EP3206884B1 - Security element and security document - Google Patents

Description

The present invention relates to security elements for secure documents.

The invention relates more particularly to security elements comprising an at least partially transparent support and layers carried by this support to reveal patterns when the element is observed in transmitted light or in reflection.

WO 2014/006416 A2 discloses a security device comprising elements forming a first pattern and a second pattern overlapping the first, the first and second patterns being spaced apart by a transparent layer, the first and second patterns in combination obstructing the passage of transmitted light to various degrees observer through the device according to the viewing position.

US 2012/025514 A1 describes a security element comprising an at least partially transparent substrate, on the front and back of which appear respectively and partially first and second marks in the form of metallizations and / or prints, the first marks mainly superimposing on the second marks, the first and second marks respectively forming first and second distinct patterns according to their respective faces, the degree of visibility of the second marks varying with the angle of observation of the front of the security element.

US 2012/189159 A1 discloses a security element comprising an optical system comprising a transparent or translucent substrate, on the side of a first face of the substrate a combined image comprising a plurality of nested coded images, a revelation screen superimposed on the combined image, allowing observe the coded images when changing the direction of observation of the security element relative to the optical system.

It is widely known to use as security element security wires constituted by a strip of a transparent thermoplastic material coated on one face with at least one metal deposit with openings formed by demetallization, showing patterns when the element is observed in transmitted light, such security is also called CLEARTEXT.

Requirement WO 2009/053673 discloses such a security feature. This document describes a safety wire comprising a support provided with a layer of metal openwork opaque defining a pattern, this layer being coated with a diffusing layer deposited in the form of a pattern. In transmitted light, the appearance of the wire is substantially the same as in the absence of a diffusing layer. However, when the observation is made in reflected light, the pattern of the diffusing layer may appear.

The invention aims to further improve the security elements, in order to provide new effects, in particular visible to the naked eye, in white, infrared or ultraviolet light, without making their manufacture too complicated.

The object of the invention is therefore, according to a first of its aspects, a security element for a secure document as defined in claim 1.

The invention makes it possible to have at least one item of information visible on only one side of the element, in reflected light, in particular on the back side and on the front side, without having to provide relatively expensive and complex optical structures to manufacture. , such as interference structures, in particular multilayer interference structures of the PVD type, on the front and back respectively.

Compared to the structure described in the publication WO 2009/053673 , the structure according to the invention makes it possible to obtain additional effects. Resistance to counterfeiting is particularly improved because it is more difficult to counterfeit a layer semi-transparent than an opaque layer. The invention also makes it possible to combine, by observation in transmitted light, the information visible in reflection respectively on the front and back. This provides a more attractive effect for the general public.

The invention makes it possible to achieve, if desired, level 1 security revealing to the naked eye and in daylight different patterns depending on the faces observed and / or the observation conditions, in transmitted light or in reflected light.

In particular, one of these patterns can appear conventionally in transmitted light in the manner of a CLEARTEXT.

The second pattern can have a position marked relative to the first pattern. In particular, the second opening may at least partially overlap the first region appearing full of the first layer. This can allow the first layer to be used to define the appearance of the second pattern in reflected light.

The first opening can at least partially overlap the second region appearing full of the second layer.

The first layer may or may not be diffusing.

The first pattern can be exclusively superimposed on the second region appearing full.

The second pattern can overlap exclusively with the first region appearing full. The openings in the first layer can be superimposed exclusively on regions that appear full of the second layer.

The first layer can be formed by printing. Alternatively, the first layer is formed by a deposit of metal. The metal deposit may be thin enough for the first region appearing full to be non-opaque.

The first region appearing full may also have its non-opaque character due to the presence of a frame.

The second layer can be formed by printing. It is in particular a non-reflective impression, preferably non-metallic.

The second layer may advantageously include a diffusing ink. The second layer may alternatively be formed by a deposit of metal. The latter may be thin enough for the second region appearing full to be non-opaque. The second region appearing full may have its non-opaque character due to the presence of a frame.

The first pattern can be completely surrounded by the first region appearing full, when viewed from the front.

The second pattern can be completely surrounded by the second region appearing full, when viewed from the front.

The first and second layers are preferably located respectively on the front and back of the support.

The different appearance of the front and back sides, especially when the first layer is metallic and the back side is white, can facilitate the production of documents incorporating the element, by constituting a visual reference very easy to discern during insertion. the element and its control.

By "at least partially transparent support" it should be understood that there is at least one region of the support which is sufficiently transparent or translucent for the first pattern of light transmitted through the security element to be observed.

By "region appearing full", it should be understood that the appearance of this region is that of a solid region. The region can be effectively full on a microscopic scale. It may also not be, but keep the appearance of a solid region, which is the case for example when producing in said region a fine frame whose lines are sufficiently close together so as not to be able to be distinguished by the naked eye because of its resolving power. In particular, a frame whose resolution is greater than 300 dots per inch (“dot per inch” or “dpi” in English) is invisible to the eye, in particular for an individual having average vision, at a distance of 25 cm ( which corresponds to an average observation distance). Thus, two points spaced about 70 µm or less cannot be distinguished at this distance.

By "identified position", it should be understood that the first pattern is arranged with a predefined and non-random positioning with respect to the second pattern due to the knowledge, during manufacture, of the position of the first pattern when the second is created.

By "layer not completely opaque", it should be understood that the layer allows white light to pass under certain observation conditions at least, with a transmission factor (or transmittance) preferably of at least 10%, better at least. minus 20% measured according to ISO 15368. We also speak of semi-transparency.

The semi-transparent nature of the layer can be independent of the angle of observation, which is for example the case for a metal deposit of homogeneous but very thin thickness. The semi-transparent nature may also depend on the angle of observation, which is the case when using opaque plates oriented in the same direction, not parallel to the plane of the substrate. In this case, when the layer is observed in said direction, it lets light pass between the plates and when it is observed in a direction substantially perpendicular to the direction of orientation of the plates, the latter obstruct light.

The security element is in particular a security thread, a film, for example a foil or a lamination film, or a patch. It is preferably a safety thread.

The invention also relates to a secure document incorporating a security element according to the invention.

Said secure document is for example a means of payment, such as a bank note, a payment card, a check or a restaurant ticket, an identity document, such as an identity card, a visa, a passport or driving license, a card, in particular an access card, a lottery ticket, a transport ticket or an entry ticket to cultural or sporting events, a loyalty card, a service card, a card subscription, a playing or collecting card, a voucher or a voucher. It is preferably a document comprising a fibrous layer, in particular when the security element is a security thread. In this case, the security element is introduced into the document secured in bulk or in window (s), and preferably in window (s).

When the security element is a film, for example a foil or a lamination film, or a patch, it is applied to the surface of the secure document.

The element being integrated into the document substrate, the presence of the second layer, visible on the back, preferably white or metallic, can reduce the visibility of the element outside any windows of the document when the latter is observed on the back side. .

Surprisingly, the appearance of the security element on the side of the first layer may appear substantially uniform in reflection, in particular when the second layer is diffusing and has substantially the same color as the substrate in which the element is inserted or on which it is fixed. So during the observation in light reflected from the front, the areas facing the openings of the second layer have the same color as the areas facing the second layer.

The security element may or may not extend from one edge of the document to the other.

The element and / or the document may include one or more other additional security elements as defined below.

Among the additional security elements, some are detectable by eye, in daylight or in artificial light, without the use of a particular device. These additional security elements include, for example colored fibers or boards, printed or metallized wires totally or partially. These additional security elements are said to be first level.

Other types of additional security features are only detectable using a relatively simple device, such as an ultraviolet (UV) or infrared (IR) emitting lamp. These additional security elements include for example fibers, boards, strips, threads or particles. These security elements may or may not be visible to the naked eye, being for example luminescent under the lighting of a Wood lamp emitting at a wavelength of 365 nm. These security elements are said to be second level.

Other types of additional security elements require a more sophisticated device for their detection. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more sources of external excitation. Automatic signal detection allows the document to be authenticated, if necessary. These additional security elements include, 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 additional security elements are said to be third level.

The additional security element or elements present within the security element according to the invention and / or of the document may have first, second or third level security characteristics.

Another subject of the invention is, according to another of its aspects, a method of authenticating a secure document as defined in claim 15. The observation can be carried out through a window of the document.

This description also discloses a method of manufacturing a document as defined above, in which the security element according to the invention is incorporated in window (s) or on the surface.

• la figure 1 représente de façon schématique un exemple de document sécurisé selon l'invention,
• la figure 2 représente en coupe transversale selon II-II le document sécurisé et l'élément de sécurité,
• les figures 3A à 3C représentent respectivement l'élément de sécurité observé en réflexion au recto, en réflexion au verso, et en transmission, et
• les figures 4 à 6 représentent des variantes d'éléments de sécurité en section transversale.

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

• the figure 1 schematically represents an example of a secure document according to the invention,
• the figure 2 shows in cross section along II-II the secure document and the security element,
• the Figures 3A to 3C respectively represent the security element observed in reflection on the front, in reflection on the back, and in transmission, and
• the figures 4 to 6 represent variants of safety elements in cross section.

In the figures, the respective actual proportions of the various constituent elements have not always been respected, for the sake of clarity of the drawing. In addition, certain layers may appear monolithic in the figures when they actually consist of several sub-layers. Adhesive layers may not have been shown between different constituent layers.

We have represented on Figures 1 and 2 an example of a secure document 1 in accordance with an example of implementation of the invention, for example a bank note.

Document 1 comprises a substrate 2, preferably made of paper, formed of one or more fibrous jets, which incorporates a security element 10 according to the invention, in the form of a wire (“thread” in English) in the example considered. .

The security element 10 comprises a support 11 made of thermoplastic material, which ensures the mechanical resistance of the wire. This support 11 is for example made of transparent thermoplastic material such as PET or polyester. The thickness e of the support 11 ranges for example from 2 to 30 μm and the width w of the element 10 from 1 to 30 mm and preferably 4 to 10 mm. The support 11 can also be an adhesive layer, in particular in the case of a foil.

The security element 10 comprises a first layer 12, for example formed by metallization and demetallization. The layer 12 thus comprises, for example, one or more regions appearing solid 12a and one or more openings 12b. The aperture (s) 12b are visible in light transmitted through a window 3 of the document 1 and define one or more first patterns M1 as illustrated on the figure 3C for example. The patterns M1 are for example alphanumeric patterns, or representations of various subjects such as characters, animals, plants, landscapes, monuments. The patterns M1 can be found elsewhere on document 1, for example being printed on the substrate or being for example a watermark.

The pattern (s) M1 can also be raster images, giving an impression of relief thanks to a shading effect. In this case, the openings 12b have sizes and a distribution suitable for creating such images.

The first layer 12 can thus form a recognizable image, the subject of which is for example present elsewhere on the document.

Although the first layer 12 preferably includes metallization, it can also include printed patterns, in positive or negative writing, for example with a metallic, magnetic or electrically conductive ink. The first layer may include a diffusing ink.

The region or regions appearing full 12a can be without microscopic opening, that is to say truly solid. In this case, the semi-transparency is obtained by sufficiently reducing the thickness of metal deposited.

The metal is for example aluminum, copper, tin, gold, nickel, chromium, silver, and one of their alloys.

As a variant, the region (s) 12a appear solid and are non-opaque thanks to the presence of microscopic openings such as close-up frames, so as to give them a semi-transparency. In this case, the thickness of metal deposited may be greater, since the semi-transparency is no longer necessarily obtained by the small thickness deposited.

The first layer 12 can allow at least 10% of the white light to pass through the regions that appear full. The transmission factor or transmittance is measured according to ISO 15368 standard.

The first layer 12 can be colored, in particular by a dye and not by a pigment, for example an azo compound.

The security element 10 comprises a second layer 13, located for example as illustrated in the figure 2 , opposite the first layer 12 relative to the support 11.

The second layer 13 may not cover the entire face 11a of the support 11 and have one or more regions appearing full 13a and one or more openings 13b. The latter define patterns M2 visible in reflection from the side of the back side 6 of the element 10, as illustrated in the figure 3B .

The second layer 13 can be non-opaque, the region or regions appearing solid 13a being semi-transparent.

This semi-transparency may be due to the non-opaque nature of the material of the second layer 13. As a variant, the regions 13a are screened, being formed from fine close-up frames which allow light to pass in transmission, but appear full in reflection.

Preferably, the second layer 13 has a color close to that of the substrate 2 of the document 1, and will therefore most often be white.

The composition of the second layer can thus be adjusted as a function of the color (L *, a *, b *) of the substrate 2 of document 1.

The second layer 13 is preferably diffusing and based on pigment (s) dispersed in a binder.

When a diffusing effect is sought, the second layer 13 may comprise a mixture of at least two charges, in particular nanometric, with different refractive indices.

Without being bound by a theory, the Applicant considers that the mixture of said at least two nanometric charges with different refractive indices makes it possible to amplify the scattering phenomenon because the nanometric charge of lower refractive index refracts little by little the incident light which travels through then a larger optical path and penetrates more within the layer, while the nanoscale index charge of higher refraction increases the number of diffusions within the layer. This results in significant penetration and significant diffusion of light within the layer, thereby allowing the layer to mask the underlying structure in reflection without the layer being opaque, which would impair the visibility of the safety element in transmitted light.

The second layer 13 can be in the form of a single masking layer, comprising said aforementioned mixture of at least two nanometric fillers.

More preferably still, at least one of the nanometric fillers comprises colloidal silica (silicon dioxide), in particular pyrogenic, better consists of colloidal fumed silica. A nanometric filler comprising silica is advantageous because it has the advantage of not absorbing UV radiation useful for luminescence, which makes it possible to produce the security element with one or more luminescent layers, in particular fluorescent under UV.

One of the nanometric fillers of the mixture, and preferably colloidal silica, can be present in a mass quantity of between 20 and 80%, better between 30 and 70%, even better between 40 and 60% relative to the mass of the second layer 13.

The colloidal silica preferably has a dimension D50 of between 30 and 1000 nm, better between 30 and 500 nm, even better between 50 and 300 nm.

The security element may comprise, as a nanometric charge, titanium dioxide in the second layer 13. Preferably, the amount of titanium dioxide is low enough not to excessively absorb UV radiation and allow use within the security element of at least one luminescent compound, in particular fluorescent under UV (365 nm), for example applied by printing on the second layer 13 or mixed with the second layer or with a varnish or with an adhesive of the element of security.

The titanium dioxide is preferably anatase in nature, since it then has the advantage of having a lower UV absorption compared to titanium dioxide of rutile nature. Titanium dioxide anatase is in particular at least partially transparent to UV, and in particular transparent over at least one range of wavelengths in the UV range.

The other of the nanometric fillers of the mixture, and preferably titanium dioxide, can be present in a mass quantity of between 1 and 40%, better between 2 and 30%, even better between 3 and 15% relative to the mass. of the second layer.

In the case of a colloidal silica-titanium dioxide mixture, the colloidal silica / titanium dioxide mass ratio is preferably between 0.5 / 1 and 4/1, more preferably between 2/1 and 3/1.

The titanium dioxide preferably has a dimension D50 of between 30 and 1000 nm, better between 30 and 500 nm, even better between 50 and 300 nm.

According to a preferred variant, said at least two nanometric fillers are respectively colloidal silica, preferably pyrogenic, and titanium dioxide, preferably anatase.

According to this variant, colloidal silica induces greater light scattering in the short wavelengths (blue) and a predominantly red-orange color is therefore obtained in transmission (therefore in specular reflection if the particles are placed on an at least partially reflective layer). Titanium dioxide makes it possible to modify the light path by increasing the diffusion within the second layer 13, which brings greater opacity and thus reduces the red-orange reflective appearance produced by colloidal silica.

According to a preferred variant, the second layer 13 also comprises a multilayer interference pigment.

The multilayer interference pigment has the particularity of preferentially selecting certain wavelengths in reflection and in transmission. For example, a blue iridescent pigment reflects in the specular direction (angle of reflection equal to the angle of incidence) more blue wavelengths than others. In transmission, the color obtained is then complementary to the color in reflection, that is to say red-orange. Multilayer interference pigments can be relatively transparent, because they are not very absorbent, and consequently a layer of multilayer interference pigment will have, in diffuse reflection (in all other directions other than the specular direction) the same color as in transmission (complementary to the color in specular reflection). Using the example above, the layer of blue iridescent pigment spread over white paper will give an orange-red color.

The term “multilayer interference pigment” should be understood to mean a pigment producing a color by an interference phenomenon by virtue of a succession on the light path of at least two materials with different refractive indices. A multilayer interference pigment is still sometimes qualified as "mother-of-pearl" in the case of layers deposited on a platelet-shaped base. A multilayer interference pigment is different from a liquid crystal, which can also generate color by an interference phenomenon due to its intrinsic structure.

By combining the color linked to the scattering of light by nanometric charges and that linked to diffuse reflection by the multilayer interference pigment, it is possible to obtain, by additive color synthesis, a color substantially close to that of the substrate of document 1 , for example white, by appropriately choosing the color of the pigment and that of the filler; preferably, nanometric charges are combined with a blue, green or blue-green multilayer interference pigment, or even a mixture of green and blue pigments.

The combination of the pigment and nanometric charges enhances the scattering of the incident light within the second layer. This combination also makes it possible to limit the proportion of the nanometric charge having the highest refractive index, in particular titanium dioxide, therefore to limit the opacification in transmitted light and, where appropriate, the absorption of UV.

Preferably, the multilayer interference pigment according to the invention comprises a transparent base, preferably mineral, coated with at least one layer of a material with a refractive index different from that of the base. The pigment may have a platelet base, preferably made of mica or glass. For example, the pigment contains mica or silica (silicon dioxide) coated with titanium dioxide.

The pigment preferably has a transparent substrate, for example made of mica, and in particular optical characteristics complementary to those of colloidal fumed silica. When the substrate is white, the pigment is preferably blue or green or blue-green. The color of the pigment is that obtained by specular reflection of non-normal incidence.

Preferably, as explained above, the interference pigment has a blue, green or blue-green color.

The average size D50 of the pigment is preferably between 2 and 150 microns, better between 5 and 40 microns, even better between 5 and 25 microns.

The multilayer interference pigment can be non-goniochromatic, and for example comprise only a single layer coating a base.

The mass quantity of multilayer interference pigment relative to the mass of the second layer 13 is preferably between 1 and 40%, better between 2 and 30%, even better between 5 and 15%.

As a variant, the second layer 13 is formed by a deposit of metal.

The element 10 may comprise a layer of heat-sealable adhesive on each of its external faces, not shown.

When the element 10 is observed in reflection from the side of the front face 5, the patterns M1 can be observed by contrast between the color of the region (s) appearing full 12a of the first layer 12 and that of the opening (s) 12b formed in this one, as illustrated in figure 3A . The patterns M2 do not appear or appear little, in particular when the second layer 13 is diffusing and its color is close to that of the substrate 2.

When the element 10 is observed in transmission from the side of the front side 5, being lit from the back side 6, not only the patterns M1 are visible but also the patterns M2, thanks to the semi-transparency of the regions 12a of the first layer 12, as illustrated in figure 3C .

When the element 10 is observed in reflection from the side of the back side 6, only the patterns M2 are visible, as illustrated in the figure 3B . They are all the more visible as the color of the first layer 12 contrasts with that of the second layer 13.

The invention is not limited to the examples which have just been described.

The security element 10 according to the invention may be in a form other than a security wire, and for example in the form of a patch or a structure applied on the surface by transfer, also called " foil " .

In a variant not illustrated, the first and second layers are located on the same side of the support 11.

The first layer 12 may, in a variant, include magnetically orientable plates. Such plates constitute an opaque screen for a certain angle of observation, generally perpendicular to their direction of orientation. When the oriented plates are observed in a direction substantially parallel to their direction of orientation, it is possible to see between them and the layer becomes semi-transparent. A first layer comprising magnetically orientable plates, which may be suitable for producing the first layer, is described in the publications. WO 2012/176169 A1 or WO 2013/190522 A2 .

The security element 10 according to the invention can receive any additional structure increasing security, such as for example a layer of liquid crystals or goniochromatic pigments, a diffraction grating, a hologram, or an optical structure such as a lens. de Fresnel, among other examples.

In the variant illustrated in figure 4 , the security element 10 comprises on the front face of the support 11 an intermediate layer of variable opacity 20 comprising magnetically oriented plates, as described in the publications WO 2012/176169 A1 or WO 2013/190522 A2 mentioned above. This intermediate layer 20 has an opacity which varies with the direction of observation. Thus, under normal incidence for example, the first layer 12 which covers the intermediate layer 20 is opaque and under an incidence which corresponds substantially to the direction of orientation of the plates, the intermediate layer 20 is non-opaque.

The intermediate layer 20 extends for example continuously over the entire surface of the support 11.

In the variant of the figure 5 , the first layer 12 is a metal layer covered by an embossed layer 12c, so as to create at each first region 12a a diffraction grating visible in reflection.

The first layer 12 can follow below the relief of the embossed layer 12c.

As a variant, the first layer 12 covers the embossed layer 12c.

In the variant of the figure 6 , the first layer 12 is formed by an impression of an absorbent ink, and it is covered by a layer 12c of cholesteric liquid crystals, which covers for example the solid regions 12a and openings 12b.

Liquid crystals are non-opaque and their goniochromatic effect is visible only where they overlap with the solid regions 12a.

The expression "comprising a" should be understood as being synonymous with "comprising at least one".

Claims (15)

1. A security element (10) for a secured document (1), comprising:

   - an at least partially transparent support (11),

   - a first layer (12) borne by the support, formed by a deposition of metal or a print, the first layer only partially covering the support so as to define at least one first region (12a) appearing solid but not completely opaque and a first opening (12b) at least partially delimiting at least one first pattern (M1),

   - a second layer (13) borne by the support, at least partially overlaid with the first, only partially covering the support so as to define at least one second region (13a) appearing solid but not completely opaque and at least one second opening (13b) at least partially delimiting at least one second pattern (M2), the first pattern (M1) being visible in transmitted light from the two faces of the security element and in reflected light only from the front face of the security element, and the second pattern (M2) being visible in transmitted light from the two faces of the security element and in reflected light only from the back face of the security element.
2. The element according to Claim 1, the second pattern (M2) having a predetermined position relative to the first pattern (M1).
3. The element according to Claim 1 or 2, the second opening (13b) being at least partially overlaid with the first region (12a) appearing solid of the first layer (12).
4. The element according to any one of Claims 1 to 3, the first opening (12b) being at least partially overlaid with the second region (13a) appearing solid of the second layer (13).
5. The element according to any one of Claims 1 to 4, the first layer (12) being formed by a print.
6. The element according to any one of Claims 1 to 4, the first layer (12) being formed by a metal deposition, the metal deposition being preferably sufficiently thin for the first region (12a) appearing solid to be non-opaque.
7. The element according to any one of Claims 1 to 5, the first layer (12) being diffusing.
8. The element according to any one of Claims 1 to 7, the first region (12a) appearing solid having its non-opaque character due to the presence of a raster.
9. The element according to any one of Claims 1 to 8, the second layer (13) being formed by a print, notably non-metallic, the second layer (13) comprising a diffusing ink.
10. The element according to any one of Claims 1 to 9, the second layer (13) being formed by a metal deposition, the metal deposition being sufficiently thin for the second region (13a) appearing solid to be non-opaque or the second region (13a) appearing solid having its non-opaque character due to the presence of a raster.
11. The element according to any one of the preceding claims, the first pattern (M1) being completely surrounded by the first region (12a) appearing solid, in front view.
12. The element according to any one of the preceding claims, the first and second layers (12, 13) being situated respectively on the front face and on the back face of the support (11).
13. The alement according to any one of the preceding claims, the second pattern (M2) being overlaid exclusively with the first region (12a) appearing solid, the first pattern (M1) being exclusively overlaid with the second region (13a) appearing solid.
14. A secured document (1) comprising a security element (10) as defined in any one of the preceding claims, the second layer (13) preferably having a colour close to that of a substrate of the document in which the element is incorporated or onto which the element is fixed, the substrate and the second layer being preferably white.
15. A method for authenticating a document as defined in Claim 14, comprising the steps of:

    - observing the security element (10) in transmission,

    - observing the security element (10) in reflection, on the back face and on the front face,

    - generating an information concerning the authenticity of the document at least on the basis of said observations.

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