With the maturity of TFT technology in the early 1990s, the color liquid crystal flat panel display developed rapidly. In less than 10 years, TFT-LCD has rapidly grown into a mainstream display, which is inseparable from its advantages. The main features are:
Good use characteristics
Low-voltage application, low driving voltage, solidified use safety and reliability improvement; flat, light and thin, saving a lot of raw materials and use space; low power consumption, its power consumption is about one tenth of CRT display, reflection The TFT-LCD is only about 1% of the CRT, which saves a lot of energy; TFT-LCD products also have a series of specifications and sizes, a variety of varieties, easy to use and flexible, easy to maintain, update, upgrade, and long service life And many other features. The display range covers the application range of all displays ranging from 1 inch to 40 inches and the large plane of projection. It is a full-size display terminal; the display quality ranges from simple monochrome character graphics to high resolution, high color fidelity, Video monitors of various specifications and models with high brightness, high contrast, and high response speed; display methods include direct-view type, projection type, perspective type, and reflective type.
Good environmental characteristics
Wide range of application
It can be used normally in the temperature range from -20℃ to +50℃, and the low-temperature operating temperature of the TFT-LCD after temperature strengthening treatment can reach minus 80℃. It can be used as a mobile terminal display, desktop terminal display, and can also be used as a large-screen projection TV. It is a full-size video display terminal with excellent performance.
degree of automation
The characteristics of large-scale industrial production are good. The technology of the TFT-LCD industry is mature, and the yield rate of large-scale production reaches more than 90%.
TFT-LCD is easy to integrate
It is the perfect combination of large-scale semiconductor integrated circuit technology and light source technology, and has great potential for continued development. There are currently amorphous, polycrystalline, and monocrystalline silicon TFT-LCDs, and in the future there will be TFTs of other materials, both glass substrates and plastic substrates.
TFT-LCD technology has matured, and the three major problems that have long plagued LCD flat panel displays: viewing angle, color saturation, and brightness have been solved. Using the multi-zone vertical arrangement mode (MVA mode) and in-plane switching mode (IPS mode), the horizontal viewing angle of the LCD panel display has reached 170 degrees. The MVA mode also shortens the response time to 20ms.
From a technical point of view, the TN+Film solution is a simpler one. TFT display manufacturers have combined the twisted nematic (TN: Twisted Nematic) technology that was used for old LCD displays in the past with TFT technology. TN+Film technology. This technology is mainly to cover the display screen with a special film to expand the viewing angle-you can expand the viewing angle from 90 degrees to about 140 degrees. As shown in Figure 6: Like standard TFT displays, TN+Film arranges liquid crystal molecules to control the image. It covers the upper surface with a thin film to increase the viewing angle. However, the shortcomings of the relatively weak contrast and slow response time of TFT displays have not changed. Therefore, TN+Film is not a good solution, and it has no merits except that it is cheaper.
IPS is the abbreviation of In-Plane Switching, which means flat panel switch, also known as Super TFT. Developed earlier by Hitachi (Hitachi), NEC and Nokia are now using 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 differently with respect to the basic arrangement. When a voltage is applied, the liquid crystal molecules are arranged parallel to the substrate.
The viewing angle of the display using this technology has reached 170 degrees, which is equivalent to the viewing angle of the cathode ray tube, but this technology also has disadvantages: in order to allow the liquid crystal molecules to be arranged in parallel, the electrode cannot be like a twisted nematic display ( TN-Film), it is on both layers of substrates and can only be placed on the lower layer substrates-the direct result of this is that the brightness and contrast of the display are significantly reduced. In order to improve the brightness and contrast, only the backlight source is enhanced brightness. As a result, response time and contrast are more difficult to improve compared to ordinary TFT displays. So this technology does not seem to be a better solution.
The MVA multi-area vertical arrangement technology was developed by Fujitsu Corporation of Japan. From a technical point of view, it takes into account both the viewing angle and the response time. Found a compromise solution. MVA technology makes the viewing angle up to 160 degrees-although it is not as good as the IPS can achieve a viewing angle of 170 degrees, but it`s still good, because this technology can provide better contrast and shorter response time.
The M in MVA stands for "multi-domains" - the meaning of multi-domains. As shown in Fig. 8, those purple protrusions constitute so-called areas. There are generally four such areas in the MAV displays currently manufactured by Fujitsu.
VA is short for "vertical alignment", meaning vertical alignment. But literally, there will be some misunderstandings, because the liquid crystal molecules are not completely perpendicular to the "protrusion" as shown. Please see the black diagram shown in Figure 8. When a voltage generates an electric field, the liquid crystal molecules are arranged parallel to each other as shown in the figure, so that the backlight light source can pass through, and can diverge the light in all directions, thereby expanding the viewing angle.
In addition, MVA also provides faster response time than IPS and TN+Film technology, which is very important for achieving good video recovery and residual visual effects. The contrast of the MVA LCD monitor has also been improved, but it will also change as the visibility changes.
The field-sequential full-color (FSFC) LCD technology developed based on the use of optical compensation bending technology (OCB) not only eliminates the color filter (CF) that accounts for one third of the cost, but also increases the resolution by 3 times , Transmittance increased by 5 times, while simplifying the process and reducing costs. The development of color film technology and backlight technology makes the color reproduction ability of TFT-LCD reach or even exceed CRT. As the main technical index of commodity display TFT-LCD, its comprehensive performance is superior in all kinds of display devices, especially the improvement of large-scale production technology of TFT-LCD products, the development space of multi-variety and multi-series products, and the scope of application . More recently, South Korea’s Samsung Electronics has produced a 38-inch single-substrate TFT-LCD liquid crystal TV and a 40-inch TFT-LCD display. With its excellent performance, it has entered the market of large-size color TVs that should be dominated by PDPs.
LCD is a product with low power consumption in all displays. Taking 13.3-inch XGA TFT-LCD as an example, its power consumption is 4.4 watts in 1998, 3.3 watts in 1999, and will be less than 2.5 watts by 2001, especially reflective TFTs -Successful development of LCD, due to the elimination of the backlight, its power consumption is an order of magnitude lower than that of transmissive TFT-LCD. At the same time, due to several improvements, the low temperature laser annealing polysilicon (P-Si) technology is mature, and even the recently developed single crystal silicon technology makes the TFT-LCD response faster, the circuit integration level is higher, and the application of phase-locked loop technology , A function update, the adoption of more complete peripheral circuits, and the development of System on Glass technology, making TFT-LCD lighter and thinner. The thickness of the 13.3-inch TFT-LCD was 7.2 mm in 1998, 5.5 mm in 1999, and fell below 5 mm in 2001. Its weight was 580 grams in 1998, 450 grams in 1999, and below 400 grams in 2001. The large-scale production technology of TFT-LCD has also matured, and has realized fully automatic production. Its fifth-generation production line will enter the practical production stage in 2002, and the production cost will continue to decline. The technological maturity and progress of TFT-LCD and its unique performance advantages determine the pattern of TFT-LCD eventually replacing CRT.
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