Tien-Jung Chen

Synthesis and frustrated phases of chiral liquid crystals derived from (R)‐3‐alkoxy‐2‐methylpropionic acids

A homologous series of chiral compounds, (R)‐6‐(3‐alkoxy‐2‐methylpropionyloxy)‐2‐naphthyl 4‐alkoxybenzoates, nMPNmB (nu200a=u200a2–5, mu200a=u200a6–13), derived from methyl (R)‐3‐hydroxy‐2‐methylpropionate, was prepared for the study of mesormorphic phases. The mesophases were determined mainly by their microscopic textures and identified by the racemic modification. The results show that most of these compounds displayed frustrated phases BP, TGBA* and TGBC*, and the N*phase. Moreover, the thermal stability of the frustrated phases is significantly affected by the length of the alkyl chain in both achiral and chiral groups of the compounds. The spontaneous polarization in the TGBC* phase of compounds nMPN10B in a surface‐stabilized geometry was measured, giving P s values of about 20u2009nCu2009cm−2.

Fast-response liquid crystal display by the VA-IPS display mode with nematic liquid crystal and polymer networks

To improve electrooptical characteristics of the vertical aligned (VA) liquid crystal displays (LCDs), the monomer material and in-plane switching (IPS) field produced by interdigital electrodes are employed in LC cells. The fast switching response and well optical transmittance of the VA-IPS display mode are successfully achieved by mixing the nematic LC with polymer networks, attributed to the surface anchoring, and the molecular orientation of the LC cell will be further governed, especially under the greater applied voltage. Furthermore, the high concentration doping of the monomer can effectively improve the response behavior, but it also results in the transmittance sacrificed due to the light scattering, and the threshold voltage (Vth) increased.

Brightness Enhancement with a Fingerprint Chiral Nematic Liquid Crystal

We demonstrate a brightness enhancement element that can be laminated to a linear polarizer for increasing the optical efficiency of a liquid crystal display device. The device structure is a chiral nematic liquid crystal (CNLC) with a fingerprint texture. For an unpolarized incident light, our experimental results show that the combination of a CNLC film and a conventional linear polarizer can achieve a transmittance of over 50%. The CNLC film increases the optical efficiency of a conventional polarizer by 21.7%. The detailed mechanism of such a CNLC-polarizer system is analyzed.

Study of Twisted Optically Compensated Bend Cell Using Patterned Alignment

We have investigated a new liquid crystal cell based on a nonchiral-doped optically compensated bend (OCB) mode. The average pretilt angle of this cell was higher than that of a conventional OCB cell; when undisturbed, the twist-to-splay energy barrier induced by topological differences remained in a twist state. We have called this twisted cell a twisted optically compensated bend (TOCB) cell. The TOCB cell does not require any warm-up time or warm-up voltage in electrical driving, and the response time of the TOCB cell was as fast as that of a conventional OCB cell. In this study, the TOCB cell was made using a polymer network pattern with high-pretilt-angle alignment, called a patterned-TOCB cell. The patterned-TOCB cell arose from the irradiation of UV light through a photomask and onto a pi cell, which was filled with nematic liquid crystal (NLC) and UV-curable polymer mixture upon a curing voltage being applied to it.

Effects of the vertically switching electric field on the photoelectric properties of polymer-stabilized blue-phase liquid crystal cells using the director model

This study uses the director model to analyze the optoelectronic properties of polymer-stabilized blue-phase liquid crystal (PS-BPLC). The director model revealed a linear relationship of refractive index change and the cosine squared of the angle between the LCs and the direction of the electric field. Moreover, we employed simulations based on the Kerr effect and compared the results with those of the director model. The simulation results also show high consistency with real circumstances. Consequently, it can be of great help to design BPLC displays that can be applied to adopting better strategies for developing next-generation LCD devices.

Effects of cell gap on the optoelectronic properties of pure blue-phase liquid crystal devices: estimating the Kerr constant

In this study, the Kerr constant of pure blue-phase liquid crystal (BPLC) without polymer doping at room temperature and the optoelectronic properties dependent on the cell thickness are explored. The relation between the phase and the voltage in oblique incident light was measured via a reasonable vertical electric field for different thicknesses of BPLC cells. It was found that the Kerr constant formula can be amended with the functions related to the cell gap. This study demonstrates a method to estimate the Kerr constant, especially for cells within a small electrical field, which will benefit optoelectronic applications.