an Orloff cylinder that transfers several different inks 3 simultaneously to the printing plate 5. However, the ink collecting cylinder OL is not absolutely necessary to achieve the desired reduction in ink loss.

[0037] The ink collecting cylinder OL can be covered on its surface with a rubber blanket GTU, which - analogous to the intermediate elements 4 - has depressions 9' in an ink surface 8' receiving the ink 3 in at least one area B', which is assigned to the image areas 6 of the printing plate 5, which depressions are arranged in a grid pattern 10'. A surface of such an ink collecting cylinder OL is Fig. 6a shown schematically. The rubber blanket GTU can have incompressible and compressible layers. It should be noted that the explanations of the recesses 9 in the present description and the drawings, in particular the Figuren 3a, 3b , 4a bis 4e , 5a bis 5e , are also to be applied mutatis mutandis to the recesses 9'. This also applies to the dimensions and shapes of the recesses 9, 9'.

[0038] The device 1 further comprises a symbolically represented doctor blade 7, which is designed to wipe off excess applied ink 3 from the printing plate 5.

[0039] The doctor blade 7 is arranged on the circumference of the printing plate 5, which in this illustration is arranged on the circumference of a plate cylinder of a gravure printing process T.

[0040] When performing a gravure printing process T, the doctor blade 7 is preferably designed as a wiping cylinder. In other embodiments, the doctor blade 7 can be a scraper, a squeegee, or a knife-like steel belt. The task of the doctor blade 7 is to wipe off the excess ink 3 from the non-image areas NBS of the printing plate 5, so that only the so-called cells, or the engravings of the printing plate 5, are filled with the ink 3 that is actually intended for the print motif DM.

[0041] Fig. 6b shows an embodiment of the device 1 which is similar to that of Fig. 1a with the difference that the intermediate elements 4 provided with the described depressions 8 directly contact the printing plate 5 and thus directly apply ink 3. In Fig. 6b are the device 1 of Fig. 1a corresponding elements are designated by the same reference numerals and their functions are the same or similar to those of the corresponding elements of Fig. 1a To avoid repetition, reference is made to the above description of the device 1 of Fig. 1 referred to.

[0042] The printing device 1 of the Fig. 1a is associated with the printing principle, in which one cylinder is pressed against another cylinder. However, device 1 is not limited to this printing principle, but can also be used for surface-to-surface printing, so-called sheet printing, or surface-to-cylinder printing.

[0043] Particularly in the cylinder against cylinder printing principle, the doctor blade 7 is designed as a wiping cylinder which, viewed in the direction of rotation of the printing plate 5 clamped onto the plate cylinder, is located after the ink collecting cylinder OL and cleans the surface of the engraved printing plate 5 outside the image areas 6 of ink 3 and compresses the ink 3 in the image areas 6.

[0044] After the printing plate 5 has passed the squeegee 7, a print object DO can be pressed against the printing plate 5. The print object DO can be understood as various printing materials, such as paper, cardboard, plastic films, metal sheets, glass, ceramics, or skins. In special applications, three-dimensional objects such as cups or bags can also be printed.

[0045] In Fig. 1a the printing plate 5 is pressed against the printing object DO by means of an impression cylinder G. After this step, the printing object DO has the color 3 of the image areas 6 and thus the desired printing motif DM.

[0046] As mentioned, the device of Fig. 1 also have far more color works 2 than shown.

[0047] The device 1 can also be designed such that a second printing plate 5 is clamped onto the counter cylinder G, so that two print motifs DM can be applied to both sides of the printed object DO. The device 1 can be used in the context of various printing processes. It should be emphasized that a reduction in ink loss is always achieved when ink 3 can no longer be returned to one of the inking units 2 during doctoring by a doctor blade 7.

[0048] In the Fig. 1b is a section of the device 1 of the Fig. 1a This shows the step in which the ink 3 has already been transferred from the intermediate element 4 to the ink collecting cylinder OL, ie the ink 3, which was previously held in the depressions 9, has already been transferred from the depressions 9.

[0049] The ink 3 is applied thicker in an area B, which is connected to the later following image areas 6, than on the non-image areas NBS. It should be noted that only through the depressions 9 can the ink 3 be particularly thinly formed over the non-image areas NBS, whereby the image areas 6 are nevertheless completely filled with ink 3. The ink 3 over the non-image areas NBS is doctored off in a further step. It is no longer returned to the inking units 2, because chemical processes may have already taken place in the ink 3 due to air contact, light contact, and / or heat input, and because in the case of the Fig. 1a In the illustrated gravure printing process T with two different inking units 2, the doctored-off ink 3 cannot be returned simply because mixed or superimposed layers of the different inks 3 of the respective inking units 2 were applied to the non-image areas NBS.

[0050] Fig. 2a shows the step of doctoring the Fig. 1a . One of the non-image areas NBS has already been freed of ink 3. The non-recessed areas are thus doctored off without ink, leaving ink 3 in the recessed areas of image area 6. It can be seen that image areas 6 of printing plate 5 are deeper than non-image areas NBS. Image areas 6 are created by engraving, etching, or a laser.

[0051] In a high-pressure printing process not shown, the non-image areas NBS would be located lower than the image areas 6.

[0052] In the Fig. 2b is another embodiment, similar to the device 1 from Fig. 1a shown. The ink 3 has not yet been transferred to a directly downstream printing plate 5, thus eliminating the need for an ink collection cylinder OL. Instead, the ink 3 is transferred directly to the printing plate 5. However, it is also conceivable that an ink collection cylinder OL is provided that has indentations whose shape is similar to the image areas 6 of a printing plate 5.

[0053] The recesses 9 are completely filled with color 3, and the color surface 8 is also covered with color 3. However, color 3 can also be present only in the recesses 9.

[0054] An enlarged section of one of the recesses 9 is shown in Fig. 2c shown. This depression 9 has a spline-like symmetrical rounding 13. It should be noted that only a cross-section in the greatest extent of the depression 9 is shown. The depression 9, or all depressions 9 of a grid pattern 10 can be rotationally symmetrical. This includes polygonal pyramid-like depressions 9, but also n-sided prismatic depressions 9. Dome-shaped, in particular hemispherical depressions 9 can also be provided. It is also conceivable that differently shaped depressions 9 are formed, even directly next to one another, with different widths 15, depths 14, and also distortions. Distortion can be understood to mean that in a plan view of an outline of a depression 9, for example a parallelogram can be seen.

[0055] From the Fig. 2b It can also be seen that similar depressions 9 are divided into an area B1 and an area B2, which coincide with the respective image areas 6 during the transfer of the ink 3. It should be emphasized here that several less deep depressions 9 do not have to lie exclusively over an image area 6 with a low engraving depth GT, as is the case in area B1. It can be expedient to also provide depressions 9 over non-image areas NBS. This can have the advantage that, for a subsequent doctoring step, ink 3 can be pushed from a non-image area onto image areas 6 by pushing on ink 3 in order to completely fill all image areas 6. This can be necessary because, during doctoring, irregularities in the ink removal repeatedly occur due to deformation of the doctor blade 7 or the printing plate 5. Ink splashes can also occur if the doctor blade 7 hits a high point orNon-image area NBS, or color thickening, thereby providing a suitable replacement for this rejected color 3.

[0056] In the area B2 shown, there are deeper image areas 6 than in the area B1, whereby the depressions 9 also have a greater depth.

[0057] In the Fig. 2b In addition, three areas are marked with dashed lines in which edges 16 are formed, forming a thickening between the two regions B1, B2. The edges 16 can, as shown, come into planar contact with the underlying non-image areas NBS, whereby the depressions 9 themselves can also be recessed from the edge 16.

[0058] Fig. 3a shows a plan view of a regular grid pattern 10 with depressions 9. The grid pattern 10 shown is a section of the Fig. 3b , in which an intermediate element 4 with two areas B1, B2 is shown in a top view. The raster pattern 10 is part of the print motif DM, which depicts the number one next to the number zero. Each of the numbers is formed in a separate area B1, B2 with different types of recesses 9 to create a different structure, coloring, color effect, and / or embossing in the print object DO.

[0059] The intermediate element 4 is provided as a stencil or stencil cylinder. This means that the print motif DM is raised above a surface of the remaining stencil, so that only ink 3 in the raised ink surface 8 is absorbed by a respective inking unit 2. The ink surface 8 is spaced apart from the print motif DM and rounded relative to it. This spacing is also called an overlap and can be approximately 10% to 20% larger than the envelope of the outermost contour of the respective print motif DM of the respective stencil.

[0060] The colour surface 8 can also have a continuous transition to the underlying surface or stencil surface, from which the colour surface 8 protrudes, in the form of a rounding.

[0061] The Fig. 3a The Cartesian grid pattern 10 shown has depressions 9 with a regular width 15. Thus, the depressions 9 each have a width 15 and are spaced apart by a width 15. The surrounding border 16 also has an extension of the order of magnitude of the width 15.

[0062] All described recesses 9 can have the following illustrated embodiments of the Fig. 4a bis Fig. 4e and Fig. 5a bis Fig. 5e , as well as variations thereof. These depressions 9 are each shown in a cross-sectional view, with their low points 11 lying in an axis of symmetry. The depth 14 is determined by a normal between the low point 11 and the color surface 8. The width 15 of the respective depression 9 lies, seen in cross-section, between two points at which the chamfer 12 or rounding 13 begins. This applies to the Fig. 4a bis Fig. 5a . The width 15 of the Fig. 5b bis Fig. 5e lies between two changing points to a smaller curvature in the course of the rounding 13. The color surface 18 can be formed only in a point-like manner between two adjacent depressions 9.

[0063] The depth 14 and width 15 of the depressions 9 can also depend on the respective engraving depth GT of the image areas 6 in the printing plate 5, particularly when true halftones are to be represented on a print motif DM. True halftones are the so-called intermediate tones between black and white. In the gravure printing process T, true halftones can be achieved by the area- and depth-variable printing plate 5. Other printing processes, such as letterpress printing, can only approximate halftones by rasterizing full-color pixels using a printing screen.

[0064] In the Fig. 4a and Fig. 5a The depth 14 of the depression 9 is 30 µm, with the width 15 being 600 µm. The engraving in the printing plate 5 can, for example, have an engraving depth GT of 21 µm to 30 µm with an engraving width GW of 620 µm, whereby a maximally saturated black can be achieved with a black color 3 in the print motif DM. The engraving depth GT and engraving width GW are shown as examples in Fig. 2c shown. It should be noted that the engraving or image areas 6 may also have rounded or chamfered edges. The image areas 6 may also be multiply serrated or hemispherical.

[0065] In the Fig. 4b and Fig. 5b The depth 14 of the recess 9 is 50 µm, with the width being 600 µm. The engraving in the printing plate 5 can, for example, have an engraving depth GT of 30 µm to 50 µm with an engraving width GW of 640 µm, whereby a less saturated black can be obtained in the print motif DM.

[0066] In the Fig. 4c and Fig. 5c the depth 14 of the depression 9 is 70 µm, where Fig. 4c the width is 600 µm and in Fig. 5c the width is 80 µm. The engraving in the printing plate 5 can, for example, have an engraving depth GT of 50 µm to 65 µm with an engraving width GW of 660 µm, whereby a gray midway between white and black can be obtained in the print motif DM.

[0067] In the Fig. 4d and Fig. 5d the depth 14 of the depression 9 is 80 µm, where Fig. 4d the width is 600 µm and in Fig. 5c the width is 800 µm. The engraving in the printing plate 5 can, for example, have an engraving depth GT of 65 µm to 75 µm with an engraving width GW of 670 µm, whereby a less saturated gray, intermediate between white and black, can be obtained in the print motif DM.

[0068] In the Fig. 4e and Fig. 5e the depth 14 of the depression 9 is 100 µm, where Fig. 4d the width is 600 µm and in Fig. 5c the width is 1000 µm. The engraving in printing plate 5 can, for example, have an engraving depth GT of over 75 µm with an engraving width GW of 680 µm, whereby a minimally saturated black can be obtained in the print motif DM.

[0069] The aforementioned depths 14, widths 15, engraving depths GT, and engraving widths GW are each subject to tolerances, in particular with a ± 15% deviation, particularly preferably with a ± 5% deviation. If an engraving depth GT is less than 21 µm, no recesses 9 can be formed.

[0070] The recesses 9 of the Fig. 4a, Fig. 4b and the Fig. 4c have a single-stage chamfer 12. In contrast, the recesses 9 of the Fig. 4d and the Fig. 4e a multi-stage or two-stage chamfer 12. The Fig. 5a bis Fig. 5e each have a rounding to 13.

[0071] It is also conceivable to form a hybrid of rounded portions 13 and depressions 12 together in a depression 9. It is also conceivable for the depressions 9 to have undercuts below the colored surface 8. It is likewise conceivable for elements to protrude from the surface of the depressions 9 in the direction of the colored surface 8, such as rods, pegs, hemispheres, or the like. The depressions 9 may also not be rotationally symmetrical. For example, if the depression 9 is cuboid-shaped, chamfers 12 may be formed on two opposite edges and rounded portions 13 on the other two opposite edges.

[0072] Fig. 7a shows a grid pattern 10 having rectangular depressions 9 with irregular dimensions. Some of the depressions 9 in the illustrated grid pattern 10 have, for example, a first width 15a, wherein a width in Fig. 7a describes a horizontal extension of a depression. Other depressions have a second width 15b, which is smaller than the first width 15a. It is possible for further depressions to have a third width and possibly further widths. Some of the depressions 9 have, for example, a first length 15c in the illustrated grid pattern 10, wherein a length in Fig. 7a describes a vertical extension of a depression. Other depressions have a second length 15d that is smaller than the first length 15c. It is possible for further depressions to have a third length and possibly further lengths. It is also possible for the depressions to be rotated, whereby the angle of rotation of an individual depression 9 is independent of the angle of rotation of another depression. Likewise, the edges 16 of different depressions 9 can be dimensioned differently.

[0073] Fig. 7b shows a grid pattern 10 having round depressions 9 with irregular dimensions. Some of the depressions 9 in the illustrated grid pattern 10 have, for example, a first width 15a, wherein a width in Fig. 7b describes a horizontal extension of a depression. Other depressions have a second width 15b, which is smaller than the first width 15a. It is possible for further depressions to have a third width and possibly further widths. Some of the depressions 9 have, for example, a first length 15c in the illustrated grid pattern 10, wherein a length in Fig. 7bdescribes a vertical extension of a depression. Other depressions have a second length 15d that is smaller than the first length 15c. It is possible for further depressions to have a third length and possibly further lengths. It is also possible for the depressions to be rotated, whereby the angle of rotation of an individual depression 9 is independent of the angle of rotation of another depression. Likewise, the edges 16 of different depressions 9 can be dimensioned differently.

[0074] It should be noted here that the recesses can be not only rectangular and / or round, but can have any geometric shape, including but not limited to triangles, squares, pentagons, hexagons (and other regular and irregular polygons), circles, ellipses, as well as combinations of the aforementioned shapes, etc. In the case of a polygon, the corners of the polygon can have rounded edges.

Claims

1. Printing device (1), comprising: - at least one inking unit (2) for providing an ink (3), which is followed by at least one intermediate element (4), wherein the intermediate element (4) is supplied with the ink (3) by the inking unit (2); - at least one printing plate (5) with image areas (6) arranged therein, which is designed to receive the ink (3) directly or indirectly from the intermediate element (4); - and at least one doctor blade (7) designed to wipe off excess applied ink (3) from the printing plate (5); characterized in that the intermediate element (4) has depressions (9) in a color surface (8) receiving the color (3) in at least one area (B, B1, B2) which is assigned to the image locations (6), wherein the depressions (9) are preferably arranged in a grid pattern (10).

2. Device (1) according to claim 1, characterized in thatan ink collecting cylinder (OL) is interposed between the at least one intermediate element (4) and the printing plate (5), which cylinder is supplied with ink by the intermediate element (4), wherein the ink collecting cylinder (OL) supplies the printing plate (5) with the ink picked up by the intermediate element (4).

3. Device (1) according to claim 2, characterized in that the surface of the ink collecting cylinder (OL) can be covered with a rubber blanket (GTU) which has depressions (9') arranged in a raster pattern (10') in an ink surface (8') receiving the ink (3) in at least one area (B') which is assigned to the image areas (6) of the printing plate (5).

4. Device (1) according to claim 3, characterized in that the depressions (9') in the ink surface (8') of the rubber blanket (GTU) assigned to the image areas (6) of the printing plate (5) are provided as an alternative to the depressions (9) in the at least one intermediate element (4).

5. Device (1) according to claim 1, characterized in that the at least one intermediate element (4) is in direct contact with the printing plate (5) and applies ink (3) to the printing plate (5).

6. Device (1) according to one of claims 1 to 5, characterized in that at least one of the depressions (9, 9') between a low point (11) and the paint surface (8, 8') is provided with a single-stage or multi-stage chamfer (12) and / or with a rounding (13).

7. Device (1) according to claim 6, characterized in thatthe low point (11) of the at least one depression (9, 9') lies at a depth (14) in the paint surface (8, 8') depending on a width (15) of the depression (9, 9'), preferably with a width (15) of 20 µm to 620 µm the depth (14) is 21 µm to 30 µm, with a width (15) of 620 µm to 640 µm the depth (14) is 30 µm to 50 µm, with a width (15) of 640 µm to 660 µm the depth (14) is 50 µm to 65 µm, with a width (15) of 660 µm to 670 µm the depth (14) is 65 µm to 75 µm, and with a width (15) of 670 µm to 680 µm the depth (14) more than 75 µm.

8. Device (1) according to one of claims 1 to 7, characterized in that the depressions (9, 9') in the color surface (8, 8') of the raster pattern (10) are surrounded by a border (16).

9. Device (1) according to one of claims 1 to 8, characterized in thatat least the surface of the intermediate element (4) and / or optionally of the rubber blanket (GTU) is provided from an elastomer or from a rubber, wherein preferably at least the surface of the intermediate element and / or optionally of the rubber blanket (GTU) is provided from ethylene-propylene-diene (monomer) rubber (EPDM) or from acrylonitrile-butadiene rubber.

10. Device (1) according to one of claims 1 to 9, characterized in that the depressions (9, 9') of the ink surface (8, 8') are formed by lasering and / or by plasma bombardment of the intermediate element (4) and / or optionally the rubber blanket (GTU).

11. Device (1) according to one of claims 1 to 10, characterized in that the printing plate (5) is that of a gravure printing process, wherein the image areas (6) of the printing plate (5) are deeper than those of non-image areas (17).

12. Device (1) according to claim 11, characterized in thatthe image areas (6) have an engraving depth (GT) and an engraving width (GW), wherein a depth (14) of the at least one depression (9) is dependent on the engraving depth (GT) and the engraving width (GW) of the image areas (6) of the printing plate (5), wherein - with an engraving depth (GT) of 21 µm to 30 µm and preferably an engraving width (GW) of 610 µm to 630 µm, the depth (14) is 10 µm to 40 µm; - with an engraving depth (GT) greater than 30 µm and less than or equal to 50 µm and preferably an engraving width (GW) greater than 630 µm and less than or equal to 650 µm, the depth (14) is 40 µm to 60 µm; - with an engraving depth (GT) greater than 50 µm and less than or equal to 65 µm and preferably an engraving width (GW) greater than 650 µm and less than or equal to 665 µm, the depth (14) is 60 µm to 75 µm; - with an engraving depth (GT) greater than 65 µm and less than or equal to 74 µm and preferably an engraving width (GW) greater than 665 µm and less than or equal to 675 µm, the depth (14) is 75 µm to 90 µm;and - with an engraving depth (GT) of more than 74 µm and preferably an engraving width (GW) of more than 675 µm and less than or equal to 685 µm, the depth (14) is 90 µm to 110 µm.; 13. Device (1) according to claim 12, characterized in that the width (15) of the at least one recess (9, 9') is between 500 µm and 1100 µm.

14. Device (1) according to one of claims 1 to 10, characterized in that the intermediate element (4) is that of a flexographic printing process, wherein the intermediate element (4) is arranged upstream of an anilox roller, and wherein the doctor blade (7) is designed to wipe off excess applied ink from the intermediate element (4) and / or from the anilox roller.

15. Device (1) according to one of claims 1 to 10, characterized in that the intermediate element (4) is that of an offset printing process and the printing plate (5) is a letterpress printing plate.

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