Patent ID: 7553059

Claim:
An optical sheet for use in illumination light control in a backlight unit for a display, comprising: a light diffusion layer which diffuses illumination light toward an emission surface side of the light diffusion layer, which is a non-incidence surface side thereof; an adhesion layer or an adhesive layer; a light reflection layer which is adhered to the light diffusion layer by the adhesion layer or the adhesive layer, which has a front surface extending along the emission surface side of the light diffusion layer, and having a high reflectivity with respect to the emission surface side of the light reflection layer, and which reflects the light diffused by the light diffusion layer toward the light diffusion layer; and a lens sheet having a flat reverse surface fixed to the other surface of the light reflection layer, and a front surface on which a plurality of unit lenses are provided, wherein: the light diffusion layer, the adhesion layer or the adhesive layer, the light reflection layer and the lens sheet are provided in this order from an incidence side of the illumination light; the light reflection layer includes opening portions which are formed therein in positions corresponding to those of the unit lenses, respectively; and the adhesion layer or the adhesive layer is thinner than the light reflection layer.