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TFT liquid crystal display works

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Update time : 2019-07-05 16:58:55
What does the TFT screen mean?

TFT (Thin Film Transistor) is a thin film field effect transistor that can "actively" control individual pixels on the screen, which can greatly improve the reaction time. Generally, the response time of TFT is relatively fast, about 80 milliseconds, and the viewing angle is large, generally reaching about 130 degrees, mainly used in high-end products. Thereby, high-speed, high-brightness, high-contrast display screen information can be achieved. TFT is an active matrix liquid crystal display, which is driven by an "active matrix" method. The method is a transistor electrode made by thin film technology. The scanning method is used to "actively pull" to control the opening of any display point. When the light source is irradiated, it is firstly transmitted upward through the lower polarizing plate, and the light is transmitted by the liquid crystal molecules, and the display is achieved by shading and light transmission.

How about the TFT screen?

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


The TFT liquid crystal is provided with a semiconductor switch for each pixel, and each pixel can be directly controlled by a point pulse, so each node is relatively independent and can be continuously controlled, which not only improves the reaction speed of the display screen, but also can accurately control The color gradation is displayed, so the color of the TFT liquid crystal is more true. The characteristics of the TFT liquid crystal display are good brightness, high contrast, strong layering, and bright colors, but there are also deficiencies in power consumption and high cost. TFT liquid crystal technology has accelerated the development of mobile phone color screens. Many of the new generation of color screen phones support 65536 color display, and some even support 160,000 color display. At this time, the high contrast and rich color advantages of TFT are very important.

TFT liquid crystal display works


(1) How TFT works is the abbreviation of "Thin Film Transistor", which is generally referred to as thin film liquid crystal display, but actually refers to thin film transistor (matrix) - which can be "active" to each individual on the screen. The pixels are controlled, which is the origin of the so-called active matrix TFT. So how exactly does the image come about? The basic principle is simple: the display consists of a number of pixels that emit light of any color, as long as the individual pixels are controlled to display the corresponding color. In the TFT LCD, 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 "louver" is opened, the light can pass through, and " When the blinds are closed, the light cannot pass through. Of course, the technical implementation is not as simple as it was just said. LCD (Liquid Crystal Display) utilizes the characteristics of liquid crystal (when heated, it is liquid, and when cooled, it crystallizes to solid state). Generally, liquid crystal has three forms:


Clay-like smectic liquid crystal (Smectic)


a silky (Nematic) liquid crystal like a fine matchstick


Cholestic liquid crystal


The liquid crystal display uses a filament shape. When the external environment changes, its molecular structure also changes, and thus has different physical properties - the purpose of letting light pass or block light - that is, the blinds just like.


Everyone knows the three primary colors, so each pixel on the display screen is composed of three similar basic components as described above, and controls the three colors of red, green and blue respectively.


The most common one currently used is the Twisted Nematic TFT LCD. The following figure explains how this type of TFT display works. The existing technologies vary widely and we will cover them in detail in the second part of this article.


There are grooves on the upper and lower layers, wherein the upper grooves are arranged longitudinally and the lower layers are arranged laterally. When the liquid crystal is in a natural state without applying voltage, the light diverging from the schematic layer of the twisted nematic TFT display works through the interlayer, and a 90 degree distortion occurs, so that the lower layer can be smoothly transmitted.


When a voltage is applied between the two layers, an electric field is generated, and the liquid crystals are arranged vertically, so that the light does not twist - the result is that the light cannot pass through the lower layer.

(2) TFT pixel structure: The color filter is divided into red, green and blue according to the color, and is sequentially arranged on the glass substrate to form a group (dot pitch) corresponding to one pixel. Each monochromatic filter is called Is a sub-pixel. That is, 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), one pixel is approximately 0.0188 inches (equivalent to 0.30mm), and for a 18.1-inch TFT display (1280 × 1024), it is 0.011 inches (equivalent to 0.28mm) .


EXSON, a professional 1.3 - 33 inch TFT LCD/OLED display manufacturer.