JP2852424B2 - Lighting equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device serving as a surface light source of uniform brightness used for a liquid crystal backlight or the like. 2. Description of the Related Art Conventionally, as an illumination device for performing planar illumination with uniform brightness over a relatively wide range, an illumination device having a configuration as shown in FIG. 4 is known. It comprises a plurality of, for example, two sets of a fluorescent lamp (elongated light source) 11 and a reflecting mirror 12 having a cross section extending in one direction with an arc or a quadratic curve. A diffusion plate 13 is provided. Since the conventional illumination device uses a reflecting mirror having a circular arc or a quadratic curve in cross section, the dimension in the thickness direction becomes large, and the device must be relatively large. Therefore, it is not suitable for a thin lighting device or the like required for a backlight of a liquid crystal. Further, even if the brightness is uniform, there is a drawback that the brightness is substantially uneven and dark. In order to make the illumination uniform, the distance between the illumination system and the diffusion plate may be increased, but the device becomes larger and darker, which is not preferable. On the other hand, in order to reduce the thickness of an illumination device that performs planar illumination, as shown in FIG. 5, fluorescent light is provided inside a reflection plate having reflection surfaces 15 inclined on both sides of a plane reflection mirror 14 as shown in FIG. Light 16
Are arranged, and a diffusion plate 17 is provided on the front surface thereof. In this way, the device can be made extremely thin and relatively bright illumination can be obtained, but it has the disadvantage that the brightness varies depending on the location, the light near and on both sides of the light source is dark, and the middle between the light sources is dark. . Further, since the boundary portion 18 between the bottom surface and the inclined surface is bent, there is a portion on the diffusion plate 17 where the luminance changes relatively sharply. [Problems to be Solved by the Invention] A problem to be solved by the present invention is to provide an illuminating device which can be made extremely thin and which can be a surface light source having uniform brightness at almost all places. It is in. [Means for Solving the Problems] The lighting device of the present invention includes a reflector, a plurality of linear light sources arranged in parallel on the reflector at intervals, and a reflector opposite to the light source. In a lighting device for a surface light source comprising a diffusion plate provided on the side, the cross-sectional shape of the reflection plate in a direction perpendicular to the light source is a straight line near each light source, and both ends of each straight line portion are the straight line portions. The center of the curve which is smoothly connected to each light source side, forms a curve in which curves having different curvatures are continuous, and at a position corresponding between adjacent light sources, a diffuser plate in which these curves are connected smoothly. This is a curve that is convex in the direction, whereby the luminance distribution can be made uniform over the entire reflector. Embodiment FIG. 1 is a cross-sectional view of an embodiment of the lighting device of the present invention.
Is a light source, 2 is a reflection plate, and 3 is a diffusion plate. In the lighting device of this embodiment, the reflecting plate 2 has a flat surface 2a (a straight line in cross section) formed immediately below and around each light source 1, respectively.
Both sides of the two planes 2a are concave surfaces (curved in cross section) 2b curved toward the diffusion plate 3 side. Moreover, this concave surface 2b has a curved center of curvature at many positions and its center of curvature and curvature are different from other positions, and the concave surface 2b is flat.
It is formed continuously including the portion of 2a (cross section is straight). The shape of the concave surface 2b complements the luminance of the middle portion 3b and the end 3c of the distribution shown in FIG. 2, which is the luminance distribution on the diffusion plate 3 when the reflection surface of the reflection plate 2 consists only of a plane. Thus, the curvature at each point is determined so as to be substantially equal to the luminance of the portion 3a immediately above the light source. As a result, the luminance distribution on the diffusion plate 3 of the lighting device using the reflection plate 2 shown in FIG. 1 is flat over the whole as shown in FIG. Moreover, the flat surface 2a and the concave surface 2b
Are continuously and smoothly connected, so that no abrupt change occurs at the boundary. The shape of the reflecting plate 2 is not easy because the concave surface 2b is a special shape and the flat surface 2a and the curved surface of the concave surface 2b are continuously connected, but the reflecting plate 2 is made of synthetic resin. If it is formed, mass production can be performed very easily at the time of actual production by accurately preparing a mold and the like. Although the illustrated embodiment has two light sources, it can be applied to those having three or more light sources. In an illumination device having a plurality of light sources as in this embodiment, it is necessary to prevent luminance unevenness due to reflected light at this portion by making the intermediate point 2c between the light source of the reflector and the light source continuous as a convex surface. is there. The reflector 2 according to the present invention can be mass-produced with high precision by molding with a synthetic resin, and can be used as a reflector as it is by using a white resin or applying a white coating on the reflective surface. The reflecting surface can be easily formed to have a high reflectivity by integrally forming an aluminum foil or vapor-depositing aluminum, and an efficient reflecting plate can be easily formed. [Effect of the Invention] The illumination device of the present invention has a very thin shape because the shape of the reflector is a plane near each light source and a curved surface is formed on both sides of these planes to correct uneven brightness. And a uniform brightness distribution can be obtained over the entire surface of the diffusion plate. In addition, since the reflector is made of synthetic resin, a large number of high-precision reflectors can be produced in spite of a complicated shape for correcting uneven brightness.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of one embodiment of a lighting device according to the present invention, FIG. 2 is a luminance distribution in a case where a reflector is only a flat portion, and FIG. 4 and 5 are perspective views of a conventional lighting device. 1 light source, 2 reflected light, 3 diffuser

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Isamu Kaneko 2-30-1 Namiki, Kawaguchi-shi, Saitama Daiichi Seiko Co., Ltd. (56) References JP-A-62-296184 (JP, A) 60-120483 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G09F 9/00 336

Claims (1)

(57) [Claims] A reflector, a plurality of linear light sources arranged in parallel at intervals on the reflector, and a diffuser provided on the opposite side of the reflector with respect to the light source, for a surface light source. In the lighting device, a cross-sectional shape of the reflector in a direction perpendicular to the light source is a straight line in the vicinity of each of the light sources, and both ends of each of the linear portions have a center of curvature that is smoothly connected to each of the linear portions. Each light source side has a continuous curve with a different curvature, and at a position corresponding to each adjacent light source, a curve is formed that is convex in the direction of the diffuser plate that smoothly connects the curves. A lighting device, comprising: