Planar illuminating device

Abstract

Provided is a planar lighting device having a first and a second light sources arranged at a given distance apart from each other and a light guide plate arranged between the first and second light sources. The light guide plate includes a light exit plane, a first light entrance plane facing the first light source and containing one side of the light exit plane, and a second light entrance planefacing the second light source and containing the opposite side to the one side, and has a shape growing thicker from the first and second light entrance planes toward the center. The light guide plate contains scattering particles for scattering light entering through the first and second light entrance planes and propagating inside by a ratio satisfying 1.1<=PhiNPLGKC<=8.2.

Description

technical field [0001] The present invention relates to a planar illuminating device applied to a liquid crystal display device and the like. Background technique [0002] A liquid crystal display device uses a backlight unit that illuminates the liquid crystal display panel by irradiating light from the back side of the liquid crystal display panel. The backlight unit is composed of a light guide plate that scatters light from a light source for illumination to illuminate the liquid crystal display panel, a prism sheet and a diffusion sheet that uniformly emit light from the light guide plate. [0003] Currently, the so-called direct-type type in which a light guide plate is arranged directly above a light source for illumination is the mainstream for backlight units of large-sized liquid crystal televisions (for example, refer to Japanese Unexamined Patent Application Publication No. 5-4133). In this method, a plurality of cold-cathode tubes as light sources are arranged ...

AI Technical Summary

Problems solved by technology

[0010] However, in the backlight unit of the tandem type, although thinning can be achieved, due to the relationship between the relative dimensions of the cold cathode tube and the reflector, it is inferior to the direct type in terms of light utilization efficiency.

In addition, when using a light guide plate in which cold cathode tubes are accommodated in grooves formed on the light guide plate, if the thickness of the light guide plate is reduced, the brightness directly above the cold cathode tubes arranged in the groove will be enhanced, so that Brightness unevenness on the light exit surface becomes conspicuous

[0011] Therefore, there is a limit to the thinning of the backlight unit in series.

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