EP1034536B1 - Data security medium - Google Patents

Description

The present invention relates to a security information medium for recording and storage of static and dynamic information relating to the traceability of a product. This support is plastic and includes magnetic particles, it is in particular in the form of a label or plastic packaging sheet. The present invention also relates to a method of manufacturing said support and a method of reading recorded information and stored.

The information is recorded magnetically using inductive heads but their reading is done by reading machines equipped with magneto-resistive sensors as it will be explained below.

To be able to identify a product and better still follow its trace in the industrial circuit and has become a requirement to fight fraud and improve control over quality, while allowing management from production to stock keeping and also up to destruction or recycling of packaging.

Indeed, for example, the question of product traceability arose acutely during of the mad cow case, because it was necessary to know the origin of the meat and its distribution channel.

Another example is linked to acts of counterfeiting carried out for the imitation of major brands or drugs or products with serious safety consequences people or property. Another example is related to the diversion acts putting the products authentic in distribution circuits parallel to selective distribution networks or. exclusive. Similarly, when products are found to be defective in use, it is imperative to be able to find them to withdraw, exchange or revise them.

Traceability is a legal obligation in the case of certain products as for automobiles and their spare parts, for products subject to approval; medication subject to marketing authorization or certain food products. More generally, according to the European directive of June 29, 1992 relating to product safety, all companies must be able to provide proof of product conformity to the general regulations.

According to the international standard ISO 8402 of July 1995 relating to the vocabulary for quality management and quality assurance, traceability is defined as "the ability to find the history, use or location of an entity by means of identifications saved ”. We can also refer to ISO 9000-2 of July 1994 relating to the application of standards for quality management and quality assurance which takes up the content of ISO 9000-2: 1993 where details are given on page 10, point 4.8 of the recommendations on the identification and traceability of a product.

Traceability applies to the monitoring of a group of same articles, bearing the same number lot as a reference, called statistical identification, or to individually identified objects, called registration, or a sequential identification of operations or operators identified.

Various means exist for identifying an object or a batch. The most common is to assign a identification code, which associates a string of numeric, alphanumeric or graphics, possibly standardized. The information relating to traceability is brought to a label and / or directly on the object or its packaging.

One of the most common ways to record data on the traceability of a product is the barcode, which comes in different forms.

We know the linear bar codes (1D), in particular the so-called logistics bar code which symbolizes the translation of the EAN 128 standardized coding system, the most dense in information currently used for logistical monitoring of a product. It symbolizes at the times the information concerning the compulsory main identifier (date of manufacture and / or number batch) and additional information relating to the logistics unit (information concerning the manufacturing. transport and customer), to ensure product traceability from its manufacture to its point of sale. A disadvantage of this type of barcode is that it requires tolerances for direct printing difficult to obtain with any medium. For example, if the media printing is porous, it will absorb too much printing ink and will not allow small, well-defined printouts, otherwise the code will be difficult to read. Another downside is that the amount of information it can contain is limited.

To partially overcome the drawbacks of the 1D barcode, the codes appeared two-dimensional bars (2D), which are formed by a stack of several linear bar codes appearing in the form of a checkerboard and, more recently, matrix codes have appeared which do not are no longer in the form of bars, but of light and dark dots or squares. They require specific decoding software which does not allow very fast data processing.

One of the drawbacks of these various bar codes is their visibility; they can be recognized optically and are therefore violable.
Another drawback is that it is an information medium with permanent memory and therefore does not have evolving memory. Indeed, part of the information can be fixed (so-called static information) such as the date and place of manufacture, the raw materials used in manufacturing, batch number, while another part of the information can vary and be individualized ( so-called dynamic information) depending on the circulation of the product.
Another disadvantage is the important place they take on the object because of their size; it is therefore difficult to apply them to an object of small dimensions.
Another drawback is their lack of aesthetics, which can prove to be particularly annoying when they are worn on luxury packaging or on containers (flasks, bottles, etc.), in particular with the desired shapes and / or patterns.

Another way to record the traceability of a developing product is the microchip. This chip is incorporated into a label or directly into the product. Although it has the possibility of storing static and dynamic information at the same time, it has the disadvantage of being too large (around 2 mm ² ) to be discreetly incorporated into a label or packaging or the product itself; it is all the thicker when it is activated, that is to say when it is implemented with an induction winding which supplies it with the operating energy and taken up in resin. Its lack of flexibility limits its incorporation into rigid supports. Furthermore, its cost price is high.
The chip can be located easily, by visual identification or by touch. It is not truly inviolable, it can be removed and replaced by another.

In patent US5520954, a method of preparing a dispersion has been described. magnetic comprising gelatin and to be applied in a layer on a film photographic to allow data recording, the layer obtained not having to interfere with the photographic properties of the film. This patent does not concern the field of the invention which is that of security supports.

In patent application GB1514758 a data carrier card has been described comprising a magnetic layer allowing the recording of data, this layer being colorless thanks to the use of colorless or almost colorless magnetic particles. It is therefore not not possible to use any type of magnetic pigments which are generally dark in color. Furthermore, these pigments are used in conventional quantities, therefore quite high. In these conditions their observation with a magnifying glass for example would be possible.

The problem is therefore to provide an information medium allowing the traceability of a product and / or process, which is invisible and difficult to spot without knowing in advance its location, and which presents an important and evolving memory, that is to say which allows to record and store a large amount of information and some being static and others dynamic.

Furthermore, this support must be compatible at least with one of the anti-theft systems known as electromagnetic devices (magnetic tab or fine alloy), circuits electronic devices remotely detectable by radio frequency or magnetoacoustic devices (vibrate and emit a frequency of 58kHz), that is to say that it must not disturb the detection, activation and deactivation of these various devices.

Another secondary property sought in addition to traceability is inviolability information and / or the medium, i.e. they cannot be altered or the alteration be highlighted.

Another property sought in addition to traceability is to be able to evidence of an attempt to tamper with a product; for example, when replacing a product given by another in a bottle, bottle or box.

Another secondary property sought in addition to traceability is compatibility with known means of authentication (so-called security elements) in the field of security documents, such as optically variable devices (holograms, iridescence, diffraction gratings, moiré, thermochromic effect ...).

An object of the present invention is therefore to provide an information medium allowing the traceability of a product which solves the problems of the means of the prior art and can present in addition to the desired secondary properties set out above.

Another object of the present invention is to be able to encode information in quantity increased compared to bar codes.

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

• lesdites particules magnétiques sont comprises dans la masse du substrat ou dans un revêtement à la surface du substrat,
• lesdites particules magnétiques n'affectent pas les caractéristiques d'aspect de ladite zone, en l'absence de tout masquage pour les rendre invisibles et,
• lesdites particules magnétiques sont réparties de manière uniforme dans ladite zone et que lesdites particules vérifient les caractéristiques de concentrations suivantes, prises séparement ou en combinaison:
• a) lesdites particules magnétiques sont comprises dans la masse dudit substrat ou dans ledit revêtement appliqué en surface du substrat, à une concentration inférieure ou égale à 1 % en poids sec dudit substrat dans ladite zone,
• b) lesdites particules sont comprises dans un revêtement appliqué en surface dudit substrat et la quantité de particules magnétiques dans ledit revêtement (dans ladite zone) est inférieure ou égale à 250 mg/m².

The present invention provides a security information medium for recording and storing static and dynamic information, characterized in that it comprises a substrate consisting of a plastic sheet and at least one zone comprising magnetic particles allowing said recordings and storage of information invisible to the magnifying glass and such as:

• said magnetic particles are included in the mass of the substrate or in a coating on the surface of the substrate,
• said magnetic particles do not affect the appearance characteristics of said zone, in the absence of any masking to make them invisible and,
• said magnetic particles are distributed uniformly in said zone and that said particles verify the following concentration characteristics, taken separately or in combination:
• a) said magnetic particles are included in the mass of said substrate or in said coating applied to the surface of the substrate, at a concentration less than or equal to 1% by dry weight of said substrate in said zone,
• b) said particles are included in a coating applied to the surface of said substrate and the amount of magnetic particles in said coating (in said zone) is less than or equal to 250 mg / m ² .

By “coating on the surface of the substrate” is meant that it is a coating which is not not necessarily, at least in part, covered by a masking layer, said coating possibly be present on the external surface of the substrate or be under or between other layers which do not not mask at least in part. By the characteristic that "magnetic particles do not affect the appearance characteristics of the said area 'means that it is not necessary to hide said area to make it invisible and more particularly means that when they are included in the mass of the substrate, or even when included in a surface coating the surface of the substrate, the particles as such are not distinguished and the appearance, in particular the brightness (L *) and / or colorimetric coordinates (L *, a *, b *) in the CIELAB system, and / or the transparency or the opacity of the substrate is not or very little modified.

In particular, when the substrates comprising said magnetic particles are transparent or translucent or possibly clear to white, the brightness L * is greater than 70 and preferably 80. Known fillers providing whiteness such as for example titanium dioxide or calcium carbonate can be added to improve whiteness, in particular at rates between 2 and 10%, in the case of white substrates.

In particular, said support has a thickness of between 1 and 2000 μm, preferably between 1 and 800 µm and more preferably between 10 and 600 µm.

The present invention is particularly advantageous when said support is a label or a packaging sheet or film.

Other characteristics of the supports according to the present invention are defined in the appended claims.

Furthermore, the invention makes it possible to associate in the same zone properties magnetic and an authentication element like those known in the field of security documents, in particular for visual effect, such as certain security threads, devices with variable optical effect such as diffraction gratings, holograms, moiré patterns, iridescent effect prints or bands, prints based on thermochromic inks or other. The visual effect or readability is not obscured by the presence of particles magnetic.

According to the present invention, the magnetic particles can therefore be associated with authentication elements (also called security elements).

Likewise, anti-theft devices can coexist with the presence of particles magnetic.

Said support with said particles can also make it possible to record and store information, in much larger quantities than previously, especially under form magnetic codes, and render the area where the magnetic information was recorded and stored invisible to the naked eye and invisible with a magnifying glass. It also allows you to record and read additional information to the initial information to follow the traceability of a product. Indeed with magneto-resistive sensors having a much higher sensitivity to heads inductive previously used, we can read encoded magnetic information or simply characterize the saturation or remanent magnetization of the pigments, this at concentrations of very weak magnetic particles, in particular, lower than the concentrations allowing a detection by inductive sensors, but making the presence of said particles invisible Such support is therefore inviolable because the areas containing the information cannot be located easily.

According to a characteristic of the invention linked to the sensitivity of the magneto-resistive heads, it is necessary that the magnetic particles do not form agglomerates or aggregates inhomogeneous. It is therefore necessary that magnetic particles are well individualized and uniformly dispersed and distributed in their substrate. Here we mean by "uniform distribution magnetic particles ", as the particle density in the area, and therefore the magnetic saturation or remanent magnetization in said zone are substantially constant so that there is little or no background noise. This feature is necessary to allow to read reliably a coded message, recorded in said zone.

A secondary aim of the present invention is therefore to confer on a support, the ability to be magnetized, recorded, detected and read by machine thanks to its magnetic properties, without it it is necessary to mask the magnetic zones to make them invisible and in particular to ability to introduce magnetic particles homogeneously and without aggregates on the surface or in the mass of a substrate over a wide area.

The magnetic particles can therefore be advantageously incorporated into the mass. of the substrate by mixing a dispersion of said particles with the base mixture to make the substrate or the coating of said information medium. This gives good individualization of the particles, which prevents re-agglomeration of said particles when incorporated into the manufacturing medium of said substrate or said coating. The particles magnetic then come in the form of pigments which can be coated with a layer, even discrete (ie not continuous) coming from the dispersion medium.

Said area comprising said particles may cover the entire substrate or a part only.

The incorporation of magnetic particles in the mass of the substrate or in a coating on the surface of the substrate in an area covering the entire substrate, allows to considerably expand the possibilities of using the present invention. However they may only be in a localized area, in particular in the form of a strip, in particular of width from 1 to 5 cm by methods known to a person skilled in the art, said zone not covering necessarily the entire substrate.

The present invention is particularly advantageous when the substrate comprising said magnetic particles is a transparent to translucent plastic substrate and / or has a light color, especially white, cream or pale yellow. In this case, as mentioned previously, the brightness L * of the CIELAB system is greater than 70 and preferably more than 80. The ISO whiteness according to ISO 2471 is preferably greater than or equal to 60% and the whiteness CIE according to the CIELAB formula is preferably greater than or equal to 20%.

When the magnetic particles are included in a coating on the surface of the substrate, this coating can consist of an ink or a varnish or a composition coating or adhesive, which can be applied respectively by a technique printing or coating. The coating composition may especially include, in addition to said magnetic particles, a binder chosen from polyvinyl alcohol (PVA) type binders, or other water-soluble binders or polymers in aqueous dispersion (latex), fillers coating, water and additives. The varnish may especially include, in addition to said particles magnetic, polymeric binder, solvent and additives.

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

As inks or varnishes, particular mention is made of printing inks or varnishes which can be applied by gravure printing, intaglio printing, offset printing or screen printing over a thickness of 1 to 5 µm. In printing varnishes, mention may be made of soluble varnishes in aqueous medium or in organic solvent which are dried by evaporation, and the varnishes fixed by UV or electronic radiation ("electron beam").

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

a) lorsque les particules sont comprises dans la masse du substrat ou dans un revêtement appliqué en surface du substrat, leur concentration est inférieure ou égale à 0,10 %, de préférence de 0,001 % à 0,10 %, de préférence encore de 0,02 % à 0,07 % en poids sec par rapport au poids dudit substrat dans ladite zone,

b) lorsque lesdites particules sont comprises dans un revêtement appliqué en surface dudit substrat, la quantité de particules magnétiques déposée est comprise entre 1 mg/m² et 100 mg/m² et de préférence encore comprise entre 5 mg/m² et 50 mg/m², plus particulièrement de 10 à 20 mg/m²,

c) les particules magnétiques ont une taille inférieure ou égale à 2 µm, de préférence inférieure à 1 µm, notamment de 0,1 à 1 µm, plus particulièrement encore de 0,1 à 0,5 µm. Par « taille », on entend ici la plus grande dimension de la particule.

To satisfy both the appearance characteristics of the support and the uniform distribution characteristics of the magnetic particles of the present invention, and to allow detection of magnetic presence or recording of a given information density, 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 or in a coating applied to the surface of the substrate, their concentration is less than or equal to 0.10%, preferably from 0.001% to 0.10%, more preferably from 0 0.02% to 0.07% by dry weight relative to the weight of said substrate in said zone,

b) when said particles are included in a coating applied to the surface of said substrate, the quantity of magnetic particles deposited is between 1 mg / m ² and 100 mg / m ² and more preferably between 5 mg / m ² and 50 mg / m ² , more particularly from 10 to 20 mg / m ² ,

c) the magnetic particles have a size less than or equal to 2 μm, preferably less than 1 μm, in particular from 0.1 to 1 μm, more particularly still from 0.1 to 0.5 μm. By "size" is meant here the largest dimension of the particle.

For quantities in the mass of the substrate less than 0.01%, or quantities less than 5 mg / m ² for a coating on the surface of the substrate, encoding and reading becomes difficult. For a light and / or transparent colored support, a good compromise between the appearance of the support and an optimum signal under the conditions of recording and reading of the data, is obtained with concentrations of particles from 0.02% to 0 0.07% by mass of the substrate or for amounts of 5 to 50 mg / m ² for a coating on the surface of the substrate as mentioned above.

Packages or labels with a hologram are sought after because they are difficult to counterfeit, while being aesthetic, and more easily authenticated by the general public. However, these holograms in previous embodiments could not be easily associated with magnetic properties for the following reasons. First, the holograms or holographic security strips consist of multilayer complexes [(1) for holograms: adhesive layer, embossing lacquer, aluminum and protective varnish; (2) for holographic bands: the same layers as for holograms but applied to the at least one layer of polyester, said strip being coated on its external faces with varnish heat sealing]. Then to have magnetic properties, you had to apply a layer magnetic in these complexes by an additional operation, the layer being moreover dark and thick. In addition, holograms are sometimes transparent holograms, say non-metallic or partially demetallized holograms. However, the presence of a layer dark magnetic 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 with recesses of the so-called “Cleartext” type.

The present invention makes it possible to associate magnetic particles with holograms of advantageously. To do this, simply mix the magnetic particles with the layers component of the hologram, such as the adhesive layer, the embossing lacquer, the protection or in the hologram adhesion primer.

When the hologram constitutes a holographic strip, it is also possible to incorporate the said holograms. magnetic particles in the mass of said strip (such as a polyester substrate) or in a heat-sealing adhesive or varnish allowing the adhesion of said strip to the support.

An additional advantage of holographic tapes is to obtain a hologram at magnetic property without affecting traditional manufacturing processes and without increasing its excessively thick.

Thus, the invention also provides a medium for recording information static and dynamic which can be a holagram. in particular chosen from the holograms transparent or partially demetallized, comprising magnetic particles

According to the present invention, the mixing of magnetic particles in the mass of the substrate or a transparent to translucent coating allows them to be distributed uniformly over the entire surface of the support and superimpose them on inscriptions or patterns, negative or positive, without alter their visibility and appearance.

According to a variant of the invention, the support allowing the recording of information static and dynamic is an integral part of the object relating to said information, the medium can be the object itself.

This variant can be applied to plastic security documents and in particular to plastic banknotes whose traceability is to be followed or to an official document such as a passport cover, an identity card or a driving license or to a substrate intended for the manufacture of such an official document, in which said magnetic particles are applied in the mass of said substrate or in a coating on the surface of the substrate.
For example, information, in particular digitized information, corresponding to an identity photograph and / or variable information can be magnetically recorded and stored without this information being visible or disturbing a standardized layout of said documents. The advantages of this solution are at least twofold: there is no longer a problem of space limitation, since the entire surface 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 alternative embodiment of the present invention, the magnetic particles are included in security inks.

The present invention also makes it possible to produce a support consisting of a sheet packaging or a plastic sheet for the manufacture of a packaging sheet, said magnetic particles being incorporated in 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 plastic security labels. particularly advantageous. Magnetic particles can be incorporated into the mass 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 a adhesive applied to the surface of said substrate on its back. In all cases, the magnetic information recorded is never visible even on the back through the label holder as a bottle, in particular, when it is a label of a wine bottle or a bottle of perfume

According to the present invention, the magnetic information can be presented according to various embodiments. In a first embodiment, the support includes magnetic particles in at least one continuous area and recording bits logic is done by magnetization with fields whose direction of magnetization is reversed in localized regions. More specifically, certain regions of the support are brought to saturation in one direction or another, said regions then corresponding to bits "0" or respectively "1" of the coded information. We analyze the data signal at each clock pulse. In this embodiment, it is not acceptable that the bits can be demagnetized because it is no longer possible to restore information before detection or reading. It is therefore preferable in this second embodiment, to use magnetic particles of medium to high coercivity, which are not likely to be found demagnetized by simple use.

In a second embodiment, the support comprises magnetic particles in at least one continuous zone and the recording is done according to an F / 2F type encoding as described in ISO standards 7811-3 and 7811-6. Clock and bit tracks are merged. If the bit is a "1" there is a flow transition that takes place between two pulses clock, if the bit is a "0", there are no flow transitions between two pulses clock.

In each of the embodiments, one can play on the length of the magnetized zones so as to create an invisible barcode.

In order to produce magnetically recordable supports, coercivity particles of 15.5 × 10 ³ to 800 × 10 ³ A / m (approximately 200 to 10,000 Oe) are used in particular. The so-called low coercivity materials have a coercivity between 15.5 x 10 ³ and 32 x 10 ³ A / m (about 200 to 400 Oe) and are generally iron oxides.
The so-called medium coercivity materials have a coercivity between 32.10 ³ and 135.10 ³ A / m (approximately 400 to 1700 Oe) and are generally iron oxides doped with cobalt or chromium dioxides.
The so-called high coercivity materials have a coercivity between 135.10 ³ and 800.10 ³ A / m (around 1700 to 10 000 Oe), such as barium or strontium ferrites, in particular BaFe ₁₂ O ₁₉ or SrFe ₁₂ O _{19 respectively.} commonly used.

The present invention also relates to a method of manufacturing a support according to the invention, characterized in that said magnetic particles are incorporated into the mass 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 characteristics appearance of said area

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

In one embodiment, a dispersion of magnetic particles is mixed in the medium organic with the base mixture for use in the manufacture of said substrate consisting of plastic sheet. The plastic sheets can in particular be based on a polyolefin such than polyethylene or polypropylene or their copolymers, and contain pigment fillers, anti-static agents. They can be obtained by extrusion or by injection. Leaves can be stretched.

In another embodiment, said particles dispersed in organic or aqueous medium in a coating applied to at least one of the faces of the substrate. Different types of coating that can be applied to the surface of said substrate have been described above.

Other objects, characteristics and advantages of the present invention will become apparent from the light of the examples of realization which will follow.

EXAMPLE 1 according to the invention:

A dispersion of magnetic particles is carried out as follows.
Magnetic particles are dispersed with stirring using a dispersing agent, such as a polyacrylate, and optionally a grinding resin, having good compatibility with the medium in which it will be incorporated later. The paste obtained is then treated in a ball mill to destroy the agglomerates and individualize the particles. The dispersion obtained comprises 10% of magnetic particles by dry weight.

Magnetic particles are barium ferrites which have a coercivity of 218.84 x 10 ³ A / m (2750 Oe). The largest particle size is less than about 1 µm.

In a twin screw extruder, the dispersion of magnetic particles is mixed and granules of a random copolymer of ethylene and propylene to form a mixture master. This mixture is brought to 210 ° C. After passing through a multi-port system, the mixture master obtained is cooled and dried. Passing through a granulator makes it possible to obtain rods (granules) of constant size.

In a twin screw extruder, this masterbatch is introduced with another masterbatch comprising an ethylene-propylene copolymer and an antistatic agent and this mixture is brought to 210 ° C. After extrusion and calendering, a sheet of format 70 X 100 cm is obtained.
The sheets obtained are translucent and have a thickness of 300 μm.
For 100 parts by weight of the copolymer, there is 0.15 part of antistatic agent and 0.05 part of magnetic particles by dry weight.

Packaging: by cutting and creasing, the sheets obtained are transformed into a packaging box for a perfume bottle.

Thanks to a pencil-type recording system, with an inductive head, by an F / 2F type encoding, permanent identification data corresponding to the product to be packaged are recorded in zone 1 according to a fictitious track located for example in top of the package. It is then possible to record new information during the circulation of the product in another zone 2 located at another place of the packaging and so on depending on the life of the product. The magnetic data is read on a pencil-type reader equipped with a magnetoresistive head. We can thus easily record the information allowing the traceability of the product.
Reading the information correctly confirms the homogeneous distribution of the magnetic particles and without re-agglomeration in the substrate.

EXAMPLE 2:

A transparent magnetic label is produced in the following way:

An acrylic adhesive in a solvent medium (mixture of ethyl acetate and heptane) which contains the magnetic particles is applied to a transparent poly (ethylene terephatalate) film, by raking coating. 0.19 parts of the magnetic particles were introduced in the form of the magnetic dispersion of Example 1 per 100 parts of the adhesive by dry weight. The amount of magnetic adhesive deposited is 23 g / m ² dry. The support film has a thickness of 23 μm before depositing the adhesive.
A transparent adhesive and magnetic label is obtained.
This label is applied to a transparent plastic bottle. The aesthetic appearance of the bottle is not altered.
Identification information (static) and dynamic information relating to the traceability of the product are recorded for example by carrying out an encoding such that each series of information is separated by a long series of “0” bits.
Alternatively, the bottle thus labeled can be packaged in the packaging of Example 1, and thus record the same information both in the packaging and in the label. There is therefore a link between the product and its packaging. .

EXAMPLE 3:

An aqueous dispersion of magnetic particles is produced as follows:
The barium ferrite powder is added with stirring to an aqueous solution of a surfactant, both wetting and dispersing, such as an ammonium salt of poly (acrylic acid) and optionally a grinding resin having good compatibility with the environment in which it will be incorporated later. The paste obtained is then treated in a ball mill to destroy the agglomerates and individualize the particles. The concentrate of individualized magnetic particles is then rediluted and stabilized against the sedimentation of the particles by adding a rheology-modifying agent, such as for example an aqueous gel of bentonites or of pyrogenic silicas.
The dispersion contains, by dry weight, 10 percent of magnetic particles.

• on réalise une feuille de polyoléfines de 400 µm,
• on applique sur la feuille par lame d'air, une composition en milieu aqueux comprenant :
  • 100 parts en poids sec d'un mélange de carbonate de calcium et de kaolin,
  • 100 parts en poids sec d'un liant styrène-butadiène carboxylé introduit sous forme d'une dispersion aqueuse stabilisée (latex),
  • 0,35 part en poids sec de particules magnétiques introduites sous forme de la dispersion des exemples précédents.

La quantité déposée est de 10 g/m² en poids sec.
On réalise un enregistrement d'informations comme à l'exemple 2.A packaging sheet is produced with a printing-writing and magnetic layer as follows:

• a 400 μm polyolefin sheet is produced,
• is applied to the sheet by air knife, a composition in an aqueous medium comprising:
  • 100 parts by dry weight of a mixture of calcium carbonate and kaolin,
  • 100 parts by dry weight of a carboxylated styrene-butadiene binder introduced in the form of a stabilized aqueous dispersion (latex),
  • 0.35 parts by dry weight of magnetic particles introduced in the form of the dispersion of the previous examples.

The quantity deposited is 10 g / m ² by dry weight.
An information recording is carried out as in Example 2.

EXAMPLE 4:

• Sur une feuille de polypropylène, on applique par couchage sérigraphique, un primer d'adhérence qui contient les particules magnétiques. Ce primer est à base d'un polymère styrène-acrylique en milieu aqueux. On a introduit 0,15 part de particules magnétiques sous forme de dispersion magnétique de l'exemple 3 pour 100 parts du primer en poids sec. On a déposé 10 g/m² en sec du primer contenant les particules.
• On applique une bande holographique transparente d'une épaisseur de 6 µm et qui comporte un adhésif thermoscellable, par la méthode connue du transfert à chaud et sous pression, sur le primer magnétique de la feuille de polypropylène.

A package is produced with a transparent holographic strip as follows:

• On a sheet of polypropylene, an adhesion primer containing the magnetic particles is applied by screen printing. This primer is based on a styrene-acrylic polymer in an aqueous medium. 0.15 part of magnetic particles was introduced in the form of a magnetic dispersion of Example 3 per 100 parts of the primer by dry weight. 10 g / m ² were deposited on a dry basis of the primer containing the particles.
• A transparent holographic strip with a thickness of 6 μm is applied, which comprises a heat-sealable adhesive, by the known method of transfer under heat and under pressure, on the magnetic primer of the polypropylene sheet.

The observation of the hologram is not affected by the presence of the magnetic layer.
Information recording is carried out as in Example 2 at the holographic strip level.
We re-read the recording without being bothered by the presence of the holographic tape.

The magnetic tests were carried out as follows on the samples:
Recording of magnetic data: for each sample, we first carry out an encoding of a 2F type signal (series of "1") and we measure the average amplitude of the signal. We then proceed to an encoding with a low density F / 2F signal (10 bits per inch, or approximately 10 bits for 2.54 cm) of the “1-1-0-1-0” type.
This recording is done using a conventional double-head inductive recording device (one for materials with low coercivity and the other for materials with high coercivity) having a writing air gap of 100 μm. . The writing width is 6.5mm and the recording speed is 200mm / s. The write current was selected at 250 mA in order to obtain an optimum signal.
The pressure forces exerted between the recording head and the samples and the head-sample distance were selected so as to have the best possible recording and a maximum amplitude of the signal during playback.

Reading magnetic data: the magnetic recording of the samples is read with a magnetoresistive read head.
This magnetoresistive read head has a sensitivity of around 10 mV per Gauss and the resolution of the sensor is 27 µG. The width of the magnetoresistive head is 3 mm. The head-sample distance is less than 200 µm. The intensity of the current in the magnetoresistor is set to 10 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.

Claims (31)

1. Security data medium making it possible to record and store static and dynamic data, characterized in that it comprises a substrate consisting of a plastic sheet and at least one zone comprising magnetic particles allowing the said data recording and storage, the said particles being invisible to a magnetic magnifier, and such that:

   the said magnetic particles are included in the thickness of the substrate or in a coating on the surface of the substrate,

   the said magnetic particles do not affect the appearance characteristics of the said zone in the absence of any masking of the said particles in order to make them invisible, and

   the said magnetic particles are distributed uniformly in the said zone and that the said particles comply with the following concentration characteristics, taken separately or in combination:

   a) the said magnetic particles are included in the thickness of the said substrate or in the said coating applied to the surface of the substrate, at a concentration less than or equal to 1% by dry weight of the said substrate in the said zone,

   b) the said particles are included in a coating applied to the surface of the said substrate and the amount of magnetic particles in the said coating (in the said zone) is less than or equal to 250 mg/m².
2. Data medium according to Claim 1, characterized in that it is a plastic sheet with a thickness of between 1 and 2 000 µm.
3. Data medium according to Claim 2, characterized in that it is a plastic sheet with a thickness of between 1 and 800 µm, preferably between 10 and 600 µm.
4. Data medium according to one of Claims 1 to 3, characterized in that the said magnetic particles are included in the said coating on the surface of the substrate, the said coating consisting of an adhesive.
5. Data medium according to one of Claims 1 to 4, characterized in that the said particles are included in a said coating on the surface of the substrate, the said coating consisting of a coating composition.
6. Medium according to one of Claims 1 to 5, characterized in that the said particles are included in a said coating on the surface of the said substrate, the said coating consisting of a varnish or an ink which can be applied by the printing techniques such as gravure printing, offset printing or screen printing.
7. Data medium according to one of Claims 1 to 6, characterized in that the said magnetic particles are included in a heat-sealing varnish applied to the surface of the substrate.
8. Data medium according to one of Claims 1 to 7, characterized in that the said medium is a plastic sheet intended for the manufacture of a label and in that the said magnetic particles are included in the thickness of the said substrate, or in a coating applied to the surface of the said substrate and/or in an adhesive applied to the surface of the said substrate.
9. Data medium according to one of Claims 1 to 7, characterized in that the said medium is a packaging sheet or a plastic sheet intended for the manufacture of a packaging sheet and in that the said magnetic particles are included in the thickness of the said substrate or in a coating applied to the surface of the said substrate.
10. Data medium according to one of Claims 1 to 10, characterized in that the said data medium is an integral part of the object relating to the static and dynamic data.
11. Data medium 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 layer constituting a hologram.
12. Data medium according to Claim 11, characterized in that the said hologram is a transparent hologram or a partly demetallized hologram.
13. Data medium according to one of Claims 1 to 12, characterized in that the magnetic particles are included in a zone comprising positive or negative inscriptions or patterns.
14. Data medium according to one of Claims 1 to 13, characterized in that the said zone covers the entire substrate.
15. Data medium according to one of Claims 1 to 14, characterized in that it comprises a succession of said zones comprising magnetic particles included in a coating on the surface of the said substrate, these said zones being separated by regions free of magnetic particles, this succession of said zones constituting a magnetic coding.
16. Data medium according to one of Claims 1 to 15, characterized in that the said zone comprises particles of coercivity greater than 32 × 10³ A/m, preferably than 135 × 10³ A/m, the said zone being of sufficient size to act as a medium for the magnetic recording of a code.
17. Data medium according to one of the preceding claims, characterized in that the said magnetic particles are included in the thickness of the substrate or in a coating applied on the surface of the substrate, at a concentration less than or equal to 0.1% by dry weight of the said substrate in the said zone.
18. Data medium according to the preceding claim, characterized in that the concentration of magnetic particles is from 0.001% to 0.1%, preferably 0.02 to 0.07%.
19. Data medium according to one of the preceding claims, characterized in that the said particles are included in a coating applied on the surface of the said substrate and in that the amount of magnetic particles in the said coating (in the said zone) is from 1 to 100 mg/m².
20. Data medium according to the preceding claim, characterized in that the amount of magnetic particles in the said coating in the said zone is from 5 mg/m² to 50 mg/m².
21. Data medium according to one of the preceding claims, characterized in that the size of the magnetic particles is less than 2 µm, preferably less than 1 µm.
22. Data medium according to the preceding claim, characterized in that the size of the magnetic particles is from 0.1 to 1 µm, preferably 0.1 to 0.5 µm.
23. Data medium according to one of the preceding claims, characterized in that the said substrate or the said coating on the surface of the substrate is transparent or translucid.
24. Data medium according to one of the preceding claims, characterized in that the substrate is of a light colour, especially a white, cream or pale yellow colour.
25. Data medium according to one of the preceding claims, characterized in that the zone of the said substrate or of a said coating comprising the said particles, has a luminosity L* according to the CIELAB system greater than 70 and preferably than 80.
26. Data medium according to either of Claims 24 and 25, characterized in that the zone of the said substrate or of a said coating comprising the said particles, has an ISO whiteness according to the ISO 2471 standard greater than or equal to 60% under a D65 illuminant without UV from an observation angle of 10°.
27. Data medium according to one of Claims 24 to 26, characterized in that the zone of the substrate comprising the said particles has a CIE whiteness according to the CIELAB formula of the substrate is greater than or equal to 20% under a D65 illuminant without UV from an observation angle of 10°.
28. Method of reading the data recorded and stored in a document according to one of Claims 1 to 27, characterized in that the reading is carried out using a reader provided with magnetoresistive sensors.
29. Method of manufacturing a security data medium according to one of Claims 1 to 28, characterized in that the said magnetic particles are incorporated in the thickness of the substrate or in a said coating on the surface of the substrate in the said zone.
30. Method of manufacturing a security data medium according to one of Claims 1 to 29, characterized in that a dispersion of the said magnetic particles is mixed with the material for manufacturing the said substrate or a said coating on the surface of the substrate.
31. Method of manufacturing a security data medium according to Claim 30, characterized in that the dispersion of magnetic particles comprises from 1 to 40% by dry weight of particles, preferably from 5 to 15%.