1. International technical level and status quo

The TFT-LCD technology has matured, and the three major problems that have plagued LCD flat panel displays for a long time have been solved: viewing angle, color saturation, and brightness. The use of multi-area vertical arrangement mode (MVA mode) and in-plane switching mode (IPS mode) enables the horizontal viewing angle of LCD flat panel display to reach 170 degrees (currently, major LCD TV manufacturers use hard screens, and the viewing angle has reached 178 degrees, almost are visible horizontally). MVA mode also reduces the response time to 20ms.

From a technical point of view, the TN+Film solution is the simplest one. TFT display manufacturers combine the twisted nematic (TN: Twisted Nematic) technology used in older LCD displays with TFT technology, resulting in TN+Film technology. This technology is mainly to expand the viewing angle by covering the display with a special film - the viewing angle can be expanded from 90 degrees to about 140 degrees. Like the standard TFT display, TN+Film realizes image control by arranging liquid crystal molecules, and it covers a layer of film on the upper surface to increase the viewing angle. However, the relatively weak contrast ratio and slow response time of TFT displays remain unchanged. So TN+Film is not a good solution, and it has no merits except that it is the cheapest.

IPS is the abbreviation of In-Plane Switching, which means flat panel switch, also known as Super TFT. It was first developed by Hitachi (Hitachi) and learned that NEC and Nokia also use this technology to make displays. The difference between this technology and the twisted nematic display (TN-Film) is that the liquid crystal molecules are arranged in different ways relative to the basic. When a voltage is applied, the liquid crystal molecules are aligned parallel to the substrate.

The viewing angle of the display using this technology reaches 170 degrees, which is equivalent to the viewing angle of a cathode ray tube, but this technology also has disadvantages: in order to allow the liquid crystal molecules to be arranged in parallel, the electrodes cannot be like a twisted nematic display ( TN-Film), both on the two-layer substrate, and can only be placed on the lower-layer substrate - the direct result of this is that the brightness and contrast of the display are significantly reduced. brightness. As a result, the response time and contrast ratio are more difficult to improve compared to ordinary TFT displays. So this technology doesn't seem like the best solution either.

MVA multi-area vertical arrangement technology was developed by Japan's Fujitsu (Fujitsu) company. From a technical point of view, it takes into account both the viewing angle and the response time. A compromise solution was found. MVA technology enables viewing angles of up to 160 degrees -- not as good as the 170 degrees of viewing angles that IPS can achieve, but it's still good because the technology provides better contrast and shorter response times.

The M in MVA stands for "multi-domains" - meaning multiple regions. Those purple protrusions make up what's called a zone. There are generally four such areas in MAV displays produced by Fujitsu.

VA is short for "vertical alignment", which means vertical alignment. However, there are some misunderstandings in the literal sense, because the liquid crystal molecules are not "protrusion" (protrusion) completely vertical. When the voltage generates an electric field, the liquid crystal molecules are aligned parallel to each other, so that the backlight light source can pass through, and can spread the light in all directions, thereby expanding the viewing angle.

In addition, MVA also provides faster response time than IPS and TN+Film technologies, which is very important to achieve good video recovery and residual visual effects. The contrast ratio of MVA LCDs has also improved, but again with the change in visibility.

Field Sequential Full Color (FSFC) LCD technology developed on the basis of Optical Compensation Bend (OCB) technology not only eliminates the color filter (CF), which accounts for one-third of the cost, but also increases the resolution by 3 times , the transmittance is increased by 5 times, and the process is simplified and the cost is reduced. The development of color film technology and backlight technology has made the color reproduction capability of TFT-LCD reach or even exceed CRT. As the main technical indicators of commercial display TFT-LCD, the comprehensive performance is the best among all kinds of display devices, especially the improvement of mass production technology of TFT-LCD products, the development space of multi-variety and multi-series products, and the application range is omnipresent. . Moreover, South Korea's Samsung Electronics has produced a 38-inch single-substrate TFT-LCD LCD TV and a 40-inch TFT-LCD display, and with its excellent performance, it has entered the large-size color TV market that is recognized as the PDP market.

LCD is the product with the lowest power consumption among all displays. Taking 13.3-inch XGA TFT-LCD as an example, its power consumption was 4.4 watts in 1998, 3.3 watts in 1999, and will be less than 2.5 watts in 2001, especially reflective TFT- The LCD has been successfully developed, and its power consumption is an order of magnitude lower than that of the transmissive TFT-LCD due to the cancellation of the backlight. At the same time, due to several improvements, the low-temperature laser annealing polysilicon (P-Si) technology has matured, and the developed single-crystal silicon technology has made TFT-LCD faster in response and higher in circuit integration. The application of phase-locked loop technology, a The use of newer functions, the adoption of more complete peripheral circuits, and the development of system on glass technology have made TFT-LCD lighter and thinner. The thickness of the 13.3-inch TFT-LCD was 7.2mm in 1998, 5.5mm in 1999, and fell below 5mm in 2001. Its weight was 580 grams in 1998, 450 grams in 1999, and fell below 400 grams in 2001. The large-scale production technology of TFT-LCD has also matured, and fully automatic production has been realized. Its fifth-generation production line will enter the practical production stage in 2002, and the production cost will continue to decline. The maturity and progress of TFT-LCD technology and its unique performance advantages determine the pattern that TFT-LCD will eventually replace CRT.

2. The current state of the technical level of TFT-LCD

(1) Both the horizontal and vertical angles reach 170 degrees;

(2) The display brightness reaches 500 nits and the contrast ratio is 500:1;

(3) The life span exceeds 30,000 hours;

(4) Field sequential full color (FSFC) technology began to be used in industrial production;

(5) Large-screen thin-film transistor liquid crystal display color TVs (TFT-LC TVs) have begun to enter large-scale industrial production, and the picture quality of TFT-LCTVs has reached or even exceeded CRTs. For example, the resolution of 28-inch TFT LC TVs is 1920× 1200, both horizontal and vertical viewing angles are 170 degrees; 38-inch TFT LC TV has been successfully developed; 40-inch TFT-LCD has also been successfully developed;

(6) The large-area low-temperature polysilicon TFT-LCD has been successfully developed and put into industrial production, and the self-scanning LCD of amorphous silicon TFT has been commercialized;

(7) The reflective TFT-LCD color display began to be commercialized. For example, a 5.8-inch reflective display with a resolution of 400×234 and a 16:9 picture has a reflectivity of 30%, a response speed of 30ms, and a power consumption of 0.15 watts.

(8) A large-screen production line for 730×920mm substrates has been successfully developed, and a large-screen production line for larger-sized substrates is under construction.

(9) Commercialization of plastic substrate TFT-LCD began. There are 5 varieties of plastic substrate products in Japan.

(10) Backlights and inverters, although reflective LCDs are being actively developed, but transmissive TFT-LCDs with backlights are still mainstream products for a long time. The backlight is its important accessory. Germany developed a flat fluorescent lamp backlight for liquid crystal modules, with a brightness of 5000-7000cd/m2 and a lifespan of 100,000 hours. Some new self-heating backlights can work normally in the range of -40°C to 85°C. OEL backlight and high-brightness LED backlight have been successfully developed and started to be used in TFT-LCD, Linfinity.

Microelectrunies invented long-life inverters for cold cathode backlights with a light source modulation range of 500:1.

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