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Planar light source

Inactive Publication Date: 2005-08-18
CITIZEN ELECTRONICS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016] An object of the present invention is to provide a planar light source wherein the luminance of the illuminating light is large and even.

Problems solved by technology

However, there is a following problem in the conventional planar light source.
Hence it is difficult to efficiently change the light entering the light guide plate 101 from the LED 102 into a sufficiently bright illuminating light.
However, there is another problem even in the thus improved planar light source when examined more closely.
However, the illuminating light also becomes uneven in luminance.
As a result, the luminance of the light exiting the light guide plate and entering an optical path adjusting means such as the diffusion panel becomes uneven depending on the position.

Method used

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first embodiment

[0065] a planar light source of the present invention is described hereinafter with reference to FIGS. 1a to 1d, FIG. 2, and FIG. 3. FIG. 1a is a perspective view showing the entire light source, FIG. 1b is an illustration showing the operation of a light guide plate provided in the light source, FIGS. 1c and 1d are diagrams describing the operation of the planar light source, FIG. 2 is a perspective view of a light guide plate provided in the light source, and FIG. 3 is a sectional view of the planar light source explaining the illuminating operation thereof.

[0066] Referring to FIG. 1a, a planar light source 20 comprises a pair of LEDs 2, a light guide plate 1, a diffusion panel 3, a Py prism sheet 4, a Px prism sheet 5, and a reflection plate 6. The reflection plate 6, light guide plate 1, diffusion plate 3, prism sheets 4 and 5 are stacked.

[0067] The light guide plate 1 is made of a transparent plastic and has an upper surface 1a, lower surface 1b and front side 1c. The LEDs 2 a...

second embodiment

[0075] In accordance with the second embodiment, the light beams, the output angles of which are limited within a desired angle, enter the entire area of the diffusion panel 3 so that the luminance of the illuminating light emitted from the planar light source is improved while maintaining the level of brightness.

[0076] Referring to FIG. 5, showing the third embodiment of the present invention, a light guide plate 11 has a flat horizontal upper surface 11a and a lower surface 11b inclining upward as the distance from a front side 11c increases. The lower surface 11b has a first anisotropic diffusion surface 11h and a second anisotropic diffusion surface 11h2 adjacent the front side 11c having the same characteristics as the second anisotropic diffusion surface 1h2 of the second embodiment. A third anisotropic diffusion surface 11h3 is formed on the upper surface 11a at an appropriate position adjacent the front side 1c. The third anisotropic diffusion surface 11h3 has the same chara...

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PUM

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Abstract

A planar light source has a light emitting source, and a light guide plate for receiving light beams emitted from the light emitting source at a front side thereof and changing direction of the light beams, discharging the light beams from an upper surface thereof. A first anisotropic diffusion surface is formed on a lower surface of the light guide plate, and a reflection member is provided on the first anisotropic diffusion surface. The first anisotropic diffusion surface is a hologram diffusion surface or a hairline diffusion surface.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a planar light source for a backlight which is, for example, provided for illuminating a liquid crystal display (LCD) panel from behind, and more particularly to a light source provided with a light guide plate, a light emitting source such as a light emitting diode (LED) disposed at a side of the light guide plate, and preferably, a light direction limiting means such as a diffusion panel disposed above the light guide plate. In such a light source, the direction of light emitted from the light emitting source is changed so that a luminous flux exits the light guide plate from the upper surface thereof, and preferably, the direction is further adjusted by the light direction limiting means. [0002] There is known a backlight unit comprising a planar light source for illuminating such a display as an LCD provided in a mobile terminal device and laptop computer. Japanese Patent Application No. 2002-146589 (Japanese Pa...

Claims

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Application Information

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IPC IPC(8): G02B6/00F21V5/08F21V8/00F21Y101/02G02F1/13357
CPCG02B6/0038G02B6/0055G02B6/0053G02B6/0051G02F1/1335
Inventor OKUWAKI, DAISAKU
Owner CITIZEN ELECTRONICS CO LTD
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