JPH10301514A - Surface light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to uniformize luminance in a whole display surface without lengthening a distance between a light source and the display surface and to narrow a space for fitting. SOLUTION: A surface light emitting device 10 is constituted of a fluorescent resin plate 1, an LED 2, a substrate 3 and a diffusion plate 4. As a sample, four pieces of LEDs 2 are mounted on the substrate 3, and respective LEDs 2 are confronted with respective corners of the fluorescent resin plate 1. The fluorescent resin plate 1 is made in such a state that a fluorescent material 13 is dispersed in a thin film like translucent resin 12. The fluorescent material 13 dispersed in the translucent resin 12 is irradiated by light from the LEDs 2 to cause exciting light. In the translucent resin 12, a diffusion reflective member 14 is stuck to the nearly whole rear side. Thus, the exciting light generated in the fluorescent material 13 is emitted in the front direction of the fluorescent resin plate 1 through the diffusion plate 4 at a nearly uniform light quantity after it is reflected on the diffusion reflective member 14 at the rear side and end surfaces of the translucent resin 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface light emitting device which constitutes a display surface of a display device for displaying display contents by irradiating a front surface with light.

[0002]

2. Description of the Related Art Some displays and push-button switches mounted on a control panel are configured to irradiate light on the front side to display display contents such as an operation state of a controlled device. In such a display device or the like, in a state where the light source image such as the position and shape of the light source can be visually recognized, the brightness of the display surface is not uniform, and the display state of the display contents is partially different and accurately. Sometimes it is not recognized. Therefore, in a display device or the like that displays display contents such as the operation state of the controlled device by irradiating light to the front surface, it is necessary to make the luminance over the entire display surface uniform in order to enhance the visibility of the display contents. is there.

For this reason, in a conventional display device or the like, as shown in FIG.
In some cases, the display surface is configured by a diffusion plate 52 that diffuses light from a light source incident from the rear surface and emits the light from the front surface. Further, the distance between the diffusion plate 52 and the light source 51 is made sufficiently long so that the position and shape of the light source cannot be visually recognized from the front side via the diffusion plate so that the light source image is erased.

[0004]

However, as shown in FIG. 4, when a large number of minute light sources 51 are provided as the light source, there is a problem that the cost is increased, and the diffusion plate 52 and the light source 51 which constitute the display surface are not provided. If the distance is long enough, the depth of the display 50 becomes long, so that a large mounting space is required, and there is a problem that the space efficiency is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the need for a large number of minute light sources, to make the luminance over the entire display surface uniform without increasing the distance between the light source and the display surface, and to provide a mounting space. It is an object of the present invention to provide a thin surface light emitting device capable of improving space efficiency by reducing the size of the light emitting device.

[0006]

According to a first aspect of the present invention, there is provided a surface light emitting device for irradiating light from a light source to a front surface from a display surface, wherein a fluorescent resin plate made of a transparent resin in which a fluorescent material is dispersed is provided. A light source is arranged opposite to the end face of the fluorescent resin plate, and a diffuse reflection member or a fluorescent member is adhered to the back surface of the fluorescent resin plate.

According to the first aspect of the present invention, light from a light source enters the translucent resin constituting the fluorescent resin plate and is irradiated on the fluorescent substance. The fluorescent substance irradiated with light from the light source is excited, and the excitation light generated in the fluorescent substance repeats total reflection when the emission angle at the boundary surface with air exceeds a certain critical angle, and the emission angle becomes smaller than the critical angle. The light exits from the fluorescent resin plate at a small position. A boundary surface with the air is not formed at the portion where the diffuse reflection member or the fluorescent member is in close contact on the back surface of the fluorescent resin plate, and the critical angle becomes large. Therefore, most of the light traveling in the rear direction in the fluorescent resin plate exits from the fluorescent resin plate to the diffuse reflection member or the fluorescent member, and after being reflected by the diffuse reflection member or the fluorescent member, re-enters the fluorescent resin plate, and the reflection member Out of the light incident on the fluorescent resin plate from the above, light having an incident angle smaller than the critical angle is emitted to the outside from the front surface of the fluorescent resin plate. The light whose incident angle to the fluorescent resin plate is smaller than the critical angle is distributed substantially uniformly over the entire surface of the diffuse reflection member or the fluorescent member, and the light emitted from the front surface of the fluorescent resin plate has a substantially uniform light amount over the entire surface.

The invention according to claim 2 is characterized in that a specular reflection member is adhered to a portion of the side end surface of the fluorescent resin plate other than a portion facing the light source.

In the invention described in claim 2, the excitation light generated from the fluorescent material of the fluorescent resin plate does not exit to the outside from the side end surface of the fluorescent resin plate, and substantially all of the excitation light generated in the fluorescent material is not emitted. Is irradiated directly or after being reflected by the reflection member toward the front surface of the fluorescent resin plate.

The invention according to claim 3 is characterized in that a light-transmitting diffusion plate is arranged on the front surface of the fluorescent resin plate.

According to the third aspect of the present invention, the excitation light generated from the fluorescent substance exits from the front surface of the fluorescent resin plate via the diffusion plate directly or after being reflected by the reflecting member, and is emitted from the fluorescent resin plate. The amount of light emitted in the front direction becomes more uniform.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an assembly diagram showing a structure of a surface emitting device according to an embodiment of the present invention. The surface emitting device 10 includes a fluorescent resin plate 1, an LED 2, a substrate 3, and a diffusion plate 4. 4 LEDs as an example
2 are mounted on the substrate 3, and each of the LEDs 2 faces each of the corners of the fluorescent resin plate 1. For this reason, the four corners of the rectangular fluorescent resin plate 1 are chamfered. As described above, only the diffusion plate 4, the fluorescent resin plate 1, and the substrate 3 are located in the thickness direction of the surface light emitting device 10, and the diffusion plate 4, the fluorescent resin plate 1, and the substrate 3 are all thin plate-like bodies. Therefore, the surface light emitting device 10 is configured to be extremely thin as a whole.

The fluorescent resin plate 1 is made of a thin transparent resin 12.
The fluorescent substance 13 is dispersed in the inside. The fluorescent substance 13 dispersed in the translucent resin 12 generates excitation light when irradiated with external light. The fluorescent substance 13 is excited by light having a short wavelength such as ultraviolet light, for example, and is converted into light having a long wavelength in a visible light region. In the translucent resin 12, a diffuse reflection member 14 is attached to substantially the entire back surface. Further, a specular reflection member 15 is attached to each side end surface of the translucent resin 12.

When the composition of the translucent resin 12 is appropriately selected and the absolute refractive index is sufficiently increased, as shown in FIG. 2, the critical angle at which the excitation light generated by the fluorescent substance 13 is emitted into the air is obtained. Is sufficiently small, and the light-transmitting resin 12 is formed in a thin plate shape, so that the fluorescent substance 1 is formed on the front and rear surfaces of the light-transmitting resin 12 having a relatively large emission angle into the air.
Most of the excitation light emitted from 3 does not exit from the translucent resin 12. At this time, if the diffuse reflection member 14 having an absolute refractive index larger than that of air is adhered to the back surface of the translucent resin 12,
As a result of the increase of the critical angle on the back surface, most of the excitation light generated by the fluorescent substance 13 is emitted to the outside of the translucent resin 12.

Therefore, of the excitation light generated in the fluorescent substance 13 irradiated with the light from the LED 2, the light whose angle with respect to the front surface of the translucent resin 12 is smaller than the critical angle is emitted from the translucent resin 12 as it is, The light is emitted toward the front of the surface light emitting device 10 via the diffusion plate 4. Also, fluorescent substance 1
3, the light having an angle larger than the critical angle with respect to the front surface of the translucent resin 12 out of the excitation light generated in the translucent resin 12
Is totally reflected on the front surface of the transparent resin 12 and advances toward the rear surface or the side end surface of the translucent resin 12.

Since the diffuse reflection member 14 is in close contact with substantially the entire back surface of the translucent resin 12, the critical angle on the back surface increases, so that most of the light traveling in the rear direction is transmitted from the translucent resin 12. The light is emitted to the diffuse reflection member 14, and the diffuse reflection member 1
After being reflected at 4, the light enters the translucent resin 12 again. Further, a specular reflection member 15 is in close contact with substantially the entire side end surface of the translucent resin 12, and most of the light traveling in the side end surface direction is emitted from the translucent resin 12 to the specular reflection member 15, and the mirror surface is reflected. After being reflected by the reflecting member 15, the translucent resin 1
2 is incident. Since the light-transmitting resin 15 has a thin plate shape, of the light that has entered the light-transmitting resin 12 from the specular reflection member 15, most of the light that has traveled toward the front surface of the light-transmitting resin 12 is entirely at the front surface. And the mirror reflection member 1
Almost all of the light that has entered the light-transmitting resin 12 from 5 advances toward the back surface where the diffuse reflection member 14 is in close contact, and is reflected again by the diffusion reflection member 14 and then enters the light-transmitting resin 12 again.

As described above, most of the excitation light generated in the fluorescent substance 13 irradiated with the light from the LED 2 is reflected by the diffuse reflection member 14 and enters the translucent resin 12. Light whose angle with respect to the front surface of the light emitting device 12 is smaller than the critical angle is emitted from the translucent resin 12 and emitted toward the front surface of the surface light emitting device 10 via the diffusion plate 4. In the light reflected by the reflection member 14, the light-transmitting resin 12
The ratio of light occupying an angle smaller than the critical angle with respect to the front surface is considered to be substantially constant over the entire surface of the reflection member 14, and the light emitted toward the front surface of the surface light emitting device 10 has a substantially uniform light amount over the entire surface. Become. Further, the excitation light generated in the fluorescent substance 13 does not exit to the outside from the rear surface and side end surfaces of the translucent resin 12, but all exits in the front direction of the fluorescent resin plate 1. 1, a sufficient amount of light is emitted in the surface direction.

As the diffuse reflection member 14, a white sheet can be used, and a white paint can be applied directly. Further, instead of the diffuse reflection member 14, a fluorescent member constituted by applying a fluorescent sheet or a fluorescent paint can be used. Further, as the mirror reflection member 15, a mirror surface formed in a sheet shape by aluminum plating can be used, and aluminum plating can be directly applied to a side end surface. In addition, the translucent resin 12
Forming a frame whose peripheral surface facing the side end surface of the is mirror-finished,
The translucent resin 12 and the LED 2 may be inserted into this frame. In addition, the arrangement position and the number of the LEDs 2 are as follows.
The number is not limited to four at each corner of the fluorescent resin plate 1, but may be two at each side of the fluorescent resin plate 1 as shown in FIG. In this case, considering the situation where the plurality of surface light emitting devices 10 are installed close to each other, FIG.
As shown in (B), the arrangement position of each side is asymmetrical with respect to the center line, so that the LEDs 2 do not face each other in the adjacent surface light emitting devices 10 and the plurality of surface light emitting devices 10 are brought closer to each other. be able to.

Further, as the substrate 3, a flexible substrate can be used. In addition, an ultraviolet LED that emits ultraviolet light can be used as the LED 2. As the diffusion plate 4, a diffusion plate that diffuses light incident from the back surface and emits the light from the front surface, or a hologram type diffusion sheet can be used. The diffusion sheet of the hologram type has approximately 9
Since 3% of the light is transmitted, external light on the front surface side of the fluorescent resin plate 1 is hardly reflected on the front surface of the fluorescent resin plate 1, and the visibility of the transmitted light of the LED 2 can be improved. .

In addition, a desired name can be displayed when the LED 2 is turned on by providing a translucent name plate in which the display content is indicated by a light-shielding substance or a translucent substance on the front surface of the diffusion plate 4. . Further, by providing a translucent touch switch on the front surface of the diffusion plate 4, a thin display push button switch can be configured.

[0021]

According to the first aspect of the invention, of the excitation light excited by the external light, most of the light traveling in the rear direction inside the fluorescent resin plate is emitted from the fluorescent resin plate to the reflecting member. ,
After being reflected by the reflecting member, it is again incident on the fluorescent resin plate, and of the light incident on the fluorescent resin plate from the reflecting member, light having an incident angle smaller than the critical angle is emitted from the front surface of the fluorescent resin plate to the outside with a substantially uniform light amount. Accordingly, cost reduction can be realized without using a large number of minute light sources, and a device for irradiating surface light without an image of a light source can be configured to be extremely thin, thereby increasing the distance between the light source and the display surface. There is no necessity, and the mounting space can be narrowed to make effective use of the space.

According to the second aspect of the present invention, the excitation light generated from the fluorescent substance of the fluorescent resin plate is prevented from being emitted to the outside from the side end surface of the fluorescent resin plate, and the amount of irradiation light in the front direction of the fluorescent resin plate is reduced. Can be increased.

According to the third aspect of the present invention, the excitation light generated from the fluorescent substance is irradiated directly or after being reflected by the reflection member from the front surface of the fluorescent resin plate via the diffusion plate, thereby providing a fluorescent light. The amount of light emitted toward the front surface of the resin plate can be made more uniform.

[Brief description of the drawings]

FIG. 1 is an assembly diagram showing a configuration of a surface emitting device which is an example of an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an optical path in a fluorescent resin plate included in the surface light emitting device.

FIG. 3 is a diagram showing a surface emitting device according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional light emitting device.

[Explanation of symbols]

 1-Fluorescent resin plate 2-LED (light source) 3-Substrate 4-Diffusion plate 12-Transparent resin 13-Fluorescent material 14-Diffuse reflection member 15-Mirror reflection member

Claims (3)

[Claims] 1. A surface light emitting device for irradiating light from a light source to a front surface from a display surface, comprising: a fluorescent resin plate made of a transparent resin in which a fluorescent substance is dispersed; and a light source facing a side end surface of the fluorescent resin plate. And a diffuse reflection member or a fluorescent member adhered to the back surface of the fluorescent resin plate. 2. The surface emitting device according to claim 1, wherein a specular reflection member is adhered to a portion of the side end surface of the fluorescent resin plate other than a portion facing the light source. 3. The surface emitting device according to claim 1, wherein a light-transmitting diffusion plate is arranged on the front surface of the fluorescent resin plate.