Patterned liquid‐crystal laser film for multi‐dimensional multi‐color emissive film technology

Abstract— A two‐dimensional array consisting of dye‐doped reflection‐mode holographic‐polymer‐dispersed liquid crystal (H‐PDLC) lasers with alternating pitch lengths is presented. These post structures each reflect at a narrow bandwidth of light. The addition of laser dye to the H‐PDLC system allows for the generation of laser emission at the edge of the reflection band, or photonic band gap. In patterning these H‐PDLC post structures, a narrow‐linewidth patterned emissive color film is realized. The potential of such films and their implication in the display industry is discussed. In creating a three‐color array, an active emissive color film could replace the backlight and color filter components within the display. Such a patterned system would possess a wide color gamut, through spatial color synthesis, formed by narrow‐linewidth lasing structures with well‐defined wavelengths of emission.     

The color properties of a reflective CMYK module using polymer‐dispersed liquid crystal (PDLC)

A reflective CMYK (cyan, magenta, yellow, and black) module using polymer‐dispersed liquid crystal (PDLC) is investigated for multi‐color reflective display. Combined with the electro‐optical properties and visible spectral reflectivity of PDLC films, the color properties of the reflective CMYK module were evaluated in terms of the Uniform Color Space‐CIE 1976 L*a*b*. It is found that the blue light reflectivity of the PDLC films is lower than green light and red light reflectivity. With the increase of the voltage applied on PDLC, the color lightness of the CMYK module generally decreases, while the color saturation increases. When the voltage changed from 0 to 70 V with a 5‐V change amplitude, modules C, M, Y, and K severally exhibit at least five, six, three, and seven colors.     

Interference and ion effects in the electro‐optical response of PDNLC films

Abstract— We have considered the interference in polymer‐dispersed nematic liquid‐crystal (PDNLC) films caused by the superposition of light beams that pass through and between the LC droplets. The relative phase retardation of the beams depends on the applied voltage, and, as a consequence, interference oscillations can occur at transmittance‐voltage curves. Typical forms of the curves for composite films with various structures are presented. Interference oscillations were revealed not only in the static electro‐optical characteristics but in the dynamic ones also. For PDLC films based on commercially available components produced without thorough purification, the combination of interference and ionic effects is observed in the dynamics of the optical response. The relaxation of transmittance due to the depolarization ionic field is presented, depending on droplet size, temperature, pulse duration, and the concentration of the ionic admixture.     

Nanoparticle‐embedded polymer‐dispersed liquid crystal for paper‐like displays

Abstract— A polymer‐dispersed liquid‐crystal (PDLC) matrix template embedded with nano/microparticles can be backfilled/infiltrated with a dye‐doped liquid crystal for a paper‐like reflective display. In this way, a desirable degree of diffusion can be realized to reduce the viewing‐angle dependency of a gain reflector and metallic glare without changing other electro‐optical properties.     

Viewing‐angle enhancement in holographic reflective displays by nanoscale holographic patterning

Abstract— This work presents a method to increase the viewing angle of holographic polymer‐dispersed liquid‐crystal (H‐PDLC) reflective displays. One of the drawbacks to H‐PDLC technology is the existence of a narrow viewing angle. We present a way to alleviate this problem by structuring the phase front of the recording beams to increase the viewing cone of the display. Analysis of the diffractive properties of these holograms shows that the macroscopic and the nanoscale morphologies both play a role in the optical properties of the films.     

Dynamic parameters of electrically controlled light scattering in helix FLC cells

Abstract— The light‐scattering structures in monomeric FLCs have been considered and a mechanism for the scattering on transient domains in the helix layers has been proposed. An optical response with a bistable characteristic of light scattering and transmission was realized at a defined electrical pulse regime and boundary conditions in electro‐optical FLC cells. The total time of the scattering switching on and switching off is less than 400 μsec at ±36 V. They are quite fast, and FLC cells are quite transparent to be used in a stack of 30–100 light‐scattering shutters for a volumetric screen of a 3‐D display.     

Properties of azo‐dye alignment layer on plastic substrates

Abstract— The alignment properties of the azo‐dye photo‐alignment material SD‐1/SDA‐2 on plastic substrates are investigated. Important liquid‐crystal cell parameters, such as azimuthal and polar anchoring energy, pretilt angle, voltage holding ratio, and the corresponding electro‐optical properties are presented. Excellent alignment with high anchoring energy can be achieved with a polarized UV dose less than 1.0 J/cm². A reflective six‐digit flexible passive‐matrix‐driven TN‐LCD for smart‐card applications showing excellent electro‐optical properties is demonstrated.     

Electro‐optical characteristics of ion‐beam‐aligned FFS‐LCDs on diamond‐like‐carbon thin film

Abstract— A fringe‐field‐switching (FFS) mode cell having LC alignment has been developed by using a non‐rubbing method, a ion‐beam‐alignment method on a‐C:H thin film, to analyze the electro‐optical characteristics of this cell. The suitable inorganic thin film for FFS‐LCDs and the alignment capabilities of nematic liquid crystal (NLC) have been studied. An excellent voltage‐transmittance (V‐T) and response‐time curve for the ion‐beam‐aligned FFS‐LCDs were observed using oblique ion‐beam exposure on DLC thin films.     

基于PDLC的可变光衰减器的研制

介绍了一种新型的低成本、小体积的的液晶可变光衰减器的设计与制作.该衰减器采用聚合物分散液晶材料,使其填充在经过耦合的带透明导电电极的两根单模光纤的间隙里,利用聚合物分散液晶在不同电场强度下引起的光的散射效应的变化,来实现对光路能量的可控连续衰减.采用体硅微细加工技术术成功地制作出了这种衰减器,并对器件进行了测试,结果表明:当传输的光波长为1550nm时,该衰减器的插入损耗为0.85dB;衰减的最大范围为0.85dB-14.21dB;驱动电压范围9V～57V.     

Application‐specific integrated filters for color‐sequential microdisplay‐based projection applications

Abstract— Application‐specific integrated filters (ASIFs), based on a unique holographic polymer‐dispersed liquid‐crystal (H‐PDLC) material system offering high efficiency, fast switching, and low switching voltage, are being developed for microdisplay‐based projection applications. The basic properties and key benefits of ASIFs in projection displays are reviewed.     

Substrate‐free cholesteric liquid‐crystal displays

Abstract— This paper demonstrates the first substrate‐free cholesteric liquid‐crystal displays. The encapsulated cholesteric displays are ultra‐thin (with a total thickness around 20 μm) and ultra‐lightweight (0.002 g/cm²). The displays exhibit unprecedented conformability, flexibility, and drapability while maintaining electro‐optical performance and mechanical integrity. All functional display layers are sequentially coated on a preparation substrate and then lifted‐off from the preparation substrate to form a free‐standing display. The display fabrication process, electro‐optical performance, and display flexibility are discussed.     

Ferroelectric liquid crystals: Excellent tool for modern displays and photonics

The ferroelectric liquid crystals, because of their fast electro‐optical response, are one of the most important classes of liquid crystals. Here, in this review, we have summarized the different electro‐optical modes for ferroelectric liquid crystals. Clark–Lagerwall effect (surface stabilized ferroelectric liquid crystal), deformed helix ferroelectric (DHF) effect, electrically suppressed helix (ESH) mode, DHF orientational Kerr effect, and ESH diffraction modes have been discussed. All of the crucial features, that is, optics, electro‐optics, dynamics, and their dependence on material parameters, operational regime, and applications, have been reviewed.     

Multistable electro‐optical modes in ferroelectric liquid crystals

Abstract— Multistable electro‐optical modes exist under certain conditions in ferroelectric liquid‐crystal (FLC) cells, which means that any light‐transmission level can be memorized after the driving voltage is switched off. The multistability is responsible for three new electro‐optical modes with different shapes of the gray‐scale curve that can be either S‐shaped (double or single dependent upon the applied‐voltage pulse sequence and boundary conditions) or V‐shaped dependent upon boundary conditions and FLC cell parameters. The origin of these modes will be described.     

Design and development of printed helical array with low mutual coupling

This article reports the design and development of 4 × 4 printed helical array antenna for a geostationary‐based Global Positioning System (GPS) augmented Indian Navigation Payload. The impact of mutual coupling between the helical elements in an array is described. The reasons for deterioration of helical element's performance in an array are discussed. Mutual coupling between the elements is reduced resulting in to directivity and cross polarization improvements of the order of 2dBiC and 5 dB, respectively. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Light‐scattering liquid‐crystal composites with reduced off‐axis haze

Abstract— The majority of liquid‐crystal (LC) composites operating in a light‐scattering mode suffer from scattering of the obliquely incident light in the field on‐state (off‐axis haze effect). This is evident in the angularly selective viewing‐angle characteristic with a maximal transmittance corresponding to the normally incident light. We consider methods to control the viewing‐angle characteristic of polymer‐dispersed LC (PDLC) and filled LC. For PDLC samples, this control is realized by modification of the refractive index of the polymer matrix with highly refractive nanoparticles (NP) having a low rate of aggregation in the polymer. By proper optimization of NP concentration, one can bring the refractive index of the polymer matrix in the range needed to reduce the haze problem. In filled LC, the viewing‐angle curve depends on the refractive‐index mismatch between the LC and NP. By optimization of this parameter, one can flatten the angular characteristic or obtain selectable viewing angles in the desirable range. These results allow for the construction of optical shutters and a scattering‐type LCD with controllable viewing‐angle characteristics, particularly with low off‐axis haze.     

Processes,characterizations, and system applications of color‐filter liquid‐crystal‐on‐silicon microdisplays

Abstract— A color‐filter liquid‐crystal‐on‐silicon (CF‐LCOS) microdisplay that integrates color filters on silicon for color will be presented. The color‐filter process on silicon was optimized to achieve fine resolution and precise alignment of the color filters on the pixel array, good adhesion to the silicon suface, and a flat surface for the liquid‐crystal cell assembly. Important optical and electrical parameters of the color filters were extracted to establish an electro‐optical model of the CF‐LCOS microdisplays for device simulation. Thermal, chemical, and light‐stability characterizations were performed to ensure the stabilty of the color filters and CF‐LCOS microdisplays. With color CF‐LCOS microdisplays already available, the projection or viewing optics is greatly simplified. This CF‐LCOS microdisplay is ideal for near‐to‐eye displays because of its low‐power consumption and compactness. The CF‐LCOS microdisplay could also withstand medium light illumination for medium‐sized projectors. A single‐panel projector based on one CF‐LCOS microdisplay of 1280 × 768 × RGB resolution was demonstrated.     

Effects of carbon‐nanotube doping on the performance of a TN‐LCD

Abstract— The electro‐optical characteristics of a 90° twisted‐nematic liquid‐crystal display (TN‐LCD) were analyzed. The test cell was composed of a minute amount of dopant, multiwalled carbon nanotubes, and a standard nematic mixture, E7, used in TN‐LCDs with direct addressing. Under the experimental conditions, no hystereses in optical transmittance were observed in either the doped cell or a neat counterpart under an applied ac voltage. Experimental results show that doping with nanotubes rectifies the electro‐optical properties of the cells by reducing the driving voltage as well as the rise time. Similar results were found in a TN cell of a TFT‐grade liquid crystal instead of the mixture consisting completely of polar compounds.     

Simulation and fabrication of a fast fringe‐field switching liquid crystal with enhanced surface anchoring enabled by controlled polymer topology

We demonstrate a fringe‐field switching nematic liquid crystal with electro‐optical behavior modulated by both bulk and surface polymer stabilization. The polymer is formed by ultraviolet irradiation‐induced phase separation of various amounts of a reactive monomer in the planar‐aligned nematic liquid crystal. Simulation is carried out to verify the effect of anchoring energy. Experimental evidence validates the effect of monomer concentration on transmittance–voltage and response times curves of fringe‐field switching cells. The polymer‐stabilized alignment with a higher polymer concentration escalates the interaction between the liquid crystal and the polymer structure and increases the surface anchoring energy. The polymer stabilization also improves the dynamic response times of liquid crystal. The enabling polymer‐stabilized alignment technique has excellent electro‐optical properties such as a very good dark state, high optical contrast, and fast rise and decay times that may lead to development of a wide range of applications.     

Depth‐enhanced integral‐imaging 3D display using different optical path lengths by polarization devices or mirror barrier array

Abstract— Depth‐enhanced integral three‐dimensional (3D) imaging using different optical path lengths by using a polarization selective mirror pair or mirror barrier array is proposed. In the proposed approach, the enhancement of image depth is achieved by repositioning two types of elemental image planes, thus effectively two central depth planes are obtained. One of the two implementation methods makes use of the two‐arm structure that has different optical path lengths and polarization‐selective mirrors. The other utilizes the mirror barrier array. The primary advantage of the method with polarization devices is that we can observe 3D images that maintain some level of viewing resolution with a large depth difference without any mechanical moving part. The mirror barrier array has the advantage of the compact thickness. We demonstrated and verified our proposals experimentally.     

Molecular design for stabilizing a blue phase III and electro‐optical switching in the blue phase

Abstract— The molecular design of a liquid crystal to stabilize a blue phase III (BPIII) is reviewed, and the electro‐optical switching with a response time on the order of 10^?2 sec for BPIII exhibited by a novel chiral liquid crystal is reported. Binaphthyl derivatives and T‐shaped compounds are presented, and the structure‐property correlations of the chiral compounds are discussed. Two origins of the twisting power of the compounds, i.e., their inherent molecular chirality and the chirality‐induced twist conformation, play an important role in the appearance of the BPIII. Furthermore, BPIII was also induced in some binary mixtures of a host nematic liquid‐crystal possessing molecular biaxiality and a conventional chiral compound. The electro‐optical switching in the BPIII is attributed to an electric‐field‐induced phase transition between the BPIII and nematic (N) phases. BPIII is on the microscopically twisted nematic order, but is macroscopically isotropic. Therefore, the present technology can offer a pronounced black state in the BPIII without surface treatment and a homogeneous bright state in the induced N phase.