JPH06289231A - Plane illuminator - Google Patents

Abstract

PURPOSE:To provide a plane illuminator which supplies uniform illumination by preventing partial high luminance on the surface in the neighborhood of the other side plane of a light transmission plate from occurring. CONSTITUTION:A reflection frame 1 formed almost in box shape provided with the side plane whose upper part is opened, the light transmission plate 6 arranged on the bottom of the reflection frame 1, a long sized substrate 14 located at the side inner than the side plane of the reflection frame 1 and also arranged confronting with one side plane of the light transmission plate 6, and plural light emission diodes 19 placed by being arranged on the substrate in the longitudinal direction so as to confront with one side plane of the light transmission plate 6 are provided. A gap is provided between the other side plane of the light transmission plate 6 and the side plane of a confronting reflection frame 1, or the bottom of the light transmission plate 6 located in the neighborhood of the other side plane of the light transmission plate 6 is formed in mirror face, or the side plane of the reflection frame is formed is concave mirror face at a position where it is confronted with the other side plane of the light transmission plate 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a flat display display,
In particular, it relates to a surface illumination device used for liquid crystal display.

[0002]

2. Description of the Related Art In recent years, many surface illumination devices used for displaying on a flat display have been developed. Among them, for example, an apparatus filed by the applicant in Japanese Patent Application No. 5-69919 is shown in a plan view of FIG. 5 and a CC sectional view of FIG. In these figures, a light guide plate 52 is arranged on a box-shaped reflection frame 51,
A rough surface composed of a plurality of convex portions 53 is formed on the back surface of the light guide plate 52. A plurality of light emitting diodes 55 are arranged so as to face one side surface 54 of the light guide plate 52.

[0003]

However, in the above-mentioned device, the brightness is locally high on the surfaces 56a, 57a, 58a near the other side surfaces 56, 57, 58 of the light guide plate 52, and uniform illumination can be obtained. There are drawbacks that cannot be avoided. When the inventors of the present invention have investigated the cause, for example, the light from the light emitting diode 55 is reflected by the convex portion 53 and is reflected by the inner surface of the side portion 59 of the reflection frame 51 that is in close contact with the other side surface 57 of the light guide plate 52. It was found that most of the light was emitted from the surface 57a near the other side surface 57 of the light guide plate. Further light emitting diode 55
Light from the light exits the light guide plate 52 directly.
There is a defect that the brightness is locally high on the surface 54a near the side surface 54. In view of the above drawbacks, the present invention provides surfaces 56a, 57a near the other side surfaces 56, 57, 58 of the light guide plate,
58a, a surface illuminating device which provides uniform illumination by preventing partial increase in brightness.

[0004]

In order to solve the above-mentioned problems, the present invention provides a substantially box-shaped reflecting frame having an open upper side and a side surface, a light guide plate disposed on the bottom surface of the reflecting frame, and a reflecting plate. A long substrate located inside the side surface of the frame and arranged to face one side surface of the light guide plate, and a long substrate aligned and placed on the substrate so as to face one side surface of the light guide plate. A plurality of light emitting diodes are provided. Then, a gap is provided between the other side surface of the light guide plate and the side surface of the reflecting frame facing the other side surface, or the bottom surface of the light guide plate located near the other side surface of the light guide plate is formed into a mirror surface, or The side surface of the reflecting frame is formed into a concave mirror shape at a position facing the other side surface.

[0005]

As described above, according to the present invention, since a gap is provided between the other side surface of the light guide plate and the side surface of the reflecting frame which faces the other side surface, the gap between the other side surface of the light guide plate and the side surface of the reflection frame is set. At this point, the light emitted from the surface near the side surface is weakened because it is refracted and reflected several times. Also, since the bottom surface located near the other side surface of the light guide plate is formed into a mirror surface, the amount of light reflected by the mirror surface is small, so it is reflected by the mirror surface and reflected by the other side surface of the light guide plate from the surface near the side surface. The emitted light is weakened. Further, since the side surface of the reflection frame is formed in the shape of a concave mirror at the position facing the other side surface of the light guide plate, the light reflected by the concave mirror on the side surface of the reflection frame is inwardly parallel to the surface of the light guide plate. As the light travels, the light emitted from the surface near the side surface is weakened.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 is a plan view of a surface lighting device according to the present embodiment, and FIG. 2 is a cross-sectional view taken along the line AA of FIG. In these figures, the reflection frame 1 is made of, for example, white ABS resin,
The external size is about 63 mm in width, about 60 mm in height, and about 4 mm in height. The reflection frame 1 is formed in a substantially box shape having side surfaces 2, 3, 4, and 5, a through hole (not shown) is formed at an end of a bottom surface thereof, and a plurality of through holes (not shown) are formed on the side surfaces 3 and 5. (Not shown) is formed. Alternatively, the reflection frame 1 may be made of a white resin such as a polycarbonate resin or polyphenylene oxide (PPO), a metal, or the like.

The light guide plate 6 is made of acrylic resin, for example,
The shape is a rectangular parallelepiped with a width of about 59 mm, a length of about 58 mm, and a height of about 2.5 mm. Two protrusions 8 are formed in the vicinity of both ends of one side surface 7 of the light guide plate 6. Desirably, a plurality of convex portions 9 are formed on the bottom surface of the light guide plate 6 by graining. The convex portions 9 are, for example, flat and substantially right-angled isosceles triangles aligned in the vertical and horizontal directions. On the other side surfaces 10, 11, 12 of the light guide plate, for example, the height is 0.1 to 0.4, respectively.
A mm convex portion 13 is formed.

In this way, the convex portion 9 on the bottom surface of the light guide plate 6 abuts on the bottom surface of the reflection frame 1, and the other side surfaces 10 and 1 of the light guide plate 1 are brought into contact.
The convex portions 13 of 1 and 12 are the side surfaces 3 and 4 of the reflection frame 1,
5, a plurality of boss portions (not shown) formed on the other side surfaces 10 and 12 of the light guide plate are engaged with the through holes on the side surfaces 3 and 5 of the reflection frame 1 described above. As described above, a gap of 0.1 to 0.4 mm is provided between the other side surfaces 10, 11, 12 of the light guide plate and the side surfaces 3, 4, 5 of the reflecting frame 1 facing each other. Depending on the case, the convex portion 13 is not provided, and a step is provided on the boss portion formed on the other side surfaces 10 and 12 of the light guide plate, or a gap of 0.1 to 0.4 is formed by other means.
mm should be secured. Further, this gap may be filled with a substance having a refractive index smaller than that of the light guide plate 6.

The substrate 14 is a long substrate in which a conductive layer 16 is printed and printed on a resin layer 15 made of, for example, glass epoxy resin, and a white coating portion 17 is formed on the surface except the vicinity of the conductive layer 16. The board 14 is provided with two power supply terminals 18. The back surface of the substrate 14 abuts on the inner surface of the side portion 2 of the reflection frame 1 so that the power supply terminal 18 penetrates the through hole formed at the end of the bottom surface of the reflection frame 1 described above. The side surface of the substrate 14 is in contact with the bottom surface of the reflection frame 1, and the surface of the substrate 14 is in contact with the protruding portion 8 of the light guide plate 6, so that the substrate 14 is arranged.

A light emitting diode 19 is fixed on the conductive layer 16 of the substrate 14 via a conductive adhesive. The light emitting diode 19 is made of gallium phosphide, for example, and is approximately 580 mm.
It emits green light and is approximately cubic with a side of about 300 μm. Twenty-two light emitting diodes 19 are arranged in the longitudinal direction of the substrate 14 at a predetermined arrangement pitch. (1 in FIG. 1
0 is displayed) and the light emitting diode 19 and other conductive layer 2
It is wired by a thin metal wire 21 between 0 and 0. Further, in order to prevent locally strong light directly emitted from the light emitting diode 19 through the light guide plate 6, it is preferable that one side surface 7 of the light guide plate is formed to have an inclination in a direction narrowing upward. Inclination angle θ
= 78 ° to 87 ° is desired. The surface illumination device of this embodiment is constituted by these components.

Illumination in this surface illumination device will be described again with reference to FIGS. 1 and 2. First, the illumination in the vicinity of the other side surface 11 of the light guide plate 6 will be described. The brightness of the light 22 emitted from the light emitting diode 19 and reflected by the convex portion 9 behind the light guide plate 6 is set to 100%, and the light guide plate 6 is
The transmittance is calculated as 93% and the reflectance of the reflection frame 1 as 90%. The brightness of the light 23 emitted from the light guide plate 6 into the air is 93%, and the brightness of the light 24 reflected by the side surface 4 of the reflection frame 1 is 9%.
3 × 0.9≈84%, and the light 2 that entered the light guide plate 6 again
The luminance of No. 5 is 84 × 0.93≈78%, and the luminance of the light 26 emitted into the air again is 78 × 0.93≈73%.
In comparison with this, in the conventional device, the light shining on the surface of the light guide plate is as high as 100 × 0.9 × 0.93≈84%. As described above, in the present device, the light is emitted from the other side surface 11 of the light guide plate. The number of times light is reflected and refracted through the air layer between the side surface 4 of the reflection frame 1 and the number of times of refraction increases. Therefore, the light emitted from the surface 11a in the vicinity of the other side surface 11 of the light guide plate is weakened as compared with the conventional case, so that there is no local high brightness area as in the conventional case. Specifically, the surface of the light guide plate 6 was divided vertically and horizontally into 10 rows and 10 columns, and the measurement was performed with a luminance meter. As a result, the average luminance is 23.2 cd / m ² , the maximum luminance on the other side surface-vicinal surface 11a of the light guide plate is 24.2 cd / m ² , and the degree of luminance variation is (24.
2−23.2) /23.2×100=4.3%.
On the other hand, the brightness variation of the conventional device is (32.3-
22.4) /22.4×100=44.2%. Moreover, as a result of the experiment, when the gap between the other side surface 11 of the light guide plate and the side surface 4 of the reflection frame 1 is smaller than 0.1 mm or larger than 0.4 mm, the brightness variation degree is rapidly deteriorated to 20 to 30%. I understood.

Next, the illumination in the vicinity of one side surface 7 of the light guide plate 6 will be described. Since the one side surface 7 of the light guide plate 1 is inclined in a direction narrowing upward, the incident angle of the light 27 emitted upward from the light emitting diode 14 entering the one side surface 7 of the light guide plate 1 is larger than in the conventional case. Therefore, one side 7 of the light guide plate
The emission angle of the light 29 shining from the surface 28 in the vicinity of is larger than that of the conventional one. Further, the light traveling substantially perpendicular to the surface of the light guide plate 6 is easily noticeable to human eyes. Therefore, the component of the light 29 in the direction substantially perpendicular to the surface of the light guide plate 6 is smaller than that in the conventional case, and the locally high brightness on the surface 28 near the one side surface 7 of the light guide plate is smaller than that in the conventional case.

Specifically, the degree of brightness variation of the surface 28 near the one side surface 7 of the light guide plate is (28.1-23.2) / 2.
3.2 × 100 = 21.1%, which is the variation degree of the conventional device (33.7−22.4) /22.4×100=5.
It is smaller than 0%. Moreover, as a result of the experiment,
It has been found that when the inclination angle θ of the side surface 7 is smaller than 78 ° or larger than 87 °, the degree of brightness variation sharply deteriorates to about 35%.

Next, a second embodiment having a simpler structure than that of the first embodiment will be described with reference to the sectional view of FIG. On the bottom surface of the light guide plate 30 located near the other side surface 31, the other side surfaces 31 to 4 are provided.
The mirror surface 32 is formed so that the unevenness of the surface is 5 μm or less in the length range of up to 15 mm. A convex portion 9 is formed on the other bottom surface. The brightness of the reflected light 33 on the mirror surface 32 is smaller than the brightness of the reflected light on the convex portion 9 of the conventional device. Therefore, the reflected light 33 is reflected by the side surface 4 of the reflection frame 1 and the brightness of the light 34 emitted from the surface 31a near the other side surface 31 of the light guide plate becomes smaller than that of the conventional one, and there is no local high brightness region as in the conventional one. .

More preferably, the light emitting diode 19 is provided below the center of the height of the light guide plate 30, that is, on the side close to the convex portion 9 of the light guide plate 30. Therefore, the distance B between the position of the light 35 emitted from the light guide plate 30 and the one side surface 36 of the light guide plate becomes longer than in the conventional case.
There is no local high brightness area at.

Next, a third embodiment capable of more uniform illumination than the first or second embodiment will be described with reference to the sectional view of FIG. The reflection frame 4 is provided at a position facing the other side surface 39 of the light guide plate 38.
A concave mirror portion 42 is formed on the side surface 41 of 0. The light 43 reflected by the convex portion 9 of the light guide plate 38 exits the light guide plate 38, is reflected by the concave mirror portion 42, and travels inward substantially parallel to the surface of the light guide plate 38. Therefore, there is no local high brightness area on the surface 44 near the other side surface 39 of the light guide plate.

Further, desirably, a convex lens portion 46 is formed for the light emitting diode 19 on one side surface 45 of the light guide plate located above the light emitting diode 19. One of the light guide plates located below the light emitting diode 19
On the side surface 45, a concave lens portion 47 is formed for the light emitting diode 19. By doing so, the light emitted upward from the light emitting diode 19 is convex lens portion 46.
The traveling direction is changed by and the traveling proceeds substantially parallel to the surface of the light guide plate 38. Therefore, there is no local high brightness region on the surface 48 near the one side surface 45 of the light guide plate.

The light emitted downward from the light emitting diode 19 travels substantially parallel to the surface of the light guide plate 38 by the concave lens portion 47. Therefore, as in the conventional case, the light emitted downward from the light emitting diode is reflected by the convex portion 9 at the end of the light guide plate 38,
Concentration on the surface 48 near the one side surface 45 of the light guide plate is prevented.

As described above, the present invention is not limited to the three embodiments, and each embodiment of the structure near the other side surface of the light guide plate and the structure near one side surface of the light guide plate is described. You may combine.

[0020]

As described above, according to the present invention, since a gap is provided between the other side surface of the light guide plate and the opposite side surface of the reflection frame, the light emitted from the light emitting diode and the other side surface of the light guide plate and the reflection frame. Since the light is refracted and reflected several times from the side surface of the light guide plate, the light emitted from the surface near the other side surface of the light guide plate is weakened. Further, according to the present invention, since the bottom surface of the light guide plate located in the vicinity of the other side surface of the light guide plate is formed into a mirror surface, the amount of light reflected from the light emitting diode in a mirror surface shape is reduced. Therefore, the light reflected by the mirror surface and the other side surface of the light guide plate and emitted from the surface near the other side surface of the light guide plate is weakened. Further, according to the present invention, since the side surface of the reflection frame is formed in a concave mirror shape at the position facing the other side surface of the light guide plate, the light from the light emitting diode exits from the other side surface and the concave lens on the side of the reflection frame is formed. Since the light is reflected by the light guide plate and travels inward substantially parallel to the surface of the light guide plate, the light emitted from the surface near the other side surface of the light guide plate is weakened.

As a result, there is no local high brightness area on the surface near the other side surface of the light guide plate, and uniform illumination can be provided.

[Brief description of drawings]

FIG. 1 is a plan view of a surface lighting device according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a surface lighting device according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a surface lighting device according to a third embodiment of the present invention.

FIG. 5 is a plan view of a conventional surface lighting device.

6 is a sectional view taken along line CC of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflection frame 2, 3, 4, 5 Side surface 6 Light guide plate 7 1 side surface of light guide plate 10, 11, 12 Other side surface of light guide plate 14 Substrate 19 Light emitting diode 32 Mirror surface 42 Concave mirror portion

Claims (1)

[Claims] 1. A substantially box-shaped reflective frame having an open upper side and a side surface, a light guide plate disposed on the bottom surface of the reflective frame, and a light guide plate located inside the side surface of the reflective frame and being provided on the light guide plate. 1
The light guide plate comprises a long substrate arranged to face a side surface and a plurality of light emitting diodes mounted on the substrate in a long direction so as to face one side surface of the light guide plate. In a surface lighting device in which light is emitted from the surface of a light plate, a gap is provided between the other side surface of the light guide plate and a side surface of the reflecting frame that faces the light guide plate, or in the vicinity of the other side surface of the light guide plate. The bottom surface of the light guide plate located is formed into a mirror surface, or the side surface of the reflection frame is formed into a concave mirror shape at a position facing the other side surface of the light guide plate. .