Matting of transparent coatings is commonly achieved using porous inorganic matting agents with high surface area and oil absorption, and a particle size in the range of 5-15μm. These materials are extremely effective in solvent-based coatings where evaporation and shrinkage during drying and curing forces the particles to protrude from the surface and creates roughness on a similar scale to the particle size.
In 100% UV systems where there is very little shrinkage, aggregated matting agents are less effective, and much higher concentrations are needed which can give problems with formulation viscosity. We describe an alternative method of matting using ultrafine, nonporous particles which have very limited effects upon rheology, and can be used at high concentrations without difficulty. Matting is achieved by the creation of microroughness on a much smaller, submicron scale. The near-nano size of the particles also leads to significant reinforcement of the coating and excellent transparency.