Fabrication of flexible light shutter using liquid crystals with polymer structure

We fabricated a light shutter using plastic substrates for high visibility of a flexible see-through display. To achieve a flexible light shutter using liquid crystals (LC), it is essential to maintain the cell gap when the light shutter is bent. We studied methods to fabricate flexible LC light shutters using plastic substrates. We demonstrated light shutters that are initially transparent and flexible with or without polymer walls. We have elucidated that polymer walls and networks provide mechanical stability against the bending of an LC light shutter without any degradation in the electro-optic characteristics. We predict that a flexible light shutter provides not only high visibility but also mechanical stability to a flexible see-through display by positioning it at the back of a flexible see-through display panel.     

The effect of terminal chain modifications on the mesomorphic properties of 4,4′-disubstituted diphenyldiacetylenes

The typical sidewalls produced in the fabrication of protrusion electrodes are proposed to create a low voltage (4.5 V_rms) and high transmittance (93%) blue-phase liquid crystal display (BP-LCD). The tilted electrodes produce a strong horizontal electrical field that reduces the operating voltage considerably. The common problem of the ‘dead zones’ is solved by reflecting the light onto the electrodes. In order to estimate the phase retardation of the reflected light, a ray tracing simulation program for anisotropic mediums has been developed. The proposed device is more competitive than vertical field switching based BP-LCD and also, has the advantages of protruded in-plane-switching structures. These facts make this technology a potential candidate for the next generation of BP-LCDs.     

Fast switching and luminance-controlled fringe-field switching liquid crystal device for vehicle display

ABSTRACT

Liquid crystal displays (LCDs) for vehicle displays should exhibit a fast response time in wide temperature range and wide-viewing angle in horizontal and downward directions without grey-scale inversion but limited brightness in the upward direction because the display images can be reproduced in the front window glass of a vehicle, affecting driver’s front visibility. Currently, fringe-field switching (FFS) liquid crystal device is widely commercialised for high resolution and wide-viewing-angle LCD; however, it needs to improve response times and limit the display brightness in the upward direction. As a solution, we propose a homogeneously aligned liquid crystal device in which liquid crystal director does tilt as well as twist deformation in a confined area by both vertical- and fringe-electric fields, exhibiting about two times faster decay response time than that of conventional FFS mode with suppressed luminance in the upward direction. The proposed liquid crystal device can be applied to LCDs for vehicle displays.     

Optically compensated double-layer electrically controlled birefringence liquid crystal display with wide-viewing-angle cone

An electrically controlled birefringence liquid crystal display has a problem over narrow viewing angle. To solve this problem, the authors proposed a double-layer electrically controlled birefringence liquid crystal display with a wide-viewing-angle cone under an applied voltage. In this device, each liquid crystal layer compensates the variation of retardation as a function of viewing angle. However, the optical compensation occurs only when certain voltages are applied. The objective of this paper is to propose a novel film compensated double-layer electrically controlled birefringence liquid crystal display that has a wide cone of view in any state. This device is based on the concept of compensation of retardation.     

Recent Progress toward white organic light emitting diodes

An efficient and stable white organic light emitting diode (WOLED) is highly desirable in potential applications such as lighting, background light source, and full color display.A series of highly fluorescent dyes based on a dipyrazolopyridine skeleton,1,7-diphenyl-l,7-dihydrodipyrazolo[3,4-b,4′,3′-e]pyridine, were synthesized and evaluated as emitting as well as charge-transporting material in the fabrication of electroluminescent devices.Several of the blue derivatives are found to be useful as the source of blue emission in fabricating bright white-emitting devices. The choice of dopants, cathode materials, electron-transporting materials as well as the device configurations greatly affect the emission profile, efficiencies, as well as the device lifetime. The latest progress in achieving a more efficient, color stable, durable white light device will be discussed.     

A microfabricated capillary electrophoresis chip with multiple buried optical fibers and microfocusing lens for multiwavelength detection

We present a new microfluidic device utilizing multiwavelength detection for high-throughput capillary electrophoresis (CE). In general, different fluorescent dyes are only excited by light sources with appropriate wavelengths. When excited by an appropriate light source, a fluorescent dye emits specific fluorescence signals of a longer wavelength. This study designs and fabricates plastic micro-CE chips capable of performing multiple-wavelength fluorescence detection by means of multimode optic fiber pairs embedded downstream of the separation channel. For detection purposes, the fluorescence signals are enhanced by positioning microfocusing lens structures at the outlets of the excitation fibers and the inlets of the detection fibers, respectively. The proposed device is capable of detecting multiple samples labeled with different kinds of fluorescent dyes in the same channel in a single run. The experimental results demonstrate that various proteins, including bovine serum albumin and beta-casein, can be successfully injected and detected by coupling two light sources of different wavelengths to the two excitation optic fibers. Furthermore, the proposed device also provides the ability to measure the speed of the samples traveling in the microchannel. The developed multiwavelength micro-CE chip could have significant potential for the analysis of DNA and protein samples.     

Low-voltage and high-transmittance blue-phase liquid crystal display with concave electrode

A low-voltage and high-transmittance blue-phase liquid crystal display (BPLCD) with concave electrodes is proposed. We use in-plane switching electrodes on the etched substrates to generate the concave electrodes. The proposed device can generate a strong in-plane field with a large horizontal component to increase the transmittance and reduce the operating voltage. As a result, a low voltage ~9 V and reasonably high transmittance ~71.7% can be achieved. Moreover, due to the generated multi-domain structures in the etched areas, this BPLCD can obtain a symmetric and wide viewing angle and the contrast ratio of 1000:1 is obtained over 60° viewing cone.     

Low voltage and high transmittance transflective blue-phase liquid crystal display with opposite polar electrodes

A single-cell-gap transflective polymer-stabilised blue-phase liquid crystal display with opposite polar pixel electrodes on an etched substrate is proposed. In the proposed structure, the space between common electrodes is adopted as transmissive region, and the space above the common electrode is adopted as reflective region. By optimising the electrode parameters of the transmissive and reflective regions, well-matched voltage-dependent transmittance and reflectance curves can be obtained. In addition, the device has good performances of low operating voltage (~3.2 V), high optical efficiency and a wide viewing angle.     

Solid-state electroluminescent devices based on transition metal complexes

Transition metal complexes have emerged as promising candidates for applications in solid-state electroluminescent devices. These materials serve as multifunctional chromophores, into which electrons and holes can be injected, migrate and recombine to produce light emission. Their device characteristics are dominated by the presence of mobile ions that redistribute under an applied field and assist charge injection. As a result, an efficiency of 10 lm/W--among the highest efficiencies reported in a single layer electroluminescent device--was recently demonstrated. In this article we review the history of electroluminescence in transition metal complexes and discuss the issues that need to be addressed for these materials to succeed in display and lighting applications.     

Fabrication of coloured liquid crystal device using photoluminescent biomolecular chlorophyll

We fabricated a coloured liquid crystal (LC) device using photoluminescent biomolecular chlorophyll. The chlorophyll molecule, which is inexpensive because of its abundance in nature, was doped in the LCs for manufacturing the coloured LC device. We confirmed the green colour property of the LC doped with chlorophyll dye using UV-vis spectroscopy. Although the LC cell filled with 0.5 wt% chlorophyll showed good vertical alignment and fast response time, the doping of LC medium with 1.5 wt% chlorophyll resulted in imperfect vertical alignment and slowed response time due to the aggregation of chlorophyll molecules at high concentration. Furthermore, the photoluminescence (PL) characteristics of the LC doped with chlorophyll were investigated using PL spectroscopy. The coloured LC cell doped with chlorophyll dye showed emission in the red wave number region under UV light. As the LC doped with chlorophyll exhibited good colour performance, conventional colour filter layers could be avoided with the employment of the proposed coloured LC device. By controlling the light source, it is possible to apply the advanced LC device for colour switching. Moreover, a full-colour-switching LC device can be realised using various biomolecular dyes that can emit other colours.     

A Simple and Cheap Device for Colorimetric Determination of Serum Iron

A simple and cheap device for colorimetric determination of serum iron and TIBC (total iron‐binding capacity) was devised. The proposed device employs an LED as a light source and a common light dependent resistor (LDR) as a detector. This device functions on the basis of the light intensity received by LDR, connected to a digit multimeter, yielding resistance readings. The serum, standard, and blank solutions were prepared according to the kits instructions and introduced into the colorimeter with a disposable syringe. The iron content of the serum was calculated from the resistance difference of serum and standard solutions. The precision of the method was assessed with two commercially available serum‐based chemistry controls. The values obtained with the proposed device indicated that the serum iron concentrations correlated well with the values obtained with the commercial automated analyzer. The calibration graph was linear for iron concentrations up to 90 μmol/L (500 μg/dL). The proposed fabricated colorimeter is considerable cheaper, requires smaller sample volumes, and is suitable for serum iron assay.     

A newly-designed self-powered electrochromic window

By converting incident light into electric power, self-powered electrochromic window (SP-ECW) can achieve color change in electrochromic layer with no need for external voltage. In this work, a newly-designed SP-ECW is proposed for altering its color between deep blue and colorless state according to on/off state of incident light. The device consists of a working electrode with planar integration of photovoltaic (PV) and electrochromic (EC) elements on one electrode, a platinum counter electrode and a redox electrolyte comprising Br^–/Br ₃ ^– couple. A high transmittance modulation of 41% at 582 nm is obtained. Electrical energy converted from light is not only sufficient to drive the device, but also can be outputted to the external circuit.     

Transflective blue-phase liquid crystal display with polar opposite electrodes

A submillisecond response, wide view and single-cell-gap transflective (TR) display employing a blue-phase liquid crystal is proposed. The device employs polar opposite in-plane switching (IPS) electrodes. To balance the optical phase retardation between transmissive (T) and reflective (R) regions, the IPS electrodes are formed with unequal gaps in the two regions. This display exhibits reasonably high optical efficiency and well-matched voltage-dependent transmittance and reflectance curves.     

紫外光固化PDLC膜的形态及电光性能

选用紫外光固化法制备了聚合物分散液晶（ＰＤＬＣ）膜，以ＳＬＭ方法对其形态结构进行了考察，进而测试了ＰＤＬＣ的电光性能，并讨论了性能与结构的关系。     

New functional polymers for liquid crystal displays review of some recent developments

Polymeric materials play an important role in the construction and performance of liquid crystal displays. New functional polymers are developed to improve the displays on brightness, power efficiency and viewing angle performance. Polymer films with a controlled molecular structure and architecture provide new polarization optics to convert non‐polarized light into polarized light with higher efficiency than the traditional polarizers based on stretched iodine doped poly(vinyl alcohol). Other films provide a polarization compensation function to maintain an angular invariant net optical retardation of the display device and therewith a better contrast to wider viewing angles. Color generation by non‐absorbing methods is believed to improve on the display brightness. Special control of the liquid crystal alignment by photo‐sensitive orientation layers, polymer protrusions or photo‐formed polymer walls provide multiple director patterns within a single pixel to average out angular LC effects.     

Beyond OLED: Efficient Quantum Dot Light‐Emitting Diodes for Display and Lighting Application

The unique features of solution‐processed quantum dots (QDs) including emission tunability in the visible range, high‐quality saturated color and outstanding intrinsic stability in environment are highly desired in various application fields. Especially, for the preparation of wide color gamut displays, QDs with high photoluminescence quantum yield are deemed as the optimal fluorescent emitter that has been utilized in the backlight for liquid crystal display. Nevertheless, the commercialization of electrically driven self‐emissive quantum dot light‐emitting diode (QLED) display is the ultimate target due to its merits of high contrast, slim configuration and compatibility with flexible substrate. Through the great efforts devoted to material engineering and device configuration, astonishing progresses have been made in device performance, giving the QLED technology a great chance to compete with other counterparts for next‐generation displays. In this review, we retrospect the development roadmap of QLED technology and introduce the essential principles in the QLED devices. Moreover, we discuss the key factors that affect the QLED efficiency and lifetime. Finally, the advances in device architectures and pixel patterning are also summarized.     

Fabrication of a controllable anti-peeping device with a laminated structure of microlouver and polymer dispersed liquid crystals film

ABSTRACT

Display devices with the narrow viewing angle (NVA) and the wide viewing angle (WVA) characteristics can simultaneously meet the demands for privacy protection and information sharing. Herein, we propose a novel method for fabricating a controllable anti-peeping device with a laminated structure of microlouver and polymer dispersed liquid crystals (PDLCs) film, and this device can be reversibly switched between a wider viewing angle range (VAR) for the WVA mode and a narrower viewing angle range (VAR) for the NVA mode at 0 V and 8 V, respectively. Also, the VARs of the controllable anti-peeping device can be dynamically tuned by varying dimensions of the microlouver structures and applying various voltages across the PDLCs film from 0 V to 8 V. The as-fabricated device provides display devices with controllable viewing angle characteristics, which can be applied in the display field with fascinating and practical functions.     

Flat optics with cholesteric and blue phase liquid crystals

ABSTRACT

The cholesteric (Ch) phase is an ancient liquid crystal (LC) phase, with its roots dating back to the days of Friedrich Reinitzer. It is most well known for its ability to selectively reflect circularly polarised light with the same rotation handedness as the helical structure, and have found applications in polarising and display devices. Most studies to date utilising the reflective properties of ChLCs, however, have treated ChLCs as simple dielectric mirrors in which light follows the law of reflection. We have recently shown that through controlling the phase of the Ch helix, it is possible to control the phase of reflected light. Because the phase can be controlled over 0–2π, the reflected wavefront from a planar device can be designed to possess non-specular properties, such as deflection and lensing. In this paper, we aim to provide a comprehensive understanding of the phenomenon by presenting theoretical and experimental results on the dependence of the reflected light phase on the helix phase, and the effect of chiral handedness on the phenomenon. Also, we show that wavefront manipulation based on the same concept can be achieved in Ch blue phases (BPs), which are chiral LCs with three-dimensional periodicity.     

An investigation on a novel PDLC film’s fabrication and its electro-optical properties

A polymer dispersed liquid crystal (PDLC) film that has good electro-optical properties is produced by the method of polymerized-induced phase separation. Based on the application foreground, its capability parameters, such as contrast ratio, work voltage, and visual angle, are characterized for the first time by a white light but not a fixed wavelength light. The results show the PDLC film has a low work-voltage of 20 V, more than 150° visual angle, high stability, and long lifetime. The differences between plastic and glass ITO-coated substrates of PDLC films are also studied in this paper. The plastic substrate has better property and will have a wider perspective especially in the portable, tender and folded display devices. Due to adjustable properties of film by electric field, PDLC has the potential application for display device, sensor, switch, grating, and new generation analytical apparatus.     

Multifunctional semitransparent organic solar cells with excellent infrared photon rejection

Semitransparent organic solar cells(ST-OSCs) have the potentials to open promising applications that differ from those of conventional inorganic ones,such as see-through power windows with both energy generation and heat insulation functions.However,to achieve so,there remain significant challenges,especially for balancing critical parameters,such as power conversion efficiency(PCE),average visible transparency(AVT) and low energy infrared photon radiation rejection(IRR) to realize the full potentials of ST-OSCs.Herein,we demonstrate the new design of ST-OSCs through the rational integration of organic materials,transparent electrode and infrared photon reflector in one device.With the assistance of optical simulation,new ST-OSCs with precise layout exhibit state-of-art performance,with near 30% AVT and PCE of 7.3%,as well as an excellent IRR of over 93%(780-2500 nm),representing one of best multifunctional ST-OSCs with promising perspective for window application.