EP1034078A2

EP1034078A2 - Electrostatic arrangement for rotogravure and flexographic printing

Info

Publication number: EP1034078A2
Application number: EP97913072A
Authority: EP
Inventors: Alfred Doppler
Original assignee: Spengler Electronic AG
Current assignee: Spengler Electronic AG
Priority date: 1997-11-27
Filing date: 1997-11-27
Publication date: 2000-09-13
Anticipated expiration: 2017-11-27
Also published as: WO1998003049A3; AU5046098A; ES2173430T3; ES2173430T5; ATE213997T1; WO1998003049A2; US20030066443A1; DE59706583D1; EP1034078B1; EP1034078B2; US6578478B2

Abstract

The electrostatic printing aid for gravure and flexographic printing machines can be operated with a voltage electrode whose dimensions have been reduced significantly, the print quality being kept at a high level. The voltage electrode, connected to a high voltage source, can be constructed with a bar-like or arc-like shape and to be non-contacting, or as a slip ring or as an electrically conductive brush. The voltage electrode is preferably arranged at one end of the three-layer impression roller of a gravure printing unit or the three-layer printing plate cylinder of a flexographic printing unit. The particular advantages of the arrangement reside in the significantly improved ease of servicing and the saving in costs, as early as at the time of purchase, in particular in the event of retrofitting printing machines already in operation.

Description

Electrostatic arrangement for a gravure and flexographic printing unit

FIELD OF APPLICATION OF THE INVENTION The present invention relates to an arrangement for transferring an electrostatic charge within a gravure and flexographic printing unit to improve the print quality by polarizing the ink drops on the printing form cylinder. In the gravure printing unit, the electrostatic charge is applied to the outer jacket of a press, from which it flows to the outer jacket of the printing form cylinder. In the flexographic printing unit, the electrostatic charge is applied to the printing form cylinder, from which it flows both to the substrate transfer roller and to the impression cylinder. Under the influence of an applied electric field, the color molecules located in the wells of the printing form cylinder (gravure printing) or on the surface of the printing form cylinder (flexographic printing) are polarized, and the color droplets experience an overall increase in volume. A flowing electrical current is absorbed in order to supply the energy necessary for the polarization work. As a result of the polarization, the ink droplets are attracted to the printing material and, moreover, the transfer of the ink droplets is promoted by their volume enlargement onto the printing material carried past.

In gravure printing it is thus ensured to a much greater extent that the wells of the printing form cylinder are emptied properly, ie the printing ink on the printing Fabric is applied. In flexσ printing, the electrostatic charge causes the printing ink to be transferred better from the substrate transfer roller to the printing form cylinder and to the printing material. Such arrangements are also referred to as "electrostatic printing aids"; they serve to achieve a full top view density in all tone levels and to avoid so-called "issing dots". The problem of "missing dots" occurs particularly with rough substrates, for example paper webs, with corresponding unevenness.

State of the art

Electrostatic printing aids of the type relevant here have been known for decades (see, for example, DE-A-27 09 254; EP-A-0 761 458). FIGS. 1A and ID in connection with FIG. IC show a two-roll system of a gravure printing unit with a multi-layer impression roller 1 - but here already three layers according to the invention -, the printing form cylinder 2 and the printing material 4 guided between the two over the deflection roller 3. A rod-shaped voltage electrode 5 is arranged over the impression roller 1 and extends over its entire length. The ink squeegee 6 is indicated for stripping excess ink from the printing form cylinder 2. The inking roller and the return, which are not shown, are seated in an ink trough 7. The voltage electrode 5 is connected to a high voltage source 8. The outer surface of the three-layer impression roller 1 has a semiconductor layer 10 and a high-conductor layer 11 underneath. Below the high conductor layer 11, as electrical insulation to the impression core 13, there is an insulator layer 12. FIG. 1B shows a three-roller system which, in deviation from the two-roller system described above, has an additionally arranged support roller 9 above the multilayer impression roller 1, which is preferably electrically insulated. The voltage electrode 5 is positioned here on the side of the multilayer impression 1.

FIG. 1E with the electrical circuit diagram of the two- or three-roller system according to FIGS. 1A to ID illustrates the current flow within the electrostatic arrangements. A direct voltage U is supplied to the voltage electrode 5 from the high voltage source 8 and the voltage electrode 5 has the internal resistance R _x . The air gap S existing between the voltage electrode 5 and impression roller 1 - usually in the size of approximately 5 mm to 30 mm - represents the resistor R _2. The upper semiconductor layer 10 and the high conductor layer 11 form the resistors R ₃ , R ₄ . The grounded insulator layer 12 acts as an oversized resistor R ₅ . From the high-conductor layer 11, the current flows through the semiconductor layer 10 lying below, which here forms the resistor R ₆ , further through the printing material 4, which represents the resistor R ₇ . The grounded printing form cylinder 2 has practically the resistance value R ₈ = 0.

According to Kirchhoff's current distribution law, the major part of the electrical current takes the path of lower resistance via the high-conductor layer 11, while a small fraction flows directly to the printing material 4 via the semiconductor layer 10. After all, lies between the lower semiconductor layer 10 and the earth E a voltage drop ΔU, which represents the so-called nip voltage, which is decisive for the polarization of the ink droplets in the wells of the printing form cylinder 2. The current I flows from the voltage electrode 5 to the earth connection E.

In order to apply the ink droplets from the cells as completely and evenly as possible to the entire width of the substrate - the web widths can exceed 3m today - sufficient energy must be supplied and the current flow must be distributed evenly over the entire width of the press. In order to meet this requirement, the length of the voltage electrode has hitherto been based on the maximum usable width of the printing form cylinder or impression roller, so that a homogeneous charge distribution in the pressure area is guaranteed on the latter (see DE-A-27 09 254, p. 11, Lines 21ff .; OLLECH, Bernd: Gravure printing - Basics and procedural steps of modern gravure printing technology, Polygraph Verlag Frankfurt am Main, 2nd edition 1993, p. 343, Fig. 15.49; company documents of Eltex-Elektrostatik GmbH, Weil am Rhein / DE, "ESA-DIREKT - A new dimension of electrostatic pressure aid", print no .: WP-d / e / f -9043 - 90 / 7-20, Fig. 17; and "eltex - Handbuch der Elektrostati- see discipline", Print no .: Üp-d-0002-93 / 12-100, p. 32,

Pressure support, Fig. Top right). Consequently, voltage electrodes over 3m in length are used. With such voltage electrodes, good printing qualities are achieved. The disadvantage, however, is the relatively rapid contamination of the open voltage electrodes, which leads to significant losses in their effectiveness and ultimately to complete failure leads, so that the print quality deteriorates rapidly.

In order to maintain the function of the electrostatic arrangements equipped in this way, a contaminated voltage electrode must be removed, cleaned and reinstalled. This is personnel-intensive, leads to lossy machine downtimes and is therefore often postponed so as not to endanger upcoming delivery times for the printed products.

To eliminate the disadvantages mentioned, electrostatic pressure aids were subsequently developed, where instead of using a long, attached stick electrode, the current was introduced into the rotating shaft of the impression roller (see e.g. DE-A-28 10 452). Now the problem of a voluminous voltage electrode was eliminated and the service was made easier, but the need for frequent cleaning remains; in addition, however, there was increased effort in isolating the impression core from the printing press.

Encapsulated electrostatic pressure aids were developed in the further development, where the current is introduced via the press core and are largely protected against contamination, so that there is practically no maintenance (see, for example, EP-A-0 115 611; company lettering of Spengler Electronic AG, Biel-Benken / CH: Electrostatic pressure aid, SR-HELIOFURN 94). These state-of-the-art printing aids to date cause a relatively high mechanical outlay, which is the case with new printing presses from the beginning equipped with it is still acceptable. However, when retrofitting older printing presses in operation with encapsulated printing aids and introducing the current into the impression core, the retrofitting effort would increase enormously, so that the earlier printing aids with long, rod-shaped voltage electrodes continue to be used for this (see, for example, recently the company name of SHINKO Co. , Ltd., Osaka / JP: ESAPRINT 21, ELECTROSTATIC ASSIST SYSTEM; print no .: 97043000).

Object of the invention

In view of the continuing disadvantages of the electrostatic printing aids which existed hitherto, the object of the invention is to create an arrangement where a contaminated voltage electrode can be quickly removed, cleaned and reinstalled by a person. Or you should be able to quickly replace the soiled voltage electrode with a clean electrode in order to clean the soiled electrode externally. Service costs and machine downtimes have to be reduced significantly. The arrangement should make do with electrodes as small as possible, in particular be suitable for retrofitting printing machines and the initial procurement costs must be kept low. However, there are still high requirements for print quality.

WPSPΠ invention

The entire world of experts previously assumed that the latest literature and products show that when power is introduced via the outer surface of the impression roller (gravure printing) or the printing form cylinder (flexographic printing) for a homogeneous layer distribution in the pressure area, the use of a voltage electrode, which extends as far as possible over the entire length of the impression cylinder or printing form cylinder, is essential. Surprisingly, it has now been found that when using a voltage electrode that is shorter than 50% of the length of the impression cylinder or the printing forme cylinder, and simultaneously using a three-layer impression cylinder (gravure printing) or a three-layer impression cylinder (flexographic printing) Print quality can be achieved, as previously only with voltage electrodes, at least in almost full length. The voltage electrode is positioned at a gap from the outer surface of the impression cylinder or the printing form cylinder and can be shortened to approx. 1% of the previous full length depending on the high voltage applied and the associated safety factors.

As alternatives to the rod-shaped voltage electrode, one found those which arch the outer surface of the impression cylinder or the printing forme cylinder at a gap distance. The same quality results can be achieved with a voltage electrode in the form of a slip ring or a brush that is in contact with the outer semiconductor layer of the impression cylinder or the printing forme cylinder and its length extension is also reduced to approx. 1% of the length of the impression cylinder or the printing plate cylinder are. The homogeneous charge distribution over the entire pressure range is achieved by using the relatively low-resistance high-conductor layer of the impression cylinder or the printing form cylinder in the axial direction and the high-resistance semiconductor layer on the other hand in the radial direction. To increase security, frontal insulation of the impression cylinder or the printing form cylinder against its cores is provided by applying an insulation coating which extends at least from the high-conductor layer into the adjacent regions of the semiconductor layer above and the insulator layer below. The insulation can also be achieved by shortening the high-conductor layer on the end face while filling the free space created by the shortening with the semiconductor or insulator layer.

Brief description of the attached drawings

Show it:

FIG. 1A: a two-roll system of a gravure printing unit with printing form cylinder, impression roller and voltage electrode arranged thereon as a basic illustration;

Figure 1B: a three-roll system of a gravure printing unit with printing form cylinder, support roller and impression roller with a voltage electrode arranged thereon; Figure IC: a two-roll system of a gravure printing unit with a rod-shaped voltage electrode according to the prior art as a perspective view,

Figure ID: the system according to Figure IC viewed in vertical section; Figure 1E: the electrical diagram of the system according to Figures 1A to ID;

Figure 2A: a three-layer impression roller in the perspective view with continuous layers according to the prior art; FIG. 2B: the three-layer impression roller according to FIG. 2A in axial vertical section;

FIG. 2C: the three-layer impression roller according to FIG. 2A with a front-side insulation coating according to the prior art;

FIG. 2D: the three-layer impression roller according to FIG. 2A with an insulation layer according to the prior art drawn up on the end face;

FIG. 2E: the three-layer impression roller with the high-conductor layer set back on the face according to the prior art;

FIG. 2F: a three-layer impression roller with a laterally open high-conductor layer as a perspective view;

FIG. 2G: the three-layer impression roller according to FIG. 2F in an axial vertical section;

FIG. 3A: an elongated voltage electrode as a perspective illustration according to the prior art;

FIG. 3B: the electrical circuit diagram of the voltage electrode according to FIG. 3A;

Figure 3C: an elongated voltage electrode with several rows of emission needles as a perspective view;

Figure 3D: a voltage electrode with a multi-row, square field of emission needles as a perspective view;

FIG. 3E: a cylindrical voltage electrode with a plurality of emission needles distributed over a circular area as a perspective illustration;

Figure 4A: an embodiment of the electrostatic arrangement according to the invention for a gravure printing unit with Elongated voltage electrode arranged on top of the impression roller as a perspective view; FIG. 4B: the arrangement according to FIG. A viewed in cross section; FIG. 4C: the arrangement according to FIG. 4A with a voltage electrode that can be positioned variably;

FIG. 5A: a further embodiment of the electrostatic arrangement according to the invention for a gravure printing unit with a impression roller and an arcuate voltage electrode attached to it as a perspective view;

Figure 5B: the semicircular voltage electrode according to

FIG. 5A shows a perspective view,

FIG. 6: a further embodiment of the electrostatic arrangement according to the invention for a gravure printing unit with a impression roller, voltage electrode attached to it in the form of a slip ring or a brush and a printing form cylinder viewed in axial vertical section;

FIG. 7A: the electrostatic arrangement according to the invention for a flexographic printing unit with an elongated tension electrode arranged on top of the three-layer printing form cylinder, the impression cylinder and the substrate transfer roller as a perspective view; FIG. 7B: the arrangement according to FIG. 7A with variably positionable voltage electrode and a scoop roller as a basic illustration; FIG. 7C: the arrangement according to FIG. 7A with a variably positionable voltage electrode and a substrate transfer roller as a basic illustration; and FIG. 7D: the arrangement according to FIG. 7A with a variably positionable voltage electrode and a substrate transfer roller with a doctor blade as a basic illustration.

embodiments

The detailed description of preferred exemplary embodiments of the arrangement according to the invention is given below with reference to the accompanying drawings. Finally, possible modifications are mentioned.

The following definition applies to the entire further description. If reference numerals are included in a figure for the sake of clarity in the drawing, but are not explained in the directly associated description text, reference is made to their mention in the preceding description of the figures. In the interest of clarity, the repeated designation of components in the following figures is mostly dispensed with, provided that it can be clearly seen in the drawing that these are "recurring" components.

Figures 2A and 2B

The three-layer impression roller 1 has a jacket over the impression roller core 13, the outer surface of which consists of a semiconductor layer 10, an underneath high-conductor layer 11 and an underlying layer which adjoins the impression roller core 13, Insulator layer 12 is made. All three layers 10, 11, 12 extend to the end faces of the impression roller 1, so that an electrical short circuit can occur in particular when they are soiled, for example by color residues. To prevent this, various isolating measures are taken. The high-conductor layer 11 is preferably of large volume and is, for example, at least 1/3 of the thickness of the semiconductor layer 10.

Figure 2C

For insulation purposes, the high-conductor layer and the insulator layer 11, 12 are each provided with an insulation coating 14 on the end face into the adjoining regions of the outer semiconductor layer 10 and the inner roller core 13.

Figure 2D

The front insulation is here a shortening of the high-conductor and semiconductor layers 11, 10 set back on both sides and filling of the space created by the shortening with the overlapping insulator layer 12 drawn up to the outer surface of the semiconductor layer 10 and covering the cut edges of both shortened layers 11 , 10 surrounds, reached.

Figure 2E

In a modification to the embodiment according to FIG. 2D, only the high-conductor layer 11 is shortened on the face side, and the space is filled with the semiconductor layer 10, which is quasi pulled down onto the insulator layer 12 and overlaps the cut edges of the high-conductor layer 11. Figures 2F and 2G

In the modification of the three-layer impression roller 1 shown, the external semiconductor layer 10 is shortened from the left end side, so that an annular surface 110 of the high-conductor layer 11 lying under the semiconductor layer 10 is exposed. As a safety precaution, an insulator coating 14 can also be provided on this end face, which covers the high-conductor layer 11 and the underlying insulator layer 12 and extends to the edge area of the adjacent impression core 13. The exposed ring surface 110 allows a voltage electrode 5a, 5b, 5c to be attached to it (see the further figures). A voltage electrode 5d with direct electrical contact, ie a brush or a slip ring, is primarily considered for this.

Figures 3A and 3B

The structure of the rod-shaped voltage electrode 5, which is provided as an inductor electrode for contactless attachment to the impression roller 1, is known per se. In an elongate insulation body 50, emission needles 51 are systematically arranged in series, for example at a distance from one another. A protective resistor 52 is connected behind each emission needle 51. Emission needles 51 and protective resistors 52 are advantageously positioned on a printed circuit board which is inserted into the insulating body 50 and is cast, for example, with synthetic resin. The connection contact of the voltage electrode 5 is connected to the high voltage source 8, so that the voltage U is present. Figure 3C

This likewise rod-shaped voltage electrode 5a differs from the embodiment according to FIG. 3A only in that three axially extending rows of emission needles 51 are now provided instead of a row of emission pins 51. This allows the overall length of the voltage electrode 5a to be further shortened and / or the required high voltage U to be reduced.

Figure 3D

With a corresponding high voltage U and other adequate machine parameters, the number of emission needles 51 can be further reduced for a voltage electrode 5a - here arranged in an approximately square field - and thus the size of the voltage electrode 5a can be further reduced.

Figure 3E

In this voltage electrode 5b, the emission needles 51 are arranged within a circular area and the insulation body 50 has a cylindrical shape.

Figures 4A to 4C

In this embodiment, as a contactless inductor electrode, the rod-shaped voltage electrode 5a, which is reduced in length, for example to 1/6 the length of the three-layer impression 1, is placed in a gravure printing unit on an impression 1 with a gap distance S. One preferably chooses one end of the impression roller 1 for the placement of the voltage electrode 5a, in order thus to facilitate lateral access for service work. Depending on the structure, the Gravure printing machine, the voltage electrode 5a can be arranged in all positions in a semicircle around the impression roller 1 over the running web of the printing material 4.

Under special conditions, the arrangement of the voltage electrode 5a below the printing substrate 4 and directed towards the semiconductor layer 11 of the impression roller 1 is also conceivable. The printing material 4, e.g. damp paper, then acts as a conductor. The voltage electrode 5a is connected to the high-voltage source 8, so that a current flows from the voltage electrode 5a through the impression cylinder 1 and the polarization of the color molecules in the cells of the printing form cylinder 2 occurs. For example, the high voltage applied is up to 30 kV DC, and the air gap S is set at 5 mm to 15 mm.

When used with the arrangement according to the invention, all common types and types of paper, plastic films, textiles and coated or laminated metal foils with insulating varnish are suitable as printing materials 4.

All ink systems that can be used on gravure printing machines, such as inks based on toluene, alcohol or ethyl acetate, as well as water colors, can be used for packaging and illustration printing.

Figures 5A and 5B

In this embodiment, also as a contactless inductor electrode, the voltage electrode 5c has a half-shell shape and surrounds the three-layer impression roller 1 with a gap spacing S. For example, the voltage electrode 5c extends with its insulation body 50 in an arc over 180 °, a row of emission needles 51 being provided therein. Here too, for the purpose of easier access for service work, the voltage electrode 5c will be arranged at least near one end of the impression roller 1. In this example, the length corresponds to the arcuate

Voltage electrode 5c approximately half the outer circumference of the impression roller 1, if the necessary increase due to the gap distance S is disregarded.

Figure 6

This embodiment of the voltage electrode 5d is designed as a slip ring or an electrically conductive brush. The slip ring or brush ends are in direct contact with the semiconductor layer 10 of the rotating impression roller 1. An air gap S is of course omitted here. The preferred positioning of the voltage electrode 5d is again at least near one end of the impression roller 1. The voltage electrode 5d is also connected to the high-voltage source 8, so that a current flow from the tension electrode 5d - not contactless here - through the impression roller 1 and the polarization of the color molecules causes in the well of the printing form cylinder 2.

FIGS. 7A and 7B The flexographic printing unit has the three-layer printing form cylinder 20, the substrate transfer roller 30 (also called inking roller or anilox roller) arranged underneath and the impression cylinder 40 (also called pressing roller) lying at the level of the three-layer printing form cylinder 20. The web of printing material 4 runs between the three-layer printing form cylinder 20 and the impression cylinder 40. A shortened rod-shaped voltage electrode 5a is placed on top of the three-layer printing form cylinder 20 with a gap distance S, which acts as a contactless inductor electrode and has, for example, approximately 1/6 the length of the three-layer printing forme 20. The voltage electrode 5a is preferably seated at one end of the three-layer printing form cylinder 20, in order thus to facilitate lateral access for service work.

The printing ink is fed to the substrate transfer roller 30 from a scoop roller 60, which is immersed in the ink tank 7. Depending on the structure of the flexographic printing press, the voltage electrode 5a can advantageously be variably arranged in all positions in a semicircle around the three-layer printing form cylinder 20 in the two free spaces between the substrate transfer roller 30 and the impression cylinder 40.

The three-layer printing form cylinder 20 has on the outside the cliché 24 made of semiconductor material, underneath there is a high-conductor layer 21 and an insulator layer 22 underneath the latter. The insulator layer 22 sits on the inner cylinder core 23. The voltage electrode 5a is connected to the high-voltage source 8; thus a current flows from the three-layer printing form cylinder 20 to the substrate transfer roller 30 on the one hand and to the impression cylinder 40 on the other hand. The electrostatic charging causes the ink particles to move better from the substrate transfer roller 30 onto the three-layer printing form cylinder 20, ie its plate 24 and ultimately be transferred to printing material 4. Figure 7C

In this flexographic printing unit there is no scoop roller 60, but the substrate transfer roller 30 itself is seated in the ink tray 7 and a doctor blade 6 is provided for stripping off excess printing ink.

Figure 7D

State-of-the-art flexographic printing units also dispense with a scoop roller 60. Here, the printing ink is sprayed onto the substrate transfer roller 30 with a squeegee 6a; Excess ink sucks off the squeegee 6a.

Thanks to the invention, an electrostatic arrangement is now available as a printing aid for gravure and flexographic printing units, which considerably simplifies service work, in particular cleaning. Special advantages arise in the accessibility of service work due to the reduced dimensions compared to the voltage electrodes used previously, especially when the voltage electrode is arranged in an end region of the impression cylinder or printing form cylinder. As a result of the smaller field expansion, deposits on machine parts of undesirably charged particles, namely ink mist and abrasion from the printing material, are reduced. The arrangement according to the invention brings significant cost advantages due to the easier assembly and the lower material expenditure. There are no losses in the homogeneity of the polarization across the entire printing width. The arrangement for retrofitting printing presses that are already in operation is primarily favorable. The inventive arrangement has thus been satisfactory in principle for a long time. gladly existing need, whereby the experts for decades stuck to the dogma of the need for extensive voltage electrodes of the local type of electrostatic printing aids.

In addition to the previously described embodiments of the electrostatic arrangement, further design variations can be implemented. Here are also explicitly mentioned:

In the three-layer impression roller 1 according to FIGS. 2F and 2G, the semiconductor layer 10 could alternatively also be shortened from the right end side, or the semiconductor layer 10 is shortened on both end sides, so that an annular surface 110 of the high-conductor layer 11 is exposed on the left and / or right .

- The arcuate voltage electrode 5c can be designed in an arc dimension of approximately 270 ° to an almost point-like dimension. Depending on the width and length of the insulation body 50, the emission needles 51 can be arranged in one or more rows and square-shaped and circular assembly patterns can be provided. In principle, it would even be conceivable to equip a voltage electrode 5a, 5b, 5c with only a single emission needle 51. The insulation body 50 could be designed to save space and material.

- The various voltage electrodes 5a, 5b, 5c, 5d can also be used in the flexographic printing unit; one can provide exposed ring surfaces of the high-conductor layer 21 (see FIG. 2G) and analogous measures are taken to isolate the Meet the end faces on the three-layer printing form cylinder 20 (cf. FIGS. 2C to 2E).

Claims

claims

1. Electrostatic arrangement for an intaglio printing unit with: a) a multi-layer impression roller (1), a voltage electrode (5) attached to it and a printing form cylinder (2), b) the implementation being carried out between the impression roller (1) and the printing form cylinder (2) the path of a printing substrate (4) is provided, and c) the arrangement for polarizing the color molecules in the wells of the printing form cylinder (2) is determined, characterized in that d) to a three-layer impression device (1) with an outer semiconductor layer (10 ), an underlying high-conductor layer (11) and an underlying insulator layer (12), which adjoins the impression core (13), a voltage electrode (5a, 5b, 5c, 5d) is attached, which e) in direct electrical contact with the Semiconductor layer (10) or is set with an air gap (S) at a distance from the semiconductor layer (10); or f) is in direct electrical contact with at least one end face of the high-conductor layer (11) or is placed with an air gap (S) at a distance from this end face; or g) is in direct electrical contact with at least one exposed ring surface (110) of the high-conductor layer (11) or with an air gap (S) at a distance from this ring surface (110); in which h) an axially longitudinally extending voltage electrode (5a, 5b) as an inductor electrode has a length in the range of approximately <50%, preferably approximately <10%, of the length of the impression roller (1); i) a voltage electrode (5b, 5c) extending radially around the impression roller (1) as an inductor electrode has an arc length in the range of approximately <270 °, preferably approximately <30 °; j) one that is in direct electrical contact with the semiconductor layer (10) or the high-conductor layer (11)

Voltage electrode (5d) is an electrically conductive slip ring or a brush.

2. Electrostatic arrangement for a flexographic printing unit with: a) a multi-layer printing form cylinder (20), a substrate transfer roller (30), an impression cylinder (40) and a voltage electrode (5) positioned in the printing unit, b) being between the multi-layer printing form cylinder (20) and the counter-pressure cylinder (40) the passage of a substrate (4) is provided, and c) the arrangement for polarizing the color molecules on the substrate transfer roller (30) and the multi-layer printing form cylinder (20) is determined, thereby characterized in that d) to a three-layer printing form cylinder (20) with an outer semiconductor layer as a cliché (24), an underlying high-conductor layer (21) and an underlying insulator layer (22) which the Cylinder core (23) is adjacent, a voltage electrode (5a, 5b, 5c, 5d) is attached, which e) is in direct electrical contact with the semiconducting cliché (24) or with an air gap (S) at a distance from the cliché (24 ) is scheduled; or f) is in direct electrical contact with at least one end face of the high-conductor layer (21) or with an air gap (S) at a distance from this end face; or g) is in direct electrical contact with at least one exposed ring surface of the high-conductor layer (21) or with an air gap (S) at a distance from this ring surface; wherein h) an axially longitudinally extending voltage electrode (5a, 5b) as inductor electrode has a length in the range of approximately <50%, preferably approximately 10%, of the length of the three-layer printing form cylinder (20); i) a voltage electrode (5b, 5c), which extends radially around the three-layer printing form cylinder (20) as the inductor electrode, has an arc length in the range of approximately <270 °, preferably approximately <30 °; j) a voltage electrode (5d) which is in direct electrical contact with the semiconducting cliché (24) or the high-conductor layer (21) is an electrically conductive slip ring or a brush.

3. Electrostatic arrangement according to claim 1 or 2, characterized in that the voltage electrode (5a, 5b, 5c) systematically spaced apart from one another on the impression roller (1) or on the three-layer printing form cylinder (20) contains emission needles (51), of their Peaks in the operating state current flows through the ionized air gap (S) into the semiconductor layer (10) of the impression roller (1) or the semiconducting cliché (24).

4. Electrostatic arrangement according to one of claims 1 to 3, characterized in that on the impression roller (1) or on the three-layer printing form cylinder (20) in each case one of the cut surfaces of the high-conductor layer (11, 21) and the insulator layer (12, 22) covering insulator coating (14) and extending into the adjoining regions of the uppermost semiconducting layer (10, 24) and of the lowest core (13, 23) is provided.

5. Electrostatic arrangement according to one of claims 1 to 3, characterized in that on the impression roller (1) or on the three-layer printing form cylinder (20) the high-conductor layer (11, 21) is reset in each case shortened and the resulting free is filled by the semiconducting layer (10, 24) drawn down to the insulator layer (12, 22), which surrounds the cut edges of the shortened layer (11, 21).

6. Electrostatic arrangement according to one of claims 1 to 3, characterized in that on the impression roller (1) or on the three-layer printing form cylinder (20) the semiconducting layer (10, 24) and the high conductor layer (11, 21) are reset in each case shortened and the resulting space from the shortening from the outer surface of the semiconducting layer (10, 24) pulled-up insulator layer (12, 22) is filled, which surrounds the cut edges of the shortened layers (10, 11; 24, 21).

7. Electrostatic arrangement according to one of claims 1 to 6, characterized in that the high voltage (U) applied to the voltage electrode (5a, 5b, 5c, 5d) is up to 30 kV.

8. Electrostatic arrangement according to one of claims 1 to 7, characterized in that the voltage electrode (5a, 5b, 5c) in an effective gap distance (S) between 5mm and 30mm on the impression roller (1) or on the three-layer printing form cylinder (20) is arranged.

9. Electrostatic arrangement according to one of claims 1 to 8, characterized in that the voltage electrode (5a, 5b, 5c, 5d) is arranged on an end region of the impression roller (1) or of the three-layer printing form cylinder (20).

10. Electrostatic arrangement according to one of claims 1 to 9, characterized in that the thickness of the high-conductor layer (11,21) is at least 1/3 of the thickness of the semiconducting layer (10,24).