A photo alignment including a copolymer of a diamine and a dianhydride, wherein the copolymer includes a repeating unit including a first group derived from the diamine and a second group derived from the dianhydride, and wherein any one of the first group and the second group includes a photoreactive group and the other one of the first group and the second group includes at least one selected from a tert-butyl group, a tert-butoxy group, a tert-butyloxycarbonyl group, and a di-tert-butyloxycarbonyl group.