EP1917396B1 - Sheet material and production method thereof - Google Patents

Description

The present invention relates to a sheet material and its manufacturing process.

We know by patent application EP 0 059 056 a method for making paper on a round-shaped paper machine comprising a rotary canvas cylinder having embossings at regular intervals, in the direction of paper formation. In this process, a safety wire is pressed against the rotary fabric cylinder before immersion in the fiber suspension contained in the tank. After the paper has been formed, pressing and drying steps make it possible to obtain windows on one side of the paper in which the security thread is visible. The process described in this application EP 0 059 056 is suitable for security wires of relatively small width. In addition, the pattern of the windows formed on the paper depends on the machines used for its manufacture so that it is difficult to obtain patterns as varied as desired.

The patent application GB 2,388,377 describes a method for manufacturing a fibrous substrate incorporating an elongated security element. The latter is incorporated into the fibrous mass during the formation of the paper in contact with a paper machine with a round shape comprising a rotary fabric cylinder provided with projecting portions for making windows in which the security element is exposed.

The patent application GB 2,381,539 describes a method for incorporating an elongated element into a paper, using a round-shape paper machine having two sets of projecting portions of different dimensions.

International demand WO 2004/050990 describes a method for manufacturing a fibrous substrate incorporating an elongated element having a variable width. During the formation of the fibrous substrate in a paper machine with a round shape, protruding portions on the rotary fabric cylinder make it possible to form on a first side of the substrate a first set of windows. The enlarged zones of the elongated element make it possible to influence the deposition of fibers so as to form on a second side of the fibrous substrate a second set of windows. This process can have the disadvantage that the outline of the windows of the second set is produced with an insufficient definition.

The patent EP-B1-690 939 (corresponding to the request WO 95/09274 ) describes a security paper comprising two layers of paper (also called jets) each with a plurality of windows arranged in line with windows of the other layer of paper. The paper can incorporate a transparent polyester strip arranged between the two layers so as to be visible through the windows. The strip is not immersed in the dispersion of fibrous material but introduced between the two paper jets before their assembly outside the respective baths.

We still know by demand WO 03/015016 a document comprising a fibrous layer and an electronic chip carried by a wire. The chip can come flush with one face of the fibrous layer while the thread is embedded in it.

Requirement WO 2004/040062 describes a strip security element intended to be partially integrated into a fibrous substrate, comprising one or more windows leaving visible portions of the security element.

The invention aims to propose a new method of manufacturing a sheet material by the papermaking process, comprising at least one fibrous layer having two opposite faces with on each of its faces at least one window.

The expression “sheet material” can denote in the description and the claims a fibrous sheet based on cellulosic and / or synthetic fibers, composite or not. A sheet material can for example have a relatively small thickness, in particular less than or equal to 3 mm, for example equal to approximately 100 μm, and be flexible. In an exemplary implementation of the invention, the sheet material can be packaged on a reel, in particular before being cut to the desired format.

• amener la structure en bande au contact de la couche fibreuse en formation, la face de la structure en bande avec la portion en relief étant disposée de manière opposée à ladite surface, la portion en relief présentant de préférence une épaisseur suffisante pour rester découverte au moins partiellement sur une face de la couche fibreuse, de manière à ménager l'une desdites fenêtres de la couche fibreuse.

According to one aspect of the invention, the fibrous layer is formed by depositing fibers on a surface, the sheet material further comprising at least one strip structure embedded at least partially in the fibrous layer, the strip structure having two faces. opposite with at least one of its faces at least a raised portion, and the method comprises the following step:

• bringing the strip structure into contact with the fibrous layer in formation, the face of the strip structure with the raised portion being disposed opposite to said surface, the raised portion preferably having a thickness sufficient to remain uncovered at least partially on one face of the fibrous layer, so as to form one of said windows of the fibrous layer.

The surface can be defined by the forming fabric of a machine with a round shape or with a flat table, a machine with a round shape being preferred.

The invention makes it possible to obtain windows of various shapes and / or sizes, simply by modifying the shape and / or the size of the raised portions of the strip structure which serve to form the windows of the fibrous layer.

Fibrous layers with different windows from one layer to another can easily be produced on the same paper machine, for example on a machine with a round shape.

The fibrous layer is preferably a monojet layer (“ single ply ” in English).

A raised portion of the strip structure can be flush with the corresponding face of the fibrous layer or, as a variant, protrude from this face of the fibrous layer and form an excess thickness sufficient to be detectable by touch in particular.

Advantageously, the raised portion of the strip structure has an at least partially hydrophobic outer surface, so as to prevent the covering of the raised portion by fibers during the formation of the fibrous layer.

In an exemplary implementation of the invention, the strip structure comprises at least one crenellated strip element defining at least one raised portion of the strip structure.

The crenellated strip element comprises at least one niche produced in particular by embossing, for example by thermal embossing.

The crenellated strip element can be made for example of plastic, in particular a hydrophobic plastic.

In another example of implementation of the invention, the strip structure comprises a strip support element with at least one face covered at least partially, for example totally, with a coating having a thickness chosen to form the portion in relief of the band structure.

The coating, preferably hydrophobic, can be deposited for example by screen printing.

The coating can be a varnish, for example a crosslinkable varnish under UV or infrared radiation, or by exposure to an electron beam.

In an exemplary implementation of the invention, one of the faces of the strip structure has no raised portion serving to form a window on one face of the fibrous layer.

The strip structure may for example comprise a first flat strip element and a second crenellated strip element assembled with the first, in particular with heat input.

As a variant, the strip structure comprises a strip support element of which only one face is at least partially covered with a coating having a thickness chosen to form the raised portion of the strip structure.

The strip structure can be porous, in particular the strip support element.

The strip structure may have openings, which may have a section of between 3 mm ² and 30 mm ² .

The area occupied by the openings can be greater than or equal to 40% of the total area of the strip structure seen from above, better greater than or equal to 50% and less than or equal to 60%.

The strip structure can include a perforated strip support element and the raised portion can be attached to the strip support element. The raised portion can be formed by a coating, in particular one or more impressions of a varnish or by an adhesive film transferred hot or cold.

The raised portion can create an additional thickness ranging from 10 μm to 50 μm, preferably from 25 to 35 μm, on the surface of the strip structure.

The strip structure may include at least one cavity in which an object, in particular a security element, is arranged at least partially. The object can be an electronic chip or a layer of liquid crystals.

The cavity can be produced in a strip support element, the object being partially covered, on at least one side, by an element at least partially defining the raised portion.

The object can be covered on both sides by elements defining raised portions of the strip structure.

In order to make windows on the face of the fibrous layer opposite to the raised portion (s) of the strip structure, the surface of the fabric forming the the fibrous layer advantageously comprises at least one hollow zone adjacent to at least one protruding zone arranged to form on the fibrous layer at least one window.

The recessed and projecting areas of the surface of the fabric forming the fibrous layer can in particular be produced by embossing.

The strip structure can be brought against the surface of the fabric forming the fibrous layer so as to make the raised portion of the strip structure coincide with a hollow area of said surface so as to form on each face of the layer fibrous a window arranged offset from the window on the other side.

As a variant, the strip structure is brought against the surface of the fabric forming the fibrous layer so as to make the raised portion of the strip structure coincide with a projecting area of said surface so as to form on each face of the fibrous layer a window opposite the window on the other side.

In an exemplary implementation of the invention, the strip structure comprises on each of its opposite faces at least one raised portion serving to form on each of the opposite faces of the fibrous layer at least one window.

The raised portions on the opposite faces of the strip structure can be opposite one another or, alternatively, arranged offset from one another, so as to form on the faces opposite of the fibrous layer, as the case may be, facing windows or offset windows.

In an exemplary implementation of the invention, the strip structure comprises first and second crenellated strip elements, forming raised portions on the two opposite faces of the strip structure.

The band structure may include a third, flat band element sandwiched between the first and second crenellated band elements.

In another example of implementation of the invention, the opposite faces of the aforementioned strip support element are each covered with a coating having a thickness chosen to form a raised portion.

Advantageously, the raised portion on the face of the strip structure coming opposite the surface for forming the fibrous layer has a thickness greater than that of the raised portion on the other face of the strip structure, which promotes the entanglement of the fibers on the side of the surface for forming the fibrous layer.

In an exemplary implementation of the invention, the strip structure comprises a single crenellated strip element used to form windows on the two opposite faces of the fibrous layer.

Preferably, the crenellated strip element is arranged in such a way that the slots do not undergo untimely deformation when the strip structure is subjected to tension stresses during the introduction of the strip structure into the layer. fibrous and / or during the formation thereof.

The fibrous layer can be produced on a round-shaped paper machine, as mentioned above, and be subjected, if necessary, to at least one of the pressing, calendering and drying operations.

At least one of the raised portions of the strip structure may have a shape defining a pattern, chosen in particular from a letter of the alphabet, a number, or a logo, this list not being limiting.

As a variant, at least one of the raised portions has a rectangular, square or circular shape.

The strip structure may comprise on a face a plurality of raised portions, in particular identical and regularly spaced.

As a variant, the strip structure comprises on a face a plurality of raised portions, at least two of which have different shapes and / or sizes.

In an exemplary implementation of the invention, the strip structure comprises at least one security element chosen from: an element with variable and / or diffractive optical effect such as for example a holographic, iridescent or liquid crystal element, interference compounds, a magnetic or crystalline coating, magnetic fibers, tracers detectable by magnetic resonance, tracers detectable by X-ray fluorescence, printing of a varnish or ink, luminescent or fluorescent tracers, photochromic, thermochromic compounds , electroluminescent and / or piezochromic and / or which change color in contact with one or more predetermined products, compounds sensitive to microwave radiation, anti-stock compounds.

The strip structure may comprise, if necessary, a strip support element at least partially covered with a coating, in particular a varnish, incorporating one or more security elements chosen in particular from the aforementioned security elements.

For example, the coating may include compounds having an effect on the polarization of light, in particular compounds of the nematic liquid crystal type.

In an exemplary implementation of the invention, the strip structure comprises, at least on one face, at least two raised portions serving to form two windows of the fibrous layer, these raised portions having properties, in particular optical , physical and / or chemical, different.

The two raised portions may for example have different colors or different magnetic properties.

As a variant, one of the raised portions can be produced for example from a magnetic material and the other from a material incorporating interference pigments.

The strip structure can, if desired, comprise a partially metallized layer, a metallized layer, or a layer of locally demetallized metal.

In an exemplary implementation of the invention, the strip structure comprises, on one face, at least one main raised portion serving to form a main window on one face of the fibrous layer and at least one additional raised portion having in particular a thickness and / or an area less than or equal to that of the main relief portion and arranged to compensate for a variation in thickness of the strip structure, in the vicinity of the main relief portion. This can facilitate the winding and unwinding operations of the strip structure by ensuring good flatness. The additional raised portion may have a thickness and an area less than that of the main portion and be entirely embedded in the fibrous layer.

Another subject of the invention is, according to another of its aspects, a sheet material comprising at least one single-jet fibrous layer, that is to say a single fibrous jet formed alone on the formation surface from a fiber-based dispersion, having two opposite faces with at least one window on each of its faces, the sheet material further comprising at least one strip structure embedded at least partially in the fibrous layer, the strip structure comprising at least one raised portion, the shape of at least one of the windows being defined by the raised portion , the latter coming for example flush with a face of the fibrous layer or projecting therefrom.

• soit est dépourvu de fenêtres en regard, de part et d'autre de la structure en bande,
• soit comporte au moins deux fenêtres en regard, l'une au moins étant formée par une portion en relief de la structure en bande.

Preferably, the sheet material:

• either has no facing windows on either side of the strip structure,
• or has at least two facing windows, at least one being formed by a raised portion of the strip structure.

The fibrous layer is advantageously devoid of at least one of its indentation faces, in particular of the type produced using recessed areas and projecting from a fabric forming a paper machine, located at the right of the band structure.

The sheet material can initially be devoid of printing an ink and can, if necessary, receive one later in order to include the useful information.

In an exemplary implementation of the invention, the windows on the opposite faces of the fibrous layer can be arranged facing one another or, as a variant, offset one with respect to the other. The facing windows can be of different size and / or shape.

At least one of the windows may, if desired, have a narrower width than that of the strip structure.

As a variant, at least one of the windows has a width equal to that of the strip structure.

The strip structure may have a width greater than 4 mm, in particular 5 mm, for example 10, 15 or 20 mm.

The strip structure may include a porous strip support element, in particular having openings having a section ranging from 3 mm ² to 30 mm ² , and at least one element defining a portion in relief on the strip structure, this portion in relief each having an apparent outer face.

The strip support element may include a cavity with an object placed inside, in particular a security element such as a chip or liquid crystals, the object and the strip support element being covered at least partially on at least one face, better on two opposite faces, by elements of the strip structure defining raised portions having visible faces.

Another subject of the invention is, according to another of its aspects, a security and / or valuable document comprising a sheet material as defined above.

The security and / or value document may consist of one of the following: a banknote, identity document, passport slip or cover, visa, coupon, document of other value than a bank note, for example a check or a credit card, a protection and / or authentication label, a traceability label.

Another subject of the invention is, according to another of its aspects, a packaging element, in particular a packaging, comprising a sheet material as defined above.

Another subject of the invention, according to another of its aspects, is a strip structure arranged to be incorporated at least partially into a fibrous layer.

In an exemplary implementation of the invention, the strip structure comprises on each of its opposite faces at least one raised portion serving to form on each of the opposite faces of the fibrous layer at least one window.

The strip structure may for example comprise a support element formed from a film with a polarization effect of light.

• la figure 1 illustre schématiquement une étape du procédé de fabrication d'un matériau en feuille selon un exemple de mise en œuvre de l'invention,
• la figure 2 représente, schématiquement et partiellement, en coupe, une structure en bande conforme à l'invention,
• les figures 3 et 4 représentent, schématiquement et partiellement, en coupe, deux exemples de matériaux en feuille incorporant la structure en bande de la figure 2,
• la figure 5 est une coupe schématique et partielle d'une structure en bande conforme à un autre exemple de mise en œuvre de l'invention,
• la figure 6 représente, schématiquement et partiellement, en coupe, un matériau en feuille incorporant la structure en bande de la figure 5,
• la figure 7 illustre schématiquement une étape du procédé de fabrication d'un matériau en feuille conforme à un autre exemple de mise en œuvre de l'invention,
• la figure 8 représente, schématiquement et partiellement, en coupe, un matériau en feuille conforme à un autre exemple de mise en œuvre de l'invention,
• la figure 9 représente, schématiquement et partiellement, une structure en bande conforme à un autre exemple de mise en œuvre de l'invention,
• la figure 10 représente, schématiquement et partiellement, en coupe, un matériau en feuille incorporant la structure en bande de la figure 9,
• les figures 11 à 13 représentent, schématiquement et partiellement, en coupe, des structures en bande conformes à différents exemples de mise en œuvre de l'invention,
• les figures 14 à 16 représentent, schématiquement et partiellement, différents exemples de documents conformes à l'invention,
• la figure 17 est une vue schématique et partielle d'une structure en bande conforme à l'invention,
• la figure 18 est une coupe transversale suivant XVIII-XVIII de la structure de la figure 17,
• la figure 19 est une vue de dessus d'un autre exemple de structure en bande réalisée conformément à l'invention, et
• les figures 20 et 21 sont des coupes longitudinales de matériaux en feuille incorporant des structures en bande réalisées selon d'autres exemples de mise en œuvre de l'invention.

The present invention will be better understood on reading the detailed description which follows, of nonlimiting examples of implementation of the invention, and on examining the appended drawing, in which:

• the figure 1 schematically illustrates a step in the process for manufacturing a sheet material according to an exemplary implementation of the invention,
• the figure 2 shows, schematically and partially, in section, a strip structure according to the invention,
• the figures 3 and 4 show, diagrammatically and partially, in section, two examples of sheet materials incorporating the strip structure of the figure 2 ,
• the figure 5 is a schematic and partial section of a strip structure in accordance with another example of implementation of the invention,
• the figure 6 shows, diagrammatically and partially, in section, a sheet material incorporating the strip structure of the figure 5 ,
• the figure 7 schematically illustrates a step in the process for manufacturing a sheet material in accordance with another example of implementation of the invention,
• the figure 8 shows, schematically and partially, in section, a sheet material in accordance with another example of implementation of the invention,
• the figure 9 shows, schematically and partially, a strip structure in accordance with another example of implementation of the invention,
• the figure 10 shows, diagrammatically and partially, in section, a sheet material incorporating the strip structure of the figure 9 ,
• the figures 11 to 13 schematically and partially represent, in section, strip structures in accordance with different examples of implementation of the invention,
• the figures 14 to 16 schematically and partially represent different examples of documents in accordance with the invention,
• the figure 17 is a schematic and partial view of a strip structure according to the invention,
• the figure 18 is a cross section along XVIII-XVIII of the structure of the figure 17 ,
• the figure 19 is a top view of another example of a strip structure produced in accordance with the invention, and
• the figures 20 and 21 are longitudinal sections of sheet materials incorporating strip structures produced according to other examples of implementation of the invention.

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.

Partially and schematically shown on the figure 1 a round-shaped paper machine. This machine comprises a tank 1 containing a suspension 4 of fibers, for example cellulose fibers and / or cotton linters and / or synthetic and / or artificial fibers, in which a canvas cylinder is partially immersed rotary 2 defining a surface 3 in contact with which continuously forms a fibrous layer 5 monojet.

A strip structure 7 is brought into contact with the fibrous layer 5 in formation so that the latter is at least partially embedded in the fibrous layer 5.

The strip structure 7 has two opposite faces 8 and 9, the face 9 being arranged opposite the submerged surface 3 of the rotary fabric cylinder 2.

The strip structure 7 comprises on the face 8 a plurality of raised portions 10 having a thickness sufficient to remain uncovered at least partially on one face 11 of the fibrous layer 5.

We have represented on figures 3 and 4 examples of sheet materials 6 obtainable by the process described with reference to figure 1 .

Each raised portion 10 of the strip structure 7 defines on the face 11 of the fibrous layer 5 a window 12.

The raised portions 10 can, as illustrated in the figure 3 , come flush with the face 11 of the fibrous layer 5 or, as a variant, as illustrated in the figure 4 , protrude on this face 11, for example by forming an excess thickness detectable to the touch.

In the example illustrated in figure 1 , the face 9 of the strip structure 7 is devoid of relief.

In order to make windows 13 on a face 14 of the fibrous layer 5 opposite to the face 11, the surface 3 of the rotary fabric cylinder 2 comprises, in the direction of formation of the fibrous layer 5, an alternation of hollow zones 16 and projecting zones 17, the latter serving to prevent the accumulation of fibers in regions of the fibrous layer 5 corresponding to the windows 13.

As illustrated in the figure 2 , the strip structure 7 may comprise a crenellated strip element 20 forming raised portions 10 and assembled, in particular heat-fixed, with a flat strip element 21.

The strip elements 20 and 21 are made of plastic, the notched strip element 20 being preferably made of hydrophobic plastic material, for example polyester, in order to promote the non-overlapping of the raised portions 10 by fibers during the formation of the fibrous layer 5.

The slots of the strip element 20 are produced by thermal embossing.

We illustrated on the figure 5 a strip structure 24 according to another example of implementation of the invention.

This structure 24 comprises a strip support element 25, for example of plastics material, substantially flat covered at least partially, on the face 8, with a coating 27 having a variable thickness to form raised portions 10.

The coating 27 may be a hydrophobic varnish which can be crosslinked under UV or infrared radiation, or by exposure to an electron beam, the varnish being deposited on the strip support element 25 in particular by screen printing.

We have represented on the figure 6 a sheet material 28 incorporating the strip structure 24 of the figure 5 .

In the examples described above, the strip structures 7 and 24 are pressed, when they are introduced into the fibrous layer 5 in formation, against the surface 3 of the rotary fabric cylinder 2 with an arrangement according to which each raised portion 10 coincides with a recessed area 16, as illustrated in the figure 1 .

As a result, the windows 12 on the face 11 of the fibrous layer 5 and the windows 13 on the face 14 are arranged alternately.

Alternatively, as illustrated in the figure 7 , the strip structure 24 is brought against the surface 3 of the rotary fabric cylinder 2 so as to make each relief portion 10 of the strip structure 24 coincide with a protruding area of the surface 3 so as to form on each face 11 of the fibrous layer 5 a window 12 facing a window 13 on the other face 14.

We illustrated on the figure 8 a sheet material 28 'obtained by the step of figure 7 .

In another example of implementation of the invention, the strip structure defines portions in relief on its two opposite faces.

We have represented on the figure 9 a strip structure 30 constituted by a crenellated strip element made of hydrophobic plastic material serving to form windows 12 and 13 alternated on the two opposite faces 11 and 14 of the fibrous layer 5.

We illustrated on the figure 10 a sheet material 31 incorporating the strip structure 30.

To form the sheet material 31, it is possible to use a rotary fabric cylinder 2 having a surface 3 ′ devoid of alternating recessed areas and projecting areas, shown flat on the figure 9 .

The crenellated strip element 30 has slots that are sufficiently rigid to withstand stresses in tension during the introduction of the strip element 30 into the fibrous layer 5 or during the formation thereof.

We will now describe other examples of band structures.

We illustrated on the figure 11 a strip structure 32 comprising first and second crenellated strip elements 33 and 34 used to form windows on the two opposite faces of the fibrous layer.

The strip structure 32 further comprises a third flat strip element 35 sandwiched between the first and second serrated strip elements 33 and 34.

We have represented on figures 12 and 13 a strip structure 37 comprising a strip support element 38 made of plastic material and covered on each of its opposite faces 8 and 9 with a varnish 39 having a variable thickness to form raised portions 10.

The raised portions 10 on the face 9 of the strip structure 37 facing the surface 3 'of the rotary fabric cylinder 2 has a thickness greater than that of the raised portions 10 on the other face 8, making it possible to promote the entanglement of the fibers on the side of the surface 3 '.

As illustrated in the figure 12 , the raised portions 10 on the face 8 can be in coincidence with those of the opposite face 9 so as to form on the opposite faces of the fibrous layer 5 of the facing windows.

Alternatively, as illustrated in the figure 13 , the raised portions 10 on the face 8 can be offset with respect to those of the other face 9 so as to form offset windows on the opposite faces of the fibrous layer 5.

The fibrous layer 5 can be subjected to at least one of the pressing, calendering and drying operations.

If desired, the strip structure 7, 24, 30, 32 or 37 may include a security element chosen from: an element with variable and / or diffractive optical effect such as for example a holographic, iridescent or liquid crystal element, interference compounds, a magnetic or crystalline coating, magnetic fibers, tracers detectable by magnetic resonance, tracers detectable by X-ray fluorescence, printing a varnish or an ink, luminescent or fluorescent tracers, photochromic, thermochromic, electroluminescent and / or piezochromic and / or color-changing compounds in contact with one or more predetermined products, compounds sensitive to microwave radiation, anti-stock compounds.

One of the aforementioned security elements can be incorporated into the layer of varnish 27 or 39.

The varnish 39 can be chosen to interact, in particular optically, with the strip support element 38.

We have represented on the figure 14 a security and / or value document 50 incorporating for example the sheet material 28 described with reference to the figure 6 .

Document 50 can be a bank note.

As a variant, the document may constitute one of the following elements: an identity document, a passport cover or sheet, a visa, a coupon, a document of value other than a banknote, for example a check or a credit card, a protection and / or authentication label, a traceability label.

The strip structure 24 extends from a first edge 51 of the document 50 to a second edge 52 opposite the first.

In the example of the figure 14 , the windows 12 formed by the strip structure 24 are identical and have a rectangular shape.

As a variant, the windows 12 can be circular in shape or have any other shape.

As illustrated in the figure 16 , the windows 12 can for example have a shape each defining a pattern such as, for example, an alphanumeric character, in particular a letter of the alphabet.

The different letters can form, if necessary, a word.

As a variant, one of the windows 12 can define a number or a logo for example.

The strip structure 24 may have a width greater than 4 mm, in particular 5 mm, for example 20 mm.

The windows 12 may have a width equal to that of the strip structure 24, as illustrated in the figure 14 or, alternatively, a narrower width than that of the strip structure 24, as illustrated in the figure 15 .

The different windows 12 of the document 50 may have different colors. For example, in the example illustrated in figure 16 , the letter A can appear in fluorescent yellow, the letter B in fluorescent red and the letter C in fluorescent blue.

The different windows 12 can have different properties. For example, in the example illustrated in figure 16 , the letter A can have “soft” magnetism properties, the letter B for fluorescence properties and the letter C for interference effects.

We illustrated on Figures 17 and 18 a strip structure 5 comprising, on one face, a plurality of main raised portions 56 serving each to form a main window on one face of the fibrous layer 5 and a plurality of additional raised portions 57 having a thickness and an area more weak than those of the main raised portions 56 and arranged to compensate for a variation in thickness of the strip structure 55.

The raised portions 57 are arranged, in the example considered, on either side of the raised portions 56.

We represented at the figure 19 a strip structure 90 comprising a porous strip support element 91 and an element 92 partially covering the strip element 91 in order to create the raised portion 10.

The element 91 is for example an element, preferably planar and not crenellated, which comprises openings 93 constituted for example by perforations.

These openings 93 extend, in the example considered, over substantially the entire surface of the element 91 elsewhere than under the element 92, the total section of the openings 93 representing for example more than 40%, better still more than 50% , of the total area of the element 91, being nevertheless for example less than or equal to 60%.

The presence of the openings 93 facilitates the entanglement of the paper fibers and therefore allows better anchoring of the strip structure within the sheet material.

This can also make it possible to use strip structures having a width for example greater than 5 mm, better still greater than 20 mm, for example of the order of 25 mm.

The section of each of the openings 93 is for example greater than 3 mm ² and less than 30 mm ² .

In the example considered, the openings 93 are holes of circular section whose diameter is preferably between 1 and 3 mm, in particular close to 2 mm.

The openings 93 can be made by perforation, for example by punching or with a punch.

The areas of the support element 91 intended to be covered by the element or elements 92 may or may not have the openings 93, and preferably do not.

The element 92 which creates the additional thickness is for example a deposit of a coating, for example one or more impressions of a varnish. The element 92 can also be an adhesive film which can be transferred cold or hot in the case of a heat-sealing adhesive.

The additional thickness created by the element 92 is for example of the order of 10 to 50 μm, preferably being close to 30 μm.

The element (s) 92 may be present only on one side only of the strip element 91 but preferably the elements 92 are present on the two opposite faces of the element 91, being arranged facing each other in pairs.

We represented at the figure 20 a sheet material, the fibrous layer 5 of which incorporates the strip structure 90, the element 91 being flush with one face 14 of the fibrous layer 5, the outer face 97 of the element 92 being flush with the opposite face 11 of the sheet material.

The strip structure may include, as illustrated in the figure 21 , at least one cavity 99 housing an object 100 such as for example a chip of an RFID device or liquid crystals. The cavity 99 can be produced in a support element in a strip 91, porous, for example having the characteristics described with reference to the figure 19 .

The cavity 99 can extend in a zone of the element 91 which is covered by the elements 92 intended to create the extra thicknesses on the strip structure, these elements 92 then ensuring protection of the object 100 against external aggressions such as for example the mechanical stresses exerted during printing.

In the example of the figure 21 , the strip structure is for example embedded in the thickness of the fibrous layer 5, so that the element 91 does not surface on the faces 11 and 14, only the outer faces 97 of the elements 92 coming out of these faces.

In variants not illustrated, the support element 91 is a knitted band, with wide stitches.

Of course, the characteristics of the various embodiments described can be combined with one another within variants not illustrated.

It is possible, for example, to produce a strip structure with a crenellated strip element on a first face and on a second face opposite the first a coating of variable thickness defining portions in relief.

At least one of the raised portions can be formed by an electronic device fixed to a strip support element, this device comprising in particular an electronic chip.

The raised portions of the strip structure can be arranged to form thicknesses detectable by touch on the two opposite faces of the fibrous layer.

The sheet material can for example be used to produce a packaging element such as packaging.

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

Claims (51)

1. Process for the manufacture of a sheet material (6; 28; 28'; 31) by a paper manufacturing route, comprising at least one fibrous layer (5) exhibiting two opposite faces (11; 14) with, on each of its faces, at least one window (12; 13), the fibrous layer being formed by deposition of fibres on a surface (3), the sheet material furthermore comprising at least one strip structure (7; 24; 30; 32; 37; 90) at least partially embedded in the fibrous layer, the strip structure exhibiting two opposite faces (8; 9) with, on at least one of its faces, at least one protruding portion (10), the process comprising the following stage:

   - bringing the strip structure (7; 24; 30; 32; 37; 90) into contact with the fibrous layer being formed, the face (8) of the strip structure with the protruding portion (10) being positioned in an opposite manner to the said surface (3), the protruding portion (10) exhibiting a thickness sufficient to remain at least partially uncovered on one face of the fibrous layer, so as to bring about one (12) of the said windows of the fibrous layer.
2. Process according to the preceding claim, the protruding portion (10) of the strip structure being flush with the corresponding face (11) of the fibrous layer.
3. Process according to Claim 1, the protruding portion (10) of the strip structure projecting from the corresponding face (11) of the fibrous layer.
4. Process according to any one of the preceding claims, the protruding portion (10) of the strip structure exhibiting an at least partially hydrophobic external surface.
5. Process according to any one of the preceding claims, the strip structure (7; 30; 32) comprising at least one crenellated strip element (20; 30; 33; 34), in particular made of plastic, defining the said at least one protruding portion (10) of the strip structure.
6. Process according to the preceding claim, the crenellated strip element (20; 30; 33; 34) comprising at least one crenellation produced by embossing, in particular by thermal embossing.
7. Process according to any one of Claims 1 to 4, the strip structure comprising a strip support element (25; 38) with at least one face at least partially covered with a coating (27; 39) exhibiting a thickness chosen in order to form the protruding portion of the strip structure.
8. Process according to the preceding claim, the coating (27; 39) being deposited on the strip support element by screen printing.
9. Process according to either of Claims 7 and 8, the coating (27; 39) being a hydrophobic coating.
10. Process according to any one of the preceding claims, one of the faces of the strip structure (7; 24) being devoid of protruding portion used to form a window on a face of the fibrous layer.
11. Process according to Claims 5 and 10, the strip structure comprising a first flat strip element (21) and a second crenellated strip element (20) assembled with the first, in particular with contribution of heat.
12. Process according to Claims 7 and 10, one face only of the strip support element (21) being at least partially covered with a coating (20).
13. Process according to any one of Claims 10 to 12, the surface (3) comprising at least one recessed zone (16) adjacent to at least one projecting zone (17) arranged in order to form, on the fibrous layer, at least one window (13).
14. Process according to the preceding claim, the strip structure being brought against the immersed surface (3) so as to cause the protruding portion (10) of the strip structure to coincide with a recessed zone (16) of the said surface in order to form, on each face of the fibrous layer, a window positioned in an offset manner with respect to the window of the other face.
15. Process according to Claim 13, the strip structure being brought against the surface (3) so as to cause the protruding portion (10) of the strip structure to coincide with a projecting zone (17) of the said surface in order to form, on each face of the fibrous layer, a window facing the window of the other face.
16. Process according to any one of Claims 1 to 10, the strip structure (30; 32; 37) comprising, on each of its opposite faces, at least one protruding portion (10) used to form, on each of the opposite faces of the fibrous layer, at least one window.
17. Process according to the preceding claim, the protruding portions (10) on the opposite faces of the strip structure facing one another.
18. Process according to Claim 16, the protruding portions (10) on the opposite faces of the strip structure being positioned in an offset manner with respect to one another.
19. Process according to Claim 4 and any one of Claims 16 to 18, the strip structure comprising first and second crenellated strip elements (33; 34).
20. Process according to the preceding claim, the strip structure comprising a third flat strip element (35) sandwiched between the first and second crenellated strip elements (33; 34).
21. Process according to Claim 7 and any one of Claims 16 to 18, the opposite faces of the strip support element (38) being each covered with a coating (39) exhibiting a thickness chosen in order to form a protruding portion.
22. Process according to any one of Claims 16 to 21, the protruding portion on the face of the strip structure facing the surface (3) exhibiting a greater thickness than that of the protruding portion on the other face of the strip structure.
23. Process according to Claims 5 and 16, the strip structure comprising a single crenellated strip element (30) used to form windows on the two opposite faces of the fibrous layer.
24. Process according to any one of the preceding claims, at least one of the protruding portions of the strip structure of the fibrous layer exhibiting a shape defining a pattern, chosen in particular from a letter of the alphabet, a number or a logo.
25. Process according to any one of the preceding claims, the strip structure comprising at least one security element chosen from: an element having a variable and/or diffractive optical effect, such as, for example, a holographic, iridescent or liquid-crystal element, interference compounds, a magnetic or crystalline coating, magnetic fibres, tracers detectable by magnetic resonance, tracers detectable by X-ray fluorescence, a printing of a varnish or of an ink, luminescent or fluorescent tracers, photochromic, thermochromic, electroluminescent and/or piezochromic compounds and/or compounds which change colour on contact with one or more predetermined products, compounds sensitive to microwave radiation or anti-Stokes compounds.
26. Process according to any one of the preceding claims, the strip structure comprising, on at least one face, two protruding portions used to form two windows of the fibrous layer, these protruding portions exhibiting different properties, in particular optical, physical and/or chemical properties.
27. Process according to the preceding claim, the said two protruding portions (10) exhibiting different colours.
28. Process according to any one of the preceding claims, the strip structure comprising, on one face, at least one main protruding portion (56) used to form a main window on a face of the fibrous layer and at least one additional protruding portion (57) having in particular a thickness and a surface area which are lower than those of the main protruding portion and which is arranged in order to compensate for a variation in thickness of the strip structure, in the vicinity of the main protruding portion.
29. Process according to any one of the preceding claims, the fibrous layer (5) being manufactured on a cylinder mould paper machine, the surface (3) being defined by the forming fabric immersed in a dispersion of fibrous substance of the machine.
30. Process according to any one of the preceding claims, the strip structure being porous, in particular the strip support element of Claim 7 being porous.
31. Process according to Claim 30, the strip structure comprising openings.
32. Process according to Claim 31, the openings having a section of between 3 mm² and 30 mm².
33. Process according to Claim 31 or 32, the surface area occupied by the openings being greater than or equal to 40% of the total surface area of the strip structure seen from above, better still greater than or equal to 50% and less than or equal to 60%.
34. Process according to any one of Claims 30 to 33, the strip structure comprising a porous, in particular perforated, strip support element and the protruding portion (10) being added to the strip element.
35. Process according to Claim 34, the protruding portion being formed by a coating, in particular one or more printings of a varnish, or by an adhesive film transferred under hot or cold conditions.
36. Process according to Claim 34 or 35, the protruding portion (10) creating an excess thickness ranging from 10 µm to 50 µm, preferably from 25 to 35 µm, at the surface of the strip structure.
37. Process according to any one of the preceding claims, the strip structure comprising at least one cavity in which an object, in particular a security element, is at least partially positioned.
38. Process according to Claim 37, the object being a chip or a layer of liquid crystals.
39. Process according to Claim 37 or 38, the cavity being produced in a strip support element and the object being partially covered, on at least one side, with an element at least partially defining the protruding portion (10).
40. Process according to Claim 37, the strip support element being porous, in particular perforated.
41. Process according to Claim 39 or 40, the object being covered on both its sides with elements defining protruding portions (10) of the strip structure.
42. Sheet material comprising at least one single-ply fibrous layer (5) exhibiting two opposite faces with at least one window on each of its faces, the sheet material furthermore comprising at least one strip structure (7; 24; 30; 32; 37; 90) at least partially embedded in the fibrous layer, the strip structure comprising at least one protruding portion, the shape of at least one of the windows being defined by the protruding portion, the latter being flush with a face of the fibrous layer or projecting from the latter.
43. Material according to the preceding claim, characterized in that the windows on the opposite faces of the fibrous layer are positioned facing one another.
44. Material according to either of Claims 42 and 43, characterized in that the windows on the opposite faces of the fibrous layer are positioned in an offset manner with respect to one another.
45. Material according to any one of Claims 42 to 44, characterized in that at least one of the windows exhibits a smaller width than that of the strip structure.
46. Material according to any one of Claims 42 to 45, characterized in that the strip structure exhibits a width of greater than 4 mm, in particular 5 mm, for example 10, 15 or 20 mm.
47. Sheet material according to Claim 42, the strip structure comprising a porous strip support element, in particular exhibiting openings (93) having a section ranging from 3 mm² to 30 mm², and at least one element defining a protruding portion (10) on the strip structure, this protruding portion having an obvious external face.
48. Sheet material according to Claim 47, the strip support element comprising a cavity having an object (100) positioned inside, in particular a security element, such as a chip or liquid crystals, the object and the strip support element being at least partially covered on at least one face, better still on two opposite faces, with elements (92) of the strip structure defining protruding portions having obvious faces.
49. Security document and/or document of value (50) comprising a sheet material as defined in any one of Claims 42 to 48.
50. Document according to the preceding claim, constituting one of the following elements: a bank note, an identity document, a passport page or cover, a visa, a ticket, a document of value other than a bank note, for example a cheque or a credit card, a protective and/or authenticating label or a traceability label.
51. Packaging element, in particular a package, comprising a sheet material as defined in any one of Claims 42 to 48.

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