A phenomenological theory is developed for light-induced reorientation of liquid crystals driven by the trans↔cis photoisomerization of photochromic molecules bound to the surface of or dispersed in liquid crystal media. The present theory successfully accounts for previous observations, which are to suggest the role played by the liquid-crytallinity of the host medium and is thus out of the range of usual explanations based on the photoselection mechanism.

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Molecular orientation in liquid crystal(LC) photo-regulated by azobenzene derivative Langmuir-Blodgett(LB) film has been studied by infrared and Raman spectroscopy. The obtained spectra show that hydrocarbon chain of the LC molecule is in disordered state in the LC cell. It is also indicated that the LC molecule slightly interacts with the LB film, so that a little regulation is occurred in the case of a 5CB of nematic LC.

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The change in refractive index of liquid-crystalline azobenzenes induced by nanosecond laser pulse was investigated with reference to optical switching. The photoresponsive liquid crystals show nematic phase in the trans form while no liquid-crystalline phase in the cis form. Intensity of reflected light from interface between sample and glass substrate depends on refractive indices of both materials, and hence the change in refractive index of sample results in change in the intensity of the reflected light. We measured the intensity of the reflected light at 633 nm (He-Ne laser) from the interface and found that the reflected light rose up in 100 ms on pulse irradiation at 355 nm (YAG laser, the third harmonic, 10 ns FWHM) and decayed in 1 ms. The decay was 1000 times faster than those observed in the transmittance-mode measurements. The fast decay may be due to different mechanism in the reflection-mode measurements. At first, molecules in the cis form diffuse into molecules in the trans form which did not photoisomerize. Next, the molecules in the trans form reorient on the glass surface. By the use of the reflection-mode light probe, we successfully obtained more rapid change in optical switching than that of the transmittance-mode light probe.

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We have determined the molecular orientation of rubbed and unrubbed polyimide films on quartz glass substrates by measuring the optical retardation. We measured it in a transmission geometry as a function of incident angle. The molecular orientation was determined by fitting the experimental results with the theoretical calculation. Since the optical retardation is caused by both the anisotropy of and the multiple reflection in the polyimide film, we calculated the optical retardation by a transfermatrix method. Using the Vuks' relation, we obtained the molecular orientation of the polyimide films. It was compared with the molecular orientation of polyimide films on Si substrates that was determined by IR absorption.

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The Scanning Probe Microscope(SPM), invented by Binnig et al. (1981), is operable in a air, gas, liquid, or, vacuum state environment. The SPM used in the measurements was the Seiko Instruments SPI3700/SPA300 system. We wouid now like to report on study of the SPM(AFM,FFM) characteristics in relation to Polyimide Films from the viewpoint of system development.

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In order to clarify the detailed mechanism of rubbing on the polymer surface, we have observed the polymer surface rubbed by only one fiber because the ordinary rubbing complicate the surface structure due to overlapping of the rubbing. In this experiment, we observed the grooved shapes by AFM and compared them with the shape of the fiber observed by SEM. From the result, we found that the dominant factor to form the microgroove is the edge structure of the fiber. Then we measured the surface anchoring strength, and found that the rayon fiber gave larger value, which is considered to be due to the shallow but wide grooves owing to the smooth structure of the edge.

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Infrared dichroic measurements were applied to the analysis of the effects of organic solvent treatments on polyimide(PI) liquid crystal(LC) alignment films. Immersion in certain kinds of solvents such as acetone or ethyl lactate reduced the dichroic difference of PI and the pretilt angle of LC. The pretilt angle decreased proportionally to the dichroic difference values.

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Recent progress of color LCDs is reviewed from the viewpoint of TFT driving and LCD addressing. To develop low voltage driving schemes and driver LSIs has realized current color TFT LCDs for notebook PC applications. Propesed novel addressing schemes will be available to realize STN LCDs with fast response in near future. To open new applications for TFT LCDs, it will be neccessary to advance novel LCDs.

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Liquid crystal(LC) molecular alignment on polymer surfaces with some microscopic morphology was studied. Experiments were carried out by pulling the substrate, which was previously prepared by SiO 60° oblique evaporation, out of the PVA aqueous solution. The state of LC alignment of directors and pretilts depended strongly on the concentration of PVA, the pull-up speeds and Pull-up directions related to the direction of oblique evaporation. Then, by controlling these parameters, the areas of differently aligned LC textures could be clearly obtained on the same substrate.

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A direction of LC alignment, a presence of pretilt and an evaluation of azimuthal anchoring force can easily be shown by observing a liquid crystal(LC) droplet on an alignment layer. LC droplets on conventional rubbed PI layers, a 60° obliquely evaporated SiO layer, a rubbed PS layer, and nonrubbed UV cured polymer layers are observed between cross polarizers using a microscope. Disclinations and textures in LC droplets on the layers are observed and are discussed about those alignment properties.

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We evaluted the azimuthal anchoring strength of the Nematic Liquid Crystal(NLC) on orientational films. In this study, Polyamic Acid Salt Langmuir-Blodgett(PA-LB) films was adopted as a non-rubbed alignment films, and compared with the conventional spin-coated and rubbed Polyimide films. By measuring the minimal optical transmission of the twisted nematic(TN) LC cell with and without the quarter wave plate, the actual twist angles in TN cell can be calculated by Jones matrix method, and we can obtain the azimuthal anchoring strength. In consequence, it was found that the order of azimuthal anchoring strength of the PA-LB film was about 10^-6 N/m, which was smaller than the rubbed PI films (about 10^-5 N/m). It was also suggested that the magnitude of the azimuthal anchoring is two order weaker than that of the polar anchoring.

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We determined the orientational distribution function of the liquid crystal(LC) monolayer on rubbed polyimide films by optical second harmonic generation(SHG) and investigated the correlation between the surface LC orientation and the pretilt angle in LC cells. The LC samples used were a homologous series of 4'-n-alkyl-4-cyanobiphenyl (nCB; n=5-8). The pretilt angles were observed as a function of rubbing strength for nCB. The dependence of pretilt angle was classified into two types according to the number of carbon atom in alkyl chain.

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We have extensively studied the molecular orientation of liquid crystal(LC) molecules adsorbed on the surface of rubbed polyimide alignment films by the use of a high-sensitive FT-IR spectrometer. It has been confirmed that LC molecules are oriented parallel to the rubbing direction and the degree of orientation tends to deteriorate with increasing the rubbing density. It has been also found out that the tilt angle of LC molecules ranges from 19° to 21° which are in fair agreement with the tilt angle of the polyimide molecular chain.

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We utilize time-resolved optical waveguide spectroscopy for studying dynamics of a nematic liquid crystal(LC), in paticular, transient molecular orientation in the presence of an applied electric field. The waveguide patterns obtained from this technique involve the whole information about anisotropic dielectric constants of the LC layer, which is successfully characterized by theoretical analysis. In this study, we employed a nematic LC, 5CB, and prepared this LC as an optical waveguide in which LC directors were parallel to the glass substrate and rubbing direction. A dc pulsed field was applied to this waveguide cell, resulting in the homogeneous-to-homeotropic transition. Analyzing the obtained time-resolved waveguide patterns by using Deuling's theory, we could determine the tilt angle profile of the 5CB molecule in the LC layer, showing that this method has a potential to clarify the dynamic behavior of LC molecules.

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Polymer stabilized liquid crystal cells using a mixture of a nematic liquid crystal(NLC) and photo-curable liquid crystalline monomer have been successfully fabricated. The conformation of the photo-cured polymer network is determined by applying external orientation forces (electric or magnetic field) in the monomer state and successive photo-curing. The resulting conformation of a NLC media is determined through the interaction with the formed network. We study on the LC molecular alignment effect by means of the observation of the Nematic-Isotropic phase transition behavior. From the results, we find that the behavior of the phase transition is different comparing with a conventional system without a polymer network. Furthermore, it is clarified that the interaction between a polymer network and LC molecules is strong.

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Static and dynamic properties of n-alkyl cyanobiphenyl(nCB) have been studied by ¹³C NMR measurements. The order-parameters(P₂), ¹³C-para positions and terminal methyl carbon-13 of nCB clearly show even-odd effect, while the ¹³C-ortho positions of nCB do not show the even-odd effect, i.e. the result displays inverse behavior as compared with the behavior of para-, and methyl carbon-13.

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It is important to investigate the surface interaction between a nematic liquid crystal(NLC) and alignment film. In this report, we study the surfacc memory effect using two kinds of magnetically-aligned non rubbing cells, in which two different alignment films having different polarity are used. The cells are theamally annealed at various temperatures above T_c. After the annealing, the measurement of the order parameter is done and we investigate how the annealing conditions such as annealing temperature and time gave an influence on the durability of uniaxial orientation of NLC. We confirm that the thermal stability of NLC cells having a alignment film with high polarity is larger than that having low polarity.

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Liquid crystal(LC) aligning characteristics of m-MOLCA method by utilizing solvent evaporation, modified Magnetically Oriented Liquid Crystalline Adsorbate(MOLCA), are studied. The influence of magnetic field strength upon LC alignment uniformities and stability of obtained LC alignment to various external forces were examined. Some pretilt angles were generated on the substrate prepared by normal SiO vacuum evaporation.

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The dielectric constants of 1-cyano-2-fluoro-4-[trans-4-(trans-4-propylcylcyclohexy)cyclohexyl]benzene(CP1) and 1,2-difluoro-4-[trans-4-(trans-4-propylcyclohexy)cyclohexyl]benzene(CP3) were observed in the non-dipolar liquid crystalline solvent (1-[trans-4-ethylcyclohexyl]-2-[4-ethyl-3-fluoro-biphenyl ethane(122) in different 5 concentrations from 25 to over the clearing point. The ferroelectric and antiferroelectric correlations were estimated for CP1 and CP3.

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This paper describes an experimental investigation of dipole-dipole interactions between molecules in an orientational ordered environment. Measurements are reported of the dielectric properties of a series of anisotropic solutions of two structurally similar dipolar solutes 1-cyano-2-fluoro-4-[trans-4-(trans-4-propylcyclohexy) cyclohexyl]benzene (CP1) and 1,2-difluoro-4-[trans-4-(trans-4-propylcyclohexy)cyclohexyl]benzene (CP3) dissolved in a in a non-polar liquid crystal solvent 1-ethyl-3-fluoro-4-trans-4-ethylbiphenylethane (I22). The results indicate that the dipolar interactions in CP1 solutions are qualitatively different from those for CP3 solutions. In particular the dielectric properties of CP1 solutions can be interpreted by assuming that solute molecules are locally ordered antiferroelectrically, while for CP3 solutions the local order appears to be ferroelectric. The results can be fitted to an association model that enables the proportion of parallel and anti-parallel species to be determined.

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An apparatus for the measurements of slow and anisotropic self-diffusion coefficients has been constructed. For the smectic Ad phase of CBOOA, the diffusion coefficient was measured as a function of the angle between the quadruplole coil axis and the main static magnetic field. From the rotation pattern, the diffusion anisotropy (D_&parsl/D_⊥) was revealed to be 2.8.

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Monosubstituted ferrocene derivatives, [4-[ω-(cholesteryloxycarbonyl)alkoxycarbonyl]phenyl]ferrocene (CAPF-n) (n is the carbon number of the methylene chain, n=1〜11, 15) have been synthesized. Some of them (CAPF-2, 4, 6, 8, 9, 10, 11, and 15) exhibited liquid crystallinity. In this study, the crystal and molecular structure of CAPF-6 was determined by X-ray diffraction method in order to discuss exactly the structure of liquid crystalline phase. The crystallographic data are as follows; C₅₁H_₇₀O₄Fe, M=802.96, monoclinic, space group P2₁, a=13.093(5)Å, b=8.977(5)Å, c=38.532(4)Å, β=93.17(2)°, V=4522(2)ų, Dc=1.179gcm^-3, λ(CuKα)=1.54178Å, μ=29.95cm^-1, F(000)=1736.00, Z=4.

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Disubstituted ferrocene derivatives, 1, 1'-bis[ω-[4-(4'-methoxyphenoxycarbonyl)phenoxy]alkoxycarbonyl]ferrocene (bMAF-n) (n: the number of carbon atoms in the methylene chain, n=2〜12) were synthesized in our laboratory. The liquid crystallinity of these compounds was investigated by thermal measurements and texture observations. In this study, X-ray diffraction experiment was carried out in order to determine the structures of liquid crystalline and crystalline phases. The result suggested that the molecule of bMAF-6 exists in an extended S geometry at both crystalline and liquid crystalline phases.

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For n-alky1 4-[4'-(4"-n-octyloxybenzoyloxy)benzylidene]aminobenzoates, [chemical formula] all homologues exhibit smectic A and nematic, while smectic C phase also appears for longer members (n≧4). In order to clear relationships between the mesophase behavior and crystal structures, single crystal X-ray analysis has been performed for the ethyl and butyl homologues. Both crystals have smectic-like structures, and each molecule is arranged alternately to cancel dipole moments each other. Furthermore, the core moieties overlap largely in both crystals with the angle of 60° made by nearest neighboring phenyl rings of adjacent molecules. However, in the ethyl crystal, the core moieties are perpendicular to layer plane, while in the butyl crystal, those are tilted (20°) in the layer, corresponding to the adjacent mesophases, S_A (n=2) and S_C (n=4).

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The first example of ²H-NMR study of cyclohexane containing liquid crystals is reported. The observed spectrum is consisted of a superposition of discrete quadrupolar doublets associated with the axial and equatorial deuterons, and is used to evaluate the orientational order parameters of the cyclohexane ring. Temperature dependence of the orientational order parameter, its biaxiality, and the alignment angle of the molecular principal axis is discussed.

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Large electrooptic effcts of liquid crystal materials can have potential applications to various optical devices for a wider wavelength region. Fundamental optical properties of liquid crystals, such as refractive indices and transmission losses are investigated by using submillimeter laser (215μm). Refractive indices of K15(BDH) for ordinary and extraordinary rays are comparable with that in the visible region, and the birefringence is also large. Although the loss is larger by about two orders of magnitude than that of quartz which is an excellent window in the submillimeter region, the transmission of the liquid crystal cell is high enough.

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Liquid crystalline hole-transport material 2-(4'-alkoxyphenyl)-6-alkylsulfanylbenzothiazole derivatives, in which higher photoconductivities are expected in mesophase with aligning of hopping sites, are newly synthesized and their photoconductive behaviors are studied. Higher photoconductivity are observed in SmA phase in direct excitation with UV light or carrier injection from c-Se layer irradiated by VIS light.

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Some of homologous series of N-(2-hydroxy-4-methoxybenzylidene)-4-alkylanilines(HMBA) in cryslal state undergo the color change on irradiation with UV light. Some of HMBA are pale yellow when freshly prepared and deepened to pale-orange on light irradiation. The life time of colored HMBA(6) was longer (114.6 min) than the other HMBAs. It may be ascribed to the high order molecular packing in HMBA(6) cryslal. Some of HMBAs exhibit the nematic liquid cryslal phase. However, the photochromism was not observed in the nematic phase. The IR spectra show that the central group of HMBA takes the trans-keto amine form in the photochromic colored state.

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Viscoelasticity of binary liquid crystal systems were studied using a light scattering method which can be applied to the determination of the decay constant associated with the ratio of the viscosity and the elastic constant for the twist deformation. For the mixtures of 7HEF, a terminal-fluorinated liquid crystal, and BCH5 containing three aromatic rings as the core group, the phase diagram shows a wide nematic region in the temperature range of about 60 ℃ to 140 ℃ at 30 mol per cent of 7HEF. The activation energy for the viscosity was evaluated from the temperature dependence of the viscoelastic constant, showing a minimum at 60 mol per cent of 7HEF. It has also been found that the viscoelastic constant is strongly dependent on the molar fraction at a constant reduced temperature, i.e, a constant ratio of the measurement temperature and the isotropic-nematic transition temperature at each molar fraction.

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An electric impedance of nematic liquid crystal cells has been measured to detect an ion behavior. The experimental and theoretical results show that a single kind of ion carries a current in nematic liquid crusyal used.

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The low frequency dispersion of complex dielectric constant was used to analyze the ionic conduction of a nematic liquid crystal. Trace quantity of TCNQ (tetracyanoquinodimethane) was introduced in liquid crystal cell to realize the ionic conduction under controlled conditions. The dispersion was analyzed by a series combination of equivalent parallel circuit of the cell and polyimide alignment layer. The validity of the model was checked by changing the thickness of the alignment layer. The experimental dispersion curves were excellently fitted by the series model by introducing a space charge distribution parameter. The conductance vs. TCNQ concentration curve was discussed with an ion dissociation mechanism.

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Flexoelectro-optic effects in nematic CCH series liquid crystals are investigated by interdigital electrode method. Dependence of applied field, frequency, polarization angle and temperture of flexoelectric coefficients are precisely measured, and found especially in this experiment the existence of critical threshold field in CCH-3.

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Heat capacities of 1,2-bis-[4-(n-octyloxy)benzoyl]hydrazine were measured with an adiabatic calorimeter in the 13-450 K range. Four phase transitions were observed at T=392.3 K(Crystal II→Crystal I), 404.4(Crystal I→Cubic phase), 417(Cubic phase→Smectic C) and 425(Smectic C→Isotropic Liquid). Of the total transition entropy, about 90 per cent is gained at the crystal-to-crystal transition and the melting, indicating that the cubic phase is characteristic of a mesoscopic state. This large transition entropy is well interpreted in terms of disordering due to conversion between the trans and gauche comformations of the n-alkyl moieties.

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The chiral twin materials having the chiral centers at the central spacer and the both sides of the peripheral aliphatic chains were prepared and mesophasic helical structures induced by these materials were investigated. The twisting power in the Ch phase produced by the chiral centers at peripheral aliphatic chains was much stronger than that induced by the chiral center at the central spacer. On the other hand, in the SmC^* phase, the chiral center intoroduced at the central spacer was found to have a siginificant effect on the helical macrostructure.

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A molecular theoretical model is used to show that asymmetry of molecular potential due to head-tail configuration of molecules contributes to stabilize the AF phase which is one of the intermediate phases between ferroelectric Sm-C^* and antiferroelectric Sm-C_A^* phase. Further in the present study we extend the model and discuss the contribution of intralayer fluctuation of molecular direction to the stability of the intermediate phases.

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The method to determine the order of phase transition is proposed, which is based on the analysis of the divergent behaviour of the correlation function. This method is applied to the phase transitions between SmA and SmCA^* which can be described by the Ising model of S=1. In addition to this model the three body interaction within the smectic layer is taken into account, which comes from the mobility of the molecular position to avoid overlapping between molecules. The correlation function and other physical quantities are calculated by MC simulation.

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Ferroelectric liquid crystals(FLCs) with an optically active alkanoyl group and a chiral group derived from lactic acid show very large spontaneous polarization (Ps) of over 1000 nC/cm^2. In order to further analyse the phase transition behavior of these FLCs, we performed IR analysis on a series of them. The FLC having the highest Ps showed an unusual behavior; that is, the IR absorption of the ketonc C=O stretching vibration shifted to a higher wavenumber at the isotropic to SmC^* phase transition, while those of the other FLCs shifted to lower wavenumber. The relationship between the molecular structure and the IR results will be discussed.

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Development of 200ns FT-IR time-resolved spectroscopy (TRS) and its application to the study of transition dynamics of ferroelectric liquid crystals are reported. The results indicate that the flexible alkyl chain appended to the rigid core undergoes a fast local motion in addition to the overall rotational motion of the entire molecule. FT-IR TRS with 200ns time-resolution has been able to isolate the internal conformational transition and provide new imformation about the molecular elementary process of ferroelectric transition in chiral smectic liquid crystals.

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We have observed orientational distribution condition of C=O of carboxyl group in the SmC^* and SmCA^* phases of antiferroelectric liquid crystals by polarized fourier transform infrared spectroscopy. Then we found that in SmCA^* C=O group rotation is hindered and C=O group lies on the tilt plane of molecular long axis. Therefore we can regard new model with occurrence of SmCA^* instead of pairing model.

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We have observed temperature dependence of the¹³C-NMR chemical shift in liquid crystalline phases for the investigation of magnetic shielding effects of keto-carbons. It gives the information to estimate the interactions of the intermolecule and intramolecule in antiferroelectric liquid crystals. We discuss the result from microscopic viewpoint about the dipole-dipole pairing model which is wellknown.

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Layer rotation in antiferroelectric liquid crystal cells with rubbed pclymer film has been studied. According to the microscopic observation under the external field of various waveforms, we found that the direction of layer rotation was positive when τ_d⁺τ_d^-, and vice versa, where τ_d⁺ and τ_d^- indicate the response time from the positive ferroelectric(F) state to the antiferroelectric(AF) state and that from the negative F state to the AF state, respectively. The layer rotation angle was in proportion to the difference between τ_d^- and τ_d^-.

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In this study, the pretilt angles in the surface stabilized ferroelectric liquid crystals(SSFLC) were evaluated by optical experiment. We measured the temperature dependence of the pretilt angles from nematic phase through smectic C^* phase by the optical measurements such as the crystal rotation method. Especialy for the SmC^* phase (SSFLC mode), the pretilt angle was calculated on a basis of the molecular orientation model of SSFLC by using the measured values of the layer tilt angle, the swiching state angles and the memory state angles. In consequence, it was found that the temperature dependence of the pretilt angle exhibited an discontinuity near the N-SmA transition temperture, and the pretilt angles in smectic A phase were smaller than that in nematic phase. Furthermore, it was suggested that the pretilt angles in the SSFLC cells depend on the alignment films in the same manner as nematic cells.

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In this study, we would like to report the experimental results and the numerical simulation on the electroclinic effect(EC), in the SmA of FLCs, TFMHPDOPB(Mitsubishi Petrochemical.) and 764E(Merck.). Firstly, we evaluated the values of Landau-coeffients for these FLC by measuring the molecular tilt angle and the displacement current. Then we calculated the temperature dependence of the dielectric constant, on a basis of the Landau-type static theory. Secondly, we calculated the dynamic EC response caused by the reorientational distribution, where the parameters evaluated by our measurement were used. In consequence, it was found that the dynamic molecular reorientational distribution is affected by the polar and/or non-polar surface anchoring strength. However, the effect of surface anchoring on the optical transmittance or dielectric response are not remarkable, therefore it seems to be impossible to estimate the surface anchoring strength experimentaly by the measurement of optical response or dielectric constant.

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Recently, the existence of the unique switching mode so-called quasi-tristable switching in the surface stabilized ferroelectric liquid crystals(SSFLC) has been reported. In these papers, oblique smectic layer structure with the high surface pretilt angle were considered, and further, alternate molecular orientational model similar to the antiferroelectric arrangement were supporsed. In this study, we calculated the dynamic response of SSFLC on a basis of continuum theory, and studied the influence of the surface polar anchoring strength on the dynamic response. From this numerical calculations, the possibility of quasi-tristable switching was discussed. When the polar-anchoring strength is adequate to originate the twist orientation in the chevron structure, uniform-twist-uniform switching may be realized by applying the triangular voltage.

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Exact value of spontaneous polarization (Ps) of ferroelectric liquid crystals were obtained by compensating ferroelectric hysteresis loop distortions. The compensated values of Ps obey the equation Ps=Po(Tc-T)β. Effects of experimental conditions on the parameters Tc, β and Po were investigated; for single domain cells, Tc and β are independent of cell thickness, however, Po increases with cell thickness and saturates at 20μm in thickness. Existence of alignment layers fixed on the cell surfaces or the screening effect of ionic charges accumulated near the electrodes were discussed.

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Polarization switching properties in terms of the surface anchoring effect were investigated. We investigated the effect on polarization switching properties by setting the following parameters; Pre-tilt angle at the interface between alignment layer and the liquid crystal molecule: Layer structure in SmC^* phase of the FLCs: Compression and Expansion environments to the FLC cells. Low frequency and low voltage applications on to each pre-tilt cell suggest that the low pre-tilt chevron geometry provides stronger surface anchoring effect. Low pre-tilt bookshelf geometry which is realized by the naphthalene base FLCs, however, indicates whole LC molecule's switchings including the interface area. This conclusion is also supported by the polarization switching study under the compression and expansion environment.

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