EP0815322A1 - Security paper with conductive fibres detectable by microwave radiation and method for making same - Google Patents

Security paper with conductive fibres detectable by microwave radiation and method for making same

Info

Publication number
EP0815322A1
EP0815322A1 EP96906824A EP96906824A EP0815322A1 EP 0815322 A1 EP0815322 A1 EP 0815322A1 EP 96906824 A EP96906824 A EP 96906824A EP 96906824 A EP96906824 A EP 96906824A EP 0815322 A1 EP0815322 A1 EP 0815322A1
Authority
EP
European Patent Office
Prior art keywords
paper according
fibers
paper
conductive fibers
coating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96906824A
Other languages
German (de)
French (fr)
Inventor
Yves Douesneau
Pierre Doublet
Isabelle Hélène THIEBLIN
Thierry Résidence Les Cèdres-de-Loire DUMERY
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ArjoWiggins SAS
Original Assignee
ArjoWiggins SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FR9502866A external-priority patent/FR2731721B1/en
Priority claimed from FR9506191A external-priority patent/FR2734584B1/en
Application filed by ArjoWiggins SAS filed Critical ArjoWiggins SAS
Publication of EP0815322A1 publication Critical patent/EP0815322A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H13/00—Pulp or paper, comprising synthetic cellulose or non-cellulose fibres or web-forming material
    • D21H13/36—Inorganic fibres or flakes
    • D21H13/46—Non-siliceous fibres, e.g. from metal oxides
    • D21H13/48—Metal or metallised fibres
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/40—Agents facilitating proof of genuineness or preventing fraudulent alteration, e.g. for security paper
    • D21H21/44—Latent security elements, i.e. detectable or becoming apparent only by use of special verification or tampering devices or methods
    • D21H21/48—Elements suited for physical verification, e.g. by irradiation

Definitions

  • Security paper incorporating conductive fibers detectable by microwave radiation and method of manufacturing such paper.
  • the present invention relates to a security paper comprising electrically conductive fibers, detectable by microwave radiation and a method of manufacturing such paper.
  • the invention relates to a security paper incorporating conductive fibers dispersed within the structure of the paper, the length of which is between 3 and 15 mm and the diameter is between 1 and 30 ⁇ m.
  • the presence of the conductive fibers in the paper makes it possible to identify the latter by reflection of microwave radiation emitted by an appropriate device.
  • Publication FR- ⁇ -2 425 937 discloses a process for manufacturing a security paper in which metal fibers are mixed with the mass of paper fibers before the sheets are formed.
  • the fibers closest to the surface of the paper are thus visible to the naked eye when the paper is light in color and they detract from the aesthetics, which can even blur the impression.
  • the fibers give the paper a mottled appearance that makes it look like recycled paper, which is widely available commercially and which counterfeiters can use to make fakes.
  • a method which consists of incorporating the metal fibers no longer into the mass of the paper fibers before the sheets are formed but by deposition between two jets of paper then assembled to form a sheet in which the fibers are confined at mid-thickness, therefore masked by paper fibers and invisible in reflected light.
  • a method requires the implementation of a relatively complex and expensive two-jet technology.
  • the object of the invention is in particular to propose a new paper overcoming the drawbacks of known papers incorporating dispersed conductive fibers.
  • the conductive fibers have a light color, close to that of paper.
  • the visibility of the fibers in reflected light is significantly reduced without the printability of the paper or its mechanical characteristics being significantly modified.
  • the conductive fibers comprise an electrically conductive core, preferably constituted by a metallic fiber, and an external masking sheath produced by depositing a layer of a coating conferring on the conductive fibers a color close to that of paper.
  • the conductive fibers can disperse homogeneously within a suspension of paper fibers despite their higher weight due to the nature of the heart.
  • the conductive fibers comprise a filler made of an electrically conductive material, incorporated in a synthetic material having a color close to that of paper and shaped into fiber.
  • said load is contained in at least one cavity extending longitudinally over the entire length of the fiber.
  • it consists of one or more filaments.
  • the conductive fibers are made of a naturally shiny metal and have a milky surface appearance.
  • the conductive fibers are made with non-magnetic materials so as not to hinder the reading of the magnetic inks sometimes used for printing security papers.
  • the conductive fibers used have a core consisting of a metallic fiber
  • the application of a masking coating on the metal can be carried out by various methods.
  • the metallic fibers used to constitute the core of the conductive fibers are immersed in a bath of a reagent in a first chemical state, comprising in suspension particles of a pigment or in solution molecules of a dye, and causing the reagent to pass into a second chemical state in which it constitutes a binder serving to fix the pigment particles or the dye molecules on the fibers.
  • said reagent is an amino polysaccharide hydrolyzed and a condensation reaction is carried out in contact with the fibers to fix particles of a pigment or molecules of a dye; in the case where the paper is white or slightly tinted, a pigment such as titanium dioxide is advantageously used.
  • the metal fibers intended to constitute the core of the conductive fibers are coated with a layer of a metal by electrolytic deposition, the metal thus deposited giving the fibers a color close to the color of the paper.
  • the metal used to coat the core of the conductive fibers is advantageously silver or aluminum which each present, after electrolytic deposition under appropriate operating conditions, a milky appearance.
  • the metal deposited on the core of the conductive fiber is the same as that constituting the core of the conductive fiber.
  • the metallic fibers intended to constitute the core of the conductive fibers are coated with a layer of an oxide or of a salt by electrolytic deposition, the presence of this oxide or of this salt giving the conductive fibers a color close to the color of the paper.
  • nickel sulphate is advantageously deposited.
  • the surface of the metallic fibers is oxidized, taking care that the presence of the oxide obtained gives the fibers a color close to that of paper.
  • FIG. 1 is a schematic perspective view of a sheet of paper incorporating dispersed conductive fibers
  • FIG. 2 shows in perspective a conductive fiber in accordance with a particular embodiment of the invention.
  • FIG. 1 a sheet of paper 1 produced by a conventional papermaking technique from a suspension of cellulose fibers, in which are dispersed electrically conductive fibers 2, detectable by microwave radiation.
  • the conductive fibers 2 have an electrically conductive core 3, covered by a layer 4 of a coating serving to mask the core in reflected light.
  • the core 3 is constituted in the example described by a stainless steel fiber.
  • the coating layer 4 has a light color close to that of the fibrous structure of the paper, white in the example described.
  • the core 3 has a length 1 of between 2 and 15 mm, preferably between 3 and 6 mm and a diameter d of between 0.5 and 29.5 ⁇ m, preferably between 5 and 12 ⁇ m, more preferably between 6 and 8 ⁇ m.
  • the core 3 of the conductive fibers 2 is constituted by metallic fibers having a length 1 equal to 5 mm and a diameter d equal to 6.5 ⁇ m.
  • the core 3 of the conductive fibers 2 is constituted by metallic fibers having a length of a few mm and a diameter ⁇ equal to 8 ⁇ m.
  • the thickness e of the coating layer 4 is preferably between 0.5 and 29.5 ⁇ m, advantageously between 3 and 10 ⁇ m and more preferably between 4 and 7 ⁇ m.
  • metallic fibers made of stainless steel obtained by wire drawing and cutting of metallic wires. These fibers are immersed in a bath of a hydroalcoholic solution of deacetylated chitin, also called chitosan, comprising in suspension fine particles of a pigment such as titanium dioxide, the size of which is less than one micron.
  • a hydroalcoholic solution of deacetylated chitin also called chitosan, comprising in suspension fine particles of a pigment such as titanium dioxide, the size of which is less than one micron.
  • the quantity of metallic fibers in suspension in the hydroalcoholic solution of chitosan is preferably chosen so that the ratio of the mass of chitin deposited on the fibers to the mass of metallic fibers is greater than 1%.
  • the concentration of chitosan does not exceed 0.1% in the hydroalcoholic solution, so that the concentration of metal fibers does not exceed 10%.
  • the pigment is added with an amount of the order of 1 to 2% relative to the weight of the metallic fibers.
  • a dispersant is added with the metallic fibers intended to avoid the formation of fiber agglomerates, in particular when the latter are magnetic.
  • This dispersant can exert a chemical or mechanical action on the metallic fibers.
  • the dispersant can consist of cellulose fibers.
  • the ratio of alcohol to water in the hydroalcoholic solution is 1/3.
  • the reacetylation reaction is carried out at a temperature between 15 and 25 ° C.
  • composition of the hydroalcoholic solution of chitosan is in the example described the following, for one liter:
  • the hydroalcoholic solution of chitosan is preferably left, after introduction of the metallic fibers, with stirring for two hours in the hydroalcoholic solution of chitosan to eliminate the air on the surface of the fibers.
  • the reacetylation solution is prepared as follows, for one liter:
  • the metal fibers serve as a crystallization nucleus and the deposit of chitin takes place on their surface with fixation of the pigment particles.
  • a coating thickness of 20 ⁇ m is a priori necessary to guarantee complete opacity when the coating consists of a deposit of particles of a pigment such as titanium dioxide, an unexpected observation has been made. significant reduction in the visibility of the core 3 from a deposit thickness equal to 1 ⁇ m, depending on the nature of the metal constituting the core 3 and its surface condition.
  • the conductive fibers are incorporated into a suspension of paper fibers according to the desired concentration. If necessary, the conductive fibers can be coated with a water-soluble binder as described in publication FR-A-2 425 937, to facilitate their dispersion.
  • the concentration of metallic fibers in the paper is preferably between 0.1 and 1% by mass, preferably between 0.3 and 0.7% and advantageously chosen equal to 0.5%, which corresponds roughly, for information, to a few thousand metallic fibers for a sheet of paper having the size of a bank note.
  • the conductive fibers 2 are typically detected by means of microwave radiation, with a frequency of the order of 24 GHz in the case of conductive fibers whose core is made of stainless steel.
  • the core 3 of the conductive fibers 2 from metals other than stainless steel or of non-metallic substances that conduct electricity, and to coat the core 3 with a masking layer formed by the deposition of particles of a pigment other than titanium dioxide fixed by a binder other than chitin.
  • a metallic core 3 has the advantage, compared to a non-metallic core, of generally offering better electrical conductivity for an equivalent diameter, and the conductive fibers 2 can then be thinner when they are made from metallic fiber ⁇ .
  • conductive fibers 2 constituted by a core of a metal coated with a sheath of synthetic material shaped as a fiber, such as a polyamide, a polyester, a polyurethane, or a mixture of these polymers.
  • Conductive fibers with a nylon sheath are sold by the company KANEBO under the name "White Belltron”. Conductive fibers whose core is made of copper, coated with a plastic sheath, are marketed by the company ALCATEL.
  • conductive fibers 2 comprising a core constituted by a metallic fiber, oxidized on the surface to give it a color close to that of paper.
  • conductive fibers 2 comprising a charge of an electrically conductive material, such as particles or filaments of a conductive material, incorporated in a synthetic material having a light color close to that of paper.
  • the conductive fibers can be dyed when the nature of the synthetic material and that of the filler allow.
  • a luminescent coating can be deposited on the core of the conductive fibers.
  • the invention is not limited to this example and conductive fibers may be used having a coating layer of non-thick uniform without departing from the scope of the invention.
  • the values relating to the thickness of the coating layer, mentioned above, should be understood as referring to an average thickness.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Paper (AREA)

Abstract

A security paper (1) has electically conductive fibres (2) dispersed within its structure, wherein said fibres can be detected by microwave radiation and are of a light colour, similar to that of the paper.

Description

Papier de sécurité incorporant des fibres conductrices détectables par rayonnement micro-ondes et procédé de fabrication d'un tel papier. Security paper incorporating conductive fibers detectable by microwave radiation and method of manufacturing such paper.
La présente invention concerne un papier de sécurité comportant des fibres conductrices de l'électricité, détectables par rayonnement micro-ondes et un procédé de fabrication d'un tel papier.The present invention relates to a security paper comprising electrically conductive fibers, detectable by microwave radiation and a method of manufacturing such paper.
Plus particulièrement, l'invention a trait à un papier de sécurité incorporant des fibres conductrices disperβées au sein de la structure du papier, dont la longueur est comprise entre 3 et 15 mm et le diamètre est compris entre 1 et 30 μm.More particularly, the invention relates to a security paper incorporating conductive fibers dispersed within the structure of the paper, the length of which is between 3 and 15 mm and the diameter is between 1 and 30 μm.
La présence des fibres conductrices dans le papier permet d'identifier ce dernier par réflexion d'un rayonnement micro-ondes émis par un dispositif approprié.The presence of the conductive fibers in the paper makes it possible to identify the latter by reflection of microwave radiation emitted by an appropriate device.
En intégrant ce dernier à un photocopieur couleur, on peut interdire par exemple la photocopie lorsque le document à photocopier est identifié comme étant un papier de sécurité.By integrating the latter into a color photocopier, it is possible, for example, to prohibit photocopying when the document to be photocopied is identified as being security paper.
On connaît par la publication FR-λ-2 425 937 un procédé de fabrication d'un papier de sécurité dans lequel on mélange des fibres métalliques à la masse des fibres papetières avant la formation des feuilles.Publication FR-λ-2 425 937 discloses a process for manufacturing a security paper in which metal fibers are mixed with the mass of paper fibers before the sheets are formed.
Dans les papiers connus du type précité, on utilise des fibres en acier inoxydable présentant une couleur sombre.In known papers of the aforementioned type, stainless steel fibers having a dark color are used.
Les fibres les plus proches de la surface du papier sont ainβi visibles à l'oeil nu lorsque le papier est de couleur claire et elles nuisent à l'esthétique, pouvant même brouiller l'impression.The fibers closest to the surface of the paper are thus visible to the naked eye when the paper is light in color and they detract from the aesthetics, which can even blur the impression.
En outre, les fibres donnent au papier un aspect chiné q i le font ressembler à du papier recyclé, largement disponible dans le commerce et que les contrefacteurs peuvent utiliser pour faire des faux.In addition, the fibers give the paper a mottled appearance that makes it look like recycled paper, which is widely available commercially and which counterfeiters can use to make fakes.
On a proposé un procédé consistant à incorporer les fibres métalliques non plus dans la masse des fibres papetières avant la formation des feuilles mais par dépôt entre deux jets de papier assemblés ensuite pour former une feuille dans laquelle les fibres sont confinéeβ à mi-épaisseur, donc masquées par les fibres papetières et invisibles en lumière réfléchie. Cependant, un tel procédé exige la mise en oeuvre d'une technologie a deux jets relativement complexe et coûteuse.A method has been proposed which consists of incorporating the metal fibers no longer into the mass of the paper fibers before the sheets are formed but by deposition between two jets of paper then assembled to form a sheet in which the fibers are confined at mid-thickness, therefore masked by paper fibers and invisible in reflected light. However, such a method requires the implementation of a relatively complex and expensive two-jet technology.
On a encore proposé d'enduire chaque face des feuilles de papier d'un revêtement opaque, destiné à masquer les fibres métalliques présentes à la surface du papier.It has also been proposed to coat each face of the paper sheets with an opaque coating, intended to mask the metallic fibers present on the surface of the paper.
Toutefois, l'imprimabilité et les caractéristiques mécaniques de la feuille de papier ainsi enduite sont modifiées notablement.However, the printability and mechanical characteristics of the sheet of paper thus coated are significantly modified.
L'invention a notamment pour objet de proposer un nouveau papier remédiant aux inconvénients des papiers connus incorporant des fibres conductrices dispersées.The object of the invention is in particular to propose a new paper overcoming the drawbacks of known papers incorporating dispersed conductive fibers.
Elle y parvient d'une manière générale par le fait que les fibres conductrices ont une couleur claire, proche de celle du papier.It achieves this in general by the fact that the conductive fibers have a light color, close to that of paper.
Ainsi, grâce à l'invention, la visibilité des fibres en lumière réfléchie est sensiblement diminuée sans que l'imprimabilité du papier ni ses caractéristiques mécaniques soient sensiblement modifiées.Thus, thanks to the invention, the visibility of the fibers in reflected light is significantly reduced without the printability of the paper or its mechanical characteristics being significantly modified.
Dans une réalisation particulière de l'invention, les fibres conductrices comportent un coeur conducteur de l'électricité, constitué de préférence par une fibre métallique, et une gaine externe de masquage réalisée par dépôt d'une couche d'un revêtement conférant aux fibres conductrices une couleur proche de celle du papier.In a particular embodiment of the invention, the conductive fibers comprise an electrically conductive core, preferably constituted by a metallic fiber, and an external masking sheath produced by depositing a layer of a coating conferring on the conductive fibers a color close to that of paper.
De façon assez inattendue, lorsque le coeur est constitué par une fibre métallique, les fibres conductrices peuvent se disperser de façon homogène au sein d'une suspension de fibres papetières malgré leur poids plus élevé dû à la nature du coeur.Quite unexpectedly, when the heart consists of a metallic fiber, the conductive fibers can disperse homogeneously within a suspension of paper fibers despite their higher weight due to the nature of the heart.
Dans une autre réalisation particulière de l'invention, les fibres conductrices comportent une charge en un matériau conducteur de l'électricité, incorporée dans une matière synthétique ayant une couleur proche de celle du papier et conformée en fibre.In another particular embodiment of the invention, the conductive fibers comprise a filler made of an electrically conductive material, incorporated in a synthetic material having a color close to that of paper and shaped into fiber.
Avantageusement, ladite charge est contenue dans au moins une cavité s'étendant longitudinalement sur toute la longueur de la fibre.Advantageously, said load is contained in at least one cavity extending longitudinally over the entire length of the fiber.
De préférence, elle est constituée par un ou plusieurs filaments.Preferably, it consists of one or more filaments.
Dans une autre réalisation particulière de l'invention, lorsque le papier est blanc ou faiblement teinté, les fibres conductrices sont constituées en un métal naturellement brillant et présentent un aspect de surface laiteux. Avantageusement, les fibres conductrices sont réalisées avec des matériaux non magnétiques pour ne pas gêner la lecture des encres magnétiques parfois utilisées pour l'impression des papiers de sécurité.In another particular embodiment of the invention, when the paper is white or slightly tinted, the conductive fibers are made of a naturally shiny metal and have a milky surface appearance. Advantageously, the conductive fibers are made with non-magnetic materials so as not to hinder the reading of the magnetic inks sometimes used for printing security papers.
Dans le cas où les fibres conductrices utilisées présentent un coeur constitué par une fibre métallique, l'application d'un revêtement de masquage sur le métal peut s'effectuer par divers procédés.In the case where the conductive fibers used have a core consisting of a metallic fiber, the application of a masking coating on the metal can be carried out by various methods.
Selon un premier procédé, on immerge les fibres métalliques servant à constituer le coeur des fibres conductrices dans un bain d'un réactif dans un premier état chimique, comportant en suspension des particules d'un pigment ou en solution des molécules d'un colorant, et on provoque le passage du réactif dans un deuxième état chimique dans lequel il constitue un liant servant à fixer les particules de pigment ou les molécules du colorant sur les fibres.According to a first method, the metallic fibers used to constitute the core of the conductive fibers are immersed in a bath of a reagent in a first chemical state, comprising in suspension particles of a pigment or in solution molecules of a dye, and causing the reagent to pass into a second chemical state in which it constitutes a binder serving to fix the pigment particles or the dye molecules on the fibers.
De préférence ledit réactif est un polysaccharide aminé hydrolyse et on réalise une réaction de condensation au contact des fibres pour fixer des particules d'un pigment ou des molécules d'un colorant; dans le cas où le papier est blanc ou faiblement teinté, on utilise avantageusement un pigment tel que du άioxyde de titane.Preferably said reagent is an amino polysaccharide hydrolyzed and a condensation reaction is carried out in contact with the fibers to fix particles of a pigment or molecules of a dye; in the case where the paper is white or slightly tinted, a pigment such as titanium dioxide is advantageously used.
Selon un autre procédé, on revêt les fibres métalliques destinées à constituer le coeur des fibres conductrices d'une couche d'un métal par dépôt électrolytique, le métal ainsi déposé conférant aux fibres une couleur proche de la couleur du papier.According to another method, the metal fibers intended to constitute the core of the conductive fibers are coated with a layer of a metal by electrolytic deposition, the metal thus deposited giving the fibers a color close to the color of the paper.
Dans le cas où le papier est blanc ou faiblement teinté, le métal servant à revêtir le coeur des fibres conductrices est avantageusement de l'argent ou de l'aluminium qui présentent chacun, après dépôt électrolytique dans des conditions opératoires appropriées, un aspect laiteux.In the case where the paper is white or weakly tinted, the metal used to coat the core of the conductive fibers is advantageously silver or aluminum which each present, after electrolytic deposition under appropriate operating conditions, a milky appearance.
Dans un mode particulier de mise en oeuvre de ce procédé, le métal déposé sur le coeur de la fibre conductrice est le même que celui constituant le coeur de la fibre conductrice.In a particular embodiment of this process, the metal deposited on the core of the conductive fiber is the same as that constituting the core of the conductive fiber.
Selon un autre procédé, on revêt les fibres métalliques destinées à constituer le coeur des fibres conductrices d'une couche d'un oxyde ou d'un sel par dépôt électrolytique, la présence de cet oxyde ou de ce sel conférant aux fibres conductrices une couleur proche de la couleur du papier. Dans le cas où le papier est blanc ou faiblement teinté, on dépose avantageusement du sulfate de nickel.According to another method, the metallic fibers intended to constitute the core of the conductive fibers are coated with a layer of an oxide or of a salt by electrolytic deposition, the presence of this oxide or of this salt giving the conductive fibers a color close to the color of the paper. In the case where the paper is white or slightly tinted, nickel sulphate is advantageously deposited.
Selon un autre procédé, on oxyde la surface des fibres métalliques en veillant à ce que la présence de l'oxyde obtenu confère aux fibres une couleur proche de celle du papier.According to another method, the surface of the metallic fibers is oxidized, taking care that the presence of the oxide obtained gives the fibers a color close to that of paper.
L'invention va être mieux comprise à la lecture de la description détaillée qui va suivre, d'un exemple de réalisation non limitatif de l'invention, et au vu du dessin annexé sur lequel :The invention will be better understood on reading the detailed description which follows, of a nonlimiting exemplary embodiment of the invention, and in view of the appended drawing in which:
- la figure 1 est une vue schématique en perspective d'une feuille de papier incorporant des fibres conductrices dispersées, etFIG. 1 is a schematic perspective view of a sheet of paper incorporating dispersed conductive fibers, and
- la figure 2 représente isolément en perspective une fibre conductrice conforme à un exemple particulier de réalisation de l'invention.- Figure 2 shows in perspective a conductive fiber in accordance with a particular embodiment of the invention.
On a représenté sur la figure 1 une feuille de papier 1 réalisée par une technique papetière classique à partir d'une suspension de fibres de cellulose, dans laquelle sont dispersées des fibres conductrices de l'électricité 2, détectables par rayonnement micro-ondes.There is shown in Figure 1 a sheet of paper 1 produced by a conventional papermaking technique from a suspension of cellulose fibers, in which are dispersed electrically conductive fibers 2, detectable by microwave radiation.
On a représenté isolément sur la figure 2 une fibre conductrice 2 conforme à un exemple particulier de réalisation de l'invention.Is shown in isolation in Figure 2 a conductive fiber 2 according to a particular embodiment of the invention.
Dans l'exemple considéré, les fibres conductrices 2 présentent un coeur 3 conducteur de l'électricité, recouvert par une couche 4 d'un revêtement servant à masquer le coeur en lumière réfléchie.In the example considered, the conductive fibers 2 have an electrically conductive core 3, covered by a layer 4 of a coating serving to mask the core in reflected light.
Le coeur 3 est constitué dans l'exemple décrit par une fibre en acier inoxydable.The core 3 is constituted in the example described by a stainless steel fiber.
La couche 4 de revêtement présente une couleur claire proche de celle de la structure fibreuse du papier, blanche dans l'exemple décrit.The coating layer 4 has a light color close to that of the fibrous structure of the paper, white in the example described.
Le coeur 3 présente une longueur 1 comprise entre 2 et 15 mm, de préférence entre 3 et 6 mm et un diamètre d compris entre 0,5 et 29,5 μm, de préférence entre 5 et 12 μm, de préférence encore entre 6 et 8 μm.The core 3 has a length 1 of between 2 and 15 mm, preferably between 3 and 6 mm and a diameter d of between 0.5 and 29.5 μm, preferably between 5 and 12 μm, more preferably between 6 and 8 μm.
Dans un premier mode de réalisation préféré de l'invention, le coeur 3 des fibres conductrices 2 est constitué par des fibres métalliques présentant une longueur 1 égale à 5 mm et un diamètre d égal à 6,5 μm. Dans un autre mode de réalisation préféré de l'invention, le coeur 3 des fibres conductrices 2 est constitué par des fibres métalliques présentant une longueur de quelques mm et un diamètre ά égal à 8 μm.In a first preferred embodiment of the invention, the core 3 of the conductive fibers 2 is constituted by metallic fibers having a length 1 equal to 5 mm and a diameter d equal to 6.5 μm. In another preferred embodiment of the invention, the core 3 of the conductive fibers 2 is constituted by metallic fibers having a length of a few mm and a diameter ά equal to 8 μm.
L'épaisseur e de la couche 4 de revêtement est de préférence comprise entre 0,5 et 29,5 μm, avantageusement entre 3 et 10 μm et de préférence encore entre 4 et 7 μm.The thickness e of the coating layer 4 is preferably between 0.5 and 29.5 μm, advantageously between 3 and 10 μm and more preferably between 4 and 7 μm.
Divers procédés peuvent être utilisés sans sortir du cadre de l'invention pour déposer la couche 4 de revêtement de masquage sur le coeur métallique 3.Various methods can be used without departing from the scope of the invention for depositing the layer 4 of masking coating on the metal core 3.
Dans un procédé préféré, on part de fibres métalliques en acier inoxydable obtenues par tréfilage et découpe de fils métalliques. Ces fibres sont immergées dans un bain d'une solution hydroalcoolique de chitine désacétylée, encore appelée chitosane, comportant en suspension de fines particules d'un pigment tel que le dioxyde de titane, dont la taille est inférieure au micron.In a preferred process, one starts with metallic fibers made of stainless steel obtained by wire drawing and cutting of metallic wires. These fibers are immersed in a bath of a hydroalcoholic solution of deacetylated chitin, also called chitosan, comprising in suspension fine particles of a pigment such as titanium dioxide, the size of which is less than one micron.
La condensation du chitosane par réacétylation permet la fixation des particules de pigment sur le métal.The condensation of chitosan by reacetylation allows the fixing of the pigment particles on the metal.
La quantité de fibres métalliques en suspension dans la solution hydroalcoolique de chitosane est de préférence choisie de sorte que le rapport de la masse de chitine déposée sur les fibres à la masse de fibres métalliques soit supérieur à 1%.The quantity of metallic fibers in suspension in the hydroalcoholic solution of chitosan is preferably chosen so that the ratio of the mass of chitin deposited on the fibers to the mass of metallic fibers is greater than 1%.
Il est préférable que la concentration en chitosane ne dépasse pas 0,1% dans la solution hydroalcoolique, de sorte que la concentration en fibres métalliques ne dépasse pas 10%.It is preferable that the concentration of chitosan does not exceed 0.1% in the hydroalcoholic solution, so that the concentration of metal fibers does not exceed 10%.
De préférence, le pigment est ajouté avec une quantité de l'ordre de 1 à 2 % par rapport au poids des fibres métalliques.Preferably, the pigment is added with an amount of the order of 1 to 2% relative to the weight of the metallic fibers.
De préférence, on ajoute avec les fibres métalliques un dispersant destiné à éviter la formation d'agglomérats de fibres, notamment lorsque ces dernières sont magnétiques.Preferably, a dispersant is added with the metallic fibers intended to avoid the formation of fiber agglomerates, in particular when the latter are magnetic.
Ce dispersant peut exercer une action chimique ou mécanique sur les fibres métalliques.This dispersant can exert a chemical or mechanical action on the metallic fibers.
En particulier, le dispersant peut être constitué par des fibres de cellulose.In particular, the dispersant can consist of cellulose fibers.
De préférence, le rapport de l'alcool à l'eau dans la solution hydroalcoolique est de 1/3. De préférence, la réaction de réacétylation s'effectue à une température comprise entre 15 et 25°C.Preferably, the ratio of alcohol to water in the hydroalcoholic solution is 1/3. Preferably, the reacetylation reaction is carried out at a temperature between 15 and 25 ° C.
A titre indicatif, la composition de la solution hydroalcoolique de chitosane est dans l'exemple décrit la suivante, pour un litre :As an indication, the composition of the hydroalcoholic solution of chitosan is in the example described the following, for one liter:
- 170 g d'isopropanol,- 170 g of isopropanol,
- 330 g d'eau,- 330 g of water,
- 0,5 g de chitosane,- 0.5 g of chitosan,
- 0,25 g d'acide acétique,- 0.25 g of acetic acid,
- particules de pigments selon l'épaisseur de revêtement souhaitée,- pigment particles according to the desired coating thickness,
- dispersant, l'ensemble étant filtré et mis sous agitation à la température de 20°c.- dispersant, the whole being filtered and stirred at a temperature of 20 ° C.
On laisse de préférence la solution hydroalcoolique de chitosane, après introduction des fibres métalliques, sous agitation pendant deux heures dans la solution hydroalcoolique de chitosane pour éliminer l'air à la surface des fibres.The hydroalcoholic solution of chitosan is preferably left, after introduction of the metallic fibers, with stirring for two hours in the hydroalcoholic solution of chitosan to eliminate the air on the surface of the fibers.
Dans l'exemple décrit, la solution de réacétylation est préparée comme suit, pour un litre :In the example described, the reacetylation solution is prepared as follows, for one liter:
- 2,5 g d'anhydride acétique,- 2.5 g of acetic anhydride,
- 15 ml de propylène glycol.- 15 ml of propylene glycol.
On veille à maintenir une agitation vigoureuse après mélange de la solution hydroalcoolique de chitosane et de la solution de réacéty1ation.Care is taken to maintain vigorous stirring after mixing the hydroalcoholic solution of chitosan and the reacylation solution.
Lors de la réaction d'acétylation conduisant à la chitine, les fibres métalliques servent de noyau de cristallisation et le dépôt de chitine se fait à leur surface avec fixation des particules de pigment.During the acetylation reaction leading to chitin, the metal fibers serve as a crystallization nucleus and the deposit of chitin takes place on their surface with fixation of the pigment particles.
Bien qu'en principe, il faille a priori une épaisseur de revêtement de 20 μm pour garantir une opacité complète lorsque le revêtement est constitué par un dépôt de particules d'un pigment tel que le dioxyde de titane, on a observé de manière inattendue une diminution sensible de la visibilité du coeur 3 à partir d'une épaisseur de dépôt égale à 1 μm, selon la nature du métal constituant le coeur 3 et de son état de surface.Although in principle, a coating thickness of 20 μm is a priori necessary to guarantee complete opacity when the coating consists of a deposit of particles of a pigment such as titanium dioxide, an unexpected observation has been made. significant reduction in the visibility of the core 3 from a deposit thickness equal to 1 μm, depending on the nature of the metal constituting the core 3 and its surface condition.
Après enrobage, les fibres conductrices sont incorporées à une suspension de fibres papetières selon la concentration souhaitée. On peut le cas échéant enrober les fibres conductrices d'un liant hydrosoluble tel que cela a été décrit dans la publication FR-A-2 425 937, pour faciliter leur dispersion.After coating, the conductive fibers are incorporated into a suspension of paper fibers according to the desired concentration. If necessary, the conductive fibers can be coated with a water-soluble binder as described in publication FR-A-2 425 937, to facilitate their dispersion.
On peut ajouter à la suspension obtenue tout adjuvant classiquement utilisé dans la fabrication des papiers.Any adjuvant conventionally used in the manufacture of papers can be added to the suspension obtained.
Dans le cas où l'on utilise des fibres conductrices ayant un coeur métallique, la concentration en fibres métalliques dans le papier est de préférence comprise entre 0,1 et 1% en masse, de préférence entre 0,3 et 0,7% et avantageusement choisie égale à 0,5%, ce qui correspond sensiblement, à titre indicatif, à quelques milliers de fibres métalliques pour une feuille de papier ayant la taille d'un billet de banque.In the case where conductive fibers having a metallic core are used, the concentration of metallic fibers in the paper is preferably between 0.1 and 1% by mass, preferably between 0.3 and 0.7% and advantageously chosen equal to 0.5%, which corresponds roughly, for information, to a few thousand metallic fibers for a sheet of paper having the size of a bank note.
Les fibres conductrices 2 sont typiquement détectées au moyen d'un rayonnement micro-ondes, de fréquence de l'ordre de 24 GHz dans le cas de fibres conductrices dont le coeur est en acier inoxydable.The conductive fibers 2 are typically detected by means of microwave radiation, with a frequency of the order of 24 GHz in the case of conductive fibers whose core is made of stainless steel.
Bien entendu, l'invention n'est pas limitée à l'exemple de réalisation qui vient d'être décrit.Of course, the invention is not limited to the embodiment which has just been described.
On peut notamment réaliser le coeur 3 des fibres conductrices 2 à partir de métaux autres que l'acier inoxydable ou de substances non métalliques conductrices de l'électricité et revêtir le coeur 3 d'une couche de masquage constituée par le dépôt de particules d'un pigment autre que le dioxyde de titane fixées par un liant autre que la chitine.It is in particular possible to produce the core 3 of the conductive fibers 2 from metals other than stainless steel or of non-metallic substances that conduct electricity, and to coat the core 3 with a masking layer formed by the deposition of particles of a pigment other than titanium dioxide fixed by a binder other than chitin.
L'utilisation d'un coeur 3 métallique présente l'avantage, par rapport à un coeur non métallique, d'offrir en général une meilleure conductivité électrique pour un diamètre équivalent, et les fibres conductrices 2 peuvent être alors plus fines lorsqu'elles sont réalisées à partir de fibreβ métalliques.The use of a metallic core 3 has the advantage, compared to a non-metallic core, of generally offering better electrical conductivity for an equivalent diameter, and the conductive fibers 2 can then be thinner when they are made from metallic fiberβ.
A titre de variante, on peut utiliser des fibres conductrices 2 constituées par un coeur d'un métal enrobé d'une gaine en matière synthétique conformée en fibre, telle qu'un polyamide, un polyester, un polyuréthane, ou un mélange de ces polymères.As a variant, it is possible to use conductive fibers 2 constituted by a core of a metal coated with a sheath of synthetic material shaped as a fiber, such as a polyamide, a polyester, a polyurethane, or a mixture of these polymers. .
Des fibres conductrices dont la gaine est en nylon sont commercialisées par la Société KANEBO sous la dénomination "White Belltron". Des fibres conductrices dont le coeur est en cuivre, revêtues d'une gaine en matière plastique, sont commercialisées par la Société ALCATEL.Conductive fibers with a nylon sheath are sold by the company KANEBO under the name "White Belltron". Conductive fibers whose core is made of copper, coated with a plastic sheath, are marketed by the company ALCATEL.
On peut encore utiliser des fibres conductrices 2 comportant un coeur constitué par une fibre métallique, oxydée en surface pour lui donner une couleur proche de celle du papier.It is also possible to use conductive fibers 2 comprising a core constituted by a metallic fiber, oxidized on the surface to give it a color close to that of paper.
On peut encore utiliser des fibres conductrices 2 comportant une charge en un matériau conducteur de l'électricité, telle que des particules ou des filaments d'une matière conductrice, incorporée dans une matière synthétique ayant une couleur claire proche de celle du papier.It is also possible to use conductive fibers 2 comprising a charge of an electrically conductive material, such as particles or filaments of a conductive material, incorporated in a synthetic material having a light color close to that of paper.
On peut le cas échéant teinter les fibres conductrices lorsque la nature de la matière synthétique et celle de la charge le permettent.If necessary, the conductive fibers can be dyed when the nature of the synthetic material and that of the filler allow.
On peut déposer sur le coeur des fibres conductrices un revêtement luminescent.A luminescent coating can be deposited on the core of the conductive fibers.
Bien que l'on ait représenté sur la figure 2 une couche 4 de revêtement d'épaisseur uniforme, l'invention n'est pas limitée à cet exemple et l'on peut utiliser des fibres conductrices présentant une couche de revêtement d'épaisseur non uniforme sans sortir du cadre de l'invention. Dans ce cas, les valeurs relatives à l'épaisseur de la couche de revêtement, mentionnées plus haut, doivent se comprendre comme se référant à une épaisseur moyenne. Although a coating layer 4 of uniform thickness has been shown in FIG. 2, the invention is not limited to this example and conductive fibers may be used having a coating layer of non-thick uniform without departing from the scope of the invention. In this case, the values relating to the thickness of the coating layer, mentioned above, should be understood as referring to an average thickness.

Claims

R E V E W D I C A T I O N S REVEWDICATIONS
1. Papier de sécurité (1) comportant des fibres conductrices de l'électricité (2) dispersées au sein de la structure du papier et détectables au moyen d'un rayonnement micro-ondes, caractérisé par le fait que lesdites fibres (2) ont une couleur claire proche de celle du papier.1. Security paper (1) comprising electrically conductive fibers (2) dispersed within the structure of the paper and detectable by means of microwave radiation, characterized in that said fibers (2) have a light color close to that of paper.
2. Papier selon la revendication 1, caractérisé par le fait que la longueur des fibres conductrices (2) est comprise entre 2 et 15 mm et de préférence entre 3 et 6 mm.2. Paper according to claim 1, characterized in that the length of the conductive fibers (2) is between 2 and 15 mm and preferably between 3 and 6 mm.
3. Papier de sécurité selon l'une des revendications 1 ou 2, caractérisé par le fait que les fibres conductrices (2) présentent un diamètre compris entre 1 et 30 μm.3. Security paper according to one of claims 1 or 2, characterized in that the conductive fibers (2) have a diameter between 1 and 30 microns.
4. Papier de sécurité selon l'une quelconque des revendications 1 à 3, caractérisé par le fait que lesdites fibres comportent un coeur (3) conducteur de l'électricité, recouvert par un revêtement (4) conférant aux fibres conductrices une couleur claire, proche de celle du papier.4. Security paper according to any one of claims 1 to 3, characterized in that the said fibers comprise a core (3) conductive of electricity, covered by a coating (4) giving the conductive fibers a light color, close to that of paper.
5. Papier selon la revendication 4, caractérisé par le fait que le diamètre du coeur (3) des fibres conductrices (2) est compris entre 0,5 et 29,5 μm, de préférence entre 5 et 12 μm et de préférence encore entre 6 et 8 μm.5. Paper according to claim 4, characterized in that the diameter of the core (3) of the conductive fibers (2) is between 0.5 and 29.5 μm, preferably between 5 and 12 μm and more preferably between 6 and 8 μm.
6. Papier selon l'une des revendications 4 et 5, caractérisé par le fait que le coeur (3) des fibres conductrices (2) est constitué par une fibre métallique dont le diamètre (d) est égal à 6,5 μm et la longueur égale à 5 mm.6. Paper according to one of claims 4 and 5, characterized in that the core (3) of the conductive fibers (2) is constituted by a metallic fiber whose diameter (d) is equal to 6.5 μm and the length equal to 5 mm.
7. Papier selon l'une des revendications 4 et 5, caractérisé par le fait que le coeur (3) des fibres conductrices (2) est constitué par une fibre métallique dont le diamètre est égal à 8 μm..7. Paper according to one of claims 4 and 5, characterized in that the core (3) of the conductive fibers (2) is constituted by a metallic fiber whose diameter is equal to 8 μm ..
8. Papier selon l'une quelconque des revendications 4 à 7, caractérisé par le fait que l'épaisseur (e) du revêtement (4) est comprise entre 0,5 et 29,5 μm, de préférence entre 3 et 10 μm et de préférence encore entre 4 et 7 μm.8. Paper according to any one of claims 4 to 7, characterized in that the thickness (e) of the coating (4) is between 0.5 and 29.5 μm, preferably between 3 and 10 μm and preferably still between 4 and 7 μm.
9. Papier selon l'une quelconque des revendications 4 à 8, caractérisé par le fait que le coeur (3) des fibres conductrices (2) est constitué par une fibre métallique et par le fait que la W0 96/28611 1 , n0_- PC / 6/09. Paper according to any one of claims 4 to 8, characterized in that the core (3) of the conductive fibers (2) is constituted by a metallic fiber and by the fact that the W0 96/28611 1, n 0_- PC / 6/0
proportion des fibres métalliques dans le papier eβt comprise entre 0,1 et 1 % en masse, de préférence entre 0,3 et 0,7 % et de préférence encore égale à 0,5 %.proportion of metallic fibers in eβt paper of between 0.1 and 1% by mass, preferably between 0.3 and 0.7% and more preferably equal to 0.5%.
10. Papier selon l'une quelconque des revendications 4 à 9, caractérisé par le fait que ledit revêtement (4) est constitué par un dépôt de particules d'un pigment, liées par un liant.10. Paper according to any one of claims 4 to 9, characterized in that said coating (4) consists of a deposit of particles of a pigment, linked by a binder.
11. Papier selon l'une quelconque des revendications 4 à 9, caractérisé par le fait que ledit revêtement (4) est constitué par une gaine d'une matière synthétique telle qu'un polyamide, un polyester, un polyurethane ou un mélange de ces polymères.11. Paper according to any one of claims 4 to 9, characterized in that said coating (4) consists of a sheath of a synthetic material such as a polyamide, a polyester, a polyurethane or a mixture of these polymers.
12. Papier selon l'une quelconque des revendications 4 à 9, caractérisé par le fait que ledit revêtement (4) eβt consituté par un dépôt électrolytique d'un métal.12. Paper according to any one of claims 4 to 9, characterized in that the said coating (4) is formed by an electrolytic deposition of a metal.
13. Papier selon la revendication 12, caractérisé par le fait que ledit dépôt électrolytique est un dépôt d'argent ou d'aluminium, qui présentent chacun après dépôt électrolytique un aspect laiteux.13. Paper according to claim 12, characterized in that said electrolytic deposit is a deposit of silver or aluminum, which each present after electrolytic deposition a milky appearance.
14. Papier selon l'une quelconque des revendication 4 à 9, caractérisé par le fait que ledit revêtement (4) est réalisé par oxydation.14. Paper according to any one of claims 4 to 9, characterized in that said coating (4) is produced by oxidation.
15. Papier selon l'une quelconque des revendications 4 à 9, caractérisé par le fait que ledit revêment (4) est réalisé par dépôt électrolytique d'un oxyde ou d'un sel.15. Paper according to any one of claims 4 to 9, characterized in that said coating (4) is produced by electrolytic deposition of an oxide or a salt.
16. Papier selon la revendiction 15, caractérisé par le fait que ledit sel est du sulfate de nickel.16. Paper according to claim 15, characterized in that said salt is nickel sulfate.
17. Papier de sécurité selon l'une quelconque des revendications 1 à 3, caractérisé par le fait que lesdites fibres conductrices comportent une charge en un matériau conducteur de l'électricité, incorporée dans une matière synthétique ayant une couleur proche de celle du papier et conformée en fibre.17. Security paper according to any one of claims 1 to 3, characterized in that the said conductive fibers comprise a filler in an electrically conductive material, incorporated in a synthetic material having a color close to that of the paper and shaped in fiber.
18. Papier selon la revendication 17, caractérisé par le fait que ladite charge est contenue dans au moins une cavité s'étendant longitudinalement sur toute la longueur de la fibre.18. Paper according to claim 17, characterized in that said filler is contained in at least one cavity extending longitudinally over the entire length of the fiber.
19. Papier selon la revendication 18, caractérisé par le fait que ladite charge est constituée par au moins un filament.19. Paper according to claim 18, characterized in that said filler consists of at least one filament.
20. Papier selon l'une quelconque des revendications précédentes, caractérisé par le fait que les fibres conductrices (2) sont non magnétiques. 20. Paper according to any one of the preceding claims, characterized in that the conductive fibers (2) are non-magnetic.
21. Papier selon la revendication 4, caractérisé par le fait que ledit revêtement est luminescent.21. Paper according to claim 4, characterized in that said coating is luminescent.
22. Procédé de fabrication d'un papier de sécurité tel que défini dans l'une quelconque des revendications 1 à 10, caractérisé par le fait qu'il comprend l'étape consistant à immerger des fibres métalliques constituant le coeur (3) des fibres conductrices (2) dans un bain d'un réactif dans un premier état chimique, comportant en βuspension des particules d'un pigment ou des molécules d'un colorant en solution, et à provoquer le passage du réactif dans un deuxième état chimique dans lequel il forme un liant servant à fixer les particules de pigment ou les molécules de colorant sur les fibres.22. Method for manufacturing a security paper as defined in any one of claims 1 to 10, characterized in that it comprises the step consisting in immersing metallic fibers constituting the core (3) of the fibers conductive (2) in a bath of a reagent in a first chemical state, comprising in βuspension particles of a pigment or molecules of a dye in solution, and to cause the passage of the reagent in a second chemical state in which it forms a binder used to fix the pigment particles or dye molecules on the fibers.
23. Procédé selon la revendication 22, caractérisé par le fait que ledit réactif est un polyβaccharide aminé sous forme hydrolysée dans ledit premier état chimique et sous forme condensée dans ledit deuxième état chimique.23. The method of claim 22, characterized in that said reagent is an amino polyβaccharide in hydrolyzed form in said first chemical state and in condensed form in said second chemical state.
24. Procédé selon la revendication 23, caractérisé par le fait que ledit réactif est du chitosane dans ledit premier état chimique et de la chitine dans le deuxième état chimique. 24. The method of claim 23, characterized in that said reagent is chitosan in said first chemical state and chitin in the second chemical state.
EP96906824A 1995-03-13 1996-03-13 Security paper with conductive fibres detectable by microwave radiation and method for making same Withdrawn EP0815322A1 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
FR9502866A FR2731721B1 (en) 1995-03-13 1995-03-13 PAPER CONTAINING SECURITY ELEMENTS WITH DETECTABLE PHYSICAL PROPERTIES AND ELEMENTS FOR THE MANUFACTURE OF SUCH PAPER
FR9502866 1995-03-13
FR9506191 1995-05-24
FR9506191A FR2734584B1 (en) 1995-05-24 1995-05-24 PAPER CONTAINING METALLIC AND NON-MAGNETIC SECURITY ELEMENTS
PCT/FR1996/000390 WO1996028611A1 (en) 1995-03-13 1996-03-13 Security paper with conductive fibres detectable by microwave radiation and method for making same

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EP0815322A1 true EP0815322A1 (en) 1998-01-07

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Publication number Priority date Publication date Assignee Title
AU7150196A (en) * 1996-09-23 1998-04-14 Petrik, Victor Ivanovich Method and system for protection against counterfeiting of titles and documents
US6598793B1 (en) 1996-12-12 2003-07-29 N.V. Bekaert S.A. Article recognition and verification
US5992741A (en) * 1996-12-12 1999-11-30 Robertson; Paul Andrew Magnetic detection of security articles
GB2531584B (en) * 2014-10-23 2019-07-10 Portals De La Rue Ltd Improvements in security papers and documents

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GB500151A (en) * 1938-04-07 1939-02-03 Samuel Saul Himmell Improvements in coated paper
AT362658B (en) * 1978-03-15 1981-06-10 Oesterr Nationalbank PAPER, METHOD FOR TESTING PAPERS AND DEVICE FOR CARRYING OUT THE TEST METHOD
FR2425937A1 (en) * 1978-05-17 1979-12-14 Arjomari Prioux FIBROUS STRUCTURE CONTAINING METAL FIBERS, ITS PREPARATION PROCESS, AND ITS APPLICATION ESPECIALLY IN THE PAPER INDUSTRY
CA1285358C (en) * 1987-01-30 1991-07-02 Yasuhiro Ogawa Conductive composite filaments and fibrous articles containing the same
US4941687A (en) * 1989-11-09 1990-07-17 Crane & Co. Security paper for currency and bank notes
GB9024910D0 (en) * 1990-11-16 1991-01-02 Zorab J L Metal coated fibres

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