Stannous Chloride → 4-Aminostilbene

In an embodiment of the invention, a method for preparing the aforesaid alignment film in a laboratory level is illustrated as an example. 10 g of 4-nitrobenzyl bromide is mixed with 12 g of triphenylphosphine and dissolved in 150 ml of a dry tetrahydrofuran solution, heated to 75° C. and agitated under reflux for 48 hours, to obtain 8.2 g of a dry white p-nitrobenzyl triphenylphosphine. The p-nitrobenzyl triphenylphosphine is mixed with 2.6 g of p-nitrobenzaldehyde in a 150 ml tetrahydrofuran solution, and agitated under room temperature for about 24 hours to obtain 4.2 g of p-nitrostilbene. The resultant p-nitrostilbene is mixed with 14.7 g of tin dichloride, dissolved in a mixed solution of 30 ml/40% hydrochloride acid and 100 ml acetone, agitated under the room temperature for about 2 hours and refluxed for 8 hours to obtain p-aminostilbene. The p-aminostilbene is mixed with 9,9′-bianthracyl tetracarboxylic dianhydride in a dry NMP (N-methyl-pyrrolidone) solution under agitation for 24 hours, under protection of nitrogen gas, to obtain the precursor of the polyimide alignment film involved in the embodiment. The precursor is heated to 230° C. to obtain the final alignment film, which is a light sensitive alignment film.