CA2848934A1 - Method for treating the surface of a banknote - Google Patents

Abstract

The present invention relates to a method of surface treatment of a banknote (1) which comprises, at least on one of its opposite faces (20, 21), at least one printing consisting of at least one pattern (3), this face (20, 21) and its associated printing (3) being covered with a transparent protective coating (R), characterized in that the implementation is carried out by printing a coating containing a varnish and an organic chemical compound incorporating fluorine atoms in the form of at least one perfluoro-polyether group (PFPE) on said face (20, 21), and drying thereof.

Description

METHOD FOR SURFACE TREATMENT OF A BANK TICKET
The bank note, initially called paper money, exists since the 10th century.This means of payment was introduced by traders Chinese tea to avoid the transport of metal coins. The first ones tickets officially issued in France were first issued in 1803.
Since its inception, paper money has been made using cotton. Since a thirty years, however, cotton gives up some ground to (x) polymer (s), more resistant according to its promoters. That ticket support either cotton or polymer (s), its manufacture and valuation remain unchanged.
A succession of printing and security processes (ex dry offset, wet offset, intaglio, flexography, screen printing or even the hot stamping ...) leads to a high value end product added.
It is thus essential to give an increased longevity to this ticket, to prevent it from deteriorating too quickly.
If one wants to increase the longevity of these valuable prints, it is to understand the reasons for withdrawing tickets.
The complexity of making a ticket is by nature a essential condition to discourage counterfeit attempts.
Effective deterrence is achieved by affixing several types of security of different levels.
First level secure elements are elements detectable with the naked eye, in daylight or artificial and not requiring not the use of a particular device.
The presence of a watermark, colored fibers, visible elements in transvision, or the tactile reliefs produced by an impression in cut soft, are examples of top-level elements.
So-called second level security are detectable elements using technologically modest devices such as UV or IR lamps.
This allows ticket authentication within various organizations (shops, banking centers, etc.). We can thus distinguish patterns or of the texts printed in invisible ink but visible under ultraviolet radiation or infrared, fluorescent fibers, magnetic wires etc ...

2 Finally, the third level of security requires sophisticated and, as a result, a high investment. Those are mainly central banks that examine these securities, such as tracers present in the notes.
One of the necessary conditions to guarantee the role of these security and their correct authentication in time is the correct aging of the ticket. Central banks must exchange any returned ticket (various causes: soiling, tearing, mutilations ...) if it is identifiable to to minus 50%. It is therefore essential to be able to discern and control multiple elements that compose it.
Central banks are thus showing more and more interest in more sustainable notes, both in terms of mechanical strength and chemical resistance.
In this way, a cleaner, more hygienic ticket and a longer service life could be put in circulation while ensuring costs lower life cycle.
However, to create such a product, it is necessary to understand what actually makes the notes more fragile, pushing for a withdrawal of the circulation.
Several studies have been conducted by central banks to characterize the possible causes of banknote withdrawals. Of the various causes quoted (DE HEIJ Hans Durable Banknotes: An Overview.
BPC / Paper Committee to the BPC, May 2002, Prague.), A cause stands out others: dirt.
It would be responsible for 60% to 80% of the withdrawal of banknotes of the circulation. One of the main elements of this smear is made of human sebum, fat naturally present on the surface of the skin.
For this reason, those involved in the business, and in particular papermakers are trying to bring solutions such as high papers Durability or anti-fouling coatings for example. They allow respectively to strengthen the mechanical strength and the chemical resistance tickets.
Thus, different assemblies are proposed by the paper manufacturers. The differences vary between the composition of the fibrous mat (100% cotton,

3 natural fiber blend, natural and synthetic fiber blend, polymer etc.) and the coating / impregnation sauces used.
For example, natural fibers other than cotton can be flax or abaca, synthetic fibers are based on polyethylene, polypropylene. The support can even be constituted exclusively bi-oriented polypropylene.
As for the anti-fouling coating, it may be for example sauces based on polyurethane or latex. These last examples are good heard non-exhaustive, each high-durability paper having its own particularities according to the different suppliers.
But, ultimately, the final properties conferred on these papers are mixed. Indeed, some papers gain in terms of resistance while others have improved in terms of properties anti-fouling but these supports must retain this characteristic inalienable that is printability.
These new papers, besides their higher cost, also have another weakness. Following the treatments they underwent during the manufacture of the If paper longevity is increased, this does not guarantee the protection of security impressions, fundamental aspect mentioned above.
In the document W002051638 is described a technique which consists in performing a flexographic varnishing of the support at the end of the process of ticket manufacture. This varnish affixed overprint improves the resistance to soiling the ticket and thus protects the print in its entirety. By a alone machine pass, without turning over, we protect both sides of the ticket, that is to say both the inks deposited and the support, dirt. This varnish UV drying is for example one of those proposed by Sicpa under the references SicpaProtect 889354 and 889405. Other references also work like the Schmidt Rhyner WESSCO Protector 36.298.42 varnishes and the one of Actega TerraGloss UV Special Coating VP-HB 100-080.
A soil test (whose operating mode will be described later) is characterized as the differential of measurement of the luminance L of a saline sample and an unsoiled control sample on a non-salted printed. Thus, a white wove paper made of 100% cotton presents, when is subjected to this test, an M of about 20-30 units and this same varnished paper with the reference SicpaProtect 889354 printed in flexography, with an anilox

4 6 / 6.5 cm3 (ie approximately 2 g / m 2 transferred) an M between 14 and 18, ie one gain around 40%.
This result is already appreciable in itself but, unfortunately, the hydrophobic and oleophobic qualities of such a varnished paper with the reference SicpaProtect 889354 are quite weak.
Moreover, he is known in the field of packaging to protect them against the aggression of juices, sauces and other fats, at least until the products they contain will to be consumed.
Solvay, for example, offers products based on fluorine whose anti-adherent properties are otherwise well known.
Many references present the properties of hydrophobicity and oleophobia sought, in particular two aqueous dispersions based on perfluoro-polyether (PFPE, X - [-(CF2-CF2-0) ,, - (CF20) O1-X). A first product, referenced FOMBLIN or 5134X
contains PFPE-urethane, another product, referenced 5135X, contains PFPE

phosphate ammonium salts. Another reference based on PFPE-urethane and containing organic solvents, is functionalized, i.e.
Basic molecule additionally contains reactive chemical functions. She is able to be mixed with matrices of polymerizable varnish under UV radiation and can therefore react by forming chemical bonds with these last to reinforce its anchoring / grip. These products were created for to address health and environmental issues related to PFOA (perfluoro-ocatnoic acid) and PFOS (perfluorooctane sulfonate). Products previously cited, based on PFPE, contain neither PFOA nor PFOS and their degradation products either.
These products give good barrier properties to oils and greases with paper and / or cardboard supports. They are both used as a surface treatment, applicable by flexography, gravure or any another usual method of sleeping.
The deposition on the surface creates an invisible chemical barrier of PFPE.
These references are commonly used in the packaging industry foodstuff bag (eg food bag for animals, boxes for pizza). In addition, their accreditation to food contact attests to their safety.

The present applicant therefore proposes to remedy the drawbacks mentioned above concerning varnishes for fiduciary purposes by a process which makes it possible to strengthen all the properties presiding over the longevity of a note, namely resistance to soiling, hydrophobicity,

Oleophobia, so as to reduce the retention of particles macroscopic dirt, to repel, thanks to quantifiable barriers effects, the water of the sweat and fat bodies of sebum.
Thus, the present invention relates to a method of surface treatment of a bank note which includes, at least on one of the of its opposite faces, at least one impression consisting of at least one pattern, this face and its associated impression being covered with a coating of transparent protection, characterized by the fact that place by printing a coating containing a varnish and a compound organic chemical incorporating fluorine atoms in the form of at least one perfluoro-polyether group, on said face, and that one carries out its drying.
Thanks to the implementation of this technique, we obtain the following results / benefits / characteristics:
- the whole of the printed value (ie the support and its impressions) is protected;
- the resistance to soiling is more efficient than that of the current varnishing method;
the hydrophobicity properties are more efficient than that of the current varnishing method;
the properties of oleophobia are more efficient than that of the current standard varnishing method described in this document;
- the improvement of the aforementioned properties does not occur at detrimental to the economic aspect and does not use physical processes complexity making the cost of ticket manufacture;
- the treatment is compatible with printing techniques usual, that is to say that the coating is itself printable;
- the treatment can be applied by the printing process flexographic, gravure or screen printing;

WO 2013/04549

6 - the processing, once the security document has been produced and its dry coating, is compatible with an epidermal contact, without being known toxic or allergenic.
According to other advantageous and nonlimiting characteristics of this process :
said coating is printed on said face in the form of two distinct layers, namely first a first layer of varnish and then a second containing said organic chemical compound incorporating fluorine atoms in the form of at least one perfluoro-polyether group, in an aqueous base or in a solvent base;
- drying said varnish under a radiation ultraviolet;
said organic chemical compound incorporating fluorine in the form of at least one perfluoro-polyether group is in a solvent base compatible with the matrix of said varnish with which it is mixed, in a functionalized form that is to say able to interact with this last by forming chemical bonds in order to strengthen its anchoring / hooking;
- the second layer is dried by radiation ultraviolet;
said chemical compound is in an aqueous base;
- drying is carried out without alteration or chemical modification of said organic chemical compound, by drying in hot air of the base aqueous;
said coating is printed on said face in the form of a mixture of said polymerizable varnish under ultraviolet radiation and said organic chemical compound incorporating fluorine atoms in the form of minus one perfluoro-polyether group, in a compatible solvent base with the matrix of said varnish with which it is mixed, in a form functionalized that is to say able to interact with the latter in forming chemical bonds to reinforce its anchoring / grip;
drying said mixture under ultraviolet radiation purple;
said coating incorporates at least one bactericidal agent and / or antifungal and / or antiviral;
said agent is incorporated in said second layer.

7 Other features and advantages of the invention will appear in reading the detailed description that follows. It will be done in reference in the accompanying drawings in which:
- Figure 1 is a top view, partial and schematic, of a bank note before implementation of the method;
FIG. 2 is a simplified view, in section, along plane II-II of FIG.
FIG. 1, of the bank note obtained in accordance with a first step of process according to the invention;
FIG. 3 is also a simplified view, in section according to the same plan, of the bank note obtained after the implementation of the second step of the method according to the invention;
FIG. 4 is a view similar to that of FIG. 1, the ticket additionally having an F-shaped pattern made of gloss varnish;
FIG. 5 is similar to FIG. 2 of the embodiment of FIG.
Figure 4;
FIG. 6 is similar to FIG. 3 of the embodiment of FIG.
figure 4.
The term "varnish" means the drying varnishes Infra Red / Hot Air and UV curing varnishes.
Preferably, it is acrylic lacquer aqueous base for the former, and epoxy or acrylate-based lacquers and solvents for the second.
A drying varnish IR / hot air is for example that of the Sicpa company such as Sicpaprotect 803688W (acrylic polymer).
For the UV curing varnish, it is possible, for example, to use the Sicpapotect 889354 based on monomers of the epoxy family cycloaliphatics such as Chissonox 221 Monomer and which polymerizes into giving a polyepoxide matrix by means of initiators such as salts of onium (eg substituted sulphonium cation and its anion) activated under UV.
Another varnish such as the Wessco Protector 36.298.42 of Schmidt Rhyner polymerizes under UV (radical mechanism) by giving a polyacrylate matrix from acrylate compounds such as, among others, the trymethylolpropane triacrylate.
Actega TerraGloss UV Special Coating VP-HB 100-080 polymerizes also by giving a polyacrylate matrix from, between other, unsaturated acrylic resin.

8 By printing consisting of a pattern, we mean any element printed, whatever the ink used, which forms any figure, by example in the form of a flat openwork or not, this figure can in particular be among others an alphanumeric character.
In Figure 1 is shown very schematically a document 1, in this case a banknote consisting of a support 2 of paper or cotton fibers for example, whose opposite faces upper and lower are referenced 20 and 21.
On the upper side 20 are printed, by any technique known to those skilled in the art, patterns 3 which consist here respectively, in the value of the note (here 100), a guilloche and a portrait.
This motif may have been printed using an ink called security.
Other impressions can of course appear on the face 20.
Of course, the opposite face 21 may also include identical, similar or different impressions.
Referring now to Figure 2, we see that the face is coated with a layer of clear varnish 4, the definition of which has been given upper.
20 Good understood, Figure 2 and the following are given as illustrative only, so that the proportions, especially in thickness, born do not reflect the reality. Moreover, only the face 20 is coated with a fine varnish explanation and not to unnecessarily burden the figures. Of course, in reality and with a view to optimum protection, the two opposite faces 20 and are coated.
This layer of varnish was printed according to the conditions following procedures and described above (varnish with reference SicpaProtect 889354 printed in flexography, with an anilox of 6 / 6.5 cm3 (approximately 2g / m2 transferred) and dried under UV HONLE mercury spectrum lamps 200 W / cm at 65% of their power).
After drying, we print in flexography with anilox identical to those described above on layer 4, another layer 5 incorporated of an organic chemical compound incorporating fluorine atoms in the form of at least one PFPE perfluoro-polyether group or at least one of its derivatives in an aqueous base version. After drying layer 5, both layers 4 and 5 then form a coating R.

9 The drying of the layer 5 is carried out by evaporation under a Infrared lamp / hot air GRAFIX at 150 C.
In a different embodiment, said drying consists of a ultraviolet radiation drying of the same type as that mentioned above, especially when the organic chemical compound incorporating fluorine in the form of at least one PFPE group and compatible with drying under UV radiation, is mixed directly with said varnish.
The embodiment of FIGS. 4 to 6 is similar to that described previously. It differs only in that a pattern 31 in form of F is printed in the form of a glossy-looking region on a matt background or surrounded by a matt background, in accordance with the published French patent application under number 2 958 209.
According to a variant not shown, the varnish and the compound organic chemical incorporating fluorine atoms are printed in the form of a single layer.
The non-stick properties of the R coating reduce the opportunities for interaction and attachment of living pathogens microscopic such as bacteria and fungi, thereby curbing their proliferation.
Moreover, it is possible to envisage that biocidal agents are inserted in the dopant state in the layer 5 so as not to oppose a passive protection against pathogenic attacks as mentioned above, but active protection as is possible for example with ions silver [see N. Stobie et al. : Silver Doped Perfluoropolyether-Urethane Coatings:
Antibacterial Activity and Surface Analysis. Colloids and Surfaces B
: Biointerfaces Vol 72,1 (2009), pp 62-67].
The interest of providing active protection to the R coating is obvious because its implementation is at the final stage of printing the ticket, just before it is formatted. This goes against the solution proposed in EP 03740577 (ARJOWIIGGINS) which describes the protection of the support alone by a couple of biocides and overlooks the antagonistic barrier effect of inks (Offset, Soft Size, Silkscreen ...) and foils (tape polyester) on the actual effectiveness of the biocide treatment.
Work has been done to observe the effects of these impressions on bank notes.

The dirt resistance was tested according to the soiling test dry (Fritsch). This is a vibrating device where small glass beads come to spread and to incrust on a test-tube of paper a composition 5 soil-based sand, peat, activated carbon, flour, and mono-oleate glycerine (fat present in sebum). The test lasts 15 minutes. As stated above, the luminance of an initially white zone is measured at several times before and after exposure to the messy composition.
The gap obtained or to, L, allows to characterize the grip of the stain on the ticket:
the more he

10 is small, the better is the resistance to dry dirt.
Hydrophobia is characterized as the resistance to penetration of water but also its ability to repel it in area called water repellency. Resistance to water penetration is therefore measured at using the Cobb test (60 s). This is the amount of water absorbed by the support in g / m2 thanks to a cylindrical impregnation template during a period of time 60 seconds. This is an otherwise common test in the field stationer to characterize paper absorption. There is also a Cobb 300 seconds, it allows to see if the effect of the layer is always present at end longer exposure time under water.
As for water repellency, it is the natural propensity of paper to make sure that the water flows in the form of drops on the surface of a paper, by simple gravity when the substrate is inclined. This is a test visual order which has been correlated with contact angle (0) measurements of a drop of water at 500 ps (from which surface tension values are also derived). It is in effect at this time that one can consider that this drop is stabilized at the paper surface.
Oleophobia is measured through body exposure tests fat. A first method called Kit Test uses a mixture castor oil (fats) and high-boiling solvents, know the toluene (aromatic solvent) and n-heptane (aliphatic solvent).
According to the different proportions of products above mentioned, a composition is obtained whose viscosity and

11 surface vary inversely with its aggressiveness, ie its capacity impregnation.
A composition rich in castor oil is at the bottom of scale, while a composition rich in heavy solvents is at the top of this same scale.
There are 12 compositions and it is accepted that a higher or equal to 6 gives a satisfactory barrier to fat. The evaluation made visually.
Another test has been implemented, this is the fatty acid test (AG). The principle is the same as mentioned above but the composition is a mixture of fatty acids, one of which is present in sebum. This is a mixture in different proportions of castor oil (heavy fraction), acid oleic (intermediate fraction) and octanoic acid (light fraction) with of the decreasing viscosities. The test is carried out at 20 ° C. and 60 ° C.
There are 11 compositions to test and the results are also expressed in the form of visual notation. The higher up the ladder, the more the barrier effect to fatty substances is important, which corresponds to a decrease in the composition of the proportion in castor oil, an increase and then a decrease of the oleic acid and finally an increase of the acid octanoic.
The following tables record the test results for a valuable print with a support made of 100% cotton wove paper, printed in last pass in flexography with SICPAPROTECT varnish 889354 on anilox 6 / 6.5 cm3 (front / back) and dried under HONLE UV spectrum lamps mercury 200 W / cm at 65% of their power, then with the reference SOLVAY 5134 X aqueous base dried in hot air under ovens with infra-red lamps red / air hot GRAFIX at 150 C.
Against all expectations, the results obtained by treating paper bank note cotton with 5134 X alone does not give satisfaction (Board 1). So, the soil test, surprisingly, is not as good as when the supports are only varnished with the SICPAPROTECT 889354 and if the hydrophobicity is excellent, the oleophobic properties are little interesting.
It is furthermore confirmed that paper without treatment has none of the desired properties and that the paper only varnish,

12 if it has proven anti-fouling properties is only slightly hydrophobic and not oleophobic.
On the other hand, the association of the varnish and the treatment with fluorinated product gives unexpected results. Real synergy functional is obtained by combining, in this order, the varnish and the product 5134 X
(Board Two). Thus significant gains are observed in antifouling and the properties hydrophobicity and oleophobia are present and it is not about the simple addition of the properties attached to each of the constituents.
Sustainability tests were conducted on previous ones samples and it turns out that the protection of the R coating is preserved after immersion tests for 30 minutes with polar solvents (ethanol, acetone, diethylene glycol), apolar (xylene, petroleum), chlorinated (tetrachlorethylene), synthetic sweat, with acids diluted to 5% (acetic, hydrochloric, sulfuric acid), sodium hydroxide diluted 5%, oxidants diluted 5% (hypochlorite sodium, hydrogen peroxide), hot water (100 C), laundry industrial (St Mark, Persil). Moreover, the coating R retains these properties after a light resistance test (48h at Suntest), exposure to heat (120 C, 30 min) and wet wrinkling. Finally, after a Fritsch soiling test as described previously the properties of hydrophobicity and oleophobia are preserved.
Other results, not shown here, have shown that was possible to increase these gains to obtain resistance values at the dirt with an M 5, a total water-repellent, a contact angle 0 110, a note from Kit Test 7 and a test score at AG 5 playing on the report quantities deposited between the varnish and the product 5134X. We can elsewhere advance that a surface pretreatment for example of the corona type whatsoever before the UV curing varnish or before the drying of the second varnish aqueous product containing 5134 X would also positively influence the results explained above.
Performance tests were conducted with the others Solvay products mentioned above and led to some protective results everything to made similar.

o Table 1 AL (Fritsch) Cobb 60 s Water repellency * Contact angle Test Kit (max 12) Test AG (max 11) **
Printed only 27.6 1.4 ¨ 60 g / m2 1 Printed calendered *** 2 sided and varnished 16,1 2,3 ¨ 50 g / m2 2 Calendered 2-sided print treated with 5134 X 21.2 1.7 2 g / m2 <3 123 3 3 0 o * 1 does not shed, fast absorption; 2 low water repellency, absorption; 3 total water repellency, no absorption ** at 20 C
co *** means that the document is printed twice in intaglio printing, a first time on the back and a second time on the front cd.) e =

Table 2 AL (Fritsch) Cobb 60 s Water repellency Contact angle Test Kit (max 12) Test AG (max 11) Printed only 27.6 1.4 ¨ 60 g / m2 1 sid Calendered 2 sided and varnished 16,1 2,3 ¨ 50 g / m2 2 Calendered 2 sided print, varnished and treated with 5134 X
8.9 2.1 2 g / m2 <3 110 1 7 8 sid

Claims (9)

14 1. A method of surface treatment of a banknote (1) which has, at least on one of its opposite faces (20, 21), at least one printing consisting of at least one pattern (3), this face (20, 21) and its associated printing (3) being covered with a protective coating transparent (R), characterized by the fact that the installation is carried out by printing of a coating containing a varnish and a chemical compound organic compound incorporating fluorine atoms in the form of at least one group perfluoro-polyether (PFPE), on said face (20, 21), and that one carries out his drying. 2. Method according to claim 1, characterized in that said coating (R) is printed on said face in the form of two layers distinct, namely first a first layer of varnish (4) and then a second (5) containing said organic chemical compound incorporating atoms fluorine in the form of at least one perfluoro-polyether group (PFPE), in an aqueous base or in a solvent base. 3. Method according to claim 2, characterized in that the varnish is dried under ultraviolet radiation. 4. The method of claim 2 or 3 wherein said organic chemical compound incorporating fluorine atoms in the form of minus one perfluoro-polyether group (PFPE) is in a solvent base compatible with the matrix of said varnish with which it is mixed, under a functionalized form that is to say able to interact with the latter in forming chemical bonds in order to strengthen its anchoring / hooking, characterized by drying of the second layer (5) by ultraviolet radiation. The method of claim 2 or 3 wherein said chemical compound is in an aqueous base, characterized by the fact that proceeds with drying without altering or modifying said compound organic chemical, by drying in hot air. 6. Process according to claim 1, characterized in that said coating (R) is printed on said face in the form of a mixture said ultraviolet-radiation curable polish and said compound organic chemical incorporating fluorine atoms in the form of at least one perfluoro-polyether group (PFPE), in a solvent base compatible with the matrix of said varnish with which it is mixed, in a form functionalized that is to say able to interact with the latter in forming chemical bonds to reinforce its anchoring / grip. 7. Method according to claim 6, characterized in that drying said mixture under ultraviolet radiation. 8. Method according to one of the preceding claims, characterized in that said coating (R) incorporates at least one agent bactericidal and / or antifungal and / or antiviral. 9. Process according to claims 2 and 8 taken in combination, characterized by the fact that said agent is incorporated in said second layer (5).