Photo alignment agent and liquid crystal display

A photo alignment agent comprising a copolymer of a diamine and a dianhydride,

• wherein the copolymer comprises a repeating unit, comprising a first group derived from the diamine and a second group derived from the dianhydride;
• wherein any one of the first group and the second group comprises a photoreactive group and the other one of the first group and the second group comprises at least one selected from a tert-butyl group, a tert-butoxy group, a tert-butyloxycarbonyl group, and a di-tert-butyloxycarbonyl group;
• and
• wherein the repeating unit comprises a first repeating unit represented by Formula 1 and a second repeating unit represented by Formula 2:
• wherein in Formula 1,
• Y1 is —(CH2)n—, wherein n is 1 to 20,
• Z1 is a group selected from
• and
• m and l are each independently an integer ranging from 1 to 4, and
• in Formula 1 and Formula 2,
• K1 and K2 are each independently a single bond, an oxygen atom or —NH—;
• X1 is
• R1 and R2 are each independently
• * indicates a point of attachment bonded to —K1—C(═O)— or —K2—C(═O)—, and
• p and q are each independently an integer ranging from 10 to 2,000.