OPTICALLY VARIABLE ELEMENT

Description

[0001] The invention relates to an optically variable element, in particular an optically variable safety element.

[0002] WO 03 / 059643 A1 discloses an optically variable element in which a first layer of a high-refractive-index material is embedded in a second, low-refractive-index material. The two interfaces between the first layer and the second material are designed as relief structures, thus providing a diffraction grating. The diffraction grating should have a grating period of no more than 500 nm. This results in a waveguide within the second material, which has the form of a continuous sine wave. This leads to zero-order diffraction, generating a color upon illumination that depends on the rotation angle and / or the illumination angle.

[0003] The rotation angle and the illumination angle are defined here with respect to a rotation that occurs in a plane defined by the optically variable element just formed ("paper plane"). The definition therefore refers to a rotation about a normal to the surface of the optically variable element.

[0004] Thus, with constant illumination, the viewing angle changes when the optically variable element is rotated in the plane. A first area of ​​the optically variable element from WO 03 / 059643 A1 can generate a first color at a first viewing angle. A second area can generate the first color at a second viewing angle. The area that generates the first color changes with a 90° rotation.

[0005] EP 0 105 099 A1 discloses an optically variable element using first and higher order diffraction structures, in which, when rotated in the plane of the paper along a predetermined path, successive areas light up in color one after the other, creating the impression of the colored area jumping along this path.

[0006] EP 2 447 743 A1 discloses an isotropic optical filter and a manufacturing process for such a filter.

[0007] DE 103 08 327 A1 discloses a grid structure for securing valuables which, when viewed in a specific spectral range, produces a zeroth-order grid image.

[0008] The invention is based on the objective of providing an optically variable element that is characterized by improved optical properties.

[0009] This problem is solved by an optically variable element, in particular an optically variable safety element, according to claim 1.

[0010] Preferably, the optically variable element has at least one first diffraction grating and at least one second diffraction grating with a respective grating period in the range of between 180 nm and 420 nm.

[0011] This allows the optically variable element to provide either the effect of a, in particular quasi-continuous, movement of a color and / or a colored image change (image flip).

[0012] The diffraction gratings in the optically variable element are preferably provided with a high-refractive-index dielectric first layer of preferably constant thickness, which acts as a waveguide. Optionally, the diffraction gratings can also be provided with a layer sequence of high-refractive-index (H) and low-refractive-index (N) dielectric layers, e.g., a three-layer system HNH. A diffraction grating has (according to a predetermined definition) an azimuth angle. In a linear grating, there is a preferred direction along which a sequence of peaks and troughs is provided. The azimuth angle describes the angle at which the lines along which the peaks and troughs of the grating follow one another are relative to a reference line that runs in the plane from which the peaks and troughs extend vertically.Although a cross grid has two distinct directions along which there is a sequence of mountains and valleys, one can choose one of these directions to define the azimuth angle.

[0013] In the optically variable element according to the invention, the two diffraction gratings exhibit a color effect in different ways, the arrangement being designed such that rotation of the optically variable element in its paper plane (or substrate plane) results in a quasi-continuous movement of a color, which is particularly noticeable and memorable to the viewer. Such security features cannot be copied with conventional copying devices due to the small grating period – these are so-called subwavelength gratings. They can be opaque or transparent and can be used, for example, on banknotes as well as in identity documents.

[0014] In a first aspect of the invention, the optically variable element comprises at least three zones that follow one another in at least one lateral direction (defined in the substrate plane), each zone having a diffraction grating, the first zone having the first diffraction grating, the second zone having the second diffraction grating, and the third zone having a third diffraction grating that differs from the first and second diffraction gratings, wherein the two diffraction gratings belonging to the zones that follow one another or are adjacent in the at least one lateral direction differ in that i) their azimuth angles differ by at least 0.1° and at most 15°, preferably by at least 0.1° and at most 9° and / or ii) their lattice periods differ by a value in the range of 1 nm to 10 nm, wherein for at least three consecutive zones of the zones the respective value for the azimuth angle and / or the grid period changes in the same direction (i.e. either upwards or downwards), preferably by the same amount for each consecutive zone.

[0015] In other words, the azimuth angle and / or the grating period vary slightly from zone to zone. Therefore, any rotation (in the plane of a substrate of the optically variable element) results in a change in the viewing angle. For example, if a first color is generated by a first zone and then rotated, this first color is generated in the second zone adjacent to the first, then in the third zone adjacent to the second, and so on. This creates the effect of a (quasi-)continuous movement of the first color. However, since this is a suitably designed zero-order diffraction, all successive zones remain colored in the color determined by the optical conditions. Thus, the effect of a quasi-continuous shift of all colors within the sequence of zones is achieved.However, the diffraction gratings can also be chosen in such a way that some of the zones become invisible to the unarmed human eye, as the reflected color migrates into the UV-A spectral range or near IR spectral range.

[0016] Preferably, the optically variable element comprises at least four, more preferably at least five, and particularly preferably six zones that follow one another in at least one lateral direction (defined in the substrate plane), each zone having a diffraction grating, wherein the two diffraction gratings belonging to the zones that follow one another or are adjacent in the at least one lateral direction differ in that i) their azimuth angles differ by at least 0.1° and at most 15° and preferably by at least 0.1° and at most 9° and / or ii) their lattice periods differ by a value from the range of 1 nm to 10 nm,

[0017] Preferably, the successive zones abut directly against each other, in particular without any gap that can be resolved by the unarmed human eye.

[0018] Color is understood as an individual visual (sensory) perception caused by light that lies within the visible spectrum for the human eye or in the adjacent ultraviolet-A and near-infrared ranges. This perception is also referred to as color perception or color impression. The colors visible to humans lie in the range between 380 nm [violet] and 780 nm [deep red] of the electromagnetic spectrum, whereby the relative sensitivity of the eye below 430 nm and above 690 nm is less than 1% of the maximum value at 555 nm. Consequently, only very intense light sources, such as ultra-bright LEDs or lasers, are perceived in the spectral ranges of 380 nm–430 nm and 690 nm–780 nm. Color, as the perceived entity, arises from the visual stimulus in color receptors in response to a color valence.Color is not a property of the perceived light (color stimulus), but rather the subjective perception of the physical cause of electromagnetic waves. According to spectral color valence (different intensities in light of different wavelengths or in radiation adjacent to light, such as ultraviolet A or near-infrared), different color stimuli are produced, resulting in different qualities of color perception, and ultimately, different colors are perceived. A spectral color is the color impression produced by monochromatic light in the visible part of the light spectrum. It is always the most intense, and therefore pure, color. Examples of spectral colors are, for blue, a monochromatic laser with a wavelength of 473 nm; for green, a monochromatic laser with a wavelength of 532 nm; and for red, a monochromatic laser with a wavelength of 635 nm.

[0019] The azimuth angle can always be specified if the diffraction grating is not rotationally symmetric. This is usually the case with conventionally used linear gratings, cross gratings, or hexagonal gratings. The cross and hexagonal gratings can have the same or different grating periods dx and dy in the two different grating directions.

[0020] In a linear grid, there is a preferred direction along which a sequence of peaks and troughs is defined. The azimuth angle is an angle defined relative to this preferred direction. In a cross grid, there are two directions along which a sequence of peaks and troughs occurs, but one of these directions can be selected to define the azimuth angle.

[0021] Preferably, the azimuth angle of the diffraction gratings of successive zones, as defined in this way, differs by an amount between 0.1° and 15°, particularly by an amount between 0.2° and 10°, and most preferably by an amount between 0.5° and 5°. At these values, a continuous migration of a color is perceived to an increasingly greater degree.

[0022] In a preferred embodiment relating to this first aspect, the grating period of two diffraction gratings of successive zones differs by a value in the range of 1 nm to 7 nm, preferably in the range of 1 nm to 5 nm, wherein the grating period is, for example, between 340 nm and 400 nm, e.g., 380 nm for the first diffraction grating, 377 nm for the second diffraction grating, etc. Even with these values, one obtains a heightened impression of continuity in the movement of the color perceived at the optically variable element.

[0023] According to the invention, one or more of the zones, and in particular each of the zones, has a dimension of more than 0.5 mm in two lateral directions, preferably a dimension of more than 1 mm in at least one lateral direction, and particularly preferably a dimension of more than 3 mm. Additionally or alternatively, the feature can be realized that one or more, and in particular each of the zones, has a dimension of at most 50 mm in two lateral directions.

[0024] The dimensions mentioned are such that when viewing the optically variable element at a suitable distance (e.g., a reading distance of 30 cm), a zone as a whole can still be visually resolved, but the optically variable element is not too large overall.

[0025] In all previously mentioned embodiments relating to the first aspect, the zones can form a straight or curved band. One perceives a movement of the same color(s) along the zone arrangement, i.e., along the band.

[0026] Alternatively or additionally, successive zones can each have the form of a curved band, which is at least partially surrounded by another zone following it, also in the form of a curved band. Preferably, concentric closed bands and particularly preferably ring-shaped bands are provided by the zones. The effect achieved here is comparable to the effect of a pumping motion. The specifications mentioned in the first aspect regarding the azimuth angle to the diffraction gratings or the grating period of the diffraction gratings ensure the impression of a color effect moving continuously from the inside out or from the outside in when the optically variable element according to the invention is rotated or tilted. This pumping effect can also be perceived as a quasi-expansion or quasi-contraction of a motif's contour.

[0027] In all previously mentioned embodiments relating to the first aspect, one or more zones can comprise a plurality of first areas and second or second and third or second, third and further areas, which provide a different optical effect than the first areas, wherein in the first areas the same diffraction grating is formed from the first diffraction grating, the second diffraction grating, the third diffraction grating or a further diffraction grating.

[0028] Interlacing the areas ensures that the first areas and the second, third, and / or subsequent areas are not perceived as independent and, if necessary, cannot be resolved by the naked eye (given a suitable size). In particular, multiple optical effects can be achieved within a single color effect area (or sub-area thereof). For this purpose, it is preferably provided that the first areas and / or the second areas and / or any third and / or subsequent areas have a dimension of less than 300 µm in a first lateral direction, preferably between 50 µm and 200 µm.

[0029] In a first variant of this embodiment with the different areas, the other optical effect consists of generating a color that depends on the respective viewing angle and the specified illumination angle. This color differs, at least for a range of rotation and illumination angles, from the color generated by the first areas. Overall, this results in a multi-colored effect that can occur either sequentially or simultaneously when rotating in the plane of the optically variable element. Such effects are particularly appealing and, at the same time, counterfeit-proof.

[0030] In a variant of the embodiment with the different areas, it may be provided that the other optical effect is based on a different physical principle. In particular, different microstructures are provided in the second, third, or further areas of the diffraction gratings (or relief structures) formed in the first areas, in particular isotropically or anisotropically scattering matte structures, holograms, diffraction gratings with a spatial frequency of between 300 lines / mm and 1800 lines / mm, and / or diffractive diffraction gratings that imitate freeform surfaces, and / or in particular refractive macrostructures, such as faceted surfaces or freeform surfaces, and / or a TRUSTSEAL® and / or a KINEGRAM®.

[0031] Isotropically scattering matte structures are characterized by irregularly arranged microstructures, with the lateral size of the microstructures typically varying around a mean value. The mean diameter of the microstructures is typically in the range of 1 µm to 50 µm. The majority of the microstructures are nearly rotationally symmetric. The mean diameter determines the scattering angle up to which the light is deflected from direct reflection. The light is scattered equally for all rotation angles ϕ (given a constant illumination angle Θ), resulting in the isotropic brightness impression.

[0032] Anisotropically scattering matte structures are also characterized by irregularly arranged microstructures, with the lateral size of the microstructures varying around a mean value. The mean diameter of the microstructures is again typically in the range of 1 µm to 50 µm. However, unlike isotropically scattering matte structures, the majority of the microstructures are not rotationally symmetric, but rotationally asymmetric, e.g., elongated. That is, the mean diameter of the microstructures in one lateral direction differs significantly from the mean diameter in the second lateral direction, which is perpendicular to it. For example, the mean diameter in one lateral direction can be at least twice as large as the mean diameter in the other lateral direction. The microstructures can, for instance, have a cigar-like shape.The different mean diameters in the two lateral directions result in different scattering angles, up to which the light is deflected from direct reflection. Consequently, the light is scattered to varying degrees when the viewing angle or rotation angle ϕ is varied, creating the anisotropic brightness impression.

[0033] In particular, if the other optical effect provided by the second and possibly further areas is based on a different physical principle or if completely different microstructures are provided, it is preferably provided that in one or more and preferably each zone, the first areas occupy at least 50% of the area covered by the respective zones, preferably between 50% and 90%, and particularly preferably between 60% and 80%. This ensures that the generated color effect is visually recognized as the most important feature.

[0034] In all variants of the embodiment with the different areas, it is preferably provided that the other optical effect, when the rotation angle and / or illumination angle is changed, consists of the appearance of movement of an optical property, which is either in the same or opposite direction to the appearance of movement of the color generated by the first areas along the successive zones. In other words, a movement effect is also created by the other optical effect. If it is in the same direction as the appearance of movement of the generated color, then the latter effect is intensified. If it is in the opposite direction, then an interesting optical effect is created.

[0035] In a second aspect of the invention, the fourth and fifth grid regions are at least partially nested within one another to form a one- or two-dimensional grid, wherein the fourth grid region contains at least one first diffraction grating and the fifth grid region contains at least one second diffraction grating. This nesting ensures that different effects are generated in the same region of the optically variable element.

[0036] By appropriately selecting the parameters, it can be ensured, for example, that within a predetermined rotation angle range and at a given illumination angle, the first and second diffraction gratings generate a respective color with a first intensity, and that outside this rotation angle range and at a given illumination angle, electromagnetic radiation from the visible light spectrum is generated only with a second intensity that is at most one-third, preferably at most one-fifth, and particularly preferably at most one-tenth of the first intensity. In this way, the visual effect of an object represented by the respective diffraction grating disappearing upon rotation in the substrate plane of the optical variable element can be achieved.

[0037] Outside the predetermined rotation angle range, a color from the ultraviolet-A or near-infrared range is generated, particularly by the respective diffraction gratings, with an intensity that is at least 50% of the first intensity. Whenever the present application refers to a color (especially when it is generated by wavelengths either smaller than 430 nm or larger than 690 nm), this also includes the case described here, where the effective second intensity is at most one-third, preferably at most one-fifth, and particularly preferably at most one-tenth of the first intensity at which a color is clearly visible. The term "color" in this context therefore also includes a faint, barely perceptible sensory impression on the eye.

[0038] In one example, the fourth grid areas, on the one hand, and the fifth grid areas, alone or in combination with sixth grid areas or with sixth and further grid areas, on the other hand, represent different objects, where an object is a motif, in particular a geometric shape, a pattern, a symbol and / or an alphanumeric character, and / or an image background. Here, it is deliberately ensured that more than one object is represented, and the nesting of the different grid areas ensures that these different objects ultimately appear to be present in the same sub-area of ​​the optically variable element.

[0039] In the latter embodiment, it is preferably provided that, at least at a first rotation angle relative to a predetermined illumination angle, the same color is generated for two different objects despite the different properties (different grating parameters) of different diffraction gratings, while at a second rotation angle relative to the predetermined illumination angle, this is not the case (namely, different colors due to different grating areas, or individual grating areas remain completely invisible). In this way, the effect can be achieved, particularly at the first rotation angle and the predetermined illumination angle, that a displayed motif is invisible against a background (since the motif and the background have very similar or the same color), but appears visually at the second rotation angle relative to the predetermined illumination angle (since the motif and the background have different colors).

[0040] Preferably, the fourth and / or fifth grid areas have a dimension of less than 300 µm in at least one lateral direction.

[0041] In a third aspect of the invention, a plurality of color areas are provided which are arranged according to a one- or two-dimensional grid and each form a pixel of a first motif, wherein the color areas have a combination of seventh and eighth or seventh, eighth and ninth sub-areas, wherein at least one first diffraction grating is provided in the seventh sub-areas, at least one second diffraction grating is provided in the eighth sub-areas and at least one third diffraction grating is provided in the ninth sub-areas that may be present.

[0042] In this third aspect, the seventh, eighth, and possibly ninth sub-areas together generate a multicolored image visible at at least one rotation angle and a given illumination angle. This involves the interaction of these different sub-areas. The diffraction gratings in the sub-areas differ primarily in the grating parameters of grating period and / or azimuth angle and / or grating depth, while the average thickness of the first layer is the same.

[0043] Preferably, one or more of the color regions have a dimension of at most 300 µm, preferably between 50 µm and 200 µm, in each lateral direction. In this way, the color regions are not, or only barely, resolvable by the naked human eye at a predetermined distance of, for example, 30 cm. These are then particularly well suited as picture elements (pixels).

[0044] Alternatively, it can be provided that one or more of the color regions have a dimension of less than 300 µm, preferably less than 80 µm, in one lateral direction (i.e., defined in the substrate plane of the optically variable element) and a dimension of more than 300 µm, preferably more than 1 mm, in a second lateral direction. In this way, an image can be composed of strip-shaped elements. This allows for interesting optical effects. In particular, if the multicolored image is visible as a true-color image when viewed along these strips, but is no longer visible as a true-color image when viewed perpendicular to the strips, an interesting optical effect is achieved at the aforementioned dimensions.

[0045] In particular, a multicolored image can be generated by the color areas at a first rotation angle and a given illumination angle, and a monochrome image can be generated by the color areas at a second rotation angle and the given illumination angle. This can again be achieved by having individual sub-areas emit electromagnetic radiation in a spectrum whose reflection peak lies beyond the range of visible light when rotated.

[0046] In all previously mentioned embodiments of the invention, it can be provided that the at least one first diffraction grating and the at least one second diffraction grating are superimposed on a blaze grating. In particular, if the blaze grating is low-frequency and more than two, preferably more than five, periods of the diffraction grating are provided per period of the low-frequency blaze grating, arranging the diffraction gratings on one flank of a blaze grating ensures that a color impression, which is normally visible when viewed perpendicularly, instead appears at an illumination and viewing angle of approximately 20° to 30°, depending on the structure depth of the low-frequency blaze grating, which can be, for example, in the range of 500 nm to 5000 nm.

[0047] The asymmetry of the low-frequency blaze gratings means that when the optically variable element is rotated by 180°, the surface normals of the diffraction grating are oriented differently, resulting in different color impressions at 0° and 180° rotation angles under illumination and viewing angles of 20° to 30°. For example, at a rotation angle of 0°, a diffraction grating on a flat surface (i.e., without superposition with a low-frequency blaze grating) and a diffraction grating on an inclined flank of a low-frequency blaze grating (i.e., with superposition) may exhibit the same or very similar colors. However, when rotated by 180°, the two diffraction gratings then exhibit significantly different color impressions compared to each other under illumination and viewing angles of 20° to 30°.

[0048] According to the invention with respect to the first, second and third aspects, the optical variable element has a first layer made of a first material and a second layer made of a second material, wherein the first diffraction grating and the second diffraction grating are provided by a (particularly diffractive) relief structure formed at the interface of the first layer to the second layer.

[0049] In this process, the first material should be highly refractive and embedded in the second layer. The second material (in the spectral range visible to the naked eye) should have a refractive index at least 0.2, preferably at least 0.5, lower, thus providing a waveguide of the type described in WO 03 / 059643 A1. Here, "high refractive" means a first material with a refractive index in the visible spectral range (typically at a wavelength of approximately 635 nm) of more than 1.7. Examples of such high-refractive-index first materials are listed in Table 1. The numerical values ​​are only rough guidelines, as the actual refractive index of a layer depends on many parameters such as crystal structure, porosity, etc. Table 1: material Sum formula Refractive index n Lead sulfide PbS 4,33 Zinc telluride ZnTe 3,04 Silicon carbide SiC 2,64 iron oxide Fe2O3 2,92 Barium titanate BaTiO 3 2,41 Titanium dioxide (refractive index depends on the crystal structure) TiO2 >2,4 Zinc sulfide ZnS 2,35 Niobden oxide Nd2O5 2,32 Zirconium oxide ZrO 2 2,21 Tantalc pentoxide Ta 2 O 5 2,2 zinc oxide ZnO 2,1 Silicon nitride Si 3 O 4 2,02 Indium oxide In 2 O 3 2,0 Silicon monoxide SiO 1,97 Hafnium oxide HfO 2 1,91 Yttrium oxide Y2O3 1,9 Aluminum oxide nitride AlON 1,79 Magnesium oxide MgO 1,74

[0050] Alternatively, the high-refractive-index first material consists of a so-called hybrid material, which comprises metal oxide polymers or nanoparticles of high-refractive-index material embedded in an organic matrix. For example, this hybrid material can consist of a mixture of poly(dibutyl titanate) polymer and poly(styrene-allyl alcohol) copolymer.

[0051] Preferably, the first material has a refractive index of more than 1.8, and more preferably of more than 2.0. This is the case, for example, with zinc sulfide and titanium dioxide.

[0052] Such a first material can be embedded in a low-refractive-index second material. Low-refractive-index means a second material with a refractive index in the visible spectral range (typically at a wavelength of approximately 635 nm) of less than 1.7 and preferably less than 1.6. Examples of such low-refractive-index materials are listed in Table 2. The numerical values ​​are only rough guidelines, as the actual refractive index of a layer depends on many parameters such as crystal structure, porosity, etc. Table 2: material Sum formula Refractive index n Poly(ethylene terephthalate) (PET) (C 10 H 8 O 4 ) n 1,64 Polystyrene (PS) (C 8 H 8 ) n 1,59 Polycarbonate (PC) - 1,58 Polyvinyl chloride (PVC) (C 2 H 3 Cl) n 1,54 Plexiglass (PMMA) (C 5 O 2 H 8 ) n 1,49 Polyacrylate - 1,49 Cellulose (C 6 H 10 O 5 ) n 1,47 Glass SiO2 1,46 Magnesium fluoride MgF 2 1,38 Polytetrafluoroethylene (PTFE) (C2F4)n 1,35

[0053] The first material can preferably be embedded in a second material made of a polymer, which second material has a refractive index of between 1.4 and 1.6, e.g. of 1.5.

[0054] Preferably, the profile depth of the relief structure is between 50 nm and 500 nm, particularly preferably between 80 nm and 250 nm.

[0055] Furthermore, the profile of the relief structure is preferably sinusoidal, rectangular or provides a blaze grid, and in particular may be sawtooth-shaped.

[0056] According to the invention, the thickness of the first layer is consistently the same or at least average, between 30 nm and 300 nm, particularly preferably between 50 nm and 200 nm. This provides a non-rotationally symmetric diffraction grating with the desired optical properties (achieving a zero-order diffraction effect) in a particularly efficient manner.

[0057] The aforementioned layer thickness is particularly suitable when the first layer is intended to provide a waveguide that is embedded in the second layer.

[0058] In all embodiments where the first material is embedded in the second material, forming a waveguide of the type described in WO 03 / 059643 A1, the following measure is preferably additionally implemented: In the color effect area, outside the zones, first material is also provided which is embedded in the second material, but without a zero-order diffractive relief structure being formed at an interface, wherein at least in some areas the first material is removed and / or wherein at least in some areas a metal layer is applied.

[0059] By removing the first layer of material (especially the high-refractive-index material), zero-order diffraction is prevented in the respective areas, meaning no color is perceived. With appropriate shaping, this allows for the integration of an additional security feature in these areas, for example, in the form of geometric shapes, patterns, symbols, and / or alphanumeric characters.

[0060] Furthermore, by specifically applying the metal layer in the form of structures (geometric shapes, patterns, symbols and / or alphanumeric characters), a higher degree of counterfeit protection is ensured.

[0061] In all the aforementioned embodiments, a color layer is preferably provided, particularly below the first layer, and optionally also below the second material in which the first layer is embedded. The color layer is preferably dark, particularly black or dark gray, dark green, dark blue, or dark red, and preferably has a patterned shape. For example, the color layer can be shaped in the form of a further motif or object. By using such a color layer, it is possible to increase the contrast intensity when providing the color effect in the color effect area and, for example, to personalize and / or modify the image presented to the viewer through a patterned design of this layer.This contrast enhancement is achieved primarily through the absorption of light components that pass through the other layers and would otherwise be reflected and scattered at a lighter substrate surface. This scattered light would be reflected back, weakening the optically variable effect or its color effect. The color layer can be a tinted lacquer layer, adhesion promoter layer, or adhesive layer. For example, the color layer can be a lacquer highly filled with pigments of carbon black, graphite, or dioxazine violet. "Highly filled" in this context means that the pigment content in the lacquer is comparatively high, particularly between approximately 5% and 40%. It can also be applied before the lacquer layer, adhesion promoter layer, or adhesive layer, and in this case, it can be applied partially—for example, in the form of a logo. Furthermore, the color layer can be used to reference the color movement effect, i.e.,The color layer can serve as an optically static element, providing orientation or a point of reference for the human eye when viewing the optically variable effects according to the invention.

[0062] The features according to the first, second and third aspects can also be realized in combination in an optically variable element.

[0063] Preferred embodiments of the invention are described in more detail below with reference to the drawing, in which Fig. 1 Figure 1 shows a non-scale section through a section of an optically variable device according to a setup as used in the invention. Fig. 2a a schematic representation of individual zones as a top view of a first embodiment of the invention with enlarged partial sections shows, Fig. 2bSeveral different reflection spectra applicable to different rotation angles are illustrated, which correspond to individual zones from the exemplary embodiment according to Fig. 2a are effective Fig. 2c - 2e in the exemplary embodiment according Fig. 2a schematically illustrate the color effect achieved at different rotation angles, Fig. 3 A second embodiment of the invention is shown in a schematic section in top view, Fig. 4a and Fig. 4b A third embodiment of the invention, viewed from different angles of rotation, will be illustrated in its basic structure from a top view, and for this purpose Fig. 4c and Fig. 4d to illustrate the respective color effect achieved, Fig. 5a a complete view in top view and Fig. 5b illustrates a partial view of an area in which a grid of individual grid elements is planned, Fig. 6 A fourth embodiment of the invention is illustrated in a top view, starting from the embodiment according to Fig. 2a a grid according to Fig. 5a / b with such raster areas that generate a different optical effect, Fig. 7a - 7c A fifth embodiment of the invention is illustrated in a top view, in which two different objects are provided, wherein Figs. 7d and 7e Represent reflection spectra, which are used to explain the respective optical effect achieved. Fig. 8a - 8e illustrate a sixth embodiment of the invention in a top view, Fig. 9a - 9c illustrate a seventh embodiment of the invention in a top view, which is a modification of the fifth embodiment, to which Fig. 9d Represent reflection spectra, which are used to explain the effect achieved, Figs. 10a to 10d show an eighth embodiment of the invention in a top view, Fig. 11a - 11c A ninth embodiment of the invention is shown in a top view, and to this end, Fig. 11d shows an exemplary layer structure, Fig. 11ea superimposition of a diffractive relief structure with a blaze grid and illustrates the application of this superimposition in an example, Fig. 12a and b Show an example of a security document in the form of a banknote in a top view, in which an embodiment of the invention is realized. Fig. 13 An example of a page of a passport document in top view shows an embodiment of the invention. Fig. 14 A schematic example of a KINEGRAM ®< TKO or KINEGRAM ®< PCI is shown.

[0064] The following are examples of optically variable elements in which a color change is achieved upon rotation.

[0065] The basic layer structure of such an optically variable element is derived from the Fig. 1As can be seen: A first layer 10 made of a high-refractive-index material such as zinc sulfide (ZnS) or titanium dioxide (TiO₂) is embedded in a polymer that is low-refractive-index, e.g., has a refractive index of 1.5. The polymer forms a Fig. 1The second layer, designated 12, has a flat surface 14. In contrast, the interface 16 between the first layer 10 and the polymer 12 is designed as, for example, a diffractive relief structure, as is the interface 18 on the underside. The interfaces 16 and 18 exhibit relief structures that are essentially parallel to each other, such that the first layer 10 has an average thickness s. This thickness of the first layer 10, which functions as a waveguide layer, is typically between 30 nm and 300 nm on average, preferably between 50 nm and 200 nm. The relief depth (relief depth = distance between the "peak" and "valley" of the relief structure) at the two interfaces 16 and 18 can be the same, but need not be. This is shown in Fig. 1A sinusoidal shape of the diffractive relief structure provides a diffraction grating. (Alternatively, a rectangular shape or an asymmetrical shape, e.g., a sawtooth to provide a blaze grating, and the like, may also be provided.) The diffraction grating has a grating period d in the range of 100 nm to 500 nm, preferably between 180 nm and 420 nm. If the relief depth t has a value between 50 nm and 500 nm, and preferably between 80 nm and 250 nm, the effect of zero-order diffraction is demonstrated, as known, for example, from WO 03 / 059643 A1: At an angle of incidence Θ, a portion of the light is diffracted into zero order, so that at an angle of reflection also Θ, light enters the eye of an observer. In other words, the color impression occurs at an angle of illumination (or angle of incidence) equal to the angle of reflection, or in direct reflection.The angle Θ is typically greater than or equal to 10°, preferably less than 45°. Another portion of the light is transmitted. Since there is typically almost no absorption in the first layer, the effects of quasi-continuous color shift or color image change described below for reflection are also present analogously in transmission. Because light of different wavelengths with different intensities is diffracted to the zeroth order, the optically variable element appears colored. The color depends on the viewing angle or rotation angle Φ. (The illumination angle can also be a factor.) The viewing angle Φ is defined here as the rotation angle about a normal N perpendicular to the planar surface 14 of the first material 12. For a planar optically variable element, this also involves a rotation in its plane.

[0066] The diffraction grating can be a linear, cross, or hexagonal grating, or even take on more complex forms. The following examples assume a linear grating with a defined azimuth angle α: This describes the angle at which the lines, along which the peaks and troughs of the grating follow one another, are relative to a reference line running in plane 14.

[0067] In a first embodiment according to Fig. 2a A first, arrow-shaped region, designated as a whole by 20, is provided in the plane of the (substrate of the) optically variable element spanned by the x and y directions. This region is subdivided into several successive zones 22 in the sequence defined by the direction of the arrow. A characteristic feature of this embodiment is that each of the zones 22 contains a linear grid as described with reference to Fig. 1The described arrangement states that the linear grids of two adjacent zones differ in the azimuth angle α. However, it is stipulated that the azimuth angle between two consecutive zones differs by only 10°, i.e., by less than 15°.

[0068] Since the color effect produced by the linear grating depends on the viewing angle or rotation angle Φ, the different zones 22 appear in different colors. This can be seen from the reflection spectrum in Fig. 2bExplain where a first, solid curve 24 shows the reflection spectrum at a rotation angle of Φ = 0°, a second curve 26 (dotted) the corresponding reflection spectrum at a rotation angle of Φ = 45°, and the corresponding reflection spectrum 28 (dashed) at a rotation angle of Φ = 90°. All reflection spectra shown in the figures were calculated using the C-method. The C-method calculates the reflection and transmission spectra by flattening the interfaces of the diffraction grating through a transformation of the coordinate system. In other words, the grating structure is then hidden in the new coordinate system. A limitation of the C-method is that the interface (and thus the profile shape of the diffraction grating) must be described by a differentiable function f(x).

[0069] The reflection spectra mentioned are valid for a lattice period of 380 nm, a lattice depth of 150 nm, using zinc sulfide as the first layer 10 with a thickness of 80 nm, which is embedded in a polymer as the material of the second layer 12 with a refractive index of approximately 1.5. The reflection peak in the reflection spectra plays the most important role in evaluating the color impression. In curve 24, the broad peak is located at approximately 500 nm, in curve 26 at approximately 540 nm, and in curve 28 at approximately 630 nm. This corresponds to a color change from green through light green to deep red.

[0070] As illustrated by a black and white representation in the Fig. 2c - 2e As explained, the starting position can therefore be seen according to Fig. 2c (Illumination angle Θ≈30°) a portion of zones 22 (with α = 90°) at the beginning of the arrow is illuminated in color F1 (approximately red), which, according to the spectrum, transitions to color F2 (approximately green) towards the arrowhead. Zones F3, also in light green, are present in between. If the optically variable device is now rotated by 45°, one sees, according to Fig. 2d In the middle of the arrow, the color F1 (red) is displayed, while towards the end and tip of the arrow, the color transitions to light green F3. If the arrow is rotated another 45°, for a total of 90°, a continuous color-shifting effect occurs in direct reflection, resulting in a multicolored arrow as shown. Fig. 2e See colors F2 and F1: The beginning of the arrow is approximately green, the tip approximately red. Overall, when rotating by 90°, a red color area moves from the beginning of the arrow to the tip.

[0071] At a Fig. 3 In the second embodiment shown, several first zones 22 are each V-shaped and adjacent to one another, and the azimuth angle of the linear diffraction grating varies by 5° from zone to zone. This can be repetitive, meaning that with relatively small zones 22, the pattern repeats itself multiple times. For linear gratings, 180° always corresponds to the next starting point. However, there can also be a jump in the azimuth angle. For example, after α = 180°, the pattern can continue with α = 90° and then with α = 95°, etc. The length of a repetitive unit is denoted by Ix. Preferably, Ix is in the range of 5 mm to 150 mm, and particularly from 5 mm to 50 mm. When the optically variable element is rotated, a motion-color effect is created, as if the tips of the V-shapes indicated a direction.

[0072] In a third embodiment, first zones 22 are provided in the form of concentric rings. In Fig. 4a Five concentric rings around a central circle are shown as an example. In In a particular embodiment, for example, thirty-five concentric rings can be provided, each containing linear grids as described above. Fig. 1 explained, it is provided that the linear grids of two adjacent concentric rings differ in their azimuth angle by 5° each.

[0073] If you turn during the transition from Fig. 4a to Fig. 4b The optically variable element, and thus the linear lattices, then results (cf. Fig. 4c und Fig. 4d The effect is a continuous color movement from the inside out (and then back again from the outside in), similar to a continuous pumping motion. Alternatively, the diffraction gratings can be chosen so that the continuous color movement shifts into spectral ranges invisible to the naked human eye (UV-A or near-IR). For example, the outer area of ​​the element can initially be invisible, and upon rotation, the color moves from the inside out. The color movement can, of course, also occur in the reverse direction.

[0074] In the first to third embodiments, the azimuth angle from zone 22 to the following zone 22 is varied. Equally, the lattice period could also be varied by a value that differs between successive zones by 1 nm to 10 nm, preferably by 1 nm to 7 nm, and most preferably by 1 nm to 5 nm.

[0075] The effect created using the first to third examples can be combined with itself (with different colors) or with other effects. If you want to combine several optical effects on a limited area in a single, optically variable effect, rasterization or nesting is recommended.

[0076] The Fig. 5a and 5bThe diagram shows the structure of zones 22 by individual (raster) areas 41, 42, 43, which are nested within each other, for example, such that first raster areas 41 are arranged side by side along a line, below them second raster areas 42 along a second line and third raster areas 43 along a third line, then again the first raster areas 41 along a fourth line, etc. Optionally, bridges 49 are provided, which have a width of approximately 15% of the raster areas 41 to 43. The optional bridges 49 make it easier to separate the raster areas 41, 42, 43 or even different raster areas of the same type from one another, and in particular to provide different diffraction gratings or other structures in the different raster areas.

[0077] It is also possible that the footbridges 49 do not frame the individual grid areas, but at least partially frame the entire zone 22. Figur 5b Figure 1 shows a schematic top view of such a zone with different grid areas 41, 42, and 43. A bridge 49 is provided, which partially frames the zones 41, 42, and 43 in an L-shape on two sides.

[0078] Different types of diffraction gratings can be provided in the first grid areas 41, 42, and 43, differing, for example, in their azimuth angle or grating period. Thus, under a specific illumination and rotation angle, red, green, and blue colors can be generated by these grid areas 41 to 43 using such different types of diffraction gratings. Alternatively, only grid area 41 or only grid areas 41 and 42 can each generate a color, while grid area 43 can be covered with a completely different microstructure or macrostructure. If the dimensions of the individual grid areas are sufficiently small (e.g., between 5 µm and 100 µm), they are not, or only barely, resolvable by the naked human eye at a predetermined distance (e.g., 30 cm).This allows one object to be visible in the same place as another object, with the two objects each being represented by different grid elements 41, 42, 43.

[0079] In a fourth embodiment according to Fig. 6 is applied to the first embodiment according to Fig. 2a linked: In The first zones 22 again feature linear grids that vary slightly in their azimuth angle from zone to zone along the arrow's length. This is interrupted, however, by a microstructure in the form of anisotropic matte structures 61, which are provided, for example, by second grid areas 42. The orientation of the anisotropic matte structures 61 also changes gradually depending on the corresponding successive zones or the azimuth angle associated with the respective linear grid. Due to the anisotropic matte structures, a bright spot appears at a specific point on the arrow, which, when the optically variable element is rotated, changes either in the direction of the arrow to enhance the effect of color movement or in the opposite direction to achieve a surprising effect. In The contour of the arrow may include additional structures such as an isotropic matte structure or a cross grid.

[0080] In a fifth embodiment, nested grid areas 41 and 42 each provide a different pattern, namely, for example, a ring 70 and a star 71, see Fig. 7a - c .

[0081] However, a different parameterization is used than in the other embodiments: For example, the Fig. 7d In a solid line, a reflection spectrum 72 of an optically variable element, which is determined above based on the Fig. 1 The described properties are represented by the parameters: lattice period of 510 nm, lattice depth of 150 nm, and zinc sulfide layer thickness of 80 nm. The lattice shape is sinusoidal. The reflection spectrum is valid for an illumination angle of 30°. At an azimuth angle α of 0°, the color red is observed (see maximum at approximately 650 nm). Changing the azimuth angle by 90° shifts the spectrum into the near-infrared range, as shown in the reflection spectrum on page 74.

[0082] Alternatively, this can be done using Fig. 7e The reflection spectrum 76 shown has a maximum in the blue range, which, according to reflection spectrum 78, shifts into the ultraviolet-A range at a different azimuth angle. Here, the grating period is 200 nm, the grating depth is 100 nm, and the thickness of the zinc sulfide layer 10 is [missing information]. Fig. 1 equal to 80 nm.

[0083] In Fig. 7a The parameters for the ring are chosen according to which the reflection spectrum 72 Fig. 7d The parameters for the star, according to which the reflection spectrum 78 applies, are Fig. 7e applies.

[0084] If you now rotate the optically variable element, i.e., ring 70 and star 71, then there is a color change of ring 70 from red ( Fig. 7a ) barely visible ( Fig. 7b ) into the near infrared, i.e. invisible to the unarmed human eye ( Fig. 7c ). Star 71 undergoes the opposite color movement of blue ( Fig. 7c ) too faintly visible ( Fig. 7b ) and not visible at all ( Fig. 7a ). In this way, by using a color movement effect, an image change can be produced, i.e., when rotating the optically variable element, at one rotation angle ϕ the ring 70 is seen in red, at another the star 71 in blue.

[0085] Additional color movement effects can be achieved by varying the azimuth angle α in the ring or in the star.

[0086] A sixth embodiment is described using the Fig. 8a bis 8e Explained: In this embodiment, four motifs are nested within each other, in this case in the form of "A", "B", "C" and "D". Fig. 8a bis 8d The elements are shown individually, with the one in Fig. 8a The "A" shown is provided by the first grid areas, which is in Fig. 8b The "B" shown is provided by second grid areas, which is in Fig. 8c The "C" shown is provided by third grid areas and that in Fig. 8d The "D" shown is provided by fourth grid areas, with the first, second, third and fourth grid areas being similar to those above, based on the Fig. 5a and 5b The layers are nested within each other, preferably without the aforementioned bridges 49. In the region of the first and third grid areas, a diffraction grating with a grating period d of 510 nm is provided. In the region of the second and fourth grid areas, a diffraction grating with a grating period d of 200 nm is provided.

[0087] The rotation angle Φ is defined such that at Φ = 0°, the "B" is seen in the correct orientation. The azimuth angle of the diffraction grating is α = 135° or -45° for the first grid regions, α = 90° for the second grid regions, α = 45° for the third grid regions, and α = 0° for the fourth grid regions. The hatching in Fig. 8a bis 8d illustrates the orientation of the diffraction gratings.

[0088] The following effect of an image change is achieved: At a rotation angle of Φ = -45°, the letter "A" is visible in deep red (reflection spectrum 72), the "B" and the "D" are very faintly present in violet, while the "C" is not visible (reflection spectrum 74). When the security element is rotated to Φ = 0°, the "B" appears in blue (reflection spectrum 76) and in the correct reading orientation, while the "A" and the "C" are faintly dark red and the "D" is not visible (reflection spectrum 78). At Φ = 45°, the "C" is deep red (reflection spectrum 72) and in the correct reading orientation, the "B" and the "D" are faintly violet, and the "A" is not visible (reflection spectrum 74). At a rotation angle of Φ = 90°, however, the "D" is blue (reflection spectrum 76) and in the correct reading orientation, the "A" and the "C" are faintly dark red, the "B" is not visible (reflection spectrum 78).

[0089] In other words, when the optically variable device is rotated, the letters A (deep red), B (blue), C (deep red), and D (blue) are displayed successively, each in the correct reading orientation. Slight variations in the arrangement and the images used also allow for image change or motion effects.

[0090] In a seventh embodiment ( Fig. 9a - 9c In the fifth embodiment, the effect of an image change is achieved in a different way. Different grid areas display the same color at a specific rotation angle Φ, even if they are covered with completely different diffraction gratings. The hatching in Fig. 9a - 9c illustrates the orientation of the diffraction gratings.

[0091] The Fig. 9d Figure 91 shows a first reflection spectrum 91 and a second reflection spectrum 92. The first reflection spectrum 91 (solid line) corresponds to grid regions where a sinusoidal and linear diffraction grating has a grating period of 380 nm and a grating depth of 150 nm, and where a zinc sulfide layer 10 has a thickness of 80 nm. The illumination angle Θ is approximately 30°. The orientation of the grating lines in these grid regions is perpendicular to the viewing direction, i.e., α = 0°. The second reflection spectrum 92 (dashed line) is the reflection spectrum of grid regions where the sinusoidal and linear diffraction grating has a grating period of 350 nm, a grating depth of 150 nm, and where the first zinc sulfide layer 10 has a thickness of 80 nm. Here, however, the orientation of the grid lines is diagonal to the viewing direction, i.e., α = 45° (or α = -45°).

[0092] In spectrum 91, the reflection peak most important for color perception lies at a wavelength of approximately 500 nm; the grid areas corresponding to spectrum 91 therefore appear green. In reflection spectrum 92, the reflection peak lies more or less at the same wavelength and is almost identical to the reflection peak of the other grid areas. (The additional narrow double peak at a wavelength of approximately 700 nm is practically invisible to the human eye and irrelevant to color perception.)

[0093] The color impression of both grid elements is therefore essentially the same.

[0094] If the ring 70 is provided by grid areas where the diffraction grating has a grating period of 380 nm and the grating lines are parallel to the viewing direction, the ring appears red. The star 71 is provided by grid areas with a diffraction grating with a grating period of 380 nm, but here the grating lines run perpendicular to the viewing direction and the reflection spectrum 91 is effective. Thus, the star appears green. In this seventh embodiment, a square background 79 is provided with the diffraction grating having a grating period of 350 nm, to which the reflection spectrum 92 is effective. Because the background then also appears green, the overall resulting image is a red ring in a green square, as schematically shown in Fig. 9a indicated. When the optically variable element is rotated by an azimuth angle of 90°, the following results: Fig. 9c Situation shown: Ring 70 and star 71 have swapped colors, but background 79 is (again) green. Overall, this results in a red star against a green background. The color impressions of the three areas differ at rotation angles between 0° and 90°. Fig. 9b (This shows the situation at a rotation angle of 45°, where the ring and the star appear the same.) The hatching clarifies the grid orientation in each case.

[0095] The seventh embodiment can be modified and, for example, linked to the sixth embodiment. For instance, a letter can be positioned against a star-shaped background (e.g., a red "A" against a green star), and when the rotation angle is changed by 90°, another letter (e.g., a "B") can appear red against a green star, or the star can remain entirely green.

[0096] In an eighth embodiment, a true-color image is provided. First raster areas according to the type in Fig. 5a The raster areas shown (41) provide the primary color red; second raster areas are determined according to the type shown in Fig. 5a The grid areas shown (42) have the base color green, and the third grid areas are shown according to the type of the grid areas shown. Fig. 5a The grid areas shown (43) have the basic color blue; together, the grid areas form a color area that serves as a pixel element.

[0097] For example, to provide these primary colors at an incidence angle and thus zeroth-order diffraction angle of Θ ~ 30° and a first-layer thickness of 80 nm, a diffraction grating with a grating period d of 380 nm and a grating depth t of 150 nm can be used to achieve the primary colors red and green, where the azimuth angle α of the diffraction grating is 90° for the primary color red and 0° for the primary color green. To provide the primary color blue, a diffraction grating with a grating period of 330 nm, a grating depth of 100 nm, and an azimuth angle of 0° is provided in third grating regions. Alternatively, all diffraction gratings can have the same grating period.

[0098] The individual raster areas can be elongated (not shown in the figure), in particular having a dimension of less than 300 µm and preferably less than 80 µm in one direction, and a dimension of more than 300 µm, preferably more than 1 mm, in the other direction. All pixels can be designed in this way, but at least 30% should be designed in this way, preferably more than 50%, and particularly preferably more than 70% of the raster elements.

[0099] Based on the Fig. 10a It will now be explained that by utilizing the information based on the Fig. 7d und 7e The spectra explained show that a true-color image can be converted into a monochrome image when the rotation angle is changed by 90°: The red components must be chosen so that they shift into the near-infrared (especially to wavelengths greater than 690 nm) when rotated by 90°, and the blue components are chosen so that they shift into the ultraviolet-A (especially to wavelengths less than 430 nm) when rotated by 90°. The green component can change to red when rotated, thus transforming the previous true-color image as described in... Fig. 10b The image now appears in solid red, as shown schematically. Alternatively, the green color component can change to blue when rotated, and the image then appears in solid blue.

[0100] In connection with a true-color image, the pumping effect explained above using the third embodiment can also be used: In this case, a frame 102 is added to the actual image 101 (see Fig. 10c und 10d ), which produces a color movement effect similar to the concentric rings from Fig. 4a-c This shows that if the color moves from an inner area of ​​the frame 102 to the outside, the true color image can then become visible when a certain color has reached the outer frame 102.

[0101] In a ninth embodiment, there are zones 110 and further zones 112 that exhibit different color effects at different rotation angles. Metallized areas 114 are present in the transition region between these zones. These form a unique pattern, which is particularly visible in transmitted light, cf. Fig. 11c Furthermore, zones 110 and 112 also exhibit a color impression when viewed in transmitted light, as well as a color effect when tilted and rotated (in the tilted state). If these zones 110 and 112 have the same relief structure, which is merely arranged at a different azimuth angle, the color impression in transmitted light is identical when viewed perpendicularly. However, if the security feature is viewed in transmitted light while tilted, the color impressions of the two zones 110 and 112 differ. Conversely, if zones 110 and 112 have different relief structures, the color impression in transmitted light is also different when viewed perpendicularly.

[0102] This can involve a layer sequence as in Fig. 11d As shown, the following is provided: A metal layer (e.g., made of aluminum) initially deposited over the entire surface is freed of metal in a manner known per se where a relief structure is provided to generate an effect according to the invention in the zeroth diffraction order (areas 110, 112), wherein the freed areas are preferably oriented in register to (relief) structures and / or mirror surfaces that are not freed of metal. Subsequently, the optically variable element is provided over its entire surface with the high-refractive-index first layer 10. Optionally, a color layer 116 can also be provided below the relief structure (in particular, a dark lacquer layer, e.g., a black adhesive layer as back printing). By using such a color layer 116, it is possible to increase the contrast strength when providing the color effect in the color effect area.This contrast enhancement is achieved primarily through the absorption of light components that pass through the other layers and would otherwise be reflected and scattered at a lighter substrate surface. This scattered light would be reflected back, weakening the optically variable effect and its color effect. Such a dark underprint cannot be perfectly integrated into the register, but it can be concealed by the perfect fit of the metal layer beneath it: The area of ​​color layer 116 with width Δx lies below metal layer 114 and is therefore not visible.

[0103] Back printing can be used to improve color contrast. It can also serve as a static reference for the human eye to the variable color movement. However, this printed reference does not necessarily have to be located beneath the relief structure. It can also be placed above it or be part of the substrate itself.

[0104] In a special embodiment according to Fig. 11e (e.g., diffractive) relief structures 111 with a small lattice period (less than 500 nm) are superimposed on an achromatic blaze grating 118 that is low-frequency (i.e., has lattice periods of more than 700 nm, preferably more than 1000 nm, and a comparatively large structure depth, e.g., between 500 nm and 5000 nm). This results in the color impression not being achieved when viewed perpendicularly, but rather when the optically variable element is tilted.

[0105] Multiple such superimposed layers can be rasterized / nested to create different color effects at rotation angles of 0°, 90°, 180°, and 270°. For example, by nesting such blaze grids with superimposed relief structures, a four-color rotation effect can be achieved, e.g., at an illumination angle Θ ≈ 10°, from red (ϕ=0°) to green (ϕ = 90°) to blue (ϕ = 180°) and to yellow (ϕ = 270°).

[0106] Alternatively, the same color, e.g., green, can become visible in different areas of the security element at different rotation angles, with only one area displaying the color intensely at any given time, while the others appear darker. Here, the orientation of the blaze grids (with, for example, a blaze angle of approximately 20°) in these areas is chosen so that the superimposed relief structure reflects the color green at the respective rotation angle. In this way, for example, a clock 117 can be represented, which in Fig. 11e This is also shown. When the optically variable element is rotated, the green color in the outer ring 119, for example, rotates. The enlarged sections show how the superimposed structures are arranged in the three example areas. In the areas in between, the superimposed structure is arranged rotated, for example, in 5° increments. In the area above the number "12," it is additionally shown how the light travels from the light source to the viewer. All areas that do not match the lighting conditions (i.e., do not direct the incident light so that it falls into the viewer's eye) appear dark.

[0107] Fig. 12a und b Figure 1 shows a specific embodiment of a sample banknote as an optically variable security element or with an optically variable element 120: In the center of the optically variable element 120, V-shaped elements 122 are provided, forming an arrow shape, as shown above as the second embodiment with reference to Figur 3 The V-shaped elements are framed by metallic areas 124, which provide further effects such as a surface relief structure or first- or higher-order diffraction in the colors of the rainbow. The entire optically variable element 120 is applied to the banknote substrate with a black-colored adhesive.

[0108] When the banknote is rotated, the green color moves from the ends of the arrows to the tips, creating a dynamic, pumping, and easily verifiable appearance. The amount "55" is provided by locally removing the first layer.

[0109] Fig. 13 Figure 1 shows the data page of a sample passport, which is provided with a transparent or translucent, multi-layered overlay containing, in particular, transparent diffractive diffraction structures molded in one layer (a so-called KINEGRAM®< TKO (TKO = Transparent KINEGRAM®< Overlay)), designated 130. This overlay has a central stripe 134 and two edge stripes 132. The color effect is designed so that when the sample passport is rotated clockwise, a green color impression runs in the side stripes from the bottom left to the top right, and in the central stripe in the opposite direction, i.e., from the top right to the bottom left. A country name, "Utopia," is also provided by locally removing the first layer 10. The adhesive is not colored in this case, but rather transparent, so that the information on the passport's data page remains legible.The resulting color movement effect, together with the resulting obstruction of the effect by the interrupted areas (letters "Utopia"), is a striking and therefore easily verifiable security feature.

[0110] Further specific embodiments of the invention are: A KINEGRAM® TKO, which is laminated onto the data page of a passport and, for example, creates a color movement effect in the upper right corner, as in Fig. 4a - d depicted, exhibits. The diameter of the pumping color circle is, for example, 15 mm. One in Fig. 14 The KINEGRAM®< TKO shown, which in the pumping color circle 141 additionally features fine guilloche lines 142 with diffractive diffraction structures and a metal reflective layer, wherein the guilloche lines 142 exhibit a diffractive rainbow effect of the first and / or higher order. Furthermore, the pumping color circle is surrounded in a ring shape by metallized diffraction structures that simulate a macroscopic freeform surface, the ring 143 having a diameter of approximately 3 mm. A KINEGRAM® PCI (PCI = Plastic Card Inlay), i.e., a transparent or translucent, multilayer film with diffraction structures molded in one layer, particularly transparent ones, laminated into an ID-1 card and featuring a color-movement effect in the upper right corner, as shown in Fig. 4a - d The pumping color circle has a diameter of, for example, 8 mm. A KINEGRAM® PCI, which additionally features fine guilloche lines with diffractive diffraction structures and a metal reflective layer within the pumping color circle, where the guilloche lines exhibit a first- and / or higher-order diffractive rainbow effect. Furthermore, the pumping color circle is surrounded in a ring shape by metallized diffraction structures that simulate a macroscopic freeform surface, with the ring having a diameter of 2 mm. Fig. 14 This also shows such a security feature schematically.

Claims

1. Visually variable element, in particular a security element, wherein the visually variable element has at least one first diffraction grating and at least one second diffraction grating having a respective grating period in the range between 100 nm and 500 nm, wherein the visually variable element has a first layer (10) consisting of a first material and has a second layer (12) consisting of a second material, wherein the first diffraction grating and the second diffraction grating are provided by a relief structure, which is formed on the interface of the first layer (10) relative to the second layer (12), wherein the second material has a refractive index that is at least 0.2 lower than the first material, wherein the average thickness of the first layer (10) is between 30 nm and 300 nm, so that a diffractive effect of the zeroth order is achieved, characterised in that the first diffraction grating and the second diffraction grating are designed so that a) a first colour is generated by the first diffraction grating at a predetermined rotational angle (Φ), which is defined in relation to a rotation about a normal (N) to a surface (14) of the visually variable element, and at a specified illumination angle (Θ), which is defined in relation to this rotation, and a second colour, differing from the first colour, is generated by the second diffraction grating, wherein the respective azimuth angle of the first and the second diffraction grating differs by at most 15° and / or b) a colour is generated by the first diffraction grating due to light with wavelengths in the range between 430 nm and 690 nm at a first rotational angle (Φ), which is defined in relation to a rotation about a normal (N) to a surface (14) of the visually variable element and at a specified illumination angle (Θ), which is defined in relation to this rotation, and a colour is generated by the second diffraction grating due to wavelengths which are less than 430 nm, and a colour is generated by the second diffraction grating due to light with wavelengths in the range between 430 nm and 690 nm at a second rotational angle, which is defined in relation to the rotation and at the specified illumination angle, and a colour is generated by the first diffraction grating due to wavelengths which are greater than 690 nm, and wherein the visually variable element comprises at least three zones (22), which follow each other in at least one lateral direction, wherein each zone (22) has a diffraction grating, of which the first zone has the first diffraction grating, the second zone has the second diffraction grating and the third zone has a third diffraction grating, differing from the first and second diffraction grating, wherein the respective diffraction grating corresponding to two zones, following each other in the at least one lateral direction, differ in that i) their azimuth angle (α) differs by at least 0.1° and at most 15°, and / or ii) their grating periods differ by a value in the range from 1 nm to 10 nm, wherein the respective value for the azimuth angle (α) and / or the grating period changes in the same direction for at least three successive zones (22), and one or more of the zones each have a dimension of more than 0.5 mm in two lateral directions, and wherein the visually variable element provides the effect of quasi continuous colour change when rotating in the substrate plane.

2. Visually variable element according to claim 1, characterised in that the azimuth angles of the diffraction grating differ from zones (22) following each other in the at least one lateral direction by an amount between 0.2° and 10°, preferably by an amount between 0.5° and 5°, and / or the grating periods of two diffraction gratings differ from zones following each other in the at least one lateral direction by a value in the range from 1 nm to 7 nm, preferably in the range from 1 nm to 5 nm.

3. Visually variable element according to claim 1 or 2, characterised in that the at least one first diffraction grating and the at least one second diffraction grating has a respective grating period in the range between 180 nm and 420 nm.

4. Visually variable element according to claim 1 to 3, characterised in that the respective diffraction grating corresponding to two zones, following each other in the at least one lateral direction, changes in its azimuth angle (α) by at least 0.1° and at most 9°, and / or the respective value for the azimuth angle (α) and / or the grating period in successive zones changes for at least three successive zones (22) each by the same amount.

5. Visually variable element according to claim 1 to 4, characterised in that each of the zones has a dimension of more than 0.5 mm in two lateral directions, preferably a dimension of more than 1 mm in at least one direction, preferably more than 3 mm, and / or each of the zones has a dimension of at most 50 mm in two directions.

6. Visually variable element according to one of claims 1 to 5, characterised in that the several successive zones (22) of the zones (22) together form a straight-lined or curved band (20), and / or several successive zones (22) of the zones (22) each have the shape of a curved band, which is at least partially surrounded by a zone (22), following the respective zone, in the shape of a curved band, wherein preferably concentric closed bands, more preferably ring-shaped bands, are provided by several of the successive zones (22).

7. Visually variable element according to one of claims 1 to 6, characterised in that one or more of the zones (22) comprise a plurality of first regions (41) and of second (42) or second and third (42, 43) or second, third and further regions, which provide another visual effect to the first regions, wherein, in the respective first regions of zones (22), the respective same diffraction grating is formed from the first diffraction grating, the second diffraction grating, the third diffraction grating or a further diffraction grating, wherein preferably the first regions (41) and / or the second regions (42) or the third regions (43) or the further regions have a dimension of less than 300 µm, preferably between 50 µm and 200 µm, in at least one first lateral direction.

8. Visually variable element according to claim 7, characterised in that the other visual effect involves generating a colour dependant on a respective rotational angle and specified illumination angles, which differs from a colour at least for one range of rotational and illumination angles, which is generated by the first regions (41) respectively, or the other visual effect is based on another physical principle.

9. Visually variable element according to one of claims 7 or 8, characterised in that in second and / or third and / or further regions (42, 43), different microstructures are provided by the diffraction gratings provided in the first regions (41), in particular isotropic or anisotropic matt structures, blazed gratings, holograms, diffraction gratings having a spatial frequency between 300 lines / mm and 1800 lines / mm, diffraction gratings that imitate free-form surfaces and / or in particular refractively acting macrostructures are provided, in particular are provided in the form of facet surfaces and / or free-form surfaces.

10. Visually variable element according to one of claims 7 to 9, characterised in that the other visual effect involves the appearance of a movement of a visual characteristic when changing the rotational angle and / or illumination angle, which is in the same direction as or opposite direction to the appearance of a movement of the colour generated by the zones along the successive zones (22).

11. Visually variable element according to one of claims 1 to 10, characterised in that fourth and fifth grid regions are at least partially interleaved into each other to form a one or two-dimensional grid, wherein the at least one first diffraction grating is provided in the fourth grid regions and the at least one second diffraction grating is provided in the fifth grid regions.

12. Visually variable element according to claim 11, characterised in that a colour with a first intensity is generated by the at least one first diffraction grating and / or the at least one second diffraction grating, each in a predetermined rotational angle range in the presence of a specified illumination, and electromagnetic radiation from the visible light range is generated outside the predetermined rotational angle range, only with a second intensity, which at most is a third, preferably at most a fifth and more preferably at most a tenth of the first intensity.

13. Visually variable element according to claim 11 or 12, characterised in that on the one hand, the fourth grid regions and on the other hand the fifth grid regions alone or with sixth or with sixth and further grid regions represent different objects, wherein an object is a motif, in particular a geometric shape, a pattern, a symbol and / or an alphanumeric sign, and / or an image background, wherein preferably an identical colour is generated for two different objects at at least one first rotational angle to a specified illumination angle despite different characteristics of a different diffraction grating, and different colours are generated at a second rotational angle relative to the specified illumination angle.

14. Visually variable element according to one of claims 1 to 13, characterised in that a plurality of colour areas are provided, which are arranged according to a one or two-dimensional grid and each form a pixel of a first motif, wherein the colour area has a combination of seventh and eighth or seventh, eighth or ninth partial areas, wherein the first diffraction grating is provided in the seventh partial area, the second diffraction grating is provided in the eighth partial area and, if necessary, a third diffraction grating is provided in the ninth partial areas, wherein preferably a multi-coloured image is generated by the colour area at a first rotational angle and a specified illumination angle and a monochrome image is generated by the colour area at a second rotational angle and the specified illumination angle.

15. Visually variable element according to one of the preceding claims, characterised by a colour layer (116) provided at least in certain regions, which preferably is coloured dark, in particular black or dark grey, dark green, dark blue or dark red and preferably has a patterned design.