DE19750259B4 - Method and printing machine for multicolor printing of non-absorbent material - Google Patents

Abstract

Method for multicolor printing of sheet-like or plate-shaped substrates with a smooth, non-absorbent surface such as plastic, plastic or metal plates (1) or webs, in which
The printing material (1) is printed by the indirect flexographic printing process,
- Each ink to be printed own printing unit (3, 13, 23, 33) containing an inking unit (6), a cylinder (5) for a flexographic printing plate (12), a transfer cylinder (7) and a counter-pressure cylinder (8), assigned .
- The color is always dried on the substrate before it is fed to the next printing unit and
- In the wells and on the flanks of the surfaces to be printed the printing plate (12) located color residues (12a) either before each re-inking of the printing plate (12) is applied as a thin film on the printing areas again, or
- The printing plate (12) is repeatedly cleaned several times during a current print job.

Description

The The invention relates to a method for multicolor printing of web-like or arched or plate-shaped Substrates with a smooth, non-absorbent surface such as For example, plastic or metal plates, films or plastic-coated Papers.

such Materials can only with restrictions be printed in conventional wet offset. While it would be possible to use these materials to print in the waterless offset method. The silicone surface of the Dry offset plates (Toray plates), however, is only partially resistant across from the required UV colors. The service life of the plates is through reduces the UV colors. The sensitivity of the silicone layer waterless offset plates is inconsistent with the required UV inks and the drying process or the anchoring of the colors on the surface of the plastic material.

at a multi-color print wet on wet can be on the other hand on plastic material and with UV inks do not achieve a particularly high print quality.

Therefore The above materials are usually used today Flexographic printing z. T. also printed with colors that over UV lamps Cured immediately after the printing process. That's the way it is, for example from the book "Technik of flexo printing ", published in 1982 by the DFTA Flexoprint Specialist Group e. V. known, cylindrical containers such as cans, tubes, etc. multicolored with UV-curable inks in flexographic printing to print. The machine described on page 12.8 has it several printing units, between which UV lamps are arranged, and should also be able to work in indirect high pressure, i. H. the Letterset method to print. However, such machines are very expensive custom-made, only for large print jobs and more Calculate machine utilization.

Furthermore here are the print quality, due to the application of high pressure procedures, limits. There is a problem An example of this is that printing ink builds up on the flexographic printing plate or accumulates in the recesses of the flexographic printing plate, so that it isolated to a color transfer the non-printing areas of the flexographic printing plate comes.

From the DE 15 71 863 C3 A simple direct high-pressure method is known in which the residual color film left over after printing is removed completely before each new coloration of the printing form. Here, the restliehe color film is removed via Farbabführwalzen of the printing plate and fed back to the ink supply. The problems with multi-color printing especially on non-absorbent surfaces is not discussed in the text.

in the Canadian Patent 1 251 688 A describes a lithographic offset printing machine with short inking unit and dampening unit, in which excess ink is scraped off the wet offset plate.

It the object of the present invention is to provide a method with the sheet or plate-shaped Substrates with non-absorbent surface are easy and cost-effective high quality can be printed in multiple colors, and one for that to create suitable printing press.

These Task is with the features specified in claims 1 and 8 respectively solved.

• – der Bedruckstoff (1) im indirekten Flexodruckverfahren bedruckt wird,
• – jeder zu druckenden Farbe ein eigenes Druckwerk (3, 13, 23, 33) enthaltend ein Farbwerk (6), einen Zylinder (5) für eine Fiexodruckform (12), einen Übertragungszylinder (7) und einen Gegendruckzylinder (8), zugeordnet ist,
• – die Farbe auf dem Bedruckstoff stets vor dessen Zuführung zum nächsten Druckwerk getrocknet wird und
• – in den Vertiefungen und an den Flanken der zu druckenden Flächen der Druckform (12) befindliche Farbe entweder vor jedem Neueinfärben der Druckform (12) als dünner Film wieder aufgetragen wird, oder
• – die Druckform während eines laufenden Druckauftrags mehrfach vollständig gereinigt wird.

The new method is distinguished by the fact that

• - the substrate ( 1 ) is printed by the indirect flexographic printing process,
• - each color to be printed has its own printing unit ( 3 . 13 . 23 . 33 ) containing an inking unit ( 6 ), a cylinder ( 5 ) for a Fiexodruckform ( 12 ), a transfer cylinder ( 7 ) and an impression cylinder ( 8th ), assigned,
• - The color is always dried on the substrate before it is fed to the next printing unit and
• In the depressions and at the flanks of the surfaces of the printing form to be printed ( 12 ), either before each recoloring of the printing form ( 12 ) is reapplied as a thin film, or
• - The printing form is repeatedly cleaned several times during a running print job.

In this way, for example, plate-shaped plastic material as it is used, inter alia, for check cards, phone cards, smart cards, print with a hitherto considered impossible quality quickly and inexpensively, reasonably, because the required for carrying out the process printing press by modifying put together for the wet offset built in larger numbers printing units. For this, among other things, only the penetration depth of the plate cylinder of typically 0.3 to 0.5 mm to 1-2 mm to change so that instead of the wet offset plates, the stronger flexographic printing plates can be clamped. Instead of the otherwise existing dampening unit then a device for removing paint from the wells or from the flanks of the printing surfaces of the flexographic printing plate is installed, either a washing device or a roller with soft, ink-absorbing surface, which is installed instead of the otherwise existing dampening roller. Finally, with the use of UV-curable inks, corresponding drying units, ie correspondingly powerfully dimensioned UV lamps, can be installed in the printing unit.

By the elimination of dampening a quick stability of the printing process is achieved and the startup waste drastically reduced, resulting in expensive plastic materials leads to a significant cost saving and quality improvement.

The In contrast, the inking unit can be retained by a short inking unit or by an anilox roller cooperating with a chamber doctor blade be replaced.

Corresponding the particular pressure requirement may be appropriate the flexographic printing form during a running print job multiple times at shorter or longer intervals to clean or even before each recoloring, to always reproducible conditions for each To ensure impression. It is therefore advantageous for this purpose a corresponding control provide, in which the cleaning intervals are entered. Because that way see them for the execution needed a print job Optimize time to the required print quality.

Especially then when the ink residue is removed before each recoloring the printing form it is appropriate to do this to do with a soft roller, in constant contact the flexographic printing is applied and excess paint residues removed from the printing form and after subsequent trituration by a second roller as a thin, even film reapplies.

Further advantages of the invention will become apparent from the following description of exemplary embodiments with reference to FIG 1 and 5 the attached drawings,

1 is a highly simplified schematic representation of a suitable for carrying out the method according to the invention printing machine,

2 shows a printing unit of the machine 1 in a slightly modified version on an enlarged scale,

3 is an enlarged schematic representation of the cleaning device for the flexographic printing plate in the printing unit after 2 .

4 u. 5 are again enlarged representations of the in the 3 correspondingly designated contact points between the rollers 20 and 21 or the roller 20 and the flexographic printing plate.

In the 1 is with 1 denotes the plate-shaped plastic material to be printed. It consists of a 0.8 mm thick polyethylene plate in the dimensions 31 cm × 61 cm, from which after the printing process later 30 telephone cards are to be punched out. In the same way described below, however, can also print substrates made of other material, such as polypropylene, polyamides, polyester, films of Hostaphan and aluminum-coated substrates print.

The plates 1 are in a feeder 2 stacked up and are from there in a known manner the first of the present case 4 fed successively arranged printing units in a row construction. The four printing units 3 . 13 . 23 and 33 are all the same structure and differ only with respect to the color printed with them. Each printing unit has a printing plate cylinder 5 , on which an aluminum-lined 1.16 millimeter flexo printing plate is mounted. Because the printing unit 3 a rebuilt wet offset printing unit is on the plate cylinder 5 So usually 0.3 mm thick offset printing plates are clamped, is the groove of the cylinder 5 according to the thickness difference, taking into account any documents used has been enlarged.

The printing plate or plate cylinder 5 is an existing inking unit that is also suitable for printing wet offset inks 6 assigned. Such an inking unit is for example in the U.S. Patent 5,388,514 and allows 2 modes of operation, as a long inking unit or as a short inking unit, depending on the type of job you want to print. However, for the covers of the ink rollers, a quality is selected which makes it possible to print UV inks. The rollers are therefore predominantly coated with polyurethane. Suitably, a soft polyurethane coating in a thickness of 6-10 mm, wherein the polyurethane has a Shore A hardness of about 35.

Printed comes with UV flexo inks. These colors have a viscosity between 20 to 30 dp in the bright colors and therefore lie with respect to their flowability close to the usual range of today's flexo inks. Your opposite solvent-containing and / or watercolors slightly higher viscosity and the higher Ensure tack a uniform, thin color transfer and a much lower dot gain. That is why the Use of very finely cliched clichés possible and a consistent Print quality over the production time guaranteed. The paints contain epoxy resins and are cured by UV radiation.

The printing unit 3 also has a transfer or blanket cylinder 7 which decreases the printed image from the flexographic printing plate. The transfer cylinder 7 assigned is an impression cylinder 8th with double cylinder diameter, which ensures that the rigid plates 1 Do not deform excessively when passing through the press. This is also the triple-size transfer cylinder 9 from which the printed plates 1 to the next printing unit 13 be handed over.

Immediately after printing in one of the four printing units 3 . 13 . 23 . 33 is the printed color of built-in the printing units UV drying units 11 hardened. These are UV medium-pressure mercury lamps with an output of approx. 150 watts per linear centimeter. The UV emitters 11 contain quartz-coated aluminum reflectors that reflect the required for the curing UV portion of the spectrum as a whole, but eliminate the infrared part on the type of cold light mirrors and thus ensure a high UV radiation density with minimal heat stress on the substrate.

Instead of the otherwise in the printing unit 3 located dampening unit is on the plate cylinder 5 a washing device 10 grown. This washing device is connected to a controller 34 connected via an input unit 35 the wash intervals are accessible, to which the on the plate cylinder 5 spanned flexographic printing plate is repeatedly cleaned during a running print job to prevent the color builds up on the flexographic printing plate or in the recesses or on the flanks between the printing raised areas of the flexographic printing plate.

When printing the plastic plates 1 so these are in the four printing units 3 . 13 . 23 and 33 printed successively in the colors black, cyan and magenta and yellow in the indirect flexographic printing process and the colors are dried immediately after each printing stage. At the same time, in short intervals of, for example, 4000 revolutions of the plate cylinder 5 the washing device 10 activated and the flexographic printing form cleaned of excess color.

The finished printed and dry plates are then as usual in the boom 4 the printing machine piled up.

That in the 2 to 5 enlarged illustrated printing unit 3 is opposite to the after 1 something modified. Otherwise, however, the remaining parts are provided with the same reference numerals and therefore need not be explained again at this point.

The printing unit 13 contains as now from the enlarged view can be seen, in addition, a washing device 17 , with the help of which on the transfer cylinder 7 clamped blanket and the impression cylinder 8th can be cleaned.

Instead of the conventional, for the wet offset optimized inking unit 6 is used to color the flexographic printing plate 12 an anilox roller 16 with a chambered scraper 26 used. Such inking on the basis of anilox roller / chamber doctor blade are known per se and therefore need not be described here.

Instead of the dampening unit are where normally the dampening roller and the Verreibewalze are arranged for dampening, a roller 20 with a soft surface made of synthetic rubber or polyurethane and an adjoining, driven and laterally iridescent rubbing roller 21 built in with hard ink accepting surface. The rollers 20 and 21 Run constantly with the roller 20 excess paint residues 12a , which form during printing on the flanks of the printing surfaces of the flexographic printing form, from the wells of the flexographic printing plate 12 removes and this after trituration by the roller 21 ( 4 ) again as a thin color film ( 12b ) on the printing areas of the flexographic printing plate 12 orders ( 5 ). To the roller 21 can also be a squeegee 22 turn on with the help of an actuator 32 to the controller 34 connected. In this way, the raised areas of the flexographic printing plates and the rollers can be 20 and 21 clean by changing the color of the synthetic rubber or polyurethane-based roller 20 requested and to the roller 21 is transferred, from the surface of which the squeegee 22 away.

1

Plastic plate (Substrate)

2

investor

3

printing unit

4

boom

5

Printing forme (plate) cylinder

6

inking

7

Transmission (blanket) cylinder

8th

Impression cylinder

9

transfer cylinder

10

Plate washer

11

UV dryer

12

flexographic printing

12a

paint residues

12b

color film

13

Second printing unit

16

anilox roller

17

Blanket wash

20

soft roller

21

hardness roller

22

doctor

23

Third printing unit

26

chambered doctor blade

32

actuator

33

4th printing unit

34

control device

35

input unit

Claims (14)

Method for multicolor printing of web-shaped or plate-shaped substrates with a smooth, non-absorbent surface such as plastic, plastic or metal plates ( 1 ) or webs, in which - the printing substrate ( 1 ) is printed in the indirect flexographic printing process, - a separate printing unit for each color to be printed ( 3 . 13 . 23 . 33 ) containing an inking unit ( 6 ), a cylinder ( 5 ) for a flexographic printing plate ( 12 ), a transfer cylinder ( 7 ) and an impression cylinder ( 8th ), - the ink is always dried on the printing material before it is fed to the next printing unit, and - in the depressions and on the flanks of the surfaces of the printing form to be printed ( 12 ) color residues ( 12a ) either before each recoloring of the printing form ( 12 ) is applied as a thin film to the printing areas, or - the printing form ( 12 ) is repeatedly cleaned several times during a running print job. The method of claim 1, wherein with UV-curable Colors are printed and the substrate behind each printing unit is irradiated with UV light. Method according to one of claims 1 to 2, wherein a metal-clad flexographic printing plate ( 12 ) is used as a printing plate. Method according to one of claims 1 to 3, wherein the color by a conventional Offset inking is applied. Method according to one of claims 1 to 3, wherein the color is applied to the printing form by a short inking unit. Method according to one of claims 1 to 3, wherein the paint by a with a chambered doctor blade ( 26 ) co-operating anilox roller ( 16 ) ( 16 ) is applied to the printing form. Method according to one of claims 1 to 6, wherein the printing form ( 12 ) during the printing process in permanent contact with a soft roller ( 20 ) stands. Printing machine for multi-color printing of web-shaped or plate-shaped substrates with a smooth, non-absorbent surface, such as plastic, plastic or metal plates ( 1 ) or webs, with - a plurality of individual printing units each assigned to one color ( 3 . 13 . 23 . 33 ), which are arranged in a row construction and at least one inking unit ( 6 ), a cylinder ( 5 ) for a flexographic printing plate ( 12 ), a transfer cylinder ( 7 ) and an impression cylinder ( 8th ), - several, each a printing unit associated drying devices ( 11 ) for the printing ink, - several, the flexographic printing plates ( 12 ) associated devices ( 10 ) for removing paint residues ( 12a ) from the recesses and from the flanks of the surfaces to be printed of the relevant flexographic printing plate ( 12 ), whereby the devices are either permanently colored ( 12a ) from the wells and from the flanks and as a thin film ( 12b ) on the print areas or repeatedly during a print job the color residues ( 12a ) completely remove from the wells and flanks. Printing machine according to claim 8, characterized by a device for removing paint residues ( 12a ) connected control ( 34 ), the cleaning intervals are entered. Printing machine according to one of claims 8 to 9, wherein the drying device ( 11 ) UV lamp contains. Printing machine according to one of claims 8 to 10, in the form of a converted wet offset printing machine, in which the puncture of the printing form cylinder ( 5 ) for receiving the flexographic printing plate ( 12 ) is increased to a value between 1 and 2 mm and in the place of the dampening units in the individual printing units in each case a device ( 10 ) for removing paint residues ( 12a ) from the depressions of the flanks of the flexographic printing plate ( 12 ) is installed. Printing machine according to claim 11, wherein the device for removing the ink residues ( 12a ) a washing device ( 10 ). Printing machine according to claim 12, wherein the device ( 10 ) for removing the paint residues ( 12a ) a roller installed in place of the dampening roller ( 20 ) with a soft, ink-accepting surface. Printing machine according to one of claims 8 to 13, wherein the impression cylinders ( 8th ) in each printing unit and the transfer cylinders ( 9 ) between the printing units at least twice the diameter as the printing forme and transfer cylinders ( 5 . 7 ).