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In order to improve the display quality, display stability and working life of the display, the interference of electromagnetic wave in the external environment on the normal operation of the display control circuit is reduced.
Whether it is the home users or business users, in the environment of using the computer, there are always other electrical equipment and communication equipment. When these devices are working, they will become electromagnetic sources one by one, and form magnetic fields around these devices and radiate electromagnetic waves. The size of the formed magnetic field and the intensity of the radiated electromagnetic waves are determined by the working power of these devices. The common sources of electromagnetic interference in the home and office environment are power supply, components, wires, connectors, cooling fans, fluorescent lamps, lightning and electrostatic discharge. In addition, there are electromagnetic fields around large power consumption household appliances such as TV, refrigerator, electric fan, or unshielded speakers, telephones and even pagers. Obviously, in the working environment of the display, more than several of the above devices are working, that is, a lot of electromagnetic radiation sources are formed beside the display, which constantly emit electromagnetic waves to interfere with the normal work of the display. It may cause the display circuit to be interfered in the work, especially affect the work of the scanning circuit, make the display picture jitter and even produce color spots. More serious will lead to the disorder of the picture.
The working principle of CRT display, that is, CRT display, is: when the electron beam emitted from the cathode of the electron gun inside the CRT becomes a small electron current after intensity control, focusing and acceleration, and then deviates to the correct target through the action of deflection coil, passes through the small hole or fence of the shadow mask and bombards the phosphor on the fluorescent screen. At this time, the phosphor is activated and gives out light. R. G, B trichromatic fluorescent spots are illuminated by different proportion of the intensity of the electron flow, will produce a variety of colors. The deflection coil is used to position the electron gun launcher, which can generate a strong magnetic field after power on. The electron gun can be moved by changing the magnetic field strength. The long-term existence of electromagnetic interference source in the working environment of the display will affect the magnetic field of the deflection coil of the display, and change its intensity and direction, which will lead to the deviation of the positioning of the electron gun launcher, and make the emitted electron flow deviate from the original orbit, which will cause the display magnetization and seriously affect the display quality.
Second, reduce the electromagnetic radiation generated by the display work. The so-called electromagnetic radiation is the propagation of alternating electromagnetic field in space. Regardless of the frequency of electromagnetic wave, there is radiation. Because the display itself will form an electromagnetic source and radiate electromagnetic waves. Electromagnetic radiation has potential danger to human body. It can induce cancer and accelerate the proliferation of human cancer cells. At the same time, it will affect the circulatory system, immune, reproductive and metabolic functions of human body, and affect people's cardiovascular system and visual system. In addition, the high dose of electromagnetic radiation will also affect and destroy the original biological current and biological magnetic field of human body. The installation of the screen cover of the display can weaken the electromagnetic wave emitted by the display, reduce the intensity of electromagnetic radiation generated by the display, and reduce its harm to human body and environment.
From the above analysis, it is not difficult to see that the display shield plays an important role in the early display. However, it is pointed out that there are many problems in the completion of the above functions. For example, because the display is a relatively high heating equipment, the heat dissipation of the whole equipment should be considered, and the screen cover of the display is made of metal, so there is a certain gap in the screen cover for heat dissipation. In this way, electromagnetic waves can still enter and exit the display through these gaps. The shielding cover can only reduce external interference and external electromagnetic radiation, but can not completely solve the problem of electromagnetic interference and electromagnetic radiation. Moreover, due to the installation of shielding cover, the production process of the display will be increased, which will lead to the increase of the cost of the display. In addition, in the pursuit of lightweight and fashionable products today, a heavy metal part in the display will be more ideal if it can be replaced.