Photoimageable composition having improved flexibility

A negative-acting photoimageable composition comprising

• A) between about 30 and about 80 wt % based on the total weight of A) plus B) of a binder polymer having acid functionality sufficient to render said photoimageable composition developable in alkaline aqueous solution,
• B) between about 20 and about 70 wt % based on the total weight of A) plus B) of an addition-polymerizable, non-gaseous α,β-ethylenically unsaturated compound(s) capable of forming a high polymer by free-radical initiated chain-propagating addition polymerization, said component B comprising between about 1 and about 70 wt %, based on total of A) plus B) of a urethane biuret oligomer having the formula:
• R—CO—NH—Z—N—(CO—NH—Z—NH—CO—R)2
• where the R's are the same or different and have the general formula:
• —Am—[—CO—NH—Z—NH—CO—]s—Ap—O—CO—CY═CH2,
• where m=6-20, p=0-20, s=0-1;
• the A's are the same or different and are selected from the group consisting of
• —[O—CHY—CHY—]—,
• where the Y's are the same or different and are selected from the group consisting of H, CH3, or C2H5,
• —[O—(CH2)3-4—]—,
• —[—O—(CH2)3-5—CO—]—
• and mixtures thereof;
• and Z is a divalent alkyl, cycloalkyl, aromatic, or alkylaromatic hydrocarbon moiety;
• and
• (C) a photoinitiator chemical system.