[go: up one dir, main page]

EP2427859A2 - Procédé de codage de produits - Google Patents

Procédé de codage de produits

Info

Publication number
EP2427859A2
EP2427859A2 EP10719248A EP10719248A EP2427859A2 EP 2427859 A2 EP2427859 A2 EP 2427859A2 EP 10719248 A EP10719248 A EP 10719248A EP 10719248 A EP10719248 A EP 10719248A EP 2427859 A2 EP2427859 A2 EP 2427859A2
Authority
EP
European Patent Office
Prior art keywords
magnetic
particle size
nanoparticles
magnetic nanoparticles
nominal particle
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Withdrawn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
EP10719248A
Other languages
German (de)
English (en)
Inventor
Johann Dietz
Karl Holschuh
Johann Bauer
Sylke Klein
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.)
Merck Patent GmbH
Original Assignee
Merck Patent GmbH
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
Application filed by Merck Patent GmbH filed Critical Merck Patent GmbH
Publication of EP2427859A2 publication Critical patent/EP2427859A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/06187—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code with magnetically detectable marking
    • G06K19/06196—Constructional details

Definitions

  • the present invention relates to a method of encoding products by means of a magnetic composition containing magnetic nanoparticles and a product having such a coding.
  • a hard magnetic acicular material of small size and low concentration is used in a transparent magnetic layer to make opaque indices contained in an underlying layer visible allow.
  • the magnetic layer can be used, for example, for recording magnetic information.
  • the magnetic particles must have a coercive force sufficient for such recording.
  • the size and concentration of the magnetic particles should be so low that a certain transparency of the magnetic layer is given, but play no role as measures for the formation of a code.
  • Marker substance is detected.
  • the magnetic signature of the marker substance is recorded in the form of a curve and the shape and position of this curve are compared with the shape and position of a previously stored magnetic signature in order to verify the authenticity of the product when the curves are identical. Preference is given to using superparamagnetic marker substances.
  • the signatures are described as unique and non-adaptable, even if marker substances of the same chemical composition are used. For this reason, the method is particularly suitable for the identification of valuable individual art objects and is not suitable for use in mass products, such as banknotes.
  • EP 1 646 057 describes a security document which contains superparamagnetic particles whose AC susceptibility is measured at different temperatures and possibly different frequencies as parameters to be detected.
  • the security document For writing and reading the stored data, the security document must be cooled to temperatures below the corresponding blocking temperature (temperature above which the magnetic particles are superparamagnetic).
  • both the material used and its blocking temperature must be known in advance. Since the magnetic nanoparticles used are embedded in the matrix of an ion exchange resin Homogeneous distribution of nanoparticles on the surface of the security document is not guaranteed. However, pigment clusters of this kind regularly lead to a very dark appearance of the magnetic security feature, since the materials used essentially have a dark brown to black intrinsic color. However, such magnetic security features are obviously visible and no longer classified as covert security features.
  • a further object of the invention was to provide a coded product which contains an individualized, concealed magnetic code based on magnetic nanoparticles, which is relatively easy to reproduce in the production and in which
  • the object of the invention was to provide a magnetic composition by means of which the method described above can be carried out and the product described above can be prepared in a simple manner.
  • the object of the invention is achieved by a method for coding products, in which a magnetic composition containing magnetic nanoparticles, applied to at least a predetermined area unit of the surface of a product and - A -
  • the magnetic composition monodisperse isotropic magnetic nanoparticles having at least a predetermined nominal particle size, with a predetermined concentration in homogeneous distribution, and wherein a code of the nominal particle size and / or from the concentration of the magnetic Nanoparticles in the magnetic composition is formed.
  • the object of the invention is also achieved by a product which contains on its surface a magnetic code, wherein a dried and / or cured magnetic composition containing magnetic nanoparticles is located on at least one predetermined unit area of the surface of the product and in the magnetic Composition monodisperse isotropic magnetic nanoparticles of at least a predetermined nominal particle size with a predetermined concentration in a homogeneous distribution and wherein the code of the nominal particle size and / or from the concentration of the magnetic nanoparticles in the magnetic composition is formed.
  • the object of the invention is achieved by a magnetic composition for carrying out the method described above and for producing the product described above, in which monodisperse isotropic magnetic nanoparticles having at least one predetermined nominal particle size are present in at least one binder in homogeneous distribution, and optionally at least one solvent and / or optionally at least one excipient is contained.
  • Magnetic nanoparticles are considered to be monodisperse for the purposes of the present invention if they have matching particle features such as size, shape and density. Nanoparticles are also included. closed, whose actual (measurable) particle size deviates by ⁇ 10% from a predetermined nominal particle size.
  • the actual particle size can be determined by means of methods known per se. The simplest method for determining the average particle size
  • the particle size is the direct observation and measurement of the longest diameter of the particles under microscopes such as the atomic force microscope (AFM) or the high-resolution electron microscope (HRTEM) with corresponding image evaluation software. This is the salt-free
  • PCS dynamic laser light scattering
  • SAXS small angle X-ray scattering
  • XRD X-ray diffraction
  • BET surface measurements
  • the particles pass a focused laser beam and scatter the light at an angle that is inversely proportional to the particle size.
  • the hydrodynamic particle size is calculated from the scattering intensity of the scattered light at a fixed angle according to the Mie model (plane wave meets z-direction on a spherical spreader).
  • SAXS high-energy X-rays
  • XRD X-ray diffraction patterns
  • Particles can be drawn with an appropriate particle model conclusions about the actual particle diameter.
  • a deliberately predetermined particle size is considered, which is to serve as a characteristic for the code to be generated.
  • this nominal particle size is in the range from 10 to 100 nm.
  • a nominal particle size for example 15 nm, 20 nm, 40 nm, etc.
  • Particle size range nominal particle size ⁇ 10%.
  • any nominal particle size ranging from 10 to 100 nm may be selected, not just the aforementioned values.
  • magnetic nanoparticles according to the invention can also be used in a mixture for coding, which are selected from two or more nominal particle sizes.
  • Care must be taken to ensure that the nominal particle sizes are selected far enough apart that the magnetic nanoparticles assigned to a given nominal particle size, because they fall within their particle size range, do not coincide with the particle size range of another, simultaneously
  • the magnetic nanoparticles used according to the invention are isotropic, i. they have the same properties in all directions. This also means that they have no preferred axis in any direction, ie in particular are not acicular particles, which are otherwise very often used for magnetic markings / records.
  • the magnetic nanoparticles used according to the invention have no specific shape, but are granules of indefinite shape or more or less deformed spherical particles or particles with cubic symmetry.
  • the density of the magnetic nanoparticles is determined by the material used.
  • the material composition of the nano-single particles is uniform, i. E. that the individual particles are composed throughout of the same material.
  • the magnetic nanoparticles used are particles whose largest body axis (particle size) has a length in the range from 10 to 100 nm.
  • particle size the largest body axis
  • the determination of the individual particle size of the nano-single particles can with the previously described methods. However, other common size determination methods may be used.
  • the magnetic nanoparticles are used in the inventive method in a magnetic composition in a homogeneous distribution.
  • the magnetic nano-single particles are uniformly distributed in the magnetic composition.
  • larger scale pigment clusters in the magnetic composition are not included as they would make it more difficult to assign the nano-sized individual particles to a particular nominal particle size, while at the same time leading to undesirable darkening of the magnetic composition.
  • the magnetic nanoparticles used in the method according to the invention show at normal temperature (273.15 K corresponding to 0 0 C) and at room temperature (293.15 K corresponding to 20 0 C) a ferrimagnetic or ferromagnetic behavior. In particular, they are not nanoparticles which have superparamagnetic properties under the conditions mentioned.
  • the material used for the magnetic nanoparticles used according to the invention are metal oxides selected from ⁇ -Fe 2 O 3 (maghemite), FeO
  • metal ions in the oxidation state (III) are referred to as M 1 ". If mixtures of magnetic nanoparticles with different nominal particle sizes are used, the differently sized nanoparticles can consist of the same material or else of different materials.
  • magnetite particles Fe “Fe” 1 2 O 4 , also referred to as Fe 3 O 4 .
  • the individual magnetic nanoparticles have an inorganic and / or organic coating which preferably completely envelopes the individual particles, but the coating of different individual particles as such does not form a common phase.
  • This coating is primarily used to stabilize the magnetic nano-single particles in their chemical and magnetic properties and to facilitate the incorporation of the magnetic nano-single particles in the magnetic composition and their homogeneous distribution in the latter.
  • the inorganic coating of the nano-single particles can also be accompanied by a lightening of the particles which at least partially conceals the dark body color which usually arises when using the abovementioned magnetic materials.
  • This lightening is very desirable for producing a hidden (invisible without aids) security feature, as when using uncoated magnetic nano-single particles, especially when they are in high concentration in a magnetic composition, some visibility of the particles in the dried or cured magnetic composition can not be completely excluded. Although this problem occurs in the inventive use of magnetic nanoparticles, which in homogeneous distribution in the magnetic
  • Composition to a much lesser extent than magnetic nanoparticles present in molecular sieves or other templates, but with the use of inorganic coatings of the individual particles, especially when these coatings SiO 2 and / or TiO 2 -containing, can be in relation to achieve significantly better results on the brightness of magnetic nanoparticles.
  • inorganic and organic coatings may also be present together on the magnetic nano-single particles.
  • Suitable inorganic materials for the coating are advantageously metal oxides or metal oxide hydrates, which are to be subsumed under the name metal oxides here.
  • the metal oxides of the metals Ti, Si, Al, Sn, Zr, Ca, Ba, Zn, Ce, Mg, In and the lanthanides are thereby preferably selected.
  • metal oxides and hydrated oxides of Si, Ti and also Ce are particularly preferred.
  • SiO 2 should be understood as meaning both the oxide and the oxide hydrate or mixtures of the two.
  • TiO 2 is understood to mean both the oxide and the hydrated oxide or mixtures of the two.
  • phosphates for example Al, Ca, Zr, Ba phosphates
  • sulfates for example Al, Ca, Ba sulfates
  • hydroxyl-containing compounds such as hydroxyl apatites used. These materials contribute in particular to both a better incorporation of the magnetic nano-single particles in the magnetic composition and to a lightening of the body color of the individual particles.
  • organic coating materials are preferably those in
  • monodisperse isotropic magnetic nanoparticles which can be homogeneously distributed in a binder system, ie present as nano-single particles, can be carried out according to a number of production methods known from the prior art.
  • organometallic precursors such as Metallcarbo- nyle, Metallacetylacetonate or Metallcupferronate in high-boiling organic solvents such as petroleum ether, toluene or long-chain ethers, which also surfactants such Contain fatty acids, oleic acid or hexadecylamines by thermal decomposition.
  • organometallic precursors such as Metallcarbo- nyle, Metallacetylacetonate or Metallcupferronate in high-boiling organic solvents such as petroleum ether, toluene or long-chain ethers, which also surfactants such Contain fatty acids, oleic acid or hexadecylamines by thermal decomposition.
  • the reaction takes place under inert gas atmosphere, but is relatively difficult to control at reaction temperatures of 100 to 320 0 C, a short nucleation time and a continuous germination over days.
  • a laser-induced pyrolysis of iron pentacarbonyl vapor in ethylene can also be carried out in an oxidizing atmosphere, eg. B. in air, O 2 or (CH 3 ) 3 NO), make metal oxide nanoparticles such as Fe 3 O 4 available. If alternatively organic nickel compounds are used, magnetic NiO nanoparticles can also be produced.
  • Oxidizing agent is usually used nitrate, but can in principle also other oxidizing agents such as atmospheric oxygen use.
  • the actual individual particle size of the magnetite nanoparticles is determined by the choice of reaction conditions.
  • ⁇ -Fe 2 O 3 nanoparticles can be prepared by refluxing a magnetite suspension at low pH for several days. But such particles can also be prepared by oxidation of magnetite with oxidants such as H 2 O 2 or air-oxygen under analogous conditions.
  • Fe (CO) 5 is decomposed under mild reaction conditions, for example by ultrasound (Prozorov et al., Thin Solid Films 340, 189, 1999) or photochemically (Khomutov et al., Colloids Surf., A 202, 243, 2002), preference is given to formation ⁇ -Fe 2 O 3 nanoparticles.
  • In the direct introduction of Fe (CO) 5 into hot Me 3 NO or by oxidation of Fe 3 O 4 with atmospheric oxygen (Tang et al., J. Phys. Chem. B 107, 7501, 2003, DE 10205332) are also ⁇ - Fe 2 O 3 nanoparticles formed.
  • Nanocrystalline ferrites are often prepared by the coprecipitation method. Thus, 40 nm MnFe 2 O 4 nanoparticles are formed (Zang et al., J. Am. Chem. Soc. 120, 1800, 1998), 6-18 nm MgFe 2 O 4
  • Nanoparticles (Chen et al., Appl. Phys. Lett. 73, 3156, 1998) and 2-45 nm 00 0.2 Zn 08 Fe 2 O 4 nanoparticles (Dey et al., J. Appl. Phys. 90, 4138, 2001) by adding the aqueous metal chloride solutions to an alkaline solution.
  • the coprecipitation method can also be applied to the decomposition of mixtures of organometallic materials such as Fe (CO) 5 and Ba (O 2 C 7 Hi 5 ) 2 by means of ultrasound, which leads to the formation of 50 nm barium ferrite particles (Shafi et al., Nanostruct. Mater 12, 29, 1999).
  • magnetite particles are to be used as magnetic nanoparticles, which is particularly preferred in the process according to the invention, a production process is of particular importance, which is described in German patent application DE 102008015365.6, the content of which is to be included in the present description in its entirety.
  • the process described therein involves the preparation of nanoparticles by preparing a basic mixture containing at least one M (II) salt, one M (MI) salt and an oxidizing agent, the molar ratio of M (II) to M (III) in the mixture is between 100: 1 and 1: 1.5, and wherein M (II) is selected from the group Fe (II), Co (II), Cr (II) and / or Mn (II) and M (III) from the group Fe (III), Co (III), Cr (III) and / or Mn (III) is selected, in a first process step, the tempering of the mixture for at least one minute at a
  • An M (II) salt according to the invention is a salt which contains at least one metal ion in the oxidation state (II).
  • An M (III) salt according to the invention is a salt which contains at least one metal ion in the oxidation state (III).
  • M (II) salts and M (III) salts have the same metal component.
  • this process is particularly suitable for the production of nano-magnetite particles from at least one Fe (II) salt and at least one Fe (III) salt.
  • Fe (II) salts are Fe (II) sulfate, Fe (II) halides, especially Fe (II) chloride, Fe (II) perchlorate, Fe (II) nitrate, Fe (II) carbonate, Fe (II) phosphate , Fe (II) arsenate, Fe (II) oxide, Fe (II) hydroxide, Fe (II) thiocyanate, Fe (II) acetyl acetonate, and the Fe (II) salts of organic acids, in particular
  • Fe (II) formate Fe (II) acetate, Fe (II) citrate, Fe (II) oxalate, Fe (II) fumarate, Fe (II) tartrate, Fe (II) gluconate, Fe (II) succinate , Fe (II) lactate.
  • Fe (II) sulfate Particularly preferred is Fe (II) sulfate.
  • the salts may contain other cations besides Fe, e.g. Ammonium, sodium or potassium.
  • Fe (III) salts are Fe (III) nitrate, Fe (III) sulfate, Fe (III) halides, especially Fe (III) chloride, Fe (III) perchlorate, Fe (III) phosphate, Fe (III) arsenate , Fe (III) oxide, Fe (III) hydroxide, Fe (III) thiocyanate, Fe (III) acetylacetonate, and the Fe (III) salts of organic acids, in particular Fe (III) formate, Fe (III) acetate, Fe (III) III) citrate, Fe (III) oxalate,
  • the salts may contain other cations besides Fe, such as ammonium, sodium or potassium.
  • the M (II) and M (III) salts are typically used in the mixture in a concentration between 0.1 mmol / L and 5 mol / L in a saline solution.
  • the pH of the M salt solutions before mixing the components is in the range of 0 to 7. It is important that the M salt solutions are not basic before mixing the components, otherwise metal hydroxides may form and precipitate ,
  • the M (II) salts and the M (III) salts may be introduced together or separately to prepare the mixture.
  • the mixture produced must be basic, i. H. have a pH> 7, so that the nanoparticles formed are precipitated.
  • the pH of the mixture is preferably between pH 9 and 13, more preferably between pH 11 and 12.
  • at least one base is added to the mixture, which makes the pH of the mixture rapidly correspondingly alkaline.
  • Suitable are all strong bases, e.g. Alkali or alkaline earth hydroxides, amines or ammonia. Preference is given to using sodium hydroxide as the base.
  • oxidizing agent it is possible to use all oxidizing agents which can be suitably metered stoichiometrically. Since this is often problematic in atmospheric oxygen, this is preferably not used as an oxidizing agent, but largely eliminated, for example, by degassing the solutions used with nitrogen or noble gases.
  • Suitable oxidizing agents are, for example, hydrogen peroxide, inorganic peroxo compounds such as, for example, peroxides, hydroperoxides, peroxodisulfates, peroxomonosulfates, peroxoborates, peroxochromates,
  • Peroxophosphates peroxocarbonates, organic peroxo compounds such as acetone peroxide or peroxycarboxylic acids, chloramine T, Chlorates, bromates, iodates, perchlorates, perbromates, periodates, permanganates, chromates, dichromates, hypochlorites, chlorine oxides or nitrates.
  • Particularly preferred oxidizing agents according to the invention are nitrates, such as potassium nitrate, sodium nitrate or ammonium nitrate.
  • the amount of oxidizing agent typically depends on the amount of metal salt to be oxidized. If the M (III) salt content is very low, then the oxidizing agent is preferably used in an approximately equimolar amount to the M (II) salt. If a high proportion of M (III) salt is present, the proportion of oxidizing agent is correspondingly reduced. When using mild oxidants such as nitrate, the oxidizing agent can also be used in excess, without further oxidation of the precipitated product takes place.
  • the oxidizing agent may be added singly to prepare the mixture, or mixed in advance with the M salts or the base.
  • a solution containing at least one M (II) salt and one M (III) salt is preferably prepared, as is a basic solution.
  • the oxidizing agent may be added to the M salt solution or, preferably, the basic solution.
  • the solvent used is usually water or mixtures of water with water-soluble organic solvents.
  • water is used as the solvent.
  • the solutions may contain additives, e.g. surface-active substances.
  • the preparation of the mixture is typically carried out at room temperature.
  • the mixing of the individual components can be carried out either in a batch process or continuously, with a continuous process being preferred.
  • the tempering is advantageously carried out at temperatures between 0 and 100 0 C, preferably between 20 and 100 0 C, more preferably between 60 and 90 0 C.
  • the tempering time is typically between one minute and one day, preferably between 10 minutes and 4 hours, particularly preferably between 20 minutes and one hour.
  • the resulting nanoparticles can optionally be washed, filtered, centrifuged, or otherwise purified or isolated. Suitably, it is washed several times with deionized water.
  • the nanoparticles obtained are isotropic and practically monodisperse (nominal particle size ⁇ 10%) and have an individual particle size (largest diameter of the individual particles) of 100 nm and smaller, preferably less than 90 nm, in particular between 10 and 80 nm and most preferably between 10 and 50 nm, up.
  • the individual and thus the nominal particle size can be adjusted by the choice of reaction conditions.
  • the choice of the molar ratio between M (II) and M (III) salts has a particular influence on the size of the nanoparticles. This molar ratio makes it possible to adjust the individual particle size of the nanoparticles obtained in a very narrow particle size range and thus to be able to determine a nominal particle size in a targeted manner.
  • Ratio, pH and ionic strength of the medium, type of salts, temperature, preferably inert gas atmosphere), the type, quality and size of the nanoparticles are determined.
  • the monodisperse isotropic magnetic nanoparticles produced by means of one of the previously described suitable processes are completely or partially coated with organic and / or inorganic materials in at least one additional process step.
  • magnetic nanoparticles in particular magnetite (Fe 3 O 4 ) nanoparticles, tend to reduce their magnetic properties (specific magnetization) by reoxidation over time.
  • gas-tight, in particular oxygen- and moisture-tight diffusion barriers which protect the magnetite particles in particular against oxidation, on the surface thereof.
  • the coating contains as inorganic materials preferably SiO 21 (Yu et al., Rev. Adv. Mater., P. 4,55,2003) TiO 2 and / or ZrO 2 , gold (Kinoshita et al., J. Alloys Compd. 359, 46, 2003), boron nitride (Kitahara et al., Diamond Relate. Mater. 10, 1210, 2001) or carbon.
  • SiO 2 alone, or SiO 2 and TiO 2 either in admixture or applied sequentially, is used.
  • the majority of the magnetic nanoparticles described also have a dark to black intrinsic color, as previously described. If such particles are present in a high concentration in their application medium, despite their small particle size, a certain optically perceptible visibility can not be ruled out.
  • metal oxides are again, preferably the metal oxides already described above, but especially SiO 2 , TiO 2 and / or ZrO 2 , and very particularly preferably SiO 2 and TiO 2 , either singly or in admixture, as well as applied successively in any order, particularly suitable.
  • metal oxides for example SnO 2 , ZrO 2 , ZnO, Ce 2 O 3 and / or Al 2 O 3, to be present in the coating. The latter is usually only in proportions of up to 20 wt .-%, based on the weight of the entire coating, the case.
  • the coating with metal oxides As an example of the coating with metal oxides, the coating with a SiO 2 -containing layer (hereinafter also referred to as SiO 2 layer) is explained.
  • the other metal oxides can be applied analogously from suitable starting materials.
  • the SiO 2 layer can be applied from inorganic or organic Si starting compounds.
  • inorganic Si compound is in particular sodium or potassium water glass into consideration.
  • the magnetic nanoparticles are introduced into an aqueous water glass solution.
  • a very dense SiO 2 layer or silicon oxide hydrate layer
  • This layer which usually first hydrous and gel precipitates, is generally excited by addition of a salt to the reaction system for better growth on the particle surface (salting out).
  • Suitable organic compounds for applying a layer containing SiO 2 are, in particular, the esters of orthosilicic acid (for example TEOS tetraethyl orthosilicate). By targeted hydrolysis of the ester, a SiO 2 -containing layer on the surface of the magnetic
  • Nanoparticles are applied.
  • the hydrolysis may be acid or base catalyzed but is usually carried out under base catalysis.
  • the solvents used are generally nonaqueous but water miscible systems or mixtures.
  • the addition of salts, as described in the first variant, may lead to a tendency for coagulation generally present in the case of magnetic nanoparticles, in particular magnetite.
  • the second, salt-free coating variant is preferred.
  • a coating with TiO 2 can be carried out by generally known (wet) coating processes, which have been developed in particular for the production of pearlescent pigments.
  • the corresponding methods are adequately described in the prior art, for example in DE 14 67 468, DE 19 59 998, DE 20 09 566, DE 22 14 545, DE 22 15 191, DE 22 44 298, DE 23 13 331, DE 15 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 11 602, DE 32 35 017, or in other patent documents known to the expert and other gene publications.
  • the substrate particles are suspended in water and admixed with one or more hydrolyzable, in particular inorganic, metal salts (for the application of the titanium dioxide layer eg suitable inorganic titanium salts such as titanium tetrachloride) at a suitable pH for the hydrolysis, the so is chosen that the metal oxides or metal oxide are precipitated directly on the substrate particles, without causing precipitation.
  • the pH is usually kept constant by simultaneous addition of a base and / or acid. Subsequently, the coated substrate particles are separated off and optionally washed and dried.
  • the dark to black intrinsic color of the magnetic nanoparticles can be well covered with such, in particular TiO 2 -containing, coating, without the magnetic properties of the nanoparticles are significantly impaired.
  • the thickness of the inorganic layers can be from 1 to 40 nm (total layer thickness). However, since the coated magnetic nanoparticles are to retain the monomodality of the magnetic starting particles, layer thicknesses of less than 10 nm, preferably from 1 to 8 nm, in particular from 1 to 5 nm, are preferred for practical use.
  • An organic coating can also be applied to the magnetic nanoparticles. This may be rather compact, so that after coating so-called core-shell particles are present. However, the organic coating may also be present as an organic surface modification that is bound only to portions of the surface of the magnetic nanoparticles. A coating with surface-active substances is also possible.
  • Natural or synthetic polymers are suitable as organic coating for the production of so-called core-shell particles (Landfester et al., J. Phys. Condens. Matter 15, 1345, 2003). Examples of natural polymers are polysaccharides such as dextran and sepharose, polypeptides such as poly-L-aspartate and poly-L-glutamate, and polylactides such as polyisocyanate.
  • Examples of synthetic polymers are polyvinyl alcohol, polystyrene (derivatives), poly (meth) acrylates and acrylamides, polypyrroles, polyesters, poly- ⁇ -caprolactam and copolymers thereof, with one another or else with natural polymers.
  • a SiO 2 layer applied by one of the methods described above can be modified by chlorine or alkoxysilanes bearing functional groups.
  • polymerization initiators can also be coupled to the magnetic nanoparticles, which form the precursor to typical core-shell particles with magnetic core and polymer shell.
  • the surface of the magnetic nanoparticles may also be coated with surface-active substances (surfactants).
  • surfactants may be selected from cationic, anionic, nonionic and amphoteric surfactants. Examples of these are organic acids and their derivatives, functionalized silanes, such as alkoxysilanes, aminosilanes, vinylsilanes, epoxysilanes or methacrylsilanes, which have already proven themselves for the surface-active coating, preferably of pigments.
  • Such surface-active compounds are applied in particular on the surface of the magnetic nanoparticles used according to the invention, if their incorporation into different magnetic compositions, for example printing inks, is to be facilitated.
  • magnetite nanoparticles In order to protect magnetite nanoparticles from undesired agglomerations and to stabilize the suspensions, they are coated, for example, with monolayers of fatty acids such as decane or lauric acid (Fu et al., J. Appl. Surf., 181, 173, 2001).
  • Cationic surfactants such as cetyltrimethylammonium bromide or anionic surfactants such as sodium dicycbenzenesulfonate are also used for stabilizing ⁇ -F ⁇ 2 ⁇ 3 nanoparticles (Guo et al., Physica E (Amsterdam) 8, 199, 2000).
  • the magnetic composition used in the process according to the invention is essentially a conventional coating composition with regard to its further ingredients and can be present, for example, as a paint, lacquer, printing ink or paste.
  • the proportion of magnetic nanoparticles in the magnetic composition is from 0.5 to 90 wt .-%, based on the composition, wherein the higher value refers to a pasty composition.
  • the proportion of magnetic nanoparticles is 0.5 to 60% by weight, preferably 1 to 35% by weight, and in particular 10 to 30% by weight, based on the weight of the composition.
  • the magnetic composition also contains at least one binder. Furthermore, one or more solvents and the usual be used for coating compositions used additives.
  • Binders which are generally used for coating compositions are customary binders, in particular those based on nitrocellulose, polyamide, acrylic, polyvinylbutyral, PVC, PUR or suitable mixtures thereof, and UV-curable binders (free-radically or cationically curing).
  • the magnetic composition according to the invention may also contain at least one solvent which consists of water and / or organic solvents or of organic solvent mixtures.
  • Suitable organic solvents are all solvents customarily used in the abovementioned coating methods, for example branched or unbranched alcohols, aromatics or alkyl esters, such as ethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, ethyl acetate, butyl acetate, toluene, etc. , or mixtures thereof are used.
  • the magnetic composition contains at least one solvent.
  • customary additives such as fillers, further color pigments or dyes, for example carbon black, UV stabilizers, inhibitors, flame retardants, lubricants, dispersants, redispersants, defoamers, leveling agents, film formers, adhesion promoters, drying accelerators, drying retardants, photoinitiators, etc. to the magnetic composition.
  • fillers for example carbon black, UV stabilizers, inhibitors, flame retardants, lubricants, dispersants, redispersants, defoamers, leveling agents, film formers, adhesion promoters, drying accelerators, drying retardants, photoinitiators, etc.
  • the concrete material composition of the respective magnetic composition and its viscosity of the type of the selected coating process and the respective printing material (surface material of the product according to the invention to be coated) are dependent.
  • the solids content of the coating composition depends on the process used, coating temperature, coating speed and type of binder,
  • Additives and type of printing material adjusted so that the viscosity of the coating composition is sufficient to achieve the best possible transfer of the coating composition from the respective coating apparatus to the substrate.
  • This adjustment of the viscosity takes place directly on the coating machine and can be carried out without any inventive step, based on the instructions of the manufacturer of the coating composition or the expertise of the printer or coating expert.
  • the determination of the viscosity is generally carried out by determining the flow time at standard temperature and a certain relative humidity in a standard flow cup or by measuring with a rheometer (eg from Brookfield E.L.V. GmbH, Lorch, Germany).
  • product surfaces can be coated which can consist of the most diverse materials (printing materials). These may be, for example, various papers, cardboard, wallpaper, laminates, tissue materials, wood, leather, glass, ceramics, stone, metals, polymeric films, metal foils, polymer plates, textile materials or multilayer materials, which components of several of these Contain substances, such as foil-laminated papers act. Special papers, such as banknotes or papers containing even more visible or invisible security features, can also be coated.
  • the printing substrates in particular paper-based printing substrates, can be subjected to an electrostatic pretreatment be and / or provided with primary layers. These consist for example of color or the so-called primer layers. Therefore, for example, the papers used can be uncoated, coated or satin-finished papers. This also applies to the other types of substrates.
  • the magnetic composition is applied to the surface of the product by means of various printing or coating processes.
  • these are preferably intaglio printing processes including intaglio printing processes, screen printing processes, paper coating processes, for example rod processes or blade processes, reverse processes, flexographic printing processes, pad printing processes, inkjet processes or offset overprint varnishing to name just a few common procedures.
  • Drying and / or curing of the magnetic composition applied to the surface of the product takes place under conditions which are generally known to the person skilled in the art and according to known methods and therefore does not need to be explained in more detail here.
  • the magnetic composition is applied to at least a predetermined area unit of the surface of a product. That is, the size, position and shape of the coated surface part are predetermined. It makes sense to apply the magnetic composition to at least a portion of the surface of a product that is readily accessible to the devices later used to authenticate the product. It goes without saying that, depending on the type and size of the product to be coded, the entire product surface can also be coated with the magnetic composition. However, in most cases, for practical and cost reasons, the magnetic composition is only applied to a portion of the surface of a product.
  • the embodiment is advantageous in which the magnetic composition applied to a partial surface of the product to be coded has a mixture of magnetic nanoparticles having two or more different predetermined nominal particle sizes.
  • the concentration of the magnetic nanoparticles of a predetermined nominal particle size in the magnetic composition may be the same as the concentration of the magnetic nanoparticles of a different predetermined nominal particle size, but the concentrations may also be different from one another.
  • a preferred embodiment is that a magnetic composition on at least two separate area units of the surface of the product is applied, wherein the predetermined nominal particle size and / or the concentration of the magnetic nanoparticles on a first area unit is equal to or different from the predetermined nominal particle size and / or the concentration of the magnetic nanoparticles on another
  • the number of different coding possibilities is very high.
  • the coated surface unit can have any shape and size, that is, be applied in geometric shapes, logos, irregular shapes, etc.
  • the position and size of the coated area unit (s) depend on the application requirements, in particular on the good accessibility of the coated product surface for the respectively selected decoding devices.
  • the nominal particle size and / or the concentration of the magnetic nanoparticles in the magnetic composition are used according to the invention.
  • the type of material used for the magnetic nanoparticles can additionally be used as the coding parameter.
  • the nominal particle size itself forms the basis for a binary code which may have state 1 (for existing) or state 0 (for nonexistent). This simply means that yes / no information about the presence of magnetic nanoparticles of a predetermined nominal particle size is a major part of the code. If magnetic nanoparticles with several different nominal particle sizes are used, a number of n different nominal particle sizes (2 n -1) results. For example, from monodisperse isotropic magnetic nanoparticles having 5 different nominal particle sizes, 31
  • the magnetic nanoparticles are also present in a (pre-) specific concentration c.
  • This concentration can also be used to form a code, either solely in the nature of a binary code similar to the nominal particle size as discussed above, or in addition to the nominal particle size. In the latter case, the number of possible codes increases to (c ⁇ -1). For example, using 5 different nominal particle sizes in 3 different concentrations each (eg: low concentration of 10% / high concentration of 40% / absent 0%) 242 different codes can be formed.
  • the simplest form of analysis of the code generated according to the invention is the analysis of the coating produced by means of the magnetic composition.
  • the constituents of this coating can be investigated by removing the coating from the surface of the substrate, separating the solid constituents and simply measuring the individual particle size of a representative number of the magnetic nanoparticles contained by means of one of the abovementioned measuring methods.
  • customary methods can be used to carry out a material analysis of the separated magnetic
  • Coating compositions containing magnetic nanoparticles can be obtained, depending on both the particle size and the concentration of the magnetic nanoparticles in different measuring methods and in this way clearly distinguishable signals can be obtained.
  • magnetic nanoparticles which exhibit ferro- or ferrimagnetic behavior at standard or room temperature such as the magnetic nanoparticles used according to the invention
  • this is significantly better and more clearly the case than, for example, with superparamagnetic nanoparticles.
  • most of the usual in practice magnetic measuring methods are preferably carried out at standard or room temperature, so that all measurements outside this temperature range, which are almost indispensable in the use of superparamagnetic nanoparticles, to increased technical effort or unworkability of the method among such deviating
  • parameters for characterizing the magnetic nanoparticles contained in the magnetic composition for example, the saturation magnetization, the magnetic moment, the hysteresis curve with remanence and coercivity and the magnetic susceptibility serve (also depending on the frequency).
  • the sensitivity and speed of reading these parameters from the coating present on the surface of the encoded product containing the magnetic nanoparticles depends on the type of magnetic field sensors used. These are commercially available in different variants.
  • Hall sensors can be used.
  • the Hall effect detection is based on the physical phenomenon of a potential difference when a current-carrying semiconductor is penetrated by a magnetic field perpendicular thereto or at an angle.
  • a change in this magnetic field by magnetic particles introduced into a coating causes a measurable change in voltage (change in the Hall voltage as a function of the size and concentration of the magnetic particles).
  • Fluxgate magnetometers are also suitable for reading the magnetic code. They allow detection of magnetic fields in the range of 0.1 nT to 1 mT. In this case, the sample to be measured is periodically brought to saturation by an alternating current field. After switching off the voltage, the decay of the induced magnetic field is detected. This decay, the so-called magnetorelaxation, depends among other things on the size and concentration as well as the type (material composition) of the magnetic materials used. Here coding is possible based on various parameters. In addition, it can be determined whether the magnetic particles are fixed in the printing ink or in the magnetic composition (relaxation exclusively according to the Neel mechanism), or whether the particles are flexibly incorporated (Neel relaxation and Brownian motion).
  • MR sensors magnetic resistive
  • All MR principles have in common that the electrical resistance of the MR sensor changes under the influence of a magnetic field. This resistance change is a few percent and can already be used with weak magnetic fields.
  • AMR sensors allows non-contact and thus non-destructive magnetic field measurement with a high signal resolution up to the MHz range.
  • the effect is exploited that changes in conductive materials, which are used for the sensors, such as FeNi, the electrical resistance as a function of the angle between current flow and an external magnetic field.
  • This resistance change is typically ⁇ 1.5% of the total resistance value, which is most easily detected with a Wheatstone bridge circuit.
  • This Anisotropic Magneto-Resistive effect can be used to determine the properties of magnetizable materials that are in close proximity to the sensor.
  • the resulting hysteresis curves allow by their shape and size conclusions on, for example, the particle size and concentration of the magnetic particles used in the coating.
  • the width of the respective ones Hysteresis curve determined by their respective positive and negative intersections with the x (H c ) and y (B) axes constant concentration of magnetic nanoparticles in the respective magnetic composition depends directly on the individual and thus also on the nominal particle size of the magnetic nanoparticles used.
  • a broad hysteresis curve in the sense of the present invention is a hysteresis curve whose double S-shape encloses a large surface area, which is not determined quantitatively, but can be clearly determined by the respective positive and negative intersections of the hysteresis curve with the x The farther apart these intersections are from the O point, the larger the area enclosed by the hysteresis curve, and the wider the hysteresis curve.
  • a ferrite or ferromagnetic behavior of the magnetic nanoparticles under measuring conditions is indispensable, because with superparamagnetic nanoparticles (whose particle sizes are so small that they fall within the size range of Weiss districts, which leads to such particles having no magnetic remanence under the present measuring conditions) not the hysteresis curve has the usual double S-loop shape, but the x- and y-axis is cut at only a single point.
  • the concentration of the magnetic nanoparticles in the magnetic composition does not result in a change in the respective positive and negative points of intersection with the x or y axis.
  • the concentration of the magnetic nanoparticles under otherwise identical conditions has a clearly attributable and reproducible influence on the magnitude of the saturation magnetization measured sample. The lower the concentration of magnetic nanoparticles in the sample, the lower is the saturation magnetization (M 5 ) and the lower the positive saturation value is.
  • This unambiguous correlation of the shape and size of the hysteresis curve with the particle size and the concentration of the magnetic nanoparticles in the magnetic composition can also be used to evaluate magnetic codes having more than one coding parameter.
  • Particularly advantageous is the fact that only a few measurement points are sufficient to mark the respective obtained hysteresis curve. Thus, it does not have to be identical with a previously recorded comparison curve over its entire course, but can only be checked at four individual points (respective points of intersection with the x and y axes).
  • AMR sensors can have much higher sensitivity (about 50 to 100 times higher) than other sensors employing measurement techniques based on known solid state magnetic effects (e.g., Hall effect). Moreover, AMR sensors are small, robust and long-term stable, so that they can easily be integrated into different devices and constructions by the user or can also be used on mobile devices.
  • GMR sensors as well as AMR sensors are suitable for reading out the codes generated by the method according to the invention.
  • the GMR (Giant Magneto Resistive) effect is a quantum mechanical phenomenon that occurs in thin layer systems between at least two ferromagnetic and one non-magnetic metallic material.
  • the resistance is greater than with parallel alignment.
  • a GMR sensor can be evaluated via a Wheatstone bridge circuit, but has a much higher sensitivity. This high sensitivity also allows the measurement of magnetic fields at greater distances to the target object.
  • the currently most sensitive sensors for the measurement of magnetic fields which can also be used to read the codes generated according to the invention, are magnetometers based on SQUIDs (Superconducting Quantum Interference Device). With them, detection limits in the fT range can be achieved.
  • a SQUID is a closed superconducting ring interrupted by two so-called Josephsen junctions. To increase the sensitivity, the SQUID is directly coupled to a flux antenna which couples the signal of the (product) sample to be detected into the device. The magnetic field induces a current in the SQUID loop that results in a measurable voltage drop across the Josephsen junctions.
  • SQUIDs are available in different designs.
  • the magnetic AC susceptibility can be determined.
  • the measured susceptibility of the sample is dependent inter alia on the concentration and the particle size of the magnetic nanoparticles used, so that conclusions can be drawn about them by means of corresponding calculations and pattern curves.
  • the particle volume can be determined from the increase in the reciprocal AC susceptibility curve as a function of the temperature for monodisperse magnetic nanoparticles (Chantrel et al., J. Magn. Mater., 40, 1, 1983).
  • a further subject of the present invention is a product which contains on its surface a magnetic coding, wherein a dried and / or hardened magnetic composition containing magnetic nanoparticles is located on at least one predetermined area unit of the surface of the product and in the magnetic composition monodisperse isotropic magnetic nanoparticles of at least a predetermined nominal particle size with a predetermined concentration in a homogeneous distribution and wherein the code is formed from the nominal particle size and / or from the concentration of the magnetic nanoparticles in the magnetic composition.
  • a product according to the present invention may, in principle, be any product which, for whatever reason, is desirably to have a visually invisible magnetic code.
  • Such codes may be used to identify the manufacturer, batch of product, place of manufacture or other coded characteristics. Often, a simple yes / no information about the presence of a particular magnetic feature is sufficient, for example, to be able to prove the authenticity of the product.
  • Particularly preferred products for the purposes of the present invention are the so-called security products. These include, for example, banknotes, checks, credit cards, shares, passports, identity documents, access authorization cards, driver's licenses, entrance tickets, tokens, tax stamps, stamps, labels, seals, packaging materials or even commodities to be protected, to name only a few.
  • the magnetic composition can only be on a single predetermined unit area of the product.
  • the magnetic composition is located on a plurality of separate surface units (partial surfaces) of the surface of the product.
  • the predetermined nominal particle size and / or the concentration of the magnetic nanoparticles on a first area unit of the surface of the product may be the same or different from the predetermined nominal particle size and / or the concentration of the magnetic nanoparticles on a further area unit.
  • the manner of encoding with magnetic nanoparticles as well as the number and amount of used types of different magnetic nanoparticles is limited only by practical reasons, such as the simplicity of the decryption of the code, or by cost reasons.
  • the subject matter of the present invention is also a magnetic composition, but in particular a printing ink or coating composition, by means of which the process according to the invention can be carried out and the corresponding coded products can be produced.
  • a magnetic composition according to the invention contains at least one binder in which monodisperse isotropic magnetic nanoparticles having at least a predetermined nominal particle size are present in homogeneous distribution.
  • the magnetic composition also contains at least one solvent.
  • at least one adjuvant it is also possible for at least one adjuvant to be present.
  • the magnetic composition according to the invention is generally prepared by simply mixing the ingredients, if appropriate also by additional milling, dispersing and / or by trituration and homogenization of the ingredients.
  • additional milling, dispersing and / or by trituration and homogenization of the ingredients In particular, in the incorporation of further colorants in the magnetic coating composition, conventional process steps such as milling, dispersing, etc., become necessary.
  • the method of encoding products with a magnetic code according to the present invention is a simple and inexpensive method of marking products that is used both in the art
  • the preparation of the constituents of the magnetic composition to be used, in particular also of the monodisperse isotropic magnetic nanoparticles, is possible in a comparatively simple and cost-effective manner.
  • the magnetic composition as such can be prepared without technical problems by simply mixing the components. In this case, the required homogeneous distribution of the magnetic nanoparticles can be done without much additional technical effort.
  • the coating of the selected product surfaces is carried out using generally customary coating technologies, preferably by known printing processes.
  • Product manufacturers can selectively read out their product-specific code with a specifically selected measuring method and only accept as genuine those products which fulfill the preselected conditions both on the material side and on the device side.
  • the code generated by the invention represents a valuable invisible (covered) security feature that is usefully combined with one or more other open or hidden security features on the product.
  • the method according to the invention is an easy-to-handle and effective means of generating such a code.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Hard Magnetic Materials (AREA)
  • Powder Metallurgy (AREA)
  • Magnetic Record Carriers (AREA)

Abstract

L'invention concerne un procédé de codage de produits, selon lequel une composition magnétique contenant des nanoparticules magnétiques est appliquée sur au moins une unité de surface prédéfinie de la surface d'un produit, et séchée et/ou durcie. Dans la composition magnétique, des nanoparticules magnétiques isotropes monodispersées, présentant au moins une taille particulaire nominale prédéfinie, sont présentes à une concentration prédéfinie en répartition uniforme. Un code est formé à partir de la taille particulaire nominale et/ou de la concentration des nanoparticules magnétiques dans la composition magnétique. L'invention concerne également un produit ainsi codé et une composition magnétique.
EP10719248A 2009-05-07 2010-04-12 Procédé de codage de produits Withdrawn EP2427859A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102009020208A DE102009020208A1 (de) 2009-05-07 2009-05-07 Verfahren zum Codieren von Produkten
PCT/EP2010/002243 WO2010127757A2 (fr) 2009-05-07 2010-04-12 Procédé de codage de produits

Publications (1)

Publication Number Publication Date
EP2427859A2 true EP2427859A2 (fr) 2012-03-14

Family

ID=42932426

Family Applications (1)

Application Number Title Priority Date Filing Date
EP10719248A Withdrawn EP2427859A2 (fr) 2009-05-07 2010-04-12 Procédé de codage de produits

Country Status (3)

Country Link
EP (1) EP2427859A2 (fr)
DE (1) DE102009020208A1 (fr)
WO (1) WO2010127757A2 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106462781B (zh) * 2014-04-22 2019-08-30 先进工程解决方案有限责任公司 用于工业过程中类皮革和皮革材料的可追踪性的方法
EP3064207B1 (fr) 2015-03-04 2017-12-20 Scandion Oncology A/S Dérivés de 4-amino-3-phenylamino-6-phenylpyrazolo [3,4-d]pyrimidine utilisés en tant qu'inhibiteurs de bcrp dans des traitements thérapeutiques
EP3720621B1 (fr) 2017-12-07 2023-11-22 University of Copenhagen Composition comprenant un oxyde de fer et charbon biologique pour la dépollution d'environnement

Family Cites Families (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL280256A (fr) 1961-06-28
DE1522572A1 (de) 1967-03-23 1969-09-18 Marcus Cantarano Verfahren und Vorrichtung zum photoelektrischen Herstellen von Reproduktionen
BE759469A (fr) 1969-11-29 1971-05-26 Merck Patent Gmbh Pigment a brillant nacre et leurs procedes de
DE2009566C2 (de) 1970-02-28 1972-06-15 Merck Patent Gmbh Verfahren zur Herstellung von Titandioxid- bzw. Titandioxidaquatüberzügen
CA964403A (en) 1971-03-26 1975-03-18 Howard R. Linton Nacreous pigments of improved luster and process for their manufacture
CA957108A (en) 1971-03-30 1974-11-05 E. I. Du Pont De Nemours And Company Pigments treated with methacrylatochromic chloride for improved humidity resistance
DE2244298C3 (de) 1972-09-09 1975-06-19 Merck Patent Gmbh, 6100 Darmstadt Perlglanzpigmente und Verfahren zu ihrer Herstellung
DE2313331C2 (de) 1973-03-17 1986-11-13 Merck Patent Gmbh, 6100 Darmstadt Eisenoxidhaltige Glimmerschuppenpigmente
DE3137808A1 (de) 1981-09-23 1983-03-31 Merck Patent Gmbh, 6100 Darmstadt Perlglanzpigmente mit verbesserter lichtechtheit, verfahren zur herstellung und verwendung
DE3137809A1 (de) 1981-09-23 1983-03-31 Merck Patent Gmbh, 6100 Darmstadt "perlglanzpigmente, ihre herstellung und ihre verwendung"
DE3151354A1 (de) 1981-12-24 1983-07-07 Merck Patent Gmbh, 6100 Darmstadt Perlglanzpigmente, verfahren zu ihrer herstellung und ihre verwendung
DE3151343A1 (de) 1981-12-24 1983-07-07 Merck Patent Gmbh, 6100 Darmstadt Perlglanzpigmente mit verbesserter lichtbestaendigkeit, ihre herstellung und ihre verwendung
DE3151355A1 (de) 1981-12-24 1983-07-07 Merck Patent Gmbh, 6100 Darmstadt "perlglanzpigmente mit verbesserter lichtbestaendigkeit, ihre herstellung und verwendung"
DE3211602A1 (de) 1982-03-30 1983-10-13 Merck Patent Gmbh, 6100 Darmstadt Verfahren zur herstellung von perlglanzpigmenten mit verbesserten glanzeigenschaften
DE3235017A1 (de) 1982-09-22 1984-03-22 Merck Patent Gmbh, 6100 Darmstadt Perlglanzpigmente
DE10118679A1 (de) 2001-04-14 2002-10-24 Henkel Kgaa Identifizierungs- oder Authentifizierungsverfahren
US6869015B2 (en) * 2001-05-30 2005-03-22 Sandia National Laboratories Tamper-indicating barcode and method
DE10205332B4 (de) 2002-02-06 2004-02-12 Berlin Heart Ag Verfahren zur Herstellung von magnetischen Nanoteilchen
GB0209564D0 (en) 2002-04-25 2002-06-05 Rue De Int Ltd Improvements in substrates
US7865722B2 (en) * 2003-07-22 2011-01-04 Agency For Science, Technology And Research Method of identifying an object and a tag carrying identification information
EP1646057A2 (fr) 2004-10-09 2006-04-12 European Central Bank Document de securité ayant la possibilité de stockage de données, et procédé et appareil pour lire et écrire cettes données
US8036415B2 (en) * 2007-01-03 2011-10-11 International Business Machines Corporation Method and system for nano-encoding and decoding information related to printed texts and images on paper and other surfaces
DE102008015365A1 (de) 2008-03-20 2009-09-24 Merck Patent Gmbh Magnetische Nanopartikel und Verfahren zu deren Herstellung

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2010127757A2 *

Also Published As

Publication number Publication date
WO2010127757A3 (fr) 2011-01-27
WO2010127757A2 (fr) 2010-11-11
DE102009020208A1 (de) 2010-11-11

Similar Documents

Publication Publication Date Title
EP2649134B1 (fr) Pigments magnétiques
DE60210932T3 (de) Magnetische dünnschicht-interferenzvorrichtung oder -pigment und zugehöriges herstellungsverfahren, drucktinten- oder anstrich-zusammensetzung, sicherheitsdokument und verwendung einer solchen magnetischen dünnschicht-interferenzvorrichtung
EP1251152B1 (fr) Pigments métalliques à effet
CN101802111B (zh) 油墨或调色剂组合物、使用方法和由其得到的制品
EP2445972B1 (fr) Pigments magnétiques constitués d'un substrat lamellaire et d'une couche de maghémite
EP1255792A1 (fr) Procede pour revetir des surfaces de substrats avec des polymeres a lcst
Joshi et al. Effect of Ni2+ substitution on structural, magnetic, dielectric and optical properties of mixed spinel CoFe2O4 nanoparticles
Šutka et al. Study of the structural phase transformation of iron oxide nanoparticles from an Fe2+ ion source by precipitation under various synthesis parameters and temperatures
EP3010980B2 (fr) Pigments d'interférence optiquement variables et transparents, aux propriétés électriquement semi-conductrices
DE69426756T2 (de) Nichtmagnetische Unterschicht für magnetischer Aufzeichnungsmedium, magnetisches Aufzeichnungsmedium und nichtmagnetische Teilchen
Wang et al. Magnetic, Luminescent Eu‐Doped Mg–Al Layered Double Hydroxide and Its Intercalation for Ibuprofen
EP2427859A2 (fr) Procédé de codage de produits
da Silva et al. Tuning magnetic and luminescent properties of iron oxide@ C nanoparticles from hydrothermal synthesis: Influence of precursor reagents
DE69814319T2 (de) Magnetisches Aufzeichnungsmedium und Substrat dafür
DE102008015365A1 (de) Magnetische Nanopartikel und Verfahren zu deren Herstellung
WO2002084608A2 (fr) Procede d'identification ou d'authentification
DE102014110573A1 (de) Mit einer Signatur auf Basis von superparamagnetischen und/oder weichmagnetischen Nanopartikeln versehener Gegenstand, Verfahren zu dessen Herstellung und Verwendung von superparamagnetischen und/oder weichmagnetischen Nanopartikeln zum Sichern von Gegenständen gegen Fälschung und Nachahmung
EP2655520A1 (fr) Elément de sécurité magnétisable coloré
DE69408253T2 (de) Körnige Magnetitteilchen und Verfahren zu ihrer Herstellung
Mdlalose et al. Chitosan coating by mechanical milling of MnFe2O4 and Mn0. 5Co0. 5Fe2O4: Effect of milling
Sudhakaran et al. Optical Band gap characterization of Novel Nanoscale CBM-CZF composite
Müssig Development of supraparticles suitable for magnetic identification tags
Sharafi et al. Preparation of Fe 3 O 4@ SiO 2 Nanostructures via Inverse Micelle Method and Study of Their Magnetic Properties for Biological Applications
CH719726B1 (de) Halbhartes magnetisches pulver mit hohem wert und verfahren zur herstellung desselben
Poulose et al. Physics Open

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20110907

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK SM TR

DAX Request for extension of the european patent (deleted)
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20121101