Abstract: A light excitation diffusion sheet for a backlight unit adapted to absorb a portion of light emitted from a light source of a blue wavelength or a mixed wavelength of a blue wavelength and at least one other wavelength, to emit light at different wavelengths from the light emitted from the light source, and to allow the rest of the light emitted from the light source to penetrate the sheet The light excitation-diffusion sheet comprises a light-exciting material exciting and amplifying the light from the light source and a light-diffusing material scattering and diffusing the light from the light source. The light-exciting material and the light-diffusing material are uniformly distributed in the light excitation-diffusion sheet The use of the light excitation-diffusion sheet enables production of edge light type and direct light type backlight units having diffusion and prism functions, good color purity and improved light efficiency at reduced costs.