CA2848934C - Method for treating the surface of a banknote - Google Patents

Abstract

The present invention relates to a method for treating the surface of a banknote (1) comprising, on at least one of its opposing surfaces (20, 21), at least a printed item comprised of at least a design (3), this surface (20, 21) and its associated printed item (3) being covered in a transparent protective coating (R), characterized by the fact that a coating is applied via printing, said coating containing a varnish and an organic chemical compound incorporating fluorine atoms in the form of at least a perfluoro-polyether (PFPE) group, on said surface (20, 21), and by the fact that it is dried.

Description

METHOD FOR THE SURFACE TREATMENT OF A BANKNOTE
The bank note, originally called paper money, exists since the 10th century. This means of payment was introduced by traders in Chinese tea to avoid the transport of metallic coins. The first ones banknotes officially issued in France were issued for the first time in 1803.
Since its inception, paper money has been made using cotton. Since a cotton, however, gives up a bit of ground in the thirties polymer (s), more resistant according to its promoters. That the ticket holder either cotton or polymer (s), its manufacture and recovery remain unchanged.
A succession of printing and security processes (e.g.
dry offset, wet offset, intaglio, flexography, screen printing or the hot stamping ...) leads to a high value end product added.
It is therefore essential to give an increased longevity to this ticket, to prevent it from deteriorating too quickly.
If we want to increase the longevity of these valuable prints, it is fundamental to understand the reasons that lead to the withdrawal of tickets.
The complexity of producing a ticket is by nature a essential condition to discourage attempts at counterfeiting.
Effective deterrence is achieved by applying several types of security at different levels.
The first level secure elements are elements detectable with the naked eye, in daylight or artificial light and requiring no 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 items.
The so-called second level safety devices 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 texts printed in invisible ink but visible under ultra-violet radiation or infrared, fluorescent fibers, magnetic wires etc ...

2 Finally, the third level of security requires devices sophisticated and, therefore, a high investment. Those are mainly central banks examining these securities, such as tracers present in tickets.
One of the conditions necessary to guarantee the role of these security and their correct authentication over time is the right one aging of the ticket. Central banks must exchange any returned banknotes (various causes: soiling, tearing, mutilation ...) if it is identifiable at at minus 50%. It is therefore essential to be able to discern and control the multiple elements that compose it.
Central banks are thus showing increasing interest in more durable notes, both in terms of mechanical strength and chemical resistance.
In this way, a cleaner, more hygienic ticket and a extended service life could be brought into circulation while ensuring costs lower life cycle.
However, to create such a product, it is necessary to understand what really weakens the banknotes, leading to a withdrawal of the circulation.
Several studies have been carried out by central banks to characterize the possible causes of withdrawal of tickets. Among the various causes cited (DE HEIJ Hans. Durable Banknotes: an overview. In: Presentation of the BPC / Paper Committee to the BPC, May 2002, Prague.), A cause stands out others: dirt.
It would be responsible, up to 60 to 80%, for the withdrawal of traffic bank notes. One of the main elements of this soiling consists of human sebum, a fatty substance naturally present on the surface of the skin.
For this reason, those involved in the trade and in particular papermakers are trying to provide solutions such as Haute Papers Durability or anti-fouling beds for example. They allow respectively to strengthen mechanical resistance and chemical resistance tickets.
Thus, various assemblies are offered by the paper manufacturers. The differences vary between the composition of the fibrous mattress (100% cotton,

3 blend of natural fibers, blend of natural and synthetic fibers, polymer etc.) and the coating / impregnation sauces used.
For example, natural fibers other than cotton can be linen or abaca, synthetic fibers are based on polyethylene, polypropylene. The support can even be constituted exclusively of bi-oriented polypropylene.
As for the anti-fouling coating, it may for example be polyurethane or latex based sauces. These last examples are good heard not 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 mechanical while others have improved in terms of properties anti-fouling but these supports must retain this characteristic inalienable that is printability.
These new papers, in addition to their higher cost, also have another weakness. Following the treatments they underwent during the manufacture of paper, if the longevity of the supports is increased, this does not guarantee the protection of security impressions, a fundamental aspect mentioned above.
Document W002051638 describes a technique which consists in operating a varnishing in flexography of the support at the end of the process of making the ticket. This overprint varnish improves the resistance to the soiling of the ticket and thus protects the entire print. By a alone passing through the machine, without turning, we protect the two 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 offered by Sicpa under the references SicpaProtect 889354 and 889405. Other references also work like Schmidt Rhyner WESSCO Protector 36.298.42 varnishes and the one of Actega TerraGloss UV Special Coating VP-HB 100-080.
A soiling test (the procedure of which will be described later) is characterized as the luminance measurement differential L of a soiled sample and an unsoiled control sample on a portion not printed. Thus, a white wove paper made of 100% cotton presents, when he is subjected to this test, an M of about 20-30 units and this same varnish paper with SicpaProtect reference 889354 printed in flexography, with an anilox of

4 6 / 6.5 cm3 (approximately 2g / m2 transferred) an M between 14 and 18, i.e. a gain around 40%.
This result is already appreciable in itself but, unfortunately, the hydrophobic and oleophobic qualities of such varnished paper with the reference SicpaProtect 889354 are quite low.
Furthermore, it is known in the field of packaging.
want to protect them from the aggression of juices, sauces and other fats, at least until the products they contain go be consumed.
Solvay, for example, offers products based on fluorine, the non-stick properties of which are also well known.
Many references present the properties of hydrophobicity and oleophobia wanted, in particular two aqueous dispersions based on perfluoro-polyether (PFPE, X - [-(CF2-CF2-0) ,, - (CF20) õ1-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, that is to say that the basic molecule additionally contains reactive chemical functions. She is suitable for being mixed with matrices of polymerisable varnishes under UV radiation and can therefore react by forming chemical bonds with these last to strengthen its anchoring / grip. These products were created for respond to health and environmental problems related to PFOA (perfluoro-ocatnoic acid) and PFOS (perfluoro-octane sulfonate). Products previously mentioned, based on PFPE, do not contain PFOA or PFOS and their neither are degradation products.
These products give good barrier properties to oils and grease to paper and or cardboard supports. They are both used as surface treatment, applicable by flexography, rotogravure or any another usual sleeping process.
Surface deposition creates an invisible chemical barrier of PFPE.
These references are commonly used in the packaging industry food (for example bag for foodstuff for animals, boxes for pizza). In addition, their accreditation for food contact attests to their harmlessness.

The present applicant therefore proposes to remedy the disadvantages mentioned above with regard to fiduciary varnishes by a process which makes it possible to reinforce all the properties presiding over the longevity of a ticket, namely resistance to soiling, hydrophobicity,

5 oleophobia, so as to decrease the retention of particles macroscopic dirt, to repel, thanks to quantifiable barrier effects, water of the sweat and fat from sebum.
Thus, the present invention relates to a method of surface treatment of a banknote which comprises, at least on one 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 the 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 we proceed to its drying.
Thanks to the implementation of this technique, we obtain the following results / advantages / characteristics:
- the whole of the printed value (i.e. the support and its prints) is protected;
- the resistance to soiling is more efficient than that of 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 aforementioned properties are not improved detriment to economics and does not use physical processes complexes significantly increasing, if not unbearable, the cost of making the ticket;
- 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, rotogravure or screen printing;

WO 2013/04549

6 - processing, once the security document has been produced and dry coating, is compatible with epidermal contact, without being known toxic or allergenic.
According to other advantageous and non-limiting characteristics of this process :
- said coating is printed on said face in the form of two separate 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 of said varnish is carried out under radiation ultraviolet;
- said organic chemical compound incorporating atoms of 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 capable of interacting with this last by forming chemical bonds to strengthen its anchoring / hanging;
- 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 the base in hot air aqueous;
- said coating is printed on said face in the form of a mixing of said polymerisable varnish under ultraviolet radiation and of said organic chemical compound incorporating fluorine atoms in the form of at least 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 capable of interacting with the latter in forming chemical bonds in order to strengthen its anchoring / grip;
- drying of said mixture is carried out under ultra-purple;
- Said coating incorporates at least one bactericidal agent and / or antifungal and / or antiviral;
- Said agent is incorporated into said second layer.

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

8 By printing consisting of a pattern means any element printed, whatever the ink used, which forms any figure, by example in the form of an openwork or not, this figure being able in particular be among others an alphanumeric character.
In FIG. 1 is shown very schematically a document 1, in this case a banknote consisting of a support 2 made of paper or cotton fibers for example, whose opposite upper and lower faces are referenced 20 and 21.
On the upper face 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 known as 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 colorless varnish 4, the definition of which has been given upper.
20 Good heard, figure 2 as well as the following are given as illustrative only, so that the proportions, in particular in thickness, born not reflect reality. Furthermore, only the face 20 is coated with a fine varnish of explanation and not to unnecessarily burden the figures. Of course, in reality and for optimal 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 SicpaProtect reference 889354 printed in flexography, with a 6 / 6.5 cm3 anilox (approximately 2g / m2 transferred) and dried under HONLE UV lamps mercury spectrum 200 W / cm at 65%
their power).
After drying, we print in flexography with anilox identical to those described above on layer 4, another layer 5 incorporated an organic chemical compound incorporating fluorine atoms in the form at least one PFPE perfluoro-polyether group or at least one of its derivatives in an aqueous base version. After layer 5 has dried, both layers 4 and 5 then form a coating R.

9 The drying of layer 5 is carried out by evaporation under a GRAFIX infrared / hot air lamp at 150 C.
In a different embodiment, said drying consists of a drying by ultraviolet radiation of the same type as that mentioned above, especially when the organic chemical compound incorporating atoms of 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 Figures 4 to 6 is similar to that described previously. It differs from it only in that a pattern 31 in form of F is printed as a glossy region on a mat background or surrounded by a matt bottom, 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 possibilities for interaction and attachment of living pathogens microscopic, such as bacteria and fungi, thereby slowing down their proliferation.
Furthermore, it is possible to envisage that biocidal agents are inserted as a dopant in layer 5 so as not to oppose a passive protection against pathogenic aggressions as mentioned above, but active protection as is possible for example with ions money [cf. 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 advantage of providing active protection to the coating R is obvious because its implementation is at the final stage of printing the ticket, just before it is finished. This goes against the solution proposed in EP 03740577 (ARJOWIIGGINS) which describes the protection of the support alone by a couple of biocides and ignores the antagonistic barrier effect of inks printing (offset, intaglio, screen printing ...) and foils (strip of polyester) on the real effectiveness of the biocidal treatment.
Work has been carried out to observe the effects of these printing on banknotes.

Resistance to soiling has been tested according to the soiling test dry (Fritsch). It is a vibrating device where small glass beads spread out and encrust a composition on a paper test tube 5 messy based on sand, peat, activated carbon, flour, and mono-oleate glycerin (fatty substance present in sebum). The test lasts 15 minutes. As stated above, the luminance of an initially white area is measured at several times before and after exposure to the messy composition.
The gap obtained or at, L, characterizes the grip of the dirt on the ticket:
the more he

10 is small, the better the resistance to dry soiling.
Hydrophobia is characterized as resistance to water penetration but also its ability to repel the latter in area called water repellency. The 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 over a period of time 60 seconds. It is an otherwise frequent test in the field stationer to characterize the absorption of the paper. There is also a Cobb at 300 seconds, this allows to see if the effect of the layer is still present at end longer exposure time underwater.
As for water repellency, it is the natural propensity of paper to make the water flow in the form of drops on the surface of a paper, for example simple gravity when the substrate is tilted. It is a test visual which has been correlated with contact angle (0) measurements from a drop of water to 500 ps (from which the surface tension values are also obtained). This is in effect at this point that we can consider that this drop is stabilized at the surface of the paper.
Oleophobia is measured using body exposure tests bold. A first method called Kit Test implements a mixture castor oil (fat) and high boiling solvents, know the toluene (aromatic solvent) and n-heptane (aliphatic solvent).
Depending on the different proportions of products mentioned above, a composition is obtained whose viscosity and tension

11 surface vary inversely with its aggressiveness, i.e. its capacity impregnation.
A composition rich in castor oil is located at the bottom of the scale, while a composition rich in heavy solvents is located at the top of this same scale.
There are 12 compositions and it is accepted that a higher grade or equal to 6 gives a satisfactory barrier to fat. The evaluation is 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. It is a mixture in different proportions of castor oil (heavy fraction), acid oleic (intermediate fraction) and octanoic acid (light fraction) with of 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 you climb the ladder, the more the barrier effect to fatty substances is significant, which corresponds to a decrease in the composition of the proportion in castor oil, an increase then a decrease in oleic acid and finally an increase in acid octanoic.
The tables below show the test results for a valuable print with a support in 100% cotton wove paper, printed in as a last pass in flexography with a SICPAPROTECT 889354 varnish on 6 / 6.5 cm3 anilox (front / back) and dried under HONLE spectrum UV lamps mercury 200 W / cm at 65% of their power, then with the reference SOLVAY 5134 X aqueous base dried with hot air under ovens equipped with infrared lamps red / air GRAFIX hot at 150 C.
Against all expectations, the results obtained by processing the paper banknote cotton with 5134 X alone is not satisfactory (Board 1). So the dirt test, surprisingly, is worse than when the supports are only varnished with SICPAPROTECT 889354 and if the hydrophobicity is excellent, the oleophobic properties are little interesting.
It is also confirmed that untreated paper does not has none of the properties sought and that only varnished paper,

12 if it has proven anti-fouling qualities is only slightly hydrophobic and not oleophobic.
On the other hand, the combination of varnish and treatment based on fluorinated product gives unexpected results. A real synergy functional is obtained by combining, in this order, the varnish and the product 5134 X
(Board 2). Thus significant gains are observed in anti-fouling and the properties hydrophobia and oleophobia are present and it is not the simple addition of the properties attached to each of the constituents.
Durability tests have been conducted on the previous ones samples and it turns out that the protection of coating R is retained after immersion tests for 30 minutes with polar solvents (ethanol, acetone, diethylene glycol), apolar (xylene, petroleum), chlorinated (tetrachlorethylene), to synthetic sweat, with acids diluted to 5% (acetic, hydrochloric, sulfuric), with sodium hydroxide diluted to 5%, to oxidizers diluted to 5% (hypochlorite sodium, hydrogen peroxide), hot water (100 C), washing powder industrial (St Marc, Parsley). Furthermore, the coating R retains these properties after a light-fastness test (48h at Suntest), exposure to heat (120 C, 30 min) and damp crumpling. Finally, after a Fritsch soiling test like describes previously the hydrophobicity and oleophobicity properties are preserved.
Other results, not shown here, have shown that was possible to increase these gains to obtain resistance values at the soiling with M 5, total water repellency, contact angle 0 110, a mark of Kit Test 7 and a mark of tests at GA 5 while playing on the report of the quantities deposited between the varnish and the product 5134X. We can by elsewhere advance that a surface pre-treatment for example of the corona type whether before UV-drying varnish or before drying of the second base varnish aqueous product 5134 X would also have a positive influence the results set out above.
Performance tests were conducted with the others Solvay products mentioned above and have led to protective results all to made similar.

o Table 1 AL (Fritsch) Cobb 60 s Water repellency * Contact angle Test Kit (max 12) Test AG (max 11) **
Printed alone 27.6 1.4 ¨ 60 g / m2 1 Calendered print *** 2 sides and varnish 16.1 2.3 ¨ 50 g / m2 2 2-sided calendered print and treated with 5134 X 21.2 1.7 2 g / m2 <3,123 3 3 0 o * 1 does not water repellency, rapid absorption; 2 low water repellency, absorption; 3 total water repellency, no absorption ** at 20 C
co *** means that the document has passed intaglio twice, 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 alone 27.6 1.4 ¨ 60 g / m2 1 sid 2-sided calendered print and varnish 16.1 2.3 ¨ 50 g / m2 2 2-sided calendered print, varnished and treated with 5134 X
8.9 2.1 2 g / m2 <3 110 1 7 8 sid

Claims (10)

14 1. Method for surface treatment of a banknote which comprises, at least on one of its opposite faces, at least one imprint consisting of at least one pattern, this face and its associated impression being covered with a transparent protective coating, characterized by the fact than we proceed with the installation by printing of said protective coating transparent which contains a varnish and an organic chemical compound incorporating fluorine atoms in the form of at least one perfluoro-polyether group, on said face, and that it proceeds to drying. 2. Method according to claim 1, characterized in that said transparent protective coating is printed on said face in the form two separate 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. 3. Method according to your claim 2, characterized in that one proceeds to dry said varnish under ultraviolet radiation. 4. The method of claim 2 or 3 wherein said compound organic chemical incorporating fluorine atoms 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 form functionalized that is to say capable of interacting with the latter by forming bonds chemicals in order to strengthen its anchoring / grip, characterized in that one proceeds to dry the second layer by ultraviolet radiation. 5. Method according to claim 2 or 3 wherein said compound organic chemical is in an aqueous base, characterized by the fact that proceeds to drying without alteration or chemical modification of said compound organic chemical, by drying under hot air. 6. Method according to claim 1, characterized in that said transparent protective coating is printed on said face in your form of a mixture of said varnish and of said organic chemical compound incorporating fluorine atoms in the form of at least one perfluoro-polyether group, in a solvent base compatible with the matrix of said varnish with which it is mixed, in a functionalized form, i.e. capable of interacting with the latter by forming chemical bonds in order to strengthen its anchoring / hanging. 7. Method according to your claim 6, characterized in that said varnish is a varnish polymerizable under ultraviolet radiation. 8. Method according to claim 7, characterized in that you proceeds to dry said mixture under ultraviolet radiation. 9. Method according to one of claims 1 to 8, characterized by the causes said transparent protective coating to incorporate at least one agent bactericidal and / or antifungal and / or antiviral. 10. Method according to your claims 2 and 9 taken in combination, characterized by the fact that said agent is incorporated into said second layer .