STUDIES ON MOLECULAR ALIGNMENT MODEL IN NEMATIC LIQUID CRYSTALS EMPLOYING DYNAMICAL IMAGE-PROCESSING TECHNOLOGY

为了分析利用图像处理技术和单、双块脉冲方法去除由少量交替脉冲组成的电场后液晶分子排列的动态变化，测量了扭转角为90°的扭曲向列相液晶(LC)薄膜中锥面图形和干涉强度的动态变化。对实验结果的细节进行了研究。发现了一些新的物理现象。1.去除电场后，液晶分子的变化持续排列1毫秒。这就是液晶分子排列的滞后变化。2.在不同的电场作用方式下，显示锥面图形的最大强度所需的时间基本相同。从粘弹性理论中修正的Voigt模型出发，结合交变电流回路理论进行数值计算，认为液晶分子的浮力、粘滞电阻和电变形对滞后变化有影响。3.用Voigt模型估算了液晶取向的变形率，该模型不考虑锚固力的影响，而是改变粘性系数与弹性模量值之比作为距薄膜表面距离的函数。我们可以指数地表示变化率的方程。4.在晶体光学的基础上，提出了锥面图形的计算机模拟方法。

The dynamical changes of the conoscopic figures and the interference intensities in the twisted nematic liquid crystal (LC) film with twisted angle of 90 degrees were measured to analyze the dynamical changes of the LC molecular alignments after the electric field composed of a small number of altemating pulsed were removed with the use of an image-processing technology and the single or double block pulse method. The details of the experimental results were studied. Some new physical phenomena were found. 1. The changes of the LC molecules continue aligning for a fes milliseconds after the electric field is removed. This is called the lagging changes of the LC molecular alignments. 2. The time required to show the maximum intensities of the conoscopic figures after the electric field is applied is almost the same regardless of the applied manners. It is considered by the numerical calculation derived from a modified Voigt model in the viscoelastic theory combining the theory of an altemating current circuit that the floating capacity, the viscosity resistance and electric deformations of the LC molecules have effects upon the lagging changes. 3. The changing rate of deformations of the LC alignments is estimated by the Voigt model with changing the ratio of the coefficient of viscisity to the elastic modulus as a function of the distance from the film surfaces instead of considering the effect of the anchoring force. We can represent the equation of the changing rate exponentially. 4. The method of computer simulations to obtain the conoscopic figures was developed on the basis of crystal optics.