Pigment–Dye–Photoinitiator Competition in Coloured Photopolymers

Coloured photopolymers contain several wavelength-dependent competitors for the incident light field. Dissolved dyes absorb, pigments absorb and scatter, photoinitiators consume photons, and photoinitiators or colourants may bleach or generate coloured products. The resulting optical state changes with depth, conversion and irradiation history. A bulk spectrum, top-surface conversion or nominal cure depth therefore cannot by itself establish through-cure, surface response, colour retention or dimensional fidelity. This review defines a measurement architecture for separating absorption, scattering, inner filtering, photoinitiator response, depth-dependent conversion, surface cure and colour-state evolution. Primary evidence includes depth-resolved acrylate cure, photoabsorbing fillers in VAT photopolymerisation, independent surface and deep conversion in a black ink, pigmented-system kinetic studies, pigmented thiol–ene chemistry, clear-versus-pigmented photoinitiator comparisons and photoinitiator-dependent colour stability in printed resin. The studies use different colourants, chemistries, geometries, sources and analytical methods, so their numerical results cannot be transferred as a universal exposure multiplier, spectral window or formulation recipe. Qualification requires matched optical, chemical and geometric evidence under declared processing and conditioning.