CN107781721B

CN107781721B - Light flux controlling member, light emitting device, surface light source device, and display device

Info

Publication number: CN107781721B
Application number: CN201611127097.8A
Authority: CN
Inventors: 平加健介
Original assignee: Enplas Corp
Current assignee: Enplas Corp
Priority date: 2016-08-30
Filing date: 2016-12-09
Publication date: 2020-04-24
Anticipated expiration: 2036-12-09
Also published as: JP2018036407A; CN107781721A; CN207349871U

Abstract

The invention relates to a light flux controlling member, a light emitting device, a surface light source device and a display device. The light flux controlling member of the present invention controls light distribution of light emitted from a light emitting element, and includes: an incident surface that is an inner surface of a concave portion formed on a back surface side so as to intersect a central axis of the light flux controlling member; and an emission surface disposed on the opposite side of the incident surface. The exit surface includes: a first emission surface which is disposed so as to intersect the central axis and which is convex toward the rear surface side; and a second emission surface which is disposed so as to surround the first emission surface and is convex toward the front surface side. When the light emitting element is disposed so as to face the recess such that the light emission center is located on the central axis, and the surface to be irradiated is disposed above the emission surface so as to be orthogonal to the central axis, the second maximum value calculated by the predetermined expression is larger than the first maximum value calculated by the predetermined expression.

Description

Light flux controlling member, light emitting device, surface light source device, and display device

Technical Field

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

Background

In recent years, light emitting diodes (hereinafter, referred to as "LEDs") have been used as light sources for illumination from the viewpoint of energy saving and downsizing. Light emitting devices that combine LEDs and a light flux controlling member that controls the distribution of light emitted from the LEDs are being used instead of fluorescent lamps, halogen lamps, and the like. In a transmissive image display device such as a liquid crystal display device, a direct-type surface light source device having a light emitting device mounted in a grid pattern is used as a backlight (see, for example, patent document 1).

Fig. 1A to 1C are diagrams illustrating a structure of a surface light source device 10 described in patent document 1. Fig. 1A is a schematic plan view of a surface light source device 10, fig. 1B is a plan view of a light emitting device 30 in the surface light source device 10, and fig. 1C is a cross-sectional view taken along line a-a shown in fig. 1B. The dotted line in fig. 1A schematically shows the irradiation range of light emitted from the light-emitting device 30.

As shown in fig. 1A to 1C, the surface light source device 10 described in patent document 1 includes a printed circuit board 20 and a plurality of light emitting devices 30 arranged in a rectangular grid pattern on the printed circuit board 20. Each of the plurality of light emitting devices 30 includes 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 rear surface side and an emission surface 45 disposed on the front surface side. The emission surface 45 includes two flat surfaces 46 parallel to the central axis CA and a curved surface 47 disposed between the two flat surfaces 46 and having an upward convex shape. In the surface light source device 10 described in patent document 1, the light emitted from the light emitting elements 35 is controlled by the light guide member 40 to be diffused in a direction in which the intervals between the plurality of light emitting devices 30 are longer (the longitudinal direction of the rectangular grid; the X direction) than in a direction in which the intervals between the plurality of light emitting devices 30 are shorter (the short side direction of the rectangular grid; the Y direction). Therefore, in the surface light source device described in patent document 1, even when the plurality of light emitting devices 30 are arranged in a rectangular grid pattern, the surface to be irradiated can be uniformly irradiated.

Documents of the prior art

International publication No. 2009-157166 of patent document 1

Disclosure of Invention

Problems to be solved by the invention

However, in the surface light source device 10 described in patent document 1, the light emitted from the plane 46 is controlled to be condensed. On the other hand, the light emitted from the curved surface 47 is controlled to be diffused. Thus, the light emitted from the flat surface 46 and the light emitted from the curved surface 47 easily intersect on the optical path reaching the surface to be irradiated. Therefore, a bright portion may be generated on the irradiated surface.

It is an object of the present invention to provide a light flux controlling member capable of suppressing the occurrence of an exposed portion on an irradiated surface even when 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 each having the light flux controlling member.

Means for solving the problems

In order to achieve the above object, a light flux controlling member of the present invention controls light distribution of light emitted from a light emitting element, and includes: an incident surface that is an inner surface of a concave portion formed on a back surface side so as to intersect a central axis of the light flux controlling member; and an emission surface disposed on an opposite side of the incident surface, the emission surface including: a first emission surface which is disposed so as to intersect the central axis and which is convex toward the rear surface side; and a second emission surface which is disposed so as to surround the first emission surface and which is convex toward the front side, wherein when the light emitting element is disposed so as to face the concave portion such that the light emission center thereof is positioned on the central axis and the surface to be irradiated is disposed above the emission surface so as to be orthogonal to the central axis, a second maximum value obtained by a "second maximum value calculation method" described below is larger than a first maximum value obtained by a "first maximum value calculation method" described below,

the calculation method of the first maximum value comprises the following steps:

(1) obtaining a first polynomial approximation function representing a relationship between a light emission angle θ 1A and an emission angle θ 3A, the light emission angle θ 1A being an angle of a traveling direction of an arbitrary light ray emitted from the light emission center between the light emission center and the incident surface with respect to the central axis in a first cross section including the central axis and a point of an outer edge of the emission surface closest to the central axis, the emission angle θ 3A being an angle of the traveling direction of the arbitrary light ray between the emission surface and the irradiated surface with respect to the central axis,

(2) finding a first curve corresponding to a first order differential of the first polynomial approximation function,

(3) taking the maximum value in the first curve as a first maximum value when the light emitting angle theta 1A is larger than 40 degrees;

the calculation method of the second maximum value includes the steps of:

(1) obtaining a second polynomial approximation function representing a relationship between a light emission angle θ 1B and an emission angle θ 3B, the light emission angle θ 1B being an angle of a traveling direction of an arbitrary light ray emitted from the light emission center between the light emission center and the incident surface with respect to the central axis in a second cross section including the central axis and a point of the outer edge of the emission surface farthest from the central axis, the emission angle θ 3B being an angle of the traveling direction of the arbitrary light ray between the emission surface and the irradiated surface with respect to the central axis,

(2) calculating a second curve corresponding to a first order differential of the second polynomial approximation function,

(3) in the case where the light emission angle θ 1B is greater than 40 °, the maximum value in the second curve is taken as the second maximum value.

In order to achieve the above object, a light flux controlling member of the present invention controls light distribution of light emitted from a light emitting element, and includes: an incident surface that is an inner surface of a concave portion formed on a back surface side so as to intersect a central axis of the light flux controlling member; and an emission surface disposed on an opposite side of the incident surface, the emission surface including: a first emission surface which is disposed so as to intersect the central axis and which is convex toward the rear surface side; and a second emission surface which is disposed so as to surround the first emission surface and which is convex toward the front side, and which satisfies the following expression (2) when the light emitting element is disposed so as to face the concave portion such that the light emission center thereof is positioned on the central axis and the surface to be irradiated is disposed above the emission surface so as to be orthogonal to the central axis,

in the above equation (2), D1 is a first arrival distance obtained by the following equation (3) that is a distance from the central axis to an arrival point on the surface to be irradiated of a first light beam emitted from the light emission center at a first light emission angle in a first cross section including the central axis and a point of the outer edge of the emission surface closest to the central axis, D2 is a second arrival distance obtained by the following equation (4) that is a distance from the central axis to an arrival point on the surface to be irradiated of a second light beam emitted from the light emission center at a second light emission angle in a second cross section including the central axis and a point of the outer edge of the emission surface farthest from the central axis, the first light emission angle being obtained by the following "method for calculating a first light emission angle", the second light emission angle being obtained by the following "method for calculating a second light emission angle",

d1 ═ h1atan θ 1a + h2atan θ 2a + h3atan θ 3a formula (3)

In the above equation (3), h1a is a distance in the direction along the central axis between the light emission center and a first incident position that is an incident point of the first light ray on the incident surface in the first cross section, h2a is a distance in the direction along the central axis between the first incident position and a first exit position that is an exit point of the first light ray on the exit surface in the first cross section, h3a is a distance in the direction along the central axis between the first exit position and a first irradiated position that is an arrival point of the first light ray on the irradiated surface in the first cross section, and θ 1a is the first light emission angle that is an angle of the traveling direction of the first light ray between the light emission center and the incident surface with respect to the central axis in the first cross section, θ 2a is an angle of the traveling direction of the first light ray between the incident surface and the exit surface with respect to the central axis in the first cross section, and θ 3a is an angle of the traveling direction of the first light ray between the exit surface and the surface to be irradiated with respect to the central axis in the first cross section,

d2 ═ h1btan θ 1b + h2btan θ 2b + h3btan θ 3b formula (4)

In the above equation (4), h1b is a distance in the direction along the central axis between the light emission center and a second incident position that is an incident point of the second light ray on the incident surface in the second cross section, h2b is a distance in the direction along the central axis between the second incident position and a second exit position that is an exit point of the second light ray on the exit surface in the second cross section, h3b is a distance in the direction along the central axis between the second exit position and a second irradiated position that is an arrival point of the second light ray on the irradiated surface in the second cross section, and θ 1b is the second light emission angle that is an angle of the traveling direction of the second light ray between the light emission center and the incident surface with respect to the central axis in the second cross section, θ 2b is an angle of the traveling direction of the second light beam between the incident surface and the exit surface with respect to the central axis in the second cross section, and θ 3b is an angle of the traveling direction of the second light beam between the exit surface and the irradiated surface with respect to the central axis in the second cross section,

the method for calculating the first light-emitting angle comprises the following steps:

(1) obtaining a first polynomial approximation function representing a relationship between a light emission angle θ 1A and an emission angle θ 3A, the light emission angle θ 1A being an angle of a traveling direction of an arbitrary light ray emitted from the light emission center between the light emission center and the incident surface with respect to the central axis in the first cross section, the emission angle θ 3A being an angle of the traveling direction of the arbitrary light ray between the emission surface and the irradiated surface with respect to the central axis,

(3) obtaining a base point of 1 or 2 or more where the slope of the first curve changes from negative to positive and a top point of 1 or 2 or more where the slope of the first curve changes from positive to negative,

(4) for each of the 1 or 2 or more base points, a vertex is determined from the 1 or 2 or more vertices, and the light emission angle theta 1A of the vertex is larger than the light emission angle theta 1A of the base point and is closest to the light emission angle theta 1A of the base point,

(5) determining a bottom point having a largest difference in differential value Δ θ 3A of the emission angle θ 3A from the 1 or 2 or more bottom points and the corresponding vertex, and setting the light emission angle θ 1A of the determined bottom point as the first light emission angle θ 1A;

the method for calculating the second light-emitting angle comprises the following steps:

(1) obtaining a second polynomial approximation function representing a relationship between a light emission angle θ 1B and an emission angle θ 3B, the light emission angle θ 1B being an angle of a traveling direction of an arbitrary light ray emitted from the light emission center between the light emission center and the incident surface with respect to the central axis in the second cross section, the emission angle θ 3B being an angle of the traveling direction of the arbitrary light ray between the emission surface and the irradiated surface with respect to the central axis,

(2) finding a second curve corresponding to a first order differential of the second polynomial approximation function,

(3) obtaining a base point of 1 or 2 or more where the slope of the second curve changes from negative to positive and a top point of 1 or 2 or more where the slope of the second curve changes from positive to negative,

(4) for each of the 1 or 2 or more base points, a vertex is determined from the 1 or 2 or more vertices, and the light emission angle theta 1B of the vertex is larger than the light emission angle theta 1B of the base point and is closest to the light emission angle theta 1B of the base point,

(5) and determining a bottom point having a largest difference in differential value Δ θ 3B of the emission angle θ 3B from the corresponding vertex among the bottom points of 1 or 2 or more, and setting the light emission angle θ 1B of the determined bottom point as the second light emission angle θ 1B.

In order to achieve the above object, a light emitting device of the present invention includes a light emitting element; and the light flux controlling member.

In addition, in order to achieve the above object, a surface light source device of the present invention includes the light emitting device of the present invention; and a light diffusion plate diffusing and transmitting light from the light emitting device.

In order to achieve the above object, a surface light source device of the present invention includes a plurality of light emitting devices of the present invention arranged such that the light emission centers of the light emitting elements are in a rectangular grid shape; and a light diffusion plate which diffuses and transmits light from the plurality of light emitting devices, the surface light source device satisfying the following formula (1),

d1 < P < D2 formula (1)

In the above equation (1), D1 is a half of a length of a long side of a unit cell of the rectangular mesh, D2 is a half of a length of a diagonal line of the unit cell of the rectangular mesh, and P is a distance between an intersection point of light rays emitted from the light emission center of the light emitting element at the light emission angle θ 1B corresponding to the second maximum value on the light diffusion plate and the central axis.

In order to achieve the above object, a display device of the present invention includes the surface light source device of the present invention; and an irradiated member irradiated with the light emitted from the surface light source device.

Effects of the invention

The light flux controlling member of the present invention can suppress the occurrence of a bright portion on an irradiated surface even if the light flux controlling member is arranged in a grid shape. Further, since the light emitting device, the surface light source device, and the display device of the present invention have the light flux controlling member that suppresses the occurrence of the bright portion on the irradiated surface, it is difficult to generate the bright portion on the irradiated surface.

Drawings

Fig. 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 illustrating a configuration of a surface light source device according to an embodiment of the present invention.

Fig. 3A and 3B are sectional views of a surface light source device according to an embodiment of the present invention.

Fig. 4 is a partially enlarged sectional view of a surface light source device according to an embodiment of the present invention.

Fig. 5A to 5C are diagrams showing the configuration of a light flux controlling member according to an embodiment of the present invention.

Fig. 6A and 6B are optical path diagrams in the light-emitting device.

Fig. 7 is a diagram for explaining a light emission angle and an emission angle.

Fig. 8A and 8B are graphs for explaining a method of calculating the first maximum value.

Fig. 9A and 9B are graphs for explaining a method of calculating the second maximum value.

Fig. 10 is a diagram for explaining the formula (1).

Fig. 11A and 11B are views for explaining the relief portion.

Fig. 12A to 12C are views for explaining the leg.

Fig. 13A and 13B are diagrams for explaining the expressions (2) to (4).

Fig. 14A and 14B are graphs for explaining a method of calculating the first light emission angle.

Fig. 15A and 15B are graphs for explaining a method of calculating the second light emission angle.

Fig. 16 is a graph showing the measurement result of the luminance in the surface light source device.

Fig. 17A and 17B are diagrams showing simulation results of luminance in the surface light source device.

Description of the reference numerals

10 area light source device

20 printed circuit board

30 light emitting device

35 light emitting element

40 light guide member

41 lens part

42 flange part

43 recess

44 incident plane

45 exit surface

46 plane

47 curved surface

100 area light source device

100' display device

107 irradiated surface

110 casing

112 base plate

114 top plate

120 light diffusion plate

200 light emitting device

210 base plate

220 luminous element

300 light beam control component

305 back side

310 recess

320 incident plane

330 exit surface

330a first exit surface

330b second exit face

330c extension

411A, 411B relief portion

421A, 421B, 421C foot

Central axis of CA beam control unit

Optical axis of OA light emitting element

Detailed Description

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, a surface light source device in which light emitting devices are arranged in a grid pattern, which is suitable for a backlight of a liquid crystal display device or the like, will be described as a representative example of the surface light source device of the present invention.

(Structure of surface light Source device and light emitting device)

Fig. 2A to 4 are diagrams illustrating a configuration of a surface light source device 100 according to an embodiment of the present invention. Fig. 2A is a plan view of a surface light source device 100 according to an embodiment of the present invention, and fig. 2B is a front view. Fig. 3A is a sectional view taken along line a-a shown in fig. 2B, and fig. 3B is a sectional view taken along line B-B shown in fig. 2A. Fig. 4 is a partially enlarged sectional view of the surface light source device 100.

As shown in fig. 2A, 2B, 3A, 3B, 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 and the like. As shown in fig. 2B, the surface light source device 100 may be used as a display device 100' in combination with a display member (irradiation target member) 107 (shown by a broken line in fig. 2B) such as a liquid crystal panel. The plurality of light-emitting devices 200 are arranged in a grid pattern (in the present 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 diffusion plate 120 is disposed so as to cover the opening, and functions as a light emitting surface. The size of the light emitting face may be, for example, about 400mm by about 700 mm.

The plurality of light emitting devices 200 are arranged at regular intervals on the substrate 210. Each of the plurality of substrates 210 is fixed to a predetermined position on the bottom plate 112 of the housing 110. In the present embodiment, a plurality of light-emitting devices 200 are arranged such that the light-emission centers (light-emitting surfaces) of the light-emitting elements 220 are arranged in a square grid pattern. The plurality of light emitting devices 200 respectively 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, for example, 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.

Light flux controlling member 300 is a lens and is fixed to substrate 210. Light flux controlling member 300 controls the distribution of light emitted from light emitting element 220, and diffuses the traveling direction of the light in the surface direction of substrate 210. Light flux controlling member 300 is disposed on light emitting element 220 such that central axis CA thereof coincides with optical axis OA of light emitting element 220 (see fig. 4). Light flux controlling member 300 is arranged such that the light emission center (light emission surface) of light emitting element 220 is located at the center of curvature in the vicinity of the top with respect to incident surface 320 described below in the direction along optical axis OA of light emitting element 220 (see fig. 4). Incident surface 320 and emission surface 330 of light flux controlling member 300 described below are rotationally symmetric (incident surface 320 is circularly symmetric, emission surface 330 is quadratically symmetric), and the rotation axis coincides with optical axis OA of light emitting element 220. The rotation axes of incident surface 320 and emission surface 330 are referred to as "central axis CA of the light flux controlling member". The "optical axis OA of the light emitting element" is a central ray of the three-dimensional outgoing beam from the light emitting element 220.

Light flux controlling member 300 can be formed by integral molding. The material of light flux controlling member 300 may be any material that can pass light of a desired wavelength. For example, the material of light flux controlling member 300 is light transmissive resin such as polymethyl methacrylate (PMMA), Polycarbonate (PC), epoxy resin (EP), and silicone resin, or glass. The main feature of the surface light source device 100 of the present embodiment is the structure of the light flux controlling member 300. Accordingly, features of the beam control member 300 to be provided will be described in additional detail.

The light diffusion plate 120 is a plate-like member having light diffusion properties, and diffuses and transmits light emitted from the light emitting device 200. The light diffusion plate 120 is disposed substantially parallel to the substrate 210 above the plurality of light emitting devices 200. The light diffusion plate 120 is generally substantially the same size as the irradiated member such as a liquid crystal panel. For example, the light diffusion plate 120 is formed of a light transmissive resin such as polymethyl methacrylate (PMMA), Polycarbonate (PC), Polystyrene (PS), and styrene-methyl methacrylate copolymer resin (MS). In order to impart light diffusion properties to the light diffusion plate 120, fine irregularities are formed on the surface thereof, or light scattering bodies such as beads are dispersed inside the light diffusion plate 120.

In the surface light source device 100 of the present invention, the light emitted from each light emitting element 220 is diffused by the light flux controlling member 300 so as to irradiate the light diffusion plate 120 over a wide range. As described below, the light distribution characteristics of light flux controlling member 300 are different in the direction along the arrangement grid of light emitting device 200 (X direction and Y direction) and in the diagonal direction of the arrangement grid, and therefore the inner surface of light diffusion plate 120 is irradiated substantially uniformly. The light reaching the light diffusion plate 120 from each light flux controlling member 300 is diffused and transmitted through the light diffusion plate 120. As a result, the surface light source device 100 of the present invention can uniformly irradiate a planar member to be irradiated (for example, a liquid crystal panel).

(Structure of light flux controlling Member)

Fig. 5A to 5C are diagrams showing the configuration of light flux controlling member 300 according to an embodiment of the present invention. Fig. 5A is a top view, fig. 5B is a bottom view, and fig. 5C is a cross-sectional view taken along line a-a shown in fig. 5A of light flux controlling member 300.

As shown in fig. 5A to 5C, light flux controlling member 300 includes an incident surface 320, which is an inner surface of concave portion 310, and an exit surface 330. Light flux controlling member 300 may include a flange portion for facilitating the operation of light flux controlling member 300, and a leg portion (both not shown) for forming a gap for allowing heat emitted from light emitting element 220 to escape to the outside and positioning and fixing light flux controlling member 300 on substrate 210. Light flux controlling member 300 of the present embodiment has a substantially square shape chamfered by R in a plan view.

Concave portion 310 is disposed in the center of rear surface 305 so as to intersect with central axis CA of light flux controlling member 300 (optical axis OA of light emitting element 220) (see fig. 4). The inner surface of the recess 310 functions as an incident surface 320. That is, the incident surface 320 is disposed to intersect the central axis CA (optical axis OA). Incident surface 320 controls the traveling direction of most of the light emitted from light emitting element 220, and causes the light to enter light flux controlling member 300. Incident surface 320 intersects central axis CA of light flux controlling member 300, and is rotationally symmetric (circularly symmetric in the present embodiment) about central axis CA as a rotation axis.

Rear surface 305 is a flat surface located on the rear surface side of light flux controlling member 300 and extending in the radial direction from the opening edge of concave portion 310.

Emission surface 330 is disposed on the front surface side (light diffusion plate 120 side) of light flux controlling member 300. Emission surface 330 controls the traveling direction of light entering light flux controlling member 300 and emits the light to the outside. The emission surface 330 intersects the central axis CA and is rotationally symmetric (quadruplicate symmetric in the present embodiment) about the central axis CA as a rotation axis.

The emission surface 330 includes a first emission surface 330a located in a predetermined range around the central axis CA, and a second emission surface 330b continuously formed around the first emission surface 330 a. The first emission surface 330a is a curved surface convex toward the back surface side. The magnitude of the curvature of the first exit surface 330a in the first cross section and the curvature of the first exit surface 330a in the second cross section is not particularly limited. In the present embodiment, the curvature of the first emission surface 330a in the first cross section is the same as the curvature of the first emission surface 330a in the second cross section. 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 is a cross section along the line a-a in fig. 5A. The "second cross section" is a cross section including the center axis CA and the point of the outer edge of the emission surface 330 farthest from the center axis CA. 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 B-B in fig. 5A.

The second emission surface 330b is a smooth curved surface which is positioned around the first emission surface 330a and is convex toward the front side. In the present embodiment, the curvature of second emission surface 330b in the first cross section is different from the curvature of second emission surface 330b in the second cross section. The second emission surface 330b has an extension 330c at a position farthest from the central axis CA in a cross section including the central axis CA. Here, the "extending portion" refers to a portion in which the outer end of second emission surface 330b protrudes outward in the direction perpendicular to central axis CA than the lower end of second emission surface 330b in the direction along central axis CA. In the present embodiment, the second emission surface 330b has the extension 330c, and thereby control is performed such that: light having a large angle with respect to the optical axis OA among the light emitted from the light emitting element 220 can also be used as light for effectively illuminating the light diffusion plate 120 (the surface to be illuminated).

(light distribution characteristics of light emitting device)

Fig. 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 a first cross section, and fig. 6B shows an optical path diagram of the light-emitting device 200 in a second cross section. In fig. 6A and 6B, hatching of light emitting element 220 and light flux controlling member 300 is omitted to show the optical path. The light rays indicating the optical paths shown in fig. 6A and 6B indicate light rays each having an emission angle of 5 ° from 0 ° to 80 °. In fig. 6A and 6B, the light diffusion plate 120 is shown to show the irradiated region of the light emitting device 200.

As shown in fig. 6A and 6B, in the first cross section and the second cross section, the light emitted from light emitting element 220 at a relatively small emission angle is controlled to be diffused and directed toward the central portion of the irradiated region formed on light diffusion plate 120 (the region near central axis CA of light flux controlling member 300). Thus, the light emitted from the light emitting device 200 uniformly irradiates the central portion of the irradiated surface without causing an excessively bright portion in the central portion of the irradiated surface. On the other hand, the light emitted from the light emitting element 220 at a large emission angle is controlled to be focused and directed toward the end of the irradiation region. Thus, the light emitted from the light emitting device 220 is controlled to have the same brightness as the central portion of the irradiated region when the end portion of the irradiated region to be illuminated by the emission light from each lamp is irradiated and overlapped with the irradiated region of the emission light from the adjacent light emitting device 220.

Light flux controlling member 300 of the present embodiment can be determined from the following two viewpoints.

[ first viewpoint ]

In the first viewpoint, as for a more specific shape of light flux controlling member 300, light flux controlling member 300 includes: the incident surface 320; and the emission surface 330 including the first emission surface 330a and the second emission surface 330b, and it is necessary to make a first maximum value obtained by the "method of calculating a first maximum value" smaller than a second maximum value obtained by the "method of calculating a second maximum value".

Here, a description will be given of a "method of calculating the first maximum value" and a "method of calculating the second maximum value". Fig. 7 is a diagram for explaining a light emission angle and an emission angle. In fig. 7, the optical path in the first cross section is shown. As shown in fig. 7, in a first cross section including center axis CA of light flux controlling member 300 and a point closest to center axis CA among outer edges of emission surface 330, an angle of a traveling direction of arbitrary light ray L emitted from the emission center with respect to center axis CA is set to "emission angle θ 1A", an angle of a traveling direction of arbitrary light ray L between emission surface 330 and irradiation target surface 107 with respect to center axis CA is set to "emission angle θ 3A", and in the present embodiment, the "first cross section" is a cross section along line a-a shown in fig. 5A. The first cross section is a cross section including a straight line connecting the central axis CA and two adjacent light emission centers on the grid line.

Similarly, in a second cross section including the center axis CA of light flux controlling member 300 and the farthest point from center axis CA of the outer edge of emission surface 330, the angle of the traveling direction of arbitrary light ray L emitted from the light emission center with respect to center axis CA is defined as "emission angle θ 1B", and the angle of the traveling direction of arbitrary light ray L between emission surface 330 and irradiation target surface 107 with respect to center axis CA is defined as "emission angle θ 3B", which is not shown. In the present embodiment, the "second cross section" is a cross section taken along line B-B shown in fig. 5A. The second cross section is a cross section including a straight line connecting the central axis CA and two light emission centers adjacent on a diagonal line of the unit cell.

Fig. 8A and 8B are graphs for explaining a method of calculating the first maximum value. Fig. 8A is a graph of a first polynomial approximation function C1 showing a relationship between a light emission angle θ 1A of a light ray emitted from a light emission center of the light emitting element 220 and an emission angle θ 3A of the light ray, and fig. 8B is a graph of a first curve C1' corresponding to a first order differential of the first polynomial approximation function C1. In fig. 8A, the abscissa represents the light emission angle θ 1A (°), and the ordinate represents the light emission angle θ 3A (°). In fig. 8B, the abscissa indicates the light emission angle θ 1A (°), and the ordinate indicates the first-order differential value of the light emission angle θ 3A (°).

Fig. 9A and 9B are graphs for explaining a method of calculating the second maximum value. Fig. 9A is a graph of a first polynomial approximation function C2 showing a relationship between a light emission angle θ 1B of a light ray emitted from a light emission center of the light emitting element 220 and an emission angle θ 3B of the light ray, and fig. 9B is a graph of a first curve C2' corresponding to a first order differential of the first polynomial approximation function C2. In fig. 9A, the abscissa represents a light emission angle θ 1B (°), and the ordinate represents an emission angle θ 3B (°). In fig. 9B, the abscissa axis represents the light emission angle θ 1B (°), and the ordinate axis represents the first-order differential value of the light emission angle θ 3B (°).

The first maximum value is calculated as follows.

(1) A first polynomial approximation function C1 (see fig. 8A) showing the relationship between the emission angle θ 1A of an arbitrary light ray L emitted from the emission center and the emission angle θ 3A of the arbitrary light ray L in the first cross section is obtained.

(2) A first curve C1' corresponding to the first order differential of the first polynomial approximation function is obtained (see fig. 8B).

(3) When the light emission angle θ 1A is larger than 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 by the above method is about 0.5, and the light emission angle θ 1A at this time is 40 ° (see fig. 8B).

The second maximum value is calculated as follows.

(1) A second polynomial approximation function C2 (see fig. 9A) showing the relationship between the emission angle θ 1B of an arbitrary light ray L emitted from the emission center and the emission angle θ 3B of the arbitrary light ray in the second cross section is obtained.

(2) A second curve C2' corresponding to the first order differential of the second polynomial approximation function is obtained (see fig. 9B).

(3) When the light emission angle θ 1A is larger than 40 °, the maximum value in the second curve C2' is set as the second maximum value (see fig. 9B).

In the present embodiment, the second maximum value that can be obtained by the above method is about 1.2, and the light emission angle θ 2A at this time is about 76 ° (see fig. 9B).

As described above, the phrase "the second maximum value is larger than the first maximum value" means that the degree of local change in brightness of the back surface (irradiated surface 107) of the light diffusion plate 120 is larger in the direction of line B-B than in the direction of line a-a in fig. 5A. As explained below, this is related to the design to suppress excessive light irradiation to the irradiation regions at the four corners of the irradiation region on the back surface (irradiated surface 107) of the light diffusion plate 120.

Next, the positions of the ends of the irradiation regions on the back surface (irradiated surface 107) of the light diffusion plate 120 in the first cross section and the second cross section will be described. 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 diffusion plate 120. In fig. 10, an irradiation region when the surface light source device 100 using the light flux controlling member 300 is viewed from the light diffusion plate 120 side is indicated by a broken line.

As shown in fig. 10, in the present embodiment, the light-emitting device 200 is disposed such that the light-emission centers of the light-emitting elements 220 are arranged in a square grid pattern. When light emitting device 200 is arranged such that the light emission center of light emitting element 220 is in a square grid pattern as described above, light flux controlling member 300 having a substantially square shape chamfered by R in plan view is arranged such that: corresponding to the square lattice, the "first cross section" (cross section along line a-a in fig. 5A) is along the side of the unit lattice of the square lattice, and the "second cross section" (cross section along line B-B in fig. 5A) is along the diagonal of the unit lattice of the square lattice.

In this case, light flux controlling member 300 (light emitting device 200) according to the present embodiment satisfies the following formula (1).

D1 < P < D2 formula (1)

As shown in fig. 10, in equation (1), D1 is the length of half of a straight line connecting two adjacent light emission centers on the side of the unit mesh of the square mesh (the length of half of the side of the unit mesh of the square mesh). Further, D2 is the length of half of a straight line connecting two light emission centers adjacent on a diagonal line of the unit mesh of the square mesh (the length of half of the diagonal line of the unit mesh of the square mesh). P is a distance between the center axis CA and an intersection of the light rays emitted from the light emitting element 220 at the light emission angle θ 1B corresponding to the second maximum value on the rear surface of the light diffusion plate 120. As shown in fig. 10, P determines the position of the end of the irradiation region by light flux controlling member 300 (light emitting device 200) in the diagonal direction of the unit mesh of the square mesh. The distance p between the center axis and the intersection of the light rays emitted from the light-emitting element 220 at the light-emission angle θ 1A corresponding to the first maximum value on the rear surface of the light-diffusing plate 120 is set to be substantially the same as the length of D1 or shorter than D1.

The present inventors have found that, when light emitting apparatus 200 is disposed such that the light emission centers of light emitting elements 220 are arranged in a square grid pattern, by adjusting the shape of emission surface 330 (particularly, second emission surface 330b) of light flux controlling member 300 so as to satisfy expression (1), it is possible to suppress the occurrence of bright portions on the back surface (irradiated surface 107) of light diffusion plate 120. The present inventors have estimated that since the brightness at the four corners of the substantially square irradiation region formed by one light-emitting device 200 is lower than the brightness at the other portions, a bright portion due to the overlapping of the four irradiation regions is less likely to occur near the central portion of the unit cell.

(Effect)

As described above, in light flux controlling member 300 according to the present embodiment, since the second maximum value is larger than the first maximum value, even when the light flux controlling member is arranged in a grid pattern, it is possible to suppress the occurrence of a bright portion on the surface to be irradiated. Further, the light emitting device, the surface light source device, and the display device provided with light flux controlling member 300 can suppress the generation of bright portions.

In this embodiment, although the case where the light emission centers of the light emitting elements 220 are arranged in a square grid is described, the present invention is not limited thereto, and the light emission centers of the light emitting elements 220 may be arranged in a rectangular grid. In the case of a rectangular grid, P is designed to be shorter than half the length of the diagonal line of the unit grid and longer than half the length of the long side of the unit grid.

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 relief portion 411A, and fig. 11B is a diagram for explaining another relief portion 411B. In fig. 11A and 11B, the light emitting element 220 is shown by a broken line in order to clarify the positions of the

moderation portions

411A and 411B.

Some of the light emitted from light emitting element 220 reaches the surface to be irradiated under the control of light flux controlling member 300. Further, of the light emitted from light emitting element 220, the other part of the light reaches the surface of base plate 112 by light flux controlling member 300. The light reaching the surface of the base plate 112 is reflected toward the irradiated surface. In this way, since part of the light reaching the surface to be irradiated is light reflected by the bottom plate 112, it is possible to suppress the occurrence of a bright portion of the surface to be irradiated by reducing the light reflected by the bottom plate 112. Therefore, the

relief portions

411A and 411B are formed in at least a partial region of the bottom plate 112 where light that can become a bright portion on the irradiated surface is reflected. As shown in fig. 11A and 11B, in the present embodiment, the

relief portions

411A and 411B are formed near the intersection of the diagonal lines of the unit cell. The structures of the moderating

portions

411A and 411B can be designed appropriately within a range in which reflection of light reaching the surface of the base plate 112 can be suppressed. As shown in fig. 11A, the moderating portion 411A may be a black printed portion that does not reflect light. In addition, as shown in fig. 11B, the relief portion 411B may be configured by cutting out a region where a bright portion is generated.

As described above, light flux controlling member 300 may have leg portions for positioning and fixing on substrate 210. Fig. 12A to 12C are bottom views of light flux controlling member 300 according to a modification. Fig. 12A is a bottom view of light flux controlling member 300 according to modification 1, fig. 12B is a bottom view of light flux controlling member 300 according to modification 2, and fig. 12C is a bottom view of light flux controlling member 300 according to modification 3.

The shape of the

leg portions

421A, 421B, 421C can be appropriately selected within a range capable of exerting the above-described effects. For example, the shape of the

legs

421A, 421B, 421C may be cylindrical or prismatic. In the present embodiment, leg 421A of light flux controlling member 300 in modification 1 and leg 421B of light flux controlling member 300 in modification 2 are both cylindrical in shape. Leg 421C of light flux controlling member 300 according to modification 3 has a prism 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 421A may be disposed on the rear surface 305 so as to surround the incident surface 320. As shown in fig. 12B, four legs 421B may be disposed on the rear surface 305 so as to surround the incident surface 320. As shown in fig. 12C, two legs 421C may be disposed on the rear surface 305 so as to sandwich the incident surface 320. As shown in fig. 12B, when four legs 421B are arranged in light flux controlling member 300, only three legs 421B of four legs 421B may be bonded. By providing

leg portions

421A, 421B, and 421C in this manner, an error in the mounting direction of light flux controlling member 300 on substrate 210 can be prevented. As shown in fig. 12B and 12C, in light flux controlling member 300 in which

leg portions

421B and 421C are arranged rotationally symmetrically about central axis CA of light flux controlling member 300 as a rotation center, the mounting direction can be changed for each light emitting device 200. Thus, the gate positions of the plurality of light emitting devices 200 used in the surface light source device 100 can be arranged at random, and thus the occurrence of luminance unevenness due to the gate at the time of injection molding can be suppressed.

[ second viewpoint ]

In the second viewpoint, as for a more specific shape of light flux controlling member 300, light flux controlling member 300 includes: the incident surface 320; and the emission surface 330 including the first emission surface 330a and the second emission surface 330b, and the following expressions (2) to (4) need to be satisfied.

Fig. 13A and 13B are diagrams for explaining the expressions (2) to (4). Fig. 13A is a diagram for explaining the expressions (2) and (3), and corresponds to the first cross section described above. Fig. 13B is a diagram for explaining the expressions (2) and (4), and corresponds to the second cross section described above. In fig. 13A and 13B, the optical path of light emitted from the light emitting element 220 is shown by a straight line to simplify the drawing.

Light flux controlling member 300 of the present embodiment satisfies the following formula (2) when: the light emitting element 220 is disposed so as to face the concave portion 310 with the light emission center thereof positioned on the central axis CA, and the surface to be irradiated is disposed above the emission surface 330 so as to intersect the central axis CA.

In the above equation (2), D1 is a first arrival distance obtained by equation (3) as a distance from the central axis CA to an arrival point P3a on the irradiated surface of the first light beam L1 emitted from the light emission center P0 of the light emitting element 220 at the first light emission angle θ 1a in a first cross section including the central axis CA and a point of the outer edge of the emission surface 330 closest to the central axis CA. D2 is a second arrival distance from the central axis CA to the arrival point P3b on the irradiated surface of the second light beam L2 emitted from the light emission center P0 of the light emitting element 220 at the second light emission angle θ 1b in the second cross section including the central axis CA and the point farthest from the central axis CA in the outer edge of the emission surface 330, which is determined by the following equation (4). The first light emission angle θ 1a is obtained by the following "method for calculating a first light emission angle", and the second light emission angle θ 1b is obtained by the following "method for calculating a second light emission angle", and in the present embodiment, the above formula (2) indicates four corners of a square irradiation target region formed on the irradiation target surface (light diffusion plate 120) where light emitted from the light emitting element 220 does not reach.

Here, a method of calculating the first arrival distance D1 will be described. The first arrival distance D1 is obtained by the following equation (3).

D1 ═ h1atan θ 1a + h2atan θ 2a + h3atan θ 3a formula (3)

As shown in fig. 13A, h1a in the above equation (3) is a distance in the direction along the central axis CA between the light emission center P0 and the first incident position P1a, which is the incident point of the first light ray L1 on the incident surface 320, in the first cross section. h2a is a distance in the direction along the central axis CA between the first incident position P1a and the first exit position P2a, which is the exit point of the first light ray L1 on the exit surface 330 in the first cross section. h3a is a distance in the direction along the center axis CA between the first exit position P2a and the first irradiated position P3a, which is the arrival point of the first ray L1 on the irradiated surface in the first cross section. θ 1a is an angle of the traveling direction of the first light ray L1 between the light emission center P0 and the incident surface 320 with respect to the central axis CA, i.e., a first light emission angle. θ 2a is an angle of the traveling direction of the first light ray L1 between the incident surface 320 and the exit surface 330 with respect to the central axis CA in the first cross section. θ 3a is an angle of the traveling direction of the first light ray L1 between the emission surface 330 and the irradiated surface with respect to the central axis CA in the first cross section. That is, the first arrival distance D1 is a distance in a direction perpendicular to the central axis CA between the central axis CA and the first irradiation position P3a on the irradiation target surface of the light emitted at the first emission angle θ 1a calculated as follows in the first cross section.

Next, a method of calculating the first light emission angle θ 1a will be described. Fig. 14A and 14B are graphs for explaining a method of calculating the first light emission angle θ 1 a. Fig. 14A is a graph showing a first polynomial approximation function C1, in which a first polynomial approximation function C1 shows a relationship between a light emission angle θ 1A of a light ray emitted from a light emission center of the light emitting element 220 and an emission angle θ 3A of the light ray, and fig. 14B is a graph showing a first curve C1' corresponding to a first order differential of the first polynomial approximation function C1. In fig. 14A, the abscissa represents a light emission angle θ 1A (°), and the ordinate represents a light emission angle θ 3A (°). In fig. 14B, the horizontal axis represents the light emission angle θ 1A (°), and the vertical axis represents the first-order differential value of the light emission angle θ 3A (°).

The first light emission angle θ 1a can be obtained by the following method.

(1) A first polynomial approximation function C1 (see fig. 14A) is obtained which represents a relationship between a light emission angle θ 1A and an emission angle θ 3A, where the light emission angle θ 1A is an angle of a traveling direction of an arbitrary light ray emitted from the light emission center P0 between the light emission center P0 and the incident surface 320 with respect to the central axis CA in a first cross section including the central axis CA and a point of the outer edge of the emission surface 330 which is closest to the central axis CA, and the emission angle θ 3A is an angle of the traveling direction of the arbitrary light ray between the emission surface 330 and the irradiated surface with respect to the central axis CA.

(2) A first curve C1' corresponding to the first order differential of the first polynomial approximation function is obtained (see fig. 14B).

(3) A base point of 1 or 2 or more at which the slope of the tangent of the first curve C1' changes from negative to positive and a vertex of 1 or 2 or more at which the slope of the tangent changes from positive to negative are obtained. In fig. 14B, the bottom point is indicated by a solid arrow, and the top point is indicated by a dashed arrow.

(4) For each of 1 or 2 or more base points, a vertex is determined from 1 or 2 or more vertices, and the light emission angle θ 1A of the vertex is larger than the light emission angle θ 1A of the base point and is closest to the light emission angle θ 1A of the base point. That is, in the graph of fig. 14B, the vertex located adjacent to the right of the bottom point is determined.

(5) The bottom point where the difference in the differential value Δ θ 3A of the emission angle θ 3A between the light emission angle θ 3A and the corresponding vertex is the largest is determined from the bottom points of 1 or 2 or more, and the light emission angle θ 1A of the determined bottom point is defined as the first light emission angle θ 1A.

In the present embodiment, the first light emission angle θ 1a that can be obtained by the above method is about 63 ° (see fig. 14B).

The first emission angle θ 1a obtained as described above is an angle at which the slope changes greatly in the first polynomial approximation function C1 shown in fig. 14A (see the solid arrow in fig. 14A). In a region where the light emission angle θ 1 is smaller than the first light emission angle θ 1a, the light emitted from the emission surface 330 is controlled to be condensed. On the other hand, in a region where the light emission angle θ 1 is larger than the first light emission angle θ 1a, the light emitted from the emission surface 330 is controlled to be diffused. That is, in the first cross section, the arrival position of the light emitted at the first emission angle θ 1a in the irradiated region is the boundary between the bright portion and the dark portion.

Next, a method of calculating the second arrival distance D2 will be described. The second arrival distance D2 is obtained by the following equation (4).

D2 ═ h1btan θ 1b + h2btan θ 2b + h3btan θ 3b formula (4)

As shown in fig. 13B, h1B in the above equation (4) is a distance in the direction along the central axis CA between the light emission center P0 and the second incident position P1B, which is the incident point of the second light ray L2 on the incident surface 320, in the second cross section. h2b is a distance in the direction along the central axis CA between the second incident position P1b and the second exit position P2b, which is the exit point of the second light ray L2 on the exit surface 330 in the second cross section. h3b is a distance in the direction along the center axis CA between the second emission position P2b and the second irradiation position P3b, which is the arrival point of the second ray L2 on the irradiation target surface, in the second cross section. θ 1b is an angle of the traveling direction of the second light ray L2 between the light emission center P0 and the incident surface 320 with respect to the central axis CA in the second cross section, that is, a second light emission angle. θ 2b is an angle of the traveling direction of the first light ray L2 between the incident surface 320 and the exit surface 330 with respect to the central axis CA in the second cross section. θ 3b is an angle of the traveling direction of the second light beam L2 between the emission surface 330 and the irradiated surface with respect to the central axis CA in the second cross section. That is, the second reached distance D3 is a distance in a direction perpendicular to the central axis CA between the central axis CA and the second irradiation position P3b on the irradiation surface of the light emitted at the second light emission angle θ 1b calculated as follows in the second cross section.

Next, a method of calculating the second light emission angle θ 1b will be described. Fig. 15A and 15B are graphs for explaining a method of calculating the second light emission angle θ 1B. Fig. 15A is a graph showing a first polynomial approximation function C2, in which the first polynomial approximation function C2 shows the relationship between the emission angle θ 1B of the light emitted from the emission center of the light-emitting element 220 and the emission angle θ 3B of the light, and fig. 15B is a graph showing a second curve C2' corresponding to the first order differential of the second polynomial approximation function C2. In fig. 15A, the abscissa represents a light emission angle θ 1B (°), and the ordinate represents a light emission angle θ 3B (°). In fig. 15B, the abscissa indicates the light emission angle θ 1B (°), and the ordinate indicates the first-order differential value of the light emission angle θ 3B (°).

The second light emission angle θ 1b can be obtained by the following method.

(1) A second polynomial approximation function representing a relationship between a light emission angle θ 1B and an emission angle θ 3B is obtained, where the light emission angle θ 1B is an angle of a traveling direction of an arbitrary light ray emitted from the light emission center P0 between the light emission center P0 and the incident surface 320 with respect to the central axis CA in a second cross section including the central axis CA and a point of the outer edge of the emission surface 330 farthest from the central axis CA, and the emission angle θ 3B is an angle of the traveling direction of the arbitrary light ray between the emission surface 330 and the surface to be irradiated with respect to the central axis CA.

(2) A second curve C2' corresponding to the first order differential of the second polynomial approximation function is obtained (see fig. 15B).

(3) The bottom point of 1 or 2 or more where the slope of the tangent of the second curve C2' changes from negative to positive and the top point of 1 or 2 or more where the slope of the tangent changes from positive to negative are obtained. In fig. 15B, the bottom point is indicated by a solid arrow, and the top point is indicated by a dashed arrow.

(4) For each of 1 or 2 or more base points, a vertex is determined from 1 or 2 or more vertices, and the light emission angle θ 1B of the vertex is larger than the light emission angle θ 1B of the base point and is closest to the light emission angle θ 1B of the base point. That is, in the graph of fig. 15B, the vertex located adjacent to the right of the bottom point is determined.

(5) The bottom point where the difference in the differential value Δ θ 3B of the emission angle θ 3B from the corresponding vertex is the largest is specified from among the bottom points of 1 or 2 or more, and the light emission angle θ 1B of the specified bottom point is defined as the second light emission angle θ 1B.

In the present embodiment, the second light emission angle θ 1B that can be obtained by the above method is about 65 ° (see fig. 15B).

The first emission angle θ 1b obtained as described above is an angle at which the slope changes greatly in the second polynomial approximation function C2 shown in fig. 15A (see the solid arrow in fig. 15A). In a region where the light emission angle θ 1 is smaller than the second light emission angle θ 1b, the light emitted from the emission surface 330 is controlled to be condensed. On the other hand, in a region where the light emission angle θ 1 is larger than the second light emission angle θ 1b, the light emitted from the emission surface 330 is controlled to be diffused. That is, in the second cross section, the reaching position of the light emitted at the second light emission angle θ 2a in the irradiated region is the boundary between the bright portion and the dark portion.

The above equation (2) obtained based on the first light emission angle θ 1a and the second light emission angle θ 1b obtained in this way indicates that four corners of the irradiated region of the substantially square shape are darker than other regions.

In the above example, the second light emission angle θ 1b is larger than the first light emission angle θ 1a with respect to the first light emission angle θ 1a and the second light emission angle θ 1b, but the present invention is not limited to this, and the first light emission angle θ 1a may be larger than the second light emission angle θ 1b, or the second light emission angle θ 1b may be substantially the same as the first light emission angle θ 1 a. In any case, desired light distribution characteristics can be obtained as long as the above-described equations (2) to (4) are satisfied.

(measurement of luminance of surface light Source device)

Next, the luminance distribution of the surface light source device 100 using the light flux controlling member 300 was measured. Fig. 16 is a graph showing the measurement result of the luminance on the surface to be irradiated (light diffusion plate 120) of the surface light source device 100. In fig. 16, the horizontal axis represents the distance (mm) from the center (central axis CA) of the irradiated surface in the first cross section, and the vertical axis represents the luminance (cd/m)²). In this measurement, the light diffusion plate 120 (irradiated surface) was disposed at a distance of 20mm from the substrate 210 so as to be orthogonal to the central axis CA. In the present measurement, the plurality of light emitting devices 200 were arranged in a square grid pattern, and only one light emitting device 200 was caused to emit light.

As shown in fig. 16, the surface light source device 100 having the light flux controlling member 300 of the present embodiment satisfying the above-described equations (2) to (4) can suppress the occurrence of an exposed portion on the surface to be irradiated (light diffusion plate 120) as described below.

(simulation)

The luminance distribution of the surface light source device 100 using the light flux controlling member 300 was simulated. In the present simulation, in the surface light source device 100 in which the plurality of light emitting devices 200 are arranged in a grid pattern, the plurality of light emitting devices 200 are turned on. For comparison, the same simulation was performed for a surface light source device using a light flux controlling member having a rectangular shape on the surface to be irradiated (hereinafter, also referred to as "surface light source device of comparative example"). The arrangement of the light emitting devices 200 in the surface light source device 100 of the present embodiment is the same as that of the light emitting devices in the surface light source device of the comparative example.

Fig. 17A is a diagram showing a simulation result of a luminance distribution in the surface light source device of the present embodiment, and fig. 17B is a diagram showing a simulation result of a luminance distribution in the surface light source device of the comparative example.

As shown in fig. 17A, the surface light source device 100 according to the present embodiment can suppress the occurrence of a bright portion on the surface to be irradiated (the light diffusion plate 120) by arranging the plurality of light emitting devices 200 in a square grid shape (matrix shape). This is considered to be because the brightness of the four corners of the irradiated region on the irradiated surface irradiated by one light-emitting device 200 is lower than the brightness of the other portions, and therefore, even if the irradiated region overlaps with the irradiated region of the adjacent light-emitting device 200, a bright portion is not easily generated.

On the other hand, as shown in fig. 17B, in the surface light source device of the comparative example, since the shape of the irradiated surface is rectangular, four corners of the irradiated region of the light in each light emitting device overlap to generate a bright portion.

(Effect)

In summary, since equations (2) to (4) described above are satisfied, even when light flux controlling member 300 according to the present embodiment is arranged in a grid pattern, it is possible to suppress the occurrence of bright portions on the surface to be irradiated. Further, the light emitting device, the surface light source device, and the display device including light flux controlling member 300 can suppress the occurrence of bright portions on the surface to be irradiated.

Industrial applicability

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

Claims

1. A light flux controlling member for controlling distribution of light emitted from a light emitting element, characterized by comprising:

an incident surface that is an inner surface of a concave portion formed on a back surface side so as to intersect a central axis of the light flux controlling member; and

an emission surface disposed on the opposite side of the incident surface,

the exit surface includes: a first emission surface which is disposed so as to intersect the central axis and which is convex toward the rear surface side; and a second emission surface which is disposed so as to surround the first emission surface and is convex toward the front side,

when the light emitting element is disposed so as to face the concave portion with the light emission center thereof positioned on the central axis and the surface to be irradiated is disposed above the emission surface so as to be orthogonal to the central axis, a second maximum value obtained by a "second maximum value calculation method" described below is larger than a first maximum value obtained by a "first maximum value calculation method" described below,

the calculation method of the second maximum value includes the steps of:

2. A light-emitting device is characterized by comprising,

a light emitting element; and

the beam steering arrangement of claim 1.

3. A surface light source device is characterized by comprising,

a plurality of the light-emitting devices according to claim 2, which are arranged such that the light-emission centers of the light-emitting elements are in a rectangular grid shape; and

a light diffusion plate diffusing and transmitting light from the plurality of light emitting devices,

the surface light source device satisfies the following formula (1),

d1 < P < D2 formula (1)

4. A light flux controlling member for controlling distribution of light emitted from a light emitting element, characterized by comprising:

an emission surface disposed on the opposite side of the incident surface,

when the light emitting element is disposed so as to face the recess such that the light emission center thereof is located on the central axis, and the surface to be irradiated is disposed above the emission surface so as to be orthogonal to the central axis, the following formula (2) is satisfied,

d1 ═ h1atan θ 1a + h2atan θ 2a + h3atan θ 3a formula (3)

d2 ═ h1btan θ 1b + h2btan θ 2b + h3btan θ 3b formula (4)

5. A light-emitting device is characterized by comprising,

a light emitting element; and

the beam steering arrangement of claim 4.

6. A surface light source device is characterized by comprising,

the light-emitting device according to claim 5; and

a light diffusion plate diffusing and transmitting light from the light emitting device.

7. A display device is characterized by comprising,

the surface light source device of claim 3 or claim 6; and

and an irradiated member irradiated with the light emitted from the surface light source device.