Mobile Phone LCD Screen Quality Control Expert

Analysis of the principle of led backlight structure

by:Kimeery     2021-08-27
The structure of the LED backlight source can be seen from the above figure. The manufacture of the LED backlight source starts with the production of a light guide plate from acrylic resin, and then makes a white dot pattern that scatters the light on the light guide plate, and then attaches a reflective film, a diffuser, and a prism. Optical films such as diaphragms are assembled, and then LED light reflectors are assembled, and the backlight is assembled. The structure and principle of the led backlight light guide plate is shown in the figure above. The LED SMD lamp backlight needs to transmit the light emitted by the SMD lamp to the light guide plate while being totally reflected in the light guide plate. The reflection point pattern at the bottom of the light guide plate changes regularly. , The part of the light energy whose incident angle is less than the total reflection angle is emitted from the surface of the light guide plate, turning the line light source into a surface light source. The spot diameter of the lamp is small and the number is small; the spot far away from the lamp has a large diameter and the number is large; and the spot farthest from the lamp is set with a reflective diaphragm, so the spot diameter is slightly smaller and the number is slightly smaller. lesser. This setting ensures that the brightness of the entire display is uniform. (1) Before the injection molding starts, first open the mold and keep a certain gap. (2) Fill the mold with resin. (3) With filling, the pressure in the mold increases, and the gap for mold opening increases with the extension of the positioning rod. (4) Before the resin filling is completed, fill the mold cavity with resin completely, and then pressurize at high speed after the filling is confirmed by detection. (5) After the resin is filled, step pressure control is performed while maintaining the pressure. (6) Before the cooling is completed, the final pressure is maintained, and the light guide plate is made after the cooling is completed. The structure and principle of led backlight brightness enhancement film The brightness enhancement film is used to improve the brightness of the screen, and it is divided into two types: refraction enhancement film (upward prism) and total reflection enhancement film (downward prism). The refraction-type brightening sheet is formed by transferring a plastic resin film under high pressure. As shown in the figure above, the apex angle of the refractive diaphragm is 90 degrees, and the upper and lower parts are orthogonal to each other. In order to produce the off-angle effect, a lower diffusion film (referred to as the diffusion film) is installed at the lower part, and a light guide plate, a reflective film, etc. are further provided; a white dot pattern is also printed under the light guide plate. Using the scattering effect of this pattern, an outgoing beam of about 60 degrees is generated, and then the scattering and refraction effect of the lower diffuser is used to turn into a 30-degree outgoing beam, and the refraction-type light-enhancing sheet is further used to make the beam normal direction to the display screen. In this way, the two light-increasing sheets orthogonal to each other concentrate the components on the light surface in the normal direction, thereby improving the brightness. In this mechanism, due to the Fresnel reflection loss and light absorption loss, the light utilization rate is reduced. The total reflection type light-enhancing sheet is formed by using a UV-curing resin on a polyester film to transfer it into the shape of the light-enhancing sheet. As shown in the figure above, the apex angle of this kind of prism film is 60-70 degrees, and it is used in combination with diffuser film, light guide plate with lens, reflective film, etc. For the light beam emitted from the light guide plate at 65-70 degrees, the total reflection effect causes the normal direction to enter the display screen. Compared with the refraction-type brightness enhancement sheet, it uses fewer parts and materials, and because the total reflection of the light is used, the Fresnel reflection loss and the light absorption loss are small, so that the light utilization rate is improved. The structure and principle of the LED backlight reflective film The LED backlight reflective film is usually set at the bottom of the light guide plate to reflect light inside the light guide plate to reduce the attenuation of the traveling light; while the reflective film located around the lamp tube is for high Take out the lights efficiently. Structure and Principle of LED Backlight Diffusion Film Diffusion film, also known as astigmatism film, is used to increase the diffusion of light, prevent display mottle, and improve the brightness of the LCD screen. Some of the production methods are to roughen the surface of the PET (poly ethylent terephthalate) film, and some are to seal the surface of the PET.
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