EP3332982A1 - Security element having fluorescent feature - Google Patents

Abstract

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

Description

The invention relates to a security element with a luminescent feature for securing security papers, documents of value and other data carriers. The invention also relates to a method for producing such a security element as well as a data carrier equipped 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. In this context, it is known to print fluorescent inks on a security paper using various printing methods. In this case, for example, a fluorescent color is printed in the form of a motif, which is not visible in normal daylight, but when viewed under UV illumination is visible. The fluorescent color can also be admixed with a visible color in daylight, so that the printed motif is visible even in daylight, with a similar or a different hue.

Counterfeiting of banknotes and documents of value are often undertaken today with inexpensive inkjet or laser printers. Because of the high prevalence of such printers, tracing counterfeits is often extremely difficult for law enforcement agencies. Even simple fluorescence features are no longer a major hurdle for potential counterfeiters, since fluorescent inks for inkjet and laser printers are now readily available commercially.

Based on this, the present invention seeks to provide a security element of the type mentioned with high protection against counterfeiting.

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

• ein Lumineszenzmaterial, das auf Beleuchtung mit UV-Anregungsstrahlung Lumineszenzstrahlung emittiert, und
• enthält in einer Effektschicht eine Vielzahl von plättchenförmigen Effektpigmenten, die in Form der gewünschten Lumineszenzmotive ausgerichtet sind,
• wobei die Effektpigmente Lumineszenzpigmente, nichtlumineszierende UV-absorbierende Pigmente oder Kombi-Pigmente darstellen, die in einem ersten UV-Wellenlängenbereich zur Lumineszenz anregbar sind und in einem zweiten UV-Wellenlängenbereich nichtlumineszierend und UV-äbsorbierend sind.

The invention provides a security element for securing security papers, documents of value and other data carriers, which has an illumination direction-selective luminescence feature which shows different luminescence motifs when illuminated with UV excitation radiation from different illumination directions. The luminescence feature contains

• a luminescent material that emits luminescent radiation upon illumination with UV excitation radiation, and
• contains in an effect layer a plurality of platelet-shaped effect pigments, which are aligned in the form of the desired luminescence motifs,
• wherein the effect pigments are luminescent pigments, non-luminescent UV-absorbing pigments or combination pigments which are excitable for luminescence in a first UV wavelength range and are non-luminescent and UV-absorbing in a second UV wavelength range.

The luminescence radiation emitted by the luminescence feature is preferably in the visible spectral range, but may in principle also be at least partially in the infrared spectral range. The luminescence can be monochromatic, but especially multicolored.

In an advantageous variant of the invention, the effect pigments already contain said luminescent material, for example in the form of a luminescent layer. However, in another advantageous variant of the invention, the luminescent material may also be present in a separate layer, for example a background layer.

As explained in more detail below, the illumination direction selectivity of the security element is created by the orientation of the effect pigments in the form of the luminescence motifs. In particular, due to the different relative orientation of the illumination direction and platelet plane of the effect pigments, a differently strong excitation of the luminescence or a different degree of UV absorption result, so that different luminescence images can be generated depending on the direction of incidence of the excitation radiation.

The platelet-shaped effect pigments advantageously have an aspect ratio which is 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 edge length to thickness of the platelets. With a high aspect ratio, in particular of 5: 1 or more, different orientations result in large differences in the incident surface which the pigments of the incident radiation offer, and thus large differences in the excited luminescence or in the UV absorption.

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

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

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

The opaque coating may in particular consist of TiO ₂ or a porous and thus scattering or covering polyester layer. In this case, the covering coating can be absorbent in a partial region of the UV spectrum. Covering coatings, eg. B. from TiO ₂ , can also also be impermeable to at least a portion of the visual (VIS) spectrum.

In an advantageous development, the effect layer is arranged at least partially over a background layer, wherein the visually visible color of the covering coating of the effect pigments essentially corresponds to the visually visible color of the background layer.

According to an alternative, likewise advantageous embodiment, the platelet-shaped core of the non-magnetic effect pigments has no covering coating.

With particular advantage, it is provided that the luminescence motifs are not visible without illumination with UV excitation radiation. This can be achieved in particular by coordinating the visually visible color of the covering coating on the visually visible color of a background layer or a substrate on which the security element is applied. In the case of normal daylighting or artificial lighting, it is then not readily apparent that a luminescence feature is present at this point in particular.

In an advantageous embodiment, the effect pigments are luminescent pigments or combination pigments which themselves form the luminescent material mentioned.

Alternatively, although the effect pigments are luminescent pigments or combination pigments, the effect layer is at least partially disposed over a background layer with said luminescent material. According to an advantageous development, the luminescence differs Luminescence pigments or combination pigments of the luminescence of the background layer in the excitation wavelength, the emission wavelength, and / or the decay time.

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

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

In another embodiment, the effect pigments are non-luminescent UV-absorbing pigments and the effect layer is at least partially disposed over a background layer with said luminescent material.

In a further advantageous variant of the invention, a further layer with a third luminescent agent is arranged at least partially over the effect layer, wherein advantageously the luminescence of the third luminescence means of 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 cooldown is different.

In another, likewise advantageous variant of the invention, the effect layer may be admixed with a fourth luminescent agent which supplements the luminescence of the luminescent pigments or combination pigments and / or the luminescence of the background layer, resulting in additive color mixing 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 luminescence agent.

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.

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 transparent in the visual spectral range.

If the effect pigments are combination pigments, they have, in particular, a structure with a carrier substrate, an optional magnetic layer, an opaque coating, a luminescence coating and a coating with a UV absorber transparent in the visual spectral range.

The first wavelength range in which the combination pigments are excitable for luminescence advantageously comprises the second UV wavelength range in which the combination pigments are UV-absorbing. For example, the first wavelength range can cover the entire UV spectral range of 200 nm to 400 nm, while the second wavelength range is only in the long-wave UVA range or only in the short-wave UVC range.

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

The effect pigments may additionally contain a visually unrecognizable IR absorber, whereby on the one hand a further authenticity feature is added to the security element, and on the other hand the effect pigments can be marked or ablated by means of IR lasers.

The security element advantageously contains a substrate on which said 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 value document. The security element substrate may be a self-non-luminescent substrate, but may advantageously also be a luminescent substrate, wherein advantageously the luminescence of the substrate and at least one luminescence of the luminescence feature differ by the excitation wavelength, the emission wavelength, and / or the decay time.

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, but 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. Also a coated substrate, in particular a painted or precoated Substrate is an option, as well as a plastic and / or paper or cardboard-based card body.

The invention also includes a data carrier with a security element of the type described. The security element may in particular be arranged in a window region of the data carrier, for example via an opening or a transparent or translucent subregion 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, as long as the security element does not have a substrate which absorbs the UV excitation radiation or the window region is UV-absorbing.

• auf ein gegebenenfalls mit einer Untergrundschicht versehenes Substrat eine Effektschicht aufgebracht wird, die eine Mehrzahl von plättchenförmigen Effektpigmenten enthält,
• wobei die Effektpigmente Lumineszenzpigmente, nichtlumineszierende UV-absorbierende Pigmente oder Kombi-Pigmente darstellen, die in einem ersten UV-Wellenlängenbereich zur Lumineszenz anregbar sind und in einem zweiten UV-Wellenlängenbereich nichtlumineszierend und UV-absorbierend sind, und
• die Effektpigmente magnetisch oder mechanisch in Form der gewünschten Lumineszenzmotive ausgerichtet werden und in der ausgerichteten Orientierung fixiert werden.

The invention further includes a method for producing a security element of the type described, in which

• on an optionally provided with a substrate layer substrate, an effect layer is applied, which contains a plurality of platelet-shaped effect pigments,
• wherein the effect pigments are luminescent pigments, non-luminescent UV-absorbing pigments or combination pigments which are excitable for luminescence in a first UV wavelength range and non-luminescent and UV-absorbing in a second UV wavelength range, and
• the effect pigments are magnetically or mechanically aligned in the form of the desired luminescence motifs and fixed in the aligned orientation.

Luminescent pigments may in particular be based on a mica or a synthetic mica which is coated with a magnetite. Subsequently, the magnetite-coated mica is coated in a sol-gel process with titanium dioxide and finally in an immersion bath with an inorganic or organic luminescent.

Inorganic luminescent substances or pigments are dispersed, for example, in a solvent-based binder matrix. Subsequently, the carrier substrates, such as. As the magnetite-coated mica, mixed. During mixing, the solvent is finally removed under vacuum. According to a production variant, the coated carrier substrates are sprayed and dried under vacuum.

The carrier substrates can also be provided with an acceptance layer, which consists for example of sheet silicates. The carrier substrates coated in this way are then mixed in the next step with a luminescence dye dissolved in a suitable solvent. The solvent is then stripped off under vacuum.

The particle size of the pigments in these cases essentially corresponds to the particle size of the inorganic carrier. Finally, this particle size can be reduced by a milling process, for example with the aid of an air jet mill.

Alternatively, layer sequences which correspond to the layer structure of the desired pigments can be applied symmetrically to a film support. Subsequently, the coating is separated from the film by these is removed, for example, over a steep angle. By the Brittleness of the applied layer sequences form pigment flakes whose size can be reduced by a subsequent grinding step, for example by means of an air jet mill, as desired. In order to optimize the particle size distribution, the film carrier is particularly preferably provided in advance by means of stamping processes or by printing with a grid structure in order to taper the coating in the region of the grid and thereby create predetermined breaking points.

The application of the layers can be effected by means of printing processes or a classical coating system, for example roll coater, blade coater, slot nozzle application or even curtain method. In a further production variant, at least the magnetizable coating is applied by means of a PVD process.

If the pigments are to be only mechanically alignable, the abovementioned magnetic layer is simply omitted in the production of the pigments.

For aligning magnetic effect pigments, the effect pigments are admixed to a binder, in particular a UV-drying binder, in order to formulate a printing ink, in particular a flexographic or screen printing ink. This ink is then printed in the desired form on a substrate or undercoat to form the effect layer. Immediately after printing, the platelet-shaped effect pigments are typically oriented with their main surface substantially parallel to the substrate surface.

In order to produce a region-wise deviating orientation of the effect pigments, the binder is still wet in an external state Applied magnetic field, which aligns the magnetic effect pigments in the form of the desired luminescence motifs. In this state, the binder of the printing ink is then dried, for example by UV exposure, in order to permanently fix the alignment of the effect pigments.

In a particularly advantageous manner, the binder is cured or cured as quickly as possible after the orientation of the effect pigments. A hardening can be done for example with a UV LED dryer. This has the advantage that it can be used in the immediate vicinity of the alignment module due to its compact design.

In an advantageous variant, the substrate is provided with a background layer, in particular with a paint, a lacquer or a transfer element, before the effect layer is applied. As a result, it is possible, inter alia, to prevent the binder from being displaced into the substrate. In addition, due to capillary forces Um- or rear-orientation of the effect pigments is prevented or at least reduced.

In the case of non-magnetic effect pigments, a mechanical alignment can take place with the aid of a raised printing form, for example a high-pressure or flexographic printing plate, the elevations of the printing form being shaped in the form of the desired luminescence motifs. The impressions of the elevations of the printing form in the not yet hardened effect layer displaces the immediately adjacent to the elevations effect pigments and brings them in an upright, or even substantially vertical orientation. After removal of the printing form, the binder of the printing ink is cured before the rear-orientation of the effect pigments, thereby permanently fixing the orientation of the effect pigments.

The examination of the luminescence feature can be done, for example, with a UV hand lamp, in particular a focused UV hand lamp at a point of sale. Depending on the position of the hand lamp, visually different luminescence motifs appear. However, the test can also be done mechanically by means of a sensor. For example, the luminescence feature can be alternately excited with a UV light source from at least two directions and the generated luminescence image can be recorded synchronized by means of a CCD chip or a line scan camera so that two different image files are formed. Alternatively, an image can be taken in two different stations with different relative arrangement of UV light source and camera.

It is understood that the described luminescence feature can be combined with other security elements, preferably with security elements, which likewise have an optical effect which corresponds particularly advantageously to the visual impression of the luminescence feature.

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 in Form eines beleuchtungsrichtungsselektiven Lumineszenzmerkmals,

Fig. 2

in (a) das erste Lumineszenzmotiv des Lumineszenzmerkmals der Fig. 1, das bei schräger Beleuchtung mit einer UV-Lampe sichtbar wird, und in (b) das zweite Lumineszenzmotiv des Lumineszenzmerkmals, das bei senkrechter Beleuchtung mit der UV-Lampe in Erscheinung tritt,

Fig. 3

einen Querschnitt durch die Banknote der Fig. 1 entlang der Linie III-III im Bereich des Sicherheitselements,

Fig. 4

den Aufbau der plättchenförmigen Lumineszenzpigmente des Lumineszenzmerkmals,

Fig. 5

unmagnetische Lumineszenzpigmente für eine alternative Ausgestaltung des Lumineszenzmerkmals,

Fig. 6

schematisch die mechanische Ausrichtung unmagnetischer Lumineszenzpigmente,

Fig. 7

eine Abwandlung des Ausführungsbeispiels der Fig. 2, bei dem die Lumineszenzpigmente in einem Bereich senkrecht ausgerichtet wurden, der in Form des Schriftzugs "Euro" gestaltet ist,

Fig. 8

ein Sicherheitselement nach einem weiteren Ausführungsbeispiel der Erfindung, bei dem die Orientierung der Lumineszenzpigmente praktisch kontinuierlich von einer waagrechten in eine senkrechte Orientierung übergeht, wobei (a) das Sicherheitselement im Querschnitt und (b) das Erscheinungsbild des Sicherheitselements bei schräger Beleuchtung zeigt,

Fig. 9

in (a) und (b) zwei Ausgestaltungen von nichtlumineszierenden UV-absorbierenden Effektpigmenten,

Fig. 10

für ein Ausführungsbeispiel mit nichtlumineszierenden UV-absorbierenden Pigmenten in (a) das bei schräger Beleuchtung erkennbare erste Lumineszenzmotiv und in (b) das bei senkrechter Beleuchtung sichtbare zweite Lumineszenzmotiv, und

Fig. 11

ein Kombi-Pigment, das Lumineszenzeigenschaften und UV-absorbierende Eigenschaften kombiniert.

Show it:

Fig. 1

1 is a schematic representation of a banknote having 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 Fig. 1 which is visible in oblique illumination with a UV lamp, and in (b) the second luminescent motif of the luminescent feature which appears when illuminated vertically with the UV lamp,

Fig. 3

a cross section through the banknote of 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 luminescence feature,

Fig. 5

non-magnetic luminescent pigments for an alternative embodiment of the luminescence feature,

Fig. 6

schematically the mechanical orientation of non-magnetic luminescent pigments,

Fig. 7

a modification of the embodiment of Fig. 2 in which the luminescent pigments were oriented vertically in a region shaped 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 practically continuously changes from a horizontal to a vertical orientation, wherein (a) shows the security element in cross-section and (b) the appearance of the security element in oblique illumination,

Fig. 9

in (a) and (b) two embodiments of non-luminescent UV-absorbing effect pigments,

Fig. 10

for an exemplary embodiment with non-luminescent UV-absorbing pigments in (a) the first luminescence motif recognizable by oblique illumination and in (b) the second luminescence motif visible under vertical illumination, and

Fig. 11

a combination pigment that combines luminescent properties and UV-absorbing properties.

The invention will now be explained using the example of hedging banknotes and other value documents. FIG. 1 shows a schematic representation of a banknote 10 with a security element 14 according to the invention in the form of a illumination direction-selective luminescence feature 16. While the luminescence feature 16 is not visible in normal daylight or artificial lighting, it shows when excited by UV radiation, such as the UV lamp of a point of sale , a colored luminescent motif indicated by dashed lines. As a special feature, different colored luminescence motifs become visible upon excitation from different directions of illumination.

Specifically, the luminescent feature 16, for example, in oblique illumination with a UV lamp in the Fig. 2 (a) illustrated first luminescent motif 20 having a yellow luminescent ellipse 22 in front of a green luminescent background 24. When illuminated vertically with the UV lamp, the luminescence motif changes and the luminescence feature 16 now shows the in Fig. 2 (b) illustrated 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 green luminesce.

In normal daylight or artificial lighting, the luminescence feature 16 appears uniformly white and thus does not stand out from the likewise white banknote paper 12 of the banknote. In particular, neither the first nor the second luminescence motif 20, 30 is visible without UV illumination, 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 illumination is in Fig. 1 indicated by the dashed lines of the ellipse 22. Since the luminescence feature 16 with its white appearance is matched to the likewise white banknote paper 12, it is not readily apparent without UV illumination that a security element 14 is present at this location of the banknote 10.

The construction of the security element 14 and the basic mode of operation of the security elements according to the invention will now be described with reference to FIG Fig. 3 explained in more detail, which is a cross section through the banknote 10 of Fig. 1 along the line III-III shows.

As in Fig. 3 is shown on the banknote paper 12 in the region of the security element 14, a background layer 40 is printed with a green luminescent phosphor. The undercoat layer 40 forms the background 24 of the first and second luminescent motifs 20, 30. Applied to the undercoat layer 40 is an effect layer 42 which contains in a binder 44 a multiplicity of differently oriented platelet-shaped luminescent pigments 50.

The structure of the luminescent pigments 50 is shown in FIG Fig. 4 shown in more detail. The luminescent pigments 50 contain as the core a carrier substrate 52 made of mica. The carrier substrate 52 is in the embodiment of Fig. 4 completely enclosed with a magnetic layer, specifically a magnetite layer 54, which allows a magnetic alignment of the luminescent pigments in an external magnetic field. The magnetite layer 54 is also completely surrounded by a covering white coating 56 of titanium dioxide, which ensures the white appearance of the luminescent pigments 50 under normal illumination. 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.

The luminescent pigments 50 are platelet-shaped with a high aspect ratio, ie a high edge-to-thickness ratio. In the embodiment of Fig. 4 For example, the luminescent pigments 50 have an edge length 1 = 15 .mu.m and a thickness d = 0.5 .mu.m, thus exhibiting an aspect ratio of AV = 1 / d = 30: 1. Due to the high aspect ratio, the luminescent pigments are strongly asymmetric and are therefore excited to different extents, depending on the orientation, to luminescence, as explained in more detail below.

To produce 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 on the background layer 40 in the form of the ellipse 22. Immediately after printing, the platelet-shaped luminescent pigments 50 with their main surface are usually substantially parallel to the substrate surface oriented. In order to produce a region-wise deviating orientation of the luminescent pigments 50, an external magnetic field was applied in the still uncured state of the binder 44, 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 generated alignment of the luminescent pigments 50 (FIG. Fig. 3 ) thereby permanently fixed.

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

For UV illumination from an oblique angle (illumination direction 70A in Fig. 3 ), the luminescent pigments 50 are all excited to be substantially equally strong for luminescence and the luminescent feature 16 thus shows in the region of the ellipse 22 a uniform yellow luminescence resulting 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 excited, while in the partial regions or interstices in which the luminescent pigments do not overlap, substantially the green luminescent background layer 40 is excited.

In a substantially vertical UV illumination (illumination direction 70B in Fig. 3 ) offer the vertically oriented luminescent pigments 50 of the central portion 28 of the excitation radiation only a greatly reduced Impact surface and are therefore hardly stimulated. The luminescence of the central region 28 is therefore dominated by the luminescence of the background layer 40 and thus appears substantially green. The region of the background layer 40 that lies outside the effect layer 42 appears with green luminescence independently of the illumination direction 70A, 70B and provides a uniform background for the changing appearance of the ellipse 22.

The two luminescence images 20, 30 are easily recognizable and testable by a user, so that the luminescence feature 16 offers a high level of security against simple readjustment with fluorescent inks.

In the embodiment of Fig. 4 the coatings 54, 56, 58 are shown fully enclosed. Depending on the method of preparation of the pigments 50, the coatings in the region of the side edges may also be present only partially or completely absent, for example when the pigments are ground in an air jet mill.

To improve the chemical and physical resistances and / or the wetting of the pigments 50 with the binder 44, the pigments 50 may optionally have a further transparent coating 60.

In an alternative embodiment, the luminescent pigments may also be non-magnetic, as in Fig. 5 shown. In this embodiment is missing compared with the embodiment of Fig. 4 the magnetic layer 54. The non-magnetic luminescent pigments 80 include a carrier substrate 52 made of mica, which with a covering white coating 56 from Titanium dioxide, a luminescent coating 58 and an optional further transparent coating is provided.

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

The non-magnetic luminescent pigments 80 may be mechanically aligned in the form of the desired luminescent motifs, as schematically shown in FIG Fig. 6 shown. For this purpose, the luminescent pigments 80 are first admixed with a UV-drying binder in order to formulate a flexographic or screen printing ink. This ink is then printed onto the background layer 40 in the desired form to form the effect layer 42. Immediately after printing, the platelet-shaped luminescent pigments 80 are oriented essentially parallel to the substrate surface. For alignment, in this case, a raised printing forme 82, for example a high-pressure or flexographic printing plate, is used, the elevations 84 of which are designed in a desired motif shape. By pressing the printing form 82 into the not yet hardened effect layer 42, the luminescence pigments 80 lying 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 ink is cured with the luminescent pigments and the orientation of the pigments 80 thereby permanently fixed.

With the described alignment methods also complex motifs can be generated. For example, the magnetic or mechanical orientation of the luminescent pigments 50, 80 in the form of characters or Codings are done. In the case of a magnetic alignment, for example, a suitable structured mask can be used for this purpose, which only transmits the magnetic field which aligns the pigments in certain areas. In the case of a mechanical alignment, a printing forme 82 with suitably shaped elevations 84 can be used, wherein in the case of larger surfaces to be aligned, a plurality of closely adjacent point or line elevations is advantageously used to ensure the desired alignment of the platelet-shaped pigments over a larger surface area.

FIG. 7 shows a modification of the embodiment of Fig. 2 in which the luminescent pigments 50, 80 are oriented vertically in a region 25 which is designed in the form of the lettering "Euro". In the case of oblique illumination with a UV light source, substantially all luminescent pigments 50, 80 are excited to luminescence independently of their orientation, so that the yellow luminescent ellipse 22 of FIG Fig. 2 (a) appears in front of a green luminescent background 24. In the case of vertical illumination, by contrast, the luminescent pigments of region 25 are practically not excited due to their perpendicular orientation, so that this region, like the background, luminesces green. This results in the Fig. 7 illustrated second luminescence motif 30, which shows a green luminescent lettering "Euro" within a yellow luminescent ellipse 22.

If the user moves the UV Hand Lamp from an oblique illumination position, such as position 70A in FIG Fig. 3 , in a vertical lighting position, such as the position 70B in Fig. 3 , the lettering "Euro" seems to appear from nowhere (change from the luminescence motif 20 of the Fig. 2 (a) to the luminescent motif 30 of the Fig. 7 ) and moving on back in an oblique illumination direction disappear again (change of the luminescence 30 of the Fig. 7 to the luminescent motif 20 of FIG Fig. 2 (a) ).

In real designs, the regions of different orientation of the luminescent pigments 50, 80, such as regions 26 and 28 of FIG Fig. 3 , usually not sharp-edged separated, but have a flowing, blurred or blurred transition. The transition region between the regions of different orientation has, in particular, a width between 20 μm and 5000 μm. The size of the transition region depends in particular on the method used to align the pigments (mechanically by embossing in the uncured state of the ink or by magnetic orientation of the pigments), substrate smoothness, substrate wetting, substrate absorbency and time delay between orientation and fixation of the pigments in the ink matrix or the binder.

In a further development, the orientation of the luminescent pigments 50 can also be transferred virtually continuously from a horizontal to a vertical orientation, as in the luminescence feature 90 of FIG Fig. 8 (a) shown. The luminescence feature 90 is up to the particular orientation of the Lumineszenzpigmente 50 as the luminescent feature 16 of Fig. 3 educated. The continuous change in orientation shown can be generated, for example, with a cylindrical magnet which is arranged below the banknote paper 12 with its longitudinal axis parallel to the surface of the banknote paper.

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

Of course, depending on the specific orientation of the luminescent pigments 50, other motion effects can also be generated. For example, by alignment with a cylindrical magnet arranged above the banknote paper 12, an in Fig. 8 (b) opposite running strip 96 are generated. By aligning with spherical magnets can produce annular moving luminescence pattern, which also often convey a three-dimensional image impression. Common to all these visual effects is that they are easy for a user to capture and test, but very difficult for a potential counterfeiter to duplicate, since such visual effects can not be produced with the commonly available fluorescent inks.

In the embodiments in which the platelet-shaped luminescent pigments 50, 80 on a background layer 40 with a luminescent agent In particular, the emission color of the luminescent agent of the background layer 40 may differ from the emission color of the luminescent pigments 50, 80. Regarding Fig. 3 In the case of a substantially vertical UV excitation 70B, a luminescent color predominantly corresponds to the luminescent color of the luminescent pigments 50 in regions 26, since these are excited much more strongly than the luminescent agent of background layer 40. By contrast, the region 28 predominantly shows the luminescence color of the background layer 40, since the luminescent pigments in this region are excited much less strongly by means of UV radiation.

Since the 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 matched to one another.

In transition areas between the areas 26 and 28, an equilibrium of the luminescent colors involved can also be set, so that in these areas, for example, a green and a red luminescence color adds to a yellow luminescent mixed color. The region 26 then shows, for example, a red luminescence, the region 28 a green luminescence and the intermediate transition region a yellow luminescence, so that the transition region acts as a differently colored corona for the region 26 or 28.
In other embodiments, the background layer 40 may also be dispensed with, or the background layer formed non-luminescent. Also in these cases, the luminescence feature shows a different intensity distribution and / or color of the luminescence. Regarding Fig. 3 For example, in the absence of a luminescent background layer 40 after a substantially perpendicular UV excitation 70B, the regions 26 show a significantly higher luminescence intensity than the region 28, since in area 28 only the edge surfaces of the pigments are excited to illuminate and the luminescence is therefore opposite to that Areas 26 is strongly suppressed.

1. 1) Die Lumineszenzpigmente 50 werden durch die einfallende UV-Strahlung angeregt und die emittierte Lumineszenzstrahlung wird direkt zur Anregungsseite zurückgeworfen.
2. 2) Die Lumineszenzpigmente 50 werden durch die einfallende UV-Strahlung angeregt, ein Teil der Lumineszenzstrahlung wird zur farbigen Untergrundschicht 40 hin emittiert, durch die Untergrundschicht 40 gefiltert und schließlich vom Substrat 12 zur Anregungsseite zurückreflektiert.
3. 3) Ein Teil der einfallenden UV-Strahlung wird von der farbigen Untergrundschicht 40 transmittiert, von dem Substrat 12 zur Anregungsseite hin reflektiert und die Lumineszenzpigmente 50 werden durch diese reflektierte UV-Strahlung zur Lumineszenz angeregt. Ist die Untergrundschicht 40 farbig und zugleich UV-absorbierend ausgebildet, so fällt dieser Beitrag zur Gesamtlumineszenz weg und die Leuchtintensität ist im Bereich 26 entsprechend geringer.

If the background layer 40 is colored but non-luminescent, then in the regions 26 (see FIG. Fig. 3 ) the following interactions take place, which contribute to an overall color impression:

1. 1) The luminescent pigments 50 are excited by the incident UV radiation and the emitted luminescence radiation is reflected directly back to the excitation side.
2. 2) The luminescent pigments 50 are excited by the incident UV radiation, a part of the luminescence radiation is emitted towards the colored background layer 40, filtered through the background layer 40 and finally reflected back from the substrate 12 to the excitation side.
3. 3) A portion of the incident UV radiation is transmitted from the colored background layer 40, reflected from the substrate 12 to the excitation side and the luminescent pigments 50 are excited by these reflected UV radiation for luminescence. If the background layer 40 is colored and at the same time UV-absorbing, this contribution to the total luminescence does not occur and the luminous intensity in the region 26 is correspondingly lower.

In the embodiments described so far, the effect layer of the luminescent feature always contains luminescent pigments 50, 80 which luminesce after excitation in one or more colors. This luminescence can be determined by the luminescence of a background layer arranged under the effect layer be supplemented, so that results in certain lighting directions additive color mixing of luminescent.

In the embodiments described below, the effect layer can also contain, as platelet-shaped effect pigments, non-luminescent UV-absorbing pigments which modify the luminescence of a background layer depending on the direction of illumination. The non-luminescent UV-absorbing pigments can otherwise be used and used like the luminescence pigments already described and, in particular, can also be magnetically or mechanically aligned.

FIG. 9 (a) shows a first embodiment of such a non-luminescent UV-absorbing pigment 100, which is magnetically aligned by a magnetic layer. The pigment 100 contains as its core a carrier substrate 52 made of mica, which is provided with a magnetic layer, for example a magnetite layer 54, which allows magnetic alignment of the pigment 100 in an external magnetic field. The magnetite layer 54 is, again completely enclosed, surrounded by a covering white coating 56 of titanium dioxide, which gives the pigment 100 a white appearance under normal illumination. The desired UV-absorbing properties are provided to the pigment 100 by a coating 102 surrounding the TiO ₂ coating with a UV absorber 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 microns and a thickness d = 0.4 microns, so an aspect ratio AV = 1 / d = 50.

In addition to the UV-absorbing pigments 100, the opaque white coating 56 may also be absorbing in a (partial) region of the UV spectrum. Thus, depending on the desired degree of absorption, TiO ₂ can be used, for example, in various modifications, in particular in the rutile or anatase modifications. Rutile absorbed in complete and anatase only in the short to medium wave UV wavelength range. By using the corresponding opaque coatings 56, excitation wavelength-specific and at the same time illumination-direction-selective luminescence features can be generated.

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

If the non-luminescent UV-absorbing pigments are mechanically aligned, then the magnetic layer can be omitted, as in Fig. 9 (b) shown. The non-magnetic UV-absorbing pigments 104 of the Fig. 9 (b) include a support substrate 52 made of mica, a covering white coating 56 of titanium dioxide, a coating 102 having a transparent in the visual spectral range UV absorber and optionally a further transparent coating.

For example, in the embodiment of Fig. 7 instead of the luminescent pigments 50, the non-luminescent UV-absorbing pigments 100 of FIG Fig. 9 (a) used, as result in oblique lighting or in vertical illumination with UV radiation, the in Fig. 10 illustrated luminescent motifs 110 and 120th

Regarding Fig. 10 (a) shows the luminescence feature in UV illumination from an oblique angle in the background region 24, the green luminescence of the substrate layer 40. In the area of the ellipse 22 occurs substantially no luminescence, since the UV-absorbing pigments 100 absorb the incident UV radiation and for the most part do not let the background layer 40 through. The wording "for the most part" takes account of the fact that due to the desired ink layer thickness and pigment concentration in the area of the ellipse 22, complete absorption of the green luminescence of the background layer 40 by the UV-absorbing pigments 100 can generally not be achieved.

In the case of a substantially vertical UV illumination, however, the pigments 100 oriented vertically in the region 25 allow the excitation radiation to pass through practically unimpaired, so that the luminescent agent of the background layer 40 is excited to emit light, and within the non-luminescent ellipse 22 a green luminescent lettering " Euro "shows how in Fig. 10 (b) shown.

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

Finally, it is also possible to use pigments 130 which combine luminescent properties and UV-absorbing properties. Regarding Fig. 11 contains such a combination pigment 130 as a core a carrier substrate 52 made of mica, which is provided with a magnetite layer 54, a covering white coating 56 of titanium dioxide, a luminescent coating 132 and a coating 134 with a transparent in the visual spectral range UV absorber. The luminescent coating 132 can be excited in 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 region 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 at the same time illumination direction-selective luminescence features can be generated.

If a corresponding luminescence feature is illuminated, for example, with long-wave UVA radiation having a wavelength of 366 nm in which the coating 134 is not absorbed, the luminescence of the luminescent coating 132 of the combination pigments 130 is excited and the reference is made to FIG FIGS. 2 to 8 already described effects. On the other hand, if the luminescent feature is illuminated with short-wave UVC radiation having 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 thus act at this excitation wavelength not as luminescent pigments, but as non-luminescent UV-absorbing pigments, so that now the at FIG. 10 described Effects result. Since different visual effects occur depending on the excitation wavelength, the counterfeiting security of security elements according to the invention is further increased by the use of such combination pigments.

The combination pigment 130 of the Fig. 11 has a magnetic layer 54 and is therefore magnetically alignable. It is understood, however, that the magnetic layer can also be missing in combination pigments and the non-magnetic combination pigments can be mechanically aligned, as above in connection with the Figures 5 and 9 (b) already described for luminescent pigments 80 or UV-absorbing pigments 104.

LIST OF REFERENCE NUMBERS

10

bill

12

Banknote paper

14

security element

16

Lumineszenzmerkmal

20

first luminescence motif

22

luminescent ellipse

24

background

25

Area in the form of the word "Euro"

26

side pieces

28

central area

30

second luminescence motif

40

Background layer

42

effect layer

44

binder

50

luminescent pigments

52

carrier substrate

54

magnetite

56

opaque white coating

58

luminescent

60

optional transparent coating

70

UV hand lamp

70A, 70B

illumination directions

80

non-magnetic luminescent pigments

82

printing form

84

surveys

90

Lumineszenzmerkmal

92

lighting position

93

Direction of movement UV hand lamp

94

Area of the effect layer

96

strip

97

Direction of movement stripes

100

UV-absorbing pigments

102

Coating with UV absorber

104

non-magnetic UV-absorbing pigments

110

first luminescence motif

120

second luminescence motif

130

Combined pigment

132

luminescent

134

Coating with UV absorber

Claims (18)

Security element for securing security papers, documents of value and other data carriers, with a light direction selective luminescence feature that shows different luminescence motifs when illuminated with UV excitation radiation from different illumination directions, wherein the luminescence feature a luminescent material which emits luminescent radiation upon illumination with UV excitation radiation, and in an effect layer contains a multiplicity of flake-form effect pigments which are aligned in the form of the desired luminescence motifs, wherein the effect pigments are luminescent pigments, non-luminescent UV-absorbing pigments or combination pigments which can be excited to luminescence in a first UV wavelength range and are non-luminescent and UV-absorbing in a second UV wavelength range. A security element according to claim 1, characterized in that the platelet-shaped effect pigments have an aspect ratio which is more than 5: 1, preferably more than 10: 1 and more preferably between 20: 1 and 400: 1. A security element according to claim 1 or 2, characterized in that the effect pigments are magnetically alignable and contain a soul with a magnetic material. Security element according to claim 3, characterized in that the magnetic material is provided on at least one of the main surfaces, preferably at least on both major surfaces with a covering coating, in particular a white or colored opaque coating. A security element according to claim 1 or 2, characterized in that the effect pigments are non-magnetic and contain a platelet-shaped core. Security element according to claim 5, characterized in that the platelet-shaped core is provided at least on one of its main surfaces, preferably at least on both major surfaces with a covering coating, in particular a white or colored opaque coating. A security element according to at least one of claims 4 to 6, characterized in that the effect layer is at least partially disposed over a background layer, and the visually visible color of the opaque coating of the effect pigments substantially corresponds to the visually visible color of the background layer. Security element according to at least one of claims 1 to 7, characterized in that the luminescence motifs are not visible without illumination with UV excitation radiation. A security element according to at least one of claims 1 to 8, characterized in that the effect pigments are luminescent pigments or combination pigments which form said luminescent material. A 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 arranged at least partially over a background layer with said luminescent material. A security element according to claim 10, characterized in that the luminescence of the luminescent pigments or combination pigments differs from the luminescence of the background layer in the excitation wavelength, the emission wavelength, and / or the decay time. A 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 luminescent agent is arranged on the opaque coating, or admixed with the opaque coating. A 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 luminescent agents which differ by the excitation wavelength, the emission wavelength, and / or the decay time. A 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 partially disposed above a background layer with said luminescent material. Security element according to at least one of claims 1 to 14, characterized in that a further layer with a third luminescent agent is at least partially disposed over the effect layer. A security element according to claim 15, characterized in that the luminescence of the third luminescence means 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. Data carrier with a security element according to at least one of claims 1 to 16. Method for producing a security element according to one of Claims 1 to 16, in which on an optionally provided with a substrate layer substrate, an effect layer is applied, which contains a plurality of platelet-shaped effect pigments, - Wherein the effect pigments are luminescent pigments, non-luminescent UV-absorbing pigments or combination pigments which can be excited to luminescence in a first UV wavelength range and are non-luminescent and UV absorbing in a second UV wavelength range, and - The effect pigments are magnetically or mechanically aligned in the form of the desired Lumineszenzmotive and fixed in the aligned orientation.

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