EP3606766B1 - Security element and method for the production thereof - Google Patents

Description

The invention relates to a motif area which is provided with a first coating and provides the motif, and a background area which is provided with a second coating different from the first coating and which provides the background.

The invention further relates to a value document with a security element.

Finally, the invention also relates to a production method in which a motif area is provided with a first coating, which provides the motif, and a background area is provided with a second coating, which is different from the first coating, and which provides the background.

Security features for banknotes contain motifs, such as symbols, images or real-color images, which are intended to achieve particularly good recognition and security against forgery. For this purpose, security elements are known in particular, the motifs of which are formed by structured, different coatings against the background. Such security elements use, for example, a coating which has a color effect that is dependent on the viewing angle for designing the motif and a coating that acts independently of the viewing angle for the background. When structuring, the register accuracy of the coating is of considerable importance. This places demands on corresponding structuring techniques, such as photolithographic processes or printing with so-called washing inks.

document WO 2013/091858 A1 discloses a security element with a plurality of microimages, each microimage being formed by a microcavity structure. document WO 2016/092040 A1 discloses a multilayer body with a partial reflective layer.

The invention is therefore based on the object of improving a security element, a value document and a production method of the type mentioned at the beginning in such a way that the producibility is facilitated and at the same time the quality of the security element is increased.

The invention is defined in claims 1, 11 and 12.

According to the invention, a security element for producing documents of value, such as bank notes, checks or the like, is provided which shows a motif against a background. The motif is generated by a motif area that is provided with a first coating. The background is provided by a background area of the security element which is provided with a second coating different from the first coating. The different coatings contribute to the visual difference between the subject and the background, but need not be the only properties of the subject area or background area that create the visual difference. Possible options will be explained later.

The background area and the motif area are separated from one another by an outline area. This is formed by a relief structure which has a geometry which is designed such that the relief structure at least partially absorbs light, so in plan view z. B. appears dark. In this way, a brightness and / or color contrast is brought about between the outline area on the one hand and the motif area and background area on the other hand. The relief structure serves to absorb register fluctuations during the application of the first and / or second coating, in that the relief structure lies under the edges of the first coating and / or second coating and is one with both coatings has a similar, preferably dark, appearance. In the manufacturing process, provision is made analogously for a motif area in the security element to be provided with a first coating and to provide the motif. A background area is provided with a different second coating and provides the background. Furthermore, an outline area is provided which delimits the motif area and the background area from one another, the outline area being formed by a relief structure. This has a geometry which is such that the relief structure at least partially absorbs light. In this way, a brightness and / or color contrast is generated between the outline area on the one hand and the motif area and background area on the other hand. The relief structure is arranged in such a way that it absorbs the register fluctuations of the first and / or second coating. The contour area is produced before the first and / or second coating is applied and is covered by one or both coatings.

Due to its relief structure, the outline area creates a clearly recognizable outline which delimits the motif and background area from one another. Due to the relief structure, the real edge of the first and / or second coating cannot be seen. The optically effective part of the motif area and background area ends at the edge of the relief structure of the outline area, regardless of any register fluctuations during the application of the first and / or second coating. In other words, fluctuations in the boundary line between the two coatings are hidden in the outline, which, regardless of the first and / or second coating, causes the brightness and / or color contrast to the adjacent motif and background areas due to its geometry of the relief structure.

The effect of the contour line area requires a certain width of the contour line area and thus the relief structure, which is selected such that it covers register fluctuations when the first and / or second coating is applied. A range from 0.1 mm to 1.0 mm has proven to be advantageous here, and a range from approximately 0.3 mm to 0.7 mm has proven to be particularly advantageous, since register fluctuations can be reduced to half of these without further effort when structuring the coatings Values, e.g. B. can be limited to +/- 0.2 mm.

The relief structure of the outline area is designed in such a way that, due to its geometry, it brings about a contrast in terms of brightness or color between the outline area and the motif and background area. The geometry is expediently chosen so that the contrast is largely independent of whether the first or second coating is on the relief structure. In a preferred embodiment, the relief structure comprises a subwavelength grating or a moth's eye structure which is designed to be light-absorbing.

The first and the second coating preferably abut one another at a boundary line. This boundary line lies above the relief structure of the outline area. Such a configuration is particularly advantageous when using moth-eye structures, since a gap there between the two coatings would result in the moth-eye structure appearing somewhat lighter in the area of this gap.

The first and second coatings are selected in such a way that the best possible contrast between the motif area and the background area is achieved. For this purpose, metallic or highly refractive coatings or a layer composite that creates a color change effect can be used. Especially a color-shifting color shift coating with a three-layer structure with reflector / dielectric / absorber can be used.

The security element also has the advantage that the motif is easier to recognize because it is delimited from the background by a high-contrast contour line.

It is also possible to provide the motif and / or background area with a then coated relief structure, which, however, differs from that of the outline area, so that the brightness and / or color contrast between the outline area on the one hand and the motif area and the background area on the other consists. The contrast between the outline area and the motif area as well as the background area can then also be enhanced, for example, by appropriate selection of the profile geometry of the relief structure. The relief structures of the motif and background area are coated, eg metallic or highly refractive. Relief structures with micromirrors, for example, are known from the prior art (cf. DE 102010049617 A1 ). These micromirrors can be arranged in pixels which each have micromirrors oriented in the same way. With the micromirrors, running effects or 3D effects can in particular also be implemented in the motif and / or background area. Fresnel structures (cf. EP 1562758 B1 ) can be used or combined with micromirrors. Relief heights of a maximum of 100 μm to a maximum of 1 μm and lateral dimensions of less than 100 μm to less than 10 μm are known for micromirrors. Of course, a different relief structure can be used for the background area and the motif area. It is crucial that the contour area dampens or cancels out the effect of the first and second coating. He especially achieves this good as a so-called moth-eye structure (cf. WO 2006/026975 A2 and EP 2453269 A1 ).

In a further development, the contour line area can be equipped with a structuring by designing the relief structure in a correspondingly structured manner. The structuring can mean an interruption of the outline area and / or comprise microtext or information that cannot be seen with the naked eye.

The outline area can also be a contour line within a complex motif. A complex motif consists of several motif components, whereby one of the motif components is to be understood visually as the background compared to the other, so that the outline area separates the background area, i.e. a motif area of the complex motif, from another motif area of the complex motif.

Fig. 1

eine Draufsicht auf eine Banknote mit einem Sicherheitselement,

Fig. 2

eine Draufsicht auf das Sicherheitselement mit mehreren Motiven vor einem Hintergrund, wobei Umrisslinien die Motive gegen den Hintergrund abgrenzen,

Fig. 3

eine vergrößerte Darstellung des Sicherheitselementes in einem Bereich, in dem ein Motiv gegen den Hintergrund durch zwei Umrisslinien abgegrenzt ist, und

Fig. 4

eine Schnittdarstellung durch das Sicherheitselement im Bereich eines in Fig. 3 eingezeichneten Bereichs.

The invention is explained in more detail below by way of example with reference to the figures, which can also show features essential to the invention. In the drawings shows:

Fig. 1

a top view of a bank note with a security element,

Fig. 2

a top view of the security element with several motifs in front of a background, with outlines delimiting the motifs against the background,

Fig. 3

an enlarged illustration of the security element in an area in which a motif is delimited from the background by two outlines, and

Fig. 4

a sectional view through the security element in the area of an in Fig. 3 marked area.

Fig. 1 shows a top view of a bank note B which has a security element S to protect against counterfeiting. The security element is in the schematic representation of the Fig. 1 a rectangular patch which, in the exemplary embodiment, is designed as a film element and is glued onto a bank note paper of bank note B. The security element could equally be used in a security thread or a window area of the B banknote.

Fig. 2 shows the security element S, the purely exemplary motif depicting a hummingbird with a year in front of a background. A motif area 1 and a background area 2 are formed by different coatings which, when reflected, form an optical contrast so that the motif can be perceived with the naked eye. The hummingbird and the year are each separated from the background by an outline. The outlines are generated in outline areas 3 by a relief structure which is designed in such a way that it forms a contrast to both the motif area 1 and the background area 2. This significantly increases the perceptibility of the motifs for a viewer.

The relief structure in the outline is provided with embossed structures which, after coating, show a contrast with respect to areas 1 and 2 and preferably become dark. The appearance of the outline is included largely regardless of whether it is provided with the coating of the motif area 1 or the coating of the background area 2. With both possible coatings, the contour area 3 is advantageously the same or almost the same dark. Due to register fluctuations, the contour line area is usually provided partly with the first and partly with the second coating. However, if its appearance with both metallizations is similarly dark (e.g. with a deviation in the degree of absorption of less than 0.2, preferably less than 0.1), this is hardly noticeable or not at all. The contrast between the contour line area 3 and the areas 1 and 2 dominates the contrast between the various coatings within the contour line. The contour areas 3 have a double function. On the one hand, they support the structuring of the motif by delimiting the motif from the background or different motif areas from one another. On the other hand, they absorb register fluctuations when the coatings are applied, since the relief structure, even with one of the two coatings, still creates a contrast between adjacent areas.

The Figs. 3 and 4 show this fact. Fig. 3 shows a section of the security element of Fig. 2 , namely a point in which the motif area 1 is bounded on both sides by the background area 2. Contour line areas 3 lie at the borders. The contour line areas 3 have a width which is selected such that it absorbs register fluctuations when the first coating is applied to the motif area 1 or the second coating to the background area 3. The width of each contour line area 3 is greater than the maximum register fluctuations when the coatings are applied.

Fig. 4 shows these relationships in a sectional view in detail 4, which is indicated by a dashed circle in Fig. 3 is symbolized. The security element S is built up on a substrate 5, on the upper side of which an embossing lacquer layer 6 is formed. The motif area 1 is characterized by a first coating 7 and the background area 2 by a second coating 8, which influence or define the reflection impression of the motif area 1 and background area 2. A transparent cover film 9 ensures a protected upper side of the security element S. The contour area 3 is formed in that a moth's eye structure 10 is embossed in the embossing lacquer layer 6 under the coatings 7, 8, which when covered with the first and / or second coating 7 or 8 the contour area is designed to be light-absorbing. The two coatings 7, 8 abut one another at a boundary line 11. This lies above the moth-eye structure 10. The visual impression, ie the boundary of the motif area 1 or the background area 2, is defined by the contour area 3 and thus by the moth-eye structure 10. Their width is selected so that register fluctuations with regard to the position of the boundary line 11 between the first coating 7 and the second coating 8 are absorbed. The width of the moth's eye structure 10 is therefore greater than register fluctuations that occur when the first and second coatings 7, 8 are applied.

Instead of a border line 11, it is also possible that there is a gap between the two coatings 7, 8, which then lies completely over the moth's eye structure 10, i.e. within the contour area 3, or that the coatings 7, 8 overlap within the contour area 3.

The production-related fluctuations in the edges of the first coating 7 and second coating 8 or the border line 11 are hidden by the underlying relief structure of the contour area 3 in the contour line, which contrasts with the neighboring ones regardless of an overlap with the first or second coating 7, 8 Areas 1, 2 and preferably looks the same or almost the same with both coatings.

An example of the first coating 7 would be, for example, a reddish or gold-colored coating (for example Au, Cu or Al-Cu alloy) or a color-shift coating, as is known as a multilayer structure from the prior art. An example of the second coating 8 of the background area 2 would be an aluminum metallization. The coatings 7, 8 can be structured using a so-called wash color printing process, which is known in the prior art. The width of the contour line area 3 is selected such that the edges of the coatings or their boundary line 11 always lie within the contour line area 2 within the scope of the register fluctuations. If, for example, a tolerance of the border line position of +/- 0.2 mm succeeds with the wash color printing, the contour line area is chosen to be at least 0.4 mm wide. The second coating in each case is then applied adjacent or with sufficient overlap to the first, so that the two different coatings abut or overlap above the boundary line, preferably at least still touching each other in all register situations. Regardless of the register fluctuations, the viewer sees two differently colored areas that are perfectly matched to one another, namely motif area 1 and background area 2, between which an exactly 0.4 mm wide outline runs.

To improve the visual impression of the contour line, it is possible in a further development to remove the coating 7, 8 in a structured manner in those areas in which it covers the relief structure, for example by irradiating laser radiation. In this way, a transparent outline is achieved, which precisely separates the differently coated areas in perfect register for embossing. Structuring, e.g. B. for the introduction of microtext or symbols in the outline is possible.

The term "outline" is not restricted to an outer boundary of a motif. It can also be an internal contour line that delimits different areas of a motif from one another, so that one motif area is to be viewed as a background area, the other as a motif area.

In order to provide the desired, contrasting structures of the contour area 3, those in FIG Figs. 1 to 4 moth-eye structures 10 used. Various possibilities for producing such moth-eye structures 10 are known from the literature. The WO 2006/026975 A2 or the EP 1434695 B1 referenced. These publications describe random surfaces which form a refractive index gradient layer and have a good absorption effect. The structure depth here is preferably more than 50 nm and the mean distance between adjacent elevations is less than 500 nm. They are therefore an example of subwavelength structures. Such random surfaces can be produced from plastic substrates, for example PMMA, using a plasma etching process. Alternatively, periodically arranged moth-eye structures can also be used. Microcavities with an average distance greater than 500 nm can also show a high absorption effect. From the EP 1434695 B1 a moth's eye structure is known which is formed by a metalized cross grating with a period of less than 420 nm. A two-dimensional periodic subwavelength grating can also be used for light absorption, as is shown, for example, in FIG WO 2012/156049 A1 is described.

The demarcation between the background area, the motif area and the outline area can be achieved by means of relief structures that act as color filters. These do not necessarily have to be black, but can also appear in a different color, e.g. red or blue. Dark colors are advantageous for the recognizability of the subject. The mentioned metallic subwavelength structures show an increased light absorption in the visible spectral range, partly due to a resonant light absorption, which leads to a colored reflection. A high contrast between the outline area and the motif area or background area is guaranteed, as the mean absorption in the visible wavelength range for relief structures is always higher than that of smooth surfaces, such as those provided in the motif and background areas. Alternatively, these structures cannot be dark from some directions.

For good visibility, the average brightness of the outline area is advantageously less than 50% of the average brightness of the subject area and of the background area in reflection.

The relief structure of the contour line area 3 is preferably produced with lithographic methods, for example an e-beam system or a laser writing system which works, for example, with a two-photon absorption process. Alternatively, it can be done in a two-step lithographic process be generated. In a first step, nanostructuring is carried out. This is done, for example, by an electron beam lithographic process. Alternatively, laser beam interference methods are also possible. Aperiodic moth-eye structures can also be created by plasma etching or by structuring with ultra-short laser pulses. In a subsequent step, such an original or a copy thereof is leveled with photoresist. Spin coating or dip coating processes are particularly suitable for this. The relief structure is then written into the photoresist in a photolithographic step and the desired areas of the structures are exposed. This process can be carried out with the help of a laser writer using the direct exposure method. The original created in this way can then be copied by electroplating or using photopolymers (e.g. Ormocere). The surface structure of a stamp produced in this way can now be reproduced next to one another over a larger area using a step-and-repeat process. An embossing cylinder can be produced by galvanic molding of this original replicated on the surface. Finally, the structure can be embossed onto foil in a continuous roll-to-roll process. Nanoimprint processes such as hot embossing or embossing in UV-curable materials come into question here.

Finally, the embossed film is provided with the two coatings. Common vapor deposition methods such as electron beam vapor deposition, thermal evaporation or sputtering can be used for this. Metals such as aluminum, silver, copper, palladium, gold, chromium, nickel, iron, cobalt and / or tungsten and their alloys can be used as the metallic material. Finally, the structure is optionally laminated and protected with the cover film 9. Instead of a simple metal coating, the relief structure can also be covered with a multiple layer become. For this purpose, so-called color shift coatings are particularly suitable, which consist of a semitransparent metal layer, a dielectric spacer layer and a metallic mirror layer located underneath. Particularly suitable dielectrics are SiO ₂ , MgF ₂ , Ta ₂ O ₅ , ZnS and polymers. As a further alternative, a dielectric coating with a highly refractive material can be used.

Reference number

1

Subject area

2

Background area

3

Outline area

4th

Cutout

5

Substrate film

6th

Embossing lacquer layer

7th

first coating

8th

second coating

9

Cover sheet

10

Moth eye structure

11

Boundary line

B.

Banknote

S.

Security element

Claims (14)

1. A security element for manufacturing documents of values, as banknotes, checks or the like, the security element showing a motive in front of a background, wherein the security element (S) comprises

   - a motive region (1) to which a first coating (7) is applied and which provides the motive, and

   - a background region (2) to which a second coating (8) being different from the first coating (7) is applied and which provides the background
   wherein

   - a contour region (3) is provided delimiting the motive region (1) against the background region (2),

   - the contour region (3) is formed by a relief structure having a geometry for light absorbing so that a lightness and/or color contrast exists on the one hand between contour region (3) and motive region (1) and on the other hand between contour line region (3) and background region (2), and

   - the relief structure (10) of the contour region (3) is at least partially covered by the first coating (7) and/or the second coating (8) and, thus, absorbs register variations of the first and/or the second coatings (7, 8).
2. The security element according to claim 1, characterized in, that the contour region (3) has a width from 0,1 mm to 1,0 mm, in particular from 0,3 mm to 0, 7mm.
3. The security element according to claim 1 or 2, characterized in, that the relief structure (10) of the contour region (2) comprises a subwavelength grid.
4. The security element according to any of claims 1 through 3, characterized in, that the two coatings (7, 8) abut at a border line or overlap at a border line, wherein the border line is located in the relief structure (10) of the contour region (3).
5. The security element according to claim 4, characterized in, that the relief structure of the contour region (3) comprises a moth eye structure (10).
6. The security element according to any of claims 1 through 5, characterized in, that the relief structure (10) of the contour region (3) effects the same or nearly the same impression of color and/or lightness of both coatings (7, 8).
7. The security element according to any of claims 1 through 6, characterized in, that the coatings (7, 8) effect different color effects outside the contour region (3).
8. The security element according to any of claims 1 through 7, characterized in, that the first and/or second coating (7, 8) is metallic, high refractive or a color effect generating layer compound.
9. The security element according to any of claims 1 through 8, characterized in, that the relief structure (10) forms the contour region (3) with a structuring of the contour region (3).
10. The security element according to claim 9, characterized in, that the structuring of the contour region (3) comprises discontinuities of the contour region (3) and/or microtext or information which cannot be seen or resolved with the naked eye.
11. A document of value with a security element according to any of claims 1 through 10.
12. A method of manufacturing for a security element (6) for manufacturing documents of value, as banknotes, checks or the like, the security element showing a motive in front of a background, wherein

    - a motive region (1) providing the motive is provided with a first coating (7), and

    - a background region (2) providing the background is provided with a second coating (8) being different from the first coating (7),
    wherein

    - a contour region (3) is provided delimiting the motive region (1) against the background region (2), and

    - the contour region (3) is formed by a relief structure (10) comprising a geometry for light absorption, so that lightness and/or color contrast is generated on the one hand between contour region (3) and motive region (1) and on the other hand between contour region (3) and background region (2),

    - the relief structure (10) is positioned such that it absorbs for register variations of the first and/or the second coatings (7, 8) in that when applying the first coating (7) and/or the second coating (8) the contour region (3) gets covered at least partially by the first coating (7) and/or the second coating (8) within the limits of the register variations.
13. The method of manufacturing according to claim 10, characterized in, that the security element (S) according to any of claims 1 through 10 is manufactured.
14. The method of manufacturing according to any of claims 12 or 13, characterized in, that the first and/or second coating (7, 8) is removed at least partially from above the relief structure (10) to provide a structuring of the contour.

Images