Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G13/00—Electrographic processes using a charge pattern
  • G03G13/26—Electrographic processes using a charge pattern for the production of printing plates for non-xerographic printing processes
  • G03G13/28—Planographic printing plates
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/043—Photoconductive layers characterised by having two or more layers or characterised by their composite structure
  • G03G5/0433—Photoconductive layers characterised by having two or more layers or characterised by their composite structure all layers being inorganic
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic
  • G03G5/087—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and being incorporated in an organic bonding material

Definitions

• This invention relates to an article capable of being transformed into a planographic printing plate, and more particularly to a treated photoconductive master sheet that can be converted electrophotographically into a planographic printing plate.
• a planographic plate is indirectly prepared on a paper base by deposition and fusing on the base of a powder image from a photoconductive plate or drum which, after :being exposed to the image to be reproduced, bears a charged latent image that has been dusted with a charged powder.
• the fused powder is oleophilic, and the plate is made ready for printing by a final treatment of its surface with a wetting solution to prepare the non-image, non-printing areas thereon.
• a photoconductively prepared sheet for example, one having a paper base usually treated with an organic or inorganic material to increase its electrical conductivity and coated with a photoconductive substance such as a dyed zinc oxide powder, is exposed electrophotographically to the image to be reproduced, for example, -by sensitizing the sheet with a corona discharge and then exposing the sensitized sheet to light through an image transparency or the like.
• the latent image thus imparted to the master is converted, or developed, to an oleophilic visible image by either of two common developing techniques, one of which utilizes a dry medium and the other a wet medium.
• Final preparation includes desensitizing and conversion of the nonimage oleophilic photoconductive areas to a hydrophilic form.
• Factors affecting the quality of planographic printing plates produced by those methods, and printed materials reproduced therewith include the density of the image, which in general is preferably high, clarity of the background and its freedom from tinting or darkening in the non-image areas, ease of development and conversion, and press life, i.e., durability on a press during actual printing.
• the masters of this invention comprise a base sheet of an electroconductive flexible material having thereon a first photoconductive coating of powdered zinc oxide dispersed in a resinous insulating binder medium and, on top of that coating, a second photoconductive coating of powdered zinc oxide dispersed in a resinous insulating binder medium, the concentration of the zinc oxide dispersed in the second coating being substantially greater than the corresponding concentration in the first coating.
• a latent image is created on the zinc oxide coating by means of an electrophotographic device.
• the surface of the zinc oxide coating is electrostatically sensitized with an electrical charge, for example, a negative charge by a corona discharge, and then the coated sensitized sheet is exposed to light which discharges the charge on the zinc oxide coating in the areas exposed to the light that correspond to non-image areas, and leaves charged areas that correspond to the desired image.
• That latent image is developed by application of an oleophilic resinous material, which will become the ink-receptive image-printing area during printing with the plate, either in the form of a dry charged powder or from a dispersion in a liquid medium.
• a coloring agent such as a pigment or a dye.
• compositions often called toners, are available commercially, for example, a dry toner, Cat. No. 32-430 from Chas. Bruning Company, and a liquid developer, Microstatic from SCM Corporation. Others are described in U.S. Patents No. 2,638,416, No. 2,689,- 670, No. 2,907,674, No. 3,058,914, No. 3,128,204 and No. 3,220,830. Thereafter the surface of the oleophilic zinc oxide coating in the non-image areas is converted by chemical reaction to a hydrophilic reaction product, and the planographic printing master is ready for use. Chemicals and compositions containing them, for elfecting conversion of the surface of the zinc oxide coating are described, for example, in U.S.
• Patents No. 2,952,536, No. 2,957,765, No. 3,001,872 and No. 3,106,158 and include particularly phosphates, ferrocyanides, ferricyanides, cobalticyanides, vanadates, molybdates, tungstates, tartarates, oxalates, tannates and citrates.
• Suitable base materials are sheets or films having sufficient flexibility to be processed by machines employing the electrophotographic method and to be used on a planographic press. They should be electroconductive to at least a small extent, and should have a reasonable degree of dimensional stability for the intended use.
• Such base materials include metals such as steel, copper and aluminum, fibrous substances such as paper, woven textiles, knitted textiles and felts, and resins such as polyesters, polycarbonates, polystyrenes, cellulose acetates, polyvinyl acetates, polyvinyl chlorides, polyethylenes, polyethylene terephthalates, polyamides and the like.
• terials that are not significantly electro-conductive can be treated to increase that property, for example, by impregnation or coating with organic or inorganic substances of relatively low resistivity.
• organic or inorganic substances include, for instance, magnesium bromide and magnesium chloride, aplied alone from aqueous solution or together with a binder such as starch, and organic hydrophilic colloids such as polyvinyl alcohol, polyvinyl acetate and carboxymethyl cellulose.
• Dimensional stability of the base materials also can be improved by coating or impregnating with suitable materials, in certain instances by some of the substances previously mentioned as well as by such things as thermosetting and epoxy resins and the like.
• a number of commercially available conductivelytreated papers are suitable as base sheet materials. Typical of such papers are those sold by Weyerhaeuser Paper Company and by International Paper Company. Paper bases are presently preferred because they appear to be economically most attractive,
• a sheet of the selected base material is coated with two dispersions of powdered zinc Oxide in resinous insulating binder media.
• insulating is meant that the binder is substantially non-electroconductive, which helps retain the charge on the surface of the zinc oxide coating.
• Suitable binders include film-forming natural and synthetic resins or resiaoids that are soluble in water or in organic solvents, or that can be used in the form of aqueous dispersion or emulsion, for example, as disclosed in US. Patent No. 3,128,204.
• a typical aqueous dispersion binder is Hycar No. l800x72 acrylic copolymer made by B. F. Goodrich Company.
• Binders in organic solvents include Pliolite S and S-7, styrene-butadiene copolymers sold by Goodyear Tire and Rubber Company, Epotuf 38-401, epoxy esters sold by Reichhold Chemical Corporation, Cellokyd 6016x, styrenated alkyd resin sold by Cellomer Corporation, and Arotap 2200-X50, alkyd resin sold by ADM Chemicals Company.
• the preferred range of thickness is about 8 to 12 microns.
• the thickness of the two coatings is desirably about the same, they can vary within ranges such that the first coating is up to about 80% of the total thickness and the second coating is up to about 90% of the total thickness.
• the concentration of zinc oxide dispersed in the binder of the coatings in terms of ratios of parts by weight, varies considerably.
• zinc oxide concentrations in proportions of about 1:10 to about 8:1 based on the binder can be used.
• concentration of zinc oxide in the first coating should be about 1:1 to about 5:1, and more advantageously about 2:1 to 4:1.
• the suitable zinc oxide concentration proportion ranges from about 2:1 to about 32:1 based on the amount of binder.
• the preferred concentration is between about 4:1 and about 12:1, and best results as well as economy appear to be attainable at proportions of about 6:1 to 10:1.
• the concentration of the second coating should be at least about half again that of the first coating, preferably about at least twice as great, and advantageously in the range of about 2 to about 4 times as great.
• a sensitizer can be included in the zinc oxide-resinous binder coating to improve the photoelectric sensitivity of the coating to electrophotographic processing.
• sensitizers include dyes, for example, those of the sulfophthaline series, the xanthane series and dibasic acids, for example, phthalic acid and its derivatives.
• the relatively higher concentration of resinous insulating binder in the first coating tends to act as a better binder to the base, which increases press life of the plate, and also to result in a greater build-up of electrostatic charge in the electrophotographic process, thereby resulting in a denser image.
• the relatively higher zinc oxide concentration in the second coating appears to enable easier conversion as well as to provide greater hydrophilicity, which results in clearer backgrounds over longer press runs.
• EXAMPLE 1 A sheet of smooth-surface paper was coated with a first layer of a dispersion containing 160 parts of zinc oxide (Photox 801 from New Jersey Zinc Co.), 100 parts of an aqueous acrylic copolymer emulsion, Hycar 1800x72, parts of water and about 1 part of a 1% aqueous solution of Bromphenol Blue. A second coating of a dispersion differing from the one described by containing 160, 50, and about 1 part, respectively, of those materials was applied over the first coat. Each coat of dispersion was dried under infrared lamps and the coated sheet was then placed in a dark chamber at 50% relative humidity and room temperature for about 5 hours.
• a dispersion containing 160 parts of zinc oxide (Photox 801 from New Jersey Zinc Co.), 100 parts of an aqueous acrylic copolymer emulsion, Hycar 1800x72, parts of water and about 1 part of a 1% aqueous solution of Bromphenol Blue.
• the sheet was then exposed electrophotographically to an image using a Model 44 SCM Coronastat co ier which uses a conventional liquid-type developing composition.
• a conversion etching solution was then used to render the non-image areas hydrophilic by reaction with the zinc oxide at the surface of the coated layer.
• the solution contained 12 parts each of monoand di-ammonium phosphate, 2.4 parts of glacial acetic acid, 12 parts of sodium ferrocyanide, 12 parts of phosphoric acid, 600 parts of gum arabic and water to make 2400 parts.
• the printing plate thus prepared was placed on a lithographic press and over 300 high quality copies were obtained. The copies had dense images and clear backgrounds.
• a sheet coated only with the first dispersion was exposed, developed and used to print, but the background of the copies tended to darken indicating poor conversion an a relatively oleophilic non-image area.
• a sheet coated only with the second dispersion tended to produce copies having less dense images.
• EXAMPLE 2 A plate was prepared as described in Example 1 using a first dispersion containing 80 parts of an alkyd resin, #6035 made by Cellomer Corporation (about 50% solids), parts of zinc oxide, Photox 801, 200 parts of xylene and a small amount of Bromphenol Blue, and a second dispersion containing 80, 320 and 240 parts, respectively. The plate was then exposed, developed and used on a press as described in Example 1, and produced high quality copies having dense images and clear backgrounds.
• an alkyd resin #6035 made by Cellomer Corporation (about 50% solids)
• Photox 801 200 parts of xylene
• Bromphenol Blue Bromphenol Blue
• EXAMPLE 3 A plate was prepared as described in Example 1 using a first dispersion containing 80 parts of an alkyd resin, #6016 made by Cellomer Corporation, 160 parts of zinc oxide, Photox 801, 200 parts of xylene and a small amount of Bromphenol Blue, and a second dispersion containing 80, 320 and 240 parts, respectively. The plate was then exposed, developed and used on a press as described in Example 1 and produced high quality copies having dense images and clear backgrounds.
• EXAMPLE 4 A plate was prepared as described in Example 1 using a first dispersion containing 100 parts of resin No. 13RE57, available from Stein-Hall Company of New York and believed to be predominantly vinyl acetatecontaining terpolymer, 100 parts of zinc oxide, Photox 801, 200 parts of xylene and a small amount of Bromphenol Blue, and a second dispersion containing 100, 250 and 240 parts, respectively.
• the plate was then exposed, developed and used on a press as described in Example 1, and produced high quality copies having dense images and clear backgrounds. Over 250 copies were made on the press without any peeling of the coated layers in contrast to a sheet coated with only the second dispersion which tended to peel after about 50 copies.
• An article adapted for conversion electrophotographically into a planographic printing plate comprising an electroconductive base, a first photoconductive coating thereon containing powdered zinc oxide in a resinous insulating binder, and a second photoconductive coating on said first coating containing powdered zinc oxide in a resinous insulating binder, the concentration of zinc oxide in said second coating being greater than the concentration of zinc oxide in said first coating.
• a planographic printing plate comprising a dimensionally stable flexible base, a first layer on said base of powdered zinc oxide in a resinous insulating binder, a second layer on said first layer of powdered zinc oxide in a resinous insulating binder, the concentration of zinc oxide in said second layer being greater than the concentration of zinc oxide in said first layer, an image area on said second layer comprising an oleophilic resinous material, and a non-image area on said second layer comprising a hydrophilic reaction product of zinc oxide.
• hydrophilic zinc oxide reaction product is a reaction product of zinc oxide and a member selected from the group consisting of phosphates, ferrocyanides, ferricyanides, cobalticyanides, vanadates, molybdates, tungstates, tartarates, oxalates, tannates and citrates.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Printing Plates And Materials Therefor (AREA)
• Photoreceptors In Electrophotography (AREA)

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Publications (1)

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Cited By (4)

Citations (7)

• 1967
  • 1967-03-17 US US623814A patent/US3481271A/en not_active Expired - Lifetime
• 1968
  • 1968-03-15 DE DE19681671645 patent/DE1671645A1/de active Granted
  • 1968-03-17 GB GB12200/68A patent/GB1149605A/en not_active Expired

Patent Citations (7)

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