| This thesis studies two kinds of zirconia composite systems for LED encapsulation.The low viscosity cycloaliphatic epoxy/anhydride has been chosen as the matrix resin of zirconia/epoxy system in the former,and matrix resin of zirconia/silicone system was a home-made silicone of low viscosity and high refractive index in the latter.In both systems,the composite was prepared by dispersion of surface modified zirconia in a common solvent with the matrix resins.The composite encapsulant was obtained after removing solvents.Physical&chemical characteristics of composites have been analyzed by X-ray diffraction(XRD),dynamic light scattering(DLS),small-angle X-ray scattering(SAXS),thermal gravimetric analysis(TGA),ultraviolet-visible spectroscopy(UV/Vis Spectrometer),transmission electron microscopy(TEM),silicon-29 liquid nuclear magnetic resonance spectroscopy(Si29 NMR),hardness tester,viscometer and refractometer.The results show that the composite resin satisfies the requirements of low viscosity,high refractive index,reasonable flexibility and good thermal/humidity durability.Maximum loading of filler for a workable encapsulant with either epoxy or silicone is 24vol%,and leads to an increase of index from 1.5001 to 1.5368 in the former case,and from 1.5413 to 1.5941 in the latter.To evaluate the performance of encapsulants,we have tested the composite encapsulants directly in working LED package.The light output power and it decay under 85oC/85%humidity operation condition was selected as the most important characteristics for an encapsulant.The results show that the incorporation of zirconia filler in either epoxy or silicone resin is beneficial for the application as LED encapsulant.Finally,we have obtained a zirconia/silicone composite with 24vol%filler content showing 13%better light extraction efficiency compared to the commercial high-refractive index silicone encapsulant(OE-6630),with a comparable durability.This zirconia/silicone composite encapsulant may have potential to become a popular encapsulation material for LED packages. |
PDF Full Text Request