Direct synthesis of zirconium containing phenyl silicone resin for LED encapsulation

Zirconia/phenylsiloxane nano-composite for LED encapsulation with high and stable light extraction efficiency

To obtain a rapid processible LED encapsulant that leads to high and stable light extraction efficiency (LEE), UV curable ZrO₂/phenyl-siloxane nano-composite (ZSC) double-layer encapsulants were prepared and optimized. The highly crystalline ZrO₂ nanoparticles with a diameter of ∼14 nm were synthesized through a modified hydrothermal method at mild conditions, and a UV curable methacryl-diphenyl-polysiloxane (MDPS) with a refractive index (RI) of 1.54 (at 633 nm) was synthesized from self-condensation of diphenylsilanediol and an end-capping reaction. High refractive indexes (RIs) from 1.54–1.61 have been obtained for ZSC composites by adding 0–20 wt% ZrO₂. Before and after sulfur vapor erosion, the double-layer encapsulated sample (M-10/M) showed 11.2% and 64.8% higher LEE respectively than that of Dow Corning OE-7662. Meanwhile, the variation of LED light color temperature (T_c) was less than 1%. The effect of the ZrO₂ nanoparticle content on LEE of double-layer and single-layer encapsulation were compared and discussed based on Fresnel loss and Rayleigh scattering theories. The double-layered UV curing processing took only 1/6 of the time needed for common thermal curing.

The double-layer encapsulation by a highly crystalline ZrO₂/polydiphenylsiloxane composite affords 11.2% and 64.8% higher LEE respectively than that of OE-7662 before and after sulfur vapor erosion.

Reactions of Zirconium (IV) n-Propoxide with SiH-Functional Polysiloxanes as a Route to Siloxane-Zirconium Hybrid Materials with Enhanced Refractive Index

The reaction of poly(hydromethylsiloxane-co-methylphenylsiloxane) with zirconium (IV) n-propoxide in dry toluene leads to extensive scission of the siloxane chain and conversion of Si-H groups. These processes produce oligomeric siloxanes and organosilanes containing moisture sensitive propoxy and siloxy-zirconate groups. The obtained post-reaction solution of zirconium containing heterosiloxane oligomers is stable under anhydrous conditions for several weeks. However, its exposure to moisture initiates the hydrolytic condensation of the reactive groups leading to cross-linking and the formation of a siloxane-zirconium composite. Spin coating of the siloxane-zirconium prepolymer followed by exposure to moisture produces thin films with excellent light transparency and increased refractive index. The final coatings are characterized by ellipsometry, UV-Vis, IR, and ²⁹ Si MAS NMR spectroscopies.