What are the working principles of LCD screen?

by:Genyu     2020-02-14

LCD screens are familiar to everyone and are used in daily life, but you may not know much about the working principle of LCD screens, how to understand it more deeply? First of all, you need to know how it works. Let's look at the following:

simply put, the basic principle that the screen can realize display is to fill the liquid crystal material between the two parallel plates, and then change the arrangement of molecules inside the liquid crystal material through voltage, so as to achieve the purpose of shading and light transmission to display images with different shades and colors, and as long as a ternary color filter layer is added between the two plates, can realize the display of color images.

LCD screen:

The structure of LCD screen is to place liquid crystal material in two parallel glass, there are many small vertical and horizontal wires in the middle of the two pieces of glass. The rod-shaped crystal molecules are controlled by whether they are electrified or not, thus changing the direction and reflecting the light. It is much better than CRT, but its price is more expensive.

liquid crystals are organic complexes composed of long rod-like molecules. In the natural state, the long axes of these rod-like molecules are roughly parallel.

The first feature of LCD: the liquid crystal must be poured between two planes with thin grooves to work normally. The slots on the two planes are perpendicular to each other (90 degree intersection) , That is to say, if the molecules on one plane are arranged in the north-south direction, then the molecules on the other plane are arranged in the east-west direction, and the molecules located between the two planes will be forced into a state of 90-degree torsion. Because the light travels along the direction of the molecules, the light will also be reversed by 90 degrees when passing through the liquid crystal. However, when a voltage is applied to the liquid crystal, the molecules will be arranged vertically again, so that the light can be directed out without any torsion.

The second characteristic of LCD: it relies more on polarization filter and light itself, and natural light is emitted randomly in all directions, polarization filters are actually a series of parallel lines that are getting thinner and thinner. These lines form a net, blocking all the rays that are not parallel to these lines, and the lines of the polarization filter are just perpendicular to the first one, so it can completely block the polarized light.

light can penetrate only when the lines of the two filters are completely parallel, or the light itself has been reversed to match the second polarization filter. The LCD is composed of two mutually perpendicular polarization filters, so under normal circumstances, all the rays that try to penetrate should be blocked. However, because the two filters are filled with twisted liquid crystal, when the light passes through the first filter, it will be twisted by liquid crystal molecules by 90 degrees, and finally it will pass through the second filter. On the other hand, if a voltage is added to the liquid crystal, the molecules will be rearranged and completely parallel, so that the light will not be reversed, so it is just blocked by the second filter. In a word, power-on can block the light, without power-on, it can make the light shoot out. Of course, the liquid crystal arrangement in the LCD screen can also be changed, so that the light will be emitted when it is powered on, and will be blocked when it is not powered on.

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