Understanding Haze: Quantification of Diffuse Scattering by Power law analysis

Different window and coating samples have different Haze performance, but what causes these differences, and is there a way to quantify their causes? We developed a parametric analysis of diffuse forward scattering for integrating sphere measurements, employing a power law representation of the monotonic changes in scattering intensity vs. wavelength. This allows a closer connection between haze and the elements (number and dimension of scattering centers) governing haze. This method yields the same ultimate quantification of haze as the standard integration method, yet embraces the subtle changes in scattering vs. wavelength. The measured power law can be related to Rayleigh-Gans (R-G) and Mie (formulated by van de Hulst) scattering theories, allowing us to interpret the power laws as pure Rayleigh (4.0), R-G (4.0 to 2.0), and Mie (2.0 to 0.0) relative to scattering size. Then by comparing the power law with the associated scattering efficiencies, we deduce an average size and number of scattering centers, giving a quantitative handle on why haze changes. In this presentation, we apply the parametric power law analysis to a variety of glasses and polymers. We show that a finer grain structure does not necessarily lead to lower haze if their numbers are large.