Takashi Iwata

62.2: Invited Paper: Fast Electro‐Optical Switching in Polymer‐Stabilized Liquid Crystalline Blue Phases for Display Application

Blue phases have two major advantages over commonly used nematic phases:1) the response is much faster, 2) the zero-electric field state is optically isotropic. We demonstrate the sufficiently large electric field-induced birefringence and the micro-second response of the polymer-stabilized blue phases and the induced-isotropic phases without any surface treatment.

39.1: Invited Paper: Optically Isotropic Nano-Structured Liquid Crystal Composites for Display Applications

In this paper, we present the phase behavior and electro-optical Kerr effect of the optically isotropic liquid crystal composites, which require no surface treatment for device fabrication. Anomalously large Kerr constant, more than 10−8 mV−2 and fast response, less than sub-milli-second were observed at a room temperature.

A method for enlarging the Kerr constant of polymer-stabilised blue phases

Polymer-stabilised blue phase (PSBP) is one of the most promising materials for display devices because of its superior electro-optical properties compared with conventional nematics. However, the application of the PSBP has a serious practical issue in that the driving voltage required is too high to drive with thin film transitors, that is, the magnitude of the Kerr constant of PSBPs is insufficient. We present a useful method for increasing the Kerr constant based on the control of polymer aggregation structure using a cross-linker with a chiral structure. The director distortion arising from polymer networks in the PSBP seems to be responsible for the resulting improvement.

Optically isotropic liquid crystal composite incorporating in-plane electric field geometry

We demonstrate an intriguing liquid crystal display (LCD) mode that comprises an optically isotropic LC composite incorporating in-plane electric field geometry. No surface treatment, such as rubbing, is required to fabricate the LCD mode because it is based on an isotropic state. The measured response time is of submillisecond order. This rapid response originates from the local reorientation of molecules in small LC clusters as well as from strong polymer stabilization. The LCD mode has several unique features such as fast response, continuous greyscale capability and a high contrast ratio.

Improvement of electro-optical properties on polymer-stabilised optically isotropic liquid crystals

A relation between preparation conditions of polymer-stabilised optically isotropic liquid crystals and their electro-optical properties was investigated based on a cyclic voltammetric (CV) method. The polymer-stabilised optically isotropic liquid crystals were prepared by an in-situ photo-polymerisation of a precursor consisting of a chiral liquid crystalline mixture with monomers in an isotropic phase with a metal halide lamp. The CV response of the cell filled with the sample showed an asymmetric profile and a symmetric profile between the positive and negative applied voltages when the cell was irradiated with the metal halide lamp without filter and with a cut-off wavelength filter (> 390 nm), respectively. The CV response profile depends on a distributed state of the polymer generated in the cell. The residual birefringence of the polymer-stabilised optically isotropic phase was suppressed when the CV profile showed a symmetric profile.

The Influence of Thermal Property of the Polymer on the Polymer-Stabilized Blue Phase

A relationship between polymer relaxation property and the stability of a polymer-stabilized liquid crystal blue phase was investigated based on differential scanning calorimetory (DSC) and polarizing optical microscopy under temperature gradient. The polymer-stabilizing effect of the blue phase was enhanced by depressing the thermal molecular mobility of the polymer networks in the BP.

Polarization Analysis of Nanostructured Chiral LC Composites

The polarization analyses of the isotropic nanostructured LC composites, which is a promising candidate of next-generation LCD material, were performed to investigate the residual birefringence after application of an electric field. The composites showed negative, positive and nearly zero in azimuth angle of optical rotation for the chiral nematic phase, the induced isotropic phase and the isotropic phase, respectively. When the residual birefringence occurred, the optical rotatory of the isotropic nanostructured LC composites exhibited slightly negative. It is suggested that the primary cause of the residual birefringence is the electric field-induced phase transition to the chiral nematic phase.