In-plane Switching Mode Research Articles

P-117: The Investigation of Photo Alignment Polyimide Material for Large Size IPS Display

A new photo alignment (PA) polyimide for in-plane switching (IPS) liquid crystal display has been presented and it has good alignment performance. It realizes alignment by irradiating linearly polarized light with wavelength of 313nm. In this paper, we have study a novel 313nm PA polyimide with only one UV step. And we also have investigated the relationship between the image sticking performance and PA polyimide structure. The optical and image sticking performance of different PA polyimide are discussed in IPS mode, respectively.

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.

In-Plane Switching Mode for Liquid Crystal Displays Using a DNA Alignment Layer.

We successfully fabricated the in-plane switching mode (IPS) LC display (LCD) based on a double stranded DNA (dsDNA) alignment layer. As widely known, the DNA has the right-handed double helical structure that has naturally grown grooves with a very regular period, which can be used as an alignment layer to control the orientation of liquid crystal (LC) molecules. The LC molecules on this topographical layer of DNA material align obliquely at a specific angle with respect to the direction of DNA chains, providing an instant and convenient tool for the fabrication of the IPS display compared to the conventional ways such as rubbing and mechanical shearing methods. The electro-optical performance and response time of this device were also investigated. Our result will be of great use in further exploration of the electro-optical properties of the other biomaterials.

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.

A Power-Efficient Driving Method for In-Plane Switching-Mode TFT-LCD Using a Negative Liquid Crystal

This paper presents an effective driving method to reduce the power consumption of an in-plane switching (IPS) mode thin-film transistor liquid crystal display (TFT-LCD) with a negative liquid crystal (LC). Despite the higher transmittance efficiency of the negative LC, it is not effective to reduce the power consumption of the IPS mode TFT-LCD because of the driving voltage, which is 30% higher than that of the positive LC. To complement the higher driving voltage, the driving method, which can modulate the amplitude of the common voltage (VCOM) inversion without side effects, is proposed for low power consumption. In addition, a novel pixel structure is developed to reduce the data load. The measured power consumption is 22.5 W at the full white gray level in a 17-in full high-definition (FHD) IPS mode TFT-LCD. The measured result shows that the proposed method can reduce the power consumption by 19% and 10% as compared to that of the conventional method using the negative LC and positive LC, respectively.

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.

A Transflective Display Using Blue Phase Liquid Crystal

A combined fringe and in-plane switching (FIS) mode single-cell-gap transflective display using blue-phase liquid crystal (BPLC) is proposed. The structure makes use of the space above the pixel electrodes of this FIS mode as reflective regions and the space between pixel electrodes as transmissive regions. The structure which can be optimized to balance the optical phase retardation between transmissive region and reflective region with simple fabrication process exhibits relatively high optical efficiency and well matched voltage of transmittance and reflectance curves.

Surface rheology of rubbed polyimide film in liquid crystal display

The rheological properties of polyimide film surfaces have an important influence on contrast reduction during the in-plane switching mode of liquid crystal displays. To clarify these properties, the slight difference of deviation angles of liquid crystal directors from the rubbing direction were measured during prolonged exposure to alternating electric fields. The results indicate that the data can be well described using the Kelvin-Voigt model. The relation between the in-plane shear modulus G and the strain at the polyimide surface was also investigated based on the torque balance between the energy density of the electric field and the elastic energy density of the polyimide surface. It was found that much smaller G than bulk polyimide materials existed on the polyimide surface in liquid crystal display.

38.2: Comparative Analysis of Alignment Characteristics of Polyimide Films Using Near Edge X‐ray Adsorption Fine Structure

AbstractWe studied the structural characteristics of poly imides (PI) chains according to the film thickness and the temperature treatment using the angle resolved near edge X‐ray adsorption fine structure (AR‐NEXAFS). The molecular directional angle a of the twisted nematic (TN) and the in‐plane switching (IPS) mode alignment film (AF) decrease the tilt angle as increasing the film thickness. These films also shows the temperature dependence of C=C * according to the annealing conditions. In case TN mode sample lost its angular dependency after annealing 230 °C for 2400 sec on the hot plate, but IPS mode sample maintained its angular dependency after same annealing condition with TN mode sample.

Tunable negative index metamaterial employing in-plane switching mode at terahertz frequencies

We analysed the response of a tunable liquid crystal metamaterial transducer in the terahertz frequency range. Tunability of scattering parameters is achieving by an in-plane switching (IPS) effect. The metamaterial structure is based on Ω-shape resonators. A full-wave analysis technique based on the finite-difference time-domain (FDTD) method was performed using the QuickWave 3D electromagnetic solver. Terahertz transmission properties of the metamaterial structure can be controlled by the director of the liquid crystal layer. The effective refractive index for operation frequency varies from negative to positive values. A novel approach to switching of metamaterial transducer by IPS mode is presented.

Film compensation to improve the dark state in the oblique directions of the horizontal-switching mode

In order to compensate for light leakage in the oblique viewing directions of the dark state of the horizontal-switching mode such as the in-plane switching and fringe field switching modes. The viewing angle performance of the horizontal-switching mode with an compensation film has been evaluated on a case by case basis according to the retardation values of the films. Consequently, we found that a much better dark state can be achieved by using an optimised compensation film.

28.1: Premium Picture Quality by Super‐Multi‐Domain Polymer Sustained Alignment LCD Technology

AbstractNew super‐multi‐domain polymer sustained alignment (PSA) liquid crystal displays are developed With this new pixel architecture, premium picture quality with very little oblique gamma distortion and color shift (Δ u‘v’ < 0.02) like in‐plane switching (IPS) mode, is obtained. Moreover, it can also realize low‐crosstalk patterned retarder 3D displays without sacrificing the 2D‐mode luminance.

Simulation of the viewing properties and optical compensation of the biaxial nematic in-plane switching mode

Using Berreman 4 × 4 optical methods and continuum theory, we investigate the theoretical viewing properties of a potential homeotropically aligned biaxial nematic display switched with in-plane fields. We determine the isocontrast, isotransmission viewing characteristics for wide-angle viewing for in-plane switching and consider the necessary requirements for optical compensation to produce a high transmission in the bright state and low transmission in the dark state. We show how compensation can be achieved with biaxial compensation layers using a homogeneous biaxial film or from birefringence.

Inorganic Layer for Homogeneously Aligned Crystals Using Ion Beam Irradiation

The authors introduce variable liquid crystal (LC) properties via ion beam (IB) irradiation on the ZrO2 layers. A uniform LC alignment characteristic was achieved on the ZrO2 thin film, and the pretilt angle was about 1.2°. We have shown that the pretilt angle can be controlled by changing ion beam parameters, such as the ion beam energy, the angle of incidence, and the irradiation time. The low pretilt angle for the nematic liquid crystal (NLC) on the ZrO2 thin film treated by ion beam irradiation could be adopted in planer alignment LCD liquid crystal display (LCD) applications as in-plane switching and fringe-field switching modes. The thermal stability of the ZrO2 thin film was sustained until 210°C. We also have shown that a liquid crystal cell aligned homogeneously by the ion beam irradiation exhibits the voltage-transmittance curve similar to that of a rubbed polyimide cell.

High-Density Poly(methyl methacrylate) Brushes as Anchoring Surfaces of Nematic Liquid Crystals

The orientation of a nematic liquid crystal (LC) on high-density poly(methyl methacrylate) (PMMA) brushes was examined. The nematic LC was injected into the cell consisting of two substrates on which PMMA chains were grafted with a density of 0.299 chains nm-2. It showed degenerate planar orientation, which became uniform on cooling from 120 °C at a magnetic field of 1 T. At ambient temperature, the aligned LC cell showed typical electro-optical properties when driven in the in-plane switching (IPS) mode, indicating that the LC molecules anchored to the brushes with the director parallel to the magnetic field direction. In contrast, at temperatures higher than 65 °C, the transmittance of the cell was time-dependent when driven over a prolonged period, suggesting that the anchoring direction rotated toward the electric field direction. Such temperature-dependent anchoring of the LC can be associated with the viscoelasticity of the PMMA brushes.

Viewing Angle Switching in In-Plane Switching Liquid Crystal Display

We demonstrated a novel viewing angle controllable display device in in-plane switching (IPS) mode with single panel. In the device, single pixel is separated into two regions, named as main pixel for displaying images and sub pixel for viewing angle control. Initially, the liquid crystal (LC) in sub pixel is homogenously aligned on substrate. For wide viewing angle mode, the LC switches in plane in the main pixel and for narrow viewing angle mode the LC switches the level of tilt angle without rotating by applying fringe electric fieldge. The proposed device is facilitated with simple manufacturing process and good viewing angle control with single panel.

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.

23.3: A Vertical‐Field‐Driven Polymer‐Stabilized Blue Phase Liquid Crystal Displays

AbstractWe demonstrate a polymer‐stabilized blue‐phase liquid crystal device PS‐BPLC, which can be driven by a vertical electric field by transforming normal incident beams into oblique ones. By attaching prism sheets to the cell, the high operating voltage and low transmittance issues on the PS‐BPLC employing conventional in‐plane field switching modes can be solved simply. The normal brightness can be enhanced by using two prism sheets on top and bottom substrates, respectively.

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.

24.1: A Vertical Common Electrodes Structure for High Aperture Ratio and Stable IPS Mode TFT‐LCD

AbstractWe developed In‐Plane‐Switching (IPS) mode structure with vertically aligned common electrodes for amorphous silicon (a‐Si) thin film transistor liquid crystal display (TFT‐LCD). We could improve an aperture ratio of the panel with this new structure by the elimination of storage area and compact design. The new vertical structure showed stabilized voltage ripple, DC charge and flicker variation by RC delay reduction and direct voltage driving from every driver IC. The panel was fabricated with the conventional a‐Si TFT process. We focused on making a new structure to get better quality of image compared to previous IPS mode TFT‐LCD.