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.     

Low‐temperature‐applicable polymer‐stabilized blue‐phase liquid crystal and its Kerr effect

Abstract— A type of polymer‐stabilized blue‐phase liquid crystal, which can be used in a low‐temperature environment, is proposed. The blue‐phase range after polymerization was widened to more than 73°C, and the blue‐phase texture is very stable even at a temperature as low as ?35°C. The electro‐optical performances dependence on polymer concentration was investigated. The results indicate that the saturation voltage increases and the hysteresis enhances as the polymer concentration increases. The rise and decay times could reach as low as 391 and 789 μsec, respectively. Such material also shows good electro‐optical behavior at a temperature of ?35°C. In addition, the Kerr constant was tested under a uniformly distributed electric field to be 2.195 nm/V² at room temperature and 2.077 nm/V² at ?35°C. The Kerr constant tested under white‐light illumination was 1.975 nm/V², which shows a small dispersion.     

A continuous‐viewing‐angle‐controllable liquid‐crystal display using a blue‐phase liquid crystal

Abstract— A continuous‐viewing‐angle‐controllable liquid‐crystal display (LCD) using a blue‐phase liquid crystal is proposed. To realize both wide‐viewing‐angle (WVA) mode and narrow‐viewing‐angle (NVA) mode with a single liquid‐crystal panel, each pixel is divided into a main pixel and a subpixel. The main pixel is for displaying images in both modes. The subpixel is for displaying images in WVA mode and controlling the viewing angle in NVA mode. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

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.     

A viewing‐angle‐controllable blue‐phase liquid‐crystal display

Abstract— A viewing‐angle‐controllable liquid‐crystal display (LCD) is proposed. When the device is only driven by an in‐plane electric field, it exhibits a wide‐viewing‐angle (WVA) mode. And it exhibits narrow‐viewing‐angle (NVA) mode when it is driven by a vertical electric field as well as an in‐plane electric field. In this manner, the viewing angle of the device can be controlled from 100° to 30°. The device exhibits a good viewing‐angle‐controlling characteristic and high transmittance.     

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.     

Electro‐optic effects of the optically isotropic state induced by the incorporative effects of a polymer network and the chirality of liquid crystal

Abstract— The electro‐optical properties of optically isotropic liquid‐crystalline composites prepared by in‐situ photo‐polymerization of cross‐linking monomers in the isotropic phase of chiral liquid crystals were investigated. The magnitude of the electric birefringence of the composites decreased as the chirality of the liquid crystal increased. The clear Kerr effect was observed for the composites with high chirality. A large Kerr constant, being relatively insensitive to temperature, was obtained for the composites even in a temperature range below the isotropic‐chiral‐nematic phase‐transition temperature. The response time of the Kerr effect at room temperature was on the order of tens to hundreds of microseconds.     

Prospects of emerging polymer‐stabilized blue‐phase liquid‐crystal displays

Abstract— The prospects of emerging polymer‐stabilized blue‐phase liquid‐crystal displays, or more generally, Kerr‐effect‐induced isotropic‐to‐anisotropic transition, are analyzed with special emphases on the temperature effects. As the temperature increases, both the Kerr constant, induced birefringence, and response time decrease but at different rates. The proposed physical models fit well with experimental results. Some remaining technical challenges associated with this promising display technology are discussed.     

Study of polymer‐network structure on polymer‐stabilized blue phase

Abstract— To understand the mechanism of the disclination defect of the liquid‐crystal (LC) phase, this study was conducted to directly analyze the polymer‐network (PN) structure of polymer‐stabilized blue phase (PSBP), which is minutely formed on all LC layers. The PN was examined after first removing the glass decap and then the LC. Important to note is that the removal of the glass decap did not affect or damage the PN structure. The PN was determined to be a stable structure without any change to the thickness of the layer. When removing the LC, both hexane and acetone solutions were used. Moreover, there was no structural deformation to the PN when using the hexane solution. The results of the study show that the actual size of the polymer chain is in fact 50–60 nm, five times larger than previous theories which estimated the size to be only 10 nm. In addition, this study confirmed that the pores between the PN are 100–200 nm. The PN structure was shown to be susceptible to change based on different heating temperatures. In summation, now that defect lines of a LC display (LCD) could be directly measured, further progress and development in the theoretical interpretations of the Kerr effect on PSBP can be realized.     

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.     

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.     

Template effect on reconstruction of blue phase liquid crystal

The reconstruction capability of the blue phase (BP) template with low polymer concentration was investigated. A threshold polymer concentration to reconstruct the BP with the chiral three‐dimensional template was confirmed in different kinds of polymer systems. The anchoring energy of the template may reassemble the double twist cylinder structure of BP liquid crystal (BPLC) by refilling either the same‐handed or reverse‐handed chiral materials within a certain range of helical twisting power (HTP). Meanwhile, because of the lowered anchoring energy, the kerr constant of the reconstructed BPLC increased by 104%, from 1.81 nm/V² to 3.70 nm/V², by refilling the reverse‐handed chiral material.     

Influence of alkyldiacrylate side‐chains on electro‐optical properties in liquid crystal/composite films

In order to realize a paper‐like display using polymer‐network liquid‐crystal (PNLC) films, an increase in backscattering intensity is required. The morphology of the films, and the molecular interactions between the liquid crystals and polymers forming the polymer network, both play an important role in determining film electro‐optical properties such as the driving voltage and the reflectance. We have analyzed several factors related to the morphology of the films. Aiming at a reduction in the driving voltage, the effects of alkyl side‐chains in diacrylates have been investigated. Based on the results, we successfully produced a prototype paper‐like display.     

A reflective polarizer‐free display using dye‐doped polymer‐stabilized blue‐phase liquid crystals

Abstract— A reflective polarizer‐free display using dye‐doped polymer‐stabilized blue‐phase liquid crystal (DDPSBP‐LC) has been demonstrated. The mechanism is a combination of electrically tunable light absorption and Bragg reflection. In this paper, the influence of light absorption in DDPSBP‐LC by changing the dye concentration and absorption paths has been studied. Increased dye concentration can improve the contrast ratio of DDPSBP‐LC; however, the response time is the tradeoff. Increasing the cell gap can improve the contrast ratio of DDPSBP‐LC; however, the response time remains the same. The study of DDPSBP‐LC can help in shutter‐glass applications of 3‐D displays and electronic paper.     

Evaluation method of electro‐optical transfer function for display devices

Abstract— Various gamma‐evaluation methods are investigated and newly suggested in order to establish a standard gamma metrology. First, test patterns are suggested and compared for display technologies that dynamically adjust gray levels such as global‐dimming LCDs and PDPs. Second, two gamma‐determination methods are compared and their accuracy determination methods are suggested. Third, two new models for gamma‐distortion phenomena are suggested. Finally, the monotonic characteristics of EOTF are investigated. For the most part of this study, a new international standard named ICDM‐DMS is suggested.     

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.     

Pixel‐isolated liquid‐crystal mode by using a patterned anisotropic phase separation for flexible LCDs

Abstract— A pixel‐isolated liquid‐crystal (PILC) mode for enhancing the mechanical stability of flexible‐display applications is proposed. Because liquid‐crystal (LC) molecules in this mode are isolated in each pixel by patterned or phase‐separated microstructures, and the two substrates are tightly attached to each other by a solidified polymer layer, the LC alignment is stable against external pressure, and the cell gap of our structure is uniformly preserved against bending deformation of the plastic substrates. The mechanical stability of the PILC structure having plastic substrates was tested for its electro‐optic properties.     

Polarization‐independent blue‐phase liquid‐crystal gratings driven by vertical electric field

Abstract— A blue‐phase liquid‐crystal grating is proposed by applying a vertical electric field with lateral periodic distribution. Simulation on electric‐field distribution was also carried out, the results of which suggest the alternation of isotropic and ordinary refractive indices in the lateral direction. Through the electrode configuration design, both 1 D and 2D gratings were demonstrated with high transmittance of ca. 85%. The diffraction efficiency of the first order reached up to 38.7% and 1 7.8% for the 1D and 2D cases, respectively. The field‐induced fast phase modulation permits a rapid switching of diffraction orders down to the submillisecond scale.     

High‐efficiency switchable optical elements for advanced head‐up displays

The Pancharatnam‐Berry optical elements (PBOEs) are utilized to enhance the performance of head‐up displays (HUDs). The Pancharatnam‐Berry lenses (PBLs) provide varifocal functionality and compensate chromatic aberrations, while the Pancharatnam‐Berry deflectors (PBDs) can function as optical combiners and waveguide couplers. Moreover, the Rigorous coupled wave analysis (RCWA) based on the scattering matrix is developed and applied in the structure optimization of PBOEs for HUD applications.     

Transflective blue‐phase liquid‐crystal display with corrugated electrode structure

Abstract— A transflective polymer‐stabilized blue‐phase liquid‐crystal display (BP‐LCD) with a corrugated electrode structure is proposed. To balance the optical phase retardation between the transmissive (T) and reflective (R) regions, two device structures are proposed. The first device structure has the same inclination angles but different cell gaps in the T and R regions. And the second device structure has the same cell gap but different inclination angles in the T and R regions. Both of the device structures can obtain well‐matched VT and VR curves. This display exhibits low operating voltage, high optical efficiency, and a wide viewing angle.