Light absorption properties of twisted-alignment guest-host devices using liquid crystal with low refractive index anisotropy

To reduce the twist angle without satisfying the Morgan condition in a twisted-alignment guest-host liquid crystal device, the authors fabricated liquid crystal cells having smaller optical anisotropy of the liquid crystals and evaluated the electrooptic properties. A birefringent phenomenon, not optical rotation, occurred here, and the authors investigated fabrication conditions in which two orthogonal polarized light components of the incident light were absorbed by a dichroic black dye that was doped into the liquid crystals. As a result of evaluating the transmittance of the liquid crystal cells, they increased light absorbance and suppressed the black level according to the selection of a liquid crystal with low refractive index anisotropy and an appropriate twist angle. According to this investigation from cell fabrication experiments, the authors clearly showed that the twist angle can be reduced, and they found that when the twist angle was in the range of up to 180°, a response time of 30 ms including both the rise and decay times, could be obtained without decreasing the response speed.