The Effect Of Polyimide Film For Liquid Crystal Display

Recently, flat panel display(FPD) technology has been progressed rapidly, thin film transistor liquid crystal display(TFT-LCD) occupies significant position in the FPD market since its indispensible role in the electronic information industry. With the stimulation of the government policy, “Bring Household Appliances to Countryside”, TFT-LCD device has been widely used among people. Meanwhile, people show higher request on the display characteristics of TFT-LCD, and expect a display mode with a perfect properties such as fast response time, high contrast ratio, wide viewing angle and low power consumption etc. Therefore, display qualities of TFT-LCD have become key issues in the academic research all over the world.As we all know, polyimide has been widely applied in the LC displays industry as the anisotropy in the distribution of the polymer chains to align LC molecules in a certain orientation and conformation with a specific pre tilt angle for LC devices to obtain a defect-free alignment and also to improve their electro-optical performance, such as driving voltage, response time, color performance and viewing angle etc.In this chapter, the influence of alignment layer on the display qualities of twist nematic display mode was investigated with both theoretical analyses and experimental confirmation. First of all, we made multiple polyimide(PI) under different process conditions. The relationship between pre tilt angle and process conditions was analyzed. Meanwhile, the display qualities such as response time, image sticking were measured, and the influence of PI under different process conditions on display characteristic was studied. Based on the dynamics of the liquid crystals and the relationship between pre tilt angle and response time, we analyzed the effect of alignment layer on dynamic response behavior of LC molecular.Through this research, it can be found that the thicknesses of alignment film and heat treatment have a certain effect on image sticking and response time. If the thickness of alignment layer decreases, or the heat treatment temperature and time are insufficient, a slight line image sticking will appear. At the same time, the response time will be faster with the decrease of the pre tilt angle.