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07 Apr 2011
LED (Light Emitting Diode), the light emitter diode, is one kind of solid state semiconductor device, it may change into directly the phonograph the light. The LED heart is a semiconductor's chip, Light emitter diode A chip's end is attached to a support, an end is a cathode, another end connection power source's positive electrode, causes the entire chip to seal by the epoxy resin. The semiconductor chip is composed of two parts, a part is the P semiconductor, the hole occupies the dominant position inside it, another end is the N semiconductor, in here is mainly the electron. But these two kind of semiconductors connect time, between them forms a P-N knot. When electric current through wire function in this chip's time, the electron will be pushed to the P area, in the P area electron with hole compound, will then send out the energy by the photon form, this will be the LED illumination principle. But the light wave length is also the light color, is by forms the material decision which P-N ties. Initial LED serves as instruments and meters' instruction photo source, afterward each kind of light color's LED obtained the widespread application in the street-traffic control lights and the big area display monitor, has had the very good economic efficiency and the social efficiency. Take 12 inch red street-traffic control lights as the example, originally uses the long life in the US, the low light effect's 140 tile incandescent lamp takes the photo source, it has 2000 lumen white lights. After red light filter, the light loses 90%, is only left over 200 lumina the thioindigo red. But in the new design's lamp, Lumileds Corporation has used 18 red LED photo sources, including the circuit loss, altogether consumes the electricity 14 tiles, then has the same light effect. The automobile signal light is also the LED photo source application important domain. Speaking of the general lighting, the people need the white the photo source. in 1998 turned white light LED to develop successfully. This kind of LED is (YAG) seals the GaN chip and the yttrium aluminum garnet is making together. The GaN chip bluing light (λp=465nm, Wd=30nm), the high temperature agglutination makes is stimulated this blue light sends out after the Ce3+ YAG luminous powder the decadent photoemission, peak value 550nm. The blue light LED substrate installs in the cup reflection cavity, the cover mixes has the YAG resin thin layer, approximately 200-500nm. The LED substrate sends out the blue light part by the luminous powder absorption, Huang Guang who another part of blue light and the luminous powder send out is mixed, may obtain the white light. Now, regarding InGaN/YAG white LED, through changes the YAG luminous powder the chemical composition and adjustment luminous powder level thickness, may obtain color temperature 3500-10000K the assorted white light.Tahitian pearl This kind obtains the white light method through blue light LED, the structure is simple, the cost is inexpensive, the technical maturity is high, therefore utilizes many. In the 1960s, the scientific and technical worker tied the illumination using semiconductor PN the principle, developed the LED light emitter diode.Freshwater pearl At that time developed LED, used the material was GaASP, its illumination color for red. After near 30 year development, everybody familiar very LED, has been able to send out, the orange red now, yellow, green, blue and so on many kinds of colored lights. However illuminated white light LED which needed only in the recent years only then to develop, here to the reader introduced that the related illumination used white light LED. 1. Visible light spectrum and LED white light relations. Audiences week it, the visible light spectrum's wavelength range is 380nm~760nm, is the seven colors of the spectrum light which the human eye may feel - - red, the orange, yellow, green, blue, is blue, is purple, but these seven kind of color's light each one is one kind of monochromatic light.South Sea pearl For example LED sends the thioindigo red peak wavelength is 565nm. Does not have the white light in the visible light spectrum, because the white light is not the monochromatic light, but by many kinds of monochromatic light synthesis compound light, just like the sunlight is by seven kind of monochromatic light synthesis white light, but in color TV set's white light is also by three primary colors red, green, synthesizes blue.Golden South Sea pearl Thus it can be seen, must make LED to send out the white light, its spectral characteristic should include the entire obvious spectral region. But must make this performance LED, under the present technological conditions is impossible. According to the people to the visible light research, the white light which the person eye can see, needs two kind of light at least the mixes, namely two wave length illuminations (blue color light + decadent light) or three wave length illuminations (blue color light + green light + red light) pattern.Jewellery Manufacturers The above two kind of pattern's white light, needs the blue color light, therefore the ingestion blue color light has become the manufacture white light the key technologies, namely the current each big LED manufacture company pursues “the blue light technology”. At present internationally masters “the blue light technology” the manufacturer only has minority several, for instance Japan's date Asia chemistry, Japan's Toyota synthesizes, US's CREE, Germany's Ou Silang and so on, therefore the white light LED promoted application, high luminance white light LED also has a process particularly in our country's promotion. LED light


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