WO2003007083A1

WO2003007083A1 - Method for producing intaglio printing plates

Info

Publication number: WO2003007083A1
Application number: PCT/EP2002/007521
Authority: WO
Inventors: Rüdiger BÜRGEL; Gunda MÜFFELMANN; Volker Müller
Original assignee: Bundesdruckerei Gmbh
Priority date: 2001-07-11
Filing date: 2002-07-05
Publication date: 2003-01-23
Also published as: DE10133701A1

Abstract

The invention relates to a multi-step method for producing intaglio printing plates comprising the following steps: a) a film (3) comprising opaque (14) and transparent (15) areas is placed over a substrate (2), which carries a polymer (1) that can be photo cross-linked, on the polymer side, b) the arrangement in step a) is exposed on the polymer side to light for a defined exposure time t1, whereby the polymer lying underneath transparent (15) areas of the film is at least partially cross-linked (4) and the polymer lying underneath the opaque (14) areas of the film remains uncross-linked, c) in a washing step, the uncross-linked polymer (5) is partially washed out in a defined washing period tw and optionally dried, to obtain a relief structure, and d) the relief structure is galvanically moulded into a master plate (12) and, e) at least one intaglio printing plate is moulded from said master plate. The method is characterised in that between steps b) and c) a step b'), in which uncross-linked polymer (5) is partially post cross-linked (7) by being exposed for a defined exposure period t2, is carried out. Several b') steps can be carried out, whereby the first simulates a post-engraving step and the second simulates a two-colour process.

Description

Process for the production of gravure printing plates.

Field of the Invention

The invention relates to a (multistage) process for the production of gravure printing plates with the following process steps: a) a film having opaque and translucent areas is arranged on the polymer side over a substrate carrying a photocrosslinkable polymer, b) the arrangement from step a) is polymer-side with light irradiated for a defined exposure time tl, polymer which is below light-transmitting areas of the film being at least partially crosslinked and polymer which is below light-blocking areas of the film remains uncrosslinked, c) in one

Washing process stage is partially washed out and, if necessary, dried with a defined washing time tw uncrosslinked polymer, whereby a relief structure is obtained, and.d) the relief structure is, preferably galvanically, molded into a master plate and e) at least one gravure plate is molded from the master plate.

The invention further relates to a master plate produced by means of such a method, and to uses of such a master plate.

State of the art

A method of the type mentioned is from Practice for the production of banknotes or other value or security documents known. However, the range of tonal values and the depth drawing, as well as the color intensity and tactility do not yet meet all requirements. In the case of classically, ie mechanically manufactured or finished gravure printing plates, a deepening of a motif is engraved by hand directly in the metallic printing plate (obtained mechanically or also by means of photopolymer technology). This is called post stitch. Post-stitching improves the tonal range and depth drawing and increases the color intensity and tactility on the printed product.

The post-stitch is costly and time-consuming due to its manual execution, which also requires specially qualified craftsmen. Also it leads to deviations between ^'the individual printing plates, and consequently to variations in the so produced value or security documents. The latter, however, is to a considerable extent disruptive due to the documents that are to be trained as uniformly as possible for security reasons or verification reasons.

The following should also be explained regarding the photopolymer technology described at the beginning. The photopolymer plates obtainable with it, ie the substrate with cross-linked photopolymer, in which the relief structure is formed, cannot be used directly in a printing process, since they are not resistant enough to the mechanical forces occurring during the printing process. So-called master plates are therefore produced from these photopolymer plates by means of galvanic shaping, of which in turn, for example by means of galvanic shaping, are used in a printing house Printing plates are available. Since the photopolymer plates are made of non-conductive plastic, they must therefore be provided with a conductive surface before electroplating. One possibility for this is the so-called silvering in the reduction process. A silver ion solution and a reducing solution are applied to the degreased photopolymer plates at the same time. When the solutions come together, the silver ions are reduced and a metallic silver layer is formed on the surface of the photopolymer plate. The electrodeposition of metals can now be carried out on the photopolymer plates made conductive in this way. Here, nickel electrolyte baths which are well scattered are expediently used.

Any number of printing plates, for example, again galvanically, can be molded from these electroplated master plates. These are then available for gravure printing.

Basics of the invention

The invention is characterized in that between process stages b) and c) a process stage b ') is carried out, in which uncrosslinked polymer is partially crosslinked by exposure with a defined exposure time t2.

By means of the post-crosslinking, a pronounced (re) relief structure is created, which is accompanied by a reduction or (partial) increase in the depth of the relief during the subsequent washing out. In this respect, an analog to a classic post-stitch is created. Compared to the previously known photopolymer technology, the result is as Advantages of an improvement in the tonal range, the depth drawing and an increase in the color intensity and tactility on the printed product, with a very high uniformity of the printed product even when using different printing plates. As a result, the advantages of different technologies are achieved in combination, with simple and inexpensive. Means.

It is of independent importance that the post-stitch according to the invention is also suitable for introducing additional information into a printing field, since a uniform or structured field generated in stage b) ^' can be provided with a finer substructure by means of stage b') - Numbers or text can be inserted in a field with blind signs. It is also possible in this way to introduce security features into a value or security document, for example by means of magnetic or otherwise detectable colors for the substructures.

Several depth exposures of process stages b 'can also be connected in series, in which case different exposure films can be used. A second process stage b 'can thus be carried out with a negative film (instead of a positive film of the first process stage b' and / or process stage b) and a two-tone process can thus be generated or simulated. It is also possible to work exclusively with a process stage b 'with a negative film.

Furthermore, the invention teaches the use of intaglio printing plates for printing value document substrates, the intaglio printing plates with the invention Processes were made.

Preferred embodiments

A preferred embodiment is characterized in that a process step c ") is carried out between process steps c) and d), in which a post-exposure of uncrosslinked polymer by a

Raster film with a defined exposure time t3 by means of parallel light. By the second

Exposure step c ') becomes a grid with less

Roughness created in the relief structure, which means that the color in the subsequent printing processes

Relief depths is maintained. Thin lines, i. e. Lines whose width is in the area of the grid size or smaller are not affected. It is necessary that a between the process steps c ') and d)

Process stage c '') is carried out, in which, with a defined washing time tw2, uncrosslinked polymer is partially washed out, dried if necessary, and cured by post-exposure. In this way, after the printing motif has been completely incorporated, completely hardened photopolymer plates are obtained, the surface of which is optimally resistant for the subsequent molding process stages.

The photopolymer used can be any commercially available photopolymer. The processing suitably depends on the manufacturer's instructions.

It is further preferred if the exposure in process stages b), b ') and / or c'') with scattered light or diffuse light, preferably in the wavelength range from ^' 350 to 400 nm takes place, tl can in particular be in the range from 30 to 60s. t2 can range from 2 to 10s. t3 can range from 2 to 4min. lie. The use of scattered light or diffuse light leads to the formation of flanks of the relief structure that are not perpendicular to the surface. Here is the

Cross-sectional shape decreasing in the direction orthogonal to the surface. This advantageously has the effect that the color can be better applied to the printing plate during the later printing process and can be transferred better to the value document substrate during the subsequent printing. The print images resulting from the subsequent printing have better tactility and are more resistant to abrasion. The

- The smallest possible line widths in the film are typically in the range from 5 to 25 μm, preferably from 12 to 17 μm. The ^'is to be achieved smallest printable depth in the plate in the range of 1 to 20 .mu.m, preferably 7-13 .mu.m.

In process stage b) (main exposure of the subject) and the subsequent washout stage, structural heights of up to 300 μm can be achieved. With a (first) process stage b ') (depth exposure, post-stitch), structural heights of up to 50 μm, preferably 5 to 20 μm, are achieved.

For washing out the uncured polymers, for example, solvents from the group consisting of "water, methanol, ethanol, butanol, n-propanol, isopropanol and mixtures of such substances" can be used. Washing out should preferably take place at temperatures in the range from 18 ° C. to 35 ° C., preferably from 18 ° C. to 22 ° C., and with a washing time tw in the range from 5 s to 10 min. be performed. The drying of the plates can be carried out in process step c) at a temperature of 70 ° C. to 90 ° C., preferably 70 ° C. to 80 ° C., and for a period of 1 to 15 minutes, preferably 5 to 10 minutes , In process stage c "'), drying can take place for a period of 1 to 30 minutes, preferably 5 to 15 minutes, at a temperature of 30 ° C. to 90 ° C., preferably 70 ° C. to 90 ° C.

The invention is explained in more detail below with reference to figures and examples which merely illustrate exemplary embodiments.

1: schematic representation of process stage b)

2: schematic representation of process stage b ^' )

Fig. 3: schematic representation of the process stage

C)

Fig. 4: schematic representation of the received ■

Photopolymer plate after process step c)

5, 6: schematic representation of process stage d)

Example 1: Production of a photopolymer plate.

1 shows a film 3 (positive) arranged on the polymer side over a substrate 2 carrying a photocrosslinkable polymer 1 and which has opaque 14 and translucent 15 regions. This arrangement is irradiated on the polymer side with light for a defined exposure time using a lamp, polymer 1, which lies below 15 translucent areas of the film, at least partially crosslinked (layer 4). Polymer 1, which lies below opaque 14 areas of the film, remains uncrosslinked (areas 5).

2 shows process stage b '), in which a further, opaque 14' and translucent 15 'areas (positive) film 6, which is on the polymer side, is arranged above the polymer. Areas of the uncrosslinked polymer 5, in which a post-stitch is to be generated, coincide with corresponding translucent areas. of film 6. This film 6 thus carries, as it were, a post-stitch pattern for structuring previously shadowed areas of the photopolymer. Then the uncrosslinked polymer is partially irradiated by exposure with a defined exposure time t2 and the photopolymer is partially post-crosslinked (area 7).

Optionally, a further or several further process steps b ') can be carried out, with deep exposure ^{' being} carried out through a negative film. Otherwise, the procedure is analogous to process step b ') described above. The second or each further process stage b ') effects a simulation of the two-tone or multi-tone.

After washing the uncrosslinked photopolymer with 80% (v / v) aqueous ethanol solution for a few minutes at a temperature of 20 ° C., the plates are dried at 80 ° C. for 10 minutes.

3 shows the process stage c '), in which a post-exposure of uncrosslinked polymer 5 through a screen film 8 (60' screen) with a defined exposure time t3 with a metal Spotlighted halide burner. The exposure step c ') produces a raster 9 with a low roughness in the relief structure, as a result of which the color is kept in the relief depths in the subsequent printing processes.

In the subsequent washing step, the plate is washed with 80% (v / v) aqueous ethanol solution for a few minutes at a temperature of 20 ° C., dried for 3 minutes at 80 ° C. and then post-exposed for 5 minutes with a metal halide burner and fully cured and the photopolymer plate 10 obtained (Figure 4).

Example 2: Production of a master plate and printing plate

A silver ion solution and a reducing solution are applied simultaneously to the photopolymer plates of Example 1. When the solutions meet, the silver ions are reduced and a metallic silver layer is formed on the surface of the photopolymer plate (FIG. 5). The plate thus obtained is then the so-called master 12. FIGS. 6 and 7 show the master plate 12 in the course of shaping (FIGS. 5 and 6) and after separation from the photopolymer plate (FIG. 7).

Any number of printing plates, again electroplated, can now be molded from the master plate 12 (work relief) thus obtained. For this purpose, then in a nickel bath (600 g / 1 nickel sulfate, 6 g / 1 nickel chloride, 40 g / 1 boric acid) with a pH of 3.5 and a temperature of 55 ° C, for 17 hours at a current density of 7 A / dm2 electroplating the pressure plate shaped. The resulting printing plate 13 is then incubated for 15 minutes in a chro (VI) acid solution (330 g / 1) with 3 g / 1 sulfuric acid at a temperature of 55 ° C. and then washed in water at room temperature. These are then available for intaglio printing.

Example 3: Printing of security document substrates. with pressure plates

Printing ink is applied to the printing plate 13 obtained in Example 2 and the excess ink is wiped off the surface of the printing plate by a washing solution, so that only color remains in the relief structure. The color is then transferred to the value document substrate to be printed. For this purpose the value document is entsubtrat flatly on the printing plate between this and a support surface disposed parallel to the pressure plate and which is at least the size of the area to be printed, applied and pressed by means of a ^'punch with a standard pressure. The value document obtained in this way corresponds in terms of tonal range, depth drawing and increase in color intensity as well as tactility to the quality known from classic gravure printing plates, on which a post-engraving was carried out by hand.

It should be particularly emphasized that various printing plates, which were produced from a photopolymer plate of Example 1, produce practically identical documents of value which are indistinguishable from the naked eye.

Claims

Claims:

1. Process for the production of rotogravure plates with the following process steps:

a) over a substrate (2) carrying a photocrosslinkable polymer (1), an opaque (14) and translucent (15) regions film (3) is arranged on the polymer side,

b) the arrangement from stage a) is irradiated on the polymer side with light for a defined exposure time t1, polymer which is below light-transmitting regions (15) of the film (3) being at least partially crosslinked and polymer which is below light-impermeable regions (14) of the film lies, remains unconnected,

c) in a washing process step, tw uncrosslinked polymer (5) is partially washed out with a defined washing time and, if appropriate, dried, a relief structure being obtained, and

d) the relief structure is electroplated into a master plate (12) and,

e) at least one gravure plate is molded from the master plate (12).

characterized,

that between process stages b) and c) a process stage b ') is carried out in which uncrosslinked polymer (5) is partially post-crosslinked by exposure with a defined exposure time t2.

A method according to claim 1, characterized in that 'between the process steps c) and d)

Process stage c ') is carried out, in which post-exposure of uncrosslinked polymer (5) through a screen film (8) with a defined

Exposure time t3 takes place, and that between the

Process stages c ') and d) a process stage c' ') is carried out, in which, with a defined washing time tW2, uncrosslinked polymer (5) is partially washed out, if necessary not washed out, photopolymer is dried and cured by post-exposure.

Method according to one of claims 1 or 2, characterized in that the exposure in process stages b), b ') and / or c') is carried out with scattered light or diffuse light.

Master plate (12) or printing plate, obtainable by a process according to one of claims 1 to 3, characterized in that structural heights produced with process stage b ') are in the range from 10 to 500 μm, preferably 10 to ^' 200 μm.

5. master plate (12) or printing plate according to claim 4, characterized in that with the process stage c ') generated structural heights are in the range from 10 to 500 μm, preferably 30 to 200 μm.

6. Use of a master plate according to claim 4 or 5 for printing value document substrates.