METHOD FOR PRODUCING A SECURITY ELEMENT AND SECURITY ELEMENT

Description

[0001] The invention relates to a method for producing a security element, as well as a corresponding security element for securing security papers, valuable documents and other data carriers.

[0002] Data storage media, such as valuables or identification documents, or other valuables, such as branded goods and packaging or outer packaging of high-quality branded goods, are often provided with security elements for security purposes. These elements allow the authenticity of the data storage media to be verified and also serve as protection against unauthorized reproduction.

[0003] During the production of security elements, a so-called washing process is often used to create areas that are only partially covered with a cover layer, as is basically described, for example, in document WO 99 / 13157. In this process, a substrate that is only partially to be covered with the desired cover layer is first printed with a desired pattern using a printing ink with a high pigment content. Due to the high pigment content, the printing ink forms a porous, raised ink layer after drying. A cover layer is then applied to the printed substrate. Due to its large surface area and porous structure, this cover layer only partially covers the ink body in the area where the ink is applied.The ink application and the overlying top layer can then be removed by washing with a suitable solvent, so that recesses in the form of the printed pattern are created in the top layer in the originally printed areas of the substrate.

[0004] EP 3 403 844 A1 describes a method for producing a security element with a metallized relief area and a narrow, demetallized flat area matched thereto.

[0005] However, it has been shown that such a washing process does not produce satisfactory results under certain circumstances. For example, if the substrate to be coated contains embossed structures that exhibit little or no height variation over large areas, there is a risk that a wash-ink toning film will be unintentionally deposited in such areas due to the large contact area with the wash-ink cylinder when applying the wash-ink, thus preventing the desired recess pattern from being created in the subsequent washing step.

[0006] Based on this, the invention is based on the object of avoiding the disadvantages of the prior art and, in particular, of providing a generic manufacturing method with which even large-area, structured partial areas can be reliably produced in a washing process. The invention is also intended to provide a security element manufactured accordingly.

[0007] This object is achieved by the features of the independent claims. Further developments of the invention are the subject of the dependent claims.

[0008] In a method for producing a security element according to a first aspect of the invention, it is initially provided that a carrier is provided with an embossing lacquer layer and the embossing lacquer layer is provided with a desired effect embossing, in particular a micromirror embossing or a hologram embossing, a color is applied to the embossed embossing lacquer layer in some areas, a cover layer is applied to the partially colored surface area of ​​the embossing lacquer layer and then the color is removed with the cover layer thereon,

[0009] It is now further provided that large-area partial areas of the effect embossing, which are to remain uncoated during the subsequent color printing, are formed with a dot and / or line grid of small spacer structures, which is not visually recognizable when viewing the security element with the naked eye and in which the spacer structures have lateral dimensions of more than 2 µm in every spatial direction.

[0010] The ink can be removed, for example, by etching, lasering, washing, or with an adhesive element. A method is disclosed, wherein a carrier is provided with an embossing lacquer layer and the embossing lacquer layer is provided with a desired effect embossing, in particular a micromirror embossing or a hologram embossing, in wash ink printing a wash ink is applied to the embossed embossing lacquer layer in some areas, and a cover layer is applied to the area of ​​the embossing lacquer layer which is partially provided with wash ink and then the wash ink is removed with the cover layer thereon.

[0011] Furthermore, it is provided that large-area partial areas of the effect embossing, which are to remain uncoated during the subsequent wash-in-ink printing, are formed with a dot and / or line grid of small spacer structures, which is not visually recognizable when viewing the security element with the naked eye, and in which the spacer structures of the dot and / or line grid have lateral dimensions of more than 2 µm in every spatial direction.

[0012] In addition to the methods, the invention also includes a security element according to claim 14.

[0013] The carrier is formed in particular from a film, for example a thermoplastic such as polymethyl methacrylate (PMMA). The spacer structures are formed in particular from the embossing lacquer of the embossing lacquer layer.

[0014] The effect embossing can also be a vellum area, which is formed, for example, as a surface area with a relatively unstructured surface. The vellum area is thus characterized by having a slight inclination, in particular less than 5°, and / or a slight height variation, in particular less than 500 nm, relative to a main surface or a surface area of ​​the carrier.

[0015] For the purposes of this description, a portion of the effect embossing is considered to be large-area if it has an extension of more than 100 µm in any lateral direction, particularly more than 250 µm. Dot grids made of spacer structures with the following properties and parameters have proven particularly advantageous: A) The spacer structures can form a grid with constant spacing between the grid elements, where the symmetry of the grid is, in particular, the symmetry of a square grid, rectangular grid, diamond grid, hexagonal grid, or parallelogram grid. The spacer structures can also be shifted relative to the initial positions of the grid sites of such grids to form a "blurred" grid that generates particularly low diffractive disturbances. The shift can be up to 5%, 10%, or even up to 25% of the initial spacing in the grid. B) The spacings between adjacent spacer structures are advantageously below 200 µm in all lateral spatial directions, in particular below 100 µm. In blurred grids, these spacings are advantageously not exceeded even for the spacer structures shifted relative to one another.For example, in a square grid, an initial spacing of A = 50 µm and an irregular shift f of up to 25% can be provided. In the "blurred" grid, the spacer structures are then shifted by up to ΔA = f*A = 12.5 µm relative to their initial positions, so that the minimum spacing between adjacent spacer structures is A min = 25 µm and the maximum spacing between adjacent spacer structures is A max = 75 µm. C) The lateral dimensions of the spacer structures are at least 2 µm in all spatial directions to minimize disruptive diffractive color splitting. Furthermore, the lateral dimensions of the spacer structures are below 40 µm, preferably below 30 µm, and in particular below 20 µm, at least in one spatial direction, and advantageously even in both spatial directions. D) The base area of ​​the structures is preferably at least 3-sided and can in particular be 4-, 5- or 6-sided.Round, particularly circular or elliptical base areas can also be considered. E) The ratio of length to width of the base area is advantageously between 0.25 and 4. F) The expedient tapering of the spacer structures reduces the base area towards the upper contact surface of the spacer structures by at least 20%, advantageously by at least 40%. In extreme cases, the flanks of the spacer structures can converge to a point, for example in the case of spacer structures in the shape of a pyramid, a cone or a hemisphere. G) The aspect ratio height:length or height:width is advantageously between 0.05 and 2, preferably between 0.1 and 1. The absolute height of the spacer structures is advantageously below 5 µm, in particular below 3 µm and is particularly advantageously around 1 to 2 µm.H) The area coverage of the spacer structures is advantageously below 20%, particularly advantageously below 17%, and especially below 10%, so as not to reduce the effective hologram area too much. Preferably, the area coverage in a vellum region is below 10%, in particular 5%, and preferably below 1%.

[0016] Since they contain numerous corresponding technical features, the manufacturing process and the security element itself will be discussed together below. It is understood that features that are designed in a certain way in the security element will be designed in the same way in the manufacturing process, and vice versa. For the sake of simplicity of description, this linguistic distinction between the process and the process result has been omitted below.

[0017] The cover layer typically consists of metal, such as aluminum, chromium, copper, and / or metal alloys. In one embodiment, the cover layer can consist of multiple layers, in particular metal layers, for example, chromium and aluminum. In one embodiment, the cover layer can be formed as an interference layer comprising a dielectric layer.

[0018] In an advantageous embodiment of the method or of the security element, the spacer structures form a regular grid with a constant spacing of the grid elements, wherein the grid has, in particular, the symmetry of a square grid, rectangular grid, diamond grid, hexagonal grid, or parallelogram grid. According to an alternative, equally advantageous embodiment, the spacer structures form an irregular grid with varying spacing of the grid elements, wherein the grid is constructed on the basis of a square grid, rectangular grid, diamond grid, hexagonal grid, or parallelogram grid, and the spacer structures are shifted by up to 25%, advantageously by up to 10%, from the starting positions with a constant spacing.

[0019] The displacement of the spacer structures is advantageously carried out irregularly, particularly in the case of a point-like grid structure, although a displacement can also be provided for a differently designed spacer structure. An irregular displacement can be generated, in particular, with the aid of random numbers or pseudorandom numbers. If the unshifted starting position of a spacer structure is equal to (x 0 , y 0 ), the nominal starting distance between two adjacent positions without displacement is r 0 , and the desired variation f of the starting distance is f = 10%, a shifted spacer structure is advantageously positioned at the position x , y = x 0 + r * cos ϕ , y 0 + r * sin ϕ , generated, where r = f*r 0 *RandomReal[] is a pseudorandom number in the interval [0, f*r 0 ] and ϕ = 2π *RandomReal[] is a pseudorandom number in the interval [0, 2π], the factor f=0.1, and the function RandomReal[] returns a new pseudorandom number in the interval [0, 1] each time it is called.

[0020] Advantageously, in the method or the security element, the spacer structures of the dot and / or line grid in the large-area effect areas have an area coverage of less than 20%, preferably less than 17% and in particular less than 10%.

[0021] In the case of line and / or dot grids, the height:width aspect ratio of the spacer structures in the method or the security element is advantageously between 0.05 and 2, preferably between 0.1 and 1. In the case of dot grids, the height:length aspect ratio of the spacer structures is also between 0.05 and 2, preferably between 0.1 and 1.

[0022] The height of the spacer structures, i.e. the vertical extension of the spacer structures above the plane of the embossed lacquer layer, is advantageously below 10 µm in the process or the security element, in particular below 4 µm and is particularly advantageously approximately 1 to 2 µm.

[0023] Spacer structures which are cuboid-shaped, pyramid-shaped, truncated pyramid-shaped, conical, truncated cone-shaped or hemispherical have proven particularly advantageous in the method or the security element.

[0024] In a further development of the method or the security element, the spacer structures are designed to taper upwards, with the upper contact surface being advantageously at least 20%, advantageously at least 40%, and particularly advantageously at least 60% smaller than the base surface. These measures minimize the contact surface of the spacer structures with the wash-ink printing cylinder, so that as little wash ink as possible is transferred to the spacer structures themselves. On the other hand, the tapered spacer structures can be demolded particularly easily from an embossing tool, ensuring reliable and precise production.

[0025] In the process or the security element, the spacer structures can also be provided with a hydrophobic nanostructure on their upper contact surface in order to suppress the adhesion of wash ink.

[0026] According to an advantageous development of the method or the security element, the spacer structures are arranged in the form of characters, patterns, or a code to form a hidden authenticity feature that can only be perceived with aids. This can be achieved by locally densifying or thinning the spacer structures.

[0027] In the process or the security element, the spacer structures can advantageously also have side surfaces provided with micro- or nanostructures to create an additional authenticity feature. Such structures are only visible from a very steep viewing angle and are not visible at viewing angles that dominate during normal handling of valuable or security documents.

[0028] According to a further development, the spacer structures are provided with a micro- or nanostructure on their upper contact surface. The micro- or nanostructure can correspond to the optical effect of the effect embossing. This allows the spacer structures to be optically aligned even further with the effect embossing, so that the spacer structures have no visual effect when viewed.

[0029] The at least one spacer structure of the spacer structures is formed with a depression, in particular in the embossing lacquer layer, that at least partially, in particular completely, surrounds the spacer structure and in particular directly adjoins the spacer structure. This is advantageous because, when the depression is created, material, in particular lacquer, of the embossing lacquer layer is displaced, which can be used to form the spacer structure. It is therefore no longer necessary to apply new material, in particular new lacquer, to the carrier or the embossing lacquer layer to form the spacer structure.

[0030] In particular, the spacer structure is formed from the material of the embossing lacquer layer removed during the formation of the recess. In particular, the recess is designed as a trench or channel. Preferably, the recess is annular. The trench can correspond to a right-angled triangle in cross-section, wherein the right angle of this triangle is formed in particular between the surface of the embossing lacquer layer and a wall of the embossing lacquer layer opposite the spacer structure or support structure.

[0031] Furthermore, it is preferably provided that the depression is formed with a depth of less than 10 µm, in particular less than 5 µm, preferably between 0.1 µm and 2 µm. This displaces sufficient material to produce the spacer structure. Furthermore, it is preferably provided that the depression is formed with a depth which corresponds to the height of the spacer structure. This makes it possible to displace the same amount of material from the depression as is required for the spacer structure with less effort. The height of the spacer structure is determined in particular by the plane through which the main surface of the embossing lacquer layer runs and the point of the spacer structure furthest away from the carrier. The depth of the depression is determined in particular by the plane through which the main surface of the embossing lacquer layer runs and the point of the depression furthest away from the carrier.

[0032] The recess is designed to be formed with an air volume equal to the material volume of the spacer structure. This also makes it easy to displace the same amount of material from the recess as is required for the spacer structure. The air volume is present in particular in the space filled with air or not filled with carrier material, which is delimited by the side walls of the recess and the imaginary solid surface of the carrier.

[0033] The invention also relates to a device for producing a spacer structure. The device comprises a base element and an embossed element, wherein the embossed element is formed at least as a recess in the base element, and the embossed element is particularly designed as a negative cone shape. The embossed element can also be cone-shaped.

[0034] The device for producing the spacer structure is preferably made of metal, for example of a nickel-based alloy.

[0035] When creating the spacer structure, the embossed elements are pressed into the embossing lacquer layer, and the material displaced by the embossed elements is moved, specifically pressed, into the recess of the base element. The spacer structure is formed by the recess of the device.

[0036] In particular, so that the material is also transported into the spacer structure, the embossed elements or pins form a direct extension of the, preferably conical, spacer structure.

[0037] In particular, the spacer structure is conical. This conical shape makes material transport to the center of the spacer structure more efficient.

[0038] The embossing element is provided with a recessed embosser that is raised above the base element and extends at least partially around the recess. The recessed embosser or the pins make it possible to displace or push material from the embossing lacquer layer. In particular, this material is displaced into the recess, creating a spacer structure there.

[0039] Furthermore, the volume of the indentation embosser is designed to be equal to the volume of the recess. This allows the spacer structure to be created entirely with material displaced by the embossing element. Furthermore, after the spacer structure has been created, there is no excess material that needs to be removed or disposed of.

[0040] The advantageous embodiments of the method according to the invention for producing the security element according to the first aspect or according to the second aspect also apply to the security element according to the invention. The physical components of the security element according to the invention are configured to carry out the method steps of the method according to the first aspect.

[0041] Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction has been omitted in order to increase clarity.

[0042] They show: Fig. 1 is a schematic representation of a section of the effect area of ​​a holographic security element during the step of applying wash ink, wherein (a) shows a cross-section and (b) a plan view of the security element, Fig. 2 is a schematic representation as in Fig. 1(b) for a modification with a slightly "blurred" dot matrix of spacer structures, Fig. 3 shows a schematic representation of a section of the effect area of ​​a micromirror security element during the step of applying wash ink, where (a) shows a cross-section and (b) a plan view of the security element, Fig. 4 shows a schematic representation of a dot matrix of small spacer structures in which a hidden authenticity feature is encoded, Fig. 5 shows a schematic sectional representation of a spacer structure with a recess, and Fig. 6 shows a schematic sectional representation of a device for producing a spacer structure with a recess.

[0043] The invention will now be explained using the example of the production of security elements for banknotes. Figure 1 shows schematically a section of the effect area of ​​a holographic security element during an intermediate step of production, namely the step of applying wash ink. Figure 1(a) shows a cross-section and Fig. 1(b) a top view of the security element.

[0044] To produce the security element 10, an embossing lacquer layer 14 was first applied to a carrier 12, for example a PET film, and this was then provided with the desired hologram embossing 16 in an embossing step. The embossing lacquer layer 14 is preferably made of a UV-curable material, for example a thermoset. In order to provide the hologram embossing 16 with a metallization with cutouts, for example a negative writing, a wash ink 24 is applied to the embossed embossing lacquer layer 14 in the areas to be cut out using a wash ink cylinder 20. After the wash ink has been applied, the embossing lacquer layer is metallized over its entire surface and the wash ink is then removed together with the metallization thereon, so that cutouts are created in the metallization precisely in the areas of the embossing lacquer layer that were previously provided with wash ink.However, the wash ink cylinder is intended to prevent unwanted transfer of the wash ink 24 to the hologram embossing 16. This could, for example, also be a wash ink toning film 22, which may be present on the surface of the wash ink cylinder in, for example, a gravure printing process or flexographic printing process.

[0045] Since the hologram embossing 16 has only slight height variations and thus a large contact area with the wash ink cylinder 20, there is a risk during this step that, in large-area effect areas 18, a wash ink toning film 22 may also be inadvertently deposited on areas of the hologram embossing 16 that are actually intended to remain uncoated. A large-area area is considered to be one that has an extension of more than 100 µm in every lateral direction, in particular more than 250 µm. For smaller areas, the risk of inadvertent deposition of a toning film has proven to be low, so no special measures are required there.

[0046] To ensure that the large surface areas 18 of the hologram embossing 16 that are not to be coated actually remain uncoated in the wash-ink step, the corresponding effect areas were formed according to the invention with a dot matrix 30 made up of small spacer structures 32. In the exemplary embodiment, the spacer structures 32 have a square base area with lateral dimensions of 5 x 5 µm 2< (i.e., length or width L = 5 µm) and a height H = 2 µm. The spacer structures are arranged in a square matrix with a nearest-neighbor spacing of A = 30 µm, so that the area coverage of the dot matrix is ​​L 2

[0047] At these sizes, the dot matrix 30 fulfills two conditions that are crucial for the present invention: On the one hand, the spacer structures 32 are so small and have such a low area coverage that the dot matrix 30 is not visually recognizable when viewing the security element 10 with the naked eye. At the same time, due to the large lateral dimension of 5 µm compared to the light wavelength, hardly any disruptive color-splitting diffraction effects occur at the spacer structures in any spatial direction. Of course, it is also essential for the desired functionality that the spacer structures 32 projecting beyond the hologram embossing 16 prevent the wash ink cylinder 20 or the wash ink toning film 22 from coming into contact with the surface of the hologram embossing in undesired areas and depositing a toning film there.

[0048] The spacer structures 32 can be produced using either electron beam lithography or laser lithography. The two lithography methods can also be combined using combined processes. Thus, the spacer structures 32 are already produced during the production of the embossed structures on the embossing tool. During the molding of the embossed tool, the embossed structures and the spacer structures are molded into the embossing resist.

[0049] To suppress diffraction effects even more, the dot matrix 30 can also be slightly "blurred", as in Fig. 2In such a shake, the positions of the spacer structures 34 are shifted irregularly by a few percent from their equidistant starting positions 36 (shown in dashed lines). In the exemplary embodiment, the shift amounts to a maximum of 10% of the starting distance, but in other designs, it can also be up to 25% of the starting distance of the starting positions.

[0050] The spacer structures 32, 34 are in the embodiment of the Figures 1 and 2 They are further tapered upwards, creating the shape of a truncated pyramid. This minimizes the contact area with the wash-ink printing cylinder, ensuring as little wash ink as possible is transferred to the spacer structures. Furthermore, the tapered spacer structures are particularly easy to demold from the embossing tool, ensuring reliable and precise production.

[0051] Dot grids made of spacer structures with the following properties and parameters have proven to be particularly advantageous: A) The spacer structures can form a grid with constant spacing between the grid elements, where the symmetry of the grid is, in particular, the symmetry of a square grid, rectangular grid, diamond grid, hexagonal grid, or parallelogram grid. The spacer structures can also be shifted relative to the initial positions of the grid sites of such grids to form a "blurred" grid that generates particularly low diffractive disturbances. The shift can be up to 5%, 10%, or even up to 25% of the initial spacing in the grid. B) The spacings between adjacent spacer structures are advantageously below 200 µm in all lateral spatial directions, in particular below 100 µm. In blurred grids, these spacings are advantageously not exceeded even for the spacer structures shifted relative to one another.For example, in a square grid, an initial spacing of A = 50 µm and an irregular shift f of up to 25% can be provided. In the "blurred" grid, the spacer structures are then shifted by up to ΔA = f*A = 12.5 µm relative to their initial positions, so that the minimum spacing between adjacent spacer structures is A min = 25 µm and the maximum spacing between adjacent spacer structures is A max = 75 µm. C) The lateral dimensions of the spacer structures are at least 2 µm in all spatial directions to minimize disruptive diffractive color splitting. Furthermore, the lateral dimensions of the spacer structures are below 40 µm, preferably below 30 µm, and in particular below 20 µm, at least in one spatial direction, and advantageously even in both spatial directions. D) The base area of ​​the structures is preferably at least 3-sided and can in particular be 4-, 5- or 6-sided.Round, particularly circular or elliptical base areas can also be considered. E) The ratio of length to width of the base area is advantageously between 0.25 and 4. F) The expedient tapering of the spacer structures reduces the base area towards the upper contact surface by at least 20%, advantageously by at least 40%. In extreme cases, the flanks of the spacer structures can converge to a point, for example in the case of spacer structures in the shape of a pyramid, a cone or a hemisphere. G) The aspect ratio height:length or height:width is advantageously between 0.05 and 2, preferably between 0.1 and 1. The absolute height of the spacer structures is advantageously below 5 µm, in particular below 3 µm and is particularly advantageously around 1 to 2 µm.H) The area coverage of the spacer structures is advantageously below 20%, particularly advantageously below 17%, and especially below 10%, so as not to reduce the effective hologram area too much. Preferably, the area coverage in the vellum area is below 10%, especially 5%, and preferably below 1%.

[0052] Figure 3 shows a further application of the spacer structures according to the invention in the step of applying wash ink during the manufacture of a micromirror security element. Figure 3(a) shows a cross-section and Fig. 3(b) a top view of the security element.

[0053] Analogous to the design of the Fig. 1To produce the security element 10, an embossing lacquer layer 14 was first applied to a carrier 12, for example a PET film, and then provided with the desired micromirror embossing 40 in an embossing step. In the relevant section of the Fig. 3 the micromirrors of the effect area are parallel to the carrier surface, i.e. they have a tilt angle α to the security element surface equal to or close to 0°.

[0054] In order to metallize the micromirror embossing in certain areas or to provide it with a high-refractive index cover layer in certain areas, a wash ink cylinder (in Fig. 3(not shown) a wash ink is applied to the embossed embossing lacquer layer 14 in certain areas. After the wash ink has been applied, the embossing lacquer layer is metallized over its entire surface or vapor-deposited with a high-refractive-index layer. The wash ink is then removed together with the cover layer located thereon, so that recesses are created in the cover layer precisely in the previously printed areas of the embossing lacquer layer.

[0055] Since the micromirror embossing 40 has only small height variations in the flat areas with mirror angles close to 0° and thus a large contact area with the wash ink cylinder, there is a risk that in large flat areas 42 a wash ink toning film is unintentionally deposited from the wash ink cylinder onto areas that are actually supposed to remain uncoated.

[0056] To remedy the problem according to the invention, these areas can be formed with a dot matrix of small spacer structures, as already described in connection with Figures 1 and 2 described in more detail. In the case of micromirror embossing, however, instead of a dot grid, line grids made up of spacer structures, in particular line grids made up of continuous or interrupted lines, such as a cross grid, can also be used.

[0057] With reference to the Figures 3(a) and (b) In the exemplary embodiment, a line grid 46 consisting of narrow, linear spacer structures 44 is formed in the large-area flat regions 42. The spacer lines 44 have a width of 4 µm, a mean spacing of 40 µm, and a height of 2 µm. The area coverage of the line grid 46 in the regions 42 is therefore 10%.

[0058] At these sizes, the spacer lines 44 are so narrow and their area coverage so low that the line grid 46 is not visually discernible when viewing the security element 10 with the naked eye. However, the width of the spacer lines, at 4 µm, is significantly above the wavelength of light, so that color-splitting diffraction effects hardly occur. Furthermore, to further suppress diffraction effects, the line grid 46 is designed to be slightly "jiggled," with the spacing between adjacent spacer lines being irregularly increased or decreased by up to 20% compared to their equidistant starting positions.

[0059] The spacer lines 44 projecting beyond the micromirror embossing 40 reliably prevent the wash ink cylinder from depositing a toning film on the flat micromirror area 42 in undesired areas.

[0060] The spacer lines 44 are in the embodiment of the Fig. 3formed with an upward taper and are provided with a hydrophobic nanostructure 48 on their upper contact surface. These measures ensure that no wash color is transferred to the spacer lines 44 themselves.

[0061] Line grids made up of spacer lines with the following parameters have proven to be particularly advantageous: A) The spacer lines can form a grid with constant line spacing. The lines can be continuous or interrupted and can also enclose an angle other than 0°. Multiple line systems can also be provided, arranged, for example, in the form of a cross grid. B) The spacer lines can be shifted relative to the starting positions of a regular grid to form a "blurred" grid that produces particularly low diffractive disturbances. The shift can be up to 5%, 10%, or even up to 25% of the starting spacing. C) The spacing between adjacent spacer lines is advantageously below 200 µm, especially below 100 µm. In blurred grids, these spacings are advantageously not exceeded even for the shifted spacer lines. D) The lateral widths of the spacer lines are at least 2 µm to minimize diffractive effects.E) The appropriate tapering of the spacer lines reduces the cross-sectional area by at least 20%, advantageously by at least 40%. In extreme cases, the flanks of the spacer lines can converge on a line, so that the spacer lines form a roof structure. F) The aspect ratio (height:width) is advantageously between 0.05 and 2, preferably between 0.1 and 1. The absolute height of the spacer lines is advantageously below 5 µm, in particular below 3 µm, and is particularly advantageously around 1 to 2 µm. G) In flat micromirror regions, the area coverage of the spacer structures (dot or line grid) can be higher than with hologram embossing, since the spacer structures themselves appear optically smooth except for the side surfaces and are therefore similar to flat micromirrors in their optical effect.The area coverage is advantageously below 20%, particularly advantageously below 15%, in particular below 10%.

[0062] Instead of a pure line grid or a pure dot grid, a combined dot and line grid can also be used for micromirror embossing, which has both dot and line-shaped spacer structures.

[0063] With reference to Fig. 4 A hidden security feature can also be encoded in a dot matrix 30 composed of small spacer structures 32. By omitting individual spacer structures 32, for example in the form of a letter (here the letter "E") or another coding, a characteristic marking 50 of the embossing tool used can be incorporated into the security element.

[0064] It is important to ensure that, despite the recessed spacer structures, the desired maximum distance between adjacent spacer structures is not exceeded. This can be achieved, for example, by only making every second spacer structure available for a possible recess, as in Fig. 4 illustrated. For an initial distance A, for example A = 30 µm, the maximum distance between two spacer structures in the coding areas is then 2A = 60 µm and is thus still below the desired maximum distance of 80 µm.

[0065] Fig. 5shows a partial sectional view of the security element 10 with the carrier 12 and the embossing lacquer layer 14. A spacer structure 32, 34 is formed in the embossing lacquer layer 14. The spacer structure 32, 34, conical in the exemplary embodiment, is surrounded, in particular completely, by a recess 52. Furthermore, according to the exemplary embodiment, the recess directly borders the spacer structure 32, 34.

[0066] The spacer structure 32, 34 has a height 52. The recess has a depth 54. The height 52 and the depth 54 are preferably equal. According to the exemplary embodiment, the height 52 and the depth 54 together amount to 1 µm to 8 µm, preferably 2 µm to 6 µm, in particular 2 µm to 3 µm.

[0067] Fig. 6 shows a device 58 for producing the spacer structure 32, 34. The device 58 is designed in particular as a stamp or embossing tool.

[0068] Preferably, the device 58 is made of metal, in particular a nickel-based alloy.

[0069] The device 58 can be produced, for example, by molding in several intermediate steps using positive and negative molds of different sizes. However, the device 58 can also be milled, for example.

[0070] The device 58 has a base element 60 and an embossing element 62. The base element 60 is designed, in particular, as a stamp base or stamp main plate. The embossing element 62 is designed to form the raised part of the, in particular conical, spacer structure 32, 34. Preferably, the embossing element 62 is rotationally symmetrical. The embossing element has a recess 66.

[0071] The device also includes a depression embosser 64. The depression embosser 64 is configured to create the depression 52. The depression embosser 64 appears in the cross-sectional drawing according to Fig. 6 as two protruding pins. Preferably, the recess embosser 64 is rotationally symmetrical. List of reference symbols

[0072] 10Security element 12Carrier 14Embossing lacquer layer 16Hologram embossing 18Large-area effect area 20Wash ink cylinder 22Wash ink toning film 24Wash ink 30Dot matrix 32Spacer structures 34Spacer structures 36Starting positions 40Micromirror embossing 42Large-area flat areas 44Spacer lines 46Line matrix 48Nanostructuring 50Marking 52Recess 54Depth 56Height 58Device for creating a spacer structure 60Base element 62Embossing element 64Recess embosser 66Recess

Claims

1. Method for producing a security element (10), in which - a carrier (12) is provided with an embossing varnish layer (14) and the embossing varnish layer (14) is provided with a desired effect embossment (16), - a colour (24) is regionally applied to the embossed embossing varnish layer (14), - a cover layer is applied to that surface region of the embossing varnish layer (14) that has been regionally provided with the colour (24), and then the colour (24) with the cover layer on top is removed, - large-area subregions of the effect embossment (16) that are to remain uncoated during the subsequent colour printing are provided with a dot pattern (30) and / or line pattern (46) made up of small spacer structures (32, 34), the pattern not being visible when the security element (10) is observed by the naked eye and in which pattern the spacer structures (32, 34) have lateral dimensions of more than 2 µm in each spatial direction, wherein at least one spacer structure (32, 34) of the spacer structures is provided with a depression (52) which runs at least partially around the spacer structure (32, 34), characterized in that the depression (52) is provided with an air volume which is the same as a material volume of the spacer structure (32, 34), and in that the large-area subregions of the effect embossment have an extent of more than 100 µm in each lateral direction.

2. Method according to Claim 1, characterized in that the spacer structures (32, 34) are in the form of an irregular pattern with variable distances between the pattern elements, wherein the pattern is constructed on the basis of a square grid, rectangular grid, rhomboidal grid, hexagonal grid or parallelogram grid, and the spacer structures (32, 34) are shifted by up to 25%, advantageously by up to 10%, from the starting positions (36) with a constant distance.

3. Method according to Claim 1 or 2, characterized in that the spacer structures (32, 34) of the dot pattern (30) and / or line pattern (46) are provided with a coverage in the large-area effect regions which in the case of a hologram surface is less than 20%, particularly advantageously less than 17% and in particular less than 10%, and in the case of a vellum region is less than 10%, in particular 5%, preferably less than 1%.

4. Method according to one of Claims 1 to 3, characterized in that the spacer structures (32, 34) are formed with an aspect ratio of height to width, and preferably also with an aspect ratio of height to length, of between 0.05 and 2, preferably between 0.1 and 1.

5. Method according to one of Claims 1 to 4, characterized in that the spacer structures (32, 34) are formed with a height of less than 10 µm, in particular less than 5 µm, preferably between 1 and 2 µm.

6. Method according to one of Claims 1 to 5, characterized in that the spacer structures (32, 34) are cuboidal, pyramidal, in the form of a truncated pyramid, conical, in the form of a truncated cone, or hemispherical.

7. Method according to one of Claims 1 to 6, characterized in that the spacer structures (32, 34) taper upwards and the upper contact surface is preferably at least 20%, particularly preferably at least 40% smaller than the base surface.

8. Method according to one of Claims 1 to 7, characterized in that, on their upper contact surfaces, the spacer structures (32, 34) are provided with a nano-structure which has a hydrophobic action.

9. Method according to one of Claims 1 to 8, characterized in that the spacer structures (32, 34) are arranged in the form of symbols, patterns or an encoding, in order to form a concealed security feature only perceptible with auxiliary means.

10. Method according to one of Claims 1 to 9, characterized in that, on their upper contact surface, the spacer structures (32, 34) are provided with a micro-or nano-structure, wherein preferably the micro- or nano-structure corresponds to the optical effect of the effect embossment.

11. Method according to one of Claims 1 to 10, characterized in that the depression (52) is formed with a depth of less than 10 µm, in particular less than 5 µm, preferably between 0.1 and 2 µm.

12. Method according to one of Claims 1 to 11, characterized in that the depression (52) is formed with a depth which is the same as the height of the spacer structure (32, 34).

13. Method according to one of Claims 1 to 12, characterized in that the spacer structure (32, 34) is formed from the material of the embossing varnish layer (14) that was removed when the depression (52) was formed.

14. Security element (10) for safeguarding security papers, documents of value and other data carriers, comprising a carrier (12) with an embossing varnish layer (14) which is provided with an effect embossment, in particular a micro-mirror embossment or a hologram embossment (16), and in the case of which a cover layer is regionally applied to the effect embossment, wherein, in large-area subregions of the effect embossment that are provided with the cover layer, a dot pattern (30) and / or line pattern (46) made up of small spacer structures (32, 34) is provided, the pattern not being visible when the security element (10) is observed by the naked eye and in which pattern the spacer structures (32, 34) have lateral dimensions of more than 2 µm in each spatial direction, wherein at least one spacer structure (32, 34) of the spacer structures is provided with a depression (52) which runs at least partially around the spacer structure (32, 34), characterized in that the depression (52) is provided with an air volume which is the same as a material volume of the spacer structure (32, 34), and in that the large-area subregions of the effect embossment that are provided with the cover layer have an extent of more than 100 µm in each lateral direction.

15. Device (58) for creating a spacer structure (32, 34), which comprises a base element (60) and an embossing element (62), wherein the embossing element (62) is at least in the form of a cutout (66) in the base element (60), wherein the embossing element (62) has a depression embosser (64) which is raised with respect to the base element (60) and runs at least partially around the cutout (66), and wherein the volume of the depression embosser (64) is the same as the volume of the cutout (66).