Aligning agent for liquid crystal

A treating agent for liquid crystal alignment in a method in which a polymer thin film formed on a substrate in a predetermined direction relative to the plane of the substrate is irradiated with polarized ultraviolet rays or by electron rays, and said substrate for aligning a liquid crystal not having been subject to a rubbing treatment, wherein said agent for liquid crystal alignment contains a polymer compound having photochemically reactive groups in the polymer main chain of at least one type selected from the group consisting of bivalent structural units (1) to (4):

• wherein each of R1, R2, R3 and R4 which are independent of one another, is hydrogen, a C1-C4 alkyl group, a C2-C4 alkenyl group, a C2-C4 alkynyl group, a C1-C4 alkoxy group, a trifluoromethyl group or fluorine, and a glass transition temperature of at least 200° C.