Development and Application of Light-Emitting Diodes for High-NTSC LCD Backlight modules

• Main Authors: Ming-Tsun Hsieh, 謝明村
• Other Authors: Dong-Sing Wuu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/15518432701683020774

碩士 === 國立中興大學 === 精密工程學系所 === 95 === Abstract The main objective of this thesis focused on how to enhance the color space of the RGB LED backlight module for liquid crystal display (LCD) applications. The standard of color space that had been approved by the National Television System Committee (NTSC) in 1953 is used as the reference and defined as 100%. We have developed an optical measurement system to investigate the matching relationship between the R/G/B LED spectra and commercial LCD color filters. In order to achieve the best visualizing result on LCD, both transmittance ratio and color gamut have to be taken into consideration in developing the new color filter as well as the LED spectra need to match the color filter. By choosing proper R/G/B single chip specifications, the three chips into one surface-mount white-light LED was fabricated to enhance the NTSC value of the R/G/B LED backlight module. In our experiments, it is found that the performance of the green LED is a key factor in determining the NTSC value of the R/G/B backlight module. In order to further improve the color space of the LED backlight module, the spectral purity of the green LED was enhanced by optical filter coating on the bare LED chip using an electron-beam evaporator. Another approach, where the optical filter was first deposited on the thin glass plate and inserted between the light bar and light guiding plate, was demonstrated to improve the color gamut from 105 to 120 % based on NTSC standard. These results show that the color space of the RGB LED backlight modules can be greatly improve using a band-pass optical coating technique. Keywords：LEDs, Backlight Module, Color Filter, NTSC, Optical Filter