Security element having diffractive structures

Abstract

The invention relates to a security element (1), in particular for value papers, security papers, or security objects, such as banknotes, identification documents, and credit cards, having a first region (2) which has first optically active diffractive structures (3), by means of which a generated overall impression appears achromatic, the first region being at least partly coated with an optical effect layer (4) such that the overall impression appears in a first color (6) at a first viewing angle (5) and in a second color (8) at a second viewing angle (7). The security element comprises a second region (9) which has second optically active diffractive structures (10) and which is likewise coated with the optical effect layer (4), and the second structures (10) are designed to have different properties than those of the first structures (3) such that the overall impression in the second region (9) appears in at least one third color (12) at the first viewing angle (5).

Description

[0001] SAFETY ELEMENT WITH DIFFRACTIVE STRUCTURES

[0002] The invention relates to a security element, in particular for securities, security papers or security items, such as banknotes, identity cards, credit cards, wherein the security element has at least one area with optically effective, diffractive structures.

[0003] Security features of the type mentioned above are commonly used to increase the counterfeit protection of securities or security documents, such as banknotes, identity cards, credit cards, debit cards, tickets, etc.

[0004] Typically, achromatic security features are represented by relief structures that rely on light reflection due to their size or structural properties. Such structures are often described as micromirrors or structures with reflective facets. The resulting optical effects are frequently motion effects (a macroscopic motif appears to be moving) or three-dimensional motifs. Diffractive structures, on the other hand, cause light diffraction and are therefore usually perceived as iridescent optical effects due to their appearance. Classic holographic motifs fall into this category. Additionally, using so-called diffractive moth-eye structures, security features that appear black across a wide viewing angle can be created, while at shallow viewing angles they exhibit the corresponding diffraction colors.These different diffractive relief structures all share the characteristic of exhibiting a colored appearance. They are frequently used to depict static motifs, although the creation of motion effects is also possible.

[0005] EP4019271 Al discloses a security element comprising a substrate and a microstructure formation layer formed on a surface of the substrate, wherein the microstructure formation layer includes a microstructure, the first microstructure comprising a convex and / or a concave section; and which has an optically variable coating covering the first microstructure. The document further discloses the combination of individual parts of the microstructure to produce a mixed color.

[0006] EP 2676802A1 discloses a safety element in which a first layer provides a diffractive structure through which incident light at a predetermined angle of incidence to a surface normal is diffracted, so that for an observer looking at a predetermined viewing angle to the surface normal a first image appears as a first-order diffraction pattern, and wherein the diffractive structure is designed such that the viewing angle is greater than 50°.

[0007] The object of the present invention is to create a security element with increased protection against counterfeiting.

[0008] This task is solved with a security element of the type mentioned above.

[0009] The security element according to the invention comprises a first area with optically effective, diffractive first structures by means of which a generated overall impression (to an unarmed eye) appears achromatic, and this first area is at least partially coated with an optical effect layer, such that the overall impression appears in a first color under a first viewing angle and in a second color under a second viewing angle, and the security element is characterized in that it has a second area with optically effective, diffractive second structures, wherein the second area is also coated with the optical effect layer and the second structures are designed differently in their (optically effective) structural properties compared to the first structures in such a way that the overall impression in the second area appears in a first color under the first viewing angle,A third color, different from the first, appears.

[0010] The solution according to the invention increases counterfeit protection by creating a color-shifting effect between the first and second viewing angles with the diffractive structures and the applied optical effect layer. This color-shifting effect exhibits at least one additional third color besides the two colors of the effect itself. The solution according to the invention achieves an optical appearance that is unique, characteristic, and easily recognizable to an observer, but extremely difficult for a counterfeiter to imitate. Simultaneously, the structures can exhibit an achromatic appearance, as is typically achieved with reflective structures. The underlying diffractive nature of the structures can be verified using appropriate optical measurement methods (e.g., angle-dependent optical measurement using high-resolution microscopes).The inventive measure also has the advantage that, based on the diffractive second structures, structures particularly similar to the first structures can be used, especially structures made of optically variable elements of the same type (with the exception of the modified structural properties), which are coated with a common optical effect layer and can nevertheless produce different colors for the eye. This makes it possible to produce different colors in at least one of the viewing angles without applying different coatings or introducing additional, other optically variable elements, thereby further increasing counterfeit protection.

[0011] Furthermore, the use of the optically effective, diffractive first and second structures has the advantage that, due to their similarity to each other, they can be combined much more harmoniously to create effects and motifs, which also improves the overall impression to be created using the first and second structures.

[0012] For the sake of completeness, it should be mentioned at the outset that the first and second colors are distinct from each other. Preferably, these are clearly distinguishable from one another by the naked eye and thus not merely minor variations in color perception. Likewise, the third color can be distinct from at least the first color, or even from the second color.

[0013] Possible color combinations would include, for example, green and magenta as the first and second colors, and blue as at least the third color.

[0014] Furthermore, regarding the viewing angles, it should be noted that the first and second viewing angles can preferably lie in a plane that is perpendicular to a surface of the security element. In addition, the viewing angles in this plane can be inclined relative to the surface such that one viewing angle is inclined more steeply and the other more gently. With respect to a security element, e.g., a security thread, a security strip, or a security patch, the plane can, for example, be oriented along a longitudinal dimension of the security element. The second structures can also preferably be designed as optically effective diffractive structures that create an achromatic impression.

[0015] In this regard, the structural properties of the security element are selectively modified in certain areas to deliberately manipulate the interference properties associated with the optical effect layer. For example, it may be intended that an achromatic impression is also achieved using the second structure, but that the structural properties result in a different additive color mixture than those of the first structure, thus producing a different color in the second area due to the optical effect layer.

[0016] The structural properties to be modified can include at least one of the following;

[0017] - Grating constant (for optical gratings)

[0018] - Depth of structures

[0019] - Angle of inclination (or slope)

[0020] - Orientation (or alignment)

[0021] - Size of the structure-forming elements (e.g. a projected area in top view)

[0022] - geometric relationship of the structures (depth to width and / or inclination), or an aspect ratio

[0023] -Form (line grid / cross grid, etc...).

[0024] In particular, the optically (effective) thickness can be changed or adjusted by the (varying) structural properties, which, depending on the viewing angle, makes the overall impression appear in a different color.

[0025] For example, the angle of inclination and / or the geometric ratio of individual secondary structures can be modified so that, at a given viewing angle in the second area, they influence the optical properties of the optical effect layer to achieve the desired different impression. Outside the second area, the first areas (depending on the viewing angle) can, together with the optical effect layer, create the overall impression in the first and second colors, particularly without being affected by the modified structural properties of the secondary structures, allowing the different colors to be clearly distinguished by the eye. An interference condition for the second area (relative to the optical effect layer) can be provided or determined, e.g.,through simulation, based on which the structural properties to be changed (depending on the existing optical properties of the first structures of the first areas) are derived or calculated to influence the optical effect layer - and are accordingly introduced into the optically effective, diffractive second structures in specific areas.

[0026] Furthermore, the second structures may be present in significantly smaller proportions than the first structures on the surface of the security element, so that they only occur in individual regions, and thus, for example, form additional colored parts of a motif or the like.

[0027] It may be intended that the first area depicts a static motif or a motif with a movement effect.

[0028] Furthermore, the second area itself can also represent a static motif or a motif with a movement effect, or form such a motif together with the first area.

[0029] The first and second structures, or the first and second areas, can be nested within each other, so that a motif is formed by both areas. Furthermore, the first and second areas can be adjacent to each other or spaced apart.

[0030] According to one possible embodiment, the second area can be completely surrounded by the first area.

[0031] One possible further development involves arranging the first and second structures (or first and second areas) in a repeating pattern along a direction in the surface plane of the security element, such that the first and third colors appear alternately and repeatedly at the first viewing angle along that direction. This repeating arrangement can be regular or irregular.

[0032] Preferably, the interaction of the second structure of the second area with the optical effect layer results in the overall impression in the second area appearing in a fourth color, different from the second color, under the second viewing angle. This further increases counterfeit protection by creating another characteristic color effect.

[0033] It is preferable to design the first color to be different from the fourth color. Such a design can create an additional characteristic interplay of colors under a second viewing angle, thanks to the additional, different fourth color, which further increases counterfeit protection.

[0034] According to an alternative embodiment, however, the structural properties of the second structures can be adapted to the first structures in such a way that the fourth color of the second area corresponds to the first color of the overall impression under the first viewing angle at the second viewing angle. Such a design can increase counterfeit protection by creating a particularly characteristic impression through a color-shifting effect, in which the color impression perceived by the eye shifts in certain areas between the viewing angles.

[0035] Furthermore, it can be provided that the second color is different from the third color. This can further increase counterfeit protection. In this regard, the previously mentioned interference properties of the optical effect layer can be coordinated with the structural properties of the second structure in such a way that the third color is clearly distinguishable from the second color.

[0036] Alternatively, the structural properties of the second structures can be adapted to the first structures in such a way that the third color of the second area corresponds to the second color of the overall impression at the second viewing angle. This, in turn, can create a particularly characteristic impression by means of a color-shifting effect, in which the color impression perceived by the eye shifts in certain areas between the viewing angles.

[0037] Regarding the previously described third and fourth colors, the interference properties of the optical effect layer—which is influenced by the second structures—can be determined by matching them with the interference properties of the optical effect layer in relation to the first structures. This ensures, for example, that under the second viewing angle, the fourth color corresponds to the first color under the first viewing angle. Similarly, this can be used to determine the interference properties for generating the third color under the first viewing angle, so that it corresponds to the second color under the second viewing angle. As mentioned earlier, this can preferably be done through simulation.

[0038] It has proven particularly advantageous that the optically effective first structures are arranged irregularly, whereby in particular a frequency, an orientation, area sizes and / or contours of areas in which the structures are arranged, and / or shapes of the first structures, for example curvatures of the first structures, can vary.

[0039] Furthermore, it may be intended that the overall achromatic impression is caused by an additive color mixing of the colors produced by the first structures.

[0040] The security element can preferably consist of an image composed of areas, in particular pixels. Such pixels can be formed, for example, by first areas as well as by second areas.

[0041] According to a preferred embodiment of the invention, it can be provided that individual areas, in particular pixels, are each formed from several optically effective first structures, wherein the optically effective first structures in individual areas, in particular pixels, are oriented such that each of these areas, in particular each of these pixels, appears achromatic. Furthermore, these areas, in particular pixels, can also be formed from several optically effective second structures.

[0042] In an advantageous embodiment of the invention, it can also be provided that the (first and second) structures are completely covered with the optical effect layer.

[0043] In general, the optical effect layer is a coating that produces a color effect, so that different colors are visible when tilted or viewed from different angles, indicating which effect layer is applied to the first and second structures. However, the respective first and second structures can also be only partially covered by the optical effect layer, whereby at least a common portion of the first and second structures is covered by the partial optical effect layer.

[0044] The optical effect layer can preferably have a uniform average layer thickness.

[0045] It has proven particularly advantageous that the first and second structures are embossed structures, especially structures embossed into an embossed lacquer layer.

[0046] It is particularly desirable that the optically effective first structures appear achromatic in top view due to additive color mixing of light diffracted at the structures.

[0047] According to an advantageous embodiment of the invention, it can be provided that the maximum extent of the areas, in particular the pixels, is smaller than the resolution limit of the human eye, in particular smaller than 300 pm.

[0048] According to an advantageous embodiment of the invention, the optical effect layer is designed as a thin-film element and has at least one absorber layer and at least one spacer layer.

[0049] It has proven particularly advantageous that the at least one absorber layer comprises at least one metallic material, in particular selected from the group consisting of nickel, titanium, vanadium, chromium, cobalt, palladium, iron, tungsten, molybdenum, niobium, aluminium, silver, copper and / or alloys of these materials, or is made from at least one of these materials.

[0050] It has also proven particularly advantageous that at least one spacer layer is a low-refractive-index dielectric material with a refractive index of less than or equal to 1.65, in particular selected from the group consisting of aluminum oxide (Al2O3), metal fluorides, for example magnesium fluoride (MgF2), aluminum fluoride (AIF3), cerium fluoride (CeFs), sodium aluminum fluorides (e.g. NasAIFr, or NasAhFu), silicon oxide (SiO3). x), silicon dioxide (SiO₂), neodymium fluoride (NdF₆), lanthanum fluoride (LaF₆), samarium fluoride (SmF₆), barium fluoride (BaF₂), calcium fluoride (CaF₂), lithium fluoride (LiF₆), low-refractive-index organic monomers and / or low-refractive-index organic polymers or at least a high-refractive-index dielectric material with a refractive index greater than 1.65, in particular selected from the group zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO₂), carbon (C), indium oxide (In₂O₃), indium tin oxide (ITO), tantalum pentoxide (Ta₂O₅), cerium oxide (CeO₂), yttrium oxide (Y₂O₃), europium oxide (EU₂O₃), iron oxides such as iron(II, III) oxide (Fe₃O₄) and iron(III) oxide (Fe₂O₃), hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO2), lanthanum oxide (La2O3), magnesium oxide (MgO), neodymium oxide (Nd2O3), praseodymium oxide (Pr6O 11), samarium oxide (Sm2O3), antimony trioxide (Sb2O3), silicon carbide (SiC), silicon nitride (Si3N4), silicon monoxide (SiO), selenium trioxide (Se2O3), tin oxide (SnO2), tungsten trioxide (WO3), high refractive index organic monomers and / or high refractive index organic polymers, or is made from at least one of these materials.

[0051] A preferred embodiment provides that the optical effect layer, designed as a thin-film element, further comprises at least one reflection layer and / or a second absorber layer, wherein the at least one spacer layer is arranged between the at least one first absorber layer and the at least one reflection layer and / or the at least one second absorber layer.

[0052] Preferably, the at least one reflective layer comprises at least one metallic material, in particular selected from the group consisting of silver, copper, aluminum, gold, platinum, niobium, tin, or nickel, titanium, vanadium, chromium, cobalt and palladium or alloys of these materials, in particular cobalt-nickel alloys, or at least a high-refractive-index dielectric material with a refractive index greater than 1.65, in particular selected from the group consisting of zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO2), carbon (C), indium oxide (In2O3), indium tin oxide (ITO), tantalum pentoxide (Ta2O5), cerium oxide (CeO2), yttrium oxide (Y2O3), europium oxide (EU2O3), iron oxides such as iron(II, III) oxide (Fe3O4) and iron(III) oxide (Fe2O3), hafnium nitride (HfN), hafnium carbide (HfC). Hafnium oxide (HfO2). Lanthanum oxide (La2O3), magnesium oxide (MgO), neodymium oxide (Nd2O3), praseodymium oxide (Pr6O 11), samarium oxide (Sm₂O₃), antimony trioxide (Sb₂O₃), silicon carbide (SiC), silicon nitride (Si₃N₄), silicon monoxide (SiO), selenium trioxide (Se₂O₃), tin oxide (SnO₂), tungsten trioxide (WO₃), high-refractive-index organic monomers and / or high-refractive-index organic polymers, or is made from at least one of these materials. Furthermore, it may be provided that it comprises a support layer made of a plastic, wherein the plastic is in particular a translucent and / or thermoplastic plastic, and that the support layer preferably comprises at least one of the materials from the group consisting of polyimide (PI), polypropylene (PP), monoaxially oriented polypropylene (MOPP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketone (PEK), polyethyleneimide (PEI), polysulfone (PSU), polyaryletherketone (PAEK), polyethylene naphthalate (PEN), and liquid crystalline polymers. (LCP), polyester, polybutylene terephthalate (PBT),Polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), cycloolefin copolymers (COC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene hexafluoropropylene fluoroterpolymer (EFEP), cellulose- or lignin-based plastics, polyhydroxyalkanoates (PHA), thermoplastic starch (TPS), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), and polybutylene adipate terephthalate (PB AT) and / or at least one recycled and / or biodegradable and / or marine-degradable plastic and / or mixtures and / or copolymers of these materials, or is made from at least one of these materials.

[0053] It may also be advantageous for the security element to be equipped with further color-changing layers, in particular layers with color-changing pigments or liquid crystals and / or with machine-readable features, wherein the machine-readable features are in particular magnetic codes, electrically conductive layers, and materials that absorb and / or re-emit electromagnetic waves. In particular, it is possible for the security element to have additional layers, which may include, in particular, protective coatings, heat-seal coatings, adhesives, primers, and / or films.

[0054] As mentioned at the beginning, an optical motif can be represented using the first area and the second area.

[0055] Furthermore, with regard to optical motifs, it can be provided that a sub-area of ​​the optical motif is formed by means of the second area, such that, due to the interaction of the second structures with the optical effect layer, this sub-area of ​​the optical motif appears in the third color, at least under the first viewing angle. Using this measure, the sub-area can, for example, reproduce information, an image, or the like, which becomes recognizable in the third color under the first viewing angle due to the interaction of the areas with the optical effect layer. This measure makes it possible to incorporate additional elements to be displayed into the first areas, thereby further increasing counterfeit protection.

[0056] According to further training, it can also be provided that the second structures of the second area are adapted in their structural properties such that they interact with the optical effect layer only under the first viewing angle, so that the sub-area of ​​the optical motif formed by the second area is not color-distinguishable within the overall impression appearing in the second color under the second viewing angle. This allows, for example, the sub-area to be visible to the naked eye only under the first viewing angle and is color-distinguishable from the second viewing angle for further division of the motif. This particularly characteristic measure can further increase counterfeit protection.

[0057] Alternatively, it can also be provided that the sub-area appears in the fourth color in the second viewing angle.

[0058] Regarding diffractive structures, it should be noted that static or moving motifs based on these structures exhibit an achromatic appearance. This is achieved by designing the individual structures in such a way that the diffraction colors produced overlap for the viewer (at a distance from the security element itself) through additive color mixing, thus creating a white appearance and simulating an overall achromatic effect.

[0059] However, the underlying diffractive character of the structures is either apparent at a very narrow angle, dependent on the diffractive lattice spacing but not negatively affecting the overall achromatic appearance, or it can be determined by appropriate optical measurement methods (e.g., angle-dependent optical measurement using high-resolution microscopes). This increases the counterfeit protection of the corresponding security elements. For a better understanding of the invention, it is explained in more detail with reference to the following figures.

[0060] They each show, in a highly simplified, schematic representation:

[0061] Fig. 1 shows a layer structure of a security element with diffractive structures;

[0062] Fig. 2 shows a safety element with first structures and second structures;

[0063] Fig. 3 a) and b) a safety element in different viewing angles;

[0064] Fig. 4 shows another embodiment of a safety element;

[0065] Fig. 5 shows another embodiment of a safety element;

[0066] Fig. 6 shows another embodiment of a safety element.

[0067] It should be noted at the outset that in the differently described embodiments, identical parts are provided with the same reference numerals or component designations, and the disclosures contained in the entire description can be applied analogously to identical parts with the same reference numerals or component designations. Furthermore, the orientation designations chosen in the description, such as top, bottom, side, etc., refer to the figure directly described and illustrated, and these orientation designations must be applied analogously to the new position if the orientation changes.

[0068] Finally, for the sake of clarity, it should be noted that, for a better understanding of the structure, some elements have been shown not to scale and / or enlarged and / or reduced in size.

[0069] Fig. 1 shows a security element 1 as it is used for the counterfeit protection of securities, security papers or security items such as banknotes, identity cards, credit cards, tickets, etc.

[0070] The security element has a first region 2 in which first structures 3 are arranged or formed. The first region 2 can extend over a part of the security element 1 or over the entire security element 1. The optically effective first structures 3 of the first region 2 form areas of an image, in particular pixels. For the sake of readability, the term "pixel" will be used instead of "area" or "pixel" in the following description. Several structures 3 can form a single pixel.

[0071] The image formed from the pixels can represent or include a motif, for example a portrait, a landscape, an abstract geometric symbol, a logo or an alphanumeric character and / or an icon and / or a code and / or a sequence of characters.

[0072] A maximum pixel size is preferably between 0.5 pm and 100 pm.

[0073] The first three structures are diffracting or diffractive structures. Diffractive structures can be used to create holograms, moving images, or static images, for example. The overall impression produced by these optically effective first three structures appears achromatic to the naked eye.

[0074] The underlying diffractive character of the structures 3 can either only be seen in a very narrow angle, which depends on the diffractive lattice spacing but does not negatively affect the overall achromatic impression, or can be determined by appropriate optical measurement methods (e.g. angle-dependent optical measurement using high-resolution microscopes).

[0075] The first structures 3 can, for example, generate a hologram and, regardless of the embodiment, can have a depth 21a greater than 150 nm, in particular between 150 nm and 4 pm, and most preferably between 200 nm and 3 pm. In this context, the depth 21a of a structure is understood to be the perpendicular distance between the level of the lowest point and the level of the highest point of the structure (with respect to the surface plane of the security element). The width 22a of a structure 3 corresponds to the minimum width of the structure 3.

[0076] As mentioned, these structural properties of the second structures differ from those of the first structures. In Fig. 1, the second structures or the second areas are not visible; these can, for example, also be arranged adjacent to the first structures 3, e.g., according to the schematic representation in the image plane behind the first structures 3.

[0077] Preferably, the first structures 3 can have an aspect ratio of 0.01- 8 (e.g.

[0078] 150nm / 15000nm - 4000nm / 500nm). For structures with a perpendicular inclination angle, such as columnar structures, the aspect ratio is the ratio of the depth 21a to the width 22a of the structures. For structures with an inclination angle other than 90°, such as sawtooth structures, the aspect ratio represents the ratio of the depth 21 to the peak-to-peak distance of the structures.

[0079] Such an aspect ratio can, for example, be set to a determined value for the second structures 10 to influence the (optical properties) so that they fulfill an interference condition in area 9, for example, to generate the additional color.

[0080] A possible design and arrangement of the second structures 10 is shown schematically in Fig. 2.

[0081] These are specifically modified in their structural properties compared to the first structures 3, so that in the second area 9 they make the overall impression (at least partially) appear in the third color 12.

[0082] As mentioned at the beginning, the altered structural properties of the second structures 10 can include, among other things, one of the following properties: depth, slope angle, orientation (or alignment to an axis perpendicular to the surface plane), size of the structure-forming elements (in top view of the surface plane), geometric ratio of the structures, shape (line grid / cross grid, etc...).

[0083] Some of the structural properties are illustrated in Fig. for easier understanding.

[0084] 2. A rough schematic representation is given. It should be noted that these may have been altered by a larger amount than necessary for ease of understanding.

[0085] As a possible example, the depth 21b, width 22b, orientation 23 and / or an inclination angle 24 of the second structures 10 are indicated, which can be specifically changed compared to these properties of the first structures 3, whereby in principle one or more of the aforementioned properties of the second structures can be adapted to the first structures in order to achieve the inventive interaction of the optical properties.

[0086] As mentioned at the beginning, the structures, or rather the first and second areas, can be nested within each other (regardless of the depicted design). Furthermore, the first area 2 and the second area 9 can be adjacent to each other or spaced apart.

[0087] Furthermore, the first area 2 and the second area 9 can together represent a motif (static or with a movement effect).

[0088] For easier understanding, Fig. 2 schematically indicates a viewing angle of a person looking at the safety element 1, as well as a possible first viewing angle 5, and second viewing angle 7.

[0089] Furthermore, the surface plane 14 is schematically indicated, which is arranged along a direction of extension of the safety element 1 (planar).

[0090] One of the viewing angles can be, for example, in a range of 65° to 95°, in particular 90°, with respect to the surface plane of the safety element, and the other viewing angle between 1° and 65°.

[0091] As shown, the first viewing angle 5 can form the steeper angle with respect to the surface plane 14 and the second viewing angle 7 the shallower angle, whereby a reverse arrangement is also possible, with a shallow first viewing angle, as indicated by the angles shown in brackets.

[0092] In principle, there are several possibilities for representing achromatic-appearing motifs using diffractive optically effective first structures.

[0093] The individual first structures 3 can, for example, be designed in such a way that the diffraction colors produced overlap at the viewer's (at a distance from the safety element itself) by means of additive color mixing and thus have a white appearance, resulting in an overall achromatic behavior.

[0094] Individual pixels can appear colored from a wide viewing angle. The specific combination of pixels with different orientations of their optically effective diffractive first structures results in distinct colors for each pixel. This additive color mixing also leads to an achromatic appearance. Alternatively or additionally, different diffractive first structures can be present within a single pixel, causing additive color mixing within that pixel, resulting in both the pixel itself and the overall image or impression appearing achromatic.

[0095] The achromatic effect of diffractive structures can be achieved, in addition to or as an alternative to additive color mixing, by arranging the structures irregularly. This essentially eliminates the need for a targeted arrangement of the diffractive structures into ordered pixels. The first area 2 can then be filled with the diffractive structures 3 according to a freeform arrangement. This suppresses the diffractive effect caused by the disorder. In this context, it is particularly advantageous if the first structures are distributed essentially randomly, whereby, in particular, the frequency, orientation, area sizes and / or contours of the areas in which the first structures are arranged, and / or shapes of the first structures, such as their curvature, can vary.

[0096] Software can be used to calculate an arrangement of the first structures 3, which, for example, determines the arrangement of the optically effective first structures 3 based on the boundary conditions mentioned above.

[0097] Similarly, the calculation regarding the arrangement and design of the second structures 10 can be based on the calculated first structures, depending on the determined first structures, in order to adapt their structural properties to the first structures. For example, if the arrangement of the first structures is done by software, this can be done using an algorithm or the like to coordinate the second structures, as well as a simulation of the determined structures.

[0098] The achromatic appearance of the optically effective structures 3 significantly increases counterfeit protection, since, as mentioned above, the diffractive nature of the structures is only visible, if at all, under very specific viewing angles or can be detected / measured using appropriate optical aids. The optical effect layer 4 can be applied to the structures 3 either completely or partially. For example, individual areas of the first structures (and possibly also the second structures) can be excluded from the color-shifting effect, so that an area can be provided in which the effect layer 4 is omitted.

[0099] It is also possible that one part of the subject to be depicted (static or moving) has an achromatic appearance, while another part, for example, deliberately exhibits a colored appearance (based on diffractive first structures 3). This allows for the targeted depiction of colored areas within an otherwise achromatic subject (and vice versa).

[0100] For example, by means of a partial arrangement of the optical effect layer, a first sub-area can form the colored appearance and the further sub-area can be only achromatic.

[0101] The colored appearance can be represented in another color in the second area 9 based on the influence of the second structures 10 of the second area 9 (or their different structural properties) on the optical effect layer under at least one of the viewing angles.

[0102] The optical effect layer 4 can be arranged directly on the first and second structures 3, 10. Alternatively, an additional adhesion promoter layer can be arranged between the structures 3, 10 and the optical effect layer 4. The material of the adhesion promoter layer can, for example, be selected from the group consisting of nickel, titanium, manganese, vanadium, chromium, cobalt, palladium, iron, tungsten, molybdenum, niobium, aluminum, silver, copper, and / or alloys of these materials, in particular at least one nickel-chromium alloy, or be made from at least one of these materials. Chromium or a nickel-chromium alloy, such as Inconel, is particularly preferred as the material of the adhesion promoter layer.

[0103] The optical effect layer 4 is preferably designed as a thin-film element. The optical effect layer 4, designed as a thin-film element, comprises at least one absorber layer 15 and at least one spacer layer 16. The absorber layer 15 can comprise a metallic material, in particular selected from the group consisting of nickel, titanium, vanadium, chromium, cobalt, palladium, iron, tungsten, molybdenum, niobium, aluminum, silver, copper and / or alloys of these materials, or be made of at least one of these materials.

[0104] The at least one spacer layer 16 can, for example, be formed from a dielectric material. Furthermore, the at least one spacer layer 7 can be at least a low-refractive-index dielectric material with a refractive index less than or equal to 1.65, in particular selected from the group consisting of aluminum oxide (Al₂O₃), metal fluorides, for example magnesium fluoride (MgF₂), aluminum fluoride (AlF₃), cerium fluoride (CeF₆), sodium aluminum fluorides (e.g., NasAlFr or NasAhFu), silicon oxide (SiO₂). x), silicon dioxide (SiO₂), neodymium fluoride (NdF₆), lanthanum fluoride (LaF₆), samarium fluoride (SmF₆), barium fluoride (BaF₂), calcium fluoride (CaF₂), lithium fluoride (LiF₆), low-refractive-index organic monomers and / or low-refractive-index organic polymers or at least a high-refractive-index dielectric material with a refractive index greater than 1.65, in particular selected from the group consisting of zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO₂), carbon (C), indium oxide (ImO₆), indium tin oxide (ITO), tantalum pentoxide (Ta₂O₅), cerium oxide (CeO₂), yttrium oxide (Y₂O₃), europium oxide (EU₂O₃), iron oxides such as iron(II,III) oxide (FC₃O₄) and iron(III) oxide (FC₂O₃), hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO2), lanthanum oxide (La2O3), magnesium oxide (MgO), neodymium oxide (Nd2O3), praseodymium oxide (Pr6O 11), samarium oxide (Sm2O3), antimony trioxide (Sb2O3), silicon carbide (SiC), silicon nitride (Si3N4), silicon monoxide (SiO), selenium trioxide (Se2O3), tin oxide (SnO2), tungsten trioxide (WO3), high-refractive-index organic monomers and / or high-refractive-index organic polymers, or be made from at least one of these materials.

[0105] The optical effect layer 4, designed as a thin-film element, can be applied directly to the structures 3 or, for example, to the adhesion promoter layer mentioned above, which can be arranged on the structures 3.

[0106] The thickness of the individual layers or layers forming the thin-film element is greatly exaggerated and not shown to scale.

[0107] The color-shifting optical effect layer 4 can also include a reflective layer 17. At least one spacer layer 16 is arranged between the absorber layer 15 and the reflective layer 17. The reflective layer 17 is applied to structures 3 and 10, and can be printed and / or vapor-deposited onto them. It is also possible to reverse this order in the optical effect layer, so that the absorber layer is arranged on the adhesion promoter layer or structures 3 and 10, followed by the spacer layer and the reflective layer. Thus, the arrangement would be as follows: structures 3 and 10 - absorber layer 15 - spacer layer 16 - reflective layer 17.

[0108] The reflective layer 17 can be a metallic material, in particular selected from the group consisting of silver, copper, aluminum, gold, platinum, niobium, tin, or nickel, titanium, vanadium, chromium, cobalt and palladium or alloys of these materials, in particular cobalt-nickel alloys, or at least a high-refractive-index dielectric material with a refractive index greater than 1.65, in particular selected from the group consisting of zinc sulfide (ZnS), zinc oxide (ZnO), titanium dioxide (TiO2), carbon (C), indium oxide (IroOs), indium tin oxide (ITO), tantalum pentoxide (Ta2Os), cerium oxide (CeO2), yttrium oxide (Y2O3), europium oxide (EU2O3), iron oxides such as iron(II, III) oxide (Fe3O4) and iron(III) oxide (Fe2O3), hafnium nitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO2), lanthanum oxide (La2O3), magnesium oxide (MgO), neodymium oxide (Nd2O3), praseodymium oxide (Pr6O 11), samarium oxide (Sm₂O₃), antimony trioxide (Sb₂O₃), silicon carbide (SiC), silicon nitride (Si₃N₄), silicon monoxide (SiO), selenium trioxide (Se₂O₃), tin oxide (SnO₂), tungsten trioxide (WO₃), high-refractive-index organic monomers and / or high-refractive-index organic polymers, or be made from at least one of these materials. This applies to all reflective coatings described in the exemplary embodiments 8.

[0109] Instead of the above-mentioned reflective layer 17, another absorber layer can also be provided (not shown).

[0110] The safety element 1 can further comprise a carrier layer 18. The carrier layer 18 can be made of a plastic material. Furthermore, the carrier layer 18 can also consist of several layers. The plastic can be made of a translucent and / or thermoplastic material. As a material for the support layer 9, at least one of the following materials can be used: polyimide (PI), polypropylene (PP), monoaxially oriented polypropylene (MOPP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketone (PEK), polyethyleneimide (PEI), polysulfone (PSU), polyaryletherketone (PAEK), polyethylene naphthalate (PEN), liquid crystal polymers (LCP), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), cycloolefin copolymers (COC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), ethylene tetrafluoroethylene (ETFE).The material may comprise or be made from at least one of the following materials: polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene hexafluoropropylene fluoropolymer (EFEP), cellulose- or lignin-based plastics, polyhydroxyalkanoates (PHA), thermoplastic starch (TPS), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), and polybutylene adipate terephthalate (PBAT), and / or at least one recycled and / or biodegradable and / or marine-degradable plastic and / or mixtures and / or copolymers of these materials. The support layer may have a thickness of 5 pm to 1000 pm, particularly preferably a thickness of 10 pm to 50 pm.

[0111] The arrangement or application of the optical effect layer 4 or its layers onto the structures 3, 10 can be carried out, for example, by a printing process and / or a vapor deposition process or by several of the same.

[0112] The optical effect layer 4 is described in the present context as a thin-film element, but it can also be realized, for example, by means of an ink or printing ink containing color-shifting pigments, a varnish containing color-shifting pigments or a liquid crystal layer, in particular in combination with a dark enhancer layer attached to a side facing away from a visible side of the liquid crystal layer.

[0113] The first structures 3 and second structures 10 can be directly embossed into the carrier layer 18. For example, by heating the carrier layer 18 and embossing the structures using an embossing tool, such as an embossing roller.

[0114] Another alternative possibility is to provide a separate additional layer 19 to accommodate the structures 3 and 10. This additional layer 19 can be applied directly to the carrier layer 18. For example, the additional layer can be formed from an embossing lacquer, which is shaped according to the arrangement of the structures. This can, in turn, be done using a molding device or a molding element in an embossing process. This additional layer, in particular an embossing lacquer layer, with the structures formed therein, can, for example, have a thickness of 0.5 μm to 300 μm, in particular from 0.8 μm to 50 μm, preferably from 1 μm to 10 μm.

[0115] Furthermore, at least one intermediate layer can be provided between layer 19 and the carrier layer 18, which may be formed, for example, by an adhesion promoter, a primer, an adhesive or the like.

[0116] As the uppermost layer or outermost layer on the optical effect layer 4, a protective layer (not shown here) can be provided, which protects the entire layer and / or layer structure from mechanical damage such as scratches, grooves, or the like. The protective layer could also be arranged on the side of the carrier layer 18 facing away from the optical effect layer. A double-sided arrangement would also be conceivable. Preferably, the protective layer can also be used to achieve a flat surface for the safety element 1.

[0117] It should be noted that the layer structure, as well as the arrangement of further layers, depends on how the safety element is attached to a safety device, since the side of the safety element being viewed after attachment is crucial. Thus, the visible side can be viewed from above, as shown in the figures, but it is also possible to view the safety element from below, e.g., through a support.

[0118] It should be noted that the phrase "a layer is applied to something" is to be understood as meaning that the layer can be applied directly, or that one or more intermediate layers may be present between the applied layer and the surface to which the layer is applied. It should also be noted that one or more intermediate layers may be arranged between the layers described in this document. Therefore, it is not essential that the described layers are in contact with each other. Furthermore, it should be noted that the term "layer" in this document is to be understood as meaning that a layer can also be composed of several sublayers.

[0119] Furthermore, the entire layered structure of the security element can be bonded to or embedded in an object to be secured, or it can be designed as a transfer element in which at least one security feature formed from the diffractive structures, together with any further layers, is transferred to the object to be secured and is thereby detached from a transfer film.

[0120] Fig. 3 shows a possible embodiment of a safety element 1, in which different impressions of the safety element are shown, depending on the current viewing angle of the viewer.

[0121] Furthermore, regarding the depicted viewing angles, it should be mentioned that these are schematically indicated outside the safety element for ease of representation, but preferably, with respect to a view of the safety element along its longitudinal extent, lie essentially in a plane perpendicular to the safety element (or its surface) and are oriented in this plane (with respect to the surface plane) according to the respective viewing angle values ​​to the safety element.

[0122] According to the depiction of the safety element's motif, it can, for example, exhibit a motion effect dependent on the viewing angle, as shown in the sequence in Fig. 3 a) and b), which is schematically visible in alternating states. It should be noted that this serves only for illustration and the invention is not limited to this. Furthermore, the viewing-angle-dependent motion effect can already exhibit alternating states within the first or second viewing angle.

[0123] Preferably, in the present invention, the motif effect in the form of a motion effect, 3D effect, or the like, is continuously recognizable in all states in the first and second viewing angles.

[0124] The motif of the safety element 1 is also recognizable in the first color 6 from the first viewing angle 5, or appears in this color, according to Fig. 3 a). Furthermore, the first color 6 can appear in lighter areas of the first color, as well as in darker areas of the first color.

[0125] In the example shown, the first viewing angle is 90° with respect to the surface plane 14 of the security element 1, or is perpendicular to it. Additionally, in the second area 9, the motif appears in the third color 12 by means of the interaction based on the changed structural properties of the second structures and the optical effect layer.

[0126] As can be further seen, the second area 9 can extend over a larger portion of the surface. Multiple arrangements of second areas 9 can also be provided, such that they are subdivided into sections and arranged at a distance from one another.

[0127] Furthermore, the second areas 9 can be designed in such a way that the regions formed by the second areas 9, e.g. pixels or the like, are structurally indistinguishable to an unarmed eye from the further first areas in which the overall impression appears in the first color 6 - and only appear in another, third color 12.

[0128] Preferably, the color tilt effect can be triggered simultaneously in the second area 9, so that at the same time, when the viewing angle is changed in the direction of the first viewing angle, the third color appears in the second area 9 as soon as the first color 6 appears in the first areas 2.

[0129] Furthermore, it may be provided that the overall impression in the second area 9 appears in a fourth color 13 under the second viewing angle 7.

[0130] Alternatively, it can be provided that in the second viewing angle 7 the overall impression appears only in the second color 8, so that in the second area(s) 9, in which the third color 12 appears in the first viewing angle 5, only the second color 8 appears to one eye in the second viewing angle 7, or rather, no fourth color appears. In other words, it can be provided that the structural properties of the second structures together with the optical effect layer cannot exhibit any perceptible interference properties under the second viewing angle for one eye, so that these are superimposed by the interference properties of the first structures together with the optical effect layer for one eye with regard to the overall impression in such a way that they are not distinguishable in terms of color.As mentioned previously, according to one possible embodiment, all 4 colors, comprising the first color, second color, third color and fourth color, can be designed differently from each other.

[0131] However, it can also be provided that the second structures 10 are adapted to the first structures 3 with respect to their structural properties in such a way that the third color 12 appearing in the second area 9 under the first viewing angle 5 corresponds to the second color 8 produced under the second viewing angle 7 by means of the first areas 2 (and the optical effect layer).

[0132] It can also be provided that the fourth color 13 of the second area 9 corresponds to the first color 6 of the first areas 2 under the first viewing angle 5.

[0133] Regarding the adaptation of the second structures to produce the same color, this can be done, for example, by calculating the optical properties, e.g., by a simulation, as mentioned previously.

[0134] According to one embodiment, it can be provided that, with regard to the color shift effect, an optically perceptible shift of the two visible colors occurs between the first viewing angle 5 and the second viewing angle 7; namely between the first areas 2 and the second areas 9.

[0135] In the previously described possible configuration with a third color corresponding to the second color and a fourth color corresponding to the first color, this can, for example, result in an inversion of the colors when transitioning from the first viewing angle 5 to the second viewing angle 7.

[0136] As can also be seen from Fig. 3, with regard to the overall coloured impression, it can be provided that the second structures of the second areas are arranged repeatingly along the extension direction of the safety element or a direction along the surface plane, such that under the first viewing angle the third colour 12 and the first colour 6 appear to alternately repeating along the direction.

[0137] Such a repetition can be provided in a longitudinal direction and / or in a lateral direction with respect to the surface plane 14 of the safety element 1. Furthermore, this repeating arrangement can be regular or irregular (e.g., with respect to the sequence of the different colors).

[0138] Furthermore, in Fig. 3, regardless of the embodiment shown, a recessed area 20 is indicated in which the first and second structures are not coated with an optical effect layer.

[0139] This can be used, for example, to display another motif, or to apply other layers, such as a metal layer, and / or a protective layer.

[0140] Furthermore, a recessed area 20 can be shaped in such a way that it forms a text, individual symbols or the like.

[0141] Fig. 4 shows another possible embodiment of a safety element 1, in which the second structures 10 are shown oriented differently than the first structures 3, as indicated by their rotated arrangement or orientation 23.

[0142] For easier understanding, another possible example of the changed structural properties of the second structures 10, which are used to influence the optical properties of the optical effect layer, is shown schematically using the orientation shown.

[0143] The first structures 3 and second structures 10 can, for example, reflect rays which, under at least one viewing angle, interfere differently with the optical effect layer, so that an additional color can be generated.

[0144] Figure 4 shows a potentially independent embodiment of the safety element, using the same reference numerals and component designations for identical parts as in the preceding figures. To avoid unnecessary repetition, reference is made to the detailed description in the preceding figures.

[0145] Figures 5 a) and b) show a section of a possible embodiment of a safety element 1, wherein a possible motif is formed by means of the first areas 2 and the second areas 9. Further sub-areas 11 of the motif can be generated by means of the second areas 9, so that the visible sub-areas 11 of the motif appear in the third color 12 at the first viewing angle 5, and thus differ from the remaining, first areas 2, which appear in the first color 6 - according to a).

[0146] When the current viewing angle is changed to the second viewing angle 7 according to Fig. 5, b), the motif appears in the second color 8 due to the first areas 2. Those sub-areas 11 in which the second structures 10 of the second areas 9 are present appear in the fourth color 13 under the second viewing angle.

[0147] As indicated in Fig. 5, the fourth color 13 can correspond to the first color 6, and the third color 12 can correspond to the second color 8, thus allowing a reversal of the colors of the motif when changing from the first viewing angle 5 to the second viewing angle 7.

[0148] Furthermore, an outer boundary or outline of the motif can be formed by arranging at least the first structures.

[0149] Regardless of the embodiment shown, it can further be provided that the second areas 9 are completely surrounded by first areas 2.

[0150] Alternatively, a full-surface arrangement of the first structures 3 can be provided, and only a partial arrangement of the optical effect layer can be used to form this outer boundary of the motif, so that the further, outer structures are not covered by this optical effect layer.

[0151] Fig. 6, a) and b), shows a section of another possible embodiment of a safety element 1.

[0152] According to Fig. 6, b), a partial area 11 of an optical motif can be formed by means of the second area 9, so that the partial area appears in the third color 12 under the first viewing angle 5.

[0153] As can be seen further in Fig. 6, a), it can be provided that under the second viewing angle 7 the second structures 10 of the second area 9 do not interact with the optical effect layer, so that the affected part 11 of the optical motif does not appear in any additional color under the second viewing angle 7 and is therefore not recognizable in color within the entirety of the motif appearing in the second color 8.

[0154] With this measure, the part of the motif under the second viewing angle 7 can preferably not be recognized by an unarmed eye, whereby, by means of a viewing angle-dependent action of the second areas (with the optical effect layer), an additional structural change of the motif between the first and second viewing angle is possible, or a viewing angle-dependent addition of information within the motif.

[0155] Regardless of the embodiment, as can be seen in Fig. 6, the second viewing angle 7 can be designed as the angle perpendicular to the surface plane of the safety element 1, and the first viewing angle 5 as the viewing angle inclined more shallowly to the surface plane.

[0156] For the sake of completeness, it should be noted that a reversed arrangement of the viewing angles shown in the figures with respect to the visible third color (and optionally fourth color) is possible, in order to clarify that the invention is not limited to the inclinations of the first and second viewing angles shown in the exemplary embodiments. Reference numerals

[0157] Safety element

[0158] first area

[0159] first structures

[0160] optical effect layer

[0161] first point of view

[0162] first color

[0163] second perspective

[0164] second color

[0165] second area

[0166] second structures

[0167] sub-area

[0168] third color

[0169] fourth color

[0170] Surface level

[0171] absorber layer

[0172] spacer layer

[0173] Reflective layer

[0174] carrier layer

[0175] layer

[0176] recessed area

[0177] depth

[0178] Width

[0179] orientation

[0180] incline angle

Claims

Patent claims 1. Security element (1) in particular for securities, security papers or security items, such as banknotes, identity documents, credit cards, wherein the security element (1) has a first area (2) with optically effective, diffractive first structures (3) by means of which a generated overall impression appears achromatic, and the first area (2) is at least partially coated with an optical effect layer (4) such that the overall impression appears in a first color (6) under a first viewing angle (5) and appears in a second color (8) under a second viewing angle (7) different from the first viewing angle (5), characterized in that the safety element has a second area (9) with optically effective, diffractive second structures (10), wherein the second area (9) is also coated with the optical effect layer (4) and the second structures (10) are designed differently in their structural properties compared to the first structures (3) such that the overall impression in the second area (9) under the first viewing angle (5) appears in a third color (12) different from the first color (6).

2. Safety element (1) according to claim 1, characterized in that by means of the interaction of the second structures of the second area (9) with the optical effect layer (4) the overall impression in the second area (9) under the second viewing angle (7) appears in a fourth color (13) different from the second color (8).

3. Safety element according to claim 2, characterized in that the first color (6) is different from the fourth color (13).

4. Safety element (1) according to claim 1 or 2, characterized in that the structural properties of the second structures (10) are adapted to the first structures (3) such that the fourth color (13) of the second area (9)) under the second viewing angle (7) corresponds to the first color (6) under the first viewing angle (5).

5. Safety element (1) according to one of claims 1 to 4, characterized in that the second color (8) is different from the third color (12).

6. Safety element (1) according to one of claims 1 to 4, characterized in that the structural properties of the second structures (10) are adapted to the first structures (3) such that the third color (12) of the second area (9) in the first viewing angle (5) corresponds to the second color (8) under the second viewing angle (7).

7. Safety element (1) according to one of claims 1 to 6. characterized in that optical effect layer (4) is designed as a thin-film element and has at least one absorber layer and at least one spacer layer.

8. Safety element (1) according to one of claims 1 to 7 characterized in that one of the viewing angles, comprising the first viewing angle (5) and the second viewing angle (7), is arranged in an angular range of 65° to 95° with respect to a surface plane (14) of the safety element (1) and the other viewing angle is arranged in an angular range of 1° to 65°.

9. Safety element (1) according to one of claims 1 to 8, characterized in that an optical motif is displayed by means of the first area (9) and the second area (9) together.

10. Safety element (1) according to claim 9, characterized in that a partial area (11) of the optical motif is formed by means of the second area (9) such that the partial area (11) of the optical motif appears in the third color (12) under the first viewing angle (5).

11. Safety element (1) according to claim 10, characterized in that the second structures (10) of the second area (9) are adapted in their structural properties such that the second structures (10) interact with the optical effect layer (4) only under the first viewing angle (5), so that the partial area of ​​the optical motif is not recognizable in color under the second viewing angle within the overall impression appearing in the second color.

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