GREY LEVEL CONTROL BY VARIATION OF THE SURFACE INTERACTION IN AFLCDS

We report the influence of the rubbing treatment of the alignment laye rs on the electro-optic characteristics of AFLCD's. We applied a diffe rent rubbing treatment on different regions within a pixel. This varia tion of rubbing strengths causes domains with different surface intera ction, which results in a different threshold voltage for each domain. In-pixel variation of the rubbing treatment and of the surface intera ction influences the double hysteresis of the transmission-voltage cha racteristic, which is made less steep. The difference between the volt ages at which the transmission starts to increase and the voltage at w hich the transmission reaches its maximum increases and so the selecti on of analogue grey levels is made easier. The results also show that the finite slope of the double hysteresis which is observed in normal AFLCD's, without extra rubbing treatment is probably caused by variati ons of the surface interaction.