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We demonstrate the effect of the ferroelectric nanoparticles dispersed in the alignment layer of a twisted nematic (TN) liquid crystal (LC) panel. In comparison to a conventional TN LC panel with a conventional polymide layer, the TN LC panel with an alignment layer doped with ferroelectric nanoparticles shows a much higher contrast ratio. The effects of barium titanate nanoparticles at several different concentrations have been studied, among which 2.5 and 5 wt % barium titanate nanoparticles mixtures show better performances. The surface texture of the alignment layers has also been studied by atomic force microscopy (AFM).

We demonstrate the polarization-dependent laser oscillation of a biphenyl-capped thiophene crystal based on stimulated resonance Raman scattering (SRRS) at room temperature. Under optical excitation at resonant absorption wavelengths, a platelet single crystal shows amplified spontaneous emission (ASE) with a full width at half maximum (FWHM) of ~5 nm. This ASE intensity is increased at the polarization perpendicular to the crystal face [i.e., transverse magnetic (TM) mode]. When excitation wavelengths approach the absorption edge, the single crystal emits a pair of further narrowed emission lines (FWHM < 0.5 nm) due to a transition into the SRRS regime. The intensity of the SRRS line at 1455 cm-1 is selectively increased at the polarization parallel to the crystal face [i.e., transverse electric (TE) mode]. On the other hand, the SRRS line at 1596 cm-1 is propagated in the TM mode. This polarization-dependent SRRS phenomenon is related to the coherent molecular vibrations in the uniaxially oriented single crystal.

Ion trapping films TOP-COAT TA606B20 are installed beneath the polyimide alignment films, which are coated over the ITO electrode films, in a polymer-stabilized ferroelectric liquid crystal display exhibiting V-shaped switching. The ion trapping films are shown to play the following two roles: one is to remove zigzag-defects owing to their planarizing function and the other is to remove mobile ions. The latter effect gives rise to the reduction of the operational voltage and an increase of the voltage holding ratio owing to the removal of the depolarization field.

The electrooptical (EO) characteristics of polymer-stabilized ferroelectric liquid crystals (PSFLCs), which are fabricated by UV photocure of doped monoacrylates with mesogenic side chains at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a bipolar square-pulsed AC electric field, depend on the polymer density. The PSFLC with low concentration of polymer exhibits a bistable EO performance accompanied by microsized domain switching. On the other hand, the PSFLC with high concentration of polymer exhibits a monostable V-shaped EO performance without a threshold. We propose a model to explain the effect of polymer density on the molecular alignment structure of the PSFLC by investigating theoretically the free energy.

Emission dynamics of the organic semiconductor material thiophene/phenylene co-oligomer (TPCO) single crystals has been studied under high-density optical excitation at 5 K. The optical amplification phenomenon is observed both on 0–1 and 0–2 vibration transitions, where these intensities increase superlinearly with the increase in excitation density. In particular, when optical amplification has started, the 0–1 emission line shows symmetric pulse-shaped emission and its pulse peak has delay time of 50 ps. Delay time and pulse width decrease with the increase in excitation density. The excitation density dependence of delay time is useful for optical devices with the variable delay time with amplification.

We found out that the modulated photocurrent (MPC) in organic photovoltaic cells with an organic semiconductor of titanyl phthalocyanine is sensitive to additional bias light. The MPC steeply decayed after the irradiation of the bias light and slowly recovered after the interruption of the bias light. Such a transient response is characteristic of the organic photovoltaic cells, since it was not observed in conventional silicon photodiodes. Injection of excess carriers due to the bias light reduced the power conversion efficiency because of the formation of space charge in organic semiconductors. Analysis of the transient response is applicable to investigate traps in organic semiconductors.

We developed a new polyimide, RN-1411, for the alignment of ferroelectric liquid crystal display (FLCD) and used it to fabricate an intrinsic FLCD showing half V-shaped switching called intrinsic H-V-mode FLCD. In this research, we particularly adopted a hybrid alignment method, typically the combination of a weak anchoring treatment for one substrate and a strong anchoring treatment for another substrate, that was actually performed by the combination of strong rubbing and weak rubbing, and the combination of photoalignment and rubbing using the same polyimide or that of rubbing and ion-beam alignment, where the same polyimide film or two different polyimide materials were used. It was shown that an intrinsic H-V-mode FLCD fabricated using this method has a defect-free molecular conformation that is realized without applying a DC voltage to remove degeneracy in the layer structure, which makes it possible to realize a high contrast ratio of 300:1 and high temperature reliability for a temperature cycling test.

We fabricated a tunable birefringent (TB) mode nematic liquid-crystal (NLC) electrooptic device using NLC-K15 (Merck) as a host NLC (called NLC-1), where the cell is doped with Pd nanoparticles covered with NLC (NLC-2) molecules, having a cyano group such as 5CB (Merck) with positive dielectric anisotropy (Δe>0) or CCN-47 (Merck) with negative Δe (Δe

Measurement of molecular conformation and motion in two kinds of polymer-stabilized ferroelectric liquid crystal displays showing thresholdless switching (V-mode PS-FLCDs) has been carried out with the objective of distinguishing molecular conformation and switching between two types of V-mode PS-FLCDs. Based on the results of molecular conformation under quiescent condition and motion under applied voltage, the different mechanisms of the thresholdless electrooptic characteristics of two types of V-mode PS-FLCDs are discussed. In addition, the reduction of the operation voltage of V-mode PS-FLCD (I) from V-mode PS-FLCD (II) has been explained.

In this study, we focus on vertical alignment ferroelectric liquid crystals (VA-FLCs), because an FLC display with a high contrast ratio is expected. In the VA, although the normal of smectic layers is vertical to the substrate surface, the director of FLC molecules must tilt to the substrate surface at the tilt angle of FLC molecules. Thus, it is usually difficult to obtain a uniform VA in FLCs. We determine the optimum conditions for the fabrication of VA-FLC cells in terms of the tilt angle of FLC molecules, the anchoring strength of the alignment film, and the cell gap. Results indicate that the FLC with a small tilt angle tends to form good VA, which can be obtained by utilizing alignment films with high surface anchoring strengths. Good VA strongly depends on the cell gap.

We report the reduction of threshold voltage, Vth, of twisted nematic liquid crystal devices by doping the nanoparticles of MgO and SiO2. The results are well explained by inserting the experimentally determined values of elastic constants and dielectric anisotropy in the formula Vth = π√Keff/e0Δe, where both of these quantities decrease due to the existence of these nanoparticles. The Vth decrease approximately as √S, where S being the order parameter. The S is also shown to decrease by doping nanoparticles.

Polymer-stabilized ferroelectric liquid crystals (PS-FLCs) photocured in the SmA phase can show monostable V-shaped electrooptical characteristics. In this study, we have researched the influence of the fabrication conditions such as polymer concentration, cell gap, and alignment film materials on the monostable electrooptical characteristics of PS-FLCs. As a result, it is confirmed that the monostable capability strongly depends on the polymer concentration. However, the driving voltage increases as the polymer concentration increases. Therefore, to fabricate practicable PS-FLC devices, it is important to investigate the effects of other factors on the monostable capability. From the investigation of the influence of the cell gap and the alignment film materials on the monostable capability of PS-FLCs, it is concluded that the surface anchoring of the alignment film strongly influences the monostable characteristics of PS-FLCs photocured in the SmA phase.

We have fabricated a twist nematic liquid crystal (TN) cell doped with guanine oligonucleotide (G10b) and measured its voltage-dependent transmittance (V–t) response. It is found that the operating voltage of a TN cell doped with G10b is higher than that of an undoped cell at 10 Hz. At a high frequency above 100 Hz, the V–t curve tends toward a saturated value equivalent to that of an undoped cell. The increase in the operating voltage depends on the concentration of G10b. This result suggests that G10b acts as an ion and produces an opposing electrical field between the electrodes.

Since liquid crystals have found wide use in liquid crystal displays, we try to apply liquid crystals to biotechnology. The purpose of this study is to describe the physical properties of the biopolymer DNA in regard to electrooptics. Synthetic oligonucleotide molecules were dispersed in a nematic liquid crystal (NLC). The ICP analyses showed that all of the oligonuleotide molecules added dispersed in the NLC. This sample was injected into the twisted nematic liquid crystal display cells, and then we measured its dielectric properties. The NLC doped with oligonucleotide molecules exhibited dielectric relaxation characteristics, depending on the concentration of oligonucleotide molecules. After analyzing this effect by using the equivalent circuit model, we found a difference in electrical conductivity between Watson–Crick base pairs (AT and GC). This result suggests that the difference might have contributed to the existence of a functional group involved in the hydrogen-bond interaction.

Twisted nematic liquid crystal display (TN-LCD) devices, composed of nematic liquid crystal (NLC), doped with palladium (Pd) nanoparticles, which are protected with the same NLC molecules of 5CB (Merck, K-15), show electrooptic characteristics that are featured by a frequency modulation and fast response. This device is called FM-TN-LCD. In this paper, we report that the frequency range in the FM-TN-LCD spreading from tens Hz to an upper limit 1 kHz, depending on the concentration of nanoparticles, correlates with that of the dielectric dispersion of the sample cell, which is expressed analytically by the Maxwell–Wagner theory on the heterogeneous dielectric medium, where the dielectric relaxation frequency, and thus the dielectric relaxation time, are primarily governed by the electrical conductivity of the doped nanoparticles of Pd and their concentrations.

Twisted nematic liquid crystal display (TN-LCD) devices, composed of nematic liquid crystal (NLC), doped with silver (Ag) nanoparticles, which are protected with the same NLC molecules of 5CB (Merck, K-15), show electrooptic characteristics that are featured by a frequency modulation and fast response. This device is called FM-TN-LCD. In this paper, we report that the frequency range in the FM-TN-LCD spreading from 40 Hz to an upper limit 2 kHz correlates with that of the dielectric dispersion of the sample cell, which is expressed analytically by the Maxwell–Wagner theory on the heterogeneous dielectric medium, where the dielectric relaxation frequency, and thus the dielectric relaxation time, are primarily governed by the electrical conductivity of the doped Ag nanoparticles.

The electrooptic characteristics of a twisted nematic (TN) liquid crystal display (LCD) fabricated by doping Ag nanoparticles protected with NLC, 5CB (K-15, Merck) molecules have been investigated, and it is shown that the device exhibits a unique electrooptic response characteristic that is sensitive to the high-frequency components of the operating voltage together with the conventional root-mean-square voltage response. We call this device frequency modulation (FM) TN-LCD. The FM-TN-LCD is switched by switching the frequency of the operating voltage while its amplitude is kept unchanged. As an example, the frequency switched from 20 Hz to 500 Hz or 50 Hz to 2 kHz, and the switching is performed with the time constant of 21 ms for the rising process and 3 ms for the falling process. This device shows a peculiar response to a burst AC square wave, where the decay time is reduced by several times compared to that of an undoped TN-LCD. The mechanism of the FM-TN-LCD is investigated through the study of its dielectric properties.

The most important issue in developing liquid crystal displays (LCDs) utilizing ferroelectric liquid crystals (FLCs) is how to obtain defect-free FLCDs. In this report, a phenomenological theory of transition between C-1 and C-2 states in FLC cells is suggested. Free energy that includes bulk elastic and surface parts has been theoretically simulated depending on parameters such as surface topography, anchoring energies, thickness of the LC medium and so forth. The critical conditions of the state transition from C-1 to C-2 have been determined. Based on this theory, we succeeded in fabricating defect-free FLCDs with uniform C-2 states by rubbing and that with uniform C-1 states by the photoalignment technique.

We fabricated new polymer-stabilized ferroelectric liquid crystal displays (PS-FLCDs) by UV photocure of doped monoacrylates with a mesogenic side chain at a temperature where the LC medium is in the SmC* phase under the application of a bipolar square-pulsed AC electric field. Then, we investgated the effect of polymer density on the molecular alignment structure of the PS-FLC by observation of the microscopic textures and measurement of the electrooptical characteristics. The PS-FLC with low concentration of polymer (4 wt%) exhibits bistable electrooptical characteristics accompanied with microsized domain switching. On the other hand, the PS-FLC with high concentration of polymer (10 wt%) exhibits monostable V-shaped electrooptical performance without a threshold.

By using a conventional commercially available ferroelectric liquid crystal (FLC), FELIX M4851/100 (Clariant Japan), which is doped with newly developed photocurable mesogenic liquid crystal monomers, 2A363 (DIC), a new FLC device exhibiting V-shaped electrooptic performance is successfully fabricated. In the fabrication process, the photocure is carried out in the smectic A phase without applying an external voltage and the mesogenic monomers may form a polymer network.

The most important issue in developing liquid crystal displays (LCDs) utilizing ferroelectric liquid crystals (FLCs) is how to obtain defect-free FLCDs. In this report, a phenomenological theory of transition between C-1 and C-2 states in FLC cells is suggested. Free energy that includes bulk elastic and surface parts has been theoretically simulated depending on parameters such as surface topography, anchoring energies, thickness of the LC medium and so forth. The critical conditions of the state transition from C-1 to C-2 have been determined. Based on this theory, we succeeded in fabricating defect-free FLCDs with uniform C-2 states by rubbing and that with uniform C-1 states by the photoalignment technique.

A photoalignment technique has been utilized for fabricating zigzag-defect-free ferroelectric liquid crystal displays (FLCDs) using polyimide RN-1199, -1286, -1266 (Nissan Chem. Ind.) and adopting oblique irradiation of unpolarized UV light. A rubbing technique was also utilized for comparison. It is shown that among these polyimide materials, RN-1199 is the best for fabricating defect-free cells with C-1 uniform states, but RN-1286 requires low energy to produce a photoaligned FLC phase. We have conducted an analytical investigation to clarify the conditions for obtaining zigzag-defect-free C-1 states, and it is theoretically shown that zigzag-defect-free C-1 state is obtained using a low azimuthal anchoring energy at a low pretilt angle, while a zigzag-defect-free C-2 state is obtained by increasing azimuthal anchoring energy above a critical value, also at a low pretilt angle. The estimated critical value of the azimuthal anchoring energy at which a transition from the C-1 state to the C-2 state occurs is 3×10-6J/m2for the FLC material FELIX M4654/100 (Clariant) used in this research; this value is shown to fall in a favorable range which is measured in an independent experiment.

New optical logic gates have been fabricated by stacking two ferroelectric liquid crystal optical diodes (LC-ODs) fabricated by polymer stabilization. The device exhibits a strong asymmetric electrooptic performance; for this reason, the device is referred to as a liquid crystal optical diode. The liquid crystal logic gates fabricated by stacking two LC-ODs are shown to enable the performance of logic calculations, such as AND, NAND, OR, XOR, and XNOR.

Surface-stabilized ferroelectric liquid crystals (SSFLCs) fabricated by adopting polymer stabilization in terms of the UV photocure of doped photocurable monoacrylates with mesogenic side chains at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a monopolar electric field, exhibit monostable electrooptical characteristics with grayscale capability without threshold. We suggest a model for explaining the monostability of this polymer-stabilized SSFLC by investigating theoretically the free energy of the SSFLC before and after the photocure.

Using a side-chain mesogenic polymer stabilized ferroelectric liquid crystal display (PS-FLCD) cell together with a two-dimensional array of red, green and blue light-emitting diodes (LEDs) as a modulated back light unit, we constructed a field sequential fullcolor (FSC) LCD. The PS-FLCD used in this research exhibits a high contrast ratio (230:1) with thresholdless monostability, grayscale capability, and a fast response speed (τ=40 µs). In the present research it is taken the advantages of the favorable characteristics of the PS-FLCD for implementing a FSC-LCD that has an 8×8 matrix format. The fabricated FSC-LCD, which is operated at the frame rate of 330 Hz, is shown to exhibit an excellent color gamut, color grayscale, and smearless moving color bars.

We have reported a new method of realizing gray-scale operation of surface-stabilized ferroelectric liquid crystal displays (SSFLCDs) by controlling the threshold voltage of the samples. The control of the threshold voltage is achieved by forming liquid crystalline polymer networks in a FLC medium using a UV-curable liquid crystalline monomer, and the threshold voltage is found to decrease with increasing concentration of the doped monomer. This phenomenon is utilized to realize the gray-scale operation, and we succeed in obtaining a quasi-tristable SSFLCD by combining it with a two-domain structure.

A new technique to deal with the time-resolved data, without referring to a dispersion relation, is proposed for an optical grating experiment on an electrooptic medium. The fundamental concept behind this approach is a simple relation among macroscopic and measurable quantities. General features concerning the behavior of the observable are formulated, some of which have been overlooked in the past studies. The most important characteristic is that the index changes measured at three different spatial frequencies are sufficicient for determining the dielectric and electrooptic properties of the medium. Possible approximations in the present approach are discussed in connection with the results of the previous time-resolved studies on LiTaO3.

In-plane switching liquid crystal displays (IPS-LCDs) have been fabricated by a photo-alignment method using poly (vinyl cinnamate), and the effect of the azimuthal anchoring energy on the electrooptical performance has been studied theoretically and experimentally. The results show a large reduction in the driving voltage of IPS samples with decreasing azimuthal anchoring energy, which demonstrates the usefulness of the photo-alignment method for fabricating IPS-LCDs.

In this study, we investigate asymmetric grating as a scheme for mapping the amplitude profile of an optical pulse onto a terahertz phonon-polariton in electrooptic crystals. The grating configuration is theoretically evaluated paying particular attention to the effect of spectral narrowing due to the spatial periodicity of the interference fringes. Its impacts and implications are fully analyzed. For an input optical pulse with a tailored profile, an important result is that the linear chirp of the optical pulse can reveal itself in the duration of the polariton and in directionally asymmetric responses. Experimental results show a temporal shift between the counter propagating wavepackets. This is one of the directional asymmetries and is sound evidence that the polariton responds to the amplitude profile of the optical pulse.

We have fabricated a new ferroelectric liquid crystal (FLC) display that exhibits monostable electrooptical characteristics with high contrast ratio (160:1) owing to freedom from defects, grayscale capability without threshold, and fast response (70 µs). A FLC(ZLI-4654-100, Merck) is subjected to polymer stabilization by UV photocure of a mixture of doped monoacrylates with a mesogenic side chain particularly at a temperature where the LC medium is in the SmC* phase under the simultaneous application of a monopolar electric field.