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What is the principle of color LCD?

- Mar 17, 2018 -

What is the principle of color LCD?


(1) physical properties of liquid crystals

The physical characteristics of the liquid crystal are: when the electricity is connected, the arrangement is orderly and the light is easy to pass through; the arrangement of the electricity is chaotic and the light passes through. Let the liquid crystal block like a gate or let the light pass through. Technically, the LCD panel contains two pretty delicate sodium - free glass materials, called Substrates, with a layer of liquid crystals in the middle. When the beam passes through this liquid crystal, the liquid crystal itself will row and stand or twist the irregular shape, thus blocking or making the beam pass smoothly. Most of the liquid crystals are organic compounds, consisting of long rod like molecules. In the natural state, the long axes of these rod like molecules are roughly parallel. The liquid crystal can be poured into a well-developed slotted plane, and the liquid crystal molecules will follow the grooves, so if the grooves are very parallel, the molecules are also completely parallel.

(two) the principle of monochromatic liquid crystal display

LCD technology is a planar liquid crystal filled in two columns with slots.  The grooves on the two planes are perpendicular to each other (intersected to 90 degrees). That is to say, if a molecule on a plane is aligned in the north and south, the molecules on the other side are arranged east-west, while the molecules located between the two planes are forced into a 90 degree torsional state. As the light travels along the direction of the molecules, the light is torn by 90 degrees when it passes through the liquid crystal. But when a voltage is added to the liquid crystal, the molecules are rearranged vertically so that the light can go out directly without any torsion.

LCD is a dependent polarizing filter (piece) and light itself. Natural light is randomly diverged in all directions. The polarizing filter is actually a series of thinner parallel lines. These lines form a net to block all light that is not parallel to the lines. The line of the polarizing filter is perpendicular to the first, so that the polarized light can be completely blocked. Only the lines of the two filters are completely parallel, or the light itself has been torsional to matching the second polarizer, and the light can penetrate.

LCD is made up of such two vertical polarizing filters, so in normal circumstances all the light that is trying to penetrate is blocked. However, because the two filters are filled with twisted liquid crystals, they will be turned 90 degrees by the liquid crystal molecules after passing through the first filter. Finally, they will pass through second filters. On the other hand, if we add a voltage to the liquid crystal, the molecules will be rearranged and completely parallel, so that the light will no longer be reversed, so it will be blocked by second filters. In a word, the light is blocked by the addition of electricity, and the light is emitted without electricity.

However, the liquid crystal arrangement in the LCD can be changed so that the light is emitted at the time of adding electricity, but it is blocked when the electricity is not added. But because the computer screen is almost always on, only the "add power to block the light" scheme can achieve the purpose of the most power saving.

From the structure of LCD, whether it is a laptop or a desktop, the LCD display is a layered structure composed of different parts. The LCD is made up of two glass plates with a thickness of about 1mm, which is separated by a uniform interval of 5 m containing a liquid crystal (LC) material. Because the liquid crystal material itself is not light, so the screen on both sides with a lamp as the light source, and a backlight in liquid crystal display on the back (or uniform plate) and reflective film, backlight board is composed of a fluorescent substance can emit light, its main function is provided for uniform background light. The light emitted by the backlight passes through the first layer of polarizing filter layer into the liquid crystal layer containing thousands of crystal drops. Crystal droplets in the liquid crystal layer are included in the tiny cell structure, and one or more cells form a pixel on the screen. The transparent electrode between the glass plate and the liquid crystal material is divided into rows and columns, and the rotatory state of the liquid crystal is changed by changing the voltage at the intersection point between the row and the column. The action of the liquid crystal material is similar to a small light valve. The periphery of the liquid crystal material is the part of the control circuit and the driving circuit. When the electrode in LCD generates electric field, the liquid crystal molecules will distort, so that the rays passing through it will be refracted regularly, and then filtered through second layers of filter layer to show on the screen.

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