1. (Polymer/Liquid Crystals) Composite Systems
The role of the display devices which interface the information with human vision will become increasingly important in future as the information exchange becomes more active and easier. Though the form of the display devices has shifted to the flat panel e.g. liquid crystal display(LCD), EL, Plasma, etc. from the conventional CRT, the display which is thin, lightweight and flexible like paper in appearance is strongly desired in pursuit of further saving of space and portability. In our group, the new liquid crystal display materials consisting of the (polymer/liquid crystal:LC) composites are developed for large area flexible displays.
The (polymer/LC) composite film can be switched between the light scattering state and the light transmitting one upon removal and application of an electric field, respectively. The scattering and light transmitting states result from the macroscopically random orientation and unidirectional one, respectively, of LC directors embedded in the three dimensional polymer networks. Since the LC possesses a large birefringence, the spatial distortion of LC directors on the order of sub-_m induced by the complicated polymer network formations is particularly supposed to be an important origin for the light scattering in addition to the mismatch of refractive indices between polymer and LC. From a viewpoint of practical applications, the composites have the features as follows.
･ Flexible(like plastic films)
･ No rubbing process(bicontinuous phase separation structure)
･ Ease of large-scale fabrication(several m2 by role to role process)
･ Bright (no polarizers)
･ High contrast (>60 at 1/8D)
･ Low driving voltage (< 6 V)

2. (Polymer/Liquid Crystal) Interface
Interfacial interactions between liquid crystal(LC)/solid interfaces are not only of much scientific interest from a fundamental standpoint but also find numerous technological applications. It has been well known that the bulk orientation of LC is sensitively affected by the anchoring effect at the interface. For understanding of the physicochemical mechanisms of the anchoring effect, it is necessary to observe the microscopic structure and the intermolecular interaction at the interface. We study the vibrational spectra of the liquid crystal molecules in direct contact with polymer surfaces by the interface-enhanced sum-frequency generation(ISFG). The ISFG method is a second-order nonlinear optical technique, which is a powerful tool to study the surface and the interface. The interfaces at 4-cyano-4ﾕ-pentylbiphenyl (5CB) and several polymers such as poly (vinyl cinnamate)(PVCi) and poly (vinyl alcohol)(PVA) were studied based on ISFG. At the (PVCi / 5CB) interface, the absorbance band of CN-stretching appeared at 2225 cm-1, which was in good agreement with CN-stretching band in the FT-IR spectrum of 5CB in the bulk state. However, at the (PVA / 5CB) interface, the band of CN-stretching was sifted 100 cm-1 to lower frequency. This results indicate that the intermolecular interaction between PVA and 5CB is much larger than the case of PVCi and 5CB.

3. Frustrated Phases
The cholesteric blue phases (BPs) are kinds of liquid crystal (LC) phases that appear in a narrow temperature range between a chiral nematic phase and an isotropic liquid phase. Since BPs have a three-dimensional cubic structure with lattice periods of several 100 nm, they exhibit the selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of the application, although BPs are of interest for fast light modulators or tunable photonic crystals, it has been a problem that the temperature range of BPs is very narrow, usually less than a few K. The stabilization of BPs was shown over a larger temperature range than 100 K (200 K-326 K) including the room temperature. Furthermore, an electro-optical switching with a response time on the order of 100 microsecond was demonstrated for the stabilized BPs at room temperature.