Patent ID: 7750130

Claim:
A fluorescent particle formed by aggregates of the azobenzene derivative denoted by general formula (II): wherein, in general formula (II), R 1 denotes a hydrogen atom, halogen atom, alkoxy group, alkyl group, cycloalkyl group, aryl group, heterocyclic group, cyano group, ester group, ketone group, -CA 3 , —(C═O)A, —(C═O)NA 2 , -BA, -OA, -SA, -NA 2 , —(P═O)A 2 or an organic fluorescent group, where A denotes a hydrogen atom, halogen atom, alkoxy group or alkyl group, as well as when multiple atoms and/or groups denoted by A are present in a single group, they are identical to or different from each other, R 2 to R 9 each independently denotes a hydrogen atom, halogen atom, alkoxy group, alkyl group, cycloalkyl group, aryl group, heterocyclic group, cyano group, ester group, ketone group, -CA″ 3 , —(C═O)A″, —(C═O)NA″ 2 , -BA″, -OA″, -SA″, -NA″ 2 , —(P═O)A″ 2 , or an organic fluorescent group, where A″ denotes a hydrogen atom, halogen atom, alkoxy group or alkyl group, as well as when multiple atoms and/or groups denoted by A″ are present in a single group, they are identical to or different from each other, wherein at least R 4 and R 5 in two phenylene rings bonded through an azo group are substituents other than hydrogen atoms, and when multiple atoms and/or groups denoted by any of R 2 to R 9 are present with n and/or m being an integer equal to or greater than 2, they are identical to or different from each other, X denotes an alkylene group optionally comprising a hetero atom, and m and n each independently denotes an integer ranging from 1 to 8, where, when multiple phenylene groups are present with n being an integer equal to or greater than 2, they are identical to or different from each other, as well as when multiple phenylene groups are present with m being an integer equal to or greater than 2, they are identical to or different from each other.