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STN LCD and TFT LCD

Source: Shenzhen new Wilson photoelectric co., LTDPopularity: 378Time: 2016-04-14SML

First, what is crystal
Junior high school physics will learn over matter has three states: solid, liquid and gas. In fact, the so-called tri-state distinction is only approximate, and some solid material can be further subdivided into the state of a different nature. Similarly, the liquid can also have different "states", where a liquid having a directivity molecular arrangement we call "liquid crystal", referred to as "liquid crystal."
General solid crystals with directivity, they also have many of the physical properties of directionality. Liquid crystal orientation in both general and a liquid crystal of liquidity. If you want to change the direction of a solid crystal must be rotated throughout the crystal, and the liquid crystal is different, its direction is controlled by electric or magnetic fields.
STN and TFT are using is called a "nematic" liquid crystal (Nematic) of the substance, it was filamentous, use an electric field to control the "filamentous" liquid crystal orientation is on the application of commonly used methods. Components for liquid crystal production, are usually liquid crystal wrapped in two glasses. Plating layer on the surface of the glass is called the agent with a substance, by its type and processing method can be controlled in the absence of an external electric field of the arrangement of the liquid crystal.

Two, STN LCD principle
The world's first liquid crystal display appeared in the early seventies, called TN type liquid crystal display (Twisted Nematic, twisted nematic). Eighties, STN type liquid crystal display (Super Twisted Nematic, super twisted nematic) appears, while TFT LCD (Thin Film Transistor, a thin film transistor) technology has been proposed.
We will first say something about the principle of TN-type liquid crystal, the same principle STN LCD display and TN LCD, but a different twist angle of the liquid crystal molecules.
Nematic liquid crystal sandwiched between two intermediate glass, on the surface of the glass first coated with a layer of transparent conductive films for use in electrodes and a thin film on the electrode surface of the glass plate with the agent to the liquid crystal along a particular direction and arranged in parallel to the glass surface. Nature of the liquid crystal has a twist of 90 degrees, the electric field can rotate the liquid crystal, the liquid crystal of the liquid crystal with the refractive index change of direction, resulting effect is that after a TN type liquid crystal light changes polarity bias occurs. Just select the appropriate thickness of the light bias polarity just changed 90 °, you can use two parallel polarizing film so that the light is completely blocked. The voltage large enough such that the liquid crystal but also the direction of the electric field parallel to the direction of bias polarity so the light does not change, the light can be passed through a second polarizer. Thus, you can control the light and shade. Said earlier, the same STN type liquid crystal and TN-type liquid crystal display principle, but the incident will rotate 180 to 270 degrees instead of 90 degrees. Moreover, a simple TN liquid crystal display device itself is only two changes of light and shade. The STN liquid crystal light green and orange-oriented places. However, if coupled with a color filter in the traditional monochrome STN LCD, monochrome display matrix and each pixel is divided into three sub-pixels, respectively, through the color filters red, green, and blue, you can display out the color.

Three, TFT LCD principle
Since the display principle of TN and STN type liquid crystal limited, if it's bigger and bigger part of the show, the central portion of the electrode reaction time may be longer. In fact it is not a big problem in terms of mobile phones, because the current phone display are relatively small, the impact of the liquid crystal response time is relatively small. But the need for laptops and other large-screen liquid crystal display device, the slow response time of liquid crystal display will seriously affect the results, so TFT LCD technology attracted the attention of manufacturers. Further, the application of color in the phone more and more, many of the new generation of products support the 65536-color display, and some even support 16 million color display, when a high-contrast TFT, color-rich advantage is all the more important .
STN type liquid crystal belonging reflective LCD device, it has the advantage of low power consumption, but in relatively dark environment, clarity is poor, so had with external lighting. The TFT LCD using the "back through" and "reflection" combination, set special fluorescent tubes in liquid crystal back. That is why we see some of the phone next to the display seems to have "lights", while others like the cell phone light is sent to the display itself why. Moreover, the LCD backlight technology has continued to progress, from monochrome to color, from thick to thin, by the side fluorescent FFL formula to formula.
Incidentally, the reflective LCD device has a black white characters (NB) black and white characters (NN) are two, recently we have seen the display is part of NB V70 type, of course, this is definitely incorporates the latest technology enhanced NB. Well, we get down to business, to continue in terms of the principle of TFT LCD display. TFT LCD technology uses "active matrix" approach to drive. The method is the use of thin-film transistor technology electrode made using scanning method "actively" control any point of a display on and off. When the first light source revealed upwardly through the lower polarizing plate, the liquid crystal molecules by means of conducting light. When the electrode is turned on, the liquid crystal molecules are arranged like the state, like the TN liquid crystal will change, but also to achieve the purpose of display by shading and lighting. It sounds and TN type liquid crystal display principle almost, indeed. But the difference is, since the FET transistor has a capacitive effect can be maintained in a potential state, has light-transmitting liquid crystal molecules will remain in this state until the next FET electrode electrically coupled with a change in its arrangement so far. The TN-type liquid crystal do not have this feature, once the liquid crystal molecules to be no electric field, immediately return to the original state, which is a TFT LCD and TN LCD biggest different principles.
For each pixel TFT LCD has a semiconductor switch formed by the process similar to the LSI. Since each pixel can be directly controlled by a pulse point, and therefore, each node is relatively independent, and can be continuously controlled, this design not only improves the response speed of the display, and gray scale display can be precisely controlled, so TFT LCD the color is more vivid, lifelike ah! !