Patent ID: 7649592

Claim:
A backlight unit for use in a liquid crystal display device, comprising: a reflection plate; a plurality of fluorescent tubes; and a diffusion plate, wherein the reflection plate includes a rectangular-shaped bottom plate section, four side plate sections respectively formed upright from four sides of the bottom plate section with a skew in the direction of moving away from the bottom plate section, and an edge plate section that protrudes from a tip end of each of the side plate sections toward outside thereof, an open space is formed by the bottom plate section and the four side plate sections in the tip end direction of the side plate sections, the fluorescent tubes are disposed above the bottom plate section in the space, a side which is one of the sides of the edge plate section in the thickness direction and is located away from the bottom plate section is formed as a first abutment plane against which the diffusion plate is abutted, at a portion of at least one of the four side plate sections closer to an inner surface of the edge plate section facing the space, a rib is protruded from the inner surface in the space, an end portion where the rib is away from the bottom plate section is extended on a plane same as the first abutment plane, and is formed as a second abutment plane for abutment by the diffusion plate, and the diffusion plate is disposed by being abutted against the first abutment plane at four sides, and by being abutted against the second abutment plane thereat.