Optically variable security element, article of value, and production method

Abstract

The invention relates to an optically variable security element (12) for securing articles of value, containing two relief layers (24, 34) arranged at different heights. Each of the relief layers (24, 34) is provided with a reflection-increasing coating (26, 36) which follows the surface topography of the respective relief layer, wherein the reflection-increasing coating (36) of the higher relief layer (34) is designed with a wavelength-based reflection and transmission in the visible spectral range. In a reflective feature region (14) within the security element, the higher relief layer (34) is designed as a relief structure and exhibits a first optically variable effect in a first color, and the lower relief layer (24) is designed as a relief structure and exhibits a second optically variable effect in a different second color through the first reflection-increasing coating (36). In a reflective neutral region (16) within the security element, the higher relief layer (34) is designed as a flat structure (34-F) and / or as a deactivation structure (34-D) which is formed by elevations and / or recesses and which suppresses the reflective and / or coloring properties of the first reflection-increasing coating (36).

Description

[0001] Optically variable security element, valuable object and manufacturing process

[0002] The invention relates to an optically variable security element for protecting valuables, a method for producing such a security element, and a data carrier equipped with such a security element.

[0003] Data storage devices, such as valuables or identification documents, as well as other valuable items such as branded goods, are often provided with security elements for security purposes. These elements allow verification of the authenticity of the data storage device and also serve as protection against unauthorized reproduction. These security elements can, for example, take the form of a security thread embedded in a banknote, a cover foil for a banknote with a hole, an applied security strip, a self-supporting transfer element, or even a feature area printed directly onto a valuable document.

[0004] Security elements with a viewing-angle-dependent or three-dimensional appearance play a special role in authenticity assurance, as these cannot be reproduced even with the most modern copying machines. For this purpose, the security elements are equipped with optically variable elements that convey a different image impression to the viewer at different viewing angles. Depending on the viewing angle, they can, for example, display a different color or brightness impression, a different perspective view, and / or a different graphic motif. Optically variable effects described in the state of the art include, for example, motion effects, pump effects, depth effects, or flip effects, which are realized using holograms, microlenses, or micromirrors.In the publication DE 10 2018 005447 A1, optically variable security elements were proposed that contain two relief structures arranged at different heights and each provided with a colored coating. The colored coating of the higher relief structure is structured as a grid, so that when viewing the security element, the colored coating of the lower relief structure appears in the spaces between the grids, enabling a seamless transition from a first to a second appearance when tilting the security element.

[0005] In a further development of such security elements described in the document WO 2021 / 155999 A1, the coating of the higher relief structure is formed by a semi-transparent coating, so that the visibility of the lower image motif no longer requires screening of the higher color coating.

[0006] Based on this, the invention is based on the object of further developing the generic optically variable security elements and proposing designs that are easy to manufacture and at the same time have a high level of security against counterfeiting and an attractive visual appearance.

[0007] This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0008] To achieve this objective, the invention includes an optically variable security element that can be used, in particular, to protect valuables. The surface area of ​​the security element defines a plane, which, without loss of generality, can be regarded as the xy plane, and a z axis perpendicular to the plane.

[0009] The security element contains two relief layers arranged at different heights in the z-direction, forming a lower and a higher relief layer.

[0010] The higher relief layer is provided with a first reflection-enhancing coating following its surface topography and the deeper relief layer is provided with a second reflection-enhancing coating following its surface topography, wherein the first reflection-enhancing coating is formed with a wavelength-dependent reflection and transmission in the visible spectral range.

[0011] In a reflective feature area within the security element, on the one hand, the higher relief layer is designed as a relief structure and shows a first optically variable effect in a first color, and on the other hand, the deeper relief layer is designed as a relief structure and shows a second optically variable effect in a second, different color through the first reflection-enhancing coating.

[0012] Furthermore, it is provided that, in a reflective neutral region within the security element, the higher relief layer is designed as a flat, planar structure and / or as a deactivation structure formed by elevations and / or depressions, which suppresses the reflective and / or color-imparting properties of the first reflection-enhancing coating. Within the context of the present description, a "relief layer" refers to a layer that has at least one partial region in the form of a relief structure, i.e., a non-planar structure with elevations and / or depressions. In addition to a relief structure, a relief layer can also have flat partial regions without a relief structure. In the region of a relief structure, a reflection-enhancing coating following the surface topography follows the relief profile of the relief structure.In the area of ​​a flat, planar structure, a reflection-enhancing coating following the surface topography is correspondingly planar, and in the area of ​​a deactivation structure, a reflection-enhancing coating following the surface topography follows the course of the elevations and / or depressions of the deactivation structure.

[0013] An area in which both the higher relief layer and the lower relief layer are each designed as a relief structure and, in addition, the two relief layers each exhibit an optically variable effect of a different color due to a suitable coating, is also referred to in this description as a "two-color area". The aforementioned reflective feature area of ​​the security element represents such a two-color area. The reflective neutral area, on the other hand, does not represent a two-color area because, in the area of ​​a flat, even though the lower relief layer can be designed as a relief structure, the higher relief layer is flat and therefore does not represent a relief structure. In the area of ​​a deactivation structure, the lower relief layer can produce an optically variable effect of a first color, but the higher relief layer produces a different color due to the reflection or luminous flux.color-suppressing effect of the deactivation structure but no optically variable effect of a second, different color. Advantageously, the first reflection-enhancing coating has a wavelength-dependent reflection and a wavelength-dependent transmission in the visible spectral range, so that the reflection-color effect of the first reflection-enhancing coating causes the higher relief structure to exhibit the first optically variable effect in the first color, and the transmission-color effect of the first reflection-enhancing coating contributes to the color effect of the second optically variable effect of the lower relief structure in the second color.

[0014] In an advantageous embodiment, the deactivation structure is formed by an anti-reflective structure in the form of a moth-eye structure, in the form of a microcavity structure with a plurality of adjacent microcavities, or in the form of a random surface with irregularly distributed elevations and / or depressions. The deactivation structure can in particular have elevations and / or depressions with a large aspect ratio of 2 or more, in particular of 5 or more. A deactivation structure as a random surface with irregularly distributed elevations and / or depressions can preferably be matte structures and / or micromirrors reflecting in different directions. In particular, the deactivation structure should reduce the reflection at the glancing angle by at least 50%, particularly preferably at least 75%, and in particular at least 85%.

[0015] It is advantageous that in the reflective neutral region, the first reflection-enhancing coating has a locally varying thickness and thus macroscopically exhibits no or a non-uniform color effect, and / or the first reflection-enhancing coating is formed with a fine grid and thus macroscopically exhibits no or a non-uniform color effect, and / or the first reflection-enhancing coating has a locally rapidly varying inclination and thus macroscopically exhibits no or a non-uniform color effect. In the reflective neutral region, the higher-lying relief structure can be formed entirely as a flat, planar layer or entirely as a deactivation structure, or can also be formed partially as a flat, planar layer and partially as a deactivation structure.

[0016] According to an advantageous embodiment, it is provided that the reflective neutral region surrounds the reflective feature region and / or that the reflective neutral region forms an edge region of the security element.

[0017] Particularly preferably, in the reflective neutral region, the deeper relief layer is formed as a relief structure and shows a colored optically variable effect through the first reflection-enhancing coating, in particular an optically variable effect in the said second color.

[0018] The first reflection-enhancing coating advantageously contains one or more high-index layers, preferably dielectric high-index layers, which have a refractive index of at least 1.7, preferably at least 2.0, and particularly preferably at least 2.2, at least in a partial range of the visible spectrum. Particularly preferably, the first reflection-enhancing coating is not a sequence of layers, but rather a high-index single layer, in particular a single layer of ZnS, TiO2, Al2O3, HfO2, Pb3O4, PBS, or ZrO, most preferably a single layer of ZnS.

[0019] Particularly advantageously, in the reflective feature region, the higher-lying relief structure and / or the deeper-lying relief structure are formed by micromirror arrangements with specularly reflecting micromirrors. The micromirrors are formed in particular by non-diffractive mirrors and do not produce any color splitting. Plane mirrors, concave mirrors and / or Fresnel-type mirrors can preferably be used. The lateral dimensions of the micromirrors are expediently below 50 μm, advantageously below 20 μm, preferably approximately 10 μm, i.e. in particular between 7 μm and 13 μm. On the other hand, the lateral dimensions of the micromirrors can also be above 2 μm, in particular above 3 μm or even above 5 μm. The pitch of the micromirrors is preferably less than 10 μm, preferably less than 5 μm, particularly preferably 3.5 μm or less.

[0020] In principle, other relief structures can be used instead of micromirrors, in particular embossed Fresnel lenses, concave mirrors, hologram structures, nanostructures, or various active blazed gratings. Achromatic diffraction gratings, so-called matte structures, can be used particularly advantageously here, as they essentially reflect white light and thus do not interfere with the color effect of the coating or any color layers by generating diffraction colors. To generate bright colors in transmission and / or reflection, the relief structures can also have subwave structures, in particular subwavelength gratings, which, in combination with the respective reflection-enhancing coating, determine or at least co-determine its color.For example, a relief structure can represent an overlay of a micromirror structure with subwavelength gratings located thereon, whereby the orientation of the micromirrors determines the direction of the reflected light and the subwavelength gratings modify the color effect of the reflection-enhancing layer applied to the relief structure. In the reflective feature area, the two relief structures are independent relief structures, i.e., they can be freely selected and their relief pattern is not dependent on each other. In particular, the two relief structures do not have the same relief pattern, nor the same relief pattern scaled only in height; rather, the two relief structures are different and formed with different relief patterns.

[0021] The second reflection-enhancing coating advantageously has a reflectance of at least 50%, preferably at least 75%, particularly preferably at least 80%, or even at least 85%, at least in a partial range of the visible spectrum. The second reflection-enhancing coating is preferably opaque with an optical density of more than 1.0, in particular more than 2.0. In the reflective feature region, one or more translucent color layers are advantageously provided between the first and second relief layers in order to influence the color impression of the optically variable effects of the first and / or second relief layer. Such translucent color layers can, in particular, not be height-structured, i.e., can be formed as flat layers. A color layer can also be formed by a colored relief-forming layer, for example a colored embossing lacquer layer.According to a preferred embodiment, it is provided that in the reflective feature region, the transmission color effect of the first reflection-enhancing coating determines the second color; or the transmission color effect of the first reflection-enhancing coating together with a reflection color effect of the second reflection-enhancing coating and / or with at least one of the translucent color layers determines the second color; or a reflection color effect of the second reflection-enhancing coating and / or the color effect of at least one of the translucent color layers determines the second color.

[0022] It is further advantageously provided that, in the reflective feature region, the first and second relief structures at least partially reflect incident parallel light into different angular ranges, wherein the two different angular ranges preferably do not overlap or overlap only slightly (maximum 5°) and are preferably separated from each other by more than 3°, particularly preferably more than 10°. The optically variable effects of the two relief structures in the reflective feature region are therefore not congruent, but are at least partially recognizable from different viewing directions.

[0023] Specifically, the formation of the higher relief structure, in particular the orientation of the micromirrors of the higher micromirror arrangement, and / or the formation of the lower relief structure, in particular the orientation of the micromirrors of the lower micromirror arrangement, can vary depending on the location in order to create a predetermined motif, in particular a three-dimensional motif or a movement motif. The relief pattern, in particular the orientation of the micromirrors, is freely selectable and essentially determined only by the predetermined motifs, but not by the orientation of laterally or vertically adjacent micromirrors.

[0024] The invention further includes a data carrier with a security element of the type described. The data carrier can be, in particular, a value document, such as a banknote, in particular a paper banknote, a polymer banknote, or a composite film banknote, a share, a bond, a certificate, a voucher, a check, a high-value admission ticket, or even an identification card, such as a credit card, a bank card, a cash payment card, an authorization card, an identity card, or a passport personalization page. The lower relief structure is generally closer to a surface of the data carrier than the higher relief structure, which is closer to the viewer's eye. In one expedient variant, the security element is arranged in an opaque area of ​​the data carrier.

[0025] The invention also includes a method for producing an optically variable security element, in particular of the type described above, in which a carrier is provided whose surface extension defines a plane and a z-axis perpendicular thereto, the carrier is provided with two relief layers which are arranged at different heights in the z-direction and form a lower and a higher relief layer, the higher relief layer is provided with a first reflection-enhancing coating following its surface topography and the deeper relief layer is provided with a second reflection-enhancing coating following its surface topography, the first reflection-enhancing coating is formed with a wavelength-dependent reflection and transmission in the visible spectral range, wherein in a reflective feature region within the security element

[0026] — the higher relief layer is formed as a relief structure and shows a first optically variable effect in a first colour, and

[0027] — the deeper relief layer is formed as a relief structure and shows a second optically variable effect in a second, different color through the first reflection-enhancing coating, and in a reflective neutral area within the security element the higher relief layer is formed as a flat, planar structure and / or as a deactivation structure formed by elevations and / or depressions, which suppresses the reflective and / or color-imparting properties of the first reflection-enhancing coating.

[0028] In principle, all described security elements can be equipped with additional, particularly machine-readable, authenticity features.

[0029] Further embodiments and advantages of the invention are explained below with reference to the figures, which are not drawn to scale or proportions for the sake of clarity. They show:

[0030] Fig. 1 schematically shows a banknote with an optically variable transfer strip according to an embodiment of the invention,

[0031] Fig. 2 and 3 to illustrate the basic principle of the invention schematically show a cross section of the transfer strip of Fig. 1 in two partial areas, and

[0032] Fig. 4 to 9 show some particularly advantageous layer structures of security elements according to the invention.

[0033] The invention will now be explained using the example of security elements for banknotes. Figure 1 shows a schematic representation of a banknote 10 with an optically variable security element 12 according to the invention in the form of an adhesive-applied transfer strip. It is understood, however, that the invention is not limited to transfer strips and banknotes, but can be used for all types of security elements, for example, labels on goods and packaging or for securing documents, ID cards, passports, credit cards, health cards, and the like. For banknotes and similar documents, in addition to transfer elements (such as strips or patches with or without their own carrier film), security threads or security strips partially or completely embedded in the document substrate are also possible.

[0034] The transfer strip 12 shown in Fig. 1 contains several subregions 14, 16, 18, which, when viewed from above, convey different visual appearances to a viewer. For example, subregion 14 forms a two-color region that displays different image motifs appearing in different colors from two different viewing directions. Subregion 16 contains a hologram and an achromatic micromirror movement effect in the form of a so-called rolling bar effect. In a further subregion 18, the transfer strip can, for example, contain a micromirror arrangement with bulging and rolling effects.

[0035] To illustrate the basic principle of the invention, Figures 2 and 3 each schematically show a cross-section of the transfer strip 12 in the partial region 14 (Figure 2) and in the partial region 16 (Figure 3), respectively. The partial region 14 of Figure 2 represents a reflective feature region within the transfer strip 12, while the partial region 16 shown in Figure 3 represents a reflective neutral region in which the optical effect of a high-index coating is neutralized in the manner described in more detail below.

[0036] To illustrate the complete structure of a transfer element, the transfer strip 12 is shown in Figures 2 and 3 with a transfer foil and release lacquer layer. It is understood, however, that after the transfer strip 12 has been applied to a target substrate, such as the banknote 10 in Figure 1, the transfer foil is removed by activating the release lacquer layer and is then no longer present in the finished banknote 10.

[0037] Referring first to the cross-section of Fig. 2, the surface area of ​​the carrier strip defines an xy plane and a z axis perpendicular thereto. A layer sequence is provided on the transfer film 20, for example a PET film, and the release lacquer layer 40. Starting from the transfer film and the release lacquer layer, this layer sequence comprises a first embossing lacquer layer 32 with an embossed relief structure 34, a first reflection-enhancing coating 36 in the form of a high-refractive-index layer, for example a ZnS layer, a first primer layer 38, a partially present translucent ink layer 30, a second embossing lacquer layer 22 with an embossed relief structure 24, a second reflection-enhancing coating 26 in the form of a highly reflective opaque metallization, for example an aluminum layer, a second primer layer 28, and a heat-seal lacquer layer 42.

[0038] The transfer strip 12 is designed for viewing in reflection from the positive z-direction, so that of the two relief layer regions 24, 34 arranged at different heights in the z-direction, the relief layer 34 located closer to the observer is also referred to as the higher relief layer and the relief layer 24 located further away from the observer is referred to as the lower relief layer.

[0039] In the partial region 14 shown in Fig. 2, the relief layer regions 24, 34 are both formed as relief structures and specifically represent micromirror embossments or micromirror arrangements 24, 34, each formed from a plurality of micromirrors inclined relative to the xy plane with lateral dimensions of approximately 10 μm. The local angles of inclination of the micromirrors are selected precisely such that the relief structures of the micromirror arrangements 24, 34, together with the respective reflection-enhancing coating, provide a desired optical appearance.

[0040] To give the appearance a desired color impression, the deeper micromirror arrangement 24 is provided with a reflection-enhancing coating 26 following the relief contour in the form of a highly reflective, opaque metallization, which in the exemplary embodiment consists of an aluminum layer. The metallization 26 is recessed in a partial area 50 to create a negative marking, for example, negative writing, in the partial area 14 of the transfer strip 12.

[0041] The higher micromirror arrangement 34 is provided over its entire surface with a reflection-enhancing coating 36 in the form of a high-refractive-index layer, specifically a ZnS layer in this exemplary embodiment, which follows the relief contour. This coating is semitransparent and has wavelength-dependent reflection and transmission in the visible spectral range. The spectral separation of regions of high reflection and high transmission enables color separation in the appearance, in which the high-refractive-index ZnS layer 36, on the one hand, has a high degree of reflection in a first spectral range, for example, in the red, thus producing a bright, red reflection color, and, on the other hand, has a high degree of transmission outside the first spectral range, for example, producing a bright, blue transmission color.

[0042] In addition, a translucent color layer 30 is provided between the two micro mirror arrangements 24, 34, which is only present in some areas, for example a blue color layer left out in the area of ​​the negative writing.

[0043] Overall, the two micromirror arrangements 24, 34 produce different images and color effects for different viewing directions, whereby the viewing direction from which the respective colored image of the higher or lower micromirror arrangement becomes visible is determined by the orientation of the micromirrors. Thus, for a viewer from a first viewing direction, the micromirrors of the higher micromirror arrangement 34 are at the glancing angle and, due to the high reflectivity of the high-refractive-index layer 36 in the red spectral range, produce a first image representation with a bright, red reflection color. Due to their orientation, the micromirrors of the lower micromirror arrangement 24 are far away from the glancing angle from this viewing direction and contribute practically nothing to the image impression.

[0044] From a second viewing direction, however, the micromirrors of the deeper micromirror arrangement 24 are at the glancing angle for the observer and produce a second image representation with a bright blue reflection color, which results from the high transparency of the high-refractive-index coating 36 for blue light, a substantially color-neutral reflection at the deeper metallization 26, and the intermediate blue translucent color layer 30. Further details on the creation of the image and color effects of a two-color area can be found in the document WO 2021 / 155999 A1, the disclosure content of which is incorporated into the present application in this respect.

[0045] Referring now to the cross-section of the transfer strip 12 in the reflective neutral region 16 shown in Fig. 3, the layer structure there contains essentially the same layers as in the feature region 14; only the translucent color layer 30 is not present in the partial region 16 or is omitted there. However, the surface topography of the higher relief layer 34 and the resulting neutralization of reflection and / or color effects of the high-refractive-index layer 36 are different.

[0046] The deeper relief layer region 24 is also formed as a relief structure in subregion 16 and is present as a hologram relief in subregion 52 and as a micromirror arrangement for generating a rolling bar effect in subregion 54. The reflection-enhancing coating 26 of the relief structure 24 is formed in subregion 16, as in subregion 14, as a highly reflective opaque metallization consisting of a chromium layer and an underlying aluminum layer, which follows the relief profile of the hologram relief (subregion 52) and the relief profile of the micromirror relief (subregion 54).

[0047] A significant difference to the feature area 14 lies in the special surface topography of the higher relief layer 34 in the neutral area 16, which is formed in a partial area 56 as a flat structure 34-F and in a partial area 58 as a deactivation structure 34-D with elevations and / or depressions for suppressing the reflective and / or color-producing properties of the high-refractive layer 36.

[0048] Since the high-refractive-index layer 36, as a coating of the relief layer 34, follows its surface topography, the high-refractive-index layer 36 is also flat in the partial region 56, in which the relief layer forms a flat, planar structure 34-F. For an observer, it therefore essentially only illuminates at the glancing angle to the light source. In partial region 58, the deactivation structure 34-D contains elevations and / or depressions to suppress the reflective and / or color-imparting properties of the high-refractive-index layer 36. For this purpose, the deactivation structure 34-D can be designed, for example, as an anti-reflective structure in the form of a moth-eye structure, in the form of a microcavity structure with a plurality of adjacent microcavities, or in the form of a random surface with irregularly distributed elevations and / or depressions, which greatly reduces the reflectivity of the high-refractive-index layer 36.Alternatively, it can be provided that the deactivation structure 34-D does not reduce the reflectivity of the high-refractive-index layer 36 per se, but only suppresses its color effect. For example, a large aspect ratio of the elevations and / or depressions during the coating leads to a locally strongly varying thickness of the high-refractive-index layer 36, so that an observer does not macroscopically see a uniform color effect of the high-refractive-index layer 36 due to the interference conditions varying from location to location. The same effect can be achieved by elevations and / or depressions with a rapidly varying local inclination, since the high-refractive-index layer 36 is deposited during the coating on steep surface sections with a smaller layer thickness than on flat or slightly inclined surface sections.As a result, the interference conditions vary rapidly from location to location, so that macroscopically no uniform color effect of the high-refractive-index layer 36 can be achieved.

[0049] Starting from the basic design of Figures 1 to 3, numerous modifications and further developments of the safety elements according to the invention are possible.

[0050] For example, the high-index layer 36 can be formed not only from ZnS, but alternatively also from one of the materials TiO, Al2O3, HfO, PbsO^, PBS, ZrO. The color of the motif shown by the higher relief layer 34 is determined in particular by the thickness of the high-index layer 36. The use of ZnS is particularly advantageous because ZnS can be applied efficiently in a PVD process. This process ensures particularly well that the shape of the structuring layer, in this case in particular the shape of the embossing of the embossing lacquer layer 32, is adopted by the high-index layer. In addition, the high-index layer has a high refractive index compared to organic compounds, in particular the embossing lacquers used.

[0051] The deeper relief layer 24 derives its color appearance not only from the transmission color of the high-refractive-index layer 36, but in particular also from the printed color layer 30, the intensity of which is amplified or shifted by the deeper metallization 26, for example made of aluminum. The deeper reflection-enhancing coating 26 can be formed from one or more metals, for example Al, Cu, Fe, or Fe:Si, or a Cr-Al layer sequence. Alloys of the aforementioned metals are also possible. In a layer sequence, a very thin layer (maximum 3 nm, preferably approximately 1 nm) of Cr or Ti can be used as an adhesion promoter. The reflection-enhancing coating can also be an interference structure, for example a color-shift structure, or can also be a high-refractive-index layer. When using interference structures, the color layer located between the relief layers can also be omitted.The color layer can be just a single color or a multi-colored image.

[0052] For a more colorful color and / or a higher reflection brightness, a multilayer structure with alternating layers, particularly of materials with high and low refractive indices such as SiO or ZnS, can be used for the first reflection-enhancing coating 36 instead of a single high-index layer. The absorption / reflection of underlying layers can also influence the color.

[0053] An increase in brightness and / or color can also be achieved by embedding the high-index layer 36 in a low-refractive-index lacquer. This applies to both the embossing lacquer and the embedding layer.

[0054] To color the visible motifs, a color can also be mixed into one of the embossing varnishes 22, 32, and a colored embossing varnish can be applied over the entire surface or just in certain areas. The color can be a single layer of color over the entire surface, but also an image with any number of colors, arranged in a favorable register with the embossing.

[0055] In a further development of the invention, a desired color can also be divided into two layers, resulting in the desired color as a mixed color of two individual colors. This makes it possible, in particular, to provide a tamper-evident effect. In an advantageous embodiment, both embossing lacquer layers 22, 32 are colored for this purpose. The second color can also be created using a colored foil instead of a single colored layer. A combination of the aforementioned variants for generating the second color is also possible.

[0056] The deeper relief layer 24 can additionally be provided with optical structures for further optical effects, for example, structures for achromatic micromirror effects such as bulge and convex effects. It is also possible to realize holographic effects, such as rainbow holograms or true-color portraits. Nanostructures for generating colors, with or without micromirrors, can also be incorporated. Furthermore, the use of microlens effects is possible.

[0057] For illustrative purposes, some particularly advantageous layer structures of security elements according to the invention are presented below with reference to Figures 4 to 9. The figures each show the reflective feature region of the security elements; however, it is understood that the security elements also each contain a neutral region in which the higher relief layer is formed as a planar, flat structure and / or as a deactivation structure, as described in Figure 3. Such a neutral region can be arranged, in particular, in an area surrounding the feature region shown, for example, an edge region of the security elements.

[0058] Figure 4 first shows the feature area of ​​a foil patch 60 according to an embodiment of the invention schematically in cross section.

[0059] In the layered structure of the foil patch 60, the two relief layers 24, 34 are arranged on opposite sides of a carrier foil 62, which remains in the layered structure of the foil patch even after application. This has the advantage that the two relief layers 24, 34 can be produced cost-effectively in a single operation on a double embossing machine by applying and embossing an embossing lacquer 22 or 32 with the desired relief structure 24, 34.

[0060] To produce the foil patch 60, the following procedure can be followed, for example, whereby two or more of the described work steps can also be combined.

[0061] First, an ink layer 30 is printed onto the carrier film 62, for example a transparent PET film. The ink can be a solvent-based, aqueous ink or a UV ink. The ink layer can contain a single color or be a multi-color print applied in register. The ink layer 30 can, as in the illustrated embodiment, be arranged above (closer to the viewer) or below the carrier film 62. To ensure that the ink(s) adhere well to the carrier film, the carrier film 62 can be provided with an appropriate double-sided acrylate coating or with an appropriate primer. In the next step, the embossing lacquer layers 22, 32 are printed and embossed onto opposite sides of the carrier film 62. The embossing on the top and bottom sides can be done in one or two steps.Advantageously, the embossings 24, 34 are in register with the color printing of the ink layer 30 and the embossing of the respective opposite embossing lacquer layer. The embossing lacquer used can be a thermoplastic embossing lacquer or—for better impression quality—preferably a UV embossing lacquer. So-called dual-cure systems can also be used. When using a UV embossing lacquer, the photoinitiator is selected so that sufficient curing is possible through the ink layer 30.

[0062] In a further development, it is provided to print a wash ink for demetallization directly in this step in order to be able to create transparent areas and / or areas without a high-refractive-index layer 36. Alternatively, a resist can be printed onto the high-refractive-index layer in a printed form only after coating, and this can be removed in sections in a subsequent etching step.

[0063] This is followed by the coating steps, for which there are two possibilities: i) first applying the high-refractive-index layer 36 to the higher relief layer 34 with spectral control of the layer, followed by applying the reflection-enhancing layer 26, for example, an aluminum layer, to the lower relief layer 24; or ii) first applying the reflection-enhancing layer 26 to the lower relief layer 24, followed, if necessary, by demetallizing this layer by washing or etching. The high-refractive-index layer 36 is then applied to the higher relief layer 34.

[0064] As mentioned, in addition to the feature region shown, the foil patch 60 also contains a reflective neutral region in which the higher relief layer 34 is formed as a flat, planar structure and / or as a deactivation structure, as described in more detail in Fig. 3. The flat structure or deactivation structure differs from the relief structure 34 of the feature region of Fig. 4 only in the surface topography of the embossing and is produced simultaneously with the latter during the embossing of the embossing lacquer 32. The high-index layer 36 follows the surface topography of the embossed structure even in the flat regions or deactivation regions, so that the effects described above also arise here.

[0065] After these operations, the optical functionality of the foil patch 60 is already established. However, for insertion or application into banknotes, the foil patch is generally further suitably equipped and also provided with protective layers to ensure sufficient circulation stability. In the exemplary embodiment shown, for example, a semi-finished product 20 consisting of two laminated PET films and a release layer 40 is laminated onto the higher relief layer 34 and the high-refractive index layer 36. The release layer 40 can in particular be a UV varnish. The second reflection-enhancing layer 36 is protected by protective varnishes and primer layers 28. Laminating a foil on this side of the security element is also possible in principle, but leads to a great overall thickness of the security element.An adhesive 42 is then applied, which can be either a conventional heat-sealing varnish or a UV-curable heat-sealing varnish, or a combination. In the next step, the contours of the patch are punched, and the unused material is removed. In the final step of film production, the film is cut into strips. The resulting patch can then be applied to paper using a roll-fed or sheet-fed application system.

[0066] Figures 5 to 7 each show a schematic cross-section of the feature area of ​​a security thread for embedding in a banknote or a valuable document. As with the exemplary embodiment in Fig. 4, these embodiments each involve a double structure in which the two relief layers 24, 34 are arranged on opposite sides of a carrier foil 62. The production of the security threads 70, 80, and 90 is largely analogous to the previously described production of the foil patch 60, so reference is made to the explanations therein for details.

[0067] Referring first to Fig. 5, to produce the security thread 70, a transparent PET carrier film 62 is provided and provided with an ink layer 30. Embossing lacquer layers 22, 32 are then printed and embossed onto the opposite sides. Advantageously, the embossings 24, 34 are in register with the color printing of the ink layer 30 and the embossing of the respective opposite embossing lacquer layer. If a washing step is to be performed to produce a negative identification mark, wash ink is printed in the designated areas.

[0068] This is followed by the coating steps for applying the high-index layer 36 and the opaque metallization 26, the latter, for example, in the form of a layer sequence consisting of an aluminum layer. This is followed by a demetallization step to remove the metallization 26 in an area 50 and thereby introduce a negative marking, for example, negative writing. This can be done using the aforementioned wash ink or, after applying the metallization 26, by printing a resist followed by an etching step.

[0069] Primer layers 28 and 38, respectively, are then applied to both sides, along with other functional layers known per se, such as a machine-readable magnetic layer or a luminescent layer, if desired. The top and bottom sides are then provided with protective lacquer layers, which are combined with the primer layers in the figure by reference numerals 28 and 38, respectively. Optionally, additional functional layers, an opaque white layer, and heat-sealing lacquer layers 42 are applied. Finally, the resulting film is cut into strips of the desired width.

[0070] The security thread 80 of the embodiment shown in Fig. 6 does not contain a separate color layer applied to the carrier foil 62; rather, the coloring in this embodiment is achieved through the use of colored embossing lacquer. For this purpose, the embossing lacquer layer 22 of the deeper relief structure is colored with a first color in a first partial area 82 and with a second, different color in a second partial area 84. In a third partial area 86, in which the metallization 26 is also left out, the embossing lacquer layer 22 is transparent.

[0071] The further design of the security thread 80, in particular the formation of the higher relief layer 34, follows the embodiment of Fig. 5. Furthermore, in the embodiment of Fig. 6, a fluorescent layer 88 containing a feature substance that fluorescent upon UV excitation is applied to the leveling primer or protective lacquer layer 28 of the lower relief layer 24. A further primer or protective lacquer layer 28 and a heat-sealing lacquer layer 42 adjoin the fluorescent layer 88.

[0072] With reference to Fig. 7, the security thread 90 shown therein represents a modification of the security thread 70 of Fig. 5, in which the color layer 30 is formed with two or more color regions 92, 94 of different colors. It is understood that negative markings can also be provided in this design through recesses in the metallization 26.

[0073] Figure 8 shows, as a further embodiment of the invention, a transfer strip 100 with a lamination structure. The advantage of such a lamination structure is in particular that the embossed relief layers, the reflection-enhancing coatings, and the color print can initially be produced on separate films, each as a semi-finished product. The complete security element is only created when the two semi-finished products are laminated together, with the lamination usually taking place in register. The release of the lower release layer should be easier than the release for application, or should be based on a different mechanism. Specifically, the film shown in Fig.The transfer strip 100 shown in Figure 8 comprises a first PET carrier film 20-1 with a first UV release layer 40-1, on which the layers of the higher relief layer structure were applied by applying and embossing a UV embossing lacquer layer 32 onto the release layer 40-1, and coating the relief layer 34 thus formed with a high-refractive index ZnS layer 36.

[0074] The layers of the deeper relief layer structure were applied to a second PET carrier film 20-2 with a second UV release layer 40-2 by applying and embossing a UV embossing lacquer layer 22 onto the release layer 40-2, and providing the resulting relief layer 24 with an opaque metallization 26 consisting of a chromium layer and an aluminum layer. Furthermore, the metallization 26 was provided with a color print 102 in one partial area and with a recess 104 in another partial area, for example, using a washing process or a resist / etching process to form a negative mark.

[0075] In a modification, the color print 102 can also be applied to the high-refractive-index ZnS layer of the first carrier film 20-1, or both reflection-enhancing coatings 26, 36 can be provided with a color print.

[0076] The layer structures created on the carrier films 20-1, 20-2 were then laminated together with a laminating adhesive 106 to form the complete two-color area of ​​the transfer strip 100. The two original layer structures meet at line 108, drawn in the figure for illustration purposes. Primer layers 28 and heat-sealing lacquer layers 42 are provided on the underside of the second carrier film 20-2 for application to a target substrate. After application, the first carrier film 20-1 can be removed by activating the first release layer 40-1.

[0077] Like the other exemplary embodiments, the transfer film 100 also contains, for example in a not-shown edge region of the film, a reflective neutral region in which the high-refractive-index layer 36 is formed as a flat, planar structure and / or as a deactivation structure in the manner described in Fig. 3.

[0078] As a further embodiment of the invention, Fig. 9 shows a transfer strip 110 with an inserter structure.

[0079] The transfer strip 110 contains a PET carrier film 20 with a UV release layer 40, onto which a first UV embossing lacquer layer 32 was applied and embossed. The resulting relief layer 34 was coated with a high-index ZnS layer 36. The ZnS layer 36 was provided with a color imprint 112 in a partial area and then coated over the entire surface with a leveling primer layer 38 and optionally further layers 28', which can be aqueous, solvent-based, or UV-curing. These further layer(s) 28' can serve as a protective layer, as a primer layer, or to promote adhesion. The layers advantageously have good adhesion to the adjacent layers and can themselves consist of several different sub-layers.

[0080] A second UV coating was then applied to the final layer 28'.

[0081] Embossing lacquer layer 22 is applied and embossed, and the resulting

[0082] Relief layer 24 is provided with an opaque metallization 26 made of an aluminum layer. Metallization 26 can also be recessed in a partial area 114 to form a negative mark in transfer strip 110. Finally, the metallized relief layer is provided with another primer layer 28 and a heat-sealing lacquer layer 42.

[0083] The embossing of the relief layers 24, 34 and the color print 112 are advantageously in register with each other. The color print 112 can also be present in a separate color layer arranged between the relief layers 24, 34.

Claims

Patent claims 1. An optically variable security element for protecting valuables, the surface area of ​​which defines a z-axis perpendicular thereto, wherein the security element contains two relief layers which are arranged in the z-direction at different heights and form a lower and a higher relief layer, the higher relief layer being provided with a first reflection-enhancing coating following its surface topography and the deeper relief layer being provided with a second reflection-enhancing coating following its surface topography, the first reflection-enhancing coating being formed with a wavelength-dependent reflection and transmission in the visible spectral range, wherein in a reflective feature area within the security element — the higher relief layer is designed as a relief structure and shows a first optically variable effect in a first colour, and — the deeper relief layer is designed as a relief structure and passes through the first reflection-enhancing coating second optically variable effect in a second, different color, characterized in that in a reflective neutral area within the security element the higher relief layer is designed as a flat, planar structure and / or as a deactivation structure formed by elevations and / or depressions, which suppresses the reflective and / or color-imparting properties of the first reflection-enhancing coating.

2. Security element according to claim 1, characterized in that the first reflection-increasing coating has a wavelength-dependent reflection and a wavelength-dependent transmission in the visible spectral range, so that due to the reflection color effect of the first reflection-increasing coating, the higher-lying relief structure shows the first optically variable effect in the first color, and the transmission color effect of the first reflection-increasing coating contributes to the color effect of the second optically variable effect of the lower-lying relief structure in the second color.

3. Security element according to claim 1 or 2, characterized in that the deactivation structure is formed by an anti-reflective structure in the form of a moth-eye structure, in the form of a microcavity structure with a plurality of adjacent microcavities or in the form of a random surface with irregularly distributed elevations and / or depressions.

4. Security element according to at least one of claims 1 to 3, characterized in that the deactivation structure has elevations and / or depressions with a large aspect ratio of 2 or more, in particular of 5 or more.

5. Security element according to at least one of claims 1 to 4, characterized in that in the reflective neutral region the first reflection-increasing coating has a locally varying thickness and therefore macroscopically shows no or a non-uniform color effect, and / or the first reflection-increasing coating is finely screened and therefore macroscopically shows no or a non-uniform color effect, and / or the first reflection-increasing coating has a locally rapidly varying inclination and therefore macroscopically shows no or a non-uniform color effect.

6. Security element according to at least one of claims 1 to 5, characterized in that the reflective neutral region surrounds the reflective feature region and / or that the reflective neutral region forms an edge region of the security element.

7. Security element according to at least one of claims 1 to 6, characterized in that in the reflective neutral region the deeper relief layer is designed as a relief structure and shows a colored optically variable effect, in particular an optically variable effect in the second color, through the first reflection-enhancing coating.

8. Security element according to at least one of claims 1 to 7, characterized in that the first reflection-increasing coating contains one or more high-refractive-index layers, preferably dielectric high-refractive-index layers, which have a refractive index of at least 1.7, preferably at least 2.0 and particularly preferably at least 2.2 at least in a partial range of the visible spectrum, particularly preferably that the first reflection-increasing coating is a high-refractive-index single layer, in particular a ZnS, TiO2, Al2O3, HfO2, PbsCU, PBS, ZrO2 single layer, very particularly preferably a ZnS single layer.

9. Security element according to at least one of claims 1 to 8, characterized in that in the reflective feature area the higher relief structure and / or the lower relief structure are formed by micromirror arrangements with directionally reflecting micromirrors, in particular with non-diffractive mirrors, and preferably with plane mirrors, concave mirrors and / or Fresnel-type mirrors.

10. Security element according to at least one of claims 1 to 9, characterized in that the second reflection-enhancing coating has a reflectance of at least 50%, preferably at least 75%, particularly preferably at least 80%, or even at least 85% in at least a partial range of the visible spectrum, preferably that the second reflection-enhancing coating is opaque with an optical density of more than 1.0, in particular more than 2.

0.

11. Security element according to at least one of claims 1 to 10, characterized in that in the reflective feature area between the first and second relief layer one or more translucent color layers are provided to influence the color impression of the optically variable effects of the first and second relief layers.

12. Security element according to at least one of claims 1 to 11, characterized in that in the reflective feature region, the transmission color effect of the first reflection-enhancing coating determines the second color; or the transmission color effect of the first reflection-enhancing coating together with a reflection color effect of the second reflection-enhancing coating and / or with at least one of the translucent color layers determines the second color; or a reflection color effect of the second reflection-enhancing coating and / or the color effect of at least one of the translucent color layers determines the second color.

13. Security element according to at least one of claims 1 to 12, characterized in that in the reflective feature area, the first and second relief structures at least partially reflect incident parallel light into different angular ranges, wherein the two different angular ranges preferably do not overlap and are preferably separated from one another by more than 3°, particularly preferably more than 10°.

14. Security element according to at least one of claims 1 to 13, characterized in that the formation of the higher relief structure, in particular the alignment of the micromirrors of the higher micromirror arrangement and / or the formation of the deeper relief structure, in particular the alignment of the micromirrors of the lower micromirror arrangement, varies depending on the location by a respective to create a given motif, in particular a three-dimensional motif or a movement motif.

15. A data carrier with an optically variable security element according to at least one of claims 1 to 14.

16. A method for producing an optically variable security element, in particular according to at least one of claims 1 to 14, in which a carrier is provided, the surface extent of which defines a plane and a z-axis perpendicular thereto, the carrier is provided with two relief layers which are arranged at different heights in the z-direction and form a lower and a higher relief layer, the higher relief layer is provided with a first reflection-increasing coating following its surface topography and the deeper relief layer is provided with a second reflection-increasing coating following its surface topography, the first reflection-increasing coating is formed with a wavelength-dependent reflection and transmission in the visible spectral range, wherein in a reflective feature region within the security element — the higher relief layer is formed as a relief structure and shows a first optically variable effect in a first colour, and — the deeper relief layer is formed as a relief structure and shows a second optically variable effect in a second, different color through the first reflection-enhancing coating, and in a reflective neutral area within the security element the higher relief layer is formed as a flat, planar structure and / or as a deactivation structure formed by elevations and / or depressions, which suppresses the reflective and / or color-imparting properties of the first reflection-enhancing coating.

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