EP0997918A1 - Herstellung einer Magnetschicht - Google Patents

Herstellung einer Magnetschicht Download PDF

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Publication number
EP0997918A1
EP0997918A1 EP99201371A EP99201371A EP0997918A1 EP 0997918 A1 EP0997918 A1 EP 0997918A1 EP 99201371 A EP99201371 A EP 99201371A EP 99201371 A EP99201371 A EP 99201371A EP 0997918 A1 EP0997918 A1 EP 0997918A1
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EP
European Patent Office
Prior art keywords
support
ions
magnetic layer
soft magnetic
process according
Prior art date
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EP99201371A
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English (en)
French (fr)
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EP0997918B1 (de
Inventor
Hieronymus Andriessen
Steven Lezy
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Agfa Gevaert NV
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Agfa Gevaert NV
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Priority to EP19990201371 priority Critical patent/EP0997918B1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/0027—Thick magnetic films
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H01F41/16—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates the magnetic material being applied in the form of particles, e.g. by serigraphy, to form thick magnetic films or precursors therefor

Definitions

  • the present invention relates to the preparation of particular types of magnetic layers and to their use in an anti-theft system.
  • H a ferromagnetic sample that is initially demagnetized
  • B a particular flux density
  • the value of H is decreased again the decreasing flux density does not follow the path of increase but decreases at a rate less than that at which it rose.
  • H has reached zero again the value of B is not reduced to zero but to a value called the retentivity or remanence.
  • the sample has retained a permanent magnetization.
  • the value of B may be reduced to zero by reversing th magnetic field to negative and increasing its value to the so-called coercive force or coercivity.
  • H By further increasing H to negative values and then again reversing its direction a hysteresis loop as represented in fig. 1 is completed.
  • a so-called soft ferromagnetic material shows a rather low coercive force ; a so-called semi-soft ferromagnetic material shows a rather high coercive force.
  • This properties are used in a special type of anti-theft labels, e.g. for preventing the theft from clothes out of shops, called EM-EAS labels ( E lectro M agnetic E lectronic A rticle S urveillance).
  • the principle works as follows.
  • a label carrier is covered on one side with a soft magnetic layer having a coercive force of about 0.5 Oe, and on the other side with a semi-soft magnetic layer having a coercive force of about 100 Oe.
  • the detection zone consists of a transmitter which transmits an alternating magnetic field with a force Z M positioned between 0.5 and 100 Oe, and of a receiver.
  • the semi-soft magnetic layer consists of a nickel mesh
  • the soft magnetic layer consists of a complex alloy of Ni a Fe b Co c (Mo) d B e .
  • the problem with these magnetic layers is the fact that they are nowadays applied by means of sputtering in vacuo, a cumbersome and expensive technique.
  • aqueous solution of nickel(II) ions is prepared.
  • a most suitable salt is Ni(NO 3 ) 2 .6H 2 O.
  • the solution is acidified with a small amount of nitric acid.
  • the nickel ions in the solution are reduced to highly dispersed metallic nickel particles of nanosize by means of the addition of a reducing agent.
  • a preferred reducing agent is KBH 4 .
  • the reducing agent can be added to the original nickel salt solution as a solid powder. More preferably, the reducing agent may be dissolved separately in a second aqueous medium and added to the nickel salt solution according to a single jet or a double jet procedure. Preferably, according to the double jet principle, the aqueous medium containing the nickel ions and the second solution containing the reducing agent are added together to a third aqueous medium.
  • the second aqueous solution comprising the reducing agent preferably also contains sulphite ions which strongly enhance the chemical stability of this solution.
  • a protective binder is preferably added to one or more of the three aqueous solutions involved.
  • this protective binder is added to the third aqueous medium wherein both others are jetted.
  • a particularly preferred protective binder is carboxymethylcellulose (CMC).
  • CMC carboxymethylcellulose
  • Other possible binders include gelatin, arabic gum, poly(acrylic acid), cellulose derivatives and other polysaccharides.
  • a complexing agent is present in one of the three aqueous media described above.
  • a preferred complexant is simply the well-known ethylenediaminetetraacetic acid (EDTA) or a homologous compound or a salt thereof.
  • EDTA ethylenediaminetetraacetic acid
  • Another preferred one is citrate, e.g. triammonium citrate.
  • Suitable complexants include diethylenetriamine-pentaacetic acid (DTPA), trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA), ethyleneglycol-O,O'-bis(2-aminoethyl)-N,N,N',N'-tetraacetic acid (EGTA), N-(2-hydroxyethyl)ethylenediamine-N,N,N'-triacetic acid (HEDTA), etc.
  • the complexing agent is preferably present in the third aqueous medium to which the other solutions are added according to the double jet principle.
  • the superfluous salts are first removed from the aqueous medium by a washing process, preferably involving ultrafiltration and/or diafiltration. Additionally or alternatively centrifugation can be used.
  • a so-called dispersing aid can be present.
  • this compound is added to the diafiltration liquid at the last stage of the preparation.
  • Suitable dispersing aids in the case of nickel are phosphates, more particularly a hexametaphosphate such as sodium hexametaphosphate.
  • the hexametaphosphate adsorbs to the surface of the alloy particles so that they become negatively charged. By electrostatic repulsion they are kept in dispersion.
  • the phosphate inhibits further oxidation of the surface of the formed nanoparticles.
  • the thin nickel oxide shell that will be formed inevitably around the nanoparticles since the reducing medium disappears during the washing step will be passivated by the hexametaphosphate.
  • the nickel particles are ultrafiltrated e.g. through a Fresenius F60 cartridge and subsequently diafiltrated against a solution of sodium hexametaphosphate in water/ethanol (98.5/1.5).
  • the hexametaphosphate is also preferably added to the third aqueous solution.
  • the obtained final colloidal composition is coated on the substrate by means of a conventional coating technique, such as slide hopper, curtain coating and air-knife coating.
  • a conventional coating technique such as slide hopper, curtain coating and air-knife coating.
  • Suitable coating agents include non-ionic agents such as saponins, alkylene oxides e.g. polyethylene glycol, polyethylene glycol/polypropylen glycol condensation products, polyethylene glycol alkyl esters or polyethylene glycol alkylaryl esters, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycol alkylamines or alkylamides, silicone-polyethylene oxide adducts, glycidol derivaties, fatty acid esters of polyhydric alcohols and alkyl esters of saccharides; anionic agenst comprising an acid group such as a carboxy, sulpho, phospho, sulphuric or phosphoric ester group; ampholytic agents such as aminoacids, aminoalkyl sulphonic acids, aminoalkyl sulphates or phosphates, alkyl betaines, and amine-N-oxides; and cationic agents such as aklylamine salt
  • Useful transparent organic resin supports include e.g. cellulose nitrate film, cellulose acetate film, polyvinylacetal film, polystyrene film, polyethylene terephthalate film, polycarbonate film, polyvinylchloride film or poly- ⁇ -olefin films such as polyethylene or polypropylene film.
  • the thickness of such organic resin film is preferably comprised between 0.05 and 0.35 mm.
  • the support is a polyethylene terephthalate layer provided with a subbing layer. This subbing layer can be applied before or after stretching of the polyester film support.
  • the polyester film support is preferably biaxially stretched at an elevated temperature of e.g.
  • the stretching may be accomplished in two stages, transversal and longitudinal in either order or simultaneously.
  • the subbing layer when present, is preferably applied by aqueous coating between the longitudinal and transversal stretch, in a thickness of 0.1 to 5 mm.
  • the subbing layer preferably contains, as described in EP 0 464 906, a homopolymer or copolymer of a monomer comprising covalently bound chlorine. Examples of said homopolymers or copolymers suitable for use in the subbing layer are e.g.
  • polyvinyl chloride polyvinylidene chloride; a copolymer of vinylidene chloride, an acrylic ester and itaconic acid; a copolymer of vinyl chloride and vinylidene chloride; a copolymer of vinyl chloride and vinyl acetate; a copolymer of butylacrylate, vinyl acetate and vinyl chloride or vinylidene chloride; a copolymer of vinyl chloride, vinylidene chloride and itaconic acid; a copolymer of vinyl chloride, vinyl acetate and vinyl alcohol, etc.
  • Polymers that are water dispersable are preferred since they allow aqueous coating of the subbing layer which is ecologically advantageous.
  • the support may be opaque, such as a paper support, e.g. a plain paper support or a polyolefin coated paper. Furtheron glass, e.g. thin glass packed on roll can be used.
  • the coated substantially pure nickel layer is ferromagnetic of the so-called semi-soft type.
  • the nickel ions are not the sole ion type undergoing reduction but they are mixed with one or more other types of ions.
  • Preferred types of salts for admixture with the nickel salt are iron salts, cobalt salts or molybdene salts, or mixtures of those.
  • soft magnetic layers By choosing the appropriate type(s) of ions and the appropriate admixture ratio(s) so-called soft magnetic layers can be prepared.
  • a support preferably a paper support
  • a semi-soft magnetic layer based on substantially pure nickel prepared according to the present invention
  • a soft magnetic layer based on an admixture of nickel particles with other metal particles prepared according to the present invention.
  • the resulting labels can be used in a EM-EAS system ( E lectro M agnetic E lectronic A rticle S urveillance). Furtheron, such a label can also be produced when a semi-soft magnetic layer prepared according to the present invention is applied to a commercially available soft magnetic layer on a support.
  • PERMALLOY (trade mark of Western Electric), METGLAS (trade mark of Allied Signal Co.), and ATALANTE (trade mark of IST/Bekaert).
  • Particularly useful METGLAS products are type 2705M, consisting of Co 69 Fe 4 Ni 1 B 12 Si 12 , and type 2826MB, consisting of Fe 40 Ni 38 Mo 4 B 12 .
  • such a label can also be produced when a soft magnetic layer prepared according to the present invention is applied to a commercially available semi-soft magnetic layer on a support.
  • Examples of such commercial products are VICALLOY (trade mark of Telecon Metals Ltd.), AMOKROME (trade mark of Arnold Engineering), and CROVAK (trade mark of Vacuumschmelze GmbH).
  • the Ni-Fe-dispersion was prepared as follows:
  • solution 1 at a flow rate of 12.4 ml/min was simultaneously added with solution 2 at 12.4 ml /min.
  • the NiFe dispersion was ultrafiltrated through a Fresenius F60 cartridge and diafiltrated with a 0.36 % solution of sodium hexametaphosphate in water/ethanol (98.5/1.5).
  • the dispersion was stirred and 10 ml of a 12.5% solution of Saponine Quillaya (Schmittmann) in water/ethanol (80/20) was added. This is the Ni-Fe dispersion.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Soft Magnetic Materials (AREA)
EP19990201371 1998-10-26 1999-04-29 Herstellung einer Magnetschicht Expired - Lifetime EP0997918B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP19990201371 EP0997918B1 (de) 1998-10-26 1999-04-29 Herstellung einer Magnetschicht

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP98203868 1998-10-26
EP98203868 1998-10-26
EP19990201371 EP0997918B1 (de) 1998-10-26 1999-04-29 Herstellung einer Magnetschicht

Publications (2)

Publication Number Publication Date
EP0997918A1 true EP0997918A1 (de) 2000-05-03
EP0997918B1 EP0997918B1 (de) 2004-07-14

Family

ID=26150879

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19990201371 Expired - Lifetime EP0997918B1 (de) 1998-10-26 1999-04-29 Herstellung einer Magnetschicht

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5767156A (en) * 1980-10-13 1982-04-23 Nec Corp Electroless plating bath
JPS583963A (ja) * 1981-06-29 1983-01-10 Nec Corp 無電解めつき方法
JPH02108221A (ja) * 1988-10-18 1990-04-20 Mitsubishi Kasei Corp 磁気記録媒体
EP0793242A1 (de) * 1996-02-28 1997-09-03 Unitika Ltd. Magnetisches Element und dessen Herstellungsverfahren

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5767156A (en) * 1980-10-13 1982-04-23 Nec Corp Electroless plating bath
JPS583963A (ja) * 1981-06-29 1983-01-10 Nec Corp 無電解めつき方法
JPH02108221A (ja) * 1988-10-18 1990-04-20 Mitsubishi Kasei Corp 磁気記録媒体
EP0793242A1 (de) * 1996-02-28 1997-09-03 Unitika Ltd. Magnetisches Element und dessen Herstellungsverfahren

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 006, no. 143 (C - 117) 3 August 1982 (1982-08-03) *
PATENT ABSTRACTS OF JAPAN vol. 007, no. 069 (C - 158) 23 March 1983 (1983-03-23) *
PATENT ABSTRACTS OF JAPAN vol. 014, no. 325 (P - 1075) 12 July 1990 (1990-07-12) *

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EP0997918B1 (de) 2004-07-14

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