Light guide plate

Abstract

A light guide plate has a light emitting surface and a prism surface opposite to the light emitting surface. The prism surface includes a plurality of grooves extending parallel to each. The grooves have a constant depth, and widths of the grooves are varied, thereby adjusting the apex angles of the grooves. The depth of the grooves can be set to be not more than 20 microns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a sectional view showing a light guide plate according to the present invention and a light source positioned with respect to the light guide plate.

FIG. 1 b is a sectional view showing the position of an injection gate of a mold when the light guide plate shown in FIG. 1a is molded.

FIG. 2 is a sectional view of a mold segment for molding a prism surface of the light guide plate shown in FIG. 1a.

FIG. 3 a is an illustration explaining a presently used lighting device for illuminating a liquid crystal display.

FIG. 3 b is an illustration explaining another type of presently used lighting device for illuminating a liquid crystal display.

FIG. 4 is a sectional view showing a basic structure of conventional light guide plate.

FIG. 5 a is a sectional view of a conventional light guide plate and a light source positioned with respect to the light guide plate.

FIG. 5 b is a sectional view showing the position of an injection gate of a mold when the light guide plate shown in FIG. 5a is molded.

FIG. 6 is a sectional view of a mold segment for forming a prism surface of the light guide plate shown in FIG. 5a.

Claims

1. A light guide plate comprising: a light emitting surface; anda prism surface opposite to said light emitting surface;wherein said prism surface comprises a plurality of grooves which extend parallel to each other to form prisms and depths of said grooves are constant and widths of said grooves are varied.

2. A light guide plate according to claim 1, further comprising: a peripheral surface extending between said light emitting surface and said prism surface, said peripheral surface including a light-receiving plane surface that receives light from a light source;wherein said grooves extend parallel to said light-receiving plane surface, and said widths of said grooves are greater in an area closer to said light source than in an area remote from said light source.

3. A light guide plate according to claim 1, wherein said widths of said grooves gradually decreases with said grooves being situated farther away from said light source.

4. A light guide plate according to claim 1, wherein a thickness of said light guide plate is not more than 1 mm.

5. A light guide plate according to claim 1, wherein said depth of said grooves is not more than 20 microns.