JP2004071576A - Surface light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light emitting device of high luminance and uniform luminance distribution. <P>SOLUTION: This surface light emitting device has a light emitting plate and a back face plate arranged parallel to form a light guide space, and at least one light source at either end of the light guide space. A prism-like light transmitting film inclined onto both end sides from the center part is provided on the light guide space side surface of the back face plate, or prism-like light transmitting films are provided at both faces of the light emitting plate, or prism-like light transmitting films are provided double on the light guide space side of the light source. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a high-brightness, thin, and lightweight planar light-emitting device used for a backlight of a liquid crystal display device or the like.

Japanese Patent Application Laid-Open No. 4-487 describes a planar light emitting device directly under a light source. However, it is difficult to reduce the thickness and weight of this device, it is necessary to strictly adjust the position of the light source in order to obtain high brightness, and the heat generated by the light source may deteriorate the liquid crystal display device. There was a point.

Japanese Patent Application Laid-Open No. 4-191704 describes a planar light emitting device in which light sources are arranged on both sides of a light guide, and a check mark pattern is arranged on the back of the light guide. Since this device uses a light guide, it is difficult to reduce the weight and thickness, and it is difficult to process the light guide with a rope pattern, and there are problems such as low brightness.
Japanese Patent Application Laid-Open No. 5-181136 describes a planar light emitting device in which light sources are arranged at both ends of a light guide space and a prism shape is provided on the inner surface of a light emitting plate. This device has a problem that the prism surface needs a reflection treatment, has no surface smoothness, it is difficult to perform a uniform treatment, and the brightness is insufficient particularly when the device is thin.

Japanese Patent Application Laid-Open No. 5-281540 describes a planar light emitting device in which light sources are arranged at both ends of a light guide space, prism plates are arranged in front of the light sources, and light from the light sources is directed to a light emitting diffuser. ing. In this apparatus, a process for giving different refractive indexes to the same prism plate is necessary, and it is practically difficult to realize the same.
Japanese Patent Application Laid-Open No. 63-318003 discloses a planar light emitting device in which light sources are arranged at both ends of a light guide space, and a light-transmitting sheet having a plurality of prism shapes parallel to one surface is arranged in the light emitting body surface and in front of the light source. Has been described. However, in this device, there is a possibility that brightness is lacking in uniformity when the device is made thin.

The present invention intends to provide a planar light emitting device which is thin and lightweight, has high luminance, and can emit light uniformly.

In order to solve the above-mentioned problem, in the first aspect, the present invention provides a light emitting plate 2 and a back plate 3 which are arranged in parallel so as to form a light guide space 4, and at least both ends of the light guide space 4. In the planar light-emitting device having at least one light source 8, a light-transmitting film 5 having a flat surface on one side and a number of parallel saw-toothed prisms on the other surface is provided on the light guide space side of the light-emitting plate 2. A first light-emitting surface light-transmitting film) on the light guide space side of the back plate 3, one surface of which is flat and the other surface of which is parallel to the direction of incidence of light from the light source. A light-transmitting film 6 having a saw-toothed prism (referred to as a rear light-transmitting film) is provided, and the rear light-transmitting film 6 is substantially connected to the light source 8 from a central portion 7 of the light-transmitting film. Characterized by having an inclined surface or an inclined curved surface To provide an optical apparatus.

The inclined surface or the inclined curved surface preferably forms an angle of 15 ° or less with respect to incident light. In a preferred aspect, the rear light-transmitting film is divided into at least two parts to form an inclined surface or an inclined curved surface.
According to a second aspect of the present invention, in the planar light emitting device of the first aspect, the light emitting plate 2 is a diffusion film (that is, a light transmitting film that diffuses and transmits light). On the opposite side of the light-emitting plate 2 from the light guide space side, a light-transmitting film 9 (hereinafter referred to as a second light-emitting surface light-transmitting film) having one flat surface and a plurality of parallel saw-toothed prisms on the other surface. ) Is further provided.

According to a third aspect of the present invention, in the planar light emitting device, the light transmitting film 10 having a plurality of parallel saw-toothed prisms on one surface and a plurality of parallel saw blade prisms on the other surface is provided on the light guide space side of the light source 8. (Referred to as a first light source translucent film).
In a fourth aspect of the present invention, in the device according to the third aspect, the first light source translucent film 10 is parallel to or in contact with the first light source translucent film 10, one surface of which is flat and a large number of other surfaces. A light-transmitting film 11 having a sawtooth-shaped prism (referred to as a second light-transmitting film) is further provided, and a prism array of the first light-source transmitting film and the second light-transmitting film are provided. The prism rows of the optical film are perpendicular to each other.

According to the fifth aspect of the present invention, at least one light source 8 is provided at each of at least both ends of the light emitting plate 2 and the rear plate 3 which are arranged in parallel to form the light guiding space 4 and at least both ends of the light guiding space. A light-transmitting film, wherein the light-emitting plate 2 is made of a diffusion film, and on both surfaces of the light-emitting plate 2, one surface is flat and the other surface has a number of parallel saw-toothed prisms. 5 and 9 (first and second light-emitting surface light-transmitting films) are provided, and at least the prism row of the light-transmitting film 5 (first light-emitting surface light-transmitting film) on the light guide space side is the same as the above. Provided is a planar light emitting device which is disposed so as to be perpendicular to an incident direction of light from a light source 8.

According to a sixth aspect of the present invention, in the apparatus according to the fifth aspect, the light-transmitting side of the light source 8 has a plurality of parallel saw-toothed prisms on one side, and a plurality of parallel saw-toothed prisms on the other side. A film 10 (first light source translucent film) is provided.
According to a seventh aspect of the present invention, in the planar light emitting device of the sixth aspect, one surface is flat and the other is parallel to or in contact with the first light source translucent film 10. A light-transmitting film 11 (second light source light-transmitting film) having a large number of sawtooth-shaped prisms on its surface is provided, and a prism row of the first light source light-transmitting film 10 and the second light source light-transmitting film 10 are arranged. The prism row of the light source translucent film 11 is in the vertical direction.

According to an eighth aspect of the present invention, in the planar light emitting device according to any one of the fifth to seventh aspects, a plurality of parallel saws are provided on one side of the light guide space of the back plate 3 and on the other side. A light-transmitting film 6 (back light-transmitting film) having an edge-shaped prism is further provided, and the prism array of the back light-transmitting film is parallel to the incident direction of light from the light source 8. is there.

According to the ninth aspect of the present invention, the light-emitting plate 2 and the back plate 3 are arranged in parallel so as to form a light-guiding space, and at least one light source 8 is provided at at least both ends of the light-guiding space. In the surface light-emitting device, a light-transmitting film 10 (first light-source light-transmitting film) having a flat surface on one side and a number of parallel saw-toothed prisms on the other surface on the light guide space side of the light source 8; A light-transmitting film 11 (second light-source light-transmitting film) having a flat surface and a plurality of parallel saw-tooth-shaped prisms on the other surface, disposed in contact with or in the vicinity thereof. Provided is a planar light emitting device in which a first light source translucent film prism array and a second light source translucent film prism array are in a vertical direction.

According to a tenth aspect of the present invention, in the planar light emitting device according to the ninth aspect, a plurality of parallel saw-toothed prisms having one flat surface and the other surface are provided on the light guide space side of the back plate 3. Is disposed, and the prism array of the rear light-transmitting film 6 is parallel to the incident direction of light from the light source 8.
According to another aspect of the present invention, the extractor 20 is provided on the light guide space side surface of the back plate 3 or the back light transmitting film 6.

に お い て In the present invention, the light emitting plate is a plate having a function of providing uniform and high-luminance light to a liquid crystal display device or the like, and is made of a light-transmitting transparent film or a diffusion film. The diffusion film is a film that has fine irregularities and projections on at least one surface thereof, or contains incident light diffusing particles, and uniformly diffuses and transmits incident light. For example, a 1-1000 μm thick film made of a material such as polycarbonate or polyethylene terephthalate and subjected to a matting process on its surface is commercially available as PCSM manufactured by Tsujimoto Electric Manufacturing Co., Ltd. And the like.

The light-transmitting film having one flat surface and a plurality of parallel saw-toothed prisms on the other surface is made of a light-transmitting material such as polycarbonate and PMMA, and the prism shape formed on one surface has a vertex angle of 60%. The interval is, for example, 10 μm to 1 mm, and the thickness is, for example, 50 to 500 μm. It is commercially available from 3M under the trade names "3M Optical Lighting Film", "3M Brightness Enhancement Film", "3M Transmission Right Angle Film" and the like.

The light-emitting plate and the light-transmitting film having a prism shape may be integrally formed or may be mechanically fixed. If integrated, a thinner light emitting device can be provided, and light scattering and absorption between the diffusion plate and the light transmitting film are small. Also, in the case of mechanical fixing, the production cost is low, and even if one of them is deteriorated, it can be easily replaced.

The rear plate does not leak light due to reflection of light, forms a light guide space together with the light emitting plate, and allows light to efficiently reach the light emitting plate. Another object is to obtain appropriate mechanical strength of the planar light emitting device.
As the material, polycarbonate, acrylic resin, PVC resin, phenol resin, epoxy resin, metal, for example, aluminum, titanium, various alloys, and, on various materials, for improving the reflection efficiency, those that have been whitened, for example, Scotch Cal (1125-25), Silverlux (SS95P), etc., manufactured by Sumitomo 3M Limited can be used.

As the material of the extractor, any light-reflective film can be used. For example, Scotchcal 1125-25 manufactured by 3M can be used.
In the device of the present invention, any light source commonly used in a planar light emitting device, for example, a cold cathode tube, a hot cathode tube, a light emitting diode or the like can be used.

Next, the configuration of the planar light emitting device of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows an exploded view (A) and a sectional view (B) of a planar light emitting device 1 according to a first embodiment of the present invention. A light guide space 4 is formed by the light emitting plate 2 and the back plate 3 which are arranged in parallel. The light guide space side of the light emitting plate 2 has a plurality of parallel saw-toothed prisms on one side and flat on the other side. A light-transmitting film 5 (may be abbreviated as a prism film) (first light-emitting surface light-transmitting film) is provided. The first light-emitting surface light-transmitting film functions to efficiently transmit light in an indeterminate direction that has passed through the light guide space to the light-emitting plate as a whole. It is preferable that the prism rows of the translucent film are substantially perpendicular to the incident direction of the light from the light source 8, for example, 90 ° ± 30 °. This is because the light from the light source efficiently reaches the light emitting plate.

Further, on the light guide space side of the back plate 3, a light-transmitting prism film 6 (back light-transmitting film) is provided. The prism rows of this film are parallel to the direction of incidence of light from the light source 8. The rear light-transmitting film 6 forms a light guide space with the light-emitting plate together with the rear plate 3 without leaking light due to the reflection of light, and functions to efficiently transmit light to the light-emitting plate 2. The rear translucent film 6 has an inclined surface or an inclined curved surface from the center portion 7 toward the light source 8. This inclined surface may have a valley at the center and may be inclined in a direction opposite to the illustrated direction.

角度 It is preferable that the angle α between the inclined surface or the inclined curved surface and the incidence is 15 ° or less. This angle is preferably 1 to 10 °, more preferably 2 to 6 °. The rear light-transmitting film may be roughly divided into two portions at the central portion 7. Thereby, processing such as bending is not required, the manufacturing cost is low, and the accuracy is improved.

In this embodiment, part of the light from the light source 8 is directly reflected, and the other part is reflected by the reflecting mirror 15 and enters the light guide space. Part of the light that has entered the light guide space directly reaches the light-emitting surface light-transmitting film 5, is refracted and emitted through the light-emitting plate 2, and part is reflected by the rear light-transmitting plate 6 to emit light. The light is emitted through the surface translucent film 5 and the light emitting plate 2. At this time, since the rear translucent film 6 is inclined, the light reflected thereby gathers at the central portion of the light emitting plate 2 and the disadvantage of the prior art that the luminance at the central portion tends to be insufficient is improved.

FIG. 2 is an exploded view of the second planar light emitting device of the present invention. In this device, a prism film 9 (second light-transmitting surface light-transmitting film) is further provided outside the light-emitting plate 2 in the device of the first embodiment shown in FIG. The first light-emitting surface light-transmitting film 5 and the second light-emitting surface light-transmitting film 9 may face each other on the prism side, or their flat surfaces may face each other. The prism rows of these two light-emitting surface translucent films may be arranged in parallel or vertically.
Preferably, the prism surface of the prism film 9 faces upward because the directivity increases, and the prism film 5 may be either. The direction of the prism is free, but preferably the prism film 9 is as shown in FIG. 2, and the prism film 5 is as shown in FIG. 2 when the prism surface is facing down, and is incident light when facing up. It is better to be parallel.

In the second embodiment, the following advantages are obtained in addition to the advantages of the first embodiment.
The prism film 9 functions as a regulating plate for regulating the direction of the diffused light emitted from the diffusion film, and the luminance in a desired direction can be increased by appropriately setting the vertex angle of the prism.

FIG. 3 shows an exploded view (A) and a sectional view (B) of the planar light emitting device according to the third embodiment of the present invention. In this device, the prism film 10 (with the second light-emitting surface light-transmitting film 9) or the device of FIG. 2 (with the second light-emitting surface light-transmitting film 9) is added to the device of FIG. A first light source translucent film) is provided. Preferably, the prism rows of the film 10 are perpendicular to the light emitting surface 2. According to this aspect, it is possible to obtain an advantage that the directivity is given to the diffused light from the light source, the brightness of the light emitting surface near the light source is suppressed, and the luminance uniformity of the light emitting surface is increased.

FIG. 4 shows an exploded view (A) and a sectional view (B) of a planar light emitting device according to a fourth embodiment of the present invention. In this device, a second light source translucent film 11 is further provided in the device of the third embodiment. The second light-transmitting film 11 is in contact with or near the first light-transmitting film 10, and the prism rows of those films are perpendicular to each other. In this embodiment, the directivity further increases, and the uniformity increases.

FIG. 5 shows an exploded view (A) and a sectional view (B) of a planar light emitting device according to a fifth embodiment of the present invention. A light guide space 4 is formed by the light emitting plate 2 and the back plate 3 arranged in parallel, and a first light emitting surface light transmitting film 5 and a second light emitting surface light transmitting film 9 are provided on both sides of the light emitting plate 2. Is arranged. Thus, extremely high brightness can be obtained by arranging two translucent films.

Preferably, the prism rows of the first light-emitting surface translucent film are in a direction perpendicular to the direction of incidence of light from the light source 8. More preferably, the prism rows of the second light-emitting surface translucent film are also perpendicular to the incident direction of light from the light source 8. By doing so, light can be efficiently and uniformly directed to the light emitting plate.
The first light-emitting surface light-transmitting film / light-emitting plate (diffusion plate) / second light-emitting surface light-transmitting film can be fixed by mechanically caulking both ends or the periphery with screws or the like, or using an adhesive. Alternatively, it is preferable to use a double-sided tape. It is preferable that a space exists between the second light-emitting surface translucent film and the light-emitting plate (diffusion plate).

FIG. 6 shows an exploded view (A) and a sectional view (B) of a planar light emitting device according to a sixth embodiment of the present invention. In this embodiment, a first light source translucent film 10 is provided in the device of the fifth embodiment. Thereby, there is obtained an advantage that the directivity is given to the diffused light from the light source, the brightness of the light emitting surface near the light source is suppressed, and the luminance uniformity of the light emitting surface is increased.

FIG. 7 shows a planar light emitting device according to a seventh embodiment of the present invention. In this embodiment, a second light source translucent film 11 is further provided in the device of the sixth embodiment. The conditions and advantages of the first light-transmitting film and the second light-transmitting film are as described in the fourth embodiment.

FIG. 8 shows a planar light emitting device according to an eighth embodiment of the present invention. In this embodiment, the device of the fifth embodiment (the light source translucent films 10 and 11 are not present), the device of the sixth embodiment (having the light source translucent film 10), and the device of the seventh embodiment ( In addition to having the light source translucent films 10 and 11), it further has a rear translucent film 6. In this embodiment, there is an advantage that the light incident on the prism film 6 at a shallow angle is totally reflected, the light can be efficiently transmitted to the central portion of the light emitting surface, and the luminance uniformity can be improved.

FIG. 9 shows a planar light emitting device according to a ninth embodiment of the present invention. A light guide space 4 is formed by the light emitting plate 2 and the rear plate 3 arranged in parallel, and light source translucent films 10 and 11 are arranged on the light guide space side of the light source 8. Thereby, the light from the light source 8 can be efficiently guided to the light guide space with directivity.
The conditions for these translucent films are as described in the fourth embodiment.

FIG. 10 shows an exploded view (A) and a cross-sectional view (B) of a planar light emitting device according to a tenth aspect of the present invention. In this aspect, in the apparatus according to the ninth aspect, a rear light-transmitting film 6 is further provided, and the prism array of the rear light-transmitting film 6 is parallel to the incident direction of light from the light source. is there. Accordingly, there is an advantage that the light incident on the prism film 6 at a shallow angle is totally reflected, the light can be efficiently transmitted to the central portion of the light emitting surface, and the luminance uniformity can be improved.

In the above various aspects of the present invention, the extractor is disposed on the surface of the back plate 3 on the light guide space side or on the surface of the back plate 3 when the back light-transmitting film is present. Is preferred. As shown in FIG. 11, the extractor is obtained by cutting a reflective film into a saw blade shape, and the width of the reflective film is wide at the center 20 and becomes narrower toward the end 21. By arranging this extractor at the center of the light guide space, the brightness at the center can be increased. As a result, it is possible to compensate for the disadvantage of the prior art that the luminance is insufficient at the central portion, and to obtain uniform light emission over the entire surface of the light emitting plate.

Next, the present invention will be described more specifically with reference to examples.
Example .
(1) To make a planar light emitting device having a width of 242 mm, a length of 197 mm, and a thickness of 10 mm, a prism film is cut into a size of 242 mm in width and 197 mm in length, and a prism film having a prism groove in the horizontal direction is a prism film. The surface was installed on the light-emitting surface with the prism face facing the light guide space side, and the prism film with the prism grooves facing the vertical direction was installed on the back surface with the prism surface facing the light guide space side. Further, a prism film having a width of 242 mm and a width of 10 mm was cut out, and two prism films were installed on the light guide space side of the linear light source, respectively, so that the grooves of the prism were perpendicular to each other.

白色 A white film with good light reflection efficiency was installed on the back of this device to return the light leaking from the prism film to the light guide space side. Also, white films having good light reflection efficiency were provided on both sides of the light guide space where no linear light source was provided. A diffusion film was provided immediately above the prism film on the light emitting surface side. As the prism film, a polycarbonate prism film having a prism apex angle of 90 °, a prism interval of 50 μm, and a film thickness of 230 μm was used. As the linear light source, a fluorescent tube having a length of 250 mm and a diameter of 4 mm was used.

The luminance at 25 points on the light emitting surface was measured from above vertically in a dark room as shown in FIG. The result is shown in FIG.
(2) The luminance was measured by placing a prism film on the light emitting surface of the surface light emitting device of Example (1). FIG. 14 shows the result.
(3) The central portion of the prism film on the back side of the planar light emitting device of Example (2) was lifted by 5 mm to measure the luminance. The result is shown in FIG.
(4) The brightness was measured by installing a light extractor just above the prism film on the back side of the planar light emitting device of Example (3). FIG. 16 shows the measurement results.

FIG. 1 shows an exploded view (A) and a sectional view (B) of a first embodiment of the planar light emitting device of the present invention. FIG. 2 shows an exploded view (A) and a sectional view (B) of the second embodiment of the planar light emitting device of the present invention. FIG. 3 shows an exploded view (A) and a sectional view (B) of a third embodiment of the planar light emitting device of the present invention. FIG. 4 shows an exploded view (A) and a sectional view (B) of a fourth embodiment of the planar light emitting device of the present invention. FIG. 5 shows an exploded view (A) and a sectional view (B) of a fifth embodiment of the planar light emitting device of the present invention. FIG. 6 shows an exploded view (A) and a sectional view (B) of a sixth embodiment of the planar light emitting device of the present invention. FIG. 7 shows an exploded view (A) and a sectional view (B) of a seventh embodiment of the planar light emitting device of the present invention. FIG. 8 shows an exploded view (A) and a sectional view (B) of an eighth embodiment of the planar light emitting device of the present invention. FIG. 9 shows an exploded view (A) and a sectional view (B) of a ninth embodiment of the planar light emitting device of the present invention. FIG. 10 shows an exploded view (A) and a sectional view (B) of a tenth embodiment of the planar light emitting device of the present invention. FIG. 11 is an explanatory diagram of the extractor. FIG. 12 is a diagram illustrating luminance measurement points in the example. FIG. 13 is a diagram showing the result of the luminance measurement of the example (1). FIG. 14 is a diagram showing a result of luminance measurement when a prism film is placed on the light emitting surface of Example (1). FIG. 15 is a diagram illustrating a result of the luminance measurement of the example (2). FIG. 16 is a diagram showing the result of the luminance measurement of the example (3).

Explanation of reference numerals

2 light-emitting plate 3 back plate 4 light-guiding space 5 first light-emitting surface light-transmitting film 6 back light-transmitting film 7 central part 8 of rear light-transmitting film 8 light source 9 second light emission Surface translucent film 10: first light source translucent film 11: second light source translucent film

Claims (8)

In a planar light emitting device having a light emitting plate and a back plate arranged in parallel to form a light guiding space, and at least one light source at each of at least both ends of the light guiding space, the light emitting plate is formed of a diffusion film. A light-transmitting film (first and second light-emitting surface light-transmitting films) having flat surfaces and a plurality of parallel saw-toothed prisms on the other surface is provided on both surfaces of the light emitting plate. The prism array of the light-transmitting film (first light-emitting surface light-transmitting film) on at least the light guide space side is arranged so as to be perpendicular to the incident direction of light from the light source. A planar light emitting device, comprising: The light-transmitting film (first light-source light-transmitting film) having a flat surface and a plurality of parallel saw-toothed prisms on the other surface is further provided on the light guide space side of the light source. 2. The planar light emitting device according to 1. A light-transmitting film having a flat surface and a large number of saw-toothed prisms on the other surface in parallel with or in contact with the first light source light-transmitting film (second light source light-transmitting film) 3. The planar light emitting device according to claim 2, further comprising: a prism array of the first light-transmitting film and a prism array of the second light-transmitting film are perpendicular to each other. apparatus. A light-transmitting film (back light-transmitting film) having a flat surface and a plurality of parallel saw-toothed prisms on the other surface is further provided on the light guide space side of the back plate. The planar light emitting device according to any one of claims 1 to 3, wherein a prism array of the optical film is parallel to an incident direction of light from the light source. A light emitting plate and a back plate arranged in parallel to form a light guide space, and a planar light emitting device having at least one light source at each of at least both ends of the light guide space; A light-transmitting film (first light source light-transmitting film) having one surface flat and a plurality of parallel saw-toothed prisms on the other surface, and being in parallel with and in contact with the first light source light-transmitting film; Or a light-transmitting film (second light-transmitting film) having a sawtooth-shaped prism having one flat surface and being parallel to the other surface, disposed at or near the first light source. A planar light emitting device, wherein a prism row of a light-transmitting film and a prism row of a second light source light-transmitting film are in a vertical direction. A light-transmitting film (back light-transmitting film) having a flat surface and a plurality of parallel saw-toothed prisms on the other surface is further provided on the light guide space side of the back plate. The planar light emitting device according to claim 5, wherein the prism rows of the optical film are parallel to the incident direction of the light from the light source. The planar light-emitting device according to claim 4 or 6, wherein an extractor is provided on the light-guiding space side surface of the rear light-transmitting film. A light-transmitting film (back light-transmitting film) having a flat surface and a plurality of parallel saw-toothed prisms on the other surface, provided on the light guide space side surface of the back plate; The planar light-emitting device according to any one of claims 1 to 3, wherein an extractor is provided on a light guide space side surface of the light-emitting device.

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