Preparation Of Thermal Composite Materials And Reflective Materials For Application Research On White LED

With the improvement of semiconductor light-emitting diode (LED) technology, white LED is developed quickly. As white LED has long life, non-pollution, low-power features, it exhibits a potential to gradually replace fluorescent, incandescent light source for next generation of "green lighting".This paper firstly briefly introduces the concept and characteristics of LED. Currently, white LED are confronted with two problems:low luminescent efficiency and bad heat dissipation. Secondly white LED light source with planar structure has been studied, combined with the application of composite materials with high thermal conductivity or high reflectivity.In this paper, micro-diamonds were incorporated into epoxy resin and their thermal performances were investigated. Scanning electron microscopy measurement showed that the micro-diamonds could be well dispersed in the epoxy resin matrix by the milling method. No notable phase separation between the micro-diamonds and epoxy resin matrix were observed. The thermal conductivities k of the composites was found to increase with the amount of micro-diamonds. There was a 45.8% enhancement in thermal conductivity with 13 wt% micro-diamonds loading in the composite as compared with the one of pure epoxy resin.Furthermore, the structure of white LED flat light source was optimized.The titanium dioxide was dispersed in polyurethane to form white reflective composite materials by physical method. A layer of reflective layer was successfully fabricated on the surface of the LED light source module by the screen printing technique. The reflectivity of reflective layer reached 80% when about 40 wt% titanium dioxide was incorporated in the polyurethane. When the thickness of reflective layer was increased to more than 160μm, the reflectivity of reflective layer in the visible range reached 93%.