Liquid crystal display LCD display 1. Basic knowledge of liquid crystal display Basic knowledge of LCD Liquid crystal display is a passive display. It cannot emit light and can only use the light of the surrounding environment. It only needs a small amount of energy to display patterns or characters. It is precisely because of low power consumption and miniaturization that LCD has become a better display method. The liquid crystal material used in liquid crystal display is an organic substance with both liquid and solid properties. Its rod-like structure is generally arranged in parallel in the liquid crystal box, but its arrangement direction can be changed under the action of an electric field. For positive TN-LCD, when no voltage is applied to the electrode, the LCD is in the \"OFF\" state, and light can pass through the LCD to appear in a white state; when a voltage is applied to the electrode, the LCD is in the \"ON\" state, and the long axis direction of the liquid crystal molecules is arranged along the direction of the electric field. Light cannot pass through the LCD and appears in a black state. By selectively applying voltage to the electrodes, different patterns can be displayed. For STN-LCD, the twist angle of the liquid crystal is larger, so the contrast is better and the viewing angle is wider. STN-LCD is based on the principle of birefringence for display. Its base color is generally yellow-green, and the font is blue, which becomes a yellow-green mode. When a purple polarizer is used, the base color will turn gray and become a gray mode. When using a polarizer with a compensation film, the base color will become close to white. At this time, STN becomes a black and white mode, which is FSTN. The polarizers of the above three modes are rotated 90°, that is, they become blue modes, and the effect will be better. 2. Structure of liquid crystal display devices The following figure is a structural diagram of a reflective TN type liquid crystal display. [pic] As can be seen from the figure, the liquid crystal display is a liquid crystal box made of two upper and lower conductive glass sheets. The box is filled with liquid crystal and sealed with a sealing material-a plastic frame (usually epoxy resin) on all sides. Polarizers are attached to the two outer sides of the box. The interval between the upper and lower glass sheets in the liquid crystal box, which is usually called the box thickness, is generally a few microns (the accuracy of people is tens of microns in diameter). The inner side of the upper and lower glass sheets, corresponding to the display graphic part, is coated with a transparent tin oxide-tin oxide (referred to as ITO) conductive film, that is, the display electrode. The main function of the electrode is to allow the external electrical signal to be added to the liquid crystal through it. The entire display area on the inner side of the glass sheet in the liquid crystal box is covered with an orientation layer. The function of the orientation layer is to align the liquid crystal molecules in a specific direction. This orientation layer is usually a thin layer of high molecular organic matter, which has been rubbed; it can also be formed by vacuum evaporation and oxidation at a certain angle on the glass surface.
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