JPH08153405A - Planar light source - Google Patents

Abstract

PURPOSE: To obtain a planer light source for back light such as light crystal display unit or electric illumination plate with its light weight, less light loss, thin-shaped, uniform brightness, and inexpensiveness. CONSTITUTION: A planner light source is provided with a box body 2 whose inner surface is formed on a reflection surface and a linear light source 1 incorporated in said box body. A number of light transmission areas 3 is evenly provided on a wall surface 2a of this box body 2 and provided so that the ratio against the one wall surface 2a of the light transmission area 3 is larger more distance from the linear light source 1, so that the light of the linear light source 1 is irradiated from the wall surface 2a.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a planar light source. More specifically, the present invention relates to a planar light source suitable for a backlight for panel display that irradiates light from the back side of a liquid crystal display panel, an illuminated signboard, or the like.

[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. 17, 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.

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 emits the light from the front surface is used as a backlight arranged on the back surface of, for example, a liquid crystal display panel. There are times when it will be. As shown in FIG. 18A, such a planar light source includes a linear light source 1, a light guide plate 12 that takes in the light of the linear light source 1 from a side wall and emits the light from the front surface side, and the light guide plate 12. A light diffusing plate 13 for diffusing the light from the liquid crystal display panel side, and directing the light from the light diffusing plate 13 to the front side,
There is known a structure including a prism sheet 14 for increasing the intensity of light viewed from the front. The light guide plate 12 is formed of a transparent plate such as acrylic resin, has a dot pattern 15 for reflecting light provided on the back surface thereof, and the reflection sheet 1 on the side surface other than the side surface on which the light source 1 of the light guide plate 12 is provided.
7 are 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. On the back side of the light guide plate 12, a reflector plate 1 made of a metal plate or the like is further provided.
6 is provided, and the light which is emitted from the back surface of the light guide plate 12 and is transmitted to the back surface side without being reflected by the dot pattern 15 is provided.
It is reflected on the surface side of the to improve the light utilization rate.
A reflective film 18 is provided around the linear 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 where the light is incident, and the regions P shown in FIGS. 18 (a), 18 (b), and 18 (c) are shown. 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 diffusion plate 13 is made of polyethylene terephthalate (PET), polycarbonate or the like and is formed to 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. 18 (a). It is formed into a triangular prism and has a thickness of about 120 to 250 μm.

[0005]

In the conventional planar light source using the 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 the transparent substrate is made of resin. Since the light propagates through the light, there is a problem that the light is attenuated and the light utilization efficiency is reduced. Also, since there is a light source at the edge, the size has an upper limit.

Further, while the light is taken in from the side surface of the light guide plate and is reflected on the back surface side of the light guide plate to emit the light to the front surface side, the reflection portion must be provided outside the light guide plate, Since the light emitted to the outside is reflected, the light utilization efficiency is further reduced. Therefore, there is a problem that a high-output linear light source is required to obtain a desired brightness. In addition to the light emitting surface, a space for arranging the linear light source and a clearance that does not contribute to the light emitting surface on the linear light source side of the light guide plate must be ensured, which requires a large area.

Further, the above-mentioned planar light source using the light guide plate is unavoidable in attenuation of the above-mentioned light, becomes heavy, and causes unevenness of brightness on the light emitting surface due to dew condensation or thermal expansion. There is a problem that it is not suitable as a light source for a large display panel such as an illuminated signboard.

The present invention solves such a problem, is light in weight even with a large surface light source, and has a small loss of light of a desired size.
Moreover, it is an object of the present invention to provide a thin and inexpensive planar light source that can obtain uniform brightness without providing a light diffusion plate on the surface through a space.

[0009]

The surface light source of 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. A large number of transmission regions are provided in a uniform manner, and the ratio of the light transmission region to the one wall surface increases as the distance from the light source increases, and the light from the light source is emitted from the wall surface. There is.

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 ratio of the light transmitting region is adjusted so that the brightness is substantially uniform on the surface of the one wall surface. That is, a light diffusion plate or the like is provided on the surface side of the one wall surface through a space. Even without it, uniform brightness can be obtained on the surface side of one wall,
A thin surface light source can be obtained.

The light transmitting region is also provided in a portion of the one wall surface facing the light source, and the rate of increase of the ratio of the light transmitting region in the portion facing the end portion in the radial direction of the light source is separated from the light source. Being formed to be larger than the rate of increase of the above-mentioned ratio, the dark part due to the shadow of the light source is eliminated, and even if there is no light diffusion plate etc. through the space, it is uniform over the entire wide surface of the wall surface. It is preferable because it gives a high brightness.

It is preferable 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 the one wall surface so that the luminance at the edge is uniform. It is preferable because it can be

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.

When the distance between the outer peripheral wall of the light source and the wall surface on which the light transmitting region is provided is 3 mm or more, deformation of the wall surface on which the light transmitting region is provided due to heat does not occur.
It is preferable because the reliability is improved.

Since the light diffusing plate is provided on the wall surface of the box body on which the light transmitting region is provided, the light transmitted from the light transmitting region can be diffused uniformly in a plane and uniform brightness can be obtained. Therefore, it is preferable.

Further, the light source comprises a linear light source, the linear light source is provided in parallel with a side wall of the box body, and at least an inner surface of the side wall facing the linear light source is formed as a light reflecting surface. Moreover, it is preferable that the light transmission region is provided so as to be inclined with respect to the vertical surface of the wall surface, because the optical path of the reflected light reflected by the side wall is changed, so that light is easily emitted from the light transmission region. .

Further, the inner surface of the wall surface of the box body facing the wall surface provided with the light transmission region is formed as a whole light reflection surface, and is inclined with respect to the wall surface provided with the light transmission region. However, similarly, the optical path of the reflected light on the bottom surface becomes irregular, and the light is easily emitted from the light transmitting region, which is preferable.

When the light reflecting surface is formed in a step shape or a mountain shape, the optical path of the reflected light becomes more irregular, and the light is easily emitted from the light transmitting area.

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

It is preferable that part or all of the side wall surface of the joint portion of each of the arrayed surface light sources is a light transmitting region because stripes are not easily formed at the joint portion of the surface light source.

A large area light source having a uniform brightness is obtained by adjusting the ratio of the light transmitting region in the light emitting surface of the seam of each of the arrayed surface light sources so as to make the brightness of the seam uniform. It is preferable because it can be obtained.

[0026]

According to the present invention, a light source is built in a box whose inner surface is a light-reflecting surface, and light is emitted from a light-transmitting region while reflecting the space inside the box on the inner surface. All of the light can be taken into the box without loss, and the light absorption in the 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 planar light source. Therefore, there is no loss at the time of taking light into the conventional light guide plate and no light absorption loss due to the progress in the light guide plate, and the light utilization efficiency is greatly improved.

Further, according to the present invention, since the ratio of the light transmitting region is small with respect to the wall surface through which light is extracted in the vicinity of the light source, and the ratio is increased as the distance increases, it is close to the light source. Where there is a large amount of light, light is emitted from a place with a large proportion of the light-transmitting region, and where there is a small amount of light-transmitting region far from the light source, light is emitted from a place with a small proportion of the light-transmitting region. Is emitted.

Further, by adjusting the ratio of the light transmitting area, it is possible to make uniform the change of the brightness due to the change in the distance between the light source and the wall surface and the brightness in the vicinity of the portion facing the light source and the side wall. It is possible to make the brightness uniform on the wall surface provided with the transmissive region.

Further, when the light transmitting region is provided on the wall surface of the portion facing the light source, the reflected light of the light on the back side of the light source does not reach, so that the light transmitting portion of the light source on the radial end side thereof is transmitted. When the increase rate of the area ratio is made larger than that of the other area, the brightness becomes uniform over the entire surface.

According to the large surface light source of the present invention, the method of claim 1
A large planar light source can be formed only by arranging the described planar light sources in an array or a matrix, and a desired size can be easily manufactured. In this case, when the brightness of the joint portion of the planar light source is not uniform, a large planar light source with uniform brightness can be easily obtained by adjusting the ratio of the light transmitting region.

[0031]

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 light from the light source 1 in the box body 2 formed by the reflecting surface, and (b) is a diagram showing the light emitted from the light transmitting region 3 provided on the front side wall surface of the box body 2. FIGS. 2 to 10 are partial cross-sectional explanatory views for explaining the path, and FIGS. 2 to 10 are views showing an example of a light transmission region provided on the front side wall surface of the box body 2.

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 the reflecting surface is provided in the surroundings. Therefore, as shown in FIG. 1A, the light travels in the direction away from the light source 1 while being reflected by the reflecting surface, and when it reaches the end side wall 4, it is reflected back by the side wall 4 and is further reflected. It advances in the box 2. By increasing the reflectance of this reflecting surface, the light travels in the box body 2 without being attenuated.

A light transmissive region 3 which does not serve as a reflecting surface is provided on the upper wall surface of the box body 2. As shown in FIG. 1B, the light traveling toward the light transmissive region 3 is a light beam. The light is radiated from the transparent 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. The light emitted from the light transmitting area 3 is
As the distance from the light source 1 increases, the amount of light in the direction in which the incident angle is large (close to parallel to the wall surface) increases, but the wall surface (bottom surface) facing the wall surface provided with the light transmission region 3 is inclined or bent. Alternatively, the direction of the reflected light beam can be changed by tilting the side wall 4, and the direction of the light emitted from the light transmitting region 3 can be adjusted.

FIG. 2 shows an example of the light transmission 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 of the light transmitting region 3 to the upper wall 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 transmission region 3 when the light source 1 is provided only at one end of the box body 2, and FIG. 3A is at both opposite ends of the box body 2. An example in which the light source 1 is provided is shown. 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 completely continuous, but strictly speaking, it is a change in the polygonal line. However, the size of each other is 0.0, for example.
It increases with a change of about 1 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.

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. 5-6, 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, as shown schematically in FIG. 7 in which the path of light emitted from the light source 1 toward the lower reflection surface is shown, only the light from the upper half of the light source 1 reaches the wall near the upper part of the light source 1. The light emitted from the lower half of the light source 1 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 changes depending on the distance between the outer peripheral wall of the light source and the wall surface provided with the light transmission region, C in FIG.
On the wall surface from the portion indicated by the point to the portion facing the light source, the reflected light from the back side does not enter, and the brightness is the lowest at point C, which is far from the light source 1. Therefore, the light transmitting area is closer to the center than this position. If 3 is provided, the light transmitting region 3 is rather used.
It is preferable that the increase rate of the area (ratio of the light transmitting area to the light emitting surface) is slightly increased to form the light transmitting area distribution as shown in FIG. 7C (G portion in FIG. 7C). Is greater than the inclination of the portion H away from the light source 1). As shown in FIG. 7B, when the reflecting surface on the bottom surface is tilted, point C in FIG. 7A is closer to the light source side.

By thus adjusting the ratio of the light transmitting area in accordance with the positional relationship with the light source 1, uniform brightness can be obtained on the surface of the wall surface and a thin surface can be obtained without providing a diffuser plate or the like through the space. 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 between the light source 1 and the wall surface provided with the light transmitting region 3 (see FIG. 7B), when a cold cathode tube which does not generate heat is used as the light source 1, the distance D is almost zero. If a cold cathode tube with a diameter of 2.4 mm is used, a planar light source with a thickness of about 3 mm can be obtained. On the other hand, light source 1
When a heat generating element is used as the above, if the distance D is too short, the heat of the light source 1 expands or deforms the wall surface, or the distribution of the light transmission region is changed due to the diffusivity of light, so that the emission intensity is made uniform. Be damaged. As a result of intensive studies by the present inventor, the distance D is 3 mm or more, more preferably 5 mm.
Providing more than mm does not change the distribution of the light transmission region,
It was found that reliability can be maintained.

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 case where the ring light source 1 is used. 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.

9 to 10 show an example in which the light transmitting region 3 is not provided in a circular shape or the like and is provided in a slit shape continuously for a certain length. In this example as well, similar to each of the above-described examples, the ratio of the light transmitting region 3 to the light emitting surface (upper wall surface) is made smaller in the vicinity of the linear light source 1, and becomes larger as the distance from the linear light source 1 increases. The width of the slit, which is the light transmitting region 3, is changed (see FIGS. 9A and 9B), or the interval between the slits is changed (see FIGS. 9C and 9D).

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 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 not at the parallel to the linear light source 1 but at the right angle direction. 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 described as an example of a circular shape or a slit shape. However, the circular or slit shape portion is used as a reflecting surface and the other portions are used as light transmitting areas. Good. In other words, when forming the upper wall surface of the box with a transparent substrate and forming a reflective surface by applying a metal film, a reflective paint, a diffuse reflection agent such as white paint, etc. to the inner surface of the box 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), etc. are used alone or arranged so as to emit linearly. . 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.

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 sandblasting pattern formation on the above-mentioned transparent substrate, pattern-form vapor deposition by lift-off method, coating, or the like. 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 area is emitted from any oblique direction or is diffused by the light diffusing plate or the like provided on the surface so that the light transmitting area 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 of the box body 2 will be described in detail.

Example 1 FIG. 11 is an exploded perspective view of a box body 2 which is an example of the planar light source of the present invention. In this embodiment, the thickness is 0.2-1.
A metal plate coated with a light-reflecting metal film such as aluminum with a length of about 0 mm.
A box body 2 having a depth of about 100 mm and a depth of about 5 mm is formed, and the upper wall surface 2a has a diameter of about 0.4 mm at the smallest and a diameter of about 0.1 mm at the largest, as shown in FIG. 2 (a). Through holes were uniformly provided at a pitch of 1 mm to form a light transmitting region 3 so as to be 8 mm.

As the linear light source 1, a fluorescent lamp having a diameter of 3 mm, a length of 100 mm and a brightness of 28,000 cd is used.
It was arranged at one end of the box body 2 and the upper wall surface 2a was sealed in the main body so that light did not leak. A light diffusion plate made of polyethylene terephthalate (PET), polycarbonate, or the like (not shown) is provided on the upper wall surface 2a.

FIG. 1 of the planar light source thus formed.
As a result of examining the luminance (unit cd) at the position shown in 1 (b), the luminance shown in Table 1 was obtained. Table 1 shows the brightness of the conventional light guide plate for comparison.

[0058]

[Table 1]

As is clear from Table 1, the variation in luminance on the surface is + 18.8% and -11.7% with respect to the average value.
The average luminance of 72% was obtained with respect to the luminance of the light source, and a planar light source with good conversion efficiency from the linear light source was obtained.

Embodiment 2 In this embodiment, when one linear light source 1 is provided at one end of the box body 2, as shown in FIG. 12A, the cross sectional shape of the box body 2 is shown. The side wall 4 of the box body 2 is inclined so that the direction in which light is reflected is changed.
By changing the regularity of the light reflection direction within the
It is designed to make it easier for light to reach. The other structure is the same as that of the first embodiment. It is sufficient that the inclination angle of the side wall 4 is about 3 to 10 ° with respect to the vertical surface of the upper wall surface 2a. However, if the inclination angle is too large, no particular problem occurs. Further, the same effect can be obtained even if it is provided on a side wall surface other than the side wall surface facing the linear light source 1. By inclining the side wall surface 4, the brightness is improved by about 5% as compared with the case of the normal side wall surface having no inclination.

As in this embodiment, the shape of the box body 2 may be changed arbitrarily, and as shown in FIGS. 12B and 12C, the box body around the linear light source 1 is formed. The cross-sectional shape of 2 may be rectangular or arc-shaped. Further, the position where the linear light source 1 is provided does not have to be at one end.
As mentioned above, you can place it in the center or at an angle,
It is also possible to arrange a plurality of them.

Embodiment 3 In this embodiment, as shown in FIG. 13 (a), a wall surface (bottom surface) facing the upper wall surface 2a provided with the light transmission region 3 is provided.
Is formed not in parallel with the upper wall surface 2a but in an inclined manner, and other structures are the same as in the second embodiment. This inclination direction may be the direction shown in FIG. 13A or the opposite direction, and the angle is about 3 to 10 °, which is sufficient as in the second embodiment. Further, as shown in FIGS. 13B and 13C,
The same applies to the curved surface R instead of the inclination. By doing so, the confinement of light in the box body 2 is eliminated as in the case of the second embodiment, and the light can be efficiently extracted from the light transmissive region 3, so that the brightness is better than if the bottom surface is not inclined. 1
It improved by 0%.

FIG. 14 shows an upper wall surface 2 provided with a light transmitting region.
The wall surface (bottom surface) 2b facing a is inclined, and the inner surface thereof is further stepped (see FIG. 14B) or chevron-shaped (see FIG. 14C). With such a shape, the reflection angle of light can be changed even if there is a limit to the inclination angle of the bottom surface, which can contribute to making the luminance of the light emitting surface uniform. Note that FIG.
14B and 14C are enlarged explanatory views of the L portion of FIG. 14A, showing the cases where they are formed in different shapes.

Example 4 In this example, as shown in FIG.
The upper wall surface 2a provided with is made of an acrylic plate (PMMA), and an aluminum film is formed on the inner surface of the aluminum plate by vapor deposition.
The film was formed to a thickness of about μm. The acrylic plate (PMMA) provided with this aluminum film transmitted about 2 to 10% of light and reflected the other light. This aluminum film was etched by a photolithography technique to form a light transmitting region 3 surrounded by a light reflecting film 5 made of an aluminum film having the same size and the same pitch as in Example 1. The wall surface and bottom surface of the box body 2 and other configurations were all formed in the same manner as in Example 1 to obtain a planar light source having a good surface diffusion property.

As in the present embodiment, a transparent substrate is used on the upper wall surface where the light transmitting region is provided, and a light reflecting surface is formed by coating a reflecting film, whereby the reflectance is adjusted and a part of the light is transmitted. The surface light source has a good diffusive property.

Embodiment 5 In this embodiment, as shown in FIG. 16, for example, FIG.
The planar light source 1 having the pattern of the light transmitting region 3 shown in FIG.
Two 0s are arranged on each fiber to form a large surface light source. The planar light source 10 is not limited to the structure shown in FIG. 5, but in order to make the joints of the planar light source 10 inconspicuous, the upper portion of the light source 1 is also provided with the light transmitting region 3 and is used as a light emitting surface. It's better.

Further, in the joint portions E and F of the planar light source 10, the side wall of each planar light source 10 is not used as a reflection surface, but the entire surface or a part of the planar light source 10 may be made transparent, or may be deleted or evenly arranged on the side wall. A light transmission region may be provided. By doing so, it is effective in terms of mechanical strength, fluorescence maintenance, and homogenization of light.

When the seam E becomes dark due to the decrease in the brightness due to the end of the light source 1 like the seam E, is it necessary to increase the area of the light transmission region 3 near the seam E? Alternatively, the discontinuity of the joint portion can be eliminated by making the region 100% light transmissive.

[0069]

According to the present invention, a linear light source is arranged in a box body formed of a reflecting surface, and a plurality of light transmitting regions provided on one wall surface of the box body while reflecting the light inside the box body. Since a planar light source is obtained by extracting light from the light source, there is little attenuation of light, and a planar light source with high brightness can be obtained for a light source having the same light amount.

Further, according to the present invention, it is possible to obtain a planar light source of uniform and high brightness even if it is very large. Furthermore, by adjusting the ratio of the light transmitting area, the brightness of the surface of the wall surface provided with the light transmitting area can be made uniform, and it is not necessary to install a diffusion plate through the space, and a thinner planar light source. Can be obtained.

Further, since it is formed of a hollow box, it is extremely lightweight and has little light attenuation, and it can be formed to have a thickness which is increased by several mm from the thickness of the light source.
A thin planar light source of about 3 to 15 mm can be obtained. Also, since it is a large planar light source or a bright planar light source, it is 33 mm.
Even if a φ-tube fluorescent lamp is used, it can be formed with a thickness of 50 mm or less. As a result, the liquid crystal display panel can be made extremely thin, and it can be used in a wide range of applications such as light sources for the backside of large display panels such as illuminated signboards, light sources for medical X-ray photography, light tables for creating illustrations, and traffic signs. Can be used.

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, or the like. 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 surface light source of the present invention, no special material is required, and the processing is easily performed by pressing a metal plate, resin processing, sheet processing, printing on a transparent substrate, a mirror device or the like. It can be obtained at a very low cost.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing an example of a light transmission region provided on the upper wall surface of the box body of the embodiment of the planar light source of the present invention.

FIG. 3 is an explanatory diagram showing another example of the light transmission region provided on the upper wall surface of the box body of the embodiment of the planar light source of the present invention.

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

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

FIG. 6 is an explanatory view showing still another example of the light transmission region provided on the upper wall surface of the box body of the embodiment of the 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-shaped fluorescent lamp are used as a light source.

FIG. 9 is an explanatory diagram showing still another example of the light transmission region provided on the upper wall surface of the box body of the embodiment of the planar light source of the present invention.

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

FIG. 11 is an exploded perspective view showing an example of the planar light source according to the present invention.

FIG. 12 is a sectional explanatory view showing another embodiment of the planar light source of the present invention.

FIG. 13 is a sectional explanatory view showing still another embodiment of the surface light source of the present invention.

FIG. 14 is a sectional explanatory view showing another embodiment of the reflecting surface of the planar light source of the present invention.

FIG. 15 is a cross sectional explanatory view showing still another embodiment of the planar light source of the present invention.

FIG. 16 is an explanatory diagram showing an example of a large area light source of the present invention.

FIG. 17 is an explanatory diagram showing an example of a conventional planar light source.

FIG. 18 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 transmitting region 4 Side wall 5 Light reflecting film 10 Planar light source

Claims (17)

[Claims] 1. A box body having an inner surface formed as a light-reflecting surface and a light source incorporated in the box body, wherein a large number of light-transmitting regions are uniformly provided on one wall surface of the box body, and A planar light source which is provided such that the ratio of the light transmission region to the one wall surface increases as the distance from the light source increases, and the light of the light source is emitted from the wall surface. 2. The surface light source according to claim 1, wherein the ratio of the light transmitting region is adjusted so that the luminance is substantially uniform on the surface of the one wall surface. 3. The light transmitting region is also provided in a portion of the one wall surface facing the light source, and an increase rate of the ratio of the light transmitting region in a portion facing the end portion in the radial direction of the light source is the light source. The planar light source according to claim 1 or 2, wherein the planar light source is formed so as to have a larger rate of increase in the ratio at a position away from. 4. The method according to claim 1, 2 or 3, 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 region on the one wall surface. Area light source. 5. The planar light source according to claim 1, 2, 3, or 4, wherein the area of the light transmitting region is formed to be large so that the ratio of the light transmitting region is increased. 6. The planar light source according to claim 1, wherein the light transmissive regions are formed so as to have a small pitch so that the ratio of the light transmissive regions is increased. 7. The wall surface of at least the light transmission region of the box body is formed of a metal plate, and the light transmission region is a through hole or a slit formed in the metal plate. The planar light source according to 4, 5, or 6. 8. A transparent substrate provided with a light reflecting film on at least a wall surface of the box body on which 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. The area light source according to claim 1, 2, 3, 4, 5, or 6, wherein the area is formed as the light transmission area. 9. The planar light source according to claim 8, wherein the light reflecting film is provided so as to transmit a part of light instead of a perfect light reflecting surface. 10. The distance between the outer peripheral wall of the light source and the wall surface on which the light transmission region is provided is 3 mm or more.
The planar light source according to 2, 3, 4, 5, 6, 7, 8 or 9. 11. A light diffusing plate is provided on a wall surface of the box body on which a light transmitting region is provided.
The planar light source according to 4, 5, 6, 7, 8, 9 or 10. 12. The light source comprises a linear light source, the linear light source is provided in parallel with a side wall of the box body, and at least a side wall facing the linear light source is perpendicular to a wall surface provided with the light transmitting region. The inclined surface is provided so as to be inclined with respect to a surface, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.
The surface light source described. 13. The inner surface of the wall surface of the box which faces the wall surface on which the light transmission area is provided is formed as a full-surface light reflection surface, and is inclined with respect to the wall surface on which the light transmission area is provided. Claims 1, 2, 3, 4, 5, 6,
7. The planar light source according to 7, 8, 9, 10, 11 or 12. 14. The planar light source according to claim 13, wherein the light reflecting surface is formed in a step shape or a mountain shape. 15. A large planar light source in which the planar light source according to claim 1 is arranged in an array or a matrix to form a large light emitting surface. 16. The large planar light source according to claim 14, wherein a part or all of the side wall surface of the joint portion of each of the arrayed planar light sources is a light transmitting region. 17. The large surface according to claim 15, wherein the ratio of the light transmitting region in the light emitting surface of the joint portion of each of the arrayed planar light sources is adjusted to uniformize the luminance of the joint portion. Light source.