EP1401660B1 - Method and device for producing different printed images on the same print substrate - Google Patents

Abstract

The invention relates to a method and device for producing a printed image on a supporting material (24) during which the surface of a print substrate (20) is coated with an ink-repellent or ink-attracting layer, and during a structuring process, ink-attracting areas and ink-repelling areas are produced in accordance with the structure of the printed image to be printed. The surface of the print substrate (20) is cleaned before a new structuring process and is coated once again with an ink-repellent or ink-attracting layer. A water layer or an ice layer is used as an ink-repellent layer.

Description

The invention relates to a method and apparatus for producing a printed image on a substrate, wherein on the surface of the print carrier ink-attracting and ink-repellent areas are generated according to the structure of the printed image to be printed on the surface of the print carrier is applied to the color adhering to ink-attracting areas and which is not accepted by the ink-repellent areas, and in which the surface-distributed ink is printed on the substrate.

In the prior art, waterless offset printing methods are known whose non-printing areas are fat-repellent and therefore do not accept printing ink. The printed areas, on the other hand, are fat-absorbing and pick up the greasy ink. According to the structure of the print image to be printed, ink-attracting and ink-repellent areas are distributed on the printing plate. The printing plate can be used for a variety of transfer printing operations. For each print image, a new plate must be created with ink-attracting and ink-repellent areas.

From the US-A-5,379,698 For example, a method is known which is called a direct imaging method in which a printing original is created in the printing device on a multilayer, silicone-coated film by selective burning away of the silicone top layer. The silicone-free areas are the ink-attracting areas that accept printing ink during the printing process. Every new print requires a new foil.

In the standard water-based offset process, hydrophobic and hydrophilic areas are formed on the surface of the print substrate in accordance with the structure of the printable Print image generated. Prior to application of the paint, a thin film of moisture is first applied to the print substrate using applicator rollers or sprayers, which wets the hydrophilic area of the print substrate. Subsequently, the inking roller transfers ink to the surface of the print substrate, which wets only those areas not covered by the moisture film. After dyeing, the color is finally transferred to the carrier material.

In the known offset printing process can be used as a print carrier multi-layer processless thermal printing plates, see. eg WO00 / 16988 , According to the structures of the print image to be printed on the surface of the print carrier, a hydrophobic layer is removed by partial burning away and exposing a hydrophilic layer. The hydrophilic layer can be wetted with an ink-repellent fountain solution. The hydrophobic areas are ink accepting and can absorb ink during the printing process. To create a new print image, a new printing plate must be used.

Furthermore, a method of the US-A-6,016,750 in which an ink-attracting substance is deposited from a film by means of a thermal transfer process, transferred to the hydrophilic surface of the print substrate and solidified in a fixing process. In the printing process, the remaining hydrophilic areas are wetted with ink-repellent dampening solution. Subsequently, the ink is applied to the surface of the print carrier, which, however, adheres only to the provided with the ink-attracting substance areas. The inked print image is then transferred to the substrate. For the creation of a new print image, a new film with the color attracting substance is necessary.

The aforementioned methods have the problem that the print carrier must be renewed before creating a new print image or the surface of the print carrier can only be cleaned outside the printing device or additional ink-absorbing substances are consumed.

From the DE-1-19911906 An apparatus and method for imaging a printing form for wet offset printing is known. In a first variant, the surface of the print carrier is completely wetted with a ink-repellent dampening solution. With the help of radiation, image areas are dried, which are then color-accepting. In a second variant, the surface of the print carrier is completely covered with paint. With the help of radiation, this color is dried at image points. At non-image areas, the color is removed by a color-repellent dampening solution.

From the US-A-3,741,118 For example, a method for producing a printed image is known in which a solvent layer is sprayed onto a lithographic printing substrate. According to the printed image, the solution is applied to the bare print carrier and / or removed therefrom. Ink is applied to the ink-attracting solvent and then transferred to the recording medium. After each transfer operation, the print carrier is cleaned and can be re-provided with the same or a different solvent image.

In another known device for producing a printed image ( GB-A-1 546 532 ), a photosensitive substance is applied to a hydrophilic metal surface of a print substrate. By exposure, the substance is removed according to a printed image. Subsequently, ink is applied to the ink-attracting areas and the printed image is reprinted. After each transfer, the surface is cleaned again. This device corresponds in principle to an electrophotographic printer.

From the document WO 98/32608 A1 For example, a method of printing a substrate using a structured layer of ice on a print substrate is known. For this purpose, ink-attracting and ink-repelling areas corresponding to the structure of the print image to be printed is generated on the surface of the print carrier. The ink-repellent areas are produced by means of an ice layer as a result of condensation.

It is an object of the invention to provide a method and a device for generating printed images that print at low cost different print content with high print quality.

This object is achieved for a method by the features of claim 1. Advantageous developments are described in the dependent claims.

In the invention, the surface of the print substrate is cleaned before a new patterning process and coated again with an ink-absorbing dampening layer. The fountain solution layer is then structured in a patterning process according to the print image to be printed. On the surface then a carrier substance is applied, which adheres to ink-attracting areas. The structured surface of the carrier is fixed. On the ink-attracting areas can then be applied color, which will be reprinted in the next step.

The print carrier can therefore be used for a variety of structuring processes. With the same print carrier so different print content can be printed without the print carrier must be replaced. Once applied to the surface of the print substrate, the structure can be used for a variety of transfer operations where the applied ink is transferred to substrate. In the method according to the invention, the consumption of printing substrate is minimized. In addition, the handling simplified, since in contrast to conventional methods, an exchange of the carrier with the image structure does not have to be done.

By additional substances, such as wetting agents and / or surfactants or a cleaning or corona or plasma treatment of the surface of the print carrier, this can be brought into a very hydrophilic state, which favors the application of the fountain solution layer.

The fountain solution layer is adapted to the applied color. If the paint contains water, this fountain solution layer is color-attracting.

The pressure-active surface of the print carrier is first completely provided with the fountain solution layer. In a subsequent structuring process, regions are generated which are free of said dampening solution layer. In this way, ink-attracting and ink-repellent areas can be generated according to the structure of the print image to be printed.

The surface of the print carrier does not have to be pretreated according to the structure of the print image to be printed, for example by etching. Rather, the pressure-active surface in the initial state is uniform and smooth. The patterning process merely involves the generation of moisture-free areas corresponding to the structure of the print image to be printed. Accordingly, different printed images can be produced on the same surface of the print carrier, wherein for each print image the initial state of the surface of the print carrier is to be produced. If a new print image is to be applied to the print substrate, the print substrate must be cleaned of the areas provided with the fountain solution layer and any ink residues. So it is not consumed the print carrier. There are also no additional consumables, such as multi-layered Films with ink-repellent layer, necessary for the production of ink-repellent areas on the surface of the print carrier.

Radiation energy is used to selectively produce dampener-free areas on the surface of the print carrier. The production of a structured fountain solution layer on the surface of the print carrier requires a comparatively low radiation energy. This automatically leads to a significant reduction of the writing time: it is at a range of 450 x 330 mm ² (resolution 2540 dpi) with 16 laser diodes à 0.7 W only about 30 s; In comparison, for example, requires the direct imaging method of a known printing machine 10 min.

Before a new structuring process, the moistening agent layer residues, the carrier substance residues and paint residues from the surface of the print carrier are eliminated by a cleaning station. Following cleaning, the surface of the print carrier is regenerated. With the help of wetting agents and / or surfactants or a corona and / or plasma treatment, the surface of the print carrier can be brought back into a hydrophilic state again. Subsequently, the surface of the print carrier can be coated again with a fountain solution layer. The print carrier remains in this cleaning process and re-structuring in the printing device, resulting in a faster printing form production. In this way, different printed images can be produced on the same print carrier and colored once or several times and re-printed without the print carrier for the cleaning process or before the re-structuring of the printing device must be removed.

According to a further aspect of the invention, a device for printing is specified. By means of this device, the method described above can be realized. In this case, the device has a dampening unit, which is the surface of a print carrier with a fountain solution coating. Blasting agents structure the dampening solution layer on the print carrier in accordance with the structure of the print image to be printed. An applicator applies a carrier to the surface. A fixing unit fixes the carrier substance as a result of a fixing process. A cleaning station cleans the surface of the print carrier before a new structuring process.

Figur 1

schematisch den Aufbau einer Einrichtung zum Dru- cken mit einem Lasersystem, einer Fixiereinrichtung und einer Reinigungsstation,

Figur 2

schematisch den Aufbau der Einrichtung nach Figur 1, die zusätzlich mit einer Auftragsvorrichtung zum separaten Auftragen einer Trägersubstanz ausgestat- tet ist, und

Figur 3

eine weitere Ausführungsform mit einem zusätzlichen Zwischenzylinder und einer zusätzlichen Reinigungs- station.

Embodiments of the invention are explained below with reference to the drawings. It shows:

FIG. 1

FIG. 2 schematically the structure of a device for printing with a laser system, a fixing device and a cleaning station, FIG.

FIG. 2

schematically the structure of the device according to FIG. 1 , which is additionally equipped with an application device for the separate application of a carrier substance, and

FIG. 3

a further embodiment with an additional intermediate cylinder and an additional cleaning station.

FIG. 1 schematically shows the structure of a device for printing, in which 20 different printed images can be generated on the same surface of a print carrier. This device comprises an inking unit 10 with four rollers 12, 14, 16, 17, is transferred by the color from a paint reservoir 18 to the surface of the print carrier 19. The inked surface of the plate cylinder 20 transfers the ink to a blanket cylinder 22. From there, the ink passes onto a paper web 24, which is pressed by a counter-pressure cylinder 26 against the blanket cylinder 22. The in FIG. 1 at the plate cylinder 20 drawn arrow P 1 indicates the direction of transport.

A dampening unit 30 with its three rollers 32, 34, 36 transfers dampening solution, for example water, from a dampening solution reservoir 38 onto the surface of the plate cylinder 20. In principle, however, other dampening solutions can also be used. Before applying the dampening solution layer, the surface of the print substrate 19 can be brought into a more hydrophilic state using wetting agents and / or surfactants or by corona and / or plasma treatment. The application of dampening solution layer can be done by means of rollers, as in the present case, or it can be used a steam or spray process. The pressure-active surface of the plate cylinder 20 is completely provided with a fountain solution layer. Subsequently, the fountain solution layer is selectively removed by energy supply by means of a laser system 40 and there is the desired image patterning. The exposure is carried out with a laser beam 42, as in FIG. 1 is indicated.

As an alternative to the fountain solution layer, an ice layer can also be used. To produce the ice layer, the print carrier contains a cooling system (not shown). The surface of the print carrier is cooled by the cooling system to a temperature below the solidification point of water. In the case of a normal environment with average humidity, the temperature of the surface of the print carrier is below 0 ° C. The water vapor contained in the ambient air is deposited as an ice layer due to condensation on the surface of the print carrier. To produce the ice layer on the surface of the print carrier, an electrothermal cooling principle is used, for example by the use of Peltier elements. Another possibility is to apply a thin film of water with a thickness in the micron range. Cooling then creates a layer of ice. For applying the water film For example, a spraying process can be used, or the application can be made using rollers. The pressure-active surface of the print carrier is completely covered with a layer of ice. The ice layer is then selectively removed by energy supply by means of the laser system. The exposure is made by the laser beam. The water of the ice layer is converted into the vapor state by exposure to the laser beam.

The coloring of the surface of the plate cylinder 20 according to FIG. 1 takes place by means of the rollers 12, 14, 16, 17 of the inking unit, which transfer color from the ink reservoir 18. The order of the paint is done here by a roller system. The paint can also be applied to the surface of the print carrier by spraying, knife coating or condensing. The above-mentioned carrier substance is therefore identical to the color in this example.

The applied after structuring paint is solidified by means of a fixing device 50. This is done by IR radiation, hot air, UV light or heat radiation. The fixed color is then dyed once or more times with ink from the inking unit 10. By curing the applied color, a printing form is created as it were, which allows a multiple recording of color and a repeated transfer of color. The applied to the plate cylinder ink is transferred to the blanket cylinder 22 and from there onto the substrate 24. The on the plate cylinder 20 distributed color can alternatively be transferred directly to the substrate 24, in which case can be dispensed with the blanket cylinder 22.

Two operating modes are possible: In a first operating mode, a large number of printing processes takes place before the surface is restructured. The print image on the print substrate is dyed and reprinted once per transfer print, i. There is a multiple coloring of the printed image. In the case of the structured ice layer on the surface of the print carrier, the temperature of this surface is kept below the freezing point by means of the cooling system.

In a second mode, a new print image is applied to the surface of the print carrier. Before that, the previous structured layer and the ink residues must be removed and the surface of the print substrate cleaned and regenerated. For this purpose, a cleaning station 60 is activated. It contains a brush 62 and a wiper lip 64, which are brought into contact with the surface of the print carrier and eliminate the structured layer and the color residues. The removal of the patterned layer is performed using ultrasound, high pressure liquid and / or steam. The surface of the print carrier is thereby cleaned by means of brushes, cloths, rollers and / or doctor blades. The cleaning may be done in one or more cycles using tools such as cleaning fluids and / or solvents. For activating and deactivating the cleaning station is pivoted in the direction of the arrow P2 to the plate cylinder 20. Any existing cooling system may be inactive during cleaning.

After cleaning, if necessary, a regeneration of the surface of the print substrate, preferably using wetting agents and / or surfactants. Also possible is a corona or plasma treatment of the surface of the print substrate so that it is brought into a hydrophilic state. It should also be mentioned that the surface of the print carrier contains coatings which have a low optical penetration depth, low reflection values and poor heat conduction.

FIG. 2 shows the structure of a printing device, in the deviating from the example according to FIG. 1 after structuring the surface of the print carrier, a carrier 74 different from the color is applied by a separate applicator 70 by means of a roller 72. The optimized for this process carrier 74 adheres to the ink-attracting areas and is not accepted by the ink-repellent areas. After application, the carrier substance is fixed by means of the fixing device 50. This is done by IR radiation, hot air, UV light and / or thermal radiation. To activate and deactivate the applicator 70 is moved in the direction of arrow P3. Subsequently, the fixed carrier substance 74 is colored once or several times by means of the inking unit 10 in the further printing process.

FIG. 3 shows the structure of a printing device according to another embodiment, wherein like elements are still designated the same. In contrast to the construction after FIG. 1 between the print carrier 20 and the blanket cylinder 22, an intermediate cylinder 76 is arranged, which causes an additional color splitting. As a result of this color splitting, a higher amount of ink can be applied to the print substrate 20, whereby the printing plate has improved stability and wear is reduced in a large number of printing operations. By a suitable surface of the intermediate cylinder 76, a further load reduction of the printing plate can be achieved. Preferably, soft and flexible surfaces are used for the intermediate cylinder 76, which ensure a uniform color splitting.

On the intermediate cylinder 76, a cleaning station 60 'is arranged, which has the same structure as the cleaning station 60. By means of the brush 62 and the wiper lip 64, which are brought into contact with the surface of the intermediate cylinder 76 by a pivoting movement in the direction of the arrow P2, ink residues are removed. As a result, the intermediate cylinder 76 is prepared for the color transfer with a new image structure.

It is possible to optimize and tune the color split, for example by using a plurality of intermediate cylinder in the manner of the intermediate cylinder 76. In this way, an optimal match between the layer thickness of the color on the substrate 24 and the thickness of the applied to the surface of the print substrate 20 color be achieved.

In FIG. 3 For example, the fixing unit 50 is effective for fixing the ink.

Claims (6)

1. Method to generate a print image on a carrier material (24), in which

   - the surface of a print substrate (20) is covered with an ink-attracting dampening agent layer,

   - in a structuring process, regions of the dampening agent layer are removed by radiation means corresponding to the structure of the print image to be printed, as a result whereof ink-attracting regions and ink-repelling regions corresponding to the print image to be printed are generated,

   - a carrier substance is applied on the surface, which substance adheres to the ink-attracting regions and is not accepted by the ink-repelling regions,

   - the carrier substance is subjected to a fixing process,

   - ink is applied on the surface, as a result whereof the ink-attracting regions are inked with ink one or several times,

   - the ink and thus the print image is transferred to the carrier material (24), and

   - in which, before a new structuring process, the surface of the print substrate (20) is cleaned and newly covered with an ink-attracting dampening agent layer.
2. Method according to claim 1, characterized in that the surface of the print substrate (20) is brought to a hydrophilic state before the application of the dampening agent layer.
3. Method according to one of the preceding claims, characterized in that as a carrier substance ink is used and is subjected to the fixing process, the fixed ink subsequently being inked with ink one or several times.
4. Method according to claim 1, characterized in that during the fixing process, IR radiation, hot air, UV light and/or radiant heat are used.
5. Method according to one of the preceding claims, characterized in that, before a new structuring of the surface, a plurality of print events occur, the print substrate (20) being inked several times.
6. Apparatus to generate a print image on a carrier material (24),

   - which comprises a dampening system (30) which covers the surface of a print substrate (20) with an ink-attracting dampening agent layer,

   - which comprises radiation means (40), by the radiation of which regions of the dampening agent layer on the print substrate (20) are removed corresponding to the structure of the print image to be printed,

   - which comprises an application device (10; 70) which applies on the surface a carrier substance which adheres to the ink-attracting regions and is not accepted by the ink-repelling regions,

   - which comprises a fixing unit (50) which fixes the carrier substance as a result of a fixing process,

   - which comprises an inking system (10) by which ink is applied on the surface, as a result whereof the ink-attracting regions are inked with ink one or several times, and

   - which comprises a cleaning station (60), which, before a new structuring process, cleans the surface of the print substrate (20).

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