PROCESS FOR MANUFACTURING A MATERIAL IN SHEET FORM, COMPRISING AT LEAST ONE FIBROUS LAYER AND SECURITY AND/OR DECORATIVE ELEMENTS

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

One objet of the present invention is, in particular, a process for manufacturing a sheet material comprising at least one fibrous layer.

Known from U.S. Pat. No. 6,270,625 is a process for manufacturing a security paper having colored strips, that comprises the following steps:

• • feeding a head box with a paper pulp via a plurality of delivery lines;
  • selectively introducing one or more coloring agents into some of the delivery lines; and
  • depositing the paper pulp on a papermaking wire.

This process makes it possible to obtain several colored strips in the bulk of the paper,

Security elements may be introduced selectively into one of the lines for distributing the paper pulp.

One drawback linked to this process described above lies in the fact that the security elements are embedded in the bulk of the paper, which may prevent them from being observed or detected or make it difficult to observe or detect them.

Known from U.S. Pat. No. 5,989,389 is a process for manufacturing a security paper such as a banknote, that consists in depositing, onto a rotating wire cylinder, two types of fibrous suspensions, one being intended to form opaque zones of the paper and the other substantially transparent zones.

The suspension of fibers that form the transparent zones may contain a filler, a binder or a transparentizing agent, and be distributed using a nozzle in contact with the papermaking wire.

Known from Patent GB 2 309 710 is a single-ply security paper incorporating security elements such as metallic or magnetic particles. The paper is formed in contact with a rotating wire cylinder and the particles are introduced into the fibrous layer being formed using nozzles spaced apart from one another and positioned at the location where the fibrous layer begins to be formed in contact with the papermaking wire.

Also known from Patent GB 696 673 is a process for manufacturing a paper, comprising the step that consists in injecting a material such as an ink, using a syringe, into the bulk of the fibrous layer being formed.

Known from Patent Application EP 490 825 is a security paper such as a banknote comprising a plurality of adjacent strips each formed by a coating of an iridescent pigment.

The iridescent pigment is deposited by coating using a rotating roller:

• • either by depositing the product onto the roller which transfers the product onto the moving paper;
  • or by direct application of the product to the paper, upstream of the rotating roller.

International Application WO 2004/087437 describes a security paper such as a banknote comprising two adjacent iridescent strips deposited on the paper, for example using the process described in the aforementioned Application EP 498 825, or by coating, printing, photogravure, flexography or offset printing.

The paper also comprises an optically variable element such as a hologram deposited by hot pressing onto at least one of the iridescent strips.

The manufacture of a security paper according to Application EP 490 825 or Application WO 2004/087437 requires the implementation of steps away from the paper production line, which can increase the final cost of the paper.

Generally, security and/or valuable documents are known that comprise security elements that make it possible to protect these documents against forgery or counterfeiting attempts.

Among the security elements, some are detectable by the naked eye, in visible light, without the use of a specific device. These security elements comprise, for example, colored planchettes or fibers.

These security elements are said to be first-level elements.

Other types of security elements are detectable only using a relatively simple device such as a lamp that emits in the ultraviolet or infrared range. These security elements comprise, for example, fibers, planchettes or particles. These security elements may be visible to the naked eye or not, being, for example, luminescent under a Wood lamp that emits at a wavelength of 365 nm. These elements may also be, for example, of the thermochromic or photochromic type.

These security elements are said to be second-level elements.

Yet other types of security elements 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 sources of external excitation. The automatic detection of the signal makes it possible to authenticate, if necessary, the document.

These security elements comprise, for example, markers that are in the form of active material, of particles or of fibers, capable of generating a specific signal when these markers are subjected to an optoelectronic, electric, magnetic or electromagnetic excitation.

These security elements are said to be third-level elements.

The security elements mentioned above may be incorporated into the bulk of the paper or at the surface of the latter.

When all of the paper must be marked using security elements, the amount of these elements used may be relatively large, which can increase the final cost of the paper.

When the security elements are incorporated into the bulk of the paper, their observation with the naked eye, when these are first-level security elements, or their detection, when these are third-level security elements, may be difficult or even impossible due to, for example, the presence of cellulose fibers or dyes which may act as a filter.

Furthermore, depending on the process for manufacturing the paper, especially during an introduction in bulk, a certain amount of security elements may be unretained, not being finally incorporated into the paper.

The present invention aims, in particular, to provide a novel process for manufacturing a sheet material having at least one fibrous layer that comprises security and/or decorative elements.

The expression “sheet material” may denote, in the description and the claims, a fibrous sheet based on cellulose and/or synthetic fibers. A sheet material may, for example, have a relatively small thickness, in particular less than or equal to 3 mm, for example equal to around 100 μm, and be at least partially, or even completely, flexible. The sheet material may be of the single-ply or multi-ply type, in particular two-ply. In one exemplary embodiment of the invention, the sheet material may be packaged as a coil, especially before being cut to the desired format.

The subject of the invention, according to one of its aspects, is a process for manufacturing a sheet material 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:

• • spraying the security and/or decorative elements onto one face of the fibrous layer, while traveling along a predetermined direction, especially when the fibrous layer is still wet, so as to form one at least of a continuous pattern having at least one edge, substantially in the direction of travel, not completely parallel to the direction of travel and a pattern comprising a succession of disjointed zones; and
  • spraying onto one face of the fibrous layer, especially when it is still wet, security and/or decorative elements of at least two different types and/or that have a variable concentration.

Owing to the invention, the amount of security and/or decorative elements used for manufacturing the sheet material may be relatively low.

For example, it is possible to spray a jet of security and/or decorative elements over a small surface area zone of the fibrous layer.

Furthermore, the invention makes it possible to limit possible losses of material.

When the security and/or decorative elements are sprayed over the still wet fibrous layer, it is possible to improve the anchoring of these elements into the fibrous bulk.

The spraying of the security and/or decorative elements onto the fibrous layer may be carried out in-line, downstream of a wet part of the papermaking machine that is used to form the fibrous layer, especially before passing into the press section, or even before passing into a drying assembly of the papermaking machine.

The deposition of the security and/or decorative elements may be facilitated since it is carried out on the papermaking machine itself, which in particular makes it possible to be able to locate the pattern or patterns of security and/or decorative elements relative to other security elements present in the fibrous layer, for example a security thread or a watermark.

The zones of the fibrous layer covered by the security and/or decorative elements may have a fuzzy or sharp contour, depending on the type of security and/or decorative elements deposited and the spraying method.

A fuzzy contour may make it possible to make an attempt to copy the sheet material by printing more difficult.

In one exemplary embodiment of the invention, the security and/or decorative elements are previously dispersed in a fluid such as water, optionally with one or more additives, for example a binder or a retention agent, in order to facilitate the anchoring of the security and/or decorative elements to the fibrous layer or a dispersant in order to facilitate the dispersion of the security and/or decorative elements.

The mixture thus obtained may be sprayed onto the fibrous layer using a pressurized fluid, especially a pressurized gas such as compressed air.

The process according to the invention may comprise at least one of the following steps:

• • dispersing security and/or decorative elements dispersed in a fluid, especially when the size of the security and/or decorative elements is sufficiently small; and
  • spraying the security and/or decorative elements onto the fibrous layer.

The spraying of the security and/or decorative elements may be carried out using a spraying system comprising one or more spray nozzles.

For example, the spraying of the security and/or decorative elements may be carried out with several spray nozzles fed with security and/or decorative elements of different types to form adjacent or overlapping patterns.

The spraying system comprises, if desired, especially depending on the type of security and/or decorative elements, a device for atomizing the liquid medium in order to create very fine droplets.

The spraying system may comprise at least one nozzle that may be alternately fed by at least two reservoirs of security and/or decorative elements capable of alternately spraying the security and/or decorative elements originating from the two reservoirs.

If necessary, the spraying system may comprise a jet divider arranged in order to divide, at the outlet of a nozzle, one jet into several jets, optionally with spaces between them in order to create one or more patterns.

Preferably, the security and/or decorative elements are sprayed while forming at least one jet, the process comprising the following steps:

• • moving the fibrous layer along a predetermined direction;
  • moving the jet along a direction that is not parallel to the direction of movement of the fibrous layer, especially in an oscillating manner.

The invention makes it possible to produce a wide variety of patterns using security and/or decorative elements.

For example, the security and/or decorative elements may be sprayed onto the fibrous layer continuously or, as a variant, intermittently, in particular periodically with a predetermined frequency.

The spraying system may, where necessary, be combined with a control system arranged in order to control the spraying of the security and/or decorative elements, especially the spraying frequency, the spraying direction, the spraying force of the security and/or decorative elements, the volume, the flow rate, and the shape and/or the dimensions of a jet of security and/or decorative elements.

The control system may comprise at least one of a pneumatic device and of a peristaltic device, or a combined pneumatic/peristaltic device, arranged in order to control the spraying frequency and volume.

A pneumatic pump may especially be arranged in order to be able to regulate the spraying frequency and volume via a system of compressed air, the flow rate and pressure of which may be easily controlled.

The spraying frequency and volume in a peristaltic pump depend, in particular, on the pump configuration (number of rotors that create the spraying pressure, for example).

The control system may comprise, if desired, a centrifugal pump or a mono pump, especially in the case of forming continuous patterns, allowing a control of the flow rates that is precise and regular, in particular reproducible and constant over time.

The security and/or decorative elements may be sprayed by forming at least one jet that has, in transverse cross section, a shape chosen from: a straight line segment, a corner such as a right-angled corner, a triangle, a rectangle or a square, a non-rectilinear curve such as an arc of a circle, a circle, an ellipse, an oval or S-shaped portion, a disk, or a wavy shape.

The jet may be hollow or solid.

In one exemplary embodiment of the invention, the security and/or decorative elements are sprayed onto the fibrous layer so as to be dispersed over only one portion of the corresponding face of the fibrous layer, the elements not covering the entirety of this face.

The process may comprise, if desired, the following step:

• • spraying, simultaneously or successively, especially alternately, security and/or decorative elements of at least two different types onto the fibrous layer, for example in order to form completely or partially overlapping, superposed, adjacent or separated patterns.

The pattern or patterns made on the sheet material may define, if desired, an identification element of the sheet material.

The pattern or patterns may define, where appropriate, a decorative pattern or a specific trademark pattern.

Security and/or decorative elements of different types may, for example, have different colors, while being of identical nature.

This or these patterns comprise, for example, one of the following elements: an alphanumeric character, a symbol, a geometric shape, a logo, or a design, this list not being limiting.

This or these patterns may or may not be alternate, optionally with a predetermined step, and/or juxtaposed or superposed.

The process may comprise the following step:

• • spraying, for example in a superposed, adjacent or separated manner, simultaneously or successively, in particular alternately, security and/or decorative elements with different flow rates over the fibrous layer in order, in particular, to form on the fibrous layer zones that have amounts of security and/or decorative elements per unit length or per unit area which are different.

It is possible to spray onto the fibrous layer a single 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.

One advantage of a mixture of security elements of different levels may be the possibility of locating the position of second- or third-level security elements owing to the presence of first-level security elements visible in daylight.

The authentication and/or identification of the sheet material may, where appropriate, rest on the verification of the set of zones formed by the security elements or on the verification of only some of these zones.

One at least of the zones formed by the security elements may define an inspection zone in order to analyze the security elements present in this inspection zone with a view to identifying the sheet material, on the basis, for example, of the spatial distribution of the security elements in the inspection zone.

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 to the naked eye, in reflection and/or in transmission, in daylight; and/or
  • elements detectable to the touch that produce a tactile effect;
  • elements detectable to the naked eye, in reflection and/or in transmission, for example under predetermined lighting, especially ultraviolet lighting, the security elements especially being undetectable to the naked eye, in visible light; and/or
  • elements arranged in order to emit a specific signal when they are subjected to an external excitation, especially an optoelectronic, electromagnetic, electric, magnetic, thermal or acoustic excitation.

The security elements may comprise, if desired, at least one of the following elements:

• • an active material, such as for example a chemical substance that absorbs in the UV or elements detectable by X-ray fluorescence;
  • a particle or a pigment, especially one that is luminescent, fluorescent and/or phosphorescent;
  • a biological, chemical or physical marker;
  • a fiber such as a magnetic fiber, especially one that is weakly magnetized, or a fiber that is optically excitable, especially by exposure to infrared radiation; and
  • a planchette.

The particles or pigments may have, for example, dimensions between 10 and 20 μm, even ranging up to 500 μm.

The fibers may have, for example, a length of 3 to 5 mm and a diameter of around 30 μm.

The decorative elements comprise, if desired, metallic particles and/or shiny or matt or colored particles, made of mineral or plastic material(s).

The sheet material may comprise at least one authentication and/or identification structure, the security and/or decorative elements covering a zone of the fibrous layer that may be superposed at least partially, or even perfectly, on the authentication and/or identification structure.

The latter may, if desired, cover the 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, especially away from the papermaking machine.

The pattern or patterns defined by the security and/or decorative elements may be present in 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 elements: a watermark, an optically variable element such as a hologram, a strip element, a foil, a patch, a security thread, or printing.

Owing to the invention, it is possible to modify the shape of a pattern, in particular by controlling:

• • the rate of travel of the fibrous layer during the application of the security and/or decorative elements;
  • the pulsation rate, in the case where a pneumatic spray nozzle is used; and
  • the lateral movement of this spraying system, especially the oscillation frequency.

It is possible, where appropriate, to vary the flow rate over time in order to create patterns, especially in a strip, with variable concentrations of security and/or decorative elements.

The variations in concentration may be used for authentication of the sheet material.

Another subject of the invention, according to another of its aspects, is a papermaking machine comprising:

• • at least one wet part for forming a fibrous layer continuously; and
  • a spraying system arranged in order to spray security and/or decorative elements over a fibrous layer that is in particular still wet, formed in the wet part of the machine.

The spraying system may comprise, where appropriate, at least one spraying device arranged in order to spray the security and/or decorative elements.

Another subject of the invention, according to another of its aspects, is a sheet material obtained, in particular, by the implementation of the process defined above.

The security and/or decorative elements may cover one portion only of one face of the fibrous layer and may, in particular, be dispersed at least partially in the bulk of the fibrous layer, over a thickness smaller than that of the fibrous layer.

This makes it possible, for example, to see the security and/or decorative elements on one face only of the fibrous layer.

The security and/or decorative elements may form a pattern having a succession of disjointed zones, in particular that are identical and/or repeated regularly.

The sheet material may comprise at least two types, for example three types, of security and/or decorative elements, the security elements of one given type in particular covering one portion only 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, having for example different colors, these zones in particular being adjacent or at least partially superposed.

The intersection zone of the aforementioned two 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 that form one at least of:

• • a continuous pattern, that extends in particular from a first edge of the sheet material to a second opposite edge; and
  • a succession of disjointed zones.

The continuous zone forms, for example, a pattern in the shape of a wavy strip or zigzag.

As a variant, the continuous zone is a strip having parallel rectilinear edges.

In one exemplary embodiment of the invention, the sheet material comprises at least one authentication and/or identification element chosen from at least one of the following elements: an element for illustrating a forgery, in particular that is visible and/or detectable using a specific detection device, an element having a variable, interference, in particular iridescent, and/or diffractive optical effect, a liquid crystal element, a magnetic coating, magnetic fibers, markers detectable by magnetic resonance, markers detectable by X-ray fluorescence, biomarkers, a varnish or an ink, luminescent (fluorescent or phosphorescent) markers, photochromic, thermochromic, electroluminescent, tribochromic and especially piezochromic compounds and/or compounds that change color in contact with one or more predetermined products (solvatochrome, ionochrome, etc.).

The invention will be better able to be understood on reading the detailed description which follows, of nonlimiting exemplary embodiments, and on examining the appended drawings, in which:

FIG. 1 represents, schematically and partially, a papermaking machine according to the invention;

FIG. 2 illustrates, schematically and partially, two spray nozzles of a spraying system of the papermaking machine from FIG. 1;

FIG. 3 represents, schematically and partially, a spray nozzle fed by two reservoirs of security and/or decorative elements;

FIGS. 4 and 5 illustrate, schematically and partially, examples of patterns obtained as a function of the method of spraying the security and/or decorative elements; and

FIGS. 6 to 17 illustrate, schematically and partially, various examples of patterns formed by the security and/or decorative elements.

In the drawings, for the sake of clarity, the relative proportions of the various elements represented have not always been respected, the views being schematic.

Represented in FIG. 1 is a papermaking machine 1 comprising a wet part 2 for forming the paper, a circuit of a take-up belt 3, especially one made of felt, a drying assembly 4 and a size press 5.

In the example illustrated, the papermaking machine 1 is of round shape.

As a variant, the papermaking machine may be of the flat table type.

As a further variant, the papermaking machine may comprise a wire for a rotating cylinder (or “former”) and a device for injecting fibrous material onto this surface with a view to forming 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 a rotating wire cylinder 13 is partially immersed, said wire cylinder defining a surface 14 upon contact with which a fibrous layer 20 is continuously formed.

The drying assembly 4 comprises a plurality of rotating cylinders 9 upon 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 the wet phase, so as to form, for example, a two-ply paper.

The papermaking machine 1 also comprises a spraying system 21 comprising one or more spray nozzles 22 arranged to spray security and/or decorative elements onto the fibrous layer 20 while moving in the direction of the arrow F, as illustrated in FIG. 2.

The system 21 may comprise a single nozzle or a plurality of spray nozzles.

In the example in question, the spraying system 21 is placed at a location of the papermaking machine 1 where the fibrous layer 20 is still wet.

For example, the spraying system 21 is placed between the wet part 2 for forming the paper and the drying assembly 4, as illustrated in FIG. 1.

As a variant, the spraying system 21 is placed, for example, between the drying assembly 4 and the size press assembly 5.

When the security and/or decorative elements are suspended in an aqueous medium, the spraying of the suspension over the fibrous layer may be combined with an atomization of the suspension in order to reduce the size of the drops sprayed.

One of the nozzles may comprise, for this purpose, an atomization device 23 comprising, for example, one or more vortex channels.

When the security and/or decorative elements comprise particles, planchettes or fibers, the spraying may be carried out using a fluid carrier such as compressed air.

One of the nozzles 22 may be fed by at least two reservoirs of security and/or decorative elements 25 and 26 in order to alternately spray the security and/or decorative elements originating from the two reservoirs 25 and 26, as illustrated in FIG. 3.

The reservoirs 25 and 26 comprise, for example, security and/or decorative elements of different types.

In one example that is not illustrated, the system 21 may comprise a jet divider arranged in order to divide, at the outlet of a nozzle, one jet into several jets.

The system 21 may comprise, if desired, two nozzles arranged to spray jets that are at least partially juxtaposed in order, for example, to form on the fibrous layer a zone having a relatively large surface area.

The spraying system 21 may be combined with a control system 28 arranged in order to control the spraying of the security and/or decorative elements by the spraying system, this control system 28 possibly controlling, for example, the spraying frequency (in particular the duration of one spraying operation and/or the duration between two successive spraying operations), the spraying direction, the spraying force, and 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 of a pneumatic device and of a peristaltic device, or a combined pneumatic/peristaltic device arranged in order to control the spraying frequency.

The control system 28 may be arranged, for example, in order to be able to move one of the jets 29 of security and/or decorative elements along a direction that is not parallel to the direction F of movement of the fibrous layer 20.

The control system 28 may comprise, if desired, a centrifugal pump or a mono pump, especially in the case of forming continuous patterns, that allows a control of the flow rates that is precise and regular, in particular that is reproducible and constant over time.

The jet 29 may, for example, be moved in a direction transverse to the direction F, in an oscillating movement.

Each nozzle 22 may be arranged in order to spray a jet 29 of security and/or decorative elements that has, in transverse cross section, a circle shape as illustrated in FIG. 2.

As a variant, each nozzle 22 may be arranged in order to spray a jet 29 that has, in transverse cross section, a shape chosen from: a straight line segment, a corner such as a right-angled corner, a rectangle or a square, a non-rectilinear curve such as an arc of a circle, an oval or ellipse or S-shaped portion, or a disk.

The jet 29 may be flat, for example, or as a variant substantially conical.

The nozzles 22 are arranged in order to spray security and/or decorative elements onto the fibrous layer 20 over one portion only of the corresponding face of this layer.

The spraying system 21 may make it possible to spray, simultaneously or alternately, security and/or decorative elements of at least two different types onto the fibrous layer 20.

It is possible to use, in order to form the spraying system 21, one at least of the nozzles sold by Spraying Systems Co. for example the nozzles sold under the names FLATJET® NOZZLE, VEEJET® NOZZLE, FLATJET® NOZZLE AIR ATOMIZING NOZZLE or GUNJET® SPRAY GUNS.

The security and/or decorative elements may comprise elements detectable to the naked eye, in reflection and/or through transparency, in visible light, or detectable to the touch.

The security and/or decorative elements may, where appropriate, comprise elements detectable to the naked eye, in reflection and/or through transparency, for example under predetermined lighting, especially ultraviolet lighting, the security elements especially being undetectable to the naked eye, in visible light.

The security elements may comprise elements arranged in order to emit a specific signal when they are subjected to an external excitation, especially an optoelectronic, electromagnetic, electric, 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 that absorbs in the UV or elements detectable by X-ray fluorescence;
  • a particle or a pigment, especially one that is luminescent, fluorescent and/or phosphorescent;
  • a marker;
  • a fiber such as a magnetic fiber, especially one that is weakly magnetized, or a fiber that is optically excitable, especially by exposure to infrared radiation; and
  • a planchette.

The decorative elements comprise, if desired, metallic particles and/or shiny or matt or colored particles, made of mineral or plastic material(s).

Various examples of patterns that may be formed by spraying security and/or decorative elements onto a fibrous layer will now be described.

Illustrated in FIG. 4(a) is a fibrous layer 20 on which two types of different patterns are formed.

The first continuous pattern 30 is produced by spraying security and/or decorative elements onto the fibrous layer 20 using a first nozzle 22 operating continuously.

The pattern 30 is a continuous strip with rectilinear and parallel edges.

The pattern 31 is formed from a row of circles, parallel to the strip 30.

The circles are formed by security and/or decorative elements sprayed as hollow jets onto 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 ellipses instead of circles in the pattern 31 as illustrated in FIG. 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 rate of travel of the fibrous layer 20 relative to the nozzle and/or the frequency of spraying operations, the space between two circles of the pattern 31 may be reduced or increased in order, for example, to have a row of circles that are closer to one another, as illustrated in FIG. 5(b).

When the spray nozzle is subjected to a lateral oscillation of predetermined frequency, a strip 33 having a substantially sinusoidal or zigzag shape is formed on the fibrous layer 20 as illustrated in FIG. 6.

In the example from FIG. 7, the fibrous layer 20 comprises, in addition to the sinusoidal strip 33, a continuous pattern 34 of a strip having parallel rectilinear 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, planchettes having a red color in daylight and a red fluorescence under radiation at 365 nm and, on the other hands fibers that are invisible in daylight and that have a yellow fluorescence under radiation at 365 nm.

The pattern 33 is formed, for example, of markers that are invisible in ambient light, such as TRACELESS™ markers sold by Creo.

These markers may be detected by a specific detector comprising a CCD camera operating in the infrared and equipped to characterize the spatial distribution of the markers.

The signal emitted by the markers dispersed in a predetermined region of the pattern 33 corresponding, for example, to a portion of the sinusoidal curve 33, may be used for identifying the fibrous layer 20.

The portion of the sinusoidal curve may be, for example, a period of the latter or a multiple of the latter.

The pattern 34 is thus formed from first- and second-level security elements, and the pattern 33 from third-level security elements. The pattern 34 is used in particular for locating the pattern 33.

In the example illustrated in FIG. 8, the fibrous layer 20 comprises a pattern 35 formed from a row of identical individual patterns repeated regularly, each individual pattern being formed, for example, from two concentric rings. These individual patterns are produced from second-level security elements, for example HILITE™ particles that are invisible in daylight and that have an orange fluorescence under radiation at 365 nm, described for example in Application EP 226 367. These particles are agglomerates, having a dimension of around 200 μm, of finer fluorescent particles.

In the example from 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 from an alternation of adjacent discontinuous zones 38a-38c that together define a general shape in the form of a continuous strip with parallel rectilinear edges.

These zones 38a-38c are each obtained, in particular, by discontinuous spraying of security and/or decorative elements of different types.

For example, the zones 38a may be formed from HILITE™ particles that are invisible in daylight and that have a blue fluorescence under UV radiation.

The zones 38b may be formed, for example, from HILITE™ particles that have a white fluorescence and the zones 38c from HILITE™ particles that have a red fluorescence under UV radiation.

Thus, under UV radiation, the pattern 38 may appear as a succession of blue/white/red three-colored flags.

As a variant, the zones 38a-38c may be formed from TRACELESS™ markers from Creo, the concentration of which varies along the zones 38a-38c. These zones may form, for example, a barcode.

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

The pattern 40 may, for example, be formed from security and/or decorative elements that are visible to the naked eye, under appropriate lighting. This pattern 40 may make it possible to locate the pattern 41 formed, for example, from security elements that are invisible to the naked eye and that are detectable only using a specific device.

In the example illustrated in FIG. 12, the fibrous layer 20 comprises a pattern 42 having a shape in the form of a strip with parallel rectilinear edges, formed for example from security elements that are invisible to the naked eye.

This pattern 42 may be superposed over authentication and/or identification structures 43 that are visible to the naked eye, for example that comprise watermarks.

The authentication and/or identification structure 43 may, as a variant, comprise at least one security thread, an optically variable element such as a holographic foil or printing such as ink printing.

The structure 43 may be applied to the fibrous layer during or after the manufacture of this layer, during a conversion or printing operation for example.

As illustrated in FIG. 13, the fibrous layer 20 may comprise a pattern 39 formed from a succession of discontinuous zones, for example of rectangular shape.

The pattern 39 is superposed over a strip or security thread 44 incorporated at least partially into the bulk of the fibrous layer 20.

The pattern 39 is obtained, for example, by spraying a dye that has electromagnetic properties and forms a specific signature for the sheet material. The dye may be of the SECUSYSTEM® type sold by Bsecure, mixed with particles that are invisible in daylight and that have a red fluorescence under radiation at 365 nm.

In the example illustrated in FIG. 14, the sheet material 20 comprises first and second patterns 44 and 45 that each have a shape in the form of a strip with parallel rectilinear edges, these patterns being adjacent, and a third pattern 46 that has a shape in the form of a sinusoidal strip that is superposed over the patterns 44 and 45.

The first pattern 44 may be formed by spraying fibers that have a red color in daylight and a red fluorescence under radiation at 365 nm.

The pattern 45 may be formed from security elements such as HILITE™ particles that have a red color in daylight and a red fluorescence under radiation at 365 nm.

The pattern 46 is formed, for example, from HILITE™ particles that are invisible in daylight and that have a yellow fluorescence under radiation at 365 nm.

In the example illustrated in FIG. 15, the fibrous layer 20 comprises a first pattern in the form of a strip 47, a second pattern in the form of a strip 48 formed within the first pattern 47 and a third discontinuous pattern 49 formed within the pattern 48.

The pattern 49 is formed from discontinuous zones, these zones being, for example, disks or similar shapes obtained by solid conical jets.

The first pattern 47 may comprise second-level security elements, for example fibers that are invisible in ambient light and that have a blue fluorescence under radiation at 365 nm.

The second pattern 48 may be formed, for example, from security elements such as HILITE™ particles that have a red color in daylight and a red fluorescence under radiation at 365 nm.

The third pattern 49 may be formed, for example, from TRACELESS™ markers.

In the example illustrated in FIG. 16, the fibrous layer 20 comprises a first continuous pattern 50 that has a shape in the form of a strip and continuous second and third patterns 51 and 52 that also have a shape in the form of a strip and that are superposed over the first pattern 50.

The second and third patterns 51 and 52 are spaced apart from one another.

In the example illustrated in FIG. 17, the fibrous layer 20 comprises two patterns 53 and 54 that each have a shape in the form of a continuous strip with parallel rectilinear edges and that are partially superposed in an intersection zone 55.

The first pattern 53 is formed by spraying a dye that has a yellow color in daylight and a yellow fluorescence under radiation at 365 nm.

The second pattern 54 is formed by spraying a dye that has 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 style of a yellow/green/blue flag.

Of course, the invention is not limited to the exemplary embodiments which have just been described.

One of the nozzles may, for example, comprise a valve in order to interrupt the spraying jet.

One of the nozzles may be able to be moved on a support, for example in translation or in rotation, especially following an oscillating movement.

One of the nozzles may be able to be moved so as to vary the distance between this nozzle and the fibrous layer.

The expression “comprising one” should be understood as being synonymous with “comprising at least one”, unless otherwise specified.

Claims

1. A process for manufacturing a sheet material comprising at least one fibrous layer and a plurality of security and/or decorative elements, the process comprising at least one of: spraying the security and/or decorative elements onto one face of the fibrous layer, while traveling along a predetermined direction, so as to form one at least of a continuous pattern having at least one edge, substantially in the direction of travel, not completely parallel to the direction of travel and a pattern comprising a succession of disjointed zones; andspraying onto one face of the fibrous layer, security and/or decorative elements of at least two different types and/or that have a variable concentration.

2. The process as claimed in claim 1, the security and/or decorative elements being sprayed onto the fibrous layer using a pressurized fluid, especially a pressurized gas.

3. The process as claimed in claim 1, comprising: dispersing security elements in a fluid; andspraying the security and/or decorative elements onto the fibrous layer.

4. The process as claimed in claim 1, the spraying of the security and/or decorative elements being carried out using a spraying system comprising one or more spray nozzles.

5. The process as claimed in claim 1, the spraying system comprising a device for atomizing a liquid medium in order to create fine droplets.

6. The process as claimed in claim 4, the spraying system comprising at least one nozzle that may be alternately fed by at least two reservoirs of security and/or decorative elements capable of alternately spraying the security and/or decorative elements originating from the two reservoirs.

7. The process as claimed in claim 4, the spraying system comprising at least one jet divider arranged in order to divide, at the outlet of a nozzle, one jet into several jets.

8. The process as claimed in claim 1, the security and/or decorative elements being sprayed while forming at least one jet, the process comprising: moving the fibrous layer along a predetermined direction;moving the jet along a direction that is not parallel to the direction of movement of the fibrous layer.

9. The process as claimed in claim 1, the security and/or decorative elements being sprayed onto the fibrous layer continuously.

10. The process as claimed in claim 1, the security and/or decorative elements being sprayed onto the fibrous layer intermittently.

11. The process as claimed in claim 4, the security and/or decorative elements being sprayed onto the fibrous layer intermittently, and the spraying system being combined with a control system arranged in order to control the spraying of the security and/or decorative elements.

12. The process as claimed in claim 11, the control system comprising at least one of a pneumatic device and of a peristaltic device, or a combined pneumatic/peristaltic device arranged in order to control the spraying frequency, or a centrifugal pump or a mono pump.

13. The process as claimed in claim 1, the security elements being sprayed by forming at least one jet that has, in transverse cross section, a shape chosen from: a straight line segment, a corner such as a right-angled corner, a triangle, a rectangle or a square, a non-rectilinear curve such as an arc of a circle, a circle, an ellipse, an oval or S-shaped portion, a disk, or a wavy shape.

14. The process as claimed in claim 1, the spraying of the security and/or decorative elements onto the fibrous layer being carried out in-line, downstream of the wet part of the papermaking machine that is used to form the fibrous layer, especially before passing into a drying assembly of the papermaking machine.

15. The process as claimed in claim 1, the security and/or decorative elements being sprayed onto the fibrous layer so as to be dispersed over only one portion of the corresponding face of the fibrous layer.

16. The process as claimed in claim 1, comprising: spraying, simultaneously or successively, especially alternately, security and/or decorative elements of at least two different types onto the fibrous layer.

17. The process as claimed in claim 1, the security and/or decorative elements comprising elements detectable to the naked eye, in reflection and/or in transmission, in daylight.

18. The process as claimed in claim 1, the security and/or decorative elements comprising elements detectable to the naked eye, in reflection and/or in transmission under ultraviolet lighting.

19. The process as claimed in claim 1, the security and/or decorative elements comprising elements arranged in order to emit a specific signal when they are subjected to an optoelectronic, electromagnetic, electric, magnetic, thermal or acoustic excitation.

20. The process as claimed in claim 1, the security elements comprising at least one of the following elements: an active material, such as for example a chemical substance that absorbs in the UV or elements detectable by X-ray fluorescence;a particle or a pigment, especially one that is luminescent, fluorescent and/or phosphorescent;a biological, chemical or physical marker;a fiber such as a magnetic fiber, especially one that is weakly magnetized, or a fiber that is optically excitable, especially by exposure to infrared radiation; anda planchette.

21. The process as claimed in claim 1, the decorative elements comprising metallic particles and/or shiny or matt or colored particles, made of mineral or plastic material(s).

22. The process as claimed in claim 1, the sheet material comprising at least one authentication and/or identification structure, the security elements covering a zone of the fibrous layer that is superposed at least partially on the authentication and/or identification structure.

23. The process as claimed in claim 22, 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, or printing.

24. A papermaking machine that makes it possible to carry out the process as claimed in claim 1, the machine comprising: at least one wet part for forming a fibrous layer continuously; anda spraying system arranged in order to spray security and/or decorative elements over a still wet fibrous layer, formed in the wet part of the machine.

25. The machine as claimed in claim 24, the spraying system comprising at least one spraying device arranged in order to spray the security and/or decorative elements.

26. A sheet material obtained by the implementation of the process as claimed in claim 1.

27. The material as claimed in claim 26, the security and/or decorative elements covering one portion only of one face of the fibrous layer, the security elements being dispersed at least partially in the bulk of the fibrous layer, over a thickness smaller than that of the fibrous layer.

28. The material a s claimed in claim 26, the security and/or decorative elements that form a pattern having a succession of disjointed zones that are identical and/or repeated regularly.

29. The material as claimed in claim 25, comprising at least two types of security and/or decorative elements, the security elements of one given type covering one portion only of the face of the fibrous layer.

30. The material as claimed in claim 29, comprising at least two zones formed respectively by security and/or decorative elements of different types, these zones being adjacent or at least partially superposed.

31. The material as claimed in claim 26, comprising security and/or decorative elements that form one at least of: a continuous pattern, that extends from a first edge of the sheet material to a second opposite edge; anda succession of disjointed zones.

32. The material as claimed in claim 31, the continuous zone forming a pattern in the shape of a wavy strip or zigzag.

33. A process as claimed in claim 1, wherein the spraying is carried out while the fibrous layer is still wet.