EP1084828A2 - Appareil et procédé d'impression intermittent par électrocoagulation - Google Patents

Appareil et procédé d'impression intermittent par électrocoagulation Download PDF

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Publication number
EP1084828A2
EP1084828A2 EP00120006A EP00120006A EP1084828A2 EP 1084828 A2 EP1084828 A2 EP 1084828A2 EP 00120006 A EP00120006 A EP 00120006A EP 00120006 A EP00120006 A EP 00120006A EP 1084828 A2 EP1084828 A2 EP 1084828A2
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EP
European Patent Office
Prior art keywords
electrode active
series
positive electrode
active surface
negative electrodes
Prior art date
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Granted
Application number
EP00120006A
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German (de)
English (en)
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EP1084828B1 (fr
EP1084828A3 (fr
Inventor
Adrien Castegnier
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.)
Toyo Ink Mfg Co Ltd
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Toyo Ink Mfg Co Ltd
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Publication date
Application filed by Toyo Ink Mfg Co Ltd filed Critical Toyo Ink Mfg Co Ltd
Publication of EP1084828A2 publication Critical patent/EP1084828A2/fr
Publication of EP1084828A3 publication Critical patent/EP1084828A3/fr
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Publication of EP1084828B1 publication Critical patent/EP1084828B1/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

Definitions

  • the present invention pertains to improvements in the field of electrocoagulation printing. More particularly, the invention relates to an intermittent electrocoagulation printing method and apparatus.
  • the positive electrode is coated with a dispersion containing an olefinic substance and a metal oxide prior to electrical energization of the negative electrodes in order to weaken the adherence of the dots of coagulated ink to the positive electrode and also to prevent an uncontrolled corrosion of the positive electrode.
  • gas generated as a result of electrolysis upon energizing the negative electrodes is consumed by reaction with the olefinic substance so that there is no gas accumulation between the negative and positive electrodes.
  • the electrocoagulation printing ink which is injected into the gap defined between the positive and negative electrodes consists essentially of a liquid colloidal dispersion containing an electrolytically coagulable polymer, a dispersing 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 adhered to the surface of the positive electrode.
  • the negative and positive electrodes, the positive electrode 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 polychromic 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 positive electrode which is used for electrocoagulation printing must be made of an electrolytically inert metal capable of releasing trivalent ions so that upon electrical energization of the negative electrodes, dissolution of the passive oxide film on such an electrode generates trivalent ions which then initiate coagulation of the ink.
  • electrolytically inert metals include stainless steels, aluminium and tin.
  • the inventor When using negative electrodes made of an active metal such as iron, the inventor has observed that the metal undergoes dissolution in the ink in the presence of the aforesaid electrolyte anions, whether the electrodes are energized or not, resulting in corrosion of the negative electrodes and contamination of the ink.
  • the metal ions which are released into the ink as a result of such a dissolution cause the formation of a gelatinous material which deposits onto the surfaces of the negative electrodes, thereby creating an electrical resistance which increases as the amount of deposited gelatinous material increases, leading to a complete blocking of the electrical signal.
  • an electrocoagulation printing apparatus comprising:
  • a multicolor electrocoagulation printing apparatus comprising:
  • the negative electrodes of each the series are mounted to a respective elongated electrode carrier along the length thereof.
  • the negative electrodes of the first and second series each have a cylindrical configuration with a circular cross-section and a diameter ranging from about 20 ⁇ m in to about 50 ⁇ m.
  • the negative electrodes of the first and second series are mounted to a single elongated electrode carrier along the length thereof, and wherein the negative electrodes of the first and second series each have a cylindrical configuration with a circular cross-section and a diameter ranging from about 20 ⁇ m to about 50 ⁇ m, and wherein the first and second series of the negative electrodes are spaced from one another by a distance ranging from about 250 ⁇ m to about 1000 ⁇ m.
  • the negative electrodes of the first and second series are formed of an electrolytically inert metal selected from the group consisting of chromium, nickel, stainless steel, titanium and gold.
  • the means for energizing the negative electrodes of the first and second series include first driver circuit means for addressing selected ones of the negative electrodes of the first series so as to apply electric current to the selected negative electrodes, second driver circuit means for addressing selected ones of the negative electrodes of the second series so as to apply electric current to the selected negative electrodes, and control means for activating the first and second drive circuit means in the controlled alternate manner.
  • the means for forming the dots of colored, coagulated ink and the means for bringing the substance into contact with the dots of colored, coagulated ink are arranged to define a printing unit, and wherein there are several printing units positioned at predetermined locations along the path and each using a coloring agent of different colored for producing several differently transferred at respective transfer stations onto the substrate in superimposed relation to provide a polychromic image.
  • an electrocoagulation printing method comprising the steps of:
  • a multicolor electrocoagulation printing method comprising the steps of:
  • an electrocoagulation printing apparatus including:
  • the inventor has found quite unexpectedly that by providing two series of negative electrolytically inert electrodes each having a surface covered with a passive oxide film and electrically energizing selected ones of the negative electrodes of these two series in a controlled alternate manner as defined above, the aforesaid gelatinous deposit does not form in an amount sufficient to create an electrical resistance which is detrimental to the electrocoagulation. It is believed that the passive oxide film of each energized electrode does not dissolve into the ink in a quantity sufficient to cause an undesirable formation of the gelatinous deposit and, upon de-energization, the passive oxide film rebuilds itself due to the presence of oxidizing substances in the ink.
  • the energizing of the negative electrodes of the first and second series is controlled to provide a continuous formation of the dots of colored, coagulated ink on the positive electrode active surface.
  • the negative electrodes of each series are mounted to a respective elongated electrode carrier along the length thereof. It is also possible to mount the negative electrodes of the first and second series to a single elongated electrode carrier along the length thereof.
  • the negative electrodes of the first and second series each have a cylindrical configuration with a circular cross-section and a diameter ranging from about 20 ⁇ m to about 50 ⁇ m.
  • the first and second series of such negative electrodes are spaced from one another by a distance ranging from about 250 ⁇ m to about 1000 ⁇ m.
  • suitable electrolytically inert metals from which the negative electrodes can be made include chromium, nickel, stainless steel, titanium and gold; stainless steel is particularly preferred.
  • the positive electrode on the other hand, can be made of stainless steel, tin or aluminum.
  • the gap which is defined between the positive and negative electrodes can range from about 35 ⁇ 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 preferably spaced from one another by a distance of about 75 ⁇ m.
  • suitable oily substances which may be used to coat the surface of the positive electrode in step (b) (ii) 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. Oleic acid is particularly preferred.
  • the micro-droplets formed on the surface of the positive electrode active surface generally have a size ranging from about 1 ⁇ m to about 5 ⁇ m.
  • the oil-coated positive active surface is preferably polished to increase the adherence of the micro-droplets onto the positive electrode active surface, prior to step (b) (ii).
  • 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.
  • steps (b) and (c) 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 polychromic image.
  • steps (a), (b) and (c) it is also possible to repeat several times steps (a), (b) and (c) to define a corresponding number of printing stages arranged in tandem relation and each using a coloring agent of different color, and to thereby produce several differently colored images of coagulated ink which are transferred at respective transfer positions onto the substrate in superimposed relation to provide a polychromic image, the substrate being in the form of a continuous web which is passed through the respective transfer positions for being imprinted with the colored images at the printing stages.
  • the printing stages defined by repeating several times steps (a), (b) and (c) can be arranged around a single roller adapted to bring the substrate into contact with the dots of colored, coagulated ink of each printing stage and the substrate which is in the form of a continuous web is partially wrapped around the roller and passed through the respective transfer positions for being imprinted with the colored images at the printing stages.
  • steps (a), (b) and (c) can be arranged around a single roller adapted to bring the substrate into contact with the dots of colored, coagulated ink of each printing stage and the substrate which is in the form of a continuous web is partially wrapped around the roller and passed through the respective transfer positions for being imprinted with the colored images at the printing stages.
  • a belt including a plastic material having a porous coating of silica can be made of a belt including a plastic material having a porous coating of silica.
  • an improved electrocoagulation printing apparatus including:
  • 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 Nos. 4,895,629 and 5,538,601.
  • the printing stages or units 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, preferably 40°C, to increase the viscosity of the coagulated ink in step (b) so that the dots of colored, coagulated ink remain coherent during their transfer in step (c), thereby enhancing transfer of the colored, coagulated ink onto the substrate or belt.
  • the positive electrode active surface can be heated at the desired temperature and the ink applied on the heated electrode surface to cause a transfer of heat therefrom to the ink.
  • step (b) (ii) of the above electrocoagulation printing method is advantageously carried out by continuously discharging the ink onto the positive electrode active surface from a fluid discharge means disposed adjacent the electrode gap at a predetermined height relative to the positive electrode and allowing the ink to flow downwardly 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 downwardly off the positive electrode active surface is collected and the collected ink is recirculated back to the fluid discharge means.
  • An electrocoagulation printing ink contains at least electrically coagulable polymer, a dispersing medium, a soluble electrolyte and a coloring agent.
  • the electrically coagulable polymer generally used is a linear polymer of high molecular weight, that is, one having a weight average molecular weight between about 10,000 and about 1,000,000, preferably between 100,000 and 600,000.
  • suitable polymers include natural polymers such as albumin, gelatin, casein and agar, and synthetic polymers such as polyacrylic acid, polyacrylamide and polyvinyl alcohol.
  • a particularly preferred polymer is an anionic copolymer of acrylamide and acrylic acid having a weight average molecular weight of about 250,000 and sold by Cyanamid Inc. under the trade mark ACCOSTRENGTH 86. Water is preferably used as the medium for dispersing the polymer to provide the desired colloidal dispersion.
  • Preferred electrolytes include alkali metal halides and alkaline earth metal halides, such as lithium chloride, sodium chloride, potassium chloride and calcium chloride. Potassium chloride is particularly preferred.
  • the coloring agent can be a dye or a pigment. Examples of suitable dyes which may be used to color the ink are the water soluble dyes available from HOECHST such as Duasyn Acid Black for coloring in black and Duasyn Acid Blue for coloring in cyan, or those available from RIEDEL-DEHAEN such as Anti-Halo Dye Blue T. Pina for coloring in cyan, Anti-Halo Dye AC Magenta Extra V01 Pina for coloring in magenta and Anti-Halo Dye Oxonol Yellow N.
  • Pina for coloring in yellow.
  • a pigment which are available from CABOT CORP. such as Carbon Black Monarch® 120 for coloring in black, or those available from HOECHST such as Hostaperm Blue B2G or B3G for coloring in cyan. Permanent Rubine F6B or L6B for coloring in magenta and Permanent Yellow DGR or DHG for coloring in yellow.
  • a dispersing agent is added for uniformly dispersing the pigment into the ink. Examples of suitable dispersing agents include the anionic dispersing agent sold by Boehme Filatex Canada Inc. under the trade mark CLOSPERSE 25000.
  • 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 fluid discharge 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 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.
  • the electrocoagulation printing ink contains water as the dispersing medium and the dots of differently colored, coagulated ink representative of the polychromic image are moistened between the aforementioned steps (d) and (e) so that the polychromic image is substantially completely transferred onto the substrate in step (e).
  • the substrate is in the form of a continuous web and step (e) is carried out by providing a support roller and a pressure roller extending parallel to the support roller and pressed thereagainst to form a nip through which the belt is passed, the support roller and pressure roller being driven by the belt upon movement thereof, and guiding the web so as to pass through the nip between the pressure roller and the porous surface of the belt for imprinting the web with the polychromic image.
  • the belt with the porous surface thereof imprinted with the polychromic image is guided so as to travel along a path extending in a plane intersecting the longitudinal axis of the positive electrode at right angles, thereby exposing the porous surface to permit contacting thereof by the web.
  • the belt is preferably guided so as to travel along a horizontal path with the porous surface facing downwardly, the support roller and pressure roller having rotation axes disposed in a plane extending perpendicular to the horizontal path.
  • the porous surface of the belt is generally cleaned to remove therefrom any remaining coagulated ink.
  • any remaining coagulated ink is removed from the porous surface of the belt by providing at least one elongated rotatable brush disposed on the one side of the belt and at least one support roller extending parallel to the brush and disposed on the opposite side of the belt, the brush and support roller having rotation axes disposed in a plane extending perpendicular to the belt, the brush being provided with a plurality of radially extending bristles made of horsehair and having extremities contacting the porous surface, rotating the brush in a direction opposite to the direction of movement of the belt so as to cause the bristles to frictionally engage the porous surface while supporting the belt with the support roller, directing jets of cleaning liquid under pressure against the porous surface from either side of the brush and removing the cleaning liquid with any dislodged coagulated ink from the porous surface.
  • a positive electrode 10 in the form of a revolving cylinder and having a passivated surface 12 defining a positive electrode active surface adapted to be coated with an oily substance by means of a positive electrode coating device (not shown).
  • a device 14 is provided for discharging an electrocoagulation printing ink onto the surface 12.
  • the electrocoagulation printing ink consists of a colloidal dispersion containing an electrolytically coagulable polymer, a dispersing medium, a soluble electrolyte and a coloring agent.
  • a printing head 16 having two series of negative electrodes 18A, 18B is used for electrocoagulating the polymer contained in the ink to form on the positive electrode surface 12 dots of colored, coagulated ink representative of a desired image.
  • the printing head 16 comprises a cylindrical electrode carrier 20 with the respective negative electrodes 18A, 18B of each series being electrically insulated from one another and arranged in rectilinear alignment along the length of the electrode carrier 20 to define a plurality of corresponding negative active surfaces 22A, 22B.
  • the two series of negative electrodes 18A, 18B are arranged in a close spaced-apart parallel relationship.
  • the printing head 16 is positioned relative to the positive electrode 10 such that the surfaces 22A, 22B of the negative electrodes 18A, 18B are disposed in a plane which is spaced from the positive electrode surface 12 by a constant predetermined gap 24.
  • the respective electrodes 18A, 18B of each series are also spaced from one another by a distance at least equal to the electrode gap 24 to prevent edge corrosion of the negative electrodes.
  • the device 14 is positioned adjacent the electrode gap 24 to fill same with the electrocoagulation printing ink.
  • the first printing head 16A comprises a cylindrical electrode carrier 20A with the series of negative electrodes 18'A being electrically insulated from one another and arranged in rectilinear alignment along the length of the electrode carrier 20A to define a plurality of corresponding negative electrode active surfaces 22'A.
  • the printing head 16A is positioned relative to the positive electrode 10' such that the surfaces 22'A of the negative electrodes 18'A are disposed in a plane which is spaced from the positive electrode surface 12' by a constant predetermined gap 24A.
  • the electrodes 18'A are also spaced from one another by a distance at least equal to the electrode gap 24A to prevent edge corrosion of the negative electrodes.
  • a device 14A is associated with the printing head 16A and positioned adjacent the electrode gap 24A to fill same with the aforementioned electrocoagulation printing ink.
  • the second printing head 16B comprises a cylindrical electrode carrier 20B with a series of negative electrodes 18'B being electrically insulated from one another and arranged in rectilinear alignment along the length of the electrode carrier 20B to define a plurality of corresponding negative electrode active surfaces 22'B.
  • the printing head 16B is positioned relative to the positive electrode 10' such that the surfaces 22'B of the negative electrodes 18'B are disposed in a plane which is spaced from the positive electrode surface 12' by a constant predetermined gap 24B.
  • the electrodes 18'B are also spaced from one another by a distance at least equal to the electrode gap 24B to prevent edge corrosion of the negative electrodes.
  • a device 14B is associated with the printing head 16B and positioned adjacent the electrode gap 24B to fill same with the aforementioned electrocoagulation printing ink.
  • the printing heads 16A and 16B are disposed so that the series of negative electrodes 18'A and 18'B are arranged in spaced-apart parallel relationship.
  • the negative electrodes 18A, 18B, 18'A and 18'B each have a cylindrical body 26 made of an electrolytically inert metal and covered with a passive oxide film 28.
  • the end surface of the electrode body 26 covered with such a film defines the aforementioned negative electrode active surface 22A, 22B, 22'A or 22'B.
  • Figure 7 is a schematic diagram illustrating how the negative electrodes 18A, 18B or 18'A, 18'B are energized in response to an input signal of information 30 to form dots of colored, coagulated ink representative of a desired image.
  • a driver circuit 32A is used for addressing selected ones of the negative electrodes 18A or 18'A so as to apply electric current to the selected negative electrodes.
  • a driver circuit 32B is used for addressing selected ones of the negative electrodes 18B or 18'B so as to apply electric current to the selected negative electrodes.
  • Such an electrical energizing causes point-by-point selective coagulation and adherence of the ink onto the oil-coated surface 12 or 12' of the positive electrode 10 or 10' opposite the electrode active surfaces 22A, 22B, 22'A or 22'B while the electrode 10 or 10' is rotating, thereby forming on the surface 12 or 12' a series of corresponding dots of colored, coagulated ink.
  • gas generated as a result of electrolysis and not consumed by reaction with the oily substance causes a breakdown of the passive oxide film 28 of each energized negative electrode 18A, 18B, 18'A or 18'B and a local dissolution of the film into the ink at the breakdown sites.
  • a control circuit 34 is used for activating the driver circuits 32A, 32B in a controlled alternate manner such that the negative electrodes 18A or 18'A are energized prior to an undesirable formation of the gelatinous deposit on the electrode active surface 22B or 22'B of each energized electrode 18B or 18'B and the negative electrodes 18B or 18'B are energized prior to an undesirable formation of the gelatinous deposit on the electrode active surface 22A or 22'A of each energized electrode 18A or 18'A.
  • the passive oxide film of each energized electrode does not dissolve into the ink in a quantity sufficient to cause an undesirable formation of the gelatinous deposit.
  • the passive oxide film of each de-energized electrode rebuilds itself due to the presence of oxidizing substance in the ink.
  • selected ones of the negative electrodes 18A or 18'A and selected ones of the negative electrodes are energized in an alternate manner for a period of about 3 to 4 seconds.
  • the driver circuits 32A, 32B are controlled by the control circuit 34 so as to provide a continuous formation of dots of colored, coagulated ink.
  • a central processing unit CPU for controlling the driver circuits associated with each color printing unit.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
  • Duplication Or Marking (AREA)
EP20000120006 1999-09-15 2000-09-14 Appareil et procédé d'impression intermittent par électrocoagulation Expired - Lifetime EP1084828B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CA 2282188 CA2282188C (fr) 1999-09-15 1999-09-15 Methode et appareil d'impression par electrocoagulation intermittente
CA2282188 1999-09-15

Publications (3)

Publication Number Publication Date
EP1084828A2 true EP1084828A2 (fr) 2001-03-21
EP1084828A3 EP1084828A3 (fr) 2001-04-04
EP1084828B1 EP1084828B1 (fr) 2004-05-12

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EP20000120006 Expired - Lifetime EP1084828B1 (fr) 1999-09-15 2000-09-14 Appareil et procédé d'impression intermittent par électrocoagulation

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EP (1) EP1084828B1 (fr)
CA (1) CA2282188C (fr)
DE (1) DE60010605T2 (fr)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2214300A1 (fr) * 1997-08-29 1999-02-28 Elcorsy Technology Inc. Methode et appareil d'impression polychrome par electrocoagulation

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2214300A1 (fr) * 1997-08-29 1999-02-28 Elcorsy Technology Inc. Methode et appareil d'impression polychrome par electrocoagulation

Also Published As

Publication number Publication date
EP1084828B1 (fr) 2004-05-12
CA2282188A1 (fr) 2001-03-15
EP1084828A3 (fr) 2001-04-04
DE60010605D1 (de) 2004-06-17
DE60010605T2 (de) 2005-10-20
CA2282188C (fr) 2005-04-26

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