TFT LCD screen, TFT display


1. What is TFT meaning?  What role does TFT play in the LCD screen?

TFT (Thin Film Transistor) is the abbreviation of Thin Film Transistor. Thin-film transistors, also known as TFT components, or TFT switching tubes, are based on the principle of field-effect tubes, that is, TFT components are tubes that use electric field effects to control current. In actual use, TFT, as a switching device, only plays an on or off role in determining whether the liquid crystal is charged or not. When the thin film transistor is on, the voltage output from its source electrode is used to charge the liquid crystal and memory capacitor. The charging voltage is determined by the driving circuit of the liquid crystal screen. TFT can be used with LCD to better control its rendering image and color to improve image quality and display more realistic.

2. What is  TFT-LCD?

Thin film transistor liquid crystal display (often referred to as TFT-LCD) is one of the most liquid crystal displays,  Each liquid crystal pixel on this type of display is driven by a thin film transistor integrated behind the pixel, each pixel has four (one black, three RGB colors) independent thin-film transistors to switch four transistors according to the color signal sent by the driver IC. It is precisely because each pixel can be precisely controlled, so TFT LCD display is more realistic. The 8bit TFT panel is equivalent to having 2 to the power of 24(8*3) 16.7m colors, that is, 24-bit true color.

3.  TFT-LCD structure

tft-lcd internal structure diagram
tft-lcd internal structure diagram

Generally, the internal structure of a TFT-LCD liquid crystal panel is mainly composed of a Color Filter Substrate (CF), a Thin Film Transistor array substrate (TFT Array Substrate), and a Liquid Crystal Layer disposed between the two substrates. The working principle is to control the rotation of the liquid crystal molecules in the liquid crystal layer by applying a driving voltage on the two glass substrates and refract the light of the backlight module to generate the image.

4.  Advantages of TFT-LCD

Speaking of the advantages of TFT-LCD, it is better to say that the TFT driver has any advantage or why TFT is used in LCD. Others should be regarded as the advantage of LCD relative to CRT or PDP.

(1) The biggest use of TFT is to accurately control the display Levels and make the color more realistic.

(2)  Higher definition and lower power consumption. If you don't use TFT and the response speed can't keep up, the refresh is likely to have a residual image.

(3) Using the FET electrode to conduct electricity, the response speed of the display screen is improved.

5.  Misunderstanding about "TFT-LCD is a color screen, TN-LCD is a monochrome screen"

LCD is a general term, including monochrome screens and color screens. Currently, almost all color LCD screens on the market adopt TFT drive technology. Although strictly speaking, TFT LCD is not the same as LCD, but if you want to find LCD color screen, it may actually be a TFT-LCD. Whether it is TN, VA, IPS or reflective, transflective, fully transmissive panels can be called TFT-LCD as long as they are driven by TFT. However, most of the early or some low-end TN LCD color screens did not use TFT.

Although the general monochrome screen uses TN liquid crystal, it does not mean that the TN-LCD is a monochrome screen. The reason why the monochrome screens often choose TN is mainly from the perspective of economic simplicity, which does not require high-end technology VA or IPS. Of course, there are also VA liquid crystals for monochrome screen objects. Again, TN describes the LCD from the liquid crystal material, and the TFT is a color display driving technology, not in the same dimension.

Of course, some people say that TN-LCD is a pseudo-color. In fact, as for color, it mainly depends on the driver IC. 6bit driver IC can control 16.2M color; 8bit driver IC can reach 16.7M, the number of colors is consistent with true color; but because of the poor reductive ability of TN liquid crystal itself, the image quality is not as good as VA or IPS, however, due to the cheaper many true color displays also use TN.

Combined with the above, here are some correct conclusions in the following:
(1)The TFT-LCD must be a color screen, and the color screen can be a TN-LCD;
(2)The monochrome screen is not necessarily a TN-LCD;
(3)TFT and TN are not the same dimension.