JP2002100226A - Surface light emitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simulate a surface light source using a light emitting diode. SOLUTION: A notch 6 is formed on one side of a light guide plate 5 made of a transparent acrylic resin having a thickness of 10 mm. A light emitting diode 7 is positioned within the notch such that the diode faces the inside of the light guide plate. Straight grooves 9 perpendicular to the axis of the LED are formed on a back face of the light guide plate. Each groove has a V shape cross section. Light emitted from the light emitting diode propagates through the inside of the light guide plate 5 and proceeds toward the back face of the light guide plate directly or after total reflection at a front face. The light goes out from the front face of the light guide plate after total reflection at the inclined faces of the V shape grooves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar illuminant that generates a surface light source in a pseudo manner using a point light source such as a light emitting diode (LED), and can be used as a guide sign.

[0002]

2. Description of the Related Art In a surface light source of this type, a light emitting diode is arranged around a transparent plate (light guide plate) so as to allow light to enter, and the light guide plate is covered with a reflector except for the front surface. Things. Usually, fine irregularities are provided on the rear surface of the light guide plate so that light is irregularly reflected. In such a device, the light incident on the inside of the light guide plate from the light emitting diode repeats total reflection on the front surface of the light guide plate and reflection on the rear reflector, and finally, the light guide, which is the only light outlet. Go out from the front of the light plate. Thus, the entire surface of the light guide plate appears to be shining to human eyes.

[0003] However, there are several problems with such a device. First, since light is repeatedly reflected inside the light guide plate before it goes out of the light guide plate, the process of light inside the light guide plate becomes longer and light is attenuated. For this reason, a light guide plate having good transparency is required. Also, when the light is reflected by the reflector, the light is attenuated.

[0004] The next problem is the problem of the angle of light exiting from the front surface of the light guide plate. It is desirable that the light exits the light guide plate at a right angle or close thereto, but such light is less due to repeated reflection, and most of the light exits along the front surface of the light guide plate. For this reason, it does not feel so bright to human eyes.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a more efficient planar light-emitting device.

[0006]

When a point light source, for example, a light emitting diode, is arranged around an ordinary (no groove) light guide plate, light emitted from the luminous body passes through the inside of the light guide plate and passes through the light guide plate. Reach front or back. Near the light source,
Most of the light exits through the front and rear surfaces of the light guide plate. However, as the distance from the light source increases, the angle of incidence with respect to the front and rear surfaces of the light guide plate gradually increases. When the angle exceeds a certain angle (about 42 degrees in the case of acrylic resin), the light is totally reflected by the front and rear surfaces of the light guide plate. It does not go outside (total reflection). The light that has been totally reflected in this manner is totally reflected again on the opposite surface, and since such total reflection is repeated many times, it is difficult to go outside.

In the planar light emitting device of the present invention, a number of linear grooves are provided in parallel on the entire rear surface of the transparent light guide plate, and the inside of the light guide plate is formed on a side portion of the light guide plate from a direction perpendicular to the grooves. A point-like light emitter that emits light is arranged. Each of these grooves has a first inclined surface slightly inclined toward the luminous body from the rear surface of the light guide plate (claim 1).

[0008] According to this structure, light from the luminous body toward the rear surface through the light guide plate is totally reflected by the first inclined surface, but the first inclined surface is slightly more luminous than the light guide plate. The light is totally reflected from the light guide plate in a direction close to a right angle. For this reason, when reaching the front surface of the light guide plate, it has a relatively small incident angle, so that the light can pass through the front surface of the light guide plate without being totally reflected at the front surface of the light guide plate and go out at an angle close to a right angle as it is. .

Further, the light that has exited the luminous body and traveled toward the front surface of the light guide plate is totally reflected at the front surface, and then travels toward the rear surface. Thereafter, as in the above case, the light is totally reflected by the first inclined surface and can go out at an angle close to a right angle from the front surface of the light guide plate.

As described above, since the light emitted from the luminous body exits from the front surface after one or two reflections, the distance passing through the light guide plate is small, and the light is not weakened. Also, since the reflection is total reflection, there is almost no attenuation of light. In addition, light that exits from the front of the light guide plate exits at an angle close to a right angle with respect to the light guide plate, so that a person viewed from the front can feel bright.

The light emitted from the luminous body in the direction of the optical axis is directed to the opposite side surface of the light guide plate. In order to effectively utilize this light without escaping, in the present invention, the light guide plate has the opposite side to the luminous body. In each of the grooves provided on the rear surface of the light guide plate, the side surface is covered with a reflector, and not only the first inclined surface but also a second inclined surface slightly inclined toward the reflector from the rear surface of the light guide plate is provided. (Claim 2).

[0012] With this configuration, light emitted from the light emitter slightly downward from the horizontal is reflected by the reflector on the opposite side surface, and travels toward the rear surface of the light guide plate. This light is totally reflected by the second inclined surface, and can go out from the front surface of the light guide plate at an angle close to a right angle to the light guide plate.

In this planar light-emitting body, most of the light exiting from the front surface is totally reflected by the grooves arranged on the rear surface, so that these grooves appear to shine in stripes. In order to eliminate such light stripes, according to the present invention, a transparent cover plate is disposed in front of the light guide plate, and grooves perpendicular to the grooves of the light guide plate are densely formed on the rear surface thereof. ). By doing so, since the light emitted from the light guide plate is reflected in various directions by the grooves of the cover plate, the stripes disappear, and the entire surface appears to shine uniformly.

As the point light emitter, an incandescent lamp can be used in addition to the light emitting diode. The light-emitting diode can be turned on using a commercial power supply, but since power consumption is small, power generated by a solar cell in the daytime can be stored in a storage battery or a capacitor, and the stored power can be used to blink at night.

The solar cell panel for driving the point light emitters may be arranged on the back side of the light guide plate. In the daytime, sunlight can pass through the light guide plate and reach the solar cell panel, thereby reducing the size of the entire device.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is used as a guide light embedded in a pavement surface will be described. FIG.
As shown in FIG. 1, the guide light 1 is housed in a box-shaped plastic case 2 composed of a main body and a lid. Reference numeral 3 denotes a water seal packing.

The light guide plate 5 housed in the case 2 is a plate made of a transparent acrylic resin having a thickness of about 10 mm, and has a notch 6 formed on one side as shown in FIG. The light emitting diodes (LEDs) 7 are arranged toward the inside of the light guide plate. On the rear surface of the light guide plate, linear grooves 9 perpendicular to the axis of the LED are densely formed. Each groove has a V-shaped cross section, the angle of the V-shaped is, for example, 120 degrees, and the depth is, for example, 0.5.
mm. The left inclined surface (facing the direction of the LED 7) of the V-shaped cross section is the first inclined surface 10 and the right inclined surface (LED
And facing the opposite direction. ) Form the second inclined surface 11. The rear surface and the peripheral surface of the light guide plate 5 are covered with a reflector (stainless steel plate) 12, as shown in FIG.

The case lid 2a is made of transparent plastic,
As shown in FIG. 3, linear grooves 13 are densely provided on the rear surface. These grooves 13 are provided at right angles to the grooves 9 of the light guide plate. The groove 13 has a V-shaped cross section, which is the same as the groove of the light guide plate.

In the case 2 and around the light guide plate 5, a total of four
One solar cell panel 15 is arranged. An electronic substrate 16 is arranged below the light guide plate 5. A capacitor 17 for storing the power of the solar cell (or a storage battery) is provided on the electronic substrate.
Attach.

First, the operation of the present device will be described with reference to FIG. 4 (block diagram of an electric circuit). When the surroundings are bright, a current flows from the solar cell 15 to the capacitor 17 through the backflow prevention diode 19, and the capacitor is charged. Is done.
When the surroundings become dark, the electromotive force of the solar cell drops, so the sunshine discriminating circuit 20 detects this, activates the transmission output circuit 21 and blinks the LED 7 with the power stored in the capacitor.

FIG. 5 is a cross-sectional view of the light guide plate showing the path of light emitted from the LED slightly downward. Light 25 that has reached the rear surface of the light guide plate directly from the LED 7 is totally reflected by the first inclined surface 10 of the V-shaped groove 9 and goes out from the front surface of the light guide plate.
The light 26 that has reached the side surface directly from the LED is reflected by the reflector 1
The light is reflected at 2 and goes to the rear surface of the light guide plate. This light is likewise V
The light is totally reflected by the second inclined surface 11 of the groove and goes out from the front surface of the light guide plate. The light exiting from the light guide plate 5 in this manner does not go out of the light guide plate, but exits at an angle close to a right angle, as can be clearly understood from FIG.

FIG. 6 shows the path of light emitted from the LED slightly upward. Light reaching the front surface of the light guide plate from the LED is totally reflected, and travels toward the rear surface or side surface of the light guide plate. The light 27 traveling toward the rear surface is totally reflected by the first inclined surface 10 of the V-shaped groove, and goes out from the front surface of the light guide plate. Further, the light 28 reaching the side surface is reflected by the reflector 12, goes to the rear surface of the light guide plate, is totally reflected by the second inclined surface 11 of the V-shaped groove, and goes out from the front surface of the light guide plate. The light exiting from the light guide plate 5 in this manner also exits at an angle close to a right angle, rather than exiting just below the light guide plate.

5 and 6, the light exiting from the front surface of the light guide plate is totally reflected immediately before by the groove 9 on the rear surface of the light guide plate. Grooves shine strongly and look like stripes. However, there is a groove 13 on the back surface of the lid 2a of the case, and the groove is oriented at a right angle to the groove of the light guide plate, so that the light emitted from the light guide plate passes through the groove of the cover plate as shown in FIG. The light is scattered, the stripes disappear, and the entire surface appears uniformly shining.

Although the front of the guide light of this embodiment merely shines brightly, it is not shown, but if characters are drawn on the cover lid 2a or a dial is attached, the characters can be brightly raised at night. be able to.

Next, an embodiment will be described in which a lane marking in a parking lot or the like is used as a marker for displaying it in an easily understandable manner. As shown in FIG. 7, the light guide plate 5 is formed to be elongated, and a V-shaped groove 9 similar to that of the above embodiment is formed on the back surface thereof. Light is sent from the light emitting diode 7 into the light guide plate, and the light is totally reflected on the back surface of the light guide plate and exits from the entire front surface, as in the case of the above-described embodiment.

There are four solar cell panels 15, all of which are mounted on the back side of the light guide plate 5 to reduce the size. During the daytime, sunlight passes through the light guide plate 5 and reaches the solar cell panel 15 without providing a reflector on the back surface of the light guide plate 5. A light emitting diode 30 is also provided at the end, which simply acts as a point light source. Code 31
Is a storage battery.

[Brief description of the drawings]

FIG. 1 is an overall view of a guide light.

FIG. 2 is a detailed view of a light guide plate.

FIG. 3 is a cross-sectional view of a case lid.

FIG. 4 is a block diagram of an electric unit.

FIG. 5 is a diagram showing a path of light emitted slightly downward from an LED.

FIG. 6 is a diagram showing a path of light emitted slightly upward from an LED.

FIG. 7 is an explanatory diagram of a parking lot section marker showing another embodiment.

[Explanation of symbols]

 2a Case lid (cover plate) 5 Light guide plate 7 Light-emitting diode (point-like illuminant) 9 Groove 11 First inclined surface 12 Second inclined surface 13 Groove 15 Solar cell panel

Claims (4)

[Claims] 1. A light guide plate made of a transparent material in the shape of a plate and having a plurality of linear grooves provided in parallel on the entire rear surface thereof, disposed on a side of the light guide plate, and viewed from a direction perpendicular to the grooves. A planar light emitting device comprising a point light emitter for emitting light inside the light guide plate, wherein each of the grooves has a first inclined surface slightly inclined toward the light emitter from a rear surface of the light guide plate. body. 2. The light guide plate, wherein a side surface of the light guide opposite to the light emitter is covered with a reflector, and each of the grooves has, in addition to the first inclined surface,
The planar light emitting device according to claim 1, further comprising a second inclined surface slightly inclined toward the reflector from a rear surface of the light guide plate. 3. The light guide plate according to claim 1, wherein a transparent cover plate is disposed in front of the light guide plate, and the cover plate has, on a rear surface thereof, a groove perpendicular to a groove of the light guide plate. 3. The planar light-emitting body according to item 1. 4. The planar light emitting device according to claim 1, wherein a solar cell panel for driving the point light emitting device is disposed on the back side of the light guide plate.