FR2983775A1 - SECURITY STRUCTURE INCORPORATING AN ELECTRONIC DEVICE - Google Patents

Abstract

The present invention relates to a multilayer security structure comprising: - an internal structure (2) comprising at least one electronic memory device (3) housed at least partially in the thickness of the internal structure and at least one optical security element (4), - a variable opacity structure (5) having at least one region (6) of reduced opacity constituted by a watermark or pseudo-watermark superimposed at least partially on the optical security element (4), the internal structure being, in the region superimposed on the watermark or pseudo-watermark (6), sufficiently opaque to prevent seeing in light transmitted through the multilayer security structure the watermark or pseudo-watermark when the multilayer security structure is observed on the side of the structure of variable opacity and illuminated in visible light on the opposite side and / or sufficiently diffusive to prevent seeing light tra nsmises the watermark or pseudo-watermark on the side opposite to the variable opacity structure when the multilayer security structure is illuminated in visible light on the watermark or pseudo-watermark side, the optical security element (4) being at least partially visible, in reflected light, under visible or invisible illuminant, through the watermark or pseudo-watermark (6).

Description

The present invention relates to security structures, in particular those intended for the production of security documents such as passports or other leaflets or any other security document. In order to make it possible to secure such documents, in particular against falsification and / or counterfeit attempts, these most often include at least one page of an inner sheet that includes security data, for example printed personal data or engraved, and possibly a photograph relating to the bearer of the document. To further improve security, this data can be covered with a holographic protective film. In addition, to enable authentication of such a document and make it more difficult to counterfeit, the document may also include one or more well-known security elements, such as a watermark or pseudo-watermark and a microcircuit device. integrated. A watermark is usually authenticated by observation in transmitted light, the light and dark portions corresponding to differences in thickness or density, these differences in opacity forming an image. Currently, so-called electronic passport covers incorporate an electronic chip housed in the thickness of an internal structure, also called inlay. The inlay is disposed between the outer cover sheet of the passport and the cover page of the booklet, which carries one or more security elements.

The authenticity of the inlay before assembly is ensured only by the presence of the chip, which requires the use of an electronic system to interrogate it if one wishes to verify it. WO 2010/089702 discloses a method of securing an opaque or translucent object, colored or not, in which is glued to the object a label having a watermark or pseudo-watermark revealing the object, a luminescent agent superimposed on the less partially to the watermark or pseudo-watermark, and between the object and the watermark or pseudo-watermark. EP 2 320 357 A2 describes examples of structure of documents such as passports.

DE 2005 022 518 A1 discloses a structure such as a bank note comprising a fibrous layer carrying a watermark and an impression of a luminescent compound superimposed on the watermark, the latter being non-opaque with respect to the radiation UV. There is a need to further increase the security of a multilayer security structure of the type comprising an internal structure incorporating an electronic device, for example an inlay, and an external structure integral with this internal structure, for example a passport booklet. The invention meets this need thanks to a multilayer security structure comprising: an internal structure comprising at least one electronic memory device, housed at least partially in the thickness of the internal structure and at least one optical security element, a structure of variable opacity having at least one region of reduced opacity constituted by a watermark or pseudo-watermark superimposed at least partially on the optical security element, the internal structure being, in the region superimposed on the watermark or pseudo-watermark, sufficiently opaque to prevent seepage transmitted through the security-multilayer structure the watermark or pseudofiligrane when the multilayer security structure is observed on the side of the variable opacity structure and illuminated in visible light on the opposite side and / or sufficiently diffusive to prevent the transmitted light from seeing the filigran e or pseudo-watermark on the opposite side to the variable opacity structure when the multilayer security structure is illuminated in visible light on the side of the watermark or pseudo-watermark, the optical security element being in all cases at least partially visible , in reflected light, under visible or invisible illuminant, through the watermark or pseudo-watermark. Thanks to the invention, there is a double security provided on the one hand by the presence of the security element on the internal structure, which allows in particular to ensure the authenticity of it before assembly with the external structure of variable opacity, without having to interrogate the electronic device, and secondly by the observation of this optical security element through the external structure of variable opacity, after assembly.

In the case of a passport, the internal structure is an inlay and the external structure of variable opacity is formed by the cover page of the booklet. Thus, the investment related to the presence of the security element on the inlay is not lost once it is integrated in the passport, since this security remains observable through the front page and contributes to secure more the document during checks. Furthermore, in the case of a passport, it can be expected that the cover page of the booklet has slots, for example obtained by punch cuts, so as to form a zone of weakness which is intended to break in case of attempted delamination of the cover page and the cover. The multilayer security structure according to the invention can be in a card-like format for example in ID 1 format according to ISO / IEC 7810. The optical security element can combine a visible color element under visible illuminant and a luminescent element. , visible on UV or IR illuminant. For example, the optical security element has two patterns that complement each other. One is visible under white light and the other becomes visible only under UV light to complete the visible pattern. For example, only the flag of a country is visible under white light and the name of the country in alphanumeric characters appears on the flag 15 under illumination W. The external structure of variable opacity may comprise a laser marking layer comprising a polymeric matrix and a photorevable composite pigment by laser irradiation, so as to form the region of reduced opacity. The optical security element may be non-luminescent and visible in daylight. The optical security element is other than an electronic RFID device and preferably the watermark or pseudo-watermark is not superimposed on the chip of an RFID electronic device or an antenna to which it would be connected or coupled. The region of reduced opacity preferably has an opacity of less than 90% according to the standard 1S02471. When the region of reduced opacity is a watermark, the fibrous layer in which it is made preferably extends over the entire extent of the multilayer security structure; in this case, the watermark is not made in a patch, in particular circular outline. The watermark is preferably made in a fibrous layer of grammage between 70 and 180 g / m 2, preferably between 80 and 110 g / m 2 measured according to the standard NF EN IS0536.

The optical security element may be delimited by a contour which differs from that of the pseudo-watermark or watermark and / or which differs from that of the external structure of variable opacity. A larger filigree or pseudo-watermark dimension is preferably greater than or equal to 5 mm. Electronic memory device The electronic device is provided, according to the invention, with a non-volatile memory, in particular FRAM, SRAM, ROM or EEPROM, which allows, after its manufacture, to record variable data, for example the name of the device. holder of the document, or even his photograph. The memory is, during the use of the electronic device to verify the authenticity of the document, read-only type or read / write. The size of the memory is preferably greater than 128 bytes, or even 256 bytes, better at 1 K bytes, even better 2 K bytes, 4 K bytes, 16 K bytes, 128 K bytes 15 256 K bytes, 512 K bytes or more. The memory can be rewritable. The electronic device is advantageously contactless communication, RF or UHF, especially in the frequency ranges 125 kHz, 134.5 kHz, 6.78 MHz, 13.56 MHz, 27.125 MHz, 40.68 MHz, 433.92 MHz , 865 to 869 MHz, 915 MHz, 2.45 GHz, 5.8 GHz or 24.125 GHz. The electronic device may comprise an integrated antenna or be connected to an antenna, which may be wired, in particular copper, or screen-printed. The electronic device may be connected to the antenna, when it is external in particular, by welding. The electronic device may be battery-free or battery-powered. The electronic device may comprise a microprocessor-type processor (PIC). The electronic device is preferably silicon-based, but may alternatively be polymer-based. The thickness of the electronic device is preferably less than 360 μm. The electronic device is still called RFID chip.

The electronic device is for example a module MOB4 (ex MMC8 marketed by the company Infineon), or MOB6, or an ICS module chip or an AOB chip ("Antenna on board", "embedded antenna") marketed by the company FEC by example.

Preferably the electronic device is arranged for RF ("Radio Frequency") or UHF ("Ultra High Frequency") communication. External structure of variable opacity The external structure of variable opacity comprises a region of reduced opacity constituted by a watermark or pseudo-watermark.

The external structure may be monolayer or multilayer, and has an apparent face, which the observer looks to see through the watermark or pseudofiligrane optical security element. The outer structure may comprise a fibrous sheet of between 50 and 200 g / m 2, more preferably 70 to 150 g / m 2, composed of cellulose, cotton, synthetic fibers or mixtures thereof. The outer structure may further be polymeric and for example comprise a thermoplastic material. The external structure can be assembled to the internal structure by a layer of hot-activated adhesive or pressure sensitive for example. The adhesive may be water-based or solvent-based, it may be an acrylic, an acrylonitrile, a styrene butadiene, a polyurethane, a polyethylene .... The adhesive can be crosslinkable by its nature or by the addition of a compound such as blocked isocyanate. Watermark or pseudo-watermark 25 "Watermark or pseudo-watermark" according to the invention means a drawn image which appears in the thickness of the external structure with variable opacity. The watermark or pseudo-filigyan can be made in various ways known to those skilled in the art. It is preferably a watermark or pseudo-watermark in clear, that is to say that the opacity is less in the region of the watermark or pseudo-watermark than elsewhere. The watermark may be a pattern engraved or pressed into a fibrous layer during its manufacture. Such a watermark can for example be seen by transparency by creating thinned or thickened dough at the time of manufacture of the fibrous layer on a paper machine with round shape with a relief or recessed imprint in the training fabric of the round form. In this way, differences in opacity are created and the denser dough areas appear darker than the less dense areas which appear lighter compared to the rest of the leaf (called the vellum part), when the leaf is observed ( after drying) in transmitted light. The watermarks having different gray levels depending on the height of the embossings are called "multitone watermarks". The watermark can still come from areas where the fibrous layer has been pressed onto a flat-bed paper machine by means of a filigree roller which has the embossing of the embossed watermark, which has the effect of strongly pressing certain areas of the fibrous layer. and to remove the water contained in the fibers at the time of formation of the fibrous layer in the wet part. The pseudo-watermark may also be produced in the finished fibrous layer by mechanical and / or chemical means by application of certain products, this drawing being always visible in transparency. The pseudo-watermark may for example be produced by depositing or printing in certain zones of the fibrous layer a composition which modifies the transparency of the fibrous layer, in particular in order to produce light areas and dark areas, similar to those of a watermark, but without obtaining a result to obtain fineness and brightness variants comparable to those of a conventional watermark. For example, the finished fibrous layer can be made transparent by applying to specific areas, for example, a generally oily composition which permanently crystallizes the fibrous layer, such as, for example, a composition made of oil and transparent mineral material as described in US Pat. No. 2,021,141 or as for example a composition in the form of a wax combined with a solvent as described in US Pat. No. 1,479,337. The finished fibrous layer can also be made transparent by locally applying a wax by heat transfer, as described in US Pat. in US Patent 5,118,526.

It is also possible to use a fibrous layer comprising a hot-melt material, for example polyethylene as described in patent EP 0 203 499, which under the local action of heat will vary in its transparency.

The finished fibrous layer can be opacified, without, however, rendering it completely opaque, by applying, in certain zones, an opacifying agent which increases the opacity of the fibrous layer, as for example described in the patent application FR 2,353,676.

The opacifying agent may for example be an aqueous suspension of a pigment or a filler or a solution of a chemical compound, a colored compound or a dye. This agent can be applied during the manufacture of the fibrous layer, on the fibrous web, and before its removal from the fabric, so that the agent penetrates the interstices of the web and causes a change in the opacity of the web to be treated in selected areas, after drying. This manufacturing technique has the disadvantage of requiring special devices rollers to apply the agent, and preferably employing a suction device to penetrate the agent in the interstices of the web. A pseudo-watermark may also be made according to the method described in W. WALENSKI, "Watermarks and Those That Are Not", Druckspiegel 52, No. 3: 66-68 (March 1997). This document describes a method of manufacturing a pseudofiligrane on uncoated paper, comprising the application under heat and pressure of a marking piece, representing the pattern of the pseudo-watermark, on a sheet of rewetted paper.

The international application WO 97/17493 also describes the manufacture of coated paper comprising pseudo-watermarks resulting from a variation of the weight of the layer applied in given zones, which induces a variation of thickness and opacity in the zones where the weight of the layer is reduced or increased. International application WO 1999/014433 also describes another method of manufacturing a pseudo-watermark on a coated paper, which provides for producing an image in the paper after the drying step which follows the last coating operation, by performing the steps in which a rewetting solution is applied to at least one side of the coated paper in one or more predetermined areas and pressure and heat is applied to the area (s) of the rewetted coated paper so as to evaporate the solution and densify the coated paper in the area or areas relative to the rest of the paper.

The pseudo-watermark may finally be made mechanically by making marks by mechanical embossing of determined areas of the fibrous layer as described in DE 3 718 452. The watermark may be a high definition watermark as disclosed in the application. WO 2011/117828 A1. The pseudo-watermark may also be made in a polymer layer by the use of mechanical means. For example, a pseudo-watermark may be made on a sheet of polymeric material by passing it between two rollers, one of which bears a recessed or embossed pattern as to form an impression as described in EP 0 655 316. The sheet is then stretched so that under transmitted light, the pattern appears in black and white corresponding to the areas marked in relief or recessed with the roller. International application WO 2007/016148 further discloses a plastic layer which can be deformed, in particular stamped by embossing or de-embossing, to form an image which appears as a watermark, then laminated without the image being damaged. The pseudo-watermark may finally be made on a polymer layer using electromagnetic radiation, such as a laser. EP 1 518 661 discloses, for example, a method for making a pseudo-watermark on a coil sheet by electromagnetic irradiation of certain areas and stretching the sheet to obtain a stretched sheet having transparent areas corresponding to the irradiated areas. . The region of variable opacity may be defined by a pseudo-watermark made in a layer of a microporous silica-filled polyolefin, such as PPG Industries, Inc.'s TESLIN, by embossing, as described in the US 2007 application. The region of variable opacity may further be an embossed layer as described in US 2007/0178295 A1 application of an oriented polypropylene based foam material. The variable opacity structure may include a laser scribing layer comprising a polymeric matrix and a laser-photoblockable composite pigment so as to form the region of reduced opacity.

Internal Structure The internal structure may be multilayer or monolayer. The internal structure can be an inlay for booklet cover, including passport.

The electronic memory device may be housed, at least partially, in the internal structure, that is to say that all or part of the electronic device is compensated in thickness by the internal structure. This allows for example to protect the electronic device, which is generally a fragile piece, while making access to it by possible forgers particularly difficult. The electronic device can be further compensated at least partially in thickness by an adhesive layer of the internal structure, serving to assemble it to one or more fibrous layers. The thickness of the structure may exceed that of the electronic device. According to an exemplary embodiment, the electronic device is flush with at least one face of the internal structure. The electronic device can be flush with each of the faces of the internal structure. The internal structure may or may not have an apparent face, on the opposite side to the variable opacity structure. The internal structure can be formed entirely when the external structure of variable opacity is assembled with it. In a variant, the internal structure may not be entirely formed when it is assembled with the external structure of variable opacity, and may not be entirely formed until after assembly with another structure, for example after gluing or transfer to a document . For example, the internal structure is formed by a visa stuck on a page of a passport booklet. Optical security element The optical security element may be present in the mass of the internal structure, in particular at least one layer thereof that is close to the external structure of variable opacity, for example an adhesive layer serving assembling the variable opacity structure to the internal structure or a fibrous structure of the internal structure, adjacent to the variable opacity layer.

The optical security element may also be attached by printing or transfer to the internal structure or be integrated therewith during its manufacture, for example in the form of a fibrous web containing colored fibers or other security elements. introduced into a fibrous layer of the internal structure during manufacture as described in WO2008 / 043965, WO2007 / 071937 or WO2007 / 071939. A heat-sealing varnish may be provided on the surface of the strip to improve its adhesion in the fibrous layer of the internal structure. Alternatively, the colored fibers or other security elements may be projected on one side of the wet-forming fibrous layer as the latter moves, so as to form the strip as described in EP2021544. The optical security element can be visible in daylight or invisible in daylight and luminescent and visible under UV or IR light.

The optical security element may be any security element called first or second level, as defined below. The optical security element may combine a visible element and an invisible element (visible at a certain wavelength) or an element which is not colored but which becomes dyed when it is subjected to an external stimulus, such as, for example: temperature ( thermochromic) pressure (piezochromie) - electric field (electrochromic) - daylight (photochromic). The optical security element may be goniochromatic or iridescent.

The optical security element may extend over less than the entire surface of the internal structure, being for example located in a region at least partially overlapping the watermark or pseudo-watermark. In a variant, the optical security element extends over the entire surface of the internal structure, except possibly one or more openings made for example to accommodate the electronic memory device. This is the case for example when the optical security element is present in the mass of a layer of the internal structure or constitutes a layer of the internal structure, for example a layer intended to compensate at least partially the thickness of the electronic memory device or an adhesive layer for assembling the internal structure and the external structure.

The optical security element may also be a colored film such as a luminescent polycarbonate film marketed under the trademark LISA by the Bayer company, for example also incorporating a fluorescent or phosphorescent agent.

Additional security element The multilayer security structure may comprise one or more additional security elements as defined below, present in the internal structure and / or in the external structure.

Among the additional security features, some are detectable by eye, daylight or artificial light, without the use of a particular device. These security elements comprise for example colored fibers or boards, fully or partially printed or metallized wires. These security elements are called first level.

Other types of additional security elements are detectable only with a relatively simple apparatus, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These security elements comprise, for example, fibers, boards, strips, wires or particles. These security elements may be visible to the naked eye or not, being for example luminescent under a lighting of a Wood lamp emitting in a wavelength of 365 nm. These security elements are said to be second level. Other types of additional security elements require for their detection a more sophisticated detection device. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. The automatic detection of the signal makes it possible to authenticate, if necessary, the document. These security elements comprise, for example, tracers in the form of active materials, particles or fibers capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are said to be third level. The additional security element (s) present within the multilayer security structure may have first, second, or third level security features. Authentication method Another subject of the invention, according to another of its aspects, is a method of authentication of a multilayer security structure according to the invention, as defined above, in which one observes through the region of opacity reduces the optical security element and from this observation is determined the authenticity of the multilayer security structure and if the document has not been falsified. The invention also relates, according to another of its aspects, to a method of manufacturing a multilayer security structure as defined above, in which the variable opacity structure and the internal structure are assembled. after manufacture of the latter. The manufacturing method may include verifying the authenticity of the internal structure prior to its assembly with the variable opacity structure. The invention will be better understood on reading the following detailed description, non-limiting examples of implementation thereof, as well as on examining the appended drawing, in which: FIG. 1 shows schematically and partially an example of multilayer security structure according to the invention, - Figure 2 shows an example of a security document incorporating a multilayer security structure according to the invention, and - Figure 3 represents a variant of structure multilayer security device according to the invention. In the figures, the actual relative proportions of the various constituent elements have not always been respected, for the sake of clarity of the drawing.

The multilayer security structure 1 shown in FIG. 1 comprises: an internal structure 2 according to the invention, comprising at least one electronic memory device 3 according to the invention, housed in the thickness of the internal structure, and at least an optical security element 4, an external structure of variable opacity according to the invention, having at least one region of reduced opacity constituted by a watermark or pseudo-watermark, superimposed at least partially on the element of optical security 4. The internal structure 2 is, in its region 8 superimposed on the watermark or pseudo-watermark, sufficiently opaque to prevent seeing in transmitted light, through the multilayer security structure 1, the watermark or pseudo-watermark 6.

The optical security element 4 is at least partially visible, in reflected light, under visible or invisible illuminant, through the watermark or pseudo-watermark 6 from the apparent face 9 of the external structure 5.

The optical security element 4 is self-reliable through the clear parts of the watermark 6 by virtue of its observation, despite the opacity of the internal structure 2. In an exemplary embodiment, the region of reduced opacity 6 is constituted by a watermark which is not observable in reflected light under visible illuminant and which becomes only under UV illuminant or fR thanks to the light emitted by fluorescence by the optical security element 4 when it is luminescent. Alternatively, the region of reduced opacity 6 is constituted by a watermark observable in visible light, by reflection. Observation of the optical security element 4 can be done in natural light, the optical security element 4 being for example colored and constituted by colored fibers, for example arranged in a strip, which is of interest to can be expensive compared to a luminescent agent. In a variant, the optical security element consists of reflective agents, for example fibers or boards. The observation can also be carried out, if necessary, by combination of natural light and UV, or by combination of IR and natural light. The optical security element 4 may have a color that changes or electrochromic, in which case it is subjected during observation to the stimulus for observing the color change. The optical security element may be metameric.

The optical security element can still be phosphorescent under UV and / or under IR. FIG. 2 shows a document with a booklet 100 such as a passport according to the invention, comprising a cover 2 and set of connected sheets 102 constituting a booklet.

The cover 2 constitutes the internal structure according to the invention, comprising the electronic memory device 3. The cover 2 comprises a fibrous intermediate layer 105 with a window 106 in which the electronic device 3 partially extends. This electronic device 3 presents itself for example in the form of a module comprising an electronic chip encapsulated in a resin and fixed on a substrate, which carries an antenna connected to two connection lugs of the electronic chip.

The cover 2 may further comprise, as illustrated, an outer layer 108 bonded to the rest of the internal structure by means of an adhesive layer 109. The outer layer 108 may for example be made of paper impregnated with a latex and receiving a plastic coating, an acrylic for example. Alternatively, the outer layer 108 is made of textile impregnated with a plastic and receiving a plastic coating. In the example considered, the cover 2 comprises an additional fibrous interlayer 110 having a window 111 of smaller section than the window 106 and arranged to partially receive the electronic device 3. The intermediate layers 105 and 110 are assembled via an adhesive layer 112, comprising for example a liquid adhesive, the electronic device 3 comprising an antenna 113 previously deposited on the layer 105, before receiving the adhesive layer 112.

The additional interlayer 110 may be made, if desired, in a material other than paper, for example polymer. The set of sheets 102 has a cover sheet 5 bonded to the structure 2, on the side of the additional fibrous layer 110, the cover page 5 constituting the external structure with variable opacity according to the invention.

The cover page 5, paper, has a region of reduced opacity constituted by a watermark 6. The watermark 6 is superimposed with an optical security element 4 carried by the layer 110, for example a fluorescent or colored printing. The set of layers 110, 112 and 105 constitutes an inlay marketed under the trademark Paperlam by the applicant, which can be visually authenticated before assembly with the sheet assembly 102 thanks to the presence of the optical security element 4 After assembly, the optical security element 4 remains observable through the watermark 6 of the front page 5, constituting additional security.

In the variant illustrated in Figure 3, the multilayer security structure 1 comprises an internal structure 2 which is not completely opaque but diffusing and allows the light to pass through.

The internal structure 2 accommodates in its thickness the electronic memory device 3 according to the invention. The multilayer security structure 1 comprises two external structures of variable opacity 5, each comprising a watermark or pseudo-watermark, and defining the external faces of the multilayer security structure 1. The external structures of variable opacity 5 comprise, for example, embossed films, for example TESLIN, or multilayer structures incorporating a filigree fibrous layer, or consist of a paper layer with a watermark. The internal structure 5 comprises on each of its faces an optical security element 4 according to the invention, which is visible in reflected light, under suitable illuminant. The elements 4 may be identical or different. In a variant, the internal structure 2 of the example of FIG. 3 is completely opaque in regions 8 superimposed on watermarks or at least pseudo-watermarks. The invention is not limited to the illustrated examples. The expression "having one" shall be understood as being synonymous with "having at least one", unless the opposite is specified.

Claims (11)

REVENDICATIONS1. Multilayer security structure (1) comprising: - CLAIMS1. Multilayer safety structure (1) comprising: - an internal structure (2) comprising at least one electronic memory device (3) housed at least partially in the thickness of the internal structure and at least one optical security element (4) ), a variable opacity structure (5) having at least one region (6) of reduced opacity constituted by a watermark or pseudo-watermark superimposed at least partially on the optical security element (4), the structure internal being, in the region (8) superimposed on the watermark or pseudo-watermark (6), sufficiently opaque to prevent seeing in light transmitted through the multilayer security structure the watermark or pseudo-watermark when the multilayer security structure is observed on the side of the structure of variable opacity and illuminated in visible light on the opposite side and / or sufficiently diffusive to prevent seeing in transmitted light the watermark or pseudo o-watermark on the opposite side to the variable opacity structure when the multilayer security structure is illuminated in visible light on the side of the watermark or pseudofiligrane, the optical security element (4) being at least partially visible, in reflected light, under illuminant visible or invisible, through the watermark or pseudo-watermark (6). 2. multilayer security structure according to claim 1, the region of reduced opacity (6) being constituted by a watermark. 3. multilayer security structure according to claim 1, the region of reduced opacity (6) being constituted by a pseudo-watermark. 4. multilayer security structure according to any one of claims 1 to 3, the optical security element (4) appearing colored under visible illuminant. 5. multilayer security structure according to any one of claims 1 to 3, the optical security element (4) being luminescent and appearing colored under invisible illuminant, especially UV or IR. 6. multilayer security structure according to any one of claims 1 to 5, the optical security element (4) combining a visible color element under visible illuminant and a luminescent element, visible under UV or IR illuminant. The multilayer security structure according to any one of the preceding claims, wherein the optical security element (4) is thermochromic, piezochromic, photochromic, metameric, electrochromic, goniochromatic or iridescent. 8. Structure according to any one of the preceding claims, the variable opacity structure comprising a thermoplastic material and the region of variable opacity (6) being obtained by embossing. 9. Structure according to any one of claims 1 to 8, the inner structure (2) being multilayer. 10. Structure according to any one of claims 1 to 9, the optical security element (4) being constituted by an impression. 11. Structure according to any one of the preceding claims, the variable opacity structure (5) comprising a laser marking layer comprising a polymeric matrix and a laser-photorevorable composite composite pigment, so as to form the region of reduced opacity ( 6).