Use of an epoxy-silicone copolymer, crosslinkable fluid composition containing same, and banknote coated with said composition

Abstract

In particular, the present invention relates to the use of an epoxy-silicone copolymer, i.e. a polyorganosiloxane provided with branches comprising epoxide functional groups, for the manufacture of an anti-graffiti surface coating of a banknote.

Description

[0001] {DESCRIPTION

[0002] Title: Use of an epoxy-silicone copolymer, crosslinkable fluid composition containing it and banknote coated with this composition

[0003] FIELD OF THE INVENTION

[0004] The present invention lies in the field of security documents. Its main subject is the use of an epoxy-silicone copolymer, a crosslinkable fluid composition containing it and a banknote coated with this composition.

[0005] STATE OF THE ART

[0006] In the field of security documents and more specifically banknotes, one of the reasons for the withdrawal of some of them by central banks is the presence of parasitic inscriptions, generally handwritten, made on the surface of these notes by users, using pens, pencils, felt-tip pens or other writing instruments.

[0007] More than just an aesthetic reason for withdrawal, writing or drawing on a banknote bearing the portrait of a living or deceased person (such as a king, queen, emir, etc.), the representation of a national symbol or a sacred entity, can be perceived in some countries as a real offense.

[0008] Current protective varnishes applied to the surface of banknotes provide barrier properties, namely that they prevent the adhesion of dry dirt particles (assessed by the Fritsch test), the penetration of aqueous substances (water resistance or hydrophobicity - assessed by the Cobb test) or greasy substances (resistance to fatty substances, grease or oleophobicity - assessed by the Test Kit) on the surface and inside the banknote.

[0009] An example of this is given in document W02013 / 045496 which describes a high-performance varnish in terms of barrier properties.

[0010] To achieve these high barrier properties, the skilled person may choose, as mentioned in the example above, to test macroscopic characteristics intended to reflect the attacks encountered by banknotes in circulation. But he may also choose to directly measure a physicochemical quantity which will be able to characterize upstream the repellent effects or the ability of a surface to be wetted through, in particular, the measurement of the interfacial tension or surface energy.

[0011] Thus in document W02014 / 067715, a high-efficiency security document varnishing solution is proposed and its performance is evaluated only by surface tension measurements, the most efficient solution having a value less than or equal to 25 mN / m.

[0012] Even if the surface energy of such coatings is very low, which generally reflects the difficulty in adhering to the surface of the security document, the present applicant has curiously noted that such varnishes do not prevent or limit sufficiently the possibility of writing on the banknotes.

[0013] In other words, it is possible to write on the note relatively easily. Despite this low surface energy, and as long as the substance (ink or similar) used for writing is not dry, it may be possible to erase what has been written with certain pens, highlighters or pencils. However, this is more difficult with a Bic brand ballpoint pen or a marker, for example. In addition, once it has dried, it is particularly difficult to erase correctly without leaving any traces.

[0014] Furthermore, it is easy to understand that a procedure implemented by central banks, consisting of attempting to systematically erase the inscriptions present on the notes, is very difficult, if not impossible to implement, unless machines are developed to clean the notes without damaging them, which would greatly increase the time and costs associated with sorting the notes before putting them back into circulation.

[0015] In a completely different field, it is known to apply anti-graffiti treatments on surfaces such as concrete, wood, masonry, metal, etc.

[0016] Again, such treatments allow for low surface energy. But the term "anti-graffiti" is misleading. Writing or applying paint with a brush or spray can (tag) to the surface is still possible, but the treatment used allows for more or less easy erasure afterward. Thus, graffiti can be completely or largely removed.

[0017] Furthermore, a state of the art of interest is constituted by documents W02015 / 091873, JPH11199673, US2016 / 060398 and W02001 / 53385. It follows from the above that there is an unresolved need for a surface coating formulation, i.e. varnish applicable to security documents and more particularly to banknotes, which not only has the barrier properties mentioned above (resistance to dry dirt, water and grease), but also anti-write properties which reflect the impossibility, or at least the difficulty, of writing on the previously varnished support, thus dissuading the man in the street from using the notes as "Post-it" (registered trademark), reminders or "vent" towards a personality or a symbol of power.

[0018] The term "anti-write" properties refers to the ability of the coating applied to a paper or plastic substrate for banknotes to resist writing. In other words, the inks of pens used during writing attempts tend to remain on the tips of the pens, to form droplets on the surface of the substrate (non-continuous line, water repellency) or to adhere with difficulty (continuous line but with low intensity and which can "bleed" easily).

[0019] In the context of the present invention, this “anti-write” property has been the subject of an instrumental and visual characterization based both on the ASTM D6578 standard entitled “Determination of Graffiti Resistance”, which is adapted to the particularity of security documents, and also on a specific test developed on this occasion to translate the difficulty of writing on the supports and therefore deter attempts at writing. More precisely, the “anti-write” property is the subject of an anti-write note described below.

[0020] STATEMENT OF THE INVENTION

[0021] This objective is achieved in accordance with the present invention.

[0022] To this end, the present invention relates firstly to the use of an epoxy-silicone copolymer, that is to say a polyorganosiloxane provided with branches comprising epoxy functions, for the manufacture of an anti-write surface coating for a banknote.

[0023] It also relates to a method for manufacturing an anti-write surface coating of a banknote in which said coating is based on epoxy-silicone copolymer, i.e. a polyorganosiloxane provided with branches comprising epoxy functions. Preferred, but not limiting, aspects of such use and such method are as follows: said polyorganosiloxane corresponds to one of the following formulas: formulas in which:

[0024] • R represent hydrocarbon groups which are identical or different from each other,

[0025] • R 1represent hydrogen atoms or hydrocarbon groups which are identical or different from each other,

[0026] • R 2 represents a hydrocarbon group with at least one carbon atom, a group which may also contain an oxygen atom,

[0027] • n > 1 and m > 1 and n > m, n and m being whole numbers,

[0028] • R 3 represents a hydrocarbon group with at least one carbon atom;

[0029] • X is a carbon atom and its index o is greater than or equal to 0, said polyorganosiloxane corresponds to one of the following formulas: (formula c) or (formula c'), formulas in which:

[0030] • R 4 is a methyl or methylene substituent bridging within the cyclohexyl and chemically stable, the combination of formula (b) and formula (c') being excluded, said polyorganosiloxane has formula (c).

[0031] Secondly, the invention relates to a fluid composition crosslinkable under ultraviolet radiation, characterized in that it comprises a cationic crosslinking matrix, as well as an epoxy-silicone copolymer, that is to say a polyorganosiloxane provided with branches comprising epoxy functions.

[0032] Preferred, but not limiting, aspects of such a composition are as follows: said polyorganosiloxane corresponds to one of the following formulas: o rule b), formulas in which:

[0033] • R represent hydrocarbon groups which are identical or different from each other,

[0034] • R 1 represent hydrogen atoms or hydrocarbon groups which are identical or different from each other,

[0035] • R 2 represents a hydrocarbon group with at least one carbon atom, a group which may also contain an oxygen atom,

[0036] • n > 1 and m > 1 and n > m, n and m being whole numbers,

[0037] • R 3 represents a hydrocarbon group with at least one carbon atom;

[0038] • X is a carbon atom and its index o is greater than or equal to 0, said polyorganosiloxane corresponds to one of the following formulas: formula c'), formulas in which:

[0039] • R 4is a methyl or methylene substituent bridging within the cyclohexyl and chemically stable, the combination of formula (b) and formula (c') being excluded, the cationically crosslinked matrix comprises a cycloaliphatic diepoxide, preferably at least 50% by weight, said polyorganosiloxane is present at least 5% by weight, preferably between 5 and 15% and even more preferably between 8 and 12%, the composition also comprises a PFPE-tetraurethane acrylate in admixture with ethyl acetate and butyl acetate, said PFPE-tetraurethane acrylate is present at least 0.5% by weight, preferably between 0.5 and 5%, and even more preferably between 2 and 4%.

[0040] Finally, the present invention relates to a banknote, at least one of its opposite faces of which carries an anti-write surface coating formed from a composition according to at least one of the aspects set out above, and which has undergone crosslinking under ultraviolet radiation.

[0041] A preferred, but not limiting, aspect of such a banknote is that said anti-write surface coating has an anti-write note

[0042] • greater than 8.5 if said at least one side is intaglio or calendered, or 4.5 otherwise,

[0043] • preferably greater than 10 if said at least one side is intaglio or calendered, or 6 otherwise,

[0044] • and more preferably greater than 13 if said at least one side is printed in intaglio or calendered, or 9 otherwise.

[0045] DETAILED DESCRIPTION OF THE INVENTION

[0046] I. EVALUATION OF THE ANTI-WRITE PROPERTY OF A VARNISHED BANKNOTE SAMPLE.

[0047] Two assessments were carried out to characterize: the ease of erasing a mark on a sample according to the ASTM D6578 standard “Determination of Graffiti Resistance”; the difficulty of writing on the sample according to a method specially developed to address the problem posed.

[0048] A. MARK REMOVAL TEST ACCORDING TO ASTM D6578 MODIFIED i. Equipment Associated with the Mark Removal Test According to ASTM D6578 Modified

[0049] Microfiber cloths;

[0050] Spectrocolorimeter marketed by the company DATACOLOR model DC45IR; Glossmeter marketed by the company BYK model 4450 Micro TRI gloss;

[0051] Tester pencils:

[0052] PentelPEN black N 50 permanent marker from PENTEL CO. LTD. (hereinafter MIN);

[0053] BIC brand SOFTfeel MED blue ballpoint pen (hereinafter SBB);

[0054] PILOT brand V Bail 0.5 Pure Liquid Ink red microball pen (hereinafter SMR);

[0055] Green erasable marker WHITEBOARD MARKER VELLEDA brand

[0056] BIC (hereinafter MEV);

[0057] Pink fluorescent highlighter Art. No. 70 / 56 refillable from the original STABILO BOSS brand (hereinafter SFR).

[0058] The selection of tester pencils and the associated references / brands are not fully specified in ASTM D6578. In fact, it is indicated: permanent marker / erasable marker / microball pen / spray paint / grease pencil for coloring.

[0059] The choice was made to replace the last two examples with a blue ballpoint pen and a pink fluorescent highlighter, as it is unlikely that spray paint or a grease pencil could be used to write on banknotes unless they were intended to be used as a work of art, but this is outside the scope of the investigation in this application. Furthermore, the colors were generally chosen to cover a wide spectral range. Cleaning agents:

[0060] MEK (Methyl Ethyl Ketone or Methyl Ethyl Ketone);

[0061] Xylene;

[0062] Gasoline (mixture of C6-C7 alkanes with a n-hexane content of less than 5%);

[0063] IPA (Isopropyl Alcohol);

[0064] 5% aqueous sodium phosphate solution;

[0065] White cotton dry cloth.

[0066] The preparation of the 5% sodium phosphate solution is done in the following proportions:

[0067] 5 g of tri-sodium phosphate dodecahydrate;

[0068] 95 g of demineralized water. ii. Carrying out the test

[0069] An area of ​​at least 1cm x 0.5cm is colored with each of the writing methods listed above. The lines must dry for at least 24 hours before carrying out the erasure test (do not exceed 48 hours of drying time).

[0070] After drying, the mark removal test is carried out with each of the cleaning agents from the list indicated above using the specified cloth. The cleaning agent used is indicated next to the removed mark. iii. Instrumental evaluations

[0071] The spectrocolorimeter is used to measure the following two characteristics for each mark made (i.e. a total of 30 measurement areas - 5 eraser pencil marks multiplied by 6 different cleaning agents (5 liquid + 1 dry):

[0072] The AE (color difference): between the area of ​​the sample chosen before making the mark and the residual mark after cleaning. Three measurements are taken at different points of the residual mark and the average is calculated. A mark is considered to be completely erased if the AE < 2. The gloss ratio ABrillance (measurement at 60°): between the area of ​​the sample chosen before making the mark and the residual mark after cleaning. Three measurements are taken at different points of the residual mark and the average is calculated. The ratio must be > 0.9 to consider that the varnish film has not been altered. iv. Rating scale

[0073] The following ratings are assigned based on the measured AE and ABrillance results (mark erased if AE < 2 and gloss ratio > 0.9):

[0074] Table 1

[0075] When half points are applied to scores of 4 and above, this means that the AE with the less aggressive cleaning agent (in decreasing order of aggressiveness: MEK, xylene, gasoline, IPA and 5% sodium phosphate solution) is close to 2 (2 < AE < 4). For example, if AE < 2 with xylene and 2 < AE < 4 with gasoline, then the score awarded will be 6.5.

[0076] Although this test is derived from an existing standard, the present applicant was able to observe in preliminary tests that the latter was not, however, sufficient to perfectly characterize the desired anti-write property. Indeed, it was observed that certain brands of tester pencils, once the ink had dried, could be particularly difficult to erase while paradoxically, it was particularly difficult to write on the treated banknotes, which would dissuade a person from any persistent attempt. A second evaluation was thus created to visually characterize the difficulty of writing on a sample.

[0077] B. WRITING DIFFICULTY ASSESSMENT TEST i. Test administration and assessment

[0078] Lines are made in several places on the sheet with each of the tester pencils, exactly as in the ASTM D6578 standard previously described and adapted to the safety document, but in this evaluation it is the behavior of the "fresh" line (i.e. the one that has just been made) which is evaluated.

[0079] This assessment is therefore done visually and a score is applied according to the rating scale detailed in the following paragraph. ii. Rating scale

[0080] The mark is awarded on the quality of the “fresh” line, in particular on its continuity, its water repellency and its intensity, according to the following cases:

[0081] Table 2

[0082] Half points allow for more precise comparisons between different samples. Between 0 and 1.5, marks are awarded based on the intensity of the line. From 2, the mark is made by observing the water repellency and the intensity of the line. C. WRITING DIFFICULTY ASSESSMENT TEST

[0083] Given that the deterrent to writing is based on the ease of being able to remove or erase the inscriptions made and to a greater extent on being able to make the support difficult to write on, the choice was made to weight the second criterion with a coefficient of 2 so as to be able to constitute a rating out of 20, that is to say:

[0084] Write-Off Score = (Mark Erasure Test Score per ASTM D6578 modified) + 2 x (Writing Difficulty Assessment Test Score).

[0085] II. TESTS FOR EVALUATING BARRIER PROPERTIES

[0086] A. FRITSCH TEST

[0087] The soiling resistance was tested using the Fritsch test, which is well known in the world of banknote printing. This test uses a vibrating device where small glass beads spread and encrust a soiling composition based on sand, peat, activated carbon, flour, and glycerin monooleate (a fatty substance found in sebum) onto a paper sample.

[0088] The test lasts 15 minutes. The luminance of an initially white area is measured several times before and after exposure to the soiling compound. The resulting difference, or AL, characterizes the adhesion of the soiling to the banknote: the smaller it is, the better the resistance to dry soiling.

[0089] B. COBB TEST ACCORDING TO ISO 535:2014 STANDARD

[0090] Hydrophobicity is described as the resistance to water penetration but also its ability to repel water on the surface, called water repellency. Resistance to water penetration is therefore measured using the Cobb test at 60 s. This is the quantity of water absorbed by the support in g / m 2 using a cylindrical impregnation template for a period of 60 seconds. This is a common test in the paper industry to characterize the absorption of paper.

[0091] C. TEST KIT ACCORDING TO TAPPI T569 STANDARD

[0092] Oil repellency or grease resistance is measured using fatty substance exposure tests. The "Kit Test" method uses a mixture of castor oil (fatty substance) and high-boiling solvents, namely toluene (aromatic solvent) and n-heptane (aliphatic solvent).

[0093] Depending on the different proportions of the above-mentioned products, a composition is obtained whose viscosity and surface tension vary inversely to its aggressiveness, i.e. its impregnation capacity.

[0094] A composition rich in castor oil is at the bottom of the scale, while a composition rich in heavy solvents is at the top of the same scale.

[0095] There are 12 compositions. A score of 0 corresponds to zero oil repellency and a score of 12 to maximum oil repellency.

[0096] III. PRINTING PROTOCOL

[0097] All samples are overprinted with the tested protective varnishes on 100% cotton wove paper, a white paper but calendered with a white intaglio (without ink) on the front to reflect the classic surface condition of a banknote printed on one side intaglio. The barrier properties of the varnishes are generally increased on the side that has been calendered intaglio (more closed paper).

[0098] The samples are varnished in flexography with a 6 cm anilox 3 / m 2 (front / back) and dried under 1ST UV lamps with mercury spectrum 200 W / cm at 65% of their power.

[0099] IV. PRELIMINARY WORK

[0100] The present applicant already had a high-performance varnishing solution dedicated to banknotes, in an attempt to resolve the technical problem posed. The varnish in question, known under the brand name ULTRA, was therefore tested and compared with a reference known in the currency market and widely used on banknotes, namely the SICPAPROTECT varnish (registered trademark) with reference 889368 marketed by the company SICPA.

[0101] These two varnishes will hereinafter be referred to as “ULTRA varnish” and “reference varnish”.

[0102] Firstly, the barrier properties were evaluated:

[0103] The average front / back results for the barrier properties of ULTRA varnish are as follows:

[0104] Table 3

[0105] Then, the tests described previously were carried out and were supplemented by surface energy measurements (see last line of the table below).

[0106] Table 4

[0107] Surprisingly, despite high barrier properties and clearly present compared to the reference varnish for a varnish weight of approximately 2 g / m 2 On the one hand, the ULTRA varnish does not show the expected anti-write properties. In any case, the ULTRA varnish has a superior anti-write property to that of the reference varnish, but this improvement is very limited and therefore needs to be reinforced.

[0108] To try to explain these results, additional measurements were carried out, in particular to evaluate the surface tension. As expected, that of the ULTRA varnish is approximately 2 times lower than that of the reference varnish but, still surprisingly, this does not translate into significantly better results with regard to the desired anti-write property.

[0109] The present applicant has therefore undertaken work to understand and test new formulations capable of exhibiting the desired anti-writing property and providing a solution to the problem posed.

[0110] Cationic polymerization varnishes generally provide effective protective coatings on banknotes (such as the reference varnish already mentioned above).

[0111] In addition, the barrier properties of cationic varnishes can be increased by choosing reaction additives in suitable dosages.

[0112] Thus, perfluoropolyether type compounds (characteristics of ULTRA varnish) are very useful for significantly improving barrier properties as mentioned previously but are not very effective in terms of anti-writing.

[0113] A possible alternative would be to use silicon-based additives such as siloxanes, some of which have anti-adhesive properties. These additives were not chosen at random. In fact, they offer, in addition to their chemical properties, economic, ecological and also safety advantages, namely: they are classified as non-hazardous, their flash point is high, notably above 94°C, their transport by road does not require the Agreement for the Carriage of Dangerous Goods by Road (or ADR), they do not produce Volatile Organic Compounds (or VOCs), and their cost is generally lower than that of perfluoropolyether compounds. In order to carry out comparative tests on different silicon-based additives, a pre-test with a discriminatory aim was carried out on a sample of siloxane-based additives.

[0114] The table below summarizes the chemical information obtained from Technical Data Sheets (TDS) and Safety Data Sheets (SDS). Several different products obtained from different suppliers were evaluated at different percentages.

[0115] Table 5

[0116] The screening pre-test carried out here and presented below in Table 6 is based, in this upstream step, on the sole difficulty in writing and with only two pencils, namely the red microball pen and the pink fluorescent highlighter because the results with these pencils are discriminating between the different varnishes tested. The reference varnish is the cationic polymerization varnish SICPAPROTECT 889368. The ULTRA varnish is the second reference and incorporates a reactive perfluoropolyether urethane compound with acrylate terminations, namely Fluorolink AD1700 (registered trademark, hereinafter AD1700) marketed by the company SOLVAY. Table 6

[0117] This pre-test confirms the previous results on the reference varnish SICPAPROTECT 889368 and on the ULTRA varnish (reference varnish + 8% AD1700), the latter presenting an interesting result on the pink fluorescent highlighter (SFR) but too fair with the red Microbead (SMR).

[0118] Although the reference varnish is predominantly cationic in polymerization, it also includes compounds capable of reacting in radical mode for optimal three-dimensional crosslinking in particular. This is the reaction mode implemented with the perfluoropolyether-urethane acrylate additive which gives excellent barrier properties, but not the expected anti-write property, or at least not in a truly significant dimension.

[0119] For the silicone products tested here according to concentrations recommended by the suppliers, surprisingly, despite acrylate functions present in some of them, none provide the desired anti-write property.

[0120] Epoxy ring-opening polymerization via cationic initiation is the main polymerization method used in the reference varnish. Cationic initiation is obtained by means of a cationic photoinitiator with, for example, triarylsulfonium hexafluorophosphate salts (for example, reference Speedcure 992 from Lambson) or diphenyl(4-phenylthio)phenylsulfonium hexafluoroantimonate salts (for example, reference DC 1176 from Comexim) which are irradiated under ultraviolet radiation. The main basic reactive compound is a cycloaliphatic diepoxide with CAS number 2386-87-0 and full name 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate. This compound is available from Cytec (under the brand UVACURE 1500), or from Comexim (under the name DOUBLEMER 420 P).

[0121] The present applicant sought a “twin” compound in terms of chemical functionality, i.e. having reactive epoxide functions and still with a siloxane structure. Thus, polyorganosiloxane compounds functionalized with epoxides were tested.

[0122] These compounds are usually used to form hydrophobic and non-stick film-forming coatings, for example on paper or synthetic plastic supports to promote the removal of adhesive materials applied to these supports, particularly reversibly, such as labels, adhesive tapes, etc.

[0123] Despite the expected chemical compatibility, it is entirely possible that the addition of these compounds will not allow the expected anti-writing property to be developed as has already been shown above. Using an additive with a reactive chemical function identical to that of the majority cationic reagent at more than 50% by mass in the formulation, the cycloaliphatic diepoxide with CAS number 2386-87-0, could be completely ineffective because it is drowned in the mass, or need to be added in too large a quantity to be economically interesting, or at worst, destabilize the formula leading to deleterious or unsuspected effects.

[0124] The same simplified protocol was used with epoxy-silicone additives from the Silcolease (registered trademark) Solventless UV range from ELKEM and reference POLY 204, RCA 200 and POLY 215 and the reference products X-62-7660 and X-62-7622 from Shin-Etsu. Table 7

[0125] In Table 7, encouraging preliminary results were obtained in anti-writing on this simplified test with the compounds cited above, which prompted the applicant to carry out complete tests. The varnishes were applied with a grammage of 1.6±0.3 g / m 2 on the front and 2.3±0.3 g / m 2 on the back. The results are shown below:

[0126] Table 8

[0127] (1) Eff = Mark Erasure Test Score per ASTM D6578 Modified (HO)

[0128] (2) Dif = score on the writing difficulty assessment test ( / 5)

[0129] The results of the 5 tester pencils are summed and averaged to obtain the overall scores below: table 9

[0130] * Face: R for recto and V for verso (1) Eff = mark erasure test score according to ASTM D6578 modified (H0)

[0131] (2) Dlf = score on the writing difficulty assessment test ( / 5)

[0132] (3) Anti-write note = (1) + 2 x (2)

[0133] Of all the additives tested, POLY 204 and X-62-7660 and x-62-7622 products achieved the best results when added at 10% in the reference varnish. These varnishes offer remarkably satisfactory anti-write performance compared to the reference varnish and the ULTRA varnish.

[0134] In order to be certain that hidden deleterious effects were not introduced by the addition of POLY 204, the barrier performances according to the tests presented above were evaluated on the following varnishes: reference varnish, ULTRA varnish, reference varnish with 10% POLY 204, reference varnish with 15% POLY 204, reference varnish with 10% POLY 204 and 3% AD1700, reference varnish with 10% X-62-7660 and reference varnish with 10% X-62-7622.

[0135] Table 10

[0136] * Face: R for recto and V for verso

[0137] (3) “xy” indicates a note between notes x and y

[0138] Regarding the dry soiling resistance test (Fritsch), no significant difference was observed between the ULTRA varnish and the varnishes incorporating 10% POLY 204, 10% X-62-7660 or 10% X-62-7622. In terms of resistance to water (Cobb) and grease, it is interesting to note that the varnish with 10% POLY204 is superior to the reference but inferior to the ULTRA. It is also of great interest to note that the 10% POLY 204 and 3% FLOROLINK AD1700 varnish has its Cobb test performance equivalent to that of the ULTRA varnish, and its Kit Test performance just one point below that of the ULTRA, which is of double interest in terms of efficiency and economy because siloxane additives are cheaper than perfluoropolyether additives.Varnishes with 10% X-62-7660 and 10% X-62-7622 also give very interesting results: if the oil resistance result is 2 points lower than that of ULTRA, particularly for X-62-7660, the water resistance is excellent and superior to ULTRA varnish without the use of perfluoropolyether additives.

[0139] The problem posed in the preamble was therefore resolved by adding an epoxidized polyorganosiloxane additive incorporated into a varnish cured by ultraviolet radiation and polymerizing mainly cationically. The anti-write property based both on the ease of erasing the lines produced and on the difficulty of making fresh inscriptions on the banknotes is satisfactory with relatively low percentages of additives, while retaining generally interesting barrier properties, with substantial environmental gains such as those mentioned above and finally, by containing the inflation of the cost price of the formulation.

Claims

DEMANDS 1. Use of an epoxy-silicone copolymer, i.e. a polyorganosiloxane with branches including epoxy functions, for the manufacture of an anti-writing surface coating for a banknote.

2. Use according to claim 1, wherein said polyorganosiloxane corresponds to one of the following formulas: formulas in which: • R represent hydrocarbon groups that are identical or different from each other, • R 1 represent hydrogen atoms or hydrocarbon groups that are identical or different from each other, • R 2 represents a hydrocarbon group with at least one carbon atom, a group which may also contain an oxygen atom, • n > 1 and m > 1 and n > m, where n and m are integers, • R 3 represents a hydrocarbon group with at least one carbon atom; • X is a carbon atom and its index o is greater than or equal to 0 3. Use according to claim 1, wherein said polyorganosiloxane conforms to one of the following formulas: rmule c'), formulas in which: • R 4 is a methyl substituent or a bridging methylene inside the cyclohexyl and chemically stable, the combination of formula (b) and formula (c') being excluded.

4. Use according to claim 3, wherein said polyorganosiloxane corresponds to formula (c).

5. A fluid composition crosslinkable under ultraviolet radiation, characterized in that it comprises a cationically crosslinked matrix, as well as an epoxy-silicone copolymer, i.e. a polyorganosiloxane provided with branches comprising epoxide functions.

6. Composition according to claim 5, characterized in that said polyorganosiloxane corresponds to one of the following formulas: (formula a) or (formula b), formulas in which: • R represent hydrocarbon groups that are identical or different from each other, • R 1 represent hydrogen atoms or hydrocarbon groups that are identical or different from each other, • R 2 represents a hydrocarbon group with at least one carbon atom, a group which may also contain an oxygen atom, • n > 1 and m > 1 and n > m, where n and m are integers, • R 3 represents a hydrocarbon group with at least one carbon atom; • X is a carbon atom and its index o is greater than or equal to 0.

7. Composition according to claim 6, characterized in that said polyorganosiloxane corresponds to one of the following formulas: rmule c'), formulas in which: • R 4 is a methyl substituent or a bridging methylene group within the cyclohexyl and is chemically stable, the combination of formula (b) and formula (c') being excluded.

8. Composition according to any one of claims 5 or 7, characterized in that the cationically crosslinked matrix comprises a cycloaliphatic diepoxide, preferably in a quantity of at least 50% by weight.

9. Composition according to any one of claims 5 to 8, characterized in that said polyorganosiloxane is present at a level of at least 5% by weight, preferably between 5 and 15% and even more preferably between 8 and 12%.

10. Composition according to any one of claims 5 to 9, characterized in that it also comprises a PFPE-tetraurethane acrylate mixed with ethyl acetate and butyl acetate.

11. Composition according to claim 10, characterized in that said PFPE-tetraurethane acrylate is present at a level of at least 0.5% by weight, preferably between 0.5 and 5%, and even more preferably between 2 and 4%.

12. Banknote, characterized in that at least one of its opposite faces bears an anti-writing surface coating formed of a composition according to any one of claims 6 to 11 which has undergone cross-linking under ultraviolet radiation.

13. Banknote according to the preceding claim, characterized in that said anti-writing surface coating has an anti-writing rating greater than 8.5 if said at least one side is printed in intaglio or calendered, or 4.5 otherwise, preferably greater than 10 if said at least one side is printed in intaglio or calendered, or 6 otherwise, and more preferably greater than 13 if said at least one side is printed in intaglio or calendered, or 9 otherwise.

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