| Summary: | 博士 === 國立臺北科技大學 === 光電工程系研究所 === 97 === In our studies, we have proposed three methods by experiment or simulation to solve the issues of the optically compensated bend (OCB) mode. We have developed a new liquid crystal cell based on a non-chiral-doped OCB mode. When no applied driving voltage, the twist-to-splay energy barrier induced by topological differences remained in a twist state. We have called this twisted cell a twist optically compensated bend (TOCB) cell. The TOCB cell has no splay state, so it dose not require any warm-up time or warm-up voltage in electrical driving.
In the first study, the TOCB cell was manufactured by the irradiation of UV light onto a π-cell, which filled with nematic liquid crystal (NLC) and UV-curable polymer mixture upon a curing voltage being applied to it. While the alignment layer forms a polymer network, the pretilt angle is controlled at 20-28°. Such that the energy barrier between the twist and splay states increases and the π-twist state might be stabilized.
In the second study, the TOCB cell was made using a polymer network pattern with high-pretilt-angle alignment, called a patterned-TOCB cell. The average pretilt angle of the patterned-TOCB cell was higher than that of a conventional OCB cell. The high-pretilt-angle alignment pattern can increase the energy barrier between the twist and splay states. The patterned-TOCB cell arose from the irradiation of UV light through a photomask and onto a π-cell, which was filled with NLC and UV-curable polymer mixture upon a curing voltage being applied to it. The UV-light-irradiated regions assume a high-pretilt-angle alignment, which enables the nonirradiated regions to assume the twist state. The light efficiencies of the TOCB and patterned-TOCB cells were higher than—and the response time was comparable to—that of a conventional OCB cell.
In the third study, the TOCB cell was produced by the lateral-electric-field, which can increase the energy barrier between the twist and splay states, and that generated by the rectangle-bar-electrodes at the common electrode, called a lateral-field-TOCB cell. The pretilt angle of the lateral-field-TOCB cell was as same as a conventional OCB cell. The rectangle-bar-electrodes are parallel to the rubbing direction. The lateral-electric-field can eliminate the concave (optical bounce) of T-V curve of a TOCB cell or a π-twist cell at low voltage. Thus, the light efficiency of the lateral-field-TOCB cell might be higher than that of a TOCB cell. The electro-optical characteristics of the lateral-field-TOCB cell are demonstrated by LCD Master Software.
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