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LCD liquid crystal display knowledge part two

LCD liquid crystal display knowledge part two

May 26, 2023

The principle of liquid crystal display (1) The physical characteristics of liquid crystal   The physical characteristics of liquid crystal are: when it is energized, the arrangement becomes orderly, allowing light to pass through; when it is not energized, the arrangement is disordered to prevent light from passing through. Let the liquid crystal block or allow light to penetrate like a gate. Technically speaking, the TFT LCD panel contains two very delicate soda-free glass materials, called Substrates, with a layer of liquid crystal in between. When the light beam passes through this layer of liquid crystal, the liquid crystal itself will stand in rows or twist in an irregular shape, thereby blocking or allowing the light beam to pass smoothly. Most liquid crystals are organic compounds, composed of long rod-shaped molecules. In the natural state, the long axes of these rod-shaped molecules are roughly parallel. Pour the liquid crystal into a well-processed slotted plane, and the liquid crystal molecules will align along the grooves, so if the grooves are very parallel, the molecules are also completely parallel. (2) The principle of monochromatic liquid crystal display  LCD technology is to fill liquid crystal between two planes lined with fine grooves. The slots on these two planes are perpendicular to each other (intersect at 90 degrees). That is to say, if the molecules on one plane are arranged north-south, the molecules on the other plane are arranged east-west, and the molecules between the two planes are forced into a 90-degree twisted state. Since the light travels along the direction of the arrangement of the molecules, the light is also twisted 90 degrees when passing through the liquid crystal. But when a voltage is applied to the liquid crystal, the molecules will be re-arranged vertically, so that the light can be directed out without any twisting. 

LCD relies on polarization filters (plates) and the light itself. Natural light diverges randomly in all directions. The polarization filter is actually a series of increasingly thinner parallel lines. These lines form a net, blocking all light that is not parallel to these lines. The line of the polarization filter is exactly perpendicular to the first one, so it can completely block the polarized light. Only when the lines of the two filters are completely parallel, or the light itself has been twisted to match the second polarized filter, the light can penetrate.

LCD is composed of two polarized filters that are perpendicular to each other, so under normal circumstances, all light that attempts to penetrate should be blocked. However, because the two filters are filled with twisted liquid crystal, after the light passes through the first filter, it will be twisted 90 degrees by the liquid crystal molecules, and finally pass through the second filter. On the other hand, if a voltage is applied to the liquid crystal, the molecules will rearrange and be completely parallel, so that the light will no longer be twisted, so it happens to be blocked by the second filter. In short, power is applied to block the light, and no power is applied to cause the light to be emitted.

However, the arrangement of the liquid crystals in the LCD can be changed so that light is emitted when power is applied, but is blocked when power is not applied. However, because the computer screen is almost always on, only the solution of "powering on and blocking the light" can achieve the most power saving purpose. 

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