The present invention relates to an
azo compound represented by the following formula (1): wherein A denotes a
phenyl group having 1 to 3 substituents such as
sulfonic acid group, amino group, lower
alkyl groups and lower alkoxyl groups, or a naphthyl group, B denotes
hydrogen atom,
sulfonic acid group, a lower
alkyl group, a lower alkoxyl group or the like, each of R1 to R4 independently denotes
hydrogen atom, a
halogen atom, a lower
alkyl group, a lower alkoxyl group or the like, D denotes —NHCO—, —N═N— or —NH—, E denotes
hydrogen atom, a lower alkyl group or a
phenyl group having 1 to 3 substituents such as hydroxyl group and amino group, n denotes 0 or 1, and m denotes 0 or 1, or a salt thereof, or a
copper complex compound of either of them, which is used for a polarizing plate having excellent polarization performance and durability and furthermore little color leakage in visible light range.