OPTICALLY VARIABLE SAFETY ELEMENT

Description

[0001] The invention relates to an optically variable security element with a reflective surface region. The invention also relates to a method for producing such a security element and a data carrier equipped with such a security element.

[0002] Data storage media, such as valuables or identification documents, as well as other valuable items such as branded goods, are often provided with security elements for security purposes. These elements allow verification of the authenticity of the data storage media and also serve as protection against unauthorized reproduction. These security elements can, for example, take the form of a security thread embedded in a banknote, a cover foil for a banknote with a hole, an applied security strip, or a transfer patch.

[0003] Security elements with a viewing-angle-dependent appearance play a special role in authenticity assurance, as these cannot be reproduced even with the most modern copying machines. The optically variable security element shows viewers, for example, different motifs or different states of a moving motif at different viewing angles. In the current state of the art, optically variable effects are described as motion effects or motif tilt effects, which are realized using holograms, microlenses, or micromirrors.

[0004] It is known to create various optically variable effects – also using different technologies – in a security element.

[0005] WO 2011 / 066991 A2 shows a motion effect created by micromirrors when a security element is tilted. A bright bar moves across a surface area. The document also proposes, for example, combining a micromirror arrangement and a lens arrangement side by side in a security element. A first motif—floating behind the security element, for example—becomes visible in the surface area of ​​the lenses, and the motion effect, for example, becomes visible in the area of ​​the micromirrors.

[0006] WO 2011 / 066990 A2 relates to an arrangement of micromirrors that are aligned such that the area is perceived as a curved surface rather than a flat surface. EP 3 401 117 A1 describes a security element with a micro-optical display arrangement that produces a stereographic display of an object with absolute depth information and / or an orthoparallactic display of the object. WO 2016 / 180522 A1 relates to a security element that displays an element floating above or below the plane of the security element.

[0007] In a surface area with micromirrors, micromirrors of different motifs can be provided in a nested manner, in particular in order to create a change of motif in the surface area when tilted.

[0008] WO 2019 / 219239 A1 proposes a micromirror region in which a motion effect of a first motif is combined with a second motif that is only recognizable within a certain viewing angle range. The document shows the preamble of claim 1.

[0009] Based on this, the invention is based on the object of further increasing the security against counterfeiting and the visual attractiveness of optically variable security elements, in particular optically variable security elements with two or more different appearances or effects in different colors are to be provided.

[0010] This object is solved by the features of independent claim 1. Further developments of the invention are the subject of the dependent claims.

[0011] The optically variable security element according to the invention is defined in claim 1.

[0012] In diffuse light, the viewer can see the difference in contour sharpness between the first security feature and the second security feature. Therefore, even if a counterfeiter were to succeed in reproducing a movement with blurred contours in diffuse light using other means, they would not be able to simultaneously depict an element with increased contour sharpness in diffuse light, which is only visible depending on the viewing angle.

[0013] Advantageously, a security element is provided that, on the one hand, displays a movement effect over a larger area that is quickly recognizable to the viewer. The viewer does not have to search for the security feature for long, as it is recognizable over a large area. At the same time, the security element is not completely blurred even in diffuse light. Furthermore, the security element is optimized in terms of its surface area. The two security features are not provided next to each other (in separate areas), but in a common surface area, specifically the second surface area.

[0014] The difference in the size of the tilt angle ranges is one of the factors that contribute to increased contour sharpness. The second tilt angle range is preferably at least twice, or particularly advantageously more than four times, the size of the first tilt angle range. Further factors that further contribute to a visible difference in contour sharpness are listed below.

[0015] In advantageous embodiments, a (large) tilt angle distance exists between the first tilt angle range and a tilt angle range at which the second moving security feature is at least partially visible in the first surface area. The tilt angle distance is preferably at least three times or even at least five times the size of the first tilt angle range. When viewing the security element in the (corresponding) tilt angle range, the second security element lies at least partially in the first surface area. The first tilt angle range is separated from the tilt angle range by the stated multiple of itself.

[0016] Preferably, there is a surrounding area adjacent to the first surface area. In the first surface area, the first security feature is only visible depending on the viewing angle, and the second security feature is visible below the area tilt angle. In a direction of movement of the second security feature, the surrounding area is at least half the size of the first surface area in the direction of movement. In the surrounding area, all microreflectors are aligned neither for the first tilt angle range nor for a first tilt angle range that is triple the size. The second security feature also moves through the surrounding area (if the tilt angle is close to the area tilt angle). However, the surrounding area is free of microreflectors, for example of the second security feature, which light up when the tilt angle is in the first tilt angle range. The contour sharpness of the first security feature orThe first surface area thus remains high even in diffuse light. In certain embodiments, the surrounding area has a minimum width of half and a maximum width of the first surface area. The surrounding area borders the first surface area on at least one side, usually on both sides. It is particularly advantageous for the surrounding area to surround the first surface area. The first subject can thus suddenly appear in the surrounding area when tilted.

[0017] Contour sharpness in this sense is a measure of the recognizability of the position of the contour of the security feature. In particular, the (outer) contour of the motif displayed to the viewer can be sharp or blurred. For a security feature with high contour sharpness, the position of the contour of the security feature is immediately recognizable. There is a contour at which a light-dark transition occurs (ideally digitally). In contrast, for a security feature with low contour sharpness, the contour of the security feature becomes blurred for the viewer. With low contour sharpness, the viewer does not see a defined contour, but only a transition area, in which there is a transition from light to dark. The shape of the security feature or the displayed motif is recognizable to the viewer, but its contour is no longer sharply defined and can only be estimated.

[0018] The two security features – regardless of whether they are presented as a flat or linear motif – have an (outer) contour, preferably in the form of a light-dark transition. The motif of the security features is created, depending on the viewing angle, by the presence or absence (or appearance of lighter or less light) of directed reflection from the microreflectors. To the observer, the security feature therefore appears brightly reflective, preferably brightly colored. The adjacent or surrounding area, in contrast, is dark, particularly because the microreflectors are oriented in other directions.

[0019] The microreflectors are arranged parallel to (or in) the plane of the security element. The movement effect of the second security feature also runs parallel to or in the plane of the security element. The orientation of the microreflectors can be specified by an inclination angle and an azimuth angle, as is the case in the preferred embodiment of micromirrors as microreflectors. The inclination angle of the microreflector relative to the plane of the security element is the decisive parameter for tilting around a given axis. In simplified terms, only those microreflectors whose azimuth angles are in the direction of the observer are effective during tilting.

[0020] Motifs on security features created with directional micromirrors are generally designed for directional light. Directional light sources include the sun or point light sources. Diffuse light, on the other hand, occurs under cloudy skies or, for example, from large-area lights (e.g., fluorescent lamps or LEDs), particularly at short distances, or from indirect lighting. For many attractive security features, such as motion effects, three-dimensional effects, or motif changes, micromirrors are used that are only slightly differently aligned at short distances. In diffuse light, the detectability of the effect generally decreases if no countermeasures are available. For moving motifs, the movement of the motif is well preserved even in diffuse light; only the contour sharpness of the moving motif noticeably decreases. The motif no longer has a clear contour.To put it simply, neighboring microreflectors, which are actually only assigned to the later tilt angles of the moving subject, also light up. The second security feature is therefore particularly advantageous because the viewer can still see the moving effect of the subject in diffuse light and at the same time recognize the reduced contour sharpness. The difference in contour sharpness of the two security features in diffuse light could encourage the viewer to also check the difference in contour sharpness of the subject of the second security feature between diffuse and directed light. At the same time, counterfeiting with completely blurred subjects is made more difficult because even in diffuse light at least one of the subjects must always appear with a sharp contour.

[0021] The tilt angle specifications and derived quantities mentioned here, such as tilt angle ranges and distances and in particular their ratios, are measured or determined in directed light - unless otherwise stated.

[0022] It is particularly advantageous if the motif of the first security feature and the motif of the second security feature appear with different color effects. The viewer sees the motif of the first security feature in a first color. The viewer sees the moving motif of the second security feature in a (different) second color. In this case, the color of the motif is preferably independent of the tilt angle. The motif (of the security features) displays the specified color (in each case) in its tilt angle range. Wherever the present application refers in a simplified manner to color or different color, this refers to shades or different shades of color (i.e., not to potentially different brightness values).

[0023] The microreflectors of the first and / or second security feature each have a color-imparting coating or a color-imparting structure.

[0024] The microreflectors typically have a reflection-enhancing coating (e.g., a metallic coating). The reflection-enhancing coating can have its own color, thus simultaneously functioning as a color-imparting coating. Likewise, the reflection-enhancing coating can comprise a color-imparting structure—e.g., mediated by an underlying embossing or relief structure—for example, a subwavelength structure. In preferred embodiments, however, a color-imparting layer, in particular a translucent color layer, is applied over the reflection-enhancing layer. Translucent color layers are advantageous because they are only semitransparent depending on the wavelength, but are clearly transparent to the observer, apart from the color.

[0025] In the preferred embodiments, the microreflectors of the first and second security features are located at different heights. Arranging the microreflectors at different heights enables easier, different coating of the nested microreflectors. Parallel to the plane of the security element, the micromirrors are thus located at a first and a second height. The different heights are perpendicular to the plane of the security element. The height difference between the two heights is greater than a maximum relief height of the microreflectors, in particular at least 1.5 times or twice as large as the maximum relief height (or pitch). The surface area of ​​the security element defines a z-direction perpendicular to the surface. The security element contains the two relief structures, which are arranged at different heights in the z-direction.The relief structures are each provided with a color coating that creates a different color impression. The relief structures are advantageously each characterized by a maximum pitch, wherein the distance between adjacent height levels in the z-direction is greater than the maximum pitch of the respective deeper embossed structure region. The distance is preferably greater than 150%, particularly preferably 200%, of the maximum pitch. Further preferably, the distance between adjacent height levels in the z-direction is between 150% and 750%, particularly preferably between 200% and 500%, further preferably between 200% and 400% of the maximum pitch of the deeper embossed structure region.

[0026] In a first variant, the micromirrors of both security features are arranged as partial relief structures at different heights in a common relief structure, which can therefore be created in a single embossing step. On the higher partial relief structure, a coating can, for example, be selectively transferred (from a donor foil after contact), lifted off (to an acceptor foil), or wiped away. Before or afterward, both partial relief structures are jointly coated with a coating, for example, a reflection-enhancing coating (before) or a second color-imparting coating (after).

[0027] In the preferred second variant, the microreflectors of the two security features are located as independent relief structures at different heights. The security element thus comprises a first relief structure with the microreflectors of the first security feature and a separate second relief structure at a different height with the microreflectors of the second security feature. Both relief structures can be produced in separate embossing steps, for example, on different sides of a carrier.

[0028] The relief structures are preferably produced by embossing a layer, in particular an embossing lacquer layer, preferably UV-curing, or a thermoplastic carrier layer.

[0029] The microreflectors preferably have a size between 1 and 60 (or 100) µm, preferably between 3 and 30 µm. The microreflectors can be formed by a micromirror with a directed, preferably planar, surface, by a directedly reflecting Fresnel structure, by a directedly reflecting diffraction structure, or by a directedly reflecting subwavelength structure.

[0030] The microreflectors are preferably implemented as micromirrors, particularly because they exhibit particularly bright and achromatic light reflection. Micromirrors reflect incident light essentially according to the principles of geometric optics. Micromirrors can be designed as flat facets. They should be so small that they can hardly or not at all be individually resolved with the naked eye. The size of the micromirrors (lateral dimensions) is below 100 µm. At the lower end of the size range, the lateral dimensions should be greater than 3 µm, preferably greater than 5 µm, and most preferably approximately 10 µm or larger to avoid unwanted diffraction effects.

[0031] In addition to the preferred design as micromirrors, other reflective micro- or nanostructures can also be used as microreflectors. For example, diffraction structures (e.g., hologram gratings with periods of approximately 0.6 µm to 2 µm, preferably achromatic "matte structures" or asymmetric "blaze gratings") or subwavelength structures can also be used. All of the microreflector types mentioned can be created using relief structures. The microreflectors are preferably embossed into an embossing lacquer (e.g., thermoplastic or radiation-curing, especially UV-curing embossing lacquer) and provided with a reflection-enhancing coating (e.g., a highly reflective opaque metallization).

[0032] The microreflectors of the security feature(s) are present in a microreflector array. The microreflectors of the security features can be nested within each other, at least in the first surface area; preferably, they are nested but at different heights. In at least one pixel of the micromirror array, both differently aligned and identically aligned microreflectors can be present. In particular, the alignment of the microreflectors in the microreflector array—including for neighboring microreflectors—can be freely selected in advance. Furthermore, microreflectors in the microreflector array can be arranged in a grid or quasi-randomly, for example, in rows and columns with a uniform size or with a quasi-random position and / or quasi-random size.

[0033] The microreflectors (e.g., micromirrors) of the first or second security feature can be interleaved in a fine striped or checkerboard pattern that a viewer can barely or not at all resolve with the naked eye, or at least cannot perceive. In advantageous embodiments, pixel sizes, or stripe widths, or field sizes of 150 µm or smaller, preferably 100 µm or smaller, or particularly preferably even 50 µm or smaller, can be used.

[0034] Of course, the motifs could match in shape and / or color. However, the two motifs of the security features preferably differ in at least two, preferably at least three, more preferably at least four, or all of the following parameters: contour, color, linear / smooth appearance, uniformity, and tilt angle variance. The (outer) contour determines the external shape of the motif. The motif can be linear, i.e., represented using lines – including the outer contour – or flat, i.e., designed as a filled area (with or without a pattern). The motif visible at a tilt angle can be uniform or non-uniform, for example: single-colored or multi-colored, solid-colored or patterned. As already mentioned, the visible motif can be independent of the specific tilt angle (invariant) or change with the tilt angle (e.g., in shape / size / uniformity).

[0035] In particularly preferred embodiments, the microreflectors of the first security feature are uniformly aligned. The first surface area, as a two-dimensional motif of the first security feature, is essentially only visible from one viewing angle.

[0036] In alternative embodiments of the first security feature, all microreflectors can have a substantially uniform component of the tilt angle for the tilt direction, but can exhibit different azimuth angles. Thus, the first security feature—as a motif the size of the first surface area—could also appear three-dimensional to the observer, in particular curved or vertically shifted. The motif appears to the observer to be curved out of the plane of the security element, or it appears to be above or below the plane of the security element.

[0037] The second security feature, on the other hand, is preferably designed as a linear motif. A line whose length and shape can change during movement moves continuously across the second surface area. For example, a straight line can move (unchanged) linearly or non-linearly across the surface area. Likewise, a contour line of a motif, such as a triangle, can move radially outwards. In this case, the size of the triangle increases (or decreases) when tilted. The contour line and thus the outer contour of the motif can also change, for example from a triangle to a star during radial movement or from a concave to a convex curved line during linear movement. In particularly preferred second security features, the line moves in a first direction and a second movement becomes visible along the line at the same time.The second movement is preferably created by creating the line as a discontinuous line whose (line breaks or) line segments move along the line.

[0038] Preferably, in directed light, the two motifs of the security features are brightly reflective in the aforementioned tilt angle ranges, particularly against a dark background that is non-reflective at the respective angle. Likewise, more preferably, in directed light, the two motifs of the security features can have comparable contour sharpness.

[0039] In further embodiments, the security element can have a further first (or third) security feature. This third security feature is also referred to as a further first security feature because it has the same properties as the first security feature. The motif of the further first security feature is only visible in a further first viewing angle range in a further first surface area. The second viewing angle range encompasses both first viewing angle ranges.

[0040] The security element is intended for embedding in or applying to a substrate, such as foil, paper, or a composite thereof, in particular a valuable document, an ID card, or a branded product. The security element can be provided, for example, as a security thread, security strip, security patch, or security layer, particularly for valuable documents but also for securing branded articles or products.

[0041] Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction has been omitted in order to increase clarity.

[0042] They show: Fig. 1 a schematic representation of a banknote with two security elements, Fig. 2 four views of a security element at different tilt angles, Fig. 3 a regular microreflector arrangement in plan view, Fig. 4 an irregular microreflector arrangement in plan view, Fig. 5 cross-section through a first embodiment of a microreflector arrangement, Fig. 6 cross-section through a second embodiment of a microreflector arrangement with partial relief structures at different heights, Fig. 7 cross-section through a third embodiment of a microreflector arrangement with two separate relief structures at different heights, Fig. 8 cross-section through a fourth embodiment of a microreflector arrangement with two separate relief structures at different heights, Fig. 9 several views of a further security element at different tilt angles.

[0043] The invention will now be explained using the example of security elements for banknotes. Figure 1 shows a schematic representation of a banknote 1 with two optically variable security elements 2 according to the invention. In this embodiment, both security elements, as a patch and as a strip, are applied to the substrate 8 of the banknote 1.

[0044] It is understood, however, that the invention is not limited to transfer elements and banknotes, but can be used for all types of security elements, for example, labels on goods and packaging or for securing documents, ID cards, passports, credit cards, health cards, and the like. For banknotes and similar documents, in addition to transfer elements (such as patches with or without their own carrier layer), embedded security elements, such as security threads or security layers as partial or full-surface layers of the substrate, are also possible.

[0045] The security elements 2 each comprise two security features 5, 6, the motifs of which are shown in the figure for a specific tilt angle of the banknote. The two motifs of the security features are generated by a common microreflector arrangement depending on the tilt angle. The star-shaped motif of the first security feature 5 is static and only visible within a specific tilt angle range. The linear motif of the second security feature 6, in contrast, moves over the security element 2 when the banknote 1 is tilted. It moves on the patch as security element 2 from left to right and - some time after the star of the first security feature has disappeared again - also across the star-shaped area. In the star-shaped area, micromirrors of both security features are nested within each other in order to be able to display both motifs.The motifs of the two security features are preferably different colors, especially visible to the observer in a first or second color. Of course, the motifs could also match in shape and / or color. However, using two different colors increases counterfeit security, as such security elements are very difficult to replicate.

[0046] On the security strip, the second security element 2 on banknote 1, the linear motif of security feature 6 moves from top to bottom for the same tilting movement. Thus, banknote 1 contains two security elements 2 with different directions of movement.

[0047] The behavior of the security features on the security element during tilting is now described with reference to Figure 2 described in more detail.

[0048] A security element 20 is in Fig. 2for four different tilt angles. The safety element 20 is tilted about a predetermined axis 27. The axis 27 lies in the plane of the safety element 20. A corresponding tilt direction 29 is indicated by an arrow. In this example one could also speak of north-south tilting. For the tilt angle α, a scale shows 29 different tilt angles α 1 to α 5 . The tilt angles α 1 and α 5 are preferably symmetrical about the vertical view. In a notation of the tilt angle with 0 degrees for a vertical view, this could therefore be + / - x degrees. Alternatively, the angles could also have only positive (or negative) values ​​or primarily positive or negative values.

[0049] Motifs 25 and 26 appear bright to the viewer due to directional reflection, depending on the tilt angle. The background remains dark, thus reflecting no light to the viewer. The motifs are preferably recognizable to the viewer in different colors, for example, as a green star 25 and a red moving line 26.

[0050] Motif 25 of the first security feature is only visible within a small tilt angle range 250. Tilt angle range 250 is defined by a lower tilt angle limit 251 and an upper tilt angle limit 252. Outside of tilt angle range 250, for example in the first, third, and fourth representations of the security element in the figure, motif 25 is not visible. Motif 26 of the second security feature, on the other hand, is visible over a much larger tilt angle range 260. Tilt angle range 260 also has a lower tilt angle limit 261 and an upper tilt angle limit 262. Motif 26 is a zigzag or W-shaped line and moves continuously across security element 20 when tilted. From the lower tilt angle limit 261, the motif is visible on the left of the security element; as the tilt angle increases, motif 26 moves to the right.In the tilt angle range 250, motif 26 is clearly different from motif 25 of the first security feature. Furthermore, it is relevant in this case that the moving motif 26 only reaches the first surface area of ​​the first security feature at a tilt angle α 4 , referred to as the tilt angle range 266. The tilt angle distance 255, formed from the difference between the tilt angle range 266 and the tilt angle upper limit 252, is large compared to the tilt angle range 250. In this example, the tilt angle distance 255 is greater than four times the tilt angle range 250.

[0051] In directed light, both motifs 25 and 26 are visible to the observer with high contour sharpness. The contour of the star as motif 25 is just as well defined against the otherwise dark background as the W-line of motif 26. In diffuse light, the observer can see in the tilt angle range 25 that the contour sharpness of motif 25 of the first security feature is noticeably higher than the contour sharpness of motif 26 of the second security feature. The movement effect is retained even in diffuse light, and the shape, i.e. the W, also remains recognizable. Instead of a line, however, the second security feature as a motif shows more of a band with a blurred contour. The brightness of the band now noticeably decreases from the center to the outside, so that the contour of the motif appears rather blurred. The static and flat area 25 of the first security feature, on the other hand, has a defined contour even in diffuse light.The large difference in the size of the tilt angle ranges 250 and 260 also contributes to this effect. The smaller the second tilt angle range, the easier it is to create a large tilt angle distance 255. The alignment of the microreflectors of the second security feature in the first surface area, the star, and in the adjacent surrounding area differs increasingly from the alignment of the microreflectors of the first security feature as the tilt angle distance increases. Overall, this approach also makes it easier to avoid microreflectors in the adjacent surrounding area, which would reflect light toward the viewer in the tilt angle range 250 under diffuse light.

[0052] If the microreflectors are implemented by micromirrors, the mirrors could be aligned upwards at the left edge of the surface area and downwards at the right edge parallel to the tilt axis, and their orientation could change continuously and monotonically from an upward to a downward orientation.

[0053] For designs with structures other than micromirrors, other structural parameters must be adjusted accordingly, which determine the viewing directions under which these structures illuminate brightly. For example, in a design with diffraction gratings, the grating period and / or an azimuth angle of the diffraction gratings can be changed depending on the intended tilt and illumination direction.

[0054] Figs. 3 and 4Each shows a top view of two different, conventional options for providing microreflectors in a microreflector array. The microreflectors, for example, as micromirrors, can be freely adjusted in their orientation, for example, with tilt angle and azimuth angle.

[0055] In the micro-reflector arrangement 32 of the Fig. 3Microreflectors 35, 36 of uniform size are arranged regularly in a regular grid. Within the micromirror arrangement 32, several microreflectors can be combined to form a pixel 39. The pixel 39 is shown with three by four microreflectors. The micromirror arrangement is thus also regularly divided into a plurality of pixels, which is indicated as pixel division 38. A first microreflector 35 of the first security feature and a second microreflector 36 of the second security feature are arranged in the pixel 39. In this case, since two motifs are to be nested, at least two microreflectors per pixel are required.

[0056] In the micro-reflector arrangement 42 of the Fig. 4Microreflectors 45, 46 of quasi-random size are arranged quasi-randomly. The figure further shows that a division 48 into pixels 49 does not have to be regular. Each pixel 49 contains two first microreflectors 45 of the first security feature and two second microreflectors 46 of the second security feature.

[0057] In both microreflector arrangements 32, 42, a pixel can comprise more than one microreflector of a security feature. For example, the brightness of a planar motif can be adjusted differently, possibly even locally. In the present case, in the first surface area (of the motif of the first security feature), a higher percentage of microreflectors are preferably provided for the first security feature than for the second security feature, for example, in a ratio of 66% to 33% or 75% to 25%.

[0058] The microreflectors are located, as can be seen from the Fig. 5 to 7described, not necessarily in a common plane (or altitude), but preferably at different altitudes.

[0059] Fig. 5 shows, in cross-section, the simplest type of arrangement of microreflectors 55, 56 in a security element 50. A continuous embossed layer 53, for example, a UV-cured embossing lacquer layer, lies on a layer 59, which can be a carrier layer. The security element 50 thus comprises a relief structure 51 in which the directed microreflectors 55, 56 are formed. Vertical dividing lines between the adjacent microreflectors are shown purely for illustrative purposes. The microreflectors 55 of the first security feature and the microreflectors 56 of the second security feature differ in their orientation, here their angle of inclination to the plane of the security element.

[0060] Typically, the microreflector array is coated with a reflection-enhancing layer, such as metallization. Likewise, or in addition, a color-imparting coating or structure can be provided for at least one of the security features. The viewer should see the motifs of the two security features in different colors.

[0061] For the design according to Figure 5 A selectively different coating of the microreflectors of the two security features is difficult to implement. Therefore, a color-imparting structure is created—preferably together with the relief structure. A diffractive structure or a subwavelength structure can serve as the color-imparting structure. These are sufficiently known in the art. The color-imparting structure is superimposed on the relief structure of the microreflectors and may also require the presence of a reflection-enhancing layer.

[0062] Fig. 6 shows a security element 60 with a (carrier) layer 69 and a relief layer 63 in which a relief structure 61 is present. The relief structure 61 comprises two partial relief structures 67, 68. The partial relief structures 67, 68 are arranged at different heights—perpendicular to the plane of the security element. The higher partial relief structure 67 comprises the microreflectors 66 of the second security feature. The lower partial relief structure 68 comprises the microreflectors 65 of the first security feature.

[0063] The partial relief structures, and thus the micromirrors of the two security features, can now be more easily selectively coated differently, as they are located at different heights. Preferably, both partial relief structures are coated with a reflection-enhancing coating. Subsequently, only one partial relief structure can be coated with a translucent color, or both partial relief structures can be coated with different translucent colors.

[0064] On the higher partial relief structure 67 in Fig. 6 Color can be transferred in a contact transfer step. Likewise, color applied to both partial relief structures 67, 68 from the higher-lying partial relief structure 67 can be wiped away or removed by means of a contact lift-off step.

[0065] Fig. 7shows a security element 70 with an intermediate layer 78 and two independent relief layers 73, 74. A separate relief structure 71, 72 is provided for each of the two security features. The first relief structure 71 comprises the microreflectors 75 of the first security feature. The second relief structure 72 comprises the microreflectors 76 of the second security feature, which are aligned differently—at least in the overlapping region. Transparent sections 77 (or recesses in the relief layer) are provided in the first relief structure 71. The transparent sections 77 can be structured or unstructured, but they are not provided with the reflection-enhancing coating. The size of the transparent sections 77 is preferably in the range of one or a few microreflectors, for example between 5 and 200 µm.The microreflectors 76 of the second security feature arranged beneath the transparent sections 77 create the motif for the viewer. At positions concealed by microreflectors 75 of the first relief structure 71, microreflectors 76 or transparent and / or unstructured sections 77 may optionally be present in the second relief structure 72. It is known per se that two transparent sections can also be arranged one above the other to form a see-through feature. For further details of such a structure, for example, for variants of the gridded arrangement of the microreflectors in the upper relief structure, reference can be made to DE 102018005447.

[0066] The microreflectors 75, 76 present in separate relief structures 71, 72 can now also be provided separately with a color-imparting coating or color-imparting intermediate layer. In a first variant, the intermediate layer 78 or the second relief layer 74 is used as the second color-imparting layer for the second microreflectors 76 of the second security feature. Optionally, the first microreflectors can be coated with a first translucent color layer of a different color. The transparent sections 77 of the first relief structure 71 remain free of the first color. However, they could theoretically also be coated if the first motif is to be visible in a mixed color of the first and second colors.In a second variant, one (or two different) translucent color layers are applied over at least one (or both) of the reflection-enhancing coatings of the first or second micromirrors 75, 76. The second relief structure 72 is accordingly first coated with color and then with a reflection-enhancing coating.

[0067] In supervision, all variants can be Fig. 5 to 8 for example, the orders according to Fig. 3 or 4 or other desired nesting arrangements can be achieved. Of course, the viewer still looks at the security elements shown in cross-section from above.

[0068] As can be deduced from the above, a coloring coating and a coloring structure can also be used in a microreflector arrangement for different security features or even for the same security feature.

[0069] Fig. 8once again shows an embodiment with two relief structures 81, 82 at two height levels in a security element 80. The further coatings 831, 832, 841 are shown figuratively for the first time. A first relief layer 83 with the first relief structure 81 is only partially provided. A reflection-enhancing layer 831 and a translucent color layer 832 are applied to the relief layer 83. First microreflectors 851 in a first surface area are uniformly aligned in a first direction. The surface area has, for example, the contour of the letter A. In this example, further first (or third) microreflectors 852 in a further first (or third) surface area are uniformly aligned in a different direction. The third surface area has, for example, the contour of the letter B. The letters A and B are visible to the observer in the color of the translucent color layer 832, for example, green.The reflection-enhancing layer 841 is located on a second relief layer 84 with the second relief structure 82 and its microreflectors 86. A color-imparting layer 88 is designed here as a height-compensating layer. Alternatively, a separate intermediate layer or a non-height-compensating layer (analogous to the color layer 832) can of course also be used as the color-imparting layer. Through the color-imparting layer 88, the viewer sees the moving motif of the second security feature, which is generated by the second microreflectors 86, 861, 862, in a different color, for example, red.

[0070] Fig. 9 shows the optical effect of a security element 90 when tilted around an axis 97. The tilt direction is again indicated by arrow 98 and could be described as east-west tilting. In this example, eight different tilt angles α 1 to α 8 are shown on the axis 99 of the tilt angle α.

[0071] The design of the motifs in Fig. 9 is based on the example from Fig. 8with two first security features, whose motifs 94, 95 become visible as two-dimensional letters depending on the tilt angle. The first motif 95 in the form of the letter A is only visible in a first tilt angle range 950 (α 3 to α 4 ) in its surface area. The further first (or third) motif 94 in the form of the letter B is only visible in a further first tilt angle range 940 (α 5 to α 6 ) in its surface area. These two first tilt angle ranges 940, 950 are very small - at least a factor of four smaller, more likely more than 10 times smaller - compared to the second tilt angle range 960 (α 1 to α 8 ) of the moving motif 96 of the second security feature. The second motif 96 is visible at tilt angle α 1 as a V-shaped line opening downwards in the lower section of the security element.The motif 96 then moves continuously upwards when tilted, changing its shape in the process, until at a tilt angle α 8 it is visible as a V-shaped, upwardly opening line in the upper section of the security element. At a tilt angle 966 (α 2 ), the motif 96 lies in the further first surface area of ​​the further first motif 94. The tilt angle distance 945 between the tilt angle 966 and the tilt angle lower limit 941 of the further first tilt angle area 940 is also large compared to the size of the tilt angle area 940 (greater than a factor of 5 or 10). The situation is similar for the first tilt angle area 950 of the first motif 95. Only at a tilt angle 967 (α 7 ) does the motif 96 lie in the first surface area of ​​the first motif 95.The tilt angle distance 955 between the tilt angle range 967 and the tilt angle upper limit 952 of the first tilt angle range 950 is also large compared to the size of the first tilt angle range 950 (a factor greater than 4 or 8). Due primarily to different color-imparting layers (via relief structures at different height levels), the motifs appear different colors to the viewer, for example, the moving motif 96 is red and the first motifs 94, 95 are green.

[0072] The observer sees the moving motif 96 of the second security feature in directed light as a linear motif with good contour sharpness. The first two motifs 94, 95 also have high contour sharpness, which is particularly comparable to the contour sharpness of the moving motif 96 for the observer. In this case, the tilt angle ranges and the tilt angle distances are selected to be large enough that the flat, static motifs 94, 95 have high contour sharpness even in diffuse light. In the first tilt angle range 940, the observer sees in diffuse light that the contour sharpness of the first motif 94 is higher than the contour sharpness of the second motif 96. The difference in contour sharpness is also observed in diffuse light for the further first motif 95 in the further first (or third) tilt angle range 950 in comparison with the second motif 96.

[0073] In Fig. 8 or 9A metallization 831 of the upper relief structure 81 should also be coated with a precisely fitting, in particular translucent, colored ink 832, so that the first two motifs 94, 95 illuminate, for example, in green at the corresponding tilt angles. Such a precisely fitting overlay of semi-transparent colored ink and metallization can be achieved, for example, by initially providing a full-surface metallization with a screened overprint of a resist, here colored green, and then etching away the metal in the areas not protected by the resist. Alternatively, the colored resist can be selectively transferred to the metallization 831 of the upper relief structure 81 in a contact transfer step.

[0074] In a simple embodiment, the surface area of ​​the further first motif 94 is filled with micromirrors that all have the same orientation. This surface area essentially only illuminates brightly at one viewing angle; for example, the viewing angle range 940 is less than or equal to 1 degree. The tilt angle range 950 of the first motif 95 can be slightly enlarged by quasi-randomly varying the orientation of its microreflectors in the surface of the motif by a predefined value. This approach is already described in more detail in DE 10 2010 047 250 A1.

[0075] In the second linear motif 96, the length and / or shape of the line can change, as shown. Likewise, or additionally, a second, motif-internal movement can be generated along the line. If the line is not represented as a continuous line, but as a regular or irregular sequence of small, bright dots, the second movement can be represented along the line. Further details on such embodiments, in particular on the representation of the lines, are described in DE 10 2010 055 688 A1.

[0076] The first motifs 94, 95 are preferably simple flat motifs. However, variants of the first motifs with curvature or movement within the motif are also conceivable. Preferably, the direction of the movement within the motif is orthogonal to the contour of the motif (as previously described in DE 10 2010 055 688 A1). Furthermore, the contour sharpness of the first motif can be better preserved with movement within the motif if only the alignment of the microreflectors in the interior surface of the motif, i.e., within the contour, is used for the movement within the motif. DE 102012020257 A1 describes a bulge-flip effect. In the present case, one of the two partial views of such a bulge-flip element can be used as a curved representation as the first motif.

[0077] The surrounding area adjacent to the first motifs 94, 95 should appear dark within the tilt angle range of these motifs. Therefore, the micromirrors of the second motif preferably have a significantly different slope than the mirrors of the first motifs 94, 95.

[0078] If the micromirrors of the first and second motifs are nested within each other, it is advisable to continue such nesting outside the actual motif areas of the first motifs. In the design according to Fig. 9The surface of the entire security element could be divided in such a way that a nesting pattern exists everywhere, in which the mirrors of the second motif 96, for example, occupy 50% of the surface. The other 50% is filled with the corresponding mirrors of motif 95 in the area of ​​motif "A," and with the mirrors of motif 94 in the area "B." Outside of these areas, the 50% of the surface not filled with mirrors of the second motif can be filled with inconspicuous structures that are dark at most viewing angles, for example, with very steeply tilted micromirrors or so-called moth-eye structures. If 100% of the surface in these areas were covered with micromirrors of the second motif, areas "A" and "B" would then be darker than their surroundings when passing through the second motif, since only 50% of the nested surface in the area of ​​"A" and "B" is covered with mirrors of the second motif.In this respect, the first motifs would be visible as a dark "negative" at tilt angle ranges other than the corresponding first tilt angle ranges, which may be undesirable, especially with regard to the highest possible security against forgery.

[0079] In the designs described so far, the first and second motifs each appear in only one (first and second) color tone. Each motif appears in its own color tone, and the colors of the motifs vary. For example, different translucent layers of color are provided at the different height levels, which, however, are uniform across the height level. In further designs, different color tones can also be provided within the first and second motifs. At a single height level, translucent layers of color with different color tones can be provided in certain areas.

[0080] For example, in Fig. 9Motif 95 can have a different color than motif 94, for example, by covering these areas with different translucent colors. Furthermore, different colors can also be present within motifs 94 and 95. For example, motif 95 could also have a substructure created by using different translucent colors in certain areas. For example, the letters "A" and "B" could not only appear uniformly green but also have a pattern in a different color, e.g., red. Such a pattern can also take the form of small motifs, for example, small value numbers or currency symbols. The letters here could, for example, be green with a pattern of small value numbers (e.g., red "50"s). Furthermore, designs with, for example, color gradients would also be possible. List of reference symbols

[0081] 1Banknote 2Security element 5First security feature 6Second security feature 8Banknote substrate 20, 90Security element 25, 95Motif of the first security feature 26, 96Motif of the second security feature 94Motif of the third security feature 28, 98Tilt direction 29, 99Tilt angle 250, 260, 940, 950, 960Viewing angle range 251, 261, 941, 951, 961Tilt angle lower limit 252, 262, 942, 952, 962Tilt angle upper limit 266, 966, 967Range tilt angle 255, 945, 955Tilt angle distance 32, 42Micromirror array 38, 48Pixel division 39, 49Pixels with micromirrors 35, 45First micromirrors of the first security feature 36, 46Second micromirrors of the second security feature 50, 60, 70, 80Security element 51, 61Relief structure 67, 68Partial relief structure 71, 81First relief structure 72, 82Second relief structure 53, 63Embossed layer 73, 83First embossed layer 74, 84Second embossed layer 55, 65, 75, 851, 852First micromirror of the first security feature 56, 66, 76, 861, 862Second micromirror of the second security feature 77Transparent element 78, 88Intermediate layer 59, 69Carrier layer 831, 841Reflection-enhancing layer 832Transparent color layer

Claims

1. Optically variable security element (2) having a first and a second security feature (5, 6), wherein - microreflectors (55; 65; 75; 851) of the first security feature (5) are oriented in such a way that, when the security element is tilted about a predefined axis, a motif of the first security feature (5) is visible to the observer only in a first tilt angle range (250; 950), wherein the motif of the first security feature (5) becomes visible in a first surface region; - microreflectors (56; 66; 76; 86) of the second security feature (6) are oriented in such a way that, when the security element is tilted about the predefined axis, a motif of the second security feature (6) is visible to the observer in a second tilt angle range (260; 960), wherein the second tilt angle range (260; 960) comprises the first tilt angle range (250; 950), and wherein during the tilting the motif of the second security feature (6) moves over a second surface region which at least partially overlaps the first surface region; characterized in that the second tilt angle range (260; 960) is significantly greater than the first tilt angle range (250; 950), preferably is at least four times the size, and in diffuse light the motif of the first security feature (5) has a visibly increased contour sharpness in comparison to the motif of the second security feature (6), wherein the contour sharpness is a measure for the perceptibility of the position of the contour of the security feature for the observer.

2. Security element according to Claim 1, characterized in that between the first tilt angle range (250, 950) and a regional tilt angle (266, 966) at which the motif of the second security feature (6) lies in the first surface region there is a tilt angle distance (255, 955) which is at least three times the size of the first tilt angle range (250, 950).

3. Security element according to Claim 1 or 2, characterized in that adjoining the first surface region there is a surrounding region which, in a movement direction of the motif of the second security feature (6), is at least half the size - lying in the movement direction - of the first surface region, wherein all the microreflectors in the surrounding region are not oriented for the first tilt angle range (250, 950) and preferably also not for a first tilt angle range which is tripled in size.

4. Security element according to one of Claims 1 to 3, characterized in that the motifs of the first security feature (5) and of the second security feature (6) appear with different colour effects.

5. Security element according to one of Claims 1 to 4, characterized in that the microreflectors of the first and second security feature (65, 66; 75, 76; 851, 86) are at different heights, preferably - as partial relief structures (67, 68) at different heights in a relief structure (61), or - as independent relief structures (71, 72; 81, 82) at different heights.

6. Security element according to one of Claims 1 to 5, characterized in that above a reflection-increasing coating (831, 841) of the microreflectors of the first and / or of the second security feature (851, 852, 861, 862) there is a corresponding first and / or second colour-imparting layer (78; 88; 832), in particular a translucent colour layer.

7. Security element according to one of Claims 1 to 6, characterized in that a reflection-increasing coating of the microreflectors has a colour-imparting sub-wavelength structure and / or an intrinsic colour.

8. Security element according to one of Claims 1 to 7, characterized in that the microreflectors have a size of between 1 to 60 µm, preferably 3 to 30 µm, and / or the microreflectors are each formed by a micromirror with a directional, preferably planar, surface, by a directionally reflective Fresnel structure, by a diffraction structure or by a sub-wavelength structure.

9. Security element according to one of Claims 1 to 8, characterized in that the microreflectors of the security features (35, 36; 45, 46) are in a micromirror arrangement (32; 42), wherein - the microreflectors of the security features (35, 36; 45, 46) are interleaved in one another at least in the first surface region; and / or - in a pixel (39; 49) of the micromirror arrangement (32; 42) there are both differently oriented and identically oriented micromirrors; and / or - the orientation of the microreflectors in the micromirror arrangement is - even for adjacent microreflectors - freely selectable in advance; and / or - the microreflectors in the micromirror arrangement are arranged in a pattern or quasi-randomly.

10. Security element according to one of Claims 1 to 9, characterized in that the microreflectors of the first security feature are uniformly oriented; or the microreflectors of the first security feature have, for the tilting direction, a substantially uniform angle of inclination but different azimuth angles, with the result that the first security feature appears three-dimensional, in particular curved, to the observer.

11. Security element according to one of Claims 1 to 10, characterized in that in directional light the two motifs of the security features are visible in brightly reflective form in the mentioned tilt angle ranges, in particular against a dark background - which is not reflective at the respective angle -, and / or in directional light the two motifs of the security features have a comparable contour sharpness.

12. Security element according to one of Claims 1 to 11, characterized in that the security element has a further first security feature (94) which is visible only in a further first viewing angle range (940) in a further first surface region.

13. Security element according to one of Claims 1 to 12, characterized in that the moving motif of the second security feature is a linear motif and / or the non-moving motif of the first security feature is formed by the first surface region as motif, wherein the linear motif of the second security feature (96) preferably changes in terms of its size and / or shape during the movement.

14. Value document having a security element according to one of Claims 1 to 13 which is introduced into a value document substrate or is applied to the value document substrate.