The Study Of White LED Optical Properties For LCD Backlight

1993, Shuji Nakamura of Japan developed the first high-brightness blue light-emitting diode, then LED entered the rapidly developed period.In the 21st century LED had gradually begin to mature, not only in the lighting field, but also in the backlight market. This article introduced the history of the development of backlight and gave a detailed description of different various backlight.With the advantages of long life, low power consumption, wide color domain and small size, in the future LED backlight will be main products of the backlight market. LED backlight can be divided into RGB and white LED backlight.They both have advantages and disadvantages. The major advantage of RGB backlight is wide color domain, but the disadvantages are also evident, for example:low efficiency with green LED, three-color mixing uneven, hot serious, serious impact on driving the development of circuit complexity and so on. The main advantage of white LED backlight is the low cost, low power consumption.Compared with the same size of RGB backlight, white LED backlight power consumption is 60% lower than the former. As the market share is determined by the cost, white LED backlight products will be the main form of the backlight. The only disadvantage of this form is the high color temperature, the lack of red light in color spectrum which makes color domain narrow. To solve this problem, I carried out research work of white LED optical properties, which is encapsulated by two phosphors to enhance red light intensity.First of all, by improving white LED used YAG:Ce3+ phosphor, the red intensity of the spectrum is enhanced. A New YAG:Ce+ phosphors were prepared by solid-state reaction. By spectral analysis this new phosphor found that there is a new red-band peak or red shift of the main peak. Second, test packaged LED.With Gaussian fitting method studied white LED's brightness, found that the white LED's brightness can suit D65 white point, and color coordinates meet Energy Star 6500K requirements.Last, with white balance test, the color domain of this LED is 73.3% of the NTSC,and color domain can include CCFL color domain.By 1400 hours'aging test the result indecade that CCT increased from 6500K to 6900K. Color offset are all less than 8 NBS, although 3 of them more than 5 NBS but it can be ignored.The stability is very good. Excessive color offset may be due to:poor stability of phosphors; poor quality blue chips; packaging process imperfections and human-induced measurement error and so on.