High refractive index substrates—used in optical applications like AR/MR glasses, AR HUDs, camera lenses, prisms, and optical sensors—may be unintentionally illuminated by light sources. This leads to unwanted reflections within the substrate, and may significantly deteriorate the performance of the optical devices. Traditionally, this phenomenon is countered by using black coating at the substrate edges to absorb the unwanted reflections. This approach, however, does not consider the refractive index difference between the black coating material and the substrate. IOB products are designed to eliminate unwanted reflections while maintaining high optical density and index matching. This portfolio of products covers a wide range of indices, from 1.6 to 1.9x, and can be formulated to match specific index targets. Optical density (OD) and thickness can be tuned to meet specific requirements, and the viscosity can be adjusted within limits to accommodate the selected processing method. Typical coating methods include dispensing and jetting.