EP2082097B1 - Security film comprising a fibrous substrate - Google Patents

Description

The invention relates to the field of security documents. It relates to a security sheet comprising a security tape and the method of manufacturing the security sheet. It also concerns the security tape itself.

Security documents are produced from particularly fibrous materials and may include banknotes, identity cards, passports, driving licenses, visas, checks, vouchers, tickets or admission tickets to a cultural or sports event.

In the manufacture of a security sheet for the production of a security document comprising security elements in tape, there are mainly two modes of obtaining strips containing said security elements: either one introduces small security elements, for example such as boards which are plastic and / or paper elements, flat and of relatively small size, or such as colored or luminescent fibers, or a fine ribbon commonly called "security thread" is introduced ". This ribbon is generally made of plastic and comprises security elements, for example luminescent.

The introduction into strips of security elements of relatively small size such as fibers or boards may in particular be done, if the paper machine is a flat-table machine, by laminar flow of a jet containing a suspension of said elements. security over a sheet of paper in formation which will then be pressed and dried according to the current papermaking process. This method of introduction is described for example in the patent application EP 1 253 241 .

In the case of a paper machine equipped with a round shape, the introduction in strip of said security elements can in particular be done by supply ducts placed along the width and opening into the shape tank nearby. from round form, before the beginning of draining of a fibrous suspension on a fabric of a round form. After draining, a security sheet is obtained which is then pressed and then dried according to the current papermaking process.

The main drawback relating to said first method of obtaining a band containing security elements is the irregular dispersion of said security elements. Due to the introduction of the elements, it is difficult to obtain a band whose edges are regular and within which the distribution of the elements of security is relatively homogeneous, in the width (x) and in the length (y) but also in the thickness (z) of said security sheet.

These variations of bandwidth and spatial distribution (x, y, z) of the security elements can be particularly troublesome in the case of recognition and / or authentication and / or identification based on the spatial distribution (x, y , z) said security elements in said security document. Indeed, because of too great variability, the use of the position or the width of said band, or the spatial distribution of said security elements, for purposes of recognition and / or authentication and / or or identification, may in particular be impossible to implement.

The terms "recognition", "authentication" and "identification" are defined here as follows: "recognition" applies when a document or element of a document is compared to a reference to determine the authenticity of that document document or element, "authentication" means determining whether the document is authentic or whether it has been falsified or counterfeited, and "identification" is the verification of the identity of the owner of a given document.

In particular, the type of problem mentioned above is encountered in the case of authentication of security elements automatically using a non-portable device based on the specific signal of one or more elements (s). ) of security. Indeed, some of said security elements are covered with a layer of fibers and / or mineral charges too thick to allow the correct detection of their specific signals by said automatic authentication device. Thus, for a signal having a given intensity, it is necessary to introduce a larger quantity of security elements in order to compensate for the loss of signal intensity.

According to said second method for obtaining a strip containing security elements, said introduced security threads generally have a width of less than 10 mm, a thickness of between 12 and 45 μm and are, in most cases, made up of ribbons of plastic materials, in particular based on polyester.

Said security son are in particular secured by visible or non-visible patterns, in positive and / or negative, optically variable devices and in particular holograms, luminescence and in particular fluorescence, magnetism, electrical conduction or still thermochromic.

Said security threads are incorporated inside the fibrous substrate constituting said security sheet is "en masse", that is to say completely covered with fibrous material, or "window", said security thread being then located on the surface of said security sheet and en masse in the latter, for example in an alternating manner. In particular, the windows thus described may or may not be through, depending on whether said security thread appears respectively on two or on one side of said security sheet.

The introduction of said security son en masse can in particular be carried out in a single jet, on a paper machine flat or round table. In the case of a round shape, the wire is introduced into the shaped tank before or shortly after the beginning of the draining of the fibrous suspension on the fabric. The position of said security thread in the thickness of the final security sheet is determined in particular by the place and the insertion inclination of said security thread. The jet thus obtained can then be married in the wet state, that is to say before drying, with other jets whose fibrous compositions can be identical or different and which can be formed on paper machines at the table flat or round.

Another way of introducing said security son en masse is to incorporate them between two successive jets produced on a flat table and / or a round shape, before the "marriage" of said successive jets by wet pressing. Said jets can themselves be married to other jets whose compositions may be identical or different and which can be formed on a flat table or a round shape, before or after the introduction of said security son. After their marriage, the two successive streams comprising said security son are eventually married to the other jets and then dried according to the current papermaking process to obtain a security sheet.

The introduction of a window security thread in a single jet is for example described in the patent applications EP 059 056 for a paper machine with round shape and EP 0 609 252 for a flat-table paper machine. The window introduction between two jets of a multijet fibrous material is described in the patent application. EP 229 645 .

In order to improve their adhesion in the fibrous substrate, said security threads may in particular be coated with an adhesive, for example heat-sealing products also called hot-reactive products.

The introduction of said security threads may in particular lead to a poor overlap of said security threads characterized, when they are introduced en masse, by a lack of material above said security threads and, when they are introduced in a window, by insufficient bridging. By bridging is meant the fibrous covering of a security thread introduced in the windows in the zones between the windows, that is to say at the places where the thread is contained in the mass of said security sheet. These lacks of fibrous material on said security thread are commonly referred to as "sparkling effect". They are all the more pronounced that said security sheet in which said security threads are introduced is of low grammage.

This sparkling effect is reflected in particular by visual defects on said security sheet and by embrittlement of said security sheet, thus constituting a drawback of the prior art security sheets containing said security threads.

In addition, the incorporation in mass or window safety son whose width exceeds about 1.5 cm is difficult because it causes breakage of the fibrous sheet at the "wet end" of the paper machine, c that is, before drying the paper sheet. In addition, the more the breaks in the sheet occur upstream on the paper machine, the more they are annoying, on the one hand because the path to bring the sheet up to winding is longer, and secondly because this course is more difficult to achieve, because of the less dry and therefore the greater fragility of the leaf. A rupture of the leaf in wet part will be more troublesome than a break in drying because it will require cleaning times, restart and put to good production more important.

These failures can in particular be caused by defects in the coverage of said security threads or their insufficient bridging as previously stated. Indeed, the more said security son are wide, the more said defects are pronounced. This results in greater embrittlement of the sheet, in particular along the insertion strips of said safety threads, and consequently a greater frequency of breaks in the sheet.

In addition, the adhesives, for example heat-sealing coatings, which can be added to said security threads develop their adhesive properties only after drying of said paper sheet containing said security threads, and the plastic materials constituting said security threads being hydrophobic, said security son of the art prior art do not develop any bond with the fibrous substrate of said security sheet during dewatering and pressing which take place in wet part, that is to say, before drying of the sheet. Consequently, the introduction of said security threads weakens said security sheet along the introduction strip, the adhesion properties of said security thread coated with an adhesive, for example a heat-sealing product, not being developed only during drying.

In addition, if said security threads are too wide, their impermeability impedes the drainage of the water contained in the fibers located above the son and thus prevents the consolidation of the fibrous mat, which causes in particular breakage of the sheet partially wet paper during the production of security sheets containing said security threads. When the width of said security son exceeds about 1.5 cm, the fibrous mat is no longer strong enough and causes too many breaks of the paper sheet to allow a correct machinability of the paper machine.

Because of the technical problems described in the preceding paragraphs, said security threads have the particular disadvantage of their limited width.

The materials of which said security threads are composed are generally plastic films which are optionally metallized and then possibly coated with varnish.

Another disadvantage of said security threads is that they can be combined only with very fine particles and, in particular, by printing and / or metallization. For example, the incorporation of flat security elements and relatively small size, such as boards, is impossible because of the materials of which said security son are constituted.

The European patent application EP 0 557 157 of the Applicant describes the manufacture of a security sheet having monochrome or polychrome signs visible in transmitted light. The security sheet is manufactured from at least two fibrous jets and a strip having monochrome or polychrome marks introduced between the two fibrous jets. The strip thus introduced advantageously comprises cellulose fibers and a soluble and / or fusible binder product so that said product can be dispersed during the incorporation of the strip between the two jets so that the band disappears within sheet and that the printed marks are intimately linked to the sheet. The band thus obtained is completely destructured within the security sheet.

Requirement FR 2 847 915 discloses the incorporation, into a secure paper, of a ribbon made of a different tissue from a paper.

The French patent application FR 2 679 934 of the Applicant describes a system for authenticating a security paper using a first chemical reagent present on the security paper, an authentication composition comprising a second chemical reagent forming a colored product with the first chemical reagent and an erasing composition of the colored product. The chemical reaction occurring during the authentication between the second reagent and the first chemical reagent only produces a coloration of the zone where the reaction occurs.

International demand WO 2006/095033 relates to a safety band comprising a ribbon of a cellulosic support formed of vegetable fibers. The cohesion and the integration of the ribbon in the substrate of the strip are ensured by the creation of chemical bonds between the vegetable fibers contained in the ribbon and in the substrate, in particular hydrogen bonds, but do not allow the ribbon to maintain its integrity. and its cohesion within the substrate of the strip, especially when the strip is placed in a wet environment, in case of an attempt to recover the strip by a counter factor, for example.

The invention aims to further improve the security sheets.

The invention relates for this purpose to a security sheet comprising a fibrous substrate in which is incorporated, at least partially, a ribbon extending between two edges of said fibrous substrate, said security tape being made of paper.

The security tape comprises, in a preferred embodiment of the invention, at least one adhesive, for example at least one heat-sealing agent.

The ribbon also comprises, in a preferred embodiment of the invention, at least one security element.

Preferably, the ribbon extends between two opposite edges of said security sheet.

The term "substrate" denotes a fibrous sheet that may especially comprise one or more fibrous layers. In particular, the term "jets" will be used to denote layers produced continuously on the same paper machine and then associated with the wet state.

The invention can make it possible to provide a security sheet with security elements arranged in a band with a relatively homogeneous spatial distribution (x, y, z).

The above adhesive optimizes the adhesion of the security tape in the security sheet

The adhesive may for example be a heat-sealing coating, for example a heat-sealing varnish, an ultraviolet (UV) cross-linkable agent, an adhesive to be irradiated, a pressure-sensitive adhesive (PSA), a varnish with a solvent base, of the type polyester for example, an adhesive in the aqueous phase, etc.

As adhesive in the aqueous phase, mention may be made especially of the following marks: Mowilith DC (aqueous dispersion of vinyl acetate homopolymer with particles of size ranging from 0.3 μm to 2 μm and glass transition temperature T _g of 38 About C °, and solids dry content between 55 and 57%) and Vinamul 3265 from the company CELANESE; DH9004, DH9017, DH9044 and DL5001 from the company COLLANO; Primal NW1845, Primal LC40, Primal P308M and Primal EP6000 from ROHM &HAAS; the 006SDW078-2 from BASF.

The adhesive may advantageously be an adhesive based on polyvinyl acetate such as Mowilith DC.

The Applicant has found that among the adhesives mentioned above, Vinamul 3265, Mowilith DC, Collano DL5001, Primal NW1845 and Primal P308M have very good results in the dry crumple test, that is to say that the porosity of the paper is not excessively affected by wrinkling.

In addition, Vinamul 3265 and Mowilith DC also perform very well in the wet crumple test. Mowilith DC has very good results in the wash test.

Also, Mowilith DC provides very good results in terms of adhesiveness, but the invention is not limited to a particular adhesive.

According to an exemplary implementation of the invention, the adhesive is not present in the form of fibers or in particulate form.

The incorporation of the adhesive into the security tape can be done by coating.

The coating can be carried out at least partially at the core, that is to say reach in depth, or even in totality the security tape, or at the surface.

Preferably, the coating is performed on the support used for the manufacture of the tape before cutting the support. Alternatively, the coating can be performed during the manufacture of the support for the manufacture of the security tape.

The coating can be performed on one side of the support or on both sides of the support. The adhesive can completely cover the face on which it is deposited.

The incorporation of the adhesive tape security can also be done by impregnation, by dipping the tape or the support for making it in a bath.

The safety tape retains its own cohesion after introduction into the fibrous substrate. Also, the structure of the security tape may be observable after its introduction into the fibrous substrate under certain conditions, for example in section or by vision in reflection or transmission. Thus, it may be possible to observe the security tape due to differences in optical properties, for example differences in contrast, hue, saturation, clarity, opacity, which make visible a border between the ribbon and the substrate or characterize the presence of the ribbon.

In order to detect the presence of the adhesive in a security sheet according to an exemplary embodiment of the invention, it is possible to observe the adhesive, for example the heat-sealing varnish, in the form of bubbles, for example using a scanning electron microscope (SEM).

The security tape may be observable by topography in the sheet.

The security tape can be observed by transparency in the sheet, in particular with the naked eye.

The security tape may comprise at least one security element on one of its faces, or even on each of its faces. The security tape may have different security features on each side.

The security tape may have irregularly shaped edges, for example in the form of broken or wavy lines, crenellations, zigzag, among others. The edges of the security tape may have the same shapes or different shapes, regular or irregular.

The security tape may be transparent or translucent or even opaque, for example a dark appearance, especially darker than the substrate. It can be introduced or not into the fibrous substrate window. The introduction in window can in particular make it possible to obtain different variations of opacity when the security tape is opaque. The security tape can optionally be combined with a strip of thermoplastic material and / or metal, for example PET, laminated or hot rolled to the ribbon before its introduction into the fibrous substrate.

The security tape can still have different characteristics perceptible for example to the sight or touch.

The security tape may for example be embossed, thus creating a particular effect, for example a touch or surface relief, the ribbon may appear partially on the surface of the fibrous substrate.

The security tape may be coated with a thermoplastic polymer and optionally embossed as a result of this coating.

The security tape can be printed with drops of varnish, resin or thermo-inking ink, among others.

When the ribbon comprises impressions, this may for example allow to obtain variable optical effects.

The security tape may comprise a heat-reflecting ink for creating at least one relief, this ink being activated before introduction of the ribbon in the fibrous substrate. Activation before incorporation reduces the risk of destructuring the sheet during swelling of the ink.

The security tape may comprise particles, for example detectable with the naked eye or with the touch, introduced in mass in the security tape, for example in the form of balls, for example balls of a synthetic material, for example the polyurethane, or mineral, for example glass, of dimension for example less than 300 microns, or by deposition by screen printing or gravure, for example in the form of beads, for example less than 100 microns in size.

The security tape may comprise a textile band, for example knitted, integrated ribbon or laminated tape.

The security tape may include an embossed print, for example screen printed.

The safety tape may have a greasy, rough, smooth, silky, soft look, among other things.

The security tape may in particular comprise polymer deposits, in particular in the form of beads, for example polyurethane (PU) beads, glass, polyamides 6 or 12, styrene-acrylic pigments, polypropylene (PP) waxes or beads, polyethylene (PE), polyvinyl chloride (PVC), methyl methacrylate-based polymers, the ribbon being for example introduced in window.

In order to obtain said security tape, it is possible to first manufacture a fibrous sheet, preferably of light weight, for example between about 15 and 90 g / m ² , according to a current papermaking process, that is to say for example by draining a suspension of fibers optionally comprising conventional fillers and additives in stationery, the possible specific safety elements, pressing of the fibrous mat obtained and drying. This sheet is then optionally calendered which allows in particular to reduce its thickness, and then cut to form ribbons which are then wound into coils.

The addition of the adhesive to the security tape may in particular be done by a coating process, for example a coating, or by processes resulting from printing techniques of a paper base after its manufacture, for example coating air-blast, rotogravure, screen printing, curtain coating, flexography, among others.

Preferably, a photogravure process is used.

Alternatively, the coating of the security tape can be done during the manufacture of the fibrous sheet, for example by surface coating on sizing press or impregnation.

The coating of the adhesive, for example on a fibrous sheet used for the manufacture of the ribbon, can be carried out for example at a rate of 2 to 15 g / m ² per side, preferably between 3 and 8 g / m ² per face.

The sealing temperature can vary between 70 and 135 ° C, for example, depending on the adhesive used, and sealing can take place during drying of the security sheet.

In an exemplary embodiment of the invention, a 20 g / m ² wet-strength fibrous sheet (REH) is coated with an adhesive in the aqueous phase at a rate of 5 g / m ^2. m ² per side, using, for example, a photogravure process. This gives a satisfactory compromise between adhesion power and amount of coated material.

The introduction of said security ribbons within said fibrous substrate can in particular be done according to the introduction modes of the plastic security threads of the art. prior as described above or by laminating said security tapes between two sheets or fibrous layers which then constitute the base of said fibrous substrate.

Said security sheet proposed by the Applicant comprises at least one paper security tape which may be wider than said security threads of the prior art without presenting fibrous overlap defects or insufficient bridging as described above. This results in particular from the permeability of said paper security ribbons which promotes drainage, as well as the good affinity between the fibers of said paper security tape and the fibrous material of said substrate.

In addition, said security tapes can be incorporated in said fibrous substrate without causing an increase in the frequency of breakage of the sheet, and this in particular because of the preferred composition of said paper security tapes. Indeed, said security tapes preferably comprise hydrophilic fibrous materials, in particular such as cellulosic fibers or synthetic fibers or optionally mineral fibers treated by sizing, so as to develop with said fibrous substrate bonds making it possible to reduce its embrittlement due to in particular to the introduction of an element into said fibrous base. The size is a fiber coating that allows in particular to make them hydrophilic.

It is therefore possible to obtain a good cohesion of said security sheet and therefore both a good machinability in the wet part and the possibility of introducing security elements in relatively wide bands.

Compared to the prior art consisting of the introduction of small band security elements, by laminar flow over a safety sheet forming on a flat table or by at least one localized supply during the formation of A security sheet in a shaped tank, the present invention can achieve if desired said elements in a band whose boundaries are clear and within which the distribution of security elements is homogeneous.

In addition, because of the mode of incorporation of said security tape in said fibrous substrate, the positioning of said security elements of said paper security tape in the thickness of said security sheet is improved. This solves the problems presented above which arise in particular for certain authentications based on the spatial distribution (x, y, z) of said security elements.

According to an exemplary embodiment of the invention, said substrate comprises, in addition to said security tape, at least one security element, in particular chosen from tracers, in particular nanoscale, security fibers, in particular metallic, magnetic (to soft and / or hard magnetism), or absorbent or excitable in the ultraviolet (UV), the visible or the infrared (IR) and in particular the near infrared (NIR), the flat and relatively small security elements such as that the boards, the pigments or agglomerates of pigments in particular absorbing or excitable under Laser illumination or in the ultraviolet (UV), the visible or the infrared (IR), in particular the near infrared (NIR), and the security threads (Generally based on plastics, in particular of polyester) comprising in particular an at least partial coating, metallic, metallized, iridescent or magnetic (with soft magnetism and / or hard), said coating being able in particular c have positive or negative motives and said patterns may in particular be obtained by demetallization, the chemical or biochemical infadification and / or authentication and / or identification reagents may in particular react with at least one agent respectively of falsification and and / or authentication and / or identification, and optically variable elements including holograms, liquid crystals, iridescent pigments or mirror effect structures, in particular dielectric layers, and combinations thereof.

Said fibrous substrate may in particular comprise security elements visible to the naked eye, but it may also comprise tracers which are in the form of active material, particles or fibers, capable of generating a specific signal when these tracers are subject to to optronic, electrical, magnetic or electromagnetic excitation. These "tracers" constitute an identifiable substance through a distinctive property and used to mark an element (a security document in this case) and ensure its follow-up, the follow-up of its evolution or allow its recognition, authentication or identification.

The dielectric structures with a mirror effect consist of an alternation of high and low index layers, for example respectively of Hafnium dioxide and of silica, and may in particular be obtained by ion etching.

The paper security tape may be based on cellulosic fibers (in particular cotton fibers) and / or natural organic fibers other than cellulosic and / or synthetic fibers, for example such as polyester or polyester fibers. polyamide, and / or optionally mineral fibers, for example such as glass fibers. The safety tape may not include polyvinyl alcohol (PVA) fibers.

Preferably, said fibers are hydrophilic, in particular so as to develop chemical bonds, mainly hydrogen, with said fibrous substrate.

Preferably, said security tape comprises by weight at least 50% of cellulosic fibers.

According to the invention, the fibrous substrate is based on fibers as described above for the ribbon.

According to a particular case of the invention, the fibrous substrate and said security tape are based on the same fibers, that is to say that their fiber composition is the same in nature and preferably in the same proportions, this allows good affinity between the two components and may, in addition, be an additional means of authentication.

According to a particular case of the invention, said security tape has a width of between 2 and 60 mm, preferably between 4 and 30 mm and more preferably between 10 and 20 mm.

In particular, said security tape may comprise perforations, in particular to promote drainage during the manufacture of said security sheet.

According to another example of implementation of the invention, said security tape has a thickness of between 20 and 120 microns, preferably between 30 and 80 microns, and more preferably between 45 and 55 microns.

According to another particular case of the invention, said security tape comprises at least one filigree pattern.

According to a particular case of the invention, said fibrous substrate comprises at least one filigree pattern.

According to a particular case of the invention, said fibrous substrate and said safety tape each comprise at least one filigree pattern, said patterns being complemented by superposition and / or association.

In particular, said filigree patterns may be superimposed so as to obtain a moire effect. Such an effect reveals a particular pattern produced by the approximation of lines during the superposition of two patterns of periodic structure and in particular screened.

The security tape may include a watermark and possibly perforations around this watermark.

The security tape can still be colored, in particular having a different color from that of the substrate.

For a papermaker producing watermarked documents, another advantage of the invention in the case of a ribbon having a watermark, is the use of its usual sheet making tools and processes. For example, it produces a stock of filigree papers, colored or not, which it cuts and stores in ribbons. At the desired moment, these ribbons will then be introduced during the production of security sheets, which will allow the paper manufacturer to work with a "veline canvas", that is to say, not embossed. Indeed the embossing of the fabric that allows the formation of watermarks on the security sheets of the prior art has the disadvantage of requiring several days of work. Thus, the incorporation of watermarks arranged on paper security ribbons makes it possible to gain flexibility in the planning of manufacture.

According to a particular case of the invention, said paper security tape comprises at least one security element chosen from tracers, in particular nanoscale, security fibers, especially metallic, magnetic (with soft magnetism and / or hard), or absorbing or excitable in the ultraviolet (UV), the visible or the infrared (IR) and in particular the near infrared (NIR), the flat and relatively small security elements such as boards, pigments or pigment agglomerates particularly absorbent or excitable under laser illumination or in the ultraviolet (UV), visible or infrared (IR), in particular the near infrared (NIR), and security son (based on plastics, especially polyester) comprising in particular an at least partial coating, metallic, metallized, iridescent or magnetic (with soft and / or hard magnetism), said coating being able to include, in particular, positive or negative patterns, and In particular, the units that may be obtained by demetallization, the chemical or biochemical infadification and / or authentication and / or identification reagents may in particular react with at least one falsification and / or authentication agent and / or identification, and optically variable elements including holograms, liquid crystals, iridescent pigments or mirror effect structures, particularly dielectric, and combinations thereof.

The incorporation of tracers in a security document by means of a security paper tape is located, which allows in particular to create an area, possibly invisible to the naked eye, recognition and / or authentication of said security document. The recognition and / or authentication of said document may in particular be based on the intensity and / or the type of the signal generated by the tracers, considered individually or not, on the density of the tracers, or on their spatial distribution in a zone. predefined or not of the document. In particular, randomly distributed tracers can form a unique signature and thus be used for identification purposes.

In particular, the introduction into a security sheet of pigments or agglomerates of absorbent pigments in the infrared or in the near infrared as mentioned above, can be used to make said sheet authenticatable, as described in the patent application. WO 2005/034049 . This same application recommends more particularly the use of kaolin and talc mixed, products that are common in the paper industry, in a security sheet area called variable distribution and especially watermarked. The use of these compounds makes it possible, in particular, to authenticate said security sheet by infrared spectroscopy, in particular near-infrared spectroscopy, and better optical reading of bar-coded watermarks. However, the minimum amount of these compounds to be introduced into said sheet to allow optical reading and / or correct authentication may be too great compared to the maximum ash quantities defined in certain specifications. The present invention thus makes it possible to solve the above problem, for example by providing a security sheet comprising a filigree security tape made of fibrous material and a mixture of kaolin and talc in a proportion sufficient to promote spectroscopic authentication. infrared of said document or optical reading of said watermark. Indeed, the kaolin and talc content will be particularly high, but only in the zone containing said security tape, so that said security sheet comprising said security tape respects the upper limits of the ash levels inscribed in said specifications.

In the particular case of a security tape according to the invention comprising magnetic fibers, an advantage of the invention relates for example to the authentication of a security document by analyzing the signal of the magnetic response. In particular, the introduction into sowing, that is to say in the fibrous suspension mixture before it is dewatered, of soft magnetism fibers called "soft magnetic" fibers makes it possible, in a reproducible manner, to homogeneously distribute said magnetic soft fibers . On the other hand, the introduction of said magnetic soft fibers in strip according to the prior art, that is to say in a round shape by localized supply ducts or by laminar flow over a flat table, induced a certain variability in the concentration of said magnetic soft fibers, but also in the width of said magnetic soft fiber band. By using a paper security tape made by cutting a sheet comprising magnetic soft fibers introduced in seedling, the invention makes it possible to reproducibly obtain a homogeneous distribution of said magnetic soft fibers. Thus, by varying the concentration of magnetic soft fibers and the width of said introduced security tape, the number of "signatures" or possible magnetic signals is multiplied.

According to a particular case of the invention, said paper security tape comprises at least two security elements chosen from those mentioned above.

According to a particular case of the invention, said paper security tape comprises between 0.1 and 1% by dry weight of magnetic fibers, in particular with soft magnetism, with respect to the total amount of fibers, and preferably between 0 , 2 and 0.6%.

According to a particular case of the invention, said paper security tape comprises a plurality of small boards divided according to a surface density of between 4000 and 25000 boards / m ² , preferably between 5000 and 20000 boards / m ² and more preferably between 11000 and 18,000 boards / m ² .

According to a particular case of the invention, said security tape comprises a series of parallel safety wires, and more particularly the succession of inter-wire spaces and / or the series of different widths of said safety wires constitute a code, in particular barcode type.

According to a particular case of the invention, said paper security tape comprises a magnetic magnet anti-theft wire.

This type of antitheft security wire can be very sharp and therefore difficult to incorporate into a security sheet, it happens in particular that said antitheft wire, when introduced according to the prior art that is to say directly in a fibrous substrate, is not completely covered with fibers. The incorporation of such an antitheft security wire according to the The present invention consists in the manufacture of a fibrous sheet in which several anti-theft security threads are introduced, said security sheet thus obtained then being cut into ribbons comprising at least one anti-theft thread. These ribbons are then introduced into said fibrous substrate. Thus, the areas of said security tape which may have fibrous covering defects are covered by the fibrous material of said fibrous substrate, and thus a security sheet is obtained comprising at least one anti-theft security thread and free of covering defects.

According to a particular case of the invention, said security tape comprises at least one electronic device. Preferably, said electronic device is a radio frequency identification device, more commonly referred to as an RFID device, and in particular an electronic chip and / or an antenna which can notably be printed on said paper security tape.

According to a particular case of the invention, said paper security tape comprises at least one chemically or biochemical chemical tampering and / or authentication and / or identification reagent reacting in a colored manner, with at least one agent respectively of falsification and / or authentication and / or identification.

In particular, a paper security tape comprising a chemical or biochemical tampering reagent that reacts in a colored manner with at least one tampering agent can in particular be located on a zone of inscription of the variable information liable to be falsified. For example: on a check, this zone includes the areas intended for registration in figures and letters of the amount of the said check or the name of the recipient of the check.

If said paper security tape comprises a chemical or biochemical authentication reagent reacting in a colored manner with at least one authentication agent, additional security of the security sheet containing said paper security tape is obtained, the reaction of authentication being in fact located on the area where said paper security tape has been incorporated.

Another advantage of the above particular case is to be able to use at least one anti-tampering reagent in documents intended to receive a surface treatment, in particular to promote the adhesion of the ink during the personalization of said documents. Indeed, the reagents of this type are generally not used because they are reagents incompatible with the mixtures of colloidal dispersions of polymers.

(Latex) commonly used in the composition of said surface treatments of papers, by way of example, mention may be made of the latex of the styrene-butadiene polymer sold under the name Latexia 301 by the company Ciba. Insofar as the ribbon is introduced in bulk, the invention therefore makes it possible to incorporate said reagents in said paper security tape and to apply at least one of said surface treatments to said fibrous substrate without encountering this type of problem. .

This particular case has the additional advantage of allowing the use of tampering reagents which react with certain adhesives, and in particular those used on adhesive-coated sheets, in particular for visas to be pasted on passports or for safety films stuck on some security documents. Indeed, the fact of incorporating said reagents into said paper security tape makes it possible to isolate the reagents and thus prevent any premature reaction between said reagents and said adhesives, especially contained on said adhesive-coated sheets, without preventing the reaction with them. reagents used in attempts to falsify said security documents containing said adhesive sheets.

In addition, in the field of said security documents, a high level of whiteness is sometimes required which may be incompatible with the use of some of said chemical or biochemical infalsification and / or authentication and / or identification reagents. The incorporation of said paper security tape then makes it possible to introduce these reagents into certain areas of a document while preserving the overall whiteness of said document.

According to a particular case of the invention, said fibrous substrate comprises at least one chemically or biochemical chemical tampering and / or authentication and / or identification reagent reacting in a colored manner, with at least one agent respectively of falsification and / or or authentication and / or identification.

In particular, said paper security tape and said fibrous substrate each comprise at least one chemically or biochemical chemical tampering and / or authentication and / or identification reagent reacting in a colored manner, with at least one respectively tampering agent and / or authentication and / or identification. Said chemical or biochemical infalsification and / or authentication and / or identification reagents are preferably different and can in particular react with one and the same agent or with two different agents.

According to a particular case of the invention, said security tape and said fibrous substrate of the security sheet each comprise at least one chemical or biochemical reagent for tampering and / or for authentication and / or identification, these reagents being chemically incompatible. The term "chemically incompatible" means that the reactants can react together because they are in contact with each other or because they involve chemical reactions, with the falsification or authentication and / or identification agents, which are incompatible with each other. .

Indeed, in the prior art the use of a single fibrous substrate sometimes prevents the combination of some of said chemical or biochemical infalsification and / or authentication and / or identification reagents which, inserted into a common substrate react together (incompatible reagents). In addition, said chemical or biochemical reagents for tampering and / or authentication and / or identification may be compatible but give rise to incompatible reactions during the attempt to falsify or to the authentication or identification of said security document that make said document is not damaged during its forgery or that the authentication reaction does not give the expected result. The use of at least one ribbon according to the invention therefore has the particular advantage of allowing the use of at least two incompatible reagents or reactions.

According to a particular case of the invention, said security tape comprises perforations in a pattern or a code. Depending on the differences in opacity and color between said substrate and said security tape, said pattern or code is observable, or observable only in transmitted or observable light in both transmitted light and reflected light. If said security tape has an invisible fluorescent print, said pattern can also be visible only under UV illumination.

In particular, said perforation pattern comprises at least one alphanumeric character or an ideogram.

According to a particular case of the invention, said paper security tape comprises perforations in a pattern and further comprises a chemical reagent or biochemical for tampering and / or authentication and / or identification reacting in a colored manner. During an attempt to falsify and / or during the authentication and / or identification of said document, said chemical or biochemical reagent reacts with the falsification and / or authentication and / or identification agent according to a reaction that gives a particular coloration to said paper security tape. Said pattern made by perforation then becomes visible by contrast between the coloring of said paper security tape and that of said fibrous substrate.

According to a particular case of the invention, said security tape is calendered. This calendering is carried out in particular to minimize the extra thickness created by the introduction of said paper security tape.

According to a particular case of the invention, said security tape is free of a surface coating, in particular free of a pigmented layer. The good affinity between said fibrous substrate and said security tape is thus favored.

According to another particular case of the invention and in particular to increase the affinity between said fibrous substrate and said safety tape, said security tape comprises a water-activatable adhesive agent, for example a polyvinyl alcohol (PVA), in particularly partially hydrolysed.

According to a particular case of the invention, said paper security tape has a wet strength (REH) with respect to traction greater than 30%, in particular so as not to cause problems when introduced into said security sheet. The resistance in the wet state in tension is measured by dividing the value of the wet tensile strength measured according to the NF Q 03.056 standard by the dry tensile strength measured according to the NF EN ISO 1924 standard. wet state may in particular be provided in a conventional manner by the addition of a wet strength agent, for example such as a polyamine-amide-epichlorohydrin resin (PAAE), a formaldehyde melamine resin, etc.

Alternatively, an additional wet strength (REH) may be obtained by adding a portion of the REH agent (s) in surfactant baths of a fibrous sheet, for example for the manufacture of the fibrous web. security.

According to a particular case of the invention, said security tape is comprised in mass or in window in said fibrous substrate. The ribbon may appear only on one side of the sheet in a window or appear on each face of the sheet in a through window.

According to a particular case of the invention, said fibrous substrate has a fibrous monolayer, in particular a single-ply, or several fibrous layers, in particular multijet. Preferably, said fibrous substrate comprises two fibrous layers, in particular a bijet structure.

According to a particular case of the invention, said security tape and at least one of the layers of said fibrous substrate have different colors. This achieves a higher security due to the presence of two fibrous layers of different colors in the same security sheet.

In particular and in order to increase the security of the security document which will comprise a security sheet according to the invention, said substrate of the security sheet and the security tape are of different colors and each comprise a filigree pattern. The security of said security document is thus improved because of the presence of two watermarks of different coloration to be counteracted, in particular because the use of transparent inks, commonly used to counterfeit watermarks, does not make it possible to create such color effects. . In addition, this security allows rapid authentication of said security document, the coloring of said watermarks being easily observable in transmitted light.

According to a particular case of the invention, said fibrous substrate comprises at least two paper safety ribbons as described above.

In particular, if said security sheet comprises two security tapes, it is then possible that they respectively contain two different reagents giving, by reaction with a single developer, two different localized colors. It is also possible that said security tapes react specifically to two different agents to give, in a localized manner, two different colors or not.

The invention also relates to a process for the papermaking of said security sheet described above wherein said fibrous material-based security tape is introduced at a wet end into said fibrous substrate. Said substrate - ribbon assembly thus obtained is then pressed and dried.

According to a particular case of the invention, said security tape is introduced in wet part, in bulk or in window in said fibrous substrate. For this purpose, known methods can be used to introduce plastic security threads of the prior art. The ribbon may have any of the features detailed above, or any combination thereof.

According to a particular case of the invention, the method uses a paper machine which is equipped with at least one round shape, and said security tape is introduced into the shaped tank of said round shape, before or shortly after the start dewatering the composition forming said fibrous substrate of the sheet.

According to a particular case of the invention, the method uses a paper machine which is equipped with at least one flat table, and said paper security tape is introduced above said flat table, during the dewatering of the paper. composition forming said substrate of the sheet.

According to a particular case of the invention, said fibrous substrate comprises at least two jets, and said safety tape is introduced before wet assembly of two successive jets, that is to say, according to the method paper maker, before drying the safety tape assembly - fibrous jets from the substrate.

According to a particular case of the invention, said paper security tape as described above is incorporated by laminating between two fibrous layers of said fibrous substrate of said security sheet.

In particular, said paper security tape may appear in the window, especially if at least one of said layers comprises perforations or areas devoid of material.

The invention also relates to the paper security tape as described above.

The invention also relates to a security document comprising a security sheet as described above.

This document can be manufactured by cutting, binding, binding, rolling, gluing and / or laminating this security sheet.

More particularly said security document is a means of payment, such as a bank note, a check or a restaurant ticket, an identity document such as an identity card or a visa or a passport or a permit. driving, a lottery ticket, a ticket or an entrance ticket to cultural or sports events.

The invention also relates to an article to be authenticated comprising said security sheet as described or obtained previously, said article being chosen from a security label, a packaging, in particular a packaging for the drugs or for food or for perfumes or for electronic parts or for spare parts, a sheet used in the medical or hospital field, including a paper used to make sterilization packaging, and still a paper art.

The invention also relates to a method of authenticating a security sheet comprising a security tape which comprises at least one chemical or biochemical reagent for tampering and / or authentication and / or identification reacting in a colored manner with at least one falsification and / or authentication and / or identification agent respectively, as well as perforations according to a pattern or a code. In the absence or before application of said falsification or authentication agent, said chemical or biochemical reagent tampering or authentication and / or unreacted identification, said pattern or said perforated code is invisible. When said security sheet is placed in the presence of a falsification or authentication and / or identification agent, the reaction between said reagent and said agent produces a coloration of said security tape which renders said pattern or said perforated code readable .

The said method is therefore characterized in that the reaction between said tampering and / or authentication and / or identification reagent, and an agent for falsification and / or authentication and / or identification, respectively, gives a coloring said paper security tape making said perforations, in particular said pattern or said perforated code, observable on said security tape.

According to another of these aspects, the invention also relates to a security sheet comprising a fibrous substrate in which is incorporated, at least partially, a security tape, preferably comprising at least one security element, extending between two edges. said fibrous substrate, said security tape being made of paper and having a watermark. The ribbon may have one or more of the above features.

According to yet another of these aspects, the invention also relates to a security sheet comprising a fibrous substrate in which is incorporated, at least partially, a security tape, preferably comprising at least one security element, and extending between two edges of said fibrous substrate, said security tape being made of paper and having a different color than at least one layer of said fibrous substrate. By "different color" is meant a color difference visible to the naked eye. The ribbon may have one or more of the above features.

The invention will be better understood on reading the non-limiting examples and the figures which follow.

PROPOSED EXAMPLES Example 1

Considering the realization, on a paper machine with round shape, a security sheet comprising a paper security tape comprising as security element boards with a fluorescent invisible printing and incorporated into a filigree fibrous substrate.

Manufacture of security tapes according to the invention:

A sheet of paper is made on a flat-table paper machine. The boards printed with a fluorescent ink are added to the aqueous suspension of refined cellulose fibers of the order of 30 ° SR, the fibrous mat containing these boards is sown and dried. Said sheet obtained once dried has a basis weight of 45 g / m ² .

This gives a sheet comprising invisible fluorescent seed boards, distributed homogeneously in space, which is then calendered, coated by gravure on all of its two faces of adhesive MOWILITH DC at a rate of 5 g / m ² per side, then cut into 1.5 cm wide ribbons, said ribbons being represented on the figure 1 . We reel the ribbons.

Manufacture of the security sheet comprising a paper ribbon according to the invention.

During the manufacture of said fibrous filigreed substrate on the round shape, said security tapes are introduced in the round shape into the round shape of the tank.

After draining, pressing and then drying the substrate-ribbon assembly, a security sheet is obtained according to the invention shown in front on the figure 2 and according to a cut in the thickness on the figure 3 .

In a variant where adhesion of the tape is not desired, the tape is not coated with the MOWILITH adhesive, all other steps being performed.

Example 2

It is considered the production of a security sheet comprising a paper security tape comprising, as a security element, soft magnetism fibers embedded in a fibrous substrate.

Manufacture of security tapes according to the invention:

A sheet is made on a flat-bed paper machine according to the traditional method, that is to say by draining, pressing and then drying an aqueous suspension of refined cellulose fibers at 32 ° SR. Said soft magnetic security fibers are fibers of an alloy of nickel and iron called Supermalloy ^® . These fibers have a diameter of 10 μm and an average length of 3 mm and are introduced as a mixture into the fibrous suspension at a level of 0.7% by weight relative to the fibrous composition in the leading vat, that is to say say before the formation of said sheet.

A sheet of a grammage of 35 g / m ² is obtained which is then calendered, coated with adhesive, for example by gravure on both sides with MOWILITH DC adhesive at a rate of 5 g / m ² per side, then cut into ribbons 3.5 cm wide. The ribbons may be reeled.

This produces safety ribbons comprising soft magnetism fibers whose spatial distribution is homogeneous.

Manufacture of the security sheet comprising a paper ribbon according to the invention.

The security sheet is made on a flat-bed paper machine by mass-introducing said security strips into the fibrous composition forming the substrate. The security tapes are introduced during dewatering, between the fibrous mat forming and the dough roll located on the forming table, and the sheet is then pressed. After drying, the security sheet thus obtained has a basis weight of 100 g / m ² .

By using a suitable magnetic detector, the homogeneous distribution of magnetic fibers in the ribbon and the regular width of said security tape make it possible to authenticate and / or identify said security sheet reliably.

In a variant where the adhesion of the ribbon is not desired, the coating with the adhesive is not carried out, all the other steps being reproduced elsewhere.

In another variant, the removal of the adhesive is carried out by gluing press.

Example 3

It is considered the realization, on a flat-table paper machine, of a security sheet comprising a security tape having as security element an iridescent layer, incorporated into the fibrous fibrous substrate of the sheet.

Manufacture of security tapes according to the invention:

By paper-making on a flat table is made a paper sheet based on refined cellulose fibers at 25 ° SR. The sheet thus obtained is calendered and then covered, by gravure printing, iridescent pigments blue-pink mica-titanium Iriodin® Merck. The composition containing the pigments may also contain the adhesive, as a co-binder, for example MOWILITH DC adhesive. This sheet which weighs 55 g / m ² is then cut into ribbons 5 mm wide.

Manufacture of the security sheet comprising a paper ribbon according to the invention.

On a round shape, the fibrous substrate of the sheet is formed in which said security strips, at the mark and in the window, are introduced, according to the method of introducing security threads onto a round-shaped paper machine described in FIG. patent application EP 059 056 .

The resulting security sheet thus comprises an iridescent coating appearing according to dashed lines because of the window introduction of said security tape.

In a variant, the adhesive is deposited on the layer of pigments.

Example 4

Considering the realization, on a round paper machine, of a security sheet comprising a white natural color fibrous substrate comprising a watermark and a yellow paper security tape comprising a watermark. Said ribbon and said substrate form a security sheet such that the two filigree patterns complement each other.

Manufacture of security tapes according to the invention.

On a round shape, a paper of yellow color and watermarked in a pattern representing a hair is made from an aqueous suspension of cellulose fibers refined at 40 ° SR comprising a yellow dye. The surfacing and coating free sheet thus obtained weighs 70 g / m ² , it is then calendered, coated by gravure printing of MOWILITH DC on both sides at a rate of 5 g / m ² per side, then cut into strips of 5 cm wide. Such a security tape is shown on the figure 4b .

Manufacture of the security sheet comprising a paper ribbon according to the invention.

On a round machine, the fibrous substrate of the sheet is formed from an aqueous suspension of refined cellulose fibers of the order of 38 ° SR and a filigree pattern is formed according to a face completing the filigree hair of the ribbon. ; said security strips are introduced into the mass of the substrate forming the mark so that the watermarks of the ribbon and the substrate complement each other to form a face. According to the method of introduction into the mass of security threads on a round-shaped paper machine, said security tapes are introduced during the dewatering of the fibrous suspension on the round shape, in the form tank. After pressing and drying, a sheet is obtained whose weight is 80 g / m ² .

The resulting security sheet therefore has a two-color watermark visible in transmitted light, such as that shown on the figure 4 .

Example 5

In this example, the tape is not coated with adhesive, because it is not the strong adhesion of the ribbon in the substrate is sought. This example implements aspects of the invention independent of the presence of adhesive on the ribbon.

Considering the realization, on a round paper machine, of a security sheet comprising a fibrous substrate comprising an authentication chemical reagent reacting in a colored manner to an external authentication agent which may be present in a pen. authentication and a security paper tape which itself comprises an authentication chemical reagent reacting in a colored manner to the authentication agent present in said pen.

Manufacture of security tapes according to the invention:

A sheet of the overlay type is formed on a flat-table machine from an aqueous suspension of refined cellulose fibers, of the order of 30 ° SR, and a paranitrophenol composition is introduced by surfacing the sheet in the press. gluer. This sheet of paper has a grammage of 30 g / m ² and therefore includes paranitrophenol as an authentication chemical reagent that can react on its entire surface in a colored manner with soda (sodium hydroxide) weakly concentrated, the soda being the external authentication agent contained in the pen. Paranitrophenol is colorless and yellow in the presence of weakly concentrated sodium hydroxide. The coating-free sheet thus obtained is then calendered and then cut into strips of 2 cm wide.

Manufacture of the security sheet comprising a paper ribbon according to the invention.

The substrate of the sheet is made on a round paper machine from an aqueous suspension of cellulosic fibers comprising another authentication chemical reagent also reacting in a colored manner with weakly concentrated sodium hydroxide. This reagent is a colored indicator for check derived from xanthene, it is colorless and takes a blue color in the presence of weakly concentrated soda, which is the authentication agent contained in said pen.

Said security tapes obtained previously are introduced in bulk during the formation of said substrate, according to a common method of mass introduction of security threads on a round-shaped paper machine as described in Example 4.

The resulting security sheet has a basis weight of 80 g / m ² .

This sheet is authenticatable with an increased level of security. Indeed, by using on said sheet an authentication pen containing weakly concentrated sodium hydroxide, a first blue color appears on the areas where there is no paper security tape and a second green color on the areas above said paper security tape, said green color resulting from mixing the yellow and blue colors respectively of said paper security tape and said fibrous substrate.

DESCRIPTION FIGURES

• The figure 1 represents a front view under UV illumination of a security tape 1 comprising boards 4 printed with an invisible fluorescent ink.
• The figure 2 represents a front view under UV illumination of a security sheet 2 containing said security tape 1 of the figure 1 .
• The figure 3 represents a section in the thickness according to (AA ') of the security sheet 3 which is the subject of the invention represented frontally on the figure 2 .
• The figure 4 represents, according to a front view, an object of the invention 3 comprising a watermark security sheet 2 represented frontally on the figure 4a in which is incorporated a watermark paper security tape 1 shown front on the figure 4b .
• The figure 5 is a front view of a security sheet 3 object of the invention in which is incorporated a paper security tape 1 perforated according to a text and which comprises an infalsification reagent reacting in a colored manner to the falsification agents.
• The figure 6 represents a transparency image of a security sheet according to the invention, comprising a security tape.
• The figure 7 represents a topographic image of a security sheet according to the invention, comprising a security tape.

The paper security tape 1 shown on the figure 1 has a width of 1.5 cm and is secured by boards 4 about 3 mm printed with an invisible ink fluorescent so that they are visible only under UV illumination. The distribution of said boards 4 in said paper security tape 1 is homogeneous and their observation under UV illumination shows a band whose edges are relatively regular.

An object of the invention 3 is represented on the figure 2 , it consists of a security sheet 2 of dimensions 6 x 12 cm comprising in its mass a security paper tape 1 secured by said boards 4 and shown on the figure 1 . This security paper tape 1 is introduced at a distance of 2 cm from the edge of the security sheet 2. Said boards 4 being invisible fluorescent, they are invisible if observed in transmitted and / or reflected light. On the other hand, under UV illumination, said boards 4 can be seen arranged in a strip corresponding to said paper security strip 1, of homogeneous distribution and with relatively regular edges.

A section according to (AA ') of the figure 2 is represented on the figure 3 . This cut in the thickness of said security sheet 3 object of the invention reveals said paper security tape 1 comprising said boards 4 and contained in the mass of the security sheet 2.

Another object of the invention 3 is represented on the figure 4 . It comprises a fibrous substrate 2 of dimensions 6 × 12 cm, watermarked and whose watermark represents a face 5a as represented frontally on the figure 4a as well as a paper security tape 1 of 5 cm wide, yellow in color and watermarked, the watermark of which represents a hair 5b as shown in FIG. figure 4b . Said security sheet 3 comprising said security paper tape 1 at a distance of 4 cm from its edge is represented on the figure 4 it contains a watermark representing a head composed of a yellow hair 5b and a face 5a in shades of gray.

An object of the invention 3 is represented on the figure 5 it comprises a security sheet 2 of dimensions 6 × 12 cm and in the mass of which is incorporated a paper security tape 1 of 2 cm wide and which comprises perforations 6 with a diameter of 2 mm, as well as a manganese sulfate which will act as an undyed tampering reagent. Said perforations 6 form the word "FALSIFIE". During normal use of said object of the invention 3, said paper security tape 1 and said perforations 6 are not observable either in transmitted light or in reflected light. On the other hand, the same object of the invention 3 having been the object of an attempt of falsification by soaking in a bath of sodium hypochlorite, and commonly used for the falsification of manual writing, is represented on the figure 5 . The manganese salt contained in said paper security tape 1 reacted with the sodium hypochlorite bath to give a brown coloring product. Said perforations 6 thus become observable and show in negative the word "FALSIFIE" signifying the attempt to falsify said object of the invention 3.

The security tape can be detected in various ways after incorporation into the security sheet.

For example, the ribbon can be detected by direct observation of the security sheet, to the naked eye in reflected light or transmitted light. Differences in hue, appearance, and / or opacity between the ribbon and the fibrous substrate may determine the presence of the ribbon.

As a variant, it is possible to obtain an image of the security sheet by topography or by transparency in order to observe, for example, the epair and the topography of the paper. For example, one can notice the presence of the security tape, in particular by differences of contrast, on the Figures 6 and 7 , which are respectively images of the security sheet by transparency and by topography.

In addition, it is still possible to identify the presence of the security tape by the presence of the adhesive, for example a heat-sealing varnish, which can be observed in the form of bubbles by observation by scanning electron microscope (SEM).

The phrase "having one" is synonymous with having "at least one".

Claims (15)

1. Security sheet comprising a fibrous substrate into which is incorporated, at least partially, a security tape comprising at least one security element and extending continuously between two edges of said fibrous substrate;
   security sheet characterized by the fact that said security tape is made of paper and comprises an adhesive.
2. Security sheet according to claim 1, characterized in that the security tape comprises a watermark.
3. Security sheet according to claim 1 or 2, characterized in that the security tape has a different color from at least one layer of said fibrous substrate.
4. Security sheet according to at least one of the preceding claims, characterized in that said security tape is based on cellulosic fibers, in particular cotton fibers, and/or natural organic fibers other than cellulosic fibers and/or synthetic fibers and/or eventually mineral fibers.
5. Security sheet according to at least one of the preceding claims, characterized in that said security tape in paper is based on hydrophilic fibers.
6. Security sheet according to at least one of claims 4 or 5, characterized in that said security tape in paper comprises at least 50% of cellulosic fibers.
7. Security sheet according to at least one of the preceding claims, characterized in that said fibrous substrate and said paper security tape are based on the same types of fibers, in particular if appropriate in the same proportions in the case of two or more sorts of fibers.
8. Security sheet according to at least one of the preceding claims, characterized in that said security tape has a width between 2 and 60 mm, preferably between 4 and 30 mm, and more preferably between 10 and 20 mm.
9. Security sheet according to at least one of the preceding claims, characterized in that said security tape has a thickness between 20 and 120 µm, preferably between 30 and 80 µm, and more preferably between 45 and 55 µm.
10. Security sheet according to at least one of the preceding claims, characterized in that said fibrous substrate and said paper security tape each comprise at least one watermark pattern and in that said patterns are complementary to one another by superimposition and/or combination, the security tape having preferably a different color from that of the substrate.
    The security sheet as claimed in claim 54, wherein said fibrous substrate is based on cellulosic fibers and/or natural organic fibers other than cellulosic fibers and/or synthetic fibers and/or mineral fibers.
11. Security sheet according to any one of the preceding claims, the adhesive comprising polyvinyl acetate.
12. Security sheet according to any one of the preceding claims, the tape comprising between 2 and 15 g/m² of the adhesive, better between 3 and 8 g/m².
13. Security sheet according to at least one of the preceding claims, characterized in that the adhesive comprises a water-activable adhesive agent that is a polyvinyl alcohol, preferably partially hydrolyzed.
14. Security sheet according to at least one of the preceding claims, characterized in that the adhesive comprises a heat sealing agent.
15. Method for fabricating a security sheet, comprising a fibrous substrate and a security tape in paper, as claimed in one of the preceding claims, characterized in that the security sheet is formed by a papermaking process which comprises the following steps :

    - in the wet end of the papermaking process, said paper security tape is inserted into said fibrous substrate in formation,

    - the substrate-tape combination thereby obtained is pressed,

    - the assembly is then dried.

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