The working principle of LCD screen:
In TN-LCD LCD display panels with a thickness of less than 1 centimeter, they are usually made of two large glass substrates with color filters, alignment films, etc. sandwiched inside, and two polarizing plates wrapped outside. They can determine the maximum luminous flux and color generation. A color filter is a filter composed of three colors: red, green, and blue, which are systematically made on a large glass substrate. Each pixel is composed of units (or sub pixels) of three colors. If there is a panel with a resolution of 1280 × 1024, it actually has 3840 × 1024 transistors and sub pixels.
The upper left corner (gray rectangle) of each sub-pixel is an opaque thin-film transistor, and a color filter can produce the three primary colors of RGB. Each interlayer contains grooves formed on electrodes and alignment films, and the upper and lower interlayers are filled with multiple layers of liquid crystal molecules (with a liquid crystal space of less than 5 × 10-6m). Within the same layer, although the positions of the liquid crystal molecules are irregular, their long axis orientations are parallel to the polarizing plate. On the other hand, between different layers, the long axes of liquid crystal molecules are continuously twisted 90 degrees along the parallel plane of the polarizing plate.
Among them, the orientation of the long axes of the two layers of liquid crystal molecules adjacent to the polarizing plate is consistent with the polarization direction of the adjacent polarizing plate. The liquid crystal molecules near the upper interlayer are arranged in the direction of the upper groove, while the liquid crystal molecules in the lower interlayer are arranged in the direction of the lower groove. Finally, it is packaged into a liquid crystal cell and connected to the driver IC, control IC, and printed circuit board.
Under normal circumstances, when light shines from top to bottom, only a single angle of light can penetrate through. It is guided into the grooves of the upper interlayer through the upper polarizing plate, and then exits the lower polarizing plate through the twisted arrangement of liquid crystal molecules, forming a complete path of light penetration.
The interlayer of the LCD display is attached with two polarizing plates, and the arrangement and transmission angle of these two polarizing plates are the same as the groove arrangement of the upper and lower interlayers. When a certain voltage is applied to the liquid crystal layer, due to the influence of external voltage, the liquid crystal will change its initial state, no longer arranged in the normal way, and become upright. Therefore, the light passing through the liquid crystal will be absorbed by the second polarizing plate, and the entire structure will appear opaque, resulting in black on the display screen. When no voltage is applied to the liquid crystal layer, the liquid crystal is in its initial state and twists the direction of incident light by 90 degrees, allowing the incident light from the backlight to pass through the entire structure, resulting in white on the display screen. In order to achieve the desired color for each independent pixel on the panel, multiple cold cathode lamps must be used as the backlight source for the display.