EP2454101B1 - Parallax effect security element - Google Patents

Description

The present invention relates to the field of security elements used for authentication and / or identification of articles, documents or various objects.

Background

In order to guard against counterfeiting or falsification and in order to increase the level of security, it is known to use security elements applied on the surface or introduced in bulk or in windows in a security article, in particular a security article. security document, or other object, for example a label, packaging, especially for drugs, food, cosmetics, electronic parts or spare parts.

The security article may in particular be chosen from among a means of payment, such as a bank note, a check or a restaurant ticket, an identity document such as an identity card, a visa, a passport or a driving license, a lottery ticket, a ticket or a ticket to events.

The revelation of animated images by a parallax effect has been known for a great many years.

Several patents based on this principle have been filed, for example US 5,098,302 , US 5,525,383 and US 6,286,873 , as well as the demand DE 10 2006 061905 .

Methods for creating motion illusions as described in the documents are known US 5,901,484 and US 6,286,873 using a support carrier of several coded images, corresponding for example to the decomposition of the movement of an object or an animal, and a transparent film carrying a network of parallel lines, placed on the support. A relative movement between the coded images and the network of parallel lines creates the illusion of movement.

US 6,286,873 teaches the possibility of observing coded images on each side of an optical system having a revelation frame and a combined image, located on either side of a substrate.

DE 10 2006 061905 discloses a security element according to the preamble of claim 1, comprising an optical system comprising a substrate, a revelation frame and images observable at different angles of observation.

We still know from publications US 3,241,429 , US 3,154,872 , US 4,645,301 , US 4,892,336 , WO 94/27254 , US 6,856,462 , US 2005/184504 , US 5,708,871 , WO 2005/052650 , WO 2005/058610 , US 2005/150964 and WO 2007/020048 various other optical systems.

It is known to make security elements with lenticular arrays associated with specific impressions, in order to produce movement effects. The SECURENCY company markets under the MOTION ^® brand.

US 2007/0279697 discloses a security element having an optical system for producing a moire effect.

summary

There is a need to benefit from security elements having an optical system capable of producing optical effects that can contribute to the authentication or identification of an article or object, and the possible incorporation into an article or object such as that a paper can be done relatively easily.

The object of the invention is, according to a first of its aspects, a security element according to claim 1.

The combined image may include at least two nested encoded images. Preferably, it comprises at least three nested coded images in order to accentuate the visual animation effect during successive observations of the coded images by changing the observation direction of the security element relative to the optical system.

The revelation of the coded images can be done by parallax effect.

The invention offers new possibilities to authenticate and / or identify an article or object carrying the security element, for example a security document.

The user can, by varying the inclination of the optical system, show a succession of images, which can create an animation effect for example.

The revelation frame may allow the human eye to visualize a different coded image at a time, the observer's brain being able to reconstitute for example a movement or observe hidden information.

The presence of metal layers on the revelation screen and / or on the combined image may allow the appearance of metal effects when the user opts for the inclination of the optical system. The metallic effect may, for example, reveal silvery, golden, coppery reflections, among others, depending on the metal. In particular, the separate observation of the revelation screen or of the combined image can reveal a first matt color (with non-metallic renderings), silver or gold for example, while the superimposition of the revelation screen and the the combined image may show metallic reflections of the same or another color depending on whether the revelation screen and the combined image are respectively of the same color or of different colors. This is explained in particular by the fact that a minimum continuous metal surface is necessary to obtain the desired metallic (shiny) effect.

According to another variant, the metal layers on the revelation screen and / or on the combined image may appear matte, that is to say without metallic effect. Such an effect makes it possible, for example, to bring clarity to the security element without its observation being disturbed by metallic reflections. Such an effect is for example obtained when the combined image is placed above the revelation frame on the side of the observer. More generally, the metallic effect is less when the combined image is placed above the revelation frame, on the observer's side.

The invention can make it possible to reveal metallic effects which are attractive to the user and effective for use as a safety element.

The security element can provide anti-photocopying security. In particular, the fineness of the revelation screen and / or the combined image, especially less than 200 microns, can prevent reproduction by photocopying and also provide protection against the use of scanners. The anti-photocopy security can be double because it can be provided both by the fineness of the revelation screen and by the reflective, glossy and metallic appearance of the security element which is not reproducible by photocopy.

The resolution of the combined image and / or the revelation frame can be directly related to the thickness of the substrate. It is greater than or equal to 800 dpi and preferably greater than 2000 dpi and more preferably greater than 3000 dpi.

The revelation screen and / or the combined image can be as such of homogeneous appearance to the naked eye, given its fineness. In particular, the revelation screen may appear to the naked eye as having an appearance, in particular a uniform color, for example silver or gold depending on the metal chosen to make the revelation screen.

The possibility of having a revelation pattern of homogeneous appearance to the naked eye due to its fineness and dullness, and the fact of revealing coded images, in particular reproducing an animation, with metallic effects (thus brilliant) can make the security element according to the invention pleasant and interesting for the general public. Indeed, the methods used for producing the metal layer of the revelation frame notably allow a very good resolution, in particular better than that obtained by printing techniques accessible to the general public, and it is in particular for that the revelation screen appears homogeneous appearance to the naked eye.

The use of a metal frame and / or a metallic image can bring clarity to the security element while ensuring an opacity equivalent to a frame and / or an image made with a non-reflective ink.

The metal layer carried by the revelation screen and / or the combined image can reflect the light and thus bring more clarity to the image. In this way, the security element can be not only pleasant and interesting for the general public, but also easily visible and attractive, thus enabling easy and intuitive authentication on the part of the general public.

In the invention, the different images that the observer can see are other than images resulting from a phenomenon of spatial interference between two superposed networks, in other words a moiré effect. Such an effect can result from an offset orientation of the superimposed arrays by a non-zero specific angle and can disappear when the arrays are exactly superimposed or are shifted by an angle different from the specific angle. The invention preferably seeks to avoid such an effect. The transition from observation of one coded image to another when the viewing angle varies can be done without a gradual transition.

The combined image may be located on the side of a first face of the substrate and the revealing frame may be located on the side of a second face of the substrate, opposite to the first.

Alternatively, the combined image and the revealing frame may be located on the side of a first face of the substrate. The security element may have on the side of a second face of the substrate, opposite to the first, a reflective surface for observing the coded images through the revelation frame. In particular, the combined image may be located between the revelation frame and the substrate.

The reflecting surface is for example formed by a metallization of the second face of the substrate. This is for example a metal deposit of at least 200 Å or a change in refractive index sufficient to cause reflection.

The authentication and / or identification can be done by observation of the front or back side of the security element.

In particular, when the revelation frame and the combined image are respectively present on either side of the substrate, the coded images can be observed in recto-side reflection, which coincides for example with the side of the revelation frame, but also with the back side. When the security element is for example integrated in a security document, for example in windows, it may be advantageous to make both the front and back sides of the security element observable.

The combined image and the revelation frame each advantageously comprise a metal layer. The layers can be made with the same metal or with different metals.

The metal layer may have recesses or areas of zero thickness. The metal layer may be discontinuous. The metal layer may thus comprise a plurality of metallic patterns.

When the combined image and the revelation frame each comprise a metal layer, the security element resulting from their superposition may have shiny metallic highlights. This effect is all the more surprising since the combined image or the revelation pattern observed alone has a matte homogeneous appearance without metallic reflection.

The metal may be chosen for example from silver, aluminum, nickel, cobalt, tin, gold, copper, and from alloys of metals, such as brass or bronze.

By metal is also meant any dielectric material. The dielectric structures with mirror effect may consist of alternating layers of high and of low index, for example Hafnium dioxide and silica dioxide respectively, and may in particular be obtained by ion etching.

The metal may be deposited by any deposit method known from the prior art. In particular, the metal may be deposited by chemical deposition or a vacuum deposition technique. The metal deposition may for example be carried out by cathodic sputtering on the substrate.

The metal deposition can be carried out by any type of printing that can use metal inks, for example offset, intaglio, laser, gravure or screen printing.

Deposition of the metal can be performed with a desired pattern using a mask directly on the substrate.

The metal layer may alternatively be obtained with the desired pattern by partially demetallizing the previously metallized substrate at points or wefts having a suitable density. Demetallization can be carried out for example by etching or by removal of metallic particles made nonadherent, in particular by means of a laser.

The metal layer may for example have a thickness greater than 150 Å, especially between 200 and 1000 Å.

One of the combined image and the revelation screen may comprise a layer of a metal selected from silver, aluminum, nickel, tin, brass, among others, and the other may include a layer of a metal selected from copper, gold, bronze, among others. In particular, when two different metals are used, one carried by the combined image and the other by the revelation weft, it is possible to use two metals of different colors as described above, in particular such as aluminum and the copper. This provides additional security, especially because the effect and color obtained are not reproducible using a single metal.

The metal layer (s) of the revelation screen and / or the combined image can be produced using metallizations and / or demetallizations. These metallizations and / or demetallizations can make it possible to avoid counterfeiting by printing. The security element is advantageously incorporated in a security document, in particular of the security thread type.

The invention may in particular make it possible to secure security articles, in particular security documents, including paper fibers, such as banknotes bank or passport, with security features having a relatively small thickness. The use of a relatively thin substrate, for example of thickness less than or equal to 50 microns, preferably 30 microns, requires the use of printing or marking systems of a very important definition, further increasing the degree of security.

The coded images can represent information hidden and revealed successively by changing the observation angle of the optical system. The security element can be configured to allow the observation of the succession of several images when the viewing direction changes, which is also called "animation effect". In the context of the invention, the term "animation" is to be understood in the broad sense. It can be several images of the same object, representing different angles of view, to provide a 3D effect or relief, rather than a motion effect. The combined image may correspond to the decomposition of the movement of a pattern, for example text, alphanumeric signs, ideograms, an object, a person and / or an animal. Coded images (also called more simply nested images) may represent successive steps in the movement of a pattern, for example an object, a person and / or an animal.

The coded images may be observable on the side of the first face and the side of the second face of the substrate.

The revelation screen may have any contour of shape, for example circular, oval, star, polygonal, for example rectangular, square, hexagonal, pentagonal or diamond, among others.

The outline of the revelation frame may for example represent a text, an alphanumeric sign, an ideogram, an object, a person and / or an animal.

Advantageously, the optical system may appear in a window of a security document, the window being at least partially transparent or formed by a lack of material, for example the local absence of paper above or below the optical system.

Examples of embodiment of windows in the security documents are for example described in GB 1 552 853 which discloses the creation of a window, in particular by means of transparency, laser cutting, abrasion or mechanical incision, EP 0 229 645 which describes the creation using masks of a window on one side or on both sides of a bijet paper, WO 2004/096482 which describes the creation of a window by laser cutting, CA 2,471 379 which describes the creation of a transparent window and association with a security element and WO 2008/006983 which describes the creation of a transparent window on a bijet paper.

The window may be through and the security element may be at least partially located in the window. The observation of the coded images can be done on the front side and on the back side of the window.

The combined image and / or the revelation weft can still be carried at least partially on the substrate by a printing process, for example offset, intaglio, laser, gravure or screen printing. For example, the combined image and / or the revelation screen may be at least partially printed with colored inks or not, visible to the naked eye, under ultraviolet (UV) and / or infrared (IR), opaque or luminescent, in particular fluorescent, thermochromic, photochromic, interferential effect, in particular iridescent, or optically variable depending on the angle of observation (gonochromatic), including liquid crystals, metallic or not, magnetic or not, among others. The combined image and / or the revelation screen can still be printed at least partially with liquid crystals, so that the coded images are for example visible only through a polarizer. When a magnetic ink is used, the drawn pattern may constitute a magnetic signature allowing additional authentication of the substrate by detecting said signature.

The optical system can be carried by a patch and / or a foil. The patch and / or the foil may comprise metallizations and / or demetallizations, for example of aluminum, or all types of prints. The optical system can still be carried by a security thread, embedded in the surface, mass or window (s) in a security article. The width of the security thread is for example between 3 and 20 mm, being for example equal to about 4 mm.

The substrate of the optical system may comprise or consist of a thermoplastic material, for example a polyolefin, for example polyethylene (PE), polyvinyl chloride (PVC), polyester, polyethylene terephthalate (PET), polycarbonate (PC ), polyester carbonate (PEC), polyethylene terephthalate glycol (PETG), acrylonitrile butadiene styrene (ABS) or a light collecting film by example of the "waveguide" type, for example a luminescent film based on polycarbonate marketed by Bayer under the name LISA ^® .

The substrate may comprise cellulosic fibers and in particular paper. In particular said substrate may be sufficiently translucent paper to allow revealing the coded images, including a tracing paper.

The substrate may also be rendered transparent by application of a generally oily composition which permanently renders it transparent, for example a composition made of oil and transparent mineral material, as described in US Pat. US 2,021,141 , or for example a composition in the form of a wax combined with a solvent, as described in the patent US 1,479,437 .

The substrate can also be made transparent by locally applying a wax by heat transfer, as described in FIG. US Patent 5,118,526 .

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

The revelation screen and the combined image may be present respectively on either side of the substrate and it may, in this case in particular, be advantageous to produce the revelation screen and / or the image combined each with at least two images. superposed metal layers of different colors, for example two superimposed metal layers each having a different appearance from each other, in particular silvered, gilded or copper-plated, so that on the reverse side the coded images are observed from one first color and front side of a second color.

The revelation frame and / or the combined image may be monochromatic or polychromatic. In particular, at least one coded image of the combined image may be monochromatic or polychromatic. The nested encoded images can still be made at least in part with thermochromic and / or photochromic inks. In this way, only a part of the coded images can for example be observable under predefined lighting and / or temperature conditions.

The combined image and / or the revelation frame can be made with different colors. In this way, it may be possible to obtain a colored animation effect when observing the coded images.

For example, all nested coded images of the combined image may have the same color and the revelation frame a different color. Alternatively, the nested encoded images of the combined image may have different colors and the revelation field may have a different color than the nested encoded or color-like images of at least one of the nested encoded images. The revelation frame and / or the combined image may or may not be opaque. In particular, the revelation screen and / or the combined image may be at least partially translucent or transparent and for example colored or absorbent at a given wavelength in the UV or IR.

The security element may also comprise two revelation frames associated respectively with two combined images, the orientation of the bands of one of the revelation frames being different from that of the other revelation frame. When the strips are non-rectilinear, their orientation is defined by the general direction in which they extend.

The security element may comprise two revealing frames juxtaposed or not, superimposed or not, with bands having different orientations or not. One of the revelation frames may be wholly or partially surrounded by the other revelation frame. The possible area of superposition of the revelation frames may reveal a grid pattern when the bands of the revelation frames have different orientations.

The thickness of the substrate is for example between 10 μm and 1 mm, in particular between 6 μm and 1 mm, preferably between 6 μm and 300 μm, preferably between 10 and 100 μm, being for example between 30 μm and 50 μm. .mu.m. It can still be less than 50 microns, especially 25 microns. The period of the revelation frame and / or the combined image is preferably less than or equal to the thickness of the substrate.

A security element with a resolution of the combined image and / or the revelation frame greater than or equal to 800 dpi, as well as with a substrate thickness and a period relationship of the revelation frame and / or the combined image and thickness of the substrate as described above can provide an animation visible to the naked eye, despite the fineness of the frame and the combined image, and enhance the safety of the device vis-à-vis - photocopies of the latter.

The number of interleaved coded images is, for example, between 2 and 15, in particular between 2 and 5, preferably being greater than or equal to 3. The distance between two elements constituting the same coded image may be between 2 μm and 1 mm, in particular between 10 .mu.m and 1 mm, preferably being substantially equal to the period of the revealing frame. The width of a constituent element of a coded image is preferably less than or equal to 500 μm, better 100 μm. The width of an opacifying strip of the revealing frame is preferably less than or equal to the thickness of the substrate, especially at 1 mm.

The revelation screen may comprise opacifying strips with parallel edges, possibly non-rectilinear. The presence of opacifying tapes with non-rectilinear edges may make it more difficult for the counterfeiter to reproduce the optical system.

The security element may also comprise a revelation frame comprising at least a first fluorescent zone capable of fluorescently emitting, in a predefined lighting condition, a visible light of a first color, and a combined image comprising at least a second fluorescent zone capable of emitting fluorescence, in the predefined lighting condition, a visible light of a second color, different from the first, at least one of the first and second fluorescent zones, in particular both, being at least partially opaque, at least in the predefined illumination condition, and the first and second fluorescent zones overlapping at least partially so that, in the predefined illumination condition, light passing successively through the two fluorescent zones presents a third color different from the first and second colors. In particular, the security element may use the principle described in the international application WO 2006/051231 . The predefined lighting condition can in particular correspond to ultraviolet lighting, especially near-visible wavelength or infrared lighting, depending on the fluorescent compounds used. At least one of the first and second fluorescent zones, in particular both, may be substantially colorless in white light.

The fluorescent zone (s) of the revelation screen and / or the combined image may be fluorescent prints that are superposed or not on the metal layers. The metal layers of the revelation frame and / or the image combined can still include non-metallized areas in which are formed fluorescent areas.

The security element may include a plurality of optical systems associated with different observation directions. For example, the security element may comprise an alternation of optical systems associated with two respective perpendicular directions, in particular optical systems whose respective revelation frames have perpendicular orientations.

The security element may be totally or partially covered with invisible material in "normal" illumination, ie when illuminated by daylight or an artificial light source. This invisible material in normal illumination is for example a visible material under a specific illumination, especially a luminescent material, for example a fluorescent or phosphorescent material visible under UV or IR illumination.

Alternatively, this material may comprise nematic liquid crystals visible on a reflective background (the frame and / or the image and / or the bottom then being reflective) with a polarizing filter, in particular circular.

Total or partial coverage by such an invisible material in "normal" illumination may provide additional security in the form of a pattern, for example a word, acronym, code, symbol, image, alphanumeric character or ideogram.

Alternatively, said invisible material in "normal" illumination does not cover the security element but is arranged in the frame and the image, being then partially but sufficiently observable.

The use of an invisible material in "normal" illumination can thus confer additional security of the second level to the security element. A second level security element is defined below.

Observation of the coded images can be further facilitated and improved by the choice of a background on which is placed the security element or on which one comes to place the security element or the security article comprising it.

The security element may thus include the bottom, the latter being located so that the revealing frame is between the bottom and the substrate, or the combined image is between the substrate and the bottom.

The bottom may still be independent of the security element. For example, the user can place the security element or the security article nearby, better in contact with the background, the latter being colored or not.

The bottom may consist of any substrate, preferably being flattened, for example a sheet of paper or a cardboard.

The bottom may be arranged in such a way that the user can observe the side of the security element having the revealing frame or the side having the combined image.

Observation in the presence of the background may allow the appearance of a contrast effect between the background, the combined image and the revelation frame. It may be a color contrast resulting in particular from the use of a combined image, a revelation frame and a background of different colors. It can also be a contrast image animated / fixed background, for example from the use of a background representing a still image, including a landscape or a still image similar to one of the images constituting the animation . The background thus highlights the "animation effect" described above.

The bottom may comprise at least one luminescent element, for example fluorescent and / or phosphorescent. The effect can be observed under predefined lighting, for example UV or IR. The bottom may still include a layer of metal.

The contrast effect can also be achieved without the presence of the background, including the simple fact of using a light source when the security element is observed in transvision on the side of the combined image or on the side of the image. the revelation plot. Indeed, the light source can play the same role as a colored background and allow the appearance of a contrast effect by the combination of the different colors of the light source, the combined image and the image frame. revelation.

The combined image and the revelation frame may have the same color, and the background may be different in color, in particular being more contrasted.

The optical system may comprise at least two combined images and a single frame allowing, during a change of the observation angle, to successively observe the nested images of the two combined images. The two combined images may be arranged in such a way that a relative movement of one image combined with the other is perceived by a user upon a change in the viewing direction of the security element relative to the system. optical.

The substrate may comprise at least two distinct layers and the optical system may comprise at least two combined images, one of them being arranged facing one another, in particular on one external face of one of the layers of the substrate and the other combined image being disposed between the two layers.

The two layers of the substrate may have the same thickness. These two layers can be transparent.

Each combined image may comprise a plurality of nested encoded images.

Each combined image may comprise the same number of coded images and / or each combined image may have the same resolution, in particular one of the resolution values mentioned above and / or the distance between two elements constituting the same coded image of the first combined image may be equal to the distance between two constituent elements of the same coded image of the second combined image.

The invention further relates, in another aspect, to a security article, including a security document, incorporating a security element as defined above. Such a security article may incorporate paper fibers. At the same time, the front and back sides of the security element can advantageously be observable on the security article.

Another subject of the invention, according to another of its aspects, is a security article, in particular a security document, in which the revelation frame, or preferably one or more coded images (coded image or original image before coding). , is made with a pattern, for example wavy opacifying strips, and the same pattern is made elsewhere on the article, incorporating a security element as defined above.

The security article may also comprise a perforation in which the security element is placed at least partially, the latter corresponding, for example, to the juxtaposition of two sub-elements, in particular in the form of foils or patches, respectively comprising a frame of revelation and the corresponding combined image.

The sub-elements may at least partially cover the edges of the perforation, with or without thickness compensation.

The security article may further comprise a revelation frame or a combined image made in the form of prints and a sub-element, in particular in the form of a foil or patch, at least partially covering the impressions formed, the sub-element comprising the combined image or the corresponding revelation frame. The prints of the combined image may for example be made on the surface of the security article.

The or each sub-element may comprise a transparent or translucent substrate.

The or each sub-element, in particular the patch or the foil, may be incorporated into the security article by gluing or by incorporation into the fibrous substrate of the article during its manufacture.

The invention further relates to a method according to claim 15. The observation can for example be made front and back sides of the substrate.

The article or object, or even the security element, especially in the form of a wire, a patch or a security foil, may include one or more other security elements, as defined below.

In general, among the security elements, some are detectable to the naked eye, in daylight or artificial light, without the use of a particular device. These security elements comprise for example colored fibers or boards, fully or partially printed or metallized wires. These security elements are called first level.

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

Other types of security elements still require for their detection a more sophisticated detection device. These security elements are for example capable of generating a specific signal when they are subjected, simultaneously or not, to one or more external excitation sources. Automatic signal detection allows to authenticate, if necessary, the document. These security elements comprise, for example, tracers in the form of active materials, particles or fibers capable of generating a specific signal when these tracers are subjected to optronic, electrical, magnetic or electromagnetic excitation. These security elements are said to be third level.

Security features within the security article may have first, second, and / or third level security features.

According to a particular variant of the invention, the security element may comprise a fluorescent printing under UV illumination. The first-level security provided by the security element according to the invention can thus be supplemented by second-level security, in particular a pattern, observed under UV illumination.

• la figure 1 représente en coupe, de façon schématique et partielle, un exemple de système optique réalisé conformément à un exemple de mise en oeuvre de l'invention,
• la figure 2 représente, en vue de face, à échelle agrandie, un exemple de trame de révélation,
• la figure 3 illustre la décomposition de l'image combinée en images codées,
• la figure 4 illustre la formation d'une image codée,
• la figure 5 représente une succession d'images codées telle qu'elle peut être observée quand l'angle d'observation varie,
• les figures 6A à 6H représentent d'autres exemples de trames de révélation,
• les figures 7 et 8 sont des vues similaires à la figure 1, de variantes de réalisation de systèmes optiques,
• la figure 9 illustre la possibilité de faire varier l'inclinaison en déformant le substrat,
• la figure 10 représente un élément de sécurité comportant plusieurs systèmes optiques correspondant à des directions d'observation respectives différentes,
• les figures 11 et 12 représentent deux exemples de documents de sécurité équipés d'éléments de sécurité selon l'invention,
• les figures 13A, 13B, 13C et 13D représentent des exemples de documents de sécurité intégrant des éléments de sécurité selon l'invention,
• les figures 14A et 14B représentent un exemple de document de sécurité comportant des éléments de sécurité selon l'invention, respectivement après photocopie et avant photocopie,
• les figures 15 et 16 illustrent des variantes d'observation d'éléments de sécurité selon l'invention,
• la figure 17 illustre une variante de réalisation de la trame de révélation et de l'image combinée,
• les figures 18 et 19 illustrent des variantes de réalisation d'articles de sécurité selon l'invention et,
• la figure 20 illustre une autre variante de réalisation d'articles de sécurité selon l'invention.

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

• the figure 1 represents in section, schematically and partially, an example of an optical system produced according to an embodiment of the invention,
• the figure 2 represents, in front view, on an enlarged scale, an example of a revelation frame,
• the figure 3 illustrates the decomposition of the combined image into coded images,
• the figure 4 illustrates the formation of a coded image,
• the figure 5 represents a succession of coded images as can be observed when the observation angle varies,
• the Figures 6A to 6H represent other examples of revelation frames,
• the Figures 7 and 8 are views similar to the figure 1 , alternative embodiments of optical systems,
• the figure 9 illustrates the possibility of varying the inclination by deforming the substrate,
• the figure 10 represents a security element comprising a plurality of optical systems corresponding to different respective viewing directions,
• the Figures 11 and 12 represent two examples of security documents equipped with security elements according to the invention,
• the Figures 13A, 13B, 13C and 13D represent examples of security documents incorporating security elements according to the invention,
• the Figures 14A and 14B represent an example of a security document comprising security elements according to the invention, respectively after photocopying and before photocopying,
• the Figures 15 and 16 illustrate variants of observation of security elements according to the invention,
• the figure 17 illustrates an alternative embodiment of the revelation frame and the combined image,
• the Figures 18 and 19 illustrate alternative embodiments of security articles according to the invention and,
• the figure 20 illustrates another alternative embodiment of security articles according to the invention.

We have shown figure 1 a security element 1 made according to the invention, which comprises a non-opaque substrate 2, for example perfectly transparent, having a first face 2a carrying a plurality of coded images I ₁ , I ₂ , ..., I _n imbricated , the constituent elements 3 of these images being for example in the form of continuous or discontinuous lines, most often discontinuous. The set of coded images I ₁ ,..., I _n forms a combined image 1, as can be seen in FIG. figure 3 .

The second face 2b of the substrate 2, opposite the first, carries a revelation screen 4 (also called decomposition filter) comprising opacifying strips 5 (or lines).

The revelation screen 4 is composed of a periodic pattern, in this case the opacifying strip 5, of constant p period, as can be seen on the figure 2 . The periodicity is observed parallel to the direction of the relative displacement X between the optical system and the observer to observe the different coded images.

The simplest embodiment of the revealing frame 4 is a succession of opacifying strips 5 of constant width at regular intervals, as illustrated in FIG. figure 2 . The period p corresponds to the sum of the width of an opacifying strip 5 and of a transparent interval between two consecutive opacifying strips 5. In the illustrated example, each of the opacifying strips 5 is oriented perpendicularly to the relative displacement axis X.

In this example, the constituent elements 3 of the coded images and the opacifying tapes 5 are formed by layers of metal, for example aluminum, but it could be otherwise. For example, other metals could be used. The constituent elements 3 and the opacifying strips 5 could be made with different metals.

The revelation weft 4 may comprise other patterns than strips of constant width with straight and parallel edges, such as crenellations or corrugations, as illustrated respectively in FIGS. Figures 6A and 6B .

If N is the total number of coded images, a possible relation between the period p of the revelation frame, the width w of the transparent area between two opacifying bands 5 of the frame 4 and the number N is: $$\mathrm{NOT}\mathrm{=}\left(\mathrm{p}\mathrm{/}\mathrm{w}\right)\mathrm{.}$$

The transparent intervals 8 of the revelation frame 4 may allow, if desired, to reveal a single image at a time. A coded image then corresponds to the portions of the combined image present in the transparent gaps of the frame for a given viewing angle. Each coded picture can be visible by shifting the observation of the width of a transparent interval 8.

All the constituent elements of the same coded image are arranged, in the example described, with the same period p as opacifying bands of the revelation frame 4, along the X axis.

We illustrated at the figure 3 an example of forming a combined image I by adding a plurality of coded images, for example four coded images I ₁ to I ₄ .

We illustrated at the figure 4 the production of an encoded image I _i from an original image J to which the image of the revelation frame 4 is subtracted.

We have shown figure 5 the appearance of the different images I ₁ to I ₄ , when the observation angle represented on the figure 1 , relative to the optical system, changes. The animation corresponding to the coded images can be revealed in reflection, revealing frame side or combined image side.

On the other hand, although only one revelation frame is used to create the combined image, several different revelation frames can be used to reveal the encoded images.

For example, all the revelation frames retaining the same period and the same pattern as the initial field, in the direction perpendicular to the translation, but with a different transparent gap width, can be used, as illustrated in FIGS. Figures 6C to 6E . This can make it possible to visualize several coded images at the same time, which can bring clarity to the animation, to the detriment of the definition.

Revelation frames having a period multiple of the period p of the initial frame also work, which amounts to artificially increasing the number N of coded images to the detriment of the definition of the images, as illustrated in FIGS. Figures 6F to 6G .

Of course, various actions over the period p and over the width of the transparent interval 8 can be simultaneously performed, as illustrated in FIG. Figure 6H .

In order to be able to view all the coded images up to an inclination angle of about 45 °, the period p is preferably less than or equal to approximately the thickness e of the substrate, as shown in FIG. figure 1 .

A safety wire, generally has a maximum thickness of 50 microns, which corresponds to a frame of less than or equal to 50 microns period. In the case where four nested images are provided, the lines 3 composing the nested images will have a width of less than or equal to 12.5 μm. The system for forming the combined image then has a minimum resolution of (2.54 × 10 ^-2 ) / (12.5 × 10 ^-6 ), i.e., 2032 dots per inch (dpi dpi).

The weft can then be in the form of a succession of lines of 3 × 12.5 = 37.5 μm in width and separated by a distance of 12.5 μm.

For example, if a substrate of about 100 μm thick e is used, the period p of the frame is less than 100 microns and the constituent elements in the form of lines 3 composing the coded images are less than 33 microns, in the case of three images by animation.

A width of 12.5 μm corresponds to about 2000 dpi, which is a limit for conventional printers that generally have a maximum definition of 600 dpi, or 1200 dpi, which is a factor of security, including copy protection or anti-photocopy.

It may thus be advantageous to have a substrate whose thickness e is less than or equal to 30 μm, better 25 μm, for example between 20 and 30 μm, or even 20 and 25 μm, limits included or excluded.

A sufficiently fine revelation frame makes it possible to provide anti-photocopying security and the existence of several coded images having details to be viewed according to different observation directions also creates a protection against the use of scanners.

Moreover, the human eye does not perceive the details less than approximately 200 microns, a sufficiently fine revelation screen appears homogeneous appearance, for example gray when using opacifying bands in a silver metal. Despite the fineness of the revelation frame, the animation can be preserved, with coded images of scale greater than one millimeter, which contrast with the homogeneous appearance of the frame.

As explained above, one might think that the resolution values mentioned above are too important to allow the observation of an optical effect, this impression being corroborated by the fact that the eye can not distinguish the lines of the frames and sees this one as a flat solid.

It can be considered that the resolving power of the human eye is one minute arc, corresponding to an observation distance of 30 cm acceptable in the case of a security document at a value of 2 x tan (1 / 120) x 30.10 ^-2 = 87.10 ^-6 m, ie 87 μm.

Despite the fineness of the frame and the combined image, the nested images can be successively visible during a loading of the viewing angle.

Resolutions over 2000 dpi, or 3000 dpi, can help secure the device.

For example, we have illustrated on Figures 14A and 14B , greatly enlarged, an exemplary security document 10 comprising a plurality of security elements 1 according to the invention.

The figure 14A represents the observation of the security document 10 after photocopying, and the Figure 14B represents the observation of the document 10 before photocopying. As can be seen, the invention provides a high anti-photocopy security. In addition, the revelation screen may be fine enough to provide a homogeneous coloring effect during the observation, contrary to what is observed on the screen. Figure 14B which is greatly enlarged.

Since the optical system can operate in transmitted or reflected light, it can be used for windows or wires introduced into windows, for example in a banknote.

It is not necessary to locate the revelation frame with respect to the combined image in the direction of the relative displacement X. But depending on the pattern of the frame, a registration may be necessary in the direction perpendicular to this displacement. For example, for a linear revelation frame as illustrated in figure 2 no identification is necessary; on the other hand, for a corrugated frame, a more or less precise location, depending on the amplitude and the frequency of the corrugations, may be desirable. The invention thus offers a possibility of modular security depending on the protection requested and the difficulty of implementation.

In an alternative embodiment of the invention, illustrated in FIG. figure 7 , the back side 2a of the substrate 2 is reflective or semi-reflective and the front face 2b has the combined image 1. The reflecting face can be made by a metallization. The reflecting face can for example define a text.

It is possible to view the coded images by reflection on the reflecting face 2a. This variant has the particular feature of allowing the coded images to be produced with a definition that is less than half the size, but requires a registration between the coded images and the revelation frame, because the revelation frame covers the lines of the combined image on the outside. Each opacifying band 5 can cover the constituent elements 3 of several coded images.

The combined image I and / or the revelation screen 4 may in addition to the metal used be at least partially formed by printing, laser marking, lithography or any other technique for fixing or displaying an image. For example, prints can be made in superposition or not to the metal layers.

To improve security, it is possible to use liquid crystal inks, for example to at least partially print the combined image I. The animation, to be revealed, may then require, in addition to the decomposition frame, the use of a polarizing filter, which may be present on the document or the substrate, or not.

For the security elements formed of a wire introduced into window (s) in a security document, the combined image 1 can be obtained at least partially by micro-photolithography of the wire and the revelation screen 4 can be made at least partially thanks to a UV offset printing performed in a second step, when printing the document.

The revelation frame 4 may be associated, where appropriate, with a printing design of the document.

The pattern of the revelation screen 4 may be printed elsewhere than in superposition with the combined image I, on the document, on the same scale or on a different scale.

The revealing frame 4 may overflow the security element 1 and extend over the security document 10, as illustrated in FIG. figure 11 .

It is possible to use several colors, for example a first color for the revelation screen 4 and one or more other colors for the combined image I, for example as many different colors as there are coded images.

It is also possible to superimpose two colors, for example two metal layers with two different appearance metals, one being for example of silver appearance and the other of golden appearance, on the revelation frame 4 and the combined image I, as shown in figure 8 which allows to have the animation of a color in case of observation of the optical system of the side of the frame and another color in case of observation of the optical system on the side of the combined image.

This double staining can still be performed at least partially by demetallization or photolithography, for example. One color may correspond to the choice of a first metal, for example gold, and the other color may correspond to the choice of a second metal of different appearance, for example silver. Colors can also be obtained by printing on metallized areas or not.

On the figure 8 , the revealing frame 4 comprises superimposed opacifying strips 5a and 5b respectively of a first color C ₁ and a second color C ₂ , the opacifying bands 5a of color C ₁ being external. The elements 3 of the combined image 1 are printed respectively with the two colors C ₁ and C ₂ superimposed, the color elements C ₂ being external. Thus, the order of color superposition can be the same on each side of the substrate 2.

For example, the choice of the color pair C ₁ / C ₂ may correspond to the choice of the pair of aluminum / copper metals.

One possibility for varying the observation direction of the optical system may be to deform the substrate, for example around a folding axis, as illustrated in FIG. figure 9 .

Several optical systems, for example having the shape of small squares or rectangles of a few millimeters of sides, may be present on the same security thread 20, as illustrated in FIGS. figures 10 and 12 .

Rotating a quarter-turn of an optical system 1 out of two may make it possible to obtain a wire producing animations from relative movements of the wire in the two main axes Y ₁ and Y ₂ relative to the observer.

When the security element is an integrated wire in window (s), as shown in Figures 13A and 13B the document 10 may comprise at least two windows 31 and 32 for respectively observing each of the faces of the wire, in reflection.

The coded images are observable through the revealing frame 4 on the side of the window 31 and with the revealing frame as background, on the side of the window 32.

The document substrate, especially at the level of the windows 31 and 32, may also have an opacity allowing the observation of the coded images on both sides of the security document, being for example at least partially transparent.

The document 10 may also include a through window 31, as shown in FIG. figure 13D , the security element 1 being located at least partially in this window. In this way, it would be possible to observe the coded images of both the front side and the back side of the security document 10.

The security element in the form of a security thread can still be incorporated into a security document 10 which has an alternation of windows 31 and 32 on the front and back sides, as shown in FIG. figure 13C . It is thus possible to observe the coded images of both the front side and the back side of the security document 10 at the windows 31 and 32.

We have illustrated on Figures 15 and 17 observation variants of security elements 1 according to the invention.

The observation of the security element 1 can be done through the use of a bottom 30 on which the security element 1 is placed or which belongs to the security element. In particular, the face 2b of the security element 1 comprising the revealing frame 4 may be in contact with the bottom 30, as shown in FIG. figure 15 . Alternatively, the face 2a of the security element 1 comprising the combined image 1 may be in contact with the bottom 30, as shown in FIG. figure 16 .

In exemplary embodiments, the revealing frame 4 is silver in color, the combined image 1 is copper-colored and the bottom 30 is white in color. In this way, the observation of the security element 1 generates a significant contrast effect resulting in particular from the choice of the colors of the revelation frame, the combined image and the background.

In the example of the figure 15 , the user can thus observe a revealing frame 4 of silver color and a spiral of copper color in contrast with the colors of the revelation frame and the background. The user can thus successively observe the coded images appearing as a mixture of silver color and copper color.

The contrast effect obtained can also result from the observation in transvision of the security element 1 facing a light source 31, for example solar light, as illustrated in FIG. figure 16 .

We have shown on the figure 17 an alternative embodiment of a revelation frame 4 and a combined image 1 that can be used in a security element 1 according to the invention.

In particular, this exemplary embodiment illustrates the possibility of producing a revelation frame 4 and a combined image 1 so that the coded images can be observable in the two main directions of inclination of the security element 1, especially in the sense of width and length.

The revelation screen 4 can thus result from the combination of two frames 4a and 4b having bands extending along perpendicular axes, as can be seen in FIG. figure 17 . In the same way, the combined image 1 may result from the combination of combined images Ia and Ib which respectively correspond to the combined images associated with the frames 4a and 4b.

The animation effect obtained can thus be observed in at least two directions of inclination of the security element 1.

We have shown on the figure 18 an example of a security article 10 comprising a perforation 40 in which at least two sub-elements are placed, in particular in the form of foils or patches, 41 and 42 to form a security element 1 according to the invention.

The sub-element 41 comprises for example a revealing frame 4 and the sub-element 42 comprises for example the corresponding combined image 1.

In the variant illustrated in figure 19 , the security article 10 comprises a combined image 1 made in the form of impressions on the surface of the security article 10. In addition, a sub-element, in particular in the form of a foil or patch, 43 is placed on the prints constituting the combined image I, the sub-element 43 comprising the corresponding revelation frame 4.

In the examples of Figures 18 and 19 the revelation frames 4 and / or the combined images 1 could be made differently, for example being incorporated or located above or below the sub-elements 41, 42 and 43.

In the example of the figure 20 , the security element 1 differs from that of the figure 1 in that it comprises two non-opaque, for example perfectly transparent, substrate layers 2 and two combined images 1 and I '. The two substrate layers here have the same thickness, for example 25 microns.

The first combined image 1 is arranged opposite the face 2b of the security element and represents for example a pattern such as a cloud.

The second combined image I 'is disposed between the two substrate layers 2 and represents in the example in question a pattern such as a horse.

The period p of the revelation frame is in the example considered equal to the thickness of a substrate layer, that is to say to 25 microns.

The nested images I _i and I ' _i forming respectively the first and the second combined image are in the example of the figure 20 arranged in the same way so that when changing the viewing angle from the face 2a of the security element, the pattern represented by the second combined image I 'will move twice as slowly as the pattern represented by the first combined image 1 since only half as many nested images I ' _i as nested images I _i will have been visualized by the eye. This example makes it possible to demonstrate the possibility with the invention of obtaining a movement effect between the patterns represented on the nested images. Such an effect, which can still be described as "effect of depth" is for example similar to that provided by the "differential scrolling" of the first video games.

The example of figure 20 may be obtained by assembling, in particular by gluing, different substrate layers 2. According to another method, the example of the figure 20 is obtained from a laser-markable monolayer substrate in which at least the combined image 1 is formed in the substrate by exposure to laser radiation. The combined image I 'and / or the revelation screen are in particular printed or labeled by laser irradiation.

The use of the laser makes it possible to mark said laser-marked substrate at the desired depth, and also to mark said substrate at at least two depths. (Thicknesses) different, for example to form in a monolayer substrate at least two of the revelation frame and the combined images.

The invention is not limited to the illustrated examples. The security element can be realized with other first, second or third level security, for example.

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

Claims (15)

1. A security element (1), comprising:

   - an optical system, comprising:

   - a transparent or translucent substrate (2),

   - a combined image (I) comprising a plurality of interleaved coded images (I₁,.., I_N),

   - an exposure screen (4) overlaid on the combined image (I), making it possible to observe the coded images (I₁, ..., I_N) upon a change of the direction of observation of the security element (1) in relation to the optical system, characterized in that the combined image (I) and/or the exposure screen (4) comprise a metal layer, the exposure screen and/or the combined image having a resolution greater than or equal to 800 dpi.
2. The security element as claimed in claim 1, the combined image (I) being situated on the side of a first face (2a, 2b) of the substrate (2) and the exposure screen (4) being situated on the side of a second face (2a, 2b) of the substrate (2), opposite from the first face.
3. The security element as claimed in claim 1, the combined image (I) and the exposure screen (4) being situated on the side of a first face (2a, 2b) of the substrate (2), the security element (1) comprising on the side of a second face (2a, 2b) of the substrate (2), opposite from the first face, a reflecting surface making it possible to observe the coded images (I₁..., I_N) through the exposure screen (4).
4. The security element as claimed in claim 3, the combined image (I) being situated between the exposure screen (4) and the substrate (2).
5. The security element as claimed in one of the preceding claims, the combined image (I) and the exposure screen (4) each comprising a metal layer, notably of one and the same metal or of metals being different from one another.
6. The security element as claimed in any one of the preceding claims, the exposure screen and/or the combined image being of homogeneous aspect to the naked eye.
7. The security element as claimed in any one of the preceding claims, comprising an alternation of optical systems associated with two respective observation directions perpendicular to each other, notably optical systems whose respective exposure screens have perpendicular orientations.
8. The security element as claimed in any one of the preceding claims, taking the form of a security thread, of a foil or of a patch.
9. The security element as claimed in any one of the preceding claims, the combined image (I), especially the coded images of the combined image, and/or the exposure screen (4) being produced with different colors.
10. The security element as claimed in any one of the preceding claims, the security element (1) comprising two exposure screens (4a, 4b) respectively associated with two combined images (Ia, Ib), the orientation of the strips of one of the exposure screens being different from that of the other exposure screen.
11. A security article, especially a security document, incorporating a security element such as defined in any one of the preceding claims.
12. The security article as claimed in the preceding claim, the recto and verso faces of the security element being observable.
13. The security article as claimed in either one of claims 11 and 12, comprising a perforation (40) in which is at least partially placed the security element (1) corresponding to the juxtaposition of two sub-elements (41, 42), especially in the form of foils or of patches, comprising respectively the exposure screen (4) and the corresponding combined image (I).
14. The security article as claimed in either one of claims 11 and 12, the exposure screen (4) or the combined image (I) being produced in the form of prints on the surface of the article, a sub-element (43), especially in the form of a foil or patch, overlapping at least partially the prints formed, the sub-element (43) comprising the combined image (I) or the corresponding exposure screen (4).
15. A method for authenticating a security element such as defined in any one of claims 1 to 10, comprising the step consisting in observing the security element while varying the direction of observation and in concluding as to the authenticity of an article or of an object associated with the security element at least as a function of the coded images observed

Images