EP2703162B1 - Method and device for printing printed material - Google Patents

Description

The invention relates to a method and a device for printing substrate in a rotary printing press with a first non-changeable printed image and a second variable printed image according to the preamble of claims 1 and 11.

Form-linked or variable printing methods are known from the prior art. Form-bonded printing processes are, for example, offset, flexographic, gravure or screen printing processes, whereas e.g. Inkjet and thermal transfer printing are referred to as variable methods.

In addition, combination printing methods are also known, which are also referred to as imprinting or "imprinting" and based on two series-connected form-linked and variable individual printing methods. However, the previously known combination printing methods are often associated with printing problems, which in particular consist in that between the printed image of the form-linked printing process and the imprinted image of the variable printing process often clearly noticeable color differences occur.

If, for example, in a sheet-fed rotary offset printing press, an inkjet printing process downstream of the offset printing, which is also referred to below as "inkjet process", is used, strong color and appearance differences usually occur, which can be attributed to the different inking systems. Also, this lack of quality is due to the fact that the non-contact inkjet process, that is to say without a printing gap, can not smooth the printed image or the ink. As a result, the otherwise smooth appearance of the pressure applied by the raised print image in the case of sequential combination printing is generally severely impaired.

Previously, the different print results were either accepted or the pressure differences minimized by optimizing the printing inks used in the inkjet printing unit. In this context, it is also known to optimize the quality of the printing result by the use of substrates that have different absorption capacity for the printing inks used. Although the quality of the print result can generally be improved as a whole, the differences between the printed image produced by the offset process and the variable printed image printed by a subsequent inkjet printer are still visible.

From the DE 10 2005 021 186A1 a sheet-fed rotary printing machine is known, which has a painting unit, which is constructed of inkjet jet heads, which apply a variable inkjet print image directly on a color-free peripheral portion of the blanket cylinder. The document gives no indication that an applied to the blanket cylinder inkjet image pattern is removed during the continuous printing operation in each revolution of the blanket cylinder. The inkjet image pattern may be the identical pattern that was previously transferred from the printing plate cylinder to the blanket cylinder in the offset process, and serves in this case to increase the layer thickness of the image pattern. Alternatively, the inkjet image pattern may be a thick layer of protective lacquer, or a lacquer application or else a functional layer for a product labeling or an electronic switching element. Accordingly, the arrangement described above is not suitable for the simultaneous printing of a form-bound printed image in the offset printing process and an individualized printed image in the inkjet process, which is changed at each cylinder revolution or at least several times, eg, 5 or 10 times per print job.

Accordingly, the document gives no indication of the use of a cleaning device which removes the variable printed image of the inkjet printing device applied to the blanket cylinder from the surface of the cylinder during each cylinder revolution or at least several times during a print job while the printing press is running, around the non-printing peripheral section thus produced by the inkjet printing device again with a variable image pattern to print.

In the DE 199 61 369 A1 describe a method and associated apparatus in which the colors are transferred by means of spray modules to a roll having a flat roll surface, which are arranged side by side viewed in the axial direction of the roller and are individually controllable in terms of color intensity and amount of ink. The different drive control of the spray modules has a negative influence on the amount of color and the quality of the color intensity.

Accordingly, the present invention has for its object to provide a method and an apparatus for performing the method with which a molded non-variable print image and a variable print image, which is varied several times during a current print job, with little color differences between the printed image form and the variable print image can be applied simultaneously to the substrate.

This object is achieved by the features of claim 1 and 11.

Further features of the invention are described in the subclaims.

The present invention comprises a method for printing substrate in a rotary printing press, which comprises a first, the printing material in a nip contacting printing press cylinder and a second printing cylinder, which transmits a previously applied to this printed image of a first ink on the substrate, and wherein an ink jet printing device for applying an additional variable print image during the continuous printing operation of the rotary printing press is provided on the substrate.

The invention is characterized in that the inkjet printing device applies the additional printed image directly to a colorless circumferential section of the second printing press cylinder directly contacting the printing material web or to a transfer cylinder transferring the printed image from the second printing press cylinder to the printing substrate, and that a cleaning device is provided which removes the additional printed image applied by the inkjet printing device from the colorless peripheral section.

In this case, the printing operation of the printing machine is referred to as the printing operation of the printing machine during which the printed images are transferred to the printing material. This is known to differ from a stand-by operation of the printing press, in which a washing device is continuously adjusted to a cylinder of the printing press and the press is operated for a predetermined period of time at a very low speed to the cylinder before printing the next print job completely clean another subject.

For this purpose, the cleaning device of the device according to the invention, which will be described in more detail below, comprises either a doctor blade which is constantly or at short intervals applied to the peripheral surface of a gravure cylinder during the continuous printing operation, or else a doctor blade which is in the region of the colorless peripheral section, in FIG the ink jet printing image is applied by the ink jet printing device during each cylinder rotation is briefly switched on and off again to the cylinder surface, to clean only this colorless peripheral portion.

Although the variable print image is preferably removed from the peripheral portion by the cleaning means during each revolution of the associated cylinder, and the colorless peripheral portion is subsequently printed by the ink jet printing apparatus with a new variable print image, it is also possible to print the variable print image during the printing operation e.g. to change only every 2, 5, 10 or more cylinder revolutions, i. several times per print job if the current print job contains a corresponding number of consecutive identical printed products.

Using the same or related color systems, the invention combines a form-linked and a variable printing method by applying the variable portion of the print image from the inkjet printing device to an intermediate carrier. This intermediate carrier is either the form cylinder of the form-bonded printing process or the common transfer cylinder for the variable process as well as the form-bonded printing process. The intermediate carrier, ie the cylinder onto which the ink is sprayed, preferably has a generally hard and wear-resistant surface, from which the applied ink or ink of the variable print image is removed, in particular by an employed doctor, preferably during each revolution of the intermediate carrier, to print this again by the ink jet printing device with a new variable printed image, which is then transferred to the substrate.

Compared to the prior art, the invention has the advantage that a standardization of the inking concept for the print run in gravure and high-pressure process combined with the simultaneous possibility of variable imprinting particular individualized image data without readily apparent to the viewer color differences between the form-bound, during a print job not changeable print image and the variable printed image occur. Another advantage of the invention is that the spraying of the variable printing image is carried out on the surface of a rotating cylinder and not on the surface of the continuous printing material, which, if it is a printing material, usually subject to continuous longitudinal and transverse vibrations , As a result, the impression of the variable print image with high register accuracy is possible, thereby further increasing the quality of the printed products produced.

Although the invention can in principle also be used in known sheet-fed rotary offset printing machines with imprinting units, it is preferably used in printing units of web-fed rotary printing presses. The invention is particularly suitable for the production of variable print images in printed products, which are created in large numbers and have over a print job away predominantly uniform printed image.

In one embodiment of the invention, it is provided that the first press cylinder is a press cylinder and the second press cylinder is a gravure cylinder a gravure printing unit having a plurality of ink receiving recesses. Here, the colorless peripheral portion, to which the variable additional print image is preferably applied directly by the ink jet printing device, is formed as a substantially flat recessed portion. In order to remove the variable printed image applied by the inkjet printing device from the recessless section, which is preferably carried out with each revolution of the gravure cylinder, a cleaning device in the form of a doctor blade is advantageously provided, which is preferably the same doctor blade used during the continuous printing operation of the gravure printing machine Abrakeln the gravure ink after coloring the gravure cylinder is made to the surface of the gravure cylinder. This results in the advantage that with a small additional device overhead, which basically consists only in the provision of inkjet printing device, in a known gravure printing individualized printed products can be produced in large numbers, in which the variable image content of the printed image despite the existing differences in the color properties between the gravure ink used and the ink of the ink jet printing device fits seamlessly into the solid printed image, so to speak, without apparent to the viewer discernible color differences and differences in color appearance. This is due to the fact that the variable printed image applied to the colorless peripheral section passes through at least one printing nip in the same way as the solid printed image before it is transferred onto the printing substrate. Although in this embodiment a printing material web is preferably printed by the method according to the invention, it is in principle likewise conceivable to print sheet-like material.

The same or similar color systems can be used for the process. If z. B. UV inks are used for both systems, which can be dried together by a downstream UV radiation source.

According to one embodiment of the invention, it is provided that the first printing press cylinder is a press cylinder and the second press cylinder is a printing form cylinder in a flexographic printing unit of a known flexographic printing machine, which prints the image onto a transfer cylinder contacting the printing web with a particular chromium-plated Surface transfers. In this embodiment of the invention, the colorless peripheral portion is formed by a recessed portion of the flexographic printing plate, and the surface of the transfer cylinder is preferably contacted by a doctor blade, which remains of the printed image and the other variable printed image after transfer to the printing substrate from the surface of the Doctoring off the transfer cylinder.

Although the squeegee in the latter embodiment is preferably a common squeegee, which extends over the entire width of the transfer cylinder and the surface of the entire transfer cylinder abrakelt, it may also be provided that instead of such a squeegee only one locally in the region of the additional variable Printed image arranged doctor blade is provided, which is made in time with the cylinder rotation to the cylinder to clean it of the remaining remnants of the applied ink, which was sprayed by the ink jet printing device previously on this area.

According to a further embodiment of the invention, it may furthermore be provided that the first printing press cylinder is a press cylinder and the second press cylinder is a gravure cylinder of a gravure printing unit for indirect gravure printing having a plurality of ink receptions on which the colorless peripheral section is closed, substantially planar shaped recessless section. The additional, preferably variable printed image is applied in this embodiment by the ink jet printing device directly on the color-free peripheral portion of the gravure cylinder, which transmits the printed image and the additional printed image via a transfer cylinder with a preferably soft surface, such as a blanket cylinder, on the substrate web. In this embodiment of the invention as well, a squeegee contacting the surface of the gravure cylinder is provided, which preferably scraps the printed image and the additional printed image jointly from the surface of the gravure cylinder after the transfer to the printing material web.

The last-described embodiment represents a method variant used in indirect gravure printing, which has the advantage that the additional printed image on the color-free peripheral portion, which in this case also acts as a raised, planar, surface without cups is formed of the gravure cylinder can be cleaned without a significant additional device overhead by the staff on the gravure cylinder doctor, so that the surface of the colorless peripheral portion can be acted upon by the ink jet printing device in the next cylinder revolution with a new variable additional printed image. This has the advantage that even existing printing units for indirect gravure printing can be subsequently operated by retrofitting an ink-jet printing device with comparatively low costs as an imprinting device, which has the aforementioned advantages over the known inkjet-based imprinting machines. In order to be able to provide the usual on gravure printing machines high production speeds on the part of the ink jet printing device, it may further be provided that the colorless peripheral portion is alternately applied to the gravure cylinder by two circumferentially spaced ink jet printing devices considered the respective squeegee viewed in the direction of rotation of the cylinder and are arranged upstream of the pressure nip between the gravure cylinder and the transfer cylinder.

Although it is in principle also possible in the previously described embodiments of the invention to use a different cleaning device, for example a wipe or the like, instead of a doctor blade, it is particularly advantageous if the surface of the respective printing press cylinder on which the ink is applied has a doctorable surface that is, a surface from which the deposited ink of the additional, preferably variable image can be removed by a staff doctor.

In the preferred embodiment of the invention, the surface of the printing press cylinder bearing the colorless peripheral portion on which the variable print image is printed by the ink jet printing device is made of a hard and wear resistant material, preferably chrome or ceramic or other suitable material having similar properties.

The invention will be described below with reference to the drawings with reference to a preferred apparatus for carrying out the method.

Fig. 1

eine erste Ausführungsvariante der Erfindung, bei der der Formzylinder eines Tiefdruckwerks durch eine Tintenstrahldruckeinrichtung mit einem zusätzlichen variablen Druckbild beaufschlagt wird,

Fig. 2

eine zweite Ausführungsvariante der Erfindung, bei der der Transferzylinder eines Flexo-Druckwerks durch eine Tintenstrahldruckeinrichtung mit einem zusätzlichen variablen Druckbild beaufschlagt wird, und

Fig. 3

eine dritte Ausführungsvariante der Erfindung, bei der Formzylinder eines Tiefdruckwerk für indirekten Tiefdruck durch eine Tintenstrahldruckeinrichtung mit einem zusätzlichen variablen Druckbild beaufschlagt wird.

In the drawings show

Fig. 1

a first embodiment of the invention, wherein the form cylinder of a gravure printing unit is acted upon by an ink jet printing device with an additional variable printed image,

Fig. 2

a second embodiment of the invention, wherein the transfer cylinder of a flexographic printing unit is acted upon by an ink jet printing device with an additional variable printed image, and

Fig. 3

a third embodiment of the invention, wherein the form cylinder of a gravure printing unit for indirect gravure printing is acted upon by an ink jet printing device with an additional variable printed image.

As in Fig. 1 1, a first printing press cylinder in the form of a press cylinder 11 and a second printing press cylinder in the form of a gravure cylinder 21 work together in a gravure printing unit, between which a printing material web 2 is guided in a known manner. The second printing press cylinder 21, which rotates to color the cylinder in the region of a schematically indicated inking unit 29, has on its surface 25 a plurality of well-like, not shown in detail recesses, which absorb ink in the inking unit 29, which are used to produce a first, non-variable Print image is transferred to the printing substrate 2. The gravure cylinder 21 has on its surface 25 further comprises a color-free peripheral portion 4, in which no recesses or wells are formed, which receive in the inking unit 29 ink. As in Fig. 1 Here, schematically indicated, the peripheral portion 4 is acted upon by an ink jet printing device 5 with ink 7, when this peripheral portion 4 is in the range of the ink jet printing device 5, to produce on this an additional variable printed image of ink 7. This second variable printed image from ink passes after a further rotation of the cylinder 21 in the direction of arrow "a" in the nip between the cylinders 11 and 21 and is transferred there under high pressure together with the first printed image on the substrate web 2, wherein in the nip at the same time an approximation of Color height of first and second printed image is done. After passing through the printing gap enter the peripheral portion 4, which is possibly wetted with residues of the ink 7, which was not completely transferred to the printing substrate 2, and the wells in this area of the cylinder surface for re-inking the inking unit 29. By a the inking unit Subsequent to the direction of rotation "a" of the cylinder 21 downstream doctor blade 8a, which extends over the entire width of the cylinder 21, the peripheral portion 4 is then cleaned of ink residues and at the same time excess gravure ink from the inking unit 29 in a known manner from the surface of the cylinder 21st doctored.

Fig. 2 shows a second embodiment of the apparatus for performing the method according to the invention, in which a first printing press cylinder in the form of a press cylinder 12 and a second printing press cylinder in the form of a known flexographic printing plate cylinder 22 are arranged in a flexographic printing unit. The second printing press cylinder 22 is dyed in the region of its surface in a known manner by an inking unit 38 and transmits the resulting on its surface first print image via a transfer cylinder 32 in a formed between the first printing press cylinder 12 and the transfer cylinder 32 printing gap on the printing substrate 2nd Auf the flexographic printing plate 9 is arranged a colorless peripheral portion in the form of a radially withdrawn portion 4 ', in which no ink of the inking unit 38 is transferred to the transfer cylinder 32 when the cylinder rotates in the direction of the arrow "b".

Like the presentation of FIG. 2 can be taken, the transfer cylinder 32 is associated with an ink jet printing device 5, which applied to the circumferential surface of the transfer cylinder 32 with a variable additional printed image of ink 7 from the recessed portion 4 'produced colorless peripheral portion 4, which after rotation of the transfer cylinder 32 in the direction of the arrow "c" is transferred together with the likewise transmitted first, non-variable printing image of the forme cylinder 22 in the gap between the cylinders 12 and 32 under high pressure on the printing substrate 2. After passing through the pressure nip, the ink residues remaining on the peripheral surface of the transfer cylinder 32 are scraped off by a downstream doctor blade 8b and collected in a drip pan 8d.

Fig. 3 shows a printing unit for indirect gravure, which differs from the in Fig. 1 differs in that the generated by the wells of the gravure form of the gravure cylinder 21 non-variable print image and applied by the ink jet printing device on the color-free peripheral portion 4 additional variable print image from ink 7 is transferred via a transfer cylinder 33 to the current printing material web 2, the preferably has a soft peripheral surface. In this case, the non-variable print image and the additional variable printed image after their generation on the gravure cylinder 21 together through a total of two printing gaps before they reach the printing material, such as a moving paper web. This results in a further homogenization and equalization of the applied pixels for the two printed images. By a in Fig. 3 indicated further cleaning device 8e can be cleaned before a circulation change deposited on the transfer cylinder ink and ink residues. Alternatively, in the last-described embodiment of the invention, not the colorless portion 4 on the gravure cylinder 21 but the colorless portion 14 formed by it on the transfer cylinder 33 may be printed by the ink jet printing device 5, in which case the cleaning device 8e is in time with cylinder rotation of the transfer cylinder 33 is employed to these to remove the variable additional printed image.

LIST OF REFERENCE NUMBERS

2

printing material

4

colorless peripheral section

4 '

returned section in flexographic printing form

5

Inkjet printing apparatus

7

ink

8th

cleaning device

8a

Doctor on gravure cylinder

8b

Squeegee on transfer cylinder of Fexo printing unit

8d

squeegee tub

9

Flexographic printing form

11

Press cylinder of the Tiedruckwerks

12

Press cylinder of the flexographic printing unit

14

colorless section on transfer cylinder

21

Gravure cylinders

22

Form cylinder of the flexographic printing unit

25

Surface of the gravure cylinder

29

inking

32

Transfer cylinder of the flexographic printing unit

33

Transfer cylinder of the gravure printing unit

Claims (13)

1. Method for printing on a printing material (2) in a rotary printing press, the press comprising a first printing press cylinder (11, 12) contacting the printing material (2) in a printing nip and a second printing press cylinder (21, 22) transferring an image in a first color that has previously been applied to said cylinder (21, 22) onto the printing material (2), wherein an inkjet printing device (5) is provided to apply an additional variable image made of ink (7) to the printing material (2) and
   wherein the inkjet printing device (5) applies the additional image directly to an ink-free circumferential section (4) of the second printing press cylinder (21) that directly contacts the printing material (2) or of a transfer cylinder (32, 33) that transfers the image from the second printing press cylinder (21, 22) to the printing material (2)
   characterized in
   that a cleaning device (8) is provided to remove the additional image applied by the inkjet printing device (5) from the circumferential section (4) during an ongoing production print run on the rotary printing press in order to print a new additional image onto the non-printing circumferential section (4) that has been created in this way, allowing the variable image to be varied multiple times during an ongoing print job.
2. Method according to claim 1,
   characterized in
   that the first printing press cylinder is a counterpressure cylinder (11) and the second printing press cylinder is a gravure cylinder (21) having a plurality of ink-receiving depressions in a gravure unit, on which cylinder the ink-free circumferential section (4) is formed as an essentially planar depression-free section, wherein the cleaning device comprises a doctor blade (8a) contacting the surface of the gravure cylinder.
3. Method according to claim 1,
   characterized in
   that the first printing press cylinder is a counterpressure cylinder (12) and the second printing press cylinder is a printing forme cylinder (22) carrying a flexographic printing forme (9) in a flexographic printing unit, which forme cylinder transfers the image to a transfer cylinder (32) that contacts the printing material (2) and has a surface that is in particular chrome-plated, and on which printing forme cylinder the ink-free circumferential section (4) is formed by a recessed section (4') of the flexographic printing forme, wherein the cleaning device comprises a doctor blade (8b) contacting the surface of the transfer cylinder (32) and scraping off residues of the image and of the additional variable image from the surface of the transfer cylinder (32) after the transfer to the printing material.
4. Method according to claim 1,
   characterized in
   that the first printing press cylinder is a counterpressure cylinder (12) and the second printing press cylinder is a gravure cylinder (21) having a plurality of ink-receiving depressions in a gravure unit for an indirect gravure process, on which gravure cylinder the ink-free circumferential section (4) is formed as a closed, essentially planar depression-free section, wherein the inkjet printing device (5) applies the additional image directly to the ink-free circumferential section (4) of the gravure cylinder, which transfers the image and the additional image to the printing material (2) via a transfer cylinder (33), the method further characterized in that a doctor blade (8c) contacting the surface of the gravure cylinder is provided to scrape off the image and the additional image from the surface of the gravure cylinder (21) after the transfer to the printing material (2).
5. Method according to claim 4,
   characterized in
   that a further cleaning device (8e) is assigned to the transfer cylinder (33).
6. Method according to any one of the preceding claims,
   characterized in
   that the surface of the printing press cylinder (21) that carries the ink-free circumferential section (4) is treatable by a doctor blade.
7. Method according to claim 6,
   characterized in
   that the surface of the printing press cylinder (21) that carries the ink-free circumferential section (4) is made of a hard, wear-resistant material.
8. Method according to claim 7,
   characterized in
   that the surface of the printing press cylinder (21) consists of a ceramic or chrome.
9. Method according to any one of the preceding claims,
   characterized in
   that the ink applied to the ink-free section (4) by the inkjet printing device (5) is UV inkjet ink.
10. Method according to any one of the preceding claims,
    characterized in
    that the rotary printing press is a web-fed rotary printing press for printing on a web of printing material (2).
11. Assembly for printing on a printing material (2) in a rotary printing press for implementing the method of any one of the preceding claims, the press comprising a first printing press cylinder (11, 12) contacting the printing material (2) in a printing nip and a second printing press cylinder (21, 22) transferring an image in a first color that has previously been applied to said cylinder (21, 22) onto the printing material (2), wherein an inkjet printing device (5) is provided to apply an additional variable image made of ink (7) to the printing material (2) and
    wherein the inkjet printing device (5) is capable of applying the additional image directly to an ink-free circumferential section (4) of the second printing press cylinder (21) that directly contacts the printing material (2) or of a transfer cylinder (32, 33) that transfers the image from the second printing press cylinder (21, 22) to the printing material (2) characterized in
    that a cleaning device (8) is provided that is capable of removing the additional image applied by the inkjet printing device (5) from the ink-free circumferential section (4) during an ongoing production print run.
12. Assembly according to claim 11,
    wherein the rotary printing press is a web-fed rotary printing press capable of printing on a web of printing material (2), and wherein during an ongoing print job, the cleaning device (8) is capable of removing the image applied by the inkjet printing device (5) after every print.
13. Assembly according to claim 12,
    wherein the cleaning device comprises a doctor blade continuously or cyclically engaged with the surface of a cylinder of the printing press, the doctor blade capable of acting on either the entire printing region of the cylinder or only the region printed on by the inkjet printing device (5).

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