Azo compound, dye-based polarizing film containing same, and polarizing plate

A dye polarizing film containing a polarizing-film base containing an azo compound or a salt thereof, represented by the following formula (6):

• wherein R1 to R4 each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a sulfo group or an alkoxy group having 1 to 5 carbon atoms and a sulfo group;
• X represents an amino group having a substituent, a phenylamino group having a substituent, a benzoylamino group having a substituent, a naphthotriazole group having a substituent or a phenylazo group having a substituent;
• m represents 3 or 4;
• n represents 1 or 2;
• and p represents 1, 2 or 3;
• wherein the phenylamino group is represented by the following formula (2):
• wherein R5 and R6 each independently represent a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group or a substituted amino group;
• or a salt thereof;
• wherein the benzoylamino group is represented by the following formula (3):
• wherein R7 represents a hydrogen atom, a hydroxy group, an amino group or a substituted amino group;
• or a salt thereof;
• wherein the naphthotriazole group is represented by the following formula (4):
• wherein o represents 1 or 2;
• or a salt thereof;
• wherein the phenylazo group is represented by the following formula (5):
• wherein R8 to R10 each independently represent a hydrogen atom, a hydroxy group, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group or a substituted amino group;
• or a salt thereof.