EP3302995A1 - Élément de sécurité optiquement variable - Google Patents

Élément de sécurité optiquement variable

Info

Publication number
EP3302995A1
EP3302995A1 EP16725364.0A EP16725364A EP3302995A1 EP 3302995 A1 EP3302995 A1 EP 3302995A1 EP 16725364 A EP16725364 A EP 16725364A EP 3302995 A1 EP3302995 A1 EP 3302995A1
Authority
EP
European Patent Office
Prior art keywords
layer
color mirror
security element
color
absorber layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP16725364.0A
Other languages
German (de)
English (en)
Other versions
EP3302995B1 (fr
Inventor
Maik Rudolf Johann SCHERER
Josef Schinabeck
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Giesecke and Devrient Currency Technology GmbH
Original Assignee
Giesecke and Devrient Currency Technology GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Giesecke and Devrient Currency Technology GmbH filed Critical Giesecke and Devrient Currency Technology GmbH
Publication of EP3302995A1 publication Critical patent/EP3302995A1/fr
Application granted granted Critical
Publication of EP3302995B1 publication Critical patent/EP3302995B1/fr
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/328—Diffraction gratings; Holograms

Definitions

  • the invention relates to an optically variable security element for securing valuables.
  • the invention also relates to a method for producing such a security element and a data carrier with such a security element.
  • Data carriers such as security 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 copying machines.
  • the security elements are thereby equipped with optically variable elements that give the viewer a different image impression at different viewing angles and, for example, show a different color or brightness impression and / or another graphic motif depending on the viewing angle.
  • Optically variable security elements are sometimes used together with color mirrors, that is to say with optical components which reflect light in the visible spectral range in a frequency-dependent manner and thus in color.
  • security elements with multilayer thin-film elements are known whose color impression changes with the viewing angle for the observer.
  • the color shift effect of such thin-film elements is based on viewing-angle-dependent interference effects due to multiple reflections in 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 a dielectric spacer layer, which defines the distance between a semi-transparent absorber layer and a reflective layer, and on the other hand varies with the respective viewing angle.
  • the dielectric spacer layers of such thin-film elements typically have a relatively large thickness between 200 nm and 400 nm and are therefore time-consuming and expensive to manufacture.
  • the object of the invention is to specify a cost-effectively producible, optically variable security element with high security against forgery and a colored visual appearance which is attractive in particular in reflection.
  • a relief structure and a two-ply color mirror are arranged one above the other and in interaction produce an optically variable and colored appearance in reflection, wherein
  • the two-layered color mirror consists of a reflective metal layer and an ultrathin absorber layer made of silicon, a silicon alloy or SiO x with x ⁇ 1 arranged on the metal layer.
  • the reflection color of a metal layer can be adjusted by varying the absorber layer thickness over a wide range by means of suitable ultrathin absorber layers.
  • the silvery reflection of an aluminum-metal layer by applied silicon absorber layers of a layer thickness between a few nanometers and about 35 nm can be adjusted virtually continuously from the silver reflection color of the pure metal layer via a golden, yellow and red reflection color to a blue reflection color .
  • this color sequence is repeated; for even greater layer thicknesses above 80 nm, the reflection spectrum shows two or more reflection minima, so that other color sequences are then formed.
  • an absorber layer with a small layer thickness which is easy to produce, gold and copper-colored metallizations can be produced in a particularly cost-effective manner.
  • An ultrathin absorber layer made of silicon has proved to be particularly advantageous, it being possible to use crystalline, polycrystalline or amorphous silicon.
  • silicon alloys such as SiAl, SiFe, SiCu or SiTi and SiO x with x ⁇ 1, preferably x ⁇ 0.5 and particularly preferably x ⁇ 0.2, are also suitable for the ultrathin absorber layer.
  • the ultrathin absorber layer advantageously has a layer thickness between 1 nm and 200 nm, preferably between 1 nm and 100 nm and particularly preferably between 5 nm and 35 nm.
  • the metal layer of the two-layer color mirror is advantageously aluminum, silver, copper, tin, zinc, iron, chromium, nickel or an alloy of these metals.
  • the layer thickness of the metal layer is advantageously between 10 nm and 100 nm, preferably between 15 nm and 80 nm.
  • the two-layered color mirror contains at least two partial regions with different layer thicknesses of the ultrathin absorber layer, including the layer thickness zero.
  • the color mirror has different reflection colors in the at least two subregions, so that the relief structure and the two-layered color mirror, in interaction, produce an at least bicoloured appearance in reflection.
  • the partial regions of different layer thickness can be formed by regions in which the layer thickness of the ultrathin absorber layer is different from zero but different in size.
  • Such a different thickness can in particular by masks in the application of the Absorber layer can be achieved by a selective removal of the absorber layer by lithographic processes or a laser application, or by a suitable design of the relief structure, associated with suitably selected conditions in the application of the absorber layer.
  • the color mirror may contain only recesses present in the ultrathin absorber layer, which form subregions of the color mirror with an absorber layer of zero layer thickness.
  • a subarea in which the optical properties of the absorber layer have been modified in such a way that it loses its absorbing property, ie becomes transparent, for example by oxidation or another material transformation, is regarded as a recess in the absorber layer.
  • the metal layer advantageously has a specular reflection.
  • the metal layer in these recesses has a reflectivity of more than 80%, in particular more than 90%, of the reflectivity of an uncoated, similar metal layer.
  • the color mirror may alternatively or additionally contain recesses which pass through the absorber layer and the metal layer and therefore form recesses in the entire color mirror. In these recesses of the color mirror, the view of a background layer is released or there are see through areas in the security element.
  • the color mirror is combined with a color layer, which is visible in the recesses of the color mirror.
  • the color layer is on the side facing away from the absorber layer Side of the metal layer in front.
  • the relief structure of the security element is advantageously formed by a diffractive structure, such as a hologram, a holographic grating image or a hologram-like diffraction structure.
  • a diffractive structure such as a hologram, a holographic grating image or a hologram-like diffraction structure.
  • achromatic structures such as a matt structure, a micromirror arrangement, a blazed grating with a sawtooth-like furrow profile or a Fresnellinsen- arrangement, or nanostructures, such as a sub-wavelength structure, come as a relief structure in question.
  • the two-ply color mirror is designed as a coating of the relief structure.
  • both the metal layer and the absorber layer of the relief structure facing.
  • the color modification by the absorber layer is visible only when viewed from the side of the absorber layer, so that the security element must be designed according to the desired viewing directions.
  • the relief structure may be formed so that it leads to partially different layer thicknesses of the absorber layer and thus to different reflection colors when applying the absorber layer.
  • the relief structure may contain micromirrors with different inclinations, and the absorber layer may be applied to the micromirrors by directional vapor deposition, in particular oblique vapor deposition.
  • the layer thickness of the applied absorber layer then depends strongly from the relative orientation of the micromirror surface and the direction of vapor deposition, so that desired color effects can be produced by suitable alignment of the micromirrors.
  • the relief structure is a lenticular array of a plurality of microlenses that is spaced from the color mirror.
  • the color mirror advantageously contains one or more reference images, which can be recognized from certain viewing directions when viewing the color mirror through the lens grid.
  • said target images comprise recesses which are present only in the absorber layer and / or recesses which penetrate the entire color mirror.
  • the lenticular and color mirrors cooperate to represent the target image (s) thereby producing an optically variable and colored appearance in reflection.
  • microlenses are lenses whose size lies below the resolution limit of the naked eye in at least one lateral direction.
  • the microlenses may be formed, for example, spherical or aspherical, but also the use of cylindrical lenses is possible.
  • Spherical or aspheric microlenses preferably have a diameter between 5 ⁇ and 100 ⁇ , in particular between 10 ⁇ and 50 ⁇ , more preferably between 15 ⁇ and 20 ⁇ .
  • Microcylinder lenses preferably have a width between 5 ⁇ and 100 ⁇ , in particular between 10 ⁇ and 50 ⁇ , more preferably between 15 ⁇ and 20 ⁇ .
  • the length of the micro-cylinder lenses is arbitrary, it may for example correspond to the use of security threads of the total width of the thread and be several millimeters.
  • the color mirror has a gold-colored or reddish, in particular copper-colored appearance in non-recessed regions, while the color mirror preferably has a silvery appearance in the recesses present only in the absorber layer.
  • the color mirror can also show several different metallic reflection colors, in particular in that the absorber layer is present in partial regions with different thicknesses.
  • the invention also includes a data carrier with a security element of the type described, wherein the security element is arranged in advantageous configurations in or over a window area or a through opening of the data carrier.
  • 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 admission ticket, but also an identity card such as a credit card, a bank card, a cash card, an entitlement card, an identity card, or a pass personalization page.
  • the invention also includes a method for producing an optically variable security element of the type described above, in which
  • the two-layered color mirror is formed from a reflective metal layer and an ultrathin absorber layer of silicon, a silicon alloy or SiO x with x ⁇ 1 arranged on the metal layer.
  • the color mirror is advantageously provided with recesses which are present only in the ultrathin absorber layer and form the subregions of the color mirror with an absorber layer of zero layer thickness.
  • the color mirror may be provided with recesses which pass through the absorber layer and the metal layer.
  • the recesses are thereby introduced with particular advantage by the action of laser radiation in the absorber layer and / or the entire color mirror.
  • the recesses in the ultra-thin absorber layer are introduced by the action of laser radiation having a laser wavelength at which the absorption of the color level is greater than the absorption of the metal layer by more than 50%, preferably more than 100%, in particular more than 200%.
  • the metal layer therefore exhibits approximately the same reflectivity in the recesses of the absorber layer as an uncoated metal layer.
  • the conversion of the laser energy to heat occurs predominantly in the absorber layer.
  • the absorber layer has been demetallised, ie removed or converted into a transparent modification, the laser radiation is reflected by the metal layer and therefore no longer absorbed or converted into heat.
  • the entire color level including the metal layer can be demetallized.
  • Fig. L is a schematic representation of a banknote with a
  • FIG. 2 shows schematically a cross section through the security element of FIG. 1,
  • Fig. 4 shows another embodiment of the invention, in which the
  • Relief structure of the optically variable security element is formed by a micromirror arrangement, a security element according to the invention, in which a relief structure in the form of a micromirror arrangement is embossed in a carrier film and coated with a metal layer, an embodiment as in FIG. 2, but with inverted layer order of the two-layer color mirror, the reflection spectrum of a 28 nm thick aluminum layer and FIG Reflectance spectrum of a gold-colored color mirror from a 16 nm thick silicon layer on a 28 nm thick aluminum layer, and
  • FIG. 9 shows a security element according to the invention with a lenticular image for the unscaled representation of two predetermined target images, which are visible from different viewing directions.
  • FIG. 1 shows a schematic representation of a banknote 10 with an optically variable security element 12 according to the invention.
  • the security element 12 shows a two-color shiny metallic hologram, in which a sitting fox appears in the exemplary embodiment as a foreground motif 14 silvery silver against a gold-colored background 16.
  • the security element 12 also contains a negative text 18 in the form of the number sequence "20", which shows no metallic appearance and does not participate in the holographic reconstruction. Rather, the negative text 18 shows the background color of the banknote substrate or, if the symbol security element 12 is arranged in a window region of the banknote 10, as a transparent see-through feature in appearance.
  • FIG. 2 schematically shows a cross section through the security element 12 in order to explain the basic structure of security elements according to the invention and the occurrence of the two-tone metallic appearance.
  • the security element 12 includes a carrier film 20, for example, a transparent polyethylene terephthalate (PET) film, which is provided with a relief structure 22 in the form of a Regehologramms reconstructed when viewed the desired motif, here the sitting fox.
  • a carrier film 20 for example, a transparent polyethylene terephthalate (PET) film
  • PET polyethylene terephthalate
  • a relief structure 22 in the form of a Reconstructed when viewed the desired motif, here the sitting fox.
  • a two-layered color mirror 30 Arranged above the relief structure 22 is a two-layered color mirror 30 which, in cooperation with the hologram relief structure 22, produces the bicolor, optically variable appearance.
  • the two-layer color mirror 30 consists of a reflective metal layer 32, in the embodiment of a 28 nm thick aluminum layer. On the metal layer 32, an ultrathin absorber layer 34 is applied, which is formed in the embodiment by a 14 nm thick silicon layer.
  • the two different reflection colors of the security element 12 are produced in that the color mirror 30 contains recesses in the absorber layer 34 in a subregion 38, so that the absorber layer has a layer thickness of zero there, while in subregions 36 outside the recesses it has the nominal layer thickness of 14 nm.
  • the two-color color mirror 30 further includes recesses 40, in which neither a metal layer 32 nor an absorber layer 34 is present and which are formed in the embodiment of FIG. 1 in the form of the numerical sequence "20".
  • the stamping hologram 22 is virtually invisible due to the lack of metallization, and the observer looks through the security element 12 onto the white or optionally printed substrate of the banknote substrate.
  • the recesses 40 appear as a transparent see-through feature.
  • the color modification of the metal layer 32 occurs only when viewing the security element 12 from the side of the absorber layer 34 (viewing direction 42).
  • the holographic motif which remains unchanged except for the mirror image, appears from the side of the metal layer 32 (viewing direction 44) with the monochrome, silvery appearance of the aluminum-metal layer 32.
  • this different color impression can be used as additional authenticity mark be used.
  • An essential feature of the present invention resides in the ultrathin silicon absorber layer 34 of the two-layer color mirror 30 applied to the metal layer 32.
  • the reflection color of a metal layer 32 can be varied within wide ranges by varying the absorber layer thickness, which results in the formation of a large number of layers visual effects and appearances.
  • 3 shows the calculated wavelength-dependent reflection behavior of a two-layer color mirror made of a reflective metal layer in the form of a 28 nm thick aluminum layer and an ultrathin absorber layer in the form of a silicon layer of thickness dsi.
  • a color mirror with such a silicon layer has a very low reflectivity in the short-wave visible spectral range, but a very high reflectivity in the long-wave visible spectral range, so that Overall, the golden appearance shown in Fig. 2 results.
  • the reflection minium of the color mirrors continuously migrates with increasing layer thickness of the silicon layer from the blue to the red end of the visible spectrum, the reflection minima lying essentially on a reflection straight line 52.
  • the layer thickness of the silicon layer With a very small layer thickness of the silicon layer of a few nanometers, the silvery color impression of the aluminum layer dominates and the color mirror appears silver.
  • the layer thickness of the silicon layer is successively increased to about 30 nm, the shift of the reflection minium into red results in succession in a golden, a yellow, a red and finally a blue color impression. From a layer thickness of the silicon layer of about 35 nm, this color sequence is repeated, since then a second, steeper reflection line 54 with reflection minima occurs, which determines the visual appearance.
  • the reflection colors of color mirrors having a silicon layer with a layer thickness above 35 nm are less sensitive to thickness fluctuations of the silicon layer.
  • 4 illustrates a further embodiment of the invention, in which the relief structure 62 of the optically variable security element 60 is formed by a micromirror arrangement.
  • the security element 60 is itself very flat with maximum height differences of about 10 ⁇ trained det, conveys the viewer but still a clear three-dimensional impression of a curved in two spatial directions motif 80, which is assumed for purposes of illustration as a spherical cap.
  • the optically variable security element 60 contains a reflective surface region 64 whose extent defines an xy plane which here coincides with the plane of the security element 60.
  • the z-axis is perpendicular to the xy plane, so that the coordinate system formed by the three axes forms a legal system.
  • FIG. 4 shows a small section of the reflective surface region 64 with a plurality of pixels 66 which lie along a contour line 84 of the curved surface 80.
  • the carrier film of the security element 60 is not formed as the relief structure 62, the viewer perceived curved surface 80 itself, but a plurality of reflective pixels 66, each containing three reflective facets 68 with the same orientation.
  • the reflective facets 68 represent small micromirrors which, by their orientation, mimic the reflection behavior of the curved surface 80.
  • the arrangement of the facets 68 is therefore also referred to in the context of this description as a micromirror arrangement.
  • the reflective pixels 66 and the reflecting facets 68 are formed by a coating of an embossing lacquer layer 70 with a two-layered color mirror 72, which for example consists of a 60 nm thick aluminum layer and an 18 nm thick layer applied to the aluminum layer Silicon layer is made, and gives the reflective surface area 64 in reflection a colorful appearance.
  • a two-layered color mirror 72 which for example consists of a 60 nm thick aluminum layer and an 18 nm thick layer applied to the aluminum layer Silicon layer is made, and gives the reflective surface area 64 in reflection a colorful appearance.
  • each facet 68 is determined by the inclination of the facet against the x-y plane and an azimuth angle, or by the indication of its normal vector.
  • the azimuth angle of a facet is the angle between the projection of the normal vector n into the x-y plane and a predetermined reference direction.
  • the facets 68 are each oriented so that their normal vector n corresponds to the local normal vector N of the curved surface 80 averaged over the extent of a pixel 66.
  • the pixels 66 are formed with a square outline, but in general they can also have any other outline shapes.
  • the edge length of the pixel 66 is below 300 ⁇ and is in particular in the range of 20 ⁇ to 100 ⁇ .
  • Length and width of the facets 68 are above 5 ⁇ to avoid color splits by the facet arrangement itself.
  • the height of the facets is only between 0 and 10 ⁇ , preferably between 0 and 5 ⁇ , so that the entire reflective surface area 64 height differences of a maximum of 10 ⁇ has, which are imperceptible to the naked eye.
  • the reflective surface area 64 exhibits substantially the same reflective properties as the three-dimensional area 80 to be imitated, as illustrated by the example of the leftmost pixel of FIG Reflective surface area 64 therefore generates the pronounced three-dimensional impression of imitated area 80 in the observer despite its small differences in height.
  • Reflecting facets 68 are overall oriented such that reflective surface area 64 is for a viewer as projecting and / or receding relative to its actual spatial form Surface 80 is perceptible.
  • the actual spatial form of the reflective surface area 64 is given by the sequence of the inclined facets, in the exemplary embodiment approximately by the regular sawtooth arrangement of the facets 68. Because of the generality of the construction described, the color-reflecting surface region 64 can be used to generate virtually any three-dimensionally perceptible motifs, such as portraits, representations of objects, animals or plants, or spatial representations of alphanumeric characters.
  • FIG. 5 shows by way of illustration a security element 90 in which a relief structure in the form of a micromirror arrangement 94 is imprinted in a carrier foil 92 and coated with a metal layer 96, for example a copper layer 60 nm thick.
  • absorber layer 98 a silicon layer is vapor-deposited, wherein a different layer thickness of the absorber layer 98 was achieved by an oblique vapor deposition 100 depending on the specular inclination. If the absorber layer is vapor-deposited in a nominal layer thickness do, this nominal layer thickness is achieved as the maximum layer thickness for micromirrors whose normal vector n is parallel to the deposition direction 100. Micro-mirrors whose normal vector with the evaporation direction 100 include a small angle, such as the micromirrors 102 of FIG.
  • the layer thickness d of the absorber layer is for a nominal layer thickness do in the case of micromirrors whose normal vector encloses an angle ⁇ with the vapor deposition direction 100
  • the color impression of micromirrors with an absorber layer of a layer thickness d can be determined, for example, with the aid of the reflection spectra as in FIG. 3.
  • the small layer thickness of the ultrathin absorber layer represents a great advantage over conventional color mirror coatings with thick dielectric layers. Thus, a significantly shorter evaporation time is sufficient for the production and less material is lost and The panels pollute more slowly.
  • FIG. 6 shows a detail of an inventive Security thread 110 which shows in a surface area a RollingStar pattern in which two parallel rows of small rectangles 112 can be seen in each tilted position.
  • Fig. 6 (a) shows the appearance in a first tilted position with a small pitch of the rectangular rows 112
  • Fig. 6 (b) shows the appearance in a second tilted position with a large pitch of the rectangular rows 112.
  • the different spacing of the rectangular rows 112 at different tilt positions can be obtained in the manner described with reference to FIG. 4 by means of a suitable arrangement of differently oriented small facets or micromirrors.
  • the kinematic effect is combined with a color effect. Since the micromirrors which form the rectangular rows 112 with a small or large spacing have different angles of inclination in order to produce the different visibility in the two tilt positions, they are also provided with differently thick absorber layers in the case of the above-described oblique vapor deposition. In this way, the color impression of the rectangular rows 112, for example, from a silver color impression at a small distance (Fig. 6 (a)) to a golden color impression at a large distance (Fig. 6 (b)) change. The attention and recognition value of the kinematic feature can be further increased in a simple manner.
  • the pitch changes and color changes of the rectangular rows 112 are typically continuous and limited to two discrete values in FIG. 6 for illustration only.
  • the micromirrors can be aligned, for example, in such a way that a first motif is visible in a first tilted position and a second motif in a second, different tilted position. Since the micromirrors have different angles of inclination in order to produce the different visibility in the two tilt positions, they are also provided with differently thick absorber layers in the oblique evaporation described above, so that the first motif appears, for example, with a silvery color impression and the second motif with a copper-like reddish color impression ,
  • FIG. 2 shows a design in which first the metal layer 32 and then the ultrathin absorber layer 34 are applied to the relief structure 22, the security element 120 of FIG. 7 shows that the reverse layer sequence is also possible. Since the color modification of the metal layer 32 is visible through the absorber layer 34 only when the security element 12 is viewed from the absorber layer 34 side, the security element 120 appears with the unchanged reflection color of the metal layer 32 viewed from the front side (viewing direction 122) , for example, silver. When viewed from the rear side (viewing direction 124), the color impression of the metal layer 32 is modified by the ultrathin absorber layer 34, so that, for example, a gold or copper-colored color impression is produced.
  • the absorber layer 34 is recessed, so that the security element 120 there also shows a silver color impression from the rear side.
  • the recess 40 there is neither a metal layer 32 nor an absorber layer 34, so that the recess 40 appears as a transparent see-through feature.
  • the relief structure of the security element is formed by a two-dimensional periodic sub-wavelength grating, as described, for example, in the publication 10 2011 101 635 A1, the disclosure content of which is incorporated in the present application.
  • the sub-wavelength grating is coated with an approximately 50 nm thick aluminum layer and a 14 nm thick silicon layer, which together form a two-ply color mirror.
  • the aluminum layer is not opaque despite its relatively large thickness, so that the security element forms a see-through security element.
  • the security element appears in review from both sides with the same color, while in supervision depending on the viewing direction results in a different color impression, since the color modification by the silicon layer when viewed in reflection occurs only from the side of the silicon layer ago.
  • a wash ink can be printed in a manner known per se and washed off after the vapor deposition.
  • the recesses in the absorber layer or in the entire color mirror are produced by laser application, in particular with pulsed laser radiation. With a sufficiently high pulse energy density, the entire color mirror can be demetallized by the laser radiation, so that recesses 40, as shown in FIGS. 2 and 7, are formed.
  • the term demetallization in addition to an ablation, also includes a conversion of the absorber layer into a transparent modification, for example by a chemical transformation, such as an oxidation.
  • FIG. 8 shows the reflection spectrum 130 of a 28 nm-thick aluminum layer and the reflection spectrum 132 of a gold-colored color mirror 30, which consists of a 16 nm-thick silicon layer on a 28 nm-thick aluminum layer.
  • the color mirror 30 below a wavelength of approximately 650 nm exhibits a greatly reduced reflection compared with the bare aluminum layer 32, which gives the human eye a golden appearance. Since the transmission of the aluminum layer 32 and the color mirror 30 is negligibly small, the non-reflected radiant energy is absorbed respectively.
  • the 16 nm-thick silicon layer 34 of a gold-colored color mirror 30 can be selectively demetallised.
  • the demetallized portions showed the original silvery appearance of the aluminum layer 32 and specular reflection, indicating a substantially undamaged Surface of the aluminum layer 32 indicates.
  • the entire color mirror 30 including the aluminum layer 32 can be demetallized.
  • the relief structure of an optically variable security element can also be formed by a microlens grid, in the focal plane of which the two-layer color mirror is arranged.
  • FIG. 9 shows a security element 140 with a lens raster image for the unscaled representation of two predetermined target images, which are visible from different viewing directions 142, 144.
  • the security element 140 has a carrier 150 in the form of a transparent plastic film, for example, about 20 ⁇ thick PET film.
  • a motif layer 154 is formed, wherein the thickness of the carrier 150 and the curvature of the microlenses 152 are coordinated so that the focal length of the microlenses 152 substantially corresponds to the thickness of the carrier 150, so that the motif layer 154 in FIG the focal plane of the microlenses 152 is located.
  • the motif layer 154 is formed in the exemplary embodiment by a colored, for example blue lacquer layer 156 and a two-layered color mirror 158 arranged above the lacquer layer 156 with a metal layer 160 and an ultrathin absorber layer 162.
  • the metal layer 160 is a 28 nm thick aluminum layer and the ultrathin absorber layer 162 is a 14 nm thick silicon layer that the color mirror in its non-recessed areas shows a golden appearance.
  • a plurality of microholes 164, 66 were inscribed in the color mirror 158 by the action of laser radiation.
  • the first microholes 164 were generated from the first viewing direction 142 in the manner described above only in the ultrathin absorber layer 162.
  • second micro-holes 166 are created that pass through the entire color mirror 158.
  • the plurality of first microholes 164 together form the first target image, and the plurality of second microholes 166 form the second target image. Because of the reversibility of the beam path, it is ensured that the target images inscribed in the color mirror 158 by means of the laser application are each visible from the same direction 142, 144 from which they were imprinted with the laser beam.
  • the first target image is formed by the microholes 164, which are present only in the ultrathin absorber layer 162, the first target image appears silver in front of the gold-colored background of the not recessed color mirror regions.
  • the second target image is formed by the microholes 166 which penetrate the entire color mirror 158, so that the blue lacquer layer 156 is visible there and the second target image appears blue in front of the gold-colored background of the not recessed color mirror regions.

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  • Diffracting Gratings Or Hologram Optical Elements (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Credit Cards Or The Like (AREA)

Abstract

L'invention concerne un élément de sécurité optiquement variable (12) destiné à la protection d'objets de valeur, une structure en relief (22) et un miroir coloré (30) bicouche étant superposés et coopérant pour générer en réflexion une image virtuelle couleur et optiquement variable, le miroir coloré (30) bicouche étant constitué d'une couche métallique (32) réfléchissante et d'une couche absorbante (34) ultramince appliquée sur la couche métallique (32) et constituée de silicium, d'alliage de silicium ou de SiOx, où x < 1.
EP16725364.0A 2015-05-27 2016-05-17 Élément de sécurité optiquement variable Active EP3302995B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102015006793.1A DE102015006793A1 (de) 2015-05-27 2015-05-27 Optisch variables Sicherheitselement
PCT/EP2016/000817 WO2016188619A1 (fr) 2015-05-27 2016-05-17 Élément de sécurité optiquement variable

Publications (2)

Publication Number Publication Date
EP3302995A1 true EP3302995A1 (fr) 2018-04-11
EP3302995B1 EP3302995B1 (fr) 2019-04-10

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EP (1) EP3302995B1 (fr)
CN (1) CN107921810B (fr)
DE (1) DE102015006793A1 (fr)
WO (1) WO2016188619A1 (fr)

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EP3302995B1 (fr) 2019-04-10
WO2016188619A1 (fr) 2016-12-01

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