Material for alignment layer of liquid crystal display

A material for alignment layer of liquid crystal display, comprising a solvent and a polymer dissolved in the solvent, the polymer comprising a backbone and a first side chain linked to the backbone, the first side chain having a stronger lateral dipole moment;

• wherein the backbone of the polymer comprises a structure of polyimide or polyamic acid, which has the following formula:
• wherein the ring A and ring B are benzene rings, aromatic rings, or fused-ring aromatic compounds;
• X and Y are linking moieties;
• and n and m represent the degree of polymerization, the values of n and m being in a range of 20 to 2000;
• wherein X and Y are represented by the following formulas:
• the value of n and m are in the range of 50 to 500;
• wherein the first side chain of the polymer comprises two obviously distinguished structures which are respectively a flexible chain linked to the backbone and a rigid chain linked to the flexible chain, the rigid chain having a stronger lateral dipole moment;
• wherein the first side chain of the polymer has one of the following formulas:
• wherein in formulas II and III, M is the flexible chain linked to the backbone and is formed by a molecular main chain composed of 3-25 C, O, S, N, and Si atoms;
• ring A, ring B and ring C are five- or six-membered rings or ring structures with or without N, S, and O heteroatoms;
• rings A, B, and C are identical or different, rings A, B and C being saturated, unsaturated, or aromatic rings;
• Z is substituted moiety on rings A, B and C and can be identical or different, being mono-substituted or polysubstituted on a single ring is allowable, Z is —CN, —F, —Cl, —Br, —NCS, —CF3, —OCF3, or —OCHF2;
• R is the terminal moiety of the first side chain which is a carbon chain composed of H or 1-8 carbons;
• wherein the first side chain of the polymer takes 5-40% molecular weight of the polymer;
• wherein the polymer takes 1-20% total weight of the material for alignment layer;
• and
• wherein the solvent is selected from one of or a mixture of multiple ones of N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, γ-butyrolactone, ethylene glycol mono-n-butyl ether, and dimethylacetamide.