Silicone type cinnamic acid derivative, preparation method thereof, UV- ray absorber, and external skin treatment agent

摘要

A silicone type cinnamic acid derivative which is a siloxane having at least one unit represented by the formula (I): ##STR1## and having the other units which may exist in the siloxane being represented by the formula:PPO.sub.(4-m)/2 SiR.sup.3.sub.mP P wherein R.sup.1 represents an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a trimethylsiloxy group, R.sup.2 is a divalent hydrocarbon group having at least two carbon atoms, which may include a heteroatom O, X is an alkoxy group, n is an integer of 0 to 3, a is an integer of 2 or 3, R.sup.3 is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a trimethylsiloxy group, and m is an integer of 0 to 3.