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
  • B42D25/324—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

Definitions

• the invention relates to an optically variable display element with a reflective surface area, which can be used as a security element to protect valuables or as a decorative element, for example for the surface design of products.
• Data carriers such as value or identification documents, but also other valuable objects, such as branded goods, are often provided with security elements for protection, which allow the authenticity of the data carrier to be checked and which also serve as protection against unauthorized reproduction.
• Security elements with a viewing angle-dependent or three-dimensional appearance play a special role in ensuring authenticity, as these cannot be reproduced even with the most modern copiers.
• the security elements are equipped with optically variable elements that give the viewer a different image impression from different viewing angles and, for example, show a different color or brightness impression and/or a different graphic motif depending on the viewing angle.
• the prior art describes, for example, movement effects, pump effects, depth effects or flip effects as optically variable effects, which are realized with the aid of holograms, microlenses or micromirrors.
• the invention is based on the object of specifying optically variable display elements with an attractive visual appearance, which can be produced inexpensively and ideally also have a high degree of security against forgery.
• the invention contains an optically variable display element with at least one reflective surface area which, when viewed in reflected light, produces a three-dimensional display for at least two different viewing directions.
• the three-dimensional representations overlap at least partially and have different colors at least in certain areas in the overlapping area.
• the at least one reflective surface area contains a plurality of reflective facets in a first and a second sub-area, which at least partially overlap each other, which are oriented in such a way that on the one hand the facets of the first sub-area have a first three-dimensional representation with ner produce a surface that protrudes and/or recedes in relation to its actual three-dimensional shape, and that on the other hand the facets of the second partial area produce a second three-dimensional representation for the observer from the second viewing direction with a surface that protrudes and/or recedes in relation to its actual three-dimensional shape.
• the representation generated for the viewer with a projecting and/or receding surface is understood here in particular to mean that the partial area can be perceived as a continuously curved surface.
• the depictions that appear curved in the present sense imitate a curvature by reproducing the reflection behavior of a curved surface. This results in an indirect impression of depth or a 3D impression. This impression can therefore also be described as a "2 Vi"-dimensional representation or relief-like representation.
• the facets of the reflective surface area are at least partially provided with sub-wavelength structures in the overlapping area of the first and second partial area, which generate the different colors of the three-dimensional representations.
• the facets of the reflective surface area are provided with a reflection-increasing coating, in particular with a metallization, a high-index layer and/or a thin-layer structure. Both the facets of the first subarea and the facets of the second subarea are provided with the reflection-increasing coating.
• the metallization can be formed, for example, by Al, Ag, Cr, Cu, Fe or an alloy of the metals mentioned be.
• a ZnS layer for example, can be provided as the high-index layer.
• color-shifting systems with an absorber/dielectric/reflector structure or symmetrical semitransparent absorber/dielectric/absorber structures come into consideration as thin-layer structures.
• the facets of the reflective surface area are advantageously formed in an embossed lacquer layer, in particular a thermoplastic or radiation-curing embossed lacquer layer.
• embossed lacquer layer in particular a thermoplastic or radiation-curing embossed lacquer layer.
• UV-curing embossing lacquer layer is particularly advantageous.
• the arrangement of the facets, including the sub-wavelength structures, is embossed into the embossing lacquer layer and the embossed structure is preferably coated with the said reflection-increasing coating.
• the embossed and preferably coated embossed structure is advantageously embedded in a further lacquer layer, for example a protective lacquer layer.
• the facets of the reflective surface area are particularly preferably formed by a micromirror arrangement with specularly reflecting micromirrors, in particular by micromirrors with a linear dimension between 3 ⁇ m and 100 ⁇ m, preferably between 5 ⁇ m and 50 ⁇ m.
• the micromirrors can in particular have a triangular, square , have a rectangular, hexagonal or other polygonal base.
• the pitch of the micromirrors is preferably less than 15 gm, preferably less than 10 gm.
• the sub-wavelength structures are advantageously characterized by periodic structures with a period length between 100 nm and 500 nm, preferably between 200 nm and 400 nm, and/or a depth between 50 nm and 400 nm, preferably formed between 100 nm and 300 nm.
• the aspect ratio of such structures i.e. the ratio between the width of an elevation or depression and the corresponding structure depth, can advantageously be between 1/4 and 4, preferably between 1/3 and 3 and particularly preferably between 1/2 and 2 .
• the period length of the sub-wavelength structures and the linear dimensions of the micromirrors are preferably coordinated with one another, so that at least 10, preferably at least 20, complete periods of the sub-wavelength structures can be accommodated on each micromirror.
• aperiodic structures can also be used, in which case the mean center-to-center distances of the sub-wavelength structures are advantageously between 100 and 500 nm, preferably between 200 and 400 nm.
• the sub-wavelength structures are formed by one-dimensional gratings, which can also have a polarizing effect.
• the sub-wavelength structures are formed by two-dimensional gratings, in particular with a rectangular, square, hexagonal or parallelogram-shaped grating symmetry.
• the subwavelength structures can be formed in particular by crossed sinusoidal gratings, crossed rectangular gratings, hexagonal grating structures, or by nanodot or nanohole arrays.
• sinusoidal gratings, rectangular gratings (binary structures), or also profile shapes with concave and/or convex sections come into consideration as profile shapes for the sub-wavelength structures.
• periodic Arrangements of nanoholes or nanodots with any outline shape can be used.
• irregularly arranged structures is also possible, which can be arranged randomly or quasi-periodically, for example, and can be characterized by the parameters outline shape, depth, profile shape (e.g. binary or other shapes with concave and/or convex sections).
• structures are also possible, as are described in the publications EP 3367140 A1 and EP 3401 712 A1, the disclosure content of which is included in the present application in this respect.
• At least two different sub-wavelength structures are advantageously provided for generating the different colors, which differ in particular in their period length and/or their depth and/or their profile shape (e.g. due to different ratios of web - and ditch width) differ.
• the sub-wavelength structures for the different colors of the three-dimensional representations are advantageously arranged registered to the facets of the reflective surface area, so that each facet is only covered with a specific type of sub-wavelength structures. In principle, however, it is also possible for the color boundaries to run independently of the facet subdivision of the surface area, so that there can also be facets with different sub-wavelength structures.
• the colors that are visible to an observer when viewing the display element are each generated by a specific type of sub-wavelength structure that is responsible for this color is characteristic.
• the colors visible to an observer when viewing the display element can also contain mixed colors that are created by mixing colors of pixel-shaped sub-areas with a dimension below the resolution limit of the human eye.
• the colors of the pixel-shaped sub-areas are each generated by a certain type of sub-wavelength structure that is characteristic of this color.
• the sub-areas preferably have a dimension of less than 150 gm, in particular less than 100 gm.
• a pixel-shaped area or a "pixel” does not necessarily have to be present as a rectangular or square area on a rectangular grid, but can also designate a differently shaped sub-area, which can result, for example, from a mosaic-like surface division.
• both the facets of the first sub-area and the facets of the second sub-area in the overlapping area are at least partially provided with sub-wavelength structures that generate the different colors of the three-dimensional representations.
• one of the different colors can also be formed by the color of a coating of the facets without the involvement of sub-wavelength structures, in particular by the color of a silver-colored, gold-colored, bronze-colored or copper-colored metallization, a white or colored appearing high-index layer or a colored multi-layer interference coating.
• White and the metallic colors of a metal coating also represent colors in the context of this description.
• at least one of the different colors of the three-dimensional representations is always generated by the sub-wavelength structures of the facets.
• the three-dimensional representations have different shapes and/or sizes, so that the viewer perceives different spatial motifs from the at least two different viewing directions.
• the three-dimensional representations have the same shape and size and are arranged congruently, so that the three-dimensional representations from the at least two different viewing directions differ only in the at least regionally different color.
• the first and second sub-areas are preferably nested in one another, for which purpose the sub-areas are preferably formed by narrow strips arranged alternately next to one another, or by small sub-areas nested in one another in two dimensions.
• the strips or sub-regions advantageously have a dimension of less than 300 gm, in particular 100 gm or less, in particular 50 gm or less, in at least one direction.
• square sub-areas measuring 100 gm x 100 gm can be nested in one another like a chessboard, with the “white chess squares” representing sub-regions of the first sub-region and the “black chess squares” representing sub-regions of the second sub-region.
• the sub-regions can also have a complex outline shape and form the tiles of a tessellation in the plane.
• the strips or sub-areas of the first or second sub-area usually each contain a plurality of facets of the associated sub-area.
• square sub-areas measuring 100 gm x 100 gm each contain 100 facets or Micromirrors with a footprint of 10 mht x 10 mht.
• each sub-area can also consist of just a single facet or a single micro-mirror.
• the display element preferably contains exactly two views for two different viewing directions. With only two views, the two views can both appear very bright and be clearly distinguishable. However, configurations with three, four or more views for a corresponding number of viewing directions are also possible, although the brightness of the individual views decreases as the number of views increases and the associated viewing directions move closer together.
• the display element is advantageously a security element for protecting objects of value, in particular a security thread, a tear-off thread, a security band, a security strip, a patch or a label for application to security paper, a document of value or the like.
• the display element can also be used as a decorative element for surface design of a product, for example for the interior design of a motor vehicle or for the surface design of electrical appliances or pieces of furniture.
• the invention also includes a data carrier that contains a display element of the type described as a security element.
• the data carrier can in particular be a document of value, such as a banknote, in particular a paper banknote, a polymer banknote or a foil composite banknote, a share, a bond, a certificate, a voucher, a check, a seal, a tax stamp, a high-quality admission ticket, but also an identity card, such as a credit card, a bank card, a cash payment card, an authorization card, an identity card or a passport personalization page.
• a banknote in particular a paper banknote, a polymer banknote or a foil composite banknote, a share, a bond, a certificate, a voucher, a check, a seal, a tax stamp, a high-quality admission ticket
• FIG. 1 shows a schematic representation of a banknote with an optically variable security element according to the invention
• Fig. 2 shows the structure of the security element of Fig. 1 schematically in
• Fig. 3 to illustrate the more precise structure and the production of the security element in (a) and (b) schematically shows the course of the modulated height functions of the two views of the 1 and in (c) schematically the course of the overall structuring after the nesting of the modulated height functions,
• FIG. 5 shows the first and second view of a security element according to a further exemplary embodiment of the invention.
• FIG. 6 shows the first and second view of a security element according to a further exemplary embodiment of the invention, in which the shape and size of the two three-dimensional motifs shown are the same.
• FIG. 1 shows a schematic representation of a bank note 10 with an optically variable security element 12 in the form of a transfer element glued on.
• the invention is not limited to transfer elements and banknotes, but can be used with all types of security elements, for example labels on goods and packaging or to protect documents, ID cards, passports, credit cards, health cards and the like same.
• transfer elements such as patches or strips, each with or without their own backing layer
• security threads or security strips for example, can also be considered.
• the display element according to the invention can also be used as a decorative element, for example in the surface design of electrical appliances.
• the security element 12 applied to the banknote 10 is itself very flat, but nevertheless shows an observer a view from at least two different viewing directions 44, 46 with a three-dimensional representation that gives the impression of a the plane of the banknote 10 bulging motif generated.
• the reflection behavior of the bulging motif is simulated by directed reflection.
• the two three-dimensional representations overlap and have a different color at least in certain areas, so that changing the viewing direction shows a visually striking flip effect, in which the color and motif of the three-dimensional representations change at the same time in the security element 12.
• the security element 12 for example, when viewed from the left as a first view 50 show a three-dimensionally arched appearing value number 14 ("50") in blue color against a flat blue background, and when viewed from the right as a second view 52 show a star 16 in yellow color that appears three-dimensionally convex in front of a flat yellow background.
• the appearance of the security element 12 changes between the first view with the three-dimensional blue value number 14 and the second view with the three-dimensional yellow star 16.
• the two three-dimensional motifs 14, 16 also appear to the viewer overlapping one another at the same location in the security element 12, as can be seen from the dashed outlines 14', 16' of the other motif in each case of views 50, 52 indicated.
• the security element 12 thus shows a tilting behavior in which two different colored motifs are visible to an observer from two viewing directions at the same location and the motif change when tilted is linked to a simultaneous color change.
• Such a flip effect is visually appealing and easy for a user to memorize. It also provides a high level of protection against counterfeiting, since reproducing the effect, for example by overprinting a reflective relief structure with translucent colors, is practically impossible with conventional printing machines because of the required register accuracy between the reflective elements of the different motif views and the associated color.
• the security elements can be produced with a considerable cost advantage, since the number of material layers and work steps used in production can be significantly reduced.
• FIG. 2 shows the structure of the security element 12 schematically in cross section.
• An embossing lacquer layer 22 is applied to a carrier substrate 20 and a relief structure in the form of a micromirror arrangement 26 is embossed in a surface area 24 .
• the micro-mirror arrangement 26 is provided with a reflection-increasing coating in the form of a metallization, for example a 50 nm thick aluminum layer, which is not shown in FIG. 2 for the sake of clarity.
• the micro-mirror arrangement 26 contains two groups of micro-mirrors 34, 36, each of which is inclined relative to the plane of the surface area 24 in such a way that for an observer 40 from the two viewing directions 44, 46 the reflection behavior of the type views 50, 52 with the three-dimensional motifs imitating the number 14 or 16.
• the individual micromirrors 34, 36 have a linear dimension I M between 5 ⁇ m and 50 ⁇ m, and thus, for example, a square base area of 10 ⁇ m ⁇ 10 ⁇ m and are therefore not recognizable as such to an observer.
• the different color effect of the views 50, 52 with the motifs 14, 16 is produced by superimposing the micromirror array 26 with different sub-wavelength structures 38, as shown in the detailed section 30 of FIG.
• the color generated by the sub-wavelength structures 38 in reflection can be adjusted through the selection of the structure parameters, in particular the grating period and the structure depth.
• the grating period of the subwavelength structures is between 200 nm and 400 nm and thus below the wavelength of the visible ficht, the depth of the structures is between 50 nm and 400 nm.
• the subdivision of the relief structure 26 into a plurality of micromirrors 34, 36 can be viewed as coarse structuring and the modulation of the micromirrors 34, 36 with the subwavelength structures 38 as fine structuring of the relief structure 26.
• the procedure for producing the security element 12 can be as follows, for example, reference being made to publication WO 2014/060089 A2 for further details of the rough structuring is, the disclosure content of which is included in the present application.
• the views with the three-dimensional motifs 14, 16 to be displayed are each characterized by a height function h(x, y) of the location coordinates x and y in the plane.
• Reduced height functions are derived from these height functions, each of which has the same local gradient as the associated height function, but does not exceed a specified maximum height h max .
• These reduced height functions each describe the profile of a micro-mirror arrangement that simulates the reflection behavior of the motif 14 or 16 to be displayed.
• the reduced height functions have a step profile with a maximum step height h max and with a step dimension I M in the plane of the surface area, the size of which corresponds to the dimensions of the micromirrors 34, 36 subsequently produced.
• the step size of the reduced height functions is 10 gm x 10 gm and the maximum step height is 10 gm.
• the local gradients of the two reduced height functions are then rescaled and each provided with an offset, so that the scaled height function describes the profile of a micromirror arrangement that simulates the reflection behavior of the motifs 14, 16 to be displayed from one of the two different viewing directions 44, 46.
• the first view 50 with the first three-dimensional motif 14 can appear at an oblique angle of approximately -53° (viewing direction 44) and the second view 52 with the second three-dimensional motif 16 at an angle of approximately +53 ° (viewing direction 46).
• the scaled height functions are each overlaid with a grating function that describes the relief profile of a sub-wavelength grating gi or g2, and thereby modulated height functions mi(x,y) or m2(x,y) are obtained.
• the scaled height function of the first view 50 is modulated with a sub-wavelength grating function g1 designed to produce a blue reflection color
• the scaled height function of the second view 52 is modulated with a sub-wavelength grating function g2 designed to produce a yellow reflection color on color is designed.
• the sub-wavelength structures therefore each produce very clear and pure colors.
• FIG. 3 shows schematically in (a) and (b) the profile of the modulated height function mi(x,y) for the first view 50 with the first motif 14 and the profile of the modulated height function m2(x,y) for the second view 52 with the second motif 16, as well as the oblique observation directions 44, 46, from which the respective views for the observation ter 40 appear.
• the modulation of the micromirror array with the sub-wavelength gratings g1 and g2 is only shown in the detailed views 30, while the rough progression of the step profile of the scaled height function can be seen in the relief progress shown in non-enlarged form.
• a common structuring r(x,y) for the profile of the relief structure 26 is then generated from the two modulated height functions of FIGS.
• the common structuring r(x,y) represents the profile of an interleaved, modulated micro-mirror array, from a first viewing direction 44 the first view 50 with the first three-dimensional motif 14 in a first color and from the second viewing direction 46 the second view 52 with the second three-dimensional motif 16 in a second color.
• the course of the structuring r(x,y) is shown in FIG. 3(c), the vertical arrows 64, 66 in FIG. y) of the first view 50 (arrows 64) and which come from the second modulated height function m2(x,y) of the second view 52 (arrows 66).
• the structure r(x,y) is thus embossed in an embossing lacquer layer and provided with a reflection-increasing coating, the relief structure 26 produced shows the first view 50 with the first motif 14 in blue color from the first viewing direction 44 and from the second viewing direction 46 the second view 52 with the second motif 16 in yellow.
• Perforated grids with periods and depths of around 250 nm can be used as sub-wavelength structures, for example, which are provided with a metallization, for example in the form of an aluminum layer approximately 50 nm thick.
• a metallization for example in the form of an aluminum layer approximately 50 nm thick.
• the grating depth and the dimensions of the individual, for example square or circular, holes can be varied to produce different colors.
• the curved motifs and/or the flat background within a view can also be designed with different colors or even multicolored.
• One of the two curved motifs or the flat background can also be formed without sub-wavelength structures and then appear with the generally metallic color of the reflection-increasing coating.
• the first view 70 may show a blue colored denomination 72 against a green background 74
• the second view 80 may show a yellow colored star 82 against a red background 84 .
• the security element is tilted 18, the appearance changes between the first view 70 and the second view 80.
• the number "50" can be composed of a blue digit "5" and a red digit "0". Provision can also be made for the color to vary within an element that appears arched.
• the first view 90 shown in FIG. 5 includes a red indicia 92 with a central blue stripe 94 and a flat red background 96, the colors of these regions being generated by sub-wavelength structures of the type described above, respectively.
• the micromirrors are not modulated with sub-wavelength structures, so that the star 102 that appears convex and the flat background 104 each appear with the silvery metallic lustrous color of the metallization of the micromirror arrangement.
• the appearance of the security element changes between the first view with the three-dimensional red/blue denomination 92, 94 against a red background and the second view with the three-dimensional metallic star 102 against a metallic background. Structurally, after the nesting of the micromirrors of the two views 90, 100 in the overlapping area, only the micromirrors of the first view are provided with subwavelength structures, while the micromirrors of the second view are not modulated by subwavelength structures.
• the shape and size of the two three-dimensional motifs shown are the same and the motifs differ only in their color.
• the security element of Fig. 6 contains a first view 110 with a curved appearing value number 112 in red color against a metallically shiny flat background 114 and a second view 120 with the same curved appearing value number 122 in green color against a metallically shiny flat background 124
• Micromirrors of the security element are each provided with sub-wavelength structures for the desired color red or green in the area of the curved denominations 112, 122, while the background area 114, 124 is formed without modulating sub-wavelength structures is.
• the security element is tilted 18, the viewer therefore sees the curved value number "50", which is visible in red when viewed from the left and in green when viewed from the right in front of the silvery metallic background of an aluminum coating of the micromirror arrangement.
• the color can advantageously change only in a partial area of the motif when tilted 18 and therefore particularly emphasize this partial area.
• a curved motif can have a color gradient from red to green from top to bottom.
• Configurations are also conceivable in which the flip effect occurs in certain areas at different tilting angles and/or tilting axes.
• a viewing angle-dependent bulging effect with a color and possibly motif change when tilting north/south
• another viewing angle-dependent bulging effect with color and possibly motif change in east/west tilting -Tilt on pray.
• the tilting axis can be the same in the different surface areas, but the tilting angle can be different in each case, as a result of which movement effects can be achieved in particular.
• first curved motifs e.g. B. three arched appearing stars in yellow color, one after the other in several, differing second arched motifs with different colors, z. B. three arched appearing letters or numbers in red color.

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• 2021
  • 2021-05-18 DE DE102021002599.7A patent/DE102021002599A1/de not_active Withdrawn
• 2022
  • 2022-05-17 CN CN202280035968.0A patent/CN117355422A/zh active Pending
  • 2022-05-17 CA CA3216109A patent/CA3216109A1/en active Pending
  • 2022-05-17 WO PCT/EP2022/025231 patent/WO2022242912A1/de active Application Filing
  • 2022-05-17 EP EP22731482.0A patent/EP4341100A1/de active Pending

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