WO2017038758A1 - Luminous flux control member, light-emitting device, planar light source device, and display device - Google Patents

Abstract

This luminous flux control member has: a plane of incidence having a first incidence plane and a second incidence plane inside a first concavity; an emission plane; and a second concavity. The intersection of the first incidence plane and the second incidence plane is disposed on the center axis side from an aperture edge portion of the first concavity. The angle of the tangent line to the first-incidence-plane-side end of the second incidence plane in relation to a first imaginary line orthogonal to the center axis is less than the angle of the tangent line to the second-incidence-plane-side end of the first incidence plane in relation to the first virtual line. The luminous flux control member satisfies the expression h1 < h2 + d × cot(θ1 + θ2), where h1 is the space between the apex of the second concavity and a second imaginary line orthogonal to the center axis and that passes through the aperture edge portion, h2 is the space between the second imaginary line and the incidence position of light on the second incidence plane, d is the distance between the incidence position and the apex in the direction orthogonal to the center axis, θ1 is the angle of refraction of light in the incidence position, and θ2 is the angle of the tangent line at the incidence position in relation to the second imaginary line.

Description

Luminous flux control member, light emitting device, surface light source device, and display device

The present invention relates to a light flux controlling member that controls light distribution of light emitted from a light emitting element, a light emitting device having the light flux controlling member, a surface light source device, and a display device.

In a transmissive image display device such as a liquid crystal display device, a direct type surface light source device may be used as a backlight. In recent years, direct type surface light source devices having a plurality of light emitting elements as light sources have come to be used.

For example, a direct type surface light source device includes a substrate, a plurality of light emitting elements, a plurality of light flux controlling members (lenses), and a light diffusing member. The light emitting element is a light emitting diode (LED) such as a white light emitting diode. The plurality of light emitting elements are arranged in a matrix on the substrate. A light flux controlling member that spreads light emitted from each light emitting element in the surface direction of the substrate is disposed on each light emitting element. The light emitted from the light flux controlling member is diffused by the light diffusing member and illuminates the irradiated member (for example, a liquid crystal panel) in a planar shape.

1A, 1B, and 1C are diagrams showing the configuration of a conventional light flux controlling member. 1A is a perspective view seen from the back side, FIG. 1B is a cross-sectional perspective view seen from the back side, and FIG. 1C is a cross-sectional view. In addition, in FIG. 1A and B, the leg part arrange | positioned at the back side is abbreviate | omitted. As shown in FIGS. 1A to 1C, the conventional light flux controlling member 20 has an entrance surface 22 and an exit surface 24. The incident surface 22 is an inner surface of the first concave portion formed on the back surface disposed to face the light emitting element, and makes the light emitted from the light emitting element incident. The exit surface 24 is disposed on the opposite side of the entrance surface 22 and emits the light incident on the entrance surface 22 to the outside.

2A and 2B are optical path diagrams of the light flux controlling member 20. FIG. FIG. 2A is an optical path diagram of a light beam emitted from the center of the light emitting surface of the light emitting element 10 at an emission angle of 30 °, and FIG. 2B shows light emitted from the center of the light emitting surface of the light emitting element 10 at an emission angle of 40 °. It is an optical path figure of a light ray. Here, the “emission angle” means an angle of the emitted light with respect to the optical axis OA of the light emitting element 10 (θ in FIG. 2A). In FIGS. 2A and 2B, the legs arranged on the back side are omitted.

2A and 2B, the light emitted from the light emitting element 10 enters the light flux controlling member 20 through the incident surface 22. The light that has entered the light flux controlling member 20 reaches the emission surface 24. Most of the light reaching the emission surface 24 is emitted from the emission surface 24 to the outside (solid arrow). At this time, the light emitted from the emission surface 24 is refracted and emitted from the emission surface 24, and its traveling direction is controlled. On the other hand, of the light reaching the exit surface 24, another part of the light is reflected by the exit surface 24 (Fresnel reflection) and reaches the back surface 26 (broken arrow). When a part of the light reaching the back surface 26 is internally reflected by the back surface 26, the amount of light directed directly above the light flux controlling member 20 becomes excessive. A uniform distribution (brightness unevenness) occurs. Further, when the light that has reached the back surface 26 is emitted from the back surface 26, the emitted light is absorbed by the substrate, so that the light use efficiency is lowered. Therefore, Patent Document 1 proposes a light flux controlling member that can solve such a problem.

3A to 3C are diagrams showing the configuration of the light flux controlling member 30 described in Patent Document 1. FIG. 3A is a perspective view seen from the back side, FIG. 3B is a cross-sectional perspective view seen from the back side, and FIG. 3C is a cross-sectional view. In addition, in FIG. 3A and B, the leg part arrange | positioned at the back side is abbreviate | omitted. As shown in FIGS. 3A to 3C, in the light flux controlling member 30 described in Patent Document 1, the inclined surface 32 is disposed on the outer side, and the second recess having the surface 34 substantially parallel to the central axis CA on the inner side is the rear surface 26. Is formed. The inclined surface 32 is rotationally symmetric (circularly symmetric) with respect to the central axis CA of the light flux controlling member 30 and is inclined at a predetermined angle (for example, 45 °) with respect to a virtual line orthogonal to the central axis CA. .

4A and 4B are optical path diagrams of the light flux controlling member 30. FIG. 4A is an optical path diagram of a light beam emitted from the center of the light emitting surface of the light emitting element 10 at an emission angle of 30 °, and FIG. 4B is a light beam emitted from the center of the light emitting surface of the light emitting device 10 at an emission angle of 40 °. FIG. In FIGS. 4A and 4B, the legs arranged on the back side are omitted. As shown in FIGS. 4A and 4B, the light internally reflected by the emission surface 24 reaches a predetermined region on the back surface 26. By forming the inclined surface 32 in the predetermined region, at least a part of the light reaching the inclined surface 32 can be reflected in the lateral direction.

As described above, in the light flux controlling member 30 described in Patent Document 1, the light internally reflected by the emission surface 24 is less likely to go directly above the light flux controlling member 30 and is less likely to be absorbed by the substrate. Therefore, the light emitting device having the light flux controlling member 30 described in Patent Document 1 can irradiate light more uniformly and efficiently than the light emitting device having the conventional light flux controlling member 20.

In recent years, a chip-on-board (COB) type LED has been used as a light source for illumination because of its ease of mounting and high luminous efficiency. It is known that a COB type LED emits more light in a lateral direction than a conventional LED in addition to emitting light upward.

JP 2011-23204 A

When a COB type LED is used as the light emitting element of the surface light source device described in Patent Document 1, light flux control is performed from the viewpoint of causing a large amount of light emitted in the lateral direction of the LED to enter the light flux control member from the incident surface 22. The member may be disposed such that the back surface of the light flux controlling member is lower than the top surface of the light emitting element. At this time, the light emitted in the lateral direction of the light emitting element and incident on the inside of the light flux controlling member at the lower part of the incident surface 22 propagates inside the light flux controlling member and forms the inner surface 34 forming the second recess. To reach. The light passes through the inner surface 34 and is scattered depending on the surface state of the surface 34. Further, most of the light transmitted through the surface 34 is refracted by the inclined surface 32 and travels toward the vicinity of the upper portion of the light flux controlling member (see FIG. 5). As described above, when a COB type LED is used in the surface light source device described in Patent Document 1, the light directed toward the upper part of the light emitting device is excessive due to scattering on the inner surface 34 and refraction on the inclined surface 32. Therefore, a region with high luminance is formed in an annular shape near the upper portion of the light flux controlling member, and luminance unevenness occurs. Further, even when the rear surface of the light flux controlling member is arranged so as to be higher than the upper surface of the light emitting element, the inner surface on which light incident from the vicinity of the outer edge of the first recess forms the second recess by refraction. 34 may be reached.

An object of the present invention is to use light that propagates in the light flux controlling member at a large angle with respect to the optical axis when used in combination with a light emitting element that emits a large amount of light in the lateral direction, such as a COB type LED. To provide a light flux control member that is less likely to cause uneven brightness in light emitted from the light flux control member even when a concave portion is formed at a position that can be easily reached.

Another object of the present invention is to provide a light emitting device, a surface light source device, and a display device having the light flux controlling member.

The light flux controlling member of the present invention is a light flux controlling member for controlling the light distribution of the light emitted from the light emitting element, and is provided on the inner surface of the first recess disposed on the back side so as to intersect the central axis of the light flux controlling member. An incident surface on which light emitted from the light emitting element is incident, an emission surface that is arranged on the front side so as to intersect the central axis, and that emits light incident on the incident surface to the outside; and the incident surface. A second concave portion disposed on the back side so as to surround the first incident surface, the outer surface of the first incident surface, and the first concave portion. A cross section including the central axis, and an intersection of the first incident surface and the second incident surface is an intersection of the first concave portion. It is arranged on the central axis side from the opening edge, and the cross section The inclination angle of the tangent at the end of the second incident surface on the first incident surface side with respect to the first imaginary straight line orthogonal to the central axis is at the end of the first incident surface on the second incident surface side. It is smaller than the inclination angle of the tangent to the first virtual straight line, and satisfies the following formula (1).

[In the above formula (1), h1 is the distance between the second imaginary straight line passing through the opening edge of the first recess and the top of the second recess in the cross section perpendicular to the central axis. , H2 is an interval between an incident position of arbitrary light emitted from the light emitting element and incident on the second incident surface in the cross section, and the second imaginary straight line, and d is the cross section, The distance between the incident position and the top of the second recess in the direction perpendicular to the central axis, θ1 is the refraction angle of the arbitrary light incident at the incident position in the cross section, and θ2 Is an inclination angle of the tangent of the incident position with respect to the second imaginary straight line in the cross section. ]

The light-emitting device of the present invention includes a light-emitting element and the light flux controlling member of the present invention, and the light flux controlling member is arranged so that the central axis coincides with the optical axis of the light emitting element.

The surface light source device of the present invention is disposed substantially parallel to the substrate, the plurality of light emitting devices according to the present invention disposed on the substrate at regular intervals, and on the plurality of light emitting devices. A light diffusing plate that diffuses and transmits light from the light emitting device, and the light emitting device has an angle range from a direction along the optical axis to a direction in which light having the highest luminous intensity is emitted from the light emitting device. The luminous intensity of the light from the beam gradually increases as the angle with respect to the optical axis increases, and satisfies the following equations (2), (3), and (4).

[In the above formulas (2), (3), and (4), P is the distance between the centers of the plurality of light emitting devices, and H is the distance between the upper surface of the substrate and the lower surface of the light diffusion plate. L is the distance from the intersection of the optical axis and the lower surface of the light diffusing plate to the point where the light with the highest luminous intensity reaches the lower surface of the light diffusing plate, and I ₀ is the light emission Is a luminous intensity of light emitted from the apparatus in the direction of the optical axis, and I _1/2 is a distance P / 2 from the intersection of the optical axis and the lower surface of the light diffusing plate on the lower surface of the light diffusing plate. It is the luminous intensity of the light emitted from the light emitting device toward the point. ]

The display device of the present invention includes the surface light source device of the present invention and an irradiated member that is irradiated with light emitted from the surface light source device.

The light flux controlling member of the present invention hardly causes uneven brightness in the emitted light even when combined with a light emitting element that emits a lot of light in the lateral direction, such as a COB type LED.

In addition, since the light emitting device, the surface light source device, and the display device of the present invention include the light flux controlling member that does not easily cause the luminance unevenness, it is difficult to cause the luminance unevenness in the emitted light.

1A to 1C are diagrams showing a configuration of a conventional light flux controlling member. 2A and 2B are optical path diagrams of a conventional light flux controlling member. 3A to 3C are diagrams showing the configuration of the light flux controlling member described in Patent Document 1. FIG. 4A and 4B are optical path diagrams of the light flux controlling member described in Patent Document 1. FIG. FIG. 5 is another optical path diagram of the light flux controlling member described in Patent Document 1. 6A and 6B are diagrams showing a configuration of the surface light source device according to Embodiment 1. FIG. 7A and 7B are cross-sectional views illustrating the configuration of the surface light source device according to Embodiment 1. FIG. 8 is a partially enlarged cross-sectional view of the surface light source device according to Embodiment 1. 9A and 9B are perspective views of the light flux controlling member according to Embodiment 1 as viewed from the back side. 10A to 10C are diagrams showing the configuration of the light flux controlling member according to the first embodiment. FIGS. 11A and 11B are partially enlarged cross-sectional views of the light flux controlling member according to Embodiment 1 for explaining the expression (1). FIG. 12 is an optical path diagram of the light-emitting device according to Embodiment 1. FIG. 13 is a partial enlarged cross-sectional view of the surface light source device according to Embodiment 1 for explaining the equations (2), (3), (4), and (5). 14A and 14B are graphs showing the light distribution characteristics of four types of light emitting devices. FIG. 15 is a graph showing the luminance distribution in the light emitting device. FIG. 16 is a graph showing H / P and L / P values for four types of surface light source devices. FIG. 17A is a graph showing values of I _1/2 / I ₀ for four types of surface light source devices. FIG. 17B is a graph showing values of I _1/4 / I ₀ for four types of surface light source devices. 18A and 18B are graphs showing the luminance distribution of the light emitting surface when only one light emitting device is turned on in the four types of surface light source devices. FIG. 19A is a diagram illustrating a luminance distribution of a light emitting surface of a surface light source device that does not have a light flux controlling member. FIG. 19B shows a surface light source device according to an embodiment of the present invention (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ > 6, I _1/4 / I ₀ ≦ 2. It is a figure which shows the luminance distribution of the light emission surface of 4). 19C to 19E show the surface light source device of the reference example (H / P ≦ 0.2, L / P ≦ 1, I _1/2 / I ₀ ≦ 6, I _1/4 / I ₀ ≦ 2.4). It is a figure which shows the luminance distribution of a light emission surface. FIG. 20 shows optical paths in the surface light source device of the reference example (H / P ≦ 0.2, L / P ≦ 1, I _1/2 / I ₀ > 6, I _1/4 / I ₀ ≦ 2.4). It is sectional drawing shown. FIG. 21A is a graph showing the light distribution characteristics of the light emitting devices (I _1/2 / I ₀ ≦ 6, I _1/4 / I ₀ ≦ 2.4) used in the surface light source devices of the present invention and the reference example. is there. FIG. 21B shows a surface light source device of the present invention and a reference example (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ ≦ 6, I _1/4 / I ₀ ≦ 2.4). 5 is a graph showing the luminance distribution of the light emitting surface when only one light emitting device is turned on. FIG. 22 shows a light emitting surface of a surface light source device (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ ≦ 6, I _1/4 / I ₀ ≦ 2.4) of a reference example. It is a figure which shows the luminance distribution. 23A and 23B are graphs showing the luminance distribution of the light emitting surface when only one light emitting device is turned on in a surface light source device having light emitting devices with different values of I _1/4 / I ₀ . FIG. 24 is a graph showing the relationship between I _1/4 / I ₀ and the luminance in the area near the light emitting device. 25A and 25B are perspective views of the light flux controlling member according to Embodiment 2 as seen from the back side. 26A and 26B are diagrams for explaining the shape of the incident surface according to the modification.

Hereinafter, the light flux controlling member, the light emitting device, the surface light source device, and the display device of the present invention will be described in detail with reference to the drawings. In the following description, a surface light source device suitable for a backlight of a liquid crystal display device will be described as a representative example of the surface light source device of the present invention. These surface light source devices can be used as a display device by combining with an irradiated member (for example, a liquid crystal panel) irradiated with light from the surface light source device.

[Embodiment 1]
(Configuration of surface light source device and light emitting device)
6 to 8 are diagrams showing the configuration of the surface light source device 100 according to the first embodiment. 6A is a plan view of surface light source device 100 according to Embodiment 1, and FIG. 6B is a front view. 7A is a cross-sectional view taken along the line AA shown in FIG. 6B, and FIG. 7B is a cross-sectional view taken along the line BB shown in FIG. 6A. FIG. 8 is a partially enlarged cross-sectional view of the surface light source device 100.

6A and 6B and FIGS. 7A and 7B, the surface light source device 100 includes a housing 110, a plurality of light emitting devices 200, and a light diffusion plate 120. The plurality of light emitting devices 200 are arranged in a matrix on the substrate 210 on the bottom plate 112 of the housing 110. The inner surface of the bottom plate 112 functions as a diffuse reflection surface. Further, the top plate 114 of the housing 110 is provided with an opening. The light diffusing plate 120 is disposed so as to close the 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. The center-to-center distance (pitch) of the light emitting device 200 is P (mm), and the distance (height) between the upper surface of the substrate 210 and the lower surface of the light diffusion plate 120 is H (mm) (see FIG. 13). The surface light source device 100 according to the present embodiment satisfies, for example, the following formula (2).

The plurality of light emitting devices 200 are arranged on the substrate 210 at regular intervals. Each of the plurality of substrates 210 is fixed at a predetermined position on the bottom plate 112 of the housing 110. As shown in FIG. 8, the plurality of light emitting devices 200 each include a light emitting element 220 and a light flux controlling member 300.

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. In the present embodiment, the light emitting element 220 is preferably a chip-on-board (COB) type LED from the viewpoint of easy mounting and high luminous efficiency.

COB type LEDs are known to emit more light in the lateral direction than conventional LEDs. Since the light emitting element 220 such as a COB type LED emits a lot of light in the lateral direction, it is necessary to make more light emitted in the side surface direction of the light emitting element 220 enter the light flux controlling member 300. Therefore, it is preferable that the upper surface of the light emitting element 220 is arranged vertically above the lower end (opening edge) of the first recess 310 described later.

The light flux controlling member 300 is a lens and is fixed on the substrate 210. The light flux controlling 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 surface direction of the substrate. The light flux controlling member 300 is disposed on the light emitting element 220 so that the central axis CA coincides with the optical axis OA of the light emitting element 220 (see FIG. 8). Note that an entrance surface 320 and an exit surface 330 of the light flux controlling member 300 described later are both rotationally symmetric (circularly symmetric), and their rotational axes coincide. The rotation axes of the entrance surface 320 and the exit surface 330 are referred to as “center axis CA of the light flux controlling member”. The “optical axis OA of the light emitting element” means a light beam at the center of the three-dimensional outgoing light beam from the light emitting element 220.

The light flux controlling member 300 can be formed by integral molding. The light flux controlling member 300 may be made of any material that can transmit light having a desired wavelength. For example, the material of the light flux controlling member 300 is light transmissive resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), epoxy resin (EP), silicone resin, or glass. The surface light source device 100 according to the present embodiment has a main feature in the configuration of the light flux controlling member 300. Therefore, the light flux controlling member 300 will be described in detail separately.

The light diffusing plate 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 plate 120 is disposed on the plurality of light emitting devices 200 substantially in parallel with the substrate 210. Usually, the light diffusing plate 120 is approximately the same size as an irradiated member such as a liquid crystal panel. For example, the light diffusion plate 120 is formed of a light-transmitting resin such as polymethyl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), styrene / methyl methacrylate copolymer resin (MS). In order to impart light diffusibility, fine irregularities are formed on the surface of the light diffusion plate 120, or light diffusers such as beads are dispersed inside the light diffusion plate 120.

In the surface light source device 100 according to the present invention, the light emitted from each light emitting element 220 is expanded by the light flux control member 300 so as to illuminate a wide area of the light diffusion plate 120. The light emitted from each light flux controlling member 300 is further diffused by the light diffusion plate 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).

(Configuration of luminous flux control member)
FIGS. 9A and 9B and FIGS. 10A to 10C are diagrams showing a configuration of light flux controlling member 300 according to Embodiment 1. FIG. 9A and 9B are perspective views of the light flux controlling member 300 as seen from the back side (substrate 210 side). 10A is a plan view of the light flux controlling member 300, FIG. 10B is a bottom view, and FIG. 10C is a cross-sectional view taken along line AA shown in FIG. 10A.

As shown in FIGS. 9A and 9B and FIGS. 10A to 10C, the light flux controlling member 300 has an incident surface 320 that is the inner surface of the first recess 310, an exit surface 330, and a second recess 340. In the present embodiment, light flux controlling member 300 has a flange 350 for facilitating handling of light flux controlling member 300. Further, the light flux controlling member 300 forms a gap for releasing heat generated from the light emitting element 220 to the outside, and has leg portions (not shown) for positioning and fixing the light flux controlling member 300 on the substrate 210. You may do it.

The first recess 310 is disposed at the center of the back surface 305 so as to intersect the central axis CA of the light flux controlling member 300. The first recess 310 is disposed so as to intersect with the optical axis OA of the light emitting element 220 (the central axis CA of the light flux controlling member 300). The inner surface of the first recess 310 functions as the incident surface 320. That is, the incident surface 320 is disposed so as to intersect the central axis CA. The incident surface 320 controls most of the light emitted from the light emitting element 220 to enter the light flux controlling member 300 while controlling the traveling direction of the light. The incident surface 320 intersects with the central axis CA of the light flux controlling member 300 and has rotational symmetry (circular symmetry) with the central axis CA as a rotation axis. The incident surface 320 includes a first incident surface 322 and a second incident surface 324.

The first incident surface 322 is disposed on the bottom side of the first recess 310 so as to intersect the central axis CA. The first incident surface 322 allows light having a small emission angle (mainly light emitted from the upper surface of the light emitting element 220) out of the light emitted from the light emitting element 220 to enter the light flux controlling member 300. The 1st entrance plane 322 may be constituted by one side, and may be constituted by a plurality of sides. In the present embodiment, the first incident surface 322 is composed of one surface. The first incident surface 322 is rotationally symmetric (circularly symmetric) with the central axis CA as a rotation axis. In the cross section including the central axis CA, the first incident surface 322 is formed so as to approach the back surface 305 as the distance from the central axis CA increases. More specifically, the first incident surface 322 is formed in a bell shape.

The second incident surface 324 is disposed on the opening side of the first concave portion 310 so as to connect the outer edge portion of the first incident surface 322 and the opening edge portion of the first concave portion 310. The second incident surface 324 causes light having a larger emission angle than the light incident on the first incident surface 322 (mainly light emitted from the side surface of the light emitting element 220) to enter the light flux controlling member 300. In the cross section including the central axis CA, the intersection of the first incident surface 322 and the second incident surface 324 is disposed closer to the central axis CA than the opening edge of the first recess 310.

In the cross section including the central axis CA, the inclination angle of the second incident surface 324 with respect to the first imaginary line orthogonal to the central axis CA of the tangent at the end on the first incident surface 322 side is the second incident surface of the first incident surface 322. It is smaller than the inclination angle of the tangent at the end on the surface 324 side with respect to the first virtual straight line. Here, “inclination angle” refers to a small angle among the angles formed by two straight lines. In the present embodiment, “the inclination angle with respect to the first imaginary line orthogonal to the central axis CA of the tangent line at the end of the second incident surface 324 on the first incident surface 322 side” is the first angle of the second incident surface 324. Of the angles formed by the tangent line at the end on the incident surface 322 side and the first imaginary straight line orthogonal to the central axis CA, this is the smaller angle. Further, “the inclination angle of the tangent at the end of the first incident surface 322 on the second incident surface 324 side with respect to the first imaginary straight line” is the tangent at the end of the first incident surface 322 on the second incident surface 324 side. Of the angles formed with the first virtual straight line orthogonal to the central axis CA, this is the smaller angle.

Furthermore, the second incident surface 324 is rotationally symmetric (circularly symmetric) with the central axis CA as the rotational axis. The shape of the second incident surface 324 in the cross section including the central axis CA may be a straight line or a curved line. In the present embodiment, the shape of the second incident surface 324 in the cross section including the central axis CA is a straight line. That is, the inclination angle of the tangent line of the second incident surface 324 with respect to the first imaginary straight line is constant from the outer edge portion of the first incident surface 322 toward the opening edge portion of the first recess 310. As described above, the second incident surface 324 is formed so as to be closer to the back surface 305 as it moves away from the central axis CA. Therefore, the light incident on the second incident surface 324 is refracted toward the emission surface 330 side. . Thereby, in the present embodiment, the light incident on the second incident surface 324 is prevented from reaching the second recess 340 directly. This point will be described in detail separately.

The back surface 305 is a flat surface that is located on the back side of the light flux controlling member 300 and extends in the radial direction from the opening edge of the first recess 310.

The emission surface 330 is disposed on the front side (light diffusion plate 120 side) of the light flux controlling member 300 so as to protrude from the flange portion 350. The exit surface 330 emits the light incident in the light flux controlling member 300 to the outside while controlling the traveling direction. The exit surface 330 intersects with the central axis CA and is rotationally symmetric (circularly symmetric) with the central axis CA as a rotation axis.

The emission surface 330 includes a first emission surface 330a located in a predetermined range centered on the central axis CA, a second emission surface 330b formed continuously around the first emission surface 330a, and a second emission surface 330b. And a third emission surface 330c that connects the flange 350 (see FIG. 10C). The first emission surface 330a is a curved surface convex on the back side. The second emission surface 330b is a smooth curved surface that is located on the front side and is located around the first emission surface 330a. The shape of the second emission surface 330b is an annular convex shape. The third emission surface 330c is a curved surface located around the second emission surface 330b. As shown in FIG. 10C, in the cross section including the central axis CA, the cross section of the third emission surface 330c may be linear or curved.

The second recess 340 is arranged on the back surface 305 so as to surround the first recess 310 (incident surface 320) with respect to the optical axis OA. The second recess 340 is a part of the light incident on the incident surface 320, is internally reflected by the output surface 330, and reflects light toward the back surface 305 in the lateral direction (radially outward with respect to the central axis CA). Let In the cross section including the central axis CA, the second recess 340 is substantially V-shaped. The second recess 340 includes an inner inclined surface 342 disposed on the optical axis OA (center axis CA) side and an outer inclined surface 344 disposed outside the inner inclined surface 342.

The inner inclined surface 342 is disposed on the central axis CA side. The inner inclined surface 342 is disposed along the central axis CA. The inner inclined surface 342 is formed in a cylindrical shape with the central axis CA as a rotation axis.

The outer inclined surface 344 is arranged farther from the central axis CA than the inner inclined surface 342. In the cross section including the central axis CA, the outer inclined surface 344 is inclined so as to approach the back surface 305 as the distance from the central axis CA increases. The shape of the outer inclined surface 344 in the cross section including the central axis CA is not particularly limited. The shape of the outer inclined surface 344 in the cross section including the central axis CA may be a straight line or a curved line. In the present embodiment, the shape of outer inclined surface 344 in the cross section including central axis CA is a straight line.

The inner inclined surface 342 and the outer inclined surface 344 may be arranged continuously or may be arranged apart from each other. When the inner inclined surface 342 and the outer inclined surface 344 are arranged apart from each other, another surface is arranged between the inner inclined surface 342 and the outer inclined surface 344.

The position of the second recess 340 is not particularly limited, but is preferably formed in a region where a lot of light reflected by the emission surface 330 reaches. Since the arrival position of the light reflected by the emission surface 330 varies depending on various factors such as the shape of the emission surface 330, it is appropriately set according to the light flux controlling member 300.

As described above, the second recess 340 is arranged at a position away from the second incident surface 324 from the central axis CA (outside the second incident surface 324). Therefore, the relationship between the second incident surface 324 and the second concave portion 340 is important for controlling the light incident on the second incident surface 324 so as not to reach the second concave portion 340 directly. Therefore, in light flux controlling member 300 according to the present embodiment, second incident surface 324 is formed so as to satisfy the following expression (1) indicating the relationship between second incident surface 324 and second recess 340. ing.

11A and 11B are partial enlarged cross-sectional views of the light flux controlling member for explaining the expression (1). As shown in FIGS. 11A and 11B, in a cross section including the central axis CA, the second virtual straight line VL2 orthogonal to the central axis CA and passing through the opening edge of the first concave portion 310 and the top of the second concave portion 340 Let h1 be the interval, and let h2 be the interval between the incident position of any light emitted from the light emitting element 220 and incident on the second incident surface 324 in the cross section including the central axis CA, and the second virtual line VL2. Further, in a cross section including the central axis CA, a distance in a direction perpendicular to the central axis CA between the incident position of arbitrary light incident on the second incident surface 324 and the top of the second recess 340 is defined as d. Further, in the cross section including the central axis CA, the refraction angle of arbitrary light incident at the incident position of the arbitrary light incident on the second incident surface 324 is θ1, and the second incident surface 324 in the cross section including the central axis CA is used. The inclination angle θ2 with respect to the second virtual straight line VL2 of the tangent of the incident position of the arbitrary light incident in step S2 is set. Here, “the inclination angle of the tangent of the incident position of arbitrary light incident on the second incident surface 324 with respect to the second virtual line VL2” is the tangent of the incident position of arbitrary light incident on the second incident surface 324. Among the angles formed by the second virtual straight line, it means a small angle.

Let H be the distance between the second virtual straight line VL2 and the arbitrary light L at the position of the top of the second recess 340 when the light flux controlling member 300 is viewed in plan. H can be represented by the following formula (1A).

Here, in order that the light L emitted from the light emitting element 220 and incident on the second incident surface 324 does not directly reach the second concave portion 340 (inner inclined surface 342), any light in the direction along the central axis CA is obtained. L needs to travel on the front side of the top of the second recess 340. Specifically, H needs to be larger than h1. That is, the second incident surface 324 and the second recess 340 need to satisfy the following formula (1).

The second incident surface 324 and the second recess 340 are designed to satisfy the above-described formula (1), so that the light L emitted from the light emitting element 220 and incident on the second incident surface 324 is directly second. Without reaching the recess 340 (inner inclined surface 342), the front side of the second recess 340 advances from the top.

The idea up to the above-described formula (1) is that the light flux controlling member 300 is designed so that the light L emitted from the light emitting element 220 and incident on the second incident surface 324 does not directly reach the collar portion 350. Can also be applied. Specifically, in the direction orthogonal to the central axis CA, an incident position where an arbitrary light L emitted from the light emitting element 220 and incident on the second incident surface 324 is incident with an inner end portion of the flange portion 350. Let the distance be d2. Moreover, the height of the collar part 350 is set to h3 in the direction along the central axis CA. θ1 and θ2 are as described above. In this case, h3 can be expressed by the following formula (1B).

Here, in order that the light L emitted from the light emitting element 220 and incident on the second incident surface 324 does not directly reach the flange 350, the light L is closer to the front side than the flange 350 in the direction along the central axis CA. Need to progress. Specifically, H needs to be larger than h3. That is, the flange 350 and the second incident surface need to satisfy the following formula (1C).

By designing the second incident surface 324 and the flange portion 350 to satisfy the above-described equation (1C), the light L emitted from the light emitting element 220 and incident on the second incident surface 324 is directly applied to the flange portion 350. Without going to the front, the front side of the collar 350 is advanced.

Further, the light utilization efficiency can be further increased by designing the light flux controlling member 300 so as to satisfy the above-described formulas (1) and (1C). In the formula (1A), H is defined by the arbitrary light L. However, the arbitrary light L is identified as light parallel to the second imaginary straight line VL2, and this light is the opening edge portion (second second) of the first recess 310. The depth h1 is defined by defining H to be greater than h1 (H> h1) when refracted at the outermost edge of the incident surface 324 and entering the light flux controlling member 300 (that is, h2 = 0). When the second concave portion is formed, the minimum value of the inclination angle θ2 of the outer edge of the second incident surface can be specified.

FIG. 12 is an optical path diagram in the light emitting device 200. In FIG. 12, hatching to the light emitting element 220 and the light flux controlling member 300 is omitted to show the optical path.

As shown in FIG. 12, out of the light emitted from the light emitting element 220, the light emitted from the upper light emitting surface enters the light flux controlling member 300 at the first incident surface 322. Of the light incident on the first incident surface 322, most of the light is emitted from the emission surface 330 to the outside of the light flux controlling member 300 while being refracted by the emission surface 330 to control the traveling direction. Among the light incident on the first incident surface 322, some of the light is internally reflected by the exit surface 330 and reaches the second recess 340 (outer inclined surface 344). Most of the light reaching the second recess 340 is reflected toward the side by the outer inclined surface 344. The light reflected by the outer inclined surface 344 is emitted from the flange 350, for example.

On the other hand, of the light emitted from the light emitting element 220, the light emitted from the side light emitting surface enters the light flux controlling member 300 at the second incident surface 324. At this time, the light emitted from the light emitting element 220 is refracted toward the emission surface 330 side at the second incident surface 324. The light incident on the second incident surface 324 is emitted from the light exit surface 330 to the outside of the light flux controlling member 300 while its traveling direction is controlled by being refracted by the light exit surface 330.

(Light distribution characteristics of surface light source device)
FIG. 13 is a partial enlarged cross-sectional view of the surface light source device 100 according to the present embodiment. In this figure, the housing 110 is omitted. In recent years, energy saving by further reducing the number of light emitting elements 220 in the surface light source device 100 and further thinning of the surface light source device 100 are required. Therefore, in the surface light source device 100 having the light flux controlling member 300 described above, the following equation (2) can be given as a condition for realizing energy saving, thinning, and reduction in luminance unevenness.

[In Formula (2), P is the distance (pitch) between the centers of the plurality of light emitting devices 200. H is the distance (height) between the upper surface of the substrate 120 and the lower surface of the light diffusion plate 120. ]

The surface light source device 100 preferably satisfies the following formula (3) in order to prevent the occurrence of luminance unevenness on the light emitting surface while satisfying the above formula (2). That is, the shapes of the entrance surface 320 and the exit surface 330 of the light flux controlling member 300 are adjusted so as to satisfy the following formula (3) in addition to the above formula (1). As shown in FIG. 13, Equation (3) means that light (l) emitted from a certain light emitting device 200 at a peak emission angle reaches farther than the adjacent light emitting devices 200. Thereby, it can suppress that a bright part (area | region with a comparatively high brightness | luminance) generate | occur | produces in the area | region between the light-emitting devices 200 of a light emission surface. In order to satisfy the expression (3), among the emission angles of light emitted from the light emitting device 200 (optical axis direction is 0 °, substrate surface direction is 90 °), the emission angle of light having the highest luminous intensity (peak emission angle) Is greater than 78.7 °.

[In Formula (3), P is the distance (pitch) between the centers of the plurality of light emitting devices 200. L is the distance from the intersection of the optical axis OA of the light emitting device 200 and the lower surface of the light diffusing plate 120 to the point where the light emitted from the light emitting device 200 at the peak emission angle reaches the lower surface of the light diffusing plate 120. . ]

In addition, the surface light source device 100 preferably satisfies the following formula (4) in order to prevent the occurrence of luminance unevenness on the light emitting surface while satisfying the above formula (3). That is, the shapes of the entrance surface 320 and the exit surface 330 of the light flux controlling member 300 are further adjusted to satisfy the following expression (4). As shown in FIG. 13, the equation (4) indicates that the light intensity (I _1/2 ) of the light toward the middle point of the two light emitting devices 200 on the lower surface of the light diffusing plate 120 is directed directly above the light emitting device 200. It means that it is more than 6 times higher than the luminous intensity (I ₀ ). Thereby, it can suppress that a dark part (area | region with a comparatively low brightness | luminance) generate | occur | produces in the area | region between the light-emitting devices 200 of a light emission surface.

[In Formula (4), I ₀ is the luminous intensity of the light emitted from the light emitting device 200 in the direction of the optical axis OA. I _1/2 is the luminous intensity of the light emitted from the light emitting device 200 toward the point at a distance of P / 2 from the intersection of the optical axis OA and the lower surface of the light diffusing plate 120 on the lower surface of the light diffusing plate 120. is there. ]

Moreover, it is preferable that the surface light source device 100 also satisfy | fills the following formula | equation (5). That is, it is preferable that the shapes of the entrance surface 320 and the exit surface 330 of the light flux controlling member 300 are further adjusted to satisfy the following formula (5). As shown in FIG. 13, Equation (5) goes to the midpoint (point of P / 4) between the midpoint between the two light emitting devices 200 and the one light emitting device 200 on the lower surface of the light diffusing plate 120. It means that the luminous intensity (I _1/4 ) of the light is 2.4 times or less of the luminous intensity (I ₀ ) of the light traveling directly above the light emitting device 200. Thereby, it can suppress that a bright part (area | region with a comparatively high brightness | luminance) generate | occur | produces in the area | region of the light emission surface vicinity of the light-emitting device 200, and can make luminance distribution more uniform in a light emission surface.

[In Expression (5), I ₀ is the luminous intensity of light emitted from the light emitting device 200 in the direction of the optical axis OA (I ₀ ≠ 0). I _1/4 is the luminous intensity of the light emitted from the light emitting device 200 toward the point at a distance of P / 4 from the intersection of the optical axis OA and the lower surface of the light diffusing plate 120 on the lower surface of the light diffusing plate 120. is there. ]

(Light distribution characteristics of light-emitting device)
The light distribution characteristics of the light emitting device 200 used in the surface light source device 100 according to the present embodiment were measured. For reference, light distribution characteristics were also measured for a light emitting device having a light flux controlling member with a different exit surface shape (hereinafter also referred to as “light emitting device according to Reference Examples 1 to 3”). Table 1 shows characteristics of the light-emitting device 200 according to the present embodiment and the light-emitting devices according to the three types of Reference Examples 1 to 3.

14A and 14B are graphs showing the light distribution characteristics of the four types of light emitting devices (P110, P60, P75, and P90) shown in Table 1. The horizontal axis represents the angle (°) when the center of the light emitting surface of the light emitting element is the origin and the optical axis OA of the light emitting device is 0 °. The vertical axis in FIG. 14A indicates the luminous intensity (cd) at each angle, and the vertical axis in FIG. 14B indicates the relative luminous intensity. FIG. 14B shows the relative luminous intensity when the luminous intensity at 0 ° is set to 1 for each light emitting device. The result of the light emitting device 200 (P110) according to the present embodiment is indicated by a thick solid line. On the other hand, the measurement results of the light emitting devices (P60, P75, and P90) according to Reference Examples 1 to 3 are indicated by thin broken lines, thin solid lines, or thin dashed lines.

As shown in FIGS. 14A and 14B, the light emitting device 200 (P110) according to the present embodiment has a peak emission angle of 78.7 ° or more, and the light emitting devices according to Reference Examples 1 to 3 (P60, P75). It can be seen that more light traveling far away can be generated compared to P90).

(Luminance distribution of light emitting device and luminance distribution of surface light source device)
Next, the luminance distribution of the light emitting device 200 according to this embodiment was measured. In this measurement, the light emitting element 220 and the light emitting device 200 satisfying the above-described formula (1) were used. And the luminance distribution on the virtual surface arrange | positioned through the light-emitting device 200 fixed to the board | substrate 210 and an air layer was measured. For comparison, the luminance on the virtual plane in the light emitting device (hereinafter also referred to as “light emitting device according to comparative example 1”) using the light flux controlling member 30 that does not have the second incident surface 324 shown in FIG. Was also measured. In the light emitting device 200 according to the present embodiment and the light emitting device according to Comparative Example 1, the optical axis OA of the light emitting element and the central axis CA of the light flux controlling member 300 are arranged so as to coincide with each other.

FIG. 15 is a graph showing a simulation result of the luminance distribution on the virtual plane arranged through the light emitting device 200 and the air layer in the cross section including the optical axis OA. The horizontal axis in FIG. 15 indicates the distance (mm) from the optical axis OA in the virtual plane, and the vertical axis indicates the luminance (cd / m ² ). The solid line in FIG. 15 shows the result of the light emitting device 200 (P110) according to the present embodiment, and the broken line shows the result of the light emitting device according to Comparative Example 1.

As shown in FIG. 15, it can be seen that in the light emitting device according to Comparative Example 1, a ring-shaped bright portion is formed immediately above the light emitting device (see the broken line arrow in FIG. 15). This is because the light flux controlling member does not satisfy the formula (1), so that the light incident on the second incident surface 324 reaches the second concave portion 340 (inner inclined surface 342), and then the output surface 330 (third output surface). It was thought to be due to light emitted from the surface 330c). On the other hand, in the light-emitting device 200 according to the present embodiment, a ring-shaped bright portion is suppressed immediately above the light-emitting device 200, and the brightness in the region outside the light-emitting device 200 is slightly increased (see the solid arrow in FIG. 15). ). This is because the light flux controlling member 300 satisfies the formula (1), so that the light incident on the second incident surface 324 does not reach the second concave portion 340 (inner inclined surface 342), and the emission surface 330 (third This was thought to be due to light emitted from the emission surface 330c).

Next, the luminance distribution was measured for the surface light source device 100 having the light emitting device 200 (P110) including the light flux controlling member 300 satisfying the expression (1) according to the present embodiment. For reference, the luminance distribution was also measured for the surface light source devices having the light emitting devices (P60, P75, and P90) of Reference Examples 1 to 3 above. Each light emitting device (P110, P60, P75, and P90) was arranged at an optimum pitch (see Table 1) inside a surface light source device having a height H of 19 mm.

FIG. 16 is a graph showing the values of H / P and L / P for each surface light source device. As shown in this graph, in the surface light source device 100 according to the present embodiment, H / P is 0.2 or less and L / P is more than 1. That is, the surface light source device 100 according to the present embodiment satisfies the above expressions (2) and (3). On the other hand, in the surface light source devices having the light emitting devices (P60, P75, and P90) of Reference Examples 1 to 3, H / P is more than 0.2 and L / P is 1 or less. That is, these surface light source devices do not satisfy the above formulas (2) and (3).

FIG. 17A is a graph showing the value of I _1/2 / I ₀ for each surface light source device, and FIG. 17B is a graph showing the value of I _1/4 / I ₀ for each surface light source device. As shown in FIGS. 17A and 17B, in surface light source device 100 according to the present embodiment, I _1/2 / I ₀ is greater than 6 and I _1/4 / I ₀ is 2.4 or less. is there. That is, the surface light source device 100 according to the present embodiment satisfies the above expressions (4) and (5). On the other hand, in the surface light source devices having the light emitting devices (P60, P75 and P90) of Reference Examples 1 to 3, I _1/4 / I ₀ is 2.4 or less, but I _1/2 / I ₀ is 6 or less. It is. That is, these surface light source devices satisfy the above formula (5) but do not satisfy the above formula (4).

FIG. 18A and FIG. 18B are graphs showing the luminance distribution of the light emitting surface when only one light emitting device is turned on in each surface light source device. The horizontal axis indicates the distance from the optical axis OA of the light emitting device. The vertical axis represents the luminance (FIG. 18A) or relative luminance (FIG. 18B) at each point. FIG. 18B shows the relative luminance when the luminance on the optical axis OA is set to 1 for each surface light source device. The result of the surface light source device having the light emitting device 200 (P110) according to the present embodiment is indicated by a thick solid line. On the other hand, the measurement results of the surface light source devices having the light emitting devices (P60, P75, and P90) of Reference Examples 1 to 3 are indicated by thin broken lines, thin solid lines, or thin dashed lines.

As shown in FIG. 18B, when the light emitting device 200 (P110) including the light flux controlling member 300 satisfying the expression (1) is arranged at a 110 mm pitch (H / P = 0.17), the light emitting device on the light emitting surface. Although sufficient brightness can be obtained at an intermediate position of 200 (± 55 mm), when the light emitting devices (P60 and P75) of Reference Examples 1 and 2 are arranged at a 110 mm pitch (H / P = 0.17), It can be seen that the brightness is insufficient at the intermediate position (± 55 mm). When the light emitting devices are arranged in a matrix with a 110 mm pitch (H / P = 0.17), the distance between the centers of the light emitting devices in the diagonal direction is about 155 mm. When the light emitting device (P90) of Reference Example 3 is arranged at a pitch of 110 mm (H / P = 0.17), the brightness is insufficient at the diagonal intermediate position (± 77.5 mm) on the light emitting surface. On the other hand, in the light emitting device 200 according to the present embodiment, it can be seen that sufficient luminance can be obtained even at the base of the luminance distribution on the light emitting surface.

FIG. 19 shows the luminance distribution of the light emitting surface when 16 light emitting devices are turned on in each surface light source device. 19A shows the luminance distribution of the light emitting surface when the light flux controlling member is removed, FIG. 19B shows the luminance distribution of the light emitting surface of the surface light source device 100 according to the present embodiment, and FIG. 19C shows Reference Example 1. FIG. 19D shows the luminance distribution of the light emitting surface of the surface light source device having the light emitting device (P75) of Reference Example 2, and FIG. 19E shows the luminance distribution of the light emitting surface of the surface light source device having the light emitting device (P60) of FIG. It is a luminance distribution of the light emission surface of the surface light source device which has the light-emitting device (P90) of the reference example 3. FIG. Each light emitting device is arranged at a pitch of 110 mm inside a surface light source device having a height H of 19 mm, and H / P is 0.17 in any surface light source device.

As shown in FIGS. 19C to 19E, the surface light source devices (H / P ≦ 0.2, L / P ≦ 1, I _1/2 / I ₀ ≦ 6, I _{In 1/4} / I ₀ ≦ 2.4), the luminance unevenness was large. On the other hand, the surface light source device 100 according to the present embodiment (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ > 6, I _1/4 / I ₀ ≦ 2.4. ), As shown in FIG. 17B, the luminance unevenness was small even though H / P was 0.2 or less. Here, “the luminance unevenness is small” means that the ratio of the minimum luminance to the maximum luminance in the region between the light emitting devices on the light emitting surface is 95% or more.

As described above, the surface light source device 100 according to the present embodiment can emit uniform light from the light emitting surface.

When the surface light source device does not satisfy the above formula (3), the light emitted from the light emitting device at the peak emission angle (for example, 63 °) reaches the region between the light emitting devices on the lower surface of the light diffusion plate. . For this reason, the surface light source device 100 ′ that does not satisfy only the expression (2) (H / P ≦ 0.2, L / P ≦ 1, I _1/2 / I ₀ > 6, I _1/4 / I ₀ ≦ In 2.4), as shown in FIG. 20, most of the light emitted from the light emitting device 40 reaches a region in the vicinity of the light emitting device 40 on the light emitting surface (region where the light emitted at the peak emission angle reaches). As a result, a region where the light amount is insufficient is generated between the light emitting devices 40 on the light emitting surface. As a result, a relatively bright bright portion B is formed in a region near the light emitting device 40 on the light emitting surface, and luminance unevenness occurs.

When the surface light source device does not satisfy the above formula (4), the light distribution characteristics of the light emitting device are as indicated by broken lines in FIG. 21A. In FIG. 21A, the solid line is a curve showing the light distribution characteristics of the light emitting device 200 (P110) according to the present embodiment. FIG. 21B is a graph showing the luminance distribution of the light emitting surface when only one light emitting device is turned on in the surface light source device having the light emitting device. In FIG. 21B, the broken line indicates a surface light source device that does not satisfy only the above formula (4) (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ ≦ 6, I _1/4 / I. ₀ ≦ 2.4) is a curve showing the luminance distribution of the light emitting surface, and the solid line is the surface light source device 100 (H / P ≦ 0.2, L / P> 1, I _{1/2 according to the} present embodiment). / _{I 0> 6,} a curve showing the intensity distribution of the light-emitting surface of the _{I 1/4 / I 0 ≦ 2.4)} . FIG. 22 shows a surface light source device (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ ≦ 6, I _1/4 / I ₀ that does not satisfy only the equation (4). ≦ 2.4) is the luminance distribution of the light emitting surface when 16 light emitting devices are turned on. From these results, it is understood that when the surface light source device does not satisfy the above formula (4), the region between the light emitting devices 40 on the light emitting surface becomes relatively dark, resulting in luminance unevenness.

Even if the surface light source device does not satisfy the above formula (5), luminance unevenness can be sufficiently suppressed if the above formulas (2) to (4) are satisfied. When Expression (5) is also satisfied, the luminance distribution on the light emitting surface becomes more uniform. FIG. 23A and FIG. 23B are graphs showing the luminance distribution of the light emitting surface when only one light emitting device is turned on in a surface light source device having light emitting devices with different values of I _1/4 / I ₀ . FIG. 23B shows an enlarged peak portion of the graph of FIG. 23A. A thick solid line indicates a surface light source device (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ > 6, I _1/4 having the light emitting device 200 (P110) according to the present embodiment. / I ₀ = 1.6) is a curve showing the luminance distribution on the light emitting surface. A thin broken line, a thin solid line, a thin one-dot chain line, and a thin two-dot chain line indicate a surface light source device having another light-emitting device (H / P ≦ 0.2, L / P> 1, I _1/2 / I ₀ > 6, I _1/4 / I ₀ = 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5). The surface light source device having the light emitting device 200 (P110) according to the present embodiment differs from the surface light source device having another light emitting device only in the value of I _1/4 / I ₀ . From these results, it can be seen that when the value of I _1/4 / I ₀ changes, the luminance of the region near the light emitting device 40 on the light emitting surface changes. From the viewpoint of making the luminance distribution on the light emitting surface more uniform, the luminance in the region near the light emitting device 40 is preferably lower than the luminance directly above the light emitting device 40.

FIG. 24 is a graph showing the relationship between I _1/4 / I ₀ and the luminance in the area near the light emitting device 40. The vertical axis represents the luminance at a point 18 mm from the optical axis OA of the light emitting device 40 on the light emitting surface (a point having a peak in the graph of FIG. 23A) when the luminance of the point immediately above the light emitting device 40 on the light emitting surface is 1. Relative values are shown. From this graph, it can be seen that when I _1/4 / I ₀ is 2.4 or less, the luminance in the vicinity of the light emitting device 40 is lower than the luminance directly above the light emitting device 40. Therefore, from the viewpoint of making the luminance distribution on the light emitting surface more uniform, I _1/4 / I ₀ is preferably 2.4 or less.

(effect)
As described above, the light flux controlling member 300 and the surface light source device 100 according to the present embodiment allow the light emitted mainly from the side surface of the light emitting element 220 to enter and refract the light toward the exit surface 330. 324. Therefore, in light flux controlling member 300 and surface light source device 100 according to the present embodiment, a ring-shaped bright portion does not occur on top of light emitting device 200, and luminance unevenness can be suppressed.

Further, in the surface light source device 100 and the display device having such a light flux controlling member 300, since the above formulas (2) to (5) are satisfied, luminance unevenness can be similarly suppressed.

[Embodiment 2]
The display device according to the second embodiment is different from the display device according to the first embodiment in the configuration of the light flux controlling member 600. Therefore, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

(Configuration of luminous flux control member)
25A and 25B are perspective views of the light flux controlling member 600 according to Embodiment 2 as viewed from the back side. As shown in FIGS. 25A and 25B, the light flux controlling member 600 in the display device according to Embodiment 2 has an incident surface 320, an exit surface 330, and a second recess 640. In addition, light flux controlling member 600 according to the present embodiment has a collar portion 350. Further, the light flux controlling member 600 may have leg portions (not shown).

The second recess 640 in the light flux controlling member 600 according to Embodiment 2 has an inner inclined surface 342 and an outer inclined surface 644. A plurality of ridges 344 d are arranged on the outer inclined surface 644.

Each of the plurality of ridges 344d has a substantially triangular cross section and is rotationally symmetric with respect to the central axis CA (n-fold symmetry when the number of ridges 344d is n). Each ridge 344d has a planar first inclined surface 344a, a planar second inclined surface 344b, and a ridge line 344c that is an intersection of the first inclined surface 344a and the second inclined surface 344b. It functions like a total reflection prism. As shown in FIG. 25, in the cross section of the light flux controlling member 600 including the optical axis OA and the ridge line 344c, the optical axis OA and the third virtual straight line VL3 including the ridge line 344c are relative to the back surface 305 in the optical axis direction. And intersect at a position farther than the outer inclined surface 644. That is, each ridge 344d is inclined in a direction (for example, 60 °) toward the back side as the ridge line 344c is away from the central axis CA.

(Light distribution characteristics of light emitting device and surface light source device)
The light distribution characteristics of the light emitting device including the light flux controlling member 600 according to the present embodiment were measured. Although not particularly illustrated, the light emitting device including the light flux controlling member 600 according to the second embodiment can generate more light traveling farther than the light emitting device according to the first embodiment. Further, in the light emitting device including the light flux controlling member 600 according to the second embodiment, a ring-shaped bright portion is suppressed immediately above the light emitting device, similarly to the light emitting device 200 according to the first embodiment. Further, in the surface light source device according to Embodiment 2 that satisfies the above-described formulas (2) to (5), the luminance unevenness was small. This is because a plurality of protrusions 344 d are arranged on the outer inclined surface 644, so that the light internally reflected by the exit surface 330 is further reflected by the substrate 210 and absorbed by the substrate 210. It was thought that the loss of light due to this could be further suppressed.

(effect)
As described above, light flux controlling member 600 according to the present embodiment has the same effect as that of the first embodiment or the effects of the first embodiment or more. In addition, since the plurality of ridges 344d function like total reflection prisms, the light internally reflected by the emission surface 330 is further reflected by the substrate 210 and is absorbed by the substrate 210. It was possible to further suppress the light loss due to.

In the first and second embodiments described above, the inclination angle of the tangent line of the second incident surface 324 with respect to the first virtual line is constant, but the inclination angle of the tangent line of the second incident surface 324 with respect to the first virtual line is If it can satisfy | fill Formula (1), it will not specifically limit. For example, the inclination angle of the tangent line of the second incident surface 324 'with respect to the first imaginary straight line may be formed so as to be gradually reduced as shown in FIG. 26A. Further, the inclination angle of the tangent line of the second incident surface 324 ″ with respect to the first imaginary straight line may be formed so that the inclination of the tangent line gradually increases as shown in FIG. 26B. However, the light incident on the second incident surfaces 324 ′ and 324 ″ does not reach the second recesses 340 and 640 directly.

This application claims priority based on Japanese Patent Application No. 2015-174013 filed on September 3, 2015 and Japanese Patent Application No. 2015-199459 filed on October 7, 2015. The contents described in the application specification and the drawings are all incorporated herein.

The light flux controlling member, light emitting device, and surface light source device of the present invention can be applied to, for example, a backlight of a liquid crystal display device or general illumination.

DESCRIPTION OF SYMBOLS 10 Light emitting element 20, 30 Light flux control member 22 Incident surface 24 Outgoing surface 26 Back surface 32 Inclined surface 34 Surface substantially parallel to the central axis 40 Light emitting device 100 Surface light source device 100 'Surface light source device 110 Case 112 Bottom plate 114 Top plate DESCRIPTION OF SYMBOLS 120 Light diffusing plate 200 Light-emitting device 210 Board | substrate 220 Light-emitting element 300, 600 Light flux control member 305 Back surface 310 1st recessed part 320 Incident surface 322 1st incident surface 324, 324 ', 324 "2nd incident surface 330 Output surface 330a 1st output Surface 330b Second exit surface 330c Third exit surface 340, 640 Second recess 342 Inner inclined surface 344, 644 Outer inclined surface 344a First inclined surface 344b Second inclined surface 344c Ridge 344d Convex 350 Hump CA Beam control member Center axis VL2 Second virtual straight line VL3 Third virtual straight line OA Optical axis of light emitting element

Claims (8)

1. A light flux controlling member for controlling the light distribution of the light emitted from the light emitting element,
   An inner surface of a first recess disposed on the back side so as to intersect with the central axis of the light flux controlling member, an incident surface on which light emitted from the light emitting element is incident;
   An emission surface that is arranged on the front side so as to intersect the central axis, and emits light incident on the incidence surface to the outside;
   A second recess disposed on the back side so as to surround the incident surface;
   Including
   The incident surface is
   A first incident surface arranged to intersect the central axis;
   A second incident surface arranged to connect an outer edge portion of the first incident surface and an opening edge portion of the first recess;
   Have
   In the cross section including the central axis, the intersection of the first incident surface and the second incident surface is disposed on the central axis side from the opening edge of the first recess,
   In the cross section, an inclination angle of a tangent line at an end of the second incident surface on the first incident surface side with respect to a first imaginary straight line orthogonal to the central axis is on the second incident surface side of the first incident surface. Smaller than the inclination angle of the tangent at the end with respect to the first virtual straight line,
   The following formula (1) is satisfied.
   Luminous flux control member.
   

   

   [In the above formula (1),
   h1 is a distance between a second imaginary straight line perpendicular to the central axis and passing through the opening edge of the first recess and the top of the second recess in the cross section;
   h2 is an interval between an incident position of arbitrary light emitted from the light emitting element and incident on the second incident surface and the second imaginary straight line in the cross section;
   d is a distance in a direction perpendicular to the central axis between the incident position and the top of the second recess in the cross section;
   θ1 is a refraction angle of the arbitrary light incident at the incident position in the cross section,
   θ2 is an inclination angle of the tangent at the incident position with respect to the second imaginary straight line in the cross section. ]
2. In the cross section, the inclination angle of the tangent line of the second incident surface with respect to the first imaginary straight line gradually decreases or gradually decreases from the outer edge portion of the first incident surface toward the opening edge portion of the first recess. The light flux controlling member according to claim 1, wherein the light flux controlling member is large or constant.
3. The second recess is
   An inner inclined surface disposed on the central axis side;
   An outer inclined surface disposed away from the central axis than the inner inclined surface;
   Have
   In the cross section, the outer inclined surface is inclined in a direction toward the back side as it is away from the central axis.
   The light flux controlling member according to claim 1 or 2.
4. A plurality of ridges having a substantially triangular cross section perpendicular to the central axis are arranged on the outer inclined surface,
   Each of the plurality of ridges has a first inclined surface, a second inclined surface, and a ridge line that is an intersection line of the first inclined surface and the second inclined surface,
   The plurality of ridges are arranged to be rotationally symmetric with respect to the central axis,
   The ridge line is inclined in the direction toward the back side as it is away from the central axis.
   The light flux controlling member according to claim 3.
5. A light emitting element;
   The light flux controlling member according to any one of claims 1 to 4,
   The light flux controlling member is disposed at a position where the central axis coincides with the optical axis of the light emitting element.
   Light emitting device.
6. The light-emitting device according to claim 5, wherein the light-emitting element is a chip-on-board (COB) light-emitting diode (LED).
7. A substrate,
   A plurality of light emitting devices according to claim 5 or 6, which are arranged on the substrate at regular intervals.
   A light diffusing plate that is disposed substantially parallel to the substrate on the plurality of light emitting devices and transmits light from the light emitting devices while diffusing;
   In the angular range from the direction along the optical axis to the direction in which the light having the highest luminous intensity is emitted from the light emitting device, the luminous intensity of the light from the light emitting device gradually increases as the angle with respect to the optical axis increases, and Satisfying Equation (2), Equation (3) and Equation (4)
   Surface light source device.
   

   

   

   

   [In the above formula (2), formula (3) and formula (4),
   P is a distance between the centers of the plurality of light emitting devices,
   H is the distance between the upper surface of the substrate and the lower surface of the light diffusing plate,
   L is the distance from the intersection of the optical axis and the lower surface of the light diffusing plate to the point where the light with the highest luminous intensity reaches the lower surface of the light diffusing plate,
   I ₀ is the luminous intensity of the light emitted from the light emitting device in the optical axis direction;
   I _1/2 is the luminous intensity of the light emitted from the light emitting device toward the point at a distance of P / 2 from the intersection of the optical axis and the lower surface of the light diffusing plate on the lower surface of the light diffusing plate. is there. ]
8. A surface light source device according to claim 7;
   A member to be irradiated with light emitted from the surface light source device;
   A display device.
   

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