JP2000268619A - Surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly generate white light without having irregular colors in a surface light source to generate white color light by using a plurality light of sources having different wavelengths. SOLUTION: In this surface light source, a red color light emitting diode 18R, a green color light emitting diode 18G, and a blue color light emitting diode 18B are concentrated to the end of a light conductive plate and disposed at one place. Each light emitting diode 18R, 18G, 18B is sealed in a transparent resin 20, and a light diffusing pattern 21R, 21G, 21B is provided on the surface of each transparent resin 20. The light diffusing pattern 21R facing the red light emitting diode 18R is comparatively coarse, the light diffusing pattern 21G facing the green light emitting diode is medium and the light diffusing pattern 21B facing the blue color emitting diode 18B is comparatively fine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface light source device that emits light from a plurality of light sources.

[0002]

2. Description of the Related Art (Surface light source device of monochromatic emission) The structure of a conventional surface light source device is shown in an exploded perspective view of FIG. The surface light source device 1 includes a light guide plate 3 for confining light introduced from a light incident surface 2, a light emitting unit 4, and a reflection plate 5. The light guide plate 3 is formed of a transparent resin having a large refractive index, such as polycarbonate resin or methacrylic resin. The diffusion pattern 7 is formed by printing or the like. The light emitting unit 4 includes a plurality of light emitting diodes (LEDs) 9 mounted on a circuit board 8, and faces the light incident surface 2 (side surface) of the light guide plate 3. The reflection plate 5 is formed of, for example, a white resin sheet having a high reflectance, and has both sides adhered to the back surface of the light guide plate 3 by a double-sided tape 10.

As shown in FIG. 2, light emitted from each light emitting diode 9 of the light emitting section 4 and incident on the inside of the light guide plate 3 from the light incident surface 2 is diffusely reflected when incident on the diffusion pattern 7, and the light is emitted. Light reflected toward the surface 6 at an angle smaller than the critical angle of total reflection is emitted from the light emitting surface 6 to the outside. Further, light that has passed through a portion of the lower surface of the light guide plate 3 where the diffusion pattern 7 does not exist is reflected by the reflector 5 and returns to the inside of the light guide plate 3 again, so that loss of light amount from the lower surface of the light guide plate 3 is prevented.

(Surface light source device for white light) The above-described surface light source device is a monochromatic surface light source device. If an attempt is made to emit white light using the surface light source device having such a structure, red and green light are emitted. ,
It is conceivable to use white light emitting diodes of three colors of blue to mix the three colors of red, green and blue to whiten. In that case, the maximum emission power is different between the red, green, and blue light emitting diodes, so that the red, green, and blue light emitting diodes have the same power.
It is necessary to install green and blue light emitting diodes on the end face of the light guide plate. Since the power ratio of the red, green, and blue light emitting diodes is about 8: 1: 2, one red light emitting diode, eight green light emitting diodes, and four blue light emitting diodes are provided on the end surface of the light guide plate. You only need to install it.

In order to make the light source emit light uniformly at the end face of the light guide plate 3, a red light emitting diode R, a green light emitting diode G, and a blue light emitting diode B may be arranged as shown in FIG. , As a whole combination,
The light emitting unit 4 in which red, green, and blue light emitting diodes R, G, and B are arranged as shown in FIG. 3A may be disposed on the end surface of the light guide plate.

[0006]

However, even if the red light emitting diode R, the green light emitting diode G, and the blue light emitting diode B are arranged as shown in FIG.
There was a problem that the light guide plate 3 was colored orange or green in the vicinity of the light emitting section 4.

The present invention has been made to solve the above-mentioned technical problems, and an object of the present invention is to use a plurality of light sources having different wavelengths to emit a mixed color thereof, for example, white light. An object of the present invention is to provide a surface light source device capable of uniformly mixing colors without causing color unevenness.

[0008]

According to a first aspect of the present invention, there is provided a surface light source device comprising: a plurality of light sources having different wavelengths; and a light guide plate for confining light from the light source and spreading the light from the light emitting surface. The plurality of light sources are arranged in an area smaller than the size of the light guide plate, and have a diffusion degree corresponding to the directivity of the light source on an optical path of light exiting the light source and entering the light guide plate. Means are provided.

[0009]

The surface light source device according to the first aspect has a plurality of light sources having different wavelengths, and a degree of diffusion according to the directivity of the light source on an optical path of light exiting the light source and entering the light guide plate. Is provided, the directivity of light of each wavelength can be adjusted by this diffusion means so as to be substantially uniform.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG.
(B) is the top view and sectional drawing which show the surface light source device 11 by one Embodiment of this invention. The light-emitting unit 12 is a light-emitting diode of three colors, red, green, and blue, which is localized and compacted, and is arranged to face one end face of the light guide plate 13. At a position facing the light emitting portion 12 of the light guide plate 13, an optical coupling portion 14 is provided in a concave shape. On the back surface of the light guide plate 13, the diffusion patterns 15 are arranged concentrically around the light emitting unit 12. The diffusion pattern 15 has a uniform shape in the circumferential direction around the light emitting unit 12. Accordingly, the light from the light emitting unit 12 is deflected in a plane perpendicular to the light emitting surface and including the direction connecting the light emitting unit 12 and the pattern, and hit the diffusion pattern 15 and is not emitted from the light emitting surface 16. Light is also guided linearly without changing the light guiding direction. Further, a reflection sheet 17 is provided on the back surface of the light guide plate 13, and the light leaking from the back surface of the light guide plate 13 is reflected by the reflection sheet 1.
7, the light is returned to the inside of the light guide plate 13 by reflection,
Light loss is reduced.

The light emitting section 12 for generating white light has red, green, and blue light sources localized by arranging red, green, and blue light emitting diodes close to each other. Red light emitting diode, green light emitting diode and blue light emitting diode, in order to equalize the luminance balance,
The number is arranged such that the total power of each color becomes substantially equal. For example, if the power ratio of the red, green, and blue light emitting diodes is about 8: 1: 2, the red, green, and blue light emitting diodes are housed in the light emitting unit 12 in the number of 1: 8: 4. ing.

The red, green, and blue lights emitted from the light emitting unit 12 and coupled to the optical coupling unit 14 are guided into the light guide plate 13 while spreading radially. Light that has entered the light guide plate 13 from the optical coupling unit 14 travels while being totally reflected inside the light guide plate 13 around the light emitting unit 12, and is linearly guided when viewed from the light exit surface 16 (the surface of the light guide plate 13). Be lighted. When light in the light guide plate 13 enters the diffusion pattern 15 and enters the light exit surface 16 at an incident angle smaller than the critical angle of total reflection, the light exits from the light exit surface 16 to the outside. The red, green, and blue lights are simultaneously emitted from the light exit surface 16 so that the light exit surface 16 emits white light.

The amount of light emitted from the light exit surface 16 of the light guide plate 13 to the outside can be represented by the product of the amount of light guided in the light guide plate 13 and the radiation loss coefficient. In this case, a uniform amount of emitted light can be obtained. The radiation loss coefficient is controlled by the density of the diffusion pattern 15. That is, in each direction,
The radiation loss coefficient is reduced by reducing the pattern density of the diffusion pattern 15 near the light emitting unit 12, and the radiation density is increased by increasing the pattern density as the distance from the light source increases.
The brightness is made uniform throughout.

In such a radiation-coupled surface light source device 11, since light is linearly guided inside the light guide plate 13, it is necessary to control the directivity of the light source according to the shape of the light guide plate 13. In addition, the directivity is controlled by the shape of the optical coupling unit 14, the light amount distribution is corrected in all directions, and the luminance distribution is made uniform.

However, simply arranging a predetermined number of red, green, and blue light-emitting diodes in opposition to the light incident surface does not enable satisfactory white light emission. That is, the red, green, and blue light emitting diodes have different directivities for each color depending on the structure. For example, the directional angle of the red light emitting diode is 130 °, the directional angle of the green light emitting diode is 140 °, and the directional angle of the blue light emitting diode is 145 °. When these light emitting diodes are used to configure the light emitting unit 12, FIG. As shown in FIG.
In the vicinity of the center of, the three colors of red, green and blue are mixed and become white, but it is colored blue-green outside the directional angle of the red light emitting diode, and colored blue outside the directional angle of the green light emitting diode. Unevenness occurs. This is due to the light emitting diode chip material and structure, and it is inevitable that light emitting diodes having different wavelengths have different directivities.

For this reason, the surface light source device 11 of this embodiment
In, the light emitting section 12 is configured with a structure as shown in FIG. It should be noted that in FIG.
R, green light emitting diode 18G, blue light emitting diode 1
8B are shown one by one.
A predetermined number of green and blue light emitting diodes 18R, 18G, and 18B are provided as described above (the same applies to the following embodiments). Red light emitting diode (chip) 1
8R, the green light emitting diode (chip) 18G and the blue light emitting diode (chip) 18B are individually housed in a white resin case 19,
0 is sealed. Each light emitting diode 18R,
Light diffusing patterns 21R, 21G, and 21B are provided on the light emitting surface 16 of the transparent resin 20 that seals 18G and 18B. Light diffusion patterns 21R, 21G, 21B
May be any pattern having a diffusion function, such as graining, a grating, and a microlens array. As the light diffusion patterns 21R, 21G, and 21B, those having a large diffusion degree (haze) are used for light emitting diodes having a small directivity angle, and small diffusion degrees are used for light emitting diodes having a large directivity angle. Things are used. Red, green and blue light emitting diodes 18
Speaking of R, 18G and 18B, the red light emitting diode 18
The light diffusion pattern 21R used for the green light emitting diode 18G is the light diffusion pattern 21R used for the green light emitting diode 18G.
The light diffusion pattern 2 used for the blue light emitting diode 18B has a coarser pattern and a higher diffusion degree than G.
1B has a finer pattern than the light diffusion pattern 21G used for the green light emitting diode 18G (the light diffusion pattern 21B may not be provided) and has a smaller degree of diffusion.

According to the light emitting unit 12 having such a configuration, the red light emitted from the red light emitting diode 18R having a narrow directivity angle is relatively largely diffused by the coarse light diffusion pattern 21R, and the green light emitting diode 18G Is diffused moderately by the light diffusion pattern 21G, and the blue light emitted from the blue light emitting diode 18B having a wide directivity angle is diffused relatively small by the fine light diffusion pattern 21B. As a result, the light diffusion pattern 21
After passing through R, 21G, and 21B, the directional angles of red light, green light, and blue light become substantially equal. When the directivity angles of the lights of the respective colors are substantially equalized, the color unevenness as shown in FIG. 5 is eliminated, and uniform white light emission is obtained.

As shown in FIG. 7, the red light emitting diode 18R, the green light emitting diode 18G and the blue light emitting diode 18B are housed in the same case 19 and sealed by a common transparent resin 20 to be integrated. Thus, the light emitting unit 12 can be downsized. In this case, the light diffusion patterns 21 having different diffusion degrees are provided on the surface of the transparent resin 20 so as to face the light emitting diodes 18R, 18G, and 18B.
R, 21G and 21B are formed.

(Second Embodiment) FIG. 8 is a sectional view showing a structure of a light emitting section 12 according to another embodiment of the present invention.
In this light emitting section 12, a red light emitting diode 18
R, the green light emitting diode 18G and the blue light emitting diode 18B are housed in the same case 19,
0 is sealed. A diffusion material 22 is dispersed in the transparent resin 20, and the diffusion material 2 is dispersed around the red light-emitting diode 18R, the green light-emitting diode 18B, and the blue light-emitting diode 18B in ascending order of the directivity angle.
2 has a large dispersion density. Therefore, even in the light emitting section 12, the light emitting diodes 18R, 18G, and 18B of the respective colors are used.
Are different from each other, the directivity angles of the lights of the respective colors emitted from the light emitting unit 12 become substantially equal, and the color unevenness of the surface light source device 11 can be eliminated.

(Third Embodiment) FIG. 9 is a sectional view showing a part of a surface light source device 11 according to still another embodiment of the present invention. In this embodiment, the surface of the transparent resin 20 of the light emitting unit 12 is formed to be smooth, and a transparent diffusion plate 23 is arranged on the front surface of the light emitting unit 12. In the diffusion plate 23, diffusion regions 24R, 24G, and 24B are formed corresponding to the front surfaces of the light emitting diodes 18R, 18G, and 18B, respectively. These diffusion regions 24R, 24G, 2
In 4B, the degree of diffusion is controlled by providing a light diffusion pattern or dispersing a diffusion substance.
In the diffusion region 24R facing the red light emitting diode 18R, the degree of diffusion is increased, and in the diffusion region 24G facing the green light emitting diode 18G, the degree of diffusion is set to medium.
In the diffusion region 24B opposed to the blue light emitting diode 18B, the degree of diffusion is reduced so that after transmitting through the diffusion plate 23, the directivity angles of the light of each color are substantially equal.

(Fourth Embodiment) FIG. 10 is a sectional view showing a part of a surface light source device according to still another embodiment of the present invention. In this embodiment, the light emitting unit 1 of the light guide plate 13
The light diffusion pattern 21 is provided at a portion (light incident surface) facing
R, 21G, and 21B are provided. The light diffusion pattern 21R facing the red light emitting diode 18R has a large diffusion degree, the light diffusion pattern 21G facing the green light emitting diode 18G has a medium diffusion degree, and the light diffusion pattern 21B facing the blue light emitting diode 18B has a diffusion degree. Is made small, and after the light enters the light guide plate 13, the directivity angles of the light of each color are made substantially equal. Therefore, even with such a configuration, the color unevenness of the surface light source device can be eliminated.

Further, as shown in FIG. 11, the light guide plate 13 is formed by dispersing a diffusion material 22 instead of the light diffusion patterns 21R, 21G and 21B, and controlling the degree of diffusion by the dispersion density of the diffusion material 22. Good.

In the above embodiment, the emission color is red,
Although the case where the green and blue light emitting diodes are used has been described, the light emitting colors of the light emitting diodes are not limited to these, and are not limited to three types.

[0024]

According to the surface light source device of the first aspect,
A diffusing means having a degree of diffusion corresponding to the directivity of the light source is provided on an optical path of light emitted from the light source and entering the light guide plate. It can be adjusted so that the properties are almost uniform. Therefore, when light of each wavelength is mixed and used as a light source, it is possible to prevent the occurrence of color unevenness.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a conventional surface light source device.

FIG. 2 is an operation explanatory view of the surface light source device of FIG. 1;

3A is a schematic diagram illustrating a configuration for whitening the surface light source device of FIG. 1, and FIG. 3B is a diagram illustrating an arrangement of red, green, and blue light emitting diodes.

FIGS. 4A and 4B are a schematic plan view and a sectional view of a surface light source device according to an embodiment of the present invention.

FIG. 5 is a diagram showing color unevenness generated in the surface light source device.

FIG. 6 is a sectional view showing a structure of a light emitting unit used in the surface light source device of FIG.

FIG. 7 is a cross-sectional view showing a light emitting unit having another structure used in the surface light source device of FIG.

FIG. 8 is a cross-sectional view illustrating a light emitting unit according to another embodiment of the present invention.

FIG. 9 is a partially broken sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 10 is a partially broken sectional view showing a surface light source device according to still another embodiment of the present invention.

FIG. 11 is a partially broken sectional view showing a surface light source device according to still another embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 12 light emitting unit 13 light guide plate 18R red light emitting diode 18G green light emitting diode 18B blue light emitting diode 21R, 21G, 21B light diffusion pattern 22 diffusion material 23 diffusion plate 24R, 24G, 24B diffusion region

Claims (1)

[Claims] 1. A light source comprising: a plurality of light sources having different wavelengths; and a light guide plate for confining light from the light source and spreading the light from a light emitting surface, wherein the plurality of light sources are compared with the size of the light guide plate. A surface light source device, wherein a diffusion unit having a diffusion degree corresponding to the directivity of the light source is provided on an optical path of light emitted from the light source and entering the light guide plate.