Motohiro Yamahara

Influence of rubbing conditions of polyimide alignment layer on optical anisotropy of immobilized liquid crystal film

The relationship between the molecular orientation of a rubbed polyimide film (alignment layer) and that of mesogens in a photopolymerized liquid crystal (LC) coated on the film has been investigated using optical measurements. LC monomers were deposited on the alignment layer and were aligned in one direction. The LC monomers were subsequently photocured. Alignment layers under various rubbing conditions were prepared. It was found that the inclination angle of the refractive index ellipsoid and the optical retardation of photopolymerized LC films are strongly related to the optical anisotropy of the rubbed polyimide film. The photopolymerized LC film exhibited high optical anisotropy when alignment layers with an inclination angle of the refractive index ellipsoid smaller than 6° were used.

Relationship between the Optical Properties of Immobilized Liquid-Crystalline Film and Polyimide Alignment Layer

The relationship between the molecular orientation of a rubbed polyimide film alignment layer and that of mesogens in liquid-crystalline (LC) films coated on the alignment layer before and after photopolymerization has been investigated using optical measurements. LC monomers were coated over the alignment layer and were aligned in one direction. The LC monomers were subsequently photocured. The inclination angle of the refractive index ellipsoid and the optical anisotropy of the immobilized LC film were found to be related to the optical properties of the rubbed polyimide films.

Filters and Films for Liquid Crystal Devices

The research on birefringence and polarization has a long history and began with the discovery of light polarization by the Dutch scientist Christiaan Huygens in 1690 when he was experimenting with two calcite plates. Then, Etienne L. Malus accidentally discovered that the light reflected at an angle from the windows of Luxembourg Palace was polarized, which he reported in 1809, and in 1812 David Brewster announced the law of light polarization by reflection and refraction, which now takes his name. Furthermore, William Herapath discovered in 1852 that a synthetic crystalline compound, iodoquinine sulfate (also called herapathite), can polarize the light of all wavelengths in the visible region, a phenomenon that is now the underlying principle of current absorption-type polarizers.

Alignment Properties of Hydrogen-Bonded Mesogens of Supramolecular Liquid-Crystalline Network Films Coated on an Alignment Layer

The films of a supramolecular liquid-crystalline (LC) network were spontaneously formed by intermolecular hydrogen bonds between multifunctional H-bond donor (HD) and H-bond acceptor (HA) molecules. A tricarboxylic acid, 2,5-bis{2-[2-(4-carboxyphenoxy)ethoxy]ethoxy}benzoic acid (1) was prepared for the use as a trifunctional H-bond donor. This donor was complexed with a bifunctional H-bond acceptor, trans-1,2-bis(4-pyridyl)ethylene (2). H-bonded complexes, 1/2, in the various ratio of donor to acceptor groups (HD/HA) were coated on a rubbed poly(vinyl alcohol) (PVA) film. These films exhibited homogeneous alignment when the ratio of HD to HA (HD/HA) was more than 1.025. These results suggest that the alignment properties of the mesogens in the complex films on the PVA film related to the value of HD/HA.