EP2438579A1 - Élément de sécurité magnéto-optique - Google Patents

Élément de sécurité magnéto-optique

Info

Publication number
EP2438579A1
EP2438579A1 EP10725381A EP10725381A EP2438579A1 EP 2438579 A1 EP2438579 A1 EP 2438579A1 EP 10725381 A EP10725381 A EP 10725381A EP 10725381 A EP10725381 A EP 10725381A EP 2438579 A1 EP2438579 A1 EP 2438579A1
Authority
EP
European Patent Office
Prior art keywords
security element
magneto
optical material
element according
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP10725381A
Other languages
German (de)
English (en)
Inventor
Alexander Bornschlegl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Giesecke and Devrient GmbH
Original Assignee
Giesecke and Devrient GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Giesecke and Devrient GmbH filed Critical Giesecke and Devrient GmbH
Publication of EP2438579A1 publication Critical patent/EP2438579A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/04—Testing magnetic properties of the materials thereof, e.g. by detection of magnetic imprint
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B42D25/369—Magnetised or magnetisable materials
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/003—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using security elements
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07D—HANDLING OF COINS OR VALUABLE PAPERS, e.g. TESTING, SORTING BY DENOMINATIONS, COUNTING, DISPENSING, CHANGING OR DEPOSITING
    • G07D7/00—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency
    • G07D7/06—Testing specially adapted to determine the identity or genuineness of valuable papers or for segregating those which are unacceptable, e.g. banknotes that are alien to a currency using wave or particle radiation
    • G07D7/12—Visible light, infrared or ultraviolet radiation

Definitions

  • the invention relates to a security element with a visually and / or machine-detectable appearance that can be changed by an external magnetic field.
  • the invention further relates to a method for producing such a security element, a security arrangement with such a security element, a correspondingly equipped data carrier and a verification device for such a security element.
  • Data carriers such as valuables or identity documents, but also other valuables, such as branded goods, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carrier and at the same time serve as protection against unauthorized reproduction.
  • the security elements can be embodied, for example, in the form of a security thread embedded in a banknote, a covering film for a banknote with a hole, an applied security strip, a self-supporting transfer element or else in the form of a feature area printed directly on a value document.
  • Security elements with a changeable visual impression which can be interactively influenced by a user, have a particularly high security against counterfeiting, since interactively triggerable optical effects can not be reproduced with copiers.
  • a security element which consists at least partially of a material which is optically changeable by an electric or magnetic field.
  • the optically variable material preferably comprises a multiplicity of particles which can be changed in their position or orientation by means of the electric or magnetic field.
  • the object of the invention is to further improve a security element of the aforementioned type and, in particular, to provide a security element which is easy to produce and has an attractive visual appearance and / or high counterfeit security.
  • the appearance should be interactively influenced by a user.
  • a generic security element contains a magneto-optical material whose Verdet constant for at least one wavelength in the visible spectral range is greater than 10 5 ° T- 1 ITr 1 in absolute terms.
  • the Verdet constant of the magneto-optical material of magnitude is even greater than 10 6 ° T "1 ⁇ r 1, more preferably even greater than 10 70 T-1 Germany. 1
  • a magneto-optical material is used, the Verdet constant is wavelength-dependent and within the visible spectral range by at least a factor of 2, in particular even by at least a factor of 4 changed or the sign changes within the visible spectral range.
  • the invention is based on the idea to exploit the extremely strong Faraday effect novel magneto-optical materials to provide magnetically influenced security elements that contain no mobile or magnetic materials.
  • novel magneto-optical materials to provide magnetically influenced security elements that contain no mobile or magnetic materials.
  • the external magnetic field always results in a mechanical change in the security element, for example by ferromagnetic particles floating in a liquid-filled capsule aligning in an external magnetic field.
  • the Faraday effect describes the rotation of the polarization plane of linearly polarized light when passing through a magneto-optical medium under the influence of a magnetic field which is oriented parallel to the propagation direction of the light.
  • the strength of the effect is expressed by a substance-specific and generally wavelength-dependent variable, the so-called Verdet constant V.
  • Verdet constant V of the order of up to several 10 3 ° T- 1 In 1 .
  • the use of such materials in visually verifiable security elements is therefore virtually impossible due to the small size of the resulting angle of rotation in conventional magnetic fields (0.1 T) of a few hundredths of a degree.
  • the conventional materials having the highest values of the Verdet constant are specially doped flint glasses or crystals which, due to their brittleness, are also unsuitable for use in security elements for value documents.
  • the present inventor has now surprisingly found that materials with extremely large values of the Verdet constant for the first time security elements can be practically realized that use the Faraday effect to produce a interactively by a magnetic field variable visual impression.
  • Particularly suitable magneto-optical materials are highly regioregular polythiophenes (PTPs) and other conjugated polymers, which have recently been discovered to have a very strong Faraday effect.
  • the high Verdet constant is based on the current understanding of the supramolecular organization of polymers, with PTP regioregularities> 95 to 97% has particularly good properties.
  • Particularly preferred presently are highly regioregular polythiophenes, preferably alkyl or alkoxy substituted, most preferably 3-hexyl, 3-decyl, 3-dodecyl or 3-octyloxy-substituted.
  • magneto-optical materials are polymers, they can be processed with the usual methods for plastics, with particularly good results being achieved by current knowledge through a coating in the spin coating process.
  • Another advantage of the preferred magneto-optic materials is that there are no problems with approval for polymer materials according to Regulation (EC) No. 1907/2006 (REACH).
  • EC Polymer Materials
  • REACH Regulation
  • the Verdet constant of the starting polymer can be significantly increased by such a measure, so that even materials with a relatively low Faraday effect, such as PMMA, in materials suitable for the invention with V> 10 5 ° T ⁇ m ⁇ can be converted.
  • inorganic nanoparticles having superparamagnetic properties or core-shell particles having a superparamagnetic core are suitable as additives for increasing the Verdet constant.
  • the color impression of the security element can be changed by the external magnetic field.
  • a magneto-optical material with a wavelength-dependent Verdet constant is used.
  • the polarization planes of light of different wavelengths are rotated to different degrees as they pass through the magneto-optical material, resulting in a color impression for the observer, as explained in greater detail below.
  • the color impression depends on the strength of the magnetic field, ie it changes when an external magnet is brought to or removed from the security element. It is understood that, in addition to the change in the color impression, optionally or only the contrast impression of the security element can be changed by the external magnetic field.
  • the change of the visually and / or machine-detectable appearance by the external magnetic field is reversible, so that adjusts itself to the removal of the external magnetic field, the original appearance.
  • the magneto-optic material is present in a marking layer having a thickness of less than 100 ⁇ m, preferably in a marking layer having a thickness between 1 ⁇ m and 20 ⁇ m, more preferably in a marking layer having a thickness between 1 ⁇ m and 10 ⁇ m , Conventional materials showed magnetoresistance of a few hundredths of a degree at these thicknesses in a magnetic field of 0.1 T, which is insufficient for visible application.
  • the security element is designed to be viewed in phantom and contains a first and a second linearly polarizing layer, between which the marking layer with the magneto-optical material is arranged.
  • the first and / or second linearly polarizing layer may advantageously be in the form of patterns, characters or a coding. This formulation should also include the case that the first and / or second linearly polarizing
  • Layer has recesses or inactive areas in the form of patterns, characters or a coding.
  • the first and second linearly polarizing layers are both in the form of patterns, characters or a coding, which are arranged in the register at least in a partial area relative to one another.
  • a visually recognizable effect occurs only in the areas arranged in the register, any other differently designed areas show no visible effect.
  • the transmission directions of the first and second linearly polarizing layer preferably enclose an angle of approximately 0 °, ie they are arranged parallel to one another.
  • interesting visual effects where the security element from opposite sides has a different chen visual impression, for example, a different color impression, can be generated when the two linearly polarizing layers enclose an angle of about 45 °, as explained in more detail below.
  • An angle of 90 ° also allows interesting effects (negative structure)
  • the security element is designed for observation in plan view and contains a reflection layer and a linearly polarizing layer, between which the marking layer with the magneto-optical material is arranged.
  • the linear polarizing layer may be in the form of patterns, characters or a code.
  • the security element may be designed for machine authenticity testing, wherein the visual appearance of the security element does not change by an external magnetic field alone, and wherein the security element has a marking layer with the magneto-optic material.
  • the security element is then brought between two parallel-aligned linear polarizers and illuminated with light of a predetermined wavelength when the magnetic field is applied.
  • the intensity of the light through the first linear polarizer, the security element and the second linear polarizer transmitted light is then a measure of the strength of the magneto-optical effect, from which the authenticity of the security element can be concluded. If the intensity of the transmitted light is carried out at two or more different magnetic field intensities, the presence or absence of the expected magneto-optical effect with excellent signal-to-noise ratio and thus be tested at high speed.
  • the authenticity check can also be carried out at two or more different wavelengths in order to achieve an even higher detection reliability.
  • the security element to be tested is placed on a reflective layer and analyzed by a linear polarizer, as described above.
  • the machine-detectable security element can also contain, in addition to the marking layer, a linearly polarizing layer on which the marking layer with the magneto-optical material is arranged. In the authenticity check it is then sufficient to analyze the security element through a linear polarizer, or to place the security element on a reflective layer and to analyze it through the linearly polarizing layer of the security element.
  • the security elements for mechanical authenticity testing just described are hidden security features, since the visual appearance of the security element alone does not change as a result of an external magnetic field. However, the security elements can also be checked visually for authenticity by the aid of additional aids, such as one or two linear polarizers.
  • Another variant of the invention consists in combining the visual recognizability and the machine readability in a security element.
  • the security element has a first subarea, in which the security element is designed for visual testability, and a second subarea, in which the security element is designed for a machine authenticity check.
  • the two subareas can each be described as described above for visually or mechanically recognizable security elements.
  • the marking layer may be in the form of a film with the magneto-optic material.
  • a polythiophene solution in a suitable solvent by spinning for example, a polythiophene solution in a suitable solvent by spinning
  • Coating to be processed into a film a conventional film substrate such as PET, BOPP and the like may be coated with such a solution or a polythiophene film may be laminated with film material.
  • a film or coated film can be used as an active Faradayelement and at the same time as a carrier material.
  • the magneto-optical material may also be in a marking layer applied by a printing method or a rotary coating method.
  • the magneto-optical material is present in the marking layer in the form of pigments, in particular in the form of platelet-shaped or spherical pigments.
  • a polythiophene film produced by a suitable process preferably with a homogeneous thickness, can be cut or broken into small platelets. The latter is easily possible, for example, in the strongly cooled state using liquid nitrogen.
  • the film may be supported, stretched, thermally treated, etc.
  • the platelet-shaped pigments can then be incorporated into a transparent binder system and used as printing ink. When printing, especially in screen printing, The pigments then align in a flaky or parallel to each other.
  • the film or fragments can be surrounded by a layer to protect the pigment from external influences or to adapt properties, such as laser markability, etc.
  • the magneto-optical material is present in the marking layer in core-shell particles, wherein either the core or the shell of the core-shell particles contain the magneto-optical material.
  • the core of the core-shell particles may contain the magneto-optical material and the shell of the core-shell particles a linearly polarizing material.
  • the core-shell particles have a reflective, in particular metallically reflecting core, while the shell of the core-shell particles contains the magneto-optical material.
  • the sheath of the core-sheath particles may also have a multilayer structure and contain, for example, an inner layer with the magneto-optical material and an outer layer with a linearly polarizing material.
  • the diameter of the core-shell particles is advantageously between about 1 .mu.m and about 100 .mu.m, in particular between about 1 .mu.m and about 80 .mu.m.
  • the magneto-optic material may be in the form of patterns, characters, or a code, for example, to individualize the security element. This also includes the possibility that the magneto-optic material has recesses or inactive areas in the form of patterns, characters or a coding. Such inactive regions may be generated by, for example, locally heating or melting the magneto-optic material.
  • the strength of the Faraday effect depends on the supramolecular arrangement of the polymer chains. By laser irradiation, the regioregularity can be selectively reduced locally and the effect size can be reduced.
  • the hue of an ink containing the magneto-optical material can be adjusted by the addition of conventional color pigments or adjusted by the use of different magneto-optical materials with different intrinsic absorption.
  • linearly polarizing layers it is preferred to use materials which permit a printing method of application for both film and paper applications.
  • Examples of such linearly polarizing printing inks are lyotropic liquid-crystal formulations or special dichroic pigments.
  • Suitable lyotropic liquid crystals are described in particular in the publication WO 2005/005727 A1, the disclosure content of which is included in the present application in this respect.
  • the lyotropic liquid crystals can already be aligned by doctoring during printing or by other shear forces. Even with cholesteric liquid crystals, in combination with the carrier films, linearly polarizing properties were observed. ob panel.
  • Dichroic paints or pigments have already been used in the art to linearly polarize light and are commercially available. They are based on the principle that the individual pigments align themselves on an oriented polyvinyl alcohol (PVA) layer and thereby produce the effect.
  • PVA polyvinyl alcohol
  • the reflection layer can be produced in particular by vapor deposition of a metallic layer on a smooth substrate.
  • the surface may have a reflective appearance, but may also be non-reflective.
  • the reflective layer should not produce any scattering that would destroy the linear polarization of the light.
  • reflection layers also polarize the reflected light itself. Since this effect is dependent on the angle, it can be used specifically for the further enhancement of reflection safety elements.
  • the invention also includes a method for producing a security element, in which a magneto-optical material is applied or introduced whose Verdet constant for at least one wavelength in the visible spectral range is greater than 10 5 ° T- 1 ITr 1 .
  • the magneto-optical material is processed into a film which forms part of the security element.
  • the magneto-optic material can be advantageously applied to a support by a printing method or a spin coating method.
  • a further advantageous possibility is that first pigments or core-shell particles are produced with the magneto-optical material and are introduced into a binder, and that the binder with the pigments or core-shell particles in a subsequent step to a Carrier is applied. Examples of suitable embodiments of the core-shell particles are mentioned above.
  • the invention further comprises a security arrangement for securing security papers, value documents, data carriers and the like with a security authentification security element of the type described and having a verification element with a linearly polarizing layer.
  • the invention further comprises a data carrier, in particular a value document, such as a banknote, a passport, a document, an identity card or the like, which is equipped with a security element of the type described or with a security arrangement of the type described.
  • a data carrier in particular a value document, such as a banknote, a passport, a document, an identity card or the like, which is equipped with a security element of the type described or with a security arrangement of the type described.
  • Suitable substrate material for the data carrier is any type of paper, in particular cotton vellum paper. Of course, it is also possible to use paper which contains a proportion of polymeric material in the range of 0 ⁇ x ⁇ 100% by weight.
  • the substrate material of the data carrier is a plastic film, for. B. a polyester film is.
  • the film may also be monoaxially or biaxially stretched. The stretching of the film leads, among other things, to rem that it receives polarizing properties that can be used as another security feature.
  • the substrate material of the data carrier is a multilayer composite which has at least one layer of paper or of a paper-like material.
  • Such a composite is characterized by an extremely high stability, which is for the durability of the disk of great advantage.
  • All materials used as substrate material can have additives which serve as authenticity features. It is primarily to think of luminescent, which are preferably transparent in the visible wavelength range and in the non-visible wavelength range by a suitable tool, for. B. a UV or IR radiation emitting radiation source, can be excited to produce a visible or at least detectable with auxiliaries luminescence. Other security features can be used with advantage, as long as they do not affect the viewing of the security element according to the invention or at least not significantly.
  • the security element can, in particular if it is present on a transparent or translucent substrate, also be arranged in or above a window area or a through opening of the data carrier. 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 and the verification element can be brought over one another by bending or folding the data carrier.
  • the invention further provides a verification device for checking the authenticity of a security element of the type described with a light source for light of a predetermined wavelength, a linear polarizer, a device for generating a magnetic field perpendicular to
  • the verification device can contain a further linear polarizer so that the security element can be brought between the two linear polarizers during the authenticity check.
  • the security elements according to the invention represent a machine or human feature. Even hidden security features can optionally be viewed visually with an additional polarization filter.
  • a magneto-optical material the use of a polymeric material having a Verdet constant in the applied form above 10 5 T -1 In.- 1 is presently preferred.
  • the magneto-optical effect can be enhanced by introducing nanoparticles.
  • the layer thicknesses of the applied marking layer are typically between 1 ⁇ m and 20 ⁇ m.
  • the marking layer of the security element is preferably combined with printed polarizers, in particular of lyotropic liquid crystal layers. Magneto-optical materials in the form of core-shell particles (microspheres) are also possible.
  • magneto-opti- A pigment can be produced and thus a printing ink can be produced. Since the currently preferred magneto-optical materials are polymeric materials, approval problems according to Regulation (EC) No. 1907/2006 concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) are not to be expected.
  • Fig. 1 is a schematic representation of a banknote with a
  • FIG. 4 schematically shows the course of the Verdet constant V of the magneto-optical material of the see-through safety element of FIG. 3 as a function of the wavelength
  • FIG. 5 shows the wavelength-dependent rotation of the plane of polarization of the light after passing through the marking layer of the see-through security element of FIG. 3, in each case for light from the blue spectral range and for light from the red spectral range, and in (a) to (d) for different values of FIG
  • FIG. 6 shows in (a) a reflection security element according to an embodiment of the invention in cross section, in (b) the visual appearance of the security element of (a) in plan without external magnetic field and in (c) the visual appearance of the security element of (a ) in supervision with external magnetic field,
  • Fig. 8 in (a) a see-through security element with a different color from opposite sides color impression and in (b) schematically the course of the Verdet constant V of in
  • FIG. 9 shows in (a) the security element of FIG. 8 (a) in an exploded view, in (b) the polarization ratios for light incident from the left, and in (c) the polarization ratios for light incident from the right, FIG. 10 to 13 each in (a) a magneto-optical pigment and in (b) a security element produced using the pigment of (a),
  • FIG. 15 shows a machine-readable security element and a corresponding checking device for the machine authenticity check, both according to further exemplary embodiments of the invention.
  • Fig. 16 is a reflection-safe unit, the combined visual recognizability and machine readability in a security element.
  • Fig. 1 shows a schematic representation of a banknote 10, which is provided with two security elements 12 and 16 according to embodiments of the invention.
  • the first security element constitutes a see-through security element 12, which is arranged over a see-through area, such as a window area or a through opening 14, of the banknote 10.
  • the second security element is designed for viewing in supervision (reflection) and is formed by a glued transfer element 16 of any shape.
  • the banknote 10 can be a conventional paper banknote with a substrate made of cotton vellum paper or else a polymer banknote or a composite film banknote.
  • the visual appearance, in particular the color impression of the security elements 12, 16 can be reversibly changed by an external magnetic field.
  • the initially colorless transparent safety element 12 can appear in an orange hue over the entire surface due to the influence of an external magnetic field.
  • the transfer element 16 appears evenly shiny without magnetic field, while under the influence of an external magnetic field the denomination "50" within the transfer element 16 appears in color.
  • the external magnetic field can be generated by a simple magnet, which may for example be part of a mobile phone, a headphone or earphone or a merchandise security system at the point of SaIe. If the magnet moves under one of the security elements 12, 16 back and forth or on one of the security elements 12, 16 and moved away, so does the strength of the color effect and / or recognizable with the strength of the magnetic field at the location of the security element Colour.
  • the interactive change of the visual appearance serves to prove the authenticity of the security elements 12 or 16 and the banknote 10 provided therewith. Due to the widespread use of magnetic field generating devices, simple verification of the security elements 12, 16 is possible even in normal cash transactions.
  • the invention is not limited to see-through security elements and transfer elements in bank notes, but can be used with all types of security elements, for example labels on goods and packaging or in the security of documents, ID cards, passports, credit cards, health cards and the same. Banknotes and similar documents come next to visual security elements and transfer elements also directly printed security elements, security threads or security strips in question.
  • the Faraday effect which is also referred to as magnetorotation or magneto-optical effect, describes the rotation of the plane of polarization of linearly polarized light 22 when passing through a magneto-optical medium 20 under the influence of a magnetic field 28 parallel to the propagation direction 24 of the Light oriented.
  • the propagation direction 24 of the light is the -z direction without limiting the generality.
  • the incident light 22 is polarized at location 30 linearly in the + y direction, as indicated by the double arrow 32 drawn along the y axis in the xy plane 38, which indicates the deflection of the electric field of the light wave 22.
  • the magneto-optical medium 20 rotates the polarization plane of the light, so that the polarization direction 36 of the emergent light 26 is rotated at location 34 by an angle ⁇ in the xy plane 38 '.
  • V denotes the substance-specific and generally wavelength-dependent detective constant.
  • the direction of rotation of the polarization plane reverses when the light direction is reversed. Therefore, if a light beam passes through the same path twice after reflection, the angle of rotation ⁇ is doubled compared to a simple passage. This effect is utilized, in particular, in the elements described below under Reflexionsconces.
  • magneto-optical materials are used according to the invention whose Verdet constant in the visible spectral range not only assumes high absolute values but is also strongly wavelength-dependent.
  • the marking layer 42 is arranged between a first linearly polarizing layer 44 and a second linearly polarizing layer 46 whose transmission directions are parallel to one another, ie enclose an angle of substantially 0 °.
  • the course 50 of the Verdet constant V of the magneto-optical material of the marking layer 42 is shown schematically in FIG. 4 as a function of the wavelength ⁇ .
  • unpolarized light 48 now impinges on the security element 40 of FIG. 3, the incident light is first linearly polarized by the first linearly polarizing layer 44.
  • the direction of incidence of the light 48 is the -z direction and the first linear polarizing layer 44 polarizes the light along the + y direction.
  • the polarization plane of the light as it passes through the marking layer 42 then becomes an angle depending on the flux density B of the magnetic field
  • the light from the second linearly polarizing layer 46 is then attenuated to different degrees, so that the light 49 transmitted in total by the security element 40 appears to the viewer with a different color impression depending on the strength of the magnetic field.
  • the magneto-optical material of the marking layer causes neither rotation of the polarization plane for blue light b nor for red light r.
  • the incident white light 48 therefore passes through the security element 40 without color change, so that the security element appears colorless transparent.
  • the intensity of a light rotated by an angle ß by a factor of cos 2 ß reduced.
  • the transmitted light 49 therefore has an overall reddish color. Since the rotation angles ⁇ b and ⁇ r scale linearly with the magnetic field flux density B, at a certain flux density B2, the plane of polarization of the blue light b in the marking layer 42 can be rotated by about 90 °, as shown in Fig. 5 (c) ).
  • the blue portion b of the incident light 48 is completely absorbed by the second linearly polarizing layer 46 in this situation.
  • the polarization plane of the red light r is rotated by 45 ° at the flux density B2, so that in the red, about 50% of the incident intensity is transmitted by the security element. After passing through the security element 40, the transmitted light 49 therefore appears with a clear red coloration.
  • the red color changes to a blue coloration of the transmitted light 49.
  • the rotation angles for blue and red light are twice as large as in the situation of FIG. 5 (c). In this case, therefore, the polarization plane of the red light r is rotated by about 90 °, so that the red portion of the incident light
  • the occurring color effects are basically also influenced by the inherent absorption of the magneto-optical material used.
  • self-absorption plays practically no role at the layer thicknesses of less than 100 ⁇ m considered.
  • the security viewing elements 40 which are for viewing purposes, may be applied to a transparent substrate, such as a polymer bank notch, or may be placed on or opaque to an opaque substrate, such as the paper banknote 10 of FIG. 1.
  • the reflection-proof element 60 of FIG. 6 (a) includes a reflective layer 62 onto which an approximately 10 .mu.m-thick marking layer 64 having a magneto-optical material and a linear polarizing layer 66 are applied.
  • Incident white unpolarized light 70 is linearly polarized by the linearly polarizing layer 66 and, when passing through the marking layer 64, undergoes a rotation of the plane of polarization, the size of which depends in particular on the external magnetic field flux density B.
  • the light After the reflection at the reflection layer 62, the light passes through the marking layer 64 a second time and finally passes again through the linearly polarizing layer 66, wherein the intensity of the light is weakened depending on the wavelength depending on the wavelength caused by the two-pass rotational angle of the polarization plane.
  • the reflected light 72 therefore appears to the viewer 74, depending on the strength of the magnetic field, with a different color impression.
  • the marking layer 64 is additionally provided with recesses 68 in the form of the denomination "50" of the banknote. Magnetorotation is not generated in the recesses 68, so that they always appear to the observer 74 independently of the external magnetic field with the metallic impression of the reflection layer 62.
  • Opposite safety elements offer the advantage over see-through security elements that the incident light 70 passes twice through the magneto-optic material, ie when the material thickness is the same, a twice as large effect occurs or the material consumption is halved for a given desired effect size.
  • reflective security elements can be more easily generated on rough and non-transparent areas of a value document or other medium.
  • the visual appearance of a reflection-proof element is influenced by the appearance of the reflection layer. This can be designed both mirroring and non-reflective. For further development of a reflection-proof element, it is also possible to use reflection layers which polarize the reflected light itself in an angle-dependent manner.
  • the magneto-optical material can also be changed, for example by local heating or melting, so that no or only a weakened magneto-optical effect occurs in the machined areas.
  • the intensity of magnetorotation in the above-mentioned polythiophenes can be selectively reduced locally by laser irradiation, as described in more detail elsewhere.
  • the marking layer can also be applied directly in the form of patterns, characters or codes, for example, instead of being printed To create recesses or inactive areas in a first fully applied marking layer.
  • Another way to introduce patterns, characters or codes that can be triggered by an external magnetic field into the security element is to create recesses 76 or inactive areas in the linearly polarizing layer 66, as shown in FIG. Since the incident light in the recessed areas 76 is not polarized, magnetorotation of the marking layer 64 there applies equally to all directions of polarization and therefore does not produce a visually detectable effect.
  • the recessed areas 76 of the linearly polarizing layer 66 therefore always appear to the observer independently of the external magnetic field with the metallic impression of the reflection layer 62.
  • see-through security elements such as shown in Fig. 3, in the described ways with patterns, characters or codes can be provided. If the latter are produced by structuring the oppositely disposed linearly polarizing layers 44, 46, the structures must be arranged in the register in order to achieve a color effect in a transparent manner.
  • see-through security elements can also be realized with magneto-optical materials which, viewed from opposite sides, each have a different color impression cause, as explained now with reference to FIGS 8 and 9.
  • the see-through security element 80 shown in Fig. 8 (a) includes a marking layer 82 containing a magneto-optic material having a Verdet constant that changes sign in the visible spectral range.
  • the marker layer 82 is disposed between a first linearly polarizing layer 84 and a second linearly polarizing layer 86, wherein the transmission direction of the second linearly polarizing layer is an angle of -45 ° (45 ° to the right) against the forward direction of the first linearly polarizing layer Layer is rotated.
  • FIG. 8 (b) schematically shows the curve 88 of the Verdet constant V of the inserted magneto-optical material of the marking layer 82 as a function of the wavelength ⁇ .
  • the magneto-optic material of the marking layer 82 thus rotates the polarization planes of red and blue light in opposite directions.
  • Fig. 9 (a) shows the security element 80 with the first linear polarizing layer 84, the marking layer 82 and the second linearly polarizing layer 86 in an exploded view
  • Fig. 9 (b) the polarization ratios for light 90 incident from the left
  • FIG. 9 (c) for the polarization ratios for light 94 incident from the right at the points along the light path 100 marked in FIG. 9 (a).
  • white unpolarized light 90 is incident on the security element 80 from the left and linearly polarized by the first linearly polarizing layer 84. 2, the incident direction of the light 90 is the -z direction and the first linear polarizing layer 84 polarizes the light along the + y direction. Therefore, after passing through the first linear polarizing layer 84, both red light r and blue light b are linearly polarized along the + y direction, as shown in array 102 of FIG. 9 (b).
  • the polarization plane of the light When passing through the marking layer 82, the polarization plane of the light is rotated by an angle ⁇ ( ⁇ ) in dependence on the external magnetic field B. In the given specifications results in blue light and for red light
  • the blue light b is transmitted substantially without attenuation, while the red light r is practically complete is absorbed as shown in box 106 of Fig. 9 (b).
  • the transmitted light 92 therefore appears blue to the observer.
  • suitable magneto-optical materials are, in particular, conjugated polymers, preferably highly regioregular polythiophenes, preferably alkyl- or alkoxy-substituted, particularly preferably 3-hexyl, 3-decyl, 3-dodecyl and 3-octyloxy-substituted.
  • Such polymers can be processed with the usual methods for plastics, with the best results, in particular the highest Verdet- constants of the applied material, are currently achieved when applying by spin coating method.
  • nanoparticles may be added to the polymers, inorganic nanoparticles having superparamagnetic properties or core-shell particles having a superparamagnetic core being preferred.
  • the magneto-optical materials can also be used in the form of pigments.
  • a polythiophene film produced by a suitable process preferably with a homogeneous thickness
  • spherical pigments 120 into a binder as shown in Fig. 10 (a).
  • a security element 125 can be produced with such intaglio printing ink, as shown in FIG. 10 (b), in which a marking layer 127 with spherical, magneto-optical pigments 120 is printed on a metallically reflecting layer 126 and then a linearly polarizing layer 128 is applied is.
  • the pigment is a core-shell particle 130 in which the core contains a magneto-optic material 131 and the shell contains a linearly polarizing material 132.
  • the core-shell particles 130 need not necessarily be spherical.
  • the core-shell particles 130 are introduced into a binder system.
  • a security element 135 can be produced with such an ink, in which a marking layer 137 with the core-shell particles 130 is printed on a metallically reflecting layer 136, as shown in FIG. 11 (b).
  • the pigment is a core-shell particle 140, in which the core is formed of a reflective, in particular metallically reflective material 141, and in which the shell is a magneto-optical Material 142 contains.
  • the resulting core-shell particles 140 need not necessarily be spherical.
  • the core-shell particles 140 are introduced into a binder system.
  • a security element 145 can be formed with such an ink, in which a marking layer 147 with the core-shell particles 140 and then a linearly polarizing layer 148 are applied on an absorbent background layer 146, as shown in FIG. 12 (b). shown.
  • the linearly polarizing layer 148 could also be represented by an external, not further shown Linear polarizer to be replaced, the z. B. by the viewer of the security element or by a suitable device on the marking layer 147 is arranged.
  • the pigment is a core-shell particle 150 in which the core is formed of a reflective, in particular, metallically reflective material 151, and the shell of the core-shell particles 150 is an inner Layer with a magneto-optical material 152 and an outer layer with a linearly polarizing material 153 contains.
  • the resulting core-shell particles 150 need not necessarily be spherical.
  • the core-shell particles 150 are introduced into a binder system.
  • such a printing ink can be used to create a security element 155 in which a marking layer 157 with the core-shell particles 150 is applied to an absorbing backing layer 156, as shown in FIG. 13 (b).
  • the see-through or reflection security elements according to the invention can also be tuned for machine detectability and be hidden visually.
  • additional aids such as a linear polarizer, which are integrated in the associated test apparatus, are required for detecting the appearance which can be changed by an external magnetic field.
  • the variable appearance of the security elements can not be recognized so that they represent hidden security features.
  • FIG. 14 shows a machine-readable security element 160 with a linearly polarizing layer 162, on which a 15 ⁇ m thick marking layer 164 is arranged.
  • the marking layer 164 includes a magneto-optical material having a Verdet constant greater than 10 5 ° T ⁇ nr 1 at a preselected wavelength ⁇ .
  • Such a security element 160 may be arranged, for example, in or on a transparent window of a paper banknote or in or on a polymer note or a composite film banknote.
  • the security element 160 is illuminated with light of the predetermined wavelength ⁇ when the magnetic field 174 is applied, and the intensity of the light transmitted through the security element 160 and the linear polarizer 172 is measured.
  • the intensity of the transmitted light through the linear polarizer 172 is then proportional to cos 2 ß, so depends strongly on the flux density B of the applied magnetic field.
  • the machine-readable security element 180 shown in FIG. 15 does not contain linearly polarizing layers, but merely has an approximately 10 ⁇ m thick marking layer 182, which contains a magneto-optical material with a Verdet constant greater than 10 6 ° T 1 In 1 a preselected wavelength ⁇ contains.
  • Such a security element 180 may be arranged, for example, in an intermediate layer of a film composite banknote.
  • a test device for the automatic authenticity check of the security element 180 includes a further linear polarizer 178, whose forward direction is oriented parallel to the forward direction of the first linear polarizer 172.
  • the security element 180 is then illuminated when the magnetic field 174 is applied with light of the predetermined wavelength ⁇ and the intensity of the light transmitted through the linear polariser 178, the safety element 180 and the linear polarizer 172 is measured. From the intensity of the transmitted light at two different magnetic field strengths, as described above, it can be reliably concluded that the presence or absence of the magneto-optical effect expected in a true security element.
  • the authenticity check can be carried out at two or more different wavelengths in order to achieve an even higher detection reliability.
  • reflection-proof elements can also be designed for machine readability. Visual recognizability and machine readability can also be combined in a security element, as shown in the embodiment of FIG. 16.
  • the re- Flexion security element 190 contains a reflection layer 192 to which an approximately 20 ⁇ m thick marking layer 194 with a magneto-optical material of high Verdet constant is applied.
  • a linearly polarizing layer 196 is applied to the marking layer 194, so that the security element 190 in this region 200 has the visually recognizable effects described in connection with FIG shows.
  • the marking layer 194 can also be provided with recesses 198 or even be applied in the form of patterns, characters or a coding, as described above.
  • the marking layer 194 is not provided with a linearly polarizing layer, so that no visually recognizable effects occur there in an external magnetic field without auxiliary means.
  • the security element can be machine-tested for authenticity with a test device containing a linear polarizer 172, as already described in principle in FIG. 14.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Polarising Elements (AREA)

Abstract

L'invention concerne un élément de sécurité (40) présentant un aspect pouvant être modulé par un champ magnétique extérieur et pouvant être détecté visuellement et/ou par machine. Selon l'invention, il est prévu que ledit élément de sécurité (40) contienne un matériau magnéto-optique (42) dont la constante de Verdet est supérieure à 105 ° T-1m-1 pour au moins une longueur d'ondes dans la plage spectrale visible.
EP10725381A 2009-06-05 2010-05-18 Élément de sécurité magnéto-optique Withdrawn EP2438579A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102009023981A DE102009023981A1 (de) 2009-06-05 2009-06-05 Sicherheitselement
PCT/EP2010/003001 WO2010139393A1 (fr) 2009-06-05 2010-05-18 Élément de sécurité magnéto-optique

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EP2438579A1 true EP2438579A1 (fr) 2012-04-11

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DE (1) DE102009023981A1 (fr)
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DE102012024175A1 (de) * 2012-12-10 2014-06-12 Giesecke & Devrient Gmbh Vorrichtung zur Untersuchung eines Wertdokuments und Verfahren zur Untersuchung eines Wertdokuments

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GB9306404D0 (en) * 1993-03-26 1993-05-19 Lucas Ind Plc Magnetic field sensor
DE10163265A1 (de) * 2001-12-21 2003-07-03 Giesecke & Devrient Gmbh Wertdokument und Verfahren und Vorrichtung zur Prüfung des Wertdokuments
DE10217632A1 (de) 2002-04-19 2003-11-06 Giesecke & Devrient Gmbh Sicherheitsdokument
DE10331798B4 (de) 2003-07-14 2012-06-21 Giesecke & Devrient Gmbh Sicherheitselement, Wertgegenstand, Transfermaterial und Herstellungsverfahren
US20090039644A1 (en) * 2007-07-20 2009-02-12 Spectra Systems Corporation Systems and methods for using microscopic capsules containing orientable materials for document security and processing applications

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DE102009023981A1 (de) 2010-12-09

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