Optically variable display element

Abstract

The invention relates to an optically variable display element (12) having at least one reflective surface region (24) with at least two visually perceptible partial regions which display at least locally different colors when viewed in reflected light. It is provided that the at least one reflective surface region (24) is at least locally coated with a surface conformal interference layer structure (32) and that the reflective surface region (24) comprises a microrelief structure (26) in a first partial region and a second partial region, respectively, which produces a dynamic effect and is configured with a plurality of microrelief structure elements (34, 36). The microrelief structure (26) of the first partial region and / or the microrelief structure (26) of the second partial region is furthermore at least locally provided with a color-altering nanostructure (38) which is formed by at least one subwavelength structure. In the first partial region and / or the second partial region, the color effect of the interference layer structure is furthermore modified by the color-altering nanostructure (38) such that the first partial region and / or the second partial region display at least one of the different colors by the combined effect of the interference layer structure (32) and the color-altering nanostructure (38).

Description

Technical Field

[0001] This invention relates to an optically variable display element having a multi-color reflective surface area, which can be used as a security element to protect valuable items. The invention also relates to a data carrier having such a display element and a method for manufacturing such a display element. Background Technology

[0002] Data carriers, such as valuable documents or identification cards, and other valuable items, such as branded goods, are typically equipped with security elements for protection. These security elements allow verification of the data carrier's authenticity and simultaneously serve as protection against unauthorized copying. Security elements with viewing angle-dependent or three-dimensional appearance play a special role in authenticity protection because they cannot be copied even using the most modern copying equipment. For this purpose, security elements are equipped with optically variable elements that convey different image impressions to the observer at different viewing angles, and for example, display different color or brightness impressions and / or different graphic patterns depending on the viewing angle.

[0003] Since the 1980s, holographic gratings, typically with periods between 600 nm and 1500 nm, have been used as security features in banknotes and identity documents. For decades, they have shaped the optical appearance of these documents and ensured their anti-counterfeiting security. To achieve this, periodic structures can be used. One-dimensional or two-dimensional periodic structures (“holographic gratings”) with periods of approximately 400 nm to approximately 5 µm typically display a colorful “rainbow” effect.

[0004] Special optically variable effects can be produced, for example, by varying the grating period and / or azimuth angle. The parameters can be changed continuously or at least in small steps (e.g., to achieve a pumping effect). Larger structures also exhibit diffraction effects, but in practice these are only observable under largely directional illumination. In contrast to gratings with symmetrical profiles (sinusoidal gratings, rectangular gratings), blazed gratings have asymmetrical profile shapes (especially sawtooth profiles). Thus, for example, the intensity of light diffracted to the +1 diffraction order can be intentionally made greater than that diffracted to the -1 diffraction order, thereby enabling the production of asymmetrical displays.

[0005] However, in recent years, the security of imprinted holograms based on diffraction physics has declined significantly due to the increasing prevalence of equipment used in their manufacture, making them almost unusable for primary protection of valuable documents.

[0006] Therefore, instead of holograms, security features based on non-diffractive micro-relief structures, such as micromirrors or microlenses, are preferred. These features are significantly more difficult to forge and give valuable documents equipped with them a still unusual and novel appearance, while possessing a high degree of dynamism that quickly attracts attention.

[0007] In this regard, the use of multilayer thin-layer elements is also highly efficient and further enhances anti-counterfeiting security. The color impression of such multilayer thin-layer elements changes with the observer's viewing angle (hereinafter referred to as the angle-dependent color effect). In such thin-layer elements, the angle-dependent color effect is based on the interference effect related to the viewing angle caused by multiple reflections through the various sub-layers of the element. The optical path difference of the light reflected at different layers depends on the optical thickness of the dielectric spacer layer, which determines the spacing between the translucent absorption layer and the reflective layer, and also varies with the corresponding viewing angle. Since the optical path difference is on the order of visible light wavelengths, the observer obtains an angle-dependent color impression due to the destructive and constructive effects of specific wavelengths. By appropriately selecting the material and thickness of the dielectric spacer layer, various different angle-dependent color effects can be designed. As the number of layers increases, the color becomes more "pure" in the spectrum, i.e., the interference peak becomes narrower. Typically, there is a three-layer structure with an absorption layer, a dielectric layer, and a reflective layer, such as an absorption layer of Cr (approximately 5 nm), a dielectric layer of SiO2 (200-500 nm), and a reflective layer of Al (approximately 50 nm).

[0008] The top-view color and tilt color (and the corresponding perceived angle-dependent color variation) of a multilayer thin-film element are uniquely determined by the thickness of the dielectric spacer layer and the refractive index of the dielectric material. This means that the color of a multilayer thin-film element cannot be arbitrarily and independently chosen for different lighting conditions / tilt angles, but is inherently determined. Therefore, the number of physically achievable angle-dependent colors, i.e., color changes (e.g., gold / green; blue / red; magenta / green), is finite.

[0009] Furthermore, it is known that (see-through) security elements have multiple thin-layer components that appear in a first color when viewed in reflected light (i.e., in reflected light) and in a second color when viewed in transmitted light (i.e., in transmitted light). Document WO 2011 / 082761 A1 describes a thin-layer component with a multi-layer structure that appears gold when viewed in reflected light and blue when viewed in transmitted light. This multi-layer structure is based on two translucent mirror layers and a dielectric spacer layer disposed between these two mirror layers.

[0010] Micromirrors are small facets that reflect incident light essentially according to the laws of optics. They have a size significantly (about 10 times) larger than the wavelength of light, especially starting at about 5 µm. Therefore, their reflective behavior is largely achromatic. Micromirrors can be arranged periodically (“sawtooth gratings”) or aperiodically. Fresnel structures can also be composed entirely or partially of micromirror structures or approximated by micromirrors. Fresnel structures are produced by cutting arbitrarily shaped surfaces at a constant height. Thus, micromirrors can, for example, have curved cross-sectional shapes and three-dimensional shapes.

[0011] Micromirrors are typically rectangular, but can also be honeycomb (hexagonal) or arbitrarily shaped ("mosaic"). The surface of the micromirror is preferably designed to be planar with a defined tilt. At least the micromirror with the steepest tilt has a step height (>1µm) in its profile that is significantly greater than the wavelength. The tilt of the steepest micromirror is typically within the range of 20°, and in special designs even within the range of 10°.

[0012] The reflectivity or color of reflected light of this micro-relief structure can be determined by a coating, which can be, for example, a simple conformal metallization such as aluminum, or a high-refractive-index coating such as ZnS, or in the form of a multilayer interference layer structure.

[0013] The generation of viewing angle-dependent effects using micromirrors coated with multilayer interference layer structures is known, for example, from documents WO 2007 / 079851 A1, WO 2011 / 066991 A2, and WO2011 / 066990 A2. The color changes achievable with this security feature using the interference layer structure are limited. Color transitions occur gradually over a large angular range. Furthermore, the local registration between the embossing responsible for the dynamic effects and the interference layer structure generally depends on the printing precision of applying the etching resist or wash ink to the embossed structure. In other words, it is impossible to precisely match the pattern represented by the embossed structure with a specific color. Temporal and spatial synchronization of dynamic effects and colors is also impossible. Accordingly, the color changes induced by the interference layer structure occur gradually, independently of any dynamic effects, when the optically variable security element is tilted.

[0014] Recently, a more complex optically variable safety element was proposed, featuring two embossed structures arranged at different height levels, each with a colored coating (see WO 2020 / 011390 A1, WO 2020 / 011391 A1, and WO2020 / 011391 A2). The colored coating of the higher-level embossed structure is either structured as a grid or left open, so that when the safety element is observed, the colored coating of the lower-level embossed structure appears in the grid gaps or open spaces.

[0015] However, manufacturing a foil structure consisting of two overlapping embossed planes in the z-direction has proven to be extremely costly. The manufacturing cost is correspondingly high. Furthermore, embossings of different colors (on the two overlapping embossed planes) can only be aligned with each other to a limited extent. Typical tolerances are many tenths of a millimeter.

[0016] Alongside microstructures, optically variable security features have been developed over the years based on the use of nanostructures with typical subwavelength ranges, i.e., dimensions less than 400 nm. These nanostructures are structured in one or two dimensions, either in the form of regular subwavelength gratings or irregular structures, such as irregularly arranged protrusions or depressions on a base surface.

[0017] Subwavelength structures are so small that no first- or higher-order diffraction effects occur when light is incident perpendicularly. The structure size is smaller than the wavelength of light. Different effects are utilized in different structures: subwavelength gratings (also referred to as "zero-order gratings" in the literature) are one- or two-dimensional regular gratings with periods within the subwavelength range (≤400 nm) and produce color through specular reflection ("zero-order"). Subwavelength gratings with metallic coatings utilize plasmon effects to produce color. In gratings with dielectric (especially high-refractive-index) coatings, color is produced through another effect—resonant excitation of polaritons. The profile shape can be, for example, rectangular or sinusoidal.

[0018] Moth-eye structures are subwavelength structures that allow light to transition almost without reflection from one medium to another. In dielectric materials, such structures serve as "anti-reflective layers." These structures can be arranged regularly (periodically) or irregularly, and have a gradually tapering cross-section, or, for example, exist as binary rectangular structures. If moth-eye structures are deposited with metal, they appear very dark, especially black.

[0019] In the case of nanostructures regularly arranged in one- or two-dimensional gratings, resonance effects, such as plasmon excitation, typically lead to color phenomena because the transmission, reflection, and absorption of light incident on the grating spectrally depend on parameters characterizing the subwavelength grating in this respect, such as period, depth, profile shape, coating type, and coating thickness. In particular, the period can be used to set a specific color impression. Colors produced in this way and perceived by the observer are generally less vibrant and optically variable than those induced by diffraction at holographic gratings, tending instead towards paler shades and possessing a rather limited color space.

[0020] Furthermore, these colors can be observed over a wide angular range without significant color shift. When observed without a polarizer, the color impressions of subwavelength gratings based on plasmon resonances are generally very similar to almost identical, even when the rotation angle is changed within the structural plane, i.e., independent of azimuth.

[0021] The anti-counterfeiting security of nanostructures relies particularly on the fact that their fabrication requires high-resolution equipment and processes, such as those used in electron beam lithography. The nanostructures to be produced are, after all, an order of magnitude smaller than imprinted holograms. Furthermore, the various shaping steps used in foil fabrication—primarily occurring during the fabrication of the imprinting tool—must be performed with predictable shape fidelity so that the structure imprinted on the foil can be seen by an observer, for example, in the desired color.

[0022] Therefore, the measures described to date for generating colored displays based on structural colors in security features are particularly well-suited for use when superimposed with microstructures. Such structures are more expensive and difficult to manufacture than subwavelength gratings known in the prior art. The microstructures make an additional contribution to suppressing diffraction phenomena, since diffraction conditions—i.e., when incident light is diffracted to the observer—also depend on the orientation of the microsurface on which the subwavelength grating is placed. Furthermore, the microstructures provide dynamism, for example, in the form of motion effects and / or 3D effects, while the subwavelength grating provides the corresponding color.

[0023] Optical variable display elements having reflective surface areas are known, for example, from document WO 2022 / 242912 A1, whereby the reflective surface area, when viewed in reflected light, generates three-dimensional displays for at least two different viewing directions by means of reflective facets, and each of the three-dimensional displays has at least locally colors generated by subwavelength structures.

[0024] Finally, as is known, for example from document WO 2024 / 008238 A1, subwavelength structures that produce color or color effects are locally covered with spaced-apart translucent color layers to provide alternative color impressions. Summary of the Invention

[0025] Based on this, the technical problem to be solved by the present invention is to provide an optically variable display element with an attractive visual appearance, which has a large color space for displaying dynamic patterns, and ideally also has high anti-counterfeiting security.

[0026] The invention is defined in the independent claims. The dependent claims relate to preferred extended designs.

[0027] In a first aspect, the present invention relates to an optically variable display element having at least one reflective surface region having at least two partially visible regions that, when viewed in reflected light, at least partially display different colors, wherein...

[0028] -The at least one reflecting surface region is at least partially coated with a surface conformal interference layer structure.

[0029] - The at least one reflective surface region contains micro-relief structures in the first and second part regions, respectively. These micro-relief structures produce dynamic effects and are constructed with multiple micro-relief structural elements.

[0030] - The micro-relief structure in the first region and / or the micro-relief structure in the second region are at least partially provided with color-changing nanostructures, which are formed by at least one subwavelength structure, and

[0031] - In the first and / or second regions, the color effect of the interference layer structure is modified by the color-modifying nanostructure, such that the first and / or second regions display at least one of the different colors through the combined effect of the interference layer structure and the color-modifying nanostructure.

[0032] According to the present invention, the color impression of an interference layer structure is altered by locally different or partially present / absent color-modifying nanostructures. Combined with the light-deflecting micro-relief structure located beneath it, an observer thus perceives different image components of different colors from a specific viewing direction. This design also ensures precise spatial registration between color and embossed pattern, allowing for abrupt and decisive color changes upon tilting. Furthermore, a large color space is opened up for displaying the pattern. In particular, new color transformations and color combinations are achieved relative to known color transformations achievable with interference layer structures. Moreover, this concept allows color to be synchronized with dynamics, enabling changes in the pattern displayed upon tilting to occur simultaneously with color changes.

[0033] It goes without saying that some regions do not have to be connected, but can also be composed of individual, for example pixel-like sub-regions, which themselves can have an extended size below the visual resolution limit in at least one dimension.

[0034] In an advantageous design, the reflective surface region produces displays for at least two different viewing directions when observed in reflected light, wherein these displays at least partially overlap and at least locally differ in color within the overlapping region. Here, a micro-relief structure in the first portion and a micro-relief structure in the second portion generate one of these displays for the observer, and the first and second portions at least partially overlap each other, wherein the first and / or second portions further display at least one of the different colors of the displays through a combination of interference layer structures and color-modifying nanostructures.

[0035] To achieve partial overlap, the first and second partial regions are advantageously staggered. For this purpose, these partial regions are preferably formed by narrow, alternating, side-by-side strip-shaped sub-regions, or by small sub-regions that stagger each other in two dimensions. Here, the sub-regions advantageously have a size of less than 300µm, especially 100µm or smaller, especially 50µm or smaller, in at least one direction. Essentially, the staggering of the partial regions, or the resulting patterns, makes it more difficult for counterfeiters to imitate.

[0036] Particularly preferably, the micro-relief structure of the first part and / or the micro-relief structure of the second part are coated with a surface conformal interference layer structure in order to produce different colors in those areas designed to be nanoscale smooth, i.e., without nanostructures (for color modification or color generation).

[0037] In the regions not coated with a surface conformal interference layer structure, the micro-relief structure of the first region and / or the micro-relief structure of the second region are advantageously provided with color-generating nanostructures, especially subwavelength structures, to produce different colors, which exhibit colors substantially based on plasmon resonances, wherein the color-generating nanostructures are particularly coated with a metallization layer or a high-refractive-index material layer.

[0038] The dynamic effects produced by the micro-relief structure advantageously induce motion effects, especially movement effects, deformation effects, pumping effects, flipping effects, stereoscopic 3D effects, and / or three-dimensional displays of surfaces that protrude forward and / or recede backward relative to the actual spatial shape of the surface area for the observer.

[0039] Here, the display produced by a surface that protrudes forward and / or recedes backward is particularly understood as one in which certain areas can be perceived as continuously arched surfaces. In this sense, an arched display appears to simulate arching by mimicking the reflective behavior of an arched surface. This creates an impression of depth or 3D only indirectly. Therefore, this impression can also be called an embossed display.

[0040] Particularly preferably, the interference layer structure is at least partially designed such that the hue of the color produced by the interference layer structure and / or the hue of the color produced by the combined effect of the interference layer structure and the color-modifying nanostructure is color-stable when tilted from a vertical view up to 30° and preferably up to 45°. Thus, while the display element can exhibit abrupt color changes (caused by the micro-relief structure) when tilted, it will not exhibit the continuous color changes known in conventional multilayer interference layer systems, or at most, will exhibit them to a very small extent.

[0041] Here, the interference layer structure is advantageously designed, at least locally, such that when tilted up to 30° and preferably up to 45° from a vertical viewpoint, the hue angle h:

[0042] a) Starting with hues where the hue angle h is between 0° and 60° when viewed from above, change the angle to less than 60°, preferably less than 30°.

[0043] b) Starting with a hue angle h between 50° and 80° when viewed from above, change the angle by less than 30°, preferably less than 15°.

[0044] c) Starting with a hue angle h between 75° and 105° when viewed from above, change the hue angle by less than 30°, preferably less than 15°.

[0045] d) Starting with a hue angle h between 100° and 180° when viewed from above, change the angle by less than 80°, preferably less than 40°.

[0046] e) Starting with a hue angle h between 170° and 220° when viewed from above, change the angle by less than 50°, preferably less than 25°.

[0047] f) Starting with a hue angle h between 210° and 300° when viewed from above, change the angle by less than 90°, preferably less than 45°, or

[0048] g) Starting with a hue angle h between 290° and 10° when viewed from above, change the angle by less than 80°, preferably less than 40°.

[0049] When the hue angle h can be attributed to a hue that falls within the range of the two hue angles given above for vertical top view, the hue angle h preferably changes at most to the smaller of the given values ​​when tilted.

[0050] In an advantageous design, the interference layer structure is formed by a multilayer structure consisting of a dielectric layer and / or a metal layer, preferably by a three-layer thin-film element. As a three-layer thin-film element, angle-dependent color-changing systems with a semi-transparent metal layer / dielectric layer / metal reflective layer structure or a semi-transparent metal layer / dielectric layer / semi-transparent metal layer structure are particularly considered. Materials for the reflective layer, for example, aluminum, copper, and titanium; dielectric materials for the dielectric layer, for example, ZnS, MgF2, TiO2, Al2O3, and HfO2; and materials for the absorbing layer, for example, chromium, titanium, aluminum, and nickel.

[0051] Furthermore, the interference effect can also be achieved through a combination of dielectric layers and / or metal layers. Optionally, a metal layer with an overlying dielectric multilayer structure consisting of alternating low and high refractive indices can be applied to the micro-relief structure, or a metal layer with an overlying multilayer structure consisting of a translucent metal layer and a dielectric layer can be applied to the micro-relief structure. Preferably, the high refractive index layer is formed, for example, of ZnS or TiO2, and the low refractive index layer is formed, for example, of a polymer, SiO2, or MgF2.

[0052] Particularly advantageously, the interference layer structure is a three-layer thin-film element with a semi-transparent metal layer / dielectric layer / metal reflective layer structure, wherein the optical thickness of the dielectric layer is at most 250 nm, preferably at most 200 nm (here, "optical thickness" is understood as the product of the refractive index and the actual layer thickness), and this three-layer thin-film element exhibits maximum reflection only at the short-wavelength end of the visible spectrum when viewed from a vertical top position. Advantageously, the optical thickness of the dielectric layer is at most half the wavelength of blue light.

[0053] Also advantageously, the interference layer structure comprises a high refractive index dielectric having a refractive index greater than 1.8, preferably greater than 2.0, and particularly preferably greater than 2.3 throughout the visible spectrum or at least in a portion of the visible spectrum.

[0054] In another advantageous design, the interference layer structure is a double-layer color reflector (or double-layer color reflector), which consists of a reflective metal layer and an ultrathin absorption layer made of silicon, silicon alloy or SiOx (where x < 1) arranged on the metal layer.

[0055] It goes without saying that different layers or layer systems can be used in segments for interference layer structures.

[0056] Preferably, the micro-relief structure is formed by a micromirror arrangement structure having micro-relief elements in the form of directional reflective micromirrors (especially a micromirror arrangement structure having planar micromirrors, or a micromirror arrangement structure having segmented constant tilting micromirrors with curved profiles or variations in one or two directions, wherein the micromirrors particularly form periodic or non-periodic sawtooth gratings), by a Fresnel structure, by an arrangement structure of concave / convex arched micro-elements, and / or by a freeform surface.

[0057] Particularly preferably, the micro-relief structural elements are formed by directional reflective micromirrors, particularly by micromirrors having linear dimensions between 3µm and 100µm, preferably between 5µm and 50µm. The micromirrors may have triangular, square, rectangular, hexagonal, or other polygonal bases. The height of the micromirrors is preferably less than 15µm, more preferably less than 10µm.

[0058] Color-modifying nanostructures and / or color-generating nanostructures are advantageously formed by structures having lateral dimensions between 50 nm and 450 nm, particularly between 100 nm and 300 nm, and / or depths between 20 nm and 450 nm, particularly between 100 nm and 300 nm.

[0059] In one advantageous design, the subwavelength structures of the color-modifying nanostructures and / or color-generating nanostructures are formed by one-dimensional gratings, which may also have polarization effects. In different, equally advantageous designs, the subwavelength structures of the color-modifying nanostructures and / or color-generating nanostructures are formed by two-dimensional gratings, particularly those with rectangular, square, hexagonal, or parallelogram grating symmetry. These gratings have a period length between 100 nm and 600 nm, particularly between 50 nm and 450 nm, in at least one direction.

[0060] Because this design exhibits a stronger color effect than, for example, a subwavelength structure formed by a grating with square grating symmetry, at least under certain observation conditions, a design with hexagonal grating symmetry is preferred. In a hexagonal grating, the spacing between each structure (“nanodot” or “nanopore”) and its adjacent structures is the same in all spatial directions, whereas in a square grating, for example, adjacent structures arranged diagonally have a larger spacing than adjacent structures located at the position of the square grating.

[0061] As for the contour shape of the subwavelength structure, cross sinusoidal gratings, cross rectangular gratings (binary structures), hexagonal grating structures, or contour shapes with concave and / or convex segments are particularly considered. Periodic arrangements of nanopores or nanodots with arbitrary planar shapes can also be used. The color effect of the nanostructure depends on whether the structure exists in the form of convex (“nanodots”) or concave (“nanopores”).

[0062] In addition to regular arrangements, irregularly arranged structures (nanodots or nanopores) can also be used. These structures can be arranged, for example, randomly or quasi-periodically, particularly by offsetting them from predetermined grating positions in random directions by random values ​​(so-called jitter), and can be characterized by parameters such as lateral extension, planar shape, depth, and profile shape (e.g., binary or other shapes with concave and / or convex segments). Furthermore, the rotation of the structure can be locally altered, as can its lateral extension, depth, and profile shape. These structures can be arranged completely irregularly, with the areal density remaining approximately constant. Here, the rotation, lateral dimensions, depth, and profile shape of the nanodots / nanopores can also be locally altered. In principle, structures as described in documents EP 3 367 140 A1 and EP 3 401 712 A1 can also be used, the disclosures of which are incorporated herein by reference.

[0063] To produce different colors, it is preferable to provide at least two subwavelength structures that differ in the structural parameters that affect the color, wherein the structural parameters include at least one of the following parameters of the subwavelength structure: the period length, depth and / or contour shape of the subwavelength structure.

[0064] It has been proven advantageous to align the micro-relief structural elements, which are used for subwavelength structures of different colors, with the micro-relief structures of the reflective surface region, so that each micro-relief structural element is configured with only a specific type of subwavelength structure.

[0065] In a favorable extended design, the micro-relief structural elements are formed by micromirrors, and one or more structural parameters of the subwavelength structure that affect color vary as a function of parameters determining the micromirror orientation, particularly as a function of the specular slope or as a function of the azimuth angle. Thus, for example, an angular color variation effect can be produced when tilting (as a function of the specular slope) or a color change can be produced when rotating about the z-axis (as a function of the azimuth angle).

[0066] Therefore, for example, all upward-oriented micromirrors (“upward” here should be understood as the display element standing vertically in front of the observer) can be equipped with a subwavelength structure that results in the first color impression, and all downward-oriented micromirrors are equipped with another subwavelength structure or not equipped with a subwavelength structure, so that these micromirrors light up with a second color impression. When tilted about the corresponding axis, then depending on the tilt angle, either only the micromirrors of the first color light up, or only the micromirrors of the second color light up, thus creating a sudden color change between them.

[0067] According to a specific implementation variation, the mirror orientation of the microrelief structure can be randomly selected, and different subwavelength structures can be configured based on the orientation of the micromirrors (e.g., whether the mirror normal has an upward or downward tilt component). This results in a view that is generally equally bright at almost all tilt angles (but appears "noisy" on small length scales), yet exhibits abrupt color changes when tilted. The subwavelength structures can also be selected based on the mirror orientation in other ways. The color changes then appear accordingly in another (predefined) movement of the display element. For example, the corresponding subwavelength structures can also be selected based on the azimuth angle of the micromirrors, thus causing color changes when the display element rotates within its plane.

[0068] When observing display elements, colors visible to the observer can particularly include mixed colors. These mixed colors are produced by mixing colors from pixel-like sub-regions with sizes below the resolution limit of the human eye, where the colors of the pixel-like sub-regions are each generated by a specific type of subwavelength structure characteristic of that color. Here, the area proportion of the subwavelength structure in the pixel-like sub-region is selected such that the desired mixed color is produced.

[0069] In an advantageous extended design of the invention, the surface extension of the display element is defined in a z-direction perpendicular to the surface extension, wherein...

[0070] - The reflective surface region includes a primary structure in the form of a first embossed paint layer, the first embossed paint layer having a first embossed structure, the first embossed structure being formed by a first micro-relief structure in the micro-relief structure.

[0071] - The first embossed paint layer is partially covered by a secondary structure, resulting in a covered area with a secondary structure and a free area without a secondary structure on the first embossed paint layer, wherein the secondary structure is formed by a second micro-relief structure in the micro-relief structure, and

[0072] - The primary structure and / or the secondary structure are at least partially provided with color-changing nanostructures, such that the color-changing nanostructures are arranged on the secondary structure in the covered region and / or on the primary structure in the free region.

[0073] In various advantageous extensions of the invention, the surface extension of the display element is defined in a z-direction perpendicular to the surface extension, wherein

[0074] - The reflective surface region contains two structures, which are arranged at different height levels in the z-direction.

[0075] These structures are each formed by one of the micro-relief structures and have a color coating, wherein at least one of the color coatings is formed by an interference layer structure.

[0076] These two structures overlap in the reflective surface area, and the color coating of the structure at the higher position is designed in the reflective surface area as a regular or irregular grid with grid elements and grid gaps, such that in the reflective surface area, from at least one viewing direction, the color coating of the structure at the lower position is revealed to the observer through the grid gaps of the color coating of the embossed structure at the higher position, and

[0077] - At least one of the structures having an interference layer structure or having an interference layer structure has a color-changing nanostructure in at least a local portion.

[0078] Here, the first color coating in the color coating is suitably formed by an interference layer structure, and the second color coating in the color coating is formed by a metallization layer or another interference layer structure. Advantageously, the structure with the metallization layer has a nanostructure that generates color.

[0079] The display element is advantageously a security element for protecting valuable items, especially security lines, tear lines, safety belts, security strips, patches, or labels applied to or introduced into security paper, valuable documents, etc.

[0080] The present invention also includes a method for manufacturing an optically variable display element, particularly an optically variable display element of the type described above, wherein at least one reflective surface region is generated in the optically variable display element, the reflective surface region having at least two partially visible regions that, when viewed in reflected light, at least partially display different colors, wherein...

[0081] - The at least one reflective surface region is provided by forming micro-relief structures with multiple micro-relief structural elements in a first and second portion region that at least partially overlap each other, the micro-relief structures producing a dynamic effect, wherein...

[0082] - At least locally superimposed color-changing nanostructures on the micro-relief structure of the first region and / or the micro-relief structure of the second region, wherein the color-changing nanostructures are formed through subwavelength structures.

[0083] - The reflective surface area is at least partially coated with a conformal interference layer structure.

[0084] -In the first and / or second regions, the color effect of the interference layer structure is modified by the color-modifying nanostructure, such that the first and / or second regions display at least one of the different colors through the combined effect of the interference layer structure and the color-modifying nanostructure.

[0085] The display element according to the invention can be manufactured in such a way that additional imprinted security features are produced in the same working step. In particular, these can be optically variable security features, such as holograms, noisy or noiseless serrated structures (for producing flipped images, kinematic effects, 3D displays, etc.), microlens or microconcave mirror arrangements, or microlens or microconcave mirror images.

[0086] In another aspect, the present invention relates to an optically variable display element having at least one multicolor reflective surface region that produces at least one display when viewed in reflected light, wherein the at least one display has at least partially different colors, wherein

[0087] - The at least one multi-color reflective surface area includes a micro-relief structure that produces dynamic effects, especially stereoscopic 3D effects, and / or has a three-dimensional display of a surface that protrudes forward and / or recedes backward relative to the actual spatial shape of the surface area, and the micro-relief structure is constructed with multiple micro-relief structural elements.

[0088] - The reflective surface area is at least partially coated with a conformal interference layer structure.

[0089] - The micro-relief structure at least partially comprises color-changing nanostructures, which are formed by at least one subwavelength structure.

[0090] -and

[0091] - The color effect of the interference layer structure is modified by the color-modifying nanostructure, so that the multicolor reflective surface region displays at least one of the different colors through the combined effect of the interference layer structure and the color-modifying nanostructure.

[0092] In one advantageous design, the colors visible to the observer when viewing the display element include mixed colors, which are generated by mixing colors from pixel-like sub-regions with sizes below the resolution limit of the human eye, wherein at least two of the colors in the pixel-like sub-regions are generated by a specific type of subwavelength structure that is characteristic of the color in conjunction with the interference layer structure.

[0093] According to another advantageous design in this aspect, the display element displays a pattern with at least one curved display depending on the viewing angle. This curved display is visible as a predetermined curve at a central position within the display area from a first viewing direction, and moves away from the central position in different directions within the display area when the safety element is tilted about two different predetermined axes. Here, the reflective surface area in the display area is provided with a plurality of reflective planar micromirrors for displaying the curved display, and the background area is provided with a plurality of reflective planar micromirrors for displaying the background area, wherein the micromirrors in the display area and / or the micromirrors in the background area are provided with color-modifying nanostructures.

[0094] Of all the inventions mentioned, the micro-relief structural element can exist in the following advantageous design:

[0095] As micro-relief elements for microstructures, micromirrors, such as those described in documents WO 2007 / 079851 A1, WO 2011 / 066991 A2 and WO2011 / 066990 A2, the disclosures of which are incorporated herein by reference. Sawtooth gratings having a grating period between 2µm and 300µm, preferably between 3µm and 100µm, and particularly preferably between 5µm and 50µm, can also be used as micromirrors, wherein the transverse dimension in the longitudinal direction can reach several millimeters.

[0096] - In some design schemes, Fresnel-like structures can be used. These are created, for example, by horizontally cutting the surface relief to be imitated into segments, then removing the internal volume segments, and lowering the segments containing a portion of the surface to the base surface. Vertical cuts can also be used instead of horizontal cuts. Equidistant cuts are preferred, but variable spacing between adjacent cuts is also theoretically possible.

[0097] Alternatively, concave or convex arched micro-elements can be used in some designs, advantageously arranged regularly. Their lateral dimensions can range from 5µm to 300µm, preferably from 10µm to 100µm, and particularly preferably from 20µm to 50µm. The concave / convex arched micro-elements can be arranged one-dimensionally and form a periodic arrangement of grooved or ribbed elements. Preferably, they can also be arranged in a two-dimensional grid, where different grating types can be used, such as square, rectangular, rhomboid, hexagonal, or parallelogram gratings. Each micro-element can completely fill the feature face, for example, in the sense of a Wigner-Seitz cell. However, gaps can also exist between the individual micro-elements, for example, when circularly defined concave or convex spherical segments are arranged on a hexagonal grating.

[0098] - As a micro-relief element of a microstructure, micromirrors, for example, those described in pending German patent applications DE 10 2024 128 848.5 and DE 10 2025 107 278.7, the disclosure of which is incorporated herein by reference. In particular, the micromirror can be designed to have a constant tilt in a first direction and a (continuous) curvature in a second direction. Alternatively, the micromirror can exist in a manner having (continuous) curvature in two mutually perpendicular directions. Here, the curved profile can be designed as a convex profile, a concave profile, or a profile that is partially convex and partially concave. Instead of a curved profile, the micromirror can also have a varying, segmented, constant tilt.

[0099] - As a micro-relief structure, arbitrary free-form surfaces can also be used, in which the morphology varies locally on a scale of a few micrometers to several hundred micrometers. Depending on the optical effect to be achieved, surface segments tilted in a specific spatial direction can be uniformly distributed. Alternatively, certain directions can be emphasized at the expense of other directions. In this way, for example, a matte effect can be produced by uniformly radiating or preferably deflecting the incident light within a predetermined solid angle range.

[0100] - It is also conceivable, and advantageously possible, to combine the micro-relief structures mentioned so far in the various surface areas of the display element.

[0101] In all the aspects of the invention mentioned, color-modifying nanostructures and / or color-generating nanostructures can exist in the following advantageous design:

[0102] - The shape of a single subwavelength structure existing as nanodots or nanopores in a top view can be circular, elliptical, square, rectangular, hexagonal, cross-shaped, star-shaped, approximately circular, elliptical, square, rectangular, hexagonal, cross-shaped, star-shaped, and / or generally formed by polygonal contours. Elliptical and rectangular nanodots / nanopores typically have different resonant frequencies in the longitudinal and transverse directions, making them preferably excited by light of different wavelengths in these two directions. Therefore, for these geometries of nanodots / nanopores, the spectral absorption, reflection, and transmission properties generally depend on the polarization state of the excitation light wave relative to the orientation of the nanodot / nanopore. The color effect of the nanostructure depends on whether the structure exists in the form of a protrusion (“nanodot”) or a depression (“nanopore”). Scanning electron microscope images of the subwavelength structures according to the invention with red or magenta color effects are shown in... Figure 11 As shown in (a), nanodots are arranged in a grating with hexagonal grating symmetry. Figure 11 (b) shows a scanning electron microscope image of another subwavelength structure according to the invention with a green color effect.

[0103] - Individual structures existing as nanodots or nanopores in subwavelength structures can exist in cross-section with one of the following profile shapes: binary (“Manhattan”), sinusoidal or quasi-sinusoidal, conical or truncated conical. The cross-sectional profile of the structure can be approximated by a Gaussian function or any other continuous function. Depending on the fill factor, constant or approximately constant orientations can also be obtained between nanodots / nanopores.

[0104] The shape of nanodots / nanopores arranged regularly or irregularly in a one-dimensional or two-dimensional grating can vary locally, for example, in terms of cross-sectional profile or top view shape.

[0105] Nanostructures can also very strongly enhance or reduce the brightness of interference layer structures or metallization layers. In extreme cases, they can produce near-black or white colors. Structures with random arrangements and high aspect ratios are particularly suitable for producing very dark colors.

[0106] Of all the inventive aspects mentioned, the micro-relief structure and color-modifying nanostructure and / or color-generating nanostructure can exist in the following advantageous design schemes:

[0107] - Micro-relief structures and subwavelength structures can each exist entirely within a specific pattern area.

[0108] - The display may contain a pattern and a background, respectively. In at least one display, the color effect of the pattern and / or background can be produced by the combined action of an interference layer structure, particularly designed to be color-stable, with at least one subwavelength structure. The pattern and / or background within a view may be formed in different colors and / or in multiple colors, respectively.

[0109] - Micro-relief structural elements and subwavelength structures can each exist within a large number of pixels indistinguishable to the naked eye. Pixels can have arbitrary shapes, such as squares, rectangles, hexagons, or strips (quasi-one-dimensional). Preferably, pixels are arranged to cover the entire surface, and pixels can also exist in different pixel shapes. The size of the pixels is preferably below the resolution of the human eye, and less than 300µm in at least one direction, preferably less than 100µm, and particularly preferably less than 50µm.

[0110] - The micro-relief structural elements within a pixel are preferably identical. In the case of micromirrors, these micromirrors preferably have the same orientation (mirror slope and azimuth angle) within the pixel.

[0111] - The subwavelength structures within a pixel preferably have the same structural parameters and uniformly fill the pixel, so that the pixel appears in a uniform color. In larger areas (patterned areas), the structural parameters of the nanostructures can be constant (e.g., a monochromatic arched pattern) or spatially varied (e.g., color gradients or patterns with multiple different colors). Variations in color intensity can be achieved by changing the pixel size and / or pixel density.

[0112] - Preferably, the pixels of the micro-relief structure and the pixels of the subwavelength structure are correlated with each other and, for example, stacked one on top of the other, respectively. In this case, a micro-relief structure element with a specific orientation is associated with a subwavelength structure of a specific color, such that light reflected from the micro-relief structure element into a predetermined solid angle range displays the color determined by the subwavelength structure (if necessary, in conjunction with the interference layer structure).

[0113] Color gradations across microrelief structures can be achieved by continuously changing one or more structural parameters characterizing the subwavelength structure. Alternatively, color gradations can also be generated using rasterization. The color gradations can optionally be synchronized with dynamic effects produced by the microrelief structure, such as motion effects.

[0114] While in the case of plane mirrors (to avoid color mixing and produce a uniform color effect), it is suitable to uniformly configure the entire mirror surface with subwavelength structures, micromirrors with curved profiles or micromirrors with varying, segmented, constant tilts possess the characteristic of reflecting light in different directions depending on the tilt of the mirror surface. In other words, a single micromirror has multiple different tilts and therefore multiple reflection directions. Thus, multiple tilts can advantageously be divided into two or more segments, where at least one segment contains a subwavelength structure that differs in at least one parameter affecting color (the period length, depth, and / or contour shape of the subwavelength structure), and thereby is equipped with a color effect different from other segments. When the display element is tilted, a color change along the curve can be produced in this way, which is equivalent to a color flip.

[0115] In the case of micromirrors with curved profiles, at least one parameter of the subwavelength structure that affects color can vary continuously depending on the tilt along one or both curvature directions. This continuous variation in structural parameters results in a continuous variation in color effect according to the reflection direction.

[0116] The display element according to the invention can be combined with other security features. For example, the display element can additionally have information in the form of patterns, characters, or codes, formed by uncoated areas within a surface region or by areas left empty within a coating. The micro-relief structural element can also be combined with holographic or quasi-holographic diffraction structures, with noisy or noiseless sawtooth structures (for producing flipped images, kinematic effects, 3D displays, etc.), microlens or microconcave mirror arrangements, and / or microlens or microconcave mirror images. For example, interleaved combinations with holograms, especially true-color holograms or kinegram images are possible.

[0117] The display element according to the invention may further include machine-readable features, particularly the introduction of phosphorescent, fluorescent, or other luminescent materials, polarization-dependent effects, specifically set conductivity (particularly through specifically set metal layer thickness), other angle-dependent color effects (e.g., based on angle-dependent color pigments), or colored imprinted paint. By appropriately combining the display element according to the invention with magnetic materials, for example by introducing a magnetic layer or combining it with magnetic ink, particularly machine-readable magnetic properties can also be provided.

[0118] The present invention also includes a data carrier having a display element of one of the described types. This data carrier may in particular be a valuable item or document, such as banknotes, especially paper banknotes, polymer banknotes, or foil composite banknotes, and may be stocks, bonds, certificates, vouchers, checks, high-value tickets, but may also be identification cards, such as credit cards, bank cards, cash payment cards, authorization cards, identity cards, or passport personal data pages.

[0119] The data carrier can be, in particular, a paper banknote having a substrate made of paper, especially cotton paper; a polymer banknote having a substrate made of plastic material; or a foil composite banknote. Of course, paper can also be used as the substrate for the data carrier, containing a polymer material in a proportion x ranging from 0 to x < 100% by weight. If the data carrier is a substrate made of plastic material, plastic foil made of polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene (PP), or polyamide (PA), or a single-layer composite substrate made of these plastic materials, is particularly preferred. Furthermore, the substrate can be designed as a multi-layer foil composite, particularly as a composite of various different plastic foils (composite material composite) or a paper-foil composite (foil / paper / foil or paper / foil / paper), wherein security elements can be disposed in, on, or between each layer of such a multi-layer composite. Attached Figure Description

[0120] The invention is further illustrated below with reference to the accompanying drawings, which also disclose the essential features of the invention. These embodiments are for illustrative purposes only and should not be construed as limiting. For example, the description of embodiments having multiple elements or components should not be construed as implying that all such elements or components are necessary for implementation. Rather, other embodiments may include alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different embodiments may be combined with each other unless otherwise stated. Modifications and variations described with respect to one embodiment may also be applied to other embodiments. To avoid repetition, identical or corresponding or functionally equivalent elements in different figures are indicated by the same reference numerals and are not repeatedly described. In the drawings:

[0121] Figure 1 A schematic diagram of a banknote having an optically variable security element according to a first aspect of the present invention is shown;

[0122] Figure 2 schematically shown Figure 1 A cross-sectional view of the structure of the safety element;

[0123] Figure 3The reflectance spectra are shown for different observation conditions at a three-layer thin-film element with an angle-dependent colorimetric structure having a MgF2 dielectric layer;

[0124] Figure 4 The effect of the refractive index of the dielectric layer material of a three-layer thin-film element that appears blue-green in a vertical top view on the hue angle H as a function of the incident angle is shown.

[0125] Figure 5 The reflectance spectra are shown for different observation conditions at a three-layer thin-film device with an angle-dependent colorimetric ZnS dielectric layer.

[0126] Figure 6 The effect of the refractive index of the dielectric layer material of a three-layer thin-film element that appears blue-red in a vertical top view on the hue angle H as a function of the incident angle is shown.

[0127] Figure 7 The reflectance spectra are shown for different observation conditions at a three-layer thin-film element with an angle-dependent colorimetric structure having a MgF2 dielectric layer;

[0128] Figure 8 The effect of the refractive index of the dielectric layer material of a three-layer thin-film element that appears purple in a vertical top view on the hue angle H as a function of the incident angle is shown.

[0129] Figure 9 The reflectance spectra calculated for different observations are shown in the double-layer interference layer system with an ultrathin silicon absorption layer;

[0130] Figure 10 The effect of the refractive index of the dielectric layer material of a three-layer thin-film element that appears blue-red in vertical top view on the hue angle H as a function of the incident angle is shown, or the corresponding effect of a two-layer color-reflecting mirror that appears blue-red in vertical top view on this change.

[0131] Figure 11 (a) shows a scanning electron microscope image of a subwavelength structure according to the invention with a red or magenta color effect, and (b) shows a scanning electron microscope image of another subwavelength structure according to the invention with a green color effect.

[0132] Figure 12 A scanning electron microscope image showing the micromirror arrangement structure according to the present invention is shown;

[0133] Figure 13 Reflectance spectra for different observation conditions are shown in (a) to (h) at three-layer thin-film elements with and without nanostructures, with or without dielectric layers of different optical thicknesses.

[0134] Figure 14Reflectance spectra for different observation conditions are shown in (a) to (h) at three-layer thin-film elements with dielectric layers of different optical thicknesses, with or without another nanostructure;

[0135] Figure 15 A diagram of the CIELAB color space is shown, in which the color coordinates of the reflectance spectrum of the selected structural color are plotted.

[0136] Figure 16 A first view and a second view of a safety element according to another embodiment of the first aspect of the present invention are shown;

[0137] Figure 17 A first view and a second view of a safety element according to another embodiment of the first aspect of the present invention are shown;

[0138] Figure 18 A first view and a second view of a safety element according to another embodiment of the first aspect of the present invention are shown;

[0139] Figure 19 The visual appearance of the relief pattern according to the second aspect of the invention is shown, wherein pixel-like sub-regions are shown in the enlarged partial detail view;

[0140] Figure 20 Different views are shown of a planar patterned area with a circular curve floating below the patterned area;

[0141] Figure 21 A portion of a safety element having a structure arranged at different height levels is schematically shown according to another embodiment of the first aspect of the invention; and

[0142] Figure 22 A portion of a safety element having a primary structure and a secondary structure is schematically shown according to another embodiment of the first aspect of the present invention. Detailed Implementation

[0143] The present invention will now be described using a security element for banknotes as an example. Figure 1 A schematic diagram of a banknote 10 showing an optically variable security element 12 in the form of an adhesive transfer element is shown. However, it is self-evident that the invention is not limited to transfer elements and banknotes, but can be used for all types of security elements, such as labels for goods and packaging, or for protecting documents, identity cards, passports, credit cards, health cards, etc. In the case of banknotes and similar documents, in addition to transfer elements (e.g., patches or strips with or without their own carrier layer), security threads or security strips are also contemplated, for example.

[0144] Reference Figure 1The security element 12 applied to the banknote 10 is designed to be very flat, but it presents a three-dimensional view to the observer from at least two different viewing directions 42, 44. This three-dimensional display creates the impression of a pattern that appears to arch out from the plane of the banknote 10. The mimicry of the reflective behavior of the arched pattern is achieved here through directional reflection. The two three-dimensional displays overlap each other and are at least partially different colors, resulting in a visually striking flipping or tilting effect when the viewing direction is changed, in which the color and pattern of the three-dimensional display change simultaneously at the same location in the security element 12.

[0145] Specifically, safety element 12 can, for example, serve as the first view when viewed from the left. Figure 20 The face value number 14 (“50”) is displayed in yellow against a flat yellow background, appearing to arch three-dimensionally, and serves as a second view when viewed from the right. Figure 20 The security element 12 appears as a three-dimensional, arched star 16 against a flat blue background. When the viewing direction is changed or the banknote 10 is tilted from left to right 18, the appearance of the security element 12 switches between a first view (with a three-dimensional yellow denomination number 14) and a second view (with a three-dimensional blue star 16). These two three-dimensional patterns 14, 16 also appear to overlap with each other in the same location within the security element 12, as seen by each viewer. Figure 20 , 20 As implied by the outlines of the corresponding pattern 14' and 16' drawn with dashed lines in the middle.

[0146] Therefore, the security element 12 exhibits a tilting behavior in which two different colored patterns are visible to an observer from two viewing directions at the same location (“pattern flipping”), and the pattern transformation during tilting is associated with a simultaneous color transformation. This tilting effect is visually appealing and easy for users to remember. It also provides high anti-counterfeiting protection because the effect is practically impossible to replicate with conventional printing presses, for example, by overprinting translucent colored inks onto a reflective embossed structure, as registration between the reflective elements and their corresponding colors is required in different pattern views.

[0147] As will be shown in the subsequent description of the structure of the safety element according to the invention, only one imprinting and one coating with the interference layer structure are required, and there is no need to use an additional colored layer.

[0148] Figure 2The structure of the safety element 12 is schematically shown in a cross-section. An embossed paint layer 22 is applied to the carrier substrate 28, in which an embossed structure in the form of a micromirror arrangement 26 is embossed in the surface region 24. The micromirror arrangement 26 has a coating in the form of a thin-layer element 32, for example, a three-layer structure consisting of an absorption layer (4nm chromium), a dielectric layer (150nm SiO2), and a reflective layer (60nm Al). For clarity, this coating is shown in... Figure 2 It is shown only schematically.

[0149] As described in detail below, the micromirror arrangement structure 26 includes two sets of micromirrors 34 and 36, which are tilted relative to the plane of the surface region 24, respectively, so that they respectively mimic the view of observer 40 observing from two observation directions 42 and 44. Figure 20 , 20 The reflective behavior of these views is such that they have three-dimensional patterns of face value numeral 14 and star shape 16, respectively. Each micromirror 34, 36 here has a lateral dimension between 5µm and 50µm, and therefore has, for example, a square base of 10µm x 10µm, and is therefore not recognizable to the observer.

[0150] Visuals with patterns 14 and 16 Figure 20 , 20 The different color effects are produced by conformally coating the micromirror arrangement structure 26 (overall) with thin-layer element 32 and by superimposing subwavelength structure 38 on the micromirror 34, such as... Figure 2 The modulation of the micromirror arrangement structure using the coated subwavelength grating g1 is shown only in detail figure 30, while the overall orientation of the stepped profile of the height function can be seen in the unmagnified relief profile.

[0151] The color produced by the combined effect of the subwavelength structure 38 and the thin-film element 32 in reflection can be set by selecting structural parameters, particularly the grating period and structural depth. The grating period of the subwavelength structure is preferably between 50 nm and 450 nm, and in this embodiment, it is 250 nm, thus below the wavelength of visible light. The structural depth is preferably between 100 nm and 300 nm, and in this embodiment, it is 120 nm. In this embodiment, the subwavelength structure is arranged within a hexagonal grating.

[0152] By modulating the micromirror arrangement structure with a subwavelength structure, the relief structure 26 can be subdivided into multiple micromirrors 34 and 36 as a coarse structure, and the micromirror 34 can be modulated with a subwavelength structure 38 as a fine structure of the relief structure 26.

[0153] For the desired color effect, the height function is superimposed with a grating function describing the relief profile of the subwavelength grating g1. Specifically, for example, in the first view... Figure 20 The height function is modulated using a subwavelength grating function g1, which, in conjunction with thin-layer elements, is designed to produce a yellow reflective color. Second view Figure 20 The height function is nanoscale smooth. The micromirror 36 used for this view has only a coating in the form of a thin-layer element 32. The relief structure containing the micromirror and one or more subwavelength structures can be produced in a single imprinting step with the advantage of precise arrangement of each other. Further details regarding the fabrication of the coarse structure are referenced in WO 2014 / 060089 A2, the disclosure of which is incorporated herein by reference.

[0154] As will be elaborated further below, the thin-layer element with a relatively thin dielectric layer is designed to be color stable and thus exhibits a blue hue that remains substantially unchanged when tilted. This blue hue appears yellow when viewed from above due to the effect of the subwavelength structure 38 superimposed on the micromirror 34. The combination of the color-stable thin-layer element and the subwavelength structure allows for a sudden angle-dependent color change effect (from yellow to blue / purple) when combined with the micromirror arrangement. When viewed from the back side, the interference layer structure appears purple in the nanostructured regions.

[0155] Essentially, the reflection spectrum and / or color coordinates of the interference layer structure can be tuned to obtain a color-stable coating. This can be achieved, for example, by selectively varying the thickness of individual sublayers, particularly the dielectric layer. The reflection spectrum and / or color coordinates can be calculated in advance using known models or determined experimentally through a series of experiments.

[0156] In practice, a common disadvantage is that, in addition to the primarily desired color difference (i.e., caused by locally different nanostructures), other color variations can occur depending on the tilt angle and lighting conditions, especially since the coating itself present on the nanostructures causes color changes when tilted. Precisely when used as a security feature, the observer should be able to visually verify the authenticity of the banknote by observing the observable optical effects without detailed knowledge and extensive training.

[0157] Given that complex color change scenarios are difficult to describe directly and therefore difficult to verify when observation and lighting conditions change, it is advantageous for the operation of the optically variable safety element to produce different colors, with or without the subwavelength structure, as "color-stable" as possible. This means that the color changes as little as possible within the typical viewing angle range, for example, about + / -45°, when the safety element is tilted, and especially without deviating from the (basic) hue (e.g., "red," "blue," "green," and corresponding levels, such as "orange-red," "indigo," "yellow-green") present in a vertical, top-down view. Contrary to the original purpose of the interference coating (i.e., to produce the fastest and most striking color changes possible), the present invention therefore also aims to determine an interference layer structure that exhibits the smallest possible color change when observation and lighting conditions change.

[0158] However, in other advantageous implementation variations, it may be desirable for the color in one region (with or without nanostructure) to change significantly upon tilting, while the color in other different regions remains constant within that tilt angle range. Thus, for example, a yellow pattern against a blue background could change color upon tilting, while the background color remains unchanged or changes only slightly.

[0159] In existing technologies or in currently available "Colourshift" products or angle-dependent color thin-film elements, chromium is mostly used as the absorbing layer, aluminum as the reflecting layer, and MgF2 or SiO2 as the dielectric layer, with the latter two having relatively low refractive indices, slightly below and slightly above 1.4, respectively. The interference colors exhibited by such thin-film elements change relatively strongly when tilted. As an example, a color change from green to magenta can be mentioned, which can be achieved, for example, with a layer system consisting of a 5 nm thick chromium absorbing layer, an approximately 565 nm thick MgF2 dielectric layer, and an aluminum reflecting layer. Figure 3 The reflectance spectra of the layer system are shown as exemplarily calculated for vertical observation and at tilt angles of 45° or 60°.

[0160] The green hue in a vertically tilted view is attributed to a strong reflectance maximum in the green wavelength range of approximately 550 nm. As the tilt increases, this maximum shifts towards shorter wavelengths, while another maximum at the upper end of the wavelength range enters the visible spectrum. Therefore, the hue changes from green in a vertically tilted view through blue to magenta (at a 45° tilt angle).

[0161] The changes in the spectrum also correspond to changes in the hue angle H, which can be calculated from the spectrum and increases from 140° at vertical incidence to slightly over 300° at a 45° tilt angle.

[0162] The HSV color space is a color space used in many color models where colors are defined by hue, saturation, and value (or darkness). To describe the color coordinates in this color space, the following parameters are used: hue is expressed as the hue angle H on the color wheel (e.g., 0° = red, 120° = green, 240° = blue); saturation S is expressed as a percentage (0% = neutral gray, 50% = low saturation, 100% = saturated pure color) or in a range of zero to one; and value V (also called darkness) is expressed as a percentage (0% = no lightness, 100% = full lightness) or in a range of zero to one. Table 1 below provides examples of some colors and their corresponding values ​​in the HSV color space.

[0163] Table 1

[0164]

[0165] Therefore, the change in hue angle H from 140° to 300° when the aforementioned thin-film element is tilted corresponds to a distinct color change from green (roughly “light blue-green” in Table 1) through blue to magenta.

[0166] If a material with a higher refractive index, such as SiO2, HfO2, or ZnS (increasing in this order) is used instead of MgF2, but with approximately the same optical thickness, such that the same hue is obtained when viewed from above with a hue angle H = 140°, then the color or hue angle H changes to varying degrees depending on the material used as the dielectric layer when tilted.

[0167] To further explain, Figure 4 This illustrates the effect of the refractive index of the dielectric layer material of a three-layer thin-film element that appears blue-green in a vertical top view on the change of hue angle when tilted. (As shown from...) Figure 4 The curve shows that SiO2, as a dielectric with a relatively low refractive index, still causes a very strong color change at a tilt angle of 45° (given by the angle of incidence), with a hue angle of approximately H = 270° (purple), although this change is not as pronounced as when using MgF2 as the dielectric. However, when using high-refractive-index dielectrics HfO2 (refractive index approximately 2.0) and ZnS (refractive index approximately 2.4), the change is significantly smaller: here, the hue angle H increases only from H = 140° to approximately H = 160° as the tilt angle increases from 0° to 45°—therefore the color remains green, changing only slightly from light blue-green to cyan (see Table 2).

[0168] Table 2

[0169]

[0170] The color produced by the aforementioned high-refractive-index dielectrics is likely to be perceived as green by most observers over the entire tilt angle range between +45° and -45° and remains virtually unchanged. Up to a tilt angle of 30°, the color change is even smaller for high-refractive-index dielectrics (HfO2, ZnS), with a hue angle change of only about 10°, and is therefore almost imperceptible.

[0171] One reason for the significantly smaller color changes observed when using high-refractive-index dielectrics such as ZnS is that the shift of the reflection spectrum towards the shorter wavelength region with increasing tilt angle is significantly smaller. For example, from... Figure 5 The calculated reflectance spectra for tilt angles of 0°, 45°, and 60° show that the maximum reflectance in the green band shifts only slightly more than 20 nm into the shortwave region when tilted from 0° to 45°. In contrast, when using MgF2 as the dielectric, the maximum reflectance shifts by approximately 75 nm at the same tilt angle.

[0172] Similar behavior can be determined for other colors produced using this three-layer interference system: the higher the refractive index of the dielectric, the smaller the color change when tilted.

[0173] Figure 6 As another example, the effect of the refractive index of the dielectric layer material of a three-layer thin-film element that appears blue and red according to Table 1 in a vertical top view on the calculated change in hue angle H when such an interference layer system is tilted is shown. For the calculation, the following layer thicknesses were assumed: MgF2: approximately 460 nm; SiO2: approximately 440 nm; HfO2: approximately 330 nm; ZnS: approximately 280 nm.

[0174] The hue angle H when viewed vertically or at a 45° tilt angle can be obtained from Table 3 below.

[0175] Table 3

[0176]

[0177] Reference Figure 6 And as shown in Table 3, the color or hue angle changes are much smaller when using high-refractive-index materials as dielectrics. While MgF2, as a dielectric, causes the hue angle to change from H = -30° (hue angle -30° corresponds to hue angle +330°) to slightly above H = 100° at tilt angles between 0° and 45°, meaning the color changes very noticeably from blue-red to approximately yellow-green upon tilting, the hue angle of HfO2 only changes from H = -30° to H = 10°. According to Table 1, this corresponds to a color change from blue-red to orange-red. Therefore, it doesn't actually leave the reddish color range upon tilting. When using ZnS as a dielectric, the change in hue angle H is less than approximately 30°, or even smaller.

[0178] According to the invention, another measure for producing very angularly stable color is to choose the dielectric layer thickness of the three-layer thin-film element to be so small that constructive interference for blue light still occurs in the layer system. This behavior typically occurs when the optical thickness of the dielectric is slightly less than 250 nm. Such a layer system exhibits a maximum reflectance in the visible spectrum only at the short-wavelength blue (violet) end when viewed vertically from above, which shifts further into the (invisible) UV region when tilted (see...). Figure 7 ).

[0179] This results in no new color being produced upon tilting; instead, the layered system essentially becomes darker. This effect was also observed in all the dielectrics studied, i.e., materials with both high and low refractive indices. This is in Figure 8 As shown in the figure. Thus, for example, for tilt angles of 0° and 45°, the following values ​​are obtained for the selected dielectric:

[0180] Table 4

[0181]

[0182] As a result, even when using MgF2 as the dielectric, the hue angle H changes only from approximately H = -82° (violet / blue magenta) to H = -72° (blue magenta) as it tilts from 0° to 45°. Therefore, using this layer system, even with a dielectric of relatively low refractive index, at least blue / violet hues can be produced, which are very color-stable and can be advantageously combined with other hues modified by subwavelength structure according to the invention.

[0183] Particularly observed in layer systems with very thin dielectric layers and angle-stable colors, even when the interference layer system is set on a nanostructure, very angle-stable colors can be obtained. As detailed below, for example, using a SiO2 dielectric (refractive index 1.46) with a layer thickness of 150 nm and a subwavelength structure according to Example 1 (hexagonal grating, period = 250 nm, approximately sinusoidal profile, depth = 120 nm, fill factor = 0.5), the (top view) blue of this interference layer system can be changed to a similarly very color-stable yellow / orange hue.

[0184] By setting up areas with and without nanostructures, novel color combinations can be created. These color combinations, combined with micro-relief structures that induce dynamic effects, can even achieve sudden, unusual, angle-dependent color effects.

[0185] Color stability can also be achieved by using a thin semiconductor layer, such as silicon, with a thickness between 3 nm and 100 nm on the metal layer. Further details regarding the color effect produced by such a color-reflecting mirror can be found in document WO2016 / 188619 A1, the disclosure of which is incorporated herein by reference.

[0186] Within the scope of this invention, this layer system stands out particularly for its very small color change upon tilting. Thus, for example, an approximately 85 nm thick Si layer on an Al reflective layer can produce a bluish-red hue when viewed from above, with a hue angle of H = 330° (or -30°), a hue that changes even less upon tilting than the change observed above for a three-layer thin-film element with a very high refractive index, ZnS. Here, the very small color change upon tilting is also attributed to the very high refractive index of Si, which is approximately 4 in the visible spectrum. In contrast to ZnS, Si has shown significant absorption in the visible spectrum.

[0187] This is Figure 9 As shown in the image. Figure 9 The reflection spectra of the Si / Al colorimetric mirror layer system are shown in vertical top view and at tilt angles of 45° and 60°. Even at a tilt angle of 90°, the reflection spectrum changes very little compared to the vertical top view. Converting the reflection spectrum to hue angle H yields... Figure 10 The changes shown are illustrated.

[0188] The corresponding values ​​for the selected tilt angles are given in Table 3 above, from which it can be seen that the hue angle H in this layer system changes by only about 10°. This change in hue angle or color transformation is almost imperceptible in practice and is significantly smaller than that when using the three-layer system with different dielectrics described above, which is also shown or given in Table 3 for comparison.

[0189] By using a three-layer structure of a semi-transparent metal layer / dielectric layer / semi-transparent metal layer, even with a small dielectric layer thickness, it is possible to produce colors that exhibit minimal color change and, in particular, color stability when tilted.

[0190] The layer systems shown in Table 5 below demonstrate this effect, in which a SiO2 dielectric is arranged between two translucent aluminum layers having a thickness between 3 nm and 20 nm, preferably between 5 nm and 15 nm, and particularly preferably about 10 nm.

[0191] Table 5

[0192]

[0193] These thin-layer elements are also colored, especially in transmitted light, and their color is essentially stable when tilted, or at least shows only small color changes. This type of interference layer system is described, for example, in document DE 10 2009 041 583A1, the disclosure of which is incorporated herein by reference.

[0194] Here, it has proven particularly advantageous to present a golden layer system when viewed from above. This color appears especially noble, and an attractive, rich blue can be seen in transmitted light (in areas without nanostructures). The golden color when viewed from above transforms into an almost colorless metallic hue when tilted, thus advantageously avoiding any striking color change when tilted.

[0195] For the discussion below, the color display or color name correspondences given in Table 1 above will be converted to the CIELCh color system or hue angle h. To this end, Table 1 is supplemented with another column containing the corresponding LCh values:

[0196] Table 6

[0197]

[0198] In the examples described below, the subwavelength structures exist in the form of depressions (“nanopores”). The described colors are visible through the embossing ink. The colors are also visible when viewed from the back, but these colors are generally different from those visible from the front.

[0199] Example 1: Micromirror arrangement structures with / without nanostructures and thin-layer elements with small dielectric layer thickness

[0200] To produce components with a yellow color effect, an imprinted structure coated with an interference layer was created, exhibiting the following characteristics:

[0201] The surface relief is composed of microstructures with superimposed nanostructures:

[0202] Micro-relief structure:

[0203] - A micro-embossed structured mesh with 20µm x 20µm pixels;

[0204] - Micromirrors with a small mirror slope (maximum mirror height 1.8µm);

[0205] - Micromirrors form aperiodic or quasi-periodic sawtooth gratings, wherein the width of the micromirrors is from approximately 5 µm to approximately 20 µm (see...). Figure 12 The illustration in the image shows a scanning electron microscope image of the micromirror arrangement used.

[0206] Nanostructure (partial):

[0207] - Nanopores arranged in a hexagonal grating;

[0208] -Structure period: 250nm;

[0209] - The outline of the structure is approximately sinusoidal;

[0210] -Depth of the structure: approximately 120 nm;

[0211] - Fill factor: approximately 0.5 (i.e., the width of the structure = the period);

[0212] coating:

[0213] Thin-layer elements having the following layers:

[0214] - Absorption layer: 4nm Cr;

[0215] -Dielectric layer: 150nm SiO2;

[0216] -Reflective layer: 60nm aluminum.

[0217] The element exhibits the following color effect relative to the coating applied to a nanoscale smooth surface.

[0218] The blue hue on the nanoscale smooth surface, when viewed from above, transforms into yellow through nanostructuring. At tilt angles up to approximately 40°, the color shows no significant change in either the unstructured or nanostructured regions, which is particularly attributed to the use of a thin SiO2 layer. Viewed from the back, the structure appears purple in the nanostructured regions.

[0219] Example 2: Variation of dielectric layer thickness for thin-film elements on micromirror arrays with / without nanostructures.

[0220] The surface relief is composed of microstructures with superimposed nanostructures:

[0221] Micro-relief structure:

[0222] - A micro-embossed structured mesh with 20µm x 20µm pixels;

[0223] - Micromirrors with a small mirror slope (maximum mirror height 1.8µm);

[0224] - Micromirrors form aperiodic or quasi-periodic sawtooth gratings, wherein the width of the micromirrors is from approximately 5 µm to approximately 20 µm (see...). Figure 12 (as shown in the illustration)

[0225] Nanostructure (partial):

[0226] - Nanopores arranged in a hexagonal grating;

[0227] -Structure period: 250nm;

[0228] - The outline of the structure is approximately sinusoidal;

[0229] -Depth of the structure: approximately 120 nm;

[0230] - Fill factor: approximately 0.5;

[0231] coating:

[0232] Thin-layer elements having the following layers:

[0233] - Absorption layer: 4nm Cr;

[0234] -Dielectric layer: SiO2; layer thickness is shown in Table 7 or Table 8A / 8B;

[0235] -Reflective layer: 60nm aluminum.

[0236] The color effect of components manufactured with the corresponding dielectric layer thickness can be obtained from Table 7. The correspondence between the measured hue angle and the corresponding color name can be obtained from Table 6.

[0237] Table 7

[0238]

[0239] in:

[0240] Velin = Unstructured region

[0241] NS = Nanostructured region (period: 250nm)

[0242] L = Lightness

[0243] C = Chroma

[0244] h = Hue

[0245] Definition: Δh = Hue deviation

[0246]

[0247] In principle, the smaller the hue deviation Δh, the more stable the hue is in terms of changes in the direction of observation. The absolute value of the deviation that is still perceptible to the observer as color stability or color constancy varies depending on the base hue (e.g., "red", "blue", "green").

[0248] In particular, when the hue deviation Δh

[0249] -Start with hues whose hue angle h is between 0° and 60° when viewed from a vertical top angle, preferably less than 60°, and ideally less than 30°.

[0250] -Start with hues whose hue angle h is between 50° and 80° when viewed from above, preferably less than 30°, and ideally less than 15°.

[0251] -Start with hues whose hue angle h is between 75° and 105° when viewed from above, preferably less than 30°, and more preferably less than 15°.

[0252] -Starting with hues whose hue angle h is between 100° and 180° in a vertical top view, less than 80°, preferably less than 40°.

[0253] -Starting with hues whose hue angle h is between 170° and 220° when viewed from above, less than 50°, preferably less than 25°.

[0254] -Starting with hues whose hue angle h is between 210° and 300° in a vertical top view, less than 90°, preferably less than 45°, or

[0255] - Starting from hues with a hue angle h between 290° and 10° when viewed from above, colors are considered color-stable when the angle is less than 80°, preferably less than 40°.

[0256] Figure 13 Tables (a) to 13(h) show the reflectance spectra of the aforementioned three-layer thin-film elements, with or without nanostructure, under different observation conditions (observed at an 8° tilt angle, i.e., in a substantially vertical top view, and observed at a 45° tilt angle). They also show that the reflectance spectra generally shift towards shorter wavelengths and attenuate upon tilting. (See table from...) Figure 13 From (a) to 13(h), it can also be concluded that the reflection spectrum with nanostructure is basically shifted to a longer wavelength relative to the reflection spectrum without nanostructure.

[0257] Tables 8A and 8B list the maximum reflection value obtained from the reflection spectrum, or the wavelength value attributable to the maximum reflection value, for the corresponding interference layer structure or dielectric layer thickness. Furthermore, the corresponding shift and attenuation of the maximum reflection value at tilt are also given. ΔR here corresponds to the attenuation of reflection (at a specific maximum value), and Δλ corresponds to the shift of the corresponding wavelength in the reflection spectrum. For coatings existing on nanoscale smooth regions, the attenuation value ΔR of the maximum reflection value is... Velin and the offset value Δλ of the wavelength belonging to the maximum reflection value Velin For comparison purposes, these are also listed in Table 8B.

[0258] Table 8A

[0259]

[0260] Table 8B

[0261]

[0262] As the measured reflection spectra have shown, the maximum reflection value in the nanostructured region shifts by approximately the same amount (towards shorter wavelengths) as the reflection spectrum of the thin-film element in the unstructured region when tilted. The shift in wavelength attributable to the (specific) maximum reflection value, Δλ, is between approximately 50 nm and approximately 100 nm for all dielectric layer thicknesses. From Tables 8A and 8B, it can also be concluded that the attenuation of the maximum reflection value in the nanostructured region is approximately consistent with the attenuation of the maximum reflection value in the nanoscale smooth region.

[0263] Example 3: Variation of dielectric layer thickness for thin-film elements on micromirror arrays with / without nanostructures.

[0264] The surface relief is composed of microstructures with superimposed nanostructures:

[0265] Micro-relief structure:

[0266] - A micro-embossed structured mesh with 20µm x 20µm pixels;

[0267] - Micromirrors with a small mirror slope (maximum mirror height 1.8µm);

[0268] - Micromirrors form aperiodic or quasi-periodic sawtooth gratings, wherein the width of the micromirrors is from approximately 5 µm to approximately 20 µm (see...). Figure 12 (as shown in the illustration)

[0269] Nanostructure (partial):

[0270] - Nanopores arranged in a hexagonal grating;

[0271] -Structure period: 320nm;

[0272] - The outline of the structure is approximately sinusoidal;

[0273] -Depth of the structure: approximately 150 nm;

[0274] - Fill factor: approximately 0.5;

[0275] coating:

[0276] Thin-layer elements having the following layers:

[0277] - Absorption layer: 4nm Cr;

[0278] - Dielectric layer: SiO2; layer thickness is shown in Table 9;

[0279] -Reflective layer: 60nm aluminum.

[0280] The color effect of components manufactured with the corresponding dielectric layer thickness can be obtained from Table 9.

[0281] Table 9

[0282]

[0283] Figure 14 Tables (a) to 14(h) show the reflectance spectra of the aforementioned three-layer thin-film elements, with or without nanostructure, under different observation conditions (observed at an 8° tilt angle, i.e., in a substantially vertical top view, and observed at a 45° tilt angle). They also show the overall shift and attenuation of the reflectance spectrum at tilt. (See table for reference.) Figure 14 From (a) to 14(h), it can also be concluded that the reflection spectrum with nanostructure is basically shifted to a longer wavelength relative to the reflection spectrum without nanostructure.

[0284] Example 4: The Influence of Nanostructuring and Interference Layer Structure on Chroma (Saturation)

[0285] Using four selected colors (yellow, magenta, blue, and green), the chroma C of the nanostructure without an interference layer (NS+Alu), the nanostructure with an interference layer (NS+CS), and the nanostructure without an interference layer (CS) are compared in Table 10 below. When selecting the layer system or nanostructure, care was taken to make the resulting hue or hue angle h as similar as possible, i.e., the corresponding values ​​of the hue angle h deviate only slightly from each other. The color coordinates of the resulting colors are also plotted in the CIELAB color space for display purposes. Figure 15 The farther the measurement point is from the center, the higher the chroma C. The angle h determines the hue (yellow, magenta, blue, green).

[0286] Table 10

[0287]

[0288] Nanostructured surfaces exhibit similar chroma regardless of whether they are coated with aluminum or with a three-layer interference layer structure (here: Cr-SiO2-Al).

[0289] Based on hue, the pure interference layer structure exhibits the highest chroma. This is especially true for green tones, where the chroma produced by this design is significantly increased. Again, using green as an example, Table 10 shows that similar hues can be produced using different nanostructure-interference layer / SiO2 combinations. In practice, this allows for the creation of specific color impressions through a wide range of possible combinations. This further expands the selection of suitable structures / coatings for the desired color combination.

[0290] Pure (unstructured) interference layer structures exhibit the highest chroma. Even though the attractiveness of a security element is primarily influenced by the color or chroma of the interference layer structure, nanostructuring (albeit with lower chroma) still provides additional color, thereby allowing for significantly greater design freedom. More vibrant colors can also be produced overall by simultaneously using regions with unstructured interference layer structures compared to colors produced by purely structural metallized nanostructures.

[0291] Example 1: Combination of colors / patterns flipped (one color for each pattern)

[0292] Reference Figure 16 View 70 is produced by an embossing structure formed by a first micromirror group and a first subwavelength structure, and coated with a particularly color-stable interference layer structure. For example, the first view 70 or the first pattern can be displayed on a background 74 of the same color, whereby the face value numeral 72 appears to be arched in a first color, the color effect of which is produced by the combined action of the first subwavelength structure and the interference layer structure, which is preferably designed to be color-stable.

[0293] View 80 is produced by an imprinted structure coated with an interference layer, which is formed by a second micromirror array and a second subwavelength structure. For example, the second view 80 or the second pattern can be displayed as a star 82 appearing to arch out in a second color against a background of the same color 84, the color effect being produced by the combined action of the interference layer structure and the second subwavelength structure. When the safety element is tilted 18, the appearance switches between the first view 70 and the second view 80.

[0294] In this design scheme, the entire surface of the face area appears either in the first color or the second color. Therefore, the so-called "shadow image" of the corresponding other pattern is less visible than in other multi-color / pattern flip combinations.

[0295] The reason for the shadowed image is particularly thought to be that, in a pattern-flipping display produced by micromirrors, each light source in the room produces its own image, which is reflected towards the observer or perceived by the observed. Ideally, with only one light source, the two patterns can be well separated by the observer during tilting. However, if there is more than one light source or the light is diffuse (e.g., on a cloudy day), in the worst-case scenario, two equally bright light sources may be located exactly in the viewing angle, and the observer's eye perceives both patterns equally strongly. Then, it becomes difficult or impossible to separate the patterns. However, there is usually a dominant light source (e.g., the sun, a ceiling light) that allows the observer to perceive a sharp reflection from that source, which is then superimposed with weak reflections from other light sources. This can lead to the observer perceiving both the pattern that is actually identifiable from that direction and the shadowed superposition of the corresponding other pattern. In the above embodiment, the shadowed image appears only faintly in a uniform color. Therefore, unlike designs where the pattern and background are formed in different colors, the actually perceived pattern may only acquire a slight color haze.

[0296] In a design scheme not shown, color flipping may also occur only in a portion of the face area. For example, while the color and pattern of a certain patterned portion switch, the color in other parts of the face area, such as the entire background, can be maintained when switching from the first view to the second view.

[0297] Example 2: Combination of color / pattern flipping (multiple colors for each pattern)

[0298] Reference Figure 17 Not only can the colors of the first and second views be different as a whole, but patterns and / or backgrounds within a view can also be formed in different colors or even in multiple colors.

[0299] View 90 is generated by an imprinted structure coated with an interference layer structure, which is formed by a first micromirror group and first and second subwavelength structures. For example, Figure 17 The first view 90 shown includes face value numerals 92 that appear to be arched in a first color in front of a contrasting background 94, the color effect of which is produced by the combined action of an interference layer structure that is advantageously designed to be color-stable with the first and second subwavelength structures.

[0300] View 100 is produced by an imprinted structure coated with an interference layer structure, which is formed by a second micromirror group and multiple, in particular three, subwavelength structures. For example, the second view 100 includes multicolored star shapes 102, 106 that appear to arch out in front of a heterochromatic background 104, the color effect of which is produced by the combined effect of the interference layer structure and, for example, three different subwavelength structures.

[0301] What has proven particularly attractive is the choice of color configuration during color / pattern flipping, where both patterns share the same primary, especially "eye-catching" color (e.g., orange or red), and both backgrounds are formed in the same secondary, especially "inconspicuous" color (e.g., purple or white) in both views (two-color pattern flipping). This design offers high recognizability.

[0302] In an exemplary design not shown, the first view or pattern displays the face value numeral "100" appearing to arch in red against a white first background. The color effects of the pattern and background are produced here by the combined action of first and second subwavelength structures with an interference layer structure preferably designed to be color-stable. The second view or pattern displays musical notes (musical notes) appearing to arch in red against a white second background, and its color effect is similarly produced by the combined action of the interference layer structure with the corresponding first or second subwavelength structure. The appearance switches between the first and second views when the safety element is tilted.

[0303] In this design (where the pattern and background in the first and second views are the same color), the patterns preferably overlap at least partially. However, to ensure high anti-counterfeiting security, the overlap of the patterns should not exceed a certain area proportion.

[0304] To create an overlapping display, portions of the security element, which provides a first pattern and a first background or a second pattern and a second background, are advantageously interleaved. For this purpose, these portions are formed, for example, by narrow, alternating side-by-side stripe sub-regions, or by small sub-regions that intersect each other in two dimensions. Essentially, the interleaving of the portions, or the resulting patterns, makes it more difficult for counterfeiters to forge the design.

[0305] For patterns of the same color that are chosen to be perfectly overlapping, such as those differing only in their structural design or micro-relief structure while maintaining the same color and outline (e.g., where both patterns produce perfectly overlapping red coin displays and only the pattern on the coin changes when the view is switched), security elements can be relatively easily counterfeited, for example, by simply overprinting with printing ink. In contrast, with non-perfectly overlapping patterns, precise overprinting is only possible at a very high cost. Because the non-overlapping parts of the pattern change color when tilted (from the pattern color in one view to the background color in another), for counterfeiting via overprinting, 100% registration with the corresponding sub-region or micromirror of the display is required. Therefore, this design provides exceptionally strong anti-counterfeiting protection.

[0306] In principle, the first and second patterns are advantageously distinguishable from each other so that their outlines can be distinguished by the naked eye. In the case of overlapping displays, the area of ​​overlap between the patterns is between 20% and 80%, particularly preferably between 30% and 70%.

[0307] Example 3: Two-color movement effect with color effect registered with dynamic effect

[0308] Figure 18 The embodiments illustrate a multi-color movement effect, the color effect being aligned with the dynamic effect. This effect can be advantageously used in safety lines, for example, in the form of successive regions 112, 116 of different colors, in which the movement effect produced by the micromirror arrangement structure appears along different directions 122, 124. In the embodiment, the surface area of ​​the safety line displays a two-color so-called RollingCube pattern, in which two rows of parallel (in) are visible at each tilt position (here illustrated exemplary by means of the first view 110 and the second view 120). Figure 18 The small rectangles or bars 114 and 118 (shown by the densely shaded lines) are as follows: Figure 18 The figures are shown with a specific spacing between them and appear in a specific color impression. When the safety line is tilted by 18, a kinematic effect occurs in which the two rectangular "rows" move toward each other (view 110) or away from each other (view 120) along arrows 122 and 124, respectively.

[0309] To produce a kinematic effect, the micromirror arrangement structure has multiple micromirrors with different tilt angles. Micromirrors with the same orientation are arranged such that the overall appearance of the lit or dark micromirrors displays a desired pattern to the observer. In particular, the micromirrors are oriented such that when the safety line is tilted by 18 degrees, the reflection conditions of all micromirrors change to the same degree. Micromirrors that meet the reflection conditions and appear bright before tilting no longer meet the reflection conditions after tilting and therefore appear dark. Conversely, micromirrors that were still dark before tilting can appear bright after tilting with a suitable mirror slope. By properly arranging and oriented the micromirrors, a desired motion effect can thus be produced, which in this embodiment is a movement effect. Alternatively or additionally, the movement effect can also be designed as described in document WO 2011 / 066991 A1, the disclosure of which is incorporated herein by reference.

[0310] Regions 112 and 116 are also designed to be colored, wherein the color impression is generated in at least one of the regions through the combined effect of the interference layer structure and the subwavelength structure (if necessary, the other region is designed to be nanoscale smooth and coated with an interference layer structure that is advantageously designed to be color stable).

[0311] It has proven particularly advantageous that at least some portions of regions 112 and 116 are selected so small that simple ink printing of the micromirrors for the purpose of replicating the effect cannot be precisely registered due to printing tolerances. The size of these portions is preferably less than 0.5 mm in at least one extending direction of the portion (e.g., perpendicular to the direction of movement of the effect), and particularly preferably less than or equal to 0.2 mm. Since the subwavelength structure can be selectively exposed onto individual micromirrors, motion effect-color registration is possible even for very narrow areas.

[0312] Example 4: Arching effect in multi-color display

[0313] Creating an arched effect using a microscope, such as in Figure 19 As used in the embodiments shown, such disclosures are known, for example, from document WO2011 / 066990 A2, and are incorporated herein by reference.

[0314] Figure 19 This reflective arching display is illustrated here in the form of statue 138. To achieve this appearance, the safety element 130 includes a reflective surface region with multiple tilted micromirrors. In practice, the micromirrors are smaller than the resolving power of the eye, making them indistinguishable on their own. For example, the micromirrors have side lengths of only 10 µm and step heights of less than 10 µm. The micromirrors can be arranged regularly in a seamless grid or irregularly. Through the varying tilts of the micromirrors, the observer sees a three-dimensional pattern (here, statue 138) arching out of the plane, its surface protruding forward and / or receding backward relative to the actual spatial shape of the surface region.

[0315] To produce true-color display, the embodiments include mixed colors visible to the observer, generated by mixing colors from pixel-like sub-regions with dimensions below the resolution limit of the human eye. Advantageously, at least two colors from the pixel-like sub-regions can be generated by a specific type of subwavelength structure with an interference layer structure that is characteristic of that color (a third color can be generated, if necessary, by an interference layer structure that is nanoscale smooth). Furthermore, the micromirror arrangement structure can also be designed with pixel-like sub-regions, wherein the arrangement of the subwavelength structure and the pixel-like sub-regions of the micromirror arrangement structure can be chosen independently of each other, or they can completely overlap.

[0316] Figure 19A partial detailed view illustrates how this mixed color is produced by the arrangement of pixels formed by "RGB" subpixels. Pixels are formed here via three-channel color planes 134, which contain corresponding subwavelength structures 136-R, 136-G, and 136-B coated with interference layers, suitable for producing red, green, and blue primary colors. These subwavelength structures produce white (or a bright color impression) through additive color mixing when the entire three-channel color plane is occupied, and through proportional color mixing when subpixels are occupied separately (e.g., ...). Figure 19 (As shown in the figure) produces the corresponding mixed color.

[0317] According to alternative design schemes not shown here, mixed colors can also be generated through dual-channel color surfaces containing two sub-pixels with complementary spectral colors, which are generated by the interaction of an interference layer structure with a first and, if necessary, a second subwavelength structure, such as cyan and red, or yellow and blue.

[0318] Example 5: Two-color 3D effect

[0319] In addition to the aforementioned possibility of generating a 3D effect by mimicking the reflective behavior of arched surfaces, a 3D effect can also be produced through stereoscopic displays. In stereoscopic displays, the observer sees the object point slightly shifted to the left and right with their left and right eyes, respectively (horizontal parallax), and then infers its spatial position in front of or behind the safety element from the parallax. Particularly advantageously, in addition to horizontal parallax, vertical parallax is also provided, so that the stereoscopic 3D impression is maintained even after the safety element has been rotated in its plane or tilted about two different axes; that is, the safety element presents a 3D impression in almost every orientation. Figure 20 This 3D display is shown.

[0320] Reference Figure 20 The display area 202 of the safety element 220 is provided with a plurality of reflective planar micromirrors arranged in a micromirror configuration. These micromirrors, for example, have a bottom surface of 15µm x 15µm and a maximum height of a few micrometers. Each planar micromirror is characterized by its tilt angle relative to the plane of the reflective surface area 224.

[0321] exist Figure 20In the middle view 200-M, a top view shows a reflective surface region 224, which includes: a display area 202 drawn with dashed lines, in which a circular curve 204 is visible as a pattern in the center when viewed vertically and appears to float below the surface region 224; and a background area 206 surrounding the display area 202. When viewed from above (view 200-O), the circular curve 204 moves to the upper edge of the display area 202, and when viewed from below (view 200-U), it moves to the lower edge. Correspondingly, when viewed from the right (view 200-R), the circular curve 204 moves to the right edge of the display area 202, and when viewed from the left (view 200-L), it moves to the left edge. This movement corresponds to the movement of an object arranged in depth, and thus creates a three-dimensional impression of a ring floating in depth.

[0322] This appearance and motion behavior are achieved, for example, by the micromirrors in display area 202 tilting away from the circular curve in a direction perpendicular to the direction vector of the circular curve 204, and the tilt angle increasing linearly with the distance between the plane and the circular curve 204, and the tilt angle parallel to the direction vector varying randomly or pseudo-randomly within the fan-shaped expansion range, regardless of the distance from the circular curve 204.

[0323] Further details regarding the generation of three-dimensional appearance and motion effects can be found in document DE 10 2015 005 959 A1, the disclosure of which is incorporated herein by reference. Details regarding the generation of similar three-dimensional effects and 3D tilting effects (whereby the first 3D pattern can be flipped into other different 3D patterns upon tilting) are described in document DE 10 2017 004586 A1, the disclosure of which is also incorporated herein by reference.

[0324] Display area 202 and background area 206 are further designed to be colored, wherein the color impression is generated in at least one of the areas through the combined effect of the interference layer structure and the subwavelength structure (if necessary, one of the areas is designed to be nanoscale smooth so that the colored appearance is generated only by the preferred color-stable interference layer structure). For example, the surface area can be displayed as a red circle against a green background.

[0325] In some other advantageous design schemes, the reflective surface area is designed as follows:

[0326] - Multi-color 3D patterns, such as the face value number "100" with "1" in red and "00" in green, or a red "100" floating above the reflective surface area and framed by a green rectangle located in the depth (i.e. below the reflective surface area), with the same or different colored backgrounds respectively;

[0327] - When the foreground pattern of the same color in front of a different colored background is tilted, the pattern switches (pattern flips), for example, the red denomination number "100" in front of a green background switches to the red character "PL" in front of a green background;

[0328] - Pattern switching accompanied by color changes: for example, the red denomination number "100" is flipped to the green character "PL".

[0329] Example 6: Two-dimensional color / pattern flipping

[0330] In the embodiments described in more detail below, a switch occurs between two patterns whose appearance is not based on a three-dimensional effect, especially not on a stereoscopic 3D effect or a three-dimensional display with surfaces that bulge forward and / or recede backward relative to the actual spatial shape of the surface area, but on a surface of constant brightness. Therefore, this impression can also be referred to as a “flat” or two-dimensional effect, and the switch is referred to as a “flat” or 2D color / pattern flip. Each pattern here is designed as a surface of constant brightness (within the range of viewing angles in which the respective pattern should be perceived) against a dark or contrasting background.

[0331] According to a favorable design scheme, the pattern can be realized here using a micromirror arrangement structure, in which each micromirror reflects in a random direction within a desired solid angle range. Uniform brightness can be achieved within the selected solid angle range through the statistically uniform distribution of the orientations of the individual micromirrors.

[0332] According to alternative design schemes, this constant brightness surface can be formed using micromirrors with curved profiles in both directions (or alternatively, with varying, segmented constant inclinations). Particularly attractive here is the selection of color configurations for certain regions, such that both patterns have the same first, especially "eye-catching" color (e.g., orange or red), and both backgrounds are formed in the same second, especially "inconspicuous" color (e.g., purple or white) in both views (bicolor pattern flip). However, it is also conceivable that the color configurations for certain regions are selected such that the colors of the pattern and background in the second view are interchanged relative to the colors of the pattern and background in the first view (pattern 1 / color 1, background 1 / color 2 versus pattern 2 / color 2, background 2 / color 1; reverse bicolor color / pattern flip).

[0333] If the background is not distinguished from the pattern by a different color arrangement, the background may, for example, be equipped with micromirrors that reflect light into a solid angle range different from the micromirror arrangement to which the pattern belongs. When viewed within the solid angle range to which the pattern belongs, the background then appears correspondingly darker.

[0334] Basically, the aforementioned optically variable display elements, such as Figure 2The structure is constructed as shown. It consists of a structured layer with micro-reliefs, which at least partially possess subwavelength structures and include an interference layer structure. In addition to the optically variable layer structure, the display element may also contain other functional layers, such as a phosphor layer or a magnetic layer. For proper functioning security features, a protective layer, a primer layer, and an adhesive layer are also required. Whether the foil is located above or below the structured layer is not important for the functionality of the display element.

[0335] Example 7: Color / pattern flipping with layer-related color design

[0336] Reference Figure 21 The manufacturing of safety element 140 can be performed, for example, as follows:

[0337] - Print the release enamel layer or primer layer onto the carrier foil;

[0338] - Print the first embossing paint (e.g., UV paint), emboss the first micro-relief, which is partially superimposed with subwavelength gratings, and then cure the UV embossing paint.

[0339] - Printing and washing out ink to produce the first layer of the system for screening and structuring;

[0340] - Evaporation absorption layer, such as Cr, Al, Ti;

[0341] - Evaporation of dielectric layers, such as SiO2, MgF2, TiO2, ZnS;

[0342] - Evaporation of reflective layers, such as Al, Ti, Fe, Cr, Cu;

[0343] - Demetallization is achieved by removing the eluent and the layer system located thereon;

[0344] - Apply a primer layer or attach foil;

[0345] -Optional printing of a translucent colored layer;

[0346] - Print a second embossing varnish (e.g., UV varnish), emboss a second micro-relief, which is partially superimposed with a subwavelength grating, and then cure the UV embossing varnish.

[0347] -Optional printing of wash ink for structuring the second layer system; vapor deposition of the second layer system (metal monolayer or interference layer structure);

[0348] - Optionally, demetallization can be performed by removing the eluent and the second layer system located thereon;

[0349] - Apply a primer layer, a protective paint layer, and an adhesive (such as a heat sealant).

[0350] The special structure of safety element 140 is now referenced. Figure 21To elaborate further, Figure 21 A portion of the safety element is schematically shown in a cross-section.

[0351] Reference Figure 21 The cross-section of the carrier substrate 28 extends to define an xy plane and a z-axis perpendicular to the xy plane. A layer sequence is provided on the carrier substrate 28 (e.g., PET foil) and the release varnish layer 160, the layer sequence extending from the carrier substrate 28 and the release varnish layer 160 including: a first embossed varnish layer 152 having an embossed first embossed structure 154; a first color coating 156; a first primer layer 158; a partially present translucent colored layer 150; a second embossed varnish layer 142 having an embossed second embossed structure 144; a second color coating 146; a second primer layer 148; and a heat-sealing varnish layer 162.

[0352] The safety element 140 is designed to be viewed from the positive z-direction, such that in the two embossed structures 144, 154 arranged at different height levels in the z-direction, the first embossed paint layer 152, which is closer to the observer, is also called the higher relief layer, and the embossed paint layer 142, which is farther away from the observer, is called the lower relief layer.

[0353] In the embodiments, the imprinted structures 144 and 154 represent micromirror imprinting or micromirror arrangement structures, respectively. They are formed by multiple micromirrors tilted relative to the xy plane, and these micromirrors have a lateral dimension of about 10µm. The micromirror arrangement structures are also locally superimposed with subwavelength structures 164 and 176, respectively.

[0354] The local tilt angle of the micromirrors is chosen precisely in this way so that the relief structure of the micromirror arrangement structures 144 and 154 produces the desired optical appearance after color coating. Specifically, in this embodiment, the tilt angle of the micromirrors is chosen such that the micromirror arrangement structure 144 produces an arched display of face value numbers within one viewing angle range, and the micromirror arrangement structure 154 produces an arched display of heraldic symbols within different viewing angle ranges.

[0355] To impart the desired color impression, the lower-level micromirror arrangement 144 is provided with a color coating 146 that follows the embossed contour. This color coating is in the form of a highly reflective, opaque metallization layer, in this embodiment composed of an aluminum layer. The metallization layer 146 has gaps in certain areas 168 to create negative markings, such as negative text. To create colored areas, the micromirror arrangement 144 in this embodiment also includes a subwavelength structure 164 that generates color.

[0356] The micromirror arrangement 154, located at a higher position, is provided with a halftone color coating 156 that follows an embossed contour and is advantageously designed as a color-stable three-layer interference layer structure, in this embodiment having a chromium / silicon dioxide / aluminum layer sequence. The micromirror arrangement is further designed to be multicolored, wherein the color impression is produced at least locally through the interaction of the color coating 156, which exists as an interference layer structure, and the subwavelength structure 176. Other areas of the micromirror arrangement 154 coated with the interference layer structure are designed to be nanoscale smooth.

[0357] According to the alternative design, the micromirror arrangement structure 144 located at the lower position can also be provided with a three-layer interference layer structure and a subwavelength structure for generating polychromaticity. The subwavelength structure generates color impressions through its interaction with the interference layer structure.

[0358] The color coating 156 of the higher-positioned micromirror arrangement 154 is designed as a regular grid 170 in one surface region of the safety element. This grid consists of grid elements 172 and grid gaps 174, where an observer views the lower-positioned micromirror arrangement 144 from the area of ​​the grid gaps 174. While the observer can theoretically perceive the micromirrors of the lower-positioned micromirror arrangement 144 from the area of ​​the grid gaps 174, their orientation is far from the specular reflection angle from other viewing directions different from the predetermined viewing direction, making them practically non-contributing to the image impression in this case.

[0359] Specifically, in this embodiment, the grid elements 172 and grid gaps 174 form a checkerboard pattern, in which each grid cell, i.e., each grid element 172 and each grid gap 174, has a size of 100 μm x 100 μm. Since micromirrors are typically significantly smaller, for example, having a side length of only 10 μm, they are comparable to... Figure 21 Unlike the simplified schematic diagram, the grid 170 of the color coating 156 typically does not coincide with the micromirror grid of the micromirror arrangement structure 154. Removal of the color coating 156 within the grid gaps 174 can be performed by elution, etching, or laser methods.

[0360] In addition, a light-transmitting colored layer 150 that exists only locally is provided between the two micromirror arrangement structures 144 and 154, such as a blue colored layer left empty in the negative text area 168.

[0361] Overall, the two micromirror arrangements 144 and 154 produce different image and color effects for different observation directions. It can be seen that the observation direction of the corresponding colored image of the micromirror arrangement located at a higher or lower position is determined by the orientation of the micromirror.

[0362] Further details regarding the image and color effects produced by this design can be found in documents WO 2020 / 011390A1, WO 2020 / 011391 A1 and WO 2021 / 155999 A1, the disclosures of which are incorporated herein by reference.

[0363] Example 8: Color / pattern flipping with layer-related color design (primary / secondary structure)

[0364] Reference Figure 22 The manufacturing of safety element 50 can be performed, for example, as follows:

[0365] - Print the release enamel layer onto the carrier foil;

[0366] - Print transparent embossing paint (such as UV paint), emboss the first micro-relief, which is locally superimposed with subwavelength gratings, so that the UV embossing paint can be cured.

[0367] - Partially print colored UV paint; emboss a second micro-relief, which is partially superimposed with a subwavelength grating to cure the colored UV paint.

[0368] - Metallize or coat the embossed structure that exists in multiple planes to create an interference layer structure.

[0369] This layered structure can be manufactured very efficiently.

[0370] This special structure is now referenced. Figure 22 To elaborate further, among which Figure 22 A portion of the security element 50 applied to the banknote 10 is shown schematically in a cross-section.

[0371] The safety element 50 includes a planar, transparent, colorless carrier 28, such as a transparent, colorless PET foil, the planar extension of which defines an xy plane and a z-axis perpendicular to it. A multi-colored reflective surface region is arranged on the carrier 28, the surface region including an imprinted structure region having two micromirror imprints 48, 64 at two different height levels.

[0372] The first embossed region 48 forming the primary structure is provided by micromirror embossing, which is applied to a first transparent embossed lacquer layer 46 on a carrier 28, with its bottom surface located at a first height above the carrier 28. The first embossed lacquer layer 46 is partially covered by a secondary structure in the form of a second embossed lacquer layer 52 having a second embossed relief structure 64 with micromirror embossing, such that there are covered regions 68'', 68''' with the second embossed lacquer layer 52 and free regions 68, 68' without the second embossed lacquer layer 52 on the first embossed lacquer layer 46.

[0373] The second embossed paint layer 52 is designed to be colored and translucent. The bottom surface of the micromirror in the second embossed area 64 is located at a second, greater height above the carrier 28, where the height and the direction of the positive z-axis are given from the carrier 28. Since the safety element 50 is designed for viewing from one side of the carrier 28, the z-axis is... Figure 22 The diagram shows the line extending downwards from the carrier.

[0374] The micromirror embossing or micromirror arrangement structures 48 and 64 each contain a plurality of micromirrors tilted relative to the xy plane. The local tilt angles are chosen such that the embossed structure of the micromirror embossing 48 and 64, in conjunction with the color effects of the interference layer structure 60 described below and, if necessary, the subwavelength structure 62 superimposed, produces the desired optical appearance. Specifically, in the embodiments, the tilt angles of the micromirrors are chosen such that the micromirror arrangement structures 48 and 64 produce an arched three-dimensional impression (e.g., face value numerals) or a motion effect (e.g., scrolling bar effect). In the embodiments, the micromirrors of the micromirror embossing 48 and 64 have a lateral dimension of 10µm x 10µm and a maximum step height of 3.5µm.

[0375] As a special feature, the two micromirror arrangements 48 and 64 are provided with a common coating that follows the relief contours of the imprinted enamel layers 46 and 52, respectively. This coating takes the form of a preferably color-stable three-layer interference layer structure 60, which is located on the second imprinted enamel layer 52 in the covered regions 68'' and 68''' and on the first imprinted enamel layer 46 in the free regions 68 and 68'. In the embodiment, the three-layer interference layer structure 60 is composed of a layer sequence starting from the imprinted enamel layer: an absorption layer 54 (4 nm chromium) / a dielectric layer 56 (150 nm SiO2) / a reflective layer 58 (60 nm Al).

[0376] In the covered areas 68'', 68''', an observer looks through the two embossed paint layers 46, 52 toward (along the positive z-axis) the micromirror arrangement structure 64 located at a higher position, causing it to appear with a first color impression. This first color impression is generated in the partial area 68'' through the combined effect of the light-transmitting colored embossed paint 52 and the interference layer structure 60 and the subwavelength structure 62, and is also generated in the partial area 68''' designed to be nanoscale smooth through the combined effect of the light-transmitting colored embossed paint and the interference layer structure.

[0377] In the free regions 68 and 68' surrounding the covered area, the observer looks at the micromirror arrangement structure 48 located at the lower position only through the first transparent embossed paint layer 46, so that it appears with a second, different color impression. This second color impression is generated in part of region 68 by the combined effect of the interference layer structure 60 and the subwavelength structure 62, and in part of region 68' designed to be nanoscale smooth by the interference layer structure.

[0378] Because the height difference between the two micromirror arrangements 24 and 34 is within a few micrometers, this height difference is imperceptible to the observer, making the two different colored patterns and different effects appear to be arranged side by side with precise alignment. Additional coloring can be integrated into the safety element 50 not only through colored imprinted paint layers but also through nanostructuring.

[0379] Further details regarding the image and color effects produced by this design can be found in document WO 2020 / 244806A1, the disclosure of which is incorporated herein by reference.

[0380] exist Figure 21 and Figure 22 In the diagram, the layer thicknesses of layers 54, 56, and 58 of the interference layer structure 60, the layer thicknesses of each layer in the layer system of the reflection enhancement coating or interference layer structures 146 and 156, and the subwavelength structure 62 ( Figure 22 ) and 164, 176 ( Figure 21 The period and depth are shown in exaggerated form for illustrative purposes. In reality, in a three-layer system with a semi-transparent metal layer / dielectric layer / metal reflective layer, the layer thicknesses are suitably between 50 nm and 600 nm (dielectric spacer layer) and between 3 nm and 20 nm (semi-transparent metal layer), and are therefore only for imprinted structures 48 and 64. Figure 22 ) or micromirror arrangement structure 144, 154 ( Figure 21 It is a small fraction of the size of ).

[0381] The security thread according to the invention is manufactured, for example, by the following process:

[0382] - Print an optional primer layer onto the PET foil;

[0383] - Printing UV embossing paint, embossing micro-relief, with subwavelength gratings superimposed on certain parts to cure the UV embossing paint;

[0384] -Optional printing of wash-out ink;

[0385] - Coating with a metal absorbing layer, such as chromium, with a layer thickness such that the chromium layer has a transmittance between 30% and 90%, preferably about 50%;

[0386] - Coating a dielectric layer, such as SiO2, with a layer thickness suitable for producing at least one maximum or minimum reflection value of a three-layer interference structure in the optical visible spectrum;

[0387] - Coating a metallic reflective layer, such as aluminum, with a layer thickness corresponding to an optical density (oD) of 1 to 5, preferably 1.5 to 3.

[0388] - If necessary, the foil may be demetallized, including elution (the elution ink and the metal / dielectric coating on it are removed);

[0389] - Printing primer and protective varnish layers;

[0390] -Optionally print magnetic areas and / or one or more fluorescent inks;

[0391] - Printing primer layer, protective varnish layer, masking white ink layer and heat-sealing varnish layer;

[0392] - Cutting.

[0393] The L-pattern according to the present invention is manufactured, for example, by the following process:

[0394] - Print the release enamel layer onto the PET foil;

[0395] - Print UV embossing paint, then emboss micro-relief, which is partially superimposed with subwavelength gratings, to cure the UV embossing paint.

[0396] -Optional printing of wash-out ink;

[0397] - Coating with a metal absorbing layer, such as chromium, with a layer thickness such that the chromium layer has a transmittance between 30% and 90%, preferably about 50%;

[0398] - Coating a dielectric layer, such as SiO2, with a layer thickness suitable for producing at least one maximum or minimum reflection value of a three-layer interference structure in the optical visible spectrum;

[0399] - Coating a metallic reflective layer, such as aluminum, with a layer thickness corresponding to an optical density (oD) of 1 to 5, preferably 1.5 to 3.

[0400] - If necessary, demetallize the PET foil, including elution;

[0401] - Lamination of foil onto micro-embossing;

[0402] -Laminate the second foil;

[0403] - Printing primer layer, protective varnish layer and heat-sealing varnish layer;

[0404] - Punch the patch shape and remove areas that are not part of the safety features;

[0405] - Cutting.

[0406] The T-LEAD strip according to the present invention is manufactured, for example, by the following process:

[0407] - Print the release enamel layer onto the PET foil;

[0408] - Print UV embossing paint, then emboss micro-relief, which is partially superimposed with subwavelength gratings, to cure the UV embossing paint.

[0409] -Optional printing of wash-out ink;

[0410] - Coating with a metal absorbing layer, such as chromium, with a layer thickness such that the chromium layer has a transmittance between 30% and 90%, preferably about 50%;

[0411] - Coating a dielectric layer, such as SiO2, with a layer thickness suitable for producing at least one maximum or minimum reflection value of a three-layer interference structure in the optical visible spectrum;

[0412] - Coating a metallic reflective layer, such as aluminum, with a layer thickness corresponding to an optical density (oD) of 1 to 5, preferably 1.5 to 3.

[0413] - If necessary, demetallize the PET foil, including elution;

[0414] - Printing primer layer, protective varnish layer and heat-sealing varnish layer;

[0415] - Cutting.

[0416] In T-LEAD strips (T: "transfer"), any carrier foil (here, PET foil) that may be present is typically removed after being applied to security paper or valuable documents.

[0417] List of reference numerals

[0418] 10 banknotes

[0419] 12 Safety Components

[0420] 14, 14' face value numeral pattern

[0421] 16' Star Pattern

[0422] 18. Inclined

[0423] 20' View

[0424] 22 Embossing paint layer

[0425] 24-sided area

[0426] 26 Micromirror arrangement structure

[0427] 28 Carrier substrate

[0428] Detailed views of parts 30 and 30'

[0429] 32 Thin-layer components

[0430] 34 and 36 microscopes

[0431] 38 Subwavelength Structure

[0432] 40 Observers

[0433] 42, 44 Observation direction

[0434] 46 First Imprinted Paint Layer

[0435] 48 First Imprint Structure 50

[0436] 50 Safety Elements

[0437] 52 Second Imprinted Paint Layer

[0438] 54 Absorption Layer

[0439] 56 Dielectric layer

[0440] 58 Reflective layer

[0441] 60 Interference Layer Structure

[0442] 62 Subwavelength Structure

[0443] 64 Second Imprint Structure

[0444] 66. Paint coating

[0445] 68, 68', 68'', 68''' (partial area)

[0446] 70 Views

[0447] 72 denomination numerals and patterns

[0448] 74 Background

[0449] 80 Views

[0450] 82 star-shaped patterns

[0451] 84 Background

[0452] 90 Views

[0453] 92 denomination numeral pattern

[0454] 94 Background

[0455] 100 Views

[0456] 102, 106 Two-color star pattern

[0457] 104 Background

[0458] 110 First View

[0459] 112 First District

[0460] 114 Bright bars

[0461] 116 Second Area

[0462] 118 Bright Stripes

[0463] 120 Second View

[0464] 122, 124 Movement direction of the first / second region

[0465] 130 Safety Element

[0466] 132 Detailed View

[0467] 134 Three-channel color plane

[0468] 136-B, 136-G, 136-R subwavelength structures

[0469] 138 Arched Pattern

[0470] 140 Safety Components

[0471] 142 Second Imprinted Paint Layer

[0472] 144 Micromirror arrangement structure / First imprint structure

[0473] 146 Reflection-enhancing coating / interference layer structure

[0474] 148 Primer layer

[0475] 150 Colored Layers

[0476] 152 First Imprinted Paint Layer

[0477] 154 Micromirror arrangement structure / Second imprint structure

[0478] 156 Interference Layer Structure

[0479] 158 Primer layer

[0480] 160 release layer

[0481] 162 Heat-sealing coating

[0482] 164 Subwavelength Structure

[0483] 168 Partial Area

[0484] 170 grid

[0485] 172 grid elements

[0486] 174 grid gap

[0487] 176 Subwavelength Structure

[0488] 200-M, 200-O, 200-U, 200-R, 200-L First View

[0489] 202 Display Area

[0490] 204 Circular Curve

[0491] 206 Background Area

[0492] 220 Safety Components

[0493] 224-sided area

Claims

1. An optically variable display element having at least one reflective surface region, said reflective surface region having at least two partially visible regions, which, when viewed in reflected light, at least partially display different colors, wherein... -The at least one reflecting surface region is at least partially coated with a surface conformal interference layer structure. - The at least one reflective surface region contains micro-relief structures in the first and second part regions, respectively. These micro-relief structures produce dynamic effects and are constructed with multiple micro-relief structural elements. - The micro-relief structure in the first region and / or the micro-relief structure in the second region are at least partially provided with color-changing nanostructures, which are formed by at least one subwavelength structure, and - In the first and / or second regions, the color effect of the interference layer structure is modified by the color-modifying nanostructure, such that the first and / or second regions display at least one of the different colors through the combined effect of the interference layer structure and the color-modifying nanostructure.

2. The display element according to claim 1, characterized in that, When observed in reflected light, the reflective surface region produces displays for at least two different viewing directions, wherein these displays at least partially overlap and at least locally have different colors in the overlapping region, wherein the micro-relief structure of the first part region and the micro-relief structure of the second part region respectively produce one of these displays for the observer, and the first part region and the second part region at least partially overlap each other, wherein the first part region and / or the second part region displays at least one of the different colors of these displays through the combined action of the interference layer structure and the color-modifying nanostructure.

3. The display element according to claim 2, characterized in that, The first and second part regions intersect each other, wherein these part regions are preferably formed by narrow, alternating, side-by-side strip-shaped sub-regions or by small sub-regions that intersect each other in two dimensions.

4. The display element according to any one of claims 1 to 3, characterized in that, The micro-relief structures in the first and / or second regions are coated with conformal interference layer structures in areas designed to be nanoscale smooth in order to produce different colors.

5. The display element according to any one of claims 1 to 4, characterized in that, The micro-relief structure in the first part of the region and / or the micro-relief structure in the second part of the region are provided with color-generating nanostructures, especially subwavelength structures, in order to produce different colors in those areas not coated with surface conformal interference layer structures. The subwavelength structures exhibit colors substantially based on plasmon resonance, wherein the color-generating nanostructures are particularly coated with metallization layers or high refractive index material layers.

6. The display element according to any one of claims 1 to 5, characterized in that, Dynamic effects create motion effects, especially movement effects, deformation effects, pumping effects, flipping effects, stereoscopic 3D effects, and / or three-dimensional displays of surfaces that protrude forward and / or recede backward relative to the actual spatial shape of the surface area.

7. The display element according to any one of the preceding claims, characterized in that, The interference layer structure is at least partially designed such that the hue of the color produced by the interference layer structure and / or the hue of the color produced by the interaction of the interference layer structure and the color-modifying nanostructure are color-stable when tilted up to 30° and preferably up to 45° from a vertical top view.

8. The display element according to claim 7, characterized in that, The interference layer structure is at least locally designed such that, when tilted up to 30° and preferably up to 45° from a vertical top view, the hue angle h h) Starting with hues where the hue angle h is 0° to 60° when viewed from above, change the angle by less than 60°, preferably less than 30°. i) Starting with a hue angle h of 50° to 80° when viewed from above, change the angle by less than 30°, preferably less than 15°. j) Starting with a hue angle h of 75° to 105° when viewed from above, change the hue angle by less than 30°, preferably less than 15°. k) Starting with a hue angle h of 100° to 180° when viewed from above, change the angle by less than 80°, preferably less than 40°. l) Starting with a hue angle h of 170° to 220° when viewed from above, change the angle by less than 50°, preferably less than 25°. m) Starting with a hue angle h of 210° to 300° when viewed from above, change the angle by less than 90°, preferably less than 45°, or n) Starting with a hue angle h of 290° to 10° when viewed from above, change the angle by less than 80°, preferably less than 40°.

9. The display element according to any one of the preceding claims, characterized in that, The interference layer structure is formed by a multilayer structure consisting of dielectric layers and / or metal layers, preferably by three thin-layer elements, wherein the three thin-layer elements particularly have a semi-transparent metal layer / dielectric layer / metal reflective layer structure or a semi-transparent metal layer / dielectric layer / semi-transparent metal layer structure.

10. The display element according to any one of the preceding claims, characterized in that, The interference layer structure is a three-layer thin element with a semi-transparent metal layer / dielectric layer / metal reflective layer structure. The optical thickness of the dielectric layer is at most 250 nm, preferably at most 200 nm, and the three-layer thin element shows the maximum reflection value only at the short-wavelength end of the visible spectrum when viewed from a vertical top position.

11. The display element according to any one of the preceding claims, characterized in that, The interference layer structure comprises a high refractive index dielectric having a refractive index greater than 1.8, preferably greater than 2.0, and particularly preferably greater than 2.3 throughout the entire visible spectrum or at least a portion thereof.

12. The display element according to any one of claims 1 to 8, characterized in that, The interference layer structure is a double-layer color-reflecting mirror, which consists of a reflective metal layer and an ultrathin absorption layer arranged on the metal layer. The ultrathin absorption layer is made of silicon, silicon alloy or SiOx, where x < 1.

13. The display element according to any one of the preceding claims, characterized in that, The micro-relief structure is formed by the following structures: a micromirror arrangement structure with directional reflective micromirrors, especially a micromirror arrangement structure with planar micromirrors or a micromirror arrangement structure with micromirrors having curved profiles or varying, segmented constant tilts in one or both directions, wherein the micromirrors particularly form periodic or non-periodic sawtooth gratings; Fresnel structures; arrangements of concave / convex arched micro-elements; and / or freeform surfaces.

14. The display element according to any one of the preceding claims, characterized in that, Color-modifying nanostructures and / or color-generating nanostructures are formed by structures with lateral dimensions of 50 nm to 450 nm, particularly 100 nm to 300 nm and / or depths of 20 nm to 450 nm, particularly 100 nm to 300 nm.

15. The display element according to any one of the preceding claims, characterized in that, The subwavelength structure of the color-modifying nanostructure and / or the color-generating nanostructure is formed by a one-dimensional grating or by a two-dimensional grating, wherein the two-dimensional grating has, in particular, rectangular, square, rhomboid, hexagonal or parallelogram grating symmetry, and the grating has a period length of 100 nm to 600 nm, particularly 50 nm to 450 nm, in at least one direction.

16. The display element according to any one of the preceding claims, characterized in that, To produce different colors, at least two subwavelength structures are provided, which differ in structural parameters that affect the color, wherein the structural parameters include at least one of the following parameters of the subwavelength structure: the period length, depth and / or contour shape of the subwavelength structure.

17. The display element according to any one of claims 13 to 16, characterized in that, Micro-relief structural elements for subwavelength structures of different colors and micro-relief structures of reflective surface areas are arranged in a coordinated manner, such that each micro-relief structural element is configured with only a specific type of subwavelength structure.

18. The display element according to claim 16 or 17, characterized in that, The micro-relief structural elements are formed by micromirrors, and one or more structural parameters of the subwavelength structure that affect color vary as a function of parameters determining the orientation of the micromirrors, particularly as a function of the mirror slope or as a function of the azimuth angle.

19. The display element according to any one of claims 1 to 16, characterized in that, When observing a display element, the colors visible to the observer include mixed colors, which are produced by mixing the colors of pixel-like sub-regions with sizes below the resolution limit of the human eye, wherein the colors of the pixel-like sub-regions are each produced by a specific type of subwavelength structure that is characteristic of that color.

20. The display element according to any one of the preceding claims, characterized in that, The surface extension of the display element is defined in the z-direction perpendicular to the surface extension, wherein - The reflective surface region includes a primary structure in the form of a first embossed paint layer, the first embossed paint layer having a first embossed structure, the first embossed structure being formed by a first micro-relief structure in the micro-relief structure. - The first embossed paint layer is partially covered by a secondary structure, resulting in a covered area with a secondary structure and a free area without a secondary structure on the first embossed paint layer, wherein the secondary structure is formed by a second micro-relief structure in the micro-relief structure, and - The primary structure and / or the secondary structure are at least partially provided with color-changing nanostructures, such that the color-changing nanostructures are arranged on the secondary structure in the covered region and / or on the primary structure in the free region.

21. The display element according to any one of claims 1 to 19, characterized in that, The surface extension of the display element is defined in the z-direction perpendicular to the surface extension, wherein - The reflective surface region contains two structures, which are arranged at different height levels in the z-direction. These structures are each formed by one of the micro-relief structures and have a color coating, wherein at least one of the color coatings is formed by an interference layer structure. These two structures overlap in the reflective surface area, and the color coating of the structure at the higher position is designed in the reflective surface area as a regular or irregular grid with grid elements and grid gaps, such that in the reflective surface area, from at least one viewing direction, the color coating of the structure at the lower position is revealed to the observer through the grid gaps of the color coating of the embossed structure at the higher position, and - At least one of the structures having an interference layer structure or having an interference layer structure has a color-changing nanostructure in at least a local portion.

22. The display element according to claim 21, characterized in that, The first color coating in the color coating is formed by an interference layer structure, and the second color coating in the color coating is formed by a metallization layer or another interference layer structure, wherein the structure with the metallization layer preferably has a nanostructure that generates color.

23. The display element according to any one of claims 1 to 22, characterized in that, Display elements are security components used to protect valuable items.

24. A data carrier having an optically variable display element according to any one of claims 1 to 23.

25. A method for manufacturing an optically variable display element, particularly an optically variable display element according to any one of claims 1 to 23, wherein at least one reflective surface region is generated in the optically variable display element, the reflective surface region having at least two partially visible regions, which, when viewed in reflected light, at least partially display different colors, wherein... - The at least one reflective surface area is provided by forming micro-relief structures with multiple micro-relief structural elements in the first and second part regions, respectively, wherein the micro-relief structures produce a dynamic effect, wherein... - The micro-relief structure in the first region and / or the micro-relief structure in the second region are at least partially superimposed with color-modifying nanostructures, wherein the color-modifying nanostructures are formed through subwavelength structures. - The reflective surface area is at least partially coated with a conformal interference layer structure. -In the first and / or second regions, the color effect of the interference layer structure is modified by the color-modifying nanostructure, such that the first and / or second regions display at least one of the different colors through the combined effect of the interference layer structure and the color-modifying nanostructure.

26. An optically variable display element having a reflective surface region that produces different displays for at least two different viewing directions when viewed in reflected light, wherein these displays are at least partially different colors themselves or among each other. - The reflective surface area is coated with a conformal interference layer structure. - The reflective surface area produces a dynamic effect, and at least one first part area and one second part area respectively contain micro-relief structures, the micro-relief structures being constructed with multiple micro-relief structural elements. - The micro-relief structure in the first region is at least partially provided with a color-modifying first nanostructure, which is formed by at least one first subwavelength structure. - The micro-relief structure in the second region either does not have a color-modifying nanostructure, or it has a second nanostructure that modifies the color produced by the interference layer structure in a manner visibly different from the first nanostructure, and the second nanostructure is formed by at least one second subwavelength structure. The differences between the displayed colors are produced by the different color modifications of the interference layer by the first nanostructure present in the first and second regions, and, if necessary, the second nanostructure.

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