Interpretation of the Appearance of the Antiferroelectric Phase in Smectic Liquid Crystals and the Application for Display Device

为了阐明近晶相液晶中反铁电性出现的原因，我们进行了两种实验：（1）绘制了二元混合物的反铁电相相图，讨论了反铁电性的强度。(2)测量了近晶层序引起的高阶X射线衍射，确定了层序参数，并从微观角度讨论了反铁电性产生的原因。利用该体系绘制了二元混合物的相图，其中一个具有较强的反铁电强度，另一个具有较强的铁电强度。在此基础上，提出了“魔鬼楼梯”模型，由于排斥体积效应所稳定的铁电性和分子二聚化所稳定的反铁电性的竞争，出现了不同的亚相，我们精确地测量了近晶层状结构所产生的高阶X射线衍射，并确定了层状序参量，发现在从smC ~（**）到SmCA ~（**）的相变点，序参量不连续地增加。这一事实表明，层结构不再是通常的正弦曲线，而是有点一维晶格的反铁电相。我们还澄清了SmCA** 中的层厚度比SmC** 中的层厚度薄。这些事实支持了分子二聚化是反铁电性出现的原因的模型

To clarify the cause of the appearance of the antiferroelectricity in smectic liquid crystals, we perfored two kinds of experiments : (1) We drew phase diagrams of binary mixtures which show the antiferroelectric phase in order to discuss the strength of antiferroelectricity. (2) We measured the higher order X-ray diffraction due to smectic layr order, determined the layr order parameter and discussed the cause of the antiferroelectricity from the microscopic point of viewWe constructed conoscopic observation system using CCD camera and image processor. Using this system, we drew phase diagrams of binary mixtures, one of which has stronger antiferroelectric strengh and the lest of which has stronger ferroelectric strengh. Based on the diagrams, we proposed the model of "devil's staircase", i.e., emergence of various subphases due to the competition of ferroelectricity stabilized by excluded volume effect and antiferroelectricity stabilized by molecular dimerization.We accurately measured the higher order X-ray diffraction due to the smectic layr structure and determined the layr order parameter, then found that the order parameter increases discontinuously at the phase transition point from smC** to SmCA**. This fact suggests that the layr structure is no longer sinusoidal as usual, but is somewhat one-dimensional lattice in the antiferroelectric phase. We also clarified that the layr thickness in SmCA** is thinner than that in SmC**. These facts supports the model of molecular dimerization as the cause of the appearance of antiferroelecticity