EP2357278A1 - Valuable document with silicon resin coating and method for its production - Google Patents

Abstract

The valuable document such as bank note, certificate, share or identification document, comprises a flat paper substrate (2), which has a dirt-repellent coating (3, 3') at each of its both major surfaces, where the coating has a composition, which contains silicone resin and/or fluorine silicone resin and polytetrafluoroethylene solid particles. The coating is uppermost cover layer of the valuable document. The valuable document is printed under the coating and/or has a coating, which is free from silicone resin and/or fluorine silicone resin. The valuable document such as bank note, certificate, share or identification document, comprises a flat paper substrate (2), which has a dirt-repellent coating (3, 3') at each of its both major surfaces, where the coating has a composition, which contains silicone resin and/or fluorine silicone resin and polytetrafluoroethylene solid particles. The coating is uppermost cover layer of the valuable document. The valuable document is printed under the coating and/or has a coating, which is free from silicone resin and/or fluorine silicone resin. The coating is present on an outer- and an inner sublayer, where both sublayers contain silicone resin and/or fluorine silicone resin. The inner sublayer is free from polytetrafluoroethylene solid particles. The average diameter of polytetrafluoroethylene solid particles is 30-200 nm. The proportion of polytetrafluoroethylene solid particles is 1-20 wt.%. The coating has a physically drying silicone resin and/or fluorine silicone resin or silicone resin crosslinked over silicon-oxygen bonds and/or fluorine silicone resin. An independent claim is included for a method for producing a valuable document.

Description

The invention relates to a value document, such as a banknote, certificate, share, identity document or the like, having a flat substrate which has a dirt-repellent coating on each of its two main surfaces. The invention also relates to a method for producing such a value document, as well as the use of a silicone resin composition for coating documents of value.

The invention will be described below with reference to banknotes, but is not limited to banknotes, but suitable for any value documents, such as the above documents, shares and identity documents.

Banknotes and other value documents are usually made of so-called security papers having security features, such as a security thread partially embedded in the paper and a watermark. In addition, the value documents are printed, to increase the security against counterfeiting often with elaborate print images. In this case, technically demanding and not accessible to everyone printing methods, such as intaglio, at least for some of the picture elements used. Furthermore, documents of value, such as banknotes, are also characterized partly by the paper substrate and partly by its treatment (such as one-sided or two-sided calendering) Steel intaglio printing), namely their grip and flexural rigidity, and the sound characteristic of deformation and wrinkling.

During their circulation, banknotes are exposed to heavy burdens of various kinds which limit their orbital period. The circulation period of a banknote depends essentially on its demand. Certain denominations are preferably used commercially and thus have a lower cycle time due to the increased exposure to environmental influences. One cause of the limitation of the circulation time is mechanical stress due to abrasion, folding or creasing. However, the main reason for the limited circulation time of banknotes is their premature pollution. Since banknote paper is very porous, it has a large surface area and a high surface roughness. The surface roughness favors dirt deposits considerably compared to a smooth surface.

Therefore, dirt is the most important factor that determines the life of a banknote or other value document. Dirt can be liquid or solid, and liquid dirt can be oily or watery. A particularly serious problem is the sensitivity of paper to oil and water. Due to the lack of oil and water repellency properties of untreated paper, oil and water penetrate rapidly into the material. Water softens the paper, thereby reducing its mechanical stability, which can lead to surface abrasion or cracking of the wet spots. Soiling of fats and oils has the additional disadvantage that they form ugly "grease stains" in the paper, which are practically indelible. The affinity of the lipophilic substances for the paper is further increased by the equipment of the paper with mass glue.

In this respect, there is a need to protect value documents, and in particular the heavily used banknotes, against contamination of any kind, thereby increasing the circulation time.

Many attempts have therefore been made to extend the life of banknotes. In the WO 98/15418 It was proposed to make banknotes entirely from a plastic substrate. However, in this case, the usual and proven security features, such as portrait watermark and window security thread, must be dispensed with, as well as the special properties, such as the sound and feel of the banknote paper. The customary in the banknote area printing in gravure, in particular intaglio printing, which serves as an additional tactile authenticity mark due to the relief resulting from the inking, is only a flat relief on plastic substrates. In addition, pure plastic banknotes are highly sensitive to heat, and in countries with climatically unfavorable conditions, the plastic substrates tend to shrink. Also applied to paper substrates protective films cause changes in feel and tactility of banknotes.

Furthermore, attempts have been made to increase their protection against contamination, and thus their circulation time, by suitable coatings of paper substrates. There are both variants in which the coating before printing, as well as variants in which the coating is made after printing the banknotes.

From the publication WO 00/00697 is a security paper for banknotes with a dirt-repellent coating known in its typical properties, such as printability, sound and color, over a uncoated paper remains largely unchanged despite the coating. On the banknote paper while a coating composition is applied, which contains only a binder, in particular acrylates, and no fillers. The composition is applied in such a layer thickness that on the one hand a smooth surface and thus little opportunities for dirt accumulation arise, and on the other hand, the coating is thin enough so as not to affect the other mentioned properties of the paper.

The publication WO 2004/072378 describes a security paper with a flat substrate, which is at least partially provided with a dirt-repellent protective layer to extend the life and fitness for circulation. The protective layer comprises at least two lacquer layers, wherein the first lower lacquer layer is formed by a physically drying lacquer layer applied to the substrate, which makes contact with the underlying substrate and closes the pores, and wherein the second upper lacquer layer protects the substrate from physical and chemical influences protects. The lower, physically drying lacquer layer is preferably a layer based on polyurethanes, and the upper lacquer layer is a radiation-curing lacquer layer. This double-layer coating of different coating systems can be applied before or after printing.

The publication DE 10 2005 052 672 discloses a security paper for producing value documents which is treated at least partially and at least on one surface with an impregnation composition which ensures an increased circulation capability, wherein the impregnation composition comprises at least one compound selected from the group consisting of fluorocarbon resins, surface-active , fluoroaliphatic polymeric esters and fluorine-containing copolymers based on acrylate. The coating provides a special protection against lipophilic and aqueous substances, which is essentially due to the reduction of the surface energy of the impregnated substrates by the fluorocarbon resins.

Each of the known coatings has certain disadvantages. Paints based on polyurethane and on acrylate are usually used in relatively high layer thicknesses. This leads to a "plastification" of banknotes. The banknote-typical "grip" and "sound" are thereby lost. In addition, common paints, especially acrylate and UV coatings, lead to relatively hard coatings, which are good dirt repellent, but weaken the entire substrate structure, that is, the sometimes sensitive mechanical-physical paper properties are weakened. In addition, hard outer layers create a kind of sandwich structure of the entire substrate, which can lead to splitting of the bank notes at the edges or at kinks.

In the DE 10 2005 052 672 Although disclosed fluorocarbon resin coatings provide quite a good protection, it is nevertheless desirable to improve the protective effect, and in particular to provide coatings which are adapted to the particular requirements of bank notes, for example special taktile security features, such as Intaglio reliefs, not leveling, but receive the tactility of the banknotes.

The publication US 2005/0075020 A1 discloses silicone coating compositions for substrates, such as paper, for producing water-repellent coatings or release coatings. The compositions contain functionalized polyorganosiloxanes with Si-H and Si-IE units (Si-IE is a group having at least one ethylenic unsaturation), wherein the Si-H and Si-IE units can react with each other under polyaddition. Crosslinkers with mono-, di- and optionally also tri- or tetra-functional Si units may be present. A coating of value documents with these coating compositions is not disclosed.

The publication EP 1 004 632 B1 discloses a silicone coating composition for the production of release coatings on substrates such as paper, metal foil or plastic. The composition contains a linear trimethylsiloxy-terminated polydiorganosiloxane containing at least two alkenyl groups, optionally a linear dimethylalkenylsiloxy-terminated polydiorganosiloxane containing at least two alkenyl groups per molecule, a polyorganohydrogensiloxane having at least three silicon-bonded hydrogen atoms per molecule, a platinum catalyst and an inhibitor. The composition may contain fillers, for example inorganic fillers, pigments, powders of organic resins, or other additives.

• Sie soll einen guten Schutz gegen Verschmutzungen aller Art, das heißt festen und flüssigen, wässrigen und öligen Schmutz, bieten.
• Sie soll die Umlaufdauer des Wertdokuments erhöhen.
• Sie soll z.B. bei Verwendung eines papierartigen Substrats den ursprünglichen Papiercharakter (Haptik) möglichst wenig verändern, so dass Griff und Klang des Wertdokuments erhalten bleiben.
• Sie soll sich z.B. bei Verwendung eines papierartigen Substrats weich dem Papier anschmiegen und Plastifizierungen, die zu Spaltung führen können, vermeiden.
• Sie soll spezielle Sicherheitsmerkmale, wie Reliefs und andere taktile Sicherheitsmerkmale oder Wasserzeichen nicht verfälschen.

The object of the present invention is to provide a composition which, when used for coating banknotes and other value documents, preferably has the following properties:

• It is intended to provide good protection against soiling of all kinds, ie solid and liquid, aqueous and oily dirt.
• It should increase the circulation time of the value document.
• When using a paper-like substrate, it should, for example, change the original paper character (haptic) as little as possible so that the handle and sound of the value document are retained.
• For example, when using a paper-like substrate, it should conform softly to the paper and avoid plastifications that can lead to cleavage.
• It should not falsify special security features, such as reliefs and other tactile security features or watermarks.

It is an object of the present invention, in particular, to provide a value document, such as a banknote, with an increased circulation time while retaining the value-document-typical properties, such as haptics and tactility.

It is also an object of the present invention to provide a method for producing such a value document.

The objects are achieved by the value document, the method and the use with the features as indicated in the respective independent claims. Specific embodiments of the invention are set forth in the respective dependent claims.

A first aspect of the invention relates to a value document, such as a banknote, certificate, share or identity document, having a flat substrate, eg a paper substrate, which has a dirt-repellent coating on each of its two main surfaces, wherein the coating has a composition comprising at least one silicone resin and / or fluorosilicone resin and PTFE solid particles.

The coating is preferably the uppermost, final cover layer of the value document, wherein the value document can be printed under the coating and / or can have a coating which is free of silicone resin and / or fluorosilicone resin.

The coating may e.g. consist of an outer and an inner sub-layer, both of which contain at least one silicone resin and / or fluorosilicone resin, wherein the inner sub-layer is preferably free of PTFE solid particles.

The average diameter of the PTFE particles is preferably 5 nm to 500 nm, more preferably 30 nm to 200 nm.

The proportion of the PTFE particles in the coating is preferably from 1 to 50 wt .-%, more preferably from 1 to 20 wt .-% in dry weight.

The coating may preferably comprise a physically drying silicone resin and / or fluorosilicone resin.

1. (a) Bereitstellen einer Lösung oder einer Dispersion eines Silikonharzes und/ oder Fluorsilikonharzes oder von Präpolymeren des Silikonharzes und/oder Fluorsilikonharzes, die außerdem PTFE-Festpartikel enthält,
2. (b) Auftragen der Lösung oder Dispersion auf jede der beiden Hauptflächen des Wertdokument-Substrats zur Erzeugung der Beschichtung, und
3. (c) Trocknen der Beschichtung durch Entfernen des flüssigen Trägermediums der Lösung oder Dispersion und gegebenenfalls Vernetzen der Präpolymere des Silikonharzes und/ oder Fluorsilikonharzes bei einer zur Vernetzung ausreichenden Temperatur.

A second aspect of the invention relates to a method of manufacturing a value document, such as a banknote; Document, share or identity document, comprising a sheet substrate, eg a paper substrate having a dirt-repellent coating on each of its two major surfaces, comprising the following steps:

1. (a) providing a solution or a dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of the silicone resin and / or fluorosilicone resin, which also contains PTFE solid particles,
2. (b) applying the solution or dispersion to each of the two major surfaces of the value document substrate to produce the coating, and
3. (c) drying the coating by removing the liquid carrier medium of the solution or dispersion and optionally crosslinking the prepolymers of the silicone resin and / or fluorosilicone resin at a temperature sufficient for crosslinking.

Optionally, after step (b) or after step (c), a solution or a dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of the silicone resin and / or fluorosilicone resin, which further contains PTFE particles, may be provided and onto at least one of the two major surfaces of the value-document substrate, wherein the solution or dispersion is the same as or different from the first-applied solution or dispersion, and wherein the applied solutions or dispersions co-produce the coating.

Optionally, prior to step (b), a solution or dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of the silicone resin and / or fluorosilicone resin containing no PTFE particles may be provided and applied to at least one of the two major surfaces of the valuable document substrate. and optionally removing the liquid carrier medium of the solution or dispersion prior to step (b), wherein the applied solutions or dispersions co-produce the coating.

Preferably, an application amount (dry) of 0.1 g / m ² to 15 g / m ² of silicone resin and / or fluorosilicone resin including PTFE particles is applied per main surface of the valuable document substrate.

The coating preferably has a thickness of 0.5 to 10 μm.

A third aspect of the invention relates to the use of a composition comprising at least one silicone resin and / or fluorosilicone resin or prepolymers of the silicone resin and / or fluorosilicone resin, and also PTFE particles, for producing a stain-resistant, circulation-time-prolonging coating of a value document, the silicone resin and / or fluorosilicone resin and the PTFE particles have the characteristics stated in the preceding description of the first aspect of the invention.

The invention will be described below with reference to preferred embodiments.

According to the invention, fully printed documents of value are finally provided on their two surfaces with a coating containing or consisting of silicone resins and / or fluorosilicone resins (hereinafter referred to collectively as "silicone resins") and polytetrafluoroethylene (PTFE) particles.

The silicone resins used according to the invention are polyorganosiloxanes in which silicon atoms are linked via oxygen atoms in a chain-like manner, and preferably also in a net-like manner. The remaining valences of the silicon are saturated by organic radicals, for example hydrocarbon radicals, in particular by methyl groups and phenyl groups, but also other hydrocarbon radicals, such as ethyl groups and propyl groups may be included. Since pure methyl silicone resins are relatively brittle, while the elasticity increases with the content of phenyl groups, polyorganosiloxanes whose silicon atoms are partially substituted with phenyl groups are preferred.

Silicone resins are in prepolymerized form, that is in the form of oligomers, commercially. The oligomers may be e.g. to linear polysiloxanes (with monofunctional and difunctional Si units), branched polysiloxanes (with mono-, di- and tri-functional Si units), cyclic polysiloxanes (from difunctional units) and already more or less cross-linked silicones ( with crosslinking by means of trifunctional and / or tetrafunctional Si units).

Preferably, solutions of silicone resins in organic solvents, such as gasoline, aromatics, esters, ketones, alcohols, are used, but also aqueous emulsions and suspensions are useful.

The silicone resin compositions are applied according to the invention on the surfaces of the "finished" value documents. Value documents are typically not produced in the form of individual benefits, but in the form of webs or sheets, from which then the individual benefits are separated. A "finished" document of value within the meaning of the present invention is a document of value which, except for the coating according to the invention still to be applied, is capable of running, irrespective of whether it is present as a single use or as a sheet or web, of which the individual benefits are still to be separated.

When the silicone resin composition is high molecular weight linear polyorganosiloxanes and / or highly branched and / or already crosslinked polyorganosiloxanes does not necessarily have to take place after application of the composition, a further polymerization or crosslinking. In this case, the coating may be physically dried, by "physically drying" it is meant that the composition solidifies by removing the carrier liquid, that is, the solvent or dispersant, without any chemical reaction of the polymer components.

Alternatively, silicone resin compositions are used with oligomers containing reactive groups which, after application of the composition, e.g. at elevated temperature and / or with the aid of catalysts, lead to chain extension and / or crosslinking of the oligomers. In particular, crosslinking is desired.

As crosslinking reactions are e.g. Polycondensation and polyaddition in question.

Condensation reactions require oligomers in which the mono- and / or di- and / or tri-functional units still contain silanol groups. The content of silanol groups depends on the desired degree of crosslinking, ie the ratio of mono-, di-, tri- and tetra-functional units in the finished crosslinked coating.

Alternatively, crosslinking may be by addition reactions. In this case, the silicone resin composition to be applied must contain both oligomers having olefinically unsaturated groups, that is, polyorganosiloxanes in which part of the organic substituents of the silicon are olefinically unsaturated substituents (for example, vinyl groups or allyl groups), as well as oligomers having a hydrosilylation reaction with these groups can enter, ie silanes and / or siloxanes with Si-H bonds. The oligomers having unsaturated groups on the one hand and the oligomers having Si-H bonds on the other hand are stored separately and mixed immediately before application. The number of olefinically unsaturated groups and the Si-H bonds determines the degree of crosslinking. Silicone resin compositions that are curable after application to paper by addition reactions are described, for example, in U.S. Pat US 2005/0075020 A1 described, the disclosure of which is fully incorporated in this regard in this invention.

Both condensation and addition require suitable catalysts as known to those skilled in the art. Suitable addition catalysts are, for example, compounds of metals of the platinum group, in particular platinum and rhodium.

Alternatively or in addition to the fluorine-free silicone resins, fluorosilicone resins may be used. Fluorosilicone resins are at least equal to non-fluorinated silicone resins in their stain-resistant properties and durability, for example, in their heat resistance. In addition, they are characterized by a comparison with the non-fluorinated silicone resins even better chemical resistance. In particular, by using a coating containing fluorosilicone resins and PTFE solid particles, the resistance of the coated value document to organic solvents such as gasoline, toluene, alcohol, ether, etc. can be increased. This increase in the resistance to organic solvents can be used, in particular, to protect against a manipulative splitting of multi-layer value-added substrates, which have, for example, superimposed plastic or polymer layers.

Chemically, the fluorosilicone resins differ from the aforementioned silicone resins in that part of the alkyl groups is replaced by fluoroalkyl groups. Both partially fluorinated and perfluorinated alkyl groups are suitable, with perfluorinated alkyl groups being preferred.

Essential to the coating compositions to be used according to the invention is that they contain polytetrafluoroethylene (PTFE) particles. The PTFE particles are dispersed in the coating composition, or dispersed in at least one of the components in two-component compositions, or dispersed therein just prior to application of the coating composition. Using surfactants, in particular ionic surfactants, it is possible to prepare stable dispersions with a content of PTFE particles of up to 60% by weight. It should be noted, however, that PTFE particles are usually white, changing the color of the paper. This means that the content of PTFE particles should not be too high, so that there are no significant color changes. Preference is given to coating compositions in which the content of PTFE particles in dry weight is from 1 to 50% by weight, more preferably from 1 to 20% by weight and especially preferably from 5 to 15% by weight.

The PTFE particles preferably have an average particle diameter of 5 nm to 500 nm, preferably from 30 to 200 nm, and particularly preferably from 60 to 150 nm.

The concentration of the silicone resins or of the oligomeric silicone resin precursors in the solutions or dispersions to be applied is preferably about 5 to 30 wt .-%, more preferably about 10 to 20 wt .-%, depending on the desired application amount or layer thickness.

In addition to the silicone resins and / or fluorosilicone resins or their precursors, the PTFE particles, the carrier liquid (aqueous, and in particular organic media), and optionally suitable catalysts, the coating compositions to be used according to the invention may also contain conventional auxiliaries. Common auxiliaries are, for example, coalescing agents, leveling agents, wetting agents, defoaming agents, viscosity modifiers, dispersing aids, dyes and diluents. Antimicrobial agents and feature substances, such as luminescent substances, may also be included in the composition.

The coating compositions are suitable for coating all common value-document substrates, in particular for paper substrates made of cotton fibers or predominantly cotton fibers, as they are preferably used in the field of security papers. However, papers made of cellulosic fibers and papers at least partially made of plastic fibers may generally be coated. It is irrelevant whether the substrate is single-layer or multi-layer, glued or unsized, or optionally with primers or any other layers, such as a lacquer layer equipped. It is very advantageous if the surfaces to be coated have a polar character, such as paper. On such surfaces, the advantageous properties of the coatings are particularly important. Furthermore, as a valuable document substrate, a plastic layer, for example a plastic film, or a film composite can be used. Such a film may additionally be monoaxially or biaxially stretched. Such a stretching of the film leads, inter alia, that it receives polarizing properties that can be used as a security feature in the document of value. Also, a multi-ply value-document substrate such as a multilayer composite can be used, which has, for example, a layer of paper or a paper-like material. On this layer, for example, a transparent plastic or polymer layer is laminated from both sides, whereby such a multilayer composite has an extremely high stability and durability. In this case, security papers are used with plastic or polymer coated paper layers for the production of composite film banknotes. Conversely, the multilayer composite may also comprise a central layer of a plastic or polymeric material, which is coated on both sides with a respective layer of paper or a paper-like material. As a multilayer substrate material, a multilayer, paper-free composite material can also be used.

The advantageous properties of the coatings according to the invention can in principle be divided into two groups, the protective properties and, thus, circulation-time-prolonging properties on the one hand, and the "character-preserving" properties on the other hand. The superiority of the silicone resin coatings (the coatings with silicone resins and / or fluorosilicone resins and PTFE particles) is particularly evident in the character-preserving properties. Namely, the silicone resin coatings can already achieve an excellent protective effect in very thin layers, ie with very low application rates. Suitable application rates in the dry state are in the range of 0.1 g / m ² to 15 g / m ² per side, preferably in the range of 0.5 g / m ² to 2 g / m ² per side, that is per main area, of the value document. The protective coatings in the dry state have a thickness of about 0.5 to 10 microns, preferably from 0.5 to 2 microns. In the order quantity and, consequently, the thickness is too Note that excessively high application rates are detrimental because silicone coatings can rub off if the layer thickness is too high. Therefore, in the present case, it is mainly a closing of the pores and a thin coating of the surface.

These low application rates and coating thicknesses cause e.g. when paper substrates are used, the original paper character (haptic of the value document) is hardly changed. In addition, the thin silicone layer follows all surface irregularities, so that surface structures, such as Intaglio reliefs, which are partially leveled by other coatings, are well preserved, so that the tactility of the value document remains substantially unchanged.

It is believed that this ability to form very thin, substrate-characterizing coatings is associated with the formation of strong physical and possibly chemical interactions with polar substrate surfaces, such as paper surfaces. Silicone resins have on the one hand a polar siloxane skeleton, and on the other hand non-polar organic radicals. Upon contact with polar surfaces, the silicone resin aligns so that as large as possible areas of the siloxane backbone are in contact with the polar surface, while the nonpolar groups point away from the surface. Theoretically, a two-dimensional mesh of silicone resin having the same dimensions as the surface to be coated is sufficient to cover the entire surface. Of course, in practice, such extreme spreading of the entangled polymers is not possible, but it is unmistakable that the silicone resin molecules tend to cover as large a surface area as possible. The coverage of large surface areas with very small amounts of silicone resin can still be supported by the use very dilute silicone resin solutions and dispersions. At high concentrations, there is a risk that the polymer molecules interfere with each other during their unfolding.

Surprisingly, it has been found that the spread of the silicone resins and fluorosilicone resins is still significantly improved by the admixture of PTFE particles. In addition, the dirt-repellent properties are further improved by the addition of PTFE particles. Without wishing to be bound by any particular theory, it is believed that the PTFE particle coating may be a type of bilayer with the silicone resin layer sandwiched between the substrate surface and a PTFE particle layer. In the silicone resin layer, the siloxane skeleton faces the substrate surface, while the organic groups point to the PTFE particle layer. This would mean that the antisoiling properties would be significantly determined by the PTFE particles. A corresponding orientation is only possible with nanoscale PTFE particles.

For the application of the compositions, basically all methods are suitable with which thin coatings of liquid phase can be applied. Examples include printing methods (such as flexographic printing), painting and spraying, spraying, dipping, doctoring. Generally suitable are textile coating processes.

The coating can be carried out on individual value documents, but is preferably carried out on sheet materials or web materials, which are then separated into the desired individual benefits. The silicone coating is always the final coating, that is, the value document to be coated is already with all the prints, such as Intaglio printing or other printing, and optionally with other coatings and / or security features equipped. The silicone layer must therefore be transparent to ensure optimum visibility of the underlying imprints, watermarks or other security features.

The coating process for producing the value document according to the invention is carried out as follows. Starting material is, apart from the coating still to be applied, finished document of value. The value document has a sheet substrate, e.g. a paper substrate, with two main surfaces, both of which are provided with a dirt-repellent coating. For this purpose, a solution or a dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of the silicone resin and / or fluorosilicone resin is first prepared and mixed with PTFE solid particles. In order to keep the PTFE particles stable in suspension, a dispersing aid is usually required. Two-component systems are preferably only mixed immediately before use in order to be able to process the system without problem within the pot life. It is understood that the solutions or dispersions, depending on the nature of the silicone resin and / or fluorosilicone resin, optionally contain suitable crosslinking catalysts. Furthermore, conventional auxiliaries may be included. The concentration or the viscosity of the solution or dispersion to be applied is optionally adjusted by dilution in such a way that a uniform application of a thin layer to the value-document surfaces is possible.

The application of the solution or dispersion of the silicone resin and / or fluorosilicone resin or the prepolymers of the silicone resin and / or fluorosilicone resin with PTFE particles, hereinafter coating composition called typically at room temperature. Suitable application methods are, for example, printing processes, such as flexographic printing, spraying and spraying, doctoring, or else dip coating. The application methods are not particularly limited, and in principle all methods are suitable which can produce a uniform, thin layer. Some application methods, such as dipping or spraying, allow simultaneous coating of both major surfaces of the value document. Otherwise, the two main surfaces are coated one after the other.

After applying the coating composition to one or both major surfaces of the value document, the coating produced is dried. For coating compositions that do not need to be further crosslinked, physical drying takes place, which drying can easily be done during a sufficiently long wait, for example, during transport of a document of value document over a sufficiently long transport distance. However, it makes sense to accelerate the physical drying by additional measures, for example by an infrared radiator. In the case of coating compositions containing prepolymers which still need to be crosslinked, the coating produced is heated to a temperature sufficient for crosslinking, with typical crosslinking temperatures being in the range of about 100 to 150 ° C.

Typically, the same coating composition is applied to both major surfaces of the value document. However, this is not mandatory. Rather, the coating compositions may differ in the nature and concentration of the silicone resins, in the sizes and concentration of the PTFE particles, and in other additives. Also different order quantities, and thus different layer thicknesses, on the two main surfaces of the value document are possible.

According to a particularly preferred embodiment of the present invention, the stain-resistant coating is not produced in a single application step, but the coating is built up from two partial layers, which may be the same or different. With the help of two partial layers, the thickness of the resulting overall coating can be further reduced compared to a coating produced in one step.

This is probably due to the fact that first an extremely thin coating with gaps is formed, and then in the second coating step, substantially the gaps are filled. The application of the coating composition in two steps can be carried out without intermediate drying, ie wet in wet, but preferably an intermediate drying is carried out. In crosslinking compositions, intermediate crosslinking may also be carried out, but is not required.

The coating compositions used to make the two sublayers of a coating, like the coating compositions for coating the two major surfaces, may be the same or different. Typically, the coating compositions for the two sub-layers are identical in the nature and concentration of the resins. With regard to the content of PTFE solid particles, the coating compositions for the two partial layers may differ, wherein the inner, that is to say the substrate-facing, partial layer preferably contains fewer PTFE particles than the outer partial layer, or contains no PTFE particles. As a result, the two sub-layers connect better to a total coating.

It is understood that the silicone resins and / or fluorosilicone resins, prepolymers and PTFE solid particles mentioned in connection with the coating method are the components described further above.

Per side of the value document substrate (eg a paper substrate) is typically an amount (dry) of 0.1 g / m ² to 15 g / m ^2, preferably from 0.5 g / m ² to 2 g / m ^2, coating composition applied. In this specific context, "coating composition" means the total dry matter of all components of the coating, regardless of whether the coating is composed of sublayers or not. With such application amounts, a total coating thickness of about 0.5 to 10 microns, preferably from 0.5 to 2 microns (dry) results.

1. 1. OKS 571 der Firma OKS Spezialschmierstoffe (Deutschland). Dabei handelt es sich um einen Gleitlack mit Silikonharz und PTFE-Partikeln in einem Benzin/ Keton-Lösungsmittel. Die Zusammensetzung wurde bei Raumtemperatur in einer Schichtdicke von etwa 1,5 µm aufgesprüht und anschließend 15 Minuten lang bei Raumtemperatur getrocknet.
2. 2. DEHESIVE 430/440 der Firma WACKER (Deutschland). DEHESIVE 430/440 ist eine additionsvernetzende Zwei-Komponenten-Silikonemulsion mit nicht-ionischem Emulgator. Die Emulsion wurde nach Herstelleranweisung verarbeitet, d.h. im Verhältnis DEHESIVE 430 (Vernetzerkomponente)/DEHESIVE 440 (Katalysatorkomponente) von 9:1. Die Beschichtung wurde ebenfalls in einer Dicke von etwa 1,5 µm aufgetragen und dann bei 140°C gehärtet.

The advantages of the invention will be explained in more detail below with reference to exemplary embodiments. Sample banknotes from a standard banknote paper were coated on both sides in each case using the following coating compositions:

1. 1. OKS 571 from OKS Spezialschmierstoffe (Germany). This is a bonded coating with silicone resin and PTFE particles in a gasoline / ketone solvent. The composition was sprayed at room temperature in a layer thickness of about 1.5 microns and then dried for 15 minutes at room temperature.
2. 2. DEHESIVE 430/440 from WACKER (Germany). DEHESIVE 430/440 is an addition-curing two-component silicone emulsion with non-ionic emulsifier. The emulsion was processed according to the manufacturer's instructions, ie in the ratio DEHESIVE 430 (crosslinker component) / DEHESIVE 440 (catalyst component) of 9: 1. The coating was also applied to a thickness of about 1.5 μm and then cured at 140 ° C.

The thus-coated bank notes and an uncoated banknote (3) were subjected to a soiling test. A soil mixture of fine sand, coloring and greasing components was well mixed and extensively rubbed on one surface of the uncoated banknote and the three differently coated banknotes. Subsequently, non-stick components of the soil mixture were blown off. It was found that the uncoated banknote (3) was very heavily polluted, while the banknote (2) was much less polluted. However, by far the best results were obtained with the banknote (1). In this case, the soiled banknote surface was only slightly darker than the non-soil treated surface and, in addition, no evidence was observed that greasy components of the soil mixture had penetrated the coated surface. Therefore, the PTFE particle-containing composition (1) showed a markedly improved protective effect attributed to the PTFE particle content as compared with the PTFE particle-free coating composition (2).

The invention will be further illustrated by means of figures. It should be noted that the figures are merely schematic representations and the proportions shown do not correspond to reality. Of course, the invention is not limited to the embodiments shown.

Fig.1 and Fig. 2 each show sections by inventively coated banknotes.

The embodiment of the banknote 1 according to Fig. 1 has a banknote substrate 2 made of paper. On one surface, the substrate 2 is provided with an intaglio print image 4, and on the other surface, it has a printed image 5 printed with ink. Both surfaces or major surfaces of the substrate 2 according to the invention are provided with a coating 3, 3 'having a composition containing at least one silicone resin and / or fluorosilicone resin and PTFE solid particles. The coatings 3, 3 'are each shown as one layer, but may equally well be formed as a double layer. To form the coating 3, a small amount of a low-concentration silicone resin solution was sprayed onto the substrate 2, taking care that the surface was substantially completely covered, even in the region of the intaglio print 4. After a short drying time of a few minutes, a small amount of the same silicone resin solution was again sprayed on. The silicone resin sprayed in the second step filled any gaps in the first sprayed sub-layer, and during the subsequent physical drying, a very thin layer 3 was formed, which closely conforms to the Intaglioruck and exactly reproduces its structure as a surface structure 4 '. The coating 3 appears as a single layer, not as a combination of partial layers. On the other surface of the banknote substrate 2, the coating 3 'was formed. To produce the coating 3 ', a highly concentrated silicone resin emulsion was knife-coated and then crosslinked at elevated temperature. At a high concentration of silicone resin and / or on PTFE particles, the surface of the coating 3 'is not exactly the structure of the coated surface again. Rather, if desired, a leveling of unevenness of the coated surface can be achieved.

The embodiment of the banknote 1 according to Fig. 2 also has a banknote substrate 2 which, however, has a watermark 6 on one surface and is printed on the other surface with a lacquer layer 7 into which fluorescent particles 8 are mixed. The surface of the substrate 2 having the watermark 6 was coated as well Fig.1 for the surface of the substrate 2 having the intaglio print 4 indicated. The structures of the watermark 6 are reproduced practically exactly as a surface structure 6 'in the outer surface of the coating 3. On the other surface, the substrate 2 is coated with the lacquer layer 7, which in turn has a print image 5 printed with ink. The lacquer layer 7 with the print image 5 is coated in the same way as the surface of the substrate 2 with the print image 5 in FIG Fig. 1 , The coating based on a silicone resin and / or fluorosilicone resin with PTFE solid particles adheres well to almost all surfaces, especially on polar surfaces.

Accordingly, the particular advantages of the coating compositions used according to the invention are that they do not appreciably alter the feel or tactility of the coated value documents and offer outstanding protection against contamination, which considerably prolongs the life of the value documents.

Claims (15)

Value document (1), such as banknote, certificate, share or identity document, having a planar substrate (2) which has a dirt-repellent coating (3, 3 ') on each of its two main surfaces, characterized in that the coating (3, 3' ) has a composition containing at least one silicone resin and / or fluorosilicone resin and PTFE solid particles. Value document (1) according to claim 1, characterized in that the coating (3, 3 ') is the uppermost, final cover layer of the value document (1), wherein the value document is printed under the coating (3, 3') and / or one Coating which is free of silicone resin and / or fluorosilicone resin. Value document (1) according to claim 1 or 2, characterized in that the coating (3, 3 ') consists of an outer and an inner sub-layer, both of which contain at least one silicone resin and / or fluorosilicone resin, wherein the inner sub-layer preferably free of PTFE Solid particles. Value document (1) according to one of claims 1 to 3, characterized in that the mean diameter of the PTFE particles is 5 nm to 500 nm, preferably 30 nm to 200 nm. Value document (1) according to one of claims 1 to 4, characterized in that the proportion of PTFE particles in the coating (3, 3 ') of 1 to 50 wt .-%, preferably from 1 to 20 wt .-% in Dry weight is. Value document (1) according to one of claims 1 to 5, characterized in that the coating (3, 3 ') comprises a physically drying silicone resin and / or fluorosilicone resin. Value document (1) according to one of claims 1 to 5, characterized in that the coating (3, 3 ') has a crosslinked exclusively via silicon-oxygen bonds silicone resin and / or fluorosilicone resin. Value document (1) according to one of claims 1 to 5, characterized in that the coating (3, 3 ') has a crosslinked by hydrosilylation silicone resin and / or fluorosilicone resin. Method for producing a value document (1), such as a banknote; Document, share or identity document, comprising a sheet-like substrate (2) having a dirt-repellent coating (3, 3 ') on each of its two major surfaces, characterized by the following steps: (a) providing a solution or a dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of the silicone resin and / or fluorosilicone resin, which also contains PTFE solid particles, (b) applying the solution or dispersion to each of the two major surfaces of the value-document substrate (2) to produce the coating (3, 3 '), and (c) drying the coating (3, 3 ') by removing the liquid carrier medium of the solution or dispersion and optionally crosslinking the prepolymers of the silicone resin and / or fluorosilicone resin at a temperature sufficient for crosslinking. A method according to claim 9, characterized in that after step (b) or after step (c) again provides a solution or a dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of silicone resin and / or fluorosilicone resin, which also contains PTFE particles and applied to at least one of the two major surfaces of the value-document substrate (2), the solution or dispersion being the same as or different from the solution or dispersion applied first, and the applied solutions or dispersions together coating the coating (3, 3) ') produce. A method according to claim 9, characterized in that before step (b) a solution or a dispersion of a silicone resin and / or fluorosilicone resin or prepolymers of silicone resin and / or fluorosilicone resin, which does not contain PTFE particles, provided and at least one of the two major surfaces of the value-document substrate (2), and the liquid carrier medium of the solution or dispersion is optionally removed before step (b), wherein the applied solutions or dispersions together produce the coating (3, 3 '). Method according to one of claims 9 to 11, characterized in that the silicone resins and / or fluorosilicone resins and the PTFE particles have the features specified in claims 4 to 8. Method according to one of claims 9 to 12, characterized in that per main surface of the valuable document substrate (2) an application amount (dry) of 0.1 g / m ² to 15 g / m ² of silicone resin and / or fluorosilicone resin including PTFE Particles is applied. Method according to one of claims 9 to 13, characterized in that a coating (3, 3 ') is produced, which has a thickness of 0.5 to 10 microns. Use of a composition containing at least one silicone resin and / or fluorine silicone resin or the prepolymer of the silicone resin and / or fluorine silicone resin, and also PTFE particles, for producing a dirt-repellent, the round trip time prolonging coating (3, 3 ') of a value document (1), characterized in that the silicone resin and / or fluorosilicone resin and the PTFE particles have the features specified in one of claims 4 to 8.

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