Patent ID: 8215793

Claim:
A backlight device that includes: a tubular fluorescent lamp which is supported on a reflective plate and in which a fluorescent film having a predetermined thickness is formed on an inner circumference; a diffusion plate which is arranged above the fluorescent lamp; and a pair of band-shaped reflective members which is provided on the reflective plate such that the reflective members are axisymmetric with respect to a tube axis of the fluorescent lamp and are parallel to each other, wherein a plurality of pairs of band-shaped window portions having no fluorescent film are formed in the inner circumference of the fluorescent lamp, and the fluorescent lamp is oriented such that a straight line intersecting a center of the fluorescent lamp and a midpoint between each of the pairs of window portions on the circumference intersects a midpoint between each of the pairs of reflective members on the reflective plate, and is arranged such that light emitted from each of the pairs of window portions is reflected off the pair of the reflective members or the reflective plate and is shone on the diffusion plate, and an opening width of the band-shaped window portions along a circumference of the fluorescent lamp decreases in portions of the band-shaped window portions located closer to a bottom portion of the fluorescent lamp.