Hirotsugu Kikuchi

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.

Nanoparticle-Stabilized Cholesteric Blue Phases

The authors report the expansion of the temperature range of cholesteric blue phases by doping nanoparticles. When spherical gold nanoparticles with a mean diameter of 3.7 nm were doped in a blue phase-exhibiting multi-component liquid crystal mixture, the temperature range of the cholesteric blue phase increased from 0.5 to 5 °C, while the clearing temperature decreased by approximately 13 °C. We believe that the mechanism stabilizing the cholesteric blue phase is similar to that of polymer-stabilized cholesteric blue phases: the nanoparticles accumulate in the lattice disclinations, stabilizing the overall cholesteric blue structure.

Liquid Crystalline Blue Phases

Blue phases are known to appear in chiral liquid crystals in a small temperature range between the chiral nematic phase and the isotropic one. They are optically active, non-birefringent, and they show Bragg diffraction of light in the visible wavelength, measuring several hundred nanometers. Their exotic structures and properties result from the competition between chiral forces and packing topology. Recently, the blue phases have attracted the attention in the field of optoelectronics and photonics. The following article summarizes the basic properties, especially the frustration in the double twist molecular alignment which is the origin of stabilization of the blue phase, and history of the blue phase studies, and describes significant advances that have been recently reported.

Optically isotropic-nanostructured liquid crystal composite with high Kerr constant

The relationship between material parameters of host nematic liquid crystals (LCs) and Kerr constant of their nanostructured chiral LC composites was investigated. We made certain that the Kerr constant of nanostrutured chiral LC composites was closely related to the parameters of their host LCs, such as value of the difference of refractive index (Δn), the dielectric anisotropy (Δe), and bend to splay elastic constant ratio (K33∕K11).

Thermally bandwidth-controllable reflective polarizers from (polymer network/liquid crystal/chiral dopant) composites

A (polymer network/nematic liquid crystal/chiral dopant) composite exhibiting a chiral nematic (N*) phase at room temperature has been developed. Because the helical twisting power of the chiral dopant increases with increasing temperature and the polymer network affects the molecular rearrangement of the liquid crystal, the bandwidth of the selective reflection spectrum of the N* phase becomes wider and narrower reversibly with increasing and decreasing temperature, respectively.

Direct Observation of Polymer-Stabilized Blue Phase I Structure with Confocal Laser Scanning Microscope

The three-dimensional structure of polymer-stabilized blue phase with the order of optical wavelength was nondestructively investigated by a confocal laser scanning microscope. The periodical patterns corresponding to the bcc lattice were observed not only on the surface but also in the internal region. The visualization mechanism was expected to be back scattering caused by liquid crystal order.

Liquid crystalline blue phase I observed for a bent-core molecule and its electro-optical performance

We investigated the liquid crystalline blue phase I (BP I) observed for a nematogenic achiral bent-core molecule doped with a small percentage of a chiral additive with a high twisting power. We also observed the electro-optical performance of BP I by incorporating in-plane electric field geometry.

Fast electro-optic switching in liquid crystal blue phase II

Electro-optic switching based on the Kerr effect was investigated in detail for liquid crystal blue phase II (BPII) with different chiral pitch. The Kerr constant of BPII was found to be proportional to the cube of the chiral pitch, although the theoretical expectation was the square of the chiral pitch. In addition, there was little hysteresis in the voltage-transmittance curve of BPII. The response of BPII was found to be very fast, at less than 1 ms, in both the regions of local director reorientation and electrostriction by applied electric field.

Electrooptic response of liquid crystalline blue phases with different chiral pitches

The relationship between the electrooptic response properties and the chiral pitch of a blue phase was experimentally investigated. The Kerr constant was found to be proportional to the cube of the chiral pitch, although a theoretical square-law was expected. It was also revealed that the effect of the chiral pitch on the response time was dependent on the type of electric field-induced birefringence of the blue phase, such as local director reorientation and electrostriction. The response of the local director reorientation process was very fast at sub-millisecond and also proportional to the cube of the chiral pitch. However, in the case of the electrostriction process, the effect of the chiral pitch on the response time was insignificant and the response time was a few milliseconds.