High performance encapsulant for light-emitting diodes (LEDs) by a sol–gel derived hydrogen siloxane hybrid

The hydrosilylation reaction is a dominant curing method for the light-emitting diode (LED) silicone encapsulant, which requires characteristics of high transparency, high refractive index, and thermal stability against the LED junction temperature. In this research, we synthesized a hydrogen containing oligosiloxane resin through non-hydrolytic sol–gel condensation. Methyldiethoxysilane (MDES) and diphenylsilanediol (DPSD) were used as precursors and a non-hydrolytic sol–gel condensation reaction was performed under acidic conditions. The synthesized hydrogen oligosiloxane resin was mixed with a phenyl and vinyl containing oligosiloxane (PVO) resin, which was prepared by a sol–gel condensation between vinyltrimethoxysilane (VTMS) and the DPSD. This blended solution was cured at 150 C for 4 hours to complete the hydrosilylation reaction. The cured material (phenyl hybrimer) shows low shrinkage during the curing reaction and provides excellent transparency ( 90% at 450 nm) and thermal stability (440 C) with a high refractive index (n 1⁄4 1.58 at 632.8 nm).