FR3012365A1 - SECURITY DOCUMENT - Google Patents

Abstract

The invention relates to a security document such as a banknote, which comprises a support of fibrous material (1) having two opposite faces recto (11) and verso (12), each of these faces being covered with a coating protection device (21, 22), characterized in that it comprises a layer (3) of a single adhesive between each of the two coatings (21, 22) and said support (1) and in that said layer (3) of adhesive comprises at least one zone of strong adhesion (32) and at least one zone of weak adhesion (31) between each of said coatings (21, 22) and said support (1).

Description

The present invention relates to a security document, more particularly but not exclusively a banknote. During their lifetime, the notes are exposed to many manipulations in a more or less aggressive outside environment. They are thus subject to the deposit of dirt, but also to mechanical damage, such as more or less pronounced folds, tears or perforations, for example. When the tickets no longer comply with the cleanliness or deterioration requirements applied in a country, they are removed from circulation and destroyed. In order to extend the running time of these tickets as well as the duration of visibility and authentication of the security elements they comprise, it has been proposed to endow them with increased resistance means. Thus known, according to the state of the art, banknotes 15 covered or impregnated with a protective layer, for example based on polyurethane. This allows to give the paper forming the ticket support, improved resistance to mechanical stresses and dirt. However, care must be taken to ensure that this protective layer does not affect the quality of the printing or the hold of the inks deposited. Another technique known in the prior art consists in coating the printed note on a standard cotton paper with a protective layer of the varnish type, and this after printing. This technique has the advantage of protecting both the support and its printing but the disadvantage of not improving the mechanical performance of the base support. In order to alleviate the aforementioned problems, the Applicant proposes to laminate the support with the aid of a continuous plastic film, coated on its face in contact with the paper, with various types of adhesives / glue. This technique, known in the field of publishing and commercial printing, makes it possible to obtain resistance results that are much higher than those obtained with a varnish, but above all to increase the support properties of the support as basic as possible. be they. However, there is then a specific problem related to the application of this technique to a security document.

According to the manufacturing techniques of the paper constituting the note, it can consist of a layer (monolayer) or of several (bilayers or bi-jets). In both cases, and in particular in the case of a bilayer paper, it is possible, using certain precautions, delaminate the ticket by separating it in two. When the paper is covered with a plastic film, this separation is still greatly facilitated. Indeed, the plastic films deposited on one and the other face of the paper, once their adhesive systems polymerized, allow to maintain the fibers and support the two layers of paper during their separation thereby preventing any tear.

It is easy to understand the interest that fraudsters would have to properly delaminate a banknote, so as to obtain two layers, one of whose faces would have original authentication characteristics. It would then suffice to postpone this layer on a support counterfeit the opposite side to obtain two banknotes from a single.

The object of the invention is to solve the aforementioned drawbacks of the state of the art and to provide a security document, comprising a support of fibrous material covered on its front and back sides with a protective coating, such as a plastic film which can not be delaminated or which is at least visibly destroyed or damaged, if it were to undergo an attempt at delamination by rendering it completely useless. To this end, the invention relates to a security document, such as a banknote, which comprises a support made of fibrous material having two opposite sides front and back, each of these faces being covered with a protective coating. According to the invention, this document comprises a layer of a single adhesive between each of the two coatings and said support, this adhesive layer comprising at least one zone of strong adhesion and at least one zone of weak adhesion between each of said coatings. and said support. According to other advantageous and nonlimiting features of the invention, taken alone or in combination: the security document comprises several zones of strong adhesion and several zones of weak adhesion, arranged alternately; said zone of strong adhesion is obtained by heating at a higher temperature than that applied to the zone of weak adhesion; there is a junction zone between the zone or at least one of the zones of strong adhesion of the front face of the support and the zone or at least one of the zones of strong adhesion of the back side of the support, this zone junction consisting of a chemical composition impregnated in the mass of the fibrous material of the support and the zone of strong adhesion corresponding to the contact zone between said junction zone and the portion of said adhesive layer situated opposite this junction zone ; the chemical composition used to form the junction zone is an ink; the ink is chosen from acrylic inks or inks with a high wetting power, such as inks comprising monomers with a very low surface tension, resins or photos of initiators; the chemical composition used to form the junction zone is an adhesive different from that of the layer placed between each of the two coatings and the support; the adhesive used to form the junction zone and the adhesive used to form the layer disposed between each of the two coatings and said support are chosen from: ethylene-vinyl acetate (EVA), polyamide copolymer-type glues ( PA), polyurethane, epoxy, polyester and copolyester; the adhesive used to form the joining zone and the adhesive used to form the layer placed between each of the two coatings and said support are chosen from: adhesives whose softening is caused by temperature and whose crosslinking is caused by a exposure to ultraviolet rays; the junction zones are in the form of several series of intersecting patterns; the layer of adhesive disposed between each of the two protective coatings and said support further comprises at least one zone of very low adhesion; the security document further comprises at least one half-cut of the support from one of its faces front or back; said protective coating is a plastic film, preferably transparent or translucent; and said plastic film is selected from mono- or bi-oriented polypropylene, polyester, polyester terephthalate, polyvinyl chloride, polycarbonate, polytetrafluoroethylene (PTFE), a fluoropolymer, acrylonitrile-butadiene-styrene (ABS) nylon (polyamide), polylactidepolymer (PLA), di-acetate or a starch-type biopolymer. Other features and advantages of the invention will appear from the description which will now be made, with reference to the accompanying drawings, which represent, by way of indication but not limitation, a possible embodiment. In these drawings: FIGS. 1, 2 and 4 are diagrams representing in cross-section various embodiments of a security document according to the invention, and FIG. 3 is a diagram showing a banknote conforming to FIG. the invention, viewed from above and in transparency. The invention relates to a security document, such as a banknote for example. As can be seen in FIG. 1, this security document 25 comprises a support made of fibrous material 1, which has two opposite faces recto 11 and verso 12, each of these faces being covered with a protective coating 21, respectively 22 The support of fibrous material 1 mainly comprises fibers of cellulosic nature and more particularly cotton fibers. However, natural flax or abaca fibers or synthetic fibers, polyethylene, polypropylene or a mixture of one or more of these fibers may be used. It is also possible to add to this support 1 fibers based on biopolymers other than cellulose or nanobiopolymers. In FIG. 1, this support 1 is shown as a single-layer or single-jet material. However, it may also have several jets or layers, assembled during manufacture in the wet state.

The protective coating 21, 22 is preferably a plastic film, more preferably transparent or translucent. By way of non-limiting example, examples of materials for producing these films are: mono- or bi-oriented polypropylene, polyester, polyester terephthalate, polyvinyl chloride, polycarbonate, polytetrafluoroethylene (PTFE) ), a fluoropolymer, acrylonitrile-butadiene-styrene (ABS), nylon (polyamide), polylactidepolymer (PLA), di-acetate or a starch-type biopolymer. Preferably, the thickness of the films 21, 22 is between 3 [Inn and 100 [Inn, more preferably between 8 [Inn and 15 [Inn. These protective coating films 21, 22 may also receive a treatment which imparts a matt appearance to the material, such as a coextrusion layer, fillers or additives in the bulk of the material, lacquer coating or deformation. of surface. More precisely, the film can be secured by visible elements of the same type as those used on the banknotes for their authentication (eg dry stamp, iridescent prints, etc.) and / or by non-visible elements of the tracer type with specific spectral imprint. and unique. The technique which makes it possible to deposit the plastic film 21 or 22 on the support 1 is known and referred to as "laminating". The adhesion between the film 21 or 22 and the support 1 is provided by a layer of a single adhesive 3, that is to say a layer of the same adhesive 25 extends over the entire surface between one of the protective coatings 21 or 22 and the support of fibrous material 1. However, adhesives of different types could be used on the front face 11 of the support and on its back side 12. Moreover, this "single" adhesive could be mono or multi-component. On the other hand, it is excluded to have a layer 3 consisting of several zones of different adhesives side by side. When this adhesive is present on the film in the dry state, it is called "dry lamination". Conversely, when it is in the form of a liquid applied to the film 21 or 22 at the time of its contact with the support 1, it is called "wet filming". In the case of "dry film coating", the adhesive previously deposited on the film 21 or 22 is reactivated in contact with a heated calender. This allows the softening of the adhesive which will partially penetrate the substrate 1 and crosslink under the effect of this rise in temperature. Without forming an exhaustive list, the adhesives that can be used are then of the copolymer type of ethylene vinyl acetate (EVA), polyamide (PA), polyurethane, epoxy, polyester or copolyester. It is also possible to use an adhesive whose softening is caused by temperature and whose crosslinking is caused by exposure to ultraviolet rays. In the case of "wet filming", it is possible to use adhesives of the solvent-free (for example polyurethane), solvent-type or ultraviolet-crosslinking type. Whatever the type of adhesive used, and in accordance with this first embodiment of the invention, a heat treatment is carried out at different temperatures of different areas of the security document, so as to form zones known as of "low adhesion" 31 and so-called "high adhesion" zones 32, schematized by an area of the layer 3 carrying crosses. This heat treatment is carried out by hot lamination. Thus, for example, areas of high adhesion 32 will be heated to higher temperatures than areas of low adhesion 31. The notions of "strong" or "weak" adhesion are relative notions which simply mean that in a zone of strong adhesion, the coating 21 or 22 adheres more with the support 1 than in a low adhesion zone. The strength of the adhesion can be measured for example by two techniques, known as internal cohesion (known as Scott Bond) or peel test (peel test in English) at 90 ° or 180 °. Preferably, the security document comprises several zones of strong adhesion 32 and several zones of weak adhesion 31, arranged alternately. These zones may be in the form of parallel strips, of identical widths or not. These widths can also be different between the front face and the back side of the support 1. Finally, patterns other than lines can also be envisaged.

Due to the presence of the zones having different adhesion forces, an attempt to delaminate the security document will lead to a visible degradation, since the film 21, 22 and the support 1 will not separate homogeneously.

A second embodiment will now be described with reference to FIG. 2. The same elements as those described above bear the same numerical references. In this case, there is a junction zone 5 between the zone or at least one of the zones of strong adhesion of the recto face 11 of the support 1 and the zone or at least one of the zones of strong adhesion of the This junction zone 5 consists of a chemical composition impregnated into the mass of the fibrous material of the support 1. The zone of strong adhesion corresponds in this case to the contact zone between the junction zone 5 mentioned above. and the portion of the adhesive layer 3 located opposite this junction zone. This zone of strong adhesion is referenced 32 '. According to a first variant embodiment, the chemical composition used to form this junction zone 5 is an ink. This ink is chosen from inks capable of penetrating into the fibers of the paper constituting the support 1, namely acrylic inks or inks with high wetting power comprising, for example, monomers with very low surface tension, resins or photos. -initiateurs. These inks can be deposited by any technique known in the field of printing: for example, offset, inkjet, letterpress, flexography, screen printing, gravure, coating and intaglio. The adhesive 3 and the ink used to form the junction zone 5 are respectively chosen so that the adhesion strength of the adhesive with the ink is greater than the internal cohesion of the fibrous material constituting the support 1. Thus, this zone of strong adhesion 32 'constitutes a point of resistance to delamination greater than that of paper alone. By "internal cohesion" is meant all the forces which maintain between them the particles of the fibrous material of the support 1. According to another variant embodiment of the invention, the chemical composition used to form the junction zone 5 is an adhesive also deposited by the printing techniques mentioned above, but also by gravure or "coating". This adhesive may be identical to or different from that used to form the layer 3 between each of the two coatings 21, 22 and the support 1.

Whatever the nature of the junction zone or zones 5, these are formed inside the support 1 prior to filming with the aid of the films 21 and 22. The junction zones 5 can be provided in the form of discrete areas or "columns" connecting the front and back sides of the support 1.

They may also be in the form of lines extending for example from one edge to the other of the note (see Figure 3) or under any other type of pattern. These junction zones 5 may be in the form of several series of patterns 6, 6 'which intersect, (here series of lines 15 shown in solid lines and series of lines shown in dotted lines in FIG. 3). According to an alternative embodiment, it is also possible to provide an area of very low adhesion 4 between each of the protective coatings 21, 22 and the support 1. This area of very low adhesion is added to the 20 zones of weak and strong adhesions above. It has been shown for illustrative purposes on the embodiment of FIG. 2 but could also be implemented in the embodiment of FIG. 1. The notion of "zone of very weak adhesion" is a relative notion which means that in this zone, the protective coating 21 or 22 25 adheres less to the support 1 than in a so-called low adhesion zone 31. This zone of very weak adhesion is obtained for example by a low temperature heat treatment or having previously deposited on said area a varnish with non-stick properties to reduce adhesion performance.

The adhesives used for the layer 3 or the junction zone 5 may also comprise security elements of the fluorescent, phosphorescent, infrared visible, magnetic, conductive elements type or any other tracer capable of emitting a particular and safe signature. Finally, in order to further strengthen the protection of the security document against delamination or in order to make it more visible, it is possible to provide in the security documents, made according to the various aforementioned modes, the realization of cuts 7 say "half-flesh" of the support 1, from one of its front faces 11 or 12 back. This embodiment variant is shown in Figure 4. These cuts half-flesh 7 can be parallel to each other or 5 no, rectilinear or not, present on one side or both and arranged in this case so that the cuts formed from the front face do not cut those formed from the reverse side. Thanks to these characteristics of the invention, and in particular to the presence of the zones of different adhesion forces, a counterfeiter can delaminate the security document in two parts, without causing visible damage. Indeed, if a forger exerted a pull to remove the two layers of coating 21, 22, the support 1 would preferentially dissociate at low adhesion areas or even very low adhesion and remain attached to the coating layers 21 and 22 to level of the 15 zones of stronger adhesion resulting in tears and a delamination perfectly unequal support canceling the interest of their reuse.

Claims (14)

REVENDICATIONS1. Security document, such as a banknote, which comprises a support of fibrous material (1) having two opposite faces (11) and (12), each of these faces being covered with a protective coating (21, 22), characterized in that it comprises a layer (3) of a single adhesive between each of the two coatings (21, 22) and said support (1) and in that said layer (3) of adhesive comprises at least one at least one zone of strong adhesion (32, 32 ') and at least one zone of weak adhesion (31) between each of said coatings (21, 22) and said support (1). 2. Security document according to claim 1, characterized in that it comprises several areas of strong adhesion (32, 32 ') and several areas of low adhesion (31), arranged alternately. 3. Safety document according to claim 1 or 2, characterized in that said zone of strong adhesion (32) is obtained by heating at a higher temperature than that applied to the zone of weak adhesion (31). 4. Security document according to claim 1 or 2, characterized in that there is a junction zone (5) between the zone or at least one of the zones (32 ') of strong adhesion of the front face (11). ) of the support (1) and the zone or at least one of the zones (32 ') of strong adhesion of the back face (12) of the support (1), in that this joining zone (5) consists of a chemical composition impregnated in the mass of the fibrous material of the support (1) and in that the zone of strong adhesion (32 ') corresponds to the contact zone between said joining zone (5) and the portion of said adhesive layer (3) located opposite this junction zone (5). 5. Security document according to claim 4, characterized in that the chemical composition used to form the junction zone (5) is an ink. 6. Security document according to claim 5, characterized in that the ink is chosen from acrylic inks or inks with high wetting power, such as inks comprising monomers with very low surface tension, resins or photos. initiators. 7. Security document according to claim 4, characterized in that the chemical composition used to form the junction zone (5) is an adhesive different from that of your layer (3) disposed between each of the two coatings (21, 22) and the support (1). 8. Security document according to claim 4 or 7, characterized in that the chemical composition used to form the junction zone (5) is an adhesive and in that this adhesive as well as the adhesive used to form your layer (3). ) disposed between each of the two coatings (21, 22) and said support (1) are chosen from: copolymer-type glues of ethylene vinyl acetate (EVA), polyamide (PA), polyurethane, epoxy, polyester and copolyester . 9. Security document according to claim 4 or 7, characterized in that the chemical composition used to form the junction zone (5) is an adhesive and in that this adhesive and the adhesive used to form the layer (3). ) disposed between each of the two coatings (21, 22) and said support (1) are selected from adhesives whose softening is caused by temperature and whose crosslinking is caused by exposure to ultraviolet rays. 10. Security document according to one of claims 4 to 8, characterized in that the junction zones (5) are in the form of several series of patterns (6, 6 ') which intersect. 11. Security document according to one of the preceding claims, characterized in that the layer (3) of adhesive disposed between each of the two protective coatings (21, 22) and said support (1) further comprises at least one zone of very weak adhesion (4). 12. Safety document according to one of the preceding claims, characterized in that it further comprises at least one cut half-flesh (7) of the support (1) from one of its front faces (11) or back (12). 13. Security document according to one of the preceding claims, characterized in that said protective coating (21, 22) is a plastic film, preferably transparent or translucent. 14. Safety document according to claim 13, characterized in that said plastic film is chosen from polypropylene mono- or bioriented, polyester, polyester terephthalate, polyvinyl chloride, polycarbonate, polytetrafluoroethylene (PTFE), a fluoropolymer, acrylonitrile-butadiene-styrene (ABS), nylon (polyamide), polylactidepolymer (PLA), di-acetate or a starch-type biopolymer.