[in Japanese]

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[in Japanese]

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Liquid crystal displays (LCDs) have been widely applied to information terminals and is recently replacing CRTs of television. According to it, higher performance such as contrast ratio, viewing angle, response speed, active temperature range and power consumption as well as more suitable structure and production process for large size display are required. In order to satisfy these requirements, fundamental research on liquid crystal and materials used in the LCDs is important. From these viewpoint, present state and future trends of LCDs will be discussed.

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[in Japanese]

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Risk management of chemicals is the method for minimizing the risk to health and ecosystem to do with chemicals safely without fear. The government controls quality and quantity of chemicals on use by laws such as Chemical Substances Control Law and PRTR, whereas enterprises do self-imposed control on their products as well as obey the laws. It is the most important for Individuals to have correct knowledge and proper awareness on chemicals and to keep 3R (Reduction, Recycle, and Re-use) for wellness of human and the earth.

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Ionic liquids are ambient-temperature isotropic liquids composed of only cations and anions. Their applications as electrolytes in ionic devices as well as solvents for organic reactions have attracted much attention. For further functionalization of ionic liquids, we have introduced liquid-crystalline structure and properties into these materials. A new class of low-dimensional ion-conductors has been obtained by using liquid-crystalline ionic liquids. The enhancement of ionic conductivity and anisotropy has been induced by the formation of oriented ion-conductive pathways at the macroscopic scale.

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Recently, a new method of non-contact alignment has been proposed ion beam (IB) bombardment on diamond like carbon (DLC). And the new technology (DLC/IB) is applied for monochrome IPS-LCD for medical use. We investigated the optical anisotoropy on DLC thin film exposed to IB by reflection ellipsometry. The experimental results are well consistent with a simple theoretical model. The optical anisotoropy, anchoring energy and pretilt angle on several inorganic and polymer films exposed to IB were measured. The relation between optical anisotropy and alignment properties for IB method is discussed.

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We have developed new alignment method of liquid crystal molecules by hydrophilic/hydrophobic patterning technique. This method of patterning can be accomplished by photocatalysis effect of TiO2. We found that 10-micrometer order hydrophilic/hydrophobic stripe pattern was successfully fabricated with ability to align liquid crystal molecules parallel to that stripe. This technique is possible to be applied to domain divided vertical alignment LCD without patterned electrode and protrusion.

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We have investigated the orientation of polyimide (Azo-PI) molecules containing azobenzene in the backbone structure induced by single oblique angle irradiation with unpolarized light (UP-light). The UP-light irradiation was performed at the incidence angle of 45 degrees on the 16 nm thick film of polyamic (Azo-PAA) acid that is the precursor of Azo-PI. The UP-light exposure was varied up to 882 J/cm². After thermal imidization of the photo-treated film, the orientational distribution of the Azo-PI backbone structure was determined using infrared absorption spectroscopy. We found that the backbone structure rotates toward the minimum electric field direction of the UP-light in the Azo-PAA film during the UP-light irradiation.

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[in Japanese]

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Sum-frequency vibrational spectroscopy and second-harmonic generation were used to study the structures of polyimide (PI) surfaces for homeotropic liquid crystal (LC) alignment and the molecular orientation of LC adsobates on these surfaces. The imide ring was perpendicular to the surface with one of CO bonds protruding out of the surface and the other pointing into the bulk rather than flat on the surface. The ester CO bond in the side chain was sticking out of the surface with a tilt angle of about 40-55 degrees from the surface normal, indicating that the rigid side chain core was, more or less, along the surface normal. The cyano biphenyl LC molecules were adsorbed on the PI preferentially with the terminal cyano group facing the PI surface.

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IR-Visible Sum Frequency Generation (SFG) Spectroscopy is used to investigate the surface/interface structure of polyimide (PMDA-ODA) films on various substrates. SFG spectra of the polyimide films clearly show the difference depending on the substrates (CaF2 and SiO2), indicating that the air/polyimide interface could have different structure and chemical composition from those of the bulk. From the detailed analysis of the peak intensity ratio of C=O symmetric and antisymmetric vibration modes, we conclude that the tilt angle of the imide plane along the long axis of the polyimide chain prepared on CaF2 is larger than that on SiO2.

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On a rubbed polymer substrate, liquid crystal (LC) molecules can be aligned in parallel to the rubbing direction. In this paper, we report a clear evidence of LC molecular orientation studied by near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The incident-angle dependence of the resonance intensity of the C-K and N-K to pi*-states in CC double bonds and CN triple bonds is explained by molecular orientation of 5CB (4-pentyl-4'-cyanobiphenyl) on the rubbed substrate of PMDA-ODA.

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The orientational order parameter S2 of the 4'-n-4-pentyl-cyanobiphenyl(5CB) ultra thin film on the 6Az10PVA (azobenzene side-chain polymer) monolayer was determined during 5CB deposition in the region of layer thickness between submonolayer thickness and several manometers. It was revealed that $S_2$ of the 5CB on the trans-form 6Az10PVA is greater than that of cis-form 6Az10PVA even in a few molecular thickness region. For 5CB film on the trans-form 6Az10PVA, S2 reaches maximum in the first 5CB layer.

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We examined the influence of an alternating current (ac) electric field on the smectic C (SmC) to cubic (Cub) phase transition of 4'-n-docosyloxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-22). The most unexpected result is that even at a temperature 8 K below the previously determined zero-field transition temperature (TSmC-Cub = ca. 408 K) and without field, the SmC-Cub transition occurs after a very long induction time of several hours; it is suggested that the 'true' transition temperature, which is difficult to determine precisely, exists around 397 K. Between 408 and 397 K, the SmC-Cub transformation is governed by the strongly restricted nucleation and growth of the Cub phase in the precusory SmC phase. The role of the ac electric field on the transition is to promote the nucleation and to accelerate the growth rate, resulting in the apparent induction of the SmC-Cub transition between 408 and 397 K.

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Phase transitions of optically isotropic, thermotropic cubic mesogens, 1,2-bis(4-n-alkyloxybenzoyl)hydrazine, BABH(n) n=8,10,11,12, were investigated under hydrostatic pressures up to 200 MPa using a high-pressure DTA, wide-angle X-ray diffraction equipped with a high-pressure vessel, a polarizing optical microscope euipped with a high-pressure optical cell. In the T-P phase diagrams for BABH(8) and BABH(10), the Cub-SmC transition lines show negative slopes (dT/dP) and the Cub phases disappear at very low pressures of about 32 and 11 MPa, respectively. In BABH(11) and BABH(12), a SmC phase is pressure-induced at pressures above about 10-11 and 16-17 MPa, respectively.

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Ferroelectric liquid crystal 8422[2F3] exhibits the de Vries Sm-A – Sm-C* phase transition. We have carried out a high resolution calorimetric study of 8422[2F3] and investigated the critical behavior associated with the transition. The result shows a significant critical heat anomaly at the transition, although it was found to be weakly first order. Detailed analyses revealed that the heat anomaly shows almost tricritical behavior in the vicinity of the transition temperature Tc ,while it exhibits a different critical behavior in the temperature range away from Tc.

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On the basis of the discrete model, we have investigated the E(Electric field)-T(temperature) phase diagram of an antiferroelectric liquid crystal MHPOCBC, in which a new phase was found in the SmCalpha* phase under electric fields by means of the birefringence measurement. It was found that the new phase is a ferrielectric phase with a period of three layers, in which the molecules are restricted in one plane perpendicular to the electric field, and a nonlinear nearest neighbor interaction is important for stabilizing the phase.

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Molecular dynamic simulation is carried out at the system of bent molecules to study the effect of the molecular shape to the liquid crystalline ordering. The molecule is a dimer of two types of Gay-Berne particles connected by harmonic spring at each end and makes a bent angle at isolated state as an energy minimum. A decrease of clearing temperature with increase of the bent angle of molecule is depicted. The Relation of the ordering to the flexibility of molecule is tested by changing the stiffness of the conecting spring. Several systems of dimer with altered length of Gay-Berne particles are also tested to study the effect of molecular shape.

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Since a rectangular molecule has lower symmetry than rod-like molecule, it is expected to exhibit different phase transition from rod-like one. A simple simulation model is assumed to be represented by tightly connected rigid spheres. We have been performed Monte Carlo simulations under constant volume on system of 512 molecules consisted of 5x2 spheres .We have found a new biaxial smectic phase in addition to isotropic, nematic and smectic phases. This biaxial phase has never appeared for rod-like molecules. The phase transitions for these systems are known to depend only on the concentration of molecule, but not on the temperature. Possibility of occurrence of ferro- and antihero-electric phases will be discussed, when molecules have intrinsic dipole moment.

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Block-spin model and chiral smectic model are proposed. It is suggested from these models that the reason why the intermediate phases appear in antiferroelectric smectics, is not frustration by competing interactions but the non-Hermitian transfer matrix, which is derived by unsymmetrical interaction energy in adjacent block-spin or in adjacent chiral molecule along layer normal.

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Continuous transformation of single layer, frustrated and bilayer smectic structures were observed in two series binary mixture of dimetric mOAM5AMOm compounds by X-ray diffraction. The transformation from the single layer smectic CA (SCAs) to the frustrated one (SCAanti) was clearly confirmed for binary mixtures of 8OAM5AMO8 and 4OAM5AMO4 by appearance off-meridional (101) reflection attributed to the two-dimension orthogonal lattice which describes the distorted layer structure in the SCAanti phase. Toward to the transformation to the bilayer smectic CA (SCAb) phase observed in binary mixture of 8OAM5AMO8 and 12OAM5AMO12, the lattice size parallel to the layer direction increases asymptotically to infinite. The number of molecules accommodated in the lattice increases from 11.3 to 19.2.

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The photonic defect modes in a cholesteric liquid crystal induced by a local deformation of its helix has been investigated. The defect modes appear in transmission spectra only when incident circularly polarized light has the same handedness as the helix. The tuning of defect mode position can be performed upon both local expansion and squeeze of helix, in which the shift direction of the defect mode wavelength is opposite. Upon controlling the degree of the deformation of helix, continuous shift of defect modes can be realized.

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Metal nanoparticles Doped TN-LCDs exhibit an FM response with short response time. This device called FM-TN-LCD. Dielectric constants of FM-TN-LCD cell increase with decreasing frequency below several hundreds Hz; this behavior is explained by Maxwell-Wagner Theory. From the variation of the threshold voltage, it is shown that the dielectric anisotropy decreases with decreasing frequency. This may give rise to a rapid temporal change in the dielectric torque and may cause a fast EO response.

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Microwave variable delay line of microstrip line structure using ferroelectric liquid crystal with large tilt angle is fabricated. Voltage dependence of the phase shift under application of triangular wave has a hysteresis. Response times of the phase shift under application and removal of voltage are measured. Rise and decay times of the phase shift increase under low voltage application and then decrease with the voltage via the peak value. Both response times are less than 30 ms under application of sufficient voltage.

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The orientation dynamics of ferroelectric liquid crystal mixtures with ultrashort pitch (FLCUSP) in the Sm-A and Sm-C* phases during the electric-field-induced switching between the two SSFLC states were investigated by means of time-resolved FT-IR spectroscopy. It was found that the dynamical behavior of orientation with layer rotation indicated by the C=O group in the chiral dopants is different from that indicated by the core moiety in the base liquid crystals in the Sm-C* phase. We also studied the orientation dynamics of SSFLC especially focusing on the relationship between orientation and rotation during the electric-field-induced switching.

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Ferroelectric phase of a MHPOBC molecule has constructed the spiral structure without the applied electric field. Spiral structure comes loose by electric field impressing or electric field intercepting to this phase, or it reconstructs. In this study, by comparing the temporal behaviors of conoscopic figures with simulation figures examined reorientation process of a liquid crystal molecule.

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In addition to symmetric bent-shaped molecules, asymmetric ones have been attracting considerable attention because of their characteristic mesophases. Here we report the evaluation of the polar structure of an asymmetric bent-shaped molecule using second-harmonic generation (SHG) experiments. SHG signal was observed under a triangular electric field in the smectic temperature range. SHG signal increased with increasing the electric field and did not saturate even under a high field. These experimental results imply the following orientational change; The molecules (dipoles) freely rotate about their long axes parallel to the layer normal in the absence of a field, and electric-field-induced dipole reorientation occurs against thermal agitation.

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For the probe molecule Phenyl Benzoate[PB] having a 13C-enriched carbonyl, 1H dipole-split 13C spectra are observed in Sa and Sc* phases, together with 13C observations, including T1, both for PB and FLC032 under 1H decoupling. Split 7 lines observed in Sa indicate rapid 180 flip motions of the two phenyl rings and different contributions to the line spacings from 1H's in the two rings. Temperature dependences of their chemical shifts show the alignment of PB with the core of FLC032 in Sa. In Sc*, two sets of split lines with 7 and 9 components are observed. With decreasing temperature, the former 7 are down-field shifted and the latter 9 up-shifted. The former ones come from PB subjected to the tilting in Sc*, while the latter are due to PB excluded into the chain region of FLC032.

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We performed isobaric Monte Carlo (MC) simulation of systems of hard spherical discs. The shape of the spherical disc is determined by a sweep of sphere of diameter L on a disc of diameter D. It is an extension of spherocylinder the shape of which is provided by a sweep of sphere of diameter D on a line segment of length L. Results of the present MC simulations indicated that increase of pressure from disordered isotropic liquid induces isotropic structure which shows local column-like structure.

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We study isotropic(Iso)-nematic(N) phase transition in mixtures of hard rods of different lengths LA and LB in an external field by using the symmetry breaking potential method with the mean field approximation. We discuss effect of the external field on a triple point and phase co-existence regions. We find Iso+N co-exitence region is moved to shorter rod side on the phase diagram by the external field.

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Nematic phase transition with both uniaxial and biaxial order parameters is studied on basis of Maier-Saupe model in the two kind of external fields which are conjugated to the order parameters, respectively. A global phase diagram in fields versus temperature space for bulk is obtained in the mean field theory, which is similar to the phase diagram of the three-state Potts model in three dimension. The phase diagram in the uniaxial field which is a cross section of the global one is applied to the phase transition at the thin systems with homeotropic and planer anchoring walls.

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Nematic ordering of the system sandwiched by parallel walls is discussed using Maier-Saupe model which qualitatively explains the nematic-isotropic phase transitions. Obliquely aligned molecules on the walls are introduced and statistical mechanics theory is developed to elucidate how the ordering occurs depending on the oblique angle. In addition, the aligning effect due to walls is examined by comparison with nematic ordering in external fields.

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We propose a simulation method for liquid-liquid interface under constant surface tension and constant normal pressure.The method introduces an anisotropic factor in the cell dynamics which avoid artifacts such as continuous expansion or contraction of the cell lengths. This allows simulation of a full range of surface tensions including when the value is 0, i.e hydrostatic pressure.The method is applied to binary systems of soft spherocylinders with different lengths.

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The micro-segregation picture of a block copolymer was applied to a low molecular weight liquid crystal (LC) to clarify the similarities between them in respect of structured mesophase formation.Calamitic LC molecules were regarded as block compounds composed of a rigid anisometric core terminated by flexible chains.Then, the incompatibility parameter chi_{core-chain} and volume fraction f_{core} were considered analogous to chi_{AB} and f_A in A-B diblock copolymers.We found good correspondence in the chi versus f phase diagram between block copolymers and block LCs.

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We study numerically the interaction between particles in a liquid crystal mediated by its elastic distortions.We employ the Landau-de Gennes continuum theory in terms of a second-order tensor order parameter for the description of the orientational order of a liquid crystal. We use bispherical coordinates to describe the geometry of the system containing two spherical particles. When the two particles are accompanied by a hyperbolic hedgehog in a nematic liquid crystal, the particles feel a power-law long-range force until a short-range repulsion due to a defect between the particles becomes dominant. Just above the nematic--isotropic transition, a capillary bridge of a nematic phase can be formed, which results in a strong attractive force whose strength is almost independent of the inter-particle distance.

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Equilibrium swelling and phase behavior is investigated for the monodomain liquid crystalline gels in nematic or isotropic solvents. The gels exhibit a large volume change accompanying an appreciable anisotropic shape change at the nematic-isotropic transtion temperature of the gels. A theory is proposed to describe the swelling and phase behavior observed.

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We experimentally investigated the volume changes of V-shaped cross-linking liquid crystal elastomers with different concentration of cross-linking agents as a function of temperature.

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Over the last decade, liquid crystalline elastomers have been paid increasing attention as a novel class of liquid crystalline materials, because they give rise to new macroscopic features by combining the mechanical properties of polymer networks with the anisotropic structure of liquid crystalline phases. In particular, smectic C elastomers composed of chiral mesogens have recently attracted both industrial and scientific interests, because of their additional properties such as pyroelectricity, ferroelectricity and second harmonic generation due to the point group C2. In this paper, the layer structure of chiral smectic C (SmC*)elastomers and their structural change through successive phase transformations have been investigated by means of X-ray measurements. An analysis of the layer reflection peaks by curve fitting shows that layer tilt angle (qL) is considerably larger than molecular tilt angle (qM) in the SmC* phase, and that, in addition, the layer tilts even in the SmA phase. Here, we will report the experimental details, discuss the molecular and layer re-arrangements on the successive phase transformations.

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This paper presents the novel results on low voltage-driven electromechanical effects of swollen liquid crystal elastomers (LCEs). Thin film LCEs were embedded in a low molecular weight liquid crystal (LMWLC), 4-n-pentyl-4-cyanobiphenyl (5CB), and introduced between transparent indium tin oxide electrodes with 100 m separation. Absorbing 5CB into LCEs, shapes changes were obtained in these materials by application of a small voltage. That is, compared to unswollen LCEs, a dramatic ~200 times decrease of the critical voltages was found for electromechanical effect in swollen LCEs.

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