To improve reliabilities of liquid crystal panels, we have performed photo-current measurements for our test cells injected various LC single compounds and mixtures. The correlation between the obtained photo-current parameters and typical properties of liquid crystals are discussed on the viewpoint of physical chemistry.

View full abstract

Zwitterions have attracted increasing attention as a new class of organic salts. They exhibit fascinating properties owing to their unique molecular structures, in which their cation and anion are covalently tethered. Recently, we have reported that the equimolar addition of bis(trifluoromethanesulfonyl)imide (HTf_2N) into imidazolium based zwitterions leads to the development of novel liquid media transporting proton selectively. For further functionalization of these zwitterions/HTf_2N systems, we have focused on the organization of zwitterions/HTf_2N mixture on a gyroid minimal surface in bicontinuous cubic liquid-crystalline nanostructures. In the present study, we succeeded in developing new zwitterions/HTf_2N systems forming bicontinuous cubic phases and examined their potential applications to proton conductive materials.

View full abstract

Ionic liquids 1 possessing imidazolium and pyridine moieties were synthesized. These two moieties could act as an ionic core and a hydrogen bonding acceptor, respectively. Carboxylic acids 2-7 were used as hydrogen bonding donors. The complexes with these carboxylic acids showed a various liquid crystalline phase behaviors. Characterizations of the phases were investigated with polarizing optical microscopy (POM) and powder X-ray diffraction.

View full abstract

Supramolecularly assembled discotic liquid crystals were prepared from isophtahlic acid derivatives substituted with 3,4,5-tridodecyloxystyryl group via intermolecular hydrogen bonding between carboxys. The compounds exhibited columnar liquid crystal phases. Structural characterization of superstructures was performed by polarized light optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) experiments.

View full abstract

Novel zwitterionic liquid crystalline compounds possessing imidazolium or ammonium as a cationic part and carboxylate as a counter ion were synthesized. Their phase transition behaviors and also the effect of the addition of lithium salts was examined. Their liquid crystalline behaviors and superstructures were investigated by polarized optical microscopy (POM) and X-ray diffraction (XRD). Hexagonal columnar structure was observed as the mesophases for both with and without the addition of lithium salts.

View full abstract

We synthesized novel tartaric acid derivatives possessing two rod-like units in twisted parallel. We investigated their helical twisting powers (HTP). Nematic liquid crystals doped with the dopants indicated high HTPs, and exhibited stable blue phases. Their liquid-crystallinities were investigated by polarized optical microscopy (POM).

View full abstract

In order to develop columnar discotic liquid-crystalline compounds with high charge transport ability, a pyrene derivative having a thiophene moiety in the side chains was synthesized and the physical and thermal properties were studied by POM, DSC, and XRD measurements. It was shown that an ordered hexagonal columnar (Col_<ho>) phase appears in the temperature range of more than 130 degrees showing the liquid crystalline phase is stable. The hole mobility determined by the time-of-flight (TOF) method was 4.8×10^<-3>cm^2V^<-1>s^<-1> in the Col_<ho> phase at 140℃.

View full abstract

Alkylated benzothieno[3,2-b][1]benzothiophenes (Cn-BTBT) have been known as a high-mobility liquid crystalline organic semiconductor. The side-chain of liquid crystalline semiconductors enormously affects to their characteristics such as a crystallinity and charge-transport properties. In this research, we measured the charge-transport properties of C₈-BTBT which was oriented by using photo-aligned self-assembled monolayers, and newly synthesized the benzothieno[3,2-b][1] benzothiophene derivatives containing carbonyl group in the alkyl side-chain.

View full abstract

We have prepared the poly(styrenesulfonate)s with various metal and quaternary ammonium ions as a counter ion. In the copolymers with a suitable compositional ratio, which show both liquid-crystalline and water-soluble properties, they possessed a lower critical solution temperature (LCST) in water. It was found that the polysulfonates act as a thermo-responsive polymer in spite of the polyelectrolytes. Furthermore, we have investigated the effect of the compositional ratio in the copolymers, the concentration of polymer solution, and the counter ions on the thermo-responsive behavior of the poly(styrenesulfonate)s.

View full abstract

Liquid-crystalline anthracene derivatives having mesogenic moieties consisting of the polar tetra(ethylene oxide) moiety and the nonpolar p-(4-trans-pentylcyclohexyl) moiety were designed and synthesized. These compounds show the smectic phases and they can form two different layer structures. In particular, anthracene derivatives 1 and 2 show the two different luminescent properties based on the changes of their layer structures. Uniaxial alignment of the anthracene derivatives can be achieved by using the rubbed polyimide thin film. The liquid-crystalline properties and the anisotropic properties of these compounds were examined.

View full abstract

Liquid crystalline dendimer (LCD) exhibits strong spontaneous vertical alignment, and a homeotropic alignment is formed in nematic LC by adding a little amount of the LCD. When LC display device was prepared using LCD/nematic LC mixture, vertical alignment (VA) mode drive operated at the device without using polyimide alignment layer. In this study, two kinds of LCDs having different smectic A/isotropic phase trantion temperatures (T_SI); 32.1 and 73.0℃, were dissolved in nematic LC having T_NI=95℃, and LC cells were prepared using the LCD/LC mixtures. The homeotropic alignment was hold at around T_NI. The homeotropic alignment structure induced by the LCDs was highly stable. The both LC cells exhibited VA-mode drive at the temperature range from 25 to 100℃ irrespective of different T_SI of the LCDs.

View full abstract

Blue phases(BP) have seen a resurgence of interest in the past decade, prompted by the development of new experimental techniques to increase their stability and to exploit their unique properties for device applications. In this study, we will present the effect of surface alignment on the stability and electro-optical properties of blue phase liquid crystal by using various alignment surfaces.

View full abstract

As for the liquid crystal display manufacture, the rubbing method has been widely used as an alignment treatment method. The rubbing scratches occur on the alignment film by directly rubbed with cloth on it. It supposed to generate relating the hardness of alignment film, however, the evaluation for the liquid crystal displays with regarded to the hardness of alignment film has not been investigated yet. In this study, the pretilt angle and the twist angle by means of ellipsometry and the surface free energy for the planar alignment film will be totally investigated from the viewpoint of Vickers hardness.

View full abstract

For the purpose of developing practical blue phase display materials, we have designed a host liquid crystal consisting of a conventional nematic liquid crystal mixture and a small amount of a T-shaped oligomer. We report here effects of the oligomer on electro optical properties in a blue phase III of the host LC doped with a chiral dopant. Furthermore, we investigated influence of molecular structure of a conventional LC on stabilizing BPIII. A newly designed material was found to show BPIII with a temperature range of 19 K. It exhibited submillisecond response and hysteresis-free switching in the BPIII.

View full abstract

We report the fast electro-optic response on the order of sub-milliseconds in nematic liquid crystal (NLC) film embedded with nano-pores (average size 40 nm) filled with a NLC. The nanocomposite film was fabricated simply by photopolymerizing NLC mixture doped with a reactive mesogen at a high concentration of 30 wt% with UV light. When an electric field was applied on the film, the birefringence shifted up to 0.14 and both the rise and decay response times showed 〜100μs due to local reorientation of molecules confined in the nano-pore.

View full abstract

The response time is well known as one of the most important parameters for the property of liquid crystal (LC) display. As for the evaluation of dynamic response, it needs to consider the response of LC molecules both in the bulk and near the surface interface. Therefore, the observation of the molecular reorientation near the interface between the substrate and LC layer is necessary. Up today, the total reflection ellipsometry was applied by using the planarly aligned LC cell. In this study, we will evaluate the dynamic response of the vertically aligned LC cell near the interface between the substrate and LC layer by the total reflection ellipsometry.

View full abstract

In the Reverse Twisted Nematic (RTN) LCD, the RTN LC director configuration is realized by applying an AC voltage to a splayed twist cell. The RTN configuration relaxes to an original splayed twist configuration if removing the applying voltage. This process is regarded as a configuration transition and relaxation. To clarify alignment material dependence of this configuration transition/relaxation we fabricated a couple of series of RTN-LCDs by using different polyimide materials as alignment layers and quantified the transitional/relaxational behavior. In this report we are going to give a criterion to realize a stable RTN-LCD and investigate its relation to the LCD performance.

View full abstract

The Electro-spray Deposition (ESD) method is known as a film forming method. The ESD technique applied to the pre-tilt control for the LC cell was proposed by our previous report; the spray process was carried out alternately using two capillaries that correspond to the solution of vertical alignment material and the horizontal one, respectively, then, two kinds of tiny areas were formed on the substrate surface. The surface anchoring energy on the alignment film formed by this method was measured.

View full abstract

ESD method is known as one of forming film methods. The tiny size of materials can be deposited on the substrate when a high voltage is applied between the capillary and the substrate. PVCi was deposited and the relief structure was formed on the substrate surface by ESD method, and the alignment condition of the nematic LC on this film and the electro-optical characteristics were investigated.

View full abstract

The bistable LCD named Bistable Twisted Direction Switching (BTDS)-LCD proposed by our group. The LCD material with Δ_ε<0 was used for the bistable LCD mode due to obtaining higher contrast ratio (CR). Our conventional BTDS-LCD has an optical CR of 15:1. The pure black state could be obtained easy in the vertical alignment state at the low applied voltage if Δ_ε<0 LC material was used. However, the display memory function was sacrificed. Then, polymer stabilization technique was attempted to use this cell due to the improvement of the memory time. As results, the display memory time of 20 sec and the CR of 230:1 were obtained.

View full abstract

The inorganic alignment film for the LC alignment is expected due to the high durability. The vertical alignment for the nematic LC is obtained by using the anodized Al film which is inorganic material is known. However, control of the pretilt angle is not so easy for this film. Some kinds of anisotropic characteristics are attempted to give on the Al film surface during the anodic oxidation treatment to induce the pretilt angle. The anodic oxidation was carried out while moving the slim cathode to the anode plane in parallel. As a result, the slight pretilt angle from the normal to the substrate was obtained, however, the alignment vector in azimuthal direction was continuously changed in the plane. The convexoconcave cased when the cathode was cut to the slim gave the electric field distribution adverse effect during the anodic oxidation treatment.

View full abstract

Highly-efficient photorefractive medium was fabricated using the low-molar-mass liquid crystals, polymer liquid crystals, and fullerene derivatives. Three kinds of fullerene derivatives were used as photoconductive sensitizers and photorefractive diffraction efficiencies were observed on varying the applied dc field, writing beam intensity, fullerene concentration and grating period. The diffraction efficiencies reached to near the theoretical maximum (33.9%) under the Raman-Nath conditions.

View full abstract

Liquid-crystal (LC) cylindrical-lenses with high resistance layer were fabricated. Rubbing directions were prepared parallel and perpendicular to the direction of slit in the electrode of the lens cells. Fringe patterns and intensity profiles were observed for both lens cells. In the case of parallel direction, lens power of over 2000 D as a cylindrical lens was obtained. On the other hand, in the case of perpendicular direction, asymmetrical focus pattern formed by asymmetrical optical phase distribution was observed.

View full abstract

The photorefractive property of photoconductive ferroelectric liquid crystalline mixtures was measured. The mixtures composed of the photoconductive chiral dopants and liquid crystals exhibit large gain coefficients in two beam coupling experiment. The influence of the structure of photoconductive chiral dopant on the photorefractive effect of liquid crystals was nvestigated. The real-time dynamic holograms were achieved in this experiment.

View full abstract

Simple and compact birefringence measurement system has been investigated by using a LC cell as a phase shifter. Some LC cells are fabricated with various LC materials, and their voltage-transmission properties are measured by using a polarization microscope system or a measurement system with He-Ne laser. Induced phase shifting error in the calibration process of the driving voltage is investigated by using the measurement results. Furthermore, we actually estimate the birefringence of potato starch during the temperature change.

View full abstract

Recently, photovoltaic cells have been attracted as a new source of energy. Photovoltaic cells have disadvantages of high capital cost and low conversion efficiency. To solve these problems, organic photovoltaic cells have been developed due to their light weight, flexibility and low cost of materials. However, the conversion efficiency of he organic photovoltaic cell is well-known to be lower than that of the inorganic one. The purpose of this study is to attempt to improve the conversion efficiency of organic photovoltaic cell by means of the intrinsic orientational property of liquid crystal molecules.

View full abstract

A high-performance LC projector, which uses a vertical alignment (VA) LC display mode, is now becoming an inevitable device for displaying extra large-size images. Stable LC alignment of LC devices against intensive light illumination is essential to make high-reliable LC projectors. In this study, we have studied vertically LC alignment control on nitrogenated SiOx (SiOxNy) for getting more stable vertical LC alignment. The results prove that VHR is improved by introducing nitrogen into SiO layer, while the vertical anchoring property is weakened with increasing the content of nitrogen in SiO.

View full abstract

Cholesteric liquid crystals (ChLCs) are known to self-organize into helical structures with periodicities of a few hundred nanometers and thus have been studied as distributed feedback (DFB) lasers. There is a drawback of low slope efficiency in the conventional ChLC lasers, in which the laser dye is directly doped in the ChLCs and the ChLC cavity is deteriorated due to heat generated by light excitation. In this study, we report an improved slope efficiency in a ChLC laser with a three-layered structure, in which gain medium is eparated from the ChLC cavity.

View full abstract

We investigate the equilibrium swelling and phase behavior of the liquid crystalline elastomers swollen in the mixtures of the two isotropic solvents with different solubilities. The gels undergo the transition between the swollen isotropic state and the shrunken nematic state at a certain solvent composition.

View full abstract

Azobenzene derivative, azobenzene crosslinker, phenylbenzoate derivative and hydroquinone crosslinker with vinyl groups were synthesized to fabricate the crosslinked liquid-crystalline polymer films. Undirectionally aligned crosslinked azobenzene liquid-crystalline polymer films with a polysiloxane backbone were prepared by hydrosilylation reaction. Two-dimensional surface labeled gratings were recorded in surface of the film with a photomask. A probe beam at 633 nm was incident to the film, and surface deformation of the film was evaluated by an external stress or ultraviolet irradiation using a light diffraction. In addition, effect of position and behavior of front and back surfaces in the film on the deformation has been investigated.

View full abstract

Cubic phase is a liquid crystal phase with a three-dimensional periodical structure formed by self-organization through intermolecular interactions. The formation is determined by the balance of the size between the alkyl chains and core part of constituent molecules. In this paper, we chose the BABH-n as a starting Cub-phase -forming compound, and intended to investigate how the extension of the central π-electron system influences the Cub phase formation. The compounds synthesized were 1,2-bis(4'-n-alkoxyphenylbenzoyl)hydrazines (BAPBH-n) having a biphenyl core part and 1,2-bis(4'-n-allkoxynaphthoyl)hydrazines (BANH-n) having a naphthyl core part.

View full abstract

Lyotropic liquid crystals form various phases, including nematic (N) phase and chiral nematic (N^*) phase, by changes in temperature and concentration. However, lyotropic blue phase has not been observed in the lyotropic liquid crystal that water is used as a solvent because an induced helical twisting of host lyotropic liquid crystal is very small. In this study, we investigated properties of chiral dopants in a lyotropic liquid crystal for an appearance of lyotropic blue phase.

View full abstract

A polymer-stabilized blue phase (PSBP) is thermodynamically stabilized by a polymer network (PN) formed through an in-situ photo-polymerization of monomers in a BP. However the electro-optical properties of PSBP depend on PN structure. In this study, we investigate that influence of monomer chemical structure on a temperature range of BP before photo-polymerization and characteristics of prepared PSBP. In the case of using monomer with bend-type structure, a relatively wide temperature range of BP before photo-polymerization and improved electro-optical properties of resulted PSBP were shown.

View full abstract

We prepared some rod-like compounds in which a 2,3-difluoro-1,4-diphenylbenzene unit and a hydroxyl unit are connected via a flexible methylene spacer. We investigated their physical properties using polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction (XRD). The compounds showed a phase sequence of Iso-N-SmC. In the low temperature region of the N phase smectic-like layer ordering was observed by XRD. We discuss structural effects of the rod-like liquid crystals on appearance of the cybotactic nematic phase.

View full abstract

We investigate the effects of frequency and crosslink density on electric field response of liquid crystal gels. Electric field intensity required for reorientation of liquid crystal increases and the resultant strain decreases when crosslink density increases. In addition, the threshold frequency of the electric field required for reorientation of liquid crystal and deformation increases when crosslink density increases.

View full abstract

Subwavelength-period gratings with an intrinsic birefringence medium were fabricated by means of both nanoimprinting lithography and photoalignment of photocrosslinkable polymer liquid crystal (PCLC) to investigate optic axis and form birefringence of them. In result total birefringence can be changed from 0.15 to 0.24 by controlling the director of PCLC. According to FDTD calculations the thickness of the translation layer, in which the director is rotated at the surface of the grating plate, was estimated to be around 60 nm.

View full abstract

We previously reported that molecular reorientation in a photo-cross-linkable liquid crystalline polymer (P6CAM) film was explored by a thermal nanoimprinting technique using a SiO_2/Si mold with a line-and-space (L&S) pattern, which direction was parallel to the mold lines. In this work, we observed molecular reorientation in P6CAM film induced by a thermal nanoimprinting technique using various molds with complex structures.

View full abstract

In the field of organic electronics, solution-processed organic semiconductors for a large and flexible electronic device which is fabricated by low temperature process, in particular field effect transistors(FETs) have gotten much attention in these years. We used organic semiconductor, 8TNAT8, solutions (e.g. 0.1wt% toluene solution) for forming an organic semiconductor layer by casting method, and fablicated bottom-gate/bottom -contact type FETs. We have investigated the influence of surface morphology and FET properties of fabricated FETs at various temperatures.

View full abstract

Ferroelectric liquid crystals can be regarded to be a multi-functional material exhibiting the charge carrier transport as an organic semiconductor and the remnant polarization as a ferroelectric material simultaneously. According to this point of view, we have investigated the electrical properties at the interface of a polarized liquid crystal and the electrode surface, and found significantly enhanced charge inject at the interface, resulting in space charge limited current at the a vey low electric field of 10⁴V/cm. We also applied it to enhance charge injaection for organic light emitting diodes.

View full abstract

In the present study, we performed Monte Carlo simulation of the mixture of liquid Crystal and dendrimers by using hard repulsive molecular models. We used hard spherocylinders as model liquid crystal molecules and hard spheres as dendrimer molecules. We also used a square platelet which was sufficiently larger than the size of the periodic boundary of the system as a substrate surface. Results show that in pure system of spherocylinders, the director takes parallel alignment on the substrate. However, in system of mixture of hard spherocylinders and hard spheres, the director indicates the homeotropic alignment near the substrate.

View full abstract

Time-resolved deuterium NMR spectroscopy has been employed to investigate the dynamic director alignment processes following the application or removal of an electric field for a low molar mass nematic (5CB-d_2). The probability distribution function for finding the director at an angle was considered as an initial director distribution in order to explore the mechanism of uniform- and non-uniform director alignments observed in the deuterium NMR spectra during the alignment process. It has been found that a spontaneous director distribution and fluctuation in a steady state is essential to understand the director dynamics under the condition of orthogonal external fields.

View full abstract

Liquid crystal exists in our living body, and liquid crystal and living body are in implication. It is expected that the fusion of both field gives us great developments such as biosensor, liquid crystal device, and materials with super high functionalities. In the present study, we focus on lyotropic liquid crystal in the water system similar to the living body, and we investigate the characteristics of liquid crystal doped with DNA molecules and then research the properties of DNA.

View full abstract

It has been reported that a solid-like interfacial layer can be formed between polymer sublayers and liquid crystals from the investigation of viscoelastic properties of the interfacial layers using a quartz crystal microbalance (QCM). In the present study, formation processes of the interfacial layers were investigated for various liquid crystals. The results indicated that the thickness and the formation rate of the solid interfacial layer were strongly dependent both on the length of alkyl chain and on the number of polar groups within a liquid crystal molecule.

View full abstract

The fabrication of operable surface-stabilized ferroelectric liquid crystals (SSFLCs) is often hampered by the occurrence of zigzag defects. In this study, we try to fabricate a defect-free SSFLC with antiparallel-rubbed films having different properties between two substrates for the energy condition in two types of chevron to be different. As a result, there is no relationship between the anchoring strength and the occurrence of zigzag defects. It is also contemplated in the current rubbing strength scratch to make the alignment film, and that this is related to the occurrence of defects.

View full abstract

The molecular orientation of disclinations in nematic liquid crystal has been investigated by microscopic polarized infrared spectroscopy. The in-plane orientation and order parameter for each region has been determined by the comparison of band intensity for parallel and perpendicular vibration modes with respect to the molecular axis. This analysis leads us to discriminate and classify the disclination that it has been characterized to the wedge disclination of strength -2π and +2π. The vertical molecular orientation will also be discussed.

View full abstract

Aim of this research is to develop the organization by appending a liquid crystallinity to Dendritic Phenylazomethines(DPA) terminal-modifying liquid crystalline molecules. We report the synthesis and self-organization of novel terminal modified liquid crystalline DPA having mesogenic groups with dodecyl droups as the spacer moiety.

View full abstract

We previously reported that discotic liquid crystals were constructed by the selfassembly of 1,3-alkadiynyl-4-benzoic acids (mPhDA) as the rod-like molecules. In this study, we investigated the structure and physical properties of the mixed liquid crystal systems using the mPhDAs with different alkyl substituents and the systems combined with 4-alkokybenzoic acids. We revealed that these mixed liquid crystal systems showed columnar and smectic mesophases depending on the structure of the mesogens and the conditions such as composition and temperature.

View full abstract

1,3-Alkadiynyl-4-benzoic acids (mPhDA) form discotic liquid crystals while 1,3-Alkadienyl-4-benzoic acids (mPhDE) and 1,3-Alkadienoic acids (mDE) form a nematic liquid crystal. In addition, mPhDA gives oligomers, mPhDE and mDE no oligomer under UV irradiation in the liquid-crystalline state. In this study, we prepared mixed liquid crystals from different mesogen molecules and co-crystals with azopyridine and bipyridine compounds, we examined the liquid-crystalline structures and polymerization properties of these compounds.

View full abstract

We synthesized diblock copolymers consisting of poly(buthyl methacrylate) (PBMA) unit and azobenzene (Az)-containing poly(methacrylate) by atom transfer radical polymerization method. The spin-coating films of PBMA-b-PAz were irradiated with polarized visible light at LC temperature. Orientation of azobenzene chromophore were investigated by polarization spectroscopy. The resulting films exhibited monoaxial orientation of microphase separated structure in thin films. We observed the cross-sectional profiles of the thin films by TEM. We will discuss the photoorientation process of microphase separated structure.

View full abstract

We synthesized nobel LC compounds featuring 2,6,7-trioxabicyclo[2.2.2]octane ring, and measured their properties required for LCD applications. The new 2,6,7-trioxabicyclo[2.2.2]-octane compounds have larger Δ_ε than comventional compounds with cyclohexane ring or dioxane ring. Those compounds are useful for the LC mixture which improve the properties of display devices, for example, low driving voltage and short response time.

View full abstract