The working principle of LCD

The working principle of LCD

Liquid crystal display, the abbreviation of LCD in English is Liquid Crystal Display, which is a kind of flat display. The liquid crystal display uses a liquid crystal solution in two pieces of polarized material, and when the current passes through the liquid, the crystal is rearranged to achieve the purpose of imaging.

(1) Physical characteristics of liquid crystal (LCD)

The physical properties of the liquid crystal are: when it is energized, it is turned on and the arrangement becomes orderly, making it easy for light to pass; when it is not energized, the arrangement is chaotic, preventing light from passing. Let the liquid crystal block or allow light to penetrate like a gate. Technically speaking, the 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, thus 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 be arranged along the grooves, so if the grooves are very parallel, the molecules are also completely parallel.

(2) Principle of Monochrome Liquid Crystal (LCD) Display

LCD technology is to pour 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 aligned north-south, the molecules on the other plane are aligned east-west, and the molecules between the two planes are forced into a 90-degree twisted state. Because the light travels along the direction of the molecular arrangement, 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 re-arrange vertically so that the light can be directed out without any twisting.

LCD relies on polarization filters (plates) and 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 those 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 crystals, after the light passes through the first filter, it will be twisted by the liquid crystal molecules by 90 degrees, 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 will be blocked by the second filter. In short, the light is blocked when power is applied, and the light is emitted when the power is not applied.

(3) Working principle of color LCD liquid crystal display

For the more complex color monitors that laptops or desktop LCD monitors need to adopt, it is also necessary to have a color filter layer for processing color display. Generally, in a color LCD panel, each pixel is composed of three liquid crystal cells, and each cell has a red, green, or blue filter in front of it. In this way, the light passing through different cells can display different colors on the screen.