Patent ID: 7967492

Claim:
A planar light source element which comprises: a light guide plate comprising a top surface, a bottom surface and edges between the top surface and the bottom surface, one or more light sources provided at one or more edges of the light guide plate, and a light diffusion film positioned on the top surface of the light guide plate comprising: a sheet body having a first major surface on a light incident side and a second major surface on a light emissive side; and a plurality of projections protruding outwardly from the first major surface of the sheet body, the projections having inclined surfaces relative to the first major surface of the sheet body and vertexes lying on the same plane; wherein the top surface of the light guide plate is in contact with the vertexes of the projections of the light diffusion film, and is operable to emit rays of light, incident on the edge of the light guide plate, to the vertexes of the projections; the light diffusion film is operable to emit rays of light, incident on the vertexes of the projections and then reflected by the inclined surfaces of the projections, outwardly from the second major surface of the sheet body, which is opposite to the first major surface having the projections formed thereon; at least the projections are at least partially formed from a particulate-matter-dispersed composition including a photocurable compound and a particulate matter, wherein rays of light entering into the vertexes of the projections are scattered within the projections by the particulate matter present in the projections; wherein the particulate matter in the particulate-matter-dispersed composition has an average particle size within the range of 1 to 10 μm; and wherein the difference in refractive index between a cured matter formed from the photocurable compound and the particulate matter, both contained in the particulate-matter-dispersed composition, is within the range of 0.03 to 0.18, and wherein the light guide plate and the vertexes of the projections of the light diffusion film are bonded together.