The liquid crystalline photoconductor, 2-(4'-octylphenyl)-6-dodecyloxynaphthalene is designed in order to realize ambipolar carrier transport, which has not been realized in organic amorphous solids except some binary material systems. This material exhibits SmB and SmA phases, in which ambipolar carrier transport was observed. The hole and electron mobilities are almost same in each phase, and are 1.6X10^-3 and 2.5X10^-4 cm²/Vs, respectively.

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The photo-voltaic effect in nematic liquid crystal cells mixed with polymer liquid crystal(1 and 3 %) and the dyestuffs of methyl yellow(3 %) with a semiconductor wafer used as one of the electrodes is investigated. The photo-electromotive force measured on the cell thickness and the temperature characteristics by the illumination strength of 1000 lux on the incident light of the fluorescent lamp. The photo-electromotive force increased on the thick cell compared with the thin cell. The photo-electromotive force changed the cell temperature indicated the peak values on about 50 ℃ . The cell with polymer liquid crystal of 3 % had the higher photo-electromotive force than the 1 % cell.

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Carrier transport of 2,3,6,7,10,11-hexahexyloxytriphenylene (HHOTP) in the discotic phase and the effects of C₆₀ doping have been studied by a time of flight method. C₆₀ is well known to capture electrons effectively. Relatively high mobility of positive carriers insensitive to temperature and also C₆₀ doping are interpreted to be hole mobility. Small and temperature dependent mobility (with activation energy of 0.3 eV) of negative carriers which are influenced slightly by C₆₀ doping is interpreted to be that of ionic carriers.

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Adsorption-desorption characteristics of cyano-phenyl type liquid crystal (LC) molecules onto rubbed polyimide and poly(vinyl alcohol) substrates were investigated by means of optical ellipsometric analysis. The LC molecules in a dilute solution irreversibly adsorbed on the rubbed polymer surface. Adsorbed mono- or bi-layer of LC molecules was formed even after almost complete rinse of the polymer surface with a solvent, indicating a stronger adsorption than a simple physical adsorption.

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The total reflection ellipsometry has been applied to investigate the behavior of Liquid Crystal(LC) molecules at the interface between LC and alignment film. The total reflection method allows to use LC cell which is not doped with dichroic dye and to observe the reflected light, which includes the imformation about the LC molecular behavoir at inaterface. From the numerical results of the reflection ellipsometry, it was found that, the phase difference versus applied voltage depends on an incident angle, a wavelengh of incident light, and the thickness of an alignment film. This analytical method is sensible enough to estimate the anchoring strength of LC cells.

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The azimuthal orientational distribution of the LC molecule at an interface was investigated by the Brewster Angle Reflection (BAR) method. For the BAR method, there is no reflection from an interface between air and a glass plate when P-polarized light are incident from air on a glass plate at the Brewster angle. The transmited light is absorbed in the bulk LC which was doped with a dichroic dye and the reflected light includes the imformation about the LC molecular orientation at an interface between LC and alignment film. From experimantal results of the BAR method, it was found that polar plots of the reflection intensity as a function of rotation angle reflects the azimuthal orientational distribution of LC molecules at an interface. Morever, experimantal results was in good agreement with numerically calculated ones.

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The electric-field induced reorientation dynamics of 5CB liquid crystals has been studied by polarization modulated spectroellipsometry (PMSE), and analyzed by a 4 x 4 matrix simulation based on the elastic continuum theory. The dynamic behavior of surface molecules (reflection PMSE observations) and of bulk molecules (transmission PMSE results) have been quantitatively reproduced. It is also shown that the PMSE experiment can distinguish the dynamics of surface molecules in strong and weak anchoring systems. These new observations can provide a direct insight into the origin of the surface anchoring effect.

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Temperature dependence of liquid crystal reorientation dynamics has been examined by polarization modulated spectroellipsometer (PMSE) equipped with a variable temperature controller. The effect of bulk elastic property of liquid crystals and that of surface anchoring on the transition dynamics have been separated by comparing the results of transmission and reflection PMSE experiments. Namely, the elastic constant ratio (k₃₃/k₁₁ - 1) of the bulk molecules exhibits a non-linear temperature dependence, but the normalized anchoring strength of the surface molecules is kept constant independent of temperature in the entire nematic range.

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To determine the correlation between the molecular orientations of a rubbed polyimide film and a surface liquid crystal (LC) layer in contact with it, we have measured the infrared absorption spectra as a function of the incident angle. The molecular orientations were determined by fitting the incident angle dependence of the absorbance with a theoretical curve. From the comparison of the orientational distribution functions of the LC molecules and the polyimide chains, we have found that: (1) the LC molecules in the surface LC layer are on average oriented along the rubbing direction with the same inclination angle as the polyimide chains in the underlying polyimide film; (2) the ordering of the LC molecules along the rubbing direction is higher than that of the polyimide chains.

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Attenuated total reflection (ATR) properties have been investigated to evaluate tilt angles of liquid crystal molecules, 5CB, in the liquid crystal cells with the polyimide (PI) LB alignment films on the aluminum electrodes. The ATR properties were explained by the surface plasmon polariton and the guided wave excitation modes when various DC voltages were applied to the cells. The tilt angles of the liquid crystal molecules were calculated near the LB films and in the middle layer region of the cells by fitting the theoretical ATR curves to the experimental ones. It is thought that the ATR measurement is very useful for evaluating the aligning properties of liquid crystal molecules in the liquid crystal cell.

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We have investigated the role of the backbone structures of polyimide with alkyl side-chains in the determination of the pretilt angle of liquid crystal (LC) in contact with a rubbed polyimide film. We have determined the inclination angles of the polyimide backbone structures in rubbed films as well as the pretilt angles of LCs in contact with the rubbed films. We examined four different polyimdes with the same backbone structure but different length of alkyl side-chains. The inclination angle of the polyimide backbone structure increases with the number of carbon atoms in the alkyl side-chains. We found a linear relation between the inclination angle of the backbone structure and the pretilt angle of LC. Furthermore,the linear relation holds for a polyimide without side-chains [Arafune et al., Surf. Sci. 368, 208 (1996)] as well. Thus we conclude that the inclination of the polyimide backbone structure determines the pretilt angle of LC. The alkyl side-chains affect the alignment of the polyimide backbone structure in the rubbing process, but they do not affect directly the pretilt angle of LC. The effect due to the alkyl side-chains is only indirect.

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We have determined second order complex nonlinear-susceptibility tensor of a liquid crystal(LC) monolayer absorbed on a second harmonic(SH)-active polyimide(PI) film. In order to separate the SH signal of LC from that of PI, we have adopted the interference method using an SH-active LB film as a local oscillator. Each component of the complex susceptibility tensor has been analyzed with use of in a 4 layer model. We found that each component actually possesses the phase relations.

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Side chain orientation of polyimide (PI) films for liquid crystal alignment has been studied by surface second-harmonic generation (SHG). SHG from two interfaces of the film was separately observed using thick films, in which SH light from the rear interface was almost absorbed in the film. Rubbing action caused in-plane anisotropy only for the air-PI interface. For as-coated films, the average tilt angle of the side chain at the air-PI interface is smaller than that of the other interface. The dstribution functions of the side chain of the rubbed PI film and bulk pretilt angle were also discussed.

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We evaluated the azimuthal anchoring strength of the nematic liquid crystal cells whose inner surfaces were treated by the different kind of alignment techniques. One is the AT(Alignment Transcription) Method using polyimide films, and the other is Photo-induced Liquid Crystal Alignment Method using photoreactive SLCPs(Side-chain Liquid Crystalline Polymers). We found that the azimuthal anchoring strength of AT method cell decreased with increase in the transcription cell gap and the order was from 10^-5 to 10^-4 J/m². The order of the anchoring strength of photo-induced LC alignment cell with the SLCPs was 10^-6 J/m².

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Anchoring properties of a liquid crystal at the interface has always been one of the most intriguing topics ofresearch in physics and applications of liquid crystals. This is because the anchored orientation imposed at theinterface serves as the indispensable boundary condition for determining the configuration of liquid crystal specimen. Moreover, due to the emergence of photoaligning processes and polymer dispersed systems in which the control of anchoring strength is believed to be vital, the demand for quantitative characterization of surface anchoring is becoming even more acute in recent years.

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Since the discovery of a Surface Freezing Effect of n-alkane, the surface structures have been the subject of recent interest. In this study, we have performed DTA (Deferential Thermal Analysis) and ultraviolet photoemission measurement to investigate the Surface Freezing Effect of n-alkane. The sample used in the experiment was pentacontane (n-C₅₀H₁₂₀:650Å ) and tetratetracontane (n-C₄₄H₉₀:600Å ) films evaporated film on Cu substrate. We have succeeded to observe of a monolayer phase transition and proved that a Surface Freezing Effect of n-alkane is the first order phase transition. Moreover, we have found that the temperature dependence of ultraviolet photoemission intensity is the useful measure of the Surface Freezing Effect.

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In the antiferroelectric smectic liquid crystals the V-shaped response of the transmittance of light to the electric field is observed, where the transition between antiferroelectric and ferroelectric phases looks as if there is no threshold between both phases and even the structure of the antiferroelectric phase is now controversial. On the other hand the antiferromagnetic Ising model with layered structure is known to have a tricritical point in the magnetic field, in which the transition between antiferromagnetic and ferromagnetic phases induced by the magnetic field can be continuous. From this point the phenonnena observed in the antiferroelectric smectics is to be explained in terms of the antiferromagnetic Isimg model with layered structure.

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We have studied the optical switching properties of two kinds of antiferroelectric liquid crystals (AFLCs) containing an azobenzen moiety by Ar⁺ laser light irradiation. In the case of an AFLC which has trifluoromethyl group connecting to the chiral center, the optical induced phase transition by Ar⁺ laser irradiation was different from that by UV light irradiation. Using this phase transition, we have demonstrated the optical switching. In addition, we discovered the optical alignment effect in these AFLCs by linearly polarized Ar⁺ laser light irradiation.

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Polarization and depolarization dynamics have been examined using (+E)0(-E)0 step-wise electric field with respect to antiferroelectric MHPOBC in its SmC_A^* phase. The switching time of the polarization process obeyed a powar law τ ∝Eⁿ with n=6〜7 whereas that of the depolarization process was 2〜3ms being independent of E. A notable overshoot phenomenon was found to occur when the applied field was switched to a slightly negative value.

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Light deflection phenomenon of SmC^* phase of R-MHPOBC under electric bias fields. The deflected lights were observed in two regions of bias field, at which the dielectric constant showed steep decreases and the apparent tilt angle showed stepwise increase, simultaneously. Characteristic dependence of the deflection angle on the angle of incidence is an evidence of the coexistence of two phases.

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Thresholdless antiferroelectric liquid crystals (TL-AFLCs) are promising materials for fast-response and wide-viewing-angle TFT-LCDs. The previously reported eqtrivalent circuit model which describe the electro-optical response of the material is compared with a reversal polarization model of SSFLCs, and it is shown that in some conditions they correspond each other. Furthermore, the equivalent circuit model is modified to include the dependence of the response speed on applied voltage.

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The switching behavior of surface stabilized ferroelectric liquid crystals has been studied using a simple uniform switching model in an applied electric field. We measured the response fime as a function of pulse voltage for ferroelectric liquid crystal materials, which show a minimum in the response time-voltage curve, and found good agreement between the theory and the experimental results. Accordingly, the parameters appearing in the switching model, the initial azimuthal angle, rotational viscosity and surface anchoring energy can be determined. Furthermore, we found the method to develop the effective material for temperature change by adjusting the combination of chiral and host compounds.

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It is known that there are two alignment, states, C1 and C2, in homogeneous alignment cells of ferroelectric liquid crystals, and the boundary between these alignment states is zig zag defect. It is very important to control these alignmnent states into one state for application of display device. We have investigated τ-V_min mode in which C2 orientation is used. C2 ratio strongly depends on ferroelectric liquid crystal material and alignment layer. In this time we report new reorientation method to obtain 100% C2, even if initial state is 0% C2.

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The Shock stability of Ferroelectric liquid crystal display(FLCD) is poorer than nematic liquid crystal. There are many investigations to improve the shock stability using resin spacer walls, and adhesive spacer ball. In this study, we investigated to realize high shock stability FLCD with spacer wall by combination of adhesive alignment layers and 2 step annealing

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Improvement of the screen brightness was investigated by using a reflective type of direct driven SSFLCD with a single polarizer. We found that wavelength dependence of retardation : Δ nd of the SSFLC cell has a significant influence on the substantial contrast ratio of the cell in terms of the reflective type of color display. Optimization of the wavelength dependence of Δ nd provides us a good contrast ratio reflective type of SSFLCD.

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Recently, We have reported that a polymer network, which is formed in SmA phase by the photocure of UV photocurable liquid crystalline monoacrylates that are doped in a surface stabilized ferroelectric liquid crystal (SSFLC), eliminates zig-zag defects in SmC^* phase, since a chevron structure is transformed into a quasi-bookshelf structure by the polymer main chain. In this study, we have observed the electrooptical effect of this polymer stabilized SSFLC (PS-SSFLC) with the aim of exploring the influence of the mesogenic side chain on the alignment structure of FLC molecules. As the experimental results, it is found that mesogenie side chain bonds strongly with main chain, and attarct FLC molecules in the rubbing direction.

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First we studied the alignment direction of FLC molecules in a mesogenic side chain polymer stabilized SSFLC cell that was photocured at a SmA phase temperature, and we found that there are two directions: the one is the direction determined by surface stabilization, the other is that of mesogenic side chain. Then, we tried to coincide these two directions with the aim of improving contrast ratio by photocure particularly at a temperature where FLC medium is in the SmC^* phase under the application of a monopolar electric field. In fact, we succeeded in fabricating a new PS-SSFLC display that exhibits monostable electrooptical characteristics with a high contrast ratio owing to defect free, a grayscale capability without threshold, and a fast response.

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Some liquid crystalline materials having a thiocyanato group and a fluorine substituent at the terminal position were prepared and investigated the thermal properties. The transition temperatures and the latent heats were measured by the polarized microscope and the differential scanning calorimeter. 4-thiocyanatophenyl 4-(4-alkoxybenzoyloxy)benzoate derivatives showed nematic and smectic A phases. On the other hands, 4-alkoxyphenyl 4-thiocyanatophenyl terephthalate derivatives showed smectic B or C phase, as well as nematic and smectic A phases. The layer spacings of the smectic phases were examined by X-ray diffractions, suggesting that the short alkoxy derivatives have a mono-layer arrangement, but the long alkoxy derivatives have a partially bilayer one.

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It is reported that 5-(4-alkoxyphenylazo)- and 5-(4-alkylphenylazo)tropolones and their methyl ethers are not mesogenic. We observed, however, the corresponding sigmatropic ester derivatives exhibited smectic mesophases. The substituent effect of the phenyl ring on the thermal stability was discussed; alkoxyl groups are more favored than alkoxycarbonyl and alkyl groups. Thus we investigated the mesogenic property of 5-(4-substituted phenylazo)tropolones.

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We synthesized new liquid crystals, 4-n-alkoxyphenylbenzyl 2'-perfluorcpropoxy-2',3',3',3'-tetrafltaoropropyl ether(APPTE) and 4-(2'-perfluoropropoxy-2',3',3',3'-tetrafluoropropoxy carbonyl) phenyl 4-alkoxy biphenyl-4-carboxylate(PTPAC) and studied their liquid crystalline plase transition and electro-optical properties. APPTE and PTPAC showed smectic A and/or C, and acted as one component lowering the anisotropy of reflactive index in ZLI-1132 solvent.

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We synthesized the new liquid crystalline materials that 2-aminoethanol urmit is attached to an azobenzene mesogenic moiety through a methylene chain and examined their phase transitions and orientational structure. The liquid crystalline materials showed smectie phases such as smectic A, C, and F phases. The liquid crystalline properties strongly depended on the length of the methylene spacer.

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The oxidative desulfurization-fluorination reaction of xanthates was applied to the synthesis of new type liquid crystals (LCs) having an aliphatic trifluoromethyl ether moiety as ,a polar function. The novel LCs were shown to exhibit mesophases in wide a range of temperatures and decrease birefringence and threshold voltage of host nematic LCs upon mixing by 20 wt%.

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We report here that a novel dichiral liquid crystal on cooling exhibits a new optically isotropic phase along with an endothermic transition enthalpy. This anomalous phenomenon was found to occur in 2-[4-[(R)-2-fluorohexyloxy]phenyl]-5-[4-[(S)-2-fluoro-2-methyldecanoyloxy]phenyl]pyrimidine (RSFPPY). In contrast, the diastereomer of RSFPPY, 2-[4-[(S)-2-fluorohexyloxy]phenyl]-5-[4-[(S)-2-fluoro-2-methyldecanoyloxy]phenyl]pyrimidine (SSFPPY) did not show the unusual transition. The effect of chirality on the transition behavior is discussed.

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We have investigated a dichiral ferroelectric liquid crystal containing fluorines with NMR, dielectric and X-ray diffraction measurements. In the DSC measurement and texture observation, this compound has a phase sequence of Iso-SmC^*-IsoX-SmX^*. In the dielectric measurement, the IsoX phase exhibits the same behavior as that in the isotropic liquid. In the X-ray diffraction measurement, however, a sharp diffraction peak corresponding to the shorter spacing than the layer in SmC^* and SmX^*. We also observed a subpeak at the wider angle than that at which the main peak was observed, which may suggest the formation of the cybotactic cluster.

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In order to study the molecular structural effect to a new optically isotropic phase (IsoX) found in 2-[4-((R)-2-fluorohexyloxy)phenyl]-5-[4-((S)-2-fluoro-2-methyldecanoyloxy)phenyl]pyrimidine, we synthesized its analogous. The analogous having different alkyl side chains exhibited the IsoX phase, whereas their diastereomers and mono-fluorineted derivatives exhibited nomal smectic phases.

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Phase transitions of 4'-n-pentadecyloxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-15) were studied by DSC, optical microscopy, infrared spectroscopy, and dynamic viscoelastic (dve) measurements. ANBC-15 shows smectic C (S_C), an optically isotropic cubic phase called D phase, smectic A (S_A) phase on the first heating, and the D phase disappears in the subsequent cooling and heating. Howaever, when the thermal cycle is done below the D-S_A phase transition temperature, ANBC-15 shows the D phase in both heating and cooling processes. The dve measurements reveal that the elastic properties of the S_C phase that precedes the D phase on heating is different from those of the S_C phase that transforms directly to the S_A phase.

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Heat capacities of the cubic liquid crystal, 1,2-bis-(4-n-octyloxybenzoyl)-hydrazine, has been measured with an adiabatic calorimeter in the 14-480 K range. A solid-solid phase transition with a large entropy change, the fusion to the cubic mesophase, two transitions to S_C phase and then to the isotropic liquid were observed. Contrary to expectation, the entropy gain at the cubic to S_C phase transition was extremely small, whereas their higher-order structures would be quite different. Entropy and enthalpy changes at each phase transition are determined and thermodynamic properties of this material has been discussed.

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Heat capacities of 4'-n-hexadecyloxy-3'-nitrobiphenyl-4-carboxylic acid were measured with an adiabatic calorimeter in the 13-482K range, and with a DSC in the 470-510K range. Four crystalline phases were found. In the liquid crystal region, S_C - D and D - S_A phase transitions were observed, and a broad heat-capacity anomaly was observed above the clearing point. Thermodynamic quantities associated with the phase transitions were determined.

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Strontium stearate (SSr) is known to have a cubic phase which is an isotoropic mesophase. In this work, we confirmed that SSr undergoes crystal(Cr)-rombohedral(R)-body-centered cubic(Q)-hexagonal (H)phase transition and measured dynamic mechanical properties over all the phases. The formation and structure of Q phase are discussed from the dynamic mechanical results.

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Alkylated sugars show thermotropic and lyotropic phase behavior due to amphiphilic character that leads to microphase separation. Various alkyl glycosides were prepared to allow for systematic strcture-property-analyses. Monosaccharides give only smectic A phases and the clearing temperature is a simple function of the intramolecular contrast in polarity and geometrical form. Di- and oligosaccharides can show polymorphism: smectic A and columnar phases as well as bicontinous mesophases. These bicontinous phases are predominatimtg in "banana-shaped" glycosides.

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