EP0931666B1 - Procede et appareil d'impression par coagulation electrique - Google Patents

Procede et appareil d'impression par coagulation electrique Download PDF

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Publication number
EP0931666B1
EP0931666B1 EP97950435A EP97950435A EP0931666B1 EP 0931666 B1 EP0931666 B1 EP 0931666B1 EP 97950435 A EP97950435 A EP 97950435A EP 97950435 A EP97950435 A EP 97950435A EP 0931666 B1 EP0931666 B1 EP 0931666B1
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EP
European Patent Office
Prior art keywords
positive electrode
ink
active surface
electrode active
electrocoagulation printing
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EP97950435A
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German (de)
English (en)
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EP0931666A1 (fr
EP0931666A4 (fr
Inventor
Adrien Castegnier
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Artience Co Ltd
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Toyo Ink Mfg Co Ltd
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Priority claimed from CA 2194128 external-priority patent/CA2194128C/fr
Priority claimed from CA 2194130 external-priority patent/CA2194130C/fr
Application filed by Toyo Ink Mfg Co Ltd filed Critical Toyo Ink Mfg Co Ltd
Publication of EP0931666A1 publication Critical patent/EP0931666A1/fr
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C1/00—Forme preparation
    • B41C1/10—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme
    • B41C1/105—Forme preparation for lithographic printing; Master sheets for transferring a lithographic image to the forme by electrocoagulation, by electro-adhesion or by electro-releasing of material, e.g. a liquid from a gel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B41M5/20—Duplicating or marking methods; Sheet materials for use therein using electric current

Definitions

  • the present invention pertains to improvements in the field of electrocoagulation printing. More particularly, the invention relates to a method of increasing coagulation efficiency and improving optical density of the printed matter during electrocoagulation printing.
  • the electrocoagulation printing ink which is injected into the gap defined between the positive and negative electrodes consists essentially of a solution or a dispersion containing an electrolytically coagulable polymer, a liquid medium, a soluble electrolyte and a coloring agent.
  • the coloring agent used is a pigment
  • a dispersing agent is added for uniformly dispersing the pigment into the ink.
  • any remaining non-coagulated ink is removed from the surface of the positive electrode, for example, by scraping the surface with a soft rubber squeegee, so as to fully uncover the colored, coagulated ink which is thereafter transferred onto the substrate.
  • the surface of the positive electrode is thereafter cleaned by means of a plurality of rotating brushes and a cleaning liquid to remove any residual coagulated ink and oily substance adhered to the surface of the positive electrode.
  • the negative and positive electrodes, the oily substance coating device, ink injector, rubber squeegee and positive electrode cleaning device are arranged to define a printing unit and several printing units each using a coloring agent of different color are disposed in tandem relation to produce several differently colored images of coagulated ink which are transferred at respective transfer stations onto the substrate in superimposed relation to provide the desired polychromatic image.
  • the printing units can be arranged around a single roller adapted to bring the substrate into contact with the dots of colored, coagulated ink produced by each printing unit, and the substrate which is in the form of a continuous web is partially wrapped around the roller and passed through the respective transfer stations for being imprinted with the differently colored images in superimposed relation.
  • the electrocoagulation printing method described in the aforementioned US Patent No. 4,895,629 is carried out at room temperature which is generally about 25 - 30°C.
  • the inventor has observed that the maximum optical density of the dots of colored, coagulated ink formed on the positive electrode active surface and then printed on the substrate, that could be reached with an ink having a temperature of 30°C and with a voltage of 55 volts applied for 4 microseconds between the negative and positive electrodes, was 1.60.
  • the concentration of the electrolyte in the ink was reduced to control the gas generation, a reduction in the optical density of the coagulated ink was observed.
  • the inventor has observed that most of the papers used as substrates for electrocoagulation printing had to be humidified with a mist of water in order to prevent a part of the dots of colored, coagulated ink from remaining on the positive electrode when being transferred from the positive electrode active surface onto the paper. Without paper humidification, only about 60 - 70% of the colored, coagulated ink were transferred onto dry paper, a substantial amount of the coagulated ink remaining on the positive electrode surface.
  • an improved electrocoagulation printing method comprising the steps of:
  • an electrocoagulation printing apparatus for carrying out the improved method of this invention, comprising:
  • an improved electrocoagulation printing method comprising the steps of:
  • Maintaining the positive electrode active surface and the ink at the temperature of from about 35°C to about 60°C causes an increase in the electric conductivity of the ink and a release of metal ions from the positive electrode active surface into the ink in step (a). Thereby the metal ions are released in a quantity sufficient to increase optical density of the coagulated ink, and a coagulation efficiency in step (a) is increased.
  • a break down of passive oxide layer occurs easily in the presence of electrolyte anions, such as Cl - , Br - and I - , there being a gradual oxygen displacement from the passive oxide layer by the halide anions and a displacement of absorbed oxygen from the metal surface by the halide anions.
  • the velocity of passive oxide layer breakdown once started, increases explosively by an electrical energizing. There is thus formation of a soluble metal halide at the metal surface. In other words, a local dissolution of the passive oxide layer at the breakdown sites, which releases metal ions into the electrolyte solution.
  • a positive electrode made of stainless steel or aluminum is utilized in inventor's electrocoagulation printing method, dissolution of the passive oxide layer on such a positive electrode generates Fe 3+ or Al 3+ ions. These trivalent ions then initiate coagulation of the ink.
  • the method according to the invention enables one to obtain dots of colored, coagulated ink having an optical density of 1.70.
  • Figure 1 shows a schematic illustration of the electrocoagulation printing apparatus (1) embodying the present invention.
  • Figure 2 shows a schematic illustration of an embodiment of the heating unit for the positive cylindrical electrode.
  • the positive cylindrical electrode is heated and maintained at the temperature of from about 35°C to about 60°C by carrying heated liquid or gas through a vent located on the central longitudinal axis of the positive cylindrical electrode.
  • Figure 3 shows a schematic illustration of another embodiment of the heating unit for heating the electrocoagulation printing ink before supplying it onto the positive electrode active surface.
  • the ink is heated and maintained at the temperature of from about 35°C to about 60°C when passing through this apparatus.
  • Figure 4 shows a schematic illustration of further embodiment of the heating unit for heating the positive electrode active surface from the outside.
  • Figure 5 shows a schematic illustration of further embodiment of the heating unit for heating the positive electrode by cleaning liquid. That is, the positive cylindrical electrode is heated by heating the cleaning liquid and directing jets thereof against the positive electrode.
  • Figure 6 shows a cross sectional schematic illustration of an embodiment of cleaning unit for cleaning the positive electrode active surface to remove therefrom any remaining coagulated ink, comprising a jet means for directing jets of the cleaning liquid against the positive electrode active surface.
  • Figure 7 is a graph showing the variation of the ink conductivity as a function of the temperature thereof. As shown in this figure, the conductivity of the ink increases with an increase in the temperature thereof.
  • Figure 8 is a graph showing an example of the connection between the temperature of the positive electrode active surface as well as of the ink and the optical density, indicating the increase of the optical density by the increase in the temperature up to 35°C and above.
  • steps (a) and (b) of the above electrocoagulation printing method are repeated several times to define a corresponding number of printing stages arranged at predetermined locations along the aforesaid path and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated ink which are transferred at the respective transfer positions onto the substrate in superimposed relation to provide a polychromatic image.
  • the positive electrode used can be in the form of a moving endless belt as described in US Patent No. 4,661,222, or in the form of a revolving cylinder as described in US Patent No. 4,895,629 or in US Patent No. 5,538,601.
  • the printing stages are arranged around the positive cylindrical electrode.
  • the positive electrode active surface and the ink are maintained at a temperature of about 35 - 60°C by heating the positive electrode active surface and applying the ink on the heated electrode surface to cause a transfer of heat therefrom to the ink.
  • step (a) of the above electrocoagulation printing method is carried out by:
  • suitable metals from which the positive and negative electrodes can be made are stainless steel, platinum, chromium, nickel, tin and aluminum.
  • the positive electrode is preferably made of stainless steel, aluminum or tin so that upon electrical energization of the negative electrodes, dissolution of the passive oxide layer on such an electrode generates trivalent ions which then initiate coagulation of the ink.
  • the gap which is defined between the positive and negative electrodes can range from about 50 ⁇ m to about 100 ⁇ m, the smaller the electrode gap the sharper are the dots of coagulated ink produced. Where the electrode gap is of the order of 50 ⁇ m, the negative electrodes are the preferably spaced from one another by a distance of about 75 ⁇ m.
  • Olefinic substances are preferably used as an oily substance for being used to coat the surface of the positive electrode in step (a)(ii).
  • suitable olefinic substances include unsaturated fatty acids such as arachidonic acid, linoleic acid, linolenic acid, oleic acid and palmitoleic acid and unsaturated vegetable oils such as corn oil, linseed oil, olive oil, peanut oil, soybean oil and sunflower oil.
  • the olefinic substance can be applied onto the positive electrode active surface in the form of an oily dispersion containing the metal oxide as dispersed phase.
  • suitable metal oxides include aluminum oxide, ceric oxide, chromium oxide, cupric oxide, magnesium oxide, manganese oxide, titanium dioxide and zinc oxide.
  • the amount of metal oxide may range from about 15 to about 40% by weight, based on the total weight of the dispersion.
  • a particularly preferred dispersion contains about 75 wt.% of oleic acid or linoleic acid and about 25 wt.% of chromium oxide. Operating at a temperature of about 35 - 60°C enables one to lower the concentration of metal oxide in the oily dispersion and thus to reduce wear of the positive electrode active surface.
  • the oily substance is advantageously applied onto the positive electrode active surface by providing a distribution roller extending parallel to the positive cylindrical electrode and having a peripheral coating comprising an oxide ceramic material, applying the oily substance onto the ceramic coating to form on a surface thereof a film of the oily substance uniformly covering the surface of the ceramic coating, the film of oily substance breaking down into micro-droplets having substantially uniform size and distribution, and transferring the micro-droplets from the ceramic coating onto the positive electrode active surface.
  • a distribution roller having a ceramic coating comprising an oxide ceramic material enables one to form on a surface of such a coating a film of the oily substance which uniformly covers the surface of the ceramic coating and thereafter breaks down into micro-droplets having substantially uniform size and distribution.
  • the micro-droplets formed on the surface of the ceramic coating and transferred onto the positive electrode active surface generally have a size ranging from about 1 to about 5 ⁇ m.
  • a particularly preferred oxide ceramic material forming the aforesaid ceramic coating comprises a fused mixture of alumina and titania.
  • a mixture may comprise about 60 to about 90 weight % of alumina and about 10 to about 40 weight % of titania.
  • the oily substance is applied onto the ceramic coating by disposing an applicator roller parallel to the distribution roller and in pressure contact engagement therewith to form a first nip, and rotating the applicator roller and the distribution roller in register while feeding the oily substance into the first nip, whereby the oily substance upon passing through the first nip forms a film uniformly covering the surface of the ceramic coating.
  • the micro-droplets are advantageously transferred from the distribution roller to the positive electrode by disposing a transfer roller parallel to the distribution roller and in contact engagement therewith to form a second nip, positioning the transfer roller in pressure contact engagement with the positive electrode to form a third nip, and rotating the transfer roller and the positive electrode in register for transferring the micro-droplets from the distribution roller to the transfer roller at the second nip and thereafter transferring the micro-droplets from the transfer roller to the positive electrode at the third nip.
  • a transfer roller parallel to the distribution roller and in contact engagement therewith to form a second nip positioning the transfer roller in pressure contact engagement with the positive electrode to form a third nip, and rotating the transfer roller and the positive electrode in register for transferring the micro-droplets from the distribution roller to the transfer roller at the second nip and thereafter transferring the micro-droplets from the transfer roller to the positive electrode at the third nip.
  • the applicator roller and the transfer roller are each provided with a peripheral covering of a resilient material which is resistant to attack by the oily substance, such as a synthetic rubber material.
  • a resilient material which is resistant to attack by the oily substance, such as a synthetic rubber material.
  • a polyurethane having a Shore A hardness of from about 50 to about 70 in the case of the applicator roller, or a Shore A hardness of from about 60 to about 80 in the case of the transfer roller.
  • step (a)(ii) of the electrocoagulation printing method of the invention is preferably carried out by providing first and second distribution rollers extending parallel to the positive cylindrical electrode and each having a peripheral coating comprising an oxide ceramic material, applying the oily substance onto the ceramic coating of the first distribution roller to form on a surface thereof a film of the oily substance uniformly covering the surface of the ceramic coating, the film of oily substance at least partially breaking down into micro-droplets having substantially uniform size and distribution, transferring the at least partially broken film from the first distribution roller to the second distribution roller so as to cause the film to substantially completely break on the ceramic coating of the second distribution roller into the desired micro-droplets having substantially uniform size and distribution, and transferring the micro-droplets from the
  • the oily substance is applied onto the ceramic coating of the first distribution roller by disposing an applicator roller parallel to the first distribution roller and in pressure contact engagement therewith to form a first nip, and rotating the applicator roller and the first distribution roller in register while feeding the oily substance into the first nip, whereby the oily substance upon passing through the first nip forms a film uniformly covering the surface of the ceramic coating.
  • the at least partially broken film of oily substance is transferred from the first distribution roller to the second distribution roller and the micro-droplets are transferred from the second distribution roller to the positive electrode by disposing a first transfer roller between the first distribution roller and the second distribution roller in parallel relation thereto, positioning the first transfer roller in pressure contact engagement with the first distribution roller to form a second nip and in contact engagement with the second distribution roller to form a third nip, rotating the first distribution roller and the first transfer roller in register for transferring the at least partially broken film from the first distribution roller to the first transfer roller at the second nip, disposing a second transfer roller parallel to the second distribution roller and in pressure contact engagement therewith to form a fourth nip, positioning the second transfer roller in pressure contact engagement with the positive electrode to form a fifth nip, and rotating the second distribution roller, the second transfer roller and the positive electrode in register for transferring the at least partially broken film from the first transfer roller to the second distribution roller at the third nip, then transferring the micro-droplets
  • the applicator roller, first transfer roller and second transfer roller are each provided with a peripheral covering of a resilient material which is resistant to attack by the oily substance.
  • the oily substance-coated positive active surface is preferably polished to increase the adherence of the micro-droplets onto the positive electrode active surface, prior to step (a)(iii).
  • a rotating brush provided with a plurality of radially extending bristles made of horsehair and having extremities contacting the surface of the positive electrode. The friction caused by the bristles contacting the surface upon rotation of the brush has been found to increase the adherence of the micro-droplets onto the positive electrode active surface.
  • Step (a)(iii) of the above electrocoagulation printing method is advantageously carried out by continuously injecting the ink onto the positive electrode active surface from a ink injection means disposed adjacent the electrode gap and allowing the ink to flow along the positive electrode active surface, the ink being thus carried by the positive electrode upon rotation thereof to the electrode gap to fill same.
  • excess ink flowing off the positive electrode active surface is collected and the collected ink is recirculated back to the ink injection means.
  • the electrocoagulation printing ink being electrolytically coagulable contains at least an electrolytically coagulable polymer, a coloring agent, a liquid medium and a soluble electrolyte.
  • the polymer generally used has a weight-average molecular weight between about 10,000 and about 1,000,000, preferably between 100,000 and 600,000.
  • the polymer include natural polymers such as albumin, gelatin, casein and agar, and synthetic polymers such as polyacrylic acid and polyacrylamide.
  • a particularly preferred polymer is an anionic copolymer of acrylamide and acrylic acid having a molecular weight of about 250,000 and sold by Cyanamid Inc. under the trade name ACCOSTRENGTH 86.
  • the polymer is preferably used in an amount of about 6.5 to about 12% by weight, and more preferably in an amount of about 7 to about 10% by weight, based on the total weight of the ink.
  • Preferred electrolytes include alkali metal halides, such as lithium chloride, sodium chloride and potassium chloride, and also alkaline earth metal halides, such as calcium chloride. Potassium chloride is particularly preferred.
  • the electrolyte is preferably used in an amount of about 4.5 to about 10% by weight, based on the total weight of the ink. Incidentally, less electrolyte may be required at a temperature of about 35 - 60°C than at room temperature in order to counterbalance the increase in the ink conductivity at 35 - 60°C.
  • the coloring agent can be a dye or a pigment. Examples of suitable dyes include indigo dye, azo dye, anthraquinone dye, fluoran dye, dioxazine dye, oxazine dye, phthalocyanine dye, etc.
  • Suitable pigments include organic pigments such as azo pigment, phthalocyanine pigment, anthraquinone pigment, dioxazine pigment, thioindigo pigment, perynone pigment, perylene pigment, isoindolinon pigment and azomethine pigment, and inorganic pigments such as carbon black.
  • a dispersing agent is added for uniformly dispersing the pigment into the ink.
  • Preferred dispersing agents include the anionic dispersing agent; a metal salt of naphthalenesulfonic acid-formaldehyde condensation product.
  • the pigment is preferably used in an amount of about 6.5 to about 12% by weight, and the dispersing agent in an amount of about 0.4 to about 6% by weight, based on the total weight of the ink.
  • Water is preferably used as the liquid medium for dissolving or dispersing the aforesaid polymer, coloring agent and electrolyte to provide the desired ink.
  • any remaining non-coagulated ink is removed from the positive electrode active surface, for example, by scraping the surface with a soft rubber squeegee, so as to fully uncover the colored, coagulated ink.
  • the non-coagulated ink thus removed is collected and mixed with the collected ink, and the collected non-coagulated ink in admixture with the collected ink is recirculated back to the aforesaid ink injection means.
  • the optical density of the dots of colored, coagulated ink may be varied by varying the voltage and/or pulse duration of the pulse-modulated signals applied to the negative electrodes.
  • the substrate is in the form of a continuous web.
  • Step (b) is preferably carried out by providing at each transfer position a pressure roller extending parallel to the positive cylindrical electrode and in pressure contact engagement therewith to form a nip and permit the pressure roller to be driven by the positive electrode upon rotation thereof, and guiding the web so as to pass through the nip.
  • the pressure roller is provided with a peripheral covering a synthetic rubber material such as a polyurethane having a Shore A hardness of about 95.
  • a polyurethane covering with such a hardness has been found to further improve transfer of the colored, coagulated ink from the positive electrode active surface onto the substrate.
  • the pressure exerted between the positive electrode and the pressure roller preferably ranges from about 50 to about 100 kg/cm 2 .
  • the positive electrode active surface is generally cleaned to remove therefrom any remaining coagulated ink.
  • the positive electrode is rotatable in a predetermined direction and any remaining coagulated ink is removed from the positive electrode active surface by providing an elongated rotatable brush extending parallel to the longitudinal axis of the positive electrode, the brush being provided with a plurality of radially extending bristles made of horsehair and having extremities contacting the positive electrode active surface, rotating the brush in a direction opposite to the direction of rotation of the positive electrode so as to cause the bristles to frictionally engage the positive electrode active surface, and directing jets of cleaning liquid under pressure against the positive electrode active surface, from either side of the brush.
  • the positive electrode active surface and the ink are preferably maintained at a temperature of about 35 - 60°C by heating the cleaning liquid to thereby heat the positive electrode active surface upon contacting same and applying the ink on the heated electrode surface to cause a transfer of heat therefrom to the ink.
  • Fig.1 shows an outline of an electrocoagulation printing apparatus 1 improved by the present invention.
  • the electrocoagulation printing apparatus 1 includes a base plate 5 supported by a plurality of legs 3.
  • a plurality of frames 7 are uprightly extended in a vertical direction.
  • a pair of vertical plates 9 are provided on upper portion of the frames 7, and a cylindrical positive electrode 11 which is rotatable by a drive motor (not shown) is sandwiched between both the vertical plates 9.
  • the positive electrode 11 is extended perpendicularly with respect to a paper surface of Fig.1, and includes a positive electrode active surface.
  • the electrocoagulation printing apparatus 1 comprises: a coating means 13 for coating the positive electrode active surface along the positive electrode 11 with an oily substance to form micro-droplets of the oily substance on the positive electrode active surface; an ink injection means 15 for supplying electrocoagulation printing ink to the positive electrode; a printing head 19 having negative electrodes 17 for forming, on the positive electrode active surface, a plurality of dots of colored, coagulated ink representing a desired image; and removing means 21 such as a squeegee for removing non-coagulated ink from the positive electrode active surface.
  • a pressure roller 23 is further provided as means for bringing a substrate W and the plurality of dots of colored, coagulated ink representing the desired image on the obtained positive electrode active surface into contact with each other to transfer the colored, coagulated ink onto the substrate from the positive electrode active surface, thereby print the image onto the substrate.
  • Cleaning means 25 is provided below the positive electrode 11 for cleaning the positive electrode active surface to remove all the remaining coagulated ink from the positive electrode active surface.
  • the micro-droplets of the oily substance is applied, by the coating means 13, onto the active surface of the rotating positive electrode 11 and then, the ink is supplied between the negative electrodes 17 and the positive electrode 11 of the printing head 19 by the ink injection means 15.
  • the supplied ink is coagulated by applying voltage between the electrodes to form dots of coagulated ink, and non-coagulated ink which was not coagulated is removed from the positive electrode active surface by the squeegee 21.
  • the electrocoagulation printing apparatus is further characterized in that heating means is provided for maintaining the positive electrode active surface and the ink at a temperature ranging from about 35°C to about 60°C.
  • the heating means heats, e.g., the positive electrode active surface, supplies the ink onto the heated positive electrode, and transfer the heat from the positive electrode active surface to the ink, thereby to maintain the positive electrode active surface and the ink at the temperature ranging from about 35°C to about 60°C.
  • Fig.2 shows one example of the heating means. Referring to Fig.2, the heating means 30 injects heated liquid or gas T from a hole 31 formed on the central axis of the rotating cylindrical positive electrode 11, and discharge the same from a hole 33 formed on the central axis of the electrode 11 through an interior of the cylindrical positive electrode, thereby to heat the positive electrode active surface from inside to maintain it at the temperature ranging from about 35°C to about 60°C.
  • the ink supplied onto the heated positive electrode active surface by the ink injection means is heated on the positive electrode active surface and is maintained at the temperature ranging from about 35°C to about 60°C.
  • the reference number 35 denotes a liquid medium accumulated in the cylindrical positive electrode when a liquid medium is used as a heating medium.
  • the ink is heated not only by the positive electrode active surface as described above, but also by the ink itself. This can be achieved, e.g., by heating the ink using an apparatus as shown in Fig.3, and by introducing the heated ink onto the positive electrode active surface through the ink injection means.
  • an ink heating apparatus 40 shown in Fig.3 an ink I introduced from an inlet port 43 to a thermostat 41 is heated up to a predetermined temperature, and is discharged from an outlet port 45 and is introduced to the ink injection means.
  • the positive electrode active surface it is possible to heat the positive electrode active surface from outside. That is, by directing the heated liquid or gas against the positive electrode active surface, the positive electrode active surface is heated to heat the ink, thereby to maintain the positive electrode active surface and the ink at the temperature ranging from about 35°C to about 60°C.
  • FIG.4 shows an example of the heating means for heating the positive electrode active surface from outside.
  • a heating means 50 is heated by a heating apparatus 53 such as an immersion heater in a water tank 51, and this is achieved by circulating, by a high pressure pump 55, water whose temperature is maintained at a constant value.
  • Warm water circulated through a delivery pipe 56 is directed against the cylindrical positive electrode 11 by jetting means 57 to heat the positive electrode active surface, and is returned into the water tank 51 through an outlet port 58 and a return pipe 59.
  • the heating means may be provided alone, but it is more preferable to combine it with cleaning means.
  • Fig.5 shows an example for heating the positive electrode by cleaning liquid.
  • the electrocoagulation printing apparatus 1 includes the heating means 50 for heating the positive electrode active surface from outside.
  • the cleaning liquid is heated and such cleaning liquid is sent to the cleaning means 25 and directed against the positive electrode surface, thereby to heat the surface of the positive electrode 11.
  • the heated cleaning liquid is sent into a cleaning unit from the delivery pipe 56 by the high pressure pump 55, and is circulated through the return pipe 59.
  • Fig.6 is a cross section showing the outline of the cleaning means 25 which cleans the positive electrode active surface and removes all the remaining coagulated ink from the positive electrode active surface.
  • the cleaning means 25 is structured by: an elongated rotatable brush 61 extending parallel to the longitudinal axis of the cylindrical positive electrode 11 rotatable in a predetermined direction, the brush being provided with a plurality of radially extending bristles 63 having extremities contacting the positive electrode active surface 65, and being rotatable in a direction opposite to the direction of rotation of the positive electrode 11 so as to cause the bristles 63 to frictionally engage the positive electrode active surface 65; and jetting means 57, 57' for directing jets of cleaning liquid under pressure against the positive electrode active surface from one side or both sides of the brush.
  • Each of the jetting means 57, 57' extends in parallel to the central axis of the positive electrode 11, and includes a pipe 69 having a plurality of nozzles 67 which are separated from one another.
  • the pipe 69 is coupled to the high pressure pump 55 though a tube 71.
  • the brush 61 rotates around the shaft 62 in a direction opposite from the rotational direction of the positive electrode 11, and the bristles 63 scrub the positive electrode active surface 65 to clean the positive electrode active surface together with the jet of the cleaning liquid.
  • the cleaning liquid is heated, and the heated cleaning liquid is directed against the positive electrode active surface to heat the positive electrode active surface, and the ink is supplied to the heated positive electrode active surface, so that the heat is transferred from the positive electrode active surface to the ink and the positive electrode active surface and the ink can be maintained at the temperature ranging from about 35°C to about 60°C.
  • the cleaning liquid directed against the positive electrode is once accumulated in a tub 73 in the apparatus, and overflowed from a drain tube 75, and returned into the water tank 51 through the valve 77 for circulation.
  • Excessive cleaning liquid remaining on the positive electrode active surface 65 is removed therefrom by a squeegee roller 81 or a squeegee blade (not shown) which rotates in a direction opposite to the positive electrode 11, and a surface of the squeegee roller 81 is continuously cleaned by a brush 83 which rotates in a direction opposite to the squeegee roller 81.
  • the squeegee roller 81 and the brush 83 are separated from the brush 61 by a partition 85.
  • the reference number 79 denotes a discharge pipe which discharges the cleaning liquid and which is adjusted by a valve 77.
  • the above described heating means should not be limited to a single means, and a plurality of heating means can be combined together.
  • a plurality of heating means can be employed to heat the positive electrode from inside and at the same time, to heat the positive electrode also from outside by the cleaning liquid.
  • means for directly heating the ink can also be employed.
  • electrocoagulation printing ink there was prepared a dispersion ink including: 8.8 weight % of carbon black as coloring agent; 8.8 weight % of polyacrylamide resin (weight-average molecular weight: 250,000) as electrolytically coagulable polymer; 8.8 weight % of potassium chloride as soluble electrolyte; and water as liquid medium.
  • Fig.5 shows the used electrocoagulation printing machine.
  • the cleaning liquid was heated by a heating apparatus disposed in a cleaning liquid tank, such heated cleaning liquid was jetted against the positive electrode, thereby to heat the positive electrode active surface and the ink to a predetermined temperature.
  • oily substance for forming micro-droplets of the oily substance on the positive electrode active surface there was used oleic acid in which about 25 weight % of metal oxide (chromium oxide) was dispersed.
  • substrate a piece of Japanese newspaper was used.
  • a voltage of 40 volts was applied between the electrodes for a predetermined time period, and a test pattern was printed.
  • rectangular patched portions in which printing density is varied stepwise, characters and photograph were formed.
  • Optical density was measured by measuring a portion having the maximum density and the patch having density of 50% using a optical density meter made by X-Rite, Inc.
  • application time of voltage is varied to vary a volume of dots of coagulated ink, thereby to vary an amount of transfer of the ink on the substrate to vary the density. Therefore, the increase of both the optical densities of both the portion having the maximum density and the patch having density of 50% can be considered as the result of improvement of the coagulating efficiency of the ink.
  • Procedures of the experiment were as follows: the test pattern was printed while varying the temperature of the circulated cleaning liquid stepwise at 22°C, 25°C, 30°C, 35°C, 40°C, 45°C and 48°C, and the optical density of the test pattern was measured. Fig.8 shows the result.
  • the electric conductivity of the ink is increased, as the temperature is increased.
  • the optical density is enhanced as the printing temperature is increased, and the optical density has substantially the constant value at 35°C or more, and it can be seen that the coagulation efficiency is enhanced by maintaining the positive electrode active surface and the ink at the temperature ranging from about 35 to about 60°C, preferably from about 35 to about 50°C, and more preferably from about 35 to about 45°C.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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  • Printing Methods (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)
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Claims (18)

  1. Procédé d'impression par électrocoagulation, comprenant les étapes consistant :
    a) à prévoir une électrode positive ayant une surface active et à former une pluralité de points d'encre de couleur coagulée représentatifs d'une image souhaitée, sur la surface active de l'électrode positive, par électrocoagulation d'une encre d'impression électrolytiquement coagulable ; et
    b) à placer un substrat en contact avec les points d'encre de couleur coagulée, pour traneférer l'encre de couleur coagulée, sur le substrat, à partir de la surface active de l'électrode positive, et à imprimer ainsi l'image sur le substrat :
    où l'étape (a) est effectuée, tout en maintenant la surface active de l'électrode positive et l'encre à une température comprise entre environ 35°C et environ 60°C.
  2. Procédé d'impression par électrocoagulation selon la revendication 1, dans lequel la surface active de l'électrode positive et l'encre sont maintenues à une température variant entre environ 35°C et environ 45°C.
  3. Procédé d'impression par électrocoagulation selon la revendication 1, dans lequel la surface active de l'électrode positive et l'encre sont maintenues à une température variant entre environ 35°C et environ 60°C, en chauffant la surface active de l'électrode positive et en fournissant l'encre sur la surface de l'électrode chauffée, provoquant ainsi une transmission de chaleur encre la surface de l'électrode et l'encre.
  4. Procédé d'impression par électrocoagulation selon la revendication 1 ou 3, dans lequel l'encre d'impression électrolytiquement coagulable comprend un polymère électrolytiquement coagulable, un milieu liquide, un êlectrolyte soluble et un colorant, le milieu liquide étant de l'eau et l'électrolyte étant sélectionné parmi le groupe se composant d'halogénures métalliques d'alcalins et d'halogénures métalliques de terre alcaline.
  5. Procédé d'impression par électrocoagulation selon la revendication 4, dans lequel l'électrolyte est présent dans l'encre suivant une quantité comprise entre environ 4,5 % ec environ 10 % en poids, cette quantité étant basée sur le poids total de l'encre.
  6. Procédé d'impression par électrocoagulation selon la revendication 4 ou 5, dans lequel l'électrolyte est du chlorure de potassium.
  7. Procédé d'impression par électrocoagulation selon l'une quelconque des revendications 1, 3 ou 4, dans lequel le substrat est du papier absorbant l'eau.
  8. Procédé d'impression par électrocoagulation selon l'une quelconque des revendications 1, 3, 4 et 7, dans lequel les étapes (a) et (b) sont répétées plusieurs fois, pour définir un nombre correspondant de stades d'impression agencés au niveau d'emplacements prédéterminés le long d'une trajectoire prédéterminée, chaque stade d'impression utilisant un colorant de couleur différente, produisant ainsi plusieurs images de couleurs différences d'encre coagulée, ces images étant transférées sur le substrat, au niveau d'emplacements de transfert respectifs, en étant superposées pour fournir une image polychrome.
  9. Procédé d'impression par électrocoagulation selon la revendication 8, dans lequel l'électrode positive est une électrode cylindrique ayant un axe longitudinal central en rotation à une vitesse pratiquement constante autour de l'axe longitudinal, et où les stades d'impression sont agencés autour de l'électrode cylindrique positive.
  10. Procédé d'impression par électrocoagulation selon l'une quelconque des revendications 1, 3, 4, 7 et 8, dans lequel l'étape (a) est effectuée :
    i) en prévoyant une pluralité d'électrodes négatives isolées électriquement les unes des autres et agencées suivant un alignement rectiligne, pour définir une série de surfaces actives d'électrodes négatives correspondantes, disposées dans un plan parallèle à l'axe longitudinal de l'électrode positive et espacées de la surface active de l'électrode positive par une distance prédéterminée constante, les électrodes négatives étant espacées les unes des autres par une distance au moins égale à la distance entre électrodes ;
    ii) en enduisant la surface active de l'électrode positive d'une substance huileuse, pour former, sur la surface, des microgouttelettes de cette substance ;
    iii) en remplissant la distance entre électrodes avec de l'encre d'impression par électrocoagulation :
    iv) en excitant électriquement certaines des électrodes négatives sélectionnées, pour provoquer une coagulation sélective point par point et pour provoquer l'adhérence de l'encre sur les surfaces actives des électrodes négatives excitées, opposées à la surface active de l'électrode positive enduite d'une substance huileuse, candis que l'électrode positive est en rotation, formant ainsi les points d'encre de couleur coagulée ; et
    v) en éliminant toute quantité résiduelle d'encre non coagulée, de la surface active de l'électrode positive.
  11. Procédé d'impression par électrocoagulation selon la revendication 10, comprenant en outre l'étape consistant à polir la surface active de l'électrode positive enduite de la substance huileuse, pour augmenter l'adhérence des microgouttelettes sur la surface active de l'électrode positive, avant de réaliser l'étape (a) (iii).
  12. Procédé d'impression par électrocoagulation selon l'une quelconque des revendications 1, 3, 4, 7, 8 et 10, comprenant en outre l'étape consistant à éliminer, après l'étape (b), toute quantité résiduelle d'encre coagulée de la surface active de l'électrode positive, où l'électrode positive est rotative dans une direction prédéterminée, et toute quantité résiduelle d'encre coagulée est éliminée de la surface active de l'électrode positive, en prévoyant une brosse rotative allongée s'étendant parallèlement à l'axe longitudinal de l'électrode positive, la brosse étant dotée d'une pluralité de poils s'étendant radialement et ayant des extrémités venant en contact sur la surface active de l'électrode positive, en faisant tourner la brosse dans une direction opposée à la direction de rotation de l'électrode positive, de façon à provoquer l'engagement par frottement des poils sur la surface active de l'électrode positive, et en dirigeant des jets de liquide de nettoyage sous pression, sur la surface active de l'électrode positive, à partir de l'un ou l'autre des côtés de la brosse.
  13. Procédé d'impression par électrocoagulation selon la revendication 12, dans lequel la surface active de l'électrode positive et l'encre sont maintenues à température, en chauffant le liquide de nettoyage, pour chauffer ainsi la surface active de l'électrode positive lorsque le liquide de nettoyage chauffé vient en contact avec cette surface active de l'électrode positive, et en appliquant l'encre sur la surface de l'électrode chauffée pour provoquer une transmission de chaleur entre la surface de l'électrode et l'encre.
  14. Appareil (1) d'impression par électrocoagulation comprenant :
    une électrode positive (11) ayant une surface active ;
    un moyen (15) pour fournir à l'électrode positive (11) une encre d'impression électrolytiquement coagulable ;
    un moyen (19) pour former une pluralité de points d'encre de couleur coagulée représentatifs d'une image souhaitée, sur la surface active de l'électrode positive, par électrocoagulation de l'encre ;
    un moyen (23) pour placer un substrat (W) en contact avec des points de l'encre de couleur coagulée, pour provoquer un transfert de l'encre de couleur coagulée, sur le substrat (W), à partir de la surface active de l'électrode positive, et imprimer ainsi l'image sur le substrat (W) ; et
    des moyens de chauffage (30, 40, 50) pour maintenir la température de la surface active de l'électrode positive et de l'encre encre environ 35°C et environ 60°C.
  15. Appareil d'impression par électrocoagulation selon la revendication 14, dans lequel le moyen de chauffage (30) chauffe la surface active de l'électrode positive, fournit l'encre sur la surface de l'électrode chauffée, pour provoquer une transmission de chaleur entre la surface active de l'électrode positive et l'encre, à partir de la surface active de l'électrode positive, maintenant ainsi la température de la surface active de l'électrode positive et de l'encre encre environ 35°C et environ 60°C.
  16. Appareil d'impression par électrocoagulation selon la revendication 14 ou 15, comprenant en outre un moyen d'enduction (13) pour enduire une substance huileuse appliquée sur la surface active de l'électrode positive, afin de former des microgouttelettes sur la surface active de l'électrode positive.
  17. Appareil d'impression par électrocoagulation selon l'une quelconque des revendications 14, 15 ec 16, comprenant en outre un moyen de nettoyage (25), pour éliminer toute quantité résiduelle d'encre coagulée de la surface active de l,électrode positive. en nettoyant la surface active de l'électrode positive.
  18. Appareil d'impression par électrocoagulation selon la revendication 17, dans lequel le moyen de nettoyage (25) est doté d'une structure comprenant : une brosse allongée rotative (61) s'étendant parallèlement à l'axe longitudinal de l'électrode positive cylindrique (11) pouvant tourner dans une direction prédéterminée, la brosse étant dotée d'une pluralité de poils (63) s'étendant radialement et ayant des extrémités venant en contact sur la surface active (65) de l'électrode positive, et pouvant tourner dans une direction opposée à la direction de rotation de l'électrode positive (11), de façon à ce que les poils (63) s'engagent par frottement sur la surface active (65) de l'électrode positive ; et des moyens (57, 57') formant des jets, pour diriger des jets du liquide de nettoyage sous pression, sur la surface active (65) de l'électrode positive, à partir de l'un ou l'autre des côtés de la brosse (61), et où la surface active (65) de l'électrode positive et l'encre sont maintenues à une température comprise entre environ 35°C et environ 60°C, en chauffant le liquide de nettoyage grâce au moyen de chauffage (50), pour chauffer ainsi la surface active (65) de l'électrode positive, en injectant le liquide de nettoyage chauffé sur la surface active (65) de l'électrode positive et en appliquant l'encre sur la surface active (65) de l'électrode positive chauffée, pour provoquer une transmission de chaleur entre la surface active de l'électrode et l'encre.
EP97950435A 1996-12-30 1997-12-26 Procede et appareil d'impression par coagulation electrique Expired - Lifetime EP0931666B1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
CA2194130 1996-12-30
CA2194128 1996-12-30
CA 2194128 CA2194128C (fr) 1996-12-30 1996-12-30 Methode pour accroitre le rendement de coagulation dans l'impression par electrocoagulation
CA 2194130 CA2194130C (fr) 1996-12-30 1996-12-30 Methode pour ameliorer le transfert d'un colloide coagule sur un substrat dans l'impression par electrocoagulation
PCT/JP1997/004903 WO1998029253A1 (fr) 1996-12-30 1997-12-26 Procede et appareil d'impression par coagulation electrique

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EP0931666A4 EP0931666A4 (fr) 1999-08-04
EP0931666B1 true EP0931666B1 (fr) 2001-07-25

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US3892645A (en) * 1973-06-06 1975-07-01 Adrien Castegnier Printing method and system by gelatin coagulation
CA1205778A (fr) * 1984-05-16 1986-06-10 Adrien Castegnier Reproduction d'images par electrocoagulation d'un colloide applique en surface
US4661222A (en) 1986-03-27 1987-04-28 Elcorsy Inc. Monochromic and polychromic printing of an image reproduced by electro-coagulation of a colloid
CA1334017C (fr) 1989-04-12 1995-01-17 Adrien Castegnier Methode et appareil d'impression par electrocoagulation rapide
US5449392A (en) 1994-01-24 1995-09-12 Elcorsy Inc. Apparatus for coating a metallic substrate with an oily substance
US5538601A (en) 1995-09-14 1996-07-23 Elcorsy Inc. Electrocoagulation printing and apparatus
US5690803A (en) * 1997-01-27 1997-11-25 Elcorsy Technology Inc. Method of enhancing transfer of coagulated colloid onto a substrate during electrocoagulation printing

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DE69705850T2 (de) 2002-04-04
EP0931666A1 (fr) 1999-07-28
DE69705850D1 (de) 2001-08-30
EP0931666A4 (fr) 1999-08-04
WO1998029253A1 (fr) 1998-07-09

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