Napp Systems (USA), Inc.

Koichi Kimoto

Sakuo Okai

Robert W Hallman

A shallow relief non-bottoming printing plate is disclosed having a polymerized layer of less than about 0.020 inch and which includes a plurality of dispersed particles sufficient to create small protuberances in non-image or background areas to prevent bottoming. Photopolymerizable elements, as well as processing techniques, are also disclosed for making such printing plates.

Shallow relief non-bottoming photopolymer printing plate

A photopolymerizable composition and photosensitive elements produced therefrom are disclosed. The photopolymerizable composition includes: (a) a monomer component, (b) a polymer component, (c) a photopolymerization initiator, and (d) an activator. The monomer component contains at least one water soluble, monofunctional unsaturated ethylenic monomer or the combination of such a monomer and at least one polyfunctional unsaturated ethylenic monomer. The polymer component includes a partially saponified water soluble, polyvinyl acetate polymer compatible with the monomer components. The polyvinyl acetate polymer contains both acetyl and hydroxyl groups and has a polymerization degree of from 300-2000. The degree of saponification of the polymer is desirably in the range of 65 to 99 percent. The preferred photopolymerizaton initiators are acetophenone derivatives such as 2,2-dimethoxy-2-phenyl acetopheonone, 2,2-diethoxy-2-phenyl acetophenone, 2,-2-diisopropoxy-2-phenyl acetophenone, benzoin alkyl, aryl, allyl or vinyl ethers, or benzophenone derivatives such as benzophenone, 2-methylbenzophenone, 2-methoxybenzophenone or 2,2'-dimethoxybenzophenone, which are compatible with the monomer component and the polyvinyl acetate polymer and are activatable by actinic light. Finally, the activator is a phosphine derivative generally described by the formula: ##STR1## wherein any of X, Y and Z are hydrogen, halogen, alkyl, alkoxy, aryl, vinyl, or allyl, although not more than one of X, Y and Z may be hydrogen. It is especially preferred in the practice of the present invention that at least one of X, Y or Z in the phosphine derivative activator component be an aryl group.

Element having phosphine activated photosensitive compositions therein

A photopolymerizable composition and photosensitive elements produced therefrom are disclosed. The photopolymerizable composition includes: (a) a monomer component, (b) a polymer component, (c) a photopolymerization initiator, and (d) an activator. The monomer component contains at least one water soluble, monofunctional unsaturated ethylenic monomer or the combination of such a monomer and at least one polyfunctional unsaturated ethylenic monomer. The polymer component includes a partially saponified water soluble, polyvinyl acetate polymer compatible with the monomer components. The polyvinyl acetate polymer contains both acetyl and hydroxyl groups and has a polymerization degree of from 300-2000. The degree of saponification of the polymer is desirably in the range of 65 to 99 percent. The preferred photopolymerization initiators are acetophenone derivatives such as 2,2-dimethoxy-2-phenyl acetophenone, 2,2-diethoxy-2-phenyl acetophenone, 2,-2-diisopropoxy-2-phenyl acetophenone, benzoin alkyl, aryl, allyl or vinyl ethers, or benzophenone derivatives such as benzophenone, 2-methylbenzophenone, 2-methoxybenzophenone or 2,2'-dimethoxybenzophenone, which are compatible with the monomer component and the polyvinyl acetate polymer and are activatable by actinic light. Finally, the activator is a phosphine derivative generally described by the formula: ##STR1## wherein any of X, Y and Z are hydrogen, halogen, alkyl, alkoxy, aryl, vinyl, or allyl, although not more than one or X, Y and Z may be hydrogen. It is especially preferred in the practice of the present invention that at least one of X, Y and Z in the phosphine derivative activator component be an aryl group.

Water developable photopolymerizable compositions containing phosphine

Letterpress and offset photopolymer printing plates are disclosed having relatively thin water developable photopolymer layers, which, after being developed, have ink-repulsive, non-image areas. Adhesive layers are provided in the disclosed printing plates that are interposed between an ink-repulsive coating contained in the printing plate substrate and the water-developable photopolymer, and provide a balance between satisfactory adhesive and ink-repulsive properties in the resulting plate.

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Oceanside, CA, United States of America

Koichi Kimoto