Classifications

• • 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
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0503—Inert supplements
  • G03G5/051—Organic non-macromolecular compounds
  • G03G5/0517—Organic non-macromolecular compounds comprising one or more cyclic groups consisting of carbon-atoms only
• • 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
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0503—Inert supplements
  • G03G5/051—Organic non-macromolecular compounds
  • G03G5/0514—Organic non-macromolecular compounds not comprising cyclic groups

Definitions

• This invention relates to improved methods for the production of lithoprinting plates from photoconductive plates.
• Lithoprinting plates are normally prepared from electrophotographic copying materials, referred to herein as photoconductive plates, which comprise an electrically conductive support having a photoconductive surface layer.
• the surface layer typically contains a photoconductive material dispersed in an electrically insulating resinous or' polymeric. binder.
• the photoconductive plate is converted to a lithoprinting plate by a process comprising the steps of:
• a difiiculty with this procedure is that the liquid developer fails to adhere closely to thelatent image area with the result that the etching liquid infiltrates and partially desensitizes the image area. As a result, the printing ink fails to spread well on the image area, and the printed images produced from the lithographic plates are of low concentration. Attempts to alleviate this problem, for example by the use of weaker etching liquids have re sulted in imperfect desensitization of the non-image areas of the lithopr'inting plate. Printed "images produced from such imperfect plates have stained backgrounds.
• This invention markedly alleviates the difficulties .of conventional methods, and provides a procedure for manufacturing lithoprinting plates capable of producing printed images of high concentration which are substantially free from background stain.
• the principal features "of the invention are the selection of photoconductive' plates iii-which the photoconductive surface layer has a contact angle with water which is 3,834,909 Patented Sept. 10, 1974 ice from to at 20 C. and 65% relative humidity, and the application of an electric charge to the developed image prior to etching.
• the invention comprises the steps The latent electrostatic image is produced in the conventional manner.
• a particular advantage of the invention is that the second charge can be imparted to the plate in the same manner using the same equipment as the first charge. It is, moreover, generally of the same order of magnitude.
• conventional polymeric binders and photoconductive substances are employed except that they are modified by mixing or coating with surface modifiers to insure that the surface will have the right contact angle.
• the surface modifiers utilized in the invention are liquids at ambient temperature (about 20 C. to 45 C.), of low volatility and may be compounded with or coated. on the photoconductive layer.
• Suitable treating agents include, for example:
• esters including:
• R R and R representj fatty acid residual radicals which may be the same or different, saturated or unsaturated and contain up to about 18 carbon atoms. This includes, falr) instance, triglyceride of -oleic acid (sesame o1 f I (b) Monohydric alcohol esters of such fatty acids as suberic' acid, azelaic acid, containing up to about ten.
• Dialkylated naphthalenes such as 1,4-dialkylated naphthalenes wherein the alkyl radical contains 1-5 carbon atoms
• (VII) Liquid paraffins The foregoing materials for improvement may be applied with the materials constituting the photoconductive layer.
• the materials constituting the photoconductive layer wherein an inorganic material is employed as the photoconductor
• the preferred range is from 1 to 30 parts by weight per 100 parts.
• the quantity of inorganic photoconductor in the photoconductive layer is desirably in the range of 100-800 parts by weight per 100 parts by weight of the resinous binder.
• the electrically insulating polymers utilized in this invention may be selected from any of a large number of conventional polymers and copolymers including, for example, acrylic resins, polyvinyl acetates, alkyd resins, cellulose resins, phenol resins, polyesters, and the like.
• the photoconductive materials which may be utilized include, for example, zinc oxide, cadmium sulfide, zinc sulfide, amorphous selenium, titanium dioxide and the like.
• Sensitizers such as Rose Bengal may be added in the usual amounts to improve the spectral sensitivity.
• the photoconductive plate may be treated on the side opposite the photoconductive surface with any of the usual materials used to improve electrical conductivity such as polyvinyl benzyl ammonium chloride.
• Typical liquid developers which can be used to develop the latent electrostatic images of this invention include, for example, those described in U.S. Pat. No. 3,554,946. Any of a wide variety of others may also be used.
• EXAMPLE 1 Water-soluble epoxy resin (l%-aqueous solution)- Styrene-butadiene resin latex (solid: 50%) 50% aqueous dispersion of clay 66 Water 100 Next, by coating a conductive liquid having the following composition on the back of the same paper and drying at 130 C., a conductive layer weighing 10 g./m. was formed thereon.
• Zinc oxide 100 Acryl resin 50% toluene solution of methyl and butyl methacrylate, mole ratio 50:50
• Silicone varnish (70% toluene solution) 3 Silicone oil '(FK-99 manufactured by Shinetsu Kagaku Co., Ltd.) 0.8 5% methanol solution of Rose Bengal 1 Toluene 120 etching.
• the etching liquid spread well on the non-image area to desensitize it, while the image area was free of adhesion of etching liquid and was not desensitized.
• a comparative copying material not containing silicone oil in its photoconductive layer was also prepared in the same way as above.
• the contact angle with water of this copying material was 120.
• concentration of the image area was as low as 0.55.
• Measurement of the contact angle was conducted by the use of a goniometer-type contact angle measuring instrument in the atmosphere of 20 C. in temperature and 65 in R.H.
• EXAMPLES 2-4 Three photoconductive plates having a contact angle with water of 145, 140 and 150, respectively, were prepared by appyling 5 parts by weight of sesame oil, 6 parts by weight of linseed oil and 4 parts by weight of mineral oil, respectively, in lieu of silicone oil employed in Example 1. When these copying materials were utilized as offset masters in the same manner as in Example 1, there were obtained prints high in concentration in the image area and free of background stain.
• a method for manufacturing a lithoprinting plate comprising the steps of:
• the photoconductive surface layer comprises an electrically insulating polymeric binder, a photoconductive substance and, for each 100 parts by weight of said binder, from 0.5 to
• R represents hydrogen, alkyl radical containing 1-6 carbon atoms, allyl radical containing 1-6 carbon atoms; and n 21, at least one R being other than hydrogen, (II) esters including:
• R R and R represent fatty acid residual radicals which are the same or different, saturated or unsaturated and contain up to about 18 carbon atoms.
• Kb monohydric alcohol esters of dicarboxylic acids containing up to about ten carbon atoms in the acid moiety and six carbon atoms in the alkoxy moiety

Landscapes

• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Printing Plates And Materials Therefor (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=11829987

Family Applications (1)

Country Status (3)

Cited By (4)

Families Citing this family (1)

• 1972
  • 1972-02-08 JP JP47013325A patent/JPS4882906A/ja active Pending
• 1973
  • 1973-01-26 GB GB402273A patent/GB1419659A/en not_active Expired
  • 1973-02-07 US US00330286A patent/US3834909A/en not_active Expired - Lifetime

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