OPTICALLY VARIABLE SURFACES PATTERN

Description

[0001] The invention relates to an optically variable surface pattern which can be provided, for example, on objects to be protected, so that the optically variable surface pattern allows the authenticity of the object to be checked and / or serves as protection against unauthorized reproduction or imitation.

[0002] Optically variable surface patterns are known that, by means of microscopically small embossed structures, simulate the impression of a macroscopically curved surface. A simple example is a metallized Fresnel lens, which a viewer perceives as a spherical surface. Further examples of more complex motifs are described, for example, in EP 1 562 758 B1.

[0003] From WO 2011 / 066990 A2, it is known to reproduce a curvature with a multitude of small reflective facets. Such surface patterns are well suited as safety features because the optical effect is easy to understand and clearly visible even in poor lighting conditions, and because reproduction using printing techniques is not possible.

[0004] The publication DE 10 2010 025 775 A1 also deals with a security element with a carrier that has a motif area which includes a micro-optical representation arrangement which, as a motif part, presents a reflective surface that appears curved compared to the actual macroscopic spatial shape of the second micro-optical representation arrangement.

[0005] Furthermore, DE 10 2010 048 262 A1 discloses a display element comprising a substrate with a surface area in which a plurality of optical elements are arranged. The display element is designed and intended to generate, upon illumination, a light spot image consisting of a plurality of light spots that appear to a viewer to be floating above or below the surface area and that are arranged in the form of a predetermined motif.

[0006] Due to the high appeal of these optical effects, they are increasingly used not only in the banknote sector but also, for example, in the packaging industry. As a result, the special status of such effects as a security feature is diminishing, and the risk of counterfeiting or imitation is increasing.

[0007] Based on this, it is the object of the invention to provide an optically variable surface pattern which is clearly distinguishable from known optically variable surface patterns in order to guarantee a high level of protection against reenactments or imitations in the future, wherein the effect provided by the optically variable surface pattern should be such that it can be easily recognized and verified by an observer for authenticity testing.

[0008] The object is achieved by an optically variable surface pattern which has a carrier with a first and a second surface region, wherein the two surface regions are designed such that the first surface region presents a curved-appearing first view in a first solid angle range and the second surface region presents a curved-appearing second view in a second solid angle range which is different from the first solid angle range, wherein at least one of the two surface regions presents the curved-appearing view by imitating the reflection behavior of a curved surface, and wherein the imitation of the reflection behavior of the curved surface is brought about by optically effective relief structures, wherein the surface regions are nested within one another.

[0009] This allows a viewer to first perceive the first view and then the second view by tilting the optically variable surface pattern. Even if the two solid angle ranges partially overlap, tilting creates viewing situations in which either only the first view or only the second view is perceptible. This effect is easy for a viewer to understand and verify.

[0010] In particular, at least one of the surface areas is designed as a reflective surface. This allows the viewer to experience a reflection behavior that corresponds to that of an actual curved, reflective surface, which is surprising and very memorable.

[0011] The solid angle ranges can be equal. However, it is also possible that they are different.

[0012] The optically effective relief structures can be formed in a lacquer layer. In particular, they can be molded into an embossed lacquer.

[0013] The optically effective relief structures can be provided with a reflective or at least reflection-enhancing coating. In particular, a metallic or high-refractive-index coating can be used.

[0014] A reflection-enhancing coating within the meaning of the present invention is, in particular, a coating that increases the reflectance, for example, from approximately 20% to approximately 50%, such as semitransparent layers. The reflection-enhancing coating can be a metallic coating, for example, vapor-deposited. Aluminum, gold, silver, copper, palladium, chromium, nickel, and / or tungsten, as well as their alloys, can be used as the coating material.

[0015] In the optically variable surface pattern according to the invention, the optically effective relief structures can comprise micromirrors. The micromirrors are preferably essentially optically effective and can be arranged regularly and / or irregularly.

[0016] The micromirrors can have dimensions between 2 µm and 300 µm, preferably between 3 µm and 100 µm and particularly preferably between 6 µm and 20 µm.

[0017] Furthermore, the relief structures can have diffraction-optical diffraction structures. These diffraction structures can, in particular, be essentially diffraction-optical. Furthermore, the diffraction structures can be symmetrical or, preferably, asymmetrical.

[0018] In the optically variable surface pattern according to the invention, the relief structures can simulate local gradient changes of the corresponding view to be presented for each view. The simulated local gradient changes preferably have gradient values ​​that differ from the corresponding local gradient values ​​of the simulated curved view.

[0019] In particular, the local gradient changes simulated by the relief structures can be selected such that incident parallel light is reflected into the corresponding solid angle range (e.g., the first or second solid angle range). Since human perception is apparently attuned to detecting gradient changes corresponding to a curvature or bulge, while the absolute gradient is difficult to detect, the curved-appearing views are perceptible as such to an observer in the different solid angle ranges.

[0020] One could also say that the relief structures recreate a height function of the corresponding curved view. To characterize the curved view, the height function usually depends on two spatial coordinates in a plane. A local gradient can be determined based on the height function. The local gradient is then changed for the different views so that the presentation occurs in the different solid angle ranges. The change in the gradient can be made depending on both spatial coordinates. However, it is also possible to change the gradient only with respect to one spatial coordinate and leave the gradient unchanged with respect to the other spatial coordinate.

[0021] Of course, it is also possible to choose the change in gradient differently for both location coordinates.

[0022] The surface areas are nested within each other in the optically variable surface pattern . In particular, the optically variable surface pattern can comprise more than two different surface areas. It can comprise three, four, or even more different surface areas, each of which presents differently curved views in different solid angle ranges.

[0023] In particular, the two solid angle ranges cannot overlap when two surface patterns are provided, or even several solid angle ranges when several surface patterns are provided.

[0024] In the optically variable surface pattern, the first and / or second surface area can reflect incident parallel light within an angular range of at least 10°, preferably at least 20°, and particularly preferably at least 30°. This ensures that the associated view becomes visible from a correspondingly large viewing angle range with a clearly recognizable curvature.

[0025] Furthermore, a security element and / or a value document with an optically variable surface pattern according to the invention (including further developments thereof) is provided.

[0026] Furthermore, a method for producing an optically variable surface pattern according to the invention (including further developments thereof) is provided, in which the gradient profiles of the curved views to be presented are determined, the gradient profile of the first view and the gradient profile of the second view are changed via different transformations and the carrier with the two surface areas is produced based on the changed gradient profiles.

[0027] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

[0028] The invention is explained in more detail below by way of example with reference to the accompanying figures, which also disclose essential features of the invention. For clarity, some of the figures are not drawn to scale or proportion. They show: Figure 1 shows a plan view of a banknote 11 with an optically variable surface pattern 10 according to the invention; Figure 2 shows a sectional view to explain the two views presented in different solid angle ranges; Figure 3 shows a sectional view of the optically variable surface pattern 10 with micromirrors 16, 17 for generating the views according to Figure 2 ; Figure 4 shows a sectional view of a surface profile to be reproduced; Figure 5 shows a sectional view of a corresponding arrangement of the micromirrors 16 for reproducing the surface profile according to Figure 4; Figure 6 a sectional view of a surface profile to be reproduced; Figure 7 a sectional view of a corresponding arrangement of the micromirrors 17 for reproducing the surface profile according to Figure 6 ; Figure 8 shows sectional views to explain the nesting of the micromirror arrays of Figures 5 and 7 ; Figure 9 an enlarged sectional view of a part of the micromirror arrangement according to Figure 5 ; Figure 10 an enlarged sectional view of a part of the micromirror arrangement according to Figure 7 ; Figure 11 a sectional view of the micromirror arrangement adapted according to the invention of Figure 9 ; Figure 12 a sectional view of the micromirror arrangement adapted according to the invention of Figure 10 Figure 13 shows an elevation profile accordingly Figure 9 Figure 14 shows an elevation profile accordingly Figure 13; Figure 15 shows the change in the height profile for the micromirrors of the first surface region brought about according to the invention; Figure 16 shows the change in the height profile for the micromirrors of the second surface region brought about according to the invention; Figure 17 shows sectional views to explain the structuring according to the invention starting from the changed structurings 22 and 23; Figure 18 shows a schematic plan view of the optically variable surface pattern 10 to explain one possibility of nesting the two surface regions 24 and 25, and Figure 19 shows a further schematic plan view of the optically variable surface pattern 10 to explain a further variant of the nesting of the two surface regions 24 and 25.

[0029] At the Fig. 1 In the embodiment shown, the optically variable surface pattern 10 according to the invention is integrated as a security element in a banknote 11 in such a way that it is Fig. 1shown front side of the banknote 11. Alternatively, the optically variable surface pattern 10 according to the invention can be present, for example, as a window thread 12.

[0030] The optically variable surface pattern 10, which can also be referred to as an optically variable element 10, is designed as a reflective element 10, which presents a user with two curved-appearing views in two different solid angle ranges α1, α2, as shown in the sectional view of Fig. 2 is indicated. Thus, the incident light L1 is reflected on the one hand into the first solid angle range α1, which extends in the plane of the drawing from the arrow L1 to the arrow L2. On the other hand, the incident light L1 is reflected into the second solid angle range α2, which extends in the plane of the drawing from the arrow L1 to the arrow L3. In the first solid angle range α1, three small, curved-appearing elevations 14 are presented, as indicated by the solid line in Fig. 2is indicated. In the second solid angle range α2, only a single larger elevation 15 is shown, as indicated by the dashed line.

[0031] The curved appearance views (the three elevations 14 and the single elevation 15, respectively) are realized by imitating the reflection behavior of such curved surfaces. This imitation can be achieved, for example, by providing micromirrors 16 to generate the first view of the three small elevations 14 and micromirrors 17 to generate the second view of the large elevations 15, each of which has the corresponding local gradient to create the desired curved appearance, as shown in the schematic sectional view in Fig. 3 The micromirrors 16, 17 are arranged alternately here and can be formed, for example, by a structured lacquer layer 18 whose structured upper side is mirrored.

[0032] The creation of the curved appearance of the three elevations 14 is described with reference to Fig. 4 and 5 explained in more detail, whereby Fig. 4 the surface profile to be reproduced and Fig. 5 shows the corresponding arrangement of the micromirrors 16. In order to achieve the desired effect of the light reflections wandering around like on a metallic relief, for example when tilting the surface pattern 10, the local gradient of the elevations 14 is adjusted by the inclination of the micromirrors 16. If the dimensions of the micromirrors 16 are sufficiently small (for example, less than 100 µm), they are no longer resolved separately by the naked human eye and the entirety of the micromirrors 16 appears to the observer as a continuous surface. Fig. 5The first structuring 19 shown with the micromirrors 16 would therefore present the observer with the three elevations 14, which are perceptible as a protruding, reflective surface compared to the actual macroscopic spatial shape of the first structuring 19.

[0033] Similarly, a second structuring 20 and the correspondingly arranged micromirrors 17 can be used, as in Fig. 7 The large survey 15 has been shown according to Fig. 6 be reproduced.

[0034] Starting from the first and second structuring 19 and 20, a third structuring 21 can then be realized, in which the micromirrors 16 and 17 are arranged alternately, as indicated by the arrows in Fig. 8is indicated. The third structuring 21 could then be formed in a lacquer layer. This would, however, result in the three small elevations 14 and the large elevation 15 being simultaneously perceptible to an observer from the same viewing direction, resulting in a semi-transparent impression. The observer would then not have a metallic impression, but rather, for example, an impression as if the elevations were made of glass. The elevations 14 and 15 thus appear to an observer simultaneously from virtually all viewing directions, and the entire optically variable surface pattern thus appears curved, but also static and unchanging.

[0035] According to the invention, the slope of the micromirrors 16 and 17 in the nested structuring 21 is therefore changed such that incident light L1 is reflected by micromirrors 16, 17 belonging to different views into different solid angle ranges α1, α2.

[0036] The curved appearances (the three small elevations 14 and the large elevation 15) can each be characterized by a height function h, where the height h = h (x, y) usually depends on two spatial coordinates x and y in a plane. For simplicity, only the spatial coordinate x is considered below, which Fig. 3 , 5, 7 and 8 shown sectional views. In Fig. 9 A schematic sectional view of a part of the first structuring 19 with the micromirrors 16 is shown. The local gradient S = dh / dx of the first structuring 19 was formed in such a way that it corresponds to the gradient of the small projections 14 with height h(x). The same applies to the second structuring 20, a part of which is in Fig. 10is shown. Here, too, the local gradient S corresponds to the gradient of the subsequent large elevation 15 with height h(x). The gradient S of the first and second structuring 19 and 20 is always between -0.5 and 0.5 in the exemplary embodiment described here. The division of the reflection directions can now be realized, for example, by specifying a gradient S1 according to S1 = 0.25 + S / 2 for the first view and thus for the first structuring 19 and a gradient S2 according to S2 = -0.25 + S / 2 for the second view and thus for the second structuring 20. The resulting modified first structuring 22 (for the small elevations 14) is shown in Fig. 11 shown.

[0037] Thus, the micromirror 16 1 still has a slope of 0.5, whereas the micromirror 16 2 now has a slope of 0 instead of -0.5. The corresponding modified second structuring 23 for the large elevation 15 is shown in Fig. 12Here, the slope of micromirror 17 1 is changed from 0.5 to 0, and the slope of micromirror 17 2 is changed from 0 to -0.25.

[0038] The gradient S1 is therefore always between 0 and 0.5, which, with perpendicular incidence of light, leads to a first angular range α1 of 0° to approximately +53° (with counterclockwise rotation), and the gradient S2 is therefore always between -0.5 and 0, which, with perpendicular incidence of light, leads to a second angular range α2 of 0° to approximately -53°. This actually corresponds to the adjustment of modified height profiles h1' or h2', which in Figs. 15 and 16 A comparison with the results shown in Figs. 13 and 14 shown original height profiles h1 and h2 shows that the modified first height profile h1' increases monotonically in the x-direction, while the modified second height profile h2' decreases monotonically in the x-direction. In Fig. 13For simplicity of illustration and better comparability, only the height profile of a single elevation is shown. The associated micromirrors 16 and 17 thus reflect, for example, light L1 incident vertically from above, as in Fig. 2 and 3 shown, into different solid angle ranges α1 and α2. The micromirrors 16 always reflect the light into the left solid angle range α1, while the micromirrors 17 always reflect the light into the right solid angle range α2.

[0039] If the micromirrors of the modified structures 22 and 23, as in Fig. 17 As indicated, they are nested together to reach the structured lacquer layer 18 (which is already in Fig. 3is shown), a very surprising effect occurs. From most viewing situations, the viewer no longer sees a superimposition of two different elevation profiles or curved-appearing views, but rather, depending on the viewing angle, usually only sees one of the two curved-appearing views.

[0040] The explanation lies in the fact that the viewer only perceives the image or view that reflects the most ambient light and thus appears significantly brighter. The other image is often so strongly overexposed that the viewer barely perceives it or doesn't perceive it at all. Assuming that the micromirrors 16 and 17 are illuminated vertically from above, as in Fig. 3As shown, when viewed from the left, an observer only sees those facets or micromirrors light up which also reflect the incident light L1 to the left, which in the described embodiment is only the case for the facets or micromirrors 16 with gradients S1. Conversely, when viewed from the right, the observer only sees facets or micromirrors with gradients S2 light up brightly, while all facets with gradient S1 are dark from this side. Viewed from the left, the observer therefore sees the height profile h1' and thus the small elevations 14 which appear curved, while the observer from the right sees the height profile h2' and thus the large elevation 15. The observer therefore sees different representations from the left and right, each of which appears curved.

[0041] Surprisingly, in practice, it's practically unnoticeable that the elevation profile h1' here rises in the x-direction, while the elevation profile h2' falls in the same direction. Human perception is apparently attuned to detecting changes in gradient corresponding to a curvature or arch, while the absolute gradient is difficult to detect. Therefore, to the observer, the arched views appear to exhibit the elevation profile h1 or h2.

[0042] It should be noted that the same effect as when viewed from different positions can also be achieved by tilting the surface pattern 10 according to the invention. It can therefore also be said that the optically variable surface pattern 10 provides a tilted image with a curved effect. Tilting the surface pattern 10 is also the far more common case in practice. A viewer tilts a surface pattern 10 according to the invention about a predetermined axis and observes how a first representation, which appears curved under certain circumstances, transitions into a second representation, which may also appear curved. The effect realized according to the invention is astonishing for a viewer in several respects and is therefore particularly memorable.Even the state-of-the-art reproduction of a macroscopic curvature with microscopically small facets is astonishing, especially when a viewer, contrary to expectations, cannot feel the curvature they perceive with their fingers on a thin film without perceptible elevations and depressions. The fact that such a representation then changes, for example, by tilting it into another, also curved, image is also contrary to common expectations. This tilting effect also increases security against counterfeiting or imitation compared to the state of the art, since it cannot be imitated by printing technology.

[0043] The elevation profiles of the individual representations are advantageously much more complex than the simple elevations 14 and 15 shown here. The first representation can, for example, show a curved-looking value number, while the second representation can show a symbol or a coat of arms. Furthermore, it is possible for one or both representations to show a curved-looking portrait, maps, lettering, and / or other curved-looking representations. Portraits are particularly advantageous because, on the one hand, they show very complex representations and are therefore extremely difficult to recreate, while, on the other hand, they can be very easily recognized and verified by the human observer.

[0044] The situation presented here for the height function h = h(x) can easily be transferred by the expert to the general case h = h(x, y).

[0045] The curved appearance is advantageously realized by an optically effective relief structure, which can be molded in an embossing lacquer 18 and preferably provided with a reflective or reflection-enhancing coating. Color-shifting coatings, e.g., thin-film interference coatings with absorber / dielectric / reflector, or coatings with cholesteric liquid crystals, are also particularly advantageous. The formation of the optically changing relief structure with reflective facets has already been used in conjunction with Figs. 1 to 17It was assumed that a micromirror 16 and 17 of the nested structures 22, 23 are always arranged alternately. However, it is also possible to provide several micromirrors, in particular with the same pitch, instead of the individual micromirror 16, 17 in order to realize a reflective facet. Thus, the reflective facets can be realized as in WO 2011 / 066990 A2. Advantageous dimensions of facet structures are between 2 µm and 300 µm, preferably between 3 µm and 100 µm, and particularly preferably between approximately 6 µm and 20 µm.

[0046] However, it is also possible that the optically effective relief structures are realized by structures that can also be referred to as Fresnel structures, as described in EP 1 562 758 B1.

[0047] The Fresnel structures advantageously have a height of less than 300 µm. Very low heights of less than 10 µm or even less than 5 µm are particularly advantageous.

[0048] Particularly advantageous are asymmetric relief structures, for example with regular or irregular sawtooth profiles. However, the effect according to the invention can also be achieved (albeit with limitations) with symmetric structures such as diffracting holographic gratings. Depending on the design, the optical effect of the relief structures can be essentially ray-optical or diffraction-optical in nature.

[0049] The optical effect according to the invention can also be realized, for example, in a volume hologram instead of relief structures, wherein a surface pattern 10 according to the invention with an optically effective relief structure 18 can serve as a master for exposure.

[0050] The different solid angle ranges α1, α2, from which the at least two different, curved-appearing representations are visible, can overlap, touch or be spaced from each other.

[0051] If they overlap, the first representation is visible from one angular range, the second from another angular range, and both from a third angular range. If they touch, then both representations are essentially only visible from different directions, although the extension of the light source can mean that both representations are visible simultaneously in certain angular ranges. If they are spaced apart, the solid angle range in which both representations are visible simultaneously can be minimized. For example, in the above example, the gradient for h1 can range between -1.2 and -0.2, and for h2 between 0.2 and 1.2.

[0052] The solid angle ranges or the gradient ranges of the different representations do not have to be symmetrical. For example, the gradients for the height profile h1 can be between -0.2 and 0.2, and for the height profile h2 between 0.5 and 0.9. An asymmetrical arrangement can be particularly advantageous if, under typical viewing conditions, the light source is not located in the mirror reflection of the substrate. In further embodiments with more than two different representations, the solid angle ranges can be selected such that the observer only needs to rotate the surface pattern according to the invention about one or two axes to view the different representations.

[0053] The curved-appearing representations in the present sense thus imitate a curvature by simulating the reflection behavior of a curved surface. They therefore contain practically only information about the local gradient of the simulated surface and no absolute depth information, as is the case, for example, with a stereogram. The curved-appearing representation is characterized in particular by the fact that light reflections wander around, for example when the surface pattern 10 according to the invention is tilted, as if on a metallic relief. Such a representation thus resembles a macroscopic embossing, as is known, for example, from coins. Tilting images known in the prior art, for example corresponding embossed holograms with different motifs dependent on the viewing angle, do not exhibit these properties.While the stereographic representations with a 3D effect known in the prior art can depict curved objects, they do not exhibit the property that light reflections move across the depicted objects like a metallic embossing. Stereographic representations or tilted images, in which the impression of curvature is created solely through static shading or similar techniques, just as a good painter can lend his pictures a certain three-dimensionality through skillful color selection, are not depictions that appear curved in the sense understood here.

[0054] The solid angle range in which one of the at least two different representations is visible also determines the corresponding range of slopes S that can be simulated to imitate the reflection behavior of a curved surface. The larger the viewing angle range, the greater the slope differences that can be simulated, and the more pronounced and contrast-rich the curvature appears. Therefore, while it is theoretically possible to nest more than two seemingly curved representations within each other, with an increasing number of different representations, a progressively smaller solid angle range is available for each individual representation, resulting in flatter and lower-contrast representations. For an effective curvature effect, slope differences corresponding to an angular range of reflection directions of at least 10°, preferably at least 20°, and particularly preferably over 30° are preferred.

[0055] In specific embodiments, the optically variable surface pattern 10 according to the invention can advantageously be combined with a known, unchanging curvature effect. Thus, in particular, even individual elements of a curved-appearing display can change depending on the viewing angle. For example, on a clock that appears curved, a hand that appears curved could rotate to a different position depending on the viewing angle, or a person that appears curved could raise their hand or turn their head, for example, when tilting.

[0056] In special designs, it may be advantageous to expand the viewing angle range belonging to one of the views appearing curved differently in different directions. For example, if two curved representations are given by height functions h A (x, y) and h B (x, y), and it is assumed that the corresponding gradients S Ax , S Ay , S Bx , and S By in the x- and y-directions were originally between -0.5 and +0.5, then, analogous to the above procedure, the viewing angle ranges can be separated according to the following transformation of the gradients in the y-direction, while simultaneously leaving the gradients in the x-direction unchanged: S 2 Ay = 0 , 25 + S Ay / 2 S 2 Ax = S Ax S 2 By = − 0 , 25 + S By / 2 S 2 Bx = S Bx .

[0057] The representations thus become somewhat flatter in the y-direction, but continue to fully utilize the specified range of gradients in the x-direction and thus appear more contrasty than if the gradients in the x-direction were also scaled down by a factor of 2. This actually results in a distortion of the recreated elevation profiles, which, surprisingly, is not perceived by the viewer.

[0058] If this example is extended to not just two but many views, the individual views will have increasingly fewer gradient differences in the y-direction and ultimately almost exclusively gradients in the x-direction. However, these are still perceived by the viewer as curved, and it has been shown that even kinematic effects can be realized that still retain the impression of curvature.

[0059] The nesting of the at least two representations can be largely arbitrary. The area of ​​a surface pattern according to the invention can, for example, be divided into individual strips ( Fig. 18 ) or pixels ( Fig. 19 ) are divided, which alternately reflect the incident light according to the curvature of the corresponding representation. In the case of the in Figs. 18 and 19 In the nesting shown in plan view, the hatched stripes or squares can comprise the micromirrors 16, and the non-hatched stripes or squares can comprise the micromirrors 17. The hatched stripes or squares together form a first surface area 24, and the non-hatched stripes or squares together form a second surface area 25.

[0060] The nesting is advantageously chosen so that it is not resolvable with the naked eye. The extent of the associated sections (e.g., strips, squares, etc.) of the areas 24, 25 should be as small as possible in at least one direction, for example, less than 100 µm or even less than 50 µm. The strips or pixels can all be the same size or have different sizes. The pixels can be arranged regularly (for example, hexagonal, rectangular, or especially square pixels on a regular grid) or irregularly and have the same or different shapes. The area proportions of the individual representations can all be the same or different. With different divisions, one of the representations can, for example, appear brighter and with higher contrast than the others.

[0061] The optically variable surface pattern 10 according to the invention can be provided, in particular, in the form of foil-based security elements for banknotes. These include versions as security strips, patches, or, in particular, as window threads 12 ( Figure 1 ) possible.

[0062] The optically variable surface pattern 10 according to the invention can advantageously be combined with other security features, such as fluorescent colors, clear text, e.g., generated by a partially reflective or at least reflection-enhancing coating, magnetic or polarization effects, other optically variable security features such as holograms, etc. List of reference symbols

[0063] 10 Optically variable surface pattern 11 Banknote 12 Window thread 13 Rectangular surface area 14 Small elevation 15 Large elevation 16 Micromirror 17 Micromirror 18 Varnish layer 19 First structuring 20 Second structuring 21 Third structuring 22 Modified first structuring 23 Modified second structuring 24 First surface area 25 Second surface area L1 Incident light L2 Reflected light of the first view L3 Reflected light of the second view α1 First solid angle area α2 Second solid angle area h1 Height profile h2 Height profile h1' Height profile h2' Height profile

Claims

1. Optically variable surface pattern (10) having a carrier (18) comprising a first and a second surface region (24, 25), wherein the two surface regions (24, 25) take such a form that in a first solid angle range (α1) the first surface region (24) presents a first view (14) that appears curved and in a second solid angle range (α2), which differs from the first solid angle range (α1), the second surface region (25) presents a second view (15) that appears curved, wherein at least one of the two surface regions (24, 25) presents the view (14, 15) that appears curved by imitating the reflection behaviour of a curved surface, and wherein the imitation of the reflection behaviour of the curved surface is effected by optically effective relief structures (16, 17), wherein the surface regions are nested.

2. Optically variable surface pattern according to Claim 1, wherein the two surface regions take the form of reflective surface regions.

3. Optically variable surface pattern according to Claim 1 or 2, wherein the optically effective relief structures take the form of a lacquer layer.

4. Optically variable surface pattern according to any of Claims 1 to 3, wherein the optically effective relief structures are provided with a reflective or at least reflection-enhancing coating.

5. Optically variable surface pattern according to any of Claims 1 to 4, wherein the optically effective relief structures comprise micromirrors, in particular wherein the micromirrors have dimensions between 2 µm and 300 µm, preferably between 3 µm and 100 µm and particularly preferably for instance between 6 µm and 20 µm.

6. Optically variable surface pattern according to any of Claims 1 to 5, wherein the optically effective relief structures have diffraction structures with a diffraction-optical effect.

7. Optically variable surface pattern according to any of Claims 1 to 6, wherein for each view, the relief structures in each case simulate local slope changes of the corresponding view to be presented, wherein in particular the local slope changes simulated by the relief structures are chosen such that incident parallel light is reflected into the corresponding solid angle range.

8. Optically variable surface pattern according to any of the preceding claims, wherein the two solid angle ranges do not overlap.

9. Optically variable surface pattern according to any of the preceding claims, wherein the first and / or second surface region reflect / reflects incident parallel light into an angular range of at least 10°, preferably at least 20° and particularly preferably at least 30°.

10. Security element having an optically variable surface pattern according to any of Claims 1 to 9.

11. Valuable document having an optically variable surface pattern according to any of Claims 1 to 9.

12. Method for producing an optically variable surface pattern (10) according to any of Claims 1 to 9, wherein - the slope profiles of the views (14, 15) to be presented are ascertained, - the slope profile of the first view (14) and the slope profile of the second view (15) are modified by way of different transformations, and - the carrier (18) having the two surface regions (24, 25) is manufactured on the basis of the modified slope profiles.