EP1456030A1

EP1456030A1 - Method for producing rotogravure forms, rotogravure forms and the use thereof

Info

Publication number: EP1456030A1
Application number: EP02803036A
Authority: EP
Inventors: Erhard Lorch; Sheila Lorch
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-11-17
Filing date: 2002-11-16
Publication date: 2004-09-15
Anticipated expiration: 2022-11-16
Also published as: DE10253654A1; ES2303567T3; DE50211895D1; ATE388819T1; WO2003041961A1; EP1456030B1

Abstract

The intaglio printing plate has a ceramic substrate (1) with recesses (2) defined by webs (3) of equal height, to give a regular and unified screen pattern. The screen is formed by a laser, with removal of molten matter from the shaped structure. The screen recesses are filled selectively by ink jets, according to the images to be printed, using a low viscose printing medium, which is hardened within the screen by polymerization using ultra violet light. The ink jet system delivers droplets of 20-40 mum diameter into the screen, by digital scanning of the original material to determine the screen filling according to tonal qualities. The substrate is covered by a protective layer to prevent leakages through its porosity. After use, the ink material is removed for the plate to be used again.

Description

Process for the production of gravure forms. Gravure forms and their use

State of the art

The invention relates to a method for producing erasable and reimageable gravure printing forms, in which a substrate is provided which is provided with a grid of defined depressions and uniformly high webs, and in the depressions for forming a grid of cells which are matched to the tonal values of the printing original , Structures are produced from at least one removable imaging material, gravure printing forms from a substrate with a grid of depressions and structures made of removable imaging material which are brought into the depressions in accordance with tonal value, and the use of such gravure printing forms. A method of this type is known from DE 38 37 941 C2.

Gravure printing plates are characterized by imaging wells, which are lower than the non-imaging printing plate surfaces and thus absorb printing ink and, after removing excess ink by means of a squeegee, from the non-imaging, uniformly high printing plate surfaces, upon contact with the printing material by splitting the ink on them transfer. In order to reproduce the print template in accordance with tonal value, it is usually resolved into a grid of lines and grid elements and the cups of the gravure printing plate are formed in the substrate in accordance with these grid elements. In conventional gravure printing, different tonal values are variable in depth, due to different cell depths with uniformly large cell openings (depth-modulated), or area-variable, with uniform cell depths with cell sizes of different sizes (amplitude-modulated), or variable in depth and area, due to different cell depths with cell openings of different sizes amplitude modulated). The larger the well opening and the deeper the well, the larger the well volume and the amount of color transferred. Grids with geometrically regularly shaped grid elements are usually used, the center or surface centers of which always have the same spacing and are referred to below as grids with a matrix arrangement. Screens with mostly constant large screen dots and any dot spacing, which can be stochastically distributed, are also described for use in area-variable gravure printing.

Gravure printing substrates are printing plates, printing cylinders or printing cylinder sleeves made of metal, ceramic or plastic. In the conventional manufacturing processes, the imaging cells are removed by material removal in the form of etching or engraving processes. drive like engraving, laser or electron beam engraving. The technical, financial and time expenditure in the production and regeneration of such rotogravure forms is considerable, but since a large number of identical prints can be produced with high quality and productivity, they are mainly used for large runs.

The known method described in DE 38 37 941 C2 is concerned with the production of an intaglio printing plate which, when colored before the printing process, takes up different amounts of ink in cells of different sizes and / or depths, an intaglio printing plate with at least one of the maximum transferred color amount of well-designed cell base grid produced and a solid substance that can be liquefied by the action of energy in a pixel transmission unit in an amount inversely proportional to the amount of color to be transferred is introduced imagewise into each of the wells. The image point transmission unit has a print head which is provided with at least one nozzle through which the liquefiable substance is sprayed out in an image by pressure in a melt spraying process. It is guided in a guide bar and transfers the substance line by line with individual addressing of each well directly or indirectly, and apparently preferred, via a transfer belt to the gravure blank. The substance is applied to a transfer film and is transferred using the thermal transfer process. A thermoplastic or wax can be used as the liquefiable substance that hardens very quickly in contact with the cold surface of the printing form cylinder. The gravure form is erased by the fact that its internal or external heating leads to liquefaction or sublimation of the substance and this is removed by an erasing device designed as a wiping and / or blowing or suction device.

However, the pictorial application of material may cause problems with the positional accuracy of the imaging. With the method used, it is not readily possible to completely insert material deposited on the webs into the wells. However, the complete introduction is necessary so that the entire transferred material also contributes in the desired manner to reducing the scooping volume.

In order to avoid these problems and to improve the positional accuracy of the imaging, the owner of this method has developed the known method described in DE 195 03 951 A1 for producing an erasable and reusable gravure form, in which the depressions of the basic pattern of the gravure form are uniform be filled by means of a liquefiable substance by an application device, then material is removed from the wells by means of an image transfer device the gravure form, which is rasterized in the image, is colored by means of a coloring system and then printed in gravure, the gravure form is regenerated after the printing process and the depressions are filled evenly again. The liquefiable substance, for which thermoplastics, photopolymers or lacquers are used, is introduced into the depressions in the liquid state by hydrodynamic forces, in particular by capillary action. The imagewise ablation is preferably carried out by the action of thermal energy, for example laser beams. The regeneration of the rotogravure form after the printing process provides that the liquefiable substance is completely removed from the depressions of the basic grid by ultrasonic cleaning or high-pressure water and this is again filled with liquefiable substance. Alternatively, only the material of the liquifiable substance removed by the image-wise ablation can be replenished.

However, since three different process media are involved in this process, namely water, printing ink and liquefiable substance, there is a certain risk of mixing the process media during production.

From a further prior publication DE 19624441 C1, a method is known in which the process concept is simplified and solvent-based paints are avoided. Here, again starting from a gravure blank with a basic grid, a filling process is carried out in which the depressions of the basic grid of the rotogravure blank are filled uniformly by means of a UV printing ink by an application device and the UV printing ink (filler) is then filled by means of a gravure blank positioned dryer is cured, creating a highly cross-linked and therefore poorly soluble and infusible substance. In the subsequent imaging process, hardened UV printing ink is removed from the depressions by thermal ablation using a pixel transfer device using a laser. Then the gravure form, which is screened in the image, is colored by means of a coloring system with UV printing ink and the printing process is carried out. For retrofitting, the gravure form undergoes an erasing process using UV printing ink, preferably by refilling the ablated image areas. Alternatively, the filler can first be removed completely by laser ablation from the depressions in the rotogravure blank and then refilled.

Another development of ink-jet media for the production of printing forms is aimed at other liquid and polymerizable materials that can be solidified by various processes in addition to UV curing. For example, EP 0 776 763 A1 describes a process for the production of lithographic printing plates using the ink-jet technique and liquid ink-jet drops, which contain resin-forming reactants and after the application polymerize the plate. According to digital image data, a resin image is thereby generated on the plate and the printing plate thus produced can be used in offset printing. Such reactants, as also described in EP 0 776 763 A1, comprise polymerizable resin-forming monomers - including low-molecular polymers, copolymers, polymer polymers and further polymerizable prepolymers such as oligomers - and initiators which bring about the polymerization and, inter alia, chemical Catalysts, air or oxygen or electromagnetic radiation can be.

It is the object of the present invention to provide a simple and reproducible method and an apparatus for producing erasable and reimageable gravure forms.

This object is achieved according to the features of independent claim 1 and claim 23 and with regard to the use according to the features of claim 32.

In the method according to the invention, in which imaging material is introduced imagewise into the depressions of a substrate using the ink-jet technique and then solidified, it is not necessary to liquefy the imaging material before the introduction, since liquid substances are used as the imaging material, which after the solidification in the wells. Non-solidified imaging materials are referred to below as precursors, which are defined as liquid, low-viscosity and non-pigmented substances, which can be introduced into the wells using the ink-jet technique and which do not have to be changed in their physical state before introduction and which are solidified physically by solvent removal and / or chemically by polymerization to form imaging material. As a result, there is no need for a complex device for metering the energy supply upstream of the introduction device, nor for any other method steps for liquefying the imaging material before it is introduced into the depressions. The solidification of the precursor can advantageously be controlled in such a way that it does not take place until the precursor is introduced into the depressions.

In the method according to the invention, common devices and also common method steps can be used to introduce the at least one precursor into the depressions accurately and reproducibly with relatively little effort, so that from the substrate with depressions depth-variable or area-variable or depth- and area-variable gravure forms with the tonal values of Print template corresponding cups arise. In the following, this process step is also introduced as an image and that in the Wells solidified imaging material referred to as an imaging structure. The substrate can be imaged outside or advantageously inside the printing press. The gravure forms produced in this way can be colored using the techniques and machines commonly used for gravure printing and used for the printing process.

The ink-jet technique can be used particularly well for the introduction of the precursors, since the prerequisite for defined individual points is optimally met and the image resolution (dots per inch) and the ink drop volumes (picoliter) are variable. In addition, both ink drops of the same volume and multiple ink drop volumes can be used, the tonal values being generated in binary form using dot density modulation of equally large pressure points (dots) and / or by modulating the individual drop volume and thus the individual pressure point. These variables can advantageously be adapted to the requirements of the method according to the invention, for example by The resolution and drop volume of the ink jet device and the depth grid are matched to one another, so that each well is addressable and can be completely filled with one or more droplets. Thanks to special raster techniques, ink jet printers with a relatively low resolution, e.g. 386 dpi, images with sufficient print quality can be generated. The process consistency in the production of the rotogravure form - and thus of the finished printed product - and the creation of the print samples (proofs) is also advantageous, since both are done using the ink-jet technique. Both methods are particularly advantageously based on the same data set and pigment-identical ink jet inks and gravure inks can be selected.

For the method according to the invention, the precursor can thus be introduced into the wells in a single-layer or multi-layer and image-wise manner in the form of defined, uniformly or variably large drops in accordance with a logged digital data inventory which was created by scanning a print file or processing digital image information. Due to the variably adjustable ink drop volume, the well filling height can be adjusted so that, according to the invention, a defined overfilling of a depression with a precursor can counteract any material shrinkage when it hardens.

It is particularly advantageous if the data set used to generate the deepening grid is used to calculate the exact data. Addressing of the droplets is included in the database. In order to optimize the addressing and to take into account any manufacturing-related deviations in the substrate or to enable precise addressing without taking into account the data set used in the generation of the depth grid, it is advantageous if the surface of the substrate is optically scanned and recorded by a scanning head upstream of the printhead and the data thus obtained are forwarded to the ink jet device for data comparison.

The intaglio printing forms according to the invention can also be produced inexpensively and with considerably less effort than conventional intaglio printing forms, in particular with the method according to the invention, which increases the data variability, although the techniques and machines used in conventional intaglio printing can be used in the printing process. As a result, they expand the use of rotogravure to medium and small print runs and offer a market-friendly and inexpensive solution for this segment, but also for large runs, which meets the high quality requirements for the printing result that are common in rotogravure printing and also includes wide substrates.

In the method according to the invention, at least some of the depressions are preferably filled with the precursor so high in one or more layers that the surfaces of the imaging structures formed thereby, hereinafter called web surfaces or web structures, with the uniformly high webs of the substrate in lie on one level and form part of the non-imaging, uniformly high printing form surface and surface variable or, if the remaining depressions are filled with imaging structures of different heights, depth and surface variable gravure forms. Particularly preferably, each recess of a substrate provided with uniformly deep and large recesses in a matrix arrangement is filled completely or not at all with web structures, as a result of which all the wells reproduce pressure points with the same tonal value, but these by image resolution using a conventional binary ink jet grid, e.g. Error diffusion are distributed so that the printed image is still reproduced in accordance with the tonal value. Well depth and size of the well openings are therefore always the same and correspond to those of the wells that have remained unchanged, which is why the wells of this rotogravure form are neither variable in depth or area in the sense of conventional rotogravure forms but binary-area variable, since the printed image is also due to the ratio of printed to unprinted areas is played.

It is particularly advantageous to additionally vary the depth of these binary-area-variable cells by means of appropriate rastering and image-wise insertion of drops of different sizes or several layers, as a result of which depth-and binary-area-variable cells are formed and, depending on the number of the selected depths, a larger tonal range can be achieved , In a further embodiment of the method according to the invention, the depressions are filled with precursors to such an extent that in the depressions imaging structures of different heights and thus depth-variable gravure forms are formed.

It is favorable for the adaptation of the rotogravure printing forms according to the invention to the conditions during their production and to the printing conditions that the imaging structures can be constructed in one or more layers, the individual layers being hardened (for example in the case of UV-curing systems) or hardened and the drops being precise can be sprayed on top of each other. In this way, relatively high imaging structures can advantageously be built up in layers, which on the one hand enables many different well depths and thus tonal values to be generated, and on the other hand can also use printing inks with volatile solvents in the printing process by means of adapted well depths. Another advantage is the expanded range of usable precursors, because e.g. Two-component systems can be used, which, by spraying the drops onto one another with pinpoint accuracy, mix on the substrate using the ink-jet device and solidify in the depressions. Hardened imaging materials, which may be deposited on the webs in smaller quantities, can also advantageously be easily scraped off with a doctor blade before curing, which can be repeated before each layer application.

With the method according to the invention, in particular variable-area and even binary-variable variable gravure printing forms can advantageously be produced by two different procedures. In one approach, the precursor is introduced directly into the depressions in an image-wise manner, and the intaglio printing plate is produced with imaging cells. The wells of the intaglio printing form thus primarily arise from imagewise material build-up and not from material removal, which means that the additional process step of imagewise ablation is not necessary.

In the other procedure, which is a two-stage reversal process, the depressions are initially covered with web structures in such a way that the areas of the depressions in the substrate that form imaging cells in the rotogravure form to be produced are covered with imaging material and any further explained below, protective layer is not attacked. If a second precursor is introduced into the then still unfilled areas of the depressions at a time determined by the hardening time of the material introduced first, which does not attack the imaging material introduced first and the possible protective layer, i.e. attack, remove or attack dissolves - and the imaging material introduced first is then removed, for example by suitable solvents, without the second imaging material and the attack any protective layer, then the gravure form to be produced with imaging wells is created. The two-stage process has the advantage, among other things, that it is relatively uncritical if smaller amounts of the imaging materials are possibly deposited on the webs, because when the first imaging material applied and the second imaging material deposited thereon are also removed.

In order to remove any imaging materials that may be deposited on the webs, the web surfaces can advantageously also be covered with a thin layer by rolling on with high-viscosity auxiliary protective layers before the imaging process, which can be removed together with any imaging materials prior to the printing process by washing with suitable solvents. To remove imaging materials from the webs and / or to remove material overfills in the depressions, it is particularly advantageous if the precursors are only hardened, excess material is then removed using a doctor blade and then further hardened, which is e.g. with UV-curing systems by exact radiation metering.

When constructing the gravure printing forms produced according to the invention and when using them, it is advantageous that a large number of different — in particular organic — materials with very different properties are available, from which the imaging materials and, if appropriate, the protective layers and also the printing inks can be selected such that they are chemically and physically compatible with one another to the extent required, as described, for example, in the two-stage reversal process, and are easily removable again.

A material that can be solidified physically by solvent removal and / or chemically by polymerization to form one of the imaging materials is advantageously used as a precursor. Materials with high mechanical resistance, e.g. Abrasion resistance and adhesion to the substrate, such as, for example, radiation-curing liquid polymers, since, above all, the web structures together with the webs, as explained below, are subjected to high mechanical stresses in the printing process. In addition, the imaging materials and the possible protective layer can be selected so that the gravure forms produced with them are suitable for various color systems that can be used in gravure printing and are therefore not limited to specific colors.

Substrates can consist of metal, plastic or ceramic, all of which can be in the form of printing cylinders, cylinder sleeves or plates and advantageously have uniformly high webs and an almost 100% doctor blade support. To be favoured ceramic substrates, which have a very high mechanical resistance and thus a long service life. This is necessary because during the inking process in the printing process, excess ink is removed from the webs by means of a doctor blade and the webs and the web structures are thereby subjected to considerable mechanical stress. In addition, the pigments incorporated in the printing inks create a strong mechanical load on the printing form in the squeegee gap. In contrast to metal or plastic surfaces, the production of ceramic substrates, for example through the use of chromium oxide with a particle size of approx. 2-30 μm, creates a finely porous and therefore absorbent substrate surface. This advantageously increases the adhesion of the imaging materials to the substrate structure, but the imaging materials or also the printing inks can become embedded in these pores, making them difficult to remove again.

It can therefore be advantageous in the described methods, e.g. In order to facilitate the detachment of the imaging materials and / or printing inks from substrates made of ceramic but also metal or plastic, the surface of the depressions or only the areas of the depressions on which imaging structures are to be produced are covered with a thin protective layer. For this purpose, low-viscosity, solvent-based materials with a defined solids content (e.g. VC copolymers), which attaches to or accumulate on these surfaces after solvent removal, can be sprayed on or rolled or knife-coated over a whole area in a defined layer thickness of approx. 1 - 3 μm be sprayed on with the ink-jet device, the capillary action of the ceramic supporting this introduction. Due to the high solvent removal (approx. 60%), neither the volume of the depressions nor the adhesion of the imaging materials to the substrate is changed significantly and the protective layer remains in the substrate structure during the print application.

In the method according to the invention, the detachment of the imaging structures from the substrate is initiated primarily by chemical processes and not by physical or mechanical measures such as heating, laser erasing, ultrasound or high pressure water and is only supported physically or mechanically. This measure advantageously allows imaging materials and printing inks to be completely removed again from the substrate, even if residues remain in the substrate after they have been removed by means of suitable solvents and mechanical cleaning, since these are detached together with the protective layer when the protective layer is removed by means of suitable solvents.

In the method according to the invention, dependency and interaction between the protective layer, precursor or imaging materials and the solvents used with them are medium groups (e.g. ketones, alcohols, petrol etc.) and the printing ink systems (e.g. alcohol / water, UV inks etc.) are used and advantageously coordinated.

The precursors are matched in their viscosity and their rheological properties to the requirements of the method according to the invention and to the use of the ink-jet technique and can also contain auxiliaries such as initiators, waxes and wetting agents. Imaging materials that harden physically through solvent removal can usually be dissolved again in common defined solvents despite these additives. In contrast, the solubility of imaging materials that can be hardened by polymerization, such as UV-curing systems, can be influenced in such a way that they are no longer attacked by normal solvents and, especially in the case of substrates made of ceramic, can only be removed from the wells by aggressive solvents such as methylene chloride in conjunction with mechanical measures release completely.

In order to be able to work with ceramic substrates and common, environmentally friendly solvents such as N-methylpyrrolidone in the process according to the invention, the properties of the ceramic substrate and the above-mentioned coordination between protective layer, precursor or imaging materials, solvent groups and printing ink systems can be advantageously combined. If a protective layer that is soluble in N-methylpyrrolidone and then a precursor that can be solidified by polymerization are introduced into the substrate, e.g. be printed with alcohol-based printing inks. After completion of the print job, the printing form is deleted and e.g. impregnated with N-methylpyrrolidone. This diffuses through the pores under the imaging material, where it dissolves the protective layer and as a result the imaging material, which cannot be attacked per se, is detached from the substrate and e.g. ultrasound-supported can be removed from the substrate with almost no residue. After all of the materials described have been removed, the cleaned substrate cylinder is reimaged.

To apply different media such as protective layer and precursor, it is favorable to apply them in separate systems to avoid mixing of the process media, whereby one or more print heads or spray heads can be used, which are arranged one after the other parallel to the substrate cylinder on a traverse in the y direction or and / or are attached in the x direction on several parallel cross members and can move in both directions of the cross members. If different or the same media are sprayed one after the other with pinpoint accuracy next to or on top of each other and the individual layers have to be hardened or hardened, the subsequent layers must be applied at suitable, media-dependent, different intervals. You can do that alternately in different running directions or, in the case of a sufficient spatial distance of the print or spray heads guiding the different media, in the same running direction. This spatial distance can preferably be set in a targeted manner in accordance with the required time interval in the y and / or x direction by means of variably placeable print heads or spray heads and / or traverses. However, it is also possible to apply only one medium with each roller revolution.

Further advantageous refinements of the method according to the invention, the gravure printing forms according to the invention and the use according to the invention are listed in the subclaims.

The invention is described below using exemplary embodiments. It show highly schematic

1 is a perspective view of an enlarged section of a ceramic substrate for rewritable gravure forms, which has depressions that are uniformly deep, have uniform openings, and form a grid in the form of a matrix arrangement,

2 shows a detailed view of the cross section through the recess grid of a ceramic substrate with unspecific roughness of the web surfaces before polishing

3 shows a detailed view of the cross section through the recess pattern of a ceramic substrate with specific roughness after polishing,

4 is a top view of an enlarged detail from the substrate shown in FIG. 2,

5 is a top view of an enlarged detail from the substrate shown in FIG. 3,

6a to 6b in plan view an enlarged and a greatly enlarged section of a ceramic substrate without a recess grid and with a porous surface structure,

7 ink-jet device with two writing heads, two UV light diodes and an upstream scanning head,

8 shows the substrate shown in FIG. 1 with binary surface-variable imaging structures 9 shows the example of a cleaning system,

10a to 10e in a schematic cross-sectional representation different stages of the manufacture and use of an erasable and reimageable binary surface variable gravure form, whereby a substrate is assumed, as shown in FIGS. 1 and 3,

11a to 11e in a schematic cross-sectional representation different stages of the production and use according to the invention of an erasable and reimageable depth- and binary area-variable gravure form, starting from a substrate, as shown in FIGS. 1 and 3,

12 is a schematic, greatly enlarged plan view of a section of a non-ceramic substrate for rewritable gravure forms, which has depressions that are uniformly deep, have uniform openings, and form a grid in the form of a matrix arrangement,

13 shows a schematic representation of an embodiment of an area-variable gravure form, in which the depressions of the substrate shown in FIG. 14 are covered with web structures,

14 shows a schematic representation of an embodiment of an area-variable gravure printing plate which has the same pattern as that in FIG. 15, but with cells instead of the web structures and web structures instead of the cells,

15a to 15e in a schematic cross-sectional representation different stages of the manufacture and use of an area-variable gravure form,

16a to 16e in a schematic cross-sectional representation different stages of the production and use of a depth-variable gravure form according to the invention.

FIG. 1 shows an enlarged section of a ceramic substrate 1 with uniformly deep, approximately identical depressions 2 in a matrix arrangement and uniformly high webs 3, which is preferably used in the method according to the invention. Due to the manufacturing process, laser ablation creates a melt deposit which, as shown in FIG. 2, causes an unspecific surface roughness 4 on the ceramic surface. This is polished off for the use of the substrate in the method according to the invention, in order as in PAGE 13 SHOULD NOT BE CONSIDERED FOR THE INTERNATIONAL / PHASE

energy-meterable light guide and one or more UV diodes 13 can be made precisely.

At least one material from the group of polymer solution, such as e.g. liquid adhesives that bind physically by solvent removal or polymerizable monomers, prepolymers and polymers such as e.g. UV-curing liquid polymers, chemically setting adhesives and one- or multi-component reaction adhesives and their chemical catalysts or initiators for the polymerization and, accordingly, as solidified imaging material, at least one material from the group consisting of plastics, from which the solvent has been removed, hardened, polymerized polymers such as radiation-hardened polymers, Kait hardened one-component systems and fully reacted two-component systems selected. In addition to the chemical catalysts or initiators and the UV rays, other electromagnetic rays, oxygen or air or oxygen deprivation can also be used as such. Act. In order to make general precursors common for ink-jet, it is usually necessary to add defined additives. A precursor of a UV curing liquid polymer then consists e.g. About 80% from prepolymerized acrylics, monomers, prepolymers and oligomers and about 20% from photoinitiators, waxes, wetting agents and auxiliaries. As already described, such additives can significantly influence the dissolving behavior of the imaging materials.

The precursors can be introduced into the wells in a single-layer or multi-layer and image-wise manner according to a logged digital data stock, the consolidation being able to be controlled in such a way that it does not take place until the precursor is introduced into the wells. In the case of polymer solutions, this is achieved by using suitable solvents with suitable evaporation numbers and in the case of polymerizable monomers and polymers, e.g. achieved by exposure to radiation after insertion or precise overlapping with chemical catalysts or initiators. The drops are jetted out of the printhead and are mixed by precise overlapping.

In the method according to the invention, the at least one precursor is introduced into the selectable, different recess grids of the substrate in such a way that either depth-variable or area-variable or depth-and area-variable and preferably binary area-variable and depth- and binary area-variable gravure forms are created. FIG. 8 shows the substrate 1 shown in FIG. 1 with depressions 2 in a matrix arrangement and with binary surface-variable imaging structures 14, the resolution and drop volume of the ink jet device being adapted to the depression grid and thus addressing each depression. became cash. As an example, a printer resolution of 386 dpi corresponds to a substrate line width of 152 lines / cm. The image resolution was frequency-modulated, for example by means of error diffusion. In the method according to the invention, however, both the screen types used in gravure printing, for example depth-modulated or amplitude-modulated screens, and the digital screen types of the ink-jet device, for example dither matrix or error diffusion, or variations and mixtures of both or other screens can be used as imaging screens become. In addition, it is possible for all gravure forms that can be produced to choose different, also stochastically distributed, depth grids. For example, the number of lines per cm of the imaging grid can be greater than, equal to or less than the number of lines of the deepening grid and the volume of the variable or uniformly large precursor drops can be greater than, equal to or less than the volume of the individual wells.

When printing with gravure forms, it is advantageous to use printing inks, also for environmental reasons, which essentially contain water or water / alcohol mixtures as a solvent. The use of such printing inks expands the range of organic materials which can be used according to the invention as imaging materials and for the protective layer, since materials can be used for these which are preferably used in solvents for organic substances such as hydrocarbons, in particular fluorocarbons, tetrahydrofuran, dimethylformamide and N-methylpyrrolidone are soluble. However, it is also possible to use other printing ink systems which are matched to these materials in accordance with the process and with various, more volatile solvents or without solvents.

After the printing process, the gravure form is cleaned of the printing inks and then deleted. Residues of ink remaining on the substrate are removed during this deletion process with the protective layer and the imaging material. To erase the gravure printing forms produced according to the invention, closed cleaning systems are preferably used, as shown in FIG. 9, in which gravure printing forms 15 are freed of imaging material and protective layer using solvent 16, such as N-methylpyrrolidone, with the aid of ultrasound 17. The porous substrate surface of the ceramic can advantageously be used in conjunction with the protective layer and its solubility, since the solvent triggers and removes the protective layer by diffusion and thus ensures an almost residue-free detachment of the protective layer, imaging material and printing ink. In the second cleaning cell 18, the remaining dirt particles are removed in a water bath 19 and evaporating solvents are fed to a recovery 20, after which the substrate 1 shown in FIG. 1 is again obtained, which is then loaded again. can be developed. The protective layer mentioned according to the invention must be renewed before each imaging.

The production of a preferred, binary area variable, erasable and reimageable gravure printing plate with the method according to the invention and the use of the gravure printing plate produced thereby will be described with reference to FIGS. 10a to 10e. The starting point is a substrate 1 shown in FIG. 1 with uniformly deep, approximately identical depressions 2 in a matrix arrangement and with webs 3 of uniform height. The grid line width is preferably approximately 60-300 lines / cm.

FIG. 10 a shows a cross section through the substrate 1 shown in FIG. 1. A protective layer (not shown) in the form of a polymer solution is first introduced into the depressions 2. A precursor is then introduced into the depressions 2 by means of the ink-jet technique, preferably in accordance with a logged digital data inventory, in one or more layers and solidified to form the web structure 21. An example of a rotogravure form which is variable in terms of binary surface is formed, the depressions either being completely filled with web structure 21 or not being filled at all, as a result of which the cups 14 correspond to the depressions with approximately identical dimensions and do not vary in depth and size of the cup opening. The wells 14 therefore all have the same volume and the tonal values result solely from the distribution of these wells 14 in the substrate. The imaging material must be removable after use, have a high mechanical resistance and must not be attacked by the printing ink systems used. Polymerisable monomers, prepolymers and their chemical catalysts or initiators, which are not soluble in water or water / alcohol mixtures after solidification, are suitable as precursors.

The structure shown in Fig. 10b is filled with printing inks 22 which e.g. contain water or water / alcohol mixtures as solvent, the protruding printing ink is stripped off with a doctor blade according to Fig. 10c, then the gravure form is brought into contact with the printing medium, e.g. a paper web.

From the structure then present, shown in FIG. 10d, which only has color residues and which practically corresponds to that shown in FIG. 10b, the imaging material is then - optionally after cleaning with the solvent for the printing inks - by adding, removing , or dissolving with solvents or solvent mixtures which dissolve the imaging material, and / or with a chemical with which the imaging material reacts, or the imaging material is removed from the sub-layer by dissolving the protective layer. strat replaced. These processes can be supported by mechanical means, for example by brushing or the use of an ultrasound device. What remains is the shape shown in FIG. 10e, which is identical to that shown in FIG. 10a. It can now be illustrated with a predecessor.

The method can also be used to generate particularly advantageous depth-variable and binary-area-variable gravure forms that can be deleted and imaged again. The depth of binary-area-variable cells is additionally varied by appropriate screening, which creates depth- and binary-area-variable cells with different volumes and, depending on the number of selected depths, a larger range of tonal values can be achieved. It is described with reference to FIGS. 11a-11e. The starting point is again a substrate 1 shown in FIG. 1 with uniformly deep, approximately identical depressions 2 in a matrix arrangement and with uniformly high webs 3. The grid line width is preferably approximately 60-300 lines / cm.

FIG. 11 a shows a cross section through the substrate 1 shown in FIG. 1. A protective layer (not shown) in the form of a polymer solution is first introduced into the depressions 2. A precursor is then introduced into the depressions 2 by means of the ink-jet technique, preferably in accordance with a logged digital data inventory, in depth and binary-area-variable form in one or more layers and solidified to form imaging material. In addition to the web structures 21, the depth of the wells which are distributed in a binary-area-variable manner is varied by means of imaging structures 23 of different heights, which in turn creates wells 14 which correspond to the depressions with approximately identical dimensions and do not vary in depth and size of the well opening, and additionally wells 24 arise, the depth of which is different. The imaging material has the same properties as that of FIGS. 10b-10d and is formed from the same precursors.

The structure shown in Fig. 11b is filled with printing inks 22 which e.g. contain water or water / alcohol mixtures as solvent, the protruding printing ink is wiped off with a doctor blade according to Fig. 11c, then the gravure form is brought into contact with the printing medium, e.g. a paper web.

From the then existing structure shown in FIG. 11d, which only has residual paint, which practically corresponds to that shown in FIG. 11b, is then deleted using the same method as described with reference to FIG. 10d. The rest remains in Fig. 11e shown form, which is identical to that shown in FIG. 11a. It can now be illustrated with a predecessor.

The process can also be used to create variable-area gravure forms that can be deleted and re-imaged. The size of the well openings is varied, while the depth of the well remains the same. They are described with reference to FIGS. 15a-15e and 13 and 14.

The production of an intaglio printing form, as shown in FIG. 13, and its use will be explained with reference to FIGS. 15a to 15e. The substrate 25 shown in FIG. 12 with uniformly deep, approximately identical depressions 2 in a matrix arrangement and with uniformly high webs 3, which represents a non-ceramic substrate, can serve as the basis for the variable-area gravure form. The grid line width is preferably about 60-300 lines / cm.

FIG. 15a shows a cross section through the substrate 25 shown in FIG. 12. A precursor is introduced into the depressions 2 by means of the ink-jet technique, preferably in accordance with a logged digital data inventory, in one or more layers and solidified to form the web structure 21. An example of an area-variable gravure form is formed, the depressions being filled with web structure 21 in such a way that wells 26 with different sizes of the well opening are created at the same depth, as a result of which the volume of the wells 26 varies and different tonal values can be generated. The imaging material has the same properties as that of FIGS. 10b-10d and is formed from the same precursors

The structure shown in Fig. 15b is filled up with printing inks 22 which e.g. contain water or water / alcohol mixtures as solvent, the protruding printing ink is wiped off with a doctor blade as shown in Fig. 15c, then the gravure form is brought into contact with the printing medium, e.g. a paper web

From the then existing structure shown in FIG. 15d, which only has residual paint, which practically corresponds to that shown in FIG. 15b, the structure is then deleted using the same method as described with reference to FIG. 10d, with no protective layer having to be removed. What remains is the shape shown in FIG. 15e, which is identical to that shown in FIG. 15a. It can now be illustrated with a predecessor. FIG. 13 shows FIGS. 15b and 15d in supervision. The depressions of the area-variable gravure form are filled with a web structure 21 in such a way that wells 26 with different sizes of the well opening are created at the same depth, whereby the volume of the wells 26 varies and different tonal values can be generated.

The gravure form shown in FIG. 14 shows the same pattern as FIG. 13, but there are wells 26 at the locations in FIG. 14 at which web structures 21 are located in FIG. 13 and vice versa, i. H. the web structures in FIGS. 13 and 14 are complementary to one another in that, taken together, they completely fill the recess grid of FIG. 12. The intaglio printing form shown in FIG. 14 can be produced by introducing the precursor directly into the depressions in an imagewise manner and thus producing the intaglio printing form with imaging cups. Alternatively, the gravure form shown in FIG. 13 can be converted into the one shown in FIG. 14 using the two-stage reversal method.

For this purpose, the depressions 2 are initially covered with web structures 21 in such a way that the areas of the depressions in the substrate which form cups in the gravure printing mold to be produced are covered with web structures 21 and a possible protective layer is not attacked in the process. If a second precursor is introduced into the then still unfilled areas of the depressions in time - determined by the hardening time of the material introduced first - which does not attack the imaging material introduced first and the possible protective layer - i.e. attack, remove or attack dissolves - and the imaging material that was brought in first becomes, for example removed by means of suitable solvents without attacking the second imaging material and the possible protective layer, then the intaglio printing form shown in FIG. 14 with web structures 21 imaging wells 26 is produced. Also rotogravure forms which are variable in area can be produced with this reversal process.

The second imaging material can be selected, for example, from the materials that are also used as the imaging material introduced first, provided that it is ensured that the imaging material introduced first is not attacked when the second one is applied and that it is not attacked when the first one is detached or detached.

The method can also be used to create depth-variable gravure forms that can be deleted and re-imaged and in which tonal values are generated only by different cell depths and not additionally by the distribution of the cells become. It is described with reference to FIGS. 16a-16e. The starting point is again a substrate 1 shown in FIG. 1 with uniformly deep, approximately identical depressions 2 in a matrix arrangement and with uniformly high webs 3. The grid line width is preferably approximately 60-300 lines / cm.

16a shows a cross section through the substrate 1 shown in FIG. 1. A protective layer (not shown) in the form of a polymer solution is first introduced into the depressions 2. A forerunner is then introduced into the depressions 2 by means of the ink-jet technique, preferably in accordance with a logged digital data inventory, in variable-depth images in one or more layers and solidified to form imaging material. An example of a variable-area gravure form is formed, the depressions being filled with imaging structures 27 in such a way that wells 28 of different depths are created with the same size of the well opening, as a result of which the volume of the wells 28 varies and different tonal values can be generated. The imaging material has the same properties as that of FIGS. 10b-10d and is formed from the same precursors.

The structure shown in Fig. 16b is filled with printing inks 22 which e.g. contain water or water / alcohol mixtures as solvent, the protruding printing ink is wiped off with a doctor blade according to Fig. 16c, then the gravure form is brought into contact with the printing medium, e.g. a paper web.

From the then existing structure shown in FIG. 16d, which only has residual paint, which practically corresponds to that shown in FIG. 16b, is subsequently deleted using the same method as described with reference to FIG. 10d. What remains is the shape shown in FIG. 16e, which is identical to that shown in FIG. 16a. It can now be illustrated with a predecessor.

In the following, the method and the use are explained in more detail using four specific examples.

Example 1:

A solution of polyvinyl chloride in tetrahydrofuran is applied to the entire surface of a substrate (see FIG. 10a). After the tetrahydrofuran has evaporated, a protective layer of polyvinyl chloride remains. A precursor, which consists of a two-component adhesive with an adhesive component based on alpha-cyanoacrylic acid and a binder component, is inserted into the depressions of the substrate coated with it by means of an ink jet Device, as described with reference to FIG. 7, introduced pictorially, in which case first the filler component of the adhesive and then the binder component are sprayed onto one another with pinpoint accuracy and web structures are produced in layers. After the reactive curing of the adhesive, which takes about three minutes, the imaging material is present (see FIG. 10b), which has a Shore hardness of about D87 and frames the cells of the gravure printing plate. The applied imaging material is not significantly attacked by a printing ink that contains a water / alcohol mixture as solvent or no solvents (UV-curing printing inks). After the printing process (see FIG. 10d), the imaging material and the protective layer are removed with N-methylpyrrolidone (see FIG. 10e).

Alternatively, the polyvinyl chloride solution can also be selective, i.e. only be applied to the substrate areas, which are then covered with the precursor. In this case, the polyvinyl chloride solution is applied with the ink-jet device from a spray head, which is connected upstream of the spray head for the binder component, precisely and in time before the components of the adhesive.

Example 2:

A solution of polyvinyl chloride in tetrahydrofuran, from which a protective layer of polyvinyl chloride is formed, is applied to the entire surface of the substrate shown in FIG. 1. A solution of nitrocellulose in ethanol is then introduced into the depressions as the first precursor by means of an ink-jet device, as described with reference to FIG. 7, by spraying several droplets onto one another, which are hardened or cured in between, the depressions having web structures First of all, the areas of the depressions in the substrate that form imaging wells in the rotogravure form to be produced are covered with web structures. The areas of the depressions not covered with the first imaging material are then filled with a second imaging material or its precursor at an interval in time determined by the solidification time of the material introduced first, using an ink-jet device, as described with reference to FIG. 7. The two-component adhesive used in Example 1, as described there, or a UV-curing liquid polymer can be used as the precursor of the second imaging material. After the nitrocellulose has been peeled off with ethanol, the gravure printing form to be produced lies with imaging. Well according to the tonal values of the print template. The gravure form is used and deleted as described in Example 1. Alternatively, and valid for each reversal process, the second imaging material can be coated, then hardened, for example when using UV-curing liquid polymers by means of UV rays, and then the substrate can be scraped off, as a result of which the excess coating and coating on the webs deposited material completely removed and the web surfaces of the imaging material lie in one plane with the surfaces of the webs.

Example 3:

A solution of vinyl chloride copolymer in N-methylpyrrolidone is applied to the entire surface of the substrate shown in FIG. 1, from which a protective layer of vinyl chloride copolymer is formed after the N-methylpyrrolidone has evaporated. A solution of an alkyd resin in acetone, which hardens very quickly, is then introduced into the depressions as the first precursor by means of an ink-jet device as described in Example 2 to form the web structures described in Example 2, additional precursors being aimed specifically at the surfaces of the Webs is injected. The areas not covered with the first imaging material are then filled as described in Example 2 with a second imaging material or its precursor, which can consist of the same materials that are also listed in Example 2. When the alkyd resin is removed with acetone or alcohol, the layer formed on the webs and with it any second imaging material which may have been deposited thereon is also removed. The gravure form to be produced with imaging cells is then available in accordance with the tonal values of the print template. The gravure form is used and deleted as described in Example 1.

Example 4:

A solution of vinyl chloride copolymer in N-methylpyrrolidone is applied to the entire surface of the substrate shown in FIG. 1, from which a protective layer of vinyl chloride copolymer is formed. In front of the imaging process, the surfaces of the webs are then covered with a highly viscous auxiliary protective layer of a plasticizer-based Alumini ^¬ umpaste thin layer by an elastic inking roller covers by rolling be ^¬. A solution of an alkyd resin in acetone is then introduced into the depressions as the first precursor by means of an ink-jet device as described in Example 2 in order to form the web structures described in Example 2. The areas not covered with the first imaging material are then filled as described in Example 2 with a second imaging material or its precursor, which can consist of the same materials that are also listed in Example 2. When removing the Aikyd resin with Ace clay or alcohol is also removed from the webs, also alcohol-soluble auxiliary protective layer made of aluminum paste and with it the possibly deposited first and / or second imaging material. The gravure form to be produced with imaging cells is then available in accordance with the tonal values of the print template. The gravure form is used and deleted as described in Example 1.

All gravure forms made with the described method can be used for both direct and indirect gravure printing. According to the current state of the art, the exchange of the printing forms between the print jobs is largely automated, which is why the imaging and deletion of the gravure forms produced can advantageously take place in the printing press or outside of it in a separate device. Both during imaging and when deleting the gravure forms, the areas of the substrate surface to be processed can be selectively heated to facilitate material application and removal, and the vapors produced can be extracted. During the deletion process, the respective solvent can also be heated in order to support the release of the different materials from the substrate. The closed cleaning system preferred during the deletion process can be located outside the printing press or can be integrated particularly advantageously into the printing press, for example by the ink application system is expanded to a closed system with which, for example, the respective solvents are applied to the rotogravure form instead of the ink and the various materials are replaced by an integrated ultrasound device.

Claims

Expectations

1. A method for producing gravure printing forms, in which a substrate (5) provided with a grid of sufficiently deep recesses is provided and in the recesses for forming a grid of cells (15) a grid of structures made of at least one matched to the tonal values of the print template a removable imaging material is produced, characterized in that at least one low-viscosity precursor of the imaging material is introduced into the depressions (6) by means of an ink-jet device and then solidified to form imaging material.

2. The method according to claim 1, characterized in that a protective layer is applied before the introduction of the precursor, which closes the porosity of the substrate.

3. The method according to any one of the preceding claims, characterized in that the at least one precursor is introduced in the form of droplets, the droplets being of uniform size and having a diameter between approximately 20 and approximately 40 μm.

4. The method according to any one of the preceding claims, characterized in that the droplets are introduced in accordance with a logged digital database, which was created by scanning a print template or by processing digital image information, matched to the tonal values of the print template.

5. The method according to claim 4, characterized in that the data set used in the generation of the deepening grid for calculating the exact addresses of the droplets is included in the database.

6. The method according to any one of the preceding claims, characterized in that a material which can be solidified physically by solvent removal and / or a material which can be hardened by polymerization to form imaging material is used as the precursor.

7. The method according to claim 6, characterized in that at least one material from the group of polymers such as UV-curing liquid polymers, chemically setting adhesives and one- or multi-component reaction adhesives, and their chemical catalysts or initiators, is selected as the precursor.

8. The method according to any one of the preceding claims, characterized in that at least some of the recesses (6) with the precursor of the imaging material (7) are so high It is filled that depth-variable gravure forms are formed with cells according to the tonal values of the print template.

9. The method according to any one of the preceding claims, characterized in that the imaging structures (12) are one or more layers.

10. The method according to claim 9, characterized in that the individual layers are composed of juxtaposed and optionally superimposed injection points.

11. The method according to any one of the preceding claims, characterized in that the depressions (6) with plateau or imaging structures (12) made of imaging material are partially so covered that initially the areas of the depressions in the substrate (5) which are in the gravure form to be produced form a grid of cells (15) according to the tonal values of the print template, with imaging material that the still unfilled areas of the wells are filled with a second imaging material, which or its precursor does not attack (attack) the imaging material applied first , and that the imaging material applied first is then removed without substantially attacking the second imaging material, as a result of which the gravure printing plate to be produced is formed with a grid of cells in accordance with the tonal values of the printing original.

12. The method according to claim 11, characterized in that the imaging material applied first is removed physically by dissolving or chemically.

13. The method according to any one of the preceding claims, characterized in that at least some of the recesses (6) are filled completely with the at least one precursor up to predetermined heights and then the recesses are covered with web structures up to their upper edge, wherein the filling and covering takes place in such a way that the wells that are created correspond to the tonal values of the print template.

14. The method according to any one of the preceding claims, characterized in that before the application of the precursor over the entire area or on the areas to be covered with precursor, a protective layer made of a material is applied to the substrate, which of the materials involved in the imaging of the gravure form and the used printing inks is not significantly attacked.

15. gravure printing plate made of a substrate with a grid of sufficiently deep depressions (6) and a grid of structures made of a removable imaging material, produced according to a method according to one of claims 1 to 14, which is applied in the depressions to the tonal values of the printing template, that the depressions are partially covered with imaging structures (12) made of the imaging material, the web surfaces of which lie approximately in one plane with the upper edge of the depressions.

16. Gravure printing plate according to claim 15, characterized in that the depressions (6) are filled to a defined height with imaging material (7) and the remaining height of the depressions between the upper edge of the filling and the upper edge of the depressions are at least partially occupied by web structures whose height is equal to the difference.

17. Gravure printing plate according to one of claims 15 to 16, characterized in that the imaging structures (12) are produced with respect to their distribution over the substrate and the size and shape of their surfaces in such a way that the wells (15) recessed in the depressions (6) ) correspond to the tonal values of the artwork.

18. Gravure printing plate according to one of claims 15 to 17, characterized in that at least one material from the group of the polymers such as UV-curing liquid polymers, chemically setting adhesives and one- or multi-component reaction adhesives, as well as their chemical catalysts or initiators, is selected as the imaging material is.

19. Gravure printing plate according to one of claims 15 to 18, characterized in that a protective layer is applied to the substrate surface in the depressions (6), which is not significantly attacked by the materials involved in the imaging of the gravure printing plate and the printing inks (8) used ,

20. Use of a gravure printing plate according to one of claims 15 to 19, characterized in that it is provided with a printing ink (8) which does not attack the imaging material in the finished gravure printing plate and, if appropriate, the protective layer, that it is printed that after the printing process is complete Imaging material, possibly the material of the protective layer, and any ink residues remaining on these materials are removed physically or chemically.

21. Use according to claim 20, characterized in that the areas of the substrate surface from which materials are removed are selectively heated during removal and that vapors are suctioned off.