The liquid crystal screen is based on the liquid crystal material as the basic component, and the liquid crystal material is filled between two parallel plates, and the arrangement of the molecules inside the liquid crystal material is changed by voltage, so as to achieve the purpose of shading and light transmission to display different shades and random arrangement. There is a uniform image, and as long as a three-color filter layer is added between two flat plates, a color image can be displayed. So what is the working principle of LCD screen, let's learn more about it.

How lcd display works：

Most of the current LCD technologies are based on TN, STN and TFT technologies, so let's explore their working principles from these three technologies.

TN type LCD technology can be said to be the most basic among LCDs, and after that other types of LCDs can also be said to be improved by using TN type as the origin. Similarly, its operation principle is also simpler than other technologies.

(1) The structure of the TN-type liquid crystal display is simple, including polarizing plates in the vertical and horizontal directions, an alignment film with fine grooves, a liquid crystal material, and a conductive glass substrate. The imaging principle is to place the liquid crystal material between two pieces of transparent conductive glass attached with a polarizer perpendicular to the optical axis. The liquid crystal molecules will rotate and arrange in sequence according to the direction of the fine grooves of the alignment film. If the electric field is not formed, the light will go smoothly. It enters from the polarizer, rotates its traveling direction according to the liquid crystal molecules, and then emits from the other side. If the two pieces of conductive glass are energized, an electric field will be generated between the two pieces of glass, which will affect the alignment of the liquid crystal molecules and twist the molecular rods, so that the light cannot penetrate, thus blocking the light source. The phenomenon of light-dark contrast thus obtained is called the twisted nematic field effect (TNFE).

(2) The liquid crystal displays used in electronic products are almost all made of twisted nematic field effect principle. The display principle of the STN type is also similar, the difference is that the liquid crystal molecules of the TN twisted nematic field effect rotate the incident light by 90 degrees, while the STN super twisted nematic field effect rotates the incident light by 180~270 degrees. What I want to explain here is that the pure TN liquid crystal display itself only has two situations of light and dark (or called black and white), and there is no way to change the color. The STN liquid crystal display involves the relationship between the liquid crystal material and the interference phenomenon of light, so the displayed tones are mainly light green and orange. However, if a color filter is added to the traditional monochrome STN liquid crystal display, and any pixel of the monochrome display matrix is divided into three sub-pixels, which pass through the color filter, the film displays the three primary colors of red, green, and blue, and then through the reconciliation of the ratio of the three primary colors, it can also display the color of the full-color mode. In addition, the larger the display screen of TN-type LCD monitors, the poorer the contrast ratio of the screen will appear. However, with the improved technology of STN, it can make up for the lack of contrast.

(3) The TFT liquid crystal display is relatively complex, and its main components include fluorescent tubes, light guide plates, polarizers, filter plates, glass substrates, alignment films, liquid crystal materials, thin-mode transistors, and so on. First of all, the liquid crystal display must first use the LED backlight, that is, the fluorescent tube to project a light source. These light sources will first pass through a polarizer and then pass through the liquid crystal. At this time, the arrangement of the liquid crystal molecules will change the angle of light that penetrates the liquid crystal. Then the light must pass through the front color filter and another polarizer. Therefore, we only need to change the voltage value of stimulating the liquid crystal to control the final light intensity and color, and then can change the color combinations with different shades on the liquid crystal panel.