Flat Lighting Device and Liguid Crystal Display Device

Abstract

The present invention makes a radiation angle of light at a portion of a light guide plate in front of an LED formed on one edge of a light guide plate and a radiation angle of light at a corner portion of the light guide plate equal to each other as much as possible. A shape of beam control elements which are arranged on a lower surface of a light guide plate is arranged concentrically about the LED.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view for explaining the constitution of a backlight of a liquid crystal display device;

FIG. 2 is a plan view of an essential part for explaining the in-plane brightness distribution of a light guide plate GLB;

FIG. 3 is a view for explaining the behavior of light radiated from an LED;

FIG. 4 is a view for explaining the relationship between a transmitted light and a refracted light;

FIG. 5A and FIG. 5B are explanatory views of a simple model for explaining the calculation of a radiation angle;

FIG. 6 is a cross-sectional view showing an essential part of the light guide plate in FIG. 5B together with a prism sheet;

FIG. 7A and FIG. 7B are explanatory views of a calculation position on the simple model shown in FIG. 5 by the calculation method explained in conjunction with FIG. 5 and FIG. 6;

FIG. 8A and FIG. 8B are explanatory view of a simple model for explaining an embodiment 1 of the present invention;

FIG. 9A and FIG. 9B are views for explaining a light guide plate of an embodiment 2 of the present invention;

FIG. 10 is a view showing the constitution in which beam control elements in the vicinity of the LED are arranged concentrically and the beam control elements remote from the LED are arranged linearly;

FIG. 11 is a view showing the constitution in which beam control elements in the vicinity of the LED are arranged in an elliptical shape and the beam control elements remote from the LED are arranged linearly;

FIG. 12 is a view for explaining an evaluation method for evaluating the average brightness and the brightness irregularities on a prototype actually;

FIG. 13 is an explanatory view of an existing light guide plate on which beam control elements are formed and a plurality of types of the light guide plate; and

FIG. 14 is a developed perspective view for explaining the whole constitution of the liquid crystal display device according to the present invention.

Claims

1. A flat lighting device comprising: a light guide plate;a downward-facing prism; anda plurality of light sources which are arranged on one side periphery of the light guide plate at a predetermined interval, whereina curved beam control pattern is formed about the light source.

2. A flat lighting device according to claim 1, wherein the beam control pattern is formed in a concentric shape.

3. A flat lighting device according to claim 1, wherein the beam control pattern is formed in an elliptical shape.

4. A flat lighting device according to claim 1, wherein the beam control pattern has a triangular cross section.

5. A flat lighting device according to claim 1, wherein the curved beam control pattern is arranged in the vicinity of the light source, and a linear beam control pattern is arranged at a portion remote from the light source.

6. A liquid crystal display device comprising: a liquid crystal display panel; anda lighting device which is arranged on a back surface of the liquid crystal display panel, whereinthe lighting device includes a light guide plate and light sources which are arranged on one side periphery of the light guide plate at a predetermined interval, andcurved beam control element patterns are formed around the light sources.

7. A liquid crystal display device according to claim 6, wherein the beam control patterns are formed in a concentric shape.

8. A liquid crystal display device according to claim 6, wherein the beam control patterns are formed in an elliptical shape.

9. A liquid crystal display device according to claim 6, wherein the beam control patterns have a triangular cross section.

10. A liquid crystal display device according to claim 6, wherein the beam control patterns having a triangular cross section are arranged in the vicinity of the light sources, and a linear beam control pattern which extends in the direction parallel to one side periphery of the light guide plate is arranged at a portion remote from the light sources.