Security element and method of manufacturing the same

Abstract

The invention relates to a security element for value documents and the like, said security element having a substrate (1, 21) which is coated with a heat-seal adhesive (2, 22), said heat-seal adhesive being tack-free at room temperature and suitable for painting the security element on a value document substrate, wherein the heat-seal adhesive (2, 22) comprises a radiation-crosslinkable component and a reaction diluent.

Description

Technical Field

[0001] This invention relates to a security element for valuable documents, etc., coated with a heat-sealing adhesive that is non-stick at room temperature and suitable for coating the security element onto a substrate of the valuable document. Furthermore, this invention relates to a method for manufacturing such a security element. Additionally, this invention relates to a valuable document having such a security element and a method for manufacturing a valuable document incorporating the security element. Background Technology

[0002] Valuable documents, especially banknotes, are often equipped with security elements to protect their security. These security elements enable verification of the authenticity of the valuable document and serve as a protective measure against unauthorized copying. Valuable documents in the sense of this invention can specifically include banknotes, stocks, certificates, credit cards, bonds, licenses, vouchers, checks, and large-denomination tickets, but can also be other forms of paper at risk of counterfeiting, such as passports and other identification documents, as well as product security elements such as labels, seals, and packaging. Hereinafter, the term "valuable document" also includes the uncirculated, early stage of a valuable document, particularly secure paper.

[0003] It is known to use security elements in the form of security threads, security belts, or patches or tags to protect valuable documents, such as banknotes.

[0004] Today, in almost all security and banknote papers, a thread coated with heat-sealing adhesive, particularly heat-sealing varnish, is inserted as a security thread into the paper on the papermaking machine. Here, the heat-sealing varnish is used to secure the thread to the paper in an improved manner. Furthermore, in banknote paper, heat-sealing varnish is used to apply holograms and holographic strips.

[0005] When applying a safety element using a heat-sealing varnish, at least one of the substrates to be bonded is coated with a solvent-based crosslinking solution, aqueous solution, or dispersion. After physical drying by heating, a non-stick surface exists at room temperature. Under the influence of temperature, the sealing material melts and acts as an adhesive.

[0006] EP 1 776 240 B1 discloses the use of a non-stick heat-sealing adhesive at room temperature for coating safety elements onto a valuable document substrate by a heat-sealing process under increased pressure and temperature. Furthermore, the heat-sealing adhesive contains components capable of cross-linking via high-energy radiation. The presence of these cross-linking components within the heat-sealing adhesive allows for radiation-induced cross-linking when the safety element is coated onto the valuable document substrate. This results in a system with a high melting point, extending to infusible, thereby achieving high stability, particularly outstanding hot water resistance. Hot water resistance can be determined, for example, by means of a washing machine. Suitable hot water tests are particularly conducted at 100°C for 30 minutes or 60°C for 1.5 hours.

[0007] Heat-sealing adhesives known from EP 1 776 240 B1 can be applied to the safety element to which they are to be applied, in the form of a solution, emulsion, or dispersion. Coatings applied in this form that are capable of radiation crosslinking melt at low temperatures and penetrate the substrate of the valuable document, making processing easier. Safety elements coated in this way, but not yet crosslinked, can ideally be stored for extended periods without a change in melting point. Therefore, films, for example, equipped with a non-stick coating at room temperature, can be rolled up and stored for longer periods without a change in melting point.

[0008] When applying a heat-sealable adhesive known in EP 1 776 240 B1 to a safety element in the form of a solution, emulsion, or dispersion, physical drying is required, for example, by slightly increasing the temperature to 80°C. In this way, any solvents and / or water present are removed from the radiation-curable dispersion, solution, or emulsion. Physical drying may require intense heat application in some cases, leading to unintended curing in the case of highly reactive adhesive systems. In the case of reactive inert adhesive systems, insufficient heat application time during the application of the safety element with the heat-sealable adhesive to the valuable document substrate will result in inadequate curing, thus causing a lack of adhesion between the safety element and the valuable document substrate. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a safety element that overcomes the shortcomings of the prior art.

[0010] The aforementioned technical problem is solved by the combination of features defined in the independent claim. Extended embodiments of the invention are the subject of the dependent claims.

[0011] Summary of the present invention

[0012] 1. (First aspect of the invention) A security element for valuable documents, the security element having a substrate (1, 21) coated with a heat-sealing adhesive (2, 22), the heat-sealing adhesive being non-stick at room temperature and suitable for coating the security element onto the valuable document substrate, wherein the heat-sealing adhesive (2, 22) comprises a component capable of radiation crosslinking and a reactive diluent.

[0013] 2. (Preferred Design) The safety element according to item 1, wherein the reactive diluent is a low molecular weight compound with a molecular molar mass M < 1000 g / mol, preferably selected from TMP(EO). x TA and DPHA.

[0014] 3. (Preferred Design) The safety element according to item 1 or 2, wherein the heat-sealing adhesive (2, 22) additionally comprises a plasticizer, which preferably has a melting point in the range of 50°C to 120°C.

[0015] 4. (Preferred Design) The safety element according to item 3, wherein the plasticizer is selected from the group consisting of: triphenylphosphonate, pentaerythritol tetrabenzoate, cyclohexyl and dimethyl gold benzoate, sucrose benzoate, and mixtures of two or more of the aforementioned elements.

[0016] 5. (Preferred design) The safety element according to item 3 or 4, wherein the plasticizer is contained in the heat-sealing adhesive (2, 22) in a weight ratio of 1% to 30%, preferably 2% to 10%, in solids.

[0017] 6. (Preferred Design) The safety element according to any one of items 1 to 5, wherein a non-stick heat-sealing adhesive (2, 22) suitable for coating the safety element onto a valuable document substrate is present at least physically dry.

[0018] 7. (Preferred Design) A security element according to any one of items 1 to 6, wherein the substrate (1, 21) is a planar substrate (1, 21) having two opposing main surfaces, wherein at least one main surface of the substrate (1, 21) is at least partially equipped with a heat-sealing adhesive (2, 22) that is non-stick at room temperature and suitable for coating the security element onto a valuable document substrate.

[0019] 8. (Preferred Design) The safety element according to any one of items 1 to 7, wherein a non-stick heat-sealing adhesive (2, 22) suitable for coating the safety element onto a valuable document substrate can be obtained by means of a coating solution, emulsion or dispersion.

[0020] 9. (Preferred Design) The safety element according to item 8, wherein a non-stick heat-sealing adhesive (2, 22) suitable for coating the safety element onto a valuable document substrate can be obtained by means of applying an aqueous dispersion.

[0021] 10. (Preferred Design) The security element according to item 8, wherein a non-stick heat-sealing adhesive (2, 22) suitable for coating the security element onto a valuable document substrate can be obtained by applying an organic solvent-based solution, wherein the organic solvent preferably contains at least butyl acetate, propyl acetate or ethyl acetate, more preferably in a weight ratio ranging from 30% to 90%, particularly preferably from 40% to 75%.

[0022] 11. (Preferred Design) The safety element according to item 10, wherein the heat-sealing adhesive (2, 22) additionally has a prepolymer that is non-sticky after physical drying at room temperature, contains an average of at least two reactive groups, and has a molecular weight of at least 600 g / mol, preferably having a molecular weight of at least 600 g / mol in a weight ratio ranging from 8% to 65%.

[0023] 12. (Preferred Design) The safety element according to item 9, wherein the dispersion is selected from the group consisting of: aliphatic polyurethane dispersion, aromatic polyurethane dispersion, acrylate, anionic acrylate modified polyurethane dispersion, polyurethane-polyether acrylate, and mixtures of two or more of the aforementioned elements.

[0024] 13. (Preferred Design) The safety element according to any one of items 1 to 12, wherein the heat-sealing adhesive (2, 22) comprises a cationic radiation-cured resin.

[0025] 14. (Preferred Design) The safety element according to any one of items 1 to 13, wherein the radiation-crosslinkable component is crosslinkable by ultraviolet radiation or electron radiation.

[0026] 15. (Preferred Design) The safety element according to any one of items 1 to 14, wherein the heat-sealing adhesive (2, 22) comprises a photoinitiator.

[0027] 16. (Preferred Design) The safety element according to any one of items 1 to 15, wherein the substrate (1, 21) is a transparent plastic film, particularly a polyethylene terephthalate (PET) film.

[0028] 17. (Second aspect of the invention) A valuable document, particularly a banknote, comprising a security element according to any one of items 1 to 16.

[0029] 18. (Third aspect of the invention) A method for manufacturing a security element according to any one of items 1 to 16, comprising the step of applying a heat-sealing adhesive (2, 22) to a substrate (1, 21), the heat-sealing adhesive being non-stick at room temperature and suitable for applying the security element to a valuable document substrate, wherein the heat-sealing adhesive (2, 22) comprises a component capable of radiation crosslinking and a reactive diluent.

[0030] 19. (Fourth aspect of the invention) A method for manufacturing a valuable document according to item 17, comprising the step of equipping a valuable document substrate, particularly a paper substrate, with a security element according to any one of items 1 to 16.

[0031] 20. (Preferred design) According to the method of item 19, wherein the safety element is coated onto the valuable document substrate (3) under increased pressure and increased temperature, and then the non-stick heat-sealing adhesive (2, 22) is at least pre-crosslinked by means of radiation.

[0032] Detailed description of the present invention

[0033] Instead of stating "heat sealant that is not sticky at room temperature", this document also uses the terms "heat sealant that is not sticky at room temperature" or "heat sealant that is substantially non-sticky at room temperature".

[0034] The term "room temperature" here should be understood as 23°C.

[0035] Instead of the term "heat sealant," the term "heat sealant varnish" is also used in this document.

[0036] The safety element according to the invention is equipped with a non-stick heat-sealing adhesive at room temperature. Furthermore, the heat-sealing adhesive contains components capable of radiation crosslinking and a reactive diluent. The invention is based on a heat-sealing adhesive known from EP 1 776240B1. The invention is based on the understanding that when a reactive diluent is added to the heat-sealing adhesive composition, the sealing temperature can be reduced while improving the wetting properties of the melt. Particularly advantageous effects can be achieved, especially in the case of aqueous formulations, when a reactive diluent is present in addition to the actual dispersed polyurethane acrylate component. Without limitation, it can be assumed that the reactive diluent migrates into the dispersion particles in the first step and is found in a smaller amount in the aqueous phase. After physical drying, it acts as a coagulant, thus promoting film formation. Depending on the formulation, complete non-stickiness, i.e., non-stick properties, can be guaranteed. An example of a dispersion that already contains a reactive diluent in a supplied form is Albertingk Lux481. Here, it contains less than 10% DPHA and 3% to 5% TMP(EO). x TA. The abbreviation "TMP(EO)TA" represents trimethylolpropane (ethoxy) triacrylate, and the abbreviation DPHA represents pentaerythritol hexaacrylate. Even TMP(EO) x Even with a TA content below 15%, exceptionally good heat-sealable dispersions can be obtained. (In formula TMP(EO)) x In TA, x is preferably selected from the range of 1 to 9, more preferably from the range of 3 to 9, wherein x is particularly preferably 3.

[0037] The heat-sealing paint formulation according to the invention is preferably an aqueous dispersion, particularly an aqueous dispersion containing 5% to 25%, preferably 9% to 16%, of a low molecular weight compound (M < 1000 g / mol) from the beginning or after addition.

[0038] The advantages of reactive diluents are that they can generally lower the sealing temperature and improve the wetting properties of the melt. One disadvantage is a reduction in bulk strength. The use of multifunctional reactive diluents can lead to high molecular weight systems after crosslinking, which may no longer be fusible. It is possible to utilize the property that, while not causing any damage, it is not necessary to deliberately pursue a melting point so high that it is no longer possible to use melting to non-destructively separate safety elements.

[0039] Suitablely, triphenyl phosphate, pentaerythritol tetrabenzoate, cyclohexanediol dibenzoate, and / or sucrose benzoate are added as soluble components in the heat-sealing varnish formulation according to the invention. These are plasticizers preferably having a melting point in the range of 50°C to 120°C. The plasticizer is preferably added (in solids) at a weight ratio of 1% to 30%, more preferably 2% to 10%. These substances, being solid at room temperature, are less important in terms of blocking behavior than liquid substances. Due to their solubility in reactive diluents, they can also be incorporated into the overall formulation.

[0040] Alternatively, if instead of starting with an aqueous dispersion, one starts with a UV system, for example, which can be obtained as a dual-curing system, particularly a solvent-based formulation, wherein butyl acetate is preferably used as a solvent, the aforementioned plasticizer can also be directly dissolved, wherein it exists in a solid state after physical drying and has little effect on clogging.

[0041] The heat-sealing varnish formulation according to the invention contains at least one solvent, which is present in a weight ratio preferably in the range of 30% to 90%, particularly preferably in the range of 40% to 75%, wherein the solvent is preferably selected from the group consisting of butyl acetate, propyl acetate, ethyl acetate, and mixtures of two or more of the aforementioned substances.

[0042] Preferably, a prepolymer is added, which is non-sticky after physical drying at room temperature, contains an average of at least two reactive groups, and has a molecular weight of at least 600 g / mol. In heat-sealing varnish formulations, the prepolymer is preferably included in a weight percentage ranging from 8% to 65%.

[0043] To improve reactivity, amino synergists can be added to the heat-sealing paint formulation.

[0044] In electron beam curing, a photoinitiator is not required. Particularly in aqueous formulations, photoinitiators TPO-L, Omnirad 500, and Omnirad 819DW are advantageous. Preferred weight percentages are 1% to 8% of the respective solids. Additionally, particularly when using photoinitiators from the BAPO series, such as photosensitizers from the ITX series for higher reactivity, may be advantageous. The abbreviation "BAPO" stands for phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and the abbreviation "ITX" stands for isopropylthionone.

[0045] In some cases, the heat-sealing varnish does not adhere directly to the safety element to be bonded. In these cases, it is appropriate to modify the safety element, for example, by using a pressure-pretreated film or by pretreating the safety element using known pretreatment methods, such as plasma or corona pretreatment, or by applying a primer to the safety element.

[0046] When selecting a suitable primer, it has been demonstrated that the UV crosslinking potential of heat-sealing varnishes, particularly those with reactive primer systems, can be fully utilized. This is exemplified, for instance, by multi-layered 2K-PU systems. In this case, it is particularly advantageous that at least one layer comprises an aliphatic isocyanate.

[0047] The reactive diluents mentioned in the section on aqueous systems and the soluble low molecular weight components or plasticizers specifically mentioned in the section on solvent systems are capable of migration. Consequently, they can distribute throughout the entire structure during corresponding storage, resulting in a loss of adhesion to the substrate and a decrease in sealing ability.

[0048] In the PVC film industry, it is common to use barrier layers to prevent plasticizer migration. In this field, solvent-based coatings with relatively high molecular weight acrylates are used. Typical materials used for this are available from the brands Decalan and Elvacite.

[0049] According to a specific modification scheme, radiation-crosslinkable heat sealant can be applied in multiple layers, wherein the first layer can be pre-crosslinked. If the first layer of heat sealant on the primer undergoes radiation crosslinking after physical drying, the first layer itself can also serve as a barrier layer against migratable components of subsequent heat sealant layers. Furthermore, it prevents potentially used spacers, such as wax, from settling into heat sealant or primer deposits.

[0050] Crosslinking of heat-sealing varnish can be carried out directly after sealing, preferably using the elevated temperature from the sealing process, because at this point the raw material still has no opportunity for crystallization, and the mobility of reactive groups is therefore better, resulting in better crosslinking. This is particularly advantageous when using a medium-pressure mercury radiator that outputs a large amount of heat for crosslinking, and when using an LED radiator with a small heat output. If the radiator's heating is insufficient, a heated roller is suitable to allow temperature control before and during crosslinking.

[0051] If UV crosslinking cannot be achieved in a spray coating machine, it can be achieved in a separate working process. A working process that inherently achieves UV crosslinking is preferred. A typical example is crosslinking on a screen printer, which, in the case of a suitable assembly, can irradiate the substrate from both sides. If the safety element to be bonded is a patch, an opaque layer that makes crosslinking difficult is typically applied only to a portion of the safety element. The edge areas are usually transparent. This allows the edge areas to be crosslinked very easily by exposure from above, while the area beneath the opaque coating is preferably exposed from below through the substrate. The opaque coating is often metallized, which reflects the corresponding light, thus allowing for better utilization of light radiating through the substrate.

[0052] Uncrosslinked heat-sealable varnishes have the property of softening under temperature. In the case of gravure printing, there are elevated temperatures and high pressures. Therefore, strong embossing can be achieved when using a large layer thickness of heat-sealable varnish. If crosslinking is subsequently performed, the embossing can be permanently fixed. This is particularly advantageous when the substrate can undergo plastic deformation in gravure printing.

[0053] In addition to the advantage of high durability, radiation-crosslinkable heat sealants also have the following disadvantages: so-called groove formation, i.e. poor smoothness, is particularly prominent after crosslinking, because it is a system that shrinks during curing and is crosslinked after curing, no longer able to flow, and the stress can hardly be relieved later.

[0054] This can be achieved, on the one hand, by adding the plasticizers described above that allow for limited deformation even after crosslinking, and on the other hand, by adding so-called chain transfer agents. This can be achieved, for example, by using thiols. During the crosslinking reaction, the chain transfer agent shifts the gel point to a later time point, thereby establishing less stress.

[0055] The top layer of the safety element in contact with the heat-sealing varnish can be, for example, a common untreated polyester film, but it can also be a co-extruded film with a layer that has low adhesion to the heat-sealing varnish. Since a double-layer film can also serve as a carrier, for example in the case of patch panels, any film with low adhesion to adhesives can be applied on top. Siliconized polyester films can also be used. A layer that is less prone to clogging can also be additionally coated onto a normal polyester film. This layer can also have larger spacers.

[0056] In UV curing, photoinitiators are defined as small molecules that can have a fixed melting point. If they are within a suitable temperature range, they can promote melting behavior.

[0057] It is common to use UV absorbers or stabilizers in aqueous dispersions for outdoor applications, while it is common to use stabilizers alone in hot melt adhesives to achieve longer temperature stability in the melt during extrusion or coating.

[0058] If necessary, benzotriazole-based UV absorbers, such as Tinuvin 9945DW, and / or triazine-based absorbers, such as Tinuvin 477DW, can be added as additives. The addition should be in small amounts to avoid affecting bulk strength. For the absorber to be effective, it should be compatible with the film of the aqueous dispersion. Ideally, the absorber should be liquid at room temperature or have a low melting point. Therefore, it is expected that adding the absorber will improve weather resistance and, in addition, seal performance. Crosslinking should not be affected in the long-wave UV range, i.e., at the boundary with the visible light range, typically at LED 395nm.

[0059] In the case of security strips to be coated on a valuable document substrate, especially a paper substrate, or transfer elements to be peeled off from a temporary carrier film, depending on the transparency of different elements, exposure can be performed from the side of the security strip after coating, through the carrier film, or after removing the carrier film, or exposure can be performed from the side of the valuable document substrate.

[0060] In the case of a security strip with a permanent carrier film to be coated on a valuable document substrate, depending on the transparency of different elements, exposure can be performed from the side of the security strip through the carrier film after coating, or exposure can be performed from the side of the valuable document substrate.

[0061] This presents limitations when applying patches or labels to a valuable document substrate. To save on carrier film and produce low-cost patch elements, the patch elements are often positioned much closer to the carrier film than they would be placed on the valuable document substrate later. Therefore, exposure can be performed after the carrier film has been removed, or exposure can be performed using a mask, for example, which can be rotated to expose only the already applied patch, not the patch element still on the carrier film, or, in the case of LED radiators, by controlling the radiator to radiate only at the correct time for patch exposure, and then effectively disconnecting it again. This aspect of patch exposure through rapid switching of the radiator is advantageous because a major problem with LED radiators is temperature. At high temperatures, they lose performance and lifespan. If the patch area to be irradiated is only about 1 / 3 of the total area, heat generation is thus reduced by 2 / 3, allowing the radiator to operate at power levels higher than it would during continuous operation in some cases, and at least saving on cooling power.

[0062] When necessary and appropriate, it is suitable to print a primer under the security element to be coated on the substrate of the valuable document. The primer can be applied to a substrate similar to the heat sealant to be used. When printing a primer that first undergoes physical drying, better adhesion is generally achieved than in the case of conventional heat sealing. If the primer and heat sealant have similar substrates, they bond optimally through heat sealing and can be indivisibly polymerized together by subsequent irradiation. In some cases, there is a difficulty where the primer also melts during the sealing process, leading to contamination of the calender or rollers; therefore, it is appropriate to achieve primer printing only on a narrower area than the security element to be sealed during testing.

[0063] The heat-sealing varnish according to the invention advantageously reduces the required sealing temperature. If a system exists, for example, with an additional primer or an additional ink-receiving layer, but which is not optimized for low melting points, printing can also be performed over a larger area, although no deposits will form on the rollers during the sealing process. The processing window can be expanded by using a non-stick coating on the corresponding rollers.

[0064] Therefore, it is conceivable to use a system with different sealing properties as a pre-coating in at least a portion of the substrate, just as it would be used as a heat-sealing varnish.

[0065] The coating according to the invention can be applied in the form of a solution, emulsion, or dispersion. The radiation-crosslinkable coating applied in this form melts at low temperatures and penetrates the substrate, making it easy to process. Therefore, the safety element according to the invention is equipped with a system that has a low melting point but is essentially non-sticky at room temperature. The presence of radiation-crosslinkable components in the coating allows for crosslinking by irradiation after coating application. Here, a system with a high melting point, even to the point of being unmeltable, is formed, thereby achieving high stability, and particularly sufficient hot water resistance, for example, in washing machine tests. Suitable hot water tests are particularly conducted at 100°C / 30 minutes or 60°C / 1.5 hours.

[0066] Crosslinking, such as through pre-printing treatment, improves the adhesion of the film to the substrate and enhances the internal strength of the coating. The temperature of the coating immediately before, during, and immediately after curing is an important parameter for determining the achievable degree of crosslinking. Higher temperatures allow for a greater degree of crosslinking because of the increased mobility of the reactive groups.

[0067] Common UV paints are liquid before crosslinking and generate a large amount of heat of reaction because many reactive groups exist in a compact space. In contrast, the radiation-curable, and particularly UV-curable, coatings according to the invention consist of molecules with relatively high molecular weights and are solid at room temperature. Due to the smaller number of reactive groups per volume unit / mass unit, less heat of reaction is generated. Therefore, external heat input plays a greater role in crosslinking. Consequently, the mechanical properties of the coating can be controlled by the curing temperature.

[0068] Safety elements coated in this way, which are not yet cross-linked, can be stored for extended periods without changing their melting point. Therefore, films, for example, equipped with a coating that is essentially non-sticky at room temperature, can be rolled up and stored for longer periods without changing their melting point.

[0069] According to an advantageous extension of the invention, the coating is substantially non-sticky at room temperature, at least physically dry. This is achieved by simply raising the temperature to, for example, 80°C, causing any solvents and / or water present in the radiation-curable dispersion, solution, or emulsion to be removed. This physical drying results in the coating being substantially non-sticky at room temperature.

[0070] Within the scope of this specification, the term "substantially non-sticky" also means substantially non-sticky in the sense of a smooth, substantially non-sticky surface. This can be checked by the following test: place approximately 100cm... 2Coated foil sheets are stacked, subjected to a 10 kg load, and stored at 40°C for 72 hours. If the foil sheets can then be easily separated from each other without damaging the coating, the coating can be considered to be essentially non-sticky.

[0071] The substrate of the safety element according to the invention can be in virtually any form. Thus, the safety element according to the invention can, for example, be made of fibers equipped with a coating that is substantially non-sticky at room temperature. However, an advantageous variation according to the invention is a planar substrate having two opposing main surfaces. Preferably, only one main surface of the substrate is provided with a coating that is substantially non-sticky at room temperature.

[0072] In principle, it is sufficient to have a coating that is substantially non-sticky at room temperature partially applied to the main surface of the substrate. However, for optimal embedding of security elements in security paper or valuable documents, it is suitable to have a coating that is substantially non-sticky at room temperature applied to the entire main surface of the substrate. Then, depending on the size of the security element, it may also be sufficient to have a coating that is substantially non-sticky at room temperature applied to only a portion of the substrate.

[0073] When the security element is fully embedded in the security paper, it proves particularly suitable that both main surfaces of the substrate are coated with a coating that is essentially non-sticky at room temperature. This variation is especially useful when the security element is inserted into the security paper or valuable document along a window security line. Here, the main surfaces can not only have the same type of coating, but also different coatings.

[0074] According to another preferred embodiment of the invention, the security element has a thickness of 1 μm to 100 μm, preferably 2 μm to 50 μm. This thickness is suitable for security elements that can be easily handled when equipping valuable documents and security paper.

[0075] Preferably, the substrate of the security element according to the invention is designed to be multilayered and / or flexible. The advantages associated with multilayering of the security element will be described in further detail below. Flexibility of the security element is often desirable because valuable documents equipped with security elements, such as banknotes or deeds, are typically flexible.

[0076] The coating, which is substantially non-sticky at room temperature, is preferably applied to the substrate as a solution, emulsion, or dispersion, followed by physical drying. Aqueous dispersions are particularly preferred.

[0077] This aqueous dispersion can be applied directly to a substrate, correspondingly pre-printed or primer-treated film (e.g., Hostaphan RNK 2600, Mitsubishi polyester film), or applied to an additional layer in the presence of the substrate and a coating that is substantially non-tacky at room temperature. The resulting film can then be rolled up, transported, and stored. By printing and applying temperature (approximately 100°C to 160°C), the film can be applied to paper, another film, or a polymer.

[0078] According to another preferred embodiment of the invention, the dispersion is selected from the group consisting of: aliphatic polyurethane dispersions, aromatic polyurethane dispersions, acrylates, anionic acrylate-modified polyurethane dispersions, polyurethane-polyether acrylates, and mixtures thereof.

[0079] Acrylic polyurethane dispersions are particularly suitable. Examples of these acrylic polyurethane dispersions include DW7770, DW7773, DW7825, DW7772, DW7849 (UCB, a surface treatment specialist company), and Actilane 340 butoxyacetoacetic acid epoxy acrylate (Akzo).

[0080] Other radiation-curable dispersions include NeoRad R-440 (NeoResins), NeoRad R-441 (NeoResins), NeoRad R-445 (NeoResins), Laromer LR 8949 (BASF), Laromer LR 8983 (BASF), Laromer LR 9005 (BASF), LUX 101UV dispersion (Alberdingk), LUX 241UV dispersion (Alberdingk), LUX 308UV dispersion (Alberdingk), LUX 352UV dispersion (Alberdingk), LUX 370UV dispersion (Alberdingk), LUX 390UV dispersion (Alberdingk), LUX 399UV dispersion (Alberdingk), LUX 331UV-Dispersion (Alberdingk), LUX 338UV dispersion (Alberdingk), and Halwedrol UV. 95 / 92W(Hüttenes-Albertus), Halwedrol UV 14 / 40W(Hüttenes-Albertus), Halwedrol UV-TN 6711 / 40W(Hüttenes-Albertus), Halwedrol UV 65 / 40W(Hüttenes-Albertus), Halwedrol UV-TN 7561-3 / 40W (Hüttenes-Albertus), Halwedrol UV-TN 7157 / 40W (Hüttenes-Albertus) and Bayhydrol UV VP LS2280 (Bayer).

[0081] The dispersions mentioned include anionic and nonionic dispersions. Most of these dispersions are aliphatic polyurethane dispersions (e.g., aliphatic polyester polyurethanes), but they can also be aromatic polyurethane dispersions and copolymers (e.g., dispersions based on aliphatic polyurethane and acrylate copolymers), acrylates (acrylate copolymers), and anionic acrylate-modified UV-curable polyurethane dispersions or polyurethane polyether acrylates.

[0082] The preferred solids content of the dispersion is between 30% and 60% by weight, and more preferably between 35% and 50% by weight. However, the solids content can be adjusted by dilution as needed.

[0083] Commercially available dispersions typically have a solids content between 38% and 51% by weight. These dispersions are preferred within the scope of this invention due to their easy availability.

[0084] The radiation-crosslinkable components in the coating are preferably crosslinked by ultraviolet radiation or by electron radiation. Iron-doped radiators are particularly suitable in terms of spectral range. Alternatively, undoped mercury radiators or gallium-doped radiators can be used. However, mercury radiators have a slightly inferior spectral range when curing through the element to which they are applied, while gallium radiators produce poorer surface curing.

[0085] According to a preferred embodiment, the coating, which is substantially non-sticky at room temperature, contains a photoinitiator. With the aid of a photoinitiator, crosslinking can be initiated and controlled in a particularly simple manner. Preferred examples of such photoinitiators are Darocur 4265 (Ciba), Darocur 1173 (Ciba), Irgacure 500 (Ciba), Irgacure 184 (Ciba), Esacure KIP 100F (Lamberti), and Irgacure 2959 (Ciba).

[0086] Particularly preferred photoinitiators are water-soluble photoinitiators, water-dispersible photoinitiators, or photoinitiators soluble in water using a water-compatible solvent. Irgacure 2959 (Ciba) is mentioned as an example of a water-soluble photoinitiator. Water-dispersible (or pre-dispersed) photoinitiators include, for example, Irgacure 819DW (Ciba). Lucirin TPO (BASF) is exemplarily mentioned as a photoinitiator soluble in other water-compatible solvents.

[0087] In the case of water-miscible solvents, an increase in the VOC content may have to be accepted during processing because a certain proportion of solvent should be present in the finished dispersion to prevent the precipitation of the photoinitiator used. If this is not possible, rheology modifiers (anti-settling additives) must be used. This prevents the dispersion from having to be re-stirred before each use.

[0088] According to another preferred embodiment of the invention, a substantially non-sticky coating exists as a cationic radiation-cured resin at room temperature. Epoxy-modified vinyl copolymers are particularly suitable. UCAR VERR-40 (The Dow Chemical Company) is mentioned as an example of such an epoxy-modified vinyl copolymer.

[0089] The cross-linking components contained in the non-stick coating are preferably cross-linked by short-wave radiation (e.g., ultraviolet radiation or short-wave visible light radiation) or by electron radiation. It is particularly preferred that a standard UV radiator (doped or undoped) or a UV light-emitting diode be used as the radiation source.

[0090] Non-sticky coatings comprising cationic radiation-curing resins preferably contain a photoinitiator suitable for cationic radiation curing. This allows crosslinking to begin in a particularly simple manner. Alternatively, the cationic radiation-curing resin can be combined with other resins. Furthermore, coatings comprising cationic curing resins can also be crosslinked simply by heat. In this case, the use of a photoinitiator is excluded.

[0091] The preferred safety element, in addition to a coating that is substantially non-sticky at room temperature, includes at least one additional layer, which is at least pre-crosslinked by radiation. This layer is preferably coated between the substrate and the coating that is substantially non-sticky at room temperature. This layer can be crosslinked by radiation, thereby eliminating the risk of subsequent melting associated with loss of adhesion due to ennetzene, while still providing good overprintability. To manufacture the safety element according to the invention, the coating according to the invention, in particular a dispersion capable of UV curing, is applied over the additional, at least pre-crosslinked by radiation layer. This additional layer is then physically dried only to achieve non-stickiness while obtaining fusibility.

[0092] In addition, to enhance anti-counterfeiting security, the security element preferably includes at least one security feature that can be inspected visually and / or by machine.

[0093] According to a preferred design, security features that can be inspected visually and / or by machine may include optically variable effects, particularly diffraction structures, holograms, color tilting effects, or other interference effects. According to another preferred design, the security element is provided with a printed image, particularly with positive or negative patterns or characters as security features. As additional security features, the security element may also contain fluorescent, phosphorescent, and / or magnetic materials, which may be present in the substrate. Clearly, combinations of these security features are also possible.

[0094] Transparent plastic films are preferably used as the substrate for the safety element according to the invention. These films have the advantage that they can be irradiated by UV light passing through them. Therefore, for example, PET films are transparent from the visible light range in the UV range up to approximately 310 nm. Thus, commercially available UV radiators can be used for irradiation. Alternatively, the substrate may (if necessary, additionally) include a paper layer.

[0095] The particularly preferred safety element includes, in addition to the substrate and the coating which is substantially non-adhesive at room temperature, at least one additional layer, which is a reflective layer at least by area.

[0096] The following embodiments are also preferred, in which the safety element, in addition to the substrate and the coating which is substantially non-adhesive at room temperature, includes at least one additional layer, wherein the layer is embossed with a diffraction structure in an embossed manner. The diffraction structure preferably has a reflective layer at least in certain areas.

[0097] Alternatively, coatings that are essentially non-sticky at room temperature can be used as embossing paints. Common thermoplastic embossing paints either require high temperature and pressure during the embossing process or become cloudy or dull when the hologram is applied to the substrate because the embossed structure softens and wrinkles under the application conditions. Common, usually liquid, UV paint systems can only cure the embossed layer continuously, making it impossible or only conditionally possible to achieve sharp-edged peel-off when manufacturing patches.

[0098] If a safety element according to the invention, having a coating on a substrate, particularly a plastic film, that is substantially non-sticky at room temperature, is used, with the plastic film provided with an insulating layer (e.g., wax) if necessary, a low-melting-point thermoplastic embossing varnish is initially present. Patterns, particularly diffraction structures in embossed form, can be embossed in this varnish layer. During or after this process (or after winding, in the block-free adjustment of the dispersion and the corresponding glass dots), the dispersion is cured by mask exposure. That is, the area to be transferred later (the patch) is exposed, but the intermediate area is not. Therefore, the intermediate area remains soft and meltable, allowing for later melting with sharp edges, while the exposed area remains hard and retains its printed structure during transfer. In other words, the coating according to the invention, which is substantially non-sticky at room temperature, can crosslink during the printing process, and is therefore dimensionally stable and glossy under high pressure and high temperature.

[0099] Therefore, according to a preferred embodiment of the invention, the safety element, in addition to the substrate, includes a coating that is substantially non-sticky at room temperature, wherein a diffraction structure in the form of an embossed design is imprinted in the coating. Here, the coating, which is substantially non-sticky at room temperature, is advantageously present in a form that is cured in zones. Preferably, the diffraction structure is provided only in the cured zones of the coating, which is substantially non-sticky at room temperature.

[0100] The regions of the hardened layer with diffraction structures are advantageously equipped with reflective layers at least according to the region. Here, the reflective layers are preferably in the form of positive or negative patterns.

[0101] The following safety elements are referred to as transfer elements: These safety elements are pre-treated on separate layers, such as plastic film, in the reverse order of their later appearance on the safety paper, and then transferred to the safety paper in the desired contour shape using an adhesive layer or varnish layer. Here, the separate layer can be removed from the layer structure of the safety element after transfer. To facilitate peeling off the separate layer after the safety element is transferred, an isolation layer can be provided between the layer and the portion of the safety element to be peeled off.

[0102] Therefore, according to another preferred embodiment, the safety element includes at least one additional layer in addition to the substrate and the coating, which is substantially non-adhesive at room temperature, wherein the layer is an insulating layer. Particularly preferred is that the insulating layer is disposed between the substrate and the coating, which is substantially non-adhesive at room temperature.

[0103] According to another preferred embodiment, the safety element has a substantially non-sticky coating at room temperature, which is printed with printing ink and cross-linked by means of radiation. Specifically, the individual coatings of the paper should be anti-fouling, provide good ink adhesion, and not become separation points between the paper and the ink during durability testing. By applying a defined temperature at which the cross-linking reaction of the substantially non-sticky coating at room temperature is carried out, the degree of cross-linking can be controlled, thus allowing for the adjustment of the balance between ink adhesion and anti-fouling properties.

[0104] Alternatively, printing can be performed either after or before the non-sticky coating has fully cross-linked. If printing is performed before cross-linking, the coating, which is essentially non-sticky at room temperature, is printed on, where the printing ink has a partial dissolving effect on the coating. The printing ink bonds with the coating, thereby further improving adhesion. To avoid problems caused by the coating being rubbed off by the paper or being excessively absorbed during the application process, rheology modifiers (especially thickeners) can be used.

[0105] In a similarly advantageous variation, the non-sticky coating is pre-crosslinked before printing with ink. However, here, full crosslinking is performed only after printing.

[0106] In the preferred design, the safety element is formed in the form of a seat belt, safety strip, patch, or other planar safety element.

[0107] The substrate of the safety element can also exist in the form of fibers, in which the fibers are surrounded by a coating that is essentially non-adhesive at room temperature.

[0108] A particular advantage is gained when the safety element is positioned above a window present in security paper or valuable articles. This window is preferably manufactured or stamped using a papermaking machine.

[0109] The present invention also includes a security paper for manufacturing secure documents or valuable documents, such as banknotes, checks, identity cards, deeds, etc., equipped with the security element described above. In addition to the security element according to the invention, the security paper advantageously has at least one additional carrier substrate. Paper is preferably used as the carrier substrate. The invention also includes valuable articles, branded articles, valuable documents, etc., having such a security element.

[0110] Preferably, the security element can be mounted on or embedded in the security paper or valuable document. Alternatively, the security element is embedded in the security paper or valuable document as a window security line and is visible on its surface in the window area of ​​the security paper or valuable document. The security element can also form a pendulum security line, which is alternately visible on opposite surfaces of the security paper or valuable document.

[0111] In a method for manufacturing one of the safety elements described above, a coating that is substantially non-sticky at room temperature is at least partially applied to a substrate. The coating, which is then substantially non-sticky at room temperature, is preferably dried, at least physically.

[0112] According to a particularly preferred method, a water-based dispersion is applied as a coating that is substantially non-sticky at room temperature.

[0113] According to another preferred method, a cationic radiation-cured resin is applied as a coating that is essentially non-sticky at room temperature.

[0114] In a preferred embodiment of the method, at least one additional layer is applied to the substrate, at least by a certain area, before applying the coating which is substantially non-sticky at room temperature. This additional layer may be a radiation-crosslinkable layer, which is pre-crosslinked by radiation before applying the non-sticky layer. Pre-crosslinking minimizes the risk of subsequent melting associated with loss of adhesion to the substrate.

[0115] In another equally advantageous modification scheme, a coating that is essentially non-sticky at room temperature is cross-linked by ultraviolet radiation or by electron radiation.

[0116] The present invention also includes a method for manufacturing the security paper or valuable article described above, wherein the security paper or valuable article is equipped with the security element described above.

[0117] Here, according to a preferred variation of the method, the safety element is coated onto a carrier substrate under increased pressure and temperature, and then at least pre-crosslinked by radiation to form a coating that is substantially non-sticky at room temperature. If the safety element is present as a transfer element, the coating that is substantially non-sticky at room temperature can be fully crosslinked after the substrate and (if present) the release layer are removed. According to another preferred variation of the method, immediately before coating the safety element onto safety paper or valuable articles, the coating that is substantially non-sticky at room temperature is irradiated from the direction of the coating using short-wave radiation, particularly short-wave visible light radiation or UV radiation, and then coated onto the carrier substrate under increased pressure and temperature. It is advantageous to start exposure from the coating side because it avoids or at least significantly reduces the load exerted by UV radiation on the carrier substrate and the UV load on the material of the safety element.

[0118] Furthermore, the present invention includes the use of one of the security elements described above in the manufacture of film composite banknotes and as a packaging material. For example, a sterilizable film package having a security element according to the invention is sealable and crosslinkable. Upon successful UV sterilization, the sealed gap is simultaneously crosslinked and cured. Attached Figure Description

[0119] Other embodiments and advantages of the present invention will now be described with reference to the accompanying drawings. For clarity, the drawings are not shown to scale.

[0120] In the attached image:

[0121] Figure 1 A schematic illustration of a safety element according to the invention, having a coating that is substantially non-sticky at room temperature, is shown in cross-section.

[0122] Figure 2 The cross-sectional view shows the equipment equipped with Figure 1 A schematic diagram of the safety paper for the safety components;

[0123] Figure 3 A schematic illustration of a safety element according to another embodiment of the present invention is shown in cross-section;

[0124] Figure 4 The cross-sectional view shows the equipment equipped with Figure 3 A schematic diagram of the safety paper for the safety components;

[0125] Figure 5 A schematic illustration of security paper according to another embodiment of the present invention is shown in cross-section;

[0126] Figure 6A cross-sectional view shows the substrate after which the safety element, configured as a transfer element, has been stripped. Figure 5 A schematic diagram of safety paper;

[0127] Figure 7 A schematic diagram of a safety element or safety paper according to another embodiment of the present invention is shown in cross-section;

[0128] Figure 8 A schematic diagram of a safety element or safety paper according to another embodiment of the present invention is shown in cross-section;

[0129] Figure 9 A schematic illustration of a safety element configured as a transfer element according to another embodiment of the present invention is shown in cross-section.

[0130] Figure 10 The cross-sectional view shows the product after exposure to UV radiation. Figure 9 A schematic diagram of the safety components;

[0131] Figure 11 A schematic illustration of security paper according to another embodiment of the present invention is shown in cross-section;

[0132] Figure 12 A schematic diagram of the valuable document is shown in top view;

[0133] Figure 13 It shows Figure 12 A cross-sectional view of a valuable document. Detailed Implementation

[0134] Figure 1 A schematic illustration of a safety element according to the invention, having a substrate 1 and a coating 2 that is substantially non-sticky at room temperature, is shown. To manufacture the safety element, a dispersion (UV dispersion) that can be cured by UV radiation is applied to the substrate 1, for example, to a plastic film, particularly PET or OPP film. The UV dispersion is dried (e.g., at 80°C), thereby forming the coating 2, which is substantially non-sticky at room temperature.

[0135] The safety element and all the safety elements described below may be equipped with other safety features not shown in the various figures, such as holograms or printed patterns.

[0136] Figure 2 The cross-sectional view shows the equipment equipped with Figure 1 A schematic diagram of safety paper containing safety components. To manufacture safety paper, [the following steps are involved]. Figure 1The safety element is transferred to a carrier substrate 3, such as paper, through a heat-sealing process under increased pressure and temperature (e.g., at 140°C). That is, a coating that is essentially non-adhesive at room temperature performs the function of a heat-sealing varnish in this case.

[0137] Subsequently, through the action of UV radiation (such as mercury and iron radiators) Figure 1 The coating 2 is cross-linked, resulting in an infusible coating 2 with radiation cross-linking and a substrate 1, such as a plastic film or safety paper, for covering.

[0138] Figure 3 A schematic illustration of a safety element according to another embodiment of the present invention is shown in cross-sectional view. To manufacture the safety element, a UV dispersion is applied to a substrate 1, for example, to a plastic film. The plastic film is, for example, a PET or OPP film. The UV dispersion is dried (e.g., at 80°C) and cross-linked by UV radiation, thereby forming an inmeltable coating 4. Another coating having a UV dispersion is applied over this coating 4 and dried (e.g., at 80°C), thereby forming a coating 2 that is substantially non-sticky at room temperature. Forming this two-layer coating has the advantage of ensuring good adhesion to the substrate 1 during subsequent heat sealing.

[0139] Figure 4 The cross-sectional view shows the equipment equipped with Figure 3 A schematic diagram of safety paper containing safety components. To manufacture safety paper, [the following steps are involved]. Figure 3 The safety element is coated onto a carrier substrate 3 made of paper through a heat-sealing process under increased pressure and temperature (e.g., at 140°C). Subsequently, it is subjected to UV radiation (e.g., by mercury and iron radiators) to... Figure 3 The coating 2 is cross-linked, resulting in a two-layer, radiation-crosslinked, infusible coating 2, 4 and a substrate 1, here a plastic film, for covering.

[0140] The described safety element is characterized by excellent adhesion between coatings 2 and 4 and substrate 1. This adhesion is not lost even at the increased temperatures of the heat-sealing process. If adhesion problems still occur in one of the plastic films used, a pressure-pretreated film (e.g., Hostaphan RNK2600, Mitsubishi polyester film) can be used, for example.

[0141] Figure 5 A schematic illustration of security paper according to another embodiment of the present invention is shown in cross-section. This is for manufacturing purposes a transfer element assembled with... Figure 5The security element of the security paper shown has an embossed varnish 6 applied to a substrate 1, such as a PET carrier film. Optionally, an insulating layer, such as one made of wax, can be applied between the PET carrier film and the embossed varnish layer 6. A reflective layer 7, such as a metal layer or a high refractive index layer, is provided to the embossed varnish 6. All metals and many metal alloys are considered as reflective materials. Examples of suitable high refractive index materials are CaS, CrO2, ZnS, TiO2, or SiO2. x The reflective layer 7 can also be coated with patterns or characters, especially positive and negative patterns. The embossing of the embossed paint 6, such as the diffraction structure in the form of relief (which is not shown here for clarity and exists on the side of the embossed paint 6 facing away from the substrate 1), can be achieved before or after coating the reflective layer 7.

[0142] A UV dispersion is applied over the reflective layer 7 and then heat-dried (e.g., at 80°C), thereby forming a coating 4 that is substantially non-sticky at room temperature. That is, this substantially non-sticky coating at room temperature can be used as a protective varnish for metallization. Furthermore, a primer / adhesive layer can be applied between the reflective layer 7 and the coating 4 if needed.

[0143] By irradiating the UV dispersion from the direction of the coating, i.e., from the side where UV radiation can substantially penetrate the safety paper, the UV dispersion is cross-linked, thereby forming an infusible coating 4. Subsequently, another coating having a UV-curable dispersion is applied onto this cross-linked UV dispersion layer and heat-dried (e.g., at 80°C). By drying the UV dispersion, a coating 2 that is substantially non-sticky at room temperature is formed.

[0144] To manufacture the safety paper shown, the safety element is then coated onto a carrier substrate 3 made of paper through a heat-sealing process under increased pressure and temperature (e.g., at 140°C). Subsequently, the coating 2 can be pre-crosslinked by the action of UV radiation (e.g., mercury and iron radiators) passing through the PET carrier film, but pre-crosslinking is not mandatory.

[0145] Subsequently, the PET carrier film and the release liner (if present) are removed. Alternatively, the PET carrier film can be left as a protective layer on the embossed paint layer 6. In this case, no release liner is provided. Finally, the pre-crosslinked coating 2 is crosslinked by UV radiation (e.g., a mercury-doped radiator) passing through the reflective layer 7, thereby finally obtaining the desired finish. Figure 6 The security paper is schematically shown in a cross-sectional view. The security paper has a carrier substrate 3 made of paper, two layers of radiation-crosslinked infusible coatings 2 and 4, a reflective layer 7, and an embossed paint layer 6.

[0146] Crosslinking via UV radiation penetrating the metal layer is not a technical problem because metallization (especially aluminum) has relatively high transparency, particularly in the UV range. Metallization of aluminum (optical density = 2.0) provides 5% to 10% transparency for long-wave UV radiation, for example. Furthermore, the embossed paint layer 6, combined with the metal layer, produces excellent oxygen exfoliation, leading to improved UV crosslinking of coatings 2 and 4.

[0147] Figure 7 A schematic illustration of a safety element or safety paper according to another embodiment of the present invention is shown in cross-section. To manufacture the safety element or safety paper, a UV dispersion is applied to the entire surface of a substrate 21 made of paper. Alternatively, the UV dispersion can be applied to both sides of the substrate 21, so that the substrate 21 is completely covered by a coating 22, which is not shown here for clarity. Furthermore, the UV dispersion may contain rheology additives if desired. The UV dispersion is dried (e.g., at 80°C), thereby forming a coating 22 that is substantially non-sticky at room temperature. Subsequently, printing ink 9 is printed onto the substantially non-sticky coating 22.

[0148] Thus, the UV-curable coating 22 "dissolves" in the area 10 opposite to the paper substrate, i.e., the printing ink bonds to the coating 22. Then, the coating 22 is cross-linked by UV radiation (e.g., a mercury or iron radiator) to obtain the safety element or safety paper according to the invention, which has a paper layer and a now radiation-crosslinked, infusible coating 22 printed with printing ink 9.

[0149] Alternatively, in order to manufacture in Figure 8 A safety element or safety paper according to another embodiment of the invention, schematically shown in a cross-sectional view, has a UV dispersion coated on the entire surface of a paper substrate 21. Alternatively, the UV dispersion can be coated on both sides of the substrate 21. The UV dispersion is dried (e.g., at 80°C), thereby forming a coating 22 that is substantially non-sticky at room temperature. Subsequently, the coating 22 is cross-linked by UV radiation (e.g., a mercury or iron radiator), thereby obtaining the safety element or safety paper according to the invention, which has a radiation-crosslinked, infusible coating 22. Printing ink 9 can then be printed onto the radiation-crosslinked coating 22, wherein the adhesion and anti-fouling properties of the printing ink can be adjusted by the degree of crosslinking of the coating 22.

[0150] Figure 9A schematic illustration of a safety element configured as a transfer element according to another embodiment of the invention is shown in cross-section. To manufacture the safety element, a coating having a UV dispersion is applied to a substrate 1, for example, a PET carrier film. The UV dispersion is heat-dried (e.g., at 80°C), thereby forming a coating 2 that is substantially non-sticky at room temperature. Optionally, an isolation layer 5 may be applied between the PET carrier film and the coating 2.

[0151] Diffraction structure 11 can be imprinted in coating 2. That is, a UV-curable dispersion is used as an embossing varnish in this case. Coating 2 is cured by UV radiation during or after this process. Exposure is performed through a mask. (As from...) Figure 10 As can be seen, UV exposure is performed only at locations 12 where the pattern of the diffraction structure 11 has been pre-imprinted. The patch to be transferred in subsequent steps is exposed in this way, but the areas in between are not exposed. Therefore, the intermediate areas 13 remain soft and meltable, allowing for sharp-edged melting when the safety element is transferred to the carrier substrate. Conversely, the exposed areas 12 remain hard and retain their printed structure even during the transfer process. Optionally, a metal layer or high-refractive-index layer (not shown here) can be applied to the coating 2 containing the diffraction structure 11, or only to the areas where the diffraction structure is provided. Furthermore, the metal layer or high-refractive-index layer can be applied in the form of patterns or characters, particularly positive and negative patterns.

[0152] Figure 11 The cross-sectional view shows the equipment equipped with Figure 10 A schematic diagram of the safety paper for the safety components. Figure 10 The diagram illustrates the cross-linking of coating 2 at location 12, where a pattern has been pre-imprinted in the form of a diffraction structure 11, via UV exposure. After applying a metal layer or a high-refractive-index layer if necessary, a patch is applied to the carrier substrate 3 using a heat-sealing adhesive 14. By restricting UV exposure at location 12, the central region 13 remains soft and meltable, thereby enabling sharp-edged melting during the transfer of the safety element via thermal stamping. Conversely, the exposed region 12 remains hard and retains its printed structure even during the transfer process.

[0153] However, a coating composed of a UV-crosslinkable dispersion can be used instead of a heat-sealing adhesive. However, it should be noted that the UV-crosslinkable dispersion is transferred only after the uncured intermediate region 13 is removed, and the dispersion is crosslinked by means of UV radiation.

[0154] Figure 12A valuable document 15, such as a banknote, is shown in top view with a through opening 16. The opening 16 is preferably produced by papermaking or by punching. The machine production of such a window opening 16 is described in DE 101 63 381A1.

[0155] Figure 13 It shows in Figure 12 The cross-sectional view of the valuable document 15 shown in the figure differs in that the opening 16 is closed by a safety element according to the invention. This safety element has a substrate 1 and a coating 2 that is substantially non-adhesive at room temperature.

[0156] The safety element is preferably arranged in the recess 17 surrounding the opening 16. The recess 17 can be created by subsequent calendering of the paper web, i.e., by compression of the paper fibers. Alternatively, the recess 17 can also be created by actually reducing the paper thickness in this area. This is most simply done directly during the manufacture of the paper web by forming a thinner sheet in this area through a correspondingly formed screen.

[0157] In another embodiment, not shown, the safety element comprises a substrate and a coating that is substantially non-sticky at room temperature. To manufacture the safety element, a cationic radiation-curing resin, particularly an epoxy-modified vinyl copolymer (e.g., UCAR VERR-40, The Dow Chemical Company), is applied to the substrate, such as a plastic film, particularly a PET or OPP film, having a photoinitiator suitable for cationic radiation curing. The cationic radiation-curing resin is then dried (e.g., at 80°C), thereby forming a coating that is substantially non-sticky at room temperature.

[0158] To manufacture safety paper equipped with the aforementioned safety elements, the safety elements are transferred to a carrier substrate, such as paper, under increased pressure and temperature (e.g., at 140°C) via a heat-sealing process. Here, thermal cross-linking begins. Subsequently, the coating, which is capable of being cured by cationic radiation, is cross-linked by UV radiation (e.g., mercury and iron radiators), ultimately yielding safety paper with a radiation-crosslinked, infusible coating and a substrate, such as a plastic film, for covering.

[0159] Alternatively, the coating can be crosslinked simply by heat. For this purpose, the safety element is transferred to a carrier substrate, such as paper, only under increased pressure and temperature (e.g., at 140°C to 160°C) via a heat-sealing process. Here, thermal crosslinking occurs within the scope of the heat-sealing process. Clearly, in this variation of the method, the use of a photoinitiator can be excluded.

[0160] Compared to free radical radiation curing, cationic radiation curing is a slower process that continues even after irradiation has ended. Free radicals are eliminated quickly, while cationic radiation curing releases an acid that catalyzes crosslinking reactions in the coating. Therefore, in another variation of the embodiments described above, the cationicly curable coating can be exposed to short-wavelength radiation (UV or short-wavelength blue light) immediately before the application of the safety element, starting from the coating side. Common UV radiators (doped or undoped) can be used as the radiation source, or preferably, UV light-emitting diodes (LEDs). In addition to the positive safety aspects, UV LEDs offer technical advantages due to lower heat input and lower energy consumption. Starting exposure from the coating side is advantageous because UV radiation does not load the carrier substrate, such as paper, and places less UV load on the material of the safety element. The crosslinking reaction is initiated by exposure. At the point of application to the carrier substrate, it has not yet progressed to a point where the coating would be difficult to melt due to the short time interval. However, because the reaction continues on its own without any other intervention, the safety paper with the safety element exhibits the required durability.

Claims

1. A security element for a valuable document, the security element having a substrate (1, 21) coated with a heat-sealing adhesive (2, 22), the heat-sealing adhesive being non-stick at room temperature and suitable for coating the security element onto the valuable document substrate. in, The heat-sealing adhesive (2, 22) contains components capable of radiation crosslinking and a reaction diluent. The reaction diluent is a low molecular weight compound with a molecular molar mass M < 1000 g / mol, wherein the low molecular weight compound is selected from TMP(EO). x TA and DPHA, and The heat-sealing adhesive (2, 22) contains 5% to 25% of a reactive diluent.

2. The safety element according to claim 1, wherein, The heat-sealing adhesives (2, 22) additionally contain plasticizers.

3. The safety element according to claim 2, wherein, The plasticizer has a melting point in the range of 50°C to 120°C.

4. The safety element according to claim 2, wherein, The plasticizer is selected from the group consisting of: triphenylphosphonate, pentaerythritol tetrabenzoate, cyclohexyl and dimethyl gold benzoate, sucrose benzoate, and mixtures of two or more of the aforementioned elements.

5. The safety element according to claim 2, wherein, The plasticizer is included in the heat-sealing adhesive (2, 22) in solid form at a weight ratio ranging from 1% to 30%.

6. The safety element according to any one of claims 1 to 5, wherein, A non-stick heat-sealing adhesive (2, 22) suitable for coating the security element onto a valuable document substrate is present at room temperature, at least physically dry.

7. The safety element according to any one of claims 1 to 5, wherein, The substrate (1, 21) is a planar substrate (1, 21) having two opposing main surfaces, wherein at least one main surface of the substrate (1, 21) is at least partially equipped with a heat-sealing adhesive (2, 22) that is non-stick at room temperature and suitable for coating the security element onto the valuable document substrate.

8. The safety element according to any one of claims 1 to 5, wherein, Non-stick heat-sealing adhesives (2, 22) suitable for coating the security element onto a valuable document substrate at room temperature can be obtained by means of a coating solution, emulsion or dispersion.

9. The safety element according to claim 8, wherein, A non-stick heat-sealing adhesive (2, 22) suitable for coating the security element onto a valuable document substrate at room temperature can be obtained by applying an aqueous dispersion.

10. The safety element according to claim 8, wherein, A non-stick heat-sealing adhesive (2, 22) suitable for coating the security element onto a valuable document substrate at room temperature can be obtained by applying an organic solvent-based solution.

11. The safety element according to claim 10, wherein, The organic solvent is at least butyl acetate, propyl acetate, or ethyl acetate.

12. The safety element according to claim 10, wherein, The heat-sealing adhesives (2, 22) additionally have a prepolymer that is non-sticky after physical drying at room temperature, contains an average of at least two reactive groups, and has a molecular weight of at least 600 g / mol.

13. The safety element according to claim 9, wherein, The dispersion is selected from the group consisting of: aliphatic polyurethane dispersions, aromatic polyurethane dispersions, acrylates, anionic acrylate-modified polyurethane dispersions, polyurethane-polyether acrylates, and mixtures of two or more of the aforementioned elements.

14. The safety element according to any one of claims 1 to 5, wherein, The heat-sealing adhesives (2, 22) comprise cationic radiation-cured resins.

15. The safety element according to any one of claims 1 to 5, wherein, The components capable of radiation cross-linking can be cross-linked through ultraviolet radiation or electron radiation.

16. The safety element according to any one of claims 1 to 5, wherein, The heat-sealing adhesives (2, 22) contain a photoinitiator.

17. The safety element according to any one of claims 1 to 5, wherein, The substrates (1, 21) are transparent plastic films.

18. A valuable document comprising a security element according to any one of claims 1 to 17.

19. A method for manufacturing a security element according to any one of claims 1 to 17, comprising the step of applying a heat-sealing adhesive (2, 22) to a substrate (1, 21), said heat-sealing adhesive being non-stick at room temperature and suitable for applying said security element to a valuable document substrate, wherein, The heat-sealing adhesive (2, 22) contains components capable of radiation crosslinking and a reactive diluent.

20. A method for manufacturing a valuable document according to claim 18, comprising the step of equipping a valuable document substrate with a security element according to any one of claims 1 to 17.

21. The method according to claim 20, wherein, The safety element is coated onto the valuable document substrate (3) under increased pressure and temperature, and then the non-stick heat-sealing adhesive (2, 22) is at least pre-crosslinked by radiation.

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