We report a full color 1/4 VGA reflective cholesteric display with 4096 colors. The display can deliver a brightness approaching 40 percent reflected luminance, far exceeding all other reflective technologies. With its zero voltage bistability, images can be stored for days and months without ny power consumption. This property can significantly extend the battery life. The capability of displaying full color complex graphics and images is a must in order to establish a market position in this multimedia age. Color is achieved by stacking RGB cells. The top layer is blue with right chirality, the middle layer is green with left chirality, and the bottom layer is red with right chirality. The choice of opposite chirality prevents the loss in the green and red spectra from the blue layer on the top. We also adjusted the thickness of each layer to achieve color balance. We implement gray scale in each layer with pulse width modulation. This modulation method is the best choice consideration of lower driver cost, simpler structure with fewer cross talk problems. Various drive schemes and modulation methods will be discussed in the conference.
Bistable reflective cholesteric liquid crystal displays (Ch- LCDs) can be modified for compatibility with various classes of NVGs (Night Vision Goggles). Stacking near-infrared reflecting displays and visible reflecting displays can produce a novel dual use display module. Due to the optical clarity of the visible display in NVIS mode, the two displays are stacked on top of each other without any visual compromise. This module has high reflectivity and contrast in both the visible, and NVIS cases. The display is also bistable, enabling a low power device. This paper describes variations in this configuration including a single cholesteric layer for both viewing conditions. Various methods of contrast optimization, and multiple color capability are also discussed. Military applications of this unique display device for cockpits and handheld devices with night vision requirements are discussed.
The first monochrome, high resolution reflective 1/8 VGA liquid crystal displays have been built using various plastic substrates for body mounted and hand held applications. These displays have a contrast ratio of over 10:1 with a wide viewing angle. The reflectivity is about 40 percent and the frame update time is less than 2 seconds.
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