In this paper, we first investigated the degradation of the performance of liquid crystals display (LCD) units after driving by a DC bias. Missed segments were found in the test LCD units. By carefully investigating the alignment layer and ITO layer separately, an explanation of the ITO failure is proposed: voltages applied to the liquid crystal cell causes accumulation of charged impurities or ions, resulting in a decomposition reaction of ITO in regions where segment and common planes overlap and there are scratches on the PI layer. Consequent, missing segments in the corresponding regions is generated.
To prevent this kind of degradation, we studied the correlation between the alignment layer and ions adsorption. Both organic alignment layer (PI2555, SE1211, and FPI) and inorganic alignment layer (SiOx, SiO2, and Al203) are analyzed by residual DC and voltage holding ratio measurement. A correlation between ion adsorption and the dielectric constant of the alignment layer is demonstrated. Alignment layer with a smaller dielectric constant is good for reducing ion adsorption in the alignment layer. Alignment layer with a bigger dielectric constant is good for reducing mobile ions in the LC device, and could be used in non-active areas of the liquid crystal device to remove ion from the active area.
We analyzed a design of a liquid crystal-based diffractive lens for the effect of thickness variations from the design
values. This diffractive lens contains 20 resets, with a focal length around 1 meter; optical phase difference (OPD) is 1
wavelength; liquid crystal cell gap of is 3 μm and a lens radius of around 4.5 mm. Our mathematical analysis is
performed by using numerical calculations that take into account the details of the electrode structure and the physical
properties of the liquid crystal material.
We demonstrate fast-switching electro-optical films (EOFs) based on polymer encapsulated liquid crystal and carbon
nanotube. EOFs are made by using the polymerization-induced phase separation method with an initially homogeneous
mixture of a pre-polymer, liquid crystal and small amount of carbon nanotubes (CNTs). The effects of the concentrations
of CNTs and liquid crystals on the electro optical properties of the EOFs are studied. The rise times for the CNTcontaining
EOFs is around 200 μs at 6V/μm, while the fall time is around 30ms at 6V/μm twice as fast as that of the
EOF without CNTS. The dielectric measurements show that the relaxation frequency of the EOFs increases with the
increase of CNT doping, indicating the decrease in droplets size. The morphology of EOFs is confirmed with SEM
morphological studies. With the increase of the concentration of CNT or liquid crystal, the threshold voltages of the
EOFs are decreased and the response times are faster.