TFT is a Thin Film Transistor, TFT refers to each LCD liquid crystal display pixels that are driven by integration in the behind of the Thin Film Transistor. Therefore, the TFT-type display has the advantages of high responsiveness, high brightness, and high contrast, and its display effect is close to that of CRT display, TFT-LCD is one of the most liquid crystal displays.TFT display is also a kind of active-matrix liquid crystal display equipment. TFT-LCD is one of the best LCD color displays, TFT-LCD has the advantages of fine and vivid image, lightweight, low power consumption, and good environmental protection performance, widely used in TV, laptop, mobile phone, monitor, medical beauty, and other equipment.
The meaning of TFT
TFT (Thin Film Transistor) LCD, is a type of active-matrix liquid crystal display (LCD) AM – one of the.
Unlike TN, TFT displays are “backlit” – the imaginary light path is not from top to bottom, as in TN, but from bottom to top. In this way, a special light tube is set on the back of the liquid crystal, and the light source shines upward through the lower polarizer. Since the upper and lower interlayer electrodes are changed into FET electrodes and common electrodes, the performance of liquid crystal molecules will also change when the FET electrode is switched on. The display purpose can be achieved through shading and light transmission, and the response time is greatly improved to about 80ms.TFT is commonly known as “true color” because it has higher contrast and richer colors than TN-LCD, and the screen updates faster.
The main feature of TFT-LCD, as opposed to TN, is one semiconductor switch per pixel. Because each pixel can be directly controlled by point pulses. Therefore, each node is relatively independent and can be controlled continuously. Such a design method not only improves the response speed of the display screen but also can accurately control the display grayscale, which is why TFT color is more realistic than DSTN.
The TFT panel is cut from a larger substrate. LCD products also have a large array of transistors to control the three primary colors, and current manufacturing technology is difficult to ensure that tens or even hundreds of millions of transistors on a large substrate are without a single problem. If there is a problem with one of the transistors, then the corresponding color of the corresponding point of the transistor will go wrong (only a certain fixed color can be displayed), and this point is commonly called “bad point”. The probability of bad spots is not fixed in position, so a substrate is likely to be wasted a lot. Generally, LCD requires that the bad point is less than 5, and some large manufacturers have narrowed the standard to 3, or even 0, which will reduce the yield rate. Some smaller manufacturers expand the bad points, which naturally reduces costs and quality, which is one reason why some manufacturers have been able to slash prices.
Although there are many manufacturers capable of producing LCDs, there are only a handful of manufacturers capable of producing TFT panels.ACER, as a well-known enterprise in the IT industry, is quite powerful. Although IT does not have the ability to produce TFT panels by itself,
The display sets the electron, the communication and the information processing technology in one body, is considered as the electron industry after the 20th-century microelectronics, the computer another important development opportunity.
With the rapid development of science and technology, a revolution is taking place in display technology. After more than 20 years of research, competition, and development, the flat-panel display has entered the role and become the mainstream of display products in the new century. There are four types of flat-panel displays with the most fierce competition:
Field emission flat panel display (FED);
Plasma flat panel display (PDP);
Organic thin-film electroluminescence device (OLED);
thin-film transistor liquid crystal flat panel display (TFT-LCD).
The principle of field emission flat display is similar to that of CRT, which only has one to three electron guns and up to six. The field emission display adopts an electron gun array (electron emission micro tip array, such as diamond film tip cone), and the display with a resolution of VGA (640×480×3) needs 921,600 electron emission micro tips with uniform performance.
Glow plasma display are through small vacuum plasma discharge excitation discharge cavity light-emitting materials, luminous effect, and low power consumption is its shortcomings (only 1.2 lm/W, and lamp luminous efficiency more than 80 lm/W, 6 watts per square inch display area), but in 102 ~ 152 cm diagonal field of the large-screen display has a strong competitive advantage.
The semiconductor light-emitting diode (LED) display scheme, due to the successful development of GaN blue light-emitting diode, has won absolute control over the market of the video display with very large screens, but this kind of display is only suitable for large outdoor displays, and video display with a small and medium screen does not have its market.
Special TFT – LCD, LCD flat panel display, is the only one in the brightness, contrast, such as power, life, volume and weight of integrated performance to catch up with and surpass that of the CRT display device, it features good performance, large-scale production, a high degree of automation, low cost of raw materials, the vast development space, will quickly become the mainstream product of the new century, is one of the highlights of the 21st-century global economic growth.
TFT-LCD, which USES liquid crystal as the excellent characteristic of the light valve, divides the luminous display device into two parts, namely the light source and the control of the light source. As a light source, no matter from luminous efficiency, full color, or life, has achieved brilliant results, but also in continuous deepening. Since the invention of the LCD, the backlight has been continuously improved, from monochrome to color, from thick to thin, from side fluorescent lamps to flat fluorescent lamps. The latest achievements in light sources will provide a new backlight for LCD. With the progress of light source technology, there will be newer and better light sources and LCD applications. Is the control of the light source, the rest of the large scale integrated circuit technology and semiconductor technology transplanted, successfully developed the thin film transistor (TFT) production technology, implements the matrix addressing the control of the liquid crystal light valve, solved the LCD light valve and the controller, so that the advantages of liquid crystal display (LCD).
How TFT works
The TFT thin-film transistor (matrix) — which “actively” controls individual pixels on the screen — is the origin of the so-called active matrix TFT.So how exactly do images come about? The basic principle is simple: a display screen consists of a number of pixels that can emit light of any color, and controlling each pixel to display a corresponding color does the trick. In TFT LCD, backlight technology is generally adopted. In order to accurately control the color and brightness of each pixel, a switch similar to a shutter needs to be installed after each pixel. When the “shutter” is opened, light can come through, but when the “shutter” is closed, light cannot come through.
Of course, it’s not as simple technically as that. Liquid Crystal Display USES the properties of Liquid crystals (Liquid when heated and solid when cooled)
There are three types of liquid crystals:
Clay-like lamination (Smectic) liquid crystals
Nematic liquid crystal resembling a thin matchstick
The Cholestatic liquid crystal
Liquid crystal displays (LCDs) are filamentous, and their molecular structure changes as the environment change, giving them different physical properties — allowing light to pass through or block it — in the case of louvers.
You know the three primary colors, so each pixel on the display needs to be made up of three similar basic components described above, which control the red, green, and blue colors respectively.
TFT color filter is divided into red, green, and blue according to the color, which is successively arranged on the glass substrate to form a group (dot pitch) corresponding to a pixel. Each monochrome filter is called a sub-pixel. That said, if a TFT display supports a maximum resolution of 1280×1024, it needs at least 1280×3×1024 sub-pixels and transistors. For a 15-inch TFT display (1024 x 768), a pixel is about 0.0188 inches.
As you know, pixels are critical to a display, and the smaller each pixel, the larger the maximum possible resolution of the display. But because of the physical limitations of transistors, the TFT is roughly 0.0117 inches (0.297mm) per pixel, so the maximum resolution for a 15-inch display is 1,280 by 1,024.
Technical features of TFT
TFT technology is the basis of liquid crystal (LC), inorganic and organic thin-film electroluminescence (EL and OEL) flat panel displays.TFT is a kind of film necessary for manufacturing circuits formed by sputtering and chemical deposition process on non-single wafers such as glass or plastic substrate, and large-scale semiconductor integrated circuit (LSIC) is produced by processing of the film. Using a non-single-crystal substrate can greatly reduce the cost, which is the extension of traditional LSI to a large-area, multi-function, and low-cost direction.
Its main features are:
TFT Large area
The first generation of the large-area glass substrate (300mm×400mm) TFT-LCD production line was put into production in the early 1990s. By the first half of 2000, the area of the glass substrate has been expanded to 680mm×880mm), and the recent 950mm×1200mm glass substrate will also be put into operation. In principle, there is no area limit.
TFT High level of integration
The 1.3-inch TFT chip used for liquid crystal projection has a resolution of one million pixels in XGA. The resolution of the SXGA (1280×1024) 16.1-inch TFT array amorphous silicon film thickness is only 50nm, and the TAB ON GLASS and SYSTEM ON GLASS technology, its IC integration, requirements for equipment and supply technology, technical difficulty than the traditional LSI.
TFT is powerful
TFT was first used as a matrix location circuit to improve the optical valve characteristics of liquid crystals. For high-resolution displays, the accurate control of object elements is realized through voltage adjustment in the range of 0-6v (its typical value is 0.2 to 4V), thus making it possible for LCD to achieve a high-quality high-resolution display.TFT-LCD is the first flat panel display in human history to surpass CRT in display quality. Now people are starting to integrate the drive IC into the glass substrate, and the whole TFT will be more powerful than traditional large-scale semiconductor integrated circuits.
Low-cost TFT advantage
The glass and plastic substrates fundamentally solve the cost problem of large-scale semiconductor integrated circuits and open up wide application space for large-scale semiconductor integrated circuits.
TFT flexible process
In addition to traditional film formation processes such as sputtering and CVD (chemical vapor deposition) and MCVD (molecular chemical vapor deposition), laser annealing technology has also been applied, which can produce amorphous and polycrystalline films as well as monocrystalline films. Not only can make silicon membrane but also can make other Ⅱ – Ⅵ and Ⅲ – Ⅴ semiconductor thin film.
Good performance TFT
Low voltage applications, low drive voltage, solid use safety, and reliability improvement; Flat, light, and thin, saving a lot of raw materials and space; Low power consumption, its power consumption is about one-tenth of the CRT display, reflective TFT-LCD is only about one percent of the CRT, saving a lot of energy; TFT-LCD products also have specifications, models, size series, variety, convenient and flexible use, maintenance, update, upgrade easy, long service life and many other characteristics. The display range covers the application range of all monitors from 1 inch to 40 inches and the large projection plane, which is a full-size display terminal; Display quality from the simplest monochrome character graphics to high resolution, high color fidelity, high brightness, high contrast, the high response speed of various specifications of video display; Display mode has direct vision type, projection type, perspective type, and reflection type.
TFT environmental protection characteristics
No radiation, no flicker, no harm to the user’s health. In particular, the appearance of TFT-LCD electronic books and periodicals will bring mankind into the era of a paperless office and paperless printing, and trigger the revolution of human learning, communication, and recording civilization.
TFT Wide range of application
The temperature range from -20℃ to +50℃ can be used normally, and the low temperature working temperature of TFT-LCD after temperature reinforcement can reach -80 ℃. It can be used as a mobile terminal display, desktop terminal display, and large screen projection TV. It is a full-size video display terminal with excellent performance.
It is mainly used in computers, video terminals, communication and instrumentation, desktop computer monitors, workstations, industrial monitors, global positioning systems (GPS), personal data processing, game consoles, video phones, portable VCD, DVD, and other portable devices.
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