EP3954543B1 - Optically variable security element - Google Patents

Description

The invention relates to an optically variable security element for protecting valuables, whose surface area defines a z-axis perpendicular thereto, with a reflective surface area that shows at least two appearances recognizable from different viewing directions. The invention also relates to a method for producing such a security element and a data carrier equipped with such a security element.

Data carriers, such as value or ID documents, but also other valuables, such as branded items, are often provided with security elements for protection, which allow the authenticity of the data carrier to be checked and which at the same time serve as protection against unauthorized reproduction. The security elements can be designed, for example, in the form of a security thread embedded in a banknote, a cover film for a banknote with a hole, an applied security strip, a self-supporting transfer element or also in the form of a feature area printed directly onto a document of value.

Security elements with a viewing angle-dependent or three-dimensional appearance play a special role in authenticity protection, as these cannot be reproduced even with the most modern copiers. For this purpose, the security elements are equipped with optically variable elements that give the viewer a different image impression from different viewing angles and, for example, show a different color or brightness impression and/or a different graphic motif depending on the viewing angle. The prior art describes, for example, movement effects, pump effects, depth effects or flip effects as optically variable effects, which are realized with the aid of holograms, microlenses or micromirrors.

Some time ago, optically variable security elements were proposed which have two relief structures arranged at different height levels and each provided with a color coating (see Fig WO 2020/011390 A1 , WO 2020/011391 A1 and WO 2020/011391 A2 ). The color coating of the higher-lying relief structure is either structured as a grid or provided with gaps, so that the color coating of the deeper-lying relief structure appears in the grid gaps or gaps when viewing the security element.

With these designs, however, it is often difficult in practice to produce the two relief structures with two colors that can be selected independently of one another and at the same time with a sufficiently small overall thickness. The processing of a security element with colors selected independently of one another also requires a large number of work steps and is therefore expensive to manufacture.

In DE 10 2018 004 433 A1 and EP 3 254 863 A1 floating pigments are used and moved by means of a magnetic field. WO 2008/095698 A1 shows a security element with two superimposed diffractive relief structures. WO 2020/011390 A1 shows the preamble of claim 1.

Proceeding from this, the invention is based on the object of specifying generic optically variable security elements which can be produced with a small total thickness with independently selectable colors of the visually recognizable appearances and which ideally require a small number of work steps during production.

This object is solved by the features of the independent claims. Developments of the invention are the subject matter of the dependent claims.

To achieve the above object, the invention contains an optically variable security element with a reflective surface area, which can be used in particular to protect valuables. The reflective surface area shows at least two appearances recognizable from different viewing directions. The surface extent of the security element defines a plane and a z-axis perpendicular to the surface.

The reflective surface area contains two relief structures which are arranged at least partially overlapping one another in the z-direction at different height levels and form a first (lower lying) and a second (higher lying) relief structure. The second relief structure includes an embossing layer.

The second relief structure is only provided in partial areas of the reflective surface area, so that the surface area has the partial areas with a reflective second relief structure and free areas without a reflective second relief structure.

The embossed layer is only provided in the partial areas of the reflective surface area, but not in the free areas.

In the present case, the reflection-increasing layer of the second relief structure is formed by floating or sunken pigments.

It is known that the orientation of platelet-shaped pigments in a dispersion medium is based on a complex interplay of various factors, such as the viscosity of the dispersion medium or the shrinkage of the dispersion medium during drying. By suitably selecting the production parameters, the pigments in the dispersion medium can be aligned essentially parallel to the surface of the dispersion medium. A distinction is usually made between two main types of the resulting spatial distribution of the pigments in the medium. Floating pigments, also known as leafing pigments, move to the surface of the dispersion medium after application. In contrast, dispersing pigments, also referred to as non-leafing pigments, disperse randomly at different heights after application in the dispersion medium. Another type of pigment, referred to in this specification as a sagging pigment, moves away from the surface of the dispersing medium after application.

According to current understanding, the different movement behavior of the pigments is a consequence of the different wetting behavior of the pigments. Leafing pigments have a high interfacial energy between the pigment and the dispersion medium, the pigments are therefore hardly wetted by the medium and float in the wet film towards the air, where the interfacial energy is lower. The dispersing (non-leafing) pigments are completely wetted by the dispersing medium and therefore disperse substantially evenly throughout the medium. Floating pigments can be produced, for example, by adding stearic acid as a lubricant in the milling step during production of the pigments. On the other hand, when oleic acid is used as a lubricant or when highly polar substances are added to the pigments, dispersing pigments are generally formed. The two reflection-increasing layers follow the course of their relief structure. The second relief structure appears for the observer with the partial areas. In contrast, the first relief structure appears in the free areas.

The second relief structure preferably comprises a color layer.

In the embossing layer, the floating or sunken pigments form the reflection-increasing layer of the second relief structure.

The reflection-increasing layer of the second (higher) relief structure is particularly preferably formed by floating pigments, which are aligned in such a way that they follow the relief profile of the second (higher) relief structure.

The first/second relief structure is sometimes abbreviated or also referred to below as the lower/higher relief structure.

In an advantageous embodiment, the second (higher) relief structure is formed by an embossing lacquer layer, on the relief-structured side of which a surface layer of aligned floating pigments forms the reflection-increasing layer of the (second) higher relief structure. This embossing lacquer layer of the second (higher) relief structure can either be colorless transparent or be colored in a translucent manner.

The second relief structure can be formed by an embossing lacquer layer, on the relief-structured side of which a surface layer made of the floating or sunken pigments forms the reflection-increasing layer of the second relief structure.

It is associated with other advantages if pigments that have floated or sunken in a reflection-increasing, preferably reflective, color layer form the reflection-increasing layer of the second relief structure.

In configurations, the second relief structure can be formed by an embossing layer and a reflection-increasing color layer. On the relief-structured side of the reflective color layer, a surface layer made of the pigments that have floated or sunken in the reflection-increasing color layer forms the reflection-increasing layer of the second relief structure.

The two sides of the reflection-increasing color layer preferably follow a relief profile of the second relief structure. In particular, the reflection-increasing layer can be arranged either on the side facing the embossed layer or on the side facing away from the embossed layer. Further preferably or alternatively, the embossed layer and the reflection-increasing color layer can be embossed together.

Alternatively, only the side of the reflection-increasing color layer that faces the embossing layer can follow a relief profile of the second relief structure. Further alternatively or additionally, only the embossed layer can be embossed and the reflection-increasing color layer is applied to the embossed embossed layer in the partial areas.

In preferred configurations, the floating or sinking pigments can be optically variable pigments; and/or anisotropic pigments, which are aligned following the relief course of the second relief structure, and/or which have a largest dimension below the lateral structure dimensions of the second relief structure.

The floating or sinking pigments have lateral dimensions that are at most a factor of 5 larger than the embossed relief structures. Pigments whose lateral dimensions are similar in size to the relief structures are particularly suitable. The pigments can advantageously also be up to a factor of 10 smaller than the embossed relief structures. The floating or sinking pigments are, in particular, anisotropic. They are therefore not spheres, but are designed with different dimensions in different directions in space. The floating or sinking pigments are advantageously in the form of flakes, the aspect ratio, ie the ratio of edge length to thickness of the flakes, being preferably more than 5:1, in particular more than 10:1.

In an advantageous embodiment, the second (higher) relief structure and/or the first (lower) relief structure are formed by micromirror arrangements with specularly reflecting micromirrors, in particular with non-diffractive mirrors, and preferably with planar mirrors, concave mirrors and/or Fresnel-like mirrors . The lateral dimensions of the micromirrors are expediently below 50 μm, advantageously at or below 20 μm, preferably at about 10 μm, ie 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.

In the case of such micromirror arrangements, the lateral structure dimensions discussed above are given by the lateral dimensions of the micromirrors. If, for example, the micromirrors of the higher relief structure have a length of 10 µm and a width of 15 µm, the largest dimension of the floating or sinking pigments should be less than 10 µm (the smaller of the length and width of the micromirrors), in particular below 6.67 µm (factor 1.5) or even below 5 µm (factor 2).

In principle, other embossed relief structures, in particular Fresnel lenses, concave mirrors, convex lenses such as lens caps, hologram structures, nanostructures or diffractive blazed gratings can also be used instead of micromirrors. Advantageously, achromatic diffraction gratings, so-called matte structures, can also be used reflect white light. To produce bright colors, the relief structures of at least the second relief structure can also have sub-wavelength structures, in particular sub-wavelength gratings, or interference structures which, in combination with the respective reflection-enhancing layer, determine or at least co-determine the color thereof.

Advantageously, the second (higher) relief structure is designed and formed to show a first optically variable effect in a first color, and the first (lower) relief structure is designed and formed in the free areas a second optically variable effect in a second to show different color. The different color effects can be produced in different ways, with advantageous variants being described in more detail below.

The first (deeper) relief structure itself is advantageously shaped in an embossing lacquer layer, which can be colorless transparent or glazing colored, and on which the reflection-increasing layer is applied following the course of the relief. It is also possible to provide a color layer for the first relief structure that does not follow the course of the relief. The embossing lacquer layer of the underlying relief structure in the finished security element preferably lies above the reflection-enhancing layer, so that the viewer looks through the embossing lacquer layer at its reflection-enhancing coating. The color effect of the underlying relief structure then results from the interaction of the coloring of the embossing lacquer layer and the color of the reflection-increasing layer.

As already mentioned above, the second (higher) relief structure is advantageously shaped in an embossing lacquer layer, which can be colorless transparent or transparent or colored, and on its relief-structured side a surface layer of aligned anisotropic pigments forms a reflection enhancing layer. Here, too, the embossing lacquer layer of the higher-lying relief structure in the finished security element preferably lies above the reflection-enhancing layer, so that the viewer looks through the embossing lacquer layer at its reflection-enhancing surface layer. The color effect of the higher relief structure results from the interaction of the coloring of the embossing lacquer layer and the color of the reflection-increasing surface layer.

The coloring of the embossing lacquer layers can be provided in particular by translucent colors, luminescent colors or nanoparticle colors, for example based on gold-blue particles.

The reflection-increasing layer of the first (deeper) relief structure is advantageously formed by a reflective color coating, in particular by a metallization, a thin-layer structure, by a glazing color deposited with a metallization, by a luminescent color with a metallic mirror coating, by a structural color and/or through a nanoparticle paint. The reflection-increasing layer of the lower-lying relief structure is particularly advantageously formed by a vapor-deposited layer that is deposited, for example, in a CVD or PVD process.

The floating or sinking pigments are advantageously formed by pigments that reflect substantially uniformly over the entire visible spectral range, such as aluminum or silver pigments. Such pigments themselves appear essentially colorless, so that the color effect of the higher-lying relief structure is provided in this case by the coloring of the base embossing varnish of the embossing varnish layer.

In a likewise advantageous embodiment, the floating or sinking pigments have an uneven reflection in the visible spectral range and thus a visually visible inherent color. The pigments can be copper or gold pigments with a reddish or gold inherent color. When using colored pigments that float or sink, a color effect of the higher-lying relief structure can also be achieved when using a colorless base embossing varnish.

In an advantageous embodiment, the partial (or paint) areas and free areas are formed at least in a partial area of the surface area as a regular or irregular grid with grid elements and grid spaces, with the dimensions of the grid elements (and grid spaces) in one or both lateral directions below of 140 μm, preferably between 20 μm and 100 μm, in particular between 20 μm and 60 μm.

In the grid areas formed by the lacquer areas and free areas, the security element advantageously shows an appearance when tilted or a corresponding change in the viewing direction that suddenly jumps from a first to a second appearance (or when tilted back from the second to the first appearance). At the same time, and without any intermediate or transitional stage, there is a change in the motif shown (e.g. value number or coat of arms) and the color (e.g. yellow or blue). Such an appearance that changes seamlessly between two different motifs with two different colors is referred to in this description as a binary color and effect change.

The grid formed by the partial (or lacquer) areas and free areas advantageously has a constant area coverage by the grid elements, which is expediently between 30% and 70%, preferably between 40% and 60%, in particular around 50%.

Alternatively or additionally, it is provided that the partial (or paint) areas and free areas are formed as an effect area at least in a partial area of the surface area, in which the partial areas and/or the free areas have lateral dimensions of more than 140 μm.

In these effect areas, the security element preferably shows two different effects (for example a three-dimensional motif and a movement effect such as a moving bar), which appear in two different colors. The areas with different color impressions and different effects are registered exactly to one another, which is also referred to below as color-to-effect registration.

At least one partial (or paint) area and/or at least one free area is advantageously formed with lateral dimensions of more than 250 μm, preferably more than 500 μm and in particular more than 1 mm.

In an advantageous embodiment, the reflection-increasing layer of the lower-lying relief structure completely covers it. Alternatively, negative identifiers can also be provided in the security element, which are formed by gaps in the reflection-increasing layer. The negative indicators can form text, symbols or value numbers, for example.

Negative markings can be provided in the raster areas that are formed by the paint areas and free areas mentioned. As a rule, however, they appear visually less attractive there, since the line width of the negative number plate is usually larger than the grid of the higher embossing layer, so that the viewer may be able to see the printed grid of the negative number plate.

In contrast, negative license plates can be integrated very well into the effect areas with color-to-effect registration because of the larger dimensions of the paint areas and free areas. In this case, negative markings are advantageously only provided in the free areas of the surface area in which only the second relief structure is present.

Transparent, colorless negative markings result from configurations in which a colorless, transparent embossing lacquer is provided with a colored metallization, for example a copper or gold layer, for the second relief structure. If, on the other hand, the color effect of the second relief structure is determined or partly determined by the coloring of the embossing varnish, colored negative marks appear in the recesses of the reflection-enhancing layer, the color of which is determined by the transparency color of the embossing varnish.

The reflective surface area of the security element described can be combined with other security features, for example with holograms, in particular real-color holograms, with sub-wavelength gratings or other sub-wavelength structures, with micromirror arrays without diffractive gratings, or with security features that special material properties such as electrical conductivity, magnetic properties, luminescence, fluorescence or the like are based.

The optically variable security element can contain further layers, such as a protective, covering or an additional functional layer, a primer layer or a heat-sealing lacquer layer. However, these are not essential for the present invention and are therefore not described in more detail.

The invention also includes a data carrier with a security element of the type described. The data carrier can in particular be a document of value, such as a banknote, in particular a paper banknote, a polymer banknote or a foil composite banknote, a share, a bond, a certificate, a voucher , a check, a premium ticket, but also an identification card, such as a credit card, a bank card, a cash card, an authorization card, an ID card or a passport personalization page.

Finally, the invention also includes a method for producing an optically variable security element with a reflective surface area that shows at least two appearances recognizable from different viewing directions. A carrier is provided, the surface extent of which defines a plane and a z-axis perpendicular thereto. The carrier is provided with a reflective surface area that contains two relief structures that are arranged at least partially overlapping one another in the z-direction at different height levels and form a first and a second relief structure. The first relief structure becomes a reflection-increasing structure following its relief profile provided layer. The second relief structure is provided with a reflection-increasing layer that follows the course of its relief. The second relief structure includes an embossing layer. The embossed layer is only provided in partial areas of the reflective surface area, but not in free areas. The second relief structure is provided only in the partial areas of the reflective surface area. As a result, the surface area has the partial areas with a reflective second relief structure and the free areas without a reflective second relief structure. In the present case, floating or sinking pigments form the reflection-increasing layer of the second relief structure.

The floating or sinking pigments are advantageously anisotropic pigments which align themselves along the course of the relief as they float or sink.

As explained further above, the designations "lower-lying relief structure" and "higher-lying relief structure" relate to the position of the relief structures in the finished security element relative to an observer. The designations therefore do not reflect the order in which the relief structures were applied during manufacture. Since the security element is designed in particular for viewing from the side of the carrier, the (later) higher-lying relief structure is generally first produced on the provided carrier during production and then the (later) lower-lying relief structure is then produced thereon.

In particularly advantageous configurations, the second relief structure is created first and then the first relief structure.

In an advantageous method, one layer is used to form the second lying relief structure with the reflection-increasing layer applied to the carrier from a pigment embossing varnish which is a dispersion of platelet-shaped floating pigments in a base embossing varnish. The desired relief structure is then advantageously embossed into the applied pigment embossing lacquer, the floating pigments being aligned by embossing along the course of the relief structure, so that a reflection-increasing surface layer with aligned pigments is formed on the surface of the pigment embossing lacquer layer.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, which are not shown to scale and proportions in order to improve clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen optisch variablen Sicherheitselement,

Fig. 2

einen Ausschnitt eines erfindungsgemäßen Sicherheitselements im Querschnitt,

Fig. 3

in (a) bis (d) Zwischenschritte bei der der Herstellung des Sicherheitselements der Fig. 2,

Fig. 4

in (a) bis (c) Zwischenschritte bei der der Herstellung eines Sicherheitselements mit Negativkennzeichen,

Fig. 5

in (a) bis (c) Zwischenschritte bei der der Herstellung eines Sicherheitselements mit einem alternativen Verfahren,

Fig. 6

in (a) bis (c) Zwischenschritte bei der der Herstellung eines Sicherheitselements mit einem weiteren alternativen Verfahren, und

Fig. 7

in (a) bis (b) Zwischenschritte bei der der Herstellung eines modifizierten Sicherheitselements mit einem weiteren alternativen Verfahren.

Show it:

1

a schematic representation of a banknote with an optically variable security element according to the invention,

2

a section of a security element according to the invention in cross section,

3

in (a) to (d) intermediate steps in the production of the security element of 2 ,

4

in (a) to (c) intermediate steps in the production of a security element with a negative mark,

figure 5

in (a) to (c) intermediate steps in the production of a security element with an alternative method,

6

in (a) to (c) intermediate steps in the production of a security element using a further alternative method, and

7

in (a) to (b) intermediate steps in the production of a modified security element with a further alternative method.

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 element. It goes without saying, however, that the invention is not limited to transfer elements and banknotes, but can be used with all types of security elements, for example labels on goods and packaging or to protect documents, ID cards, passports, credit cards, health cards and the like. In the case of banknotes and similar documents, in addition to transfer elements (such as patches or security strips—each with or without their own carrier layer), security threads, for example, can also be considered.

The security element 12 applied to the banknote 10 is itself very flat, but nevertheless gives the viewer the three-dimensional impression of a motif 14 apparently arching out of the plane of the banknote 10 and appearing in a first color. In practice, the motif 14 can, for example, be a denomination, a portrait or some other represent a graphic motif. A movement effect in a second color is visible in a partial area 16 within the motif 14 . For example, when the bank note 10 is tilted, a bright bar can move back and forth along the curved partial area 16 and produce a so-called rolling bar effect. The areas with different colors (first and second color) and different effects (three-dimensional motif or running bar) are precisely matched to each other. This registration is also referred to below as color-to-effect registration.

For a more detailed explanation, the security element 12 with reference to the cross section of the 2 a flat transparent carrier 18, the surface extent of which defines an xy plane and a z-axis perpendicular thereto. A multicolored reflective surface area 20 is arranged on the carrier 18, which contains two embossed structures 24, 34, which are arranged in the z-direction at two different height levels in relation to the planar carrier 18. In the exemplary embodiment, the different height levels of the embossed structures 24, 34 are defined by the different heights of the base areas of the micromirror arrangements 24, 34 above the carrier 18.

The two embossed structures 24, 34 are each embossed into an embossing lacquer layer 22, 32, which can be colorless, transparent or colored, depending on the desired color effects. In the exemplary embodiment, the embossed structures each represent embossed micromirrors or micromirror arrangements 24, 34, which are each formed from a multiplicity of micromirrors inclined with respect to the xy plane. The local angles of inclination of the micromirrors are selected in such a way that the relief structure of the micromirror arrangements 24, 34 together with the respective reflection-increasing layer produces a desired optical appearance, such as the arched three-dimensional impression of the motif 14 or the rolling bar effect of the partial area 16.

In order to produce the desired appearance of the security element 12 with two independently selectable colors, the micromirror arrangements 24, 34 are each provided with a reflection-enhancing layer 26, 36 on the one hand, and on the other hand the embossing lacquer layers 22, 32 can also be colored and thus together with the reflection-enhancing layers 26 , 36 produce a desired color effect of the respective micromirror array.

The security element 12 of 2 is designed for viewing from above (or in reflection), ie for viewing through the transparent carrier 18 . The micromirror array 24 farther from the viewer is therefore referred to as the lower micromirror array and the micromirror array 34 closer to the viewer is referred to as the higher micromirror array. The carrier 18 can remain in the security element after the security element 12 has been applied to a target substrate (as in 2 ), but it can also be deducted. In the latter case, of course, the support does not have to be transparent.

In the exemplary embodiment, the two micromirror arrangements 24, 34 are arranged one above the other, with the higher-lying micromirror arrangement 34 having at least one large-area recess 42, for example in the form of a 5 mm wide and 2 cm long curved strip ( 1 ). In the area of the recess 42, the viewer looks at the lower-lying micro-mirror arrangement 24 with the reflection-enhancing layer 26, while the visual impression of the surface area 20 in the area 44 outside of the recess 42 is determined by the higher-lying micro-mirror arrangement 34 with the reflection-enhancing layer 36.

In the exemplary embodiment shown, the reflection-increasing layer 26 is formed by a full-area vapor-deposited layer that was vapor-deposited onto the embossing lacquer layer 22 after it had been applied and embossed.

In contrast, the reflection-increasing layer 36 is not a layer that is applied later, but represents a surface layer of the embossing lacquer layer 32 with a large number of aligned, reflective, platelet-shaped pigments 38 that follows the relief process. This surface layer is created by the special properties of the pigments used and the work steps in production that are tailored to them , as linked below 3 described in more detail.

When viewing the security element 12 in reflection, the viewer perceives the motif 14 generated by the micromirror arrangement 34 with a first color in the areas 44 outside of the recess 42, which is determined by the color of the aligned pigments 38 of the surface layer 36 and the color of the embossing lacquer layer 32 is determined.

A movement effect occurs within the recess 42, in which, for example, when the bank note 10 is tilted, a light bar of a second color appears within the curved partial area 16 ( 1 ) seems to run back and forth. The second color is determined by the color of the vapor deposition layer 26 and the color of the embossing lacquer layer 22 . The height difference between the two micromirror arrays 24, 34 is in the range of a few micrometers or a few tens of micrometers and is therefore imperceptible to the viewer. The two differently colored motifs and the different effects 14, 16 therefore appear to the viewer to be arranged in exact register with one another.

The inventive production of such security elements is now with reference to 3 described in more detail in Fig. 3(a)-(d) shows each intermediate step of the production.

First, with reference to 3(a) a carrier 18, for example provided in the form of a transparent PET film. The surface extent of the carrier 18 defines an xy plane and a z-axis perpendicular thereto. In a surface area 20 of the carrier 18, a first embossing lacquer layer 32 made of a pigment embossing lacquer 30 is applied to the surface in desired partial areas, which represents a dispersion of platelet-shaped floating metal pigments 38 in a base embossing lacquer 31. In the exemplary embodiment, the floating pigments 38 are aluminum pigments that reflect in the entire spectral range, and the base embossing lacquer 31 is glazed with a desired first color. In other configurations, the floating pigments 38 themselves can have a desired coloring and can be formed, for example, by copper or gold pigments, while the base embossing lacquer is transparent and colorless.

Because of their wetting properties, the leafing pigments 38 in the base embossing lacquer 31 float to the surface of the applied embossing lacquer layer 32, as in FIG 3(a) shown. The embossing lacquer layer 32 is then provided with a first embossing in the form of the desired micromirror embossing 34 . As explained in more detail above, the pigments 38 are aligned along the course of the embossed structure by the embossing due to their floating properties, as in FIG 3(b) shown. A reflection-increasing surface layer 36 with aligned pigments 38 thus arises on the surface of the embossing lacquer layer 32, which largely follows the relief profile of the micromirror embossing 34.

After the application and embossing of the pigment embossing lacquer 30 there are, on the one hand, lacquer areas 52 with an embossed, reflective embossing lacquer layer 32, 34, 36 and, on the other hand, free areas 54 without an embossing lacquer layer in the surface area 20 . The free areas 54 correspond to the desired recesses 42 in the finished security element ( 2 ), the lacquer areas 52 the desired areas 44 outside of the recesses 42. In order to ensure that the desired free areas 54 also arise on the surface of the carrier 18 in addition to the lacquer areas 52, the wetting properties of the pigment embossing lacquer 30 both on the carrier 18 and also selected or set according to the embossing tool itself, which is not shown.

A full-surface second embossing lacquer layer 22 is then applied to the structure formed in this way and this second embossing lacquer layer 22 is provided with a second embossing in the form of the desired micromirror embossing 24, as shown in FIG 3(c) shown.

Both the first and the second embossing lacquer layer are preferably applied by means of screen printing, offset printing, flexographic printing or gravure printing. UV varnish, a thermoplastic varnish or a dual cure system, i.e. a combination of UV embossing varnish and thermoplastic varnish, can be used as the base embossing varnish 31 of the pigment embossing varnish 30 and as the embossing varnish for the second embossing varnish layer 22 .

The surface area 20 is then metallized over the entire surface using a PVD method, for example, and is thereby provided with a vapor-deposited layer 26 that follows the relief profile of the second micromirror embossing 24, as shown in FIG 3(d) shown. The double embossing structure produced in this way is applied to the target substrate, for example the banknote paper of the banknote 10, via an adhesive layer 28, as shown in FIG 2 shown.

It goes without saying that, depending on the intended use of the security element, other production steps known per se can also be carried out to finish the product. For example, primer layers, protective layers and/or a machine-readable magnetic layer can be located between the full-surface vapor deposition layer 26 and the adhesive layer 28 .

In this way, the surface area 20 of the security element according to the invention can be produced with two colors which can be selected completely independently of one another. At the same time, the number of operations required is low and the overall thickness of the security element can be kept small. For example, the layer thickness of the security element is 2 below 45 µm.

Of course, all figures only show the basic structure, but not the possible number of areas 44 and/or the possible number of recesses 42 in conceivable sizes and relative arrangements. Also on the variants in WO 2020/011390 A1 , WO 2020/011391 A1 and WO 2020/011391 A2 can be referred to in this regard.

In a further development, the security elements described can be provided with negative markings, for example in the form of text, symbols or numerical values, for additional security.

Regarding 4 this is a security element 60 first as in connection with the 3 described manufactured. After the embossing of the second embossing lacquer layer 22 but before the metallization, a wash color 64 is printed onto the second embossing lacquer layer 22 in the areas 62 that are to remain metal-free, as in FIG Fig.4(a) shown. The areas 62 lie completely within the free areas 54, i.e. do not overlap with the lacquer areas 52 with the first embossing lacquer layer 32.

Then the surface area 20 is metallized over the entire surface together with the washing paint 64 and is thereby provided with the metal layer 26, as in Fig.4(b) shown. Subsequently, the washing ink 64 is washed out together with the part of the metallization 26 lying on the washing ink and the in Fig.4(c) shown, partially demetallized metal layer 26 obtained. Depending on its purpose, the security element is then completed by providing further layers 28 .

The security element 60 is oriented when viewed from the side of the carrier 18, whether the carrier remains permanently in the security element or is peeled off after application to a target substrate. The areas 62 form negative indicia in the finished security element 60, which allow the security element to be looked through. If the second embossing lacquer layer 22 is colorless and transparent, the negative markings 62 also appear colorless and transparent. In the case of a colored second embossing lacquer layer 22, the negative indicia 62 appear with the transparent color of the embossing lacquer layer 22.

The demetallization can also be carried out, for example, by an etching process, with an etching resist being applied before the etching step in the areas in which the metal is not to be removed, which is removed again after the etching process. Area-by-area removal of a metal layer that was initially applied over the entire area by laser impingement can also be considered for demetallization.

Regarding figure 5 , with its illustrations a to c, an alternative method for producing a security element 70 is described.

A continuous embossed layer 72 is arranged on a carrier 18 and can be designed, for example, as a thermoplastic layer or as an embossed lacquer layer. A reflective color layer 75 is applied, in particular printed, only in partial areas 44, as can be seen in representation a. The reflective color layer 75 comprises a binder 77, sinking pigments 78 and colorants 73, as a dissolved dye or as color pigments. The sinking pigments 78 sink to the underside of the (still unembossed) color layer 75 and form a reflective (or reflection-increasing) layer 76 there.

In the second representation b of figure 5 it can be seen that both layers 72, 75 are embossed together. The surface of the relief structure 34 is formed in the partial areas 44 by the surface 34a of the embossed reflective color layer 75 and in the free areas 42 by the surface 34b of the embossed embossed layer 72.

The further (first) relief structure 24 is shown in the third illustration c. An embossing lacquer layer 71 is applied to the existing (second) relief structure 34, embossed differently and metallized with a reflection-increasing layer 26. See-through areas 62 can of course also be produced here or afterwards.

This in figure 6 The method presented here differs primarily from the method shown in FIG figure 5 that an embossing layer 82 is first embossed on the carrier 18 and then the colored layer 75 is applied.
The surface of the relief structure 34 is formed in the free areas 42 by the embossed surface 34b of the embossed embossed layer 82 . In the partial areas 44, the color layer 75 with its sunken pigments 78 lies on the embossed surface of the embossed embossing layer 82. Since both surfaces of the color layer 75 follow the embossed structure, the sunken pigments 78 in turn form the reflection-enhancing layer 76 of the second relief structure 34.

A multicolored paint layer 83 is applied to an optional intermediate layer 84, which is shown in the figure with two differently colored sections. The embossing lacquer layer 81 of the first relief structure is applied thereto, onto which (before or) after the embossing a metal layer or HRI layer is vapour-deposited as a reflection-increasing layer 89 . With the help of an optional adhesive layer 88, the security element 80, which is designed as a strip or patch, could be transferred, for example to a banknote substrate. The carrier 18 can optionally remain in turn or be removed from the embossed layer 82 after the transfer. A see-through area 62 can again be seen as a sub-area of the free area 42 .

The security element 90 in 7 comprises a second relief structure 34 in addition to a first relief structure with an embossed embossing layer 22 and a vapor-deposited reflection-increasing layer 99.

The following further aspects can be individually, as in figure 7 or combined in other ways.

The relief structure 34 comprises at least two sub-areas 44 of different construction. In a first of the sub-areas 44, sinking pigments 38, for example in an embossing lacquer layer 32 (or in an ink layer), are used, and in a second of the sub-areas floating pigments 98 are used.

The floating pigments 98 which form the reflection-enhancing layer 96 are contained in a reflection-enhancing color layer 95 which has been applied to an embossed embossing layer 92 . The reflection-enhancing layer follows the surface relief of the embossed embossing layer 92, which is in particular an embossing lacquer layer. The reflection-enhancing color layer 95 also includes a colorant 93 in a binder 97.

In the configuration shown, the reflection-increasing color layer 95 follows the relief with only one of its two surfaces. The second surface of the color layer 95 does not have the relief or has no relief.

An embossing lacquer layer is used in the first of the sub-areas 44 and a reflection-increasing color layer is used in the second of the sub-areas.

The relief structure 34 has different embossed layers 32, 92 in the partial areas 44 with the sections 34d and 34e, which are embossed together (with and/or without colorants or with and/or without floating or sinking pigments).

Also shown in the figure 7 (b) that the security element 90 could also (alternatively) be attached to the carrier 18 by means of an overlying adhesive layer 88 instead of an underlying adhesive layer.

Reference List

10

bank note

12

security element

14

motive

16

subarea

20

reflective surface area

22, 71, 81

first embossing layer

24

first embossing structure

26, 79, 99

reflection enhancing layer

28, 84, 88

adhesive layer

30

pigment embossing varnish

31

base embossing varnish

32

second embossing layer

34

second embossing structure

36, 76, 96

reflection enhancing layer

38, 78, 98

floating/sinking pigments

42

recess

44

Sections outside the recess

52

sub-areas

54

free areas

60,70,80,90

security element

62

see-through areas

64

wash color

72, 82, 92

embossing layer

73, 93

colorant

75, 95

reflective paint layer

77.97

binder

83

paint layer

Claims (20)

1. Optically variable security element for securing objects of value whose surface area defines a z-axis that is perpendicular thereto, having a reflective surface region which shows at least two appearances that are recognizable from different viewing directions, wherein

   - the reflective surface region contains a first relief structure (24) and a second relief structure (34), which are arranged at different height levels in the z-direction such that they at least partially overlap each other,

   - the first relief structure (24) is provided with a reflection-enhancing layer (26),

   - the second relief structure (34) has a reflection-enhancing layer (36),

   - the second relief structure (34) comprises an embossing layer (32; 72), and

   - the reflective surface region has subregions (44) with a reflective second relief structure (34, 36) and free regions (42) without a reflective second relief structure (34, 36),

   characterized in that

   the embossing layer (32) is provided only in the subregions (44) of the reflective surface region, but not in the free regions (42),

   the second relief structure (34) is provided only in the subregions (44) of the reflective surface region, and the reflection-enhancing layer (36) of the second relief structure (34) is formed by leafing or sunken pigments.
2. Security element according to Claim 1, characterized in that the second relief structure (34) comprises an ink layer (75) .
3. Security element according to either of Claims 1 and 2, characterized in that pigments leafing or sunk in the embossing layer (32) form the reflection-enhancing layer (36) of the second relief structure (34).
4. Security element according to any of Claims 1 to 3, characterized in that the second relief structure (34) is formed by an embossing varnish layer (32) on whose relief-structure side a surface layer, made of the leafing or sunken pigments, forms the reflection-enhancing layer (36) of the second relief structure.
5. Security element according to either of Claims 1 and 2, characterized in that pigments (78) leafing or sunk in a reflection-enhancing, preferably reflective, ink layer (75) form the reflection-enhancing layer (76) of the second relief structure (34).
6. Security element according to any of Claims 1, 2 or 5, characterized in that the second relief structure (34) is formed by an embossing layer (72) and a reflection-enhancing ink layer (75), wherein on the relief-structured side of the reflective ink layer a surface layer made of pigments (78) leafing or sunk in the reflection-enhancing ink layer (75) forms the reflection-enhancing layer (36) of the second relief structure.
7. Security element according to Claim 6, characterized in that both sides of the reflection-enhancing ink layer (75) follow a relief profile of the second relief structure, wherein in particular the reflection-enhancing layer (76) is arranged on the side that faces the embossing layer (72; 82) or faces away therefrom.
8. Security element according to Claim 6 or 7, characterized in that the embossing layer (72; 82) and the reflection-enhancing ink layer (75) have been embossed together.
9. Security element according to Claim 6, characterized in that only the side of the reflection-enhancing ink layer (75) that faces the embossing layer (82) follows a relief profile of the second relief structure.
10. Security element according to Claim 6 or 9, characterized in that only the embossing layer (82) has been embossed and the reflection-enhancing ink layer (75) has been applied on the embossed embossing layer (82) in the subregions (44).
11. Security element according to at least one of Claims 1 to 10, characterized in that the leafing or sinking pigments are

    optically variable pigments; and/or

    anisotropic pigments, which are oriented so as to follow the relief profile of the second relief structure and/or have a maximum dimension below the lateral structure dimensions of the second relief structure.
12. Security element according to at least one of Claims 1 to 11, characterized in that the second relief structure and/or the first relief structure are formed by micro-mirror arrangements with directionally reflective micro-mirrors, in particular with non-diffractively acting mirrors, and preferably with plane mirrors, concave mirrors and/or Fresnel-type mirrors.
13. Security element according to at least one of Claims 1 to 12, characterized in that the second relief structure exhibits a first optically variable effect, in particular in a first colour, and the first relief structure exhibits in the free regions of the surface region a second optically variable effect, in particular in a second, different colour, viewed preferably from the same side of the security element.
14. Security element according to at least one of Claims 1 to 13, characterized in that the reflection-enhancing layer (26) of the first relief structure (24) is formed by a reflection-enhancing colour coating, in particular by a metallization, by a thin-film structure, by a translucent ink backed by a metallization, by a luminescent ink that is metallically reflective and/or by a nano-particle ink.
15. Security element according to at least one of Claims 1 to 14, characterized in that the reflection-enhancing layer (26) of the first relief structure (24) is formed by an evaporation layer.
16. Security element according to at least one of Claims 1 to 15, characterized in that the subregions (44) and free regions (42) are designed at least as a regular or irregular grid with grid elements, wherein the dimensions of the grid elements in one or both lateral directions lie below 140 µm, preferably between 20 µm and 100 µm, in particular between 20 µm and 60 µm; wherein in particular the grid formed by the subregions and free regions is designed with a constant area coverage by the grid elements of, expediently, between 30% and 70%, preferably between 40% and 60%, with further preference of approximately 50%.
17. Security element according to at least one of Claims 1 to 15, characterized in that the subregions (44) and free regions (42) are designed, at least in part of the surface region, as an effective region in which the subregions and/or the free regions have lateral dimensions of more than 140 um; wherein in particular at least one subregion and/or at least one free region is designed with lateral dimensions of more than 250 µm, preferably of more than 500 µm and in particular of more than 1 mm.
18. Security element according to at least one of Claims 1 to 17, characterized in that

    negative features are formed as a security feature in the security element by way of cutouts (62) in the reflection-enhancing layer of the first relief structure, wherein cutouts are present, in particular congruently, in the reflection-enhancing layer of the second relief structure or free regions; and/or

    a further security feature which is visible to the viewer or is machine-readable is contained in the security element, which further security feature is arranged in particular in the reflective surface region or outside thereof.
19. Data carrier having an optically variable security element according to any of Claims 1 to 18, which is preferably applied as transfer element on the substrate of the data carrier, created on the substrate of the data carrier or introduced into the substrate of the data carrier, and optionally comprises further security features or security elements which are visible to the viewer or are machine-readable.
20. Method for producing an optically variable security element having a reflective surface region which shows at least two appearances that are recognizable from different viewing directions, in particular according to any of Claims 1 to 18, in which

    - a carrier (18) whose surface area defines a plane and, perpendicular thereto, a z-axis is provided,

    - the carrier (18) is provided with a reflective surface region containing two relief structures (24, 34), which are arranged at different height levels in the z-direction such that they at least partially overlap each other and form a first and a second relief structure, wherein the second relief structure (34) comprises an embossing layer (32; 72), wherein

    - the first relief structure (24) is provided with a reflection-enhancing layer (26) which follows the relief profile of the former, and

    - the second relief structure (34) is provided with a reflection-enhancing layer (36) which follows the relief profile of the former,

    - wherein the reflective surface region has subregions (44) with a reflective second relief structure (34, 36) and free regions (42) without a reflective second relief structure (34, 36),

    characterized in that

    the embossing layer (32; 72) is provided only in the subregions (44) of the reflective surface region, but not in the free regions (42),

    the second relief structure (34) is provided only in the subregions (44) of the reflective surface region, and leafing or sinking pigments form the reflection-enhancing layer (36) of the second relief structure (34).

Images