JPH10233112A - Surface light source device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of providing uniform brightness and a method for manufacturing the same. SOLUTION: A surface light source device comprises a casing surrounded by side walls on which light reflecting surfaces are formed and a light source enclosed in the casing, and causes reflected light in the casing to radiate from a number of light-transmitting regions provided on the side walls. In this case, the farther it is from the position of the light source, the greater the proportion at which the area distribution AD1 of the light transmitting regions consists of a first stage 1 of a curve rising roughly in the shape of S, a second stage II of a curve rising in the shape of an arc, and a third stage III of a falling curve.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source device and a method for manufacturing the same. More specifically, the present invention relates to a planar light source device suitable for a backlight for panel display that irradiates light from the back side such as a liquid crystal display panel or a panel of an illuminated signboard such as an advertisement for a station, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a conventional planar light source device, a reflection surface is provided on an inner surface of a main body containing a light source, and is parallel to a diffusion transmitting member provided between the light source and an exposure surface and on the entire surface of the reflection surface. And a light-transmitting reflector having a non-uniform reflection pattern is provided so as to cover the reflection pattern, and the reflection pattern is formed such that its density increases as the distance from the light source decreases (see Japanese Patent Publication No. 59-1984). No. 8809). Such an apparatus increases the amount of reflection in a portion with a large amount of light flux directly above the light source and reduces the amount of reflection in a portion with a small amount of light, so that light in a bright portion is repeated between the reflection plate and the reflection surface on the inner surface of the main body. The light flux transmitted through the reflector while being reflected is averaged as a whole.

[0003]

However, in such an apparatus, the reflection pattern is simply formed such that its density increases as the distance from the light source decreases, but FIG. The reflector 5 near the upper part of the light source 51 is schematically shown
In No. 2, only light in the upper half of the light source 51 reaches, and light emitted from the lower half of the light source 51 does not reach the reflector 52 near the upper portion of the light source 51. That is, there is a problem that the reflected light from the back surface does not enter the wall surface from the portion indicated by the point C in FIG. 8 to the portion facing the light source 51, and the luminance is most reduced at the point C far from the light source 51.

[0004] In view of the circumstances described above, an object of the present invention is to provide a planar light source device capable of obtaining uniform luminance and a method of manufacturing the same.

[0005]

A planar light source device according to the present invention comprises a box surrounded by a side wall on which a light reflecting surface is formed, and a light source built in the box. A planar light source device that emits reflected light from a plurality of light transmitting regions provided on the side wall, wherein an area distribution of the light transmitting region increases in a substantially S-shape as the distance from the position of the light source increases. It is characterized by comprising a first stage, a second stage having a curve rising in a bow shape, and a third stage having a falling curve.

A method of manufacturing a planar light source device according to the present invention comprises a box surrounded by a side wall on which a light reflecting surface is formed, and a light source built in the box, and reflects reflected light in the box. A method of manufacturing a planar light source device that emits light from a plurality of light transmitting regions provided on the side wall, wherein the area of the light transmitting region is increased in a substantially S shape from the position of the light source, and then increased in an arc shape. And then reduce it.

Here, the light source is 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 linear arrangement of the light sources, which includes a linear light source and a ring-shaped light source that emit light over an elongated range.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A planar light source device according to the present invention and a method for manufacturing the same will be described below with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of the planar light source device of the present invention, FIG. 2 is a sectional view of the planar light source device of FIG.
FIG. 3 is a plan view showing another embodiment of the planar light source device of the present invention, FIG. 4 is a sectional view of the planar light source device of FIG. 3, and FIG.
FIG. 6 is a diagram showing an area distribution of a light transmitting region in the planar light source device of FIG. 3, FIG. 6 is a diagram showing an area distribution of a light transmitting region in the planar light source device of FIG. 3, and FIG. FIG. 4 is a diagram illustrating an area distribution of a transmission region.

As shown in FIGS. 1 and 2, when a light source 1 is placed in a box 2 formed of a light reflecting surface, light is emitted from the light source 1 in all directions, but light is Due to the presence of the reflecting surface, the light travels in a direction away from the light source 1 while being reflected by the light reflecting surface, and when reaching the terminal side wall 4, is reflected by the side wall 4 and returns, and further travels inside the box 2 while being repeatedly reflected. By increasing the reflectance of the light reflecting surface, the light travels inside the box 2 without being attenuated.

The upper side wall 5 on the front surface side of the box 2 is provided with a light transmitting region 3 which does not become a light reflecting surface, and light traveling toward the light transmitting region 3 is transmitted from the light transmitting region 3 to the outside of the box 2. Is radiated. Therefore, with the light emitted from the light source 1,
The light traveling toward the light reflecting surface is reflected and travels inside the box 2, and the light traveling toward the light transmitting region 3 is emitted from the light transmitting region 3 to the outside of the box 2. The light radiated from the light transmission region 3 to the outside of the box 2 includes light radiated in an oblique direction, and the light appears to be radiated between the light transmission regions 3. Uniform radiation is obtained over the entire surface of. In particular, by providing a light diffusing plate (not shown) on the surface of the upper side wall 5 provided with the light transmitting region 3, non-directional uniform light emission can be obtained on the surface of the light diffusing plate. The light diffusion plate may be separately provided on the surface of the upper side wall 5 provided with the light transmission region, or a wall surface provided with the light transmission region using a diffusion plate or a laminate of a diffusion sheet and a transparent substrate. And the light diffusion plate may be integrally formed. The light radiated from the light transmission region 3 has a larger incident angle (closer to the wall surface) as the light transmission region 3 is farther from the light source 1, but the wall surface on which the light transmission region 3 is provided The direction of the reflected light beam can be changed by inclining, curving, or inclining the side wall 4 opposite to the wall surface (bottom surface), thereby adjusting the direction of the light emitted from the light transmission region 3. it can.

The intensity of the light radiated from the light source 1 is strong near the linear light source 1 and weakens as the distance from the light source 1 increases. The reflected light from the wall does not enter and the brightness decreases.
Therefore, in the present invention, the rate of increase in the area of the light transmission region 3 is slightly increased as the position of the light source 1 increases. In the vicinity of the side wall 4 far from the light source 1, the side wall 4
Since the amount of reflected light increases, the light intensity increases. Therefore, in the present invention, the rate of increase in the area of the light transmission region 3 is suppressed as approaching the side wall 4. That is, in the present invention, as the distance from the position of the light source 1 increases, the area distribution of the light transmitting region 3 becomes approximately S, as shown in FIG.
A first stage I of a curve rising in a letter shape, a second stage II of a curve rising in a bow shape, and a third stage of a falling curve
III.

As described above, the area of each light transmitting region 3 is
By adjusting the position according to the above, uniform luminance can be obtained on the surface of the upper side wall 5, and a thin planar light source device can be obtained. Note that the change in the area of the light transmitting region 3 also changes depending on the distance between the light source 1 and the side wall surface surrounding the light source 1, and the light transmitting region 3 is adjusted by adjusting the area of the light transmitting region 3 in any state. Can be made uniform on the surface side of the upper side wall 3 provided with.

Regarding the distance D (see FIG. 2) between the light source 1 and the upper side wall 5 provided with the light transmitting region 3, when a cold cathode tube which does not generate heat is used as the light source 1, the distance D is almost zero.
When a cold cathode tube having a diameter of 2.4 mm is used, a planar light source device having a thickness of about 3 mm can be obtained. On the other hand, when a heat generating material is used as the light source 1, if the distance D is too small, the heat of the light source 1 causes expansion or deformation of the wall surface or light diffusing property, etc. Since the area distribution is changed and the uniformity of the emission intensity is impaired, the distance D is 3 mm or more, more preferably 5 mm or more.
With the provision of not less than mm, the reliability can be maintained without changing the area distribution of the light transmitting region.

A point light source such as a light bulb as the light source 1;
Alternatively, even in the case of using a ring-shaped light source, by adjusting the area distribution of the light transmitting region 3 so as to have the three levels described above, efficient and uniform luminance can be obtained over the entire light emitting surface. Those light sources having a circular outer shape in plan view are suitable for a planar light source device having a circular light emitting surface, but may be formed into a square planar light source device using a point or ring light source. Alternatively, a circular planar light source device using a linear light source can be used, and uniform brightness can be obtained over the entire light emitting surface by adjusting the area distribution of the light transmitting region in three stages.

The shape of the light transmitting region 3 is not limited to a circle, but can be formed in any other shape such as an elliptical shape, a polygonal shape, and a slit shape. Further, as shown in FIG. 1, the arrangement of the light transmitting regions 3 may not be arranged for each row and each column, but may be arranged to be shifted by half a pitch every other column. With such an arrangement shifted by half a pitch, the circular diameter of the light transmitting region 3 can be formed to be larger than the pitch of the light transmitting region 3, and even if the brightness becomes weak at a position far from the light source 1, many light can be obtained. This is convenient for extracting the amount of light.

The shape of the light transmission region 3 may be a slit shape continuously for a certain length, instead of a separately provided shape such as a circle. In this case,
The area distribution of the light transmitting region is adjusted in three stages by changing the width of the slit, which is the light transmitting region, or changing the interval between the slits.

Further, as shown in FIGS. 3 and 4, a linear light source 1 can be provided at the center of the box 2, and a large planar light source for an electric sign or the like can be obtained. For example, linear light sources may be arranged at all four ends of a rectangular shape, and the area distribution of the light transmitting region may be formed in three stages as the distance from the position of the linear light source increases, as described above.

The case where the shape of the light transmitting region is a circle or a slit has been described. However, the present invention is not limited to this. The other area may be a light transmitting area. In other words, when the upper surface of the box is formed of a transparent substrate, and the inner surface is coated with a metal film, a reflective paint, or a diffuse reflector such as a white paint, etc., the reflective surface is formed. Alternatively, any outer side may be a light reflecting surface. In this case, the distribution of the circular area or the area of the slit portion per unit area is formed to be smaller as the distance from the light source is increased, contrary to the above. In short, the shape may be arbitrary as long as the area distribution of the light reflecting surface and the light transmitting area is fixed and the area distribution of the light transmitting area is formed in three steps as the distance from the light source position increases.

As the light source 1, a fluorescent lamp, a halogen lamp, an electroluminescent, a light-emitting diode, a tungsten lamp (incandescent lamp), or the like arranged in such a manner as to emit light alone or linearly is used. . As a material of the light reflection surface, a metal plate having a high reflectance such as a mirror, a light reflection metal film such as aluminum on a plastic such as an acrylic resin (PMMA), or a light reflection paint such as a white paint having a high reflectance. What coated the like is used. The white paint has a lower reflectance than that of the mirror, but is preferred because of its diffuse reflection.

When the side wall of the box 2 is made of a material that does not transmit light, such as a metal plate, the light transmitting region 3 is formed by providing through holes or slits having an arbitrary shape such as a circular or polygonal shape. In addition, the side wall of the box 2 has a light reflecting film on a transparent substrate such as an acrylic resin (PMMA), a glass plate or a polycarbonate mirror, a vinyl chloride mirror, an acrylic mirror, a transparent acrylic, and a milk semi-acryl having relatively high optical transparency. When the mirror is formed by coating such a mirror, 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, there is no hole or slit penetrating the side wall, and the box is shielded from the outside air via the transparent substrate, so that entry of dust and the like can be prevented.

As a method of providing a light reflecting film on the transparent substrate, for example, a film of aluminum or the like is formed on the entire surface by a vapor deposition method or a thermal transfer method, a resist film is provided, and a series of photolithography techniques of exposure, development, and etching are performed. By etching, the aluminum film of only the light transmitting region 3 is removed, and a light transmitting region of an arbitrary shape can be formed. 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, it can be almost completely reflected completely. At about 2 μm, about half of the incident light is reflected and about half is transmitted, forming a half mirror. By adjusting the film thickness during this time, the ratio between the reflectance and the transmittance can be freely adjusted.

Another method of providing the light reflecting film is as follows.
Silk printing, gravure printing, screen printing or inkjet printing of the transparent substrate, pattern formation by sand blasting or vapor deposition of a pattern shape by a lift-off method, coating, or machining, light punching or laser processing of a light transmitting region on a reflection plate For example, a method of providing such a method can be adopted.

As described above, the light transmitted from the light transmitting region is radiated from an arbitrary oblique direction, or is diffused by a light diffusion plate or the like provided on the surface so that the light transmitted between the light transmitting region and the portion where the light reflecting film is provided. The section is blurred and uniformed, and becomes a planar light source device radiated from the entire surface. However, where the area of the light transmitting region on the wall surface is small, such as the portion near the light source, it may be difficult to obtain complete uniformity of the entire side wall. In such a case, it is preferable to provide the light reflecting film so that the light reflecting film does not completely reflect the light but transmits about 10% or less. If the transmittance of this light becomes too large, the light reflected inside the box will decrease, and the light will reach a place far from the light source, and the uniform light cannot be obtained from the entire side wall surface provided with the light transmission region. is there. In addition, the distance between the light transmitting regions is reduced as a whole while the area of the light transmitting region is increased as the distance from the light source increases (while the area ratio between the light transmitting region and the light reflecting film portion is kept constant, In the case of reducing each one), the transmittance at the light reflecting film portion can be set to 0, and the lower limit differs depending on the method of forming the light transmitting region.

In a normal internal light source device, when the distance from the fluorescent tube to the light emitting surface is 150 mm and the pitch of the plurality of fluorescent tubes is 100 mm, the brightness (luminance) is about 700 c.
d / mm ² . On the other hand, in the present invention, the fluorescent tube is brought to the light emitting surface (display section) and the total thickness is 40 m.
Even if the fluorescent tube pitch is tripled with m, the effective use of the light under the fluorescent tube (highly reflective foam sheet) shortens the distance from the lower light emission to the display unit and darkens in inverse proportion to the distance multiplied by two. As the distance to the display surface becomes shorter, the amount of light increases, and the light at the top of the tube is suppressed, the surplus amount of light is carried away, and the light is brightened by the synergistic effect of the respective lights. 3x tube pitch 300mm
To third of 1 cd / mm ² shall not surface average luminance of about 1500 cd / mm ² next energy saving also, space-saving member, light weight, it is possible to reduce the high emission and running cost.

Next, the planar light source device of the present invention will be described based on embodiments, but the present invention is not limited to only such embodiments.

Embodiment 1 In this embodiment, a planar light source device in which a linear light source 1 is arranged at one end of a box 2 as shown in FIGS.

The box 2 is made of a metal reflector having a high reflectivity, such as a mirror having a thickness of about 0.5 to 2 mm. 40m
m. The light source 1 has a diameter of 28 mm, a length of 600 mm, and a power consumption of 20 W.
Was used.

On the upper side wall 5 of the box 2, a large number of circular light transmitting regions 3 are formed so as to obtain uniform brightness over the entire light emitting surface.

As a result, as shown in FIG.
Of the area distribution AD1 rises in a substantially S shape from the position of the light source (first stage I), and then rises in an arc shape near the side wall 4 far away from the light source (a position P slightly closer to the light source) (second stage). Stage), and then a curve descending from the peak point P toward the side wall 4 (third stage). The size of the light transmitting region 3 is about 0.5 mm at the minimum at the position of the light source 1 and about 1.4 mm at the maximum at the peak point P.
Met.

Embodiment 2 In this embodiment, a metal plate coated with a foam sheet of white paint having high reflectivity was used in place of the mirror reflector of the box 2 in the first embodiment. Other structures are the same as in the first embodiment.

A large number of circular light transmitting regions 3 are formed on the upper side wall 5 of the box 2 so as to obtain uniform brightness over the entire light emitting surface.

As a result, as shown in FIG.
Is increased in a bow shape with a larger radius of curvature in the second stage II than in the second stage II in the first embodiment, but is found to have three stages as in the first embodiment. .

Embodiment 3 In this embodiment, a planar light source device in which a linear light source 1 is arranged at the center of a box 2 as shown in FIGS.

The box 2 is made of a metal plate having a thickness of about 0.5 to 1 mm coated with a foam sheet of a white paint having a high reflectivity.
It was manufactured to have a size of 0 × 400 mm and a depth of 40 mm. A fluorescent lamp having a diameter of 28 mm, a length of 580 mm, and a power consumption of 20 W was used as the light source 1.

On the upper side wall 5 of the box 2, a large number of circular light transmitting regions 3 are formed on both sides of the light source 1 so as to obtain uniform luminance over the entire light emitting surface.

As a result, as shown in FIG. 6, the area distribution AD3 of the light transmittance 3 was formed so as to be symmetric with respect to the position of the light source 1 in the left-right direction. The respective area distribution AD
It was found that 3a was composed of three stages, a first stage I, a second stage II, and a third stage III, as in Examples 1 and 2. The size of the light transmission region 3 is about 0.4 mm at the minimum at the position of the light source 1 and about 1.4 m at the maximum at the peak point P.
m.

When a mirror reflector is used instead of the side wall coated with the white paint,
As a result of examining the area distribution of the light transmitting region, the curved shapes of the first to third stages were different, but exhibited the same area distribution as in the present example.

Embodiment 4 In this embodiment, a linear light source 1 is arranged at the center of a box 2 as shown in FIGS. 3 and 4, and the light source 1 emits light from an upper side wall 5 and a lower side wall 6. A light source device was used.

The box body 2 is made of a metal reflector having a high reflectivity such as a mirror having a thickness of about 0.5 to 2 mm. 40m
m. The light source 1 has a diameter of 28 mm, a length of 580 mm, and a power consumption of 20 W.
Was used.

The upper side wall 5 and the lower side wall 6 of the box 2 are provided with a uniform luminance over the entire light emitting surface.
A large number of circular light transmitting regions 3 were formed.

As a result, as shown in FIG.
(Only the upper side wall 4 side is shown for explanation) is formed so as to be symmetrical in the left-right direction with the position of the light source 1 as the center. It was found that each area distribution AD4a was composed of three stages of a first stage I, a second stage II, and a third stage III, as in the first to third embodiments. The size of the light transmitting region 3 is as follows.
The minimum was about 0.5 mm at the position of the light source 1 and the maximum was about 1.4 mm at the peak point P.

In the case where a side wall coated with white paint is used instead of the mirror reflector,
As a result of examining the area distribution of the light transmitting region, the curved shapes of the first to third stages were different, but exhibited the same area distribution as in the present example.

Embodiment 5 In this embodiment, the luminance of the planar light source device was examined.

The box uses a reflector coated with a highly reflective foam sheet, and has a light emitting surface of one veneer (about 10).
(00 mm × 1800 mm) and the total thickness was 45 mm. A fluorescent tube 35W ×
Nine (315 W), 35 W × 4 fluorescent tubes (140 W) and 35 W × 3 (105 W) fluorescent tubes were arranged so that the fluorescent tube pitches were 200 mm, 400 mm, and 500 mm, respectively.

The area distribution for each light source was configured to have three stages as shown in the above-described Examples 1 to 4.

As a result of examining the luminance of the planar light source device thus obtained, the luminance shown in Table 1 was obtained. Table 1 shows a comparison between the brightness of a normal internal illumination type light source device. The measurement was performed at a temperature of 20 ° C.

[0048]

[Table 1]

As is clear from Table 1, it can be seen that the planar light source device of this embodiment is brighter than the internally illuminated light source device usually used for a signboard or the like.

[0050]

As described above, according to the present invention,
The area distribution of the light transmitting region is divided into three steps as the distance from the light source position increases, that is, a curve (first stage) that rises substantially in an S shape, a curve (second stage) that rises in a bow shape, and a descending curve (third stage). As a result, the influence of the lowering of the reflected light from the lower half (back side) of the light source and the effect of the reflected light of the side wall far from the light source are eliminated, and the luminance of the entire light emitting surface can be made uniform.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a planar light source device according to the present invention.

FIG. 2 is a sectional view of the planar light source device of FIG.

FIG. 3 is a plan view showing another embodiment of the planar light source device of the present invention.

FIG. 4 is a sectional view of the planar light source device of FIG. 3;

FIG. 5 is a diagram showing an area distribution of a light transmitting region in the planar light source device of FIG. 1;

6 is a diagram showing an area distribution of a light transmitting region in the planar light source device of FIG.

FIG. 7 is a diagram showing an area distribution of a light transmitting region in a two-side emission type planar light source device.

FIG. 8 is a diagram schematically showing the paths of light emitted to the front side and the back side of the light source in the conventional planar light source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Box 3 Translucent area 4 Side wall 5 Upper wall 6 Lower wall I 1st stage II 2nd stage III 3rd stage AD1, AD2, AD3, AD4 Area distribution

Claims (2)

[Claims] 1. A box surrounded by a side wall on which a light reflecting surface is formed, and a light source incorporated in the box, and a plurality of light transmitting members provided on the side wall for reflecting the reflected light in the box. A planar light source device for emitting light from an area, wherein the area distribution of the light transmitting area is approximately S as the distance from the position of the light source increases.
A planar light source device comprising: a first stage having a curve rising in a letter shape; a second stage having a curve rising in an arc shape; and a third stage having a falling curve. 2. A box surrounded by a side wall on which a light reflecting surface is formed, and a light source built in the box, and a plurality of light transmitting members provided on the side wall for reflecting the reflected light in the box body. A method of manufacturing a planar light source device that emits light from a region, wherein the area of the light transmitting region is increased in a substantially S shape from the position of the light source, then increased in a bow shape, and then reduced. Manufacturing method of planar light source device.