Planar luminous body with improved light-extraction efficiency

摘要

A composite thin film-holding substrate for a surface light emitter, which is a transparent substrate including a composite thin film containing fine particles and a binder formed on the surface of a transparent base material. The refractive index of the composite thin film is higher than the refractive index of the transparent base material. The difference in the refractive index between the fine particles and the binder contained in the composite thin film is at least 0.1, and the ratio of (solid content mass of the fine particles)/(solid content mass of the binder+solid content mass of the fine particles) of the composite thin film is from 0.01 to 0.5. A surface light emitter can use the substrate.