Photoalignment technique has been applicable to LC photoalignment and birefringent film fabrication. We have carried out systematic studies on the photoinduced molecular reorientation of photosensitive liquid crystalline polymer (PLCP). Based on the axis-selective photoreaction of the mesogenic side groups in PLCPs, exposed PLCP films indicate small optical anisotropy and the thermal stimulation due to LC characteristics of the material induces large molecular motion to achieve homogeneous molecular alignment. Herein, we introduce basic design, synthesis, photoalignment mechanism and their application of photoalignable PLCPs, and our recent results on the birefringent patterning based on in situ formation of photoalignable mesogenic side groups.

When azobenzene derivatives are incorporated into calamitic liquid crystalline materials, they show fascinating molecular alignment and motile functions upon light irradiation. The actions and motions are highly cooperative and thus lead to large dynamic molecular processes with obvious amplifications. The processes can be applied to photoalignment and photomotile functions in thin film systems. The research has been achieved over 30 years, but this lecture will mainly concentrate on the overview of our achievements around 15 years at Nagoya University.

Displays for VR application is necessary for fast response. We developed Short-range Lurch Control - IPS (SLC-IPS), which archived fast response for VR-HMD. In this study, we compare the response time and the transmittance of SLC-IPS and conventional-IPS, and explain the superiority of SLC-IPS.

A demand for the 5th generation mobile communication (5G) system is now arising for the purpose of realizing the vehicle autonomous system with super high speed, large capacity, no delaying and multiple simultaneous connection. Since 5G system will use the millimeter wave which is currently used in radar etc., materials used in the 4th generation (4G/LTE) are not suitable due to the large transmission loss, so the liquid crystalline polymer (LCP) is currently attracting considerable attention because of its excellent dielectric properties. We would propose new LCPs designed to realize such performance of 5G system, which are also good matching to the flexible circuit board manufacturers’ equipment.

The market of the displays for automotive application becomes rapidly growing in recent years. However, demands for reliability and image quality of the automotive displays are strictly high compared to the displays for other applications. In this report, we show the development of our liquid crystal displays (LCDs) for the automotive application and their LC materials.

In screen printing, there is an increasing demand for fine-diameter high-mesh fabric. Fiber required for this type of fabric needs to have a fine diameter, high strength, and abrasion resistance. To this end, we commenced a study focusing on liquid crystal polymer (LCP) fiber, a high strength fiber. Our analysis conducted to figure out the reason for the poor abrasion resistance of the LCP fiber revealed that separation of fibrils from the fiber surface (fibrillation) advances. This result led us to conclude that it is effective to minimize fibril structures to improve the abrasion resistance of an LCP fiber. In order to achieve this, we made use of the characteristics of an LCP fiber, and successfully produced a highly-oriented low crystallinity LCP fiber by heat treating a solid phase polymerized LCP fiber at a high temperature, achieving higher strength and improved abrasion resistance.

By exploiting the effect of dynamic soft elasticity in nematic liquid crystal elastomers (LCE), the temperature-dependent control of adhesion to a solid glass surface is demonstrated. The adhesion strength of LCE is more than double in the nematic phase, in comparison to the isotropic phase, further increasing at the higher detachment rates. The observed enhanced adhesion in the nematic phase is primarily attributable to the increased internal energy dissipation during the detachment process.

Cholesteric liquid crystal elastomers (CLCEs) are a soft matter with a helical structure, showing selective reflection in a specific wavelength corresponding to the helical pitch. Therefore, such materials can be utilized stimuli-responsive materials for various application. In this study, we prepared a CLCE film which shows reversible color change by mechanical elongation. The results suggest that materials have potential applications as flexible sensors in wearable devices and soft robots.

In this study, we investigated the liquid-crystalline property of the mixtures of 4-butyl-4’-methoxyazobenzene and 4-pentyl-4’-cyanobiphenl (BMAB+5CB) with various BMAB contents, and photoplasticization of poly(methyl methacrylate) (PMMA) using the BMAB+5CB mixtures as photoresponsive plasticizers. We found that a BMAB+5CB exhibited a crystal-like phase at the specific molar ratio of 50/50 mol%. Then, the crystal-like phase transformed into isotropic liquid upon UV-light irradiation at room temperature. By means of the photochemical crystal-like-to-isotropic phase transition, we achieved remarkably large decrease in Tg of PMMA (Tg before photoplasticization

Zeolites are crystalline aluminosilicates with molecular-sized pores. They show promise for high-performance catalysts; however, they are quickly deactivated because the diffusion limitations; the pores are clogged with the products. If the size of the zeolites decreased, the clogging could be suppressed. We focused on the synthesis method of nanosheets inside bilayers of hyperswollen lyotropic lamellar (HL) phases of amphiphile solutions, which we named Two-dimensional Reactors in Amphiphilic Phases (TRAP) method. In this work, we report the application of TRAP method for the synthesis of amorphous aluminosilicate nanosheets as a common precursor to synthesize various zeolite nanosheets and its transformation to the zeolite nanosheets.

Recently, we have developed various kinds of anisotropic soft materials by using an aqueous dispersion of titanate nanosheets with the liquid crystalline property. During the course of our studies, we found that the nanosheets, dispersed in water, become to form a monodomain lamellar structure by the application of a strong magnetic field. Here, we report that such a monodomain structure generates a unidirectionally propagating wave upon a chemical perturbation. The characterization of wave structure, elucidation of its formation mechanism, and its application will be discussed.

Reentrant liquid crystals are low ordered phases, which reappear at lower temperatures than that of higher ordered phases. We investigate the possibility of reentrant liquid crystals appearing when the volume is kept constant, even when the chemical interaction among the molecules are the same. The method of canonical hydrostatic molecular dynamics simulation is used for this purpose. Canonical hydrostatic simulation results are compared with simulation results of isobaric-isothermal ensemble. Reentrant smectic A and hexatic smectic phases appear in several model systems.

We present a mean field theory to describe uniaxial ($N_{TB,U}$) and biaxial twist-bend nematic ($N_{TB,B}$) phases of banana-shaped liquid crystalline molecules with an axial chirality. We first derive a tensor order parameter for the banana-shaped molecules as a function of a bend angle ($0^{¥circ}<¥theta_{AB}<180^{¥circ}$), a torsion angle $¥xi$ for the axial chirality, and four orientational order parameters, which describe uniaxial and biaxial nematic phases. Depending on the bend angle and the strength of an oblique twisting power of the banana-shaped molecules, we calculate phase diagrams on the temperature$-$bend angle plane. We derive the analytical formulas for two Landau points (LPs): one is at the bend angle $109.5^{¥circ}$ and the other is at $¥theta_{AB}(¥xi)(>70.5^{¥circ})$, which depends on the torsion angle. We also find that the $N_{TB}$ phase appears outside the two LP angles and the phase diagrams show a rich variety of phase transitions, such as the second-order uniaxial nematic ($N_U)-N_{TB,B}$ and the second-order $N_{TB,U}-N_{TB,B}$ phase transitions, etc.

We studied the applied-electric-field dependence of the structure change of the SmCα* phase by with nanaometer-sized helical structure at zero electric field. By the electric-field- birefringence and resonant X-ray scattering measurements, it was found that he structure change depends on the helical pitch at zero field; from the in short pitch range less than 3 layers (lower temperature range of SmCα*), the pitch elongates and attains to 3 layers with increasing the applied field, while in longer pitch range than 3 layers (higher temperature range of SmCα*), the pitch elongates and attains to 4 layers. In addition, 4 layer-unit field-induced transition phase is suggested to be unexpectedly antiferroelectric-like, because the optical birefringence is almost zero or negative under the applied field.

We have shown both experimentally and numerically that a thin film of a chiral liquid crystal exhibits various exotic ordered structures. Here we discuss Kossel diagrams exhibited by such structures. Kossel diagrams visualize the direction along which monochromatic incident light is strongly reflected. Although Kossel diagrams have been used for the investigation of bulk crystal structures, we show that they can be applied also to the study of structures in thin films. We numerically construct Kossel diagrams by solving the Maxwell equations for light waves, and almost perfectly reproduce experimental Kossel diagrams. We also show that Kossel lines from a thin system are attributable to guided-mode resonance inside the system, not Bragg reflections that are responsible for Kossel lines from bulk crystals.

In the JLCS annual meetings 2017 and 2018, the speaker reported that some vector fields have invariant tori arranged similarly to double-twist cylinders in cholesteric blue phases and discussed this similarity by using cubic magnetic groups. In this talk, the same approach is applied to hexagonal cases and two vector fields are derived. The arrangement of their invariant tori is observed to vary according to the ratio of the magnitude of <001> twist to that of <210>.

The flicker phenomenon associated with Fringe Field Switching(FFS)-LCD panels has not been elucidated yet enough. Based on the liquid crystal material, alignment material layer and SiNx material layer, the flicker amplitude accordingly increases while driving the LCD. Such a phenomenon is termed as ”flicker shift” or ”Vcom drift.” In the proposed simulation study, Boltzmann distribution was applied for modeling the space charge density of the aforementioned material layers. It is observed that energy levels and ion concentrations of such material layers generate asymmetric potentials in the liquid crystal layer, which cause the flicker phenomenon.

We discuss the image-sticking problem caused by residual DC voltage from the viewpoints of the DC offset-transmittance (D-T) property varying like a quadratic function. When flexoelectric (FE) effect exists, the bottom positions of D-T property change according to gray levels, because FE makes transmittances between positive and negative frames different. We simulated D-T property using simulation software LCD master 2D and study influence of cell parameters in DT property.

We discuss the flicker shift phenomenon generated by several factors in FFS-mode LCD. We propose the method to compare measurement result with simulation result of flicker minimum and transmittance minimum DC offset voltage at each gray level. Although flicker minimum and DC minimum DC offset voltage vary depending on gray level, measurement result and simulation result show similar tendency. Through this method we separate separate flicker shift factors.

We have investigated a reverse mode LC cell which has a transparent off-state and light scattering on-state. We propose the reverse mode LC cell prepared by combining the polymer composite and microlens array systems to improve light scattering property. Electrooptical properties, POM images and light scattering pattern have been investigated in three types of reverse mode cells with index mismatching effect, microlens effect and combination of them.

The liquid crystal (LC) containing photocurable monomers and left handed chiral agent in the TN cell twisted clockwise in 90 degrees formed the Splay Twisted structure twisted counterclockwise in 90 degrees. The Reverse Twisted Nematic (RTN) mode twisted clockwise was formed, when 10 V was applied to the Splay Twisted structure. The obtained RTN structure could be stabilized by UV irradiation. In this study, we tried to stabilize the RTN structure by using thermal energy with low voltage application. By 1.5 V application to Splay Twisted structure at 80℃, and UV stabilization the formation counterclockwise Super Twisted Nematic structure was confirmed.

Some discotic molecules possessing the chirality form the columnar liquid crystal (LC) phases in which the column has the helical structure. While it has been reported that each enantiomer of an octahedral metal complex shows the chiral columnar liquid crystals, the molecular orientational structure at microscopic scale was not clearly understood by the optical experimental studies. In order to investigate the microscopic structure of the chiral columnar LCs composed of the metal complex molecule, we carried out molecular dynamics simulations for its enantiomeric system and analyze the detail structure of the column.

The inner structure of chiral columnar liquid crystal phases is still poorly understood compared to chiral calamitic ones. We here report the octahedral metallomesogens that show columnar liquid crystal properties. Because the Delta and Lambda chirality of the octahedral metal complexes is positioned at the center of mesogens, the chiral information can be suitably transferred along intracolumnar direction and to affect resultant phase behaviors. The inner stacking structure revealed by GI-SAXS measurements and molecular dynamics calculation will be presented.

There are three types of chiral molecules : point asymmetry, axial asymmetry and planar asymmetry. So far, we have mainly studied azobenzene compounds with point asymmetry, but in this study, we focus on the axial asymmetry based on binaphthyl group which is known to exhibit high helical twisting power (HTP). We investigated the effect of asymmetry type and molecular structure of chiral azobenzene molecules on HTP accompanying the photoisomerization from trans-form to cis-form of azobenzene groups by ultraviolet light irradiation.

A widely used class of materials for fabricating photonic elements are cholesteric liquid crystals (CLCs) that possess a helically self-assembled molecular orientation, manifesting unique optical properties such as reflection, refraction, diffraction depending on the one dimensional pattern of the helical axis orientation. However, two or more dimensional control of helical axis is still scientifically challenging. To address the issue, here we have firstly developed facile technology of the two-dimensional control of helical axis orientation. We irradiated a polymerizable CLCs with a patterned UV light, which causes in-situ formation of a confined structure located only at an irradiated region. This confined structure provoked a uniform arrangement of a sub-micron sized fingerprint texture, well-known for two-dimensionally self-assembled helical axis structure. We also investigated the detailed optical properties of the resultant film.

The laminated films composed of　photoresponsive liquid crystalline (LC) polymer layer on a photoinert LC polymer film surface were prepared by Langmuir-Schaefer method. Then, the laminated films were irradiated with UV light through a photomask at LC temperature. We newly found that a surface relief pattern with a larger height difference than the photoresponsive layer were formed. This result indicates that the photoinduced mass transfer were propagated from the topmost surface photoresponsive layer. In this presentation, we discuss the photoinduced mass transfer in terms of surface tension gradient and viscosity change of polymer materials.

Colloidal nanoparticles based on strontium carbonate (SrCO3) have been developed through biomineralization-inspired approaches utilizing an amorphous precursor stabilized by water-soluble acidic polymers. Amorphous states stabilized by acidic polymers gradually crystallize in aqueous solutions, leading to the formation of nanorods with a narrow size distribution. The size of nanorods was estimated to be several hundred nanometers in length and around 100 nanometers in width. Thesenanorods exhibit liquid crystalline (LC) phases in aqueous dispersion states at a certain range of the concentration. Size of SrCO3 nanorods was tuned by the change of crystallization condition for theenhancement of dynamic properties of LC SrCO3 materials.

The phase transition mechanism of a bimesomorphic alkoxyazobenzene-tripgenylene mesogen (C14 homolog) was studied with synchrotron radiation XRD measurements for its aligned samples to reveal face-to-face interaction of triphenylene moieties initiate SmA-Colr transition.

Establishment of design principles for the molecules that form the bicontinuous cubic (Cub) phases is demanded to control/tune their structure and properties. For this purpose, we have been investigating effects of chemical modification of 1,2-bis(aryloyl)hydrazine framework and/or attachment of lateral substituent(s) to it on the phase behavior, especially on the formation of the Cub phase. In this presentation, we discuss what type of modifications is favorable to lower and/or expand the temperature range of the Cub phase.

Bicontinuous cubic liquid crystals form 3D continuous gyroid nanostructures. Owing to their 3D nanostructures, a variety of new applications have recently been expected for them. In this 15 years, we have focused on the development and improvement of molecular design principles for bicontinuous cubic liquid crystals based on ionic compounds. For these new bicontinuous cubic liquid crystals, we have examined their functions and properties and then their potential applications have been investigated.

We prepared cubic and amorphous blue phase liquid crystals. The mixtures were photopolymerized in a cell　to form their polymer-stabilized blue phases. We investigated nano structures of cubic BP and amorphous BPIII by field-emission scanning electron microscopy (SEM) observation of the polymer networks imprinting along topological defect in the BPs. A bicontinuous cubic structure with relatively ordered pores can be seen in the cubic BP. On the other hand, the pores with different diameter sizes exist randomly in the BPIII. We propose the nano structure of an amorphous BPIII and discuss how the photopolymerization widens the BPIII temperature range.

Liquid crystalline cholesteric blue phases (BPs) attract interest for their fast response times and quasi-polarization-independent phase modulation capabilities. BPs possess a three-dimensional cubic structure and typically form polydomain textures when filled in conventional sandwich cells. Here, we have found that the texture of BPs that appears random is in fact composed of crystallographic twins. Results of detailed polarized optical microscopy are presented to provide an insight into the structure of the twin. Our finding shows that crystal twinning, conventionally observed in atomic crystals, can also occur in a fluid crystal with a much larger lattice constant.

We are studying to control the defect number of the nematic shell by applying a magnetic field. In this work, we focused on the effect of shell thickness and diameter on the defect of the nematic under a constant magnetic field. Three types of reorientation processes were observed; (1) In the thin shells, defects did not merge but director aligned along magnetic direction and bipolar configuration was formed. (2) In the slightly thicker shells, two of +1/2 defects merged in one of +1 defect at the pole of the bipolar configuration. (3) In the thick shell, defects nucleated at the pole of the shells and replaced the initial defects. We focus on defect marge phenomena, and observed the reorientation under the magnetic field at various temperatures. As a result we found critical angle between two of +1/2 defects before marge.

Formation of solitonic structures is one of the hot topics in the modern physics. For instance, the nanoscopic solitonic state of electronic spin waves in a chiral magnetic medium is well-known as Skyrmions, in which spins are toroidally swirling to form a unique topological structure. In fact, liquid crystals also form such solitonic structures, i.e. baby Skyrmions or Hopfions, as reported in many recent scientific articles. However, most of those are static states. Here in our study, we demonstrate electrically-induced dynamic solitons, actively swimming in the nematic director field. Although they have a topologically trivial structure without defect, their swimming directions and speeds are controllable with the field frequency or amplitude.

Here we report a self-excited oscillation induced in cholesteric liquid crystalline droplets under temperature gradient. Using a cholesteric liquid crystal, we made cylindrical droplets with twisted cross-like patterns in a liquid solvent. In the droplet a point defect existed at the center of the pattern. When the temperature gradient was applied, the defect moved to high-temperature side together with pattern deformations, owing to the flow induced by the gradient. Here, applying the temperature gradient further, we found that a periodic movement of the defect was induced when the droplet was sufficiently large.

Droplets of cholesteric liquid crystals exhibit unidirectional rotation of their stripe textures when subjected to a temperature gradient perpendicular to their helical axes. The phenomenon is well-known as a typical thermomechanical cross-coupling, however, there has been an argument whether the textural rotation is ascribed to rigid-body rotation of the droplets or pure director rotation. To distinguish the two possibilities, we dispersed micron-size particles in a cholesteric-isotropic coexisting sample and visualized the flow-field by tracing the particles. The result showed that the particles adhering onto the cholesteric droplets rotated at the same angular velocity as the droplets. This observation provided a clear evidence of the rigid-body rotation of the droplet and settled the argument.

We fabricated cholesteric (Ch) double twist cylinder (DTC)-aggregates coexisting with its isotropic phase and investigated the size dependence of the unidirectional rigid-body rotation of DTC-aggregates. In experiment, the angular velocity of the DTC-aggregates is proportional to the height and inversely proportional to the square of the radius, which agrees with our phenomenological model. The cross-coupling constant between the heat flux and the torque for DTC-aggregates is approximately identical with the reported value for director rotation. Thus, we concluded that the heat-driven torque on director is efficiently converted to the torque for rigid-body rotation of DTC-aggregates.

As a simple model of biomembranes, we prepared a lipid monolayer on a glycerol surface and embedded cholesteric LC droplets in it. Owing to our preparation process, the droplets spontaneously formed a lattice structure, which was accompanied by the phase separation of the monolayer. When the cholesteric droplets were given an ethanol vapor transferring across the monolayer, they exhibited unidirectional orientational rotation because of the Lehmann effect. We also found that the rotating droplets sometimes showed translational motion, the speed of which was nearly linear to the rotational velocity.

Here, we unveil fluorescence anisotropies of a series of phosphole oxide-based dyes with an elongated -conjugated system, on which the transition dipole moment lies, in nematic liquid crystals. We observe that, as the number, size, and rigidity of substituents protruding from the pi-conjugated plane increase, the transition dipole moment tends to tilt away from the nematic director over the magic angle, ~54.7°, showing conspicuous negative fluorescence anisotropy. Analysis of molecular shapes suggests that the substitutions modulate the interaction with the nematic mean field, impacting the direction of the principal molecular axis aligned with the nematic director.

Influences of two kinds of nonequilibrium structures in MBBA from polymer networks formed by photopolymerization were investigated. It was found that an umbilic pattern formed in the homeotropic system can be immobilized at the transient nonequilibrium state. For electroconvective patterns in the planar system, increases of threshold voltages, distortions of patterns, and a slowing of the motion of turbulent patterns were found.

A series of photoconductive chiral compounds was added to ferroelectric liquid crystal blends to investigate the efficiency on the photorefractive effect. Using the samples, physical properties such as dielectric relaxation phenomena and photorefractive characteristics were investigated. We confirmed the existence of two response modes (Goldstone mode and Soft mode) observed in the Chiral Smectic C phase, and examined the influence on photorefractive properties combined with the orientation state. In addition, four types of photoconductive chiral compounds were prepared, and photorefractive properties of those samples were compared.

A simple model for estimating band edge wavelengths of a selective reflection from cholesteric liquid crystals (CLCs) for oblique incidence is proposed. The proposed method is based on geometrical optics. Average refractive indices and propagation angles in a CLC at the short and long wavelength edges of the reflection band are calculated by based on the model. The band edge wavelengths are determined by substituting the average refractive indices and propagation angles into Bragg’s law. The angular dependences of the band edge wavelengths show a good agreement with those calculated by Berreman’s 4×4 matrix method. Although the derived equations are not exact solutions of Maxwell’s equations, our method can predict the angular dependence of the center wavelength, bandwidth, and band edge wavelengths of the selective reflection in CLCs.

Summary: We developed high-efficiency red fluorescent dyes for opt-electronic devices and applied them to cholesteric liquid crystal laser experiments. Dyes with the methoxy group showed similar steady state absorption and fluorescence dichroic ratios to those with the methyl group. Laser oscillation occurred at both ends of the selective reflection band in the former, but occurred only at the long-wavelength edge in the latter. To clarify the origin of different lasing behavior, we performed transient polarized fluorescent measurements. We found a difference in the relaxation process between the two groups. We explain the difference of lasing behavior based on the difference in the relaxation process.

We propose a liquid crystal (LC) lens with an electrically tunable Fresnel lens-type refractive index distribution. The LC lens is prepared using a glass substrate with transparent circular-electrode and ring-patterned electrodes of different widths. Both negative and positive lens properties of smoothly parabolic optical-phase-retardation can be realized by applying appropriate voltages across the patterned electrodes and common flat electrode. The lens properties can be tuned with preserving the good optical quality over the entire focal range.

In recent years, much attention has been focused on LC-based phase shifters for terahertz wave. However, LC technology with high expertise in thin-film devices such as LC displays has many problems in thick-film devices for terahertz wave applications. One of the most significant problems is the response speed in field-induced realignment of LC molecules. So far, almost all of previous studies have reported response times greater than seconds, hindering the practical use of LC devices in terahertz frequencies. In this study, we demonstrated a tunable terahertz phase shifter using the structure of polymer dispersed LCs with honeycombed polymer morphology. The device exhibited an outstandingly short response time of 30 ms.

We have proposed a hybrid aligned nematic (HAN) reverse mode cell with a dual frequency liquid crystal (DFLC). The scattering intensity becomes weak at a certain oblique incident angle. In this study, the cell was fabricated by irradiating with UV light under the voltage application of high (30 kHz) and low (1kHz) frequency. The incident angle can be changed by the curing voltage and frequency. The relation between incident angle and transmittance was theoretically analyzed by estimating indices of LC and RM.

The alignment dependency of three dimensional twisted alignment structure for generating optical vortex beam was numerically investigated. Our results show that three dimensional twisted anisotropic structure can generate optical vortex with high purity and efficiency within broadband spectrum range, so that it would be useful for applications of vortices such as optical communication, ultrafast spectroscopy, and astronomical coronagraph.