Due to the advent of high-luminance blue LEDs , white LEDs can be easily obtained using a combination of phosphors and blue LEDs. At present, white LED has become the main backlight illumination source for portable information products, and it can even become a general household illumination source in the future. In addition, in recent years, high-power near-ultraviolet LEDs have emerged, and the same phosphors can be turned into white LEDs. LEDs are characterized by small size, low power consumption, and long life. If they are color-designed, stable, and easy to handle, When the phosphors are combined, they can become a new illumination source.
When a LED is usually combined with a phosphor, a typical method is to place the phosphor in the vicinity of the LED. The main reason is that the phosphor can efficiently convert the light generated by the LED to a wavelength, and the phosphor is disposed in a region with a high radiation density. The easiest way to convert wavelengths. In addition, the phosphor packaging method determines the luminous efficiency and color tone of the white LED, and therefore, the packaging technology of the LED and the phosphor will be further studied from the viewpoint of whitening.
White LED package of blue LED+YAG phosphor
It is a commercial white LED, in particular, it disperses YAG:Ce phosphor which can produce yellow light in a transparent epoxy resin, and then converts it into light generated by a blue LED provided in a cup. White light, this way of white light illumination mechanism is to use the LED to generate blue light, part of the blue light will stimulate the YAG phosphor to turn yellow, and the remaining blue light will be directly mixed with blue and yellow light to become white light. The characteristic of this type is that the structure is simple, and it is only necessary to add a phosphor coating process to the production of the LED, so that the manufacturing cost can be greatly suppressed, and another feature is that the chromaticity adjustment is very simple.
As long as the color coordinates are within a straight line formed by the two-color coordinates of the LED and the YAG phosphor, the color tone can be arbitrarily adjusted. According to this, when the concentration of the YAG phosphor is low, the ratio of the blue penetrating light is large, and the overall ratio is The blue tone is white light; if the concentration of the YAG phosphor is relatively high, the ratio of the yellow converted light is large, and the whole is yellow-based white light.
As described above, the partial blue LED is regarded as a complementary color, and high-density (percentage of resin) coating is not required, so that the amount of the phosphor used can be effectively reduced. Generally, the percentage of the phosphor to the resin varies with the conversion efficiency of the YAG phosphor and the shape of the cup, but a low mixing ratio of about 10 to 20 wt% can obtain white light. In addition, due to the intensity of the light emitted by the blue LED, the distribution of the central axis and the surrounding is not the same. Even if the density of the YAG phosphor around the LED chip is exactly the same, the light on the shaft and the surrounding area will be uneven, which is also necessary in the future. One of the problems to overcome.
Both the Lead Frame Type and the Chip Type are used to place the blue LED in a cup and then coated with a resin coated with a quantitative YAG phosphor. LEDs are widely used in backlighting light sources for portable information products such as mobile phones and PDAs, as well as in the field of trail guide lamps, because of their small size, power saving, and longevity.
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