Security element and method for producing security element

Abstract

The invention relates to a security element for protecting value documents, comprising a substrate body (2) with a first grid surface (8) and a second grid surface (10), said first grid surface (8) being formed by a first partial grid surface (4) and a second partial grid surface (6) of a different color. The first and second local grid faces are indistinguishable to the naked eye and collectively produce a mixed color. The first or the second grid surface consists of a luminescent pigment which is recognizable when irradiated with ultraviolet radiation and which is transparent when irradiated with light only in the visible spectrum, and the other grid surface consists of a main pigment. In at least one angle relative to the front face, the second grid face appears to only partially overlap the first grid face. The security element has at least two regions, wherein the degree of overlap between the second grid surface and the first partial grid surface is different from the degree of overlap between the second grid surface and the second partial grid surface. The mixed color in the two regions varies differently upon irradiation with a combination of ultraviolet radiation and light of the visible spectrum.

Description

Technical Field

[0001] The invention relates to a security element for protecting value documents, comprising a substrate body having a front side and a first and a second printed layer applied to the front side of the substrate body. Background Art

[0002] For example, DE 102014018512 A1 describes such a security element. It describes a multi-colored security feature, the so-called "motion feature", which shows the observer the movement of a two-dimensional image visual object when the viewing angle is changed. EP 3475096 B1 discloses a film with such a multi-colored motion feature, the so-called "color dynamic film" (CDF). These "motion features" or "color dynamic films" are produced as follows: at least one main pigment is applied linearly to the embossed structure. The substrate forming the background is either highly reflective or provided with a reflective silver coating. Usually, at least two different main pigments are used, which appear as mixed colors when viewed from above and thus make the appearance of the security element unsightly. The effect of the corresponding main pigment is only revealed when the security element is tilted. DE 102018010078 A1 and EP 4013626 B1 extend the multi-colored motion feature to a three-dimensional image visual object. 2D and 3D motion effects that depend on the viewing angle increase security against counterfeiting because they are impossible to reproduce even with the most advanced copying equipment and therefore play a significant role in protecting the authenticity of valuable documents such as banknotes, checks, credit or other payment cards, and ID cards. These motion effects are directly visible when illuminated by light in the visible wavelength range, which is present in ambient conditions such as sunlight. Consequently, the visual objects of these images are recognizable to the naked eye when the security element is illuminated by light in the visible wavelength spectrum and therefore do not surprise the observer.

[0003] Likewise known are security features which display different information to an external observer when exposed to radiation in the ultraviolet wavelength range and when exposed to light in the visible wavelength range, such as those known from EP 3621821 B1, WO 2018 / 206936 A1, US Pat. No. 10,787,019 B2 or EP 2766193 B1.

[0004] Furthermore, EP 1554700 B1 and EP 1765602 B1 disclose the use of moiré patterns in combination with fluorescent inks. These moiré patterns provide different information to the viewer depending on direction by magnifying specific microimage elements with microlenses. When illuminated with ultraviolet light, they produce a motion or magnification effect. However, when illumination is changed to the ultraviolet range, no additional information is generated for the visual objects of the image visible when illuminated with light in the visible spectrum.

[0005] Further security elements are known from EP 1 567 358 B1, WO 2017 / 011476, EP 2 889 152 B1, EP 3766 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. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to improve the visual impression of an optically variable security element and to increase the anti-counterfeiting safety.

[0007] The invention is defined by a security element, a value document having an optically variable security element and a method for producing a security element for protecting a value document.

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

[0009] First and second printed layers are applied to the front side of the substrate body. The first printed layer comprises a first grid surface, which is constructed from a first partial grid surface and a second partial grid surface of a different color. The first and second partial grid surfaces are indistinguishable to the naked eye and together produce a mixed color. The second printed layer comprises the second partial grid surface.

[0010] The first or second grid surface consists of a luminescent pigment which is visible when irradiated with ultraviolet radiation and is transparent only when irradiated with light in the visible spectrum, and the other grid surface consists of a bulk pigment.

[0011] A bulk color material or bulk pigment is understood here to be a layer that re-emitted a portion of the incident light spectrum (radiation in the visible wavelength range) and absorbed another portion of the spectrum, so that the spectral distribution of the incident light differs from the spectral distribution of the emitted light, and the layer thus appears colored. A bulk pigment is therefore a non-autoluminescent pigment.

[0012] It goes without saying that, although this application refers to UV radiation, this UV radiation does not occur solely when UV irradiation is performed outside a UV chamber; irradiation with radiation in the UV range always also includes a contribution from light in the visible wavelength range that impinges on the security element. Therefore, the term "UV radiation" includes both pure UV radiation, such as that supplied inside a UV chamber, and UV radiation plus a visible light contribution.

[0013] Grid surfaces made of luminescent pigments are translucent, that is, they allow a certain portion of the incident light to pass through. If light strikes one side of the grid surface, a certain portion of the light can penetrate to the other side of the grid surface and be re-emitted there. The greater the percentage of light that passes through, relative to the incident light, the higher the transparency of the grid surface. If the percentage is at least 90%, that is, the grid surface allows the incident light to pass through almost unattenuated, like a window, then the grid surface is said to be transparent. If, on the other hand, the grid surface allows less than 10%, preferably approximately 0%, of the incident light to pass through, that is, the portion of light that passes through is low or close to zero or equal to zero relative to the incident light, then it is said to be opaque or light-proof. If the luminescent grid surfaces are illuminated only with visible light, they are completely transparent. If a portion of ultraviolet light is added, for example, with sunlight, the grid surface appears slightly yellowish to the naked eye.

[0014] Even when irradiated with pure UV radiation, for example without residual natural light, the grid surface with luminescent pigments can be discerned. In this case, the upper grid surface composed of one or more host pigments can act as an absorber for the UV-excited and emitted visually visible radiation. Alternatively, the grid surface with luminescent pigments can be positioned on a grid surface composed of host pigments, so that the luminous intensity of the luminescent grid surface can be displayed in a variable manner depending on the application density and optical density (or hue) of the visually visible grid elements. When excited with pure UV radiation, a portion of the UV radiation is reflected by the substrate, while another portion is absorbed in the grid surface composed of host pigments.

[0015] The first and second grid surfaces interact optically. At at least one angle relative to the front surface, the second grid surface appears to only partially overlap the first grid surface, with the degree of overlap between the first grid surface and the first and second partial grid surfaces each ranging from 0% to 100%. This allows adjustment of the portion of the grid surface located at the bottom of the layer sequence that is visible and the portion that is invisible. This allows adjustment of the color impression when illuminated with light in the visible wavelength range and with ultraviolet radiation. The angle can be the observation angle and / or the illumination angle at which the grid surfaces overlap. While the first and second grid surfaces partially overlap, this also includes the second grid surface partially overlapping the first partial grid surface but not the second partial grid surface, or vice versa. In particular, it is also possible for the second grid surface to completely cover the first partial grid surface, i.e., 100% overlap, while the second grid surface does not overlap the second partial grid surface, i.e., 0% overlap. Even so, the first and second grid surfaces still partially overlap.

[0016] The security element has at least two areas in which the degree of overlap between the second grid surface and the first partial grid surface differs from the degree of overlap between the second grid surface and the second partial grid surface. When illuminated by a combination of ultraviolet radiation and light from the visible spectrum, the mixed color in the two areas changes to different degrees. The degree of overlap between the second grid surface and the grid surface can change the recognizable color in the areas. Thus, when illuminated with ultraviolet and / or visible spectrum light, the first area appears different from the other area. This synergistic effect can, for example, produce a 3D effect when the illumination changes.

[0017] A plurality of different 3D objects can be generated as image visual objects. In the UV radiation, the image visual object in the first sub-area is brighter than the image visual object in the other sub-area. This creates a plasticity of the 3D effect. This is not a stereoscopic 3D effect.

[0018] The luminous grid surface can consist of a mixture of RGB fluorescent pigments, or it can also have a phosphorescent component, or be applied as a dual fluorescent pigment with different emission colors at different excitation wavelengths, such as 254 nm and 365 nm. The fluorescent and / or phosphorescent pigments can be excited in different wavelength ranges, such as UV-A, UV-B, and / or UV-C.

[0019] The luminescent pigment is preferably a fluorescent pigment or a fluorescent pigment, thereby providing a fluorescent grid surface. Particularly preferably, encapsulated fluorescent pigments, for example, fluorescent pigments known from DE 102015014525 A1, DE 102015014537 A1, DE 102015014539 A1 or DE 102015014526 A1, are used for the luminescent grid surface. The fluorescent pigments achieve different fluorescent tones in a larger range of color selection (instead of only using red, orange, yellow, yellow-green and blue in value paper printing as before). In addition, the tones mixed by these pigments do not produce or only produce a slight change in tones after being affected by external stimuli such as chemicals or sunlight. This makes it possible for the first time for the quality of any luminescent mixed tones in the security feature to remain unchanged even under the influence of environmental factors. That is, it is possible to produce an aesthetically pleasing image visual object with chemical and / or physical resistance, which has a variety of luminescent pigments that can be used.

[0020] The first and / or second grid surface can preferably be a dot grid or a line grid. The line grid is preferably formed from a plurality of non-intersecting lines. The first or second grid surface can be applied as a grid composed of different primary pigments, for example, arranged as lines or dots of different colors. The illuminated grid points or grid lines can also have a variety of different colors.

[0021] The first and second grid surfaces interact optically. A change in information occurs when the illumination changes from light in the visible spectrum to ultraviolet radiation. When the illumination changes within a region, the displayed 2D or 3D image, for example, changes, or a 2D visual object can be supplemented with a 3D effect. This occurs when the first grid surface is supplemented by the second grid surface with other visual objects or 3D effects. In the layer sequence, the upper grid surface composed of the primary pigment selectively covers a portion of the lower grid surface composed of the luminescent pigment, so that the uncovered luminescent grid surface displays additional image information that is not visible under natural light, in addition to the image information of the upper grid surface composed of the primary pigment. These two pieces of image information, or, for example, two visual objects, can be independent of each other. For example, the image information of the primary pigment grid surface could be a portrait of an artist, while the image information of the UV-visible luminescent grid surface could be a three-dimensional sculpture of the artist. These two pieces of information, or, for example, visual objects, can also complement each other. This is due to the different shapes of the first and second grid areas, since in the layer sequence that part of the grid area which is closer to the substrate body (“below”) always remains visible.

[0022] The second grid surface preferably differs from the first grid surface not only in shape but also in color. Under UV radiation, this layer sequence reveals additional information, particularly information about perspective and color, relative to the first information provided by the grid surface composed of the primary pigment. If the additional color information is added during UV exposure, the color of the area changes. Supplementing the first information with the second information is achieved solely through the combination of the first and second grid surfaces, and therefore creates a higher barrier to counterfeiting, as the two printed layers must be precisely matched to one another—that is, the optical effect depends on the degree of overlap between the first and second grid surfaces, particularly the visible proportions of the respective colors. Thus, the grid of the printed layer composed of primary pigment could be a dotted grid of flowers. Under UV radiation, the grid of the illuminated printed layer could, for example, reveal bees, allowing the two visual objects to be identified complementary to each other when there is little residual natural light and the UV radiation is sufficiently strong. For example, it is also possible to visualize a rectangle as a two-dimensional visual object composed of primary pigment, and for UV exposure to reveal a woven structure on the rectangular surface with a modulated brightness, such as that of a basket.

[0023] In an embodiment, both the first grid surface and the second grid surface can be luminous grid surfaces, provided that the respective other grid surface is formed by a host pigment.

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

[0025] The optical interaction of the first and second grid surfaces is also referred to herein as a static effect. This static effect does not require a relief structure. For example, if the dot grid of the second grid surface does not completely cover the line grid of the first grid surface, the dot grid of the second grid surface located above the line grid of the first grid surface is sufficient to produce the static effect. This static effect requires the first grid surface to be aligned with the second grid surface and not only improves the optical impression or visual impression of the security element, but also increases the anti-counterfeiting security of the security element. By means of the static effect, areas of the security element can differ from other areas on the security element in terms of color or displayed objects. Under ultraviolet radiation, these areas can also differ independently of each other in terms of their color or color intensity, for example in terms of brightness due to regional modulation of the line thickness of the grid surface, and in terms of their visual representation as an object or pattern. Repeating geometric shapes such as rhombuses, rectangles, triangles, lines, or geometric figures in perspective (prisms, cubes, spheres) can be implemented as patterns, as can repeated parts of visual objects, twisted ropes, knots, and so on. More complex objects can also be displayed, such as 3D representations of animals (e.g., bees), rings, and tires, as well as symbols and characters (e.g., letters or numbers). The interaction between the first and second grid surfaces also allows for the combination of a 3D-effect background pattern with a 3D object displayed in the foreground. This allows two different 3D visual objects to be precisely aligned with each other, further enhancing anti-counterfeiting security.

[0026] During the printing process, one of the two printed layers is preferably provided in the form of a decoder printing plate in the form of a regular pattern of dots, symbols, grid-like elements or lines with a fixed repeating pattern (fixed pitch), and is applied during the printing process to the other of the two printed layers, which is provided on the visual object printing plate, for example in the form of modulated lines with a fixed repeating pattern. The two printed layers are therefore preferably applied by means of repeated printing, wherein the dots / lines / symbols / grid-like elements are repeatedly applied at a fixed pitch during the printing process, thereby forming the image visual object.

[0027] In one static effect variant, a first grid surface, for example a line grid, is present on the front side of the substrate body in the form of a main pigment. A second luminous grid surface, for example a dot grid, is applied to the first grid surface and thereby decodes information.

[0028] Decoding is understood to mean the display of information with a visual object by superimposing a first grid surface on a second grid surface. The information of the first printed layer is only visible as a visual object with varying intensity levels or shades if the parameter set is adapted, i.e., if the repeating pattern and repetition frequency correspond. The sizes of the repeating patterns of the first and second grids are preferably approximately the same or multiples of each other. For example, the repeating pattern of the modulated line grid averages 290 to 310 μm, while the repeating pattern of the decoding grid is 300 μm. Unprinted areas may exist between the line grids of different colors to prevent color contamination; however, the line grids of different colors can also be printed abuttingly, i.e., directly adjacently or overlappingly.

[0029] In this variant, the bulk pigment is located below the luminescent pigment. Compared to a grid surface composed of bulk pigments arranged above the luminescent grid surface, the contrast of the optical effect is lower because, for example, the fluorescence of the upper pigment is stimulated, but there is no back reflection of the UV radiation from the substrate or of the fluorescent color.

[0030] Advantageously, the host pigment has a high absorptivity for UV radiation in the range of 254 nm to 365 nm and / or a high absorptivity in the emission wavelength range of the luminescent pigment used. This results in a particularly high-contrast and attractive optical effect. High absorptivity means an absorptivity of at least 70%, preferably above 90%, and particularly preferably 95%, in the relevant spectral range / emission wavelength.

[0031] In another variant, a first grid, such as a line grid of a luminescent grid surface, is applied to the front surface of the substrate body. A second (decoding) grid, consisting of a second grid surface, such as a dot grid composed of a primary pigment or multiple primary pigments, is applied to these luminescent grid surfaces, thereby decoding the information of the first grid surface via the second grid surface. The absence of a relief structure results in the aforementioned static effect. The first and second grid surfaces can be composed of multiple primary pigments or multiple luminescent pigments. The grids of both grid surfaces can also take the form of regularly arranged lines, dots, symbols, grid-like elements, etc.

[0032] A decoder printing plate or a visual printing plate can be used to print a grid surface composed of a primary pigment, while a corresponding second plate is used to apply a luminescent grid surface. The visual printing plate preferably prints lines as a luminescent grid surface that is invisible without UV radiation, while the decoder printing plate prints dots as a grid surface composed of the primary pigment, which is discernible to the naked eye. The described printing technique results in a larger coverage area of the luminescent grid surface, resulting in a higher brightness under UV radiation. This enhances the effect of the second grid surface.

[0033] As an alternative, the grid surface of the main pigment can also be printed as lines, and the decoding can be achieved by printing a brightly lit grid surface (such as yellow-green).

[0034] The first and second grid surfaces are preferably printed using a (wet or dry) offset printing process, for example by printing in a super-synchronous printing press with multiple printing units or in a tandem printing press to achieve optimal matching. Alternative printing processes include inkjet, screen printing, and gravure printing. Combining two different printing processes significantly enhances tamper protection. Inkjet printing allows for a particularly high degree of personalization.

[0035] If, for example, a dot grid made of different subject pigments is provided, the individual dots of the dot grid can be applied very easily using an inkjet process, for example onto a luminous pre-printed line in a preceding printing step. This allows, for example, a personalized portrait made of subject pigments with a constant luminous background effect.

[0036] In banknote printing, a multi-color decoding color grid can be applied by simultaneous printing using multiple printing plates. This decoding color grid itself can also have a color gradient, for example, a rainbow gradient. It is important that the host pigment used in one of the two printing layers has sufficient UV absorption in the UV range of 254 nm and 365 nm, which is relevant for banknote inspection, or that the underlying emitting luminescent pigment has sufficient UV absorption, for example, in the range of 400 nm to 500 nm for blue, 490 nm to 540 nm for green, and 560 nm to 780 nm for yellow and red.

[0037] It is feasible to produce the static effect by means of various printing processes, or a plurality of printing processes can be combined with each other. It is particularly preferred to monitor the pigment application thickness by means of a measuring device to adapt the pigment in each sub-step, thereby producing a better optical effect.

[0038] The static effect described makes it possible to achieve a security feature with a resolution that is significantly higher than the viewing angle-dependent motion security feature ("MOVE" feature) described at the beginning, since, by dispensing with the relief structure, the repetitive pattern can be reduced to 20 μm when printing a repetitive pattern, i.e., a resolution that is 15 times finer than the 300 μm repetitive pattern in known security features.

[0039] Preferably, a relief structure is provided between the substrate body and the grid surface closer to the substrate body (the "lower"), comprising a plurality of periodically arranged raised or recessed structural elements. These structural elements are preferably produced by blind embossing in a gravure printing process after the first grid surface has been printed on the substrate body using an offset printing process. The structural elements are preferably formed by raised or recessed circular structures, in particular sunken hemispherical structures, or spherical caps with a circular or elliptical base. The structural elements can also preferably be designed as linear, i.e., the relief structure can have a plurality of peaks, valleys, or grooves.

[0040] The luminous grid surface is preferably combined with the relief structure in such a way that at least a portion of the luminous grid surface is present on essentially every structural element, so that for the observer, the position-dependent modulation of the grid surface produces a surface that projects and / or recedes relative to the surface of the security element in the form of a three-dimensional visual object. The grid of the first and / or second grid surface particularly preferably comprises two or more line grids, wherein each line grid is modulated independently of the corresponding other line grids in a position-dependent manner, so that the line grids produce different motion effects or the same motion effect in the same or different directions. The interaction of the first and second grid surfaces can also produce a visual object with a three-dimensional depth effect and / or different motion effects when the security element is tilted about different axes. These effects are preferably provided regionally and differ in at least two regions.

[0041] With regard to the application of the grid to the relief structure, reference is made to DE 102018010078 A1, the content of which is incorporated herein in its entirety. The grid width of the structural elements (i.e., the "grid elements" therein) is preferably designed as described in this publication and a position-dependent modulation is performed using a phase function. The main difference, however, is that one of the two grids is luminous and supplements the information of the other grid, usually the main pigment grid, in the ultraviolet range. When the irradiation changes from light in the visible spectrum wavelength range to irradiation with ultraviolet radiation, the information changes and / or the information supplementation occurs. In a particularly preferred embodiment, reflective or highly reflective surfaces, in particular on the substrate body, can be omitted.

[0042] In one embodiment, a relief structure, for example produced by blind embossing, is combined with gravure printing to produce a dynamic effect under UV radiation. This is understood to mean that a static effect is supplemented, for example by the additional provision of a relief structure and the position-dependent modulation of the luminous grid surface on the relief structure, so that under UV radiation and when the viewing angle and / or illumination angle are changed, the 3D visual object produced by the static effect appears to move. Under UV radiation and when the viewing angle and / or illumination angle are changed, the 3D visual object produced by the static effect can also have different shades and depth effects as dynamic effects. When the UV radiation is changed, the dynamic effect can manifest itself as dynamic color changes in the UV light, such as color shifts, intensity shifts, perspective shifts, brightness shifts, etc.

[0043] In one embodiment, an image composed of a primary pigment exhibits a 3D effect under UV radiation, exhibiting varying color dynamics, such as changes in hue or brightness levels, as the intensity and direction of the UV radiation source change (or shift). The intensity of a visually perceptible color channel under UV radiation can range from 0% to 100%, and it is also possible for two or more color channels to be mixed to form a mixed color. Thus, as the UV radiation changes, an enhanced dynamic 3D effect can be achieved, in which one or more light on / off effects and / or brightness gradients with smooth hue transitions can be achieved as the viewing angle and / or irradiation angle of the respective luminescent pigments vary. For example, when using green and red fluorescent light, a transition from a reddish (or light red) to a yellowish and greenish color can also be achieved.

[0044] The relief structure produced on the front side of the substrate body in the form of a uniformly circular structural element (approximately hemispherical) of protrusions / recesses is produced directly in the substrate body or produced in an embossing layer applied to the front side of the substrate body by blind embossing. The size of the structural element for the value document is preferably in the range of 200nm to 300μm. The structural height is less than 200μm, preferably less than 100μm, and particularly preferably 20μm to 80μm. The protruding structural elements can be nested in each other or spaced apart from each other. In one embodiment, it is also possible to replace the hemispherical convex point production and use an alternating structure consisting of linear grooves (valleys and peaks) as the structural element of the relief structure. The structural elements can also be different regionally. For example, the structural elements can be constructed linearly in some areas and be protruding / recessed circular structures, spherical caps, etc. in other areas. Therefore, the area with the relief structure can also be combined with the area without the relief structure, thereby regionally showing a static effect and regionally showing a dynamic effect.

[0045] As mentioned at the outset, a pure matrix of pigments is sufficient to decode information (a relief structure is not always necessary). Additional embossing can create a motion effect stimulated by UV radiation, which creates a smooth transition from one hue to another. If objects are displayed 3D in a line grid, regular arrays of embossed raised dots, micromirrors, or Fresnel concave mirrors can be used for decoding.

[0046] In addition to design variants with static effects, there are other variants with the aforementioned dynamic effects. In another variant, a first grid of a first luminous grid surface is printed on a relief structure, wherein the relief structure for angle-dependent decoding is applied to the front side of the substrate body, so that, when the security element is tilted and irradiated with UV radiation, for example, a 3D effect, a brightness gradient, etc., can be seen. In addition, a second grid consisting of a second grid surface is printed on the first grid with a base pigment, which forms the decoding grid. Under UV radiation, a first static effect then appears (for example, a 3D effect of a 2D image visual object when irradiated with light in the visible wavelength range), and when the radiation source is tilted or the viewing angle changes, the 3D effect reveals dynamic depth information, color changes, movement, etc. These effects can also be applied only regionally.

[0047] Of course, the order of the process steps and the layer structures can be interchanged in all variants of static and dynamic effects, with blind embossing always being particularly preferred at the end. In one embodiment, blind embossing can also be performed first and then the grid surface can be applied to the relief structure, particularly preferably by printing directly onto the structural elements of the relief structure, for example using an inkjet process.

[0048] The first and second grid planes are particularly preferably located on two separate areas of the surface of the substrate body. This allows, for example, self-verification when the security elements are stacked on top of one another, when a window is provided in the substrate body, such as a polymer or hybrid banknote. For example, the first grid plane can be located in the window, while the second grid plane can be located on the banknote's substrate body, or vice versa. Thus, when the separate areas are stacked on top of one another, i.e., for self-verification, the luminous grids are each combined with the grid composed of the main pigment. For example, it is possible to combine the moiré grid in the window with the luminous moiré grid on the substrate body in a precisely matched manner, so that they only reveal the encoded information when they interact, while each moiré grid itself represents a differently designed superstructure. For example, the moiré grid in the window displays a bee, while the moiré grid on the substrate body displays a flower; if these two areas are stacked on top of one another for self-verification, they jointly display the value 50.

[0049] Particularly preferably, it is also possible that the first grid surface is applied in the window on the front side of the substrate body and the second grid surface is applied on the back side of the substrate body, or vice versa. In this case, the first and second grid surfaces also provide the coded information in combination.

[0050] Also provided are valuable documents having security elements of the type described. The security element is applied to a security substrate, for example a banknote substrate - a cotton substrate, a mixed substrate, a window substrate or a polymer substrate. The security element can also be introduced into a card body (document, identity document) as a multi-layer laminated structure. In this case, the security element is located inside the multi-layer valuable document. The security element can, for example, be applied as a transfer element to the inner surface of a multi-layer substrate body. The multi-layer laminated structure can be fluorescently printed on the front and / or back of one or more laminated layers. The security element can be located outside and / or inside. The production of the security element can be easily integrated into the banknote production process and can therefore be used as an upgrade / update for existing banknote designs, identity documents, etc.

[0051] A method for producing a security element for protecting valuable documents is also disclosed. A substrate body including a front face is provided, and first and second printed layers are applied to the front face. The first printed layer comprises a first grid surface, which is constructed from a first partial grid surface and a second partial grid surface of different colors. The first and second partial grid surfaces are indistinguishable to the naked eye and together produce a mixed color. The second printed layer comprises a second grid surface, and either the first or the second grid surface comprises a luminescent pigment that is visible under ultraviolet radiation and transparent only when illuminated with light in the visible spectrum. The other corresponding grid surface comprises a bulk pigment. At at least one angle relative to the front face, the second grid surface appears to only partially overlap the first grid surface, with the second grid surface having a degree of overlap ranging from 0% to 100% with each of the first and second partial grid surfaces. At least two areas are provided on the security element, in which the degree of overlap between the second grid surface and the first partial grid surface is different from the degree of overlap between the second grid surface and the second partial grid surface, and when illuminated by a combination of ultraviolet radiation and light in the visible spectrum, the mixed color in the two areas changes to different degrees.

[0052] It goes without saying that the method can be modified in the same way as the security element and the value document.

[0053] In this method, for example, the object that will later be visible under UV radiation is first created in a 3D graphics program and a grayscale gradient (corresponding to the desired exposure orientation) is generated. This grayscale image is then used with the aid of software to generate a "high-relief image" as printable lines, thereby creating a depth and 3D effect. The lines to be printed in the other luminescent print layers have a line offset or line modulation in thickness and position, similar to contour lines on a tourist map. If a multicolor effect or color change is desired under UV radiation, multiple luminescent pigments can be printed closely together in the form of lines in the luminescent print layer.

[0054] A grid of dots, lines, or objects is preferably printed as the decoding structure, with the dimensions of the grid being less than twice the width of the modulated lines. For example, for a modulated line with a maximum line thickness of 150 μm, the diameter of the upper / lower main pigment dots is a maximum of 300 μm, preferably less than 150 μm. This results in areas where at least one luminous line can be completely covered by the dots, and other areas where the luminescent pigment is not covered. The uncovered areas form the secondary information, which is later visible under UV radiation.

[0055] The two printing layers are prepared as dot-modulated or line-modulated printing for offset / wet offset printing or nylon printing. The two printing layers are then printed in the form of a grid surface using a combination of two different printing presses (one for the first printing layer and one for the second printing layer) or using at least one additional printing mechanism of a single printing press. This method has the advantage that, for example, the brightness modulation of the sub-areas is determined by the line thickness or width of the illuminated line grid, rather than solely by the coloring of the print. This allows for, for example, more subtle differences in grayscale to be displayed without having to rely on the grid structure of the illuminated printing layer. This is particularly advantageous in that it avoids the potential dot gain associated with the grid structure used to generate grayscale during the printing process. The blank spaces within the visual image object allow for the placement of additional information, such as characters or numbers, which further advantageously increases anti-counterfeiting security.

[0056] A security element for protecting valuable documents, comprising a substrate body (2) consisting of a first grid surface (8) and a second grid surface, wherein the first grid surface (8) consists of a first partial grid surface (4) and a second partial grid surface (6) of a different color. The first partial grid surface (4) and the second partial grid surface (6) are indistinguishable to the naked eye and together produce a mixed color. The first grid surface (8) or the second grid surface (10) consists of a luminescent pigment which is recognizable when irradiated with ultraviolet radiation and is transparent when irradiated only with light in the visible spectrum, and the other grid surface (8, 10) consists of a bulk pigment. At at least one angle relative to the front side, the second grid surface (10) appears to overlap only partially with the first grid surface (8), wherein a degree of overlap between the second grid surface (10) and the first partial grid surface (4) and the second partial grid surface (6) is respectively provided in the range of 0% to 100%, and the security element has at least two areas, wherein the degree of overlap between the second grid surface (10) and the first partial grid surface (4) is different from the degree of overlap between the second grid surface (10) and the second partial grid surface (6). Upon illumination with a combination of ultraviolet radiation and light in the visible spectrum, the mixed colors in the two areas are altered differently. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The present invention is described in more detail below based on embodiments with reference to the accompanying drawings, which also disclose features important to the present invention. These embodiments are for illustration only and should not be considered restrictive. For example, the description of an embodiment with multiple elements or components should not be interpreted as all of these elements or components being necessary for implementation. Rather, other embodiments may also include alternative elements and components, fewer elements or components, or additional elements or components. Unless otherwise stated, elements or components of different embodiments may be combined with each other. Modifications and variations described for one embodiment may also apply to other embodiments. In the drawings:

[0058] Figure 1 The value document is shown in a top view;

[0059] Figure 2 The cross-sectional view shows the Figure 1 Anti-counterfeiting elements;

[0060] Figure 3 The security element with grayscale gradient is shown in a top view;

[0061] Figure 4 Shown according to Figure 3 Detail view of the view;

[0062] Figure 5 Shown according to Figure 4 Schematic diagram of the details;

[0063] Figure 6 A line printed pattern of an object is shown;

[0064] Figure 7 A line printed pattern of another object is shown;

[0065] Figure 8 shows an ab diagram of the fluorescence of the encapsulated fluorescent pigment in the LAB color space;

[0066] Figure 9 A security element in another embodiment is shown in a cross-sectional view;

[0067] Figure 10 A security element in another embodiment is shown in a cross-sectional view;

[0068] Figure 11 shows a cross-sectional profile of a structural element designed as a sunken hemispherical structure;

[0069] Figure 12 shows a top view of a relief structure having structural elements in a 0° / 90° layout;

[0070] Figure 13 shows a top view of a relief structure having structural elements arranged in a honeycomb pattern;

[0071] Figure 14 A plan view of a relief structure is shown, the base areas of the structural elements of which are elliptically distorted. DETAILED DESCRIPTION

[0072] Figure 1 The security element 1 is shown in a top view. The section line S is marked. Figure 2 A sectional view along the cutting line is shown. The first partial grid surface 4 is applied to the front side V of the substrate body 2 in the form of a line grid. The second partial grid surface 6 is also applied to the front side V of the substrate body 2 in the form of a line grid. A spacing B representing a gap is provided between the first partial grid surface 4 and the second partial grid surface 6. The two partial grid surfaces 4 and 6 together constitute the first grid surface 8 of the first printed layer. The second grid surface 10 is applied to the two partial grid surfaces 4 and 6 in the form of a dot grid, but does not completely cover them. If the second grid surface 10 is applied above the spacing B, the second grid surface fills the spacing B between the two partial grid surfaces 4 and 6 (as shown in FIG. Figure 2 shown).

[0073] The first partial grid surface 4 and the second partial grid surface 6 are positioned below the second grid surface 10. The two partial grid surfaces 4 and 6 have different colors, but are indistinguishable to the naked eye, resulting in a mixed color in the areas where they are applied. The second grid surface reveals hidden, coded, or encrypted image information within the printed image of the partial grid surfaces 4 and 6, for example, by modulating line thickness or varying line position. In other words, depending on the degree of overlap between the first partial grid surface 4 and the second partial grid surface 6 and the second grid surface 10, the visible portion of the first partial grid surface 4 and the second partial grid surface 6 increases or decreases, thereby influencing the color by the position of the second grid surface 10 on the partial grid surfaces 4 and 6. This is achieved regionally, resulting in different color effects in at least two areas on the security element 1. The second grid surface 10 acts as a decoder; without the second grid surface 10, the image information of the partial grid surfaces 4 and 6 is unreadable or only very difficult to discern.

[0074] By varying the relative position of the second grid surface 10 with respect to the first grid surface 8, or by modulating the line thickness and orientation of the local grid surfaces 4 and 6, it is possible to achieve both motion and 3D effects through regional color modulation. For example, a 3D image of an object can be encoded as a printable line modulation and printed as local grid surfaces 4 and 6 on the substrate body 2. This encoded information is then decoded by the second grid surface 10, applied in the form of a dot grid, and irradiated with an ultraviolet radiation source, thereby making the 3D image of the object clearly visible again.

[0075] Figure 1 and Figure 2 A layer structure is shown for generating a visual object with such a static effect, for example a 3D effect. The visual object with the static effect has a high color gradient component. The color gradient component represents the change from one (starting) color to a (target) color with a different hue, color saturation, and / or color brightness.

[0076] The first grid surface 8 or the second grid surface 10 is designed as a luminous grid surface, wherein the corresponding other grid surface is printed with at least one main pigment. These luminous grid surfaces are not recognizable when illuminated solely with light in the visible spectrum, i.e., they are transparent, but can be recognized when irradiated with ultraviolet radiation. Therefore, the described static effect is only recognizable when additionally irradiated with radiation in the ultraviolet range. A two-dimensional image visual object visible without ultraviolet light is supplemented with depth information under ultraviolet radiation, for example, to form a 3D image visual object—this is known as a static effect. This static effect is surprising to an external observer because it only becomes apparent after the addition of ultraviolet radiation, thereby increasing anti-counterfeiting security. The image visual object of the second grid surface 10 can also differ from the image visual object displayed by the two partial grid surfaces 4 and 6, in which case a change in information occurs. The optical impression of the security element 1 is improved.

[0077] It is also possible, but not shown, to apply the layers in reverse, so that the second grid surface 10 is arranged below the partial grid surfaces 4, 6. In this case, the dot grid is arranged below the line grid. It is also possible to print the first grid surface 8 with a matrix color and the second grid surface 10 with light.

[0078] Figure 3 The visually perceptible information 12 is shown, namely a grayscale gradient, which in other embodiments (not explicitly shown) represents a multi-colored, host-based visually perceptible information 12, for example in the form of a multi-colored portrait. Figure 4 The details are shown again in detail 14.

[0079] Figure 5 The schematic diagram shows the Figure 4 Same details as 14. It can be seen that the structure is the same as that according to Figure 1 The security element 1 corresponds to a second grid surface 10 arranged above the partial grid surfaces 4 and 6. The line thickness of the partial grid surfaces 4 and 6 is 140 μm, the spacing B is 10 μm, and the repeating pattern of the partial grid surfaces 4 and 6 is 300 μm. The second grid surface 10 applied in a dotted manner has a diameter of 250 μm and a repeating pattern of 300 μm.

[0080] As an alternative to the grayscale gradient shown, the visually visible information 12 represented by the second grid surface 10 can also be a multi-colored portrait or different objects, patterns, numbers or similar information. The individual points of the dot grid of the second grid surface 10 differ regionally in their color or gray tone.

[0081] like Figure 3As shown, the partial grid areas 4 and 6 are invisible in a top view when illuminated solely with light, typically in the visible wavelength range, because they are printed on the substrate body 2 as luminous lines, and their visual content only appears as monochromatic or multicolored information under ultraviolet radiation. The visual content and color impression of the partial grid areas 4 and 6 depend on the degree of overlap of the second grid area 10 with the respective partial grid area 4 and 6. The intermediate areas between the dots of the second printed layer 8 appear colorless when illuminated with light.

[0082] Figure 6 A first line print pattern 16 in the form of a donut is shown, which is generated by representing the 3D object as a grayscale image in program code. Figure 7 A second line print 18 is shown in the form of a crown. For example, it is also possible for the object to appear as a 3D object in a top view and with additional UV radiation, or to change its color regionally. However, other forms such as letters, insects, water drops, balls, flowers, interwoven ropes, etc. are also possible.

[0083] If a change from a first color to a second color is desired, this can be achieved by printing two or more colors alternately as lines in the two partial grid surfaces 4, 6. Rainbow color changes or rainbow color gradients can also be achieved in such modulated lines.

[0084] Under illumination and without UV excitation, only the grid-like surface of the second grid surface 10, consisting of individual points or, alternatively, lines, is visible. Under additional UV radiation, the luminous lines are partially absorbed by the main pigment, and a moiré amplification is thereby produced. The effect produced here is initially static, but can be recognized as a 3D visualization of the object / structure; the image information is preferably different from the image information of the second partial grid surface 10. However, it can also be associated with a three-dimensional visualization and intercept information or display this information in a perspective manner in front of or behind the three-dimensional object. In other words, Figure 3 The dot grid in FIG. 1 can, for example, represent a chef holding a cooking spoon and appear when the security element 1 is irradiated with UV radiation. Figure 6 Donuts shown.

[0085] Figure 8The representation of color coordinates in an ab diagram, which represents the fluorescent LAB color space, is shown. The x-axis (coordinate a) shows the color types and color intensities between green and red, and the y-axis (coordinate b) shows the color types and color intensities between blue and yellow. The color impression in the luminous print layer can be achieved along and within the color coordinates shown. This is due to the use of special HPP pigments ("high performance pigments"), which are encapsulated fluorescent pigments that enable the use of different fluorescent hues within a wide range of choices. Such pigments are particularly preferred for luminous grid surfaces, and an additional advantage of such pigments is that the hues formed from them do not show noticeable changes in hue after being influenced by external stimuli such as chemicals or sunlight - they are physically and chemically resistant (or durable or stable).

[0086] The described static effect can be extended by providing a relief structure 22 between the first grid surface 8 and the substrate body 2 . Figure 9 and Figure 10 These embodiments are shown.

[0087] exist Figure 9 In the embodiment, a plurality of protrusions 24 are applied on the front side V of the substrate body 2. These protrusions 24 can be formed directly in the substrate body 2, or an embossing lacquer layer can be applied on the front side V of the substrate body 2, and the protrusions 24 are formed in the embossing lacquer layer. Figure 10 The visible recesses 26 can also be applied in the same manner to the front side V of the substrate body 2. The security element 1 can also partially contain elevations 24 and partially contain recesses 26. It is also possible for elevations 24 / recesses 26 to be present in some areas and no relief structure in others—in this case, static effects are regionally combined with dynamic effects. If the following refers to elevations 24, the same applies to recesses 26.

[0088] Figure 11 A cross-sectional profile 28 of a hemispherical structure is shown, which can be used for both the elevations 24 and, naturally, the depressions 26, mirrored along the x-axis. The dimensions in the x- and y-directions are given in μm. For the relief structure 22, raised or recessed circular structures can be used as elevations 24 / depressions 26; sunken hemispherical structures or spherical caps with a circular or elliptical base can also be used. The type of relief structure 22 can also vary regionally. Figure 11 The cross-sectional profile shown shows a hemispherical shape only by way of example; in reality, however, a distorted hemispherical shape may be involved. These dimensions for blind embossing by engraving intaglio printing are 200 μm to 300 μm for the x-axis and 20 μm to 80 μm for the y-axis.

[0089] like Figure 9 and Figure 10 As shown, the first and second partial grid surfaces 4, 6, or first grid surface 8, are applied directly to the protrusions 24 or recesses 26 of the relief structure 22. The first and second partial grid surfaces are in direct contact with the surface of the relief structure 22. The first grid surface 8 is arranged on the protrusions 24 such that at least a portion of the first grid surface 8 is present on each protrusion 24. Position-dependent modulation occurs, which produces a surface that projects and / or retracts relative to the surface of the security element, for example, in the form of a three-dimensional visual object, for the observer. As shown, the first grid area 8 comprises a plurality of partial grid surfaces 4, 6, each having its own grid with its own color. Each grid cell of the partial grid surfaces 4, 6 can thus be modulated independently of the other grid cells in a position-dependent manner, resulting in the grid cells displaying different motion effects in different directions. Naturally, the grid cells can also display the same motion effect in different directions, or different motion effects in the same direction. For example, it is possible that when the security element 1 is tilted about its horizontal axis, the grid of the first partial grid surface 4 produces a first color change, and when the security element 1 is tilted about its vertical axis, the grid of the second partial grid surface 6 produces a second color change that is different from the first color change. The corresponding visual object or color effect depends on the degree of overlap between the second grid surface and the first grid surface, just like the static effect.

[0090] The second grid surface 10 is applied over the two partial grid surfaces 4, 6, but does not completely cover them. The interaction of the relief structure 22, the first grid surface 8, and the second grid surface 10 produces an optical effect that complements the aforementioned static effect; this is referred to as a dynamic effect. Because one of the two grid surfaces 8, 10 is luminescent and the other consists of a host pigment, only one of the first or second grid surfaces 8, 10 is visible when illuminated with light in the visible spectrum; for example, the second grid surface 10, which is located uppermost in the layer sequence and is applied, for example, as a dot grid. Under illumination with visible light, the second grid surface produces a 2D visual object. This visual object is supplemented by the underlying luminescent first grid surface 8 when additionally illuminated with ultraviolet radiation (which renders the first grid surface 8 visible) to form a 3D visual object. Because the first and second grid surfaces 8, 10 are printed on the relief structure 22, the effect of a 3D visual object is produced in the ultraviolet range, depending on the viewing angle and / or illumination angle. While motion effects can be generated in this manner, dynamic effects, such as changes in color, intensity, perspective, or brightness, also occur when the viewing and / or illumination angles are changed. Such dynamic effects cannot be easily reproduced by a copier and thus significantly increase the security against counterfeiting.

[0091] Figures 12 to 14 The layout of the relief structure 22 is shown in a top view. The protrusions 24 are arranged periodically and can be applied as hemispherical protrusions 24 arranged in a 0° / 90° grid ( Figure 12 ). However, the projections can also be structural elements with an elliptically twisted base surface, which are applied in the form of a 0° / 90° grid ( Figure 13 ), or can also be applied in a tilted / offset layout, e.g. Figure 14 The elevations 24 are shown in a honeycomb arrangement. The same arrangement can of course also be used for the recesses 26. Each arrangement can be provided only regionally on the security element 1.

[0092] Reference Signs List

[0093] 1. Anti-counterfeiting element

[0094] 2. Substrate body

[0095] 4 First local grid surface

[0096] 6 Second local grid surface

[0097] 8 First grid surface

[0098] 10 Second grid surface

[0099] 12 Visually Visible Information

[0100] 14 Details

[0101] 16 First Line Printing Pattern

[0102] 18 Second line printing pattern

[0103] Figure 20a-b

[0104] 22 Relief structure

[0105] 24 protrusion

[0106] 26 recess

[0107] B spacing

[0108] S Cutting Line

[0109] V front

Claims

1. A security element for protecting valuable documents, comprising: - a substrate body (2) having a front side (V) on which a first printed layer and a second printed layer are arranged, wherein The first printed layer is formed by a first grid surface (8), which is constructed from a first partial grid surface (4) and a second partial grid surface (6) of a different color, wherein: The first partial grid surface (4) and the second partial grid surface (6) are indistinguishable to the naked eye and together produce a mixed color, - the second printed layer is formed by the second grid surface (10), - the first grid surface (8) or the second grid surface (10) consists of a luminescent pigment which is recognizable when irradiated with ultraviolet radiation and is transparent only when irradiated with light in the visible spectrum, and the respective other grid surface (8, 10) consists of a bulk pigment, - in at least one angle relative to the front face, the second grid surface (10) appears to overlap only partially with the first grid surface (8), wherein a degree of overlap between the second grid surface (10) and the first partial grid surface (4) and the second partial grid surface (6) is respectively provided in the range of 0% to 100%, and - The security element has at least two areas in which the degree of overlap between the second grid surface (10) and the first partial grid surface (4) differs from the degree of overlap between the second grid surface (10) and the second partial grid surface (6), and in which the mixed colors in the two areas are modified differently when illuminated by a combination of ultraviolet radiation and light from the visible spectrum.

2. The anti-counterfeiting element according to claim 1, characterized in that: The luminescent pigment is a fluorescent pigment.

3. The anti-counterfeiting element according to claim 1 or 2, characterized in that: Due to the partial overlap of the first grid surface (8) and the second grid surface (10), a 2D visual object can be seen with the naked eye when irradiated with light in the visible wavelength range, which is supplemented to a 3D visual object when irradiated with ultraviolet radiation.

4. The security element according to claim 1, characterized in that A relief structure (22) is applied to the front side (V) of the substrate body (2) in at least one of the regions, the relief structure having a plurality of periodically arranged raised or recessed structural elements (24, 26).

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

6. Security element according to one of the preceding claims, characterized in that The structural element (24, 26) is, in at least one region, a convex or concave round structure, in particular a sunken hemispherical structure or a spherical cap with a circular or elliptical base area.

7. The security element according to any one of claims 4 to 6, characterized in that The grid surface (8, 10) is combined with the relief structure (22) in such a way that essentially at least a portion of the grid surface (8, 10) is present on each structural element (24, 26), so that for an observer, a surface that protrudes and / or is recessed relative to the surface of the security element (1) in the form of a three-dimensional visual object is generated by the position-dependent modulation of the grid surface (8, 10).

8. Security element according to one of the preceding claims, characterized in that The first grid surface (8) and / or the second grid surface (10) is a dot grid.

9. Security element according to one of the preceding claims, characterized in that The first grid plane (8) is a line grid having a plurality of non-intersecting lines.

10. The security element according to claim 1, characterized in that The first partial grid plane (4) and the second partial grid plane (6) are two line grids, wherein each line grid is modulated independently of the corresponding other line grid in a position-dependent manner, so that the line grids produce different movement effects or the same movement effect in the same or different directions. 11 . A value document comprising an optically variable security element according to claim 1 .

12. A method for producing a security element for protecting valuable documents, wherein - providing a substrate body (2) comprising a front face (V), and - applying a first and a second printed layer on the front side (V), wherein The first printed layer is formed by a first grid surface (8), which is constructed from a first partial grid surface (4) and a second partial grid surface (6) of a different color, wherein: The first partial grid surface (4) and the second partial grid surface (6) are indistinguishable to the naked eye and together produce a mixed color, - the second printed layer is formed by the second grid surface (10), - the first grid surface (8) or the second grid surface (10) consists of a luminescent pigment which is recognizable when irradiated with ultraviolet radiation and is transparent only when irradiated with light in the visible spectrum, and the respective other grid surface (8, 10) consists of a bulk pigment, - in at least one angle relative to the front face, the second grid surface (10) only partially overlaps the first grid surface (8), wherein a degree of overlap between the second grid surface (10) and the first partial grid surface (4) and the second partial grid surface (6) is respectively provided in the range of 0% to 100%, At least two areas are provided on the security element, in which the degree of overlap between the second grid surface (10) and the first partial grid surface (4) is different from the degree of overlap between the second grid surface (10) and the second partial grid surface (4). the degree of overlap between the surfaces (6), and when illuminated by a combination of ultraviolet radiation and light of the visible spectrum, The mixed colors in these two areas change to different degrees.

Images