An ethylamine derivative of formula (I): ##STR1## wherein A represents a carbon atom or a nitrogen atom;B represents a substituted or unsubstituted aralkyl or aryl group;C represents hydrogen, alkyl, aralkyl, or aryl, each of which may optionally be substituted orC may optionally be bonded to A to form an alkylene bridge which is optionally substituted,Q represents a substituted or unsubstituted aryl group, said group optionally being substituted by hetero atom(s) or substituent(s) optionally containing hetero atom(s); andX represents an alkylene bridge having from 2 to 20 carbon atoms and is optionally substituted with groups which include hetero atoms with the non-hetero atom substituents optionally containing hetero atoms.