Reflectivity enhancement of full color tri-layer electrowetting display with polymer cholesteric liquid crystal films

Abstract

Electronic paper display has received increasing attention due to its outstanding properties of wide viewing angle, bistable state and lower energy consumption. Among various electronic paper display technologies, electrowetting e-paper (EWD) is the most promising as it can achieve full-color display by using stacked layers or RGB color filter. However, the EWD is faced with several challenges, including poor color brightness, low contrast ratio and small color gamut. To improve the performance of the EWD, we proposed a new configuration of EWD consisting of three independent PCLC reflection films based on the cholesteric liquid crystal materials. We designed and experimentally fabricated three types of reflection films, and then added the PCLC films to the tri-layered EWD device. We experimentally characterized the reflectivity and color gamut of the sample in the dark room. It is found that the experimental results and simulation results match with each other. It is demonstrated that with the PCLC films, the reflectivity is improved by 20%, while the color gamut is improved by 80%, which is sufficient for the daily display demand of E-paper. The proposed EWD device containing PCLC reflection films provide a new strategy to improve the brightness and color gamut of current EWD device, and is promising for realizing the full-color E-paper display.

Video‐Rate Switching of High‐Reflectivity Hybrid Cavities Spanning All Primary Colors

“…Another important benchmark parameter is the device lifetime, which is extremely important for commercialization but rarely mentioned in tuneable color studies. [6][7][8][9][10][11][12][13][14][15][16]18,19,21] The nanocave structure is found to significantly improve the color uniformity of the hybrid material and prolong its lifetime. Comparing the switching speeds of nanocaves structures with those having only a polymer middle layer (Figure 4b) (using in each case samples with optimal deposition cycles, Figure S8, Supporting Information), shows that even after 10 000 switches (pulse duration 30 ms), the switching speed with nanocaves is only lengthened by ≈5 ms, and retains video rate capability.…”

“…This device superimposes three dyed microfluidic layers and individually modulates the optical transmittance of each layer to generate any color. However, due to the inevitable optical absorption from each electrochromic layer, their reflectivity is only ≈10%, [ 9 ] which prevents market acceptance even after 20 years of development. In recent years, various tunable color technologies using only a single electrochromic layer have been developed.…”

Video-rate switching of high-reflectivity hybrid cavities spanning all primary colors

“…This device superimposes three dyed micro uidic layers and individually modulates the optical transmittance of each layer to generate any color. However, due to the inevitable optical absorption from each electrochromic layer, their re ectivity is only ~ 10% 9 , which prevents market acceptance even after 20 years of development. In recent years, various tunable color technologies using only a single electrochromic layer have been developed 7,10,11,12,13 .…”