TFT LCD screen
https://tmsmicro.com/detailed-analysis-of-the-type-of-lcd-screen-and-its-principle/
TN-LCD, STN-LCD and DSTN-LCD display principle is basically the same, the difference is that the liquid crystal molecule distortion Angle is somewhat different. The following is a typical TN-LCD as an example, to introduce its structure and working principle. In the TN-LCD LCD panel, which is less than 1 cm thick, it is usually made of two large glass substrate, sandwiched with color filter, orientation film, etc., and wrapped with two polarizing plates, which can determine the maximum light flux and color generation. Color filters are red, green, and blue filters that are regularly made on a large glass substrate. Each pixel is made up of three colored units, or subpixels. If you have a panel with a resolution of 1280 x 1024, it actually has 3,840 x 1024 transistors and subpixels. The upper left corner of each subpixel (gray rectangle) is an opaque thin film transistor, and the color filter produces RGB primary colors. Each sandwich contains electrodes and grooves formed in the orientation film, and the upper and lower sandwich is filled with multiple layers of liquid crystal molecules (the liquid crystal space is less than 5×10-6m). In the same layer, the position of liquid crystal molecules is irregular, but the orientation of the long axis is parallel to the polarizer. On the other hand, between the different layers, the long axis of the liquid crystal molecule continuously twists 90 degrees along the parallel plane of the polarizer.
The orientation of the long axis of the two layers of liquid crystal molecules adjacent to the polarizing plate is consistent with the direction of the polarized light of the adjacent polarizing plate. Liquid crystal molecules near the upper interlayer are arranged in the direction of the upper groove, while those in the lower interlayer are arranged in the direction of the lower groove. Finally, it is packaged into a liquid crystal box, and connected with the driver IC, control IC and printed circuit board.
Under normal circumstances, when light is irradiated from top to bottom, usually only one Angle of light can penetrate down, and then lead through the upper polarizer into the groove of the upper sandwich, and then pass through the lower polarizer through the tortuous arrangement of liquid crystal molecules, forming a complete light penetration path. The mezzanine of the LCD is attached to two polarizers whose arrangement and transmittance Angle are the same as the grooving arrangement of the upper and lower mezzanine. When a voltage is applied to the liquid crystal layer, due to the influence of the external voltage, the liquid crystal will change its initial state, no longer in accordance with the normal way of arrangement, and become erect. Therefore, the light passing through the liquid crystal will be absorbed by the second layer of polarizer and the whole structure will appear light 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 will reverse the direction of the incident light by 90 degrees, so that the incident light of the backlight can pass through the entire structure, resulting in a white appearance on the display screen. In order for each individual pixel on the panel to produce the color you want, multiple cold cathode lamps must be used as a backlight for the display.
