Surface light source device and display device

Abstract

To provide a surface light source device capable of suppressing unevenness in brightness caused by passage of light emitted from a light emitting element through a plurality of luminous flux control members.SOLUTION: A surface light source device includes a base plate, a plurality of light emitting devices 200 each including a light emitting element 220 and a luminous flux control member, and a light diffusion member 120. The luminous flux control member includes an incidence surface for making incident the light emitted from the light emitting element, which is an inner surface of a concave part disposed so as to intersect with a central axis of the luminous flux control member on the reverse side of the luminous flux control member, and an emission surface disposed on the front side of the luminous flux control member so as to intersect with the central axis for emitting the light made incident on the incidence surface to the outside. The light emitted from an emission center of the light emitting element 220 at an emission angle of 80° or less with respect to an optical axis of the light emitting element 220, made incident on the incidence surface, and emitted from the emission surface in one light emitting device 200 of the plurality of light emitting devices 200 reaches the light diffusion member 120 without reaching the other light emitting devices 200 of the plurality of light emitting devices 200.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a surface light source device and a display device.

Background Art

[0002] In recent years, in transmissive image display devices such as liquid crystal display devices, a direct-lit type surface light source device having a plurality of light-emitting elements as a light source has been used. Further, in a direct-lit type surface light source device, many light-emitting elements may be arranged in order to irradiate light over a wide range (for example, see Patent Document 1).

[0003] Patent Document 1 discloses a surface light source device including a substrate, a plurality of light-emitting diodes arranged in a matrix on the substrate, a plurality of lenses arranged so as to cover each light-emitting diode, and a diffusion plate arranged to face the plurality of lenses. The lens has an incident surface that is the inner surface of a recess formed on the back side, and an exit surface that is formed on the front side and is convex toward the front side. The light emitted from the light-emitting diode enters through the incident surface and then exits from the exit surface so as to be spread over the entire diffusion plate. Thereby, the light emitted from the light-emitting diode irradiates the entire diffusion plate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the surface light source device described in Patent Document 1, since the lens spreads the light emitted from the light-emitting diode in the plane direction of the diffusion plate, some of the light emitted from the first lens may directly reach the adjacent second lens. Some of the light that reaches the second lens from the first lens passes through the second lens, is reflected by the substrate, passes through the second lens again, and reaches the diffusion plate. Thus, in the surface light source device described in Patent Document 1, since some of the light emitted from a certain lens passes through other lenses, unintended luminance unevenness may occur.

[0006] An object of the present invention is to provide a surface light source device that can suppress luminance unevenness caused by light emitted from a light-emitting element passing through a plurality of light flux control members while using a type of light flux control member that expands light as a light flux control member for controlling the light distribution of the light emitted from the light-emitting element. Another object is to provide a display device having the surface light source device.

Means for Solving the Problems

[0007] A surface light source device according to an embodiment of the present invention includes a substrate, a plurality of light-emitting devices each including a light-emitting element disposed on the substrate and a light flux control member for controlling the light distribution of the light emitted from the light-emitting element, and a light diffusion member that diffuses and transmits the light emitted from the plurality of light-emitting devices. The light flux control member includes an inner surface of a recess disposed on the back side of the light flux control member so as to intersect the central axis of the light flux control member, the inner surface being an incident surface for allowing the light emitted from the light-emitting element to enter, and an emission surface disposed on the front side of the light flux control member so as to intersect the central axis and for emitting the light incident on the incident surface to the outside. In one of the plurality of light-emitting devices, the light emitted from the light-emitting center of the light-emitting element at an emission angle of 80° or less with respect to the optical axis of the light-emitting element, and the light that enters the incident surface and is emitted from the emission surface reaches the light diffusion member without reaching other light-emitting devices among the plurality of light-emitting devices.

[0008] The display device according to an embodiment of the present invention includes the surface light source device of the present invention and a display member irradiated with light emitted from the surface light source device.

Effect of the Invention

[0009] According to the present invention, it is possible to suppress luminance unevenness caused by light emitted from a light-emitting element passing through a plurality of light beam control members.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, as a representative example of the surface light source device according to the present invention, a surface light source device suitable for a backlight of a liquid crystal display device or the like will be described. These surface light source devices can be used as a display device 100' by combining with a display member 102 (for example, a liquid crystal panel) irradiated with light from the surface light source device (see FIG. 1B).

[0012] (Configuration of the surface light source device) FIGS. 1A, B, 2A, B and 3 are diagrams schematically showing the configuration of a surface light source device 100 according to an embodiment of the present invention. FIG. 1A is a plan view of the surface light source device 100 according to an embodiment of the present invention, and FIG. 1B is a front view. FIG. 2A is a cross-sectional view taken along line A-A shown in FIG. 1B, and FIG. 2B is a cross-sectional view taken along line B-B shown in FIG. 1A. FIG. 3 is a partially enlarged cross-sectional view of a part of FIG. 2B.

[0013] As shown in FIGS. 1A, B, 2A, B and 3, the surface light source device 100 includes a housing 110, a plurality of light emitting devices 200, and a light diffusing member 120.

[0014] The inner surface of the bottom plate 112 of the housing 110 functions as a diffusing reflection surface. On the bottom plate 112, a substrate 210 on which the light emitting device 200 is disposed is disposed at a predetermined position. Further, an opening is provided in the top plate 114 of the housing 110. The light diffusing member 120 is disposed so as to close this opening and functions as a light emitting surface. The size of the light emitting surface can be, for example, about 400 mm × about 700 mm. In the present embodiment, the distance H between the substrate 210 and the light diffusing member 120 is preferably 10 mm or less, and more preferably 5 to 7 mm (see FIG. 6). When H exceeds 10 mm, the effects of the present invention may be difficult to exhibit.

[0015] The plurality of light-emitting devices 200 are arranged in a grid pattern on the substrate 210 on the bottom plate 112 of the housing 110. Here, "arranged in a grid pattern" means arranged such that the unit cells are polygons. Examples of unit cells include rectangular grids, square grids (orthogonal grids), and triangular grids. In the present embodiment, the plurality of light-emitting devices 200 are arranged in a square grid pattern. The plurality of light-emitting devices 200 each have a light-emitting element 220 and a light beam control member 300.

[0016] The distance H between the substrate 210 and the light diffusing member 120 with respect to the distance P between the central axis CA of the light-emitting device 200 (first light-emitting device) and the central axis CA of the light-emitting device 200 (second light-emitting device) adjacent to the light-emitting device 200 (first light-emitting device) among the plurality of light-emitting devices 200 is preferably 0.21 or more, and more preferably 0.25 to 0.35. Thus, in the present embodiment, it exhibits a particularly effective effect in the thin surface light source device 100.

[0017] Although details will be described later, in one of the plurality of light-emitting devices 200, the light emitted from the light-emitting center of the light-emitting element 220 at an emission angle of 80° or less with respect to the optical axis of the light-emitting element 220 and incident on the incident surface 310 and emitted from the emission surface 320 reaches the light diffusing member 120 without reaching the other light-emitting devices 200 among the plurality of light-emitting devices 200. Also, in the light-emitting device 200 arranged other than the outermost of the plurality of light-emitting devices 200, the light emitted from the light-emitting center of the light-emitting element 220 at an emission angle θ1 of 80° or less with respect to the optical axis OA of the light-emitting element 220 and incident on the incident surface 310 and emitted from the emission surface 320 reaches the light diffusing member 120 without passing through other members. In the outermost light-emitting device 200 among the plurality of light-emitting devices 200 arranged in a grid pattern, the light emitted outward from the emission surface 320 may reach the light diffusing member 120 after being reflected by the housing 110, or may directly reach the light diffusing member 120.

[0018] The light-emitting element 220 is a light source of the surface light source device 100 and is mounted on the substrate 210. The light-emitting element 220 is a light-emitting diode (LED) such as a white light-emitting diode, for example. In the present embodiment, the light-emitting element 220 is arranged such that its light-emitting center (optical axis OA) is located on the central axis CA of the light beam control member 300. Here, the "optical axis OA of the light-emitting element 220" means the central ray of the three-dimensional emitted light beam from the light-emitting element 220. The light-emitting surface of the light-emitting element 220 may be arranged to be at the same height as the back surface of the light beam control member 300, or may be arranged to be at a position lower than the back surface of the light beam control member 300. In the present embodiment, the light-emitting surface of the light-emitting element 220 is arranged to be at a position lower (on the substrate 210 side) than the back surface of the light beam control member 300.

[0019] The light beam control member 300 is a so-called diffusing lens and is fixed on the substrate 210. The light beam control member 300 controls the light distribution of the light emitted from the light-emitting element 220 and expands the traveling direction of the light in the plane direction of the substrate 210. The light beam control member 300 is arranged on the light-emitting element 220 such that its central axis CA coincides with the optical axis OA of the light-emitting element 220 (see FIG. 3). Note that the incident surface 310 and the exit surface 320 of the light beam control member 300 described later are rotationally symmetric (circularly symmetric in the present embodiment), and the rotation axes of these coincide with the optical axis OA of the light-emitting element 220. The rotation axis of the incident surface 310 and the exit surface 320 is referred to as the "central axis CA of the light beam control member 300".

[0020] The light beam control member 300 can be formed by integral molding. The material of the light beam control member 300 may be any material that can transmit light of a desired wavelength. For example, the material of the light beam control member 300 is a light-transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), epoxy resin (EP), silicone resin, or glass. The features to be provided in the light beam control member 300 will be described in detail separately.

[0021] The light diffusion member 120 is a plate-like member having light diffusibility, and transmits the light emitted from the light emitting device 200 while diffusing it. The light diffusion member 120 is disposed substantially parallel to the surface of the substrate 210 above a plurality of light emitting devices 200. Usually, the light diffusion member 120 is approximately the same size as the irradiated member such as a liquid crystal panel. For example, the light diffusion member 120 is formed of a light transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), or styrene-methyl methacrylate copolymer resin (MS). In order to impart light diffusibility, fine irregularities are formed on the surface of the light diffusion member 120, or light diffusing particles such as beads are dispersed inside the light diffusion member 120.

[0022] In the surface light source device 100 according to the present invention, the light emitted from each light emitting element 220 is controlled by the light beam control member 300 to illuminate a predetermined irradiation region of the light diffusion member 120. As will be described later, each light emitting device 200 appropriately illuminates a predetermined irradiation region within the light diffusion member 120, so that the inner surface of the light diffusion member 120 is illuminated substantially uniformly. The light that has reached the light diffusion member 120 from each light emitting device 200 (light beam control member 300) is diffused while passing through the light diffusion member 120. As a result, the surface light source device 100 according to the present invention can uniformly illuminate a planar irradiated member (for example, a liquid crystal panel).

[0023] (Configuration of the light beam control member) FIGS. 4A, B and FIGS. 5A, B are diagrams showing the configuration of the light beam control member 300. FIG. 4A is a plan view of the light beam control member 300. FIG. 4B is a bottom view of the light beam control member 300. FIG. 5A is a right side view of the light beam control member 300, and FIG. 5B is a cross-sectional view taken along line A-A shown in FIG. 4A.

[0024] As shown in FIGS. 4A, B and FIGS. 5A, B, in the present embodiment, the light beam control member 300 has an incident surface 310, an exit surface 320, a back surface 330, a flange portion 340, and a leg portion 350. In the present embodiment, a gate trace 360 remains.

[0025] The incident surface 310 causes most of the light emitted from the light emitting element 220 to enter the inside of the light flux control member 300 while controlling the traveling direction of the light. The incident surface 310 is the inner surface of the recess 312 that opens toward the back side. The recess 312 opens at the center of the back surface 330 so as to intersect the central axis CA (optical axis OA of the light emitting element 220) of the light flux control member 300 (see FIG. 5B). That is, the incident surface 310 is arranged so as to intersect the central axis CA (optical axis OA). The incident surface 310 intersects the central axis CA of the light flux control member 300 and is rotationally symmetric (circularly symmetric in this embodiment) about the central axis CA as the rotation axis.

[0026] The exit surface 320 is arranged on the front side (light diffusing member 120 side) of the light flux control member 300. The exit surface 320 causes the light incident on the inside of the light flux control member 300 to exit to the outside while controlling the traveling direction. The exit surface 320 intersects the central axis CA and is rotationally symmetric (circularly symmetric in this embodiment) about the central axis CA as the rotation axis.

[0027] In this embodiment, the exit surface 320 includes a first exit surface 320a located within a predetermined range centered on the central axis CA, a second exit surface 320b continuously formed around the first exit surface 320a, and a third exit surface 320c connecting the second exit surface 320b and the flange portion 340 (see FIG. 6D). The first exit surface 320a is a curved surface convex toward the back side. The second exit surface 320b is a smooth curved surface convex toward the front side and located around the first exit surface 320a. The shape of the second exit surface 320b is an annular convex shape. The third exit surface 320c is a curved surface located around the second exit surface 320b.

[0028] The back surface 330 is located on the back side of the light flux control member 300, is connected to the opening edge of the recess 312, and is formed so as to be away from the opening edge of the recess 312. In this embodiment, an annular groove 334 having a plurality of ridges 333 is arranged on the back surface 330.

[0029] The annular groove 334 is formed on the back surface 330 so as to surround the concave portion 312 (the incident surface 310). The annular groove 334 is rotationally symmetric about the central axis CA. The annular groove 334 includes a first inner surface 331 disposed on the central axis CA side and a second inner surface 332 disposed farther from the central axis CA than the first inner surface 331. Further, a plurality of ridges 333 are disposed on the second inner surface 332.

[0030] The first inner surface 331 may be arranged to be parallel to the central axis CA, or may be inclined toward the front side as it moves away from the central axis CA. In the present embodiment, the first inner surface 331 is arranged to be parallel to the central axis CA.

[0031] The second inner surface 332 is formed on the back side of the light beam control member 300 so as to surround the first inner surface 331. The second inner surface 332 is inclined toward the back side as it moves away from the central axis CA.

[0032] The position of the annular groove 334 on the back surface 330 can be set as appropriate. The position of the annular groove 334 on the back surface 330 is preferably formed in a region where a large amount of light internally reflected at the exit surface 320 reaches. Note that the second inner surface 332 is located in the above region. The arrival position of the light reflected at the exit surface 320 varies depending on various factors such as the shape of the exit surface 320, and thus is appropriately set according to the light beam control member 300. Note that the light internally reflected at the exit surface 320 has little influence on the luminance distribution on the light diffusion member 120.

[0033] The plurality of ridges 333 are each formed such that a cross-section orthogonal to the ridge line 338 is substantially triangular, and is rotationally symmetric with respect to the central axis CA (n-fold symmetry when the number of ridges 333 is n). Each ridge 333 has a planar first inclined surface 336, a planar second inclined surface 337, and a ridge line 338 disposed between the first inclined surface 336 and the second inclined surface 337, and functions like a total reflection prism. The ridge line 338 is inclined in the direction toward the back surface 330 as it moves away from the central axis CA. The plurality of ridges 333 reflect the light internally reflected at the exit surface 320 toward the light diffusion member 120.

[0034] The flange portion 340 is disposed on the outer peripheral portion of the light beam control member 300. The flange portion 340 facilitates the handling of the light beam control member 300. The number of the flange portions 340 is not particularly limited. The number of the flange portions 340 may be one or plural. In the present embodiment, the number of the flange portions 340 is five. The planar shape of the flange portion 340 is also not particularly limited. In the present embodiment, the planar shape of the flange portion 340 is substantially semi-circular.

[0035] The leg portion 350 is used to fix the light beam control member 300 to the substrate 210. The shape of the leg portion 350 can be appropriately set as long as the above-described function can be exhibited. In the present embodiment, the leg portion 350 is formed in a substantially cylindrical shape. The number of the leg portions 350 is not particularly limited. The number of the leg portions 350 may be one or plural. In the present embodiment, the number of the leg portions 350 is three.

[0036] (Simulation) Here, the optical path of the light emitted from the light emitting element 220 will be described in detail. For comparison, the optical path of the light emitted from the light emitting device 200A in the surface light source device 100A that does not have the characteristics of the surface light source device 100 according to the present embodiment was also examined. FIGS. 6A and 6B are schematic diagrams for explaining the optical path of the light emitted from the light emitting element 220. FIG. 6A is a diagram for explaining the position where the light emitted from the light emitting device 200 reaches the light diffusing member 120. FIG. 6B is a diagram showing the relationship between the emission angle (first emission angle; emission angle θ1) of the light emitted from the light emitting element 220 and the emission angle (second emission angle; angle θ2) of the light emitted from the light beam control member 300.

[0037] Figs. 7A - D and Figs. 8A - D are optical path diagrams of the light emitted from the light-emitting device 200 in the surface light source device 100 according to the present embodiment. Fig. 7A is an optical path diagram of the light when the emission angle θ1 is greater than 0° and less than or equal to 10°. Fig. 7B is an optical path diagram of the light when the emission angle θ1 is greater than 10° and less than or equal to 20°. Fig. 7C is an optical path diagram of the light when the emission angle θ1 is greater than 20° and less than or equal to 30°. Fig. 7D is an optical path diagram of the light when the emission angle θ1 is greater than 30° and less than or equal to 40°. Fig. 8A is an optical path diagram of the light when the emission angle θ1 is greater than 40° and less than or equal to 50°. Fig. 8B is an optical path diagram of the light when the emission angle θ1 is greater than 50° and less than or equal to 60°. Fig. 8C is an optical path diagram of the light when the emission angle θ1 is greater than 60° and less than or equal to 70°. Fig. 8D is an optical path diagram of the light when the emission angle θ1 is greater than 70° and less than or equal to 80°. In these figures, the light after being reflected by the substrate 210 is omitted.

[0038] Figs. 9A - D and Figs. 10A - D are optical path diagrams of the light emitted from the light-emitting device 200A in the surface light source device 100A according to the comparative example. Fig. 9A is an optical path diagram of the light when the emission angle θ1 is greater than 0° and less than or equal to 10°. Fig. 9B is an optical path diagram of the light when the emission angle θ1 is greater than 10° and less than or equal to 20°. Fig. 9C is an optical path diagram of the light when the emission angle θ1 is greater than 20° and less than or equal to 30°. Fig. 9D is an optical path diagram of the light when the emission angle θ1 is greater than 30° and less than or equal to 40°. Fig. 10A is an optical path diagram of the light when the emission angle θ1 is greater than 40° and less than or equal to 50°. Fig. 10B is an optical path diagram of the light when the emission angle θ1 is greater than 50° and less than or equal to 60°. Fig. 10C is an optical path diagram of the light when the emission angle θ1 is greater than 60° and less than or equal to 70°. Fig. 10D is an optical path diagram of the light when the emission angle θ1 is greater than 70° and less than or equal to 80°. In these figures, the light after being reflected by the substrate 210 is omitted.

[0039] In these figures, the distance H from the surface of the substrate 210 to the back surface of the light diffusion member 120 was set to 5 mm. Also, the center-to-center distance P between adjacent light-emitting devices 200 was set to 20 mm. The minimum diameter (the distance corresponding to the line A-A in Fig. 4) when the light beam control member 300 in the surface light source device 100 according to the present embodiment is viewed in plan is 6.2 mm. The minimum diameter (the distance corresponding to the line A-A in Fig. 4) when the light beam control member 300A in the surface light source device 100A according to the comparative example is viewed in plan is 12.0 mm. In these figures, the hatching of the light beam control members 300 and 300A is omitted. Note that the light beam control member 300 in the present embodiment and the light beam control member 300A according to the comparative example differ in the shapes of the incident surfaces 310 and 310A and the shapes of the exit surfaces 320 and 320A, respectively.

[0040] In the surface light source device 100 according to the present embodiment, as shown in FIGS. 6A, 7A to D, and 8A to D, in one of the plurality of light-emitting devices 200, the light emitted from the light-emitting center of the light-emitting element 220 at an emission angle θ1 of 80° or less with respect to the optical axis OA of the light-emitting element 220, incident on the incident surface 310 and emitted from the exit surface 320, can be seen to reach the light diffusion member 120 without reaching the other light-emitting devices 200 among the plurality of light-emitting devices 200. Thus, among the light emitted from the light-emitting device 200, most of the light reaches the light diffusion member 120 without directly reaching the adjacent light-emitting device 200 or reaching other members. That is, the incident surface 310 and the exit surface 320 of the light beam control member 300 according to the present embodiment are formed so that the light emitted from the light-emitting element 220 travels as described above. Here, the light incident on the incident surface 310 and internally reflected by the exit surface 320 is not considered. The same applies hereinafter.

[0041] Further, as shown in FIGS. 6A, 7A to 7D, and 8A, in the first light-emitting device 200 among the plurality of light-emitting devices 200, light emitted at an emission angle θ1 (where 0° < θ1 ≦ 50°) with respect to the optical axis OA of the light-emitting element 220 from the light-emitting center of the light-emitting element 220 is incident on the incident surface 310 and is emitted at an angle θ2 with respect to a straight line parallel to the optical axis OA from point a on the emission surface 320. Let the distance between the central axis CA of the first light-emitting device 200 and the central axis CA of the second light-emitting device 200 adjacent to the first light-emitting device 200 among the plurality of light-emitting devices 200 be P, the distance between the substrate 210 and the light diffusion member 120 be H, the distance between point a and the substrate 210 be A, and the distance between point a and the central axis CA in the first light-emitting device 200 be B. In this case, it is preferable to satisfy 0 < (H - A)tanθ2 ≦ (P - B). That is, when considering two adjacent light-emitting devices 200 corresponding to the sides of the lattice, in one light-emitting device 200, light emitted at an angle θ1 greater than 0° and less than or equal to 50° reaches the region of the light diffusion member 120 on the side of one light-emitting device 200 rather than the central axis CA of the adjacent other light-emitting device 200. Thereby, the light emitted from the light-emitting device 200 can reach only a predetermined region of the light diffusion member 120.

[0042] Further, as shown in FIGS. 6B, 7A to 7D, and 8A and 8B, in one light-emitting device 200 among the plurality of light-emitting devices 200, when light emitted at an emission angle θ1 (where 0° < θ1 ≦ 60°) with respect to the optical axis OA of the light-emitting element 220 from the light-emitting center of the light-emitting element 220 is incident on the incident surface 310 and is emitted at an angle θ2 with respect to a straight line parallel to the optical axis OA from point a on the emission surface 320, it is preferable to further satisfy the following formula (1). Δθ2 / Δθ1 ≧ 0 ···(1) In formula (1), it is the slope of the tangent line of the curve showing the value of θ2 with respect to the change in θ1 in a graph with the horizontal axis θ1 and the vertical axis θ2. That is, in the light-emitting device 200, when θ1 is greater than 0° and within the range of 60° or less, it is preferable that as the emission angle θ1 of the light-emitting element 220 increases, the angle θ2 of the light emitted from the emission surface 320 increases. Thereby, since light with a large amount of light can reach a desired region of the light diffusion member 120, luminance unevenness can be suppressed. In the present embodiment, the light with θ1 of 60° reaches directly above another adjacent light-emitting device 200.

[0043] On the other hand, when the emission angle θ1 is greater than 60° and less than 80°, it is preferable to satisfy the following formula (2). Δθ2 / Δθ1 < 0 ···(2) That is, when considering two adjacent light-emitting devices 200 corresponding to the sides of the lattice, within the range where θ1 in one light-emitting device 200 is greater than 60° and less than 80°, it is preferable that as the emission angle θ1 of the light-emitting element 220 increases, the angle θ2 of the light emitted from the emission surface 320 decreases. Note that since the amount of light within the range where the angle θ2 is greater than 60° and less than 80° is smaller than the light with an angle θ2 of less than 60°, it has almost no influence on the luminance distribution on the light diffusion member 120.

[0044] Also, although not particularly shown, the light with an emission angle θ1 greater than 80° enters from the back surface 330 instead of the incident surface 310 and is emitted from the emission surface 320. However, since the amount of light is smaller compared to the light with other emission angles, it has almost no influence on the luminance distribution on the light diffusion member 120.

[0045] On the other hand, as shown in FIGS. 9A to 9D and FIGS. 10A to 10D, in the surface light source device 100A according to the comparative example, particularly as shown in FIGS. 9D and 10A, in the case of light with an angle θ2 from the emission surface 320A being 35° or more and less than 55°, there was light emitted from the light emitting device 200A that directly reached an adjacent light emitting device 200A. It can be seen that the light that directly reached the adjacent light emitting device 200A reached the substrate 210 while being condensed near the light emitting element 220 by the emission surface 320A and the incident surface 310A of the light flux control member 300A. Although not particularly shown, the light that reached the substrate 210 was reflected by the substrate 210, passed through the light flux control member 300A again, and reached an unintended area of the light diffusion member 120.

[0046] (Effect) As described above, in the surface light source device 100 according to the present embodiment, the light emitted from the light emitting device 200 does not directly reach an adjacent light emitting device 200, but directly reaches the light diffusion member 120, so that the light can reach a desired position in the light diffusion member 120. Therefore, in the surface light source device 100 according to the present embodiment, uneven brightness can be suppressed.

Industrial Applicability

[0047] The light emitting device and the surface light source device according to the present invention can be applied to, for example, a backlight of a liquid crystal display device or general lighting.

Explanation of Reference Numerals

[0048] 100, 100A Surface light source device 100’ Display device 102 Display member 110 Housing 112 Bottom plate 114 Top plate 120 Incident surface 120 Light diffusion member 200, 200A Light emitting device 210 Substrate 220 Light emitting element 300, 300A Light flux control member 310, 310A Incident surface 312 Concave portion 320, 320A Exit surface 320a First exit surface 320b Second exit surface 320c Third exit surface 330 Rear surface 331 First inner surface 332 Second inner surface 333 Rib 334 Annular groove 336 First inclined surface 337 Second inclined surface 338 Ridge line 340 Flange portion 350 Leg portion 360 Gate trace CA Central axis OA Optical axis θ1 Exit angle θ2 Angle

Claims

1. A substrate, a plurality of light-emitting devices each including a light-emitting element disposed on the substrate and a light flux control member for controlling the light distribution of light emitted from the light-emitting element, a light diffusion member that diffuses and transmits the light emitted from the plurality of light-emitting devices, and having, wherein the light flux control member, on the back side of the light flux control member, an inner surface of a recess disposed so as to intersect the central axis of the light flux control member, the inner surface being an incident surface for allowing the light emitted from the light-emitting element to enter, and an emission surface disposed on the front side of the light flux control member so as to intersect the central axis, the emission surface being for emitting the light incident on the incident surface to the outside, in one of the plurality of light-emitting devices, light emitted at an emission angle of 80° or less with respect to the optical axis of the light-emitting element from the light-emitting center of the light-emitting element enters the incident surface and is emitted from the emission surface, and the light reaches the light diffusion member without reaching other light-emitting devices among the plurality of light-emitting devices, in a first light-emitting device among the plurality of light-emitting devices, when light emitted at an emission angle θ1 (where 0° < θ1 ≤ 50°) with respect to the optical axis of the light-emitting element from the light-emitting center of the light-emitting element enters the incident surface and is emitted from a point a on the emission surface at an angle θ2 with respect to a straight line parallel to the optical axis, let the distance between the central axis of the first light-emitting device and the central axis of a second light-emitting device adjacent to the first light-emitting device among the plurality of light-emitting devices be P, let the distance between the substrate and the light diffusion member be H, let the distance between the point a and the substrate be A, and when the distance between the point a and the central axis in the first light-emitting device is B, 0 < (H - A)tanθ2 ≤ (P - B) is satisfied, a surface light source device.

2. When light emitted at an emission angle θ1 (where 0° < θ1 ≤ 60°) with respect to the optical axis of the light-emitting element from the light-emitting center of the light-emitting element in one of the plurality of light-emitting devices enters the incident surface and is emitted from a point a on the emission surface at an angle θ2 with respect to a straight line parallel to the optical axis, the surface light source device according to Claim 1, further satisfying the following formula (1). Δθ2 / Δθ1 ≥ 0...(1) [In formula (1), Δθ2 / Δθ1 is the slope of the tangent line of the curve shown in the graph with the horizontal axis θ1 and the vertical axis θ2.]

3. The plurality of light-emitting devices are arranged in a grid pattern, In a light-emitting device disposed other than the outermost of the plurality of light-emitting devices, light emitted from the light-emitting center of the light-emitting element at an emission angle of 80° or less with respect to the optical axis of the light-emitting element, incident on the incident surface and emitted from the emission surface, reaches the light diffusion member without passing through other members. The surface light source device according to claim 1 or claim 2.

4. The incident surface and the emission surface are rotationally symmetric about the central axis. The surface light source device according to any one of claims 1 to 3.

5. The H is 10 mm or less. The surface light source device according to claim 1.

6. The surface light source device according to any one of claims 1 to 5, A display member irradiated with light emitted from the surface light source device, A display device having.

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