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
  • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
  • B42D25/29—Securities; Bank notes
• • 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
  • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
  • B42D25/21—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose for multiple purposes
• • 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
  • B42D25/351—Translucent or partly translucent parts, e.g. windows
• • 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
• • 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
  • B42D25/369—Magnetised or magnetisable materials
• • 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
• • 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
• • B42D2035/24—

Definitions

• the invention relates to a security element for securing valuables, a method for producing such a security element and a security paper and a data carrier with such a security element.
• 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.
• security elements can be designed, 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 applied directly to a value document.
• a special role in authenticity assurance is played by security elements that show viewing-angle-dependent visual effects, since they can not be reproduced even with state-of-the-art copiers.
• the security elements are equipped with optically variable elements that give the viewer a different image impression under different viewing angles and, for example, show a different color or brightness impression and / or another graphic motif depending on the viewing angle.
• the present invention seeks to further improve a security element of the type mentioned above and in particular to provide a security element with an attractive visual appearance and high security against counterfeiting.
• a relief structure over which a thin-film element with color-shift effect is arranged in an overlap region, wherein the thin-film element contains an absorber layer with recesses in the region of which no color-shift effect can be recognized, and
• a semitransparent ink layer which is arranged in the region of the recesses of the absorber layer above the thin-film element and the relief structure, wherein the color impression of the thin-film element is adapted to the color impression of at least a portion of the semitransparent ink layer when viewed under predetermined viewing conditions.
• a relief structure in particular a microrelief structure of the kind described in more detail below, is combined with two different color areas, which act very similar from a certain viewing direction, but behave differently when the security element is tilted
• Semitransparent color layer covered, color-shifting areas the color impression of the relief structure for the viewer changes when tilting the security element, while the recessed and covered areas remain color constant when tilted.
• Such a combination of color-constant and color-variable relief structure areas is optically attractive and self-explanatory for the user, since the color-constant areas simultaneously form a visually quiescent pole and a comparison point for the color-variable areas in the authenticity check.
• the combination of two color effects in the immediate vicinity makes it difficult to adjust the security element, as freely available colors or transparencies with color-shift effects can no longer be used directly.
• the thin-film element can be arranged partially or completely over the relief structure, or even protrude beyond it.
• the semitransparent ink layer completely fills the region of the recesses in the absorber layer. Color constants and color-variable areas then complement each other to the complete picture impression of the security element.
• the semitransparent ink layer does not completely fill the region of the recesses in the absorber layer, but only partially. In addition to the color-variable and the color-constant areas, this creates another type of reflection areas which have a metallic appearance, since their visual impression is determined by the reflection layer of the thin-film element. The design freedom for the design of the security elements is further increased by this measure.
• the semitransparent ink layer is additionally present in non-recessed areas of the absorber layer above the thin-film element. Such areas remain largely when tilted, if usually not completely color constant. Their use is particularly suitable in those cases in which fine characters or patterns are to be surrounded as color-constant relief areas of color-variable relief areas, where it is often difficult to save the absorber layer accurately under very small color layer areas. Especially with small structures and adjacent, strongly farbkippenden areas, the slightly lower color constancy is virtually imperceptible to the viewer.
• the semitransparent color layer preferably has a light transmittance between 30% and 95%, more preferably between 60% and 95% and very particularly preferably between 80% and 95% % on.
• the semi-transparent ink layer can be applied in various ways; it is advantageously printed on it, for example in screen-printing, gravure printing, flexographic, or any other suitable printing process.
• the semitransparent ink layer can be printed directly onto the thin-film element, but it is also possible to provide between the ink layer and the thin-film element transparent intermediate layers which, for example, act as a protective layer or adhesive layer. It is also possible to provide such transparent intermediate layers between the color layer and the phase delay layer.
• the recesses in the absorber layer and / or the semitransparent ink layer are preferably in the form of characters, patterns or codes.
• This also includes designs in which the color layer has recesses in the form of characters, patterns or codes.
• the characters, patterns or codes of the recesses and the color layer can be congruent, for example if the color layer completely fills the recesses of the absorber layer.
• the respective characters, patterns or codes can also differ, for example if the ink layer only partially fills the recesses or is also present in regions outside the recesses.
• the semitransparent ink layer can also have several subregions with different color impressions, in which case the color impression of the thin film element is adapted to the color impression of at least one of the subregions when viewed under predetermined viewing conditions.
• a particularly attractive effect can be achieved if the thin-film element and the semi-transparent ink layer are matched to one another such that when the security element is viewed vertically Color impression of the thin-film element outside the covered areas substantially corresponds to the color impression of at least a portion of the semi-transparent ink layer.
• the color-variable and the color-constant areas initially convey essentially the same color impression.
• the color impression changes in the color-variable areas, while it remains unchanged in the color-constant covered areas.
• the thin-film element has a reflection layer, an absorber layer and a dielectric spacer layer arranged between the reflection layer and the absorber layer.
• the color shift effect in such thin-film elements is based on viewing angle-dependent interference effects due to interference of the light beams reflected at the different sub-layers of the element.
• the path difference of the light reflected at the different layers depends, on the one hand, on the optical thickness of the dielectric spacer layer, which defines the distance between the absorber layer and the reflection layer, and on the other hand varies with the respective viewing angle.
• the reflection layer of the thin-film element is preferably formed by an opaque or by a semitransparent metal layer, in particular aluminum.
• an at least partially magnetic layer can also be used so that a further authenticity feature can be integrated without requiring an additional layer in the layer structure.
• the reflective layer may further comprise recesses in the form of patterns, characters or codes that form transparent or semi-transparent regions in the thin-film element.
• the transparent or semi-transparent recess areas the observer has a striking contrast to the surrounding color effects.
• the patterns, characters or codes in transmitted light can light up brightly when the thin-film element and the relief structure are applied to a transparent or translucent carrier.
• the recesses in the reflection layers can also be grid-like, preferably with a small areal proportion of 40% or less, so that they are practically inconspicuous in reflected light and only appear in transmitted light.
• the thin-film element can also be formed by superimposed absorber layers and dielectric spacer layers, it also being possible for a plurality of absorber and spacer layers to be arranged alternately one above the other.
• Such thin-film elements also show a color-tilting effect, but are not opaque, so that the color-shift effect is also visible from the rear side of the security element.
• the dielectric spacer layer is preferably produced by a vacuum vapor method.
• the distance layer can also be formed by a printing layer or by an ultrathin film, in particular a stretched polyester film.
• Particularly preferred is currently a design in which the dielectric spacer layer is formed by a low-refractive dielectric layer, in particular a vapor-deposited SiCte layer or an MgF 2 layer.
• the relief structure of the security element can in particular represent a diffractive structure, such as a hologram, a holographic grating image or a hologram-like diffraction structure, or else an achromatic structure, such as a matt structure with a non-colored, typically silvery matt appearance, a micromirror structure. tion, a Blazegitter with a sawtooth groove profile or Fresnellinsen- arrangement.
• the dimensions of the structural elements of the diffractive relief structures are usually in the order of magnitude of the wavelength of the light, that is to say generally between 300 nm and 1 ⁇ m.
• Some relief structures also have smaller structural elements, such as sub-wavelength lattices or moth-eye structures, whose structural elements may also be smaller than 100 nm.
• the structural elements of achromatic relief structures are sometimes larger than 1 .mu.m, the dimensions of micromirrors or Blazegitterlinien extend approximately to a height of about 15 microns and a lateral extent of about 30 microns.
• Relief structures with structural elements of a dimension below 30 ⁇ m and in particular relief structures with structural elements of the order of magnitude of the light wave In the context of this description, wavelength or less are referred to as microstructure structures.
• a transparent phase-delay layer is arranged over the thin-film element in regions, forming a phase-shifting layer for light from the visible wavelength range.
• Phase-retarding layers which in the context of this description are also sometimes called phase-shifting layers, are optically active layers which act on the phase of a transmitted light wave.
• the partial beams of an incident polarized light wave receive a path difference and thus a phase difference due to different refractive indices. If the phase difference of the two partial beams is just one-half or one-quarter wavelength, so-called ⁇ / 2 or ⁇ / 4 layers are obtained.
• the phase delay of the phase retardation layer in the invention corresponds to a retardation between about ⁇ / 6 and about ⁇ / 2, more preferably between about ⁇ / 4 and about ⁇ / 2.
• the path difference is given modulo ⁇ , ie in the range between 0 and ⁇ , since a layer with a path difference of, for example, 5/4 * ⁇ or 9/4 * ⁇ causes the same phase delay as a ⁇ / 4 layer.
• the phase-shifting layer is formed from nematic liquid-crystalline material and / or that the phase-delay layer is in the form of patterns, characters or a coding.
• the semi-transparent ink layer is selected such that it substantially preserves the polarization state of transmitted light from the visible wavelength range.
• the patterns, characters or codes formed by the phase retardation layer can be made equally visible in both the color-variable and color-constant regions.
• the security element is preferably present on a substrate, which may be formed in particular by a plastic film.
• the substrate can be removed from the layer structure of the security element or it can remain as a protective layer as an integral part of the security element in the layer structure.
• a release or release layer for example a wax, can also be provided between the security element and the substrate.
• the security element is a security thread, a security tape, a security strip, a patch or a label for application to a security paper, document of value or the like.
• the security element can also have further layers, such as protective layers or additional effect layers with other security features.
• the invention also includes a method for producing a security element of the type described, in which
• an embossing lacquer layer is applied to a substrate and embossed in the form of a desired relief structure
• a thin-film element with a color-shift effect is arranged in a region of overlap above the relief structure. Sorber Mrs of the thin-film element is provided with recesses in the area no color shift effect is recognizable, and
• a semitransparent ink layer is arranged above the thin-film element and the relief structure, the color impression of the thin-film element, when viewed under predetermined viewing conditions, being adapted to the color impression of at least one subregion of the semitransparent ink layer.
• a transparent phase retardation layer is arranged in regions over the thin-film element, forming a phase-shifting layer for light from the visible wavelength range.
• the semitransparent ink layer is advantageously printed in the process according to the invention, in particular in screen printing, gravure printing or flexographic printing processes.
• the phase retardation layer can also be advantageously printed on the thin-film element and optionally the previously applied ink layer.
• the phase delay layer can be applied to a separate carrier foil and transferred to the thin-layer element with the applied color layer.
• the invention further comprises a security paper with a security element of the type described, as well as a data carrier, which is equipped with such a security element.
• the data carrier may in particular be a banknote, a value document, a passport, a document or an identity card.
• the security elements described, security papers or data carriers can be used in particular for securing objects of any kind. 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.
• FIG. 1 is a schematic representation of a banknote with a security element according to the invention
• FIG. 2 shows a cross section through a security element according to a
• FIG. 3 shows schematically the visual impression of a security element according to the invention (a) when viewed vertically and (b) when viewed obliquely, in each case without aids,
• Fig. 4 shows a cross section through a security element according to another embodiment of the invention, in which the semi-transparent ink layer, the region of the recesses in the
• FIG. 5 shows a color-shift hologram according to a further exemplary embodiment of the invention, in which the color-constant and color-variable regions are combined with a hidden security feature
• FIG Fig. 6 shows the visual impression of the security element of Fig. 5 when viewed perpendicularly with an applied circular polarizer.
• FIG. 1 shows a schematic diagram of a banknote 10 with a security element 12 according to the invention in the form of a glued-on transfer element.
• the invention is not limited to transfer elements and 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 like ,
• security threads and, in addition to supervisory elements also translucent elements are considered in addition to transfer elements.
• FIG. 2 represents a cross section through the security element and Fig. 3 in (a) and (b) schematically the visual impression of the security element of different Viewing directions shows.
• the security element 12 contains a carrier foil 20 and an embossed and cured UV lacquer layer 22 applied to the carrier foil 20.
• the embossed structures of the lacquer layer 22 form a diffractive relief structure in the form of a hologram.
• the embossed structures can also be a holographic grating image, a hologram-like diffraction structure or an achromatic Represent microstructure with a non-colored, for example, silvery matt appearance.
• a thin-film element 24 with a color-shift effect is applied to the relief structure of the lacquer layer 22, which comprises a reflection layer 26 formed by an opaque aluminum layer, a dielectric SiO 2 spacer layer 28 deposited on the reflection layer 26 and a partially transparent absorber layer 30 made of chromium.
• the color shift effect of such a thin-film element 24 is based on interference effects due to multiple reflections in the partial layers 26, 28, 30 of the element.
• the absorber layer 30 has recesses 32, in the region of which the thin-film element 24 has no color-shift effect due to the lack of interference.
• the security element 12 further contains a semi-transparent ink layer 34, which is arranged in the region of the recesses 32 of the absorber layer 30 above the thin-film element 24 and the relief structure, the semitransparent ink layer 34 in the exemplary embodiment shown in FIG. 2, the recessed areas 32 of the absorber layer completely filled out. In areas 36 outside the recessed areas 32, the thin-film element 24 is present without a printed ink layer. In the idealized illustration of FIG. 2, the ink layer 34 ends in registration with the recesses 32 of the absorber layer.
• the ink layer 34 may slightly overlap the absorber, or the non-recessed absorber region may protrude slightly into the ink layer regions 34.
• the thin-film element 24 and the semitransparent ink layer 34 are coordinated with one another in such a way that they produce substantially the same color impression at a perpendicular viewing angle.
• the color impression of the thin-film element 24 changes in the uncovered areas 36 due to the color shift effect occurring there, while the color impression in the first areas 32, 34 covered by the color layer does not change during tilting.
• the thin-film element 24 may be designed so that its color impression changes from magenta when viewed perpendicularly to green when viewed obliquely. Coordinated with this, the semitransparent ink layer 34 when viewed perpendicularly conveys a likewise magenta color impression, which, unlike the color impression of the thin-film element 24, remains unchanged when the security element 12 is tilted.
• the security element 12 thus shows the viewer a hologram motif 40 with two color areas, which behave differently when the security element is tilted.
• the covered areas 32, 34 and the uncovered areas 36 when viewed vertically have a very similar or even the same color impression.
• the color impression of the uncovered areas 36 changes from magenta to green as the tilt angle increases, while the color impression in the areas covered by the color layer 34 remains constant magenta.
• recesses 42 may also be incorporated in the reflector layer 26 of the thin-film element 24, which form, for example, a negative writing.
• the thin-film element 24 is transparent or translucent, so that in addition to the described effects there is a striking contrast effect in the transmitted light.
• translucency is used here in the sense of a certain translucency, with translucent layers generally reducing the brightness of the objects located behind or below them and / or changing their color.
• the security element 50 shown in FIG. 4 largely corresponds in its design to the security element 12 of FIGS. 2 and 3.
• the semitransparent ink layer 34 in the security element 50 fills the area of the recesses 32 in the absorber layer 30 of the thin-film element 24 not completely, but only partially.
• another hologram region 56 is formed, in which the visual impression of the security element 50 is determined by the aluminum reflection layer 26, so that the hologram there is silvery-metallic appears.
• the variety of combinations and the creative freedom for the designer are further enhanced by this measure.
• the semi-transparent ink layer 54 additionally exists in non-recessed areas 52 of the absorber layer 30.
• such areas 52, 54 produce substantially the same color impression as the covered areas 32, 34 and the uncovered areas 36.
• the color impression of the regions 52, 54 varies to some extent upon tilting of the security element 50, since the changing tilt color of the thin-film element 24 differs due to the semi-transparent ink layer 34, depending on the degree of transparency of the light , something shines through.
• largely color-constant regions 52, 54 can be particularly advantageous if fine characters or patterns are to be surrounded by color-variable relief regions as color-constant relief regions. In this case, it is often difficult, if not impossible, to accurately expose the absorber layer 30 under the very small ink layer areas 54. Although the largely color-constant areas 52, 54 have a slightly lower color consistency when tilting than the completely color-constant areas 32, 34, this is practically not the case for the viewer, especially in the case of small structures and compared to the adjacent, strongly color-tilting areas 36 imperceptible.
• Figures 5 and 6 show, as a further embodiment of the invention, a color-shift hologram in which the visual effects described above are combined with a hidden security feature.
• the security element 60 of FIG. 5 contains a transparent phase delay layer 62, which is arranged in the form of a pattern in regions 64 above the thin-film element 24.
• the phase retardation layer 62 is made of a birefringent material, for example of nematic liquid crystalline material.
• the layer thickness of the phase retardation layer 62 is typically selected so that its phase delay corresponds to a path difference between about ⁇ / 6 and about ⁇ / 2, preferably about ⁇ / 4, where ⁇ represents a wavelength from the visible spectral range.
• the regions 64 with the phase retardation layer 62 are practically undetectable, since the phase retardation of the layer 62 acts equally on all polarization directions of the incident light and its light absorption is negligibly small.
• the operation of the hidden security feature will now be exemplified by means of a ⁇ / 4 phase retardation layer 62 and an applied circular polarizer 70 which transmits only right circularly polarized light. Under these conditions, incoming unpolarized Only the right circularly polarized portion of the circular polarizer 70 is allowed to pass through. In the subregions 66 of the security element without phase retardation layer 62, the right circularly polarized light is reflected by the metallic reflector layer 26 of the thin film element 24 with the polarization direction reversed, that is to say as left circularly polarized light. The reflected left circularly polarized light is blocked by the circular polarizer 70 so that the partial areas 66 appear dark to the viewer.
• the right circularly polarized light is converted to linearly polarized light by the phase retardation layer 62 prior to reflection at the reflector layer 26.
• the unaltered linearly polarized light after reflection passes through the phase retardation layer 62 again and is thereby converted into right-circularly polarized light, which can easily pass through the circular polarizer 70 under the chosen conditions.
• the pattern of the open security feature therefore appears to the viewer essentially unchanged as bright.
• the semi-transparent ink layer 34, 54 largely preserves the polarization state of the transmitted light. This ensures that the pattern formed by the phase retardation layer 62 can be made equally visible in the color-variable and color-constant regions.
• the reflective layer and the absorber layer of the embodiment of Figures 5 and 6 may be provided with recesses, for example a produce negative metallic writing or local areas of transparency in an otherwise opaque security element.
• the semi-transparent ink layer can also have a plurality of partial regions with different color impressions.
• the color impression of the thin-film element can then be adapted to the color impression of one or more of the subregions for one or also for a plurality of predetermined viewing conditions.
• a thin-film element whose color impression changes from magenta to green when tilted can be combined with a semi-transparent color layer having two partial regions, of which the first partial region appears magenta and the second partial region green.
• the color impression of the thin-film element substantially corresponds to the color impression of the first subregion of the color layer (magenta), while it corresponds obliquely to the color impression of the second subregion of the color layer (green).
• Such layer sequences also have a color-shift effect, but are not opaque, so that the color-shift effect is also visible from the rear side of the security element.
• Security elements with such thin-film Elements can be used in particular for documents with viewing areas.
• the mentioned recesses in the reflection layers can also be grid-like, preferably with a small areal proportion of 40% or less.
• the recesses of the reflection layers are then practically not incident on reflected light, but only appear in transmitted light.

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• Business, Economics & Management (AREA)
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• Finance (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Credit Cards Or The Like (AREA)
• Printing Methods (AREA)

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• 2007
  • 2007-12-20 DE DE102007061827A patent/DE102007061827A1/de not_active Withdrawn
• 2008
  • 2008-12-17 WO PCT/EP2008/010740 patent/WO2009080262A1/fr active Application Filing
  • 2008-12-17 EP EP08865891A patent/EP2225109B1/fr not_active Not-in-force
  • 2008-12-17 AT AT08865891T patent/ATE516968T1/de active
  • 2008-12-17 US US12/809,002 patent/US8613471B2/en active Active

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