Studies Of High Refractive Index Materials Prepared By Nano ZrO₂ And TiO₂ Hybrid Silicone Epoxy Resin

Light emitting diode (LED) is one fast developing lighting device for its very efficient energy conservation and long duration. However, the ultraviolet (UV) emitting of bright LED is harmful to currently using packaging materials of epoxy resins and benzene containing silicone, which lead to decreased light output intensity and usage life time. In this paper, sol gel method was employed to prepare ZrO₂ and TiO₂ ZrO₂ nano particles hybrid with silicone epoxy to get nano hybrid materials of high refractive index, which can increase light extraction efficiency. The effects of preparation conditions and the compositions on the properties of the nano hybrid materials were studied.First, organic inorganic hybrid materials with high refractive index and transparency were prepared and characterized. It began with the hydrolysis of tetrabutoxytitanate, zirconium n tetrabutanoxide to get ZrO₂ and TiO₂ ZrO₂ nano sol, followed by hydrolysis ofγGlycidoxypropyl trimethoxysilane(GPTMS) on the inorganic nano sol to get nano hybrid sol materials of GPTMS/ZrO₂, GPTMS/TiO₂ ZrO₂. Hybrid thin films were obtained through dip and spin coating on glass substrates, followed by thermal curing at 130℃. The effect of ZrO₂, TiO₂ ZrO₂ on refractive index, transmittances, thermal properties, surface morphologies of the hybrid film was studied. The transmittances of all hybrid ?lms prepared are higher than 90% in visible region. Thermal stability of ?lms was improved. The refractive index of the hybrid films at the wavelength of 632.8 nm increases with the increasing of ZrO₂, TiO₂ ZrO₂ contents; When the content of ZrO₂ is 29%, the refractive index reaches 1.551, and when the content of TiO₂ ZrO₂(Ti/Zr=3/1) reaches 50%,the refractive index equal 1.618. Atomic force microscopy (AFM) showed that the films have excellent surface planarity and a low surface roughness. SEM pictures showed no significant cracks.Second, UV irradiation aging properties of some hybrid films were studied. A series of films with 10wt% of different TiO₂/ZrO₂ mole ratio were prepared, and followed by UV lighting. The aging properties of the films were analyzed by Fourier transform infrared spectroscopy (FTIR), UV visible spectroscopy (UV vis) and scanning electron microscopy (SEM). The result showed that transmittance decreased slightly, about 2 4%. Cracks are observed at TiO₂ /GPTMS and TiO₂/ZrO₂ (molar ratio of 10:1, 3:1), while no cracks at ZrO₂/ GPTMS and TiO₂/ZrO₂ (molar ratio of 1:1)/ GPTMS. Yellow factor of the films are low than 10%.