Narrow‐gap field‐sequential TN‐LCD with and without nanoparticle doping

Abstract— The fabrication and demonstration of field‐sequential‐color (FSC) LCDs using modules of narrow‐gap twisted‐nematic (NTN) LCDs with and without doping of newly synthesized PγCyD‐ZrO² nanoparticles is reported. Two types of FSC‐LCDs are demonstrated: one is a direct multiplexed NTN‐LCD and the other is TFT driven. The advantages of FSC‐LCDs include their high legibility even under direct sunlight, and the mechanism for the doping of nanoparticles in LCDs is discussed.     

Active‐matrix and flexible liquid‐crystal displays with carbon‐nanotube pixel electrodes

Abstract— The necessary processes to use random carbon‐nanotube networks as transparent conductors in twisted‐nematic liquid‐crystal displays have been developed, replacing indium tin oxide. Because the nanotubes are deposited vacuum‐free from suspension, the potential advantages are lower costs for material, equipment, and production. Nanotube networks are also much better suited for flexible displays than the commonly used metal oxides. With the developed processes, the world's first full‐color active‐matrix LCDs as well as directly addressed flexible displays on plastic substrates with carbon‐nanotube pixel electrodes, have been realized.     

An introduction to PSS‐LCDs: A fast‐optical‐response smectic LCD

Abstract— A new type of fast‐optical‐response liquid‐crystal display is introduced. This display uses a certain type of smectic liquid‐crystal material that has a fast optical response as well as a native wide viewing angle. Unlike well‐known smectic‐based LCD technologies, this new type of LCD technology is highly compatibile with most nematic‐based LCDs. This compatibility provides advantages for practical uses. Here, the initial molecular alignment and drive concept as well as the general performance of this new display technology are discussed.     

Towards a low‐cost high‐quality carbon‐nanotube field‐emission display

Abstract— We have developed field‐emission‐display technology driven by chemical‐vapor‐deposition‐grown carbon‐nanotube emitters incorporated in a simple, low‐cost device structure. Here, we report on frit‐sealed test displays with a brightness of 3000 cd/m² at 3 kV and a lifetime of 9000 hours with only 45% degradation. We also demonstrate the scalability of the technology with a uniform high‐brightness 6‐in. QVGA that displays video images with a switching voltage of 40 V.     

The manufacture of a thin‐film LCD

LCDs with internal polarizers were designed and fabricated as production prototype TN‐LCDs. Optiva? Thin Crystalline Films (TCFs) were used as the polarizers for these displays. The design and processes for fabrication of a TN‐LCD with Optiva internal polarizers will be discussed.     

Suspension‐deposited carbon‐nanotube networks for flexible active‐matrix displays

Abstract— The unique properties of carbon nanotubes (CNTs) promise innovative solutions for a variety of display applications. The CNTs can be deposited from suspension. These simple and low‐cost techniques will replace time‐consuming and costly vacuum processes and can be applied to large‐area glass and flexible substrates. Single‐walled carbon nanotubes (SWNTs) have been used as conducting and transparent layers, replacing the brittle ITO, and as the semiconducting layer in thin‐film transistors (TFTs). There is no need for alignment because a CNT network is used instead of single CNTs. Both processes can be applied to glass and to flexible plastic substrates. The transparent and conductive nanotube layers can be produced with a sheet resistance of 400 Ω/□ at 80% transmittance. Such layers have been used to produce directly addressed liquid‐crystal displays and organic light‐emitting diodes (OLED). The CNT‐TFTs reach on/off ratios of more than 10⁵ and effective charge‐carrier mobilities of 1 cm²/V‐sec and above.     

Reduced dc offset and faster dynamic response in a carbon‐nanotube‐impregnated liquid‐crystal display

Abstract— Liquid crystals have been extensively employed in photonic devices, especially in current flat‐panel displays. Demands on high‐quality electro‐optical performance of liquid‐crystal displays have continued to impel delicate molecular designs, chemical syntheses, as well as advanced cell‐manufacturing processes, leading to a reduced dc offset and faster intrinsic response in the devices. Here, a novel approach toward the reduction of the residual dc and response time is reported based on carbon‐nanotube doping. It is demonstrated that a minute amount of carbon nanotubes as a dopant can suppress the unwanted ion effect, invariably lower the rotational viscosity, and modify other physical properties of the liquid crystals, giving the approach an opportunity in display applications.     

Uniform carbon‐nanotube emitter for field‐emission displays

Abstract— The synthesis of carbon‐nanotube (CNT) field emitters for FEDs by thermal chemical vapor deposition (CVD) and their structural and emission characterization are described. Multi‐walled nanotubes (MWNTs) were grown on patterned metal‐base electrodes by thermal CVD, and the grown CNTs formed a network structured layer covering the surfaces of the metal electrode uniformly, which realized uniform distribution of electron emission. A technique for growing narrow MWNTs was also developed in order to reduce the driving voltage. The diameter of MWNT depends on the growth temperature, and it has changed from 40 nm at the low temperature (675°C) to 10–15 nm at the high temperature (900–1000°C). Moreover, narrower MWNTs were grown by using the metal‐base electrode covered with a thin alumina layer and a metal catalyst layer. Double‐walled nanotubes (DWNTs) were also observed among narrow MWNTs. The emission from the narrow CNTs showed a low turn‐on electric field of 1.5 V/μm at the as‐grown layer.     

Switching of carbon‐nanotube emitters by an integrated MOSFET

Abstract— The integration of carbon‐nanotube (CNT) emitters with a metal‐oxide‐semiconductor field‐effect transistor (MOSFET) can stabilize and control the emission current of CNTs. CNTs were grown by using the resist‐assisted patterning (RAP) process and plasma‐enhanced chemical vapor deposition (PECVD) and were connected to the drain part of an external MOSFET. The electron‐emission current of CNTs was switched by applying a low gate voltage to the MOSFET, and the switching current was very stable because the MOSFET was operated in the saturation region. Based on these results, the emission current of CNTs was stabilized and switched by using a low‐voltage‐driven MOSFET.     

Large‐area FEDs with carbon‐nanotube field emitter

Abstract— Application of carbon nanotubes (CNTs) as field emitters for large‐area FED panels is described. In 1998, we presented the first experimental devices: light‐source tubes for outdoor large‐area displays and a diode‐type flat‐panel display, both with screen‐printed CNT cathodes. The fisrt practical high‐luminance color CNT‐FED panel was built in 1999. It employed the new triode‐structure panel was x‐y addressable. The CNT‐FED structure was further optimized for large‐area display panels by improving the luminous uniformity. This paper also describes the design and performance of a new, experimental, 40‐in.‐diagonal panel, which showed that the CNT‐FED technology is suitable for use in large‐area displays.     

New era for TFT‐LCD size and viewing‐angle performance

Abstract— Samsung has announced the development of a full‐high‐definition (1920 × 1080) 82‐in. TFT‐LCD panel using Super‐PVA (S‐PVA) technology, the world's largest TFT‐LCD. In addition to the size breakthrough, this product achieves 600 nits of brightness, a contrast ratio of over 1200:1, an angle of view of 180°, a color gamut of 92%, and an 8‐msec response time. Several key enabling technologies were developed to achieve these specifications, including two‐transistor direct‐driven independently controlled S‐PVA subpixels, non‐even‐area‐ratio subpixels for optimal off‐axis gamma, gate overlap driving for larger driving margin, new CCFL technology for higher color gamut, and advanced fabrication techniques including the use of Samsung's new Gen 7 line. Many of these technologies will be applied to other products within Samsung's LCD‐TV product line. Samsung's broader development efforts toward the overall LCD‐TV market, including production status of the Gen 7 facility, will be updated.     

Reduced cross‐talk in shutter‐glass‐based stereoscopic LCD

Abstract— It is expected that 3‐D will be the next step in the enhanced viewing experience. At present, there are two competing 3‐D technologies for glasses‐based consumer TVs: active shutter glasses and passive polarized glasses. With the ongoing reduction in response time of liquid‐crystal displays (LCDs), this article will focus on shutter‐glass‐based stereoscopic LCDs. In this paper, the properties of such a display system is described and it is demonstrated that by adding a line‐scanning backlight, the cross‐talk can be reduced to less than 1.4%, allowing for excellent 3‐D portrayal. For images of extreme contrast, this is perceivable, but not judged annoying by a panel of expert viewers. Which characteristics of the display and shutter glasses that should be optimized to create an inexpensive, cross‐talk‐free, 3‐D LCD are discussed.     

Viewing‐angle compensation of TN‐ and ECB‐LCD modes by using a rod‐like liquid‐crystalline polymer film

Abstract— A liquid‐crystal line retardation‐film technology by using a rod‐like liquid‐crystalline polymer (LCP) for various LCD modes have been developed. In particular, considerable improvements in viewing‐angle performance have been achieved for the twisted‐nematic (TN) and the transmissive/transflective electrically controlled birefringence (ECB) modes by using hybrid aligned nematic film (NH Film).     

High‐performance high‐efficiency LED‐backlight driving system for LCD panels

Abstract— A high‐performance high‐efficiency LED‐backlight driving system for liquid‐crystal‐display panels is presented. The proposed LED‐backlight driving system is composed of a high‐efficiency DC‐DC converter capable of operating over a universal AC input voltage (75–265 V) and a high‐performance LED‐backlight sector‐dimming controller. The high efficiency of the system is achieved by using an asymmetrical half‐bridge DC‐DC converter that utilizes a new voltage‐driven synchronous rectifier and an LED‐backlight sector‐dimming controller. This controller regulates current using lossless power semiconductor switches (MOSFETs). The power semiconductor switches of the proposed DC‐DC converter, including the synchronous rectifier switch, operate with zero voltage, achieving high efficiency and low switch voltage stress using the asymmetrical‐PWM and synchronous rectifier techniques. To achieve high performance, the proposed driving system performs the sector dimming and the current regulation using low‐cost microcontrollers and MOSFET switching, resulting in high contrast and brightness. A100‐W laboratory prototype was built and tested. The experimental results verify the feasibility of the proposed system.     

Polyimide‐free LCD by dissolving dendrimers

Vertical alignment (VA) and in‐plane switching modes have been widely used for liquid crystal displays (LCDs). They require a polyimide (PI) alignment layer in the pixel structure. PI‐free LCDs have been proposed to exploit the VA of liquid crystals (LCs) obtained by dissolving dendrimers without PI. In this paper, we report a new PI‐free VA mode with a pixel structure that has in‐plane electrodes. The PI‐free VA is achieved by dissolving an LC dendrimer in a positive LC mixture. We measured the test cell properties and obtained a lower voltage and a higher brightness in the voltage–brightness curve. In addition, we analyzed the alignment surface of LC dendrimer by time‐of‐flight secondary ion mass spectrometry and scanning electron microscopy observations. We found that dendrimer molecules are uniformly adsorbed on the glass surface and that the layer was generally one molecule thick. These properties are responsible for the lower voltage and higher brightness of the PI‐free VA mode. The use of dendrimers allows the PI process to be omitted and reduces the power consumption of the VA mode. It is thus possible to reduce the high manufacturing costs and improve the performance of the VA mode.     

Novel WV film for wide‐viewing‐angle TN‐mode LCDs

Abstract— A new optical compensation film refered to as WV‐EA film for TN‐mode TFT‐LCDs has been developed, resulting in higher contrast ratio, wider‐viewing‐angle characteristics, and improved color shift than their predecessors, especially in the horizontal direction. These features of the new WV film were achieved as a result of haze reduction and optimizing the optical characteristics of the polymerized discotic material layer and TAC film. These features are suitable for large‐sized and wide‐aspect‐ratio LCD monitors and TVs.     

Angular dependence of the performance of stereoscopic liquid‐crystal‐display (LCD) television using shutter glasses (SG)

Abstract— 3‐D cross‐talk typically represents the ratio of image overlap between the left and right views. For stereoscopic LCDs using shutter‐glasses technology, 3‐D cross‐talk for stereoscopic LCD TV with a diagonal size of 46 in. and vertical alignment (VA) mode was measured to change from 1% to 10% when the stereoscopic display is rotated around the vertical axis. Input signals consist of the left and right images that include patterns of different amounts of binocular disparity and various gray levels. Ghost‐like artifacts are observed. Furthermore, intensities of these artifacts are observed to change as the stereoscopic display is rotated about the vertical axis. The temporal luminance of the LCD used in stereoscopic TV was found to be dependent on the viewing direction and can be considered as one cause of the phenomenon of angular dependence of performance for stereoscopic displays.     

Cell‐gap and pretilt‐angle determination of a vertically aligned reflective liquid‐crystal display

Abstract— A simple method for determining the cell gap and pretilt angle of a vertically aligned reflective liquid‐crystal display has been developed. By extrapolating the phase‐retardation curve of the VA—LC cell in the high‐voltage regime, we can determine the cell gap. With this value for the cell gap and the low‐voltage part of the phase‐retardation curve, we can determine the pretilt angle.     

Growth of uniform carbon‐nanotube arrays with sandwich technology

Abstract— In this work, a novel approach to grow structured, highly oriented carbon nanotubes (CNTs), which are vertically aligned to the substrate and show large field emission is reported. Growth is performed on lithographically defined dots of catalysts, which can be deposited on metallic, semiconducting, and glass substrates. A sandwiched catalyst structure and microwave plasma chemical vapor deposition enables the formation of uniform CNT arrays of 1.6 × 1.6 μm². The method is easily scalable to large areas. The CNT arrays exhibit a stable field emission of 20 mA and a macroscopic current density of 50 mA/cm² at a rather low electric field of 5.33 V/μm. Modeling of space charge indicates that space charge reduces the magnitude of the CNT emission at high field strength: this agrees satisfactorily with the measurements.     

Liquid‐crystal mixtures having tolane substances for field‐sequential‐color TN‐LCDs

Novel liquid‐crystal (LC) mixtures featuring high optical anisotropy Δn) and small rotational viscosity (γ¹) were developed for field‐sequential‐color TN‐LCD applications. The dynamic behavior of the TN cells in a narrow‐gap range was studied and new tolane LC substances were introduced. The newly developed LC mixtures, having a narrow‐gap cell, enable a TN‐LCD to switch fast enough to be applied to field‐sequential‐color displays not only at a room temperature but also at low temperatures. It was also confirmed that the voltage‐holding ratio (VHR) is sufficiently high in field‐sequential addressing conditions and, therefore, the LC mixtures can be used in active‐matrix LCDs. For practical use, a storage test of the TN cells under light irradiation was performed to evaluate their voltage‐holding property. It was also confirmed that their high VHR can be maintained for over 10,000 hours under practical conditions.