[in Japanese]

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A kinetic model of the mechanism for photodecomposition alignment of liquid crystal (LC) by polyimide exposed to linearly polarized deep UV (LPDUV) light is described. A three-dimensional model is applied to anisotropic bulk characteristics, such as retardation of the LPDUV-exposed polyimide, as a function of the UV dosage, and a two-dimensional model is applied to anisotropic surface characteristics, such as the anchoring energy of the interface between the liquid crystal and polyimide. The experimental data are well fitted by these models. The maximum values of the order parameter of the LC and anchoring energy are obtained at the same dosage of LPDUV, and show that the maximum surface anisotropy is obtained with polyimide exposed to 1 J/cm^2 LPDUV.

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We have measured the polarized infrared (IR) absorption spectra of poly[4,4'-oxydiphenylen-l,2,3,4- cyclobutanetetracarboxyimide] (CBDA-ODA) films irradiated with linearly polarized ultraviolet light (LPUVL) of wavelength 〜 250 nm. The measurement was carried out for a very thin film (10 nm thick) as a function of the LPUVL exposure. The dichroic difference, A_⊥- A_//, of the phenyl C-C stretching vibration of CBDA-ODA, which is polarized along the polyimide chain, has a maximum around 3 J/cm^2. Here A_//and A_⊥ are the absorbance for the IR light polarized parallel and perpendicular to the polarization direction of LPUVL, respectively. The dichroic difference per unit film thickness at 3 J/cm^2 was greater than that of a rubbed CBDA-ODA film with the same film thickness. Although the average IR absorbance, (A_⊥+ A_//)/2, decreases monotonically over the entire measurement range of LPUVL exposure, A_⊥ increases up to 1 J/cm^2. This result shows that the number of polyimide molecules oriented perpendicular to the polarization direction of LPUVL increases. We conclude that the photo-induced orientation contributes to the large surface anisotropy of LPUVL-exposed CBDA-ODA films in addition to the anisotropic photo-induced decomposition.

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Alignment of liquid crystal induced by rubbing is not only interesting in physical chemistry but also important as a fundamental technology of production of liquid crystal devices. However, the universal definition of the rubbing strength has not yet been established, and its relation to the anchoring strength has not been understood completely. In this paper, in order to clarify the detailed mechanism of rubbing on the polymer surface and to determine the rubbing strength quantitatively, we have proposed the rubbing line density S and have investigated the relation between S and the anchoring strength from microscopic view. As the result, it was confirmed that there is a good correlation between them and we made it possible to deal with the pressure depth quantitatively by using S.

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Molecular dynamics (MD) simulations of 8CB molecules on amorphous SiO_2 substrate have been conducted and their alignment properties investigated. The force fields we used were the DREIDING for 8CB molecules and Kawamura's for inorganic substrate. Simulations showed that a CN group is attached to the hydrophilic SiO₂ substrate. As for the hydrophobic SiO₂, such a tendency of the CN group is not obtained. The first layer of the evaporated multilayers exhibited a different tilt angle from that of the monolayer.

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Changes of molecular alignment due to the electric field are studied by constant temperature molecular dynamics simulation of the Gay-Berne system sandwiched by walls, where every particle has a permanent dipole along the molecular long axis. The homeotropically anchored smectic phase (SmA2) driven by electric field at homogeneous anchoring wall is observed under the condition where the homogeneous anchored one (SmA1) is stable without the field, while SmA1 is induced at homeotropic anchoring wall by the transverse electric field. The order of smectic A is destabilised by the dipole-dipole interaction and eventually a sort of order of smectic C phase appears in the strong electric field region.

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We found that the alignment of PBLG liquid crystals on a glass substrate depends on the relative permittivity of the solvent as well as on the molecular weight of PBLG: In a cell having the thickness of the order of 0.1 mm, a homeotropic alignment occurs when the relative permittivity of the solvent is rather high and, at the same time, the molecular weight is lower than some critical value. Otherwise, planar alignment prevails. It will be shown that this behavior can successfully be explained as due to the competition between the repulsive electrostatic interaction of polar polypeptide molecule with the glass substrate (the image force) along with the repulsive van der Waals interaction, and the excluded volume interaction of PBLG molecule with the substrate which always favors the planar alignment.

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Statistical mechanical studies on the surface tension of the nemafic liquid crystals contacting with various surfaces are reviewed. Assuming the liquid crysyml is an assembly of cylindrical rods interacting via anisotropic attractive force as well as the hard-core repulsion, the general features and special characteristics of the interfacial propeffles, such as surface orientations of molecules, the anchoring energies, and so on, are interpreted comprehensively.

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The influence of surface anchoring to the molecular reorientation in a smectic thin film transferred onto the substrate from the freely suspended film has been studied using ellipsometry method. The threshold electric field of electro-optical effect has been measured as a function of the scan rate of the triangular electric field and film thickness. The threshold field decreases with decreasing the scan rate of applied field, and it is essentially zero in the freely suspended film. On the other hand, it has existed even at extremely slow scan rate in the transferred film. The film thickness dependence of the threshold field, it has been found the threshold field in a freely suspended film is independent of the thickness, although in the transferred film, the threshold field increases with decreasing the film thickness. In the case of the transferred films, we found that the influence from the substrate is about 200 smectic layers.

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Deuterium nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the field-induced director dynamics in a nematic liquid crystal, 4-pentyl-d_2-4'-cyanobiphenyl (5CB-d_2) deuteriated in the α-position of the pentyl chain, confined between two glass plates. The NMR spectra have been measured as a function of time after turning an electric field on and off. It is demonstrated that the field-induced director dynamics in the nematic liquid crystal cells can be successfully time-resolved. In addition, it is found that the doublet NMR spectra are changed into powder-like spectra during the turn-on and turn-off processes. It is shown that values for the rotational viscosity and the diamagnetic anisotropy of 5CB-d_2 can be determined from the time-resolved NMR spectra by assuming uniform alignment of the director.

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Electro-optical responses in hybrid TN (HTN) cells constructed with different types of substrates were investigated. The substrate surfaces were coated with PI or PVA for parallel orientation, and silane coupling agents(AY43) for perpendicular orientation. The cells were filled with nematic liquid crystalline mixture including a chiral dopant to exhibit hybrid alignment with a twisted structure. The electro-optical responses depend upon the surface treatment for parallel orientation and the concentration of the chiral dopant.

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Flexo-electrooptic effects of CCH liquid crystals was investigated by interdigital electrode method, and analyzed by Jones Matrix method. We report these results and especially dependence of applied field, frequency and temperature of molecular dynamics.

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Dielectric relaxation ε‖ of liquid crystal materials was investigated from the view point of the physical properties. The physical properties were calculated by AM1 method and the order parameter S was determined by measurement of the temperature dependence of the refractive indexes. It was found by the investigation that the molecular interaction does not induce a significant difference on the relaxation frequency among the materials but the inertia moment causes the difference of the relaxation frequency.

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The phase transition behaviors of dimer (CCH-2)-monomer (CCH-3,4,5,7) mixtures in CCH liquid crystal series are investigated. Large deviations from the theoretical expectation are found at the upper and lower sides of the nematic range, and also found a special critical ratios of 75 % CCH-2 and 25 % CCH-7 mixture which is only nematic range and has no smectic phase.

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We have investigated the photo polymerization induced phase separation process in liquid crystal/polymer composite films. The differences of morphology depending on the type of diacrylate are observed with SEM microscopy. Obviously, the shape of the polymer phase is sensitive to the molecular structure in diacrylets. In the confocal laser microscopy, it is turned out that the behavior on the nematic domains in the kinetics of phase separation can be distinguished by the type of diacrylate. In the HDDA and the C2000, the faster nuclear growth rate and the frequent coalescence of neighboring nematic domains accelerate the growth of LC domains. In the AE-67, the nematic domains at 1 μm continue to gradually grow with a slight coalescence. It is presumed that the kinetics in the phase separation process play a important role to determine the morphology. This work was performed under the management in ASET project supported by NEDO.

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Liquid crystal / polymer composite films have a potential to use direct view LC displays. It is necessary to improve reflectance properties to use these films for direct view LCDS. We investigate influence of various properties on reflectance. It is proved that not only using high △ n LCs but also improving polymer network morphology were needed to obtained high reflectance films.

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Methods to reduce the Hysteresis in Polymer Dispersed Liquid Crystals (PDLC) Panels have been investigated. We found the Hysteresis was reduced by increasing UV strength. Especially the strong UV irradiation, which is more than 100mW/cm^2 was effective to reatizc low Hysteresis. Polymerization speed(C10-90) also increased with increasing UV strength. These results suggest the structure of Liquid Crystals Matrix is important to reduce Hysteresis.

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Rheological properties in the lyotropic nematic phase of poly(nonylisocyanate)/l,4-dioxane binary system were investigated under an application of a.c. electric field p to 3 MVm using a home-made viscometer, which can be used between room temperature and 363 K under the electric field of 0 〜 3.5 MVm^<-1>. The temperature of the sample was accurately controlled within ± 0.016 K. A precision and an accuracy of the apparatus are within 1% and 5 %.

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An atomistic simulation method is proposed for the evaluation of rotational viscosity of liquid crystals. The method is based on a nonequilibrium molecular dynamics in which the director of a liquid-crystalline structure is forced to rotate by an artificial force termed aligning force. The evaluation procedure is outlined by using PCH-5 as an example.

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We have calculated tile rotational viscosity (γ_1) of nematic liquid crystal materials using an atomistic-level molecular dynamics simulation. Several PCH-based LCs with different side chain length and different polar endgroup are selected, and their γ_1 values have been calculated and compared with experimental values, either by magnetic field rotation method or transient current method. A very good correlation is found between them, in the absolute value as welt as relative relationship.

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Influence of the anisotropy in shape or intermolecular force on phase formation has been examined by molecular dynamics simulations using a chain model molecule with L/D=6. Calculations for the system composed of diblock molecules are also carried out at hydrostatic pressure 10.0.

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The photoconductive properties of dihydroxo[5, 10, 15, 20-tetrakis(4-n-dodecylphenyl)porphyrinato]silicon(IV) (abbreviated as C_<12>TPPSi(OH)_2) were investigated for an ITO sandwich cell (ITO/C_<12>TPPSi(OH)_2/ITO) both in a solid (25 ℃) and a lamellar columnar mesophase (100 ℃) of C_<12>TPPSi(OH)_2. This complex shows only one mesophase with a wide temperature range between 84 and 211 ℃. It was observed negative electrode illumination gives larger photocurrent than positive one. This photocurrent rectification behaviour is quite opposite to that of the corresponding porphyrin free base (C_<15>TPPH_2) and unusual for symmetrical ITO cells of porphyrins. We also report action spectra of photocurrent for the ITO/C_<12>TPPSi(OH)_2/ITO cell as a function of wavelength.

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The phase transition behaviour of an octaoctadecylthiophthalocyanine and its Cu and V=O complexes was studied in terms of melting behaviour and intracolumnar structutre. All these compounds show hexagonal disordered columnar mesophase. However, the metal-free and Cu complex exhibit complicated melting behaviour strongly depending on cooling process from the mesophase, whilst the V=O complex does not. XRD studies on these compounds indicated the difference of intracolumnar structure and/or molecular dynamical situation in a column between V=O complex and the other. These results imply that the central part of disc-shaped mesogen certainly influences on molecular stacking manner in columns, which could lead to remarkable difference in charge migration phenomena.

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Mesogenic phthalocyanines are particularly attractive materials for studies of the photonic and electronic properties in mesophase. In this work, the dc photo- and dark-conductivity of 2,3,9,10,16,17,23,24-octa(octadeclythio)phthalocyanine (C_<18>SPcH_2) has been studied with the phase transition behavior. The temperature dependence of the dark- and photo-currents (for positive and negative electrode illuminations) has been measured for a symmetrical cell (ITO/C_<18>SPcH_2/ITO) in the temperature range from 25℃ (crystal) to 245℃ (isotropic liquid). The steady state dark- and photocurrents increase with the first phase transition from a room temperature crystal on heating. At the phase transition to hexagonal columnar mesophase, dark- and photo-currents were once drastically decreased but gradually increased until the isotropic phase.

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Molecular architecture through self-organization or self-assembly processes of organic compounds has attracted much attention for development of new functional materials. Folic acid forms mesophases in alkaline aqueous solution by tetramedc self-organization through hydrogen bonding. For the development of new supramolecular discotic liquid-crystalline materials, we synthesized folic acid derivatives containing lipophilic long alkyl chains. These compounds exhibited both thermotropic and lyotropic liquid-crystalline phases in wide range of temperatures. Furthermore, complexes of the folic acid derivatives with NaCF_3SO_3 formed thermotropic hexagonal columnar phases, which shows that the self-organized structures were controlled by the addition of alkaline metal salts.

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Liquid crystalline Binary systems consisting of amphiphilic compounds and water-soluble polymer were prepared. Their thermal and liquid crystalline properties were estimated. The amphiphilic compounds easily mixed with the water-soluble polymer such as poly(vinyl alcohol) (PVA). The thermotropic binary systems consisting of PVA and the amphiphilic compound with a butyl terminal group showed a columnar mesophase. The thermotropic binary systems having PVA and the amphiphilie compound with a nitro terminal group exhibited a smectie A mesophase.

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Biphenyl esters are typical mesogens with various mesophases according to substiments. Relationships between molecular structures and molecular packings are essential to understand the mesophase behavior. We have determined crystal structures for biphenyl esters, X-C_6H_4-C_6H_4-COO-C_6H_4-Y, where X, Y = C_8H_<17>O and/or C_8H_<17> (series 8-8) and X, Y = C_8H_<17>O, C_8H_<17>and/or CH_3O, CH_3 (series 8-1). Almost all compounds have one-dimensional chains of close arrangements of ester linkages. The arrangements are classified as follows. Pattern I is close arrangements of ester C=O・・・C=O. Pattern II is C=O・・・O-C=O, which is divided into two subgroups according to the O・・・O distances, shorter (3.28Å〜3.37Å ) (II-(1)) and longer (3.83Å 4.17Å) (I-(2)). The exception is the biphenyl ester with X = methyl and Y = octyl, which shows no special interaction between ester linkages. The packing modes of ester linkages are closely related to the melting points.

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Crystal structures of 4-cyano-4'-alkylbiphenyls (nCB) and 4-cyano-4'-alkoxylbiphenyls (nOCB) show a different tendency: a remarkable even-odd effect for the former and dominant CN-CN interaction for the latter. In order to elucidate the difference between the two series, FT-IR spectra have been measured. CN stretching vibration frequencies for dilute solutions of CCl_4 (0.01 mol/l) are 0.5 cm^<-1> higher for nCB than for nOCB, giving a direct evidence of the different intramolecular interaction for isolated moleculeS. In mesophases, the frequencies on average are 1.0 cm^<-1> higher for nCB than for nOCB. Thus, the difference in mesophases (1.0 cm^<-1>) is larger than that for isolated molecules (0.5 cm^<-1>). Similar results were obtained for 4-cyanophenyl 4-alkoxybenzoates and 4-alkoxyphenyl 4-cyanobenzoates, showing the difference of intra- and intermolecular interactions due to the reversed directions of ester linkages with respect to the CN groups.

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We synthesized new series of octakis(4-(N-(4-alkoxyphenyl)iminomethyl)phenoxy)cyclotetra phosphazene [PN(OC_6H_4CH=NC_6H_4OC_nH_<2n+1>)_2]_4 (OCTP-n), where n is a carbon number of end alkoxy groups. Their liquid crystalline phase transition and mesogenicity were studied by DSC measurements and polarizing microscope observations. A series of OCTP showed an enantiotropic smectic A phase for n ≦ 7.

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Hekisakis(3,4-didodecyloxyphenoxy)cyclotriphosphazene(PN(OC_6H_2(OC_<12>H_<25>)_3)_2)_3 and hekiakis(3,4,5-tridodecyloxy)cyclotriphosphazene(PN(OC_6H_3(OC_<12>H_<25>)_2)_2)_3were synthesized and their phase transition and mesogenicity were studied using DSC measurements and polarizing microscopy. An enantiotropic discotic phase was observed for the former and a monotropic discotic phase was observed for the latter.

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A series of 2-(4-alkoxyphenyl)-5-(4-methyl)pyridines (CH_3C_5H_3 NC_6H_4O-C_nH_<2n+1>) (2R-Pn, n= 1〜9) were synthesized and their mesogenicity was studied. In the 2R-Pn homologues, no mesomorphic phase appeared in n= 1〜5 and only a monotropic nematic phase was observed in n= 6〜9. The mesomophic potential is relatively weaker for the 2R-Pn than that in 3R-Pn and 4R-Pn. This caused due to the lack of phenyl ring between the pyridine ring and the methyl group.

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All-optical control of selective reflection of cholesteric liquid crystals (Ch-LCs) containing an azobenzene derivative as a photoresponsive chiral dopant was investigated. The photoresponsive Ch-LCs was comfirmed first to reflect selectively visible light in narrow wavelength range at room temperature. Photoisomerization of the azobenzene occurred in the Ch-LC phase upon irradiation with ultraviolet or visible light. The observed effect was revealed to be due to change in the selective reflection. Color change between two different reflective lights was reversibly controlled by alternating irradiation of ultraviolet and visible lights. The photoresponsiveness of the Ch-LCs depended on the chirality of an azobenzene molecule.

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Three chiral azobenzene compounds were prepared. A cholesteric phase was induced by mixing the chiral azobenzene compounds in a host nematic LC. A twising power of the three chiral azobenzene compounds was depended on the distance between azobenzene moiety and chiral moiety. The twisting power of the chiral azobenzene compounds was decreased by UV irradiation to cause trans to cis photoisomerization of the azobenzene compounds. Next, a compesated nematic phase was induced by mixing of a chiral dopant and a chiral azobenzene compound in the host nematic LC. The transmittance of the compesated nematic LC was drecreased by the UV irradiation, and restored by Vis irradiation. The reversible change in the transmittance can be interpreted in terms of the photochemical phase transition between the compesated nematic and the cholesteric phases.

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Novel photo-induced layer alignment control has been proposed in an azo-dye doped ferroelectric liquid crystal with N^*-C^* phase transition. This layer alignment control is based on the N^*-C^* phase transition induced by the photoisomerization of azo-dye. Novel electric field-induced layer re-arrangement has also been observed in this system.

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Temperature dependence of order parameter in fluorinated liquid crystals has been investigated. The molecular parameters, i.e., polarizability and its anisotropy, have been calculated using the ab-initio method. In addition, the refractive index anisotropy was measured using wedge-shaped liquid crystal cell.

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We prepared a chiral smectic C liquid crystalline polymer film (SmC^* film), which had a fixed and uniformly-aligned helical smectic structure. The SmC^* film showed the property of diffraction grating. The diffraction angle of the film could be easily controlled by changing the optical purity of the chiral unit in the polymer. The film was applied to reflective LCDs for improvement of the brightness.

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New driving methods for a liquid crystal microlens with divided electrode structure were proposed for the improvement of transient behaviors. With this structure, a field parallel to the substrates could be exerted, and in the presence of which, when the external driving voltage was switched off, the reorientation of director in the lens region became much faster, resulting in a decay time decreasing.

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A novel nematic liquid crystal (LC) cell that is stacked parallel to the millimeter wave propagation direction is proposed for an application to the millimeter wave devices by using the relatively large birefringence of liquid crystal materials in the millimeter wavelength region. It is expected that the stacked structure LC cell has large variation for long path length to the wavelength. Then the LC cell is fabricated adopting the way normal LC cells are piled up, and the transmission properties of the 50Hz millimeter wave are investigated by applying a voltage to the liquid crystal.

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We investigated of photothermal effects in guest-host liquid crystals (GHLCs) by use of the heat conduction analysis. Photo-thermal effects were occurred by heat that generated by irradiating the GHLCs with a laser beam. The phase of the laser beam was modulated by the photothermal effects and the laser beam was defocused due to the phase modulation. Refractiveindex change(δn) due to the photothermal effects was estimated from the Kirchhoffs diffraction analysis for beam profile and heat conduction analysis.

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Limiting factors on the speed in photorefractive polymer dissolved low-molar-mass liquid crystal composite (PDLCC) were investigated. In order to understand what might be the limiting factor, we considered both the generation of the space charge field and the reorientation speed of the liquid crystal molecules. High- performance photorefractive PDLCC were presented that exhibit the fastest response time of 15 ms, while maintaining large gain coefficient of 270 cm^<-1> and the low operating voltage of 0.18 V/μm required.

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The photorefractive effect of low-molecular-weight ferroelectric liquid crystals (FLCs) doped with photoconductive compounds was investigated using two-beam coupling experiments. An asymmetric energy exchange was observed in the surface-stabilized state of the FLCs which do not possess strong electron withdrawing substituent. The effects of temperature, applied electric field and the magnitude of spontaneous polarization were investigated.

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Geometries of several liquid crystalline compounds in solution at room temperature are proposed by comparison of experimental UV/vis absorption spectra with calculated ones. in the case of biphenyl compounds calculated in this study, the UV/vis absorption spectra are very sensitive to changes in the torsion angle between aromatic rings, and this torsion angle is remarkably affected by the nature of the substituent at the para-position. It was found that calculated polarizabilities using geometries which could reproduce experimental UV/vis absorption spectra have a good qualitative relation with clearing points observed.

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To study the effect of the alkyl chain on the liquid crystalline phase of nCB (4-n-alkyl-4-cyanobiphenyl) by molecular dynamics (MD) simulations, we have determined a coarse grained potential for nCB based on the united atom potential by the OPLS force field. An nCB molecule was divided into a rigid part (4-methyl-4'-cyanobiphenyl moiety; CB), and a flexible part represented by a chain of united atoms (UA's). In order to approximate the CB part as an ellipsoid, the OPLS potential between the CB-CB (or CB-UA) pair was averaged over the rotation of CB around the axis of the ellipsoid. The UA-UA potential was assumed to be the same as the original OPLS potential. The resulting potential surface was fitted into the Gay-Berne (GB) potential between two ellipsoids (or between an ellipsoid and a sphere). The resulting potential was validated by MD simulations for nCB.

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The ordering property in the systems composed of a linear or bent molecule with five successive atoms has been studied by Monte Carlo simulation using the method of Vacatello and Iovino based on the Flory-Ronca-Irvine mean field theory. The value of the N-I transition temperature has been decreased with increasing the bent angle. No correlation has been observed between the bent angle and the angle distribution function in the nematic phase.

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Polyimide films irradiated with linearly polarized UV light can align liquid crystals(LC) perpendicularly to its polarization direction. In this paper, we have adopted near edge X-ray absorption fine structure(NEXAFS) spectroscopy with high surface sensitivity to study their LC alignment mechanisms. Observed dichroic ratio on the O K-edge π^* peak, originated from a C=O bond, clearly showed a good correlation with LC alignment capability.

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Photo-induced in-plane alignments of the nematic liquid crystal (LC) molecule, 5CB, have been investigated in the cell with alternate layer-by-layer films of polyelectrolyte and low-molecular weight dyes on the gold electrodes using the attenuated total reflection (ATR) measurement method. Direct red 80 (DR80), azo dye, was employed as an anion; poly(diallyldimethylammonium chloride) (PDADMAC) was used as a polycation. The surface plasmon polaritoh (SPP) was observed in the ATR curves of the LC cells. The properties were sensitively changed by re-orientations of the LC molecules by means of the irradiation of the linearly polarized visible light to the LC cell. In-plane alignments of the LC molecules adjacent to the aligning layer were evaluated by fitting the theoretical ATR curves to the experimental ones.

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After filling the Liquid Crystal into the Liquid Crystal Display(LCD), the cell gap may be changed by the capillary attraction. That's why the way to measure the actual cell gap has been eagerly required. Nowadays, an optical measurement technique such as ellipsometry was applied to investigate the characteristics of LCD. We demonstrate a new application to evaluate the actual cell gap by using ellipsometry. By measuring the ellipsometric parameters Δ and φ, and fitting numerical calculation based on the 4 × 4 matrix method, it, is found that the actual cell gap can be evaluate quantitatively.

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