JP2504417B2 - Surface lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface illumination device applied to a backlight of a transmissive display panel such as a liquid crystal transmissive display panel.

[Background technology]

FIG. 2 shows a conventional example. That is, this surface illuminating device is flat and has one side surface as a light introducing surface 50 and one surface as a Fresnel type reflecting surface 51 for reflecting incident light incident from the light introducing surface 50 and the other surface as a diffusive surface. A light guide plate 53 which is a transmissive light emitting surface 52, a transmissive display plate 55 located in front of the diffusive transmissive light emitting surface 52, and a light source 54 which emits light to the light introducing surface 50 are provided. The rays of light are as shown by arrows, and the transmissive display plate 55 is uniformly illuminated by the critical angle reflection of the diffusive transmissive light emitting surface 52 and the reflection of the reflective surface 51.

FIG. 3 shows another conventional example. That is, in this surface lighting device, the reflecting surface 51 performs a critical angle reflection of a smooth surface, and the outer surface of the reflecting surface 51 is subjected to reflection processing by a reflecting plate or the like.

In all of these conventional examples, it is the diffusive transmissive light emitting surface 52 having a light scattering effect that has brightness.

However, these conventional examples are geometrically critical because they control the direction of light by specular reflection until the light incident on the light introduction surface 50 is scattered from the diffusive transmission light emission surface 52. There is a drawback that unevenness in brightness and unevenness in color easily occur due to variations in size, shape and position of each element of the optical system.

Further, in order to reduce the unevenness of brightness and the unevenness of color, when a transmissive diffusion plate is added to the front surface of the diffusive transmissive light emitting surface 52, the brightness distribution surface is the diffusive transmissive light emitting surface 52 and is close to the transmissive diffuser plate, so There is a drawback that the efficiency cannot be made uniform without using a transmissive diffusion plate having a low transmittance at the sacrifice of efficiency and the light efficiency is lowered. In addition, there is a drawback that the transmission diffusion plate 55 is separated from one another and becomes large in size.

Further, as shown in FIG. 4, in order to obtain a large area and high brightness, when the opposite sides of the pair of light guide plates 53 to the light introduction surface 50 are integrally connected, the brightness peaks at the central portions 56 of the light guide plates 53, 53. Alternatively, there are drawbacks that a dip can be made and that the light guide plates 53, 53 are likely to have a brightness difference due to variations in the light source 54.

[Object of the Invention]

An object of the present invention is to provide a surface illuminating device capable of achieving high brightness and uniform brightness distribution without increasing the size and reducing the light efficiency.

[Disclosure of Invention]

The surface lighting device of the present invention is a flat plate and has one side surface as a light introduction surface and one surface as a diffuse reflection surface for incident light incident from the light introduction surface, and the other surface as a diffuse reflection surface. The light-introducing surface of the transmissive surface is a top surface of a convex curved surface that is a transmissive surface that transmits light and that reflects incident light incident from the light-introducing surface to a side opposite to the light-introducing surface of the diffuse reflection surface by a critical angle. A light guide plate formed on the side, a transmissive diffusion plate disposed on the front surface of the transmissive surface, and a light source that emits light to the light introducing surface.

According to the configuration of the present invention, since the side opposite to the transmissive surface of the light guide plate is the diffuse reflective surface, the diffuse reflective surface serves as a pseudo light source, and since the diffuse reflective surface and the transmissive diffuser plate are separated from each other, the size can be increased as in the conventional case. It is possible to achieve high brightness and uniform brightness distribution without lowering the light efficiency. Further, since the convex curved surface is formed on the light introduction surface side of the transmission surface, the reflected light can be sufficiently sent to the side of the diffuse reflection surface away from the light introduction surface, and the brightness distribution of the diffuse reflection surface can be made uniform. Therefore, the brightness of the transmission diffusion plate can be made more uniform.

Embodiment An embodiment of the present invention will be described with reference to FIG. That is, this surface illuminating device is flat and has one side surface as a light introduction surface 1 and one surface as a diffuse reflection surface 2 for incident light incident from the light introduction surface 1 and the other surface as the diffuse reflection surface. The convex surface 3 is used as a transmission surface 4 that transmits the scattered light of the surface 2 and that reflects the incident light incident from the light introduction surface 1 to the opposite side of the diffuse reflection surface 2 from the light introduction surface 1 by a critical angle.
A light guide plate 5 whose top surface is formed on the light introduction surface 1 side of the transmission surface 4, a transmission diffusion plate 6 arranged in front of the transmission surface 4, and a light source which emits light to the light introduction surface 1. 7 and 7.

The light guide plate 5 is formed of a transparent material such as acrylic resin in a flat plate shape.

The diffuse reflection surface 2 is diffused so as to scatter light by painting, printing, adhesion of a diffusible resin plate, sandblasting, or chemical treatment. The diffuse reflection surface 2 has a function of a pseudo light source that diffuses the incident light a incident from the light introduction surface 1 and makes it incident on the transmission diffusion plate 6 from the transmission surface 4. Since this diffuse reflection surface 2 is separated from the transmission diffusion plate 6, the effect of eliminating uneven brightness and uneven color of the diffuse reflection surface 2 is high, and uniform light emission can be obtained. If there is light leaking outward from the diffuse reflection surface 2, a reflection member (not shown) may be further provided near the outside of the diffuse reflection surface 2.

Although the transmitting surface 4 is a smooth surface, the convex curved surface 3 is formed in order to make the luminance distribution of the diffuse reflecting surface 2 uniform.
That is, when the convex curved surface 3 is not provided, the incident light entering from the light introducing surface 1 is more incident on the side closer to the light introducing surface 1 of the diffuse reflection surface 2, so that the brightness is high and the farther from the light introducing surface 1, the lower the brightness. Become. On the other hand, since the convex curved surface 3 is provided so that the critical-angle reflected light b on the back surface side of the transmission surface 4 is incident on the diffuse reflection surface 2 on the side away from the light introduction surface 1, the brightness of the diffuse reflection surface 2 is reduced. The distribution can be made uniform.

The light introduction surface 1 is formed as a smooth surface, but is inclined so as to approach the transmission surface 4. Thereby, the light introduction surface 1 of the diffuse reflection surface 2 of the incident light incident from the light introduction surface 1
The incident light to the side is decreased, and the light incident on the inner surface of the convex curved surface 3 is increased to increase the reflected light to the position of the diffuse reflection surface 2 away from the light introduction surface 1 to increase the brightness of the diffuse reflection surface 2. The distribution is uniform.

The transmission diffusion plate 6 is a sheet or a plate member and is arranged in front of the transmission surface 4. By the way, diffuse reflection surface 2
Since the incident angle of the light incident on the light is extremely small, the position of the incident light incident on the diffuse reflection surface 2 varies greatly depending on the shape accuracy of the light guide plate 5 and the displacement of the light source 7, etc., which causes uneven brightness. Further, if the path of the incident light incident on the diffuse reflection surface 2 is different, color unevenness due to the spectrum due to refraction or the spectral characteristic of the transmittance of the light guide plate 5 may occur. However, by providing the transmissive diffusion plate 6, the final brightness can be made uniform.

As the light source 7, for example, an aperture type straight tube fluorescent lamp is used as an example so that the utilization efficiency of light is increased, and an opening 8 having a width narrower than the thickness of the light introducing surface 1 is provided.
Facing.

The side surfaces of the light guide plate 5 other than the light introduction surface 1 and the transmission surface 4 are provided with a reflection plate 10 for preventing light from leaking from the light guide plate 5, or are subjected to a reflection treatment (not shown).

Further, a transmissive display plate 9 is arranged in front of the transmissive diffusion plate 6.

According to this embodiment, since the side opposite to the transmissive surface 4 of the light guide plate 5 is the diffuse reflective surface 2, the diffuse reflective surface 2 serves as a pseudo light source, and the diffuse reflective surface 2 and the transmissive diffuser plate 6 are separated from each other. It is possible to achieve high brightness and uniform brightness distribution without increasing the size and without transmitting light efficiency. Further, since the convex curved surface 3 is formed on the light introducing surface 1 side of the transmitting surface 4, the reflected light can be sufficiently sent to the side of the diffuse reflecting surface 2 away from the light introducing surface 1, and the brightness distribution of the diffuse reflecting surface 2 can be improved. Therefore, the brightness of the transmission diffusion plate 6 can be made more uniform.

In addition, since the light emitting surface is enlarged, even if the structure is configured as shown in FIG. 4, it is difficult for a brightness peak or a dip in the central portion of the light guide plates 5 and 5 and a brightness difference between the light guide plates 5 and 5 to appear. It can emit light uniformly.

The transmissive display plate 9 may be formed by printing a pattern on, for example, a milky white acrylic plate to form the transmissive diffusion plate 6 as the transmissive display plate 9.

〔The invention's effect〕

According to the surface lighting device of the present invention, since the side opposite to the transmissive surface of the light guide plate is a diffuse reflective surface, the diffuse reflective surface serves as a pseudo light source, and since the diffuse reflective surface and the transmissive diffuser plate are separated from each other, the size is increased as in the conventional case. It is possible to achieve high brightness and uniform brightness distribution without decreasing the light efficiency. Since a convex curved surface is formed on the light introduction surface side of the transmission surface,
The reflected light can be sufficiently sent to the side of the diffusive anti-slope that is far from the light introduction surface, and the luminance distribution of the diffuse reflection surface can be made uniform. Therefore, the luminance of the transmissive diffusion plate can be made even more uniform. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention, FIGS. 2 and 3 are side views of another conventional example, and FIG. 4 is a case where a pair of light guide plates are connected. It is explanatory drawing seen from the side surface. 1 ... Light introduction surface, 2 ... Diffuse reflection surface, 3 ... Convex curved surface, 4
...... Transparent surface, 5 ...... Light guide plate, 6 ...... Transparent diffusion plate, 7 ......
light source

Claims (3)

(57) [Claims] 1. A flat plate having one side surface as a light introduction surface and one surface as a diffuse reflection surface for incident light incident from the light introduction surface, and the other surface for transmitting scattered light from the diffuse reflection surface. And a top surface of a convex curved surface that reflects the incident light incident from the light introduction surface to the side opposite to the light introduction surface of the diffuse reflection surface by a critical angle is formed on the light introduction surface side of the transmission surface. 2. A surface lighting device comprising: the light guide plate, a transmissive diffusion plate disposed in front of the transmissive surface, and a light source that emits light to the light introducing surface. 2. The surface lighting device according to claim 1, wherein the transmissive diffusion plate is configured as a transmissive display plate arranged in front of the transmissive surface. 3. The surface lighting device according to claim 1, wherein the light introduction surface is inclined so as to approach the transmission surface side.