OPTICALLY VARIABLE ELEMENT

Description

[0001] The invention relates to an optically variable element with a flat motif area with a first motif and to a value document with such an optically variable element.

[0002] Such optically variable elements are often reflective, with the first motif being represented, for example, by micromirrors with a high-refractive-index transparent coating. In this case, however, the first motif is often very difficult to see, especially if the optically variable element is intended to create additional effects, such as a tilt effect, where different motifs can be displayed when the flat motif area is tilted. This often requires near-optimal lighting conditions with as parallel light as possible to ensure that these effects are visible.

[0003] To improve visibility, such largely transparent images are often placed against a dark background, which increases contrast and improves the image's visibility. However, such a dark background, especially when it's large, is often undesirable for design reasons.

[0004] Furthermore, even with a point light source, many effects are only visible within a very small solid angle. To expand the solid angle, for example, horizontally, the micromirrors must reflect into the correspondingly larger solid angle. This can be achieved, for example, by using appropriately curved micromirrors. However, expanding the solid angle is associated with reduced brilliance, as the incident light is now distributed over a larger solid angle. Visibility is thus further impaired.

[0005] From the publication DE 10 2004 006 771 A1, a method for generating a flat or curved grid image that displays at least one predefined image with individual image regions is known. According to the method, a spatial orientation for the grid image is defined, in which the predefined image is to be visible, and a color is defined for each image region in which the respective image region appears at the defined orientation.

[0006] DE 10 2005 061 749 A1 describes an optically variable security element with an achromatically reflecting microstructure in the form of a mosaic composed of a multitude of achromatically reflecting mosaic elements. The mosaic elements form a predetermined motif by having different groups of mosaic elements reflect incident light into different spatial regions.

[0007] EP 0 375 833 B1 deals with a surface pattern embossed into a substrate, which is divided into M grid fields. Each grid field is divided into N field portions, each field portion being assigned to a pixel of one of N representations and each having a diffraction element containing information about a color value, a brightness level, and a viewing direction.

[0008] From the document FR 2 942 811 A1, a security element is known comprising an array of raised lines, each line comprising at least one flank, each of which defines an angle of inclination relative to the direction of the normal of the array. The angle of inclination of the flank of at least one line of the array varies stepwise along the line, thus creating a graded optical effect with respect to light reflection, which changes depending on the viewing angle of the security element.

[0009] Based on this, the object of the invention is to provide an optically variable element with a flat motif area with a first motif that is still visible with very good contrast in a larger solid angle.

[0010] According to the invention, the object is achieved by an optically variable element having the features of claim 1.

[0011] Due to the substructures, a viewer sees the bright parts of the corresponding substructure very brightly and with good contrast to the dark parts. Therefore, the first subject appears sharp and high-contrast, even though the solid angle within which the subject is visible is enlarged by the multiple substructures.

[0012] Using substructures, the same motif can be represented at a larger spatial angle, ensuring the viewer always receives the same impression. Only the substructures may be perceived slightly displaced. In particular, the substructures themselves can be perceived, always representing the first motif.

[0013] In the optically variable element, the planar motif area has a second motif (preferably a plurality of second motifs) which contains a plurality of substructures extending over the entire motif, each of which has alternately arranged light and dark sub-areas, wherein each substructure of the second motif is visible only at exactly one of the first viewing angles when the first viewing angle is varied, and all first viewing angles of the substructures of the second motif are different, wherein each motif is visible only at exactly one of the second viewing angles when a second viewing angle lying in a second plane is varied relative to the direction of illumination, and all second viewing angles are different, so that the corresponding motif with the corresponding substructure is perceivable depending on the first and second viewing angles,where the first and second motifs present a cinematic effect when the second viewing angle changes.

[0014] In this way, multiple motifs can be displayed at different second viewing angles, allowing for tilt effects, kinematic effects, stereographic representations, etc. At the same time, the correspondingly visible motif exhibits the substructure according to the first viewing angle, thus achieving an enlarged spatial angle in which the motifs are visible sharply and with high contrast.

[0015] Visibility under the first and / or second viewing angle preferably refers to the idealized case in which the flat subject area is illuminated with parallel light along the illumination direction, so that the light is reflected at exactly one angle per substructure. Of course, in practice, a beam of rays will always be reflected with a certain divergence angle, for example, because the illumination is not ideally parallel and the substructures themselves cause beam expansion upon reflection. In this case, the first and / or second viewing angle preferably refers to the principal ray of the respective reflected beam.

[0016] Furthermore, the optically variable element according to the invention can have a plurality of second motifs for different second viewing angles and each with corresponding substructures, so that, for example, the tilting effects and the kinematic effect can be made more optically attractive since more than two different motifs can be provided.

[0017] The formation of the substructures is preferably the same for all motifs. This simplifies the manufacturability of the optically variable element according to the invention.

[0018] According to the invention, when the first viewing angle is changed, the different substructures present a kinematic effect on a smaller length scale compared to the kinematic effect of the motifs.

[0019] The optically variable element can be designed, in particular, as a reflective element. However, a transparent or semi-transparent design is also possible.

[0020] In at least one of the substructures, the alternating light and dark subregions can repeat periodically, at least locally.

[0021] Furthermore, in at least one of the substructures, the bright partial areas can be formed by a line or curve pattern of at least locally parallel lines or curves. However, any other pattern is also possible.

[0022] For example, non-linear, bright sub-areas can be arranged periodically, at least locally.

[0023] It is preferred that the bright sub-areas be arranged with a spatial frequency between 0.5 / mm and 10 / mm (i.e., 0.5 to 10 bright sub-areas per mm), and preferably with a spatial frequency of 1 / mm to 5 / mm. A spatial frequency of 3 / mm is particularly preferred. This ensures that excellent contrast is still visible. It also ensures that the resolution of the motif is not unnecessarily impaired due to the substructure.

[0024] Furthermore, in the optically variable element according to the invention, the distance between the bright partial regions in at least one of the substructures can be smaller by at least a factor of 5, preferably at least a factor of 10, than the extension of the first motif in the direction of the distance between the bright partial regions.

[0025] Preferably, the first and second planes are perpendicular to each other. In particular, the first and second planes can also be perpendicular to the plane of the flat motif area.

[0026] The flat motif area can have directionally reflective elements (in particular reflective facets). Their dimensions within the flat motif area are preferably at least 3 µm, preferably at least 5 µm, and particularly preferably at least 10 µm.

[0027] The directionally reflective elements can be configured as mirror surfaces (particularly flat mirror surfaces) or the reflective effect can be generated by means of diffractive structures. In particular, the diffractive structures can be configured as asymmetric grating structures with a period of a maximum of 5 µm, preferably a maximum of 3 µm, and particularly preferably a maximum of 2 µm.

[0028] Furthermore, it is also possible for the planar motif area to have reflective elements which are formed by essentially ray-optically reflecting grating periods of more than 5 µm and preferably of more than 10 µm.

[0029] The directionally reflective elements are preferably arranged in a grid-like pattern in the flat motif area. This is preferably also the case for the corresponding elements in the embodiment in which the optically variable element according to the invention is designed as a transmissive element.

[0030] In the optically variable element according to the invention, the flat motif area can have a color-shifting coating.

[0031] The optically variable element according to the invention can be designed such that the angular range for the first and / or second viewing angle under which the motif(s) are visible is at least 40°, preferably at least 60° and particularly preferably at least 90°.

[0032] Furthermore, the substructures in the optically variable element according to the invention can be designed such that an observer can perceive them as such with the naked eye. The dimensions of the substructures are preferably selected such that they always form the corresponding motif for an observer (with the naked eye), but are still perceptible as such.

[0033] In the optically variable element according to the invention, the flat motif area can be formed as an embossed structure with a reflection-enhancing coating. Of course, the flat motif area can also have additional layers or elements.

[0034] The optically variable element according to the invention can be designed and / or used, in particular, as a security element. In particular, it can be a security element for a security paper, valuable document, or the like.

[0035] The optically variable element can be designed, in particular, as a security thread, tear-off thread, security tape, security strip, patch, or as a label for application to a security paper, valuable document, or the like. In particular, the optically variable element can span transparent or at least translucent regions or recesses.

[0036] The value document can be, for example, a banknote, a chip card, a passport, an identification card, an ID card, a share, a certificate, a voucher, a check, an admission ticket, a credit card, a health card, etc.

[0037] The term security paper is understood here in particular to mean the precursor to a value document that is not yet fit for circulation and which, in addition to the optically variable element according to the invention, can also have, for example, further authenticity features (such as luminescent substances provided in the volume).

[0038] Valuable documents are also understood here to mean documents made of security paper. Valuable documents can also be other documents or objects that can be provided with the optically variable element according to the invention so that the valuable documents have non-copyable authenticity features, thus enabling authenticity verification and simultaneously preventing unwanted copying.

[0039] Furthermore, a value document with an optically variable element according to the invention (including all further developments according to the invention) is provided.

[0040] Furthermore, an embossing tool with an embossing surface for embossing the shape of the planar motif area of ​​the optically variable element according to the invention (including all further developments according to the invention) is provided. The desired surface structure of the planar motif area can be embossed using the embossing tool.

[0041] The embossing surface of the embossing tool preferably has the inverted shape of the surface structure to be embossed.

[0042] Furthermore, a master for producing an optically variable element is provided. In particular, the master can also be used to produce the inventive developments of the optically variable element. The described embossing tool can be produced using the master. Furthermore, it is possible to form volume holograms using such a master.

[0043] It is understood that the features mentioned above and those to be explained below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention. The invention is explained in more detail below by way of example with reference to the accompanying drawings, which also disclose essential features of the invention. For clarity, the figures are not drawn to scale or proportions. They show: Figure 1 shows a plan view of a banknote with an optically variable element 1 according to the invention; Figure 2 shows an enlarged plan view of the first motif 4 of the optically variable element 1; Figure 3 shows a cross-sectional view along the line AA of Figure 2; Figure 4A shows a perspective view to explain the solid angle covered by a micromirror; Figures 4B and 4C show views to explain the first and second viewing angles; Figure 4D shows a perspective view to explain the enlarged solid angle in the optically variable element 1 according to the invention; Figures 5A-5E show schematic views of the substructures forming the first motif 4 for different viewing directions; Figures 6A and 6B show views to explain conventional designs for the first motif in an optically variable element; Figure 6C shows a comparison with the inventive design of the first motif 4; Figures 7A-7C show perspective views for the designs according to Figures 6A-6C; Figure 8A shows a perspective view to explain a further embodiment of the optically variable element according to the invention; Figures 8B and 8C show schematic plan views to explain the first and second motifs 4 and 10; Figures 9A-9C show schematic views to explain the second embodiment; Figure 10 shows a schematic plan view of the arrangement of the micromirrors 5 for the second embodiment; Figures 11A-11C show further views to explain the second embodiment of the optically variable element; Figure 12A shows a view to explain the change in the visible substructure 8 when tilting the planar motif area 3 about the y-axis; Figure 12B shows an enlarged view of the detail D1 from Figure 12A ; Figure 13A a representation to explain the change in the visible motif when tilting the flat motif area 3 around the x-axis; Figure 13B an enlarged representation of the detail D2 from Figure 13A; Figures 14-17 illustrate further possible designs of the substructures 8, and Figures 18 and 19 illustrate a stamping tool according to the invention.

[0044] At the Figure 1 In the embodiment shown, the optically variable element 1 according to the invention is arranged on the Figure 1 shown front of a banknote 2 and serves as a security element or security feature to verify the authenticity of banknote 2.

[0045] The security element 1 is reflective and has a flat motif area 3 containing a first motif 4 in the form of a square reflective surface. The first motif 4 can, for example, have an area of ​​10 mm × 10 mm.

[0046] As shown in the enlarged schematic diagram of Figure 2 in conjunction with the sectional view of Fig. 3 along the section line AA in Fig. 2As can be seen, the first motif 4 is divided into strip-shaped micromirrors 5, which extend along the y-direction over the entire extent of the first motif 4 and have a width (extension in the x-direction) of 200 µm, wherein the mirror inclination β y varies.

[0047] As is particularly evident from the non-scale sectional view in Figure 3 As can be seen, a group of five micromirrors 5 1 , 5 2 , 5 3 , 5 4 and 5 5 with different mirror inclinations is arranged periodically. The group of five micromirrors is arranged 10 times next to each other. Fig. 3 To simplify the illustration, only three groups of the five micromirrors 5 1 -5 5 are shown.

[0048] The inclination β y of the micromirrors 5 1 -5 5 is chosen so that with perpendicular light incidence, as indicated by the arrow P1 in Figure 3As indicated, the reflected light forms an angle α × (in the xz-plane) with the direction of incidence, which is -20°, -10°, 0°, 10° and 20° for the five micromirrors 5 1 -5 5. Since in practice the reflected light is not, as in Figure 3 is indicated, is only reflected in a single direction, but a divergence angle of e.g. 10° is present, a viewing angle range in the xz plane of 50° is provided with the optically variable element 1 according to the invention, as will be described in detail below.

[0049] For the description of the embodiments of the optically variable element 1 according to the invention, a rectangular coordinate system with x, y, z axes is assumed, wherein the planar motif area 3 and thus the first motif 4 lies in the xy plane and the planar motif area 3 is illuminated with parallel light incident from the z direction. A viewer should view the surface pattern in the direction of the z axis or from a direction deviating from the x direction or y direction by an angle α x or α y, as shown in Figures 4A-4C for the aforementioned divergence angle of 10°. In these figures, a single micromirror 53 is schematically illustrated in such a way that the solid angle 20 is indicated, in which the observer can detect the light reflected by the micromirror 53.

[0050] If the viewing direction 21 lies within the solid angle 20, the observer sees a bright reflection. The viewing direction 21 can be determined by a first viewing angle α x in the xz-plane ( Fig. 4B ) and a second viewing angle α y in the yx-plane ( Fig. 4C ) are clearly described.

[0051] If a viewer now looks at the security element 1 in such a way that the second viewing angle α y lies within the range Δα y specified by the divergence, the viewer sees, depending on the first viewing angle α x , not the entire surface of the first motif as a bright surface, but only the reflected light of the micromirrors 5 1 , 5 2 , 5 3 , 5 4 or 5 5 of the mirror groups, where the reflected light falls into the corresponding solid angle range 20 1 , 20 2 , 20 3 , 20 4 or 20 5 . In Figure 4Dthe solid angle ranges 20 1 , 20 2 , 20 3 , 20 4 and 20 5 assigned to the micromirrors 5 1 -5 5 are shown, whereby to simplify the illustration only the associated first viewing angle range Δα x of each solid angle 20 1 -20 5 is shown.

[0052] For simplicity, we assume that the observer changes their position and the position of the flat subject area 3 and the illumination direction remain unchanged. This description is equivalent, for example, to the more practical case in which the viewing direction and the illumination direction remain fixed and the flat subject area 3 is tilted (e.g., around the x- or y-axis).

[0053] Due to the described designs and arrangements of the micromirrors 5 1 -5 5 , the observer sees a striped pattern of spaced-apart, brightly lit stripes, which represents the desired first motif 4.

[0054] In Figure 5A The case is shown where an observer perceives the light reflected by the micromirrors 5 1 into the solid angle 20 1 when viewing the security element 1. The brightly illuminated stripes 6 are shown here as black lines. In addition, a square border 7 is drawn, which is not visible when viewing the first motif 4, but only serves to clarify the motif effect created by the brightly illuminated stripes 6. In Figures 5B to 5E the stripe patterns 8 are shown for the different viewing angles α x , at which only the reflections at the micromirrors 5 2 , 5 3 , 5 4 or 5 5 are perceptible, since the first viewing angles α x lie in the corresponding solid angles 20 2 -20 5 .

[0055] In all representations, due to the directed reflection of the micromirrors 5, on the one hand, there is a high brightness of the visible bright stripes 6 and, on the other hand, there is a high contrast between the brightly perceptible stripes 6 and the darker areas in between.

[0056] The Figures 5A to 5E The striped pattern shown thus consists of various substructures 8 with light and dark sub-areas, with each substructure 8 extending over the entire first motif 4. The first motif 4 is therefore always visible with only one of the substructures 8, with the viewing angle α x determining which of the substructures 8 form the first motif 4 visible to the viewer.

[0057] Even if the micromirrors 5 are only weakly reflective (for example, if they are formed by a structured surface of an embossing lacquer coated with an approximately 50 nm thick high-refractive TiO 2 layer), the human eye can perceive the described periodic line arrangements according to Figures 5A-5F Even with only slight differences in brightness, the first motif 4 can be separated very well from the background. The optically variable element 1 according to the invention thus enables a high-contrast and clearly recognizable representation of the first motif 4 to be achieved.

[0058] The following comparison with previously known solutions shows particularly clearly the advantage of the optically variable element according to the invention.

[0059] In Figure 6AThe first motif 4 is shown schematically for the case where it is realized by a single flat mirror surface, as has been the case so far. In this case, there is a high brightness (represented by the black color), but only in a relatively small solid angle 20, as in Fig. 7A is shown schematically.

[0060] If one now desires a larger angular range for the first viewing angle α x , one has previously, for example, modified the reflecting surface so that the divergence angle of the reflected radiation in the xz-plane becomes larger. However, such an expansion of the viewing angle range is associated with a lower brilliance, since the incident light quantity is now distributed over a larger angular range Δα x or solid angle ( Fig. 7B ). This is shown schematically in Figure 6Brepresented by showing the area only in gray. This can even lead to the first motif 4 standing out so weakly from the background that it is no longer perceptible.

[0061] With the inventive design of the optically variable element 1, over the entire larger angular range Δα x according to Figure 7C one of the Figures 5A-5F shown stripe patterns are created, one of which is shown for comparison in Figure 6C This clearly shows that by concentrating on the individual reflective stripes, they have a significantly higher amount of light, thus achieving the described improved visibility. Figure 7C It is indicated that each substructure 8 is designed for a solid angle 20 1 , 20 2 , 20 3 , 20 4 and 20 5. Thus, the same angle range Δα x is used compared to Fig. 7B covered, but with the described better visibility for a viewer.

[0062] In the optically variable element 1 according to the invention, the entire surface of the first motif 4 is covered with the micromirrors. The first motif 4 thus reflects the maximum possible amount of light into the desired range of the first viewing angle α x and thus optimally utilizes the available surface for the best possible brightness.

[0063] The spacing of the micromirrors in the respective substructure 8 is selected to ensure, on the one hand, the highest possible contrast sensitivity for the human eye and, on the other hand, to avoid unnecessarily degrading the resolution of the first motif 4. Approximately 1 to 5 lines per millimeter, and in particular, three lines per millimeter, have proven particularly advantageous.

[0064] The described representation of the first motif 4 by the substructures 8 can be further developed in a further embodiment such that the first motif 4 is no longer visible upon a change in the viewing direction (e.g., by changing the second viewing angle α y ), and instead a second motif is perceptible to the viewer. This allows, for example, kinematic effects to be realized. Thus, the used solid angle is increased by increasing the range of the second viewing angle α y , as in Fig. 8A is indicated, in which two solid angles 20 6 and 20 7 are drawn.

[0065] In Fig. 8B The first motif 4 is a star. The second motif 10 is Fig. 8Ca larger star 10 is shown. If several second stars 10 are provided, a so-called "pumping star" can be realized. This pumping star should be visible, for example, when rotating the optically variable element 1 around the x- and y-axis in the range from -40° to +40°. Concentrically arranged stars thus serve as the first motif and as the second motifs, whereby the stars are rotated in the direction of the arrows P2 when rotating the motif area 3 around the x-axis (changing the second viewing angle α y in the yz-plane). Figure 9A become larger.

[0066] In order to achieve this, the micromirrors 5 are no longer strip-shaped, as in Figure 2 is indicated, but for example square, as in the top view of Figure 10is shown schematically. The edge length of the individual micromirrors can be, for example, 20 µm. Each of the micromirrors 5 is designed as a plane mirror and tilted relative to the xy plane, whereby the tilt of each micromirror can be uniquely described by the two tilt angles β y and β x . The tilt angle β y is the angle between the projection of the surface normal of the micromirror 5 into the xy plane and the direction of the x axis, and the tilt angle β x is the angle between the projection of the surface normal of the tilt mirror into the yz plane and the direction of the z axis.

[0067] The tilt angle β x is selected for all micromirrors 5 so that the Figure 9A indicated pumping effect is realized.

[0068] In Figure 9B the tilt angle β x of the micromirrors 5 is indicated, whereby the tilt angle β x is determined by a Figure 9B or Figure 9Cshown line to the next line increases from -20° to +20° in order to cover the desired angular range Δα y from -40° to +40° for the second viewing angle α y. This can be done, for example, in five to ten steps, so that between two lines there are always five to ten different tilt angles β x of the micromirrors 5.

[0069] An observer from a specific viewing direction thus only sees the micromirrors 5 brightly illuminated, which are tilted so that the light is reflected into the solid angle in which the viewing direction lies. The representation in Figure 11A shows an example of the area of ​​the subject area 3 covered by the micromirrors 5, in which the tilt angle β y matches the viewing direction. The illustration in Figure 11Bshows, as an example, the area of ​​the motif area 3 covered by the micromirrors 5, in which the tilt angle β x matches the viewing direction, so that for a viewer the Figure 11C shown. Here, too, the dark stripes represent the brightly lit areas.

[0070] Changes now occur for the observer, for example, when tilting the optically variable element 1 around the y-axis, as in Figure 12A in conjunction with the enlarged detail D1 in Figure 12B The dotted lines 11 show the starting position as a reference according to Figure 11C and the solid lines 12 show the representation now perceivable by the viewer. The viewer thus perceives the same first motif 4 as in Fig. 11C . Only substructure 8 is different. Substructure 8 according to Fig. 12Bis slightly shifted in x-direction to the substructure 8 in Figure 11C .

[0071] If the viewer tilts the optically variable element 1 around the x-axis, the image perceived by the viewer changes from that of Figure 11C to the according to Figures 13A and 13B , where Figure 13B an enlarged view of detail D2 of Figure 13A Even when presented in accordance with Figures 13A and 13B the dotted lines 11 show the representation according to Figure 11C and the solid lines 12 the image now perceivable by the observer. The described pumping effect is clearly visible. The stars shown are in Figures 13A and 13B smaller than in Figure 11C , since the observer now sees a second motif 10 (the smaller star) again with a fine or substructure 8.

[0072] A particular advantage of the embodiment described here is that the entire flat motif area 3 is covered with the micromirrors 5. The flat motif area 3 thus reflects the maximum possible amount of light into the desired spatial angle and thus optimally utilizes the available area to achieve the best possible brightness when displaying the motifs.

[0073] Furthermore, the similarly aligned micromirrors 5 of each substructure 8 allow the viewer to perceive very bright lines with small spacing. This, on the one hand, makes the motif 4, 10 represented by the substructure 8 appear very sharp and high-contrast. On the other hand, this also results in a very distinctive appearance of the motifs, which contributes to a high recognition value. This is particularly advantageous when using the optically variable element as a security element.

[0074] Even with only weakly reflecting mirrors 5, such as those that can be provided by mirrors coated with a high-refractive dielectric and embedded on both sides, for example, in embossed lacquer or protective lacquer with a reflection factor significantly below 1, it is possible to create clearly recognizable motifs even against a white background.

[0075] Furthermore, an attractive security element 1 with a color-changing effect when tilted can be created, for example, using a color-shifting coating (e.g. a thin-film vapor deposition with reflector / dielectric / absorber).

[0076] In the embodiments described so far, the substructure 8 was a line grid in which the lines extend in the y-direction and are spaced apart from each other in the x-direction. The substructures 8 are, of course, not limited to this. For example, diagonal line patterns, as in Figure 14 shown, or wavy line patterns, as in Figure 15shown, for which substructures 8 are used.

[0077] In the embodiments described so far, the tilt angle β y of the micromirrors 5 preferably varies in a direction perpendicular to the lines of the substructures 8.

[0078] In Figure 16 An embodiment is schematically shown in which the substructures 8 are realized by curves that follow the contours of the stars 4, 10. Here, the kinematic effect of the substructures 8 runs in the same direction as that of the stars 4, 10, which can also be referred to as coarse motifs. Thus, the coarse motifs 4, 10 pump on a large length scale when the motif area 3 is tilted about a first axis, while when the motif area 3 is tilted about a second axis, the fine lines of the substructures 8 describe slightly larger or smaller stars.

[0079] The substructures do not necessarily have to be made up of line structures, but can also show point-like representations, as in Fig. 17 is indicated.

[0080] Although in the described embodiments the substructures or motifs vary when tilting about the y-axis and the coarse motifs 4, 10 when tilting about the x-axis, the effects can of course also be adapted for tilting about other axes of rotation by selecting the inclination of the micromirrors 5 accordingly.

[0081] Of course, each coarse motif 4 can be designed as a largely arbitrary motif and, for example, depict outlines of letters, symbols, value numbers, etc. The described kinematic effect of the coarse motifs is, of course, not limited to the described "pumping effect" and the described tilting image (transition from a first to a second image). For example, the coarse motifs can be used to depict other kinematic effects (e.g., movement in a specific direction) or they can also display a stereographic image. A stereographic image could be realized by varying the tilt angle β x of the micromirrors 5 according to the coarse motif and, for example, by varying the tilt angle β y of the micromirrors 5 according to a fine motif with horizontal lines.

[0082] Instead of the aforementioned micromirrors 5, diffractive grating structures, in particular asymmetric grating structures (e.g., designed as sawtooth gratings), can also be provided. Their dimensions can be such that diffractive effects (diffraction for small structure sizes of up to a few micrometers) or ray-optical effects (for structure sizes of many micrometers) dominate for the directed reflection of the incident light desired according to the invention.

[0083] Furthermore, the reflective optically variable element 1 according to the invention can also be used to expose a volume hologram, as described in principle, for example, in DE 10 2006 016 139 A1. For this purpose, a master based on micromirrors 5 or sawtooth gratings can be used, for example, based on the optically variable element according to the invention. A volume hologram obtained in this way then also exhibits a particularly high-contrast image visible over a large solid angle.

[0084] Although in the embodiments described so far, the optically variable element 1 was always designed as a reflective element, in an embodiment not covered by the claimed invention, the optically variable element 1 can also be designed as a transmissive element. In this case, for example, instead of the micromirrors 5, corresponding transmissive microelements, such as prism elements, are arranged, which effect the desired directed beam deflection during transmission.

[0085] It is also possible to apply a color-shifting coating to the microelements. This can be, for example, a thin-film system (with, for example, an absorber, dielectric, and reflector) or liquid crystals, particularly cholesteric liquid crystals.

[0086] The microelements, in particular the micromirrors, preferably have dimensions between 5µm and 50µm and can be designed, for example, as sawtooth gratings with an essentially ray-optical effect (e.g. grating period greater than 5µm).

[0087] When formed with diffractive structures, the diffraction grating can in particular be a sinusoidal grating or an asymmetric grating (for example a sawtooth grating), wherein the grating period is up to a maximum of 5µm and preferably up to a maximum of 2µm.

[0088] The transparent coating used to form the micromirrors 5 is, in particular, a high-refractive dielectric (e.g., TiO2) whose refractive index is at least 0.2 higher than that of the coated material (e.g., the embossing lacquer). To protect against molding, in particular, the high-refractive dielectric coating is preferably embedded between a transparent embossing lacquer and a likewise transparent protective lacquer.

[0089] In Figures 18 and 19 A possible production of the optically variable element 1 is shown schematically. A substrate 15 is provided, which can be, for example, a conventional embossing lacquer, into which the structure of the micromirrors 5 is embossed by means of an embossing tool 16 ( Fig. 19 ). For this purpose, the embossing tool 16 has an embossing surface 17 in which the inverted form of the surface structure to be embossed is formed ( Fig. 18 ).

[0090] The optically variable element 1 according to the invention can be combined with holograms and micromirror images, in particular with a convex effect, stereograms, etc. These can be embossed into the same embossing lacquer in one operation.

[0091] Furthermore, the optically variable element 1 can also be combined with other security features. For example, the optically variable element can be equipped with clear text (recesses in the form of a sequence of numbers, letters, and / or characters in an opaque, particularly metallic, coating), color-shift effects, magnetic features, liquid crystals, and / or fluorescent features.

[0092] The optically variable element 1 can be designed as a foil-based security element. For example, it can be a transfer strip, laminate strip, patch or window thread 19 ( Fig. 1). For this purpose, it can be formed, for example, on a carrier film, from which it can be transferred in a known manner to the value document, such as the banknote 2. It is also possible to form the security element 1 directly on the value document. Thus, direct printing with subsequent embossing of the security element on a polymer substrate can be carried out in order to form a security element according to the invention, for example in the case of plastic banknotes.

[0093] The security element 1 according to the invention can be formed in a wide variety of substrates. In particular, it can be formed in or on a paper substrate, a paper with synthetic fibers, i.e., paper with a proportion x of polymeric material in the range of 0 < x < 100 wt. %, a plastic film, e.g., a film made of polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PN), polypropylene (PP), or polyamide (PA), or a multilayer composite, in particular a composite of several different films (composite composite) or a paper-film composite (film / paper / film or paper / film / paper), wherein the security element can be provided in, on, or between each of the layers of such a multilayer composite.

[0094] Furthermore, a metal layer can be formed on the substrate 15 to form the micromirrors. The material used can be, for example, aluminum, silver, copper, chromium, iron, and / or another metal or alloys thereof. List of reference symbols

[0095] 1Security element 2Banknote 3Flat motif area 4First motif 5Micromirror 6Line 7Border 8Submotif 10Second motif 11Dotted line 12Solid line 15Substrate 16Embossing tool 17Embossing area 19Window thread 20Solid angle 21Viewing direction P1Illumination direction / light incidence P2Direction of the pumping effect α x First viewing angle α y Second viewing angle β x , β y Tilt angle of the micromirrors

Claims

1. Optically variable element having a planar motif region (3) having a first motif (4), which contains a plurality of substructures (8) extending over the entire first motif (4) and each comprising bright and dark partial regions arranged alternately, wherein each substructure (8), upon variation of a first viewing angle (αx) - lying in a first plane - relative to a predefined illumination direction (P1), is visible only at exactly one of the first viewing angles (αx) and all the first viewing angles (αx) are different, with the result that the first motif (4) with only the corresponding substructure (8) is perceptible in a manner dependent on the first viewing angle (αx), wherein the planar motif region (3) comprises directionally reflective elements (5), wherein the directionally reflective elements reflect incident light into a solid angle corresponding to the first viewing angle (αx), wherein the bright partial regions of each substructure are perceptible by way of directional reflection of the corresponding directionally reflective elements, wherein the planar motif region (3) comprises at least one second motif (10), which contains a plurality of substructures (8) extending over the entire second motif (10) and each comprising bright and dark partial regions arranged alternately, wherein each substructure (8) of the at least one second motif (10), upon variation of the first viewing angle (αx), is visible only at exactly one of the first viewing angles (αx) and all the first viewing angles (αx) of the substructures (8) of the at least one second motif (10) are different, wherein each motif, upon variation of a second viewing angle (αy) - lying in a second plane - relative to the illumination direction (P1), is visible only at exactly one of the second viewing angles (αy) and all the second viewing angles (αy) are different, with the result that the corresponding motif (4) with only the corresponding substructure (8) is perceptible in a manner dependent on the first and second viewing angles (αx, αy), wherein the first motif (4) and the at least one second motif (10) present a kinematic effect when there is a change in the second viewing angle (αy), wherein when there is a change in the first viewing angle (αx), the different substructures (8) present a kinematic effect on a smaller length scale in comparison with the kinematic effect of the motifs (4, 10).

2. Optically variable element according to Claim 1, wherein at least in the case of one of the substructures (8), the bright and dark partial regions arranged alternately are at least locally periodically repeated.

3. Optically variable element according to either of the preceding claims, wherein at least in the case of one of the substructures (8), the bright partial regions are formed by a line pattern having at least locally parallel lines.

4. Optically variable element according to any of the preceding claims, wherein the spacing of the bright partial regions in the case of at least one of the substructures (8) is smaller than the extent of the first motif (4) in the direction of the spacing of the bright partial regions by at least a factor of 5, preferably at least a factor of 10.

5. Optically variable element according to any of the preceding claims, wherein the first and second planes are perpendicular to one another.

6. Optically variable element according to any of the preceding claims, wherein the planar motif region (3) comprises reflective facets having dimensions within the planar motif region (3) of at least 3 µm, preferably at least 5 µm and particularly preferably at least 10 µm.

7. Optically variable element according to any of the preceding claims, wherein the planar motif region (3) comprises directionally reflective elements in which the reflective effect is produced by means of diffractive structures, wherein the diffractive structures are embodied as asymmetrical grating structures having a period of a maximum of 5 µm, preferably a maximum of 3 µm and particularly preferably a maximum of 2 µm.

8. Optically variable element according to any of Claims 1 to 6, wherein the planar motif region comprises directionally reflective elements embodied by gratings which are substantially reflective in terms of geometric optics and which have periods of more than 5 µm and preferably more than 10 µm.

9. Optically variable element according to any of the preceding claims, wherein the optically variable element is at least partly transparent.

10. Optically variable element according to any of the preceding claims, wherein the planar motif region (3) is embodied as an embossing structure having a reflection-increasing coating, and / or wherein the planar motif region comprises a colour-shifting coating.

11. Optically variable element according to any of the preceding claims, wherein a plurality of second motifs for different second viewing angles and each having corresponding substructures are provided.

12. Optically variable element according to any of the preceding claims, wherein the substructures extend over the entire planar motif region.

13. Optically variable element according to any of the preceding claims, wherein the substructures as such are perceptible.

14. Valuable document having an optically variable element according to any of the preceding claims.