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Today, the white LED is still there luminous uniformity is poor, and the closed material of life long problem, can not play the white led application is expected advantages. However, the demand perspective, not only the general lighting purposes, with the wide range of mobile phones, LCD TV, automotive, medical and other applications, so that the most appropriate development of stable white light LED technology research on a wide range of attention.
Improve white LED luminous efficiency, there are two directions, one is to increase the area of the led chip to increase the amount of light emitted. Second, several small chips packaged together in the same module.
To increase the amount of light emitted by increasing the chip area
Although the area of the LED chip to be large to be able to obtain a much higher brightness, but over a larger area, in the application process and results will appear counterproductive. Therefore, for such a problem, the part of the LED industry according to an electrode structure improved and the structure of the flip chip, the chip surface modified to achieve the luminous efficiency of 50lm / W. For example, in the white LED portion of the flip chip package, since the light-emitting layer is very close to the vicinity of the package, the light emitting layer is dissipated to the outside when the electrode is not obscured, but the drawback is that the generated heat is not easily dissipated.
The use of encapsulation several small area LED chips rapid increase in luminous efficiency
LED chips and a large area compared to the use of small-power LED chip packages into one module, this is to be able to quickly achieve high brightness requirements, for example, Citizen will eight small LED package together, so that the luminous efficiency of the module is reached 60lm / W, called the industry's first.
Addition to the the chip light extraction efforts needs to be done, and expect to be able to obtain a higher light efficiency, part of the package is necessary to do some improvements. In fact, for every multi-project will increase a light extraction efficiency bring some impact However, this does not mean that, because the encapsulation process will increase the higher light loss, like flat light source Japanese OMROM developed technology, we can greatly enhance the light extraction efficiency, such a structure is the light emitted by the LED, using LENS optical system and the reflective optical system to make control, so OMROM called "Double reflection". With such a structure, the light loss may be caused by the traditional shell-type package such as the LED for wide-angle reflection of the package to obtain a higher light efficiency, further processing is formed on the surface of Mesh form a double reflection effect, in such a manner can be obtained a good light extraction efficiency. Because of this special design, the use of the reflection effect to achieve high light-extraction efficiency of the LED, the main purpose is for LCD TV backlight applications.
Increase in the importance of the encapsulating material and fluorescent material
If you expect to be used as the LCD TV backlight applications, the the NA problem will need to overcome more. Because the LCD TV of the continuous use time is as long as a few hours, or even 10 hours, therefore, due to such a long period of use cases, the white LED used as a backlight must have not generated because of the continuous use luminance attenuation.
High-power white LED, has published its luminous power is a low-power white LED brightness dozens of times, because the use of high power white LEDs instead of fluorescent lamps as lighting equipment, a must overcome difficulties is the brightness decreasing situation. For example, white LED prolonged continuous use 1W of cases, will cause continuous use the brightness of the half time of gradually reducing the phenomenon, not only a high-power white LED will be such a situation, low-power white LED also the existence of such problem, but because of the different applications of low power white, so, and will not therefore particularly highlights the troubled.
The amount of heat of the high power led is ten times the number of low-power LED and, therefore, will appear as the temperature rises, while the problem of reduced luminous power, Therefore, in the development of the the high packaging material be able to heat resistance, relative significant very important .
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