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We report on a treatment of a thiol-based self-assembled monolayer with long alkyl chains on source/drain electrodes of organic thin-film transistors with a bottom-contact configuration. The performance of organic thin-film transistors such as field effect mobility and on/off ratio is improved by performing this treatment in the early stage. However, excessive treatment conversely reduces the field-effect mobility with a threshold voltage shift. We have found these results due to the difference in the density and the orientation of the thiol molecules. Thiol molecules adsorbed on source/drain electrodes in the lying-down phase cause a significant effect to reduce the contact resistance between the electrodes and a semiconductor depending on the energy barrier height at the interface.

Surface specific sum-frequency vibrational spectroscopy (SFVS) and second-harmonic generation (SHG) were used to study the structures of polymer surfaces modified by linearly polarized UV irradiation or mechanical rubbing. The spectroscopic results show that the surface anisotropy of a polyimide surface resulting from bond breaking by linearly polarized UV irradiation is extremely small compared to a rubbed surface. On a rubbed polystyrene surface, the phenyl sidegroups are well aligned by rubbing in the direction perpendicular to rubbing but tilt from the surface normal with a broad distribution.

This report describes the physical principles underlying the switching of nematic liquid crystals (LCs) by an electric field in the plane of the substrate. The results have contributed to development of an IPS-mode-TFT-LCD, which is now commercially available and one of the most popular TFT-LCDs with ultra-wide viewing angle characteristics. The report summarizes work in the Glenn Brown prize winning PhD thesis, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo, 152-8551 Japan.

In-plane switching (IPS) of liquid crystals showed advantageous voltage-holding ratio (VHR) characteristics so that liquid crystals with low resistivity could provide higher VHRs compared with the twisted nematic effect. This experimental result was obtained when electric fields were applied approximately parallel to the substrate plane using the IPS electro-optical effect. We found that the in-plane electric field generates supplementary capacities which support retention of an externally applied voltage over the liquid crystal layer during non-selected periods of the active matrix driving scheme, because the liquid crystal layer can be connected with an insulating layer, an orientation layer and even a substrate in parallel. Based on these advantageous VHR characteristics, liquid crystal materials suitable for the IPS effect were appropriately optimized. We propose evaluation parameters, derived from the physical switching principles of the liquid crystals, to obtain lower driving voltage and faster res...

This article compares switching behaviors between negative (Nn) and positive (Np) dielectro-anisotropic nematic liquid crystals driven by an in-plane electric field which is generated with interdigital electrodes. Even for Np type liquid crystals, excellent viewing angle characteristics were obtained as expected. Theoretical descriptions of the switching principle, i.e., threshold behavior and response mechanism, could be applied to both the Nn and Np type liquid crystals. However, the orientational deformation of the Np type liquid crystals caused by a distorted electric field which occurred near the edges of electrodes was not the same as that of the Nn type liquid crystals. The switching of the Np type liquid crystals near the edges of the electrodes by this field was followed by the in-plane switching of the liquid crystals between the electrodes. This remarkably distinctive dynamical behavior implied a difference in the response of the longitudinal axes for Nn and Np type liquid crystal molecules. The longitudinal axes of the latter seemed to be sensitive to the electric field component perpendicular to the substrates when applying the in-plane electric field. Furthermore, these experimentally obtained results were supported by computer simulations which analyzed the liquid crystal director distribution and transmittance pattern from edge-to-edge of a pair of electrodes when applying the in-plane electric field.

We have investigated the switching and response mechanism of the in-plane switching (IPS) mode which is a novel technique for wide viewing-angle liquid crystal displays. In the IPS mode, an in-plane electric field is applied to the liquid crystals along the direction parallel to the plane of the substrates. First, it was made clear that it was the electric field and not the voltage that drove the liquid crystals in the IPS mode. An inversely proportional relationship between the threshold voltage and the cell gap was found to hold. Second, the relaxation time of the liquid crystals when removing the electric field was described as a proportional relationship to the square of cell gap. A thinner cell gap also proved to be effective to obtain fast response time in the IPS mode. In contrast, the electric field strength governed the switching-on time when applying the in-plane electric field.

We have investigated the electro-optical effects and physical switching principle of homogeneously aligned nematic liquid crystals when applying an in-plane electric field with interdigital electrodes. By using the in-plane switching (IPS) of the liquid crystals which is achieved by the in-plane electric field, the viewing angle characteristics of the electro-optical effects were confirmed to be far superior to those of the conventional twisted nematic mode in which the electric field is applied along the direction perpendicular to the substrates. The non-reversal region of grey scales was extremely wide in which a high contrast ratio was kept, even along quite an oblique direction in the IPS mode. In order to clarify the switching principle of the liquid crystals in the IPS mode, a simplified expression describing the threshold behaviour of the device was derived with the assumption that a uniform in-plane electric field was applied along a direction perpendicular to the director and parallel to the homo...

Research of numerical calculation and theoretical considerations have been applied in relation to the electrical double layer effect on the threshold voltage of liquid crystals in order to understand the drop in threshold voltage often observed at low frequencies. Decreased resistivity of an alignment film was found to contribute to this threshold voltage drop. Moreover, dielectric dispersion due to the electrical double layer at the interface between the liquid crystal and alignment film layers is thought to exist in the frequency range in which the drop in threshold voltage was obtained experimentally. Therefore Debye type dielectric dispersion of the electrical double layer in the system consisting of the nematic liquid crystal and the alignment film also influences the threshold behaviour at low frequencies.

Measurements are reported for threshold voltage dependence on the frequency of a nematic liquid-crystalline system composed of cyanophenylcyclohexanes (PCHs). The PCH liquid crystals having a strong dipole only at the terminal position of the molecules showed a frequency independent of threshold voltage at low frequencies. In their mixture, increasing permittivity affected the threshold behavior, finally causing a drop in threshold voltage at low frequencies. The difference in systems with and without the drop in threshold voltage was found to be related to the drift of charge carriers. Relaxation time measurements of transmittance against direct current bias revealed a tendency for the drift of charge carriers in the liquid crystal layer. The liquid-crystalline system composed of PCHs showed relatively slower relaxation than the system with increased permittivity due to addition of certain dopants. In the migration of charge carriers, a model is proposed considering the changes of permittivity. ...

In order to homeotropically align liquid crystals (LCs) at the nanosized surface grooves processed by nanoimprint lithography technology (NIL), we propose to design a hybrid-type homeotropic polymer material consisting of two distinct moieties with largely different thermo-mechanical properties and surface activity. Surface contact angle measurements and sum-frequency vibrational spectroscopy allow us to conclude that the polymer film is a functionally separated composite suitable for the homeotropic LC alignment processed by NIL. As one of the potential applications using the hybrid-type homeotropic polymer, we demonstrate that the nanoimprinted grooves at the polymer surface can achieve a zenithal nematic LC bistability.

Measurements of tilt bias angles of a nematic liquid crystal were carried out, by using several alkylene polyimides synthesized from 3,3′,4,4′-biphenyltetracarboxylic dianhydrides and diamines with different chain lengths as alignment layers. The tilt bias angle dependence on the alkylene chain length of polyimides shows an anomalous odd-even effect. Small tilt bias angles, less than one degree, were observed with odd-number alkylene chain lengths. Relatively high tilt bias angles, however, were observed with even-number lengths. We have made an attempt to explain this effect from X-ray diffraction and scanning electron microscope measurements and molecular mechanics calculations of the polyimides with alkylene chain. As a result, this odd-even effect of the tilt bias angle is due to the difference of surface structures between alkylene polyimides with odd alkylene lengths and those with even ones.

X-ray diffraction measurements of thin chiral smectic C (Sc∗) liquid crystals between solid plates coated with rubbed polymer film were performed under an electric field. A variety of local layer structures which depend upon the boundary conditions could be observed, including bookshelf and chevron, and some distorted structures. Moreover, the method of layer deformation could be seen in a stepwise induced field, and seven deformation types could be detected. The relation between a bistability effect and the type of layer deformation was clarified and four deformation types were found favourable to bistability. A vertical layer structure at the boundary, like the bookshelf structure, was necessary to produce bistability. A high pretilt film seemed to have a smectic layer reform a tilted structure even under an induced field and it was difficult to produce bistability with the high pretilt one.

The nature of the third-harmonic generation (THG) process in a nematic liquid crystal is investigated for the case of tightly focused, low intensity, laser beams. Colloidal particle induced topological defects in a liquid crystal are visualized in three-dimensions using the dependence of the THG signal on both changes in non-linear susceptibility and the orientation of the liquid crystal director relative to the incident laser polarization state. We have found that the interpretation of THG images in a liquid crystal is complicated not only by the change in polarisation of the electric field as it propagates through the medium but also by anisotropic refractive index mismatch induced aberrations.

Terahertz time-domain spectroscopy has been used to study the dielectric relaxation of pure 4'-n-pentyl-4-cyanobiphenyl (5CB) liquid crystal (LC) and its mixtures with 10 mum SiO2 particles in the frequency range 0.2-2 THz. For the pure sample, we find that spatial inhomogeneities consisting of oriented domains, comparable in size to our probe area (~1 mm(2)), cause a large scatter in the measured dielectric function, due to varying contributions from the ordinary and extraordinary components. In the LC/particle mixtures, ordering of the LC at the surface of the SiO2 particles results in a break-up of these domains, giving rise to a spatially much more homogeneous dielectric response. The inferred dielectric function can be interpreted using effective medium theory and the Debye relaxation model. We observe this stabilizing effect for interparticle distances~30 mum, setting a lower limit for the size of oriented domains in the bulk LC.

A large-scale, prospective study of tardive dyskinesia (TD) was performed in 11 psychiatric facilities in Japan. A total of 1595 psychiatric patients were enrolled in this study in 1987. The progress of these patients, with the exception of 490 dropouts, has now been followed up to 1988. The prevalence of TD at study entry was 7.6%, the annual incidence rate was 3.7% and the annual remission rate was 28.7%. Newly developed TD patients tended to be older, to have undergone more psychosurgery, and to have had lower neuroleptic doses than the patients who had not developed TD, whereas no specific variable could be detected as a factor associated with remission of TD. The results suggest that the incidence of TD is lower in Japan than that in Europe and North America.

The prescription ordering system has been on-lined to a fully automatic tablet packaging machine in order to transmit the host data for inpatient periodical prescription.In this time, we tried to improve the method of transmitting the host data for prescription and drug files in the data converter, and also tried to change the operating machine for one dose packaging in order to dispense tablets more automatically.These resulted in the success of the automatic one dose packaging without modifying the host data by hand, even if the amount of drug component or unequal dispensing was inputted to the computer for prescription.Drug files enable to be changed automatically by using the hard disk in case of the partial replacement of tablet cassettes in the fully automatic tablet packaging machine.Moreover, the new operating machine for one dose packaging enables to input the data by hand easier and to record the amount of tablet consumed over all tablets automatically.

Complete suppression of color shift in in-plane switching mode liquid crystal displays (LCDs) has been realized. The LCDs have a multidomain structure obtained by unidirectional rubbing and use of zigzag electrodes. The design concept and performance of the devices are described in this paper.

A response mechanism of nematic liquid crystals following the switching‐on and off of an in‐plane electric field when using the in‐plane switching (IPS) mode was investigated. Simplified theoretical expressions, which were derived with an assumption that an in‐plane electric field was applied to the liquid crystals, were used to explain the dynamical switching process in the IPS mode. In particular, the relaxation time of the liquid crystals when removing the electric field was described as a proportional relationship to the square of the cell gap. A thinner cell gap also proved to be effective in obtaining a fast response time in the IPS mode. By contrast, the switching‐on time when applying the in‐plane electric field proved to be inversely proportional to the difference between the square of the electric field strength and the square of the critical electric field strength at which the liquid crystals begin to deform.

Surface-specific sum-frequency vibrational spectroscopy and second-harmonic generation were used to study the structures of polyimide (PI) surfaces for homeotropic liquid crystal (LC) alignment and the molecular orientation of LC adsobates on these surfaces. The imide ring was perpendicular to the surface with one of $\text{CO}$ bonds protruding out of the surface and the other pointing into the bulk rather than flat on the surface. The ester $\text{CO}$ bond in the side chain was sticking out of the surface with a tilt angle of about $45\ifmmode^\circ\else\textdegree\fi{}--55\ifmmode^\circ\else\textdegree\fi{}$ from the surface normal, indicating that the rigid side chain core was, more or less, along the surface normal. The part of alkyl chain on the top of the side chain followed the orientation of the side chain core and protruded out of the surface with some gauche defects. The cyano biphenyl LC molecules were adsorbed on the PI preferentially with the terminal cyano group facing the PI surface.

Electro‐optical characteristics related to the threshold behavior of liquid crystals when using the in‐plane switching (IPS) mode were investigated with interdigital electrodes. In order to analyze the switching behavior of liquid crystals, an equation, which expresses the threshold transition, was derived using the continuum elastic theory. It was made clear that it was the electric field and not the voltage that drives the liquid crystals in the IPS mode. Significantly, an inversely proportional relationship between the threshold voltage and the gap between the substrates was found to hold. Furthermore, the electro‐optical characteristics were recognized to change with the variation of the gap between the substrates. This behavior is due to the independence of electric field on liquid crystal layer normal.

Surface second harmonic generation was used to obtain approximate orientational distributions of the side chains and the adsorbed liquid crystal (LC) molecules on a rubbed side-chain polyimide surface. Both the side chains and the LC molecules appear to be well aligned in the rubbing direction but tilted away from the surface in the antirubbing direction. The latter yields a negative pretilt angle in a homogeneously aligned LC film sandwiched between two such surfaces. The side chains and the LC molecules, however, have antiparallel orientations at the surface.

Electro-optical performances of in-plane switching mode active matrix addressed liquid crystal (LC) displays were analyzed by using device simulations. Practical combinations of 2D simulations to analyze precise electric and LC director fields and fast 1D simulations to grasp electro- optical characteristics were systematically utilized. Electrode geometries and tilt angle of the LC molecules at the substrate surface were identified as key points to optimize the electronic performance and optical performance, respectively.

Variable angle spectroscopic ellipsometry and sum-frequency vibrational spectroscopy have been used to study molecular orientations in thin films used in an organic light-emitting-diode. The films consist of sterically bulky and cross-shaped molecules that have small anisotropy in shape, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN). As a result, anisotropic molecular orientation in the amorphous films has been observed with respect to the surface normal. The short axis of anthracene in MADN molecules, more or less, slightly tilts from the surface plane but preferentially close to the surface with a certain orientational distribution, while the long axis of anthracene is, on average, oriented close to the magic angle from the surface normal. This anisotropic molecular orientation gives rise to better carrier transportation properties than the isotropic orientation.

We investigated fluorescence from hemicyanine dye molecules in a liquid crystal (4,4′-n-pentylcyanobiphenyl) (5CB) medium at different temperatures. The fluorescence decay lifetime decreased monotonically irrespective of the thermodynamic phases of the host medium as the temperature was increased. This behavior is due to an intramolecular motion of the dye promoted with the decrease in the viscosity of the medium facilitating a nonradiative decay of the excited dye molecules. By contrast, fluorescence intensity from the dyes in the nematic phase was about 3 times stronger than that in the crystalline or isotropic phase. This fluorescence enhancement in the nematic phase was found to be due to an anisotropic alignment of the dye molecules following the anisotropic alignment of the host liquid crystal medium along the pump-beam polarization direction. This light-induced liquid crystal molecular alignment was markedly enhanced by the guest dyes preferentially excited along the pump-beam polarization direction. The orientational order parameter of the dyes in the liquid-crystalline phase deduced from fluorescenceanisotropy measurement was similar to the known order parameter of the liquid crystalline 5CB.

The higher-order component in liquid crystal (LC) surface free energy beyond the Rapini–Papoular anchoring potential was examined for azimuthal anchoring by analyzing nematic LC alignment on nanogrooved surfaces treated by rubbing or photoalignment. We confirmed that the surface anchoring energy for large director deviations cannot be properly described with the Rapini–Papoular form and should include higher order contributions in a power series of sin2 ϕ, as ∑n=12Wn sin2n ϕ, with ϕ being the azimuthal angular deviation. Based on the corrected Berreman’s theory, we obtained the anchoring ratio between the first and second order terms, W2/W1≈−1/4, and the surface elastic constant, K24≈−0.846K22, for 4-n-pentyl-4′-cyanobiphenyl.

Materials and components available for the mass production of Super-TFTs IPS-TFT-LCDS were optimized and redesigned on the basis of a fundamental analysis of the IPS mode. As a result, we developed 18.0-inch diagonal Super-TFTs with a fast response speed of 25 msec., which is the total on +off response time between white and black levels. Moreover, we found that the IPS mode has a relatively higher potential for displaying a moving gray level image compared with that of the conventional TN-mode.

The allowable range of marginal variation of the cell gap to ensure uniform optical properties when using in-plane switching (IPS) of liquid crystals was evaluated quantitatively. The analysis yielded relationships of transmittance into the cell gap in bright, selected bright and selected intermediate states. The selected state was defined as the state in which a particular constant voltage was applied to the liquid crystals to obtain the desired state in a series of evaluations for different cell gaps. The relationships were used to evaluate normalized variations of transmittance (|ΔT/T|) corresponding to the difference in the cell gap from the optimal value (Δd), and the variations were compared with those in the twisted and supertwisted nematic modes. As a result, the marginal variation for a uniform display using the IPS of liquid crystals was quantitatively confirmed to be much narrower than that in the twisted nematic mode. In the selected bright state, the variation was between those of the twisted and supertwisted nematic modes, while it was comparable to the cell gap margin of the supertwisted nematic mode in the intermediate state; i.e., the variation of ±0.1 µ m in the twisted nematic mode corresponded to that in a range of ±0.02 to ±0.04 µ m in the IPS mode.

Unusual characteristics of the voltage-holding ratio were found when using in-plane switching of homogeneously oriented nematic liquid crystals. Even when employing liquid crystals with much lower resistivity than is applicable to the conventional active matrix driving technique, voltage-holding ratio characteristics were higher than those in conventional electric fields applied along the direction perpendicular to the substrate plane. The unusual holding ratio characteristics were attributed to the electric field direction being approximately parallel to the substrate plane.

Viewing angle characteristics were systematically obtained when using in-plane switching (IPS) of liquid crystals. Although the IPS mode originally shows stable electro-optical performance regardless of viewing directions, the viewing angle characteristics are found to be strongly dependent on pretilt angle (slant angle of the liquid crystals from the substrate). Experimentally, the smaller the pretilt angle of the liquid crystal, the much wider the viewing angle characteristics, while larger pretilt angles of liquid crystals cause the characteristics to deteriorate. This deterioration occurs in a particular viewing direction, i.e. at right angles to the initial orientation direction of the liquid crystal when there is no in-plane electric field. The experimentally observed behaviour of the viewing angle dependence on the pretilt angle was also confirmed by computer simulations. Calculated iso-contrast contour lines, as a function of the pretilt angles, nearly coincide with the experimentally obtained vie...