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

采用图像处理技术和单块或双块脉冲法，测量了扭曲90度向列液晶（LC）膜的视像图和干涉强度的动态变化，分析了由少量交变脉冲组成的电场去除后LC分子排列的动态变化。对实验结果进行了详细研究。发现了一些新的物理现象。1. 在电场被移除后，LC分子的变化继续对齐5毫秒。这被称为LC分子排列的滞后变化。2. 在施加电场后，无论施加方式如何，显示conconscopic图形的最大强度所需的时间几乎是相同的。结合交流电路理论，采用粘弹性理论中修正的Voigt模型进行数值计算，认为LC分子的浮动容量、粘阻和电变形对滞后变化有影响。3. 采用Voigt模型，不考虑锚固力的影响，通过改变黏度系数与弹性模量之比作为距膜面距离的函数来估计LC对准的变形变化率。我们可以用指数表示变化率方程。4. 在晶体光学的基础上，提出了用计算机模拟的方法获得锥面图形。

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.