JP2002289024A - Surface lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface lighting device comprising a cylindrical light source and a light guide plate for improving luminous efficiency of a light source. SOLUTION: The surface lighting system is provided with a cylindrical light source 1, and the light guide plate 2 wherein one end surface 2a is extendedly disposed along this light source 1 to emit the incident lights from the end surface 2a through a surface 2b. In this system, a cross-sectional shape of the end surface 2a on the light guide plate 2 in a plane perpendicular to the lengthwise direction of the light source 1 has at least one recessed portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface lighting device,
More particularly, the present invention relates to a surface illuminating device including a rod-shaped light source and a light guide plate provided with one end surface extending along the light source and emitting light incident from the end surface from the surface.

[0002]

2. Description of the Related Art Conventionally, as a surface lighting device used for a backlight of a liquid crystal display panel, for example, a rod-shaped light source,
There is known a light guide plate provided with one end face extending along the light source and a light guide plate for emitting light incident from the end face from the surface. More specifically, this type of surface illumination device emits light that is incident from the one end surface of the light guide plate and travels through the light guide plate by scattering it on the surface (generally, only one surface), and It is widely known that a fluorescent material excited by light incident thereon is dispersed in a light guide plate and the fluorescent light emitted from the fluorescent material is emitted from the surface.

[0003] In such a conventional surface illumination device, the one end surface of the light guide plate is a flat surface.

[0004]

In the conventional surface illuminating device composed of the rod-like light source and the light guide plate, there is a problem that the light use efficiency of the light source is low.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a surface illuminating device which is composed of a rod-like light source and a light guide plate, and has high light use efficiency of the light source.

[0006]

The surface illuminating device according to the present invention is, as described above, provided with a rod-like light source and one end face extending along the light source, and receiving light incident from the end face on the surface. A light guide plate that emits light from the light source, wherein a cross-sectional shape of one end surface of the light guide plate in a plane perpendicular to a length direction of the light source has a shape having at least one concave portion. It is characterized by the following.

The above-mentioned cross-sectional shape is a concave shape that gradually projects toward the light source side from the center in the thickness direction of the light guide plate to both surface sides, that is, a shape having only one concave portion. Is desirable.

More specifically, the shape of the concave portion may be an arc, a parabola, or a V-shape.

On the other hand, in the above configuration, a round light source can be suitably used as the light source.

[0010]

According to the study of the present inventor, in the conventional surface illuminating device including the rod-shaped light source and the light guide plate, the problem that the light use efficiency of the light source is low is that most of the light emitted from the light source is conducted. It has been found that the light is reflected by the end face of the light plate.

FIG. 5 illustrates this fact. In FIG. 5, reference numeral 1 denotes a fluorescent lamp which is a light source having a round rod shape, and reference numeral 2 denotes a light guide plate. The light guide plate 2 is formed of, for example, a transparent resin, and is disposed so that one end face 2a 'thereof extends along the fluorescent lamp 1.
Light traveling inside is emitted from one surface 2b. Reference numeral 3 denotes a diffusion layer formed on the light guide plate surface 2b, and reference numeral 4 denotes a reflection layer formed on the other surface 2c of the light guide plate 2.

Since the end surface 2a 'of the light guide plate 2 is a flat surface, as shown in FIG.
The light perpendicularly incident on a 'is hardly reflected,
As shown by B in the figure, most of the light obliquely incident on the end face 2a 'is reflected there. Therefore, the amount of light incident on the light guide plate 2 is reduced, and the amount of light L emitted from the front surface 2b is reduced.

On the other hand, as shown in FIG. 2, for example, the end surface 2a of the light guide plate 2 is
If it is a curved surface (that is, a surface whose cross-sectional shape is a circular arc in a plane perpendicular to the length direction of the fluorescent lamp 1) along the line a, the light including the light B shown in FIG. Is perpendicularly incident on the end face 2a. So in this case,
Light reflected on the end face 2a is reduced, and a large amount of light is incident on the light guide plate 2, so that light use efficiency is improved.

Further, from the viewpoint of making more light incident on the end face 2a in a perpendicular manner, the concave portion having an arc shape or the like has one concave portion.
It is effective even if a cross-sectional shape possessed by not only a plurality of places but also a plurality of places is adopted.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a perspective shape and a side surface shape of a surface illumination device according to a first embodiment of the present invention, respectively. As shown in the figure, the surface illumination device of the present embodiment has a round rod-shaped fluorescent lamp 1 as a light source.
And the light guide plate 2. The light guide plate 2 is formed of, for example, a transparent resin, and is disposed so that one end face 2a extends along the fluorescent lamp 1, and the end face 2a
The light incident on the light guide plate 2 and traveling through the light guide plate 2 is emitted from one surface 2b.

A diffusion layer 3 is formed on the light guide plate surface 2b, and a reflection layer 4 is formed on the other surface 2c of the light guide plate 2. The diffusion layer 3 is formed of, for example, a light-diffusing coating layer, and uniformly diffuses the light L emitted from the light guide plate surface 2b. In addition, instead of using such a coating layer,
The light guide plate surface 2b may be roughened to be a diffusion surface. On the other hand, the reflection layer 4 reflects the light emitted from the other surface 2c of the light guide plate 2 toward the opposite surface 2b.

Here, the end surface 2a of the light guide plate 2 has a curved surface along the peripheral surface 1a of the round rod-shaped fluorescent lamp 1 (an arc-shaped cross section in a plane perpendicular to the length direction of the fluorescent lamp 1). Some aspects). In other words, the end face 2a has a concave shape that gradually projects toward the fluorescent lamp 1 as going from the center in the thickness direction of the light guide plate 2 to both surface sides.

Since the end face 2a has such a shape, a large amount of light including the light indicated by B in FIG. 2 is vertically incident on the end face 2a. Therefore, the amount of light reflected on the end face 2a is reduced, and a large amount of light is incident on the light guide plate 2, so that the light use efficiency is improved.

Next, a second embodiment of the present invention will be described. FIG. 3 shows a side surface shape of a main part of a surface illumination device according to a second embodiment of the present invention. In FIG. 3, elements that are the same as the elements in FIG. 2 are given the same reference numerals, and descriptions thereof will be omitted unless otherwise necessary (the same applies hereinafter).

In this embodiment, the end surface 2a of the light guide plate 2 is
The cross-sectional shape in a plane perpendicular to the length direction of the fluorescent lamp 1 is a parabolic concave surface. That is, in this example, the end face 2
“a” has a concave shape that gradually projects toward the fluorescent lamp 1 as going from the center in the thickness direction of the light guide plate 2 to both surface sides.

Since the end face 2a is formed in such a shape, a large amount of light is also transmitted to the end face 2a in this embodiment.
The light is perpendicularly incident on a. Therefore, the amount of light reflected on the end face 2a is reduced, and a large amount of light is incident on the light guide plate 2, so that the light use efficiency is improved.

Next, a third embodiment of the present invention will be described. FIG. 4 shows a side surface shape of a main part of a surface illumination device according to a third embodiment of the present invention. In the present embodiment, the end surface 2a of the light guide plate 2 is a concave surface having a V-shaped cross section in a plane perpendicular to the length direction of the fluorescent lamp 1. That is, also in this example, the end surface 2a has a concave shape that gradually projects toward the fluorescent lamp 1 as going from the center in the thickness direction of the light guide plate 2 to both surface sides.

Since the end face 2a is formed in such a shape, a large amount of light is also transmitted to the end face 2a in this embodiment.
The light is perpendicularly incident on a. Therefore, the amount of light reflected on the end face 2a is reduced, and a large amount of light is incident on the light guide plate 2, so that the light use efficiency is improved.

The cross-sectional shape of the end surface of the light guide plate is not limited to those described in the above embodiments, and other shapes can be adopted. For example, as in the fourth embodiment shown in FIG. 6, a sectional shape having two concave portions,
A cross-sectional shape having three concave portions as in the fifth embodiment shown in FIG. 8, a cross-sectional shape having four concave portions as in the sixth embodiment shown in FIG. A cross-sectional shape having more concave portions as in the embodiment can be adopted. As described above, even when a cross-sectional shape having two or more concave portions is employed, each concave portion may have a shape as shown in FIGS. 3 and 4 in addition to the arc shape.

In each of the embodiments described above, the round-bar-shaped fluorescent lamp 1 is used. However, the present invention is not limited to such a light source, and may be applied to a case where a round-bar-shaped light source or the like is used. The present invention is applicable, and in such a case, the same effects as those in the above-described embodiments can be obtained.

According to the present invention, as described above, a phosphor which is excited by light incident on the light guide plate is dispersed, and the fluorescent light emitted by the phosphor is emitted from the surface. Applicable to devices, in which case,
The same effects as in the above embodiments can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a surface illumination device according to a first embodiment of the present invention.

FIG. 2 is a side view showing a main part of the surface lighting device of FIG. 1;

FIG. 3 is a side view showing a main part of a surface lighting device according to a second embodiment of the present invention;

FIG. 4 is a side view showing a main part of a surface lighting device according to a third embodiment of the present invention.

FIG. 5 is a side view showing a main part of a conventional surface lighting device.

FIG. 6 is a side view showing a main part of a surface lighting device according to a fourth embodiment of the present invention.

FIG. 7 is a side view showing a main part of a surface lighting device according to a fifth embodiment of the present invention.

FIG. 8 is a side view showing a main part of a surface illumination device according to a sixth embodiment of the present invention.

FIG. 9 is a side view showing a main part of a surface lighting device according to a seventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluorescent lamp 1a Peripheral surface of fluorescent lamp 2 Light guide plate 2a Light incident end face of light guide plate 2b, 2c Surface of light guide plate 3 Diffusing layer 4 Reflecting layer

Claims (6)

[Claims] 1. A surface lighting device comprising: a rod-shaped light source; and a light guide plate provided with one end face extending along the light source and emitting light incident from the end face from the surface. A surface lighting device, wherein a cross-sectional shape of one end surface of the light guide plate in a plane perpendicular to the length direction has a shape having at least one concave portion. 2. A cross-sectional shape of one end surface of the light guide plate in a plane perpendicular to a length direction of the light source gradually approaches the light source side as going from a center in a thickness direction of the light guide plate to both surface sides. 2. The surface lighting device according to claim 1, wherein the surface lighting device has a protruding concave shape. 3. The surface lighting device according to claim 1, wherein a concave portion on one end surface of the light guide plate is in an arc shape. 4. The surface lighting device according to claim 1, wherein a concave portion on one end surface of the light guide plate is parabolic. 5. The surface lighting device according to claim 1, wherein a concave portion on one end surface of the light guide plate has a V-shape. 6. The surface lighting device according to claim 1, wherein the light source has a round bar shape.