Security element having fluorescent feature

Abstract

The invention relates to a security element (14) for securing security documents, valuables, and other data carriers, comprising an illumination-direction-selective luminescence feature (16) that exhibits different luminescence motifs (20, 30) when illuminated with UV excitation radiation from different illumination directions (70A, 70B). The luminescence feature (16) contains a luminescence material (40) that emits luminescence radiation upon illumination with UV excitation radiation, and in an effect layer (42) a plurality of platelet-shaped effect pigments (50) that are aligned in the form of the desired luminescence motifs (20, 30). The effect pigments are luminescent pigments (50), non-luminescent UV-absorbing pigments or combination pigments that can be excited to luminescence in a first UV wavelength range and are non-luminescent and UV-absorbing in a second UV wavelength range.

Description

[0001] The invention relates to a security element with a luminescent feature for protecting security papers, valuable documents, and other data carriers. The invention also relates to a method for producing such a security element and a data carrier equipped with such a security element.

[0002] Data storage devices such as valuables or identification documents, as well as other valuable items such as branded goods, are often provided with security elements for security purposes. These allow the authenticity of the data storage device to be verified and also serve as protection against unauthorized reproduction. In this context, it is known to print fluorescent inks onto security paper using various printing processes. For example, a fluorescent ink is printed in the form of a motif that is not visible in normal daylight but becomes visible when viewed under UV lighting. The fluorescent ink can also be mixed with a color visible in daylight, so that the printed motif is also visible in daylight, with a similar or even a different color tone.

[0003] Attempts to counterfeit banknotes and valuable documents are often made using inexpensive inkjet or laser printers today. Due to the widespread use of such printers, tracing counterfeits is often extremely difficult for law enforcement agencies. Even simple fluorescent markings no longer pose a significant hurdle for potential counterfeiters, as fluorescent printing inks for inkjet and laser printers are now readily available commercially.

[0004] US 2012 / 0068450 A1 relates to a security device comprising a luminescent material for generating luminescent radiation of a first and second wavelength, and an optically variable structure. The optically variable structure causes the relative emissivity of the security device for luminescent radiation of the first and second wavelengths to change with a change in the emission angle, so that the security device generates an angle-dependent color shift in the emitted luminescent radiation.

[0005] Document WO 2012 / 130370 A1 describes security elements with an optically variable color layer containing a plurality of microcapsules. The microcapsules each have a capsule shell, a carrier liquid enclosed in the capsule shell, and at least one optically variable pigment that can be freely rotated within the microcapsule and reversibly aligned by an external magnetic field. Document WO 2009 / 074284 A2, in turn, discloses a security element with a color layer containing first, optically variable effect pigments for generating a viewing-angle-dependent visual impression and second, reversibly aligned by an external magnetic field.The publication WO 2014 / 086495 A1 relates to a security element with a dark background layer arranged on a substrate and an optically variable color layer structure arranged above the background layer, comprising a first effect layer and a second effect layer. The first effect layer contains effect pigments that can be reversibly aligned by an external magnetic field, while the second effect layer is an optically variable layer arranged on and / or adjacent to the first effect layer.

[0006] EP 3 098 086 A1 relates to a piezochromic security element with at least one feature region comprising an elastomer and a plurality of magnetically alignable particles. The particles are magnetically arranged in the elastomer in the form of a regular lattice to form a photonic crystal. Without external force, the feature region exhibits a first visual appearance; upon application of tensile or compressive forces, a second visual appearance due to a change in the lattice spacing, which exhibits a perceptible color change compared to the first visual appearance.

[0007] Security pigments with an intrinsic hidden and / or forensic security feature are known from the publication DE 10 2007 058 601 A1.

[0008] Based on this, the object of the invention is to provide a security element of the type mentioned at the outset with a high level of protection against counterfeiting.

[0009] This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0010] The invention provides a security element as defined in claim 1 for securing security papers, valuable documents and other data carriers.

[0011] The luminescence radiation emitted by the luminescent feature is preferably in the visible spectral range, but can also, in principle, be at least partially in the infrared spectral range. The luminescence can be monochromatic, but especially multichromatic.

[0012] In one advantageous variant of the invention, the effect pigments already contain the aforementioned luminescent material, for example in the form of a luminescent layer. However, in another advantageous variant of the invention, the luminescent material can also be present in a separate layer, for example, a substrate layer.

[0013] As explained in more detail below, the illumination direction selectivity of the security element arises from the orientation of the effect pigments in the form of luminescence motifs. In particular, the different relative orientation of the illumination direction and the platelet plane of the effect pigments results in varying degrees of luminescence excitation or UV absorption, allowing different luminescence images to be generated depending on the direction of incidence of the excitation radiation.

[0014] The platelet-shaped effect pigments advantageously have an aspect ratio of more than 5:1, preferably more than 10:1, and particularly preferably between 20:1 and 400:1. The aspect ratio of the platelet-shaped effect pigments is the ratio of the edge length to the thickness of the platelets. With a high aspect ratio, particularly 5:1 or more, different orientations result in large differences in the impact area presented by the pigments to the incident radiation, and thus large differences in the excited luminescence or UV absorption.

[0015] In an advantageous variant of the invention, the effect pigments are magnetically alignable and contain a core with a magnetic material. The core comprises, in particular, a carrier substrate and a magnetic layer present on the carrier substrate. Alternatively, the carrier substrate itself can also be magnetic. The magnetic material advantageously comprises magnetite (Fe 3 O 4 ), carbonyl iron, and / or a magnetizable polymer.

[0016] Advantageously, the magnetic material is provided with an opaque coating, in particular a white or colored opaque coating, on at least one of the main surfaces of the effect pigment, preferably at least on both main surfaces. The opaque coating may, but does not have to, also coat the narrow side edges of the effect pigment.

[0017] In another, equally advantageous variant of the invention, the effect pigments are non-magnetic and contain a platelet-shaped core. Advantageously, the platelet-shaped core is provided with an opaque coating, in particular a white or colored opaque coating, on at least one of its main surfaces, preferably at least on both main surfaces. The opaque coating can, but does not have to, also coat the narrow side edges of the effect pigment.

[0018] The opaque coating can consist, in particular, of TiO2 or a porous and thus scattering or opaque polyester layer. The opaque coating can be absorbent in a sub-range of the UV spectrum. Opaque coatings, e.g., made of TiO2, can also be opaque to at least a sub-range of the visual (VIS) spectrum.

[0019] In an advantageous further development, the effect layer is arranged at least partially over a substrate layer, wherein the visually visible color of the opaque coating of the effect pigments essentially corresponds to the visually visible color of the substrate layer.

[0020] According to an alternative, equally advantageous embodiment, the platelet-shaped core of the non-magnetic effect pigments does not have an opaque coating.

[0021] It is particularly advantageous that the luminescent motifs are invisible without illumination with UV excitation radiation. This can be achieved, in particular, by matching the visually visible color of the opaque coating to the visually visible color of a background layer or substrate on which the security element is applied. Under normal daylight or artificial light, it is then not immediately apparent that a luminescent feature is present at this particular location.

[0022] In an advantageous embodiment, the effect pigments are luminescent pigments or combination pigments which themselves form the said luminescent material.

[0023] Alternatively, the effect pigments are luminescent pigments or combination pigments, but the effect layer is at least partially arranged over a substrate layer containing the aforementioned luminescent material. According to an advantageous development, the luminescence of the luminescent pigments or combination pigments differs from the luminescence of the substrate layer in the excitation wavelength, the emission wavelength, and / or the decay time.

[0024] The invention advantageously provides that the effect pigments are luminescent pigments or combination pigments in which a luminescent agent is arranged on the opaque coating or is admixed with the opaque coating. In the latter case, the opaque coating preferably has the lowest possible UV absorption in the range of the preferred excitation wavelength of the luminescent agent.

[0025] Furthermore, it can advantageously be provided that the effect pigments are luminescent pigments or combination pigments which contain at least two different luminescent agents which differ in the excitation wavelength, the emission wavelength and / or the decay time.

[0026] In another embodiment, the effect pigments are non-luminescent UV-absorbing pigments and the effect layer is arranged at least partially over a substrate layer with the said luminescent material.

[0027] In a further advantageous variant of the invention, a further layer with a third luminescent agent is arranged at least partially above the effect layer, wherein the luminescence of the third luminescent agent advantageously differs from the luminescence of the luminescent pigments or combination pigments and / or the luminescence of the background layer by the excitation wavelength, the emission wavelength, and / or the decay time.

[0028] In another, equally advantageous variant of the invention, a fourth luminescent agent can be added to the effect layer, which complements the luminescence of the luminescent pigments or combination pigments and / or the luminescence of the background layer, resulting in an additive color mixture of luminescent colors. The orientation of the platelet-shaped effect pigments has no or only a negligible influence on the luminescence of such an additional luminescent agent.

[0029] If the effect pigments are luminescent pigments, they have in particular a structure with a carrier substrate, an optional magnetic layer, an optional opaque coating and a luminescent coating.

[0030] If the effect pigments are non-luminescent UV-absorbing pigments, they have in particular a structure with a carrier substrate, an optional magnetic layer, an optional opaque coating and a coating with a UV absorber that is transparent in the visual spectral range.

[0031] If the effect pigments are combination pigments, they have a structure with a carrier substrate, an optional magnetic layer, an opaque coating, a luminescent coating and a coating with a UV absorber that is transparent in the visual spectral range.

[0032] The first wavelength range in which the combination pigments can be excited to luminescence advantageously encompasses the second UV wavelength range in which the combination pigments are UV-absorbing. For example, the first wavelength range can encompass the entire UV spectral range from 200 nm to 400 nm, while the second wavelength range lies only in the long-wave UVA range or only in the short-wave UVC range.

[0033] To improve the chemical and physical resistance and / or the wetting of the effect pigments with a binder, the effect pigments can be provided with a final, transparent coating.

[0034] The effect pigments can additionally contain an IR absorber that is not visually detectable, which on the one hand adds an additional authenticity feature to the security element and on the other hand makes the effect pigments markable or ablatable using an IR laser.

[0035] The security element advantageously contains a substrate onto which the aforementioned luminescent material and the effect layer are applied. This security element substrate can also be formed by the substrate of a data carrier, for example, a valuable document. The security element substrate can be a non-luminescent substrate itself, but can also advantageously be a luminescent substrate, wherein the luminescence of the substrate and at least one luminescence of the luminescent feature advantageously differ by the excitation wavelength, the emission wavelength, and / or the decay time.

[0036] The security element substrate can be a film, in particular a thread, strip, patch, or a film substrate of a polymer banknote based on BOPP or PET. However, it can also be a paper-based substrate based on cellulose pulp, a hybrid substrate with a paper core and film lamination, or a polymer core and an outer paper layer. A coated substrate, in particular a varnished or pre-coated substrate, is also possible, as is a plastic and / or paper- or cardboard-based card body.

[0037] The invention also includes a data carrier with a security element of the described type. The security element can be arranged, in particular, in a window region of the data carrier, for example, above an opening or a transparent or translucent portion of the data carrier. In this case, the described illumination direction selectivity of the security element can be observed on both sides of the data carrier, provided the security element does not have a substrate that absorbs UV excitation radiation or the window region is UV-absorbing.

[0038] The invention further includes a method for producing a security element of the type described, as defined in claim 18.

[0039] Luminescent pigments can be based on mica or synthetic mica coated with magnetite. The magnetite-coated mica is then coated with titanium dioxide in a sol-gel process and finally with an inorganic or organic luminescent substance in an immersion bath.

[0040] For example, inorganic luminescent substances or pigments are dispersed in a solvent-based binder matrix. Subsequently, the carrier substrates, such as magnetite-coated mica, are added. During mixing, the solvent is removed under vacuum. According to one manufacturing variant, the coated carrier substrates are sprayed and dried under vacuum.

[0041] The carrier substrates can also be coated with an acceptance layer, for example, made of layered silicates. The coated carrier substrates are then mixed with a luminescent dye dissolved in a suitable solvent. The solvent is then removed under vacuum.

[0042] In these cases, the particle size of the pigments essentially corresponds to the particle size of the inorganic carrier. This particle size can then be further reduced through a grinding process, for example, using an air jet mill.

[0043] Alternatively, layer sequences corresponding to the layer structure of the desired pigments can be applied symmetrically to a film carrier. The coating is then separated from the film, for example, by removing it at a steep angle. The brittleness of the applied layer sequences results in the formation of pigment flakes, the size of which can be further reduced as desired by a subsequent grinding step, for example, using an air jet mill. To optimize the particle size distribution, the film carrier is particularly preferably provided with a grid structure in advance using an embossing process or by printing in order to taper the coating in the area of ​​the grid and thereby create predetermined breaking points.

[0044] The coatings can be applied using a printing process or a conventional coating system, such as a roll coater, blade coater, slot-jet coating, or curtain coating. In another manufacturing variant, at least the magnetizable coating is applied using a PVD process.

[0045] If the pigments are only to be mechanically alignable, the magnetic layer mentioned above is simply omitted during production.

[0046] To align magnetic effect pigments, the effect pigments are mixed with a binder, especially a UV-curing binder, to formulate a printing ink, especially a flexographic or screen printing ink. This printing ink is then printed in the desired shape onto a substrate or underlying layer to form the effect layer. Immediately after printing, the platelet-shaped effect pigments are typically oriented with their main surface essentially parallel to the substrate surface.

[0047] To create a slightly different orientation of the effect pigments in certain areas, an external magnetic field is applied while the binder is still wet, which aligns the magnetic effect pigments into the desired luminescent motifs. In this state, the binder of the printing ink is then dried, for example, by UV exposure, to permanently fix the orientation of the effect pigments.

[0048] Particularly advantageous is the binder curing or complete curing as quickly as possible after the effect pigments have been aligned. This can be achieved, for example, with a UV-LED dryer. This has the advantage of being able to be used in close proximity to the alignment module due to its compact design.

[0049] In an advantageous variant, the substrate is coated with a base layer, particularly a paint, varnish, or transfer element, before applying the effect layer. This prevents, among other things, the binder from penetrating the substrate. Furthermore, reorientation or reorientation of the effect pigments caused by capillary forces is prevented or at least reduced.

[0050] For non-magnetic effect pigments, mechanical alignment can be achieved using a raised printing form, such as a letterpress or flexographic printing form, with the raised portions of the printing form designed in the shape of the desired luminescent motifs. Pressing the raised portions of the printing form into the not yet cured effect layer displaces the effect pigments immediately adjacent to the raised portions and brings them into an upright or even essentially vertical orientation. After the printing form is removed, the binder of the printing ink is cured before the effect pigments are reoriented, thus permanently fixing their orientation.

[0051] The luminescence feature can be inspected, for example, using a UV handheld lamp, particularly a focused UV handheld lamp, at a point of sale. Depending on the position of the handheld lamp, different luminescence patterns appear visually. However, the inspection can also be performed mechanically using a sensor. For example, the luminescence feature can be alternately excited with a UV light source from at least two directions, and the resulting luminescence image can be recorded synchronously using a CCD chip or a line scan camera, creating two different image files. Alternatively, an image can be recorded at two different stations with different relative arrangements of the UV light source and camera.

[0052] It is understood that the described luminescent feature can be combined with other security elements, preferably with security elements that also have an optical effect that corresponds particularly advantageously to the visual impression of the luminescent feature.

[0053] Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction has been omitted in order to increase clarity.

[0054] They show: Fig. 1 a schematic representation of a banknote with a security element according to the invention in the form of an illumination direction-selective luminescence feature, Fig. 2 in (a) the first luminescence motif of the luminescence feature of the Fig. 1 , which becomes visible under oblique illumination with a UV lamp, and in (b) the second luminescence motif of the luminescence feature, which appears under perpendicular illumination with the UV lamp, Fig. 3 a cross-section through the banknote of the Fig. 1 along the line III-III in the area of ​​the security element, Fig. 4 the structure of the platelet-shaped luminescent pigments of the luminescent feature, Fig. 5 non-magnetic luminescent pigments for an alternative design of the luminescent feature, Fig. 6 schematically the mechanical alignment of non-magnetic luminescent pigments, Fig. 7 a modification of the embodiment of the Fig. 2 , in which the luminescent pigments were aligned vertically in an area designed in the form of the lettering "Euro", Fig. 8 a security element according to a further embodiment of the invention, in which the orientation of the luminescent pigments transitions practically continuously from a horizontal to a vertical orientation, wherein (a) shows the security element in cross-section and (b) the appearance of the security element under oblique illumination, Fig. 9 in (a) and (b) two designs of non-luminescent UV-absorbing effect pigments, Fig. 10 for an embodiment with non-luminescent UV-absorbing pigments in (a) the first luminescent motif visible under oblique illumination and in (b) the second luminescent motif visible under vertical illumination, and Fig. 11 a combination pigment that combines luminescent properties and UV-absorbing properties.

[0055] The invention will now be explained using the example of securing banknotes and other valuable documents. Figur 1 1 shows a schematic representation of a banknote 10 with a security element 14 according to the invention in the form of an illumination-direction-selective luminescent feature 16. While the luminescent feature 16 is not visible under normal daylight or artificial light, when excited by UV radiation, for example, the UV lamp of a retail outlet, it displays a colored luminescent motif indicated by dashed lines. As a special feature, different colored luminescent motifs become visible when excited from different illumination directions.

[0056] Specifically, the luminescence feature 16, for example, shows the Fig. 2(a) The first luminescence motif 20 shown has a yellow luminescent ellipse 22 against a green luminescent background 24. When illuminated vertically with the UV lamp, the luminescence motif changes and the luminescence feature 16 now shows the Fig. 2(b) shown second luminescence motif 30, in which only the two side pieces 26 of the ellipse 22 luminesce yellow, while the central area 28 as well as the background 24 luminesce green.

[0057] Under normal daylight or artificial light, the luminescent feature 16 appears uniformly white and thus does not stand out from the equally white banknote paper 12 of the banknote. In particular, without UV illumination, neither the first nor the second luminescent motif 20, 30 is visible, since there is no color or brightness contrast between the side pieces 26 of the ellipse, the central region 28 of the ellipse, and the background 24. The invisibility of the luminescent feature under normal lighting is Fig. 1 indicated by the dashed lines of the ellipse 22. Since the luminescent feature 16, with its white appearance, is matched to the likewise white banknote paper 12, it is not immediately apparent without UV illumination that a security element 14 is present at this particular location on the banknote 10.

[0058] The structure of the security element 14 and the basic functioning of the security elements according to the invention will now be described with reference to Fig. 3 which shows a cross-section through the banknote 10 of the Fig. 1 along the line III-III.

[0059] As in Fig. 3 As shown, a background layer 40 containing a green luminescent luminescent agent is printed on the banknote paper 12 in the area of ​​the security element 14. The background layer 40 forms the background 24 of the first and second luminescent motifs 20, 30. An effect layer 42 is applied to the background layer 40, which contains a plurality of differently aligned platelet-shaped luminescent pigments 50 in a binder 44.

[0060] The structure of the luminescent pigments 50 is Fig. 4 The luminescent pigments 50 contain a carrier substrate 52 made of mica as a core. The carrier substrate 52 is in the embodiment of the Fig. 4 Fully enclosing a magnetic layer, specifically a magnetite layer 54, which enables magnetic alignment of the luminescent pigments in an external magnetic field. The magnetite layer 54 is also fully enclosed by an opaque white coating 56 of titanium dioxide, which ensures the white appearance of the luminescent pigments 50 under normal lighting. The desired luminescent properties are imparted to the pigments 50 by a luminescent coating 58 surrounding the white coating, which, in the exemplary embodiment, contains a red luminescent luminescent agent.

[0061] The luminescent pigments 50 are platelet-shaped with a large aspect ratio, i.e. a large ratio of edge length to thickness. In the embodiment of the Fig. 4 For example, the luminescent pigments 50 have an edge length of 1 = 15 µm and a thickness of d = 0.5 µm, thus exhibiting an aspect ratio of AV = 1 / d = 30:1. Due to the large aspect ratio, the luminescent pigments are highly asymmetric and are therefore stimulated to luminescence with varying degrees of intensity depending on their orientation, as explained in more detail below.

[0062] To create the effect layer 42, the luminescent pigments 50 were mixed with a UV-drying binder 44 to formulate a flexographic or screen printing ink. This printing ink was then printed in the shape of the ellipse 22 onto the substrate layer 40. Immediately after printing, the platelet-shaped luminescent pigments 50 are usually oriented with their main surface substantially parallel to the substrate surface. In order to create a region-specific orientation of the luminescent pigments 50, an external magnetic field was applied while the binder 44 was still uncured, which aligns the magnetic luminescent pigments 50 in the central region 28 of the ellipse substantially perpendicular to the substrate surface. In this state, the binder 44 of the printing ink was dried by UV exposure, and the resulting alignment of the luminescent pigments 50 ( Fig. 3 ) is thereby permanently fixed.

[0063] The different orientation of the luminescent pigments 50 leads to significantly different luminescence images 20, 30 ( Fig. 2(a), (b) ).

[0064] When UV illumination is applied from an oblique angle (illumination direction 70A in Fig. 3 ), the luminescent pigments 50 are all stimulated to luminescence with essentially the same intensity, and the luminescent feature 16 thus displays a uniform yellow luminescence in the region of the ellipse 22, which results from the additive color mixing of the green luminescence of the background layer 40 and the red luminescence of the luminescent pigments 50. Thus, in the partial regions of the ellipse 22 in which the platelet-shaped luminescent pigments 50 overlap, the red luminescent luminescent agent is stimulated, while in the partial regions or spaces in which the luminescent pigments do not overlap, essentially the green luminescent background layer 40 is stimulated.

[0065] With essentially vertical UV illumination (illumination direction 70B in Fig. 3 ) The vertically aligned luminescent pigments 50 of the central region 28 offer only a greatly reduced impact area to the excitation radiation and are therefore barely excited. The luminescence of the central region 28 is therefore dominated by the luminescence of the background layer 40 and thus appears essentially green. The region of the background layer 40 lying outside the effect layer 42 appears with green luminescence regardless of the illumination direction 70A, 70B and represents a uniform background for the changing appearance of the ellipse 22.

[0066] The two luminescence images 20, 30 are easily recognizable and verifiable as different for a user, so that the luminescence feature 16 offers a high level of security against simple replication with fluorescent inks.

[0067] In the embodiment of the Fig. 4 The coatings 54, 56, 58 are each shown fully enclosing. Depending on the manufacturing process of the pigments 50, the coatings may be only partially present or completely absent in the area of ​​the side edges, for example, when the pigments are ground in an air jet mill.

[0068] To improve the chemical and physical resistance and / or the wetting of the pigments 50 with the binder 44, the pigments 50 can optionally have a further transparent coating 60.

[0069] In an alternative embodiment, the luminescent pigments can also be non-magnetic, as in Fig. 5 In this embodiment, compared to the embodiment shown, the Fig. 4 the magnetic layer 54. The non-magnetic luminescent pigments 80 contain a carrier substrate 52 made of mica, which is provided with an opaque white coating 56 made of titanium dioxide, a luminescent coating 58 and an optional further transparent coating.

[0070] In an alternative embodiment not shown here, the opaque coating 56 of the non-magnetic luminescent pigments 80 may also be omitted, such as in embodiments in which the carrier substrate is transparent or translucent and preferably colorless.

[0071] The non-magnetic luminescent pigments 80 can be mechanically aligned in the form of the desired luminescent motifs, as shown schematically in Fig. 6 shown. For this purpose, the luminescent pigments 80 are first mixed with a UV-drying binder to formulate a flexographic or screen printing ink. This printing ink is then printed in the desired shape onto the background layer 40 to form the effect layer 42. Immediately after printing, the platelet-shaped luminescent pigments 80 are oriented essentially parallel to the substrate surface. In this case, a raised printing form 82, for example a letterpress or flexographic printing form, is used for alignment, the elevations 84 of which are designed in a desired motif shape. By pressing the printing form 82 into the not yet cured effect layer 42, the luminescent pigments 80 located directly next to the elevations 84 are mechanically displaced and thereby brought into an upright orientation.Before the reorientation of the luminescent pigments 80, the printing ink is cured with the luminescent pigments and the orientation of the pigments 80 is thereby permanently fixed.

[0072] Complex motifs can also be created using the alignment methods described. For example, the magnetic or mechanical alignment of the luminescent pigments 50, 80 can be achieved in the form of characters or codes. In the case of magnetic alignment, a suitable structured mask can be used, for example, which only allows the magnetic field aligning the pigments to pass through in specific areas. In the case of mechanical alignment, a printing form 82 with suitably designed elevations 84 can be used. In the case of larger areas to be aligned, a plurality of closely spaced point- or line-shaped elevations is advantageously used to ensure the desired alignment of the platelet-shaped pigments over a larger surface area.

[0073] Figur 7 shows a modification of the embodiment of the Fig. 2 , in which the luminescent pigments 50, 80 are vertically aligned in an area 25, which is designed in the form of the lettering "Euro". Upon oblique illumination with a UV light source, essentially all luminescent pigments 50, 80 are excited to luminescence, regardless of their orientation, so that the first luminescent motif 20 is again the yellow luminescent ellipse 22 of the Fig. 2(a) appears against a green luminescent background 24. In contrast, with perpendicular illumination, the luminescent pigments of area 25 are practically not excited due to their perpendicular orientation, so that this area luminesces green like the background. This results in the Fig. 7 illustrated second luminescent motif 30, which shows a green luminescent lettering "Euro" within a yellow luminescent ellipse 22.

[0074] If the user moves the UV hand lamp from an oblique illumination position, such as position 70A to Fig. 3 , into a vertical illumination position, such as position 70B in Fig. 3 , the lettering "Euro" seems to appear out of nowhere (change from the luminescent motif 20 of the Fig. 2(a) to the luminescence motif 30 of the Fig. 7 ) and to disappear again when moving back in an oblique direction of illumination (change from the luminescence motif 30 of the Fig. 7 to the luminescence motif 20 of the Fig. 2(a) ).

[0075] In real designs, the areas of different orientation of the luminescent pigments are 50, 80, such as areas 26 and 28 of the Fig. 3 , are generally not separated from one another by sharp edges, but exhibit a flowing, soft-focus or blurred transition. The transition area between the areas of different alignment has a width of between 20 µm and 5000 µm. The size of the transition area depends in particular on the process used to align the pigments (mechanical by embossing in the uncured state of the printing ink or by magnetic orientation of the pigments), the substrate smoothness, the substrate wetting, the absorbency of the substrates and the time delay between orientation and fixation of the pigments in the printing ink matrix or the binder.

[0076] In a further development, the orientation of the luminescent pigments 50 can also change practically continuously from a horizontal to a vertical orientation, as in the luminescent feature 90 of the Fig. 8(a) The luminescence feature 90 is, except for the special orientation of the luminescence pigments 50, like the luminescence feature 16 of the Fig. 3 The continuously changing orientation shown can be generated, for example, with a cylindrical magnet arranged beneath the banknote paper 12 with its longitudinal axis parallel to the surface of the banknote paper.

[0077] With such an alignment of the luminescent pigments 50, there is practically for each illumination position 92 of the UV hand lamp 70 a corresponding region 94 of the effect layer in which the platelet-shaped luminescent pigments 50 are aligned with their platelet plane essentially parallel to the illumination direction. In this region, the luminescent pigments 50 are therefore hardly excited upon illumination, so that the green luminescence of the background layer 40 dominates there. As a result, the observer sees a narrow, green luminescent stripe 96 within the magenta-colored luminescent ellipse 22, as shown in Fig. 8(b) shown. If the UV hand lamp 70 is moved in direction 93 over the luminescent feature 90, the green luminescent stripe 96 moves accordingly in direction 97 along the ellipse 22 to the right, since the area 94 with the pigments 50 oriented parallel to the direction of illumination is in the representation of the Fig. 8(a) continuously shifts to the right.

[0078] Depending on the specific alignment of the luminescent pigments 50, other movement effects can of course also be created. For example, by aligning them with a cylindrical magnet arranged above the banknote paper 12, a Fig. 8(b) opposing stripes 96 are generated. By alignment with spherical magnets, ring-shaped, moving luminescence patterns can be created, which also often convey a three-dimensional image impression. What all of these visual effects have in common is that they are easy for a user to perceive and verify, but very difficult for a potential counterfeiter to replicate, since such visual effects cannot be created with conventionally available fluorescent inks.

[0079] In the embodiments in which the platelet-shaped luminescent pigments 50, 80 are applied to a substrate layer 40 with a luminescent agent, in particular the emission color of the luminescent agent of the substrate layer 40 can differ from the emission color of the luminescent pigments 50, 80. With reference to Fig. 3 With a substantially perpendicular UV excitation 70B, a luminescent color is then displayed in the regions 26 that predominantly corresponds to the luminescent color of the luminescent pigments 50, since these are excited significantly more strongly than the luminescent agent of the background layer 40. Region 28, on the other hand, predominantly displays the luminescent color of the background layer 40, since the luminescent pigments in this region are excited significantly less strongly by UV radiation.

[0080] Since luminescent colors are self-luminous colors, the laws of additive color mixing are applicable to them, so that in particular a green, a blue and a red luminescent color add up to a luminescent white if the proportions of the individual colors are appropriately matched to one another.

[0081] In transition areas between areas 26 and 28, an equilibrium of the luminescent colors involved can also be established, so that, for example, a green and a red luminescent color combine to form a yellow luminescent mixed color. Area 26 then exhibits, for example, a red luminescence, area 28 a green luminescence, and the transition area in between a yellow luminescence, so that the transition area acts like a differently colored corona for area 26 or 28.

[0082] In other designs, the background layer 40 can be omitted, or the background layer can be designed to be non-luminescent. In these cases, too, the luminescence feature exhibits a different intensity distribution and / or color of the luminescence. With reference to Fig. 3 For example, if a luminescent background layer 40 is omitted, the regions 26 show a significantly higher luminescence intensity than the region 28 after a substantially vertical UV excitation 70B, since in the region 28 practically only the edge surfaces of the pigments are excited to glow and the luminescence is therefore strongly suppressed compared to the regions 26.

[0083] If the background layer 40 is colored but non-luminescent, the areas 26 ( Fig. 3 ) the following interactions take place, which contribute to an overall colour impression: 1) The luminescent pigments 50 are excited by the incident UV radiation, and the emitted luminescent radiation is reflected directly back to the excitation side. 2) The luminescent pigments 50 are excited by the incident UV radiation; a portion of the luminescent radiation is emitted toward the colored background layer 40, filtered by the background layer 40, and finally reflected back by the substrate 12 to the excitation side. 3) A portion of the incident UV radiation is transmitted by the colored background layer 40, reflected by the substrate 12 to the excitation side, and the luminescent pigments 50 are excited to luminescence by this reflected UV radiation. If the background layer 40 is colored and simultaneously UV-absorbing, this contribution to the total luminescence is eliminated, and the luminous intensity in region 26 is correspondingly lower.

[0084] In the designs described so far, the effect layer of the luminescent feature always contains luminescent pigments 50 and 80, which luminesce in one or more colors upon excitation. This luminescence can be supplemented by the luminescence of a background layer arranged beneath the effect layer, resulting in an additive color mixture of luminescent colors under certain illumination directions.

[0085] In the designs described below, the effect layer can also contain non-luminescent UV-absorbing pigments as platelet-shaped effect pigments that modify the luminescence of a substrate layer depending on the direction of illumination. The non-luminescent UV-absorbing pigments can otherwise be employed and used in the same way as the luminescent pigments described above and, in particular, can also be magnetically or mechanically aligned.

[0086] Figur 9(a) shows a first embodiment of such a non-luminescent UV-absorbing pigment 100, which is magnetically alignable by a magnetic layer. The pigment 100 contains as its core a carrier substrate 52 made of mica, which is fully enclosingly provided with a magnetic layer, for example a magnetite layer 54, which enables magnetic alignment of the pigment 100 in an external magnetic field. The magnetite layer 54 is, in turn, fully enclosingly surrounded by an opaque white coating 56 made of titanium dioxide, which gives the pigment 100 a white appearance under normal illumination. The desired UV-absorbing properties are imparted to the pigment 100 by a coating 102 surrounding the TiO 2 coating with a UV absorber that is transparent in the visual spectral range, e.g. Tinuvin®< 400 (BASF). The pigment 100 of the embodiment of the Fig. 9(a) has an edge length 1 = 20 µm and a thickness d = 0.4 µm, i.e. an aspect ratio AV = 1 / d = 50.

[0087] In addition to the UV-absorbing pigments 100, the opaque white coating 56 can also be absorbent in a (partial) range of the UV spectrum. Depending on the desired degree of absorption, TiO2 can be used in different modifications, particularly in the rutile or anatase modifications. Rutile absorbs the entire UV wavelength range, while anatase absorbs only the short- to medium-wave UV wavelength range. By using the corresponding opaque coatings 56, excitation wavelength-specific and simultaneously illumination direction-selective luminescence features can be generated.

[0088] Even with the non-luminescent UV-absorbing pigments 100, the coatings 54, 56, 102 may be only partially present or completely absent in the region of the side edges. The pigments may also optionally have an additional transparent coating 60 to improve the chemical and physical resistance and / or the wetting of the pigments with a binder.

[0089] If the non-luminescent UV-absorbing pigments are mechanically aligned, the magnetic layer can be omitted, as in Fig. 9(b) The non-magnetic UV-absorbing pigments 104 of the Fig. 9(b) contain a carrier substrate 52 made of mica, an opaque white coating 56 made of titanium dioxide, a coating 102 with a UV absorber transparent in the visual spectral range and optionally another transparent coating.

[0090] For example, in the embodiment of the Fig. 7 instead of the luminescent pigments 50 the non-luminescent UV-absorbing pigments 100 of the Fig. 9(a) used, oblique illumination or vertical illumination with UV radiation results in the Fig. 10 shown luminescence motifs 110 and 120.

[0091] With reference to Fig. 10(a) When illuminated under UV light from an oblique angle in the background region 24, the luminescence feature reveals the green luminescence of the background layer 40. In the region of the ellipse 22, essentially no luminescence occurs because the UV-absorbing pigments 100 absorb the incident UV radiation and largely prevent it from passing through to the background layer 40. The phrase "largely" reflects the fact that, due to the desired ink layer thickness and pigment concentration in the region of the ellipse 22, complete absorption of the green luminescence of the background layer 40 by the UV-absorbing pigments 100 cannot generally be achieved.

[0092] However, with a substantially vertical UV illumination, the vertically aligned pigments 100 in the area 25 allow the excitation radiation to pass through practically unattenuated, so that the luminescent agent of the background layer 40 is excited to glow, and a green luminescent lettering "Euro" is displayed within the non-luminescent ellipse 22, as in Fig. 10(b) shown.

[0093] If the user moves a UV hand lamp from an oblique illumination position to the vertical illumination position, the lettering "Euro" appears to appear out of nowhere within the ellipse (change from the luminescence motif 110 of the Fig. 10(a) to the luminescence motif 120 of the Fig. 10(b) ) and disappear again when moving in an oblique direction of illumination (change from the luminescence motif 120 of the Fig. 10(b) to the luminescence motif 110 of the Fig. 10(a) ). The visual effects when using UV-absorbing pigments are therefore essentially the opposite of the effects when using UV-luminescent pigments.

[0094] Finally, it is also possible to use pigments 130 that combine luminescent properties and UV-absorbing properties. With reference to Fig. 11 Such a combination pigment 130 contains, as its core, a carrier substrate 52 made of mica, which is provided with a magnetite layer 54, an opaque white coating 56 made of titanium dioxide, a luminescent coating 132, and a coating 134 with a UV absorber that is transparent in the visual spectral range. The luminescent coating 132 can be excited over the entire wavelength range of the UV spectrum from 200 nm to 400 nm, while the UV absorber of the coating 134 absorbs only in a partial range of the UV spectrum, for example, in the range from 200 nm to 280 nm. By using such combination pigments 130, excitation wavelength-specific and simultaneously illumination direction-selective luminescent features can be generated.

[0095] If a corresponding luminescent feature is illuminated, for example, with long-wave UVA radiation of a wavelength of 366 nm, at which the coating 134 does not absorb, the luminescence of the luminescent coating 132 of the combination pigments 130 is excited and the results with reference to Figuren 2 bis 8 effects already described. If, however, the luminescent feature is illuminated with short-wave UVC radiation of a wavelength of 254 nm, the coating 134 absorbs the incident UV radiation and the luminescent coating 132 is not excited. The combination pigments 130 therefore do not act as luminescent pigments at this excitation wavelength, but as non-luminescent UV-absorbing pigments, so that the Figur 10 Since different visual effects occur depending on the excitation wavelength, the counterfeit protection of the security elements according to the invention is further increased by the use of such combination pigments.

[0096] The combo pigment 130 of the Fig. 11 has a magnetic layer 54 and is therefore magnetically alignable. However, it is understood that the magnetic layer may also be omitted in combination pigments and the non-magnetic combination pigments may be mechanically aligned, as described above in connection with the Figuren 5 and 9(b) already described for luminescent pigments 80 and UV-absorbing pigments 104. Bezugszeichenliste

[0097] 10 Banknote 12 Banknote paper 14 Security element 16 Luminescent feature 20 First luminescent motif 22 Luminescent ellipse 24 Background 25 Area in the shape of the lettering "Euro" 26 Side pieces 28 Central area 30 Second luminescent motif 40 Underlayer 42 Effect layer 44 Binder 50 Luminescent pigments 52 Carrier substrate 54 Magnetite layer 56 Opaque white coating 58 Luminescent coating 60 Optional transparent coating 70 UV hand lamp 70A, 70B Illumination directions 80 Non-magnetic luminescent pigments 82 Printing form 84 Elevations 90 Luminescent feature 92 Illumination position 93 Direction of movement of UV hand lamp 94 Area of ​​the effect layer 96 Stripes 97Direction of movement stripes 100UV-absorbing pigments 102Coating with UV absorber 104Non-magnetic UV-absorbing pigments 110First luminescent motif 120Second luminescent motif 130Combination pigment 132Luminescent coating 134Coating with UV absorber

Claims

1. Security element (14) for safeguarding security papers, documents of value and other data carriers, having a luminescence feature (16) which is selective to the direction of illumination and shows different luminescence motifs (20, 30) when illuminated with UV excitation radiation from different directions of illumination (70A, 70B), wherein the luminescence feature (16) - contains a luminescence material (40) that emits luminescence radiation on illumination with UV excitation radiation, and - contains, in an effect layer (42), a multitude of effect pigments in platelet form (50) that are aligned in the form of the desired luminescence motifs (20, 30), wherein the effect pigments are aligned differently by area, - wherein the effect pigments are luminescent pigments (50), non-luminescent UV-absorbing pigments or combination pigments that are excitable to luminescence in a first UV wavelength range and are non-luminescent and UV-absorbent in a second UV wavelength range.

2. Security element according to Claim 1, characterized in that the effect pigments in platelet form have an aspect ratio of more than 5:1, preferably more than 10:1 and more preferably between 20:1 and 400:1.

3. Security element according to Claim 1 or 2, characterized in that the effect pigments are magnetically alignable and contain a core with a magnetic material.

4. Security element according to Claim 3, characterized in that the magnetic material has been provided with an opaque coating, in particular a white or coloured opaque coating, at least on one of the main surfaces, preferably at least on both main surfaces.

5. Security element according to Claim 1 or 2, characterized in that the effect pigments are nonmagnetic and contain a core in platelet form.

6. Security element according to Claim 5, characterized in that the core in platelet form has been provided with an opaque coating, in particular a white or coloured opaque coating, at least on one of its main surfaces, preferably at least on both main surfaces.

7. Security element according to at least one of Claims 4 to 6, characterized in that the effect layer is disposed at least partly on top of a substrate layer, and the visible colour of the covering coating of the effect pigments corresponds essentially to the visible colour of the substrate layer.

8. Security element according to at least one of Claims 1 to 7, characterized in that the luminescence motifs are invisible without illumination with UV excitation radiation.

9. Security element according to at least one of Claims 1 to 8, characterized in that the effect pigments are luminescent pigments or combination pigments that form said luminescence material.

10. Security element according to at least one of Claims 1 to 8, characterized in that the effect pigments are luminescent pigments or combination pigments and the effect layer is disposed at least partly on top of a substrate layer comprising said luminescence material.

11. Security element according to Claim 10, characterized in that the luminescence of the luminescent pigments or combination pigments differs from the luminescence of the substrate layer in the excitation wavelength, in emission wavelength, and / or in decay time.

12. Security element according to at least one of Claims 4 to 11, characterized in that the effect pigments are luminescent pigments or combination pigments in which a luminescer has been disposed atop the covering coating, or has been mixed with the covering coating.

13. Security element according to at least one of Claims 1 to 12, characterized in that the effect pigments are luminescent pigments or combination pigments and contain at least two different luminescers which differ in terms of excitation wavelength, emission wavelength, and / or decay time.

14. Security element according to at least one of Claims 1 to 8, characterized in that the effect pigments are non-luminescent UV-absorbing pigments and the effect layer is at least partly disposed on top of a substrate layer comprising said luminescence material.

15. Security element according to at least one of Claims 1 to 14, characterized in that a further layer with a third luminescer is disposed at least partly on top of the effect layer.

16. Security element according to Claim 15, characterized in that the luminescence of the third luminescer differs from the luminescence of the luminescent pigments or combination pigments and / or the luminescence of the substrate layer by excitation wavelength, emission wavelength, and / or decay time.

17. Data carrier comprising a security element according to at least one of Claims 1 to 16.

18. Method of producing a safety element (14) according to any of Claims 1 to 16, wherein - an effect layer (42) is applied to a substrate optionally provided with a substrate layer (40) and contains a multitude of effect pigments in platelet form (50), - wherein the effect pigments are luminescent pigments (50), non-luminescent UV-absorbing pigments or combination pigments that are excitable to luminescence in a first UV wavelength range and are non-luminescent and UV-absorbent in a second UV wavelength range, and - the effect pigments (50) are aligned magnetically or mechanically in the form of the desired luminescence motifs (20, 30) and fixed in the aligned orientation, wherein the effect pigments are aligned differently by area.

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