Light flux control member, light-emitting device, and area light source device

The purpose of the present invention is to provide a light flux control member capable of suppressing brightness variation due to light refracted by an inclined surface. The light flux control member comprises: an entry surface which is an inner surface of a recess portion formed on a back side; an emission surface which is formed on a front side; and an annular groove portion which is formed on the back side and outside the entry surface. The annular groove portion includes an outside inclined surface and an inside surface. The inside surface includes a plurality of retroreflective portions.

TECHNICAL FIELD

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

BACKGROUND ART

Some transmission type image display apparatuses such as liquid crystal display apparatuses use a direct surface light source device as a backlight. In recent years, direct surface light source devices having a plurality of light emitting elements as the light source have been used.

For example, a direct surface light source device includes a substrate, a plurality of light emitting elements, a plurality of light flux controlling members (lens) and a light diffusion member. Each of the light emitting elements is, for example, a light-emitting diode (LED) such as a white light-emitting diode. The light emitting elements are disposed on the substrate in a matrix. The light flux controlling member that spreads the light of the light emitting element in the surface direction of the substrate is disposed over each light emitting element. The light emitted from the light flux controlling member is diffused by the light diffusion member so as to illuminate an illumination member (for example, a liquid crystal panel) in a planar fashion.

FIGS. 1A to 1Cillustrate a configuration of a conventional light flux controlling member.FIG. 1Ais a perspective view as viewed from a rear side,FIG. 1Bis a perspective view illustrating a cross-section as viewed from a rear side, andFIG. 1Cis a sectional view. It is to be noted that the leg part provided on the rear side is omitted inFIGS. 1A and 1B. As illustrated inFIGS. 1A to 1C, conventional light flux controlling member20includes incidence surface22on which light emitted from a light emitting element is incident, and emission surface24configured to emit light incident on incidence surface22to the outside. Incidence surface22is a surface recessed with respect to the light emitting element, and is formed to face the light emitting surface of the light emitting element.

FIGS. 2A and 2Billustrate light paths of light flux controlling member20.FIG. 2Aillustrates light paths of light beams emitted from a light emission center of light emitting element10at an emission angle of 30 degrees, andFIG. 2Billustrates light paths of light beams emitted from a light emission center of light emitting element10at an emission angle of 40 degrees. Here, the “emission angle” is an angle (θ inFIG. 2A) of a light beam with respect to light axis LA of light emitting element10. It is to be noted that the leg part provided on the rear side is omitted inFIGS. 2A and 2B.

As illustrated inFIGS. 2A and 2B, light emitted from light emitting element10enters light flux controlling member20from incidence surface22. The light having entered light flux controlling member20reaches emission surface24and is emitted from emission surface24to the outside (solid line arrow). At this time, the light is refracted by the shape of emission surface24, and accordingly the travelling direction of the light is controlled. Meanwhile, a part of the light having reached emission surface24is reflected (fresnel-reflected) at emission surface24and reaches rear surface26opposite to the substrate on which light emitting element10is mounted (broken line arrow). When the light having reached rear surface26is reflected at rear surface26, the light travelling toward a part right above light flux controlling member20is excessively increased, and consequently non-uniformity of the distribution (luminance unevenness) of the luminance of the light applied by the light-emitting device is caused. In addition, when the light having reached rear surface26is emitted from rear surface26, the light is absorbed by the substrate and consequently significant loss of light results. In view of this, PTL 1 proposes a light flux controlling member for solving the above-mentioned problems.

FIGS. 3A to 3Cillustrate a configuration of light flux controlling member disclosed in PTL 1.FIG. 3Ais a perspective view as viewed from a rear side,FIG. 3Bis a perspective view illustrating a cross section as viewed from a rear side, andFIG. 3Cis a sectional view. It is to be noted that the leg part provided on the rear side is omitted inFIGS. 3A and 3B. As illustrated inFIGS. 3A to 3C, in light flux controlling member30disclosed in PTL 1, a recess is formed on rear surface26. The recess includes inclined surface32which is provided on the outer side, and parallel surface34which is substantially parallel to central axis CA and is provided on the inner side. Inclined surface32is rotationally symmetrical (circularly symmetrical) about central axis CA of light flux controlling member30, and is tilted at a predetermined angle (for example, 45 degrees) to a virtual line orthogonal to central axis CA.

FIGS. 4A and 4Billustrate light paths of light flux controlling member30.FIG. 4Aillustrates light paths of light beams emitted from a light emission center of light emitting element10at an emission angle of 30 degrees, andFIG. 4Billustrates light paths of light beams emitted from a light emission center of light emitting element10. It is to be noted that the leg part provided on the rear side is omitted inFIGS. 4A and 4B. As illustrated inFIGS. 4A and 4B, light fresnel-reflected at emission surface24reaches a predetermined portion of rear surface26. By forming inclined surface32in the above-mentioned predetermined portion, at least a part of the light reaching inclined surface32can be reflected in the lateral direction (seeFIGS. 4A and 4B).

In this manner, in light flux controlling member30disclosed in PTL 1, light reflected at emission surface24does not tend to be directed toward a part right above light flux controlling member30, or does not tend to be absorbed by the substrate. Accordingly, a light-emitting device having light flux controlling member30disclosed in PTL 1 can uniformly and efficiently emit light in comparison with a conventional light-emitting device having light flux controlling member20.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, the light incident on the incidence surface of the light flux controlling member disclosed in PTL 1 travels inside the light flux controlling member, and a part of the light reaches inner surface34of the recess. A large part of the light reaching inner surface34passes through inner surface34and is refracted by inclined surface32(seeFIG. 11). Accordingly, when the light that has passed through inner surface34is refracted by inclined surface32, the quantity of light travelling in a particular direction is excessively large. Thus, an annular high luminance region is formed in the light emitted from the light flux controlling member, and consequently luminance unevenness results.

To solve such problems, an object of the present invention is to provide a light flux controlling member that includes an inclined surface configured to reflect light reflected by the emission surface and can reduce luminance unevenness resulting from light refracted by the inclined surface.

In addition, another object of the present invention is to provide a light-emitting device including the light flux controlling member, and a surface light source device including the light-emitting device.

Solution to Problem

A light flux controlling member according to the embodiment of the present invention is configured to control distribution of light emitted from a light-emitting element, the light flux controlling member including: an incidence surface that is an interior surface of a recess formed to intersect a central axis of the light flux controlling member on a rear side of the light flux controlling member, the incidence surface being configured to allow incidence of light emitted from the light-emitting element; an emission surface formed to intersect the central axis on a front side of the light flux controlling member, the emission surface being configured to emit, to outside, light incident on the incidence surface; and an annular groove part formed outside the incidence surface on the rear side to surround the central axis. The annular groove part includes an outer inclined surface tilted such that a distance of the outer inclined surface from the central axis increases toward the rear side, and an inner surface disposed on an inner side relative to the outer inclined surface with respect to the central axis, the outer inclined surface is tilted at an angle at which at least a part of light which has entered the light flux controlling member from the incidence surface and has been fresnel-reflected by the emission surface is reflected in a direction away from the central axis, and the inner surface includes a plurality of retro-reflection parts configured to reflect, at least two times, the light which has entered the light flux controlling member from the incidence surface to retro-reflect the light toward the incidence surface.

A light-emitting device according to the embodiment of the present invention includes: a light-emitting element; and the above-mentioned light flux controlling member. The central axis of the light flux controlling member and a light axis of the light-emitting element coincide with each other.

A surface light source device according to the embodiment of the present invention includes: the above-mentioned light-emitting device; and a light diffusion member configured to allow light from the light-emitting device to pass through the light diffusion member while diffusing the light.

Advantageous Effects of Invention

The light flux controlling member according to an embodiment of the present invention does not tend to cause luminance unevenness of emission light. In addition, the light-emitting device and the surface light source device according to the embodiment of the present invention include the light flux controlling member that does not tend to cause luminance unevenness, and therefore do not tend to cause luminance unevenness of emission light.

DESCRIPTION OF EMBODIMENTS

A light flux controlling member, a light-emitting device, and a surface light source device according to an embodiment of the present invention are described in detail below with reference to the accompanying drawings. In the following description, as a typical example of the surface light source device according to the embodiments of the present invention, a surface light source device suitable for a backlight of a liquid crystal display apparatus will be described. When used with a member (for example, a liquid crystal panel) configured to be irradiated with light from the surface light source device, the surface light source device can be used as a display apparatus.

(Configurations of Surface Light Source Device and Light-Emitting Device)

FIGS. 5A to 7illustrate a configuration of the surface light source device according to the embodiment of the present invention.FIG. 5Ais a plan view, andFIG. 5Bis a front view.FIG. 6Ais a sectional view taken along line6A-6A ofFIG. 5B, andFIG. 6Bis a sectional view taken along line6B-6B ofFIG. 5A.FIG. 7is a partially enlarged sectional view ofFIG. 6B.

As illustrated inFIGS. 5A to 6B, surface light source device100according to the embodiment of the present invention includes casing110, a plurality of light-emitting devices200and light diffusion member120. Light-emitting devices200are disposed in a matrix on bottom plate112of casing110. The inner surface of bottom plate112functions as a diffusive reflection surface. In addition, top plate114of casing110is provided with an opening. Light diffusion member120is disposed to cover the opening, and functions as a light emitting surface. The light emitting surface may have a size of, for example, approximately 400 mm×approximately 700 mm.

As illustrated inFIG. 7, light-emitting devices200are fixed on substrate210. A plurality of substrates210are fixed at respective predetermined positions on bottom plate112of casing110. As illustrated inFIG. 7, each light-emitting device200includes light emitting element220and light flux controlling member300.

Light emitting element220is a light source of surface light source device100, and is mounted on substrate210. Light emitting element220is a light-emitting diode (LED) such as a white light-emitting diode, for example. Light emitting element220may be an LED of chip-on-board (COB) type from the viewpoint of the ease of mounting and high light emission efficiency.

LEDs of COB type are known to emit a greater quantity of light in the lateral direction in comparison with conventional LEDs. In the case where light-emitting element220is an LED of a COB type and the like which emits a large quantity of light in the lateral direction, it is preferable that the top surface of the light emitting element be located on the upper side relative to the lower end of recess310(described later) of the light flux controlling member in the vertical direction from the viewpoint of facilitating incidence on the light flux controlling member of a large quantity of light which is emitted in the lateral direction of the LED. It is to be noted that light-emitting element220inFIG. 7is a normal LED (an LED of a package type).

Light flux controlling member300is a lens, and is fixed on substrate210. Light flux controlling member300controls the distribution of light emitted from light emitting element220, and spreads the light travelling direction in the plane direction of the substrate. Light flux controlling member300is disposed over light emitting element220in such a manner that its central axis CA matches light axis LA of light emitting element220(seeFIGS. 7A to 7C). It is to be noted that each of incidence surface320and emission surface330of light flux controlling member300described later is rotationally symmetrical (circularly symmetrical), and the rotational axes thereof coincide with each other. The rotational axes of incidence surface320and emission surface330are referred to as “central axis CA of light flux controlling member.” In addition, “light axis LA of light emitting element” refers to a central light beam of a stereoscopic light flux from light emitting element220.

Light flux controlling member300can be formed by integral molding. The material of light flux controlling member300is not limited as long as light of a desired wavelength can pass therethrough. For example, the material of light flux controlling member100is an optically transparent resin such as polymethylmethacrylate (PMMA), polycarbonate (PC), epoxy resin (EP); and silicone resin, or glass.

A main feature of surface light source device100according to the embodiment of the present invention is the configuration of light flux controlling member300. Therefore, light flux controlling member300will be separately described in detail.

Light diffusion member120is a plate-shaped member (diffusion plate) having a light diffusing property, and allows the light emitted from light-emitting device200to pass therethrough while diffusing the light. Normally, the size of light diffusion member120is substantially the same as that of the member to be irradiated such as a liquid crystal panel. For example, light diffusion member120is formed of a light transmissive resin such as polymethylmethacrylate (PMMA), polycarbonate (PC), polystyrene (PS), and styrene methyl methacrylate copolymerization resin (MS). For the purpose of providing a light diffusing property, minute irregularities are formed on the surface of light diffusion member120, or diffusing members such as beads are dispersed in light diffusion member120.

In surface light source device100according to the embodiment of the present invention, the light emitted from light emitting elements220are spread by respective light flux controlling members300so as to illuminate light diffusion member120over a wide range. The light emitted from each light flux controlling member300is further diffused by light diffusion member120. As a result, surface light source device100according to the embodiment of the present invention can uniformly illuminate a planar member (for example, a liquid crystal panel).

(Configuration of Light Flux Controlling Member)

FIGS. 8 to 9Dillustrate a configuration of light flux controlling member300according to the embodiment of the present invention.FIG. 8is a perspective view as viewed from a rear side (substrate210side), in which a gate part and a leg part are omitted.FIG. 9Ais a plan view,FIG. 9Bis a front view,FIG. 9Cis a bottom view, andFIG. 9Dis a sectional view taken along line9D-9D ofFIG. 9A.

As illustrated inFIG. 8, light flux controlling member300includes recess310that forms incidence surface320, emission surface330, annular groove part340, and flange part350. InFIG. 8, the leg part provided on the rear surface of light flux controlling member300is omitted.

Recess310is formed at a center portion on the rear side (light emitting element220side) of light flux controlling member300. The inner surface of recess310functions as incidence surface320. Incidence surface320allows most or all of light emitted from light emitting element220to enter light flux controlling member300while controlling the travelling direction of the light. Incidence surface320intersects central axis CA of light flux controlling member300, and is rotationally symmetrical (circularly symmetrical) about central axis CA.

Emission surface330is formed on the front side (light diffusion member120side) of light flux controlling member300to protrude from flange part350. Emission surface330emits the light having entered light flux controlling member300to the outside while controlling the travelling direction of the light. Emission surface330intersects central axis CA, and is rotationally symmetrical (circularly symmetrical) about central axis CA.

Emission surface330includes first emission surface330alocated in a predetermined range around central axis CA, second emission surface330bcontinuously formed at the periphery of first emission surface330a, and third emission surface330cthat connects second emission surface330band flange part350(seeFIG. 9D). First emission surface330ais a curved surface protruding toward the rear side. Second emission surface330bis a smooth curved surface located at the periphery of first emission surface330aand protruding toward the front side. Second emission surface330bhas an annular protruding shape. Third emission surface330cis a curved surface located at the periphery of second emission surface330b. In the cross section ofFIG. 9D, third emission surface330cmay have a linear shape, or a curved shape.

Annular groove part340is formed on rear surface360that extends in the radial direction from the opening edge of recess310on the rear side (substrate210side) of light flux controlling member300(seeFIGS. 8 and 9C). To be more specific, annular groove part340is formed at a position outside recess310(in a region remote from central axis CA relative to recess310) on the rear side of light flux controlling member300in such a manner as to surround central axis CA. Annular groove part340includes outer inclined surface342and inner surface344disposed on the inner side of outer inclined surface342with respect to central axis CA. Here, the inclined surface means a surface that is tilted with respect to a virtual line orthogonal to central axis CA (a surface that intersects the virtual line at a predetermined angle).

Outer inclined surface342is tilted such that the distance thereof from central axis CA increases toward the rear side. The inclination angle of outer inclined surface342with respect to the virtual line orthogonal to central axis CA is set to an angle at which at least a part of light which has entered light flux controlling member300from incidence surface320and has been fresnel-reflected by emission surface330is reflected in a direction away from central axis CA, and for example, the inclination angle is 45 degrees or smaller.

In the case where the inclination surface has a linear shape in the cross section including central axis CA, the inclination angle of outer inclined surface342with respect to the virtual line orthogonal to central axis CA (hereinafter also referred to simply as “inclination angle”) means an angle between the straight line of the linear shape and the virtual line orthogonal to central axis CA, whereas in the case where the inclination surface has a curved shape in the cross section including central axis CA, the inclination angle means an angle between the virtual line orthogonal to central axis CA and a straight line that connects a point closest to emission surface330and a point remotest from emission surface330on the inclination surface in the cross section including central axis CA.

With this configuration, at least a part of the fresnel-reflected light which reaches outer inclined surface342is reflected in the lateral direction by outer inclined surface342. It is thus possible to reduce luminance unevenness which is caused when the light fresnel-reflected at emission surface330is further reflected at substrate210, and to reduce loss of light which is caused when the light is absorbed at substrate210(seeFIG. 4).

Outer inclined surface342is provided in a region where the light that has entered light flux controlling member300from incidence surface320and has been fresnel-reflected by emission surface330reaches. The region where the light that has entered light flux controlling member300from incidence surface320and has been fresnel-reflected by emission surface330reaches can be set to a region including regions where most of the light paths reach in a simulation in which light paths are simulated by changing the inclination angle of outer inclined surfaces342among different angles, for example.

Inner surface344includes a plurality of retro-reflection parts344e. Retro-reflection parts344ehave a function of retro-reflecting, in a direction toward incidence surface320, light incident on incidence surface320which reaches inner surface344. The “retro-reflection” used herein means a control of light to travel toward incidence surface320by reflecting, at least two times, light which is directly incident on inner surface344from incidence surface320(particularly, light which travels in a direction substantially orthogonal to central axis CA). Specifically, the “direction toward incidence surface320” means a direction toward central axis CA.

In the present embodiment, a plurality of first protrusions344drotationally symmetrical about central axis CA are provided on the inner side in annular groove part340(seeFIGS. 8 and 9C). First protrusion344dincludes first inclined surface344athat forms inner surface344, second inclined surface344bthat forms inner surface344, and ridgeline344cthat is an intersection line of first inclined surface344aand second inclined surface344b(seeFIG. 8). Retro-reflection part344eincludes first inclined surface344aand second inclined surface344b.

Each of first inclined surface344aand second inclined surface344bhas a planar shape. Preferably, the angle between first inclined surface344aand second inclined surface344bis 90 degrees, and may be any angle as long as light directly incident on incidence surface320(particularly, light which travels in a direction substantially orthogonal to central axis CA) can be retro-reflected in a direction toward incidence surface320.

Ridgeline344cis parallel to central axis CA, or is tilted such that the distance thereof from central axis CA increases toward the front side. In the case where ridgeline344cis tilted such that the distance thereof from central axis CA increases toward the front side, it is preferable that the angle of ridgeline344cwith respect to central axis CA (the inclination angle of ridgeline344c) in the cross section including central axis CA be smaller than 5 degrees in view of ensuring a sufficient angle as a removal taper in the shaping of light flux controlling member300. Preferably, ridgeline344cis parallel to central axis CA from the view point of the ease of retro-reflection, in a direction toward incidence surface320, of light which is incident on inner surface344.

One first inclined surface344aand one second inclined surface344bof retro-reflection part344eform one protrusion.

Flange part350is located between the outer periphery portion of emission surface330and the outer periphery portion of light flux controlling member300on the rear side thereof, and is protruded outward with respect to central axis CA. Flange part350has a substantially annular shape. Flange part350is not an essential component; however, by providing flange part350, the ease of the handling and alignment of light flux controlling member300increases. The thickness of flange part350is determined in consideration of a desired dimension of emission surface330, formability of flange part350and the like.

A plurality of leg parts370, which are optionally formed, are substantially columnar shaped members protruding from the rear side of light flux controlling member300. Leg parts370support light flux controlling member300at a suitable position with respect to light emitting element220(seeFIGS. 9B and 9C).

The operation of the light flux controlling member according to the present embodiment is described by comparison betweenFIGS. 10A and 10B, andFIG. 11.FIG. 10Aillustrates light paths of the light flux controlling member illustrated inFIG. 8, andFIG. 10Billustrates light paths as viewed from the bottom surface ofFIG. 10A.FIG. 11illustrates light paths of a light flux controlling member for comparison.

In a conventional light flux controlling member, the inner surface of the annular groove part is a curved surface that is approximately parallel to with respect to central axis CA, and the plurality of retro-reflection parts344eare not provided (see, for example, surface34inFIG. 11). Consequently, a large part of the light which travels in a direction substantially orthogonal to central axis CA passes through the inner surface, and is refracted in a particular direction by the outer inclined surface (see, for example, light paths inFIG. 11). With such light, luminance unevenness is generated in the light applied from the surface light source device.

In contrast, in light flux controlling member300according to the present embodiment, inner surface344of annular groove part340is provided with a plurality of retro-reflection parts344e. With this configuration, light which travels from incidence surface320in a direction substantially orthogonal to central axis CA is reflected by first inclined surface344aand then further reflected by second inclined surface344b, whereby the light can be retro-reflected to the incidence surface320side (see light paths inFIGS. 10A and 10B). In this manner, it is possible to reduce a situation where the amount of light which is refracted by the outer inclined surface in a particular direction excessively increases as illustrated inFIG. 11. In addition, the light retro-reflected by retro-reflection part344etravels in the lateral direction of the light flux controlling member (see the light paths inFIG. 10A). Accordingly, retro-reflection parts344eprovided at inner surface344of annular groove part340can reduce a situation where the amount of light which is refracted by the outer inclined surface in a particular direction excessively increases, and can suppress the generation of the luminance unevenness.

(Simulation Result of Luminance Distribution)

Now, results of a simulation of the luminance distribution on a diffusion plate in the case where a diffusion plate is disposed over light flux controlling member300are described. Also, for comparison, results of a simulation of the luminance distribution on a diffusion plate in the case where a diffusion plate is disposed over the light flux controlling member for comparison having the same configuration except that a plurality of retro-reflection parts344eare not provided are described.

The luminance distribution on a diffusion plate located on the upper side of light flux controlling member300or the light flux controlling member for comparison was examined with light-emitting element220that is an LED, and light flux controlling member300or the light flux controlling member for comparison disposed on substrate210as illustrated inFIG. 7. It is to be noted that light-emitting element220was placed such that the top surface thereof is located below the lower end of recess310of light flux controlling member300or the light flux controlling member for comparison. The two light flux controlling members used in the simulation, light flux controlling member300and the light flux controlling member for comparison, are different from each other only in whether the plurality of retro-reflection parts344eare provided. The angle between first inclined surface344aand second inclined surface344bin retro-reflection part344ewas set to 90 degrees. The parameters of light flux controlling member300and the light flux controlling member for comparison were as follows.

Outer diameter of light flux controlling member: 19.0 mm

Outer diameter of emission surface: 18.6 mm

Opening diameter of recess: 2.25 mm

Height from substrate surface to edge of incidence surface: 0.7 mm

Internal diameter of outer inclined surface: 12.0 mm

Outer diameter of outer inclined surface: 19.0 mm

Height of internal diameter portion of outer inclined surface: 0.7 mm

Distance between substrate surface and diffusion plate: 19 mm

FIG. 12shows simulation results of the luminance distribution on the diffusion plate in the case where the diffusion plate is disposed over each of the light flux controlling member for comparison illustrated inFIG. 11and light flux controlling member300illustrated inFIG. 8. InFIG. 12, the ordinate indicates luminance (cd/m2), and the abscissa indicates a distance (mm) from central axis CA of light flux controlling member in the horizontal direction. The broken line indicates simulation results of the light flux controlling member for comparison, and the heavy line indicates simulation results of light flux controlling member300.

As is clear fromFIG. 12, in the light flux controlling member for comparison, portions (indicated with two arrows in the drawing) where the luminance is high relative to surrounding portions are generated in regions approximately 25 mm from central axis CA of light-emitting device in the horizontal direction. In contrast, in light flux controlling member300according to the present embodiment, such high luminance portions were not generated.

While first protrusion344dis formed in a columnar shape having a substantially triangular cross-sectional shape in the direction orthogonal to ridgeline344cin the present embodiment, the present invention is not limited to this. For example, first protrusion344dmay be formed in a grid. The protrusions of the grid may have a triangular pyramid shape or a square pyramid shape, for example.

In addition, while a plurality of first protrusions344dare provided on the inner side in annular groove part340in the present embodiment, the present invention is not limited to this.FIG. 13illustrates another configuration of the light flux controlling member according to the embodiment of the present invention. As illustrated inFIG. 13, a plurality of second protrusions342drotationally symmetrical about central axis CA may further be provided on the outer side in annular groove part340.

Second protrusion342dincludes third inclined surface342athat forms outer inclined surface342, fourth inclined surface342bthat forms outer inclined surface342, and ridgeline342cthat is the intersection line of third inclined surface342aand fourth inclined surface342b. Each of third inclined surface342aand fourth inclined surface342bhas a planar shape. Such a plurality of second protrusions342dfacilitate the reflection in a direction away from central axis CA of light which has entered light flux controlling member300from incidence surface320and has been fresnel-reflected by emission surface330. As a result, generation of luminance unevenness can be remarkably suppressed. Also, it may suppress a situation where stray light in the system of surface light source device100enters light flux controlling member300from emission surface330, reaches outer inclined surface342so as to be reflected by a plurality of second protrusions342d, and then reaches the substrate immediately below light flux controlling member300. This may suppress the reduction in light use efficiency.

This application is entitled to and claims the benefit of Japanese Patent Application No. 2015-174771 filed on Sep. 4, 2015, the disclosure each of which including the specification, drawings and abstract is incorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The light flux controlling member, the light-emitting device and the surface light source device according to the embodiments of the present invention are applicable to, for example, a backlight of liquid crystal display apparatuses or generally-used illumination apparatuses.

REFERENCE SIGNS LIST