Classifications

• • 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
• • 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

• This invention relates to printing and, more particularly, to a method of making a printing plate by electric coagulation and printing ordinary paper.
• the patented method may suffer adverse secondary effects and speed restrictions, making it less suitable for more-demanding applications and for achieving sustained reliable performance, such as for computer printers and photocopying.
• the colloids used in the patented method make it impossible to print on ordinary paper, since it requires gelatinized paper, which is expensive.
• the albumin or gelatin used in the above-noted patent is not usually of consistent quality due to the high variance of its molecular weight and its different chemical pre-treatment, as well as its ability to be adversely affected by the bacterial decomposition in ambient air.
• the present invention includes a method of recording an image comprising the steps of interposing a thin layer in substantially-liquid state containing water, an electrolyte and an electrolytically-coagulable colloid between and in contact with a plurality of negative electrodes, and a single positive electrode, the positive electrode being electrolytically inert, successively and selectively biasing said electrodes with direct current for a short period of time and concurrently sweeping the positive electrode by the negative electrodes to thereby cause point-by-point selective coagulation and adherence of the colloid onto said positive electrode and removing the non-coagulated colloid, whereby the coagulated colloid is representative of a desired image.
• the improved method uses a colloid selected from the group consisting of water-dispersable synthetic linear colloid polymers, of high molecular weight the colloid polymer being capable, when coagulated, of absorbing an agent soluble in an alcohol. More specifically, the colloid is selected from the group of water dispersable synthetic linear colloid polymers of a molecular weight between 100,000 and 600,000 and, preferably, between 200,000 and 450,000 and including polyacrylic acid and polyacrylamide resins.
• the uniform characteristic of the synthetic colloid polymers, with a well-controlled molecular weight, has been found to provide reliably-uniform and superior results over the albumin and gelatin used in the above-noted U.S. patent.
• the electrolyte used in the composition is either an acid or a salt selected from the group consisting of lithium,sodium, potassium and ammonium chloride.
• the composition also preferably includes an electrode depolarizing agent to minimize the deposition of gas against the electrodes.
• an agent is preferably selected from the group of manganese and nitrate compounds and H2O2, which combines with the gas produced against the electrodes upon breakdown of a water molecule into oxygen and hydrogen ions.
• Lead nitrate, manganese chloride and H2O2 have been found suitable as a depolarizing agent.
• the positive electrode must be electrolytically inert. Metals suitable for making the positive electrode are selected from stainless steel, aluminum and tin, with stainless steel 316 being preferred as giving the best results.
• the non-coagulated colloid composition is removed by washing or scraping the positive electrode with a soft rubber squeegee.
• the anode with the coagulated synthetic dots adhering thereto form the printing plate.
• a water solution of a dye and of a swelling agent for the coagulated dots of the printing plate is then applied to the printing plate and the coagulated dots become swollen as they absorb the solvent and absorb the dye.
• This swelling agent is a solvent for said colloid.
• the swelled, dyed, coagulated image is pressed in close contact with ordinary paper previously slightly wetted with an alcohol. Since the swelling agent is soluble in the alcohol, the dye of the dots is transferred onto the paper surface.
• Any ordinary paper can thus be printed, including uncoated paper, such as bond paper and coated paper, more specifically kaolin-coated and synthetic resin-coated paper.
• the preferred swelling agent is a water solution of a compound selected from the group consisting of one or more of glycerol, ethylene glycol and sorbitol. These compounds act as a solvent for polyacrylic acid and polyacrylamide resin, and they are also soluble in the alcohol used as a paper-wetting agent and swell the coagulated dots much more and for a longer time than just water. Thus, dye transfer from the printing plate to the paper is highly efficient, fast and accurate.
• Preferred alcohols for paper wetting are selected from the group consisting of methanol, ethanol and isopropylic alcohol. These alcohols possess high paper wetting property and, therefore, the colored glycerol or ethylene glycol or sorbitol, or mixtures thereof, are absorbed by the paper fibers where they remain.
• the dye transfer on paper just described cannot work with the gelatin and albumin colloids mentioned in the above-noted U.S. patent.
• Sorbitol and ethylene glycol have only a very slight swelling effect on gelatin or albumin and are totally unsatisfactory for the above-described printing step.
• Gelatinized paper must be used to effect printing from the printing plate where the coagulated dots are gelatin or albumin.
• This water solution has a pH of 2,25.
• This solution was used as a layer between the negative and positive electrodes in the above-described method for recording an image.
• the positive electrode was stainless steel 316.
• the gap between the negative and positive electrodes was 50 microns.
• the negative electrodes were insulated copper wires of 250 microns in diameter arranged in a linear array.
• the electrodes were successively biased by successively and selectively applying to the negative electrodes a power supply of 25 watts (50 volts and 500 milliamperes).
• the operating temperature was 30°C.
• a speed of coagulation of 300,000 dots per second was achieved, with the size of the dots being 250 microns in diameter. This means that an electric pulse at each electrode of one-three hundred thousandths of a second was necessary to effect coagulation.
• the experiment was repeated several times and the coagulation results were very constant from one experiment to the other. Additional experiments were repeated using the same liquid composition but using negative electrodes having a diameter of 125 microns instead of 250 microns. The resulting speed of coagulation was found to be 1,000,000 dots per second, that is requiring an electrical pulse for each negative electrode of one millionth of a second.
• liquid electrolytically-coagulable colloid composition of any of the above noted examples, was added a depolarizing agent consisting of two percent by weight of a compound selected from lead nitrate, manganese chloride and H2O2, with even better results.
• a depolarizing agent consisting of two percent by weight of a compound selected from lead nitrate, manganese chloride and H2O2, with even better results.
• the glycerol acts as a solvent of the polyacrylic acid, or polyacrylamide resin, the coagulated dots became swollen and absorbed the dye. The surplus dye solution was then removed and the swelled, dyed coagulated image was pressed in close contact with a kaolin-coated paper previously wetted with methanol.
• the methanol which is a solvent for glycerol, caused the transfer of the dye to the paper surface, resulting in the image transfer to the paper.
• About seven paper sheets were thus printed with the same printing plate, while recharging the synthetic dots with the dye and swelling agent each time; it was found that up to about seven sheets could be printed. To print additional sheets, it was necessary to remake the printing plate.
• the paper wetting agent was ethanol and similar results as in Example V were obtained.
• Example V The same experiments as Example V were carried out but using the following coloring and swelling agent composition for treating the coagulated dots of the printing plate image:
• Isopropylic alcohol was used as the paper wetting agent.
• the dye transfer to the paper was less than in Examples V and VI, since sorbitol is a poorer solvent and, therefore, a poorer swelling agent than glycerol or ethylene glycol for the coagulated dots of the colloids named in Examples I to IV.
• sorbitol when admixed with either or both glycerol and ethylene glycol, the coagulated colloid swelling efficiency can be adjusted for maximum dye transfer to the paper.

Landscapes

• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Colloid Chemistry (AREA)
• Cosmetics (AREA)
• Manufacture Or Reproduction Of Printing Formes (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)
• Printing Plates And Materials Therefor (AREA)
• Printing Methods (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

Family

ID=24441277

Family Applications (1)

Country Status (10)

Families Citing this family (5)

Family Cites Families (4)

• 1985
  • 1985-04-25 CA CA000480015A patent/CA1250249A/en not_active Expired
  • 1985-05-01 ZA ZA853270A patent/ZA853270B/xx unknown
  • 1985-05-06 KR KR1019850003073A patent/KR850008299A/ko not_active Application Discontinuation
  • 1985-05-07 AU AU42059/85A patent/AU578092B2/en not_active Ceased
  • 1985-05-08 DE DE8585105621T patent/DE3582188D1/de not_active Expired - Lifetime
  • 1985-05-08 AT AT85105621T patent/ATE61764T1/de not_active IP Right Cessation
  • 1985-05-08 EP EP85105621A patent/EP0160979B1/en not_active Expired - Lifetime
  • 1985-05-10 BR BR8502230A patent/BR8502230A/pt unknown
  • 1985-05-10 JP JP60098140A patent/JPS60245592A/ja active Granted
  • 1985-05-11 ES ES543069A patent/ES8605417A1/es not_active Expired

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