Security substrate, security paper and production method
Patent Information
- Application Number
- EP2023840618
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-13
- Filing Date
- 2023-12-12
- Publication Date
- 2025-10-22
AI Technical Summary
The limited circulation time of banknotes due to early contamination and microbial stress, which is exacerbated by the porous and rough surface of traditional paper substrates, necessitates an improvement in security substrates that maintain typical paper properties while enhancing durability and dirt resistance.
A security substrate comprising a fiber substrate body with 40% to 96% fibers, 1% to 20% anionic polymer, and 0.5% to 5% cationic precipitant, further enhanced with a dirt-repellent layer on its surfaces, either as a film or coating, which can include acrylate or polyurethane compositions with biocidal additives, to increase mechanical strength and resistance to rotation.
The enhanced security substrate achieves extended circulation time by minimizing dirt accumulation, maintaining sound, color, grip, and transmission properties, while providing high z-strength and resistance to rotation, and incorporating biocidal additives for antimicrobial protection.
Smart Images
Figure 1.1
Abstract
Description
[0001] Security substrate, security paper and manufacturing process
[0002] The invention relates to a security substrate for the production of security and value documents, a security paper with such a security substrate and a method for producing such a security substrate.
[0003] Banknotes and other valuable documents are made from security substrates, which are often made of paper or have a paper core and have special security features, such as an at least partially embedded security thread or a watermark.
[0004] It is known that the circulation life of banknotes depends heavily on the wear and tear they are subjected to. Early soiling is considered one of the main causes of the limited circulation life of banknotes. Because banknote paper is highly porous, it has a relatively large surface area and high surface roughness. Although the size of the resulting protrusions and cavities is below the resolution limit of the human eye, they nevertheless represent points of entry for dirt deposits compared to a smooth surface.
[0005] WO 2021 / 023601 A1 proposes a crease- and soil-resistant fiber substrate obtained by a wet process, which has high mechanical strength, in order to prevent banknotes made from the fiber substrate from being exposed to excessive microbial stress during their aging in circulation.
[0006] Based on this, the invention seeks to further improve the circulation life of known security substrates. Ideally, typical properties of paper banknotes, such as sound, color, feel, and transmission properties, are retained.
[0007] This object is achieved by the features of the independent claim. Further developments of the invention are the subject of the dependent claims.
[0008] According to the invention, a security substrate for the production of security and value documents comprises a fiber substrate body which contains by mass:
[0009] 40% to 96% dry weight of fibers, in particular cellulose fibers, based on the dry weight of the fiber substrate body,
[0010] 1% to 20% dry weight, based on the dry weight of the fibers, of at least one anionic polymer with a glass transition temperature T gabove - 40 °C, especially a carboxylated polymer, and
[0011] 0.5% to 5% dry weight of at least one cationic precipitant, based on the dry weight of the fibers, wherein the anionic polymer is present in a precipitated form on the surface of the fibers.
[0012] As a special feature, the fiber substrate body is provided with a dirt-repellent layer on at least one of its main surfaces.
[0013] A fiber substrate body of the aforementioned type was proposed as a fiber substrate in WO 2021 / 023601 A1. The inventors have now discovered that, although the known fiber substrate body has a high z-strength, measured using the Scott Bond method, its wear resistance can surprisingly be further increased by an additional dirt-repellent layer. In a first advantageous embodiment, the fiber substrate body is provided with a dirt-repellent film on each of its opposite main surfaces, and together these two films form a composite security substrate.
[0014] According to a second advantageous embodiment, the fiber substrate body is provided with a dirt-repellent coating on at least one of its main surfaces. The fiber substrate body can also be provided with a dirt-repellent coating on its two opposite main surfaces in order to achieve particularly high resistance to wear and tear.
[0015] In an advantageous variant of the invention, the dirt-repellent coating consists of a composition containing an acrylate system as the sole binder and no fillers. The composition preferably lies on the fiber substrate body at a basis weight of between 1 and 6 g / m 2 , especially between 2 and 3 g / m 2In particular, the dirt-repellent coating may consist of a composition as described in WO 00 / 00697 A1, the disclosure of which is incorporated into the present application.
[0016] Advantageous embodiments of the composition are described in WO 00 / 00697 A1. Thus, the composition can contain, in particular, acrylates or a mixture of polymers or copolymers with a high acrylate content as binders. The composition can also contain, in low concentration, at least one substance with a visually and / or mechanically detectable property for security features and / or coding. Said substance advantageously has luminescent, magnetic, electrically conductive, light-diffractive, light-interfering, or light-polarizing properties, and it can also be provided only partially, preferably in the form of a pattern in the coating.
[0017] According to another, equally advantageous variant of the invention, the dirt-repellent coating is formed on the basis of polyurethanes.
[0018] In this case, the dirt-repellent coating can advantageously consist of a composition containing 50% to 70% dry weight of a transparent or translucent binder and 30% to 50% of a silicon oxide and optionally at least one functional additive, the sum of said components constituting 100% of the composition, and the elastomeric binder being selected from the group consisting of polyurethanes usable in the form of stabilized aqueous dispersions. Further details and advantageous embodiments of such a composition can be found in WO 2002 / 020902 A1, the disclosure of which is incorporated into the present application in this respect.
[0019] A dirt-repellent coating formed on the basis of polyurethanes can also consist of a composition containing a non-pigmented polyurethane and optionally at least one functional additive. Further details and advantageous embodiments of such a composition can be found in WO 96 / 28610 A1, the disclosure of which is incorporated into the present application in this respect. In all variants of the invention, the dirt-repellent coating advantageously contains biocidal additives, in particular fungicidal, bactericidal, and / or virucidal additives, as functional additives. Suitable biocidal additives include, in particular, quaternary ammonium salt compounds, diiodomethyl-p-tolylsulfone, 3-iodo-2-propynylbutylcarbamate (IPBC), and thiabendazole.These and other advantageously usable biocidal additives are described in WO 2022 / 189043 A1, the disclosure of which is incorporated into the present application. The use of singlet oxygen catalysts as biocidal additives is also advantageous.
[0020] According to an advantageous development of the invention, the dirt-repellent coating contains visually and / or mechanically verifiable feature substances as functional additives. Luminescent, IR-absorbing, and / or magnetic feature substances are particularly suitable.
[0021] The fiber substrate body itself can also have a biocidal treatment and contain, for example, 0.001% to 1% dry weight of at least one biocidal agent. For enhanced effectiveness, a biocidal treatment of the fiber substrate body itself can be combined with the above-described biocidal treatment of the dirt-repellent coating of the fiber substrate body.
[0022] The anionic polymer of the fiber substrate body is advantageously selected from carboxylated styrene-butadiene copolymers. The fiber substrate body is advantageously designed like the fiber substrate of WO 2021 / 023601 A1, the disclosure content of which is incorporated in its entirety into the present application. This applies in particular to the advantageous embodiments of the anionic polymer, the cationic precipitant, and the fibers of the fiber substrate body described in WO 2021 / 023601 A1. A biocide, a humectant, and fillers, as described in more detail in WO 2021 / 023601 A1, can also be present in the fiber substrate body.
[0023] According to an advantageous development of the invention, a partial or full-surface inner printing layer is provided between the fiber substrate body and at least one dirt-repellent layer. The inner printing layer can be, for example, an offset, intaglio, or screen-printed layer. The security substrate then represents a pre-printed security substrate whose inner printing layers are well protected by the dirt-repellent layer.
[0024] The invention also includes a security paper with a security substrate of the type described and at least one partial or full-surface outer print layer applied to a dirt-repellent layer. The outer print layer can, in particular, be an offset, intaglio, or screen-printed layer. To prevent dirt from accumulating on an outer print layer, outer print layers can be covered with a further layer, for example, a varnish layer or a further dirt-repellent layer. The further dirt-repellent layer can, in particular, be a film or a coating of the type described above.The term 'outer print layer' therefore refers only to the position of the print layer outside the aforementioned dirt-repellent layers on the fiber substrate body and does not mean that such a print layer represents the outermost layer of the security paper.
[0025] The security paper can in particular represent a banknote or other valuable document.
[0026] Finally, the invention also includes a method for producing a security substrate of the type described. First, a fiber substrate body having the above-mentioned composition is provided. The fiber substrate body can advantageously be produced by one of the methods described in WO 2021 / 023601 A1.
[0027] Then, in a first process variant, a dirt-repellent coating is applied to one or both main surfaces of the fiber substrate body. The dirt-repellent coating is preferably applied with a basis weight of between 1 and 6 g / m 2 , especially between 2 and 3 g / m 2 doctored or printed. Before applying the dirt-resistant coating, a print layer can be applied to the fiber substrate to form an internal print layer within the security substrate. After applying the dirt-resistant coating, the security substrate can be further processed to increase the smoothness of the surface, for example, by calendering.
[0028] In another process variant, the fiber substrate body is provided with a dirt-repellent film on both sides to form a composite security substrate. For this purpose, the fiber substrate body can, for example, be laminated together with the two films. Further embodiments and advantages of the invention are explained below with reference to the figures, which are not drawn to scale or proportions for the sake of clarity.
[0029] They show:
[0030] Fig. 1 is a schematic representation of a banknote with a security substrate according to the invention,
[0031] Fig. 2 and 3 each show a security substrate according to an embodiment of the invention,
[0032] Fig. 4 shows a printed security paper produced using the security substrate of Fig. 3,
[0033] Fig. 5 shows a security substrate according to a further embodiment of the invention,
[0034] Fig. 6 shows a printed security paper produced using the security substrate of Fig. 5, and
[0035] Fig. 7 shows a security substrate according to a further embodiment of the invention with dirt-repellent films.
[0036] The invention will now be explained using the example of security substrates for banknotes. Figure 1 shows a schematic representation of a banknote 10 with a security substrate 12 provided with printing elements 14, 16, a portrait watermark 18, and optionally other security features not shown in the figure.
[0037] Figure 2 shows an embodiment of a security substrate 20 usable in the production of the banknote 10. The security substrate 20 contains a fiber substrate body 22 and a dirt-repellent coating 24 applied to the fiber substrate body 22.
[0038] The fiber substrate body 22 is designed as described in more detail above. In the exemplary embodiment of Fig. 2, the fiber substrate body 22 specifically comprises 60% to 96%, preferably even 70% to 96%, by dry weight of fibers, in particular cellulose fibers, based on the dry weight of the fiber substrate body. It further comprises 1% to 10%, preferably 3% to 8%, by dry weight of a carboxylated styrene-butadiene copolymer, which preferably has a glass transition temperature of -30°C to -20°C and particularly preferably -25°C, as well as 0.8% to 3.5%, by dry weight of at least one cationic precipitant, based on the dry weight of the fibers, preferably a polyamide-polyamine-epichloridrine resin.
[0039] The fiber substrate body 22 has a particularly high z-strength or splitting strength, which can be determined, for example, using the Scott-Bond method.
[0040] The dirt-repellent coating 24 applied to the fiber body consists of a composition containing an acrylate system as the exclusive binder and no fillers. In the embodiment, the coating 24 was applied over the entire surface of the fiber substrate body 22 by a doctor blade or printing, the basis weight of the coating being between 1 and 6 g / m 2 and in particular 2-3 g / m 2 amounts.
[0041] Since the dirt-repellent coating 24 contains no fillers, the composition wets the fibers of the fiber substrate body 22 in the surface area and forms a closed surface film that minimizes access to the fibers. The dirt-repellent coating 24 then provides a smooth surface that offers little opportunity for dirt to accumulate. At the same time, the layer thickness of the coating 24 is so thin that the familiar and desired properties of the fiber substrate body 22, such as its grip and printability, are not impaired. The transmission properties of the fiber substrate body are also retained, so that the recognizability of watermarks, such as the portrait watermark 18 of Fig. 1, is not impaired by the dirt-repellent finish.
[0042] Particularly preferably, the fiber substrate body 22 is provided on its two opposite main surfaces with a dirt-repellent coating 24, 26 of the type described, as shown in the security substrate 25 of Fig. 3.
[0043] The security substrates 20, 25 of Figures 2 and 3 exhibit high z-strength due to the fiber substrate body used and also particularly high circulation resistance due to the dirt-repellent coating. The coatings 24, 26 also provide an ideal printing surface for high print resolution and good ink adhesion. Nevertheless, the typical properties of the fiber substrate body 22, such as color, sound, feel, and transmission properties, are retained. The dirt-repellent coating 24 advantageously contains biocidal additives, in particular fungicidal, bactericidal, and / or virucidal additives, as functional additives. For this purpose, the dirt-repellent coating 24 can contain, for example, a benzalkonium halide and a compound selected from the group consisting of didecyldimethylammonium halides, 3-iodo-2-propynylbutylcarbamate, diiodomethyl-p-tolylsulfone, and thiabendazole.
[0044] Figure 4 shows, by way of example, a printed security paper 30 produced using the security substrate 25 of Figure 3. A front-side print 34 and a back-side print 36 are applied to the dirt-repellent coatings 24, 26, for example, using offset, intaglio, or screen printing. The printed security paper 30 can, in particular, be a banknote, such as the banknote 10 of Figure 1.
[0045] In a further development of the invention illustrated in Fig. 5, a partial or full-surface internal printing layer 42 is provided between the fiber substrate body 22 and one of the dirt-repellent coatings 24 in a security substrate 40. It is understood that such an internal printing layer can also be provided on both sides of the security substrate 40 between the fiber substrate body 22 and the respective dirt-repellent coating 24, 26. The dirt-repellent coating can also be provided on only one of the two main surfaces of the fiber substrate body 22, as in Fig. 2.
[0046] With reference to Fig. 6, a pre-printed security substrate 40 according to
[0047] Fig. 5 can be provided with additional outer printing layers applied to the dirt-repellent coatings 24, 26, for example in the form of a front and / or back print 34, 36, to obtain a printed security paper 50. For example, the inner printing layer 42 can provide a common background print for an entire banknote series, while the front and back prints 34, 36 form individual designs for the various denominations.
[0048] Figure 7 shows a security substrate 60 according to a further embodiment of the invention, in which a fiber substrate body 22 of the type described above is provided on its opposite main surfaces with a dirt-repellent film 62 and together these two films form a composite security substrate.
[0049] During further processing into a security paper, a front or back print can be applied to the dirt-repellent films 62, as already fundamentally described above in connection with Figures 4 and 6. In addition, a partial or full-surface print layer can be provided between the fiber substrate body 22 and one or both of the dirt-repellent films 62 in order to obtain a partially pre-printed security substrate.
[0050] The dirt-repellent films 62 can be provided with a biocidal treatment, for example based on quaternary ammonium salt compounds.
[0051] 10 banknotes
[0052] 12 Security substrate 14, 16 Printing elements
[0053] 18 Portrait Watermarks
[0054] 20, 25 Safety substrate
[0055] 22 fiber substrate bodies
[0056] 24, 26 dirt-repellent coating 30 printed security paper
[0057] 34 Front printing
[0058] 36 Back printing
[0059] 40 Security substrate
[0060] 42 inner printing layer 50 printed security paper
[0061] 60 security substrate
[0062] 62 dirt-repellent film
Claims
Patent claims 1. Security substrate for the production of security and valuable documents, with a fiber substrate body containing by mass: 40% to 96% dry weight of fibers, in particular cellulose fibers, based on the dry weight of the fiber substrate body, 1% to 20% dry weight, based on the dry weight of the fibers, of at least one anionic polymer with a glass transition temperature T g above - 40 °C, especially a carboxylated polymer, and 0.5% to 5% dry weight of at least one cationic precipitant, based on the dry weight of the fibers, wherein the anionic polymer is present in a precipitated form on the surface of the fibers, characterized in that the fiber substrate body is provided with a dirt-repellent layer on at least one of its main surfaces.
2. Security substrate according to claim 1, characterized in that the fiber substrate body is provided on its opposite main surfaces with a dirt-repellent film and together these two films form a composite security substrate.
3. Security substrate according to claim 1, characterized in that the fiber substrate body is provided with a dirt-repellent coating on at least one of its main surfaces.
4. Security substrate according to claim 3, characterized in that the dirt-repellent coating consists of a composition containing an acrylate system as the sole binder and no fillers.
5. Security substrate according to claim 3, characterized in that the dirt-repellent coating is formed on the basis of polyurethanes.
6. Security substrate according to claim 5, characterized in that the dirt-repellent coating consists of a composition containing 50% to 70% by dry weight of a transparent or translucent binder and 30% to 50% of a silicon oxide and optionally at least one functional additive, the sum of said components constituting 100% of the composition, and wherein the elastomeric binder is selected from the group formed by polyurethanes usable in the form of stabilized aqueous dispersions.
7. Security substrate according to claim 5, characterized in that the dirt-repellent coating consists of a composition containing a non-pigmented polyurethane and optionally at least one functional additive.
8. Security substrate according to at least one of claims 3 to 7, characterized in that the dirt-repellent coating contains biocidal additives, in particular fungicidal, bactericidal and / or virucidal additives, as functional additives.
9. Security substrate according to at least one of claims 3 to 7, characterized in that the dirt-repellent coating contains visually and / or mechanically verifiable feature substances as functional additives.
10. Safety substrate according to at least one of claims 1 to 9, characterized in that the fiber substrate body contains 0.001% to 1% dry weight of at least one biocidal agent.
11. Security substrate according to at least one of claims 1 to 10, characterized in that the anionic polymer of the fiber substrate body is selected from carboxylated styrene-butadiene copolymers.
12. Security substrate according to at least one of claims 1 to 11, characterized in that a partial or full-surface inner printing layer is provided between the fiber substrate body and at least one dirt-repellent layer.
13. Security paper with a security substrate according to one of claims 1 to 12 and with at least one partial or full-surface outer printing layer applied to a dirt-repellent layer.
14. Security paper according to claim 13, characterized in that the outer printing layer is covered with a further dirt-repellent layer, in particular a dirt-repellent coating.
15. A method for producing a security substrate according to any one of claims 1 to 12, wherein a fiber substrate body is provided which contains by mass: 40% to 96% dry weight of fibers, in particular cellulose fibers, based on the dry weight of the fiber substrate body, 1% to 20% dry weight, based on the dry weight of the fibers, of at least one anionic polymer with a glass transition temperature T g above -40 °C, especially of a carboxylated polymer, and 0.5% to 5% dry weight of at least one cationic precipitant, based on the dry weight of the fibers, wherein the anionic polymer is present in a precipitated form on the surface of the fibers, and the fiber substrate body is provided on at least one of its main surfaces with a dirt-repellent layer, in particular with a dirt-repellent coating or dirt-repellent films.
16. A method according to claim 15, characterized in that a dirt-repellent coating with a basis weight between 1 and 6 g / m 2 , especially between 2 and 3 g / m 2 is applied by squeegee or printing.