Royann Lynn Stewart-Davis

The use of experimental design techniques to meet reflected color targets in pyrolytic low emissivity coatings

Abstract Low emissivity coatings are common in architectural applications and the marketplace dictates an increasingly complex set of process and optical requirements. The coatings must reflect infrared light, and, simultaneously, must have little or no visible reflected color. The first step in commercializing a new coated product is to develop a theoretical thin film stack that meets the target optical requirements while incorporating real-world materials and production requirements. The experimental design process requires a definition of the input or control factors (determined by the process and economics) and a clearly defined target response (determined by the marketplace). In the application of experimental design to thin film modeling, the control factors are the refractive indices and thicknesses of the various coating layers. The target responses are gross properties of the coated glass product, such as its reflected color and emissivity. The infinite combination of layer thicknesses and refractive indices are represented by a simple empirical model that quantifies the responses with minimal test cases or experiments. The models can then be used to find a workable solution for the design problem and provide insight into the macroscopic behavior of the color as a function of the film stack structure.