At present, most liquid crystal display technology to TN/HTN/STN/FSTN TFT and other technologies as the main axis, so we will discuss their operating principles from these technologies.
TN liquid crystal display technology can be said to be the most basic liquid crystal display, and after other kinds of liquid crystal display can also be said to be improved by TN type as the origin. Again, it works much simpler than other technologies, see the picture below. The diagram shows a simple structure of a TN LCD, including vertical and horizontal polarizers, a directional film with fine grooves, liquid crystal materials and conductive glass substrates. The principle of display is to place the liquid crystal material between two transparent conductive glass with vertical polarizer attached to the optical axis. The liquid crystal molecules will rotate and arrange in order according to the direction of the fine groove of the film. If the electric field is not formed, the light will be smoothly shot into the polarizer, and the liquid crystal molecules will rotate their direction of travel, and then shot out from the other side. If the two pieces of conductive glass are electrified, an electric field will be created between the two pieces of glass, which will affect the arrangement of the liquid crystal molecules between them, causing their molecular rods to twist, and the light cannot penetrate, thus blocking the light source. The phenomenon of light and dark contrast thus obtained is called twisted Nematic field effect, or TNFE (Twisted Nematic Field Effect).
Almost all liquid crystal displays used in electronic products are made by torsional nematic field effect principle. 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 90 degrees, while the STN super torsional nematic field effect rotates the incident light 180~270 degrees. To explain here is that the pure TN LIQUID crystal display itself only light and dark two situations (or called black and white), and there is no way to do color change. And STN LCD involves the relationship between liquid crystal materials, as well as light interference phenomenon, so the color of the display are mainly light green and orange. However, if a color filter is added to the 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 proportion of the three primary colors is harmonized. It can also display colors in full color mode. In addition, TN type LCD display if the larger the display screen, the screen contrast will appear poor, but by the improved TECHNOLOGY of STN, can make up for the lack of contrast.
TFT type LIQUID crystal display is more complex, the main composition includes, fluorescent tube, light guide plate, polarizer, filter plate, glass substrate, direction film, liquid crystal material, thin mode transistor and so on. First, the LCD must use a backlight, or fluorescent tube, to project a light source that passes through a polarizer and then through the liquid crystal, where the molecules align in a way that changes the Angle of light passing through the liquid. The light must then pass through a colored filter film and another polarizer in front of it. So we can control the intensity and color of the light as long as we change the voltage of the liquid crystal, and then can change the color combinations of different shades on the liquid crystal panel.