Abstract: Orifices, cavities or interstices which are formed when printing plates are mounted on plate cylinders are closed and/or sealed by means of a sealing or closing compound, a pasty material which is viscoplastic at room temperature and based on a dispersion of a solid, highly fluorinated olefin polymer powder in an inert, sparingly volatile, organic dispersing liquid being used as the sealing or closing compound.

Abstract: A photosensitive recording element possessing a photosensitive recording layer which is applied to a dimensionally stable base, if desired on top of one or more intermediate layers, and has good photochemical properties and a long shelf life contains special sulfo-containing azo or azoxy dyes for controlling the photochemical properties in the photosensitive recording layer and/or in any intermediate layer present. Dyes which are suitable for use according to the invention can be obtained, for example, by autocondensation of 5-nitro-o-toluenesulfonic acid.

Abstract: Orifices, cavities or spaces which are formed when printing plates are mounted on a plate cylinder are closed and/or sealed by means of a pasty, photocurable sealing or closing compound consisting of one or more photopolymerizable, ethylenically unsaturated low molecular weight compounds (a), one or more polymeric binder (b) which are compatible with the said compounds of component (a), one or more photopolymerization initiators (c) and one or more finely divided oxidic fillers (d) which, when mixed with components (a) to (c), give mixtures which are transparent to long-wavelength UV light. After it has been applied, this sealing or closing compound is cured by exposure and can then be mechanically processed. The process is particularly suitable for closing and/or sealing orifices, cavities or spaces in gravure printing plates mounted on plate cylinders.

Abstract: Photosensitive recording elements which possess a photosensitive recording layer which is applied to a dimensionally stable base, if necessary via one or more intermediate layers, and have good photochemical properties and a long shelf life contain a compound of the general formula (I) ##STR1## where M is a hydrogen atom or proton, an alkali metal cation, the ammonium cation or an amine cation and R.sup.1 and R.sup.2 are identical or different and are each a substituted s-triazine ring, in the photosensitive recording layer and/or any intermediate layer present, in order to control the photochemical properties.

Abstract: Negative correction of gravure printing plates by filling undesirable depressions in the printing layer of the gravure printing plate with a correcting agent is carried out by a method in which the correcting agent used is a pasty material which is viscoplastic at room temperature and is based on a dispersion of a solid, highly fluorinated olefin polymer powder in an inert, sparingly volatile, organic dispersing liquid.

Abstract: For coating printing cylinders or sleeves with a seamless, smooth photosensitive layer, two or more strata of a thin, prefabricated, essentially solvent-free, unsupported, thermoplastically processible, solid, photosensitive layer are applied to the printing cylinder or the sleeve, without bubbles and with displacement of the air between the individual strata, and the total photosensitive layer material is then heated under pressure and with joining or fusion of the individual strata to form a single, continuous photosensitive layer, and the surface of the resulting photosensitive layer is aftertreated to shape it exactly to size and is smoothed, with formation of an exactly cylindrical shape.

Abstract: Acylphosphine compounds of the formula I ##STR1## where X is oxygen, sulfur or an electron pair, R.sup.1 is R.sub.4 or OR.sup.4, R.sup.2 is --OM, where M is a monovalent cation, R.sup.3 is aryl which is substituted at least at the two positions ortho to the carbonyl group, and R.sup.4 is hydrogen, alkyl or aryl, are very effective photoinitiators for photopolymerizable materials, such as coating compositions, finishes, printing inks, unsaturated polyesters, recording media and preferably aqueous polymer dispersions or solutions.

Abstract: Photopolymerizable water-soluble or water-dispersible mixtures essentially consisting of a base polymer, at least one polymerizable ethylenically unsaturated compound and at least one photoinitiator and/or photosensitizer are stabilized to thermal polymerization by treating the base polymer with a halogen, a pseudohalogen or a polyhalide.

Abstract: A photopolymerizable composition for the production of water-developable printing plates and relief plates, based on a water-soluble or water-dispersible mixture, containing a photoinitiator, of(a) one or more water-soluble or water-dispersible polymers containing copolymerized N-vinylpyrrolidone units and/or one or more polymers containing vinyl alcohol units and(b) one or more olefinically unsaturated photopolymerizable monomers,which comprises, as an additive or as the sole polymer, a water-soluble modified vinyl alcohol polymer which contains from 5 to 75, especially from 10 to 60, % by weight of chemically bonded oxyethylene units. These modified vinyl alcohol polymers are in particular oxyethylated polyvinyl alcohol or hydrolyzed graft polymers of vinyl esters onto polyethylene glycols. The compositions are easier to process into printing plates and relief plates, and exhibit a long shelf life.

Abstract: A photopolymerizable composition for the manufacture of printing plates and relief plates, based on a mixture, containing a photoinitiator, of photopolymerizable olefinically unsaturated monomers and a polymeric binder, contains up to 0.1% by weight of an etherified thioanthraquinone for improving the relief image in the production of relief plates.The composition advantageously also contains a small amount of an organic tertiary amine or of an aromatic .alpha.-ketocarboxylic acid or its ester and/or of an inhibitor, e.g. the salt of an organic N-nitrosohydroxylamine.