EP3157756B1 - Security papers and processes of their manufacturing - Google Patents

Description

The present invention relates to fibrous substrates having at least one region of variable opacity, preferably a watermark, and at least partially incorporating a security thread.

Banknotes and other security documents, including checks, money orders, identity cards, credit cards or guarantee cards made from papers incorporating security threads, that is to say more or less wide bands, have been in circulation for a number of years and are now widely used in many countries.

The security threads are in these documents in some cases exposed to the sight, in reflected light, in predefined regions present on at least one side of the paper, these regions being commonly called "windows".

Security threads make the imitation of security documents more difficult. They contribute to the authentication of security documents generally by giving documents a different appearance in transmitted light and reflected light.

To increase the security provided by the incorporation of such security elements, it is customary to provide additional verifiable properties, including magnetic properties, electrical conductivity, X-ray absorption and / or luminescence, for example fluorescence.

Methods of manufacturing a paper having a security thread incorporated into windows are known EP 0059056 , WO 93/08327 and WO 03/095188 .

EP 0059056 discloses a method of manufacturing a paper incorporating a security thread into windows by papermaking on round form. The round shape canvas is embossed to create projecting areas. The security thread is brought into contact with these protruding regions before entering the tank containing the aqueous suspension of paper fibers. The fibers do not accumulate in the areas of contact of the wire with the fabric of the round form. After its formation, the paper jet is extracted and dried. The finished paper has windows visible in reflected light on one side, allowing the security thread to appear locally.

The paper comprising the security thread may locally have an excess thickness at the thread. This extra thickness is amplified during the stacking of the paper when winding roll paper or when cutting into sheets. In order to overcome this problem, it is known to impose on the yarn an oscillation in the direction perpendicular to the direction of manufacture of the paper during its integration into the paper. The projecting regions therefore have a width greater than the width of the wire. Thus, when viewing the paper transmitted light, the latter has on both sides of the wire an alternation of dark regions adjacent to the bridges and light areas adjacent to the windows.

WO 93/08327 discloses a method of making a paper incorporating a security thread on a flat-bed paper machine.

It is also known from the application WO 03/095188 a method of manufacturing a paper incorporating a security thread, visible through windows with particular patterns.

Requirement EP 2 275 602 describes a paper incorporating a security thread incorporated into windows and watermarks spaced from the latter.

Requirement WO 2009/083689 discloses the combination of a watermark and a security structure that is at least partially superimposed on the watermark, and includes semi-reflective areas for at least partial viewing of the underlying watermark. This watermark can be a screened watermark. The security structure can be glued to one side of the papermaking substrate opposite to the watermark, or on the same face. The security structure remains on the surface of the paper substrate over its entire length and it is not in this document a security structure consisting of a security wire integrated into windows.

Requirement WO 2009/115766 teaches how to mechanically reinforce a paper-based substrate in the corners using dark watermarks. A security element may be disposed on the surface of the substrate.

Requirement WO 2009/081017 proposes a filigree substrate incorporating a ribbon, in particular fibrous, which is superimposed at least partially on the watermark. The watermark thus has different aspects in its portion which is superimposed on the ribbon and in its non-superimposed portion ribbon. The watermark can be a screened watermark. The purpose of this request is not to facilitate the recognition of a conventional integrated security wire in windows, but to create a modification of the appearance of the watermark.

Meal vouchers with watermarks and a security thread overlaid with watermarks were marketed and found on one side of the paper in the watermark area.

There is a need to further improve the security of papers against counterfeit attempts, including providing first-level security easily recognizable by the man in the street, while having a paper relatively easy to achieve and attractive appearance

summary

The invention aims to meet this need by providing a security paper according to claim 1.

The invention makes it possible to attractively combine at least two superimposed first level safeties, namely the security son or wires visible in windows and the region of variable opacity, superimposed on the security element at the level of the one or more bridges.

Such a combination, for example of a security thread in windows and a watermark, makes it possible to significantly increase the difficulty of counterfeiting.

The security paper may comprise a plurality of security threads, in particular two security threads integrated into windows in the fibrous substrate. The security threads can be juxtaposed or not and be integrated in the same window or not.

The security son or son advantageously comprise a plastic support film, in particular thermoplastic material.

The security son or son are generally at least partially covered by the fibrous substrate at the bridges. This makes it possible to increase the security of the security paper by at least partially integrating the security thread or threads inside the substrate.

According to an exemplary implementation of the invention, the region or regions of variable opacity are located exclusively at the bridge or bridges. For example, there is a variable opacity region at each bridge or a region of opacity that varies every n bridges, where n is an integer greater than one.

According to an exemplary implementation of the invention, the fibrous substrate has at least one other region of variable opacity appearing to border the son or son at at least one window when the paper is observed in transmitted light. The other region (s) of variable opacity preferably extend along the wire (s) at the level of the windows, without overflowing on the bridges extending between the windows. For example, there is a region of variable opacity on either side of the security son or son at each window and not extending on the adjacent bridges. We can have for each window a region of variable opacity that extends on either side of the son or son at this window, or such a region of variable opacity for n windows, with n integer greater than a.

By region of variable opacity "bordering" the security son or son, it should be understood that said region extends along a longitudinal edge of the security son or son. It can be superimposed on at least one longitudinal edge of the security son or son or extend a sufficiently small distance from the longitudinal edge, for example less than 2 mm so that visually the observer has, in transmitted light, the impression that the security son or son are substantially contiguous with or superimposed on said region. The substrate may have a plurality of regions of variable opacity, some of them at the bridges without overflowing in the windows and some of them, preferably reproducing a different pattern, extending along the windows without overflowing on the bridges.

The presence of regions of variable opacity appearing to border the son or son at the windows without overflowing on the bridges makes it possible to attractively combine two adjoining first level safeties, namely the security son or sons visible in windows and the region. variable opacity bordering the security son or son.

In an exemplary implementation, the thickness of the substrate is never zero at the bridge, and the security son or son are thus always covered by fibers of the substrate. Alternatively, the region of variable opacity is such that regions of lower opacity thereof are constituted by holes in the fibrous substrate which open onto the security son or son, revealing the security son or son in the holes, or which are such that the thickness of the substrate covering the security son or son is sufficiently low so that the son or son of security are visible in reflected light in the holes. The son or son can thus become locally visible at a bridge in reflected light. However, preferably in this case, the total section of the hole or holes remains a minority relative to the total section of the bridge elsewhere, so as to maintain mechanical cohesion ensuring good maintenance of son or son within the substrate. As a variant again, the bridges only partially cover the safety wire or wires so that that these remain partially visible. For example, the bridges may have the form of half-bridges covering only one side or the security son on less than their entire width. Alternatively, the bridges may be open, preferably substantially in their center, revealing the son or son at the opening.

When the security son or son are directly exposed in a bridge or security son advantageously comprise visible security at this level; it may be a visible security in reflection, for example producing a particular optical effect such as a goniochromatic effect.

The security son or son advantageously comprise at least one luminescent security, including fluorescent security. The region of variable opacity can improve the visibility of luminescent security because of its less opacity in places; for example, in the zone or zones of less opacity of the region of variable opacity, the light produced by luminescence is less attenuated by its diffusion through the substrate, or even not attenuated. It is possible to create an effect under UV or IR light for exciting the luminescence, which is particularly attractive visually.

When the paper is cut into the format of a secure document, the secure document may include one or more windows along the one or more threads between the edges of the document where the ends of the one or more threads end.

The invention also relates, independently or in combination with the foregoing, to a security paper comprising a fibrous substrate and at least one integrated security thread in windows in this substrate, the fibrous substrate having at least one region of opacity variable overlapping the wire in two areas and extending between these areas, preferably at a non-zero distance (s) of the wire.

substratum

The term "substrate" designates a fibrous sheet that can in particular comprise one or more fibrous layers, also called "jets". The substrate is preferably bijet, the windows being obtained during the manufacture of these jets.

The substrate may comprise one or more regions of variable opacity having identical or different characteristics.

The substrate may include or receive at least one additional security element, constituting first, second or third level security, particular chosen from tracers, in particular nanoscale, security fibers, especially metallic, magnetic (soft and / or hard), absorbent or excitable in the ultraviolet (UV), visible or infrared (IR) and in particular the Near infrared (NIR), flat and relatively small security elements such as boards, pigments or pigment agglomerates, especially absorbent or excitable under laser illumination or in the ultraviolet (UV), visible or infrared (IR), in particular the near-infrared (NIR), the chemical or biochemical reagents for tampering and / or authentication and / or identification, which may especially react with at least one agent, respectively of falsification and / or of authentication and / or identification, and optically variable elements, in particular holograms, liquid crystals, iridescent pigments or mirror-effect structures, in particular with dielectric layers es, and their combinations.

The fibrous substrate may in particular comprise additional security elements visible to the naked eye, but it may also include tracers which are in the form of active material, particles or fibers, capable of generating a specific signal when these tracers are subject to optronic, electrical, magnetic or electromagnetic excitation.

The fibrous substrate may include a plurality of windows alternating with a plurality of bridges extending between the windows. The wire (s) may extend at each window between two regions of variable opacity and / or each bridge may include a region of variable opacity. Alternatively, a single bridge has a region of variable opacity.

Bridges can completely cover the safety wire or wires. As a variant, the bridges partially cover the safety wire or wires, the latter then remaining partially visible at the level of the bridges. The bridges may be as described in the European patent application EP 2 260 142 .

The windows may be formed by at least a portion of a recessed relief of the substrate.

Bridges can be the same height in the direction of thickness as vellum. Alternatively, the bridges may be formed by a portion of a relief projecting from the substrate.

By "at the level of", it is necessary to understand at the same longitudinal position, measured along the son or son.

The fibers of the substrate may be fibers of natural origin and / or synthetic fibers.

The substrate may comprise cellulosic fibers, cotton or linen.

The substrate may comprise opacifying charges, especially mineral.

The substrate may comprise a synthetic binder and receive on the surface a printing coating and / or antifouling.

The substrate may comprise on at least one of its faces, preferably on both sides, a protective plastic film.

The substrate may comprise on at least one of its faces, preferably on both sides, an impregnation, a surfacing, a coating, in particular a coating, and / or a varnish.

Region of variable opacity

By "region of variable opacity", it is necessary to understand a portion of the substrate whose opacity varies in its plane when observed in transmitted light at normal incidence. The opacity variations are preferably visible in light transmitted to the naked eye, in white light of the day. The region of variable opacity may be defined by a watermark, for example multiton or multiton effect, a pseudo-watermark obtained by embossing and / or compression and / or by use of a transparentizing substance, especially an oily substance, or a region of water. variable opacity obtained by laser ablation.

Preferably, the region of variable opacity is a halftone region of variable opacity.

The presence of the region of variable opacity, including raster, reinforces the level of security by drawing the attention of the observer on the security or safety carried by the security son or adjacent. Indeed, many security threads embedded in windows are often counterfeited by sticking pieces of son on the surface of the paper, their visibility on the security document, including printed, usually being relatively low.

When the region of variable opacity, including raster, is superimposed on the security son or son at a bridge, the visibility of the security son or son can find improved in reflected light and / or transmitted, because of a lower local opacity in places of the substrate due to the variation of its opacity.

By "halftone region of variable opacity", it is necessary to understand a region whose pattern created by the variation of opacity and visible in transmitted light is a halftone image. It can be an image formed with weft points whose spacing is constant or variable, and whose size is constant or variable.

The raster points of the raster image may be small enough so that the image observed in transmitted light creates a level of homogeneous gray, different from that of vellum when observed with the naked eye at a distance of 20 cm for example By "vellum" is meant the fibrous substrate outside the zones of variable opacity, in particular outside the regions of variable opacity according to the invention.

The raster points appear, especially when the raster region of variable opacity is observed in transmitted light, positive and / or negative.

The raster points can still remain visually discernible to the naked eye at a distance of 20 cm, when the raster image is observed in transmitted light, giving for example the impression to the observer of a grid or a network of points, for example regularly distributed in the plane of the substrate.

The raster points may have a density and / or dimension variation from one zone to another of the rasterized region.

The shape of the raster points may or may not be circular, these possibly consisting of lines whose width and / or spacing varies. Thus, the term "raster dot" should not be understood in a limiting sense. It is in particular a geometric or alphanumeric shape, and preferably a linear, circular, oval, polyhedral, especially square, quadrilateral, hexagonal or octagonal, or alphanumeric. Alternatively it is a text element, that is to say a set of several alphanumeric characters.

A raster region of variable opacity may have a relatively large number of raster points in the form of light or dark islands on the image, which may appear as pixels constituting the image.

The image rendered by the halftone region may be other than a grid or a regular network of points, and may reproduce the appearance of a subject in perspective, if necessary. restoring the relief thanks to shadows on the image and / or thanks to variations of density and / or dimension of the points, one speaks in this case of a three-dimensional effect.

The subject reproduced by the halftone region can be an inanimate object, a landscape, a monument, a character, a plant (flower, plant, tree) or an animal, as is usually found on banknotes for example. In this case, the raster points can be arranged according to a modulation of amplitude or frequency in order to reproduce the light and dark regions of the image, according to several levels of gray for example.

The largest dimension of a weft dot may be between 0.1 and 1.5 mm, for example between 0.2 and 1.0 mm.

The smallest dimension of a raster dot, especially when the raster points consist of lines, can be between 0.1 and 1.5 mm, for example between 0.2 and 1.0 mm.

The number of raster points, which appear either in brighter or in darker than the rest of the image, is for example between 10 and 2500 per cm ² , for example between 25 and 625 per cm ² per halftone region. variable opacity.

Each region of variable opacity disposed at least partially at a bridge, that is to say where the security son or son are at least partially buried in the substrate, can be superimposed totally or partially on the security wires in this area.

When the substrate is multijet, the variable opacity region may be formed by a watermark made on a separate jet which is assembled with the one in which the windows are made, especially in the case of a variable opacity region appearing to border the or the wires at the level of at least one window In an exemplary implementation, the regions of variable opacity extend only where they are superimposed at least partially on the security son or wires; alternatively, the regions of varying opacity extend both above and across the yarns, in particular on one or both sides of the yarn (s); for example, the outline of a region of variable opacity at a bridge is rectangular of large side wider than the son or son and oriented perpendicular to the longitudinal axis of the son or son. The maximum distance over which a region of variable opacity extends in a direction perpendicular to the direction longitudinal length of the son or son, beyond the son or son, is preferably less than or equal to 40 mm

As a variant, when the bridges are each formed by at least a portion of a relief projecting from the substrate, the regions of variable opacity extend partially over the bridges, in particular extending longitudinally and / or transversely over a smaller distance. to that of bridges.

Each region of variable opacity bordering the security son or wires at a window, ie where the security element is flush with the surface of the substrate, can totally border at least one side of the or visible security threads, in particular both sides, in this zone, all along its length between two consecutive bridges. Alternatively, the variable opacity region only partially borders this side of the son or son, and in this case extends for example along a length, or son of security son, which is less than that separating two bridges consecutive.

The fibrous substrate may comprise a plurality of regions of variable opacity, identical to each other, and preferably distributed at regular intervals on the substrate.

Preferably, the regions of variable opacity all have an identical transverse dimension, in particular between 10 and 40 mm. The transverse dimension is measured perpendicular to the longitudinal axis of the security son or son. As a variant, the regions of variable opacity that follow each other are not all identical and / or do not have the same transverse dimension. Preferably, there are found on the substrate with a certain periodicity of regions of variable opacity of identical aspects.

The regions of variable opacity can form a main pattern of any contour when observed in transmitted light. Preferably, the regions of variable opacity form a main pattern of polygonal or ovoid contour. The term "main pattern" designates the pattern defined by the set of the variable opacity region, and not the shape of a clear or dark individual island constituting a pixel of the image produced.

The region or regions of variable opacity preferably each comprise a watermark, a pseudo-watermark, each better constituted by a watermark, that is to say that they are obtained by papermaking by a local accumulation more or less papermaking fibers, preferably by embossing or using a mask disposed on a web forming a jet of paper. Such a mask is still called "galvano". In a variant, the region or regions of variable opacity comprise microperforations, in particular obtained by laser ablation.

In the case of a watermark or pseudo-watermark, the watermark or pseudo-watermark carried by the fibrous substrate can be a clear watermark. In this case, the light areas of the watermark have a mass density strictly less than that of the areas outside said watermark. Dark areas have the same area density as areas outside said watermark or higher density. As a variant, the watermark may be a dark watermark, in which case the dark areas of the watermark have a density that is strictly greater than that of the zones outside said watermark. The light areas may have the same density at the same time as the areas outside the said watermark or a lower density.

The variation in surface density is related to a local variation in the thickness of the substrate.

"Area density of the light / dark areas of the watermark" means the density of the substrate fibers of the light areas and / or the dark areas of the watermark, that is to say not taking into account the wire or wires. of security.

Preferably, the watermark or pseudo-watermark is a halftone multitone effect watermark comprising a set of light areas arranged in the manner of a halftone image and distributed to form an image having a plurality of gray levels according to the density of the light areas on the surface. Thus, for example, those portions of the substrate having a high surface density of bright areas appear in a light tone and the portions having low surface density of bright areas appear in a dark tone. Alternatively, the watermark may comprise a set of dark areas arranged in the manner of a raster image. The patent application EP 1 122 360 discloses the production of such a screened watermark.

The watermark can be a multitone watermark made by embossing the substrate, so that the latter has reliefs of various levels.

The watermark may be a multitone watermark produced as described in the application WO 2011/117828 , that is to say a watermark made from a perforated mask of varying thickness. The perforations are especially équiréparties and flared shape. Thicker areas are perforated with a smaller hole than the thinner areas. The different gray levels then depend on the size of the perforations, depending on the thickness of the mask itself.

The watermark can be an electrotype watermark ("high contrast single tone watermark").

The watermark may be a watermark obtained on a flatbed machine, in particular by means of a watermarking roll.

The watermark can be obtained by means of a perforated mask or by means of a perforated mask with reliefs.

In a variant, the openwork masks are embossed, in particular at the same time as the training fabric.

Alternatively, the watermark or pseudo watermark may be obtained by compression and / or by use of a transparentizing substance, especially oily and / or laser ablation.

The clear areas of the watermark at the bridges may be formed by recesses or not through the fibrous substrate revealing the underlying security son or son, as mentioned above. The light areas may be such that there is always a non-zero thickness of substrate at the bridges between the outer surface of the substrate and the security son or son.

When the regions of variable opacity are constituted by a pseudo-watermark, this can be obtained by means of a local transparency of the substrate using a suitable substance, for example an oily substance.

When the regions of variable opacity are constituted by a pseudo-watermark, this can also be obtained by the methods of applying a rewetting solution of the substrate and applying a pressure or heat to densify the substrate in certain areas to form a substrate. watermark. Such methods are described in the applications WO 99/14433 and WO 00/32874 The recesses can be made by laser. In the case of a region of variable opacity comprising microperforations made in the fibrous substrate, the latter are preferably produced by laser. The intensity of the laser is chosen during manufacture so as to create a recess or not through the substrate without destroying the underlying security son or son. The use of a laser allows a greater precision in the pattern and its positioning and allows a customization of the latter.

Security threads

The security son or son may comprise conventionally a plastic support film, in particular thermoplastic material, preferably polyester or polyethylene terephthalate (PET). Preferably, this support film is transparent.

The width of the son or son may be between 0.5 and 15 mm, better between 3 and 8 mm The thickness of the support film may range from 6 to 60 microns The support film may carry a metallization / demetallization on at least one of its faces, defining a micro text or other visible patterns in transmitted light. The metal is, for example, aluminum, copper, nickel, gold, and / or silver. The support film may in particular carry a layer of metal deposited by a vacuum metallization technique, with zones demetallized to define the micro text or other patterns.

The security son or son may comprise at least one printing, in particular a metallized ink, iridescent or luminescent. This impression can be carried by the face of the security thread facing the screened region and / or by the opposite face.

The security son or son may have microreliefs, especially diffractive or refractive and in particular holographic. These microreliefs can be formed by embossing a varnish.

The incorporation of the security son or son to the fibrous substrate may not generate extra thickness in the paper.

Preferably, the security son or son extend between two opposite edges of the paper.

The security son or son may have straight and parallel edges, or alternatively not straight, for example of curved shape.

The security son or son may have a different color from that of the fibrous substrate to increase its visibility, especially through regions of low opacity present on the bridges and superimposed on the security son or son.

The security son or son may have magnetic, electrical, photochromic, thermochromic, piezochromic properties, among others.

The security son or son may comprise a luminescent compound, in particular fluorescent, visible or invisible in white light of the day. The luminescent compound may be incorporated into the bulk of the support film or be present only on its surface. The luminescent compound can fluoresce when excited by ultraviolet (UV) or infrared (IR) light. This can increase security and facilitate the authentication of the document. In particular, the fluorescence or luminescence can be detectable in regions of low opacity present on the fibrous substrate bridges and superimposed on the security son or son, and can form a fluorescent or luminescent pattern.

The security son or son may still have characteristics perceptible to the touch. The security son or son can thus create a tactile effect, for example by embossing a varnish deposited on the surface of the support film or the deposition by printing of a layer having large particles. The tactile effect is particularly noticeable in the windows of the fibrous substrate where the son or son are on the surface.

The security son or son may comprise one or more optically variable elements such as holograms, liquid crystals, interferential multilayer structures, iridescent pigments and combinations thereof. These optically variable elements may be visible in the windows of the fibrous substrate and may also appear at least partially in the regions of low opacity present on the bridges of the fibrous substrate superimposed on the security son or son.

The security son or son may include, where appropriate, at least one electronic device, including RFID.

Secure document

The invention also relates to a secure document comprising a paper according to the invention.

This secure document can be a means of payment, such as a bank note, a check or a restaurant ticket, an identity document such as an identity card or a visa or a passport or a driver's license, a lottery ticket, a ticket or an entrance ticket to cultural or sports events.

The document can have a single window or alternatively several windows, depending on its width and the distance separating two consecutive windows during the manufacture of the paper. When the document has only one window, however, the areas of the substrate covering the wire or wires and which extend on either side of the window in the longitudinal direction of the wire or wires of "bridges" are nevertheless described. .

Manufacturing process

• amener au moins un fil de sécurité au contact d'une toile de formation d'un jet de papier, comportant une ou plusieurs premières zones de formation d'une ou plusieurs fenêtres, et une ou plusieurs deuxièmes zones de formation d'un ou plusieurs ponts s'étendant entre les fenêtres sur le papier formé, et au moins un masque ajouré présentant des régions pleines disposées comme les parties de plus faible opacité d'une région d'opacité variable, ce masque ajouré étant disposé dans l'une des deuxième zones, le masque ajouré venant se superposer au moins partiellement au fil de sécurité.

The invention also relates to a method for manufacturing a security paper according to the invention, comprising the step of:

• bringing at least one security thread into contact with a paper jet forming fabric, having one or more first formation areas of one or more windows, and one or more second formation zones of one or more bridges extending between the windows on the formed paper, and at least one perforated mask having solid regions arranged as the portions of lower opacity of a region of variable opacity, this openwork mask being disposed in one of the second zones, the openwork mask being superimposed at least partially on the security thread.

The forming fabric may be a web of a flat-table filigree roller or, preferably, of a round shape, as disclosed in WO 93/08327 . The forming fabric may comprise recessed reliefs defining the zones of formation of the bridges.

The windows are preferably formed by protrusions projecting from the forming fabric. In this case, when it is desired to achieve regions of variable opacity at the windows, it is possible to have on these protruding reliefs openwork masks for forming regions of corresponding variable opacity. In a variant, the paper forming fabric does not have protruding reliefs and the windows are made with the masks themselves.

To achieve the regions of variable opacity on the bridges extending between the windows, it is possible to arrange the openwork masks in the recessed reliefs of the paper forming fabric.

It is then possible to use very thin masks to produce the watermarks of the regions of variable opacity because the masks are protected from the stresses and mechanical stresses likely to degrade them by their position set back on the canvas, which prevents them from contact with the or the sons.

The thickness of a mask is preferably less than or equal to 1 mm, preferably between 0.2 and 0.8 mm

The openwork masks may be made by machining, injection, sintering, in particular laser sintering, in particular of SLS (Selective Laser Sintering) or SLM (Selecting Laser Melting) type, or 3D printing.

The machining technique is preferred for perforated masks without relief, the SLM technique is preferred for perforated masks provided with relief.

The invention further relates, independently or in combination with the foregoing, to a method of manufacturing a security paper comprising at least one integrated security thread in windows, using a training fabric of a papermaking substrate, which is preferably embossed and which has an alternation of raised reliefs and protruding reliefs, which is characterized by the fact that at least one formation mask of a variable opacity region is available in a hollow relief. Such a method is suitable for producing a region of variable opacity as defined above. The openwork mask may be made to form a watermark, including a screened watermark. Such an embodiment in itself presents an interest independent of the image restored by the watermark, screened or not, as this may make the safety son or son more visible at the bridges. Such increased visibility is advantageous especially when the security son or son have a luminescence property, especially UV or IR fluorescence, or a different color of the substrate at the bridges, because the light produced by luminescence or the difference in color may produce an effect at the bridges, and particularly at the level of the areas of least opacity of the bridges.

The invention also relates, independently or in combination with the foregoing, to a method of manufacturing a security paper comprising at least one integrated security thread in windows in a substrate, in which the substrate is produced at the level of the substrate. bridges extending between the windows at least one recess with the aid of a laser. When the recess or recesses are made on a bridge, the thickness of the substrate extending between the security thread and the surface of the paper is thus locally reduced, and the visibility of the at least one wire can be improved at the level of bridges, with the same advantages as those mentioned above.

The thickness of the fibrous substrate may, locally, be sufficiently small for the safety son or son to be visible by transparency of the fibrous substrate.

It is also possible, in addition, laser to produce recesses in the substrate along the son or son at the windows, in particular on each side of the son or son; it is thus possible to produce regions of variable opacity as defined above, contributing in particular to modifying the appearance of the substrate, which can facilitate the identification of the son or son by the observer and make the paper more visually appealing.

A portion of the recesses may be through to locally allow visibility in reflected light of the underlying security son or son.

The invention also relates, in another of its aspects, to a security paper comprising a fibrous substrate and at least one integrated security thread in windows, the fibrous substrate having at least one region of variable opacity that is at least partially at a bridge of the fibrous substrate extending between two successive windows along the at least one security thread.

The fibrous substrate may comprise a plurality of distinct halftone variable opacity regions. Regions of variable opacity may be exclusively at bridges. Within each window, the son or son may be bordered by a halftone variable opacity region. Alternatively, the halftone opacity regions may border the one or more wires at one window every n windows, where n is an integer greater than one.

The invention also relates, in another of its aspects, to a security paper comprising a fibrous substrate and at least one security thread integrated into windows, the fibrous substrate having at least one region of variable opacity constituted by a watermark or multiton pseudo-watermark located at least partially at a bridge of the fibrous substrate extending between two successive windows along the at least one security thread.

The one or more watermarks or pseudo-watermarks multitons can be rasterized, it is in particular a watermark known as "multiton effect".

The fibrous substrate may comprise a plurality of watermarks or pseudo-watermarks multitons. According to this aspect of the invention, multiton watermarks or pseudo-watermarks can exclusively be located at the bridges. The son or son may be lined at each window by a watermark or pseudo-watermark multiton. Alternatively, the multiton watermarks or pseudo-watermarks can border the son (s) at a window, all n windows, n being an integer greater than one.

The characteristics described above, in particular with regard to the substrate and the safety wire or wires, are also applicable to these other aspects of the invention.

The subject of the invention is also a method for manufacturing a security paper comprising at least one integrated security thread in windows in a substrate, comprising the step of bringing the at least one security thread into contact with a forming fabric of a paper jet, comprising one or more first training zones one or more windows, and one or more second formation areas of one or more bridges extending between the windows on the formed paper, and at least one openwork mask having solid regions disposed as the portions of lower opacity a multiton, or screened, watermark, this openwork mask being disposed in a second zone.

The windows can be formed by protrusions protruding from the training fabric.

The subject of the invention is also a method of forming a security paper comprising at least one integrated security thread in windows, using a fabric for forming a papermaking substrate, which is preferably embossed, and which has an alternation of raised reliefs and protruding reliefs, which is characterized by the fact that at least one perforated mask for the formation of a multitone or woven filigree is provided in a recessed relief, with preferably the at least one security thread not coming into contact with the mask if it is disposed in a recessed relief.

• amener au moins un fil de sécurité au contact d'une toile de formation d'un jet de papier, comportant une ou plusieurs premières zones de formation d'une ou plusieurs fenêtres ; et une ou plusieurs zones de formation d'un ou plusieurs ponts s'étendant entre les fenêtres sur le papier formé, pour avoir un papier avec au moins un fil de sécurité intégré, et
• embosser un pont pour former un filigrane, notamment un filigrane multiton.

The invention also relates to a method of manufacturing a security paper comprising the steps of:

• bringing at least one security thread into contact with a web for forming a paper jet, comprising one or more first formation zones of one or more windows; and one or more forming zones of one or more bridges extending between the windows on the formed paper, to have a paper with at least one integrated security thread, and
• Emboss a bridge to form a watermark, including a multitone watermark.

• la figure 1 représente schématiquement, en vue de face, le recto d'un document sécurisé comprenant un exemple de papier de sécurité,
• la figure 2 illustre de façon schématique un exemple de disposition des régions d'opacité variable,
• les figures 3 à 5 sont des vues analogues à la figure 2, de variantes de réalisation selon l'invention,
• les figures 6A à 6C représentent des variantes de disposition des régions d'opacité variable relativement au fil de sécurité,
• les figures 7A à 7C représentent des exemples, parmi d'autres, de points de trame pouvant être présents au sein de régions tramées d'opacité variable,
• la figure 8 illustre, de façon schématique et partielle, une machine de fabrication du papier selon l'invention,
• les figures 9 à 11 représentent des exemples de disposition des masques ajourés sur la toile de formation,
• les figures 12 à 14 sont des sections respectivement selon XII-XII, XIII-XIII et XIV-XIV de la figure 1,
• les figures 15 et 16 sont des sections respectivement selon XV-XV et XVI-XVI de la figure 3,
• la figure 17 illustre en coupe un exemple de région d'opacité variable superposée au fil de sécurité,
• la figure 18 illustre en vue de face, observé en lumière réfléchie, une variante de papier de sécurité,
• la figure 19 est une section selon XIX-XIX de la figure 18,
• la figure 20 est une vue analogue à la figure 18 représentant une variante de papier de sécurité,
• la figure 21 est une section selon XXI-XXI de la figure 20,
• la figure 22 est une section selon XXII - XXII de la figure 18,
• la figure 23 est une vu analogue à la figure 2, d'une variante de réalisation,
• la figure 24 est une section selon XXIV - XXIV de la figure 23,
• la figure 25 est une section selon XXV - XXV de la figure 23,
• les figures 26 et 27 représentent deux autres exemples d'agencement du fil de sécurité et des régions d'opacité variable, et
• la figure 28 illustre un point de trame sous forme de motif.

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 schematically represents, in front view, the front of a secure document including an example of security paper,
• the figure 2 schematically illustrates an example of arrangement of regions of variable opacity,
• the Figures 3 to 5 are similar views to the figure 2 , variants of embodiments according to the invention,
• the Figures 6A to 6C represent alternative arrangements of regions of variable opacity relative to the security thread,
• the Figures 7A to 7C are examples, among others, of raster points that may be present within raster regions of variable opacity,
• the figure 8 illustrates, schematically and partially, a papermaking machine according to the invention,
• the Figures 9 to 11 represent examples of the arrangement of openwork masks on the training fabric,
• the Figures 12 to 14 are sections respectively according to XII-XII, XIII-XIII and XIV-XIV of the figure 1 ,
• the Figures 15 and 16 are sections respectively according to XV-XV and XVI-XVI of the figure 3 ,
• the figure 17 illustrates in section an example of region of variable opacity superimposed on the security thread,
• the figure 18 illustrates in front view, observed in reflected light, a variant of security paper,
• the figure 19 is a section according to XIX-XIX of the figure 18 ,
• the figure 20 is a view similar to the figure 18 representing a variant of security paper,
• the figure 21 is a section according to XXI-XXI of the figure 20 ,
• the figure 22 is a section according to XXII - XXII of the figure 18 ,
• the figure 23 is a view similar to the figure 2 , an embodiment variant,
• the figure 24 is a section according to XXIV - XXIV of the figure 23 ,
• the figure 25 is a section according to XXV - XXV of the figure 23 ,
• the Figures 26 and 27 represent two other examples of arrangement of the security thread and regions of variable opacity, and
• the figure 28 illustrates a raster point in the form of a pattern.

We have shown on figures 1 and 12 a secure document 1, such as a bank note, made from a security paper 4 comprising a fibrous substrate 8 incorporating a security thread 7 integrated in windows.

The security paper 4 has windows 10 in which the security thread 7 is at the surface of the substrate 8 and the bridges 13 where the security thread 7 is covered by the fibrous substrate 8.

The fibrous substrate 8 comprises at least one region of variable opacity 16, in this case a succession of such regions 16 arranged exclusively at the level of the windows 10 in the example of FIG. figure 1 . These regions 16 make it possible in particular to draw the attention of the observer to the security thread 7, when the document 1 is observed in transmitted light, for example according to the arrow O of the figure 12 . The regions of variable opacity 16 consist of raster regions in the example under consideration.

The windows 10 may be formed by at least a portion of a hollow relief 17 of the fibrous substrate 8 and the bridges 13 may be formed by a solid portion of the fibrous substrate 8, for example at the same height in the direction of the As a variant, the bridges 13 may be formed by a portion of a raised projection of the fibrous substrate with respect to the vellum, in particular by a portion of greater height in the thickness direction than the vellum.

As illustrated on the figure 13 , the recessed relief 17 may be wider w + d1 + d2 than the wire w .

The security thread 7 extends continuously between the two opposite edges 19 and 22 of the security paper 4, preferably the long sides of the document.

As illustrated on Figures 1 and 2 , the regions of variable opacity 16 extend on either side of the wire at each window 10. Preferably, the regions of variable opacity 16 extend only in the hollow relief 17.

The regions of variable opacity 16 do not extend in the longitudinal direction X of the wire 7 beyond the corresponding windows 10, and the bridges 13 are completely devoid of them in this example.

For example, it has been reported, on the figure 2 , by the abscissae x _d and x _a , the extent along the X axis of one of the bridges 13, by the abscissae x _a and x _b that of an adjacent window 10, and by the abscissae x _b and x _c that of the next bridge 13.

It can be seen that the variable opacity region 16 associated with the window 10 between the abscissae x _a and x _b does not extend along the X axis beyond this window.

In the transverse direction, the regions of variable opacity 16 may extend a distance d from the apparent edge of the wire 7 in the window 10, which may be greater than the width w of the wire 7.

For example, w is between 3 and 8 mm and d is between 0 and 37 mm.
The regions of variable opacity 16 may extend laterally at a recessed relief 17 over a distance p greater than the width w of the wire 7, as illustrated, the wire being for example centered or not with respect to the to regions of variable opacity bordering it.

In the case where the wire 7 is bordered on both sides by a region of variable opacity 16, as illustrated in FIGS. Figures 1, 2 and 13 in particular, the two regions 16 may not necessarily extend over the same distance transversely from the apparent edge of the wire 7. For example, with the notations present on the figure 13 , d ₁ > d ₂ or d ₂ > d ₁ .

Preferably, all the windows 10 are each associated with two regions of variable opacity 16 visible on either side of the wire 7, as illustrated in FIG. figure 2 , but it may be otherwise, and in particular there may be only one region of variable opacity 16 associated with a single window 10 on one side of the wire, as illustrated in FIG. Figure 6C .

It is possible to have all regions of variable opacity 16 located on the same side of the wire or regions alternately on either side of it.

In the example of the figure 2 , the regions of variable opacity 16 are screened and in particular constituted by screened clear watermarks and extend in the hollow relief 17.

The regions of variable opacity 16 visible on either side of the wire in the direction perpendicular to the X axis may have identical raster points 28 and represent substantially the same patterns, being for example obtained with the aid of FIG. the same mask, as detailed below.

Preferably, all regions of variable opacity 16 have identical weft points 28 and represent substantially the same pattern.

The spacing t along the X axis between two successive bridges 13, namely the length of a window 10, is for example between 3 and 50 mm. The length m of a bridge 13 along the X axis is for example between 3 and 50 mm.

According to the invention, which corresponds to the variant illustrated in figures 3 , 15 and 16 , the regions of variable opacity 16 are arranged on the bridges 13 and are at least partially superimposed on the security element 7.

In this case, the regions of variable opacity 16 do not extend along the X axis beyond the bridges 13 and the zones bordering laterally the wire at the level of the windows 10 are devoid of them, as illustrated in FIG. figure 16 .

The regions of variable opacity 16 preferably extend over the entire length m of the bridge 13 along the X axis. As a variant illustrated on FIGS. Figures 23 and 24 , the regions of variable opacity 16 may extend over a bridge 13 along the X axis over a distance z less than the length m of a bridge 13 along the axis X. As a result, the opacity region variable 16 does not extend along the X axis over the entire length m of the bridge 13.

Preferably, all the bridges 13 have a region of variable opacity 16. But it may be otherwise, and in particular, there may be only one region of variable opacity 16 arranged on a single bridge 13, all the n bridges, with for example n equal to two.

The regions of variable opacity 16 may extend laterally at a bridge 13 over a distance p greater than the width w of the wire 7, as illustrated, the wire 7 being for example centered or not with respect to each halftone region. 16.

As illustrated on Figures 23 and 25 , the region or regions of variable opacity 16 may be arranged on a bridge 13 and the distance p relative to the lateral extension of the region or regions of variable opacity 16 may be less than the extent k of the bridge 13 perpendicular to the X axis, especially when the bridge 13 forms a vellum relief.

Regions of variable opacity 16 may be raster regions of identical appearance.

In the variant illustrated on the figure 4 , regions of variable opacity 16a extend along the X axis at the level of the windows 10 and regions of variable opacity 16b are arranged at the level of the bridges 13.

In the example considered, a window 10 extends between the abscissae x _a and x _d along the X axis of the wire and one of the adjacent bridges 13 between the abscissae x _d and x _e .

The regions of variable opacity 16a extend on either side of the window 10 between the abscissae x _b and x _c , with x _a <x _b and x _c <x _d . For example, we have: $$\left|{\mathrm{x}}_{\mathrm{at}}-{\mathrm{x}}_{\mathrm{b}}\right|\le \left|{\mathrm{x}}_{\mathrm{b}}-{\mathrm{x}}_{\mathrm{vs}}\right|\mathrm{and}\left|{\mathrm{x}}_{\mathrm{d}}-{\mathrm{x}}_{\mathrm{vs}}\right|\le \left|{\mathrm{x}}_{\mathrm{vs}}-{\mathrm{x}}_{\mathrm{b}}\right|$$

Regions of variable opacity 16a and 16b may have raster points, especially raster points 28a and 28b, of the same shape or, alternatively, raster points of different shapes.

Preferably, all the bridges 13 have a region of variable opacity 16b. Preferably, all regions of variable opacity 16b arranged on the bridges 13 are constituted by screened clear watermarks. The regions of variable opacity 16b present on the bridges 13 may all be identical 28b frame points and represent substantially the same pattern.

Similarly, the wire is lined at the windows 10 by two regions of variable opacity 16a. Preferably, all the regions of variable opacity 16a at the windows 10 are constituted by screened clear watermarks. The regions of variable opacity 16a at the windows 10 may all be identical frame points 28a and represent substantially the same pattern.

Preferably, the regions of variable opacity 16a and 16b have the same transverse dimension p, and the regions of variable opacity 16b extend continuously transversely to the wire 7.

Preferably, all the windows 10 are of the same shape, in particular rectangular, and of substantially the same dimensions.

Preferably, all the bridges 13 are of identical shape, in particular rectangular, of substantially the same dimensions.

In the variant shown in figure 5 , the fibrous substrate 8 has regions of varying opacity of different aspects at the windows 10, with variable regions of fancy opacity 23 and 24.

The substrate 8 comprises identical regions 25a, which extend along the axis X each a distance u , at the level of the windows 10, and regions 25b at the bridges 13, which extend over a distance z .

The substrate 8 also comprises a fancy variable opacity region 23 between two bridges 13, instead of a region 25a. We thus observe the succession, along the wire 7, a framed region 25a, a bridge 13, the framed region 23, a bridge 13, and a new framed region 25a.

The region 23 has for example substantially the same extent u along the X axis as the regions 25a but an upper width o .

We see on the figure 5 also that the regions 25a may be rectangular in outline while the region 23 has a different shape, for example hexagonal.

The regions of variable opacity present on the bridges 13 may comprise, as illustrated, identical regions 25b and at least one fancy variable opacity region 24 all the n bridges 13 for example, with n being strictly greater than one.

For example, the region 24 has the same extent z along the X axis as the regions 25b, but extends perpendicularly to the X axis over a smaller distance q . The regions of variable opacity 25b are for example of rectangular contour while the fancy region 24 is for example of oblong contour with rounded ends, as illustrated.

The windows 10 and / or the bridges 13 may be of other than rectangular contour, as illustrated in FIG. Figure 6A .

The windows 10 and / or the bridges 13 may have rectilinear transverse edges 26, as illustrated in FIG. Figure 6A , or curves, as illustrated on the Figure 6B .

Regions of variable opacity are preferably screened.

Within a region of variable opacity, the raster points 28 may be of polygonal shape, in particular rectangular or square, as shown in FIG. Figure 7A , oblong, as illustrated on the Figure 7B or circular, as shown in Figure 7C .

The raster points 28 can all be identical in the same region of variable opacity, as illustrated in FIGS. Figures 7B and 7C or be different, as shown on the Figure 7A .

The region of variable opacity may be formed by identical grid points which succeed each other at regular intervals in one or two directions of the plane. The largest dimension of a weft dot is for example between 0.2 and 1.0 mm. The smallest dimension of a raster point, especially when the raster points consist of lines, is for example between 0.2 and 1.0 mm.

In a variant, the region of variable opacity may be formed by frame points 28 of variable size which may or may not succeed each other at variable intervals.

The region of variable opacity 16 may be a rasterized watermark, including multiton effect as described in the application EP 1 122 360 .

Alternatively, the region of dithered variable opacity may form an identifiable pattern, such as a portrait, an alphanumeric character, an animal, a plant, a monument, or any other motif.

Alternatively, the regions of variable opacity 16 may not be rasterized but be watermarks or pseudo-watermarks, preferably multitons. The watermarks or pseudo-watermarks can be made by embossing or as described in the application WO 2011/117828 .

The bridges 13 may further be formed by protruding reliefs and the windows 10 may be of the same height in the thickness direction as the vellum 9. The regions of variable opacity 16 are then arranged on the protruding relief or in the space between two protruding reliefs.

The security paper can be made with a round-shaped paper machine as shown in FIG. figure 8 . Such a machine comprises a web 33 for forming the paper which rotates in a vat 40 where there is a suspension of paper fibers. The forming fabric is embossed and has an alternation in the circumferential direction of recessed reliefs 38 and projecting reliefs 36. The security thread 7 is brought into contact with the forming fabric 33 and is unwound to accompany the rotation of it. The papermaking fibers fill the cavities 43 formed between the wire 7 and the bottom of the recessed reliefs 38, where the wire is not in contact with the forming fabric 33. Thus, the cavities 43 allow the formation of the bridges 13. The security thread 7 comes into contact with the protruding reliefs 37 and locally hinders the accumulation of paper fibers on the fabric 33, which leads to the formation of the windows 10.

In the configuration illustrated in figure 8 it is sought to produce watermarks at the bridges 13 by virtue of the presence in the reliefs 38 of perforated masks 39 fixed to the surface of the forming fabric 33. These masks 39 locally modify the permeability of the fabric 33 and allow the formation of a watermark.

The openwork masks 39 used are for example made by laser sintering according to the SLM technique, as disclosed in the application WO 2011/117828 A1 for example.

The thickness of the openwork masks 39 is for example between 0.2 and 0.8 mm.

We obtain with the arrangement of the masks 39 illustrated in the figure 8 a result which corresponds for example to that represented in figure 3 , where only the bridges 13 comprise a region of variable opacity 16.

The figure 9 corresponds to the configuration illustrated in the figure 8 .

To obtain a result such as that illustrated in figure 2 the masks 39 are disposed on the protruding reliefs 36 of the forming fabric 33, as illustrated in FIG. figure 10 . The hollow reliefs 38 are devoid of it, which allows the formation of bridges 13 of uniform thickness. Preferably, the projecting reliefs 36 are wider than the security thread 7. The masks 39 locally counteract the accumulation of paper fibers and lead to the formation of watermarks corresponding to the regions of variable opacity 16. Each mask 39 presents a dimension p, measured perpendicular to the axis X. Where the wire 7 comes into contact with the mask 39, the paper fibers can not accumulate and the window 10 is formed. The mask 39 is preferably wider than the thread 7 and less wide than the projecting relief 36.

To obtain the results illustrated in Figures 2 or 3 , respectively, all the projecting reliefs 36 and all the recessed reliefs 38 are provided with masks 39. In a variant, and to reduce the manufacturing time of the fitted fabric, it is possible to provide a mask 39 only protruding relief 36 or recessed 38 of n , with n > 1 .

In a variant of the manufacturing process, the forming fabric 33 is devoid of projecting reliefs 36 and recesses 38 and the relief necessary for the formation of the bridges 13 is obtained thanks to the thickness of the masks 39 on which the thread 7 comes in support. The presence of the masks prevents the accumulation of paper fibers in the areas where they are in contact with the security thread 7, thus forming windows.

In the variant illustrated on the figure 11 , the forming fabric 33 is equipped with masks 39a and 39b preferably different, respectively for the formation of watermarks at the windows 10 and the bridges 13. The result obtained is for example that illustrated in FIG. figure 4 with regions 16a at windows 10 and regions 16b at bridges 13.

We illustrated at the figure 17 the possibility for the region of variable opacity 16, at a bridge 13, to include recesses 51 not going to the wire 7 and others deep enough to reach it. It may be advantageous if the yarn 7 comprises at least one layer 52 of a luminescent or colored compound, for example deposited by printing on the wire support film 55. In this case, the presence of the recesses 50 and 51 can promote the excitation and / or the observation of the luminescent or colored layer 52.

We have illustrated Figures 18 to 21 , the possibility that the bridges 13 do not completely cover the security thread 7 as described in the application EP 2 260 142 .

The fibrous substrate at the bridges may not completely cover the safety wire.

As illustrated on Figures 18 and 19 at the bridges, the fibrous substrate may not completely cover the safety wire and leave the apparent wire at the center of the bridge 13.

The bridge 13 may comprise two parts 13a and 13b each of which partially cover a corresponding zone 41 and 43 of the security thread 7. The central portion 45 of the security thread 7 remains visible.

The regions of variable opacity can be made on the bridges 13, as illustrated, or border the wire at the windows 10. Preferably, the portions 13a and 13b of the bridges 13 symmetrically cover the safety wire with respect to the axis As a variant, the parts 13a and 13b are asymmetrical. The extent of overlap q of each portion 13a and 13b in the direction perpendicular to the X axis is for example greater than or equal to 1 mm or between 1 and 6 mm.

In the variant illustrated on the Figures 20 and 21 , the bridges 13 partially cover the security thread from a single edge thereof. All bridges 13 may overlap the wire alternately from one edge of the wire and the opposite edge.

Alternatively, the security paper 4 may comprise a plurality of security son 7, preferably two security son 7. The security son 7 may be juxtaposed or not, and be integrated in the same windows 10 or not extending for example, side by side in the same window 10. The presence of two son has the advantage over a wider wire to facilitate the dripping during the manufacture of security paper 4. The region of variable opacity 16 may extend over a bridge 13 of the fibrous substrate 8 superimposed on the security threads 7 and situated between two successive windows 10 along the security threads 7.

In the variants of Figures 26 and 27 , the region of variable opacity 16 extends along several bridges or windows.

More particularly, on the figure 26 it can be seen that the region of variable opacity 16 appears to border several windows 10, on either side of the wire, in zones 16a.

The area 16e of variable opacity which connects two areas 16a located on the same side of the wire 7, for example the right side, extends at a non-zero distance r of the wire.

The zone 16e located on the opposite side of the wire, namely left in the example in question, extends at a distance from the wire 7 which may be the same or different.

The entire region of variable opacity 16 can reproduce a pattern, for example alphanumeric, for example the number 2 as illustrated. This pattern can be found elsewhere on the paper or wire, for example by being printed or engraved.

The region of variable opacity 16 may be a watermark, especially multiton, or a pseudo watermark. If necessary, the pattern of the raster point is the same as that of the region of variable opacity.

On the figure 27 , the region of variable opacity 16, for example a watermark, especially multiton, or a pseudo watermark, is superimposed on the wire 7 in several disjoint locations along the wire. Two areas where the region of variable opacity is superimposed on the wire may be connected together by another region of the region of variable opacity, which extends for example at a non-zero distance s of the wire, as illustrated.

The region of variable opacity may form a pattern, including an alphanumeric pattern or symbol found elsewhere on the paper or wire, in this case the number 6 in the illustrated example.

We illustrated on the figure 28 the possibility of making a raster point of the region of variable opacity in the form of an alphanumeric pattern, which is found for example elsewhere on the document. These are, for example, the initials of a central bank or the value of the break.

It is also possible to combine, in non-illustrated variants, features of the examples of the Figures 26 and 27 with, for example, for the same region of variable opacity at the same time zones which are superimposed on the wire, others which seem to border the wire, and still others which extend at a non-zero distance from the wire along the wire. of it.

The invention is not limited to the illustrated examples. In particular, the regions of variable opacity, including raster, can be obtained otherwise than using watermarks. For example, the regions of variable opacity are made using a laser that makes recesses in the papermaking substrate. The depth of these recesses may be sufficiently small to maintain a certain thickness of substrate between the wire 7 and the bottom of the recess, which may reduce the risk of degrading the wire 7 with the laser during the formation of the recess. .

The regions of variable opacity can also be made by localized localization of the fibrous substrate using suitable substances, such as oily compounds.

The particularities of the examples illustrated can be combined within non-illustrated variants. The arrangement of regions of variable opacity may be different.

Regions of varying opacity may not be present at all windows or on all decks.

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

Regions of varying opacity may not be present at all windows or on all decks.

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

Claims (14)

1. Security paper comprising a fibrous substrate (8) and at least one security thread (7) incorporated into windows in this fibrous substrate, the security thread or threads preferably comprising a supporting film made of plastic, particularly thermoplastic material, the fibrous substrate having at least one region of variable opacity (16; 16b; 25b, 24) at least partly extending over a bridge (13) of the fibrous substrate situated between two successive windows (10) along the security thread, the region of variable opacity (16; 16b; 25b; 24) at least partly overlapping the security thread (7).
2. Security paper according to claim 1, the region or regions of variable opacity being situated exclusively at the level of the bridge or bridges (13) or the fibrous substrate having at least one region of variable opacity (16; 16a; 25a; 23) appearing to border the thread or threads at the level of at least one window (10), when the paper is observed in transmitted light, the fibrous substrate having a region of variable opacity for each window (10) in particular, which extends on both sides of the thread or threads (7) at the level of this window, or the fibrous substrate having a region of variable opacity every n windows (10), with n being a whole number greater than 1.
3. Paper according to claim 1 or 2, the fibrous substrate having a region of variable opacity at the level of each bridge (13) or the fibrous substrate having a region of variable opacity every n bridges (13), with n being a whole number greater than one.
4. Paper according to any one of the previous claims, each region of variable opacity

   i) being a woven region, with weaves of points or lines in particular, the points being able to be motifs such as alphanumerical characters, the woven region or regions of variable opacity preferably each being made up of a watermark comprising a set of light or dark areas arranged to form a woven image in particular, comprising woven points (25), particularly woven points in the form of alphanumerical motifs, particularly identical in form and preferably arranged at regular intervals, and/or

   ii) being made up of a watermark, a pseudo-watermark and/or micro-perforations and/or

   iii) comprising micro-perforations of the fibrous substrate made by laser and/or

   iv) having at least one recess (50) crossing the fibrous substrate, letting the thread or threads (7) appear, or the thickness of the substrate (8) covering the thread or threads at the level of a region of variable opacity situated on a bridge (13) never being zero.
5. Security paper according to any one of the previous claims, the security thread or threads (7) having luminescent, preferably fluorescent, optical properties, the security thread having at least one luminescent area overlapping an area of less opacity of the region of variable opacity in particular.
6. Security paper according to any one of the previous claims, comprising regions of variable opacity at the level of the windows (10) and regions of variable opacity at the level of the bridges (13), preferably with an interval separating a region of variable opacity situated at the level of a window (10) and a region of variable opacity situated at the level of a bridge (13), the security paper preferably having at least one region of variable opacity at the level of a window (10) that has a different appearance from that of a region of variable opacity at the level of a bridge (13).
7. Security paper according to any one of the previous claims, having at least two regions of variable opacity with the same appearance, associated with two windows or two bridges respectively, and a third region of variable opacity (23; 24), associated with a window or a bridge with a different appearance from that of the other windows.
8. Security paper according to any one of the previous claims, the bridges each being formed by at least one part of a raised area of the substrate, the region or regions of variable opacity partly extending over the bridges, extending longitudinally and/or transversely over a distance that is smaller than that of the bridges in particular.
9. Security paper according to any one of the previous claims, the region of variable opacity overlapping the thread at several unconnected locations along the thread, particularly two areas where the region of variable opacity overlaps the thread being linked together by another area of the region of variable opacity.
10. Paper according to any one of the previous claims, the region of variable opacity appearing to border several windows, the region of variable opacity appearing to border the windows on both sides of the thread in particular.
11. Security document comprising a security paper according to any one of the previous claims.
12. Method for manufacturing a security paper as defined in any one of claims 1 to 10, comprising the step consisting of bringing at least one security thread (7) into contact with a forming fabric (33) for a ply of paper, comprising several first areas (38) for forming several windows (10) and one or several second areas (37) for forming one or several bridges (13) extending between the windows (10) on the paper formed, and at least one openwork mask (39) having solid regions arranged like the parts with lower opacity of a region of variable opacity, this openwork mask being arranged in one of the second areas, the openwork mask (39) at least partly overlapping the security thread (7), the windows (10) being formed by raised areas (37) of the forming fabric (33) in particular, the forming fabric preferably being a fabric with a round shape comprising depressed areas (38) defining the areas for forming bridges (13), in which openwork masks (39) are arranged for forming regions of variable opacity in particular.
13. Process according to claim 12, the fabric (33) comprising at least one openwork mask (39) having solid regions arranged like the parts with lower opacity of a region of variable opacity, this openwork mask being arranged in one of the first areas (38), particularly on a raised area (37) of the forming fabric.
14. Process for manufacturing a security paper according to any one of claims 1 to 10,

    i) in which at least one recess (51, 50) is made in the substrate at the level of the bridges (13) extending between the windows (10) using a laser, at least one of the recesses (51, 50) at least partly overlapping the security thread (7), or

    ii) comprising the step consisting of: bringing at least one security thread (7) into contact with a forming fabric (33) for a ply of paper, comprising several first areas (38) for forming several windows (10) and one or several second areas (37) for forming one of several bridges (13) extending between the windows (10) on the paper formed, to have a paper with at least one security thread (7) incorporated, and embossing a bridge (13) to form a watermark, particularly a multitone watermark.

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