TFT-LCD Panel Research Articles

Simplified Impact Analysis Based on Equivalent Static Analysis for Impact Design of TFT-LCD Panels

Simplified Impact Analysis Based on Equivalent Static Analysis for Impact Design of TFT-LCD Panels

An Effective Method for Measuring Elastic Modulus of Large TFT-LCD Panels

An Effective Method for Measuring Elastic Modulus of Large TFT-LCD Panels

3.2: Integrated a‐Si Gate Driver Circuit for TFT‐LCD Panel

AbstractWe developed an a‐Si TFT‐LCD panel with integrated gate driver circuit using a standard 5‐MASK process. To minimize the effect of the a‐Si TFT current and LC's capacitance variation with temperature, we developed a new a‐Si TFT circuit structure and minimized coupling capacitance by changing vertical architecture above gate driver circuit. Integration of gate driver circuit on glass substrate enables single chip and 3‐side free panel structure in a‐Si TFT‐LCD of QVGA(240*320) resolution.

TFT-LCD 모듈의 충격해석에 관한 연구

The impact behavior of TFT-LCD module is very complicated because the module is assisted with three parts such as back light unit, LCD Panel and top chassis. Especially, the back light unit is constructed with several small and thin parts made by plastics or steels. The design of the back light unit is very important because the recent demand is more lighter, thinner and narrower module. The aim of the present study is the investigation of mechanical characteristics during impact loading. The back light unit must assist TFT-LCD Panel made by glass and guide qualification of handling<br/> environment. This paper focus on the dynamic behavior of module and carries out a series of computer simulation using LS-DYNA program. Comparing with test results previously performed, dynamic characteristics of TFT-LCD module are estimated.

A new solution for splay‐to‐bend transition in OCB mode with a twisted area

Abstract— Quick, stable transition from splay‐to‐bend alignment in optically compensated bend (OCB) mode is crucial for practical use. This has been achieved by surface treating part of a pixel with a chiral dopant to induce a twist alignment while controlling the twist direction. The effectiveness of this new method was confirmed in a prototype TFT‐LCD panel.

48.4: Pre‐Emphasis Driving Method for Large Size and High Resolution TFT‐LCDs

AbstractAs the size and resolution of TFT‐LCD panels increase, the parasitic capacitance and resistance of the data lines and one row‐line‐time become larger and shorter, respectively. Because of the large RC‐delay of the data line, it becomes insufficient to transfer the video signal voltage to a pixel through the data line during one row‐line‐time. In this paper, we proposed the preemphasis driving method and its circuit which can compensate the RC‐delay and efficiently transfer the video signal voltage to the pixel within one row‐line‐time by adding pre‐emphasis voltage on the video signal voltage. Simulation results show that the charging time of transferring display signal through data line which has resistance of 20kΩ and capacitance of 200pF is 5.3μsec(within 2mV error).

57.2: Fabrication of High‐Transmittance TFT‐LCD Panels Using Low‐k CVD Films

AbstractFabrication of TFT‐LCD panels of high resolution and aperture ratio was demonstrated by using a low‐k dielectric film as a passivation layer for the first time. The low‐k dielectric films were successfully deposited and patterned using a conventional PECVD and plasma‐assisted etching techniques, causing no drastic modification to the standard TFT process. Thin film transistors having the a‐Si:C:O:H passivation showed a transfer characteristics similar to that of conventional TFT's. The high transmittance panel showed brightness approximately 30% higher than that of a standard panel without degrading other display characteristics, such as cross‐talk.

10.1: Invited Paper: 50/60 V Hivision LCD Rear‐projection TV GRAND WEGA with Excellent Picture Quality

AbstractWe developed 3‐panel transmissive LCD rear‐projection TVs for home use Commercial name: GRAND WEGA with large 42/50/60″ screens which display excellent pictures of high resolution and quality befitting the digital TV era: with high resolution and contrast and excellence of tonal and color reproduction. This paper focuses on a high temperature poly‐Si TFT‐LCD panel technology with 1.05 million pixels 1366 × 768 and a new driving method, the dot‐line inversion method.

Fabrication of Novel TFT LCD Panels with High Aperture Ratio Using a-SiCO:H Films as a Passivation Layer

AbstractFabrication of a novel TFT-LCD panel, using amorphous silicon oxycarbide (a-SiCO:H) films as a passivation layer, was successfully demonstrated for the first time. The a-SiCO:H low-k films were deposited using a standard PECVD (plasma-enhanced chemical vapor deposition) reactor from a gas mixture of trimethylsilane[Si(CH3)3H] and N2O. The resulting films have a dielectric constant between 2.7 and 3.5 and high optical transmittance in the range of visible lightThe transfer characteristics of the TFT's having a-SiCO:H as a passivation layer were comparable with that of a conventional TFT with a PECVD-grown SiNx passivation layer. Stability of the resulting TFT was performed under prolonged bias conditions, and the source-drain current was fairly constant over the test period. The LCD panel with the a-SiCO:H passivation layer showed 30% higher brightness than that of the standard panel.

28.2: Development of a 312ppi 4.1‐inch XGA Display with Low Temperature Poly‐Si Technology

AbstractA 312 ppi super high resolution TFT LCD panel with integrated scan driver and de‐multiplexer is developed by employing PMOS of the Low Temperature Poly‐Silicon technology. On the panel, 192 data inputs, driven by exclusive ASIC with 6‐bit gray‐scale to display 262,144 colors, are de‐multiplexed into 16 phases for all the data lines.

A New Measurement Method for Ion Density in TFT-LCD Panels

A novel measurement method has been developed to optically measure ion density in TFT-LCD panels. We investigated the optical response of twisted-nematic (TN) cells when ions were transported by applying an alternating electric field. A characteristic flickering of transmitted light was observed when a rectangular voltage with a low frequency of 1 Hz was applied to the cells. A peak in light intensity was observed during voltage application. Its height was found to be related to ion density in a linear way. This density was measured by using the transient current technique. We conclude that ion density can be determined by measuring optical response.

Field Sequential LCD using Organic EI Backlighting

We have proposed a new field sequential full-color display composed of an optical compensated birefringent (OCB) mode, p-Si TFT LCD panel and a multicolored organic electro luminescent device (OEL). In this display system, each merits of the LC device with high-resolution capability and the OEL device with high-speed response are combined. In addition, by using synchronously scan method, we could realize the field sequential display with a conventional TFT panel. We fabricated a trial display and confirmed its promising characteristics as a field sequential full-color display in the next generation.

A novel air-bridge type gate-data line-crossover reducing signal delay for large-size TFT-LCD panel

A new gate-to-data line-crossover employing an air-bridge has been proposed and fabricated in order to reduce the line-crossing capacitance. The proposed structure is composed of a low-dielectric air-gap between the gate and data line-crossover while the conventional one employs an oxide as a dielectric material. The capacitance between the gate and data line in the TFT-LCD panel is decreased considerably due to the low-dielectric air-gap. The signal delay of the new panel structure is reduced by about ten times compared with that of the conventional panel. The mechanical stability of the new panel structure passivated with an oxide is comparable with the conventional one.

P‐1: A New TFT‐LCD Panel Structure with High Aperture Ratio and Small Signal Delay by fabrication TFT in Line‐Crossover

AbstractWe have proposed and fabricated a poly‐Si TFT integrated gate‐data line‐crossover structure in order to increase the aperture ratio and to reduce the signal delay. The poly‐Si TFT is integrated in the gate‐data line‐crossover without sacrificing the electrical characteristics so that the aperture ratio of the panel was improved by about 3% because the TFT is located under a metal line. We employ a low dielectric air‐gap between the gate‐data line crossover, which reduces the capacitance between the gate and the data lines, so that the signal delay of the data line is decreased significantly. The fabricated TFT was successfully operated, and the proposed structure reduces the delay time by about 9 times compared with the conventional panel that does not employ any air‐bridges.

Low‐temperature poly‐Si TFT data drivers for an SVGA a‐Si TFT‐LCD panel

Abstract—Low‐temperature poly‐Si TFT data drivers for an SVGA a‐Si TFT‐LCD panel have been developed. The data drivers include shift registers, sample‐and‐hold circuits, and operational amplifiers, and drive LCD panels using a line‐at‐a‐time addressing method. To reduce the power consumption of the shift register, a dot‐clock control circuit has been developed. Using this circuit, the power consumption of the shift register has been reduced to 36% of that of conventional circuits. To cancel the offset voltage generated by the operational amplifier, an offset cancellation circuit for low‐temperature poly‐Si TFTs has been developed. This circuit is also able to avoid any unstable operation of the operational amplifier. Using this circuit, the offset voltage has been reduced to one‐third of the value without using the offset cancellation circuit. These data drivers have been connected to an LCD panel and have realized an SVGA display on a 12.1‐in. a‐Si TFT‐LCD panel.

Recessed gate-data line-crossover structures employing an air-gap to reduce signal delay for TFT-LCD panel

Two new line-crossover structures entitled "recessed air-bridge structure" and "recessed gate-line structure," which have improved mechanical durability and reduced data-tine signal delay in active matrix liquid crystal display (AMLCD) panel, have been proposed and fabricated. In the recessed air-bridge structure, the air-gap line-crossover is located at the bottom of the oxide trench so that the floated upper lines lie flush with the panel's surface. The recessed gate-line structure was fabricated by recessing the whole gate-line into the bottom of an oxide trench. Both of the fabricated structures, without any passivation layer, were proved sufficiently robust to withstand a rubbing process, which applied realistic mechanical stresses to the AMLCD panel. Experimental results show that the signal delays of the proposed structure are less than about 20% of the conventional structure.

A study on the poly-Si TFT and novel pixel structure for low flicker

We propose a new pixel structure based on complementary 2-TFTs switching structure. This structure is capable of reduction of DC level shift by Cgs coupling and improvement of defect tolerance, so making large, high image quality TFT-LCD panel fabrication both easy and economical. The compensating characteristics for reducing DC level shift in complementary 2-TFTs switching architecture were investigated using a TFT equivalent model. However, the number of gate lines and TFTs doubles as compared with a fundamental structure without redundancy. To minimize this problem (reduction of aperture ratio), a new pixel structure called a complementary 2-TFTs structure, which has one contact hole, was proposed. This technology has a low hardware overhead and is very capable of redundancy for open circuit defects in a TFT-LCD panel.

7.2: Invited Paper: Fourth‐Generation TFT‐LCD Production Line

AbstractWith the explosive growth of Note‐PC and Desktop‐PC monitor market, TFT LCD market was confronted with the entire supply shortage in 1999. Forecasting a more boooming stage for the next several years, many TFT LCD panel manufacturers continue to expand the capacity of their existing plants and also make an additional investment in building new plants. The new investment is concentrated on the 4th generation TFT LCD line in order to improve investment efficiency. The setup of a Samsung's 3.5th generation line progressed satisfactorily with a glass size of 600×720mm2. We have continuously reviewed several issues regarding the glass size for our next 4th generaton line, which leads to adopt 730×920mm2. Due to the continuous enlargement of a substate size and following difficulty in transferring cassettes, the next line is expected to be the last line that employs “cassette transfer”. The layout of the next line will shift from conventional “concentration‐type” to “separation‐type” configuraton for the purpose of reducing transfer distance as well as transfer time. The details will be discussed in this paper.

Design of poly-Si TFT-LCD panel with integrated driver circuits for an HDTV/XGA projection system

Design techniques of 2.25-in. diagonal poly-Si TFT-LCD panel for an HDTV/XGA projection system are described, especially focusing on the driver circuits. The area-efficiency of the driver circuits is a very important design issue, because the integrated poly-Si driver circuits takes a very large area due to inferior device characteristics of single crystal-Si transistors. For area-efficiency, the pixel with a novel structure of the line memory has been proposed, and the analog switch circuits have been carefully designed in respect of area-efficiency without sacrificing the other performances. A novel gate driver architecture has been also proposed which can provide both progressive and dual-line scanning patterns for HDTV and XGA images. The gate drivers using tri-state buffers are established at both sides of the panel for redundancy, so that a defective one can be electrically separated from gate lines by a control signal instead of a conventional laser-cutting method. Area-efficiency is also discussed in designing the gate driver. Using the proposed design techniques, a 2.25-in. diagonal poly-Si TFT-LCD panel with source driver circuits of 1100 /spl mu/m-width and gate driver circuits of 2650 /spl mu/m-width for an HDTV/XGA projection system has been successfully developed.

A Novel Air-Bridge Type Gate-Data Line Inter-Crossing to Reduce Signal delay for Large size AMLCD

AbstractA new TFT-LCD panel with an air-bridge type gate to data line inter-crossing has been proposed and its characteristics have been measured. The proposed structure has air-gap between gate and data line intercrossing. This air-bridge TFT-LCD panel has very small amount of capacitance between gate and data line. The new panel structure achieves 9 times faster signal delay compared with conventional panel, which enables to have enough design margin of over 20-inch diagonal size UXGA panel. We have examined thermal and mechanical durability of new panel to verify capability for commercial AMLCD application.