DE102014014082A1 - Optically variable security element with reflective surface area - Google Patents

Optically variable security element with reflective surface area

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Publication number
DE102014014082A1
DE102014014082A1 DE102014014082.2A DE102014014082A DE102014014082A1 DE 102014014082 A1 DE102014014082 A1 DE 102014014082A1 DE 102014014082 A DE102014014082 A DE 102014014082A DE 102014014082 A1 DE102014014082 A1 DE 102014014082A1
Authority
DE
Germany
Prior art keywords
facets
reflective
security element
grating
element according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
DE102014014082.2A
Other languages
German (de)
Inventor
Maik Rudolf Johann Scherer
Christian Fuhse
Michael Rahm
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Giesecke and Devrient GmbH
Original Assignee
Giesecke and Devrient GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Giesecke and Devrient GmbH filed Critical Giesecke and Devrient GmbH
Priority to DE102014014082.2A priority Critical patent/DE102014014082A1/en
Publication of DE102014014082A1 publication Critical patent/DE102014014082A1/en
Application status is Withdrawn legal-status Critical

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B44DECORATIVE ARTS
    • B44FSPECIAL DESIGNS OR PICTURES
    • B44F7/00Designs imitating three-dimensional effects
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B42BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42DBOOKS; 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
    • B42D25/00Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30Identification or security features, e.g. for preventing forgery
    • B42D25/324Reliefs
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B42BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42DBOOKS; 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
    • B42D25/00Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30Identification or security features, e.g. for preventing forgery
    • B42D25/328Diffraction gratings; Holograms

Abstract

The invention relates to an optically variable security element (12) for protecting valuables, comprising a support having a reflective area (20) whose extent defines an x-y plane and a z-axis perpendicular thereto. According to the invention, it is provided that the reflective area (20) contains a multiplicity of reflective pixels (30) each having one or more identically oriented reflective facets (32), an orientation of each facet (32) relative to the xy Level is determined by the indication of its normalized normal vector, - the reflective facets (32) are oriented such that the reflective surface area (20) is perceptible to an observer as a surface (40) that protrudes and / or recesses relative to its actual spatial form, and - At least a portion of the facets (32) is provided with a diffractive grating pattern (34) of a plurality of grid lines (36) whose grid vector is parallel to the cross product of the unit vector in the z direction with the normal vector of the respective facet (32).

Description

  • The invention relates to an optically variable security element for safeguarding valuables, having a carrier with a reflective surface area whose extent defines an x-y plane and a z axis perpendicular thereto. The invention also relates to a method for producing such a security element as well as a correspondingly equipped data carrier.
  • Data carriers, such as valuables or identity documents, or other valuables, such as branded articles, are often provided with security elements for the purpose of security, which permit verification of the authenticity of the data carriers and at the same time serve as protection against unauthorized reproduction.
  • Security elements with viewing-angle-dependent effects play a special role in the authentication of authenticity since they can not be reproduced even with the most modern copiers. The security elements are thereby 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.
  • A technique widely used in the field of security elements, which gives a practically flat film a three-dimensional appearance, are various forms of holography. However, for use in security features, particularly banknotes, these techniques have some disadvantages. On the one hand, the quality of the three-dimensional representation of a hologram depends strongly on the lighting conditions. Especially with diffuse lighting, the representations of holograms are often difficult to recognize. In addition, holograms have the disadvantage that they are now present in everyday life in many places and therefore their special position disappears as a mark of authenticity.
  • Based on this, the present invention seeks to provide an optically variable security element of the type mentioned above, which avoids the disadvantages of the prior art, and in particular to provide a security element, despite flat design, a visually attractive three-dimensional appearance with high attention and Recognition value has.
  • This object is solved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.
  • According to the invention, it is provided in a generic security element that
    • The reflective surface area contains a plurality of reflective pixels, each having one or more equally oriented reflective facets, an orientation of each facet relative to the xy plane being determined by the indication of its normalized normal vector,
    • - The reflective facets are oriented so that the reflective surface area is perceptible to an observer as compared to its actual spatial shape and / or recessed surface, and at least a part of the facets is provided with a diffractive grid pattern of a plurality of grid lines whose grating vector is parallel to the cross product of the unit vector in the z-direction with the normal vector of the respective facet.
  • By these measures, the security element despite extremely flat design with a maximum height difference of, for example, only 10 microns produce a clear three-dimensional impression of the subjects shown. In addition, the special coordination of the orientation of the facets and the diffractive grating pattern formed on the facets allows the dispersion of the light in ground transparent materials, such as glass or diamond, to be reproduced convincingly, as explained in detail below.
  • As usual, the grating vector of a grating pattern is a vector which is perpendicular to the grating lines and whose magnitude indicates the grating period.
  • The reflective pixels preferably each contain two or more equally oriented facets, but it is also possible that a portion of the pixels or all pixels each contain only one facet. At least a part of the pixels and / or the facets is advantageously formed with an outline in the form of a motif, in particular in the form of characters or symbols. The particular outlines may be used as an additional authentication feature that will only be visible under magnification. Furthermore, a microtext may additionally be inscribed in a part of the pixels or facets. The microtext can be written both on the facets or instead of some of the facets on the carrier.
  • In an expedient development of the invention, of the facets lying parallel to the xy plane, at least one part is provided with a diffractive grating pattern of a multiplicity of grating lines whose grating vector lies substantially parallel to the grating vectors of the grating patterns of adjoining facets. This requirement takes into account the fact that the above condition applies to the grid vector parallel to the xy plane lying facets can not be applied because the cross product of the unit vector in the z-direction with the normal vector then disappears. In order to obtain a uniform dispersion impression, the facets lying parallel to the xy plane are therefore advantageously provided with a grid pattern whose grid vector lies substantially parallel to the grid vectors of the grid patterns of adjacent facets. For example, the grating vector of such a facet may be chosen as the average of the grating vectors of the adjacent facets with a valid grating vector.
  • The reflective facets are advantageously oriented so that the reflective area can be perceived by a viewer as a curved, in particular continuously curved, surface. With particular advantage, the reflective area can be perceived as an arched in two spatial directions, in particular continuously curved surface.
  • The grating patterns of the reflective facets advantageously produce colored reflections in the first and possibly higher diffraction orders, which are perceptible to a viewer as a dispersion of a transparent material, such as glass or diamond.
  • The inclination of the reflective facets against the x-y plane preferably has no dominant preferred direction, so that there is no plane perpendicular to the x-y plane in which more than 80% of the normal vectors of the reflective facet lie.
  • In a preferred embodiment, the grid lines of all of the facets provided with a diffractive grid pattern have a grid vector parallel to the cross product of the unit vector in the z direction with the normal vector of the respective facet. The diffractive grating patterns advantageously have a grating period between 0.3 μm and 4 μm, preferably between 0.6 μm and 3 μm.
  • In an advantageous variant of the invention, all grid patterns of the area area have the same grid period. Alternatively, the grating period of individual facets can be chosen differently, whereby the strength of the imitated dispersion can be varied.
  • The facets are preferably formed essentially as planar surface elements. The wording "substantially" takes into account the fact that in practice production-related can not produce perfectly flat surface elements. Alternatively, the facets can also be formed as curved, in particular concave, convex or corrugated surface elements. In general, a facet can be described by specifying the facet surface h (x, y), where a planar facet is a facet surface of the shape h 1 (x, y) = c x * x + c y * y + c 0 , for (x, y) ε B with constants c x , c y , and c 0 and a contiguous area B of the xy plane.
  • In an expedient embodiment, the reflective facets are arranged in a periodic grid and in particular form a sawtooth grid. Alternatively, the reflective facets are arranged aperiodically, with an aperiodic arrangement of the facets currently being preferred, as this can avoid unwanted diffraction effects resulting from regular arrangements of the facets.
  • Another possibility to suppress unwanted diffraction effects is to aperiodically offset the facets in their height above the surface area. With an aperiodic displacement of the facets, there is no simple, regular relationship between the heights of adjacent facets, so that constructive interference of the light reflected at neighboring facets and thus the emergence of a superimposed diffraction pattern are reliably prevented. Details of such aperiodic displacement of the document WO 2012/055506 A1 are removed, the disclosure content of which is included in the present application in this respect.
  • The facets advantageously have a dimension of 10 μm or more, preferably 20 μm or more, particularly preferably 30 μm or more, in the direction of the grating vector of the grating pattern. In the direction perpendicular to the grating vector, the facets advantageously have a dimension between 5 μm and 30 μm, preferably between 7.5 μm and 15 μm, and the height of the facets is advantageously between 0 and 10 μm, preferably between 0 and 5 μm.
  • In advantageous embodiments, the reflective facets have a metallic coating, a high-index coating, or a coating with a color-shifting layer.
  • In an advantageous embodiment of the invention, a part of the facets is formed without a diffractive grid pattern. Due to the proportion of lattice-free facets, the degree of the imitated dispersion can be adjusted.
  • The described reflective surface area can be combined with other security features, for example with holograms, in particular true color holograms Sub-wavelength gratings or other sub-wavelength structures, with micromirror arrangements without diffractive gratings, or with security features based on specific material properties, such as electrical conductivity, magnetic properties, luminescence, fluorescence or the like. The other security features may for example be provided in gaps of the reflective surface area and be nested therewith.
  • Finally, it should be noted that the specified condition that the grid vector is parallel to the cross product of the unit vector in the z direction with the normal vector of the respective facet, for real structures, of course, must not be mathematically exactly met or can, but that it understands the expert in that small, for example production-related, unavoidable deviations from the mathematically exact conditions do not impair the described effects and the functioning of the security elements.
  • The invention also includes a data carrier with a security element of the type described. The data carrier may in particular be a value document, such as a banknote, in particular a paper banknote, a polymer banknote or a film composite banknote, a share, a bond, a certificate, a coupon , a check, a high-quality entrance ticket, as well as an identification card, such as a credit card, a bank card, a cash card, an authorization card, an identity card or a pass personalization page.
  • The invention further includes a method for producing an optically variable security element of the type described above, in which
    • A support is provided and provided with a reflective surface area, the extent of which defines an xy plane and a z axis perpendicular thereto,
    • Wherein the reflective area is formed with a plurality of reflective pixels, each having one or more similarly oriented reflective facets, wherein an orientation of each facet relative to the xy plane is determined by the indication of its normalized normal vector,
    • - The reflective facets are oriented so that the reflective surface area is perceptible to an observer as compared to its actual space shape and / or receding surface, and
    • - At least a portion of the facets is provided with a diffractive grating pattern of a plurality of grid lines whose grating vector is parallel to the cross product of the unit vector in the z-direction with the normal vector of the respective facet.
  • To produce a security element according to the invention, the reflective facets can be written together with the diffractive grating patterns, for example by means of gray scale lithography, into a photoresist, then developed, galvanically molded, embossed into a UV varnish and mirrored. The mirror coating can be realized for example by an applied, for example vapor-deposited metal layer. Typically, an aluminum layer with a thickness of, for example, 50 nm is applied. Of course, other metals such as silver, copper, chromium, iron, nickel or alloys thereof may also be used. Also, as an alternative to metals, semiconductors such as silicon, high-index coatings, for example made of ZnS, Al 2 O 3 or TiO 2 , or also color-shifting layers can be applied. The application, in particular vapor deposition can be carried out over the entire surface, but it is also possible to perform a coating only in regions or grid-shaped, so that the security element is partially transparent or translucent.
  • Further exemplary embodiments and advantages of the invention are explained below with reference to the figures, in the representation of which a representation true to scale and proportion has been dispensed with in order to increase the clarity.
  • Show it:
  • 1 a schematic representation of a banknote with an optically variable security element according to the invention in the form of a glued transfer element,
  • 2 illustrates the realization of the three-dimensional appearance of the security element of 1 .
  • 3 a detail of the reflective area with three pixels along a contour line of 2 shown curved surface,
  • 4 a perspective view of a single facet with its grid pattern,
  • 5 a section of a reflective surface area of a security element according to the invention, in which each pixel consists of only one facet and in which the pixels or facets are arranged aperiodically in the xy plane,
  • 6 the reflective surface area of a security element according to a further embodiment of the invention in cross section, and
  • 7 in (a) to (c) the mirror reflections and the dispersion effect occurring during tilting on the basis of the representation of the value "50" of 1 . wherein (a) shows a plan view without representation of the dispersion effect, and (b) and (c) on the one hand the movement of the colorless and bright reflections in the 0th diffraction order and on the other hand, the appearance of colored reflections when tilting the security element.
  • The invention will now be explained using the example of security elements for banknotes. 1 shows a schematic representation of a banknote 10 with an optically variable security element according to the invention 12 in the form of a glued transfer element. It should be understood, however, that the invention is not limited to transfer elements and banknotes, but can be used with all types of security elements, such as labels on goods and packaging or in the security of documents, ID cards, passports, credit cards, health cards and the like. For banknotes and similar documents, in addition to transfer elements, for example, security threads or security strips may also be considered.
  • This in 1 shown security element 12 is itself extremely flat with maximum height differences of about 10 microns formed, conveys the viewer but still a clear three-dimensional impression of the depicted subjects, such as the brilliant 14 and the one from the plane of the banknote 10 apparently arched outstanding value 16 , In addition, the two motifs show 14 . 16 when going back and forth of the security element 12 colored reflections, as they occur in the dispersion of light in ground transparent materials, such as glass or diamond. The security element 12 therefore has a high value and also a high attention and recognition value.
  • The optically variable security element 12 contains a reflective surface area 20 whose extent defines an xy plane, which here coincides with the surface of the banknote 10 coincides. The z-axis is perpendicular to the xy plane so that the coordinate system formed by the three axes forms a legal system.
  • The construction of security elements according to the invention and the realization of the three-dimensional representation with imitated dispersion will now be described with reference to FIGS 2 to 4 explained in more detail. First illustrated 2 the realization of the three-dimensional appearance of the security element 12 , wherein the reference numeral 40 by the viewer when viewing the security element 12 perceived perceived, in two spatial directions curved surface. 3 shows a detail of the reflective surface area 20 with three pixels 30 along a contour line 44 the arched area 40 and 4 shows a perspective view of a single facet 32 with her grid pattern 34 ,
  • Coming back to the presentation of the first 2 is in the carrier 38 of the security element 12 not the curved surface perceived by the viewer 40 trained, but a variety of reflective pixels 30 , each with three reflective facets 32 contained with the same orientation, and by the orientation of the facets 32 the reflection behavior of the curved surface 40 imitated.
  • Here is the orientation of each facet 32 by the inclination of the facet against the xy plane and an azimuthal angle or by the indication of their normalized normal vector n = (n x, n y, n z) | n | = 1 and positive z-component determined. The azimuth angle of a facet is the angle between the projection of the normal vector n into the xy plane and a predetermined reference direction R (FIG. 3 ). To the reflection behavior of the curved surface 40 to reproduce are the facets 32 each oriented such that their normal vector n just over that of the extension of a pixel 30 averaged local normal vector N of the curved surface 40 equivalent.
  • In the exemplary embodiment, the pixels 30 formed with a square outline, but they can also have other outline shapes, in particular a motif shape, such as characters or symbols in general. The edge length of the pixels 30 is below 300 microns and is in particular in the range of 20 microns to 100 microns. Length and width of the facets 32 are above 5 microns to avoid color splits by the facet assembly itself. The height of the facets is only between 0 and 10 microns, preferably between 0 and 5 microns, so that the entire reflective surface area 20 Height differences of a maximum of 10 microns, which are imperceptible to the naked eye.
  • Since the geometric reflection condition "angle of incidence equals angle of reflection" for the reflection of directed light 42 only from the local orientation of the normal vector of the reflecting surface 40 . 20 depends and the pixels 30 Moreover, they are very small and therefore do not appear themselves, as shown by the reflective surface area 20 essentially the same reflection properties as the three-dimensional surface to be imitated 40 and therefore produces in the viewer, despite its small height differences, the pronounced three-dimensional impression of the imitated surface 40 ,
  • The reflective facets 32 are altogether oriented so that the reflective surface area 20 for a viewer as opposed to his actual spatial form projecting and / or recessed surface 40 is perceptible. The actual spatial form of the reflective surface area 20 is by the sequence of the inclined facets, in the embodiment, for example, by the regular sawtooth-like arrangement of the facets 32 given. Because of the generality of the construction described can be with the reflective surface area 20 generate practically any three - dimensional perceptible motifs, such as portraits, representations of objects, animals or plants, or spatial representations of alphanumeric characters, for example the accentuated value number "50" of the 1 ,
  • To think about the imitation of the three-dimensionality of the surface 40 In addition, to be able to mimic the dispersion of light occurring in polished transparent materials, are the reflective facets 32 of the surface area 20 additionally with diffractive lattice patterns 34 each provided with a plurality of parallel grid lines 36 consist. The orientation of the grid lines 36 is in the context of the invention just chosen so that the grating vector g of the grating pattern 34 , by definition, perpendicular to the grid lines 36 and whose magnitude indicates the grating period, is parallel to the cross product of the unit vector e z in the z-direction with the normal vector n of the respective facet.
  • With e z = (0, 0, 1) and n = (n x , n y , n z ) we have g || (e z × n) and the grating vector of each facet can be expressed as g = (g x , g y , 0) with the grating period | g | to be written. In 4 is the relationship between the normal vector n, the unit vector e z and the grating vector g of the grating pattern 34 for a facet 32 graphically illustrated. Also plotted is the inclination γ of the facet against the xy plane.
  • The detail of the 3 shows three pixels in supervision 30 each with three facets 32 that go along a contour line 44 the arched area 40 of the 2 Therefore, they essentially do not differ in the inclination γ of the facets against the xy plane, but only in the azimuth angle A of the facets. In 3 is for the pixels 30 in each case the projection of the normal vector n into the xy plane, the reference direction R and the azimuth angle A are plotted. 3 also shows the resulting grating vector g and the associated grating lines 36 of the grid pattern 34 , For the sake of clarity, the grid lines 36 only in one of the three facets 32 each of the pixels 30 located. Because the facets 32 of a pixel 30 all are the same orientation, the other facets of the pixel point 30 the same normal vector n and thus also the same grating vector g and thus also the same grating pattern 34 on. As in 3 represented are the boundary lines of the outline of the facets 32 with advantage as far as possible perpendicular to the grid lines 36 , It can thereby be achieved that with each orientation of the facets the largest possible number of grid lines 36 for the diffraction and thus for a brilliant appearance is available. In addition, larger facet heights can be largely avoided, especially in the case of micromirrors with the same mirror slope.
  • At first only a reflective facet for a better explanation 32 without diffractive grid pattern 34 considered, so does the lattice-free facet 32 as an achromatically reflecting micromirror that reflects incident light without color splitting according to the laws of geometric optics. Is from a viewing direction that is in the plane spanned by the normal vector and the z-axis, for the facet 32 If the reflection condition "angle of incidence equals angle of reflection" is fulfilled, the facet appears colorless bright, otherwise dark. Since the reflection condition is exactly fulfilled only for one tilt angle, an abrupt, discrete change in brightness results when tilting the reflective facet perpendicular to the plane mentioned.
  • Now take the diffractive grid pattern 34 In addition, so that in addition the diffraction of the incident light must be considered on the grid pattern, so instead of the direction of the geometrically directionally reflected light beam, the direction of the 0-th diffraction order of the grid pattern occurs. In the direction of the 0th order of diffraction, the reflection condition "angle of incidence equal to the angle of reflection" is satisfied, the facet appears bright and colorless, though typically with somewhat less brightness than in the lattice-free case described above, because a portion of the light is diffracted in other spatial directions.
  • In the grid patterns 34 the propagation direction of the diffracted light is in a plane spanned by the grating vector g and the direction of the 0th diffraction order. Within this plane, the direction of the diffracted light is determined by the grid equation sinα + sinβ = mλ / | g | in which m is the order of diffraction, | g | the amount of the grating vector and thus the grating period, and λ denote the wavelength. The angles α and β, respectively, are the angles of the incident or reflected light projected into the plane spanned by the grating vector g and the normal vector n. The angle α is always taken positive, the angle β positive if it, as usual in the embodiments according to the invention, with respect to the lattice normal on the same side as α, otherwise negative.
  • For the above-mentioned viewing direction in the plane of the normal vector and the z-axis The angles α and β of the lattice equation do not change when tilting the reflective facet about an axis perpendicular to said plane. On the other hand, with a tilt about another axis, tilting also gradually changes the angles α and β in the grid equation. In such a tilting so a gradual change in color and / or intensity occurs, in particular by the color impression of the facet 32 changed continuously.
  • Now you return to a reflective surface area 20 back, coming from a variety of facets 32 with different inclination angles γ and azimuth angles A, the totality of the facets does not have an excellent tilting axis. Rather, every tilt around any axis becomes part of the facets 32 show a discrete intensity change, while another part shows a gradual change in color and / or intensity. The colorless and bright reflections in the 0th diffraction order contribute to the impression of a three-dimensional arched surface 40 at, as they reflect through the curved surface 40 reenacted.
  • The colored reflections of the first and higher orders of diffraction additionally suggest to the viewer the occurrence of dispersion familiar to him from ground transparent objects. Of particular importance is that the colored reflections of adjacent pixels 30 are not independent of each other, as well as the orientations of the facets 32 adjacent pixels are not independent of each other, but rather are just chosen so that the pixels 30 in their entirety precisely the reflection behavior of the three-dimensional surface 40 reproduce. With the spatial orientation are therefore also the colored reflections of adjacent pixels 30 correlates and leads to macroscopically recognizable colored reflections, which, as the inventors have surprisingly found, mimic the occurrence of dispersion in transparent materials.
  • The above-mentioned condition according to which the grating vector g of the grating pattern should lie parallel to the cross product of the unit vector in the z direction e z with the normal vector n of the respective facet can not be applied to facets lying parallel to the xy plane since the cross product is there is equal to zero. As described above, the facets lying parallel to the xy plane are therefore advantageously provided with a grid pattern whose grid vector lies substantially parallel to the grid vectors of the grid patterns of adjacent facets.
  • Further, the above condition applies to the grating vector g only its direction, but not its magnitude. Rather, can be adjusted by the choice of the grating period, regardless of the previous considerations, the degree of the imitated dispersion. Smaller grating periods lead to a more pronounced spatial fanning of the light into spectral colors and thus to colored reflections of lesser intensity. Thus, after determining the direction of the grating vector, the grating period will be in accordance with the magnitude of the desired dispersive appearance of the curved surface 40 selected.
  • Another way to adjust the degree of mimic dispersion is to form a certain part of the facets without lattice patterns and to reduce the degree of mimic dispersion by the proportion of lattice-free facets.
  • The reflective pixels 30 or the reflective facets 32 can, as in 3 shown, arranged in a regular grid and form, for example, a regular Blazegitter. However, the surface areas according to the invention are not limited to regular pixel or facet arrangements, but rather even aperiodic pixel or facet arrangements are used, as this unwanted diffraction effects, such as may occur through regular arrangements are avoided.
  • 5 shows an embodiment in which for the sake of simplicity, each pixel 30 from just one facet 32 and in which the pixels or facets are arranged aperiodically in the xy plane. In order to obtain a surface area with clear diffraction colors, despite the height differences of adjacent facets and the associated phase jump, the dimension of the facets in the direction of the grating vector g of the grating pattern containing them is 34 at least 10 microns, preferably at least 20 microns, more preferably at least 30 microns. In the direction perpendicular to the grating vector g, the dimension of the facets is in each case between 5 μm and 30 μm, preferably between 7.5 μm and 15 μm. The height of the facets is between 0 and 10 microns, preferably between 0 and 5 microns. As in 3 are the boundary lines of the outline of the facets 32 or the pixel 30 with advantage as far as possible perpendicular to the grid lines 36 , As a result, regardless of the orientation of the facets or pixels, there is a maximum number of grid lines 36 for the diffraction and thus for a brilliant appearance available. Also, larger facet heights can be largely avoided.
  • Another possibility to suppress unwanted diffraction effects by the division of the surface area in facets is to aperiodically offset the facets in their height above the surface area. For example, shows 6 the reflective surface area 50 a security element 12 in cross-section, in which the facets shown in the cutout 52 Although all have the same inclination, but are offset in aperiodic, especially in an irregular manner by a height offset between zero and at least half a wavelength from its regular starting position. This makes the gait differences between different facets 52-j . 52-k changed in an irregular manner by a value between zero and at least one entire wavelength. The different facets 52-j . 52-k reflected light rays 54-j and 54-k then stand in a random phase relationship, leaving the grid of facets 52 despite a periodic arrangement of equally aligned facets 52 does not act as a diffractive structure and therefore no disturbing secondary diffraction effects occur.
  • 7 schematically illustrates the mirror reflexes and the dispersion effect occurring when tilting on the basis of the representation of the value number 16 of the 1 , Regarding 7 (a) the value appears 16 with domed and out of the xy plane of the surface area 20 clearly outstanding numbers 60 , The appearing in the figure white inner digit areas make it bright mirror reflections 62 which convey to the viewer the illusion of an opposing surface. This illusion is caused by the apparent movement of the mirror reflexes 62 when tilting around one of the tilting axes 70 . 72 even stronger. As in 7 (b) represented, the mirror reflexes wander 62 when tilting about the horizontal tilting axis in the figure 70 upwards or when tilting in the opposite direction downwards and behave as well as the mirror reflections on the imitated three-dimensional surface. The mirror reflexes migrate in the same way 62 when tilting about the vertical axis in the figure tilting axis 72 to the right or when tilting in the opposite direction to the left, as in 7 (c) shown and behave like the mirror reflexes on the imitated three-dimensional surface.
  • In addition to this movement of mirror reflexes 62 , which is caused by the colorless and bright reflections in the 0th diffraction order, generate the lattice patterns 34 the facets 32 in the first and the higher diffraction orders colored reflections 64 , As in 7 (b) and 7 (c) Illustrated are the colored reflections 64 because of the special orientation of the grid pattern 34 when tilting around the horizontal tilting axis 70 in the vertical areas 66 the mirror reflexes 62 more pronounced and are when tilting about the vertical tilt axis 72 in the horizontal areas 68 the mirror reflexes 62 pronounced. Such colored reflections 64 They usually occur with polished transparent objects and thus suggest to the viewer the presence of corresponding objects. The appealing and impressive visual effect increases the attention and recognition value and thus also the forgery security of the security element 12 ,
  • LIST OF REFERENCE NUMBERS
  • 10
    bill
    12
    security element
    14
    brilliant motive
    16
    value number
    20
    reflective surface area
    30
    pixel
    32
    reflective facets
    34
    diffractive grid pattern
    36
    gridlines
    38
    carrier
    40
    arched area
    42
    Reflection of directional light
    44
    contour
    50
    reflective surface area
    52, 52-j, 52-k
    facets
    54-y, 54-k
    reflected light rays
    50
    reflective surface area
    52, 54
    subregions
    60
    digits
    62
    mirror reflections
    64
    colored reflections
    66
    vertical areas
    68
    horizontal areas
    70, 72
    tilting axes
  • QUOTES INCLUDE IN THE DESCRIPTION
  • This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.
  • Cited patent literature
    • WO 2012/055506 A1 [0019]

Claims (17)

  1. An optically variable security element for securing valuables, comprising a support having a reflective area whose extent defines an xy plane and a z-axis perpendicular thereto, characterized in that - the reflective area contains a plurality of reflective pixels, each one or have a plurality of identically oriented reflective facets, wherein an orientation of each facet relative to the xy plane is determined by the specification of its normalized normal vector, the reflective facets are oriented so that the reflective surface area for a viewer as compared to its actual spatial form and / or the recessed surface is perceptible, and - at least a part of the facets is provided with a diffractive grating pattern of a plurality of grating lines whose grating vector is parallel to the cross product of the unit vector in the z direction with the normal vector of the respective facet lies.
  2. A security element according to claim 1, characterized in that of the facets lying parallel to the xy plane at least one part is provided with a diffractive grating pattern of a plurality of grating lines whose grating vector is substantially parallel to the grating vectors of the grating patterns of adjacent facets.
  3. Security element according to claim 1 or 2, characterized in that the reflective facets are oriented such that the reflective surface area is perceptible to a viewer as a curved, in particular continuously curved surface, preferably as a curved in two spatial directions, in particular continuously curved surface is perceptible.
  4. A security element according to at least one of claims 1 to 3, characterized in that the lattice patterns of the reflective facets in the first and possibly higher orders of diffraction produce colored reflections perceptible to a viewer as a dispersion of a transparent material such as glass or diamond.
  5. A security element according to at least one of claims 1 to 4, characterized in that the inclination of the reflective facets against the xy plane has no dominant preferential direction, that is, there is no plane perpendicular to the xy plane in which more than 80% of the Normal vectors of the reflective facet lie.
  6. A security element according to at least one of claims 1 to 5, characterized in that the diffractive grating patterns have a grating period between 0.3 μm and 4 μm, preferably between 0.6 μm and 3 μm.
  7. A security element according to at least one of claims 1 to 6, characterized in that all the grating patterns of the surface area have the same grating period.
  8. Security element according to at least one of claims 1 to 7, characterized in that the facets are formed substantially as planar surface elements.
  9. Security element according to at least one of claims 1 to 8, characterized in that the reflective facets are arranged in a periodic grid and in particular form a sawtooth grid.
  10. Security element according to at least one of claims 1 to 8, characterized in that the reflective facets are arranged aperiodically.
  11. A security element according to at least one of claims 1 to 10, characterized in that the facets are aperiodically offset in height from each other over the surface area.
  12. A security element according to at least one of claims 1 to 11, characterized in that the lattice-patterned facets in the direction of the lattice vector of the lattice pattern have a dimension of 10 μm or more, preferably 20 μm or more, particularly preferably 30 μm or more, and / or that the facets in the direction perpendicular to the grating vector have a dimension between 5 μm and 30 μm, preferably between 7.5 μm and 15 μm, and / or that the height of the facets is between 0 and 10 μm, preferably between 0 and 5 microns.
  13. Security element according to at least one of claims 1 to 12, characterized in that the reflective facets have a metallic or semiconductive coating, a high refractive index coating or a coating with a color-tipping layer.
  14. Security element according to at least one of claims 1 to 13, characterized in that a part of the facets is formed without a diffractive grid pattern.
  15. Security element according to at least one of claims 1 to 12, characterized in that at least a part of the pixels is formed with an outline in the form of a motif, in particular in the form of characters or symbols.
  16. Data carrier with a security element according to at least one of claims 1 to 15.
  17. A method of manufacturing an optically variable security element according to any one of claims 1 to 16, wherein A support is provided and provided with a reflective surface area, the extent of which defines an x-y plane and a z axis perpendicular thereto, Wherein the reflective area is formed with a plurality of reflective pixels, each having one or more equally oriented reflective facets, an orientation of each facet relative to the x-y plane being determined by the indication of its normalized normal vector, - The reflective facets are oriented so that the reflective surface area is perceptible to an observer as compared to its actual space shape and / or receding surface, and - At least a portion of the facets is provided with a diffractive grating pattern of a plurality of grid lines whose grating vector is parallel to the cross product of the unit vector in the z-direction with the normal vector of the respective facet.
DE102014014082.2A 2014-09-23 2014-09-23 Optically variable security element with reflective surface area Withdrawn DE102014014082A1 (en)

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EP15002684.7A EP3000614B1 (en) 2014-09-23 2015-09-16 Optically variable security element having reflective surface area

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