EP1311399B1 - Method for producing a printing plate, in particular for letterpress printing and a printing plate for letterpress printing - Google Patents

Abstract

With the method according to the invention for producing a printing plate, in particular for flexoprinting, a layer of a curable elastomer is applied to a carrier (15) with a cylindrical surface area (26), subsequently the elastomer layer is cured to an essentially cylindrical endless printing form blank and possibly ground to a cylindrical peripheral form or processed otherwise, and afterwards the printing form blank (33) is separated along a line which is essentially parallel to the axial direction of the carrier and the printing plate produced in such a manner.

Description

The invention relates to a method for producing a Pressure plate especially for high pressure and is also on a pressure plate for high pressure, especially for the Flexographic printing directed with a lower support foil or plate and an applied on this elastomer layer is provided.

For the high pressure, in particular the flexo printing become frequent Continuous forms used in which a seamless elastomeric layer arranged on a cylindrical support and on their surface is engraved to match the color of the selected Bodies to transfer. From DE 197 56 327 A1 is a cylindrical printing form known whose elastomer layer of a thermosetting one-component or two-component silicone polymer is formed.

A particularly advantageous endless printing plate or a method for its preparation is known from DE 196 25 749 C2, to which expressly incorporated herein by reference and the content of their disclosure to the disclosure of the present Invention is made. In the known, seamless Printing form is the elastomer layer of a cold-curing Silicone polymer or silicone fluoropolymer formed by the rotational casting on the cylindrical surface of a Carrier is applied and after curing in particular advantageously engravable directly with a working laser is.

In addition to continuous printing plates are also for flexographic printing Plate printing forms needed, including a Gummiklischees and on the other hand photopolymer printing plates are available, the for high-quality flexo printing nowadays often with the "Computer to plate" procedures are prepared for printing. Here, the surface of a photopolymer plate, the is curable by exposure to ultraviolet light, first coated with a black, opaque layer, then partially followed by a computerized, the image data transmitting laser is opened. The thus exposed areas of the polymeric plate are exposed by exposure hardened and then the black layer and the underlying, uncured areas of the printing plate washed off to complete the printing plate. The procedure in the manufacture of photopolymer printing plates is as such known and need not be explained in detail here.

For printing with the plate printing forms these are on cliché sleeves or format cylinders mounted, including corresponding Adhesive tapes or films - so-called "tapes" - are used, where it is for different print areas or print qualities also different compressible tapes are. Especially with very thin printing plates it is necessary between the cylindrical support and the pressure plate a compressive To arrange intermediate layer, because of the low intrinsic flexibility a thin printing plate otherwise no clean printed image is obtained. In addition to fixing the printing plates on the Carrier with the help of tapes or foils it is also possible the material of the photopolymer plate on a ferromagnetic Foil or plate, such as a tinplate to arrange, which are then adhered to magnetic cylinders can.

The known photopolymer plates, be they Einschichtplatten, Multi-layer plates or plates made from liquid photopolymers are produced, have the disadvantage that their surface only after the platesetting their required for printing Final hardness and thus the surface quality before the exposure can vary, which often causes bumps reduce print quality in the plate surface. A mechanical one Post-processing of the photopolymer plates for smoothing its surface after the exposure is again not possible as a result, the upstanding, printing parts of the plate again would be damaged.

The object of the invention is to provide a method for producing a Specify printing plate, with which it is possible, a printing plate for the high pressure, the mechanical on their surface can be edited with high precision before the print data on the plate will be transferred. The procedure should be particular for the production of thin printing plates and printing plates with ferromagnetic metal base are suitable on magnetic cylinders can be used.

a) Auftragen einer Schicht eines aushärtbaren Elastomers auf einen Träger mit zylindrischer Mantelfläche;

b) Aushärten der Elastomerschicht auf dem Träger zu einem im wesentlichen zylindrischen, endlosen Druckformrohling;

c) Auftrennen des Druckformrohlings entlang einer im wesentlichen parallel zur Achsrichtung des Trägers verlaufenden Schnittlinie; und

d) Entnahme der so erzeugten Druckplatte von der Mantelfläche des Trägers.

This object is achieved with the invention by a method which is characterized by the following method steps:

a) applying a layer of a curable elastomer on a carrier with a cylindrical surface;

b) curing the elastomeric layer on the carrier to form a substantially cylindrical, continuous printing block blank;

c) separating the printing block blank along a substantially parallel to the axial direction of the carrier cutting line; and

d) removal of the pressure plate thus produced from the lateral surface of the carrier.

The process of the invention is thus similar to the printing plate according to DE 196 25 749 initially an endless printing plate generated by a curing elastomer on a cylinder or a hollow cylindrical sleeve with a cylindrical outer surface is applied after curing of the elastomer layer is cut from one to the other end of the cylinder and so the pressure plate forms. As a curing elastomer can thereby preferably a silicone polymer, a silicone fluoropolymer or else a Poyuethanpoymer be used. Most notably vorzuillhaft is the use of a cold-curing Silicone polymer or silicone fluoropolymer as indicated by the older patent specification 196 25 749 is proposed. As well as There, the hardening ellastomer is useful in Rotationsgießverfahren on the outer surface of the carrier preferably descriptive of a helix, caterpillar-like material strand applied.

Preferably, on the cylindrical outer surface of the carrier applied a release layer before applying the elastomer, then after curing and separating the printing block blank its easy removal guaranteed by the lateral surface of the wearer. The release layer can be made of a flexurally elastic Foil or a plate that surround the cylindrical surface the vehicle is placed. Preferably, the arrangement doing so made that the film or plate under education a seam line is placed around the wearer and that the later Cutting line along the seam line runs, so that only that too the cured blank mold elastomer is separated must to remove the pressure plate from the cylindrical support can.

It is particularly expedient if the carrier is made essentially from a vacuum cylinder and the film or plate by means of Negative pressure is maintained on the cylindrical jacket surface, thereby ensuring that they are during manufacture the pressure plate close to the cylinder surface applies and after Decrease of the pressure plate from the carrier this no bumps having. Preferably, the foil or plate is along its Seam edges with an adhesive tape or the like. to an endless separation layer closed to a gaping at the seam edges to avoid. The film or plate is preferably made of a essentially incompressible material, for example made of plastic or metal, in particular ferromagnetic metal like tinplate or the like, whereby the pressure plate later on Magnetic cylinders is used.

The printing plate produced by the process according to the invention can after its removal from the lateral surface of the carrier be machined on their surface. Most notably However, it is advantageous if already the printing block blank after curing of the elastomer layer and before separation machined a cylindrical peripheral shape, in particular ground becomes. By rotating the carrier and simultaneously turning it on a rotating grinding wheel against the surface of the Cured elastomer layer is obtained a printing form blank with highly accurate cylindrical surface, which after the subsequent Separating maintains its accuracy and an exact ensures smooth surface of the printing plate, as with photopolymer Plates in the past can not be obtained could. In particular, it is through this processing of the surface the elastomer layer possible, even very thin printing plates with a thickness of 1 to 5 mm and a very even surface to obtain as they preferred to achieve optimum print quality be used.

It is particularly advantageous if that the release film or the Separating plate along its seam edges occlusive tape or the like. has a thickness corresponding to the thickness of the elastomeric layer their processing on the cylindrical peripheral shape at least equivalent. This has the advantage that for the removal of the Printing form blanks of the cylindrical support this not means a separate tool or the like. along the seam edges must be cut open, but that only the tape, the release liner or separator plate along its seam edges connects, must be deducted to the previously endless, but already ground or wacked printing blank as a printing plate to be able to remove.

The printing plate produced by the process according to the invention has substantially the same features and advantages as the continuous printing plate according to DE 196 25 749, to the description thereof thus expressly referenced. The cured Elastomer layer of the printing plate can in particular by means of engraving be directly engraved by a working laser, causing the finished printing form produced particularly quickly and inexpensively can be.

In a particularly advantageous manner, according to the invention Process produced printing plate after their removal from the lateral surface of the carrier at its back with a compressible Be provided underlayer. The arrangement of compressible Lower layer, especially for very thin printing plates required to achieve a very good print result is done, in any case, after the plate on its top on a hard surface, preferably on a steel cylinder machined, in particular ground or turned off. This has the advantage that the Elastomer layer not in their processing of their surface their back can dodge, which ensures that the plate after its processing over its entire surface has a uniform thickness.

With the method according to the invention, it is more advantageous Way also possible, the printing form after editing the Printing form blanks on the cylindrical peripheral shape, but before the Engrave separation to form the printing plate. After removal the already prepared for printing plate of the wearer can then use the compressible at its back Underlayer are provided and then to print on a cliché sleeve or a format cylinder are mounted, whereby by the already in the cylinder shape engraving The pressure plate does not require a distortion factor to take account of the fact that in the plane manufactured and then mounted on cylinder Pressure plates stretched on their surface by a certain value become. In fact, this particular approach will work the printed image upon removal of the printing plate from the cylindrical Support compressed and then when mounting on the format cylinder or the cliche sleeve the compressed picture again stretched to the same conditions that existed when engraving have, as long as the diameter of the cylindrical support and the diameter of the later used cliché sleeve or the format cylinder matched accordingly are.

As already mentioned, the engraving of the printing plate can preferably done by laser engraving, one also during engraving the endless printing plates according to DE 196 25 749 used coming working laser ensures that even large areas the elastomer layer to the required depth in comparison can be removed in a short time.

With the invention, a pressure plate for the high pressure, in particular created for flexographic printing, which consists essentially of a lower support sheet or plate and one applied thereto Elastomeric layer of silicone polymer, Silicon fluoropolymer or polyurethane exists after their Apply to the carrier foil or carrier plate and cure to Forming a flat surface edited, in particular is ground. The elastomer layer preferably consists of cold-curing silicone polymer or silicone fluoropolymer. At the Rear side of their support sheet or plate, the inventive Pressure plate preferably with a compressible coating be provided as this to produce a high print quality especially in so-called thin-pressure plates is advantageous and is often required. To get the most even and possible to achieve reproducible layer thickness of the elastomer layer, can this be in the form of juxtaposed, confluent, caterpillar-like strands of material on the carrier foil or be applied to the plate.

Fig 1 eine Einrichtung zur Durchführung des erfindungsgemäßen Verfahrens zum Herstellen einer erfindungsgemäßen Druckplatte in einer vereinfachten Vorderansicht;

Fig. 2 den Gegenstand der Fig. 1 in einem Schnitt längs der Linie II-II;

Fig 3 die Bearbeitung des Druckformrohlings an seinem Umfang mittels einer Schleifeinrichtung in einem Ausschnitt und

Fig. 4 einen Schnitt durch eine erfindungsgemäße Druckplatte.

Further features and advantages of the invention will become apparent from the following description and the drawing, wherein a preferred embodiment of the invention will be explained in more detail by way of example. It shows:

1 shows a device for carrying out the method according to the invention for producing a printing plate according to the invention in a simplified front view;

Fig. 2 shows the subject of Figure 1 in a section along the line II-II.

3 shows the processing of the printing block blank at its periphery by means of a grinding device in a section and

4 shows a section through a pressure plate according to the invention.

The device 10 shown in FIGS. 1 and 2 serves for Production of printing plates, in particular of printing plates 11 according to the invention or else for the production of continuous printing plates, as in the earlier patent application DE 197 56 327 A1, which is hereby incorporated by reference becomes.

The device 10 consists essentially of a machine bed 12, one arranged at one end, driven Headstock 13 and provided at the other end tailstock 14, between which a vacuum roller 15 with its stub axles 16 is arranged so that they rotate upon rotation of the spindle Headstock is rotated about its axis, as indicated by the Arrow 17 is indicated.

On the machine bed of the device 10 is a longitudinal slide 18 stored, with the aid of a non-illustrated drive from one end of the device on the tailstock to the other End at the headstock and can be moved back, like this indicated by the double arrow 19. The longitudinal slide carries on a support arm 20 a mixing and dosing head 21 as well a transverse to the axis 22 of the roller 15 engageable grinding device 23 with a rotatably driven grinding wheel 24 and a also against the vacuum roller engagable cutting element 25, whose meaning is described in detail below becomes.

As is apparent in particular from FIGS. 2 and 3, is for the production a printing plate or implementation of the invention the inventive method on the cylindrical surface 26 of the vacuum roller 15 a thin, but not flexible stretchable carrier sheet 27 disposed on the periphery of the vacuum roll wrinkle-free and over arranged in the circumference Suction holes 28 of the vacuum roller rotatably on the lateral surface is held. At the axis parallel to the axis of rotation of the vacuum roll 15 extending seam 29 of the support film 27 are the seam edges 30 with a very thick adhesive tape 31 together connected, as can be seen well in Fig. 3.

With the help of the mixing and dosing is on the support film 27th a composite of two components in the mixing head elastomeric material 32 on the rotating roller 15 in the form of a Applied material strand, resulting from the superposition the rotational movement of the roller and the longitudinal movement of the mixing head schraubenlinig deposits on the circumference of the roller and thereby with the at the respective preceding revolution deposited material melts. The elastomer material is a Two-component silicone polymer material, which in this preferred Embodiment is cold-curing and after the Order on the laid around the vacuum roller 15 support film 27th hardens and thus a substantially cylindrical, endless Compression blank forms, whose radius indicated in Fig. 3 at 33 is.

After curing of the elastomer material to the printing plate blank becomes the grinding device also arranged on the support arm 23 so in the direction of the previous step coated vacuum roller hired that their Grinding wheel 24, the printing block blank 33 on its peripheral surface 34 processed when the vacuum roller and the grinding wheel be driven in rotation and the support arm 20 with the arranged thereon grinding device in the longitudinal direction of the machine bed between headstock 13 and tailstock 14 moves. Through this grinding, the printing block blank receives a very exact, cylindrical circumferential shape. Since the support film 27 while flexible, but in the radial direction of the roller practically incompressible is, when grinding from the grinding wheel up The radial forces exerted on the blank are optimally absorbed without undesirable deformations or evasion of the printing block blank comes radially inward.

After grinding the printing block blank 33 to the desired Thickness of the elastomer layer will be the most complete Printing form removed from the vacuum roller 15. This can be done by using the against the vacuum roller 15 employed cutting elements 25 in the printing form a Paraxial cut through the elastomer layer and the carrier foil 27 is produced by the arm from one end the device is moved to the other end while the drive is stopped for the headstock 13 and thus the vacuum roller does not turn. In the preferred embodiment However, in which the printing block blank 33 with the Grinding wheel 24 was ground so far that the thick adhesive tape 31 is exposed during grinding, as shown in FIG. 3 is shown, it is sufficient simply to remove the adhesive tape 31, to go over the entire thickness of the elastomer layer Channel above the seam 29 expose so that it after switching off the negative pressure in the vacuum roll possible is, now no longer endless pressure plate 11 of the lateral surface 26 of the pressure roller lift off.

With the method described above, one obtains Printing plate with exceptionally high surface accuracy, as it was previously known only from continuous printing plates. The Pressure plate can immediately after its removal from the cylindrical Roller are engraved and in a preferred manner by direct engraving by means of a computer-controlled laser, the the areas that should not print later, from the surface the printing plate works out. It is also possible that Engraving in the printing plate already before they are produced by the Cloak surface of the cylinder lifted and designed in a level position becomes. This approach, which can be useful if the printing plate later on a cliché sleeve or a Format cylinders of the same diameter as the vacuum roller to be reared, has the advantage that then in the execution the engraving of the plate does not take into account any distortion factor must be that of the plate expansion, so the extension of the printing motif when mounting the flat plate on a cylindrical Sleeve or a cylinder takes into account.

As can be seen from Fig. 4, the after the above Method produced printing plate on the back 35 of her Carrier film are provided with a compressible coating 36, after being removed from the lateral surface of the carrier 15 has been. This compressible coating provides in particular small printing plate thicknesses less than 2.5 mm thickness of the ground Elastomer layer for the compressibility desired during printing the entire pressure plate at a given pressure level. The Coating 36 may consist of an elastic adhesive film (tape), as for the attachment of printing plates on cliché sleeves or the like. known per se. Because the elastic coating only after removing the pressure plate from the lateral surface the carrier cylinder 15 takes place and not on this one elastic underlayer is applied before the support sheet 27th and then the elastomer layer are applied is ensured that by machining the elastomer layer achieved at its periphery by grinding a high accuracy becomes.

Instead of a support film 27 may also be a thin support plate Tinplate can be used on the vacuum cylinder 15 at the circumference of which and then the silicone polymer is applied. The production of the printing plate with the ferromagnetic Support plate corresponds to the manufacturing process of a such with a plastic support sheet or the like .. The use However, a ferromagnetic support plate has the advantage that produced by the process according to the invention Pressure plate is also usable on so-called magnetic cylinders, on which they use for example for label printing held by permanent magnets firmly on the circumference.

With the method according to the invention can also be such materials to (flat) printing plates are processed so far used only for the production of continuous forms could become. A particular advantage of the method lies in that so that also the Rotationsgießverfahren for the production can be used by flat printing plates, in the processing of silicone polymer and / or silicone fluoropolymer materials proved to be particularly advantageous has, as in the older publications 196 25 749 C2 and DE 197 56 327 A1 of the applicants are described. It can thus first time by the inventive method the same material qualities be achieved with flat printing plates, the with the known from the cited documents of the applicants Materials were previously reserved for continuous printing plates and it is possible to use the method according to the invention produced printing plates on their back with any to provide compressible underlayer, with which the desired Compressibility to be set accurately during later printing can.

Claims (18)

1. Method for producing a printing plated in particular for relief printing, characterized by the following steps:

   a) applying a layer (32) of a curable elastomer to a carrier (15) having a cylindrical surface area (26);

   b) curing the elastomer layer on the carrier (15) into an essentially cylindrical, endless printing form blank (33);

   c) separating the printing form blank (33) along a section line essentially parallel to the axial direction (22) of the carrier; and

   d) withdrawal of the printing plate (11), which is produced in such a manner, from the surface area (26) of the carrier (15).
2. Method according to claim 1, characterized in that a silicone polymer, a silicone fluorine polymer or a polyurethane polymer is used as the curing elastomer (32).
3. Method according to claim 1 or 2, characterized in that a cold curing silicone polymer or silicone fluorine polymer is used as the curing elastomer (32).
4. Method according to one of claims 1 to 3, characterized in that the elastomer (32) is applied with a rotational casting method to the surface area (26) of the carrier (15).
5. Method according to one of claims 1 to 4, characterized in that the elastomer (32) is applied as a track-like material strand describing a helical line.
6. Method according to one of claims 1 to 5, characterized in that a separating layer (27) is applied to the cylindrical surface area (26) of the carrier (15) prior to the application of the elastomer (32).
7. Method according to one of claims 1 to 6, characterized in that the separating layer (27) consists of a flexible foil or plate.
8. Method according to one of claims 1 to 7, characterized in that the foil (27) or the plate is placed around the carrier (15) while forming a seam line (29) and that the later section line runs along the seam line (29).
9. Method according to one of claims 1 to 8, characterized in that the carrier (15) essentially consists of a vacuum cylinder (15) and that the foil (27) or plate is held to the cylindrical surface area (26) by means of a vacuum.
10. Method according to one of claims 1 to 9, characterized in that the foil (27) or the plate is closed along its seam edges (30) to an endless separating layer by means of an adhesive tape (31) or the like.
11. Method according to one of claims 1 to 10, characterized in that the foil (27) or the plate consists of a material which is essentially incompressible.
12. Method according to one of claims 1 to 11, characterized in that the foil (27) or the plate consists of plastics or metal, in particular of ferromagnetic metal.
13. Method according to one of claims 1 to 12, characterized in that the printing form blank (33) is processed, in particular ground, into a cylindrical peripheral form after curing the elastomer layer (32) and before the separation.
14. Method according to one of claims 1 to 13, characterized in that the adhesive tape (31) or the like, which closes the separating foil (27) or the separating plate along their seam edges (30), has a thickness corresponding to at least the thickness of the elastomer layer (32) after its processing to the cylindrical peripheral form.
15. Method according to one of claims 1 to 14, characterized in that the printing plate (11) is provided with a compressible bottom layer (36) at its rear side (35) after its withdrawal from the surface area (26) of the carrier (15).
16. Method according to one of claims 1 to 15, characterized in that the printing form (11) is engraved after the processing of the printing form blank (33) to the cylindrical peripheral form, but before the separation, for forming the printing plate (11).
17. Method according to one of claims 1 to 16, characterized in that the engraving of the printing plate (11) takes place by means of laser engraving.
18. Printing plate for relief printing, in particular for flexo-printing, obtainable with the method according to one of claims 13 to 17, whereas the elastomer layer (32) consists of silicon polymer, silicon fluorine polymer or polyurethane and has been applied to a lower carrier foil or plate (27) and whereas the elastomer layer is processed, in particular ground, after its application to the carrier foil or plate and curing for forming an even surface.

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