As efficient artificial light sources, nitride-based light-emitting diodes (LEDs) have been widely used. However, III nitride white light-emitting diodes (WLEDs) are mostly fabricated by combining a blue LED chip with yellow phosphors, which results in inevitable problems, such as low color-rendering index (CRI) and detrimental effect to human eyes. As a solution for healthy lighting, we report a strategy to produce a WLED with an emission spectrum perfectly matched with natural daylight. By utilizing near-ultraviolet LED chips and a mixture of blue/cyan/amber/red phosphors, a CRI (Ra) of 97.9 is achieved for the WLEDs at a correlated color temperature of around 5000 K. The resemblance ratio of these solar-spectrum WLEDs with the standard normalized daylight spectrum (5000 K) is found to as high as 93.4%. Residual UV light in the normalized spectrum is <5 % . The method will benefit the development of high-efficiency healthy artificial light sources.
KEYWORDS: RGB color model, LED backlight, LCDs, Light emitting diodes, Color reproduction, Data modeling, Green light emitting diodes, Lead, Blue light emitting diodes, Fluctuations and noise
Comparing with the conventional CCFL (Cold Cathode Fluorescent Lamp) backlight, three-basic-color LEDs backlight
has some advantages such as good color reproduction, long life and lead free etc. Theoretically, the color gamut is
determined by x, y coordinates of the three basic colors in CIE chromaticity diagram, and the x, y coordinates of each
basic color can derived from the relative spectrum distribution (RSD) of the LED. In this paper, the red, green and blue
LEDs' RSD models are established to calculate and analyze the color gamut of a backlight. By simulating those models,
the relationships that the color gamut of a LED backlight varies with each color are analyzed, and the optimum
combination of three colors is obtained within the given wavelengths ranges. Moreover, the combinations of three colors
for the gamut of 115% NTSC and 110% NTSC are plotted in pictures, respectively.
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