DE102016121000A1 - Method for decorating containers and apparatus for carrying out the method - Google Patents

Abstract

The inventive method for decorating objects comprises the steps of providing a color artwork as a halftone image or as a raster image, converting the provided artwork by means of a data processing in a print screen image in which a plurality of predetermined raster cells non-overlapping the original image, wherein at least some of the plurality each of these subcells has an area fraction of the area of the raster cell and / or a proportional number of pixels of a total pixel number of the raster cell and the degree of color occupancy for each of these subcells for the at least some is calculated from the plurality of raster cells; Structuring of a respective screen printing plate assigned to a process ink, such that the respective screen printing plate is designed to transfer the calculated color assignment of the respective process color of all subcells to an intermediate carrier so that the respective screen printing plate has print screen sub-image; sequential, register-accurate transfer of the Druckrasterteilbilder on an intermediate carrier for designing a print screen image on the intermediate carrier; Transfer of the print screen image from the subcarrier to the object. ()

Description

The invention relates to a method for decorating objects, in particular of containers such as beverage cans, as well as a device for carrying out the method.

In particular, in the printing of beverage cans or containers for household cleaning agent high demands on the one hand to the throughput of the printing system and on the other to the quality of the printing. Due to the high throughput of, for example, several thousand impressions per minute in such systems, some conventional printing techniques in multicolor printing, especially in the field of beverage cans, are not feasible. For example, in a conventional four-color printing (CMYK) to increase the print quality, the grid of the four mixed colors are offset at an angle to each other, so that overlap on the substrate, the various color applications. However, this measure has the consequence that the individual, each provided for one of the process colors printing plates are contaminated with other process colors in the course of operation due to the high throughputs, which is detrimental to the quality of the print or a regular and costly cleaning of parts of the printing system necessary. For the reason described above, it is common, in particular in the field of printing on beverage cans, to convert a template image with which the container is to be printed into a printed image which consists of a plurality of surface regions which are each printed over the entire surface with one of the special colors provided , Depending on the printing system i.d.R. be provided six to eight special colors, which are applied to the respective container on different surface areas. However, the described method leads to a loss of color fidelity of the printed image compared to the original image, since with the available six to eight spot colors that are specified specifically for the respective template image and applied as non-overlapping special colors, always only an approximation of the printed image to the Print template can be realized, which can be particularly problematic in a complex with respect to its color design artwork.

The invention is based on the object to enable the decoration of objects, in particular of containers such as beverage cans with high throughput and also to provide an improved print quality in relation to the detail and color fidelity of the printed image to the original image.

• - Bereitstellen einer Farbdruckvorlage als Halbtonbild oder als Rasterbild, insbesondere in Form von Bilddaten in einem CMYK- Format;
• - Umwandeln der bereitgestellten Farbdruckvorlage mittels einer Datenverarbeitung in ein Druckrasterbild, bei welchem eine Mehrzahl von vorgegebenen, in ihrer Flächenausdehnung identischen Rasterzellen das Vorlagebild nicht überlappend abdeckt, wobei zumindest einige aus der Mehrzahl der Rasterzellen jeweils eine vorgegebene Anzahl von, jeweils einer Prozessfarbe zugeordneten und sich nicht überlappenden Unterzellen aufweist, und wobei jeder dieser Unterzellen ein Flächenanteil der Fläche der Rasterzelle und/oder eine anteilige Pixelzahl eine gesamt Pixelzahl der Rasterzelle aufweist und der Grad der Farbbelegung für jede dieser Unterzellen für die zumindest einige aus der Mehrzahl der Rasterzellen, insbesondere unter Maßgabe einer vorgegebenen Farbtreue zwischen Farbdruckvorlage und Druckbild, berechnet wird;

• - Strukturieren einer Mehrzahl von, jeweils einer Prozessfarbe zugeordneten Rasterdruckplatte derart, dass die jeweilige Rasterdruckplatte zum Übertragen der berechneten Farbbelegungen der jeweiligen Prozessfarbe aller Unterzellen der Mehrzahl der Rasterzellen auf einen Zwischenträger ausgebildet ist, sodass die jeweilige Rasterdruckplatte ein von erhabenen Bereichen und dazwischenliegenden Vertiefungen gebildetes Druckrasterteilbild aufweist;
• - Sequenzielles und registergenaues Übertragen der Druckrasterteilbilder auf einen Zwischenträger zur Gestaltung eines Druckrasterbildes auf dem Zwischenträger;
• - Bedrucken des Objektes durch Übertragen des Druckrasterbildes vom Zwischenträger auf das Objekt.

This object is achieved by the present invention on the method side with a method for decorating objects, in particular containers, the method comprising the steps:

• Providing a color print original as a halftone image or as a raster image, in particular in the form of image data in a CMYK format;
• - Converting the provided color print template by means of a data processing in a print screen image in which a plurality of predetermined, identical in their surface area grid cells overlapping the template image, at least some of the plurality of grid cells each having a predetermined number of, each associated with a process color and and wherein each of these subcells has an area fraction of the area of the raster cell and / or a proportional number of pixels has a total number of pixels of the raster cell and the degree of color occupancy for each of these subcells for the at least some of the plurality of raster cells, in particular under certain conditions a given color fidelity between color artwork and printed image, is calculated;

• - Patterning a plurality of, each associated with a process color screen printing plate such that the respective screen printing plate for transmitting the calculated color assignments of the respective process color of all sub-cells of the plurality of screen cells is formed on an intermediate carrier, so that the respective screen printing plate formed by raised areas and intermediate recesses Druckrasterteilbild having;
• - Sequential and register accurate transfer of Druckrasterteilbilder on an intermediate carrier for designing a print screen image on the intermediate carrier;
• - Printing the object by transferring the print screen image from the subcarrier on the object.

By converting a template image into a specific print screen image in which the halftone cells have specific, separate subcells for each process color, wherein in the respective subcells, the color population is calculated in terms of the number of dots (pixels) or area within the respective subcell and this print image via an intermediate carrier on the actual carrier, ie the object is transmitted, halftone images can now be realized with the inventive method, so that the print image quality can be significantly increased. Mixed colors are not generated by physical overlays of the process colors on the carrier or object, but by Side-by-side printing of the different color-different halftone dots or pixels, which are not spatially differentiated from the viewer's eye and thus perceived by the viewer as a mixed color. This is achieved by the invention in that the multicolor print screen image is applied to a carrier, such as a blanket, in a number of steps, without overlapping the individual blanker sub-images with respect to the color assignment. For this purpose, a grid printing plate is produced for each process ink in accordance with the calculated print screen image, on which all subcells assigned to the respective process color are structured with their respective calculated degree of color assignment. In this case, in the respective sub-cells raised areas and intermediate recesses can produce the respective print screen sub-image, wherein the raised areas for receiving ink and delivery to the intermediate carrier and non-raised areas for non-recording of ink and thus for not delivering ink to the intermediate carrier may be formed. One after the other and aligned with one another, the various print-fritter partial images can then be transferred to the intermediate carrier, so that ultimately the entire print-grid image initially arises on the intermediate carrier, the color applications of the different process colors never overlapping. The inventive method is particularly suitable for a high-pressure process in which increased, ie raised areas of a printing plate absorb color and deliver it to a carrier.

The calculation of the degree of the respective color assignment of the respective lower cell within a particular grid cell can be carried out in accordance with different criteria for the assessment of the matching of the printed image to the original image. Expedient parameters for this assessment can be, for example, the parameters hue, color brightness and color saturation or a combination of several of these parameters. An acceptable match may be considered sufficient if the print image and the original image differ by less than a predetermined difference with respect to at least one such image parameter.

Further inventive features and development of the invention are specified in the general description, the description of the figures and the drawings.

Conveniently, in order to simplify the conversion of the original image into the printed raster image described, it may be provided that the area fraction or the proportional pixel number of a subcell at the respective raster cell is identical and constant, i.e. identical and constant, for each of the subcells assigned to one process color. identical over all grid cells, is. "Area fraction" or "proportional pixel number" means the maximum proportion of the area or pixel number of the grid cell available for the respective calculated color occupation. This specification may be particularly useful in those cases where the colors in the original image are rather reduced in terms of saturation of the colors.

In a particular embodiment, it can also be provided to provide the possibility of reproducing a customary color contrast in the printed image by appropriate selection of the process colors, in particular also with constant and identical subcells with respect to their areal proportion or pixel number to the raster cell. For example, it may be provided according to the invention to select process colors with higher color saturation compared to conventional CMYK process colors, so that a sufficient color contrast can be generated in the print image despite the fact that a particular process color can not completely occupy a raster cell, but only the subcell associated with the process color , For example, this can be provided when using 4 process colors for the design of halftone colors, the color saturation of at least one of the process colors by at least a factor of 2, in particular by a factor of 4, i. in the example described, according to the number of process colors, to increase the color saturation of conventional CMYK process colors.

In particular, in situations in which the original image has brilliant, rich color sections and high color contrasts, it may be expedient in one embodiment for the subcell assigned to a respective process color to represent the calculated halftone cell in relation to its area fraction or its proportional number of pixels Color saturation or color brilliance is set larger than that of other sub-cells, respectively process colors, in the respective grid cell. The described increase or decrease in the sub-cell size and thus the maximum size of the respective grid point results in a further degree of freedom for better matching of the print screen image to the original. In certain embodiments, it may also be provided that the size of one or more sub-cells, each associated with a process color, are reduced to zero in order to increase one of the other process colors with respect to the saturation or color brilliance of this screen cell. The size of the respective sub-cell within a grid cell thus determines the maximum color assignment of the respective printing ink for the respective grid cell. In contrast, in all embodiments, the respective total area or the maximum pixel number of a single grid cell, each of which by addition over all Subcells of the grid cell result in being identical across all grid cells.

Conveniently, the subcells within a grid cell may be arranged as a contiguous area within which the respective print pixels or pixels may be arranged as the smallest print area.

For the design of the grid cells, which can completely and preferably completely cover the respective image, a large number of designs are possible with regard to their outer contour. Such a grid cell may in particular have a polygonal shape, for example be formed as a triangle, quadrangle or hexagon. The respective boundary or shape defining the surface of the grid cell can be selected so that an arbitrary surface can be covered gaplessly and without overlapping by placing a plurality of these cells of the same construction in their outer dimensions.

The basic number of sub-cells within a grid cell may preferably correspond to the number of process colors for designing halftone color sections, i. be basically identical with this. In the case of four-color printing for the design of halftone colors, the grid cells basically comprise four subcells, that is to say one subcategory each for the colors cyan, magenta, yellow and black or key (CMYK). As already explained above, in one embodiment, the proportion of a specific subcell in a particular grid cell may also be zero in order to produce a specific color impression in this area of the halftone print image.

For the geometric arrangement of the sub-cells within a grid cell a variety of designs is possible. For example, all subcells can basically have the same geometric shape and, for example, be polygonal. In a particular embodiment, it may also be provided that at least one of the subcells within a raster cell is surrounded in terms of area, in particular in terms of area, by at least one further subcell, for example by designing a subcell having the shape of a square frame. As a result, a distribution of the process color sections which is as symmetrical as possible within a single raster cell is achieved, for example in order to avoid print image disturbances.

Such print image disturbances, such as moiré effects, can also be avoided according to the invention by virtue of the fact that grid cells which have rotational symmetry with respect to their boundary or peripheral line are rotated relative to one another. In particular, in the above-mentioned polygon shapes of the grid cell, a rotational symmetry with respect to the outer contour can be adjusted. For example, a square grid cell merges with respect to its outer contour when rotated by 90, 180, 270 and 360 degrees. Similarly, rotational symmetries can be adjusted in a hexagonal or triangular grid cell.

It may be particularly useful with respect to the rotation of adjacent grid cells, if this rotation is set stochastically, that is by means of a random variable. In the cases described, otherwise occurring print image disturbances can be avoided by changing the arrangements of the sub-cells within a grid cell by rotating adjacent grid cells to each other. Similarly, it can also be provided to interchange the assignment of respective lower cell to the respective ink with respect to their geometric arrangement within the grid cell in adjoining grid cells to avoid a printed image disorder.

The respective degree of color assignment of a process color within a grid cell can be implemented by an amplitude-modulated screening, a frequency-modulated screening or a combination of both screening methods in the respective sub-cell. For example, in the case of amplitude-modeled screening, a lower cell assigned to a process color has a single halftone dot which, depending on the calculated hue value, has a specific area of the lower cell or a pixel proportion of the total pixel number, ie. the maximum pixel number of the subcell includes or occupies. The maximum tone value can be set by transmitting all the pixels or dots of the respective sub-cell to represent this screen dot color and the screen printing plate is designed accordingly.

In principle, the method according to the invention can be applied to arbitrary screen widths and printing pixels, ie dots or recorder elements (REL). An exemplary screen ruling lies approximately in the interval 30 to 80 lines / cm at a pixel rate of, for example, at least 1000 dots / cm (dpcm). In the case of a screen width of 50 lines / cm and a pixel rate of 1000 dpcm, a single screen cell has 400 pixels and with an even distribution of the sub-cells and the four process colors for representing the respective screen dot with an amplitude-modulated screen, each subcell has 100 pixels. Accordingly, in this embodiment, the color occupancy of each sub cell may be between 0 and 100 pixels. The conditions in a frequency-modulated screening are similar, wherein the pixels for representing the respective halftone dot for a process color within the respective Subcell are not arranged in each case contiguous, but may be distributed over the surface of the subcell.

Although halftone color prints having a high throughput are now also possible with the method according to the invention, it is additionally possible to provide, in addition to the process colors for the design of halftone color sections on the object, the possibility of printing partial surfaces of the object over the entire surface with a single process ink, for example a branding color can be. Such a method is readily possible with the use of a further pressure plate, which can be formed at least in a partial area over the entire surface for receiving and dispensing a process color. In this case, the intermediate carrier, for example a rubber blanket, may be structured in an associated partial area, e.g. by means of laser engraving, so that on the object after the transfer of the color applications from the intermediate carrier to the object in addition to the described halftone color sections may also have at least one further printed portion which, in particular image structured, is covered with a single process color. Although the individual process colors are not superimposed in the halftone color sections in the method according to the invention, the individual process colors in these sections are restricted to the respective subcells, while the further section occupied by a single process color on the intermediate carrier or the object is fundamentally arbitrary large, continuous, optionally structured surface may include, in terms of area, for example, may have a plurality of grid cells.

The structuring of the printing plate or screen printing plate can be realized in a conventional manner. For example, the patterning of the respective screen printing plate associated with a process color can be carried out by laser engraving such that the respective screen printing plate has a printing block sub-image of the respective printing ink formed by raised areas and intermediate depressions for transferring the calculated color assignments of this printing ink of all the respective sub-cells of the plurality of screen cells to one subcarrier. Such a printing plate can be, for example, a photopolymer or an elastomer plate which can be surface-structured by means of a laser.

In order to avoid a physical overlap of color areas or points on the intermediate carrier or the object, it can be provided that a spacing is provided between two adjoining subcells of a respective grid cell, in particular in the size of at least one, at least 4, between four to ten, or at least 7 printing pixels of the screening, for example in the form of a corresponding number of free pixels of the screening, which are not designed to transfer color to the object. This spacing can be provided over the entire boundary line of the respective subcell. Preferably, it can also be provided in the same way to provide a spacing between two adjoining subcells of two adjacent grid cells.

In order to avoid a physical overlap of color areas or points of different colors on the intermediate carrier or the object, it can be provided that a spacing is provided between each two adjoining grid cells, in particular in the size of at least one, at least 4, between four to ten , or at least 7 printing pixels, for example in the form of a corresponding number of free pixels of the screening, which are each not designed to transfer color to the object. This spacing can be expediently provided over the entire boundary line of the respective grid cell.

The printing plates produced in the context of the method according to the invention can be used in an otherwise conventional printing device for decorating objects. For this purpose, the device may comprise, for example, a plate cylinder with a plurality of successively circumferentially arranged pressure plates, which are each full area or at least partially full surface or as, each with a Druckrasterteilbild structured screen printing plate are formed, wherein the respective screen printing plate one of raised areas and recesses lying therebetween has formed Druckrasterteilbild for receiving and transmitting the respective associated process color. In this case, a blanket cylinder may be provided which is rollingly engaged with the plate cylinder and in its circumferential direction sequentially carries a plurality of blankets, each at least partially full area, especially flat, and for sequential, register accurate recording of the colors of the individual print fritter partial pictures on a single Blanket are formed, wherein the so applied to the individual blanket print screen image is then delivered in one step on the container to be decorated.

In addition to the process colors for generating color halftone values, in one particular embodiment, the printing device may be provided with at least one additional printing plate for the partial transfer of a further process ink to the intermediate carrier, the further process ink being transferred to a section of the intermediate carrier from the printing plate which does not Has color assignment of one of the other process colors. In this case, it may further be provided that the intermediate carrier is structured in these sections, for example in such a way that it has a printed image formed by raised areas and recessed areas therebetween, wherein the raised areas remove ink from the printing cylinder during operation and deliver it to the container to be decorated ,

• 1 ein Flussdiagramm, das Verfahrensschritte zur Umsetzung des erfindungsgemäßen Verfahrens zum Dekorieren von Objekten im Ablauf,
• 2a bis 2f geometrische Umrisse von beispielhaften Rasterzellen einschließlich ihrer jeweiligen Unterzellen,
• 3a, 3b beispielhafte Anordnungen von benachbarten Rasterzellen zur Vermeidung von Druckbildstörungen,
• 4a einen Bildausschnitt eines nach dem erfindungsgemäßen Verfahren gestalteten Druckrasterbildes,
• 4b im Vergleich zu der Darstellung gemäß 4a, einen Ausschnitt eines herkömmlichen Druckrasterbildes in einer Detailansicht, und
• 5 in einer Prinzipskizze den Aufbau einer Druckvorrichtung zum Dekorieren von Objekten zur Umsetzung des erfindungsgemäßen Verfahrens

zeigen.The invention will be explained in the following by describing some embodiments with reference to the attached figures, wherein

• 1 a flowchart, the method steps for implementing the method according to the invention for decorating objects in the process,
• 2a to 2f geometric outlines of exemplary grid cells including their respective subcells,
• 3a . 3b exemplary arrangements of adjacent grid cells to avoid print image disturbances,
• 4a a detail of a designed according to the method of the invention print screen image,
• 4b in comparison to the illustration according to 4a , A section of a conventional print screen image in a detailed view, and
• 5 in a schematic diagram of the structure of a printing device for decorating objects for implementing the method according to the invention

demonstrate.

The invention will be explained below with reference to the printing of beverage cans. Corresponding systems have a throughput of at least two thousand cans per minute, which was previously only possible by reducing the color template image for designing the print screen image. The course of the method according to the invention is in 1 specified. The starting point is a colored original image, which is usually in the form of a halftone image or raster image, in particular in the form of image data in a CMYK format. The provided template image is converted into a print screen image in step S2, wherein the data processing based on the grid cell is constructed in a specific manner. As usual, a plurality of raster cells cover the original image, wherein, according to the invention, at least some of the plurality of raster cells each have a predetermined number of subcells each assigned to one process color and not overlapping. In this case, each of these subcells is assigned an area fraction of the total area of the raster cell and / or a proportional pixel number of a total pixel number of the raster cell, wherein the degree of color occupancy for each of these subcells is calculated for at least one of the plurality of raster cells. Basis for this calculation, for example, a predetermined color fidelity or approximation of the hue, the color brightness or the color saturation of the print screen image to the original image.

In a particular embodiment, moreover, provision may be made for the individual subcells, or their outlines, to be separated from one another within the raster cell, in particular by a single pixel, in order to avoid colors with the disadvantages described above being superimposed upon the occurrence of slight registration errors transferred to the subcarrier or printed on the object.

With the calculated print raster image, the corresponding dots or pixels are present for structuring a respective raster printing plate in the form of a raster subframe in which the respective color rendition of the assigned subcells of the raster cells is transferred from the raster printing plate assigned to a process color to the intermediate carrier to produce the desired print screen image on the subcarrier or the object as a whole. This structuring can take place, for example, in the case of a printing plate designed as a photopolymer plate in that the corresponding recorder elements on the printing plate are removed with a laser, which should not pick up and transfer color. Preferably, the method according to the invention is suitable for a high-pressure process, in which projecting areas or pixels of the printing plate absorb ink and transfer them to the intermediate carrier, for example a rubber blanket. In step S4, the successive transferring of the individual print-framer partial images of all screen printing plates to a single intermediate carrier takes place, so that the color assignments of all the printing-framer partial images are transferred to the intermediate carrier, wherein the printing grid plates are aligned and adjusted very precisely to the intermediate carrier, i. must be registered in order to achieve a pixel-precise overlay of all print-fritter part images on the intermediate carrier, so that individual color dots or pixels do not overlap.

In the last step S5 then takes place the transfer of the print screen image from the intermediate carrier to the beverage can, in which this rolls on the blanket and receives the entire color assignments on the intermediate carrier.

The 2a to 2f show exemplary designs of raster cells on which Basis of the inventive method can be performed. As explained, in the described embodiment the process according to the invention is carried out with four process colors for the realization of color halftone stages. In this respect, the respective grid cell basically has four areas in the form of sub-cells, wherein each of these four sub-cells of a grid cell is associated with one of the four process colors. 2a shows an exemplary grid cell A with a square outline, wherein the individual sub-cells A1, A2, A3 and A4, symbolized by different shades in the figure, are formed as an inner square for one of the colors and with respect to the other colors as a square square frame. In an embodiment, it is provided that the respective area or number of pixels of the sub-cells are identical. In 2a and the other 2 B - f is the respective maximum area occupancy or max. Pixel number or dot size specified for the respective color or subcell.

In the in 2 B given another example of a grid cell B this is in turn formed square in outline, wherein the four sub-cells B1, B2, B3, B4 are formed according to the colors used here as equilateral triangles.

In the embodiment of a grid cell as shown in FIG 2c is the grid cell C formed as an equilateral triangle, the associated sub-cells C1, C2, C3 and C4 in the same way.

In the embodiments of the 2d and 2e indicates the respective grid cell D . e again a square outline, while the 4 sub-cells D1 - D4, E1 - E4 are again the same area, here rectangular or L-shaped.

In the embodiment according to 2f has the grid cell F a hexagonal outline, here six process colors are used for the design of halftone colors and accordingly six sub-cells F1 - F6, here in the form of isosceles triangles, designed. In the 2f specified grid cell F is therefore suitable for hexachromatic prints. Also in the examples of 2 a to 2f, the respective sub-cells are indicated for clarity of illustration, each with a 100% color assignment.

Depending on the symmetry of the cell, adjacent raster cells can be rotated with respect to their outline to adjacent raster cells, which is an example of square raster cells in FIG 3a is specified. 3b shows an embodiment in which the sub-cells of adjacent grid cells are arranged differently geometrically to each other to avoid print image disturbances.

To safely avoid overlapping a grid cell with an adjacent grid cell, spacing between adjacent grid cells may occur Δ1 be provided, for example in the form of one or more pixel spacings. Similarly, to avoid crosstalk or overlap of a subcell to an adjacent subcell, a spacing may be used Δ1 be provided, for example in the form of one or more pixel spacings.

4a shows for clarity a section of a print screen image applied according to the invention, in which the color parts of a single screen cell do not overlap. In contrast to the representations of the 2a-f and 3a, b are in 4 the actual color assignment in a sub-cell to achieve the desired color half tone in the respective grid cell R indicated. In the case of amplitude-modulated screening, these color assignments can be referred to as a raster point. For clarity, the outline of a grid cell R is indicated by dashed lines. In contrast, the in 4b specified section, which shows a conventional, colored print screen image in which overlap the individual color grid points. The in the 4a and 4b specified print grid are formed as amplitude modulated raster.

5 shows a schematic diagram of a device for decorating objects as it can be used to implement the method according to the invention. The device 1 comprises a plate cylinder having a plurality of circumferentially successively arranged printing plates 11a-11e in which the printing plates 11a-11d are structured as screen printing plates for forming a color printing screen image, so that the process colors processed by the screen printing plates 11a-11d serve to form halftone inks. In this respect, the grid printing plates carry the respective image information. The printing plate 11e is formed in the described embodiment for transferring a spot color in a partial area of the image on the object. The printing plates are designed as high-pressure plates and take insofar from the respective inking unit 12a-12e Color on the raised areas and transfer them on blankets 10a-k, which on a blanket cylinder 9 are arranged circumferentially successively.

Each blanket takes so far the respective print-fritter part image of each screen printing plate 11a-11d and the full color of the full-surface area of the printing plate 11e, which may also be structured, so that after passing through all the printing units on the respective blanket, the entire information to be transmitted is applied. The blankets are unstructured, at least in the area of the printing block partial images. When successively applying all the printing block partial images on the respective blanket, an exact alignment of the blanket and the respective printing grid plate takes place so that no areas of different color overlap on the blanket. In the in 5 given operating situation is applied to the blanket 10e image information in one step on the object, here a soda can 13 , transferred by the soda can 13 on the blanket 10e unrolls.

LIST OF REFERENCE NUMBERS

1

printing device

9

Blanket cylinder

10a-10k

blanket

11a-11e

printing plate

12a-12e

inking

13

beverage can

A, B, C, D, E, F

grid cell

A1..A4

subcell

B1..B4

subcell

C1..C4

subcell

D1..D4

subcell

E1..E4

subcell

F1..F6

subcell

S1-S5

step

Δ1, Δ2

spacing

Claims (19)

Method for decorating objects, in particular containers such as beverage cans, comprising the steps: - Providing (S1) a color artwork as a halftone image or raster image, in particular in the form of image data in a CMYK format; - Converting (S2) of the provided artwork by means of a data processing in a print screen image in which a plurality of predetermined, identical in their surface area grid cells (A, B, C, D, E) non-overlapping the original image, wherein at least some of the plurality of Grid cells each having a predetermined number of, each one process color associated and non-overlapping sub-cells (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4), and each of these subcells having an area fraction of the area of the halftone cell and / or a proportional number of pixels of a total pixel number of the halftone cell, and the degree of color occupancy for each of these subcells for the at least some of the plurality of halftone cells (A, B, C, D, E) is calculated; Structuring (S3) a plurality of screen printing plates (11a-11e) assigned in each case to a process ink, such that the respective screen printing plate for transferring the calculated color assignment of the respective process color of all sub-cells (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) of the plurality of grid cells (A, B, C, D, E) is formed on an intermediate carrier, so that the respective screen printing plate one of raised areas and recesses lying therebetween formed formed Druckrasterteilbild; - Sequential, register accurate transfer (S4) of the Druckrasterteilbilder on an intermediate carrier for designing a print screen image on the intermediate carrier; and - Printing (S5) of the object by transferring the print screen image from the subcarrier to the object. Method according to Claim 1 , characterized in that the area proportion or the proportional number of pixels of a subcell at the respective grid cell (A, B, C, D, E, F) for each of the one process color associated sub-cells (A1 ... A4, B1 ... B4 , C1 ... C4, D1 ... D4, E1 ... E4) is identical and constant. Method according to Claim 1 , characterized in that the subcells (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) associated with a respective process color are related to their area fraction or their area proportional pixel number of the respective grid cell for displaying calculated color saturation and / or color brilliance is set larger than that of other sub-cells, respectively process colors in the respective grid cell. Method according to one of Claims 1 to 3 , characterized in that at least one of the process colors has a higher color saturation compared to conventional CMYK process colors. Method according to Claim 1 . 2 . 3 or 4 , characterized in that the respective subcell (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) comprises a contiguous area of the respective grid cell. Method according to one of Claims 1 to 5 , characterized in that the grid cells (A, B, C, D, E, F) have a polygonal shape, in particular as a triangle, square or hexagon are formed. Method according to one of Claims 1 to 6 , characterized in that grid cells (A, B, C, D, E, F) have 4 or 6 sub-cells. Method according to one of Claims 1 to 7 , characterized in that at least one of the subcells (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) of a raster cell (A, B, C, D , E, F) is enclosed in area by at least one further subcell. Method according to one of Claims 1 to 8th , characterized in that adjoining grid cells (A, B, C, D, E, F) are rotated to each other to avoid a print image disorder. Method according to Claim 9 , characterized in that the rotation of adjacent grid cells (A, B, C, D, E, F) is set stochastically to each other. Method according to one of Claims 1 to 10 , characterized in that in adjacent raster cells (A, B, C, D, E, F) to avoid a print image disorder, the assignment of respective sub-cell (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) to respective ink with respect to their arrangement within the grid cell (A, B, C, D, E, F) is reversed. Method according to one of Claims 1 to 11 , characterized in that for setting a respective degree of the calculated color assignment of the respective subcell (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) of the respective grid cell an amplitude-modulated and / or frequency-modulated screening is performed. Method according to Claim 12 , characterized in that the grid width of the grid cells (A, B, C, D, E, F) is approximately in the interval of 30 to 60 l / cm with a pixel rate of at least 1000 dpcm. Method according to one of Claims 1 to 13 , characterized in that at least a partial surface of the object is printed over the entire surface with a single spot color. Method according to one of Claims 1 to 14 , characterized in that the structuring of the respective, a process color associated screen printing plate (11a ... e) is carried out by laser engraving so that the respective screen printing plate has a raised areas and intervening depressions formed Druckrasterteilbild the respective ink for transmitting the calculated color assignment the respective printing ink of all respective sub-cells of the plurality of screen cells (A, B, C, D, E, F) on an intermediate carrier. Method according to one of Claims 1 to 15 , characterized in that between two adjoining subcells (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) of a respective screen cell (A, B, C, D, E, F) in each case a spacing is provided, in particular in the form of at least one pixel. Method according to Claim 16 , characterized in that between each two adjacent sub-cells of two raster cells each have a spacing is provided, in particular in the form of at least one pixel. Method according to one of Claims 1 to 17 , characterized in that between each two adjoining grid cells (A, B, C, D, E, F) is provided in each case a spacing, in particular in the form of at least one pixel. Apparatus for decorating objects, in particular containers such as beverage cans (13), comprising: - a plate cylinder having a plurality of circumferentially successively arranged printing plates (11a - 11e) which are formed as screen printing plates structured in each case with a printing screen sub-image, the respective ones Rasterdruckplatte has a subcarrier cylinder, which is rollingly engaged with the plate cylinder from raised areas and intervening depressions, which in its circumferential direction successively a plurality of intermediate carriers, in particular blankets (10a - 10k) carries at least are formed over the entire area for sequential and register-accurate recording of the print-fritter partial images of the printing plates (11a - 11e), so that a raster image is recorded on the respective intermediate carrier, that from a plurality of detent (A, B, C, D, E, F) composed, and which is transferable from the respective subcarrier to an object, characterized in that s a respective grid cell (A, B, C, D, E, F) a plurality has non-overlapping, each one process color associated sub-cells (A1 ... A4, B1 ... B4, C1 ... C4, D1 ... D4, E1 ... E4) for displaying halftone colors.

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