Liquid crystal is a special substance between solid and liquid. It is an organic compound, which is liquid under normal conditions, but its molecular arrangement is as regular as solid crystal, so it is called liquid crystal. Another special property of liquid crystal is that if an electric field is applied to liquid crystal, it will change its molecular arrangement, and if it is given a polarizer, It has the function of blocking the passage of light (when the electric field is not applied, the light can pass through smoothly). If the color filter is used to change the voltage added to the liquid crystal, the amount of light transmission of a certain color can be changed, and it can also be vividly said that changing the voltage at both ends of the liquid crystal can change its transmittance (but in practice this must be matched with the polarizer). In the past, there was not a tutorial on making screens that you can only see on the Internet, that is, the principle of liquid crystal.