JPH0552825U - Surface lighting device - Google Patents

Abstract

(57) [Summary] [Object] To provide a surface illuminating device that uniformly illuminates an object to be illuminated, has a large effective light emitting area, and increases the amount of light entering the light guide plate. A light guide plate having a concave portion formed on a side surface and having a diffusing means therein, a long substrate arranged on the side surface and having a white inner surface, and a long substrate along a longitudinal direction of the substrate. A light emitting diode linearly arranged and fixed to the front surface of the substrate and positioned in the recess, and a reflection frame arranged to cover the back surface and the top surface of the substrate and the vicinity of the side surface of the light guide plate are provided.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a surface lighting device used for flat panel display, especially for liquid crystal display.

[0002]

[Prior Art]

 In recent years, a surface lighting device used for displaying on a flat display has been disclosed in Japanese Examined Patent Publication No. 2-43282. However, since a fluorescent lamp or the like is used as a light source in this apparatus, the thickness of the apparatus including the reflector for the fluorescent lamp is about 8 to 10 mm, and the apparatus cannot be said to be sufficiently thin. Therefore, for the purpose of reducing the thickness, an apparatus applied by the applicant of the present application in Japanese Patent Application No. 3-184925 is shown in a sectional view of FIG. In this figure, the light guide plate 31 has a recess 32 formed on the bottom surface close to the side surface. The light emitting diode lamp 33 is arranged so as to be housed in the recess 32. A light emitting diode lamp 33 is fixed on a reflecting plate 35 on a circuit board 34 with an adhesive 36. The frame 37 of the light emitting diode lamp 33 is bent and attached to the circuit board 34. The liquid crystal display 38 is arranged on the light guide plate 31.

[0003]

[Problems to be solved by the device]

 However, the above-mentioned device has a drawback that the illumination of the liquid crystal display 38 becomes non-uniform. In particular, it is non-uniform in the Z-axis direction orthogonal to the XY plane of the liquid crystal display 38. This is because only one light emitting diode lamp 33 is provided as a point light source in the Z-axis direction, that is, along the side surface of the light guide plate. Furthermore, in this device, the area of the light guide plate 31 just above the light emitting diode lamp 33, that is, the portion C is too bright to place an object to be illuminated. Since the length of the light emitting diode lamp 33 is relatively long, the C portion is also long, about 10 mm, and the effective light emitting area is small. Furthermore, since the light from the light emitting diode lamp 33 leaks through the gap between the frame 37 and the light guide plate 31, there is a drawback that the amount of light entering the light guide plate 31 is reduced. Therefore, the present invention solves the above-mentioned drawbacks, that is, provides a surface illuminating device which uniformly illuminates the liquid crystal display 38, has a large effective light emitting area, and increases the amount of light entering the light guide plate.

[0004]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a light guide plate having a concave portion formed on a side surface and having a diffusing means inside thereof, and a long substrate arranged on the side surface and having a white inner surface. The LED is linearly aligned and fixed on the surface of the substrate along the longitudinal direction of the substrate, and is arranged so as to cover the back surface and the upper surface of the substrate and the vicinity of the side surface of the light guide plate. And a reflective frame which is formed.

[0005]

[Action]

 As described above, the present invention linearly illuminates the direction along the side surface of the light guide plate by arranging the light emitting diodes as the point light source linearly and providing the diffusing means inside the light guide plate. Lighting is obtained. In the present invention, as described above, by covering the back surface and the upper surface of the substrate and the vicinity of the side surface of the light guide plate with a reflective frame, it is possible to mitigate that the end portion of the light guide plate is too bright and to prevent light leakage, and The amount of light entering is increased. Further, since the present invention uses a light emitting diode smaller than a light emitting diode lamp as a light source, the length of the too bright end of the light guide plate is shortened and the effective light emitting area is increased.

[0006]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a surface lighting device according to this embodiment, and FIG. 2 is an exploded perspective view of the device. In these figures, the light guide plate 1 is a substantially rectangular parallelepiped mainly made of acrylic resin and having a thickness of about 4 mm. A recess 3 is formed on the side surface 2 of the light guide plate 1. The width of the recess 3 is about 2 mm and the depth B is about 2 mm. Specifically, the light guide plate 1 has a reflection plate 1a at the bottom, transparent plates 1b, 1c and 1d laminated on the bottom, and a diffusion plate 1e provided thereon. The light guide plate 1 has a diffusion means inside. That is, as is well known, the transparent plates 1b, 1c and 1d are spots of white paint printed on the back surface of an acrylic plate. Alternatively, the back surface of a plate made of acrylic or the like may be embossed so that light is diffusely reflected on the back surface to improve the light diffusion property. The diffusion plate 1e is also made of an acrylic plate. Desirably, synthetic paper is pasted on the surfaces of the three side surfaces 2a, 2b, 2c other than the side surface 2 with an adhesive. The synthetic paper prevents the light from leaking from the side surface, and the light is effectively extracted from the upper surface of the light guide plate.

In the substrate 4, the power supply terminal 6 and the conductive layers 7a, 7b, 7c are printed and printed on the resin layer 5 made of, for example, glass epoxy resin, and the white coating portion 8 is formed on the surface except the periphery of the conductive layer 7b. It is a long one. The white coating section 8 is coated with a coating material such as a white resist. The substrate 4 has three through holes 9 having a diameter of about 1.5 mm and a thickness of about 0.5 mm.

A light emitting diode 11 is fixed on the conductive layer 7b of the substrate 4 via a conductive adhesive 10 such as silver paste. The light emitting diode 11 is made of, for example, gallium phosphide, emits green light having a wavelength of about 580 nm, and is a substantially cubic shape having a side of about 300 μm. The light emitting diodes 11 are fixed in line on the surface of the substrate 4 along the longitudinal direction of the substrate 4 at a pitch of about 2 mm. If the pitch is larger than this, the illumination unevenness becomes large in the linear direction of the substrate 4. If the pitch is smaller than this, it is difficult to perform work such as wiring, so about 2 mm is appropriate. A thin metal wire 12 is provided between the light emitting diode 11 and another conductive layer. Three pins 13 formed on the side surface 2 of the light guide plate 1 are inserted into the through holes 9 of the substrate 4 so that the light emitting diode 11 is located in the concave portion 3 of the light guide plate 1 and are guided to the surface of the substrate 4. The side surface 2 of the light plate 1 is in contact.

The reflection frame 14 is made of, for example, glass-filled polycarbonate resin, has a thickness of about 1 mm, and is formed in an inverted L-shaped cross section. As described above, the reflective frame 14 is made of white resin and is selected from a material having high reflectivity. By inserting the through holes 9 of the substrate 4 and the through holes 15 of the reflection frame 14 into the three pins 13 of the light guide plate 1 and welding the ends, the substrate 4 and the reflection frame 14 are fixed to the light guide plate 1. There is.

The reflection frame 14 is arranged so as to cover the back surface 16 and the top surface 17 of the substrate 4 and the vicinity 18 of the side surface of the light guide plate 1. By covering the vicinity 18 of the side surface in this way, the light emitted from the light emitting diode 11 is reflected and does not radiate to the outside, so that the end portion of the light guide plate 1 can be prevented from being too bright. Further, between the vicinity 18 of the side surface of the light guide plate 1 and the reflection frame 14, a reflection plate 19 made of, for example, an aluminum foil having a thickness of 0.1 mm and slightly longer than the reflection frame 14 may be arranged. By providing the reflection plate 19 with an appropriate length, it is possible to completely adjust the brightness of the end portion of the light guide plate 1 and completely eliminate the uneven illumination. The liquid crystal display 20 and the circuit board 21 are arranged above and below the light guide plate 1, respectively.

Next, the substrate on which the light emitting diode is fixed, which is used in the surface lighting device of this embodiment, will be described in detail. 3 is a sectional view taken along line AA of FIG. 1, and FIG. 4 is a drawing of the substrate. In these figures, conductive layers 7a, 7b, 7c made of copper foil or the like are formed on the surface of the resin layer 5 of the substrate 4. The light emitting diode 11 is fixed on the conductive layer 7c or 7b. Then, it is wired to the other conductive layer 7b or 7a by the thin metal wire 12. The four light emitting diodes 11 are connected in series, and two sets thereof are connected in parallel. The dummy terminal 22 is not electrically connected to the conductive layers 7a, 7b, and 7c, but is formed to serve as a nail when the board 4 is fixed to the circuit board 21 and to maintain the strength of the board 4. .. A white coating portion 8 is formed on the surface of the substrate 4 excluding the through holes 9, the power supply terminals 6, the dummy terminals 22, and the eight window portions 23.

[0012]

[Effect of the device]

 As described above, the present invention linearly illuminates the direction along the side surface of the light guide plate by arranging the light emitting diodes as the point light source linearly and providing the diffusing means inside the light guide plate. Lighting is obtained. Furthermore, by covering the upper surface near the side surface of the light guide plate with a reflection frame, the light from the light emitting diode is not reflected by this reflection frame and radiated to the outside. Therefore, the edge of the light guide plate can be prevented from being too bright, and more uniform illumination can be obtained. Specifically, by arranging the light-emitting diodes at an arrangement pitch of about 2 mm, the same degree of illumination uniformity as when a fluorescent lamp is used as a light source can be obtained. Moreover, since the light emitting diode is much smaller than a fluorescent lamp, a thin surface lighting device with a thickness of 5 mm can be obtained.

According to the present invention, by covering the back surface and the upper surface of the substrate and the vicinity of the side surface of the light guide plate with the reflection frame as described above, it is possible to alleviate that the end portion of the light guide plate is too bright and prevent light leakage. The amount of light entering the light plate increases. Further, since the present invention uses a light emitting diode smaller than a light emitting diode lamp as a light source, the length of the excessively bright end portion of the light guide plate is about 2 mm as compared with the conventional light guide plate of about 10 mm, and the effective light emitting area is increased. ..

Further, in the prior art, a light reflector is required as a separate component under the light guide plate in order to guide light toward the upper surface of the light guide plate, and therefore workability is poor due to the alignment of the light reflector when assembling the device. However, in the present invention, since the reflection plate is built in the light guide plate, workability is facilitated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a surface lighting device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the surface lighting device.

FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 4 is a front view of a substrate on which a light emitting diode is fixed, which is used in a surface lighting device according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional surface lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Side surface of light guide plate 3 Recessed portion 4 Substrate 11 Light emitting diode 14 Reflective frame 16 Back surface of substrate 17 Upper surface of substrate 18 Near side surface of light guide plate

Claims (1)

[Scope of utility model registration request] 1. A light guide plate having a concave portion formed on a side surface and having a diffusing means therein, a long substrate arranged on the side surface and having a white inner surface, and a longitudinal direction of the substrate. A light emitting diode linearly aligned and fixed to the surface of the substrate and positioned in the recess, and a reflection frame arranged so as to cover the back surface and the top surface of the substrate and the vicinity of the side surface of the light guide plate. A surface lighting device that is characterized.