Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260–326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10−4 s for the stabilized blue phases at room temperature.

Polymer-stabilized liquid crystal blue phases

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

An object of the present invention is to decrease the resistance of a power supply line, to suppress a voltage drop in the power supply line, and to prevent defective display. A connection terminal portion includes a plurality of connection terminals. The plurality of connection terminals is provided with a plurality of connection pads which is part of the connection terminal. The plurality of connection pads includes a first connection pad and a second connection pad having a line width different from that of the first connection pad. Pitches between the plurality of connection pads are equal to each other.

Semiconductor device and display device

To provide a semiconductor device and a display device which can be manufactured through a simplified process and the manufacturing technique. Another object is to provide a technique by which a pattern of wirings or the like which is partially constitutes a semiconductor device or a display device can be formed with a desired shape with controllability.

Semiconductor device, electronic device, and method of manufacturing semiconductor device

Liquid crystal 'blue phases' are highly fluid self-assembled three-dimensional cubic defect structures that exist over narrow temperature ranges in highly chiral liquid crystals. The characteristic period of these defects is of the order of the wavelength of visible light, and they give rise to vivid specular reflections that are controllable with external fields. Blue phases may be considered as examples of tuneable photonic crystals with many potential applications. The disadvantage of these materials, as predicted theoretically and proved experimentally, is that they have limited thermal stability: they exist over a small temperature range (0.5-2 degrees C) between isotropic and chiral nematic (N*) thermotropic phases, which limits their practical applicability. Here we report a generic family of liquid crystals that demonstrate an unusually broad body-centred cubic phase (BP I*) from 60 degrees C down to 16 degrees C. We prove this with optical texture analysis, selective reflection spectroscopy, Kossel diagrams and differential scanning calorimetry, and show, using a simple polarizer-free electro-optic cell, that the reflected colour is switched reversibly in applied electric fields over a wide colour range in typically 10 ms. We propose that the unusual behaviour of these blue phase materials is due to their dimeric molecular structure and their very high flexoelectric coefficients. This in turn sets out new theoretical challenges and potentially opens up new photonic applications.

Liquid crystal ‘blue phases’ with a wide temperature range

We report the first observation of cholesteric blue phases in chiral anisotropic polymer networks. In two-component mixtures of a chiral and a non-chiral diacrylate, we observed typical textures of BPI, BPII and BPIII phases. By photopolymerization of these materials at constant temperature we obtained blue phase networks. After polymerization, the blue phases were stored, which enabled us to further study them without any temperature control.

Observation of blue phases in chiral networks

The smectic-A (SmA) phases exhibited by several homologs belonging to the newly synthesized 4-isothiocyanatophenyl-4′-n-alkyloxybenzoate series (n.O.NCS) show unusual features. Although the X-ray studies show that the layer thickness/molecular length ratio (dll) of the lower homologs is less than 1 indicating a monolayer packing, dielectric studies reveal the existence of strong antiparallel correlations near the isotropic-SmA phase transition, a feature that has hitherto not been observed for any polar monolayer SmA phase. Miscibility studies prove that the SmA phase of these materials is miscible with both the monolayer (SmA1) and the partial bilayer (SmAd) phases.

Unusual Smectic-A Layering in a Homologous Series of Isothiocyanato Compounds

The dielectric constants and the elastic coefficients for splay and bend of the discotic nematic phase of three homologous hexakis-((4-alkylphenyl)ethynyl)benzenes and of 1,2,3,5,6,7-hexakis((4-nonyl-phenyl)ethynyl)naphthalene have been determined by studying the electric field induced bend deformation using a capacitance method. For all compounds a negative dielectric anisotropy was found. The bend elastic constants are between 1*10−12N and 4*10−12N which is in the same order of magnitude as for nematic phases consisting of rod-like molecules. An inverse behaviour to that generally expected for rod-like molecules is found for the homologues of the benzene series: K1 is larger than K3 and the ratio K1/K3 decreases slightly with temperature as well as with increasing alkyl chain length.

A. Ranft

Papers

Observation of blue phases in chiral networks

Unusual Smectic-A Layering in a Homologous Series of Isothiocyanato Compounds

Bend and Splay Elastic Constants of Some Discotic Nematic Compounds