EP2768678A1

EP2768678A1 - Method for producing an optically variable security element having a microcapsule-based ink layer and thus obtained security element

Info

Publication number: EP2768678A1
Application number: EP12773209.7A
Authority: EP
Inventors: Alexander Bornschlegl; Christoph Mengel
Original assignee: Giesecke and Devrient GmbH
Current assignee: Giesecke and Devrient GmbH
Priority date: 2011-10-20
Filing date: 2012-09-24
Publication date: 2014-08-27
Also published as: DE102011116494A1; WO2013056779A1

Abstract

The invention relates to a method for producing an optically variable security element (14) having a microcapsule-based ink layer (34), and the thus obtained security element, wherein • U) a base layer (30, 32) is applied to a substrate • F) a microcapsule-based ink layer (34) is applied to the base layer (30, 32), which contains, in a binding agent, a plurality of microcapsules (36) which respectively have a capsule covering (38), a carrier liquid (40) closed in the capsule cover and a plate-shaped pigment (42; 60; 82) which can be magnetically aligned and which can be essentially freely rotated in the microcapsule (36) and can be reversibly aligned due to the effect of an external magnetic field (62), • M) an external magnetic field (62) is applied in order to align the rotatable pigments (42; 60; 82) in the microcapsules (36) at least in a sub-area of the ink layer (34), and • L) at least part (92) of the pigments and/or at least one sub-area (68; 94) of the base layer is modified, by laser exposition (64) with a marking laser, in the sub-area comprising the aligned pigments (60).

Description

METHOD FOR PRODUCING AN OPTICAL VARIABLE SAFETY ELEMENT WITH A MICROCAPSE-BASED COLOR LAYER AND SAFETY ELEMENT THEREFOR PREVENTED

The invention relates to a method for producing an optically variable security element with microcapsule-based ink layer. The invention further relates to a security arrangement with such a security element and a correspondingly equipped data carrier.

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

Security elements play a special role in authenticity assurance, showing visual effects that depend on the viewing angle, as they can not be reproduced even with state-of-the-art copiers. For some time, encapsulated magnetically orientable effect pigments have been used for this purpose, which can be magnetically aligned in the form of a motif to be displayed.

25

Proceeding from this, the object of the invention is to specify a method for producing optically variable security elements with a microcapsule-based ink layer with which such security elements with an attractive visual appearance and high counterfeit security 30 can be produced. This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

According to the invention, it is provided in a method for producing an optically variable security element with a microcapsule-based ink layer

U) a subbing layer is applied to a substrate F) a microcapsule-based ink layer is applied to the subbing layer containing, in a binder, a plurality of microcapsules each having a capsule shell, a carrier liquid enclosed in the capsule shell, and a magnetically orientable platelet Pigment, which is substantially freely rotatable in the microcapsule and reversibly alignable by an external magnetic field, an external magnetic field is applied to align the rotatable pigments in at least a portion of the color layer in the microcapsules, and in the portion with the aligned pigments Laser application of a marking laser at least a portion of the pigments and / or at least a portion of the background layer is modified.

In this case, each laser-induced, visually visible or machine detectable change in the pigments or the background layer is a modification. Although in the present application, the modification due to the variety of advantages by laser exposure, ie by means of laser radiation, it is understood that other electromagnetic radiation can be used in principle for modification. In this connection, it would be conceivable, for example, to modify the undercoat layer and / or the pigments by exposure by means of suitable radiation, for example ultraviolet radiation. In this case, for example, suitable UV radiation sources are used, which is not a laser. By way of example, suitable UV lamps are conceivable which, when a suitable mask is used, make possible the partial modification of the undercoat layer or the pigments. Typically, the modification consists in a change in the color, the brightness or the reflection behavior (glossy / matt) of the pigments or the background layer. The changes that can be detected by machine can, for example, be changes that are detectable only in the infrared or ultraviolet wavelength range. Modifications of the pigments or of the background layer, which can only be detected by machine, are characterized by the fact that they provide high protection against counterfeiting for the modified security element, whereby the authenticity check of such a security element can be reliably carried out by suitable means for automatic detection.

In an advantageous variant of the method, a laser-modifiable background layer is applied in step U), preferably a background layer with infrared-absorbing printing inks and / or metal layers. In step L), at least a portion of the background layer is then advantageously modified by laser application, in particular destroyed or bleached. Due to the modification of the background layer, in particular the contrast between a transparent state of the microcapsule-based ink layer, in which the pigments are perpendicular to the plane of the Color layer are aligned, and a non-transparent state of the microcapsule-based ink layer in which the pigments are aligned parallel to the plane of the ink layer, can be significantly increased, as shown in detail below.

If both the pigments and the background layer are modified by laser application, in particular a motif can be introduced into the background layer and the color layer at the same time and with registration accuracy. If only the pigments are modified, it is possible in particular for a motif to be introduced into the ink layer which is only visible in certain orientations of the pigments.

According to an expedient embodiment, a microcapsule-based ink layer is applied in step F) whose platelet-shaped pigments are reflective for the wavelength of the marking laser. The reflective pigments can be formed in particular by oxidic multilayer interference-layer pigments.

According to another, likewise expedient embodiment, a microcapsule-based ink layer is applied in step F), the platelet-shaped pigments of which are laser-modifiable with the marking laser. The laser-modifiable pigments can be formed in particular by multilayer interference pigments with metallic layers. The encapsulated pigments are preferably platelet-shaped, the ratio of the largest to the smallest diameter (diameter-to-thickness ratio) of the platelet-shaped pigments being more than 4: 1, preferably more than 10: 1, and particularly preferably between 20: 1 and 200 : 1 is. The largest diameter of the platelet-shaped pigments lies preferably between 2 μπ \ and 150 μπι, in particular between 5 μηι and 50 μιη.

In a preferred embodiment it is provided that the pigments are stabilized by a suitable treatment, in particular the coating of the surface of the pigments, so that the magnetic and optically variable properties of the pigments according to the invention can be maintained for as long as possible. It is also conceivable to stabilize the microcapsules in general or the pigments in particular by a stabilizer added to the carrier liquid.

According to a further, likewise expedient embodiment, a microcapsule-based ink layer is applied in step F), the binder of which contains particles which have a scattering or absorbing effect at the wavelength of the marking laser. The scattering or absorbing particles may in particular be formed by titanium dioxide or iron oxide particles. In the visible spectral range, the particles are preferably inconspicuous.

In all embodiments, the microcapsule-based ink layer is advantageously applied by screen printing or flexographic printing. The microcapsules themselves have a diameter between 1 μπι and 200 μπν, preferably between 2 μπι and 80 μπι on. It is understood that the diameter of the microcapsules is advantageously matched to the size of the encapsulated pigments. The wall thickness of the microcapsules is typically between 2% and 30%, preferably between 5% and 15% of the diameter of the microcapsules.

Advantageously, in step M), the pigments are aligned at least in a partial region of the ink layer perpendicular to the loading direction of the marking laser in step L). This will be in this area a achieves a particularly high level of interaction between laser radiation and pigments. Also advantageously, in step M), the pigments are aligned at least in a partial region of the ink layer parallel to the direction of impingement of the illumination laser in step L). As a result, a particularly high permeability of the color layer for the laser radiation is achieved in this area and thus enables a high level of interaction between the laser radiation and the background layer.

In advantageous embodiments, the pigments in step M) are aligned differently in different subregions of the ink layer, so that different effects in the different subregions can be generated simultaneously by the laser application.

Of course, the microcapsules may each contain a plurality of pigments, for example a magnetically alignable and an optically variable pigment. It is also possible to use in a security element encapsulated pigments having different properties, in particular different magnetic properties or different interaction strengths with the radiation used, so that first and second information are introduced into the security element by different strong radiation or by the different properties of the pigments can.

The laser application can be made over the entire surface, so that the different Lehe influencing of pigments and background layer is only generated by the magnetic orientation of the pigments. In some embodiments, however, it may be advantageous if the laser application in step L) takes place in a subarea in the form of patterns, characters or an encoding. The radiation itself can be full surface and the Subregion are selected by a suitable mask with predetermined, transmissive to the radiation areas. Alternatively, a suitably focused beam in the form of the portion to be modified can be guided over the security element.

In all embodiments, the background layer in step U) is advantageously applied in the form of information, in particular a pattern, a character or a coding. Suitable application methods for the background layer are, in particular, screen printing, flexographic printing or intaglio printing.

For the laser application in step L), preferably an infrared laser is used as the marking laser, preferably an infrared laser in the wavelength range from 0.8 μm to 3 μm, such as a Nd: Y AG laser or Nd: YV04 laser. Preferably pulsed marking lasers are used. The laser parameters, in particular wavelength, power density, pulse duration and exposure time, and the materials of pigments and substrate are suitably matched to one another depending on the desired modification (only pigments, only background layer or both).

In all variants of the present invention, a translucent or transparent carrier liquid can be used. Also conceivable is an opaque carrier liquid. However, the perception of the pigments enclosed in the microcapsules is generally considerably impaired by an opaque carrier liquid. At present, therefore, microcapsules with a transparent carrier liquid are particularly preferred, since this allows a particularly good perception of the pigments by the viewer. The very high recognition value therefore further increases the counterfeit protection of the security element in such embodiments. In the above discussion of the carrier liquid it is understood, with regard to the capsule shell, that it must be transparent or translucent in order to enable the viewer to perceive the carrier liquid or the magnetically orientable pigments.

In the context of the present invention, a "transparent" material is understood as meaning a material which allows substantially complete passage of incident electromagnetic radiation at least in the visible wavelength range from about 380 nm to about 780 nm In the present invention, in particular a "transparent" carrier liquid, the transmittance is T> 0.8, where T is defined as the quotient of the radiant power L transmitted through the material and the radiant power Lo radiated onto the substrate This exact definition of the transmittance (T = L / Lo) corresponds to the definition given in "Lexikon der Optik", Spektrum Akademischer Verlag, Heidelberg 2003, volume 2, page 366, term "transmittance".

In the context of the present invention, an "opaque" or "opaque" material has a transmittance T <0.1, where T is defined as the quotient L / Lo (see above). In the context of the present invention, therefore, an opaque material does not substantially transmit incident electromagnetic radiation, at least in the visible wavelength range from about 380 nm to about 780 nm. A "translucent", "translucent" or "semitransparent" material, in particular a "translucent" carrier liquid, in the context of the present invention, at least in the visible wavelength range of about 380 nm to about 780 nm, a transmittance T greater than 0.1 and smaller 0.8 on, ie 0.1 <T <0.8. It should also be noted here that the subjective perception of a transparent, translucent or opaque material by a viewer may in some cases deviate significantly from the exact definition given above for transparent, translucent or opaque material. In the case of series of measurements that led to the definition of the transmittances listed above for transparent, translucent and opaque materials, it was found that the subjective perception of a transparent, translucent or opaque material depends very much on the lighting situation, ie whether the material is viewed by the viewer in reflection, transmission or in a combination of reflection and transmission. For example, a viewer under certain circumstances perceives a security element as transparent, even if the transmittance of the security element is more than z. B. is 0.7, ie, less than 30% of the incident light is reflected or absorbed. The same applies to a carrier liquid with a transmittance of 0.7. Such a transparent to the viewer carrier liquid is then optionally a translucent material in the sense of the definition given above (0.1 <T <0.8). In addition, the light scattering of the observed material has a similarly large influence on the subjective perception of a viewer because, among other things, the scattering influences the contrast between light and dark areas of the viewed material. Irrespective of the possible difference between the subjective perception of a viewer and the above definitions of transparent, translucent or opaque materials, all the variants according to the invention described in the context of this application can be carried out, ie can be easily reproduced by the person skilled in the art. With regard to the carrier liquid contained in the microcapsules it should be noted at this point that in all variants of the invention in this carrier liquid additional security features may be included, which give the microcapsule and the security element produced therewith an additional functionality, in particular a further increased counterfeit protection. For example, the carrier liquid may have a special colorant or a luminescent, in particular fluorescent material. Also conceivable is a material which can be influenced by means of electromagnetic radiation, in particular laser radiation, in a physical size, in particular in its color. For example, in such a material the exposure to electromagnetic radiation, in particular laser radiation, could lead to a color change of the substances present in the carrier liquid, so that the viewer can see the areas of the security element which contain microcapsules charged with electromagnetic radiation from the areas without application can distinguish with electromagnetic radiation, ie the viewer perceives the acted upon by radiation or not acted areas in a different color. It is understood that the additional substances provided in the carrier liquid can alternatively or additionally be provided in the capsule shell of the microcapsules. That is to say that the capsule shell can have, for example, a colorant, a luminescent, in particular fluorescent material or a material which can be marked by electromagnetic radiation, in particular laser radiation. Also by the provision of the above-mentioned substances in the capsule shell, a further functionality for the microcapsule can be provided. The additional functionality of the capsule shell or of the carrier liquid (see above) contributes synergistically Increase the protection against counterfeiting of the invention described in the present application.

The invention also includes a security arrangement for securing security papers, documents of value and the like, with a security element which can be produced according to a method described above, and with a verification element with a magnetic area. Magnetic material advantageously has magnetic material in the form of patterns, lines, characters or a coding. The motif represented by the magnetic material may be openly visible to a viewer or hidden even without aids, for example by covering with a dark printing layer. Preferably, the magnetic region is magnetized substantially perpendicular to the plane of the verification element. The invention further comprises a data carrier, in particular a value document, such as a banknote, a passport, a document, an identification card or the like, which is equipped with a security element that can be produced according to a method described above or with a security arrangement of the type described. If the data carrier contains both a security element according to the invention and an associated verification element, these are advantageously geometrically arranged on the data carrier such that the security element can be brought over the verification element by bending or folding the data carrier. Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation in terms of scale and proportions has been dispensed with in order to increase the clarity. Show it:

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

2 shows a cross section through a security element with a reversible change of the visual appearance, in the left half without and in the right half with Verifier,

3 shows an intermediate step in the production of a security element with a method according to the invention,

Fig. 4 in (a) and (b) the appearance of the background layer of

3 before the laser application and in (c) and (d) after the laser application,

5 (a) to (c) show a further exemplary embodiment of the invention in which a motif is introduced into the background layer as well as into the ink layer both simultaneously and precisely by the magnetic field-induced transparency change, and

Fig. 6 in (a) to (e), a further embodiment of the invention, in which a motif is introduced only in the microcapsule-based ink layer.

The invention will now be explained using the example of security elements for banknotes and other value documents. 1 shows a schematic representation of a banknote 10 with a directly onto the banknote pallet. However, the invention is not limited to printed security elements and bank notes, but can be used in all types of security elements, for example, labels on goods and packaging or in the hedge of documents, passports, passports, and the like.

In particular, the invention can also be used with cards such as identity cards, bank cards, credit cards, health cards or driver's licenses. In addition to printed elements, for example, transfer elements, security threads or security strips and also supervisory elements in addition to supervisory elements in question.

Returning to the illustration of FIG. 1, the security element 14 contains a reversible authenticity mark which can be interactively triggered by a magnetic verification device (FIG. 2). Without a verification device, the security element 14 shows a uniform appearance, for example a metallic luster. If the security element 14 is placed on the magnetic verification device by a user, the visual appearance of the security element 14 is changed interactively and reversibly. In the exemplary embodiment, the metallic luster of the security element 14 disappears when it is placed on the verification device and an information-carrying base layer 16 with the denomination "5" of the banknote becomes visible, as shown by dashed lines in FIG Verification device 20, turns after a short time, the uniform initial state again, in which the sub-base layer 16 is hidden from the viewer. The structure of the security element 14 and the occurrence of the reversible change in the visual appearance will now be explained in more detail with reference to the cross-sectional view of Fig. 2. In this case, the left half of the figure shows the security element 14 without Verificationsein- device 20 or a region 28 away from the magnet 20, while the right half shows a portion 26 of the security element, which is located directly above the magnet 20.

On the banknote paper 12 of the banknote 10, a background layer 30 is applied in the area of the security element 14, which may contain any information, such as a representation of the denomination "5" of the banknote 10. The background layer 30 may consist of one or more colors exist and is typically applied in offset, Letterset-, flexo or intaglio.

By way of this background layer 30, a color layer 34 which is largely opaque under normal conditions and applied on a microcapsule is applied by screen printing. The ink layer 34 contains a multiplicity of microcapsules 36 which each have a capsule shell 38, a carrier liquid 40 enclosed in the capsule shell 38 and at least one platelet-shaped, magnetically alignable pigment 42. The pigments 42 are substantially freely rotatable in the microcapsules 36 and can be reversibly aligned by an external magnetic field, such as the field 22 of the magnet 20. In the exemplary embodiment shown, the pigments 42 are platelet-shaped iron pigments prepared from reducing-treated carbonyl iron powder with a high ratio of platelet diameter to platelet thickness of 20: 1 or more. The (largest) plate diameter is preferably between 2 μπ \ and 150 μπι, in particular between 5 μιη and 50 μη, and the platelet thickness is preferably between 40 nm and 1.5 μητι, in particular between 200 nm and 1.3 μτ ^η .

Depending on the intended application, the pigments 42 may be mono- or multi-layered and, in the latter case, have at least one non-magnetic layer in addition to at least one magnetic layer. For example, oxide multilayer interference pigments can be used as laser radiation-reflecting pigments, and multilayered interference pigments with metal layers can be used as laser radiation absorbing pigments.

Since the pigments 42 in the carrier liquid 40 within the capsule shell 38 are substantially freely rotatable, they have no preferential orientation without an external magnetic field, but rather are essentially random and thus altogether isotropically aligned. The uniform distribution of the orientation of the pigments 42 in all directions is shown schematically in the left half of FIG.

In the region 26 directly above the magnet 20, however, the magnetically alignable pigments 42 are magnetically aligned due to their free rotation in the capsule shell 38. In the situation shown in FIG. 2, the magnetic field lines 22 in the area 26 pass substantially perpendicularly through the ink layer 34 and thus also essentially orient the pigments 42 substantially perpendicular to the plane of the ink layer 34 (right half of FIG. 2).

Because of their platelet-like shape, the pigments 42 act to the viewer like the slats of a venetian blind, which look at the underlying release or block completely or partially. In regions 28 in which the pigments 42 are arranged substantially isotropically in their capsule shells 38 (left half of FIG. 2), they greatly limit the view of the background layer 30 that the color layer 34 in this region depends on the concentration Microcapsules 36 appears largely opaque and the metallic luster of the pigments 42 dominates the visual impression of the security element 14.

In region 26, in which the pigments 42 are oriented substantially perpendicular to the plane of the ink layer 34 by the magnet 20, they, like the slats of a blind placed in parallel, provide a view of the underlying background layer 30 and the representation of the denomination "5 Because of the large ratio of platelet diameter to platelet thickness of 20: 1 or more, there is a high contrast between opaque subregions 28 and translucent subregions 26. In addition, the motif created by platelet alignment in subregions 26, 28 appears to be human When the security element 14 is removed again from the magnet 20, the magnetically oriented pigments 42, due to their mobility within the capsule shell 38, after some time relax back to the essentially isotropic initial state of the left half of FIG 2. The change in the visual appearance of the security element 14 is thus triggered interactively and is completely reversible. The rate at which the pigments 42 return to their initial state can be adjusted as desired, for example, by the viscosity of the carrier liquid 40 to a large extent. Fig. 2 illustrates the change in visual appearance when viewing a finished security element 14. However, the present inventors have surprisingly found that magnetic alignment of the platelet pigments 42 can also be used to advantage in the production of microcapsule-based color coat security elements.

The invention is based on the observation that a microcapsule-based ink layer 34 defined by an external magnetic field of a transparent state in which the pigments 42 are aligned perpendicular to the plane of the ink layer (right half of FIG. 2, magnetic field perpendicular to the color layer plane ) can be converted into a non-transparent state, in which the pigments 42 are aligned parallel to the plane of the ink layer (magnetic field parallel to the color layer plane). This property can be exploited in order to specifically modify the background layer 30 (in the transparent state of the ink layer 34) and / or the pigments 42 themselves (in the non-transparent state of the ink layer 34) during the manufacturing process of the security element 14 by laser application of magnetically aligned regions ,

In a first embodiment described with reference to Figures 3 and 4, the magnetic field-induced transparency change allows to significantly increase the contrast of the interactively representable information.

4 (a) shows the appearance 50 of a background layer 30 of a security element 14 with a printed information 32 in the form of the letter "a" in the transparent state of the ink layer 34. Mente 42 are aligned in this case in the microcapsules 36 perpendicular to the ink layer 34 and give the view of the information 32 free unhindered.

If the pigments 42 in the microcapsules 36 are now aligned parallel to the color layer plane by a magnetic field, the microcapsules 36 largely block the view of the background layer 30, as shown schematically in FIG. 4 (b). However, as a rule, even with highly pigmented color layers 34, there are individual points 54 at which no microcapsules 36 are present. Even in the non-transparent state of the ink layer 34, a residual 56 of the information 32 can thus still be seen in the appearance 52 of the security element.

In order to be able to display the information 32 with a particularly high contrast between transparent and non-transparent microcapsule state, with reference to FIG. 3, a laser-modifiable background layer 30 with the desired information 32 is first applied to the substrate 12. The laser-modifiability of the background layer 30 can be, for example, that the information 32 is printed with an infrared-absorbing ink that can be destroyed or bleached, for example, by the infrared radiation of a Nd: Y AG laser used as a marking laser.

Onto this laser-modifiable undercoat layer 30 is applied a microcapsule-based ink layer 34 which contains in a binder a plurality of microcapsules 36 having platelet-shaped magnetizable pigments 60 which are highly reflective at the wavelength of the Nd: Y AG marking laser. Then, an external magnetic field 62 is applied which aligns the pigments 60 parallel to the plane of the color layer 34. In the aligned state of the pigments 60, the background layer 30 and the color layer 34 are exposed to laser radiation 64 of a Nd.Y AG marking laser, wherein the laser parameters, in particular power density, pulse duration and exposure time, are selected such that the highly reflective pigments 60 themselves are exposed by the laser radiation 64 are not changed, but that they reflect the irradiated laser light 64 as far as possible (reference numeral 66). On the other hand, outside of the microcapsules 36, the laser radiation 64 penetrates all the way down to the laser-modifiable background layer 30 and destroys the infra-red absorbing ink of the information 32 in the applied areas 68.

As a result, in the non-transparent state of the ink layer 34, the appearance 70 shown in FIG. 4 (c) is formed, in which the information 32 is just removed in the regions 68 outside of the microcapsules 36. In the non-transparent state of the ink layer 34, therefore, no or virtually no remainder of the information 32 is more visible. Although the destroyed regions 68 of the information 32 are also lacking in the appearance 72 of the background layer 30 in the transparent state of the color layer 34, as shown in FIG. 4 (d), in practice only a slight brightening of the information 32 shown.

By contrast, the contrast between transparent and non-transparent state is substantially increased by the described measure. If, for example, 5% of the information 32 is still visible after the application of background layer 30 and color layer 34 in the non-transparent state (situation of FIG. 4 (b)), then the contrast between the transparent and non-transparent state can be specified. If 4/5 of the applied areas 68 are destroyed by the laser application, ie 4% points with respect to the original information 32, only 1% of the original information is visible in the non-transparent state (situation of FIG. 4 (c)). ) and in the transparent state still 96% of the original information visible (situation of Fig. 4 (d)). The contrast after laser exposure has thus increased

Knach = 96% / 1% = 96, so almost increased by a factor of 5. This increase in contrast is much more important in the consideration than the slight brightening of the information 32 shown.

In this embodiment, for example, oxidic multilayer interference pigments with a magnetic layer which ensure magnetic alignment can be considered as highly reflective pigments 60. In addition to infrared-absorbing printing inks, the laser-modifiable background layer 30 may also contain metal layers, for example of aluminum, copper or gold. Due to the magnetic field 62, the pigments 60 are advantageously aligned perpendicular to the direction of incidence of the laser radiation 64 of the marking laser. When laser applied perpendicular to the ink layer 34, as shown in Fig. 3, the pigments are then aligned parallel to the color layer plane. If the laser application at a certain angle to the vertical, preferably also the pigments 60 are aligned by the magnetic field 62 correspondingly at a certain angle to the color layer plane.

The information is usually not completely destroyed by the laser radiation 64 in the applied areas 68 in practice, as already taken into account in the above calculation of the contrast ratio. The laser-induced change may, instead of destruction, also be a bleaching or other modification of the applied areas. The laser-modifiable background layer 30, the highly reflective pigments 60 and the laser parameters, in particular wavelength, power density, pulse duration and exposure time, are advantageously matched to one another such that a high modification of the background layer 30 is accompanied by a slight influence on the pigment 60. Under certain circumstances, a certain change in the pigments 60 can be accepted by the laser treatment.

FIG. 5 shows a further exemplary embodiment of the invention in which a motif can be introduced into the background layer 30 as well as into the ink layer 34 at the same time and in register by the magnetic field-induced transparency change.

The starting point is a security element 80 of the type shown in principle in FIG. 2, wherein the security element 80 contains a laser-modifiable background layer 30, for example a background layer with infrared-absorbing printing inks, with metal layers, such as aluminum, copper or gold, or with irreversible thermochromic dyes, combined with infrared absorbers. The microcapsules 36 of the microcapsule-based ink layer 34 in the exemplary embodiment of FIG. 5 contain platelet-shaped, magnetically alignable pigments 82, which are likewise laser-modified. bar are formed. For this purpose, for example, magnetic, multilayer interference pigments with metallic layers into consideration.

An external magnetic field 84 is then applied, which aligns the pigments 82 in a partial region 86 of the ink layer parallel to the plane of the ink layer 34 (left half of the image in FIG. 5 (a)) and in another partial region 88 perpendicular to the plane of the ink layer 34 (FIG. right half of Fig. 5 (a)). The partial regions 86, 88 forms a predetermined motif, for example a pattern of alternating strips 86, 88.

In the aligned state of the pigments 82, the background layer 30 and the color layer 34 are then exposed to laser radiation 90 of a marking laser at a normal angle of incidence. In the subregion 86 in which the pigments 82 are parallel to the color layer plane and thus perpendicular to the direction of the laser radiation 90, only the pigments 82 are predominantly modified by the laser radiation 90, as indicated by the white filling of the modified pigments 92 in FIG hardly laser radiation 90 penetrates to the background layer 30 (left half of the figure in Fig. 5 (a)). The modification of the pigments may be, for example, a laser-induced change in color, brightness or gloss.

On the other hand, in the partial region 88 in which the pigments 82 are oriented perpendicular to the color layer plane and thus parallel to the laser radiation 90, the color layer 34 is transparent, so that the laser radiation 90 reaches and modifies the background layer 30, as shown in the figure by the narrow hatching the modified background layer 94 indicated (right half of the figure in Fig. 5 (a)). The modification of the background layer can consist, for example, of a laser-induced change in color, brightness or gloss. If, when viewing the security element 80, the pigments 82, 92 are now aligned parallel to the color layer plane by an external magnetic field 84, as shown in FIG. 5 (b), the pigments 82, 92 block the view of the background layer 30. The viewer gazes Therefore, in the portion 86 on the modified pigments 92 and in the partial area 88 on the unmodified pigments 82, so that the stripe pattern formed by the portions 86, 88 due to the different appearance of the pigments 82, 92 appears with a first visual impression. On the other hand, when the pigments 82, 92 are aligned perpendicular to the color layer plane by an external magnetic field 84, as shown in Fig. 5 (c), the pigments 82, 92 release the view of the background layer 30. The observer therefore looks in the partial area 86 at the unmodified background layer 30 and at the partial area 88 at the modified base layer 94, so that, depending on the design and modification of the background layer 30, the striped pattern formed by the partial areas 86, 88 has a second visual impression occurs.

By simultaneously producing the modification of the pigments 82 and the background layer 30, the modified areas of the color layer 34 and background layer 30 are in perfect register.

In the embodiment of FIG. 6, a motif is introduced only into the micropump-based ink layer 34. The starting point is a security element 100 of the type shown in principle in FIG. 2, wherein the security element 100 contains an arbitrary background layer 30. On the background layer 30, a microcapsule-based ink layer 34 is applied, whose microcapsules contain platelet-shaped, magnetically alignable and laser-modifiable pigments 82, for example magnetic, multilayer interference pigments with metallic layers. The binder 102 of the color layer 34 in this embodiment contains particles 104 which are barely visible to a viewer but which have a strong scattering or absorbing effect at the wavelength of the marking laser. The particles 104 may be formed for an Nd: Y AG marking laser, for example, from titanium dioxide or iron oxide.

To introduce the motif into the ink layer 34, an external magnetic field 84 is applied, which aligns the pigments 82 of the ink layer parallel to the plane of the ink layer 34. In the aligned state of the pigments 82, the color layer 34 is then subjected to the laser radiation 108 of the Nd: YAG marking laser in a subregion 106 corresponding to the motif. The partial region 106 can form, for example, the denomination "5" of the banknote 10. The laser parameters, in particular the power density, pulse duration and exposure time, are selected so that the pigments 82 are modified in the desired manner (reference symbol 92).

Due to the scattering or absorbing action of the particles 104, the energy of the laser radiation 108 is distributed in the ink layer 34, so that the laser radiation 108 in the background layer 30 arrives only with an intensity which is not sufficient for a visible change.

If, when viewing the security element 100, the pigments 82, 92 are then aligned by an external magnetic field 84 perpendicular to the color layer plane, as shown in FIG. 6 (b), the pigments 82, 92 release the view of the background layer 30. The observer thus sees information possibly contained in the background layer 30, for example the logo 32 shown in the plan view of FIG. 6 (c). On the other hand, when the pigments 82, 92 are aligned parallel to the color layer plane by an external magnetic field 84, as shown in Fig. 6 (d), the pigments 82, 92 obstruct the view of the background layer 30. The observer therefore looks in the partial area 106 due to the different appearance of the pigments 82, 92 now appears to the viewer the motif formed by the portion 106 in the form of the denomination "5", as in the plan view of Fig. 6 (e).

It should also be noted that in the context of the present invention the background layer can be applied to any substrates, in particular paper, plastic or a paper-plastic composite.

LIST OF REFERENCE NUMBERS

10 banknote

12 banknote paper

14 security element

16 background layer

20 verification device

22 magnetic field lines

26, 28 areas

30 background layer

32 information

34 microcapsule-based paint layer

36 microcapsules

38 capsule shell

40 carrier liquid

42 pigment

50, 52 appearances

54 digits without microcapsules 56 Remainder of the information

60 highly reflective pigments

62 external magnetic field

64 laser radiation

66 reflected laser radiation 68 destroyed areas

70, 72 appearances

80 security element

82 laser-modifiable pigments

84 external magnetic field 86, 88 sections

90 laser radiation

92 modified pigments

94 modified background layer ^A

100 security element

102 binder

104 scattering or absorbing particles

106 subarea

108 laser radiation

Claims

P a n t a n s p r e c h e

A method of making an optically variable security element of a microcapsule-based ink layer comprising applying a substrate layer to a substrate, applying a microcapsule-based ink layer to the substrate layer containing in a binder a plurality of microcapsules each having a capsule shell, one in the capsule shell having enclosed carrier liquid and a magnetically alignable, platelet-shaped pigment, which in the microcapsule is substantially freely rotatable and reversibly alignable by an external magnetic field, an external magnetic field is applied to align the rotatable pigments at least in a portion of the color layer in the microcapsules, and

L) in the partial area with the aligned pigments by laser irradiation with a marking laser at least a portion of the pigments and / or at least a portion of the background layer is modified.

2. The method according to claim 1, characterized in that in step U) a laser-modifiable background layer is applied, preferably a background layer with infrared-absorbing inks and / or metal layers.

3. The method according to claim 2, characterized in that in step L) at least a portion of the background layer is modified by laser exposure, in particular destroyed or bleached.

4. The method according to at least one of claims 1 to 3, characterized in that in step F) a microcapsule-based ink layer is applied, the platelet-shaped pigments for the wavelength of the marking laser are reflective and are preferably formed by oxide multilayer interference layer pigments.

5. The method according to at least one of claims 1 to 3, characterized in that in step F) a microcapsule-based ink layer is applied, the platelet-shaped pigments are laser-modifiable with the marking laser and are preferably formed by multi-layer interference pigments with metallic layers.

6. The method according to at least one of claims 1 to 5, characterized in that in step F) a microcapsule-based ink layer is applied, the binder contains particles which act at the wavelength of the marking laser scattering or absorbing and preferably by titanium dioxide or iron oxide Particles are formed.

7. The method according to at least one of claims 1 to 6, characterized in that in step M) the pigments are aligned at least in a partial area of the ink layer perpendicular to the loading direction of the marking laser in step L).

8. The method according to at least one of claims 1 to 7, characterized in that in step M) the pigments at least in a Teilbe- rich of the color layer parallel to the loading direction of the marking laser in step L) are aligned.

9. The method according to at least one of claims 1 to 8, character- ized in that the laser application in step L) takes place in a partial area in the form of patterns, characters or a coding.

10. The method according to at least one of claims 1 to 9, characterized in that the background layer in step U) in the form of an information, in particular a pattern, characters or a coding is applied.

11. The method according to at least one of claims 1 to 10, characterized in that the laser application in step L) with an infrared laser in the wavelength range of 0.8 μπι to 3 μπ \, in particular with a Nd: Y AG laser and / or a Nd: YVC »4 laser.

12. Security arrangement for securing security papers, documents of value, data carriers and the like with a producible according to one of claims 1 to 11 security element and with a verification element with a magnetic region.

13. Safety arrangement according to claim 12, characterized in that in the magnetic area magnetic material in the form of patterns, lines, characters or a coding is present and / or that the magnetic area is magnetized substantially perpendicular to the plane of the verification element.

14. A data carrier with a producible according to one of claims 1 to 11 security element, or with a security arrangement according to one of claims 12 or 13, wherein in the latter case, the security element and the verification element of the security arrangement are preferably arranged geometrically on the disk that the security element can be brought over the verification element by bending or folding the data carrier.