What is a TFT screen and how it works
What does a 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 up to about 130 degrees, and it is mainly used in high-end products. Thus, the screen information can be displayed at high speed, high brightness, and high contrast. TFT belongs to an active matrix liquid crystal display. It is technically driven by an "active matrix" method. The method is to use the transistor electrodes made by thin film technology, and use the scanning method to "actively pull" to control the opening and closing of any display point. When the light source is irradiated, it first passes through the lower polarizer upward, and the liquid crystal molecules conduct the light, and the purpose of display is achieved by shading and transmitting light. Many of the new generation of color screen mobile 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. The main components of TFT-type liquid crystal displays include: fluorescent tubes, light guide plates, polarizing plates, filter plates, glass substrates, alignment films, liquid crystal materials, thin-mode transistors, etc.
How about TFT screens
TFT also improves the phenomenon of STN flickering (water ripples) and blur, and effectively improves the ability to play dynamic images. Compared with STN, TFT has excellent color saturation, restoration ability and higher contrast, but the disadvantage is that it consumes more power and is more expensive. TFT liquid crystal has a semiconductor switch for each pixel, and each pixel can be directly controlled by a dot pulse, so each node is relatively independent and can be controlled continuously, which not only improves the response speed of the display, but also can accurately control the display color level, so the color of TFT liquid crystal is more realistic. The characteristics of TFT liquid crystal display are good brightness, high contrast, strong layering, and bright colors, but there are also shortcomings such as relatively high power consumption and high cost. TFT liquid crystal technology has accelerated the development of mobile phone color screens. Many new generation color screen mobile 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.
Working principle of TFT LCD display
(1) How does TFT work? TFT is the abbreviation of "Thin Film Transistor", which generally refers to thin film liquid crystal display, but actually refers to thin film transistor (matrix) - it can "actively" control each independent pixel on the screen, which is the origin of the so-called active matrix TFT. So how is the image produced? The basic principle is very simple: the display screen is composed of many pixels that can emit light of any color. As long as each pixel is controlled to display the corresponding color, the purpose can be achieved. In TFT LCD, backlight technology is generally used. In order to accurately control the color and brightness of each pixel, a switch similar to a shutter needs to be installed behind each pixel. When the "shutter" is opened, light can pass through, and when the "shutter" is closed, light cannot pass through. Of course, the actual implementation is not as simple as just said in terms of technology. LCD (Liquid Crystal Display) makes use of the characteristics of liquid crystal (liquid when heated, and crystallizes into solid when cooled). Generally, liquid crystal has three forms: smectic liquid crystal similar to clay, nematic liquid crystal similar to thin matchsticks, and cholestic liquid crystal. Liquid crystal displays use filaments, and when the external environment changes, its molecular structure will also change, thus having different physical properties - it can achieve the purpose of letting light through or blocking light - that is, the blinds just compared. Everyone knows the three primary colors, so each pixel on the display needs to be composed of the three similar basic components introduced above, which control the three colors of red, green and blue respectively. The most commonly used one at present is the twisted nematic TFT liquid crystal display (Twisted Nematic TFT LCD). The following figure explains the working principle of this type of TFT display. The existing technologies vary greatly, and we will introduce them in detail in the second part of this article. There are grooves on both the upper and lower layers. The grooves on the upper layer are arranged vertically, while those on the lower layer are arranged horizontally. When no voltage is applied, the liquid crystal is in a natural state. After the light radiates from the light-emitting layer through the interlayer, it will be twisted 90 degrees, so that it can pass smoothly through the lower layer. When voltage is applied between the two layers, an electric field will be generated. At this time, the liquid crystal will be arranged vertically, so the light will not be twisted - the result is that the light cannot pass through the lower layer.
(2) TFT pixel architecture: Color filters are divided into three types according to color: red, green, and blue. They are arranged in sequence on the glass substrate to form a group (dot pitch) corresponding to one pixel. Each monochrome filter is called 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), a pixel is about 0.0188 inches (equivalent to 0.30mm), and for an 18.1-inch TFT display (1280 × 1024), it is 0.011 inches (equivalent to 0.28mm). As we all know, pixels are decisive for displays. The smaller each pixel, the greater the maximum resolution that the display can achieve. However, due to the limitations of the physical properties of transistors, the size of each TFT pixel at this stage is basically 0.0117 inches (0.297mm), so for a 15-inch display, the maximum resolution is only 1280 × 1024.
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