EP3023259A2 - Security element - Google Patents

Abstract

Security element (10), in particular security thread, for security document, the security element comprising first (18) and second (21) zones separated by an intermediate zone (24) comprising an intermediate structure (33), the first and second zones having respective first (27) and second (30) optically variable structures arranged so that for a first viewing direction (O1) the first and second structures have different aspects than the first one; other and for a second direction of observation (02) different from the first, the first and second structures have each on the one hand each changed aspect with respect to their appearance when observed according to the first direction of observation, and on the other hand have different aspects from each other, the intermediate structure comprising non-magnetic particles and / or a semi-transparent layer.

Description

The present invention relates to security elements, in particular security threads, and valuable or security documents incorporating such elements.

Security features are very often used in banknotes to help make counterfeits more difficult and to authenticate them.

Numerous elements have been described which aim both to provide security difficult to reproduce and to produce a visually appealing appearance.

WO 2013/034476 discloses a safety strip having two zones extending in a longitudinal direction of the strip and having different aspects visible by reflection.

It is also known, for example from US 7,047,883 , US 2006/0198998 and of US 2013/0087060 directing magnetic pigments deposited on a substrate under the effect of a magnetic field so as to form a security element comprising an optically variable structure in which the orientation of the pigments varies gradually, thus providing a visual appearance movement when the viewing direction of the security element varies.

EP 1 819 525 B1 discloses a security element comprising platelet-shaped pigments which can be oriented under the effect of a magnetic field so as to make it possible to observe, for a direction of observation substantially parallel to the orientation of the pigments, a subtle impression. core. The security element has two zones whose pigments are oriented differently so that the appearance / disappearance of the underlying patterns can be observed when the direction of observation changes.

FR 2 976 954 A1 discloses a safety wire having two optically variable structures separated in a direction transverse to the longitudinal direction of the wire by a third security structure, comprising platelet pigments oriented differently in the two zones and allowing the observation of underlying impressions according to respective observation directions substantially parallel to the orientations of the pigments.

FR 2 992 255 A1 discloses a safety wire having two optically variable structures extending in the longitudinal direction of the wire, on which is superimposed a layer of variable opacity, the optically variable structures having platelet pigments oriented differently in the two areas. When observed through the layer of variable opacity, optically variable structures appear reflective or transparent, depending on the direction of observation.

EP 0 310 707 A2 , EP 1 618 006 A1 and WO 2011/026829 describe security features having regions having areas of varied magnetic properties. The distribution of these areas within these security elements defines magnetic signatures that are unique to them and that can be detected magnetically.

The book "Optical Document Security (Third edition)," Rudolf L. Van Renesse, Artech House, Boston / London, 2005, describes page 252 , figure 7.21 a security document presenting a first zone on which is affixed a photo of identity and a second zone on which an eagle is represented, these two zones being separated by a zone on which a hologram can appear. The first and second zones comprise optically variable structures.

WO 97/47478 describes a security element comprising a support having visual indicia on each of the faces of the support, the visual index on the first face being superimposed on the visual index on the opposite face of the support.

EP 1 780 040 discloses a security element in which an image comprises a layer with a hologram and a layer with magnetically oriented particles.

WO 2011/012520 discloses a transfer foil comprising a coating in the form of a pattern having an optically variable oriented magnetic pigment, the orientation of the pigment representing an image, a clue, or a pattern.

The invention aims to further improve the security elements, especially so that these elements offer different levels of visually detectable security, and optionally magnetically, thanks to a security element, including security thread, for secure document, the security element extending in a longitudinal direction and having first and second zones separated in the longitudinal direction by an intermediate zone having an intermediate structure, the first and second zones having respective first and second optically variable structures, arranged so that for a first direction of observation the first and second structures have different aspects from each other and for a second direction of observation different from the first, the first and second structures have on the one hand each changed appearance by compared to their appearance when observed in the first direction of observation, and on the other hand have different aspects of each other.

According to one aspect of the invention, the intermediate structure comprises non-magnetic particles and / or a semi-transparent and preferably semi-reflective layer, which may be defined by non-magnetic particles or by a deposition of a metal. According to another aspect of the invention, the intermediate structure comprises magnetic particles oriented flat. According to another aspect of the invention, the intermediate zone consists of a metal flat surface, preferably semi-reflective. The first and second structures and the intermediate structure may in particular be obtained by embossing a support, in particular covered with metal, for example in the form of a flat, preferably semi-reflecting, as described for example in WO 2007/079851 and WO 2009/080264 .

When viewed in reflected light, a semi-transparent structure appears opaque and when observed in transmitted light, it is possible to see through it. The semi-transparency can be obtained by a metal deposit, such as aluminum, whose adjustment of the optical density, that is to say the adjustment of the thickness of the layer of deposited metal, allows to modulate the transmittance. The optical density is advantageously chosen between 0.2 and 1.6, preferably between 0.4 and 1. The semi-transparency of a structure comprising particles, for example of platelet-shaped form, dispersed in a binder can be obtained by determining the optical properties of the binder and adjusting the thickness of the structure and the particle size so that in transmitted light, the structure does not appear opaque.

A semi-reflecting structure may be such that, when observed in reflection, it exhibits, for at least one direction of observation, an aspect of specular gloss and appears non-opaque, in particular transparent, for a different direction of observation. For example, a structure comprising platelet particles in themselves opaque dispersed in a transparent binder and all oriented in the same direction of orientation may appear non-opaque when observed in a direction parallel to the direction of orientation of the particles and appear opaque, in an oblique direction of observation with respect to the large faces of the platelet particles, the incident light beam being reflected by these large faces.

A semi-reflecting structure may be such that, when observed in reflection, it exhibits, for at least one direction of observation, an aspect of specular gloss, and appears opaque and matt for another direction of observation.

A structure can be both semi-transparent and semi-reflective.

An interesting visual effect can be obtained by successively placing the first optically variable structure, the intermediate structure and the second optically variable structure in succession with each other. The same visual aspect can pass from the first zone to the second zone when the observation direction changes, and can also pass through the intermediate zone. In particular, the aspect in question can be the same color, a gloss, for example metallic, a transparency, a shape, a drawing, for example a face or a landscape, or a succession of alphanumeric characters.

The security element may extend in a longitudinal direction and the first and second zones may be separated in the longitudinal direction by the intermediate zone.

According to a third direction of observation different from the first and second observation directions, the intermediate structure may have an appearance identical to the appearance of the first zone observed in the first direction of observation. It may also have an appearance identical to the appearance of the second zone observed in the second direction of observation. On the other hand, the transition from the first observation direction to the second observation direction through the third observation direction provides the observer of the security element with a visual impression of movement between the first zone of observation , the intermediate zone and the second zone.

The first and second optically variable structures preferably comprise the same pigment which is deposited differently on the first and second zones, in particular with a different orientation. This gives a "tilting" effect, for example with a luminous "extinction" of a part of the security element when it is observed in reflected light in a certain direction of observation, and an inversion of the extinguishing another part of the security element when changing enough direction of observation.

Preferably, this pigment is magnetic and platelet-shaped. It can thus be oriented using magnetic devices during the manufacture of the security element.

The first and second optically variable structures and the intermediate structure may be arranged on the same side of a support of the security element, made of a thermoplastic material, preferably polyethylene terephthalate (PET).

The first and second optically variable structures and the intermediate structure may be semi-transparent. They can also be semi-reflective.

The security element optionally includes a fourth structure superimposed on the first and second optically variable structures and the intermediate structure. The fourth structure can define a pattern, for example a sequence of alphanumeric characters, a drawing, a face, a barcode. The fourth structure thus makes it possible to improve the security of the security element. For example, it is visible in reflected light in a fourth direction of observation and in transmitted light in a fifth direction of observation different from the fourth direction of observation. It may be a magnetic layer, in particular obtained by printing a magnetic ink.

The fourth structure may have a first, second or third level security feature.

"First-level security" means security that is detectable by the eye, in daylight, or in artificial light, without the use of a particular device.

Other types of additional security structures are detectable only with a relatively simple apparatus, such as a lamp emitting in the ultraviolet (UV) or infrared (IR). These safety structures can be visible to the naked eye or not, being for example luminescent under a lighting of a Wood lamp emitting in a wavelength of 365 nm. These security structures are called second level.

Other types of security structures require for their detection a more sophisticated detection device. These security structures 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 element. These security structures comprise, for example, tracers in the form of active materials, particles or fibers capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security structures are said to be third level.

• une impression,
• une démétallisation,
• une couche magnétique, créant une sécurité de troisième niveau, ou
• un élément coloré ou à effet goniochromatique, métallique, holographique, entre autres possibilités.

The fourth security structure may comprise or be constituted by:

• an impression,
• a demetallization,
• a magnetic layer, creating a third level security, or
• a colored or goniochromatic element, metallic, holographic, among other possibilities.

The fourth and fifth observation directions may be parallel to the first and second observation directions, respectively. As a variant, they may be different, which advantageously makes it possible to improve the security of the element, by providing multiple aspects according to the directions of observation. The first and second optically variable structures and the intermediate structure may be disposed on one side of a support and the fourth structure may be disposed on an opposite face of the support. A first aspect can then be observed when the observer looks at one face of the support in one of the first, second and third viewing directions. When the observer looks at the opposite face in one of the fourth and fifth directions of observation, he can observe another aspect, not observed on the other side.

The first optically variable structure and / or the second optically variable structure may cover underlying impressions. The underlying impressions are preferably arranged between the support and the optically variable structures. Thus, in the case where an optically variable structure appears transparent for a defined viewing direction, the underlying impression can be revealed, and can disappear when, after changing the observation direction, the optically variable structure appears opaque. .

The first and second optically variable structures may be semitransparent and shaped so that when the security element is observed in transmitted light, the underlying printing is visible, and when the safety is observed according to at least one observation direction in reflected light, the underlying impression is not visible.

The security element may comprise a layer defining a first level security and / or second level and superimposed at least partially on the first optically variable structure and / or the second optically variable structure and / or the intermediate structure. In particular, this layer may be in the form of a pattern chosen from a series of alphanumeric characters, a demetallization, a bar code, a representation of a semitone halftone pattern, in perspective, in particular a portrait, a landscape, a plant, an animal, or a monument. In particular, said layer can be invisible under an illuminant having at least one wavelength in the spectrum of visible light and be revealed to the eye by an infrared illuminant and / or an ultraviolet illuminant, because it contains a luminescent compound, especially fluorescent.

The intermediate structure is preferably contiguous with the first optically variable structure and / or the second optically variable structure. It is thus possible to obtain a visual effect passing from the first zone to the intermediate zone and then to the second zone, which appears continuous to the observer.

The security element may be a wire whose width is between 2 and 10 mm or a foil whose width is between 2 and 45 mm.

Alternatively, the first and second optically variable structures and the intermediate structure are obtained by printing on a substrate of a secure document.

Non-magnetic particles

The non-magnetic particles are preferably platelet-shaped. They may have opposite main faces which are substantially flat and parallel, for example with a deflection angle of one relative to the other of less than 15 °.

They may have a number-average thickness of between 0.5 μm and 4 μm, preferably between 1 μm and 3 μm, and / or a number-average length of between 10 μm and 60 μm, preferably between 15 μm. and 30 μm.

They may be elongated along a longitudinal axis, and their average length L may be greater than their average thickness e, measured between said main faces, the average form factor L / e being preferably greater than or equal to 2, preferably greater than 5, or even greater than 10, the averages of the lengths, thicknesses and form factor being expressed in number. Preferably, L / e is between 15 and 25.

Preferably, the non-magnetic particles intrinsically have an opaque character.

The non-magnetic particles preferably comprise a metal core, which makes it possible to obtain a metallic reflective effect. The fact of having a metal core makes it possible in addition to be able to perform transformations of the chemical or laser demetallization type or phase modification by means of a laser in order to personalize the intermediate structure. To allow a chemical demetallization, it is preferable not to use metals or anti-corrosion alloys to constitute the heart.

The thickness of the metal core layer may be greater than or equal to 100 angstroms.

The metals used to make the core may be selected from transition metals and poor metals, especially from aluminum, stainless steel, tin, copper, zinc, titanium, chromium, silver, gold and their alloys. Examples of pigments that may be suitable as particles according to the invention are described in US 6,686,042 B1 . Preferably, the core of the non-magnetic particles is aluminum. Non-magnetic particles in their entirety may be aluminum, if any.

The non-magnetic particles may be dispersed within a binder to form a semi-transparent layer, i.e., when viewed in reflected light, appears opaque and when observed in light transmitted, allows to see through.

The binder may comprise any transparent substance allowing good dispersion and holding of non-magnetic particles, for example a solution of PVA, polyurethane (PU), polyacrylic, etc.

The semi-transparency can be obtained by a metal deposit, such as aluminum, whose adjustment of the optical density, that is to say the adjustment of the amount of deposited metal, makes it possible to modulate the transmittance . The optical density is advantageously chosen between 0.2 and 1.6, preferably between 0.4 and 1.

The non-magnetic particles are preferably oriented substantially parallel to a plane perpendicular to a direction of observation of the security element, and in this plane are preferably oriented randomly.

The thickness of the intermediate structure may be between 2 and 50 microns, better still between 5 and 15 microns. Preferably, the thickness of the semi-transparent layer is less than or equal to 15 μm since this facilitates obtaining a monolayer of non-magnetic particles and therefore particularly satisfactory metal reflection and semi-transparency aspects. The non-magnetic particles can thus be present, within the binder, in the form of a monolayer.

The concentration by dry weight of the non-magnetic particles within the layer is preferably between 5 and 50%, relative to the total weight of the binder and said particles, more preferably between 15 and 45%. The volume occupied by the non-magnetic particles within the semi-transparent layer is preferably between 5 and 80%, better still between 20 and 50%, relative to the total volume of the layer.

Intermediate structure

The intermediate structure can be customized through a modification showing a pattern in reflected light. This pattern is advantageously formed by laser, which modifies the structure of the non-magnetic particles, in particular the crystalline phase of the metal of the non-magnetic particles to make it amorphous, and therefore more transparent. This conversion can be done with a Nd YAG type laser which generates a punctually very high temperature causing vitrification of the metal at the point of impact. As the laser moves, the metal returns to ambient temperature almost instantaneously, making it possible to freeze the metal in the amorphous or partially amorphous state.

We can, particularly with regard to this technique, refer to the publication "Metal surface amorphization regimes during continuous laser scanning treatment", Metal Fizika i himiā obrabotki materialov ISSN 0015 3214, 1984, No. 3, pp. 25-32 (12 ref.), KLEBANOV YU.D ;

Alternatively, the customization is by selective etching. In this case, the binder can be degraded punctually.

Thus, the intermediate structure can be rendered differently in different places, including more transparent or otherwise reflecting light, which allows to enter variable data, for example related to the holder of the secure document incorporating the security element according to the invention. invention, for example his photograph or his name.

Preferably, the modification of the intermediate structure takes place without completely losing its semi-transparent character, by not affecting all the non-magnetic particles of the zone whose appearance is to be modified, to the point of their to lose all their reflective and / or opacifying power.

The non-magnetic particles of the intermediate structure may, for at least some or all of them, exhibit goniochromatic properties.

Thus, it is possible to observe, in addition to an aspect of metallic gloss, a color change of the intermediate zone, during a change in the direction of observation.

A single non-magnetic particle structure can be used within the semi-transparent layer. The non-magnetic particles may in particular be goniochromatic. In particular, a mixture of particles of the same structure but with Different goniochromatic properties can be used, and in this case, the total particle content according to the invention is chosen so as to obtain the desired result.

According to a third aspect, the invention relates to a security element, in particular a security thread, for a security document, comprising a magnetic layer superimposed on at least one optically variable structure comprising magnetic and oriented platelet pigments.

The security element may extend in a longitudinal direction and the magnetic layer may extend in this longitudinal direction.

A security element according to this third aspect of the invention thus provides visual security and third-level security.

The difference between the remanence measured on a zone of greater remanence, where the magnetic layer is superimposed on the optically variable structure, and the remanence measured on a lower remanence zone, where the optically variable structure is absent, is preferably included. between 10 nWb / m and 200 nWb / m, preferably between 30 nWb / m and 170 nWb / m. The variation of magnetic remanence along the security element thus makes it possible to define a third level security, for example a magnetic code.

The magnetic layer may in particular define a pattern, for example a succession of letters. Preferably, the pattern may be defined by openings through the layer from one side to another in its thickness.

The optically variable structure may be disposed on the face of a support of the security element and the magnetic layer be disposed on the opposite side of the support. In this way, the security element provides magnetic security and visually detectable security that is not degraded by the presence of magnetic security.

The optically variable structure may cover an underlying impression, which is preferably disposed between the optically variable layer and the face of the support. As previously described, depending on the viewing angle, the printing may or may not be revealed, providing additional security.

The security element may comprise an additional structure comprising non-magnetic platelet particles, spaced from the optically variable structure in the longitudinal direction. Such an additional structure may have all the characteristics of the intermediate structure of the security element according to the first and second aspects of the invention.

The non-magnetic particles are preferably oriented in a direction different from the direction of orientation of the magnetic platelet pigments.

The magnetic layer may in particular be superimposed on first and second optically variable structures comprising magnetic and oriented platelet pigments, the first and second optically variable structures being spaced in the longitudinal direction.

The orientation of the magnetic platelet pigments of the first optically variable structure is preferably different from the orientation of the magnetic platelet pigments of the second optically variable structure.

The magnetic layer may define a pattern selected from a sequence of alphanumeric characters or a bar code positive or negative, for example. It can in particular be obtained by printing, in particular a magnetic ink.

• a. déposer sur un substrat des pigments magnétiques sous forme de première et deuxième bandes et des particules non magnétiques sous forme d'une bande intermédiaire située entre les première et deuxième bandes de façon à former un film de base ;
• b. découper le film de base dans une direction transversale à la direction longitudinale d'une bande déposée à l'étape a), de façon à former un élément de sécurité selon l'invention.

The invention also relates to a method of manufacturing a security element according to the invention. In one aspect, the manufacturing method according to the invention comprises the steps of:

• at. depositing on a substrate magnetic pigments in the form of first and second strips and non-magnetic particles in the form of an intermediate strip located between the first and second strips so as to form a base film;
• b. cutting the base film in a direction transverse to the longitudinal direction of a strip deposited in step a), so as to form a security element according to the invention.

• c. déposer sur un substrat au moins un matériau sous forme de première et deuxième bandes et d'une bande intermédiaire située entre les première et deuxième bandes, de façon à former un film de base;
• d. embosser les première et deuxième bandes, et de préférence la bande intermédiaire, de façon à former une structure multifacette en surface de chacune des bandes,
• e. optionnellement, déposer un métal sur chaque structure multifacette, notamment de sorte à former un aplat,
• f. découper le film de base dans une direction transversale à la direction longitudinale d'une bande déposée à l'étape c) de façon à former un élément de sécurité selon l'invention.

In another aspect, the manufacturing method according to the invention comprises the steps of:

• vs. depositing on a substrate at least one material in the form of first and second strips and an intermediate strip located between the first and second strips, so as to form a base film;
• d. embossing the first and second strips, and preferably the intermediate strip, so as to form a multifaceted structure on the surface of each of the strips,
• e. optionally, depositing a metal on each multifaceted structure, in particular so as to form a solid surface,
• f. cutting the base film in a direction transverse to the longitudinal direction of a strip deposited in step c) so as to form a security element according to the invention.

The method according to the invention may further comprise at least one of the following features.

The first band and / or the second band and / or the intermediate band may be discontinuous (s) or continuous (s).

The first and second strips and the intermediate strip are preferably parallel, which simplifies the deposition and arrangement of the strips on the substrate.

The first band, respectively the second band, and the intermediate band may each have a non-rectilinear longitudinal edge, in particular having an aperiodic or periodic or even pseudoperiodic ripple. In particular the ripple can be sinusoidal. It can also be crenated or serrated, for example sawtooth. The corrugation may have an elementary pattern repeated periodically, in sinusoidal arch, or triangular, or rectangular or semicircular. The elementary pattern may have a length of between 1 and 10 mm. The corrugation of the longitudinal edge of the first band or the second band is preferably nested in the corrugation of the longitudinal edge of the intermediate band.

The first band and / or the second band and / or the intermediate band may each have longitudinal non-rectilinear edges, in particular corrugated, the two longitudinal edges of a band being non-rectilinear, each edge having an identical corrugation. Alternatively, a longitudinal edge of a strip may have a corrugation, the edge being for example serrated, and the opposite longitudinal edge may have an identical or different corrugation, the edge being for example crenellated.

In step b), the transverse cutting direction is preferably perpendicular to the direction of a strip formed in step a).

In step a), an ink comprising the non-magnetic pigments is preferably deposited on the substrate to form the intermediate band. It may further comprise a dispersing agent and / or a wetting agent and / or a wax-based additive, in particular a wax in a solvent phase, which makes it possible to improve the dispersion and the orientation of the non-magnetic particles.

The method according to one of the aspects of the invention may be such that step d) of embossing the first and second strips and optionally the intermediate band is implemented before step c) of depositing the strips on the substrate .

In step a) a magnetic field is preferably applied to orient the magnetic pigments of the first and second strips. It can be applied between the deposition of the magnetic pigments of the first band on the one hand and the deposition of the magnetic pigments of the second band on the other hand. In particular, it can be applied so that the orientation of the magnetic particles of the first band is different from the orientation of the magnetic particles of the second band.

The non-magnetic particles may be deposited in step a) between the deposition of the magnetic pigments of the first band on the one hand and the deposition of the magnetic pigments of the second band, on the other hand.

The strips can be made by printing, by deposition of magnetic pigments or non-magnetic particles, by successive passes on the substrate. The substrate can be turned between the passes, which is a simple and effective way to orient the pigment particles differently, if necessary.

• dans une première direction d'observation du film de base la première bande paraisse d'un premier aspect, notamment colorée, réfléchissante, transparente, semi-transparente ou mate, et la deuxième bande paraisse d'un deuxième aspect, différent du premier aspect, notamment colorée, réfléchissante, opaque, transparente, semi-transparente ou mate, et que
• dans une deuxième direction d'observation du film de base, différente de la première direction, la première bande paraisse avec le deuxième aspect et la deuxième bande avec le premier aspect.

The first and second strips can be made such that in a first viewing direction of the base film, the first and second strips are optically variable and have different aspects, and in a second viewing direction different from the first one. , the first and second bands have each changed appearance and the first band has a different appearance from that of the second band. The first and second strips can be made in such a way that:

• in a first direction of observation of the base film the first band appears in a first aspect, in particular colored, reflective, transparent, semi-transparent or matte, and the second band appears in a second aspect, different from the first aspect, especially colored, reflective, opaque, transparent, semi-transparent or matte, and that
• in a second direction of observation of the base film, different from the first direction, the first band appears with the second aspect and the second band with the first aspect.

In particular, the following combinations can be used: first matt appearance and second reflective appearance or vice versa, first and second aspects of different colors, first transparent or semi-transparent appearance and second opaque appearance.

The first and second strips preferably comprise magnetic and oriented pigments as described above.

The magnetic pigments oriented in the same band may have substantially all the same orientation. The pigments of the first and second strips on the base film may have different orientations, for example symmetrical orientations on either side of a median plane perpendicular to the substrate and the strips or to the cutting direction.

The base film may comprise at least one pattern and / or one luminescent layer which is superimposed at least partially on at least one of the strips, especially when these strips are produced using oriented pigments, and which then becomes visible when one observes in a direction substantially parallel to the direction of orientation of the pigments. When viewed in a direction substantially perpendicular to the direction of orientation of the pigments, the pattern or the luminescent layer which is superimposed on the pigments is masked and not visible.

Each band may also comprise a lenticular network, in particular a network comprising convex lenses, in particular substantially hemispherical lenses. The lenses of the lenticular network make it possible to observe or not, depending on the angle of observation, at least one underlying pattern element. An exemplary lenticular network that may be suitable is described in the application WO2012085773 .

The width of the strips may be between 1 and 30 mm, better between 2 and 15 millimeters. The bands may or may not have the same width.

Two adjacent bands may be separated by an interval. The substrate can then carry a security element at least partially visible in said interval.

The spacing between two strips may still be substantially the same on the base film. The spacing between two strips is for example between 0.1 and 3 mm, better between 0.4 and 1 mm. This spacing may be less than the width of the strips, better represent between 1/20 and ¼ of their width.

The presence of a spacing between two bands makes it possible, if desired, to have additional security between them. This security can be present on the substrate on the same side thereof as the strips, or alternatively on the opposite side, and be at least partially visible in reflected light, or in transmitted light if necessary, because of the transparency of the substrate.

• une démétallisation,
• une couche magnétique, s'étendant notamment en bande, créant une sécurité de troisième niveau, ou
• un élément coloré ou à effet goniochromatique, métallique ou holographique, entre autres possibilités.

The base film may comprise, in particular between two strips and / or at least partially superimposed on at least one of the strips, on the side of the same face of the substrate as the strips or the opposite side:

• a demetallization,
• a magnetic layer, extending in particular in band, creating a third level security, or
• a colored or goniochromatic element, metallic or holographic, among other possibilities.

The substrate of the base film is preferably synthetic, made of thermoplastic material, preferably polyethylene terephthalate. The substrate is preferably transparent, and more preferably colorless.

Each strip made on the base film can be continuous or discontinuous in the direction of its length, and be of homogeneous appearance or not along its entire length.

The invention also relates to a security document comprising a security element according to the invention, according to any of its aspects.

In particular, the security element can be placed on the surface or in the window of the security document.

In particular, the security element can be arranged in a window of the secured document, the outline of the window having an aperiodic or periodic or even pseudoperiodic ripple. The outline of the window may be sinusoidal, serrated or serrated. The outline may in particular have a periodic repetition of an elementary pattern. The elementary pattern may have a length of between 0.5 mm and 45 mm. Preferably, the outline is crenellated or serrated, the serrations preferably having a triangular or semicircular pattern.

The subject of the invention is also a method for authenticating or identifying a document comprising a security element according to any one of the first and second aspects of the invention, in which the change of appearance of the first and second optically variable structures, or even the intermediate structure, by changing the observation direction of the security element.

The subject of the invention is also a method for authenticating a document comprising a security element according to the third aspect of the invention and where appropriate according to any one of the first and second aspects of the invention, in which we measure with a suitable device the variation of remanence between different areas of the security element.

A "magnetic" material is magnetized under the effect of an externally applied magnetic field, for example by a permanent magnet. In other words, it is ferromagnetic. Iron is a magnetic metal, aluminum is not.

By "security document" is meant a valuable document, for example a means of payment, such as a bank note, a check or a restaurant ticket, a lottery ticket, a ticket or a ticket giving access to a cultural or sporting event and / or a document for the identification of persons, such as an identity card, a visa, a passport or a driving license.

By "opacity", we consider the attenuation of the intensity of an illuminant that passes through a material. The opacity of a material can vary between zero opacity (or transparency) and total opacity, where the illuminant is not transmitted.

By "illuminant" is meant light visible to the human eye, for example daylighting illuminant D65, defined by CIE Lab 1976, infrared (IR) or ultraviolet (UV) radiation.

By "variable opacity" is considered a structure which has in different areas of its plane absorption properties different from a predefined illuminant, including visible light.

The phrase "having one" is synonymous with "comprising at least one".

• la figure 1 représente, de face, un exemple de document de valeur selon l'invention,
• la figure 2 représente isolément et de face, l'élément de sécurité,
• les figures 3 et 4 illustrent des aspects observables sur une face d'éléments de sécurité selon différents modes de réalisation, observés sous différentes directions d'observation,
• les figures 5, 6, 8, 11 et 13 représentent en coupe longitudinale différents modes de réalisation d'un élément de sécurité selon l'invention,
• la figure 7 illustre une variante de réalisation de la structure intermédiaire, vue de face et isolée du reste de l'élément de sécurité,
• La figure 9 illustre l'aspect d'un élément de sécurité selon un mode de réalisation, observé de face en lumière transmise,
• la figure 10 illustre la variation de rémanence magnétique mesurée en différentes zones de l'élément de sécurité,
• les figures 12 et 14 illustrent des aspects procurés par les éléments de sécurité représentés sur les figures 11 et 13 respectivement, observés sous différentes directions d'observation,
• la figure 15 représente des étapes du procédé de fabrication d'un élément de sécurité selon l'invention,
• la figure 16 illustre avec des photographies acquises avec un microscope électronique à balayage, les orientations des pigments magnétiques et des particules non magnétiques au sein des structures optiquement variables et de la structure intermédiaire d'un élément de sécurité selon un mode de réalisation de l'invention, lesdites structures étant observées en coupe longitudinale,
• les figures 17 et 18 illustrent des variantes de l'élément de sécurité selon l'invention,
• la figure 19 illustre un élément de sécurité selon l'invention disposé en fenêtre d'un document de sécurité, et
• la figure 20 illustre une variante de mise en oeuvre du procédé.

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:

• the figure 1 represents, from the front, an example of a document of value according to the invention,
• the figure 2 stands alone and face, the security element,
• the figures 3 and 4 illustrate aspects observable on one side of security elements according to different embodiments, observed under different viewing directions,
• the figures 5 , 6 , 8 , 11 and 13 represent in longitudinal section various embodiments of a security element according to the invention,
• the figure 7 illustrates an alternative embodiment of the intermediate structure, seen from the front and isolated from the rest of the security element,
• The figure 9 illustrates the aspect of a security element according to an embodiment, viewed from the front in transmitted light,
• the figure 10 illustrates the variation of magnetic remanence measured in different zones of the security element,
• the Figures 12 and 14 illustrate aspects provided by the security elements represented on the figures 11 and 13 respectively, observed under different directions of observation,
• the figure 15 represents steps of the method of manufacturing a security element according to the invention,
• the figure 16 illustrates with photographs acquired with a scanning electron microscope, the orientations of the magnetic pigments and non-magnetic particles within the optically variable structures and the intermediate structure of a security element according to an embodiment of the invention, said structures being observed in longitudinal section,
• the Figures 17 and 18 illustrate variants of the security element according to the invention,
• the figure 19 illustrates a security element according to the invention disposed in the window of a security document, and
• the figure 20 illustrates an alternative embodiment of the method.

In the appended drawing, the actual proportions of the constituent elements of the security document are not always respected for the sake of clarity of the drawing. On the other hand, some elements may not be represented in contact with each other while they may be in practice.

We have shown figure 1 a security document 5 according to the invention, for example a bank note, which comprises a substrate 8 and a security element 10 according to the invention in the form of a wire. As illustrated, the security element may extend between two opposite edges 12a and 12b of the document.

The security element may be incorporated at least partially in mass in the security document substrate, and only a part of the wire appears visible, for example through one or more windows formed in the substrate. An example of incorporation into windows is described in the document EP 59056 .

On the figure 19 two security elements 10 are arranged in a window, the contour 16 of each window 15 being serrated or crenellated. So, the outline defines a shape that can help to attract the observer's gaze to the security element. A serration may in particular be a triangular pattern 18.

Preferably, the security document substrate incorporating the security element is made of natural fibrous materials, for example cellulose and / or cotton, and / or synthetic fibers. The substrate can also be made from plastic materials, such as a PolyartTM film sold by the company ARJOBEX Ltd.

As illustrated on the figure 2 , the security element comprises first 18 and second 21 zones separated in the longitudinal direction X of the security element by an intermediate zone 24. The first and second zones comprise first 27 and second 30 optically variable structures and the zone intermediate comprises an intermediate structure 33.

The intermediate structure may be contiguous with the first optically variable structure and / or the optically variable structure.

At least one of the first and second optically variable structures and the intermediate structure, or all these structures, can extend transversely from one edge to the other of the security element. The optically variable and intermediate structures may each define a continuous strip extending in the longitudinal direction of the security element. When the security element is viewed from the front, they can also occupy the entire observed face of the security element. They may be in the form of strips, for example having sinuosities, but preferably rectilinear. These strips preferably extend generally in the longitudinal direction of the security element. They may have the same shape, in particular a rectangular shape.

In the variant illustrated on the Figures 17 and 18 at least a part of the contour of the intermediate structure and at least a part of the contour of the first, and / or respectively of the second optically variable structure, each have an aperiodic or periodic corrugation 25, 26, 28, 31. Preferably, the corrugations each have an elementary pattern repeated periodically, preferably forming a crenellated or serrated edge, in particular with a triangular or rectangular elementary pattern. Each elemental pattern can be repeated at least twice.

The undulation of the longitudinal edge of the intermediate structure is preferably imbricated in the corrugation of the longitudinal edge of the first and / or respectively of the second optically variable structure.

The figure 17 illustrates a basic niche pattern. On the figure 18 , an elementary pattern of length l is repeated twice.

We illustrated on the figure 3 the aspects that can be observed according to different directions of observation of the security element.

According to a first observation direction O1, the first 18 and second 21 optically variable zones have respective aspects A1 and C1, different from each other. Intermediate zone 24 then has an aspect B1. According to a second observation direction 02, different from the first observation direction, the first and second optically variable zones have respective aspects A2 and C2, different from the respective A1 and C1 aspects observed in the first observation direction. The intermediate zone has an aspect B2 which may be different or identical to the aspect B1. According to a third observation direction 03, different from the first and second observation directions, the first optically variable zone has the aspect A2 observed according to the second observation direction, and the second optically variable zone has the aspect C1 observed according to the first direction of observation. The intermediate zone has an aspect B3, which may be different or identical to the appearance B2 observed according to the second observation direction and / or the aspect B1 observed in the first observation direction.

Preferably, the aspects B1 and B2 observed in the first and second directions are identical, and preferably also different from the aspect B3 observed in the third direction.

Preferably, the aspects B1 and B2 observed along the first and second directions are identical to one of the aspects of the first and second optically variable zones observed along one of the first and second viewing directions.

Preferably, the aspect A1 of the first optically variable zone observed in the first direction of observation and the aspect C2 of the second optically variable zone observed in the second direction of observation, are identical.

Preferably, the aspect A2 of the second optically variable zone observed in the second direction of observation and the aspect C1 of the first optically variable zone observed in the first direction of observation, are identical.

In addition, the respective aspects B1 and C1 of the intermediate zone and of the second optically variable zone observed in the first observation direction may be identical. The respective aspects B2 and A2 of the intermediate zone and of the first optically variable zone, observed along the second observation direction, can be identical. In addition, for an observation direction different from the first, second and third viewing directions, the first and second optically variable zones and the intermediate zone may all have the same aspect, in particular already observed along one of these three directions. .

In other words, as illustrated on the figure 4 , according to the first observation direction O1, the first optically variable zone may have a first aspect A and the intermediate zone and the second optically variable zone may have a second aspect B, different from the first aspect A. According to the second direction of observation 02, the second optically variable zone may have the first aspect A and the first optically variable zone and the intermediate zone may have the second aspect B. According to the third observation direction 03, the first and second optically variable zones may have the second aspect B, and the intermediate zone may have the first aspect A.

Thus, when the security element is observed successively in the first, third and second directions of observation, a particularly interesting visual animation is obtained, providing the observer with the illusion that the first aspect A propagates along the longitudinal direction of the security element.

We have shown on the figure 5 in longitudinal section a variant of the security element described above, which may have the shape of a wire. The security element comprises a support 35, preferably of a transparent thermoplastic material, for example polyester or PET.

The support is of flattened cross section, in particular rectangular as illustrated.

First 27 and second 30 optically variable structures are disposed on a first face 38 of the carrier in the form of strip-like layers along the wire. Preferably, they comprise platelet reflective and magnetic pigments.

The pigments are oriented differently between the first and second structures, as shown in FIG. figure 5 . Preferably, in each of these structures, more than 80% or even more than 90% by number of the pigments have an identical orientation. Thus, for a first observation direction O1 substantially parallel to the orientation direction of the platelets of the pigment, a first transparency effect of the first layer 27 is observed, the pigments of the second layer 30 appearing reflective. For a second observation direction 02 different and substantially parallel to the orientation of the pigments of the second layer, the pigments of the second layer appear transparent and a second effect is observed, the first layer appearing reflective. Thus, first 18 and second 21 optically variable zones are obtained and the change in appearance of the first and second layers, illustrated in FIG. figure 4 when the observer moves from the first to the second observation direction.

An intermediate structure 33, in the form of a layer, is disposed between the first and second optically variable layers on the same face 38 of the support. In the embodiment of the figure 5 the intermediate structure is spaced apart from the first and second optically variable layers. Alternatively, as illustrated on the figure 6 it may be contiguous with said layers.

In the embodiment illustrated on the Figures 5 to 8 , the intermediate structure comprises non-magnetic particles 45. As illustrated on the figure 7 the particles are preferably distributed randomly flat and isotropically within the layer. In other words, the non-magnetic particles do not have a specific orientation in a longitudinal median plane of the layer. Thanks to this distribution of non-magnetic particles, an intermediate zone is obtained which, when observed in reflected light, has a substantially opaque metallic gloss appearance for a first set of different observation directions, and appears matte, that is, say non-gloss for a second set of different directions.

The security element can be made, in particular that illustrated on the Figures 5 to 8 such that the appearance changes of the first and second optically variable zones and the intermediate zone occur when the viewing direction rotates about a transverse axis, preferably perpendicular to the longitudinal direction of the element. safety, or alternatively about an axis parallel to said longitudinal direction.

Preferably, the first and second optically variable zones on the one hand and the intermediate zone on the other hand appear reflective for different viewing directions, at different angles with respect to a direction of observation of the element's face. of security.

Preferably, the first and second optically variable zones appear reflective in an observation direction at an angle of between 55 ° and 65 °, preferably between 58 ° and 62 ° with respect to a zone normal, for incident illumination parallel to normal.

The intermediate zone appears reflective in a direction of observation parallel to a normal to the intermediate zone, for an illumination parallel to the normal to the zone.

In the first and second optically variable structures, the pigments can be oriented according to the axis around which the observation direction has to turn to observe the desired change of appearance.

In an alternative embodiment of the security element, the intermediate structure comprises or even consists of a semi-reflective layer formed by depositing a metal on the support.

In another variant, the first and second optically variable structures may be made otherwise than with orientable magnetic pigments. For example, they can be realized using lenticular networks, as described in the application WO2012085773 .

The security element described on the figure 8 differs from the element shown on the figure 5 in that it comprises a fourth security structure 48 disposed on the face of the support, said backside, opposite 51 to that 38 on which the first and second optically variable structures and the intermediate structure are disposed, said recto.

• une bande magnétique, qui peut contenir un code magnétique,
• un texte ou autres motifs formés par démétallisation,
• une structure holographique,
• un pigment goniochromatique ou tout autre structure à effet de changement de couleur, ou
• un pigment thermochromique.

The fourth security structure may consist of:

• a magnetic tape, which may contain a magnetic code,
• text or other motifs formed by demetallization,
• a holographic structure,
• a goniochromatic pigment or other color-changing structure, or
• a thermochromic pigment.

The fourth security structure may extend continuously or discontinuously in the longitudinal direction of the security element, particularly in band.

In particular, the fourth security structure may comprise openings 54 passing right through it in its thickness. These openings can be superimposed on the intermediate structure. They can define a pattern, for example a sequence of alphanumeric characters, reproducing for example the name of the currency, the nominal value of the denomination, or the name of the issuing bank.

These openings can be obtained for example by selective demetallization of a metallized layer.

The openings may be located, where appropriate, in a manner identified with respect to at least one pattern 57 formed by modification, in particular by laser, of the semi-transparent layer.

For example, when the structure is observed in transmitted light, according to the direction V of the figure 8 by illuminating the side of the intermediate layer 33 and observing through the security element on the side of the fourth structure 48, the back side pattern is not visible, the intermediate layer having a gray appearance for example uniform. The back side pattern, formed in the fourth structure, appears. The observed result is substantially the same when the security element is observed in transmitted light, according to V of the figure 4 , illuminating on the reverse side and observing the front side through the security element.

In reflected light observation of the intermediate structure on the front side under the incidence VI, as on the figure 6 , the front-side motif, for example the name of the security element holder, appears in negative writing within a colored solid area having a certain color. When the angle of incidence changes to incidence VII, the color of the solid color changes, with the front side pattern remaining visible.

When the security element is observed in back-side reflection, the front-side pattern is not visible and only the back-side pattern is eventually visible.

In a variant not shown, the fourth structure comprises platelet pigments, as described above, preferably oriented in a direction different from that of the first and second optically variable structures.

The security element, observed according to the back side of the support in a fourth direction of observation, may have a reflective appearance. When the back side of the support is observed in a fifth direction of observation parallel to the oriented pigments, the platelet pigments of the fourth structure may appear transparent.

Preferably, the fourth and fifth viewing directions of the reverse side are different from the first and second viewing directions of the front face. The fourth direction of observation is preferably different from the fifth direction of observation. This results in variations of aspects that occur for different angle variations depending on whether the face or back side is observed, increasing the security of the security element.

On the figure 9 is illustrated the aspect of a security element that does not differ from that of the figure 8 in that the fourth security structure consists of a series of patterns printed on the back of the medium, in the form of a succession of letters. Thus, when the security element is observed in transmitted light on the front side, this succession of patterns 60 appears to the observer, while it is invisible to the observer when he observes the security element in reflection on the same side. For example, on the figure 9 , there is shown a pattern with the letters "AWS" printed on the back of the support, which appear darker to the observer in transmitted light than the rest of the first and second optically variable zones and the intermediate zone.

As will be detailed later, these impressions can be made using a magnetic ink, locally increasing the magnetic remanence of the security element.

The fourth structure may have, in addition to the impressions and openings described above, magnetic properties. The fourth structure may be a magnetic material, or be covered with a layer of a magnetic material superimposed on the support.

The figure 10 ) a) illustrates an embodiment of a security element 10 having such a magnetic layer 48 which extends in a continuous band. This magnetic layer is disposed on the face of the support opposite to that on which are deposited the first 27 and second 30 optically variable structures and the intermediate structure 33. The optically variable structures comprise magnetic particles and the intermediate structure comprises non-magnetic particles.

The superposition of the fourth magnetic structure 48 with the first optically defined structure defines a first zone 60 of greater remanence. Similarly, the superposition of the fourth magnetic structure 48 with the second structure defines a second zone 63 of greater remanence.

In addition, the superposition of the fourth magnetic structure 48 with the intermediate structure defines a zone of less remanence 66, where the remanence is lower than in the area of greatest remanence.

The figure 10 ) b) illustrates the variation ΔR of remanence R which can be measured along the security element.

The zone of least remanence 66 is particularly located between the first 60 and second 63 areas of greatest remanence. The succession of larger and smaller areas Less remanence thus makes it possible, in addition to the visually detectable security by appearance change, to define an additional, third-level, magnetic security that can be detected by means of devices making it possible to measure the remanence.

In particular, the remanence of each of the first and second optically variable structure can be 65 nWb / m and the remanence of the fourth structure can be 300 nWb / m. In this way, the remanence of the areas of greatest remanence 60, 63 can be 365 nWb / m and the remanence of the area of least remanence can be 300 nWb / m. The transition from a zone of high remanence to a zone of less remanence then results in a variation of the remanence ΔR of 65 nWb / m.

Moreover, to create a specific magnetic code, the lengths on which the structures comprising magnetic pigments on the one hand and comprising non-magnetic particles on the other hand, may be different.

Moreover, the oriented magnetic pigments of the first and second optically variable structures may be of materials having different magnetic properties, and chosen so as to have aspects, for example of reflected light brightness, substantially identical. We thus obtain different remanence variations by passing from the first zone of greater remanence to the zone of least persistence on the other hand, and from the second zone of greatest remanence to the zone of least remanence on the other hand, while maintaining identical appearance changes.

The figure 11 illustrates another alternative embodiment of the security element, which has optically variable areas.

The first 18 and second 21 optically variable zones comprise first 70 and second 73 impressions, arranged between the first 27 and second 30 optically variable structures respectively on the one hand, and the support 35 on the other hand.

The prints can be made directly on the support, as is the case on the figure 11 , or alternatively on an independent transparent layer, for example PET, laminated by means of an adhesive on the rest of the security element. Thus, the security element may comprise a multilayer support.

The first and second impressions may have a colored background corresponding, where appropriate, to different colors of the goniochromatic particles of the intermediate structure. Furthermore, the first and second impressions may comprise a pattern corresponding, if necessary, to a pattern formed by modification, in particular laser, of the semi-transparent layer 33.

Thus, as illustrated in figure 12 ) a), according to the first observation direction O1, the oriented plates of the first optically variable structure appear transparent and the first underlying impression 70 is revealed. As an illustration, on the figure 12 , the first underlying impression is the succession of letters "AWS" on a colored background. The second optically variable zone and the intermediate zone appear reflective.

According to the second observation direction 02, as illustrated on the figure 12 d), the second underlying impression 73 is revealed, and the other zones appear reflective. The second underlying impression may include a pattern, for example with the letters "AWS" on a colored background. In particular, the colors of the pattern and the background of the first and second impressions may be different.

For the third observation direction 03, as illustrated on the figure 12 ) b), optically variable structures appear reflective. In addition, the intermediate zone appears opaque. The pattern 72 formed in the semi-transparent layer comprises for example the same succession of letters "AWS" as the first impression underlying.

In particular, the pattern and the background observed along the third direction 03 in the intermediate zone may have the same colors as the pattern and the background observed in the first optically variable zone in the first direction of observation.

For another direction of observation O3 ', as illustrated figure 12 ) c), the optically variable structures appear reflective and the intermediate area appears opaque. However, with respect to the aspect observed in the third direction, the color of said pattern has changed thanks to the goniochromatic properties of the non-magnetic particles.

In particular, the pattern and the background observed in the other direction O3 'in the intermediate zone may have the same colors as the pattern and the background observed in the second optically variable zone in the second direction of observation.

Thus, a particularly interesting visual effect is obtained, where a color variation of a pattern and the background on which it rests is added to the animation provided by the appearance / disappearance of the pattern in the different observation areas.

On the figure 13 there is shown an embodiment of a safety wire in which a variable opacity structure 80 is superposed on the first 27 and second 30 optically variable structures and on the intermediate structure 33.

The superposition of the variable opacity structure with the structures 27 and 30 defines first 83 and second 86 zones and an intermediate zone 89 all of less opacity.

These areas of least opacity 83, 86, 89 overlap at least partially with the first 18 and second 21 optically variable zones and with the intermediate zone 24.

In addition, this superposition defines a surrounding area of greater opacity 92, extending around areas of less opacity.

Thus, a particular visual appearance, in particular a brilliant reflection effect, can pass from the first zone of less opacity to the second zone of less opacity and / or to the intermediate zone of less opacity with a change in the direction of observation, an optical characteristic of the zone of greater opacity (in particular its color) being for example conserved. A variation in the appearance of the first and second optically variable structures as well as the intermediate structure, through the areas of least opacity, is obtained by choosing the suitably variable opacity structure. Thus, it is possible to define areas of least opacity in the form of a letter, a text, a pattern or a drawing, so that they present alone in the security element an optically variable.

As shown on the figure 13 the optically variable structure may consist of an opaque layer 80, defining an area of greater opacity, and having apertures 95, preferably passing through the opaque layer from side to side. These openings thus define an area of less opacity.

The security element as shown on the figure 13 further comprises first 70 and second 73 impressions, arranged as previously described with respect to the example of the figure 11 .

The prints may consist of a uniform color background and the variable opacity structure may have the same color as the background.

Thus, when the first and second optically variable structures are observed in directions such that they do not appear to be reflective, for example according to the first O1 and second O2 observation directions, the first and second optically variable zones appear opaque with a uniform color.

The non-magnetic particles of the intermediate structure can be chosen so that, under the third direction of observation, they have the same effect, and in particular the same color, as the zone of greater opacity.

On the figures 14 ) a) to 14) c), different aspects observed according to the first to third observation directions, respectively.

According to the first observation direction O1 ( figure 14a )), the platelet particles of the first structure are "transparent" and reveal the underlying impression, which corresponds to a background having the same color as the area of greater opacity. By "transparent" it should be understood that the platelet particles of the first structure are oriented in substantially the same manner as the first observation direction O1. Thus, for this direction of observation, the appearance of the first optically variable zone is monochrome.

The second optically variable structure and the intermediate structure are reflective for this first observation direction. The opaque structure defining a zone of less opacity having the form of a succession of letters, the observer perceives only this succession of letters to shine. The same is true for the first zone and the intermediate zone of least opacity for the second direction of observation ( figure 14 )vs)).

For the third observation direction 03, the succession of letters appears brilliant in the first and second zones of less opacity, the platelet particles being reflective. The non-magnetic particles of the intermediate zone appear in a color identical to that of the optically variable structure, not allowing the observer to detect the intermediate zone of least opacity ( figure 14 ) B)).

Alternative embodiments of the security element illustrated on the figure 14 may have a structure of variable opacity that may have the characteristics described in FR 2 992 255 A1 .

For example, the optically variable structure may be superimposed at least partially, or even totally, on the first and second optically variable structures and the intermediate structure.

For observation in visible light, the variable opacity structure can be obtained by metallization / demetallization. This structure comprises a surrounding area of greater opacity, corresponding to a metal layer, and areas of less opacity corresponding to openings resulting from the demetallization. In visible light, the metal layer appears completely opaque, and the openings are transparent.

In another exemplary embodiment of the invention, for an observation under a UV or IR illuminant, the variable opacity structure comprises an impression, on the zone of greater opacity, with an ink comprising a transparent pigment when observed in visible light, but opaque when illuminated under UV or IR.

The variable opacity structure may completely or partially cover the first and second optically variable structures and the intermediate structure.

The area covered by the first and second zones and the intermediate zone of less opacity may be less extensive, or on the contrary larger, than the area covered by the surrounding area of greater opacity.

The area covered by the first and second zones and the intermediate zone of less opacity may be 1.5 times, preferably twice, more preferably 3 times, even 5 times, or even even 10 times, less extensive than the covered area. by the surrounding area of greater opacity. One can define first and second zones and an intermediate zone of less opacity taking the form of letters, a text, a pattern, a drawing. In this way, it is particularly possible to focus on these first and second zones and intermediate zone of less opacity the attention of the observer who authenticates a document comprising such an element.

Preferably, the variable opacity structure extends longitudinally along the support, and may be in the form of a band. The zone of greater opacity can define the opposite edges of this band, which can be continuous, the areas of less opacity extending behind these edges.

Preferably, the width of the variable opacity structure is between 1 to 10 mm, more preferably from 4 to 8 mm.

The variable opacity structure may have opacity depending on the type of illuminant used for the observation.

• une métallisation/démétallisation, notamment avec une démétallisation qui représente une ou plusieurs lettres, un dessin, un motif ; dans ce cas, les zones de moindre opacité correspondent aux zones démétallisées et les zones de plus grande opacité correspondent aux zones métallisées ; le ou les motifs formés par les zones démétallisées peuvent se retrouver ailleurs sur le document qui intègre l'élément de sécurité ; il s'agit par exemple de la valeur de la coupure, de la devise ou du nom du pays ou de la banque émettrice ; le métal peut être choisi par exemple parmi l'argent, l'aluminium, le nickel, le cobalt, l'étain, l'or, le cuivre, et parmi les alliages de métaux, notamment le laiton ou le bronze ; le métal peut être remplacé par tout matériau diélectrique ; des structures diélectriques à effet miroir ou interférentiel constituées d'une alternance de couches de haut et de bas indices, par exemple respectivement du dioxyde d'hafnium et de la silice, notamment obtenus par gravure ionique, peuvent être utilisées ;
• une structure en un matériau coloré ou à effet goniochromatique, métallique, holographique, entre autres possibilités, afin de faire varier l'opacité de la structure sur des zones prédéfinies ;
• une structure en un matériau dont l'opacité peut varier par exemple par application sélective sur des zones définies d'un traitement thermique ou d'un traitement laser ;
• une structure obtenue par embossage, notamment à chaud, d'un matériau aux propriétés initiales d'absorption de la lumière homogènes, de sorte que la variation d'opacité résulte de la variation d'épaisseur causée par l'embossage ;
• une impression avec différentes encres, colorées ou non, visibles à l'oeil nu ou non, par exemple des encres visibles uniquement sous lumière ultraviolette ou infrarouge, opaques en lumière visible, fluorescentes, phosphorescentes, thermochromiques, photochromiques, translucides et/ou transparentes.

The variable opacity structure may include, or even consist of:

• a metallization / demetallization, in particular with a demetallization which represents one or more letters, a drawing, a pattern; in this case, the zones of less opacity correspond to the demetallized zones and the zones of greater opacity correspond to the metallized zones; the pattern (s) formed by the demetallized zones can be found elsewhere on the document that integrates the security element; for example, the value of the denomination, the currency or the name of the country or issuing bank; the metal may be chosen for example from silver, aluminum, nickel, cobalt, tin, gold, copper, and among metal alloys, especially brass or bronze; the metal can be replaced by any dielectric material; dielectric structures having a mirror or interference effect consisting of alternating layers of high and low indices, for example hafnium dioxide and silica, for example obtained by ion etching, may be used;
• a structure made of a colored material or with a goniochromatic effect, metallic, holographic, among other possibilities, in order to vary the opacity of the structure on predefined zones;
• a structure of a material whose opacity may vary for example by selective application to defined areas of a heat treatment or a laser treatment;
• a structure obtained by embossing, in particular when hot, a material with homogeneous initial properties of light absorption, so that the variation in opacity results from the thickness variation caused by the embossing;
• a printing with different inks, colored or not, visible to the naked eye or not, for example inks visible only under ultraviolet or infrared light, opaque in visible light, fluorescent, phosphorescent, thermochromic, photochromic, translucent and / or transparent.

To manufacture a security element as described in the previous examples, it is possible to implement the method illustrated in the figure 15 and described below.

A first band which comprises magnetic pigments, as described above, is deposited on a substrate 100, for example PET. To perform this deposition, the metallic pigments can be dissolved in a solvent, for example an ink. The solution obtained has rheological properties, in particular a viscosity, adapted so that the solution can be easily spread on the substrate. The solution can be deposited, for example by printing, in particular by flexography, gravure and screen printing with a relative displacement of the print head relative to the substrate to form the first band 103.

The magnetic pigments 40 of the first band, at the end of their deposition on the substrate, are generally oriented in a substantially random manner ( figure 15 )at)).

On the figure 15 ) a), only a first band is illustrated. Of course, a succession of first bands can be deposited. These first bands can expand parallel to each other. Preferably, the difference between two successive first bands is greater than 2 times, or even 3 times, the width of a first band.

The first bands may or may not have the same width.

They can in particular be deposited in a single pass.

An intermediate band 106, comprising non-magnetic particles 45 as described above, is deposited next to the first band so as to extend parallel to the first band. In the embodiment shown on the figure 15 ) b), the first band and the second band are spaced apart. However, they can be contiguous to each other along their length.

The intermediate band is preferably disposed on the same side of the substrate as the first band.

Preferably, the intermediate strip is deposited by printing an ink comprising the non-magnetic particles. Preferably, the non-magnetic particles have an average thickness of between 0.5 μm and 4 μm, preferably of between 1 μm and 3 μm, and / or an average length of between 10 μm and 60 μm, preferably between 15 μm and 10 μm. μm and 30 μm. Thus, they disperse easily in the ink, and once deposited on the substrate, they are oriented flat, that is to say substantially parallel to the longitudinal median plane of the substrate.

Preferably, once their deposition is carried out, the particles of the intermediate band are oriented flat and in a substantially random manner, when observed in a direction of observation perpendicular to the substrate.

To improve the dispersion of the particles in the intermediate band, the ink may comprise a dispersing agent chosen from the group formed by the Byk® brand Disperbyk® produced by ALTANA and their mixtures and / or an additive based on wax, for example chosen from the group of Cerafax® brand Byk® and mixtures thereof. Such additives make it possible to limit the sedimentation of the non-magnetic particles within the ink.

As described above for the first bands, it is conceivable to deposit a succession of intermediate bands, each intermediate band being deposited between two successive first bands. Preferably, each intermediate band is deposited so that a second band comprising magnetic particles can be deposited between the intermediate band and one of the first two successive bands.

The intermediate bands may or may not have the same width.

They can be filed in one pass.

After the deposition of the first band and the intermediate band, a magnetic field is applied to the first band, by means of a magnetization device 107, so as to orient the magnetic pigments of the first band in a direction desired. The oriented magnetic pigments preferably have an orientation in a direction which is oblique with respect to the longitudinal median plane of the substrate. The figure 16 ) a) illustrates a substrate 100 covered with an ink 108 comprising magnetic pigments 40 and oriented substantially in an orientation direction D1.

The particles 45 of the intermediate band being non-magnetic, their orientation is not affected by the application of the magnetic field. They thus retain the orientation resulting from their deposit, as observed on the figure 16 ) B).

A second strip 109 comprising magnetic pigments 40 is then deposited along the intermediate strip, so that the intermediate strip is disposed between the first and second strips.

The second band is preferably disposed on the same face of the substrate as the first face and / or the intermediate band.

Preferably, the first and second strips and the intermediate strip are located on the same face of the substrate.

The second strip may be deposited using an ink comprising the magnetic pigments. Preferably, the magnetic pigments of the first and second strips are identical. Preferably, the ink deposited to form the first band is identical to that deposited to form the second band.

In particular, once the ink is deposited, the particles of the second band are dispersed and oriented in a random manner, like the particles of the first band before the application of a magnetic field ( figure 14 ) D)).

The second strips can be deposited in the form of a succession of second strips, in particular in a single pass. In particular, they may be deposited so that the assembly constituted by the succession of a first band, an intermediate band and a second band, forms a pattern that repeats itself regularly on the substrate.

Preferably, the deposition of the magnetic pigments to form the first and second strips and the deposition of the non-magnetic particles is carried out with the same deposit machine, so the same application method, for example the same printing machine.

The first band and / or the second band and / or the intermediate band may extend entirely from one edge to an opposite edge of the substrate, or as illustrated in FIG. figure 15 they may have a shorter length than the edge-to-edge distance of the substrate, measured in the direction in which the strips extend.

By the way, in the base film illustrated on the figure 20 , the first band and the intermediate band 106 each have a non-rectilinear and castellated longitudinal edge 104, 107, the crenellations of the longitudinal edge of the first band being nested in the serrations of the longitudinal edge of the intermediate band. The second band and the intermediate band 106 each have a longitudinal edge 110, 105 non-rectilinear and crenellated, the crenellations of the longitudinal edge of the second band being interleaved in the crenellations of the longitudinal edge of the intermediate band.

For example, on the figure 20 , the undulations of the longitudinal edges of the first strip and the interleaved intermediate strip each have a triangular elementary pattern of length l repeated periodically.

Once the second strip has been deposited, a magnetic field 110 is applied so as to orient the magnetic pigments of the second strip in a desired direction ( figure 14 ) E)). This magnetization device 110 gives the pigments of the second band a specific orientation. As an illustration, on the figure 16 c) the substrate 100 is covered with an ink 108 comprising magnetic pigments 40 oriented substantially in a direction of orientation D2, different from D1.

The magnetic field can be applied to the whole of the substrate 100. It is then preferable, before applying said magnetic field, to ensure that the magnetic pigments of the first band are fixed in the binder which contains them. way that their specific orientation is not modified by the application of the magnetic field.

Alternatively, the magnetic field can be applied locally, so that the effects it generates are felt only in the second band.

Preferably, the magnetic fields applied to orient the magnetic pigments of the first and second strips are chosen so that the pigments of the first band have an orientation symmetrical to those of the second band, relative to a plane extending in parallel. said strips and normal to one side of the substrate.

A base film 112 is thus obtained, comprising the substrate 100, the first 103 and second 109 strips comprising oriented pigments and an intermediate band.

In another variant not shown, magnetic pigments and non-magnetic particles are deposited to form respectively first and second bands on the one hand and an intermediate band on the other, then magnetic fields are applied to the first and second bands to orient the magnetic pigments.

The deposition of the pigments and particles can be carried out simultaneously in a single pass. The application of the magnetic fields to the first and second bands can be performed jointly, in a single operation.

The base film 112 is then cut, so as to form a security element 10 according to the invention. Preferably, the cut is made in a direction perpendicular to at least one of the directions in which the first and second strips and the intermediate strip extend, preferably perpendicular to all these directions.

Thus, a security element is obtained in which the portions of the first web, intermediate web and second web resulting from the cutting define first respective optically variable structure, intermediate structure and second optically variable structure.

In a particularly preferred mode, not illustrated, the method further comprises a step of depositing, preferably on the face of the substrate opposite to that where the first and second strips and the intermediate strip are deposited, a magnetic material, for example diluted in a solvent to form an ink.

This deposition step of a magnetic material can be performed before or after step a) of depositing the first and second strips and the intermediate strip. It is preferably performed before the step of cutting the substrate covered by said strips.

The magnetic material may be layered, in particular in the form of a strip, extending for example in a direction perpendicular to that in which extends the first and / or the second strip and / or the intermediate strip.

The layer of magnetic material is superimposed at least partially, or totally, on said strips.

It can also partially or completely cover the corresponding face of the substrate. It can also be formed in successive steps of metallization / metallization, leaving open patterns, for example one or more letters or an image.

The deposition of the magnetic layer can be performed by printing, for example ink jet.

By cutting a film comprising such a magnetic material, it is thus possible to obtain a security element according to the invention comprising a fourth structure as described above.

Claims (20)

Security element (10), in particular security thread, for security document (5), the security element comprising first (18) and second (21) zones separated by an intermediate zone (24) comprising an intermediate structure ( 33), the first and second zones having respective first (27) and second (30) optically variable structures arranged so that for a first viewing direction (O1) the first and second structures have different aspects; one of the other and for a second direction of observation (02) different from the first, the first and second structures have on the one hand each of them changed appearance with respect to their appearance when observed in the first direction of observation, and on the other hand have different aspects from each other, the intermediate structure comprising non-magnetic particles (45) and / or a semi-transparent layer,
wherein when the element is observed in a third direction of observation different from the first and second observation directions, the intermediate zone has an appearance identical to that of the first zone observed in the first observation direction and / or that of the second zone observed according to the second direction of observation. Security element according to the preceding claim, wherein the semi-transparent layer is semi-reflective. Security element according to any one of the preceding claims, wherein the first and second optically variable structures each comprise a faceted structure, preferably obtained by embossing, optionally covered with a metal, in particular in the form of a flat metal. Security element according to any one of the preceding claims, wherein the first and second optically variable structures comprise the same pigment which is deposited differently on the first and second zones, in particular with a different orientation. Security element according to any one of the preceding claims, wherein the first and second optically variable structures and the intermediate structure are arranged on the same side (38) of a support (35). A security element as claimed in any one of the preceding claims, having a fourth structure (48) superimposed on the first and second optically variable structures and the intermediate structure. Security element according to claim 6, wherein the fourth structure is a magnetic layer, in particular obtained by printing a magnetic ink, and / or is disposed on the face (51) of the support opposite to that on which the first and second structures and the intermediate structure are arranged. Security element according to any one of the preceding claims, wherein the non-magnetic particles are platelet. Security element according to any one of the preceding claims, wherein the non-magnetic particles are at least partially, or totally, of aluminum. Security element according to any one of the preceding claims, wherein the non-magnetic particles are semi-reflective and / or goniochromatic. Security element according to any one of the preceding claims, wherein the non-magnetic particles are dispersed within a binder so as to form a semitransparent, preferably semi-reflective layer, and / or in which the non-magnetic particles The magnets are oriented randomly and substantially parallel to a plane, preferably perpendicular to a direction of observation of the security element. A manufacturing method comprising the steps of: at. depositing on a substrate (100) magnetic pigments in the form of first (103) and second (109) strips and non-magnetic particles in the form of an intermediate strip (106) located between the first and second strips so as to form a base film (112); b. cutting the base film in a direction transverse to the longitudinal direction of a strip deposited in step a) so as to form a security element (10) according to any one of the preceding claims. A manufacturing method comprising the steps of: vs. depositing on a substrate (100) at least one material in the form of first (103) and second (109) strips and an intermediate strip (106) located between the first and second strips so as to form a base film (112) ); d. embossing the first and second strips, and preferably the intermediate strip, so as to form a multifaceted structure on the surface of each of the strips, e. optionally, depositing a metal on each multifaceted structure, preferably so as to form a solid surface, f. cutting the base film in a direction transverse to the longitudinal direction of a strip deposited in step c) so as to form a security element (10) according to any one of claims 1 to 11. Method according to the preceding claim, wherein step d) is carried out before step c). Method according to one of the three immediately preceding claims, wherein the first band and / or the second band and / or the intermediate band is (are) discontinuous. Method according to the preceding claim, wherein the first band and / or the second band and / or the intermediate band is (are) continuous. A method according to any one of claims 12 to 16, wherein in step b) the transverse cutting direction is perpendicular to the direction of a web formed in step a). A method as claimed in any of claims 12 and 15 to 17, wherein in step a), an ink comprising the non-magnetic pigments is deposited on the substrate to form the intermediate strip. A method according to any one of claims 12 and 15 to 18, wherein in step a) a magnetic field is applied to orient the magnetic pigments of the first and second strips. Secure document incorporating a security element according to any one of claims 1 to 11.

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