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A tunable liquid crystal (LC) polarization rotator that can rotate the polarization axis of linearly-polarized broadband light is achieved by using an asymmetrically-anchored negative LC cell. Interdigitated electrodes are used to apply an in-plane field to control the twist angle. The use of the asymmetrical anchoring in the LC cell enables continuous change of the twist angle by increasing the applied electric field. For uniform transmission, we used an LC that has negative dielectric anisotropy to avoid tilting of LC molecules by the vertical component of the electric field. We theoretically and experimentally confirmed that the fabricated LC cell could continuously change the twist angle and rotate the polarization axis of the linearly-polarized broadband incident light. [ABSTRACT FROM AUTHOR]

Reported herein is a method for the formation of a polymer structure on a plastic substrate through the phase separation of a liquid crystal mixture. Polymer walls can be formed on a specific location through phase separation induced by a spatial differences in elastic energy and electric field intensity. The fabricated polymer walls were observed through various methods. The measured aspect ratio of the fabricated polymer walls was about 12.9, with a 10.3 μm height and a 0.8 μm width. [ABSTRACT FROM AUTHOR]

Chiral photonics has emerged as a key technology for future optoelectronics, such as quantum information and encryption, by making use of photonic waves from enantiomeric structures. An inevitable challenge for realizing such chiral optoelectronics is the development of near‐infrared circularly polarized (NIR CP) light‐sensing photodetectors that convert optical power and circular polarization direction into distinguishable electrical signals. Herein, a simple and promising strategy for high‐performance NIR CP light‐sensing organic phototransistors (NIR CPL‐OPTRs) applicable to highly secure optoelectronic encryption is proposed. By directly assembling a standalone cholesteric liquid‐crystal network film in a thin‐film NIR CPL‐OPTR, remarkable responsivity and distinguishability are achieved. The synergetic effect of amplification of the photocurrent signal by the applied electric field and improved light absorption by the reduced reflection in the multilayered structure leads to high responsivity. As a proof‐of‐concept, the chiral phototransistor arrays are demonstrated as a physically unclonable function device and exhibit enhanced cryptographic characteristics. [ABSTRACT FROM AUTHOR]

We propose a dual mode liquid crystal display (LCD), which can realize dynamic and memory operating LCD modes in a display panel. Horizontal switching and bistable chiral splay nematic LCD modes are used for the dynamic and memory operations, respectively. As the horizontal switching is applied to the dynamic operation, it is possible to use the same LC texture of splay for realizing dark states of both the dynamic and memory operations. Because, for each operation, pixel division is not required in the proposed dual mode LCD, there is no decrease in aperture ratio and resolution. In order to obtain superior display performance for both operations, a wideband half-wave configuration is employed to the proposed dual mode LCD. Due to the wideband configuration, very low light leakages at the dark state and good dispersion characteristics for the entire visible range are obtained. As a result, the proposed dual mode LCD shows a high contrast ratio of over 100:1 for both the dynamic and memory operations. [ABSTRACT FROM AUTHOR]

The authors demonstrate through dark injection space-charge-limited current (DI-SCLC) and trap-free SCLC measurements that an indium tin oxide (ITO)/buckminsterfullerene (C60) electrode can form a quasi-Ohmic contact with N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl) benzidine (NPB). The DI-SCLC results show a clear peak current along with a shift of the peak position as the field intensity varies, implying an Ohmic (or quasi-Ohmic) contact. A theoretical simulation of the SCLC also shows that ITO/C60 forms an Ohmic contact with NPB when the electric field intensity is higher than 30 kV/cm. The Ohmic contact makes it possible to estimate the NPB hole mobility through the use of both DI-SCLC and trap-free SCLC analysis. [ABSTRACT FROM AUTHOR]

When an electric field is applied to a nematic liquid crystal cell with splay alignment layers, which is realized by mechanical parallel rubbing, the system exhibits abnormal reverse tilt domains. Even though the system has pretilt angle due to symmetry breaking by rubbing, existence of singular point in a cell by splay geometry and shift of that by locally asymmetric pretilt angle configurations result in the abnormal reverse tilt domains. On the basis of Oseen-Frank theory, dependence of singular point upon the abnormal reverse tilt domains is theoretically investigated for a splay alignment liquid crystal cell. By using the Dickman’s Q-tensor method [SID Int. Symp. Digest Tech. Papers 24, 638 (1993)], liquid crystal director field is calculated for the splay-aligned liquid crystal cell that an electric field is applied to. We presume a model to explain the abnormal reverse tilt domains, and derive the conditions required for the generation and elimination of these domains. [ABSTRACT FROM AUTHOR]

We report control of the haze value in a liquid crystal (LC) cell driven by a fringe electric field. When a fringe field is applied to a vertically aligned (VA) cell, a large spatial phase difference with a short grating period is induced in the LC layer. The average grating period of a VA cell driven by a fringe field is a quarter of the pitch of the interdigitated electrodes, which is half of the grating period of a VA cell driven by an in-plane field. Moreover, a sharper spatial phase profile is built around the edges of the interdigitated electrodes, which led to a high haze of 84.3% in the translucent state. The device was haze-free in the transparent state owing to the use of an LC layer without a polymer structure. To increase the haze value of the LC device while retaining a short response time, we developed an LC cell with crossed interdigitated electrodes where a large spatial phase difference is induced with little dependence on the azimuth angle. By applying a fringe electric field to a 20 μm thick LC cell using crossed interdigitated electrodes, we demonstrated a very high haze of 95.4% and a response time of less than 5 ms. [ABSTRACT FROM AUTHOR]

We report approaches for sub‐millisecond switching of vertically‐aligned nematic liquid crystals (LCs). When an in‐plane field is applied to a vertical alignment (VA) cell, virtual walls are built at the center of the interdigitated electrodes and at the middle of the gaps between them. The LC molecules are confined not only by the two substrates but also by the virtual walls so that the turn‐off time of a VA cell driven by an in‐plane field is dependent on the pitch of the interdigitated electrodes as well as the cell gap. Therefore, the turn‐off time of a VA cell driven by an in‐plane field can be reduced simply by decreasing the pitch of the interdigitated electrodes as a result of the enhanced anchoring provided by the virtual walls. We experimentally obtained a sub‐millisecond response time in the VA cell. The measured turn‐on and turn‐off times of the fabricated VA‐FFS cell was 0.33 ms and 0.41 ms, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we present a diffractive liquid crystal (LC) device capable of rapid switching between the transparent and translucent states for window display applications. In contrast to previously reported LC light shutters based on light scattering, the proposed LC device relies on diffraction of white incident light by an electric field-induced periodic continuous LC profile. It can be switched between the transparent and translucent states without a complicated driving scheme or a polymer structure. This device exhibits outstanding features for window display applications, such as a high transparency and a wide viewing angle in the transparent state, a low operating voltage, and a short response time. [ABSTRACT FROM PUBLISHER]

To reduce power consumption by light shutters, bistable light shutters using cholesteric liquid crystal have been proposed. However, these bistable light shutters, which utilize the scattering of the incident light, are switchable only between transparent and translucent states. In this work, we successfully demonstrate a bistable light shutter that is switchable between transparent and opaque states because it utilizes not only scattering, but also the absorption of the incident light. We hide the objects behind a display panel and provide black color by switching the light shutter that is positioned at the backside of a see-through display. We realized a good opaque state by optimization of the electrode structure. [ABSTRACT FROM PUBLISHER]

Although the fringe-field-switching (FFS) mode based on a two-domain (2D) electrode structure has been widely used for wide viewing angle in a liquid crystal display (LCD), it still suffers from color shift and asymmetric luminance distribution at off-axis. We propose a four-domain (4D) electrode structure for wide viewing angle characteristics in an FFS LCD. We demonstrate that the use of the 4D electrode structure instead of the 2D-chevron structure can reduce the off-axis color difference from 0.038 to 0.010 at a low gray level and from 0.019 to 0.002 at a mid-gray level. Moreover, the off-axis gamma distortion is reduced from 0.159 to 0.007. [ABSTRACT FROM PUBLISHER]

We propose a homogeneously aligned liquid crystal (LC) cell with double-side protrusion electrodes for fast response and low-voltage operation. In the proposed device, both the bottom and top substrates have pixel electrodes to generate the fringe electric field. Because the penetration depth of the electric field is increased owing to the protrusion electrodes, the operating voltage is very low and the turn-on time is dramatically reduced compared with the conventional in-plane switching (IPS) mode. Moreover, LC molecules anchored strongly to the penetrated protrusion electrodes on both substrates exert a strong restoring force, resulting in a fast turn-off time. We found that the total response time of the LC cell with the proposed structure is three times faster than that of the conventional IPS mode. [ABSTRACT FROM AUTHOR]

We report a method for fast gray-to-gray (GTG) switching of a homogeneously aligned liquid crystal (LC) cell. Homogeneously aligned LCs are instantly vertically aligned by applying a vertical electric field for a short period of time before switching to a target gray level. Once the LCs are vertically aligned, we apply an in-plane voltage higher than the data voltage that corresponds to a target gray level, while maintaining the vertical electric field. Then, at the time the vertical field is removed, we apply a data voltage required for switching to the target gray level. We experimentally demonstrate GTG switching of a homogeneously aligned LC cell at a low temperature (-20°C), which is 7.5 times faster than a fringe-field switching (FFS) cell at the same temperature, which is comparable to the switching speed of a fringe-field switching cell at room temperature (23°C). [ABSTRACT FROM AUTHOR]

We propose a method for fast grey-to-grey (GTG) switching of a homogeneously aligned liquid crystal (LC) cell. Homogeneously aligned LCs are instantly vertically aligned by applying a vertical electric field for a short time before switching to a target grey level. Once the LCs are vertically aligned, we apply an in-plane voltage higher than the data voltage that corresponds to a target grey level, while maintaining the vertical electric field. Then, at the time the vertical field is removed, we apply a data voltage required for switching to the target grey level. We experimentally demonstrated GTG switching of a homogeneously aligned LC cell, which is 11 times faster than a fringe-field switching cell. [ABSTRACT FROM AUTHOR]

We propose a vertical alignment (VA) liquid crystal (LC) device with reduced off-axis gamma shift. We can form a multi-domain structure by simply designing the electrode structure . By applying a different bias voltage to each sub-pixel, we obtained a threshold voltage difference of 2.4 V, without any complex manufacturing process. We confirmed that the off-axis gamma shift can be significantly reduced by the proposed method. We believe that the proposed method can be easily applied to reduce the off-axis gamma shift in vertical alignment LC devices. [ABSTRACT FROM PUBLISHER]

In this work we propose a liquid crystal mode in which vertically-aligned negative nematic liquid crystals are switched on by applying a fringe electric field. In the proposed mode, vertically-aligned negative liquid crystals can be switched on by the vertical as well as in-plane components of an applied fringe field so that high transmittance can be achieved. By fabricating a test cell, we experimentally obtained a transmittance of 33.7 %, which is 8.7 % higher than a homogeneously-aligned fringe field switching cell using positive liquid crystals. [ABSTRACT FROM AUTHOR]

We reported electrical circuit modeling to analyze the optical performance degradation in an ion-doped liquid-crystal (LC) cell, which exhibited advantages, such as excellent optical performance and simple switching process, but suffered from long-term reliability issues. When an electric field was applied to the cell for an extended period of time, the optical performance became nonuniform, and the haze in the opaque state decreased. By measuring the impedance and fitting the measured data by using an equivalent circuit model, we confirmed the changes of the parameters in the electrochemical impedance spectroscopy and electrophysical properties of the ion-doped LC cell with time. According to the measurement of the optical and physical characteristics, the optical performance degradation was caused mainly by the ionic materials. [ABSTRACT FROM AUTHOR]