Reflective Liquid Crystal Research Articles

Reflective Dual Mode Liquid Crystal Display with Dynamic Mode Utilizing the Transition Behavior between the Two Stable States of Its Memory Mode

In this study, we have proposed a dual-mode liquid crystal display (D-LCD) that can display both the memory and dynamic modes in one cell. The two stable states of the memory mode use splay and -π-twist states. The operation of the dynamic mode is realized by the transition behavior between the two stable states of its memory mode. For a green display, we have also proposed a reflective D-LCD with an optically compensated structure. We found that both the memory and dynamic modes have contrast ratios (CRs) of 30:1 by a good wavelength dispersion of dark state.

Cholesteric Liquid Crystal Display With Wide Viewing Angle Based on Multi-Domain Phase-Separated Composite Films

A reflective cholesterol liquid crystal (CLC) display with a wide viewing angle is demonstrated using the phase-separated composite film (PSCOF) method. The PSCOF-based CLC is formed by periodic and gradient UV illumination, slow polymerization and phase separation of the LC and prepolymer mixture. The helical axis of CLC is aligned normal to the protrusion of the PSCOF structure, and the multi-domain CLC structure can provides a wide viewing angle and low color shift. The conformation of PSCOF was also verified by AFM and SEM. The multi-domain PSCOF-based CLC display is simple to fabricate and suitable for use in a low-temperature flexible plastic process.

Low Power 6.0-Inch Extended Graphics Array Reflective Liquid Crystal Display using Indium Gallium Zinc Oxide Semiconductor with Electronic Paper Function

We focused on the ultra-low leakage current of indium gallium zinc oxide (IGZO) field-effect transistors (FETs). The power consumption of an liquid crystal display (LCD) panel can be markedly reduced by significantly lowering frame frequency, i.e., stopping unnecessary data rewrites at the time of displaying still images. We successfully fabricated a 6.0-in. extended graphics array (XGA) reflective liquid crystal display (RLCD) panel integrally including a data selection demultiplexer and a scan driver and capable of displaying still images at 1/180 fps. Thus, the panel is suitable for electronic paper displays.

6.0-Inch Extended Graphics Array Reflective Liquid Crystal Display Using Oxide Semiconductor Thin Film Transistors for Electronic Paper Display

We focused on the off-state current (Ioff) of oxide semiconductor thin film transistors (TFT) (In–Ga–Zn-oxide TFTs), which is lower than that of amorphous silicon TFTs and successfully made a prototype of a 6.0-in. extended graphics array (XGA) reflective liquid crystal display (RLCD) panel integrally including a data selection demultiplexer and a scan driver and capable of displaying still images at 1/180 fps. When still images are displayed, the frame frequency can be set low. This means that the frequency of rewrites of image data is markedly reduced. This leads to the reduction in the power consumption of an LCD panel. Our panel can solve the problems of electronic paper displays: high drive voltage and difficulty of displaying moving images. Thus, our panel is suitable for electronic paper displays.

High Speed Resolution Enhancement by Optical Pupil Function Modulating System

Superresolution fluorescent microscopy (nanoscopy) offers unprecedented resolution of biological structures by overcoming the fundamental diffraction limit of light. There are several superresolution technologies like stimulated emission depletion (STED), structured illumination microscopy (SIM), stochastic optical reconstruction microscopy (STORM) and fluorescence photoactivation localization (FPALM) all show promise as they offer subdiffraction limit optical resolution. The further challenge in superresolution is the improvements of the temporal resolution, because the temporal resolutions of the above four methods are too low to pursue the movements of proteins at ms timescales. However, it looks so difficult because FPALM and STORM are based on single molecular detection and stochastic photoswitching while STED and SIM require laser illumination scanning. Here, we constructed a microscopic system that can voluntarily modulate optical transmission of the pupil function by placing a reflective liquid crystal micro mirror array (LCMM) onto the Fourier plane that alters the point spread function (PSF) shape. It has been reported that the diffraction limit was overcome by subtracting the normal PSF from the low-pass filtered PSF (∗). Our present system can obtain a subtracted image of superresolve-masked image and the low-pass filtered image within one frame of a camera. We achieved 2 ms temporal resolution at 120 nm spatial resolution without any special probes and scanning systems. Furthermore, because the present technique is compatible with fluorescent probes that lack polarization or coherency, we can apply it to various biological investigations. In this meeting, we show basic principles and constructions of our present nanoscopy, and demonstrate the potentials of it for live cell imaging both on the membrane and intracellular, and for single particle tracking.(∗) Heintzmann R, Sarafis V, Munroe P, Nailon J, Hanley QS, Jovin TM., Micron. 34,293-300 (2003).

New Developments in Full Color Flexible Reflective Cholesteric Liquid Crystal Displays

We present recent developments in full color bistable reflective cholesteric liquid crystal displays on flexible substrates. The approaches include stacking of three reflective layers (red, green and blue) on top of each other or a spatial separation (area sharing approach) of reflective layers from each other within one layer. Stacking is possible due to selective reflection properties of cholesteric layers. Each layer of the display can be addressed independently to vary the reflectance of each color yielding many possible colors. The advantage of the approach is that the display is producing a full brightness of each primary color. The advantage of the area sharing approach is its superior contrast and simplicity, as only one layer is required; that can significantly reduce the cost of the device. The developed cholesteric materials for full color displays can be easily laminated between the flexible substrates, and, possible, coated or printed. We are currently successfully implementing the developed technologies enabling low cost, low power, low weight and rugged display applications, such as writing tablets, electronic skins and electronic books.

Formation of self-assembled periodic grooves via thermal drawing lithography for alignment layers in liquid crystal devices

In this paper, we present a fascinating soft lithography—thermal drawing lithography (TDL)—to fabricate self-assembled periodic grooves. The pre-patterned silicon mold with protruding grating is placed on a bottom substrate spin-casted with a polymer film. According to the image charge-induced electrohydrodynamic-instability (ICE) model, the attractive electrostatic force between upper and lower substrates would cause a heat-induced melting polymer film to rise and form a positive replica grating pattern similar to the upper mold. In our work, we confirm that thermal drawing lithography could be achieved without an external electric field and fit the ICE model with experimental results. We have utilized these self-assembled grooves to align liquid crystal molecules for both reflective and transmissive liquid crystal (LC) cells. As well as for LC displays, this straightforward approach could be utilized for fabricating submicrostructures and possibly nanostructures.

High slope efficiency liquid crystal lasers

In this letter, we demonstrate high slope efficiency laser emission from reflective liquid crystal laser devices with a silicon backplane. Three different cell architectures were fabricated and each resulting laser device was then characterized in terms of the excitation threshold and the slope efficiency when optically excited close to the absorption maximum of the gain medium (pyrromethene 597). By combining a high gain medium with double-pass geometry, as well as the optimum cell thickness, the results demonstrate that it is possible to reduce thresholds by 25% and achieve slope efficiencies as high as 60%.

Reflective dual-mode liquid crystal display switchable between dynamic and memory modes

This study proposes a reflective dual-mode liquid crystal display (RD-LCD) that can be operated in memory mode or dynamic mode according to the image contents. The proposed RD-LCD needs three states to represent dark and bright states, while a general reflective liquid crystal display has two states. Nevertheless, a compensation structure that can obtain high contrast ratios in both dynamic and memory modes has been optimized. The proposed RD-LCD can be operated without internal backlighting, thus making it a candidate for real green display.

White light reconstruction of image plane digital holograms

A real-time system is developed that employs a CCD sensor for recording and a reflective high-resolution liquid crystal display for reconstructing of image plane digital holograms. Two types of light sources, namely, the coherent (laser) and white light (LED) are used for optical reconstructions of static and dynamic object wave fronts. As expected, white light reconstructions exhibit improved properties compared to the corresponding monochrome reconstructions. However, these improvements become substantial in cases in which digital holograms are preprocessed by applying the common algebraic operations such as subtraction.

P‐113: Color Management for Multiple‐Primary Flexible Cholesteric‐LCD

AbstractThe reflective cholesteric liquid crystal display suffers from voltage‐induced color shift and viewing angle‐dependent color shift. In this paper, three solutions are presented to overcome these problems. First, four types of cholesteric liquid crystals were prepared and characterized to find the best mixture with the lowest voltage‐induced color shift and reflectance reduction. Secondly, 5‐primary (red, yellow, green, cyan and blue) cholesteric liquid crystals were prepared such that the color gamut and reflectance were enhanced. Finally, the viewing angle‐dependent color shift was characterized and then compensated by adjusting their chromaticity by using red/green/blue LED light sources.

P‐195L: Late‐News Poster: Ultra‐Low Drive Voltage Bistable Reflective Liquid Crystal Display in Flexible Format

AbstractThis paper reports on the development of an ultra‐low drive voltage bistable reflective liquid crystal display. As compared to the state‐of‐the‐art technologies that require ≥25V drive voltage, the new display can be driven under 4V.

One-unit system to reconstruct a 3-D movie at a video-rate via electroholography

We have developed a one-unit system, including creating and displaying a hologram for real-time reproduction of a three-dimensional image via electroholography. We have constructed this one-unit system by connecting a special-purpose computer for holography and a special display board with a reflective liquid crystal display as a spatial light modulator. Using this one-unit system, we succeeded in reproducing a three-dimensional image composed of 10,000 points at a speed of 30 frames per second, which is the video rate in NTSC format. In addition, we were able to control a three-dimensional image in real-time using our system.

High efficiency reflective liquid crystal polarization gratings

We experimentally demonstrate a reflective-mode liquid crystal polarization grating with high reflectance, small grating period, and subms switching times. This switchable optical element can diffract ∼100% into a single order, have highly polarization-sensitive first orders, and have a polarization-insensitive zero order. Here we introduce an absorbing layer that overcomes the reflection of the (ultraviolet) holographic beams, which otherwise prevents high quality fabrication. At a grating period of 2.1 μm, we report 98% diffraction efficiency, 90% reflectance, ∼600:1 contrast-ratio, and ∼3000:1 polarization contrast. These elements can therefore be configured as polarization-independent modulators or switchable polarizing beam splitters, for use in telecommunications, displays, spatial-light modulators, and polarimetry.

Advanced wide viewing angle technology in liquid crystal display modes

This paper reviews the advanced optical configurations for in-plane switching (IPS) and vertical alignment (VA) liquid crystal (LC) cells with wide viewing angle in a visible wavelength range. Optical compensation and optimisation to eliminate off-axis light leakage in the dark state is performed on a Poincaré sphere using the trigonometric and the Muller matrix method. By optimising the wavelength dispersion of used optical retardation films, we could achieve wide-view characteristics for both the IPS and VA LC cells. In addition, we show the advanced wide-view technology for a reflective LC mode.

Black-white Reflective Liquid Crystal Display Prepared with Two Color Reflective Layers

Black-white reflective cholesteric liquid crystal display was prepared with two color liquid crystal layers, the combination of yellow color liquid crystal and blue color liquid crystal. The rubbing of cholesteric liquid crystal panel affects the brightness and color spectrum due to increase the planar domain texture. The CIE chromaticity coordinate of white is (0.31, 0.31).

Fabrication of antireflection structures on TCO film for reflective liquid crystal display

The cholesteric liquid crystals display (ChLCD) is one kind of reflective liquid crystal display, the antireflective layer on its transparent conduction oxides (TCO) film is needed for good contrast and color performance. In this study, the finite difference time domain (FDTD) simulation and nanoimprinting fabrication of AR structures on the TCO film are developed. Finally, the reflectance of AR structures on TCO film is just half of the original film, and this result is useful for the reflective ChLCD product commercialized in the future.

Blue-white Reflective Cholesteric Liquid Crystal Displays by Single Liquid Crystal Layer

Blue-white reflective cholesteric liquid crystal display was prepared by a unique method of single liquid crystal layer, the combination of yellow color liquid crystal and blue color backplane. The dopant and host combination of chlolesteric liquid crystal affects the color spectrum. The CIE chromaticity coordinates of blue and white are (0.10, 0.16) and (0.29, 0.30), respectively. The relatively low driving voltages of 32 V for blue-white display are obtained.

Wavefront correction based on a reflective liquid crystal wavefront sensor

A novel wavefront sensor (WFS) based on liquid crystal on silicon (LCOS) is demonstrated. The design of the liquid crystal microlens array with LCOS is given in detail. To save the energy of the incident light, an optimized optical design of the WFS is also considered. In addition, closed loop wavefront correction experiments were conducted based on the designed LC WFS with square and hexagonal microlens arrays, respectively. In the experiment, the corrector was a tilt and tip mirror. The results indicated that the Zernike coefficients of the tilt and tip were decreased to less than 0.1λ(633 nm) after correction.

Assessment of Mobile Technologies for Displaying Medical Images

We compared the characteristics of state-of-the-art mobile display systems based on reflective and transmissive liquid crystal displays (LCDs) and an organic light-emitting display with respect to physical characterization metrics and observer studies. Physical performance factors provided information on the differences among display technologies. Observer studies resulted in different system ranking between the task-based performance and user-preference approaches. The results of the physical characterization and preference study showed that the reflective LCD ranked lower. We also found that ambient illumination played a lesser role than previously seen in large-format workstation displays. The methodology developed in this study provides an initial insight into the comparison of alternative technologies for display of diagnostic images in small portable devices.