JP2018036407A - Luminous flux control member, light emitting device, surface light source device, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminous flux control member capable of suppressing the occurrence of bright parts on a surface to be irradiated, even in the case where light emitting devices are arranged like a grid.SOLUTION: The luminous flux control member controls distribution of light emitted from a light emitting element and has an incident surface being an inside surface of a concave portion formed on a rear side thereof and an emission surface disposed in the opposite side of the incident surface so that they cross a center axis of the luminous flux control member. The emission surface includes a rearward convex first emission surface and a frontward convex second emission surface disposed so as to surround the first emission surface, which are disposed so as to cross the center axis. When the light emitting element is disposed to face the concave portion so as to have the center of light emission located on the center axis and a surface to be irradiated is disposed above the emission surface so as to cross the center axis, a second maximum value calculated by a prescribed formula is greater than a first maximum value calculated by the prescribed formula.SELECTED DRAWING: Figure 6

Description

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

  In recent years, a light emitting diode (hereinafter also referred to as “LED”) has been used as a light source for illumination from the viewpoint of energy saving and miniaturization. And the light-emitting device which combined LED and the light beam control member which controls light distribution of the light radiate | emitted from LED is used instead of a fluorescent lamp, a halogen lamp, etc. Further, in a transmissive image display device such as a liquid crystal display device, a direct-type surface light source device in which the light emitting device is mounted in a lattice shape as a backlight is used (for example, see Patent Document 1).

  FIG. 1 is a diagram illustrating a configuration of a surface light source device 10 described in Patent Document 1. As illustrated in FIG. 1A is a schematic plan view of the surface light source device 10, FIG. 1B is a plan view of the light emitting device 30 in the surface light source device 10, and FIG. 1C is a cross section taken along line AA shown in FIG. 1B. FIG. The dashed line in FIG. 1A schematically shows the irradiation range of the light emitted from the light emitting device 30.

  As shown in FIGS. 1A to 1C, a surface light source device 10 described in Patent Document 1 includes a printed wiring board 20 and a plurality of light emitting devices 30 arranged in a rectangular lattice pattern on the printed wiring board 20. . The plurality of light emitting devices 30 each include a light emitting element 35 and a light guide member (light flux controlling member) 40 disposed so as to cover the light emitting element 35.

  The light guide member 40 includes a substantially hemispherical lens portion 41 and a flange portion 42 disposed so as to surround the lens portion 41. The lens unit 41 includes an incident surface 44 that is an inner surface of the concave portion 43 disposed on the back side, and an output surface 45 disposed on the front side. The emission surface 45 includes two planes 46 parallel to the central axis CA and an upwardly convex curved surface 47 disposed between the two planes 46. In the surface light source device 10 described in Patent Document 1, the light emitted from the light emitting element 35 is guided by the light guide member 40 in the direction in which the intervals between the plurality of light emitting devices 30 are short (the short side direction of the rectangular lattice; the Y direction). As compared with the above, the distance between the plurality of light emitting devices 30 is controlled so as to expand in a long direction (long side direction of the rectangular lattice; X direction). Therefore, in the surface light source device described in Patent Document 1, the irradiated surface can be uniformly irradiated even when the plurality of light emitting devices 30 are arranged in a rectangular lattice shape.

International Publication No. 2009/157166

  However, in the surface light source device 10 described in Patent Document 1, the light emitted from the flat surface 46 is controlled to be condensed. On the other hand, the light emitted from the curved surface 47 is controlled to spread. Thereby, the light emitted from the flat surface 46 and the light emitted from the curved surface 47 are likely to intersect on the optical path to the irradiated surface. Therefore, there is a possibility that a bright part may occur on the irradiated surface.

  Accordingly, an object of the present invention is to provide a light flux controlling member that can suppress the occurrence of bright portions on the irradiated surface even when the light emitting devices are arranged in a grid pattern. 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 according to 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 formed on the inner surface of the recess formed on the back side so as to intersect the central axis of the light flux controlling member. A first incident surface having a certain incident surface and an exit surface disposed on the opposite side of the incident surface, wherein the exit surface is disposed so as to intersect the central axis, and is convex toward the back side A second light-exiting surface that is arranged so as to surround the first light-emitting surface and is convex toward the front side, and that faces the light-emitting element to the concave part so that the light emission center is located on the central axis When the irradiated surface is arranged above the exit surface so as to be orthogonal to the central axis, the second maximum value obtained by the following “how to obtain the second maximum value” is: It is larger than the first maximum value obtained by the following “How to obtain the first maximum value”. Flux control member.
[How to find the first maximum value]
(1) In the first cross section including the central axis and a point closest to the central axis among the outer edges of the emission surface, the emission center of the arbitrary light beam emitted from the emission center and the incident surface Between the emission angle θ1A, which is the angle of the traveling direction in relation to the central axis, and the emission angle θ3A, which is the angle of the arbitrary light ray between the emitting surface and the irradiated surface, relative to the central axis A first polynomial approximation function representing is obtained.
(2) Find a first curve corresponding to the first derivative of the first polynomial approximation function.
(3) When the light emission angle θ1A exceeds 40 °, the maximum value in the first curve is set as the first maximum value.
[How to find the second maximum]
(1) In a second cross section including the central axis and a point farthest from the central axis among the outer edges of the emission surface, between the emission center and the incident surface of an arbitrary ray emitted from the emission center Between the emission angle θ1B, which is the angle of the traveling direction between the light emitting surface and the central axis, and the emission angle θ3B, which is the angle of the arbitrary light beam between the emitting surface and the irradiated surface, with respect to the central axis A second polynomial approximation function representing is obtained.
(2) A second curve corresponding to the first derivative of the second polynomial approximation function is obtained.
(3) When the light emission angle θ1B exceeds 40 °, the maximum value in the second curve is set as the second maximum value.

  Moreover, the light-emitting device which concerns on this invention has a light emitting element and the light beam control member which concerns on this invention.

［上記式（１）において、Ｄ１は、前記矩形格子の単位格子の長辺の長さの半分である。Ｄ２は、前記矩形格子の単位格子の対角線の長さの半分である。Ｐは、前記第２最大値に対応する前記発光角度θ１Ｂで前記発光素子の前記発光中心から出射された光線の前記光拡散板における交点と、前記中心軸との距離である。］ Moreover, the surface light source device according to the present invention transmits a plurality of light emitting devices according to the present invention in which the light emission centers of the light emitting elements are arranged in a rectangular lattice shape while diffusing light from the plurality of light emitting devices. A surface light source device having a light diffusing plate and satisfying the following formula (1).

[In the above formula (1), D1 is half the length of the long side of the unit cell of the rectangular cell. D2 is half the length of the diagonal of the unit cell of the rectangular lattice. P is the distance between the intersection point of the light diffusion plate of the light beam emitted from the light emission center of the light emitting element at the light emission angle θ1B corresponding to the second maximum value and the central axis. ]

  Moreover, the display apparatus which concerns on this invention has the surface light source device which concerns on this invention, and the to-be-irradiated member irradiated with the light radiate | emitted from the said surface light source device.

  The light flux controlling member according to the present invention can suppress the occurrence of bright portions on the irradiated surface even when arranged in a grid pattern. In addition, since the light emitting device, the surface light source device, and the display device according to the present invention have the light flux control member that can suppress the occurrence of bright portions on the irradiated surface, it is difficult for the bright portions to be generated on the irradiated surface.

1A to 1C are diagrams illustrating a configuration of a surface light source device described in Patent Document 1. FIG. 2A and 2B are diagrams showing a configuration of a surface light source device according to an embodiment of the present invention. 3A and 3B are cross-sectional views of a surface light source device according to an embodiment of the present invention. FIG. 4 is a partially enlarged cross-sectional view of the surface light source device according to the embodiment of the present invention. 5A to 5C are diagrams showing a configuration of a light flux controlling member according to an embodiment of the present invention. 6A and 6B are optical path diagrams in the light emitting device. FIG. 7 is a diagram for explaining the emission angle and the emission angle. 8A and 8B are graphs for explaining how to obtain the first maximum value. 9A and 9B are graphs for explaining how to obtain the second maximum value. FIG. 10 is a diagram for explaining the expression (1). 11A and 11B are diagrams for explaining the mitigation unit. 12A to 12C are diagrams for explaining the legs.

  Hereinafter, a light flux controlling member, a light emitting device, a surface light source device, and a display device according to the present invention will be described in detail with reference to the accompanying drawings. In the following description, as a representative example of the surface light source device of the present invention, a surface light source device in which light emitting devices are arranged in a lattice shape suitable for a backlight of a liquid crystal display device will be described.

(Configuration of surface light source device and light emitting device)
2-4 is a figure which shows the structure of the surface light source device 100 which concerns on one embodiment of this invention. 2A is a plan view of the surface light source device 100 according to an embodiment of the present invention, and FIG. 2B is a front view. 3A is a cross-sectional view taken along the line AA shown in FIG. 2B, and FIG. 3B is a cross-sectional view taken along the line BB shown in FIG. 2A. FIG. 4 is a partially enlarged cross-sectional view of the surface light source device 100.

  As shown in FIGS. 2A, B, 3A, B, and 4, the surface light source device 100 includes a housing 110, a plurality of light emitting devices 200, and a light diffusion plate (irradiated surface) 120. The surface light source device 100 of the present invention can be applied to a backlight of a liquid crystal display device. Moreover, as shown in FIG. 2B, the surface light source device 100 is combined with a display member (irradiated member) 107 such as a liquid crystal panel (indicated by a dotted line in FIG. 2B), so that the display device 100 ′ can be used. Can be used. The plurality of light emitting devices 200 are arranged in a grid pattern (in this embodiment, a square grid pattern) 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 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. In the present embodiment, the plurality of light emitting devices 200 are arranged so that the light emission centers (light emitting surfaces) of the light emitting elements 220 are positioned in a square lattice pattern. Each of the plurality of light emitting devices 200 includes 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. The light emitting element 220 is disposed such that the light emission center thereof is located on the central axis CA.

  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 210. 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. 4). The light flux controlling member 300 is arranged such that the light emission center (light emission surface) of the light emitting element 220 is positioned at the center of curvature with respect to the vicinity of the top of the incident surface 320 described later in the direction along the optical axis OA of the light emitting element 220. (See FIG. 4). Note that an incident surface 320 and an output surface 330 of a light flux controlling member 300 described later are rotationally symmetric (the incident surface 320 is circularly symmetric and the output surface 330 is four-fold symmetric), and this rotational axis is the optical axis OA of the light emitting element 220. Matches. 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, features that the light flux controlling member 300 should have will be described in detail separately.

  The light diffusing plate 120 is a plate-like member having light diffusibility, and allows light emitted from the light emitting device 200 to be diffused and transmitted. 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. As will be described later, the light distribution characteristics of the light flux controlling member 300 are different in the direction (X direction and Y direction) along the array grid of the light emitting device 200 and in the diagonal direction of the array grid. The inner surface of is illuminated substantially uniformly. Light that reaches the light diffusion plate 120 from each light flux controlling member 300 passes through the light diffusion plate 120 while being diffused. 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)
5A to 5C are diagrams showing a configuration of light flux controlling member 300 according to an embodiment of the present invention. 5A is a plan view of light flux controlling member 300, FIG. 5B is a bottom view, and FIG. 5C is a cross-sectional view taken along line AA shown in FIG. 5A.

  As shown in FIGS. 5A to 5C, the light flux controlling member 300 has an incident surface 320 that is an inner surface of the recess 310 and an output surface 330. The light flux controlling member 300 forms a flange for facilitating the handling of the light flux controlling member 300 and a gap for releasing heat generated from the light emitting element 220 to the outside, and the light flux controlling member 300 is attached to the substrate 210. May be provided with leg portions (both not shown) for positioning and fixing. The planar view shape of light flux controlling member 300 in the present embodiment is an approximately square shape with an R chamfer.

  The 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 optical axis OA of the light emitting element 220) (see FIG. 4). The inner surface of the recess 310 functions as the incident surface 320. That is, the incident surface 320 is disposed so as to intersect the central axis CA (optical axis OA). 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 in the present embodiment) with the central axis CA as a rotational axis.

  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 recess 310.

  The exit surface 330 is disposed on the front side (light diffusion plate 120 side) of the light flux controlling member 300. 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 (four-fold symmetry in the present embodiment) with the central axis CA as a rotational axis.

  The emission surface 330 has a first emission surface 330a located in a predetermined range centered on the central axis CA, and a second emission surface 330b formed continuously around the first emission surface 330a. The first emission surface 330a is a curved surface convex on the back side. The magnitude | size of the curvature of the 1st output surface 330a in a 1st cross section and the curvature of the 1st output surface 330a in a 2nd cross section is not specifically limited. In the present embodiment, the curvature of the first emission surface 330a in the first cross section and the curvature of the first emission surface 330a in the second cross section are the same. Here, the “first cross section” is a cross section including the central axis CA and a point closest to the central axis CA among the outer edges of the emission surface 330, and refers to a cross section taken along line AA in FIG. 5A. The “second cross section” is a cross section including the central axis CA and a point farthest from the central axis CA among the outer edges of the emission surface 330. In the present embodiment, the “second cross section” is a cross section obtained by rotating the first cross section by 45 ° about the central axis CA, and is a cross section taken along line BB in FIG. 5A.

  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. Moreover, in this Embodiment, the curvature of the 2nd output surface 330b in a 1st cross section differs from the curvature of the 2nd output surface 330b in a 2nd cross section. In the cross section including the central axis CA, the second outgoing surface 330b has an overhang portion 330c at a position farthest from the central axis. Here, the “overhang portion” means that the outer end portion of the second exit surface 330b is further in the direction perpendicular to the central axis CA than the lower end portion of the second exit surface 330b in the direction along the central axis CA. The part that protrudes outward. In the present embodiment, since the second emission surface 330b includes the overhang portion 330c, light having a large angle with respect to the optical axis OA out of the light emitted from the light emitting element 220 is also effectively used. It is controlled so that it can be used as light for illuminating the irradiation surface.

(Light distribution characteristics of light-emitting device)
6A and 6B are optical path diagrams in the light emitting device 200. FIG. 6A shows an optical path diagram of the light emitting device 200 in the first cross section, and FIG. 6B shows an optical path diagram of the light emitting device 200 in the second cross section. In FIGS. 6A and 6B, hatching to the light emitting element 220 and the light flux controlling member 300 is omitted to show the optical path. 6A and 6B, the light beam indicating the optical path indicates each light beam having an emission angle of 0 ° to 80 ° in increments of 5 °. Further, in FIGS. 6A and 6B, the light diffusing plate 120 is illustrated in order to show the irradiated region of the light emitting device 200.

  As shown in FIGS. 6A and 6B, in the first cross section and the second cross section, the light emitted from the light emitting element 220 and having a relatively small emission angle is spread and irradiated on the light diffusion plate 120. Control is performed so as to go to the central portion of the region (region in the vicinity of the central axis CA of the light flux controlling member 300). Thereby, the light emitted from the light emitting device 200 uniformly irradiates the central portion of the irradiated surface without creating an excessively bright portion in the central portion of the irradiated surface. On the other hand, light with a large emission angle emitted from the light emitting element 220 is controlled to be directed toward the end of the irradiated region while being condensed. Thereby, the light emitted from the light emitting device 220 is applied to the end of the irradiated region to be illuminated by the emitted light per lamp, and the irradiated region and the end by the emitted light of the adjacent light emitting device 220 empty. When the images overlap, the brightness is controlled so as to be approximately the same as the central portion of the irradiated region.

  With respect to a more specific shape of the light flux controlling member 300, the light flux controlling member 300 has the aforementioned incident surface 320, the aforementioned exit surface 330 including the aforementioned first exit surface 330a and the aforementioned second exit surface 330b. In addition, it is necessary that the first maximum value obtained by “how to obtain the first maximum value” is less than the second maximum value obtained by “how to obtain the second maximum value”.

  Here, “how to obtain the first maximum value” and “how to obtain the second maximum value” will be described. FIG. 7 is a diagram for explaining the emission angle and the emission angle. FIG. 7 shows an optical path in the first cross section. As shown in FIG. 7, in the first cross section including the central axis CA of the light flux controlling member 300 and the point closest to the central axis CA among the outer edges of the emission surface 330, an arbitrary light beam L emitted from the emission center. The angle with respect to the central axis CA in the traveling direction between the light emission center and the incident surface 320 is “light emission angle θ1A”, and the central axis in the traveling direction between the emission surface 330 of the arbitrary light L and the irradiated surface 107. The angle with respect to CA is defined as “exit angle θ3A”. In the present embodiment, the “first cross section” is a cross section taken along line AA shown in FIG. 5A. The first cross section is also a cross section including the central axis CA and a straight line connecting two adjacent light emission centers on the lattice line.

  Similarly, although not shown, any light beam emitted from the emission center in the second cross section including the central axis CA of the light flux controlling member 300 and a point farthest from the central axis CA among the outer edges of the emission surface 330. The angle with respect to the central axis CA in the traveling direction between the L emission center and the incident surface 320 is “emission angle θ1B”, and the center in the traveling direction between the emission surface 330 of the arbitrary light L and the irradiated surface 107. The angle with respect to the axis CA is defined as “exit angle θ3B”. In the present embodiment, the “second cross section” is a cross section taken along line BB shown in FIG. 5A. The second cross section is also a cross section including the central axis CA and a straight line connecting two adjacent emission centers on the diagonal of the unit cell.

  8A and 8B are graphs for explaining how to obtain the first maximum value. 8A is a graph showing a first polynomial approximation function C1 showing the relationship between the light emission angle θ1A of the light emitted from the light emission center of the light emitting element 220 and the light emission angle θ3A, and FIG. 8B shows the first polynomial. It is a graph which shows 1st curve C1 'corresponding to the 1st derivative of the approximate function C1. The horizontal axis in FIG. 8A indicates the light emission angle θ1A (°), and the vertical axis indicates the emission angle θ3A (°). Further, the horizontal axis of FIG. 8B indicates the light emission angle θ1A (°), and the vertical axis indicates the first-order differential value of the emission angle θ3A (°).

  9A and 9B are graphs for explaining how to obtain the second maximum value. FIG. 9A is a graph showing a first polynomial approximation function C2 showing the relationship between the emission angle θ1B of the light beam emitted from the light emission center of the light emitting element 220 and the emission angle θ3B of the light beam, and FIG. 9B shows the first polynomial function. It is a graph which shows 1st curve C2 'corresponding to the 1st derivative of approximate function C2. The horizontal axis in FIG. 9A indicates the light emission angle θ1B (°), and the vertical axis indicates the emission angle θ3B (°). Further, the horizontal axis of FIG. 9B indicates the light emission angle θ1B (°), and the vertical axis indicates the first-order differential value of the emission angle θ3B (°).

  The method for obtaining the first maximum value is as follows.

  (1) In the first cross section, a first polynomial approximation function C1 representing the relationship between the emission angle θ1A of an arbitrary light beam L emitted from the light emission center and the output angle θ3A of the arbitrary light beam L is obtained (see FIG. 8A). ).

  (2) Obtain a first curve C1 'corresponding to the first derivative of the first polynomial approximation function (see FIG. 8B).

  (3) When the light emission angle θ1A exceeds 40 °, the maximum value in the first curve C1 ′ is set as the first maximum value (see FIG. 8B).

  In the present embodiment, the first maximum value that can be obtained as described above is about 0.5, and the light emission angle θ1A at that time is 40 ° (see FIG. 8B).

  The method for obtaining the second maximum value is as follows.

  (1) In the second cross section, a second polynomial approximation function C2 representing the relationship between the emission angle θ1B of an arbitrary ray emitted from the emission center and the emission angle θ3B of the arbitrary ray is obtained (see FIG. 9A).

  (2) Obtain a second curve C2 'corresponding to the first derivative of the second polynomial approximation function (see FIG. 9A).

  (3) When θ1A exceeds 40 °, the maximum value in the second curve C2 ′ is set as the second maximum value (see FIG. 9A).

  In the present embodiment, the second maximum value that can be obtained as described above is about 1.2, and θ2A at that time is about 76 ° (see FIG. 9B).

  Thus, “the second maximum value is greater than the first maximum value” means that the back surface of the light diffusing plate 120 (irradiated) is greater in the direction of the BB line than in the direction of the AA line in FIG. 5A. It shows that the local change degree of light and dark in the surface 107) is large. This is related to being designed to suppress excessive light irradiation to the irradiation areas at the four corners of the irradiation area on the back surface (irradiated surface 107) of the light diffusion plate 120, as will be described later. .

  Next, the position of the edge part of the irradiation area | region in the back surface (irradiation surface 107) of the light diffusing plate 120 about a 1st cross section and a 2nd cross section is demonstrated. FIG. 10 is a diagram for explaining the position of the end of the irradiation region on the back surface (irradiated surface 107) of the light diffusing plate 120. FIG. In FIG. 10, an irradiation area when the surface light source device 100 using the light flux controlling member 300 is viewed from the light diffusing plate 120 side is indicated by a broken line.

  As shown in FIG. 10, in the present embodiment, the light emitting device 200 is arranged so that the light emission centers of the light emitting elements 220 are positioned in a square lattice pattern. Thus, when the light emitting device 200 is arranged so that the light emission center of the light emitting element 220 has a square lattice shape, the substantially square light flux controlling member 300 having a chamfered shape in plan view corresponds to the square lattice. , “First cross section” (cross section taken along line AA in FIG. 5A) is along the side of the unit lattice of the square lattice, and “second cross section” (cross section taken along line BB in FIG. 5A) is the unit lattice of the square lattice. It arrange | positions along the diagonal line of.

In this case, light flux controlling member 300 (light emitting device 200) according to the present embodiment satisfies the following expression.

  As shown in FIG. 10, in the formula (1), D1 is half the length of a straight line connecting two adjacent emission centers on the side of the unit lattice of the square lattice (one side of the unit lattice of the square lattice). Half the length). D2 is the length of half of the straight line connecting two adjacent emission centers on the diagonal of the unit lattice of the square lattice (half the length of the diagonal of the unit lattice of the square lattice). Further, P is the distance between the intersection point on the back surface of the light diffusion plate 120 of the light beam emitted from the light emitting element 220 at the light emission angle θ1B corresponding to the second maximum value, and the central axis CA. As shown in FIG. 10, P specifies the position of the end of the irradiation region by the light flux controlling member 300 (light emitting device 200) in the diagonal direction of the unit lattice of the square lattice. The distance p between the intersection point on the back surface of the light diffusing plate 120 emitted from the light emitting element 220 at the light emission angle θ1A corresponding to the first maximum value and the central axis is substantially the same as or shorter than D1. Set to

  When the light emitting device 200 is arranged so that the light emission centers of the light emitting elements 220 are arranged in a square lattice shape, the inventor of the light flux controlling member 300 satisfies the above formula (1) (particularly the second emission surface). It has been found that by adjusting the shape of the surface 330b), it is possible to suppress the occurrence of bright portions on the back surface (irradiated surface 107) of the light diffusion plate 120. This is because the luminance of the four corners of the substantially square irradiation region formed by one light emitting device 200 is lower than the luminance of the other portions, so that the four irradiation regions overlap in the vicinity of the central portion of the unit cell. It is guessed that the bright part is hard to occur.

(effect)
As described above, the light flux controlling member 300 according to the present embodiment has the second maximum value larger than the first maximum value, so even if it is arranged in a lattice shape, the bright portion on the irradiated surface Generation can be suppressed. Further, in the light emitting device, the surface light source device, and the display device having the light flux controlling member 300, the occurrence of bright portions can be suppressed.

  Note that although the case where the light emission center of the light emitting element 220 is arranged to be a square lattice has been described in this embodiment mode, the present invention is not limited thereto, and the light emission center of the light emitting element 220 is a rectangular lattice. It may be arranged. In the case of a rectangular lattice, P is designed to be shorter than the half length of the diagonal of the unit lattice and to be longer than the half length of the long side of the unit lattice.

  Further, the bottom plate 112 may have a relaxation portion for further relaxing (suppressing) the occurrence of the bright portion. FIG. 11A is a diagram for explaining the relaxation unit 411A, and FIG. 11B is a diagram for explaining another relaxation unit 411B. In FIGS. 11A and 11B, the light emitting element 220 is illustrated by a dotted line in order to clarify the positions of the relaxing portions 411A and 411B.

  Part of the light emitted from the light emitting element 220 is controlled by the light flux controlling member 300 and reaches the irradiated surface. In addition, some of the light emitted from the light emitting element 220 is controlled by the light flux controlling member 300 to reach the surface of the bottom plate 112. The light that reaches the surface of the bottom plate 112 is reflected toward the irradiated surface. As described above, part of the light reaching the irradiated surface is reflected by the bottom plate 112. Therefore, if the amount of light reflected by the bottom plate 112 is reduced, generation of bright portions on the irradiated surface is prevented. Further suppression is possible. Accordingly, the relaxing portions 411A and 411B are formed in at least a partial region of the bottom plate 112 that reflects light that can be a bright portion on the irradiated surface. As shown in FIGS. 11A and 11B, in the present embodiment, relaxing portions 411A and 411B are formed in the vicinity of the intersection of diagonal lines of the unit cell. The configurations of the relaxing portions 411A and 411B can be appropriately designed within a range in which reflection of light reaching the surface of the bottom plate 112 can be suppressed. As shown in FIG. 11A, the relaxing portion 411A may be a black printed portion that does not reflect light. Moreover, as shown in FIG. 11B, the relaxing part 411B may be configured by cutting out a region where a bright part is generated.

  Further, as described above, the light flux controlling member 300 may have legs for positioning and fixing to the substrate 210. 12A to 12C are bottom views of the light flux controlling member 300 according to the modification. 12A is a bottom view of the light flux controlling member 300 according to the first modification, FIG. 12B is a bottom view of the light flux controlling member 300 according to the second modification, and FIG. 12C is a light flux controlling member according to the third modification. FIG.

  The shapes of the leg portions 421A, 421B, and 421C can be appropriately selected within a range in which the above functions can be exhibited. For example, the shape of the leg portions 421A, 421B, and 421C may be cylindrical or prismatic. In the present embodiment, the shapes of the leg portions 421A of the light flux controlling member 300 according to Modification 1 and the legs 421B of the light flux controlling member 300 according to Modification 2 are both cylindrical. Further, the leg portion 421C of the light flux controlling member 300 according to the modification 3 has a prismatic shape. In these cases, the leg portions 421A, 421B, and 421C are bonded to the substrate 210 with an adhesive or the like. As shown in FIG. 12A, three leg portions 421 </ b> A may be arranged on the back surface 305 so as to surround the incident surface 320. Further, as shown in FIG. 12B, four leg portions 421 </ b> B may be arranged on the back surface 305 so as to surround the incident surface 320. Furthermore, as shown in FIG. 12C, two may be arranged so as to sandwich the incident surface 320. As shown in FIG. 12B, when four leg portions 412B are arranged on the light flux controlling member 300, only three leg portions 412B of the four leg portions 412B may be bonded. Thus, by having the leg portions 421A, 421B, and 421C, it is possible to prevent an error in the mounting direction of the light flux controlling member 300 with respect to the substrate 210. Also, as shown in FIGS. 12B and 12C, in the light flux control member 300 arranged so that the legs 421B and 421C are rotationally symmetric with respect to the central axis CA of the light flux control member 300, the mounting direction is determined. It can be changed for each light emitting device 200. Thereby, since the gate position of the several light-emitting device 200 used for the surface light source device 100 can be arrange | positioned at random, generation | occurrence | production of the brightness nonuniformity by the gate at the time of injection molding can be suppressed.

  The light flux controlling member, 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 illumination.

DESCRIPTION OF SYMBOLS 10 Surface light source device 20 Printed wiring board 30 Light emitting device 35 Light emitting element 40 Light guide member 41 Lens part 42 Gutter part 43 Recessed part 44 Incident surface 45 Outgoing surface 46 Plane 47 Curved surface 100 Surface light source device 100 'Display device 107 Irradiated surface 110 Housing Body 112 Bottom plate 114 Top plate 120 Light diffusing plate 200 Light emitting device 210 Substrate 220 Light emitting element 300 Light flux controlling member 305 Back surface 310 Recessed portion 320 Incident surface 330 Ejecting surface 330a First emitting surface 330b Second emitting surface 330c Overhang portions 411A and 411B Relaxation 421A, 421B, 421C Leg CA Central axis of light flux controlling member OA Optical axis of light emitting element

Claims (4)

A light flux controlling member for controlling the light distribution of the light emitted from the light emitting element,
An incident surface that is an inner surface of a recess formed on the back side so as to intersect with the central axis of the light flux controlling member;
An exit surface disposed on the opposite side of the entrance surface;
Have
The exit surface is disposed so as to intersect with the central axis, the first exit surface is convex toward the back side, and the second exit is disposed so as to surround the first exit surface and is convex toward the front side. And including a surface,
When the light emitting element is disposed so as to face the concave portion so that the light emission center is located on the central axis, and the irradiated surface is disposed above the emission surface so as to be orthogonal to the central axis. The second maximum value obtained by the following “how to obtain the second maximum value” is larger than the first maximum value obtained by the following “how to obtain the first maximum value”.
Luminous flux control member.
[How to find the first maximum value]
(1) In the first cross section including the central axis and a point closest to the central axis among the outer edges of the emission surface, the emission center of the arbitrary light beam emitted from the emission center and the incident surface Between the emission angle θ1A, which is the angle of the traveling direction in relation to the central axis, and the emission angle θ3A, which is the angle of the arbitrary light ray between the emitting surface and the irradiated surface, relative to the central axis A first polynomial approximation function representing is obtained.
(2) Find a first curve corresponding to the first derivative of the first polynomial approximation function.
(3) When the light emission angle θ1A exceeds 40 °, the maximum value in the first curve is set as the first maximum value.
[How to find the second maximum]
(1) In a second cross section including the central axis and a point farthest from the central axis among the outer edges of the emission surface, between the emission center and the incident surface of an arbitrary ray emitted from the emission center Between the emission angle θ1B, which is the angle of the traveling direction between the light emitting surface and the central axis, and the emission angle θ3B, which is the angle of the arbitrary light beam between the emitting surface and the irradiated surface, with respect to the central axis A second polynomial approximation function representing is obtained.
(2) A second curve corresponding to the first derivative of the second polynomial approximation function is obtained.
(3) When the light emission angle θ1B exceeds 40 °, the maximum value in the second curve is set as the second maximum value. A light emitting element;
The light flux controlling member according to claim 1,
Light emitting device. A plurality of light emitting devices according to claim 2, wherein the light emitting centers of the light emitting elements are arranged so as to form a rectangular lattice.
A light diffusing plate that diffuses and transmits light from the plurality of light emitting devices;
Have
The following formula (1) is satisfied.
Surface light source device.

[In the above formula (1), D1 is half the length of the long side of the unit cell of the rectangular cell. D2 is half the length of the diagonal of the unit cell of the rectangular lattice. P is the distance between the intersection point of the light diffusion plate of the light beam emitted from the light emission center of the light emitting element at the light emission angle θ1B corresponding to the second maximum value and the central axis. ] A surface light source device according to claim 3,
A member to be irradiated with light emitted from the surface light source device;
A display device.

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