JPH04107507A - Plane light source unit - Google Patents

Abstract

PURPOSE:To irradiate a surface uniformly without any irregularity in brightness by forming plural recessed grooves which guide light from a light source in the reflecting-body side bottom surface of a light guide plate on the sides of the light source arrangement surface and opposite surface. CONSTITUTION:Light guides 8 formed of air layers are partitioned in the recessed grooves 7 of the light guide plate 2 to form two media which are the light guides 8 in the light guide plate 2 and recessed grooves 7. The light from the light source 5 while propagated in the light guide 2 is refracted or reflected in the light guides 8 of the air layers wherein the light is hard to attenuate and distributed into the light guide plate 2, and the light reaches points in the light guide plates 2 at distances from the light source 5, travels around in the light guide plate 2, and further enters a light diffusion plate 3. Consequently, the surface can be irradiated uniformly without any brightness irregularity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flat light source device used as a backlight in a display such as a liquid crystal display board installed in a personal computer, word processor, watch, etc.

[Conventional technology]

A side light source type flat light source device, commonly known as an edge light, has a light source placed on one or both sides of a light guide made by overlapping a light guide plate and a light diffusing plate, and the light source that serves as the illumination surface. It is constructed by covering the light guide and the light source except for the surface of the diffuser plate with a reflector. In this flat light source device, when the light guide is thin, uneven brightness occurs, such as when the backlight of a digital watch is turned on, where only the area near the light source is bright and the distance from the light source becomes darker. Another disadvantage is that a thick and heavy light guide must be used in order to suppress this uneven brightness.

For this reason, as a means to eliminate uneven brightness on the illumination surface without increasing the thickness of the light guide plate, for example, Japanese Patent Laid-Open No. 55-14086
In No. 8, means such as serrations are provided on at least a portion of the surface other than the charge/emission surface of the light guide plate that is superimposed on the light diffuser plate to reflect the light transmitted through the light guide plate and incident thereon toward the inside of the light guide plate. Also, in Japanese Patent Application Laid-Open No. 62-73206, the bottom surface of the light guide plate on the reflector side is formed in a step-like manner so that light can spread throughout the light guide plate.

[Invention or problem to be solved]

In these configurations, measures are taken to increase the number of light reflections and to reduce the thickness of the light guide plate as it moves away from the light source, which causes uneven light distribution. However, since the light is spread through a resin light guide plate, attenuation of the amount of light is unavoidable, and it has not been possible to sufficiently solve the problem of uneven brightness on the illumination surface.

The present invention was made against the background of the above circumstances, and provides a flat light source device that can sufficiently spread the light from the light source to the entire light guide plate and uniformly illuminate the illumination surface without uneven brightness. is intended to provide.

[Means to solve the problem]

In accordance with the purpose of master and slave, in the first invention, a light guide plate and a light diffusing plate are stacked to form a light guide body, a light source is disposed on one side of the light guide body, and the light source serves as a light illumination surface. In a side light source type flat light source device in which the light guide and the light source except for the surface of the diffuser plate are covered with a reflector, on the bottom surface of the light guide plate on the reflector side,
The second invention is characterized in that a plurality of concave grooves for guiding the light from the light source are formed across a side surface where the light source is arranged and an opposite side surface facing thereto. A side light source type in which a light guide is formed together, light sources are arranged on both sides of the light guide, and the light guide and the light source are covered with a reflector except for the surface of the light diffusing plate which becomes the illumination surface. The flat light source device is characterized in that a plurality of concave grooves for guiding light from the light sources are formed on the bottom surface of the light guide plate on the reflector side, extending over both sides where the light sources are arranged.

[For production]

In these configurations, an optical path of an air layer is defined within the groove of the light guide plate, and two media are formed: the inside of the light guide plate and the optical path within the groove. In addition to being transmitted through the light guide plate, the light from the light source is distributed within the light guide plate while being refracted or reflected along the optical path of the air layer, where light is less attenuated than the light guide plate, and is then distributed into the light guide plate away from the light source. The light reaches far from the light plate, spreads over the entire light guide plate, and then enters the light diffusion plate to evenly illuminate the light surface.

〔Example〕

Hereinafter, each embodiment of the present invention will be described based on the drawings.

1 to 5 show a first embodiment, in which a one-lamp type flat light source device 1 has a light guide plate 4 overlaid with a light diffusing plate 3 on a light guide plate 2. A light source 5 is arranged on one side of the body 4, and the outside of the light guide 4 and the light source 5 except for the surface 3a of the light diffusing plate 3 which becomes the illumination surface is covered with a plate-shaped reflector 6. .

On the bottom surface of the light guide plate 20 on the reflector side, a plurality of concave grooves 7 having a triangular cross section are formed on the light source arrangement side surface 2a and the opposite side surface 2b opposite thereto.
A light path 8 for guiding light from the light source 5 is defined in each groove 7. As a result, the light guide plate 2
In this case, two media are formed: the inside of the light guide plate 2 and the light path 8 of the air layer, and in addition to the light emitting surface 2c of the light guide plate 2, which is overlapped with the light diffuser plate 3, there is a concave groove 7 or a light path of the light source. It becomes a new critical surface that refracts or reflects light.

Further, the surface 3a of the light diffusing plate 3 is roughened to the level of matte processing, so that the light received from the light emitting surface 2C of the light guide plate 2 is more finely and diffusely reflected, and the liquid crystal disposed above it is A display such as a display board (not shown) can be illuminated evenly and evenly.

For example, the light path 8 has the size of the light guide plate 2 in the order of length x
When the width is 8 times the thickness is 3 times, the light is formed continuously with a depth of about 0.4 mm and a pitch of 0.5 m, and a part of the light irradiated from the light source 5 is transmitted to the light guide plate 2, which is one medium. Enter (light path A
), and the other part is a light path 8 newly defined as a medium.
In addition to entering the light path (optical path B), the remaining portion is further reflected by the reflector 6 and enters the light guide plate 2 and the optical path 8 (optical path C).

These optical paths A, B, and C hit critical surfaces such as the light emitting surface 2C and the groove 7 in the light guide plate 2, and the incident angle smaller than the critical angle becomes refracted light that enters the adjacent second medium.
Also, if the incident angle exceeds the critical angle, it becomes reflected light that returns to the first culture medium from the critical surface. Of these, the light inside the light guide plate 2 is
As before, refraction and reflection are repeated, and a part of the refraction is reflected in the light path 8.
In addition to bending inward, it also reaches the light emitting surface 2c.

Furthermore, the light in the light path 8 is repeatedly refracted and reflected, and since it is far from the light source 5, it is distributed to the light guide plate 2 and the light emitting surface 2.
This leads to c. Since this light path 8 is the culture medium or air layer, the light guide plate 2 is made of a resin material such as an acrylic plate.
The inclination angle of the concave groove 7 reflects the light in a complex manner and changes the distribution to the light guide plate 2 in a variety of ways, so the light guide plate 2 far from the light source 5 is The light reaches the opposite side 2b sufficiently.

In this way, the light paths A, B, and C passing through the light guide plate 2 and the light path 8 disperse the light from the light source 5 over the entire light emitting surface 2C, so that the surface 3a of the light diffusing plate 3 is uniformly irradiated. Therefore, a flat light source device 1 without uneven brightness can be obtained.

Planar light source device 10 shown in the second embodiment of FIGS. 6 to 8
This is a two-lamp type in which light sources 5 are arranged on both sides of the light guide plate 4, and the bottom surface of the light guide plate 2 on the reflector side has a groove 7 similar to that of the first embodiment, or a groove 7 on the side surface of both light sources. A plurality of stages are provided over the grooves 2a, 2a, and a light path 8 for an air layer is defined in each of these grooves 7.

In this embodiment, by using two light sources 5, the light from the light sources 5 can reach every corner of the light guide plate 2 more easily than in the single-lamp type first embodiment, so that uneven brightness can be further eliminated. .

Further, the flat light source device 20 of the third embodiment shown in FIGS. 9 to 11 is a two-lamp type on one side in which two light sources 5 are arranged on one side of the light guide plate 2, and the bottom surface of the light guide plate 2 on the reflector side A plurality of grooves 21 having a rectangular cross section are formed between the light source arrangement side surface 2a and the opposite side surface 2b opposite thereto, and a light path 22 of an air layer is formed in each groove 21. will be accomplished. This light path 22 has a length of 40 m+s, for example, the size of the light guide 4.
In the case of x width 8 mm x thickness 2 m + s, the depth and width are approximately 0.2 and the spacing is 0.6 + nm.

For the light sources 5, 5, two colors other than white, such as red, blue, and yellow, are used, and the light source 5 of the first embodiment is arranged at the center of one side of the light guide 4. On the other hand, they are provided at both corners of one side of the light guide 4, and are used by lighting either one of them, if necessary. In this embodiment, even when only one corner of one side of the light guide 4 is illuminated, the surface 3a of the light diffusing plate 3 is uniformly illuminated by the light path 22 of the air layer, which is different from the conventional method. It becomes possible to use a two-color light source system that uses one color at a time, which was previously not possible.

As illustrated in the third embodiment, the present invention allows light to be transmitted through the light path of the air layer even if the light source is deviated from the center of the side of the light guide, regardless of whether it is a one-lamp type or a two-lamp type. Since the light can be distributed sufficiently to every corner of the light guide plate, the mental effort required to accurately assemble the light source to the center of the side of the light guide is eliminated, and the assembly time is shortened. It can be manufactured at low cost.

Note that the cross-sectional shape of the concave groove of the light guide plate may be a polygon of pentagon or more, a circular arc, or an ellipse, and the size with respect to the light guide plate is not particularly limited.

〔Effect of the invention〕

As explained above, in the flat light source device of the present invention, a light source is disposed on one side or both sides of a light guide formed by overlapping a light guide plate and a light diffusing plate, and the light source serves as a light illumination surface. The light guide and the light source, excluding the surface of the diffuser plate, are covered with a reflector, and a plurality of grooves for guiding the light from the light source are formed on the bottom surface of the light guide plate on the reflector side. It is formed over both sides of the light source arrangement, and defines a light path with an air layer in each concave groove through which light can easily pass, so that the light from the light source is sufficiently distributed throughout the light guide plate, and the light is diffused. The illumination surface of the plate can be uniformly irradiated.

In addition, the mental effort required for arranging the light sources is relieved, and the assembly time can be shortened and manufacturing can be carried out at low cost.

[Brief explanation of the drawing]

1 to 5 show a first embodiment of the present invention, FIG. 1 is an enlarged sectional front view of a flat light source device, FIG. 2 is a plan view, and FIG. 3 is a ■A sectional view, FIG. 4 is a bottom view of the flat light source device with a part cut away, FIG. 5 is an enlarged side view of the main part, and FIGS. 6 to 8 show the second embodiment.
Fig. 6 is a plan view of the flat light source device, and Fig. 7 is the ■- of Fig. 6.
■Cross-sectional view, Figure 8 is a partially cutaway bottom view of the flat light source device, Figures 9 to 11 show the third embodiment, and Figure 9 is a cross-sectional plan view of the flat light source device; FIG. 10 is a sectional view taken along the line xx in FIG. 9, and FIG. 11 is an enlarged side view of the main parts. 1.1020...Flat light source device, 2.Light guide plate, 2a...
Light source arrangement side surface, 2b... Opposite side surface facing the light source arrangement side surface 2a, 2C... Light emitting surface, 3... Light diffusing plate, 3a
. . . - surface serving as a light illumination surface, 4 . . . a light guide composed of a light guide plate 2 and a light diffusing plate 3, 5 . . . a light source, 6. a reflector, 7, 21 . 8,22...Mitsudo, A, B,
C... Optical path procedure amendment 1゜Indication of the case 1990 Patent Application No. 22 70 2゜Name of the invention Flat light source device 3゜Relationship with the case Patent applicant Yukiko Heijo 4゜

Claims (1)

[Claims] 1. A light guide is constructed by overlapping a light guide plate and a light diffusing plate, and a light source is disposed on one side of the light guide, and the light diffusing plate serves as a light illumination surface. In a side light source type flat light source device in which the light guide and the light source except for the surface are covered with a reflector, a plurality of grooves for guiding the light from the light source are formed on the bottom surface of the light guide plate on the side of the reflector. 1. A flat light source device characterized in that the flat light source device is formed over an opposite side facing the . 2. A light guide is formed by overlapping a light guide plate and a light diffusion plate, and a light source is arranged on both sides of the light guide, and the light guide except for the surface of the light diffusion plate that becomes the illumination surface. In a side light source type flat light source device in which a light source is covered with a reflector, a plurality of concave grooves for guiding light from the light source are formed on the bottom surface of the light guide plate on the side of the reflector, extending over both side surfaces where the light sources are arranged. A flat light source device featuring: