Introduction to TFT-LCD Technology and Production Process

　　TFT (Thin Film Transistor) LCD is a thin film field effect transistor LCD, which is a type of active matrix liquid crystal display (AM-LCD). Liquid crystal flat panel display, especially TFT-LCD, is currently the only display device that catches up with and exceeds CRT in comprehensive performance such as brightness, contrast, power consumption, life, volume and weight. It has excellent performance, good large-scale production characteristics, high degree of automation, low raw material cost, and broad development space. It will quickly become a mainstream product in the new century and a highlight of global economic growth in the 21st century.

　　Main Features

　　Unlike TN technology, TFT display uses "back-through" illumination - the imaginary light source path is not from top to bottom like TN liquid crystal, but from bottom to top. This is done by setting a special light tube on the back of the liquid crystal, and the light source is transmitted upward through the lower polarizer when irradiated. Since the electrodes of the upper and lower layers are changed to FET electrodes and common electrodes, the performance of the liquid crystal molecules will also change when the FET electrodes are turned on. The purpose of display can be achieved by shading and transmitting light, and the response time is greatly improved to about 80ms. Because it has a higher contrast and richer colors than TN-LCD, and the screen update frequency is also faster, TFT is commonly known as "true color".

　　Compared with DSTN, the main feature of TFT-LCD is that a semiconductor switch device is configured for each pixel. Since each pixel can be directly controlled by a dot pulse, each node is relatively independent and can be controlled continuously. This design method not only improves the response speed of the display, but also can accurately control the display grayscale, which is why TFT colors are more realistic than DSTN.

　　Key Benefits

　　With the maturity of TFT technology in the early 1990s, color LCD flat panel displays developed rapidly. In less than 10 years, TFT-LCD quickly grew into the mainstream display, which is inseparable from its advantages. The main features are:

　　(1) Good usage characteristics

　　Low voltage application, low driving voltage, solid use safety and reliability are improved; flat, thin and light, saving a lot of raw materials and use space; low power consumption, its power consumption is about one tenth of CRT display, reflective TFT-LCD is even only about one hundredth of CRT, saving a lot of energy; TFT-LCD products also have specifications, models, sizes, varieties, convenient and flexible use, easy maintenance, update, upgrade, 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, and is a full-size display terminal; the display quality ranges from the simplest monochrome character graphics to high resolution, high color fidelity, high brightness, high contrast, and high response speed video displays of various specifications; the display modes include direct view, projection, perspective, and reflection.

　　(2) Good environmental protection characteristics

　　No radiation, no flicker, no harm to the health of users. In particular, the emergence of TFT-LCD electronic books and periodicals will bring mankind into the era of paperless office and paperless printing, triggering a revolution in the way humans learn, spread and record 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 the temperature-hardened TFT-LCD 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

　　Large-scale industrial production has good characteristics. The TFT-LCD industry technology is mature, and the yield rate of large-scale production reaches 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 further development. Currently, there are amorphous, polycrystalline and single-crystal silicon TFT-LCDs, and in the future there will be TFTs made of other materials, both glass substrates and plastic substrates.

　　TFT Process

　　1. Array Process