Further low-power and high-image-quality display devices have been highly required with the progress of information society, and new types of display devices instead of conventional LCDs is expected to be realized. In this study, a new type of display device using waveguided light is proposed; light intensity transmitted through a polymer waveguide cladded with a LC medium is controlled by applying a voltage to a LC clad. We show experimental results of the proposed device performance with the device simulation and demonstrate the potentialities of the device as future display devices.

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We prepared some BPIII materials doped with 3.4 wt% of a liquid crystal oligomer and investigated their phase transition behavior. A linear dimer in which phenylpyrimidine and cyanobiphenyl units are connected via an octamethylene spacer was found to raise the Iso-BPIII transition temperature by 26.6 K. A temperature range of BPIII was extended to more than 80 K by polymer-stabilization. The PS-BPIII exhibited fast response and hysteresis-free switching at room temperature.

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The bistable LCD with a mesh structure of polymer filament in the cell has been proposed. The Nn*-LC mixture (d/p=0.76) was used for this mode. Polymer filaments consisted of hydroxypropyl cellulose were spun by electro spinning method. One of the bistable states was a S90° with a vertical orientation as a dark state, the other one was an AS270° with a horizontal orientation as a bright state. The LC orientation with AS270° state was held by restraining force from the polymer filament surrounding that texture since LC directors oriented along a stretched direction of such a filament or fiber. The good memory characteristic was obtained by filament mesh structure.

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To realize active-matrix flexible liquid crystal displays (LCDs), high heat resistance and high dimensional stability are required for plastic substrates. We have developed the fabrication process of flexible LCDs based on the coat-debond formation method using ultrathin polyimide (PI) substrates. In this paper, we fabricated post spacers on the PI substrates by photolithography and investigated the influence of spacer pitch on the image quality of flexible LCDs. As a result, we clarified that we can suppress the degradation of image quality of flexible LCDs in both non-curved and curved states by using narrow pitch post spacers.

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A bistable LCD, switched between Symmetric (π-φ) twisted state and Anti-Symmetric (φ) opposite_twisted state, using negative nematic materials has been investigated. It has a possibility to realize a high contrast display due to obtaining a pure dark state under the vertical alignment at S(π-φ). However, to obtain the memory in a long time is difficult due to the specific bistable mechanism. We took notice of the application a concentric rubbing method to evaluate or observe the region of bistable transitions in our cells, that is, the angle of rubbing directions between the upper and lower substrates can be continuously varied in the LC cell.

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Recently, "in-cell" technology has been attracting people's attention for improving LCD performance, in which optical components such as retardation films and/or polarizers are fabricated inside glass substrates. For the technology, the use of UV-curable LC materials combined with a photo-alignment method are expected to bring LCDs into further improvement in the performance. In this study, we focus on fabricating "in-cell" gest-host-type polarizers, in which we use UV-curable LC materials dissolved with dichroic dyes. We report optical properties of the polarizers and also show the device performance of a VA cell having in-cell polarizers.

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Cholesteric liquid crystalline (CLC) phases have self-assembled helical structures. CLC droplets with tangentially aligning boundary condition show the omnidirectional selective reflection because helical axes are arranged in a radial fashion. Moreover, a close-packed array of the CLC droplets gives rise to colorful patterns due to photonic communication between each pair of adjacent CLC droplets. In this study, we numerically simulated the propagation of light reflected from the linearly-aligned array of CLC droplets using the finite-difference time-domain (FDTD) method. To confirm whether this method is appropriate for such curved photonic structure, we compared the simulation results with the experimental results and geometric optical calculation.

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With a recent increased interest in health and environmental issues, people have shifted their attention to the development of biosensors for the detection of illnesses as well as toxic substances. To develop these sensors, we focused on the idea of utilizing the unique property of selective reflection in cholesteric liquid crystals (CLCs). We measured the changes in selective reflection upon contact of volatile organic compounds (VOCs) gases with CLCs of various compositions. Thereafter, we understood that the degree and direction of change in color in CLCs differ amongst different compositions upon contact with the same VOC gas. Hence, we think that there is potential in the use of CLCs as a form of biosensor.

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We report electro-optic effects in a planarly aligned cholesteric liquid crystal with an in-plane electric field. At zero field, the sample under crossed polarization showed a dark state, while at field-on state showed a bright field. This results from the electric-field-induced birefringence with an optical axis along the electric field. Furthermore, the response time of the electro-optic switching was very short (〜10 μs).

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π-Electron liquid crystal (LC) is one of the candidates for use in soft optics and electronics, because the alignment of LC can be easily changed and controlled by external fields. Recently, anthraquinone and oligothiophne-doped LC systems are known to undergo photoinduced molecular reorientation upon photoirradiation in the fields of nonlinear optics. Although the reorientation behavior has been interpreted as a phenomenon based on interaction between the dye molecules and the electric field of light, the effect of the molecular structure on the photoinduced reorientation and details of the reorientation mechanism are not clear. In this study, the effect of molecular structures in coumarin dyes on photoresponsive behavior of LC system was explored.

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Axis-selective photoreaction, photoinduced orientation of liquid-crystalline copolymers with N-benzylideneaniline (NBA) and phenylaldehyde derivative side group are explored. Irradiating with linearly polarized ultraviolet (LPUV) light generates coordinated molecular reorientation of the NBA side groups based on the axis-selective trans-cis-trans photoisomerization. of the NBA groups, but the reorientation performance depend on the copolymerization ratio. Furthermore, thermally stimulated amplification of the photoinduced optical anisotropy occurs upon exposing films to LP 365 nm light and subsequently annealing in the liquid crystalline temperature range of the materials.

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Polymer/cholesteric liquid crystal nanocomposites and polymer stabilized blue phase liquid crystals enable polarization-independent phase modulation with fast response times below 1 ms. Even though both liquid crystalline phases can be observed in the same material by changing the temperature, comparison of the electro-optic properties has not been performed. Here, we compare the optical properties of polymer/liquid crystal composites fabricated in cholesteric phase and blue phase I. Polymerization in cholesteric phase is advantageous for wide-range tuning of the refractive index, while polymerization in the blue phase is advantageous where narrow-range tuning is required at low voltages, because there is no threshold.

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Many researchers have been studied cholesteric liquid crystals as a one-dimensional photonic crystal. However, there are not so many studies of ferroelectric liquid crystals as a photonic crystal owing to low refractive index contrast. In this study, we focus on the full pitch band of a ferroelectric liquid crystal whose bandwidth becomes wider at highly oblique incidence. By varying an angle of incidence and an electric field, we independently control the peak wavelength and the bandwidth of the full pitch band of a ferroelectric liquid crystal.

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Chiral liquid crystals, such as cholesteric liquid crystal or ferroelectric liquid crystal are expected to be a candidate of a tunable photonic crystal. These liquid crystals have a property of selective reflection. Ferroelectric liquid crystals have a full pitch band that does not exist in cholesteric liquid crystals. The bandwidth of the full pitch band becomes wider at highly oblique incidence. In this study, we calculate deformations in a helical structure of a ferroelectric liquid crystal by applying voltage using continuum theory. Furthermore, we also calculate transmission spectra of the full pitch band of the ferroelectric liquid crystal with the helix deformation at oblique incidence.

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The photorefractive property of photoconductive ferroelectric liquid crystalline blends was measured. The mixtures composed of the photoconductor and chiral dopants and liquid crystals exhibit large gain coefficients in two beam coupling experiment. The influence of the viscosity reducing agent on the photorefractive effect of ferroelectric liquid crystals blends was investigated.

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The photorefractive property of the photoconductive ferroelectric liquid crystalline mixtures was investigated. The mixtures composed of the photoconductive chiral dopants, liquid crystals and electron acceptor exhibit large gain coefficients in two beam coupling experiment. To clarify the influence of the concentration of the chiral dopant on the photorefractive properties, photoconductive chiral dopant blended with the chiral and non-chiral compounds were prepared. The photorefractive properties of these samples were examined by two beam coupling experiment.

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We introduced n-alkane between layers in a chiral tilted smectic liquid crystal, called it "a swollen chiral tilted smectic liquid crystal", and investigated the swollen effect by n-alkane on the excluded volume interaction between layers by dynamic light scattering measurement under reflection scattering geometry and polarization reversal current measurement. As a result, it was found that the twist elastic constant related to excluded volume interaction becomes lower in the swollen chiral tilted smectic liquid crystal. This result suggests that n-alkane prevents the direct collisions among liquid crystal molecules between layers, and excluded volume interaction between layers is weakened by the swollen effect.

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We investigate the thermal response of the cholesteric liquid crystal elastomer films with the helical axis normal (N-ChE) and parallel (P-ChE) to the film surface. In the N-ChE films, as the temperature increases, the characteristic wavelength for selective reflection becomes longer and the elastomers become thicker along the helical axis. The helical pitch varies with the film thickness in affine manner in response to temperature change. Under the crossed nicols condition, the P-ChE films exhibit a stripe pattern with a pitch length of about 180μm at 40℃. As the temperature changes, the P-ChE films exhibit periodic surface modulation as a result of a change in local order of the liquid crystals.

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Binary mixtures composed of polar and non-polar LC molecules often form highly-ordered smectic phases. We recently found that when several percent of dialkyl-terminated azobenzene is added to 8CB, the mixture considerably loses the fluidity without showing any phase transitions. To understand the origin of this phenomenon, we tried to examine the molecular diffusional in the mixture by means of gas permeation experiment.

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A binary system between 8BBAA, which is a Schiff-base mesogen exhibiting SmB and SmA phases, and n-decane was investigated. Its phase diagram was determined by using DSC. Temperature dependences of lattice parameters (a, b, and c) of SmB phase were determined by WAXD measurements. The layer spacing along the c axis (the staking direction of layers) lineally increases with decreasing temperature, while interlayer lattice parameters (a and b) hardly change against temperature. These results suggest that SmB phase of 8BBAA has two sublayers consisting of rigid core and alkyl chain moieties, and n-decane molecules are hold in the alkyl chain sublayer.

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The anisotropic interaction between LC droplets dispersed in isotropic phases is examined under an AC electric field. We measured the forces between nematic droplets and between cholesteric droplets, respectively, and found that there is no significant differences. The simple linear analysis assuming the averaged dielectricity inside the droplets does not fit the observation, which may suggest the complicated polarization mechanism in the cholesteric droplets with helix.

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By means of MD simulation, we investigated the cross correlation between c-director rotation and gas permeation through SmC* monolayers with applying a rotational electric field. Our simulation results agree with Onsager relation, which predicts that both the c-director rotation and the gas permeation should linearly depend on the rotational E-field and pressure gradient of the gas.

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Alignment control of functional anisotropic molecules is effective for fabricating specialty films. Recently we have developed a new method to align molecules with unpolarized UV light: fabrication of unidirectionally aligned polymer films is achieved when anisotropic monomers are photopolymerized through a moving photomask. In this study, we used two monomers with different lengths of alkyl spacer in order to examine the effect of molecular structure. Both mesogens were unidirectionally aligned by photopolymerization; however, polarized UV-VIS spectra revealed that alignment direction became different depending on the alkyl spacer length.

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We designed an amphiphilic compound 1 composed of a semiperfluorinated alkyl chain and a cyanobiphenyl mesogenic moiety. The compound showed a phase sequence of Iso-SmA-SmC. We prepared a ternary mixture of compound 1 (20 mol%), 4-butyloxy-4'-cyanobiphenyl (40 mol%), and 5-butyloxy-2-(4-octyloxyphenyl)pyrimidine (40 mol%), and investigated the phase transition behavior using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction (XRD). On cooling the mixture, a smectic-nematic-smectic phase transition was observed. We discuss how intermolecular interactions cause such an unusual phase transition.

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Photo-induced liquid and solid phase transition at room temperature of the sugars substituted with azobenzene, and their application to photoresposive adhesives have been reported. In this study, we synthesize the slide-ring materials which exhibit photo-induced phase transition from solid not to liquid but to gel in order to produce the easy-to-peel off adhesives.

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Studies of self-assembled system of partially fluorinated compounds; 2-alkoxy-6-[4-(2-perfluorohexyl)-ethylsulfanylphenyl]naphthalene are described. They produce lamellar organization as liquid crystals. On the other hand, they produced fibrous self-assembly (i.e. act as gelator) in organic solvents at low concentration. Structure of self-assembly was decided by whether an organic solvent present or not.

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1,2-bis(4'-n-alkoxybenzoyl)hydrazines (BABH-n, n is the number of carbon atoms in the alkyl chain) are typical liquid crystalline compounds exhibiting bicontinuous cubic (Cub_<bi>) phases. The central core part of the BABH-n molecule is composed of hydrazine group and π-conjugated system. We synthesized new eight compounds. In those compounds, the π-conjugated system is extended from benzene to biphenyl, stilbene, phenylacetylenephenyl, and naphthyl rings while the hydrazine group is preserved. We discuss effects of the chemical structure of the core part on the molecular aggregation state in the Cub_<bi> phases.

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In the organic semiconductor, the orientation of the molecules is important for the mobility enhancement. In order to improve the orientation, liquid crystalline semiconductors attract a great deal of considerable attention. In this study, we focus on the low-dimensional liquid crystal phase in which the alignment can be easily controlled. By using a photocurable mesogenic monomers, a uniform alignment structure is obtained, and the organic semiconductor with high mobility would be obtained by solidification of the alignment. In this report, we investigate the mobility enhancement effect originated in the uniformity improvement.

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Liquid-crystalline (LC) semiconductors have a good carrier transport property and good film forming behavior. For further functionalization of LC semiconductors, it is important to control their carrier density. For this purpose, it is required that electron-donating groups stabilize the radical cations of the LC molecules. In oligo (ethylenedioxythiophene) (olig-EDOT) moieties, stable cation radicals are produced because of the presence of electron-donating ethylenedioxy groups. We have already reported the improvement of the solubility and the stabilization of LC phase by modification with the cyclotetrasiloxane unit which can polymerize and insolubilize the LC thin films. In this study, we have synthesized and characterized oligo (EDOT) derivatives having cyclotetrasiloxane rings at the terminal of the side-chains.

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It is necessary to develop a flexible organic transistor with high mobility to realize a flexible display with high image quality. Thus far, we have clarified that it is possible to control the crystalline orientation of the organic semiconductor by growing soluble high-mobility organic semiconductor single crystals in the aligned liquid crystal solvents. In this study, we considered the single crystal molecular arrangement by evaluating the refractive index anisotropy for visible light and the absorption anisotropy for polarized ultraviolet light in the single crystal films formed by the liquid crystal solvent method.

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With characteristics of high specific surface area and nano size effects, nanofiber obtained from electrospinning method has attracted considerable interests in many fields such as medical and energy. With small pore size, we expected that nanofibers have interaction with nematic liquid crystal molecules. In our research, nanofiber/liquid crystal (LC) composites are prepared by inserting aligned nanofiber into thick LC layer. We confirm that composite devices have faster response time than that of pure LC device and the response time of composite devices is proportional to the concentration of fiber.

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Solution-processed organic devices have advantage in terms of low cost and large area fabrication. However, it is difficult to make multilayer structures by the solution processes because solvent dissolves the first layer when making the second layer. In this study, we investigate to make a double layered structure by one-step spin-coating technique from a liquid crystalline organic semiconductor/polymer mixture solution, and characterized the double layered structure by water contact angle measurements and the performance of organic field effect transistors of this structure. The results indicate that a thin layer of a liquid crystalline organic semiconductor was formed on a polymer layer, and it gives FET performance as good as that of single layered FETs.

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