Microcapsules containing at least one leuco dye, at least one photopolymerisation initiator and at least one photopolymerisable monomer corresponding to the following formula wherein A stands for a 3- to 6-valent organic group having the following meanings: a) a saturated hydrocarbon group having 5 to 25 carbon atoms or b) ##STR1## or c) ##STR2## wherein A.sub.1, A.sub.2, R.sub.3, R.sub.4, o and p have the meanings indicated in the description, X denotes O or NR.sub.2, L.sub.1 denotes a divalent...