SECURITY DOCUMENT WITH A TRANSPARENT WINDOW FORMED IN ITS SUBSTRATE

Description

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

[0002] WO 2017 / 081447 A1 discloses the preamble of claim 1 or a method for producing an image element array for an optical variable security device, comprising: a) providing a production tool with a surface pattern of color-receiving elements spaced apart from one another by non-color-receiving areas, wherein the color-receiving elements define the image elements of the desired image element array; b) applying a multicolored first image formed from a plurality of printing inks to only the color-receiving elements of the surface pattern and not to the areas between them; c) transferring only the sections of the multicolored first image corresponding to the image elements of the desired image element array from the production tool to a substrate by bringing the plurality of printing inks on the surface pattern into contact with the substrate or with a transfer unit.which then comes into contact with the substrate, thereby forming an image element array on the substrate; d) wherein the surface pattern on the production tool is configured such that the color-receiving elements defining the image elements of the image element array are periodic in at least one direction in at least a first region of the image element array, whereby, when a viewing element array with corresponding periodicity is superimposed on the image element array, each viewing element within the first region of the image element array directs light from one of the image elements or from one of the spaces between the image elements depending on the viewing angle, whereby the viewing element array in the first region directs light from either the array of image elements or from the spaces between them depending on the viewing angle, such that when the viewing angle is changed,The first image of the image elements in combination across the first area of ​​the image element array is displayed at a first viewing angle range and not at a second viewing angle range.

[0003] US patent 2018 / 0196980 A1 discloses a safety substrate comprising: a polymer substrate with a first and a second surface; an arrangement 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, the transparent base layer comprising either the polymer substrate or a layer established thereon;an optical matching layer arranged on the transparent base layer over a second region of the polymer substrate, wherein the second region includes at least the first region, wherein the optical matching layer has a first surface in contact with the surface relief of the transparent base layer and an opposing second surface with a profile that is not effective for focusing visible light, wherein the optical matching layer comprises a first transparent material extending over a first subregion of the arrangement of focusing elements, wherein the first subregion comprises the entire first region or only a part of the first region, wherein the first transparent material has a refractive index different from that of the transparent base layer, and wherein the focusing elements in the first subregion of the arrangement are functional focusing elements;and at least one first masking layer comprising a reflective and / or non-transparent material arranged above the optical matching layer over a third region of the polymer substrate, wherein the third region defines at least one slit in the first masking layers, the slit enclosing at least a part of the first subregion such that functional focusing elements of the arrangement are disclosed through the at least one slit.

[0004] German patent DE 11 2009 002 538 T5 discloses a device for the precise registration of an embossed security feature on a document, comprising: a) a first printing station for applying an embossable printing ink to an area of ​​a substrate; b) an embossing station with embossing means for embossing at least part of the area of ​​the embossable printing ink to form the embossed security feature; wherein the first printing station is arranged to print a registration area of ​​embossable printing ink on the substrate, and the embossing means is arranged to emboss at least part of the registration area to form a registration mark; c) printing means for applying an at least partially printed registration mark to the substrate; d) detection means for detecting the position of the registration mark and for detecting the position of the registration mark;e) Comparison means for comparing the relative positions of the register key and the register mark and adjustment means for adjusting the position of the printing medium relative to the embossing medium if the register key and the register mark are not aligned with perfect registration.

[0005] US Patent 2019 / 0232708 A1 discloses a security device comprising an arrangement of focusing elements with regular periodicity in at least a first direction, wherein each focusing element has an optical footprint, the different sections of which are directed towards the viewer depending on the viewing angle; and an arrangement of image elements with regular periodicity in at least the first direction, which overlaps the arrangement of focusing structures, wherein the image elements represent sections of at least two respective images, and wherein at least one image element of each respective image is located in the optical footprint of each focusing structure; wherein the security device includes a first region and a second region, which is laterally offset from the first region.wherein the image elements in the first region are laterally displaced 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 direct image elements corresponding to a first image to the viewer in such a way that the first image is displayed via the first region of the device, and simultaneously, in the second region of the device, the focusing structures direct image elements corresponding to a second image to the viewer in such a way that the second image is displayed via the second region of the device, and at a second viewing angle the second image is displayed via the first region of the device and simultaneously the first image is displayed via the second region of the device, and wherein the safety device further comprises a color filter which is located in the insertion between the image elements and the viewer,wherein the color filter overlaps at least part of the arrangement of the focusing elements and the arrangement of the 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.

[0006] EP 2 493 700 A2 discloses a method for manufacturing a safety device, the method comprising: providing an arrangement of lens-shaped focusing elements on one side of a transparent substrate; and providing a corresponding arrangement of sets of image strips on the other side of the transparent substrate, wherein the image strips and the lens-shaped focusing elements define a lens-shaped device such that, under different viewing directions, a corresponding image strip from each set is viewed via respective lens-shaped focusing elements.

[0007] WO 2011 / 107783 A1 discloses a security document comprising a document substrate with at least two transparent or see-through windows spaced apart from each other, and a device comprising a transparent substrate carrying: i) a uniform arrangement of micro-focusing elements on a first surface, wherein the focusing elements define a focal plane; ii) a corresponding first arrangement of micro-image elements in a first color and located in a plane that substantially coincides with the focal plane of the focusing elements;and, iii) a corresponding second arrangement of micro-image elements, in a color different from the first and located in a plane that substantially coincides with the focal plane of the focusing elements, wherein the divisions of the micro-focusing elements and of the first and second arrangements of micro-image elements and their relative positions are such that the arrangement of micro-focusing elements cooperates with each of the first and second arrangements of micro-image elements to generate respective enlarged versions of the micro-image elements of each arrangement due to the moiré effect; and wherein at least one section of the first arrangement of micro-image elements is not overlapped by the second and at least one section of the second arrangement of micro-image elements 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, wherein the device is registered with respect to the document substrate such that the enlarged version of the first micro-image element arrangement is visible through the first of the two windows and the enlarged version of the second micro-image element arrangement is visible through the second of the two windows, wherein the transition between the two micro-image element arrangements is concealed by the document substrate between the two windows.

[0008] 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 comprises a plurality of microlenses shaped in or on one side of a transparent or translucent material with the image elements on the opposite side, wherein the lens array has a measurement thickness corresponding to the distance from the apex of each microlens to the object plane, wherein each microlens has a set of lens parameters, the measurement thickness and / or at least one lens parameter being 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 measurement thickness of the lens array is preferably less than the focal length of all 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 such that in a section plane lying parallel to the principal plane of the microlens in a cone or angle field of the light incident on the image elements in the direction of the image elements, only one of the adjacent image elements is ever arranged, whereby for a viewer looking at the printed image from a certain viewing angle, only a single frame is ever perceptible at a certain time.

[0009] The invention is based on the objective of creating a security document with a transparent window formed in its substrate.

[0010] The problem is solved by a security document with the features of claim 1. The dependent claims describe advantageous embodiments and / or further developments of the solution found.

[0011] An exemplary embodiment is shown in the drawings. They show: Fig. 1 a security document with a security element having an optically imaging structure; Fig. 2 a highly magnified sectional view of an arrangement having at least one printed image and a single plano-convex microlens integrated into an optically imaging structure with light incidence from a first viewing angle; Fig. 3 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 reverse side; Fig. 6 a security document according to the invention with a contrast-enhancing reverse side and with means for self-authentication; Fig. 7 a simplified schematic representation of a printing press for production a security document, in particular according to Fig. 5 or 6 .

[0012] The embodiments of Figuren 1-5 are not claimed and are examples that facilitate understanding of the invention.

[0013] In optics, the term "lens" refers to a component transparent to light with at least one refractive surface positioned in the path of the light rays. Here, "light" refers to the portion of electromagnetic radiation visible to the human eye. In the electromagnetic spectrum, the range of light spans wavelengths from approximately 380 nm (violet) to 780 nm (red). The following discussion focuses on converging lenses, i.e., lenses that focus incident light, particularly plano-convex lenses. Preferred designs include rotationally symmetric spherical or aspherical lenses and axially symmetric rod-shaped lenses, where the respective axis of symmetry of the lens and its optical axis coincide. The optical axis is thus typically 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, e.g., a convex one, is given by its radius of curvature, which originates on the optical axis. A flat lens surface is defined by an infinitely large radius of curvature.

[0014] Rod-shaped lenses are formed in the form of either a right circular cylinder or an elliptical cylinder, bisected by its rod length, with the axis of symmetry of each such lens extending orthogonally to its respective rod length. In a spherically shaped lens, the refractive surface is formed as a section of a sphere, for example, in the form of a spherical cap. An aspherically shaped lens has at least one refractive surface that deviates from a spherical or planar shape. The shape of rotationally symmetric aspherical surfaces is generally 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 path of the light rays, called enclosing surfaces. With regard to light focusing, by definition, light enters a plano-convex converging lens at its convex enclosing surface, and light exits the lens at its flat enclosing surface. These enclosing surfaces are interfaces between different media through which the light propagates. One of these media is the material of the lens itself. At least one other medium is the space, usually filled with air, in which the lens is located. Since at least two of the media in the path of the light rays have different optical material properties, the light is refracted at the interface between these adjacent media.Thus, light refraction occurs at at least one of the surfaces of each lens, particularly at its curved surface. The optical material property associated with light refraction is expressed by the refractive index of the medium in question. The refractive index is a dimensionless physical quantity that indicates by what factor the wavelength and phase velocity of light are smaller in the medium than in a vacuum. When two media with different refractive indices share a common interface, the medium with the higher refractive index is called the optically denser. The Abbe number, also known as the Abbe 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 property of a lens to produce an optical image of an object viewed through the lens depends on the refractive index of the material of the respective lens and on the shape of its enclosing surfaces that form interfaces between different media.

[0016] The principal plane of a lens is a plane arranged orthogonally to the lens's axis of symmetry. In the case of a thin lens, where its greatest dimension along the axis of symmetry—that is, the lens thickness—is very small compared to the radius of curvature of its convex surface (for example, because the radius of curvature of the convex surface is at least five times greater than this thickness), only a single principal plane can usually be used with sufficient accuracy to determine the lens's properties. 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 and its focus (focal point), where the focus is defined as the intersection of parallel light rays that are bundled by the lens.The light rays entering the lens parallel to each other do not necessarily strike it parallel to its optical axis, but rather at an arbitrary angle of incidence with respect to the principal plane of the lens, in particular an acute angle. A plane arranged orthogonally to the optical axis at the focus is called the focal plane.

[0017] The surface of the lens that receives light has two opposing points, symmetrically aligned with its optical axis, that define the boundaries of this surface, for example, in the principal plane of the lens. The distance between these two points determines the width of the lens. The aperture of a lens is its free opening or diameter, through which light rays can pass unimpeded, and is at most equal to the lens width. The point where the optical axis intersects the surface of the lens that receives light is called the vertex. This vertex is located furthest from the focus of the lens on the surface that receives light.

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

[0019] Several rotationally symmetrical or aspherical lenses, arranged in a preferably uniform grid consisting of either square or hexagonal grid cells, preferably without gaps or overlaps, form a lens group, also known as a lens array. Several axially symmetrical rod-shaped lenses, arranged orthogonally to their rod length, preferably also without gaps or overlaps, form a lens grid, also known as a lenticular. Several lenses arranged in a grid-shaped lens group and / or several lenses arranged in a lens grid, in their respective combinations, form an optically imaging structure extending over a flat or curved surface in the form of a geometric figure. The surface of the optically imaging structure can have any contour, e.g.,Rectangular, round, oval, or polygonal. In geometry, a geometric figure is understood as a set of points. With regard to the optical imaging structure, at least a subset of the points forming the geometric figure has a lens positioned on each of them.

[0020] In an optical imaging structure, either one or more lattice-shaped lens groups, or one or more lenses arranged in a lens grid, or a mixture of these two lens arrangements, can be arranged together, so that both lattice-shaped lens groups and lenses arranged in a lens grid are present in the same optical imaging structure. The lens grids formed in the optical imaging structure can, for example, each have a different orientation, with the respective orientation of the lens grid being determined by the direction of the rod length of the lenses involved in the assembly of the respective lens grid.

[0021] A microlens is a miniaturized form of a conventional lens. Here, the term microlens refers to a lens with a width of less than 100 µm, preferably 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 a plastic or resin can be produced, for example, using injection molding, injection embossing, or printing processes. Optically imaging structures consisting of microlenses are also called micro-optical structures.

[0022] When an optical imaging structure, particularly one composed of microlenses, is combined with a preferably planar printed image, for example by applying this optical imaging structure to a substrate bearing the printed image, various effects can be generated for a viewer observing the printed image through the optical imaging structure. For instance, an arrangement consisting of at least one printed image and at least one optical imaging structure can produce so-called flip images, spatial (i.e., three-dimensional) effects, morphing effects, zoom effects, and / or animations. These effects are perceptible to a viewer without optical aids when they view the printed image alternately from different angles.The perception presented to the viewer through different viewing angles is also called a lenticular image.

[0023] The printed image, typically a two-dimensional surface, is formed on the preferably two-dimensional substrate, for example, in an industrial manufacturing process, preferably using a printing press. The substrate is, for example, a web or a printed sheet. The printed image is applied to the substrate, for example, in a dot-like or line-like grid. The printed image therefore consists, for example, of several, in particular a plurality, pixels and / or lines. A pixel size or line thickness is in the 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, each contributing to the formation of a printed image used together with an optically imaging structure, e.g.,each are 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 optically imaging structure in question.

[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 to be perceived as separate pixels or lines. The resolving power of the naked human eye varies from person to person. Normally sighted adults can usually still distinguish structures 150 µm apart at a distance of 25 cm. This corresponds to a visual angle of approximately 2 arcminutes, which is referred to as angular resolving power. At low contrasts, the visual acuity of the human eye decreases noticeably, with visual acuity being the inverse of resolving power. The lens width of a microlens is therefore typically smaller than the resolving power of the naked eye of a normally sighted adult.

[0025] To produce a colorful printed image, the substrate is printed with several printing inks; for example, the primary colors red, green, blue, and optionally black are applied to the substrate. A printed image typically consists of an arrangement of several small image elements positioned at different locations within the image. Each image element preferably comprises several pixels or lines and generally extends over a length of less than 100 µm. Each image element, or a group of adjacent image elements, forms, for example, an object viewed through a lens. The individual image elements are arranged within a printed image to form a print motif that determines the informational content of the image. Due to its limited size,Due to insufficient resolution, individual image elements used in conjunction with a microlens are not normally perceptible to the naked human eye. A person's perceived color impression of the printed image, or at least of a part of it, arises from an additive color mixing process in the viewer's eye and brain, where pixels and / or lines in the respective image elements are printed in different inks. The superposition of any two primary colors results in the secondary colors yellow, cyan, and magenta. The superposition of all three primary colors results in the color impression white. A color register, i.e., registration accuracy, i.e.,The accuracy of the pixels and / or lines of different printing inks in their relative arrangement to each other is, in the embodiments of the invention considered here, less than 20 µm, preferably less than 10 µm, and is in particular in the range of about 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 preferably produced as or by superimposing several partial printed images, wherein several or preferably each of the partial printed images is printed, for example, in a different printing ink. The superimposition can be effected by successive overprinting onto the substrate or, preferably, by collecting the partial printed images on a printing element, e.g., on a cylinder, and simultaneously transferring them to the substrate. The partial printed images themselves 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 viewed by an observer looking at a printed image, the several partial printed images involved in this printed image overlap in their perception, e.g. to form an overall color impression.

[0027] An arrangement consisting of at least one printed image and at least one optically imaging structure allows a viewer observing the printed image to perceive several different individual images from different viewing angles. A sequence of these individual images creates, in the viewer's perception, a flip image, a spatial (i.e., three-dimensional) effect, a morphing effect, a zoom effect, and / or an animation. Each of these individual images is also referred to as a frame.The individual images perceptible to the viewer from a specific viewing angle are created by a selection, determined by the optical imaging structure, from the set of partial print images perceptible 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 superimposing all partial print images present and perceptible at that position. The optical imaging structure arranged in combination with a print image is therefore an optical masking of the partial print images involved in the respective print image, which are arranged in alignment with the surface of the optical imaging structure.

[0028] To allow a viewer viewing the printed image to perceive several frames simultaneously from a specific viewing angle, in order to realize, for example, more complex and / or differentiated animations, the following is used, for example:An arrangement comprising a printed image and an optically imaging structure consisting of several plano-convex microlenses, wherein several, preferably more than three, in particular between five and ten image elements are arranged side by side under at least one microlens of the optically imaging structure, wherein these image elements are arranged between the extent of the lens width of the microlens and its focus in a cutting plane parallel to the principal plane of the microlens, wherein the cutting plane is arranged intersecting a cone or an angular field of the light incident through the lens width of the microlens in the direction of the adjacently arranged image elements, wherein several different image elements are arranged in a row simultaneously in the cutting 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 several plano-convex microlenses, wherein each of these microlenses has a lens width preferably of less than 100 µm along the printed image, wherein the printed image comprises a plurality of image elements, wherein several image elements are arranged under at least one of the microlenses of the optically imaging structure, wherein these several image elements arranged under at least one of the microlenses of the optically imaging structure are arranged side by side along the lens width and each extend in the direction of the lens width over a shorter length than the lens width.wherein several, preferably at least three, and in particular more than three, different image elements are arranged in a row between the extent of the lens width of the microlens in question and its focus in a cross-sectional plane lying parallel to the principal plane of the microlens in question, within the cone or angular field of the light incident through the lens width of the microlens in the direction of the adjacently arranged image elements. With this arrangement, several frames are perceptible simultaneously to a viewer viewing the printed image from a specific viewing angle, resulting in complex and / or differentiated animations as well as, with appropriately colored image elements, smooth color transitions and / or, with different print motifs formed from the image elements, smooth frame transitions.

[0030] The substrate is, for example, a fibrous printing material, particularly paper, or a film, preferably a polymer film. The substrate can be opaque or transparent. The substrate can be single-layered or multi-layered, particularly partially multi-layered. Different layers of a multi-layered substrate can be made of different materials, for example, one layer of paper and another layer of a polymer film. The substrate, or at least each layer of this substrate, has a material thickness, i.e., a thickness, for example, of less than 100 µm, preferably less than 50 µm, particularly about 25 µm. A printed image formed on the substrate has a layer thickness, for example, of less than 10 µm, preferably less than 5 µm, particularly in the range of 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 printed image and 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, identity cards, driver's licenses, deeds of ownership, travel documents such as airline or train tickets, admission tickets, academic transcripts, and other official or governmental documents such as birth, death, or marriage certificates. This list is only exemplary and by no means exhaustive. Preferably, however, the documents in question are banknotes.

[0032] Fig. 1 Figure 2 shows an example of 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, either partially or completely, wherein the respective optically imaging structure 03 is preferably designed as a micro-optical structure 03 formed from microlenses 11. The optically imaging structure 03 in question 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, in particular, as an excerpt from the... Fig. 1 The depicted security element 01 or document 02 shows, in a highly magnified sectional view, 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 simultaneously 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, in which case the axis of symmetry 12 extends orthogonally to the length of the rod. The microlens 11 is manufactured, for example, from a transparent plastic or resin by injection molding, casting, stamping, or printing. The microlens 11 has a convex surface 13 for light entry, and, for example, a bundle of parallel light rays 14 strikes this surface 13.The microlens 11 has two opposing edge points 16 and 17 bounding the convex surface 13, symmetrically to its optical axis 12, which passes through the vertex 37 of the convex surface 13. The distance between these two edge points 16 and 17 determines the width of this microlens 11, which is 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 and 17 of the convex surface 13 lie in a plane orthogonal to the optical axis 12 of the microlens 11, which is also referred to as the principal plane 19 of this microlens 11. In the [reference to the figure] Fig. 2 In the illustrated embodiment, the principal plane 19 forms a planar surface 21 of the microlens 11. The distance between the principal plane 19 of the microlens 11 and its focus 23 (focal point) constitutes the focal length 22 of the microlens 11, where the focus 23 is the intersection point of the focused light rays 14 incident on the microlens 11, particularly parallel ones. The focal length 22 of a microlens 11 is less than 100 µm. A plane arranged orthogonally to the optical axis 12 at the focus 23 is called the focal plane 24.

[0034] In the Fig. 2 In the illustrated embodiment, the microlens 11 is part of a lens array or lens grid in which a plurality of microlenses 11 are arranged, preferably without gaps or overlaps, with respect to a specific area of ​​arbitrary contour. The lens array or lens grid is arranged on a substrate 26, the substrate 26 being, for example, a fibrous printing material with a transparent window, in particular paper, or a film, preferably a transparent polymer film. The substrate 26 has a material thickness 29 of, for example, less than 100 µm, preferably less than 50 µm, in particular about 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 surface 21 of the respective microlens 11.

[0035] In the Fig. 2 In the illustrated embodiment, a printed image 27 of a small layer thickness 36, e.g., less than 10 µm, is applied to the back of the substrate 26, i.e., to the side of this substrate 26 facing away from the microlens 11. This printed image 27 comprises a plurality of individual, distinct image elements 28. These individual image elements 28 are very small and extend parallel to the lens width 18 over only a few micrometers, e.g., a maximum of 10 µm. Therefore, it is possible to arrange several, e.g., ten, such image elements 28a to 28j side by side in the area covered by the flat surface 21 of the microlens 11. At least one of these image elements 28a to 28j preferably has pixels and / or lines printed in different inks, depending in particular on the number of, e.g.,The image elements 28a to 28j, arranged side by side, have pixels with a pixel size 38 and / or lines with a line thickness 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 a superimposed print or a layering of several partial printed images, each printed in different inks. The image elements 28a to 28j, arranged side by side in the area covered by the planar surface 21 of the microlens 11, i.e., under the microlens 11, preferably belong to different print motifs.

[0036] The image elements 28a to 28j, arranged side by side under the 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 microlens 11 and its focus 23 in a section plane 31 parallel to the principal plane 19 of the microlens 11, wherein the section plane 31 intersects a cone 32 or an angular field 32 of the light incident through the lens width 18 of the microlens 11 in the direction of the image elements 28a to 28j, which are arranged side by side, and wherein several of the image elements 28a to 28j are preferably arranged in a row within the cone 32 or the angular field 32 in the section plane 31. Fig. 2 In the illustrated embodiment, within the cone 32 or the angular field 32, the five image elements 28c to 28g are arranged in a row, whereas the remaining image elements 28a, 28b, and 28h to 28j, arranged in the area covered by the flat surface 21 of the microlens 11, are not perceptible to a viewer observing the printed image 27 at a first viewing angle 33 corresponding to the incident light rays 14, e.g., an acute angle. If the viewing angle of a viewer observing the printed image 27 is now changed to a second viewing angle 34 that differs from the first viewing angle 33, e.g., an obtuse angle, the image elements 28a to 28j perceptible to him also change. This is shown in the Fig. 3 shown, 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 exhibits. Due to the second viewing angle 34 differing from the first viewing angle 33, the following are present in the Fig. 3 In the illustrated embodiment, for a viewer looking at the printed image 27, only the image elements 28d to 28h are perceptible, the others are not.

[0037] As mentioned, the ones in the Fig. 2 and 3The image elements 28a to 28j, arranged in the area covered by the flat surface 21 of a single microlens 11, are formed by pixels and / or lines, preferably printed in different inks. Typically, the pixel size 38 and / or line thickness 38 of the respective lines are significantly smaller than the lens width 18 of the microlens 11, preferably in the range of a few micrometers, particularly less than 20 µm. 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 comprises pixels and / or lines printed using special printing fluids, particularly inks, which differ in their optical properties from conventional printing fluids, especially conventional printing inks.These special printing fluids include, for example, inks that are invisible to the naked eye of a person with normal vision without excitation outside the visible electromagnetic spectrum. In particular, they are infrared-absorbing inks, infrared-reflecting inks, infrared-converting inks, ultraviolet-fluorescent inks, or magnetic inks. These inks, which are invisible, especially under daylight conditions, can become perceptible in different shades, such as blue, green, or red, after appropriate excitation, just like other printing inks. This excitation is preferably electromagnetic or magnetic.

[0038] The term "ink" here refers to an intensely colored and coloring liquid, usually consisting of a solution or dispersion of colorants in water or other solvents. These solvents contain no binder, or in the case of inks formulated as India ink, very little binder. Colorants are color-imparting substances, such as pigments and dyes, which can be inorganic or organic, natural or synthetic. In contrast, printing inks are mixtures containing colorants that are transferred to a substrate, i.e., a printing material, using a printing plate. Printing inks contain inorganic and organic pigments, such as titanium dioxide as a white pigment or carbon black as a black pigment, as well as binders that encapsulate 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 (NIR) range, with radiation having 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) contains, for example, inorganic, pigment-like luminophores that emit radiation in the visible and / or infrared (NIR) spectral range after absorbing energy. An ink that converts infrared radiation into the visible spectrum contains so-called anti-Stokes pigments.

[0040] Ultraviolet radiation, or UV radiation for short, is electromagnetic radiation invisible to the human eye, with wavelengths shorter than visible light. According to a widely accepted classification, the ultraviolet spectrum encompasses wavelengths from 100 nm to 380 nm, i.e., from the short-wavelength range to the boundary of visible light. Ultraviolet fluorescent ink contains fluorescent pigments that glow intensely under ultraviolet irradiation and can also, if present, reflect the ultraviolet rays of daylight.

[0041] Magnetic ink is understood to be an ink, in particular one containing iron oxide particles. These particles can be magnetized by an external magnetic field, which differs from the Earth's magnetic field, and thus analyzed and read out magneto-optically, with reference to the substrate 26 and the optically imaging structure 03.

[0042] An arrangement advantageous with regard to machine readability comprising 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 planar 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 its side facing the optically imaging structure 03 and has at least one image element 28a to 28j with at least one pixel and / or a line, wherein this pixel and / or this line is formed by a printing fluid, wherein the printing fluid is only visible to the human eye due to excitation lying outside the electromagnetic spectrum visible to the human eye.This printing fluid is preferably configured as an infrared radiation absorbing ink, an infrared radiation reflecting ink, an infrared radiation converting ink into the visible spectrum, an ultraviolet radiation fluorescent ink, or a magnetic ink. The relevant at least one image element 28a to 28j of the machine-readable printed image 27 is thus an integral part of the relevant arrangement, e.g., 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, is directed with respect to the optical imaging structure 03 covering at least parts of the printed image 27, either from the front, i.e., towards the respective convex surface 13 of the microlenses 11, if this excitation is configured to act through the optical imaging structure 03, or from the rear, i.e., on the substrate side.directed at the respective planar 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 due to 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 relevant pixels and / or the line thickness 38 of the relevant 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 relevant arrangement of substrate 26 and optically imaging structure 03, at several individual positions in the group comprising multiple plano-convex microlenses 11 or in the grid comprising multiple plano-convex microlenses 11, the respective microlens 11 of the respective optically imaging structure 03 remains unformed, and at least one image element 28a to 28j of the printed image 27 with at least one pixel and / or a line is arranged at the respective defect location, wherein this pixel and / or this line is formed by the printing fluid, which is visible to the human eye only due to excitation lying outside the electromagnetic spectrum visible to the human eye. The printing fluid, which is not visible to the human eye under normal conditions, is therefore 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 form a printed image 27, which, when viewed with the naked eye through the optically imaging structure 03, allows a normally sighted observer to perceive several different individual images from different viewing angles. A sequence of individual images creates, in the observer's perception, a 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. These different individual images are also referred to as frames. Each of these aforementioned effects is based on several partial printed images, from which the respective printed image 27 is composed.To form an arrangement consisting of substrate 26 and optically imaging structure 03 with at least one machine-readable printed image 27, it is provided that the printed image 27 has several partial printed images, at least in the area covered by the optically imaging structure 03. At least one of these partial printed images has image elements 28a to 28j with at least one pixel and / or a line, wherein the pixel and / or line in question is formed by the printing fluid, which is visible to the human eye only due to excitation lying outside the electromagnetic spectrum visible to the human eye.In an alternative or additional embodiment, it may be provided that at least one image element 28a to 28j of at least one partial print image of the machine-readable print image 27 comprising several partial print images is formed by a mixture, wherein this mixture comprises a printing fluid visible to the human eye, particularly under daylight conditions, and a printing fluid visible to the human eye only as a result of excitation lying outside the electromagnetic spectrum visible to the human eye.

[0046] Furthermore, 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 visible to the human eye, particularly 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 visible to the human eye only due to excitation lying outside the electromagnetic spectrum visible to the human eye.

[0047] Notwithstanding the specific design of the substrate 26 and / or the specific 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 visible to the human eye, particularly under daylight conditions, or a printing fluid visible to the human eye only 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 for the formation of a security element 01 or a security document 02, the following may be provided.

[0048] Fig. 4 Figure 2 shows an example of a security document 02, e.g., a banknote, whose substrate 26 consists, for example, of a fibrous printing material, in particular 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 area of ​​the respective transparent window 04, a micro-optical structure 03 is arranged, partially or completely covering this window 04. This micro-optical structure 03 is designed as a lens array or as a lenticular, each consisting of plano-convex microlenses 11. In the case of a lens array, these microlenses 11 are rotationally symmetrical spherical or aspherical, and in the case of a lenticular, for example, axially symmetrical rod-shaped.Outside and spaced apart 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, a printed image 27 is formed or applied, wherein this printed image 27 may be formed by a printing fluid visible to the human eye, particularly under daylight conditions, or by a printing fluid visible to the human eye only due to excitation lying outside the electromagnetic spectrum visible to the human eye. The printed image 27 in question may contain information directly recognizable to humans or be solely machine-readable. This printed image 27 is applied to the substrate 26 in a grid consisting of, for example, dot-shaped or line-shaped image elements 28a to 28j and preferably in an industrial printing process, e.g.produced in an offset printing process. A pixel size 38 or a line thickness 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 therefore significantly less than 100 µm, preferably about 20 µm or less. If the window 04 on this substrate 26 of the security document 02, which is partially or fully covered by the micro-optical structure 03, also has a further printed image 27 on the reverse side, i.e., on the side of the substrate 26 of the security document 02 facing away from the micro-optical structure 03, preferably also produced in an offset printing process, then this further printed image 27 arranged in the area of ​​the transparent window 04 has at least one unprinted area in the area covered by the micro-optical structure 03.a recess 06, so that the recess 06 in question partially exposes the micro-optical structure 03 applied to the substrate 26 of this security document 02 in the further printed image 27 arranged in the area of ​​the window 04 and allows a view through the transparent window 04 onto the respective planar enveloping surface 21 of the plano-convex microlenses 11 arranged in the micro-optical structure 03.

[0049] One method for authenticating a security document 02 having a micro-optical structure 03 consists in the fact that the substrate 26 of the security document 02 - as in the Fig. 4 As indicated by an arrow, the security document 02 is folded along a crease line 07, preferably running through it, thereby bringing the printed image 27, formed or applied outside and spaced apart from the area of ​​the transparent window 04, 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 in the printed image 27 arranged in the area of ​​the window 04 that partially expose the micro-optical structure 03, or at least making it possible to bring it into alignment. The substrate 26 of the security document 02 can be – as shown in the Fig. 4 As indicated, the substrate 26 can be folded approximately in half at the fold line 07, so that the folded part, which displays 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, which displays the transparent window 04 and the micro-optical structure 03. By folding the substrate 26 of the security document 02, the printed image 27, which is applied outside and at a distance from the area of ​​the transparent window 04, is placed in the transparent window 04 of the substrate 26 of this security document 02 onto the respective flat surface 21 of the plano-convex microlenses 11 arranged in the micro-optical structure 03.

[0050] If necessary, by performing a relative movement between the micro-optical structure 03 and the printed image 27, which is aligned 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 performing a tilting movement of the entire security document 02 folded at 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 towards the printed image 27 in question, which is in the Fig. 4 This is exemplified by an ampersand (&) sign that is preferably readable by humans.

[0051] The advantage of the solution found is that the security document 02 can be authenticated without the use of external means. The proposed procedure thus enables self-authentication of the security document 02 solely using features inherent in the document itself. The authentication proposed here therefore provides proof, valid anytime and anywhere, that the security document 02 is an original, specifically a genuine banknote.

[0052] It was found that a printed image 27, which was 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 that is generally visible to the human eye under daylight conditions, is sometimes not sufficiently visible, especially under dim light conditions, e.g., twilight conditions, when viewed from the direction of the convex enveloping surface 13 through the micro-optical structure 03 in question.

[0053] To improve the visibility of such a printed image 27, particularly for the human eye, the invention proposes overprinting 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 color of the printing fluid used to create the 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 is used to overprint this printed image 27 which has a lighter shade than the lightest shade of the printing fluid used to create the printed image 27.Preferably, the printed image 27 applied to the back of the substrate 26 in the area of ​​the transparent window 04 is at least partially overprinted with a layer 39 of white ink. This layer 39 forms an extensive top layer consisting of light, in particular white, ink for the printed image 27 applied to the back of the substrate 26 in the area of ​​the transparent window 04. According to the invention, this top layer is partially transparent to electromagnetic radiation with a wavelength in the range of approximately 380 nm (violet) to 780 nm (red). The partial transparency is gradually varied across the two-dimensional area of ​​the top layer, so that some areas of the top layer are more transparent than others. The degree of transparency for incident light can preferably be between 10% and 90%.

[0054] It therefore follows - as in the Fig. 5 As an example, a security document 02 is shown with a transparent window 04 formed in its substrate 26, wherein at least in the area of ​​the transparent window 04, a micro-optical structure 03 consisting of microlenses 11 is arranged on one side of the substrate 26, and at least one printed image 27 is arranged on the other side of the substrate 26 opposite this micro-optical structure 03. The printed image 27 has several image elements 28a to 28j in a dot-like or line-like grid, wherein these image elements 28a to 28j are formed in a color other than white. A pixel size 38 or a line thickness 38 of these image elements 28a to 28j is each smaller than a lens width 18 of the microlenses 11 arranged in the micro-optical structure 03. For contrast enhancement, it is provided that at least on a partial area, i.e.,On a section of the printed image 27, on the side facing away from the micro-optical structure 03, an extensive layer 39 covering the printed image 27 is arranged, wherein this layer 39 consists of a lighter shade than the at least one shade other than white that makes up the printed image 27. Preferably, this layer 39 is white. As mentioned above, the layer 39 covering the printed image 27 is transparent to electromagnetic radiation with a wavelength in the range of 380 nm to 780 nm, wherein the degree of transparency for this electromagnetic radiation is, for example, between 10% and 90%.Furthermore, the transparency of the layer 39 covering the printed image 27 is gradually varied across its two-dimensional surface area, such that some areas of this layer 39 have a different degree of transparency than other areas. This allows certain image elements 28a to 28j of the printed image 27 to be emphasized by their improved visibility to the human eye, while other image elements 28a to 28j of the printed image 27 remain deliberately less visible. In the preferred embodiment, this is...According to the invention, the layer 39 covering the relevant printed image 27 is produced in an inkjet printing process or in an offset printing process (not claimed) or in a screen printing process (not claimed), whereas the relevant printed image 27 arranged on the other side of the substrate 26 opposite the micro-optical structure 03 is produced in an offset printing process.

[0055] By overprinting the printed image 27 applied in the area of ​​the transparent window 04 on the back of the substrate 26, a contrast is increased 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.

[0056] 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 to the back of the substrate 26 in the area of ​​the transparent window 04 with a layer 39 of a light, in particular white, ink, the contrast of several, preferably most, and in particular all image elements 28a to 28j of the printed image 27 is increased when viewed from the direction of the convex surface 13 through the micro-optical structure 03. This makes the printed image 27, or at least the information it contains, more easily recognizable to the human eye, especially under low-light conditions, e.g., dim lighting.

[0057] In one embodiment of the invention, a security document 02 is provided 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 This shows in the Fig. 5 Exemplary security document 02 with a transparent window 04 formed in its substrate 26, wherein at least in the area of ​​the transparent window 04 a micro-optical structure 03 consisting of microlenses 11 is arranged on one side of the substrate 26 and a first printed image 27 is arranged on the other side of the substrate 26 opposite this micro-optical structure 03. In this embodiment as well, this first printed image 27 has several image elements 28a to 28j in a dot-like or line-like grid, wherein these image elements 28a to 28j are preferably formed in a color other than white. A pixel size 38 or a line thickness 38 of these image elements 28a to 28j is each 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 facing away from the micro-optical structure 03 a layer 39 covering this first printed image 27 is arranged, wherein this layer 39 preferably consists of a lighter shade than the at least one shade other than white of which the first printed image 27 consists.

[0059] This now according to the Fig. 6 The proposed security document 02 differs from the one in the Fig. 5 The embodiment shown is characterized by the fact that a second, i.e., a further, preferably also offset-printed image 41 is arranged on the side of the layer 39 facing away from the micro-optical structure 03, which partially covers the first printed image 27. This second printed image 41 is arranged on the layer 39 that partially covers the first printed image 27 in such a way that, after execution of a process described in the Fig. 6 fold indicated by an arrow at a crease line 07 preferably running through the security document 02 - as in the Fig. 4 As illustrated by way of example, the micro-optical structure 03 applied to the other side of the substrate 26 of this security document 02 is aligned, or at least can be aligned, in such a way that this second printed image 41, or at least information contained therein, is visible and / or recognizable when viewed from the direction of the micro-optical structure 03. The fold line 07, at which the substrate 26 of this security document 02 is folded, is preferably arranged outside the layer 39 that partially covers the first printed image 27, i.e., spaced apart from this layer 39. This fold 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] Even in the embodiment of the invention according to the Fig. 6 It may 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 which partially covers the first printed image 27 consists of a lighter color tone than the at least one color tone different from white from which the first printed image 27 consists.

[0061] Based on the Fig. 7 It will now be explained how a security document 02, in particular according to the requirements in the Fig. 5 oder 6 The illustrated embodiments can be produced. This printing machine is not claimed; this example facilitates understanding of the invention. As already mentioned, the layer 39 covering the relevant printed image 27, particularly the contrast-enhancing layer, can 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 relevant 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 about 5 µm to 10 µm.A color register of the image elements 28a to 28j, each printed in different printing inks, i.e. the accuracy of their relative arrangement to each other, is less than 20 µm in the embodiments considered here, preferably less than 10 µm and is in particular in the range of about 5 µm.

[0062] The production of the printed image 27 with the aforementioned color register is carried out, for example, in a printing press designed as a rotary printing press, particularly in a printing press used for high-value printing, wherein the substrate 26, designed, for example, as a web or a sheet, is guided over a cylinder designed, for example, as an impression cylinder 42, wherein the printing inks involved in the printed image 27 are applied to the substrate 26 by successive overprinting, or wherein, in a preferred embodiment, the printing inks involved in the printed image 27 are collected, for example, on a transfer cylinder 43 and transferred together from this transfer cylinder 43 to the substrate 26 guided by the impression cylinder 42. The substrate 26 is designed, for example, as a web in the form of a polymer film or as a sheet of paper.

[0063] At least two form cylinders 44 are attached to, or at least can be attached to, the circumference of the transfer cylinder 43, each of these form cylinders 44 transferring one of the printing inks involved in the respective printed image 27 to the transfer cylinder 43. The respective direction of rotation of the impression cylinder 42, transfer cylinder 43, and form cylinder 44 is specified in the Fig. 7 Each is indicated by an arrow indicating the direction of rotation. It is known to those skilled in the art that each of the forming cylinders 44 has a [missing information] in the Fig. 7 The inking unit is not shown. In the preferred embodiment, the printing inks transferred by the form cylinders 44 attached to the transfer cylinder 43 differ in their hue.

[0064] Downstream of the transfer point, where the transfer cylinder 43 prints the printing inks collected on it onto the substrate 26 guided by the impression cylinder 42 to create the print image 27, a printing device is provided on the same side of the substrate 26 as the print image 27 created at the transfer point. This printing device overprints the print 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 printhead 46. In the preferred embodiment, the color of the ink printed by the respective inkjet printhead 46 is lighter than the respective color of the printing inks applied to the substrate 26 by the transfer cylinder 43.

[0065] The printing press preferably also includes an embossing device 47, which forms the micro-optical structure 03, consisting of microlenses 11, on the substrate 26. This embossing device 47 can 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, with the micro-optical structure 03, consisting of microlenses 11, being formed by this embossing device 47 and positioned on the substrate 26 guided by the impression cylinder 42 during its rotation. The microlenses 11, which are made, for example, of a plastic or resin, have a lens width 18 of, for example, less than 100 µm, preferably between 20 µm and 65 µm.

[0066] This results in a printing machine for producing a security document 02, wherein a counter-pressure cylinder 42, which guides a substrate 26 of the security document 02, and a transfer cylinder 43, which interacts with the counter-pressure cylinder 42 at a transfer point and prints a printed image 27 onto the substrate 26, are provided. The substrate 26 of the security document 02 has at least one transparent window 04, wherein at least in the area of ​​the relevant transparent window 04 on one side of the substrate 26 a micro-optical structure 03 consisting of microlenses 11 is provided.The counter-pressure cylinder 42 and the transfer cylinder 43 are arranged to interact in such a way that, in a printing process, at least in the area of ​​the relevant transparent window 04 on one side of the substrate 26, the micro-optical structure 03, consisting of microlenses 11, and at least one printed image 27 are 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 the at least one printed image 27, produced by the counter-pressure cylinder 42 and transfer cylinder 43 in the area of ​​the transparent window 04, can occur simultaneously at the aforementioned transfer point or at different points along the circumference of the counter-pressure cylinder 42 with a time offset.

[0067] The printing press also includes a printing device, which applies a layer 39 covering at least one section of the printed image 27 on the side facing away from the micro-optical structure 03. This printing device is located downstream of the transfer point, where the transfer cylinder 43 prints the printed image 27 onto the substrate 26 guided by the counter-pressure cylinder 42, on the same side of the substrate 26 as the printed image 27 created at the transfer point, and is designed as at least one inkjet printhead 46.In its preferred embodiment, the printed image 27 has several 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 shade other than white, wherein the layer 39 formed by the at least one inkjet printhead 46 consists of a lighter color shade than the color shades other than white from which the printed image 27 consists.

[0068] Advantageously, to ensure high register accuracy, the impression cylinder 42 has an 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, on the substrate 26 guided by the impression cylinder 42 during its rotation, i.e., during an ongoing printing process. A pixel size 38 or a line thickness 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.

[0069] In a preferred embodiment of this printing machine, at least two form cylinders 44 are provided which are attached to or at least attachable to the circumference of the transfer cylinder 43, wherein each of these form cylinders 44 transfers one of the printing inks involved in the relevant printing image 27 to the transfer cylinder 43, wherein the transfer cylinder 43 collects these different colored printing inks and wherein the printing inks collected on the transfer cylinder 43 are jointly transferred to the substrate 26 guided by the counter-pressure cylinder 42. Reference symbol list

[0070] 01 Security element 02 Security document 03 Optically imaging structure; micro-optical structure 04 Window 05- 06 Recess 07 Fold line 08- 09- 10- 11 Microlens 12 Axis of symmetry; optical axis 13 Convex enclosing surface 14 Light ray 15- 16 Edge point 17 Edge point 18 Lens width 19 Principal plane 20- 21 Plane enclosing surface 22 Focal length 23 Focus 24 Focal plane 25- 26 Substrate 27 Printed image 28 Image element (28a to 28j) 29 Material thickness; thickness 30- 31 Section plane 32 Cone; angular field 33 First viewing angle 34 Second viewing angle 35- 36 Layer thickness 37 Vertex 38 Pixel size; Line thickness 39 Layer 40-41 Print image 42 Counter-pressure cylinder 43 Transfer cylinder 44 Form cylinder 45-46 Inkjet printhead 47 Embossing unit

Claims

1. Security document (02) including 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 at least one print image (27) being arranged on the other side of the substrate (26), located opposite this micro-optical structure (03), at least in the region of the transparent window (04), the relevant 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 the relevant print image (27), being arranged at least on a section of the relevant print image (27), on the side thereof facing away from the micro-optical structure (03), the layer (39) covering the relevant print image (27) being created in an ink jet printing method, characterized in that this layer (39) is designed to allow electromagnetic radiation having a wavelength in the range of 380 nm to 780 nm to pass, a degree of the transparency with respect to this electromagnetic radiation being in the range between 10% and 90%, the transparency being designed so as to gradually vary over the two-dimensional planar extension of the layer (39) covering the relevant print image (27) so that at least one area of the layer (39) or several areas of the layer (39) is or are designed to have a different degree of transparency than other areas of this layer (39), 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), the second print image (41) being arranged on the layer (39) that covers a part of the first print image (27) in such a way that this 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 this security document (02), after carrying out a folding process at a bending line (07), in such a way that this 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 relevant print image (27) are designed in a hue different from white, the layer (39) that covers the relevant print image (27) being made of a lighter hue than the at least one hue different from white of which the relevant print image (27) is made.

3. Security document (02) according to claim 1 or 2, characterized in that the layer (39) is made of a white hue.

4. Security document (02) according to claim 1 or 2 or 3, characterized in that the relevant 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.

5. Security document (02) according to claim 1 or 2 or 3 or 4, 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.

6. Security document (02) according to claim 1 or 2 or 3 or 4 or 5, 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), 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.

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

8. Security document (02) according to claim 1 or 2 or 3 or 4 or 5 or 6 or 7, characterized in that the relevant print image (27) is designed to contain a piece of information that is directly discernible for people or to only be machine-readable.

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 bending line (07) is arranged so as to be spaced apart from the layer (39) that partly covers the first print image (27).

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 the substrate (26) is a fibrous print substrate or a polymer film.

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 security document (02) is designed as a bank note.