Security element, value document and method for the production thereof

Abstract

The invention relates to a security element for protecting a value document, comprising a carrier substrate, a coating provided with an optical surface marking, and a heat-sealable adhesive layer suitable for bonding the security element to the value document substrate, characterized in that the surface of the adhesive layer is provided with a coating which can be washed off when in contact with a cleaning liquid.

Description

Technical Field

[0001] The invention relates to a security element for protecting a valuable document, comprising a carrier substrate, a coating provided with optical surface markings and a heat-sealable adhesive layer suitable for bonding the security element to the valuable document substrate. The invention also relates to a valuable document, in particular a banknote, provided with a security element according to the invention, and a method for producing a valuable document. Background Art

[0002] For security purposes, valuable documents, in particular banknotes, are usually provided with security elements which make it possible to check the authenticity of the valuable documents and at the same time serve as protection against unauthorized copying. Security elements with an effect that depends on the viewing angle play a special role in authenticity protection, since they cannot be reproduced even with the most modern copiers. In this case, the security elements are equipped with optically variable elements which give different image impressions to the observer at different viewing angles and, for example, display different color or brightness impressions and / or different graphic patterns depending on the viewing angle.

[0003] It is known to introduce security elements in the form of security threads into value documents, such as banknotes, or to apply them in the form of security strips or security patches or security labels. The security element usually has a heat-sealable adhesive layer, which serves to anchor the security element to the paper. When heat is applied, the heat-sealable adhesive layer melts and acts as an adhesive.

[0004] Patent document EP1776240B1 describes a security element for protecting valuable documents, the security element having a heat-sealable adhesive layer which is substantially non-tacky at room temperature and is suitable for bonding the security element to a valuable document substrate, wherein the adhesive layer is additionally UV-curable. During the UV curing process, the adhesion of the security element to the valuable document substrate is improved.

[0005] The security elements provided during the production of valuable documents are usually in the form of a continuous film. The heat-sealable adhesive layer provided on the security elements can sometimes lead to mutual adhesion of the stacked security elements present in the wound continuous film. In particular, there is the risk of mutual adhesion in the presence of UV-curing, heat-sealable adhesive layers. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to provide a security element of the above-mentioned type which avoids the disadvantages of the prior art.

[0007] This object is achieved on the basis of the feature combinations defined in the independent claims.

[0008] Improvements of the invention are the subject matter of the dependent claims.

[0009] Overview

[0010] 1. (First aspect of the invention) A security element for protecting valuable documents, comprising a carrier substrate, a coating provided with optical surface markings and an adhesive layer suitable for bonding the security element to the valuable document substrate, in particular a substantially non-sticky, heat-sealable adhesive layer at room temperature, characterized in that the surface of the adhesive layer is provided with a coating that can be washed off when in contact with a cleaning liquid.

[0011] 2. (Preferred embodiment) Security element according to clause 1, wherein the heat-sealable adhesive layer which is suitable for bonding the security element to the value-document substrate, in particular which is essentially tack-free at room temperature, is additionally UV-curable.

[0012] 3. (Preferred design) A security element according to clause 1 or 2, wherein the coating provided with the optical surface marking has an optically variable effect, in particular a diffraction pattern, a hologram, a micromirror arrangement, a tilt color change effect or a color change that changes when observed in reflected light and when observed in reflected light.

[0013] 4. (Preferred design) A security element according to one of clauses 1 to 3, wherein the coating provided with the optical surface marking has an embossed lacquer provided with an embossed relief and a metallized structure, wherein the metallized structure is in particular a multilayer thin-layer element, such as a reflector / dielectric / absorber multilayer arrangement, or a multilayer arrangement having two semi-transparent metallized structures with a dielectric layer embedded therebetween.

[0014] 5. (Preferred design) The security element according to any one of clauses 1 to 4, wherein the security element is a security thread, a security strip or a security patch.

[0015] 6. (Second aspect of the invention) A valuable document comprising a security element according to one of clauses 1 to 5 provided therewith.

[0016] 7. (Preferred design) A valuable document according to clause 6, wherein the valuable document is a banknote.

[0017] 8. (Third aspect of the invention) A method for producing a value document according to clause 6 or 7, comprising:

[0018] - providing a valuable document substrate;

[0019] - providing a security element comprising a carrier substrate, a coating provided with optical surface markings and a heat-sealable adhesive layer which is suitable for bonding the security element to a value-document substrate, in particular substantially tack-free at room temperature, wherein a surface of the adhesive layer is provided with a coating which can be washed off upon contact with a cleaning liquid;

[0020] - removing the removable coating by means of a cleaning liquid, thereby exposing the adhesive layer;

[0021] - Providing the value-document substrate with the security element through the exposed adhesive layer under elevated pressure and elevated temperature.

[0022] 9. (Preferred design) The method according to clause 8, wherein the adhesive layer is additionally UV-curable and, during the provision of the security element to the value-document substrate, curing of the adhesive layer is additionally carried out by UV radiation.

[0023] 10. (Preferred design) The method according to clause 8 or 9, wherein the security element is a security thread, and before embedding the security thread in the valuable document substrate, a step of washing away the washable coating with a cleaning liquid to thereby expose the adhesive layer is performed.

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The invention is based on the idea that a security element for protecting a valuable document is provided with a heat-sealable adhesive layer which is suitable for bonding the security element to a valuable document substrate, in particular substantially non-sticky at room temperature, wherein the surface of the adhesive layer is provided with a coating which can be washed off when in contact with a cleaning liquid. The coating which can be washed off when in contact with a cleaning liquid is preferably produced by printing pigments in printing technology. The coating which can be washed off when in contact with a cleaning liquid is therefore referred to for simplicity as a "cleaning pigment".

[0026] Suitable coatings that can be washed off when in contact with a cleaning liquid are known in the prior art. Patent document EP1972462B1 describes a cleaning pigment for producing a security element with a clear negative font. Once the cleaning pigment comes into contact with the cleaning liquid, gas is generated. Even a small amount of gas can lead to a strong increase in pressure, thereby exerting a strong mechanical force so that the metallized structure present above the cleaning pigment is torn apart. The grooves in the metallized structure obtained in this way are especially formed in the form of characters, patterns or codes, which are perceived by the observer as a clear negative font.

[0027] The basic concept of the present invention is based on the use of cleaning pigments known in the prior art as a covering for a heat-sealable adhesive layer. The security element to be manufactured, in particular a security thread, a security strip or a security patch, is additionally provided with a cleaning pigment at the location where the heat-sealable adhesive layer is present. The application of the cleaning pigment is preferably carried out by printing technology. The washing off of the cleaning pigment is preferably carried out by water as a suitable cleaning liquid. After the cleaning pigment is detached, the heat-sealable adhesive layer exists in a free form and can be connected unhindered to the valuable document substrate to be protected by the security element, for example a paper substrate.

[0028] For example, EP 1972462 B1 describes suitable coatings that can be washed off when in contact with cleaning fluids. Cleaning pigments are based in particular on water-soluble binders, such as hydroxypropylcellulose, polyethylene glycol, casein and / or polyvinylpyrrolidone, to which one or more fillers, such as titanium dioxide, silicates and / or polymethylurea, are added if necessary. Large amounts of fillers are used to impart porosity to the cleaning pigments, which allows for rapid ingress of the cleaning medium.

[0029] The security element according to the invention is usually in the form of a continuous film. The heat-sealable adhesive layer provided on the security element is additionally provided with a wash-off pigment in order to prevent mutual adhesion of the stacked security elements present in the wound continuous film. In particular, there is the risk of mutual adhesion when UV-curing, heat-sealable adhesive layers are present.

[0030] The security element for protecting a valuable document according to the invention comprises a carrier substrate and a coating provided with optical surface markings, the carrier substrate preferably being a polyethylene terephthalate (PET) film. The coating provided with optical surface markings ensures reproducibility that is difficult for counterfeiters, thereby increasing the anti-counterfeiting security of the valuable document equipped with the security element according to the invention. The coating provided with optical surface markings preferably has an optically variable effect, in particular a diffraction pattern, a hologram, a micromirror arrangement, a tilt color effect or a color change that changes when observed in reflected light and when observed in reflected light.

[0031] The coating provided with an optical surface marking preferably has an embossing lacquer and a metallized structure provided with an embossed relief, wherein the metallized structure is in particular a multilayer thin-layer element, such as a reflector / dielectric / absorber multilayer arrangement, or a multilayer arrangement having two semi-transparent metallized structures with a dielectric layer embedded therebetween. As an embossing lacquer, in particular, an embossing lacquer crosslinked by UV radiation can be used. The tilt-discoloring reflector / dielectric / absorber multilayer arrangement can be, for example, an Al / SiO2 / Cr multilayer arrangement, which can be obtained in particular by vapor deposition. Multilayer arrangements with color changes when observed in reflected light and when observed in reflected light are known, for example, from patent documents WO2011 / 082761A1 and WO2019 / 068362A1, and in particular a multilayer arrangement having two semi-transparent metallized structures with a dielectric layer embedded therebetween, such as an Al / SiO2 / Al multilayer arrangement or an Ag / SiO2 / Ag multilayer arrangement.

[0032] According to a preferred embodiment, security element according to the present invention is implemented as, heat-sealable adhesive layer that is suitable for bonding security element to valuable document substrate, especially substantially non-sticky at room temperature, and coating that is present above the adhesive layer and can be washed off when in contact with cleaning fluid, respectively structuredly exists in the form of pattern, word or coding.Here, heat-sealable adhesive layer and cleaning pigment present above the adhesive layer are arranged outside the region of the coating that is provided with optical surface marking according to special modification.Structural heat-sealable adhesive layer is known in the prior art, referring to, for example, patent documentation EP1880864A1.According to the present invention, the structured arrangement of heat-sealable adhesive layer and cleaning pigment can be preferably carried out in the edge region of security element, especially with the regional registration of the coating that is provided with optical surface marking.This structured arrangement is advantageous, especially when security element according to the present invention exists as security thread. In particular, in the case where the security element according to the invention is present as a so-called window security thread, the heat-sealable adhesive layer and the washing pigment are preferably structured in the area where the paper tab is to be provided (when the security thread is embedded in the paper substrate), in particular in register with the area where the coating with optical surface markings is provided (see, for example, Figure 4a of patent document EP1880864B1).

[0033] Suitable for bonding security element to valuable document substrate, especially substantially non-sticky at room temperature, heat-sealable adhesive layer is preferably UV-cured in addition.In the process that security element is applied to the valuable document substrate to be protected with it, for example on the paper substrate, the internal strength of the adhesive layer of security element on the valuable document substrate is improved and cured in the UV crosslinking process to increase with a favorable degree.The temperature of the adhesive layer directly existing before, during and after UV crosslinking is an important parameter for determining achievable crosslinking degree.High crosslinking degree can be achieved in higher temperatures, because the mobility of reactive groups is higher.Suitable heat-sealable adhesive layer substantially non-sticky at room temperature, additionally being UV-cured is known in the prior art, see for example patent documentation EP1776240B1.

[0034] The invention furthermore relates to a valuable document comprising an associated security element according to the invention, wherein the valuable document is in particular a banknote.

[0035] The invention also relates to a method for producing a value document, comprising:

[0036] - providing a valuable document substrate;

[0037] - providing a security element comprising a carrier substrate, a coating provided with optical surface markings and a heat-sealable adhesive layer which is suitable for bonding the security element to a value-document substrate, in particular substantially tack-free at room temperature, wherein a surface of the adhesive layer is provided with a coating which can be washed off upon contact with a cleaning liquid;

[0038] - removing the removable coating by means of a cleaning liquid, thereby exposing the adhesive layer;

[0039] - Providing the value-document substrate with the security element through the exposed adhesive layer under elevated pressure and elevated temperature.

[0040] According to a preferred embodiment, the adhesive layer is additionally UV-curable, wherein during the provision of the security element to the valuable document substrate, the adhesive layer is additionally cured by UV radiation. In this case, the security element is in particular a security thread, wherein before the security thread is embedded in the valuable document substrate, a step of washing off the washable coating with a cleaning liquid is performed in order to thereby expose the adhesive layer. For optimal cleaning, a nozzle can be used if necessary. The cleaning liquid is preferably water.

[0041] Suitable hot presses for carrying out the method according to the invention are known in the prior art. Patent document EP3173232B1, for example, describes a suitable hot press with a film application unit designed to transfer or laminate a film material onto a substrate fed in the form of a continuous sheet by hot pressing, wherein the hot press additionally has a UV curing unit.

[0042] Further advantages of the invention are explained below on the basis of exemplary embodiments in conjunction with schematically greatly simplified drawings, in which the reproduction according to scale and proportion is omitted in order to increase the clarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 shows a security element according to the invention according to a first embodiment;

[0044] FIG. 2 shows a value document provided with a security element according to the invention according to a first embodiment;

[0045] 3 and 4 show a security element according to the invention according to a second embodiment;

[0046] FIG. 5 shows a security element according to the invention according to a third exemplary embodiment. DETAILED DESCRIPTION

[0047] FIG. 1 shows a cross-sectional view of a security element 1 according to the invention according to a first embodiment, in the example a security patch. A polyethylene terephthalate (PET) film is used as a substrate 2. The substrate 2 is provided with a UV embossing lacquer 3, which has an embossed relief on the main surface opposite to the substrate 2. For simplicity, the embossed relief is not shown in FIG. 1. The embossed relief can, for example, have a micro- and / or nanostructure, so that in combination with a reflective layer, for example a high-refractive layer or a metallized structure, a diffraction optical effect, a hologram effect or a micromirror effect can be produced. In the case of a metallized structure, it can be a thin-layer element, for example a reflector / dielectric / absorber multilayer arrangement with a tilted color-changing effect, if necessary. Examples of high-refractive materials are CaS, CrO2, ZnS, TiO2, SiO x The reflective layer 4 can also be applied in the form of a pattern or lettering, in particular a positive or negative pattern. A UV dispersion is applied over the reflective layer 4 and dried thermally, for example at 80° C., thereby producing an essentially tack-free, heat-sealable, additionally UV-curing adhesive layer 5 suitable for bonding the security element to a valuable document substrate at room temperature. The surface of the adhesive layer 5 is subsequently coated by printing technology with a coating 6 that can be washed off when in contact with a cleaning liquid.

[0048] Optionally, a release layer, such as a wax layer, can be arranged between the substrate 2 and the UV embossing lacquer 3 so that the substrate 2 can be peeled off after the security element 1 is applied to the value document to be protected therewith. In addition, a primer layer or an adhesion promoter layer can be arranged between the reflective layer 4 and the adhesive layer 5 if necessary.

[0049] Since the heat-sealable adhesive layer 5 for the security element 1 shown in FIG1 is additionally provided with a washing pigment 6, the stacked security elements 1 present in the wound continuous film are prevented from adhering to each other. In particular, there is a risk of mutual adhesion when UV-curing, heat-sealable adhesive layers 4 are present.

[0050] The washing off of the washing pigment 6 is preferably carried out by water as a suitable washing liquid. After the washing pigment 6 is detached, the heat-sealable adhesive layer 5 is present in free form and can be connected unhindered to the value document substrate 6, for example a paper substrate, to be protected by the security element (see Figure 2).

[0051] FIG. 2 shows a value document 7 , in this case a banknote, which is protected by a security element 1 according to the invention according to a first embodiment.

[0052] FIG. 3 shows a cross-sectional view of a security element 8 according to the invention according to a second embodiment, in this case a security thread. The cross section shown in FIG. 3 is perpendicular to the longitudinal direction of the security thread 8. The security thread 8 is based on a substrate 2, in the example a polyethylene terephthalate (PET) film, with an upper side 9 and a lower side 10. The substrate 2 is provided with a UV embossing lacquer 3 on its upper side 9 in a central region, and the UV embossing lacquer has an embossed relief on the main surface opposite to the substrate 2. For simplicity, the embossed relief (or embossed relief) is not shown in FIG. 3. The embossed relief can, for example, have a micron and / or nanostructure, so that in combination with a reflective layer, for example a high refractive layer or a metallized structure, a diffractive optical effect, a hologram effect or a micromirror effect can be produced. A UV dispersion is applied to the upper side 9 of the substrate 2 in two edge regions and thermally dried, for example at 80° C. This produces a substantially non-sticky, heat-sealable adhesive layer 5 at room temperature, which is suitable for bonding to a paper tab when the security thread 8 is embedded in a banknote. The adhesive layer 5 is additionally, in particular, UV-cured. The surface of the adhesive layer 5 is subsequently coated by printing technology with a coating 6 which can be washed off when it comes into contact with a cleaning liquid.

[0053] A UV dispersion is applied to the entire surface of the underside 10 of the substrate 2 and thermally dried, for example at 80° C. This results in a heat-sealable adhesive layer 5 that is essentially tack-free at room temperature and is suitable for reliably anchoring the security thread 8 in the paper when the security thread 8 is embedded in the banknote. The adhesive layer 5 is additionally UV-cured in particular. The surface of the adhesive layer 5 is subsequently coated by printing technology with a coating 6 that can be washed off when it comes into contact with a cleaning liquid.

[0054] FIG. 4 shows a top view of the upper side of the safety thread 8 shown in FIG. 3 .

[0055] FIG5 shows a top view of the upper side of a security element 9 according to the invention according to a third embodiment. The third embodiment is based on the second embodiment according to FIGS. 3 and 4 . As in FIG. 3 , the layers 5 and 6 are arranged over their entire surface on the lower side 10 of the substrate 2. On the upper side 9 of the substrate 2, in the case of a window security thread 9, the layers 3 and 4 on the one hand and the layers 5 and 6 on the other hand are spatially arranged differently than in the case of the security thread 8. In the case of the window security thread 9 shown in FIG. 5 , the heat-sealable adhesive layer 5 and the washing pigment 6 are structuredly arranged in the area where the paper tab is to be provided when the security thread 9 is embedded in the paper substrate, i.e. in register with the area of ​​the coating provided with the optical surface marking (see reference numerals 3 and 4 ).

Claims

1. A security element for protecting a valuable document, comprising a carrier substrate, a coating provided with optical surface markings and a heat-sealable adhesive layer suitable for bonding the security element to the valuable document substrate, characterized in that The surface of the adhesive layer is provided with a coating that is washable when in contact with a cleaning fluid.

2. The security element according to claim 1, wherein: The heat-sealable adhesive layer which is suitable for bonding the security element to the value-document substrate is additionally UV-curing.

3. The security element according to claim 1 or 2, wherein: The coating provided with the optical surface marking has an optically variable effect, in particular a diffraction pattern, a hologram, a micromirror arrangement, a tilt-chromic effect or a color change which changes when viewed in reflected light and when viewed in transmitted light.

4. The security element according to claim 1, wherein: The coating provided with the optical surface marking comprises an embossing lacquer provided with an embossed relief and a metallization structure, wherein the metallization structure is in particular a multilayer thin-film element, for example a reflector / dielectric / absorber multilayer arrangement or a multilayer arrangement having two semitransparent metallization structures with a dielectric layer embedded therebetween. 5 . The security element according to claim 1 , wherein the security element is a security thread, a security strip or a security patch.

6. A valuable document comprising a security element according to one of claims 1 to 5 provided therewith.

7. The valuable document according to claim 6, wherein: The value document is a banknote.

8. A method for producing a value document according to claim 6 or 7, comprising: - providing a valuable document substrate; - providing a security element comprising a carrier substrate, a coating provided with optical surface markings and a heat-sealable adhesive layer suitable for bonding the security element to a value-document substrate, wherein a surface of the adhesive layer is provided with a coating that can be washed off upon contact with a cleaning liquid; - removing the removable coating by means of a cleaning liquid, thereby exposing the adhesive layer; - Providing the value-document substrate with the security element through the exposed adhesive layer under elevated pressure and elevated temperature.

9. The method according to claim 8, wherein: The adhesive layer is additionally UV-curable and, during the provision of the value-document substrate with the security element, curing of the adhesive layer is additionally carried out by UV radiation.

10. The method according to claim 8 or 9, wherein: The security element is a security thread and, before embedding the security thread in the value-document substrate, a step of washing away the washable coating by means of a washing liquid is performed to thereby expose the adhesive layer.

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