JP2001256817A - Light guide plate for led light source and surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light guide plate for LED light source improving a property of light diffusion and luminance, and of a good property of color mixing and a surface light source using the same. SOLUTION: A flat plate shaped light guide plate has a light guide part that is an inclined plane formed at the end part of the flat plate shaped light guide plate and through which light guided from a LED light source to a lower surface of an end part of the flat plate shaped light guide plate enter into the flat plate shaped light guide plate. The inclined plane is the light guide plate for LED light source having a concave surface against LED as a light source and is a surface light source using the same. Further, the concave surface part is mirror-surface-finished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for an LED light source and a planar light source.

[0002]

2. Description of the Related Art Liquid crystal display devices are widely used as thin and lightweight display devices. Since the liquid crystal display device is a light receiving type display device, it is used in combination with a backlight or a front light so that it can be used even in an environment without light. Hereinafter, a backlight will be described as an example, but the present invention can be similarly applied to a front light.

[0003] A backlight is a direct type in which a light source is arranged on the lower surface of a liquid crystal display device, and light is introduced into a light guide plate from a side surface or a peripheral portion of a flat light guide plate (hereinafter simply referred to as a light guide plate). An edge light method in which light is diffused by a light source and supplied to a liquid crystal display device as a surface light source is mainly used. In particular, the edge light method is frequently used because it can be made thin as a liquid crystal display device using a backlight.

Although a cold cathode tube has been used as a light source, a light source is required to have high luminance, low power, small size, and long life, and a light emitting diode (hereinafter, referred to as an LED) has been used. . FIG. 1 and FIG.
FIG. 1 is a perspective view of a planar light source in which an LED is arranged on a corner side surface of a light guide plate, which is a technique disclosed in Japanese Patent No. In this structure, the light-emitting surface of the LED 2 is arranged at the corners A and B with the light-emitting surface facing the light guide plate 1. In FIG.
Two ED2s are used.

FIG. 3 is a perspective view of a conventional light guide plate. An LED (not shown) in which a thick portion 5 having a light guide portion 5a is formed at one end of the light guide plate 4, and is disposed below the light guide portion 5a.
From the light guide plate, and the guided light is reflected by a curved surface 5b formed at the end of the light guide plate to enter the light into the light guide plate 4. The upper curved surface 5b of the light guide 5a is subjected to a blast treatment for roughening the surface for light diffusion.

[0006]

The planar light source of the system shown in FIGS. 1 and 2 can realize a uniform surface light source with a small number of light sources.
A single-color LED can be used, but a multi-color LED has poor color mixing properties, and a plurality of lights cannot be mixed with desired light. Also, the light guide plate needs to be at least thicker than the height of the LED, and is not suitable for thinning.

A planar light source of the type shown in FIG. 3 can provide a uniform planar light source with high luminance, but has a low reflection efficiency at the blast portion, and requires a large number of LEDs to increase the luminance and consumes high power. Become. Also, when used in a multi-color LED, the color mixing is poor. An object of the present invention is to provide a light guide plate for an LED light source that improves light diffusivity, improves luminance, and has good color mixing, and a planar light source using the same.

[0008]

Means for Solving the Problems The lower surface of the end of the light guide plate is provided with L
In a light guide plate having a light guide portion for guiding light from an ED light source and for making the guided light incident on the light guide plate at a slope formed at an end of the light guide plate, the slope is concave with respect to an LED as a light source. LED light source plate having a shape.

At least an LED and a light guide portion on the lower surface at the end of the light guide plate, which guides light from the LED light source and guides the guided light to the light guide plate at an inclined surface formed at the end of the light guide plate. In the planar light source including the light guide plate, the slope at the end of the light guide plate is a planar light source having a concave shape with respect to the LED as the light source.

The concave surface is mirror-finished.

[0011]

FIG. 4 is a view showing one embodiment of the light guide plate of the present invention, wherein (A) is a top view, (B) is a front view,
(C) is an XX cross-sectional view. LE on the corner of the light guide plate 6
A light guide section 7 for guiding light from the D light source and diffusing the guided light to the light guide plate 6 and entering the light guide plate 6 is formed. An inclined surface 7a is formed on the upper surface of the light guide unit 7, and the inclined surface 7a is processed into a concave shape having a curvature as shown by the XX section.

FIGS. 5A and 5B are diagrams in which three-color LEDs are arranged below the light guide section, wherein FIG. 5A is a top view and FIG. 5B is a front view. The upper surface 7a of the light guide 7 is a slope, and FIG.
It has a curvature (hereinafter referred to as R1) shown in (C),
Further, it also has a slightly concave curvature (hereinafter referred to as R2) in a direction perpendicular to XX. Three-color LEDs 8 are arranged below the light guide 7 in an arrangement as shown in the figure. B is an LED that emits light in blue (wavelength is 470 nm), SO is soft orange (wavelength is 615 nm), and PG is an LED that emits pure green light (wavelength is 525 nm), and is made into a chip component as one element.

The light emitted from the LED enters from the lower surface of the light guide 7 (made of plastic such as polycarbonate having a high light transmittance), is totally reflected by the upper surface 7a of the light guide, and FIG. The light travels to the right in B) and enters the light guide plate 6. Since the upper surface 7a has a combined curved surface of R1 and R2, it is diffused by R1 in the direction of the arrow shown in FIG. The curvature of R1 is preferably determined so that the light can be uniformly diffused according to the extent of diffusion from the light guide 7 to the light guide plate 6 (in FIG. 4, the diffusion angle is about 90 degrees, but other angles are possible). . R2 is a curvature for diffusing in the direction of the arrow shown in FIG. 5B and is a diffusion in the thickness direction of the light guide plate 6, so that the curvature is large and close to a straight line. It is preferable that the curvature is set to obtain a diffusion in which light easily reaches from the light guide portion 7 to a far portion of the light guide plate 6. That is, R1≪R2.

As a specific example, when the outer shape of the light guide plate shown in FIG. 4 is 31 mm × 24 mm × 1 mm, R1 = 10 m
With m and R2 = 200 mm, a planar light source with good color mixing, high brightness, and good diffusivity (without spots) was obtained.

[0015]

According to the present invention, by forming the light guide portion reflecting surface in a concave shape (combination of R1 and R2), light can be diffused in the horizontal and vertical directions. The color mixing property is good even if is used, and a desired color can be mixed.

Since the light can be diffused in the shape of the curvature of the reflection surface, the reflection surface can be mirror-finished (because it is not necessary to diffuse the light on the rough surface (blast surface or the like) formed on the reflection surface). Since the light enters the light guide plate by total reflection, the light use efficiency is increased and the luminance can be increased.

A thin planar light source can be obtained irrespective of the size of the LED.

[Brief description of the drawings]

FIG. 1 is a perspective view of a planar light source in which LEDs according to the related art are arranged on the corner side surfaces of a light guide plate.

FIG. 2 is a perspective view of a planar light source in which LEDs according to the related art are arranged on the corner side surfaces of a light guide plate.

FIG. 3 is a perspective view of a light guide plate according to the related art.

FIG. 4 is a view showing one embodiment of a light guide plate of the present invention;
(A) is a top view, (B) is a front view, and (C) is an XX cross-sectional view.

FIGS. 5A and 5B are diagrams in which three-color LEDs are arranged below a light guide unit, where FIG. 5A is a top view and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide plate 2 LED 3 Light guide plate 4 Light guide plate 5 Thick part 5a Light guide part 5b Curved surface 6 Light guide plate 7 Light guide part 7a Slope part 8 Three-color LED A Corner part B Corner part

Claims (5)

[Claims] 1. A light guide for guiding light from an LED light source to a lower surface of an end portion of a flat light guide plate, and entering the guided light into the flat light guide plate at an inclined surface formed at an end portion of the flat light guide plate. A light guide plate for an LED light source, wherein the inclined surface has a concave shape with respect to an LED as a light source. 2. A flat light guide plate having at least an LED and an inclined surface formed at the end of the flat light guide plate by guiding light from the LED light source to the lower surface of the end of the flat light guide plate. And a flat light guide plate having a light guide portion having a light guide portion incident on the flat light guide plate.
A planar light source having a concave shape with respect to the ED. 3. The planar light source according to claim 2, wherein the LED is a multicolor LED. 4. The light guide plate for an LED light source according to claim 1, wherein the concave surface has a mirror finish. 5. The surface light source according to claim 2, wherein the concave surface has a mirror finish.