WO2015136431A1

WO2015136431A1 - Safety document, and synthetic particles

Info

Publication number: WO2015136431A1
Application number: PCT/IB2015/051723
Authority: WO
Inventors: Pierre Sarrazin
Original assignee: Arjowiggins Security
Priority date: 2014-03-13
Filing date: 2015-03-10
Publication date: 2015-09-17
Also published as: EP3116720A1; FR3018474B1; FR3018474A1

Abstract

The invention relates to a protected item (1) comprising synthetic silicate, particularly phyllosilicate, particles (10) that have a crystalline structure and are detectable via Raman spectroscopy and near-infrared spectroscopy.

Description

Security document and synthetic particles

The present invention relates to the use, within security documents, of detectable particles by spectroscopy, in particular Raman and near infrared, and the authentication and / or identification of such documents.

Some securing means, said second or third level, integrated in a security document, are capable of generating a specific signal when they are submitted, simultaneously or not, to one or more external excitation sources. The automatic detection of the signal, thanks to the use of a suitable detection device, makes it possible to authenticate and / or identify, if necessary, the document. These securing means comprise for example tracers in the form of active materials, particles or fibers.

Raman spectroscopy analysis makes it possible to identify a target compound very precisely. Each compound has a unique Raman spectral signature, which is not generally the case in infrared (FTIR) or ultraviolet (UV) spectrometry analysis.

The Surface Enhanced Raman Spectroscopy (SERS) technology makes it possible to very quickly characterize very small quantities of material thanks to the amplifying effect, or plasmonic effect, of a metal placed near the target. The metal plays the role of a mirror vis-a-vis electromagnetic waves excitatory and / or diffused during the analysis.

SERS technology is used in biotechnology for the analysis of very small quantities of active principle: a noble metal is deposited in a thin layer, called nanometric, on a support, for example silicone. The element to be analyzed is subsequently deposited on this metal layer before being introduced into a spectrophotometer. Particles called core / bark are synthesized for use in vivo, the core being the noble metal, the bark a protective layer against external aggressions, in particular chemical, thermal or mechanical. The target molecule can be trapped in the nucleus, in the bark and / or between these two elements. These particles can thus have three different configurations depending on the location of the target molecule. This technique is for example described in the international application WO 2010/135351. It has already been proposed to use the technique of Raman analysis in the field of security documents, including SERS technology in particulate systems.

US patent application 2011/0226954 discloses a printed security mark using an ink that may comprise carbon nanotubes or a nanocrystal, allowing Raman detection.

US patent application 2011/043331 discloses an identification system comprising a nanometric metallic element associated with a Raman response element or a near infrared response element. The metallic element has no intrinsic Raman or near-infrared response, but serves to improve the analysis effects of these two responses.

The patent application US 2011/0049239 discloses a method for generating coded sequences of points formed with substances having a Raman response, notably allowing the protection of security documents. A mixture of metal nanoclusters and substances having a Raman response is used.

International application WO 2008/028476 discloses a security document, in particular a bill, comprising particles having an SERS response. Metallic particles are disposed between layers incorporating target molecules. These target molecules can also be deposited on the surface of metal particles.

It is known from patent applications EP 0 806 460 and US 2006/0038979 to use SERS technology in a security element, by incorporating an ink or a varnish comprising metal particles and target molecules adsorbed on their surface. This ink or varnish can be applied to a hologram or foil type security element. The incorporation of the particles in inks or varnishes makes it possible to avoid a loss of quality of the SERS Raman effect, which can occur during a direct introduction of the particles into the mass of diffusing media such as paper or plastic.

The international application WO 2012/164054 describes, in a security document, a detection by Raman spectroscopy using the phenomena of agglomeration and dispersion of nanoparticles of precise composition, in particular particles of mullite, cerium oxide, titanium oxide, potassium and sodium niobate, cobalt oxide, and / or iron. It is difficult to control the agglomeration of nanoparticles reproducibly, agglomeration being by definition a physicochemical phenomenon not reproducible. The compounds used in this application are also relatively rare and expensive.

The synthesis of SERS particles with nucleus, bark and target molecule requires a strong expertise in order to correctly create the three layers within nanometric particles. The SERS effect is provided mainly by metal particles, which can be expensive and difficult to synthesize.

Furthermore, natural talc, belonging to the family of phyllosilicates, is a hydrated magnesium silicate of formula Si ₄ Mg ₃ O 10 (OH) ₂ . These particles allow a good near infrared response, as indicated in the article "Crystal-chemistry of talc: a near infrared (NIR) spectroscopy study", American Mineralogist vol 89, 2004. It is thus known to authenticate security documents. in the near infrared, in particular using talc particles, in particular international applications WO 2005/034049 and WO 02/28954. For many applications, a high purity, a fineness of talc particles and good crystalline properties are sought, as determining for the quality of the final product. The grinding of the natural talc does not make it possible to control the purity, the lamellarity and the size of the particles of talc obtained. In addition, this grinding irremediably leads to amorphization thereof, or at least a significant decrease in its crystallinity.

There is a need for further refinement of secure articles and documents incorporating a detectable element by Raman and / or near infrared spectroscopy, and particles that may be used for this purpose.

The invention responds to this need with a secure article comprising silicate synthetic particles with crystalline structure, in particular phyllosilicate, detectable by Raman spectroscopy and near infrared.

The invention makes it possible to use a single compound providing a dual unit spectroscopic response, both near infrared and Raman, contrary to known techniques, which makes it possible to obtain responses that are all the more discriminating and difficult to reproduce.

Controlling the chemical synthesis of silicate synthetic particles makes it possible to achieve a wider range of unique Raman and near infrared spectroscopic responses and thus to discriminate and uniquely identify a large number of species. security article. This is not possible with natural silicate particles, for example natural talc, because they will always have the same Raman and near infrared response.

Authentication and / or identification of the secure article by spectroscopy is thus very robust. As the two Raman and near infrared signatures are unique, the combination of these two responses is difficult to counteract. This makes it possible to obtain a third level or second level security element in the case where the spectroscopic analysis devices used are portable.

The use of synthetic silicate particles also makes it possible to simplify obtaining the compound with a spectroscopic response, in particular Raman. The use of these synthetic particles overcomes the disadvantages of grinding natural talc.

Synthetic particles

The phyllosilicates, which are lamellar silicates, consist of an irregular stack of elementary sheets of crystalline structure, the number of which varies from a few units to a few tens of units. Among the phyllosilicates, the group comprising in particular talc, mica and montmorillonite is characterized in that each elemental sheet is constituted by the association of two layers of tetrahedrons located on either side of a layer of octahedra . This group corresponds to silicates 2/1.

The particles according to the invention have different Raman and near-infrared responses of the natural silicate particles.

In Raman excitation, in particular at 785 nm, the silicated synthetic particles do not have luminescence, unlike other compounds, which makes it possible to improve the quality of the Raman response, the luminescence strongly interfering with the Raman effect.

Obtaining synthetic silicate particles that may be suitable for the invention is described in patent applications FR 2 903 680, FR 2 977 580 and FR 2 969 594.

The synthetic particles according to the invention are advantageously derived from a hydrogel precursor of said particles, produced by a co-precipitation reaction and subjected to a hydrothermal treatment. The co-precipitation reaction preferably takes place between at least one compound comprising silicon, in particular sodium metasilicate, and at least one compound comprising at least one metal element, in the presence of at least one carboxylate salt of formula R ₂ -COOM 'in which: M 'denotes a metal selected from the group consisting of Na and K, and

- R ₂ is chosen from H and the alkyl groups containing less than 5 carbon atoms.

The carboxylate salt (s) of formula R ₂ -COOM 'may be present in order to have, relative to the silicon, a molar ratio R ₂ -COOM' / Si included between 0, 1 and 9.

The compound comprising at least one metal element may be a dicarboxylate salt of formula M (R 1 -COO) ₂ in which:

Ri is chosen from H and alkyl groups comprising less than 5 carbon atoms, and

M denotes at least one divalent metal having the formula Mgy ₍ i ₎ Coy (2) Zny ₍ 3 ₎ Cuy (4) Mn _{y (} s) Fey (6) Niy (7) ry (8), each y (i) representing a real number of the interval [0; 1], and such that Σ ₍ i = i _: % ₎ y (i) = 1.

The groups R1 and R2, which may be identical, are preferably selected from the group consisting of CH3-, CH3-CH2- and CH3-CH2-CH2-.

The precursor hydrogel of said synthetic particles is preferably a silico / germano-metallic hydrogel of formula (Si _x Gei- _x ) 4M ₃ 0ii, n'H ₂ 0, where x is a real number of the interval [0; 1], and not relating to a number of molecule (s) of water associated (s) with said silico / germano-metallic hydrogel.

The hydrothermal treatment of the precursor of the synthetic particles can be carried out at a temperature between 150 ° C and 400 ° C. Said hydrothermal treatment can be carried out at a pressure of between 5 bar and 200 bar.

The synthetic particles are advantageously phyllosilicate mineral particles having at least one non-swelling phase formed of a stack of elementary sheets of 2/1 phyllosilicates type and of chemical formula (Si _x Gei _x ) 4M ₃ O 10 (OH) ₂ , in which x is a real number of the interval [0; 1], and M denotes at least one divalent metal having the formula Mg _y ( ₁ ) Coy (2) Zny (3) Cuy (4) Mn _y ( ₅ ) ¥ ey ( ₆ ) ^' N y (7) ry (8) ), each y (i) representing a real number of the interval [0; 1], and such that Σ ₍ i = i _: % ₎ y (i) = 1.

A proportion of the divalent metal M contained in the synthetic particles, in particular a proportion of magnesium Mg, may be substituted by other elements, such as nickel, iron, cobalt or other divalent materials mentioned above, and may thus be result in a modification of the Raman and near infrared spectroscopic responses, this which makes it possible to obtain single-signature compounds. A large proportion of magnesium is advantageously substituted by these other elements, for example a magnesium proportion of between 0.1% and 100%, preferably 40% to 90%, relative to the total number of magnesium atoms in a mesh. elemental structure of the crystalline particles.

Advantageously, a mixture of different synthetic particles according to the invention having different near-infrared and Raman responses can be produced in order to obtain a large diversity of different signatures, moving away from the signature of the natural silicate particles.

The particles that are mixed differ, for example, by the magnesium-substituted metal and / or the proportion of substituted magnesium.

The synthetic particles used are advantageously nanometric, making it possible to guarantee the transparency of the zone of the article containing them. Thus, the secure article may further include visible security elements beneath the layer including the synthetic particles.

The largest dimension of the particles can be between 1 nm and

1000 nm.

Secure article

The article may be a security element to be incorporated or applied to a sheet material, for example a paper jet, or to be itself a sheet and to constitute for example a printing medium for making a banknote or an identity document or a label.

The secure article preferably comprises a substrate, which serves as a support.

This substrate may be made of a plastic material, especially thermoplastic, for example PET. This substrate may be that of a security element to be introduced en masse, in whole or in part, into a paper or a film to be applied to the surface thereof, for example to protect variable data.

This substrate may be made of a metallic material so as to constitute a foil-type security element, this metal substrate advantageously making it possible at the same time to constitute a security and to provide an SERS effect.

The substrate can still be part of a multilayer structure of a document, for example entirely plastic or hybrid plastic / paper. In a variant, the substrate is fibrous. In this case, the fibrous substrate is preferably paper, and may comprise natural and / or synthetic fibers, especially cellulose fibers, in particular cotton. The fibrous substrate may comprise a single paper jet or be multijet.

The thickness of the substrate may be between 2 μπι and 800 μπι, better between

6 μπι and 33 μπι, especially for a substrate made of PET.

The synthetic particles according to the invention can be incorporated in a layer carried by the substrate, for example directly to its contact or not.

The substrate, when fibrous, may comprise a watermark, which may be at least partially superimposed or not with the layer comprising the synthetic particles according to the invention.

The synthetic particles may be present in bulk in the substrate of the secured article.

The synthetic particles may be randomly disposed on the article, or may be arranged at predefined positions thereof.

The total thickness of the secured article may be between 4 and 820μπι. The secure article according to the invention may be at least partially opaque, in particular completely opaque, and / or be at least partially transparent and / or at least partially translucent.

The particles according to the invention may be arranged at least partially on an at least partially transparent or at least partially translucent area of the article. The non-opacity of this zone can result from a demetallization, in particular of the "Clear text ^® " type, or the presence of a window in the article.

Layer with particles

The layer comprising the synthetic particles according to the invention may comprise a binder, allowing a good resistance of the particles according to the invention. The binder advantageously has no Raman and / or near infra-red response, or its Raman and near-infrared responses are advantageously located outside the spectral zone of the corresponding responses of the synthetic particles.

The layer comprising the synthetic particles may be deposited by printing, in particular by inkjet printing, gravure printing, screen printing or flexography, or by impregnation, surfacing, coating, spraying or coating, in particular by air-jet coating, by the use of a roll reverse roll, in English, or a roll-roll, called roll flex in English, by sleeping off-line, or Champion , especially over the entire surface of the article.

The print can be in the form of patterns. The use of nanometric synthetic particles is particularly suitable for the formulation of inks for inkjet printing. This type of printing is suitable for marking all types of media, whatever their volumes and / or surface conditions.

The binder can be polymeric, being for example based on a polyurethane, a polyacrylic, a polyvinyl alcohol, or a polyvinyl acetate, which have good film-forming characteristics. The binder is preferably based on a polyurethane. The binder is preferably transparent.

The binder may have adhesion properties, for example being thermoadhesive. This property can promote the adhesion of the layer comprising the synthetic particles to the substrate while dispensing with the additional step of depositing an adhesive layer. This is particularly advantageous in the case, for example, where the layer comprising the synthetic particles represents a security thread inserted at least partially into the substrate. The nanometric size of the synthetic particles makes it possible to avoid modifying the adhesive property of the binder, as can the known micrometric particles.

When the particles according to the invention are applied on a support in the form of a fluid composition while being mixed with a binder, the proportion of particles according to the invention within the composition, in dry weight, is preferably 1 at 80%, better 5 and 50%. This composition may be water-based or organic solvent.

In a variant, the synthetic particles according to the invention are mixed with extruded material.

The synthetic particles may be present in a layer intended to provide durability or a varnish.

The synthetic particles according to the invention can be incorporated in a security ink comprising interferential pigments, deposited for example in the form of an iridescent strip, or in an ink with magnetically steerable pigments.

In the case where the synthetic particles according to the invention are incorporated in a layer carried by a support, the latter can be deposited on a component of security comprising micro-optical structures, such as diffraction gratings, micro-mirrors or microlenses. The layer comprising the particles according to the invention is in this case preferably transparent, which makes it possible to avoid having a negative visual effect on the security elements.

According to a particular embodiment of the invention, a lens array is disposed above the layer comprising the synthetic particles according to the invention. This lens array may be as described in International Application WO 03/061983. This network of lenses makes it possible to focus the beam of the source used in the Raman detection and thus to improve the detection. Preferably, this lens array is part of a security element and is associated with a set of micro-images so as to generate an optical effect, for example a magnifying moiré effect. Preferably, the focal length of these lenses is adapted to focus the radiation of the source used for the detection of the article on the layer comprising the particles.

The layer comprising the synthetic particles may be transparent when the binder it contains, if any, is transparent and the particles are sufficiently small, especially nanometric. Advantageously, this arrangement makes it possible to display security elements arranged under the layer, in particular on the secured article.

The synthetic particles according to the invention preferably also have the advantage of having three refractive indices and, thus, a birefringence property. This makes it possible not to alter the optical effects of the security elements that can be arranged under the layer.

The article may comprise a metal layer, for example made of gold or aluminum, advantageously located between the substrate and the layer comprising the synthetic particles according to the invention. This metal layer makes it possible to mask all the products present on the substrate which can hinder the associated spectroscopic responses, either by luminescence or by having spectral similarities with the synthetic particles. This metallization can also make it possible to provide an SERS effect.

This metal layer makes it possible in particular to amplify the waves and to mask the Raman response of the substrate of the secure article to be analyzed, for example in the case of a substrate made of a PET thermoplastic material. The metal layer may be structured, that is to say have a surface relief, or "grating" in English, preferably with a pattern of nanometric size repeated regularly every 1 to 1000 nanometers, which allows to improve detection via the SERS effect. This metal layer may be a hologram, comprising surface reliefs. The synthetic particles according to the invention, because of their birefringence, do not alter the other optical effects and are for example compatible with a high refractive index layer, or "High Refractive Index" in English (HRI).

The metal layer preferably has an optical density greater than 1, that is to say a transmittance of less than 10%, measured according to the NF ISO 15368 standard in directional-directional geometry, that is to say by means of directional excitation and directional measurement.

The metal layer is advantageously nanometric, its thickness being for example between 10 nm and 200 nm, better between 40 nm and 80 nm. A thin layer whose optical density is greater than 1 makes it possible to maintain a semi-reflective and transparent effect, which can be useful when it is desired to maintain a certain transparency in the article or document that contains it, at least in an area containing particles according to the invention.

The synthetic particles used are generally formed from very stable materials, which are not very sensitive to oxidation or hydration. Nevertheless, the layer comprising the particles according to the invention may be covered by at least one layer of a material which is relatively inert with respect to the desired detectability, such as aluminum, glass, a silicate, or another material. oxide, in order to protect the synthetic particles from the external environment and to make the secure article more resistant.

The layer comprising the synthetic particles according to the invention may be covered by a layer made of an organic material, for example a polymer, in order to improve the maintenance of the layer on the substrate.

In the case where the particles are present in bulk in the substrate, the latter may be covered by a layer of a relatively inert material and / or a layer made of an organic material, as described above. Security document

The secure article according to the invention may form all or part of a security element for securing a document, or the document itself.

The invention thus also relates to a security document, comprising or consisting of a secure article according to the invention.

The security document is preferably a means of identification of person, including a passport, an identity card, a driver's license, or a means of payment, including a payment card, a bank note, a credit card purchase, a voucher, a specific payment method such as a token or a wafer used in particular in casinos, or a secure label, a transport card, a loyalty card, a service card or a subscription card , a packaging, a card or an access ticket, or an interactive playing or collectible card.

The security element according to the invention may be in the form of a security thread intended to be introduced into a substrate, for example in window (s), a foil or a patch, or under the as an insert on a substrate, such as a rolled or laminated safety film. Alternatively, the security element carries a hologram or security ink, present on the surface of the security document. In yet another variant, the security element is a planchette or a flat fibrette.

The security element is preferably wholly or partially on the surface of the document, to facilitate Raman and near infrared detections.

The security element can extend from one edge to the other of the document, especially when it is in the form of wire or foil.

The security element and / or the security document may comprise the particles according to the invention as sole security means, but preferably the particles according to the invention in combination with other security means.

Among the other means of securing, some are detectable to the naked eye, in daylight or artificial light, without the use of a particular device. These additional securing means comprise, for example, colored fibers or boards, totally or partially printed or metallized wires, surface holograms or touch-effect elements. These security means are said to be first level. Other types of securing means are detectable only with a relatively simple apparatus, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These securing means comprise, for example, fibers, boards, strips, wires or particles. These securing means may be visible to the naked eye or not, being for example luminescent under a lighting of a Wood lamp emitting at a wavelength of 365 nm. These security means are called second level.

Other types of security elements are called third level and 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 structure or the article. These security elements comprise for example tracers in the form of active material, particles or fibers, capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation.

The additional security means or means present within the document or the security element that it comprises may have first, second or third level security features.

Authentication and / or identification of the security document, by the presence of the synthetic particles, is advantageously nondestructive.

Authentication and / or identification process

The subject of the invention is also a method for authenticating and / or identifying a secure article comprising particles of crystalline synthetic silicate structure detectable by combined Raman and near infrared spectroscopies, in particular as defined above, or a secure document in particular as defined above, process in which:

a signature of the article resulting from the combined measurement by Raman and near-infrared spectroscopies is extracted,

this signature is compared with reference data, and

depending on the result of the comparison, information is generated concerning the authenticity and / or identity of the article or document. The process according to the invention advantageously comprises the following steps: an area of the article comprising the synthetic particles according to the invention is subjected to a particularly intense monochromatic light source in order to acquire the Raman spectrum of the article and to analyze it by Raman spectroscopy,

the same area of the article is subjected to radiation emitted in the near infrared in order to acquire and analyze by spectroscopy the resulting near-infrared spectral data,

the data resulting from the Raman and near-infrared spectroscopic analyzes are compared with reference data relating to the article, and

the authenticity of the secure article is validated if both the data resulting from the Raman spectroscopic analysis and the resultant data of the near infrared spectroscopic analysis correspond to the reference data relating to the article.

The Raman spectrum can be detected using a Raman detection system including the intense monochromatic light source.

The monochromatic light source may be an Nd: YAG laser. The monochromatic light source for performing Raman detection can emit at a wavelength of between 200 nm and 1200 nm, preferably being a source emitting in the infrared range at 785 nm.

Since the intensity of the lines of the Raman spectrum is very low, one or more filters can be used to block the laser radiation coming directly from the monochromatic source, these filters being notably inserted in the Raman detection system.

The Raman detection system may include a monochromator, that is, a system for producing narrow monochromatic bands of radiant energy from the monochromatic source, to acquire the intensity of the Raman signals at different lengths of time. 'wave. The Raman detection system may further include any optical system suitable for Raman detection.

The Raman detection system is advantageously compact. The Raman detection system is for example a microscope, the excitation light of the source, in particular laser, being diffused through the objective of the microscope, and the resulting signal being acquired by this same objective. The Raman detection system may be a microscope with a lens having a small magnification, such as 5x or 10x. A Raman spectrum for a region of small area can thus be measured, which is particularly useful when the synthetic particles are located in a specific region of the article. In the opposite case, a system for locating the randomly arranged synthetic particles may be included in the Raman detection system.

The Raman detection system advantageously comprises a multi-channel detector, for example of the charge-coupled device (DTC) type, which makes it possible to detect the Raman spectrum once. This avoids performing a frequency sweep or wavelength over time, which facilitates the analysis of the Raman spectrum, by locating the desired peaks of the Raman spectrum in a very short period of time. Thus, the authentication speed of the article is increased.

Near-infrared spectroscopy can be implemented as described in the article "Crystal-chemistry of talc: a near infrared (NIR) Spectroscopy Study" by Sabine PETIT et al, American Mineralsogist, Volume 89, 2004.

Near infrared spectral data can be acquired by transmission, reflection or transreflection.

Near infrared spectral data can be analyzed by Fourier Transform Near Infrared Spectroscopy (FTIR).

The reference data relating to the article are advantageously the Raman and near infrared reference signatures of the synthetic particles incorporated in the article to be authenticated.

The reference data relating to the article may be stored in a database beforehand, for example installed on a computer or a portable system.

Advantageously, the reference data are present on the secure article according to the invention. In this case, the reference data can be encoded and present on the article in the form of an impression, for example in the form of a one-dimensional barcode or a two-dimensional Datamatrix code, visible or invisible. In one variant, the reference data are stored in an electronic chip. This makes it possible to authenticate the article without having to access an external database.

A single detection system can be used, including the Raman detection system and the near-infrared radiation source. This system can be portable, which makes it possible to authenticate the article in a simple and fast way. The unique detection system may be connected to a computer system by any means, for example by a wireless connection, the computer system comprising the elements necessary for the analysis of the data, and the database including the relative reference data. to the article, if any.

The article or document can be authenticated when it is verified that the synthetic particles according to the invention are present.

The article or document may be identified where it is possible, based on the detected signature, to distinguish a given article from other articles also bearing synthetic particles according to the invention.

The invention will be better understood on reading the detailed description which follows, examples of non-limiting implementation thereof, and on examining the appended drawing, in which:

FIGS. 1 to 6 show, in section, various examples of secured articles comprising synthetic particles according to the invention,

FIG. 7 represents an example of a pattern that can be obtained using synthetic particles according to the invention, and

FIG. 8 represents an example of a security document according to the invention.

A secure article 1 according to the invention is shown in FIG. 1. This article comprises phyllosilicate synthetic crystalline structure particles 10, detectable by combined Raman and near infrared spectroscopies, and obtained as explained above.

A proportion of the divalent metal M, for example magnesium Mg, contained in the synthetic particles 10 may be substituted by other elements, such as nickel, iron or cobalt. For example, a magnesium atom may be replaced by a nickel atom.

The secure article 1 according to the invention comprises a substrate 2, visible in FIGS. 1 to 6.

The substrate 2 may be made of a plastic material, in particular thermoplastic, for example PET, or may be fibrous, then being preferably paper. The thickness e of the substrate 2 is for example between 2 μιη and 800 μπι, better between 6 μιη and 33 μπι, in particular for a PET substrate.

The total thickness W of the secured article 1 is for example between 4 and

820μιη.

In the example of Figure 1, the synthetic particles 10 are incorporated in a layer 3 carried by the substrate 2. This layer 3 may be the outermost of the article or alternatively an inner layer.

The layer 3 comprises a binder, for example thermoadhesive, in which are homogeneously dispersed the synthetic particles 10, whose Raman and near-infrared responses are located outside the spectral region of the corresponding responses of the synthetic particles 10. The binder is for example a polyurethane, and can be transparent.

The layer 3 comprising the synthetic particles 10 may have been deposited on the substrate 2 by any means, for example by printing, spraying or coating.

As shown in FIG. 7, in the case of an impression, this can be in the form of an alphanumeric pattern 30 formed by several zones 31, comprising synthetic particles 10. The zones 31 can be disjointed or not.

In a variant not shown, the synthetic particles 10 are incorporated in a security ink, for example an iridescent strip, or an ink with magnetically steerable pigments.

In the example of FIG. 1, synthetic particles 10 have been deposited on the entire surface of article 1.

In the variant represented in FIG. 2, the secure article 1 further comprises a metal layer 4, for example made of aluminum, situated between the substrate 2 and the layer 3 comprising the synthetic particles 10. This metal layer 4 may be nanostructured and preferably has an optical density greater than 1. The thickness of the metal layer 4 is for example between 10 nm and 200 nm, more preferably between 40 nm and 80 nm.

The metal layer 4 can have recesses so as to define, for example, units in positive or negative, for example of the "Clear text ^®".

The layer 3 may cover only certain areas of the substrate 2, for example a central zone. The metal layer 4 may be completely covered or not by the layer

3.

Layers 3 and 4 can be superimposed exactly, if necessary.

In the example of FIG. 3, the layer 3 comprising the synthetic particles 10 is deposited on a security element 50 comprising microoptic structures 5, such as diffraction gratings, micromirrors or microlenses.

In this case, care can be taken to ensure that the formulation of the layer 3 makes it possible to preserve the optical effect provided by the security element 50.

In a variant shown in FIG. 4, a lens array 6 is disposed above the layer 3 comprising the synthetic particles 10. The presence of the lenses 6 can make it possible to focus the Raman excitation light on the particles according to FIG. invention, which can further improve the signal-to-noise ratio.

In the variant of FIG. 5, the synthetic particles 10 are present in mass in the substrate 2 of the article 1, at least on the surface.

Thus, the mass dispersion of the particles according to the invention may not be homogeneous in the thickness of the substrate. It is preferable that the concentration of the particles is higher on the surface, so as to limit the losses by absorption and diffusion.

In the case of a mass dispersion, the substrate 2 is for example fibrous, in particular papermaker.

In the example of FIG. 6, the synthetic particles 10 according to the invention present in the substrate 2 are covered by a layer 7 of a material intended to protect the synthetic particles 10 from the external environment and to make the secure article 1.

The synthetic particles 10 according to the invention can be covered by a layer 7 made of an organic material, for example a polymer, which can contribute to improving the adhesion of the synthetic particles 10 to the substrate 2.

The layer 7 is preferably inert with respect to Raman and near-infrared detection.

FIG. 8 shows an exemplary security document 100 according to the invention, comprising synthetic particles according to the invention 10. More specifically, these particles 10 are accessible for Raman and near-infrared analysis in a zone of the document 100 which extends for example in a window 101 of the document, but which could alternatively present any contour and be located at any location of the security document 100 for this detection.

The security document 100 is a bank note in the example described, and the particles according to the invention extend over a security thread visible in the window 101. The invention is however not limited to a particular type document or security element carrying the particles.

Preferably, and as illustrated, the synthetic particles 10 are observable at least partially from the surface of the document 100, to facilitate Raman and near-infrared detections.

The security document 100 may comprise, in addition to the synthetic particles

10, another securing means, for example an iridescent band 102, as illustrated.

In the example of FIG. 8, the synthetic particles 10 according to the invention are incorporated in a thread such as that represented in FIG. 2, which extends from one edge to the other of the document, and which is incorporated in window. The particles 10 are present in a layer 3 with a binder, polyurethane, deposited on a metal layer 4 of aluminum. The substrate 2 is made of PET. The layer 3 comprises between 1 and 80% of synthetic talc particles according to the invention, better between 5 and 50%. The amount of composition, binder and synthetic talc, in dry weight, deposited on the support constituted by the metallized PET yarn, ranges from 0.5 to 20 g / m ² , better still from 1 to 10 g / m ² . The binder is thermoadhesive in the example described.

The document can be authenticated in the following manner: an area of the article 1 comprising the synthetic particles 10 is subjected to a monochromatic light source in order to acquire the Raman spectrum of the article and to analyze it by Raman spectroscopy. The same area of Item 1 is subjected to near-infrared radiation to acquire and analyze by spectroscopy the resulting near-infrared spectral data; the data resulting from the Raman and near infrared spectroscopic analyzes are compared with the Raman and near infrared reference signatures of the synthetic particles incorporated in Article 1; the authenticity of the secure article 1 is validated if both the data resulting from the Raman spectroscopic analysis and the resultant data of the near infrared spectroscopic analysis correspond to said reference signatures. The invention is not limited to the illustrated examples. The particularities of the examples illustrated can be combined within non-illustrated variants.

Thus, in a variant, the secure article 1 according to the invention comprises a substrate 2 carrying a layer 3 comprising synthetic particles 10 according to the invention, a metal layer 4 disposed between the layer 3 and the substrate 2, and a network of lenses 6 disposed above the layer 3.

The expression "comprising one" is synonymous with "comprising at least one", except when the opposite is specified.

Claims

1. Secure article (1) comprising synthetic silicic particles (10) with a crystalline structure, in particular phyllosilicate, detectable by Raman spectroscopy and near infrared spectroscopy.

2. The secure article according to claim 1, wherein the synthetic particles (10) are derived from a hydrogel precursor of said particles (10) produced by a co-precipitation reaction and subjected to a hydrothermal treatment, said co-precipitation reaction. taking place between at least one compound comprising silicon, in particular sodium metasilicate, and at least one compound comprising at least one metal element, in the presence of at least one carboxylate salt, in particular having the formula R ₂ - COOM 'in which :

M 'denotes a metal selected from the group consisting of Na and K, and

R ₂ is chosen from H and the alkyl groups comprising less than 5 carbon atoms,

said compound comprising at least one metal element being in particular a dicarboxylate salt of formula M (Ri-COO) ₂ in which:

Ri is chosen from H and alkyl groups comprising less than 5 carbon atoms, and

M denotes at least one divalent metal having the formula

Mgy ₍ i ₎ Coy (2) Zny ₍ 3 ₎ Cuy (4) Mn _{y (} s) Fey (6) Niy (7) ry (8), each y (i) representing a real number of the interval [0; 1], and such that Σ ₍ i = i _: % ₎ y (i) = 1,

the groups R1 and R2, being in particular identical, being in particular chosen from the group formed of CH3-, CH3-CH2- and CH3-CH2-CH2-,

the precursor hydrogel of said synthetic particles (10) being in particular a silico / germano-metallic hydrogel of formula (Si _x Gei- _x ) 4M ₃ 0ii, n'H ₂ 0, x being a real number of the interval [0; 1], and not relating to a number of molecule (s) of water associated (s) with said silico / germano-metallic hydrogel.

3. Secure article according to any one of claims 1 or 2, wherein the synthetic particles (10) are phyllosilicate mineral particles having at least one non-swelling phase formed of a stack of elementary sheets phyllosilicates 2/1 type and chemical formula (Si _x Gei _-x) 4M ₃ Oio (OH) _2, wherein x is a real number of the interval [0; 1], and M denotes at least one divalent metal having the formula Mg _{y (i} _j C0y _₍₂₎ Z _{y (3} _j Cuy ₍₄₎ M _y _(s) ^'Fe _y ₍₆₎ Ni _y ₍₇₎ r _y (8), each y (i) representing a real number of the interval [0; 1], and such that Σ ₍ i = i _: %) y (i) = 1.

4. Secure article according to any one of the preceding claims, wherein the synthetic particles (10) are synthetic particles with crystal structure identical to that of talc.

5. Secure article according to any one of the preceding claims, comprising a substrate (2).

6. Secure article according to the preceding claim, wherein the synthetic particles (10) are incorporated in a layer (3) carried by the substrate (2).

7. Secure article according to the preceding claim, wherein the layer (3) of synthetic particles (10) comprises a binder having no Raman response and / or near infra-red or having Raman and near-infrared responses located outside of the spectral zone of the corresponding responses of the synthetic particles (10).

8. Secure article according to the preceding claim, wherein the binder of the layer (3) of synthetic particles (10) has adhesion properties, being in particular a thermoadhesive.

9. Secure article according to any one of claims 6 to 8, wherein the layer (3) comprising the synthetic particles (10) is deposited by printing on the substrate (2), including gravure, screen printing, inkjet or flexography, especially over the entire surface of the article (1).

10. Secure article according to any one of claims 6 to 8, wherein the layer (3) comprising the synthetic particles (10) is deposited by coating on the substrate (2), in particular by coating air knife, by use of a reversing cylinder or a breaker roller, by offline coating or Champion, especially over the entire surface of the article (1).

1 1. Secure article according to any one of claims 6 to 10, wherein the layer (3) comprising the synthetic particles (10) is transparent, in particular to display security elements disposed under the layer (3).

12. Secure article according to any one of claims 1 to 8, wherein the synthetic particles (10) are present in mass in the article (1).

The secure article of any one of claims 1 to 8, wherein the synthetic particles (10) are incorporated in a security ink.

14. The secure article as claimed in claim 1, in which a proportion of the magnesium Mg of the divalent metal M contained in the synthetic particles (10) is substituted by one or more other elements, in particular nickel, iron or cobalt. .

15. Secure article according to the preceding claim, wherein a mixture of different synthetic particles (10) having different near-infrared and Raman responses is achieved.

16. The secure article as claimed in claim 1, in which the synthetic particles (10) are nanometric, in particular having a larger dimension of between 1 nm and 1000 nm.

17. Secure article according to any one of the preceding claims, comprising a metal layer (4), preferably located between the substrate (2) defined in claim 8 and the layer (3) comprising the synthetic particles (10), defined in claim 9

18. Secure article according to the preceding claim, the metal layer being of optical density greater than 1, and in particular being gold.

19. Secure article according to any one of claims 6 to 18, wherein the layer (3) comprising the synthetic particles (10) is deposited on security elements with micro-optical structure (5), including diffraction gratings. , micro-mirrors or micro-lenses

20. Secure article according to any one of claims 6 to 18, wherein a lens array (6) is disposed above the layer (3) comprising the synthetic particles (10).

21. Secure article according to any one of the preceding claims, being a security element, including a board, a flat fibrette, a hologram, a security ink, a security thread, including window (s), a foil or a patch, or laminated or glued safety film, preferably a foil, patch or security thread.

22. Security document (100) comprising or being constituted by a secure article (1) according to any one of the preceding claims, the document of security (100) preferably being a means of identification of person, including a passport, an identity card, a driver's license, or a means of payment, including a payment card, a bank note, a gift certificate purchase, a voucher, a specific payment method such as a token or a wafer used in particular in casinos or a secure label, a transport card, a loyalty card, a service card or a subscription card, a card or an access ticket, or an interactive playing or collectible card, preferably a bank note.

23. A method for authenticating and / or identifying a secure article (1) comprising particles of crystalline silicate synthetic structure (10) detectable by combined Raman and near infrared spectroscopies, in particular as defined in any one of Claims 1 to 21, or a security document (100) in particular as defined in the preceding claim, in which method:

a signature is extracted from the article (1) or from the document (100) resulting from the combined measurement by Raman and near-infrared spectroscopies,

this signature is compared with reference data, and

according to the result of the comparison, information is generated concerning the authenticity and / or the identity of the article (1) or the document (100).

24. Method according to the preceding claim, comprising the following steps:

an area of the article (1) comprising the synthetic particles (10) is subjected to a monochromatic light source, in particular a laser, preferably emitting at a wavelength between ... nm and ... nm , in order to acquire the Raman spectrum of the article (1) and to analyze it by Raman spectroscopy,

the same area of the article (1) is subjected to radiation emitted in the near infrared so as to acquire the resulting near-infrared spectral data, in particular by transmission, reflection or transreflection, and to analyze the said data by near-infrared spectroscopy ,

the data resulting from the Raman and near-infrared spectroscopic analyzes are compared with reference data relating to the article (1), and

the authenticity and / or the identity of the secure article (1) is validated if both the data resulting from the Raman spectroscopic analysis and the data resulting from the near-infrared spectroscopic analysis correspond to the reference data for item (1).

25. Method according to the preceding claim, wherein the Raman spectrum is detected by using a Raman detection system, in particular a microscope, comprising the monochromatic light source, and comprising in particular one or more filters, a monochromator, and / or a detector. multichannel.

The method according to any one of claims 23 to 25, wherein the reference data relating to the article (1) are the Raman and near infrared reference signatures of the synthetic particles (10) incorporated in the article (1). ), these data being in particular stored in a database.