LCD liquid crystal display knowledge part three

From the perspective of the structure of the liquid crystal display, whether it is a laptop or a desktop system, the LCD display used is a layered structure composed of different parts. The LCD consists of two glass plates, about 1mm thick, separated by a uniform interval of 5μm containing liquid crystal (LC) material. Because the liquid crystal material itself does not emit light, there are lamps as light sources on both sides of the display screen, and there is a backlight plate (or even light plate) and reflective film on the back of the liquid crystal display screen. The backlight plate is composed of fluorescent materials. Can emit light, its main function is to provide a uniform background light source. The light emitted from the backlight enters the liquid crystal layer containing thousands of crystal droplets after passing through the first layer of polarizing filter layer. The crystal droplets in the liquid crystal layer are all contained in a small cell structure, and one or more cells constitute a pixel on the screen. There are transparent electrodes between the glass plate and the liquid crystal material. The electrodes are divided into rows and columns. At the intersection of the rows and columns, the optical rotation state of the liquid crystal is changed by changing the voltage. The liquid crystal material acts like a small light valve. Around the liquid crystal material are the control circuit part and the drive circuit part. When the electrodes in the LCD display module generate an electric field, the liquid crystal molecules will be twisted, so that the light passing through it will be regularly refracted, and then filtered by the second layer of filter layer and displayed on the screen. (3) The working principle of color LCD display 　 For the more complex color display that needs to be adopted by the notebook computer or desktop LCD display, it is also necessary to have a color filter layer for processing color display. Generally, in a color LCD panel, each pixel is composed of three liquid crystal cells, and each cell has a red, green, or blue filter in front of it. In this way, the light passing through different cells can display different colors on the screen.

LCD overcomes the shortcomings of CRT's bulkiness, power consumption, and flicker, but it also brings problems such as high cost, low viewing angle, and unsatisfactory color display. CRT display can choose a series of resolutions, and can be adjusted according to the requirements of the screen, but the LCD screen only contains a fixed number of liquid crystal cells, and can only use one resolution display on the full screen (each cell is a pixel).

Liquid crystal display circuit diagram CRT usually has three electron guns, and the emitted electron flow must be accurately concentrated, otherwise a clear image display will not be obtained. But LCD does not have a focus problem, because each liquid crystal cell is individually switched. This is why the same picture is so clear on the LCD screen. LCD does not need to care about the refresh rate and flicker. The liquid crystal cell is either on or off, so the image displayed at a low refresh rate of 40-60 Hz will not flicker more than the image displayed at 75 Hz. However, the liquid crystal cell of the LCD screen is prone to defects. For a 1024×768 screen, each pixel is composed of three units, which are responsible for the display of red, green, and blue respectively, so a total of about 2.4 million units (1024×768×3=2359296) are required. It is difficult to guarantee that all these units are intact. Most likely, part of it has been short-circuited (“bright spots” appear), or disconnected (“black spots” appear). Therefore, the display products that are not so expensive will not have defects