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.     

V‐shaped electro‐optical mode based on deformed‐helix ferroelectric liquid crystal with subwavelength pitch

Abstract— V‐shaped electro‐optical response is shown, both theoretically and experimentally, to be an inherent property of a deformed‐helix ferroelectric liquid‐crystal cell (DHFLC) under a special choice of the applied rectangular alternating‐electric‐field waveform, frequency, and cell geometry. In contrast to other known V‐shaped ferroelectric liquid‐crystal (FLC) modes, the discovered V‐shaped switching is observed in a broadband frequency range including 1 kHz, and not at a certain characteristic frequency. This type of V‐shaped switching allows for a drastic increase in the operating frequency of field‐sequential‐color (FSC) LCD cells in comparison with fast nematic liquid‐crystal (NLC) modes.     

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.     

A novel polarizer‐free dye‐doped polymer‐dispersed liquid crystal for reflective TFT displays

Abstract— A novel preparation method for dichroic dye‐doped polymer‐dispersed liquid crystals has been developed. This was achieved by creating a porous polymer matrix first by washing out the liquid crystal from a polymer‐dispersed liquid crystal (PDLC), which is then refilled with dye‐doped liquid crystal. Optimizing the liquid crystal used in the refilling results in decreased turn‐on voltage and faster response time. Poster‐standard reflectivity and newspaper‐standard contrast was demonstrated with a 3.8‐in. QVGA reflective TFT display with a drive voltage of 10 V.     

Improvement of electro‐optical properties of PSBP LCD using a double‐sided IPS electrode

Abstract— In this work, a low‐hysteresis polymer‐stabilized blue‐phase LCD is developed by controlling the polymerization temperature and using a double‐sided IPS (DS‐IPS) electrode. Compared to a conventional IPS LCD, this DS‐IPS LCD has a driving voltage of 45 V, which is lower than that, 62 V, of a conventional single‐sided IPS LCD. The transmittance is increased approximately 23%. The hysteresis is reduced to 0.44% which decreases as a function of the operating voltage. Furthermore, simulations of the maximum transmittance and operation voltage associated with the offset between the electrodes in the top and bottom substrates were also evaluated.     

Ecotoxicological properties of liquid‐crystal compounds

To obtain information on the ecotoxicological properties of liquid‐crystal (LC) compounds, the aquatic toxicity of selected LCs was investigated. Therefore, ten single LCs and one LC mixture were tested for their toxicity to the two standard organisms, daphnia (immobilization) and algae (growth inhibition). Water solubilities and detection limits were determined in the test media. Up to the limit of water solubility, the LCs as well as the LC mixture did not cause any adverse effects to the tested organisms.     

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.     

Ferroelectric liquid crystal aligned on SiO2 thin films using ion‐beam deposition

Abstract— Results for a ferroelectric‐liquid‐crystal (FLC) display cell, aligned on inorganic SiO₂ thin‐film surfaces by using oblique ion‐beam sputtering deposition on the substrates, is presented. A large deposition angle from 60° to 80° can be employed for the thin alignment layer, with thicknesses varying from 5 to 40 nm. Two types of uniform alignment, chevron (before electrical treatment) and quazi‐bookshelf (after electrical treatment), were studied. High‐quality alignment on large‐sized substrates was also easily be achieved because of the linear design of the ion‐beam sputtering source, which was previously a significant challenge for FLC on SiO_x layers.     

A single‐cell‐gap transflective blue‐phase liquid crystal display based on fringe in‐plane switching electrodes

A transflective blue‐phase liquid crystal display (TRBP‐LCD) based on fringe in‐plane switching (FIS) electrodes is proposed. The proposed structure generates combined fringe and in‐plane electric fields that cause more liquid crystal (LC) molecules to reorient almost in plane above and between the pixel electrodes. The fringe field is mainly generated in the transmissive (T) region, and the horizontal electric field is mainly generated in the reflective (R) region. By optimizing the width of the pixel electrodes and the gap between two adjacent pixel electrodes, the different electric field intensity in the T and R regions contribute to balance the optical phase retardation between the T and R regions. As a result, the proposed TRBP‐LCD exhibits a low operating voltage and high optical efficiency, while it preserves a relatively simple fabrication process.     

Novel photo‐aligned LC‐polymer compensation film for wide‐view TN displays

Abstract— We demonstrate a novel TN‐display compensation film with excellent contrast and minimal color shift, meeting the requirements for avionics displays. The film configuration was identified via extensive computer modeling. The experimental implementation based on ROLIC's LPP/LCP (linearly photopolymerizable polymer/liquid‐crystal polymer) technology results in excellent agreement with theoretical predictions.     

Reduced cross‐talk in shutter‐glass‐based stereoscopic LCD

Abstract— It is expected that 3‐D will be the next step in the enhanced viewing experience. At present, there are two competing 3‐D technologies for glasses‐based consumer TVs: active shutter glasses and passive polarized glasses. With the ongoing reduction in response time of liquid‐crystal displays (LCDs), this article will focus on shutter‐glass‐based stereoscopic LCDs. In this paper, the properties of such a display system is described and it is demonstrated that by adding a line‐scanning backlight, the cross‐talk can be reduced to less than 1.4%, allowing for excellent 3‐D portrayal. For images of extreme contrast, this is perceivable, but not judged annoying by a panel of expert viewers. Which characteristics of the display and shutter glasses that should be optimized to create an inexpensive, cross‐talk‐free, 3‐D LCD are discussed.     

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.     

A design method for flicker‐free liquid crystal display panels based on indium‐gallium‐zinc‐oxide thin‐film transistors

This paper proposes a design method to reduce the flicker of liquid crystal display panels based on indium‐gallium‐zinc‐oxide (IGZO) thin‐film transistors (TFTs). The proposed design method employs a human factor model to convert the flicker measured at low frame frequency (F _FRAME) to a modification value of the measured flicker (MVMF ) having a frequency sensitivity of flicker, which can distinguish between no blinking and weak blinking. To investigate the causes and characteristics of flicker, the frequency component and increase factor of flicker are analyzed using the checkerboard and solid images. The increase factor in flicker is examined using IGZO TFTs with different antenna ratios (AR s) that cause the variation in threshold voltage of IGZO TFT. To verify the proposed design method, two test panels are implemented with asymmetric and symmetric AR s. The MVMF s of the 15 Hz component at a low F _FRAME of 30 Hz show that the solid image with a symmetric AR has an MVMF of ?62.9 dB, which is improved by 24.3 dB compared to that with an asymmetric AR . Therefore, the proposed method is applicable for a flicker‐free liquid crystal display panels at a low F _FRAME.     

Tailored liquid‐crystal switching on ferroelectric polymer films

Abstract— The development of voltage‐controlled visible‐wavelength progression in displays and optical data storage devices using ferroelectric polymers and liquid crystals is described. Ferroelectric polymers are materials that have a ready distribution of dipoles which can be oriented by manipulating material composition and external fields. Utilizing the charge polarization distribution, their performance as an alignment layer for inducing liquid‐crystal alignment is presented. The switching response of the devices was tailored by changing the material composition through copolymers and nanoclay doping.     

Optimal design of optical performance of reflective ferroelectric‐ and anti‐ferroelectric liquid‐crystal displays

Abstract— In an in‐plane optical geometry, such that the average optic axis lies on the plane parallel to both substrates, the optical properties of a reflective ferroelectric liquid‐crystal (FLC) or antiferroelectric liquid‐crystal (AFLC) cell were studied within the framework of the 2 × 2 Jones matrix formalism. To obtain good achromaticity and high brightness, the cell parameters such as the molecular rotation angle and the effective phase retardation of the AFLC layer were optimized. The device performances of the AFLC cell were experimentally demonstrated in this geometry.     

Blue phase dual‐view liquid crystal display based on directional backlight system

We design a blue phase dual‐view liquid crystal display (BP DVLCD) based on a directional backlight system. Combining the patterned electrodes with the directional backlight system, the cross‐talk ratio is reduced to only 1.17%. Moreover, the resolution and brightness will be tripled by using field‐sequential color display. In the preferred viewing area, the BP DVLCD has a high contrast ratio of ~1700:1.     

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.     

Plasma‐beam alignment of passive liquid crystals (Invited Paper)

Abstract— A plasma‐beam process, developed for the alignment of liquid crystals (LC) in electro‐optic applications, has been successfully applied to align “non‐standard” LC, such as crystalline materials with LC phases at elevated temperatures and reactive mesogenes. In addition to the high alignment quality of the materials, there is no need for an intermediate layer between the substrate and the LC layer. Furthermore, the construction of our source simplifies the alignment procedure of large‐area rigid substrates and the roll‐to‐roll processing of flexible films. This method opens new horizons for optical retarders and polarizers, as well as anisotropic semiconducting films for organic electronics.