Sol–gel synthesized linear oligosiloxane-based hybrid material for a thermally-resistant light emitting diode (LED) encapsulant

The thermal resistance against discoloration of a high refractive index phenyl-siloxane hybrid material (hybrimer) was studied for LED encapsulation. The phenyl hybrimer was fabricated by a hydrosilylation reaction of linearly-structured vinyl oligosiloxane and hydrogen oligosiloxane resins using a platinum (Pt) catalyst. The linear oligosilxane resins were synthesized by a non-hydrolytic sol–gel condensation reaction of di-functional silane precursors, containing vinyl, hydrogen, and phenyl groups. The oligosiloxane, having a higher degree of condensation and molecular size compared with the branched oligosiloxane, provided low shrinkage and an effective curing behavior. The phenyl hybrimer showed high optical transparency and a refractive index of up to 1.57. In particular, the amount of Pt catalyst was minimized to inhibit yellowing of the hybrimer under long-term aging at 180 °C. These results suggest that the linear oligosiloxane-derived phenyl hybrimer could be used as a high performance LED encapsulant.