Conventional In-plane Switching Research Articles

P‐13: Picture Quality of In‐Plane Switching Liquid Crystal Displays with Deep Black

In‐Plane Switching (IPS) liquid crystal display (LCD) is one of leading technologies in display industrials because of its superior picture quality. This paper provides picture quality of high contrast IPS LCD in terms of color contrast, dynamic range, color expression and PQ‐EOTF accuracy in HDR compared to conventional IPS LCD. Furthermore, to evaluate its performance as a gaming display, reaction time between two IPS LCDs have different contrast ratio was tested. Experimental results indicate that observer's reaction time for high contrast IPS LCD was faster than conventional IPS LCD because of superior color contrast and color gamut at low luminance level.

Asymmetrically anchored liquid crystal cell for display and photonics applications

ABSTRACTAsymmetrically anchored liquid crystal (LC) cells have different anchoring energies between the top and bottom substrates. A substrate with patterned electrodes has comparatively weak anchoring energy. Therefore, asymmetrically anchored LC cells exhibit more twisted deformation in the on-state than conventional in-plane switching or fringe-field switching cells. In this study, we introduced asymmetrically anchored LC cells for display and photonic applications. We first introduced asymmetrically anchored LC cells to achieve high transmittance for LC displays. The LC molecules can rotate between the two substrates more easily because one of the two substrates has weaker anchoring energy. This resulted in a significant increase in transmittance. Three-terminal electrodes can be used to provide a vertical trigger pulse to an LC cell, thereby overcoming the delayed turn-off switching of an asymmetrically anchored cell without reducing transmittance. Next, we introduced an adjustable polarisation rotator with an asymmetrically anchored LC cell. To offer optical waveguiding, the arrangement of LC molecules can be controlled into a twisted configuration. During the cover of the wavelength range of 400–800 μm, we confirmed that the proposed LC cell can rotate the polarisation axis of linearly polarised light by up to 90°.

A high transmittance and fast response in-plane switching liquid crystal display with the zero-azimuth anchoring layers on the electrodes

An in-plane switching (IPS) liquid crystal display (LCD) containing the zero-azimuth anchoring layers formed only on the electrodes and rubbed polyimide (PI) covered on the other areas was successfully developed. This configuration was realized using photoreactive PI with photo-radical generation units and the mask exposure technique. The maximum transmittance (Tmax) of this LCD was 1.12 times higher than that of a conventional IPS LCD. This was attributed to a large aperture in the voltage-on state because the nematic liquid crystals (NLCs) on the electrodes were barely anchored to the surface, such that the NLCs could be rotated by applying a small in-plane electric field above the electrodes, and by an elastic torque caused by the twisted NLCs between the electrodes. Furthermore, the response times of this LCD were equivalent to those of a conventional IPS LCD because the NLCs between the electrodes quickly recovered to their initial orientation after removing the electric field, and the NLCs on the electrodes followed this movement. This novel LCD is termed a ‘partially zero-azimuth anchoring IPS (PZ-IPS) LCD’, which is the first practical LCD utilizing these weak anchoring characteristics in the history of LCDs.

Fast response time of micropixels with in-plane switching of positive liquid crystals using crossed patterned electrodes

Demonstrated herein is a fast in-plane switching (IPS) cell with positive dielectric anisotropy liquid crystals using crossed patterned electrodes in three different conditions. The ineffectiveness of one of these three structures due to the ‘Faraday cage’ effect was shown. With another structure, a fast response time was also shown to be impossible to achieve due to several contrast issues. In the third structure, a fast response time was achieved due to a combination of high-driving and crossed patterned electrodes allowing fast turn-off. Two of the three structures was manufactured. With the first one, an experiment confirmed the ‘Faraday cage’ effect. In the second structure, a response time four to eight times faster than the conventional IPS mode was experimentally demonstrated using two different kinds of liquid crystal.

Low-gamma shift asymmetrical double-side blue-phase liquid crystal display

ABSTRACT A single-domain blue-phase liquid crystal display (BPLCD), which has asymmetrical double-side electrode structure, is proposed to reduce gamma shift. Firstly, the electro-optical curve and gamma shift of the proposed BPLCD are discussed under the comparison with conventional in-plane switching (IPS) BPLCD. And then, its gamma shift is investigated under various conditions. Compared with the conventional IPS-BPLCD, the operating voltage can be reduced by ~31%, and the transmittance is increased by ~6%. The indistinguishable gamma shift can be obtained under various electrodes’ sizes, when the cell gap is appropriate. The results also indicate that if the electrodes’ height and Kerr constant of BPLC increase, the operating voltage can be further reduced (only 9.6 V in this work), and the gamma shift almost do not change. Moreover, a certain misalignment between the top and bottom glasses are permitted, which is good for reducing the fabrication difficulty. In terms of viewing angle, the proposed BPLCD has an average contrast ratio of ~5000:1, and the gamma shifts at full viewing angles are all indistinguishable.

Low gamma shift blue-phase liquid crystal display with electric field induced multi-domain electrode structure

ABSTRACTTo reduce the gamma shift of blue-phase liquid crystal display (BPLCD), the multi-domain electrode structure with four sub-electrodes is proposed. The effects of electrodes’ parameters on electro-optical curve and gamma shift are calculated, and the gamma shift and contrast ratio at full viewing-cone are also investigated. For the proposed protrusion BPLCD, the operating voltage is reduced by ~73%, and the transmittance is increased by ~20% compared with the conventional in-plane switching BPLCD. The results also show that the off-axis image distortion index can be reduced from 0.4318 to 0.0875 at the polar angle of 60°, and it works well under various electrodes’ sizes. Moreover, the indistinguishable gamma shift can be obtained at full viewing-cone for the proposed BPLCD, and the uniform light distribution and high contrast ratio can be obtained as well.

Low voltage blue-phase liquid crystal display with insulating protrusion sandwiched between dual-layer electrodes

ABSTRACTIn order to lower the operating voltage of blue-phase liquid crystal display (BPLCD), a BPLCD with insulating protrusion, which is sandwiched between dual-layer electrodes, is proposed. There are four electrodes in this structure; thus, we investigate different driving methods to find a proper driving method. The effect of protrusion’s dielectric constant on operating voltage of the proposed BPLCD is explored under various electrodes’ parameters. As a result, the operating voltage of the proposed BPLCD with protrusion’s dielectric constant of 1,000 is 9.8 V, which is reduced by ~ 4.67× compared with that of conventional in-plane switching (IPS) BPLCD (45.8 V). Moreover, the zigzag electrode structure is adopted to reduce the large off-axis image distortion index. Besides, the azimuth distortion index is defined to describe the gamma shift between the minimum and maximum gamma shift curves at a certain polar angle. The results show that the off-axis image distortion index can be reduced to 0.0834, the azimuth distortion index is 0.0810 and the viewing cone of contrast ratio larger than 1,000:1 is over 50ºas the zigzag proposed BPLCD is used.

81‐2: Novel In‐Plane Switching (IPS) Mode with High Transmittance using Negative Dielectric Liquid Crystal

We propose a novel In‐Plane Switching (IPS) mode with higher transmittance than conventional IPS mode using electrode modification and negative dielectric liquid crystals (nLC). In this configuration, nLC minimize the tilt angle which can prevent the transmittance decrease and therefore transmittance is increased about 20% compare to the conventional IPS mode. Moreover, reflectance of panel is dramatically decreased by substitution of metal electrode.

Macroscopic model for analyzing the electro-optics of uniform lying helix cholesteric liquid crystals

A macroscopic model is developed for analyzing the electro-optics of short-pitch uniform lying helix (ULH) cholesteric liquid crystals (CLCs). Both flexoelectric effect and dielectric effect make important contributions to the maximum transmittance and operation voltage of the ULH devices. Based on the proposed macroscopic approximation, we derive an analytical expression to quantitatively evaluate the relative strength of these two effects. Very good agreement between theory and experiment is achieved. We also investigate the viewing angle of ULH CLC displays and find that their viewing angle characteristics are similar to those of conventional in-plane switching liquid crystal displays.

Flexoelectric in-plane switching (IPS) mode with ultra-high-transmittance, low-voltage, low-frequency, and a flicker-free image.

The demands for a power-saving mode for displaying static images are ubiquitous not only in portable devices but also in price tags and advertising panels. At a low-frequency driving in liquid crystal displays (LCDs) for low-power consumption, the flexoelectric effect arises even in calamitic liquid crystals and the optical appearance of this physical phenomenon is found to be unusually large, being noticed as an image-flickering. Although the inherent integrated optical transmittance of in-plane switching (IPS) mode is relatively lower than that of fringe-field switching (FFS) mode, the IPS mode shows no static image-flickering but an optical spike (the so-called optical bounce), at the transient moment between signal positive and negative frames. Here, we demonstrate an IPS mode using negative dielectric anisotropy of liquid crystals (Δε < 0) and fine-patterned electrodes (the width w of and the space l between electrodes ≤ 3 μm) with reduced operation voltage (up to 40.7% to a conventional FFS mode with Δε < 0), reduced optical bounce (up to 4.4%. to a conventional FFS mode with Δε < 0) and enhanced transmittance (up to 32.1% to a conventional IPS mode with Δε > 0). We believe the result will contribute not only to the scientific understanding of the optical appearance of flexoelectric effect but also pave the way for engineering of a superior low-power consumption LCD.

A liquid crystal cell with double-side protrusion electrodes for fast response and low-voltage operation

ABSTRACTWe 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.

43.2: New Fast Response Time In‐Plane Switching Liquid Crystal Mode

We have developed an in‐plane switching (IPS) liquid crystal display with a fast response time that is three times faster than that for the comparable optical performance in the conventional IPS mode. The elastic energy function under the electric field is also analyzed.

Fast in-plane switching of negative liquid crystals using crossed patterned electrodes

We demonstrated fast in-plane switching (IPS) of negative liquid crystals by using crossed patterned electrodes. Switching to the bright state can be achieved by applying an in-plane field using the bottom patterned electrodes, whereas switching to the dark state can be obtained by applying an in-plane field using the top patterned electrodes. We obtained, experimentally, turn-off switching that was four times faster than that of the conventional IPS mode.

P‐114: A Liquid Crystal Mode with Combined Fringe and In‐Plane Switching Fields by Using a Bottom Floating Electrode

AbstractWe demonstrate a liquid crystal (LC) mode switched by combined fringe and in‐plane switching (IPS) fields, which are self‐adjusted by adopting a bottom floating electrode for enhanced electro‐optical properties. In our LC mode structure, conventional IPS electrodes are formed as pixel electrodes and common electrodes on an insulating layer, and floating electrodes that are patterned per the sub‐pixels are formed under the insulating layer. When the areas of the pixel and common electrodes are same, the voltage of the bottom floating electrode is spontaneously determined to be half the value of the pixel voltage, which ideally generates symmetric fringe fields with both pixel and common electrodes. Due to the in‐plane fields additionally generated between the pixel and common electrodes, the proposed LC structure shows higher transmittance than fringe‐field switching (FFS) and IPS LC modes. Transmittance of the conventional FFS and IPS LC modes is highly sensitive to the in‐plane electrode's width and spacing condition, but the proposed LC mode shows good transmittance without degradation under large variation condition of the in‐plane electrode's spacing‐to‐width ratio.

Mixed-field-switching liquid crystal mode using in-plane and fringe fields self-adjusted by bottom floating electrode for transmittance enhancement

We demonstrate a liquid crystal (LC) mode switched by mixed electric fields of in-plane and fringe fields, which are self-adjusted by adopting a bottom floating electrode for enhanced electro-optical properties. In our LC mode structure, conventional in-plane switching (IPS) electrodes are formed as pixel electrodes and common electrodes on an insulating layer and floating electrodes that are patterned per the sub-pixels. When the areas of the pixel and common electrodes are identical, the voltage of the bottom floating electrode is spontaneously determined to be half the value of the pixel voltage, which ideally generates symmetric fringe fields with both pixel and common electrodes. Due to the in-plane fields additionally generated between the pixel and common electrodes, the proposed LC structure operates by mixed-field switching (MFS), which shows higher transmittance than fringe-field switching (FFS) and IPS LC modes. Transmittance of the conventional FFS and IPS LC modes is highly sensitive to the in-plane electrode’s width (w) and spacing (l) condition, but the proposed MFS LC mode shows good transmittance without degradation with large variations of the in-plane electrode’s spacing-to-width ratio (l/w).

Retardation Free In-plane Switching Liquid Crystal Display with High Speed and Wide-view Angle

In this paper, we propose an in-plane switching (IPS) mode for liquid crystal displays (LCDs) that, in principle, is free of retardation of the LC cell. Basically, the optical configuration of the LC cell consists of an A-plate and an LC layer for switching between the dark and bright states. We could achieve a fast response time compared with the conventional in-plane LC cell because the free retardation condition of the proposed LC cell enables us to reduce the cell gap even by quarter-wave retardation without any change of the optimized LC material in the transmissive mode. Experiments for verification of the proposed in-plane switching LC cells have shown a significant reduction of the rising time and falling time simultaneously due to the small cell gap. Furthermore, we also proposed an optical configuration for wide viewing property of the retardation free IPS LCD by applying the optical films. We proved the wide-view property of the retardation free IPS LCD by comparing its optical luminance with the calculated optical property of the conventional IPS LCD.

69.4: High Speed In‐Plane Switching LCD with Free Retardation

AbstractWe propose a high speed In‐Plane Switching (IPS) liquid crystal display (LCD) with free retardation and wide view property. The proposed IPS mode can considerably reduce the response time of the LC cell. The optical configuration of the proposed IPS LC cell is composed of an A‐plate and LC layer. We could achieve a fast response time without any change of an LC material in transmissive mode. The calculated and experimental results for an optical response of the proposed LC cell have shown a significant reduction of the falling time. Also, we investigated an optical configuration for wide viewing angle property of the high speed IPS LCD and compared iso‐luminance with the conventional IPS LC cell.

Novel Electrode Design for High Transmittance In-Plane Switching (HT-IPS) LC Cell

This paper proposes a novel hexagonal electrode structure for optimal operation of the in-plane switching (IPS) mode liquid crystal cell. The proposed electrode architecture was designed in an effort to ensure the enhanced light transmittance and wider viewing angle characteristics as well as reduced color shift. We looked into the dynamic response of LC molecules and the consequent light transmission behavior under the electric field with a three-dimensional finite element method simulator. Our numerical study indicate that the proposed IPS cell with hexagonal electrode structure exhibits a higher peak transmittance over the conventional IPS architecture such as super-in-plane switching (S-IPS) mode. Our simulation revealed that a design optimization is needed due to the increase of threshold voltage despite the increase of the peak light transmittance.

Wall-shaped electrodes for reducing the operation voltage of polymer-stabilized blue phase liquid crystal displays

Polymer-stabilized blue phase liquid crystal displays based on the Kerr effect are emerging due to their submillisecond response time, wide view and simple fabrication process. However, the conventional in-plane switching device exhibits a relatively high operating voltage because the electric fields are restricted in the vicinity of the electrode surface. To overcome this technical barrier, we propose a partitioned wall-shaped electrode configuration so that the induced birefringence is uniform between electrodes throughout the entire cell gap. Consequently, the operating voltage is reduced by ∼ 2.8× with two transistors. The responsible physical mechanisms are explained.

Electro-optical characteristics of a chiral hybrid in-plane switching liquid crystal mode for high brightness

We propose a new in-plane switching (IPS) nematic liquid crystal (LC) mode which uses a twist effect with a hybrid LC alignment and interdigitated electrodes as an approach for a high brightness. This is optimized to a normally white mode to minimize loss of transmittance at the electrode compared to the conventional IPS mode. The proposed mode shows an excellent dark state because the bulk LCs are aligned in parallel to the optic axis of the polarizer under low electric fields. Consequently, this proposed mode exhibits a much higher contrast ratio (980:1) than that of the conventional IPS mode (550:1).