Summary: What does TFT screen mean? TFT (Thin Film Transistor) is a thin film field effect transistor. The so-called thin film transistor means that each liquid crystal pixel on the liquid crystal display is driven by a thin film transistor integrated behind it. This can display screen information at high speed, high brightness, and high contrast. TFT is an active matrix liquid crystal display. Let's take a look at the TFT liquid crystal display.

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[TFT screen] What does TFT screen mean? The working principle of TFT LCD

What does TFT screen mean

TFT (Thin Film Transistor) is a thin film field effect transistor, which can "actively" control each independent pixel on the screen, which can greatly improve the response time. Generally , the response time of TFT is relatively fast, about 80 milliseconds, and the viewing angle is large, generally reaching about 130 degrees, which is mainly used in high-end products. This can display screen information at high speed, high brightness, and high contrast. TFT is an active matrix liquid crystal display, which is technically driven by an "active matrix" method. The method is to use thin film technology to make transistor electrodes, and use the scanning method to "actively pull" to control the opening of any display point. When the light source is irradiated, the light source first passes through the lower polarizer to transmit the light upward, and the light is transmitted by the liquid crystal molecules, and the purpose of display is achieved by shielding and transmitting light.

Many of the new generation of color-screen mobile phones support 65536 color displays, and some even support 160,000 color displays. At this time , the high contrast and rich color advantages of TFT are very important.

The main components of a TFT -type liquid crystal display include: fluorescent tubes, light guide plates, polarizing plates, filter plates, glass substrates, alignment films, liquid crystal materials, thin-mode transistors, and so on.

How about TFT screen

TFT also improves the STN flicker ( water ripple ) blur phenomenon, effectively improving the ability to play dynamic pictures. Compared with STN , TFT has excellent color saturation, reduction ability and higher contrast, but the disadvantage is that it consumes more power and costs more.

TFT liquid crystal has a semiconductor switch for each pixel, and each pixel can be directly controlled by dot pulses, so each node is relatively independent and can be continuously controlled, which not only improves the response speed of the display, but also can be accurately controlled Display color gradation, so the color of TFT liquid crystal is more real. The TFT liquid crystal display is characterized by good brightness, high contrast, strong layering, and bright colors, but it also has the disadvantages of relatively power consumption and high cost. TFT LCD technology has accelerated the development of mobile phone color screens. Many of the new generation of color-screen mobile phones support 65536 color displays, and some even support 160,000 color displays. At this time , the high contrast and rich color advantages of TFT are very important.

The working principle of TFT LCD

( 1 ) How TFT works TFT is the abbreviation of " Thin Film Transistor ", generally refers to thin film liquid crystal displays, but actually refers to thin film transistors (matrix)-can be "active" to each independent on the screen Pixels are controlled, which is the origin of the so-called active matrix TFT ( active matrix TFT ). So how exactly is the image produced? The basic principle is simple: the display screen is composed of many pixels that can emit light of any color, and the purpose can be achieved by controlling each pixel to display the corresponding color. In TFT LCD , the backlight technology is generally used. In order to accurately control the color and brightness of each pixel, it is necessary to install a shutter-like switch after each pixel. When the "blinds" are opened, light can pass through. When the shutters are closed, light cannot pass through. Of course, technically it is not as simple as the one just mentioned. LCD ( Liquid Crystal Display ) utilizes the characteristics of liquid crystals (liquid when heated and crystallized into solid when cooled). Generally, liquid crystals have three forms:

Smectic liquid crystal similar to clay

Nematic liquid crystal resembling a fine matchstick

Similar cholesterol like ( Cholestic ) liquid crystal

The liquid crystal display uses filaments. When the external environment changes, its molecular structure will also change, and thus have different physical properties -it can achieve the purpose of letting light pass through or blocking light-which is just like the blinds just now.

Everyone knows the three primary colors, so each pixel on the display screen needs three similar basic components described above to control the three colors of red, green and blue respectively.

The most commonly used twisted nematic TFT liquid crystal display ( the Twisted Nematic the LCD TFT ), such that the interpretation of FIG TFT operation principle of the display. The existing technologies vary greatly, and we will cover them in detail in the second part of this article.

There are grooves on the upper and lower layers. The grooves on the upper layer are arranged longitudinally and the grooves on the lower layer are arranged horizontally. When no voltage is applied to the liquid crystal in its natural state, the light emitted from the light-emitting layer of the twisted nematic TFT display working principle diagram of Figure 2a will be twisted by 90 degrees after passing through the interlayer , so that it can be smoothly transmitted through the lower layer.

When a voltage is applied between the two layers, an electric field is generated. At this time, the liquid crystals are aligned vertically, so the light will not be twisted -the result is that the light cannot pass through the lower layer.

( 2 ) TFT pixel structure: color filters are divided into red, green, and blue according to the color, which are arranged on the glass substrate to form a group ( dot pitch ) corresponding to a pixel. Each monochromatic filter is called It is a sub-pixel . In other words, if a TFT display supports a maximum resolution of 1280 × 1024 , then at least 1280 × 3 × 1024 sub-pixels and transistors are required. For a 15 -inch TFT display ( 1024 × 768 ), then a pixel is about 0.0188 inches (equivalent to 0.30mm ), for an 18.1 -inch TFT display ( 1280 × 1024 ), it is 0.011 inch (equivalent to 0.28mm ).

As we all know, pixels are decisive for the display. The smaller each pixel is, the larger the maximum resolution that the display can achieve. However, due to the limitation of the physical characteristics of the transistor, the size of each pixel of the TFT at this stage is basically 0.0117 inches ( 0.297mm ), so for a 15 -inch display, the maximum resolution is only 1280 × 1024 .