In-plane Switching Cell Research Articles

IPS mode investigation of liquid crystal alignment on organic hybrid overcoat layer via ion beam irradiation

The nematic liquid crystal alignment capability and electro‐optical (EO) performance characteristics of in‐plane switching (IPS) cells were first demonstrated on organic hybrid overcoat layers via ion beam irradiation. Usually the organic hybrid overcoat is used as the material for making a plate alignment layer in a colour filter process. To characterise the organic hybrid overcoat layer, we analysed the surface composition of the organic hybrid overcoat by X‐ray photoelectron spectroscopy. The results show that the intensity of C = O and C–O bonding undergoes a change corresponding to the changes in energy of the ion beam exposure. Moreover, EO performance characteristics of IPS cells on the organic hybrid overcoat layer via ion beam irradiation were observed to have similar characteristics to the polyimide.

Electro Optical Performance Characteristic of In-Plane Switching Cell Treated on Nitrogen-Doped Diamond-Like Carbon Thin Film Surfaces by Ion Beam Alignment

The nematic liquid crystal (NLC) alignment capability achieved by ion beam alignment on a nitrogen-doped diamond-like carbon (NDLC) thin film was investigated. To characterize the NDLC thin film, we analyzed the obtained atomic force microscopy (AFM) images and pretilt angle. Moreover, we investigated the electro optical (EO) performance characteristics of ion-beam-aligned in-plane switching (IPS) cell with the NDLC thin film. The EO performance characteristics of the ion-beam-aligned IPS cell were observed by ion beam exposure on the NDLC thin film and compared with those of a rubbing aligned polyimide (PI) thin film. Finally, similarly prominent capacitance–voltage (C–V) characteristics were achieved in the ion-beam-aligned NDLC thin film compared with the rubbing-aligned PI thin film.

Transflective In-Plane Switching Liquid Crystal Display

A single cell gap, single gamma curve, and low operating voltage transflective liquid crystal display (LCD) using an in-plane switching (IPS) cell is proposed. In the IPS cell, the pixilated transparent indium tin oxide electrodes are on the top substrate and the reflectors are on the bottom substrate. The electro-optic properties of the transflective IPS LCD are calculated using three-dimensional simulation software. By optimizing the reflector width, the voltage-dependent transmittance and reflectance curves can be matched

DYNAMIC RESPONSE OF CARBON NANOTUBES DISPERSED IN NEMATIC LIQUID CRYSTAL

The alignment and dynamic response of carbon nanotubes (CNTs) in nematic liquid crystal (NLC) medium induced by strong electric field have been observed through polarizing optical microscope. Density-functional calculations suggest that LC molecule anchors helically to the CNT wall to enhance π-stacking with a binding energy of nearly -2.0 eV due to a considerable amount of charge transfer from LC molecule to CNT, resulting in the formation of excess charges and permanent dipole moment in CNTs. Under strong electric field, the motion of CNTs distorted the director of adjacent LC molecules. Our detailed analysis of dynamics revealed that the four-lobe textures in vertical cell and two vertical stripes in in-plane switching cell were strongly correlated, i.e., the side view of textures by the vertical motion of CNTs in vertical cell was similar to the textures in in-plane switching cell. Interestingly, the magnitude of textures in microscope was strongly dependent on the size of CNTs and the applied field strength. The statistical size distribution of textures similar to that of CNTs provided information for the degree of dispersion of CNTs.

Optimization of Electrode Structure and Rubbing Angle in In-Plane-Switching Liquid Crystal Cell for Single-Gamma Transflective Display

We studied the effects of the electrode structure and rubbing angle on the electro-optic characteristics of an in-plane switching (IPS) cell. We found that the threshold voltage and the steepness of the voltage–transmittance (reflectance) [V–T(R)] curve for an IPS cell can be controlled separately by varying the distance between electrodes and the rubbing angle, respectively. We applied these results to realize a single gamma in a transflective IPS cell.

Optical configuration of a horizontal-switching liquid-crystal cell for improvement of the viewing angle

We propose an optical configuration of a horizontal-switching liquid-crystal cell, consisting of a splayed liquid-crystal cell and uniaxial films, to improve the viewing angle characteristics by compensating for the phase dispersion in a diagonal direction. The optical design of the proposed configuration was performed on a Poincaré sphere with geometric calculations. By fabricating in-plane switching cells with the introduced configuration, we demonstrated their optical performances. As a result, we found that the diagonal viewing angle of the proposed horizontal-switching cell could be increased by 80% compared to a symmetrical viewing cone.

Study on colour characteristics depending on orientation of liquid crystal in the in‐plane switching mode

The degree of colour shift depending on viewing direction in the in‐plane switching (IPS) mode has been investigated. The IPS cell with pure twist deformation exhibits a stronger colour shift than that of the IPS cell with tilt as well as twist deformation, although the former has better luminance uniformity in the bright state than the latter. Furthermore, the IPS cell with multi‐directional LC orientation, with tilt as well as twist deformation, shows the least colour shift.

Influence of Ion Transport on Liquid Crystal Switching

The coupled interaction between the reorientation of a liquid crystal and the migration of ionic impurities in the presence of an applied electric field is investigated for two device types commonly used in displays, the planar and the in-plane switching (IPS) cell. Simulated optical measurements and transient currents are compared to experimental results in order to discover means to alleviate the problems associated with ion migration. IPS cells have a lower electrode surface area than planar cells, and are therefore more sensitive to the movement of a given ion concentration. As a means to reduce this sensitivity, the effect of altering the electrode width and gap is studied.

Optimization on the Thickness of Organic Insulator Layer for Advanced Super-In-Plane Switching Mode Thin-Film-Transistor Liquid Crystal Displays

The growth rate of thin-film-transistor liquid crystal display (TFT-LCD) industries is faster than predicted due to the possible replacement of a cathode-ray tube television (CRT-TV) by a liquid crystal display television (LCD-TV). The in-plane switching (IPS) mode has been known as an excellent technology for realizing a wide viewing angle for LCD-TV, but it has the drawback of a low aperture ratio. An advanced super-IPS (AS-IPS) structure with an organic insulator layer was invented to achieve a high aperture ratio with increasing manufacturing cost. In this paper, we proposed a simple method of analyzing the optimum thickness of the organic insulator layer for AS-IPS. We derived the capacitive coupling ratio (CCR) of the IPS cell and analyzed the delay time of the AS-IPS panel to quantify the crosstalk properties. Furthermore, we also analyzed our electrode structure (AS'-IPS), which not only increases substantially the aperture ratio over that of AS-IPS but also reduces the crosstalk using the same optimized thickness of the organic insulator layer.

Crosstalk Studies of In-Plane Switching Mode under Different Pixel- and Common-Electrode Configurations

In thin-film-transistor liquid-crystal display (TFT-LCD), particularly pixel-electrode configuration of in-plane switching (IPS) mode, crosstalk caused by capacitive coupling between pixel electrodes and data lines could result in image degradation. We derived the capacitive coupling ratio (CCR) of the IPS cell and analyzed the CCR of three conventional TFT-IPS pixel- and common-electrode structures to quantify the crosstalk properties. The effect of coupling voltage on electro-optics characteristics has been investigated. Our results showed that a common electrode placed adjacent to the data line could shield capacitive coupling between the data line and the pixel electrodes, and reduce CCR from 13% to 2.4% and crosstalk intensity ratio (CIR) from 21.2% to 3.9%. We also report the common-overlapping-pixel structure that not only increases the aperture ratio by 1.28 times but also reduces CCR from 13% to 9.1%.

Crucial influence of polar alignment on the dynamics of in-plane switching cells

We investigated theoretically the dynamics of in-plane switching (IPS) cells with small pretilt angle and found that the liquid crystal director variation causes optical bounce after switching on an applied voltage. We analysed the behaviour of the director by computer simulation and found that the optical bounce occurs during the rising period with the normal twist and tilt angles of the directors in the IPS cell in the absence of the field-induced backflow effect. Pretilt angle is the source of this optical bounce.

Electro-optic characteristics of 4-domain vertical alignment nematic liquid crystal display with interdigital electrode

We have fabricated a vertically aligned 4-domain nematic liquid crystal display cell with thin film transistor. Unlike the conventional method constructing 4-domain, i.e., protrusion and surrounding electrode which needs additional processes, in this study the pixel design forming 4-domain with interdigital electrodes is suggested. In the device, one pixel is divided into two parts. One part has a horizontal electric field in the vertical direction and the other part has a horizontal one in the horizontal direction. Such fields in the horizontal and vertical direction drive the liquid crystal director to tilt down in four directions. In this article, the electro-optic characteristics of cells with 2 and 4 domain have been studied. The device with 4 domain shows faster response time than normal twisted-nematic and in-plane switching cells, wide viewing angle with optical compensation film, and more stable color characteristics than 2-domain vertical alignment cell with similar structure.