EP0473947A1 - Mounting for engravings and engraving foil - Google Patents

Abstract

In a printing plate, in particular for the indirect gravure printing or pad printing method, wherein the plate having the gravure (22) consists of metal and can be inserted in a plate receptacle (1) of a printing machine, the manufacturing costs of the plate are reduced considerably due to the fact that the plate (3) is constructed as a smooth and flexible metal foil which fits snugly on the surface of the plate receptacle (1). <IMAGE>

Description

The invention relates to a printing plate, in particular for the indirect gravure or pad printing process, the plate having the engraving being designed as a film plate consisting of metal, which has a smooth surface and can be used in a plate holder of a printing press.

Printing clichés in plate form have been known for a long time. These printing blocks are made of hardened, high-alloy tool steel that is absolutely flat and therefore has a relatively large thickness to ensure flatness. However, this is associated with high costs, particularly in the case of relatively large clichés, since the surface having the printed image has to be lapped and hardened. If necessary, the material of the cliché is artificially aged before processing, thereby avoiding a later delay. Due to the high costs, steel clichés produced in this way are only used economically for long runs of 200,000 prints and more. Due to the relatively large thickness of the cliché steel plates of up to 10 mm and more, the material costs are not negligible. In addition, the cost of transportation and warehousing are relatively expensive due to the high weight and size of the clichés. Since relatively aggressive colors are often used for printing, the material for the cliché of corrosion-resistant steel can be used, which further increases the material costs.

For small or medium runs, i.e. For runs in the range of a few 100 to 50,000 prints, photopolymeric clichés can be used instead of the expensive steel clichés. These clichés usually have a support plate made of metal and have a plastic-coated surface in which the engraving is incorporated. The squeegee shears over this plastic surface to remove excess ink from the engraving. However, since the surface made of plastic is relatively soft, it is extremely sensitive both to the doctor blade running over it and to contamination. Contamination of the printing ink, dust or dirty squeegees cause scratches in the engraving and make the cliché unusable.

Printing presses with a closed ink and doctoring cup (EP 140 165 B 1) only require the steel plate printing blocks mentioned at the outset, since only these have the required flat surface, which ensure clean printing in such printing presses. The surface unevenness may not exceed 2 µm, otherwise there is a risk that ink will leak from the doctor cup. This would result in the machine being so dirty with ink after a short time that a clean printing process can no longer be guaranteed. Because of the small number of prints, the photopolymeric cliché therefore has the disadvantage that the printing often has to be interrupted in order to change the cliché. These interruptions require low quantities and require constantly present personnel who change the cliché.

A "cliché film for the ceramic industry is known from the" Ceramic Journal, 41st year, No. 6, 1989, pages 395 ff ". Here, ground glass and the like are used as the color, a large amount of which is required for each print or for each color application. Since these ceramic colors are very thick, the engraving in the cliché must have a minimum depth of 70 to 80 µm in order to be able to absorb the color. Accordingly, the cliché itself must have a corresponding thickness of 0.5 mm to 1 mm, so that the engraving can be introduced at all and the required rigidity of the cliché is still guaranteed. However, clichés with such thickness dimensions are stiff and have the disadvantage with large-area line engravings that there is a not inconsiderable risk that the doctor blade sags into the engraving, although the surface is ground clean but has poor flatness. Relatively thin printing inks, such as those used in machines with a closed ink system, already flow through gaps of 1 µm in depth. It is therefore absolutely essential that the film itself has a uniform thickness.

DE-OS 34 12 496 a tampon rotary printing machine with a stretched film is known. However, neither the features of the film nor its dimensions can be removed.

However, such clichés have the disadvantage that, although they have a super-ground surface, they have surface unevenness of several micrometers. If such clichés are used in printing presses with doctor blades, there is a risk that the Ink from the squeegee cup gradually runs out due to the surface unevenness.

The invention is therefore based on the object of providing a printing plate of the type mentioned at the outset, with which high print runs can be achieved, and the costs for the production and preparation of the plate are substantially reduced.

This object is achieved in that the cliché is designed as a flexible metal foil which conforms to the surface of the cliché holder and transmits the contour of the surface and has a thickness of 0.02 mm to 0.25 mm, in particular a thickness of 0.07 mm to 0.15 mm, a maximum surface unevenness of 3 µm, in particular of 2 µm, and a wear resistance suitable for hard metal doctoring cups.

This printing plate, which is designed as a metal foil, has the material properties of a hardened and lapped precision steel plate, but the steel plate has a thickness of 10 mm to 20 mm, while the metal foil is made much thinner. The advantages achieved by this, such as excellent surface flatness, high flexural and impact resistance, excellent surface quality and high wear resistance, good etching properties for photoengraving and high corrosion resistance to solvents and thinners of pad printing inks guarantee long print runs of over 500,000. The use of a metal foil as a printing plate also has cost advantages, since only a fraction of the material and manufacturing costs are incurred, as well as the shipping and storage costs due to the lower weight are significantly reduced. The overall photochemical costs are also lower, since metal foils are much easier to handle than the relatively heavy solid steel plates. Conventional systems for the production of multilayers can thus be used for the etching process. The excellent properties of this foil cliché are achieved in that the engraved metal foil has the excellent surface properties of the steel cliché. Ensure films with such a small thickness that the film conforms to the plate holder in such a way that the surface contour of the plate holder is transferred. If the support surface of the cliché holder is flat, the foil cliché also assumes a flat shape. Because the film cliché is supported on the flat cliché holder, onto which it is pressed either by the squeegee or the squeegee or ink cup, so that the cliché can nestle against the cliché holder, the film cliché adopts exactly the surface contour of the cliché holder. This cliché holder can be, for example, a steel plate with a highly precisely machined surface, with holders made of stone being preferred since they are made of a dead material and there is therefore no fear of warping of the holder.

Furthermore, the printing plate according to the invention ensures high print runs when used with hard metal doctoring cups, since scoring and the like are almost impossible and gaps between the plate and the edge of the doctoring cup are kept sufficiently small, ie in the range of 1 to 2 μm, since the wear is minimal is.

The metal foil preferably has a martensitic structure. The martensitic structure results in great wear resistance and increased hardness of the cliché.

The metal foil is preferably designed as a stainless steel foil, in particular as a chromium-molybdenum steel foil, such as 7C27Mo2. A preferred embodiment provides that the metal foil consists of stainless steel and a directional alloy of <0.4% c, approximately 0.4% Si, approximately 0.6% Mn, approximately 13% Cr and approximately 1% Mo owns. In a further development, the metal foil has a good sliding surface for doctor pots with a hard metal coating and for doctor steel. Another embodiment provides that the metal foil is designed as a galvanically produced foil made of nickel or chromium or of a nickel-chromium alloy. Such metal foils are used in particular in rotary printing. The cliché film is supported on a roller that forms the cliché holder. The foil can also consist of copper, which is coated with stainless steel. In another embodiment, the metal foil consists of a spring bronze alloy.

The surface of the film cliché is preferably tempered. The production of the printed image is simplified in that the film is easy to etch. Because the film shows an anti-corrosive behavior, printing inks can be used, to which aggressive solvents and thinners are added, without the film cliché being damaged.

A preferred further development provides that the film, as a semi-finished product, carries a photo emulsion provided with an opaque protective film. Such clichés can easily be provided with the desired engraving on site, since no complex photochemical equipment is required. In particular, the foil cliché is much easier to handle than the solid steel cliché.

A preferred further development provides that the film is designed as a flat film band having one or more engravings. This foil cliché is designed as a band cliché and can have any length and can therefore be provided with any number of engravings. This ribbon cliché can be moved on the cliché holder by means of a suitable feed, and a different print image can thereby be brought into the engagement area of the tampon. This creates the possibility that the engraving can be changed within a very short time, regardless of how many editions of this printed image are to be printed. Thus, even for the smallest runs or for a constantly changing print, the print images required for this can be brought to the printing point by specifically feeding the printing block. This reduces the set-up time to seconds.

Another embodiment provides that the film is designed as a cylindrical film sleeve. This film sleeve can, for example, be drawn onto rollers by means of compressed air or other suitable tensioning devices and used in rotary printing devices. The film is designed in such a way that it clamps onto the roller either by means of a tensioning device or because of the dimensions, and conforms to it so that it adopts the surface contour of the roller.

Another embodiment provides that the film is designed as a flat film disc having one or more engravings. This film disc is rotatably mounted on the plate holder in such a way that different sectors of this film disc can be moved one after the other under the tampon. This also creates the possibility that print images can be changed within a very short time, so that different prints, in particular alternately, can be carried out with a single printing press.

A simple mounting of the film on the plate holder is achieved in that the film fastening devices, e.g. in the form of an edge perforation. Catch pins provided on the surface of the cliché holder engage in this perforated edge. This attachment also has the advantage that the film cliché can be quickly and easily fixed and removed from the cliché holder. This significantly reduces set-up times.

To ensure good print quality, the film has a surface with a roughness of <2 µm. Films of this type are used in particular in closed systems in which the printed image is inked by means of an ink cup, the underside of which is designed as a doctor blade. A roughness of less than 2 µm ensures that no ink runs out of the ink cup, even if the printing machine e.g. stops overnight or at the weekend.

Regardless of the shape and design of the film cliché it can be provided that the film several Has engravings. These engravings can be used by suitably inserting the foil cliché into the printing device.

A further improvement in the print quality is achieved in that the surface of the plate having the engraving can be compacted. This compression is achieved by the doctor blade or the doctor cup, which strokes the surface of the film plate with each printing process and exerts a compressive force on the plate.

The pad printing machine that receives the film cliché preferably has a receptacle that supports the printing cliché in the area of the doctor blade and the tampon and that has a flat surface with a roughness of <2 μm. This plate holder determines the flatness of the film plate and is therefore manufactured with high precision. It consists e.g. made of metal, in particular steel, stone, glass, or another suitable material.

In order to be able to change the print image, the holder is designed such that the printing block can slide along the holder. Once the desired print image has been positioned, the film cliché is held in this position by suitable holding or fastening devices. In the case of stationary film printing blocks, these are e.g. held over catch pins that engage in a perforated edge of the cliché.

Fig. 1

eine erste Ausführungsform des Folienklischees mit einem an der Oberseite angedeuteten, überschüssige Farbe abstreifenden Rakel;

Fig. 2

die gleiche Anordnung wie Fig. 1, wobei jedoch an der Oberseite des Folienklischees ein Farbtopf vorgesehen ist;

Fig. 3

ein als Bandklischee ausgebildetes Folienklischee mit einem überschüssige Farbe abstreifenden Rakel;

Fig. 4

die gleiche Ausgestaltung wie Fig. 3, wobei jedoch an der Oberseite des Bandklischees ein Farbtopf vorgesehen ist;

Fig. 5

eine Druckwalze mit aufgezogener zylindrischer Folienhülse in perspektivischer Ansicht; und

Fig. 6

eine perspektivische Ansicht eines scheibenförmig ausgebildeten Folienklischees mit in Sektoren unterteilter Oberfläche.

Further advantages, features and details of the invention emerge from the following description, in which: Preferred embodiments are described in detail with reference to the drawing. Show:

Fig. 1

a first embodiment of the film cliché with a doctor blade indicated on the top, scraping off excess ink;

Fig. 2

the same arrangement as Figure 1, but with a paint pot is provided on the top of the film block.

Fig. 3

a foil cliché designed as a band cliché with an excess ink-wiping doctor blade;

Fig. 4

the same design as Figure 3, but with a paint pot is provided on the top of the cliché.

Fig. 5

a pressure roller with mounted cylindrical film sleeve in a perspective view; and

Fig. 6

a perspective view of a disc-shaped foil cliché with surface divided into sectors.

In Fig. 1, a cliché holder designated 1 is shown in a schematic representation, which consists, for example, of metal, in particular steel, stone or glass. This plate holder has a surface with a roughness or unevenness of <2 µm. In the edge area, this cliché holder is provided with catch pins 2 which slightly protrude beyond the surface of the cliché holder 1. In this catch pins 2 is attached to a cliché 3, the catch pins 2 engaging in holes in an edge perforation (not shown). Another fastening device, not shown, provides that the film 3 is fixed on the receptacle 1, for example by means of a magnetic holder. The film plate 3 is thus secured against slipping on the plate holder 1. 1 shows a tampon 8 which is movable in the vertical direction in accordance with the double arrow 4 and in the horizontal direction in accordance with the double arrow 5. In addition, a squeegee 6 is shown, which strips excess ink 7 from the cliché. Finally, the cliché has an engraving (22, FIG. 6), which is located below the tampon 8.

The operation of the device is briefly explained below. After the printing image of the plate 3 located under the tampon 8 has been inked, the squeegee 6 strips off the excess ink from the engraving 22 in that the plate holder 1 moves to the left in accordance with the arrow 9. When the plate holder 1 has reached its left end position, the tampon 8 is pressed onto the engraving and fetches the ink in the recesses of the printed image etched into the plate 3, which adheres to the tampon 8, which consists of a silicone rubber. The tampon 8 then moves upward again in the direction of the arrow 4 and lifts off the cliché 3. Now the plate holder 1 moves to its right end position according to arrow 9 and the engraving is colored again. Since the plate holder 1 is in its right end position, the tampon 8 can be moved downward beyond the plane of the plate holder 1 and onto an object to be printed provided below this plane be pressed on. After the tampon 8 has reached its upper end position again, the plate holder 1 again moves into its left end position. The doctor blade 6 in turn strips off the excess ink from the printed image. Since the squeegee 6 rests on the film cliché 3 with a certain pressure force 23, the squeegee 6 presses the film cliché 3 onto the surface of the cliché holder 1. The film cliché 3 assumes the contour of this surface. Since this is highly precise and flat, the film cliché 3 also assumes a flat shape. This ensures that the squeegee 6 removes the excess ink cleanly from the surface of the film printing block 3, without ink residues remaining in any depressions caused by unevenness of the surface. The doctor blade 6 consists, for example, of a high-alloy steel.

In the arrangement shown in FIG. 2, the printing ink 7 is in a squeegee or ink cup 10, which is arranged such that it comes to lie exactly above the engraving of the cliché 3 due to the displacement of the cliché holder 1. The engraving takes up ink from the doctor cup 10. If the plate holder 1 is moved back to its left end position, the lower edge 11 of the doctor cup 10, which is designed as a doctor blade, brushes across the engraving and ensures that only color remains in the depressions of the printed image. Here, too, the cliché 3 is pressed onto the cliché holder 1 by the pressure force 23 and the weight of the doctor cup 10, which is of the order of 10 to 15 kilograms. The cliché 3 nestles against the surface in such a way that its contour is transferred to the film. Since, as already mentioned above, the plate holder 1 is manufactured with high precision and flat, the film plate also takes 3 this flat shape and thereby ensures that, in particular in the area of the printed image, there are no depressions caused by unevenness in which ink residues remain when doctoring. The good nestling is achieved in particular by the small thickness of the film 3 from 0.05 mm to 0.15 mm. The surface of the film plate 3 which has the printed image also has the excellent material properties of a solid steel plate. It should also be mentioned that the squeegee edge 11 of the squeegee pot 10 is preferably made of hard metal or ceramic and that the property can be achieved with a suitable foil cliché 3 that the surface of the foil cliché 3 is gradually compacted by the reciprocating doctor blade pot 10, which increases the flatness even further. It should also be mentioned that the movement conditions of tampon 8, squeegee 6 or squeegee pot 10, and plate holder 1 can be selected in a variety of ways. For example, the plate holder 1 can be arranged rigidly in the printing device, the tampon 8 and the doctor 6 or the doctor cup 10 being moved.

In the embodiment shown in FIGS. 3 and 4, the film plate 3 is designed as a plate band. The two ends 12 and 13 of the film cliché 3 are wound on rollers 14 which form a film cassette. This foil cliché 3, which is designed as a band, has a plurality of engravings arranged one behind the other at a distance. These engravings can either show the same print image, but they can also show different print images. In the former case, the advantage is achieved that, although very high runs can be achieved with the film printing plate 3 according to the invention and therefore a printing plate change is only required after a long time, this printing plate change can be carried out very quickly in that the film cliché 3 is pulled off the one roll 14 by means of a suitable drive and wound up on the other roll 14. The cliché 3 is moved a distance in this process until the next engraving is in position. This can be done in seconds. Printing machines of this type can thus run both overnight and at weekends without the need for personnel to change over. In the other case, a wide variety of printed images can be printed without the foil cliché 3 having to be replaced for this. The foil cliché can be moved back and forth in such a way by means of a suitable control, whereby it unwinds from the one roll 14 and onto the other roll 14 until the desired engraving on the cliché holder 1 is in position. A single object to be printed can alternately be printed with two different print images. The cliché 3 runs back and forth constantly. In this arrangement, both the doctor blade 6 and the doctor blade cup 10 press with a certain force onto the film plate 3, so that it clings to the surface of the plate holder 1.

The arrangement shown in FIG. 5 shows a tension roller 15, as is required in particular for rotary printing. A sleeve-shaped film cliché 3 is clamped onto this cylindrical roller 15 with a highly precise surface. This foil cliché 3 can be designed by a suitable choice of dimensions so that it rests under tension on the roller 15, and thus already clings well to the surface of the roller 15. The roller 15 forms the plate holder. In addition, the cliché 3 is pressed by the squeegee onto the surface of the roller 15. In another embodiment, not shown, the film cliché 3 is clamped onto the roller 15 using a suitable clamping device. Here, too, the cliché 3 is supported on the surface of the roller 15 and takes over its contour.

6 shows a further embodiment of the film printing plate 3 according to the invention, which now has the shape of a disk. This disk is divided into individual sectors 16 to 21, each sector being provided with an engraving 22. The disc-shaped film cliché 3 is mounted on a suitably designed cliché holder 1 and can be rotated via a suitable drive such that the individual sectors 16 to 21 can be moved under the tampon 8 and the doctoring cup 10 in such a way that the engraving 22 is colored and the color with the Tampon 8 can be removed. The individual engravings 22 can either have the same design, as shown in FIG. 6, with different motifs or printed images. As in the embodiment of FIGS. 3 and 4, the disk-shaped film cliché 3 creates the possibility that a different print image can be moved into the printing area in a matter of seconds, so that different prints can be carried out with one and the same printing press without the machine having to be converted must become.

Claims (12)

Printing plate, in particular for the indirect gravure or pad printing process, whereby the plate (3) with the engraving (22) is designed as a plate plate made of metal, which has a smooth surface and can be inserted into a plate holder (1) of a printing machine characterized in that the cliché (3) is designed as a flexible metal foil which conforms to the surface of the cliché holder (1) and transfers the contour of the surface a thickness of 0.02 mm to 0.25 mm, in particular a thickness of 0.07 mm to 0.15 mm, - A maximum surface unevenness of 3 microns, in particular of 2 microns, and - Has a wear resistance suitable for hard material doctor pots (10). Printing cliché according to claim 1, characterized in that the flexible metal foil consists of stainless steel and a directional alloy of <0.4% C, approx. 0.4% Si, approx. 0.6% Mn, approx. 13% Cr and approx. Owns 1% Mo. Printing block according to claim 1 or 2, characterized in that the metal foil has a martensitic structure. Printing block according to one of the preceding claims, characterized in that the metal foil is designed as a stainless steel foil. Printing block according to one of the preceding claims, characterized in that the metal foil is designed as a galvanically produced foil made of nickel or chromium or a chromium-nickel alloy. Printing cliché according to one of the preceding claims, characterized in that the film (3) is surface-coated or coated and / or can be easily etched. Printing cliché according to one of the preceding claims, characterized in that the film (3) exhibits an anti-corrosive behavior. Printing cliché according to one of the preceding claims, characterized in that the film (3), as a semi-finished product, carries a photo emulsion provided with an opaque protective film. Printing cliché according to one of the preceding claims, characterized in that the film (3) is designed as a flat film strip or film disc having one or more engravings (22). Printing block according to one of the preceding claims, characterized in that the film (3) is designed as a cylindrical film sleeve. Printing cliché according to one of the preceding claims, characterized in that the metal foil has fastening devices, in particular edge perforations. Printing block according to one of the preceding claims, characterized in that the film (3) has a plurality of engravings (22).

Images