E.i. Dupont De Nemours and Company

Peter F Warfield

Michael G Fickes

Stanley H Munger

Robert R Gruetzmacher

Process for improving ozone resistance of photosensitive flexographic relief printing plates prepared from at least 30% by weight of a block copolymer as defined, at least 1% by weight of at least one addition polymerizable ethylenically unsaturated compound, and a polymerization initiator wherein there is applied to the dry relief surface of said plates a solvent solution containing at least 1% by weight of a nickel or zinc dialkyldithiocarbamate compound where alkyl is from 1 to 4 carbon atoms. The treated plates which possess improved ozone resistance are useful for flexographic printing.

Preparation of ozone resistant printing plates

Process for providing improved solvent resistant surfaces of relief flexographic printing plates prepared by imagewise exposure and liquid development of the unexposed areas of a layer of a photosensitive elastomeric composition comprising a polymer of a conjugated diolefin hydrocarbon, and a monomeric compound wherein, after drying, the developed surface is in either order (1) postexposed to actinic radiation, and (2) contacted for about 15 seconds to 40 minutes with an aqueous treatment solution of an alkali monopersulfate, e.g., 2KHSO.sub.5.KHSO.sub.4.K.sub.2 SO.sub.4 and a bromide salt, e.g., potassium bromide.

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Westfield, NJ, United States of America

Peter F Warfield