P-169: Photoaligned Bistable FLC Displays with Birefringent Color Switching

In this paper, color switching bistable ferroelectric liquid crystal (FLC) displays have been studied. Memorizable colors were obtained. The spectra, chromaticity and viewing characteristics of the displays were studied in simulation. Using results of the simulations we fabricated prototypes of Black&Green, Black&Yellow, Blue&Yellow, and Green&Pink FLC displays. 1. Introduction Recently, there is much effort to develop the low power consumption displays such as portable devices, smart card applications, information boards etc. In such cases, bistable liquid crystal displays (LCDs) become an excellent candidate owing to their superior characteristics such as light weight, low power consumption and small size [1]. Among the developed bistable LCD technologies , FLC displays are a good choice for the demands mentioned above since they own very fast response times at µs order, high contrast ratio and wide viewing angles [2]. In the traditional alignment process for FLC displays, the rubbing technique is not suitable due to the high sensitivity of FLC to mechanical shocks. Thus, our group exploits photoalignment technology to align the FLC, which enables us to avoid the mechanical brushing during the alignment process. By using this technique, our group reported recently a FLC display with remarkable bistability, wide viewing angle, unlimited memorized grayscale by forming micro-domains [3], extremely fast response time and very high contrast ratio [2]. In low power consumption devices, thin film transistor (TFT) technology is not widely used due to its relatively high power consumption and high cost. In this context, passively addressed chromatic bistable displays become more attractive and perspective in many applications. Since monochromatic displays can satisfy most of requirements of low power devices, the application of passive monochromatic bistable display can further reduce the cost of display part and provide better optical performance. To obtain an FLC display with desirable colors, optical properties of FLC cell placed between a pair of polarizers should be studied. It is known that visual characteristics of FLC displays such as transmittance, contrast ratio and color significantly depend on display structure and configuration parameters like the optical retardation of the liquid crystal layer, the cone angle of molecules, orientations of the polarizers and the retardation film, if it is included. In this paper, we theoretically analyze the display structure and the configuration parameters for monochromatic and dichromatic FLC displays. We focus on four regimes of the color switching: Black to Yellow, Black to Green, Blue to Yellow and Green to Pink. …