FR2901286A1 - METHOD FOR MANUFACTURING SHEET MATERIAL COMPRISING AT LEAST ONE FIBROUS LAYER AND SECURITY AND / OR DECORATIVE ELEMENTS - Google Patents

Abstract

A process for manufacturing a material in sheet form, comprising at least one fibrous layer and a plurality of security and/or decorative elements, the process comprising at least one of the following steps: the security and/or decorative elements are sprayed onto one face of the fibrous layer, which is running along a predetermined direction, especially when the fibrous layer is still wet, so as to form at least one continuous pattern having at least one edge, approximately along the run direction, not entirely parallel to the run direction, and a pattern comprising a succession of separate zones, and security and/or decorative elements of at least two different types and/or having a variable concentration are sprayed onto one face of the fibrous layer, especially when it is still wet.

Description

The subject of the present invention is in particular a manufacturing method

  a sheet material comprising at least one fibrous layer. US Pat. No. 6,270,625 discloses a method for manufacturing a security paper comprising colored strips, comprising the following steps: feeding a head box with a paper pulp via a plurality of dotted lines; feeding - selectively introducing one or more coloring agents into some of the feed lines, - depositing the paper pulp on a paper forming web.

  This process makes it possible to obtain several colored bands in the mass of the paper. Safety elements can be selectively introduced into one of the pulp distribution lines. A disadvantage of the method described above is that the security elements are buried in the mass of the paper, which can prevent or make difficult their observation or detection. US Pat. No. 5,989,389 discloses a method for producing a security paper such as a bank note, consisting in depositing on a rotating roll cylinder two types of fibrous suspensions, one of which is intended to form opaque zones. 20 and the other substantially transparent areas. The fiber suspension forming the transparent areas may contain a filler, a binder or a transparent agent, and be dispensed with a nozzle into contact with the paper forming fabric. Patent GB 2,309,710 discloses a single-purpose security paper incorporating security elements such as metal or magnetic particles. The paper is formed in contact with a rotating roll barrel and the particles are introduced into the forming fibrous layer by means of nozzles spaced from each other and arranged at the location where the fibrous layer begins to form at contact of the training web. Patent GB 696,673 still discloses a process for producing a paper, comprising the step of injecting, by means of a syringe, a material such as an ink into the mass of the forming fibrous layer.

  The patent application EP 490 825 discloses a security paper such as a bank note, comprising a plurality of adjacent strips each formed by a coating of an iridescent pigment. The iridescent coating is deposited by coating with the aid of a rotating roller: either by depositing the product on the roll which transfers the product onto the moving paper, or by direct application of the product on the paper, upstream of the rotating roller.

  The international application WO 2004/087437 discloses a security paper such as a bank note, comprising two adjacent iridescent strips deposited on the paper, for example using the method described in the aforementioned EP 498 825, or by coating , printing, rotogravure, flexography or offset printing. The paper further comprises an optically variable element such as a hologram deposited by hot pressing on at least one of the iridescent strips. The manufacture of a security paper according to the application EP 490 825 or the application WO 2004/087437 requires the implementation of steps outside the papermaking line, which can increase the final cost of the paper. Security and / or security documents having security features to protect these documents against tampering or counterfeiting are generally known. Among the security elements, some are detectable to the naked eye, in visible light, without the use of a particular device. These security elements comprise for example colored fibers or boards. These security elements are said to be first level. Other types of security elements are detectable only with a relatively simple device such as a lamp emitting in the ultraviolet or infrared. These security elements comprise for example fibers, boards or particles. These security elements may be visible to the naked eye or not, being for example luminescent under a Wood lamp emitting at a wavelength of 365 nm. These elements can still be for example of the thermochromic or photochromic type.

  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. The automatic detection of the signal makes it possible to authenticate, if necessary, the document. These security elements comprise for example tracers in the form of active material, particles or fibers, capable of generating a specific signal when these tracers are subject to optoelectronic excitation, electrical, magnetic or electromagnetic. These security elements are said to be third level. The security elements mentioned above may be incorporated in the mass of the paper or on the surface thereof. When all paper is to be marked with security features, the amount of paper used may be relatively large, which may increase the final cost of the paper. When security features are incorporated into the mass of paper, their observation with the naked eye, when it comes to first-level security elements, or their detection, when dealing with elements of Third-level safety can be difficult if not impossible, for example due to the presence of cellulosic fibers or dyes which can act as a filter. Furthermore, depending on the papermaking process, especially during a mass introduction, a certain amount of security elements can be unretained, not being finally incorporated in the paper.

  The present invention aims in particular to provide a novel method of manufacturing a sheet material comprising at least one fibrous layer comprising security and / or decorative elements. The expression sheet material may denote in the description and the claims a fibrous sheet based on cellulosic and / or synthetic fibers. A sheet material may, for example, have a relatively small thickness, especially less than or equal to 3 mm, for example equal to about 100 m, and be at least partially or even entirely flexible. The sheet material may be of the monojet or multijet type, in particular bijet. In an exemplary implementation of the invention, the sheet material may be packaged in a reel, in particular before being cut into the desired format. The object of the invention is, according to one of its aspects, a method of manufacturing a sheet material comprising at least one fibrous layer and a plurality of security and / or decorative elements, the method comprising one at least one of the following steps: projecting the security and / or decorative elements onto one face of the fibrous layer, traveling in a predetermined direction, particularly when the fibrous layer is still wet, so as to form at least one of a continuous pattern having at least one edge, substantially in the direction of travel, not entirely parallel to the direction of travel and a pattern comprising a succession of disjoint areas, - projecting on one face of the fibrous layer, especially when the latter is still wet, safety and / or decorative elements of at least two different types and / or having a variable concentration. Thanks to the invention, the amount of security and / or decorative elements useful for the manufacture of sheet material can be relatively small. For example, it is possible to project a stream of security and / or decorative elements over a small area of the fibrous layer.

  In addition, the invention makes it possible to limit any loss of material. When the security and / or decorative elements are projected on the fibrous layer still wet, it is possible to improve the attachment of these elements to the fibrous mass. The projection of the security and / or decorative elements on the fibrous layer can be carried out in line, downstream of a wet part of the paper machine used to form the fibrous layer, in particular before passing over the press section, or even before crossing over a dryer assembly of the paper machine. The deposition of the security and / or decorative elements can be facilitated because performed on the paper machine itself, which can allow in particular to be able to identify the pattern (s) of security and / or decorative elements with respect to other safeties present in the fibrous layer, for example a security thread or a watermark.

  The areas of the fibrous layer covered by the security and / or decorative elements may have a fuzzy or sharp outline, depending on the type of security and / or decorative elements deposited and the projection mode. A fuzzy outline may make it more difficult to copy the sheet material by printing. In an exemplary implementation of the invention, the security and / or decorative elements are dispersed beforehand in a fluid such as water, optionally with one or more additives, for example a binder or a retention agent for facilitate the attachment of the security and / or decorative elements on the fibrous layer 10 or a dispersing agent to facilitate the dispersion of the security and / or decorative elements. The mixture thus obtained can be projected onto the fibrous layer using a pressurized fluid, especially a pressurized gas such as compressed air. The method according to the invention may comprise at least one of the following steps: dispersing safety and / or decorative elements dispersed in a fluid, especially when the size of the security and / or decorative elements is sufficiently low, spraying the security and / or decorative elements on the fibrous layer. The projection of the security and / or decorative elements can be carried out by means of a projection system comprising one or more projection nozzles. For example, the projection of the security and / or decorative elements may be carried out with a plurality of projection nozzles fed with security and / or decorative elements of different types to form adjacent or entangled patterns. The projection system comprises, if desired, in particular depending on the type of security and / or decorative elements, a device for atomizing the liquid medium in order to create very small droplets. The projection system may comprise at least one nozzle that can be fed alternately with at least two safety and / or decorative element reservoirs and capable of alternately projecting the security and / or decorative elements from the two reservoirs.

  Where appropriate, the projection system may comprise a jet splitter arranged to divide, at the outlet of a nozzle, a jet in several streams, possibly with spaces between them to create one or more patterns. Preferably, the security and / or decorative elements are projected by forming at least one jet, the method comprising the following steps: - driving the fibrous layer in displacement in a predetermined direction, - moving the jet in a non-parallel direction to the direction of displacement of the fibrous layer, in particular oscillating manner. With the aid of security and / or decorative elements, the invention makes it possible to produce a wide variety of patterns. For example, the security and / or decorative elements may be projected onto the fibrous layer continuously or, alternatively, intermittently, in particular periodically with a predetermined frequency. The projection system may, where appropriate, be associated with a control system arranged to control the projection of the security and / or decorative elements, in particular the frequency of the projections, the direction of the projections, the projection force of the elements of the projection. safety and / or decorative, volume, flow, shape and / or dimensions of a stream of security and / or decorative elements. The control system may comprise at least one of a pneumatic device and a peristaltic device, or a combined pneumatic / peristaltic device, arranged to control the frequency and the projection volume. In particular, a pneumatic pump can be arranged to regulate the frequency and the volume of the projections by a compressed air system whose flow and pressure can be easily controlled. The frequency and the volume of the projections in a peristaltic pump depend in particular on the configuration of the pump (number of rotors which create the projection pressure for example). The control system may comprise, if desired, a centrifugal pump 30 or a mono-pump, particularly in the case of continuous pattern formation, allowing a precise flow control and regular, including reproducible and constant over time.

  The security and / or decorative elements may be projected by forming at least one jet having, in cross section, a shape selected from: a straight line segment, a corner such as a right angle corner, a triangle, a rectangle or a square, a non-rectilinear curve such as an arc, a circle, an ellipse, an oval portion or an S, a disk, a wavy shape. The jet may be hollow or full. In an exemplary implementation of the invention, the security and / or decorative elements are projected onto the fibrous layer so as to be dispersed over only a portion of the corresponding face of the fibrous layer, the elements not covering the all of this face. The method may comprise, if desired, the following step: projecting, simultaneously or successively, in particular alternately, on the fibrous layer, security and / or decorative elements of at least two different types, for example to form entangled patterns that are totally or partially overlapping, adjacent or separated. The pattern (s) made on the sheet material may define, if desired, an identification element of the sheet material. The motif (s) may define, where appropriate, a decorative motif or a specific motif of a trade mark.

  Security and / or decorative elements of different types may for example have different colors, while being of identical nature. This or these patterns include for example one of the following: an alphanumeric character, a symbol, a geometric shape, a logo, a drawing, this list is not limiting.

  This or these patterns may be alternated or not, possibly with a predetermined pitch, and / or juxtaposed or superimposed. The method may comprise the following step: projecting, for example superimposedly, adjacent or separately, simultaneously or successively, in particular alternately, on the fibrous layer, security and / or decorative elements with different flow rates, in particular to form on the fibrous layer areas with different amounts of security and / or decorative elements per unit length or area.

  It is possible to project on the fibrous layer only one type of security and / or decorative elements or a mixture of several types of security and / or decorative elements, for example elements of different levels of security. An advantage of a mixture of security elements of different levels may be the ability to locate the position of second or third level security elements through the presence of first-level security elements visible in daylight. The authentication and / or the identification of the sheet material may, where appropriate, be based on the verification of all the zones formed by the security elements or on the verification of only some of these zones. At least one of the areas formed by the security elements may define an inspection area to analyze the security elements present in this inspection area in order to identify the sheet material, for example based on the spatial distribution of security elements in the inspection area.

  This inspection zone corresponds, for example, to the intersection of two zones formed by security elements of different types and / or concentrations. The security elements may comprise: elements detectable with the naked eye, in reflection and / or in transmission, in daylight, and / or tactile detectable elements producing a tactile effect, elements detectable by the eye, naked eye, in reflection and / or transmission, for example under a predetermined illumination, especially ultraviolet, the security elements being in particular undetectable to the naked eye, in visible light, and / or - elements arranged to emit a signal specific when they are subjected to external excitation, including optoelectronic, electromagnetic, electrical, magnetic, thermal or acoustic. The security elements may comprise, if desired, at least one of the following elements: an active material, such as for example a chemical substance absorbing in the UV or elements detectable by X-ray fluorescence, a particle or a pigment, in particular a luminescent, fluorescent and / or phosphorescent pigment, a biological, chemical or physical tracer, a fiber such as a magnetic fiber, in particular with a soft magnetism, or an optically excitable fiber, in particular by exposure to infrared radiation , - a small board.

  The particles or pigments may have, for example, dimensions of between 10 and 20 m, and even up to 500 m. The fibers may have, for example, a length of 3 to 5 mm and a diameter of about 30 m. The decorative elements comprise, if desired, metallic particles and / or glossy or matt or colored particles, of mineral or plastic material. The sheet material may comprise at least one authentication and / or identification structure, the security and / or decorative elements covering an area of the fibrous layer that may overlap at least partially or even perfectly with the structure of the structure. authentication and / or identification. This can, if desired, cover security and / or decorative elements. The authentication and / or identification structure may comprise, for example, a foil or patch or a hologram applied to the fibrous layer, in particular outside the paper machine. The pattern (s) defined by the security and / or decorative elements may be present at a security thread or a zone of reduced opacity or a watermark for example. The authentication and / or identification structure may be chosen from at least one of the following: a watermark, an optically variable element such as a hologram, a strip element, a foil, a patch, a security thread, an impression. Thanks to the invention, it is possible to modify the shape of a pattern, in particular by controlling: the speed of travel of the fibrous layer during the application of the security and / or decorative elements, the pulsation speed in the case where a pneumatic spray nozzle is used, - the lateral movement of the spray system, in particular the oscillation frequency. It is possible, if necessary, to vary the flow rate over time to create patterns, especially in band, with varying concentrations of security and / or decorative elements. Concentration variations can be used for authentication of the sheet material. The invention further relates, in another of its aspects, to a paper machine comprising: at least one wet part for forming a continuous fibrous layer, a projection system arranged to project safety elements and or decorative on a fibrous layer, in particular still wet, formed in the wet part of the machine. The projection system may comprise, where appropriate, at least one spraying device arranged to project the security and / or decorative elements. The invention further relates, in another of its aspects, a sheet material obtained in particular by the implementation of the method defined above. The security and / or decorative elements may cover only a portion of one face of the fibrous layer and in particular be dispersed at least partially in the mass of the fibrous layer, to a thickness less than that of the fibrous layer. This allows for example to see the security and / or decorative elements on one side only of the fibrous layer. The security and / or decorative elements may form a pattern having a succession of disjoint zones, in particular identical and / or repeated in a regular manner. The sheet material may comprise at least two types, for example three types, of security and / or decorative elements, the security elements of a given type covering in particular only a portion of the face of the fibrous layer. The sheet material may comprise at least two zones formed respectively by security and / or decorative elements of different types, for example having different colors, these areas being for example adjacent or overlapping at least partially.

  The intersection zone of the two aforementioned zones may, where appropriate, have a color corresponding to the superposition of the two colors of said zones. The sheet material may comprise security and / or decorative elements forming at least one of: a continuous pattern, extending in particular from a first edge of the sheet material to a second opposite edge; succession of disjointed zones. The continuous zone forms, for example, a corrugated strip or zig-zag pattern. In a variant, the continuous zone is a strip with parallel straight edges.

  In an exemplary implementation of the invention, the sheet material comprises at least one authentication element and / or identification element chosen from at least one of the following elements: a highlighting element of a falsification, in particular visible and / or detectable by means of a specific detection device, an element with variable, interferential, in particular iridescent, and / or diffractive optical effect, with a liquid crystal, a magnetic coating, magnetic fibers, tracers detectable by magnetic resonance, tracers detectable by X-ray fluorescence, biomarkers, a varnish or an ink, luminescent tracers (fluorescent or phosphorescent), photochromic compounds, thermochromic, electroluminescent, tribochromic, especially piezochromic and / or which change from color in contact with one or more predetermined products (solvatochrome, ionochrome, etc.). The invention will be better understood on reading the following detailed description, non-limiting examples of implementation, and on examining the appended drawing, in which: FIG. 1 represents, schematically and partially, a paper machine according to the invention, - Figure 2 illustrates, schematically and partially, two spray nozzles of a projection system of the paper machine of Figure 1, - Figure 3 shows, schematically and partially, a projection nozzle fed by two reservoirs of security and / or decorative elements, - Figures 4 and 5 illustrate, schematically and partially, examples of patterns obtained depending on the projection mode of the security elements and / or decorative and FIGS. 6 to 17 illustrate, schematically and partially, various examples of patterns formed by the security and / or decorative elements. In the drawing, for the sake of clarity, the relative proportions of the various elements represented have not always been respected, the views being schematic. FIG. 1 shows a paper machine 1 comprising a wet part 2 for forming the paper, a circuit of a gripper strip 3, in particular made of felt, a set of dryers 4 and a press-gluer 5 (or size press). ). In the example shown, the paper machine 1 is round. Alternatively, the paper machine may be flat-table type. In another variant, the paper machine may comprise a web of a rotating cylinder (or form) and a device for injecting fibrous material onto this surface in order to form the fibrous layer. The wet part 2 comprises a tank 11 containing a suspension 12 of fibers, for example cellulose fibers, in particular cotton linters and / or synthetic and / or artificial fibers, in which is partially immersed a cylinder of rotating fabric 13 defining a surface 14 in contact with which a fibrous layer 20 is continuously formed. The drying assembly 4 comprises a plurality of rotating cylinders 9 in contact with which the fibrous layer 20 is displaced. It is possible to manufacture a sheet material with a single fibrous layer 20, which may, if desired, receive a coating. As a variant, the sheet material may comprise at least two fibrous layers, in particular assembled in a wet phase, so as to form, for example, a bi-jet paper. The paper machine 1 further comprises a projection system 21 having one or more projection nozzles 22 arranged to project security and / or decorative elements onto the fibrous layer 20 in displacement in the direction of the arrow F, as illustrated. in Figure 2.

  The system 21 may comprise a single nozzle or a plurality of spray nozzles. In the example, the projection system 21 is disposed at a location of the paper machine 1 where the fibrous layer 20 is still wet.

  For example, the projection system 21 is disposed between the wet part 2 forming the paper and the dryer assembly 4, as shown in Figure 1. Alternatively, the projection system 21 is arranged for example between the assembly 4. When the security and / or decorative elements are suspended in an aqueous medium, the spraying of the suspension on the fibrous layer can be associated with an atomization of the suspension in order to reduce the size of the sprayed drops. One of the nozzles may comprise for this purpose an atomizing device 23 comprising for example one or more vortex channels. When the security and / or decorative elements comprise particles, boards or fibers, the spraying can be carried out using a driving fluid such as compressed air. One of the nozzles 22 may be powered by at least two security and / or decorative element reservoirs 25 and 26 in order to alternately project the security and / or decorative elements from the two reservoirs 25 and 26, as illustrated in FIG. The tanks 25 and 26 comprise, for example, security and / or decorative elements of different types. In an example not illustrated, the system 21 may comprise a jet splitter arranged to divide, at the outlet of a nozzle, a jet in several streams.

  The system 21 may comprise, if desired, two nozzles arranged to project jets juxtaposing at least partially for example to form on the fibrous layer an area having a relatively large area. The projection system 21 can be associated with a control system 28 arranged to control the projection of the security and / or decorative elements by the projection system, this control system 28 can control for example the frequency of projections (including the duration projection and / or that between two successive projections), the direction of projections, the projection force, the shape and / or the dimensions of a jet 29 of security and / or decorative elements. The control system 28 comprises for example at least one pneumatic device and a peristaltic device, or a combined pneumatic / peristaltic device, arranged to control the projection frequency. The control system 28 may be arranged for example to be able to move one of the jets 29 of security and / or decorative elements in a direction not parallel to the direction F of displacement of the fibrous layer 20. The control system 28 may include, if desired, a centrifugal pump or a mono-pump, particularly in the case of continuous pattern formation, allowing a precise flow control and regular, including reproducible and constant over time. The jet 29 may for example be moved in a direction transverse to the direction F, according to an oscillating movement.

  Each nozzle 22 may be arranged to spray a jet 29 of security and / or decorative elements having, in cross-section, a circle shape, as illustrated in FIG. 2. Alternatively, each nozzle 22 may be arranged to spray a jet 29 having, in cross section, a shape chosen from: a straight line segment, a corner such as a right angle corner, a rectangle or a square, a non-rectilinear curve such as an arc of a circle, a portion of a oval or ellipse or an S, a disc. The jet 29 may be flat for example or, alternatively, substantially conical. Nozzles 22 are arranged to project on the fibrous layer 20 security and / or decorative elements on only a portion of the corresponding face thereof. The projection system 21 can make it possible to project, simultaneously or alternately, on the fibrous layer 20, security and / or decorative elements of at least two different types. It is possible to use to form the projection system 21 at least one of the nozzles marketed by SPRAYING SYSTEMS Co., for example the nozzles marketed under the name F1atJet Nozzle, VeeJet Nozzle, Flat Jet Nozzle Air Atomizing Nozzle, GunJet Spray Guns.

  The security and / or decorative elements may comprise elements detectable with the naked eye, in reflection and / or by transparency, in visible light, or detectable to the touch. The security and / or decorative elements may, where appropriate, comprise elements detectable with the naked eye, in reflection and / or by transparency, for example under a predetermined lighting, in particular ultraviolet, the security elements being in particular undetectable to the naked eye, in visible light. The security elements may comprise elements arranged to emit a specific signal when they are subjected to external excitation, in particular optoelectronic, electromagnetic, electrical, magnetic, thermal or acoustic excitation. The security element comprises for example at least one of the following elements: an active material, such as, for example, a chemical substance absorbing in the UV or elements detectable by X-ray fluorescence, a particle or a pigment, in particular luminescent, fluorescent and / or phosphorescent, - a tracer, - a fiber such as a magnetic fiber, in particular with mild magnetism, or an optically excitable fiber, in particular by exposure to infrared radiation, - a small board. The decorative elements comprise, if desired, metal particles and / or glossy or matte or colored particles, of mineral material (s) or plastic (s). Various examples of patterns that can be formed by the projection of the security and / or decorative elements on a fibrous layer will now be described. FIG. 4 (a) illustrates a fibrous layer 20 on which two different types of patterns are formed. The first continuous pattern is achieved by projecting security and / or decorative elements onto the fibrous layer 20 using a first continuously operating nozzle 22. Pattern 30 is a continuous strip with straight and parallel edges. The pattern 31 is formed of a row of circles, parallel to the band 30.

  The circles are formed by safety and / or decorative elements projected in hollow jets on the fibrous layer 20 using, for example, a pneumatic spray nozzle 22. By increasing the relative speed of the spray nozzles relative to the fibrous layer 20, it is possible to obtain in the pattern 31, in place of the circles, ellipses, as shown in Figure 4 (b). In the example illustrated in FIGS. 5 (a) and 5 (b), the circles of the pattern 31 are formed using a pneumatic spray nozzle. By controlling the speed of travel of the fibrous layer 20 with respect to the nozzle and / or the frequency of the projections, the spacing between two circles of the pattern 31 can be reduced or increased in order for example to have a row of circles more close to each other as shown in Figure 5 (b). When the projection nozzle is subjected to a lateral oscillation of predetermined frequency, a band 33 having a substantially sinusoidal or zig-zagous shape is formed on the fibrous layer 20, as illustrated in FIG. 6. In the example of FIG. In FIG. 7, the fibrous layer 20 comprises, in addition to the sinusoidal band 33, a continuous band pattern 34 with parallel straight edges. The pattern 34 is formed in particular by a mixture of security elements of two different types, namely for example, on the one hand, boards having a red color under daylight and a red fluorescence under a radiation at 365 nm and, on the other hand, invisible fibers in daylight and having a yellow fluorescence under radiation at 365 nm. The pattern 33 is formed for example of tracers invisible in ambient light, such as TracelessTM tracers marketed by the company CREO. These tracers can be detected by a specific detector comprising a CCD camera operating in the infrared and arranged to characterize the spatial distribution of the tracers. The signal emitted by the tracers dispersed in a predetermined region of the pattern 33, corresponding, for example, to a portion of the sinusoid 33, may serve for the identification of the fibrous layer 20. The portion of the sinusoid may be, for example, a period of it or a multiple of it.

  The pattern 34 is thus formed of first and second level security elements, and the pattern 33 of third level security elements. The pattern 34 serves in particular to mark the pattern 33. In the example illustrated in FIG. 8, the fibrous layer 20 comprises a pattern 35 formed by a row of identical elementary patterns repeated in a regular manner, each elementary pattern being formed for example by two concentric rings. These elementary patterns are made from second-level security elements, for example HiliteTM particles invisible in daylight and having an orange fluorescence under a radiation at 365 nm, described for example in the application EP 226 367.

  These particles are agglomerates with a dimension of about 200 m, finer fluorescent particles. In the example of FIG. 9, the fibrous layer 20 comprises a pattern 36 obtained by varying the width of the jet of security and / or decorative elements so that the width of the pattern 36 varies, in particular periodically.

  In the example illustrated in FIG. 10, the fibrous layer 20 comprises a pattern 38 formed by an alternation of adjacent discontinuous zones 38a and 38c and together defining a general shape in continuous strip with parallel straight edges. These zones 38a-38c are each obtained, in particular by discontinuous projection of security and / or decorative elements of different types.

  For example, zones 38a may be formed by HiliteTM particles invisible in daylight, and having blue fluorescence under UV radiation. The zones 38b may be formed for example by HiliteTM particles having a white fluorescence and the zones 38c by HiliteTM particles having a red fluorescence under UV radiation.

  Thus, under UV radiation, the pattern 38 may appear as a succession of blue / white / red tricolor flags. Alternatively, the zones 38a-38c may be formed by TracelessTM tracers of the company CREO, the concentration of which varies according to the zones 38a-38c. These areas can form for example a bar code.

  In the example illustrated in FIG. 11, the fibrous layer 20 comprises two continuous patterns 40 and 41 each having a strip shape with parallel straight edges, these patterns 40 and 41 being adjacent along their entire length.

  The pattern 40 may for example be formed by security and / or decorative elements visible to the naked eye, under appropriate lighting. This pattern 40 can identify the pattern 41 formed for example by security elements invisible to the naked eye and detectable only with the aid of a specific device.

  In the example illustrated in Figure 12, the fibrous layer 20 comprises a pattern 42 having a strip shape with parallel straight edges, formed for example by security elements invisible to the naked eye. This pattern 42 may be superimposed on authentication and / or identification structures 43 visible to the naked eye, comprising, for example, watermarks.

  The authentication and / or identification structure 43 may alternatively comprise at least one security thread, an optically variable element such as a holographic foil or an impression such as an ink printing. The structure 43 may be applied to the fibrous layer during or after the manufacture of this layer, during a transformation or printing, for example.

  As illustrated in FIG. 13, the fibrous layer 20 may comprise a pattern 39 formed by a succession of discontinuous zones, for example of rectangular shape. The pattern 39 is superimposed on a safety band or thread 44 incorporated at least partially in the mass of the fibrous layer 20. The pattern 39 is obtained for example by spraying a dye having electromagnetic properties and forms a specific signature of the material in sheet. The dye may be of the SecuSystem type sold by the company Bsecure, mixed with invisible particles in daylight and having a red fluorescence under radiation at 365 nm. In the example illustrated in FIG. 14, the sheet material 20 has first and second patterns 44 and 45 each having a strip shape with parallel straight edges, these patterns being adjacent, and a third pattern 46 having a strip shape. The first pattern 44 may be formed by spraying fibers having a red color in daylight and red fluorescence under 365 nm radiation.

  The pattern 45 may be formed by security features such as HiliteTM particles having a red color in daylight and red fluorescence under 365 nm radiation.

  The pattern 46 is formed for example by HiliteTM particles invisible in daylight and having a yellow fluorescence under radiation at 365 nm. In the example illustrated in FIG. 15, the fibrous layer 20 comprises a first strip pattern 47, a second strip pattern 48 formed within the first pattern 47, and a third discontinuous pattern 49 formed within the pattern 48. The pattern 49 is formed of discontinuous areas, these areas being for example disks or the like obtained by solid conical jets. The first pattern 47 may include second level security elements, e.g., fibers invisible to ambient light and having blue fluorescence under 365 nm radiation. The second pattern 48 may be formed for example by security features such as HiliteTM particles having a red color in daylight and red fluorescence under 365 nm radiation. The third pattern 49 may be formed, for example, by TracelessTM tracers. In the example illustrated in FIG. 16, the fibrous layer 20 has a first continuous pattern 50 having a strip shape and second and third continuous patterns 51 and 52 having also a strip shape and superimposed on the first pattern 50. The second and third patterns 51 and 52 are spaced from each other. In the example illustrated in FIG. 17, the fibrous layer 20 comprises two patterns 53 and 54 each having a continuous strip shape, with parallel straight edges, and partially overlapping in an intersection zone 55. The first pattern 53 is formed by spraying a dye having a yellow color in daylight and a yellow fluorescence under radiation at 365 nm. The second pattern 54 is formed by spraying a dye having a blue color in daylight and a blue fluorescence under radiation at 365 nm. The intersection zone 55 has a color corresponding to the superposition of the yellow and blue colors of the patterns 53 and 54 so that the patterns 53-54 form, under UV radiation, three colors, in the manner of a yellow / green flag /blue. Of course, the invention is not limited to the implementation examples which have just been described.

  One of the nozzles may for example include a shutter to interrupt the jet projection. One of the nozzles may be movable on a support, for example in translation, in rotation, in particular in an oscillating movement.

  One of the nozzles may be movable so as to vary the distance between this nozzle and the fibrous layer. The expression containing one must be understood as being synonymous with at least one, unless the opposite is specified.

Claims (8)

  A method of manufacturing a sheet material comprising at least one fibrous layer (20) and a plurality of security and / or decorative elements, the method comprising at least one of the following steps: security and / or decorative elements on one side of the fibrous layer (20), traveling in a predetermined direction (F), especially when the fibrous layer is still wet, so as to form at least one of a pattern continuous film having at least one edge, substantially in the running direction, not entirely parallel to the running direction and a pattern comprising a succession of disjoint zones, - projecting on one side of the fibrous layer (20), especially when the latter is still wet, safety and / or decorative elements of at least two different types and / or having a variable concentration.   2. Method according to the preceding claim, the security and / or decorative elements being projected onto the fibrous layer using a fluid under pressure, in particular a gas under pressure.   3. Method according to one of claims 1 and 2, comprising the following steps: - disperse security elements in a fluid, -spray the security elements and / or decorative on the fibrous layer (20).   4. Method according to any one of the preceding claims, the projection of the security and / or decorative elements being carried out using a projection system (21) comprising one or more projection nozzles (22).   5. Method according to the preceding claim, the projection system comprising an atomization device (23) of a liquid medium to create fine droplets.   6. Method according to one of the two preceding claims, the projection system (21) comprising at least one nozzle (22) can be fed alternately by at least two tanks (25; 26) of security and / or decorative elements. and capable of alternately projecting the security and / or decorative elements from the two tanks.   7. Method according to any one of claims 4 to 6, the projection system comprising at least one jet splitter arranged to divide, at the outlet of a nozzle, a jet in several streams.   8. Method according to any one of the preceding claims, the security and / or decorative elements being projected by forming at least one jet (29), the method comprising the following steps: - driving the fibrous layer (20) in displacement following a predetermined direction (F), - move the jet (29) in a direction not parallel to the direction of displacement of the fibrous layer, in particular oscillating manner. 11. Method according to any one of the preceding claims, the security elements and / or decorative being projected onto the fibrous layer (20) continuously. 12. Method according to any one of claims 1 to 8, the security and / or decorative elements being projected on the fibrous layer (20) intermittently, in particular periodically with a predetermined frequency. 13. The method of claim 4 and the preceding claim, the projection system (21) being associated with a control system (28) arranged to control the projection of security and / or decorative elements, including the frequency of projections, the projection direction, the projection force of the security elements, the volume, the flow, the shape and / or the dimensions of a stream of security and / or decorative elements. 14. Method according to the preceding claim, the control system comprising at least one of a pneumatic device and a peristaltic device, or a combined pneumatic / peristaltic device arranged to control the frequency of projection, or a centrifugal pump. or a mono-pump. 15. Method according to any one of the preceding claims, the security elements being projected by forming at least one jet (29) having, in cross section, a shape chosen from: a line segment, a corner such as a corner at right angles, a triangle, a rectangle or a square, a non-rectilinear curve such as a circle arc, a circle, an ellipse, an oval portion or an S, a disc, a wavy shape. 16. A method according to any one of the preceding claims, the projection of the security and / or decorative elements on the fibrous layer being carried out in line, downstream of the wet part (2) of the paper machine (1) used to form the fibrous layer, especially before passing over a dryer assembly (4) of the paper machine. 15. A method according to any one of the preceding claims, the security and / or decorative elements being projected onto the fibrous layer (20) so as to be dispersed on only a portion of the corresponding face of the fibrous layer. 16. Method according to any one of the preceding claims, comprising the following step: -project, simultaneously or successively, in particular alternately, on the fibrous layer, security elements and / or decorative of at least two different types. 18. Method according to any one of the preceding claims, the security and / or decorative elements comprising elements detectable to the naked eye, in reflection and / or transmission, in daylight. 19. Method according to any one of the preceding claims, the security and / or decorative elements comprising elements detectable with the naked eye, in reflection and / or in transmission, under a predetermined lighting, in particular ultraviolet light, the security elements. and / or decorative being particularly undetectable to the naked eye, in visible light. 20. Method according to any one of the preceding claims, the security and / or decorative elements comprising elements arranged to emit a specific signal when they are subjected to external excitation, in particular optoelectronic, electromagnetic, electrical, magnetic, thermal or acoustic. 21. Method according to any one of the preceding claims, the security elements comprising at least one of the following elements: an active material, such as, for example, a chemical substance absorbing in the UV or elements detectable by X-ray fluorescence; a particle or a pigment, in particular luminescent, fluorescent and / or phosphorescent, a tracer, biological, chemical or physical, a fiber such as a magnetic fiber, in particular with a soft magnetism, or an optically excitable fiber, particularly by exposure to infrared radiation, - a planchette.21. Process according to any one of the preceding claims, the decorative elements comprising metallic particles and / or glossy or matt or colored particles, made of mineral material (s) or plastic (s). 22. Method according to any one of the preceding claims, the sheet material comprising at least one authentication and / or identification structure, the security elements covering an area of the fibrous layer overlapping at least partially, particularly perfectly. , to the authentication and / or identification structure. 23. Method according to the preceding claim, the authentication structure being chosen from at least one of the following elements: a watermark, an optically variable element such as a hologram, a strip element, a foil, a patch, a security thread, an impression. Paper machine (1) for carrying out the method according to any one of the preceding claims, the machine comprising: at least one wet part (2) for forming a fibrous layer (20) continuously, - A projection system (21) arranged to project security and / or decorative elements on a fibrous layer still wet, formed in the wet part of the machine. 25. Machine according to the preceding claim, the projection system comprising at least one spraying device (23) arranged to project the security elements and / or decorative. Sheet material obtained by carrying out the method according to any one of claims 1 to 23. Material according to the preceding claim, the security and / or decorative elements covering only a portion of one face of the fibrous layer, the security elements may in particular be dispersed at least partially in the mass of the fibrous layer, to a thickness less than that of the fibrous layer. 28. Material according to one of claims 26 and 27, the security elements 30 and / or decorative forming a pattern having a succession of disjoint zones (31; 35; 38; 39; 49), including identical and / or repeated regularly.29. Material according to any one of Claims 25 to 27, comprising at least two types, for example three types, of security and / or decorative elements, the security elements of a given type covering in particular only a portion of the face the fibrous layer. 30. Material according to the preceding claim, comprising at least two zones respectively formed by security elements and / or decorative different types, these areas being in particular adjacent or overlapping at least partially. 31. Material according to any one of claims 26 to 30, comprising security and / or decorative elements forming at least one of: - a continuous pattern (30; 33; 36; 40; 41; 42; -48; 50-55), extending in particular from a first edge of the sheet material to a second opposite edge, - a succession of disjoint areas (39). 32. Material according to the preceding claim, the continuous zone forming a corrugated or zig-zag strip pattern.