Multilayered ridge structure for wide-angle color reflection

Abstract

Physically, light is an electromagnetic wave, and color is the information that the light intensity depending on the wavelength is interpreted by visual system. Objects around us have their own colors because the degree of interaction with light depends on the wavelength. Among them, the color generated by interference of light waves scattered from structure is called structural color, and a typical example that generates the structural color is multilayer structure. Because the multilayer structure can selectively reflect light of a desired wavelength band, it has been widely applied to color filter, textile, paint, and so on. However, its viewing angle is narrow, since the reflection only occurs at specular angle. The solution to the narrow viewing angle can be found from the wide-angle color reflection phenomenon from the two-dimensional multilayered ridge structure of Morpho butterfly wing. In this dissertation, two-dimensional multilayered ridge structures were investigated to widen the viewing angle of one-dimensional multilayer structure. First, the effects of the width and shape of a single multilayered ridge structure on the viewing angle and the reflected color were investigated by numerical simulation. And, to achieve a macroscopic reflected intensity, an array of single ridge structures was fabricated by arranging them on the surface. The fabricated array structure may cause an abrupt color change depending on viewing angle due to the light dispersion caused by the periodicity of arrangement. In this research, the problem of the color change has been solved by introducing inter-structural disorder among the single ridge structures by using spin-coating of randomly sized microspheres, directional deposition, lithography, and so on. Lastly, the color reflection property of an actual Morpho butterfly wing could be explained based on the principles investigated.