Stabilization of Bend Alignment Using Optical Polymerization of UV Curable Liquid Crystalline Monomers

Abstract

Director profiles and electrooptical properties in polymer-stabilized π cells used in optically compensated bend (OCB) liquid crystal displays (LCDs) are theoretically investigated by introducing an additional term which expresses the effect of polymer stabilization on the free energy density. The conditions required to stabilize the bend alignment definitively have been theoretically clarified and experimentally confirmed. As a result, the bend alignment is successfully stabilized even if the twist state is more stable than the bend state before the application of polymer-stabilization treatment.

Multi-Dimensional Liquid Crystal Alignment Effect of Polymer Wall on Vertically Aligned Liquid Crystal Cell

“…[5][6][7][8] By the interaction between the LCs and a polymer wall, the LC molecules are re-oriented near the wall, and the total elastic free energy of the LC cell is changed. 9) As a result, the MDA effect of the polymer wall is important in stabilizing the specified LC states in the pi cell, 5,6) or bistable TN LC cell. 7,8) From these reports, it is expected that the MDA effect will also affect the electrooptic characteristics of LCDs.…”

Transient Response Characteristics of Polymer Stabilized Bend Alignment State of Nematic Liquid Crystal in Pi-Cell

“…In our previous paper, 9,11) we introduced an additional term F stab as shown in eq. ( 1), which represents the contribution of polymer stabilization to the free energy density F of the liquid crystal bulk, to calculate theoretically the behaviors of polymer-stabilized LC cells.…”

“…8) In our previous paper, we reported that the effect of polymer stabilization on the static characteristics of polymer stabilized bend (PSB) cell can be well explained in terms of the polymer stabilization coefficient A stab , 10) which is introduced in the additional term to the free energy density. 11) However, in our recent experiments, we knew that the transient response characteristics cannt be explained only in terms of the effect of A stab . Concretely speaking, although we obtained experimental results in which both the rise and decay times in the transient responses of the bend cell are deteriorated by the polymer stabilization treatment, the theoretically calculated results that are based on the elastic hydrodynamics theory in which the polymer stabilization term was taken into account are inconsistent with those of experimental results.…”

Analysis of electro‐optical properties of polymer‐stabilized OCB and the application to TFT‐LCDs

“…13 In OCB mode, the stability of the initial bend alignment has been recently studied using a simulation considering various conditions of weak-anchoring strength. 14 However, the dependence on the electro-optical properties such as retardationvoltage (R-V) dependence was not discussed in previous analyses, possibly because the influence of the process parameters on the resulting properties is complicated due to various phenomena such as the change in the microscopic dispersion of the monomer during the cure process.…”