FR2771111A1 - Security document - Google Patents

Abstract

The security document has a substrate of paper or cardboard or an extruded plastics film, with at least one zone containing magnetic particles. The magnetic particles are integrated into the body of the substrate, or are bonded to its surface, without altering the visual appearance. The magnetic particles are evenly distributed in their zones. The magnetic particles are part of a security element for the document, such as a plastics strip embedded in or bonded to the surface of the substrate. The surface bonding is through layering with the substrate material or an adhesive composition with a paper substrate. The magnetic particles can be contained in a varnish or ink to be printed by heliogravure, offset printing or silk-screen printing. The security element is bonded to the substrate surface by an adhesive or by a plastics film containing the particles. The magnetic particles can be applied to a hologram or to the hologram bonding layer. The hologram is transparent or at least partially demetallized, fitted to a security strip which is at least part of the substrate and visible through sections which show at the document surface. The magnetic particles are bonded in position where there are positive or negative printings, on a security strip wholly or partially in the substrate. The magnetic particles can be contained in a heat sealing varnish applied to the security strip surface or integrated into the mass of the plastics strip. The magnetic particles can cover the whole surface of the substrate, or they can be arranged in different zones to show a magnetic code, which can be a barcode. The zones contain magnetic particles with a coercive force of 23.873 \* 10<3> A/m (300 Oe) and pref. 79.577 \* 10<3> A/m (1000 Oe) to give a magnetic register of a code. The magnetic particles are in a concentration of 0.1 wt% of the substrate and pref. 0.05 wt%, or 0.001-0.1 wt% and pref. 0.01-0.1 wt%. The magnetic particles comprise 1 wt% of the bonding or 0.01-0.1 wt%. The magnetic particle size is 2 m and pref. 1 m, or 0.1-1.0 m and pref. 0.1-0.5 m. The substrate is a paper with a light color and especially white, cream or a pale yellow. The bonding is transparent or translucent. The security strip has a thickness of 10-30 m and a width of 0.5 mm to 5.0 cm, and preferably 1-5 mm. An Independent claim is included for the security document production where the magnetic particles are mixed with the substrate material, such as the paper or cardboard pulp, or the bonding agent to be applied to the substrate surface.

Description

SECURITY DOCUMENT
CONTAINING MAGNETIC PARTICLES
The present invention relates to security documents, in particular security papers comprising magnetic particles allowing in particular the detection of magnetism and / or the storage and reading by sorting or reading machines equipped with magneto-resistive sensors of recorded information, in particular in the form of codes, with inductive heads.

The term “security document” is understood to mean any document comprising a security element, ie an authentication means making it possible to detect counterfeiting and / or making counterfeiting difficult to carry out, in particular by photocopying. In particular, these may be official documents, such as passports or identity cards or means of payment such as banknotes, checks or even fiduciary papers, tickets or payment vouchers, but also any paper that may be issued. 'we want to be able to authenticate, such as contracts, deeds or certificates, labels or packaging. Security paper is understood to mean a said security document comprising a substrate consisting of a sheet of paper or cardboard. According to the present invention, the term “paper” is understood to mean any sheets obtained by the wet process using a suspension of natural cellulose fibers and / or synthetic fibers and which may contain various mineral fillers and various additives, such as binders commonly used. in stationery.

Until now, the visibility of magnetic particles has considerably limited their possibility of use in security documents, in particular security papers. By visibility is meant here that it was impossible to include them as such in the mass or on the entire surface of the documents, in particular of the papers, without considerably affecting the appearance characteristics of the latter. For this reason, magnetism has been applied mainly to the surface of security bands, incorporated into banknotes.

Indeed, it is known, in order to authenticate papers, in particular banknotes, to incorporate therein a narrow plastic strip, called a security strip or thread, often made of a transparent polyester covered with a layer of deposited metal. vacuum-packed or printed. The narrow security band can be incorporated in the mass of the paper in whole or in part according to methods well known to those skilled in the art. These narrow bands can be incorporated in the paper only partially, that is to say, the band appears on the surface of the document in certain places, called windows, and this, on at least one side of the document. The main function of these security bands is to constitute a technical difficulty which is difficult to counterfeit, which can be detected visually by the public by observation in transmitted light, and to allow detection or reading by a machine.

Security threads comprising a magnetic coating have been known for a long time (EP 310 707). And, the magnetism applied to security tapes, has established itself as the most reliable security for reading on a sorting machine.

The security tapes may be coated with a continuous layer of magnetic particles capable of receiving encoded information by magnetic recording or may be covered only intermittently with magnetic pads which are printed so as to create a code (WO 90/08 367).

Magnetic information is read mainly using inductive effect heads
Lobby. These read heads called inductive heads measure a difference in magnetic flux. The magnetism layer must be sufficiently concentrated in particles and thick to generate enough flux and allow a good reading. In practice, the thickness of the magnetic layers is of the order of 10 to 15 μl. In addition, the magnetic layers, given their high concentration of magnetic particles appear very dark, even black. When a strip that is too dark is introduced into the paper, it becomes very difficult to make it invisible under observation in reflected light and it can then be reproduced by photocopying. To make the tape coated with a magnetic layer less visible in reflected light, a metallic masking layer is generally deposited, composed of reflective particles such as silver or ahunmnm which hides the black of the magnetic pigments but increases the cost of tape manufacturing. In addition, the superposition of the layers necessary for the realization of these bands the thickness of the band itself (approximately 12, u) being added to the thickness of the magnetic layer (approximately 12, u), to that of the metallic layer (approximately 3 p) and that of a heat-sealing varnish (approximately 2, u) applied to the front and back of the strip for its adhesion in the paper lead to a total strip thickness which can exceed 30 II, this which causes great difficulties of incorporation into the paper and difficulties of stacking the paper due to the excess thicknesses created by the security bands incorporated in the paper.

Furthermore, to make the strip visually detectable, by observation in transmitted light, it has been proposed (EP 279 880, EP 319 157, EP 516 790 and WO 96 0443) to bear inscriptions in positive or negative by printing or by printing. demetallization on the strip surface.

All these layer deposition operations, and possibly the demetallization of layers - which have different demetalization kinetics - considerably increase the final cost of the strip and considerably complicate its manufacture.

The traditional inductive sensors which measure a difference in magnetic flux by variation of the intensity in the coil, require, for a correct reading of the coded information, that the speed of travel of the wire relative to the reading head is constant. This is why it has been proposed in EP 610 917 to use not inductive sensors but magneto resistive sensors because these sensors measure the remanent magnetization linked to a variation of resistivity in the sensor, which allows reading at speed. variable of the wire relative to the sensing head.

However, in EP 610 917, the magnetic coating of the wire comprises more than 15% of magnetic particles mixed in a layer of aluminum and has an opaque dark color, so that recesses created in said layer allow detection. by observation in transmitted light of a negative inscription created in said layer,
An object of the present invention is to give a security document, in particular a security paper, the ability to be recorded, detected and read by machine thanks to its magnetic properties, without it being necessary to mask the layers. magnetic or magnetic particles to make them invisible.

In particular, an aim of the present invention is to be able to introduce magnetic particles at the surface or in the mass of the paper over a wide area.

Another object of the present invention is to be able to encode magnetic information in an increased quantity compared to the prior embodiments.

Other objects and advantages of the present invention will appear in the description of the embodiments of the invention, below.

The present invention provides a security document comprising a substrate consisting of a sheet of paper or cardboard or a plastic sheet obtained by extrusion and at least one zone comprising magnetic particles characterized in that
a) said magnetic particles are included in the mass of the substrate or in a coating on the surface of the substrate.
b) said magnetic particles do not affect the appearance characteristics of said area, and
c) said magnetic particles are uniformly distributed in said zone.

The present invention is more particularly advantageous when said security document is security paper, that is to say when said substrate consists of a sheet of paper or cardboard.

The magnetic particles can be included directly in the mass or in a coating on the surface of the substrate, in particular paper, or indirectly, ie via a security element. In the latter case, said magnetic particles are included in the mass of said security element or in an applied coating and on the surface of said security element, said security element itself being included in the mass of the substrate, in particular of the paper or applied. on the surface of it.

Magnetic particles are understood to mean particles in the form of pigments. By security element is meant any element associated with the substrate, in particular with paper and contributing to the authentication of the document or making it difficult to counterfeit. It may be, in particular, a particular coating on the surface of the substrate, in particular paper, or an element included in the mass or applied to the surface of the substrate, in particular paper, such as a plastic strip. included, in whole or in part, in the bulk of the substrate, in particular paper, small boards or a hologram applied to the surface of the substrate, in particular paper or on another security element.

Other characteristics of security documents, in particular security papers according to the present invention are defined in the appended claims.

According to the present invention, it has been discovered that the magnetoresistive sensors having a much higher sensitivity than the Hall effect inductive heads used previously, it is possible to read encoded magnetic information or simply characterize the saturation or remanent magnetization of the pigments, at concentrations of highly spinable magnetic particles, in particular, lower than the concentrations allowing detection by inductive sensors, but making the presence of said particles invisible.

The characteristic that magnetic particles do not affect the appearance characteristics of the zone means that when they are included in the mass of the substrate, in particular paper or included inside a security element, it even included, in whole or in part, in the bulk of the substrate, in particular of the paper, or even when they are included in a coating on the surface of the substrate, in particular of the paper or of the said security element, the particles as such, and the appearance, in particular the whiteness and / or the colorimetric coordinates (L *, a *, b *) in the CIELAB system, of the substrate, in particular of the paper and / or of the security element is not or very little changed.

More particularly, the Delta E * color difference in the CIELAB formula between a control document without magnetic particles and the same document which is distinguished only by the presence of magnetic particles according to the present invention, is less than 10.

More particularly still, when the substrate comprising said magnetic particles
is white, its ISO whiteness according to the ISO 2471 standard (reflectance at 457 nm) is greater than or equal to 65% and / or its CIE whiteness according to the CIELAB formula is greater than or equal to 30%, even in the absence of optical brightener.

This visual characteristic of said magnetic particles, and of the document, in particular of the paper comprising it, makes it possible to associate them in the same zone with a security element and / or an identification element with visual effect, such as an element comprising inscriptions intended to be seen, without the presence of the magnetic particles obscuring the desired visual effect with said security element or identification element.

According to the present invention, the magnetic particles can therefore be associated with all the security elements existing in security documents, in particular security papers, and / or on large areas of said security documents, which was not the case. case previously.

They can also make it possible to record and store quantities of information, much greater than previously, in particular in the form of magnetic codes and, make the area where the magnetic information has been recorded and stored invisible to the eye. naked and invisible with a magnifying glass.

According to a characteristic of the invention linked to the sensitivity of the magnetoresistive heads, it is necessary that the magnetic particles do not form agglomerates or inhomogeneous aggregates. It is therefore necessary for the magnetic particles to be uniformly dispersed and distributed in their substrate. Here, by uniform distribution of the magnetic particles is meant that the volume density of particles in said zone, and therefore the saturation or remanent magnetic magnetization in said zone are substantially constant so that there is little or no background noise and in particular that the ratio (meaning background noise) is greater than 20 dB, in particular when the width of the magneto-resistive read head is less than or equal to the width of the inductive recording head. This characteristic is necessary to make it possible to read a coded message, recorded in said zone, in a reliable manner.

Said zone comprising said particles may cover the whole of the substrate or only part of it.

The direct incorporation of the magnetic particles in the mass of the substrate, in particular paper or in a coating on the surface of the substrate, in particular paper, in a zone covering the whole of the substrate, makes it possible to considerably extend the possibilities of using the present invention. However, when the magnetic particles are included directly in the mass of the substrate, in particular paper or in a coating on the surface of the substrate, they can be included in a localized zone, in particular in the form of a strip, in particular of width of 1 to 5 cm by methods known to those skilled in the art, said zone not necessarily covering all of the substrate.

The magnetic particles can advantageously be incorporated into the mass of the paper by mixing an aqueous dispersion of said particles with the mixture of flora, in particular of cellulose or cotton, and of conventional papermaking adjuvants for producing the sheet of paper. The present invention is particularly advantageous when the substrate comprising said magnetic particles is a paper substrate and has a light color, in particular white, cream or pale yellow. In this case, as mentioned previously, the ISO whiteness according to the ISO 2471 standard is preferably greater than or equal to 65% and the whiteness
CIE according to the formula CIELAB is preferably greater than or equal to 30%;
The coating on the surface of the substrate, in particular of paper, may also consist of a plastic film in the mass of which the magnetic particles are incorporated, in particular a film with a thickness of 10 to 500 μm.

When the magnetic particles are included in a coating on the surface of the substrate, in particular paper or on the surface of said security element, this coating may consist of an ink or a varnish or else a coating or sizing composition, which can be applied by printing or papermaking respectively. The coating composition may comprise in particular, in addition to said magnetic particles, a binder of the polyvinyl alcohol (PVA), starch or latex type, water and additives.

The coating composition can be applied by means known to those skilled in the art with coating installations, such as a size press, metal blade coater, air knife coater, CHAMPION type rotary bar coater, pre-dosed film transfer coater.

As inks or varnishes, mention is more particularly made of printing inks or varnishes which can be applied by gravure printing, intaglio printing, offset printing or screen printing to a thickness of 1 to 5 μm.

The surface coating comprising magnetic particles, according to the present invention, can also consist of an adhesive composition applied to the surface of the substrate, in particular of paper or of said security element, in particular a heat-sealing varnish facilitating the holding of said element. security in the mass of the substrate, in particular paper.

When said particles are included in a coating on the surface of the substrate, in particular paper or a security element, said coating can advantageously be transparent or translucent.

To satisfy both the appearance characteristics of the paper, in particular the ISO and CIE whiteness values mentioned above, and the uniform distribution characteristics of the magnetic particles of the present invention, and to allow detection of a sufficient signal as well as recording an information density at least equal to that used on magnetic stripes of bank cards, in particular a recording density of at least 8 flow transitions / mm / track, it is advantageous that said particles verify the following concentration and size characteristics, taken separately or in combination:
a) when the particles are included in the mass of the substrate, in particular paper or in a coating applied to the surface of the substrate, in particular paper, their concentration is less than or equal to 0.1%, in particular 0.05%, preferably from 0.001% to 0.1%, more preferably 0.01% to 0.1% based on the weight of said substrate in said zone.
b) when said particles are included in a coating applied to the surface of said substrate, in particular paper or a said security element, the concentration of magnetic particles in said coating is less than or equal to 1%, more particularly 0.01 % at
1%, more particularly still from 0.01% to 0.1% of the weight of the coating in said zone.
c) the magnetic particles have a size less than or equal to 2 KL, preferably less than 1 H, in particular from 0.1 to 1>, more particularly still from 0.1 to 0.5, u. By size is meant here the largest dimension of the particle.

For quantities less than 0.01%, more particularly less than 0.001%, the signal becomes difficult to detect, in particular with a ratio (signal to background noise) of less than 20 dB under the conditions mentioned above.

When said security document is a banknote, said security element is optionally constituted by a security strip of plastic material included, in whole or in part, in the mass of the substrate, in particular of the paper, said particles being included in the bulk. mass or in a surface coating of said strip.

According to the present invention, it is possible to apply to a security tape, transparent magnetic layers of thickness from 1 to 5, allowing the recording and detection of encoded magnetic information. Taking into account the appearance characteristics of said magnetic layer, applied to the security tape, it is not necessary to coat the magnetic layer with a metallic masking layer. The thickness of the threads of the security tapes, according to the present invention, is therefore considerably reduced compared to previous embodiments of magnetic security tapes. A subject of the present invention is therefore also security strips as defined above and more particularly strips of thickness 10 to 30 C1 and of a width of 0.5 mm to 5 cm, preferably 1 to 5 mm.

It will be noted that the concentrations of magnetic particles necessary for detection by a magnetoresistive head are so low (a magnetoresistive detector can detect unit grains of pigments) that the pigments can be incorporated into the security strip by depositing 'a specific magnetic layer or simply by mixing with existing layers, such as the heat-sealing varnish layer, printing inks or even incorporated into the mass of the plastic wire itself.

Security documents, in particular security papers or security tapes included in said documents, in particular said papers, comprising a hologram, are sought after because they are difficult to counterfeit, while being aesthetic, and more easily authenticated by the general public. . However, these tapes in the prior embodiments could not easily be associated with magnetic properties for the following reasons. First of all, the holograms themselves consist of multilayer complexes (adhesive layer, embossing lacquer, protective varnish). And, applying a dark magnetic layer involves applying an additional layer. In addition, security holograms are often transparent, ie non-metallized, or partially demetallized holograms. However, the presence of a dark magnetic layer is on the one hand incompatible with the transparency properties of the hologram and on the other hand, resists the partial demetallization treatment of the hologram, making it impossible to carry out an inscription. of type Cleartext.

The present invention makes it possible to associate magnetic particles with holograms in an advantageous manner. To do this, it suffices to mix the magnetic particles with the layers making up the hologram, such as the embossing lacquer, the protective varnish when the hologram is applied to a security tape, said magnetic particles can be incorporated in the mass of said strip or in the heat-sealing varnish, allowing said strip to adhere to the mass of the paper. The present invention provides in particular transparent or partially demetallized holograms, comprising magnetic particles.

The present invention provides security tapes, comprising magnetic particles and positive or negative inscriptions in the form of recesses. These types of wires are usually called Magnetic Cleartext. In the prior art, there are essentially two embodiments. In a first embodiment, a magnetic code is printed.

In the areas of the security strip adjacent to the recessed parts constituting the negative inscriptions, the quantity of magnetic pigments and therefore the density of the residual magnetic flux is variable depending on the shape of the recess. In addition, in some cases, the recesses are very large and the density of the magnetic flux is insufficient to be detected, thus destroying part of the encoded message. In a second embodiment, a magnetic track recorded adjacent to a track bearing inscriptions in negation is combined. This requires that the inscriptions be very small in size, while the search is for security bands bearing the most insignificant inscriptions. wide possible that can be easily checked visually. Especially for a 3mm wide wire, it is difficult to create letters more than 1mm high in a tape coated with a conventional magnetic layer.

According to the present invention, the mixing of the magnetic particles in the mass of the strip or with a transparent layer of small thickness makes it possible to distribute them uniformly over the entire surface of the security strip. On the other hand, the magnetic particles can be superimposed with respect to said negative inscriptions, which makes it possible to overcome the aforementioned drawbacks.

According to the present invention, for a strip 3 mm wide, it is possible to create letters 2.7 mm high, which on the one hand, increases the visibility of the inscriptions by a factor of 3 to 4 and in addition, simplifies the process for making negative inscriptions and reduces the cost thereof.

In a variant embodiment of the invention, the magnetic particles are included in a flini. This variant makes it possible to produce plastic security bands with particles in the mass, said bands being cut from said plastic film incorporating said particles.

This variant is also particularly suitable for producing passports or identity cards or other documents which are covered with a film for protecting the variable particulars carried on the document.
It is known to digitize information corresponding to an identity photograph or variable mentions and to record them magnetically in the form of a 2 D bar code on a sheet of paper. The major drawbacks of these recordings in barcode form reside in that they are visible, easy to copy and require a large space available on the document. The space available to record and store all the desired magnetic information, if it is desired that the latter not be visible, is very small so as not to interfere with the standardized layouts.

According to the present invention, it is possible to record and store magnetically information, in particular digitized information, corresponding to an identity photograph and / or to the variable mentions of the passport or of the identity card in the very mass of the protective film. without this information being visible. The advantages of this solution are at least twofold: there is no longer any problem of space limitation, since the entire page can be used as a support for recording the standardized information, and the place where the information is recorded is not. visible.

According to another variant embodiment of the present invention, the magnetic particles are included in an adhesive. The advantages of this variant, in addition to those mentioned above for the transparent plastic film, are that the adhesive constitutes a malleable recording medium and hot ductile relatively more brittle than film. Thus if the adhesive is formed by the adhesive of the protective film of the passport, any attempt to lift the film alters the adhesive and destroys the magnetic information recorded, which constitutes additional security.

The present invention therefore makes it possible to produce a security document consisting of a passport or identity card sheet or a substrate intended for the manufacture of a passport or identity card sheet in which said magnetic particles are applied. in the mass of said substrate or on a transparent protective plastic film of said passport or identity card sheet or else in an adhesive allowing said film to adhere to said sheet.

The present invention also makes it possible to produce a security document consisting of a wrapping sheet or a sheet of paper or plastic intended for the manufacture of a wrapping sheet, said magnetic particles being incorporated into the mass of the substrate constituting said. sheet or in a coating applied to the surface of said substrate.

The present invention also makes it possible to produce particularly advantageous paper or plastic security labels. The magnetic particles may be incorporated in the bulk of the substrate or in a coating applied to the surface of the substrate on the front of the label, in particular in a coating of the transparent varnish type, or on the back, in particular in an adhesive applied to the label. surface of said substrate on its back. In all cases, the magnetic information recorded does not occur during use of the support, it suffices to remagnetize the zones (pads) by bringing them to magnetic saturation before carrying out the detection.

In the second embodiment, the medium is completely covered with magnetic particles and the recording of the bits is done by magnetization with fields whose direction of magnetization is reversed in localized regions. More precisely, certain regions of the medium are brought to saturation in one direction or another, said regions then corresponding to the magnetic bits 0 or respectively 1 of the coded information. In this second embodiment, it is not acceptable for the bits to be demagnetized because it is then no longer possible to restore the information before detection or reading. It is therefore necessary in this second embodiment, to use magnetic particles of high coercivity, which do not run the risk of being demagnetized by simple use.

In each of the two embodiments, it is possible to vary the length of the magnetized zones so as to create a bar code.

To produce documents, in particular magnetically recordable papers, use is made, in particular, of particles with a coercivity of 23.873 x 103 to 795.775 x 103 A / m (300 to 10,000 Oe). Materials with high coercitivities of the order of 79.577 x 103 to 397.887 x 103 (1000 to 5000 Oe), such as barium and strontium ferrites in particular BaFel2019 or Str Fel2019 are commonly used.

The present invention also relates to a method of manufacturing a security document according to the invention, characterized in that said magnetic particles are incorporated in the bulk of the substrate or in a coating on the surface of the substrate in said zone. , said particles having a size and a concentration such that they do not affect the appearance characteristics of said zone.

More particularly, a dispersion of magnetic particles is mixed with the base material of the substrate or with a coating applied to the surface of the substrate. Different types of coating that can be applied to the surface of the substrate have been described above.

In one embodiment, an aqueous dispersion of magnetic particles according to the invention is mixed with the paper pulp to be used in the manufacture of said substrate consisting of a sheet of paper or cardboard.

In another embodiment, said particles are incorporated in the mass of a security element or in a coating applied to the surface of the security element, and said security element is incorporated in the mass of said substrate or said said substrate is applied. security element on the surface of said substrate. Different types of coating that can be applied to the surface of said security element have been described above.

Other objects, characteristics and advantages of the present invention will appear in the light with the exemplary embodiments which will follow.

Comparative EXAMPLE 1 and Examples 2 to 6 according to the invention:
We make a magnetic paper as follows:
Cellulose fibers comprising 60% long fibers and 40% short fibers are suspended in water; this suspension is refined at 40 degrees Schoepper-Riegler. Then an aqueous predispersion of magnetic pigments is added at different rates as indicated in Table 1, Comparative Example 1 not comprising magnetic pigments and 6%, by dry weight relative to the fibers, of sodium dioxide pigments is also added. titanium as mineral fillers providing whiteness and opacity. A neutral sizing agent (0.4% by dry weight of an alkyl ketene dimer) and a retention agent [0.6% by dry weight of a poly (ethylene imine)] are added; the percentages being expressed relative to the cellulose fibers.

The predispersion of magnetic pigments is achieved by introducing the pigments into water with a rheology regulating agent such as poly (vinyl alcohol) and a dispersant and wetting pigments. This dispersion thus has a good affinity with cellulose and is stabilized so that the pigments do not agglomerate when the dispersion is diluted and then mixed with the paper composition.

Magnetic pigments are strontium ferrite particles and have a coercivity of 159.155 x 103 A / m (2000 Oe); the largest particle size is less than about 1 Fm.

The sheets of paper obtained have an average basis weight of 93 g / m2.

As usual, the surface of the paper obtained in a size press is treated with a solution of starch and a starch insolubilizer, a melamine-formaldehyde resin, in order to improve their printability.

The samples are subjected to light calendering.

The finished samples have a basis weight of 95 g / m2 and an average thickness of 122 Clm
The respective amounts of the compounds introduced into the samples are given in the
Table 1, as well as the colorimetric results.

The papers obtained are tested under the conditions described below.

It is considered that the magnetic papers having a Delta E * in color difference strictly less than 10 are suitable, which is corroborated with the fact that the magnetic papers having an ISO whiteness greater than or equal to 65% are suitable. the papers must therefore contain at most 0.2% of magnetic pigments.

Preferably, magnetic papers have a Delta E * in color difference less than or equal to 5.

A good recording and a good reading of the magnetic data is obtained on all the samples comprising magnetic pigments with a ratio (signal / background noise) greater than 20 dB.

The control without pigments exhibits a background signal but much lower than the samples according to the invention.

Comparative EXAMPLE 7 and Example 8:
Magnetic paper is produced which may be suitable as a paper for making a banknote as follows
A pulp of cotton fibers is suspended in water to which is added the aqueous predispersion of magnetic pigments used in the preceding examples, at a rate of 0.05% by dry weight, Comparative Example 7 not comprising magnetic pigments and 6%, by dry weight relative to the fibers, of titanium dioxide pigments are also added as mineral fillers providing whiteness and opacity; this suspension is refined to 55 degrees Schoepper-Riegler. Then a wet strength agent (3% by dry weight, a melamine-formaldehyde resin) and a retention agent [0.5% by dry weight of a polyacrylamide] are added; the percentages being expressed relative to the cotton fibers. .

The sheets of paper obtained have an average weight of 85 g / m2.

The paper is impregnated with a solution of poly (vinyl alcohol) and optionally with a composition of glycerin to improve the printability of the paper and provide the necessary resistance to the circulation of the note.

The papers are subjected to a light calendering.

The finished samples have a basis weight of 87 g / m2 and an average thickness of 120 µm.

The respective amounts of the compounds introduced into the samples as well as the colorimetric results are given in Table 1.

The papers obtained are tested under the conditions described below.

A good recording and a good reading of the magnetic data is obtained on the sample comprising magnetic pigments with a ratio (signal / background noise) greater than 20 dB. The control without pigments exhibits a background signal but much lower than the samples according to the invention.

EXAMPLE 9:
We make a security thread as follows:
On a polyester film of about 19 m thick, an impression is made so that the significant characters are constituted by transparent recesses entirely surrounded by an opaque zone, these characters have a height of 0.8 mm .

On this impression, a layer is deposited containing the magnetic pigments used in the preceding examples as a mixture in a heat-sealable polyester varnish.

The magnetic layer is deposited by gravure coating at a rate of 4 gim2 and contains 1% of magnetic pigments, it is 4 ssm thick.

The heat-sealable varnish alone is deposited on the other side of the wire in order to hold the wire firmly in the sheet of paper.

The total thickness of the film is 30 Fm.

The film is cut into 1.2 mm wide threads (strips).

The thread is introduced into a paper for banknotes so as to make the thread appear in windows according to the method described in European patent EP 59056.

Magnetic data is recorded and read under the conditions described below.

An advantage of this wire is that it is magnetically detectable and that the significant characters are observed well on the wire; it allows writing of the magnetic data and / or significant characters visible over the entire width of the wire (the magnetic layer being transparent).

Compared to the prior art, it does not require a masking layer of the magnetic zones to make them non-photocopiable and reduces the extra thickness associated with its introduction into a sheet of paper (because it is approximately 5 μm thick less compared to to a prior art thread having the same information data).

The papers are tested under the conditions described below.

CONDITIONS OF MEASUREMENTS AND TESTS: - The basis weight is measured according to the ISO 536 standard after conditioning according to the ISO 187 standard.

- Colorimetric tests: the measurements of the colorimetric and whiteness characteristics to define the appearance of the paper were carried out on an ELREPHO 2000 spectrocolorimeter in the CIE system under illuminant D65 (daylight and without UV) and at an observation angle of 10 degrees, the sheets being superimposed in sufficient number to have a thickness giving the required opacity.

The colorimetric coordinates L *, a *, b * in the CIELAB system were measured and from these we calculated the Delta E * color difference between the control sample (without magnetic pigments) and the samples with magnetic pigments. , according to the following formula:
Delta E * = square root [(L * oL * i) 2 + (a * 0-a * s) 2 + L * o, a * 0, b * o being the CIELAB coordinates of the witness, L * i,, b * i being the CIELAB coordinates of sample i.

The CIE whiteness is also determined according to the CIELAB formula.

The ISO whiteness is also determined according to the ISO 2471 standard (reflectance at 457 nm).

- Magnetic tests:
Magnetic data recording: for each sample, eight magnetic flux transitions (denoted ft) (that is to say eight successive regions of opposite magnetizations) per millimeter are recorded on a track, according to the NF EN ISO standard. / IEC 10373.

This recording is made using a conventional inductive recording head having a write air gap of 50 lm. The writing width is 1cm and the recording speed is 200mm / s.

The pressure forces exerted between the recording head and the paper samples and the head-to-sample distance have been selected so as to have the best possible recording and maximum signal amplitude during playback.

Magnetic data reading: The magnetic recording of samples is read with a magnetoresistive read head.

This magnetoresistive read head has a magnetoresistance coefficient of 2% and the saturation field is less than 7.957 x 103 A / m (100 Oe) and it has a read width of 1 cm. The head-to-sample distance is less than 200 µm. The intensity of the current in the magnetoresistor is set at 12 mA.

Thanks to an operating unit, an output signal is read in millivolts (voltage difference resulting from the variation of the resistivity of the head during the passage of the sample) which translates, in absolute value, the magnetic flux transitions recorded. The output signal / background noise ratio R is also determined, this ratio having to be at least equal to 2 to be acceptable.

- The dosage of total iron is made according to standard NF-T-12025.

example <SEP> 1 <SEP> example <SEP> 2 <SEP> example <SEP> 3 <SEP> example <SEP> 4 <SEP> example <SEP> 5 <SEP> example <SEP> 6 <SEP> example <SEP> 7 <SEP> example <SEP> 8
<tb> comparative <SEP> comparative
<tb> quantity <SEP> of <SEP> 0 <SEP> 0.003 <SEP> 0.005 <SEP> 0.010 <SEP> 0.100 <SEP> 0.200 <SEP> 0 <SEP> 0.050
<tb> pigments
magnetic <tb>
<tb> introduced <SEP> (%)
<tb> quantity <SEP> of <SEP> iron <SEP> total <SEP> 0.0042 <SEP> 0.0054 <SEP> 0.0070 <SEP> 0.0083 <SEP> 0.0452 <SEP> 0 , 0800 <SEP> 0.0033 <SEP> 0.080
<tb> dosed <SEP> (%)
<tb> Delta <SEP> E * <SEP> 0.0 <SEP> 0.8 <SEP> 1.1 <SEP> 1.9 <SEP> 9.1 <SEP> 13.4 <SEP> 0, 0 <SEP> 4.3
<tb> Whiteness <SEP> CIE <SEP> (%) <SEP> 71.8 <SEP> 69.8 <SEP> 68.8 <SEP> 66.5 <SEP> 42.1 <SEP> 29.3 <SEP> 77.9 <SEP> 63.1
<tb> Whiteness <SEP> ISO <SEP> (%) <SEP> 85.6 <SEP> 84.0 <SEP> 83.3 <SEP> 81.4 <SEP> 65.0 <SEP> 56.4 <SEP> 87.5 <SEP> 77.1
<tb> TABLE 1

Claims (37)

1. Security document comprising a substrate consisting of a sheet of paper or cardboard or a plastic sheet obtained by extrusion and at least one zone comprising magnetic particles characterized in that: a) said magnetic particles are included in the mass of the substrate or in a coating on the surface of the substrate, b) said magnetic particles do not affect the appearance characteristics of said area, c) said magnetic particles are uniformly distributed in said zone. 2. Security document according to claim 1, characterized in that it is a security paper, said substrate consisting of a sheet of paper or cardboard. 3. Security document according to claim 1 or 2, characterized in that said magnetic particles are included directly in the mass of the substrate or in a coating on the surface of the substrate. 4. Security document according to claim 3, characterized in that said magnetic particles are included in a security element or a coating applied to the surface of a security element, said security element being included in the mass or applied to the surface. of said substrate. 5. Security document according to claim 4, characterized in that said security element consists of a security strip of plastic material included in whole or in part in the mass of the substrate. 6. Security document according to one of claims 1 to 5, characterized in that said particles are included in a said coating on the surface of the substrate, said coating consisting of a coating composition when the substrate is made of plastic or paper. or a sizing composition when the substrate is made of paper. 7. Document according to one of claims 1 to 5, characterized in that said particles are included in a said coating on the surface of said substrate or of a said security element, said coating consisting of a varnish or an ink which can be applied by printing techniques such as gravure printing, offset printing or screen printing. 8. Security document according to one of claims 1 to 5, characterized in that said magnetic particles are included in said coating on the surface of the substrate or of said security element, said coating consisting of an adhesive. 9. Security document according to one of claims 1 to 8, characterized in that said magnetic particles are included in said coating on the surface of the substrate, said coating consisting of a plastic film in the mass of which said particles are incorporated. 10. Security document according to one of the preceding claims, characterized in that the magnetic particles are included in a coating applied to a hologram or in a constituent layer of a hologram. 11. Document according to claim 5, characterized in that said hologram is a transparent hologram or partially demetallized hologram. 12. Security document according to claim 10 or 11, characterized in that said hologram is applied to a security strip included in part in said substrate, said hologram being visible in the parts appearing on the surface of the document. 13. Security document according to one of the preceding claims, characterized in that the magnetic particles are included in a coating applied to an area comprising inscriptions in positive or negative, on a security strip included, in whole or in part, in said substrate. 14. Security document according to claims 5, 12 or 13, characterized in that said magnetic particles are included in a heat-sealing varnish applied to the surface of said security strip or in the mass of said plastic strip. 15. Security document according to one of the preceding claims, characterized in that said security document is a banknote or a sheet of paper or plastic intended for printing a banknote. 16. Security document according to one of claims 1 to 9, characterized in that said document is a label or a sheet of paper or plastic intended for the manufacture of a label and said magnetic particles are included in the mass of said substrate, or in a coating applied to the surface of said substrate on its front side, or in an adhesive applied to the surface of said substrate on its back side. 17. Security document according to one of claims 1 to 9, characterized in that said document is a passport sheet or identity card or a substrate for the manufacture of a passport sheet or card. identity and said magnetic particles are applied in the bulk of the substrate, or on a transparent protective plastic film of said passport or identity card sheet, or in an adhesive allowing the adhesion of said film on said sheet. 18. Security document according to one of claims 1 to 9, characterized in that said document is a wrapping sheet or a sheet of paper or plastic intended for the manufacture of a wrapping sheet. 19. Security document according to one of claims 1 to 18, characterized in that said zone covers the entire substrate. 20. Security document according to one of claims 1 to 18, characterized in that it comprises a succession of said zones comprising magnetic particles included in a coating on the surface of said substrate or of said security element, these said zones being. separated by regions devoid of magnetic particles, this succession of said zones constituting a magnetic coding. 21. Security document according to one of claims 1 to 20, characterized in that said zone comprises particles of coercivity greater than 23.873 x 103 A / m (300 Oe), preferably 79.577 x 103 A / m (1000 Oe ), said zone being slfEsemment extended to serve as a support for the magnetic recording of a code. 22. Security document according to one of the preceding claims, characterized in that said magnetic particles are included in the mass of the substrate or in a coating applied to the surface of the substrate, at a concentration less than or equal to 0.1%, preferably 0.05. % by weight of said substrate in said area. 23. Security document according to claim 22, characterized in that the concentration of magnetic particles is 0.001% to 0.1%, preferably 0.01% to 0.1%. 24. Security document according to one of the preceding claims, characterized in that said particles are included in a coating applied to the surface of said substrate or of said security element and the concentration of magnetic particles in said coating is less than or equal. to 1% by weight of the coating in said area. 25. Security document according to claim 24, characterized in that the concentration of magnetic particles in said coating of said zone is from 0.01 to 0.1%. 26. Security document according to one of the preceding claims, characterized in that the size of the magnetic particles is less than 2, preferably less than 1 p. 27. Security document according to claim 26, characterized in that the size of the magnetic particles is from 0.1 to 1, preferably 0.1 to 0.5 p. 28. Security document according to one of the preceding claims, characterized in that the substrate is made of paper and has a light color, in particular white, cream or pale yellow. 29. Security document according to one of the preceding claims, characterized in that the ISO whiteness according to ISO standard 2471 of the substrate is greater than or equal to 65%. 30. Security document according to one of the preceding claims, characterized in that the CE whiteness according to the CIELAB formula of the substrate is greater than or equal to 30%. 31. Security document according to one of the preceding claims, characterized in that said coating on the surface of the substrate or of said security element is transparent or translucent. 32. Security strip intended to be incorporated into a document according to one of the preceding claims, characterized in that it comprises the characteristics of the security strip defined in claims 5, 7, 8, 12 to 15, 20 to 27, and 31. 33. Security tape according to claim 32, characterized in that it has a thickness of preferably 10 to 30 m and a width of 0.5 mm to 5 cm, preferably 1 to 5 min. 34. A method of manufacturing a security document according to one of claims 1 to 31, characterized in that said magnetic particles are incorporated in the bulk of the substrate or in a coating on the surface of the substrate in said zone, said particles having a size and a concentration such that they do not affect the appearance characteristics of said zone. 35. A method of manufacturing a security document according to claim 34, characterized in that a dispersion of magnetic particles is mixed with the base material of the substrate or of a coating applied to the surface of the substrate. 36. The method of claim 34 or 35, characterized in that mixing an aqueous dispersion of magnetic particles with the paper pulp to be used in the manufacture of the substrate consisting of a sheet of paper or cardboard. 37. Method according to one of claims 34 to 36, characterized in that said particles are incorporated in the mass of a security element or in a coating applied to the surface of the security element, and said said particles are incorporated. security element in the mass of said substrate where said security element is applied to the surface of said substrate.