EP3802141B1 - Method for producing a value document, value document and printing device - Google Patents

Description

The invention relates to a method for producing a document of value, in particular a bank note, and a printing device for carrying out the method.

Data carriers, such as value or ID documents, or other valuables, such as branded items, are often provided with security elements for protection, which allow the authenticity of the data carrier to be checked and which also serve as protection against unauthorized reproduction. Security elements with effects that depend on the viewing angle play a special role in securing authenticity, as these cannot be reproduced even with the most modern copiers. The security elements are equipped with optically variable elements that give the viewer a different image impression from different viewing angles and, for example, show a different color or brightness impression and/or a different graphic motif depending on the viewing angle.

Thin-layer systems that generate a viewing-angle-dependent color impression on the viewer by means of interference are known in the prior art. This optical effect can serve as an optically variable security element. A large-area thin-layer system can be comminuted using various techniques. The size of the resulting flakes or platelets can be up to a few micrometers laterally, but the size usually ranges from 2 µm to 100 µm. The vertical structure of a plate is determined by the requirements for the interference layers and is usually as thin as possible, eg in a range from 200 nm to 800 nm. Such plates are used, for example, in an optically variable color (so-called OVI color). , which serves to provide a security element.

Also known is the possibility of applying the thin-layer systems producing a color impression to a ferromagnetic material. Thus, the pigment platelets have a magnetic moment. Magnetic-orientable effect pigments are commercially available, for example, under the trade name ^OVMI® from SICPA (the abbreviation OVMI stands for the term “optically variable magnetic ink”). The pigments have a platelet-like structure and are present in the form of a layered composite, which often contains two layers of optical effect layers and a magnetic layer embedded in between. With regard to the optical effect layers, metallic-reflecting layers as well as color-shifting layer systems, eg with an absorber/dielectric/reflector structure, are possible. The embedded magnetic layer is usually not visible, but is required to align the pigments.

It is also known in the prior art to use color pigments that have a magnetic moment to provide optically variable security elements. For this purpose, the pigments are introduced into a transparent binder. Using an external magnetic field, the alignment of the pigments can be influenced immediately after printing on a substrate. The binder is then cured, e.g. by means of UV radiation, in order to fix the alignment of the pigments. By skilfully adjusting the spatial progression of the pigment orientations, it is possible to equip the printed substrate with optical movement effects.

The DE 10 2010 035313 A1 describes a security element for security papers, documents of value and other data carriers, with a color layer with magnetically aligned magnetic pigments that form a first motif in the form of patterns, characters or a code that when tilting the Security element shows a dynamic movement effect. According to the invention, the first, dynamic motif is combined with a second motif in the form of an embossed structure that has raised embossed elements with flanks of different orientation, so that the magnetic pigments arranged on flanks of different orientation reflect incident light differently and the second motif shows a tilting effect when the security element is tilted . The DE 10 2010 035313 A1 discloses almost all the features of claim 1, but not that the magnetic field is a continuously rotating magnetic field.

The WO 2014/108303 A1 describes an optical effect layer (OEL) that exhibits an optical effect that is dependent on the viewing angle, devices and methods for producing this OEL and objects that carry this OEL, and uses of the OEL as a means of protecting against forgery on documents. The OEL comprises a plurality of non-spherical magnetic or magnetizable particles dispersed in a coating composition comprising a binder material, the OEL comprising two or more looped regions interleaved around a common central region surrounded by the innermost looped region wherein in each of the looped regions at least a portion of the plurality of non-spherical magnetic or magnetizable particles are oriented to be in a cross-section perpendicular to the OEL layer extending from the center of the central region to the outer boundary of the outermost looped region , the longest axis of the particles in each of the cross-sectional areas of the looped regions follows a tangent to either a negatively curved or a positively curved portion of hypothetical ellipses or circles.

The object of the present invention is to provide a method by which control over the arrangement of the thin-layer pigments or effect pigments of an optically variable ink applied to a printing material.

This object is achieved on the basis of the combinations of features defined in the independent claims.

Developments of the invention are the subject matter of the dependent claims.

1. 1. (Erster Aspekt der Erfindung) Verfahren zum Herstellen eines Wertdokuments, z.B. eine Banknote, gemäß Anspruch 1.

Summary of the Invention

1. 1. (First aspect of the invention) Method for producing a value document, e.g. a banknote, according to claim 1.

It is preferred that step c2) is carried out after step c1).

The value document substrate provided in step a) is in particular a paper substrate, a plastic substrate, a foil/paper/foil composite substrate (see, for example, WO 2006/066431 A1 ) or a paper/foil/paper composite substrate (see e.g. the WO 2004/028825 A2 ).

According to one variant, the document of value substrate provided in step a) is a film substrate for the production of security strips, security threads or security patches or security labels, which are suitable for protecting documents of value, eg banknotes.

The magnetic field can be generated by an electromagnet, for example. It is advantageous here that the different magnetic field vectors lie parallel to the value document substrate. This causes the pigments to align parallel to the value document substrate as desired.

According to a special embodiment variant, there is the possibility of using a thermoplastic UV varnish. In this case it is advantageous to use a heated embossing tool. As an alternative to the thermoplastic UV varnish, there could be a thermoplastically deformable layer underneath the varnish containing the magnetically orientable effect pigments.

2. (Second aspect of the invention) Printing apparatus for carrying out the method according to clause 1, wherein the printing apparatus is defined according to claim 9.

Detailed Description of Preferred Embodiments

In the present description, the abbreviation ^OVMI® pigments is used instead of the wording “magnetically orientable effect pigments”. The pigments have a platelet-like structure. The abbreviation OVI ^® stands for optically variable color, OVI ^® pigments mean effect pigments or thin-layer pigments of an optically variable color.

The advantages of the invention are explained below with reference to the diagrammatically greatly simplified figures, which are illustrated on a scale and proportionate reproduction was omitted in order to increase clarity.

• Figur 1 die Ausrichtung von "Leafing"-Pigmenten in einem auf einen Bedruckstoff aufgebrachten Lack;
• Figur 2 die Ausrichtung von "Non-Leafing"-Pigmenten in einem auf einen Bedruckstoff aufgebrachten Lack;
• Figur 3 die Anordnung von Pigmenten in einem auf einen Bedruckstoff aufgebrachten Lack vor dem Prägevorgang;
• Figur 4 die Anordnung von Pigmenten in einem auf einen Bedruckstoff aufgebrachten Lack nach dem Prägevorgang.
• Figur 5 die Ausrichtung von in einem UV-härtbaren Lack dispergierten OVMI^®-Pigmenten, die einem rotierenden Magnetfeld ausgesetzt sind, bei der Betrachtung in Querschnittansicht;
• Figur 6 die Ausrichtung von in einem UV-härtbaren Lack dispergierten OVMI^®-Pigmenten, die einem rotierenden Magnetfeld ausgesetzt sind, bei der Betrachtung in Draufsicht; und
• Figuren 7 und 8 die Anordnung von OVMI-Pigmenten, die einem rotierenden Magnetfeld ausgesetzt sind, in einem auf einen Bedruckstoff aufgebrachten UV-härtbaren Lack jeweils vor und nach dem Prägevorgang.

Show it:

• figure 1 the alignment of "leafing" pigments in a varnish applied to a substrate;
• figure 2 the alignment of "non-leafing" pigments in a varnish applied to a substrate;
• figure 3 the arrangement of pigments in a varnish applied to a printing material before the embossing process;
• figure 4 the arrangement of pigments in a coating applied to a substrate after the embossing process.
• figure 5 the orientation of OVMI ^® pigments dispersed in a UV-curable varnish exposed to a rotating magnetic field when viewed in cross-sectional view;
• figure 6 the orientation of OVMI ^® pigments dispersed in a UV-curable varnish exposed to a rotating magnetic field when viewed in plan; and
• Figures 7 and 8 the arrangement of OVMI pigments, which are exposed to a rotating magnetic field, in a UV-curable varnish applied to a substrate before and after the embossing process.

The method of the present invention preferably involves embossing a dispersion solution containing thin layer pigments. It is known in the prior art that the orientation of the pigments of an optically variable ink ( ^OVI® pigments) in the dispersion medium is based on the complex interaction of various factors such as the viscosity of the medium and shrinkage during drying. If the production parameters are chosen correctly, it is possible for the pigments to align themselves approximately parallel to the interface of the dispersion medium. A distinction is made here between "leafing" pigments and "non-leafing" pigments: "Leafing" pigments, after being applied to a printing material, move towards the surface of the dispersion medium (see FIG. 1; the reference number 1 designates the value document substrate, in the example a paper substrate; the reference number 2 denotes "leafing"pigments; the reference number 3 denotes the dispersion medium, eg a UV-curable lacquer), whereas "non-leafing" pigments 4 (see the figure 2 ) are distributed randomly and at different heights within the dispersion medium.

"Leafing" pigments can arrange themselves both at the "substrate-paint" boundary layer and at the "paint-air" boundary layer.

The dispersion medium advantageously meets the following requirements: 1) embossability of the cured or at least partially cured UV varnish; 2) controlled UV curability.

The combination of dispersion medium (UV-curing lacquer) and OVI ^® pigments is referred to below as "OVI embossing lacquer".

It is preferred to apply the OVI embossing varnish evenly to the value document substrate to be printed.

In order to emboss the OVI embossing varnish, a suitable embossing tool 5 must be used (see the figure 3 ). The lower limit for the dimensions of the embossed structure is given in particular by the size of the pigments 2 (in the example "leafing" pigments), for example in a range from 2 μm to 100 μm. According to a variant, the pigments present in a relatively large size (ie in a size greater than the dimensions of the embossed structure) may be broken into smaller fragments during embossing.

If the OVI embossing varnish is now embossed, the local layer height of the varnish changes: in some places the OVI embossing varnish is strongly pressed in by the embossing structure of the embossing tool and the layer height is reduced. In other words, a transfer of the OVI embossing varnish takes place, which leads to local fluid dynamics of the embossing varnish: a buoyancy gradient is created, ie the buoyancy acting on the pigments is less strong at embossed depressions than at elevations. Therefore, the pigments move downwards in the places where the embossing varnish is strongly pressed, whereas the pigments move upwards in the places where the embossing structure shows a ridge (or the pigments move downwards less strongly). ). The movement can also be different along a pigment, resulting in a tilting of the pigment. Thus, the pigments are aligned along the orientation of the embossing structure immediately above (see the figure 4 ). The pigments follow the embossed structure of the paint.

During the embossing process, or even before the embossing process, the OVI embossing varnish can be fully cured by UV radiation. In this way, the pigments are immobilized and fixed with regard to their final orientation.

Since the embossing structure of the embossing tool can be produced with great creative freedom, e.g. by milling, 3D printing, lithography or the like, the process enables a high level of detail. In particular, embossing structures can easily be produced in such a way that adjacent flanks have gradients that differ greatly from one another.

1. a) das Bereitstellen eines Wertdokumentsubstrats;
2. b) das Bedrucken des Wertdokumentsubstrats mit magnetisch orientierbaren Effektpigmenten bzw. OVMI^®-Pigmenten, die in einem UV-härtbaren Lack dispergiert sind;
3. c) den Schritt c1) des Aussetzens des die magnetisch orientierbaren Effektpigmente enthaltenden Lacks an ein dynamisches, nämlich ein kontinuierlich rotierendes, Magnetfeld, sodass sich die Effektpigmente im Lack parallel zum Wertdokumentsubstrat und insbesondere Stoß-an-Stoß anordnen; den Schritt c2) des Bestrahlens des die Effektpigmente enthaltenden Lacks mit UV-Strahlung, wobei der c2) insbesondere nach dem Schritt c1) erfolgt oder gleichzeitig zusammen mit dem Schritt c1) erfolgt;
4. d) den Schritt des Verprägens des gehärteten oder zumindest teilweise gehärteten UV-Lacks, der die parallel zum Wertdokumentsubstrat und insbesondere Stoß-an-Stoß angeordneten Effektpigmente aufweist, sodass im Lack eine geprägte, dem Betrachter ein optisch variables Bild vermittelnde Reliefstruktur mit sich an das Relief anpassenden Effektpigmenten ausgebildet wird.

A method for producing a document of value, eg a bank note, is described below, comprising

1. a) providing a value document substrate;
2. b) the printing of the value document substrate with magnetically orientable effect pigments or ^OVMI® pigments, which are dispersed in a UV-curable lacquer;
3. c) the step c1) of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic, namely a continuously rotating, magnetic field, so that the effect pigments in the lacquer are arranged parallel to the value document substrate and in particular end-to-end; step c2) of irradiating the paint containing the effect pigments with UV radiation, c2) taking place in particular after step c1) or taking place simultaneously with step c1);
4. d) the step of embossing the cured or at least partially cured UV varnish, which has the effect pigments arranged parallel to the document of value substrate and in particular end-to-end, so that the varnish has an embossed relief structure that conveys an optically variable image to the viewer is formed with effect pigments that adapt to the relief.

The combination of dispersion medium (UV-curing lacquer) and ^OVMI® pigments is also referred to herein as “OVMI embossing lacquer”.

The figure 5 Figure 12 illustrates the alignment of ^OVMI® pigments 6 dispersed in a UV curable varnish 3 exposed to a rotating magnetic field when viewed in cross-sectional view. The reference number 1 designates the value document substrate, in the example a paper substrate. The UV-curable lacquer 3 comprising the ^OVMI® pigments 6 was applied to the paper substrate 1 by screen printing. The rotating magnetic field is generated by means of a magnetic stirrer arranged below the paper substrate 1 (in Fig figure 5 not shown) and in the example is a continuously rotating magnetic field with a speed of 150 revolutions per minute. As a result of the rotating magnetic field, the ^OVMI® pigments 6 form an essentially homogeneous, reflective surface. The individual OVMI ^® pigments are arranged "butt to butt", so to speak.

The figure 6 shows a section of the "butt-to-butt" alignment of ^OVMI® pigments 6 dispersed in a UV-curable lacquer, which can be seen under the microscope and which are exposed to a rotating magnetic field, when viewed from above.

According to the Figures 7 and 8 takes place in addition to step c1) of exposing the UV-curable lacquer 3 containing the magnetically orientable effect pigments 6 to a rotating magnetic field, so that the effect pigments 6 in the lacquer 3 are arranged end-to-end along the surface of the value-document substrate 1, at the same time step c2) irradiating the effect pigments 6 containing lacquer 3 with UV radiation. Depending on the duration or dose of the UV treatment, the UV irradiation leads to a cured or at least partially cured UV lacquer 3 which has the effect pigments 6 arranged end-to-end along the surface of the value-document substrate 1 . In the step of embossing by means of an embossing tool 5, for example an intaglio printing plate, an embossed relief structure 7 conveying an optically variable image to the viewer is formed in the lacquer 3 with effect pigments 8 adapting to the relief.

As a result of the interaction of the four measures 1) ^OVMI® pigments, 2) dynamic, namely continuously rotating, magnetic field, 3) UV irradiation and 4) embossing, the method according to the invention enables an extremely advantageous control of the pigment orientations, so that in particular homogeneously glossy, structured surfaces can be imitated. A granular, noisy texture known in the art can also be generated.

1. a) das Bereitstellen eines Wertdokumentsubstrats;
2. b) das Bedrucken des Wertdokumentsubstrats mit magnetisch orientierbaren Effektpigmenten, die in einem UV-härtbaren Lack dispergiert sind;
3. c) den Schritt c1a) des Aussetzens des die magnetisch orientierbaren Effektpigmente enthaltenden Lacks an ein dynamisches, nämlich ein rotierendes, Magnetfeld, sodass sich die Effektpigmente im Lack parallel zum Wertdokumentsubstrat und insbesondere Stoß-an-Stoß anordnen, um die Effektpigmente auf diese Weise in Form einer Vor-Orientierung anzuordnen; den Schritt c1b), in dem ein weiteres Orientieren bzw. Ausrichten der im Zuge des Schritts c1a) vororientierten, magnetisch orientierbaren Effektpigmente durch Anlegen eines statischen magnetischen Feldes erfolgt, sodass die Effektpigmente eine von der Vor-Orientierung geänderte Orientierung annehmen; den Schritt c2) des Bestrahlens des die Effektpigmente enthaltenden Lacks mit UV-Strahlung, wobei der Schritt c2) insbesondere nach den Schritten c1a) und c1b) erfolgt;
4. d) den Schritt des Verprägens des gehärteten oder zumindest teilweise gehärteten UV-Lacks, der die zunächst parallel zum Wertdokumentsubstrat und insbesondere Stoß-an-Stoß angeordneten, vororientierten Effektpigmente und darauffolgend einer geänderten Orientierung unterzogenen Effektpigmente aufweist, sodass im Lack eine geprägte, dem Betrachter ein optisch variables Bild vermittelnde Reliefstruktur mit sich an das Relief anpassenden Effektpigmenten ausgebildet wird.

According to a preferred variant, the method according to the invention includes the following steps:

1. a) providing a value document substrate;
2. b) the printing of the value document substrate with magnetically orientable effect pigments that are dispersed in a UV-curable lacquer;
3. c) the step c1a) of exposing the lacquer containing the magnetically orientable effect pigments to a dynamic, namely a rotating, magnetic field, so that the effect pigments in the lacquer are arranged parallel to the value document substrate and in particular end-to-end, in order in this way to to arrange form of a pre-orientation; the step c1b), in which a further orientation or alignment of the in the course of step c1a) pre-oriented, magnetically orientable effect pigments takes place by applying a static magnetic field, so that the effect pigments adopt an orientation that differs from the pre-orientation; the step c2) of irradiating the paint containing the effect pigments with UV radiation, step c2) taking place in particular after steps c1a) and c1b);
4. d) the step of embossing the cured or at least partially cured UV varnish, which has the pre-oriented effect pigments, which are initially arranged parallel to the document of value substrate and in particular end-to-end, and then effect pigments subjected to a changed orientation, so that in the varnish an embossed, the viewer a relief structure conveying an optically variable image is formed with effect pigments that adapt to the relief.

The preferred variant achieves a particular attractiveness and brilliance of the color layer containing the effect pigments. The effects obtained are due to the fact that the effect pigments not only change their alignment (i.e. the tilt angle) in the alternating field, but also their arrangement (i.e. the position in the paint). In the case of a rotating bar magnet, the effect pigments seem to collect in one plane and arrange themselves "end to end". The effect pigments thus form a layer that is as closed as possible, which leads to an increased, usable, reflecting surface and thus to increased brilliance. In this way, the quantitative requirement for the effect pigments to be used can also be reduced.

Claims (10)

1. Method for producing a value document, comprising

   a) providing a value document substrate (1);

   b) printing the value document substrate (1) with magnetically orientatable effect pigments (6) which are dispersed in a UV-curable varnish (3);

   c) the step c1) of exposing the varnish (3) containing the magnetically orientatable effect pigments (6) to a dynamic, specifically a continuously rotating, magnetic field, so that the effect pigments (6) in the varnish (3) arrange themselves parallel to the value document substrate (1) and more particularly edge to edge; the step c2) of irradiating the varnish (3) containing the effect pigments (6) with UV radiation;

   d) the step of embossing the cured or at least partially cured UV varnish (3) which has the effect pigments (6) arranged parallel to the value document substrate (1) and more particularly edge to edge, so that in the varnish (3) an embossed relief structure (7) is formed which conveys an optically variable image to the viewer and has effect pigments (6) which conform to the relief.
2. Method according to Claim 1, wherein step c2) takes place after step c1) or takes place simultaneously together with step c1).
3. Method according to Claim 1 or 2, wherein the dynamic, specifically continuously rotating, magnetic field in step c) has a speed in the range from 50 revolutions per minute to 1500 revolutions per minute, preferably a speed in the range from 100 revolutions to 1500 revolutions per minute and especially preferably a speed in the range from 100 revolutions per minute to 500 revolutions per minute.
4. Method according to one of Claims 1, 2 or 3, wherein the step of embossing d) takes place by means of an intaglio printing plate.
5. Method according to any of Claims 1 to 4, wherein the step b) of printing the value document substrate with magnetically orientatable effect pigments which are dispersed in a UV curable varnish takes place in a selected region which is present in particular in the form of a pattern, in the form of characters or in the form of a coding.
6. Method according to any of Claims 1 to 5, wherein step c) has the following (sub)steps:
   c) the step c1a) of exposing the varnish containing the magnetically orientatable effect pigments to a dynamic, specifically a continuously rotating, magnetic field, so that the effect pigments in the varnish arrange themselves parallel to the value document substrate and more particularly edge to edge, in order in this way to arrange the effect pigments in the form of a pre-orientation; the step c1b), in which a further orientation or alignment of the magnetically orientatable effect pigments, preorientated in the course of step c1a), takes place by application of a static magnetic field, so that the effect pigments adopt an orientation altered from the pre-orientation; the step c2) of irradiating the varnish containing the effect pigments with UV radiation, wherein step c2) takes place in particular after steps c1a) and c1b).
7. Method according to Claim 6, additionally comprising the step d) of embossing the cured or at least partially cured UV varnish, which has the preorientated effect pigments initially arranged parallel to the value document substrate and more particularly edge to edge and effect pigments subsequently subjected to an altered orientation, so that in the varnish an embossed relief structure is formed which conveys an optically variable image to the viewer and has effect pigments which conform to the relief.
8. Method according to any of Claims 1 to 7, wherein the value document is a banknote.
9. Printing apparatus for performing the method according to any of Claims 1 to 8, comprising a device for providing a value document substrate (1), a device for printing the value document substrate (1) with a UV-curable varnish (3) based on magnetically orientatable effect pigments (6), a device for providing a dynamic, specifically a continuously rotating, magnetic field which is suitable for aligning the effect pigments (6), a device for curing the UV varnish (3) by means of UV radiation, and a device for embossing the cured or at least partially cured UV varnish (3).
10. Printing apparatus according to Claim 9, wherein the device for embossing is an intaglio printing plate.

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