RU2611503C2 - Method for treating surface of a banknote - Google Patents

Abstract

FIELD: polygraphy.

SUBSTANCE: invention relates to a method for treating surface of a banknote, comprising, on at least one of its opposing faces, at least a printed image, comprised of at least a design. This face and its associated printed image have a transparent protective coating. Coating is applied via printing and dried. Coating contains a varnish and an organic compound, incorporating fluorine atoms in the form of at least a perfluoro-polyether (PFPE) group, on said face.

EFFECT: invention provides increased durability of banknotes in terms of mechanical strength and chemical resistance at its regular authentication and higher protection.

12 cl, 6 dwg, 2 tbl

Description

Banknotes, originally called paper money, have existed since the 10th century. This means of payment was introduced into circulation by Chinese tea merchants to avoid the transport of metal coins. The first banknotes officially appeared in France in 1803. From the very beginning, paper money was made from cotton. However, over the past three decades, cotton has gradually given way to polymers, which, according to manufacturers, are more durable. At the same time, regardless of whether banknotes are made of cotton or polymer (s), their manufacture and their valorization do not change.

The sequence of printing processes and the implementation of security features (for example, dry offset printing, wet offset printing, flexography, screen printing or hot stamping ...) allows you to get the final product with a high added value.

The primary goal is to increase the circulation period of this banknote and to prevent its premature wear.

With the goal of increasing the life of this valuable printed product, it is necessary, first of all, to understand the reasons that lead to the withdrawal of banknotes from circulation.

The complexity of manufacturing a banknote, by definition, is the main condition for preventing attempts to counterfeit it.

An effective way to combat counterfeiting is to use several types of protection at different levels.

The protective elements of the first level are elements distinguishable to the naked eye in daylight or artificial lighting and do not require the use of a special device.

The presence of a watermark, dyed fibers, elements that are visible to the light, or relief elements distinguished by touch, obtained by intaglio printing, are examples of first level elements.

The so-called second-level protection is represented by elements that can be detected using technologically simple devices, such as ultraviolet lamps and infrared lamps. This provides authentication of banknotes within various institutions (trading, banking, etc.). Thus, it is possible to distinguish between drawings or texts printed with invisible ink, which becomes visible in ultraviolet or infrared light, fluorescent fibers, magnetic filaments, etc.

Finally, the third level of protection requires the use of complex devices and, therefore, high costs. Tracking these security features, such as labeled atoms in banknotes, is mainly done by central banks.

One of the conditions necessary to ensure the role of these types of protection and their proper authentication over time is the normal aging of the banknote. Central banks are required to exchange any returned banknote (for various reasons: pollution, tearing, damage ...) if it can be identified by at least 50%. Therefore, it is very important to be able to distinguish and control the numerous elements that make up the banknote.

Consequently, central banks are increasingly interested in increasing the durability of banknotes both in terms of mechanical strength and in terms of chemical resistance.

Thus, a cleaner, more hygienic and more durable bank ticket can be put into circulation while ensuring a lower cost of its circulation cycle.

However, to obtain such a product, it is necessary to understand what really affects the fragility of banknotes and leads to their withdrawal from circulation.

Central banks have initiated numerous studies to characterize the possible reasons for the seizure of banknotes. Among the various reasons indicated (DE HEIJ Hans. Durable Banknotes: an overview. In: Presentation of the BPC / Paper Committee to the BPC, May 2002, Prague), apart from all the others, one thing stands out: pollution.

It is 60-80% the reason for the withdrawal of banknotes from circulation. One of the main elements of this pollution is human skin fat, naturally present on the surface of the skin.

For this reason, the main players in the industry, and in particular paper manufacturers, are trying to find solutions, such as “high-strength” paper or, for example, anti-pollution coatings. They allow you to respectively increase the mechanical strength and chemical resistance of banknotes.

So, paper manufacturers have proposed various formulations. The differences vary between the composition of the fiber layer (100% cotton, a mixture of natural fibers, a mixture of natural and synthetic fibers, polymers, etc.) and the “solutions” used to form / impregnate the layer.

For example, natural fibers, besides cotton, can be flax or abacus fibers, synthetic fibers are fibers based on polyethylene, polypropylene. The substrate can even be made exclusively of polypropylene oriented in two directions.

As for the anti-pollution coating, we can speak, for example, of compositions based on polyurethane or latex. Of course, these examples are not limiting, and each high-strength paper may have its own characteristics depending on different manufacturers.

However, as a result, the final properties of these types of paper are smoothed. Indeed, some types of paper are superior to others in terms of mechanical strength, while others have better anti-pollution properties, but all of these substrates must retain one inherent characteristic: printability.

In addition to the increased cost, these new types of paper have another weak point. As a result of all types of processing to which they are subjected during the manufacture of paper, even if the service life of the substrates is increased, this does not protect the protective printing elements, which, as mentioned above, is a fundamental aspect.

WO 02051638 describes a technology for applying a varnish coating to a substrate by flexography at the end of a banknote manufacturing process. This varnish, applied by means of additional printing, increases the banknote's resistance to pollution and, thus, completely protects the printed image. Through one pass in the machine without overturning, both sides of the banknote, that is, simultaneously applied paint and the substrate, are protected from contamination. This UV drying varnish is, for example, one of the varnishes offered by Sicpa under the names SicpaProtect 889354 and 889405. You can also mention Schmidt Rhyner WESSCO Protector 36.298.42 and Actega TerraGloss UV Special Coating VP-HB 100-080.

The contamination test (which will be described below) is characterized as the difference in the brightness measurement L of the contaminated sample and the uncontaminated control sample in the area without printing. So, when conducting this test, white velvet paper made 100% from cotton shows ΔL of about 20-30 units, and the same paper coated with SicpaProtect 889354 varnish, applied by flexography using anilox roll of 6 / 6.5 cm ³ ( that is, when transferring 2 g / m ² ), it shows ΔL from 14 to 18, that is, the improvement is about 40%.

This result is noteworthy in itself, but unfortunately, the hydrophobic and oleophobic properties of such SicpaProtect 889354 lacquered paper are rather low.

In addition, attempts have been made in the field of food packaging to protect these packaging from the aggressive effects of juices, sauces and fats, at least until the consumption of the products contained therein.

For example, Solvay introduced fluoride-based products known for their anti-stick properties. Many substances possess the desired hydrophobic and oleophobic properties, in particular, two aqueous dispersions based on perfluoropolyether (PFPE, X - [- (CF ₂ -CF ₂ -O) _m - (CF ₂ O) _n -] - X). The first substance called FOMBLIN or 5134X contains PFPE-urethane, the other substance called 5135X contains ammonium salts of PFPE-phosphate. Another PFPE-urethane-based substance containing organic solvents was functionalized, that is, the base molecule additionally contains reactive chemical functional groups. It can be mixed with varnish matrices, polymerized by UV radiation, and can thus react with the formation of chemical bonds with these matrices to enhance its bonding / adhesion. These substances were created in response to health and environmental concerns associated with PFOC (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonate). The above substances based on PFPE do not contain either PFOC or PFOS, as well as their decomposition products.

These substances give good oil and grease protection properties to paper or paperboard substrates. They are used for surface treatment and applied by flexography, heliogravure or any other known application method.

The coating creates an invisible chemical barrier of PFPE on the surface. These substances have been widely used in the manufacture of food packaging (for example, animal feed bags, pizza boxes). In addition, a check on contact with food products showed their harmlessness.

The applicant set himself the task of eliminating the above disadvantages associated with the use of varnish in the manufacture of banknotes, using a method that can enhance the combination of properties that increase the life of the banknote, such as resistance to pollution, hydrophobia, oleophobia, the ability to repel sweat water and oily bodies sebum, due to quantitatively defined barrier effects.

In this regard, an object of the present invention is a method for surface processing of a banknote, which, at least on one of its opposite sides, contains at least one printed image representing at least one drawing, moreover, this side and its the corresponding printed image has a transparent protective coating, according to which, by printing, a coating is applied containing varnish and a chemical organic compound containing fluorine atoms in the form of at least one perfluoropoly ether group on the specified side, and produce its drying.

Thanks to the use of this technology, the following results / advantages / characteristics are obtained:

- ensuring the protection of all valuable printed product (that is, the substrate and its printed elements);

- increased resistance to pollution in comparison with the known method of applying a varnish coating;

- improved hydrophobic properties compared with the known method of applying a varnish coating;

- improvement of oleophobic properties compared with the known method of applying a standard varnish coating described in this document;

- improvement of the above properties does not occur to the detriment of economic efficiency and without the use of complex physical processes leading to a significant and even unacceptable increase in the cost of manufacturing banknotes;

- processing is compatible with existing printing technologies, that is, the coating itself has the ability to print;

- processing can be applied using the printing method by flexography, heliogravure or screen printing;

- after the production of the security document and the application of a dry coating on it, the treatment is compatible with the epidermal contact and is not toxic or allergenic.

According to other preferred and non-limiting distinguishing features of the method:

- the specified coating is applied by printing to the specified side in the form of two different layers, namely, first the first layer of varnish and then the second layer containing the specified chemical organic compound with fluorine atoms in the form of at least one perfluoropolyether group in a water base or base solvent;

- drying the specified varnish produce ultraviolet radiation;

- the specified organic chemical compound with fluorine atoms in the form of at least one perfluoropolyether group is the basis of the solvent, compatible with the matrix of the specified varnish, with which it is mixed, in a functionalized form, that is, it is able to react with this matrix and form chemical bonds for strengthening its fastening / adhesion;

- the second layer is dried by ultraviolet radiation;

- the specified chemical compound is in a water base;

- the specified coating is applied by printing to the specified side in the form of a mixture of the specified varnish, polymerized by ultraviolet radiation, and the specified chemical organic compounds with fluorine atoms in the form of at least one perfluoropolyether group in the solvent base, compatible with the matrix of the specified varnish, with which it mixed, in a functionalized form, that is, capable of reacting with this matrix and forming chemical bonds to enhance its bonding / adhesion;

- drying the specified mixture produce ultraviolet radiation;

- the specified coating includes at least one bactericidal and / or antifungal and / or antiviral agent;

- the specified tool is included in the specified second layer.

Other features and advantages of the invention will be more apparent from the following detailed description with reference to the accompanying drawings.

In FIG. 1 shows a banknote before applying the claimed method, a partial schematic top view;

in FIG. 2 shows a banknote obtained after the first stage of the claimed method, a simplified sectional view along the plane II-II of FIG. one;

in FIG. 3 shows a simplified sectional view along the same plane of a banknote obtained after the second stage of the claimed method;

in FIG. 4 shows a banknote, additionally containing a pattern in the form of F, made of glossy varnish, a view similar to FIG. one;

in FIG. 5 is a view similar to FIG. 2 of the embodiment of FIG. four;

in FIG. 6 is a view similar to FIG. 3 of the embodiment of FIG. four.

The term “varnish” means infrared / hot air-dried varnishes and UV-varnishes.

Preferably, it is a water-based acrylic varnish in the case of the first varnishes and a varnish based on epoxide or acrylate and solvents in the case of the second varnishes.

The infrared / hot air drying varnish is, for example, a varnish manufactured by Sicpa, such as Sicpaprotect 803688W (acrylic polymer).

As regards UV drying varnish, for example, Sicpaprotect 889354 can be used based on monomers of the cycloaliphatic epoxides family, such as Chissonox 221 Monomer, which polymerize to produce a polyacrylate matrix from acrylate compounds, including trimethylol propane triacrylate.

The varnish "Actega terraGloss UV Special Coating VP-HB 100-080" is also polymerized to produce a polyacrylate matrix, including from an unsaturated acrylic resin.

The term "printed image in the form of a picture" should be understood as any printed element, regardless of the ink used, which forms any pattern in the form of an openwork or non-openwork plane, and this design can also include an alphanumeric character.

In FIG. 1 very schematically shows document 1, in this case a banknote containing a substrate 2, for example, of paper or cotton fibers, the upper and lower opposite sides of which are indicated by 20 and 21.

On the upper side, using any method known to the person skilled in the art, print figures 3, which in this case are respectively the face value of the banknote (in this case 100), the guilloche and the portrait.

This pattern can be printed using so-called protective ink.

Of course, other printing elements may also be present on side 20.

Of course, the opposite side 21 may also contain identical, similar or other printing elements.

As shown in FIG. 2, side 20 is covered with a layer of colorless varnish 4, the definition of which was given above.

Of course, FIG. 2 and the figures following it are presented only as an example, and the proportions, in particular, the dimensions in thickness do not correspond to reality. In addition, for the purpose of explanation and in order not to clutter the figures, the varnish coating is shown only on side 20. Of course, in reality and for the purpose of optimal protection, the coating is applied to both opposite sides 20 and 21.

ртутного спектра 200 Вт/см при 65% их мощности).This varnish layer was printed under the following operating conditions and was described above (varnish called SicpaProtect 889354, applied by flexography using anilox roll 6 / 6.5 cm ³ (that is, with a transfer of about 2 g / m ² ) and dried with UV lamps

mercury spectrum 200 W / cm at 65% of their power).

After drying by the method of flexography and using anilox rolls identical to the above, another layer 5 is applied to layer 4, containing a chemical organic compound with fluorine atoms in the form of at least one perfluoropolyether group or at least one of its derivatives in version water base. After drying layer 5, both layers 4 and 5 form a coating R.

Layer 5 is dried by evaporation using a GRAFIX infrared / hot air drying lamp at 150 ° C.

In another embodiment, said drying is ultraviolet drying of the aforementioned type, in particular when a chemical organic compound with fluorine atoms in the form of at least one PFPE group compatible with ultraviolet drying is directly mixed with said varnish.

The embodiment of FIG. 4-6, similar to the above option. It differs only in that it prints pattern 31 forming “F” in the form of a glossy area on a matte background or surrounded by a matte background, as described in document FR 2958209.

According to a version not shown in the figures, the varnish and the fluorine-containing chemical organic compound are applied by printing in the form of only one layer.

The sticking properties of the coating R reduce the possibilities of interaction and adhesion of living macroscopic pathogenic organisms, such as bacteria and fungi, and thereby prevent their spread.

In addition, it is possible to provide for the inclusion of layer 5 biocidal agents in the form of a dopant in such a way as to provide not “passive” protection from pathogenic effects, as mentioned above, but “active” protection, as is the case, for example, with silver ions [ cm. N. Stoble et al .: "Silver Doped Perfluoropolyether-Urethane Coatings: Antibacterial Activity and Surface Analysis. Colloids and Surfaces B: Biointerfaces, Volume 72, 1 (2009). Pp. 62-67].

The advantage of giving the R coating an active protection property is obvious, since this occurs at the last stage of printing a banknote before giving it the final format. This is fundamentally different from the solution proposed in EP 03740577 (ARJOWIIGGINS), which describes the protection of only the substrate with a pair of biocidal products and does not mention the barrier repellent effect of printing inks (offset, intaglio printing, screen printing) and “films” (polyester tapes) on the real effectiveness of biocidal treatment.

Studies have been conducted to observe the effects of these printed elements on banknotes.

Pollution resistance was tested using a dry contamination test (Fritsch test). It is a vibrating device in which small glass balls are rolled and a contaminant based on sand, silt, activated carbon, flour and glycerol monooleate (a fatty substance present in skin fat) is rolled and pressed into a paper sample. The test lasts 15 minutes. As indicated above, the brightness of the initially white zone is measured in several passes before and after exposure to a contaminant. The difference obtained or ΔL allows us to characterize the adhesion of dirt to the banknote: the smaller this difference, the higher the resistance to dry pollution.

Hydrophobicity is characterized as resistance to water penetration, as well as the ability to push this water to a surface called water repellent. Water penetration resistance is measured using a Cobb test (60 s). We are talking about the amount of water in g / m ² absorbed by the substrate using a cylindrical impregnation template for a time of 60 seconds. This is a test common in the field of paper production and designed to characterize the absorption of paper. There is also a Cobb test in 300 seconds, which allows you to determine whether the effect of the layer persists after a longer stay under water.

As for water repulsion, it is a natural process, as a result of which water flows in the form of drops on the surface of the paper due to a simple “gravity” when the substrate is tilted. This is a visual test, which is associated with measurements of the contact angle (θ) of a water drop for 500 μs (the values of surface tension are also taken into account). Indeed, it is at this moment that we can assume that this drop stabilizes on the surface of the paper.

Oleophobia is measured using tests for the effects of fatty substances. The first method, called the “whale test,” is to use a mixture of castor oil (a fatty substance) and high boiling point solvents, namely toluene (an aromatic solvent) and n-heptane (an aliphatic solvent).

Depending on various proportions of the aforementioned substances, a composition is obtained whose viscosity and surface tension vary inversely with its aggressiveness, that is, its saturating ability.

A composition with a high content of castor oil is at the bottom of the scale, while a composition with a high content of heavy solvents is at the top of the same scale.

Testing 12 compositions, and it is believed that a score of 6 characterizes a satisfactory barrier to fats. Assessment is carried out visually.

Another test was also used, and in this case we are talking about a test for fatty acids (FA). The principle remains the same, but the composition is a mixture of fatty acids, one of which is present in human skin fat. This is a mixture with different proportions of castor oil (heavy fraction), oleic acid (intermediate fraction) and octanoic acid (light fraction) with decreasing viscosity values. The test is carried out at a temperature of from 20 ° C to 60 ° C.

11 compositions are tested and the results are also expressed as a visual assessment. The higher the position on the scale, the greater the barrier effect with respect to fatty substances, which corresponds to a decrease in the content of castor oil in the composition, an increase, then a decrease in the amount of oleic acid and, finally, an increase in the amount of octanoic acid.

ртутного спектра 200 Вт/см при 65% их мощности, затем вещество под названием SOLVAY 5134 X на водной основе, высушенное горячим воздухом под печами оборудованными лампами инфракрасной/горячей воздушной сушки GRAFIX при 150°C.The following tables show the test results for securities, the backing of which is 100% cotton velor paper, on which, in the last pass, SicpaProtect 889354 varnish was applied on flexographic printing on anilox rollers 6 / 6.5 cm ³ (front and back) and dried using UV lamps

a mercury spectrum of 200 W / cm at 65% of their power, then a substance called SOLVAY 5134 X water-based, dried with hot air under ovens equipped with GRAFIX infrared / hot air drying lamps at 150 ° C.

It should be noted that SOLVAY 5134 X (www.solvay.com/en/markets-and-products/featured-products/solvera.html) is sold under the Solvera® PT 5060 brand and has the following formula:

This polymer is obtained by the reaction of a perfluoropolyether diol with isophorondiisocyanate, accompanied by an extension of the chain of dimethylolpropionic acid, according to the following scheme:

Contrary to all expectations, the results obtained when processing banknotes made of cotton paper with only one varnish 5134 X were not satisfactory (Table 1). It suddenly turned out that the contamination test gave less good results than if the substrates were coated only with SicpaProtect 889354 and if the hydrophobicity was excellent, as for the oleophobic properties, they are not significant.

In addition, it was confirmed that untreated paper does not have any of the desired properties and that paper coated only with varnish has anti-pollution properties, but is only slightly hydrophobic and not oleophobic at all.

On the other hand, the combination of varnish coating and fluorine-containing treatment gives unexpected results. Real functional synergy was achieved with the combined use of first varnish and then 5134 X (Table 2). A significant increase in the properties of resistance to pollution and the obvious presence of the properties of hydrophobicity and oleophobicity were noted, and this is not a simple addition of the properties associated with each of the components.

Resistance tests were carried out on various samples, and it turned out that the R coating protection was preserved after immersion tests for 30 minutes using polar solvents (ethanol, acetone, diethylene glycol), non-polar solvents (xylene, kerosene), chlorine solvents (tetrachlorethylene) , synthetic sweat, acids at a concentration of 5% (acetic, hydrochloric, sulfuric), soda at a concentration of 5%, oxidizing agents at a concentration of 5% (sodium hypochlorite, hydrogen peroxide), hot water (100 ° C), industrial liquors (St Marc, Persil). In addition, the R coating retains these properties after the light resistance test (48 hours of sun test, heat resistance (120 ° C, 30 min) and wet crease. Finally, after the test of the above Fritsch test, the hydrophobic and oleophobic properties are retained.

Other results not shown in the tables allowed us to establish that this gain can be increased to obtain values of resistance to pollution at ΔL≤5, changing the ratio between the amounts of applied varnish and substance 5134X. In addition, it can be assumed that preliminary surface treatment, for example, of the type of coronary, before applying UV drying varnish or before drying the second water-based varnish containing 5134 X, can positively affect the above results.

Tests were also conducted using the other Solvay products mentioned above, which led to similar protection results.

Claims (12)

1. The method of processing the surface of a banknote (1) containing at least one of its opposite sides (20, 21) at least one printed image representing at least one pattern (3), and this side (20, 21 ) and its corresponding printed image (3) have a transparent protective coating (R), characterized in that by printing a coating is applied containing a varnish and a chemical organic compound containing fluorine atoms in the form of at least one perfluoropolyether group (PFPE) on the indicated side (20, 21 ), and produce its drying. 2. The method according to p. 1, characterized in that the said coating (R) is applied by printing to the specified side in the form of two different layers - first the first layer (4) of varnish and then the second layer (5) containing the specified chemical organic compound with fluorine atoms in the form of at least one perfluoropolyether group (PFPE), water-based or solvent-based. 3. The method according to p. 2, characterized in that the drying of the specified varnish produce ultraviolet radiation. 4. The method according to p. 2 or 3, characterized in that the specified chemical organic compound with fluorine atoms in the form of at least one perfluoropolyether group (PFPE) is based on a solvent compatible with the matrix of the specified varnish, with which it is mixed, in a functionalized form, that is, it is able to react with this matrix and form chemical bonds to enhance its bonding / adhesion, while the second layer (5) is dried by ultraviolet radiation. 5. The method according to p. 2 or 3, characterized in that said chemical compound is in a water base, and drying is carried out using hot air without deterioration or chemical change of said chemical organic compound. 6. The method according to p. 1, characterized in that the coating (R) is applied by printing to the specified side in the form of a mixture of the specified varnish, polymerized by ultraviolet radiation, and the specified chemical organic compounds with fluorine atoms in the form of at least one perfluoropolyether group ( PFPE) based on a solvent compatible with the matrix of the specified varnish with which it is mixed, in a functionalized form, that is, capable of reacting with this matrix and forming chemical bonds to enhance its bonding / sec captivity. 7. The method according to p. 6, characterized in that the said mixture is dried by ultraviolet radiation. 8. The method according to one of paragraphs. 1-3, 6, 7, characterized in that the said coating (R) includes at least one bactericidal and / or antifungal and / or antiviral agent. 9. The method according to p. 4, characterized in that said coating (R) includes at least one bactericidal and / or antifungal and / or antiviral agent. 10. The method according to p. 5, characterized in that said coating (R) includes at least one bactericidal and / or antifungal and / or antiviral agent. 11. The method according to p. 8, characterized in that the said coating (R) is applied by printing to the indicated side in the form of two different layers - first the first layer (4) of varnish and then the second layer (5) containing the specified chemical organic compound with fluorine atoms in the form of at least one perfluoropolyether group (PFPE), water-based or solvent-based, wherein said antiviral agent is included in said second layer (5). 12. The method according to p. 9 or 10, characterized in that the said coating (R) is applied by printing to the specified side in the form of two different layers - first the first layer (4) of varnish and then the second layer (5) containing the specified chemical organic a compound with fluorine atoms in the form of at least one perfluoropolyether group (PFPE), water-based or solvent-based, wherein said antiviral agent is included in said second layer (5).

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