High transparency in the structural color resin films through quasi-amorphous arrays of colloidal silica nanospheres

Periodic crystals are angle-dependent structures that typically exhibit iridescent colors, thus limiting their practical application. Consequently, uniform structural colors have substantial potential for use in optical devices. This paper presents a simple and inexpensive method for fabricating novel structural color resin films with high optical transparency, uniform reflection color, and physical rigidity. Quasi-amorphous resin films were fabricated through a molding process because of the shear-induced order and polymerization caused by the formation of quasi-amorphous structures trapped inside the polymer resin. A low index difference between colloidal silica nanospheres and the polymer resin led to the high transparency of composite resin films and uniform weak reflection colors. The reflectance spectra of the silica nanospheres showed reflection peaks from the ultraviolet to near-infrared regions depending on the nanosphere size. Angle-resolved reflection and scattering spectrometry results showed that the structural color of the sample originated from the constructive interference of quasi-amorphous structures. In addition, we demonstrated the quasi-amorphous resin films as novel optical filters for developing white light-emitting diodes (WLEDs). This study successfully developed a novel technique that can be applied in optical devices such as displays, sensors and WLEDs.