Researchers prepare a new type of optical material with highly tunable refractive index

It is reported that researchers from Beijing University of Chemical Technology and BOE Technology Group Co., Ltd. have collaborated to develop a transparent organic-inorganic composite optical adhesive material with highly tunable refractive index. The related research paper was recently published in Engineering.

In the early days, glass was the main raw material for optical components. In recent years, organic resin based optical materials have developed rapidly due to their advantages of easy molding, light weight, and low cost. However, currently commercialized organic optical resins are often limited by the structural characteristics of organic molecules and polymer chains, with refractive indices generally limited to 1.4-1.6.

Refractive index is one of the important parameters of optical materials. High refractive index can reduce the thickness and curvature of optical components, while maintaining optical functional effects and achieving miniaturization of components, expanding their application range.

Based on the molecular structure characteristics of acrylic resin based UV curable optical adhesive and the practical application needs in optoelectronic display devices, the R&D team has developed a highly transparent and high refractive index optical adhesive material by optimizing the preparation of titanium dioxide nanoparticles and their composite process with acrylic resin.

The R&D personnel used electron microscopy imaging and atomic force microscopy to analyze and test the microstructure of the composite material, confirming that titanium dioxide nanoparticles are uniformly dispersed in the composite material, and the cured film has good flatness. When the mass fraction of titanium dioxide in the composite optical adhesive is 30wt% (mass percentage), the refractive index of the composite material can reach 1.67.

In addition, after being cured into a film by ultraviolet (UV), the refractive index of the material can even reach 2.0, while maintaining high transparency of over 98% and low haze of less than 0.05% in the visible light range. Moreover, precision processing of optical microstructures can be further achieved through embossing technology, which can be used to make new optical components such as display light guides. In the paper, the R&D team demonstrated that using a new type of optical adhesive to manufacture a micro prism type light guiding film can effectively improve illumination and reduce energy consumption. In the future, this achievement is expected to be widely applied in fields such as precision medicine, health lighting, and new display products.

Article source: Science and Technology Daily