Photosensitive diacrylate and dimethacrylate compositions

A photosensitive composition comprising

• (a) 5-65% by weight of a compound of formula (Ia) or (Ib),
• wherein the substituents R1 are each independently of the other hydrogen or methyl,
• R2 is an unsubstituted C1-C20alkyl group or a C1-C20 alkyl group which is substituted by one or more than one substituent selected from the group consisting of hydroxy, C6-C14aryl and halogen, an unsubstituted phenyl group or a phenyl group which is substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy or halogen, or is a radical of formula —CH2—OR3, wherein R3 is an unsubstituted C1-C20alkyl group or a C1-C20alkyl group which is substituted by one or more than one substituent selected from the group consisting of hydroxy, C6-C14aryl and halogen, an unsubstituted phenyl group or a phenyl group which is substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy and halogen, or is a C2-C6alkenyl group, a C2-C20acyl group or an unsubstituted cyclohexylcarbonyl group or a cyclohexylcarbonyl group which is substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, hydroxy and halogen,
• Z is a group of formulae (IIa)-(IIe)
• wherein Y is a direct bond, C1-C6alkylene, —S—, —O—, —SO—, —SO2— or —CO—, and R1 is hydrogen or methyl, and wherein the aromatic and cycloaliphatic rings of formulae (IIa)-(IIe) are unsubstituted or substituted by one or more than one substituent selected from the group consisting of C1-C6alkyl, chloro and bromo,
• (b) 15-70% by weight of one or more than one bifunctional acrylate or methacrylate having a molecular weight in the range from 150 to 450 and differing from the compound of formula (Ia) or (Ib),
• (c) 0-40% by weight of one or more than one monomeric polyfunctional acrylate or methacrylate having a functionality of not less than 3 and a molecular weight of not more than 600,
• (d) 0-10% by weight of at least one monofunctional acrylate or methacrylate,
• (e) 0-10% by weight of N-vinylpyrrolidone or N-vinylcaprolactam,
• (f) 2-10% by weight of at least one photoinitiator, and
• (g) 0-60% by weight of at least one urethane acrylate or methacrylate having a functionality of 2-4 and a molecular weight in the range from 500-10000.