Reduced operating voltage and grey-to-grey response time in a vertically aligned liquid crystal display using a mixture of two polyimide alignment materials

Abstract

We proposed a method to reduce the operating voltage and the grey-to-grey switching time of a vertically aligned liquid crystal display using a mixture of planar and vertical polyimide alignment materials. The surface anchoring energy of the two-polyimide mixture was smaller than that of the pure vertical polyimide and consequently, liquid crystal molecules were easily switched to a planar state with an electric field, resulting in a greater maximum retardation than that of the pure polyimide at the same applied voltage. Rising time was also significantly reduced due to the suppressed optical bouncing effect in the mixed planar polyimide, and the decaying time showed negligible change. With the proposed approach, we can reduce the cell gap to obtain half-wave retardation allowing for faster response time while keeping a low operating voltage.

Simulation and fabrication of a fast fringe‐field switching liquid crystal with enhanced surface anchoring enabled by controlled polymer topology

“…However, for a fast response cell, the high γ 1 effect should be reduced. The τ on is proportional to the γ 1 (∝ S )/Δ ε (∝ S ) and 1/( V driving − V th ) 2 , the increased γ 1 effect can be reduced by increasing γε and can be smoothed out by a higher driving voltage applied to the cell . Therefore, the 3 wt.% polymer cell shows largest difference between V Tmax and V th compared with others, as shown in Fig.…”

“…For an FFS cell with finite surface anchoring, the dependence of threshold voltage on anchoring energy is described by Eq. where E th is the threshold electric field, l is the gap between the electrode stripes, d is the cell gap, W is the anchoring energy, and b is the extrapolation length.…”

Photopolymerization of Reactive Amphiphiles: Automatic and Robust Vertical Alignment Layers of Liquid Crystals with a Strong Surface Anchoring Energy

“…As described in the Experimental Section, the fitted slope of the graph corresponds to 2 K 33 / Wd. By substituting the bend elastic constant of NLC ( K 33 ) and the cell gap ( d ), the W of the alignment layer can be obtained. − The W value in the LC test cell with 0.4 wt % Ita3C 12 increases from 9.071 × 10 –5 to 1.404 × 10 –4 J/m 2 during the polymer-stabilization process. The increase of W is presumably originated from the increased hardness of the surface alignment layer and the growth of nanosized protrusions during the polymer-stabilization process.…”

P‐95: Anchoring Energy Enhancement and Pre‐tilt Angle Control of Liquid Crystal Alignment on Polymerized Surfaces

“…The surface extrapolation length b =K/W is equal to zero under infinite surface anchoring, where K and W is the elastic constant and surface anchoring energy, respectively. In fact, the anchoring energy of a VA LC cell is finite and the modified Vth is given by [10,11] ( 1) where K 33 is the bend elastic constant of LC, ∆ε is the dielectric anisotropy. As the anchoring energy increases, the extrapolation length is reduced, which results in the increase of threshold voltage as indicated in the figure.…”