Bistable Cholesteric Liquid Crystal Films with Excellent Electro-Optical Performance and Spacing Stability for Reflective Displays

Abstract

A bistable cholesteric liquid crystal display offers the Bragg selective reflection over the incidence of light to address various needs in energy conservation, long image storage time, and no backlight; yet, most of the existing technologies still suffer from unstable cell spacing in the curved state. In this work, a bistable cholesteric liquid crystal film with polymer spacer columns for flexible displays was prepared by stepwise UV light polymerization. By investigating the effects of cross-linking agent concentration and liquid crystal content, a formulation composition with optimal electro-optical performance was determined. Then, the influences of different process conditions for mask polymerization on the morphologies of polymer spacer columns and the electro-optical performance were systematically investigated. The results show that films with polymer spacer columns exhibit better electro-optical performance and spacing stability compared to conventional bistable liquid crystal films. Therefore, the bistable liquid crystal films reported in this paper show broad application prospects, especially in flexible displays.

A hyper-reflective cholesteric liquid crystal polymer network with double layers

“…During the last few decades, the polymer-stabilized CLC (PSCLC) and the CLC polymer network (CLCN) films with singlehandedness have been widely studied for their applications as polarizers, 9,10 mirrors, 11 filters, [12][13][14] and sensors [15][16][17][18] and for anticounterfeiting 19 and displays. [20][21][22] Theoretically, the reflectance of the single-handed PSCLC films is not higher than 50%. [23][24][25] For the preparation of the PSCLC and CLCN films with hyper-reflectance, several approaches have been developed.…”

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films

“…When the mixed mixture was poured into the prepared LC cell, it was in a stable planar texture that could selectively reflect wavelengths, as shown in Figure 9a. According to Bragg's law of reflection, λ = nPsinϕ, the incident lights that satisfied the law would be reflected, while the other lights would be transmitted, and the maximum selected reflection wavelength could be obtained when the angle ϕ between the incident light and the liquid crystal surface reached 90 • [25,26]. For example, LC2 reflected the wavelengths between 480-550 nm in the planar state without fluorescent dye, and the other wavelengths, except 480-550 nm, were transmitted.…”

Research Progress of Electrically Driven Multi-Stable Cholesteric Liquid Crystals

“…The mechanical properties of the devices were significantly improved due to the support of the spacer columns. And the introduction of the polymer spacer columns also resulted in devices with more excellent contrast and driving voltage [ 85 ]. In general, the introduction of non-liquid crystalline polymer networks is the key to improving the mechanical properties of devices.…”