In the weeks, the wavelength range of visible light spectrum is 380nm~760nm, which is the seven colors of the human eye--red, orange, yellow, green, green, blue and violet, but the light of these seven colours are each monochromatic light.
For example, the peak wavelength of red light emitted by LEDs is 565nm. There is no white light in the spectrum of the visible light, because the white light is not a single color, but a composite light synthesized by a variety of monochromatic rays, just as the sunlight is made of seven kinds of single shade of white, and the white light in the color TV is also composed of three primary colors red, green and blue
Therefore, to make the LED Glow white, its spectral characteristics should include the entire visible spectrum range. But to make this kind of performance led, under the conditions of the process is not possible. According to the study of visible light, the white light visible to human eyes requires at least two kinds of light, namely two-wavelength luminescence (blue light + yellow light) or three-wavelength luminescence (blue light + green light + red light). The above two models of white light, all need blue light, so the uptake of blue light has become the key technology to create white, that is, the current major led manufacturing companies chasing the "Blu-ray technology." The International Master of "Blu-ray technology" manufacturers only a few, so the application of white led, especially the high brightness white led in China's promotion has a process.