EP1467871B2 - Steel gravure method for the production of a security document, steel gravure plate and intermediate product for the same and method for production thereof - Google Patents

Abstract

A method for producing a security document having printed image 1 produced by steel intaglio printing and embossed microstructures 2 of an order of magnitude of less than 100 microns is carried out by one printing plate 8 on which both the steel intaglio structures and the microstructures are present. The parts of the microstructures closest to printing plate surface 9 are located 20 to 100 microns below the printing plate surface so that they are not touched and destroyed by the wiping cylinder. Alternative methods for producing a steel intaglio printing plate with integrated microstructures are provided. The microstructures can be used for embossing a diffractive relief or a blind embossing.

Description

The invention relates to a method for producing a security document, in particular a security such as banknote, check and the like, with a printed image applied by the steel gravure process and with an embossed microstructure region whose structures are on the order of less than 100 μm. The invention further relates to tools suitable for the manufacturing process, namely steel gravure printing plates, and to the production thereof, including semi-finished products, namely originals and intermediate molds for the production of the steel gravure printing plates and the security documents produced therewith. The steel gravure corresponds to intaglio printing, whereby the printing plate is made of steel. As a result, a longer service life of the printing plate is achieved and allows for the securities and in particular the banknote printing required high volumes.

It is known to provide security documents in addition to a printed image applied by the steel gravure printing method with particular authenticity features, of which for the present invention, in particular optically variable elements, such as embossed holograms or gratings (US Pat. DE-A-40 02 979 ) and blind embossing ( DE-A-198 45 552 ) are of interest.

Blind embossing is sometimes produced together with the steel gravure image in a common printing process using a single, partially inked steel gravure plate. During the printing process, the paper is pressed into the recesses of the blind embossing areas and in this way permanently deformed. The blank embossing areas of the printing plate, unlike the print image areas, are not filled with ink, so that the substrate material of the security document is only sustainably deformed, ie embossed, in these areas. WO 97/48555 ; DE-A-198 45 552 ).

Such a method also discloses US 6176 522 B1 , Here, a security document from a substrate comprises both printed indicia and a section of transparent plastic. The latter has an embossed image which may contain a matrix of lines, dots or embossed structure. Such a security document is produced by means of a gravure printing plate which, in addition to engraved gravure structures, has a plurality of embossing plates arranged at intervals in the peripheral surface of a printing cylinder.

Out WO 00/20216 For example, a gravure printing method for printing contiguous color areas of different ink layer thickness is known. In this case, a first and a second color surface are directly adjacent to one another and are separated from one another by a sharp boundary line which is invisible to the naked eye when viewed. This boundary line is generated by a separating edge between the two engraving areas of the corresponding printing plate, the upper edge of which tapers to the level of the printing plate surface. The engraving areas may in this case be formed flat or have a roughness pattern for better adhesion of the printing ink.

When looking at blind embossing, there are special three-dimensional visual impressions due to light and shadow effects. In addition, blind embossing with corresponding dimensions can also be detected tactilely.

The structures for the steel gravure image and for the blind embossings are usually introduced into the printing plate surface by means of a stylus, laser or by etching. Regardless of the deployment technique used, these structures will also be referred to generally below as "engravings". However, the fineness of the structures is limited, on the one hand by the engraving techniques themselves, but on the other hand also by the fact that particularly fine structures, the mechanical influences of the wiping cylinder, wiped with the excess ink from the partially inked printing plate, not withstand in the long run. Due to the slightly iridescent movement and the friction, which prevails at a corresponding contact pressure of the wiper cylinder, embossed structures are on the order of significantly less than 100 microns (hereinafter referred to as "microstructures") damaged in no time. Accordingly, embossments having microstructures significantly smaller than 100 μm are produced to produce special optical effects in an embossing process performed separately from the printing operation for applying the steel gravure image.

The same applies to the application of optical diffraction structures, such as holograms and gratings. The order of magnitude of these diffraction structures is in the wavelength range of visible light, ie less than 1 μm. In the DE-A-198 45 552 It is proposed to prefabricate a security with all security elements, including, for example, embossed diffraction structures, and as a last procedural step to print the paper, for example by means of steel gravure printing. In this connection, it is described as a possible variant to build up the diffraction structures in layers on a previously locally smoothed area of the security substrate by first applying a curable lacquer to the smoothed area and providing it with an extremely thin, reflecting metal layer. In this coated lacquer layer is then impressed with a die an optical diffraction-relief structure, and the diffraction structure thus produced is then covered with a protective lacquer.

The production of embossed microstructures in a security document, whether as a blind embossing in the substrate material itself or as a diffraction-optical relief structure in a lacquer layer specially provided for this, thus requires a separate working step in addition to the printing process for the production of the Steel intaglio printed image.

The object of the present invention is to propose a method for producing a security document, with which steel gravure images and embossed microstructures can be produced more easily.

A further object is to propose tools for carrying out the method and a method for producing these tools and their semi-finished products.

These objects are achieved by the methods and objects having the features of the independent claims. In dependent claims advantageous embodiments and developments of the invention are given.

Accordingly, the steel gravure image and the embossed microstructures are produced in a common printing process using a common printing plate in which both the print image engraving and the microstructures are present. In order to prevent the microstructures from being damaged by the action of a wiping cylinder wiping across the printing plate, the microstructures are slightly lowered relative to the printing plate surface, so that they are not detected by the wiping cylinder, but nevertheless allow a perfect embossing process. The dimension of the retraction of the microstructures depends on the area size of the microstructure area on the one hand and on the compressibility of the wiping cylinder material and the wiping cylinder contact pressure on the other hand. The microstructures should therefore be at least 40 .mu.m to 100 .mu.m below the printing plate surface, preferably at least 40 .mu.m and at most 60 .mu.m, these details referring to the components of the microstructures closest to the printing plate surface. For example, a square microstructure area should have an area of less than 100 mm ² to preclude advancement of the wiping cylinder down to the underlying microstructures. In other words, the dimension of the microstructure area in the direction parallel to the axis of rotation of the wiping cylinder and parallel to the printing plate surface should be less than 10 mm.

Several microstructure regions can together form a larger microstructure surface, wherein the individual microstructure regions are separated by webs reaching up to the printing plate surface. The webs have on the printing plate surface such a width that they can carry the wiper cylinder, without being permanently damaged by its contact pressure. In this way, an arbitrarily shaped and arbitrarily large area matrix can be generated from smaller microstructure areas.

The dimensions of the microstructures, i. their height and lateral structure size are on the order of between 5 .mu.m and 100 .mu.m, if simple blind embossings are to be produced. If, on the other hand, a diffraction-optical relief structure is to be embossed with the microstructures, for example in a lacquer layer which is optionally metallized for this purpose and applied specifically to the security document material, the order of magnitude of the microstructures in the wave-optical region is less than 1 μm.

Since the microstructures due to their small dimensions with the usual methods for the production of gravure plates, for example by means of stylus, laser or by etching, can not always produce sufficiently accurate, the invention provides a two-stage printing plate production. In this case, on the one hand, an original printing plate with the print image engraving and on the other hand, one or more dies with the microstructures separately produced in a conventional manner and the original printing plate or a molded thereon Mater is then combined with the original embossing dies or embossing stamp duplicates.

According to a first embodiment, intermediate forms, the Mater, are first embossed with the original printing plate. As many mater are shaped as the finished steel gravure plate should have benefits. The microstructure embossing dies also produce a number of duplicates corresponding to the usefulness of the steel gravure printing plate. The materials are then combined with the duplicates of the microstructure stamps, for example by juxtaposition and proper bonding. This complex then serves as the actual intermediate form for reshaping one or more duplicate printing plates, which are then used as steel gravure printing plates in the printing units.

According to another embodiment, one or more areas are removed from the original printing plate into which the printed image is engraved, into which the original microstructure stamping die (s) are / are inserted so that the microstructures lie below the plate surface. The Matern are then formed by the resulting complex. A number of mats assembled in the desired utility configuration then form the intermediate mold for the manufacture of the steel gravure printing plates.

In addition, the printing plate can be engraved with the opposite of the ungravierten printing plate level lowered Mikroprägestrukturen directly. However, the prerequisite is the use of a Präzisionsgraviervorrichtung, since standard equipment for the engraving of intaglio printing plates do not have sufficient accuracy to reproducibly produce predetermined structures whose dimensions are smaller than 100 microns. Precision engraving can be achieved both by mechanical, i. machined engraving as well as done by laser engraving.

While the ink-receiving depressions provided for the printed image can be engraved in the printing plate surface in the usual way, the regions provided for the embossing microstructures can first be removed by the value by which the depression is to take place. In this below the level of unedited Pressure plate surface lying areas are then introduced by a precision engraving of the microstructures. In principle, it is also possible first to produce the microstructures in the predetermined desired depth and, if still necessary, subsequently to remove any remaining printing plate material in order to achieve the desired reduction in one area.

The printing plate original provided with the microstructures can be used directly as a combined printing and embossing plate. The original can also be duplicated with the usual reproduction and impression techniques.

The intaglio printing plates according to the invention ensure on the securities produced therewith even after long runs even concise embossing structures with high contour sharpness.

Due to the very high pressure applied in the stitch forming process, the substrate material, for example cotton paper, is compacted even in the unprinted or unembossed areas and permanently compressed. The lowering of the embossed structures in the printing plate causes in the corresponding region of the processed substrate a non-compressed or at least less compressed region from which the embossed microstructures rise. As wear protection, the embossed microstructures can be provided with stabilizing protective layers.

Fig.1

eine Banknote mit einem Stahltiefdruckbild und geprägten Mikrostrukturen,

Fig. 2

die Banknote aus Fig.1 im Querschnitt, wobei die Mikrostrukturen als Blindprägung vorliegen,

Fig. 3a bis 3c

die Banknote aus Fig.1 im Querschnitt zu unterschiedlichen Herstellungszeitpunkten, wobei die Mikrostrukturen als optisches Beugungsmuster vorliegen,

Fig. 4a bis 4d

die einzelnen Schritte zur Herstellung einer erfindungsgemäßen Stahltiefdruckplatte gemäß einer ersten Ausführungsform,

Fig. 5

eine Banknote, ähnlich der Banknote aus Fig.1 mit mehreren zueinander beabstandeten Mikrostrukturbereichen, und

Fig. 6a bis 6e

die einzelnen Schritte zur Herstellung einer erfindungsgemäßen Stahltiefdruckplatte gemäß einer zweiten Ausführungsform.

The invention will be described by way of example with reference to the figures. Show:

Fig.1

a banknote with a steel gravure image and embossed microstructures,

Fig. 2

the banknote Fig.1 in cross-section, with the microstructures present as blind embossing,

Fig. 3a to 3c

the banknote Fig.1 in cross section at different production times, the microstructures being in the form of an optical diffraction pattern,

Fig. 4a to 4d

the individual steps for producing a steel gravure printing plate according to the invention according to a first embodiment,

Fig. 5

a banknote, similar to the banknote Fig.1 with a plurality of spaced apart microstructure regions, and

Fig. 6a to 6e

the individual steps for producing a steel gravure printing plate according to the invention according to a second embodiment.

Fig. 1 By way of example, one of many possible types of security documents shows a banknote in plan view with a printed image 1 produced by steel gravure printing and a microstructure embossment 2 likewise produced by the steel gravure process. For example, the microstructure embossment 2 can be a blind embossing in the paper substrate or a diffraction-optical relief structure in a plastic layer applied to the paper substrate be.

Fig. 2 shows a cross section through the banknote Fig.1 , wherein the microstructure embossment 2 is present as a blind embossing in the surface of the banknote substrate 3. The applied by steel gravure printing, the print image 1 forming ink "stands" on the surface of the substrate 3 and is therefore tactile detectable.

The raised microstructure of the microstructure embossment 2 is, for example, a line grid with a screen ruling in the range from 5 to 100 μm. Such a structure can be visually perceived as a fine light / shadow pattern and also the surface can optionally be tactilely distinguished from the surrounding unembossed surface.

In the Fig. 3a to 3c an embodiment is shown, in which the microstructure embossment 2 is designed as a diffraction-optical relief structure. In this case, the structures have a magnitude of about 1 micron or less than 1 micron, that is in the wavelength range of visible light. Fig. 3a shows the still unprinted banknote substrate 3, which is smoothed in a zone 4, so that an embossing 5 adheres particularly well in this area on the substrate 3. The embossing lacquer 5 is vapor-deposited with a thin metal layer 6. In the next method step, on the one hand the printed image 1 and on the other hand the diffraction-optical microstructure embossment 2 are applied to the thus prepared substrate 3 in the steel gravure printing process ( Fig. 3b ). Subsequently, the microstructure embossing 2 is covered with a scratch-resistant protective lacquer 7 ( Fig. 3c ).

The printed image 1 and the microstructure 2 according to the embodiments according to Fig. 2 and Fig. 3a to 3c are manufactured in a single printing process using a single printing plate. Suitable printing plates 8 are exemplary in the Fig. 4d and 6e shown in cross section. Fig. 4d It can be seen that in the printing plate surface 9, on the one hand, there are steel gravure printing structures 10 for producing the printed image 1 and, on the other hand, microstructures 11 for producing the microstructure embossment 2. The microstructures 11 are slightly embedded in the pressure plate surface 9, so that the uppermost microstructure areas, that is, the tips of the microstructure relief lie at a small distance d below the pressure plate surface 9. The distance d measures between 40 and 100 μm, preferably between 40 and 60 μm. For the production of a security printing, the ink is first partially applied in the area of the steel gravure structures 10 on the printing plate surface 9, and by means of a not shown Wiping cylinder excess ink is wiped from the printing plate surface 9. By lowering the microstructures 11 it is achieved that the wiping cylinder does not come into contact with the filigree microstructures 11 and can not damage them. In the subsequent printing process, the substrate of the security document is pressed into the steel gravure structures 10 and into the microstructures 11, whereby on the one hand the ink is taken up from the steel gravure structures 10 and adheres to the substrate surface, and on the other hand the substrate is embossed on its surface in the region of the microstructures 11, that is permanently deformed, will.

The pressures and temperatures of the plate cylinder used in the steel gravure printing process for the production of the printed image are suitable for the embossing of conventional security papers, so that the simultaneous embossing and printing of security paper with a single steel gravure plate is easily possible. A typical heating temperature of the plate cylinder is around 80 ° C, but it can also be between 50 and 90 ° C.

The following are based on the Fig. 4a to 4d and 6a to 6e two alternative methods for producing the printing plate 8 with deeper microstructures 11 described.

In a first step ( Fig. 4a On the one hand, steel intaglio structures 10 are introduced in a conventional manner in an original printing plate O, for example by means of a stylus or in the etching process. Separately, one or optionally several different dies D with microstructures 11 are also produced in a conventional manner, for example with the same methods that are usually used for the production of diffraction-optical relief structures.

In a second step ( Fig. 4b ) Duplicates of the original printing plate O and the die D are produced. The production of the duplicate of the original printing plate O, that is the Mater M, can be done, for example, by embossing the original printing plate in a plastically deformable plastic, which then forms the Mater M (Cobex embossing). But there are also other Abformungstechniken known and usable. A number of mats M ₁ , M ₂ ..., M _n corresponding to the number of uses of the steel gravure printing plate to be produced are produced. Also of the die or dies D with the microstructures 11 correspondingly many embossing stamp duplicates DD ₁ , DD ₂ , ... are produced. The molding process of the embossing stamp duplicate DD is preferably carried out by electroforming, in that the microstructure 11 is first rendered electrically conductive and then metallised, for example with copper. The copper layer is then back-cast, such as with tin, to stabilize the structure, and backfilled with lead or plastic to make embossing punch duplicate DD manageable.

In a third step ( Fig. 4c ), the mats M ₁ , M ₂ ,... and the embossing die duplicates DD ₁ , DD ₂ ,... are juxtaposed and firmly joined to one another by suitable bonding techniques, such as gluing, to form an intermediate shape Z. In the in Fig. 4c In each case, an intermediate and intermediate stamping die pair M ₁ , DD ₁ or M ₂ , DD ₂ etc. form a utility of the steel gravure printing plate 8 to be produced by means of the intermediate mold Z. It can be seen that the microstructures referred to here as negative microstructures 11 '. are present, slightly above the impression plane 9 'of the intermediate form Z lie.

The molding of the steel gravure plate 8 of the intermediate form Z ( Fig. 4d In turn, the printing plate surface 9 can be hardened by nickel plating, chromium plating in a further production step.

An alternative method of manufacturing the printing plate 8 is shown in FIGS Fig. 6a to 6e shown. Accordingly, first the original printing plate O is produced with the intaglio printing structures 10 ( Fig. 6a ). From the original printing plate O, certain surface areas are subsequently extracted in segments, for example by high-precision milling technology ( Fig. 6b ). In the recess 13 thus produced is then the die D with the microstructures 11, as in Fig. 4a shown is used ( Fig. 6c ). This requires a precise machining of the embossing die D, so that the microstructures after insertion of the embossing die D in the recess 13 by a defined distance d lower than the surface of the original printing plate O. The thus prepared original printing plate O is then used for embossing Matern M ( Fig. 6d ), wherein the embossing, for example, takes place again in the coexpression method. In this case, each material M serves for the further production of a complete benefit of the steel gravure printing plate 8 to be produced. It is therefore of the original printing plate O with embedded embossing stamp D ( Fig. 6c ) As many Matern M ₁ , M ₂ , M ₃ , ... produced, as the finally to be produced steel gravure plate 8 benefits. The mats M ₁ , M ₂ , M ₃ ,... Are in turn combined by suitable joining techniques to form an intermediate form Z (FIG. Fig. 6e ), from which the steel gravure printing plate 8 is formed by electroplating.

Alternatively, the stamping of the original plate of Fig. 6c into a sufficiently large intermediate mold Z may be repeated according to the number of desired uses. In this case, the step of assembling the individual materials M ₁ , M ₂ , M ₃ ,... To the intermediate form Z is omitted.

The abovementioned alternative production methods are thus equally suitable for producing positive structures 10, 11 in the finished steel gravure printing plate 8 from the original steel gravure printing structures 10 and original microstructures 11 via "negative structures" 10 ', 11' of the intermediate form Z. That in terms of Fig. 6a to 6e described manufacturing method is to be preferred inasmuch as the onset of Microstructures 11 at any point within a printed image 1 by inserting corresponding dies D in recesses 13 of the original printing plate O ( Fig. 6c ) is simpler than the exact assembly of printed-plate duplicates or Matern M with embossing stamp duplicates DD ( Fig. 4c ). In particular, a steel gravure printing plate 8 can be used to produce a printed image 1 with microstructure embossings 2 integrated therein, as in FIG Fig. 5 represented by a manufacturing method according to Fig. 6a to 6e make it especially good. In the steel gravure image 1, which in Fig. 5 is indicated only by its outer border, forming a plurality of microstructure embossings 2 a field of microstructure embossments in which the individual microstructure embossings 2 are spaced apart. These distances 12 'are a consequence of the fact that the individual microstructure regions 11 of the steel gravure plate 8 for protection against damage by a wiper cylinder must not exceed a maximum size and are therefore separated by separating webs 12 ( Fig. 4d ). These dividers 12 extend to the printing plate surface 9 and have a necessary width to accommodate the pressure of the wiping cylinder can.

Claims (18)

1. A steel intaglio printing plate (8) comprising a printing plate surface (9) having at least one first area with steel intaglio structures (10) for producing a steel intaglio printed image by means of ink and at least one second area separate from the first area and having embossed structures (11) for producing a blind embossing or a diffractive relief structure, wherein the embossed structures (11) of the blind embossing area or diffractive relief structure area have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns, and wherein the parts of the embossed structures (11) closest to the printing plate surface (9) are located at a distance (d) of 40 microns to 100 microns below the printing plate surface (9).
2. A mold (Z) for producing steel intaglio printing plates (8) according to claim 1 comprising at least one first segment (M) having negative steel intaglio structures (10') and at least one second segment (DD) different from the first segment (M) and having negative embossed structures (11') which have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns, wherein the mold (Z) has a molding plane (9') and wherein the parts of the negative embossed structures (11') closest to the molding plane (9') are located 40 microns to 100 microns above the molding plane (9').
3. A mold (Z) for producing steel intaglio printing plates (8) according to claim 1 comprising at least one segment (M) having negative steel intaglio structures (10') in a first area and negative embossed structures (11') which have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns in a second area separate from the first area, wherein the mold (Z) has a molding plane (9') and wherein the parts of the negative embossed structures (11') closest to the molding plane (9') are located 40 microns to 100 microns above the molding plane (9').
4. An original printing plate for producing a mold according to claim 3 having steel intaglio structures (10) and at least one gap (13) into which an embossing die (D) with embossed structures (11) which have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns is so inserted that the parts of the embossed structures (11) closest to the surface of the original printing plate (O) are located 40 microns to 100 microns below said surface.
5. An object according to any of claims 1 to 4, wherein the parts of the embossed structures (11) closest to the printing plate surface (9) or molding plane (9') are located at most 60 microns away from the printing plate surface (9) or molding plane (9').
6. An object according to any of claims 1 to 5, wherein the area of the embossed structures (11) has an area size of less than 400 square millimeters, preferably less than 100 square millimeters.
7. An object according to any of claims 1 to 6, wherein a plurality of areas with embossed structures (11) constitute an embossed structure grid.
8. An object according to any of claims 1 to 7, wherein the embossed structures (11) are separated from the steel intaglio structures (10) or from another area with embossed structures (11) by a separation bar (12) extending as far as the printing plate surface (9) or molding plane (9') and having a width of at least 0.5 millimeters.
9. A method for producing an object according to any of claims 1, 2 or 5 to 8 comprising the following steps:

   - producing a steel intaglio structure (10) in an original printing plate (O) and producing at least one matrix (M) from the original printing plate (O),

   - producing an embossing die (D) with embossed structures (11), wherein the embossed structures (11) have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns, and producing at least one embossing die duplicate (DD),

   - producing a mold (Z) with a molding plane (9') by disposing side by side and connecting one or more matrices (M, M₁, M₂, ...) and one or more embossing die duplicates (DD, DD₁, DD₂, ...) so that the parts of the embossed structures closest to the molding plane are located 40 microns to 100 microns above the molding plane (9').
10. A method for producing an object according to any of claims 1 or 3 to 8 comprising the following steps:

    - producing steel intaglio structures (10) in an original printing plate (O),

    - producing at least one gap in the surface of the original printing plate (O) having the steel intaglio structures (10),

    - producing an embossing die (D) with embossed structures (11), wherein the embossed structures (11) have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns,

    - inserting the embossing die (D) into the gap (13) such that the parts of the embossed structures (11) closest to the surface of the original printing plate (O) are located 40 microns to 100 microns below said surface.
11. A method according to claim 10, wherein a plurality of matrices (M ₁, M ₂, ...) are embossed from the original printing plate (O) with the embossing die (D) inserted into the gap (13), said matrices being disposed side by side and connected to constitute a mold (Z).
12. A method according to claim 9 or 11, wherein a steel intaglio printing plate (8) is molded from the mold (Z).
13. A method according to claim 12, wherein the molding of the steel intaglio printing plate (8) from the mold (Z) is effected by galvanoplasty.
14. A method for producing a steel intaglio printing plate (8) according to any of claims 1 or 5 to 8 comprising the following steps:

    - producing steel intaglio structures (10) in a steel intaglio printing plate (8) for producing a steel intaglio printed image by means of ink in a first area,

    - producing embossed structures (11) in the steel intaglio printing plate (8) for producing a blind embossing or a diffractive relief structure, wherein the embossed structures (11) have a height and lateral structural size of less than 1 micron or in the range of 5 to 100 microns, by engraving a second area separate from the first area such that the parts of the embossed structures (11) closest to the surface of the steel intaglio printing plate (8) are located 40 to 100 microns below said surface.
15. A method for producing a security document by steel intaglio printing using a steel intaglio printing plate according to any of claims 1 and 5 to 8 comprising the steps of:

    - filling the steel intaglio structures (10) of the steel intaglio printing plate (8) with ink without filling the embossed structures (11) with ink,

    - printing a security document by means of the steel intaglio printing plate (8) partially filled with ink and embossing the embossed structures in a printing operation while applying a pressure that suffices for transferring the ink from the steel intaglio structures (10) to the security document, on the one hand, and embossing the security document in the area of the embossed structures (11), on the other hand.
16. A method according to claim 15, wherein the embossing of the security document in the area of the embossed structures (11) is a blind embossing.
17. A method according to claim 15, wherein the security document has an embossable coating (5, 6) and wherein the embossing of the security document is effected in the area of said embossable coating such that diffractive relief structures are embossed into the embossable coating.
18. A method according to claim 17, wherein the embossed coating is covered with a transparent protective layer (7).

Images