Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/004—Photosensitive materials
  • G03F7/06—Silver salts
  • G03F7/063—Additives or means to improve the lithographic properties; Processing solutions characterised by such additives; Treatment after development or transfer, e.g. finishing, washing; Correction or deletion fluids

Definitions

• Lithographic printing plates are prepared from imaged silver halide photographic elements by contacting the element with a benzotriazole substituted in the 4, 5, 6, and/ or 7 positions. Portions of the element containing silver halide are rendered oleophilic and thus receptive to oily printing inks, while portions free of halide are unreactive and thus oleophobic.
• This invention relates to lithographic printing, and more particularly concerns the provision of a lithographic printing plate from an imaged photographic emulsioncoated element. Otherwise stated, the invention concerns the conversion of a silver halide photographic image to an oleophilic, or oil-receptive, lithographic printing plate.
• a photographic image is converted into a medium that is receptive to oily or greasy inks.
• Desired objectives of methods for effecting this conversion include: a method which is simple, rapid, convenient, and low in cost; reagents which are readily prepared and are stable and consistent in use; lithographic printing plates which may be stored for long periods, either wet or dry, and in the presence of comparatively strong light; and a method which permits a positive printing plate to be made directly from a photographic negative.
• imaged silver halide photographic elements, or layers may be converted to lithographic plates of outstanding quality by contacting the elements with certain benzotriazole derivatives, that is, one or more benzotriazoles substituted in the 4, 5, 6, and/or 7 positions, and having the formula:
• the substituents may be any functional groups that do not react adversely with components of the conversion reagent, and may, for example, be alkyl, 'aryl (including fused ring), halo, nitro, amino, nitroso, hydroxy, alkoxy, etc., and combinations thereof.
• the process of the invention converts silver halide to an oleophilic ink-receptive medium, and in all respects meet the desired objectives above.
• the reagents of the invention are applied to a negative silver halide photographic element which has been developed by the action of a conventional developer, or reducing agent, and which has not been treated with a fixing solution.
• Developing converts exposed portions of silver halide to metallic silver, which is not reactive with the benzotriazole reagent, while retaining unexposed silver halide in the element.
• the metallic silver remains oleophobic and hydrophilic.
• a printing plate may be prepared directly from an imaged but undeveloped photographic element.
• the element is simultaneously developed and converted to an oleophilic medium by treatment in a monobath containing both a developer and the conversion. reagent.
• the conversion reagent should be replenished or replaced more frequently than in multibath processing.
• the reagents of the invention may be used with many of the common silver halide photographic elements, preferably those in which the halide is chloride, alone or with additional amounts of bromide and/or iodide.
• the silver halidegelatin emulsion may be applied onto a suitable photographic base, whether transparent, translucent or opaque. These bases are usually subbed or otherwise treated to make them accept an aqueous emulsion, as known in the art.
• Treatment of the developed photographic element with a benzotriazole derivative reagent of the invention is conveniently elfected in an aqueous alkaline medium.
• Optimum reagent concentrations have been determined for S-chlorobenzotriazole, and presumably are within i50% of these values for other benzotriazoles.
• the alkali concentration (for S-chlorobenzotriazole) is advantageously about 1% by weight, and may range from less than 0.1% to more than about 4% sodium or potassium hydroxide.
• a portion of the hydroxide may be replaced with an alkaline salt such as the carbonate.
• an alkaline salt such as the carbonate.
• the conversion reagent may include wetting agents such as the non-ionic detergents; gelatin hardening agents such as sodium sulfate and sodium and/or chromic acetate; water soluble polymers; and other materials found useful for maintaining a clean print background.
• benzotriazole derivatives may be used for the invention.
• the substituted benzotriazoles include the preferred 5-chloro, the satisfactory S-methyl, 5,6-dimethyl, and 4,5-dichloro, and the somewhat less effective 5-nitr0 compounds.
• the 4-amino, 6-amino, o-dimethylamino, 6-hydroxy, and other derivatives may also be used as required.
• Unsubstituted benzotriazole is unsatisfactory.
• the benzotriazole derivatives of the invention may be shipped and stored either as the solid products, the solid products mixed with an anhydrous alkali such as sodium or potassium hydroxide, or in aqueous solution either with or without the alkali. Alkalies are helpful in dissolving the derivatives. Wetting agents, hardening agents, water soluble polymers, and other materials may, if desired, be included in the solid products or in concentrates.
• anhydrous alkali such as sodium or potassium hydroxide
• EXAMPLE I In this example a silver chloride photographic element is converted to a printing plate by the action of 5-chlorobenzotriazole.
• a contrasty silver chloride emulsion is coated on a photographic paper base to a coating weight of about 5.8 grams of liquid emulsion per 'squ'afefoot'The silver content of the emulsion is equivalent to 30 grams Water to make 1000 ml. at room temperature.
• the element is squeegeed, contacted with the converting reagent at 70 F. for about 20-3O seconds, squeegeed dried, and etched by swabbing with a suitable starting solution, e.g. APECO Starting Solution before use.
• a suitable starting solution e.g. APECO Starting Solution before use.
• Printing is with a Multilith A/M #1250 offset duplicator press, using ink (A/M, black ml-pd #304), and as fountain, APECO Starting Solution diluted 1:7 with water. At least 1000 good prints were obtained in 50 pound paper stock.
• the benzotriazole is then incorporated" onto the element itself, advantageously in a gelatin emulsion layer adjacent the silver halide-containing layer. Immersionin an alkaline developer thereby activates the benzotriazole. and simultaneously develops the image and renders it oleophilic.
• a method of forming a; lithographic printing plate from an imaged silver halide photographic element having portions containing silver halide and portions*free of silver halide which comprises: contacting said element, while in an aqueous alkaline environment providing an alkalinity equivalent to about 0.01%to 4% of sodiun'fo'r potassium hydroxide, with a benzotriazolesubstitutedat least one of the 4, 5, and 6 positions-with-a substitue-nt selected from the group methyLchloro and combinations thereof, in a concentration equivalent to from about 0.25
• Method of claim 1 including the step, prior to sa d contacting, of developing said element. M I n v 3. Method of claim 1 wherein said element is simul ⁇ taneously treated with amonobath containing developer and said benzotriazole. 4. Method of claim 1 wherein said benzotriazole is 5-chlorobenzotriazole. w 5. Method of claim 1 where said benzotriazole is S-methylbenZotriazole. 6. Method of claim 1 wherein "said benzotriazole is. ,6-dime hylbenzotriazole. a

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Cited By (3)

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• 1971
  • 1971-04-15 US US00134399A patent/US3764323A/en not_active Expired - Lifetime
• 1972
  • 1972-04-12 CA CA139,515A patent/CA964514A/en not_active Expired
  • 1972-04-14 IT IT7260/72A patent/IT957189B/it active
  • 1972-04-14 FR FR7213281A patent/FR2136447A5/fr not_active Expired
  • 1972-04-14 DE DE2218054A patent/DE2218054A1/de active Pending
  • 1972-04-17 GB GB1766872A patent/GB1393785A/en not_active Expired

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