Backlight unit and liquid crystal display unit using backlight unit
To compensate for uneven brightness in the longitudinal direction of fluorescent lamps of a backlight unit and achieve a display screen with an even brightness, a reflection unit of the backlight unit, the fluorescent tube surface of the fluorescent lamps or a diffusion unit is used to either reduce the reflectance, transmittance, or radiation brightness of the high-voltage side of the fluorescent lamps or increase the reflectance, transmittance, or radiation brightness of the low-voltage side thereof so as to compensate for uneven brightness of the illumination light and thereby ensure an even brightness. For example, dot pattern regions D 1 , D 2 and D 3 , i.e., the regions whose density increases in stages, are imparted to the portion of a reflection layer 13 of the backlight unit with a relatively high brightness. As for the display device, on the other hand, the display image data supplied to a liquid crystal panel or the aperture ratio of the liquid crystal panel is controlled, for example, to compensate for uneven brightness in the longitudinal direction of the fluorescent lamps and ensure an even brightness.
1. A backlight unit comprising:
a plurality of straight tube fluorescent lamps arranged substantially parallel to one another in the longitudinal direction of the fluorescent lamps;
driving means arranged on one-end side of the plurality of fluorescent lamps for driving the plurality of fluorescent lamps by applying a high voltage to one-end terminals of the plurality of fluorescent lamps; and
a reflection portion adapted to emit the light from the plurality of fluorescent lamps in a specific direction, wherein
brightness compensation means are provided for compensating for uneven brightness in the longitudinal direction of the plurality of fluorescent lamps by decreasing the brightness of the fluorescent lamps on one end side or increasing the brightness of the fluorescent lamps on the other end side or controlling brightness in combination from the both end sides,
the reflection portion is made up of first and second reflection layers having given optical reflectance and transmittance levels,
as the brightness compensation means, the reflection portion is configured with a first region having the first and second reflection layers stacked one above another in the direction of incidence of light and a second region made up only of the first reflection layer, and
the reflectance of the reflection portion is controlled using the first region with a relatively high reflectance and the second region with a reflectance lower than that of the first region.