PROCESS FOR PROTECTING A DOCUMENT, PROTECTIVE DEVICE COMPRISING AN ADHESIVE LAYER AND DOCUMENT

Abstract

The invention relates to a process for protecting variable inscriptions of a document in which: a transparent film is bonded to a face of said document with a view to protecting variable inscriptions of said document, by at least one adhesive layer comprising at least one thermoplastic polymer having a glass transition temperature between 40 C. and 110 C. and having a hydroxyl value between 3 mg of KOH/g and 60 mg of KOH/g and/or an acid value between 2 mg of KOH/g and 150 mg of KOH/g, said adhesive layer comprises a crosslinking agent having at least 2.8 functions selected from the group formed of isocyanates, carbodiimides, aziridines and alkoxysilanes, during the bonding, a crosslinking of said adhesive layer is carried out. The invention also relates to a protective device and to a document.

Claims

1. A process for protecting a document, comprising: bonding a transparent film to a face of said document with a view to protecting variable inscriptions of said document, by at least one adhesive layer comprising at least one thermoplastic polymer, wherein said thermoplastic polymer is chosen from the group made up of thermoplastic polymers having a hydroxyl number, measured according to the 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 the standard DIN EN ISO 2114, of between 2 mg of KOH/g and 150 mg of KOH/g, copolymers thereof and blends thereof, wherein said thermoplastic polymer has a glass transition temperature, measured by differential scanning calorimetry, of between 40 C. and 110 C., wherein said adhesive layer also comprises at least one crosslinking agent, each crosslinking agent: being chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, having on average at least 2.8 functions, chosen from the group made up of isocyanates, carbodiimides, aziridines and alkoxysilanes, per molecule of crosslinking agent, wherein, during the bonding of said transparent film to said document, crosslinking of said thermoplastic polymer and of said crosslinking agent of the adhesive layer is carried out.

2. The process as claimed in claim 1, wherein, prior to crosslinking of said thermoplastic polymer and of said crosslinking agent, said adhesive layer comprises 0.5% to 10% by weight of crosslinking agent relative to the total weight of said thermoplastic polymer.

3. The process as claimed in claim 1, wherein said crosslinking of said adhesive layer is carried out at a temperature of between 60 C. and 220 C.

4. The process as claimed in claim 1, further comprising hot laminating, under pressure, said document coated with said transparent film.

5. The process as claimed in claim 1, wherein said thermoplastic polymer is chosen from the group of thermoplastic polymers having, before said crosslinking, a weight-average molecular weight, measured by size exclusion chromatography, of between 3000 g/mol and 65 000 g/mol.

6. A protective device for a document having variable inscriptions to be protected, said protective device comprising: at least one transparent film bearing at least one adhesive layer comprising at least one thermoplastic polymer, wherein said thermoplastic polymer is chosen from the group made up of thermoplastic polymers having a hydroxyl number, measured according to the 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 the standard DIN EN ISO 2114, of between 2 mg of KOH/g and 150 mg of KOH/g, copolymers thereof and blends thereof, wherein said thermoplastic polymer has a glass transition temperature, measured by differential scanning calorimetry, between 40 C. and 110 C., and wherein adhesive layer also comprises at least one crosslinking agent, each crosslinking agent chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, having on average at least 2.8 functions, chosen from the group made up of isocyanates, carbodiimides, aziridines and alkoxysilanes, per molecule of crosslinking agent.

7. The device as claimed in claim 6, wherein said adhesive layer comprises between 0.5% and 10% by weight of crosslinking agent relative to the total weight of said thermoplastic polymer.

8. The device as claimed in claim 6, wherein said transparent film comprises a plurality of superimposed layers.

9. The device as claimed in claim 6, wherein said transparent film comprises at least one layer, in particular at least one thermoplastic extreme layer.

10. The device as claimed in claim 6, wherein said thermoplastic polymer is chosen from the group made up of thermoplastic polymers having a weight-average molecular weight, measured by size exclusion chromatography, of between 3000 g/mol and 65 000 g/mol.

11. The device as claimed in claim 6, wherein said adhesive layer comprises at least one thermoplastic material chosen from the group made up of polyurethanes, polyesters, polyacrylics, polyethers, polyvinyl butyrals, polyvinyl acetals, cellulose, copolymers thereof and blends thereof.

12. A document comprising: a base sheet; variable inscriptions associated with said base sheet; and at least one adhesive layer comprising at least one thermoplastic polymer, said adhesive layer extending in contact with an extreme layer of said base sheet, wherein said thermoplastic polymer is chosen from the group made up of 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 the standard DIN EN ISO 2114, of between 2 mg of KOH/g and 150 mg of KOH/g, copolymers thereof and blends thereof, wherein said thermoplastic polymer has a glass transition temperature, measured by differential scanning calorimetry, of between 40 C. and 110 C., and wherein said adhesive layer also comprises at least one crosslinking agent, each crosslinking agent: being chosen from the group of aliphatic compounds comprising between 4 and 50 carbon atoms, having on average at least 2.8 functions, chosen from the group made up of isocyanates, carbodiimides, aziridines and alkoxysilanes, per molecule of crosslinking agent.

13. The document as claimed in claim 12, wherein at least one transparent film extends in contact with said adhesive layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Other objectives, characteristics and advantages of the invention emerge on reading the following description of one of the preferential embodiments thereof, given by way of nonlimiting example, and which refers to the appended figures in which:

[0058] FIG. 1 is a diagrammatic view of a first step of a process according to the invention in which a transparent film is represented in section,

[0059] FIG. 2 is a diagrammatic view of a second step of a process according to the invention in which a protective device according to the invention is represented in section,

[0060] FIG. 3 is a diagrammatic view of a third step of a process according to the invention in which a protective device and a document according to the invention are represented in section,

[0061] FIG. 4 is a diagrammatic view of a fourth step of a process according to the invention in which a protective device and a document according to the invention are represented in section,

[0062] FIG. 5 is a sectional diagrammatic view of a protective device obtained by means of a process according to the invention and bonded to an official document, and

[0063] FIG. 6 is a diagrammatic view of an official document protected by a protective device according to the invention.

DETAILED DESCRIPTION

[0064] FIG. 1 represents a thin translucent or transparent film 2 made of polymer material, which acts as 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 of the document to be protected. In one implementation variant, the transparent film 2 may also be chosen so as to have a size which exceeds that of the surface to be covered of the document to be protected.

[0065] The transparent film 2 can be formed of at least one layer of material chosen from thermosetting materials, and thermoplastic materials (in particular chosen from polycarbonates, PVCs, polyesters (polyethylene terephthalate PET, polyethylene terephthalate glycol PETG) and coextruded films of polyester and of polycarbonate (PEC), etc.). Other examples are possible.

[0066] The transparent film 2 may for example be formed of a stack of a plurality of layers superimposed on top of one another and having been subjected to hot lamination under pressure. The majority of the layers are preferably formed of a thermoplastic material, in particular chosen from polycarbonates, PVCs, polyesters (polyethylene terephthalate PET, polyethylene terephthalate glycol PETG), and coextruded films of polyester and of polycarbonate (PEC). In some advantageous embodiments, in particular for the applications of bank card, identification card or transport card type, the transparent film 2 is formed of a plurality of layers of polycarbonate. There is nothing to prevent the transparent film 2 from incorporating layers of different materials, including layers made of a material other than a thermoplastic material. The total number of layers constituting a protective device 1 according to the invention is not important within the context of the present invention. The transparent film 2 may also be a film of Fasprotek type (Fasver, Baillargues, France) or else a film of Fasfilm type (Fasver, Baillargues, France).

[0067] The transparent film 2 is in the general form of a sheet or a card and thus has two opposite external flat main faces, and a relatively small thickness. Throughout the remainder of the text, only one main face, termed extreme face 3, is described and has the characteristics of the invention, it being understood that the other extreme main face may just as easily have the same characteristics, or, on the contrary, have other characteristics. Consequently, it is assumed throughout the remainder of the text that the face opposite the extreme face 3 under consideration is an extreme main face of the transparent film 2 represented in section in FIG. 1, without this implying any limitation, such a transparent film 2 possibly itself consisting of a more or less thick layer or plurality of more or less thick layers, not described in the present description.

[0068] The transparent film 2 comprises security inscriptions 8, 9 such as inscriptions prepared using photoluminescent pigments (chosen from fluorescent pigments and phosphorescent pigments), reflective metalized inscriptions, etc.

[0069] 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, termed crosslinking agent 7, suitable for allowing crosslinking of said adhesive layer. As thermoplastic polymer, use may for example be made, in the adhesive layer, of: [0070] copolyester resins having the references Dynapol L and LH from the company Evonik Degussa Corporation (New Jersey, USA), [0071] acrylic resins having the reference Neocryl from the company DSM (Zwolle, Holland), [0072] cellulose-based resins such as those referenced CAB-551 from the company Eastman Chemical Company (Kingsport, USA), [0073] or else polyvinyl (butyral/acetal) resins having the reference S-LEC B/K from the company Sekisui Chemical Company (Dusseldorf, Germany).

[0074] As crosslinking agent, use may for example be made, in the adhesive layer, of: [0075] curing agents of 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 (Leverkusen, Germany), [0076] curing agents of aliphatic polyisocyanate type which are blocked (that is to say the reactive functions of which become reactive starting from a predetermined temperature, for example about 150 C.), such as those referenced Trixene BI7950, BI7951, BI7960, BI7961, BI7963, BI7982, BI791, BI7992, sold by the company Braxenden Chemicals Ltd (Lancashire, United Kingdom), or referenced Desmodur BL3175, BL4265, BL5375, PL350, PL340, BL3370, BL3475, BL3272, BL2078 sold by the company Covestro (Leverkusen, Germany), [0077] curing agents of polycarbodiimide type, such as those referenced Picassian XL-701 and XL-725 from the company Stahl (Waalwijk, the Netherlands), [0078] curing agents of polyaziridine type, such as those referenced PZ-33 and PZ-28 sold by the company PolyAziridine LLC (New Jersey, USA), [0079] or else alkoxysilanes, such as those referenced A-186, A-187, A-link 25, A-link 35 sold by the company Momentive (New Jersey, USA).

[0080] The adhesive layer 5 deposited on the transparent film 2 comprises at least one thermoplastic material chosen from the group made up of polyurethanes (PUs), polyesters, polyacrylates, polyethers, polyvinyl butyrals, polyvinyl acetals, cellulose, copolymers thereof and blends thereof.

[0081] The 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 crosslinking agent.

[0082] The thickness of the adhesive layer 5 may be between 5 m and 50 m.

[0083] After having deposited the adhesive layer 5 at the surface of the transparent film 2, a protective device 1 according to the invention is obtained. A release film (not represented) can optionally be deposited at the surface of the adhesive layer 5 in order to protect the external surface of the adhesive layer before bonding thereof in contact with a document.

[0084] FIG. 3 represents the bonding of this protective device 1 to a document such as an official document 10 having an upper face 11 and a lower face 12. The protective device 1 is bonded to the upper face 11 of the official document 10.

[0085] Such an official document 10 may for example be chosen from the group made up of passports, passport pages, customs cards, visas, identity cards, driver's licenses, vehicle registration cards (registration documents), bank cards, loyalty cards, bank checks, diplomas, certificates, transport documents, access control cards, badges, labels, legal writs, contracts, legal registers, cadastral maps, fiduciary documents, bank notes, packagings and manufacturing drawings.

[0086] The official document 10 has various security markings 8, 9, 13, 14, 15 representing information (common information) and/or constituting security markings intended to reinforce the resistance to attempts at falsification and/or to prevent reproduction by optical reading.

[0087] After having deposited the protective device at the surface of a document, the crosslinking of the adhesive layer is activated. This can be carried out immediately after having affixed the protective device to the document, or subsequently if storage is required before final personalization of the document.

[0088] The crosslinking of the adhesive layer 5 is carried out by subjecting said adhesive layer to a temperature above a predetermined temperature for crosslinking the adhesive layer 5. The crosslinking of the adhesive layer 5 can also be carried out by carrying out at least one step of hot lamination, under pressure, of the document 10 coated with the previously prepared protective device 1.

[0089] FIG. 4 illustrates the step of hot lamination, under pressure, of the official document 10 comprising the protective device 1 by means of a lamination roll 20. The lamination roll 20 moves in contact with the extreme surface 4 of the transparent film 2 of the protective device 1 in a direction of movement defined by the arrow present in FIG. 4, so as to activate and to allow the crosslinking of the adhesive layer 5. FIG. 4 thus shows a transverse section of the lamination roll 20, the roll moving in a direction orthogonal to the longitudinal direction of the roll 20. The hot lamination under pressure can be carried out under the temperature and pressure conditions such that the temperature is between 60 C. and 220 C., and in particular between 80 C. and 200 C., and at a pressure of between 310.sup.5 Pa and 610.sup.5 Pa, the roll moving at a speed of 5 mm/s to 30 mm/s. In the context of a continuous manufacture, a single pass of the lamination roll over the surface of the official document may suffice. However, it is of course possible to provide for several successive passages of the lamination roll, in particular as a function of the other parameters (lamination temperature and pressure, respective natures and proportions of the thermoplastic material and of the crosslinking agent, thickness of the protective film, etc.).

[0090] Alternatively, the hot lamination under pressure may be carried out in a lamination press at temperatures of between 150 and 200 C. under a pressure of between 1010.sup.5 Pa and 2010.sup.5 Pa.

[0091] FIG. 6 represents an official document 10 (for example an identity card) onto which has been transferred the protective device as previously prepared. The official document 10 has 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 iridescent pigments, reflective metalized inscriptions or else markings made by laser gravure.

[0092] The inventors have noted that a document protected according to the invention exhibits excellent resistance to handling and withstands detachment by successive flexing (in accordance with the standards applicable to official documents such as passports or identity cards in particular). The inventors have also noted that a document protected according to the invention exhibits 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 protective device and a protected document according to the invention do not turn yellow over time.

Example 1

[0093] A transparent polyester (PET) support film having a thickness of 100 m, sold by the company Dupont Teijin Films (Tokyo, Japan) under the reference Melinex, having been subjected to a heat and surface treatment of Politherm/Polibond type carried out by the company Technifilm (Valence, France), which may contain security printing for authentication, is chosen and a layer of adhesive in the format of the official document to be protected is printed thereon.

[0094] The adhesive layer is formed by printing on the above film an adhesive liquid composition by means of screen printing carried out using a fabric of which the mesh comprises 77 threads/cm having a diameter of 55 m.

[0095] The adhesive composition is composed of: [0096] 30% by weight of a polyester thermoplastic resin having the reference Dynapol L210 sold by the company Evonik Degussa Corporation (New Jersey, USA), having a concentration of between 25% and 30% by weight. This thermoplastic resin has a glass transition temperature of 63 C., a hydroxyl number, measured according to the standard DIN 53 240/2, of 5 mg KOH/g and a weight-average molecular weight, measured by size exclusion chromatography (SEC), of 20 000 g/mol, [0097] 1% by weight of a crosslinking agent having the reference Desmodur N75 from the company Covestro (Leverkusen, Germany), each molecule of crosslinking agent containing 3 reactive isocyanate functions and 21 carbon atoms, [0098] 69% by weight of a solvent, ethyl 3-ethoxypropionate.

[0099] The transparent support film on which a layer of this adhesive composition has been deposited forms a protective device which is bonded to an official document to be protected, by lamination.

[0100] The official document comprises a sheet of synthetic paper sold under reference Teslin (range SP1000) by the company PPG Industries (Ohio, USA). The sheet of Teslin may contain a printed security background.

[0101] The lamination process is a roll process, the setpoint temperature of which is 150 C., the lamination of the official document being carried out at a speed of 17 mm/s under approximately 510.sup.5 Pa.

[0102] Following the bonding by lamination, heat activation for 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.

[0103] Example of protective device detachment resistance test:

[0104] The official document obtained is immersed for more than 72 hours in a bath of ethanol. The transparent film of the protective device does not detach from the official document.

[0105] The official document obtained is gradually heated on a hotplate, the temperature is gradually increased up to a temperature of 180 C. At each further increase of 2 C., an attempt is made to remove the transparent film from the protective device.

[0106] At no time does the transparent film of the protective device detach from the official document.

[0107] The invention may be the subject of a very large number of implementation variants. In particular, it is possible to prepare a protective device comprising two different adhesive layers, one adhesive layer being placed on each face of the transparent film. Alternatively, it is possible to place a transparent film according to the invention on each of the two faces of an official document in such a way as to protect each of the faces of said document against falsification.