In a variety of liquid crystal display devices are generally used PI (polyimide) orientation film, usually with a solution of PA (polyamide acid), we coated the orientation agent is actually PA solution (polyamide acid dissolved in organic solvent NMP), and then through heating and curing to form a stable polyimide orientation film that does not melt or dissolve, with the conflict method to control the orientation direction of the liquid crystal molecules. PI material has good heat resistance and stability, excellent insulation characteristics and transparency.

Orientation characteristics: The orientation of the long axis of the liquid crystal molecules along the direction determined by the conflict is the most basic orientation characteristics as a horizontal orientation treatment agent. In terms of horizontal orientation, if the long axis of the liquid crystal molecule is oriented completely parallel to the substrate in the absence of an electric field, a misorientation called skewed domains occurs when a voltage is applied. This phenomenon is caused by the energy equivalent of the molecules tumbling in either direction when the liquid crystal molecules stand up. Therefore, in order to avoid this phenomenon, it is necessary to make the orientation of the liquid crystal molecules and the substrate surface into a certain point of view (skewed orientation) in the absence of electric field, and this skew angle is called the pre-tilt angle. 

It is used to fix and seal the two pieces of glass that make up the liquid crystal box together, so it is required to have:

　　A. Satisfactory mechanical strength and reliability

　　B. There will be no impact on the LCD display components free into the LCD box

　　C. Does not have any chemical reaction with LCD (liquid crystal), etc

Now the more common sealing adhesive material is epoxy resin-based adhesive. Epoxy adhesive has the following outstanding characteristics:

　　1) High adhesive strength

　　2) Expansion coefficient and shortening rate is small

　　3) Excellent chemical resistance

　　4) Excellent electrical function

Epoxy resin at room temperature viscosity is large, distribution and use is not convenient. So often participate in a certain amount of diluent to reduce viscosity, add its fluidity and permeability, and can extend the application period. But the amount of more, the function of the adhesive will have an impact.