JPH08241051A - Both side light emission type surface light source - Google Patents

Abstract

PURPOSE: To inexpensively provide a both side light emission type surface light source which is thin, light in weight, is easy to handle, is low in light loss and provides uniform and high luminance in spite of the surface light source of being a both side light emission type. CONSTITUTION: This surface light source consists of a box 2 of which inside surfaces are formed as light reflection surfaces, and light sources 1 built in the box. At least the two wall surfaces 5, 6 facing each other of the box are uniformly provided with many pieces of light transparent regions 3. These light transparent regions 3 are so formed that the ratio of the light transparent regions to the wall surfaces is higher the furtherer from the light sources. The light of the light source is radiated from at least the two wall surfaces facing each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual emission type planar light source. More specifically, the present invention relates to a double-sided light emitting surface light source for panel display, which is suitable for street signboards, hanging advertisements in cars such as trains, and other illuminated signboards to be observed from both sides.

[0002]

2. Description of the Related Art Conventionally, a light bulb, a fluorescent lamp, or the like has been used as a light source for a panel display that irradiates light from the back side used for a liquid crystal display panel, an electric signboard for advertising in stations, and the like. For example, as shown in FIG. 16, the configuration is such that light sources such as a fluorescent lamp 21 are arranged in a reflection case 22, and a display panel or the like is irradiated through a diffusion plate 23 or directly. In order to uniformly irradiate the entire surface of the panel using the panel, it is necessary to separate the panel and the light source (for example, a panel of 1 m square has to be separated by 15 cm or more), and a large depth space is required.
When using such a device to make a dual-sided emission type planar light source with both front and back sides as display panels, double the thickness is required,
Requires more depth space.

On the other hand, in order to reduce the depth of the back surface of the display panel, a planar light source that takes in light from the side surface of the light guide plate and radiates the light from the surface is arranged on the back surface of, for example, a liquid crystal display panel. Sometimes used as. As shown in FIG. 17A, such a planar light source includes a linear light source 1, a light guide plate 12 that takes in the light of the light source 1 from a side wall and emits the light from the front surface side, and from the light guide plate 12. Light diffusing plate 13 for diffusing the above light to the liquid crystal display panel side, and a prism sheet 1 for directing the light from the light diffusing plate 13 to the front side to increase the intensity of the light viewed from the front.
4 is known. The light guide plate 12 is formed of a transparent plate such as acrylic resin, and a dot pattern 15 for reflecting light is provided on the back surface of the light guide plate 12.
A reflection sheet 17 is provided on the side surfaces other than the side surface on which the light source 1 is provided. The dot pattern 15 is provided by screen printing or the like by mixing glass spheres in the ink, and the light emitted to the back surface side of the light guide plate 12 is reflected by the glass spheres and radiated to the front surface side.
A reflection plate 16 made of a metal plate or the like is further provided on the back surface side of the light guide plate 12, and the light which is emitted from the back surface of the light guide plate 12 and is not reflected by the dot pattern 15 and transmitted to the back surface side is transmitted to the front surface side of the light guide plate 12. The light is reflected to improve the light utilization rate. Further, a reflection film 18 is provided around the light source 1 so that the light from the light source 1 is effectively introduced into the light guide plate 12. Therefore, on the side where the light is introduced into the light guide plate 12 in the vicinity of the light source 1, uniform light cannot be obtained at the end portion where the light is incident, and the area P of each of the regions P shown in FIGS. The range must be secured as a clearance separately from the light emitting surface Q.

The light diffusing plate 13 is provided on the surface side of the light guide plate 12 so that even light emitted in an oblique direction is uniformly radiated in all directions on the surface. Further, a prism sheet 14 is provided so that the light is condensed on the front side. The light diffusing plate 13 is made of polyethylene terephthalate (PET), polycarbonate or the like, and is formed to have a thickness of about 120 to 150 μm. The prism sheet 14 is made of polycarbonate or the like, and the surface cross section thereof is as shown in FIG. It is formed into a triangular prism and has a thickness of about 120 to 250 μm. If a double-sided light emission type planar light source with both front and back surfaces as display panels is used in such a device, the dot pattern 15 and the reflection plate 16 cannot be provided on the back surface of the light guide plate, and the inside of the light guide plate is the first. The light cannot be propagated to, and the light is emitted only from the upper and lower surfaces near the light source,
It is not possible to emit light uniformly over the entire surface. Therefore, even when a planar light source of the dual emission type is manufactured using the planar light source using the light guide plate, the structure having the structure as shown in FIG. 17 (a) must be stacked with the reflector plates back to back. .

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In order to make both sides emit light in the conventional illuminated signboard system using a fluorescent light or electric light as a light source, a depth of about twice that of single-sided light emission is required. The thickness is 25 cm or more, and a uniform planar light source cannot be obtained unless the number of light sources is increased. Therefore, a large space is required and a large amount of power is required. Therefore, it is difficult to use a double-sided display panel that uses a light source because a double-sided illuminated signboard is installed on the street, a moving sign is installed in an automobile, etc. There is.

Further, in a planar light source using a light guide plate, since the light guide plate is made of acrylic resin or the like, the weight becomes heavier as the size becomes larger, and becomes heavier when stacked back to back. Furthermore, even in the case of a transparent substrate, the light travels in the resin, so the light is attenuated, the light is taken in from the side surface of the light guide plate, and the light is reflected on the back surface side of the light guide plate and radiated to the front surface side. There is a problem that the efficiency of introducing light into the light plate is poor, the light utilization efficiency is extremely reduced, and a light source with a large output is required to obtain a desired brightness.

Further, in addition to the light emitting surface, a space for arranging the light source and a clearance which does not contribute to the light emitting surface on the light source side of the light guide plate must be secured, which requires a large area, and this planar light source is arrayed. Alternatively, there is a problem that a large screen cannot be formed by arranging them in a matrix.

The present invention solves such a problem, and even a planar light source of a dual emission type is thin and lightweight, easy to handle, has a small light loss, is uniform, has high brightness, and has a desired size. An object is to provide a mold surface light source at low cost.

[0009]

A dual emission type surface light source according to the present invention comprises a box body having an inner surface formed as a light reflecting surface and a light source incorporated in the box body, and at least the box body. A large number of light transmission regions are provided evenly on two opposing wall faces, and the light transmission regions are provided such that the ratio of the light transmission regions to the wall face increases as the distance from the light source increases. The light from the light source is emitted from the two wall surfaces.

Here, the light source means a light bulb, a halogen lamp,
A point light source such as a light emitting diode, a rod-shaped light source such as a rod-shaped fluorescent lamp, or a line-shaped arrangement of the point light sources is meant to include a linear light source that emits light over an elongated range and a ring-shaped light source.

The light transmitting region is also provided in a portion of the two facing wall surfaces facing the light source, and the increase rate of the ratio of the light transmitting region in the portion facing the end portion in the radial direction of the light source is the above. Being formed to be larger than the increase rate of the above ratio at the position away from the light source eliminates the dark part due to the shadow of the light source and allows a wide surface on the wall surface without providing a light diffusion plate or the like through the space. It is preferable because uniform brightness can be obtained over the entire area.

It is formed at the edge portion that the ratio of the light transmission region at the farthest end from the light source is smaller than the maximum value of the ratio of the light transmission region on each of the two wall surfaces. It is preferable because the brightness can be made uniform.

In order to increase the ratio of the light transmitting regions, the areas of the light transmitting regions may be sequentially increased, or the pitch thereof may be decreased.

At least the wall surface of the box body on which the light transmission region is provided is made of a metal plate, and the light transmission region is a through hole or a slit formed on one wall surface of the box body made of the metal plate. It is preferable because it can be easily formed with a mold or the like.

Further, at least the wall surface of the box body on which the light transmission region is provided is made of a transparent substrate provided with a light reflection film, and a part of the transparent substrate is provided with a region where the light reflection film is not provided. Even if the region is the light transmitting region, the light reflecting film can be easily formed by printing or the like, and the box is sealed without holes or slits penetrating therethrough, which is preferable because dust or the like does not enter. .

Since the light reflecting film is provided so as to transmit a part of light instead of a perfect light reflecting surface, it is possible to make the brightness uniform between the light transmitting area on the surface and the light reflecting surface. It is preferable for the purpose.

At least a part of the side walls adjacent to each of the two facing wall surfaces is a light transmitting wall or a wall surface provided with light transmitting regions uniformly, and at least a part of the side walls is also a light emitting surface. However, the side wall is also preferable because it can be used as the display surface.

If the reflectors for reflecting the light of the light source to the two wall surfaces facing each other are provided in the box body, the brightness of the light emitting surface can be made uniform by adjusting the angle of the reflectors. It is preferable because it is easy to plan.

It is rare that the light source is provided in the central portion of the reflector so that the light can be supplied into two spaces surrounded by the reflector and each of the two facing wall surfaces. It is easy to achieve uniform brightness on the light emitting surface.

In the large-sized dual emission type planar light source of the present invention, the dual emission type planar light sources according to claim 1 are arranged in an array or a matrix.

[0021] A part or all of the side wall surface of the joint portion of each of the arrayed dual emission type planar light sources is removed,
Alternatively, it is preferable that the light-transmitting wall or the light-transmitting region is formed on the wall surface provided uniformly, because it is difficult to form stripes at the joint portion of the planar light source.

The ratio of the light transmitting region in the light emitting surface of the joint portion of each of the arrayed dual emission type planar light sources is adjusted so that the luminance of the joint portion is made uniform.
This is preferable because a large-sized dual emission type planar light source with uniform brightness can be obtained.

[0023]

According to the present invention, a light source is built in a box whose inner surface other than the light transmitting region is a light reflecting surface, and the light is at least opposed to each other while reflecting the space in the box on the inner surface. Since the light is emitted from the light transmission area provided on one wall,
All the light from the light source can be taken into the box without loss,
Light absorption in space is very small, and almost all the light from the light source is taken out from the light transmitting region and contributes as a double-sided emission type planar light source. Therefore, there is no loss when light is taken into the conventional light guide plate, and there is no light absorption loss due to the progress in the light guide plate.
The light utilization efficiency is greatly improved. In addition, since the light transmitting areas are provided on the two facing wall surfaces, light is emitted from both surfaces, while the light reflecting surfaces are provided except for the light transmitting areas, so that the light is reflected inside the box even between the two facing wall surfaces. While the light advances. Moreover, since the interior is a space, it can be made lightweight and thin.

Further, according to the present invention, since the ratio of the light transmission region to the wall surface for extracting light is small in the vicinity of the light source and increases as the distance increases, it becomes closer to the light source. Where there is a large amount of light, light is emitted from a place with a small proportion of the light-transmitting region, and where there is a small amount of light from a light source, light is emitted from a place with a large proportion of the light-transmitting region, resulting in light with uniform brightness from the surface. Is emitted. In this case, when the light emitted from the two opposite wall surfaces is obtained from the common light source, the patterns of the light transmitting regions of the two opposite wall surfaces are formed in the same manner, and the inside is partitioned by the reflection plate to separate the different light sources. When used, a pattern of light transmitting regions is formed according to the distance from each light source.

When the light transmitting region is also provided on the wall surface of the portion facing the light source, the reflected light from the wall surfaces facing each other with the light source interposed therebetween does not reach, so that the light source faces the end portion in the radial direction. If the rate of increase of the ratio of the light transmitting region of a part is made larger than that of the other part, the brightness becomes uniform over the entire surface.

According to the large-sized double-sided surface light source of the present invention, a large-sized double-sided surface light source is formed only by arranging the double-sided surface light sources according to claim 1 in an array or matrix. It is possible to easily make a desired size. In this case, if the brightness of the seam of the planar light source is not uniform, adjust the ratio of the light transmission area or set it to 100%.
By forming the light transmitting region, a large-sized dual emission type planar light source with uniform brightness can be easily obtained.

[0027]

EXAMPLES Next, the surface light source of the present invention will be described.
FIG. 1 is a diagram for explaining the principle of the planar light source of the present invention, (a)
Is a cross-sectional explanatory view showing the progress of the light from the light source 1 in the box body 2 formed by the reflecting surface, and (b) is radiated from the light transmitting regions 3 provided on the upper and lower two wall surfaces of the box body 2 facing each other. 2 to 10 are views showing an example of a light transmission region provided on the front side upper wall surface of the box body 2 (the same light transmission is performed on the opposite back side wall surfaces). The pattern of the area is formed, but its description is omitted).

When the light source 1 is arranged in the box body 2 formed of a light reflecting surface (hereinafter, also simply referred to as a reflecting surface), light is emitted from the light source 1 in all directions, but light is transmitted through the box body. As shown in FIG. 1 (a), since the area other than the area is a reflecting surface, the reflecting surface reflects the light and advances in a direction away from the light source 1, and when it reaches the end side wall 4, the side wall 4 reflects and returns. ,
Further, it advances in the box body 2 while repeating reflection. By increasing the reflectance of this reflecting surface, the light travels in the box body 2 without being attenuated.

Light-transmitting regions 3 that do not serve as reflecting surfaces are provided on the opposite wall surfaces on the front surface side and the back surface side of the box body 2, and as shown in FIG. The traveling light is emitted from the light transmitting region 3 to the outside of the box body 2. Therefore, of the light emitted from the light source 1, the light traveling toward the reflecting surface is reflected and travels inside the box body 2, and the light traveling toward the light transmitting area 3 is emitted from the light transmitting area 3 to the outside of the box body 2. It The light emitted from the light transmitting region 3 to the outside of the box body 2 may be the light emitted in an oblique direction as shown in FIG. 1B, and the light is also emitted in the gap between the light transmitting regions 3. It seems to be present, and uniform radiation is obtained over the entire surface. In particular, by providing a light diffusing plate (not shown) on the surface of the wall surface provided with the light transmitting region 3, omnidirectional and uniform light emission can be obtained on the surface of the light diffusing plate. The light diffusing plate may be separately provided on the surface of the wall surface provided with the light transmitting region, or a light diffusing plate or a laminate of a diffusion sheet and a transparent substrate may be used to form the light transmitting region and the light. The diffusing plate may be integrally formed. Further, the light emitted from the light transmitting region 3 has a larger incident angle (closer to the wall surface) in the direction in which the incident angle is larger as the light transmitting region 3 is farther from the light source 1.
As shown in FIGS. 12 to 13, a reflection plate is inserted between two wall surfaces facing each other, and the shape of the reflection plate is changed to the light transmission region 3.
The direction of the reflected light beam can be changed by inclining, bending, or inclining the side wall 4 with respect to the wall surface provided with, and the direction of the light emitted from the light transmitting region 3 can be adjusted. it can.

FIG. 2 shows an example of the light transmitting region 3 provided on the wall surface on the front surface side of the box body 2. The intensity of the light emitted from the light source 1 is strong in a portion close to the linear light source 1 and weakens as the distance increases. In the present invention, in order to make the light emission distribution on the light emitting surface uniform despite the non-uniform light intensity distribution in the box body 2,
As shown in FIG. 2A, the light transmission region 3 is formed such that the area of the light transmission region 3 (the ratio of the light transmission region to the light emitting surface) increases as the distance from the light source 1 increases. That is, as the area of the light transmitting region 3 or the ratio to the light emitting surface increases, the ratio of light emission increases. Therefore, the ratio of radiation increases in a place where the brightness is lowered away from the light source 1, and as a result, a uniform light emission amount can be obtained on the light emitting surface on the surface of the box body 2. FIG. 2B shows an example of the relationship between the distance from the light source 1 and the diameter of the circular light transmission region 3, for example. In the example shown in FIG. 2B, the light transmission regions 3 arranged in the direction along the light source 1 are all formed to have the same size, and the light transmission regions 3 arranged in the direction orthogonal to the linear light source 1 are separated from the light source 1. It is shown that they are formed so as to become gradually larger as they increase, and the reflected light of the side wall 4 increases at the terminal end, so that they are formed so as to become slightly smaller. For example, the light emitting surface is vertical A × horizontal B is 160 m
In the case of the size of m × 206 mm, the diameter of the circle which is the light transmitting region 3 is about 0.4 mm in the vicinity of the linear light source 1, and the diameter of the largest circle near the end side surface 4 is about 1.4 mm. ,
The pitch is about 1 mm, and the middle thereof is formed so that the diameter of the circle changes greatly in sequence as shown in FIG. 2 (b). FIG. 2A is an example of a change in the diameter of the light transmitting region 3 when the light source 1 is provided only on one end of the box body 2, and FIG. In the case where the light source 1 is provided in each of FIGS. In addition, in these examples, the diameter of the light transmitting region 3 is shown as a curve that continuously changes, but it is schematically shown, and the light transmitting regions 3 are formed individually. ,
The size cannot be perfectly continuous, but strictly it is a change in the polygonal line. However, the sizes of the neighbors are, for example, 0.
It increases with a change of about 01 to 0.05 mm and can be regarded as almost continuous. Instead of such a continuous change, this change in size may be changed stepwise with some of the same size.

Further, the light transmitting region 3 may be formed in any other shape such as an elliptical shape, a polygonal shape, a slit shape, etc., instead of the circular shape. Further, as shown in FIGS. 2 to 3, the arrangement of the light transmitting regions 3 is not arranged in each row and each column, but as shown in FIG. You can also By arranging such an array shifted by a half pitch, the light transmission region 3
The circular diameter can be made larger than the pitch of the light transmitting regions 3, and it is convenient to take out a large amount of light even if the brightness becomes weak at a position far from the light source 1.

In order to obtain a large surface light source for an illuminated signboard, for example, as shown in FIG. 4 (b), linear light sources 1 are arranged at all four ends of a rectangle, Similar to each of the above-described examples, the area of the light transmission region 3 can be increased as the distance from the linear light source 1 increases.

Further, as shown in FIGS. 5 (a) and 5 (b), a linear light source 1 may be arranged in the central portion of the box body 2, or as shown in FIG. It is also possible to dispose the light source 1 in the shape of a box in a box body at an angle. In either case, the area of the light transmitting region 3 is reduced near the linear light source 1 and is increased as the distance from the linear light source 1 increases, so that a planar light source with uniform brightness can be obtained and The area of the part can be used without waste, and a planar light source with no dead space can be obtained.

As shown in FIGS. 5 and 6, a linear light source 1
When the light transmitting region 3 is also provided on the wall surface portion facing the light source 1, the ratio of the light transmitting region 3 of the portion facing the light source 1 is close to the light source 1. Not exclusively. That is, FIGS. 7A and 7B
In the wall surface near the upper part of the light source 1, only the light from the upper half of the light source 1 reaches the lower half of the light source 1, as schematically shown in FIG. The light emitted from the section does not reach the wall surface near the upper portion of the light source 1. Therefore, only half the light contributes. On the other hand, the brightness of light is inversely proportional to the square of the distance from the light source. Therefore, although it varies depending on the distance between the outer peripheral wall of the light source and the wall surface provided with the light transmission region, the light reflected from the back surface side is the wall surface from the portion indicated by point C in FIG. 7A to the portion facing the light source. Light source 1
Since the brightness drops most at point C, which is far away from, when the light transmission region 3 is provided on the center side of this position, the area of the light transmission region 3 (ratio of the light transmission region to the light emitting surface) is rather increased. It is preferable to form the distribution of the light transmission region as shown in FIG.
The inclination of the G portion in (c) is larger than the inclination of the portion H away from the light source 1). As shown in FIG. 7B, when the reflection plate 7 is provided and its reflection surface is inclined, the point C in FIG. 7A is closer to the light source side.

By adjusting the ratio of the light transmitting area in accordance with the positional relationship with the light source 1 as described above, uniform brightness can be obtained on the surface of the wall surface without providing a diffuser plate or the like through the space, and a thin surface can be obtained. A light source can be obtained. It should be noted that this change in the ratio of the light transmitting area changes depending on the distance between the light source 1 and the wall surface, etc., and in any state, by adjusting the ratio of the light transmitting area, the surface side of the wall surface provided with the light transmitting area is adjusted. Uniform brightness can be obtained.

Regarding the distance D (see FIG. 7B) between the light source 1 and the wall surface provided with the light transmission region 3, the light source 1
If a cold cathode tube that does not generate heat is used, the distance D can be set to almost 0, and if a cold cathode tube of 2.4 mmφ is used, a planar light source having a thickness of about 3 mm can be obtained. On the other hand, when the light source 1 that generates heat is used, the above-mentioned distance D
If too close, the heat of the light source 1 expands or deforms the wall surface or changes the distribution of the light transmission region due to the diffusivity of light, etc., and the uniformity of the emission intensity is impaired. As a result of intensive studies, the present inventor has found that providing the distance D of 3 mm or more, and more preferably 5 mm or more can maintain the reliability without changing the distribution of the light transmission region.

FIG. 8A shows an example of the distribution of the light transmission region 3 when the light source 1 is a point light source 1 such as a light bulb and FIG. 8B is a ring light source 1. Show. Even with these light sources having different shapes, by increasing the ratio of the light transmission region as the distance from the light source 1 increases, it is possible to obtain efficient and uniform luminance over the entire light emitting surface. The light source 1 having a circular outer shape in plan view is suitable for a planar light source having a circular light emitting surface, but a point or ring light source 1 may be used to form a rectangular planar light source. It is also possible to use a linear light source 1 to form a circular planar light source, and by adjusting the pattern of the light transmitting region, it is possible to obtain a uniform brightness on the entire light emitting surface.

FIGS. 9 to 10 show an example in which the light transmitting region 3 is not provided in an individually provided shape such as a circle, but is provided in a slit shape continuously for a certain length. Also in this example, as in each of the above-described examples, the ratio of the light transmitting region 3 to the light emitting surface (wall surface) is reduced in the vicinity of the linear light source 1, and the light is increased so as to increase as the distance from the linear light source 1 increases. The width of the slit, which is the transparent region 3, can be changed (see FIG.
(See (a) and (b)), and the intervals of the slits were changed (Fig. 9).
(See (c) and (d)).

FIG. 9A shows a box body 2 having a rectangular planar shape similar to that of FIGS. 2 to 6, and linear light sources 1 on both side surfaces thereof.
Is provided, a slit-shaped light transmission region 3 is provided in parallel with the linear light source 1 on the upper wall surface of the box body 2, and the slit-shaped width of the light transmission region 3 is provided with the linear light source 1. It is an example in which it is formed so as to widen from the both side surfaces toward the central portion. In this way, by widening the width of the slit on the side of the central portion away from the light source 1, the intensity of light weakened by the distance from the light source 1 is offset, and uniform brightness can be obtained on the surface.

FIG. 9B shows a box body 2 having a rectangular planar shape.
In the example in which the linear light source 1 is arranged in the central part of the, and the slit-shaped light transmitting region 3 is provided in parallel with the linear light source 1 as in FIG. Since the linear light source 1 is further away from the side, the width of the slit shape is increased on both side surfaces.

In FIG. 9 (c), linear light sources 1 are provided on both side surfaces as in the example of FIG. 9 (a), and slit-shaped light transmission regions 3 are provided in parallel with the linear light sources 1. Although formed, in this example, the width of the slit shape, which is the light transmission region 3, is constant, and the interval (pitch) becomes narrower toward the central portion away from the linear light source 1, and as a result, the light for a predetermined area is reduced. It is formed so that the area ratio of the transmissive region 3 is large.
Similarly, in FIG. 9D, the interval (pitch) of the slits is narrowed on both side surfaces far from the linear light source 1 arranged in the central portion to make the brightness uniform on the surface.

The shape of the slit, which is the light transmitting region 3, is shown in FIG.
As shown in (a) to (d), even if one slit has a uniform width from one end to the other end,
Although it may be slightly non-uniform, when the light intensity differs between the end side and the center side of the linear light source 1, it is preferable to widen the slit width on the side where the light intensity is weak.

FIGS. 10A and 10B show an example in which the slit shape which is the light transmitting region 3 is formed in a direction perpendicular to the linear light source 1 rather than parallel to it. In this case, the width of the slit, which is the light transmitting region 3, is not uniform, and is formed so as to become wider as the distance from the linear light source 1 increases. That is, in the example shown in FIG. 10A, the width of the slit, which is the light transmission region 3, becomes wider toward the central portion side away from the linear light sources 1 provided on both side surfaces,
A slit having a non-uniform width is formed in a direction perpendicular to the linear light source 1. In FIG. 10B, the outer shape of the slit is not a straight line but a curved line.
Is the same as

In each of the examples of the light transmitting area 3, the shape of the light transmitting area 3 is circular or slit. However, the circular or slit portion is a reflecting surface and the other portions are light transmitting areas. Good. That is, when the light emitting surface of the box is formed of a transparent substrate and the reflecting surface is formed by applying a metal film, a reflective paint, or a diffuse reflection agent such as white paint to the inner surface of the box, the inner surface such as a circle Alternatively, either side of the outside can be used as the reflecting surface. In this case, the circular area and the ratio of the area of the slit portion per unit area are formed so as to be smaller as the distance from the light source is opposite to the above-mentioned examples. In short, the shape may be arbitrary as long as the ratio of the area of the reflection surface to the area of the light transmission region is constant, and the area ratio of the light transmission region increases as the distance from the light source increases.

As the light source 1, a hot or cold cathode fluorescent lamp, a halogen lamp, an electroluminescent device, a light emitting diode, a tungsten lamp (incandescent light bulb) or the like is used alone or arranged so as to linearly emit light. . As the material of the reflecting surface, a metal plate having a high reflectance such as a mirror, a light reflecting metal film such as aluminum on a plastic such as acrylic resin (PMMA), a light reflecting paint such as a white paint having a high reflectance, etc. Those coated with are used. Although the white paint has a lower reflectance than that of the mirror, it is preferable because it causes diffuse reflection. Also, do not thin the light reflecting film to form a perfect reflecting surface,
By allowing about 0% of light to pass through, a light emitting surface with good diffusivity can be obtained.

If the wall surface of the box body 2 is made of a material such as a metal plate that does not transmit light, the light transmitting area 3 is formed by providing through holes or slits of any shape such as circular or polygonal. The wall of the box body 2 has a relatively high light transparency, such as acrylic resin (PMMA), a glass plate, a polycarbonate mirror, a vinyl chloride mirror, an acrylic mirror, a transparent acrylic, or a milky acrylic. When it is formed by coating a mirror such as, for example, only the light transmitting region 3 is formed by not providing a light reflecting film in an arbitrary shape such as a circular shape or a slit shape or an inverted shape thereof. In the latter case, holes or slits penetrating the wall surface are not provided, and the box body is shielded from the outside air through the transparent substrate, so that invasion of dust and the like can be prevented.

As a method of providing the light reflecting film on the transparent substrate, for example, aluminum or the like is formed on the entire surface by a vapor deposition method or a thermal transfer method, and a resist film is provided to expose, develop,
By etching using a series of etching photolithography techniques, the aluminum film only in the light transmitting region 3 can be removed to form a light transmitting region having an arbitrary shape. In this case, for example, in order to form a light-reflecting film by forming aluminum, if the film is formed to a thickness of about 10 to 20 μm, total reflection can be almost completely performed, but the film thickness is, for example, 2 μm. About half of the incident light is reflected and about half of it is transmitted to become a half mirror.
By adjusting the film thickness in the meantime, the ratio between the reflectance and the transmittance can be freely adjusted.

As another method of providing the light reflecting film, silk-screen printing, gravure printing, screen printing, ink jet printing or the like, pattern formation by sandblasting, vapor deposition or coating of a pattern shape by a lift-off method, or the like is applied to the transparent substrate. It is possible to employ a method of providing a light transmitting region on the reflection plate by mechanical processing, punching, laser processing, or the like.

As described above, the light transmitted from the light transmitting region is radiated from an arbitrary oblique direction or is diffused by the light diffusing plate or the like provided on the surface to form the light transmitting region and the portion where the light reflecting film is provided. The division is blurred and uniformized, and becomes a planar light source emitted from the entire surface. However, if the distance between the light transmitting regions is large, it may be difficult to achieve complete homogenization over the entire wall surface, particularly in a portion where the ratio of the light transmitting regions on the wall surface is small, such as a portion near the light source. In such a case, it is preferable to provide the light reflection film so that the reflectance of the light reflection film is not completely reflected and about 10% or less is transmitted. This is because if the transmittance of this light becomes too large, less light will be reflected inside the box, and the light will reach far away from the light source, and uniform light emission cannot be obtained from the entire wall surface provided with the light transmission region. . Further, the distance between the light transmitting regions is increased as the distance from the light source increases, but the gap between the light transmitting regions is formed as a whole (while keeping the area ratio of the light transmitting region and the light reflecting film part constant, In this case, the transmittance at the light reflecting film portion can be made zero, and the lower limit depends on the method of forming the light transmitting region.

Next, the specific structure will be described in detail. Note that FIGS. 11 to 14 are conceptual diagrams in which the thickness and spacing of the reflective film 9 are exaggerated.

Example 1 FIG. 11 is a cross-sectional explanatory view of Example 1 of the dual emission type planar light source of the present invention. In Example 1, two wall surfaces 5 and 6 of the box body 2 facing each other are made of transparent substrates. The light is radiated as indicated by the arrow on the wall surface on which the light-transmitting region 3 which is the region without the reflection film 9 is provided uniformly on the inner surface thereof. Reference numeral 4 denotes a side wall, which is another wall surface of the box body 2, which is formed on a reflection surface and facilitates trapping light in the box body 2 by vapor deposition of a mirror or application of white paint.

As shown in FIG. 5, the two wall surfaces 5 and 6 have a small ratio of the light transmitting region 3 to the area of the wall surfaces 5 and 6 near the light source 1, and the ratio increases as the distance from the light source 1 increases. Is formed. Further, since the inner surface of the wall surface (side wall 4) other than the wall surfaces 5 and 6 provided with the light transmission region 3 is a reflection surface, light directed toward the wall surface other than the wall surface provided with the light transmission region 3 is provided. Is reflected in the box body 2 and travels, and the light is emitted toward the light transmitting region 3 of the front side wall surface 5 or the rear side wall surface 6. The side wall 4 may not be a perfect reflecting surface, but may be a light emitting surface in which light transmitting regions are evenly provided, or may be a transparent side wall.

FIG. 11A shows an example in which one linear light source 1 is provided in the box body 2, and FIG. 11B shows an example in which two linear light sources 1 are provided. Yes, but the action is the same. With such a structure, it is necessary to provide a space of 3 mm or more, more preferably 5 mm or more between the outer peripheral surface of the light source 1 and the wall surfaces 5 and 6 due to the influence of heat of the light source and the diffusibility of light. The thickness of the light source 1 is increased by about 10 mm to provide a planar light source of double-sided emission that can obtain uniform brightness.

Example 2 FIG. 12 is a cross-sectional explanatory view of Example 2 of a dual emission type planar light source according to the present invention. In Example 2, the reflector 7 is provided in a direction along the diagonal line of the cross section of the box body 2. The structure is the same as that of the first embodiment, which is a structure in which a box body having a triangular cross section is provided and connected by the reflection plate 7. The reflector is made of a reflective material such as resin or metal.

According to the present invention, the overall size such as the interval between the two wall surfaces 5 and 6 provided with the light transmitting region 3 is the same as in the first embodiment.
It is a thin and compact dual-sided emission type planar light source, which is the same as the above.
Although individual pieces are required, the light path in the box body 2 becomes short, and bright brightness can be obtained for the same light source. Further, since the reflection plate 7 is inclined with respect to the light emitting surface (wall surfaces 5 and 6), it is easy to reflect light toward the light emitting surface even at a place far from the light source 1. In the embodiment shown in FIG. 12, the light source 1 on the wall surfaces 5 and 6
The light-transmitting area is not provided in the portion facing the reflection plate 5
Although a and 6a are used, a light transmitting region may be provided and the entire surface may serve as a light emitting surface as in the first embodiment. Alternatively, the side wall 4 may not be a reflector, and the wall surface or the entire surface where the light transmitting regions are evenly provided may be a transparent side wall.

Example 3 In Example 3, as shown in the sectional explanatory views of FIGS. 13 (a) and 13 (b), the reflecting plate 8 was provided on both sides with the structure folded back at the center. A linear light source 1 is provided at the center. With such a structure, only one light source 1 is required while partitioning the inside of the box body 2 with a reflecting plate, and the reflecting plate 8 can effectively extract light to the light emitting surface (wall surfaces 5 and 6) side. .

FIG. 13A shows a structure in which the reflecting plate 8 is inclined with respect to the light emitting surface (wall surfaces 5 and 6), and FIG. 13B shows the reflecting plate 8 curved with respect to the light emitting surface. It is a structure. With either structure, a planar light source that emits light from both sides with the same thickness as in Examples 1 and 2 can be obtained.

In the third embodiment, even if there is only one light source 1, the reflector 8
Thus, the direction of light reflection can be adjusted, and a dual emission type planar light source with efficient and uniform brightness can be obtained. Note that, also in the third embodiment, the side wall 4 may not be a perfect reflection surface, but a wall surface where light transmitting regions are evenly provided or an entire side wall may be a transparent side wall.

Embodiment 4 In this embodiment, the side wall 4 also has a light emitting surface in which light transmitting regions are evenly provided, which are shown in plan views in FIGS. 14 (a) and 14 (b), respectively. In FIG. 14, Examples 1-3
Light is radiated from the wall surfaces corresponding to the opposite wall surfaces 5 and 6 to the front surface side and the back surface side of the paper surface, and the side wall 4 also radiates light in four directions and radiates light from all surfaces, as indicated by arrows. The surface light source is a multi-facet emission type.

In FIGS. 14A and 14B, the light source 1 can be made into a point-shaped or ring-shaped light bulb-like one to form a thin multi-faceted light-emitting type, or the light source 1 like a rod-shaped fluorescent tube. It is also possible to make a box-shaped multi-facet light emitting type that is close to a cubic shape by making it a linear shape and increasing the depth. Other structures and the reference numerals in FIG. 14 are the same as those in the first to third embodiments.

Embodiment 5 In this embodiment, as shown in FIG. 15, for example, FIG.
The double-sided light emission type planar light source 10 having the pattern of the light transmitting region 3 shown in FIG. The dual emission type planar light source 10 is not limited to the structure shown in FIG. 5, but in order to make the joint of the dual emission type planar light source 10 inconspicuous, the light transmission region 3 is also provided on the upper part of the light source 1. Therefore, it is better to use it as a light emitting surface.

Further, at the joint portions E and F of the dual emission type planar light source 10, the side wall of each dual emission type planar light source 10 is not used as a reflection surface, but the entire surface or a part thereof may be made transparent or deleted. Alternatively, a uniform light transmitting region may be provided on the side wall. By doing so, it is effective in terms of mechanical strength, maintenance of the fluorescent tube, and homogenization of light.

When the joint E becomes dark due to the decrease in the luminance due to the end portion of the light source 1 like the joint E, the area of the light transmitting region 3 near the joint E should be increased. This makes it possible to eliminate the discontinuity at the seam.

[0064]

According to the present invention, a light source is arranged in a box body formed of a reflecting surface, and a plurality of light beams provided on at least two wall surfaces of the box body facing each other while reflecting the light inside the box body. Since a double-sided emission type planar light source is obtained by extracting light from the transmissive region, it is possible to obtain a double-sided emission type planar light source that is thin and has little light attenuation, and has a large brightness for a light source having the same light amount. Therefore, the double-sided light source of the present invention can be used as an illuminated signboard for a street signboard, a hanging advertisement in a car, a signboard that is preferable for viewing from both sides such as a destination display, and the like.

Further, according to the present invention, a very large double-sided light source can be obtained uniformly and with high brightness. Furthermore, by adjusting the ratio of the light transmission area, the brightness of the surface of the wall surface where the light transmission area is provided can be made uniform, and it is not necessary to install a diffusion plate through the space, and a thinner double-sided emission type An area light source can be obtained.

Further, since it is formed of a hollow box, it is extremely lightweight and has little attenuation of light, and it can be formed as thin as twice the thickness of the light source, which is about a few mm. It is possible to obtain a thin dual emission type planar light source of about 5 to 50 mm.

Further, since it is lightweight, thin, and consumes little power, it can be loaded on a car or the like and used as a moving signboard for advertisements, campaign posters, and the like. In this case, since it is a double-sided emission type, it can be observed from both sides, which is preferable. Also, as an illumination light source, an illumination device having a bright brightness with indirect light can be thin and lightweight.

Further, according to the dual emission type surface light source of the present invention, no special material is required, and the processing can be performed by pressing a metal plate, resin processing, sheet processing, printing on a transparent substrate, a mirror device or the like. It is easy to form and very inexpensive to obtain.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of a dual emission type planar light source of the present invention.

FIG. 2 is an explanatory diagram showing an example of a light transmission region provided on one of two facing wall surfaces of a box body of an embodiment of a dual emission type planar light source of the present invention.

FIG. 3 is an explanatory view showing another example of a light transmission region provided on one wall surface of a box body of an embodiment of the dual emission type planar light source of the present invention.

FIG. 4 is an explanatory view showing still another example of the light transmission region provided on one wall surface of the box body of the embodiment of the dual emission type planar light source of the present invention.

FIG. 5 is an explanatory view showing still another example of the light transmission region provided on one wall surface of the box body of the embodiment of the dual emission type planar light source of the present invention.

FIG. 6 is an explanatory view showing still another example of the light transmission region provided on one wall surface of the box body of the one embodiment of the dual emission type planar light source of the present invention.

FIG. 7 is a diagram schematically showing paths of light emitted to the front surface side and the back surface side of a light source.

FIG. 8 is a diagram showing an example of a pattern of a light transmission region when a light bulb and a ring fluorescent lamp are used as a light source.

FIG. 9 is an explanatory view showing still another example of the light transmission region provided on one wall surface of the box body of the embodiment of the dual emission type planar light source of the present invention.

FIG. 10 is an explanatory view showing still another example of the light transmitting region provided on the upper wall surface of the box body of the embodiment of the dual emission type planar light source of the present invention.

FIG. 11 is a cross-sectional explanatory diagram of Example 1 of the dual emission type planar light source of the present invention.

FIG. 12 is a cross-sectional explanatory view showing Example 2 of the dual emission type planar light source of the present invention.

FIG. 13 is a cross-sectional explanatory view showing Example 3 of the dual emission type planar light source of the present invention.

FIG. 14 is a plan view showing Example 4 of the dual emission type planar light source of the present invention.

FIG. 15 is an explanatory view showing an example of a large-sized dual emission type planar light source of the present invention.

FIG. 16 is an explanatory diagram showing an example of a conventional planar light source.

FIG. 17 is a side view illustrating another example of the conventional planar light source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Box body 3 Light transmission region 4 Side walls 5, 6 Opposing wall surfaces 7, 8 Reflector 9 Reflective film 10 Double-sided emission type planar light source

Claims (14)

[Claims] 1. A box body having an inner surface formed as a light-reflecting surface and a light source built in the box body, and a large number of light-transmitting regions are provided uniformly on at least two wall surfaces of the box body facing each other. And the light transmitting region is provided such that the ratio of the light transmitting region to the wall surface increases as the distance from the light source increases, and the light from the light source is emitted from the at least two opposing wall faces. Area light source. 2. The rate of increase of the ratio of the light transmission region of the portion of the two wall surfaces facing each other facing the light source, the light transmission region being provided at a portion facing the end portion in the radial direction of the light source. 2. The dual emission type planar light source according to claim 1, wherein is formed so as to be larger than an increase rate of the ratio at a position distant from the light source. 3. The method according to claim 1, wherein the ratio of the light transmission region at the farthest end from the light source is smaller than the maximum value of the ratio of the light transmission regions on each of the two wall surfaces. Dual-sided light emitting planar light source. 4. The dual emission type planar light source according to claim 1, 2 or 3, wherein the light transmission region is formed so as to have a large area to increase the ratio of the light transmission region. 5. The dual emission type planar light source according to claim 1, wherein the light transmitting regions are formed so as to have a small pitch so that the ratio of the light transmitting regions is increased. . 6. The wall surface of the box body on which at least the light transmission region is provided is made of a metal plate, and the light transmission region is a through hole or a slit formed in the metal plate. 4. The dual emission type planar light source according to 4 or 5. 7. A transparent substrate provided with a light reflecting film on at least a wall surface of the box body where the light transmitting region is provided, and a region where the light reflecting film is not provided is formed on a part of the transparent substrate. 6. The dual emission type planar light source according to claim 1, wherein the area is the light transmitting area. 8. The dual emission type planar light source according to claim 7, wherein the light reflection film is provided so as to transmit a part of light instead of a complete light reflection surface. 9. A light-transmitting wall or a wall surface provided with light-transmitting regions in a uniform manner is formed on at least a part of each of the side walls adjacent to the two facing wall surfaces, and at least a part of the side wall is also a light-emitting surface. Claims 1, 2, 3, 4, 5,
The dual emission type planar light source according to 6, 7, or 8. 10. A reflection plate for reflecting the light of the light source to the two wall surfaces facing each other is provided inside the box body. 9. A dual emission type planar light source according to item 9. 11. The light source according to claim 10, wherein the light source is provided at a central portion of the reflector so that light can be supplied into two spaces surrounded by the reflector and each of the two opposite wall surfaces. Double-sided emission type planar light source. 12. A large-sized dual emission type planar light source in which the dual emission type planar light source according to claim 1 is arranged in an array or a matrix to form a large emission surface. 13. A part or all of a side wall surface of a joint portion of each of the arrayed double-sided light emitting surface light sources is removed, or a light transmitting wall or a light transmitting region is formed into a wall surface provided uniformly. The large-sized dual emission type planar light source according to claim 12. 14. The uniformity of the brightness of the seam is adjusted by adjusting the ratio of the light transmission region in the light emitting surface of the seam of each of the arrayed double-sided light emitting surface light sources. Large-sized dual-sided planar light source.