Bend-Mode Liquid Crystal Cells Stabilized by Aligned Polymer Walls

Abstract

We have studied ways of stabilizing the bend configuration in π-cells by forming polymer walls. This novel device with polymer walls, which makes an initial splay-bend transition unnecessary, incorporates minute structures fabricated by applying the processes of local photopolymerization-induced phase separation and electric field orientation. In fabricating the device, a mixed solution of nematic liquid crystal and an ultraviolet (UV)-curable liquid-crystalline monomer was subjected to an electric field to induce the bend transition, and UV light was illuminated on selected regions in this mixed solution to cause photopolymerization, so that minute aligned polymer walls could be selectively formed inside the device. We examined the operation of the device and found that the bend-alignment cells performed basic functions in the stable bend state, and that this state can be maintained even if the cells are set to a small pre-tilt angle, such as 1°.

Color Sequential Mobile LCDs

“…Unlike conventional homogeneous cells, in a pi-cell, the surface pre-tilt angles are in a parallel direction, as shown in Figure 5.4. There have been numerous successful efforts to develop methods that could speed up this initial 'splay to bend' transition and maintain the bend orientation even at a low voltage, such as using polymer network formation [20][21][22][23], high surface pre-tilt angle [24,25], or special driving schemes and fields with irregular electrode layouts [26,27]. As the voltage increases above the critical voltage, certain nuclei will be generated near the surface and propagate towards the bulk region to transform the alignment into a low bend state.…”

Dependence of the electrooptical properties of polymer-dispersed vertical aligned liquid crystals on the surface affinity of the liquid crystal and monomer

“…Polymer-dispersed liquid crystal (PDLC) has been widely studied for applications of flexible displays and various electro-optical components [1][2][3][4][5]. In PDLC system, the polymer matrix often results in the orientational deformation of the liquid crystal (LC) molecules near the polymer surface [6][7].…”

Dopant effects of photoreactive ZnO nanoparticles on fast response LC materials in optical compensated bend (OCB) mode liquid crystal displays

“…Therefore, splay mode suppression or reduction for response time and threshold voltage needs further investigation. Based on the prior literature, many of methods have been developed to improve the response time and stabilize the bend alignment, such as processes of chiral dopants (Huang et al, 2007) and organic reactive monomers to generate polymer walls by UV curing approaches (Kikuchi et al, 2005;Chien et al, 2002;Asakawa et al, 2007). Moreover, nano-sized dopant materials, including nanoparticles (Kobayashi et al, 2004;Kobayashi et al, 2002;Miranda, 2006;Boilot et al, 2007;Kobayashi et al, 2007) and nanotube dopants, (Huang et al, 2006) have also been used to enhance the electro-optical properties of various LCDs.…”