Planar light source device and display apparatus incorporating same

Abstract

A planar light source device with highly uniform intensity and high light utilization efficiency, and a display apparatus incorporating the same, are provided. A light guide plate, configured by a material such as plate-shaped and transparent acryl resin, polycarbonate resin, or glass, causes incident light to propagate within the light guide plate and then to exit the light through an exit surface as a surface emitting light. A first recess is formed substantially in the center of the exit surface. The first recess is cylinder-shaped, and on a bottom thereof is provided a lens that refracts incident light from a light source, in a direction away from the center of a circle on the bottom.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a planar light source device from which light is shined on the rear or back side of a display element such as a liquid crystal display, and to a display apparatus incorporating the same.[0003]2. Description of the Related Art[0004]As disclosed in, for example, Japanese Patent No. 3427636 (hereinafter called Patent Document 1), a conventional planar light source device is provided with a cone-shaped recess having a triangular cross section at the rear center of a light guide plate, in which recess a light source is disposed. In such a planar light source device as disclosed in Patent Document 1, the amount of light is small toward the front of the light source. However, light intensity at a portion of the above cone-shaped recess can be higher than that at the rest of portions, so that uniformities of intensity distribution cannot in some cases be achieved.[0005]Furthermore, a planar ligh...

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Benefits of technology

[0007]The object of the present invention is to provide a planar light source device with highly uniform intensity and high light utilization efficiency, and a display apparatus incorporating the same.

Problems solved by technology

However, light intensity at a portion of the above cone-shaped recess can be higher than that at the rest of portions, so that uniformities of intensity distribution cannot in some cases be achieved.

However, a problem with such a planar light source device as disclosed in Patent Document 2 is that light emitted toward the front of the light source is mostly absorbed by the light reflective surface, thus resulting in reduction in light utilization efficiency.

However, a problem with such a liquid crystal display device as disclosed in Patent Document 3 is that although direct light emitted from a cold-cathode fluorescent lamp is adjusted by the light-transmission adjusting film, the light is not diffused adequately, thus causing intensity irregularities at the front of the light source.

However, a problem with such a backlight device as disclosed in Patent Document 4 is that because light emitted from the light source is transmitted radially, a part of the light, which does not propagates toward the oblique faces of the recess, exits in the proximity of the light exit surface, thereby causing intensity irregularities in the proximity of the light source.

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