What Does LTPS / TFT-LCD Mean

LTPS     TFT LCD can be divided into polycrystalline silicon (poly Si TFT) and amorphous silicon (a-Si TFT). The difference between them lies in the different transistor characteristics. The molecular structure of polycrystalline silicon is arranged orderly and directionally in a grain, so the electron mobility is 200-300 times faster than that of amorphous silicon; TFT-LCD generally refers to amorphous silicon. At present, the technology is mature and is the mainstream product of LCD. Polycrystalline silicon products mainly include high temperature polycrystalline silicon (HTPs) and low temperature polycrystalline silicon (LTPs). Low temperature poly silicon (LTPs) thin film transistor liquid crystal display uses excimer laser as the heat source in the packaging process. After the laser light passes through the projection system, a laser beam with uniform energy distribution will be generated and projected on the glass substrate of amorphous silicon structure. When the glass substrate of amorphous silicon structure absorbs the energy of excimer laser, It will be transformed into polycrystalline silicon structure. Because the whole treatment process is completed below 600 ℃, it can be applied to general glass substrates. LTPS-TFT LCD has the advantages of high resolution, fast reaction speed, high brightness and high opening rate. In addition, since the silicon crystal arrangement of LTPS-TFT LCD is more orderly than a-Si, the electron movement rate is relatively higher than 100 times. The peripheral driving circuit can be fabricated on the glass substrate at the same time, so as to achieve the goal of system integration, save space and drive IC cost. At the same time, because the drive IC circuit is directly made on the panel, it can reduce the external contact of the component, increase reliability, simplify maintenance, shorten the assembly process time and reduce EMI characteristics, so as to reduce the design time of the application system and expand the design freedom. The highest technology of LTPS-TFT LCD is to achieve system on panel. The first generation LTPS-TFT LCD uses built-in driver circuit and high-performance pixel transistor to achieve high resolution and high brightness, which has made a great difference between LTPS-TFT LCD and a-Si. Through the progress of circuit technology, the second generation LTPS-TFT LCD changes from analog interface to digital interface to reduce power consumption. The carrier mobility of this generation of LTPS TFT LCD is 100 times that of a-Si TFT, and the electrode pattern linewidth is 4 μ M, the LTPS-TFT LCD characteristics have not been fully utilized. The integration of the 3rd generation LTPS-TFT LCD in the peripheral large scale integrated circuit (LSI) is more complete than that of the 2nd generation. Its purpose is: (1) no peripheral parts can make the module lighter and thinner, and can also reduce the number of parts and assembly man hours; (2) Simplifying signal processing can reduce power consumption; (3) Equipped with memory to minimize power consumption. Because LTPS-TFT LCD has the advantages of high resolution, high color saturation and low cost, it is expected to become a new wave of display. With its advantages of high circuit integration and low cost, it has absolute advantages in the application of small and medium-sized display panels. However, there are two problems in p-Si TFT at present. One is that the off state current (i.e. leakage current) of TFT is large (ioff = nuvdw / L); However, it is difficult to prepare p-Si materials with high mobility at low temperature and large area, and there are some difficulties in the process. It is a new generation technology product derived from TFT LCD. LTPS screen is manufactured by adding laser processing process to the traditional amorphous silicon (a-Si) TFT-LCD panel. The number of components can be reduced by 40%, and the connecting part can be reduced by 95%, greatly reducing the probability of product failure. This screen has greatly improved energy consumption and durability. The horizontal and vertical viewing angles can reach 170 degrees, the display response time can reach 12ms, the display brightness can reach 500 nits, and the contrast can reach 500:1.   There are mainly two integration modes of low-temperature p-Si driver: one is the hybrid integration mode of scanning and data switch, that is, the row circuit is integrated together, the switch and shift register are integrated in the column circuit, and the multi-channel addressing driver and amplifier are externally connected to the flat panel display screen with inheritance circuit; Second, all driving circuits are integrated on the display screen; Third, the drive and control circuits are integrated on the display screen. In 2007, BOE Hyundai (Beijing) display technology Co., Ltd. was the first company in China to start mass production of small-size LTPS modules. TFT (thin film transistor) LCD is a kind of active matrix liquid crystal display (am-lcd). Liquid crystal flat panel display, especially TFT-LCD, is the only display device that fully catches up with and exceeds CRT in terms of brightness, contrast, power consumption, service life, volume and weight. It has excellent performance, good mass production characteristics, high degree of automation, low cost of raw materials and broad development space. It will quickly become the mainstream product in the new century, It is a bright spot of global economic growth in the 21st century.   The main feature is different from TN technology. TFT display adopts "back transparent" irradiation mode - the hypothetical light source path is not from top to bottom like TN liquid crystal, but from bottom to top. In this way, a special light tube is arranged on the back of the liquid crystal, and the light source shines upward through the lower polarizing plate. Since the electrodes of the upper and lower interlayer are changed into FET electrodes and common electrodes, the performance of liquid crystal molecules will also change when the FET electrode is turned on. The purpose of display can be achieved by 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 faster screen update frequency. 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 point pulse. Therefore, each node is relatively independent and can be controlled continuously. This design method not only improves the response speed of the display screen, but also can accurately control the display gray, which is the reason why TFT color is more realistic than DSTN.