EP2200840B1 - Visually variable security element - Google Patents

Description

The invention relates to an optically variable security element for securing valuables. The invention further relates to a method and an apparatus for producing such a security element as well as a security paper and a data carrier with such a security element.

Data carriers, such as valuables or identity documents, but also other valuables, such as branded goods, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carrier and at the same time serve as protection against unauthorized reproduction. The security elements can be embodied, for example, in the form of a security thread embedded in a banknote, a covering film for a banknote with a hole, an applied security strip, a self-supporting transfer element or else in the form of a feature area printed directly on a value document.

A special role in the authenticity assurance play security elements, the viewing angle-dependent visual effects show, as they can not be reproduced even with the latest copiers. The security elements are equipped with optically variable elements that give the viewer a different image impression under different viewing angles and, for example, show a different color or brightness impression and / or another graphic motif depending on the viewing angle.

In this context, it is known to use security elements with multi-layered thin-film elements whose color impression changes for the viewer with the viewing angle, and when tilting the security feature for example, from green to blue, from blue to magenta, or from magenta to green. The occurrence of such color changes when tilting a security element is referred to below as a color shift effect.

From the publication WO 02/073250 A2 Optically variable thin-film elements are known in whose layer structure at least one magnetic layer is integrated. The magnetic properties of these optically variable thin-film elements can then be used as an additional authenticity mark.

In the publication EP 1780 040 A2 describes a security element in which in a partial area magnetically oriented pigment particles are present, which produce a kinematic visual effect. The magnetically oriented pigment particles may in particular also have optically variable properties.

The publication EP 1 669 213 A1 discloses a security element having a coating that appears transparent from certain viewing directions and provides visual access to the underlying information while remaining opaque from other viewing angles.

The publication WO 2004/024836 A2 refers to diffractive pigment flakes that are selectively aligned to form an image. In one embodiment, the flakes have a magnetic layer and are shaped to allow alignment in a magnetic field. In another embodiment, the flakes contain a magnetically discontinuous layer.

The publication EP 1 806 238 A2 relates to an optically variable article in which on a surface two spaced optical devices are provided. One optical device contains diffractive flakes, the second optical device contains non-diffractive flakes that may have other special effects such as a color shift effect. At an angle of incidence or a viewing angle close to the vertical, the colors of the optical devices are the same, but at other angles they do not match. The diffractive flakes are preferably magnetically aligned so that the grating structures are parallel.

The publication WO 2007/120683 A2 is a document under Article 54 (3) EPC. It relates to a security image formed from flakes of a first color evenly mixed within a carrier with flakes of a second color. The second color flakes are magnetically alignable and the first color flakes are non-magnetic and do not align in a magnetic field.

The publication EP 1 970 753 A1 is a document under Article 54 (3) EPC. It provides an identification medium having a layered structure comprising laminated layers of a magneto-controllable layer in which magnetic microcapsules are dispersed and a color-shifting layer.

Proceeding from this, the object of the invention is to further improve a security element of the aforementioned type and, in particular, to provide a security element with an attractive visual appearance and high security against counterfeiting, which moreover allows an intelligent combination with further, in particular underlying, security features.

This object is achieved by the security element having the features of the main claim. A method and an apparatus for producing such a security element, a security paper and a data carrier with such a security element are in the sibling Claims specified. Further developments of the invention are the subject of the dependent claims.

According to the invention, a generic security element has an at least partially translucent, optically variable color layer which shows a motif in the form of patterns, characters or a coding, and in which the color layer of the security element contains first, optically variable effect pigments and second, magnetically alignable effect pigments , which are magnetically aligned in the shape of the motif to be displayed.

Such a security element offers a combination of attractive visual effects, namely, on the one hand, the optically variable effect of the first effect pigments and, on the other hand, the motif produced by the magnetic alignment of the second effect pigments, which has a pronounced three-dimensional appearing appearance. Due to their at least partially present translucency, the optically variable ink layer can also be combined with other underlying security features, such as an information-carrying print layer or a see-through area.

In the context of the present description, "translucent" means translucent in the sense of a certain or complete translucency and thus also includes transparency. A translucent layer makes it possible to perceive the objects behind or below it, even if the brightness of the objects can be reduced by the translucent layer and / or the color of the objects can be changed. On the other hand, if the light transmission of a layer is so low that the objects behind or underneath are no longer recognizable, it is no longer translucent but is called opaque or opaque.

The invention is based on the idea to use a color layer with two different effect pigments with different specific properties. The first effect pigments are optically variable, while the second effect pigments are magnetically alignable. Essentially only the latter, but not the first effect pigments are magnetically oriented in the orientation by an external magnetic field in the form of the motif to be displayed.

This decoupling of the optically variable and the magnetic properties allows cost-effective production, since effect pigments, which combine optically variable and magnetic properties, require a higher manufacturing outlay and thus also a higher cost. In addition, such effect pigments are typically opaque, so that an intelligent combination with other printing processes or printing inks is possible only to a very limited extent. In addition, the required layer structure of the pigments and the associated selective reflection makes stringent demands on the possible layer thicknesses of the magnetic material. This leads to limitations in the magnetic properties, in particular the remanence and the coercive field strength, which make it difficult to produce machine-readable security elements.

In the invention, the optically variable ink layer contains a pigment mixture with the first and second effect pigments.

The first effect pigments are pigments prepared on the basis of cholesterol liquid crystalline polymers

The second effect pigments are preferably formed on the basis of high-purity iron powder and can be prepared, for example, from reducing-treated carbonyl iron powder. Advantageous platelet-shaped iron pigments can in particular the document EP 1 251 152 B1 are taken from the disclosure of the preparation and properties of such pigments in the present description.

In an advantageous embodiment of the invention, the second effect pigments are hard magnetic and thus allow in a particularly reliable manner a machine magnetic readout of the motif shown. Preferably, the second effect pigments are in the form of a machine-readable magnetic coding, such as a bar code, aligned. Of course, the second effect pigments may in principle also be soft magnetic, although soft magnetic effect pigments for the mechanical magnetic readings are not as well suited as hard magnetic pigments.

Preferably, the second effect pigments are non-spherical, for example acicular. Particular preference is given to effect pigments which have a platelet form. Hereinafter, the largest diameter of a non-spherical pigment is referred to as the length or size of the pigment, while the thickness of the pigment is referred to as the pigment thickness. In general, the thickness of the pigments with the smallest diameter of the pigment will be identical. Furthermore, the terms length, size and largest diameter of the pigment as well as thickness and smallest diameter of the pigment are used synonymously. The ratio of the largest to the smallest diameter, ie the diameter-to-thickness ratio of the non-spherical second effect pigments is preferably more than 5: 1, preferably more than 10: 1. This ratio is particularly preferably between 40: 1 and 400: 1. The largest diameter, ie the length of the non-spherical second effect pigments is advantageously more than 2 μm, preferably more than 5 μm, more preferably more than 10 μm and very particularly preferably about 13 μm to about 15 μm.

The use of magnetically alignable effect pigments in the micrometer range and in particular in the stated size range on the one hand has the advantage that the particle concentration can be kept lower compared to nanoparticles. In addition, due to the more favorable diameter-to-thickness ratio without external forces, these pigments align better parallel to the layer surface.

Platelet-shaped effect pigments, in particular in the preferred size range and in the preferred diameter-to-thickness range, can be obtained by an external magnetic field relative to the layer plane can be oriented as desired. They then, like the slats of a blind, depending on the orientation of the underlying layers either largely free (approximately vertical orientation relative to the layer plane) or block it partially (oblique orientation relative to the layer plane) or completely (substantially horizontal orientation relative to the layer plane ). With high diameter-to-thickness ratios, high contrasts between translucent and opaque layer areas can be set.

According to a preferred embodiment of the invention, the second effect pigments are platelet-shaped and are aligned in first partial areas substantially perpendicular to the plane of the color layer to form translucent portions of the color layer. Alternatively or additionally, platelet-shaped second effect pigments may be aligned in second partial areas substantially parallel to the plane of the color layer in order to form opaque partial areas of the color layer.

The optically variable ink layer is preferably formed by a screen printing layer, in some embodiments also by a gravure printing layer. It may additionally be blind-embossed in all the aforementioned embodiments, in particular for enhancing the 3D effect of the magnetically oriented effect pigments.

To fix the magnetically oriented motif, the ink layer with the pigment mixture is preferably formed on the basis of a UV-curing ink system, pure UV systems, UV / water-based systems or even UV / solvent-based systems being considered. In addition to the first and second effect pigments, the color layer may also contain other pigments, in particular isotropic pigments and / or soft magnetic pigments. Of course, the further pigments or, more generally, further additives may have all visually and / or machine-detectable properties which do not or only slightly impair the visual impression of the security element according to the invention.

In an advantageous embodiment, the optically variable ink layer is applied to a banknote paper or on a colored background layer. The substrate material for the banknote paper is any kind of paper, in particular cotton vellum paper. Of course, it is also possible to use paper which contains a proportion of polymeric material in the range of 0 <x <100% by weight.

Furthermore, it is basically conceivable, although not currently preferred, for the substrate material of the banknote or, more generally, of a data carrier to be a plastic film, e.g. B. a polyester film is. The film may also be monoaxially or biaxially stretched. The stretching of the film, inter alia, leads to it receiving polarizing properties that can be used as another security feature.

It may also be expedient if the substrate material of the banknote paper is a multilayer composite which has at least one layer of paper or a paper-like material. Such a composite is characterized by an extremely high stability, which is for the durability of the paper or disk of great advantage.

It is also conceivable, however, to use a multilayer, paper-free composite material as the substrate material. These materials are also not preferred at present, but can be used with advantage in certain climatic regions of the earth.

All materials used as substrate material may have additives that serve as a mark of authenticity. It is primarily to think of luminescent, which are preferably transparent in the visible wavelength range and in the non-visible wavelength range by a suitable tool, for. B. a UV or IR radiation emitting radiation source can be excited to produce a visible or at least detectable with auxiliary luminescence. Other security features can be used with advantage, as long as they do not affect the viewing of the security element according to the invention or at least not significantly.

Background layers with dark colors usually lead to a particularly high brilliance of the optically variable effects. However, a transparent or translucent film is also suitable as a substrate. In this case, the security element can advantageously be used in or above a window area or a through opening of a value document as a see-through security element. The film may be formed as a patch covering a partial surface of the substrate or as a strip extending substantially the entire length or width of the security paper or document of value. The materials used for the film are primarily the plastics PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate), PP (polypropylene), PA (polyamide), PE (polyethylene) into consideration. The film may also be monoaxially or biaxially stretched.

In some embodiments, the opening is already created in the manufacture of the security paper used for the bill and has a fibrous, irregular edge. Such an edge is characteristic of apertures already made during sheet formation and can not be generated later. Details of the production of the fibrous, irregular edge can the WO 03/054297 A2 be removed. In that regard, the disclosure of the WO 03/054297 A2 included in the present application. In other embodiments, the opening is produced only after papermaking by punching or cutting, for example by laser beam cutting.

In one development of the invention, the optically variable ink layer can be applied to an information-carrying background layer, in particular a screen-printing layer or a gravure printing layer. Since the information is recognizable in the translucent areas of the color layer, but hidden in the opaque areas, the color layer and background layer can cooperate to produce a further authenticity feature, as explained in more detail below.

The background layer can advantageously also have thermochromic properties in order to create an interactively influenceable security element. Such a thermochromic background layer can in particular be designed so that when it is activated by increasing the temperature, the optically variable effect of the first effect pigments for the viewer disappears.

The invention also encompasses a method for producing an optically variable security element for securing valuables, claim 11.

In this case, the first and second effect pigments are preferably mixed to form a pigment mixture and co-printed, preferably by screen-printing or intaglio printing.

The motive generated by the magnetic alignment is permanently fixed in an advantageous embodiment by UV curing of the ink layer or the pure magnetic layer.

The invention further comprises a security paper for the production of value documents or the like and a data carrier, in particular a value document, such as a banknote, a passport, a document, an identity card, credit card or the like. The security paper or the data carrier are equipped according to the invention with a security element of the type described. The security element can, in particular if it is present on a transparent or translucent substrate, also be arranged in or above a window area or a through opening of the security paper or the data carrier.

The invention further provides an apparatus for carrying out the described manufacturing method, comprising means for applying the optically variable ink layer to a substrate and means for magnetically aligning the second effect pigments, wherein the means for magnetic alignment preferably formed by an arrangement of permanent magnets or electromagnets are.

Advantageously, while the optically variable ink layer is applied by a suitable method on the intended substrate and the second effect pigments then aligned, z. B. by a magnetic pressure cylinder. Subsequently, the optically variable ink layer is permanently fixed together with the motif formed by the orientation of the second effect pigments, which z. B. can be done by the above-mentioned UV curing.

In an expedient embodiment, the means for magnetic alignment are formed by a magnetic sieve, so that the second effect pigments are already magnetically alignable in screen printing when printing the ink layer or the pure magnetic layer.

Becomes. the ink layer applied by intaglio printing, the means for magnetic alignment may also be formed by a magnetic throat plate, so that the second effect pigments are already magnetically alignable during the printing of the ink layer or the pure magnetic layer in intaglio printing.

Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.

Fig. 1

eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Sicherheitselement,

Fig. 2

die Banknote der Fig. 1 im Bereich des Sicherheitselements im Querschnitt,

Fig. 3

ein interaktiv beeinflussbares Sicherheitselement nach einem anderen Ausführungsbeispiel der Erfindung im Querschnitt,

Fig. 4

ein Sicherheitselement nach einem weiteren Ausführungsbeispiel der Erfindung im Querschnitt,

Fig. 5

eine Banknote mit einem erfindungsgemäßen Durchsichtssicherheitselement, das über einer durchgehenden Öffnung angeordnet ist, und

Show it:

Fig. 1

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

Fig. 2

the banknote of Fig. 1 in the area of the security element in cross section,

Fig. 3

an interactively influenceable security element according to another embodiment of the invention in cross-section,

Fig. 4

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

Fig. 5

a banknote having a see-through security element according to the invention, which is arranged over a continuous opening, and

The invention will now be explained using the example of a banknote. Fig. 1 shows a schematic representation of a banknote 10, with an in Fig. 2 provided in cross-section security element 12 according to the invention.

With reference to the representation of Fig. 2 is applied to the banknote paper 20 in the region of the security element 12, a printing layer 22, the any information, such as a line pattern 24, an alphanumeric string, a logo or the like may represent. The printing layer 22 can be applied to the banknote paper 20 by screen printing or intaglio printing, for example, with the application of the printing layer 22 particularly preferably taking place together with further printed layers not illustrated in detail in the figures, which form the so-called background printing of the data carrier. The further printing layers can be formed, for example, as guilloches or similar patterns and, like the printing layer 22, can be applied to the data carrier in flexographic printing.

About the information-carrying print layer 22 is an optically variable ink layer 26 is printed with a color shift effect in the screen printing process, in which the color impression of the layer 26 for the viewer when tilting the security element 12 z. B. changes from green when viewed perpendicularly to blue when viewed obliquely. It is also conceivable a color change of z. B. coppery green or from gold to green.

Next, the color layer 26 includes a motif, which in the embodiment of the Fig. 2 for illustration in the form of a simple stripe pattern 28, 30 is executed. As explained in more detail below, this motif 28, 30 has a pronounced 3D effect for the viewer due to its formation due to the different orientation of platelet-shaped pigments 34, 36.

In the region of the strips 30, the ink layer 26 is translucent, so that in the partial regions 30 the information 24 can be seen through the ink layer 26. On the other hand, in the area of the strips 28, the ink layer 26 is opaque, where the information 24 of the printing layer 22 is hidden.

In order to produce this combination of a motif with 3D effect, color shift effect and partial visibility of the background printing layer 22, the color layer 26 is printed using a pigment mixture of first effect pigments 32 and second effect pigments 34, 36.

The first effect pigments 32 are optically variable pigments, namely pigments produced on the basis of liquid-crystalline polymers

In addition to these optically variable first effect pigments 32, the pigment mixture contains, as second effect pigments, magnetically alignable, platelet-shaped iron pigments 34, 36 which are produced in the exemplary embodiment from reducing-treated carbonyl iron powder. Such platelet-shaped iron pigments can be produced with a high ratio of platelet diameter to platelet thickness, wherein the (largest) platelet diameter is preferably between 6 .mu.m and 60 .mu.m and the platelet thickness in particular between 40 nm and 250 nm. Details of the preparation and properties of such platelet-shaped iron pigments can be found in the document EP 1 251152 B1 are removed, the disclosure of which is included in the present description.

For the production of the color layer 26, the first and second effect pigments 32, 34, 36 were mixed and jointly printed by screen printing. Then, the magnetically alignable second effect pigments were partially aligned by an external magnetic field. The iron pigments 34, 36 are oriented with the platelet expansion along the magnetic field lines, so that the iron pigments 36 are aligned substantially perpendicular to the plane of the ink layer in those regions 30 in which the magnetic field lines are substantially perpendicular to the substrate plane during the alignment step, as in FIG Fig. 2 shown. In those regions 28 in which the magnetic field lines run essentially parallel to the substrate plane, a corresponding orientation of the iron pigments 34 results essentially in the plane of the ink layer.

The platelet-shaped iron pigments 34, 36 are aligned according to the invention in the form of a desired motif, in the embodiment in the form of the stripe motif 28, 30. For the human eye, the motifs created in this way appear with an effective, three-dimensional appearance, which in the context of this description is also referred to as a 3D effect or 3D impression of the motif.

In the embodiment of Fig. 2 For the sake of simplicity, only two orientations, namely perpendicular (90 °, pigments 36) and parallel (0 °, pigments 34) to the substrate plane are shown. It is understood, however, that any angle α between the iron pigment platelets and the layer plane can be adjusted by appropriate orientation of the magnetic field lines. In particular, it is also possible to generate continuous, spatially slowly varying transitions in the orientation of the iron pigments.

The non-magnetic first effect pigments 32 are not or hardly influenced by the external magnetic field during the alignment step, their orientation is therefore the same in the subregions 28 and 30.

After the magnetic alignment of the second effect pigments 34, 36, the color layer 26 is dried. In order to be able to fix the magnetically generated motif permanently, in particular UV-curing color systems are used, pure UV systems, UV / water-based systems or even UV / solvent-based systems being considered.

Like also in Fig. 2 As a result of their platelike shape, the aligned effect pigments 34, 36 act like the slats of a venetian blind, which can clear the view of the underlying layers or completely or partially block them. In regions 28 in which the iron pigments 34 are aligned substantially parallel to the substrate plane, they limit the view of the underlying print layer 22 so much that the color layer 26 appears opaque in this region. It should be remembered that in practice, the opacifying effect of the pigments 34 is naturally brought about by a variety of pigments, which are the few pigments 34 of the schematic representation of Fig. 2 exceeds many times. In contrast, the iron pigments 36 release the view of the print layer 22 in the regions 30 in which they are aligned essentially perpendicular to the substrate plane.

Due to the relatively high ratio of platelet diameter to platelet thickness, a high contrast can be generated between covering partial regions 28 and translucent partial regions 30. It is understood that by a continuous transition of platelet orientation also a soft, continuous transition between translucent and opaque areas of the ink layer 26 can be generated.

The color shift effect of the first effect pigments 32, which are not substantially influenced by the external magnetic field, remains visible in both partial areas 28, 30. Due to the superimposition of the metallic luster of the second effect pigments 34 oriented parallel to the substrate surface, however, it is generally markedly weaker in the partial region 28 than in the partial region 30. The brilliance of the color shift effect in the partial region 30 also depends on the design of the background layer the use of dark colors a particularly high brilliance is achieved.

The embodiment of Fig. 3 shows a security element 40, which allows an interactive influence on the visual appearance. For this purpose, a substrate 42 is provided with an imprint 43, in particular an offset imprint, in the form of patterns and / or characters 45. On the imprint 43, a thermochromic background layer 44 is applied, for example by screen printing or intaglio printing. On this thermochromic layer 44 is then an optically variable ink layer 26 with motif, as in connection with Fig. 2 described, printed and magnetically aligned.

The thermochromic layer 44 is designed such that the color shift effect of the color layer 26 disappears upon activation of the thermochromic layer 44 for the viewer and only the coarse structure of the aligned magnetic pigments 34, 36 is visible. For example, if the thermochromic layer 44 changes color from black (or generally a dark appearance) to white (or generally a bright appearance) upon activation by temperature elevation, the brilliance of the color-shift effect is significantly reduced upon activation, to a degree . in which the optically variable effect of the first effect pigments 32 completely disappears for the viewer. At the same time, the imprint 43 can be recognized by the very light layer 44 for the viewer. Upon cooling, the color of the thermochromic layer 44 changes back to black or to the original dark appearance, and the color shift effect of the color layer 26 reappears. At the same time, the dark layer 44 then covers the imprint 43 arranged below it again.

In this way, 3D information and / or an optically variable effect can be deleted interactively by increasing the temperature or reduced to two-dimensional information. Furthermore, the thermochromic layer 44 acts as an interactive switch, with which the view of the imprint 43 or the information 45 can be released for the viewer. The described embodiment therefore has a great recognition value for the viewer and generally a very high security against counterfeiting.

The thermochromic layer 44 may further be formed over the entire surface or with information, for. B. in the form of patterns and / or characters, be provided. It can also have a mixture of different thermochromic colors with different activation temperatures, so that a cascade of changing optically variable effects arises when the temperature increases.

As a further embodiment of the invention shows Fig. 4 a security element 50, in which on a substrate 52, a background layer 54 is applied with image information. About the background layer 54, an optically variable ink layer 56 is printed by screen printing with a pigment mixture 58, 60, the first effect pigments 58 on the basis are made of cholesteric liquid crystalline polymers. These translucent optically variable effect pigments 58 appear in a vertical plan view z. Green and tilting blue. Of course, a color change from copper to green or from gold to green can be realized.

The second effect pigments 60 are formed by platelet-shaped iron pigments, which in the exemplary embodiment have a mean platelet diameter of 20 μm to 30 μm and a thickness of a few tens to a few hundred nanometers (nm). If these second effect pigments 60 are aligned by an external point-shaped magnet 66, the result is a rotationally symmetric orientation pattern, as shown in FIG Fig. 4 is shown schematically in cross section. For clarity, the second effect pigments 60 are in FIG Fig. 4 with short dashes and the first effect pigments 58 shown as circular disks, although the latter may also be formed non-spherical, for example in the form of needles or platelets. However, since the first effect pigments 58 are virtually unaffected by the external magnetic field, their orientation over the entire area of the printed ink layer 56 is substantially homogeneous.

After the magnetic alignment of the second effect pigments 60 has been fixed, an annular 3D motif combined with the color-shift effect of the first effect pigments 58 with soft continuous transitions is produced. In a central region 62 in which the second effect pigments 60 are oriented substantially perpendicular to the substrate plane, the color layer 56 is translucent when viewed perpendicularly and the image information of the background layer 54 is visible to the viewer 64. Outside the central region 62, the second effect pigments 60 are increasingly off the vertical tilted, so that the color layer 56 acts increasingly covering in the manner of a closing blind until the image information for the viewer 64 is no longer recognizable.

As in Fig. 4 can also be seen results in oblique viewing of the security element, a slightly shifted area 62 'in which the second effect pigments 60 for the viewer 64' are oriented vertically and the color layer 56 thus appears translucent. Accordingly, a slightly shifted section of the image information of the background layer 54 can be recognized by the observer 64 ', while the image information outside the area 62' is increasingly obscured.

When tilting the security element 50, therefore, a slightly different area of the image information is recognizable, so that the image information for the viewer "wegzuschwimmen" seems. Of course, this motion effect is combined with the already described 3D effect of the subject and the color shift effect of the first effect pigments 58.

Instead of the simple ring structure described by way of example, as can be generated by means of a point magnet, it is of course also possible to generate much more complex motifs by means of a suitable magnetic alignment.

The optically variable ink layer with the pigment mixture may be printed not only on an opaque or substantially opaque substrate but also on a transparent or translucent film. As in Fig. 5 As shown, such a film having the optically variable ink layer may be disposed over a window portion or through opening 72 of a bill 70 and form a see-through security element 74.

In review, only the magnetic orientation of the second effect pigments can be seen, which in Fig. 5 is indicated by a ring structure 76, for example. The color-shift effect of the first effect pigments is virtually invisible on account of the light background when viewed through. If the banknote 70 is placed on a dark background, in addition to the 3D effect of the magnetically oriented motif 76, the color-shift effect of the first effect pigments also appears.

Such a dark background may also be provided on the banknote 70 itself. For example, a dark printing area may be arranged on the banknote such that the see-through security element 74 comes to rest on the dark printing area by folding the note. For further authenticity assurance, the printing area may contain additional information, from which only the portion lying in the translucent area is visible after folding the banknote.

In all described embodiments, the optically variable ink layer can also be blind embossed in intaglio, in particular for enhancing the 3D optical impression. The platelet-shaped iron pigments preferably used are hard-magnetic, so that their orientation pattern can also be used as a machine-readable authenticity mark.

Furthermore, resulting from the anisotropic geometry of the iron platelets and a partially different orientation anisotropic magnetic properties of the ink layer. In this way, by applying a motif-forming magnetic field in a homogeneously applied ink layer regions with different magnetic properties can be generated, which can also be read by machine. It is understood that the first and second effect pigments can also be combined with further pigments, in particular with isotropic pigments and / or soft magnetic pigments, which in themselves make substantially no modulation of the magnetic properties of the color layer possible. In the screen printing process, the orientation of the magnetically alignable effect pigments can also be achieved by using magnetic sieves. In intaglio printing, the use of magnetic throat plates is considered for this purpose. As already mentioned, the magnetic alignment of the effect pigments is furthermore possible in a particularly simple manner after the application of the optically variable ink layer by means of a suitable magnetic field.

Claims (13)

1. An optically variable security element for safeguarding valuable articles, having an optically variable ink layer that is translucent in at least some regions and that displays a motif in the form of patterns, characters or a code, in which the optically variable ink layer includes a pigment mixture having first and second effect pigments,

   - the first effect pigments being non-magnetic, optically variable effect pigments that are formed by pigments manufactured on the basis of cholesteric liquid crystal polymers, and

   - the second effect pigments being magnetically alignable effect pigments that are aligned magnetically in the form of the motif to be depicted.
2. The security element according to claim 1, characterized in that the second effect pigments are formed on the basis of ultra-pure iron powder and/or are hard-magnetic.
3. The security element according to claim 1 or 2, characterized in that the second effect pigments are developed to be non-spherical, especially platelet-shaped, the ratio of the largest to the smallest diameter (diameter-to-thickness ratio) of the non-spherical second effect pigments especially being more than 5:1, preferably more than 10:1, and particularly preferably being between 40:1 and 400:1.
4. The security element according to claim 3, characterized in that the largest diameter of the non-spherical second effect pigments is more than 2 µm, preferably more than 5 µm, particularly preferably more than 10 µm and very particularly preferably approx. 13 µm to approx. 15 µm.
5. The security element according to at least one of claims 1 to 4, characterized in that the second effect pigments are developed to be platelet shaped and, in first sub-regions, are aligned substantially vertical to the plane of the ink layer to form translucent sub-regions of the ink layer, and/ or in that the second effect pigments are developed to be platelet shaped and, in second sub-regions, are aligned substantially parallel to the plane of the ink layer to form opacifying sub-regions of the ink layer.
6. The security element according to at least one of claims 1 to 5, characterized in that the optically variable ink layer is formed by a screen printing layer or by an intaglio printing layer.
7. The security element according to at least one of claims 1 to 6, characterized in that the ink layer having the pigment mixture is formed on the basis of a UV-curing ink system, and/ or in that the ink layer includes, in addition to the first and second effect pigments, further pigments, especially isotropic pigments and/ or soft-magnetic pigments.
8. The security element according to at least one of claims 1 to 7, characterized in that the optically variable ink layer is applied on a banknote paper, on a colored background layer, preferably a background layer having a dark color, or on a transparent or translucent foil.
9. The security element according to at least one of claims 1 to 8, characterized in that the optically variable ink layer is applied on an information-bearing background layer, especially a screen printing layer or an intaglio printing layer.
10. The security element according to at least one of claims 1 to 9, characterized in that the optically variable ink layer is applied on a thermochromic background layer, the thermochromic background layer preferably being designed such that, upon its activation by temperature increase, the optically variable effect of the first effect pigments disappears for the viewer, and the thermochromic background layer preferably being arranged over an imprint, especially an imprint in the form of patterns and/or characters.
11. A method for manufacturing an optically variable security element for safeguarding valuable articles, in which

    - to a substrate is applied an optically variable ink layer that is translucent in at least some regions and that includes a pigment mixture having first and second effect pigments,

    -- the first effect pigments being non-magnetic, optically variable effect pigments that are formed by pigments manufactured on the basis of cholesteric liquid crystal polymers, and

    -- the second effect pigments being magnetically alignable effect pigments, and

    - the second effect pigments are aligned by an external magnetic field to form a motif in the form of patterns, characters or a code, the first effect pigments not being magnetically oriented in the form of the motif upon the alignment of the second effect pigments.
12. The method according to claim 11, characterized in that the first and second effect pigments are mixed to form a pigment mixture and are printed together.
13. A security paper or data carrier having a security element according to at least one of claims 1 to 10, the security element preferably being arranged in or over a window region or a through opening of the security paper or data carrier, and the data carrier preferably being a banknote, a value document, a passport, a certificate or an identification card.

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