Fundamental Study of Ferroelectric Liquid Crystals for their Practical Use in Fast Displays

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The structure of SSFLC states and the switching processes among them have been studied. Observation of the switching processes using stroboscopic micrographs was very useful for clarifying the structure. In most cases where Sm A exists as a high temperature phase, directors in the upper half of a cell and those in the lower half rotate on a cone in the opposite sense; hence the director in the middle which cannot move continuously because of the symmetry requirement make a sudden jump, forming a disclination loop. Occurrence of the switching process characterized by the internal disclination formation inevitably requires selective pretilting of the C-directors at the bounding surfaces. The simpler switching process originally proposed by Clark and Lagerwall, where all directors move in the same sense, is rather exceptional, though sometimes occurs.Taking account of the high resolution X ray diffraction study by Clark et al., the real cause of the C-director selective pretilting must be the bending or kinking of the smectic layers. There are two ways in which the layers kink, i.e. <<< and >>>. Zigzag defect lines so far considered by us as dislocations decorated by disclinations are now identified as the misarrangement of the layer kinks, such as <<<*>>>*<<<. This identification successfully explains the characteristic features played by the zigzag lines during the switching processes.Polarized transmittance spectra of the SSFLC states have been obtained by combining a spectrometer with a polarizing microscope. Based on the layer bending or the C-director selective pretilting, we can nearly reproduce the spectra using the 4 x 4 matrix method. Experiments concerning the tilt angle described in the research proposal has not been performed, but instead a noble method has been proposed for measuring the viscosity constants. Preliminary studies have also been done in a case where Sm A does not exist as a high temperature phase.