Bis(azo-benzene) diamine monomers and a method of synthesizing the monomers are provided. The bis(azo-benzene) diamine monomers, in combination with amine reactive monomers, form polymers, such as polyimides and copolyimides, having photomechanical and thermomechanical properties.

An ink composition includes, as dyes, a dye (Bk-1) represented by the formula (Bk-1); and a dye (Bw-1) represented by the formula (Bw-1), in which a content ratio A (dye (Bk-1):dye (Bw-1)) of the dye (Bk-1) and the dye (Bw-1) is 100:18 to 100:40.