The present invention provides a backlight device which uses
solid-state light emitting elements capable of emitting lights of three colors consisting of red, green and blue as a
light source, can enhance the light utilizing efficiency, and can be made light-weighted. Further, the invention provides a
display device which exhibits the high brightness uniformity and the high
chromaticity uniformity. The backlight device includes a main
light guide plate which has a
light irradiation surface which irradiates light forwardly by developing the light
in plane and has a
light reflection surface which faces the
light irradiation surface in an opposed manner and reflects the light toward the
light irradiation surface; a sub
light guide plate which is arranged on a back surface of the main
light guide plate, is divided into a first sub light guide plate and a second sub light guide plate on both end sides by way of a first
air layer disposed at a center portion, and forms light incident surfaces on facing end surfaces of the first sub light guide plate and the second sub light guide plate in the inside of the first
air layer; a
first light reflection plate which is arranged on a front surface of the sub light guide plate which faces the main light guide plate; a second
light reflection plate which is arranged on a back surface of the sub light guide plate which faces the
first light reflection plate in an opposed manner; reflectors which are arranged on both end surfaces of the main light guide plate and the sub light guide plate and optically couple the main light guide plate and the sub light guide plate; and a
light emitting diode board which is mounted in a state that the
light emitting diode board faces a back surface of the sub light guide plate and light emitting diodes capable of emitting light of plurality of colors in the inside of the first
air layer are arranged at least in a row. Due to such a constitution, a light-source light from the light emitting diodes capable of emitting lights of plurality of colors is subjected to color mixture and an effective
optical path can be elongated and hence, the light utilizing efficiency can be enhanced and, at the same time, the backlight device can be made light-weighted.