BACKLIGHT DEVICE, LIQUID-CRYSTAL DISPLAY DEVICE, AND LENS

A backlight device (2) provided with: a light-source unit (3) comprising a plurality of light-emitting diodes (9) and lenses (10) that spread the light from said light-emitting diodes (9); a housing (4) that contains said light-source unit (3); a diffusion panel (5) disposed so as to cover an opening (6a) in said housing (4); and a reflective sheet (6) that reflects light from the light-source unit (3) towards the diffusion panel (5). The light-emitting diodes (9) are arranged in one or more rows in the middle of the light-source unit (3). The lenses (10) in the light-source unit (3) have input surfaces (11) onto which the light from the light-emitting diodes (9) is incident and output surfaces (12) from which the incident light, having been spread out, is transmitted. In a cross-section of each lens, said cross-section containing the optical axis (Z) as seen from a side surface in the direction in which the output surfaces (12) are arranged, the optical axis (Z) forms an angle (θi) between 60° and 80° with a line (Li) connecting the position of the light source on the optical axis (Z) to the center of a tiny segment of the output surface (12) having maximum curvature (C).