Ultra‐FFS TFT‐LCD with super image quality,fast response time,and strong pressure‐resistant characteristics

Fringe‐field‐switching (FFS) devices using liquid‐crystal (LC) with a negative dielectric anisotropy exhibit high transmittance and wide viewing angle simultaneously. Recently, we have developed an “Ultra‐FFS” thin‐film‐transistor (TFT) LCD using LC with a positive dielectric anisotropy that exhibits high transmittance, is color‐shift free, has a high‐contrast ratio in a wide range, experiences no crosstalk and has a fast response time of 25 msec. In this paper, the device concept is discussed, and, in addition, the pressure‐resistant characteristics of the devices compared with that of the twisted‐nematic (TN) LCD is discussed.     

Comb‐on‐plane switching electrodes for liquid‐crystal displays

Abstract— Although the common twisted‐nematic liquid‐crystal displays (TN‐LCD) has excellent contrast and low color dispersion, it suffers from small viewing angle when driven into the homeotropic state. Among the many techniques proposed, in‐plane switching (IPS) has been quite effective in improving viewing angle. However, there may be difficulty in adopting conventional IPS to higher‐definition displays because it suffers from limited storage capacitance and reduced transmittance. A new comb‐on‐plane switching (COPS) electrode design is proposed. Compared to conventional IPS, COPS allows for lower switching voltage and offers advantages including naturally scalable storage capacitance, wide viewing angle with TN‐like high transmittance, and low color dispersion.     

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.     

A high‐aperture‐ratio and low‐crosstalk pixel structure design for in‐plane‐switching‐mode TFT‐LCDs

Abstract— The TFT‐LCD market is growing rapidly, and the replacement of CRT TV by LCD TV requires the implementation of LC modes with wide viewing angles and high brightness. The IPS mode is an excellent technology to realize wide viewing angles, but it has a low aperture ratio that has now been improved by Advanced Super‐IPS (AS‐IPS). In this paper, we propose a novel pixel structure design that not only increases the aperture ratio but also reduces the crosstalk. We have improved the current AS‐IPS aperture ratio by 1.25 times and effectively reduced the capacitive coupling ratio from 1.2% to 0.05%.     

Maximizing electro‐optic performances in the fringe‐field switching liquid crystal mode with negative dielectric anisotropic liquid crystal

The fringe‐field switching (FFS) mode that uses liquid crystals (LCs) with negative dielectric anisotropy is used in high‐resolution FFS liquid crystal display owing to its higher transmittance over positive LC, although its response time becomes slow and operating voltage (V_op) becomes high. In the device, reduction of the cell gap is required to achieve fast response time, which results in increase in V_op in general. In this paper, we propose the FFS mode with electrode width 1 µm and distance between the electrodes 1.5 µm. In such an electrode structure, V_op decreases with decreasing cell gap to 2 µm so that a proper V_op, high LC's light efficiency of 90%, a high color temperature, and a fast response time less than 10 ms, can be achieved, which maximizes electro‐optic performance of the FFS mode.     

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.     

Electro‐optical characteristics of ion‐beam‐aligned FFS‐LCDs on diamond‐like‐carbon thin film

Abstract— A fringe‐field‐switching (FFS) mode cell having LC alignment has been developed by using a non‐rubbing method, a ion‐beam‐alignment method on a‐C:H thin film, to analyze the electro‐optical characteristics of this cell. The suitable inorganic thin film for FFS‐LCDs and the alignment capabilities of nematic liquid crystal (NLC) have been studied. An excellent voltage‐transmittance (V‐T) and response‐time curve for the ion‐beam‐aligned FFS‐LCDs were observed using oblique ion‐beam exposure on DLC thin films.     

Fast‐response liquid‐crystal displays using crossed fringe fields

Abstract— A fast‐response and wide‐view liquid‐crystal display (LCD) using the crossed fringe‐field‐switching (CFFS) mode is proposed, where the fringe‐field electrodes exist on both the top and bottom substrates. The bottom fringe field is used to turn on the LC directors and the top fringe field is used to assist in the LC decay process. The decay time is reduced by ～2× compared to that of the conventional FFS mode between the full bright and dark states, and more than a 2× improvement is obtained for other gray‐scale transitions. This CFFS mode also preserves the wide‐view characteristics as the conventional FFS mode. Its applications to LCD TVs and monitors for reducing image blur are addressed.     

Viewing‐angle‐switching device based on array of optical micro‐rods incorporated with electrophoretic material systems

We have successfully demonstrated a control device for a viewing angle that enables switching between two states, a wide‐viewing angle, and a narrow‐viewing angle. It is composed of a light‐transmitting portion formed with an array of optical micro‐rods and a shielding/transmitting changeable portion of cross stripes designed with electrophoretic material systems consisting of black particles and an optically transparent medium. When the black particles are fully dispersed in the optically transparent medium, the cross stripe portion plays the role of a non‐transmitting material as the shielding portion in a similar manner to a conventional viewing angle control film. When the black particles are completely gathered electronically to one side in the optically transparent medium, in contrast, the cross stripe portion filled by the optically transparent medium can transmit incident light. These functions allow us to select electrically either of two modes between a limited viewing angle and a non‐limited viewing angle. The optical properties for the limited viewing angle mode were +/?30° of the visible angle and 50% of the transmittance, and the one for the non‐limited viewing mode was 58% of the transmittance. The response time from the narrow‐viewing angle to wide‐viewing angle was 1 s at 20 V of applied voltage.     

Viewing angle switchable blue‐phase liquid crystal display with low voltage and high transmittance

We propose a viewing angle switchable blue‐phase liquid crystal display with low voltage and high transmittance. In this device, in‐plane protrusions are used to lower operating voltage and improve the transmittance. Besides, the top electrode can control viewing angle of the proposed display. When no voltage is applied to the top electrode, the display shows wide viewing angle mode. On the contrary, this display shows narrow viewing angle mode. So, this device exhibits low operating voltage, high transmittance, and good viewing angle controllable characteristics.     

Light‐scattering liquid‐crystal composites with reduced off‐axis haze

Abstract— The majority of liquid‐crystal (LC) composites operating in a light‐scattering mode suffer from scattering of the obliquely incident light in the field on‐state (off‐axis haze effect). This is evident in the angularly selective viewing‐angle characteristic with a maximal transmittance corresponding to the normally incident light. We consider methods to control the viewing‐angle characteristic of polymer‐dispersed LC (PDLC) and filled LC. For PDLC samples, this control is realized by modification of the refractive index of the polymer matrix with highly refractive nanoparticles (NP) having a low rate of aggregation in the polymer. By proper optimization of NP concentration, one can bring the refractive index of the polymer matrix in the range needed to reduce the haze problem. In filled LC, the viewing‐angle curve depends on the refractive‐index mismatch between the LC and NP. By optimization of this parameter, one can flatten the angular characteristic or obtain selectable viewing angles in the desirable range. These results allow for the construction of optical shutters and a scattering‐type LCD with controllable viewing‐angle characteristics, particularly with low off‐axis haze.     

Switchable transmissive and reflective liquid‐crystal display using a multi‐domain vertical alignment

Abstract— A wide‐view transflective liquid‐crystal display (LCD) capable of switching between transmissive and reflective modes in response to different ambient‐light conditions is proposed. This transflective LCD adopts a single‐cell‐gap multi‐domain vertical‐alignment (MVA) cell that exhibits high contrast ratio, wide‐viewing angle, and good light transmittance (T) and reflectance (R). Under proper cell optimization, a good match between the VT and VR curves can also be obtained for single‐gamma‐curve driving.     

Fast response fringe‐field switching mode liquid crystal development for shutter glass 3D

A type of fast response time (RT) liquid crystal (LC) was developed to adopt in fringe‐field switching (FFS) mode for shutter glass 3D display device, the average gray to gray level (GTG) RT can reduce from 7.43 ms to 4.48 ms at a refreshing rate of 60 Hz, and the transmittance can increase by 15.4% compared with conventional LC based on the same cell gap. Meanwhile, the correlation among optical efficiency, correlative color temperature (CCT) of module and retardation of LC for FFS mode was studied. Transmittance is proportional to the retardation of LC; however, the CCT is inversely proportional to the retardation. The fast response LC can keep almost the original optical efficiency and CCT.     

High‐transmittance in‐plane switching liquid crystal display device driven by three‐level voltages

We propose a single‐layered electrode structure using three voltage levels instead of two to achieve high transmittance in an in‐plane switching liquid crystal display device. The proposed structure consists of two pixel electrodes and one common electrode. By using three voltage levels, we can generate an in‐plane electric field higher than that in a conventional in‐plane switching device. We confirmed that by using the proposed structure, the transmittance of a liquid crystal device can be increased from 29% to 35% at a slightly lower operating voltage without using the double‐layered electrode structure required for the fringe‐field switching mode. The transmittance of the proposed device is higher than that of the fringe‐field switching device.     

Single‐cell‐gap transflective liquid‐crystal display using double‐ and single‐mode approaches

Abstract— In this paper, many popular methods to study transflective liquid‐crystal‐displays (LCDs) have been discussed, and several new transflective LCD configurations with a single‐cell gap have been proposed. The traditional double‐cell‐gap method gives the best match of the transmittance/reflectance voltage curve (TVC/RVC) and also the widest viewing angle, but also brings the highest fabrication complexity. The single‐cell‐gap transflective LCD is much easier to fabricate and also shows a good match of TVC/RVC. A new methodology has been shown to find optimal configurations for single‐cell‐gap transflective LCDs. New configurations using multimode in a single pixel include twisted nematic (TN) optically compensated bend (OCB), TN electrically controlled birefringence (ECB), and TN low‐twisted nematic (LTN). TN and hybrid‐aligned nematic (HAN) modes have been investigated for single‐mode transflective LCDs. The results exhibit high contrast ratio, a good match of TVC/RVC, as well as wide viewing angle.     

Requirements for large‐sized high‐resolution TFT‐LCDs

Abstract— A 22‐in. prototype TFT‐LCD with a resolution of 200 pixels per inch and wide‐viewing‐angle capability has been developed and its requirements in terms of screen quality and technology will be discussed. An in‐plane‐switching mode with dual‐domain structure, post‐spacers, and high‐resolution process were implemented to achieve superior front‐of‐screen quality. And, also, in order to improve reliability and productivity, we developed a new injection method for liquid crystals which enabled us to eliminate injection holes.     

Advanced liquid‐crystal materials for TFT monitor and TV applications

Notebook applications have been one of the most important driving forces behind the remarkable growth of liquid‐crystal displays (LCDs). LCDs have recently been well accepted in the monitor market and large growth is forecasted because of the replacement of CRTs. The next challenge for LCDs is the TV market. These new application areas are supported by advanced LC technologies such as film‐compensated twisted nematic (TN), in‐plane switching (IPS), and vertically aligned (VA) modes. Each TFT technology requires a corresponding LC material improvement. We will review the recent liquid‐crystal material development for these advanced LC technologies.     

A new pixel design and a novel driving scheme for multi‐domain vertically aligned LCDs

Abstract— By using a new pixel design and a novel driving scheme that adds a bias electrode and a bias TFT to the ordinary pixel structure, a high‐contrast‐ratio and wide‐viewing‐angle LCD mode, refered to as the biased vertical‐alignment (BVA) mode, has been sucessfully developed. Compared to the published data on the PVA and MVA modes, the BVA mode has a distinct advantage of lower manufacturing cost due to the elimination of a lithographic process step that forms either ITO cuts or protrusions on the color‐filter substrates. The BVA mode requires ITO cuts on the TFT substrate similar to that for the PVA and MVA modes. The 15‐in. BVA‐mode XGA prototype exhibits a high contrast ratio of 1200:1 and high cell transmittance of 4.3%.     

A novel portable LCD using a new AFFS technology for outdoor readability

Abstract— The advanced fringe‐field switching (AFFS) mode is suitable for portable display devices. It has high transmittance, wide viewing angle, low power consumption, high contrast ratio, and a ripple‐free property resistant to pressure. Recently, a 10.4‐in. XGA prototype which demonstrates excellent transmittance and very good outdoor readability has been developed. To obtain these properties, a new pixel structure has been designed which has a large aperture and a metal embossing pattern for inner reflectance without the use of a black matrix on the embossing metal pattern. Precise control of the liquid‐crystal electrodynamics and surface reflectance using an AR polarizer was achieved. This new panel shows distinguished characteristics for outdoor readability with the backlight on under a bright outside light source.     

Transflective IPS‐LCD with improved reflective contrast ratio

Abstract— In order to improve the reflective contrast ratio of transflective IPS‐LCDs, a novel pixel design for a normally white reflective IPS has been proposed. In this design, the large‐inter‐electrode‐spacing layout using a novel driving method and a double‐layered electrode have effectively reduced the light leakage. By applying these two technologies, a transflective IPS‐LCD has been successfully demonstrated with a high contrast ratio (15:1) in the reflective mode and a wide‐viewing‐angle characteristic in the transmissive mode.