A compound represented by general formula: wherein Z represents a conjugated group having 1 to 50 carbon atoms selected from an unsaturated aliphatic hydrocarbon group, an aromatic hydrocarbon group, an aromatic heterocyclic group, and a group composed of one or more of these groups; R2 represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms; R30, R31, R32, R33, R40, R41, R42, R43, and R44 each independently represent a hydrogen atom or an optionally substituted hydrocarbon group; R30 and R31, R40 and R41, R41 and R42, R42 and R43, or R33 and R44 being optionally connected to each other to form a ring; R5 represents a hydrogen atom or a cyano group; and R11 represents a group represented by structural formula or: wherein n represents an integer of 1 to 4; ring A represents a benzene ring, a naphthalene ring, a cyclohexane ring, a cyclohexene ring, or a cyclohexadiene ring; the hydrogen atoms other than that of the carboxyl group in formulae and being optionally displaced by a carboxyl group, a cyano group, an amino group, an amide group, a nitro group, an aliphatic hydrocarbon group having 1 to 4 carbon atoms and substituted by at least one group selected from a carboxyl group, a cyano group, an amino group, an amide group and a nitro group, or an unsubstituted aliphatic hydrocarbon group having 1 to 4 carbon atoms, characterised in that R1 represents an aromatic hydrocarbon group having 6 to 20 carbon atoms, an aromatic hydrocarbon group having 7 to 20 carbon atoms and substituted by an aliphatic hydrocarbon group, or an aliphatic hydrocarbon group having 1 to 20 carbon atoms, the aromatic hydrocarbon group having 6 to 20 carbon atoms, the substituted aromatic hydrocarbon group having 7 to 20 carbon atoms, and the aliphatic hydrocarbon group being substituted by at least one of a carboxyl group, a cyano group, an amino group, an amide group, and a nitro group, the aliphatic hydrocarbon group being optionally interrupted by an interrupting group selected from 24 24 24 -O-, -COO-, -OCO-, -NR -, -NR COO-, and -OCONR - at up to 3 positions and, upon the interruption occurring at 2 or 3 positions, the interrupting groups not being adjacent to each other; 24 wherein R represents an aromatic hydrocarbon group having 6 to 10 carbon atoms, an aromatic hydrocarbon group having 7 to 15 carbon atoms and substituted by an aliphatic hydrocarbon group, or an aliphatic hydrocarbon group having 1 to 10 carbon atoms, the aromatic hydrocarbon group having 6 to 10 carbon atoms, the substituted aromatic hydrocarbon group having 7 to 15 carbon atoms, and the aliphatic hydrocarbon group being optionally substituted with a carboxyl group, a cyano group, an amino group, an amide group, or a nitro group. wherein Z represents a conjugated group having 1 to 50 carbon atoms selected from an unsaturated aliphatic hydrocarbon group, an aromatic hydrocarbon group, an aromatic heterocyclic group, and a group composed of one or more of these groups; R2 represents a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 20 carbon atoms; R30, R31, R32, R33, R40, R41, R42, R43, and R44 each independently represent a hydrogen atom or an optionally substituted hydrocarbon group; R30 and R31, R40 and R41, R41 and R42, R42 and R43, or R33 and R44 being optionally connected to each other to form a ring; R5 represents a hydrogen atom or a cyano group; and R11 represents a group represented by structural formula or: wherein n represents an integer of 1 to 4; ring A represents a benzene ring, a naphthalene ring, a cyclohexane ring, a cyclohexene ring, or a cyclohexadiene ring; the hydrogen atoms other than that of the carboxyl group in formulae and being optionally displaced by a carboxyl group, a cyano group, an amino group, an amide group, a nitro group, an aliphatic hydrocarbon group having 1 to 4 carbon atoms and substituted by at least one group selected from a carboxyl group, a cyano group, an amino group, an amide group and a nitro group, or an unsubstituted aliphatic hydrocarbon group having 1 to 4 carbon atoms,