The structures of cubic phases of 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxylic acids (ANBC-n, where n is the number of carbon atoms in the alkoxy group) have been studied by X-ray diffraction technique. It was found that the cubic region of ANBC-n contains two types of cubic phases, Cub I with Im3m symmetry and Cub II with Ia3d. Very surprisingly, the phase type of cubic phases of ANBC-19, -20, and -21 is of Im3m type in the whole temperture region of each, and thus, the region of Ia3d type is divided into two, n=15-18 and n≧22.

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The heat capacity measurement has been carried out on a liquid crystal which shows the isotropic-chiral-smectic-C-isotropic-X phase sequence. The heat anomaly due to the chiral-smectic-C-isotropic phase transition showed a peculiar thermal hysteresis. A very broad peak in the heat capacity was observed in the isotropic phase.

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A periodical texture with two types of periodical domains is induced in a nematic liquid crystal cell under the existence of an elastic wave propagating on a glass plate. The shorter periodical domain and the Williams domain are induced in the same liquid crystal cell. The dark and bright regions are observed in the Williams domain, while two color regions are recognized in the bright region of the shorter periodical domain. The liquid crystal flows along the dark region in the shorter periodical domain, while the flow directors in the neighboring dark regions are in the antiparallel direction.

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Molecular orbital (MO) calculation and molecular dynamics (MD) simulation were carried out for a set of smectic liquid crystalline molecules, 8O-O8 (4-octyloxyphenyl-4'-octyloxybiphenyl-4-carboxylate) and 8O-8 (4-octylphenyl-4'-octyloxybiphenyl-4-carboxylate), to understand the molecular origin of different crystalline structure formation and to predict their conformational property in liquid crystalline phases. The results of MO and MD analyses indicate that the structure of 8O-O8 and 8O-8 in crystalline phase is essentially determined by intramolecular interactions and the experimentally observed structure is chosen as a consequence of intermolecular packing constraints.

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We have calculated the rotational viscosities of isothiocyanato-substances, by using atomistic-level molecular dynamics simulation. A good correlation has been found between the measured and simulated values in the absolute scale as well as in the temperature dependence.

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An atomistic molecular dynamics simulation method is proposed for the computation of Frank elastic constants of nematic liquid crystals. The method uses spatially modulated aligning forces that cause distortion in the spatial distribution of the nematic director. Test calculations on the 5CB molecule indicate very good agreement between the simulation and experiment.

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Rotational entropy, or the entropy loss due to molecular alignment, has never been considered to contribute to Frank elasticity in previous molecular theories of nematic liquid crystals. Using a field-theoretical technique developed in polymer physics. we show that rotational entropy does yield Frank elasticity, which is attributed to the inherent non-local nature of orientational order due to the finite size of the molecules. We also give an exact cxpression of rotational entropy contribution to Frank elasticity for rod-like liquid crystals in terms of the orientational tensor order parameter.

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The chemical potential of the system of hard molecules is given as logarithm of probability of insertion of a molecule to the system. The scaled particle theory is an assumption of the interpolation between the insertion probability of a infinitesimal molecule and that of a large molecule of macroscopic scale. In this study we estimate the insertion probability directly with Monte Carlo simulation and discuss the accuracy of the scaled particle theory.

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CBOBP (4-cyanobenzoyloxy-[4-octylbenzoyloxy]-p-phenylene), exhibits a transition sequence, I-N-S_<Ad>-N-S<Al>-crystal (doubly reentrance sequence) on lowering the temperature. The second N phase is called reentrant nematic (RN). Due to this peculiarity, the nature of this transition sequence has been one of the interesting topics in recent liquid crystal research. We made neutron diffraction study to clarify the structure of the liquid crystalline phases and hence to clarify the microscopic mechanism of this phenomenon. For this purpose a compound with perdeuterated chain, CBOBP-d17 was prepared. SANS-U instrument was used at an wavelength of 7Å with a velocity selector.

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To predict whether a system of rod-like molecules exhibit thermotropic liquid crystal phase, we must estimate not only the clearing temperature Tc but also the melting temperature Tm. Though we have simple theoretical formula to estimate Tc, not theoretical formula to predict Tm. On the basis of many experimental results, we consider Tm molecular theoretically for typical rod-like mesogens with terminal hydrocarbon chains.

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The molecular theory is considered on a simple model potential which stabilizes the anticlinic smectic-C_A phase (Sm- C_A) with respect to the synclinic smectic-C phase (Sm-C). Conventional dispersion and steric interactions between mesogenic molecules gellerally do not promote Sm- C_A. It may be stabilized by interlayer orientational correlations between transverse molecular dipoles located in the flexible chains. A simple phase diagram of the perfectly ordered smectic liquid crystal is presented which contains Sm-A, Sm-C and Sm- C_A.

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The surface stabilized smectic A phase of homeotropic alignment (SmAII) appears even under the homogeneous anchoring due to an effect of walls as the symmetry breaking field to the smectic layer. As an analogue of the Freedericksz transition at nematic phase, a response of the transverse electric field at SmAII is studied by the constant temperature molecular dynamics simulation of the Gay-Berne system sandwiched by the walls, where each molecule has an electric dipole along the molecular long axis. At a threshold of the field strength, the system changes to the smectic A phase with layer normal being parallel to the electric field (SmAI) via an intermediate phase like a smectic C phase. By reducing the field, again SmAII appears directly, showing a hysteresis characteristic to the discontinuous transition. The dipole-dipole interaction is proved to stabilize the layer structure of smectics, while SmAI changes to smectic C phase in the electric field.

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The effect of the wall to the smectic layer ordering is studies at thin liquid crystalline system by generalizing the McMillan theory on smectics. Every order of smectic layers is proved not to vanish, and a crossover from a long range order to a surface sustained one is shown to occur near a bulk transition temperature which is explained as the critical behaviour even at such thin system. The dependence of transition temperature between smectic phase and nematic one at the parallel aligned case is obtained, where the transition temperature is determined from the global behaviour of the order averaged over the whole system.

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In antiferroelectric smectic materials, various types of responses such as V-shaped, normal and abnormal ones have been observed at a transmittance of light, to the electric field. In order to elucidate the mechanism of the responses, dynamics of ANNNI model are studied under the alternating field. It is shown that the appearances of those responses depend not only on frustration due to the weakcned interaction but also on the frequency of the electric field and two relaxation times of the order parameter and surface polarization.

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We have observed the rise in nematic-isotropic transition temperature (T_<NI>) in many nematic 5CB and non-nematic binary systems. These T_<NI> increases have been attributable to the formation of intermolecular hydrogen bonding between the cyano-group of 5CB and the OH group of solutes. To ascertain these, we have studied the effect of thiol derivatives as solutes. The effects of phenol and benzoic asid derivatives on the T_<NI> of some cholesteric and ester type nematic liquid crystals were studied in this work.

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The complex dielectric constant of 4-n-pentyl-4'-cyanobiphenyl (5CB) was measured between 0.0001Hz and 1kHz in nematic and isotropic phases. The dielectric dispersion due to space-charge polarization was observed for both phases. The diffusion coefficient D and the mobility μ and the number density n of ions in 5CB were determined in the analysis of the experimental result. In a nematic phase, the anisotropy of the μ was estimated by controlling the molecular orientation under a magnetic field. Furthermore, the relationship between the mobility and the viscosity coefficients of 5CB was investigated.

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Determination of the surface anchoring strength at a liquid crystal-substrate interface is a highly delicate measurement which could be easily corrupted by a number of experimental and conceptual ambiguities. Although the high-electric-field technique has been established as a reliable method for polar anchoring measurement, it still suffers from a few shortcomings associated with the use of electric field and optical retardation; as a result, it remains difficult to apply the method to the extremely high anchoring strength and to the azimuthal anchoring measurement. We show in this paper that the use of mechanical torque measurement in conjunction with a strong magnetic field removes all these problems. thereby making the high-field technique universally applicable to both polar and azimuthal anchoring without loss of precision even for the strong anchoring cases.

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Optical second harmonic generation (SHG) was used to study how mechanical rubbing modifies the surface structure of a polyimide (poly[4,4'-oxydiphenilenepyromellitimide], PMDA-ODA) film and how the rubbed polyimide surface aligns a liquid crystal monolayer (4'-n-octyl-4-cyanobiphenyl, 8CB) adsorbed on it. It was found that rubbing would align the polymer chains and make the polymer surface more polar and hence more SHG-active. The rubbed polymer surface would then align the adsorbed 8CB monolayer via molecule-molecule interaction in an orientational epitaxy manner. Approximate orientational distributions for molecules at the rubbed polymer surface and in the aligned 8CB monolayer were deduced from the measurements.

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We have studied the dependence of the pretilt angle on the preparing conditions of a vertical alignment film and on NLC materials in a photo alignment, method. From this study, we showed that the high temperature baking of the alignment film and using a NLC material with large An are needed to create a low pretilt angle. And we succeeded in controlling the pretilt angle as low as 70 degrees without any alignment defects.

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We have studied the UV-exposure effect on the polar anchoring energy of homeotropically-aligned liquid crystal (LC) samples. With increasing UV exposure energy to an alignment film, the wettability of LC on the film is increased, resulting in decreasing the polar anchoring energy of the sample. This result indicates that the surface density of alkyl-side-chains is decreased with UV light exposure to an alignment film, and this reduction of the surface alkyl-side-chain density results in changing the wetting property of LC and the polar anchoring energy of the sample

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In order to achieve a strong anchoring state in a photo-alignment method, we have studied the azimuthal anchoring energy of twisted nematic (TN) cells fabricated by a photo-alignment technique. Two types of polyimides having different wetting properties of liquid crystal (LC) are used as an alignment layer. The azimuthal anchoring energy for a photo-processed alignment layer with higher wettability is shown to be higher than that for a lower wetting sample. This result indicates that, for realizing a strong surface anchoring state in a photo-alignment method, the wetting properties of LC on an alignment surface is important to achieve a strong anchoring state in a photo-alignment method.

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Alignment of LCs is photocontrollable by photochemical modifications of molecules introduced to substrate surfaces. In these phenomena, the reorientation of LC molecules on surfaces occurs first, followed by the transfer of the reorientation to a bulk layer. The photoinduced reorientation of ultra-thin films of LCs on command surfaces was investigated. Surface plasmon resonance (SPR) technique was mainly used in this study on account of the high sensitivity to changes in optical properties and thickness of ultra-thin films and the availability to estimate molecular orientation of LCs. SPR spectra displayed reversible changes when the sample was irradiated alternatively with UV (365nm) and visible (440nm) light, indicating that the reorientation of LC molecules follows the photoisomefization of the surface azobenzene.

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Among many display technologies, one of the most promising approaches for the low power consumption electronic display will be the reflective type liquid crystal display (RLCD). However, there are still technological problems unsolved for the practical use of RLCD. The most important one is how to achieve enough brightness. In this review paper, many different approaches toward to this target will be discussed. Many of the results obtained from ASET project will be referred. Especially, the stacked three layered structure, HPDLC scheme, the directive reflector devices and image-memory LCDs are emphasized because of their high potentialities.

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The comprehension of the mechanism of alignment of a liquid crystal by a rubbed polymer layer is a current interest from a fundamental point of view but also in regards to applications. To understand the mechanism of alignment it is necessary to clarify how the liquid crystal is oriented near a surface. A nematic liquid crystal (LC) has no longer a uniaxial symmetry near a rubbed polymer surface but exhibits a biaxial orientation. We probed the thickness dependence of the orientation of a LC using Fourier Transform Infra-Red Spectroscopy. By this method it can be shown that the order parameter is lower near the surface than in the bulk.

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Polyvinyl alcohol (PVA) films with some of different saponification degrees and polymerization degrees are investigated as a liquid crystal alignment film in the homogeneous cell. An azimuthal anchoring energy increases with the polymerization degree. The glass transition temperature also influences the anchoring energy. Thermal stability of the surface memory alignment on the PVA with high polymerization degree is higher than that with low polymerization degree.

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Fine structures for liquid crystal alignment were formed on the alignment layer by an atomic force microscopy. A structure is check pattern, which is consisted of multi-domains with two writing directions. As the distance from the surface increases, the direction of director in the bulk seems to be merged into a direction. The merging distance is supposed to be proportional to the domain size. The same phenomenon occurs with the circular pattern. Merging of the aligning direction in the bulk is due to the tendency to reduce the elastic energy.

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The electrical response of the LC directors in the bulk and near the surface were investigated by transmission and total reflection (TRE) ellipsometries, respectively. Since the static response of the phase difference on the electric field measured by the TRE depends on the interfacial LC director reorientation, the polar anchoring strength of the LC cell was evaluated quantitatively. The director reorientation in the bulk was also analyzed by the transmission ellipsometry, which was taken the anchoring energy into account.

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The optical flickering effect in a nematic ECB cell has been studied using total-reflection time-resolved spectroellipsometry (TRSE). Under an applied bipolar electric field, optical flickering arises from a change in internal electric field caused by various factors such as the presence of ionic impurities and surface charges. In the present study, in order to investigate the relationships between flickering frequency and the various factors that cause optical flickering, we examine the frequency dependence of flickering magnitude and waveform. We found that the magnitude of optical flickering in the middle frequency region (0.1lkHz to lkHz) caused by high-mobility ionic impurities increases after the aging process.

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For the study of local dynamics of liquid crystal (LC) molecules at the alignment film interface, we developed a novel observation method based on near-field scanning optical microscopy (NSOM) with 3-dimensional resolving power. By employing a high-quality NSOM fiber probe, we could apply a uniform electric field to LC molecules and detect LC orientation change with high sensitivity and spatial resolution as high as 100 nm. To measure and regulate the distance between the probe end and the alignment film surface, we utilized the depth profile of evanescent field intensity penetrating from the interface as a feedback signal.

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A scanning near-field optical microscope (SNOM) has been optimized for observation of liquid crystal (LC) orientation at the LC/substrate interface. This novel system enables the LC orientation distribution image to be observed with high spatial resolution (less than 100 nm) under an applied local electric field. The present study demonstrates that the developed SNOM allows, for the first time, microscopic analysis of the LC orientation at the IPS substrate surface.

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