Optical Application of (Pigmented) Sol-Gel Coatings

The performance of the anti-reflection stack antimony-doped tin oxide/SiO2 improves considerably if the refractive index of the SiO2 layer decreases from ∼1.45 to 1.41 by the introduction of porosity. Porosity can be introduced by the addition of high-boiling co-solvents (or templates e.g. sebacates) to the coating liquid. Fine-tuning of the liquid composition allows the formation of a homogeneous, non-scattering SiO2 layer with a refractive index of 1.41 and pencil hardness of H7-H8 on large screens (diagonal >1 meter) if a curing temperature of 160°C was used.