JP2005302485A - Surface lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface lighting device which prevents nonuniformity in brightness from occurring in the neighborhood of a positioning projection formed on a light guide plate and can make brightness uniform all over an output surface. <P>SOLUTION: Protrusions 11a, 11b, 11c, 12a, 12b, 12c are formed on sides 11, 12 of a light guide plate 1 to position the light guide plate 1 to a frame body 7. Recesses 20a, 20b, 20c, 21a, 21b, 21c are formed on the frame body 7 for housing the light guide plate 1 corresponding to the protrusions on the light guiding plate 1, respectively. Notches 13a, 13b, 13c, 14a, 14b, 14c are formed at the ends of the respective protrusions far away from LEDs 2. The recess is formed into a rectangular shape. A notch is formed into a shape with an edge of a protrusion cut into a plane (corner-chamfered) or into a shape with the edge round (round-chamfered), where the protrusion has the same shape as the recessed part in a rectangular shape. This reduces the amount of the light which proceeds to the center of the light guide plate 1 after reflecting at the sides of the protrusions plural times, and prevents nonuniformity in brightness from occurring in the neighborhood of the protrusion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sidelight type planar illumination device, and more particularly to a planar illumination device having a configuration in which a light guide plate and a light source are housed in a frame.

  Liquid crystal display devices that are characterized by being thin, occupying a small volume, and being light are used in many electric products such as mobile phones and personal computers. By the way, since the liquid crystal itself of the liquid crystal display device does not emit light itself, the liquid crystal is irradiated separately from the liquid crystal display device when used in a dark place where the brightness of sunlight or room illumination cannot be taken in sufficiently. A lighting means is required. While further miniaturization of the liquid crystal display device is desired, the liquid crystal display portion of the liquid crystal display device is desired to be enlarged, and in order to meet this requirement, the illumination means for irradiating the liquid crystal is also miniaturized. Furthermore, it has become necessary to realize low power consumption.

  Therefore, in order to realize downsizing and low power consumption of the illumination means, each member such as a light source that constitutes the illumination means, a light guide plate, or the like that uses an LED that is a point light source as a light source of the illumination means is predetermined. A device that efficiently uses light by fixing it to the position of has been developed. For example, as a means for fixing each member constituting the illumination means at a predetermined position, there is one using a frame that houses each member. A protrusion is provided on the side surface of the light guide plate, and a recess is provided in the frame corresponding to the position of the protrusion. When the light guide plate is housed in the frame, the protrusion and the recess are combined to fix the position of the light guide plate. However, with this means, the light reflected from the base of the projection out of the light emitted from the light source behaves differently from the light reflected from other parts and reaches the exit surface of the light guide plate. There is a problem that streaky emission lines are generated toward the surface.

  As means for solving this problem, there is one disclosed in Patent Document 1. As shown in FIG. 7, the positioning projection 12H of the light guide plate 12 housed in the frame is used as the exit surface 12C of the side surface 12G of the light guide plate 12. A structure that is formed to be offset to the side is disclosed. According to this, the base of the protrusion 12H is formed small, and the base of the protrusion 12H can be disposed away from the protrusion formed by a pair of inclined surfaces (12E, 12F) formed on the back surface of the light guide plate 12, so that it is brightly illuminated. It is possible to make it difficult to perceive a streak-like region having a high luminance level that is generated when the base of the projected protrusion 12H is visually recognized from the exit surface 12C.

  However, the invention of Patent Document 1 is effective when the thickness of the light guide plate is relatively large, but when the thickness of the light guide plate is relatively thin, a streaky region with high luminance is observed on the exit surface. There was a drawback of end. Therefore, as means for solving this drawback, there is one disclosed in Patent Document 2, and as shown in FIG. 8, the projection of the light guide plate is not used as a positioning member with respect to the frame. A configuration is disclosed in which the side surface is formed on the back surface 4B side from the imaginary line that bisects the side surface in the thickness direction. Further, the protrusion 4H is made thin, and the side surface 4HD of the protrusion 4H is formed by a plane inclined obliquely with respect to the bottom surface 4HB so that the thickness of the protrusion 4H gradually decreases as the wedge tip is moved toward the tip. The structure to perform is disclosed. According to this, the light reflected by the base of the protrusion 4H can be emitted immediately from the emission surface 4C in the vicinity of the side surface.

JP 11-265609 A Japanese Patent Laid-Open No. 2001-154028

  However, the invention of Patent Document 1 has a drawback that a streak-like region with high luminance is observed on the exit surface when the thickness of the light guide plate is relatively thin as described above. Moreover, in the invention of Patent Document 2, it is necessary to make the protrusion thin, and when used as a positioning member for the frame, there is a disadvantage that the possibility of breakage is high.

  Therefore, the present invention has been made in view of such circumstances, and the projections provided on the light guide plate can perform proper positioning with respect to the frame, and also prevent uneven brightness generated in the vicinity of the projections. It is an object of the present invention to provide a planar illumination device that can realize uniform luminance over the entire emission surface.

  In order to solve the above-described problems, an invention of a planar illumination device according to claim 1 includes a light guide plate made of a light-transmitting material, a light source disposed to face a side surface of the light guide plate, and the light guide plate. A projection that is provided on a side surface that is orthogonal to a side surface of the light guide plate on which the light source is disposed, and that includes a projection for determining an arrangement position of the light guide plate in the frame body; In the planar lighting device including the concave portion formed in the frame body into which the projection portion of the light guide is inserted, the shape of the concave portion is rectangular, and the length of the side surface on which the projection portion is provided In the direction, a notch along the short side direction of the side surface on which the protrusion is provided is formed at the end of the protrusion far from the point light source.

  By forming a notch along the thickness direction of the light guide plate, that is, along the lateral direction of the side surface on which the protrusion is provided, at the end of the protrusion formed on the light guide plate on the side far from the light source After the light is reflected by the protrusion, the light that is reflected by the side surface farther from the light source in the protrusion and travels in the direction of the light guide plate is reduced, and the occurrence of luminance unevenness in the vicinity of the protrusion is suppressed.

  In order to solve the above-described problem, the invention of the planar lighting device according to claim 2 is the invention according to claim 1, wherein the notch of the protrusion has an acute angle with respect to the side surface on which the protrusion is provided. It is formed by a certain C chamfer. C chamfering means that the ridge portion of a rectangular projection is cut into a flat shape and processed.

  In order to solve the above-described problem, the invention of the planar lighting device according to claim 3 is characterized in that, in the invention of claim 1, the notch of the protrusion is formed by R chamfering. is there. R chamfering refers to processing a ridge portion of a rectangular projection portion with a rounded round shape.

  According to the planar lighting device according to the present invention, the light guide plate can be fixed at an appropriate position with respect to the frame by combining the protrusion formed on the light guide plate into the recess provided in the frame. The light from the light source can be used efficiently. In addition, by forming a notch along the thickness direction of the light guide plate at the end of the protrusion formed on the light guide plate on the side far from the light source, the brightness near the protrusion generated by the light reflected by the protrusion Unevenness can be prevented, and the brightness of the entire emission surface can be made uniform.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of a planar lighting device according to the invention will be described with reference to the accompanying drawings.
FIG. 1 is an exploded perspective view showing the planar illumination device M and the object N to be illuminated arranged on the upper side of the planar illumination device M. FIG. The planar illumination device M is schematically configured from a light guide plate 1, a point light source 2, a reflection plate 3, a light diffusion sheet 4, brightness enhancement films 5 and 6, and a frame body 7 in which these members are accommodated. Has been. FIG. 2 is a perspective view showing the planar illumination device M in a state where each member is accommodated in the frame body 7.

  As shown in FIGS. 1 and 2, the point light source 2 housed in the frame body 7 is disposed on the one end face 8 side of the light guide plate 1. For example, an LED is used as the point light source 2. The LED 2 has a configuration in which an LED chip is covered with a resin case, and an emission window is formed in the case so that emitted light is efficiently emitted in one direction from the emission window. . Hereinafter, one direction of the LED from which the emitted light is efficiently emitted is referred to as a light emission direction side and is referred to as the front surface of the LED. One or a plurality of LEDs 2 are provided, and the front surfaces thereof are arranged close to each other so as to face one side surface 8. Therefore, most of the light emitted from the LED 2 enters the light guide plate 1 from one side surface 8. Hereinafter, the side surface 8 of the light guide plate 1 is also referred to as an incident surface 8.

  The light guide plate 1 is made of a highly transparent material such as polystyrene, polyester, polyolefin, fluorine-based transparent polymer, and epoxy resin, in addition to polycarbonate resin, acrylic resin, and amorphous polyolefin resin, which have an excellent balance of moldability and optical properties. It is configured. The light guide plate 1 may be formed by injection molding, extrusion molding, casting method, or the like in addition to injection molding which is excellent in productivity and accuracy. The light emitted from the LED 2 is incident from the incident surface 8 of the light guide plate 1 and is emitted from the output surface 9 which is the surface of the light guide plate 1 by repeating refraction and reflection. On the rear surface 10 of the light guide plate 1, that is, the surface facing the light exit surface 9, a light beam path changing element not shown so that the light incident from the LED 2 into the light guide plate 1 can be uniformly emitted on the entire light exit surface 9. (Light scattering pattern) is provided. The light scattering pattern is composed of a fine prism, fine protrusions or depressions, a fine rough surface pattern, a fine print pattern, and the like.

  The light guide plate 1 has a substantially rectangular shape, and the side surfaces 11 and 12 orthogonal to one side surface 8 of the light guide plate 1 on which the LEDs 2 are arranged extend in the vertical direction with respect to the side surfaces 11 and 12. Protrusions 11a, 11b, 11c, 12a, 12b, and 12c are provided. These protrusions determine the position of the light guide plate 1 in the frame 7 and fix the light guide plate 1 at that position when the light guide plate 1 is housed in the frame 7 described later. belongs to. Of the protrusions 11a, 11b, and 11c provided on the side surface 11, the protrusions 11a and 11c are provided near the emission surface 9 of the light guide plate 1, and the protrusion 11b is provided near the back surface 10. Yes. Of the protrusions 12 a, 12 b, and 12 c provided on the side surface 12, the protrusions 12 a and 12 c are provided near the emission surface 9 of the light guide plate 1, and the protrusion 12 b is provided near the back surface 10. It has been. That is, the protrusions provided on each of the side surface 11 and the side surface 12 are formed thinner than the thickness of the light guide plate 1, and adjacent protrusions are staggered with different heights in the thickness direction of the light guide plate 1. Is provided. The light guide plate 1 is securely fixed at an appropriate position with respect to the frame body 7 by inserting these protrusions into the recesses of the frame body 7 described later.

  On the back surface 10 side of the light guide plate 1, the reflection plate 3 is provided so as to cover the back surface 10. The reflection plate 3 is made of a reflective material such as a white resin or a silver plating plate, and reflects light emitted from the back surface 10 of the light guide plate 1 to the outside of the light guide plate so as to be re-input into the light guide plate 1. is there. Therefore, the member that reflects this light is not limited to the reflector 3, and for example, a reflective material is applied to the bottom of the frame 7 that houses and holds each member integrally, and the reflector You may comprise so that it may serve also.

  A light diffusion sheet 4 is provided on the front side of the light guide plate 1, that is, on the emission surface 9 side. The light diffusion sheet 4 is for diffusing light so that a user does not visually recognize the shape of the pattern formed on the light guide plate 1, for example, the shape of a light scattering pattern not shown. There are agents kneading type, random unevenness processing type, etc. The light diffusion sheet 4 has a thickness of usually 10 μm or more, preferably 20 to 300 μm. The light diffusion sheet 4 is made of a transparent resin, and examples of the resin include polycarbonate, polyester, and polymethyl methacrylate.

  Further, on the upper side of the light diffusion sheet 4, brightness enhancement films 5 and 6 are laminated and provided. The brightness enhancement films 5 and 6 are made of an optical film in which a prism pattern is precisely formed on the surface of polyester, acrylic resin or the like having excellent transparency. By arranging the film in which the fine prism structures are arranged in this manner so as to overlap with the upper side of the emission surface 9 of the light guide plate 1, the luminance of the light emitted to the illuminated object N side can be improved. By superimposing the two brightness enhancement films 5 and 6 in the direction where the prism structure intersects 90 degrees, the performance is improved, the blurring of the screen is eliminated, and the stripe pattern (reflective moire) of the shining part and the diffusing part of the light is improved. ).

  Next, the frame body 7 is a frame-shaped member that accommodates other members such as the light guide plate 1 and the LEDs 2 constituting the planar illumination device M. For example, the frame body 7 is made of a translucent resin material such as polycarbonate resin. Light reflection member (white pigment such as titanium oxide) is mixed inside. Accordingly, the frame body 7 is a highly light-reflective member, which diffuses and reflects the light emitted to the outside from the light guide plate 1 and re-enters the light guide plate 1 to increase the utilization efficiency of the light emitted from the LED 2. Yes. The frame body 7 is formed with recesses 20a, 20b, 20c, 21a, 21b, and 21c. When the planar lighting device M is assembled, the protrusions 11a, 11b, 11c, 12a, 12b, and 12c of the light guide plate 1 are assembled. Are inserted into these recesses, and the light guide plate 1 is held by the frame body 7.

  These recesses are illustrated in FIG. FIG. 3A shows a plan view of the frame body 7. The recesses 20 a, 20 b, 20 c, 21 a, 21 b, 21 c have a rectangular shape and are formed to extend in the vertical direction from the inner wall surfaces of the side walls 22, 23 of the frame body 7. As shown in FIGS. 3B and 3C, the recesses 21 a, 21 b, 21 c of the recesses 21 a, 21 b, 21 c provided on the side wall 23 are provided near the upper wall surface 24 of the side wall 23. The recess 21b is provided closer to the lower wall surface 25. This structure is the same also about the recessed parts 20a, 20b, and 20c provided in the side wall 22. FIG. That is, the concave portions provided in the side wall 22 and the side wall 23 are alternately provided so that adjacent concave portions have different heights in the vertical thickness direction of the side walls. This corresponds to the positions of the protrusions 11a, 11b, 11c, 12a, 12b, and 12c provided on the light guide plate 1, and the light guide plate 1 is framed by inserting the protrusions into these recesses. 7 is securely fixed at an appropriate position.

  Next, a liquid crystal display device, for example, is disposed as an object to be illuminated N on the upper side (light emission surface 9 side) of the light guide plate 1 on which the light diffusion sheet 4 and the brightness enhancement films 5 and 6 are provided. The liquid crystal display device N is provided with a display area 31 in which a liquid crystal display element is provided and a non-display area 32 which is a peripheral part in which no liquid crystal display element is provided. The liquid crystal display device N is a so-called backlight type display device that is irradiated from the back side of the liquid crystal display device N by the light emitted from the emission surface 9 of the light guide plate 1. Thereby, the brightness | luminance of the liquid crystal display device N improves and visibility improves.

  FIG. 4 is a plan view showing the planar illumination device M in a state where each member is accommodated in the frame body 7. Cutouts 13a, 13b, 13c, 14a, 14b, and 14c are formed in the protrusions 11a, 11b, 11c, 12a, 12b, and 12c, respectively. These notches are formed in the end portions of the long sides of the light guide plate 1 in the longitudinal direction of the side surface 11 and the side surface 12 on the far side of the respective protrusions when viewed from the LED 2. Further, the notch is formed in a shape in which the ridge portion on the side farther from the LED 2 of the protruding portion having the same shape as the rectangular concave portion shown in FIG. 3 is cut into a flat shape (C chamfered). That is, the surface of the chamfered cutout portion has an acute inclination angle with respect to the side surfaces 12 and 13 on which the protrusions are provided. Further, the C chamfer is formed along the thickness direction of the light guide plate 1, that is, along the short side direction of the side surface 11 and the side surface 12 in the vertical direction with respect to the emission surface 9 of the light guide plate 1. .

  On the other hand, the end portions of the projections on which the notches are not formed, that is, the end portions of the respective projection portions on the side close to the LED 2 are recessed portions 20a, 20b, 20c, It has the same shape as the ends of 21a, 21b, 21c. That is, the end portion of the protrusion portion on which the notch is not formed has a rectangular shape. For example, in the case of the protrusion portion 12a, a surface 15a extending in the vertical direction with respect to the side surface 12 of the light guide plate 1 and It is formed by a surface 16a extending in parallel.

  With such a configuration, the light is reflected and guided by the side surfaces constituting the protrusions 11a, 11b, 11c, 12a, 12b, 12c and the side surfaces constituting the recesses 20a, 20b, 20c, 21a, 21b, 21c. Of the light traveling in the central direction of the light plate 1, the amount of light traveling after being reflected from the side surface a plurality of times can be reduced. The luminance unevenness region extending in the direction can be reduced. Therefore, uniform surface light emission can be realized on the entire light exit surface 9 of the light guide plate 1, and the display area 31 of the liquid crystal display device N can be enlarged.

  Further, the positional deviation of the light guide plate 1 with respect to the frame body 7 is prevented by the side face 17 of the light guide plate 1 coming into contact with the side wall 26 of the frame body 7 with respect to the deviation in the direction in which the light guide plate 1 is separated from the LED 2. Further, regarding the deviation in the direction in which the light guide plate 1 approaches the LED 2, the side surfaces of the projections 11 a, 11 b, 11 c, 12 a, 12 b, and 12 c of the light guide plate 1 (the surface 15 a in terms of the projection 12 a) This is prevented by coming into contact with the side surface of the recesses 20a, 20b, 20c, 21a, 21b, 21c on the LED2 side. Moreover, about the shift | offset | difference to the side surface 11 or the side surface 12 direction of the light-guide plate 1, the side surface (The surface 16a in terms of the projection part 12a) of the projection parts 11a, 11b, 11c, 12a, 12b, 12c of the light-guide plate 1 is a frame. This is prevented by coming into contact with the concave surfaces of the concave portions 20a, 20b, 20c, 21a, 21b, 21c of the body 7.

  In the above embodiment, the case where the notches of the protrusions 11a, 11b, 11c, 12a, 12b, and 12c are formed by chamfering is described. However, the present invention is not limited to this embodiment. For example, FIG. As shown in the protruding portion 11a ', the ridge portion on the side farther from the LED 2 of the protruding portion having the same shape as the rectangular concave portion (see FIG. 3) is rounded in an R shape, that is, notched by R chamfering. 18a may be provided. Moreover, although the case where LED which is a point light source was used as a light source was demonstrated in the said form, it can replace with this and can also use point light sources, such as a halogen lamp. The light source is not limited to a point light source, and may be a linear light source such as a fluorescent tube that can be disposed on one side surface of the light guide plate.

  The uniformity of luminance was observed with the planar illumination device according to the present invention. The light guide plate 1 has a size of 2 inches, and its effective area, that is, the area used as the display area 31 of the liquid crystal display device N is about 40 × 30 mm. Further, the thickness of the light guide plate 1 is 0.8 mm, a transparent polycarbonate resin material is used, and fine rough surface patterns are formed on the upper and lower surfaces (the emission surface 9 and the back surface 10). Two LEDs 2 are arranged. In the frame body 7, an appropriate amount of white pigment is mixed in a polycarbonate material. Other configurations are the same as those of the above-described planar illumination device M unless otherwise specified. For comparison, the conventional form was also observed.

  FIG. 6 is a partially enlarged view showing the protrusion and the recess of the frame. (A) In the figure, the light guide plate 1 is provided with a protrusion having the same shape as the conventional one, that is, a protrusion 11d having the same shape as the rectangular recess in FIG. This is a conventional planar lighting device provided with three rectangular recesses 20a. In this case, abnormal light emission (luminance unevenness) occurs in the vicinity of the protrusion 11d. (B) The figure shows a planar illumination device in a state where the light guide plate 1 is provided with the same protrusion 11d as in (a) and the frame body 7 is not attached. In this case, luminance unevenness in the vicinity of the protrusion 11d did not occur. (C) The figure shows a planar illumination device in which the light guide plate 1 is provided with the same protrusion 11d as in (a) and the frame 7 is provided with a rectangular recess 20d. The recess 20d is formed longer than the length of the protrusion 11d, and a space is provided between the side surface of the protrusion 11d far from the LED 2 and the side wall of the recess 20d. In this case, uneven brightness occurred in the vicinity of the protrusion 11d.

  (D) The figure shows a planar lighting device in which the light guide plate 1 is provided with a projection 11a having a notch 13a formed by chamfering, and the frame 7 is provided with a recess 20e having the same shape as the projection 11a. In this case, uneven brightness occurred in the vicinity of the protrusion 11a. (E) is a planar illumination device according to the present invention shown in FIGS. 1 to 4, and the light guide plate 1 is provided with a protrusion 11 a formed with a chamfered portion 13 a by C chamfering. The rectangular recess 20a of FIG. 3 is provided. FIG. 5 shows another embodiment of the planar lighting device according to the present invention, in which a notch 18a is provided in the protrusion 11a 'by R chamfering, and the rectangular recess 20a in FIG. It is a thing. In any of the planar illumination devices according to the present invention, luminance unevenness in the vicinity of the protrusions 11a and 11a ′ did not occur.

  As shown in the conventional form of FIG. 6A, the luminance unevenness that occurs in the vicinity of the protrusion is after light (indicated by an arrow 35) is reflected by the surface 36 of the protrusion 11d and the surface 37 of the recess 20a. It is considered that this occurs due to the fact that the projection 11d reflects from the side surface 38 on the side far from the LED 2 and then travels toward the center of the light guide plate 1. Therefore, by reducing the amount of light reflected by the side surface of the protrusion portion far from the LED 2, it is possible to prevent the occurrence of luminance unevenness in the vicinity of the protrusion portion. That is, as shown in the form of the planar lighting device according to the present application in FIG. 6 (e) and FIG. 5, by providing the notches 13a and 18a at the ends of the protrusions 11a and 11a ′ far from the LED 2, The amount of light reflected by the notched surface (the surface corresponding to the side surface 38 in FIG. 6A) can be reduced, and the occurrence of uneven brightness near the protrusion can be prevented.

  This will be described with reference to FIG. 6 (e). After reflecting on the surface 36 of the protrusion 11d and the surface 37 of the recess 20a as shown by the arrow 35 in FIG. 6 (a), the light is reflected on the side surface 38 of the protrusion 11d. In FIG. 6E, the light that has traveled is not reflected by the surface 36 of the protrusion 11a and the surface 37 of the recess 20a, but is reflected by the notch surface of the notch 13a. However, from the relationship of the incident angle of light when entering the notch surface, most of the light hitting the notch surface travels through the notch surface, and thus reflects on the notch surface and is reflected by the light guide plate 1. The amount of light traveling toward the center of the light source is reduced. However, as shown in FIG. 6D, when the concave portion of the frame body 7 is formed in the same shape as the protruding portion 11a, the light transmitted through the notched surface is reflected by the concave surface and enters the light guide plate 1 again. Therefore, luminance unevenness occurs in the vicinity of the protrusion 11a. Therefore, the shape of the recess of the frame 7 needs to be a rectangular recess 20a shown in FIG.

It is a disassembled perspective view which shows one form of the to-be-illuminated body arrange | positioned above the planar illumination device which concerns on this invention, and a planar illumination device. It is a perspective view when the planar illuminating device shown in FIG. 1 is assembled. (A) is a top view which shows the frame of the planar illuminating device shown in FIG. (B) is sectional drawing in the AA of (a). (C) is sectional drawing in the BB line of (a). It is a top view when the planar illuminating device shown in FIG. 1 is assembled. It is the elements on larger scale which show another one form of the planar illuminating device which concerns on this invention. (A) is the elements on larger scale which show one form of the conventional planar illuminating device for contrast with the planar illuminating device which concerns on this invention. (B) is the elements on larger scale which show one form of the planar illuminating device for contrast with the planar illuminating device which concerns on this invention. (C) is the elements on larger scale which show one form of the planar illuminating device for contrast with the planar illuminating device which concerns on this invention. (D) is the elements on larger scale which show one form of the planar illuminating device for contrast with the planar illuminating device which concerns on this invention. (E) is the elements on larger scale which show one form of the planar illuminating device which concerns on this invention. It is a figure which shows the prior art example of the light-guide plate which provided the protrusion part for positioning. It is a figure which shows the other conventional example of the light-guide plate which provided the projection part.

Explanation of symbols

M Surface illumination device N Object to be illuminated (liquid crystal display device)
1 Light Guide Plate 2 Point Light Source (LED)
7 Frame 8 Entrance surface 9 Output surface 10 Back surface 11a, 11b, 11c, 12a, 12b, 12c Protrusion 13a, 13b, 13c, 14a, 14b, 14c Notch 20a, 20b, 20c, 21a, 21b, 21c Recess

Claims (3)

A light guide plate made of a translucent material;
A light source disposed to face the side surface of the light guide plate;
While having a frame that houses the light guide plate and the light source,
Protruding portions that are provided on the side surface orthogonal to the side surface of the light guide plate on which the light source is disposed, and for determining the arrangement position of the light guide plate in the frame body;
In the planar lighting device provided with a recess formed in the frame body, into which the protrusion of the light guide is inserted,
The concave portion has a rectangular shape,
In the longitudinal direction of the side surface provided with the projection, a notch is formed at the end of the projection far from the light source along the lateral direction of the side surface provided with the projection. A planar lighting device. The planar illumination device according to claim 1, wherein the notch of the protrusion is formed by C chamfering having an acute angle with respect to the side surface on which the protrusion is provided. The planar illumination device according to claim 1, wherein the notch of the protrusion is formed by R chamfering.

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