Security element and method for producing a security element

Abstract

A security element for protecting valuable documents, comprising a substrate body (2) with first grid areas (8) composed of first partial grid areas (4) and second, differently colored partial grid areas (6), and second grid areas. The first partial grid areas (4) and the second partial grid areas (6) are indistinguishable with the naked eye and together result in a mixed color. The first grid areas (8) or the second grid areas (10) are formed from luminescent colors, are detectable when illuminated with UV radiation and transparent when illuminated only with light from the visible spectrum, and the respective other grid areas (8, 10) are formed from body colors.At at least one angle to the front side, the second raster areas (10) appear to only partially overlap the first raster areas (8), wherein between the second raster areas (10) and the first partial raster areas (4) and the second partial raster areas (6) there is in each case a degree of overlap in the range from 0% to 100%, and the security element has at least two regions in which the degree of overlap between the second raster areas (10) and the first partial raster areas (4) differs from the degree of overlap between the second raster areas (10) and the second partial raster areas (6). When illuminated with a combination of UV radiation and light from the visible spectrum, the mixed color is modified differently in the two regions.

Description

[0001] The invention relates to a security element for securing value documents, which comprises a substrate body having a front side and a first and a second printing layer applied to the front side of the substrate body.

[0002] Such security elements are known, for example, from DE 10 2014 018 512 A1. This document describes a multicolored security feature, a so-called "MOVE feature," which presents a viewer with a movement of a two-dimensional image motif when changing their viewing angle. EP 3 475 096 B1 discloses a foil with such a multicolored movement feature, a so-called "colored dynamic foil" (CDF). These "MOVE features" or "colored dynamic foils" are created by applying at least one solid color in a line-like manner to an embossed structure. The substrate forming the background either has a high reflectivity or is provided with a reflective silver layer. Typically, at least two different solid colors are used, which appear as a mixed color when viewed from above and thus render the visual appearance of the security element unattractive.The effect of the corresponding body color(s) only appears when the security element is tilted. DE 10 2018 010 078 A1 and EP 4 013 626 B1 extend the described multi-color movement features to three-dimensional image motifs. The viewing angle-dependent movement effects in 2D and 3D increase security against counterfeiting, as they cannot be reproduced even with the most modern copiers and thus play a major role in the authenticity protection of valuable documents such as banknotes, checks, credit or other payment cards, ID cards, or the like. They are directly visible when illuminated with light from the visible wavelength range, which occurs under ambient conditions such as sunlight. The image motif is therefore visible to the naked eye when the security element is illuminated with light from the visible wavelength spectrum and therefore does not appear surprising to the observer.

[0003] Also known are security features which show an external observer different information when illuminated with radiation from the UV wavelength range and when illuminated with light from the visible wavelength range, for example from EP 3 621 821 B1, WO 2018 / 206936 A1, US 10,787,019 B2 or EP 2 766 193 B1.

[0004] Furthermore, EP 1 554 700 B1 and EP 1 765 602 B1 disclose the use of moiré grids in combination with fluorescent inks. These moiré grids present a viewer with different information depending on the direction by magnifying certain microimage elements using microlenses. A movement or magnification effect is created when illuminated with UV radiation. However, no additional information is created for an image motif visible when illuminated with light from the visible spectrum when the illumination changes to the UV range.

[0005] Further security elements are known from EP 1 567 358 B1, WO 2017 / 011476, EP 2 889 152 B1, EP 3 766 702 A1, DE 10 2021 002 416 A1, DE 10 2016 014 665 A1, DE 10 2019 006 890 A1, DE 10 2014 004 753 A1, EP 3 225 417 B1, EP 3 452 299 B1, EP 3 332 982 A1, EP 3 339 049 B1, EP 3 403 843 A1, EP 3 470 236 B1, DE 10 2019 006 315 A1, DE 10 2020 002 429 A1 and EP 3 825 141 B1.

[0006] The object of the invention is to improve the optical impression of an optically variable security element and to increase the security against counterfeiting.

[0007] The invention is defined in independent claims 1, 11 and 12. The dependent claims relate to preferred developments.

[0008] A security element is intended for protecting valuable documents. The security element comprises a substrate body with a front side. The substrate body can be a film substrate, such as PET substrates, cotton-based paper substrates, or a combination of paper and film substrates.

[0009] A first and a second printing layer are applied to the front side of the substrate body. The first printing layer is formed from first screen areas, which are composed of first partial screen areas and second, color-different partial screen areas. The first and second partial screen areas are indistinguishable to the naked eye and together produce a mixed color. The second printing layer is formed from second screen areas.

[0010] The first grid areas or the second grid areas are formed from luminescent colours, visible when illuminated with UV radiation and transparent when illuminated only with light from the visible spectrum, and the other grid areas are formed from body colours.

[0011] A body pigment, or body paint, is understood here as a layer that remits part of the spectrum of incoming light (radiation in the visible wavelength range) and absorbs another part, so that the incoming light has a different spectral distribution than the emitted light, and the layer therefore appears colored. A body pigment is therefore a non-luminous dye.

[0012] It is understood that although the application refers to UV radiation, this UV radiation does not occur in isolation during UV irradiation outside a UV booth. Illumination with radiation from the UV range always includes a portion of light from the visible wavelength range that impinges on the security element. The term "UV radiation" as claimed therefore encompasses both pure UV radiation, supplied, for example, in a UV booth, as well as UV radiation plus portions of visible light.

[0013] The screen surfaces made of luminescent colors are translucent, i.e. the screen surfaces made of luminescent colors allow a certain proportion of incident light to pass through. If light hits one side of the screen surface, a certain proportion of the light is allowed to pass through to the other side of the screen surface and exits there again. The greater the percentage of light passing through in relation to the incident light, the more translucent the screen surface is. If the percentage is at least 90%, i.e. the screen surface allows the incident light to pass through almost unattenuated, like a window, the screen surface is referred to as transparent. On the other hand, a screen surface that allows less than 10% and preferably about 0% of the incident light to pass through, i.e.A surface in which the proportion of transmitted light relative to the incident light is small, close to, or equal to zero, is referred to as opaque or non-transparent. If the luminescent grid surfaces are illuminated only with visible light, they are completely transparent. If UV components are added, such as when illuminated with sunlight, they present a slightly yellowish hue to the naked eye.

[0014] Even when illuminated with pure UV radiation, e.g., without residual daylight, the grid areas with the luminescent colors are visible. In this case, either the overlying grid areas made of one or more body dyes act as absorbers of the UV excitation as well as the emitted visually visible radiation. Or the grid areas with the luminescent color are located on the grid areas made of body dye(s), so that the luminous intensity of the luminescent grid areas can be varied depending on the application density and the optical density (or color tone) of the visually visible grid elements. When excited with pure UV radiation, part of the UV radiation is reflected by the substrate, and part is absorbed by the grid areas made of body dye(s).

[0015] The first grid areas and the second grid areas interact optically. At at least one angle to the front side, the second grid areas only appear to partially overlap the first grid areas, with the degree of overlap between the first grid areas and the second partial grid areas and the second partial grid areas each having a range of 0% to 100%. This makes it possible to adjust the proportion of the grid areas located at the bottom of a layer sequence that are visible and the proportion that are not. In this way, the color impression can be adjusted when illuminated with light from the visible wavelength range and when irradiated with UV radiation. The angle at which the grid areas overlap can be the viewing angle and / or the illumination angle.While the first and second grid areas partially overlap, this also includes the second grid area overlapping the first partial grid area to a certain extent, but not overlapping the second partial grid area, and vice versa. In particular, it is also possible for the second grid area to completely cover the first partial grid area, i.e., overlap 100%, and for the second grid area not to overlap the second partial grid area, i.e., overlap 0%. Even then, a partial overlap of the first and second grid areas is present.

[0016] The security element has at least two areas in which the degree of overlap between the second grid areas and the first partial grid areas differs from the degree of overlap between the second grid areas and the second partial grid areas, and when illuminated with a combination of UV radiation and light from the visible spectrum, the mixed color in the two areas is modified to different degrees. The degree of overlap between the second grid areas and the partial grid areas can vary the perceivable color in the areas. For example, a first area appears a different color than the other area when illuminated with UV light and / or when illuminated with light from the visible spectrum. This interaction can be used to create 3D effects, for example, when the lighting changes.

[0017] A variety of different 3D objects can be created as image motifs. Under UV radiation, the image motifs appear brighter in one area than in another. This creates the three-dimensionality of the 3D effect. Therefore, these are not stereoscopic 3D effects.

[0018] The luminescent grid areas can be composed of a mixture of RGB fluorescent colors, they can have a phosphorescent component, or they can be designed as a bifluorescent dye, which has a different emission color at different excitation wavelengths, for example, at 254 nm and 365 nm. The fluorescent and / or phosphorescent colors can be excited in different wavelength ranges, e.g., UV-A, UV-B, and / or UV-C.

[0019] The luminescent ink is preferably a fluorescent ink, so that fluorescent screen areas are provided. It is particularly preferred to use encapsulated fluoropigments, such as those known from DE 10 2015 014 525 A1, DE 10 2015 014 537 A1, DE 10 2015 014 539 A1, or DE 10 2015 014 526 A1, for the luminescent screen areas. They allow for various fluorescent color shades in a wider range of colors (not just the colors red, orange, yellow, yellow-green, and blue in security printing, as previously). Furthermore, in the colors mixed from these pigments, no or only a minor color change is detectable after exposure to an external stimulus such as chemicals or sunlight. This enables, for the first time, consistent quality of any luminescent mixed color in a security feature, even under the influence of environmental factors.It is therefore possible to create attractive chemically and / or physically stable image motifs with a wide range of potentially usable luminescent colors.

[0020] Preferably, the first and / or second grid areas can represent a dot grid or a line grid. Particularly preferably, the line grid is formed from a plurality of non-intersecting lines. The first or second grid areas can be applied in a grid of different body colors, which are provided, for example, as differently colored lines or dots. The luminescent grid points or lines can also have several different colors.

[0021] The first and second raster areas interact optically. In particular, an information change occurs when the lighting changes from illumination with light from the visible spectrum to illumination with UV radiation. For example, the displayed 2D or 3D image can change when the lighting changes in these areas, or a 3D effect can be added to a 2D image motif when the lighting changes, namely when the first raster areas supplement the second raster areas with another image motif or a 3D effect. For example, the raster areas made of body colors at the top in the layer sequence specifically mask out part of the raster areas made of luminescent colors below, so that the uncovered part of the luminescent raster areas reveals additional image information under UV irradiation to the image information of the raster areas made of body colors above that is not visible under daylight.The two pieces of image information, for example, two image motifs, can be independent of each other. The image information of the grid areas made of the body dye can represent, for example, the portrait of an artist, and the image information of the luminescent grid areas, which are visible under UV light, can represent, for example, a 3D sculpture of the artist. The two pieces of information, for example, the image motifs, can also complement each other. This is due to the different shapes of the first and second grid areas, since a portion of the grid areas located closer to the substrate body ("bottom") in the layer sequence always remains visible.

[0022] Preferably, the second halftone areas differ from the first halftone areas not only in their shape but also in their color. Such a layer sequence reveals additional information under UV radiation, in particular additional perspective and color information, in addition to the first information, which the halftone areas present from body colors. If the additional color information is added under UV irradiation, the color of the area can, for example, change. This addition of the second information to the first information results solely from the combination of the first and second halftone areas and thus represents a high barrier to counterfeiting, since both print layers must be precisely coordinated - the optical effect depends on the degree of overlap between the first and second halftone areas; in particular, on the proportion of the respective color that is visible. For example,The grid of the printed layer of body colors can be a dot grid of a flower. The grid of the luminescent printed layer can, for example, depict a bee under UV radiation, so that in low residual daylight and sufficiently strong UV radiation, both motifs are recognizable in addition. It is also possible, for example, for a rectangle to be visible as a two-dimensional motif of body colors, and under UV radiation, a woven structure with modulated brightness appears on the rectangular surface, like a basket.

[0023] In embodiments, both the first grid areas and the second grid areas may be the luminescent grid areas, provided that the other grid areas consist of body colors.

[0024] The security element according to the invention produces a visually appealing optical effect when illuminated with light from the visible wavelength range, which is surprisingly complemented or enhanced when illuminated with radiation from the UV wavelength range. This optical effect is surprising because it is not visible under normal indoor lighting (e.g., D65).

[0025] The effect of the first and second grid areas visually interacting is also referred to here as a static effect. No relief structure is required for this static effect. For example, a dot grid of the second grid areas over a line grid of the first grid areas is sufficient to create the static effect if the dot grid of the second grid areas does not completely cover the line grid of the first grid areas. The static effect requires registration of the first and second grid areas and not only improves the visual impression of the security element, but also increases its security against counterfeiting. The static effect allows areas of the security element to differ in color or in the object depicted, independently of other areas on the security element.When exposed to UV radiation, the areas can then differ, also independently of one another, in their color or color intensity, e.g. in their luminosity through a region-specific line thickness modulation of the raster areas, as well as in their visual representation as an object or pattern. Patterns can be recurring geometric shapes, e.g. rhombuses, rectangles, triangles, lines or geometries with a perspective effect (prisms, cuboids, spheres), as well as recurring partial motifs of an object, twisted ropes, knots, etc. The representation of more complex objects, e.g. 3D representations of animals (e.g. bees), rings, tires, as well as symbols and signs (e.g. letters or numbers) are also possible. The combination of a 3D-looking background pattern with a 3D object displayed in the foreground is also possible due to the interaction of the first raster areas with the second raster areas.

[0026] Then two different 3D motifs are precisely coordinated, which in turn increases security against counterfeiting.

[0027] In a printing process, one of the two printing layers is preferably provided in the form of a decoding printing plate in the form of regular dots, symbols, rasterized elements, or lines with a fixed repeat (specified spacing) and is applied during the printing process to the other of the two printing layers, which is provided on a motif printing plate, for example, in the form of modulated lines with a fixed repeat. The two printing layers are therefore preferably applied using repeat printing, in which recurring dots / lines / symbols / rasterized elements are applied at a specified spacing during the printing process, thereby creating an image motif.

[0028] In a variant of the static effect, the first grid areas, for example, as a line grid on the front of the substrate body, are present in a body dye. Luminescent second grid areas are applied to this line grid in a second grid, for example, a dot grid, and the information is decoded with them.

[0029] Decoding is understood as the revelation of motif-like information by overlaying the first screen areas with the second screen areas. Only with a suitable set of parameters, i.e. when the repeat corresponds to the repetition frequency, does the information of the first print layer become visible as a motif in various intensity gradations or shades. The repeat of the first and second screens are preferably approximately the same size or are multiples of each other. For example, the repeat of a modulated line screen is on average between 290 and 310 µm, while the decoding screen is 300 µm. Unprinted areas can be placed between differently colored line screens to prevent ink contamination, but they can also be printed butt-to-butt, i.e. directly adjacent to one another, or overlapping.

[0030] In this variant, the body color is placed beneath a luminescent color. The optical effect is then somewhat less contrasting than when the grid areas of body colors are arranged above the luminescent grid areas, since, for example, fluorescence of the overlying color is stimulated, but without the back-reflection of the UV radiation from the substrate and without back-reflection of the fluorescent color.

[0031] It is advantageous if the body dye has a high absorption of UV radiation in the range of 254 nm to 365 nm and / or a high absorption in the range of the emission wavelength of the luminescent colors used. This creates a particularly high-contrast and appealing optical effect. High absorption is achieved with an absorption level of at least 70%, preferably above 90%, and particularly preferably 95% within the relevant spectral range / emission wavelength.

[0032] In a further variant, there is a first grid, for example a line grid of luminescent grid areas, which is applied to the front side of the substrate body. A second (decoding) grid consisting of second grid areas, for example a dot grid of one or more body dyes, is applied to these luminescent grid areas, and the information of the first grid areas is thus decoded with the second grid areas. There is no relief structure, so that the described static effect arises. The first and second grid areas can consist of several body dyes or several luminescent dyes. The grids of both grid areas can also be in the form of regularly arranged lines, dots, symbols, rasterized elements, etc.

[0033] Either the decoder plate or the motif plate can be used to print the halftone areas using a solid color, while the other plate applies the luminescent halftone areas. The motif plate preferably prints lines as luminescent halftone areas that are invisible without UV illumination, while the decoder plate prints dots in solid-color halftone areas that are visible to the naked eye. The printing technique described creates a higher area coverage of the luminescent halftone areas and thus a higher luminosity under UV irradiation. This enhances the effect of the second halftone areas.

[0034] Alternatively, the body-colored raster areas can be printed as a line and the decoding can be implemented by printing highly luminescent raster areas (e.g. yellow-green).

[0035] The first and second halftone areas are preferably printed using (wet or dry) offset printing processes, e.g., optimally registered by printing on a super-simultaneous printing press with multiple printing units or by printing on a serial printing press. Alternative printing processes include inkjet, screen printing, and intaglio printing. Tamper protection is particularly enhanced by combining two different printing processes. Inkjet printing, however, allows for a particularly high degree of customization.

[0036] If a dot matrix is ​​intended, for example, consisting of different body-colored dots, the individual dots of the dot matrix can be easily applied using the inkjet process, for example, onto a luminescent line preprint from a previous printing step. This enables, for example, a personalized person image made of body color with a consistent luminescent background effect.

[0037] In banknote printing, a multi-color denominated color screen can be applied using multiple printing plates using simultaneous printing. This denominated color screen can also have a color gradient within itself, such as a color iris gradient. It is important that the body dye used for one of the two printing layers has sufficient UV absorption in the UV ranges of 254 nm and 365 nm, which are relevant for banknote verification, or in the emitting luminescent color below it, e.g., for blue luminescent substances in the range of 400 nm to 500 nm, for green in the range of 490 nm to 540 nm, and for yellow and red in the range of 560 nm to 780 nm.

[0038] It is possible to generate the described static effect using various printing processes and even to combine several printing processes. Monitoring the ink application thickness using a measuring device to adjust the colors in the individual sub-steps is particularly preferred in order to create an improved visual effect.

[0039] Due to the described static effect, a significantly higher resolution of the security feature is possible than with the viewing angle-dependent movement security features ("MOVE" features) explained at the beginning, because if a relief structure is omitted, the repeat in repeat printing can be reduced to 20 µm, i.e. compared to the 300 µm repeat in the known security features, a 15-fold finer resolution is possible.

[0040] Preferably, a relief structure with a plurality of periodically arranged, raised or depressed structural elements is provided between the substrate body and the grid areas located closer to the substrate body ("below"). These structural elements are particularly preferably produced after the substrate body has been printed with the first grid areas in an offset printing process by blind embossing using the intaglio printing process. Particularly preferably, the structural elements are formed by raised or depressed circular structures, in particular by compressed hemispherical structures or domes with a circular or elliptical base area. Likewise preferably, the structural elements can be linear, i.e., the relief structure can have a plurality of peaks and valleys or furrows.

[0041] Preferably, the luminescent grid areas are combined with the relief structure in such a way that at least a portion of the luminescent grid areas lies essentially on each structural element, so that, for the observer, a surface in the form of a three-dimensional image motif is created by a location-dependent modulation of the grid areas that protrudes and / or recedes relative to the surface of the security element. Particularly preferably, the grid of the first and / or second grid areas comprises two or more line grids, each line grid being location-dependently modulated independently of the other line grid, so that the line grids produce different movement effects or identical movement effects in the same or different directions.The interaction of the first and second grid areas can also create an image motif with a three-dimensional depth effect and / or different motion effects when the security element is tilted around different axes. These effects are preferably provided in specific areas and differ in at least two areas.

[0042] Regarding the application of the grid to the relief structure, reference is made to DE 10 2018 010 078 A1, the content of which is incorporated herein in its entirety. In particular, the explanations regarding grid widths of the structural elements (there referred to as "grid elements") and the location-dependent modulation based on a phase function are preferably presented as in this publication. A key difference, however, is that one of the two grids is now luminescent and supplements the information of the other, usually body-colored, grid in the UV range. A change in information and / or information supplementation occurs when switching from illumination with light in the wavelength range of the visible spectrum to UV irradiation. In a particularly preferred embodiment, specular or highly reflective surfaces, especially on the substrate body, can be dispensed with.

[0043] In some embodiments, a relief structure, for example created by blind embossing, is combined with intaglio printing to create a dynamic effect under UV irradiation. This means that the static effect is supplemented, for example, by the 3D image motif created by the static effect appearing to move upon UV irradiation and changes in the viewing and / or illumination angle due to the additional provision of a relief structure and a location-dependent modulation of the luminescent grid areas on the relief structure. As a dynamic effect, a different shading intensity, a depth effect, etc. of the 3D image motif created by the static effect is also possible under UV irradiation and when the viewing and / or illumination angle changes.With changing UV irradiation, a dynamic color change in UV can also be shown as a dynamic effect, such as a color change, a change in intensity, a change in perspective, a change in brightness, etc.

[0044] In one embodiment, an image made of body pigments unfolds its 3D effect under UV irradiation and exhibits changing color dynamics, for example, changing hue values ​​or brightness levels, with changing intensity and direction of the UV radiation source. Intensities of the color channels visually perceivable under UV irradiation from 0 to 100% are possible, and it is also possible to mix two or more color channels to create mixed colors. Under changing UV illumination, an increased dynamic 3D effect can be achieved, producing more than just a light on / off effect and / or a brightness gradient with smooth hue transitions for the respective luminescent color present, depending on the viewing and / or illumination angle. For example, when using green fluorescence and red fluorescence, a transition from reddish to yellowish and greenish can also be achieved.

[0045] A preferred method for creating the relief structure in the form of raised / recessed, uniform, round structural elements (approximately hemispheres) on the front side of the substrate body—either directly into the substrate body or into an embossing lacquer layer applied to the front side—is blind embossing. For value documents, the size of the structural elements is particularly preferably in the range of 200 nm to 300 µm. The structural height is less than 200 µm, preferably less than 100 µm, and particularly preferably between 20 µm and 80 µm. The raised structural elements can be nested within one another or spaced apart from one another. Thus, in some embodiments, an alternation of linear grooves (valley and peak) can be created and used as structural elements of the relief structure instead of hemispherical nubs. The structural elements can also differ in certain areas.Thus, the structural elements can be linear in some areas and raised / recessed round structures, domes, etc. in other areas. Accordingly, areas with relief structures can be combined with areas without relief structures, creating a static effect in some areas and a dynamic effect in others.

[0046] As described above, a pure body color grid is sufficient to decode information (a relief structure is not necessarily required). Additional embossing can create a UV-stimulated motion effect, enabling a smooth transition from one color tone to another. If 3D objects are represented in a line grid, a regular array of embossed knobs, micromirrors, or Fresnel convex mirrors can be used for decoding.

[0047] In addition to the design variants with a static effect, further variants with the dynamic effect described above are available. In another variant, a first grid of luminescent first grid areas is printed onto the relief structure, with the relief structure being applied to the front of the substrate body for angle-dependent decoding, so that, for example, a 3D effect, brightness gradient, etc., can be detected when the security element is tilted and illuminated with UV radiation. A second grid of second grid areas is additionally printed onto the first grid with a body dye, which represents the decoding grid.Then, under UV irradiation, a first static effect occurs (for example, a 3D effect of the 2D image motif visible when illuminated with light from the wavelength range of visible light is revealed), and when the radiation source is tilted or the viewing angle is changed, the 3D effect reveals dynamic depth information, a color change, movement, etc. These effects can also be provided only in certain areas.

[0048] Of course, the order of the process steps and layer structures can be reversed in all variants of the static and dynamic effect, although blind embossing is always preferred last. In some embodiments, blind embossing can also be performed first, followed by raster areas applied to the relief structure. Particularly preferred, for example, is printing directly onto the structural elements of the relief structure using the inkjet process.

[0049] Particularly preferably, the first and second grid areas are located on two separate regions on the surface of the substrate body. This enables so-called self-verification when the security element is folded together, for example, if a window is provided in the substrate body, for example, of a polymer or hybrid banknote. Then, for example, the first grid areas can be located in the window and the second grid areas on the substrate body of the banknote, or vice versa – thus, a luminescent grid is combined with a grid of body colors when the separate regions are folded together, i.e., when self-verification takes place.For example, it is possible to precisely combine a moiré grating in the window with a luminescent moiré grating on the substrate body, so that they only reveal coded information when interacting with each other. However, each moiré grating represents a differently designed superstructure. For example, the moiré grating in the window depicts a bee, and the moiré grating on the substrate body depicts a flower. If the two areas are then folded together for self-verification, they together reveal the value 50.

[0050] It is also particularly preferred for the first raster areas to be applied in a window on the front side of the substrate body and the second raster areas to be applied on the back side of the substrate body, or vice versa. In this case, the first and second raster areas combined also provide coded information.

[0051] A security document with the security element of the described type is also provided. The security element is applied to a security substrate, e.g., a banknote substrate—a cotton substrate, a hybrid substrate, a window substrate, or a polymer substrate. It can also be incorporated into a card body (passport, ID document) as a multi-layer laminate. In this case, the security element is internal in a multi-layer security document. The security element can, for example, be applied as a transfer element to an inner surface of a multi-layer substrate body. A multi-layer laminate fluorescent print can be applied to the front and / or back of one or more laminate layers. The security element can therefore be external and / or internal.The production of the security element can be easily integrated into the banknote production process and can therefore be used as an upgrade of existing banknote designs, identification documents, etc.

[0052] A method for producing a security element for protecting value documents is further disclosed. A substrate body comprising a front side is provided, and a first and a second printing layer are applied to the front side. The first printing layer is formed from first grid areas composed of first partial grid areas and second, color-different partial grid areas, wherein the first partial grid areas and the second partial grid areas are indistinguishable to the naked eye and together result in a mixed color. The second printing layer is formed from second grid areas, and the first grid areas or the second grid areas are formed from luminescent inks, are detectable upon illumination with UV radiation, and are transparent when illuminated only with light from the visible spectrum. The other grid areas are formed from body colors.At least one angle to the front side, the second raster areas appear to only partially overlap the first raster areas, with a degree of overlap in the range from 0% to 100% being provided between the second raster areas and the first partial raster areas and the second partial raster areas. At least two areas are provided on the security element in which the degree of overlap between the second raster areas and the first partial raster areas differs from the degree of overlap between the second raster areas and the second partial raster areas, and when illuminated with a combination of UV radiation and light from the visible spectrum, the mixed color in the two areas is modified to different degrees.

[0053] It is understood that the method can be varied in the same ways as the described security element and the value document.

[0054] In the process, for example, the object that will later be visible under UV radiation is first created in a 3D illustration program and generated with grayscale gradients (corresponding to a desired exposure orientation). Then, using software, a kind of "elevation relief map" is created from this grayscale image as printable lines – this creates a sense of depth and a 3D effect. The lines to be printed on the additional luminescent print layer exhibit a line offset or a line modulation in thickness and position, comparable to an elevation isobar on a hiking map. Several luminescent colors can be printed closely together as lines in the luminescent print layer if a multi-color effect or a color change under UV radiation is desired.

[0055] For decoding, a grid consisting of dots, lines, or objects with a size less than twice the line width of the modulated lines is preferably printed. For example, for a modulated line with a maximum line thickness of 150 µm, the body color dot above / below it has a maximum diameter of 300 µm, preferably less than 150 µm. Thus, there are areas where at least one of the luminescent lines can be completely covered by the dot, and areas where the luminescent color is not covered. The uncovered parts form the second piece of information that is later visible under UV radiation.

[0056] Both printing layers are prepared for offset printing / wet offset or Nyloprint printing using dot or line modulation before being printed in the form of screen areas using a combination of two printing steps, either on two different printing presses (one for the first printing layer and one for the second printing layer) or on at least one additional printing unit in a single printing press. One advantage of this method is that, for example, the brightness modulation of the sub-areas is achieved by the line thickness or line width of the luminescent line screen and not just by the ink flow of the print. This means that finer differences can be represented, for example in grayscale, without having to resort to screening the luminescent printing layer.This advantageously avoids the problems associated with screening to create grayscale, such as potential dot gain during the printing process. Cutouts within the image motif allow for additional information such as characters, numbers, etc., to be incorporated, further increasing counterfeit security.

[0057] A security element for protecting valuable documents, comprising a substrate body (2) with first grid areas (8) composed of first partial grid areas (4) and second, differently colored partial grid areas (6), and second grid areas. The first partial grid areas (4) and the second partial grid areas (6) are indistinguishable with the naked eye and together result in a mixed color. The first grid areas (8) or the second grid areas (10) are formed from luminescent colors, are detectable when illuminated with UV radiation and transparent when illuminated only with light from the visible spectrum, and the respective other grid areas (8, 10) are formed from body colors.At at least one angle to the front side, the second raster areas (10) appear to only partially overlap the first raster areas (8), wherein between the second raster areas (10) and the first partial raster areas (4) and the second partial raster areas (6) there is in each case a degree of overlap in the range from 0% to 100%, and the security element has at least two regions in which the degree of overlap between the second raster areas (10) and the first partial raster areas (4) differs from the degree of overlap between the second raster areas (10) and the second partial raster areas (6). When illuminated with a combination of UV radiation and light from the visible spectrum, the mixed color is modified differently in the two regions.

[0058] The invention is explained in more detail below using exemplary embodiments with reference to the attached drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as restrictive. For example, a description of an embodiment with a large number of elements or components should not be interpreted to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the embodiments may also be applicable to other embodiments.The figures show: . Fig. 1 a security element in plan view; Fig. 2 the security element according to Fig. 1 in the sectional view; Fig. 3 a security element with the grayscale gradient shown in plan view; Fig. 4 a detailed view of the representation according to Fig. 3 ; Fig. 5 a schematic representation of the detail according to Fig. 4; Fig. 6 a line print pattern of an object; Fig. 7 a line print pattern of a further object; Fig. 8 an ab diagram in the LAB color space of the fluorescence of encapsulated fluoropigments; Fig. 9 a security element in a sectional view in a further embodiment; Fig. 10 a security element in a sectional view in a further embodiment; Fig. 11 a profile section of a structural element as a compressed hemispherical structure; Fig. 12 a plan view of a relief structure with structural elements in a 0° / 90° arrangement; Fig. 13 a plan view of a relief structure with structural elements in a honeycomb arrangement, and Fig. 14 a plan view of a relief structure with structural elements with an elliptically distorted base area.

[0059] Fig. 1 shows a security element 1 in plan view. A section line S is drawn along the Fig. 2a sectional view. First partial grid areas 4 are applied in a line grid on a front side V of a substrate body 2. Second partial grid areas 6 are also applied as a line grid on the front side V of the substrate body 2. A spacing B in the sense of a gap is provided between the first partial grid areas 4 and the second partial grid areas 6. Both partial grid areas 4, 6 together form first grid areas 8 of a first printing layer. Second grid areas 10 are applied as a dot grid on the two partial grid areas 4, 6, but not completely covering them. If the second grid areas 10 are applied over the spacing B, they fill the spacing B between the two partial grid areas 4, 6 (shown in Fig. 2 ).

[0060] The first partial raster areas 4 and the second partial raster areas 6 are positioned below the second raster areas 10. The two partial raster areas 4, 6 differ in their color, but are indistinguishable with the naked eye, so that they create a mixed color in the area in which they are applied. The second raster areas reveal hidden, coded or encrypted image information in the print image of the partial raster areas 4, 6, which was realized, for example, by a line thickness modulation or a change in the line position. This means that depending on the degree to which the first partial raster areas 4 or the second partial raster areas 6 are overlapped by the second raster areas 10, more or fewer portions of the first partial raster area 4 or the second partial raster area 6 are recognizable, so that the color is influenced by the position of the second raster areas 10 on the partial raster areas 4, 6.This occurs in regions, so that the color effects differ from each other in at least two regions on the security element 1. The second raster areas 10 act as decoders, i.e., without the second raster areas 10, the image information of the partial raster areas 4, 6 is not recognizable or is difficult to recognize.

[0061] By changing the relative position of the second raster areas 10 with respect to the first raster areas 8 or by modulating the line thickness and direction of the partial raster areas 4, 6, both motion effects and 3D effects can be implemented due to the area-by-area color modulation. As an example, a 3D image of an object is encoded into a printable line modulation and printed as partial raster areas 4, 6 onto the substrate body 2. This encoded information is then decoded by the second raster areas 10, which are applied as a dot matrix, and irradiated with a UV radiation source, thus making the 3D image of the object visible again.

[0062] The Fig. 1 and 2show a layered structure for creating an image motif with such a static effect, for example, a 3D effect. Image motifs with a static effect exhibit a high color gradient component. A color gradient component represents a change from a (starting) color to a (target) color with a different hue, color saturation, and / or color brightness.

[0063] Either the first grid areas 8 or the second grid areas 10 are designed as luminescent grid areas, with the other one being printed in at least one body pigment. These luminescent grid areas are not visible when illuminated with light only from the visible spectrum, i.e. they are transparent, but are visible when illuminated with UV radiation. As a result, the described static effect is only visible with additional illumination with radiation from the UV range. The two-dimensional image motif, visible without UV, is then supplemented with depth information when exposed to UV radiation, for example, to create a 3D image motif - this is referred to as the static effect. This static effect is surprising to an outside observer, as it only becomes apparent when UV radiation is added, thus increasing security against counterfeiting.The image motif of the second grid areas 10 can also differ from the image motif revealed by the two partial grid areas 4, 6, in which case a change in information occurs. The visual impression of the security element 1 is improved.

[0064] It is also possible, but not shown, for the layers to be applied in exactly the opposite order, so that the second grid areas 10 are arranged below the partial grid areas 4, 6. In this case, a dot grid would be arranged below a line grid. The first grid areas 8 could also be printed in solid colors, and the second grid areas 10 could be luminescent.

[0065] Fig. 3shows a visually visible information 12, namely a grayscale gradient, which in further (not explicitly shown) embodiments represents a multicolored body color-based visually visible information 12, for example in the form of a multicolored portrait. A detail 14 is marked, which in Fig. 4 is explicitly shown again.

[0066] Fig. 5 represents the same detail 14 of the Fig. 4 in a schematic representation. It can be seen that the structure of the security element 1 according to Fig. 1 , wherein the second grid areas 10 are arranged above the partial grid areas 4, 6. The line thickness of the partial grid areas 4, 6 is 140 µm each, the spacing B is 10 µm, and the repeat of the partial grid areas 4, 6 is 300 µm. The dot-shaped second grid areas 10 have a diameter of 250 µm with a repeat of 300 µm.

[0067] The visually visible information 12, which is represented by the second raster areas 10, can, as an alternative to the displayed grayscale gradient, also be a portrait in multiple colors or a different type of object, a pattern, a number, or the like. The individual points of the dot matrix of the second raster areas 10 differ in their color or gray tone in certain areas.

[0068] How Fig. 3As shown, the partial grid areas 4, 6 are generally not visible in plan view when illuminated only with light from the visible wavelength range, because they are printed as luminescent lines on the substrate body 2, the motif of which only reveals itself as single- or multi-colored information under UV radiation. The motif and the color impression of the partial grid areas 4, 6 depend on the degree of overlap of the second grid areas 10 with the respective partial grid areas 4, 6. The intermediate areas between the dots of the second print layer 8 represent colorless areas when illuminated with light.

[0069] Fig. 6 now shows a first line print pattern 16 in the form of a donut, which was generated from the representation of a 3D object as a grayscale image by a program code. Fig. 7shows a second line print pattern 18 in the shape of a crown. It is also possible, for example, for the object to appear as a 3D object when viewed from above and exposed to additional UV radiation, or to change its color in certain areas. Of course, other shapes such as a letter, an insect, a drop, a sphere, a flower, intertwined ropes, etc. are also possible.

[0070] If a color change from a first to a second color is desired, this can be achieved by alternately printing two or more colors as lines in the two partial raster areas 4, 6. An iris gradient is also possible within such modulated lines.

[0071] Under light and without UV excitation, only a rasterized area of ​​the second raster areas 10 consisting of individual dots or alternatively lines can be recognized. Under additional UV radiation, the luminescent lines are partially absorbed by the body color and thus result in a moiré magnification. The resulting effect is initially static, but is recognizable as a 3D visualization of an object / structure, the image information preferably differs from the image information of the second partial raster areas 10. However, it can also be related to the 3D visualization and pick up information or represent this information in perspective in front of or behind the three-dimensional object. This means that the dot matrix in Fig. 3 could, for example, depict a chef with a wooden spoon and if you irradiate the security element 1 with UV radiation, the Fig. 6 depicted donut.

[0072] The Fig. 8shows a representation of color coordinates in an ab diagram, which represents the LAB color space of fluorescence. The x-axis (coordinate a) represents a chromaticity and color intensity between green and red, and the y-axis (coordinate b) represents a chromaticity and color intensity between blue and yellow. Color impressions can be achieved in the luminescent printing layer along and within the color coordinates shown. This results from the use of special HPP pigments ("high-performance pigments"), which are encapsulated fluoropigments that allow the use of a wide range of different fluorescent color shades.Such pigments, which are particularly preferred for the luminescent screen surfaces, have the additional advantage that the colors mixed from them do not show any perceptible color change after exposure to an external stimulus such as chemicals or sunlight - they are physically and chemically stable.

[0073] The described static effect can be extended by providing a relief structure 22 between the first grid areas 8 and the substrate body 2. Such embodiments are described in Figs. 9 and 10 shown.

[0074] In Fig. 9A plurality of elevations 24 is applied to the front side V of the substrate body 2. These elevations 24 can either be formed directly in the substrate body 2, or an embossing lacquer layer can be applied to the front side V of the substrate body 2, in which the elevations 24 are formed. In the same way, depressions 26, which are in Fig. 10 are visible, are applied to the front side V of the substrate body 2. A security element 1 may also have elevations 24 and depressions 26 in some areas. There may also be elevations 24 / depressions 26 in some areas and no relief structures in others—in this case, a static effect is combined with a dynamic effect in some areas. If reference is made to elevations 24 below, the same applies equally to depressions 26.

[0075] Fig. 11shows a profile section 28 of a hemispherical structure, which can be used both for the elevations 24 and, naturally mirrored on the x-axis, for the depressions 26. The dimensions in the x- and y-direction are given in µm. Thus, raised or depressed round structures can be used for the relief structure 22 as elevations 24 / depressions 26; compressed hemispherical structures or calottes with a circular or elliptical base are also possible. The type of relief structure 22 can also vary in certain areas. The cross-sectional profile of the Fig. 11 This only represents a hemispherical shape as an example; in practice, however, they are more likely to be distorted hemispheres. The dimensions for blind embossing by intaglio printing are in the x-axis range from 200 µm to 300 µm and in the y-axis from 20 µm to 80 µm.

[0076] As the Figs. 9 and 10show, the first partial grid areas 4 and the second partial grid areas 6, i.e. the first grid areas 8, are applied directly to the elevations 24 and the depressions 26 of the relief structure 22. They lie directly against the surface of the relief structure 22. The first grid areas 8 are arranged on the elevations 24 in such a way that at least part of the grid of the first grid areas 8 lies on each elevation 24. A location-dependent modulation takes place, which creates for the observer a surface that projects forward and / or backward relative to the surface of the security element, for example in the form of a three-dimensional image motif. As shown, the first grid areas 8 have a plurality of partial grid areas 4, 6, each of which has its own grid in its own color.Thus, each grid of the partial grid areas 4, 6 can be modulated independently of the other grid, depending on the location, so that the grids show different movement effects in different directions. They can of course also show the same movement effects in different directions or different movement effects in the same directions. It is also possible, for example, for the grid of the first partial grid areas 4 to produce a first color change when the security element 1 is tilted about its horizontal axis, and the grid of the second partial grid areas 6 to produce a second color change, different from the first color change, when the security element 1 is tilted about the vertical axis. As with the static effect, the respective motifs or color effects depend on the degree of overlap of the second grid areas with the first grid areas.

[0077] The second grid areas 10 are applied to the two partial grid areas 4, 6, but do not completely overlap them. The interaction of the relief structure 22, the first grid areas 8, and the second grid areas 10 creates an optical effect that complements the previously explained static effect; this is referred to as a dynamic effect. Due to the fact that one of the two grid areas 8, 10 luminesces and the others consist of body colors, only one of the first or second grid areas 8, 10 is visible when illuminated with light from the visible spectrum; for example, the second grid areas 10 on the topmost layer sequence, which are applied, for example, as a dot grid.They create a 2D image motif under visible illumination, which, due to the first grid areas 8 located underneath, which are then luminescent, is supplemented to form a 3D image motif upon additional illumination with UV radiation (which first makes the first grid areas 8 visible). Due to the imprinting of the first and second grid areas 8, 10 onto the relief structure 22, a viewing and / or illumination angle-dependent effect of the 3D image motif is created in the UV range. A movement effect can be created in the manner described, but dynamic effects can also occur when the viewing and / or illumination angle changes, such as a change in color, a change in intensity, a change in perspective, or a change in brightness. This dynamic effect cannot be easily copied by photocopiers and thus significantly increases security against counterfeiting.

[0078] The Fig. 12 to 14show arrangements of the relief structure 22 in plan view. The elevations 24 are arranged periodically and can be applied as hemispherical elevations 24 in a 0° / 90° grid ( Fig. 12 ). They can also be structural elements with an elliptically distorted base, which are applied in a 0° / 90° grid ( Fig. 13 ), or in an angled / offset arrangement, as for example in Fig. 14 , which shows a honeycomb arrangement of the elevations 24. The same arrangements are, of course, equally possible for the depressions 26. Each of the arrangements can only be provided in certain areas on the security element 1. List of reference symbols

[0079] 1Security element 2Substrate body 4First partial grid areas 6Second partial grid areas 8First grid areas 10Second grid areas 12Visually visible information 14Detail 16First line print pattern 18Second line print pattern 20a-b diagram 22Relief structure 24Elevation 26Depression BSpacing SSection line VFront side

Claims

1. A security element for protecting valuable documents, comprising: - a substrate body (2) having a front side (V) on which a first printing layer and a second printing layer are arranged, wherein - the first printing layer is formed from first grid areas (8) composed of first partial grid areas (4) and second, color-different partial grid areas (6), wherein the first partial grid areas (4) and the second partial grid areas (6) are indistinguishable to the naked eye and together form a mixed color, - the second printing layer is formed from second grid areas (10), - the first grid areas (8) or the second grid areas (10) are formed from luminescent colors, are detectable when illuminated with UV radiation and transparent when illuminated only with light from the visible spectrum, and the other grid areas (8, 10) are formed from body colors,- at least one angle to the front side, the second raster areas (10) appear to only partially overlap the first raster areas (8), wherein between the second raster areas (10) and the first partial raster areas (4) and the second partial raster areas (6) there is a degree of overlap in the range from 0% to 100%, and - the security element has at least two regions in which the degree of overlap between the second raster areas (10) and the first partial raster areas (4) differs from the degree of overlap between the second raster areas (10) and the second partial raster areas (6), and when illuminated with a combination of UV radiation and light from the visible spectrum, the mixed color in the two regions is modified differently.

2. Security element according to claim 1, characterized in that the luminescent colors are fluorescent colors.

3. Security element according to one of claims 1 or 2, characterized in that Due to the partial overlap of the first grid areas (8) with the second grid areas (10), a 2D image motif can be perceived with the naked eye when illuminated with light from the visible wavelength range, which is supplemented to form a 3D image motif when illuminated with UV radiation.

4. Security element according to one of the above claims, characterized in that on the front side (V) of the substrate body (2) in at least one of the regions a relief structure (22) with a plurality of periodically arranged, raised or recessed structural elements (24, 26) is applied.

5. Security element according to one of the above claims, characterized in that the structural elements (24, 26) are linear in at least one region.

6. Security element according to one of the above claims, characterized in thatthe structural elements (24, 26) are raised or recessed round structures in at least one area, in particular compressed hemispherical structures or calottes with a circular or elliptical base area.

7. Security element according to one of claims 4 to 6, characterized in that the raster surfaces (8, 10) are combined with the relief structure (22) in such a way that at least a part of the raster surfaces (8, 10) lies essentially on each structural element (24, 26), so that for the viewer, a surface in the form of a three-dimensional image motif that projects forward and / or backward relative to the surface of the security element (1) is produced by a location-dependent modulation of the raster surfaces (8, 10).

8. Security element according to one of the above claims, characterized in that the first grid areas (8) and / or the second grid areas (10) represent a dot grid.

9. Security element according to one of the above claims, characterized in thatthe first grid areas (8) represent a line grid with a large number of non-intersecting lines.

10. Security element according to one of the above claims, characterized in that the first partial grid areas (4) and the second partial grid areas (6) are two line grids, each line grid being modeled location-dependently independently of the other line grid, so that the line grids produce different movement effects or the same movement effects in the same or different directions.

11. A value document with an optically variable security element according to one of claims 1 to 10.

12. A method for producing a security element for protecting value documents, in which - a substrate body (2) comprising a front side (V) is provided, and - a first and a second printing layer are applied to the front side (V), wherein - - the first printing layer is formed from first grid areas (8) which are constructed from first partial grid areas (4) and second, color-different partial grid areas (6), wherein the first partial grid areas (4) and the second partial grid areas (6) are indistinguishable to the naked eye and together result in a mixed color, - the second printing layer is formed from second grid areas (10), - the first grid areas (8) or the second grid areas (10) are formed from luminescent colors, are detectable when illuminated with UV radiation and are transparent when illuminated only with light from the visible spectrum, and the respective other grid areas (8,10) are formed from body colours, - at least at one angle to the front side, the second raster areas (10) appear only partially overlapping the first raster areas (8), wherein a degree of overlap in the range from 0% to 100% is provided between the second raster areas (10) and the first partial raster areas (4) and the second partial raster areas (6), and - at least two areas are provided on the security element in which the degree of overlap between the second raster areas (10) and the first partial raster areas (4) differs from the degree of overlap between the second raster areas (10) and the second partial raster areas (6), and when illuminated with a combination of UV radiation and light from the visible spectrum, the mixed colour in the two areas is modified to different degrees.

Images