Photopolymerizable compositions and flexographic printing plates derived therefrom

A photopolymerizable composition, which comprises:

• (a) from 20 to 98.9% by weight, based on the weight of components (a) and (b), of one or more thermoplastic elastomeric block copolymers comprising a thermoplastic elastomeric block copolymer of the formula
• A-C-A (1)
• or
• (A-C)nX (2)
• wherein each A independently represents a polymer block of predominantly a monovinyl aromatic hydrocarbon having an apparent molecular weight in the range of from 7,000 to 25,000, wherein n is an integer equal to or greater than 2 and wherein X is the residue of a coupling agent, and wherein each C independently represents a substantially random copolymer block (I/B) of predominantly isoprene and butadiene in a mutual weight ratio in the range of from 20/80 to 80/20, wherein said polymer block C has a glass transition temperature (Tg) of at most 0° C., (determined according to ASTM E-1356-98), and having a vinyl bond content (the 1,2 and/or 3,4-addition polymerization of the isoprene and butadiene) in the range of from 5 to 70 mole %, said thermoplastic block copolymer having a poly(monovinyl aromatic hydrocarbon) content in the range of from 10 to 45 wt % and having an apparent molecular weight of the complete block copolymer in the range of from 100,000 to 1,500,000,
• (b) from 1 to 60% by weight, based on the weight of components (a) and (b), of one or more photopolymerizable ethylenically unsaturated low molecular weight compounds,
• (c) from 0.1 to 10% by weight, based on the total photomerizable composition of one or more polymerization initiators, and optionally
• (d) from 0 to 40% by weight, based on the total photopolymerizable compositions, of one or more auxiliaries.

A flexographic printing plate derived from a photopolymerizable composition, said flexographic printing plate comprising a support layer, an optional adhesive layer and/or antihalation layer, one or more photopolymerizable layers, an optional elastomeric intermediate layer and a cover layer, said one or more photopolymerizable layers comprising:

• (a) from 20 to 98.9% by weight, based on the weight of components (a) and (b), of one or more thermoplastic elastomeric block copolymers comprising a thermoplastic elastomeric block copolymer of the formula
• A-C-A (1)
• or
• (A-C)nX (2)
• wherein each A independently represents a polymer block of predominantly a monovinyl aromatic hydrocarbon having an apparent molecular weight in the range of from 7,000 to 25,000, wherein n is an integer equal to or greater than 2 and wherein X is the residue of a coupling agent, and wherein each C independently represents a substantially random copolymer block (I/B) of predominantly isoprene and butadiene in a mutual weight ratio in the range of from 20/80 to 80/20, wherein said polymer block C has a glass transition temperature (Tg) of at most 0° C., (determined according to ASTM E-1356-98), and having a vinyl bond content (the 1,2 and/or 3,4-addition polymerization of the isoprene and butadiene) in the range of from 5 to 70 mole %, said thermoplastic block copolymer having a poly(monovinyl aromatic hydrocarbon) content in the range of from 10 to 45 wt % and having an apparent molecular weight of the complete block copolymer in the range of from 100,000 to 1,500,000,
• (b) from 1 to 60% by weight, based on the weight of components (a) and (b), of one or more photopolymerizable ethylenically unsaturated low molecular weight compounds,
• (c) from 0.1 to 10% by weight, based on the total photomerizable composition of one or more polymerization initiators, and optionally
• (d) from 0 to 40% by weight, based on the total photopolymerizable compositions, of one or more auxiliaries.