EP4037913B1 - Method for producing a security paper and security paper obtainable by said method - Google Patents

Description

The invention relates to a method for producing a security paper, which has the following steps: providing a flat substrate that has a front and a back, applying a transfer element to the front, which is delimited by at least one edge, and applying a stabilizing coating the back in a section of the substrate that covers the transfer element in top view.

The invention further relates to a security paper which has: a flat substrate with a front and a back, a transfer element on the front which is delimited by at least one edge, and a stabilizing coating on the back in a section of the substrate which is the Transfer element covered in top view.

The WO 2011/015622 A1 describes a generic method for producing a security paper and a security paper.

It is also known not to print a stabilizing coating on the back, but rather to transfer a second film-based transfer element to the back.

The EP 1727684 B2 discloses a security and/or value document. The WO 2004/024464 A1 concerns a reinforced security document. From the EP 2411232 B1 and the EP 2860040 B1 Other security elements and manufacturing processes are known for this.

WO 2015/085438 A1 shows a security document with a foil security element and reinforcement on the back. WO 2005/095118A2 relates to a security document with a window, which has a film security element on the front and a seal on the back. WO 2013/075811 A2 describes a device for providing a substrate with a film security element on both sides.

The invention is based on the object of improving a substrate paper when a transfer element is provided. This applies in particular with regard to anti-counterfeiting and processability.

The invention is defined in independent claims 1 and 14. The dependent claims concern preferred further training.

In the manufacturing process, a flat substrate is provided. The substrate has a front and a back. The terms “front” and “back” serve here only to differentiate and are not intended to imply a preference for one of the two main sides of the substrate. A transfer element is applied to the front of the substrate. The transfer element has at least one edge which lies within the longitudinal extent of the substrate, i.e. does not coincide with an edge of the substrate. A stabilizing layer is applied to the opposite back. The stabilizing coating is applied to the back in a section of the substrate in such a way that it covers the transfer element in the top view of the substrate. The section of the substrate thus also covers the transfer element, in particular its edge. The section also has at least two surface sections. On these two surface sections, the stabilizing coating is designed in different ways, namely with different coating materials. The stabilizing coating therefore has a different perceptible or measurable appearance on the two surface sections from the back.

The term “appearance” refers to how the stabilizing coating can be perceived by the viewer from the back can be measured by machine, in particular machine readable. Perception should occur optically, that is, through observation. The noticeable difference is in the visible spectrum and is clear enough to be noticed by the viewer. The different appearance can alternatively or additionally be measurable by machine. The difference is preferably machine-readable or more preferably only machine-readable (i.e. not perceptible). The measurable difference is adapted to be automatically measured by a machine (machine readable). For example, different infrared properties, magnetic properties, etc. of the stabilization coating can be measured automatically.

The stabilization layer improves the processability and flatness of the security substrate obtained in this way with subsequent processes, especially in intaglio printing. This is surprising in that it initially appears counterproductive to create an additional thickening through the stabilization coating in the area of the transfer element, which already results in a thickening of the substrate. Nevertheless, it has surprisingly been found that the stabilization coating improves the flatness and processability of the substrate paper.

The stabilizing coating preferably extends - seen in a top view of the flat substrate - to the edge of the transfer element and can in particular cover it. Optionally, it is not applied to the entire surface of the back of the substrate, for example it delimits an inner part of the transfer element in a top view. However, the stabilizing coating is preferably provided over the entire surface of the two surface sections of the substrate.

In embodiments, it is sufficient to simply cover or cover the edge of the transfer element in such a way that (only) one strip on both sides of the edge is covered. If the transfer element is designed as an elongated strip that extends over a longitudinal extent of the security substrate, the transfer element consequently only has two edges within the relevant section of the substrate. The stabilizing coating can then have the form of two strips, each of which covers an edge. If, on the other hand, the transfer element is designed as a so-called “patch”, the stabilizing coating can be designed in the shape of a frame, with the frame width and dimensions being chosen so that the edge of the patch is covered. In other embodiments, the stabilization coating completely covers the transfer element and is made slightly larger so that a strip beyond the edge of the transfer element is also covered. It is therefore advantageous for all variants that the stabilizing coating does not cover the entire back of the substrate, but only protrudes beyond the edge of the transfer element by the strip already mentioned at the beginning. The width of this projection (over the edge or over each edge) is preferably not more than 10 mm, particularly preferably not more than 5 mm, very particularly preferably in the range between 2 mm and 4 mm.

In a preferred embodiment of the invention, the surface sections of the substrate have the stabilizing coating due to printing or coating with the different coating materials. The stabilizing coating is therefore applied by printing or coating. In addition, coatings that differ in appearance but have the same stabilizing effect are preferably applied to the two surface sections.

The stabilizing coating has at least a first coating section and at least a second coating section. The first coating section lies in the first surface section and the second coating section lies in the second surface section. A plurality of first and second coating sections can lie in the first and/or the second surface section. The first and second coating sections differ in their appearance, for example in the perceived color. However, the first and second coating sections have the same stabilizing effect, i.e. in particular also the same layer thickness.

The coating sections in their surface section are preferably spaced apart from one another and alternatively applied adjacent to one another. Likewise, coating sections of the first surface section are preferably applied at a distance from coating sections of the second surface section. An overlapping arrangement, on the other hand, would only be theoretically conceivable, since otherwise the thickness of the coating sections would add up.

The coating sections are preferably applied over the entire surface. The coating is then continuous in the coating sections. Coating sections applied to partial areas are conceivable. For example, a grid or a network could be used as a partial coating section. The surface coverage of the coating in the partial coating sections will be greater than 30%, preferably greater than 50%, but less than 75%.

If one considers the relative area coverage of the stabilizing coating on the substrate, it is above 50%, preferably above of 66% and more preferably above 75% and in each of the cases more preferably below 98%. The coating sections are preferably formed over the entire surface. If all full-surface coating sections are arranged without any gaps, there is 100% relative surface coverage. In preferred embodiments with the aforementioned surface coverage, the coating sections are formed over the entire surface and spaced apart from one another.

In particular, varnishes, especially UV-curing varnishes, can be used as a stabilizing coating. Water-based paint systems are possible. The stabilizing coating is a non-self-supporting (support-free) layer. In contrast to a film-based transfer element, it cannot, for example, span a window in the substrate.

The stabilization coating means that deformation of the substrate paper, for example the formation of grooves or bulging, is significantly reduced or prevented, particularly during further moistening processing, as is carried out in intaglio printing. The stabilizing coating affects the substrate paper in the sheet during further processing of the sheet. However, it also improves the flatness of the individual banknote, thus improving its further processing or handling, for example in banknote checking devices, banknote sorting devices or banknote counting devices. This is the first effect of the stabilization coating. Furthermore, the stabilization coating with at least two distinguishable surface sections increases the barrier to counterfeiting, since additional security features are applied to the substrate with the help of the respective surface sections of the stabilization coating.

The substrate only optionally has no opening in the section, i.e. it is continuous and the front and back are uninterrupted in this area.

The stabilizing coating has the property known in the prior art that the processability of the substrate is not impaired by the transfer element, e.g. with regard to flatness, etc. The stabilizing coating has a uniform layer thickness, in particular since it is intended to have a uniform stabilizing effect.

The stabilizing coating, the surface sections and/or the coating sections can have an independent surface shape. The independent surface shape can be designed as a pattern, symbol or symbol. A surface shape is considered independent if it does not correspond to the surface shape of the transfer element - possibly minus an optional window. The stabilization coating itself can, for example, have a different surface shape (oval, circular, symbol-like, ...) than the transfer element (rectangular, oval, circular, ...). However, due to the stabilizing function, the approximate size and surface shape of the stabilizing coating is partially determined by the transfer element. However, the selection of the surface shape is much more flexible when it comes to the surface sections and/or the coating sections. These can be selected independently of the transfer element. Thus, in further embodiments, for example, coating sections with a constant, independent surface shape could also be used for different transfer elements.

In particular, at least one of the two different coating materials can comprise an additive which has the corresponding perceptible effect or machine-readable appearance. Preferably, the stabilizing coating comprises a first additive on the first surface sections and a second additive on the second surface sections. The stabilizing coating can contain the same ingredients on both surface sections - apart from noticeable or machine-readable additives.

The different appearance of the stabilizing coating on the two surface sections of the substrate is preferably created by different additives. The additives are perceptible to the viewer or recognizable by machine. Particularly suitable additives are: colorants, such as dyes or color pigments; optically variable pigments, such as interference layer pigments or liquid crystal pigments; magnetically alignable (optionally optically variable) pigments; luminescent substances that, for example, emit in the same area or a different area after excitation in the UV/IR or VIS range; invisible additives, in particular additives that can only be detected in the UV or IR range, magnetic additives or conductivity-increasing additives. Such additives are well known in themselves. The stabilizing coating is preferably uniformly formed on the two surface sections (or in their coating sections) - apart from the additives. It includes the same ingredients on both surface sections (or in its coating sections) and thus the same stabilizing effect. The additives are particularly preferably of the same type of additive.

In a preferred embodiment, at least one surface section is printed with optically variable and/or luminescent coating materials. In addition, in a preferred embodiment at least one of the surface sections is photochromically and/or thermochromically coated. All of these design options for the surface sections of the stabilizing coating increase the number of security features of the substrate, which can further raise the barrier to counterfeiting. Each substrate can contain one or more of the additives mentioned in a surface section of the stabilizing coating. Different colorants are preferably used as additives on the two surface sections or different photochromic or thermochromic additives are used on the two surface sections. Alternatively, a colorant can be present on the first surface section and a photochromic or thermochromic additive can be present on the second surface section.

The stabilizing coating preferably has an opaque surface with at least 80% - preferably 100% - area coverage. It is preferably precisely registered to the transfer element.

In addition to the possibility of optically perceptible differentiation based on the different design of the stabilizing coating on the surface sections of the substrate, in a preferred embodiment only machine differentiation is made based on different IR substances (filtering or absorbing a given IR wavelength) or UV substances (a given UV wavelength filtering or absorbing), different magnetization or different conductivities provided on the surface sections. The surface sections (or the coating sections) can be arranged - for example alternately - in such a way that a machine-recognizable coding is created, in particular an IR code, a magnetic code or a conductivity code.

The transfer element can have its own carrier layer, in particular carrier film. Alternatively, the transfer element is carrier-free, i.e. does not have its own carrier layer, such as carrier film. In a known manner, the transfer element - with or without its own carrier film - is transferred as an element from an intermediate carrier to the substrate when it is applied to the substrate.

In a further embodiment, the substrate is designed so that it has a window (or an opening). The transfer element spans the window. This feature also contributes to stabilization and to increasing the barrier to counterfeiting. The coating can be applied before or after the window is introduced into the substrate.

In a preferred embodiment, at least one further printing element is applied to another location on the substrate in the same printing cycle with the stabilizing coating. This adds additional security features to the substrate and also makes it possible to speed up the production process of the substrate. It should be noted that a printing element under or over a stabilization layer does not form a distinguishable stabilization coating.

Since the aim here is not to provide a stabilizing coating that is chemically or mechanically improved by its ingredients (but rather by the additives), reference can be made to the known processes and ingredients.

The stabilizing coating improves the mechanical properties, such as tensile strength and/or flexural rigidity, of the security paper in the section. The tensile strength and/or the bending strength of the security paper in the section is preferably increased by at least 2%, preferably at least 4%, more preferably at least 5% by the stabilizing coating. In particular, the increase is a maximum of 50%, usually less than 25%. The security paper with substrate and transfer element is measured before and after the stabilization coating is applied. In preferred embodiments, the tensile strength and/or the flexural strength of the stabilizing coating is in the range from 25% to 150%, preferably 33% to 99%, more preferably 33% to 75% of the tensile strength or flexural strength of the transfer element. In further embodiments, the mechanical property, such as tensile strength and/or flexural strength, of the stabilizing coating is at least a factor of 1.1 greater, preferably at least a factor of 1.5 greater, than a substrate layer of the same thickness. The maximum factor is 5. The values mentioned can advantageously be present in combination with one another.

Furthermore, a security paper is also provided which has a flat substrate which has a front and a back side. A transfer element is applied to the front, which is delimited by at least one edge. Furthermore, a stabilizing coating is applied to the back in a section of the substrate. Furthermore, when viewed from above, the transfer element is covered by the stabilizing coating on the back. Within the section, at least two surface sections of the substrate are printed or coated differently by the stabilizing coating. The properties and features mentioned above in connection with the manufacturing processes also apply to the security paper itself.

The substrate can be a single-layer or multi-layer substrate and can consist of paper, optionally with the addition of a plastic film. Any type of paper can be used, especially cotton. Of course, paper can also be used that contains a proportion of plastic material, for example a polymeric material.

The security paper can be used in particular to produce a security document, in particular a banknote. Such a security document is therefore also provided.

Fig. 1A und 1B

Draufsichten auf ein Banknotenpapier, das mehrere Nutzen bereitstellt,

Fig. 2A und 2B

Draufsichten auf eine Vorderseite eines Nutzens in zwei Varianten,

Fig. 3A und 3B

Draufsichten auf eine Rückseite des Nutzens in zwei Varianten,

Fig. 4

eine Schnittdarstellung durch den Nutzen der Fig. 2A und 3A,

Fig. 5A-L

Draufsichten auf die Rückseite des Nutzens der Fig. 2A und 3A in verschiedenen Weiterbildungen,

Fig. 6

eine Schnittdarstellung durch einen Nutzen in einer Ausführungsform mit sich überlappenden Flächenabschnitten.

The invention will be explained in more detail below using exemplary embodiments with reference to the accompanying drawings, which also reveal features essential to the invention. These embodiments are for illustrative purposes only and are not to be construed as limiting. For example, a description of an embodiment including a plurality of elements or components should not be construed to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the embodiments may also be applicable to other embodiments. To avoid repetition, the same or corresponding elements in different figures are designated with the same reference numerals and are not explained more than once. Show in the figures:

Figures 1A and 1B

Top views of a banknote paper providing multiple benefits,

Figures 2A and 2B

Top views of a front of a panel in two variants,

Figures 3A and 3B

Top views of the back of the panel in two versions,

Fig. 4

a sectional view of the benefits of the Figures 2A and 3A ,

Fig. 5A-L

Top views of the back of the utility Figures 2A and 3A in various further training courses,

Fig. 6

a sectional view through a panel in an embodiment with overlapping surface sections.

Figures 1A and 1B show a schematic top view of a banknote paper 1. The banknote paper is made up of several panels 2, which adjoin one another at boundaries 3 and are enclosed by a sheet edge 4. Each panel 2 provides a substrate for subsequent processing steps.

Fig. 1A shows a strip-shaped application area 5 in the exemplary embodiment for applying a strip-shaped transfer element 6 and a strip-shaped stabilizing coating 7, Fig. 1B a patch-shaped application area 8 for applying a patch-shaped transfer element 9 and a patch-shaped stabilization coating 10.

Each of the embodiments and configurations explained below using a strip-shaped application area 5 can also be implemented for a patch-shaped application area 8.

Fig. 2A shows a single use 2 of the banknote paper 1 with a view of a front side 11. In the strip-shaped application area 5 on the front side 11, a strip-shaped primer 12 is first applied, onto which the strip-shaped transfer element 6 is applied. The strip-shaped transfer element 6 includes optically or otherwise recognizable security features that improve the security against counterfeiting of the benefit 2 or a banknote made with it. The strip-shaped transfer element can comprise a film as a carrier or can be carrier-free. It can be continuous, but can also include a recess. Fig. 2A shows a window 13 which is formed in the substrate. The window 13 is preferably closed by the transfer element 6. It would be conceivable that the transfer element also has a window 13, which lies either over a substrate section without a window or congruently over the window of the substrate.

Fig. 2B also shows the individual use 2 of the banknote paper 1 with a view of the front side 11. In the patch-shaped application area 8, a patch-shaped primer 14 is first applied to the front side 11, onto which the patch-shaped transfer element 9 is applied. The substrate of the benefit 2 may include a window 13. The patch-shaped transfer element 9, like the strip-shaped transfer element 6, will generally be designed to be continuous. It closes the window 13 of the substrate. Only in exceptional cases does the transfer element 9 have a window 13 (possibly shared with the substrate). In those explained below In embodiments, the transfer elements have one or two edges and/or a peripheral edge.

Fig. 3A and Fig. 3B show a back 15 opposite the front 11. This is in Fig. 3A a strip-shaped stabilizing coating 7 is applied here. This stabilizing coating 7 is in Fig. 3A continuously. The stabilizing coating 7 is left out in the optional window 13 of the substrate (and/or the transfer element). In Fig. 3B a patch-shaped stabilizing coating 10 is applied to the back 15. Like the strip-shaped stabilization coating 7, this can be designed to be continuous and have a window 13 together with the substrate (and/or the transfer element).

Fig. 4 shows the benefit 2 in a sectional view using the example of a strip-shaped application area 5. As described, the strip-shaped primer 12 and the strip-shaped transfer element 6 are applied to the front side 11. Furthermore, the strip-shaped application area 5 can be designed with an optional paper thinner 16. The strip-shaped stabilization coating 7 is applied to the back 15, which laterally covers the strip-shaped transfer element 6 (and optionally the strip-shaped primer 12) in the sectional view. This coverage is designed in the same way for a patch-shaped application area 8. The coverage significantly improves the processability and in particular the flatness of the panel 2 and/or the banknote paper 1. This is of great advantage, particularly with subsequent intaglio printing on the front and/or back 11, 15.

Fig. 5A-L concern design options for the back 15. Figs. 5A-F show a strip-shaped stabilization coating that is applied to a first and a second surface section of the panel is applied and is designed differently in these surface sections, for example by different printing or coating. The stabilizing coating contains different additives on the two surface sections. This enables optical or mechanical differentiation, which creates an additional security feature in the stabilization coating.

In embodiments, for example according to Fig. 5A or 5B , this is achieved by at least two coating sections 17 and 18 on the surface sections. The first coating section 17 is applied to the first surface section and the second coating section 18 is applied to the second surface section. In these embodiments, the coating sections and the surface sections are optionally congruent in plan view.

In the Fig. 5A or 5B, the coating sections are as longitudinal stripes ( Fig. 5A ) or as a horizontal stripe ( Fig. 5B ) executed. In a further embodiment, a machine-readable IR code is applied with the help of the different surface sections 17 and 18, as in Fig. 5C is shown. Furthermore, in further embodiments, the coating sections 17, 18 are designed as patterns, ornaments and/or characters, as in Fig. 5D-F and 5 HL upset. The strip-shaped stabilizing coating is shown in a further embodiment with gradient color tones, as shown in Fig. 5G is shown. In addition, in another embodiment, tonal motifs 19 and watermarks 20 ( Fig. 5H ), further printing elements 21 ( Fig. 5K ), as well as information as negative text 22 and/or as positive text 23 ( Fig. 5L ) applied.

The coating sections, i.e. the stabilizing coating 7, are preferably produced by a printing process and the further printing elements mentioned are applied to the back of the substrate 15 in the same printing process as the stabilizing coating 7.

All embodiments apply to the patch-shaped application area 8 in the same way.

Each of the combinations of features mentioned is possible both alone and in conjunction with at least one of the other features mentioned.

Fig. 6 shows a section through the benefit 2 in a further embodiment. Here an overlap of the two coating sections 17, 18 of the stabilizing coating 7 is realized. This creates an overlap area 24. This is possible analogously with a patch-shaped application area 8. This overlap area of the two coating sections 17, 18 of the stabilizing coating further increases the stability of the benefit 2, while at the same time making it more attractive with further security features through the variation options for the coating sections 17, 18 described in the previous figures, and at the same time further increasing the hurdle for counterfeiting .

Examples of embodiments with two coating sections 17, 18 on two corresponding surface sections of the section of the substrate were described above. Embodiments are not limited to this; rather, a variety of coating sections can be used. In particular, individual coating sections can be designed in the form of a pixel to produce a multi-tonal or colorful image become. In addition, the coating sections or the surface sections do not have to directly border one another; Gaps are possible. Even then, the stabilizing coating still has sufficient effect to improve the processability of the substrate.

Reference symbol list

1

Banknote paper

2

To use

3

Border

4

sheet edge

5

Strip-shaped application area

6

Strip-shaped transfer element

7

Strip-shaped stabilizing coating

8th

Patch-shaped application area

9

Patch-shaped transfer element

10

Patch-shaped stabilizing coating

11

front

12

Strip primer

13

Window

14

Patch-shaped primer

15

back

16

Optional paper thinning

17

First coating section

18

Second coating section

19

Tonal element

20

Watermark

21

Printing element

22

Information as negative text

23

Information as positive text

24

Overlap area

Claims (16)

1. Method for producing a security paper, comprising the following steps:

   providing a substrate (2) which extends in a planar manner and has a front side (11) and a rear side (15),

   applying, to the front side (11), a transfer element (6; 8) which is delimited by at least one edge, and

   applying a stabilizing coating (7; 10) to the rear side (15) in a portion of the substrate,

   the portion of the substrate that has the applied stabilizing coating (7; 10) covering the applied transfer element (6; 8) in plan view,

   characterized in that

   the stabilizing coating (7; 10) is applied in such a way that the portion has at least two surface portions on which different coating materials are applied and which differ with respect to an appearance of the stabilizing coating (7; 10) that is perceptible or measurable from the rear side (15).
2. Method according to claim 1, characterized in that the two surface portions are printed or coated with the different coating materials.
3. Method according to either of the above claims, characterized in that in plan view, the stabilizing coating (7; 10) extends at least up to the edge of the transfer element (6; 8), preferably completely covers the transfer element (6; 8).
4. Method according to any of the above claims, characterized in that the stabilizing coating (7;10) has a first and a second coating portion (17, 18), of which the first coating portion is located in the first surface portion and the second coating portion is located in the second surface portion, a plurality of the corresponding first and second coating portions (17, 18) preferably being located in one of the two or in the two surface portions.
5. Method according to claim 4, characterized in that the coating portions (17, 18) are applied so as to be adjacent to one another or spaced apart from one another and/or the coating portions (17, 18) are applied over the entire surface or over part of the surface.
6. Method according to any of the above claims, characterized in that at least one of the two different coating materials comprises an additive that causes the corresponding perceptible or machine-readable appearance, the stabilizing coating (7;10) preferably comprising a first additive on the first surface portions and a second additive on the second surface portions; and/or
   the stabilizing coating (7;10) comprises, apart from perceptible or machine-readable additives, the same ingredients on the two surface portions.
7. Method according to any of the above claims, characterized in that the stabilizing coating, the surface portions and/or the coating portions have a distinct surface shape, in particular in the form of patterns, symbols, embellishments or characters.
8. Method according to any of the above claims, characterized in that for the different appearance, an additive is present in the stabilizing coating on at least one of the surface portions, preferably different additives are present in the stabilizing coating on the two surface portions.
9. Method according to claim 8, characterized in that the stabilizing coating comprises, in at least one of the surface portions, a perceptible additive, in particular:

   comprises a photochromic and/or thermochromic additive;
   and/or

   comprises a colorant as an additive, in particular in a bright hue or in the form of optically variable pigments, and/or a luminescent additive;

   preferably different colorants being present as additives on the two surface portions, different photochromic or thermochromic additives being present on the two surface portions, or a colorant being present on the first surface portion and a photochromic or thermochromic additive being present on the second surface portion.
10. Method according to any of the above claims, characterized in that the stabilizing coating is formed on the surface portions such that the different appearance, in particular in the form of differences in the infrared or ultraviolet, in magnetization or in conductivity, is machine readable; and/or
    the different appearance of the stabilizing coating is present in the form of a coding, for example in the form of infrared code, magnetic code or conductivity code.
11. Method according to any of the above claims, characterized in that the substrate (2) is continuous in the portion such that the front side (11) and the rear side (15) are uninterrupted in said portion.
12. Method according to any of claims 1 to 10, characterized in that the substrate has, in the portion, a window which is spanned by the transfer element (6; 8) in plan view.
13. Method according to any of the above claims, characterized in that the stabilizing coating (7; 10) is applied in a printing cycle in combination with a further printing element (21).
14. Security paper that has:

    - a substrate (2) that extends in a planar manner and has a front side (11) and a rear side (15),

    - a transfer element (6; 8) on the front side (11), which element is delimited by at least one edge, and

    - a stabilizing coating (7; 10) on the rear side (15) in a portion of the substrate that covers the transfer element (6; 8) in plan view,

    characterized in that
    the stabilizing coating (7; 10) is applied to the rear side (15) in such a way that the portion has at least two surface portions to which different coating materials are applied and which thus differ with respect to an appearance of the stabilizing coating (7; 10) that is perceptible or measurable from the rear side (15).
15. Security paper according to claim 14, characterized in that the security paper can be produced by a method according to any of claims 1 to 13.
16. Security document, in particular a bank note, comprising a security paper according to either claim 14 or claim 15.

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