Criteria of Color Contrast in a Nematic Liquid Crystal Display

Color contrast in a nematic liquid crystal display is defined experimentally. Liquid crystal cell shows a positive dielectric anisotropy and is operated in a tunable birefringence mode. Munsell color chips used as background color. Colorimetric data are shown in the 1976 CIE (L*, a*, b*) color scale. First, a predict equation of color shift induced by background color is derived and shows a good agreement with the result of experiment. Second, criterial of color contrast is established by taking into account the color shift. The values of criteria nearly coincide with that of psychophysical experiment by single-stimulur method, and the validity of criteria is confirmed.     

Synthesis and Physicochemical Properties of Novel Liquid Crystal Compounds with Negative Dielectric Anisotropy with a Tetrahydropyran Ring: Part 2

With the aim of improving the properties of liquid crystal (LC) mixtures for VA-LCD and PSA-LCD, JNC has newly synthesized 2-(4’-ethoxy-2’,3’-difluorobiphenyl-4-yl)-5-alkenyltetrahydro-2H-pyran derivatives with alkenyl substituents as side chains, and then measured various physicochemical properties to compare their properties to LC compounds with alkyl substituents as side chains. We have shown that several LC compounds with side-chain alkenyl substituents lead to the development of a larger negative dielectric anisotropy (Δ?) than for side-chain alkyl substituents. We considered the reason for this using a quantum chemical calculation. As a result, it was found that, compared to alkylated compounds, there exist several LC compounds with side-chain alkenyl substituents, which have a higher existence probability of conformers with a β angle, making expression of a larger |Δ?| possible in an effective manner. It was understood from this study that the physicochemical properties of LC mixtures for VA-LCD and PSA-LCD, which consist of LC compounds as a structural component, newly developed by JNC, show useful properties.     

A Study of a Ferroelectric Liquid Crystal Using Second Optical Harmonic Generation

The phase-matched generation of the optical second harmonic was investigated in the chiral smectic C* phase of a classical ferroelectric liquid crystal (DOBAMBC). The phase-matching was achieved either by incidence angle or by temperature tuning. The temperature behaviour of the second order nonlinear susceptibility was studied.     

Influence of a.c. Electric Field on Infrared Absorption Spectra of Liquid Crystals and Determination of Orientational Order Parameter by Infrared Dichroism. II. Molecules with Weak Negative Dielectric Anisotropy

The influence of a.c. electric field (10 kHz) on the IR spectra of the nematic phase of six p-alkoxybenzylidene-p,n-butylanilines with weak negative dielectric anisotropy was studied and the temperature dependence of the orientational order parameter and threshold voltage have been investigated. The values of band elastic constants K₃₃ were calculated for MBBA and EBBA.