Filler size dependence of optical reflectance for polymeric-filler reflectors

The study investigates the effect of filler size on optical performance of silicone-filler polymeric composite reflectors. The experimental results demonstrate for the first time that the filler size dependence is non-monotonic and the reflectance exhibits a maximum at round 1 micron for Al₂O₃ particles and 0.2 micron for TiO₂ particles. The results are discussed in terms of light reflectance with samples made of inorganic fillers with different particle sizes, volume fractions and thicknesses. A 30% difference in optical reflectance between 1 micron and 20 micron Al₂O₃ at 0.1 volume fraction was observed. By utilizing optimized filler particle size and volume fraction, great improvement in reflectivity for silicone based composite reflectors can be realized in an approach to increase amount of light re-directed at the desired location and therefore reduce the amount of energy needed to produce the required lighting output.