Classifications

• • 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 a delible magnetic ink particularly for marking documents and the like, and its process of manufacture.
• magnetic inks i.e. inks which contain, inside them, particles of magnetic material which allow to magnetically read the document on which the ink has been printed or in any way applied, are already commercially available.
• indelible magnetic inks are a valid support for the magnetic reading of the document on which a code made with indelible magnetic ink is applied, for example, but they cannot constitute a safety element which clearly reveals the forgery of the document in the region where the magnetic ink is applied.
• the aim of the invention is indeed to solve the above described problem by providing a delible magnetic ink particularly for marking documents and the like which allows to modify its initial characteristics if the region where said delible magnetic ink has been printed or in any way applied is treated with chemical deletion products or with mechanical means such as erasers or scratch knives.
• a particular object of the invention is to provide a delible magnetic ink which can be printed or in any case applied by using conventional printing methods, thus allowing to provide, for example, a bar code which, besides allowing the magnetic reading of the document, constitutes a forgery-preventing safety element, since it clearly reveals the attempt at forgery, by modifying its arrangement on the document, and thus making the code no longer readable or being in any case removed from said document.
• Another object of the present invention is to provide a delible magnetic ink which, by virtue of its peculiar characteristics of execution, is capable of giving the greatest assurances of reliability and safety in use.
• Not least object of the present invention is to provide a delible magnetic ink which can have a very wide range of applications, especially in all those cases in which it is necessary to ensure, besides the authenticity of the document, also the fact that it has not been forged.
• a delible magnetic ink particularly for marking documents and the like characterized in that it comprises a mixture of water, gum arabic, colored pigment and finely ground magnetic material mixed with an easily hydratable vehicle.
• the delible magnetic ink contains magnetic particles obtained by taking ferrite (iron oxide) of the gamma type with an initial needle-shaped particle measuring 0.001 by 0.006 mm, with a 1/6 ratio, grinding it with a hyperfast colloidal mill with zirconia spheres, in a microsphere agitator of the Fryma type with a kinetic chamber, until the particles are reduced to a size of 0.004 mm with a 1/4 ratio.
• ferrite iron oxide
• the iron oxide which constitutes the magnetic particles thus obtained is then mixed with easily hydratable vehicles, such as for example glycerol, sorbitol and the like, which have the function in practice of creating, upon a chemical attack of the ink, a displacement of the particles of magnetic material and consequently a modification of the initial conditions which clearly reveal the occurrence of an attempt at forgery.
• easily hydratable vehicles such as for example glycerol, sorbitol and the like
• the magnetic ink is obtained by mixing 10/15% magnetic material, as previously described, with 10/15% colored pigment together with 10/15% water, 10/15% glycerol, 30/35% gum arabic and 5/10% mineral filler.
• the ink thus produced it is possible to print on documents codes which are magnetically detectable and can, for example, be constituted by a bar code with bars 0.08 mm wide spaced from one another by 0.04 mm, with the possibility of decoding by means of a reading head and a controlled-speed machine in order to obtain a bit sequence the peaks whereof are spaced by 0.12 mm and the individual bit has a distance of 0.08 mm between the positive peak and the negative peak.
• the positive peaks and the negative peaks are reduced and no longer have a distance of 0.08 mm but will arrive at a distance of 0.10 mm, consequently modifying the width of the interspace and consequently varying the reading conditions.
• the gum arabic allows an easy mechanical removal of the ink by acting either with a normal eraser or with scrapers or other similar elements.
• the delible magnetic ink according to the invention comprises, in a mixture, a non-polar solvent commonly termed high-boiling aliphatic solvent with a boiling interval comprised between 240 and 310 o C and with an aromatic compound content of less than 5% and with no polynuclear aromatic compounds.
• a non-polar solvent commonly termed high-boiling aliphatic solvent with a boiling interval comprised between 240 and 310 o C and with an aromatic compound content of less than 5% and with no polynuclear aromatic compounds.
• the solvent is added to a grinding vehicle which is constituted by phenolic resins or cresolformaldehyde, or possibly by maleic resins with a melting point between 150 and 170 o C, which are mixed with cross-linking unsaturated polyesters commonly termed alkyd resins, with an oil content between 65 and 80%.
• a grinding vehicle which is constituted by phenolic resins or cresolformaldehyde, or possibly by maleic resins with a melting point between 150 and 170 o C, which are mixed with cross-linking unsaturated polyesters commonly termed alkyd resins, with an oil content between 65 and 80%.
• the alkyd resin has the power of solubilizing the phenolic or maleic resin, whereas the non-polar aliphatic solvents are used so as to decrease the viscosity of the vehicle, bringing it all to a viscosity of approximately 500 poises, which in practice constitutes the ink base.
• the inks are substantially prepared according to a conventional method, by loading into a blade-fitted agitator the grinding vehicle obtained as described above, adding the organic pigments, derived from food-product dyes laked, i.e. coated, on barium salts, and the inorganic pigments, which constitute the magnetic material or finely ground ferrite.
• the inorganic pigments which constitute the magnetic material are preferably constituted by ferrite (F2O3) of the gamma type with an initial needle-like particle measuring 0.001 x 0.006 mm, thus with a 1/6 ratio; during the preparation of the inks, the organic pigments and the magnetic material are mixed until a 500-poise viscosity paste is obtained; said paste is refined in a three-cylinder refining unit until a grinding degree of less than 5 microns is obtained.
• F2O3 ferrite
• the preparation of the ink one uses 70 to 63% grinding vehicle, 10 to 12% organic pigment, 15 to 20% magnetic material, to which 5% aliphatic solvent is added so as to bring the viscosity of the ink to approximately 200 poises, possibly varying the addition of aliphatic solvent.
• the organic pigment used one obtains various colors, such as yellow, red, blue and green; the inks can furthermore be mixed perfectly with one another, so that it is possible to obtain all the further shades of color required.
• the inks thus obtained can be lithographed so as to obtain safety backgrounds, by means of wet offset or dry offset plates, with an extremely high fineness and printing definition.
• the inks as described above furthermore react to chemical agents, solvents or erasers, such as potassium permanganate ink-remover, ball-point pen ink-remover, ethyl alcohol CH3CH2OH, Cellosolve H2H5OCH2CH2OH, 10% sulphuric acid H2SO4, 15% hydrochloric acid HCl, 2% caustic soda NaOH, bleach (sodium hypochlorite) NaOCl, or possibly even to erasers, such as for example the erasers used to erase ball-point pens of the Replay type.
• chemical agents such as potassium permanganate ink-remover, ball-point pen ink-remover, ethyl alcohol CH3CH2OH, Cellosolve H2H5OCH2CH2OH, 10% sulphuric acid H2SO4, 15% hydrochloric acid HCl, 2% caustic soda NaOH, bleach (sodium hypochlorite) NaOCl, or possibly even to erase

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

Applications Claiming Priority (4)

Publications (2)

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Cited By (1)

Citations (6)

• 1991
  • 1991-06-19 EP EP19910110061 patent/EP0464474A3/en not_active Withdrawn

Patent Citations (6)

Non-Patent Citations (1)

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