Security document with a transparent window formed in the security document substrate

Abstract

The invention relates to a security document (02) with a transparent window (04) which is formed in the security document substrate (26). A micro-optical structure (03) consisting of microlenses (11) is arranged on one face of the substrate (26) at least in the region of the transparent window (04), and a first printed image (27) is arranged on the other substrate (26) face lying opposite the micro-optical structure (03) at least in the region of the transparent window (04), wherein the first printed image (27) has multiple image elements (28a to 28j) in a punctiform or linear pattern, and the pixel size (38) or the line thickness (38) of said image elements (28a to 28j) is designed to be smaller than the lens width (18) of the microlenses (11) arranged in the micro-optical structure (03) in each case. A laminar expanded layer (39) which covers the first printed image (27) is arranged on a part of the first printed image (27) on the printed image face facing away from the micro-optical structure (03), and a second printed image (41) is arranged on the layer (39) which covers a part of the first printed image on the layer face facing away from the micro-optical structure (03). The second printed image (41) is arranged on the layer (39) which covers a part of the first printed image (27) such that the second printed image (41) can be brought into register with the micro-optical structure (03) applied onto the other face of the substrate (26) of the security document (02) after carrying out a folding process at a folding line (07) such that the second printed image (41) or at least one piece of information contained therein becomes visible and / or detectable when viewed from the direction of the micro-optical structure (03).

Description

[0001] The invention relates to a security document having a transparent window formed in its substrate according to the preamble of claim 1.

[0002] WO 2006 / 087138 A1 discloses a security element for protecting valuables with at least one first authenticity feature, wherein the first authenticity feature comprises a first arrangement with a plurality of focusing elements which are present in a first grid, and a second arrangement with a plurality of microscopic structures which are present in a second grid, wherein the first and the second arrangement are arranged such that the microscopic structures of the second arrangement can be seen in magnification when viewed through the focusing elements of the first arrangement, and a second authenticity feature which is machine and / or visually verifiable and is unaffected by the first arrangement of the first authenticity feature.

[0003] WO 2016 / 011249 A2 discloses an improved polymer film material for use in the production of polymer security documents, such as banknotes, which is made of a polymer substrate or polymeric substrate having a thickness greater than or equal to approximately 60 micrometers and one or more integrated optical security devices projecting one or more synthetic images, wherein the one or more optical security devices are integrated into all or part of the substrate, wherein the one or more integrated optical security devices are aligned with one or more clear windows and one or more opaque areas on the substrate, and an array of metallized hybrid refractive / reflective focusing elements arranged below a first array of image symbols on an upper surface of the substrate,and a second array of image symbols disposed immediately below the first array of image symbols and the array of metallized hybrid refractive / reflective focusing elements on a lower surface of the substrate, wherein one or more opaque regions are disposed on the second array of image symbols, wherein one or more synthetic images are projected through the polymer film material in reflected and transmitted light, wherein the one or more opaque regions enable viewing of reflected light, and wherein the one or more clear windows enable viewing of transmitted light that exceeds viewing of reflected light.

[0004] US 10,766,293 B2 discloses a method for manufacturing a safety device, which comprises: a) providing a depth map of a macro image representing a three-dimensional object, the depth map representing the depth of each part of the three-dimensional object relative to a reference plane using different colors and / or different tones of a color; b) segmenting the depth map into a plurality of regions based on the colors and / or tones of the depth map, each region comprising the part(s) of the depth map having a color or tonal value within a respective predetermined range; c) creating, for each region, a respective spectrum of microimage elements, the microimage elements forming the spectrum of microimage elements arranged on a regular grid in one or two dimensions with a gradient and orientation that are constant across the region, the edge region of the spectrum of microimage elements substantially corresponding to that of the region,wherein the resulting plurality of spectra of the micro-image elements are arranged relative to one another in the positions of the respective regions on the depth map to form a first image layer, and d) providing a scanning element spectrum of a predetermined slope and orientation, wherein the scanning element spectrum overlaps the plurality of spectra of the micro-image elements, wherein the slopes of the scanning image spectrum and the spectra of the micro-image elements and their relative positions are determined such that the scanning element spectrum cooperates with each of the spectra of the micro-image elements to generate enlarged versions of the micro-image elements in each region as a result of the moiré effect, wherein the slope and / or orientation of each respective spectrum of the micro-image elements is different and is configured such that the enlarged versions of the micro-image elements generated in any of the regions,have a different apparent depth relative to those produced in the other area(s), thus forming a three-dimensional representation of the macro image.

[0005] US 2018 / 0196980 A1 discloses a security substrate comprising: a polymer substrate having a first and a second surface; an array of focusing elements in the form of a surface relief over a first region of the polymer substrate, wherein the surface relief is defined in the surface of a transparent base layer, wherein the transparent base layer comprises either the polymer substrate or a layer disposed thereon;an optical matching layer disposed on the transparent base layer over a second region of the polymer substrate, the second region including at least the first region, the optical matching layer having a first surface in contact with the surface relief of the transparent base layer and an opposing second surface having a profile that is not effective to focus visible light, the optical matching layer comprising a first transparent material extending over a first subregion of the array of focusing elements, the first subregion comprising all or only a portion of the first region, the first transparent material having a refractive index different from that of the transparent base layer, the focusing elements in the first subregion of the array being functional focusing elements;and at least one first masking layer comprising a reflective and / or non-transparent material disposed over the optical matching layer over a third region of the polymer substrate, the third region defining at least one gap in the first masking layers, the gap enclosing at least a portion of the first sub-region such that functional focusing elements of the array are revealed through the at least one gap.;

[0006] US 2019 / 0232708 A1 discloses a security device comprising an array of focusing elements with regular periodicity in at least a first direction, each focusing element having an optical footprint whose different portions are directed towards the viewer depending on the viewing angle; and an array of image elements with regular periodicity in at least the first direction, which overlaps the array of focusing structures, the image elements representing portions of at least two respective images, and at least one image element of each respective image being located in the optical footprint of each focusing structure; wherein the security device includes a first region and a second region laterally offset from the first region,wherein the image elements in the first region are displaced laterally in at least the first direction relative to the image elements in the second region such that, at a first viewing angle, in the first region of the device, the focusing structures guide image elements corresponding to a first image to the viewer such that the first image is displayed over the first region of the device, and simultaneously, in the second region of the device, the focusing structures guide image elements corresponding to a second image to the viewer such that the second image is displayed over the second region of the device, and at a second viewing angle, the second image is displayed over the first region of the device and simultaneously, the first image is displayed over the second region of the device, and wherein the security device further comprises a color filter located in use between the image elements and the viewer,wherein the color filter overlaps at least part of the array of focusing elements and the array of image elements, wherein the color filter has a first color in the first region of the device and a different color in the second region of the device such that the color appearance of the first and second images is different in the respective first and second regions of the device.

[0007] EP 2 493 700 A2 discloses a method for manufacturing a security device, the method comprising: providing an array of lenticular focusing elements on one side of a transparent substrate; and providing a corresponding array of sets of image strips on the other side of the transparent substrate, the image strips and the lenticular focusing elements defining a lenticular device such that, under different viewing directions, a corresponding image strip from each set is viewed via respective lenticular focusing elements.

[0008] WO 2011 / 107783 A1 discloses a security document comprising a document substrate having at least two transparent or translucent windows spaced apart from one another, and a device comprising a transparent substrate carrying: i) a uniform array of micro-focusing elements on a first surface, the focusing elements defining a focal plane; ii) a corresponding first array of micro-image elements in a first color and located in a plane substantially coinciding with the focal plane of the focusing elements;and, iii) a corresponding second array of micropixels, in a color different from the first color and located in a plane substantially coinciding with the focal plane of the focusing elements, wherein the pitches of the microfocusing elements and the first and second arrays of micropixels and their relative positions are such that the array of microfocusing elements cooperates with each of the first and second arrays of micropixels to generate respective magnified versions of the micropixels of each array due to the moiré effect; and wherein at least a portion of the first array of micropixels is not overlapped by the second and at least a portion of the second array of micropixels is not overlapped by the first;wherein the device is incorporated into the document substrate or applied in alignment with the at least two windows thereon, the device being registered with respect to the document substrate such that the enlarged version of the first micropixel array is visible through the first of the two windows and the enlarged version of the second micropixel array is visible through the second of the two windows, the transition between the two micropixel arrays being obscured by the document substrate between the two windows;

[0009] DE 11 2010 000 957 T5 discloses a lens array for imaging a plurality of image elements in an object plane, wherein the lens array contains a plurality of microlenses formed in or on one side of a transparent or translucent material with the image elements arranged on the opposite side, wherein the lens array has a measured thickness that corresponds to the distance from the apex of each microlens to the object plane, wherein each microlens has a set of lens parameters, wherein the measured thickness and / or at least one lens parameter are optimized such that each microlens has a focal point size in the object plane that is substantially equal to the size of the image elements in the object plane, or that deviates from the size of the image elements by a predetermined amount. The measured thickness of the lens array is preferably less than the focal length of all the microlenses. The image elements can, for example, take the form of points or lines.The lens array of DE 11 2010 000 957 T5 is designed in such a way that in a sectional plane lying in a cone or angular field of the light incident into the microlens in question in the direction of the image elements parallel to the main plane of the microlens in question, only one of the adjacently arranged image elements is arranged, whereby for a viewer viewing the printed image from a certain viewing angle, only a single frame is perceptible at a certain time.

[0010] The invention is based on the object of creating a security document with a transparent window formed in its substrate.

[0011] The problem is solved by a security document having the features of claim 1. The dependent claims show advantageous embodiments and / or further developments of the solution found.

[0012] An embodiment is shown in the drawings. They show: Fig. 1 shows a security document with a security element having an optically imaging structure; Fig. 2 shows a greatly enlarged sectional view of an arrangement comprising at least one printed image and a single plano-convex microlens integrated into an optically imaging structure with light incident from a first viewing angle; Fig. 3 shows the arrangement according to the Fig. 2 with a light incidence from a second viewing angle; Fig. 4 a security document with means for self-authentication; Fig. 5 a security document with a contrast-enhancing back; Fig. 6 a security document with a contrast-enhancing back and with means for self-authentication; Fig. 7 a simplified schematic representation of a printing machine for producing a security document, in particular according to Fig. 5 oder 6 .

[0013] In optics, the term "lens" refers to a light-transparent component with at least one refractive surface arranged in the light beam path. The term "light" refers to the part of electromagnetic radiation visible to the human eye. In the electromagnetic spectrum, the light range encompasses wavelengths from approximately 380 nm (violet) to 780 nm (red). The following are based on converging lenses, i.e., lenses that focus incident light, particularly plano-convex lenses. Preferred designs are, on the one hand, rotationally symmetrical spherical or aspherical lenses, and, on the other hand, axially symmetrical rod-shaped lenses, with the respective axis of symmetry of the lens in question and its optical axis congruent. The optical axis is thus usually a straight line passing through the center of curvature of a convex lens surface.For a flat lens surface, the optical axis is perpendicular to it. The curvature of a refractive surface, such as a convex surface, is determined by its radius of curvature, where the radius of curvature originates at the optical axis. A flat lens surface is defined by an infinitely large radius of curvature.

[0014] Rod-shaped lenses are designed in the form of either a right circular cylinder or an elliptical cylinder, each halved along its rod length, with the respective axis of symmetry of such a lens extending orthogonal to its respective rod length. In a spherically shaped lens, the refractive surface is formed as a surface section of a sphere, e.g. in the form of a spherical cap. An aspherically shaped lens has at least one refractive surface that deviates from a spherical or flat shape. The shape of rotationally symmetric aspherical surfaces is usually specified as a conic section (circle, ellipse, parabola, hyperbola) plus a correction polynomial for higher-order deformations.

[0015] A lens has two surfaces intersected by the light beam path, so-called enveloping surfaces. With regard to light bundling, it is by definition the case that light enters a plano-convex converging lens at its convex curved enveloping surface and light exits this lens at its flat enveloping surface. The enveloping surfaces are interfaces between different media, in which the light propagates. One of these media is formed by the material of the lens in question. At least one other medium is the space, usually filled with air, in which the lens in question is located. Since at least two of the media arranged in the light beam path have at least their respective optical material properties different from one another, the light is refracted at the interface between these adjacent media.Thus, light is refracted at at least one of the enveloping surfaces of the respective lens, in particular at its curved enveloping surface. The optical material property associated with light refraction is expressed by the respective refractive index of the medium in question. The refractive index is a dimensionless physical quantity that indicates the factor by which the wavelength and phase velocity of light are smaller in the medium in question than in a vacuum. Of two media with different refractive indices forming a common interface, the medium with the higher refractive index is said to be the optically denser one. The Abbe number, also called Abbe's number, is a dimensionless quantity used to characterize the optical dispersive properties of a lens and indicates how much its refractive index changes with the wavelength of light.The ability of a lens to produce an optical image of an object viewed through the lens in question depends on the refractive index of the material of the respective lens and on the shape of its enveloping surfaces forming interfaces between different media.

[0016] The principal plane of a lens is a plane in this component that is arranged orthogonally to the axis of symmetry of the lens in question. In the case of a thin lens, where the greatest extent along the axis of symmetry, i.e. the thickness of the lens, is very small compared to the radius of curvature of its convex envelope, because the radius of curvature of the convex envelope is, for example, at least five times greater than this thickness, only a single principal plane can be used with sufficient accuracy to consider the properties of the lens in question. In a plano-convex lens, this principal plane coincides with the flat lens surface. The focal length of a lens is the distance between the principal plane of the lens in question and its focus (focal point), where the focus of a lens is understood to be the point of intersection of light rays bundled by the lens and incident parallel to the lens.The parallel light rays entering the lens do not necessarily enter parallel to its optical axis, but at any angle of incidence, particularly an acute angle, relative to the principal plane of the lens in question. A plane positioned at the focus orthogonal to the optical axis is called a focal plane.

[0017] The enveloping surface of the lens in question, which serves to admit light, has two opposite edge points that are axially symmetrical to its optical axis and delimit this enveloping surface, for example, located in the principal plane of this lens. The distance between these two edge points determines the width of the lens in question (= lens width). The aperture or opening width of a lens refers to its free opening or diameter through which light rays can be received unhindered and corresponds at most to the lens width. The point that lies at the intersection of the optical axis with the enveloping surface of the lens in question, which serves to admit light, is called the vertex. The vertex is located on the enveloping surface, which serves to admit light, furthest from the focus of the lens.

[0018] A rotationally symmetrical, spherical or aspherical lens focuses incident light into a cone, with the diameter of the base of this cone corresponding at most to the lens width, and the height perpendicular to the base of this cone corresponding to the focal length of the lens in question. An axially symmetrical, rod-shaped lens focuses incident light into an acute angular field, with the origin of the angular field at the focus of the lens. The numerical aperture describes the ability of a lens to focus light. It determines the minimum size of the light spot that can be created at its focus and is therefore an important parameter that limits resolution.

[0019] A plurality of rotationally symmetrical, spherical or aspherical lenses, which are arranged in a preferably uniform grid consisting of either square or hexagonal grid cells, in particular each without gaps and without overlap, form a lens group, which is also referred to as a lens array. A plurality of axially symmetrical, rod-shaped lenses, which are each arranged orthogonally to their rod length, also preferably each without gaps and without overlap, form a lens grid, which is also referred to as a lenticular. A plurality of lenses arranged in a grid-shaped lens group and / or a plurality of lenses arranged in a lens grid each form, in their respective combination, an optically imaging structure in the form of a geometric figure extending over a flat or curved surface. The surface of the optically imaging structure can have any desired contour, e.g.rectangular, round, oval, or polygonal. In geometry, a geometric figure is understood as a set of points. With respect to the optically imaging structure, a lens is arranged at at least a subset of the points forming the geometric figure.

[0020] In an optically imaging structure, either only one or more lattice-shaped lens groups or only one or more lenses arranged in a lenticular array, or both of these lens arrangements can be arranged together with the other lens arrangement, so that both lattice-shaped lens groups and lenses arranged in a lenticular array are arranged together in the same optically imaging structure. In this case, lenticular arrays formed in the respective optically imaging structure can, for example, each have a different orientation, with the respective orientation of the respective lenticular array being determined by the respective direction of the rod length of the lenses involved in the construction of the respective lenticular array.

[0021] A microlens is a miniaturized form of a conventional lens. The term "microlens" refers to a lens with a lens width of less than 100 µm and preferably in the range between 20 µm and 65 µm. Microlenses have a focal length of less than, for example, 100 µm, preferably a maximum of 95 µm. Microlenses can now be manufactured industrially. Microlenses made of plastic or resin can be manufactured, for example, using an (injection) molding process, (injection) embossing process, or printing process. Optically imaging structures consisting of microlenses are also referred to as micro-optical structures.

[0022] If an optically imaging structure, in particular formed from microlenses, is or is combined with a preferably flat printed image, for example by applying this optically imaging structure to a substrate containing the printed image, various effects can be generated for a viewer viewing the printed image through the optically imaging structure. For example, an arrangement consisting of at least one printed image and at least one optically imaging structure can generate so-called alternating images or wobbly images (flips) and / or spatial, i.e. three-dimensional effects and / or morphing effects and / or zoom effects and / or animations. These effects are perceptible to a viewer without optical aids if they view the printed image alternately from different viewing angles.The perception presented to the viewer through different viewing angles is also called a lenticular image.

[0023] The usually flat print image is formed on the preferably two-dimensional substrate, e.g. in an industrial production process, preferably with a printing press. The substrate is e.g. a printing material web or in the form of a printing sheet. The print image is e.g. applied to the substrate in a dot-shaped or line-shaped grid. The print image therefore consists e.g. of several, in particular a large number of pixels and / or lines. A pixel size or a line thickness is in a range of less than 100 µm, preferably less than 50 µm, in particular less than 20 µm, e.g. in the range of approximately 5 µm to 10 µm. In the following, it is assumed that the pixel size of pixels and / or the line thickness of lines, which are each involved in the formation of a print image used together with an optically imaging structure, e.g.are each at most as large, preferably smaller, in particular less than half as large as the respective lens width of the lenses involved in the construction of the respective optically imaging structure.

[0024] In optics, resolving power refers to the ability to distinguish fine structures, i.e. the minimum distance that, for example, two pixels or two lines must be from each other in order to be perceived as separate pixels or lines. The resolving power of the naked human eye varies from person to person. Adults with normal vision can usually still distinguish structures at a distance of 150 µm at a distance of 25 cm. This corresponds to a visual angle of approximately 2 angular minutes, which is referred to as angular resolving power. With weak contrasts, the visual acuity of the human eye decreases noticeably, with visual acuity being the inverse of the resolving power. The lens width of a microlens is therefore usually less than the resolving power of the naked eye of an adult with normal vision.

[0025] To produce a colorful print image, the substrate is printed with a plurality of printing inks. For example, the primary colors red, green, blue and optionally black are applied to the substrate. A print image usually consists of an arrangement of a plurality of small-area image elements arranged at different positions on the print image in question. Each image element preferably has a plurality of pixels or lines and generally extends over a length of less than 100 µm. Each image element or a group of neighboring image elements forms, for example, an object to be viewed through the lens. The individual image elements are usually arranged in a print image to form a print motif that determines the informational content of the print image. Due to its limited area, it is usually...Due to insufficient resolution, individual image elements used in conjunction with a microlens are normally not individually perceptible to the naked human eye. A color impression of the printed image or at least part of this printed image perceived by a person is created by an additive color mixing in the eye and brain of the viewer of pixels and / or lines printed in different printing colors in the respective image elements. A superposition of two primary colors results in the color impressions yellow, cyan and magenta, known as secondary colors. A superposition of all three primary colors results in the color impression white. A color register, i.e. a registration, i.e.In the embodiments of the invention considered here, the accuracy of fit of pixels and / or lines of different printing inks in their relative arrangement to one another is less than 20 µm, preferably less than 10 µm, and in particular in the range of approximately 5 µm.

[0026] The optically imaging structure provided in connection with the embodiments of the invention considered here is preferably arranged in combination with pixels and / or lines of different printing inks. The printed image is or is preferably produced as or by superimposing several partial printed images, wherein several or preferably each of the partial printed images is or is printed, for example, in a different printing ink. The superimposition can be effected by successive overprinting on the substrate or preferably by collecting the partial printed images on a printing element, e.g. on a cylinder, and simultaneously delivering them to the substrate. The partial printed images, in turn, each consist of pixels and / or lines, wherein the pixel size of these pixels and / or the line thickness of the respective lines are each in the micrometer range, e.g. in the range of less than 20 µm.When a viewer looks at the printed image, the several partial print images involved in this printed image overlap in their perception, for example to create an overall color impression.

[0027] An arrangement consisting of at least one printed image and at least one optically imaging structure allows a viewer viewing the printed image to perceive several different individual images at different viewing angles, with a sequence of individual images creating, in the viewer's perception, an alternating image or flip image and / or a spatial, i.e., three-dimensional effect and / or a morphing effect and / or a zoom effect and / or an animation. Each of these individual images is also referred to as a frame.The individual images perceivable by the viewer at a specific viewing angle are created by a selection determined by the optically imaging structure from the set of partial print images perceivable at the respective positions of the microlenses due to the at least one image element or elements present there. The overall color impression related to a position of the print image is created by the superimposition of all partial print images present and perceivable at that position. The optically imaging structure arranged in combination with a print image therefore optically masks the partial print images involved in the respective print image and arranged in register with the surface of the optically imaging structure.

[0028] In order to allow a viewer viewing the printed image to perceive several frames at the same time from a specific viewing angle, in order to create more complex and / or differentiated animations, for example,an arrangement comprising a printed image and an optically imaging structure consisting of a plurality of plano-convex microlenses is used, in which a plurality of, preferably more than three, in particular between five and ten, image elements are arranged next to one another under at least one microlens of the optically imaging structure in question, these image elements being arranged between the extent of the lens width of the microlens in question and its focus in a sectional plane lying parallel to the main plane of the microlens in question, the sectional plane being arranged so as to intersect a cone or an angular field of the light incident through the lens width of the microlens in question in the direction of the image elements arranged next to one another, wherein a plurality of different image elements are arranged in a row in the sectional plane within the cone or the angular field.

[0029] This results in an arrangement comprising a printed image and an optically imaging structure consisting of a plurality of plano-convex microlenses, each of these microlenses having a lens width of preferably less than 100 µm along the printed image, the printed image having a plurality of image elements, a plurality of image elements being arranged under at least one of the microlenses of the respective optically imaging structure, these plurality of image elements each arranged under at least one of the microlenses of the respective optically imaging structure being arranged next to one another along the lens width and each extending in the direction of the lens width over a length less than the respective lens width,wherein, between the extent of the lens width of the respective microlens and its focus, in a sectional plane lying parallel to the main plane of the respective microlens in the cone or angular field of the light incident through the lens width of the respective microlens in the direction of the adjacently arranged image elements, several, preferably at least three, in particular more than three, respectively different image elements are arranged in a row. With this arrangement, a viewer viewing the printed image can perceive several frames simultaneously at a specific viewing angle, which allows for complex and / or differentiated animations as well as smooth color transitions with correspondingly colored image elements and / or smooth frame transitions with different print motifs formed from the image elements.

[0030] The substrate is, for example, a fibrous printing material, in particular paper, or a film, preferably a polymer film. The substrate can be opaque or transparent. The substrate can be single-layered or multi-layered, in particular multi-layered in sections. Different layers of a multi-layer substrate can be made of different materials, e.g. one layer made of paper and another layer made of a polymer film. The substrate or at least one respective layer of this substrate has a material thickness, i.e. thickness, of e.g. less than 100 µm, preferably less than 50 µm, in particular about 25 µm. A printed image formed on the substrate has a layer thickness, e.g. less than 10 µm, preferably less than 5 µm, in particular in the range from 1 µm to 2 µm. The substrate can be printed on one or both sides.

[0031] In the preferred embodiment of the invention, the arrangement of the printed image and the optically imaging structure is part of a security element or a document, in particular a security document. These documents include, for example, banknotes, credit cards, checks, securities, share certificates, passports, ID cards, driver's licenses, title deeds, travel documents such as airline or train tickets, admission tickets, student documents, and other official or governmental documents such as birth, death, or marriage certificates. This list is merely exemplary and by no means exhaustive. However, banknotes are preferred.

[0032] Fig. 1 shows, by way of example, a document 02, in particular a security document 02, on or in which at least one security element 01 is arranged. The document 02 and / or the security element 01 in question have at least one optically imaging structure 03 over part of its surface or over its entire surface, wherein the respective optically imaging structure 03 is preferably designed as a micro-optical structure 03 formed from microlenses 11. The respective optically imaging structure 03 is arranged such that it, for example, at least partially covers a printed image 27 formed or applied to the document 02.

[0033] Fig. 2 shows, by way of example, in particular as an excerpt from the Fig. 1 illustrated security element 01 or document 02 in a greatly enlarged sectional view of an arrangement with a single plano-convex microlens 11 which is integrated into a group or grid of microlenses 11. The microlens 11 in question has an axis of symmetry 12 which at the same time also forms the optical axis 12 of this microlens 11. The microlens 11 can be rotationally symmetrical, spherical or aspherical, or it can be, for example, axially symmetrical and rod-shaped, wherein in the case of an axially symmetrical, rod-shaped microlens 11 the axis of symmetry 12 extends orthogonal to its rod length. The microlens 11 is produced, for example, from a transparent plastic or resin by injection molding, casting, embossing or printing. The microlens 11 has a convex envelope surface 13 which serves to admit light, wherein, for example, B. a bundle of parallel light rays 14 strikes this enveloping surface 13.The microlens 11 has two opposite edge points 16; 17 that delimit the convex envelope surface 13 and are axially symmetrical to its optical axis 12, which runs through the apex 37 of the convex envelope surface 13, the distance between these two edge points 16; 17 determining a width of this microlens 11, referred to as the lens width 18. The lens width 18 of a microlens 11 is less than 100 µm. The two edge points 16; 17 of the convex envelope surface 13 lie in a plane that is arranged orthogonal to the optical axis 12 of the microlens 11 in question, which plane is also referred to as the principal plane 19 of this microlens 11. In the . Fig. 2 In the illustrated embodiment, the main plane 19 forms a flat enveloping surface 21 of the respective microlens 11. A distance between the main plane 19 of the microlens 11 and its focus 23 (focal point) forms the focal length 22 of the respective microlens 11, wherein the focus 23 is an intersection point of the bundled light rays 14, in particular those incident parallel into the microlens 11. The focal length 22 of a microlens 11 is less than 100 µm. A plane arranged at the focus 23 orthogonal to the optical axis 12 is called a focal plane 24.

[0034] In the Fig. 2 In the exemplary embodiment shown, the microlens 11 is part of a lens array or a lenticular grid in which a plurality of microlenses 11 are arranged, preferably without gaps and without overlapping, with respect to a specific area of any desired contour. The lens array or the lenticular grid is arranged on a substrate 26, wherein the substrate 26 is designed, for example, as a fibrous printing material with a transparent window, in particular paper, or as a film, preferably as a transparent polymer film. The substrate 26 has a material thickness 29 or thickness 29, for example, of less than 100 µm, preferably of less than 50 µm, in particular approximately 25 µm. The substrate 26 is preferably part of a security element 01 or a document 02, in particular a security document 02. The substrate 26 is transparent at least in the area covered by the planar envelope surface 21 of the respective microlens 11.

[0035] In the Fig. 2 In the exemplary embodiment shown, a printed image 27 of a small layer thickness 36, for example of less than 10 µm, is applied to the back of the substrate 26, i.e. on the side of this substrate 26 facing away from the microlens 11, this printed image 27 having a multiplicity of individual, respectively different, image elements 28. These individual image elements 28 are formed with a very small area and extend parallel to the lens width 18 over only a few micrometers, for example over a maximum of 10 µm. It is therefore possible to arrange several, for example ten, such image elements 28a to 28j in the area covered by the flat envelope surface 21 of the microlens 11, for example in a row next to one another. At least one of these image elements 28a to 28j preferably has image points and / or lines printed in different printing colors, wherein in particular depending on the number of, for example,image elements 28a to 28j arranged next to one another, the respective image points of which have an image point size of 38 and / or the lines of which have a line thickness of 38, each in the range of a few micrometers, preferably in the range of less than 20 µm. The printed image 27 preferably consists of an overprint or an overlay of several partial printed images, each printed in different printing colors. The image elements 28a to 28j arranged next to one another in the area covered by the flat enveloping surface 21 of the microlens 11, ie under the relevant microlens 11, in particular preferably each belong to different printed motifs.

[0036] The image elements 28a to 28j arranged, for example, next to one another, under the respective microlens 11 are advantageously arranged closer to the microlens 11 than its focus 23. Preferably, these image elements 28a to 28j are arranged between the respective microlens 11 and its focus 23 in a cutting plane 31 lying parallel to the main plane 19 of the respective microlens 11, wherein the cutting plane 31 is arranged so as to intersect a cone 32 or an angular field 32 of the light incident through the lens width 18 of the respective microlens 11 in the direction of the image elements 28a to 28j arranged, for example, next to one another, wherein in the cutting plane 31 within the cone 32 or the angular field 32, preferably several of the image elements 28a to 28j are arranged in a row. In the Fig. 2 In the exemplary embodiment shown, the five image elements 28c to 28g, for example, are arranged in a row within the cone 32 or the angular field 32, whereas the remaining image elements 28a, 28b and 28h to 28j arranged in the area covered by the planar enveloping surface 21 of the microlens 11 are not perceptible to a viewer viewing the printed image 27 at a first viewing angle 33 corresponding, for example, to the incident light rays 14. If the viewing angle for a viewer viewing the printed image 27 is changed to a second viewing angle 34 different from the first viewing angle 33, for example, an obtuse angle, the image elements 28a to 28j that are perceptible to him also change. This is shown in the Fig. 3 which has the same arrangement with a printed image 27 and an optically imaging structure 03 consisting of several plano-convex microlenses 11 as the Fig. 2 Due to the second viewing angle 34 being different from the first viewing angle 33, in the Fig. 3 In the embodiment shown, only the image elements 28d to 28h are perceptible to a viewer viewing the printed image 27, but not the others.

[0037] As mentioned, the Fig. 2 and 3The image elements 28a to 28j shown in the area covered by the flat enveloping surface 21 of an individual microlens 11 are formed by pixels and / or lines, preferably each printed in different printing inks. As a rule, the respective pixel size 38 of the respective pixels and / or the line thickness 38 of the respective lines is each significantly smaller than the lens width 18 of the respective microlens 11, preferably in the range of a few micrometers, in particular in the range of less than 20 µm. In particular, in order to make the printed image 27 containing these image elements 28a to 28j machine-readable, at least one of these image elements 28a to 28j has pixels and / or lines, for the printing of which special printing fluids, in particular inks, are used, which differ in their optical properties from conventional printing fluids, in particular from conventional printing inks or inks.These special printing fluids include, for example, inks that are invisible to the naked eye of a normal-sighted observer without excitation outside the electromagnetic spectrum visible to the human eye, in particular inks that absorb infrared radiation, inks that reflect infrared radiation, inks that convert infrared radiation into the visible, inks that fluorescently emit ultraviolet radiation, or magnetic inks. These inks, which are invisible in daylight conditions in particular, can, like other printing inks, become perceptible in different shades of color upon appropriate excitation, e.g., in the blue, green, or red color ranges. This excitation is preferably electromagnetic or magnetic.

[0038] The term ink is understood here to be an intensely colored and coloring liquid, which usually consists of a solution or dispersion of colorants in water or other solvents, whereby these solvents contain no or, in the case of inks in the form of India ink, little binding agent. Colorants are color-imparting substances, e.g. pigments and dyes, which can be inorganic or organic, natural or synthetic. In contrast, printing inks are colorant-containing mixtures that are transferred to a substrate, i.e. a printing material, with the help of a printing form. Printing inks contain inorganic and organic pigments, e.g. titanium dioxide as a white pigment or carbon black as a black pigment, as well as binding agents that coat the pigments. Both conventional printing inks and inks, including inks invisible to the human eye under daylight conditions, can be subsumed under the term printing fluid.

[0039] The aforementioned special inks that react to infrared radiation (IR) are used, for example, in conjunction with electromagnetic radiation from the near infrared range (NIR), with radiation with a wavelength in the range between 780 nm and 2000 nm being preferred, particularly in the range between 780 nm and 1200 nm. An ink that reacts to infrared radiation (IR; NIR), for example, contains inorganic, usually pigment-like luminophores that, after absorbing energy, emit radiation in the visible spectral range and / or the infrared range (NIR). An ink that converts infrared radiation into the visible range contains so-called anti-Stokes pigments.

[0040] Ultraviolet radiation, or UV or UV radiation for short, is electromagnetic radiation invisible to the human eye. It has wavelengths shorter than visible light. According to widely accepted classification, the ultraviolet spectrum encompasses wavelengths from 100 nm to 380 nm, i.e., from the short-wavelength range to the edge of visible light. Ultraviolet fluorescent ink contains fluorescent color pigments that glow intensely when exposed to ultraviolet radiation and, where appropriate, utilize the ultraviolet rays of daylight.

[0041] A magnetic ink is understood to be an ink mixed, in particular, with iron oxide particles. These particles can be magnetized by an external magnetic field, which is different from the Earth's magnetic field, with respect to the respective arrangement comprising the substrate 26 and the optically imaging structure 03, and thus can be magneto-optically analyzed and read out.

[0042] An arrangement which is advantageous in terms of machine readability and has a printed image 27 applied to a substrate 26 and an optically imaging structure 03 covering at least parts of the printed image 27 provides that the optically imaging structure 03 has a group or a grid of several plano-convex microlenses 11, wherein the flat enveloping surface 21 of the microlenses 11 faces the substrate 26, wherein the printed image 27 arranged on the substrate 26 is preferably arranged on the side thereof facing the optically imaging structure 03 and has at least one image element 28a to 28j with at least one image point and / or one line, wherein this image point and / or this line is formed by printing technology using a printing fluid, wherein the printing fluid is only visible to the human eye as a result of excitation which lies outside the electromagnetic spectrum visible to the human eye.This printing fluid is preferably in the form of an ink that absorbs infrared radiation, an ink that reflects infrared radiation, an ink that converts infrared radiation into the visible, an ink that fluorescently emits ultraviolet radiation, or a magnetic ink. The relevant at least one image element 28a to 28j of the machine-readable printed image 27 is therefore an integral component of the relevant arrangement, for example on a security element 01 or a document 02, in particular on a security document 02. The excitation of the printing fluid, which lies outside the electromagnetic spectrum visible to the human eye, takes place with respect to the optically imaging structure 03 covering at least parts of the printed image 27, on the front side, i.e. directed onto the respective convex enveloping surface 13 of the microlenses 11 if this excitation is designed to act through the optically imaging structure 03, or on the back side, i.e. on the substrate side ordirected onto the respective planar enveloping surface 21 of the microlenses 11 if the optically imaging structure 03 is designed to block this excitation.

[0043] If it is intended that the pressure fluid, which is only visible to the human eye as a result of an excitation lying outside the electromagnetic spectrum visible to the human eye, should not interact with the microlenses 11 of the optically imaging structure 03, then in such an arrangement the respective pixel size 38 of the respective pixels and / or the line thickness 38 of the respective lines are, for example, each larger than the lens width 18 of the respective microlens 11.

[0044] Furthermore, it can be provided that in the respective arrangement of substrate 26 and optically imaging structure 03, the respective microlens 11 remains undeveloped at several individual positions in the group comprising a plurality of plano-convex microlenses 11 or in the grid comprising a plurality of plano-convex microlenses 11 of the respective optically imaging structure 03, and at least one image element 28a to 28j of the printed image 27 with at least one pixel and / or one line is arranged at the respective defect. This pixel and / or line is formed by printing technology using the printing fluid that is only visible to the human eye due to the excitation lying outside the electromagnetic spectrum visible to the human eye. The printing fluid, which is invisible to the human eye under normal conditions, is accordingly applied or arranged at selected defects in the respective optically imaging structure 03.

[0045] As mentioned, the arrangement of substrate 26 and optically imaging structure 03 can have a printed image 27 which allows a normal-sighted observer viewing the printed image 27 through the optically imaging structure 03 with the naked eye to perceive several different individual images at different viewing angles, wherein a sequence of individual images creates an alternating image or wobbly image (flip) and / or a spatial, i.e. three-dimensional effect and / or a morphing effect and / or a zoom effect and / or an animation in the perception of the observer. These different individual images are also referred to as frames. These aforementioned effects are each based on several partial printed images from which the at least one printed image 27 in question is composed.To form an arrangement comprising substrate 26 and optically imaging structure 03 with at least one machine-readable printed image 27, it is provided that the respective printed image 27 has a plurality of partial printed images, at least in the area covered by the optically imaging structure 03. At least one partial printed image of these partial printed images has image elements 28a to 28j with at least one pixel and / or one line, wherein the respective pixel and / or the respective line is formed by printing fluid that is only visible to the human eye due to the excitation lying outside the electromagnetic spectrum visible to the human eye.In an alternative or additional embodiment, it can be provided that at least one image element 28a to 28j of at least one partial print image of the print image 27, which is to be machine-readable and has a plurality of partial print images, is formed by a mixture, wherein this mixture comprises a print fluid that is visible to the human eye, in particular under daylight conditions, and a print fluid that is only visible to the human eye as a result of the excitation lying outside the electromagnetic spectrum visible to the human eye.

[0046] Furthermore, in order to form an arrangement with at least one machine-readable printed image 27, it can be provided that in this arrangement comprising a substrate 26 having the printed image 27 and a structure 03 optically imaging this printed image 27, in a first area covered by the optically imaging structure 03, the image elements 28a to 28j of the printed image 27 arranged therein are each formed by a printing fluid that is visible to the human eye, in particular under daylight conditions, and in a second area covered by the optically imaging structure 03, the image elements 28a to 28j of the printed image 27 arranged therein are each formed by a printing fluid that is visible to the human eye only as a result of the excitation lying outside the electromagnetic spectrum visible to the human eye.

[0047] Irrespective of the respective design of the substrate 26 and / or the respective design of the optically imaging structure 03 formed thereon and / or the printing fluid used to form at least one printed image 27, whether a printing fluid that is visible to the human eye, in particular under daylight conditions, or whether a printing fluid that is only visible to the human eye due to excitation lying outside the electromagnetic spectrum visible to the human eye is used, or whether both of the aforementioned types of printing fluids are used together to create the same printed image 27 to form a security element 01 or a security document 02, what is described below can be provided.

[0048] Fig. 4 shows, by way of example, a security document 02, e.g. a banknote, whose substrate 26 consists, for example, of a fibrous printing material, in particular of paper, and has at least one transparent window 04. Alternatively, the substrate 26 of the security document 02 can also be a film, preferably a transparent polymer film or a film with a transparent window 04. On one side of the security document 02, at least in the region of the relevant transparent window 04, a micro-optical structure 03 is arranged that partially or completely covers this window 04. This micro-optical structure 03 is designed as a lens array or as a lenticular lens, each of which consists of plano-convex microlenses 11.

[0049] These microlenses 11 are rotationally symmetrical, spherical or aspherical in the case of a lens array and, for example, axially symmetrical and rod-shaped in the case of a lenticular lens. Outside and at a distance from the area of the transparent window 04, on the other side of this security document 02, i.e. on the side of the security document 02 not having the aforementioned lens array or lenticular lens, a printed image 27 is formed or applied, wherein this printed image 27 can be formed by a printing fluid that is visible to the human eye, in particular under daylight conditions, or by a printing fluid that is only visible to the human eye as a result of excitation that lies outside the electromagnetic spectrum visible to the human eye. The printed image 27 in question can contain information that is directly recognizable by humans or can be designed to be machine-readable alone. This printed image 27 is, for example,dot-shaped or line-shaped grid consisting of image elements 28a to 28j is applied to the substrate 26 and preferably created in an industrial printing process, e.g. in an offset printing process. A pixel size 38 or a line width 38 of the image elements 28a to 28j of the printed image 27 applied to the substrate 26 is smaller than a lens width 18 of the microlenses 11 arranged in the lens array or lenticular and is thus significantly less than 100 µm, preferably approximately 20 µm or less. If the window 04 partially or completely covered by the micro-optical structure 03 is also on the back of this substrate 26 of the security document 02, ieon the side of the substrate 26 of the security document 02 facing away from the micro-optical structure 03 has a further printed image 27, preferably also created using an offset printing process, this further printed image 27 arranged in the region of the transparent window 04 has at least one unprinted area, i.e. a recess 06, in the area covered by the micro-optical structure 03, so that the relevant recess 06 in the further printed image 27 arranged in the region of the window 04 partially exposes the micro-optical structure 03 applied to the substrate 26 of this security document 02 and allows a view through the transparent window 04 onto the respective flat enveloping surface 21 of the plano-convex microlenses 11 arranged in the micro-optical structure 03.

[0050] A method for authenticating a security document 02 having a micro-optical structure 03 now consists in that the substrate 26 of the security document 02 - as in the Fig. 4 indicated by an arrow - folded along a crease line 07 preferably running through this security document 02, and thereby the printed image 27 formed or applied outside and spaced from the area of the transparent window 04 is brought into alignment with the micro-optical structure 03 applied on the other side of the substrate 26 of this security document 02 or at least with one of the recesses 06 partially exposing the micro-optical structure 03 in the printed image 27 arranged in the area of the window 04, or at least can be brought into alignment. The substrate 26 of the security document 02 can - as in the Fig. 4 indicated - be folded over approximately in half at the fold line 07, for example, so that the folded part of the substrate 26 having the printed image 27 applied outside and at a distance from the area of the transparent window 04 is placed or at least can be placed on the other part of this substrate 26 having the transparent window 04 and the micro-optical structure 03. By folding the substrate 26 of the security document 02, the printed image 27 applied outside and at a distance from the area of the transparent window 04 in the transparent window 04 of the substrate 26 of this security document 02 is placed on the respective flat enveloping surface 21 of the plano-convex microlenses 11 arranged in the micro-optical structure 03.

[0051] If necessary, by carrying out a relative movement between the micro-optical structure 03 and the printed image 27 which is brought into registration with this micro-optical structure 03 and is formed or applied outside and at a distance from the area of the transparent window 04, or by carrying out a tilting movement of the entire security document 02 folded along the fold line 07, this printed image 27 or at least the information contained therein becomes visible or recognizable when viewed from the direction of the convex enveloping surface 13 through the micro-optical structure 03 onto the printed image 27 in question, which is shown in the Fig. 4 exemplified by a preferably human-readable "&" character.

[0052] The advantage of the proposed solution is that the security document 02 can be authenticated without the aid of external means. The proposed method thus enables self-authentication of the security document 02 in question solely using means inherent in the security document 02 itself. The authentication proposed here therefore provides proof, anywhere and at any time, that the security document 02 in question is an original, in particular a genuine banknote.

[0053] It was found that a printed image 27 which has been created in the area of the transparent window 04 on the back of the substrate 26, i.e. on the side of this substrate 26 facing away from the micro-optical structure 03, with a printing fluid which is generally visible to the human eye under daylight conditions, is sometimes not sufficiently clearly recognizable, particularly under dim light conditions, e.g., dim light conditions, when viewed from the direction of the convex enveloping surface 13 through the micro-optical structure 03 in question onto the printed image 27 in question.

[0054] To improve the recognizability of such a printed image 27, particularly for the human eye, it is proposed to overprint the printed image 27 created in the area of the transparent window 04 on the back of the substrate 26 with a printing fluid that has a lighter shade than the shade of the printing fluid used to create the respective printed image 27. If the printed image 27 applied in the area of the transparent window 04 on the back of the substrate 26 has been created from several printing fluids of different shades, a printing fluid that has a lighter shade than the lightest shade of the printing fluid used to create the respective printed image 27 is used to overprint this printed image 27 created in this way.Preferably, the printed image 27 applied in the region of the transparent window 04 on the back of the substrate 26 is at least partially overprinted with a layer 39 of white ink. This layer 39 forms a surface-extending cover layer made of light, in particular white, ink for the printed image 27 applied in the region of the transparent window 04 on the back of the substrate 26. This cover layer can be opaque, i.e. impermeable to electromagnetic radiation with a wavelength in the range of approximately 380 nm (violet) to 780 nm (red), or partially transparent to electromagnetic radiation with a wavelength in the range of approximately 380 nm (violet) to 780 nm (red).The partial transparency can be designed to vary gradually across the two-dimensional surface area of the cover layer, so that some areas of the cover layer are more transparent than others. The degree of transparency for incident light can preferably be in the range between 10% and 90%.

[0055] It follows, therefore, as in the Fig. 5 shown by way of example - a security document 02 with a transparent window 04 formed in its substrate 26, wherein at least in the region of the transparent window 04 on one side of the substrate 26 a micro-optical structure 03 consisting of microlenses 11 is arranged and on the other side of the substrate 26 opposite this micro-optical structure 03 at least one printed image 27 is arranged. The printed image 27 in question has a plurality of image elements 28a to 28j in a dot-shaped or line-shaped grid, wherein these image elements 28a to 28j are formed in a color tone other than white. A pixel size 38 or a line thickness 38 of these image elements 28a to 28j is in each case smaller than a lens width 18 of the microlenses 11 arranged in the micro-optical structure 03. For contrast enhancement, it is now provided that at least on a partial area, ieon a section of the printed image 27 in question, on the side of which facing away from the micro-optical structure 03, there is arranged a layer 39 which covers the printed image 27 in question and which is extended over an area, said layer 39 consisting of a lighter color than the at least one color different from white from which the printed image 27 in question consists. This layer 39 is preferably formed in the color white. As previously mentioned, the layer 39 covering the printed image 27 in question can be formed to be opaque to electromagnetic radiation with a wavelength in the range from 380 nm to 780 nm, or this layer 39 can be formed to be transparent to electromagnetic radiation with a wavelength in the range from 380 nm to 780 nm, wherein a degree of transparency for this electromagnetic radiation is in the range, for example, between 10% and 90%.In addition, the transparency can be designed to vary gradually over the two-dimensional areal extent of the layer 39 covering the respective printed image 27, so that some areas of this layer 39 have a different degree of transparency than other areas of this layer 39. As a result, certain image elements 28a to 28j of the respective printed image 27 can be emphasized by their improved recognizability for the human eye, whereas other image elements 28a to 28j of the respective printed image 27 deliberately remain less recognizable. In the preferred embodiment,the layer 39 covering the respective printed image 27 is produced using an inkjet printing process or an offset printing process or a screen printing process, whereas the respective printed image 27 arranged on the other side of the substrate 26 opposite the micro-optical structure 03 is produced using an offset printing process.

[0056] By overprinting the printed image 27 applied in the area of the transparent window 04 on the back of the substrate 26, the contrast between the image elements 28a to 28j contained in this printed image 27, i.e., its pixels and / or lines, and their respective immediate periphery is increased. Contrast is generally defined as the difference in brightness between adjacent light and dark areas in an image.By overprinting the printed image 27 applied in the area of the transparent window 04 on the back of the substrate 26 with a layer 39 of a light, in particular white, ink, the contrast of several, preferably most, in particular all, image elements 28a to 28j of the printed image 27 in question is increased when viewed from the direction of the convex enveloping surface 13 through the micro-optical structure 03, so that this printed image 27 or at least the information contained therein is or becomes more easily recognizable to the human eye, in particular even under low-light, e.g. dim lighting conditions.

[0057] In a particularly advantageous embodiment of the invention, a security document 02 is obtained with a contrast-enhancing layer 39 on the back of the substrate 26 together with means for self-authentication, as shown by way of example in a sectional view in the Fig. 6 is shown and described below.

[0058] The Fig. 6 shows this in the Fig. 5 security document 02 shown by way of example with a transparent window 04 formed in its substrate 26, wherein at least in the region of the transparent window 04 on one side of the substrate 26 there is a micro-optical structure 03 consisting of microlenses 11 and on the other side of the substrate 26 opposite this micro-optical structure 03 there is a first printed image 27. In this exemplary embodiment too, this first printed image 27 has a plurality of image elements 28a to 28j in a dot-shaped or line-shaped grid, wherein these image elements 28a to 28j are preferably formed in a color tone other than white. A pixel size 38 or a line thickness 38 of these image elements 28a to 28j is in each case smaller than a lens width 18 of the microlenses 11 arranged in the micro-optical structure 03. Here too, it is provided for contrast enhancement that at least on a partial area oron a section of the first printed image 27 on the side of which is remote from the micro-optical structure 03, a layer 39 is arranged which extends over the entire surface and covers this first printed image 27, this layer 39 preferably consisting of a lighter color than the at least one color different from white of which the first printed image 27 consists.

[0059] This is now according to the Fig. 6 The proposed Safety Document 02 differs from the one in the Fig. 5 shown embodiment in that on the side of the layer 39 partially covering the first printed image 27 facing away from the micro-optical structure 03, a second, ie a further, preferably also produced in an offset printing process, printed image 41 is arranged. This second printed image 41 is arranged on the layer 39 partially covering the first printed image 27 in such a way that this second printed image 41 after execution of a Fig. 6 by an arrow indicated folding line 07 preferably running through the security document 02 - as shown in the Fig. 4 shown by way of example - is brought into register with the micro-optical structure 03 applied on the other side of the substrate 26 of this security document 02, or at least can be brought into register with it, in such a way that this second printed image 41 or at least an item of information contained therein is or becomes visible and / or recognizable when viewed from the direction of the micro-optical structure 03. The folding line 07, at which the substrate 26 of this security document 02 is folded, is preferably arranged outside the layer 39 partially covering the first printed image 27, i.e. at a distance from this layer 39. This folding line 07 is preferably arranged in that part of the first printed image 27 which is not covered by the layer 39 arranged on the first printed image 27.

[0060] Also in the embodiment of the invention according to the Fig. 6 It can be provided that the image elements 28a to 28j of the first printed image 27 are formed in a color tone different from white, wherein the layer 39 partially covering the first printed image 27 consists of a lighter color tone than the at least one color tone different from white of which the first printed image 27 consists.

[0061] In addition, the embodiment of the invention according to the Fig. 6 in any technically reasonable combination, have at least some of the features already associated with the Fig. 1 and 5 were described.

[0062] Based on the Fig. 7 It will now be explained how a safety document 02 is to be created, in particular in accordance with the Fig. 5 oder 6 shown embodiments. As already mentioned, the particularly contrast-enhancing layer 39 covering the respective printed image 27 can indeed also be produced using an offset printing process or a screen printing process, although in the preferred embodiment it is produced using an inkjet printing process, whereas the respective printed image 27 arranged on the other side of the substrate 26 opposite the micro-optical structure 03 is produced using an offset printing process. The printed image 27 consists of several image elements 28a to 28j printed in at least two different printing inks, wherein these image elements 28a to 28j in turn form pixels and / or lines. A pixel size 38 or line thickness 38 is preferably in a range of less than 20 µm, e.g. in the range of approximately 5 µm to 10 µm. A color register of the image elements 28a to 28j printed in different printing inks, iethe accuracy of their relative arrangement to one another, in the embodiments considered here is less than 20 µm, preferably less than 10 µm and is in particular in the range of approximately 5 µm.

[0063] The production of the printed image 27 with the aforementioned color register accuracy takes place, for example, in a printing press designed as a rotary printing press, in particular in a printing press used in security printing, wherein the substrate 26 designed, for example, as a printing material web or as a printing sheet is guided over a cylinder designed, for example, as an impression cylinder 42, wherein the printing inks involved in the respective printed image 27 are applied to the substrate 26 by successive overprinting or wherein, in the preferred embodiment, the printing inks involved in the respective printed image 27 are collected, for example, on a transfer cylinder 43 and are delivered jointly by this transfer cylinder 43 to the substrate 26 guided by the impression cylinder 42. The substrate 26 is designed, for example, as a printing material web in the form of a polymer film or as a printing sheet made of paper.

[0064] At least two forme cylinders 44 are positioned or at least positionable around the circumference of the transfer cylinder 43, each of these forme cylinders 44 transferring one of the printing inks involved in the respective print image 27 to the transfer cylinder 43. The respective direction of rotation of impression cylinder 42, transfer cylinder 43 and forme cylinder 44 is shown in the Fig. 7 The person skilled in the art will know that each of the forme cylinders 44 is assigned a Fig. 7 not shown. In the preferred embodiment, the printing inks transferred by the forme cylinders 44 attached to the transfer cylinder 43 differ in their color tone.

[0065] Downstream of the transfer point, at which the transfer cylinder 43 prints the printing inks collected on it to create the printed image 27 onto the substrate 26 guided by the impression cylinder 42, a printing device is provided on the same side of the substrate 26 as the printed image 27 created at the transfer point, this printing device overprinting the printed image 27 at least partially with a layer 39 of a light-colored, preferably white, ink. This printing device is preferably designed as at least one inkjet print head 46. In the preferred embodiment, the color tone of the ink printed by the respective inkjet print head 46 is lighter than the respective color tone of the printing inks applied to the substrate 26 by the transfer cylinder 43.

[0066] The printing press preferably also includes an embossing device 47, with which the micro-optical structure 03 consisting of microlenses 11 is formed on the substrate 26. This embossing device 47 can thus be arranged upstream of the impression cylinder 42 in the printing press. In a particularly advantageous embodiment, however, the impression cylinder 42 has this embossing device 47 on its circumference, wherein the micro-optical structure 03 consisting of microlenses 11 is formed with this embossing device 47 and, during the rotation of this impression cylinder 42, is arranged on the substrate 26 guided by this impression cylinder 42. The microlenses 11, which are formed, for example, from a plastic or resin, have a lens width 18, for example, of less than 100 µm, preferably between 20 µm and 65 µm.

[0067] This results in a printing press for producing a security document 02, wherein an impression cylinder 42 guiding a substrate 26 of the security document 02 and a transfer cylinder 43 cooperating with the impression cylinder 42 at a transfer point and printing a print image 27 onto the substrate 26 are provided. The substrate 26 of the security document 02 has at least one transparent window 04, wherein a micro-optical structure 03 consisting of microlenses 11 is provided on one side of the substrate 26 at least in the region of the respective transparent window 04.The impression cylinder 42 and the transfer cylinder 43 are arranged to cooperate in such a way that, in a printing process, the micro-optical structure 03 consisting of microlenses 11 is arranged on one side of the substrate 26 at least in the area of the relevant transparent window 04, and the at least one printed image 27 is arranged on the other side of the substrate 26 opposite this micro-optical structure 03, at least in the area of the transparent window 04. This arrangement of the micro-optical structure 03 consisting of microlenses 11, produced by the embossing device 47, and of the at least one printed image 27 generated by the impression cylinder 42 and transfer cylinder 43 in the area of the transparent window 04 can take place simultaneously at the aforementioned transfer point or at different points with a time offset with respect to the circumference of the impression cylinder 42.

[0068] A printing device is also provided in the printing press, wherein this printing device applies a layer 39 covering the relevant print image 27 at least on a section of the relevant print image 27 on the side facing away from the micro-optical structure 03. This printing device is arranged downstream of the transfer point, at which the transfer cylinder 43 prints the print image 27 onto the substrate 26 guided by the impression cylinder 42, on the same side of the substrate 26 as the print image 27 created at the transfer point, and is designed according to the invention as at least one inkjet print head 46.In its preferred embodiment, the print image 27 in question has a plurality of differently colored image elements 28a to 28j in a dot-shaped or line-shaped grid, wherein these image elements 28a to 28j are each formed in a color tone different from white, wherein the layer 39 formed by the at least one inkjet print head 46 consists of a lighter color tone than the color tones other than white of which the print image 27 in question consists.

[0069] To maintain high register accuracy, the impression cylinder 42 advantageously has the embossing device 47 on its circumference, wherein the embossing device 47 forms the micro-optical structure 03 consisting of microlenses 11 and is arranged such that it forms the micro-optical structure 03 consisting of microlenses 11 during the rotation of this impression cylinder 42, i.e., during an ongoing printing process, on the substrate 26 guided by this impression cylinder 42. In this case, a pixel size 38 or a line width 38 of the image elements 28a to 28j of the respective printed image 27 is preferably each smaller than a lens width 18 of the microlenses 11 arranged in the micro-optical structure 03.

[0070] In a preferred embodiment of this printing press, at least two forme cylinders 44 are provided which are positioned or at least positionable on the circumference of the transfer cylinder 43, each of these forme cylinders 44 transferring one of the printing inks involved in the respective print image 27 to the transfer cylinder 43, the transfer cylinder 43 collecting these different colored printing inks and the printing inks collected on the transfer cylinder 43 being transferred together to the substrate 26 guided by the impression cylinder 42. List of reference symbols

[0071] 01Security element 02Security document 03Optically imaging structure; micro-optical structure 04Window 05- 06Recess 07Crease line 08- 09- 10- 11Microlens 12Axis of symmetry; optical axis 13Convex enveloping surface 14Light beam 15- 16Edge point 17Edge point 18Lens width 19Principal plane 20- 21Plane enveloping surface 22Focal length 23Focus 24Focal plane 25- 26Substrate 27Printed image 28Image element (28a to 28j) 29Material thickness; thickness 30- 31Section plane 32Cone; angular field 33First viewing angle 34Second viewing angle 35- 36Layer thickness 37Vertex 38Picture point size; line thickness 39Layer 40- 41Print image 42Impression cylinder 43Transfer cylinder 44Forme cylinder 45- 46Inkjet print head 47Embossing device

Claims

1. Security document (02) having a transparent window (04) formed in the substrate (26) thereof, a micro-optical structure (03) composed of microlenses (11) being arranged on one side of the substrate (26), at least in the region of the transparent window (04), and a first print image (27) being arranged on the other side of the substrate (26), located opposite the micro-optical structure (03), at least in the region of the transparent window (04); this first print image (27) including a plurality of image elements (28a to 28j) in a punctiform or linear grid; a dot size (38) or a line thickness (38) of these image elements (28a to 28j) in each case being designed to be smaller than a lens width (18) of the microlenses (11) arranged in the micro-optical structure (03); a layer (39), which has a planar extension and covers this first print image (27), being arranged on a part of the first print image (27), on the side thereof facing away from the micro-optical structure (03), and a second print image (41) being arranged on the layer (39) that partly covers the first print image (27), on the side facing away from the micro-optical structure (03), characterized in that the second print image (41) is arranged on the layer (39) that covers a part of the first print image (27) in such a way that the second print image (41) can be brought into alignment with the micro-optical structure (03) applied to the other side of the substrate (26) of the security document (02) after carrying out a folding process at a bending line (07), in such a way that the second print image (41), or at least a piece of information contained therein, becomes visible and / or recognizable when viewed from the direction of the micro-optical structure (03).

2. Security document (02) according to claim 1, characterized in that the image elements (28a to 28j) of the first print image (27) are designed in a hue different from white, wherein the layer (39) that partly covers the first print image (27) is made of a lighter hue than the at least one hue different from white of which the first print image (27) is made.

3. Security document (02) according to claim 1 or 2, characterized in that the bending line (07) is arranged so as to be spaced apart from the layer (39) that partly covers the first print image (27).

4. Security document (02) according to claim 1 or 2 or 3, characterized in that the bending line (07) is arranged in that part of the first print image (27) which is not covered by the layer (39) arranged on the first print image (27).

5. Security document (02) according to claim 1 or 2 or 3 or 4, characterized in that the first print image (27) arranged on the side of the substrate (26) located opposite the micro-optical structure (03) is created in an offset printing method.

6. Security document (02) according to claim 1 or 2 or 3 or 4 or 5, characterized in that the layer (39) that partly covers the first print image (27) is created in an inkjet printing method.

7. Security document (02) according to claim 1 or 2 or 3 or 4 or 5, characterized in that the layer (39) that partly covers the first print image (27) is created in an offset printing method.

8. Security document (02) according to claim 1 or 2 or 3 or 4 or 5, characterized in that the layer (39) that partly covers the first print image (27) is created in a screen printing method.

9. Security document (02) according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8, characterized in that the relevant print image (27) arranged on the side of the substrate (26) located opposite the micro-optical structure (03) is composed of an overprint or a superposition of a plurality of print image segments that are each printed in differing printing colors.

10. Security document (02) according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9, characterized in that a plurality of image elements (28a to 28j) of the relevant print image (27) which are arranged under the micro-optical structure (03) in the viewing direction are designed so as to belong to different print motifs.

11. Security document (02) according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10, characterized in that the micro-optical structure (03) is designed as a lens array or as a lenticular lens, the lens array or the lenticular lens in each case being composed of plano-convex microlenses (11), and these microlenses (11) having a rotationally symmetric, spheric or aspheric design in the case of a lens array and an axially symmetric, rod-shaped design in the case of a lenticular lens.

12. Security document (02) according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11, characterized in that the substrate (26) is a fibrous print substrate or a polymer film.

13. Security document (02) according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12, characterized in that the security document (02) is designed as a bank note.

Images