WO2025067977A1 - Optically variable security element, article of value, and production method - Google Patents

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

Optically variable security element, valuable object and manufacturing process

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.

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

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 equipment. 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 color coating. The color coating of the higher relief structure is structured as a grid, so that when the security element is viewed, the color 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 the security element is tilted.

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.

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.

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

To achieve the stated object, the invention contains an optically variable security element, which can be used in particular to protect valuables. The surface area of the The safety element defines a plane which, without loss of generality, can be regarded as the xy-plane and a z-axis perpendicular to the plane.

The security element contains two relief layers arranged at different heights in the z-direction, forming 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, wherein the first reflection-enhancing coating is formed with a wavelength-dependent reflection and transmission in the visible spectral range.

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.

It is further provided 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. In 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 planar 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 region of a planar, flat structure, a reflection-enhancing coating following the surface topography is correspondingly planar, and in the region of a deactivation structure, a reflection-enhancing coating following the surface topography follows the profile of the elevations and/or depressions of the deactivation structure.

An area in which both the higher relief layer and the lower relief layer are each formed as a relief structure and, in addition, the two relief layers each exhibit an optically variable effect of a different color through 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, planar structure, the lower relief layer may be formed as a relief structure, but the higher relief layer is planar 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 does not produce an optically variable effect of a second, different color due to the reflection- or color-suppressing effect of the deactivation structure. It is advantageous that 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-lying relief structure to show 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-lying relief structure in the second color.

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%.

It is advantageous that in the reflective neutral area the first reflection-enhancing coating has a locally varying thickness and thus macroscopically shows 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 relief structure can be formed entirely as a flat, planar layer or entirely as a deactivation structure, or can also be formed partly as a flat, planar layer and partly as a deactivation structure.

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.

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.

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 layer sequence, but a high-index single layer, in particular a ZnS, TiO2, Al2O3, HfO2, Pb ₃ O ₄ - PBS, ZrO - single layer, most preferably a ZnS single layer.

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 around 10 μm, i.e. in particular between 7 μm and 13 μm. On the other hand, the lateral dimensions of the micromirrors are also 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.

In principle, other relief structures, in particular embossed Fresnel lenses, concave mirrors, hologram structures, nanostructures, or various active blazed gratings, can be used instead of micromirrors. Achromatic diffraction gratings, so-called matte structures, can be used particularly advantageously here, as they essentially reflect white light and thus do not disrupt 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 that is only scaled in height; instead, the two relief structures are different and designed with different relief patterns.

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.

It is further advantageously provided that in the reflective feature region, the first and second relief structures reflect incident parallel light at least in certain regions 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.

Specifically, 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 lower relief structure, in particular the alignment 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 alignment of the The micromirror can be freely selected and is essentially determined only by the given motifs, but not by the alignment of laterally or vertically adjacent micromirrors.

The invention further includes a data carrier with a security element of the type described. The data carrier can in particular be a value document, such as a banknote, in particular a paper banknote, a polymer banknote or a film composite banknote, a share, a bond, a certificate, a voucher, a check, a high-value admission ticket, but also 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 deeper 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.

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, 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 in the z-direction at different heights 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 lower relief layer is provided with one of its surface topography following second reflection-enhancing coating, the first reflection-enhancing coating is 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 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, level 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.

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

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

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

Fig. 2 and 3 schematically illustrate the basic principle of the invention, a cross-section of the transfer strip of Fig. 1 in two partial areas, and

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

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 adhesively bonded 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.

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

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 (Fig. 2) and in the partial region 16 (Fig. 3), respectively. The partial region 14 of Fig. 2 represents a reflective feature region within the transfer strip 12, while the partial region 16 shown in Fig. 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.

To illustrate the complete structure of a transfer element, the transfer strip 12 is shown in Figures 2 and 3 with 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 of Figure 1, the transfer foil is removed by activating the release lacquer layer and is then no longer present in the finished banknote 10.

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. On the transfer film 20, for example a PET film, and the release lacquer layer 40, a layer sequence is provided which, starting from the transfer film and the release lacquer layer, 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 Color 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-sealing lacquer layer 42.

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 closer to the observer is also referred to as the higher relief layer and the relief layer 24 further away from the observer is referred to as the lower relief layer.

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 x-y 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.

In order to give the appearance a desired color impression, the deeper micro mirror arrangement 24 is provided with a reflection-enhancing coating 26 following the relief profile in the form of a highly reflective, opaque metallization, which in the exemplary embodiment consists of an aluminum layer. The metallization 26 is in a Partial area 50 is cut out in order to produce a negative marking, for example a negative writing in the partial area 14 of the transfer strip 12.

The higher micromirror arrangement 34 is provided over its entire surface with a reflection-enhancing coating 36 following the relief contour in the form of a high-refractive-index layer, specifically a ZnS layer in the exemplary embodiment. 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.

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.

Overall, the two micromirror arrays 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 array is visible is determined by the orientation of the micromirrors. Thus, for a viewer from a first viewing direction, the micromirrors of the higher micromirror array 34 are at the glancing angle and, due to the high reflectivity of the high-refractive index layer 36, produce Spectral range, a first image representation with a bright, red reflection color. Due to their orientation, the micromirrors of the lower micromirror array 24 are far from the glancing angle from this viewing direction and contribute virtually nothing to the image impression.

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.

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.

The deeper relief layer region 24 is also formed as a relief structure in the partial region 16 and is present in the partial region 52 as a hologram relief and in the partial region 54 as a micromirror arrangement for generating a rolling bar effect. The reflection-enhancing coating 26 of the Relief structure 24 is formed in sub-area 16 as in sub-area 14 as a highly reflective opaque metallization from a chromium layer and an underlying aluminum layer, which follows the relief course of the hologram relief (sub-area 52) and the relief course of the micro mirror relief (sub-area 54).

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 to suppress the reflective and/or color-imparting properties of the high-refractive layer 36.

Since the high-refractive-index layer 36, as a coating on 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 this reason, it essentially only illuminates an observer 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 coating leads to a locally strongly varying thickness of the high-refractive-index layer 36, so that a macroscopically uniform color effect of the high-refractive-index layer 36 does not result for an observer 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 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 a macroscopically uniform color effect of the high-refractive-index layer 36 cannot be achieved.

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.

For example, the high-index layer 36 can be formed not only from ZnS, but alternatively also from one of the materials TiO , Al 2 O , 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-refractive index layer has a high refractive index compared to organic compounds, especially the embossing lacquers used.

The deeper relief layer 24 obtains 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 about 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 represent 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-color image.

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 indexes 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.

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

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 only in certain areas. The color can be a single layer of color over the entire surface, but it can also be an image with any number of colors, arranged in a favorable register with the embossing.

In a further development of the invention, a desired color can also be divided into two layers, so that the desired color is created 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.

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.

For illustration purposes, some particularly advantageous layer structures of the invention are shown below with reference to Figures 4 to 9. Security elements are presented. 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 flat, planar structure and/or as a deactivation structure, as described in Fig. 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.

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

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 system by applying and embossing an embossing lacquer 22 or 32 with the desired relief structure 24, 34.

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.

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 can be a multi-color print applied in register. The ink layer 30 can, as shown in the Embodiment, can 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 carried out 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 opposite embossing lacquer layer. The embossing lacquer used can be a thermoplastic embossing lacquer or - due to the better impression quality - preferably a UV embossing lacquer. So-called dual-cure systems can also be used. When using a UV embossing varnish, the photoinitiator is selected so that sufficient curing through the ink layer 30 is possible.

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 document only after coating, and this can be removed in sections in a subsequent etching step.

This is followed by the coating operations, for which there are two possibilities: i) firstly applying the high-refractive layer 36 to the higher relief layer 34 with a spectral control of the layer and subsequent application of the reflection-enhancing layer 26, for example an aluminum layer, to the deeper relief layer 24; or ii) first application of the reflection-enhancing layer 26 to the deeper relief layer 24, followed, if necessary, by demetallization of this layer by washing or etching. Subsequently, the high-index layer 36 is applied to the higher relief layer 34.

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.

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 usually further suitably equipped and additionally provided with protective layers to ensure sufficient circulation resistance. In the illustrated embodiment, 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 film on this side of the security element is also possible in principle, but this would result in a greater overall thickness of the security element. An adhesive 42 is then applied, which can be either a conventional heat-sealing varnish or a UV-crosslinkable heat-sealing varnish, or a combination. In the next step, the contours of the patch are punched, and the unnecessary material is removed. In the final step of film production, the film is cut into strips. The patch produced in this way can then be applied to paper using a roll-fed or sheet-fed application system.

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 value 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.

Referring first to Fig. 5, for the production of the security thread 70, a transparent PET carrier film 62 is provided and provided with an ink layer 30. Then, embossing lacquer layers 22, 32 are printed and embossed on 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 opposite embossing lacquer layer. If a washing step is required to create a negative mark, wash ink is printed in the designated areas.

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. A demetallization step then follows 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 above-mentioned wash ink or, after applying the metallization 26, by printing a resist followed by an etching step.

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 and an opaque white layer, as well as heat-sealing lacquer layers 42, are applied. Finally, the produced film is cut into strips of the desired width.

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

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 are applied to the fluorescent layer 88.

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.

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 generally 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 transfer strip 100 shown in Fig. 8 contains 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.

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 imprint 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.

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.

The layer structures produced 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 originally present layer structures meet at the line 108 shown in the figure for illustration. 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.

Like the other exemplary embodiments, the transfer film 100 also contains, for example in a non-illustrated 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.

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

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-refractive index ZnS layer 36, the ZnS layer 36 was provided with a color print 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.

Subsequently, a second UV

Embossing lacquer layer 22 is applied and embossed, and the resulting

Relief layer 24 with an opaque metallization 26 made of a The metallization 26 can also be recessed in a partial area 114 to form a negative mark in the transfer strip 110. The metallized relief layer was finally provided with a further primer layer 28 and a heat-sealing lacquer layer 42.

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 at different heights in the z-direction 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 lower 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 has a 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-enhancing coating has a locally varying thickness and therefore macroscopically shows no or a non-uniform color effect, and/or the first reflection-enhancing coating is finely screened and therefore macroscopically shows no or a non-uniform color effect, and/or the first reflection-enhancing 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 in at least 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 of 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 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 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 whose surface extent 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 — 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, level structure and/or as a deactivation structure formed by elevations and/or depressions, which suppresses the reflective and/or color-providing properties of the first reflection-enhancing coating.