JP6559073B2 - Lighting device - Google Patents

Description

  The present invention relates to a thin plate-like lighting device having a small thickness.

  The present applicant has proposed a flat illuminating device designed so that the brightness of the light exit surface is uniform as a whole including the peripheral portion (see, for example, Patent Document 1). The illumination device described in Patent Document 1 is formed in a square flat plate shape. The lighting device includes a light guide plate formed in a square flat plate shape, a plurality of LED light sources arranged along each of four end faces of the light guide plate, and one side of the light guide plate in the thickness direction of the light guide plate A light diffusing plate disposed on the side of the light exit surface, which diffuses light emitted from the light guide plate, and a reflector disposed on the other side of the light guide plate in the thickness direction of the light guide plate. The LED light source is mounted on the LED substrate. The LED substrate is attached to the frame. The frame includes a base portion disposed so as to face the end surface of the light guide plate, and two light shielding portions extending from both ends of the base portion in the thickness direction of the light guide plate toward the light guide plate.

  In the illumination device described in Patent Literature 1, light scattering particles are included in the light guide plate and the diffusion plate. The diffusion plate is formed in a square flat plate shape. In addition, the diffusion plate includes a protruding portion (protruding portion) that protrudes toward the light guide plate. The protrusion is formed on the peripheral edge of the diffusion plate so as to face the peripheral edge of the light exit surface of the light guide plate, and is formed in a square frame shape. One light shielding part of the two light shielding parts formed on the frame emits light from the light guide plate so as to shield a part of the light incident on the protrusion from the peripheral edge of the light emission surface of the light guide plate. It is arrange | positioned between the peripheral part of the surface, and the protrusion part.

  Moreover, in the illumination device described in Patent Document 1, the outer peripheral surface of the projecting portion forms a part of the end surface of the diffusion plate, and includes two planar outer surfaces parallel to each other and the two outer surfaces. Are formed by a total of four outer surfaces including two planar outer surfaces orthogonal to each other and parallel to each other. Moreover, the inner peripheral surface of the protrusion is configured by four planar inner surfaces parallel to each of the four outer surfaces. At the corner of the diffuser plate formed in a square flat plate shape, the two inner surfaces intersect so as to be orthogonal to each other, and the inner peripheral surface of the protrusion when viewed from the thickness direction of the diffuser plate is a square It has become. On the inner side surface of the projecting portion, light incident from the inside of the projecting portion to the inner side surface of the projecting portion exceeding the critical angle is totally reflected.

  In the illuminating device described in Patent Document 1, the light shielding portion is disposed between the peripheral portion of the light emitting surface of the light guide plate and the protruding portion, and the light emitted from the light source does not directly enter the diffusion plate. It is possible to prevent the light source portion from appearing as a point light source on the light exit surface of the diffuser plate (that is, the light exit surface of the illumination device). In addition, the brightness of the peripheral edge of the light exit surface of the diffuser near the light source is likely to be higher than the brightness of the central portion. Since the light shielding part is arranged, it is possible to limit the amount of light incident on the diffusion plate from the light guide plate, and to suppress the luminance of the peripheral portion of the light exit surface of the diffusion plate. Further, in this lighting device, since the light shielding part is arranged between the peripheral part of the light emitting surface of the light guide plate and the projecting part, the light shielding part affects the peripheral part of the light emitting surface of the diffusion plate. Although there is a possibility that a dark part such as an edge is generated, the diffuser plate contains light scattering particles, and a part of the light incident on the projecting part is totally reflected on the outer peripheral surface and the inner peripheral surface of the projecting part. Since the light is emitted from the peripheral portion of the light emitting surface, it is possible to prevent a dark portion such as an edge from being generated at the peripheral portion of the light emitting surface of the diffusion plate. As described above, in the illumination device described in Patent Document 1, it is possible to suppress brightness unevenness on the light emission surface of the illumination device and to make the brightness of the light emission surface of the illumination device uniform.

JP 2014-235784 A

  In the illuminating device described in Patent Document 1, for example, when the corner of the light guide plate formed in a square flat plate shape is fixed to the diffusion plate with screws, the frame cannot be arranged over the entire end face of the light guide plate. There is. That is, in this illuminating device, there may be a portion at the corner of the illuminating device that cannot be blocked by the light shielding portion between the peripheral portion of the light exit surface of the light guide plate and the protruding portion. Therefore, in the illuminating device described in Patent Literature 1, the luminance of the corner portion of the light emission surface of the illuminating device may be higher than the luminance of other portions of the light emission surface.

  In addition, in the lighting device described in Patent Document 1, a part of light incident on the inner surface of the protruding portion from the inside of the protruding portion is totally reflected in a specific direction. Then, at the corner portion of the diffuser plate, the two inner surfaces of the protruding portion intersect so as to be orthogonal to each other. Therefore, at the corner portion of the diffuser plate, the light totally reflected in a specific direction on the inner surface of the protruding portion. As a result, it became clear that the luminance at the corner of the light exit surface of the illuminating device tends to be higher than the brightness at other portions of the light exit surface. In particular, in the illumination device described in Patent Document 1, LED light sources are arranged along each of the four end faces of the light guide plate, and two LED light sources are arranged in the vicinity of the corners of the diffusion plate. Therefore, at the corner of the diffuser plate, the light totally reflected in a specific direction on the inner surface of the protruding portion is more likely to concentrate on the corner of the diffuser plate, and the luminance of the corner of the light exit surface of the illuminating device is light emitted. It became clear by examination of this inventor that it becomes easy to become higher than the brightness | luminance of the other part of a surface.

  Therefore, an object of the present invention is to make the brightness of the light exit surface of the illumination device more uniform by suppressing the luminance of the corners of the light exit surface of the illumination device in the illumination device formed in a polygonal flat plate shape. It is in providing the illuminating device which can do.

  In order to solve the above-described problems, an illumination device of the present invention includes a light guide plate formed in a polygonal plate shape, a light source disposed so as to face an end surface of the light guide plate, and a light guide in the thickness direction of the light guide plate. A diffusion plate that is disposed on the light exit surface side, which is one side of the light plate, is formed in a polygonal plate shape that is substantially the same shape as the light guide plate, and diffuses light emitted from the light guide plate, and the light guide plate and the diffusion plate The light guide plate and the diffusion plate are arranged so that the end surface of the light guide plate and the end surface of the diffusion plate are parallel to each other, and the diffusion plate is along the end surface of the diffusion plate. And a protrusion that protrudes toward the light guide plate and is disposed at a position facing the periphery of the light emission surface, and the light shielding member is a part of the light incident on the protrusion from the periphery of the light emission surface Is arranged between the peripheral edge of the light exit surface and the protrusion, and the protrusion is a part of the end face of the diffusion plate. A plurality of inner surfaces parallel to each of the plurality of outer surfaces, and corners of the diffuser plate formed in a polygonal plate shape Are formed in a polygonal frame shape having a corner inner side surface which is a surface non-parallel to the outer side surface on the inner peripheral side of the projecting portion.

  In the illuminating device of the present invention, in the corner portion of the diffuser plate formed in a polygonal plate shape, a corner inner side surface that is a surface non-parallel to the outer surface is formed on the inner peripheral side of the protruding portion. Therefore, according to the present invention, at the corner portion of the diffuser plate, light incident on the inner side surface of the projection portion from the inside of the projection portion can be totally reflected in various directions by the inner side surface of the corner portion. Therefore, according to the present invention, it is possible to prevent the light totally reflected at the corner inner side surface of the projecting portion from concentrating on the corner of the diffusion plate at the corner of the diffusion plate. As a result, in the present invention, it is possible to suppress the luminance at the corners of the light exit surface of the illumination device and to make the brightness of the light exit surface of the illumination device more uniform.

  In the present invention, for example, when viewed from the thickness direction of the diffusion plate, the corner inner surface faces one inner surface of two inner surfaces adjacent to each other in the circumferential direction of the protruding portion toward the other inner surface. The first virtual extension line extended and the second virtual extension line extending the other inner side surface toward one inner side surface are arranged on the inner peripheral side of the protruding portion. In this case, when viewed from the thickness direction of the diffuser plate, the inner surface of the corner is disposed on the outer peripheral side of the protruding portion rather than at least one of the first virtual extension line and the second virtual extension line As compared with the above, the inner side surface of the corner can be easily formed.

  In the present invention, at the corner where the inner surface of the corner of the diffusion plate is formed, the intersection of the first virtual extension line and the second virtual extension line is a virtual intersection when viewed from the thickness direction of the diffusion plate, Assuming that the direction from the corner of the diffuser plate to the virtual intersection is the first direction, the distance between the virtual intersection in the first direction and the inner corner surface of the diffuser at the corner portion where the inner corner surface is formed is It is preferable that it is equal to or less than the width of the protrusion, which is the shortest distance from the inner surface parallel to the outer surface, and equal to or more than 1/8 of the width of the protrusion. When the distance between the virtual intersection in the first direction and the inner surface of the corner is 1/8 or more of the width of the protruding portion, the light incident on the inner surface of the protruding portion from the inner side of the protruding portion can be varied in various directions depending on the inner surface of the corner As a result, in the corner of the diffuser plate where the inner surface of the corner is formed, the light totally reflected by the inner surface of the corner of the protrusion is concentrated on the corner of the diffuser. It becomes possible to prevent effectively. In addition, a part of the light emitted from the light exit surface of the diffusion plate enters the corner inner surface from the outside of the protrusion, but the distance between the virtual intersection in the first direction and the corner inner surface is less than the width of the protrusion. In this case, light incident on the inner side surface of the corner from the outside of the protruding portion can easily reach the corner of the diffusion plate, so that it is possible to prevent an extreme decrease in luminance at the corner of the diffusion plate.

  In the present invention, the distance between the virtual intersection in the first direction and the inner surface of the corner is more preferably ½ or less of the width of the protrusion. With this configuration, light incident on the inner side surface of the corner from the outside of the protruding portion is more likely to reach the corner of the diffuser plate, so that it is possible to effectively prevent an extreme decrease in luminance at the corner of the diffuser plate. Is possible.

  In the present invention, the inner side surface of the corner is preferably formed in a concave curved surface shape. In this case, for example, the inner side surface of the corner portion is formed so that the shape when viewed from the thickness direction of the diffusion plate is an arc shape that smoothly connects the end portions of the inner side surfaces adjacent in the circumferential direction of the protruding portion. Has been. If comprised in this way, it will become possible to totally reflect the light which injects into the corner | angular side inner surface of a protrusion part from the inner side of a protrusion part in various directions by a corner | angular part inner surface, As a result, in a corner | angular part of a diffuser plate, It is possible to effectively prevent the light totally reflected on the inner surface of the corner of the portion from being concentrated on the corner of the diffuser plate. Moreover, when comprised in this way, when a diffusion plate is seen from the light-projection surface of a diffusion plate, an inner surface of a corner | angular part becomes difficult to stand out.

  In the present invention, when the second direction is a direction perpendicular to the thickness direction of the diffuser plate and along the end surface of the diffuser plate, the end of the inner surface at the corner of the diffuser plate where the inner side surface of the corner is formed. It is preferable that the portion is disposed outside the outer end of the light source in the second direction in the second direction. If comprised in this way, it will become possible to suppress the fall of the extreme brightness | luminance in the corner | angular part of a diffusion plate. That is, a part of light incident on the inner surface of the protrusion from the inner side of the protrusion is totally reflected toward the end surface of the diffuser on the inner surface of the protrusion, thereby reducing the luminance at the peripheral edge of the diffuser. Although being suppressed, when the end of the inner surface (that is, the end of the inner surface of the corner) is arranged in the second direction inside the outer end of the light source in the second direction, the corner of the diffuser plate In this case, the amount of light totally reflected toward the end face of the diffusion plate is reduced, and the luminance at the corners of the diffusion plate may be extremely reduced. On the other hand, when the end portion of the inner side surface (that is, the end portion of the inner side surface of the corner portion) is disposed outside the outer end of the light source in the second direction in the second direction, Thus, it is possible to secure the amount of light that is totally reflected toward the end face of the diffusion plate, and it is possible to suppress an extreme decrease in luminance at the corners of the diffusion plate. In the present specification, the “outer end of the light source in the second direction” refers to the second direction of the plurality of light sources when a plurality of light sources are arranged along the end face of the light guide plate. The outer end in the second direction of the light source arranged on the outermost side. When one light source is arranged along the end face of the light guide plate, the outer end in the second direction of the light source. Say.

  In the present invention, the surface roughness of the corner inner side surface is preferably equal to or greater than the surface roughness of the inner side surface. With this configuration, the surface of the inner surface of the corner can be roughened, so that light incident on the inner surface of the corner of the protrusion from the inside of the protrusion can be irregularly reflected by the inner surface of the corner. As a result, in the corner portion of the diffuser plate, it is possible to effectively prevent the light totally reflected on the inner surface of the corner portion of the protrusion from concentrating on the corner portion of the diffuser plate. Moreover, since it becomes possible to make the surface of an inner surface smooth by comprising in this way, it becomes possible to totally reflect the light which injects into an inner surface from the inner side of a protrusion part in a specific direction by an inner surface. .

  As described above, in the present invention, in the lighting device formed in a polygonal flat plate shape, the brightness of the light emitting surface of the lighting device is more uniform by suppressing the luminance at the corners of the light emitting surface of the lighting device. It becomes possible to become.

It is a perspective view of the illuminating device concerning embodiment of this invention. It is a disassembled perspective view of the illuminating device shown in FIG. It is sectional drawing of the EE cross section of FIG. (A) is a top view for demonstrating the structure of the corner | angular part of the illuminating device shown in FIG. 1, (B) is an enlarged view of the F section of (A). It is a figure for demonstrating the effect of the illuminating device shown in FIG. It is a figure for demonstrating the structure of the corner | angular part inner surface concerning other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Whole structure of lighting device)
FIG. 1 is a perspective view of a lighting device 1 according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the lighting device 1 shown in FIG. FIG. 3 is a cross-sectional view taken along the line EE of FIG.

  The illuminating device 1 of this embodiment is a light-emitting device designed so that the brightness of the light exit surface 3a of the illuminating device 1 is uniform as a whole including the peripheral portion, and is formed in a thin flat plate shape. Specifically, the illumination device 1 is formed in a rectangular flat plate shape. This lighting device 1 is used alone. Or this illuminating device 1 is used combining multiple sheets. For example, two lighting devices 1 are used in combination in a rectangular shape, or four lighting devices 1 are used in combination in a rectangular shape. Moreover, the illuminating device 1 is installed and used for the indoor wall surface as illumination which served as interior, for example.

  In the following description, the thickness direction of the lighting device 1 (the Z direction in FIG. 1 and the like) is referred to as “front-rear direction”, and the longitudinal direction of the rectangular lighting device 1 among the directions orthogonal to the front-rear direction (FIG. 1). X direction) is referred to as “left-right direction”, and the short side direction (Y direction in FIG. 1 and the like) of the lighting device 1 orthogonal to the front-rear direction and the left-right direction is referred to as “vertical direction”. In addition, the front side (the Z1 direction side in FIG. 1 and the like) of the lighting device 1 in the front-rear direction is the “front” side, and the back side (the Z2 direction side in FIG. 1 and the like) of the lighting device 1 that is the opposite side. “Back (back)” side.

  The lighting device 1 includes a light guide plate 2, a diffusion plate 3 that is disposed on the front side of the light guide plate 2 and diffuses light emitted from the light guide plate 2, a reflection sheet 4 that is disposed on the rear side of the light guide plate 2, and a reflection sheet 4. And a reinforcing frame 5 disposed on the rear side of the frame. In addition, the lighting device 1 includes a plurality of light sources 6 (see FIG. 3) that emit light toward the end surface 2 a of the light guide plate 2, a substrate 7 on which the plurality of light sources 6 are mounted, and the light source 6 via the substrate 7. And a light source holding member 8 for holding the light source. Furthermore, the lighting device 1 includes a case 9 in which the light guide plate 2, the reflection sheet 4, the frame 5, the light source 6, the substrate 7, and the light source holding member 8 are accommodated. In addition, illustration of the light source 6 is abbreviate | omitted in FIG.

  The light guide plate 2 is made of an acrylic resin having a high light transmittance. The light guide plate 2 is a light scattering light guide containing a large number of light scattering particles that are spherical particles, and light incident on the light guide plate 2 is scattered by the light scattering particles in the light guide plate 2. The light scattering particles contained in the light guide plate 2 are formed of, for example, silicone particles disclosed in Japanese Patent Application Laid-Open No. 2014-150049. The light guide plate 2 is formed in a rectangular flat plate shape, and is arranged so that the thickness direction of the light guide plate 2 matches the front-rear direction. That is, the front-rear direction is the thickness direction of the light guide plate 2. The light guide plate 2 is arranged so that the longitudinal direction of the light guide plate 2 formed in a rectangular shape coincides with the left-right direction. The light guide plate 2 is formed with a total of four end surfaces 2 a including two end surfaces 2 a orthogonal to the vertical direction and two end surfaces 2 a orthogonal to the horizontal direction. The front surface of the light guide plate 2 is a light exit surface 2 c of the light guide plate 2.

  The diffusion plate 3 is formed in a rectangular plate shape that is substantially the same shape as the light guide plate 2. Specifically, the diffusion plate 3 is formed in a rectangular substantially flat plate shape. The diffusion plate 3 is arranged so that the thickness direction of the diffusion plate 3 and the front-rear direction coincide with each other. That is, the front-rear direction is the thickness direction of the diffusion plate 3. The diffusion plate 3 is arranged so that the longitudinal direction of the diffusion plate 3 formed in a rectangular shape coincides with the left-right direction. That is, the light guide plate 2 and the diffusion plate 3 are arranged so that the four end surfaces 2 a of the light guide plate 2 and the four end surfaces 3 j of the diffusion plate 3 are parallel to each other. The front surface of the diffusion plate 3 is a light exit surface 3 a of the diffusion plate 3. The light emission surface 3 a is a light emission surface of the lighting device 1. When the light diffusing plate 3 is viewed from the front in front of the light exit surface 3a (that is, when viewed from the direction orthogonal to the light exit surface 3a), the diffusion plate 3 is in the outer shape of the light exit surface 3a. The size is such that the components of the lighting device 1 can be accommodated. A specific configuration of the diffusion plate 3 will be described later.

  The reflection sheet 4 is formed of a material having a high reflectance such as an aluminum foil, for example. The reflection sheet 4 is formed in a rectangular shape so as to cover the entire rear surface (back surface) of the light guide plate 2. The front surface of the reflection sheet 4 is a reflection surface 4 a that reflects light traveling through the light guide plate 2. The reflection sheet 4 is disposed so as to be in close contact with the rear surface of the light guide plate 2. Instead of the reflective sheet 4, a reflective plate formed in a thin flat plate shape may be disposed on the rear side of the light guide plate 2, or a reflective coating is applied to the rear surface of the light guide plate 2 instead of the reflective sheet 4. May be.

  The frame 5 is formed of a metal plate having a high thermal conductivity. For example, the frame 5 is made of an aluminum alloy. The frame 5 is formed in a flat plate shape in which the outer shape of the frame 5 is rectangular when viewed from the front-rear direction. Specifically, the frame 5 includes a flat frame portion 5a formed in a rectangular frame shape and a flat bracing portion 5b formed in an X shape and connecting diagonals of the frame portion 5a. Yes. The frame 5 is arranged so that the thickness direction of the frame 5 coincides with the front-rear direction. The frame 5 is arranged so that the longitudinal direction of the frame portion 5a having a rectangular frame shape coincides with the left-right direction. The frame 5 is disposed so as to be in close contact with the rear surface of the reflection sheet 4.

  The light source 6 is an LED (Light Emitting Diode) light source, and is mounted on the substrate 7 as described above. Each of the LED elements constituting the light source 6 is a white LED, and the light source 6 emits white light. The substrate 7 is a flexible printed circuit board (FPC (Flexible Printed Circuits)). As shown in FIG. 2, the substrate 7 is formed in an elongated strip shape. A plurality of light sources 6 are linearly arranged and mounted on the substrate 7 along the longitudinal direction of the substrate 7, and the plurality of light sources 6 are disposed so as to face the end surface 2 a of the light guide plate 2. Specifically, a plurality of light sources 6 are arranged so as to face each of the four end surfaces 2 a of the light guide plate 2. The light source 6 may be a package of a red LED element, a green LED element, and a blue LED element.

  The light source holding member 8 is formed by bending a thin metal plate into a predetermined shape. Specifically, the light source holding member 8 includes a base portion 8a disposed to face the end surface 2a of the light guide plate 2, a first extending portion 8b extending from both ends of the base portion 8a in the front-rear direction to the light guide plate 2 side, and The second extending portion 8c is provided and is formed in an elongated rectangular groove shape as a whole. That is, the light source holding member 8 is formed so that its cross-sectional shape is substantially U-shaped (substantially U-shaped). The first extending portion 8b is connected to the front end of the base portion 8a, and the second extending portion 8c is connected to the rear end of the base portion 8a. As shown in FIG. 3, the light source 6 and the substrate 7 are disposed between the first extending portion 8b and the second extending portion 8c. Moreover, the light source 6 and the board | substrate 7 are arrange | positioned between the base 8a and the end surface 2a, and are arrange | positioned along the end surface 2a. The light guide plate 2, the reflection sheet 4, and the frame 5 are sandwiched between the first extending portion 8b and the second extending portion 8c. The first extending portion 8 b is in contact with the front surface of the light guide plate 2, and the second extending portion 8 c is in contact with the rear surface of the frame 5.

  The case 9 is formed of a thin metal plate such as a steel plate or an aluminum alloy plate. The case 9 is composed of a bottom surface portion 9a and a side surface portion 9b rising from the outer peripheral end of the bottom surface portion 9a toward the front side, and is formed in a flat rectangular box shape having an open front side. The side surface portion 9b is formed in a rectangular frame shape, and the shape of the case 9 when viewed from the front-rear direction is a rectangular shape. The case 9 is disposed such that the longitudinal direction of the side surface portion 9b having a rectangular frame shape coincides with the left-right direction. As described above, the light guide plate 2, the reflection sheet 4, the frame 5, the light source 6, the substrate 7, and the light source holding member 8 are accommodated in the case 9. The opening on the front end side of the case 9 is closed by the diffusion plate 3. In this embodiment, as shown in FIG. 1 and the like, the outer peripheral surface of the diffusion plate 3 and the outer peripheral surface of the case 9 are arranged on the same surface. However, the outer peripheral surface of the case 9 may be disposed inside the outer peripheral surface of the diffusion plate 3.

  The light guide plate 2, the frame 5, and the light source holding member 8 are fixed to the diffusion plate 3 by screws not shown. The light source holding member 8 is also fixed to the frame 5 with screws not shown. The case 9 is fixed to the frame 5 with screws not shown. In this embodiment, the light guide plate 2, the frame 5, and the light source holding member 8 are fixed to the diffusion plate 3, and the case 9 is fixed to the frame 5 after the light source holding member 8 is fixed to the frame 5.

(Diffusion plate configuration)
4A is a plan view for explaining a configuration of a corner portion of the lighting device 1 shown in FIG. 1, and FIG. 4B is an enlarged view of a portion F in FIG. 4A. In addition, illustration of the light-guide plate 2 is abbreviate | omitted in FIG.4 (B).

  The diffusion plate 3 is made of an acrylic resin or polycarbonate having a high light transmittance. The diffusion plate 3 is a light scattering light guide containing a large number of light scattering particles, and light incident on the diffusion plate 3 is scattered by the light scattering particles in the diffusion plate 3. The diffusion plate 3 contains light scattering particles similar to the light scattering particles contained in the light guide plate 2. That is, the light scattering particles contained in the diffusing plate 3 are formed of, for example, silicone particles disclosed in Japanese Patent Application Laid-Open No. 2014-150049.

  As described above, the diffusion plate 3 is disposed on the front side of the light guide plate 2. That is, the diffusing plate 3 is disposed on the side of the light emitting surface 2 c that constitutes the front surface of the light guide plate 2. The diffusion plate 3 includes a protruding portion 3b that protrudes toward the light guide plate 2 (that is, protrudes rearward). The protrusion 3b is formed along the four end faces 3j of the diffusion plate 3, and is formed in a rectangular frame shape. The protrusion 3b includes four planar outer surfaces 3k constituting a part of the rear end side of the end surface 3j of the diffusion plate 3, and the outer surface of the protrusion 3b is constituted by the four outer surfaces 3k. Has been. The protrusion 3b includes four flat inner surfaces 3n parallel to the four outer surfaces 3k on the inner peripheral side of the protrusion 3b. Of the four outer surfaces 3k, two outer surfaces 3k are orthogonal to the left-right direction, and the remaining two outer surfaces 3k are orthogonal to the vertical direction. Of the four inner side surfaces 3n, two inner side surfaces 3n are orthogonal to the left-right direction, and the remaining two inner side surfaces 3n are orthogonal to the vertical direction.

  As shown in FIG. 4, in each of the four corners of the diffusion plate 3 formed in a rectangular flat plate shape, the circumferential direction of the projection 3b formed in a frame shape is provided on the inner peripheral side of the projection 3b. A corner inner side surface 3r which is a surface connecting the end portions 3p of the adjacent inner side surfaces 3n is formed. The inner surface 3n is parallel to the outer surface 3k up to the end 3p. That is, the end 3p is an end of a portion where the inner side 3n is parallel to the outer side 3k. The corner inner side surface 3r is formed in a concave curved surface shape. That is, the corner inner side surface 3r is non-parallel (not parallel) to the outer side surface 3k. Specifically, the corner inner side surface 3r has a circular arc shape (more specifically, the end portion 3p of the two inner side surfaces 3n adjacent to each other in the circumferential direction of the protruding portion 3b when viewed from the front-rear direction. Are formed so as to have a ¼ arc shape). That is, as shown in FIG. 4B, in each of the four corners of the diffusion plate 3, when viewed from the front-rear direction, of the two inner side surfaces 3n adjacent in the circumferential direction of the protrusion 3b A virtual line obtained by extending one inner side surface 3n toward the other inner side surface 3n is defined as a first virtual extension line CL1, and a virtual line obtained by extending the other inner side surface 3n toward the one inner side surface 3n is defined as a second virtual line. Assuming that the extension line CL2 is provided, the corner inner side surface 3r is disposed on the inner peripheral side of the projecting portion 3b with respect to the first virtual extension line CL1 and the second virtual extension line CL2 at each of the four corners of the diffusion plate 3. ing. In this embodiment, the inner peripheral surface of the projecting portion 3b is formed by the four inner side surfaces 3n and the four corner inner side surfaces 3r.

  As shown in FIG. 4B, at each of the four corners of the diffusing plate 3, when viewed from the front-rear direction, the intersection of the first virtual extension line CL1 and the second virtual extension line CL2 is a virtual intersection. C, and a direction from the corner 3s of the diffusion plate 3 (more specifically, the corner 3s closest to the virtual intersection C of the four corners 3s of the diffusion plate 3) toward the virtual intersection C (FIG. 4B ) (The direction of arrow V) is the first direction, the distance D between the virtual intersection C in the first direction and the corner inner side surface 3r in each of the four corners of the diffusion plate 3 is The width W is equal to or smaller than the width W of the protruding portion 3b which is the shortest distance from the inner side surface 3n parallel to the outer side surface 3k, and is equal to or larger than 1/8 of the width W. In this embodiment, the distance D is ½ or less of the width W. Specifically, since the radius of curvature of the corner inner side surface 3r of this embodiment is 2 (mm), the distance D is 0.83 (= 2√2-2) (mm). Moreover, since the width W of this embodiment is 5 (mm), the distance D is about 1/6 of the width W.

  Further, as shown in FIG. 4B, the end portion 3p of the inner side surface 3n orthogonal to the left-right direction (that is, the end portion 3p of the inner side surface 3n parallel to the vertical direction) is disposed on the outermost side in the vertical direction. The light source 6 is disposed on the outer side in the vertical direction with respect to the outer end 6a in the vertical direction. Similarly, the end portion 3p of the inner side surface 3n orthogonal to the up-down direction (that is, the end portion 3p of the inner side surface 3n parallel to the left-right direction) is the outer end in the left-right direction of the light source 6 arranged on the outermost side in the left-right direction. It arrange | positions on the outer side of the left-right direction rather than 6a. That is, when the second direction is a direction perpendicular to the front-rear direction and along the end surface 3j of the diffusion plate 3, the end 3p of the inner surface 3n is the first in each of the four corners of the diffusion plate 3. It is arranged on the outer side (the virtual intersection C side) in the second direction than the outer end 6a of the light source 6 in the two directions. Further, the surface roughness of the corner inner side surface 3r is equal to or greater than the surface roughness of the inner side surface 3n. In this embodiment, the surface roughness of the corner inner side surface 3r is equal to the surface roughness of the inner side surface 3n.

  The protrusion 3b is disposed at a position facing the peripheral edge 2d (see FIG. 3) of the light exit surface 2c of the light guide plate 2. The rear surface of the protrusion 3b is formed in a planar shape orthogonal to the front-rear direction, and serves as a light incident surface 3c on which light emitted from the light emission surface 2c is incident. The inside of the protrusion 3b is a rectangular recess 3d that is recessed toward the front side, and the diffusion plate 3 has a space surrounded by the protrusion 3b. The bottom surface of the recess 3d is a light incident surface 3e on which light emitted from the light emitting surface 2c is incident. The light incident surface 3e is formed in a planar shape orthogonal to the front-rear direction. The peripheral edge 2d is a portion of the light exit surface 2c that faces the light incident surface 3c in the front-rear direction, and is formed in a rectangular frame shape.

  The light incident surfaces 3c and 3e are orthogonal to the end surface 3j and the inner surface 3n of the diffusion plate 3. Further, the light incident surfaces 3c and 3e and the corner inner side surface 3r are orthogonal to each other. The end surface 3j is a surface in contact with air. Further, the inner side surface 3n and the corner inner side surface 3r also face the recess 3d and are surfaces that come into contact with air. For this reason, light that enters the end surface 3j beyond the critical angle from the inside of the protrusion 3b is totally reflected by the end surface 3j. In addition, light incident on the inner side surface 3n from the inside of the protruding portion 3b beyond the critical angle is totally reflected by the inner side surface 3n, and light incident on the inner side surface 3r of the corner portion 3b from the inner side of the protruding portion 3b exceeds the critical angle. Total reflection is performed at the corner inner side surface 3r.

  The first extending portion 8b of the light source holding member 8 is disposed between the protruding portion 3b and the light guide plate 2, and is in contact with the light incident surface 3c of the protruding portion 3b. As shown in FIG. 3, the width of the first extending portion 8b in the direction from the base portion 8a toward the light guide plate 2 is narrower than the width of the protruding portion 3b in this direction. Further, the tip of the first extending portion 8b is disposed closer to the center of the light guide plate 2 than the end surface 2a. The first extending portion 8 b performs a light shielding function that prevents the light emitted from the light source 6 from directly entering the diffusion plate 3. Moreover, the 1st extension part 8b has restrict | limited the light which injects into the protrusion part 3b from the peripheral part 2d of the light-projection surface 2c.

  A portion of the light incident surface 3c covered by the first extending portion 8b is a shielding region 3g, and a portion of the light incident surface 3c inside the shielding region 3g is an incident region 3h. . The area of the shielding area 3g and the area of the incident area 3h are set so that the overall brightness of the light exit surface 3a is uniform. The first extending portion 8b of the present embodiment is a light shielding member disposed between the peripheral edge portion 2d and the protruding portion 3b so as to block part of light incident on the protruding portion 3b from the peripheral edge portion 2d of the light emitting surface 2a. It is. In this embodiment, the light source holding member 8 is not disposed over the entire end surface 2a of the light guide plate 2, and the four corners of the lighting device 1 protrude from the peripheral portion 2d of the light exit surface 2c. There is a portion where the first extending portion 8b is not disposed between the portion 3b.

(Light path in the lighting device)
As shown in FIG. 3, after a part of the light emitted from the light source 6 enters the light guide plate 2 from the end surface 2a of the light guide plate 2, for example, as indicated by a one-dot chain line L1, the light guide plate 2 While proceeding toward the center of the light guide plate 2 while being totally reflected by the light exit surface 2c and the reflection surface 4a of the reflection sheet 4, the light travels while being scattered by the light scattering particles. Further, the other part of the light emitted from the light source 6 proceeds while being scattered by the light scattering particles without being totally reflected by the light emitting surface 2c, and is emitted from the light emitting surface 2c. Since the light in the light guide plate 2 is totally reflected by the light emitting surface 2c and the reflecting surface 4a and scattered by the light scattering particles, the luminance of the light emitting surface 2c is in a uniform state.

  A part of the light emitted from the light exit surface 2 c of the light guide plate 2 enters the incident area 3 h of the light incident surface 3 c of the diffusion plate 3. A part of the light incident from the incident region 3h proceeds while being totally reflected by the inner side surface 3n of the projecting portion 3b and the end surface 3j of the diffusion plate 3 and scattered by the light scattering particles as indicated by a one-dot chain line L2. The light exits from the area corresponding to the projecting portion 3b (that is, the peripheral edge of the light exit surface 3a). In addition, a part of the light incident from the incident region 3h travels while being totally reflected by the corner inner side surface 3r and the end surface 3j of the protrusion 3b, and travels while being scattered by the light scattering particles, mainly on the light exit surface 3a. Injected from the area corresponding to the corner. Further, part of the light incident on the light incident surface 3e travels while being scattered by the light scattering particles, and is emitted from the light emitting surface 3a.

(Main effects of this form)
As described above, in this embodiment, a part of the light incident surface 3c of the diffusion plate 3 is covered with the first extending portion 8b, and the light emitted from the light source 6 does not enter the diffusion plate 3 directly. In the light exit surface 3a of the diffusion plate 3, it is possible to prevent the light source 6 from appearing as a point light source. In this embodiment, since the portion of the light incident surface 3c covered by the first extending portion 8b is the shielding region 3g, the amount of light incident on the protruding portion 3b is limited, and the light exit surface It becomes possible to suppress the luminance of the peripheral edge of 3a. On the other hand, since the light incident surface 3c is covered by the first extending portion 8b, there is a possibility that a dark portion such as an edge is generated at the peripheral portion of the light emitting surface 3a due to the influence of the first extending portion 8b. However, in this embodiment, a part of the light incident on the protruding portion 3b is totally reflected by the end face 3j, the inner peripheral surface 3n, and the corner inner side surface 3r, and scattered by the light scattering particles contained in the diffusion plate 3, so that the light emission It is possible to prevent a dark portion that is edged around the peripheral portion of the surface 3a. Furthermore, in this embodiment, since the light source 6 is disposed so as to face each of the four end surfaces 2a of the light guide plate 2, the entire light emission surface 3a is brightened by the light emitted from all the light sources 6. Is possible. From the above, in this embodiment, it is possible to make the brightness of the light exit surface 3a uniform.

  Further, in this embodiment, in each of the four corners of the diffusing plate 3, the corner inner side surface that connects the end portions 3 p of the inner side surface 3 n adjacent in the circumferential direction of the projection 3 b to the inner circumference side of the projection 3 b. 3r is formed, and the corner inner side surface 3r is formed in a concave curved surface having a circular arc shape that smoothly connects the end portions 3p of the two inner side surfaces 3n when viewed from the front-rear direction. Therefore, in this embodiment, in each of the four corners of the diffusing plate 3, the light incident on the corner inner side surface 3r from the inside of the protrusion 3b can be totally reflected in various directions by the corner inner side surface 3r. Become. Therefore, in this embodiment, it is possible to prevent the light totally reflected by the corner inner side surface 3r from concentrating on the corner of the diffusion plate 3 at the corner of the diffusion plate 3, and the corner of the light emission surface 3a. It is possible to suppress the brightness of the image. As a result, in this embodiment, the brightness of the light exit surface 3a can be made more uniform.

  In particular, in this embodiment, since the distance D between the virtual intersection C in the first direction and the corner inner side surface 3r is 1/8 or more of the width W of the protruding portion 3b, the inner side of the protruding portion 3b is changed to the corner inner side surface 3r. Incident light can be totally reflected in more various directions by the corner inner side surface 3r. Further, in this embodiment, the surface roughness of the corner inner side surface 3r is equal to or greater than the surface roughness of the inner side surface 3n, and the surface of the corner inner side surface 3r can be roughened. Light incident on the corner inner side surface 3r can be irregularly reflected by the corner inner side surface 3r. Therefore, in the present embodiment, it is possible to effectively prevent the light totally reflected by the corner inner side surface 3r from being concentrated at the corner of the diffusion plate 3 at the corner of the diffusion plate 3. As shown in FIG. 5, in the lighting device 1, when two inner side surfaces 3 n adjacent in the circumferential direction of the protruding portion 3 b intersect each other so as to be orthogonal to each other, as indicated by a one-dot chain line in FIG. 5. In addition, the light that is totally reflected in the vicinity of the end portion of the inner surface 3 n is concentrated on the corner portion of the diffusion plate 3. Therefore, in this case, the brightness of the corners of the light exit surface 3a is increased, and brightness spots are likely to occur on the light exit surface 3a.

  In this embodiment, in each of the four corners of the diffusing plate 3, the end 3p of the inner surface 3n is disposed outside the outer end 6a of the light source 6 in the second direction in the second direction. Therefore, in this embodiment, it is possible to suppress an extreme decrease in luminance at the corners of the diffusion plate 3. That is, a part of the light incident on the inner side surface 3n from the inside of the protruding portion 3b is totally reflected by the inner side surface 3n toward the end surface 3j, so that a decrease in luminance at the peripheral portion of the light exit surface 3a is suppressed. However, if the end portion 3p of the inner side surface 3n (that is, the end portion of the corner inner side surface 3r) is disposed inside the second direction with respect to the outer end 6a of the light source 6 in the second direction, the diffusion plate 3 In this corner, the amount of light totally reflected toward the end face 3j is reduced, and the brightness of the corner of the diffusion plate 3 may be extremely lowered. On the other hand, in this embodiment, the end 3p of the inner side surface 3n is disposed outside the second end in the second direction with respect to the outer end 6a of the light source 6 in the second direction. It is possible to secure the amount of light that is totally reflected toward the end face 3j, and it is possible to suppress an extreme decrease in luminance at the corners of the diffusion plate 3.

  Further, in this embodiment, in each of the four corners of the diffusion plate 3, the distance D between the virtual intersection C in the first direction and the corner inner side surface 3r is ½ or less of the width W of the protrusion 3b. Therefore, the light incident on the corner inner side surface 3r from the outside of the protrusion 3b (specifically, from the recess 3d side) can easily reach the corner 3s of the diffusion plate 3. Therefore, in this embodiment, it is possible to prevent an extreme decrease in luminance at the corners of the diffusion plate 3.

  In this embodiment, the surface roughness of the inner side surface 3n is smaller than the surface roughness of the corner inner side surface 3r. Therefore, in this embodiment, the surface of the inner side surface 3n can be smoothed. As a result, a part of the light incident on the protrusion 3b is directed in a specific direction (specifically, the end surface) by the inner side surface 3n. It becomes possible to totally reflect (toward 3j). Therefore, in this embodiment, it is possible to effectively prevent the dark part that is fringed at the peripheral part of the light emitting surface 3a. Further, in this embodiment, the shape of the corner inner side surface 3r when viewed from the front-rear direction is an arc shape that smoothly connects the end portions 3p of the two inner side surfaces 3n. When the exit surface 3a is viewed, the corner inner side surface 3r is less noticeable.

(Other embodiments)
In the embodiment described above, the corner inner side surface 3r is formed in a concave curved surface shape, but the corner inner side surface 3r may be formed in a planar shape. For example, as shown in FIG. 6, the corner inner side surface 3r may be a plane formed to be inclined by 135 ° with respect to each of the two inner side surfaces 3n adjacent in the circumferential direction of the protruding portion 3b. . The corner inner side surface 3r may be a combination of a concave curved surface and a flat surface. In the above-described embodiment, the corner inner side surface 3r is disposed on the inner peripheral side of the protruding portion 3b with respect to the first virtual extension line CL1 and the second virtual extension line CL2, but the corner inner side surface 3r is the first virtual extension line CL1. You may arrange | position on the outer peripheral side of the protrusion part 3b rather than virtual extension line CL1 and 2nd virtual extension line CL2. That is, a recess that is recessed from the end 3p of the inner surface 3n toward the outer peripheral side of the diffusion plate 3 may be formed, and the side surface of the recess may be the corner inner surface 3r. However, as in the above-described embodiment, the corner inner side surface 3r is easier when the corner inner side surface 3r is arranged on the inner peripheral side of the protruding portion 3b than the first virtual extension line CL1 and the second virtual extension line CL2. Can be formed. In the embodiment described above, the corner inner side surface 3r is a surface that is not parallel to the inner side surface 3n in the left-right direction and the vertical direction, but may be a surface that is not parallel to the inner side surface 3n in the front-rear direction. good.

  In the embodiment described above, the corner inner side surface 3r is formed at each of the four corners of the diffusion plate 3. However, the corner inner side surface 3r is formed in the four corners of the diffusion plate 3. There may be no corners. If the corner inner side surface 3r is formed in at least one of the four corners of the diffusion plate 3, the corner inner side surface 3r is formed in all the four corners of the diffusion plate 3. Compared with the case where there is no light, it is possible to make the brightness of the light exit surface 3a uniform.

  In the embodiment described above, the inner side surface 3n of the protruding portion 3b is formed in a planar shape, but minute irregularities may be formed on the inner side surface 3n. That is, the inner surface 3n may be substantially planar, and the “substantially planar” includes both a planar surface having no unevenness and a substantially planar shape on which minute unevenness is formed. . Moreover, in the form mentioned above, although the distance D of the virtual intersection C in the 1st direction and the corner | angular part inner surface 3r is below the width W of the protrusion part 3b, the distance D may exceed the width W. . In the embodiment described above, the distance D is equal to or greater than 1/8 of the width W, but the distance D may be less than 1/8 of the width W. Further, in the embodiment described above, the end 3p of the inner surface 3n is disposed outside the outer end 6a of the light source 6 in the second direction in the second direction, but the end 3p of the inner surface 3n is You may arrange | position inside the 2nd direction from the outer side edge 6a of the light source 6 in 2 directions. In the embodiment described above, the surface roughness of the corner inner side surface 3r is equal to or greater than the surface roughness of the inner side surface 3n, but the surface roughness of the corner inner side surface 3r is less than the surface roughness of the inner side surface 3n. There may be.

  In the embodiment described above, the light source 6 is arranged so as to face the four end faces 2a of the light guide plate 2, but the light source 6 may be arranged so as to face only the two end faces 2a parallel to each other. . Further, the light source 6 may be arranged so as to face only three end faces 2a arbitrarily selected from the four end faces 2a. In this case, the reflecting plate may be arranged so as to face the end surface 2a where the light source 6 does not face. Moreover, in the form mentioned above, although the light source 6 which is an LED light source is mounted in the board | substrate 7, the light source 6 mounted in the board | substrate 7 may be light sources other than an LED light source. The light source 6 may be a CCFL (Cold Cathode Fluorescent Lamp), a light bulb such as an incandescent light bulb, or a fluorescent light. Depending on the type of the light source 6, the substrate 7 on which the light source 6 is mounted may be unnecessary. In this case, the light source 6 is directly held by the light source holding member 8. In the embodiment described above, instead of the first extending portion 8b of the light source holding member 8, a light-shielding tape may be attached to the light incident surface 3c, or a light-shielding paint is applied. Also good. In this case, a light shielding tape or paint serves as the light shielding member.

  In the embodiment described above, the lighting device 1 is formed in a rectangular flat plate shape. However, the lighting device 1 may be formed in a square flat plate shape, or a rectangular flat plate shape other than the rectangular shape and the square shape. May be. Moreover, the illuminating device 1 may be formed in polygonal flat plates other than quadrangle, such as a pentagon, a hexagon, or an octagon. That is, the light guide plate 2 and the diffusing plate 3 may be formed in a square flat plate shape, may be formed in a flat plate shape of a rectangle other than a rectangle and a square, or a quadrangle such as a pentagon, a hexagon, or an octagon. Other than the above, it may be formed in a polygonal flat plate shape. Even in this case, in each of a plurality of corner portions of the diffusion plate 3 formed in a polygonal flat plate shape, a corner inner side surface corresponding to the corner inner side surface 3r is formed on the inner peripheral side of the protruding portion 3b. Is done.

DESCRIPTION OF SYMBOLS 1 Illuminating device 2 Light-guide plate 2a End surface 2c Light emission surface 2d Peripheral part 3 Diffusion plate 3b Projection part 3j End surface 3k Outer side surface 3n Inner side surface 3p End part (End part of inner side surface)
3r corner inner side 3s corner (diffuser plate corner)
6 Light source 8b First extending portion (light shielding member)
C Virtual intersection point CL1 First virtual extension line CL2 Second virtual extension line D Distance between the virtual intersection point and the inner side surface of the corner in the first direction V First direction W Width of protrusion Z Thickness direction of light guide plate, thickness of diffuser plate Direction

Claims (8)

A light guide plate formed in a polygonal plate shape, a light source disposed so as to face an end surface of the light guide plate, and a light exit surface that is a surface on one side of the light guide plate in the thickness direction of the light guide plate A diffusion plate that is disposed on a side and is formed in a polygonal plate shape that is substantially the same shape as the light guide plate and diffuses light emitted from the light guide plate, and a light shield disposed between the light guide plate and the diffusion plate With members,
The light guide plate and the diffusion plate are arranged so that an end surface of the light guide plate and an end surface of the diffusion plate are parallel to each other,
The diffusing plate includes a projecting portion that is formed along an end surface of the diffusing plate and that is disposed at a position facing a peripheral portion of the light emitting surface and projects toward the light guide plate,
The light shielding member is disposed between a peripheral portion of the light emitting surface and the protruding portion so as to block a part of light incident on the protruding portion from a peripheral portion of the light emitting surface.
The protrusion includes an outer peripheral surface constituted by a plurality of planar outer surfaces constituting a part of an end surface of the diffusion plate, a plurality of inner surfaces parallel to each of the plurality of outer surfaces, and a polygon. In the corner portion of the diffuser plate formed in a plate shape, a corner frame inner surface that is a surface that is not parallel to the outer surface is formed in a polygonal frame shape on the inner peripheral side of the protruding portion. A lighting device.   When viewed from the thickness direction of the diffuser plate, the corner inner surface faces one of the two inner surfaces adjacent in the circumferential direction of the projecting portion toward the other inner surface. The first virtual extension line extended and the second virtual extension line extending the other inner side surface toward the one inner side surface are arranged on the inner peripheral side of the projecting portion. The lighting device according to claim 1. At the corner of the diffusion plate where the inner side surface of the corner is formed, the intersection of the first virtual extension line and the second virtual extension line is a virtual intersection when viewed from the thickness direction of the diffusion plate. When the direction from the corner of the diffuser plate toward the virtual intersection is the first direction,
In the corner of the diffusion plate where the inner side surface of the corner is formed, the distance between the virtual intersection in the first direction and the inner side surface of the corner is the distance between the outer surface and the inner surface parallel to the outer surface. The lighting device according to claim 2, wherein the lighting device has a width equal to or shorter than the width of the protruding portion, which is the shortest distance, and equal to or larger than 1/8 of the width of the protruding portion.   The lighting device according to claim 3, wherein a distance between the virtual intersection in the first direction and the inner side surface of the corner is not more than ½ of the width of the protrusion.   The lighting device according to claim 1, wherein the inner side surface of the corner is formed in a concave curved surface shape.   The corner inner side surface is formed so that the shape when viewed from the thickness direction of the diffuser plate is an arc shape that smoothly connects the end portions of the inner side surfaces adjacent in the circumferential direction of the protruding portion. The lighting device according to claim 5. When the second direction is a direction perpendicular to the thickness direction of the diffusion plate and along the end surface of the diffusion plate,
In the corner portion of the diffusion plate where the inner side surface of the corner portion is formed, an end portion of the inner side surface is disposed outside the outer end of the light source in the second direction in the second direction. The illumination device according to claim 1, wherein the illumination device is a light source.   8. The lighting device according to claim 1, wherein a surface roughness of the inner surface of the corner is equal to or greater than a surface roughness of the inner surface.

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