JP2001351424A - Plane light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plane light-emitting device, thin yet with superb uniformity of extremely bright plane illumination with a light source arranged on a plane. SOLUTION: With the plane light-emitting device with one or a plurality of light sources arranged on a plane and a lens placed in front of the light source(s), the irradiating face side of the lens in the light source axis is dented toward the light sources side so that light from the specific spot where the light source is placed is completely reflected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat light emitting device including an indicator light using an LED (light emitting diode), and more particularly, to a flat and excellent uniform light emitting device which realizes bright illumination, and is capable of designing a total reflection lens. The present invention relates to a flat light emitting device including an LED indicator.

[0002]

2. Description of the Related Art In a conventional indicator light or flat light emitting device using a plurality of point light sources, a light source is arranged on a lateral side of a surface, and light is radiated to a diffusion surface using total reflection to provide a uniform light source. The method of realization is widely used. In this method, since the light sources are arranged on the horizontal side, the number of light sources arranged is limited, and the area where the LEDs are arranged cannot be formed as an illuminating surface, and the illuminated area is reduced.

On the other hand, when LEDs are arranged on a plane to serve as a light source, the arrangement of the LEDs becomes uneven as it is, and the diffusers are arranged apart from each other by a pitch equal to or greater than the arrangement pitch of the point light sources to eliminate unevenness of each point light source. That is being done. In this case, there is a disadvantage that the distance between the light source and the light emitting surface becomes long and the device becomes large.

Further, in order to eliminate the unevenness, the thickness of the diffusion plate is increased or the transmittance is reduced. However, in this case, the unevenness is eliminated at the expense of luminance.

In order to improve this, the point light source LE
Potting (filling) D with a transparent resin to form a front lens having a certain thickness is performed. As a result, of the light from the point light source, light above the critical angle is totally reflected at the lens exit surface, and light within the critical angle is diffused outward at the exit surface, and as a result, the position of the diffuser is brought closer to the light source. However, a configuration in which unevenness is less noticeable can be achieved.

A disadvantage of this method is that the LED is made of a transparent resin.
However, it requires a lot of equipment and cost for potting, and the size cannot be significantly reduced.

FIG. 3 shows a display lamp in which a plurality of LEDs 101 are arranged on a plane and illuminates a diffusion plate 102. In this indicator light, in order to eliminate unevenness on the illuminated surface, a diffusion plate 10 is required.
It is necessary to keep a distance of 2 and the surface A has a long distance and a high height. However, there is much light unevenness on the B side.

FIG. 4 shows a conventional example in which the indicator lamp of FIG. 3 is improved.
3 shows a configuration for potting. In this configuration, light incident at an angle larger than the critical angle causes total internal reflection,
While illuminating the LED-side diffusion surface, light within the critical angle becomes divergent light and travels toward the external diffusion plate 202.

However, in the conventional example shown in FIG. 4, light within the critical angle goes directly to the outside, so that the diffusion surface is expanded or
There is no change in that the unevenness must be eliminated by lowering (darkening) the transmittance of the diffusion plate 202.

In the conventional example shown in FIG. 4, the distance to the diffusion plate 202 can be reduced as compared with the conventional example shown in FIG. 3, but a certain distance is required. Inadequate in terms.

[0011]

However, the present invention provides:
In view of the above circumstances, it is an object of the present invention to provide a flat light-emitting device in which LEDs are arranged on a flat surface and which is extremely bright and thin while having excellent surface illumination uniformity.

[0012]

Generally, this type of unevenness and unevenness of the illuminated surface is directly attributable to uneven light incident on the diffuser. This has multiple light sources,
This is because concentrated light from the light source causes non-uniformity. A means must be provided to solve the problem of brightness and size (distance between the light source and the diffuser), which is in opposition to this uniformity.

In order to solve the problem, it is necessary to prevent concentrated light from being directly incident on the diffusing plate. For this purpose, the principle of total reflection and the means of indirect illumination from the diffusing plate are used.

Means for directly blocking light to prevent direct incidence are conceivable. However, since light must someday emerge from the surface and illuminate the diffuser, the direct light can be seen from all angles. Leakage that does not leak results in a reduction in the optical path of the reflected light and a significant decrease in brightness.

The total reflection employed in the present invention is a phenomenon that occurs on the surface of a transparent medium. Light from a specific point (light source) causes total reflection depending on the design of the lens, but light from other parts is generated. Has the advantage that it can be transmitted without being shielded from light.

That is, when the LED side is viewed through the present lens, the LED which is the light source cannot be seen from any angle, but the result that the surface other than the LED is brightly illuminated is obtained.

The totally reflected light diverges and hits a highly reflective diffusion surface provided on the LED light source side, and this surface is illuminated. In other words, a point light source is converted into a surface light source.

This not only avoids concentrated luminous flux but also makes the conventional diffusing surface the same as the LED (ie, the separation distance =
Since the first diffusing surface is formed in 0), the diffusing surface is as close as possible to the LED light source surface, which is effective in shortening the overall length.

If the first diffusion surface (LED light source surface) is designed to have sufficient uniformity, it is not necessary to provide a diffusion plate on the lens exit surface side.

In order to further obtain uniformity, a second diffuser is provided through the thickness of the lens, and the light is diffused simultaneously in the thickness of the lens. In this space, reflection and diffusion are simultaneously performed. The space is reduced and the space factor is extremely excellent.

That is, the means of converting a point light source to a surface light source by a total reflection lens is the best solution for simultaneously realizing uniformity and miniaturization.

Further, according to the present invention, in order to provide a device which has a sufficient tolerance against direct light leakage due to misalignment of the arrangement of the LED and the lens, the shape of the surface for accommodating the LED is formed on a cone in advance. The shape is such that reflection easily occurs.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to a specific embodiment shown in the accompanying drawings using an indicator light as an example.

The present invention provides means for solving the above-mentioned problems, and a specific configuration example is shown in FIG.
FIG. 2 is an enlarged view showing the relationship between the LED 1 of the present invention and the lens 2 disposed on the front surface.

In FIG. 1, not only light other than the critical angle but also light within the critical angle is not directly transmitted through the lens 2 but totally reflected to illuminate the LED-side diffusion surface 3. Most of the light falling on the diffusion surface 3 within the critical angle passes through the lens 2. That is, the singular point (LED arrangement point) constituted by the lens surface
A lens is used which does not transmit light from the other surface and transmits most of the light from the other surface.

Referring to FIG. 2, a specific lens configuration will be described. The feature of the present invention is that the high refractive index side on the optical axis of the LED 1 is recessed in the cone-shaped recess 4.

In a typical example, the cone-shaped recess 4
If the outside of is matched with the point corresponding to the critical angle, the light larger than the critical angle is totally reflected in the plane as before, and the light within the critical angle is set such that the inclination of the cone-shaped recess 4 causes the total reflection. If so, this also causes total reflection, so that all direct light does not leak outside.

In order to realize total reflection stably on an industrial scale, variations in assembly must be considered.

That is, due to variations in the arrangement points of the LEDs 1 and the positions of the lenses 2, if a part of the adjustment light leaks to the outside, the intended place cannot be realized. For this reason, it is desirable to design a lens having a tolerance for some variation such as increasing the inclination of the cone-shaped depression 4 or increasing the outer diameter of the cone-shaped depression 4 as compared with the above typical example.

If this is to be realized only by the lens portion of the cone-shaped depression 4, problems such as an increase in the thickness of the lens 2 and leakage of light incident on the cone-shaped depression 4 from an adjacent light source will occur. In order to solve this, in the example shown in FIG. 2, a surface where light further diverges with respect to the optical axis is arranged around the LED, and a pre-processing in which total reflection easily occurs is performed.

As described above, direct light is totally reflected, and LED
Since the light is diffused to the side diffusion surface 3, the diffusion surface 3 is lowered at once to the arrangement surface of the LEDs 1 as compared with the example shown in FIG. 4, and the overall length is essentially shortened. Actually, even if the lens 2 is arranged on the front surface of the LED 1, the total height cannot be less than this thickness. However, if the illumination pattern (superposition of each node pattern) on the LED side diffusion surface 3 is uniform, An extremely thin planar LED light source can be realized without disposing a diffusion plate on the front surface of the lens.

The problem is the illumination pattern on the LED side, which can be optimally designed in advance by LED pitch and lens shape by computer simulation of ray tracing and superposition of each node pattern.

Even if the pattern is optimally designed, there is some unevenness. If it is desired to eliminate the unevenness, as shown in FIG.
The surface light source on the first diffusing surface 3 is further diffused by the thickness of the lens 2, so that an illuminating surface with extremely excellent uniformity can be obtained.

[0034]

As described above, according to the present invention, since a total reflection lens is disposed on the front surface on each optical axis of a plurality of point light sources, the point light source is converted into a surface light source and the diffusion distance is within the reflection lens. Therefore, an extremely thin planar light emitting device can be provided.

Further, since the light source is a surface light source, it is possible to form an illuminated surface with extremely uniform uniformity. As a result, the total length of the indicator light can be reduced, the space can be reduced, and the space factor of the device can be improved. Further, the height of the display section from the mounting panel surface can be reduced, and a panel having a flat appearance can be provided.

Further, the present invention can be widely applied to not only the indicator lamp but also to a device requiring planar illumination, and can exert the same effect.

[Brief description of the drawings]

FIG. 1 is a schematic view of an indicator light according to a specific embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a schematic view of a conventional indicator light.

FIG. 4 is a schematic view of another conventional indicator light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... LED 2 ... Lens 3 ... LED side diffusion surface 4 ... Cone-shaped recess 5 ... Diffusion plate

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazichi Oishi 3-4-1-1, Nomura, Kusatsu-shi, Shiga Fuji Electric Industries Co., Ltd.

Claims (7)

[Claims] 1. A flat light emitting device in which one or more light sources are arranged on the same plane and a lens is arranged in front of the light source, wherein the lens totally reflects light from a specific point where the light source is arranged. A light emitting axis of the light source, wherein a light exit side of the lens is concave toward the light source. 2. An indicator lamp in which one or a plurality of LEDs are arranged on the same surface and a lens is arranged on the front surface of the LED, wherein the lens totally reflects light from a specific point where the LED is arranged. An indicator light characterized in that the lens emission surface side of the LED light emitting axis is recessed toward the LED light source side. 3. A plurality of lenses on the front surface of the plurality of LEDs are integrated, each having a total reflection surface having a conical recess, and having a diffusion surface on the LED arrangement side. The indicator lamp according to claim 2. 4. The indicator lamp according to claim 2, wherein a diffusion plate is provided adjacent to the surface on the light exit side of the lens, or a diffusion surface having a diffusion surface having a roughened lens surface has a very short diffusion distance. . 5. An indicator lamp comprising only a total reflection lens having a diffusion surface according to claim 2 and having no other diffusion plate. 6. A lens structure for a light source, wherein a coupling portion between the LED light source and the lens is formed of a cone-shaped low refractive index medium (including air) surrounding the LED. 7. A total reflection lens structure in which the lens according to claim 2 is formed of a light diffusing medium.