Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/09—Colouring agents for toner particles
  • G03G9/0926—Colouring agents for toner particles characterised by physical or chemical properties

Definitions

• the present invention relates to a powder intended for the development of latent images, as well as to its manufacturing process.
• This powder finds more particularly, although not exclusively, its application in magnetic printing machines in which the printing of the characters is carried out without calling upon the impact of types of printing of the characters on a sheet of receiving paper.
• Printing machines of this type include a recording element consisting, for example most often, either of a rotating drum or an endless belt. On the surface of this element, sensitized zones, by magnetic means, can be formed. These areas, also called magnetic latent images, correspond to the characters to be printed. These latent images are then developed, that is to say made visible, using a powder developer which, deposited on the recording element, is only attracted by the sensitized zones of the latter. this. The application of this powder developer is carried out by an applicator device, of known type, in front of which the recording element passes. After which, the developer particles which have thus been deposited on the latent images are transferred to a support sheet, such as a sheet of paper for example, on which they are permanently fixed.
• a support sheet such as a sheet of paper for example
• Powder developers that are used in magnetic printing machines must meet many conditions. These developers must in fact be able not only to adhere to the magnetized zones of the recording element, but also to be transferred easily and entirely on the sheet of receiving paper with which they are then placed. contact. These developers must also be able to melt technically at a relatively low temperature, so that the temperature of their fixing device on the paper can be adjusted to a value such that the risks of ignition or carbonization of the paper are eliminated. However, these developers must not have too low a melting point, otherwise they will soften, which, by making them sticky, will make them adhere more to the recording element and thus prevent them from being transferred entirely to the paper. In addition, it is necessary that these developers do not generate an unpleasant odor or dangerous vapors when they undergo a fusion. In addition, they must be able to mix with a dye that is often forced to add to increase the contrast between the background color of the paper and that of the images on this paper.
• these powder developers consist of relatively fine solid particles, in order to produce good quality images on paper.
• these developers when they are melted, must neither spread on the paper, nor diffuse widely inside it, otherwise the images formed on this paper appear blurred.
• These powdery developers must also not be influenced by humidity. Finally, their properties should practically not undergo changes over time.
• This MIDAX toner due to its resins, is suitable for fixing to paper by cold pressure and not for fixing by infrared radiation or flash lamp as is the case in magnetography.
• These toners known from the prior art are totally unsuitable for magnetographic applications, since they do not have the properties explained above. Because they do not have the physicochemical properties necessary for magnetographic applications which are a certain coercivity to allow a good revelation, a sufficiently low conductivity, a well defined particle size, and the presence of a thinning agent and a lubricating agent, they would damage a magnetographic printer.
• a first object of the invention relates to a magnetographic powder for the development of latent images which makes it possible to increase the degree of security of the documents printed using this powder.
• the developing powder comprising fine dry black particles in daylight and associated with a pigment not visible in daylight incorporated to make the impression, obtained with this powder, luminescent under l action of ultraviolet (UV) radiation in any shade of color is characterized in that the dry particles each consist of a hard magnetic pigment formed of a magnetic oxide coated with a point-coating coating substance melting below 150 ° C, and one or more powdery fluidizing agents.
• Another object of the invention relates to a first method of manufacturing the aforementioned developing powder.
• Another object of the invention relates to a second method of manufacturing the aforementioned developing powder.
• This second method is characterized in that it consists, after having prepared a magnetic or magnetizable toner powder from organic resin of an optional bridging agent and hard magnetic pigment incorporated in the resin, in making a powder mixture dry from 0.01 to 30% by weight of the aforementioned luminescent pigments with a fluidizing agent, a lubricating agent and an antistatic and contrasting agent, which are usually incorporated at this stage.
• the fluidizing agent is a mineral powder or an oxide in the proportion of 0.01% to 10% by weight of mixture.
• the fluidizing agent is silica in the proportion of 0.01 to 10% by weight of the mixture.
• a lubricating agent consisting of a fluoropolymer in the proportion of 0.01% to 10% by weight of mixture.
• the lubricating agent is a polytetrafluoroethylene in the proportion of 0.01 to 10% by weight of the mixture.
• the antistatic and contrasting agent is a carbon black in the proportion of 0.01 to 10% by weight of the mixture.
• the proportion of magnetic particles is of the order of 1 to 90% and the proportion of resin is additionally of the order of 10 to 99% by weight of the mixture.
• the developing powder comprises very fine dry particles each consisting of a magnetic core formed by a hard magnetic pigment coated with a coating substance, this coating substance itself being formed from at least one associated organic resin. optionally with a bridging agent, for example of the silane or titanate type.
• the organic resin used in fusion on the order of 100 ° to 150 ° C.
• ketone resins for example a ketone-aldehyde, acrylic and methacrylic resins, acrylic and methacrylic copolymers, polyester resins and cellulose esters, resins styrene-acrylic, epoxy, polypropylene, polyethylene and olefin copolymers.
• Magnetic or magnetizable particles for example magnetic iron oxide, whose dimensions are generally less than five microns, are also incorporated into the resin. It should be noted, however, that other ferromagnetic products, such as alloys and oxides of nickel, iron or cobalt, or chromium, or even ferrites, can also be used.
• the quantity of magnetic particles which must be added to the resin in order to obtain a powder of satisfactory development represents from 1 to 90% of the total weight of the final powder.
• the magnetic powder is dispersed in a molten mixture of the resin (s) and optionally of the bridging agent.
• the molten mixture is then allowed to cool until it solidifies in the mass. After which, it is ground into particles which are classified according to their average dimensions of approximately 5 to 40 microns.
• a small amount of fluoropolymer resin is then added to the powder particles thus obtained, this amount representing approximately from 0.001 to 10% of the total weight of the final developing powder.
• Powdered fluidizing agents can also be added to the dry powder particles to improve their flowability.
• a suitable thinning agent can be, for example, divided colloidal silica. This incorporation is carried out in a proportion of the order of 0.01 to 10% of the total weight of the final developing powder.
• carbon black particles can be added in a proportion of between 0.01 and 10% of the total weight of the final developing powder.
• These carbon black particles can be of any of the known types. It should be noted here that this addition of carbon black can be carried out indifferently, either during the operation of melting the organic resin, or after the operations of grinding the solid mixture resulting from the incorporation into this resin of the agent bridging and magnetic particles.
• the hard magnetic oxide particles which are incorporated into the organic resin are either permanently magnetized particles or particles of a material capable of being permanently magnetized.
• the magnetization of these particles can be carried out, either during the incorporation of these particles into the organic resin, or after the grinding operations mentioned above.
• this magnetization or pre-magnetization operation is carried out using a constant magnetic induction whose value is between 10 -2 and 2 Teslas.
• this magnetic induction has a value of the order of 0.2 Tesla.
• the following examples are given to illustrate the preferred embodiments of developing powders according to the invention.
• the proportions are understood by weight of the overall composition of the developing powder.
• the order of addition of the constituents which corresponds to the order of quotation and the quantities play a preponderant role in obtaining a toner having the desired properties.
• the magnetite marketed by Magnox under the reference B 350 or that marketed by Bayer under the reference MAG1730 are "hard" magnetic oxides, that is to say having a coercive force greater than 150 Oersteds, so as to obtain forces magnetic enough to reveal the latent image created on the recording element.
• a developing powder is prepared with the following products according to the first process known as "hot”: WITCO EURELON 913 polyamide resin 40% HULS SK Aldehyde Ketone Resin 20% Magnetite MAGNOX B 350 30% Silane A 187 by UNION CARBIDE 2% Luminescent pigment FLUO YELLOW PJ / UV by PETREL 4% Silica CAB-O-SIL M 5 by CABOT CORPORATION 1% ALGOFLON L 206 Polytetrafluoroethylene from MONTEDISON 2% CABOT CORPORATION VULCAN XC 72 R Carbon Black 1%
• this mixture is heated, for example in a twin screw extruder, so as to melt the two resins and, after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then crushed and reduced to fine pulverulent particles using a very fine grinding device such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the particles thus separated are then dry mixed in a rapid mixer first with 1% by weight of colloidal silica, then with 1% by weight of polytetrafluoroethylene, and finally with 1% of carbon black.
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener, has a very accentuated yellow color under the action of UV radiation.
• a developing powder is prepared according to the second so-called cold process with the following products WITCO EURELON 913 polyamide resin 30% HULS SK Aldehyde Ketone Resin 20% Magnetite MAGNOX B 350 40% TYZOR TPT Titanate by DU PONT 2% CAB-O-SIL M 5 silica from CABOT CORPORATION 1% PETREL FLUO YELLOW PJ / UV luminescent pigment 4% ALGOFLON L 206 Polytetrafluoroethylene from MONTEDISON 2% CABOT CORPORATION VULCAN XC 72 R Carbon Black 1%
• this mixture After placing the polyamide resin, the ketone-aldehyde resin, the titanate, the magnetic oxide in a slow mixer and thus obtaining a fairly homogeneous mixture, this mixture is heated, for example in a twin screw extruder, so as to melt these two resins, and after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then crushed and reduced to fine pulverulent particles using a very fine grinding apparatus such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the particles thus separated are then dry mixed in a rapid mixer first with 1% by weight of colloidal silica then with 4% by weight of luminescent pigment then with 2% by weight of polytetrafluoroethylene (PTFE), and finally with 1 % carbon black.
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener, has a very accentuated yellow color under the action of UV radiation.
• a developing powder is prepared according to the second so-called cold process with the following products
• this mixture After placing the polyamide resin, the ketone-aldehyde resin, the silane, the magnetic oxide in a slow mixer and thus obtaining a fairly homogeneous mixture, this mixture is heated, for example in a twin screw extruder, so as to melt these two resins, and after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then crushed and reduced to fine pulverulent particles using a very fine grinding apparatus such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the particles thus separated are then mixed dry and in the following order in a rapid mixer first with 1% by weight of silica then with 10% by weight of luminiscent pigment then with 2% by weight of polytetrafluoroethylene (PTFE) and finally with 1% by weight of carbon black.
• PTFE polytetrafluoroethylene
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener, has a very accentuated yellow color under the action of UV radiation.
• this mixture After placing the polyamide resin, the ketone-aldehyde resin, the silane, the magnetic oxide in a slow mixer and thus obtaining a fairly homogeneous mixture, this mixture is heated, for example in a twin screw extruder, so as to melt these two resins, and after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then crushed and reduced to fine pulverulent particles using a very fine grinding apparatus such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the silica then the carbon then the luminescent pigment and finally the PTFE are, as in Example 2, added in the order and the proportions given in the fast mixer.
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener has a very accentuated blue color under the action of UV radiation.
• this mixture After placing the styrene-acrylic resin, the magnetic oxide, the silane in a slow mixer and thus obtaining a fairly homogeneous mixture, this mixture is heated, for example in a twin screw extruder, so as to melt these two resins, and after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then ground and reduced to fine powdery particles using a very fine grinding device such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the silica and then the luminescent pigment are, as in Example 4, added in the order and the proportions indicated in the rapid mixer, before the P.T.F.E. and carbon.
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener, has a very accentuated green color under the action of UV radiation.
• a developing powder is prepared according to the second so-called cold process with the following products PLIOTONE PTR 6953 styrene-acrylic resin by GOODYEAR 40% BAYER MAG 1730 magnetite 50% Silane A 174 by UNION CARBIDE 2% CAB-O-SIL M 5 silica from CABOT CORPORATION 1% INVISIBLE FLUO ROSE 21 luminescent pigment by PETREL 5% Polyetrafluoroethylene MP 1000 from DU PONT 1% DEGUSSA CORAX L Carbon Black 1%
• the powder particles consisting of a mixture of styrene-acrylic resin, magnetic oxide, silane, silica then the luminescent pigment, then the PTFE, and finally the carbon are added in the rapid mixer in the order and in the proportions indicated.
• a development powder is thus obtained which, after printing and fusing on a paper without optical brightener, has a very accentuated pink color under the action of UV radiation.
• a developing powder is prepared according to the second so-called cold process with the following products WITCO EURELON 913 polyamide resin 40% Huls SK Aldehyde Ketone Resin 19% Magnetite MAGNOX B 350 30 % Silane A 187 by UNION CARBIDE 2% CAB-O-SIL M 5 silica from CABOT CORPORATION 1% CAROT CORPORATION VULCAN XC 72 R Carbon Black 2% Lumenux Blue Luminescent Pigment CD729 by RIEDEL by HAEN 3% DU PONT Polytetrafluoroethylene MP 1600 3%
• this mixture After placing the polyamide resin, the ketone-aldehyde resin, the silane, the magnetic oxide in a slow mixer and thus obtaining a fairly homogeneous mixture, this mixture is heated, for example in a twin screw extruder, so as to melt these two resins, and after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then crushed and reduced to fine pulverulent particles using a very fine grinding apparatus such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the particles thus separated are then mixed dry and in the following order in a rapid mixer first with 1% by weight of silica then with 2% by weight of carbon, then with 3% by weight of luminiscent pigment and finally with 3% by weight of PTFE
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener, has a very accentuated blue color under the action of UV radiation.
• a developing powder is prepared according to the second so-called hot process with the following products
• this mixture is heated, for example in a twin screw extruder, so as to melt the two resins and, after fusion, obtain a homogeneous molten mixture.
• the mixture thus formed is then crushed, then crushed and reduced to fine pulverulent particles using a very fine grinding device such as an air jet mill.
• the powder is then sorted, for example by means of an air selector, so as to separate the powder particles whose dimensions are between 5 and 40 microns.
• the particles thus separated are then dry mixed with silica, with carbon then with PTFE, in the order and the proportions indicated in the example, in a fast mixer.
• a development powder is thus obtained which, after printing and melting on a paper without optical brightener, has a very accentuated yellow color under the action of UV radiation.
• a developing powder is prepared according to the second so-called hot process with the following products KAO CORPORATION Binder Z-2 polyester resin 50% Magnetite MAGNOX B 350 30 % PETREL FLUO YELLOW PJ / UV Luminiscent Pigment 15% CAB-O-SIL M 5 silica from CABOT CORPORATION 1% CABOT CORPORATION VULCAN XC 72 R Carbon Black 2% DU PONT Polytetrafluoroethylene MP 1600 2%
• Example 8 The same process as for Example 8 is applied with only a variation in the proportions depending on the pigment used.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Developing Agents For Electrophotography (AREA)

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Citations (6)

• 1994
  • 1994-12-09 FR FR9414819A patent/FR2728086B1/fr not_active Expired - Fee Related
• 1995
  • 1995-12-08 EP EP95402766A patent/EP0716352A1/de not_active Withdrawn

Patent Citations (7)

Non-Patent Citations (1)

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