Multiple Light Scattering Model Applied to Reflective Display Materials

An estimate for the minimum film thickness required to give the scattering state of a reflective display material, such as a polymer dispersed liquid crystal (PDLC) or polymer stabilized cholesteric texture (PSCT), a desired diffuse luminous reflectance is presented. It is concluded that single scattering models are not suited for this task. To account for the multiple scattering of light, a previously developed model based on Mie scattering and two-flux radiative transfer theory is implemented. This simple model relates the size, composition, and the volume fraction of the scattering entities to the diffuse reflectance of the material. It is shown that the diffuse reflectance predictions from this model are in good agreement with measurements from other turbid systems. Using assumptions intended to produce an underestimate, it is concluded that the most birefringent liquid crystal materials currently available would require a film thickness between 11.5 µm and 17 µm to give an ideal black substrate a diffuse luminous reflectance of 60%.