EP3206885A1

EP3206885A1 - Security element for a security document

Info

Publication number: EP3206885A1
Application number: EP15784595.9A
Authority: EP
Inventors: Jacques MACHIZAUD; Stéphane Mallol
Original assignee: ArjoWiggins Security SAS
Current assignee: Oberthur Fiduciaire SAS
Priority date: 2014-10-13
Filing date: 2015-10-12
Publication date: 2017-08-23
Anticipated expiration: 2035-10-12
Also published as: FR3026988A1; WO2016059005A1; FR3026988B1; EP3206885B1

Abstract

The invention relates to a security element (10) for security document, comprising: an at least partially transparent support (11); a first security structure (12) borne by the support and defining at least a first pattern visible under transmitted light; and a second security structure (14,15) borne by the support, at least partially overlapping the first structure (12) and comprising a non-opaque masking layer (14) and a non-diffusing, non-opaque pattern layer (15), said pattern layer externally covering the masking layer (14) and, by means of contrast with the masking layer, defining at least a second pattern visible only in reflection on the side of the pattern layer (15).

Description

SECURITY ELEMENT FOR SECURE DOCUMENT

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 security structures carried by this support for revealing patterns when the element is observed in transmitted light or in reflection.

It is widely known to use as security element security threads consisting of a strip of a transparent thermoplastic coated on one side of at least one metal deposit with openings formed by demetallization, showing patterns when the element is observed transmitted light, such security is still called CLEARTEXT.

The application WO 2009/053673 discloses such a security element. This document describes a security thread comprising a support provided with a perforated opaque metal layer defining a pattern, this layer being coated with a scattering 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 diffusing layer. However, when the observation is carried out in reflected light, the pattern of the scattering layer may appear. Moreover, when the scattering layer comprises magnetic particles, the magnetic signal is relatively weak because the concentration of magnetic particles must be low to maintain the invisibility in transmitted light of the scattering layer and thus not to disturb the observation in transmitted light of the CLEARTEXT.

The patent application US 2012/0025514 relates to a security element having two distinct patterns superimposed. The security element having a substrate at least partially transparent, on the front and back of which there are first and second marks in the form of metallizations and / or prints, the first marks superimposed mainly on the second marks, the first and second marks respectively forming first and second distinct patterns on their respective faces, the degree of visibility of the second marks varying with the angle of observation of the front of the security element. The application WO 2009/149831 discloses a security element comprising at least one multilayer structure, which can create interference, consisting of at least one reflective layer having holes, at least one partial transmission layer having at least one pattern-shaped hole and at least one dielectric layer disposed between these two layers.

The invention aims to further improve the security elements, in particular to provide a visible effect in transmitted light and a distinct visible effect in reflection, without unduly complicating their manufacture.

The invention thus has, according to a first of its aspects, a security element for secure document, comprising: an at least partially transparent support, a first security structure, carried by the support and defining at least a first visible pattern in transmitted light, a second security structure carried by the support and at least partially superimposed on the first structure, comprising a non-opaque masking layer and a non-diffusing and non-opaque pattern layer covering the masking layer on the outside and defining in contrast with the latter, at least one second visible pattern in reflection on the side of the pattern layer.

The invention makes it possible to have at least one piece of information, in particular said second pattern, visible on one side of the element, in reflected light, especially on the back side thanks to the pattern layer.

The invention makes it possible, if desired, a level 1 security revealing to the naked eye and white light different patterns transmitted light and reflection.

The use of a non-diffusing and non-opaque pattern layer is advantageous in that it makes it possible to obtain a visual contrast showing a pattern in reflected light, while retaining a relatively transparent appearance in transmitted light, not disturbing In addition, the visibility of the visible pattern in transmitted light. Thus, the visibility of the transmitted light pattern layer can be reduced, if desired, and the pattern that appears in transmitted light can conventionally appear in the manner of a CLEARTEXT.

The non-diffusing pattern layer is preferably formed of a dye ink printing, in particular free of particulate fillers the size of which is greater than 50 nm, preferably completely free of particulate charges. Alternatively, the non-diffusing pattern layer is formed of a semitransparent metal deposit.

The size of the particulate fillers is especially the size D90, for example in number, and it is preferably the largest dimension.

The element may comprise a magnetic layer at least partially covered by the masking layer. This magnetic layer may be discontinuous.

The element may comprise a metal intermediate layer between the masking layer and the magnetic layer, further reducing the visibility in reflected light of the magnetic layer, the intermediate layer is preferably formed of a reflective metal.

The intermediate metal layer may be discontinuous.

The first structure may be formed of a metal layer selectively present on the substrate, in particular with openings defining the first pattern or patterns.

Preferably, the masking layer is diffusing, and comprises a pigment load.

The masking layer may be white.

The masking layer may also, alternatively, be semitransparent metallic, in particular metal thin and / or metal halftone.

Whether diffusing or not, the masking layer can extend continuously.

The masking layer can cover more than 50% of the face of the support it covers, better more than 75%, even better 100%.

The pattern layer may cover less than 100% of the masking layer, more preferably less than 50%.

The first and second structures are preferably disposed on opposite sides of the support.

The pattern layer may be substantially transparent to UV radiation at 365 nm, which does not affect how one or more additional security means, carried by the security element or the document, react. The support may comprise, in particular, consist of a film of transparent thermoplastic material, preferably PET.

The element may be in the form of a security thread.

The different appearance of the front and back faces, especially when the first structure is metallic and the masking layer of white and visible color through the openings of the pattern layer, can facilitate the manufacture of documents incorporating the element, constituting a visual cue very easy to discern when inserting 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 that is sufficiently transparent or translucent that the first transmitted light pattern can be observed through the security element.

By "non-opaque masking layer" it should be understood that the layer passes white light under at least some observation conditions, with a transmission factor of preferably at least 10%, better still at least 20% measured according to ISO 15368. Also known as semi-transparency.

By "non-diffusing pattern layer", it should be understood that said layer has a transmittance measured according to ISO 15368 with the aid of a goniospectrophotometer equal to 0 at an angle other than 0 ° ± 2 ° and different from 0 at an angle equal to 0 ° ± 2 °.

The semi-transparent nature of the masking layer may be independent of the angle of observation, which is for example the case for a metal deposit of homogeneous thickness but very thin or the use of a pigment layer having a sufficiently low concentration of pigments.

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 security 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, passport or a driving license, a card, including access, a lottery ticket, a ticket or a ticket for admission to cultural or sports events, a loyalty card, a service card, a subscription card, a playing or collectible card, a voucher or a voucher. It is preferably a document comprising a fibrous layer, especially when the security element is a security thread. In this case, the security element is introduced into the secure mass or window document (s), and preferably extends into 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 can be integrated into the document substrate. The presence of the masking layer, visible on the back, especially when white or metallic color, can reduce the visibility of the element out of the possible windows of the document, when the latter is observed on the back side.

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

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

Among the additional security features, some are detectable to the eye, daylight or artificial light, without the use of a particular device. These additional security elements comprise, for example, colored fibers or boards, fully or partially printed or metallized wires. These additional security features are said to be 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 additional security elements include, 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 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 for their detection a more sophisticated 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 additional security features for example, have 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 features are said to be third-level.

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

The invention further relates, in another of its aspects, a method of authenticating a secure document comprising a security element as defined above. Observation can be done through a window of the document.

The authentication method may comprise the steps of: observing the security element in transmitted light, observing the security element in reflected light, on the front and back, generating at least one information concerning the authenticity of the document on the basis of the observations made.

According to another of its aspects, the subject of the invention is also a method of manufacturing a secure document as defined above, in which the security element is incorporated in window (s) or on the surface. 'invention.

The invention will be better understood on reading the following detailed description, non-limiting examples of implementation thereof, and on examining the appended drawing, in which: FIG. schematically an example of secure document according to the invention, Figure 2 shows in cross-section along II-II the security element, Figures 3 and 4 are schematic cross sections of variants of security elements according to the 5 to 6 respectively represent the security element observed in transmitted light and reflection on the back, and Figures 7 to 9 show in section other variants of security elements according to the invention.

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, some layers may appear monolithic in the figures when they are actually made up of several sub-layers. Adhesive layers may not have been shown between different constituent layers.

FIG. 1 shows an example of a secure document 1 according to an exemplary implementation of the invention, for example a banknote.

The document 1 comprises a substrate 2, preferably made of paper, formed of one or more fibrous jets, which integrates a security element 10 according to the invention, in the form of a thread ("thread" in English) in the example under consideration. .

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

The security element 10 may comprise on the front a first security structure 12, which may be of varied construction, and for example comprise a perforated metal layer, as in the examples of Figures 3 and 4.

On the back side, the element 10 may comprise, as illustrated in FIGS. 2 to 4, a second security structure comprising a masking layer 14 covered externally by a pattern layer 15.

When the first security structure 12 is a layer formed by metallization and / or demetallization, particularly as in the case of the examples of Figures 3 and 4, this layer may comprise one or more solid regions 12a and one or more openings 12b. The opening or openings 12b are visible in transmitted light through a window 3 of the document 1 and then define one or more first patterns Ml as illustrated in FIG. 5 for example. The patterns Ml are for example alphanumeric patterns, or representations of various subjects such as characters, animals, plants, landscapes or monuments. The M1 patterns can be found elsewhere on the document 1, being for example printed on the substrate or being for example a watermark.

The term "metallization and / or demetallization" means any process comprising at least one metallization step or demetallization. This is in particular a selective metallization process or a metallization process then selective demetallization. Preferably, it is a metallization process then selective demetallization.

The term "selective metallization" or "selective demetallization", respectively a metallization or a non-total demetallization, that is to say that is not done on the entire surface of the support and thus allows to form at least one pattern.

According to one variant, the first pattern is formed by printing a metallized ink, in particular a metallic ink.

The pattern (s) M1 can still be raster images, giving a relief impression thanks to a shading effect. In this case, the openings 12b have sizes and a distribution adapted to create such images.

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

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

The metal of the layer 12 is, for example, aluminum, copper, tin, gold, nickel, chromium, silver, one of their alloys or one of their mixtures.

The layer 12 can pass less than 10% of the white light in the solid regions 12a.

The layer 12 may be colored, in particular with a dye, for example an azo compound.

The first security structure 12 can still be performed differently

In a variant, the first security structure 12 is constituted by a lenticular network covered or covering a metallization or printing having openings, which will be visible in transmitted light. In another variant, the first security structure 12 consists of a multilayer interference structure formed by deposition, in particular by a PVD technique, of thin layers of different refractive indices, this interferential structure being covered by or covering a metallization or a impression presenting openings.

In another variant, the first security structure 12 is a hologram in reflection, whose reflective layer is perforated.

The first security structure may further comprise a layer comprising magnetic platelet particles oriented so as to have an opacity that varies with the angle of observation.

Figure 7 shows an example of such a structure. In this figure, it can be seen that the oriented particle layer 12c can be covered by an opaque printing having openings 12b.

In the variant of Figure 8, the first structure 12 is a diffraction grating 12a which does not cover the entire front face of the support 11. This network may have a bilayer structure, with an embossed layer and a reflective layer.

FIG. 9 shows a variant in which the first structure 12 comprises a layer of cholesteric liquid crystals 12c and an underlying absorbent layer 12a, of dark color, especially black, with openings 12b.

The masking layer 14 may not cover the entire corresponding face 11a of the support 11 and have one or more solid regions and one or more openings. Preferably, however, the masking layer 14 completely covers the face 11a.

The masking layer 14 is non-opaque. The semi-transparency of the masking layer 14 may be due to the non-opaque nature of the material of the layer 14.

The composition of the masking layer 14 can be adjusted according to the color (L *, a *, b *) of the substrate 2 of the document 1, in particular to have substantially the same color.

The masking layer 14 is preferably diffusing and based on pigment (s) dispersed in a binder.

The masking layer 14 may comprise a mixture of at least two charges, in particular nanometric charges, of different refractive indices. Without being bound by a theory, the Applicant estimates that the mixture of the said at least two nanometric charges of different refractive indices makes it possible to amplify the diffusion phenomenon because the nanometric charge of a lower refractive index refracts little the incident light which runs through then a larger optical path and penetrates further into the layer, while the nanoscale load of higher refractive index increases the number of diffusions within the layer. This provides a significant penetration and diffusion of light within the layer, allowing the layer to hide the underlying structure in reflection without the layer is opaque, which would adversely affect the visibility of the security element in transmitted light.

The masking layer 14 may be in the form of a single masking layer, as illustrated, comprising said aforementioned mixture of at least two nanometric charges.

More preferably, at least one of the nanometric fillers comprises colloidal silica (silicon dioxide), in particular pyrogenic silica, and is better composed of fumed colloidal silica. A nanometric charge comprising silica is advantageous because it has the advantage of not absorbing the 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 charges of the mixture, and preferably the colloidal silica, may be present in a mass quantity of between 20 and 80%, better still between 30 and 70%, and still more preferably between 40 and 60% relative to the mass of the mixture. the masking layer 14.

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

The security element may comprise as titanium dioxide nanoscale in the masking layer 14. Preferably, the amount of titanium dioxide is low enough not to excessively absorb the UV radiation and allow the use within the security element of at least one luminescent compound, especially fluorescent under UV (365 nm), for example applied by printing on the masking layer 14 as present in the pattern layer 15 or mixed with a varnish or an adhesive of the security element. Titanium dioxide is preferably of anatase nature, because it then has the advantage of having a lower UV absorption compared to titanium dioxide of rutile nature. The anatase titanium dioxide is in particular at least partially transparent to UV, and in particular transparent over at least one wavelength range of the UV range.

The other nano metric charges of the mixture, and preferably titanium dioxide, may be present in a mass quantity of between 1 and 40%, better still between 2 and 30%, and even more preferably between 3 and 15% relative to the mass of the masking layer 14.

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

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

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

According to this variant, the colloidal silica induces a greater scattering of the light in the short wavelengths (blue) and one thus obtains a predominantly red-orange color in transmission (thus in specular reflection if the particles are placed on an at least partially reflective layer). Titanium dioxide makes it possible to modify the path of light by increasing the diffusion within the masking layer 14, which brings greater opacity and thus reduces the red-orange reflective appearance produced by the colloidal silica.

According to a preferred variant, the masking layer 14 further 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 the 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 As a result, 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 mirror-reflecting color). Using the example above, the layer of blue iridescent pigment spread on a white paper will give a red-orange color.

The term "multilayer interference pigment" is intended to mean a pigment producing a color by an interference phenomenon by virtue of a succession in the path of light of at least two different refractive index materials. A multilayer interference pigment is still sometimes referred to as "nacre" in the case of layers deposited on a platelet-based base. A multilayer interference pigment is different from a liquid crystal, which can also generate a color by an interference phenomenon due to its intrinsic structure.

By combining the color associated with the scattering of light by the nanometric charges and that related to the diffuse reflection by the multilayer interference pigment, it is possible to obtain, by additive synthesis, colors, a color substantially similar to that of the substrate 2 of the document. 1, for example white, by suitably choosing the color of the pigment and that of the load; preferably, a blue, green or blue-green multi-layer interference pigment, or a mixture of green and blue pigments, is combined with the nanometric fillers. The combination of the pigment and the nanometric charges enhances the diffusion of the incident light within the masking layer 14. This combination also makes it possible to limit the proportion of the nanometric filler having the highest refractive index, in particular the titanium, thus limiting opacification in transmitted light and, if necessary, UV absorption. Preferably, the multilayer interference pigment according to the invention comprises a transparent base, preferably mineral, coated with at least one layer of a refractive index material different from that of the base. The pigment may comprise a platelet base, preferably of mica or glass. For example, the pigment comprises 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 that are complementary to those of fumed silica. colloid. When the substrate is white, the pigment is preferably blue or green or blue-green. The color of the pigment is that obtained in 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, more preferably between 5 and 40 microns, more preferably between 5 and 25 microns.

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

The mass quantity of multilayer interference pigment relative to the mass of the masking layer 14 is preferably between 1 and 40%, better still between 2 and 30%, and more preferably between 5 and 15%.

Alternatively, the masking layer 14 is formed by a metal deposit. In this case, the deposited metal thickness is low enough to maintain a semi-transparency.

Alternatively, the masking layer 14 is deposited in the form of a frame and the semi-transparency is obtained by the presence of microscopic openings between the lines of the frame.

The pattern layer 15 is preferably formed by printing on the masking layer 14.

Preferably, the pattern layer 15 is formed using a non-diffusing dye ink. Such an ink may be devoid of pigment. The advantage of such an ink is its non-diffusing nature.

The pattern layer 15 may or may not include a luminescent compound, especially fluorescent.

As inks that can be used to form the pattern layer 15, mention may be made of the liquid LEVACELL black liquid NP marketed by Kemira.

The content of particles (in particular pigments and mineral fillers) of the ink used may be between 0 and 5% by weight, preferably being less than or equal to 2% and more preferably less than 1%. The pattern layer 15 may be devoid of luminescent compound, especially fluorescent at 365 nm or in the infrared.

Preferably, the ink is relatively dilute, so as not to absorb too much visible light. The amount of dye in the ink may be less than or equal to 5% based on the weight of the ink.

The patterns M2 may not be positioned at the mark relative to the patterns Ml. In other words, there is not necessarily a predefined relative positioning between a pattern M1 and a pattern M2 along the security element.

The element 10 may have, on the back side, only the masking layer 14 and the pattern layer 15, as illustrated in FIGS. 2 and 3.

Alternatively, as illustrated in FIG. 4, the masking layer 14 covers a discontinuous magnetic layer 17.

The solid regions of this magnetic layer 17 are preferably superimposed exclusively on the solid regions 12a of the layer 12, so as not to interfere with the M1 units defined by the openings 12b. Alternatively, the solid regions of the magnetic layer 17 participate in the definition of the visible M1 patterns in transmitted light.

The solid regions of the magnetic layer 17 may be covered by a metal intermediate layer 18, for example aluminum, so as to reduce their visibility on the back side. The intermediate layer 18 is itself covered by the masking layer 14.

In the illustrated examples, the masking layer 14 is continuous and preferably extends over the entire length of the element. As a variant, the masking layer 14 is for example interrupted on certain sections of the element.

The patterns M2 defined by the pattern layer 15 may be varied and different from the M1 patterns.

The patterns M2 are for example alphanumeric patterns or images of characters, monuments, landscapes, plants or animals. The images can be raster images and generate a 3D appearance through a shading effect.

M2 patterns can be found elsewhere on the document. The secure document is not limited to a bank note and may be another means of payment or an identity document or entry ticket to cultural or sports events.

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

When the element 10 is observed in reflection on the side of the front face, one can observe the effect produced by the security structure 12 in reflected light.

When the first security structure 12 is formed by a perforated metal layer, as in the examples of Figures 3 and 4, and when the element 10 is observed in transmission on the side of the front face, being illuminated from the reverse side, the patterns M1 are visible in the manner of a CLEARTEXT, as illustrated in FIG. 5. The pattern layer 15 does not unduly hinder the visibility of the patterns M1.

When the element 10 is observed in reflection on the side of the back side 6, only the M2 patterns are visible, as shown in Figure 6. They are even more visible that the color of the pattern layer 15 contrasts with that the masking layer 14.

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 thread, and for example in the form of a patch or a structure applied on the surface by transfer, also called "foil" . In this case, the support 11 may be an adhesive layer, as mentioned above.

In a variant not shown, the first and second safety structures are located on the same side of the support 11.

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

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

Claims

Security element (10) for secure document (3), comprising:

a support (11) at least partially transparent,

a first security structure (12) carried by the support and defining at least a first visible pattern (M1) in transmitted light,

a second security structure (14, 15) carried by the support and superposed at least partially on the first structure (12), comprising a semi-transparent masking layer (14) and a non-transparent pattern layer (15); diffusing and semi-transparent, externally covering the masking layer (14) and defining in contrast therewith, at least one second pattern (M2) visible only in reflection on the side of the pattern layer (15).

2. Element (10) according to claim 1, the non-diffusing pattern layer (15) being formed of a printing dye ink, in particular completely free of particulate charges.

3. Element according to claim 1, the non-diffusing pattern layer (15) being formed of a metal deposit.

4. Element according to any one of claims 1 to 3, comprising a magnetic layer (17) at least partially covered by the masking layer (14).

5. Element according to claim 4, the magnetic layer (17) being discontinuous.

6. Element according to claim 4 or 5, comprising a metal intermediate layer (18) between the masking layer (14) and the magnetic layer (17).

7. Element according to claims 5 and 6, the metal intermediate layer (18) being discontinuous.

8. Element according to any one of the preceding claims, the first structure (12) being formed of a metal layer selectively present on the substrate, in particular with openings (12b) defining said first pattern (Ml).

9. Element according to any one of the preceding claims, the masking layer (14) being diffusing.

10. Element according to claim 9, the masking layer (14) comprising a pigment filler.

1. Element according to one of claims 9 or 10, the masking layer (14) being white.

12. Element according to any one of claims 1 to 8, the masking layer (14) being semi-transparent metal, in particular metal thin and / or metal halftone.

13. Element according to any one of claims 1 to 12, the masking layer (14) extending continuously.

14. Element according to any one of claims 1 to 13, the masking layer (14) covering more than 50% of the face (l ia) of the support (1 1) it covers, better more than 75% o , even better 100%.

15. Element according to any one of claims 1 to 14, the pattern layer (15) covering less than 100% of the masking layer (14), better less than 50%>.

An element according to any one of the preceding claims, the first and second structures being disposed on opposite faces (11a, 11b) of the support.

17. Element according to any one of the preceding claims, the pattern layer (15) being substantially transparent to UV radiation at 365 nm.

18. Element according to any one of the preceding claims, the support

(1 1) comprising, in particular consisting of a transparent thermoplastic film, preferably PET.

19. Element (10) according to any one of the preceding claims, being in the form of a security thread.

20. Secure document (1) comprising a security element (10) according to any one of the preceding claims.

21. Document according to claim 20, the element (10) being a security wire extending in window (s) (3).

22. A method of authenticating a document (1) according to one of claims 20 and 21, comprising the steps of:

- observe the security element (10) in transmitted light,

- observe the security element (10) in reflected light, on the front and back, - generate at least one information concerning the authenticity of the document (1) on the basis of the observations made.