Process for making an anti-reflective coating composition and a porous coating made therefrom

The invention relates to a process of making an anti-reflective coating composition comprising the steps of 1) preparing an oil-in-water emulsion by mixing an apolar organic compound A; a cationic addition copolymer C as emulsion stabilizer; and aqueous medium of pH 2-6; at a mass ratio C/A of 0.1 to 2, to result in 1-50 mass % (based on emulsion) of emulsified droplets of average particle size 30-300 nm; and 2) providing an inorganic oxide shell layer to the emulsified droplets by adding to the emulsion obtained in step 1) at least one inorganic oxide precursor, to result in organic-inorganic core-shell nano-particles with mass ratio core/shell of from 0.2 to 25. An advantage of this process is that the dispersion of nano-particles obtained is stable under different conditions, and allows altering its concentration and solvent system, and addition of different binders and auxiliary components. The invention also relates to a coating composition as obtained with said process, and to a process of applying a porous anti-reflective-coating on a substrate using such composition, and to the resulting coated substrate.