EP0279066B1 - Printing machine - Google Patents

Description

The invention relates to a printing press which works in the planographic printing process and is equipped with a printing form which has wettable and non-wettable areas corresponding to an image to be printed, means being provided by means of which these areas of the printing form for changing the image locally and without the To have to remove printing form, can be reversed and a control device is assigned to the printing press, with which the electrical control signals for local influencing of the printing form can be generated.

In printing machines that work according to the planographic printing process, printing forms are used which are clamped on a printing form cylinder and which are used for image transmission for the printing process. For this purpose, the printing form contains two areas, namely the water-repellent area representing the image parts and the water-accepting area representing the non-image parts.

During the printing process, the printing form is wetted by means of a so-called dampening system with dampening solution, such as a water / alcohol mixture, the dampening solution being bound to the surface of the printing form in the non-image areas. The dampening solution is thus only displaced or emulsified into the hydrophobic image areas by the printing ink subsequently applied to the printing form. The color thus applied to the printing form is finally printed on a sheet of paper using a rubber cylinder.

In general, the printing form is produced outside of the printing press with the respective image, so that there are downtimes and personnel costs for the machine for the replacement of printing forms. For the production of the printing forms, electronically stored data can be used today, which contain all of the information to be printed.

An electrochemical imaging method is known from US Pat. No. 4,068,588, in which an electrolyte containing an electrochromic material is introduced between two direct current electrodes, the printing form to be imaged as an anode and the counter electrode coated with a photoconductor as a cathode. An electrochromic image is thus deposited on the printing form by means of the photoconductor. This is intended to solve the task of creating a printing form in which visual control of the image quality is facilitated.

In IBM TECHNICAL DISCLOSURE BULLETIN, Volume 20, No. 10, March 1978, pages 4176 to 4177, a manufacturing method for electrochemically reversible materials is disclosed.

EP-A 0 160 920 discloses a one-step electrochemical process for reproduction layers. However, such an image formation process is obviously not carried out within a printing press.

A printing press is known from EP-A 101266 with which such electronically coded printing information is used in order to carry out a direct production or new production of the printing form located in the printing press. As a result, it is no longer necessary to change the printing form and the associated downtime of the machine and the personnel expenditure.

The known printing press is characterized in that the printing form cylinder surface has a hydrophilic surface forming the printing form, which is washed by means provided in the printing press, coated with a hydrophobic layer and then, for. B. can be acted upon by a laser beam. The redesign of the printing form requires a brief interruption in the printing process by switching on the washing, coating and laser device when the image changes while the machine is in operation. The previous color layer is washed off and the hydrophobic layer is renewed, which is removed locally with the laser beam in accordance with the image to be printed. The laser beam is controlled using the coded print information.

The invention has for its object to find another solution for a printing press of the type mentioned, with which the printing area can be converted in a simple manner and with simple manufacturing technology.

The object is achieved with the features characterized in claim 1.

This results in the possibility of creating or changing the printing template within the printing press on the printing form without having to stop the printing press and having to replace the printing form. Rather, the coded information is transmitted via an electrical control of the printing form, which means that a significant saving in space and simplification of the process can be achieved compared to the known device. In addition, no expensive coating and blasting devices are required and there is no material transfer that has to be removed before each image renewal.

The printing form can be designed in the form of a film which is clamped onto a plate or a cylinder, wherein either the entire film or only the film surface consists of the electrically controllable material. But it is also possible to design the plate or cylinder surface as a printing form, i. i.e. to coat with the material.

With selectively applied electrical currents or fields from different directions, the controllable material is selectively brought into one or the other state. The sum of the points in one state represents the image areas and that of the other the non-image areas. The state of the associated material point can be reversed by reversing the polarity of the electrical signal. The control can also be carried out electrochemically with a suitable electrolyte solution.

According to one embodiment of the invention, the material is an electrically conductive polymer.

As is known, electrically conductive polymers can be produced by electrochemical polymerization of aromatics and heteroaromatics or their substitution products. During the polymerization, flexible, electrically conductive polymer films are formed on the anode, which contain positively charged polymer chains and negative counterions from the electrolyte solution. The polymer formed on the anode by electrochemical oxidation is hydrophilic due to its salt-like character. Polymers charged in this way can be reversibly converted into an uncharged state which is hydrophobic by a simple electrochemical reduction. From this state, it can be returned to the charged state by electrochemical oxidation.

By electrical control, i.e. H. the properties of this material can be repeated and partially varied between the two states by partial oxidation or reduction. Appropriate local control means that the information to be printed can be transferred to the polymer forming the printing form in such a way that uncharged areas and non-image areas are created for the image parts.

A suitable polymer for a printing form is, for example, polypyrrole, which has the following structure:

In this state the polypyrrole is hydrophobic. By anodic oxidation in an electrolytic solution, this polymer changes into a salt-like state, which, using e.g. B. NH₄Br as the electrolyte receives the following structure for a polymer unit:

This oxidation brings the polypyrrole into a hydrophilic state.

Aromatics and heteroaromatics such as thiophene, pyrrole, furan, indole, carbazole, benzothiophenes and their substitution products such as 3-alkyl-, especially 3-methyl-, 3-alkyloxy are particularly suitable as monomers which can be converted into suitable polymers by oxidative polymerization -, 3,4-dialkyloxy-, mainly 3-methoxy-, 3,4-dimethoxy-, 3-alkylthio-, especially 3-methylthio-, 3,4-bis (methylthio) -thiophene, -pyrrole, -furan, 2,2ʹ-bithienyl, 2,2ʹ , 5ʹ, 2ʺ-terthienyl, di-2-thienyl sulfide, methane, 1,2-di-2-thienylethylene, aniline, substituted anilines, p-phenylenediamine, diphenylamine, 4,4ʹ-diaminodiphenylmethane, ether, sulfide.

Inert salts are used as conductive salts under the conditions of the electrochemical reaction, in particular inorganic conductive salts such as ammonium, lithium, sodium tetrafluoroborates, -perchlorates, -sulfates, -hydrogen sulfates; quaternary ammonium salts such as tetraalkylammonium perchlorates, tetrafluoroborates, hexafluorophosphates, hexafluoroantimonates, hexafluoroarsenates, methanesulfonates, toluenesulfonates, trifluoromethanesulfonates, trifluoroacetates; other alkyl sulfonates and sulfates such as lauryl sulfate and other anionic surfactants such. B. alkyl carboxylates. These salts are dissolved in solvents which are also inert under the conditions of the electrochemical reaction, such as acetonitrile, 1,2-dimethoxyethane, methanesulfonic acid, dichloromethane, 1-methyl-2-pyrrolidone, nitrobenzene, nitroethane, nitromethane, dichloromethane, propionitrile, propylene carbonate, Tetrahydrofuran, benzonitrile and sulfolane.

To carry out the conversion, an electrolyte solution and electrodes are assigned to the printing form, which are integrated into the printing press. The electrolyte solution preferably contains conductive salts which are inert under the conditions of the electrochemical reaction and have sufficient solubility in the solvent used in each case.

Organic solvents such as acetonitrile, nitromethane, but also water with conductive salts such as tetrabutylammonium and tetraethylammonium salts can be used as solvents. Alkali metal salts and alkyl sulfonates are best used for aqueous solvents.

The surface of the forme cylinder which forms or receives the printing form can be used as the first electrode, in that it is designed accordingly and configured either as a homogeneous or matrix-like electrode. The counterelectrode is an electrode provided as an additional component in the printing press, which, depending on the configuration of the first electrode, is designed in a matrix-like or homogeneous manner, in such a way that one electrode is homogeneous and the other is matrix-like.

When using a matrix-like first electrode, the counterelectrode can be designed as a metal roller with a slightly roughened surface, which is rotatably mounted in a tub with electrolyte solution and serves to convey the electrolyte solution. This function can also be performed with a counterelectrode, which has a sieve-like outer surface, but which at the same time can have a cleaning effect on the printing form, if the counterelectrode is designed in such a way that electrolyte solution under sufficient pressure into the contact zone between printing form and Counter electrode can be pressed. This embodiment has the advantage that the printing form is simultaneously freed from the color of the previous printing process during a rewriting process.

When using a homogeneous first electrode, it is possible to provide one or more counter electrodes. If multiple counter electrodes are used, a reduction in the grid density on the counter electrode is possible.

Several counter electrodes can be designed in the form of electrode strips, each with a width of one or more grid spacings. A single electrode strip is also conceivable, which is controlled anew for each new line.

The microprocessors required to control the rewriting process can preferably be attached to the rear of the matrix electrode.

The invention extends to a method for producing a printing form, which is characterized by the features of claims 14 to 17.

Fig. 1

die Druckwalzen einer Druckmaschine im Querschnitt,

Fig. 2

eine Steuereinheit im Blockschaltbild,

Fig. 3

ein Detail aus Fig. 1.

Fig. 4

ein zweites Ausführungsbeispiel.

The invention is explained in more detail with reference to exemplary embodiments schematically shown in the drawing. Show it:

Fig. 1

the printing rollers of a printing machine in cross section,

Fig. 2

a control unit in the block diagram,

Fig. 3

a detail from Fig. 1st

Fig. 4

a second embodiment.

In Fig. 1, the image transfer cylinders of a printing press are shown, which work according to the flat printing or offset printing method. The paper (10) to be printed is guided between a printing cylinder (11) and a rubber cylinder (12) and takes up the printing ink applied to the rubber cylinder (12). The color distributed according to a typeface or a graphic image is transferred from a printing form (13), which is clamped on a likewise rotatable form cylinder (14), to the rubber cylinder (12). The image to be printed is imaged on the printing form (13) by areas which are water-repellent, ie. H. are hydrophobic. During the printing process, the printing form (13) passes through a dampening unit (15). The hydrophobic areas are not wetted by the dampening solution on the surface, while the dampening solution is bound to the hydrophilic areas. The moistened surface then passes through an inking unit (16), with which the printing ink is applied. The hydrophilic areas do not accept any printing ink. On the other hand, the color is assumed at the hydrophobic areas representing the image parts.

The printing form (13) can be produced from any material which can assume both a water-absorbing and a water-repellent state, a change in state in one or the other direction being able to be brought about by means of electrical or electrochemical pulses. Examples of such materials are electrically conductive polymers that can be produced by electrochemical polymerization.

An electrically conductive polymer can be produced, for example, as follows:
0.05 to 0.1 mol / l of monomer and 0.1 to 1 mol / l of a conducting salt, for example an alkali metal salt, are dissolved in a solvent. A polymer is deposited on the anode by using a current density of 0.1 to 1 mA / cm².

Medium-polar organic solvents such as acetonitrile, nitromethane or dichloromethane can be used as solvents, which are suitable for less polar monomers, such as. B. thiophene and its derivatives and tetrabutylammonium or tetraethylammonium salts are suitable as a monomer or conductive salt. Other solvents are water or water / organic solvent mixtures, for which polar monomers such as pyrrole, aniline and their derivatives and salts such as alkali metal salts or alkyl sulfonates are suitable. In principle, all salts which are inert under the conditions of the electrochemical reaction used and which have sufficient solubility in the solvent used in each case are suitable as conductive salts. In addition, in the case of electrochemical polymerization, the conductive salt and monomer should be present in a sufficient amount in solution, while the resulting polymer should be insoluble in the solvent used.

The printing form (13) is formed according to FIG. 1 as a layer up to about 10 μm thick, which is applied to the form cylinder (14). The layer (13) is preferably deposited by electrochemical polymerization directly onto the forme cylinder (14) designed as an anode. The layer can also be applied to a carrier film (eg made of aluminum) and stretched onto the forme cylinder with this film.

A washing system (17) and an electrolyte system (18) are also provided in the printing press. After the printing sequence of an original has ended, the washing system (17) and the electrolyte system (18) are switched on without switching off the printing machine. After the printing ink has been delivered to the rubber cylinder (12), the printing form (13) passes through the washing system (17), with which the ink residues are washed off the printing form, in order then to be acted upon by the electric field of the electrolyte system (18). This is where the printing form (13) is reversed to produce a new image, as will be described below.

2 shows a basic arrangement for the reversal. The printing form (13) is in contact with an electrolyte solution (20) and is located with it between a first electrode (21), which is formed by the forme cylinder (14), and a counter electrode (22), which is designed as an electrode roller according to FIG. 1 is. The electrolyte solution (20) consists of a conductive salt dissolved in a sufficient amount in a solvent. The substances used in the production of the polymer can be used as conductive salts and solvents. Water is preferably used as the solvent of the conductive salt for the reversal in the machine.

To initiate the electrolyte process, an information transmission unit (24) is provided, which consists of an information distribution system (25) located in the editorial office and a control unit (26) located on or in the printing press. In the editorial office the entire information intended for printing is electronically stored via so-called full-page wrap systems or full-page assembly systems for newspaper and illustration printing or electronically encoded on the way via facsimile transmission systems. This information is passed on via an interface to a machine computer, which processes the information into control signals (27) with which voltage or current pulses (23) are applied to the electrodes (21, 22) via microprocessors (28).

Depending on the direction of tension, the polymer forming the printing form (13) is reversibly charged or discharged, i. that is, a transfer or rewriting of the printing form (13) takes place by reversing the voltage.

In order to be able to produce the image areas on the printing form (13), the image is broken down into halftone dots, as is customary in printing technology. For example, a grid of 30 / cm is common in newspaper printing, and a grid of 120 / cm in high-quality illustration printing. Each of these halftone dots must be separately controllable in order to produce the print areas by reversing them according to the image. For this purpose, the electrode (21) located on the surface of the forme cylinder (14) is designed as an electrode matrix, each electrode element being assigned to a grid point.

3 shows a top view of the greatly enlarged electrode matrix (21). A large number of microprocessors (28) are provided for controlling the individual electrode elements (30), a certain number of electrode elements (30) being assigned to a microprocessor (28). The microprocessors are arranged in the forme cylinder (14) on the back of the electrode (21), as shown in cross section in FIG. 1 and with thicker lines in FIG. 3. For example, a 1 cm² grid area could be controlled by a microprocessor (28).

To produce a print pattern (31) on the printing form (13), the electrode elements (30) (Fig. 3) are controlled or not controlled with the control device, depending on whether the point in question already has the state desired for the new image or not . The electrode elements (30) can be activated in sequence or line by line at the same time.

1, the electrolyte solution (20) in a container is conveyed by the counter-electrode roller (22), which is designed as a homogeneous electrode with a rough surface. The electrolyte solution can also be introduced into the reversing zone with a separate feed device.

For a reversal process, in which the electrolytic system (18) is put into operation, the counter electrode roller (22) is rotated, thereby entraining an electrolyte film (40) over the rough surface and into the gap (29) between the printing form (13) and the counter electrode (22) promoted.

Another variant is the formation of an electrode with a sieve-like outer surface, through which electrolyte solution is pressed into the contact zone (29) under sufficient pressure during the rewriting process and the color is thereby kept out of the gap. This makes it possible to save a separate cleaning process with a separate washing system (17).

The arrangement and configuration of the homogeneous or matrix-like electrodes can be carried out as desired. Of course, the electrode on the forme cylinder (14) can be homogeneous and the counterelectrode (22) can be designed in a matrix. With a matrix electrode as the counter electrode, it can also be made in several parts. If several counter electrodes are used, the grid density can be reduced. It is conceivable to produce the matrix electrode from electrode strips in single or multiple grid spacing or to use only one electrode line with which the entire printing form is treated line by line by the printing form (13) passing through the forming zone.

Another way of producing the matrix electrode is to use a homogeneous electrode, for example a metal roller, which is coated with a photoconductor. FIG. 4 shows an exemplary embodiment in which the forme cylinder (51) receiving the printing form (50) is designed as a homogeneous electrode, while the counter electrode (52) takes over the function of the matrix electrode.

The counter electrode consists of a homogeneous electrode jacket, for example made of metal, which is coated with a photoconductor (53). The photoconductor is exposed imagewise on a surface line of the counterelectrode (52) by means of a radiation source (54). The photoconductor (53) becomes conductive at the exposed points (55), so that when the conductive point (55) enters the contact zone (56) to the forme cylinder (51), the required current between the forme cylinder electrode (51) and the counter electrode (52 ) can flow to reverse the printing form (50). The information to be transmitted is controlled via the light source (54) and briefly stored on the photoconductor (53).

The photoconductor preferably has the property of only briefly maintaining the conductivity introduced by the exposure. The conductivity should be maintained up to the contact zone (56). After the line to be transferred has left the contact zone (56) again, the conductive points (55) do not have to become conductive again in order to allow a new description for the next rotation of the counter electrode (52). Organic photoconductors can in particular be used as the photoconductor (53).

The desired opening and closing requirements of the photoconductor (53) can be influenced by applying or inserting afterglow substances such that the conductive state is prolonged. Thermal treatment is also conceivable with which the exposed areas (57) after passing through the contact area (56) accelerated to be made non-conductive. Otherwise, the diameter of a drum-like counterelectrode (52) and the arrangement of the radiation source (54) will be determined in accordance with the switch-on and switch-on characteristics of the selected photoconductor.

Claims (20)

1. Printing machine which operates in the planographic process and is equipped with a printing forme which has hydrophobic and hydrophilic regions corresponding to an image to be printed, means being provided whereby for image change these regions of the printing forme can be changed over locally and without having to remove the printing forme from the printing machine, and associated with the printing machine is a control device with which the electrical control signals can be produced for local influencing of the printing forme, characterised in that the printing forme (13, 50) contains as changeable material (13) an electrically conductive polymer which can be converted from a hydrophobic state into a hydrophilic state and vice versa by means of the electrical control signals.
2. Printing machine according to claim 1, characterised in that an electrochemical control means (20 to 23) is provided.
3. Printing machine according to claim 1 or 2, characterised in that the material is a polymer produced by oxidative polymerisation of aromatic substances or heteroaromatic substances.
4. Printing machine according to one of the preceding claims, characterised in that associated with the printing forme (13) are electrodes (21, 22) which can be locally controlled by the control signals (23) to influence the printing forme electrochemically.
5. Printing machine according to claim 2, characterised in that the electrolytic solution (20) for the electrochemical process contains conducting salts which are inert under the conditions of the electrochemical reaction.
6. Printing machine according to claim 4, characterised in that the printing plate or the surface of the forme cylinder (14) receiving the printing forme (13) is constructed as an electrode (21), and in that there is provided a counter electrode (22) arranged in the electrolytic solution (20) and fitted movably with respect to the forme cylinder (14).
7. Printing machine according to one of the preceding claims, characterised in that one of the electrodes (21) is constructed to be controllable in raster fashion.
8. Printing machine according to claim 7, characterised in that the electrode controllable in raster fashion comprises a series of electrodes which can be controlled again for each line.
9. Printing machine according to claim 7, characterised in that the surface of the printing plate or forme cylinder (14), or the counter electrode (22), is constructed as an electrode matrix.
10. Printing machine according to claim 4, characterised in that the counter electrode (22) is constructed as a rotatable cylinder which conveys the electrolytic solution to the printing forme (13).
11. Printing machine according to claim 4, characterised in that means are provided with which the electrolytic solution can be pressed into the changing zone.
12. Printing machine according to one of the preceding claims, characterised in that the counter electrode (52) is coated with a photoconductor (53) and in that a radiation source (54) used for the point-wise illumination of the photoconductor is associated with the counter electrode.
13. Printing machine according to claim 7, characterised in that microprocessors (28) are arranged on the back of the matrix electrode (21) for controlling the matrix electrode elements (30).
14. Process for the production of a printing forme which can be converted by an electrical or electrochemical control means from a hydrophobic into a hydrophilic state and vice versa, characterised in that a polymer forming at least the printing forme surface is produced by electrochemical reaction of a monomer in an electrolytic solution which contains a conducting salt as well as the monomer.
15. Process according to claim 14, characterised in that aromatic substances or heteroaromatic substances such as thiophene, pyrrole, furan, indole, carbazole, benzothiophene or their substitution products are used as monomers, which are dissolved in solvents which are inert under the conditions of the electrochemical reaction.
16. Process according to claim 14, characterised in that acetonitrile, nitrobenzene, dichloromethane, sulpholane or the like are used as solvents.
17. Process according to one of claims 14 to 16, characterised in that inorganic conducting salts, quarternary ammonium salts, alkyl sulphonate or anionic surfactants are used as the conducting salt and are inert under the conditions of the electrochemical reaction.
18. Process according to one of claims 14 to 17, characterised in that electrodes are used which are inert under the reaction conditions.
19. Process according to one of claims 14 to 18, characterised in that electrodes are used which are made of metal oxide at least on the surface.
20. Process according to one of claims 14 to 18, characterised in that electrodes of carbon, in particular carbon fibre, are used.

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