JPH11126505A - Flat-type lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat-type lighting system having high brightness of little unevenness which is light-weighted, low in cost, easy for maintenance, and suitable for the backlight of a large desktop LCD, particularly larger than 15 inches. SOLUTION: This lighting system is composed by disposing a linear light source 6 inside a housing 5 having an inner base surface 1a and an inner side surface 2a and an opening surface 3 facing the inner base surface 1a and a covered with a light diffusing plate 4. The inner base surface 1a and the inner side surface 2a are opaque reflectors of white having light diffusivity. On the inner base surface 1a, waveform projections and depressions triangular in cross section are formed together with the linear light source 6 disposed slightly separated from each valley of valleys 7 forming the waveform projections and depressions. The surface facing the light source of the light diffusing plate 4 is a gloss surface 4a having regular reflectivity. The tilt angles ϕ which slanting surfaces forming the waveform projections and depressions triangular in cross section form with a surface parallel to the opening surface 3 are from 12 to 17 degrees and the inner side surface 2a is connected continuously to peaks 8 of the inner base surface 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-emitting type illuminating apparatus which can be widely applied as a backlight for liquid crystal, an illumination signboard, a general illuminating device, etc., and more particularly to a planar light source having high luminance and uniform luminance. The present invention relates to a surface-emitting lighting device that functions as a lighting device.

[0002]

2. Description of the Related Art At present, a so-called surface-emitting illuminating device is
Broadly classified into types. One is a surface-emitting lighting device having a structure directly below a light source. In a lighting device having this type of structure, a light source is disposed immediately below (behind) a light-emitting surface. For example, a plurality of linear light sources such as fluorescent lamps are disposed inside a rectangular box (for example, substantially at the center). On the other hand, it has a structure in which a pair of opposing opening surfaces constituting a box are covered with a light-diffusing plate having a light-transmitting property (for example, an acrylic resin half-plate). Is used as In the illumination device having this type of structure, only one of the pair of opposing surfaces is opened and covered with a light-diffusing plate having a light-transmitting property, while the other opposing surface is simply a white opaque planar reflecting surface. Some of them have a structure that emits light only on the front surface, and are widely used as lighting equipment and the like to be fitted into ceilings of general households, subway stations, wall surfaces inside buildings, and the like.

Another one is a surface-emitting type illuminating device having a light source edge arrangement type structure. Lighting devices of this type of structure
In order to avoid the appearance of a so-called lamp image, a light source is arranged at an edge portion of the light emitting surface so as to avoid a portion immediately below (behind) a light emitting surface. For example, an inner peripheral edge portion of a flat rectangular box (for example,
A fluorescent lamp as a linear light source is disposed on two outer sides facing each other, one outer side, or two outer sides adjacent to each other in an L-shape. A light guide plate made of acrylic resin or the like is provided, and the light guide plate diffuses light from a linear light source disposed at an edge portion over the entire light emitting surface. Therefore, one surface of the light guide plate is printed in a white dot shape having a reflection function, and the other surface (namely, the opening side surface on the illumination side) is a light scattering plate or a Fresnel lens sheet. Are superimposed. In particular, when configured as a lighting device (hereinafter abbreviated as a backlight) for a liquid crystal display (hereinafter abbreviated as an LCD), a cold-cathode tube having a small diameter is used as a fluorescent lamp.

[0004] Instead of dot printing, the light guide plate itself is provided with a fine pattern, and the cross-sectional shape of the surface emitting type illumination device or light guide plate is devised so that uniform scattered light is emitted to the opening surface by reflection of the portion. There are also wedge-shaped surface-emitting lighting devices, which are widely used for small LCDs, for example, LCDs for vehicle navigation devices, mobile phones, and mobile personal computers.

FIGS. 6 to 8 show an example of a surface-emitting type illuminating device having such a light source edge arrangement type structure.

FIG. 6 shows a cross section of an LCD backlight using one lamp. The upper side is a required illumination surface, L is a lamp, R is a reflector of the lamp, G is a wedge-shaped light guide plate, D is a prism sheet, DR is a light diffusing material, B
Is the outer case. As shown in the figure, a wedge-shaped light guide plate G made of acrylic resin or the like is used. In the figure, a fine pattern is engraved on the lower side of the light guide plate G, and consideration is made so that uniform light is emitted to the upper side of the figure by reflection of that part. α indicates a minute angle in the pattern, and adjusts the light reflected upward by skillfully utilizing the total reflection angle determined by the refractive index of the light guide plate G, the so-called critical angle. However, no matter how sophisticated and fine optical calculations are performed, it is not possible to perform the processing exactly as it is, so trial and error will actually be repeated.

FIG. 7 shows a cross section of an LCD backlight using four lamps. The upper side is a required illumination surface, L is a lamp, R is a reflector of the lamp, D is a light scattering sheet, P is a prism sheet, G is a light guide plate, RD is a light diffusion sheet, and B is an outer case. It turns out that it is a very complicated structure. The lamp L is placed on both sides of the light guide plate G
A total of four books are arranged. Lamp L in a narrow space
Therefore, increasing the number of lamps L is dangerous from this point. The light guide plate G is made of a transparent plate of acrylic resin, and white dots of various shapes are printed on the opposite side of the illumination surface, that is, on the lower side of FIG. There is also a form in which dots are printed on another film and attached to the light guide plate. Since the reflection of dots alone is insufficient, a light diffusion sheet RD made of a low-reflection polystyrene sheet having a high reflectance is generally inserted further below the light guide plate G.

FIG. 8 is a plan view showing a typical state of dot printing of the lamp L and the light guide plate G of FIG. Two lamps L are arranged on each of the left and right sides, and dot printing DP is applied on the back side of the light guide plate G. Indicates that the density of dot printing is different, the density of is low, that is, the reflectance near the light source is suppressed, and the density of is high, that is, the reflectance at positions away from the light source is increased. doing.

FIGS. 9 and 10 show an example of a more general lighting device, which is shown just in case to clarify a difference from the present invention described later. FIG. 9 shows a conventional ceiling-mounted fluorescent light fixture. In a so-called inverted Fuji type, only one fluorescent lamp is set at the top of the inverted Fuji type, that is, at a position closest to the floor.

It is to be noted that the point that the linear light source is arranged not at the valley but at the peak is different from the structure of the present invention described later. Note that R is a main plane reflecting surface, L is a lamp, and S is a lamp socket. Some lighting fixtures of this type are covered with covers of various materials and shapes, but the brightest is just below the lamp. FIG. 10 shows a conventional lighting device without an office cover. 3 fluorescent lights
The book is used. The lower side is an aperture surface for providing illumination light. Use it embedded in the ceiling. The main reflecting surface is a plane parallel to the floor surface, and the flat reflecting surface of the side wall is formed so as to taper inward toward the upper side. It should be noted that the present invention is different from the present invention described later in that the reflecting surface is not a reflecting surface having a corrugated unevenness having a triangular cross section but is a plane parallel to a floor surface. Although it is a flat lighting device, it is hard to say that attention is paid so that uneven brightness is reduced and light distribution characteristics are parallel to the floor. Note that R
Is a main reflecting surface, B is an outer case, L is a fluorescent lamp, and S is its socket.

[0011]

The size of the opening surface (light-emitting surface) of a general signage lighting device belonging to a surface-emitting lighting device having a structure directly below a light source is large, several meters, and small. It is about 50 cm, and the depth, that is, the dimension perpendicular to the opening surface, is 30 cm or more in a large size and 2 mm in a small size.
It is about 0 cm. Because of its large size and weight, it is not used at all as an illumination light source for LCDs. Although there is almost no problem in using a surface-emitting illuminating device of this type for an advertising signboard, in order to realize a planar light source with uniform luminance, luminance unevenness is large and a lamp image, that is, a linear There is a disadvantage that a bright transmitted image of the lamp is strongly generated, and in order to eliminate the problem, it is necessary to increase the depth of the apparatus and increase the number of light source lamps to be used.

On the other hand, as described above, an LCD lighting device using a cold-cathode tube has recently been developed as a surface-emitting lighting device of a light source edge arrangement type, as described above. That is, this is an apparatus using a plate or a film in which an appropriate translucent dot printing is applied to a light scattering material provided on the opening surface to eliminate luminance unevenness and a lamp image. In this device, the density of dots is increased near the lamp to reduce the light transmittance.

However, it is necessary to change the pattern of the dots in accordance with the number and position of lamps, the dimensions of the device, the required brightness, and the like. In addition, since light near the lamps is blocked, light use efficiency is deteriorated, and it is necessary to increase the number of lamps. In addition, when the brightness of the lamp decreases over time, a lamp image is generated, and it is very difficult to keep the brightness unevenness within a necessary limit for a long period of time.

The type using a light guide plate is widely used at present for an illumination light source for LCDs.
At present, it is difficult to develop future LCD lighting devices of inches or larger.

The reasons are as follows: 1) The light guide plate becomes large, and as a result, the weight of the lighting device increases.

2) Since the lamp is arranged on the periphery of the light guide plate,
The area near the lamp, that is, only the periphery, becomes bright, and it is extremely difficult to make the luminance unevenness of the entire aperture surface uniform and high.

3) It is difficult to match with an LCD having a low strength, the number of parts is increased, and the device is complicated, which increases not only the lighting device but also the assembly cost.

4) It is extremely difficult to design a light guide plate. Because of the need to repeat trial and error, there are always problems with time and cost.

5) Lamp replacement is almost impossible due to the complexity of the apparatus.

By the way, in recent years, a liquid crystal panel which is superior in image performance of a conventional cathode ray tube and which has high definition and excellent color tone has been developed. However, this type of panel inevitably has a low light transmittance and is more natural. In order to obtain a bright image close to the above, it is necessary to use a surface-emitting type illuminating device having a significantly higher luminance than the conventional one and having a uniform luminance.

Based on the above trends, there is a strong demand for the development of the following surface-emitting type illumination device.

1) Even a large-sized lighting device should be light in weight.

2) High luminance and low luminance unevenness.

3) The cost is low.

4) Maintenance such as lamp replacement can be easily performed.

5) The depth of the device, that is, the thickness is as small as possible.

The present invention has been made under the above-mentioned technical background, and an object thereof is to provide a high-brightness and low-luminance unevenness which is particularly suitable for a backlight of a large-sized desktop LCD of 15 inches or more. Another object of the present invention is to provide a flat lighting device which is lightweight, inexpensive, and easy to maintain.

[0028]

SUMMARY OF THE INVENTION The invention described in claim 1 of the present application is directed to a box having an inner bottom surface and an inner side surface, and an opening surface facing the inner bottom surface covered with a light diffusing plate. A linear light source is arranged, and the inner bottom surface and the inner side surface are opaque white reflectors having a light diffusing property.
The corrugated unevenness having a triangular cross section is formed, and the linear light source is disposed at each of the valleys forming the corrugated unevenness slightly apart from the valley, and the surface of the light diffusion plate facing the light source is A glossy surface having specular reflectivity, wherein a value of an inclination angle formed by a slope parallel to the opening surface with a slope constituting the triangular waveform corrugations is between 12 degrees and 17 degrees; Is connected to the mountain on the inner bottom surface so as to be continuous.

The invention according to claim 2 of the present application is characterized in that the inner surface is flat and is slightly inclined so as to expand toward the light diffusing plate. The planar illuminating device according to the above.

The invention according to claim 3 of the present application is characterized in that one or more linear Fresnel lens sheets or lenticular sheets having a light converging property are added to the outside of the light diffusing plate in an overlapping manner. 1. The planar illumination device according to item 1.

According to a fourth aspect of the present invention, in the planar illumination device according to the first aspect, the top of the peak or the bottom of the valley constituting the corrugated unevenness has a slight roundness. It is in.

The principle of the present invention is presumed as follows.
In the confined space, light emitted from a light source such as a fluorescent lamp travels straight toward the confined wall surface. If the wall is specular, the light will be specularly reflected according to the law. If one of the spaces is open, a part of the light goes to the opening surface, but the light emitted from the opening surface has an extremely uneven distribution of intensity. In other words, the light that goes directly from the light source to the aperture surface has the highest intensity, and the light that enters the wall at a very shallow angle from the light source exits at a very shallow angle in the opposite direction to the light source due to the law of reflection. And hardly go to the opening surface. Therefore, the intensity of light on the opening surface of that portion becomes very low.

This is because, when the space in which light is confined is not much different from the size of the light source, it depends on the configuration of the reflecting surface. Suggests suitability. Footlights and searchlights are typical applications. On the other hand, if the aperture surface is very large compared to the size of the light source, it is difficult to obtain a uniform illumination surface if the reflection surface is a mirror surface, no matter how good the light scattering plate covers the aperture surface. Is also shown. If it is desired to obtain uniform brightness at the opening of the lighting fixture as described above, it is necessary to increase the distance between the light source and the opening. Then, the light amount of the light source decreases in inverse proportion to the square of the distance, and the luminance decreases. Therefore, it is extremely difficult to realize a large and thin flat illuminating device having a mirror inner surface.

In the above case, if the reflecting mirror surface is a white opaque diffuse reflecting surface, the light from the light source diffusely reflects, so that the light intensity distribution on the aperture surface is considerably leveled. However, when the light source and the reflection surface are extremely close, even if it is irregular reflection, the gap of the intensity distribution becomes large, and the intensity of light from the reflection surface slightly away from the light source to the aperture surface becomes extremely small. In general lighting devices and signboard lighting devices, the number of light source lamps is increased, or the distance from the light source to the aperture surface is increased to compensate for the reduced emitted light. Recent L
Some CD illuminating devices, that is, backlights, have light-impermeable dot printing that gives an appropriate density distribution to the scattering plate provided on the aperture surface in order to reduce the intensity of light emitted directly from the light source. . However, in this case, since the light emitted directly from the light source is blocked, the light use efficiency is reduced as described above.

The present inventors have realized various kinds of mirror reflection devices, diffusion plane reflection devices, reflection surfaces having an aspherical shape, and linear aspherical lenses disposed on an aperture surface.
A number of devices were fabricated and the behavior of the lamp light source was observed in detail. As a result of these studies, we have devised and filed a patent application for a flat lighting fixture whose main reflecting surface is white, smooth, off-axis, aspheric, and has a hollow interior. Came to a conclusion.

1) In order to improve the luminance of a large flat lighting device,
Increasing the number of linear light source lamps such as fluorescent lamps is an absolute requirement.

2) The reflecting surface facing the opening surface is made of a reflecting material that is as close as possible to a perfect diffusing surface, and is not just a plane, but is 12 to 17 degrees, most preferably a plane parallel to the opening surface. It is composed of a combination of flat peaks and valleys having a 15-degree inclination angle (waveform irregularities having a triangular cross section), and is slightly above the valleys, specifically 0.5 to 2.5 times the lamp diameter. If a linear light source lamp is placed at a position and the opening surface is covered with a light scattering plate with a glossy surface that reflects light regularly on the light source side, the intensity of reflected light can be increased even at a position distant from the lamp, that is, at the top of the mountain. Becomes possible.

3) It is desirable that the pitch between the peaks and valleys is equally spaced, and the size of the inclined surface does not exceed at most 10 times the lamp diameter.

4) When the inclination angle of the peaks and valleys is set to 12 degrees or less or 17 degrees or more, the reflected light shows the maximum intensity at a position slightly distant from the lamp. Occurs.

5) When the inclination angles of the peaks and valleys are set to 5 degrees or less,
The brightness of the reflected light extremely decreases at a position distant from the light source, and if the angle of inclination is 20 degrees or more, the reflected light returns to the light source, and the brightness decreases at the top of the mountain. This produces a bright lamp image on the aperture surface.

6) Inferring to the item 2), that is, since a lamp such as a fluorescent lamp has a size called a diameter,
The light from the light source does not illuminate the reflecting surface at a certain angle. Therefore, the primary reflected light produces a certain range of intensity distribution. When the opening surface is covered with a light-scattering plate having a glossy surface having a regular reflection function on the inner surface, light from the light source is inclined with respect to the glossy surface.
Furthermore, complicated reflection is repeated between the light-scattering plate and the light-source lamp, the light is uniformly mixed inside the light-scattering plate, and finally emitted from the light-scattering plate to the outside.

7) If a slight lamp image still remains, change the position of the light scattering plate with respect to the light source or change the light transmittance of the scattering plate to eliminate this. It depends on the diameter of the lamp and the optical properties of the scattering plate or the reflector forming the peaks and valleys. For example, if the total light transmittance of the scattering plate is in the range of 30-80%, Suitably, the position is 3 to 12 times the lamp diameter and away from the lamp. When the lamp diameter is large, the position of the scattering plate is made closer to the lamp. If the light transmittance of the scattering plate is low, the position of the scattering plate is also closer to the lamp.

8) If a so-called prism sheet (hereinafter, abbreviated as a prism sheet) such as a Fresnel lens sheet is added to the emission side of the light diffusion plate so that the light emitted to the outside of the apparatus is not diffused immediately after the emission, the luminance in a certain angle direction is increased. Is improved.

Thus, the present inventors have carried out the invention of claims 1 to 4. The operation of the present invention will be described as follows.

That is, the planar lighting device of the present invention has a hollow box shape except for a linear lamp having a light source inside, and the bottom and side surfaces of the box are reflecting surfaces, and the bottom surface faces the bottom surface. One aperture surface is the required lighting surface, which is covered by a light scattering plate, which is a very simple structure lighting device that provides a very uniform high brightness brightness.

The bottom surface is made of a white reflective material of a material close to a perfect diffusion surface, and is made up of equally-spaced peaks and valleys parallel to a plane, and its inclination angle is 12 to 1 with respect to a plane parallel to the opening surface.
It is made in the range of 7 degrees, and the linear lamp is arranged above the valley without touching the valley.

In general, when a plurality of linear lamps are mounted on a box-shaped lighting device, the bottom surface is formed of a mere white plane reflecting surface (for example, see the conventional example of FIG. 10), and the opening surface is made of a translucent milky white. For example, even when covered with an acrylic resin sheet, a bright lamp image cannot be erased even after passing through the sheet. In places with relatively high ceilings, such as offices,
It is not necessary to cover the lamp with a translucent sheet because it is rare to see the lamp directly, but at homes, hotels, or shopping streets inside buildings, it is necessary to avoid exposure to a bare light source as much as possible, so the lamp image is inevitable. It is currently used as it is.

By inclining the bottom surface of the box-shaped lighting device, the present inventors can make the lamp image extremely small, and cover the opening surface with a light scattering material having an appropriate light transmittance. As a result, we succeeded in developing a flat luminaire with high brightness and uniform brightness, in which almost no image of the lamp image or the shadow of the lamp socket part was produced. As a suitable light scattering material, a conventionally used white translucent plate of acrylic resin or PVC or a polyester film can be used as long as the light source side has a glossy surface having a regular reflection function. However, since the former has a low light transmittance and the latter has a high light transmittance, it is not suitable for an LCD backlight. An acrylic resin or a styrene resin obtained by addition polymerization of a certain rubber component was found to be suitable for an LCD backlight from the viewpoint of color temperature and the like.

Further, when a so-called prism sheet (linear Fresnel lens sheet, lenticular sheet, etc.) having a light converging property is added to the outgoing light side of the illumination device,
It was also found that the brightness was improved. However, depending on the characteristics of the prism sheet, the field of view of the illumination surface may be narrowed even if the luminance is improved.

The top of a mountain or the bottom of a valley may have a slight curvature. The curvature varies depending on the diameter of the lamp, the required range of luminance unevenness, and the method of manufacturing the lighting equipment. However, if the curvature is too large, the luminance unevenness may increase.

The inner reflecting surface of the device along the peaks and valleys is preferably in principle perpendicular to the opening surface. However, even if an angle is set so as to open slightly outward with respect to the opening surface, the performance is not affected. There is no.

The position where the main reflecting surface (inner bottom surface) is in contact with the reflecting surface (inner side surface) is always in contact with the mountain.

The lighting apparatus according to the present invention is expected to be widely used in the future, such as LCDs, lighting equipment for homes and hotels, wall lighting in buildings, billboards, and outdoor billboards.

[0054]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some preferred embodiments of the planar lighting device according to the present invention will be described below in detail with reference to FIGS.

Embodiment 1 FIG. 1 shows a backlight manufactured for an LCD, in which a central portion is cut away so that the internal structure can be easily understood. The upper side is the required illumination surface. In this example, the cold cathode fluorescent lamp 6 has a diameter of 2.2 mm and a length of 295 mm.
Is drawn with six lines in the figure, but actually eight parts were used. The dimensions of the box 5 of the lighting fixture are 320 mm wide, 240 mm long and 29 mm deep. In FIG. 1, 1 is a bottom plate, 1a is an inner bottom surface, 2 is a side plate, 2a is an inner side surface, 3 is an opening surface, 4 is a light scattering plate having a thickness of 1 mm, 4a is a glossy surface, 5 is a box, 6 is A linear light source (cold cathode ray tube), 7 is a valley (valley bottom) of triangular wave-shaped irregularities, 8 is a peak (top) of triangular wave-shaped irregularities, and 9 is a thickness added to be superimposed on the outer surface side of the light scattering plate. The prism sheet having a thickness of 0.2 mm, LW is a lead wire of the lamp.

FIG. 2 explains the gist of the present invention more clearly. FIG. 2 is a view having the same effect as the cut surface at the center of the lighting apparatus of FIG. 1 but using eight lamps. The numbers in the figure are the same as those in FIG. hf is the dimension from the bottom of the main reflecting surface to the top of the mountain, p is the dimension from the valley to the bottom of the next valley, and p = 2 to obtain uniform brightness at the aperture surface.
hf.

As is clear from FIGS. 1 and 2, this planar illumination device has a bottom plate 1 forming an inner bottom surface 1a and a side plate 2 forming an inner side surface 2a, and is opposed to the inner fixed surface 1a. A linear light source (cold cathode ray tube) 6 is arranged in a box 5 whose opening surface 3 is covered with a light diffusion plate 4. The inner bottom surface 1a and the inner side surface 2a are opaque white reflectors having a light diffusing property. The inner bottom surface 1a is formed with corrugations having a triangular cross section, and the linear light source 6 is disposed at each of the valleys 7 constituting the corrugations to be slightly separated from the bottom of the valley 7. I have. The surface of the light diffusion plate 4 facing the light source 6 is a glossy surface 4a having regular reflectivity. The value of the inclination angle φ that the slope forming the triangular cross-sectional waveform irregularities forms a plane parallel to the opening surface is 12 degrees to 1 degree.
It is between 7 degrees. Further, the inner side surface 2 a is
It is connected so as to be continuous with the mountain 8 of a.

FIG. 3 shows a state in which the side surface parallel to the valley of the lighting fixture shown in FIG. The numbers are the same as in FIG. According to such a configuration, it was confirmed that the luminance was further increased.

Under the application conditions of DC 12 V and current consumption 2 A,
Applied 15 minutes after the results of the brightness measurement at the light scattering plate 4 500 millimeters away of, 8,300cd / m ^2, is measured at the same conditions at the time of the liquid crystal panel mounting was 370cd / m ^2. The luminance unevenness was 2% or less in each case. The luminance was measured under the same conditions as above, but with a depth dimension of 10 mm.
00 cd / m ² , 12,550 c with ^two prism sheets
d / m ² . The luminance unevenness was 5%. The temperature rise was such that after lighting for 4 hours, the surface temperature of the lamp drive circuit, which became the highest, was 42 ° C., and the temperature of the illuminating portion was 32 ° C., and no problem occurred. At this time, the room temperature was 27 ° C.

[Embodiment 2] FIG. 4 shows a lighting apparatus according to the present invention, which is a system with a cover which is directly attached to a ceiling in a hotel, office, or home. The left side of the lower lighting cover is partially cut away for easy understanding of the internal structure. The lower side is the required lighting surface. A part of the left side of the cover is cut out so that the inside can be seen. In the figure, 10 is a bottom plate functioning as a main reflecting surface, 11 is a valley (valley bottom) of corrugations formed on the bottom plate 10, 12 is a crest (peak) of corrugations formed on the bottom plate 10, and 13 is a crest of corrugations. A fluorescent lamp which is a linear light source arranged in the valley 11,
Reference numeral 14 denotes a milky white translucent cover functioning as a light diffusing plate for covering the front opening of the box, 15 denotes an outer case, S denotes a fluorescent lamp socket, and IP denotes a lower surface of the lighting cover 14, that is, a lighting surface. . This example can be summarized in FIG.
In the embedded lighting device having the flat reflecting surface described above with reference to FIG. 0, the reflecting surface is simply provided with peaks and valleys. Since the reflective surface can be made of a white, opaque plastic sheet that performs regular reflection by pressure molding or vacuum molding, the production cost can be kept low.

The lamp 11 has a diameter of 30.5 mm and a length of 1,
It was manufactured using a total of four 000 mm, 30 W fluorescent lamps. The size of the lighting equipment is 1,320 mm in width and 1,240 in height.
Mm, 115 mm deep. Numeral 14 denotes a cover made of a white translucent plate of acrylic resin having a thickness of 2 mm, which is a vacuum-formed product and provides an illumination surface required by this cover. The box bottom plate 10 functioning as a main reflecting surface was made of a white opaque polycarbonate sheet having a thickness of 2 mm, and the peaks and valleys were formed by bonding the sheets. The luminance of the fluorescent lamp 13 is 8,800
cd / m ² , the measured brightness of the cover 14 at a location 2 meters away from the instrument was 4,300 cd / m ² .
The luminance unevenness was 5%. The luminance was measured under the same conditions as above except that the thickness of the cover 14 was 2.5 mm. As a result, the luminance was 3,200 cd / m ² and the luminance unevenness was 2%. The temperature rises after lighting for 4 hours, the surface temperature of the transformer of the lamp drive circuit where the temperature becomes the highest is 54 ° C, and the temperature inside the fixture is 40 ° C.
° C, and the room temperature at this time was 30 ° C.

[Embodiment 3] FIG. 5 shows a lighting fixture to which the present invention is applied, which is a ceiling-mounted type using a circular fluorescent lamp, a so-called circle light. The bottom plate 10 functioning as a main reflecting surface is formed with corrugated irregularities whose cross section in the radial direction has a triangular wave shape, and therefore has concentric valleys 11 and peaks 12. As the circle light functioning as the linear light source 13, two light sources, a 30W light at the inner circumference and a 80W light at the outer circumference, are used. However, the reflective surface in the center of the instrument is made flat for manufacturing convenience. The numbers and symbols are the same as in FIG.

[0063]

Many of the LCD backlights currently used use a light guide plate, but are so-called edge lights with a screen size of up to about 14 ". Even the brightest one has a luminance of 6,000 cd / m ² and luminance unevenness of 10 to 20.
%. At this brightness, the light transmittance of the liquid crystal panel is 4
%, It is 240 cd / m ² on the LCD screen, which is equivalent to the brightest CRT, and it is hard to say that the LCD is particularly excellent as a product.

Since the number of lamps of the illuminating device according to the present invention is not limited in principle, it is possible to easily obtain the luminance required for the backlight of a high-performance liquid crystal panel. In addition, since the position of the light scattering plate placed on the opening surface can be freely changed, it is free to suppress the luminance unevenness to a desired range.
For example, it is possible to obtain a luminance of 12,000 cd / m ² . Even if the light transmittance of the liquid crystal panel is 3.5%, the LCD screen is 420 cd / m ² , so the screen becomes brighter than the cathode ray tube, and the commercial value can be sufficiently enhanced. In the future, it is expected that computer displays and televisions will make a significant contribution to the replacement of CRTs (CRTs) with LCDs.

Further, since a lamp image or a socket image does not appear in a general lighting device, it is possible to provide bright and high-quality lighting. Since the structure is simple, the production cost does not increase and the maintenance is easy, so we expect that it will contribute to the general public widely.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a backlight for an LCD according to an embodiment of the present invention, with a part thereof being cut away.

FIG. 2 is a cross-sectional view illustrating a main part of the backlight of FIG. 1 for easier understanding.

FIG. 3 is a diagram showing a state in which a side surface parallel to a valley of the lighting fixture shown in FIG. 2 is inclined outward by θ as approaching an opening.

FIG. 4 is a partially cutaway perspective view showing a lighting device with a cover for office or home use according to the present invention.

FIG. 5 is an exploded perspective view showing a ceiling-mounted type lighting apparatus to which the present invention is applied using a circular fluorescent lamp, a so-called circle light.

FIG. 6 is a sectional view showing the internal structure of a conventional LCD backlight using one lamp.

FIG. 7 is a sectional view showing an internal structure of a conventional LCD backlight using a light guide plate.

8 is a plan view showing a typical state of dot printing of the lamp and the light guide plate of FIG. 7;

FIG. 9 is a perspective view showing a conventional ceiling-mounted fluorescent lamp apparatus.

FIG. 10 is a perspective view illustrating a conventional lighting device without an office cover.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bottom plate 1a Inner bottom surface 2 Side plate 2a Inner surface 3 Opening surface 4 Light diffusing plate 4a Glossy surface 5 Box 6 Linear light source 7 Waveform uneven valley (valley bottom) 8 Waveform uneven ridge (peak) 9 Prism sheet 10 Box body Bottom plate 11 Valley of corrugations 12 Peak of corrugations 13 Linear light source 14 Cover constituting light diffusion plate 15 Outer case L Lamp R Reflector of lamp G Light guide plate D Prism sheet DR Light diffusion plate B Outer case S Socket

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Suzuki 1-4-24 Shiromi, Chuo-ku, Osaka-shi, Osaka Within NEC Home Electronics Co., Ltd. (72) Inventor Shunji Uchio 4-chome, Higashicho, Koganei-shi, Tokyo No. 42 No. 1 Inside the Light Energy Application Laboratory

Claims (4)

[Claims] 1. A linear light source is disposed in a box having an inner bottom surface and an inner side surface, and an opening surface facing the inner bottom surface is covered with a light diffusing plate. Is an opaque white reflector having a light-diffusing property, and the inner bottom surface is formed with a triangular-wave-shaped cross-sectional waveform unevenness, and the linear light source is located in each of the valleys that form the waveform unevenness. The light-diffusing plate is disposed slightly apart from the valley, and the surface of the light diffusion plate facing the light source is a glossy surface having regular reflectivity, and the slope that forms the triangular cross-sectional waveform irregularities is the opening surface. The value of the inclination angle which forms a parallel surface is between 12 degrees and 17 degrees, The said inner surface is connected so that it may be connected to the mountain | top of the said inner bottom surface, The planar illumination device characterized by the above-mentioned. 2. The planar lighting device according to claim 1, wherein the inner side surface is flat and slightly inclined so as to expand toward the light diffusing plate. 3. The planar lighting device according to claim 1, wherein one or more linear Fresnel lens sheets or lenticular sheets having light converging properties are added to the outside of the light diffusing plate. 4. The planar illumination device according to claim 1, wherein a top of a peak or a bottom of a valley constituting the corrugated unevenness has a slight roundness.