Water developable photopolymerizable compositions containing phosphine activators and saponified polyvinyl acetate

A photopolymerizable composition for water-developable printing plates which can be exposed and developed without pre-exposure conditioning comprising:

• a. about 0.1 to 3.0 parts by weight of a monomer component including at least one water-soluble monofunctional monomer, or the combination of said monofunctional monomer and at least one polyfunctional unsaturated ethylenic monomer, said monomers capable of forming a polymer by photoinitiated polymerization in the presence of a polymerization initiator activatable by actinic light;
• b. about 0.1 to 3.0 parts by weight of a water soluble polymer component including a partially saponified, water-soluble, polyvinyl acetate polymer compatible with said monomer component containing both acetyl and hydroxy groups, and having a polymerization degree of about 300 to 2,000 and a saponification degree of about 65 to 99 mole percent;
• c. about 0.001 to 0.3 parts by weight of a photopolymerization initiator said initiator being compatible with said monomer component and said polyvinyl acetate polymer, and activatable by actinic light;
• and
• d. about 0.001 to 0.3 parts by weight of an activator including a phosphine derivative described by the formula:
• ##STR4## wherein any of X, Y and Z are hydrogen, halogen, alkyl, alkoxy, aryl, allyl, or vinyl, but not more than one of the X, Y and Z is hydrogen, and at least one of X, Y and Z is aryl.

A water-developable photopolymerizable composition for water-developable printing plates which can be exposed and developed without pre-exposure conditioning comprising:

• a. about 0.1 to 3.0 parts by weight of at least one unsaturated ethylenic monomer polymerizable by actinic light in the presence of a photopolymerization initiator;
• b. about 0.001 to 0.3 parts by weight of a photopolymerization initiator
• c. about 0.1 to 3.0 parts by weight of a water soluble partially saponified polyvinyl acetate having both acetyl groups and hydroxy groups produced by saponification, said polyvinyl acetate having a saponification degree of about 65 to 99 mole percent and a polymerization degree of about 300 to 2,000, and
• d. about 0.001 to 0.3 parts by weight of a phosphine derivative described by the formula:
• ##STR5## wherein any of X, Y and Z are hydrogen, halogen, alkyl, alkoxy, aryl, allyl, or vinyl, and at least one of X, Y and Z is aryl.