EP3820715B1 - Optically variable security element with reflective area - Google Patents

Description

The invention relates to an optically variable security element with a reflective surface area. The invention also relates to a method for producing such a security element and to a data carrier equipped with such a security element.

Data carriers, such as value or ID documents, but also 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 at the same time serve as protection against unauthorized reproduction. The security elements can be designed, for example, in the form of a security thread embedded in a banknote, a cover film for a banknote with a hole, an applied security strip, a self-supporting transfer element or also in the form of a feature area printed directly onto a document of value.

Security elements with a viewing angle-dependent or three-dimensional appearance play a special role in authenticity protection, as these cannot be reproduced even with the most modern copiers. For this purpose, 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. The prior art describes, for example, movement effects, pump effects, depth effects or flip effects as optically variable effects, which are realized with the aid of holograms, microlenses or micromirrors.

DE 102007034716 A1 relates to a multi-layer security element with translucent and opaque sections. WO 97/19820 A1 shows an optical information carrier with two optically active structures which are arranged in different planes and which together produce a characteristic optical effect. DE 102007061827 A1 relates to a security element according to the preamble of claim 1 for protecting valuables with only one relief structure, over which a thin-layer element with a color-shift effect is arranged, the thin-layer element containing an absorber layer with gaps in the area of which no color-shift effect is recognizable, and with a semi-transparent color layer , which are in the area of the recesses of the absorber layer is arranged over the thin-film element and the relief structure, wherein the color impression of the thin-film element is adapted to the color impression of at least a partial area of the semi-transparent color layer when viewed under predetermined viewing conditions.

Proceeding from this, the object of the invention is to further increase the security against forgery and the visual attractiveness of generic optically variable security elements and in particular to provide optically variable security elements with two or more different appearances or effects in different colors with good recognizability.

This object is solved by the features of the independent claims. Developments of the invention are the subject matter of the dependent claims.

The present optically variable security element has a multicolored reflective surface area whose surface extent defines a z-direction perpendicular thereto. The multicolored reflective surface area contains an upper and a lower relief structure, which are arranged at different height levels in the z-direction. The upper and lower relief structure are provided with a respective upper and different lower color coating. The two relief structures overlap in an overlapping area.

• in z-Richtung unter der oberen Farbbeschichtung ein verdeckter Abschnitt der unteren Farbbeschichtung und
• in z-Richtung unter der Aussparung ein offenliegender Abschnitt der unteren Farbbeschichtung angeordnet ist.

The upper color coating has a recess in the overlapping area, so that

• in the z-direction under the top paint coat, an obscured portion of the bottom paint coat, and
• an exposed section of the lower color coating is arranged in the z-direction below the recess.

The embossed structures are micromirror arrays that include a plurality of directional micromirrors. The respective color coating only appears as a reflective color depending on the viewing angle.

In one viewing angle, the lower color coating appears with parts of the covered section and the exposed section in its color impression.

Since hidden parts of the color coating also become optically effective, a better visual effect is created. The colored reflecting effective area is enlarged in the present case.

Advantageously, the portion of the covered portion that appears is more than 2.5%, preferably more than 5%, of the surface that appears.

The relief structures are preferably embossed structures. In particular, embossing in a hardenable layer, such as UV lacquers, for example, is further preferred. Alternative production methods, such as subtractive lasering or additive construction, for example using 3D printing, are conceivable but less cost-effective.

The first or second relief structure of the multicolored reflective surface area, together with its color coating, preferably forms a first or second monochromatic reflective relief structure. The color coatings appear colored and reflective depending on the viewing angle. At the viewing angle, the light is reflected from the relief structure to the viewer and thus appears in the present sense. The color coating determines the color impression. Since the incoming light also has a preferred direction--in particular essentially perpendicular--a clearly perceptible colored light reflex is produced for the viewer, as is known. The relief structure determines the optically variable effect.

The upper color coating preferably has a plurality of recesses.

In a first variant, the dimensions of the recess in the overlapping area are more than 140 μm, in particular more than 250 μm or even more than 500 μm. The appearing portion of the hidden portion may constitute between 2.5% and 12%, preferably between 4% and 10% of the appearing area.

In a second variant, the upper color coating is designed as a regular or irregular grid with grid elements and grid spaces as the recesses, the dimensions of the grid elements and/or the grid spaces being less than 140 μm in at least one direction. The apparent proportion of the hidden portion is between 10% and 90%, preferably between 15% and 40% (or between 60% and 85%) of the apparent area.

Other color coatings, in particular with a third and/or a fourth color impression, can be used in other parts of the overlapping area of the relief structures or outside of the overlapping area. Different two-color features, in particular with a third (together with the first or second) color impression or with a third and fourth color impression, can thus be present in further gaps. Likewise, one of the (first, second, third or fourth) color coatings outside of the present feature or outside of the overlapping area can have a different hue.

The micro-mirror array(s) is (are) achromatic micro-mirror array(s) which is (are) non-diffractive in particular.

The directed mirrors of the micromirror arrangement are distinguished by a preferred direction of reflection, which can be set, for example, by means of an angle of inclination and/or an azimuth angle. Arrangements of small, ray-optically acting reflective facets, which direct incident light like small mirrors into a reflection direction given by the condition "angle of incidence equals angle of emergence", are referred to as micromirror arrangements. Depending on their orientation for the viewing angle, the individual directional micromirrors of the micromirror array either reflect the light towards the viewer or not (bright or dark). It is only through the color coating that the micromirror then appears as a reflective color or not (light or dark color). Since the micromirror arrangements represent embossed structures, they are sometimes also referred to as micromirror embossings in this description. Plane micromirrors are particularly suitable as directed micromirrors. Alternatively, directed concave mirrors and/or directed Fresnel-like (ie multi-part) mirrors can be used.

In the case of micromirror arrangements, the micromirrors are advantageously formed with an edge length of between 4 μm and 100 μm, preferably between 5 μm and 30 μm. The micromirrors preferably have a (maximum) pitch of less than 20 μm, in particular less than 10 μm, more preferably less than 5 μm. The micromirrors are preferably arranged in one or both of the micromirror arrangements in a periodic grid with a period length of between 4 μm and 100 μm, preferably between 5 μm and 30 μm.

Surfaces aligned only parallel or perpendicular to the multicolored reflective surface area are not directed micromirrors or micromirror arrays in the present sense. The directional micromirrors can be formed regularly or irregularly (eg the same shape or varying shape) and/or arranged (eg in a pattern or distributed quasi-randomly).

It is conceivable that the multicolored reflective surface area - in particular at least one of the two relief structures, the difference in height levels and/or at least one of the color coatings - is adjusted in order to increase the proportion of the covered section of the lower color coating that is visible to the viewer in the viewing angle. For two given relief structures, the height difference at which they are placed can be chosen to optimize the effective fraction of hidden portions. The color coatings can also be chosen so that they are matched to one another, ie, for example, the upper color coating has increased transmission for the color/the color range of the lower color coating.

In a regular structure of relief elements, in particular of micromirrors, at least one relief element is shifted in the relief plane, shifted in the z-direction, adjusted in terms of its size or adapted in terms of its shape. In particular, if both relief structures are generated simultaneously and in register, it makes sense to adjust the position of individual relief elements in the upper or lower relief structure in favor of the reflected intensity. The extent of the adjustments is primarily limited only by the given optical effect of the relief structure (movement, three-dimensionality,...).

In developments, the multicolored reflective surface area - in particular a reflectivity of the upper relief structure or at least one of Color Coatings - Adjusted to provide more reflective light for the covered section.

In at least part of the feature area, depending on the viewing angle, either the color coating of the upper relief structure or the color coating of the lower relief structure appears to the observer.

In an advantageous variant of the invention, the reflective surface area contains exactly two relief structures, each of which is arranged at a specific height level.

The two relief structures of the reflective surface area are each advantageously characterized by a maximum pitch, the distance between adjacent height steps in the z-direction being greater than the maximum pitch of the embossed structure region lying deeper in each case. Preferably, the distance is greater than 150%, more preferably 200%, of the maximum pitch. More preferably, the distance between adjacent height steps in the z-direction is between 150% and 750%, particularly preferably between 200% and 500%, more preferably between 200% and 400% of the maximum pitch of the lower-lying embossed structure area.

gegeben, wobei die einzelnen Mikrospiegel je nach Neigungswinkel eine Ganghöhe zwischen 0 und G_max haben können. Der Abstand der Mikrospiegelanordnung zur darüber liegenden Mikrospiegelanordnung ist dann vorteilhaft größer als 5,8 µm und liegt insbesondere zwischen 8,7 µm (150% von G_max) und 23,2 µm (400% von G_max). In der Regel weisen die Mikrospiegel eine einheitliche Größe, insbesondere Kantenlänge, auf. In anderen bevorzugten Ausgestaltungen weisen die Mikrospiegel der Mikrospiegelanordnung eine maximale Ganghöhe jedoch unterschiedliche Kantenlängen auf. Wenn für Mikrospiegel mit höherem Winkel eine kleinere Kantenlänge gewählt wird, kann eine kleinere maximale Ganghöhe eingehalten werden. Vorzugsweise sind Mikrospiegel mit einem Neigungswinkel unter einem Grenzwinkel mit einer einheitlichen Größe (bzw. Kantenlänge) und Mikrospiegel mit einem Neigungswinkel über dem Grenzwinkel mit verringerter Größe (bzw. Kantenlänge) vorgesehen. Im oben berechneten Beispiel mit G_max= 5,8 µm in einer Mikrospiegelanordnung können auf diesem Weg Mikrospiegel bis zu einer maximalen Neigung von etwa 49 Grad vorliegen, wenn deren Kantenlänge nur 5µm statt 10 µm beträgt.The pitch of the micromirrors depends on their lateral dimensions and their tilt angles. Even with the same lateral dimensions, the angles of inclination of the micromirrors are typically different, so that the micromirrors have different pitches. However, the maximum pitch of its micromirrors is characteristic of the micromirror arrangement. The above maximum aisles ("Pitch less than") are preferred. If the micromirrors have, for example, an edge length of 10 μm and a maximum angle of inclination of 30°, then the maximum pitch of the micromirror arrangement is through $${\mathrm{G}}_{\mathrm{Max}}=10\mathrm{\mu }\mathrm{m*tan}\left(30°\right)=5.8\mathrm{\mu m}\mathrm{.}$$

given, whereby the individual micromirrors can have a pitch between 0 and G _max depending on the angle of inclination. The distance between the micromirror arrangement and the micromirror arrangement above it is then advantageously greater than 5.8 μm and is in particular between 8.7 μm (150% of G _max ) and 23.2 μm (400% of G _max ). As a rule, the micromirrors have a uniform size, in particular edge length. In other preferred configurations, the micromirrors of the micromirror arrangement have a maximum pitch but different edge lengths. If a smaller edge length is chosen for higher angle micromirrors, a smaller maximum pitch can be maintained. Preferably, micromirrors with a tilt angle below a critical angle are provided with a uniform size (or edge length) and micromirrors with a tilt angle above the critical angle are provided with a reduced size (or edge length). In the example calculated above with G _max = 5.8 μm in a micro-mirror arrangement, micro-mirrors with a maximum inclination of about 49 degrees can be present in this way if their edge length is only 5 μm instead of 10 μm.

In advantageous configurations, the color coatings of the relief structures are formed by translucent colors. Also metallizations, for example Aluminum, silver or an alloy such as copper and aluminum are suitable, as are thin-film structures, in particular color-shifting thin-film structures, color-stable, color-filtering thin-film structures (different colors in reflectance and transmission) or silicon-aluminum thin-films. The color coatings can also be formed by translucent colors with a metallic mirror coating underneath, for example made of aluminum. The color coatings can represent a translucent image made up of several translucent colors, which is backed by a mirror coating, for example made of aluminum. Luminescent colors, in particular fluorescent colors with a metallic mirror coating, can also be used as color coatings. The color coatings can also be formed by structural colors. Finally, nanoparticle colors can also be considered as color coatings, such as gold-blue particles, various effect pigments, color-shifting pigments or super silver.

A color coating preferably follows the relief course of a relief structure. One surface (or both surfaces) of the color coating follows the relief structure. The second surface of the color coating(s) preferably also follows the relief structure. Alternatively, the second surface can be flat. In a further alternative—which is more difficult to produce—the second surface of the color coating comprises a color-imparting colored structure, such as a sub-wavelength, nano or binary structure. The color coatings are preferably applied directly to the relief structures, in particular the micromirror arrays. Different color coatings can also be present next to each other or on top of each other in certain areas. With multi-layer trained color coatings, such as a translucent color with background metallization, however, it is also possible that only part of the several layers, for example the background metallization, is applied directly to the relief structures. The remaining part of the layers, for example the glazing paint, can then be arranged above the relief structures, for example between the coated relief structure and the adjacent, higher-lying relief structure. The second surface of a reflective partial layer of the color coating(s) preferably also follows the relief structure. The second surface of a translucent partial color layer of the color coating(s) can also follow the relief structure, be flat or follow the other relief structure. The remaining part of the layers can also be combined with further layers. For example, the embossing varnish for the adjacent, higher-lying relief structure area can be colored and thus represent a continuous colored partial coating for the lower-lying relief structure area. Preferably, the lower surface of the (first) colored embossing varnish follows the lower relief structure and the upper surface of the colored embossing varnish forms the upper (first) relief structure.

The color impressions of the first and second color coatings are different, they differ in their shade. Both color coatings preferably produce a chromatic shade. Alternatively, one of the two color coatings can produce an achromatic hue, preferably silver, for the viewer, and the other a chromatic hue.

In addition to the color coating of the higher-lying relief structure, the color coating of the lower-lying relief structure can only be present in certain areas. Color coatings that are present in certain areas can either be applied in certain areas and/or selectively removed again after application over the entire surface. A number of advantageous methods are described below, with which the above-mentioned color coatings can only be applied in certain areas can be provided. The person skilled in the art is aware that not every method is suitable for all types of color coatings. In particular, if several different color coatings are used in a security element, several different methods can also be used in the structuring.

Structured color coatings with metallic colors, thin-layer colors, structural colors or nanoparticles can be created, for example, by using a wash color. For this purpose, wash ink is printed in insetter printing for the respective embossing structure, then the entire surface is metallized and then washed. To avoid any tolerance that may exist when printing the wash color, the relief structure can be further adjusted. In some areas, the relief structure can comprise an adhesion-reducing (and/or an adhesion-increasing) fine structure, which in particular has a hydrophobic (or hydrophilic) effect. The adhesion-reducing fine structure in one area thus in particular prevents the wash color from adhering to the area. A first area with an adhesion-reducing fine structure can optionally adjoin a second area with an adhesion-increasing fine structure. The use of an optionally colored etching resist is particularly advantageous in combination with translucent colors. For this purpose, the embossing structure can first be completely coated, then the etch resist is printed, with the desired areas remaining unprinted, and finally the coating is etched. Laser treatment can be used to remove metallic paints, metallic coatings, and laser-sensitive, translucent paints with high resolution. A light-absorbing fine structure, such as for example moth-eye structures or quasi-random structures, can be provided in regions in the relief structure. The absorption of light is thereby increased, so that no more lasers must be used. Normal light sources such as UV lamps or LEDs can also be used for removal. Metallic flakes, nanoparticle ink or super silver (usually nanoscale aluminum particles) can be printed directly in register. Instead of the etching resist mentioned above, an optionally colored photoresist can first be applied over the entire surface and then exposed in certain areas. Depending on the resist used, the exposed or unexposed areas then dissolve in the etching bath, so that the underlying metal dissolves, while the metallic areas covered by the photoresist remain protected from the etch.

Color coatings can also be created by a metal transfer process. Areas that are to be demetallized are embossed using an embossing tool. The foil that has been pretreated in this way is then completely metalized and the metal on the embossed areas is selectively removed with another foil so that only metal remains in the depressions. A color transfer can also be generated in a similar way. Areas that are later to appear in color are embossed compared to the remaining areas. A colorant, such as flakes, nanoparticle color, super silver or a translucent color is applied to a roller and selectively transferred to the embossed areas of the film. Conversely, in a color filling process, a desired color coating is created by embossing areas that are later to appear colored relative to the remaining areas. A colorant, for example flakes, nanoparticle color, super silver or a translucent color is printed over the entire surface and then removed with a hard chambered squeegee or wiped off with a cloth so that the color only remains in the depressions.

The security element described can also be equipped with colorless or colored negative markings. For this purpose it can be provided in particular that the overlapping area additionally contains partial areas with a negative marking, in which the color coating of the higher embossed structure area and at least partially also the color coating of the lower embossed structure area is omitted.

The color coating of the lower-lying relief structure can be left out completely in the partial areas of the negative marking, so that the negative marking does not produce any of the color impressions of the two color coatings. In particular, the negative mark appears colorless and is particularly easy to recognize in transmitted light.

In another embodiment, the color coating of the lower-lying relief structure is multi-layered, with at least one of the multiple layers being omitted in the partial areas of the negative marking, so that a colored negative marking is produced. Advantageously, the color coating of the lower-lying relief structure contains an opaque partial layer, in particular a metallization, and a translucent color layer, with the opaque partial layer being left out in the negative identification partial areas, but not the translucent color layer, so that a negative identification with the color effect of the translucent color layer is left out arises.

The line widths of the overlapping gaps in a negative identifier are advantageously above 100 μm, preferably above 150 μm, particularly preferably above 300 μm, in order to ensure that the negative identifier can be easily recognized.

In the case of a negative mark, the gaps in the color coating of the lower-lying relief structure are advantageously formed with a slightly larger area than the gaps in the color coating of the higher-lying relief structure in order to compensate for register fluctuations between the two relief structures.

In an advantageous embodiment, the relief structures are arranged on opposite sides of a transparent carrier film. Alternatively, relief structures are arranged one above the other on the same side of a carrier film. The relief structures can be arranged directly one above the other or be separated from one another by an adhesive layer, for example a laminating adhesive layer or a laminating film. The laminating film can also form the flat carrier of the security element. After the security element has been applied to a target data carrier, the carrier of the target data carrier can also represent the flat carrier of the security element.

The invention also includes a data carrier with a security element of the type described. The data carrier can in particular be a document of value, such as a banknote, in particular a paper banknote, a polymer banknote or a foil composite banknote, a share, a bond, a certificate, a voucher , a check, a premium ticket, but also an identification card, such as a credit card, a bank card, a cash card, an authorization card, an ID card or a passport personalization page.

• ein Träger bereitgestellt wird, dessen Flächenausdehnung eine x-y-Ebene und eine darauf senkrecht stehende z-Achse definiert,
• der Träger mit einem mehrfarbigen reflektiven Flächenbereich versehen wird, der mit zumindest zwei Reliefstrukturen ausgebildet wird, die in z-Richtung in unterschiedlichen Höhenstufen bezogen auf den flächigen Träger angeordnet werden,
• die Reliefstrukturen jeweils mit einer Farbbeschichtung versehen werden, die einen unterschiedlichen Farbeindruck erzeugen,
• die beiden Reliefstrukturen überlappend ausgebildet werden,
• wobei die obere Farbbeschichtung im Überlappungsbereich eine Aussparung aufweist, so dass
  • in z-Richtung unter der oberen Farbbeschichtung ein verdeckter Abschnitt der unteren Farbbeschichtung und
  • in z-Richtung unter der Aussparung ein offenliegender Abschnitt der unteren Farbbeschichtung angeordnet ist, und

• die Prägestrukturen Mikrospiegelanordnungen sind, die eine Vielzahl gerichteter Mikrospiegel umfassen, wobei die jeweilige Farbbeschichtung erst betrachtungswinkelabhängig farbig reflektierend in Erscheinung tritt, und
• in einem Betrachtungswinkel die untere Farbbeschichtung mit Anteilen des verdeckten Abschnittes und des offenliegenden Abschnittes in seinem Farbeindruck in Erscheinung tritt.

Finally, the invention also includes a method for producing a security element of the type described above, in which

• a carrier is provided, the surface area of which defines an xy plane and a z-axis perpendicular thereto,
• the carrier is provided with a multicolored reflective surface area which is formed with at least two relief structures which are arranged in the z-direction at different height levels in relation to the planar carrier,
• the relief structures are each provided with a color coating that creates a different color impression,
• the two relief structures are designed to overlap,
• where the upper color coating has a recess in the overlapping area, so that
  • in the z-direction under the top paint coat, an obscured portion of the bottom paint coat, and
  • an exposed portion of the lower color coating is arranged in the z-direction under the recess, and

• the embossed structures are micromirror arrangements which comprise a multiplicity of directed micromirrors, the respective color coating only appearing as a reflective color depending on the viewing angle, and
• in one viewing angle the lower color coating with parts of the covered section and the exposed section appears in its color impression.

For the sake of completeness, it should be noted that the resulting color impression is determined by the color coating, so that the present relief structures could also be referred to as achromatic relief structures. Colored structures, such as diffraction gratings, sub-wavelength gratings or blazed gratings, which filter, diffract and/or reflect white light wavelength-selectively and produce their own color impression, are not relief structures in the present sense. In configurations, the carrier can be a part of the security element. In other configurations, the security element is removed from the carrier, for example when the security element is transferred from the carrier to a target substrate.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, which are not shown to scale and proportions in order to improve clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Sicherheitselement,

Fig. 2

schematisch einen Ausschnitt des Sicherheitselements der Fig. 1 im Querschnitt,

Fig. 3

eine Aufsicht auf einen Ausschnitt des Sicherheitselements der Fig. 1,

Fig. 4

eine Abwandlung der Ausgestaltung der Figuren 2 und 3, bei der die Farbbeschichtung der höher liegenden Mikrospiegelanordnung alternierend streifenförmige Aussparungen und gleich große, streifenförmige stehengelassene Bereiche aufweist,

Fig. 5

in (a) bis (d) einige vorteilhafte Folienaufbauten erfindungsgemäßer Sicherheitselemente,

Fig. 6

ein erfindungsgemäßes Sicherheitselement mit einem zusätzlich Bereich mit einer farblosen Negativkennzeichnung, und

Fig. 7

ein erfindungsgemäßes Sicherheitselement mit einem zusätzlich Bereich mit einer farbigen Negativkennzeichnung.

Show it:

1

a schematic representation of a bank note with a security element according to the invention,

2

schematically shows a section of the security element 1 in cross section,

3

a top view of a section of the security element 1 ,

4

a modification of the design of the Figures 2 and 3 , in which the color coating of the higher-lying micromirror arrangement has alternating stripe-shaped recesses and stripe-shaped left areas of the same size,

figure 5

in (a) to (d) some advantageous film structures of security elements according to the invention,

6

a security element according to the invention with an additional area with a colorless negative marking, and

7

a security element according to the invention with an additional area with a colored negative marking.

The invention will now be explained using the example of security elements for banknotes. figure 1 shows a schematic representation of a banknote 10 with an optically variable security element 12 according to the invention in the form of an adhesively bonded transfer element. It goes without saying, however, that the invention is not limited to transfer elements and banknotes, but can be used with all types of security elements, for example labels on goods and packaging or to protect documents, ID cards, passports, credit cards, health cards and the like. In the case of banknotes and similar documents, in addition to transfer elements (such as patches with or without their own backing layer), security threads or security strips, for example, can also be considered.

This in 1 The security element 12 shown is itself very flat, but nevertheless gives the viewer the three-dimensional impression of a motif 14 apparently arching out of the plane of the bank note 10 and appearing in a first color, for example blue. The motif 14 can, for example, represent a denomination, a portrait or another graphic motif. Within the blue motif 14, a movement effect in a second color is visible in a sub-area 16, for example a red sub-area 16 in which a light bar appears to move up and down along the sub-area when banknote 10 is tilted, and a so-called rolling bar -Effect created. As an essential feature the areas of different colors (red or blue) and different effects (three-dimensional motif or running bar) are precisely matched to each other. This registration is therefore also referred to below as color-to-effect registration.

The special structure of optically variable security elements according to the invention will now be described with reference to FIG Figures 2 and 3 explained in more detail, where 2 a section of the security element 12 schematically in cross section and 3 shows a top view of a section of the security element 12 to illustrate the visual appearance.

Referring first to the cross section of the 2 the security element 12 contains a flat carrier 18 whose surface extent defines an xy plane and a z-axis perpendicular thereto.

A multicolored reflective surface area 20 is arranged on the carrier 18, which contains two embossed structure areas 24, 34, which are arranged in the z-direction at two specific, different height levels in relation to the planar carrier 20. In the exemplary embodiment, the embossed structure areas each represent micromirror embossings or micromirror arrangements 24, 34, which are each formed from a multiplicity of micromirrors inclined with respect to the xy plane. The local angles of inclination of the micromirrors are selected in such a way that the relief structure of the micromirror arrangements 24, 34 produce a desired optical appearance after the color coating, for example the arched three-dimensional impression of the motif 14 or the rolling bar effect of the subarea 16. The different height levels are given by the different heights H ₁ , H ₂ of the base areas of the micromirror arrays 24 , 34 above the carrier 18 .

To produce a visual contrast of the desired color effect, the micromirror arrangements 24, 34 are each provided with a color coating 26, 36, which produce the different color impression of the micromirror arrangements for the viewer 40 when viewed from above. In the exemplary embodiment, the micromirror arrangement 24 is coated with a red, glazing paint 26 , while the micromirror arrangement 34 is coated with a blue, glazing paint 36 . Sections 26o of the color coating 26 are therefore open in the z-direction under the recess 42 . A covered section 26v of the lower color coating 26 lies in the z-direction below the upper color coating 36. For the observer 40, the lower color coating 26 with portions of the covered section 26v and the exposed section 26o appear in their color impression at one viewing angle. The effective area can thus be increased. The smaller the recess 42 (or more such recesses are), the larger the percentage increase. In particular, the alignment of the micromirrors belonging to the portions of the open and covered portions 26o and 26v should be matched to one another. In the example shown, the orientation is identical, for example.

The micromirror arrangements 24, 34 are each embossed in a transparent embossed lacquer layer 22, 32 and, after the application and, if necessary, structuring of the respective color coating 26, 36, are leveled with a transparent top lacquer layer 28 or 38, respectively. The top coat layers have essentially the same refractive index as the embossing coat layers 22, 32, so that the micromirrors do not appear visually in areas without a color coating due to the lack of a refractive index difference between the embossing coat layer and the top coat layer.

The security element 12 is designed for viewing from above--in particular from a viewing direction different from the z-direction--so that the micromirror arrangement 24 that is further away from the viewer 40 than the lower-lying micromirror arrangement and the micromirror arrangement 34 that is closer to the viewer 40 than the higher lying micromirror array is referred to.

In the exemplary embodiment, the two micromirror arrangements 24, 34 are arranged one above the other in the entire surface area 20 of the security element 12. In partial area 16, the color coating 36 of the higher-lying micromirror arrangement 34 has a large-area recess 42, for example in the form of a 5 mm wide and 2 cm long curved strip. In the area of the cutout 42, the micromirrors of the micromirror arrangement 34 do not develop any optical effect due to the lack of a difference in refractive index between the lacquer layers 32, 38, so that the viewer 40 looks through these lacquer layers to the micromirror arrangement 24 with its red color coating 26 that lies deeper. On the other hand, outside of the recess 42 the visual impression of the surface area 20 is determined by the higher-lying micromirror arrangement 34 with its blue color coating 36 .

As in 3 illustrated, the observer therefore perceives the blue motif 14 generated by the micromirror arrangement 34 outside the recess 42, while the red rolling bar effect appears within the recess 42, in the partial area 16, in which when the banknote 10 a bright bar 16-A seems to run back and forth in the direction of arrow 16-B. The difference in height between the two micromirror arrangements 24, 34 is in the range of a few micrometers or a few tens of micrometers and is therefore imperceptible to the viewer 40. The two different colors Motifs and the different effects 14,16 therefore appear to the viewer 40 to be arranged side by side in exact register.

figure 4 shows a modification of the design of Figures 2 and 3 , in which the color coating 36 of the higher-lying micromirror arrangement 34 alternately has strip-shaped recesses 42 and strip-shaped left-over areas of the same size. In the embodiment of 4 the local angles of inclination of the micromirrors of the micromirror arrangements 24, 34 are selected in such a way that the micromirror arrangements each produce a rolling bar effect running in opposite directions to one another. When the security element is tilted, the observer sees a blue rolling bar effect in the partial areas 14 in which the blue color coating 36 was left and in exact register thereto a red rolling bar effect in the gaps in the partial areas 16 . The blue bars 14-A and the red bars 16-A each move in the opposite direction for the viewer, as in FIG 4 illustrated.

Some advantageous film structures of security elements according to the invention are in figure 5 shown. In the security element 50 of Fig.5(a) a transparent embossing lacquer layer 22, 32 with the desired micromirror embossing 24, 34, the color coating 26, 36 and the transparent top lacquer layer 28, 38 is arranged on the two opposite sides of a transparent PET carrier film 18. The security element 50 is designed for viewing from the side of the color coating 36, so that the color coating 36 of the higher-lying micro-mirror arrangement 34 is provided with large-area recesses 42 in which the viewer looks at the lower-lying micro-mirror arrangement 24 with the colored coating 26.

The security element 52 of Fig.5(b) already indicates it 2 described layer structure. Both micromirror embossings 24, 34 are arranged on the same side of the carrier film 18, which does not have to be transparent in this configuration. The first embossing lacquer layer 22 with the first, deep micromirror embossing 24, the first color coating 26, the first transparent cover layer 28, the second, transparent embossing lacquer layer 32 with the second, higher micromirror embossing 34, the second color coating 36 and the second transparent cover layer 38 is arranged. The security element 52 is designed for viewing from the side of the color coating 36, so that the color coating 36 of the higher-lying micro-mirror arrangement 34 is provided with large-area recesses 42 in which the viewer looks at the lower-lying micro-mirror arrangement 24 with the colored coating 26.

Other variants of are not shown separately in the figures Figure 5b . A transparent film can also be arranged above the further layers 22, 26, 28 and 32, 36, 38. The transparent film can be the carrier film 18 of the security element, be another carrier film or serve as a protective film. The order of the further layers 22, 26, 28 and 32, 36, 38 can be unchanged. Alternatively, the first embossing lacquer layer 22 can lie above the first top layer 28 and/or the second embossing lacquer layer 32 can lie above the second top layer 38 . Below the transparent film 18 arranged at the top, for example, the further layers follow in the order 32, 36, 38, 22, 26, 28.

Regardless of the position of the carrier film 18 are starting from Figure 5b the following variants are possible. The color coating 26 and the top layer 28 and / or the color coating 36 and the top layer 38 can through a color coating 26 or 36 with - be formed upper surface - in particular flat. The color coating 26 and/or 36 comprises a reflective sub-layer (such as metallization) which follows its relief structure with both surfaces, and a translucent color sub-layer whose lower surface follows the relief structure, while the upper surface of the translucent color sub-layer does not follow the relief structure, is preferably flat. In a further variant, an upper, colored, glazed partial layer forms the lower color coating 26 in Figure 5b the lower cover layer 28 and at the same time the upper embossing lacquer layer 32. The color coating 26 preferably in turn comprises a reflective partial layer (such as metallization), which follows its relief structure with both surfaces. A transparently colored partial layer, preferably an embossing lacquer layer, follows the color coating 26 with its lower surface of the lower relief structure 24 and with its upper surface of the upper relief structure 34. In an even more extensive variant, the lower color coating comprises at least (or exactly) three partial layers, one reflective Sub-layer, a leveling sub-layer and a sub-layer with translucent color, preferably colored embossing varnish. The reflective partial layer follows with one (or both) surface(s) of the second, lower relief structure 24 and the colored transparent partial layer follows with its upper side the first, upper relief structure 34.

In other configurations, two foils 18-A, 18-B can also be used in the production of the security element, which are each separately provided with one of the micromirror structures 22-28 or 32-38 and then suitably laminated together.

When the security element 54 of Fig.5(c) the two carrier films 18-A, 18-B are laminated together in such a way that the micromirror structures 22-28 or 32-38 inside. The laminating 56 can comprise a laminating film or also be formed only by a laminating adhesive. In this configuration, one or both of the carrier foils 18-A, 18-B can be removed after lamination in order to make the security element 54 as thin as possible. In particular when using a laminating film, both carrier films 18-A, 18-B can even be removed, since the stability of the security element 54 is ensured by the laminating film, which then acts as a flat carrier of the security element. The security element 54 is also designed for viewing from the side of the color coating 36, so that the color coating 36 of the higher-lying micro-mirror arrangement 34 is provided with large-area recesses 42, in which the viewer looks at the lower-lying micro-mirror arrangement 24 with the colored coating 26.

When security element 58 of Fig.5(d) the carrier foils 18-A, 18-B are laminated together in such a way that one micromirror structure 22-28 is on the inside and the other micromirror structure 32-38 is on the outside. The laminating 56 can comprise a laminating film or can only be formed by a laminating adhesive. The carrier film 18-A lying on the outside can be pulled off after lamination in order to make the security element 58 as thin as possible. The large-area recesses 42 are also provided here in the color coating 36 of the higher-lying micro-mirror arrangement 34 in order to enable the viewer to look at the lower-lying micro-mirror arrangement 24 with the colored coating 26 .

Finally, another variant not shown in the figures consists in laminating the carrier foils together in such a way that both micromirror structures 22-28 or 32-38, 42 are on the outside.

As already explained in more detail above, the color coatings 26, 36 can be formed not only by translucent colors, but also, for example, by metallizations, by thin-film structures, by translucent colors backed with a metallization, by luminescent colors with metallic mirroring, by structural colors or by nanoparticle colors.

As also already explained, the carrier film 18 is an optional element. It can therefore be omitted in any of the variants shown, mentioned or below. For example, the carrier film can be 18 in Fig.5(b) , the carrier foil(s) 18-A/B in Fig.5(c) or the carrier film 18-A in Figure 5d be removed before (or after) the security element is applied to a target substrate. A release layer, not shown, which lies between the carrier film and the further layers, is provided in such configurations.

The security elements according to the invention can also contain areas with negative markings, for example negative writing, as shown in FIG Figures 6 and 7 illustrated. For the sake of simplicity, only the micromirror structures 22-28 and 32-38 without carrier films or further layers of the layer structure are shown in these figures.

The security element 60 of 6 is basically like the security element 12 of 2 constructed, in particular contains the color coating 36 of the higher-lying micro-mirror array 34 in portions 16 recesses 42 which are arranged over coated areas 26 of the lower-lying micro-mirror array 24 and produce the color-to-effect registration described above. In addition, the security element 60 also contains partial areas 62 in which the color coatings 26, 36 of both micromirror arrangements 24, 34 are recessed (recesses 44 or 42) so that the security element 60 does not show any of the color impressions of the two color coatings in these areas.

The shape of the partial areas 62 forms a negative identifier, in particular negative writing, which can be seen particularly well in transmitted light given an at least translucent configuration of the further layers of the security element. In the partial areas 62, the cutouts 44 in the color coating 26 of the micromirror arrangement 24 lying deeper are formed with a somewhat larger area than the associated cutouts 42 in the color coating 36 in order to absorb register fluctuations between the two embossed structures 24, 34. The line widths of the gaps 42, 44 lying one above the other are greater than 100 μm, in particular greater than 300 μm, in order to ensure that the negative markings can be recognized well.

Colored negative marks can also be provided, as is the case with the security element 70 of FIG 7 illustrated. In this exemplary embodiment, the color coating 26 of the lower-lying micromirror arrangement 24 consists of a glazing color 74 backed by a metallization 72. In the partial areas 16, the recesses 42 of the color coating 36 are as in FIG 6 over completely coated areas 26 of the lower-lying micromirror arrangement 24, so that the already described color-to-effect registration results in these partial areas.

In addition, the security element 70 contains partial areas 76 in which, in addition to the color coating 36 of the higher-lying micromirror arrangement 34, the metallization 72 of the color coating 26 of the lower-lying micromirror arrangement 24 is cut out, but the glazing color 74 is retained is. While the security element 70 appears colored and opaque in the sub-areas 16 due to the metallization 72, the sub-areas 76 are colored and translucent due to the lack of metallization 72 there. The shape of the partial areas 76 thus forms a colored negative mark, in particular a colored negative writing, which can be seen particularly well in transmitted light given an at least translucent configuration of the further layers of the security element. Even in the embodiment of 7 For example, the recesses in the metallization 72 are advantageously formed with a slightly larger area than the recesses 42 in the color coating 36 in order to absorb register fluctuations. The line widths of the superimposed recesses are preferably greater than 100 μm, in particular greater than 300 μm, in order to ensure that the colored negative identification can be easily recognized.

Reference List

10

bank note

12

security element

14

bulging motif

16

subarea

16-A

bright bar

16-B

direction of movement

18

carrier

18-A, 18-B

carrier films

20

reflective surface area

22

embossing layer

24

micromirror array

26

color coating

26o

exposed section of bottom paint coat

26v

hidden section of bottom paint coat

28

topcoat layer

32

embossing layer

34

micromirror array

36

color coating

38

topcoat layer

40

viewer

42

large recess

44

recesses

50, 52, 54

security element

56

lamination

58

security element

60

security element

62

Section with a negative indicator

70

security element

72

metallization

74

glazing color layer

Claims (15)

1. Optically variable security element having a polychromatically reflective surface region, the planar extent of which defines a z-direction perpendicular thereto, wherein

   - the polychromatically reflective surface region contains an upper relief structure and a lower relief structure (34, 24) arranged at different levels in the z-direction,

   - the two relief structures are each provided with an upper colour coating and a different lower colour coating (36, 26),

   - the two relief structures overlap in an overlap region,

   - the upper colour coating has a cutout (42) in the overlap region such that

   a concealed portion (26v) of the lower colour coating (26) is arranged under the upper colour coating (36) in the z-direction and

   an exposed portion (26o) of the lower colour coating (26) is arranged under the cutout (42) in the z-direction,

   - wherein, at an observation angle, the lower colour coating (26) becomes visible with components of the concealed portion (26v) and the exposed portion (26o) in its colour impression, characterized in that
   the relief structures are micromirror arrangements which comprise a multiplicity of directed micromirrors, wherein the respective colour coating only becomes visible in chromatically reflective fashion depending on the observation angle.
2. Security element according to Claim 1, characterized in that the part of the concealed portion becoming visible forms more than 2.5%, preferably more than 5%, of the area becoming visible.
3. Security element according to any of Claims 1 and 2, characterized in that the upper colour coating has a plurality of cutouts.
4. Security element according to any of Claims 1 to 3, characterized in that the dimensions of the cutout in the overlap region are more than 140 µm, in particular more than 200 µm or even more than 500 µm.
5. Security element according to Claim 4, characterized in that the part of the concealed portion becoming visible forms between 2.5% and 12%, preferably between 4% and 10%, of the area becoming visible.
6. Security element according to any of Claims 1 to 3, characterized in that the upper colour coating is formed as a regular or irregular raster with raster elements and raster interspaces as the cutouts, with the dimensions of the raster elements (52) and/or raster interspaces (54) being below 140 µm in at least one direction.
7. Security element according to Claim 6, characterized in that the part of the concealed portion becoming visible forms between 10% and 90%, preferably between 25 and 75%, of the area becoming visible.
8. Security element according to any of Claims 1 to 7, characterized in that the polychromatically reflective surface region - in particular at least one of the two relief structures, the difference of the levels and/or at least one of the colour coatings - is adjusted to increase the part of the concealed portion of the lower colour coating visible to the observer at the observation angle.
9. Security element according to any of Claims 1 to 8, characterized in that in a regular structure of relief elements, micromirrors, at least one relief element is displaced in the relief plane, displaced in the z-direction, adapted in terms of its size or adapted in terms of its shape.
10. Security element according to any of Claims 1 to 9, characterized in that the polychromatically reflective surface region - in particular a reflectivity of the upper relief structure or at least one of the colour coatings - is adjusted in order to provide more reflectable light to the concealed portion.
11. Security element according to at least one of Claims 1 to 10, characterized in that the embossed structure regions are each characterized by a maximum pitch and the spacing of adjacent levels in the z-direction is greater than the maximum pitch of the embossed structure region located further down, preferably is between 150% and 750%, particularly preferably between 200% and 500% of the maximum pitch of the embossed structure region located further down.
12. Security element according to at least one of Claims 1 to 11, characterized in that the colour coatings are formed by transparent inks, by metallizations, thin-film structures, by transparent inks deposited with a metallization, by luminescent inks with a metallic reflection, by textured inks and/or by nanoparticle inks.
13. Security element according to at least one of Claims 1 to 12, characterized in that in at least one part of the feature region either the colour coating (36) of the upper relief structure (24) or the colour coating (26) of the lower relief structure (34) becomes visible to the observer depending on the observation angle.
14. Data carrier having an optically variable security element according to at least one of Claims 1 to 13.
15. Method for producing an optically variable security element according to at least one of Claims 1 to 14, wherein

    - a carrier is provided, the planar extent of which defines an xy-plane and a z-axis perpendicular thereto,

    - the carrier is provided with a polychromatically reflective surface region which is formed with at least two relief structures arranged at different levels in the z-direction in relation to the flat carrier,

    - the relief structures are each provided with a colour coating which generates a different colour impression, and

    - the two relief structures are formed in overlapping fashion,

    - wherein the upper colour coating has a cutout in the overlap region such that

    a concealed portion of the lower colour coating is arranged under the upper colour coating in the z-direction and

    an exposed portion of the lower colour coating is arranged under the cutout in the z-direction, and

    the relief structures are micromirror arrangements which comprise a multiplicity of directed micromirrors, wherein the respective colour coating only becomes visible in chromatically reflective fashion depending on the observation angle, and,

    at an observation angle, the lower colour coating becomes visible with components of the concealed portion and the exposed portion in its colour impression.

Images