An effective method for evaluating the image-sticking effect of TFT-LCDs by interpretative modelling of optical measurements

The conventional method of evaluating the image-sticking effect of a LCD mo dule is inspection by sight, because the residual optical difference betwee n two stressing areas is small and viewing angle-dependent, so that it is d ifficult to obtain a significant optical difference value by instrumental m easurement. We propose an effective method for evaluating the image-stickin g effect of a TFT-LCD module by directly measuring its time evolution of tr ansmission with the TFT glass turned off after a period of pattern stress. In this way, the liquid crystal system under charge equilibrium in constant -charge mode shows a dramatically amplified optical difference. Further, we interpret the measured results by a modelling that combines the calculatio n of liquid crystal director orientation and ionic charge distribution. It is supposed that there are four time constants that dominate the overall st icking phenomenon and belong to four transient processes: adsorption of ion s, desorption of free ions, desorption of stuck ions, and TFT leakage. The modelling shows good accordance between measured and simulated results when fitting parameters are properly chosen.