Liquid crystal is an organic compound consisting of long rod like molecules. Under natural conditions, the long axis of these rod molecules is approximately parallel.
The first characteristic of the LCD LCD is that the liquid crystal must be poured into the two columns with a slot to work properly. The grooves on the two planes are perpendicular to each other (90 degrees intersecting), that is, if the molecules on one plane are arranged in the north-south direction, the molecules on the other plane are arranged, and the molecules between the two planes are forced into a state of 90 degree torsion. As the light travels along the direction of the molecules, the light passes through the liquid crystal and is turned 90 degrees. But when a voltage is added to the liquid crystal, the molecules will be rearranged vertically so that the light can go straight without any twisting.
The second feature of the LCD LCD screen is that it depends on the polarized filter and the light itself. The natural light is scattered randomly in all directions. The polarizing filter is actually a series of thinner parallel lines. These lines form a net that blocks all light that is not parallel to the lines, and the line of the polarizing filter is perpendicular to the first, so that the polarized light can be completely blocked. Only the line of the two filters is completely parallel, or the light itself has been twisted to match the second polarizing filters, so that the light can penetrate.
The LCD LCD screen is made up of two vertical polarizing filters, so it should block all the light that is trying to penetrate under normal circumstances. However, since the two filters are filled with twisted liquid crystals, the liquid crystal molecules are twisted by 90 degrees after the first filter is worn out, and finally through the second filters. On the other hand, if a voltage is added to the liquid crystal, the molecules are rearranged and completely parallel, so that the light is no longer torsional, so it is just blocked by second filters. In short, the power is used to block the light, and the light is emitted without electricity. Of course, it can also change the liquid crystal alignment in LCD, so that the light can be emitted when it is energized, and it will be blocked without electricity. But because the LCD screen is almost always on the bright side, the only way to add power is to block the light.