A compound represented by the following formula (I):
##STR1##
wherein R1, R2 and R3each represents an
aryl group, a heterocyclic group or an aliphatic hydrocarbon group, provided that
at least one of R1, R2 and R3 represents an aryl
group or a heterocyclic group and at least one of the aryl group and heterocyclic
group contains a group represented by formula (II), R1, R2 and
R3 may be linked to each other to form a ring,
##STR2##
wherein R4, R5 and R6, each represents a
hydrogen atom or a substituent; X1 represents an oxygen atom, a sulfur
atom, NRX1 or CRX2RX3; RX1,
RX2,RX3 each represents a hydrogen atom or a substituent;
R4, R5, R6 and X1 may be linked to
each other to form a ring; Y represents an oxygen atom, a sulfur atom, or NRY1;
and RY1 represents a hydrogen atom or a substituent.