Method for manufacturing a multilayer body, multilayer body, method for authenticating a multilayer body, and authentication system

Abstract

The present invention relates to a method for manufacturing a multilayer body (1), in particular a laminate film or a transfer film. A replication layer (12) is applied to a carrier layer (11), a first graphic code (21) is Fourier-transformed into a two-dimensional Fourier pattern (23), the two-dimensional Fourier pattern (23) is binarized to obtain a binarized two-dimensional Fourier pattern (24), the binarized two-dimensional Fourier pattern (24) is transferred onto a stamping tool, and the binarized two-dimensional Fourier pattern (24) is formed as a stamping structure in the replication layer (12) at least partially in a first region by the stamping tool.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a multilayer body and to a multilayer body. The present invention also relates to a method for authenticating a multilayer body and to an authentication system.

Background Art

[0002] It is known to equip a multilayer body with security functions for protection against forgery. In addition to the scope of holograms, Fourier patterns are also suitable for this.

[0003] From German Patent Application Publication No. 102017206466, a machine-readable graphic code is provided, the graphic code is embedded in a two-dimensional discrete complex function, the two-dimensional discrete complex function is Fourier-transformed, and binarized to form a two-dimensional image. A method for generating a security feature is known. The binarized Fourier image is printed at a pixel resolution high enough that the machine-readable graphic code can no longer be read after inverse transformation in the case of a copy of this binarized Fourier image by a conventional printer and copier having a maximum scan or print resolution of 600×600 dpi. The scan or print resolution of 600×600 dpi indicates the data printed by the printer. The dpi values specified for conventional printers and copiers are not necessarily actually achieved in reality.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, a disadvantage of known methods and multilayer bodies is that the Fourier pattern is applied by digital printing. Thus, such multilayer bodies are basically susceptible to attempts at imitation and copying by skilled persons using specialized equipment (so-called expert copy) having a scan or print resolution exceeding 600 dpi in particular.

[0005] The object of the present invention is to provide a method for manufacturing a multilayer body and a multilayer body which improve protection against forgery and are not limited to digital printing methods in production.

Means for Solving the Problems

[0006] This object is achieved by a method for manufacturing a multilayer body, in particular a laminate film or a transfer film, in which a replication layer is applied to a carrier layer, a first graphic code is Fourier-transformed into a two-dimensional Fourier pattern, the two-dimensional Fourier pattern is binarized to obtain a binarized two-dimensional Fourier pattern, the binarized two-dimensional Fourier pattern is transferred to a stamping tool, and the binarized two-dimensional Fourier pattern is formed as a stamping structure at least partially in a first region in the replication layer by the stamping tool.

[0007] This object is further achieved by a multilayer body, in particular a laminate film or a transfer film, preferably manufactured according to any one of claims 1 to 32. The multilayer body has a carrier layer and a replication layer disposed thereon, and the first graphic code, which is Fourier-transformed into a binarized two-dimensional Fourier pattern and embedded, is formed as a stamping structure at least partially in a first region in the replication layer.

[0008] This object is achieved by a method for authenticating a multilayer body, in particular a multilayer body manufactured by the method according to any one of claims 33 to 52, preferably according to claims 1 to 32, using an authentication system. In this method, an image of the binarized two-dimensional Fourier pattern of the multilayer body is captured using a camera of a mobile terminal, the captured image is inverse Fourier-transformed, the inverse Fourier-transformed image is supplied to a first reading algorithm for the first graphic code, the first graphic code is read out, and the first graphic code is checked.

[0009] Furthermore, this object is also achieved by an authentication system for authenticating a multilayer body according to any one of claims 33 to 52, which is manufactured by the method according to any one of claims 1 to 32 in particular. The authentication system includes a camera for capturing an image of a binarized two-dimensional Fourier pattern of a multilayer body protected against forgery, and a transceiver unit through which data of the multilayer body captured by the camera can be transmitted to an authentication server for use therewith. The authentication system further includes a mobile terminal having the above components, a Fourier inverse transform program by which the binarized two-dimensional Fourier pattern can be inverse Fourier transformed therewith, a first reading algorithm for a first graphic code read from the inverse Fourier transformed image, and an authentication server data-carrier connected to the mobile terminal. The authentication server stores the multilayer body in which the read first graphic code is included, in particular stores the batch number, authenticates the read first graphic code transmitted by the mobile terminal, in particular the batch number, and outputs an authentication signal to the mobile terminal.

[0010] It has been shown that, by the multilayer body according to the invention, the method according to the invention for manufacturing a multilayer body, the method for authenticating a multilayer body, and the authentication system, a multilayer body in which a first graphic code is included in a binarized two-dimensional Fourier pattern can be obtained. The binarized two-dimensional Fourier pattern is introduced into the multilayer body as a stamping structure. Therefore, the binarized two-dimensional Fourier pattern is read by the authentication system, and at the same time, due to the optical variability brought about by the stamping structure, a binarized two-dimensional Fourier pattern with enhanced protection against forgery is provided. Therefore, due to the optical variability, it is impossible to copy the binarized two-dimensional Fourier pattern using conventional printing or copying.

[0011] Further, by using the multilayer body according to the present invention and the method according to the present invention for manufacturing the multilayer body, a multilayer body in which a binarized two-dimensional Fourier pattern is not introduced or is not applied by digital printing is obtained. In the case of Fourier patterns applied by digital printing, hitherto, it has been necessary to print these Fourier patterns partially at a printing resolution of up to 1200 dpi. In order to be able to print such a high resolution with high quality, a very expensive printer is required. By the multilayer body according to the present invention and the method according to the present invention for manufacturing the multilayer body, it becomes possible to introduce a Fourier pattern into the multilayer body without performing digital printing.

[0012] Furthermore, the binarized two-dimensional Fourier pattern provided as a stamping structure additionally offers the advantage that it can be captured by a conventional mobile terminal and read out by appropriate software. For capture, the camera of a commercially available smartphone is sufficient. This is because only the binarized two-dimensional Fourier pattern is captured by the camera as a normal photograph. For example, unlike when a computer-generated hologram is read out, the light directly diffracted by the Fourier pattern is not captured in this way. In the case of computer-generated holograms (CGHs), i.e., these need to be read out by a monochromatic laser by diffraction into the hologram structure. For this reason, the lateral structure of the CGH needs to be on the order of the size of the wavelength of the light used, otherwise the light will not be effectively diffracted. For example, the structure of the CGH needs to have a size substantially from 500 nm to 10 μm. This corresponds to an effective resolution from 50,000 dpi to 2500 dpi. In contrast to the structure of the CGH, in the case of the binarized two-dimensional Fourier pattern, there is a lower resolution. The effective resolution of the binarized two-dimensional Fourier pattern is preferably at most 2500 dpi, preferably at most 1200 dpi, and particularly preferably at most 900 dpi. The lower resolution is necessary so that the structure can actually also be captured by a commercially available camera by normal imaging. For recognition by a commercially available camera, an effective resolution of the binarized two-dimensional Fourier pattern of 650 dpi is usually used. A binarized two-dimensional Fourier pattern with a resolution of 650 dpi can be generated by a printer / scanner having at least a scan or print resolution of 650 dpi, but the copy produced is not optically variable.

[0013] More preferably, the binarized two-dimensional Fourier pattern is shaped with an effective resolution of at most 2500 dpi, preferably at most 1200 dpi, and particularly preferably at most 900 dpi.

[0014] Further advantageous designs of the invention are described in the dependent claims.

[0015] The multilayer body can be designed as a laminate film, a transfer film, particularly a hot stamping film or a cold stamping film. Therefore, the multilayer body can be used for various applications. For example, the multilayer body is used in the packaging industry to decorate the packaging so as to be protected against forgery. However, the multilayer body may be used, for example, to protect security documents such as identity cards and passports, and securities. In addition, the multilayer body is used whenever the product should be authenticated with respect to authenticity. This is because the authenticity of the product can be checked by an authentication server via a machine-readable binarized two-dimensional Fourier pattern in which the first graphic code is embedded again.

[0016] In this specification, "packaging" is a general term meaning both a product, such as a sales package for a toothpaste tube, and an exterior, such as a folding box for the product. Further, the packaging may be a part of the packaged product, for example, a label attached to an exterior product. The packaged product may be a box in which some exterior products of the product are packaged.

[0017] In the present invention, "transparent" particularly means a region having a transmittance exceeding 50%, preferably exceeding 70%, particularly preferably exceeding 80% in the wavelength range of light visible to a human observer.

[0018] In the present invention, "opaque" particularly means a region having a transmittance of less than 40%, preferably less than 30%, particularly preferably less than 20% in the wavelength range of light visible to a human observer.

[0019] First, the generation of the Fourier pattern will be described in more detail below.

[0020] The machine-readable first graphic code is embedded in the real amplitude function of the two-dimensional discrete complex function G(fx, fy) having fx frequency coordinates and fy frequency coordinates. Thus, for embedding, the code is arranged in a two-dimensional, preferably square, image template, and the x and y values of the image template are interpreted as the fx frequency and the fy frequency, respectively.

[0021] In principle, a complex number or a complex function can be represented as the sum of a real part and an imaginary part, or as the sum of a real function and an imaginary function, or, in polar notation, as the product of an amplitude function and a phase function.

[0022] The method according to the invention starts by providing a machine-readable first graphic code as the amplitude function of the two-dimensional discrete complex function G(fx, fy). The amplitude function preferably has either function value 0 or function value 1 over two frequency coordinates fx, fy. Function value 1 is represented in particular by the black coordinate points of the code arranged within the image template, and function value 0 is represented in particular by the white coordinate points of the code arranged within the image template. Here, the highest frequency used in the fx direction or the fy direction is preferably at least 600 dpi.

[0023] An appropriate phase function e iφ (fx, fy) is preferably added to the real amplitude function by multiplication.

[0024] The phase function has the purpose of smoothing the frequency spectrum of the amplitude function.

[0025] The phase function e iφ(fx, fy) can be a random phase. The first graphic code for generating the phase correlation function is preferably first formed as a random grayscale image. The contour of the grayscale image corresponds to the first graphic code, except that the values are random grayscale values between white and black rather than 0 (white) and 1 (black) as in the construction of the amplitude function. An assignment of grayscale values to numbers between 0 and 2π occurs. If the grayscale value is black, the phase is 2π, and if the grayscale value is white, the phase is 0. Other grayscale values are assigned an angle (in radian measure) between 0 and 2π according to the grayscale. The darker the color, i.e., the darker it is, the larger the angle. In this way, the random grayscale image is uniquely converted into the phase correlation function e iφ (fx, fy), and the complex-valued function G(fx, fy) is obtained by multiplying the amplitude function by the phase correlation function. The random phase further provides the advantage that the random phase is assigned to each frequency range, thereby making the subsequent Fourier pattern easier to read.

[0026] However, other phase correlation functions can also be added to the real amplitude function.

[0027] Next, the two-dimensional discrete complex function G(fx, fy) is Fourier-transformed, and the resulting Fourier transform g(x, y) is binarized to form a two-dimensional image. For binarization, the real part of the Fourier transform g(x, y) is checked and can be binarized by a threshold value. The real part of the Fourier transform also includes grayscale. Here, binarization of an image means that a value of 1 is assigned to each pixel of the image where the grayscale exceeds the threshold value, and a value of 0 is assigned to each pixel where the grayscale is below the threshold value. Further, 10% binarization means that, that is, 10% of the pixels are black and 90% of the pixels are white. Further, 50% binarization means that, that is, 50% of the pixels are black and 50% of the pixels are white, and so on. Alternatively, the imaginary part or phase of the Fourier transform g(x, y) is also checked and can be binarized by a threshold value. Further possibilities of binarization are known from the prior art (Goodman, J.W., Introduction to Fourier Optics, McGraw-Hill (New York) (1996)).

[0028] The real part of the Fourier transform is preferably binarized, and a binarized two-dimensional Fourier pattern is thereby formed.

[0029] The binarized two-dimensional Fourier pattern is preferably generated with a binarization of less than 50%, preferably less than 20%. The binarization is usually about 15%.

[0030] The carrier layer consists in particular of a self-supporting material and / or a plastic material. The carrier layer is preferably selected individually or in combination from the following material classes as a composite material: PET; polyolefins in particular from OPP, BOPP, MOPP, PP, PE; PMMA; PEN; PA; ABS. The carrier layer may already be pre-coated by the manufacturer, and a multilayer body may be constructed on this pre-coated material. The carrier layer may be a biodegradable and / or compostable carrier layer. Here, EVOH is preferably used.

[0031] The layer thickness of the carrier layer is preferably between 4 μm and 500 μm, particularly between 4.7 μm and 250 μm.

[0032] The multilayer body is formed as a laminate film having a carrier layer and a multilayer wear layer, such as a multilayer decorative ply, and in particular a heat-activatable adhesive layer, and the carrier layer and the wear layer are arranged together in the form of a stamping layer on a target substrate.

[0033] In particular, the multilayer body is formed as a transfer film. The transfer film particularly preferably has a transfer ply formed from several layers, which are individually or multiply or in combination selected in particular from an adhesive layer, an adhesion promoter layer, a primer layer, a barrier layer, a compensation layer, a metal layer, an oxide layer, a color layer, a replication layer, a protective layer.

[0034] The transfer film further has a carrier layer, and the transfer ply is removable from the carrier layer. In order to facilitate removal of the transfer ply, a release layer may be arranged between the transfer ply and the carrier layer.

[0035] Preferably, the release layer and / or the protective layer is applied to the carrier layer, and in particular the release layer and / or the protective layer is arranged between the carrier layer and the replication layer.

[0036] The release layer in particular ensures that the layers of the multilayer body can be separated non-destructively from the carrier layer as a transfer primer. The release layer is preferably formed from wax, polyethylene (PE), polypropylene (PP), cellulose derivatives and / or poly(organo)siloxanes. The above-mentioned wax can be a natural wax, a synthetic wax or a combination thereof. The above-mentioned wax is, for example, carnauba wax. The above-mentioned cellulose derivatives are, for example, cellulose acetate (CA), cellulose nitrate (CN), cellulose acetate butyrate (CAB) or a mixture thereof. The above-mentioned poly(organo)siloxanes are, for example, silicone binders, polysiloxane binders or mixtures thereof. The release layer preferably has a layer thickness between 1 nm and 500 nm, in particular between 5 nm and 250 nm, particularly preferably between 10 nm and 250 nm.

[0037] When the multilayer body is used, for example, as a laminate film for label and / or sticker applications, the connection between the carrier layer and the subsequent layer or the wear layer is usually maintained during application. Thus, in the case of a laminate film, in principle, the release layer is omitted, or, for example, in the case of a laminate film for security applications, the separation of the carrier layer from the wear layer is preferably designed to occur only after application.

[0038] The release layer can be produced by known printing methods. In particular, application by gravure printing, flexographic printing, screen printing, inkjet printing or slot die is suitable. However, the release layer can also be formed by evaporation, physical vapor deposition (PVD), chemical vapor deposition (CVD) and / or sputter deposition.

[0039] The protective layer is preferably a thermoplastic layer or a thermosetting layer or a radiation-curing layer of varnish, which is selected individually from several sub-layers and / or as a mixture, from PMMA, PVC, melamine, acrylate, polyurethane, crosslinking agent, photoinitiator, additive, defoaming agent, leveling agent, wetting agent. The protective layer can also consist of a radiation-curing dual-curing varnish. This dual-curing varnish can be thermally pre-crosslinked in a first step during and / or after application in liquid form. Preferably, in a second step, especially after treatment of the multi-layer film, the dual-curing varnish is radically post-crosslinked via especially high-energy radiation, preferably UV radiation. This type of dual-curing varnish can consist of different polymers or oligomers having unsaturated acrylate or methacrylate groups. These functional groups can be radically crosslinked with each other, especially in the second step. For the thermal pre-crosslinking in the first step, in the case of these polymers or oligomers, it is advantageous if at least two or more alcohol groups are also present. These alcohol groups can be crosslinked with polyfunctional isocyanates or melamine formaldehyde resins. Different UV raw materials such as epoxy acrylate, polyether acrylate, polyester acrylate, especially acrylate acrylate, etc., are preferably considered as unsaturated oligomers or polymers. Both blocked representatives and unblocked representatives based on TDI (TDI = toluene-2,4-diisocyanate), HDI (HDI = hexamethylene diisocyanate) or IPDI (IPDI = isophorone diisocyanate) can be considered as isocyanates. The melamine crosslinking agent can be in the fully etherified version, in the imino type, or can represent a benzoguanamine representative.

[0040] The protective layer preferably has a layer thickness between 50 nm and 30 μm, preferably between 1 μm and 3 μm. The protective layer can be produced by gravure printing, flexographic printing, screen printing, inkjet printing, by slot die, and / or by vapor deposition, especially by physical vapor deposition (PVD), chemical vapor deposition (CVD) and / or sputter deposition. Vapor deposition is carried out especially in the case of thinner protective layers of less than 1 μm.

[0041] In particular, the metal layer and / or the HRI layer and / or the primer layer and / or the adhesive layer can preferably be applied to the replication layer partially or over the entire surface after the replication varnish has cured. Furthermore, it is also possible for the metal layer and / or the HRI layer and / or the primer layer and / or the adhesive layer to be disposed on the replication layer.

[0042] The metal layer can be applied over the entire surface and to both predetermined regions. The metal layer is preferably formed to be patterned and can represent a pattern and / or motif, and in particular, may be arranged in alignment with the print and / or the stamping structure of the replication layer. Furthermore, it is also possible for the metal layer to be disposed in a first region at least partially or over the entire surface. As described above, the stamping structure of the binary two-dimensional Fourier pattern is provided at least partially in the first region. Since the metal layer is similarly provided in the first region, it is guaranteed that the binary two-dimensional Fourier pattern is metallized to obtain a metallic appearance.

[0043] Also, preferably, the metal layer is formed in alignment with the stamping structure.

[0044] Matched or matching or accurate alignment or precisely matching or alignment accuracy or matching accuracy means the positional accuracy of two or more layers relative to each other. Alignment (registration) accuracy means falling within a predefined tolerance so as to be as small as possible. At the same time, the alignment (registration) accuracy of several elements and / or layers relative to each other is an important feature for enhancing process reliability and / or product quality and / or protection against counterfeiting. Positionally accurate positioning can be performed in particular, preferably optically, by means of alignment marks or matching marks that are detectable sensually. These alignment marks or matching marks can represent specific distinct elements or regions or layers, or can themselves be part of the elements or regions or layers to be positioned.

[0045] The metal layer is preferably formed individually, or as an alloy, or as a eutectic, and is selected from aluminum, chromium, gold, copper, tin, indium, silver. The metal layer is preferably manufactured by vapor deposition, in particular by physical vapor deposition. The vapor-deposited metal layer is formed over the entire surface, optionally preserved over the entire surface, or structured by known demetallization methods such as etching, lift-off (cleaning varnish method) or photolithography, whereby it may subsequently only be present partially. The layer thickness of the metal layer is in particular between 10 nm and 500 nm.

[0046] However, the metal layer may also consist of a printed layer, in particular a printed layer of metal pigments in a binder. These printed metal pigments may be applied over the entire surface or partially, and / or may have different colorings in different regions of the surface. The layer thickness of the metal layer of the metal pigments is in particular between 1 μm and 10 μm.

[0047] The metal layer may be manufactured from a varnish having conductive metal pigments, in particular the varnish may be printed and / or poured.

[0048] Alternatively, instead of the metal layer, an HRI or LRI layer (high refractive index - HRI, low refractive index - LRI) may be used. Such a dielectric HRI or LRI layer consists, for example, of a vapor-deposited layer of metal oxides, metal sulfides, titanium oxide, etc. The layer thickness of such a layer is preferably between 10 nm and 500 nm.

[0049] Furthermore, a first metal layer with a translucent design may be provided as the optical filter layer. Such a metal layer may consist of, for example, a thin metal (Al, Cr), or a vapor-deposited layer of a thinly applied metal oxide, metal sulfide, silicon oxide, etc. The layer thickness of such a layer is selected such that the optical density is particularly in the range of 0.1 to 0.9 OD (OD = optical density). The subsequent dielectric spacer layer required for the thin film color gradient effect is coated in the same manner as the replication layer, and the layer thickness range is preferably between 0.1 μm and 1.0 μm, and / or the composition particularly corresponds to the replication layer. In this case, the spacer layer may also function directly as the replication layer. The spacer layer may be vapor-deposited as a ceramic spacer layer. Typically, then, a metal or semi-metal oxide such as SiO2, TiO2, Na3AlF6 or MgF2 is vapor-deposited according to one of the methods mentioned for the metal layer. The layer thickness here is particularly between 20 nm and 500 nm. The spacer layer may be printed as a transparent varnish layer.

[0050] This optical filter layer may already be applied before the replication layer. In this case, the replication layer particularly functions as a dielectric spacer layer, and the layer thickness range is preferably between 0.1 μm and 1.0 μm.

[0051] Next, adjacent to the dielectric spacer layer, an opaque or translucent metal layer is vapor-deposited, particularly as described above.

[0052] The adhesive layer and / or primer layer is preferably formed from a varnish and is individually selected from PMMA, PVC, acrylate, polyamide, polyvinyl acetate, hydrocarbon resin, polyester, polyurethane, chlorinated polyolefin, polypropylene, epoxy resin, polyurethane polyol in several sub-layers and / or as a mixture, particularly in combination with an inactivating isocyanate, fillers such as SiO2 and / or TiO2. A primer layer may also be provided in addition to the adhesive layer.

[0053] The layer thickness of the adhesive layer and / or the primer layer is preferably between 0.5 μm and 20 μm, particularly preferably between 1.5 μm and 5 μm. The adhesive layer and / or the primer layer can be manufactured by application by gravure printing, flexographic printing, screen printing, inkjet printing and / or slot die.

[0054] The replication layer preferably has, in at least one, preferably one upper region thereof, a two-dimensional Fourier pattern binarized as a stamping structure. The replication layer is preferably formed from a thermoplastic varnish or a radiation-curable varnish and is individually selected from acrylates, cellulose, PMMA, polyurethanes, isocyanates in several sublayers and / or as a mixture. The surface structure is particularly preferably shaped into the thermoplastic replication layer by heat and pressure by the action of a stamping tool.

[0055] Furthermore, it is also possible that the replication layer has a UV-curable replication varnish that is pre-cured or fully cured by UV radiation after the shaping of the stamping structure. The stamping structure is shaped into a replication layer that is not yet finally cured by the action of a stamping tool, and the replication layer is cured by irradiating it directly with UV light during or after shaping. Further irradiation with UV light can be carried out before and / or during shaping.

[0056] In principle, the replication layer can be manufactured by known printing methods. In particular, gravure printing, flexographic printing, screen printing or inkjet printing is suitable. However, production by slot die is also possible.

[0057] Preferably, the binarized two-dimensional Fourier pattern is provided as a nanostructure and / or as a microstructure, in particular as a diffraction grating, a scattering matte structure, a reflective facet and / or a reflective microstructure. Furthermore, it is possible that the binarized two-dimensional Fourier pattern is shaped into the replication layer as a nanostructure and / or as a microstructure, in particular as a diffraction grating, a scattering matte structure, a reflective facet and / or a reflective microstructure.

[0058] As already further described above with respect to the generation of the Fourier pattern, the binarized two-dimensional Fourier pattern is preferably formed from light pixels and dark pixels. These light pixels and dark pixels are preferably arranged within a two-dimensional grid having a resolution of M×N pixels.

[0059] Commercially available printers have been shown to have a printing resolution of about 600 dpi. As a result, when the binarized two-dimensional Fourier pattern is photographed and the photographed binarized two-dimensional Fourier pattern is printed out again, a great deal of information is lost and the reconstruction of the first graphic code is no longer possible. If the binarized two-dimensional Fourier pattern is to be copied and the information contained therein is to be preserved, at least the effective resolution of the binarized two-dimensional Fourier pattern must be preserved during the copying process. For example, if either the scanner used or the printer used during the copying process has a resolution lower than the effective resolution of the binarized two-dimensional Fourier pattern, the binarized two-dimensional Fourier pattern will only be incompletely transferred and the first graphic code contained therein will be damaged and, as a result, will no longer be readable. In the case of the above pixel size, it has been shown that protection against copying using a commercially available office copier is guaranteed. However, since the binarized two-dimensional Fourier pattern is designed as a stamping structure, the optical variability of the binarized two-dimensional Fourier pattern due to the stamping structure cannot be mimicked by a copier, thereby further improving protection against forgery.

[0060] The effective resolution is preferably the resolution that the binarized two-dimensional Fourier pattern has. The effective equivalent resolution is preferably the resolution that the binarized two-dimensional Fourier pattern introduced into the stamping structure has.

[0061] The effective equivalent resolution of the binarized two-dimensional Fourier pattern introduced into the stamping structure is determined by the positioning of the first graphic code within the image template that is performed before the Fourier transform. The horizontal and vertical axes of the image template are here interpreted as (spatial) frequency axes. Frequency 0 is located at the center of the image template, and the highest frequency fx_limit or fy_limit achievable in the stamping process is located at the edge of the image template. The positioning of the first graphic code within the image template in the fx and fy directions establishes the maximum horizontal distance fx_max of the first graphic code from the image center, as well as the maximum vertical distance fy_max of the first graphic code from the image center. The quotients fx_max / fx_limit and fy_max / fy_limit are determined. The effective resolution in the x direction is the product of the quotient fx_max / fx_limit multiplied by the resolution used in the stamping process,

Number

Number

[0062] The maximum effective resolution is the larger of the value of the effective resolution in the x direction and the effective resolution in the y direction. The first graphic code is preferably positioned far outside the image template such that the value of fx_max or fy_max increases as the maximum effective equivalent resolution exceeds 600 dpi. When the first graphic code is positioned exactly at, for example, the edge of the image template, the maximum effective equivalent resolution exactly corresponds to the resolution used in the stamping process. When the first graphic code is positioned, for example, halfway between the center and the edge of the image template, the maximum effective equivalent resolution exactly corresponds to half of the resolution used in the stamping process.

[0063] At the same time, the maximum effective equivalent resolution is preferably at most about the same as the typical resolution of the camera of the authentication system. In particular, in the case of a mobile authentication system, the maximum effective equivalent resolution must not exceed 1200 dpi.

[0064] In particular, bright pixels and dark pixels can be formed from a diffraction grating, and the gratings of the bright pixels and the dark pixels differ in grating period and / or grating depth and / or orientation. The grating may be a linear grating or an intersecting grating or a meandering grating, or may include a more complex deformed form. The profile shape may be a sine wave, blazed, or may be more complex.

[0065] Furthermore, the grating period of the diffraction grating is in the range of 200 nm to 20 μm, preferably 250 nm to 10 μm, and / or the grating depth of the diffraction grating is in the range of 50 nm to 2 μm, and / or the grating depth of the diffraction grating can be 5% to 20% of the grating period.

[0066] When the contrast between the diffraction gratings of the bright pixels and the dark pixels is generated by different grating periods, the difference in this period is preferably at least 20 nm, more preferably at least 50 nm, and particularly preferably at least 100 nm.

[0067] In one embodiment, the grating is a sine wave linear grating or a meandering grating in which the orientation of the grating lines in the bright pixels and the dark pixels differs by at least 30°, preferably more than 45°, more preferably at least 60°, and particularly substantially 90°.

[0068] Alternatively, the bright and dark pixels may be formed by a structure that appears bright or dark in direct reflection, where the structure that appears dark includes a high-frequency and deep crossed grating structure and / or a crossed grating and / or a hexagonal grating and / or a mirror, and / or the structure that appears bright includes a static and / or dynamic matte structure and / or a Fourier hologram. The structure that appears dark may here appear neutrally colored and thus may appear dark gray to black, or may appear a dark color such as dark red for example. The structure that appears bright may similarly appear neutrally colored and thus may appear light gray to white, for example gold.

[0069] The structure that appears dark is preferably formed from a high-frequency and deep crossed grating structure also known as a mirror or a sub-wavelength grating. Preferably, the grating period of the crossed grating and / or the hexagonal grating is in the range of 200 nm to 450 nm, and the grating depth of the crossed grating and / or the hexagonal grating can be more than 150 nm. The crossed grating and / or the hexagonal grating offer the advantage of displaying a stronger color impression compared to a linear grating. This is advantageous especially when a binary two-dimensional Fourier pattern is to be designed to be colored.

[0070] In addition, preferably, the average spacing of the matte structure is in the range of 500 nm to 5 μm, and the average depth of the matte structure is in the range of 100 nm to 2 μm.

[0071] Alternatively, the bright and dark pixels may be formed by a blazed grating, and the orientations of the blazed gratings of the bright and dark pixels may differ by at least 150°, and in particular may be about 180°. Preferably, the grating period of the blazed grating is in the range of 3 μm to 20 μm, and / or the grating depth of the blazed grating is in the range of 500 nm to 2 μm. Thereby, a white appearance is generated, and in addition, such a blazed grating can be well replicated thermally.

[0072] To compensate for the surface roughness of the target substrate, the multilayer can also preferably include at least one compensation layer disposed between the replication layer and the adhesive layer or primer layer, or between the metal layer and the adhesive layer or primer layer. Such a compensation layer is used especially when the multilayer or the transfer ply of the multilayer is applied to a target substrate having a relatively high surface roughness, for example, uncoated cardboard or uncoated paper. The compensation layer improves the capture and reading of the binary two-dimensional Fourier pattern by the mobile terminal. It is also possible to provide several compensation layers, especially between different layers of the transfer ply. For example, between the adhesive layer and the primer layer.

[0073] The compensation layer can be produced by gravure printing, flexographic printing, screen printing, inkjet printing, by slot die, and / or by vapor deposition, especially by physical vapor deposition (PVD), chemical vapor deposition (CVD) and / or sputter deposition.

[0074] The compensation layer preferably has a layer thickness in the range of 5 μm to 20 μm.

[0075] The compensation layer can especially include materials selected individually or in combination from acrylates, polyurethanes, nitrocellulose, fillers, additives.

[0076] When the multilayer body is a hot stamping film, compensation for surface roughness may preferably be performed by preliminary printing for smoothing onto the base material. This is particularly advantageous when the target base material is paper or cardboard. By means of the preliminary printing onto the base material, so-called coated paper or coated cardboard is obtained. The preliminary printing onto the base material is preferably the deposition of a binder for smoothing the surface of the paper or cardboard. The binder preferably contains one or more components selected from chalk, kaolin, and calcium carbonate. The binder is preferably applied uniformly over the entire surface of the paper or cardboard by a doctor blade, thereby sealing the surface. If appropriate, the cardboard or paper is also guided through a calendar, during which the surface of the cardboard or paper is smoothed and calendered using rollers under the action of heat and pressure. Since the surface of the target base material is smoothed, after application of the multilayer body or the transfer ply of the multilayer body, the binary two-dimensional Fourier pattern appears more strongly, so that it is easier for a mobile terminal to capture even when the illumination quality is low.

[0077] Alternatively, when the multilayer body is used as a hot stamping film for a target base material, particularly uncoated cardboard or uncoated paper, the multilayer body may be provided to coat the surface of the target base material with water glass. Water glass means glassy and amorphous water-soluble sodium silicate, potassium silicate, and / or lithium silicate solidified from a melt or its aqueous solution. In order to be able to apply solid water glass to paper or cardboard, it is first ground into a powder. From this, by dissolving in water in the range of high temperature, particularly in the range of 100°C to 200°C, and high pressure, particularly in the range of 1 bar to 8 bar, liquid water glass (so-called liquid glass) can also be obtained as a transparent colloidal alkaline solution or as an alkaline gel. Then, this solution or gel can be applied to paper or cardboard for coating. After a predetermined drying time, the target base material has a smooth surface. Here too, after application of the multilayer body or the transfer ply of the multilayer body, the binary two-dimensional Fourier pattern appears more strongly, and thus it is easier for a mobile terminal to capture.

[0078] When the multilayer is used as a cold stamping film, a relatively thick adhesive layer can be used to compensate for surface roughness. During cold stamping, the adhesive layer is first applied immediately before application, either on the underside of the multilayer or on the upper side of the target substrate. For this purpose, cold glue, especially UV-curable cold glue, is preferably used. The cold glue is preferably applied to the target substrate and / or the multilayer at an application weight in the range of 5 g / m 2 ~6 g / m 2 of the range.

[0079] Furthermore, when the multilayer is used as a cold stamping film, it is also possible to perform pre-printing of the substrate on the target substrate before application of the multilayer or the transfer ply of the multilayer. Regarding the specifications of the pre-printing of the substrate, the above description applied here is also referred to.

[0080] Preferably, the first graphic code is a machine-readable code, especially a 2D barcode, a QR code (registered trademark) or a data matrix code. The first graphic code may be a batch-specific code, and in particular, a batch number may be provided when the first graphic code is read.

[0081] For this reason, a series of multilayers is preferably first, preferably divided into separate batches. A batch-specific batch number is assigned to each multilayer of the batch. Within the batch and within the master, several serial numbers can be used by equipping the stamping cylinder and / or the stamping tool with different unique serial numbers.

[0082] Accordingly, in particular, the multilayer body is assumed to have a second graphic code. The second graphic code is a unique code, in particular a code unique to the item or unique to the series. Particularly preferably, it is preferred that a serial number is provided when the second graphic code is read. The second graphic code is preferably openly readable. Being openly readable means that it can be captured by a conventional reading algorithm downloaded to a commercially available mobile terminal having a camera, such as a smartphone, and the information contained therein, such as the serial number, can be read. Being openly readable also means that the meaning of the second graphic code can be understood by a person without assistance. This can be, for example, a date specification or a sequential serial number or item number.

[0083] The batch number can be, like the serial number, a sequence of numbers, a sequence of characters, a sequence of characters, or a combination of the above characters. The batch number and the serial number are items of information by which a batch or an individual multilayer body can be identified. It can also be a two-dimensional array of characters or images.

[0084] The batch-specific batch number is encoded by a machine-readable and batch-specific first graphic code. The unique serial number is encoded by a unique machine-readable second graphic code. The first graphic code and / or the second graphic code are preferably conventional machine-readable codes such as 2D barcodes, in particular Data Matrix codes or QR codes. They can also be one-dimensional barcodes, but can also be Trillcode, QuickMark code, ShotCode, etc. Machine-readable graphic codes generally include optoelectronically readable symbols, which consist of lines or dots of different widths and the gaps between them having the highest possible contrast.

[0085] However, the URL of the authentication server may be stored in the second graphic code. With this URL, the user can connect to the authentication server. Such a URL can be, for example, https: / / www.authserver.com / , and the serial number is preferably part of the URL, for example, https: / / www.authserver.com / serialnumber / 12345, where 12345 is the serial number. Therefore, the consumer can connect to the authentication server via an Internet browser by scanning the machine-readable second graphic code with a smartphone.

[0086] In particular, the first graphic code, especially the batch number, and / or the second graphic code, especially the serial number, are stored in the authentication database of the authentication server, and in particular, they are stored in pairs in the authentication database of the authentication server.

[0087] Preferably, the binarized two-dimensional Fourier pattern and / or the second graphic code are captured by a mobile terminal, a data transfer connection is generated between the mobile terminal and the authentication server, and one authentication software is capable of comparing the data captured by the mobile terminal and transmitted to the authentication server with the read first graphic code, especially the batch number, and / or the read second graphic code, especially the serial number, stored in the authentication database.

[0088] Particularly preferably, the second graphic code is applied in the form of a print in front of the replication layer, at least partially in the second area, by applying the print to the carrier layer and / or the release layer and / or the protective layer, and / or the second graphic code is applied in the form of a print behind the replication layer, at least partially in the second area, by applying the print to the replication layer and / or the metal layer and / or the HRI layer and / or the adhesive layer and / or the primer layer.

[0089] These two configurations enable different optical effects. For example, when observed from the carrier layer, in the case of printing after the structuring replication step, the stamping structure can be superimposed on the print. This is not possible when observed from the carrier layer if the printing has already been carried out before the structuring replication step. In applications where the multilayer body is observed from both the carrier layer and the opposite side of the carrier layer, particularly in window or transparent substrate regions, the targeted positioning of one or more prints behind the replication layer, either in front of the carrier layer or from the carrier layer, thus enables different visual effects on the observation side.

[0090] The above two configurations preferably offer the advantage that the print is protected against both external mechanical influences and attempts at manipulation.

[0091] In this printing method step, an open machine-readable second graphic code is preferably printed on the multilayer body by means of a digital printing method, preferably with a lower resolution. The machine-readable graphic code can contain at least one unique serial number as information. By means of the unique serial number, the number is meant to be used only once in a series of multilayer bodies and is thus unique. The serial number is preferably selected from a large range of numbers or generated cryptographically, so that potential forgers cannot guess a valid serial number.

[0092] The printing can be carried out by means of a digital printing method and can potentially be selected from the group of inkjet printing, thermal transfer printing, laser printing, laser engraving.

[0093] It is also conceivable that the print or the ink is applied to the substantially smooth surface of the replication layer, particularly to the replication layer that has not yet been replicated. Here, the surface is preferably replicated at least in a predetermined region at a later point in time.

[0094] The ink can be formed as transparent, translucent, opaque, invisible, colored and / or colorless. Similarly, in principle, the print is not limited to a specific design. The print can be formed as transparent, translucent, opaque, invisible, colored and / or colorless.

[0095] Furthermore, it is also conceivable that additional machine readability can be added by providing luminescent ink, luminescent ink that is both transparent and colored, fluorescent ink, fluorescent ink that is both transparent and colored, phosphorescent including chemiluminescent ink, phosphorescent ink that is both transparent and colored, and / or liquid crystal ink having a particularly dichroic color effect, and / or ink having laser sensitivity and / or tagant.

[0096] Both photocurable, particularly UV curable ink and solvent ink and / or aqueous ink can be used.

[0097] When the print is applied to a replicated layer where the replication has already occurred, the corresponding replicated structure is preferably weakened at this point. With appropriate printing varnish and layer thickness of the printing layer, the replicated structure can even be erased or almost erased, thereby locally destroying the optical effect of the structure. The surface of the printing layer that forms a shape towards the air during the printing process is preferably smooth or isotropically matte after the drying of the printing layer. When it is preferred that a transparent print is applied in this way, neither the structure nor the print itself is visible or is hardly visible at this point. When it is preferred that an opaque print is applied, the structure is no longer visible at this point. The print appears in the corresponding coloration. The area having the erased structure preferably appears as a mirror surface or a matte surface to the observer and / or sensor after the metal layer is applied to the replicated layer.

[0098] The thickness of the applied or printed ink layer is preferably between 0.1 μm and 30 μm, particularly between 0.5 μm and 15 μm, most preferably between 0.5 μm and 15 μm, and advantageously between 1 μm and 8 μm. When solvent ink and / or aqueous ink is used, the layer thickness is preferably about 0.5 μm. When UV-curable ink is used, the layer thickness is between about 1 μm and 30 μm, preferably between 1 μm and 15 μm, most preferably between 1 μm and 8 μm.

[0099] Furthermore, it is also possible for the replication layer to be replicated together with the print applied thereto.

[0100] Furthermore, the print contains ink, preferably UV-curable ink, and / or the print is overmolded, coated, and / or encapsulated with a UV-curable replication varnish, whereby in particular initial crosslinking and / or crosslinking can also occur. Initial crosslinking is incomplete, only partial crosslinking. In particular, in addition to surface crosslinking, in particular by crosslinking of a particularly thin UV-curable layer, for example, the destructive inhibition effect by atmospheric oxygen can be prevented, so that the complete curing of the UV-curable ink can also be improved by overmolding and / or encapsulation with a UV-curable replication varnish. In particular, this can be particularly advantageous because, in the case of a UV-curable ink applied thinner than about 1.5 μm, as the layer thickness of the UV-curable ink decreases, the inhibition effect has a stronger influence or the print or ink remains sticky, for example, to the extent that the printed multilayer body cannot be wound up as a roll, preventing surface and layer crosslinking.

[0101] To cure a thin UV-curable layer, usually, during UV curing, particularly during UV curing under a protective gas such as argon or nitrogen, complex and expensive inactivation means are required. Also, when printing with a UV-curable ink is performed in the same manufacturing step as UV replication without winding up the multilayer body, these complex and expensive measures can be avoided by overlaying a UV-curable replication varnish downstream of the UV-curable print.

[0102] In addition, the UV drying process used during UV replication represents an additional post-curing for UV printing that is effective for minimizing inhibition. In particular, after any pinning (UV pre-curing), the UV curing device for UV replication can also be used during the application of the UV print without the need for an additional UV curing device to cure the print itself.

[0103] In particular, by combining the printing of UV curable ink with the UV replication process immediately downstream, it becomes possible to apply the UV ink much thinner than would actually be possible without the complex means determined by curing.

[0104] In particular, by the "initial crosslinking" of the UV curable ink or UV curable print onto the matrix around the UV replication varnish, the print will be joined to the polymer substantially inseparably at this time, and the print will advantageously no longer represent a separate layer by itself. This further makes the operation more difficult.

[0105] In particular, this is advantageous when there is a possibility of post-crosslinking of the UV curable ink due to the UV curing of the UV curable replication varnish, which can result in a higher stability of the UV curable ink.

[0106] Particularly regardless of the material composition of the print, it is further advantageous that the mechanical and / or thermal stress on the print, especially due to the contact pressure or particularly due to the temperature that occurs during thermal replication, is significantly reduced for the application of UV replication to the print.

[0107] Furthermore, it is also possible to apply a print to the already replicated surface of the replication layer. This means that a stamping structure is already provided in the replication layer. The ink is preferably applied to the structured surface or the stamping structure at least in a predetermined area. The deposition of the print is preferably carried out in alignment with the stamping structure. Ideally, the ink is applied such that the ink only partially fills the stamping structure. In particular, when the thickness of the finally applied ink layer is smaller than the depth of the stamping structure of the binarized two-dimensional Fourier pattern, partial filling of the structure occurs. Furthermore, the ink can also be applied over a part of the surface within the grid such that the ink covers only a part of the surface area of the stamping structure. The resolution of the grid is preferably below the resolution of the human eye, and the adjacent grid elements of the ink preferably have an interspacing within the range of 5 μm to 250 μm, preferably 20 μm to 200 μm, and / or the line width and / or the dot diameter and / or the individual element diameter of the grid elements are within the range of 5 μm to 250 μm, preferably 20 μm to 200 μm.

[0108] Under certain conditions, the ink can also completely fill the stamping structure of the binarized two-dimensional Fourier pattern without them being optically erased. This applies in particular when the ink has reflective or high refractive properties and its complex refractive index differs from that of the replication layer by more than 0.2 in particular. Examples of reflective inks are inks containing metallic effect pigments or metallic flakes. Examples of high refractive index inks are inks based on liquid crystals. For partial filling, in particular macroscopic structures, i.e., in particular non-diffraction-effective structures, are also suitable for the replication layer. Since the stamping structure of the binarized two-dimensional Fourier pattern is not optically erased by the print, all information is retained within the Fourier pattern, ensuring that it can always be captured and evaluated by the mobile terminal when the Fourier pattern is read out.

[0109] Preferably, the first region and the second region are arranged adjacent to each other, spaced apart from each other, or overlapping each other in at least a predetermined region. Since the binarized two-dimensional Fourier pattern is arranged in the first region and the second graphic code is arranged by printing in the second region, various creative designs are possible.

[0110] For example, the binarized two-dimensional Fourier pattern can be arranged spaced apart from the second graphic code. However, ideally, the spacing should be selected such that both the binarized two-dimensional Fourier pattern and the second graphic code can always be captured simultaneously, preferably in one acquisition, using a mobile terminal. For this purpose, the resolution of the camera used is decisive.

[0111] Alternatively, the binarized two-dimensional Fourier pattern and the second graphic code may partially overlap. Thus, the second graphic code can be arranged such that, for example, a part of the second graphic code is surrounded by the binarized two-dimensional Fourier pattern and another part of the second graphic code is surrounded by another background. For example, all decorative layers such as, for example, a color layer and / or a metal layer and / or a printing layer are considered as the background here. It is also possible for the other background itself to represent further security features. For example, all decorative layers can be a diffraction structure such as a hologram or a Kinegram(R), and / or a matte structure, and / or a blazed grating, and / or a computer-generated hologram (CGH).

[0112] Furthermore, it is also conceivable that the second region is completely arranged within the first region. Then, the second graphic code is within the binarized two-dimensional Fourier pattern. As already explained above, the print or ink of the second graphic code is applied such that the print or ink only partially fills the stamping structure of the binarized two-dimensional Fourier pattern. Thereby, all the information of the Fourier pattern can be obtained. Such a configuration provides the advantage that both the binarized two-dimensional Fourier pattern and the second graphic code can always be captured in one acquisition.

[0113] Furthermore, additional stamping structures may be provided in the third region or in a region where the binarized two-dimensional Fourier pattern does not exist. These can be, for example, individually, or in combination and / or superimposed structures selected from, among others, optical diffraction micro- or nanostructures, photorefractive micro- or nanostructures, light concentrating micro- or nanostructures, binary or continuous Fresnel lenses, binary or continuous Fresnel freeform surfaces, diffraction macrostructures, refractive macrostructures, especially lens structures or microprism structures, mirror surfaces, matte structures, especially anisotropic or isotropic matte structures, computer-generated hologram structures, blazed gratings, volume holograms, kinegrams (registered trademark), etc. This ensures an optically attractive overall impression and / or additional protection against forgery.

[0114] Both spatial separation of the binarized two-dimensional Fourier pattern from the additional stamping structure and integration of the binarized two-dimensional Fourier pattern in at least one design element of the additional stamping structure are conceivable. As used herein, spatial separation preferably means the distance between the binarized two-dimensional Fourier pattern and the additional stamping structure. As used herein, a design element preferably means a complete motif and an incomplete motif, i.e., a fragment of a motif. A motif is in particular selected from images, symbols, logos, emblems, flags, portraits, alphanumeric characters, or combinations thereof. For example, the binarized two-dimensional Fourier pattern can be integrated into a motif to generate a particularly high level of protection against counterfeiting of the multilayer body.

[0115] Furthermore, at least one glossy color layer can be arranged over the entire surface, or at least partially, within a predetermined area, or over the entire surface behind at least one first area and / or second area in the viewing direction of the observer. If the glossy color layer is arranged behind the first area where the binarized two-dimensional Fourier pattern is arranged and / or behind the second area where the second graphic code is arranged, the effect of the glossy color layer is preferably only visible at the point where the binarized two-dimensional Fourier pattern has bright pixels and / or the second graphic code has bright pixels, in particular white or transparent pixels.

[0116] This glossy color layer can be directly adjacent to the metal layer or separated from the metal layer by a dielectric intermediate layer. The at least one glossy color layer here acts as a colored background and thus as an optically contrasting area, generating a capturable color impression in the corresponding coloring of the color layer for the observer. In addition, the contrast with the background is increased, which also improves the capture of the binarized two-dimensional Fourier pattern by the mobile terminal.

[0117] This is particularly advantageous when at least one glossy color layer that reflects directly, preferably over an inclination angle range of at least 0° to 30° and / or preferably over an inclination angle range of at least 30° to 60° with respect to the normal, in particular in the CIELAB color space, has a total color difference dE of 50 to 270, preferably 100 to 270, more preferably 130 to 270, from the first region and / or the second region.

[0118] Furthermore, it is particularly advantageous when at least one glossy color layer that reflects directly, preferably over an inclination angle range of at least 0° to 30° and / or preferably over an inclination angle range of at least 30° to 60° with respect to the normal, has a lighter color with a particularly higher lightness value L and the first region and / or the second region with a particularly lower lightness value L, in particular the dark pixels of the first and / or second regions. Thereby, the color effect of the glossy color layer can act through the bright pixels, thereby further enhancing the contrast of the bright pixels with respect to the dark pixels.

[0119] For authentication, the first-mentioned authentication method is advantageously carried out, which is preferably carried out using an authentication system. The authentication method is suitable for being carried out using one of the above-mentioned multilayer bodies or one of a series of multilayer bodies manufactured according to one of the above-mentioned manufacturing methods.

[0120] The authentication method is carried out according to the present invention using a mobile terminal having a camera. The mobile terminal may be a commercially available smartphone, and the camera may be a commercially available camera incorporated in the smartphone.

[0121] Image capture by the camera is typically performed as an RGB color image having an image representation of three color channels: red (0 ≦ R ≦ 255), green (0 ≦ G ≦ 255), and blue (0 ≦ B ≦ 255). For evaluation, the color image is converted into a grayscale image. The respective grayscale value of each pixel can be determined as the weighted sum of the color channels. G = CR· R + C G· G + C B· B

[0122] Coefficient C R , C G , and C B may vary depending on the type of sensor used and the conversion algorithm.

[0123] Combination C R = 1 / 4, C G = 1 / 2 and C B = 1 / 4 (Bayer sensor) or C R = C G = C B = 1 / 3 (HSI model) is preferably used.

[0124] Contrast, in this context, refers to the value K calculated from the maximum grayscale value I max and the minimum grayscale value I min of the binary two-dimensional Fourier pattern according to the following formula.

Equation

[0125] Tests on the readout behavior revealed that a minimum contrast of K = 0.05 is required in an ideal lighting situation.

[0126] On the other hand, under actual conditions where the lighting quality changes, a minimum contrast of K = 0.1 is preferred for a robust readout process.

[0127] In particular, the contrast K in the grayscale image of the stamping structure is preferably in the range of 0.1 to 0.2. These two limit values are also included in the above range.

[0128] The contrast of the binary two-dimensional Fourier pattern is generated, as described above, through the bright and dark pixels formed by the stamping structure.

[0129] Due to the generated contrast, it is possible to completely capture the first graphic code of the multilayer body.

[0130] In particular, when an image is captured, it is also possible to capture the second graphic code of the multilayer body. The captured image is supplied to a second reading algorithm for the second graphic code, the second graphic code is read, and the read first graphic code and the read second graphic code are checked.

[0131] Furthermore, a batch number is provided by reading the first graphic code, a serial number is provided by reading the second graphic code, and it is possible to check the batch number and the serial number. In this process, it is preferably checked whether the batch number and the serial number and their assignment to each other are valid.

[0132] First, a batch-specific batch number and a unique serial number are assigned to each other in a pair and preferably stored in a database. The serial number is preferably formed in a non-consecutive manner and encrypted cryptographically so that a forger cannot easily recall or infer a valid serial number.

[0133] Furthermore, the read first graphic code, in particular the read batch number, is supplied to an authentication server and compared with a valid first graphic code, in particular a batch number, stored in the authentication server. It is also possible to be authenticated when the read first graphic code, in particular the batch number, matches one of the stored valid first graphic codes, in particular the batch number.

[0134] Furthermore, the read second graphic code, particularly the read serial number, is supplied to the authentication server and compared with the valid second graphic code, particularly the serial number, stored in the authentication server. It can be authenticated when the read second graphic code, particularly the serial number, matches one of the stored valid second graphic codes, particularly the serial number.

[0135] Particularly preferably, when the first graphic code is authenticated, or when both the first graphic code, particularly the batch number, and the second graphic code, particularly the serial number, are authenticated, the multilayer body is authenticated.

[0136] When the combination of the read first graphic code, particularly the batch number, and the read second graphic code, particularly the serial number, is authenticated, the multilayer body is preferably authenticated.

[0137] Therefore, both the serial number and the batch number are stored in the database, where the database is connected to the authentication server by a data transfer method. The serial number and the batch number are compared with the serial number and the batch number stored in the database. When both numbers match individually and as a pair, the multilayer body is authenticated. Thus, it is the original multilayer body.

[0138] If the batch number or the first graphic code cannot be read because, for example, it is a blurred photocopy of the binarized two-dimensional Fourier pattern of the multilayer body, the multilayer body is not authenticated. If the serial number or the second graphic code has already been queried once or multiple times, the serial number or the second graphic code is preferably no longer authenticated in the case of the next query. The serial number or the second graphic code is preferably queried once or a specific number of times and then blocked or invalidated.

[0139] All or part of the Fourier inverse transform program required for the authentication method, the first reading algorithm, and / or the second reading algorithm may be arranged in the mobile terminal. However, it is also conceivable that one or more of these programs are stored in the authentication server. A database storing a pair of a valid batch number and a serial number is preferably also stored in the authentication server.

[0140] It is also checked whether the assignment of the stored serial number and the stored batch number matches the assignment of the read batch number and the read serial number. If the individual numbers and assignments match, an authentication signal is output to the mobile terminal. The connection between the mobile terminal and the database server can be made via a conventional, preferably wireless connection such as a WLAN connection to the Internet, a 3G / 4G / 5G connection to the Internet, or a similar connection.

[0141] In particular, the authentication system described first is used to execute the authentication method.

[0142] Furthermore, it is possible for the authentication system to further have a second reading algorithm for a second graphic code that reads the second graphic code, and the read first graphic code, in particular the batch number, and the read second graphic code, in particular the serial number, are authenticated by the authentication server.

[0143] In particular, the inverse Fourier transform program can be downloaded onto a mobile terminal, and this also applies when the binarized two-dimensional Fourier pattern captured by the camera is transmitted by the transceiver unit to the authentication server. Similarly, the first and second reading algorithms can be stored either on the mobile terminal or on the database authentication server. Conveniently, however, both reading programs, such as the inverse Fourier transform program, are stored on the mobile terminal, so that only the batch number specific to the batch already read or the first graphic code and the unique serial number read or the second graphic code need to be transmitted to the authentication server via the transceiver unit of the mobile terminal. The numbers can be transmitted in a data volume much smaller than the Fourier pattern scanned by the camera.

[0144] Hereinafter, the present invention will be described with reference to several embodiments using the accompanying drawings. The embodiments should not be understood as limiting.

Brief Description of the Drawings

[0145]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10a

Figure 10b

Figure 11a

Figure 11b

Figure 11c

Figure 12a

Figure 12b

Figure 12c

Figure 13a

Figure 13b

Embodiments for Carrying Out the Invention

[0146] FIG. 1 shows a schematic view of a multilayer body 1. The multilayer body 1 can be, for example, a laminate film or a transfer film. Also, the multilayer body 1 can serve to provide at least one security element protected against forgery to a security document.

[0147] As shown in FIG. 1, the multilayer body 1 has a carrier layer 11 and a replication layer 12. The first graphic code 21 that has been Fourier-transformed into the binarized two-dimensional Fourier pattern 24 is embedded in the replication layer 12 by a stamping structure. In the design according to FIG. 1, the stamping structure is designed over the entire surface. However, the stamping structure may be at least partially formed in a first region within the replication layer 12. In addition, the multilayer body 1 has a metal layer 13 applied over the stamping structure of the replication layer 12. Thereby, the binarized two-dimensional Fourier pattern 24 appears optically variable. Thereby, the protection against forgery of the Fourier pattern is significantly improved. This is because the optical variability of the Fourier pattern cannot be captured by conventional copying by a commercially available copier or a combination of a commercially available camera and a commercially available printer.

[0148] The metal layer 13 is preferably formed individually, as an alloy, or as a eutectic, and is selected from aluminum, chromium, gold, copper, tin, indium, and silver. The metal layer 13 is preferably manufactured by vapor deposition, particularly by vacuum vapor deposition. The vapor-deposited metal layer 13 is achieved over the entire surface, optionally preserved over the entire surface, or structured by a known demetallization method such as etching, lift-off (cleaning varnish method), or photolithography, whereby it can subsequently only be present partially. The layer thickness of the metal layer is particularly between 10 nm and 500 nm.

[0149] However, the metal layer 13 may also consist of a printed layer, particularly a printed layer of metal pigments in a binder. These printed metal pigments may be applied over the entire surface or partially, and / or may have different colorings in different regions of the surface. The layer thickness of the metal layer of the metal pigments is particularly between 1 μm and 10 μm.

[0150] The metal layer 13 may be manufactured from a varnish having conductive metal pigments, particularly the varnish may be printed and / or poured.

[0151] Alternatively, instead of the metal layer 13, an HRI or LRI layer (High Refractive Index - HRI, Low Refractive Index - LRI) may be used. Such a dielectric HRI or LRI layer consists of, for example, a vapor deposition layer of a metal oxide, a metal sulfide, titanium oxide, etc. The layer thickness of such a layer is preferably 10 nm to 500 nm.

[0152] Also, the multilayer body 1 according to FIG. 1 includes an adhesive layer 14. The adhesive layer 14 provides adhesion to the target substrate after application. As an alternative, a primer layer may be present. In this case, the adhesive layer 14 is applied to either the multilayer body 1 or the target substrate before application. The primer layer enhances the adhesiveness to the adhesive.

[0153] The adhesive layer 14 and / or the primer layer 14 are preferably formed from a varnish and are individually selected from PMMA, PVC, acrylate, polyamide, polyvinyl acetate, hydrocarbon resin, polyester, polyurethane, chlorinated polyolefin, polypropylene, epoxy resin and / or polyurethane polyol, in some sub - layers and / or as a mixture, especially in combination with an inactivated isocyanate, a filler such as SiO2 and / or TiO2. The adhesive layer 14 or the primer layer 14 can further contain a filler such as SiO2 and / or TiO2. In addition to the adhesive layer, a primer layer can also be provided.

[0154] The layer thickness of the adhesive layer 14 and / or the primer layer 14 is preferably between 0.5 μm and 20 μm, particularly preferably between 1.5 μm and 5 μm. The adhesive layer 14 and / or the primer layer 14 can be manufactured by gravure printing, flexographic printing, screen printing, inkjet printing, and / or by a slot die.

[0155] Furthermore, the adhesive layer 14 or the primer layer 14 serves the purpose of filling the depressions of the stamping structure. Thereby, it is guaranteed that the depressions and / or protrusions of the stamping structure are encapsulated and thus protected from the influence of the external environment.

[0156] The target substrate is, for example, a security document, in particular an identity card or a passport. However, the target substrate may also be a packaging material. However, a target substrate made of cardboard or paper is also envisaged.

[0157] Figure 2 shows a further schematic view of the multilayer body 1. The multilayer body 1 in Figure 2 corresponds to the structure of the multilayer body 1 according to Figure 1, but differs in that the release layer 15 and the protective layer 16 are arranged between the carrier layer 11 and the replication layer 12. The release layer 15 can be present both partially and over the entire surface.

[0158] The release layer 15 in particular ensures that the layers of the multilayer body 1 can be separated from the carrier layer 11 non-destructively. The release layer 15 is preferably formed from wax, polyethylene (PE), polypropylene (PP), cellulose derivatives and / or poly(organo)siloxanes. The above wax can be a natural wax, a synthetic wax, or a combination thereof. The above wax is, for example, carnauba wax. The above cellulose derivatives are, for example, cellulose acetate (CA), cellulose nitrate (CN), cellulose acetate butyrate (CAB) or a mixture thereof. The above poly(organo)siloxanes are, for example, silicone binders, polysiloxane binders or mixtures thereof. The release layer 15 preferably has a layer thickness in the range of 1 nm to 500 nm, in particular in the range of 5 nm to 250 nm, particularly preferably in the range of 10 nm to 250 nm.

[0159] The release layer 15 can be produced by known printing methods. In particular, gravure printing, flexographic printing, screen printing, inkjet printing, or application by slot die is suitable for this. However, the release layer 15 may also be formed by evaporation, physical vapor deposition (PVD), chemical vapor deposition (CVD) and / or sputter deposition.

[0160] The protective layer 16 is preferably a thermoplastic layer, a thermosetting layer or a radiation-curing layer of varnish, which is individually selected from several sub-layers and / or as a mixture, from PMMA, PVC, melamine, acrylate, polyurethane, crosslinking agent, photoinitiator, additive, defoaming agent, leveling agent, wetting agent. The protective layer can also consist of a radiation-curing dual-curing varnish. This dual-curing varnish can be thermally pre-crosslinked in a first step during and / or after application in liquid form. Preferably, in a second step, especially after processing of the multi-layer film, the dual-curing varnish is radically post-crosslinked via especially high-energy radiation, preferably UV radiation. This type of dual-curing varnish can consist of different polymers or oligomers having unsaturated acrylate or methacrylate groups. These functional groups can be radically crosslinked with each other, especially in the second step. For the thermal pre-crosslinking in the first step, in the case of these polymers or oligomers, it is advantageous that at least two or more alcohol groups are also present. These alcohol groups can be crosslinked with polyfunctional isocyanates or melamine formaldehyde resins. Different UV raw materials such as epoxy acrylate, polyether acrylate, polyester acrylate, especially acrylate acrylate, are preferably considered as unsaturated oligomers or polymers. Both blocked representatives and unblocked representatives based on TDI (TDI = toluene-2,4-diisocyanate), HDI (HDI = hexamethylene diisocyanate) or IPDI (IPDI = isophorone diisocyanate) can be considered as isocyanates. The melamine crosslinking agent can be in a fully etherified version, in an imino type, or can represent a benzoguanamine representative.

[0161] The protective layer 16 preferably has a layer thickness in the range of 50 nm to 30 μm, preferably 1 μm to 5 μm. The protective layer 16 can be produced by gravure printing, flexographic printing, screen printing, inkjet printing, or by slot die, and / or by vapor deposition, especially physical vapor deposition (PVD), chemical vapor deposition (CVD) and / or sputter deposition.

[0162] A further schematic view of the multilayer body 1 is shown in FIG. 3. This multilayer body 1 substantially corresponds to the multilayer body 1 in FIG. 2, but differs in that this multilayer body 1 further has at least one compensation layer 17. This compensation layer 17 can be arranged between the replication layer 12 and the adhesive layer 14 or the primer layer 14, or between the metal layer 13 and the adhesive layer 14 or the primer layer 14 as shown in FIG. 3.

[0163] When the multilayer body 1 is applied to a target substrate having a rough substrate, for example, uncoated cardboard, the reading of the binary two-dimensional Fourier pattern 24 is improved by the compensation layer 17. Tests under different light conditions have revealed that the reading of the Fourier pattern by a smartphone is made more difficult without the compensation layer 17.

[0164] The compensation layer 17 is preferably applied by a printing method. Gravure printing, flexographic printing, screen printing, inkjet printing, or by slot die is preferably suitable for this. However, the compensation layer 17 can also be formed by evaporation, physical vapor deposition (PVD), chemical vapor deposition (CVD), and / or sputter deposition.

[0165] A further schematic view of the multilayer body 1 is shown in FIG. 4. The multilayer body 1 substantially corresponds to the embodiment according to FIG. 2, but differs in that a second graphic code is applied in the form of a print 18 behind the replication layer 12 by applying the print 18 to the replication layer 12 at least partially in a second region.

[0166] The stamping structure of the binary two-dimensional Fourier pattern 24 is applied over the entire surface in the first region. The first region extends over the entire surface area of the multilayer body 1. The second region is arranged overlapping the first region. Thereby, the print 18 covers the binary two-dimensional Fourier pattern 24 within the second region.

[0167] Print 18 can be applied to the replication layer 12 that has not yet been replicated. The replication layer 12 or the replication varnish, in particular, still has a smooth surface. Then, the replication is performed, especially after the print 18 is provided. The stamping structure of the binarized two-dimensional Fourier pattern 24 can be introduced into both the print 18 and the replication layer 12 by replication. The batch-specific items of information within the replication layer 12 in the form of the binarized two-dimensional Fourier pattern 24 can be combined, for example, with the individualized, especially series-specific print 18 in the form of a second graphic code. The replication in the print 18 can represent an additional protection means against forgery since the print 18 is thereby further integrated into the entire multilayer film system by one more layer.

[0168] Ideally, the print 18 is applied to the substantially smooth surface of the replication layer 12 or the replication varnish, and then the surface is preferably replicated at least in a predetermined region at a later point in time.

[0169] However, it is also possible for the print 18 to be applied to the replication layer 12 that has already been replicated, and thus to the replication layer 12 in which the stamping structure of the binarized two-dimensional Fourier pattern 24 has already been provided. The print 18 is preferably applied to the stamping structure or the replication layer 12 at least in a predetermined region or at least partially in a second region.

[0170] When the print 18 is applied to the replication layer 12 that has already been replicated, if the print 18 has a refractive index similar to that of the replication layer 12, especially a refractive index with a difference smaller than 0.2, at least a partial region of the stamping structure can be erased thereby. This occurs especially when the print 18 is applied with a layer thickness greater than the depth of the structure. However, it is also possible for the ink to be applied with a smaller layer thickness such that the print 18 follows the topology of the structure and thus becomes especially part of the diffraction. This is especially conceivable when solvent ink is used.

[0171] Furthermore, the print 18 can also be applied such that the print 18 only partially fills the stamping structure on the surface of the replication layer 12. In particular, when the finally applied layer thickness of the print 18 is smaller than the depth of the replication structure 28, only a partial filling of the stamping structure occurs. Under certain conditions, the print 18 can also fill the stamping structure without the stamping structure being optically erased. This applies in particular when the print 18 has reflective or high refractive properties and its complex refractive index differs from that of the replication layer 12 by more than 0.2 in particular. Examples of reflective prints are inks containing metallic effect pigments or metal flakes. Examples of high refractive index inks are inks based on liquid crystals.

[0172] The print 18 is preferably applied to the replication layer 12 with a layer thickness greater than the depth of the stamping structure to be introduced into the replication layer 12. In particular, the layer thickness of the applied print 18 is substantially twice the thickness of the layer thickness of the stamping structure to be introduced into the replication layer 12. A layer thickness of the print 18 that is at least twice the depth of the structure to be introduced into the replication layer 12 is advantageous when replication is not carried out until after the application of the ink. Thereby, during replication, it is prevented that the introduced stamping structure completely penetrates the applied print 18. Thus, it is thereby ensured that the second graphic code can always be captured by a machine.

[0173] In another embodiment, the print 18 is preferably applied with a layer thickness less than the depth of the stamping structure to be introduced into the replication layer 12. During replication, the print 18 can thereby be penetrated by the introduced stamping structure through the entire layer thickness of the print 18. Thereby, the print 18 is also visible from the carrier layer 11 through the passing stamping structure and can receive a high-resolution microstructuring that exceeds the printing resolution of a conventional inkjet printer and thus represents a further security feature.

[0174] The replication layer 12 is preferably formed from a thermoplastic varnish or a radiation-curable varnish and is individually selected from acrylates, celluloses, PMMA, polyurethanes, isocyanates in some sub-layers and / or as a mixture. The replication layer 12 can also consist of a thermoplastic varnish. The stamping structure is preferably shaped into the varnish by heat and pressure 18 by the action of a stamping tool. Furthermore, it is also possible that the replication layer 12 is formed by a UV-crosslinkable varnish and the stamping structure is shaped into the replication layer 12 by UV replication. The surface structure is shaped onto the uncured replication layer 12 by the action of a stamping tool, and the replication layer 12 is cured directly during or after shaping by irradiation with UV light. The stamping tool can be manufactured directly or via further manufacturing steps such as, for example, galvanic forming and / or laser engraving and / or mechanical forming, or can function as a template for a further stamping tool.

[0175] In principle, the replication layer 12 can be manufactured by known printing methods. In particular, gravure printing, flexographic printing, screen printing or inkjet printing are suitable. However, production by slot die is also possible.

[0176] The stamping structure shaped into the replication layer 12 is preferably a nanostructure and / or a microstructure, in particular a diffraction grating, a scattering matte structure, a reflective facet and / or a reflective microstructure, which forms a binary two-dimensional Fourier pattern 24.

[0177] The binary two-dimensional Fourier pattern 24 is preferably formed from light pixels 31 and dark pixels 32 arranged in a two-dimensional grid having a resolution of M×N pixels.

[0178] When the bright pixels 31 and the dark pixels 32 of the binary two-dimensional Fourier pattern 24 are formed from a diffraction grating, preferably, the gratings of the bright pixels 31 and the dark pixels 32 differ in grating period and / or grating depth and / or orientation. The grating may be a linear grating, or an intersecting grating, or a meandering grating, or may include more complex deformation patterns. The profile shape can be sinusoidal, blazed, or more complex. The grating period of the diffraction grating is preferably in the range of 200 nm to 20 μm, preferably 250 nm to 10 μm. In particular, the grating depth of the diffraction grating is in the range of 50 nm to 2 μm. Further, it is possible that the grating depth of the diffraction grating is 5% to 20% of the grating period.

[0179] However, it is also possible that the bright pixels 31 and the dark pixels 32 are formed by a structure that appears bright or dark in direct reflection, and the structure that appears dark includes a high-frequency and deep intersecting grating structure and / or an intersecting grating and / or a hexagonal grating and / or a mirror, and / or the structure that appears bright includes a static and / or dynamic matte structure and / or a Fourier hologram. The grating period of the intersecting grating and / or the hexagonal grating is preferably in the range of 200 nm to 450 nm. Further, it is possible that the grating depth of the intersecting grating and / or the hexagonal grating is more than 150 nm. Preferably, the average interval of the matte structure is in the range of 500 nm to 5 μm, and the average depth of the matte structure is in the range of 100 nm to 2 μm.

[0180] However, it is also conceivable that the bright pixels 31 and the dark pixels 32 are formed by a blazed grating, and the orientations of the blazed gratings of the bright pixels 31 and the dark pixels 32 differ by at least 150°, particularly about 180°. The grating period of the blazed grating is preferably in the range of 3 μm to 20 μm, and / or the grating depth of the blazed grating is in the range of 500 nm to 2 μm.

[0181] The replication layer 12 preferably has a layer thickness between 200 nm and 5 μm. When the replication layer 12 has a diffraction surface structure, the layer thickness is preferably between 0.3 μm and 6 μm.

[0182] The replication or structuring of the surface of the replication layer 12 can be carried out in different ways. In the case of the thermoplastic replication layer 12, thermal replication is carried out, in particular under the action of heat and / or pressure 18. The print 18, in particular the second graphic code, may already be applied to the replication layer 12 at this point. In this case, the print 18 is applied substantially to the smooth surface of the replication layer 12.

[0183] UV replication can also be considered. If the print 18, in particular the second graphic code, is formed of UV-curing ink, the UV print can advantageously be protected by a UV-curing replication varnish. Reactive groups that "initially crosslink" on the UV-curing replication varnish are arranged on the surface of the UV-curing ink. By encapsulating in the UV replication varnish during UV curing, the inhibition effect that becomes active, especially in the case of particularly thin UV-curing layers, is minimized, so that the crosslinking, and thus the stability, of particularly thin prints made of UV-curing ink can be particularly improved. With the described encapsulation, a smaller layer thickness of the print 18 formed of UV-curing ink can also be achieved without complex and expensive inactivation means. As in the case of thermal replication, mechanical stress and / or thermal stress due to contact pressure can also be reduced.

[0184] The replication layer 12 is preferably provided with a metal layer 13 or a high refractive index (HRI) layer with a high refractive index. The metal layer 13 and the HRI layer are opaque, translucent or transparent, and in particular the transparency can depend on the viewing angle.

[0185] As can be seen in FIG. 4, the metal layer 13 covers the print 18, in particular the second graphic code, over the entire surface. However, since the direction of observation of the applied multilayer body 1 is brought onto the replication layer 12, the metal layer 13 forms the background of the print 18 or the second graphic code.

[0186] FIG. 5 shows a further schematic view of the multilayer body 1. The multilayer body 1 substantially corresponds to the embodiment according to FIG. 4, but differs in that the multilayer body 1 further has a compensation layer 17. As already explained in connection with FIG. 3, the compensation layer 17 can be arranged between the replication layer 12 and the adhesive layer 14, or between the metal layer 13 and the adhesive layer 14 as shown in FIG. 5. For the specifications of the compensation layer 17, please refer to the foregoing text.

[0187] FIG. 6 shows a further schematic view of the multilayer body 1. This corresponds to the structure of the multilayer body 1 according to FIG. 4. It differs in that the print 18 or the second graphic code in FIG. 6 is applied in front of the replication layer 12.

[0188] As can be seen in FIG. 6, the print 18 is applied to the protective layer 16 at least partially in the second region. The protective layer 16 is preferably formed over the entire surface. Thereby, a multilayer body 1 is obtained in which the print 18 or the second graphic code is arranged on the protective layer 16 within at least a predetermined region. In particular, the print 18 is arranged under the protective layer 16 in the viewing direction and is thus also protected by the protective layer 16 from mechanical, chemical and / or physical influences.

[0189] In an alternative design, the print 18 can be applied to the release layer 15 at least partially in the second region, especially where the release layer 15 is formed over the entire surface. Thereby, a multilayer body 1 is obtained in which at least one print 18 or the second graphic code is arranged on the release layer 15 within at least a predetermined region.

[0190] FIG. 7 shows a further schematic view of the multilayer body 1. The multilayer body 1 corresponds to the structure of the multilayer body 1 according to FIG. 6, but differs in that the multilayer body 1 according to FIG. 7 also has a compensation layer 17.

[0191] The batch number 20 in the Data Matrix code as the first graphic code 21, in this case the encoding of the sequence ABCDEF is shown in FIG. 8. The batch number 20 is designed as desired and can be a sequence of characters, characters, numbers, bits, or combinations thereof. The batch number 20 is encoded into the Data Matrix code according to FIG. 8. The Data Matrix code is a machine-readable first graphic code 21 in this embodiment. The Data Matrix code is the same for each multilayer body 1 of a batch.

[0192] The batch number 20 can also be encrypted with any other machine-readable code. For example, the batch number 20 in FIG. 8 can also be encoded with a QR code or a barcode.

[0193] Next, the first graphic code 21, here the Data Matrix code, is preferably converted into a related Fourier pattern. For this purpose, the first graphic code 21 is positioned within the empty image template 22 according to FIG. 9. This plane is regarded as the frequency plane. The function is defined within the frequency plane covered by the fx frequency and the fy frequency. Depending on where the Data Matrix code is positioned within the fx, fy plane, it is formed by higher or lower frequencies. The image template has a size of M×N pixels.

[0194] Next, the function G(fx, fy) is formed from the arrangement of the first graphic code 21 in the empty image template. The M×N pixel image template forms the definition range of the function G(fx, fy). The function G(fx, fy) consists of the product of an amplitude function and a phase function. The amplitude function is illustrated in FIG. 10a for the Data Matrix code of FIG. 8. The amplitude function is 0 at white points and 1 or another constant value at black points. This means that the amplitude function is formed as a real-valued function having function values 0 and 1.

[0195] The amplitude function is multiplied by the appropriate phase function e iφ (fx, fy). The phase function eiφ (fx, fy) can be a random phase, but other phase distributions are also known in the state of the art (Akahori, H., Comparison of deterministic phase coding with random face coding in terms of dynamic range, Appl. Opt. 12, pp. 2336-43 (1973)). However, in the case of a random phase, there is a substantial advantage that the random phase is assigned to each frequency in the image template. This makes it easier to later read out the binarized two-dimensional Fourier pattern 24.

[0196] The phase φ(fx, fy) selected here is formed as a random grayscale value of the data matrix code and is shown in FIG. 10b. The contour of the phase corresponds to the data matrix code, except that the values are random grayscale values between white and black instead of 0 (white) and 1 (black). Within the data matrix code, random grayscale values between white and black are assigned to each pixel. Here, the assignment of grayscale values to numbers between 0 and 2π occurs. If the grayscale value is black, the phase is 2π, and if the grayscale value is white, the phase is 0. Other grayscale values are assigned angles between 0 and 2π according to the grayscale. The darker the color, the larger the angle. In this way, the random grayscale image can be uniquely converted into a phase correlation function, and the amplitude function illustrated in FIG. 10a is multiplied by the phase correlation function e iφ (fx, fy) to obtain the complex-valued function G(fx, fy).

[0197] The complex function G(fx, fy) is formed over the defined range according to FIG. 9 of M×N pixels. M indicates the number of pixels in the fx direction, and N indicates the number of pixels in the fy direction. In this example, M = N = 512. The complex function G(fx, fy) is Fourier-transformed in the normal way, thereby forming a new two-dimensional complex function, the two-dimensional Fourier transform g(x, y), for the M×N pixels. As an alternative to the Fourier transform, in this method, an inverse Fourier transform or a Fourier inverse transform can also be used because, due to the symmetry condition between the Fourier transform and the inverse Fourier transform, no differences related to the present invention occur.

[0198] The real part of the Fourier transform g(x, y) is here called the two-dimensional Fourier pattern 23 and is shown in FIG. 11a. The two-dimensional Fourier pattern 23 is also batch-specific and has gray-scale values between white and black.

[0199] FIGS. 11b and 11c show the so-called binarized Fourier pattern 24 of the Fourier pattern 23 of FIG. 11a. Binarization means that either a pixel value of 1 or a pixel value of 0 is assigned to each pixel of the Fourier pattern 23 of FIG. 11a. Black is used as the pixel value of 1, and white is used as the pixel value of 0. However, two different gray-scale values or two different color values are also conceivable. For binarization, various methods are known from the literature on computer-generated holograms, for example, the phase-stepping method (Goodman, J.W., Introduction to Fourier Optics, McGraw-Hill (New York) (1996)).

[0200] A preferred method also used here is the discrete binarization of the real part of the Fourier transform g(x,y). Here, a threshold is selected, and all values of the real part of the Fourier transform g(x,y) below the threshold are assigned a pixel value of 0, and all other values are assigned a pixel value of 1. The threshold can be selected such that, as occurs in FIG. 11b, 50% obtains a pixel value of 1 and is thus black, and 50% obtains a pixel value of 0 and is thus white. FIG. 11b represents a two-dimensional Fourier pattern 24 that is 50% binarized. However, the threshold can also be selected such that any other desired percentage receives a pixel value of 1 and the remaining pixels receive a pixel value of 0. A two-dimensional Fourier pattern 24 that is 20% binarized is shown in FIG. 11c. The percentage of binarization is preferably less than 50%, more preferably less than 20%. The binarization is typically about 15%.

[0201] The amplitudes of the inverse Fourier transforms 25, 26 of the Fourier patterns 23, 24 in FIGS. 11a, 11b, and 11c are shown in FIGS. 12a, 12b, and 12c. By using the real part as the Fourier pattern, it can be seen that symmetric, so-called negative orders form. Furthermore, it can be seen that binarization increases noise (the gray shadow of the background), and lower binarization leads to greater noise. Nevertheless, the inverse Fourier patterns 25, 26 in FIGS. 12a, 12b, and 12c remain machine-readable in any case.

[0202] The multilayer body 1 applied on a paper substrate when the surface of the multilayer body 1 is observed vertically is shown in FIG. 13a. FIG. 13a is a black-and-white scan with a scan resolution of 1200 dpi. The transfer prime of the multilayer body 1 was applied to this paper substrate over the entire surface by cold stamping, and then the carrier layer 11 was peeled off. Thus, the binarized two-dimensional Fourier pattern 24 over the entire surface that is optically variable is recognizable to the observer. Since the binarized two-dimensional Fourier pattern 24 is optically variable, it cannot be replicated by a conventional printer or copier. Thus, additional protection against forgery is provided. A GC2 chromoboard was used as the paper substrate.

[0203] The layer structure of the multilayer body 1 to be applied can correspond to the structure shown in FIG. 3. Accordingly, the applied transfer ply of the multilayer body 1 includes, in the following order, a protective layer 16, a replication layer 12, a metal layer 13, a compensation layer 17, and a primer layer. The binary two-dimensional Fourier pattern 24 is formed as a stamping structure over the entire surface of the replication layer 12 in a first region extending over the entire surface of the entire multilayer body 1.

[0204] A detailed view of the nickel shim used for replicating the stamping structure onto the replication layer 12 of the applied multilayer body 1 in FIG. 13a is shown in FIG. 13b. The section of the nickel shim shown in FIG. 13b corresponds to the upper left corner of the binary two-dimensional Fourier pattern 24 in FIG. 13a. The total size of the original section corresponds to a surface area of about 15 mm 2 The nickel shim can be used directly or via further manufacturing steps such as, for example, galvanic forming and / or laser engraving and / or mechanical forming as a stamping tool or can function as a template for a stamping tool.

[0205] The bright pixels 31 and dark pixels 32 of the stamping structure are recognizable in FIG. 13b, and each pixel has a surface area of 30 μm 2 The dark pixels 32 are designed as diffraction gratings and the bright pixels 31 are designed as scattering matte structures. This combination achieves a sufficiently good contrast between the bright pixels 31 and the dark pixels 32, which can be captured later by a mobile terminal and its camera.

[0206] The pixels have a length in two lateral directions, preferably less than 45 μm, in particular less than 30 μm. The surface area of the pixels is preferably less than 1800 μm 2 and in particular less than 900 μm 2 and less than.

[0207] As already explained, the protection against copying for conventional printers and copiers is ensured by the resolution of the binarized two-dimensional Fourier pattern 24. Commercially available printers usually have a printing resolution of less than 600 dpi. As a result, when the binarized two-dimensional Fourier pattern 24 is photographed and the photographed binarized two-dimensional Fourier pattern 24 is printed out again, a great deal of information is lost and the reconstruction of the first graphic code 21 is no longer possible.

[0208] However, the effective resolution of the binarized two-dimensional Fourier pattern 24 is preferably greater than the equivalent printing resolution of conventional printers, in particular greater than 600 dpi. More preferably, the binarized two-dimensional Fourier pattern has an effective resolution of up to 2500 dpi, preferably up to 1200 dpi, particularly preferably up to 900 dpi. Such a low resolution is necessary so that the structure can actually be captured by a commercially available camera by normal imaging.

[0209] The binarized two-dimensional Fourier pattern 24 over the entire surface is advantageously combined with at least one further optically variable nanostructure and / or microstructure. This further optically variable nanostructure and / or microstructure can take the form of additional information such as a logo, lettering or icon. Fine line design elements such as guilloches are also possible. This is represented in FIG. 14 as the letters "OK" by way of example. In this example, a diffractive linear grating is provided in the surface area having the letters, so that these letters light up with a characteristic rainbow effect when tilted. The further optically variable nanostructure and / or microstructure preferably reduces the surface area of the binarized two-dimensional Fourier pattern 24 in the example according to FIG. 14. To ensure reliable reading of the binarized two-dimensional Fourier pattern 24, the surface coverage of the further optically variable nanostructure and / or microstructure is preferably less than 50%, more preferably less than 30%, particularly preferably less than 20% with respect to the total surface area of the binarized two-dimensional Fourier pattern 24.

[0210] Furthermore, the logo, lettering and / or icon may be integrated into the binary two-dimensional Fourier pattern 24 binarized over the entire surface such that they are not visible in normal observation and become recognizable only when tilted about the horizontal axis and / or the vertical axis. Different from the design shown in FIG. 14, this does not result in a loss of the surface area of the binary two-dimensional Fourier pattern 24. This is represented, by way of example, in FIGS. 15a to 15c. This can preferably be achieved by locally modifying the nanostructure and / or microstructure of dark or bright pixels such that they display a dark or bright appearance in normal observation but have an optically variable behavior different from the background of the binary two-dimensional Fourier pattern 24 when tilted.

[0211] For example, the dark pixels 32 can be provided with a high-frequency linear grating having a grating period of 400 nm (sub-wavelength grating) and a grating depth of 200 nm. This linear grating is preferably deposited with aluminum and then embedded in one or more polymer layers. This linear grating preferably absorbs a part of the incident visible light, whereby these pixels appear dark in normal observation. This linear grating is preferably provided with an azimuth angle of 0° in the dark pixels 32 within a partial region of the binary two-dimensional Fourier pattern 24 having additional information, for example the letters "OK" in FIGS. 15a to 15c, and an azimuth angle of 90° in the dark pixels 32 within a partial region of the binary two-dimensional Fourier pattern 24 where no additional information is present. All the pixels provided with the linear grating appear dark in normal observation. FIG. 15a schematically shows this with reference to an exemplary section having a partial region of the letter "O". In the partial region, the two linear gratings having azimuth angles of 0° and 90° are represented by different shades in the dark pixel 32.

[0212] Here, FIG. 15b shows the entire binary two-dimensional Fourier pattern 24 over the entire surface, and the characters "OK" are integrated into six regions by changing the azimuth angle of the linear grating structure at the dark pixels 32. In this example, an azimuth angle of 0° was selected. When tilted greatly about the horizontal axis, the first diffraction order of the sub-wavelength grating hits the observer's eye, so these characters light up brightly. On the other hand, pixels without additional information with a linear grating having an azimuth angle of 90° do not light up and appear dark. Thus, it can be easily checked whether the binary two-dimensional Fourier pattern 24 was created with nanostructures and / or microstructures or was instead printed.

[0213] Here, when a multilayer having the binary two-dimensional Fourier pattern 24 over the entire surface in a greatly tilted state is rotated by 90°, the pixels of the linear grating (linear sub-wavelength grating) without additional information light up brightly, and the linear grating ("OK" characters) containing additional information appears dark. This change in contrast is a security feature that is easy to check.

[0214] The pixels that appear dark can preferably be further better realized by high-frequency crossed gratings. This is due to the fact that the linear grating mainly absorbs one polarization direction of the incident light, while the other polarization direction is not absorbed or hardly absorbed. On the other hand, the crossed grating can absorb both polarization directions. Thus, these high-frequency crossed gratings absorb the incident visible light more efficiently than the linear grating. In the case of the crossed grating, these are preferably rotated by 45° in azimuth in the sub-region with additional information compared to the sub-region without additional information. The change in contrast between the brightly lit characters and the dark background and the dark characters on the bright background is caused by the 45° rotation.

Explanation of Reference Numerals

[0215] 1 Multilayer 11 Carrier layer 12 Replication layer 13 Metal layer 14 Adhesion layer / Primer layer 15 Release layer 16 Protective layer 17 Compensation layer 18 Print 20 Batch number 21 First graphic code 22 Empty image template 23 Two-dimensional Fourier pattern 24 Binary two-dimensional Fourier pattern 25 Inverse Fourier transform of two-dimensional Fourier pattern 26 Inverse Fourier transform of binary two-dimensional Fourier pattern 31 Bright pixel 32 Dark pixel

Claims

1. A method for manufacturing a multilayer body (1), The replication layer (12) is applied to the carrier layer (11), The first graphic code (21) is Fourier transformed into a two-dimensional Fourier pattern (23), The aforementioned two-dimensional Fourier pattern (23) is binarized to obtain a binarized two-dimensional Fourier pattern (24). The binarized two-dimensional Fourier pattern (24) is transferred to a stamping tool. The binarized two-dimensional Fourier pattern (24) is formed as a stamped structure on the replica layer (12) in at least a portion of the first region by the stamping tool. A method characterized by applying at least one of a metal layer (13), an HRI layer, a primer layer (14), and an adhesive layer (14) to the replica layer (12).

2. At least one of the release layer (15) and the protective layer (16) is applied to the carrier layer (11). The method according to claim 1, characterized in that at least one of the release layer (15) and the protective layer (16) is disposed between the carrier layer (11) and the replication layer (12).

3. The binarized two-dimensional Fourier pattern (24) is provided as a nanostructure or microstructure, or The binarized two-dimensional Fourier pattern (24) is provided as at least one of a diffraction grating, a scattering mat structure, a reflection facet, and a reflection microstructure, or The method according to claim 1, characterized in that the binarized two-dimensional Fourier pattern (24) is formed from bright pixels (31) and dark pixels (32) arranged in a two-dimensional grid having a resolution of M × N pixels.

4. The bright pixels (31) and the dark pixels (32) are formed from a diffraction grating. The grids of the bright pixels (31) and the dark pixels (32) differ in at least one of the grid period, grid depth, and orientation. The lattice period of the diffraction grating is in the range of 200 nm to 20 μm. The grating depth of the diffraction grating is in the range of 50 nm to 2 μm, or The method according to claim 3, characterized in that the grating depth of the diffraction grating is 5% to 20% of the grating period.

5. The bright pixels (31) and the dark pixels (32) are formed by a structure that appears bright or dark in direct reflection. The dark-looking structure includes at least one of the following: high-frequency and deep cross-grid structures, cross-grids, hexagonal grids, and mirrors, or The brightly appearing structure includes at least one of a static mat structure, a dynamic mat structure, and a Fourier hologram. The lattice period of at least one of the crossed lattice and the hexagonal lattice is within the range of 200 nm to 450 nm. The lattice depth of at least one of the crossed lattice and the hexagonal lattice is greater than 150 nm, or The average spacing of the aforementioned mat structure is within the range of 500 nm to 5 μm. The method according to claim 3, characterized in that the average depth of the mat structure is in the range of 100 nm to 2 μm.

6. The bright pixels (31) and the dark pixels (32) are formed by a blazed grid. The orientation of the blazed grid in the bright pixels (31) and the dark pixels (32) differs by at least 150°, or The lattice period of the blazed lattice is within the range of 3 μm to 20 μm, or The method according to claim 3, characterized in that the lattice depth of the blazed lattice is in the range of 500 nm to 2 μm.

7. The replica layer (12) has a UV-curable replica varnish that is pre-cured or fully cured by UV radiation after the stamping structure is formed. The method according to claim 1, characterized in that a metal layer (13) is applied to the replica layer (12) at least partially or over its entire surface.

8. The first graphic code (21) is a machine-readable code, a 2D barcode, a QR code, or a data matrix code, or The method according to claim 1, characterized in that the first graphic code (21) is a batch-specific code, and a batch number (20) is provided when the first graphic code (21) is read.

9. The second graphic code is applied in the form of the print (18) in front of the replicating layer (12) by applying the print (18) to the carrier layer (11), release layer (15), or protective layer (16) in at least a portion of the second region, or The second graphic code is applied in the form of the print (18) behind the replica layer (12) by applying the print (18) to the replica layer (12), metal layer (13), HRI layer, adhesive layer (14), or primer layer (14) at least in part in the second region. The print (18) is performed by a digital printing method, selected from the group consisting of inkjet printing, thermal transfer printing, laser printing, and laser engraving. The print (18) contains ink or, The method according to claim 1, characterized in that the print (18) is overmolded, coated, or embedded with a UV-curing replicating varnish, thereby causing at least one of initial crosslinking and crosslinking.

10. The application of the aforementioned ink, or the provision of the aforementioned print (18), is carried out in the same manufacturing steps as UV replication. The ink and the UV-curing varnish are cured together. The ink undergoes post-crosslinking by UV curing of the UV-cured replicating varnish, or The method according to 9, characterized in that the ink is applied to a substantially smooth surface of the replica layer (12).

11. The duplicate layer (12) is duplicated together with the applied print (18), or The method according to 9, characterized in that the print (18) is applied to the already replicated surface of the replica layer (12) (18, 24).

12. The second graphic code is a machine-readable code, a 2D barcode, a QR code, or a data matrix code, or The aforementioned second graphic code is a unique code, an item-specific code, or a series-specific code. When the second graphic code is read, a serial number is provided, or The method according to 9, characterized in that the URL of the authentication server is stored in the second graphic code.

13. The first region and the second region are arranged to be adjacent to each other, separated from each other, or at least partially overlapping each other, or At least one additional compensation layer (17) is applied, The method according to 9, characterized in that the at least one compensation layer (17) is disposed between the replication layer (12) and the adhesive layer (14) or primer layer (14), or between the metal layer (13) and the adhesive layer (14) or primer layer (14).

14. At least one of the first graphic code (21) and the second graphic code is stored in the authentication database of the authentication server, or is stored as a pair in the authentication database of the authentication server. At least one of the binarized two-dimensional Fourier pattern (24) and the second graphic code is captured by a mobile terminal, and a data transport connection is formed between the mobile terminal and the authentication server. The method according to 9, characterized in that one authentication software compares data captured by the mobile terminal and transmitted to the authentication server with at least one of a first graphic code (21) stored in and read from the authentication database and a second graphic code that has been read.

15. The method according to claim 1, characterized in that the binarized two-dimensional Fourier pattern is formed with an effective resolution of up to 2500 dpi.

16. A multilayer body (1) manufactured according to claim 1, The multilayer (1) comprises a carrier layer (11) and a replication layer (12) disposed thereon. The embedded first graphic code (21), which has been Fourier transformed into a binarized two-dimensional Fourier pattern (24), is formed as a stamping structure on the replication layer (12) in at least a portion of the first region. The multilayer (1) is characterized in that at least one of a metal layer (13), an HRI layer, a primer layer (14), and an adhesive layer (14) is disposed on the replication layer (12).

17. The multilayer (1) according to claim 16, characterized in that at least one of a release layer (15) and a protective layer (16) is disposed between the carrier layer (11) and the replication layer (12).

18. The binarized two-dimensional Fourier pattern (24) is formed on the replication layer (12) as a nanostructure or microstructure, or The binarized two-dimensional Fourier pattern (24) is formed on the replica layer (12) as at least one of a diffraction grating, a scattering mat structure, a reflection facet, and a reflection microstructure, or The multilayer (1) according to claim 16, characterized in that the binarized two-dimensional Fourier pattern (24) is formed from bright pixels (31) and dark pixels (32) arranged in a two-dimensional grid having a resolution of M × N pixels.

19. The bright pixels (31) and the dark pixels (32) are formed from a diffraction grating. The grids of the bright pixels (31) and the dark pixels (32) differ in at least one of the grid period, grid depth, and orientation. The lattice period of the diffraction grating is in the range of 200 nm to 20 μm. The grating depth of the diffraction grating is in the range of 50 nm to 2 μm, or The multilayer (1) according to claim 18, characterized in that the lattice depth of the diffraction grating is 5% to 20% of the lattice period.

20. The bright pixels (31) and the dark pixels (32) are formed by a structure that appears bright or dark in direct reflection. The dark-looking structure includes at least one of the following: high-frequency and deep cross-grid structures, cross-grids, hexagonal grids, and mirrors, or The brightly appearing structure includes at least one of a static mat structure, a dynamic mat structure, and a Fourier hologram. The lattice period of at least one of the crossed lattice and the hexagonal lattice is within the range of 200 nm to 450 nm. The lattice depth of at least one of the crossed lattice and the hexagonal lattice is greater than 150 nm, or The average spacing of the aforementioned mat structure is within the range of 500 nm to 5 μm. The multilayer (1) according to claim 18, characterized in that the average depth of the mat structure is in the range of 100 nm to 2 μm.

21. The bright pixels (31) and the dark pixels (32) are formed by a blazed grid. The orientation of the blazed grid of the bright pixels (31) and the dark pixels (32) differs by at least 150°. The lattice period of the blazed lattice is within the range of 3 μm to 20 μm, or The multilayer (1) according to claim 18, characterized in that the lattice depth of the blazed lattice is in the range of 500 nm to 2 μm.

22. The first graphic code (21) is a machine-readable code, a 2D barcode, a QR code, or a data matrix code, or The multilayer according to claim 16, characterized in that the first graphic code (21) is a batch-specific code.

23. The second graphic code is applied in the form of the print (18) in front of the replicating layer (12) by applying the print (18) to at least one of the carrier layer (11), release layer (15), and protective layer (16) in at least a portion of the second region. The second graphic code is applied in the form of the print (18) behind the replica layer (12) by applying the print (18) to at least one of the replica layer (12), metal layer (13), HRI layer, adhesive layer (14), and primer layer (14) in at least part of the second region. The second graphic code is a machine-readable code, a 2D barcode, a QR code, or a data matrix code, or The multilayer (1) according to claim 16, characterized in that the second graphic code is a unique code, an item-specific code, or a series-specific code.

24. The first region and the second region are arranged to be adjacent to each other, separated from each other, or at least partially overlapping each other, or The multilayer (1) has at least one compensation layer (17), The multilayer (1) according to claim 23, characterized in that the at least one compensation layer (17) is disposed between the replication layer (12) and the adhesive layer (14), or between the metal layer (13) and the adhesive layer (14).

25. The multilayer according to claim 16, characterized in that the binarized two-dimensional Fourier pattern has an effective resolution of up to 2500 dpi.

26. A method for authenticating a multilayer body (1) manufactured by the method described in any one of claims 16 to 25, using an authentication system, wherein By capturing an image of the binarized two-dimensional Fourier pattern (24) of the multilayer (1) using the camera of a mobile device, The captured image is subjected to an inverse Fourier transform, The inverse Fourier transformed image is supplied to a first reading algorithm for a first graphic code (21). A method characterized by reading the first graphic code (21) and checking the first graphic code (21).

27. When the aforementioned image is captured, the second graphic code of the multilayer (1) is also captured. The captured image is supplied to a second reading algorithm for the second graphic code. The second graphic code is read, and the read first graphic code (21) and the read second graphic code are checked. The batch number (20) is provided by reading the first graphic code (21). The serial number is provided by reading the second graphic code. The batch number (20) and the serial number are checked. The read-out first graphic code (21) is supplied to the authentication server and compared with a valid first graphic code (21) stored on the authentication server. The read first graphic code (21) is authenticated if it matches one of the stored valid first graphic codes (21), or The retrieved second graphic code is supplied to the authentication server and compared with a valid second graphic code stored on the authentication server. The method according to 26, characterized in that the read second graphic code is authenticated if it matches one of the stored valid second graphic codes.

28. If the first graphic code (21) is authenticated, or if the first graphic code (21) and the second graphic code are authenticated, the multilayer (1) is authenticated, or The method according to 26, characterized in that the multilayer (1) is authenticated when the combination of the read first graphic code (21) and the read second graphic code is authenticated.

29. An authentication system for authenticating a multilayer body (1) according to any one of claims 16 to 25, manufactured by the method described in any one of claims 1 to 15, A mobile terminal having a camera for capturing an image of a binarized two-dimensional Fourier pattern (24) of a multilayer (1) protected against counterfeiting, and a transceiver unit for transmitting the data of the multilayer (1) captured by the camera to an authentication server, A Fourier inverse transform program that performs an inverse Fourier transform on the binarized two-dimensional Fourier pattern (24), A first reading algorithm for a first graphic code (21) read from an inverse Fourier transformed image, Authentication server and Equipped with, The authentication system is characterized in that the authentication server is connected to the mobile terminal in a data transportable manner, stores a multilayer (1) on which the read first graphic code (21) is stored, authenticates the read first graphic code (21) transmitted by the mobile terminal, and outputs an authentication signal to the mobile terminal.

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