Novel materials for optical data storage based on a new recording method are described. Instead of pits or refractive index changes being produced in the recording medium, marks are the result of the generation of near-IR absorbing dyes, which leads to a change in the absorption of light from the read laser. The new materials, thin films of tellurium(IV) dihalide bound in a glass together with a sensitizing dye. undergo thermal reductive elimination of halogen on exposure to laser radiation. This technique could find applications in electrophotographic mastering.