Patent Publication Number: US-2023161096-A1

Title: Surface light source

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-190118 filed on Nov. 24, 2021, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present disclosure relates to a surface light source. 
     2. Description of Related Art 
     Light-emitting modules in which light-guiding plates and light-emitting elements such as light-emitting diodes are combined have been widely used for surface light sources such as backlights for liquid-crystal display devices (for example, see Japanese Unexamined Patent Application Publication No. 2020-13714). 
     SUMMARY OF THE INVENTION 
     An object of an exemplary embodiment of the present disclosure is to provide a surface light source in which unevenness in luminance can be reduced. 
     In an exemplary aspect of the present disclosure, a light-guiding member includes a plurality of light-emitting portions separated by grooves; and a plurality of light sources each corresponding to a respective one of the plurality of light-emitting portions. The plurality of light-emitting portions include a plurality of outer portions, and at least one inner portion located in a region surrounded by the plurality of outer portions in a plan view. Each of the plurality of outer portions is adjacent to a smaller number of the light-emitting portions than a number of the light-emitting portions adjacent to a single inner portion of the at least one inner portion in a plan view. An area of a single outer portion of the plurality of outer portions is smaller than an area of the single inner portion in the plan view. 
     According to an exemplary embodiment of the present disclosure, a surface light source having reduced unevenness in luminance can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a schematic plan view of an exemplary surface light source according to an exemplary embodiment. 
         FIG.  1 B  is a schematic plan view of an exemplary surface light source of an exemplary embodiment. 
         FIG.  2    is a schematic enlarged plan view of a portion of the exemplary surface light source of the exemplary embodiment. 
         FIG.  3    is a schematic cross-sectional view taken along the line III-III of  FIG.  2   . 
         FIG.  4    is a schematic cross-sectional view taken along the line IV-IV of  FIG.  1 A . 
         FIG.  5 A  is a schematic bottom view of an exemplary light source of an exemplary embodiment. 
         FIG.  5 B  is a schematic cross-sectional view taken along the line VB-VB of  FIG.  5 A . 
         FIG.  5 C  is a schematic cross-sectional view of a modification of the exemplary light source of the exemplary embodiment. 
         FIG.  5 D  is a schematic cross-sectional view of a modification of the exemplary light source of the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A certain embodiment will be described below referring to the accompanying drawings. Each drawing schematically shows the embodiment. Therefore, the scales, the distances, the positional relationships, and the like of members may be exaggerated, or illustration of portions of members may be omitted. Also, cross-sectional end views showing only cut surfaces of members may be shown as cross-sectional views. 
     In the description below, components having substantially the same function will be shown with the same reference numerals, and repeated descriptions of such components may be omitted. Terms representing particular directions or positions (such as “up/upper,” “down/lower,” and other terms containing the meanings of these terms) may be used. These terms are used merely for the sake of ease of explanation, representing relative directions or relative positions in the reference drawings. As far as the relative directions or positions mentioned by the terms “upper,” “lower,” and the like designate the same directions or positions in the reference drawings, drawings other than shown in the present disclosure, actual products, and the like do not have to be the same arrangement as shown in the reference drawings. The term “parallel” in the present specification indicates not only the case in which two straight lines, sides, surfaces, or the like do not intersect even when extended but also the case in which two straight lines, sides, surfaces, or the like intersect to form an angle within the range of 10° or less. The positional relationship represented as “on” in the present specification include both the case in which components are in contact with each other and the case in which a component is not in contact with but is located above another component. 
       FIG.  1 A  is a schematic plan view of an exemplary surface light source of an exemplary embodiment. 
     The surface light source of the embodiment includes a light-guiding member  10 . The light-guiding member  10  has a first surface  11  and a second surface  12  (shown in  FIG.  3    and the like described below) opposite to the first surface  11 . In the present specification, two directions parallel to the first surface  11  of the light-guiding member  10  and orthogonal to each other are referred to as a first direction X and a second direction Y. A direction that extends from the second surface  12  toward the first surface  11  and is orthogonal to the first direction X and the second direction Y is referred to as a third direction Z. For example, the shape of the light-guiding member  10  in a plan view is a quadrangular shape having two sides extending in the first direction X, two sides extending in the second direction Y, and four corners (a first corner  10   a , a second corner  10   b , a third corner  10   c , and a fourth corner  10   d ). The shape of the light-guiding member  10  may be a polygonal shape such as a hexagonal shape and an octagonal shape having a plurality of corners. In the present specification, the polygonal shape includes shapes having recessed, projecting, or rounded corners in addition to mathematical polygonal shapes. 
     The light-guiding member  10  includes a plurality of light-emitting portions  1  separated from each other in the first direction X and the second direction Y by grooves  14 . Each light-emitting portion  1  can be used as, for example, a unit of driving of local dimming. 
     The light-emitting portions  1  include a plurality of outer portions. The outer portions include first outer portions  1   b  and second outer portions  1   c . The second outer portions  1   c  are located at the corners of the light-guiding member  10  in a plan view. In the surface light source of the embodiment, the second outer portions  1   c  are respectively located at the first corner  10   a , the second corner  10   b , the third corner  10   c , and the fourth corner  10   d . That is, the outer portions include four second outer portions  1   c . A plurality of first outer portions  1   b  are located between the second outer portion  1   c  located at the first corner  10   a  and the second outer portion  1   c  located at the second corner  10   b  along the first direction X. A plurality of first outer portions  1   b  are located between the second outer portion  1   c  located at the third corner  10   c  and the second outer portion  1   c  located at the fourth corner  10   d  along the first direction X. A plurality of first outer portions  1   b  are located between the second outer portion  1   c  located at the first corner  10   a  and the second outer portion  1   c  located at the third corner  10   c  along the second direction Y. A plurality of first outer portions  1   b  are located between the second outer portion  1   c  located at the second corner  10   b  and the second outer portion  1   c  located at the fourth corner  10   d  along the second direction Y. The first outer portions  1   b  and the second outer portions  1   c  are located at the outermost periphery of the region in which the light-emitting portions  1  are arranged in a plan view. 
     The light-emitting portions  1  further include at least one inner portion  1   a  located in a region surrounded by a plurality of outer portions in a plan view. In the examples shown in  FIG.  1 A  and  FIG.  1 B , a plurality of inner portions  1   a  are located in the region surrounded by a plurality of first outer portions  1   b  and a plurality of second outer portions  1   c  in a plan view. For example, the number of inner portions  1   a  is larger than the number of first outer portions  1   b  and the number of second outer portions  1   c.    
     In a plan view, a single first outer portion  1   b  is adjacent to a smaller number of light-emitting portions  1  in the first direction X and the second direction Y than the number of light-emitting portions  1  adjacent to a single inner portion  1   a  in the first direction X and the second direction Y. In a plan view, a single second outer portion  1   c  is adjacent to a smaller number of light-emitting portions  1  in the first direction X and the second direction Y than the number of light-emitting portions  1  adjacent to a single inner portion  1   a  in the first direction X and the second direction Y. In a plan view, a single second outer portion  1   c  is adjacent to a smaller number of light-emitting portions  1  in the first direction X and the second direction Y than the number of light-emitting portions  1  adjacent to a single first outer portion  1   b  in the first direction X and the second direction Y. 
     In a plan view, a single inner portion  1   a  is adjacent to four light-emitting portions  1  in the first direction X and the second direction Y. In a plan view, a single first outer portion  1   b  is adjacent to three light-emitting portions  1  in the first direction X and the second direction Y. In a plan view, a single second outer portion  1   c  is adjacent to two light-emitting portions  1  in the first direction X and the second direction Y. 
       FIG.  2    is a schematic plan view of the region in which the inner portions  1   a  are located in  FIG.  1 A  and  FIG.  1 B .  FIG.  2    schematically shows the region in which four inner portions  1   a  are located as an example. 
       FIG.  3    is a schematic cross-sectional view taken along the line III-III of  FIG.  2   . 
     The surface light source of the embodiment includes a plurality of light sources  20 A in addition to the light-guiding member  10 . The surface light source of the embodiment can further include a supporting member  50 , first light-transmissive members  30 , and first light-reflective members  40 . 
     Components constituting the surface light source of the embodiment will be described below. 
     &lt;Light-Guiding Member&gt; 
     The light-guiding member  10  is a member adapted to transmit light emitted from the light sources  20 A. For example, the light-guiding member  10  preferably has a transmittance of 50% or more, more preferably 70% or more, at a peak wavelength of the light sources  20 A. 
     Examples of the material of the light-guiding member  10  include thermoplastic resins such as acrylic, polycarbonates, cyclic polyolefins, poly(ethylene terephthalate), and polyesters, thermosetting resins such as epoxies and silicones, and glass. 
     For example, the light-guiding member  10  has a thickness of 150 μm or more and 800 μm or less. In the present specification, the thickness of each member indicates the maximum distance between an upper surface and a lower surface of each member in the third direction Z. The light-guiding member  10  may be constituted of a single layer or a layered body of a plurality of layers in the third direction Z. In the case in which the light-guiding member  10  is constituted of a layered body, light-transmissive adhesive layers may be disposed between respective layers. Different types of main materials may be used for the layers of the layered body. Examples of the material of the adhesive layers include thermoplastic resins such as acrylic, polycarbonates, cyclic polyolefins, poly(ethylene terephthalate), and polyesters and thermosetting resins such as epoxies and silicones. 
     The light-guiding member  10  has first holes h 1  extending from the first surface  11  to the second surface  12 . For example, each of the first holes h 1  can have a circular shape in a plan view as shown in  FIG.  2   . Alternatively, the first hole h 1  may have, for example, an elliptic shape or a polygonal shape such as a triangular shape, a quadrangular shape, a hexagonal shape, and an octagonal shape in a plan view. The term “in a plan view” as used in the present specification refers to viewing in the third direction Z. 
     As described above, the light-guiding member  10  has the grooves  14  separating the light-emitting portions  1  from one another. For example, the grooves  14  can suppress warpage or the like of the surface light source due to generation of heat from the light sources  20 A. As shown in  FIG.  3   , the grooves  14  each include a first groove portion  14   a  that is open to the first surface  11  side and a second groove portion  14   b  that is open to the second surface  12  side. The first groove portion  14   a  communicates with the second groove portion  14   b  in the third direction Z. The width of the first groove portion  14   a  is larger than the width of the second groove portion  14   b . The width of the first groove portion  14   a  and the width of the second groove portion  14   b  are widths in a direction orthogonal to the direction in which the groove  14  extends. 
     A dividing member  15  can be disposed in the first groove portion  14   a . The dividing member  15  is adapted to reflect light emitted from the light sources  20 A. For example, the dividing member  15  is a resin member containing light scattering particles. Examples of the light scattering particles used for the dividing member  15  include particles of titania, silica, alumina, zinc oxide, magnesium oxide, zirconia, yttria, calcium fluoride, magnesium fluoride, niobium pentoxide, barium titanate, tantalum pentoxide, barium sulfate, and glass. Examples of the resin material for the dividing member  15  include thermoplastic resins such as acrylic resins, polycarbonate resins, cyclic polyolefin resins, poly(ethylene terephthalate) resins, and polyester resins and thermosetting resins such as epoxy resins and silicone resins. The dividing member  15  may be a metal member made of aluminum, silver, or the like. For example, the dividing member  15  is disposed along an inner surface of the first groove portion  14   a  in the form of a film. Alternatively, the dividing member  15  may be filled into the first groove portion  14   a.    
     The dividing member  15  inhibits light from being guided between adjacent light-emitting portions  1 . For example, the dividing member  15  inhibits light from being guided from a light-emitting portion  1  that is emitting light to a light-emitting portion  1  that is not emitting light. The control of the luminance of every light-emitting portion  1  is thus facilitated in the case in which local dimming is performed using each light-emitting portion  1  as the unit of driving. 
     In  FIG.  3   , the groove  14  extends from the first surface  11  to the second surface  12  of the light-guiding member  10 . The groove  14  may be a groove having an opening on the first surface  11  side and a bottom not reaching the second surface  12 . The groove  14  may be a groove having an opening on the second surface  12  side and a bottom not reaching the first surface  11 . The groove  14  may be a hollow groove located inside the light-guiding member  10 . 
     &lt;Light Source&gt; 
     The light sources  20 A are disposed in the first holes h 1  of the light-guiding member  10 . Each of the first holes h 1  is located in a respective one of the light-emitting portions  1 . The light sources  20 A are therefore disposed on the respective light-emitting portions  1 . 
     The light sources  20 A each include a light-emitting element  21 . The light-emitting element  21  includes a semiconductor layered body. For example, the semiconductor layered body includes a substrate such as a sapphire or gallium nitride substrate, an n-type semiconductor layer and a p-type semiconductor layer that are disposed on the substrate, and a light-emitting layer between these layers. The light-emitting element  21  also includes an n-side electrode electrically connected to the n-type semiconductor layer and a p-side electrode electrically connected to the p-type semiconductor layer. The light source  20 A further includes a pair of positive and negative electrodes  25  disposed on the lower surface side. One of the pair of electrodes  25  is electrically connected to the p-side electrode, and the other is electrically connected to the n-side electrode. 
     The semiconductor layered body in which the substrate has been removed may be used. The light-emitting layer may have a structure with a single active layer, such as a double heterostructure and a single quantum well (SQW) structure, or a structure with a group of active layers, such as a multiple quantum well (MQW) structure. The light-emitting layer is configured to emit visible light or ultraviolet light. The light-emitting layer can be configured to emit blue to red light as the visible light. The semiconductor layered body including such a light-emitting layer can contain, for example, In x Al y Ga 1-x-y N (0≤x, 0≤y, and x+y≤1). The semiconductor layered body can include at least one light-emitting layer configured to emit light as described above. For example, the semiconductor layered body may include one or more light-emitting layers between the n-type semiconductor layer and the p-type semiconductor layer or may include a repetitive structure including the n-type semiconductor layer, the light-emitting layer, and the p-type semiconductor layer in order. In the case in which the semiconductor layered body includes a plurality of light-emitting layers, light-emitting layers configured to emit light with different peak emission wavelengths may be included, or light-emitting layers configured to emit light with the same peak emission wavelength may be included. The term “the same peak emission wavelength” as used herein indicates that variations of, for example, about several nanometers are included. An appropriate combination of such light-emitting layers can be selected. In the case in which the semiconductor layered body includes two light-emitting layers, a combination of blue light and blue light, green light and green light, red light and red light, ultraviolet light and ultraviolet light, blue light and green light, blue light and red light, or green light and red light can be selected for the light-emitting layers. The light-emitting layers may include a plurality of active layers configured to emit light with different peak emission wavelengths or a plurality of active layers configured to emit light with the same peak emission wavelength. 
     The light source  20 A can further include a second light-transmissive member  22 . The second light-transmissive member  22  covers the upper surface and lateral surfaces of the light-emitting element  21 . The second light-transmissive member  22  protects the light-emitting element  21  and has the function of wavelength conversion, light diffusion, or the like according to particles added to the second light-transmissive member  22 . 
     For example, the second light-transmissive member  22  contains a light-transmissive resin and may further contain a phosphor. Examples of the light-transmissive resin include silicone resins and epoxy resins. Examples of the phosphor include yttrium-aluminum-garnet-based phosphors (such as Y 3 (Al,Ga) 5 O 12 :Ce), lutetium-aluminum-garnet-based phosphors (such as Lu 3 (Al,Ga) 5 O 12 :Ce), terbium-aluminum-garnet-based phosphors (such as Tb 3 (Al,Ga) 5 O 12 :Ce), CCA-based phosphors (such as Ca 10 (PO 4 ) 6 C 12 :Eu), SAE-based phosphors (such as Sr 4 Al 14 O 25 :Eu), chlorosilicate-based phosphors (such as Ca 8 MgSi 4 O 16 Cl 2 :Eu), oxynitride-based phosphors such as β-SiAlON phosphors (such as (Si,Al) 3 (O,N) 4 :Eu) and α-SiAlON phosphors (such as Ca(Si,Al) 12 (O,N) 16 :Eu), nitride-based phosphors such as SLA-based phosphors (such as SrLiAl 3 N 4 :Eu), CASN-based phosphors (such as CaAlSiN 3 :Eu), and SCASN-based phosphors (such as (Sr,Ca)AlSiN 3 :Eu), fluoride-based phosphors such as KSF-based phosphors (such as K 2 SiF 6 :Mn), KSAF-based phosphors (such as K 2 Si 0.99 Al 0.01 F 5.99 :Mn), and MGF-based phosphors (such as 3.5MgO.0.5MgF 2 GeO 2 :Mn), phosphors having a perovskite structure (such as CsPb(F,Cl,Br,I) 3 ), and quantum-dot phosphors (such as CdSe, InP, AgInS 2 , and AgInSe 2 ). 
     For the phosphor added to the second light-transmissive member  22 , a single type of phosphor or a plurality of types of phosphors may be used. 
     The KSAF-based phosphors may have the composition represented by Formula (I) below. 
       M 2 [Si p Al q Mn r F s ]  (I)
 
     In Formula (I), M represents an alkali metal, and at least K may be contained. Mn may be in the form of tetravalent Mn ions. The values p, q, r, and s may satisfy 0.9≤p+q+r≤1.1, 0&lt;q≤0.1, 0&lt;r≤0.2, and 5.9≤s≤6.1. The relationships 0.95≤p+q+r≤1.05 or 0.97≤p+q+r≤1.03, 0&lt;q≤0.03, 0.002≤q≤0.02, or 0.003≤q≤0.015, 0.005≤r≤0.15, 0.01≤r≤0.12, or 0.015≤r≤0.1, and 5.92≤s≤6.05 or 5.99≤s≤6.025 may be preferably satisfied. Examples of the composition include K 2 [Si 0.946 Al 0.005 Mn 0.049 F 5.995 ], K 2 [Si 0.942 Al 0.008 Mn 0.050 F 5.992 ], and K 2 [Si 0.939 Al 0.014 Mn 0.047 F 5.986 ]. Such a KSAF-based phosphor can provide emission of red light with a high luminance and a narrow half-width of a peak emission wavelength. 
     A wavelength conversion sheet containing any of the phosphors described above may be disposed on the surface light source. The wavelength conversion sheet absorbs a portion of blue light emitted from the light source  20 A to emit yellow, green, and/or red light, thereby providing a surface light source that emits white light. For example, white light can be obtained by combining a light source  20 A that can emit blue light and a wavelength conversion sheet containing a phosphor that can emit yellow light. Alternatively, a light source  20 A that can emit blue light and a wavelength conversion sheet containing a red phosphor and a green phosphor may be combined. Alternatively, a light source  20 A that can emit blue light and a plurality of wavelength conversion sheets may be combined. As the wavelength conversion sheets, for example, a wavelength conversion sheet containing a phosphor that can emit red light and a wavelength conversion sheet containing a phosphor that can emit green light can be selected. Alternatively, a light-emitting element  21  that can emit blue light, a light source  20 A including a second light-transmissive member  22  containing a phosphor that can emit red light, and a wavelength conversion sheet containing a phosphor that can emit green light may be combined. 
     Preferable examples of the yellow phosphor used for the wavelength conversion sheet include the yttrium-aluminum-garnet-based phosphors described above. Preferable examples of the green phosphor used for the wavelength conversion sheet include the phosphors having a perovskite structure and the quantum-dot phosphors described above having narrow half-widths of peak emission wavelengths. Preferable examples of the red phosphor used for the wavelength conversion sheet include the KSF-based phosphors, the KSAF-based phosphors, and the quantum-dot phosphors described above having narrow half-widths of peak emission wavelengths as with the green phosphor. The quantum-dot phosphors have short afterglow times and can be particularly suitably used for a surface light source in which local dimming is performed. 
     The light source  20 A can further include a covering member  24 . The covering member  24  is disposed on the lower surface of the light-emitting element  21 . The covering member  24  is disposed such that the lower surfaces of the electrodes  25  of the light source  20 A are exposed from the covering member  24 . The covering member  24  is also disposed on the lower surface of the second light-transmissive member  22  covering the lateral surfaces of the light-emitting element  21 . 
     The covering member  24  is adapted to reflect light emitted from the light source  20 A. For example, the covering member  24  is a resin member containing light scattering particles. Examples of the light scattering particles used for the covering member  24  include particles of titania, silica, alumina, zinc oxide, magnesium oxide, zirconia, yttria, calcium fluoride, magnesium fluoride, niobium pentoxide, barium titanate, tantalum pentoxide, barium sulfate, and glass. Examples of a resin material for the covering member  24  include thermoplastic resins such as acrylic resins, polycarbonate resins, cyclic polyolefin resins, poly(ethylene terephthalate) resins, and polyester resins and thermosetting resins such as epoxy resins and silicone resins. 
     The light source  20 A can further include a second light-reflective member  23 . The second light-reflective member  23  is disposed on the upper surface of the light source  20 A. The second light-reflective member  23  covers the upper surface of the light-emitting element  21 . The second light-reflective member  23  is disposed on the upper surface of the second light-transmissive member  22  and controls the amount and direction of emission of light emitted from the upper surface of the second light-transmissive member  22 . The second light-reflective member  23  is adapted to reflect and transmit light emitted from the light-emitting element  21 . A portion of light emitted from the upper surface of the second light-transmissive member  22  is reflected at the second light-reflective member  23 , and another portion of the light is transmitted through the second light-reflective member  23 . For example, the transmittance of the second light-reflective member  23  for light emitted from the light-emitting element  21  is preferably 1% or more and 50% or less, more preferably 3% or more and 30% or less. With such a transmittance, the luminance directly above the light source  20 A is reduced, thereby reducing unevenness in luminance of the surface light source. 
     The second light-reflective member  23  can be constituted of a light-transmissive resin and light scattering particles mixed in the light-transmissive resin. Examples of the light-transmissive resin include thermoplastic resins such as acrylic resins, polycarbonate resins, cyclic polyolefin resins, poly(ethylene terephthalate) resins, and polyester resins and thermosetting resins such as epoxy resins and silicone resins. Examples of the light scattering particles include particles of titania, silica, alumina, zinc oxide, magnesium oxide, zirconia, yttria, calcium fluoride, magnesium fluoride, niobium pentoxide, barium titanate, tantalum pentoxide, barium sulfate, and glass. Examples of the second light-reflective member  23  include a metal member made of Al or Ag and a dielectric multilayer film. 
     The light source may not include the covering member  24 . For example, a lower surface of a light source  20 B shown in  FIG.  5 C  is constituted of the lower surface of the light-emitting element  21  and the lower surface of the second light-transmissive member  22 . 
     The light source may be constituted of the light-emitting element  21  only. A light source  20 C shown in  FIG.  5 D  does not include the second light-transmissive member  22  or the covering member  24 . In the light source  20 C, the second light-reflective member  23  may be disposed on the upper surface of the light-emitting element  21 . The covering member  24  is not disposed on the lower surface of the light-emitting element  21  of the light source  20 C in  FIG.  5 D , but the covering member  24  may be disposed on the lower surface of the light-emitting element  21 . 
     &lt;First Light-Transmissive Member&gt; 
     The first light-transmissive member  30  is disposed between lateral surfaces of the light source  20 A and the light-guiding member  10  and on the light source  20 A in the first hole h 1  of the light-guiding member  10 . The first light-transmissive member  30  covers the upper surface and lateral surfaces of the light source  20 A. The first light-transmissive member  30  is preferably in contact with the light-guiding member  10  and the light source  20 A. This structure facilitates guiding of light from the light source  20 A to the light-guiding member  10 . 
     The first light-transmissive member  30  is adapted to transmit light emitted from the light source  20 A. For example, the first light-transmissive member  30  preferably has a transmittance of 50% or more, more preferably 70% or more, at a peak wavelength of the light source  20 A. For example, a resin can be used for the material of the first light-transmissive member  30 . For example, the same resin as the light-guiding member  10  or a resin with a small difference in refractive index from the material of the light-guiding member  10  can be used for the material of the first light-transmissive member  30 . 
     The first light-transmissive member  30  may be constituted of a single layer or a layered body of a plurality of layers in the third direction Z. The first light-transmissive member  30  may contain a phosphor and/or a light-diffusing material. In the case in which the first light-transmissive member  30  is a layered body, each layer may or may not contain a phosphor and/or a light-diffusing material. For example, the first light-transmissive member  30  may include a layer containing a phosphor and a layer containing no phosphor. 
     &lt;First Light-Reflective Member&gt; 
     The first light-reflective member  40  is disposed on the first light-transmissive member  30 . The first light-reflective member  40  is disposed above the light source  20 A with the first light-transmissive member  30  therebetween. The first light-reflective member  40  may be in contact with the first light-transmissive member  30  and the light source  20 A. The first light-reflective member  40  may be disposed above the first light-transmissive member  30  and the light source  20 A with an adhesive resin therebetween. Examples of the adhesive resin include thermoplastic resins such as acrylic resins, polycarbonate resins, cyclic polyolefin resins, poly(ethylene terephthalate) resins, and polyester resins and thermosetting resins such as epoxy resins and silicone resins. As shown in  FIG.  2   , the first light-reflective member  40  is disposed at a position overlapping the first hole h 1  in which the light source  20 A and the first light-transmissive member  30  are disposed in a plan view. 
     The first light-reflective member  40  is adapted to reflect and transmit light emitted from the light source  20 A. For example, the transmittance of the first light-reflective member  40  at a peak wavelength of the light source  20 A is preferably 1% or more and 50% or less, more preferably 3% or more and 30% or less. 
     The first light-reflective member  40  can be constituted of a light-transmissive resin and light scattering particles contained in the light-transmissive resin. Examples of the light-transmissive resin include thermoplastic resins such as acrylic resins, polycarbonate resins, cyclic polyolefin resins, poly(ethylene terephthalate) resins, and polyester resins and thermosetting resins such as epoxy resins and silicone resins. Examples of the light scattering particles include particles of titania, silica, alumina, zinc oxide, magnesium oxide, zirconia, yttria, calcium fluoride, magnesium fluoride, niobium pentoxide, barium titanate, tantalum pentoxide, barium sulfate, and glass. In the first light-reflective member  40 , the light-transmissive resin described above may not contain light scattering particles but may contain a large number of air bubbles. Examples of the first light-reflective member  40  include a metal member made of aluminum or silver and a dielectric multilayer film. 
     The upper surface of the first light-reflective member  40  functions as the light-exiting surface (light-emission surface) of the surface light source together with the first surface  11  of the light-guiding member  10 . The first light-reflective member  40  reflects a portion of light traveling toward a position above the first hole h 1  in which the light source  20 A is disposed and transmits another portion of the light. This configuration reduces the difference on the light-exiting surface of the surface light source between the luminance directly above the light source  20 A and its vicinity and the luminance in another region. The unevenness in luminance on the light-exiting surface of the surface light source can thus be reduced. 
     The first light-transmissive member  30  is disposed between the first light-reflective member  40  and the second light-reflective member  23  of the light source  20 A. The first light-transmissive member  30  has a higher transmittance for light emitted from the light source  20 A than the first light-reflective member  40  and the second light-reflective member  23 . The transmittance of the first light-transmissive member  30  with respect to light emitted from the light source  20 A can be twice or more and 100 times or less as high as the transmittance of the second light-reflective member  23  and the transmittance of the first light-reflective member  40  in the range of 100% or less. Light emitted from the lateral surfaces of the light source  20 A, light reflected by a third light-reflective member  53  described below, and the like travel round and are guided to the first light-transmissive member  30  between the first light-reflective member  40  and the second light-reflective member  23 . This allows for preventing the region directly above the light source  20 A from being excessively bright or excessively dark, so that unevenness in luminance in the light-exiting surface of the surface light source can be reduced. 
     Transmission of a portion of light emitted directly upward from the light source  20 A is suppressed by the second light-reflective member  23 , so that the transmittance of the first light-reflective member  40  for light emitted from the light source  20 A is preferably higher than the transmittance of the second light-reflective member  23  to prevent the region directly above the light source  20 A from being excessively dark. 
     &lt;Supporting Member&gt; 
     The supporting member  50  supports the light-guiding member  10  and the light sources  20 A. The light-guiding member  10  is disposed on the supporting member  50  such that the second surface  12  faces the upper surface of the supporting member  50 . On the supporting member  50 , each of the light sources  20 A is disposed in a respective one of the first holes h 1 . 
     The supporting member  50  includes a wiring board  60 . The wiring board  60  includes an insulating base member  61  and at least one wiring layer  62  disposed on at least one surface of the insulating base member  61 . The insulating base member  61  may be a rigid substrate or a flexible substrate. In order to slim down the surface light source, the insulating base member  61  is preferably a flexible substrate. The insulating base member  61  may be constituted of a single layer or a layered body of a plurality of layers in the third direction Z. For example, the insulating base member  61  may be constituted of a single layer of a flexible substrate or a layered body of a plurality of rigid substrates. For example, a resin such as a polyimide can be used for the material of the insulating base member  61 . The wiring layer  62  is a metal film such as a copper film. 
     The supporting member  50  further includes a first adhesive layer  51  disposed on the wiring board  60 , the third light-reflective member  53  disposed on the first adhesive layer  51 , and a second adhesive layer  52  disposed on the third light-reflective member  53 . 
     The first adhesive layer  51  is disposed on a surface of the insulating base member  61  opposite to the surface on which the wiring layer  62  is disposed. The first adhesive layer  51  is disposed between the insulating base member  61  and the third light-reflective member  53  and bonds the insulating base member  61  and the third light-reflective member  53 . For example, the first adhesive layer  51  is a resin layer containing light scattering particles. Examples of the light scattering particles include particles of titania, silica, alumina, zinc oxide, magnesium oxide, zirconia, yttria, calcium fluoride, magnesium fluoride, niobium pentoxide, barium titanate, tantalum pentoxide, barium sulfate, and glass. Examples of the resin in the first adhesive layer  51  include thermoplastic resins such as acrylic resins, polycarbonate resins, cyclic polyolefin resins, poly(ethylene terephthalate) resins, and polyester resins and thermosetting resins such as epoxy resins and silicone resins. 
     The third light-reflective member  53  is disposed below the second surface  12  of the light-guiding member  10 , below the light sources  20 A, below the first light-transmissive members  30 , and below the grooves  14 . The third light-reflective member  53  is adapted to reflect light emitted from the light sources  20 A. For example, a resin member containing a large number of air bubbles or a resin member containing light scattering particles can be used for the third light-reflective member  53 . For example, the resin for the third light-reflective member  53  can be selected from the resins listed above as the resins that can be used for the first adhesive layer  51 . For example, the light scattering particles can be selected from the light scattering particles listed above as the light scattering particles that can be used for the first adhesive layer  51 . 
     In the region between the third light-reflective member  53  and the first surface  11  of the light-guiding member  10 , light emitted from the light sources  20 A is guided toward the grooves  14  through the light-guiding member  10  while reflection is repeated between the third light-reflective member  53  and the first surface  11 . A portion of light traveling toward the first surface  11  is extracted from the first surface  11  to the outside of the light-guiding member  10 . A portion of light traveling toward the second surface  12  is reflected by the third light-reflective member  53  toward the first surface  11 , so that the luminance of light extracted from the first surface  11  can be improved. A resin member containing a large number of air bubbles is preferably used for the third light-reflective member  53 . The amount of light reflected by the third light-reflective member  53  increases, which facilitates guiding of light emitted from the light sources  20 A toward the grooves  14  through the light-guiding member  10 . Further, if the first adhesive layer  51  disposed on the lower surface of the third light-reflective member  53  is light-reflective, the luminance of light extracted from the first surface  11  can be further improved. 
     The second adhesive layer  52  is disposed between the third light-reflective member  53  and the second surface  12  of the light-guiding member  10  and bonds the third light-reflective member  53  and the light-guiding member  10 . The light sources  20 A are disposed on the second adhesive layer  52  in the first holes h 1  of the light-guiding member  10 . The second adhesive layer  52  is adapted to transmit light emitted from the light sources  20 A. For example, the material of the second adhesive layer  52  can be selected from the resins listed above as the resins that can be used for the first adhesive layer  51 . The second adhesive layer  52  may contain light scattering particles that can be selected from, for example, the light scattering particles listed above as the light scattering particles that can be used for the first adhesive layer  51 . 
     The supporting member  50  further includes electroconductive members  70 . For example, the electroconductive members  70  include a resin and metal particles mixed in the resin. Examples of the resin for the electroconductive members  70  include epoxy resins and phenolic resins. For example, copper or silver particles can be used for the metal particles. 
     Each of the electroconductive members  70  includes a connecting portion  71  and a wiring portion  72 . The connecting portions  71  extend through the second adhesive layer  52 , the third light-reflective member  53 , the first adhesive layer  51 , and the insulating base member  61  in the third direction Z. The wiring portions  72  are disposed on the surface of the wiring board  60  on which the wiring layer  62  is disposed and are connected to the connecting portions  71 . For example, the connecting portion  71  and the wiring portion  72  can be integrally formed of the same material. A portion  72   a  of the wiring portion  72  is connected to the wiring layer  62 . 
     A pair of electroconductive members  70  are disposed separately from each other to correspond to the pair of positive and negative electrodes  25  of each light source  20 A. The connecting portion  71  of one electroconductive member  70  is connected to the positive electrode  25  below the light source  20 A, and the connecting portion  71  of the other electroconductive member  70  is connected to the negative electrode  25  below the light source  20 A. The electrodes  25  of the light source  20 A are electrically connected to the electroconductive members  70  and the wiring layer  62 . 
     The supporting member  50  further includes an insulating layer  54 . The insulating layer  54  covers and protects the surface of the wiring board  60  on which the wiring layer  62  is disposed, the wiring layer  62 , and the electroconductive members  70 . 
     The first outer portions  1   b  and the second outer portions  1   c  include the same members as in the inner portions  1   a  described above.  FIG.  4    is a schematic cross-sectional view taken along the line IV-IV of  FIG.  1 A  and schematically shows a cross section of a portion of a first outer portion  1   b  including an outer lateral surface not adjacent to another light-emitting portion  1 . The outer lateral surfaces of the second outer portions  1   c  not adjacent to other light-emitting portions  1  have the same configuration as the outer lateral surfaces of the first outer portions  1   b.    
     The number of light-emitting portions  1  adjacent to a single first outer portion  1   b  in a plan view is smaller than the number of light-emitting portions  1  adjacent to a single inner portion  1   a , and the number of light-emitting portions  1  adjacent to a single second outer portion  1   c  is smaller than the number of light-emitting portions  1  adjacent to a single inner portion  1   a . Accordingly, the amount of light entering the single first outer portion  1   b  from its adjacent light-emitting portions  1  is smaller than the amount of light entering the single inner portion  1   a  from its adjacent light-emitting portions  1 , and the amount of light entering the single second outer portion  1   c  from its adjacent light-emitting portions  1  is smaller than the amount of light entering the single inner portion  1   a  from its adjacent light-emitting portions  1 . Therefore, in an all-lit state in which all the light-emitting portions  1  emit light, the perimeter of the light-guiding member  10  on which the first outer portions  1   b  and the second outer portions  1   c  are located therefore tends to be darker than the region in which the inner portions  1   a  are located. 
     In the present embodiment, in a plan view, the area of a single first outer portion  1   b  is smaller than the area of a single inner portion  1   a  as shown in  FIG.  1 A . The emission intensity of a single first outer portion  1   b  per unit area can thus be higher than the emission intensity of a single inner portion  1   a  per unit area in a state in which the same amount of electricity is supplied to the light sources  20 A each corresponding to a respective one of the first outer portion  1   b  and the inner portion  1   a . Similarly, the area of a single second outer portion  1   c  is smaller than the area of a single inner portion  1   a  in a plan view. The emission intensity of a single second outer portion  1   c  per unit area can thus be higher than the emission intensity of a single inner portion  1   a  per unit area in a state in which the same amount of electricity is supplied to the light sources  20 A each corresponding to a respective one of the second outer portion  1   c  and the inner portion  1   a . Accordingly, the reduction in luminance on the perimeter of the light-guiding member  10  can be compensated in the all-lit state, and the unevenness in luminance on the light-exiting surface of the surface light source can be reduced. 
     For example, the area of a single outer portion can be smaller than at least the area of the inner portion  1   a  closest to the center of the light-guiding member  10  in a plan view as shown in  FIG.  1 A . The center of the light-guiding member  10  in a plan view refers to the centroid of the light-guiding member  10 . For example, in the case in which the light-guiding member  10  has a quadrangular shape, the center of the light-guiding member  10  is located at the intersection point of the two diagonals of the light-guiding member  10  in a plan view. In the case where an inner portion  1   a  overlaps the center of the light-guiding member  10  in a plan view, the inner portion  1   a  overlapping the center of the light-guiding member  10  serves as the inner portion  1   a  closest to the center of the light-guiding member  10 . In the case where the inner portion  1   a  does not overlap the center of the light-guiding member  10  in a plan view, an inner portion  1   a  having an outer edge (lateral surface adjacent to a groove  14 ) closest to the center of the light-guiding member  10  is the inner portion  1   a  closest to the center of the light-guiding member  10 . In this case, a plurality of inner portions  1   a  can be closest to the center of the light-guiding member  10 , and any of the inner portions  1   a  may be regarded as the inner portion  1   a  closest to the center of the light-guiding member  10 . 
     In the present specification, a single first outer portion  1   b  having an area smaller than the area of an inner portion  1   a  is a first outer portion  1   b  among a plurality of first outer portions  1   b . Also, a single second outer portion  1   c  having an area smaller than the area of an inner portion  1   a  is a second outer portion  1   c  among a plurality of second outer portions  1   c . There may be a case in which a plurality of first outer portions  1   b  have respective areas each smaller than the area of an inner portion  1   a , or in which a plurality of second outer portions  1   c  have respective areas each smaller than the area of an inner portion  1   a . All the first outer portions  1   b  and all the second outer portions  1   c  may each have an area smaller than the area of one inner portion  1   a . In this case, the unevenness in luminance in the all-lit state on the light-exiting surface of the surface light source can be further reduced. 
     Each first outer portion  1   b  may have any appropriate area. The area of a single first outer portion  1   b  is preferably 0.5 times or more and 0.8 times or less as large as the area of a single inner portion  1   a . When the area of a single first outer portion  1   b  is 0.5 times or more as large as the area of a single inner portion  1   a , the first outer portion  1   b  can be easily prevented from being excessively bright. When the area of a single first outer portion  1   b  is 0.8 times or less as large as the area of a single inner portion  1   a , the first outer portion  1   b  can be easily prevented from being excessively dark. Each second outer portion  1   c  may have any appropriate area. The area of a single second outer portion  1   c  is preferably 0.2 times or more and 0.7 times or less as large as the area of a single inner portion  1   a . When the area of a single second outer portion  1   c  is 0.2 times or more as large as the area of a single inner portion  1   a , the second outer portion  1   c  can be easily prevented from being excessively bright. When the area of a single second outer portion  1   c  is 0.7 times or less as large as the area of one inner portion  1   a , the second outer portion  1   c  can be easily prevented from being excessively dark. 
     Among the outer portions, the number of light-emitting portions  1  adjacent to one second outer portion  1   c  located at a corner of the light-guiding member  10  is smaller than the number of light-emitting portions  1  adjacent to one first outer portion  1   b  located at a position other than the corners. The luminance at the corner tends to be particularly dark in the outer peripheral portion of the light-guiding member  10  in the all-lit state. The emission intensity of one second outer portion  1   c  per unit area is thus preferably higher than the emission intensity of one first outer portion  1   b  per unit area in a state in which the area of one second outer portion  1   c  is smaller than the area of one first outer portion  1   b  and in which the same amount of electricity is supplied to the light sources  20 A of the respective first outer portions  1   b  and second outer portions  1   c.    
     The unevenness in luminance on the light-exiting surface of the surface light source in the all-lit state can be further reduced by making the light sources  20 A of the first outer portions  1   b  and/or the second outer portions  1   c  brighter than the light sources  20 A of the inner portions  1   a  in addition to making the area of one first outer portion  1   b  and/or one second outer portion  1   c  smaller than the area of one inner portion  1   a . For example, the light sources  20 A of the first outer portions  1   b  and/or the second outer portions  1   c  can be brighter than the light sources  20 A of the inner portions  1   a  by making the amount of electricity supplied to the light sources  20 A of the first outer portions  1   b  and/or the second outer portions  1   c  larger than the amount of electricity supplied to the light sources  20 A of the inner portions  1   a . For example, when the sizes of the light sources  20 A of the first outer portions  1   b  and/or the second outer portions  1   c  is larger than the sizes of the light sources  20 A of the inner portions  1   a , the light sources  20 A of the first outer portions  1   b  and/or the second outer portions  1   c  can be brighter than the light sources  20 A of the inner portions  1   a.    
     The grooves  14  include first grooves  14 - 1  and second grooves  14 - 2  as shown in  FIG.  1 A . The first grooves  14 - 1  are located between adjacent first outer portions  1   b  and between the first outer portions  1   b  and the second outer portions  1   c . The second grooves  14 - 2  are located between adjacent inner portions  1   a . The first grooves  14 - 1  and the second grooves  14 - 2  are located on the same straight lines in the first direction X. The first grooves  14 - 1  and the second grooves  14 - 2  are located on the same straight lines in the second direction Y. The grooves  14  further include third grooves  14 - 3  located between the first outer portions  1   b  and the inner portions  1   a  and between the second outer portions  1   c  and the inner portions  1   a . The first grooves  14 - 1  between the first outer portions  1   b  and the second outer portions  1   c  adjacent to each other in the second direction Y and the third grooves  14 - 3  are located on the same straight lines in the first direction X. The first grooves  14 - 1  between the first outer portions  1   b  and the second outer portions  1   c  adjacent to each other in the first direction X and the third grooves  14 - 3  are located on the same straight lines in the second direction Y. 
     The structure shown in  FIG.  1 A  is obtained by disposing the light-guiding member  10  on the supporting member  50 , forming the grooves  14 , and dividing the light-guiding member  10  into a plurality of light-emitting portions  1 . The method of disposing the light-guiding member  10  on the supporting member  50  and then dividing the light-guiding member  10  into a plurality of light-emitting portions  1  makes the manufacture easy as compared with a method of disposing on the supporting member  50  individual light-emitting portions  1  separated before being disposed on the supporting member  50 . Also, the accuracy of position of each light-emitting portion  1  on the supporting member  50  can be enhanced. The structure shown in  FIG.  1 A  can also be obtained by disposing on the supporting member  50  individual light-emitting portions  1  separated before being disposed on the supporting member  50 . 
     The first grooves  14 - 1  and the second grooves  14 - 2  can be misaligned in the first direction X and can be misaligned in the second direction Y as in the example shown in  FIG.  1 B . The misalignment of the first grooves  14 - 1  and the second grooves  14 - 2  in the first direction X can inhibit the surface light source from being bent. The light-guiding member  10  is divided by the grooves  14 . The strength of the portions of the surface light source at which the grooves  14  are located tends to be reduced. With the first grooves  14 - 1  and the second grooves  14 - 2 , which tend to cause reduction in the strength of the surface light source, located apart from each other in the first direction X can suppress bending of the surface light source along the second direction Y. Similarly, with the first grooves  14 - 1  and the second grooves  14 - 2  arranged offset from each other in the second direction Y, bending of the surface light source can be reduced. The first grooves  14 - 1  between the first outer portions  1   b  and the second outer portions  1   c  adjacent to each other in the second direction Y and the third grooves  14 - 3  are located on the same straight lines in the first direction X. The first grooves  14 - 1  between the first outer portions  1   b  and the second outer portions  1   c  adjacent to each other in the first direction X and the third grooves  14 - 3  are located on the same straight lines in the second direction Y. The first grooves  14 - 1  between the first outer portions  1   b  and the second outer portions  1   c  adjacent to each other in the second direction Y and the third grooves  14 - 3  may not be located on the same straight lines in the first direction X. This structure allows for reducing bending of the surface light source. The first grooves  14 - 1  between the first outer portions  1   b  and the second outer portions  1   c  adjacent to each other in the first direction X and the third grooves  14 - 3  may not be located on the same straight lines in the second direction Y. This structure allows for reducing bending of the surface light source. 
     The structure shown in  FIG.  1 B  can be obtained by dividing the light-guiding member  10  into a plurality of light-emitting portions  1  by the grooves  14  and then disposing the light-emitting portions  1  on the supporting member  50 . The structure shown in  FIG.  1 B  can also be obtained by disposing the light-guiding member  10  on the supporting member  50 , forming the grooves  14 , and dividing the light-guiding member  10  into a plurality of light-emitting portions  1 . In one example of other manufacturing methods, a first portion constituting a plurality of inner portions  1   a  of the light-guiding member  10  is disposed on the supporting member  50 . The first portion disposed on the supporting member  50  is a structure that has not been divided yet. The grooves  14  are then formed in the first portion disposed on the supporting member  50  to separate the first portion into a plurality of inner portions  1   a . After that, a plurality of separated first outer portions  1   b  and second outer portions  1   c  are disposed on the supporting member  50 . The structure shown in  FIG.  1 B  can be obtained also in this manner. 
     An exemplary embodiment of the present invention has been described with reference to specific examples. However, the present invention is not limited by these specific examples. All embodiments that can be implemented by a person skilled in the art by appropriately changing configurations on the basis of the embodiment of the present invention described above are within the scope of the present invention as long as the gist of the present invention is included. In addition, a person skilled in the art can think of other various modifications and amendments within the idea of the present invention, and the modifications and amendments are also within the scope of the present invention.