EP3184319B1 - Safety element for security papers, valuable documents or the like and method for manufacturing a safety element - Google Patents

Safety element for security papers, valuable documents or the like and method for manufacturing a safety element Download PDF

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Publication number
EP3184319B1
EP3184319B1 EP16002760.3A EP16002760A EP3184319B1 EP 3184319 B1 EP3184319 B1 EP 3184319B1 EP 16002760 A EP16002760 A EP 16002760A EP 3184319 B1 EP3184319 B1 EP 3184319B1
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EP
European Patent Office
Prior art keywords
micro
grating
sub
reflector
reflectors
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.)
Active
Application number
EP16002760.3A
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German (de)
French (fr)
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EP3184319A1 (en
Inventor
Hans Lochbihler
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Giesecke and Devrient Currency Technology GmbH
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Giesecke and Devrient Currency Technology GmbH
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Publication of EP3184319A1 publication Critical patent/EP3184319A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
    • B42D25/23—Identity cards
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
    • B42D25/24—Passports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/20—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof characterised by a particular use or purpose
    • B42D25/29—Securities; Bank notes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/324—Reliefs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/328—Diffraction gratings; Holograms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/342—Moiré effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/351—Translucent or partly translucent parts, e.g. windows
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/30—Identification or security features, e.g. for preventing forgery
    • B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
    • B42D25/373—Metallic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
    • B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
    • B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
    • B42D25/40—Manufacture
    • B42D25/405—Marking
    • B42D25/425—Marking by deformation, e.g. embossing
    • 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
    • B42D25/40—Manufacture
    • B42D25/405—Marking
    • B42D25/43—Marking by removal of material

Definitions

  • the invention relates to a security element for an object to be protected, such as.
  • a security paper, document of value or the like comprising a plurality of microreflectors arranged in a pattern and a plurality of microstructures which together with the microreflectors produce an image perceptible by a viewer.
  • the invention further relates to a security paper or document of value.
  • the invention also relates to a method for producing a security element for an object to be protected, such.
  • a security paper, document of value or the like wherein on a substrate a plurality of microreflectors arranged in a pattern and a plurality of microstructures are formed, which together with the microreflectors produce an image perceptible by a viewer.
  • Items to be protected are often provided with a security element that allows verification of the authenticity of the item and thus serves as protection against unauthorized reproduction.
  • Such items are, for example, security papers, identification or value documents (such as banknotes, chip cards, passports, identification cards, identity cards, shares, bonds, certificates, vouchers, checks, tickets, credit cards, health cards) as well as product security elements such. Labels, seals and packaging. It can also be products themselves, such as a capsule of a drug for which fakes are to be feared.
  • This synthetic image has properties (for example, an ortho-parallactic effect) that are not reproducible by simply copying the images.
  • the focusing elements can be designed as microlenses or microreflectors. The latter construction is the subject of the publications WO 2010/136339 A2 and the WO 2011/012460 A2 ,
  • microimages are a greatly reduced form of at least a partial section of the synthetic image. They are formed for example by the image content corresponding relief surfaces which are filled with color, or which otherwise have light-absorbing properties.
  • microimages and focusing elements require a distance between microimages and focusing elements, which corresponds approximately to the focal length of the focusing elements.
  • this requirement is generally met by the fact that microimages and microfocusing elements are arranged on opposite sides of a film whose thickness corresponds approximately to the focal length of the focusing elements. This procedure requires a double-sided embossing of the film in very exact register each other. This is expensive and therefore disadvantageous.
  • the publication WO 2012/156049 A1 is concerned with a two-dimensionally periodic, color-filtering grating which has a contiguous high-index base layer defining a lattice plane. Above the base layer, the grating has a two-dimensionally regular pattern of individual high refractive surface elements which has a periodicity between 100 nm and 800 nm in at least two directions which are parallel to the grating plane.
  • a security element with a flat, transparent body which, in a first area, has a basic element structure which conveys different color impressions in plan view of the body from the front and the back.
  • the publication WO 2011/066992 A1 relates to a security element with a carrier whose top is height-modulated, and having a multi-layer structure acting as a color filter, which is formed on the height-modulated upper side and thus also height-modulated.
  • the publication DE 10 2012105 571 A1 describes a decorative element with a microstructure, which generates an optical effect in reflected light and / or transmitted light.
  • the microstructure is designed in such a way that a color is generated by interference of the light reflected at a base surface and element surfaces in incident light and / or in particular by interference of the light transmitted through the element surfaces and the base surfaces in transmitted light.
  • the generic document WO 2014/012667 A1 also deals with a security element. It consists of a large number of microreflectors arranged in a pattern, at the bottom of each of which there is a reflective grating, which diffracts incident radiation and directs it towards the microreflector, which then reflects it back to the viewer. Thus, incident light from the array of micromirrors and gratings is completely reflected to the viewer. The grids bend the incident light in the first diffraction order. By varying the relative position of microreflector to grating in the pattern, an image can be generated. Proceeding from this, the object of the invention is to achieve greater protection against forgery and applicability in the case of a security element, a security paper or document of value as well as in a production method for these objects.
  • the invention provides a security element as defined in independent claim 1 for an article to be protected, such as a security paper, a document of value or the like.
  • the security element comprises a substrate having a plurality of microreflectors arranged in a pattern and a plurality of microstructures which, together with the microreflectors, produce an image perceptible by a viewer.
  • Each microstructure is designed as a sub-wavelength grating and assigned to one of the microreflectors, whereby grating reflectors comprising in each case a microreflector and at least one sub-wavelength grating are formed.
  • Each subwavelength grid is designed to that visible radiation, ie light incident through an aperture of the micro-reflector from the half-space, diffractively diffracts into a zeroth reflection diffraction order, wherein preferably for each grating reflector, the sub-wavelength grating and the microreflector are matched to one another such that the microreflector at least a part of radiation diffracted by the sub-wavelength grating into the zeroth reflection diffraction order is reflected back into the half-space as re-radiation.
  • the sub-wavelength grating is formed as a semi-transparent sub-wavelength grating which transmissively diffracts a second portion of the visible radiation incident through the aperture of the microreflector from the half space into a zeroth transmission diffraction order.
  • the subwavelength grating and the microreflector are matched to one another in such a way that the subwavelength grating transmits the radiation incident through the aperture of the microreflector from the half space and reflected by the microreflector in the zeroth transmission diffraction order through the substrate.
  • the sub-wavelength grating is formed as an opaque sub-wavelength grating.
  • the subwavelength gratings are configured with structures whose period is smaller than the wavelength of the visible light spectrum. They are further designed so that they bend the majority of radiation coloring in the zeroth order of diffraction. If higher diffraction orders occur for certain angles of incidence in the short-wave wavelength range, only a small portion of the incident radiation is diffracted into these orders. For example, get 50%, 60% or 70% of the incident radiation in the zeroth order of diffraction, either in reflection or in transmission.
  • the subwavelength grating can be designed in such a way that approximately half of the radiation is reflected and the other half is transmitted, and furthermore a small proportion of the radiation is absorbed. Other divisions are possible.
  • the sub-wavelength grating is semi-transparent in this sense and causes a color in reflection and transmission. For certain parameters, the proportion of radiation that is absorbed may also be dominant.
  • the reflection and transmission properties of the subwavelength grating are particularly dependent on the wavelength of the incident radiation. In particular, only radiation in a specific wavelength range in the zeroth diffraction order is diffracted or reflected diffracted. Thus, it is possible to determine the color or the color appearance of the image generated by the grating reflector in reflection and / or transmission.
  • the reflection and transmission properties of the subwavelength grating also depend on the profile geometry and on the material properties of the subwavelength grating.
  • the transmission takes place through the substrate, which is therefore preferably at least partially transparent or translucent for the radiation.
  • the substrate is preferably made transparent at least in the region of a bottom of the grating reflectors, in particular the substrate is completely transparent, for example a transparent film.
  • the substrate may be opaque, for example, coated with a sub-wavelength absorbing grating to provide a black background for the image.
  • the subwavelength grating and the microreflector are in particular arranged such that the radiation transmitted or reflected by the first or higher diffraction order is not reflected or transmitted as far as possible to the microreflector or at such shallow angles that the microreflector rejects radiation from the higher diffraction orders compared to the one in the zeroth Diffraction order transmitted only to a lower intensity component or reflected in the half space.
  • the security element is characterized in particular by the fact that the security element displays an image or several images to an observer, both when it is in the same half-space as the security element illumination (reflected image or supervisory image) and when the illumination of the security device Security element and the observer with respect to the security element are located in two different half-spaces (transmitted image or transparency).
  • the security element thus shows an image from both sides, the images being the same or different, e.g. B. with regard to a color impression can be.
  • the sub-wavelength grating of the security element is not used in advantageous embodiments for the absorption of radiation, but for the reflection and transmission of radiation.
  • the part of the radiation absorbed by the sub-wavelength grating and / or the security element is extremely small, for example less than 50% of the incident radiation.
  • the absorption ratio is greater for a sub-wavelength grating than for a first-order diffraction grating, since electromagnetic resonances occur here for specific wavelengths which lead to light absorption, as for example in the documents DE 10 2011101635 A1 and DE 10 2009 056 933 A1 described.
  • the sub-wavelength grating is used only for the reflection of radiation and acts as a so-called subtraction color filter.
  • the (opaque) sub-wavelength grating absorbs radiation in a certain wavelength range in the visible part of the radiation spectrum, the remaining part of the radiation spectrum is reflected. Thus, for example, if the blue portion of the radiation is absorbed, the subwavelength grating appears in reflection in the complementary color of blue.
  • the diffracted back and transmitted transmission radiation may optionally be mirrored prior to diffraction (transmission or transmission) or after or before diffraction (reflection) at the micro-reflector. In all cases, the direction in which it is emitted, the angle of radiation and the color of the formation of the grating reflector depends. By arranging differently configured grating reflectors in the pattern, colored symbols or images can be generated, both in a plan view and in a transparent view.
  • the portion of the incident radiation deflected by the grating reflector is responsible for producing the reflected (top view) or transmitted (see through) image. Due to the design of the grating reflector such that as much light is deflected, a particularly light-intensive image can be generated.
  • the degree of deflection depends inter alia on the diameter of the aperture. The larger the diameter of the Aperture, the smaller the angular range in which the incident light is deflected by the grating reflector. On the other hand, as the diameter of the aperture increases, the convergence of the laterally deflected light increases. Thus, although a larger diameter lattice reflector of the aperture is capable of deflecting light from a wider range of angles, the divergence of the deflected light is also greater, which reduces the intensity of the image.
  • the size of the deflection also depends on the depth of the grating reflector, which is measured from the bottom of the grating reflector to its aperture.
  • the depth of the grating reflector increases, so does the divergence of the reflected or transmitted light.
  • the acceptance angle of the incident light and the divergence of the reflected light or transmitted light can be selected accordingly to provide for the respective security element best parameters for generating the image.
  • the image information is only achieved by the interaction of the grating reflectors in the pattern. Preference is given to multiple grating reflectors with different configurations (combination of microreflector and microstructure in the respective grating reflector) provided so that there is a difference in color or intensity between the grating reflectors, which produces a total of the perceptible image.
  • a plurality of equal grating reflectors can be arranged side by side, with their arrangement carrying the image information. In this way, for example, letters or symbols are displayed.
  • the image information is preferably generated by the security element in that each grating reflector consisting of microreflector and subwavelength grating has the function of a pixel for image generation.
  • the sublength wave gratings in combination with the microreflectors generally have strongly angle-dependent properties, it is also possible to generate parallax images as in a moire magnification arrangement. It is also possible to form stereograms, for example by appropriate alignment of the microreflectors so that some grating reflectors provide image information for the left eye, others for the right eye (corresponding to the visual angle difference).
  • grating reflectors can be combined with known structures such as holograms, micromirror arrangements and / or light-absorbing structures such as moth-eye structures or microcavities.
  • the security element can be produced in a single molding process. It is not necessary to carry out registration steps to be carried out in register with one another on different sides of a transparent film. Rather, it is possible with a single embossing process, a substrate, for. As a film to be designed so that both the structures of the microreflectors and the sub-wavelength grating are generated. The relative position (and shape) of subwavelength grating and associated microreflector is determined by the given embossing tool, so that no mutually in the register standing sequences of processing steps on the substrate are necessary. This simplifies the production.
  • the minimum thickness of the security element is not predetermined by a focal length of focusing elements.
  • the thickness is limited only by the depth of the microreflectors. This depth corresponds approximately to the height which microlenses would have for known moiré magnification arrangements, with the result that the minimum thickness of the security element is only a fraction of that of conventional security elements with moiré magnification arrangements. Nevertheless, a moiré effect can be realized equally.
  • the micro-reflectors can be configured as channel-shaped reflectors. They are then gutters, which preferably have a flat bottom. The flat floor does not necessarily have to be reflective. At the level bottom of the sub-wavelength grating is arranged, which is then also designed as a linear grating. Especially with channel-shaped reflectors, it is also possible to arrange more than one sub-wavelength grating along the channels of the reflector.
  • the micro-reflectors may be designed as a concave mirror, which preferably have a flat bottom on which the sub-wavelength grating is located. Again, the floor does not have to be reflective.
  • the planar bottom of the microreflectors can in particular be configured obliquely, so that the sub-wavelength grating tends toward the microreflector.
  • microreflectors whose bottom is not flat but, for example, arched.
  • the micro-reflectors are formed as a concave mirror, which are rotationally symmetric, for example, have the shape of the lateral surface of a spherical layer or ellipsoid layer.
  • a lateral surface is obtained when a layer is cut out of an ellipsoid or a sphere by two parallel planes which actually cut the sphere or the ellipsoid.
  • the smaller of the two parallel circular surfaces or ellipses created by the cut then represents the bottom of the concave mirror. This does not have to be mirrored.
  • microreflectors have, in addition to the bottom, a side wall which is parabolic in cross-section, straight, elliptical or formed as a hybrid form thereof.
  • the sidewall may be divided into several sections, each section being parabolic, straight, elliptical, or a hybrid form thereof. It is also possible that the individual sections are formed differently. If an aperture of hexagonal cross-section is provided, each section of a wall may correspond to the hexagonal aperture. Alternatively, the aperture can be rectangular and thus the micro-reflector cuboid, wherein each side wall in cross-section corresponding parabolic, straight, elliptical or formed as a hybrid form thereof.
  • the shape of the side wall in cross section depends in particular on the size of the microreflector and the arrangement of the subwavelength grating in the microreflector.
  • the alignment of the side walls of the individual grid reflectors makes it possible to transmit image information.
  • the sidewalls are oriented in a first direction, so that these grating reflectors are visible in a first viewing direction.
  • the side walls are aligned in a second direction, so that these grating reflectors can be seen in a second viewing direction.
  • micro-deflectors are asymmetrical in cross-section, wherein in particular a first part of the side wall is straight and a second part of the side wall is concave, in particular parabolic or elliptical.
  • the first part of the side wall and the second part of the side wall are arranged opposite each other.
  • two sections of the side wall are located opposite one another.
  • the first part of the side wall which is currently formed, may be arranged perpendicular to the ground.
  • the straight part shields a region of the bottom from the incident radiation, i. shaded, and thus does not contribute to the undeflected portion of the incident radiation. Consequently, the proportion of radiation that is deflected laterally increases.
  • each sub-wavelength grating has a grating period between 100 nm and 500 nm, particularly 240 nm to 420 nm, the sub-wavelength grating being one-dimensionally periodic or even two-dimensional can be formed periodically.
  • the grating period and the profile of the subwavelength grating depend in particular on the color which is to be reflected or transmitted in the zeroth diffraction order.
  • the microreflectors and the sub-wavelength gratings are advantageously coated with at least one metallic layer, preferably with Al, Ag, Au, Cu, Cr or an alloy containing these metals.
  • the microreflectors and the subwavelength gratings can be provided on their side facing the half space with a multilayer coating, e.g. B. as a trilayer of two superimposed metal or semiconductor layers with an intervening dielectric layer can be constructed.
  • the shape of the microreflector Due to the shape of the aperture, the shape of the microreflector is determined in particular. Thus, the arrangements of the side surfaces are given and consequently also the reflected radiation from the side walls. For example, by using a rotationally symmetrical microreflector with a circular aperture, an image can be generated in many directions. When using a cuboid microreflector with a rectangular aperture individual observation directions may be preferred. The same applies to a cylindrical microreflector with a hexagonal aperture.
  • Grid reflectors with round apertures are preferably arranged in a hexagonal pattern, since in this way the highest possible area filling can be achieved.
  • the individual grid reflectors can be formed with webs surrounding them, i. H. at least some adjacent grille reflectors then do not abut each other directly, but are separated by a web. Between the grid reflectors are thus web surfaces, which are preferably formed by flat surfaces. By coating the web surfaces and / or shaping the thickness of the substrate in the region of the web surfaces, it is possible to ensure that light incident on the web surfaces is differently reflected and / or transmitted. The effect is preferably designed to be laterally variable in order additionally to encode symbols and make them visible in transmission. This additional counterfeit security is achieved.
  • a laterally varying coating of the web surfaces is preferably realized in that the web surfaces are first provided with a coating, for example with a metallization, and this is partially removed again, for. B. by an etching process.
  • a coating for example with a metallization
  • the micro-reflectors can basically have any shape in their aperture (opening), for example square, circular or rectangular apertures.
  • the aperture has a diameter and the microreflector has a depth from the aperture to the bottom, wherein within a pattern at least one of the following properties of the grating reflectors varies to produce an image: location of the subwavelength gratings to the respective associated microreflector The diameter of the aperture, the depth of the microreflector, the orientation of the microreflector, the shape of the microreflector and / or the grating period of the subwavelength grating.
  • one or more parameters are changed between the individual grating reflectors of the pattern.
  • a region of the image can be generated by grating reflectors with a first parameter set, while a second region of the image is generated by grating reflectors with a second parameter set. In this way, for example, generate stereograms.
  • the parameters within the image may change continuously to produce moiré effects, for example.
  • the security element may in particular be designed as a security thread, tear-open thread, security strip, security strip, patch or label.
  • the security element can cover transparent areas or recesses of an object to be protected.
  • the security element can be part of a precursor that can not yet be processed to a value document, which, for example, can also have additional authenticity features (such as, for example, luminescent substances provided in the volume, etc.).
  • value documents here on the one hand understood the document having security element, on the other hand value documents can also be other documents or items that can be provided with the security element according to the invention, so they have non-copyable authenticity features.
  • Chip or security cards such. As bank or credit cards are other examples of value documents.
  • the invention relates to a defined in the independent claim 12 method for producing a security element for an object to be protected, such as.
  • a security paper, document of value or the like wherein on a substrate a plurality of microreflectors arranged in a pattern and a plurality of microstructures are formed, which together with the microreflectors produce an image perceptible by a viewer.
  • Each microstructure is formed as a sub-wavelength grating and associated with one of the microreflectors, thereby forming grating reflectors each comprising a microreflector and at least one sub-wavelength grating.
  • Each sub-wavelength grating is formed to reflectively deflect visible radiation incident through an aperture of the micro-reflector from a hemisphere into a zeroth reflection diffraction order, preferably matching the sub-wavelength grating and the microreflector for each grating reflector such that the microreflector matches Reflected radiation from the sub-wavelength grating in the zeroth reflection diffraction order reflected back radiation in the half space back.
  • the sub-wavelength grating is formed as a semi-transparent sub-wavelength grating which transmissively diffracts a second portion of the visible radiation incident through the aperture (24) of the microreflector (22) from the hemisphere into a zeroth transmission diffraction order.
  • the sub-wavelength grating and the microreflector are preferably further tuned to one another such that the sub-wavelength grating transmits the radiation incident through the aperture of the microreflector from the half-space and reflected by the microreflector in the zeroth transmission order.
  • the sub-wavelength grating is formed as an opaque sub-wavelength grating.
  • direct exposure techniques are suitable for producing the microreflectors, e.g. B. photolithographically with the help of a laserwriter.
  • the preparation can be carried out analogously to the known production method for microlenses.
  • the structure of the subwavelength gratings is generated.
  • the two processes are preferably carried out accurately in one and the same photoresist.
  • two different Belackungsvorerie are possible.
  • an exposed original can then be galvanically molded, thus producing an embossing stamp.
  • the structure is replicated via a stamping process, for example in UV varnish on film.
  • a nanoimprint method can be used. More elaborate methods of original manufacture, such as electron beam or focused ion beam exposure techniques, allow for even finer geometry design and are therefore particularly suitable for the production of subwavelength gratings.
  • the manufacturing method according to the invention can be designed so that the described preferred embodiments and embodiments of the security element are produced.
  • the safety element 12 is made of a substrate 14, for example a transparent film, on whose upper side (the term is to be understood purely by way of example and is not intended to indicate a preferred direction) an embossed structure is formed.
  • the embossing structure comprises a plurality of microreflectors 22, which in the embodiments of the Fig. 1 to 4 are formed as elliptical reflectors with a flat bottom 16. In other embodiments, for example, in which the Fig. 5 and 6 the micro-reflectors are designed in other geometries, in particular not rotationally symmetrical.
  • Each grid reflector 10 thus has the bottom 16 and at least one side wall 18.
  • a semi-transparent sub-wavelength grating 20 is provided on the bottom 16 of the grating reflector 10.
  • the at least one side wall 18 and the bottom 16 form the microreflector 22, which is open to the top and thus to a half space through an aperture 24 with a diameter a.
  • the distance from the bottom 16 to the aperture 24 determines the depth t of the grating reflector 10.
  • the substrate 14 is at least partially transparent in the region of the bottom 16.
  • the side wall 18 of Fig. 1 illustrated grid reflectors 10 is designed parabolic in cross section. Furthermore, here the grating reflector 10 is designed rotationally symmetrical.
  • the grating reflectors 10, which are in Fig. 1a and 1b are shown to have the same diameter a of the aperture 24, but differ in their depth t.
  • the ratio of the diameter a of the aperture 24 to the depth t of the grating reflector 10 is 0.8 in Fig. 1a and 0.55 in Fig. 1b ,
  • the proportion of the radiation incident from the half-space, which falls on the sub-wavelength grating 20, is reflected directly there and transmitted to a second part.
  • the other remainder of the visible radiation incident to be reflected by the micro-reflector 22 onto the sub-wavelength grating 20 is also partially diffracted by the sub-wavelength grating 20 in zero diffraction order and partially transmitted. Reflection in the zeroth reflection diffraction order means that the angle of incidence is equal to the angle of reflection, but z. B. the color properties of the diffraction are dependent on the direction of the incident light.
  • the proportion of light which is first reflected at the micro-reflector 22 is thus reflected differently at the sub-wavelength grating and transmitted as the directly incident light component.
  • the incident radiation is deflected laterally with respect to the angle of incidence, so that it creates a visible image for the observer.
  • the amount of light deflected laterally can be increased by providing an asymmetrical grating reflector 10 as shown in FIG Fig. 2a and 2b is shown.
  • a first part 26 of the side wall 18 is straight in cross-section and is in particular perpendicular to the bottom 16.
  • a second part 28 of the side wall 18, which is arranged opposite the first part 26, is as in FIG Fig. 1 parabolic shaped.
  • the ratio of the diameter a of the aperture 24 to the depth t of the grating reflector 10 is 1 in Fig. 2a and 0.53 in Fig. 2b ,
  • Fig. 2a and 2b is represented by the left light beam
  • the first portion 26 of the side wall 18 shadows a portion of the sub-wavelength grating 20 in the incident radiation. This increases the proportion of the light which is deflected by the grating reflector 10.
  • Fig. 3 shows three different depth grating reflectors 10 with a constant diameter a of the aperture 24 and the same sub-wavelength grating 20 at the bottom 16 of the grating reflector 10.
  • results for the grating reflector 10 of Fig. 3b an aspect ratio of 1.
  • the marginal rays of the incident and the diffracted radiation are drawn, which are first diffracted at the sub-wavelength grating 20 in the zeroth order and then deflected by the side wall 18 of the microreflector 22.
  • the transmitted radiation is in Fig. 3 not shown because the semi-transparent sub-wavelength grating 20 transmits the drawn, incident light without deflection.
  • the comments on the FIGS. 3 and 4 also apply by way of example to such embodiments.
  • the rays each relate to a fixed point of incidence on the subwavelength grating 20.
  • the acceptance angle of the incident light and the light scattering depend on the depth t, as shown by way of example in the table below.
  • Depth t Acceptance angle of incident light Divergence of the reflected light 0.3 12.5 ° 20.5 ° 0.4 11.0 ° 16.3 ° 0.5 9.5 ° 15.1 °
  • the numbers indicate that as the depth t of the microreflector 22 increases, the divergence of the deflected radiation decreases; H. is focused to the viewer, since the exit angle describes the bundling.
  • the radiation reflected at the subwavelength grating 20 and at the microreflector 22 undergoes significant scattering. Furthermore, the acceptance angle of the incident light and the divergence of the reflected light decrease for increasing depths t of the micro-reflector 22. Finally, it should be mentioned that all the impact points on the sub-wavelength grating 20 must be considered to characterize the overall scattering of a grating reflector 10.
  • Fig. 4 The edge rays of the incident and the diffracted radiation are also drawn, which are first diffracted at the sub-wavelength grating 20 in the zeroth order and then deflected by the micro-reflector 22.
  • the impact point selected in this example is shifted to the left with respect to the symmetry axis of the micro-reflector 22.
  • the acceptance angles of the incident light and the light scattering of the reflected light are summarized in the following table: Diameter a Acceptance angle of incident light Divergence of the reflected light 0.3 17.0 ° 30.1 ° 0.4 15.5 ° 25.1 ° 0.5 14.0 ° 21.5 °
  • the variation of the diameter a of the aperture 24 also leads to a variation of the acceptance angle of the incident light and to a change in the divergence of the reflected light.
  • the pattern of many juxtaposed grid reflectors 10 can be used to represent subjects in a security element 12. It is z. B. two variants of structural geometries, preferably a different reflector geometry, in the respective areas before.
  • Fig. 5 shows such a varied arrangement of grating reflectors 10, in which the depth t is selected differently in the areas I and II.
  • the diameter of the aperture 24 of the microreflectors 22 is designated by a
  • the extent of the subwavelength gratings 20 is denoted by b.
  • the depth t of the microreflectors 22 in the regions I and II is t 1 and t 2, respectively.
  • the pattern of the grating reflectors 10 allows a variety of different reflector geometries. Exemplary are the micro-reflectors 22in Fig. 5a with a parabolic and in Fig. 5b represented with a conical shape.
  • the microreflectors 22 may have a non-rotationally symmetric and / or asymmetric shape in cross section. Examples of unilaterally parabolic microreflectors 22 and microreflectors 22 having a trapezoidal cross section without curvature are shown in FIG Fig. 6 shown.
  • Fig. 7 shows some examples of grating reflectors 10 having the following aperture shapes: square, circular and hexagonal.
  • the grid reflectors 10 of Fig. 7a and Fig. 7b are arranged orthogonally.
  • An optimal area coverage is achieved by a hexagonal arrangement, as in Fig. 7c is shown.
  • the location of the subwavelength gratings 20 within the individual microreflectors 22 may be shifted laterally.
  • a continuous shift of the subwavelength gratings 20 relative to the aperture 24 of the microreflectors 22 can be used in particular for generating moiré effects, stereoscopic effects or running effects.
  • Stereograms by means of the grating reflectors 10 is based on the in Fig. 8 illustrated example explained. Stereograms require at least two images, one for left-eye perception and the other for right-eye perception. Such stereograms can be generated by the grating reflectors 10 described herein both in reflection and in transmission.
  • Fig. 8 shows a security element 12 in the form of a stereogram.
  • the area of the two letters "AB” is filled with a plurality of grid reflectors 10.
  • the surrounding background contains a homogeneous sub-wavelength grating 20.
  • the incident light is directed in the exemplary embodiment by a semicylindrical reflector geometry in different directions.
  • the grid reflectors 10 in the letter “A” are oriented so that they preferentially direct the light to the right eye.
  • the light reflected by the grille reflectors in the letter "B” is primarily perceived by the left eye.
  • the orientation is determined by the side walls 18 of the micro-deflectors 22. With a correspondingly small pixelization, these two symbols can also be nested one inside the other.
  • the grating reflectors described here provide 10 a wide range of possible designs and symbols.
  • the desired color is accomplished by the appropriate selection of the grating period of the sub-wavelength grating 20.
  • the pattern with many grating reflectors 10 also colored symbols or images can be generated, which are visible at a certain angle.
  • at least one of the above-mentioned parameters of the grating reflectors 10 in the pattern is laterally varied. Since the grating reflectors 10 have strongly angle-dependent properties, in particular parallax images can also be generated thereby. As a result, both parallactic movements and spatial effects can be realized.
  • Fig. 9 schematically shows a security element 12 with motifs, which are formed by a pattern of grating reflectors 10 in front of a homogeneous background. This surrounding area is filled in the exemplary embodiment with a homogeneous sub-wavelength grating 20. Due to the light deflection through the grating reflectors, the motif "star" is visible in oblique view in transmission, while the background appears dark ( Fig. 9a ).
  • Fig. 9b shows a motif with the letters "A” and "B", which are formed by differently shaped asymmetric grating reflectors 10.
  • the curved side wall 18 (second part 28; Fig. 2 ) at the letter “A” below, at the letter “B”, the second part 28 of the side wall 18 in the micro-reflector 22 is arranged above.
  • the motifs with differently oriented grating reflectors 10 can be nested. The different motifs can then be perceived one after the other and depending on the subject at the same location of the security element when tilting a pattern designed in this way.
  • Fig. 9 shown security element 12 is used in particular in see-through windows of banknotes use. However, it is also possible to use only the reflection properties of this structure, for example for a security thread or a security strip (eg LEAD (Longlasting Economical Anticopy Device) strip).
  • a security thread or a security strip eg LEAD (Longlasting Economical Anticopy Device) strip.
  • subwavelength grating 20 not only one-dimensional periodic gratings can be used. Also, the subwavelength gratings need not be combined with microreflectors 22 that are curved in the same spatial direction. There are also sub-wavelength grating 20 conceivable, which are rotated about an axis of symmetry of the micro-reflector 22, wherein the rotation is varied within the pattern.
  • cross gratings are particularly suitable, the grating period preferably being perpendicular to the curvatures of a microreflector having a rectangular aperture 24.
  • Circular gratings are particularly suitable for reflectors with round apertures 24.
  • hybrid forms or elliptical subwavelength gratings 20 in microreflectors 22 with elliptical apertures 24 are possible.
  • grating reflectors 10 formed in each case from subwavelength grating 20 and microreflector 22 are arranged next to one another, their configuration varying laterally in order to form an image, for example, as a colored symbol.
  • the variation of the diffraction characteristics of the subwavelength gratings 20, or the position of the subwavelength gratings 20 to the respective associated microreflector 22 or the reflection characteristic of the microreflectors 22, the alignment of the microreflectors 22, or the grating period of the subwavelength grating 20, or a combination thereof, causes a color or intensity contrast in the Motive.
  • the web surfaces are preferably formed by flat surfaces. In an exemplary construction, the web surfaces are laterally structured such that some web surfaces are provided with a metallization, but others are not.
  • the security element 12 is structured in this way in two areas that differ in their reflection behavior and also in their transmission behavior. As a result of the lateral structuring of the metallization, additional information can thus be coded in the security element 12. Instead of a metallization It is also possible to use a different reflection layer.
  • an absorption layer can also be formed.
  • the lateral structuring of the web surfaces then has no effect on the reflection behavior, but on the transmission behavior.
  • the security element 12 of the Fig. 1 used principle provides a large building block with which patterns or symbols can be designed by grating reflectors 10.
  • the variation of the grating reflectors 10 in the pattern can be realized by many parameters.
  • the structure of the security element 12 can be made very easily in a single embossing process. All you need is a corresponding embossing tool that has a corresponding negative shape for each grid reflector 10, which thus generates both the microreflectors 22 and the sub-wavelength gratings 20.
  • the subwavelength gratings 20 must be precisely formed in the embossing tool. Specifically, the fabrication of the original of the sub-wavelength grating 20 can be accomplished by electron beam writing or interferometric techniques.
  • the microreflectors 22 typically have a depth t of 2 to 30 microns, a particularly preferred range is between 5 and 20 microns. Lower depths t are advantageous both with regard to the production of the embossing tool and the subsequent duplication.
  • the sub-wavelength grating 20 is optically particularly effective when at least 4 to 10 grating periods can be accommodated at the bottom 16. This gives one lower limit for the size of the microreflectors 22 before.
  • An upper limit arises when one wants to use the grating reflectors 10 as pixels, which should naturally be as small as possible and in particular should no longer be resolved with an unarmed eye.
  • as flat an embossing as possible is advantageous in copying.
  • the microreflectors 22 are first produced in a variant, for example photolithographically by direct laser writing. Independently, the structure of the subwavelength gratings 20 is generated. These two processes are preferably carried out accurately in one and the same photoresist, which is the basis for the embossing tool as a template. Alternatively, two different Belackungsvor réelle are possible.
  • micro-reflectors 22 are imprinted in the direct exposure process with a laserwriter, so that the subwavelength lattice 20 is exposed in the middle of the individual microreflectors after development.
  • the laserwriters used can work with 2-photon absorption processes. It is then possible to generate microreflectors 22, such as sub-wavelength gratings 20, in a single process.
  • the template produced for the embossing tool is now copied electroplated or in a nanoimprint process.
  • a plurality of security elements 12 are usually to be produced in one embossing step in the embossing process of a film, it is preferable to provide a plurality of adjacent stamp elements in the embossing tool, each of which has been produced from a template in the above-described manner.
  • the embossed film is preferably coated with an opaque metal layer.
  • a metal layer For this purpose, sputtering, electron beam evaporation or thermal evaporation come into question.
  • Particularly suitable metals are aluminum, silver, gold, nickel or chromium or alloys of these materials. But there are also multi-layer structures in question, which contain at least one layer of metallic material. The thicknesses of the metal layer are between 20 and 100 nm.
  • the metal surface is preferably coated with a protective layer or laminated with a cover film.
  • a corresponding coating is preferably first applied to all web surfaces and then removed again from some web surfaces.
  • the removal is performed by demetallization.
  • an etching process or the metal transfer process according to WO 2011/138039 A1 come into use. It is also possible to remove the layer, for example demetallization with the aid of ultrashort pulse lasers and the use of a writing laser beam.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Business, Economics & Management (AREA)
  • Accounting & Taxation (AREA)
  • Finance (AREA)
  • Credit Cards Or The Like (AREA)
  • Diffracting Gratings Or Hologram Optical Elements (AREA)

Description

Die Erfindung betrifft ein Sicherheitselement für einen zu schützenden Gegenstand, wie z. B. ein Sicherheitspapier, Wertdokument oder dergleichen, das mehrere, in einem Muster angeordnete Mikroreflektoren und mehrere Mikrostrukturen aufweist, die zusammen mit den Mikroreflektoren ein von einem Betrachter wahrnehmbares Bild erzeugen.The invention relates to a security element for an object to be protected, such as. A security paper, document of value or the like comprising a plurality of microreflectors arranged in a pattern and a plurality of microstructures which together with the microreflectors produce an image perceptible by a viewer.

Die Erfindung bezieht sich weiter auf ein Sicherheitspapier oder Wertdokument.The invention further relates to a security paper or document of value.

Die Erfindung bezieht sich schließlich auch auf ein Verfahren zum Herstellen eines Sicherheitselementes für einen zu schützenden Gegenstand, wie z. B. ein Sicherheitspapier, Wertdokument oder dergleichen, wobei auf einem Substrat mehrere, in einem Muster angeordnete Mikroreflektoren und mehrere Mikrostrukturen ausgebildet werden, die zusammen mit den Mikroreflektoren ein von einem Betrachter wahrnehmbares Bild erzeugen.Finally, the invention also relates to a method for producing a security element for an object to be protected, such. A security paper, document of value or the like, wherein on a substrate a plurality of microreflectors arranged in a pattern and a plurality of microstructures are formed, which together with the microreflectors produce an image perceptible by a viewer.

Zu schützende Gegenstände werden häufig mit einem Sicherheitselement ausgestattet, das eine Überprüfung der Echtheit des Gegenstandes erlaubt und somit als Schutz vor unerlaubter Reproduktion dient. Solche Gegenstände sind beispielsweise Sicherheitspapiere, Ausweis- oder Wertdokumente (wie z. B. Banknoten, Chipkarten, Pässe, Identifikationskarten, Ausweiskarten, Aktien, Anleihen, Urkunden, Gutscheine, Schecks, Eintrittskarten, Kreditkarten, Gesundheitskarten) sowie Produktsicherungselemente, wie z. B. Etiketten, Siegel und Verpackungen. Es kann sich auch um Produkte selbst handeln, wie beispielsweise eine Kapsel eines Medikamentes, für das Fälschungen zu befürchten sind.Items to be protected are often provided with a security element that allows verification of the authenticity of the item and thus serves as protection against unauthorized reproduction. Such items are, for example, security papers, identification or value documents (such as banknotes, chip cards, passports, identification cards, identity cards, shares, bonds, certificates, vouchers, checks, tickets, credit cards, health cards) as well as product security elements such. Labels, seals and packaging. It can also be products themselves, such as a capsule of a drug for which fakes are to be feared.

Für Sicherheitselemente sind im Stand der Technik ausführlich sogenannte Moire-Vergrößerungsanordnungen beschrieben, beispielsweise in den Druckschriften EP 1434695 B1 , WO 2005/106601 A2 , EP 1979768 A1 , EP 1182054 B1 , WO 2011/029602 A2 , WO 2002/101669 A2 , EP 1476317 A1 und EP 1893074 A2 . Diese Vergrößerungsanordnungen kombinieren Fokussierelemente mit Mikrobildern, welche sich in der Bildebene der Fokussierelemente befinden. Die Mikrobilder sind zu den Fokussierelementen so ausgerichtet, dass sich bei Betrachtung des Sicherheitselements durch den sogenannten Moire-Effekt ein synthetisches Bild ergibt. Dieses synthetische Bild hat Eigenschaften (beispielsweise einen ortho-parallaktischen Effekt), die durch einfache Kopie der Bilder nicht reproduzierbar sind. Die Fokussierelemente können als Mikrolinsen oder Mikroreflektoren ausgebildet sein. Letztere Bauweise ist Gegenstand der Druckschriften WO 2010/136339 A2 und der WO 2011/012460 A2 .For security elements, so-called moire magnification arrangements are described extensively in the prior art, for example in the documents EP 1434695 B1 . WO 2005/106601 A2 . EP 1979768 A1 . EP 1182054 B1 . WO 2011/029602 A2 . WO 2002/101669 A2 . EP 1476317 A1 and EP 1893074 A2 , These magnification arrangements combine focusing elements with microimages, which are located in the image plane of the focusing elements. The microimages are aligned with the focusing elements in such a way that a synthetic image results when the security element is viewed through the so-called moiré effect. This synthetic image has properties (for example, an ortho-parallactic effect) that are not reproducible by simply copying the images. The focusing elements can be designed as microlenses or microreflectors. The latter construction is the subject of the publications WO 2010/136339 A2 and the WO 2011/012460 A2 ,

Bekannten Moire-Vergrößerungsanordnungen ist es gemein, dass die Mikrobilder eine stark verkleinerte Form zumindest eines Teilausschnittes des synthetischen Bildes sind. Sie sind beispielsweise durch dem Bildinhalt entsprechende Reliefoberflächen gebildet, welche mit Farbe gefüllt sind, oder welche anderweitig lichtabsorbierende Eigenschaften haben.It is common for known moiré magnification arrangements that the microimages are a greatly reduced form of at least a partial section of the synthetic image. They are formed for example by the image content corresponding relief surfaces which are filled with color, or which otherwise have light-absorbing properties.

Die bekannten Sicherheitselemente benötigen einen Abstand zwischen Mikrobildern und Fokussierelementen, der in etwa der Fokuslänge der Fokussierelemente entspricht. Im Stand der Technik wird diese Anforderung in der Regel dadurch erfüllt, dass Mikrobilder und Mikrofokussierelemente auf gegenüberliegenden Seiten einer Folie angeordnet sind, deren Dicke in etwa der Fokuslänge der Fokussierelemente entspricht. Dieses Vorgehen erfordert eine beidseitige Prägung der Folie in sehr exaktem Register zueinander. Dies ist aufwendig und deshalb nachteilig.The known security elements require a distance between microimages and focusing elements, which corresponds approximately to the focal length of the focusing elements. In the prior art, this requirement is generally met by the fact that microimages and microfocusing elements are arranged on opposite sides of a film whose thickness corresponds approximately to the focal length of the focusing elements. This procedure requires a double-sided embossing of the film in very exact register each other. This is expensive and therefore disadvantageous.

Die Druckschrift WO 2012/156049 A1 befasst sich mit einem zweidimensional periodischen, farbfilternden Gitter, das eine zusammenhängende hochbrechende, eine Gitterebene definierende Grundschicht aufweist. Über der der Grundschicht weist das Gitter ein zweidimensional regelmäßiges Muster aus einzelnen hochbrechenden Flächenelementen auf, das in mindestens zwei Richtungen, die parallel zur Gitterebene verlaufen, eine Periodizität zwischen 100 nm und 800 nm hat.The publication WO 2012/156049 A1 is concerned with a two-dimensionally periodic, color-filtering grating which has a contiguous high-index base layer defining a lattice plane. Above the base layer, the grating has a two-dimensionally regular pattern of individual high refractive surface elements which has a periodicity between 100 nm and 800 nm in at least two directions which are parallel to the grating plane.

Aus der Druckschrift WO 2014/023415 A1 ist ein Sicherheitselement mit einem flachen, transparenten Körper bekannt, der in einem ersten Bereich eine Grundelementstruktur aufweist, die in Draufsicht auf den Körper von Vorder- und Rückseite unterschiedliche Farbeindrücke vermittelt.From the publication WO 2014/023415 A1 For example, a security element with a flat, transparent body is known which, in a first area, has a basic element structure which conveys different color impressions in plan view of the body from the front and the back.

Die Druckschrift WO 2011/066992 A1 betrifft ein Sicherheitselement mit einem Träger, dessen Oberseite höhenmoduliert ist, und mit einer als Farbfilter wirkenden Mehrschichtstruktur, die auf der höhenmodulierten Oberseite ausgebildet und dadurch ebenfalls höhenmoduliert ist.The publication WO 2011/066992 A1 relates to a security element with a carrier whose top is height-modulated, and having a multi-layer structure acting as a color filter, which is formed on the height-modulated upper side and thus also height-modulated.

Die Druckschrift DE 10 2012105 571 A1 beschreibt ein Dekorelement mit einer Mikrostruktur, welche im Auflicht und/oder im Durchlicht einen optischen Effekt generiert. Die Mikrostruktur ist dazu derart ausgebildet, dass durch Interferenz des an einer Grundfläche und Elementflächen reflektierten Lichts im Auflicht und/oder insbesondere durch Interferenz des durch die Elementflächen und die Grundflächen transmittierten Lichts im Durchlicht eine Farbe generiert wird.The publication DE 10 2012105 571 A1 describes a decorative element with a microstructure, which generates an optical effect in reflected light and / or transmitted light. The microstructure is designed in such a way that a color is generated by interference of the light reflected at a base surface and element surfaces in incident light and / or in particular by interference of the light transmitted through the element surfaces and the base surfaces in transmitted light.

Die gattungsbildende Druckschrift WO 2014/012667 A1 befasst sich ebenfalls mit einem Sicherheitselement. Es besteht aus einer Vielzahl von in einem Muster angeordneten Mikroreflektoren, an deren Boden jeweils ein reflektives Gitter liegt, das einfallende Strahlung beugt und zum Mikroreflektor hin leitet, der sie dann zum Betrachter wieder zurück reflektiert. Somit wird einfallendes Licht von der Anordnung aus Mikrospiegeln und Gittern zu dem Betrachter vollständig reflektiert. Die Gitter beugen das einfallende Licht in der ersten Beugungsordnung. Durch eine Variation der Relativlage von Mikroreflektor zu Gitter im Muster kann ein Bild erzeugt werden. Ausgehend davon liegt der Erfindung die Aufgabe zugrunde, bei einem Sicherheitselement, einem Sicherheitspapier oder Wertdokument sowie bei einem Herstellverfahren für diese Objekte eine größere Fälschungssicherheit und Anwendbarkeit zu erreichen.The generic document WO 2014/012667 A1 also deals with a security element. It consists of a large number of microreflectors arranged in a pattern, at the bottom of each of which there is a reflective grating, which diffracts incident radiation and directs it towards the microreflector, which then reflects it back to the viewer. Thus, incident light from the array of micromirrors and gratings is completely reflected to the viewer. The grids bend the incident light in the first diffraction order. By varying the relative position of microreflector to grating in the pattern, an image can be generated. Proceeding from this, the object of the invention is to achieve greater protection against forgery and applicability in the case of a security element, a security paper or document of value as well as in a production method for these objects.

Diese Aufgabe wird durch die Merkmale der unabhängigen Ansprüche gelöst. Die abhängigen Ansprüche beziehen sich auf bevorzugte Ausführungsformen der Erfindung.This object is solved by the features of the independent claims. The dependent claims relate to preferred embodiments of the invention.

Die Erfindung stellt ein in dem unabhängigen Anspruch 1 definiertes Sicherheitselement für einen zu schützenden Gegenstand bereit, wie beispielsweise ein Sicherheitspapier, ein Wertdokument oder dergleichen. Das Sicherheitselement weist ein Substrat mit mehreren, in einem Muster angeordneten Mikroreflektoren und mehreren Mikrostrukturen auf, die zusammen mit den Mikroreflektoren ein von einem Betrachter wahrnehmbares Bild erzeugen. Jede Mikrostruktur ist als Subwellenlängengitter ausgebildet und einem der Mikroreflektoren zugeordnet, wodurch Gitterreflektoren umfassend jeweils einen Mikroreflektor und mindestens ein Subwellenlängengitter gebildet sind. Jedes Subwellenlängengitter ist so ausgebildet, dass es sichtbare Strahlung, also Licht, die durch eine Apertur des Mikroreflektors aus dem Halbraum einfällt, in eine nullte Reflexions-Beugungsordnung reflektierend beugt, wobei bevorzugt für jeden Gitterreflektor das Subwellenlängengitter und der Mikroreflektor so aufeinander abgestimmt sind, dass der Mikroreflektor mindestens einen Teil der von dem Subwellenlängengitter in die nullte Reflexions-Beugungsordnung gebeugten Strahlung als Rückstrahlung in den Halbraum zurückreflektiert.The invention provides a security element as defined in independent claim 1 for an article to be protected, such as a security paper, a document of value or the like. The security element comprises a substrate having a plurality of microreflectors arranged in a pattern and a plurality of microstructures which, together with the microreflectors, produce an image perceptible by a viewer. Each microstructure is designed as a sub-wavelength grating and assigned to one of the microreflectors, whereby grating reflectors comprising in each case a microreflector and at least one sub-wavelength grating are formed. Each subwavelength grid is designed to that visible radiation, ie light incident through an aperture of the micro-reflector from the half-space, diffractively diffracts into a zeroth reflection diffraction order, wherein preferably for each grating reflector, the sub-wavelength grating and the microreflector are matched to one another such that the microreflector at least a part of radiation diffracted by the sub-wavelength grating into the zeroth reflection diffraction order is reflected back into the half-space as re-radiation.

In einer bevorzugten Ausgestaltung ist das Subwellenlängengitter als halbtransparentes Subwellenlängengitter ausgebildet, das einen zweiten Teil der sichtbaren Strahlung, die durch die Apertur des Mikroreflektors aus dem Halbraum einfällt, in eine nullte Transmissions-Beugungsordnung transmittierend beugt. Bevorzugt sind dabei in jedem Gitterreflektor das Subwellenlängengitter und der Mikroreflektor so aufeinander abgestimmt, dass das Subwellenlängengitter die durch die Apertur des Mikroreflektors aus dem Halbraum einfallende und von dem Mikroreflektor reflektierte Strahlung in der nullten Transmissions-Beugungsordnung durch das Substrat transmittiert.In a preferred embodiment, the sub-wavelength grating is formed as a semi-transparent sub-wavelength grating which transmissively diffracts a second portion of the visible radiation incident through the aperture of the microreflector from the half space into a zeroth transmission diffraction order. Preferably, in each grating reflector the subwavelength grating and the microreflector are matched to one another in such a way that the subwavelength grating transmits the radiation incident through the aperture of the microreflector from the half space and reflected by the microreflector in the zeroth transmission diffraction order through the substrate.

Nach einer ebenfalls bevorzugten Ausgestaltung ist das Subwellenlängengitter als opakes Subwellenlängengitter ausgebildet.According to another preferred embodiment, the sub-wavelength grating is formed as an opaque sub-wavelength grating.

Die Subwellenlängengitter sind mit Strukturen ausgestaltet, deren Periode kleiner als die Wellenlänge des sichtbaren Lichtspektrums ist. Sie sind weiter derart ausgebildet, dass sie den Großteil der Strahlung farbgebend in die nullte Beugungsordnung beugen. Falls höhere Beugungsordnungen für bestimmte Einfallswinkel im kurzwelligen Wellenlängenbereich auftreten, wird nur ein kleiner Anteil der einfallenden Strahlung in diese Ordnungen gebeugt. Beispielsweise gelangen 50%, 60% oder 70% der einfallenden Strahlung in die nullte Beugungsordnung, entweder in Reflexion oder in Transmission. Insbesondere kann das Subwellenlängengitter derart ausgebildet sein, dass in etwa die Hälfe der Strahlung reflektiert und die andere Hälfte transmittiert wird, wobei ferner ein geringer Anteil der Strahlung absorbiert wird. Andere Aufteilungen sind möglich. Das Subwellenlängengitter ist in diesem Sinne halbtransparent und bewirkt eine Farbgebung in Reflexion und Transmission. Für bestimmte Parameter kann der Anteil der Strahlung, der absorbiert wird, auch dominierend sein.The subwavelength gratings are configured with structures whose period is smaller than the wavelength of the visible light spectrum. They are further designed so that they bend the majority of radiation coloring in the zeroth order of diffraction. If higher diffraction orders occur for certain angles of incidence in the short-wave wavelength range, only a small portion of the incident radiation is diffracted into these orders. For example, get 50%, 60% or 70% of the incident radiation in the zeroth order of diffraction, either in reflection or in transmission. In particular, the subwavelength grating can be designed in such a way that approximately half of the radiation is reflected and the other half is transmitted, and furthermore a small proportion of the radiation is absorbed. Other divisions are possible. The sub-wavelength grating is semi-transparent in this sense and causes a color in reflection and transmission. For certain parameters, the proportion of radiation that is absorbed may also be dominant.

Die Reflexions- und Transmissionseigenschaften des Subwellenlängengitters sind insbesondere von der Wellenlänge der einfallenden Strahlung abhängig. Insbesondere wird nur Strahlung in einem bestimmten Wellenlängenbereich in nullter Beugungsordnung transmittierend oder reflektierend gebeugt. Somit ist es möglich, die Farbe bzw. das farbliche Erscheinungsbild des durch den Gitterreflektor in Reflexion und/oder in Transmission erzeugten Bildes festzulegen. Daneben hängen die Reflexions- und Transmissionseigenschaften des Subwellenlängengitters auch von der Profilgeometrie sowie von den Materialeigenschaften des Subwellenlängengitters ab.The reflection and transmission properties of the subwavelength grating are particularly dependent on the wavelength of the incident radiation. In particular, only radiation in a specific wavelength range in the zeroth diffraction order is diffracted or reflected diffracted. Thus, it is possible to determine the color or the color appearance of the image generated by the grating reflector in reflection and / or transmission. In addition, the reflection and transmission properties of the subwavelength grating also depend on the profile geometry and on the material properties of the subwavelength grating.

Die Transmission erfolgt durch das Substrat, das deshalb bevorzugt für die Strahlung zumindest teiltransparent oder transluzent ist. Das Substrat ist vorzugsweise mindestens im Bereich eines Bodens der Gitterreflektoren transparent ausgestaltet, insbesondere ist das Substrat komplett transparent, beispielsweise eine durchsichtige Folie. Außerhalb der Gitterreflektoren kann optional das Substrat intransparent sein, beispielsweise mit einem absorbierenden Subwellenlängengitter beschichtet sein, um einen schwarzen Hintergrund für das Bild bereitzustellen.The transmission takes place through the substrate, which is therefore preferably at least partially transparent or translucent for the radiation. The substrate is preferably made transparent at least in the region of a bottom of the grating reflectors, in particular the substrate is completely transparent, for example a transparent film. Optionally, outside of the grating reflectors, the substrate may be opaque, for example, coated with a sub-wavelength absorbing grating to provide a black background for the image.

Das Subwellenlängengitter und der Mikroreflektor sind insbesondere derart angeordnet, dass die von der ersten oder höheren Beugungsordnung transmittierte oder reflektierte Strahlung möglichst nicht zum Mikroreflektor oder unter derart flachen Winkeln reflektiert oder transmittiert wird, dass der Mikroreflektor Strahlung aus den höheren Beugungsordnungen verglichen mit der in der nullten Beugungsordnung nur zu einem geringeren Intensitätsanteil transmittiert oder in den Halbraum reflektiert.The subwavelength grating and the microreflector are in particular arranged such that the radiation transmitted or reflected by the first or higher diffraction order is not reflected or transmitted as far as possible to the microreflector or at such shallow angles that the microreflector rejects radiation from the higher diffraction orders compared to the one in the zeroth Diffraction order transmitted only to a lower intensity component or reflected in the half space.

Die Anordnung des Subwellenlängengitters und des Mikroreflektors erfolgt im Vergleich zum Ansatz der WO 2014/012667 A1 nicht hinsichtlich der Reflexion in erster Beugungsordnung, sondern in nullter Beugungsordnung. Darüber hinaus ist das Sicherheitselement insbesondere dadurch gekennzeichnet, dass das Sicherheitselement einem Beobachter ein Bild oder mehrere Bilder zeigt, sowohl, wenn dieser sich in demselben Halbraum wie die Beleuchtung für das Sicherheitselement befindet (reflektiertes Bild oder Aufsichtsbild) als auch, wenn sich die Beleuchtung des Sicherheitselements und der Beobachter mit Hinblick auf das Sicherheitselement in zwei verschiedenen Halbräumen befinden (transmittiertes Bild oder Durchsichtsbild). Das Sicherheitselement zeigt also von beiden Seiten ein Bild, wobei die Bilder gleich oder unterschiedlich, z. B. hinsichtlich eines Farbeindrucks, sein können.The arrangement of the subwavelength grating and the microreflector takes place in comparison to the approach of WO 2014/012667 A1 not with regard to the reflection in the first diffraction order, but in the zeroth order of diffraction. In addition, the security element is characterized in particular by the fact that the security element displays an image or several images to an observer, both when it is in the same half-space as the security element illumination (reflected image or supervisory image) and when the illumination of the security device Security element and the observer with respect to the security element are located in two different half-spaces (transmitted image or transparency). The security element thus shows an image from both sides, the images being the same or different, e.g. B. with regard to a color impression can be.

Das Subwellenlängengitter des Sicherheitselements wird in vorteilhaften Ausgestaltungen nicht zur Absorption von Strahlung, sondern zur Reflexion und Transmission von Strahlung genutzt. Insbesondere ist der von dem Subwellenlängengitter und/oder dem Sicherheitselement in Transmission absorbierte Teil der Strahlung äußerst gering, beispielsweise unter 50% der einfallenden Strahlung. Im Allgemeinen ist der Absorptionsanteil bei einem Subwellenlängengitter größer als bei einem Beugungsgitter erster Ordnung, da hier elektromagnetische Resonanzen für bestimmte Wellenlängen auftreten, welche zur Lichtabsorption führen, wie beispielsweise in den Druckschriften DE 10 2011101635 A1 und DE 10 2009 056 933 A1 beschrieben.The sub-wavelength grating of the security element is not used in advantageous embodiments for the absorption of radiation, but for the reflection and transmission of radiation. In particular, the part of the radiation absorbed by the sub-wavelength grating and / or the security element is extremely small, for example less than 50% of the incident radiation. In general, the absorption ratio is greater for a sub-wavelength grating than for a first-order diffraction grating, since electromagnetic resonances occur here for specific wavelengths which lead to light absorption, as for example in the documents DE 10 2011101635 A1 and DE 10 2009 056 933 A1 described.

In weiteren vorteilhaften Ausgestaltungen wird das Subwellenlängengitter nur zur Reflexion von Strahlung genutzt und wirkt als sogenanntes Subtraktionsfarbfilter. Das (opake) Subwellenlängengitter absorbiert dabei Strahlung in einem bestimmten Wellenlängenbereich im sichtbaren Teil des Strahlungsspektrums, der verbleibende Teil des Strahlungsspektrums wird reflektiert. Wird also beispielsweise der blaue Strahlungsanteil absorbiert, erscheint das Subwellenlängengitter in Reflexion in der Komplementärfarbe von Blau.In further advantageous embodiments, the sub-wavelength grating is used only for the reflection of radiation and acts as a so-called subtraction color filter. The (opaque) sub-wavelength grating absorbs radiation in a certain wavelength range in the visible part of the radiation spectrum, the remaining part of the radiation spectrum is reflected. Thus, for example, if the blue portion of the radiation is absorbed, the subwavelength grating appears in reflection in the complementary color of blue.

Die gebeugte Rück- und transmittierte Durchsicht-Strahlung können optional vor der Beugung (Durchsicht oder Transmission) oder nach oder vor der Beugung (Reflexion) am Mikroreflektor gespiegelt werden. In allen Fällen hängt die Richtung, in der sie abgegeben wird, der Abstrahlwinkel und die Farbe von der Ausbildung des Gitterreflektors ab. Durch die Anordnung verschieden ausgestalteter Gitterreflektoren im Muster können farbige Symbole bzw. Bilder erzeugt werden, sowohl in Aufsicht als auch in Durchsicht.The diffracted back and transmitted transmission radiation may optionally be mirrored prior to diffraction (transmission or transmission) or after or before diffraction (reflection) at the micro-reflector. In all cases, the direction in which it is emitted, the angle of radiation and the color of the formation of the grating reflector depends. By arranging differently configured grating reflectors in the pattern, colored symbols or images can be generated, both in a plan view and in a transparent view.

Der durch den Gitterreflektor abgelenkte Teil der einfallenden Strahlung ist für die Erzeugung des reflektierten (Aufsicht) oder transmittierten (Durchsicht) Bildes verantwortlich. Durch die Ausgestaltung des Gitterreflektors derart, dass möglichst viel Licht abgelenkt wird, kann ein besonders lichtintensives Bild erzeugt werden. Der Grad der Ablenkung hängt unter anderem von dem Durchmesser der Apertur ab. Je größer der Durchmesser der Apertur ist, desto geringer ist der Winkelbereich, in welchem das einfallende Licht durch den Gitterreflektor abgelenkt wird. Auf der anderen Seite steigt mit zunehmendem Durchmesser der Apertur die Konvergenz des seitlich abgelenkten Lichts. Somit ist ein Gitterreflektor mit größerem Durchmesser der Apertur zwar geeignet, Licht aus einem größeren Winkelbereich abzulenken, die Divergenz des abgelenkten Lichts ist jedoch ebenfalls größer, was die Intensität des Bildes mindert.The portion of the incident radiation deflected by the grating reflector is responsible for producing the reflected (top view) or transmitted (see through) image. Due to the design of the grating reflector such that as much light is deflected, a particularly light-intensive image can be generated. The degree of deflection depends inter alia on the diameter of the aperture. The larger the diameter of the Aperture, the smaller the angular range in which the incident light is deflected by the grating reflector. On the other hand, as the diameter of the aperture increases, the convergence of the laterally deflected light increases. Thus, although a larger diameter lattice reflector of the aperture is capable of deflecting light from a wider range of angles, the divergence of the deflected light is also greater, which reduces the intensity of the image.

Auf der anderen Seite hängt die Größe der Ablenkung auch von der Tiefe des Gitterreflektors ab, welche von dem Boden des Gitterreflektors zu dessen Apertur gemessen wird. Je tiefer der Gitterreflektor ist, desto geringer wird der Akzeptanzwinkel des einfallenden Lichtes, d.h. nur in einem speziellen, kleiner werdenden Winkelbereich wird Licht durch den Gitterreflektor seitlich abgelenkt, so dass ein sichtbares Bild entsteht. Allerdings nimmt mit zunehmender Tiefe des Gitterreflektors auch die Divergenz des reflektierten bzw. transmittierten Lichts ab.On the other hand, the size of the deflection also depends on the depth of the grating reflector, which is measured from the bottom of the grating reflector to its aperture. The deeper the grating reflector is, the lower the acceptance angle of the incident light, i. Only in a special, decreasing angle range is light deflected laterally by the grating reflector, so that a visible image is formed. However, as the depth of the grating reflector increases, so does the divergence of the reflected or transmitted light.

Durch eine geeignete Wahl des Durchmessers der Apertur und der Tiefe des Gitterreflektors kann somit der Akzeptanzwinkel des einfallenden Lichts und die Divergenz des reflektierten Lichts bzw. transmittierten Lichts entsprechend gewählt werden, um für das jeweilige Sicherheitselement beste Parameter zur Erzeugung des Bildes bereitzustellen.By a suitable choice of the diameter of the aperture and the depth of the grating reflector thus the acceptance angle of the incident light and the divergence of the reflected light or transmitted light can be selected accordingly to provide for the respective security element best parameters for generating the image.

Ein Betrachter nimmt aus einer Betrachtungsrichtung einen einzelnen Gitterreflektor mit einer durch dessen Ausgestaltung festgelegten Intensität und/oder Farbe, aber ohne Bildinformation wahr. Die Bildinformation wird erst durch das Zusammenwirken der Gitterreflektoren im Muster erreicht. Bevorzugt werden mehrere Gitterreflektoren mit verschiedener Ausbildung (Kombination aus Mikroreflektor und Mikrostruktur im jeweiligen Gitterreflektor) vorgesehen, so dass zwischen den Gitterreflektoren ein Farb- oder Intensitätsunterschied besteht, der insgesamt das wahrnehmbare Bild erzeugt. Außerdem können mehrere gleiche Gitterreflektoren nebeneinander angeordnet werden, wobei deren Anordnung die Bildinformation trägt. Auf diese Weise werden beispielsweise Buchstaben oder Symbole dargestellt. Die Bildinformation wird vom Sicherheitselement bevorzugt dadurch erzeugt, dass jeder Gitterreflektor bestehend aus Mikroreflektor und Subwellenlängengitter die Funktion eines Pixels zur Bilderzeugung hat.A viewer perceives from a viewing direction a single grating reflector with an intensity and / or color determined by its design, but without image information. The image information is only achieved by the interaction of the grating reflectors in the pattern. Preference is given to multiple grating reflectors with different configurations (combination of microreflector and microstructure in the respective grating reflector) provided so that there is a difference in color or intensity between the grating reflectors, which produces a total of the perceptible image. In addition, a plurality of equal grating reflectors can be arranged side by side, with their arrangement carrying the image information. In this way, for example, letters or symbols are displayed. The image information is preferably generated by the security element in that each grating reflector consisting of microreflector and subwavelength grating has the function of a pixel for image generation.

Da die Sublängenwellengitter in Kombination mit den Mikroreflektoren in der Regel stark winkelabhängige Eigenschaften besitzen, können auch Parallaxenbilder wie bei einer Moire-Vergrößerungsanordnung erzeugt werden. Es ist ferner die Bildung von Stereogrammen möglich, beispielsweise durch entsprechende Ausrichtung der Mikroreflektoren, so dass einige Gitterreflektoren Bildinformationen für das linke Auge, andere für das rechte Auge (entsprechend dem Sehwinkelunterschied) bereitstellen.Since the sublength wave gratings in combination with the microreflectors generally have strongly angle-dependent properties, it is also possible to generate parallax images as in a moire magnification arrangement. It is also possible to form stereograms, for example by appropriate alignment of the microreflectors so that some grating reflectors provide image information for the left eye, others for the right eye (corresponding to the visual angle difference).

Schließlich verbleibt zu erwähnen, dass die oben beschriebenen Gitterreflektoren mit bekannten Strukturen wie Hologrammen, Mikrospiegelanordnungen und/oder lichtabsorbierenden Strukturen wie Mottenaugenstrukturen oder Mikrokavitäten kombiniert werden können.Finally, it should be noted that the above-described grating reflectors can be combined with known structures such as holograms, micromirror arrangements and / or light-absorbing structures such as moth-eye structures or microcavities.

Das Sicherheitselement kann in einem einzigen Abformverfahren hergestellt werden. Man benötigt keine registerhaltig zueinander auszuführenden Abformschritte auf verschiedenen Seiten einer transparenten Folie. Es ist vielmehr möglich, mit einem einzigen Prägeprozess ein Substrat, z. B. eine Folie, so zu gestalten, dass sowohl die Strukturen der Mikroreflektoren als auch der Subwellenlängengitter erzeugt werden. Die Relativlage (und Form) von Subwellenlängengitter und zugeordnetem Mikroreflektor wird durch das entsprechende Prägewerkzeug vorgegeben, so dass keine zueinander im Register stehenden Folgen von Bearbeitungsschritten am Substrat nötig sind. Dies vereinfacht die Herstellung.The security element can be produced in a single molding process. It is not necessary to carry out registration steps to be carried out in register with one another on different sides of a transparent film. Rather, it is possible with a single embossing process, a substrate, for. As a film to be designed so that both the structures of the microreflectors and the sub-wavelength grating are generated. The relative position (and shape) of subwavelength grating and associated microreflector is determined by the given embossing tool, so that no mutually in the register standing sequences of processing steps on the substrate are necessary. This simplifies the production.

Weiter ist die Mindestdicke des Sicherheitselementes nicht durch eine Fokallänge von Fokussierungselementen vorgegeben. Die Dicke ist ausschließlich durch die Tiefe der Mikroreflektoren beschränkt. Diese Tiefe entspricht in etwa der Höhe, welche Mikrolinsen bekannter Moiré-Vergrößerungsanordnungen hätten, was zum Ergebnis führt, dass die Mindestdicke des Sicherheitselementes nur ein Bruchteil der von herkömmlichen Sicherheitselementen mit Moiré-Vergrößerungsanordnungen ist. Dennoch kann ein Moire-Effekt gleichermaßen realisiert werden.Furthermore, the minimum thickness of the security element is not predetermined by a focal length of focusing elements. The thickness is limited only by the depth of the microreflectors. This depth corresponds approximately to the height which microlenses would have for known moiré magnification arrangements, with the result that the minimum thickness of the security element is only a fraction of that of conventional security elements with moiré magnification arrangements. Nevertheless, a moiré effect can be realized equally.

Die Mikroreflektoren können als rinnenförmige Reflektoren ausgestaltet werden. Sie sind dann Rinnen, die vorzugsweise einen ebenen Boden haben. Der ebene Boden muss nicht zwingend reflektierend sein. Am ebenen Boden ist das Subwellenlängengitter angeordnet, das dann ebenfalls als Lineargitter ausgebildet ist. Insbesondere bei rinnenförmigen Reflektoren ist es auch möglich, mehr als ein Subwellenlängengitter entlang der Rinnen des Reflektors anzuordnen. Optional dazu können die Mikroreflektoren als Hohlspiegel gestaltet sein, die vorzugsweise einen ebenen Boden haben, an dem das Subwellenlängengitter liegt. Auch hier muss der Boden nicht reflektierend sein. Der ebene Boden der Mikroreflektoren kann insbesondere schräg ausgestaltet sein, so dass sich das Subwellenlängengitter zum Mikroreflektor hin neigt.The micro-reflectors can be configured as channel-shaped reflectors. They are then gutters, which preferably have a flat bottom. The flat floor does not necessarily have to be reflective. At the level bottom of the sub-wavelength grating is arranged, which is then also designed as a linear grating. Especially with channel-shaped reflectors, it is also possible to arrange more than one sub-wavelength grating along the channels of the reflector. Optionally, the micro-reflectors may be designed as a concave mirror, which preferably have a flat bottom on which the sub-wavelength grating is located. Again, the floor does not have to be reflective. The planar bottom of the microreflectors can in particular be configured obliquely, so that the sub-wavelength grating tends toward the microreflector.

Alternativ können auch Mikroreflektoren eingesetzt werden, deren Boden nicht eben, sondern beispielsweise gewölbt ausgestaltet ist.Alternatively, it is also possible to use microreflectors whose bottom is not flat but, for example, arched.

Die einzelnen Gitterreflektoren als Pixel einzusetzen, ist dann besonders einfach, wenn die Mikroreflektoren als Hohlspiegel ausgebildet sind, die rotationssymmetrisch sind, beispielsweise die Form der Mantelfläche einer Kugelschicht oder Ellipsoidschicht haben. Eine solche Mantelfläche erhält man, wenn man aus einem Ellipsoid oder einer Kugel durch zwei parallele, die Kugel bzw. das Ellipsoid echt schneidende Ebenen eine Schicht herausschneidet. Die kleinere der beiden durch den Schnitt entstehenden parallelen Kreisflächen oder Ellipsen stellt dann den Boden des Hohlspiegels dar. Dieser muss nicht verspiegelt sein.To use the individual grating reflectors as pixels, is particularly simple if the micro-reflectors are formed as a concave mirror, which are rotationally symmetric, for example, have the shape of the lateral surface of a spherical layer or ellipsoid layer. Such a lateral surface is obtained when a layer is cut out of an ellipsoid or a sphere by two parallel planes which actually cut the sphere or the ellipsoid. The smaller of the two parallel circular surfaces or ellipses created by the cut then represents the bottom of the concave mirror. This does not have to be mirrored.

Es ist bevorzugt, dass die Mikroreflektoren neben dem Boden eine Seitenwand aufweisen, welche im Querschnitt parabelförmig, gerade, ellipsenförmig oder als eine Mischform daraus ausgebildet ist.It is preferred that the microreflectors have, in addition to the bottom, a side wall which is parabolic in cross-section, straight, elliptical or formed as a hybrid form thereof.

Die Seitenwand kann in mehrere Abschnitte eingeteilt sein, wobei jeder Abschnitt parabelförmig, gerade, ellipsenförmig oder als eine Mischform daraus ausgestaltet ist. Es ist auch möglich, dass die einzelnen Abschnitte unterschiedlich ausgebildet sind. Wenn eine Apertur mit hexagonalem Querschnitt vorgesehen ist, kann jeder Abschnitt einer Wand der hexagonalen Apertur entsprechen. Alternativ kann auch die Apertur rechteckförmig und damit der Mikroreflektor quaderförmig sein, wobei jede Seitenwand im Querschnitt entsprechend parabelförmig, gerade, ellipsenförmig oder als eine Mischform daraus ausgebildet ist. Die Form der Seitenwand im Querschnitt hängt insbesondere von der Größe des Mikroreflektors und der Anordnung des Subwellenlängengitters im Mikroreflektor ab.The sidewall may be divided into several sections, each section being parabolic, straight, elliptical, or a hybrid form thereof. It is also possible that the individual sections are formed differently. If an aperture of hexagonal cross-section is provided, each section of a wall may correspond to the hexagonal aperture. Alternatively, the aperture can be rectangular and thus the micro-reflector cuboid, wherein each side wall in cross-section corresponding parabolic, straight, elliptical or formed as a hybrid form thereof. The shape of the side wall in cross section depends in particular on the size of the microreflector and the arrangement of the subwavelength grating in the microreflector.

Die Ausrichtung der Seitenwände der einzelnen Gitterreflektoren ermöglicht es, Bildinformationen zu übertragen. Beispielsweise sind bei einer ersten Gruppe von Gitterreflektoren die Seitenwände in eine erste Richtung ausgerichtet, so dass diese Gitterreflektoren in einer ersten Blickrichtung zu sehen sind. Bei einer zweiten Gruppe von Gitterreflektoren sind die Seitenwände in eine zweite Richtung ausgerichtet, so dass diese Gitterreflektoren in einer zweiten Blickrichtung zu erkennen sind.The alignment of the side walls of the individual grid reflectors makes it possible to transmit image information. For example, in a first group of grating reflectors, the sidewalls are oriented in a first direction, so that these grating reflectors are visible in a first viewing direction. In a second group of grating reflectors, the side walls are aligned in a second direction, so that these grating reflectors can be seen in a second viewing direction.

Es ist bevorzugt, dass die Mikroreflektoren im Querschnitt asymmetrisch sind, wobei insbesondere ein erster Teil der Seitenwand gerade und ein zweiter Teil der Seitenwand konkave, insbesondere parabelförmig oder ellipsenförmig ausgebildet sind.It is preferred that the micro-deflectors are asymmetrical in cross-section, wherein in particular a first part of the side wall is straight and a second part of the side wall is concave, in particular parabolic or elliptical.

Vorzugsweise sind der erste Teil der Seitenwand und der zweite Teil der Seitenwand sich gegenüberliegend angeordnet. Zum Beispiel liegen sich bei einem quaderförmigen Mikroreflektor zwei Abschnitte der Seitenwand gegenüber. Durch die Verwendung von asymmetrischen Reflektoren kann der Lichtanteil, der seitlich abgelenkt wird, vergrößert werden. Somit kann der Kontrast des aus dem Muster entstehenden Bildes erhöht werden.Preferably, the first part of the side wall and the second part of the side wall are arranged opposite each other. For example, in the case of a cuboid microreflector, two sections of the side wall are located opposite one another. By using asymmetric reflectors, the amount of light that is deflected laterally can be increased. Thus, the contrast of the image resulting from the pattern can be increased.

Weiter kann der erste Teil der Seitenwand, welche gerade ausgebildet ist, zu dem Boden senkrecht angeordnet sein. Dadurch kann insbesondere erreicht werden, dass der gerade Teil einen Bereich des Bodens von der einfallenden Strahlung abschirmt, d.h. beschattet, und somit nicht zum nicht abgelenkten Anteil der einfallenden Strahlung beiträgt. Folglich erhöht sich der Strahlungsanteil, der seitlich abgelenkt wird.Further, the first part of the side wall, which is currently formed, may be arranged perpendicular to the ground. As a result, it can be achieved in particular that the straight part shields a region of the bottom from the incident radiation, i. shaded, and thus does not contribute to the undeflected portion of the incident radiation. Consequently, the proportion of radiation that is deflected laterally increases.

Für übliche optische Ausführungen ist es bevorzugt, dass die Mikroreflektoren eine Tiefe von 2 bis 30 µm haben, bevorzugt von 5 bis 20 µm. Weiter ist es bevorzugt, dass jedes Subwellenlängengitter eine Gitterperiode zwischen 100 nm und 500 nm, insbesondere 240 nm bis 420 nm, hat, wobei das Subwellenlängengitter eindimensional periodisch oder auch zweidimensional periodisch ausbildet sein kann. Solche Strukturabmessungen ergeben gute Resultate bei zugleich einfacher Herstellbarkeit. Die Gitterperiode sowie das Profil des Subwellenlängengitters hängen insbesondere von der Farbe ab, welche in nullter Beugungsordnung reflektiert oder transmittiert werden soll.For common optical designs, it is preferred that the microreflectors have a depth of 2 to 30 microns, preferably from 5 to 20 microns. Further, it is preferable that each sub-wavelength grating has a grating period between 100 nm and 500 nm, particularly 240 nm to 420 nm, the sub-wavelength grating being one-dimensionally periodic or even two-dimensional can be formed periodically. Such structural dimensions give good results with at the same time easy manufacturability. The grating period and the profile of the subwavelength grating depend in particular on the color which is to be reflected or transmitted in the zeroth diffraction order.

An ihrer dem Halbraum zugewandten Seite sind die Mikroreflektoren und die Subwellenlängengitter mit Vorteil mit mindestens einer metallischen Schicht beschichtet, bevorzugt mit Al, Ag, Au, Cu, Cr oder einer diese Metalle enthaltenden Legierung.On its side facing the half-space, the microreflectors and the sub-wavelength gratings are advantageously coated with at least one metallic layer, preferably with Al, Ag, Au, Cu, Cr or an alloy containing these metals.

Möchte man die Buntheit in Reflexion steigern, können die Mikroreflektoren und die Subwellenlängengitter an ihrer dem Halbraum zugewandten Seite mit einer Multilayerbeschichtung, z. B. als Trilayer aus zwei übereinanderliegenden Metall- oder Halbleiterschichten mit einer dazwischen liegenden dielektrischen Schicht, aufgebaut werden.If one wishes to increase the chroma in reflection, the microreflectors and the subwavelength gratings can be provided on their side facing the half space with a multilayer coating, e.g. B. as a trilayer of two superimposed metal or semiconductor layers with an intervening dielectric layer can be constructed.

Durch die Form der Apertur wird insbesondere auch die Form des Mikroreflektors festgelegt. Damit sind auch die Anordnungen der Seitenflächen vorgegeben und folglich ebenfalls die von den Seitenwänden reflektierte Strahlungsrichtung. Beispielsweise kann durch Verwendung eines rotationssymmetrischen Mikroreflektors mit einer kreisförmigen Apertur ein Bild in viele Blickrichtungen erzeugt werden. Bei der Verwendung eines quaderförmigen Mikroreflektors mit einer rechteckigen Apertur können einzelne Beobachtungrichtungen bevorzugt sein. Ähnliches gilt für einen zylinderförmigen Mikroreflektor mit sechseckiger Apertur.Due to the shape of the aperture, the shape of the microreflector is determined in particular. Thus, the arrangements of the side surfaces are given and consequently also the reflected radiation from the side walls. For example, by using a rotationally symmetrical microreflector with a circular aperture, an image can be generated in many directions. When using a cuboid microreflector with a rectangular aperture individual observation directions may be preferred. The same applies to a cylindrical microreflector with a hexagonal aperture.

Gitterreflektoren mit runden Aperturen werden bevorzugt in einem hexagonalen Muster angeordnet, da sich auf diese Weise eine möglichst hohe Flächenfüllung erzielen lässt.Grid reflectors with round apertures are preferably arranged in a hexagonal pattern, since in this way the highest possible area filling can be achieved.

Die einzelnen Gitterreflektoren können mit sie umgebenden Stegen ausgebildet werden, d. h. zumindest einige benachbarte Gitterreflektoren stoßen dann nicht direkt aneinander, sondern sind durch einen Steg getrennt. Zwischen den Gitterreflektoren liegen folglich Stegflächen, die bevorzugt durch ebene Flächen gebildet sind. Durch Beschichtung der Stegflächen und/oder Gestaltung der Dicke des Substrates im Bereich der Stegflächen kann man dafür sorgen, dass auf die Stegflächen einfallendes Licht unterschiedlich reflektiert und/oder transmittiert wird. Der Effekt wird bevorzugt lateral variabel ausgestaltet, um zusätzlich Symbole zu kodieren und in Transmission sichtbar zu machen. Damit ist eine zusätzliche Fälschungssicherheit erreicht.The individual grid reflectors can be formed with webs surrounding them, i. H. at least some adjacent grille reflectors then do not abut each other directly, but are separated by a web. Between the grid reflectors are thus web surfaces, which are preferably formed by flat surfaces. By coating the web surfaces and / or shaping the thickness of the substrate in the region of the web surfaces, it is possible to ensure that light incident on the web surfaces is differently reflected and / or transmitted. The effect is preferably designed to be laterally variable in order additionally to encode symbols and make them visible in transmission. This additional counterfeit security is achieved.

Eine lateral variierende Beschichtung der Stegflächen wird vorzugsweise dadurch realisiert, dass die Stegflächen zuerst mit einer Beschichtung, beispielsweise mit einer Metallisierung versehen werden, und diese bereichsweise wieder entfernt wird, z. B. durch ein Ätzverfahren. Alternativ ist es möglich, die auf den Stegflächen vorliegende Beschichtung durch Kaschieren mit einer Akzeptorfolie bereichsweise zu transferieren und damit bereichsweise von den Stegflächen zu entfernen. Weitere Einzelheiten zu einem derartigen Metalltransferverfahren können der Druckschrift WO 2011/138039 A1 entnommen werden.A laterally varying coating of the web surfaces is preferably realized in that the web surfaces are first provided with a coating, for example with a metallization, and this is partially removed again, for. B. by an etching process. Alternatively, it is possible to partially transfer the coating present on the web surfaces by laminating with an acceptor film and thus to remove it from the web surfaces in certain areas. Further details of such a metal transfer process can the document WO 2011/138039 A1 be removed.

Die Mikroreflektoren können in ihrer Apertur (Öffnung) grundsätzlich jede beliebige Form haben, beispielsweise quadratische, kreisförmige oder rechteckige Aperturen.The micro-reflectors can basically have any shape in their aperture (opening), for example square, circular or rectangular apertures.

Es ist bevorzugt, dass die Apertur einen Durchmesser hat und der Mikroreflektor von der Apertur bis zum Boden eine Tiefe hat, wobei innerhalb eines Musters mindestens eine der folgenden Eigenschaften der Gitterreflektoren variiert, um ein Bild zu erzeugen: Lage der Subwellenlängengitter zu dem jeweils zugeordneten Mikroreflektor, Durchmesser der Apertur, Tiefe des Mikroreflektors, Ausrichtung des Mikroreflektors, Form des Mikroreflektors und/oder Gitterperiode des Subwellenlängengitters.It is preferred that the aperture has a diameter and the microreflector has a depth from the aperture to the bottom, wherein within a pattern at least one of the following properties of the grating reflectors varies to produce an image: location of the subwavelength gratings to the respective associated microreflector The diameter of the aperture, the depth of the microreflector, the orientation of the microreflector, the shape of the microreflector and / or the grating period of the subwavelength grating.

Durch diese variable Anordnung können besondere Arten des Bildes erzeugt werden. Insbesondere ist es damit möglich, Bilder aufgrund eines Moire-Effekts, eines stereoskopischen Effekts und/oder eines Laufeffekts zu erzeugen.By this variable arrangement special types of image can be generated. In particular, it is thus possible to generate images due to a moiré effect, a stereoscopic effect and / or a running effect.

Insbesondere werden ein oder mehrere Parameter zwischen den einzelnen Gitterreflektoren des Musters verändert. Beispielsweise kann ein Bereich des Bildes durch Gitterreflektoren mit einem ersten Parametersatz erzeugt werden, während ein zweiter Bereich des Bildes durch Gitterreflektoren mit einem zweiten Parametersatz generiert wird. Auf diese Weise lassen sich beispielsweise Stereogramme erzeugen.In particular, one or more parameters are changed between the individual grating reflectors of the pattern. For example, a region of the image can be generated by grating reflectors with a first parameter set, while a second region of the image is generated by grating reflectors with a second parameter set. In this way, for example, generate stereograms.

Alternativ können sich die Parameter innerhalb des Bildes kontinuierlich verändern, um beispielsweise Moire-Effekte zu erzeugen.Alternatively, the parameters within the image may change continuously to produce moiré effects, for example.

Das Sicherheitselement kann insbesondere als Sicherheitsfaden, Aufreißfaden, Sicherheitsband, Sicherheitsstreifen, Patch oder als Etikett ausgebildet sein. Insbesondere kann das Sicherheitselement transparente Bereiche oder Ausnehmungen eines zu schützenden Gegenstandes überdecken.The security element may in particular be designed as a security thread, tear-open thread, security strip, security strip, patch or label. In particular, the security element can cover transparent areas or recesses of an object to be protected.

Das Sicherheitselement kann insbesondere Teil einer noch nicht umlauffähigen Vorstufe zu einem Wertdokument sein, das beispielsweise auch zusätzliche Echtheitsmerkmale (wie z. B. im Volumen vorgesehene Lumineszenzstoffe etc.) aufweisen kann. Unter Wertdokumenten werden hier einerseits das Sicherheitselement aufweisende Dokumente verstanden, andererseits können Wertdokumente auch sonstige Dokumente oder Gegenstände sein, die mit dem erfindungsgemäßen Sicherheitselement versehen werden können, damit sie nicht kopierbare Echtheitsmerkmale aufweisen. Chip- oder Sicherheitskarten, wie z. B. Bank- oder Kreditkarten, sind weitere Beispiele für Wertdokumente.In particular, the security element can be part of a precursor that can not yet be processed to a value document, which, for example, can also have additional authenticity features (such as, for example, luminescent substances provided in the volume, etc.). Under value documents here on the one hand understood the document having security element, on the other hand value documents can also be other documents or items that can be provided with the security element according to the invention, so they have non-copyable authenticity features. Chip or security cards, such. As bank or credit cards are other examples of value documents.

Ferner betrifft die Erfindung ein in dem unabhängigen Anspruch 12 definiertes Verfahren zum Herstellen eines Sicherheitselementes für einen zu schützenden Gegenstand, wie z. B. ein Sicherheitspapier, Wertdokument oder dergleichen, wobei auf einem Substrat mehrere, in einem Muster angeordnete Mikroreflektoren und mehrere Mikrostrukturen ausgebildet werden, die zusammen mit den Mikroreflektoren ein von einem Betrachter wahrnehmbares Bild erzeugen. Jede Mikrostruktur wird als Subwellenlängengitter ausgebildet und einem der Mikroreflektoren zugeordnet, wodurch Gitterreflektoren umfassend jeweils einen Mikroreflektor und mindestens ein Subwellenlängengitter gebildet werden. Jedes Subwellenlängengitter wird so ausgebildet, dass es sichtbare Strahlung, die durch eine Apertur des Mikroreflektors aus einem Halbraum einfällt, in eine nullte Reflexions-Beugungsordnung reflektierend beugt, wobei bevorzugt für jeden Gittereflektor das Subwellenlängengitter und der Mikroreflektor so aufeinander abgestimmt werden, dass der Mikroreflektor die vom Subwellenlängengitter in die nullte Reflexions-Beugungsordnung gebeugte Strahlung als Rückstrahlung in den Halbraum zurück reflektiert.Furthermore, the invention relates to a defined in the independent claim 12 method for producing a security element for an object to be protected, such as. A security paper, document of value or the like, wherein on a substrate a plurality of microreflectors arranged in a pattern and a plurality of microstructures are formed, which together with the microreflectors produce an image perceptible by a viewer. Each microstructure is formed as a sub-wavelength grating and associated with one of the microreflectors, thereby forming grating reflectors each comprising a microreflector and at least one sub-wavelength grating. Each sub-wavelength grating is formed to reflectively deflect visible radiation incident through an aperture of the micro-reflector from a hemisphere into a zeroth reflection diffraction order, preferably matching the sub-wavelength grating and the microreflector for each grating reflector such that the microreflector matches Reflected radiation from the sub-wavelength grating in the zeroth reflection diffraction order reflected back radiation in the half space back.

Nach einer vorteilhaften Verfahrensvariante wird das Subwellenlängengitter als halbtransparentes Subwellenlängengitter ausgebildet, das einen zweiten Teil der sichtbaren Strahlung, die durch die Apertur (24) des Mikroreflektors (22) aus dem Halbraum einfällt, in eine nullte Transmissions-Beugungsordnung transmittierend beugt. In jedem Gittereflektor werden dabei bevorzugt das Subwellenlängengitter und der Mikroreflektor ferner so aufeinander abgestimmt, dass das Subwellenlängengitter die durch die Apertur des Mikroreflektors aus dem Halbraum einfallende und vom Mikroreflektor reflektierte Strahlung in nullter Transmissions-Ordnung transmittiert.According to an advantageous variant of the method, the sub-wavelength grating is formed as a semi-transparent sub-wavelength grating which transmissively diffracts a second portion of the visible radiation incident through the aperture (24) of the microreflector (22) from the hemisphere into a zeroth transmission diffraction order. In each lattice reflector, the sub-wavelength grating and the microreflector are preferably further tuned to one another such that the sub-wavelength grating transmits the radiation incident through the aperture of the microreflector from the half-space and reflected by the microreflector in the zeroth transmission order.

Nach einer weiteren vorteilhaften Verfahrenvariante wird das Subwellenlängengitter als opakes Subwellenlängengitter ausgebildet.According to a further advantageous variant of the method, the sub-wavelength grating is formed as an opaque sub-wavelength grating.

Für das erfindungsgemäße Herstellungsverfahren kommen zur Herstellung der Mikroreflektoren insbesondere Direktbelichtungstechniken in Frage, z. B. photolithographisch mit Hilfe eines Laserwriters. Die Herstellung kann analog zu den bekannten Herstellungsverfahren für Mikrolinsen erfolgen. Unabhängig davon wird die Struktur der Subwellenlängengitter erzeugt. Die beiden Vorgänge nimmt man bevorzugt passgenau in ein und demselben Photolack vor. Alternativ sind auch zwei unterschiedliche Belackungsvorgänge möglich. Nach Entfernung des belichteten Anteils des Photolacks kann ein belichtetes Original anschließend galvanisch abgeformt und somit ein Prägestempel erzeugt werden. Letztendlich wird die Struktur über einen Prägeprozess beispielsweise in UV-Lack auf Folie repliziert. Alternativ kann ein Nanoimprint-Verfahren eingesetzt werden. Aufwendigere Verfahren zur Originalherstellung wie Elektronenstrahl- oder "Focussed Ion Beam"-Belichtungsverfahren erlauben eine noch feinere Ausgestaltung der Geometrie und eignen sich damit insbesondere zur Herstellung der Subwellenlängengitter.For the production method according to the invention, in particular direct exposure techniques are suitable for producing the microreflectors, e.g. B. photolithographically with the help of a laserwriter. The preparation can be carried out analogously to the known production method for microlenses. Regardless, the structure of the subwavelength gratings is generated. The two processes are preferably carried out accurately in one and the same photoresist. Alternatively, two different Belackungsvorgänge are possible. After removal of the exposed portion of the photoresist, an exposed original can then be galvanically molded, thus producing an embossing stamp. Ultimately, the structure is replicated via a stamping process, for example in UV varnish on film. Alternatively, a nanoimprint method can be used. More elaborate methods of original manufacture, such as electron beam or focused ion beam exposure techniques, allow for even finer geometry design and are therefore particularly suitable for the production of subwavelength gratings.

Das erfindungsgemäße Herstellungsverfahren kann so ausgebildet werden, dass die beschriebenen bevorzugten Ausbildungen und Ausführungsformen des Sicherheitselementes hergestellt werden.The manufacturing method according to the invention can be designed so that the described preferred embodiments and embodiments of the security element are produced.

Es versteht sich, dass die vorstehend genannten und die nachstehend noch zu erläuternden Merkmale nicht nur in den angegebenen Kombinationen, sondern auch in anderen Kombinationen einsetzbar sind, ohne den Rahmen der vorliegenden Erfindung zu verlassen, soweit dies von dem Schutzumfang der Ansprüche erfasst ist.It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations, but also in other combinations, without departing from the scope of the present invention, insofar as this is covered by the scope of the claims.

Nachfolgend wird die Erfindung beispielshalber anhand der beigefügten Zeichnungen, die auch erfindungswesentliche Merkmale offenbaren, noch näher erläutert. Zur besseren Anschaulichkeit wird in den Figuren auf eine maßstabs- und proportionsgetreue Darstellung verzichtet. Es zeigen:

Fig. 1
in a) und b) Gitterreflektoren mit jeweils symmetrischen Mikroreflektoren und unterschiedlichen Tiefen;
Fig. 2
in a) und b) Gitterreflektoren gemäß einer zweiten Ausführungsform mit asymmetrischen Mikroreflektoren und unterschiedlicher Tiefe;
Fig. 3
in a) bis c) den Gitterreflektor aus Fig. 1 mit jeweils unterschiedlicher Tiefe;
Fig. 4
in a) bis c) den Gitterreflektor aus Fig. 1 mit jeweils unterschiedlichem Durchmesser einer Apertur;
Fig. 5
in a) und b) zwei verschiedene Typen von Gitterreflektoren mit konischer und Parabel-Querschnittsform und unterschiedlicher Tiefe;
Fig. 6
in a) und b) verschiedene Typen von Gitterreflektoren mit asymmetrischen Mikroreflektoren mit Parabel-Form und konischer Form sowie unterschiedlicher Tiefe;
Fig. 7
in a) bis c) drei verschiedene Ausführungsformen von Sicherheitselementen, bei welchen sich die Lage eines Subwellenlängengitters hinsichtlich des Mikroreflektors über das Sicherheitselement ändert;
Fig. 8
ein Sicherheitselement aus einer Anordnung von Mikroreflektoren mit Subwellenlängengittern, bei denen die Mikroreflektoren je nach Gruppe unterschiedlich orientiert sind; und
Fig. 9
die Entstehung des durch das Sicherheitselement hervorrufbaren Bildes.
The invention will be explained in more detail by way of example with reference to the accompanying drawings, which also disclose features essential to the invention. For better clarity, a scale and proportioned representation is omitted in the figures. Show it:
Fig. 1
in a) and b) grating reflectors, each with symmetrical micro-reflectors and different depths;
Fig. 2
in a) and b) grating reflectors according to a second embodiment with asymmetrical microreflectors and different depths;
Fig. 3
in a) to c) the lattice reflector Fig. 1 each with different depths;
Fig. 4
in a) to c) the lattice reflector Fig. 1 each with a different diameter of an aperture;
Fig. 5
in a) and b) two different types of grating reflectors with conical and parabolic cross-sectional shape and depth;
Fig. 6
in a) and b) various types of grating reflectors with asymmetrical microreflectors with parabolic shape and conical shape and depth;
Fig. 7
in a) to c) three different embodiments of security elements in which the position of a sub-wavelength grating with respect to the micro-reflector changes via the security element;
Fig. 8
a security element of an array of microreflectors with subwavelength gratings, in which the microreflectors are oriented differently depending on the group; and
Fig. 9
the emergence of the image elicited by the security element.

Die Fig. 1 bis 9 zeigen Gitterreflektoren 10 eines Sicherheitselements 12. Das Sicherheitselement 12 ist aus einem Substrat 14, beispielsweise einer transparenten Folie, gefertigt, an deren Oberseite (der Begriff ist rein exemplarisch zu verstehen und soll keine Vorzugsrichtung angeben) eine Prägestruktur ausgebildet ist. Die Prägestruktur umfasst eine Vielzahl von Mikroreflektoren 22, die in den Ausführungsbeispielen der Fig. 1 bis 4 als elliptische Reflektoren mit einem ebenen Boden 16 ausgebildet sind. In anderen Ausführungsbeispielen, beispielsweise in denen der Fig. 5 und 6 sind die Mikroreflektoren in anderen Geometrien, insbesondere nicht rotationssymmetrisch ausgeführt.The Fig. 1 to 9 The safety element 12 is made of a substrate 14, for example a transparent film, on whose upper side (the term is to be understood purely by way of example and is not intended to indicate a preferred direction) an embossed structure is formed. The embossing structure comprises a plurality of microreflectors 22, which in the embodiments of the Fig. 1 to 4 are formed as elliptical reflectors with a flat bottom 16. In other embodiments, for example, in which the Fig. 5 and 6 the micro-reflectors are designed in other geometries, in particular not rotationally symmetrical.

Jeder Gitterreflektor 10 weist somit den Boden 16 und mindestens eine Seitenwand 18 auf. Ein halbtransparentes Subwellenlängengitter 20 ist an dem Boden 16 des Gitterreflektors 10 vorgesehen. Die mindestens eine Seitenwand 18 und der Boden 16 bilden den Mikroreflektor 22, welcher zur Oberseite und damit zu einem Halbraum offen ist und zwar durch eine Apertur 24 mit einem Durchmesser a. Die Strecke von dem Boden 16 zu der Apertur 24 bestimmt die Tiefe t des Gitterreflektors 10. Das Substrat 14 ist im Bereich des Bodens 16 zumindest teilweise transparent.Each grid reflector 10 thus has the bottom 16 and at least one side wall 18. A semi-transparent sub-wavelength grating 20 is provided on the bottom 16 of the grating reflector 10. The at least one side wall 18 and the bottom 16 form the microreflector 22, which is open to the top and thus to a half space through an aperture 24 with a diameter a. The distance from the bottom 16 to the aperture 24 determines the depth t of the grating reflector 10. The substrate 14 is at least partially transparent in the region of the bottom 16.

Die Seitenwand 18 der Fig. 1 dargestellten Gitterreflektoren 10 ist im Querschnitt parabelförmig ausgestaltet. Ferner ist hier der Gitterreflektor 10 rotationssymmetrisch ausgestaltet. Die Gitterreflektoren 10, die in Fig. 1a und 1b gezeigt sind, weisen den gleichen Durchmesser a der Apertur 24 auf, unterscheiden sich jedoch in ihrer Tiefe t. Das Verhältnis von Durchmesser a der Apertur 24 zu Tiefe t des Gitterreflektors 10 beträgt 0,8 in Fig. 1a und 0,55 in Fig. 1b.The side wall 18 of Fig. 1 illustrated grid reflectors 10 is designed parabolic in cross section. Furthermore, here the grating reflector 10 is designed rotationally symmetrical. The grating reflectors 10, which are in Fig. 1a and 1b are shown to have the same diameter a of the aperture 24, but differ in their depth t. The ratio of the diameter a of the aperture 24 to the depth t of the grating reflector 10 is 0.8 in Fig. 1a and 0.55 in Fig. 1b ,

Der Anteil der aus dem Halbraum einfallenden Strahlung, der auf das Subwellenlängengitter 20 fällt, wird direkt dort reflektiert und zu einem zweiten Teil transmittiert. Der andere Rest der sichtbaren Strahlung, der derart einfällt, dass er von dem Mikroreflektor 22 auf das Subwellenlängengitter 20 reflektiert wird, wird von dem Subwellenlängengitter 20 in nullter Beugungsordnung gebeugt ebenfalls zu einem Teil reflektiert und zu einem Teil transmittiert. Reflexion in nullter Reflexions-Beugungsordnung bedeutet, dass Einfallswinkel gleich Ausfallswinkel ist, jedoch z. B. die Farbeigenschaften der Beugung von der Richtung des einfallenden Lichts abhängig sind. Der Lichtanteil, der zuerst an dem Mikroreflektor 22 reflektiert wird, wird somit anders am Subwellenlängengitter reflektiert und transmittiert als der direkt einfallende Lichtanteil. Die einfallende Strahlung wird gegenüber dem Einfallswinkel seitlich abgelenkt, so dass daraus für den Beobachter ein sichtbares Bild entsteht.The proportion of the radiation incident from the half-space, which falls on the sub-wavelength grating 20, is reflected directly there and transmitted to a second part. The other remainder of the visible radiation incident to be reflected by the micro-reflector 22 onto the sub-wavelength grating 20 is also partially diffracted by the sub-wavelength grating 20 in zero diffraction order and partially transmitted. Reflection in the zeroth reflection diffraction order means that the angle of incidence is equal to the angle of reflection, but z. B. the color properties of the diffraction are dependent on the direction of the incident light. The proportion of light which is first reflected at the micro-reflector 22 is thus reflected differently at the sub-wavelength grating and transmitted as the directly incident light component. The incident radiation is deflected laterally with respect to the angle of incidence, so that it creates a visible image for the observer.

Der Lichtanteil, der seitlich abgelenkt wird, kann durch das Vorsehen eines asymmetrischen Gitterreflektors 10 erhöht werden, wie dies in Fig. 2a und 2b dargestellt ist. Ein erster Teil 26 der Seitenwand 18 ist im Querschnitt gerade ausgebildet und ist insbesondere senkrecht zu dem Boden 16. Ein zweiter Teil 28 der Seitenwand 18, welche dem ersten Teil 26 gegenüberliegend angeordnet ist, ist wie in Fig. 1 parabelförmig ausgestaltet. Das Verhältnis von Durchmesser a der Apertur 24 zu Tiefe t des Gitterreflektors 10 ist 1 in Fig. 2a und 0,53 in Fig. 2b.The amount of light deflected laterally can be increased by providing an asymmetrical grating reflector 10 as shown in FIG Fig. 2a and 2b is shown. A first part 26 of the side wall 18 is straight in cross-section and is in particular perpendicular to the bottom 16. A second part 28 of the side wall 18, which is arranged opposite the first part 26, is as in FIG Fig. 1 parabolic shaped. The ratio of the diameter a of the aperture 24 to the depth t of the grating reflector 10 is 1 in Fig. 2a and 0.53 in Fig. 2b ,

Wie dies in Fig. 2a und 2b durch den linken Lichtstrahl dargestellt ist, schattet der erste Teil 26 der Seitenwand 18 einen Teil des Subwellenlängengitters 20 in der einfallenden Strahlung ab. Dadurch erhöht sich der Anteil des Lichts, welcher von dem Gitterreflektor 10 abgelenkt wird. Je geringer die Tiefe t des Gitterreflektors 10 ist, desto geringer ist der abgeschattete Bereich, so dass der abgelenkte Strahlungsanteil mit abnehmender Tiefe t sinkt.Like this in Fig. 2a and 2b is represented by the left light beam, the first portion 26 of the side wall 18 shadows a portion of the sub-wavelength grating 20 in the incident radiation. This increases the proportion of the light which is deflected by the grating reflector 10. The smaller the depth t of the grating reflector 10, the lower the shaded area, so that the deflected radiation component decreases with decreasing depth t.

Fig. 3 zeigt drei unterschiedlich tiefe Gitterreflektoren 10 mit konstanter Durchmesser a der Apertur 24 und jeweils gleichem Subwellenlängengitter 20 am Boden 16 des Gitterreflektors 10. Dieser Figur können folgende dimensionslose Werte zugeordnet werden: a=0,4 sowie t=0,3; 0,4 und 0,5 für die unterschiedlichen Tiefen t. Somit ergibt sich beispielsweise für den Gitterreflektor 10 der Fig. 3b) ein Aspektverhältnis von 1. Im dargestellten Beispiel von Fig. 3 besitzen die Gitterreflektoren 10 eine elliptische Geometrie mit einem Durchmesser a=0,4 der Apertur 24 und dem Scheitelpunkt s=0,45, wobei das Subwellenlängengitter 20 zentrisch am Boden 16 angeordnet ist. In Fig. 3 sind die Randstrahlen der einfallenden und der gebeugten Strahlung eingezeichnet, welche zunächst am Subwellenlängengitter 20 in der nullten Ordnung gebeugt und dann durch die Seitenwand 18 des Mikroreflektors 22 abgelenkt werden. Fig. 3 shows three different depth grating reflectors 10 with a constant diameter a of the aperture 24 and the same sub-wavelength grating 20 at the bottom 16 of the grating reflector 10. This figure can be assigned the following dimensionless values: a = 0.4 and t = 0.3; 0.4 and 0.5 for the different depths t. Thus, for example, results for the grating reflector 10 of Fig. 3b ) an aspect ratio of 1. In the example shown of Fig. 3 The grating reflectors 10 have an elliptical geometry with a diameter a = 0.4 of the aperture 24 and the vertex s = 0.45, wherein the sub-wavelength grating 20 is arranged centrally on the bottom 16. In Fig. 3 the marginal rays of the incident and the diffracted radiation are drawn, which are first diffracted at the sub-wavelength grating 20 in the zeroth order and then deflected by the side wall 18 of the microreflector 22.

Die transmittierte Strahlung ist in Fig. 3 nicht dargestellt, da das halbtransparente Subwellenlängengitter 20 das eingezeichnete, einfallende Licht ohne Ablenkung transmittiert. Bei Einsatz eines opaken Subwellenlängengitters findet keine Transmission des einfallenden Lichts statt, so dass die Ausführungen zu den Figuren 3 und 4 auch exemplarisch für solche Ausgestaltungen gelten.The transmitted radiation is in Fig. 3 not shown because the semi-transparent sub-wavelength grating 20 transmits the drawn, incident light without deflection. When using an opaque sub-wavelength grating no transmission of incident light takes place, so that the comments on the FIGS. 3 and 4 also apply by way of example to such embodiments.

Die Strahlen beziehen sich in diesem Beispiel jeweils auf einen festen Auftreffpunkt am Subwellenlängengitter 20. Hier zeigt sich, dass der Akzeptanzwinkel des einfallenden Lichts und die Lichtaufstreuung von der Tiefe t abhängt, wie dies in nachstehender Tabelle beispielhaft dargestellt ist. Tiefe t Akzeptanzwinkel des einfallenden Lichts Divergenz des reflektierten Lichts 0,3 12,5° 20,5° 0,4 11,0° 16,3° 0,5 9,5° 15,1° In this example, the rays each relate to a fixed point of incidence on the subwavelength grating 20. Here it can be seen that the acceptance angle of the incident light and the light scattering depend on the depth t, as shown by way of example in the table below. Depth t Acceptance angle of incident light Divergence of the reflected light 0.3 12.5 ° 20.5 ° 0.4 11.0 ° 16.3 ° 0.5 9.5 ° 15.1 °

Die Zahlenangaben zeigen, dass mit zunehmender Tiefe t des Mikroreflektors 22 die Divergenz der abgelenkten Strahlung abnimmt, d. h. verstärkt zum Betrachter gebündelt wird, da der Austrittswinkel die Bündelung beschreibt.The numbers indicate that as the depth t of the microreflector 22 increases, the divergence of the deflected radiation decreases; H. is focused to the viewer, since the exit angle describes the bundling.

Daraus ist ersichtlich, dass die am Subwellenlängengitter 20 und am Mikroreflektor 22 reflektierte Strahlung eine deutliche Aufstreuung erfährt. Weiterhin verringern sich der Akzeptanzwinkel des einfallenden Lichts und die Divergenz des reflektierten Lichts für zunehmende Tiefen t des Mikroreflektors 22. Schließlich sei erwähnt, dass alle Auftreffpunkte am Subwellenlängengitter 20 berücksichtigt werden müssen, um das gesamte Streuhalten eines Gitterreflektors 10 zu charakterisieren.It can be seen that the radiation reflected at the subwavelength grating 20 and at the microreflector 22 undergoes significant scattering. Furthermore, the acceptance angle of the incident light and the divergence of the reflected light decrease for increasing depths t of the micro-reflector 22. Finally, it should be mentioned that all the impact points on the sub-wavelength grating 20 must be considered to characterize the overall scattering of a grating reflector 10.

Die in Fig. 3 vorgenommene Variation der Reflexionseigenschaften der Mikroreflektoren 22, exemplarisch anhand der Tiefe t erläutert, ist eine von mehreren Möglichkeiten, die optischen Eigenschaften der Gitterreflektoren 10 zu verändern und damit das Muster aus Gitterreflektoren 10 zu modulieren und letztlich Bildinformation zu erzeugen. Eine Variation kann auch durch Veränderung anderer Geometrieparameter der Gitterreflektoren 10 aus Subwellenlängengitter 20 und Mikroreflektor 22 erreicht werden. Nun wird für dieselbe Reflektorgeometrie wie in Fig. 3b der Durchmesser a der Apertur 24 variiert. In Fig. 4 sind drei Mikroreflektoren 22 mit einem Subwellenlängengitter 20 für die Durchmesser a=0,3; 0,4 und 0,5 der Aperturen 24 dargestellt, bei denen die Tiefe t=0,4 konstant ist. In Fig. 4 sind ebenfalls die Randstrahlen der einfallenden und der gebeugten Strahlung eingezeichnet, welche zunächst am Subwellenlängengitter 20 in der nullten Ordnung gebeugt und dann durch den Mikroreflektor 22 abgelenkt werden. Der in diesem Beispiel ausgewählte Auftreffpunkt ist nach links hinsichtlich der Symmetrieachse des Mikroreflektors 22 verschoben. Die Akzeptanzwinkel des einfallenden Lichts und die Lichtaufstreuung des reflektierten Lichts sind in folgender Tabelle zusammengefasst: Durchmesser a Akzeptanzwinkel des einfallenden Lichts Divergenz des reflektierten Lichts 0,3 17,0° 30,1° 0,4 15,5° 25,1° 0,5 14,0° 21,5° In the Fig. 3 Variation of the reflection properties of the microreflectors 22, explained by way of example on the basis of the depth t, is one of several possibilities for changing the optical properties of the grating reflectors 10 and thus modulating the pattern of grating reflectors 10 and ultimately producing image information. Variation can also be achieved by changing other geometry parameters of the grating reflectors 10 from sub-wavelength grating 20 and micro-reflector 22. Now for the same reflector geometry as in Fig. 3b the diameter a of the aperture 24 varies. In Fig. 4 are three microreflectors 22 with a sub-wavelength grating 20 for the diameters a = 0.3; 0.4 and 0.5 of the apertures 24 in which the depth t = 0.4 is constant. In Fig. 4 The edge rays of the incident and the diffracted radiation are also drawn, which are first diffracted at the sub-wavelength grating 20 in the zeroth order and then deflected by the micro-reflector 22. The impact point selected in this example is shifted to the left with respect to the symmetry axis of the micro-reflector 22. The acceptance angles of the incident light and the light scattering of the reflected light are summarized in the following table: Diameter a Acceptance angle of incident light Divergence of the reflected light 0.3 17.0 ° 30.1 ° 0.4 15.5 ° 25.1 ° 0.5 14.0 ° 21.5 °

Die Variation des Durchmessers a der Apertur 24 führt ebenfalls zu einer Variation des Akzeptanzwinkels des einfallenden Lichts sowie zu einer Veränderung der Divergenz des reflektierten Lichts.The variation of the diameter a of the aperture 24 also leads to a variation of the acceptance angle of the incident light and to a change in the divergence of the reflected light.

Das Muster aus vielen, nebeneinander angeordneten Gitterreflektoren 10 kann zur Darstellung von Motiven in einem Sicherheitselement 12 verwendet werden. Dabei liegen z. B. zwei Varianten von Strukturgeometrien, vorzugsweise eine unterschiedliche Reflektorgeometrie, in den jeweiligen Bereichen vor. Fig. 5 zeigt eine derart variierte Anordnung von Gitterreflektoren 10, bei denen die Tiefe t in den Bereichen I und II unterschiedlich gewählt ist. Der Durchmesser der Apertur 24 der Mikroreflektoren 22 ist mit a, die Ausdehnung der Subwellenlängengitter 20 ist mit b bezeichnet. Die Tiefe t der Mikroreflektoren 22 beträgt in den Bereichen I und II t1 bzw. t2. Das Muster der Gitterreflektoren 10 erlaubt eine Vielzahl unterschiedlicher Reflektorgeometrien. Exemplarisch sind die Mikroreflektoren 22in Fig. 5a mit einer parabelförmigen und in Fig. 5b mit einer konischen Form dargestellt.The pattern of many juxtaposed grid reflectors 10 can be used to represent subjects in a security element 12. It is z. B. two variants of structural geometries, preferably a different reflector geometry, in the respective areas before. Fig. 5 shows such a varied arrangement of grating reflectors 10, in which the depth t is selected differently in the areas I and II. The diameter of the aperture 24 of the microreflectors 22 is designated by a, the extent of the subwavelength gratings 20 is denoted by b. The depth t of the microreflectors 22 in the regions I and II is t 1 and t 2, respectively. The pattern of the grating reflectors 10 allows a variety of different reflector geometries. Exemplary are the micro-reflectors 22in Fig. 5a with a parabolic and in Fig. 5b represented with a conical shape.

Die Mikroreflektoren 22 können eine nicht-rotationssymmetrische und/oder im Querschnitt asymmetrische Form haben. Beispiele von einseitig parabelförmigen Mikroreflektoren 22 und Mikroreflektoren 22 mit einem trapezförmigen Querschnitt ohne Krümmung sind in Fig. 6 dargestellt.The microreflectors 22 may have a non-rotationally symmetric and / or asymmetric shape in cross section. Examples of unilaterally parabolic microreflectors 22 and microreflectors 22 having a trapezoidal cross section without curvature are shown in FIG Fig. 6 shown.

Die Form der Apertur 24 kann ebenfalls unterschiedlich ausgelegt sein. Fig. 7 zeigt einige Beispiele von Gitterreflektoren 10 mit folgenden Aperturformen: quadratisch, kreisförmig und hexagonal. Die Gitterreflektoren 10 der Fig. 7a und Fig. 7b sind orthogonal angeordnet. Eine optimale Flächenbedeckung erreicht man durch eine hexagonale Anordnung, wie sie in Fig. 7c dargestellt ist.The shape of the aperture 24 can also be designed differently. Fig. 7 shows some examples of grating reflectors 10 having the following aperture shapes: square, circular and hexagonal. The grid reflectors 10 of Fig. 7a and Fig. 7b are arranged orthogonally. An optimal area coverage is achieved by a hexagonal arrangement, as in Fig. 7c is shown.

Die Lage der Subwellenlängengitter 20 innerhalb der einzelnen Mikroreflektoren 22 kann lateral verschoben sein. Eine kontinuierliche Verschiebung der Subwellenlängengitter 20 relativ zur Apertur 24 der Mikroreflektoren 22 kann insbesondere zur Erzeugung von Moiré-Effekten, stereoskopischen Effekten oder Laufeffekten eingesetzt werden.The location of the subwavelength gratings 20 within the individual microreflectors 22 may be shifted laterally. A continuous shift of the subwavelength gratings 20 relative to the aperture 24 of the microreflectors 22 can be used in particular for generating moiré effects, stereoscopic effects or running effects.

Die Erzeugung von Stereogrammen mit Hilfe der Gitterreflektoren 10 wird anhand des in Fig. 8 dargestellten Beispiels erläutert. Stereogramme erfordern mindestens zwei Bilder, wobei ein Bild für die Wahrnehmung durch das linke Auge, das andere Bild für die Wahrnehmung durch das rechte Auge bestimmt ist. Solche Stereogramme können durch die hier beschriebenen Gitterreflektoren 10 sowohl in Reflexion als auch in Transmission erzeugt werden.The generation of stereograms by means of the grating reflectors 10 is based on the in Fig. 8 illustrated example explained. Stereograms require at least two images, one for left-eye perception and the other for right-eye perception. Such stereograms can be generated by the grating reflectors 10 described herein both in reflection and in transmission.

Fig. 8 zeigt ein Sicherheitselement 12 in Form eines Stereogramms. Die Fläche der beiden Buchstaben "AB" ist mit einer Vielzahl von Gitterreflektoren 10 gefüllt. Der umgebende Hintergrund enthält dagegen ein homogenes Subwellenlängengitter 20. Das einfallende Licht wird im Ausführungsbeispiel durch eine halbzylinderförmige Reflektorgeometrie in unterschiedliche Richtungen gelenkt. Die Gitterreflektoren 10 im Buchstaben "A" sind dabei so orientiert, dass sie das Licht bevorzugt zum rechten Auge lenken. Das von den Gitterreflektoren im Buchstaben "B" reflektierte Licht wird dagegen in erster Linie vom linken Auge wahrgenommen. Die Ausrichtung wird dabei durch die Seitenwände 18 der Mikroreflektoren 22 bestimmt. Bei einer entsprechend kleinen Pixellierung können diese beiden Symbole auch ineinander verschachtelt vorliegen. Fig. 8 shows a security element 12 in the form of a stereogram. The area of the two letters "AB" is filled with a plurality of grid reflectors 10. In contrast, the surrounding background contains a homogeneous sub-wavelength grating 20. The incident light is directed in the exemplary embodiment by a semicylindrical reflector geometry in different directions. The grid reflectors 10 in the letter "A" are oriented so that they preferentially direct the light to the right eye. In contrast, the light reflected by the grille reflectors in the letter "B" is primarily perceived by the left eye. The orientation is determined by the side walls 18 of the micro-deflectors 22. With a correspondingly small pixelization, these two symbols can also be nested one inside the other.

Durch die große Anzahl von zur Verfügung stehenden Geometrieparametern, die lateral variiert werden können, bieten die hier beschriebenen Gitterreflektoren 10 eine breite Gestaltungsmöglichkeit von Mustern und Symbolen. Die gewünschte Farbe wird dabei durch die entsprechende Auswahl der Gitterperiode des Subwellenlängengitters 20 bewerkstelligt.Due to the large number of available geometry parameters that can be varied laterally, the grating reflectors described here provide 10 a wide range of possible designs and symbols. The desired color is accomplished by the appropriate selection of the grating period of the sub-wavelength grating 20.

Durch das Muster mit vielen Gitterreflektoren 10 können auch farbige Symbole oder Bilder erzeugt werden, welche unter einem bestimmten Winkel sichtbar sind. Um einen Farb- bzw. einen Intensitätskontrast im Motiv zu erzeugen, wird hierzu mindestens einer der oben erwähnten Parameter der Gitterreflektoren 10 im Muster lateral variiert. Da die Gitterreflektoren 10 stark winkelabhängige Eigenschaften besitzen, können dadurch insbesondere auch Parallaxenbilder erzeugt werden. Hierdurch lassen sich sowohl parallaktische Bewegungen als auch räumliche Effekte realisieren.By the pattern with many grating reflectors 10 also colored symbols or images can be generated, which are visible at a certain angle. In order to produce a color or an intensity contrast in the motif, for this purpose at least one of the above-mentioned parameters of the grating reflectors 10 in the pattern is laterally varied. Since the grating reflectors 10 have strongly angle-dependent properties, in particular parallax images can also be generated thereby. As a result, both parallactic movements and spatial effects can be realized.

Fig. 9 zeigt schematisch ein Sicherheitselement 12 mit Motiven, welche durch ein Muster von Gitterreflektoren 10 vor einem homogenen Hintergrund gebildet sind. Dieser Umgebungsbereich ist im Ausführungsbeispiel mit einem homogenen Subwellenlängengitter 20 ausgefüllt. Aufgrund der Lichtablenkung durch die Gitterreflektoren ist das Motiv "Stern" bei schräger Betrachtung in Transmission sichtbar, während der Hintergrund dunkel erscheint (Fig. 9a). Fig. 9 schematically shows a security element 12 with motifs, which are formed by a pattern of grating reflectors 10 in front of a homogeneous background. This surrounding area is filled in the exemplary embodiment with a homogeneous sub-wavelength grating 20. Due to the light deflection through the grating reflectors, the motif "star" is visible in oblique view in transmission, while the background appears dark ( Fig. 9a ).

Es sind auch Anordnungen denkbar, welche unter verschiedenen Betrachtungswinkeln unterschiedliche Motive in Transmission zeigen. Fig. 9b zeigt ein Motiv mit den Buchstaben "A" und "B", welche von unterschiedlich gestalteten asymmetrischen Gitterreflektoren 10 gebildet sind. Im Ausführungsbeispiel befindet sich die gekrümmte Seitenwand 18 (zweiter Teil 28; Fig. 2) beim Buchstaben "A" unten, beim Buchstaben "B" ist der zweite Teil 28 der Seitenwand 18 im Mikroreflektor 22 oben angeordnet. Wie bereits zuvor erläutert, wird hier ein Teil der Transmission im Bereich von "A" nach oben abgelenkt, während ein Teil des transmittierten Lichts im Bereich von "B" nach unten gelenkt wird. Der Betrachter nimmt diese Motive daher bei unterschiedlichen Betrachtungswinkeln in Transmission wahr. Auch bei dieser Ausgestaltung können die Motive mit unterschiedlich orientierten Gitterreflektoren 10 ineinander verschachtelt sein. Die unterschiedlichen Motive können dann nacheinander und abhängig vom Motiv auch an derselben Stelle des Sicherheitselements beim Kippen eines derart gestalteten Musters wahrgenommen werden.Arrangements are also conceivable which show different motives in transmission at different viewing angles. Fig. 9b shows a motif with the letters "A" and "B", which are formed by differently shaped asymmetric grating reflectors 10. In the embodiment, the curved side wall 18 (second part 28; Fig. 2 ) at the letter "A" below, at the letter "B", the second part 28 of the side wall 18 in the micro-reflector 22 is arranged above. As already explained above, here a part of the transmission in the range of "A" becomes deflected above, while a portion of the transmitted light in the range of "B" is directed downward. The observer therefore perceives these motifs at different viewing angles in transmission. Also in this embodiment, the motifs with differently oriented grating reflectors 10 can be nested. The different motifs can then be perceived one after the other and depending on the subject at the same location of the security element when tilting a pattern designed in this way.

Das in Fig. 9 dargestellte Sicherheitselement 12 findet insbesondere bei Durchsichtsfenstern von Banknoten Verwendung. Es können aber auch nur die Reflexionseigenschaften dieser Struktur, beispielsweise für einen Sicherheitsfaden oder einem Sicherheitsstreifen (z. B. LEAD-(Longlasting Economical Anticopy Device)Streifen), genutzt werden.This in Fig. 9 shown security element 12 is used in particular in see-through windows of banknotes use. However, it is also possible to use only the reflection properties of this structure, for example for a security thread or a security strip (eg LEAD (Longlasting Economical Anticopy Device) strip).

Als Subwellenlängengitter 20 können nicht nur eindimensional periodische Gitter verwendet werden. Die Subwellenlängengitter müssen auch nicht mit Mikroreflektoren 22 kombiniert werden, die in dieselbe Raumrichtung gekrümmt sind. Es sind auch Subwellenlängengitter 20 denkbar, die um eine Symmetrieachse des Mikroreflektors 22 verdreht sind, wobei die Verdrehung innerhalb des Musters variiert ist.As the subwavelength grating 20, not only one-dimensional periodic gratings can be used. Also, the subwavelength gratings need not be combined with microreflectors 22 that are curved in the same spatial direction. There are also sub-wavelength grating 20 conceivable, which are rotated about an axis of symmetry of the micro-reflector 22, wherein the rotation is varied within the pattern.

Bei zweidimensionalen periodischen Subwellenlängengittern 20 eignen sich in besonderem Maße Kreuzgitter, wobei die Gitterperiode bevorzugt senkrecht zu den Krümmungen eines Mikroreflektors mit einer rechteckigen Apertur 24 verläuft. Zirkulargitter sind hingegen besonders für Reflektoren mit runden Aperturen 24 geeignet. Natürlich sind auch Mischformen oder elliptische Subwellenlängengitter 20 in Mikroreflektoren 22 mit elliptischen Aperturen 24 möglich.In the case of two-dimensional periodic subwavelength gratings 20, cross gratings are particularly suitable, the grating period preferably being perpendicular to the curvatures of a microreflector having a rectangular aperture 24. Circular gratings, however, are particularly suitable for reflectors with round apertures 24. Of course, also hybrid forms or elliptical subwavelength gratings 20 in microreflectors 22 with elliptical apertures 24 are possible.

Zur Erzeugung der Motive sind jeweils aus Subwellenlängengitter 20 und Mikroreflektor 22 gebildete Gitterreflektoren 10 nebeneinander angeordnet, wobei ihre Ausgestaltung lateral variiert, um ein Bild beispielsweise als farbiges Symbol auszubilden. Die Variation der Beugungseigenschaften der Subwellenlängengitter 20, oder der Lage der Subwellenlängengitter 20 zum jeweiligen zugeordneten Mikroreflektor 22 oder der Reflexionseigenschaft der Mikroreflektoren 22, die Ausrichtung der Mikroreflektoren 22, oder die Gitterperiode des Subwellenlängengitters 20 oder einer Kombination daraus bewirkt einen Farb- bzw. Intensitätskontrast im Motiv.In order to generate the motifs, grating reflectors 10 formed in each case from subwavelength grating 20 and microreflector 22 are arranged next to one another, their configuration varying laterally in order to form an image, for example, as a colored symbol. The variation of the diffraction characteristics of the subwavelength gratings 20, or the position of the subwavelength gratings 20 to the respective associated microreflector 22 or the reflection characteristic of the microreflectors 22, the alignment of the microreflectors 22, or the grating period of the subwavelength grating 20, or a combination thereof, causes a color or intensity contrast in the Motive.

Zwischen benachbarten Gitterreflektoren 10 können Stege im Substrat 14 verbleiben, die in Stegflächen resultieren, welche zwischen den einzelnen Gitterreflektoren 10 liegen. Dies ist in den Figuren nicht dargestellt. Die Stegflächen sind bevorzugt durch ebene Flächen gebildet. In einer beispielhaften Bauweise sind die Stegflächen lateral dahingehend strukturiert, dass einige Stegflächen mit einer Metallisierung versehen sind, andere jedoch nicht.Between adjacent grid reflectors 10 webs may remain in the substrate 14, resulting in land areas, which lie between the individual grid reflectors 10. This is not shown in the figures. The web surfaces are preferably formed by flat surfaces. In an exemplary construction, the web surfaces are laterally structured such that some web surfaces are provided with a metallization, but others are not.

Durch die nur bereichsweise Metallisierung der Stegflächen werden zwei Bereiche geschaffen, in denen die Stegflächen mit Metallschicht vorgesehen sind bzw. ohne Metallschicht. Die Metallisierung bewirkt, dass einfallende Strahlung, die auf eine metallisierte Stegfläche trifft, als Reflex zurückgeworfen wird. In den Bereichen, in denen die Stegflächen nicht metallisiert sind, wird die einfallende Strahlung hingegen nicht reflektiert. Das Sicherheitselement 12 ist auf diese Weise in zwei Bereiche strukturiert, die sich in ihrem Reflexionsverhalten und auch in ihrem Transmissionsverhalten unterscheiden. Durch die laterale Strukturierung der Metallisierung kann damit im Sicherheitselement 12 zusätzliche Information kodiert werden. Statt einer Metallisierung kann auch eine andersartige Reflexionsschicht verwendet werden.By only partially metallization of the web surfaces two areas are created in which the web surfaces are provided with metal layer or without metal layer. The metallization causes incident radiation, which strikes a metallized land surface, to be thrown back as a reflex. In areas where the land areas are not metallized, however, the incident radiation is not reflected. The security element 12 is structured in this way in two areas that differ in their reflection behavior and also in their transmission behavior. As a result of the lateral structuring of the metallization, additional information can thus be coded in the security element 12. Instead of a metallization It is also possible to use a different reflection layer.

Anstelle einer Metallisierung oder Reflexionsschicht kann auch eine Absorptionsschicht ausgebildet werden. Die laterale Strukturierung der Stegflächen wirkt sich dann nicht auf das Reflexionsverhalten, jedoch auf das Transmissionsverhalten aus.Instead of a metallization or reflection layer, an absorption layer can also be formed. The lateral structuring of the web surfaces then has no effect on the reflection behavior, but on the transmission behavior.

Das im Sicherheitselement 12 der Fig. 1 verwendete Prinzip stellt einen großen Baukasten bereit, mit dem Muster oder Symbole durch Gitterreflektoren 10 gestaltet werden können. Die Variation der Gitterreflektoren 10 im Muster kann durch viele Parameter realisiert werden.The security element 12 of the Fig. 1 used principle provides a large building block with which patterns or symbols can be designed by grating reflectors 10. The variation of the grating reflectors 10 in the pattern can be realized by many parameters.

Die Struktur des Sicherheitselementes 12 kann sehr einfach in einem einzigen Prägeprozess hergestellt werden. Dazu benötigt man lediglich ein entsprechendes Prägewerkzeug, das eine entsprechende negative Form für jeden Gitterreflektor 10 hat, das also sowohl die Mikroreflektoren 22 als auch die Subwellenlängengitter 20 erzeugt. Um eine hohe Ausbeute der Gitterreflektoren 10 zu erreichen, müssen die Subwellenlängengitter 20 dabei im Prägewerkzeug präzise ausgebildet sein. Speziell die Herstellung des Originals des Subwellenlängengitters 20 kann mittels Elektronenstrahlschreibanlagen oder interferometrischen Verfahren erreicht werden.The structure of the security element 12 can be made very easily in a single embossing process. All you need is a corresponding embossing tool that has a corresponding negative shape for each grid reflector 10, which thus generates both the microreflectors 22 and the sub-wavelength gratings 20. In order to achieve a high yield of the grating reflectors 10, the subwavelength gratings 20 must be precisely formed in the embossing tool. Specifically, the fabrication of the original of the sub-wavelength grating 20 can be accomplished by electron beam writing or interferometric techniques.

Die Mikroreflektoren 22 haben typischerweise eine Tiefe t von 2 bis 30 µm, ein besonders bevorzugter Bereich liegt zwischen 5 und 20 µm. Geringere Tiefen t sind sowohl hinsichtlich Herstellung des Prägewerkzeugs als auch der späteren Vervielfältigung vorteilhaft. Jedoch entfaltet das Subwellenlängengitter 20 seine Wirkung optisch besonders gut, wenn mindestens 4 bis 10 Gitterperioden am Boden 16 untergebracht werden können. Dies gibt eine untere Grenze für die Größe der Mikroreflektoren 22 vor. Eine obere Grenze ergibt sich dann, wenn man die Gitterreflektoren 10 als Pixel einsetzen möchte, die naturgemäß möglichst klein sein sollen und insbesondere nicht mehr mit unbewaffnetem Auge aufgelöst werden sollten. Andererseits ist eine möglichst flache Prägung bei der Vervielfältigung vorteilhaft.The microreflectors 22 typically have a depth t of 2 to 30 microns, a particularly preferred range is between 5 and 20 microns. Lower depths t are advantageous both with regard to the production of the embossing tool and the subsequent duplication. However, the sub-wavelength grating 20 is optically particularly effective when at least 4 to 10 grating periods can be accommodated at the bottom 16. This gives one lower limit for the size of the microreflectors 22 before. An upper limit arises when one wants to use the grating reflectors 10 as pixels, which should naturally be as small as possible and in particular should no longer be resolved with an unarmed eye. On the other hand, as flat an embossing as possible is advantageous in copying.

Bei der Herstellung des Originals werden in einer Variante zuerst die Mikroreflektoren 22 erzeugt, beispielsweise photolithographisch durch Direct-Laserwriting. Unabhängig davon wird die Struktur der Subwellenlängengitter 20 erzeugt. Diese beiden Vorgänge nimmt man bevorzugt passgenau in ein und demselben Photolack vor, der als Vorlage Basis für das Prägewerkzeug ist. Alternativ sind auch zwei unterschiedliche Belackungsvorgänge möglich.In the production of the original, the microreflectors 22 are first produced in a variant, for example photolithographically by direct laser writing. Independently, the structure of the subwavelength gratings 20 is generated. These two processes are preferably carried out accurately in one and the same photoresist, which is the basis for the embossing tool as a template. Alternatively, two different Belackungsvorgänge are possible.

Auch ist es in einer Variante möglich, zuerst ein homogenes Subwellenlängengitter 20 zu erzeugen, dieses zu belacken und dann lateral unterschiedlich ausgebildete Mikroreflektoren 22 zu erzeugen, beispielsweise per Laserwriting. Dazu wird zunächst ein Subwellenlängengitter 20, beispielsweise mithilfe eines Elektronenstrahl-Belichtungsverfahrens, hergestellt und abgeformt. Anschließend wird dieses Gitter-Substrat mit einem Photolack in ausreichender Dicke, z. B. 10 µm, beschichtet. Dann werden Mikroreflektoren 22 im Direktbelichtungsverfahren mit einem Laserwriter einbelichtet, so dass das Subwellenlängengitter 20 in der Mitte der einzelnen Mikroreflektoren nach dem Entwickeln frei liegt.It is also possible in a variant to first produce a homogeneous sub-wavelength grating 20, to lacquer it and then laterally to produce differently shaped micro-reflectors 22, for example by laser writing. For this purpose, first a sub-wavelength grating 20, for example by means of an electron beam exposure method, produced and molded. Subsequently, this grid substrate with a photoresist in sufficient thickness, for. B. 10 microns coated. Then microreflectors 22 are imprinted in the direct exposure process with a laserwriter, so that the subwavelength lattice 20 is exposed in the middle of the individual microreflectors after development.

Die verwendeten Laserwriter können mit 2-Photonenabsorptionsprozessen arbeiten. Es ist dann möglich, Mikroreflektoren 22 wie Subwellenlängengitter 20 in einem einzigen Prozess zu erzeugen.The laserwriters used can work with 2-photon absorption processes. It is then possible to generate microreflectors 22, such as sub-wavelength gratings 20, in a single process.

Die für das Prägewerkzeug hergestellte Vorlage wird nun galvanisch oder in einem Nanoimprint-Verfahren umkopiert.The template produced for the embossing tool is now copied electroplated or in a nanoimprint process.

Da im Prägeverfahren einer Folie üblicherweise eine Vielzahl von Sicherheitselementen 12 in einem Prägeschritt erzeugt werden sollen, ist es zu bevorzugen, im Prägewerkzeug mehrere nebeneinanderliegende Stempelelemente vorzusehen, die jeweils auf die vorbeschriebene Art aus einer Vorlage erzeugt wurden.Since a plurality of security elements 12 are usually to be produced in one embossing step in the embossing process of a film, it is preferable to provide a plurality of adjacent stamp elements in the embossing tool, each of which has been produced from a template in the above-described manner.

Die geprägte Folie wird bevorzugt mit einer opaken Metallschicht überzogen. Hierzu kommen Sputtern, Elektronenstrahlbedampfung oder thermisches Verdampfen in Frage. Als Metalle eignen sich besonders Aluminium, Silber, Gold, Nickel oder Chrom oder Legierungen aus diesen Materialien. Es kommen aber auch Mehrschichtaufbauten in Frage, welche mindestens eine Schicht aus metallischem Material enthalten. Die Dicken der Metallschicht liegen zwischen 20 und 100 nm. Die Metalloberfläche wird dann abschließend bevorzugt mit einer Schutzschicht überzogen oder mit einer Deckfolie kaschiert.The embossed film is preferably coated with an opaque metal layer. For this purpose, sputtering, electron beam evaporation or thermal evaporation come into question. Particularly suitable metals are aluminum, silver, gold, nickel or chromium or alloys of these materials. But there are also multi-layer structures in question, which contain at least one layer of metallic material. The thicknesses of the metal layer are between 20 and 100 nm. Finally, the metal surface is preferably coated with a protective layer or laminated with a cover film.

Zum Erzeugen einer lateral strukturierten Beschichtung der Stegflächen wird bevorzugt zuerst eine entsprechende Beschichtung auf alle Stegflächen aufgebracht und dann wieder von einigen Stegflächen entfernt. Im Falle einer Metallisierung wird das Entfernen durch eine Demetallisierung ausgeführt. Dabei kann ein Ätzprozess oder das Metalltransferverfahren gemäß WO 2011/138039 A1 zur Anwendung kommen. Auch ist eine Entfernung der Schicht, beispielsweise eine Demetallisierung mit Hilfe von Ultrakurzpulslasern und dem Einsatz eines schreibenden Laserstrahls möglich.To produce a laterally structured coating of the web surfaces, a corresponding coating is preferably first applied to all web surfaces and then removed again from some web surfaces. In the case of metallization, the removal is performed by demetallization. In this case, an etching process or the metal transfer process according to WO 2011/138039 A1 come into use. It is also possible to remove the layer, for example demetallization with the aid of ultrashort pulse lasers and the use of a writing laser beam.

Bei der Entfernung der Schicht kann man gezielt verhindern, dass eine Metallisierung im Bereich der Gitterreflektoren 10 entfernt wird. So ist es möglich, die metallisierte Struktur komplett mit einem Photoresist aufzufüllen, d. h. einzuebnen. Dann kann man den Photoresist bis auf die Niveaus der Stegflächen 11 ätzen und die derart freigelegte Beschichtung strukturieren, beispielsweise eine Metallschicht ätzen. Eine anschließende Entfernung des Photoresists legt dann die Gitterreflektoren 10 wieder frei, die auf diese Art und Weise vom Eingriff an der Stegfläche 11 nicht betroffen sind.When removing the layer, it is possible to selectively prevent a metallization in the area of the grating reflectors 10 from being removed. Thus, it is possible to completely fill the metallized structure with a photoresist, ie level. Then you can etch the photoresist to the levels of the land surfaces 11 and structure the thus exposed coating, for example, etch a metal layer. Subsequent removal of the photoresist then exposes the grating reflectors 10 again, which in this manner are not affected by engagement with the land surface 11.

BezugszeichenlisteLIST OF REFERENCE NUMBERS

1010
Gitterreflektorgrating reflector
1212
Sicherheitselementsecurity element
1414
Substratsubstratum
1616
Bodenground
1818
SeitenwandSide wall
2020
Subwellenlängengittersubwavelength
2222
Mikroreflektormicro-reflector
2424
Aperturaperture
2626
erster Teilfirst part
2828
zweiter Teilsecond part
aa
Durchmesserdiameter
bb
Ausdehnungexpansion
tt
Tiefedepth

Claims (21)

  1. Security element for an object to be protected, which security element has a substrate (14) with a plurality of micro-reflectors (22) and micro-structures arranged in a pattern, wherein
    - each of the micro-structures (20) is assigned to one of the micro-reflectors (22), as a result of which a plurality of grating reflectors (10) each comprising a micro-reflector (22) and at least one of the micro-structures (20) are formed,
    - each of the micro-structures (20) is embodied in such a way that it diffracts in a reflective fashion the visible radiation which is incident from a half-space through an aperture (24) of the micro-reflector (22),
    - the grating reflectors (10) arranged in the pattern generate an image which can be perceived by a viewer, and
    - each micro-structure is embodied as a sub-wavelength grating (20) which diffracts in a reflective fashion a first portion of the visible radiation which is incident from the half-space through the aperture (24) of the micro-reflector (22), characterized in that
    each of the sub-wavelength gratings (20) diffracts the first portion into a zero order of reflection/diffraction.
  2. Security element according to Claim 1, characterized in that the sub-wavelength grating (20) is embodied as a semi-transparent sub-wavelength grating which diffracts in a transmissive fashion a second portion of the visible radiation which is incident from the half-space through the aperture (24) of the micro-reflector (22), wherein each of the sub-wavelength gratings (20) diffracts the second portion into a zero order of transmission/diffraction.
  3. Security element according to Claim 2, characterized in that in each grating reflector (10) the sub-wavelength grating (20) and the micro-reflector (22) are adjusted with respect to one another in such a way that the sub-wavelength grating (20) transmits radiation which is incident from the half-space through the aperture (24) of the micro-reflector (22) and is reflected by the micro-reflector (22) into the zero order of transmission/diffraction.
  4. Security element according to Claim 1, characterized in that the sub-wavelength grating (20) is embodied as an opaque sub-wavelength grating.
  5. Security element according to one of Claims 1 to 4, characterized in that in each grating reflector (10) the sub-wavelength grating (20) and the micro-reflector (22) are adjusted with respect to one another in such a way that the radiation which has been diffracted by the sub-wavelength grating (20) into the zero order of reflection/diffraction is reflected back by the micro-reflector (22) at least partially as reflection into the half-space.
  6. Security element according to one of Claims 1 to 5, characterized in that the micro-reflectors (22) are each embodied as a concave mirror or trench with a level floor (16), wherein the sub-wavelength grating (20) is arranged on the level floor (16), wherein the micro-reflectors (22) preferably have, in addition to the floor (16), a side wall (18) which is embodied with a parabolic, straight or ellipsoidal cross section, or as a mixed form thereof.
  7. Security element according to one of the above claims, characterized in that the micro-reflectors (22) are asymmetrical in cross section and have a floor (16) and at least one side wall (18), wherein, in particular, a first part (26) of the side wall (18) is embodied in a straight fashion and a second part (28) of the side wall (18) is embodied in a concave fashion, in particular in a parabolic or ellipsoidal fashion, in particular in that a first part (26) of the side wall (18) is perpendicular with respect to the floor (16).
  8. Security element according to one of the above claims, characterized in that each sub-wavelength grating (20) has a grating period between 100 nm and 500 nm, in particular between 240 nm and 420 nm.
  9. Security element according to one of the above claims, characterized in that the micro-reflectors (22) and the sub-wavelength gratings (20) are coated on their side facing the half-space with at least one metallic layer, preferably with Al, Ag, Au, Cu, Cr or an alloy containing these metals, and/or in that the micro-reflectors (22) and the sub-wavelength gratings (20) have, on their side facing the half-space, a trilayer coating composed of two metal layers or semiconductor layers located one on top of the other and having a dielectric layer located between them.
  10. Security element according to one of the above claims, characterized in that the aperture (24) has a diameter (a), and the micro-reflector (22) has a depth (t) from the aperture (24) as far as a floor (16), wherein at least one of the following properties of the grating reflectors (10) varies within the pattern in order to generate the image: position of the sub-wavelength gratings (20) in relation to the respectively assigned micro-reflector (22), diameter (a) of the aperture (24), depth (t) of the micro-reflector (22), orientation of the micro-reflector (22), shape of the micro-reflector (22) and/or grating period of the sub-wavelength grating (20), wherein the property of the grating reflectors (10) preferably varies continuously within the pattern in such a way that the image is generated by means of the Moire effect.
  11. Security paper or valuable document, characterized by a security element (12) according to one of Claims 1 to 10.
  12. Method for manufacturing a security element (12) for an object to be protected, wherein micro-reflectors (22) and a plurality of micro-structures arranged in a pattern are formed on a substrate (14), wherein
    - each of the micro-structures (20) is assigned to one of the micro-reflectors (22), as a result of which a plurality of grating reflectors (10) each comprising a micro-reflector (22) and at least one of the micro-structures (20) are formed,
    - each of the micro-structures (20) is embodied in such a way that it diffracts in a reflective fashion the visible radiation which is incident from a half-space through an aperture (24) of the micro-reflector (22),
    - the grating reflectors (10) arranged in the pattern generate an image which can be perceived by a viewer, and
    - each micro-structure is embodied as a sub-wavelength grating (20) which diffracts in a reflective fashion a first portion of the visible radiation which is incident from the half-space through the aperture (24) of the micro-reflector (22), characterized in that
    each of the sub-wavelength gratings (20) diffracts the first portion into a zero order of reflection/diffraction.
  13. Method according to Claim 12, characterized in that the sub-wavelength grating (20) is embodied as a semi-transparent sub-wavelength grating which diffracts in a transmissive fashion a second portion of the visible radiation which is incident from the half-space through the aperture (24) of the micro-reflector (22), wherein each of the sub-wavelength gratings (20) diffracts the second portion into a zero order of transmission/diffraction.
  14. Method according to Claim 13, characterized in that in each grating reflector (10) the sub-wavelength grating (20) and the micro-reflector (22) are adjusted with respect to one another in such a way that the sub-wavelength grating (20) transmits radiation which is incident from the half-space through the aperture (24) of the micro-reflector (22) and is reflected by the micro-reflector (22) into the zero order of transmission/diffraction.
  15. Method according to Claim 12, characterized in that the sub-wavelength grating (20) is embodied as an opaque sub-wavelength grating.
  16. Method according to one of Claims 12 to 15, characterized in that in each grating reflector (10) the sub-wavelength grating (20) and the micro-reflector (22) are adjusted with respect to one another in such a way that the radiation which has been diffracted by the sub-wavelength grating (20) into the zero order of reflection/diffraction is reflected back by the micro-reflector (22) at least partially as reflection into the half-space.
  17. Method according to one of Claims 12 to 16, characterized in that the micro-reflectors (22) are each embodied as a concave mirror or trench with a level floor (16), wherein the sub-wavelength grating (20) is arranged on the level floor (16), wherein the micro-reflectors (22) are preferably configured to have, in addition to the floor (16), a side wall (18) which is embodied with a parabolic, straight or ellipsoidal cross section, or as a mixed form thereof.
  18. Method according to one of Claims 12 to 17, characterized in that the micro-reflectors (22) are asymmetrical in cross section and are configured with a floor (16) and at least one side wall (18), wherein, in particular, a first part (26) of the side wall (18) is embodied in a concave fashion, in particular in a parabolic or ellipsoidal fashion, in particular in that a first part (26) of the side wall (18) is configured to be perpendicular with respect to the floor (16).
  19. Method according to one of Claims 12 to 18, characterized in that each sub-wavelength grating (20) is embodied with a grating period between 100 nm and 500 nm, in particular between 240 nm and 420 nm.
  20. Method according to one of Claims 12 to 19, characterized in that the micro-reflectors (22) and sub-wavelength gratings (20) are coated, on their side facing the half-space, with at least one metallic layer, preferably with Al, Ag, Au, Cu, Cr or an alloy containing these metals.
  21. Method according to one of Claims 12 to 20, characterized in that the aperture (24) has a diameter (a), and the micro-reflector (22) has a depth (t) from the aperture (24) as far as the floor (16), wherein at least one of the following properties of the grating reflectors (10) is varied within the pattern in order to generate the image: position of the sub-wavelength gratings (20) in relation to the respectively assigned micro-reflector (22), diameter (a) of the aperture (24), depth (t) of the micro-reflector (22), arrangement of the micro-reflector (22), shape of the micro-reflector (22) and/or grating period of the sub-wavelength grating (20), wherein the property of the grating reflectors (10) preferably is varied continuously within the pattern in such a way that the image is generated by means of the Moire effect.
EP16002760.3A 2015-12-23 2016-12-22 Safety element for security papers, valuable documents or the like and method for manufacturing a safety element Active EP3184319B1 (en)

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