A Study of the Design of the Light Guide Plate of the Backlight Module of LED for Middle-Small Size LCDs

• Main Authors: Zhi-Ting Yeh, 葉志庭
• Other Authors: Hsien-Chuen Huang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/45544304111667767271

碩士 === 清雲科技大學 === 電機工程研究所 === 94 === Abstract While designing the LED backlight module of liquid crystal displays, as the LED has certain diffusion angles for the light radiated from it, thus making the emission of light from the backlight module uneven. The thesis first puts forward the method of block division dots in order to improve the traditional matrix-type design. The method divides the light guide plate into several blocks in accordance with the distribution characteristics of the light energy of the LED and in terms of the intensity of luminance, so as to adjust the luminance close to the light source and to complement insufficient luminance in the marginal areas. The thesis expounds the design of light guide plates with the best evenness of luminance, using 2.2-inch and 3-inch ones as examples. Then, the study suggests a method of design that transfers point light sources into linear light sources. With an outward extension of 5 mm of the backlight module at the front of the light guide plate, the design engraves two rows of flat-convex structures in the 5-mm protrusion of the light guide plate as a light expansion area. Using light guide plates of 3, 6, and 12 inches as examples, the study successfully achieves the effect of transferring the point light sources of the LED into what comes closest to the effect of the cold cathode fluorescent tube. Next, the design comes out with a light guide plate that has the best evenness of light emission by means of the conventional matrix of diffuser dots. The results of the simulation prove that this method of design is not only direct and simple but easy in manufacturing, and that the light guide plate has also the best characteristics of linear radiance. The method not only reduces the difficulties in the design of the point light sources of the LED, but eliminates the difficulties in the installation of extensional optic parts by using the protruded area of the front of the light guide plate as a place of light expansion, thus reducing manufacturing costs.