The Alignment Film

The alignment film is a thin film with straight scratches, which is used to guide the alignment direction of liquid crystal molecules. On the glass substrate on which the transparent conductive film (ITO) has been evaporated, use PI coating solution and a roller to print parallel grooves on the ITO film. At the same time, the liquid crystal can follow the direction of the grooves. Lying in the groove to achieve the purpose of aligning the liquid crystals in the same direction. This film with one direction is called an alignment film.

The reason why liquid crystal can be applied to the screen is that the induced electric rate in the parallel molecular direction and the vertical molecular direction is different, so it can be driven by an electric field. On the other hand, due to the liquid crystal also has a refractive index (i.e. birefringence), which can change the polarization direction of polarized light. Finally, because of the strong Anchoring Strength at the interface between the liquid crystal and the alignment film, the liquid crystal will rely on the elastic coefficient (recovery force) after the electric field is turned off. Returning to the original arrangement, it can be seen that the liquid crystal cannot work without the existence of the alignment film. However, in the application of the liquid crystal screen, the liquid crystal molecules and the surface of the alignment film are inclined at a certain angle (i.e. the pretilt angle), so that the uniform alignment effect can be achieved.

The coating of the alignment film involves non-roll wet coating, and the methods include the traditional directional brushing method and the current UV light alignment method, electron paste alignment and ion beam alignment.

The axis angle optical measurement instrument for alignment film developed by Suzhou PTC Optical Instrument Co., Ltd., it adopts a manual rotating platform and an illuminometer to measure the axis angle of the alignment film in the polarizing light detection field. The polarizing field is provided by our equipment: Polariscope PSV-801.

Due to the phase retardation of the alignment film in the polarizing field, the final transmitted light intensity is different at different axial angles. The terminal illuminometer is used for energy collection, the value is displayed in real time, and the angle of the alignment film is manually determined.