The liquid-crystal display because matches to the method is different , common has the TN monitor , the STN monitor , and the MVA monitor . Because these match to the method difference , therefore liquid crystal molecule pretilt angle is also different . Present liquid crystal molecule pretilt angle choice way includes : (1) Chooses the different polyimide material , after specific rubded intensity , but produces specific pretilt angle. (2) Uses low pretilt angle the polyimide material , mixes high pretilt angle according to the different proportion the polyimide material , but achieved accent of the pretilt angle changes . But in this research proposed double alignment layers , takes the first floor by homotropic layers , uses homogenous layers does for the upper formation , the surface free energy of the alignment layer can be easily controlled by adjusting the thickness of the top polyimide layer, similarly may achieve the accent to change liquid crystal molecule pretilt angle the effect . And may compensate the liquid crystal display to be insufficient because of rubbed polyimide , but has the question which dark condition is exposed , has a higher contrast gradient . Because this experiment scope accent changes the effect in liquid crystal molecule higher pretilt angle good , also kneading board various regions liquid crystal molecule pretilt the angle uniformity is higher , therefore may effectively apply on various types homotropic liquid crystal display component , for example: MVA , VA-STN , DSTN liquid-crystal display .