Photocurable organopolysiloxane compositions

Abstract

A novel photocurable composition suitable for preparing, for example, release papers is proposed which is formulated with photocrosslinkable organopolysiloxanes necessitating no conventional photosensitizers. Thus, the composition comprises (a) an organopolysiloxane having at least two mercaptoalkyl, e.g. mercaptopropyl, groups bonded to the silicon atoms in a molecule, (b) an organopolysiloxane having at least two alkenyl, e.g. vinyl groups directly bonded to the silicon atoms in a molecule, and (c) an organopolysiloxane having at least one benzoin group ##STR1## where Ph is a phenyl group, bonded to the silicon atom in a molecule, which component (c) serves as a photosensitizing ingredient. Alternatively, the inventive composition comprises (a) a mercaptoalkyl-containing organopolysiloxane as above and (b') an organopolysiloxane having, simultaneously, at least two alkenyl groups and at least one benzoin group directly bonded to the silicon atoms in a molecule, which component (b') serves both as the crosslinking agent and as the photosensitizing ingredient simultaneously. Owing to the unquestionable affinity of the photosensitizing ingredient with the other components, the inventive compositions have very high sensitivity in photocuring along with several other advantageous characteristics.

Dependencies are inferred from the claim text.