Composition for photo-alignment film, photo-alignment film, and optically anisotropic medium

A composition for a photo-alignment film, comprising an azo compound of formula (1) by general formula (1) and a polymer that exhibits mutual solubility with the azo compound represented by the general formula (1):

• wherein R1 and R2 each independently represents a hydroxyl group or a polymerizable functional group selected from the group consisting of a (meth)acryloyl group, (meth)acryloyloxy group, (meth)acryloylamino group, vinyl group, vinyloxy group and maleimide group, provided that at least one of R1 and R2 represents a polymerizable functional group,
• A1 and A2 each independently represents a single bond or a divalent hydrocarbon group that may be substituted with an alkoxy group, and B1 and B2 each independently represents a single bond, —O—, —CO—O—, —O—CO—, —CO—NH—, —NH—CO—, —NH—CO—O— or —O—CO—NH—, provided that a —O—O— linkage is not formed in a link to R1 and R2,
• m and n each independently represents an integer of 0 to 4 wherein, when m or n is 2 or greater, a plurality of A1, B1, A2, and B2 groups may be respectively identical or different, and an A1 or A2 group sandwiched between two B1 groups or B2 groups represents a divalent hydrocarbon group that may be substituted with an alkoxy group,
• R3 to R6 each independently represents a hydrogen atom, halogen atom, halogenated alkyl group, allyloxy group, cyano group, nitro group, alkyl group, hydroxyalkyl group, alkoxy group, carboxyl group or alkali metal salt thereof, alkoxycarbonyl group, halogenated methoxy group, hydroxyl group, sulfonyloxy group or alkali metal salt thereof, amino group, carbamoyl group, sulfamoyl group, or a polymerizable functional group selected from the group consisting of a (meth)acryloyl group, (meth)acryloyloxy group, (meth)acryloylamino group, vinyl vinyloxy group, and maleimide group, wherein
• the polymer that exhibits mutual solubility with the azo compound of formula (1) by the general formula (1) is a polymer having a substituent represented by any one of the structure shown below:
• wherein Y represents a hydroxyl group, —ONa, —OK, —OLi, or an amino group.