What Is LCD Technology

TN liquid crystal display technology can be said to be the most basic liquid crystal display, and other types of liquid crystal displays can be said to be improved based on TN type as the origin. Again, it is much simpler than other techniques, as shown below. The diagram shows the simple structure of the TN LCD, including vertical and horizontal polarizers, directional films with fine grooves, liquid crystal materials, and conductive glass substrates.

The principle of the display is to place the liquid crystal material between two transparent conductive glasses, and the vertical polarizer is attached to the optical axis. The liquid crystal molecules will rotate and arrange in order according to the direction of the thin slots of the membrane. If no electric field is formed, light will be smoothly directed into the polarizer, and the liquid crystal molecules will rotate their direction of travel and then shoot out from the other side. If two conductive pieces of glass are charged with electricity, an electric field is generated between the two pieces of glass, which affects the arrangement of liquid crystal molecules between them, causing their molecular rods to twist so that light cannot penetrate, thus blocking the light source. The resulting contrast is called the twisted Nematic field effect (TNFE).

Almost all liquid crystal displays used in electronics are made by the principle of torsional nematic field effects. The display principle of STN type is similar, but the difference is that the liquid crystal molecule of TN torsional nematic field effect rotates the incident light by 90 degrees, while the STN supertorsional nematic field effect rotates the incident light by 180 ~ 270 degrees. What is to be explained here is that the pure TN LCD itself has only two cases of light and dark (or black and white), and there is no way to change the color.

STN LCD involves the relationship between liquid crystal materials, as well as the phenomenon of light interference, so the color of the display is mainly light green and orange. However, if a color filter is added to a traditional monochrome STN LCD, and any pixel of the monochrome display matrix is divided into three sub-pixels, and the red, green and blue primary colors are displayed through the color filter respectively, and then the ratio of the three primary colors is coordinated. It can also display colors in full color mode. In addition, if the TN LCD display is larger, the screen contrast will appear poor, but through the improvement of STN technology, it can make up for the lack of contrast.

TFT type liquid crystal display is more complex, the main components include fluorescence tube, light guide plate, polarizer, light filter plate, glass substrate, direction film, liquid crystal material, thin film transistor and so on. First, the LCD must use a backlight or fluorescent tube to project a light source that passes through the polarizer and then through the liquid crystal, where the molecules are arranged in a way that changes the Angle of the light that passes through the liquid. The light must then pass through a color filter film and another polarizer in front of it. Therefore, just by changing the voltage of the liquid crystal, we can control the intensity and color of the light, and then we can change the color combination of different tones on the liquid crystal panel.