DE102022133075A1 - Security substrate, security paper and manufacturing process - Google Patents

Abstract

The invention relates to a security substrate (20) for the production of security and value documents, with a fiber substrate body (22) 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 Tg of over - 40 °C, in particular 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. According to the invention, the fiber substrate body (22) is provided with a dirt-repellent layer (24, 26; 62) on at least one of its main surfaces.

Description

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.

Banknotes and other valuable documents are made from security substrates, which often consist of paper or have a paper core and have special security features, such as an at least partially embedded security thread or a watermark.

It is known that the circulation time of banknotes depends heavily on the stress they are subjected to. Early soiling is one of the main reasons for the limited circulation time of banknotes. Since banknote paper is very porous, it has a relatively large surface and a high level of surface roughness. The size of the resulting protrusions and cavities is below the resolution limit of the human eye, but compared to a smooth surface they still represent starting points for dirt deposits.

In the print WO 2021/023601 A1 A wrinkle- and dirt-resistant fibre substrate obtained by a wet process and having high mechanical strength is proposed in order to prevent banknotes made from the fibre substrate from being exposed to excessive microbial stress during their ageing in circulation.

Based on this, the invention is based on the task of further improving the circulation time of known security substrates. Ideally, typical properties of paper banknotes, such as sound, color, feel and transmission properties, are retained.

This object is achieved by the features of the independent claim. Further developments of the invention are the subject of the dependent claims.

• - 40 % bis 96 % Trockengewicht an Fasern, insbesondere Zellulosefasern, bezogen auf das Trockengewicht des Fasersubstratkörpers,
• - 1 % bis 20 % Trockengewicht, bezogen auf das Trockengewicht der Fasern, mindestens eines anionischen Polymers mit einer Glasübergangstemperatur T_g von über - 40 °C, insbesondere eines carboxylierten Polymers, und
• - 0,5 % bis 5 % Trockengewicht mindestens eines kationischen Fällungsmittels, bezogen auf das Trockengewicht der Fasern,

wobei das anionische Polymer in einer ausgefällten Form an der Oberfläche der Fasern vorliegt.According to the invention, a security substrate for the production of security and value documents comprises a fiber substrate body which contains by mass:

• - 40% to 96% dry weight of fibres, in particular cellulose fibres, based on the dry weight of the fibre substrate body,
• - 1% to 20% dry weight, based on the dry weight of the fibres, of at least one anionic polymer with a glass transition temperature T _g of more than - 40 °C, in particular a carboxylated polymer, and
• - 0.5% to 5% dry weight of at least one cationic precipitant, based on the dry weight of the fibres,

wherein the anionic polymer is present in a precipitated form on the surface of the fibers.

As a special feature, the fiber substrate body is provided with a dirt-repellent layer on at least one of its main surfaces.

A fiber substrate body of the type mentioned is described in the publication WO 2021/023601 A1 as a fiber substrate. The inventors have now found that the known fiber substrate body does indeed have a high z-strength, measured according to the Scott-Bond method, but that its resistance to rotation can surprisingly be 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 safety substrate.

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 a particularly high resistance to circulation.

In an advantageous variant of the invention, the dirt-repellent coating consists of a composition which contains an acrylate system as the exclusive binder and no fillers. The composition is preferably present on the fiber substrate body in a weight per unit area of between 1 and 6 g/m ² , in particular between 2 and 3 g/m ² . In particular, the dirt-repellent coating can consist of a composition as described in the publication WO 00/00697 A1 , the disclosure content of which is incorporated in the present application.

Advantageous embodiments of the composition are described in the WO 00/00697 A1 The composition can contain acrylates or a mixture of polymers or copolymers with a high acrylate content as a binder. The composition can also contain at least contain a substance with a visually and/or machine-detectable property for security features and/or coding. The substance mentioned 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.

According to another, equally advantageous variant of the invention, the dirt-repellent coating is formed on the basis of polyurethanes.

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 making up 100% of the composition, and the elastomeric binder being selected from the group formed by polyurethanes which can be used in the form of stabilized aqueous dispersions. Further details and advantageous embodiments of such a composition can be found in the document WO 2002/020902 A1 , the disclosure content of which is incorporated into the present application.

A dirt-repellent coating based on polyurethanes can also consist of a composition that contains a non-pigmented polyurethane and optionally at least one functional additive. Further details and advantageous embodiments of such a composition can be found in the publication WO96/28610 A1 , the disclosure content of which is incorporated into the present application.

The dirt-repellent coating in all variants of the invention advantageously contains biocidal additives as functional additives, in particular fungicidal, bactericidal and/or virucidal additives. In particular, quaternary ammonium salt compounds, diiodomethyl-p-tolylsulfone and 3-iodo-2-propynylbutylcarbamate (IPBC) and thiabendazole come into consideration as biocidal additives. These and other advantageously usable biocidal additives are described in the publication WO 2022/189043 A1 described, the disclosure content of which is incorporated into the present application. The use of singlet oxygen catalysts as biocidal additives is also advantageous.

According to an advantageous development of the invention, the dirt-repellent coating contains visually and/or mechanically testable feature substances as functional additives. In particular, luminescent, IR-absorbing and/or magnetic feature substances come into consideration.

The fiber substrate body itself can also have a biocidal finish and contain, for example, 0.001% to 1% dry weight of at least one biocidal agent. For an enhanced effect, a biocidal finish on the fiber substrate body itself can be combined with the above-described biocidal finish on the dirt-repellent coating of the fiber substrate body.

The anionic polymer of the fiber substrate body is advantageously selected from carboxylated styrene-butadiene copolymers.

The fiber substrate body is advantageously like the fiber substrate of the publication WO 2021/023601 A1 whose disclosure is fully incorporated in the present application. This applies in particular to the WO 2021/023601 A1 described advantageous embodiments of the anionic polymer, the cationic precipitant and the fibers of the fiber substrate body. A biocide, a humectant and fillers as described in the WO 2021/023601 A1 described in more detail may be present in the fiber substrate body.

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, engraving or screen printing layer. The security substrate then represents a pre-printed security substrate whose inner printing layers are well protected by the dirt-repellent layer.

The invention also includes a security paper with a security substrate of the type described and at least one partial or full-surface external printing layer applied to a dirt-repellent layer. The external printing layer can in particular be an offset, intaglio or screen printing layer. In order to prevent dirt from accumulating on an external printing layer, external printing layers can be covered with a further layer, for example a lacquer 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 'external printing layer' therefore refers only to the position of the printing layer outside the aforementioned dirt-repellent layers on the fibre substrate body and does not mean that such a printing layer represents the outermost layer of the security paper.

The security paper can in particular represent a banknote or other valuable document.

Finally, the invention also includes a method for producing a security substrate of the type described. First, a fiber substrate body with the above-mentioned composition is provided. The fiber substrate body can advantageously be produced according to one of the methods described in the WO 2021/023601 A1 described methods.

Then, in a first process variant, a dirt-repellent coating is applied to the fiber substrate body on one or both main surfaces. The dirt-repellent coating is preferably applied by knife coating or printing with a basis weight of between 1 and 6 g/m ² , in particular between 2 and 3 g/m ² . Before the dirt-repellent coating is applied, a printing layer can be applied to the fiber substrate in order to form an internal printing layer in the security substrate. After the dirt-repellent coating has been applied, the security substrate can be further processed in order to increase the smoothness of the surface, for example by calendering.

In another process variant, the fiber substrate body is provided with a dirt-repellent film on both sides in order to form a composite safety substrate together with these. The fiber substrate body can be laminated together with the two films, for example.

Further embodiments and advantages of the invention are explained below with reference to the figures, in which a true-to-scale and true-to-proportion reproduction was omitted in order to increase clarity.

• 1 eine schematische Darstellung einer Banknote mit einem erfindungsgemäßen Sicherheitssubstrat,
• 2 und 3 jeweils ein Sicherheitssubstrat nach einem Ausführungsbeispiel der Erfindung,
• 4 ein bedrucktes Sicherheitspapier, hergestellt unter Verwendung des Sicherheitssubstrats der 3,
• 5 ein Sicherheitssubstrat nach einem weiteren Ausführungsbeispiel der Erfindung,
• 6 ein bedrucktes Sicherheitspapier, hergestellt unter Verwendung des Sicherheitssubstrats der 5, und
• 7 ein Sicherheitssubstrat nach einem weiteren Ausführungsbeispiel der Erfindung mit schmutzabweisenden Folien.

Show it:

• 1 a schematic representation of a banknote with a security substrate according to the invention,
• 2 and 3 each a security substrate according to an embodiment of the invention,
• 4 a printed security paper produced using the security substrate of the 3 ,
• 5 a security substrate according to another embodiment of the invention,
• 6 a printed security paper produced using the security substrate of the 5 , and
• 7 a security substrate according to a further embodiment of the invention with dirt-repellent films.

The invention will now be explained using the example of security substrates for banknotes. 1 shows a schematic representation of a banknote 10 with a security substrate 12, which is provided with printing elements 14, 16, a portrait watermark 18 and possibly further security features not shown in the figure.

2 shows an embodiment of a security substrate 20 that can be used 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.

The fiber substrate body 22 is designed in the manner described above. In the embodiment of the 2 Specifically, the fiber substrate body 22 comprises 60% to 96%, preferably even 70% to 96%, 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%, dry weight of a carboxylated styrene-butadiene copolymer, which preferably has a glass transition temperature of -30°C to -20°C and particularly preferably of -25°C, and 0.8% to 3.5% dry weight of at least one cationic precipitant, based on the dry weight of the fibers, preferably a polyamide-polyamine-epichloride resin.

The fiber substrate body 22 has a particularly high z-strength or splitting strength, which can be determined, for example, according to the Scott-Bond method.

The dirt-repellent coating 24 applied to the fiber body consists of a composition that contains an acrylate system as the sole binding agent and no fillers. In the exemplary embodiment, the coating 24 was applied over the entire surface of the fiber substrate body 22 by a doctor blade or printed on, the basis weight of the coating being between 1 and 6 g/m ² and in particular 2-3 g/m ² .

Since the dirt-repellent coating 24 does not contain any 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 by dirt. 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 small 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 the 1 , which is not affected by the dirt-repellent properties.

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 in the security substrate 25 of the 3 shown.

The safety substrates 20, 25 of the 2 and 3 have a high z-strength due to the fiber substrate body used and a 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.

4 shows an example of a printed security paper 30 which is produced using the security substrate 25 of the 3 A front print 34 and a back print 36 are applied to the dirt-repellent coatings 24, 26, for example by offset, intaglio or screen printing. The printed security paper 30 can in particular be a banknote, such as the banknote 10 of the 1 act.

In a 5 In the illustrated development of the invention, a partial or full-surface inner print layer 42 is provided in a security substrate 40 between the fiber substrate body 22 and one of the dirt-repellent coatings 24. It is understood that such an inner print 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 2 only be provided on one of the two main surfaces of the fiber substrate body 22.

Regarding 6 a pre-printed security substrate 40 can be 5 with additional external printing layers applied to the dirt-repellent coatings 24, 26, for example in the form of a front and/or back print 34, 36, in order to obtain a printed security paper 50. For example, the inner printing layer 42 can provide a background print common to an entire series of banknotes, while the front and back prints 34, 36 form individual designs for the various denominations.

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.

During further processing into a security paper, a front or back print can be applied to the dirt-repellent films 62, as described above in connection with 4 and 6 already described in principle. In addition, a partial or full-surface printing 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.

The dirt-repellent films 62 can be provided with a biocidal treatment, for example based on quaternary ammonium salt compounds.

List of reference symbols

10

Banknote

12

Security substrate

14,16

Printing elements

18

Portrait watermark

20, 25

Security substrate

22

Fibre substrate body

24, 26

dirt-repellent coating

30

printed security paper

34

Front printing

36

Back printing

40

Security substrate

42

internal printing layer

50

printed security paper

60

Security substrate

62

dirt-repellent film

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2021023601 A1 [0004, 0009, 0021, 0025]
• WO 0000697 A1 [0012, 0013]
• WO 2002020902 A1 [0015]
• WO 9628610 A1 [0016]
• WO 2022189043 A1 [0017]

Claims (16)

Security substrate for the production of security and value documents, with a fiber substrate body 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 of above - 40 °C, in particular 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. Safety 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 safety substrate. Safety 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. Safety substrate according to Claim 3 , characterized in that the dirt-repellent coating consists of a composition containing an acrylate system as the exclusive binder and no fillers. Safety substrate according to Claim 3 , characterized in that the dirt-repellent coating is based on polyurethanes. Safety substrate according to Claim 5 , characterized in that the anti-stain 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 representing 100% of the composition, and wherein the elastomeric binder is selected from the group formed by polyurethanes which can be used in the form of stabilized aqueous dispersions. Safety 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. Security substrate according to at least one of the Claims 3 until 7 , characterized in that the dirt-repellent coating contains biocidal additives, in particular fungicidal, bactericidal and/or virucidal additives, as functional additives. Security substrate according to at least one of the Claims 3 until 7 , characterized in that the dirt-repellent coating contains visually and/or mechanically testable feature substances as functional additives. Security substrate according to at least one of the Claims 1 until 9 , characterized in that the fiber substrate body contains 0.001% to 1% dry weight of at least one biocidal agent. Security substrate according to at least one of the Claims 1 until 10 , characterized in that the anionic polymer of the fiber substrate body is selected from carboxylated styrene-butadiene copolymers. Security substrate according to at least one of the Claims 1 until 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. Security paper with a security substrate according to one of the Claims 1 until 12 and with at least one partial or full-surface external printing layer applied to a dirt-repellent layer. 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. Method for producing a security substrate according to one of the Claims 1 until 12 , in which - a fibrous substrate body is provided which contains by mass: -- 40 % to 96 % dry weight of fibres, in particular cellulose fibres, based on the dry weight of the fibrous 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 of more than - 40 °C, in particular 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. Procedure according to Claim 15 , characterized in that a dirt-repellent coating with a basis weight between 1 and 6 g/m ² , in particular between 2 and 3 g/m ² is doctored or printed onto the fiber substrate body on one or both main surfaces.

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