Acetal polymers and use thereof in photosensitive compositions and lithographic printing plates

A photosensitive composition comprising:

• (i) a diazonium polycondensation product or a free radical polymerizable system consisting of photoinitiators and free radical polymerizable components or a hybrid system consisting of a diazonium polycondensation product and a free radical polymerizable system consisting of photoinitiators and free radical polymerizable components, and
• (ii) a binder
• containing the units A, B, C, D and E, wherein A is present in an amount of 10 to 60 mole % and is of the formula ##STR13## B is present in an amount of 1 to 30 mole % and is of the formula ##STR14## C is present in an amount of 5 to 60 mole % and is of the formula ##STR15## D is present in an amount of 0 to 60 mole % and is of the formula ##STR16## E is present in an amount of 1 to 40 mole % and is of the formula ##STR17## wherein X is an aliphatic, aromatic or araliphatic spacer group, R.sup.1 is hydrogen or an aliphatic, aromatic or araliphatic group, R.sup.2, R.sup.3 and R.sup.4 are hydrogen or alkyl groups with carbon numbers of from 1 to 18 and Y is a saturated or unsaturated chain- or ring-shaped spacer group.