Single-polarizer reflective twisted nematics

Abstract— A general expression for the reflectance of a single-polariser twisted-nematic device is given. From this, solutions of liquid-crystal parameters that will convert linear-to-circular (L-C) and linear-to-linear (L-L) polarizations are derived. A comparison of the field behavior for some normally black and normally white devices made from the lower Δnd/λ solutions of the L-C and L-L are presented. The effect of doping on normally white devices is considered.     

A 320-dpi 4-in. reflective stacked crossed guest-host display

Abstract— We describe a 320-dpi, 4-in. diagonal a-Si:H TFT-driven monochrome reflective display panel, in which two guest-host nematic liquid-crystal layers separated by a thin polymer film are orthogonally aligned to realize high reflectivity and high contrast ratio simultaneously. The TFT manufacturer used a four-mask process with a high aperture ratio. The structure and characteristics of the panel are presented.     

Axially symmetric aligned microcell (ASM) mode: Electro-optical characteristics of new display mode with excellent wide viewing angle

Abstract— The new LCD display mode (ASM mode) which has the axially symmetric orientation of liquid crystal molecules and the micro-cell structure corresponding to each pixel is described in this paper. The electro-optic characteristics of this mode afford high contrast (CR ≥ 200, at normal direction) and the wide viewing angle characteristics without contrast inversion (±60° in both up-down and left-right directions).     

A model of the fast-switching polymer-stabilized in-plane-switching configuration

Abstract— A significant improvement in the dynamic response times of IPS-mode LCDs is achieved through polymer stabilization. The improvement is a result of the introduction of a low-density stabilizing polymer network that causes the LC director to favor the zero-field orientation. We report on the effect of the polymer concentration and network orientation on the electro-optic performance of our novel polymer-stabilized IPS-mode cells. Furthermore, we present a detailed model derived using elastic continuum theory to explain our observations.     

Development of “Advanced TFT‐LCD” with good legibility under any ambient light intensity

A new LCD referred to as an “Advanced TFT‐LCD” has been developed. It consists of both transmissive and reflective electrodes in every pixel. Its subjective legibility and characteristics, such as contrast ratio, color gamut, and luminance, have been investigated at several ambient illumination intensities. As a result, it was confirmed that Advanced TFT‐LCDs offer better legibility than transmissive LCDs under any ambient illumination intensity.     

TFT-addressed full-color reflective-type display using mixed-mode twisted-nematic LCD

Abstract— A high-performance reflective-type TFT-LCD with full-color and video-rate capabilities has been developed. This display utilizes a single-polarizer geometry associated with a mixed-mode twisted-nematic (MTN) effect. The twist angle of the liquid-crystal cell is optimized by evaluating the light efficiency, contrast ratio, chromaticity, and gray-shading reproducibility with respect to the variation of cell-gap uniformity. Attractive features of this display such as low driving voltage, fast response, wide viewing angle, rich gray scales with superior color reproducibility, and clear image with no parallax are demonstrated.     

Ultra-low-power STN-LCDs using multiple-line addressing for mobile telecommunication applications

Abstract— Ultra-low-power-consumption STN-LCDs with high display quality driven by MLA (multiple line addressing) technique have been developed. They realized 3-V driving voltage for 1/33 duty ratio and 5-V driving voltage for 1/65 duty ratio. These are most suitable for mobile telecommunication applications.     

Alignment layers for cholesteric displays on glass and plastic substrates

Abstract— The optical performance of surface-stabilized cholesteric liquid-crystal displays (SCT-LCDs) has been optimized by using obliquely sputtered SiO₂ as the alignment layer. A comparison with polyimides used up to now showed an improvement in the contrast ratio by a factor of 2 for glass displays. A second advantage of this material is the absence of high temperatures during the manufacturing process. Therefore, it is possible to use obliquely sputtered SiO₂ for the preparation of plastic display prototypes. We have realized a 6-in. VGA display with approximately 130 dpi. This is the largest cholesteric display with the highest resolution fabricated on plastic substrates to date.     

Displays for hand-held portable electronic products

Abstract— The hand-held electronic-product field includes most telecommunication, palm computing, and navigation products, making this a large market for smaller displays (typically from 1 to 4 in. on the diagonal). Historically, this market has demanded displays with low power and cost, rather than high image quality, as evidenced by the historical dominance of monochrome TN and STN displays. However, within these constraints there is a strong trend toward larger displays capable of higher information content, including a migration toward low-power color solutions.     

Dichroic dye‐doped bistable polymer‐stabilized cholesteric‐texture light valve

Abstract— We have carried out systematic investigations on a non‐polar dichroic‐dye‐doped bistable polymer‐stabilized cholesteric‐texture (PSCT) normal‐mode light modulator. The addition of a small amount of dichroic dye (～1.0 wt.%) helps considerably to reduce the transmittance in the OFF state and therefore gives rise to an overall improvement in contrast ratio. Furthermore, collection‐angle dependence of the contrast ratio is reduced by the addition of the dichroic dye.     

A 53° twisted-nematic cell for a color reflective liquid-crystal display

Abstract— A 53° twisted-nematic cell for a color reflective liquid-crystal display was developed. It has a mirror electrode inside the panel on the TFT substrate, a twisted-nematic alignment structure, an RGB color filter, a single polarizer, and a light-control film covering the panel. Its advantages include gray-scale capability, low driving voltage, and a wide viewing angle. We discuss the Δn?d, the twist angle, and the front-light control film.     

Numerical approach to the physical behavior of fluorinated nematic liquid crystals

Abstract— A numerical approach to the physical behavior of fluorinated liquid crystals has been investigated. The molecular parameters, such as dipole moment and polarizability were calculated using a semiempirical molecular orbital (MO) method. Using these molecular parameters and the Maier-Meier theory, the temperature dependence of the dielectric anisotropy divided by the order parameter (Δ?/S) has been estimated. In addition, taking the temperature dependence of the order parameter S into account, the temperature dependence of the dielectric anisotropy Δ? has been estimated. The calculated results are in good agreement with experimental results.     

Multiple color high resolution reflective cholesteric liquid crystal displays

Abstract— 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.     

Recent studies on multiplex driving of BTN‐LCDs

The main parameters of driving waveforms for BTN‐LCDs were investigated, and the effects on the display operation and dependence on temperature were measured. Based on experimental results, we have determined the most useful driving waveforms for practical operation, and also proposed a new driving method.     

Flexible and bistable FLC and cholesteric displays on plastic substrates for mobile applications and smart cards

Abstract— New smart-card applications like purse cards, etc. require an integrated display which allows the card-holder to read information which is stored on the IC of the card. On the other hand, the integration of a display into a plastic card requires some very specific features like flexibility and pressure stability, low-voltage CMOS-addressing, memory capability, and, of course, a reflective mode since no backlight is available. In this paper, two bistable reflective LCD solutions using ferroelectric and cholesteric LCs are discussed and very promising prototype results are presented. Pressure and bending tests as well as contrast measurements are compared in order to show the potential of meeting the requirements for use in smart cards.     

Reflective and transflective color LCDs with double polarizers

Abstract— Reflective color LCDs with double polarizers have been developed by means of optimizing liquid-crystal modes, aperture ratio, color-filter properties, thickness of the glass substrate, polarizers, reflectors, etc. These LCDs are sufficiently bright, display many colors, have good hue, and are light weight with thin outline and low power consumption. Since they have double polarizers, a very high contrast ratio can be obtained. Therefore, they are superior in text character displays. Moreover, transflective color LCDs have been developed without visible deterioration of reflective displays by adoption of a reflective polarizer and backlight system in place of a lower polarizer and reflector.     

A reflective tri-layered guest-host color TFT-LCD

Abstract— We have developed a new reflective tri-layer color TFT-LCD with CMY guest-host LC materials. Optical improvements and optimization have resulted in high reflectance and good color image. We have shown that the tri-layer structure has high feasibility for bright color LCDs.     

Demonstration of the waveguide-based LCD

Abstract— We demonstrate a waveguide-based liquid-crystal display. Instead of using polarizers to control light intensity, high optical efficiency is obtained by using a liquid crystal to switch light out of a waveguide. Wide viewing angle is obtained by using a scattering screen.     

Low‐power‐consumption TFT‐LCD with dynamic memory embedded in the pixels

A low‐power‐consumption thin‐film‐transistor liquid‐crystal display (TFT‐LCD) with dynamic memory cells embedded in each pixel using low‐temperature poly‐Si technology has been developed. By holding data in the memory, the operating rate of the data driver can be dramatically reduced to 4 Hz. Eight levels of gray scale with low power consumption can be achieved by using the area‐ratio gray‐scale method. This TFT‐LCD can be used for displaying fine still images, with low power consumption.     

Electro-optical properties of a twisted hybrid aligned nematic mode for reflective liquid crystal displays

Abstract— A twisted hybrid aligned (THA) mode is proposed for reflective liquid-crystal displays. In the reflective configuration, a single polarizer and a reflective electrode are used to achieve electrooptical switching between the black and white states in the THA mode of a chiral nematic liquid crystal. Numerical simulations are performed to optimize the cell parameters such as the cell thickness and the amount of the twist in the hybrid geometry. The reflective THA mode is found to give wider viewing and faster response characteristics than a twisted nematic one. The role of an optical retardation film on device performance of such a reflective THA cell is also discussed.