DE102017009226A1 - Optically variable see-through security element and data carrier - Google Patents

Abstract

The invention relates to an optically variable see-through security element for securing valuables, having a planar, optically variable surface pattern which shows a different color in plan view in plan view and having virtually no color shift effect, the optically variable surface pattern having a plurality of substantially radiation-optical effect Facets whose orientation is characterized in each case by an inclination angle α against the plane of the surface pattern lying in a range of 0 ° to 30 °, the facets having a semitransparent, appearing in a different color as viewed in supervision and in The optically variable surface pattern contains at least two partial regions, each with a multiplicity of similarly oriented facets, the facets of one partial region having a small inclination angle α and the facets d it further portion have a high inclination angle α, so that the optically variable surface pattern in view in the partial area in which the facets have a small inclination angle α, appears in a high chroma and chroma and in the partial area in which the facets have a high inclination angle α , appears in a small chroma or chroma.

Description

The invention relates to an optically variable see-through security element for securing valuables, with a flat, optically variable surface pattern, which shows a different color as seen in plan view.

Data carriers, such as valuables or identity documents, but also other valuables, such as branded articles, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carrier and at the same time serve as protection against unauthorized reproduction. Increasingly transparent security features, such as transparent windows in banknotes, are becoming increasingly attractive.

The WO 2016/096094 A1 describes an optically variable see-through security element for securing valuables, with a flat, optically variable surface pattern, which shows in phantom a colored appearance with a viewing angle-dependent multi-color color change.

Proceeding from this, the object of the invention is to specify a see-through security element which combines an appealing visual appearance with an improved security against counterfeiting and, ideally, can be produced in the commercial scale required in the security area.

This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

Summary of the invention

• - das optisch variable Flächenmuster eine Vielzahl von im Wesentlichen strahlungsoptisch wirkenden Facetten enthält, deren Orientierung jeweils durch einen Neigungswinkel α gegen die Ebene des Flächenmusters, der in einem Bereich von 0° bis 30° liegt, charakterisiert ist,
• - die Facetten mit einer semitransparenten, in Durchsicht in einer anderen Farbe wie in Aufsicht erscheinenden und in Durchsicht nahezu keinen Farbkippeffekt aufweisenden Funktionsschicht versehen sind, und
• - das optisch variable Flächenmuster zumindest zwei Teilbereiche mit jeweils einer Vielzahl ähnlich orientierter Facetten enthält, wobei die Facetten des einen Teilbereichs einen geringen Neigungswinkel α und die Facetten des weiteren Teilbereichs einen hohen Neigungswinkel α aufweisen, sodass das optisch variable Flächenmuster in Durchsicht im Teilbereich, in dem die Facetten einen geringen Neigungswinkel α aufweisen, in einer hohen Buntheit bzw. Chroma erscheint und im Teilbereich, in dem die Facetten einen hohen Neigungswinkel α aufweisen, in einer geringen Buntheit bzw. Chroma erscheint.

1. (First aspect of the invention) Optically variable see-through security element for hedging valuables, with a flat, optically variable surface pattern, which shows a different color as seen in plan view and having almost no color shift effect in a transparent, characterized in that

• the optically variable surface pattern contains a multiplicity of essentially radiation-optical facets whose orientation is characterized in each case by an inclination angle α with respect to the plane of the surface pattern lying in a range from 0 ° to 30 °,
• - The facets are provided with a semi-transparent, in review in a different color as in supervision appearing and in review almost no color shift effect having functional layer, and
• - The optically variable surface pattern includes at least two subregions, each having a plurality of similarly oriented facets, wherein the facets of one subregion have a small inclination angle α and the facets of the further subregion have a high inclination angle α, so that the optically variable surface pattern in the partial area, in the facets have a small inclination angle α, appears in a high chroma or chroma and in the partial area in which the facets have a high inclination angle α, appears in a low chroma or chroma.

The chroma describes the relative color effect in relation to the reference white, ie in comparison to a certain brightest point of a color space. The chroma is suitable as a measurement value for conical color spaces, for example, where it can be measured from the top. These systems are useful in the printing industry, where paper white is the neutral color and rich black requires as much color as deep red. White has a chroma of 0, shades (hues) and deep black up to 100%, mid-gray 50%.

The optically variable surface pattern is based, in particular, on a relief structure impressed into an embossing lacquer layer, namely a reflective microstructure in the form of a mosaic of a multiplicity of reflecting mosaic elements or facets which can be characterized by the parameters size, outline shape, relief shape, reflectivity and spatial orientation and which form a predetermined motif in that different groups of mosaic elements with different characteristic parameters reflect incident light into different spatial areas, the mosaic elements having a lateral dimension 1 below the resolution limit of the eye. The lateral dimension 1 of a mosaic element is in the 2 of the EP 1966 769 B1 illustrated graphically. In this case, the semitransparent functional layer, which appears in a different color as viewed in a plan view and has virtually no color-shift effect in view, serves as the reflective layer.

2. (Preferred embodiment) see-through safety element according to paragraph 1 , characterized in that the area occupied by each sub-area on the optically variable area pattern is at least 50 times, preferably at least 100 times, more preferably at least 1000 times larger than the area occupied by a single facet of that area area on average.

3. (Preferred embodiment) see-through safety element according to paragraph 1 or 2 , characterized in that the facets of at least two sub-areas in the angle of inclination against the plane by 5 ° or more, preferably by 10 ° or more, different.

4. (Preferred embodiment) See-through security element according to one of the paragraphs 1 to 3 , characterized in that the facets of the one subregion which have a low inclination angle α have an inclination angle α in a range of 0 ° to 15 °, preferably in a range of 0 ° to 10 °, and the facets having a high inclination angle α Partial region an inclination angle α in a range of 15 ° to 30 °, preferably in a range of 20 ° to 30 °.

5. (Preferred embodiment) See-through security element according to one of the paragraphs 1 to 4 , characterized in that the facets are each provided with a semi-transparent, appearing in review in another color as in top view functional layer whose layer thickness varies with the inclination angle α of the facets, preferably decreases with increasing inclination angle α.

6. (Preferred embodiment) See-through security element according to one of the paragraphs 1 to 5 , characterized in that the at least two subregions are arranged in the form of a motif and the motif appears in review with two or more different chroma values visually distinguishable with the naked eye.

7. (Preferred embodiment) See-through security element according to one of the paragraphs 1 to 6 , characterized in that the optically variable surface pattern in the subregions additionally has a black mask, which has been adapted to the inclined facets and which serves to adjust the translucent brightness of the facets in the respective subregions.

8. (Preferred embodiment) see-through safety element according to one of the paragraphs 1 to 7 , characterized in that the facets are embossed into an embossing lacquer layer having a first refractive index and a lacquer layer having a second refractive index, which differs from the first refractive index by less than 0.3, in particular by less than 0.1, is applied over the semitransparent functional layer ,

9. (Preferred embodiment) see-through security element according to at least one of the paragraphs 1 to 8th , characterized in that the semitransparent functional layer has a multilayer structure with two semitransparent metallic layers and a dielectric layer arranged between the two semitransparent metallic layers.

10. (Preferred embodiment) see-through safety element according to paragraph 9 characterized in that the two semitransparent metallic layers are independently formed of a metal and the metal is selected from the group consisting of Al, Ag, Ni, Cr, Cu, Au and an alloy of one or more of the aforementioned elements, and the dielectric layer is an SiO ₂ layer, a ZnO layer, an Al ₂ O ₃ layer, a TiO ₂ layer, a layer of a nitride or oxynitride of one of the elements Si, Zn, Al or Ti or an MgF ₂ - Layer or a, for example, technically available, nitrocellulose layer.

11. (Preferred embodiment) see-through safety element according to paragraph 9 , characterized in that the two semitransparent metallic layers are selected independently of each other of Al or Ag and the dielectric layer is a SiO ₂ layer.

12. (Preferred embodiment) see-through safety element according to one of the paragraphs 1 to 11 , characterized in that the optically variable area pattern when viewed in a transparent shows a blue color and when viewed in supervision shows a golden color.

13. (Preferred Embodiment) See-through security element according to at least one of the paragraphs 1 to 12 , characterized in that the facets are formed substantially as planar surface elements.

14. (Preferred embodiment) See-through security element according to at least one of the paragraphs 1 to 13 , characterized in that the facets are arranged in a periodic grid and in particular form a sawtooth grid, or that the facets are arranged aperiodically.

15. (Preferred embodiment) see-through security element according to at least one of claims 1 to 14, characterized in that the facets a smallest dimension (or lateral dimension 1 ) of more than 2 μm, preferably of more than 5 μm, in particular of more than 10 μm, and / or that the facets have a height of less than 100 μm, preferably less than 50 μm, in particular less than 10 μm.

16. (Second aspect of the invention) Data carrier with a see-through security element according to at least one of the paragraphs 1 to 15 wherein the see-through security element is preferably arranged in or above a window area or a through opening of the data carrier.

17. (Preferred embodiment) Data carrier according to paragraph 16 , wherein the data carrier is a value document, in particular a banknote.

Detailed Description of the Preferred Embodiments

• - es ein ebenes, optisch variables Flächenmuster enthält, das in Durchsicht eine andere Farbe wie in Aufsicht zeigt und in Durchsicht nahezu keinen Farbkippeffekt aufweist,
• - das optisch variable Flächenmuster eine Vielzahl von im Wesentlichen strahlungsoptisch wirkenden Facetten enthält, deren Orientierung jeweils durch einen Neigungswinkel α gegen die Ebene des Flächenmusters, der in einem Bereich von 0° bis 30° liegt, charakterisiert ist,
• - die Facetten mit einer semitransparenten, in Durchsicht in einer anderen Farbe wie in Aufsicht erscheinenden und in Durchsicht nahezu keinen Farbkippeffekt aufweisenden Funktionsschicht versehen sind, und
• - das optisch variable Flächenmuster zumindest zwei Teilbereiche mit jeweils einer Vielzahl ähnlich orientierter Facetten enthält, wobei die Facetten des einen Teilbereichs einen geringen Neigungswinkel α und die Facetten des weiteren Teilbereichs einen hohen Neigungswinkel α aufweisen, sodass das optisch variable Flächenmuster in Durchsicht im Teilbereich, in dem die Facetten einen geringen Neigungswinkel α aufweisen, in einer hohen Buntheit bzw. Chroma erscheint und im Teilbereich, in dem die Facetten einen hohen Neigungswinkel α aufweisen, in einer geringen Buntheit bzw. Chroma erscheint.

According to the invention, it is provided in a generic optically variable see-through security element that

• it contains a flat, optically variable surface pattern which, when viewed, shows a different color as in plan view and has virtually no color shift effect when viewed through,
• the optically variable surface pattern contains a multiplicity of essentially radiation-optical facets whose orientation is characterized in each case by an inclination angle α with respect to the plane of the surface pattern lying in a range from 0 ° to 30 °,
• - The facets are provided with a semi-transparent, in review in a different color as in supervision appearing and in review almost no color shift effect having functional layer, and
• - The optically variable surface pattern includes at least two subregions, each having a plurality of similarly oriented facets, wherein the facets of one subregion have a small inclination angle α and the facets of the further subregion have a high inclination angle α, so that the optically variable surface pattern in the partial area, in the facets have a small inclination angle α, appears in a high chroma or chroma and in the partial area in which the facets have a high inclination angle α, appears in a low chroma or chroma.

The chroma describes the relative color effect in relation to the reference white, ie in comparison to a certain brightest point of a color space. The chroma is suitable as a measurement value for conical color spaces, for example, where it can be measured from the top. These systems are useful in the printing industry, where paper white is the neutral color and rich black requires as much color as deep red. White has a chroma of 0, shades (hues) and deep black up to 100%, mid-gray 50%.

The see-through security element according to the invention is optically variable, i. different representations arise at different viewing angles.

Compared with that from the WO 2016/096094 A1 known optically variable see-through security element, which shows a colorful appearance with a viewing angle-dependent multi-color color change, the inventive, in review virtually no color shift effect optically variable see-through security element with its supervisory / transparent color change by its attractive color effects in supervision and in review , in which, by means of the adjustment of the facet angle of inclination and the thus obtained chroma of the see-through color, an increase in contrast and thus a highlight of certain elements of a motif can be effected. By adjusting the transmission properties of the semitransparent functional layer, a broad color palette can be provided in phantom, especially from gray to deep blue. The increase in contrast causes an additional check level in the authenticity verification and thus offers improved protection against counterfeiting.

The invention is based on the finding that the chroma when subjected to reflection in transmitted light strongly depends on the embossed structure or the relief which is vapor-deposited with the semitransparent functional layer. If the optically variable surface pattern contains a subregion (so-called "smooth" subregion) in which the facets have a small inclination angle α, or if a smooth or unembossed subregion without any facets or micromirrors is present, the viewer sees the transparency in a high chroma or chroma. The high chroma is due to the fact that the embossing lacquer on its surface is relatively smooth or even, ie the light is not broken or scattered in the course of transmission through the film structure and meets straight into the eye of the beholder. Of Furthermore, the thickness of the semitransparent functional layer in the case of a flat or smooth substrate corresponds to the desired thickness and is therefore optically particularly effective. If the optically variable surface pattern contains a subregion (so-called "rough" subregion) in which the facets have a high inclination angle .alpha., The viewer sees the transparency in a low chroma or chroma, ie the transparency color appears pale or pale. The low chroma is due to the fact that the embossing lacquer on its surface has a strongly pronounced, depressions, elevations and / or edges containing relief, ie the light is diffracted in the course of transmission through the film structure diffused in all spatial directions or scattered. Corresponding to the refraction angle, the optical path through the semitransparent functional layer and thus the transmission spectrum is also different. Different color spectra result in a total gray tone. Furthermore, in the case of a rough substrate, the thickness of the semitransparent functional layer does not correspond to the desired thickness and is therefore optically less effective, ie deviations from the actual optical see-through effect result.

Suitable semitransparent, in review in another color as appearing in supervision and in review almost no color shift effect having functional layers are for example from WO2011 / 082761 A1 known. The WO2011 / 082761 A1 describes a semitransparent thin-film element exhibiting a golden color when viewed in reflected light and a blue color exhibiting almost no color-shift effect when viewed in transmitted light.

• - die beiden semitransparenten metallischen Schichten werden bevorzugt von Al oder Ag gewählt; die dielektrische Schicht ist insbesondere eine SiO₂-Schicht oder eine MgF₂-Schicht, bevorzugt eine SiO₂-Schicht;
• - im Falle, dass jede der beiden semitransparenten metallischen Schichten auf Al beruht, liegt die jeweilige bevorzugte Schichtdicke in einem Bereich von 5 nm bis 20 nm, insbesondere bevorzugt in einem Bereich von 10 nm bis 14 nm; die dielektrische SiO₂-Schicht hat vorzugsweise eine Schichtdicke in einem Bereich von 50 nm bis 450 nm, weiter bevorzugt in einem Bereich von 80 nm bis 260 nm und insbesondere bevorzugt in einem Bereich von 210 nm bis 260 nm, wobei die Bereiche von 80 nm bis 100 nm und von 210 nm bis 240 nm speziell für die Bereitstellung eines Gold/Blau-Farbwechsels besonders bevorzugt werden;
• - im Falle, dass jede der beiden semitransparenten metallischen Schichten auf Ag beruht, liegt die jeweilige bevorzugte Schichtdicke in einem Bereich von 15 nm bis 30 nm, insbesondere bevorzugt von 15 nm bis 25 nm; die dielektrische SiO₂-Schicht hat vorzugsweise eine Schichtdicke in einem Bereich von 50 nm bis 450 nm, weiter bevorzugt in einem Bereich von 80 nm bis 260 nm und insbesondere bevorzugt in einem Bereich von 210 nm bis 260 nm, wobei die Bereiche von 80 nm bis 100 nm und von 210 nm bis 240 nm speziell für die Bereitstellung eines Gold/Blau-Farbwechsels besonders bevorzugt werden.

A suitable semitransparent functional layer is based, for example, on a multilayer structure with two semitransparent metallic layers and a dielectric layer arranged between the two semitransparent metallic layers. Such a functional layer is obtainable, for example, by means of a vacuum vapor deposition method. Suitable multilayer structures having two semi-transparent metallic layers and a dielectric layer arranged between the two semitransparent metallic layers preferably have the following physical properties:

• the two semitransparent metallic layers are preferably selected from Al or Ag; the dielectric layer is in particular an SiO ₂ layer or an MgF ₂ layer, preferably an SiO ₂ layer;
• in the case where each of the two semitransparent metallic layers is based on Al, the respective preferred layer thickness is in a range of 5 nm to 20 nm, particularly preferably in a range of 10 nm to 14 nm; the SiO ₂ dielectric layer preferably has a layer thickness in a range of 50 nm to 450 nm, more preferably in a range of 80 nm to 260 nm, and particularly preferably in a range of 210 nm to 260 nm, wherein the ranges of 80 nm up to 100 nm and from 210 nm to 240 nm are especially preferred for providing a gold / blue color change;
• in the case where each of the two semitransparent metallic layers is based on Ag, the respective preferred layer thickness is in a range from 15 nm to 30 nm, particularly preferably from 15 nm to 25 nm; the SiO ₂ dielectric layer preferably has a layer thickness in a range of 50 nm to 450 nm, more preferably in a range of 80 nm to 260 nm, and particularly preferably in a range of 210 nm to 260 nm, wherein the ranges of 80 nm to 100 nm and from 210 nm to 240 nm are especially preferred for providing a gold / blue color change.

• - ein Silber/ Dielektrikum/ Aluminium-Schichtsystem, wobei die Schichtdicken der Silber-Schicht und der Aluminium-Schicht identisch oder verschieden sind;
• - ein Silber/Dielektrikum/Silber-Schichtsystem, wobei die Schichtdicken der beiden Silber-Schichten verschieden sind;
• - ein Aluminium/Dielektrikum/ Aluminium-Schichtsystem, wobei die Schichtdicken der beiden Aluminium-Schichten verschieden sind.

The above-mentioned multilayer structures having two semi-transparent metallic layers and a dielectric layer disposed between the two semitransparent metallic layers may have a symmetrical three-layer structure in which both the material and the layer thickness of the two semitransparent metallic layers are identical. Alternatively, however, there may also be an asymmetrical three-layer structure in which the material and / or the layer thickness of the two semitransparent metallic layers are different, eg

• a silver / dielectric / aluminum layer system, wherein the layer thicknesses of the silver layer and the aluminum layer are identical or different;
• - A silver / dielectric / silver layer system, wherein the layer thicknesses of the two silver layers are different;
• - An aluminum / dielectric / aluminum layer system, wherein the layer thicknesses of the two aluminum layers are different.

• - im Auflicht Magenta, im Durchlicht Blau-Grün;
• - im Auflicht Türkis, im Durchlicht Orange-Gelb;
• - im Auflicht Gold, im Durchlicht Blau-Violett;
• - im Auflicht Silber, im Durchlicht Violett.

The abovementioned multi-layered layer structures not only make it possible to produce a semitransparent functional layer that appears gold-colored when viewed in reflected light and shows a blue hue when viewed in transmitted light, but further color changes can be produced depending on the choice of the layer thickness, in particular of the dielectric layer, eg

• Magenta in transmitted light, blue-green in transmitted light;
• - in incident light turquoise, in transmitted light orange-yellow;
• - in reflected light gold, in transmitted light blue-violet;
• - in reflected light silver, in transmitted light violet.

The mosaic elements form a predetermined motif in that different groups of mosaic elements with different characteristic parameters reflect incident light into different spatial areas. In addition, the mosaic elements have a lateral dimension below the resolution limit of the eye.

The mosaic elements preferably have a lateral dimension of less than 100 μm, particularly preferably less than 30 μm. Such small mosaic elements can be produced on the one hand in established film technology due to the small profile associated with low profile depth, on the other hand creates the small element size a variety of possible arrangements for the Mosaic elements, as described in more detail below together with the associated advantages.

The mosaic elements advantageously have a lateral dimension of more than 3 μm, preferably more than 5 μm. These dimensions ensure that wavelength-dependent light diffraction effects are negligible and that the incident light is reflected achromatically by the mosaic elements without disturbing color effects.

The mosaic elements expediently have a square, rectangular, round, oval, honeycomb-shaped or polygonal-limited outline shape. Advantageously, the lateral dimensions of the mosaic elements in no direction are more than five times the dimension in one of the other directions.

In an advantageous variant of the invention, the mosaic elements have a simple relief shape with exactly one reflection surface inclined towards the surface of the security element. The angle of inclination of the reflection surface of the mosaic elements is expediently less than 90 °, preferably less than approximately 45 °. The reflection surface of the mosaic elements may be flat or concave or convex.

In other likewise advantageous variants of the invention, the mosaic elements have relief shapes with two or more reflection surfaces inclined in different directions against the surface of the security element. In particular, the mosaic elements may have a roof structure or a multi-sided pyramidal structure. Also in this variant, the angle of inclination of the reflecting surfaces of the mosaic elements is expediently less than 90 °, preferably less than about 45 °, and the reflecting surfaces of the mosaic elements can be both flat and concave or convex.

In a further advantageous variant of the invention, the mosaic elements in regions a simple relief shape with a central, against the surface of the security element inclined reflection surface (the so-called average orientation). The angles of inclination of the reflection surface of the mosaic elements have a substantially random variation by area-wise predetermined different average orientations. In this way, a glittering effect results which is practically the same as the appearance of magnetically oriented pigments of optically variable security inks. For this purpose, the mean orientation of the reflection surfaces (or facets) of different mosaic elements (or pixels) is selected analogously to the mean orientation of the pigments. The glittering effect of such colors is based on the fact that the individual pigments do not reflect exactly in a given direction, but that there is a certain random variation of the reflection directions. Optically variable security elements with such a microstructure are known from the WO 2011/066991 A2 known. The variation of the reflection directions predetermined by the variation of the orientations of the facets of different pixels is preferably at least about 1 °, preferably at least about 3 °, particularly preferably at least about 10 °.

According to a further advantageous variant of the invention, mosaic elements form retroreflectors, ie multi-reflective structures that reflect light incident from a certain angle range back into the direction of incidence. In particular, the mosaic elements in this case have a cube corner structure with a relief shape of three reflecting surfaces which are substantially perpendicular to one another and face each other. The three reflection surfaces define an optical axis, which is given for a cube corner structure by the spatial diagonal of the associated cube. The thus defined optical axis preferably points in a preselected direction for each mosaic element so that one or more image motifs can be displayed, as described in more detail below.

The mosaic itself preferably represents a raster image of a plurality of pixels, each pixel being formed by one or more achromatically reflective mosaic elements. The brightness of the pixels of the raster image can be determined by one or more of the parameters size, contour shape, relief shape, reflectivity and spatial orientation of the mosaic elements of the respective pixel, or by the number of mosaic elements with certain characteristic parameters in the respective pixel.

In a further development of the security element according to the invention, a further information is encoded in the arrangement of the mosaic elements within a pixel.

According to the invention, the mosaic of the security element can also reflect two or more different image motifs in different spatial areas, so that a tilt or movement image is created for the viewer with a corresponding movement of the security element. In another embodiment, the mosaic may also reflect an enlarging or reducing contour of an image motif in different spatial areas, so that a pump image is created for the viewer with a corresponding movement of the security element. If the mosaic reflects at least two views of an image motif in different spatial regions, a stereo image of the image motif is created for the viewer at a preselected viewing distance.

In all the embodiments described, the parameters size, outline shape, relief shape, reflectivity and spatial orientation of the mosaic elements may be selected such that one or all of the motif images are visible to the viewer when the security element is levelly aligned.

Alternatively or additionally, these parameters may also be selected such that one or all of the motif images appear to the viewer only when a preselected deformation of the security element occurs.

In addition to the embodiments in which the viewer views the security element itself, configurations in which the parameters size, outline shape, relief shape, reflectivity and spatial orientation of the mosaic elements are selected so that the security element of one or all of the motif images with preselected lighting on projected a collection area of preselected geometry.

The security elements according to the invention can be combined with other security features. For example, a security element may additionally include information in the form of patterns, characters, or encodings formed by nonreflective areas within the mosaic. The reflective microstructures can also be combined with holographic or hologram-like diffraction structures, or with incorporated magnetic materials, with incorporated phosphorescent, fluorescent or other luminescent substances, with specifically adjusted conductivity, in particular through a specifically set thickness of a metallic reflection layer, with color shift effects or colored embossing lacquer and the like be provided.

The invention also relates to a method for producing a security element of the type described, in which the surface profile of the optically variable surface pattern, in particular a microstructure, is embossed into a lacquer layer and the embossed lacquer layer is provided with a semitransparent functional layer, e.g. is coated by PVD. The surface profile is thereby preferably embossed in a UV-curable lacquer layer and the lacquer layer cured after embossing.

The surface profile of the optically variable surface pattern, in particular a microstructure, can in principle be incorporated into all known materials which are accessible to the embossing process. In addition to the already mentioned and preferred UV-curable coatings can therefore z. B. also be used thermoplastic embossing. As thermoplastic embossing z. As thermoplastic plastic materials into consideration, in which by means of a suitable embossing tool under the action of heat, the surface profile of the invention is impressed. Very common are z. B. thermoplastics, which are provided by means of a nickel die as embossing tool at a temperature of about 130 ° C with the microstructure according to the invention.

The optically variable see-through security element according to the invention can be present in particular as a patch or label, as a security thread or as a security strip.

The invention further comprises a data carrier, in particular a value document, such as a banknote, an identity card or the like, which is equipped with a security element of the type described.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

• 1 eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen optisch variablen Durchsichtsicherheitselement,
• 2 ein Sicherheitselement gemäß einem ersten Ausführungsbeispiel bei der Betrachtung in Aufsicht,
• 3 das Sicherheitselement gemäß dem ersten Ausführungsbeispiel bei der Betrachtung in Durchsicht,
• 4 schematisch den Aufbau des Sicherheitselements gemäß dem ersten Ausführungsbeispiel im Querschnitt,
• 5 die Reliefstruktur eines Sicherheitselement gemäß einem zweiten Ausführungsbeispiel im Querschnitt,
• 6 die Reliefstruktur eines Sicherheitselement gemäß einem dritten Ausführungsbeispiel im Querschnitt,
• 7 den Ausschnitt eines einzelnen Mikrospiegelbereichs innerhalb eines glatten Teilbereichs eines optisch variablen Flächenmusters, und
• 8 den Ausschnitt eines einzelnen Mikrospiegelbereichs innerhalb eines rauen Teilbereichs eines optisch variablen Flächenmusters.

Show it:

• 1 a schematic representation of a banknote with an optically variable transparent security element according to the invention,
• 2 a security element according to a first embodiment when viewed in supervision,
• 3 the security element according to the first embodiment when viewed in review,
• 4 FIG. 2 schematically the structure of the security element according to the first embodiment in cross-section; FIG.
• 5 the relief structure of a security element according to a second embodiment in cross-section,
• 6 the relief structure of a security element according to a third embodiment in cross-section,
• 7 the section of a single micromirror region within a smooth portion of an optically variable surface pattern, and
• 8th the section of a single micromirror region within a rough portion of an optically variable surface pattern.

The invention will now be explained using the example of security elements for banknotes. 1 shows a schematic representation of a banknote 1 with an optically variable see-through security element according to the invention 2 , this in Shape of a patch over a through opening of the banknote 1 is arranged. The security element 2 shows in supervision a different colored appearance as in review.

According to a first embodiment, the security element 2 when viewed in reflected light a golden color, where the subject 3 a domed cross three-dimensional in the foreground area in front of a nested, noisy background area 4 highlights (see 2 ).

When viewed in transmitted light shows the security element 2 a blue color, being the subject 3 in rich deep blue high contrast from the light blue to gray background area 4 takes off (see 3 ).

4 schematically the structure of the security element 2 according to the first embodiment in cross-section (along the dashed line in the 2 and 3 ).

The security element is based on a carrier foil 5 For example, a polyethylene terephthalate (PET) film coated with a transparent embossing lacquer 6 is provided. In the embossing lacquer 6 a relief structure is embossed, which is such that a planar, optically variable surface pattern with a plurality of essentially radiation-optical facets 7 is formed. The facets 7 are formed by flat patches and are each characterized by their shape, size and orientation. The orientation of a facet 7 is due to the inclination α to the plane 8th of the area specified.

The facets 7 have in the exemplary embodiment on a square outline with a dimension of 20 microns × 20 microns.

Like in the 4 shown have the facets 7 in the subareas 9 and 11 the same inclination angle α, for example, α = 30 °, on. In the subarea 10 lie the facets 7 at an angle of α = 0 °. The subareas 9 and 11 each form a so-called rough area, the subarea 10 forms a so-called smooth area.

The semitransparent functional layer 12 can be formed, for example, from a three-layer thin-film structure Al / SiO ₂ / Al or Ag / SiO ₂ / Ag produced by vapor deposition or PVD, which is gold-colored when viewed in reflected light and shows a blue color when viewed in transmitted light and in transmitted light has almost no color shift effect.

Above the semitransparent functional layer 12 is another layer of paint 13 applied, which has substantially the same refractive index as the lacquer layer 6 which ensures that incident light the layer sequence of the security element regardless of the local inclination angle α of the facets 7 traversed substantially without directional deflection, thus creating a uniform brightness distribution in the plane of the surface pattern.

The subarea 10 appears to the viewer when viewed in transmitted light in a rich deep blue, while the sections 9 and 11 each show a light blue to gray color, so that the colorful section 10 in the form of a foreground area rich in contrast from the diffuse, achromatic background areas 9 and 11 takes off.

In the in the 4 shown, the first embodiment are the facets 7 in the surface of the embossing lacquer 7 so formed that the smooth part area 10 is present in the form of facets with an inclination angle α = 0 °. However, it is also possible to form the smooth portion by facets with a small inclination angle. 5 shows a security element according to a second embodiment, wherein in the figure, for the sake of simplicity, only the relief structure of the embossing lacquer is shown. The facets in the subareas 15 and 17 have the same inclination angle a, for example, α = 30 ° on. In the subareas 14 and 16 the facets are each at an angle of α = 5 °. The subareas 15 and 17 each form a rough area, the subareas 14 and 16 each form a smooth area.

In the in the 6 shown, the first embodiment are the facets 18 in the surface of the embossing lacquer so oriented that for a viewer of the surface area is perceived as compared to its actual space form forward and / or recessed surface. Such relief structures are from the WO 2011/066990 A2 known.

Based on 7 and 8th the transmission of a light beam is clarified by the layer structure according to the invention.

The 7 shows the section of a smooth portion of the optically variable surface pattern. The layer structure contains the carrier film 19 , the embossing lacquer 20 and the semitransparent functional layer consisting of Al layers 21 . 23 and an SiO ₂ layer 22 interposed therebetween. The light beam 24 is not broken or scattered in its transmission through the layer structure and meets straight into the eye of the beholder.

8th shows the detail of a single micromirror region within a rough portion of the optically variable area pattern. At the interface between the semitransparent Functional layer and the embossing lacquer, the light beam is scattered or broken, resulting in a gray tone.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2016/096094 A1 [0003, 0028]
• EP 1966769 B1 [0008]
• WO 2011/082761 A1 [0030]
• WO 2011/066991 A2 [0040]
• WO 2011/066990 A2 [0066]

Claims (17)

Optically variable see-through security element for securing valuables, with a flat, optically variable surface pattern, which shows a different color as seen in plan view and has almost no color shift effect in the clear, characterized in that - the optically variable surface pattern a plurality of substantially radiation-optically effective Facets whose orientation is characterized in each case by an inclination angle α against the plane of the surface pattern lying in a range of 0 ° to 30 °, - the facets with a semitransparent, appearing in a different color as in supervision and in The optically variable surface pattern contains at least two partial areas, each with a multiplicity of similarly oriented facets, the facets of one partial area having a small angle of inclination α and the facets of the partial area have a high inclination angle α such that the optically variable surface pattern in the partial region in which the facets have a small inclination angle α appears in a high chroma and in the subregion in which the facets have a high inclination angle α, appears in a low chroma or chroma. See-through security element after Claim 1 , characterized in that the area occupied by each sub-area on the optically variable area pattern is at least 50 times, preferably at least 100 times, more preferably at least 1000 times larger than the area occupied by a single facet of that area area on average. See-through security element after Claim 1 or 2 , characterized in that the facets of the at least two partial regions in the angle of inclination to the plane differ by 5 ° or more, preferably by 10 ° or more. See-through security element according to one of Claims 1 to 3 , characterized in that the facets of the one subregion which have a low inclination angle α have an inclination angle α in a range from 0 ° to 15 °, preferably in a range from 0 ° to 10 °, and the facets having a high inclination angle α Partial region an inclination angle α in a range of 15 ° to 30 °, preferably in a range of 20 ° to 30 °. See-through security element according to one of Claims 1 to 4 , characterized in that the facets are each provided with a semi-transparent, appearing in review in another color as in top view functional layer whose layer thickness varies with the inclination angle α of the facets, preferably decreases with increasing inclination angle α. See-through security element according to one of Claims 1 to 5 , characterized in that the at least two subregions are arranged in the form of a motif and the motif appears in review with two or more different chroma values visually distinguishable with the naked eye. See-through security element according to one of Claims 1 to 6 , characterized in that the optically variable surface pattern in the subregions additionally has a black mask, which has been adapted to the inclined facets and which serves to adjust the translucent brightness of the facets in the respective subregions. See-through security element according to one of Claims 1 to 7 , characterized in that the facets are embossed into an embossing lacquer layer having a first refractive index and a lacquer layer having a second refractive index, which differs from the first refractive index by less than 0.3, in particular by less than 0.1, is applied over the semitransparent functional layer , See-through security element according to at least one of Claims 1 to 8th , characterized in that the semitransparent functional layer has a multilayer structure with two semitransparent metallic layers and a dielectric layer arranged between the two semitransparent metallic layers. See-through security element after Claim 9 characterized in that the two semitransparent metallic layers are independently formed of a metal and the metal is selected from the group consisting of Al, Ag, Ni, Cr, Cu, Au and an alloy of one or more of the aforementioned elements, and the dielectric layer is an SiO ₂ layer, a ZnO layer, an Al ₂ O ₃ layer, a TiO ₂ layer, a layer of a nitride or oxynitride of one of the elements Si, Zn, Al or Ti or an MgF ₂ - Layer or a, for example, technically available, nitrocellulose layer. See-through security element after Claim 9 , characterized in that the two semitransparent metallic layers are selected independently of each other of Al or Ag and the dielectric layer is a SiO ₂ layer. See-through security element according to one of Claims 1 to 11 , characterized in that the optically variable area pattern when viewed in a transparent shows a blue color and when viewed in supervision shows a golden color. See-through security element according to at least one of Claims 1 to 12 , characterized in that the facets are formed substantially as planar surface elements. See-through security element according to at least one of Claims 1 to 13 , characterized in that the facets are arranged in a periodic grid and in particular form a sawtooth grid, or that the facets are arranged aperiodically. See-through security element according to at least one of Claims 1 to 14 , characterized in that the facets have a smallest dimension (or lateral dimension 1) of more than 2 μm, preferably of more than 5 μm, in particular of more than 10 μm, and / or that the facets have a height of less than 100 μm , preferably below 50 microns, in particular less than 10 microns. Data carrier with a see-through security element according to at least one of Claims 1 to 15 wherein the see-through security element is preferably arranged in or above a window area or a through opening of the data carrier. Disk after Claim 16 , wherein the data carrier is a value document, in particular a banknote.

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