| 摘要 |
944,395. Electrophotographic development; photomechanical printing plates. KALLE A. G. Aug. 30, 1960 [Sept. 4, 1959], No. 29880/60. Headings G2H and G2M. A printing plate is prepared by developing an exposed and charged photoconductive plate with a dry mixture of positive and negative toners which are in the same range of particle size and which are selectively removable from the developed image by the action of heat or by treatment with water or an acid or alkaline liquid, the two toners adhering respectively to the exposed and unexposed parts of the image, fixing the image, and removing one toner component selectively by the action of water or an acid or alkaline liquid if not already removed by heat during fixing. The support may be of aluminium and the photoconduc- tor also may be removed in those areas where the toner has been removed. Exhaustive lists are given of compounds useful as one or other of the toner components and these include polystyrene, vinyl and acrylic resins, coumarone and ketone resins, metal resinates, natural resins, organic carboxylic and sulphonic acids and their salts and derivatives, aromatic hydroxy compounds, organic amines, imidazoles, triazoles and pyrazoles. Waxes, organic compounds of low melting point (many specified), dyes (including their metal salts) and pigments such as carbon black, zinc oxide,titanium dioxide, barium sulphate and red lead may be included in the particles of one or both toners. The particles of each toner may be formed by fusing together a mixture of ingredients and finely grinding the product. The developed image may be fixed by heat or by the use of solvent vapours. The developed and fixed image may be treated with a lacquer before treatment with the solvent for removing one of the toners, particularly when the two toners are both soluble in alkali but at different rates. In the examples, the developed and fixed image is treated with one of the following aqueous solutions to remove one toner component and make a printing plate; (a) monoethanolamine, polyethylene glycol and sodium silicate or glycerine, (b) polyethylene glycol and ammonia or diethanolamine, (c) phosphoric or acetic acid to which a little gum arabic was added, (d) trisodium phosphate, sodium hexametaphosphate and sodium metasilicate, and (e) dilute sodium hydroxide. Specification 944,394 is referred to.
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