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Introduction to TFT-LCD technology and production process

Introduction to TFT-LCD technology and production process

Sep 19, 2022

TFT (Thin Film Transistor) LCD, or thin film field effect transistor LCD, is one of the active matrix type liquid crystal displays (AM-LCD). Liquid crystal flat panel displays, especially TFT-LCDs, are currently the only display devices that fully catch up with and exceed CRTs in terms of brightness, contrast, power consumption, lifespan, volume, and weight. It has excellent performance and good mass production characteristics. With a high degree of automation, low cost of raw materials and broad development space, it will quickly become a mainstream product in the new century and a bright spot for global economic growth in the 21st century.


main feature

Different from the TN technology, the custom TFT screen adopts a "back-through" illumination method-the imaginary light source path is not from top to bottom like TN liquid crystal, but from bottom to top. This method is to install a special light pipe on the back of the liquid crystal, and the light source will penetrate upward through the lower polarizer when irradiated. Since the upper and lower interlayer electrodes are changed to FET electrodes and common electrodes, when the FET electrodes are turned on, the performance of the liquid crystal molecules will also change. The purpose of display can be achieved through light shielding and light transmission, and the response time is greatly increased to about 80ms. Because it has a higher contrast ratio and richer colors than TN-LCD, the screen update frequency is also faster, so TFT is commonly known as "true color".


Compared with DSTN, the main feature of TFT LCD is to configure a semiconductor switching device for each pixel. Because each pixel can be directly controlled by dot pulses. Therefore, each node is relatively independent and can be continuously controlled. This design method not only improves the response speed of the display screen, but also can accurately control the display gray level, which is why the TFT color is more realistic than DSTN.


main advantage

With the maturity of TFT technology in the early 1990s, color LCD flat-panel displays 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:

(1) Good use characteristics

Low-voltage applications, low drive voltages, and improved safety and reliability of solid-state use; flat panels, light and thin, saving a lot of raw materials and use space; low power consumption, its power consumption is about one-tenth of that of CRT displays, reflection TFT-LCD is even only about one percent of CRT, saving a lot of energy; TFT-LCD products also have specifications, models, and sizes in series, diverse varieties, convenient and flexible use, easy to maintain, update, and upgrade, and have a long service life. And many other features. The display range covers the application range of all displays from 1 inch to 40 inches and large projection planes. It is a full-size display terminal; the display quality ranges from the simplest monochrome character graphics to high resolution and high color fidelity. Video displays of various specifications and models with high brightness, high contrast, and high response speed; display methods include direct view, projection, see-through, and reflective.

(2) Good environmental protection characteristics

No radiation, no flicker, no harm to the user's health. In particular, the emergence of TFT-LCD e-books will bring mankind into the era of paperless office and paperless printing, triggering a revolution in human learning, dissemination, and recording of civilization.

(3) Wide scope of application

It can be used normally in the temperature range from -20℃ to +50℃, and the low temperature working temperature of TFT-LCD after temperature hardening can reach minus 80℃. It can be used as a mobile terminal display, a desktop terminal display, and a large-screen projection TV. It is a full-size video display terminal with excellent performance.

(4) High degree of automation of manufacturing technology

The characteristics of large-scale industrial production are good. The TFT-LCD industry technology is mature, and the mass production yield rate has reached more than 90%. (5) TFT-LCD is easy to integrate and upgrade

It is a perfect combination of large-scale semiconductor integrated circuit technology and light source technology, and has great potential for continued development. At present, there are amorphous, polycrystalline and monocrystalline silicon TFT-LCDs. In the future, there will be TFTs of other materials, including glass substrates and plastic substrates.


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