JP2002133928A - Illuminating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily inexpensively improve variations in brightness on the light- emitting surface of an illuminating apparatus used as a backlight, etc., of a liquid crystal display element. SOLUTION: The illuminating apparatus is provided with: a reflective case 1 comprising a curved inner bottom surface 1a; a light guide 2 having a front surface as a light emitting surface 2a and a rear surface with serration 2b, which guiding body is mounted on the inner bottom surface 1a of the reflective case 1; and a light source 3 emitting light into the inside of the light guide 2 so as to cause the light-emitting surface 2a to emit light. In this illuminating apparatus, serration 1c is provided at a suitable position on the inner surface 1a of the reflective case 1 in order to supply reflective light from behind to a specific region on the light-emitting surface 2a. This makes it possible, when relatively dark area is found in the light-emitting surface 2a at the sample making stage, to easily improve the variation of brightness in the light-emitting surface 2a by providing serration 1c in the reflective case behind the dark area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device suitable for use as a backlight of a liquid crystal display element or the like, in which a light guide has a relatively large light emitting surface.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional illuminating device used as a backlight of a liquid crystal display device, and FIG. 4 is an enlarged view of a portion A in FIG. In the illuminating device shown in FIG. 3, a light guide 2 having a flat light emitting surface 2a on the front side is mounted on a reflective case 1 made of a resin material such as white having a high light reflectance. The light of the light source 3 composed of a small light bulb or the like mounted on the light guide 2 is applied to the inside of the light guide 2 so that the light emitting surface 2a emits light. The light guide 2 has a serration 2 for diffusing light to almost the entire area on the rear surface thereof.
b (see FIG. 4). Further, since the inner bottom surface 1a of the reflection case 1 on which the light guide 2 is mounted is curved so as to rise as the distance from the light source 3 increases, most of the light incident on the inner bottom surface 1a from the light source 3 side is The light is reflected toward a region far from the light source 3 in the light emitting surface 2a. That is, since the distance from the light emitting surface 2a of the light guide 2 to the light source 3 differs depending on the location, the light emitting surface 2a
Although the intensity of the light traveling straight toward the light source becomes weaker as the distance from the light source 3 increases (toward the right in FIG. 3), if most of the light traveling toward the rear side of the light guide 2 is directed to a region distant from the light source 3,
It is possible to emit light with substantially uniform brightness over the entire area of the light emitting surface 2a. In addition, a liquid crystal display element (LCD) (not shown) is incorporated in the upper opening 1b of the reflection case 1 in a state of being close to the light emitting surface 2a of the light guide 2, and the liquid crystal display element is disposed from behind by the light emitting surface 2a. Since the light is illuminated, if the light emitting surface 2a has uneven brightness that varies in brightness depending on the location, uneven brightness occurs on the display screen of the liquid crystal display element, thereby deteriorating the display quality.

[0003]

In the conventional illumination device described above, the light is diffused by the serrations 2b of the light guide 2 and the reflected light is separated from the light source 3 by the curved inner bottom surface 1a of the reflection case 1. However, it is difficult to completely eliminate the uneven brightness of the light emitting surface 2a having a relatively large area. Of course, it is possible to improve the brightness unevenness of the light emitting surface 2a to some extent by changing the shape of the serration 2b for each location or devising the curved shape of the inner bottom surface 1a, but such measures are trial and error. It is a complicated method of finding the optimal shape for the light guide, and if the size and shape of the light guide are different, the same complicated work must be repeated each time, so that the design cost will increase significantly. There are difficulties.

[0004] The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to provide an illuminating device capable of easily and inexpensively improving luminance unevenness of a light emitting surface.

[0005]

According to the present invention, a serration is provided at an appropriate position on the inner bottom surface of a reflection case on which a light guide is mounted, so that a large amount of light diffusely reflected by the serration is supplied to a front light emitting surface. I made it. Thus, if there is a relatively dark area in the light emitting surface at the prototype stage, serration is provided in the reflection case behind the light emitting surface, so that the dark area of the light emitting surface can be brightened. Irregularities can be easily improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An illumination device according to the present invention has a curved inner bottom surface, at least the inner bottom surface of which is made of a material having high light reflectance, and a reflection case mounted on the inner bottom surface of the reflection case; An illumination device comprising: a light guide having a front surface as a light emitting surface and serrations provided on a rear surface; and a light source that emits light into the light guide and emits light from the light emitting surface. The serration for supplying the reflected light from the rear to the specific region of the light emitting surface is provided at an appropriate position of the light emitting surface.

As described above, when serrations are provided at appropriate places on the inner bottom surface of the reflection case on which the light guide is mounted, light leaking from the back surface of the light guide is irregularly reflected by the serrations, and the irregular reflection is performed. The light largely reaches a region of the light emitting surface of the light guide where the distance to the serration is short, that is, a region substantially in front of the serration. Therefore, when the light emitting surface has uneven brightness, if serrations are provided on the inner bottom surface of the reflection case located behind the dark region, light that is diffusely reflected by the serrations can lighten the dark region of the light emitting surface. Therefore, it is possible to easily improve the brightness unevenness of the light emitting surface.

In the above arrangement, if the pitch of the serrations provided on the inner bottom surface of the reflection case is set to be different from the serration of the light guide opposed to the serration, the serrations of the light guide pass through. Light can be efficiently diffusely reflected by the serrations of the reflection case.

The serrations provided on the inner bottom surface of the reflection case are preferably set so that the apex angle of each protruding ridge portion is 30 to 120 degrees.
That is, if the apex angle of the ridge portion is less than 30 degrees, there is a possibility that the production of the mold of the reflection case may be hindered, and if the apex angle of the ridge portion is larger than 120 degrees, light Cannot be sufficiently diffusely reflected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an illuminating device according to the embodiment, and FIG.
3 is an enlarged view of a portion B of FIG. 3, and portions corresponding to those in FIGS. 3 and 4 used in the description of the conventional example are denoted by the same reference numerals.

The illuminating device shown in FIG.
It is used as a backlight of a liquid crystal display element. This illuminating device includes a reflection case 1 made of a resin material such as white having a high light reflectivity, a light guide 2 made of a transparent acrylic resin or the like and having a flat light-emitting surface 2a on the front side, and a circuit board 4. And a light source 3 composed of a small light bulb or the like mounted on the reflection case 1, and a curved inner bottom surface 1a of the reflection case 1.
The light guide 2 is mounted thereon, and the inside of the light guide 2 is irradiated with light from the light source 3 so that the light emitting surface 2a emits light. A serration 2b for diffusing light is provided in almost the entire area on the back surface of the light guide 2, but the reflected light is supplied from a back to a specific area of the light emitting surface 2a at an appropriate position on the inner bottom surface 1a of the reflection case 1. A serration 1c is provided. However, it is designed so that the pitches of the serrations 1c and 2b opposed to each other do not match. Further, since the inner bottom surface 1a of the reflection case 1 is curved so as to rise as the distance from the light source 3 increases, the light incident from the light source 3 side is formed in the portion of the inner bottom surface 1a where the serrations 1c are not formed. Are reflected toward a region far from the light source 3 in the light emitting surface 2a. However, since the portion where the serrations 1c are formed diffusely reflects light leaking from the back surface of the light guide 2, the diffusely reflected light is transmitted to the light-emitting surface 2a in a region relatively close to the serrations 1c and substantially in front. Reach many.

Therefore, in this embodiment, the reflection case 1
Light emitting surface 2 when serrations 1c are not present on inner bottom surface 1a
The luminance unevenness of a is checked beforehand, and then the serrations 1c are provided on the inner bottom surface 1a of the reflection case 1 located behind the relatively dark area in the light emitting surface 2a.
Determine the final design. Thereby, Serration 1
Since the dark area of the light emitting surface 2a can be brightened by the light diffusely reflected by c, the uneven brightness of the light emitting surface 2a can be easily improved. In addition, a liquid crystal display element (not shown) is incorporated in the upper opening 1b of the reflection case 1 in a state close to the light emitting surface 2a of the light guide 2, and the liquid crystal display element is illuminated from behind by the light emitting surface 2a. It has become.

As described above, in the lighting device according to this embodiment,
Serrations 1c are provided at appropriate locations on the inner bottom surface 1a of the reflection case 1 on which the light guide 2 is mounted, and a large amount of light irregularly reflected by the serrations 1c is supplied to the front light emitting surface 2a. When there is uneven brightness in the light emitting surface 2a, the reflection case 1 located behind the dark area
By providing serrations 1c on the inner bottom surface 1a,
Brightness unevenness of the light emitting surface 2a can be improved. Therefore, in various illuminating devices in which the size and shape of the light guide 2 are different, it is easy to design and manage the specific area of the light emitting surface 2a with the reflected light from the serrations 1c of the reflective case 1 to eliminate uneven brightness. Can be done. As a result, the display quality of a liquid crystal display device using such an illuminating device as a backlight can be easily and inexpensively improved.

In order to efficiently and irregularly reflect the light passing through the serrations 2b of the light guide 2 with the serrations 1c provided on the inner bottom surface 1a of the reflection case 1, as described above, two opposite serrations are used. It is better to form 1c and 2b at different pitches. However, in the serration 1c of the reflection case 1, it is preferable that the apex angle α (see FIG. 2) of each of the protruding ridges is set in the range of 30 to 120 degrees. That is, if the apex angle α of the ridge portion is less than 30 degrees, there is a possibility that the production of the mold of the reflection case 1 may be hindered.
If the angle is larger than 20 degrees, light cannot be sufficiently diffused.

[0015]

The present invention is embodied in the form described above and has the following effects.

A serration is provided at an appropriate position on the inner bottom surface of the reflection case on which the light guide is mounted, so that a large amount of light diffusely reflected by the serration is supplied to the front light emitting surface. When there is a relatively dark area in the surface, serration is provided in the reflection case behind the area, so that the dark area of the light emitting surface can be brightened. Therefore, it is possible to easily and inexpensively improve the luminance unevenness of the light emitting surface having a relatively large area, and the practical effect is high in improving the display quality of a liquid crystal display element or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of an illumination device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion B in FIG.

FIG. 3 is a cross-sectional view of an illumination device according to a conventional example.

FIG. 4 is an enlarged view of a portion A in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflective case 1a Inner bottom surface 1c Serration 2 Light guide 2a Light emitting surface 2b Serration 3 Light source 4 Circuit board

Claims (3)

[Claims] 1. A reflection case having a curved inner bottom surface, at least the inner bottom surface of which is made of a material having high light reflectivity, and mounted on the inner bottom surface of the reflection case, the front surface being a light emitting surface and the serration being serrated. And a light source that emits light into the light guide and emits light from the light-emitting surface, in an appropriate position on the inner bottom surface of the reflection case, An illumination device comprising a serration for supplying reflected light to a specific area from behind. 2. The illumination device according to claim 1, wherein a pitch of serrations provided on an inner bottom surface of the reflection case is different from a pitch of serrations of the light guide body facing the serration. 3. The serration provided on the inner bottom surface of the reflection case according to claim 1 or 2, wherein the apex angle of each of the serrations is set to 30 degrees to 120 degrees. An illumination device characterized by the above-mentioned.