EP3700756A1 - Élément de sécurité réfléchissant - Google Patents

Élément de sécurité réfléchissant

Info

Publication number
EP3700756A1
EP3700756A1 EP18792849.4A EP18792849A EP3700756A1 EP 3700756 A1 EP3700756 A1 EP 3700756A1 EP 18792849 A EP18792849 A EP 18792849A EP 3700756 A1 EP3700756 A1 EP 3700756A1
Authority
EP
European Patent Office
Prior art keywords
layer
security element
element according
light
reflective
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.)
Granted
Application number
EP18792849.4A
Other languages
German (de)
English (en)
Other versions
EP3700756B1 (fr
Inventor
Winfried HOFFMÜLLER
Christoph HUNGER
Kai Herrmann SCHERER
Michael Sobol
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 Currency Technology GmbH
Original Assignee
Giesecke and Devrient Currency Technology 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 Currency Technology GmbH filed Critical Giesecke and Devrient Currency Technology GmbH
Publication of EP3700756A1 publication Critical patent/EP3700756A1/fr
Application granted granted Critical
Publication of EP3700756B1 publication Critical patent/EP3700756B1/fr
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • 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
    • B42D25/378—Special inks
    • B42D25/391—Special inks absorbing or reflecting polarised light
    • 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
    • B42D25/324—Reliefs
    • 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
    • B42D25/328—Diffraction gratings; Holograms
    • 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
    • B42D25/364—Liquid crystals
    • 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
    • B42D25/373—Metallic materials

Definitions

  • the invention relates to a reflective security element, a data carrier equipped with such a security element and a method for checking the authenticity of a reflective security element.
  • Data carriers such as banknotes, stocks, bonds, certificates, vouchers, checks, high-quality admission tickets, but also other counterfeit securities, such as passports or other identity documents, are often provided with security elements that provide security
  • Verification of the authenticity of the value document and at the same time serve as protection against unauthorized reproduction.
  • liquid-crystalline materials are exploited for this purpose and, above all, turned to the viewing angle-dependent color impression and the particular light-polarizing properties of liquid crystal layers.
  • Reflective safety elements with liquid crystals can be subdivided into at least two groups.
  • a first group of security elements contains a reflector which specifically reflects only circularly polarized light and which is formed on the basis of cholesteric liquid crystals.
  • security elements of the first group can also be detected from a greater distance, since the origin of the light which is reflected by the security element does not play a role.
  • a second group of security elements includes a reflector that not only reflects circularly polarizing light.
  • a reflector that not only reflects circularly polarizing light.
  • an optically anisotropic layer is arranged above a metallic reflector, which does not have a depolarizing effect.
  • a polarizing filter is used, which is usually must be placed directly on the security element, since the light incident on the security element must already be polarized to ensure that the reflected light is polarized and can be detected with the then acting as an analyzer polarizing filter.
  • the direct application of the polarizer is required, in particular, to minimize unpolarized stray light.
  • a cholesteric reflector as contained in the security elements of the former group, is not desirable, since such a reflector reflects only in a limited wavelength range and also reflects at most half of the light incident in this wavelength range. False light must also be avoided by an absorbent substrate.
  • the second group of security elements is in principle not suitable for checking the authenticity with increased observation distance, since in all cases both the incident and the reflected light must be passed through a polarizer / analyzer. Because of the reflection condition "angle of incidence equals angle of reflection" an authenticity check is therefore only possible if the security element is either almost exactly perpendicular to the direction of irradiation and observation direction or irradiation unit and analysis unit are arranged at exactly the same angle symmetrical to the security element. Such a specification is not realized in many applications or not at all feasible, so that the use of such security elements of the second group is limited only possible.
  • the object of the invention is to provide a reflective security element which has the disadvantages of the prior art avoids and that in particular can be easily checked for authenticity even from a larger observation distance.
  • the invention provides a security element for polarized light fastness testing which includes a retroreflective layer and a birefringent layer patterned on the retroreflective layer.
  • a structured birefringent layer with a retroreflective layer offers the decisive advantage that the optical anisotropy of the birefringent layer can be easily interrogated from a distance of a few meters or even several tens of meters.
  • the use of the retroreflective layer achieves that the incident light is reflected on the light source itself and a small angular range around the light source. Disturbing extraneous light, such as sunlight, a room lighting or license plate number, for example, a number plate lighting is also strongly suppressed because of the extraneous light, only a vanishing part in the direction of the light / observer is reflected.
  • the birefringent layer is formed with an outline in the form of patterns, characters or a coding.
  • the birefringent layer may include two or more regions of different optical power, in the form of patterns, characters or a code are formed.
  • the authenticity test in polarized light produces a desired image contrast.
  • the contrast between the areas in which the birefringent layer is present and the areas without the birefringent layer arises; in the second-mentioned case, the areas of different effect appear in the area
  • the retroreflective layer comprises a multi-reflective microprismatic layer, which in particular comprises embossed structures having a depth of between 10 ⁇ m and 1 mm and / or embossed structures having a period of between 10 ⁇ m and 1 mm.
  • the retroreflecting layer can also comprise focusing, single-reflecting structures, in particular back-side spherical gradient index lenses, which are also known as Lüneburg lenses.
  • a Lüneburg lens consists of a sphere of a lossless dielectric material with location-dependent dielectric constant. Due to its mirrored back side, it reflects incident light back exactly in the direction of its source, thus acting as a retro reflector.
  • the refractive index in the interior of the sphere is chosen such that rays incident in parallel are focused as far as possible in a point which is opposite to the contact point of the wavefront.
  • n (r) Sqrt [2 - (r / R) 2], where Sqrt [] represents the square root function, R the radius of the sphere and r the distance from the center of the sphere.
  • the rear-side mirrored spherical Gradientenindexlinsen have in particular a diameter between 20 ⁇ and 200 ⁇ .
  • the birefringent layer of the security element particularly advantageously comprises a liquid-crystal layer, in particular a nematic liquid-crystal layer.
  • the birefringent layer may also be formed only by a single liquid crystal layer, in particular a nematic liquid crystal layer.
  • the birefringent layer may also be formed by an optically anisotropic stretched film, such as a PET film or a PP film, by a birefringent polycarbonate film, by mica, or by a layer of birefringent pigments.
  • Said liquid crystal layer is preferably arranged directly above an alignment layer, which is advantageously formed from a linear photopolymer, a finely structured layer or a layer oriented by the application of shear forces.
  • the birefringent layer forms with particular advantage an X / 4 layer.
  • Other contrast mechanisms may rely on the use of dichroic dyes or films that absorb differentially light in aligned form, depending on the polarization. Irradiated unpolarized light is selectively linearly polarized by the dye or film by absorbing other polarization fractions. With a corresponding analyzer can then unpolarized light (background of the security element) of linearly polarized light (in the areas with the dichroic dyes or the film) can be distinguished.
  • the security element appears colored and / or structureless in unpolarized light, at least in the region of the structurally arranged birefringent layer, so that the structured birefringent layer forms a hidden security feature together with the retroreflective layer, which only works with Tools can be read.
  • the security element can appear completely colorless and / or structureless in unpolarized light, so that it is not recognizable without auxiliary means that a security element is present at all.
  • the security element can also have a hologram or a hologram-like diffraction structure in a subarea.
  • the hologram or the hologram-like diffraction structure is advantageously formed by an embossing, which also represents an alignment layer for the alignment of the liquid crystal layer.
  • the hologram or the hologram-like diffraction structure is provided with a metallization or a transparent high-index layer.
  • the invention also includes a data carrier with a security element of the type described.
  • the data carrier may be, in particular, a license plate number or another license plate, a value document, such as a banknote, a share, a bond, a certificate, a coupon, a check, a high-quality entrance ticket or even an identification card, such as a credit card, a bank card, a cash card, an authorization card, an identity card or a pass-page personalization page.
  • the invention further includes a method for checking the authenticity of a security element with a polarization feature, in which the security element is exposed to polarized light from any direction of impingement, the light reflected by the security element is detected visually or by machine substantially from the direction of impingement by a polarizer, and the appearance or the predetermined change of the appearance of the polarization feature in polarized light is regarded as a sign of the authenticity of the security element.
  • a planar security element in particular the direction of application is not perpendicular to the surface of the security element.
  • the polarization feature in unpolarized light is not even recognizable and is only visible in polarized light when viewed through the polarizer.
  • the detection of the reflected light is preferably carried out visually, but can also be done by machine, for example by a sensor.
  • the same polarizer can be used for the polarization of the impinging radiation and the analysis of the reflected radiation.
  • a second analysis polarizer may also be used which is located at a small angular distance from the first polarizer.
  • the second polarizer can then be designed in a different polarization mode (or circular instead of linear) and / or a different polarization direction than the first polarization direction. In order to obtain a high-contrast image of the structured birefringent layer.
  • the polarization feature can be detected by irradiating the security element with polarized light in the vicinity of the light source by observation through a polarizing filter.
  • the security element is irradiated with an area-wise anisotropic ⁇ / 4 layer (orientation 45 °) with linearly polarized light (polar filter position 0 °).
  • the incident light is converted from the ⁇ / 4 layer to circularly polarized light. This is reflected at the interface of Lüneburg lenses, for example on a metal layer.
  • the reflected circularly polarized light upon re-passage through the optically anisotropic layer, becomes linearly polarized light with the polarization plane rotated by 90 °. If the user observes the security element through an analyzer (in the example linear polarizing filter) in the position 0 °, the element appears dark. On the other hand, the adjoining area without an optically anisotropic layer appears bright. When one or both polarizing filters are rotated, the contrast ratios can change or even reverse.
  • the principle explained can be used, for example, when lighting security labels with a polarized flashlight or when illuminating license plates with one or more polarized headlamps of a police vehicle and each observation through a polarizing filter.
  • Another simple detection method is the Set a camera with polarizer in front of a flash and in front of the lens.
  • independent polarizers can be used with selectable position to each other.
  • the detection of the polarization feature even under actually very unfavorable lighting conditions (much false light) is possible, since the polarized flash light only has to prevail over the stray light in the short exposure time.
  • Nematic liquid crystals as an anisotropic layer have a phase-shifting effect both in visible light and in the adjacent wavelength ranges (UV, IR).
  • detection by irradiation with invisible light is also possible.
  • an infrared flash during speed checks with the aid of a suitable analyzer, if appropriate with a wavelength filter, the authenticity of a license plate can be checked unnoticed.
  • the sensors of normal digital cameras ⁇ are already sufficiently sensitive for such analysis purposes for IR light.
  • the optically anisotropic layer can be applied as a motif, can be applied in a spatially resolved with different orientation, or the layer material can be fixed in a spatially resolved state in another state.
  • the fixation can be done by, for example, irradiation with UV light.
  • the orientation may be, for example, by pressure of the liquid crystals (or a solution containing the potentially liquid crystalline substance) on a Substrate done, which allows the alignment.
  • This can be a PET film of good surface quality.
  • the uniformity can be improved in the desired preferred direction by mechanical pretreatment, for example, rubbing with velvet or a relatively soft felt or with suitable wipes.
  • any substrates can be made suitable for alignment by the use of additional alignment layers.
  • Suitable alignment layers are, for example, polyimides, but also polyvinyl alcohol or gum arabic. Generally, the solubility of the polymers which form an alignment layer in the liquid crystalline substance is very low.
  • the chemical substances mentioned are preferably prestructured mechanically, although the mechanical pre-structuring has the disadvantage that it is sometimes difficult to realize regions with spatially resolved different alignments.
  • a spatially resolved alignment can be achieved, for example, with photoalignment.
  • a substance is applied which, for example, by exposure to polarized (UV) light, obtains a structure which allows the orientation in a defined orientation to the polarization of the UV light. Exposure through a mask and sequential exposure (s) with a different polarization can create high-resolution images.
  • embossed structures Another method for spatially resolved alignment is the use of embossed structures.
  • the orientation of the embossed structures induces a corresponding orientation of the liquid crystals deposited thereon. Since in principle any orientation is possible, gray scale images can be generated in the later security element. But the best contrast is achieved if only two orientations are chosen, in such a way that a black and white contrast is created.
  • Liquid crystalline material may be applied by dissolving liquid crystals in a suitable solvent such as butyl acetate, butyl propionate, cyclopentanone, THF, MEK, toluene and mixtures thereof.
  • a suitable solvent such as butyl acetate, butyl propionate, cyclopentanone, THF, MEK, toluene and mixtures thereof.
  • This solution is low viscosity and can be applied by conventional printing methods such as flexographic printing, gravure printing, inkjet, die coating and the like. After physical drying, the alignment and crosslinking takes place, for example, with UV or ESH. Line widths down to about 80 ⁇ m can be printed easily using conventional printing methods.
  • the liquid-crystalline mixture is melted and pressed in the molten state.
  • the viscosity can be adapted to the desired printing process.
  • Particularly advantageous are screen printing and flexographic printing. If the chosen printing method does not allow acceptable spatial resolution, a patterned alignment layer must be used that allows for different orientation of the liquid crystals in the coating area. If the printing process is reaching spatial resolution, the desired motif can be printed directly, with a uniform alignment in the print area is acceptable and suitable. For the optical effect, other layers in the finished product are also important. Cast films are usually optically isotropic and do not interfere with the polarization effect.
  • optically anisotropic layers occur throughout the observed range (product surface up to and including the reflective layer / region) (for example stretched films) or scattering, for example through pigments or fillers, this can be unobtainable for the overall effect if, for example, the dispersion of an additional optically anisotropic layer in the light wavelength range in which the observation takes place is not too strong.
  • the retroreflective layer must be designed to reflect polarized light when exposed to polarized light. The polarization of the light may well be changed, only a strong depolarization must take place and the polarization change which may take place should be largely uniform over the entire area of the security element.
  • Particularly suitable retroreflective layers have been found to be Lüneburg lenses and microprismatic structures.
  • the security element can extend over the entire data medium over the entire data carrier (for example, the entire license plate number), but it can also be used as a patch or as a patch.
  • the security element can extend over the entire data medium over the entire data carrier (for example, the entire license plate number), but it can also be used as a patch or as a patch.
  • a transfer patch in which the carrier film is removed in a subsequent step, several concentric circumferential lines can be punched to avoid an uncontrolled flutter.
  • additional lines and motifs can be punched in the patch, which make it difficult to detach from the later data carrier, but do not obstruct the production process.
  • polarization features based on nematic liquid crystals in the banknote area of the polarizing filter is usually placed directly on the security feature and thus procured same polarizer and analyzer (namely inevitably identical) and also still in the same position, the requirements and possibilities are included Labels and license plates with retroreflective properties different.
  • the light source used for the verification is provided with a linear polarization filter, it may well be that a different, for example elliptical polarization of the light comes back through birefringent layers in the beam path and must be analyzed with optimum contrast. Therefore, in one embodiment, either the polarizer or the analyzer may carry additional birefringent layers to achieve optimum contrast in the sum.
  • Another embodiment is the additional introduction of a full-surface birefringent layer in the security feature in order to compensate for existing anyway birefringent layers for technical reasons.
  • This may be either a full-area liquid-crystalline layer of suitable orientation or, for example, a birefringent film, such as a stretched film. This effect can also be exploited for less finely structured polarization features.
  • a birefringent film is laminated or used as an intermediate layer from which certain characters, patterns, symbols and the like punched out, the pattern can be detected as well as positive patterns, characters or codes.
  • Another possibility is to destroy the birefringence of a film present after production by means of a suitable after-treatment. This can be done by short-term strong heating, for example by means of laser, or by dissolving the film material (if soluble by local application of solvent) and optionally drying / re-solidification, thereby partially birefringent stretched film and partially present a film that is analogous to a cast film is.
  • Security elements in two variants 3 is a detailed explanation of the operation of the security element of FIG. 2 (a) in an exploded view
  • FIG. 5 shows a representation like FIG. 4 for a further polarization feature
  • FIG. 7 is an illustration of the further processing of the polarization features of FIG. 6 into a stamped-out structured patch
  • FIG. 8 shows a security element with a retroreflective layer and a patch according to FIG. 7, and FIG.
  • FIG. 1 (a) illustrates a schematic diagram of the basic principle of the authentication of a retroreflective security element 30 according to an embodiment of the invention present on a data carrier, for example a motor vehicle license plate 10.
  • the security element 30 is shown hatched in FIG. 1 (a) for illustration, in fact the security element 30 appears colorless and structureless under normal illumination conditions, as shown in FIG. 1 (b), so that its presence is not readily apparent.
  • the retroreflective security element 30 of the tag 10 is exposed to polarized light and the light retroreflected by the security element 30 is viewed through an analyzer as shown in Fig. 1 (a).
  • unpolarized light 14 is polarized by a user 12 through a linear polarizer 16 and the indicator 10 is acted upon by the polarized light 18.
  • the reflected light 20 travels back to the user 12 within a small retroreflective cone due to the retroreflective properties of the security element 30, again passing the linear polarizer 16.
  • the light 22 passed through the linear polarizer 16 is due to the foregoing interference the polarization state of the light in the security element 30 is no longer structureless, but shows as authenticity proof a desired appearance 32.
  • FIG. 1 (c) shows the security element 30 in the polarized light in the analyzer with the word "OK".
  • this authenticity check can be carried out by the user 12 from virtually any desired position, since the retroreflective properties of the security element 30 ensure that the incident light 18 is always reflected back to the user 12.
  • Figure 2 shows the basic structure of inventive security elements. The operation of the security elements is explained in more detail in the exploded view of FIG. 3 using the example of the embodiment of FIG. 2 (a).
  • a security element 40 comprises a retroreflective layer 42 and a birefringent layer 44 applied in the form of the word "OK."
  • the retroreflective layer 42 is formed on the basis of microprismatic structures, for example, and is the birefringent layer For example, a nematic liquid crystal layer which acts as X / 4 layer due to their layer thickness.
  • the birefringent layer 46 is present in its entirety and contains various regions 48 A, 48 B with different optical effects, which are formed in the form of the lettering "OK".
  • the areas 48A represent the letters of the lettering "OK” and the areas 48B the complementary background areas.
  • the retroreflecting layer 42 of the security element 40 in this embodiment is applied only in regions, namely in the form of the lettering "OK", so that it is adjacent to regions 52 in which a nematic ⁇ / 4 liquid crystal layer 44 is present, there are also regions 50 without nematic liquid crystal layer.
  • Fig. 1 (a) polarized by the user 12 emitted by a light source unpolarized light 54 by a linear polarizer 16
  • the polarized light 56 strikes in areas 50 without Nematen für 44 on the retroreflective layer 42 and becomes reflected back in the direction of incidence substantially without changing the polarization state of the incident light.
  • the reflected light 58 therefore has the same state of polarization as the incident light 56 and can pass through the linear polarizer 16 unhindered (reference numeral 60).
  • the areas 50 in the polarized light therefore appear bright.
  • the linearly polarized light 56 is converted from the Nematen layer to circularly polarized light 62.
  • the circularly polarized light 62 strikes the retroreflective layer 42 and is reflected back from it in the direction of incidence.
  • the reflected circularly polarized light 64 again traverses the ⁇ / 4 Nematen slaughter 44 and is thereby converted into linearly polarized light 66, the polarization vector is now, however, perpendicular to the output polarization.
  • the linearly polarized light 66 therefore can not pass the linear polarizer 16 (reference numeral 68) so that the areas 52 for the viewer 12 appear dark.
  • the polarizer for polarizing the incident light and the analyzer for viewing the reflected from the security element Because of the small but in practice finite aperture cone of retroreflection, the polarizer for polarizing the incident light and the analyzer for viewing the reflected from the security element
  • the polarizer may be disposed on the headlight of a police vehicle while the analyzer is in spectacles worn by a police officer sitting in the police vehicle.
  • polarizer and analyzer spatially separated they can also be designed differently.
  • the polarizer may be a linear polarizer and the analyzer may be a circular polarizer or a linear polarizer with a different polarization vector.
  • FIGS. 4 to 9. 4 shows a cross section of a first polarization feature 70.
  • a PET film 72 having a thickness of 23 ⁇ m is provided and provided with a UV lacquer as a release layer 73 and a further UV embossing lacquer layer 74.
  • the desired hidden motif is embossed with an alignable structure 76.
  • a hologram embossing can be made in addition.
  • a nematic liquid-crystalline solution is printed on the structure 76 which can be aligned.
  • the nemate layer 78 is present in a layer thickness between 0.8 ⁇ m and 3 ⁇ m, preferably of about 1.2 ⁇ m.
  • the liquid crystals are aligned by the alignment structure 76.
  • the liquid crystals are crosslinked, for example by UV exposure, preferably at reduced oxygen concentration (nitrogen inertization). Designs in which the PET film 72 is to remain in the finished security element are formed without a release layer 73.
  • a structured or unstructured metal layer for example of aluminum or chromium
  • the structuring can take place, for example, by covering a partial area with a wash color, metallization and subsequent removal of the wash color with the metallization applied there.
  • other structuring methods such as etching methods can be used.
  • the polarizing feature 70 is provided with primer (s) and heat sealing lacquers or other adhesives and applied to the desired target substrate.
  • the production can also be a
  • Cutting and / or punching process to transmit the polarizing feature 70 with a desired shape can take place in such a way that only partial regions of the formed polarization feature are transferred, while other partial regions remain on the carrier foil 72.
  • partial regions of the polarization feature can be removed from the carrier foil 72 and the remaining partial regions can then be completely transferred.
  • the polarization feature 80 of FIG. 5 is basically constructed like the polarization feature 70, wherein the UV embossing lacquer layer 74 is provided in the embodiment of FIG. 5 with an embossment 82, both an alignment embossing for the alignment of the liquid crystals of the Nematen- layer 78 and represents a hologram embossing.
  • an alignment embossing for the alignment of the liquid crystals of the Nematen- layer 78 and represents a hologram embossing.
  • a reflection hologram is visible when viewed.
  • FIG. 6 (a) shows an exemplary embodiment of a second polarization feature 90.
  • a smooth PET film 92 having a good surface quality with a thickness of 23 ⁇ m is provided and printed directly with a liquid-crystalline solution having the desired hidden motif , for example in gravure printing. Subsequently, the liquid-crystalline solution is dried and crosslinked. More precisely, the printed solution itself is not yet in the liquid-crystalline state, but rather the substances contained in the nematic liquid crystal do not pass until after and after physical drying.
  • a transfer auxiliary layer 96 is provided in the form of a UV lacquer layer.
  • FIG. 6 (b) is based on the embodiment of FIG. 6.
  • a UV embossing lacquer 102 is applied to the UV lacquer layer 96, embossed with a hologram embossing 104 and provided with metallization 106 in partial regions.
  • a UV embossing lacquer 102 is likewise applied to the UV lacquer layer 96, provided with a hologram embossing 104, and overlaid with a higher refractive UV lacquer 112.
  • the hologram motif of the hologram embossing is visible in this embodiment by the refractive index difference of the lacquer layers 102, 112.
  • FIG. 7 illustrates this further processing into a punched out structured patch.
  • the starting point is a polarization feature 120 with a carrier foil 122, for example according to one of the embodiments of FIGS. 4, 5 or 6 (a), (b) or (c).
  • an approximately 12 .mu.m thick PET film 124 is laminated with a laminating adhesive 126 on the lacquer side of the polarization feature 120 of FIG.
  • a laminating adhesive 126 On the opposite side is laminated with a laminating adhesive 126, a 12 ⁇ also thick support film 128.
  • the resulting layer composite is then punched from the lacquer side to the extent (reference numeral 134) that the polarization feature 120 with the containing liquid crystal layer 78 or 94 and the optional transfer assist layer 96 are punched.
  • the punching on the support film 122 ends, but a Ans dance the carrier film 122 does not bother, since the support film 128 prevents further tearing.
  • the intermediate areas between the generated patches 136 may be truncated. Eventually required tax stamps are advantageously printed on the opposite side or remain when Ausmittern. Finally, the film is suitably cut with the layer composite.
  • the adhesive is present only in the region of the patches 132, the geometry of a stamp used for application is not critical. Only the desired unit will be transmitted. The detachment from the carrier film 122 can be supported by a suitable adjustment of the take-off angle, for example with dispensing wedges.
  • FIG. 8 shows a security element 140 according to the invention with a retroreflective layer 42 onto which patches 136 according to FIG. 7 are applied in regions via suitable intermediate layers 142.
  • the layer sequence 121 of the polarization feature 120 is embodied, for example, analogously to FIG. 4, that is to say comprising a thickness of nematic layer 78 which is approximately 1.2 ⁇ m thick and a UV embossing lacquer layer 74 for the alignment of the liquid crystals.
  • the patches 136 are shown with the outline of a desired icon, such as a coat of arms, or with the outline of a desired font. zugs, such as the lettering shown in Fig. 1 "OK" applied. After application, the patches were still provided with suitable final layers 144, for example a protective layer.
  • the patches 136 are colorless and structureless under normal lighting conditions and only appear when illuminated with polarized light and when viewed in reflected light through a polarizing filter.
  • FIG. 9 (a) shows a license plate number 150 onto which a security element 140 according to FIG. 8 with a patch 136 in the form of a coat of arms is laminated in a partial area.
  • the crest 136 is not visible under normal lighting conditions, but appears only when the polarization light plate 150 is illuminated and when a reflected light is reflected through a polarizing filter.
  • a conventional hologram patch 152 is shown, which is also visible under normal lighting conditions.
  • a security film 154 is laminated on the entire area of the license plate 150, which in principle is designed like the security element 140 of FIG. 8 and carries a multiplicity of regularly spaced crest-shaped patches 136.
  • FIG. 9 (c) shows an inverse design in which a security foil 156 of the type described in FIG. 8 was laminated over the entire surface of the license plate 150 from which previously emblem-shaped symbols 158 were punched out.
  • the positive crests of FIG. 9 (b) and the negative crest - shaped recesses of FIG. 9 (c) are not visible under normal lighting conditions but only appear when the illuminator is illuminated Flag 150 with polarized light and when viewing the reflected light through a polarizing filter in appearance.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Polarising Elements (AREA)
  • Credit Cards Or The Like (AREA)

Abstract

L'invention concerne un élément de sécurité réfléchissant (40) permettant le contrôle d'authenticité sous lumière polarisée (18), ledit élément de sécurité comprenant une couche rétro-réfléchissante (42) et une couche biréfringente (44) structurée située sur la couche rétro-réfléchissante (42).
EP18792849.4A 2017-10-25 2018-10-22 Élément de sécurité réfléchissant Active EP3700756B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102017009936.7A DE102017009936A1 (de) 2017-10-25 2017-10-25 Reflektives Sicherheitselement
PCT/EP2018/000481 WO2019081056A1 (fr) 2017-10-25 2018-10-22 Élément de sécurité réfléchissant

Publications (2)

Publication Number Publication Date
EP3700756A1 true EP3700756A1 (fr) 2020-09-02
EP3700756B1 EP3700756B1 (fr) 2021-09-29

Family

ID=63965621

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Application Number Title Priority Date Filing Date
EP18792849.4A Active EP3700756B1 (fr) 2017-10-25 2018-10-22 Élément de sécurité réfléchissant

Country Status (5)

Country Link
US (1) US20210086544A1 (fr)
EP (1) EP3700756B1 (fr)
CN (1) CN111556813B (fr)
DE (1) DE102017009936A1 (fr)
WO (1) WO2019081056A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102023100676B3 (de) 2023-01-12 2024-03-07 Melzer Maschinenbau Gmbh Sicherheitselement für ein Sicherheitsdokument

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5169707A (en) * 1991-05-08 1992-12-08 Minnesota Mining And Manufacturing Company Retroreflective security laminates with dual level verification
US6157486A (en) * 1998-01-13 2000-12-05 3M Innovative Properties Company Retroreflective dichroic reflector
JP5481250B2 (ja) * 2010-03-26 2014-04-23 富士フイルム株式会社 複屈折パターンを有する物品
JP2013073021A (ja) * 2011-09-28 2013-04-22 Fujifilm Corp 潜像を有する物品
WO2015134255A1 (fr) * 2014-03-07 2015-09-11 3M Innovative Properties Company Source de lumière incorporant un film optique multicouche

Also Published As

Publication number Publication date
CN111556813B (zh) 2022-03-22
CN111556813A (zh) 2020-08-18
EP3700756B1 (fr) 2021-09-29
WO2019081056A1 (fr) 2019-05-02
US20210086544A1 (en) 2021-03-25
DE102017009936A1 (de) 2019-04-25

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