radiation - sensitive compositions which are especially useful in the production of negative - working lithographic printing plates comprise a photocrosslinkable polymer containing the photosensitive group ## str1 ## as an integral part of the polymer backbone and , in an amount sufficient to improve the properties of the composition , both a poly and an unsaturated polyester such as a polyester derived from fumaric acid and a 4 , 4 &# 39 ;- isopropylidenediphenol . the combination of a poly and an unsaturated polyester improves the properties of the radiation - sensitive composition in regard to such factors as shelf life , image contrast , developability , ink receptivity and reduction in mottle and thereby provides a superior lithographic printing plate .