what is TFT Screen?

TFT LCD stands for Thin-Film Transistor - Liquid Crystal Display. TFT LCD technology is a clever integration of microelectronics and liquid crystal display techniques. It involves transplanting microelectronics fabrication techniques from silicon to large-area glass to create TFT arrays. These arrays are then combined with another substrate containing a color filter to form a mature LCD technology, resulting in a liquid crystal box. Later, post-processing steps such as attaching polarizing films are performed to create the liquid crystal display (screen).

In a TFT LCD, the TFT acts as a switching device, typically a three-terminal device. It is fabricated on a glass substrate, with source and drain terminals connected on both ends. A gate insulator film is set between the gate electrode and the semiconductor layer. The voltage applied to the gate electrode controls the current between the source and drain.

For the display panel, each pixel can be simplified as a liquid crystal layer sandwiched between the pixel electrode and the common electrode. From an electrical perspective, it can be seen as a capacitor. To charge the pixels in row J and column I, it is necessary to turn on the switch T(i, J) and apply the target voltage to the signal line D(i). When the pixel electrode is fully charged, even if the switch is turned off, the charge in the capacitor is retained, and the liquid crystal layer between the electrodes continues to have an applied voltage field. Data (column) drivers are used to apply the target voltage to the signal lines, while gate (row) drivers are used to turn on and off the switches. Since the display voltage applied to the liquid crystal layer can be stored in the storage capacitors of each pixel, the liquid crystal layer can work stably. This display voltage can be rewritten by the TFT in a short time, allowing even high-definition LCDs to meet the requirements without compromising image quality.

The key to image display lies in the molecular orientation of the liquid crystal under the influence of an electric field. Generally, different display modes can be achieved by orienting the inner side of the substrate, allowing the liquid crystal molecules to produce the desired structural deformation. When a particular display mode is selected, the orientation of the liquid crystal molecules changes under the electric field. Coupled with polarizers, the intensity of light passing through the liquid crystal layer changes, resulting in image display.

In summary, TFT LCD is distinct from the simple matrix of passive TN-LCD and STN-LCD. It incorporates a thin-film transistor (TFT) in each pixel of the LCD screen, effectively overcoming crosstalk during non-gate control. This allows the static characteristics of the LCD screen to be independent of the number of scan lines, thus significantly improving image quality. The characteristics of the switching unit (TFT) should meet the requirements of low on-resistance and very large off-resistance.