Patent ID: 8031302

Claim:
A directional diffusion film with diffusion properties that vary depending on an incidence angle, wherein a diffusion axis direction is in a range of 20° to 50° with respect to a normal direction of the film, and a diffusion half-value angle is at least 20° and lower than 90°, where the diffusion axis direction is a light irradiation direction in which the strongest diffusion light is obtained when the film is irradiated with light, and the diffusion half-value angle is a diffusion angle at which intensity of outgoing diffusion light at a plane A is 50% of a peak intensity, with the plane A containing the normal direction and the diffusion axis direction of the directional diffusion film, when collimated light is incident at an incidence angle of 30° from the normal direction of the directional diffusion film in the plane A.