Xiao-Yang Huang

Transient Dielectric Study of Bistable Reflective Cholesteric Displays and Design of Rapid Drive Scheme

Transient dielectric measurement is used to study the transitions among the planar, focal conic, and homeotropic states of cholesteric liquid crystals. If the initial state is the field‐induced homeotropic state, at low bias fields, the liquid crystal transforms to the planar state in a sequence of homeotropic‐transient planar–planar; at high bias fields, the liquid crystal transforms to the focal conic state. The homeotropic‐transient planar transition is on the order of 1 ms while the homeotropic‐focal conic transition is on the order of 100 ms. Large hysteresis is observed in the transitions between the homeotropic and the focal conic state. Based on the rapid homeotropic‐transient planar transition and the hysteresis effect in the focal conic‐homeotropic transition, we have designed a drive scheme which can address bistable reflective cholesteric displays at the speed of one line per millisecond.

Multiple color high resolution reflective cholesteric liquid crystal displays

— A high-resolution multiple-color and black-on-white surface-stabilized reflective cholesteric liquid-crystal display with reflectivities as high as 40% is reported. The double-stacked 1/8-VGA, 100-dpi prototype shows four vivid colors with negligible parallax. The potential for eight colors and ultimately full color is demonstrated in a high-resolution triple-stacked prototype.

27.4: Super High Brightness Reflective Cholesteric Display

A unique way to dramatically enhance the brightness of single layer and stacked reflective cholesteric LCDs is shown. The LC aligning surfaces are treated to provide varying degrees of homogeneity while maintaining the bistability. The result is reflective displays with exceptionally high brightness approaching that of printed paper.

The transient response and dynamic drive of cholesteric liquid-crystal displays

— Transient phenomena play important roles in switching bistable reflective cholesteric liquid-crystal displays (Ch-LCDs). The transition to the transient planar state through the conic helical relaxation is discussed. The transition time is on the order of 1 ms and is utilized in the design of the dynamic drive scheme to substantially improve the drive speed of Ch-LCDs. Systematic studies of the electro-optical response under this drive scheme are presented as well as the drive-scheme implementation.

Full-color reflective cholesteric liquid crystal display

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.

Low-power cholesteric LCDs and electronic books

We discuss the state of the art of the bistable reflective cholesteric liquid crystal display technology. Numerous applications from low resolutions signs, to medium resolution instrumentation type displays, and high resolution electronic books are discussed. Different modes of the technology are discussed as being viable for the respective display applications. Special emphasis is paid to electronic book applications.

22.4: Novel Drive Techniques and Temperature Compensation Mechanisms in Reflective Cholesteric Displays

The driving techniques used for bistable reflective cholesteric displays are typically a function of application, temperature, and other material constraints. As such, new and unique driving techniques are employed continuously in order to optimize the updating methods of cholesteric displays. This paper focuses on several such techniques and related issues with these methods.

Reflective cholesteric displays: development and applications

Reflective cholesteric liquid crystal displays (Ch-LCDs) are attracting more interest because power efficient displays are needed for the rapid growing mobile computation applications. Its capability of high-resolution full color with passive matrix drive method provides the market with a very powerful alternative display technology. In this paper, we will review the history of Ch-LCDs as well as the most recent developments.

54.1: Ultra Low Power Black and White Cholesteric Display with COG and Solar Array

The first chip-on-glass polymer modified black and white reflective cholesteric display is reported. The COG module contains an integrated solar array panel for energy harvesting providing an ultra low power concept for electronic books. The module is addressed with an enhanced dynamic drive scheme to enable higher voltage operation and improved image uniformity.

Novel bistable reflective cholesteric liquid crystal display device for use with night vision goggles

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.