FR3073450B1 - DEVICE AND METHOD FOR PROTECTING A DOCUMENT COMPRISING AN ENCAPSULATED RETICULATING AGENT AND A DOCUMENT - Google Patents

Abstract

The invention relates to a protection device (1) for a document (10) having variable inscriptions to be protected, comprising a transparent film carrying an adhesive layer (5) comprising at least one thermoplastic polymer, characterized in that: - said polymer thermoplastic having a glass transition temperature between 40 ° C and 110 ° C and being selected from the group consisting of polymers having a hydroxyl value of between 3 mg and 60 mg KOH / g, thermoplastic polymers having an acid number Between 2 mg and 150 mg KOH / g and mixtures thereof, said adhesive layer comprises microcapsules, each microcapsule containing at least one crosslinking agent: • selected from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, • presenting at least two functions selected from the group consisting of isocyanates, carbodiimides, azyridines and alkoxysilanes. The invention also relates to a protection method (1) and a document (10).

Description

The invention relates to a device for protecting a document, in particular an official document, comprising an adhesive layer, and such a document, in particular an official document. comprising at least one such protection device. The invention also relates to a method of protecting a document using a protective film. Official documents are documents which, due to their nature and / or the rights which they may confer, must be protected against attempts at falsification and / or counterfeits and / or to guarantee authentication and / or to guarantee their integrity (i.e. the fact that they have not been altered or modified). These may include passports, visas, identity cards, driving licenses, gray cards, loyalty cards, bank cards, bank checks, diplomas, certificates, transport tickets, access control cards, badges, labels, legal acts, contracts, legal registers, cadastral plans, fiduciary documents, banknotes, manufacturing plans or other plans ... Official documents bear inscriptions, such as variable personalization details (surname, first name, address, photo, signature ... of a holder or of the parts ...) and / or common information (security reasons, matrices, frames, field names, seals, holograms, signatures, values, ...).

Throughout the text, "inscription" means any sign or pattern produced on a layer of a document, which can be read by humans and / or by machine (OCR), at least under certain conditions (especially under normal lighting in visible light; and / or under specific lighting; and / or after activation of an electronic device (screen) or other ...). This may include variable personalization details (name, marital status, photograph, value, dates ...) of an official document or common and / or security information; texts (handwriting or printed characters); codes (ASCII, universal codes with optoelectronic reading such as bar codes, QR codes ...); drawings, images or photographs; of tasks or flat areas ... Official documents generally contain inscriptions, known as security inscriptions, to prevent or make their reproduction or falsification very complex. These security inscriptions can be of the type visible in the visible field by simple observation with the naked eye (first level security); or of the type that can be controlled using a specific device such as an ultraviolet lamp (second level security); or of the type that can only be checked in a certified laboratory (third level security).

Throughout the text, the expression "at least appreciably" indicates, in the usual way, that a characteristic, structural or functional, should not be taken as marking an abrupt discontinuity, which would have no physical meaning, but covers not only this structure or this function, but also slight variations of this structure or this function which produce, in the technical context considered, an effect of the same nature, if not of the same degree.

Many official documents such as bank cards, identity cards, driving licenses, individual access cards to sites or public transport, passport sheets, customs forms, visas, fiduciary documents, banknotes ... are formed of several layers assembled together for example using an adhesive.

However, the presence of such an adhesive layer constitutes a weak point of said official documents in the face of the different falsification methods, despite the presence of particular security elements in the layers forming the document. In fact, most of the adhesives used and compatible with such documents are often thermoplastic materials, having a temperature above which they soften. The adhesive properties of such thermoplastic adhesives increase with increasing temperature, which allows bonding. The separation of the layers assembled by such adhesives can therefore be carried out at least by heating above a predetermined temperature. In addition, it is also possible to separate the different layers forming the document by dissolving the adhesive layer and / or the adjacent layers in solvents or by mechanical sanding of the adjacent layers. DE 10 2011 112 951 describes for example a security document and a heat-sealable lacquer in which an encapsulated adhesive is used. However, it turns out that the use of such a heat-sealing composition does not make it possible to obtain satisfactory results in terms of manufacturing (need to choose a particular adhesive, need to heat to a temperature predetermined, ...), nor in terms of anti-forgery, falsification and detachment of the different layers assembled by heating remaining possible. The invention therefore aims to overcome these drawbacks by proposing a device for protecting a document, a document and a protection method making it possible to protect variable inscriptions carried by said document. The invention also aims to propose a device for protecting a document and a protection method making it possible to protect said document against falsification and / or for its authentication and / or to guarantee its integrity. The invention aims more particularly to allow the production of a protective device which can be bonded, and in particular transferred, irreversibly to a document, in particular an official document, said protective device having a strong adhesive power. The invention also aims to propose a device for protecting a document which can be stored, in particular at room temperature, for several months, or even several years before being stuck on a document, without affecting the adhesive power of the protection device. on said document. The invention also aims to provide a document protection device and a protection method for protecting a document without imparting to it a rigidity which would not be desired and / or which would be greater or significantly greater than its initial rigidity. The invention also aims to provide a document protection device and a protection method for protecting a document against most methods of falsification of known official documents (in particular contact with a hot plate, soaking in the hot water, soaking in solvents such as acetone or White Spirit® ...).

To do this, the invention relates to a protection device for a document having variable inscriptions to be protected, said protection device comprising: - at least one transparent film carrying at least one adhesive layer comprising at least one thermoplastic polymer, characterized in that than :

- Said thermoplastic polymer is chosen from the group formed by thermoplastic polymers having a hydroxyl index measured according to standard DIN 53 240/2 comprised between 3 mg of KOH / g and 60 mg of KOH / g, thermoplastic polymers having an index of acid measured according to DIN EN ISO 2114 between 2 mg KOH / g and 150 mg KOH / g, their copolymers and their mixtures, - said thermoplastic polymer has a glass transition temperature between 40 ° C and 110 ° C , and in that: said adhesive layer further comprises microcapsules, each microcapsule comprising: a solid outer shell made of at least one polymeric material, an inner core, said outer shell containing said inner core, said inner core comprising at least one agent crosslinking agent, each crosslinking agent: • being chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, • having at least two fo Actions selected from the group consisting of isocyanates, carbodiimides, azyridines and alkoxysilanes. The invention also relates to such a protection device for implementing a method for protecting a document according to the invention. The invention also relates to a document comprising a base sheet, variable inscriptions associated with said base sheet and at least one protection device according to the invention. The invention also relates to a method of protecting a document in which: - a transparent film is bonded to one face of said document in order to protect variable inscriptions of said document, by means of at least one adhesive layer comprising at least minus one thermoplastic polymer, characterized in that: - said thermoplastic polymer is chosen from the group formed by thermoplastic polymers having a hydroxyl number measured according to standard DIN 53 240/2 between 3 mg of KOH / g and 60 mg of KOH / g, thermoplastic polymers having an acid number measured according to DIN EN ISO 2114 between 2 mg of KOH / g and 150 mg of KOH / g, their copolymers and their mixtures, - said thermoplastic polymer has a transition temperature glassy between 40 ° C and 110 ° C, - said adhesive layer further comprises microcapsules, each microcapsule comprising: • a solid outer shell in at least one polymer material, • an internal core, said external envelope containing said internal core, said internal core comprising at least one crosslinking agent, each crosslinking agent: o being chosen from the group of aliphatic compounds comprising between 4 and 50 atoms of carbon, o having at least two functions chosen from the group formed by isocyanates, carbodiimides, azyridines and alkoxysilanes, - when said transparent film is bonded to said document, crosslinking of said thermoplastic polymer and of said crosslinking agent is carried out.

The inventors have found that the choice of an adhesive layer comprising such a thermoplastic polymer and such an encapsulated crosslinking agent makes it possible, after their crosslinking together, during the bonding of said transparent film to a document, to obtain a very strong bonding and a protected document. effectively against any type of forgery. A method and a protection device according to the invention therefore make it possible to guarantee the authenticity and integrity of a document by protecting the layers placed under said transparent film, while retaining the original flexibility and transparency of the document, the layer adhesive not affecting this transparency (at least in the visible area).

This is quite surprising and goes against the properties of known adhesives. Indeed, to overcome the falsification problems linked to the use of thermoplastic adhesives, one would have thought that it was enough to use conventional thermosetting adhesives. However, the inventors have found that the use of known thermosetting adhesives was very unsatisfactory and resulted in weakening of the document to be protected and too low resistance to delamination. In addition, thermosetting adhesives do not maintain the transparency of a document. Quite surprisingly, the inventors have found that, by crosslinking an adhesive comprising at least one such thermoplastic polymer and at least one such crosslinking agent, once released from the microcapsules in which it is contained, it is possible to prepare a protection device and a document with which exceptional results are obtained in terms of bonding, in particular as regards the resistance to delamination of the transparent film and of the document. The invention relates in particular to a document obtained by a method for protecting a document according to the invention. It is possible to encapsulate the thermoplastic polymer alone.

Any encapsulation technique can be used to prepare said microcapsules. The microcapsules can be prepared for example by physicochemical processes, such as phase separation or coacervation, evaporation - solvent extraction or thermal gelling of emulsions or mechanical processes, such as nebulization / drying (spray- drying), gelation or freezing of drops or chemical processes, coating in a fluidized bed (spray-coating), extrusion / spheronization, and in particular chemical processes such as interfacial polycondensation, interfacial polymerization, polymerization in a dispersed medium (emulsion, miniemulsion, microsuspension ...) by radical or anionic way. The outer shell of the microcapsules is formed of at least one material that is not soluble in said thermoplastic polymer, that is to say that the outer shell of the microcapsules is chosen and prepared so as to prevent the release of each crosslinking agent included. in the inner core, and the release of any solvent present within the microcapsules. On the other hand, the material forming the external envelope of the microcapsules is non-porous with respect to said crosslinking agent and said solvent so as to prevent any departure of said crosslinking agent and / or said solvent before any desired release of the agent crosslinking, that is to say under storage conditions or before the application of a pressure and / or a temperature allowing the rupture or destruction of the external envelope of the microcapsules.

Advantageously and according to the invention, the envelope of said microcapsules is formed of at least one material chosen from the group consisting of polyamides (PA), polyurethanes, polyurea (PU), polyesters (PE), urea-formaldehyde resins (UL), and melamine-formaldehyde resins (ML).

Throughout the text, the term "urea-formaldehyde resins" (or "urea-formaldehyde") means any polymer or any resin obtained by polycondensation of formaldehyde (formaldehyde) and urea.

Throughout the text, the term "melamine-formaldehyde resins" (or "melamine-formaldehyde") means any polymer or any resin obtained by polycondensation of formaldehyde (formaldehyde) and melamine.

The internal core of the microcapsules can comprise one or more crosslinking agent (s) and optionally at least one solvent or any other additive. Advantageously and according to the invention, said internal core is liquid. Advantageously and according to the invention, said internal core comprises at least one solvent. The internal core of the microcapsules can comprise at least one solvent chosen from the group of fatty acid esters and fatty alcohols.

In a particularly advantageous variant of a device and a method according to the invention, said microcapsules are prepared by an interfacial polymerization process in which: - at least one surfactant is chosen from the group formed from maleic anhydride copolymers and styrene (SMA), maleic anhydride and methyl vinyl ther (MVE), their copolymers and their mixtures, - an aqueous dispersion comprising said surfactant is prepared, - a solution is prepared comprising at least one precursor of said polymer forming the outer shell of the microcapsules chosen from the group consisting of urea, formaldehyde, melamine, isocyanates, diacids, diamines, carboxylic acids, - a solution is prepared comprising a solvent and said crosslinking agent.

Advantageously and according to the invention, said microcapsules have an average spherical equivalent diameter between 0.5 pm and 100 pm, in particular an average spherical equivalent diameter between lpm and 50 pm.

Advantageously and according to the invention, said microcapsules are adapted to be able to release said crosslinking agent when a pressure of at least 300 OOOPa, in particular a pressure between 300 OOOPa and 600 OOOPa, is applied to the document coated with said transparent film.

Once the adhesive layer has been applied to the transparent film, the adhesive layer is adapted to allow the bonding of the protective device to a document immediately after the preparation of the protective device (in particular after the application of the adhesive layer to the transparent film) or later, in particular several days to several months after the adhesive layer has been deposited on the transparent film. This makes it possible to have a protective device capable of being irreversibly bonded to a document while being able to choose the moment when it is desired to make this bonding. In particular, the operator bonding the protection device on a document does not need to have mixing devices between at least two components, nor to apply himself, in particular in liquid form, an adhesive but can trigger or activate the bonding itself at the desired time, for example by applying a pressure allowing the external envelope of the microcapsules to be broken.

Once the adhesive layer is placed in contact with a document to be protected, the crosslinking reaction of the adhesive layer can be activated in any way making it possible to cause a rupture of the external envelope of the microcapsules, and in particular any technique involving an increase temperature and / or application of pressure.

In an advantageous embodiment of a method according to the invention, said transparent film is bonded to said document at a temperature between 90 ° C and 220 ° C. In cases where the outer shell of the microcapsules has a melting temperature less than or equal to the temperature at which bonding is carried out, such a temperature makes it possible to initiate crosslinking by causing the outer shell of the microcapsules to rupture, which releases the crosslinking agent which will then react with the thermoplastic polymer, allowing the crosslinking of said adhesive layer by reaction of the crosslinking agent in particular with the OH groups and / or the acid groups of the thermoplastic polymer.

In combination or in another advantageous embodiment of a method according to the invention, said transparent film is bonded to said document by applying pressure to said document coated with said transparent film. Such a temperature makes it possible to initiate crosslinking by causing a rupture of the external envelope of the microcapsules which releases the crosslinking agent which will then react with the thermoplastic polymer.

In an advantageous embodiment of a method according to the invention, said transparent film is bonded to said document by carrying out at least one step of hot and pressure lamination of said document, in particular of the document coated with said protection device. This hot lamination can be carried out at a temperature between 60 ° C and 220 ° C, and in particular between 80 ° C and 200 ° C, the crosslinking can in particular take place during this lamination step.

Advantageously and according to the invention, said transparent film comprises a plurality of superimposed layers. Advantageously and according to the invention, said transparent film is formed of layers of at least one material chosen from the group of thermoplastic materials and synthetic papers. In particular, a transparent film used in a method and a protection device according to the invention can advantageously be formed by hot lamination and under pressure of a plurality of layers of a thermoplastic material chosen from polycarbonates, PVC, papers synthetics, their mixtures and their associations.

Any printing technique can be used to print said adhesive layer on the transparent film and / or the document, in particular chosen from screen printing, gravure printing, flexography, offset printing, or the like.

Advantageously and according to the invention, said transparent film comprises at least one layer, in particular at least one extreme thermoplastic layer.

The protection device, and in particular the transparent transparent film used, may include safety inscriptions such as inscriptions prepared using photoluminescent pigments (chosen from fluorescent pigments and phosphorescent pigments), inscriptions prepared with using iridescent pigments, reflective metallic inscriptions, markings made by engraving and / or laser marking.

In certain embodiments, advantageously and according to the invention, said protection device, in particular the transparent film and said adhesive layer, are transparent at wavelengths not only in the visible range but also in the ultraviolet range (long ultraviolet and / or short ultraviolet) and / or infrared. In particular, advantageously and according to the invention, said transparent film does not exhibit fluorescence when it is exposed to wavelengths in the ultraviolet range, in particular to wavelengths substantially equal to 354nm. In particular, once stuck on a document, the protection device, and in particular the transparent film, remain transparent at wavelengths in the visible range but also in the ultraviolet range (long ultraviolet and / or short ultraviolet) and / or infrared, so that the protected inscriptions remain visible (and readable) as well as, for example, secure authentication inscriptions that are invisible but luminescent under UVA and / or under UVC and / or under infrared.

In certain embodiments, advantageously and according to the invention, said thermoplastic polymer included in the adhesive layer has a glass transition temperature between 50 ° C and 85 ° C and has a hydroxyl number between 3 mg of KOH per gram of said thermoplastic polymer and 50 mg of KOH per gram of said thermoplastic polymer, and / or an acid number measured according to DIN EN ISO 2114 between 3 mg of KOH per gram of said thermoplastic polymer and 50 mg of KOH per gram of said thermoplastic polymer.

Advantageously and according to the invention, the hydroxyl index of said thermoplastic polymer is measured according to standard DIN 53 240/2. Advantageously and according to the invention, the hydroxyl index represents the mass of potassium hydroxide in milligrams necessary for the neutralization of the acid which combines by acylation to 1 gram of said thermoplastic polymer. The method for determining the hydroxyl number involves acetylation of the free hydroxyl groups of said thermoplastic polymer with acetic anhydride (ethanoic anhydride) in a solvent such as pyridine. After this acetylation, water is added and the unreacted acetic anhydride is converted to acetic acid and measured by titration using potassium hydroxide.

Advantageously and according to the invention, the acid number of said thermoplastic polymer is measured according to standard DIN EN ISO 2114 (or according to standard DIN EN ISO 3682). Advantageously and according to the invention, the acid index represents the mass of potassium hydroxide in milligrams necessary for the neutralization of the free acids present in 1 gram of said thermoplastic polymer.

The inventors have found that the use, on the one hand, of at least one thermoplastic polymer having such a hydroxyl number and / or such an acid number and, on the other hand, of at least one agent crosslinking agent having at least two functions chosen from the group formed by isocyanates, carbodiimides, azyridines and alkoxysilanes makes it possible to react said thermoplastic polymer and said crosslinking agent so as to obtain a very strong bonding, the adhesive force on a document being very high while making it possible to form a transparent adhesive layer, at least in the visible range and thus without affecting the transparency of the transparent film, or of the document on which the transparent film is applied.

In certain embodiments, advantageously and according to the invention, said thermoplastic polymer is chosen from the group of thermoplastic polymers having, in particular before said crosslinking, a molecular mass of between 3000 g / mol and 65000g / mol. In fact, the inventors have found that these polymers, being in particular different from the low molecular weight polyols sometimes used, make it possible to obtain better bonding while having satisfactory mechanical properties for the preparation of a document and of a device. protection for such a document, including an official document.

In certain embodiments, advantageously and according to the invention, said adhesive layer comprises at least one thermoplastic material chosen from the group formed of polyurethanes (PU), polyesters, polyethers, polyacrylics, polyvinyl butyral, polyacetals of vinyl, cellulose, their copolymers and their blends.

Each crosslinking agent is chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms and has at least two functions chosen from the group formed by isocyanates, carbodiimides, azyridines and alkoxysilanes. In particular, this means that a composition, known as crosslinking composition, comprising at least one such crosslinking agent is used, said crosslinking composition comprising on average at least two functions chosen from the group formed by isocyanates, carbodiimides, azyridines and alkoxysilanes .

In certain embodiments, advantageously and according to the invention, said crosslinking agent is chosen from the group formed from polyisocyanates, polycarbodiimides, polyazyridines and alkoxysilanes, said crosslinking agent having at least two functions chosen from the group formed from isocyanates, carbodiimides, azyridines and alkoxysilanes. In certain embodiments, advantageously and according to the invention, said crosslinking agent is chosen from the group consisting of compounds having between two and six functions, and in particular between 2 and 3.5 (values included) functions chosen from the group formed isocyanates, carbodiimides, azyridines and alkoxysilanes.

Throughout the text, the term isocyanate function is understood to mean any group of formula -N = C = O, the isocyanate function being linked to the crosslinking agent by the nitrogen atom (N). Throughout the text, the term “carbodiimide function” is understood to mean any group of formula -N = C = N-, the carbodiimide function being linked to the crosslinking agent by at least one of the nitrogen atoms (N).

Throughout the text, the term azyridine function is understood to mean any group of formula: -ΝςΑ; Η2 ch2, the azyridine function being linked to the crosslinking agent by the nitrogen atom (N).

Throughout the text, the term “alkoxysilane function” is understood to mean any group of formula -Si-O-, the alkoxysilane function being linked to the crosslinking agent by the silicon atom (Si) and / or the oxygen atom ( O).

In certain embodiments, advantageously and according to the invention, prior to said crosslinking reaction, said adhesive layer comprises 0.5% to 10% by weight of crosslinking agent relative to the total weight of said thermoplastic polymer, and in particular 1 % to 5% by weight of crosslinking agent relative to the total weight of said thermoplastic polymer. A protective device 30 according to the invention, and in particular said adhesive layer, therefore comprises, before being affixed to a document to be protected, 0.5% to 10% by weight of crosslinking agent relative to the total weight of said thermoplastic polymer. The inventors have found that a small percentage of crosslinking agent is sufficient to allow excellent bonding of the transparent film to a document and that adding a higher proportion of crosslinking agent to said adhesive layer would on the contrary be harmful. when obtaining such a bonding. The crosslinking agent can be added in liquid or solid form directly by mixing with the thermoplastic material of the adhesive layer.

In certain embodiments, advantageously and according to the invention, the adhesive layer is prepared and applied so as to form said adhesive layer from a composition, called an adhesive composition, comprising: at least 10% by weight, and in particular 10% to 60% by weight of thermoplastic polymer relative to the total weight of said composition, said thermoplastic polymer being chosen from the group formed by thermoplastic polymers having a hydroxyl number measured according to standard DIN 53 240/2 of between 3 mg of KOH / g and 60 mg of KOH / g, thermoplastic polymers having an acid number measured according to DIN EN ISO 2114 between 2 mg of KOH / g and 150 mg of KOH / g, their copolymers and their mixtures, and in the group formed by thermoplastic polymers having a glass transition temperature between 40 ° C and 110 ° C, - at least 0.5% by weight, and in particular 0.5% to 10% by weight, d crosslinking agent relative to the total weight of said composition, said crosslinking agent being chosen from the group formed of aliphatic compounds comprising between 4 and 50 carbon atoms, and from the group formed of compounds having at least two functions chosen from the group formed isocyanates, carbodiimides, azyridines and alkoxysilanes.

In particular, advantageously and according to the invention, such an adhesive composition also comprises one or more solvent (s) of said thermoplastic polymer, that is to say any liquid in which said thermoplastic polymer or said crosslinking agent is miscible or which can be used to dilute said thermoplastic polymer or said crosslinking agent. Any solvent suitable for being able to prepare such an adhesive composition also comprising said thermoplastic polymer and said crosslinking agent can be used.

In other variants according to the invention, the crosslinking agent and the thermoplastic material are not present in the same layer. A layer comprising the thermoplastic material can for example be applied to the support film while a layer comprising the crosslinking agent and optionally a binder can be applied directly to the document to be protected, or vice versa.

In an alternative embodiment of a method according to the invention, the adhesive layer is deposited directly on the document to be protected, then the transparent film is applied in contact with the adhesive layer deposited on the document. The invention extends to a document, in particular an official document, comprising a base sheet, variable inscriptions associated with said base sheet and at least one protection device according to the invention.

An official document according to the invention can in particular be chosen from the group formed by passports, passport sheets, customs sheets, visas, identity cards, driving licenses, vehicle registration cards (cards ), bank cards, loyalty cards, bank checks, diplomas, certificates, transport tickets, access control cards, badges, labels, legal acts, contracts, registers legal, cadastral plans, fiduciary documents, banknotes, packaging and manufacturing plans.

Advantageously and according to the invention, said protection device covers at least one surface portion of said official document and extends in a format adapted to the format of said surface portion.

Advantageously and according to the invention, said protection device extends in a format similar to that of the document. The invention also relates to a method for protecting a document, a protection device and a document characterized in combination by all or some of the characteristics mentioned above or below. Other objects, characteristics and advantages of the invention appear on reading the following description of one of its preferred embodiments given by way of non-limiting example, and which refers to the appended figures in which: Figure 1 is a schematic view of a first step of a method according to the invention in which a transparent film is shown in section, Figure 2 is a schematic view of a second step of a method according to the invention in which a protection device according to the invention is shown in section, FIG. 3 is a schematic view of a third step of a method according to the invention in which a protection device and a document according to the invention are represented in section, - Figure 4 is a schematic view of a fourth step of a method according to the invention in which a protection device and a document according to the invention are shown tees in section, - Figure 5 is a schematic sectional view of a protection device obtained by a method according to the invention and glued to an official document, - Figure 6 is a schematic view of an official document protected by a protection device according to the invention.

FIG. 1 represents a thin translucent or transparent film 2 made of polymer material, acting as a support film. The transparent film 2 is generally chosen so as to have a size substantially identical to that of the surface to be covered with the document to be protected. In an alternative embodiment, the transparent film 2 can also be chosen so as to have a size which exceeds that of the surface to be covered with the document to be protected.

The transparent film 2 can be formed from at least one layer of material chosen from thermosetting materials, thermoplastic materials (especially chosen from polycarbonates, PVC, polyesters (polyethylene terephthalate PET, polyethylene terephthalate glycol PETG) and co films. -extruded from polyester and polycarbonate (PEC) ...). Other examples are possible.

The transparent film 2 can for example be formed by a stack of a plurality of layers superimposed on each other and having been subjected to hot lamination and under pressure. The majority of the layers is preferably formed from a thermoplastic material, in particular chosen from polycarbonates, PVC, polyesters (polyethylene terephthalate PET, polyethylene terephthalate glycol PETG), and co-extruded films of polyester and polycarbonate (PEC) . In certain advantageous embodiments, in particular for applications of the bank card, identification card or transport card type, the transparent film 2 is formed from a plurality of polycarbonate layers. Nothing prevents the transparent film 2 incorporating layers of different materials, including layers in a material other than a thermoplastic material. The total number of layers constituting a protection device 1 according to the invention does not matter in the context of the present invention. The transparent film 2 can also be a Fasprotek ™ type film (FASVER, Baillargues, France) or a Fasfilm ™ type film (FASVER, Baillargues, France).

The transparent film 2 is in the general form of a sheet or a card and therefore has two opposite main outer planar faces, and a relatively small thickness. In the following, only one main face, known as the end face 3, is described and has the characteristics of the invention, it being understood that the other extreme main face can just as easily have the same characteristics, or on the contrary have other features. Consequently, it is assumed hereinafter that the face opposite to the extreme face 3 considered is an extreme main face of the transparent film 2 shown in section in FIG. 1, without this implying any limitation, such a transparent film 2 can be itself consisting of a layer or a plurality of more or less thick layers not described in this description.

The transparent film 2 includes safety inscriptions 8, 9 such as inscriptions prepared using photoluminescent pigments (chosen from fluorescent pigments and phosphorescent pigments), reflective metallic inscriptions ...

FIG. 2 represents the transparent film 2 on which a thermoplastic polymeric adhesive layer 5 has been deposited. The adhesive layer 5 comprises at least one thermoplastic material and at least one compound, called encapsulated crosslinking agent 7, adapted to allow crosslinking of said adhesive layer. As thermoplastic polymer, it is possible, for example, to use, in the adhesive layer: - copolyester resins of Dynapol L® and LH® references from the company Evonik Degussa Corporation® (New Jersey, USA), - acrylic resins of Neocryl references ® from the company DSM® (Zwolle, Holland), - cellulose resins such as those referenced CAB-551® from the company Eastman Chemical Company® (Kingsport, USA), - or poly (butyral / acetal) vinyl resins from reference S-LEC B / K® from Sekisui Chemical Company® (Dusseldorf, Germany). As crosslinking agent, it is possible, for example, to use, in the adhesive layer: - hardeners of the aliphatic polyisocyanate type such as those referenced Desmodur® N 100®, N75®, N3200®, N3300®, N3390®, N3600®, N3790®, N3800®, XP2675®, E XP 2747®, XP2599®, E3265®, E3370®, Z4470®, XP2489®, XP2838®, XP2763® sold by the company Covestro® (Lervekusen, Germany), - hardeners aliphatic polyisocyanate type blocked (i.e. whose reactive functions become reactive from a predetermined temperature, for example of the order of 150 ° C) such as those referenced Trixene® BI7950®, B17951®, ΒΓ7960 ®, B17961®, B17963®, B17982®, B1791®, BI7992® sold by Braxenden Chemicals Ltd® (Lancashire, United Kingdom), or referenced Desmodur® BL3175®, BL4265®, BL5375®, PL350®, PL340® , BL3370®, BL3475®, BL3272®, BL2078® sold by the company Covestro® (Lervekusen, Germany), - polycarbodiimide hardeners such as those referenced Picassian® XL-701® and XL-72®5 from the company Stahl® (Waalwijk, Netherlands), - polyaziridine hardeners such as those referenced PZ- 33® and PZ-28® sold by the company PolyAziridine LLC® (New Jersey, USA), - or alkoxysilanes such as those referenced A-186®, A-187®, A-link 25®, A-link 35 ® sold by Momentive® (New York, USA).

The adhesive layer 5 deposited on the transparent film 2 comprises at least one thermoplastic material chosen from the group formed by polyurethanes (PU), polyesters, polyacrylates, polyethers, polyvinyl butyral, polyvinyl acetal, cellulose, of their copolymers and of their mixtures. The encapsulated crosslinking agent 7 is chosen from the group of aliphatic polyisocyanates. The adhesive layer comprises between 0.5% and 10%, in particular between 1% and 5%, in particular between 2% and 4% - by weight of microcapsules comprising at least one crosslinking agent. The thickness of the adhesive layer 5 can be between 5 pm and 50 pm.

After having deposited the adhesive layer 5 on the surface of the transparent film 2, a protective device 1 according to the invention is obtained. A release film (not shown) can optionally be deposited on the surface of the adhesive layer 5 in order to protect the external surface of the adhesive layer before it is bonded in contact with a document.

FIG. 3 represents the bonding of this protection device 1 on a document such as an official document 10.

Such an official document 10 can for example be chosen from the group formed by passports, passport sheets, customs sheets, visas, identity cards, driving licenses, vehicle registration cards (gray cards ), bank cards, loyalty cards, bank checks, diplomas, certificates, transport tickets, access control cards, badges, labels, legal acts, contracts, legal registers , cadastral maps, fiduciary documents, banknotes, packaging and manufacturing plans.

The official document 10 presents various security markings 8, 9, 13, 14, 15 representing information (common statements) and / or constituting security markings intended to reinforce resistance to attempts at falsification and / or to prevent reproduction by reading. optical.

After placing the protective device on the surface of a document, the crosslinking of the adhesive layer is activated. This can be done immediately after affixing the protection device on the document or later if storage is necessary before final personalization of the document.

The crosslinking of the adhesive layer 5 is carried out by subjecting said adhesive layer to a temperature higher than a predetermined crosslinking temperature of the adhesive layer 5. It is also possible to crosslink the adhesive layer 5 by carrying out at least one lamination step to hot and pressurized document 10 coated with the protective device 1 previously prepared.

FIG. 4 illustrates the step of hot and pressure lamination of the official document 10 comprising the protection device 1 using a lamination roller 20. The lamination roller 20 moves in contact with the end surface 4 of the transparent film 2 of the protection device 1 in a direction of movement defined by the arrow present in FIG. 4 so as to activate and allow the crosslinking of the adhesive layer 5. In FIG. 4, we therefore see a cross section of the lamination roller 20, the roller moving in a direction orthogonal to the longitudinal direction of the roller 20. Hot lamination and under pressure can be carried out under temperature conditions and of pressure such that the temperature is between 60 ° C and 220 ° C, and in particular between 80 ° C and 200 ° C, and at a pressure between 3.105Pa and 6.105Pa, the roller moving at a speed of 5mm / s to 30mm / s. In the case of continuous production, a single pass of the lamination roller over the surface of the official document may be sufficient. However, it is of course possible to provide for several successive passages of the lamination roller, in particular as a function of the other parameters (temperature and pressure of lamination, types and respective proportions of the thermoplastic material and of the crosslinking agent, thickness of the protective film. .).

Alternatively, hot lamination under pressure can be carried out in a lamination press at temperatures between 150 ° C and 200 ° C under a pressure between 10.105Pa and 20.105Pa.

FIG. 6 represents an official document 10 (for example an identity card) onto which the protection device as previously prepared has been transferred. Official document 10 presents various security markings 8, 9, 13, 14, 15 such as inscriptions prepared using photoluminescent pigments (chosen from fluorescent pigments and phosphorescent pigments), inscriptions prepared using pigments iridescent, reflective metallic inscriptions or markings made by laser engraving.

The inventors have found that a document protected according to the invention has excellent resistance to manipulation and resists detachment by successive flexions (in accordance with the standards applicable to official documents such as passports or identity cards in particular).

The inventors have also found that a document protected according to the invention has excellent temperature resistance, in particular excellent climatic resistance (in particular during climatic resistance tests carried out between 35 ° C and 70 ° C). In addition, a protection device and a document protected according to the invention does not yellow over time. EXAMPLE 1

A transparent polyester (PET) support film is chosen having a thickness of 100 μm sold by the company Dupont Teijin Lilms TM (Tokyo, Japan) under the reference Melinex®, having undergone a heat and surface treatment of the Politherm / Polibond® type. carried out by the company Technifilm® (Valence, France), which may contain secure authentication prints on which a layer of adhesive is printed in the format of the official document to be protected.

The adhesive layer is formed by printing on the preceding film an adhesive liquid composition using a screen printing screen produced from a fabric of which the mesh comprises 77 threads / cm and having a diameter of 55 μm.

The adhesive composition is composed of: 30% by weight of a Dynapol L210® reference polyester thermoplastic resin sold by the company Evonik Degussa® Corporation (New Jersey, USA), with a concentration between 25 to 30% by weight. This thermoplastic resin has a glass transition temperature of 63 ° C, a hydroxyl number measured according to DIN 53 240/2 of 5 mg KOH / g and a molecular mass of 20,000 g / mol, 1% by weight of microcapsules enclosing a crosslinking agent of reference Desmodur® N75 from the company Covestro (Leverkusen, Germany), each molecule of crosslinking agent containing 3 reactive functions and carbon atoms, - 69% by weight of a solvent, ethyl 3-ethoxypropionate .

The microcapsules have an outer shell formed of melamine formaldehyde resin, and were prepared by a chemical encapsulation process comprising several stages: in a first stage a stable microemulsion of oil-in-water type is formed, with the crosslinking agent dissolved in the oily phase, in a second step a prepolymer of melamine formaldehyde resin is added to the microemulsion. The prepolymer will finish polymerizing on the surface of the microcapsule by thermal activation.

The microcapsules formed are then precipitated and dried to form a powder which can be used in the adhesive composition.

The transparent support film on which a layer of this adhesive composition has been deposited forms a protection device which is stuck on an official document to be protected by lamination.

The official document includes a sheet of synthetic paper sold under the reference Teslin® (SP1000® range) by the company PPG industries® (Ohio, USA). The Teslin® sheet may contain a printed security background.

The lamination process is a roller process with a set temperature of 150 ° C, the lamination of the official document being carried out at a speed of 17mm / s under approximately 5.105Pa. Following bonding by lamination, a thermal activation of 5 min at 150 ° C of the official document obtained makes it possible to finalize the crosslinking of the reactive functions of the thermoplastic resin with those of the crosslinking agent.

Example of the protective device peeling resistance test:

The official document obtained is immersed for more than 72 hours in an ethanol bath. The transparent film of the protection device does not come off the official document.

The official document obtained is gradually heated on a hot plate, the temperature is gradually increased to a temperature of 180 ° C. With each new increase of 2 ° C, an attempt is made to remove the transparent film from the protection device. At no time does the transparent film of the protection device come off the official document. The invention can be the subject of very numerous variant embodiments. In particular, it is possible to prepare a protection device comprising two different adhesive layers, an adhesive layer being placed on each side of the transparent film. Or, it is possible to have a transparent film according to the invention on each of the two sides of an official document so as to protect each of the sides of said document against forgery.

Claims (14)

CLAIMS 1 / - Protection device (1) for a document (10) having variable inscriptions to be protected, said protection device comprising: - at least one transparent film carrying at least one adhesive layer (5) comprising at least one thermoplastic polymer , characterized in that: - said thermoplastic polymer is chosen from the group formed by thermoplastic polymers having a hydroxyl index measured according to standard DIN 53 240/2 between 3 mg of KOH / g and 60 mg of KOH / g, polymers thermoplastics having an acid number measured according to DIN EN ISO 2114 of between 2 mg of KOH / g and 150 mg of KOH / g, of their copolymers and of their mixtures, - said thermoplastic polymer has a glass transition temperature of between 40 ° C and 110 ° C, and in that: said adhesive layer further comprises microcapsules, each microcapsule comprising: - a solid outer shell in at least one ma polymeric material, an internal core, said external envelope containing said internal core, said internal core comprising at least one crosslinking agent, each crosslinking agent: • being chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, • having at least two functions chosen from the group formed by isocyanates, carbodiimides, azyridines and alkoxysilanes. 2 / - Device according to claim 1, characterized in that said solid outer shell of the microcapsules is formed of at least one polymer material chosen from the group formed of polyamides (PA), polyurethanes (PU), urea-formaldehyde resins (UF), polyesters (PE) and melamine formaldehyde resins (MF). 3 / - Device according to one of claims 1 or 2, characterized in that said inner core is liquid. 4 / - Device according to one of claims 1 to 3, characterized in that said internal core comprises at least one solvent. 5 / - Device according to one of claims 1 to 4, characterized in that said adhesive layer (5) comprises between 0.5% and 20% by weight of microcapsules relative to the total weight of said thermoplastic polymer. 6 / - Device according to one of claims 1 to 5, characterized in that said thermoplastic polymer is chosen from the group formed by thermoplastic polymers having a molecular weight between 3000g / mol and 65000g / mol. 7 / - Device according to one of claims 1 to 6, characterized in that said transparent film (2) comprises a plurality of superimposed layers. 8 / - Device according to one of claims 1 to 7, characterized in that said adhesive layer (5) comprises at least one thermoplastic material selected from the group formed of polyurethanes, polyesters, polyacrylics, polyethers, polybutyral vinyl, polyvinyl acetal, cellulose, their copolymers and their mixtures. 9 / - Document (10) comprising: - a base sheet, - variable inscriptions (13) associated with said base sheet, - at least one adhesive layer (5) comprising at least one thermoplastic polymer, said adhesive layer s extending in contact with an extreme layer of said base sheet, characterized in that: - said thermoplastic polymer is chosen from the group formed by thermoplastic polymers having a hydroxyl number measured according to standard DIN 53 240/2 of between 3 mg of KOH / g and 60 mg of KOH / g, thermoplastic polymers having an acid number measured according to DIN EN ISO 2114 between 2 mg of KOH / g and 150 mg of KOH / g, their copolymers and their mixtures, - Said thermoplastic polymer has a glass transition temperature between 40 ° C and 110 ° C, and in that said adhesive layer further comprises microcapsules, each microcapsule comprising: - an outer shell soli of at least one polymeric material, - an internal core, said external envelope containing said internal core, said internal core comprising at least one crosslinking agent, each crosslinking agent: • being chosen from the group of aliphatic compounds comprising between 4 and 50 atoms carbon, • having at least two functions chosen from the group formed by isocyanates, carbodiimides, azyridines and alkoxysilanes. 10 / - Document (10) according to claim 9, characterized in that at least one transparent film (2) extends in contact with said adhesive layer (5). 11 / - Method for protecting a document (10) in which: - a transparent film (2) is bonded to one face of said document in order to protect variable inscriptions from said document (10) at least one adhesive layer (5) comprising at least one thermoplastic polymer, characterized in that: - said thermoplastic polymer is chosen from the group formed by thermoplastic polymers having a hydroxyl index measured according to standard DIN 53 240/2 between 3 mg of KOH / g and 60 mg of KOH / g, thermoplastic polymers having an acid number measured according to DIN EN ISO 2114 between 2 mg of KOH / g and 150 mg of KOH / g, their copolymers and their mixtures, - said thermoplastic polymer has a glass transition temperature between 40 ° C and 110 ° C, - said adhesive layer further comprises microcapsules, each microcapsule comprising: • a solid outer shell in at least u n polymer material, • an inner core, said outer shell containing said inner core, said inner core comprising at least one crosslinking agent, each crosslinking agent: o being chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, o having at least two functions chosen from the group consisting of isocyanates, carbodiimides, azyridines and alkoxysilanes, - during the bonding of said transparent film (2) on said document, crosslinking of said thermoplastic polymer and of said crosslinking agent is carried out. 12 / - Method according to claim 11, characterized in that the bonding of said transparent film (2) is carried out on said document at a temperature between 90 ° C and 220 ° C. 13 / - Method according to one of claims 11 or 12, characterized in that the bonding of said transparent film (2) is carried out on said document by exerting pressure on said document (10) coated with said transparent film (2). 14 / - Method according to one of claims 11 to 13, characterized in that the bonding of said transparent film is carried out on said document by performing at least one step of hot and pressure lamination of said document (10) coated with said film (2) transparent.