Planar light source

Abstract

To suppress luminance unevenness generated in a peripheral edge, in a planar light source whose planar shape is an irregular shape.SOLUTION: A planar light source has: a mounting substrate; a plurality of light sources arrayed two-dimensionally on the mounting substrate in a planar view; a frame body having a first bottom part and side walls surrounding the mounting substrate; a wavelength conversion member arranged on the side walls; and a light diffusion plate arranged above the plurality of light sources and the wavelength conversion member. A distance between the wavelength conversion member and the light source arranged outermost among the plurality of light sources is larger than a distance between two adjacent light sources among the plurality of light sources.SELECTED DRAWING: Figure 18B

Description

[Technical Field]

[0001] The present disclosure relates to a surface light source. [Background technology]

[0002] 2. Description of the Related Art Planar light sources using light-emitting elements such as light-emitting diodes are widely used as various light sources for displays, backlights of liquid crystal display devices, and the like.

[0003] An example of such a surface light source is a configuration including light emitting elements arranged two-dimensionally and a light diffusion plate arranged above each light emitting element. In this surface light source, the light diffusion plate contains diffusion particles for diffusing light from the light emitting portions of the light emitting elements, and is integrally formed with convex portions that protrude in a gently curved shape toward the light emitting elements on at least an area of ​​the surface facing the light emitting elements, corresponding to the light emitting portions of the light emitting elements. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-221779 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to suppress brightness unevenness that occurs at the periphery of a surface light source having an irregular planar shape. [Means for solving the problem]

[0006] A surface light source according to one embodiment of the present disclosure includes a mounting substrate, a plurality of light sources arranged two-dimensionally on the mounting substrate in a planar view, a frame having a first bottom and side walls surrounding the mounting substrate, a wavelength conversion member arranged on the side walls, and a light diffusion plate arranged above the plurality of light sources and the wavelength conversion member, wherein the distance between the wavelength conversion member and the light source arranged at the outermost position among the plurality of light sources is greater than the distance between two adjacent light sources among the plurality of light sources. [Effects of the Invention]

[0007] According to an embodiment of the present disclosure, it is possible to suppress uneven brightness occurring at the periphery of a surface light source having an irregular planar shape. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic plan view illustrating the surface light source according to the first embodiment. [Figure 2] FIG. 2 is a schematic partial enlarged plan view of part E in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] 2 is a plan view schematically illustrating the arrangement of light sources in the surface light source according to the first embodiment. FIG. [Figure 5] 3 is a plan view schematically illustrating a light diffusion plate in the surface light source according to the first embodiment. FIG. [Figure 6] FIG. 4 is a partially enlarged cross-sectional view of the vicinity of the light source in FIG. 3. [Figure 7] FIG. 10 is a schematic plan view (part 1) illustrating the width of the thin plate portion. [Figure 8] FIG. 10 is a schematic plan view (part 2) illustrating the width of the thin plate portion. [Figure 9] FIG. 10 is a diagram (part 1) showing the results of a simulation regarding a light diffusion plate. [Figure 10] FIG. 10 is a diagram (part 2) showing the results of a simulation regarding a light diffusion plate. [Figure 11] FIG. 2 is a schematic cross-sectional view illustrating the arrangement of optical members. [Figure 12]10 is a schematic partial enlarged cross-sectional view (part 1) illustrating a light diffusion plate in a surface light source according to Modification 1 of the first embodiment. FIG. [Figure 13] FIG. 10 is a schematic partially enlarged cross-sectional view (part 2) illustrating the light diffusion plate in the surface light source according to Modification 1 of the first embodiment. [Figure 14] FIG. 10 is a schematic partially enlarged cross-sectional view (part 3) illustrating the light diffusion plate in the surface light source according to Modification 1 of the first embodiment. [Figure 15] 15 is a plan view schematically illustrating the light diffusion plate of FIG. 14. FIG. [Figure 16] FIG. 10 is a schematic partial enlarged plan view of a partition member according to Modification 2 of the first embodiment. [Figure 17] FIG. 17 is a cross-sectional view taken along line BB in FIG. [Figure 18A] FIG. 1 is a schematic enlarged partial cross-sectional view (part 1) of the vicinity of the outer edge of the surface light source. [Figure 18B] FIG. 2 is a schematic enlarged partial cross-sectional view (part 2) of the vicinity of the outer edge of the surface light source. [Figure 19] FIG. 10 is a schematic plan view illustrating the outer shape of a substrate in a surface light source according to Modification 3 of the first embodiment. [Figure 20] FIG. 10 is a configuration diagram illustrating a liquid crystal display device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a description will be given of an embodiment of the invention with reference to the drawings. In the following description, terms indicating specific directions or positions (e.g., "upper," "lower," and other terms including these terms) will be used as necessary. However, the use of these terms is intended to facilitate understanding of the invention with reference to the drawings, and the meaning of these terms does not limit the technical scope of the present invention. Furthermore, parts that appear with the same reference numerals in multiple drawings indicate the same or equivalent parts or components.

[0010] Furthermore, the embodiments shown below are intended to exemplify a surface light source embodying the technical concept of the present invention, and are not intended to limit the present invention. Furthermore, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described below are intended for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, the content described in one embodiment can also be applied to other embodiments and modified examples. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0011] First Embodiment (Surface light source 10) FIG. 1 is a schematic plan view illustrating a surface light source according to the first embodiment. FIG. 2 is a schematic partially enlarged plan view of part E in FIG. 1. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 4 is a schematic plan view illustrating the arrangement of light sources in the surface light source according to the first embodiment, with the partitioning member and light diffusion plate removed from FIG. 1. FIG. 5 is a schematic plan view illustrating the light diffusion plate in the surface light source according to the first embodiment. FIG. 6 is a partially enlarged cross-sectional view of the vicinity of the light source in FIG. 3.

[0012] 1 to 6, the surface light source 10 is a surface-emitting light-emitting device having a substrate 11, a light source 12, a partitioning member 13, and a light diffusion plate 14. However, the partitioning member 13 is not an essential component of the surface light source 10, and is provided as needed. When the partitioning member 13 is not provided, for example, a support for supporting the light diffusion plate 14 may be provided.

[0013] In the following description, a planar view refers to viewing an object from the normal direction of the upper surface 11m of the substrate 11, and a planar shape refers to the shape of the object viewed from the normal direction of the upper surface 11m of the substrate 11.

[0014] A plurality of light sources 12, each including a light emitting diode, are arranged on a mounting substrate 11. There is no limit to the number of light sources 12 arranged on the substrate 11, and any number of light sources 12 may be arranged on the substrate 11.

[0015] The partitioning member 13 is disposed on the same side of the substrate 11 as the light sources 12. The partitioning member 13 includes top portions 13a arranged in a lattice pattern in a plan view and wall portions 13b surrounding each of the light sources 12 in a plan view, and has a plurality of regions surrounding the light sources 12. The wall portions 13b of the partitioning member 13 extend, for example, from the top portions 13a toward the substrate 11, and in a cross-sectional view, the width of the region surrounded by the opposing wall portions 13b becomes narrower as it approaches the substrate 11.

[0016] The range (i.e., area and space) surrounded by the wall portion 13b is defined as one compartment C, and the compartment member 13 includes a plurality of compartments C. In this embodiment, one light source 12 is arranged in one compartment C. However, two or more light sources 12 may be arranged in one compartment C. In this case, for example, three light sources 12 of red, green, and blue may be arranged in one compartment C. Alternatively, two light sources 12 of daylight color and warm white color may be arranged in one compartment C.

[0017] The light diffusion plate 14 is an optical member placed on the top 13a of the partition member 13 and disposed above the light source 12. The planar light source 10 can improve the uniformity of light by including the light diffusion plate 14. The light diffusion plate 14 according to this embodiment has a thin portion at the periphery to suppress uneven brightness that occurs at the periphery of the planar light source 10.

[0018] The outermost contour portion of each component in plan view is referred to as the outer edge, and the area having a width including the outer edge is referred to as the periphery. In particular, the periphery of the light diffuser plate 14 is the area of ​​the light diffuser plate 14 that is located outside the light sources 12 arranged at the outermost periphery in plan view. The periphery does not necessarily refer to an annular area.

[0019] Each element constituting the surface light source 10 will be described in detail below.

[0020] (Substrate 11) The substrate 11 is a member for mounting a plurality of light sources 12 and has an irregular shape. Here, an irregular shape refers to a shape other than a rectangular shape, such as a shape that is partially or entirely deformed from a perfect rectangular shape in order to fit the shape of a specific product.

[0021] 6, conductor wirings 18A and 18B for supplying power to light sources 12 such as light emitting elements 12a are formed on an upper surface 11m of the substrate 11. It is preferable that regions of the conductor wirings 18A and 18B that are not electrically connected are covered with a covering member 15.

[0022] The material of the substrate 11 may be any material capable of insulating and isolating at least one pair of conductor wirings 18A and 18B, and examples thereof include ceramics, resins, composite materials, etc. Examples of ceramics include alumina, mullite, forsterite, glass ceramics, nitrides (e.g., AlN), carbides (e.g., SiC), and LTCC. Examples of resins include phenolic resins, epoxy resins, polyimide resins, BT resins, polyphthalamide (PPA), and polyethylene terephthalate (PET). Examples of composite materials include those obtained by mixing the above-mentioned resins with inorganic fillers such as glass fiber, SiO2, TiO2, and Al2O3, glass fiber reinforced resins (glass epoxy resins), and metal substrates in which an insulating layer is formed on a metal member.

[0023] The thickness of the substrate 11 can be selected appropriately. The substrate 11 may be either a flexible substrate or a rigid substrate that can be manufactured by a roll-to-roll method. The rigid substrate may be a thin rigid substrate that can be bent. The material of the conductor wirings 18A and 18B is not particularly limited as long as it is a conductive member, and materials that are normally used as wiring layers for circuit boards and the like can be used. A plating film, a light-reflecting film, or the like may be formed on the surface of the conductor wirings 18A and 18B.

[0024] The covering member 15 is preferably made of an insulating material. Examples of materials for the covering member 15 include the same materials as those exemplified as materials for the substrate 11. By using the above-mentioned resin containing a white filler or the like as the covering member 15, the light emitted from the light source 12 is reflected, thereby improving the light extraction efficiency of the surface light source 10.

[0025] (Light source 12) The light sources 12 are arranged two-dimensionally in a first direction and a second direction perpendicular to the first direction on the substrate 11 in a plan view. The first and second directions are, for example, the X and Y directions in FIG. 1, etc.

[0026] The light source 12 is a light-emitting component, and includes, for example, a light-emitting element that emits light itself, a light-emitting element sealed with a translucent resin, or a surface-mounted light-emitting device (also called an LED) in which a light-emitting element is packaged. For example, as shown in FIG. 6, the light source 12 may be a light-emitting element 12a covered with a sealing member 12b. The light source 12 may be a single light-emitting element 12a, or a plurality of light-emitting elements may be used to form a single light source 12. The light source 12 may also be configured to include a resin containing a light-reflective material that surrounds the side surfaces of the light-emitting element, and a translucent member that covers the upper surface of the light-emitting element and the upper surface of the resin containing the light-reflective material. The light-transmitting member may also be configured to include a translucent member that covers the upper surface of the light-emitting element, and a resin containing a light-reflective material that surrounds the side surfaces of the light-emitting element and the side surfaces of the translucent member. The translucent member may contain a phosphor. A translucent bonding member that bonds the light-emitting element and the translucent member may be provided between the light-emitting element and the translucent member.

[0027] The light sources 12 may have any light distribution characteristics, but preferably have a wide light distribution so as to emit light with less brightness unevenness in each section C surrounded by the wall portions 13b of the partitioning member 13. In particular, it is preferable that each of the light sources 12 has a batwing light distribution characteristic. This reduces the amount of light emitted directly above the light sources 12, widens the light distribution of each light source 12, and irradiates the widened light onto the wall portions 13b and the second bottom portion 13c, thereby reducing brightness unevenness in each section C surrounded by the wall portions 13b.

[0028] Here, the batwing light distribution characteristic is defined as having an emission intensity distribution in which, with the optical axis OA set to 0°, the emission intensity is stronger at angles where the absolute value of the light distribution angle is greater than 0°. Note that the optical axis OA is defined as a line that passes through the center of light source 12 and perpendicularly intersects with upper surface 11m of substrate 11, as shown in Fig. 6.

[0029] In particular, as shown in Fig. 6, an example of a light source 12 having a batwing light distribution characteristic is one that uses a light-emitting element 12a having a light-reflecting film 12c on its upper surface. By providing the light-reflecting film 12c on the upper surface of the light-emitting element 12a, most of the light emitted upward from the light-emitting element 12a is reflected by the light-reflecting film 12c, thereby reducing the amount of light directly above the light-emitting element 12a and achieving a batwing light distribution characteristic. Because the light-reflecting film 12c can be formed directly on the light-emitting element 12a, there is no need to separately combine a special lens to achieve the batwing light distribution, and the thickness of the light source 12 can be reduced.

[0030] The light-reflecting film 12c may be a metal film such as silver or copper, a resin containing a white filler, or a combination thereof. The light-reflecting film 12c may also be a dielectric multilayer film (DBR film) that has reflectance angle dependency on the incident angle for the wavelength of light emitted from the light-emitting element 12a. Specifically, the reflectance of the light-reflecting film 12c is preferably set to be lower for oblique incidence than for perpendicular incidence. This reduces the change in brightness directly above the light-emitting element 12a, preventing the area directly above the light-emitting element 12a from becoming too dark, such as a dark spot.

[0031] The light source 12 may have a height of 100 μm to 500 μm for the light emitting element 12a directly mounted on the substrate 11. The thickness of the light reflecting film 12c may be 0.1 μm to 3.0 μm. The thickness of the light source 12 including the sealing member 12b may be about 0.5 mm to 2.0 mm.

[0032] The plurality of light sources 12 can be driven independently of one another, and are preferably wired on the substrate 11 so that dimming control (for example, local dimming or high dynamic range) for each light source 12 is possible.

[0033] (Light-emitting element 12a) Known light-emitting elements 12a can be used. For example, it is preferable to use light-emitting diodes as the light-emitting elements 12a. Light-emitting elements 12a with any wavelength can be selected. For example, blue and green light-emitting elements can be made of nitride-based semiconductors such as GaN, InGaN, AlGaN, and AlInGaN. Red light-emitting elements can be made of GaAlAs, AlInGaP, and the like. Semiconductor light-emitting elements made of other materials can also be used. The composition, light-emitting color, size, number, and other factors of the light-emitting elements used can be selected appropriately depending on the purpose.

[0034] 6, the light emitting element 12a may be flip-chip mounted via a bonding member 19 so as to straddle a pair of positive and negative conductor wirings 18A and 18B provided on the upper surface 11m of the substrate 11. However, the light emitting element 12a may be face-up mounted as well as flip-chip mounted.

[0035] The bonding member 19 is a member for fixing the light emitting element 12a to a substrate or conductive wiring, and may be made of an insulating resin or a conductive member. In the case of flip-chip mounting as shown in Fig. 6, a conductive member is used. Specific examples include an Au-containing alloy, an Ag-containing alloy, a Pd-containing alloy, an In-containing alloy, a Pb-Pd-containing alloy, an Au-Ga-containing alloy, an Au-Sn-containing alloy, an Sn-containing alloy, an Sn-Cu-containing alloy, an Sn-Cu-Ag-containing alloy, an Au-Ge-containing alloy, an Au-Si-containing alloy, an Al-containing alloy, a Cu-In-containing alloy, and a mixture of a metal and flux.

[0036] (Sealing member 12b) The sealing member 12b covers the light-emitting element 12a for the purposes of protecting the light-emitting element 12a from the external environment and optically controlling the light output from the light-emitting element 12a (for example, to obtain a bad wing light distribution characteristic). The sealing member 12b is formed of a light-transmitting material. Examples of materials that can be used for the sealing member 12b include light-transmitting resins such as epoxy resin, silicone resin, or a mixture thereof, and glass. Of these, silicone resin is preferred in view of its light resistance and ease of molding. The sealing member 12b may contain a diffusing agent for diffusing the light from the light-emitting element 12a, a coloring agent corresponding to the light-emission color of the light-emitting element 12a, and the like. Diffusing agents, coloring agents, and the like that are known in the art can be used.

[0037] The sealing member 12b may be in direct contact with the substrate 11. The sealing member 12b has a viscosity adjusted to allow printing, dispenser application, or the like, and can be cured by heat treatment or light irradiation. Examples of the shape of the sealing member 12b include, but are not limited to, a substantially hemispherical shape, a vertically elongated convex shape in cross-section, a flattened convex shape in cross-section, and a circular or elliptical shape in plan view. Here, a vertically elongated convex shape refers to a shape in which, in cross-section, the maximum length in a direction perpendicular to the top surface 11m of the substrate 11 is longer than the maximum length in a direction parallel to the top surface 11m of the substrate 11. Furthermore, a flattened convex shape refers to a shape in which, in cross-section, the maximum length in a direction parallel to the top surface 11m of the substrate 11 is longer than the maximum length in a direction perpendicular to the top surface 11m of the substrate 11. The sealing member 12b may be disposed as an underfill 12d between the lower surface of the light-emitting element 12a and the top surface 11m of the substrate 11.

[0038] (compartment member 13) The walls 13b of the partitioning member 13 can be arranged in a lattice pattern in a plan view. In a plan view, the boundaries between adjacent partitions C can be regarded as tops 13a. It is preferable that the partitioning member 13 has second bottoms 13c that connect to the lower ends of the walls 13b within the partitions C. In other words, it is preferable that the partitioning member 13 defines the partitions C by the second bottoms 13c and the walls 13b. The second bottoms 13c may extend to the periphery of the substrate 11 in a plan view. In this case, the second bottoms 13c may be located closer to the outer edge of the substrate 11 than the outermost wall portions 13b. The periphery of the partitioning member 13 may have a portion that overlaps with the periphery of the substrate 11. It is preferable that the partitioning member 13 is a reflective material.

[0039] The partitioning member 13 has a through-hole 13d in which the light source 12 is disposed, for example, approximately at the center of the second bottom 13c in the partition C. As shown in Fig. 6, the light source 12 is preferably disposed in the through-hole 13d. The shape and size of the through-hole 13d may be any shape and size that allows the entire light source 12 to be exposed, and it is preferable that the outer edge of the through-hole 13d be positioned only near the light source 12. This makes it possible for the light from the light source 12 to be reflected by the second bottom 13c as well, improving the light extraction efficiency, when the partitioning member 13 has reflectivity.

[0040] Apex 13a is the highest part of wall 13b. Apex 13a may be flat, but preferably the vicinity of apex 13a has a ridge shape. In other words, the vertical cross section of wall 13b constituting apex 13a preferably forms an acute triangle, and more preferably forms an acute isosceles triangle.

[0041] The acute angle of the acute triangle or acute isosceles triangle, i.e., the angle (α in FIG. 6) on the apex 13a side of the wall portion 13b, is preferably set to, for example, 60° to 90°. By setting the angle in this range, the space and area occupied by the partition member 13 can be reduced, the height of the partition member 13 can be reduced, and the surface light source 10 can be made smaller and thinner.

[0042] The pitch P between the tops 13a of the partitioning member 13 can be adjusted as appropriate depending on the size of the light source used, the size and performance of the intended planar light source, etc. The pitch P can be, for example, 1 mm to 50 mm, preferably 5 mm to 20 mm, and more preferably 6 mm to 15 mm. The wall 13b surrounding the light source 12 is preferably configured by an inclined surface that widens upward from the vicinity of the second bottom 13c and the upper surface 11m of the substrate 11 on the partition C side.

[0043] Furthermore, the height of the partitioning member 13 itself, i.e., the length from the underside of the second bottom 13c of the partitioning member 13 to the top 13a, is preferably 8 mm or less, and is preferably about 1 mm to 4 mm when an even thinner planar light source is desired. Furthermore, the distance from the underside of the second bottom 13c of the partitioning member 13 to the light diffusion plate 14 is preferably about 8 mm or less, and is preferably about 2 mm to 4 mm when an even thinner planar light source is desired. This allows the backlight unit, including optical members such as the light diffusion plate 14, to be made extremely thin. The thickness of the partitioning member 13 can be, for example, 100 μm to 300 μm.

[0044] The shape of the section C formed by the partitioning member 13 surrounding the light source 12, i.e., the shape of the area partitioned by the wall portion 13b, is rectangular in plan view, but is not limited to this. For example, it may be circular, elliptical, or the like. However, in order to efficiently arrange multiple light sources 12, a polygonal shape such as a triangle, a rectangle, or a hexagon is preferable. This makes it easy to partition the light-emitting area into any number of areas by the wall portion 13b according to the area of ​​the light-emitting surface of the planar light source 10, and allows the light-emitting areas to be arranged at a high density.

[0045] The number of compartments C divided by the wall portions 13b can be set arbitrarily, and the shape and arrangement of the wall portions 13b and the number of compartments C can be changed depending on the desired size of the surface light source. Depending on the number and positions of the light sources 12 arranged on the substrate 11, the compartment member 13 can have various shapes in a planar view, such as three compartments C adjacent to each other with the ends of the three vertices converging at one point, four compartments C adjacent to each other with the ends of the four vertices converging at one point as shown in Figure 2, or six compartments C adjacent to each other with the ends of the six vertices converging at one point. When four compartments C are adjacent to each other with the ends of the four vertices converging at one point, the shape of the compartment C in a planar view is rectangular.

[0046] The partitioning member 13 is preferably disposed on the substrate 11, and the lower surface of the second bottom portion 13c of the partitioning member 13 is preferably fixed to the upper surface 11m of the substrate 11. In particular, it is preferable to fix the periphery of the through-hole 13d using a light-reflective adhesive member so that light emitted from the light source 12 does not enter between the substrate 11 and the partitioning member 13. For example, it is more preferable to arrange a light-reflective adhesive member in a ring shape along the outer edge of the through-hole 13d. The adhesive member may be double-sided tape, a hot-melt adhesive sheet, or a resin-based adhesive such as a thermosetting resin or a thermoplastic resin. It is preferable that these adhesive members have high flame retardancy. However, the partitioning member 13 may be fixed to the substrate 11 using screws or the like.

[0047] As described above, it is preferable that the partition member 13 has light reflectivity. This allows the light emitted from the light source 12 to be efficiently reflected by the wall portion 13b and the second bottom portion 13c. In particular, when the wall portion 13b has an inclination as described above, the light emitted from the light source 12 is irradiated onto the wall portion 13b, and the light can be reflected upward. Therefore, even when the adjacent partition C is not lit, the contrast ratio can be further improved. Furthermore, the light can be more efficiently reflected upward.

[0048] The partition member 13 may be formed using a resin containing a reflective material made of metal oxide particles such as titanium oxide, aluminum oxide, or silicon oxide, or may be formed using a resin that does not contain a reflective material and then a reflective material is applied to the surface. Alternatively, a resin containing a plurality of fine bubbles may be used. In this case, light is reflected at the interfaces of the bubbles. Examples of resins used for the partition member 13 include thermoplastic resins such as acrylic resin, polycarbonate resin, cyclic polyolefin resin, polyethylene terephthalate (PET), or polyester, and thermosetting resins such as epoxy or silicone. The partition member 13 is preferably set so that its reflectance for light emitted from the light source 12 is 70% or more.

[0049] The partition member 13 can be formed by a molding method using a mold, a molding method using stereolithography, etc. Molding methods using a mold include injection molding, extrusion molding, compression molding, vacuum molding, pressure molding, and press molding. For example, by vacuum molding using a reflective sheet made of PET or the like, the partition member 13 in which the second bottom portion 13c and the wall portion 13b are integrally formed can be formed.

[0050] (Light diffuser 14) The light diffusion plate 14 is an irregularly shaped member that diffuses and transmits incident light, and one light diffusion plate 14 can be disposed above the plurality of light sources 12. The light diffusion plate 14 is preferably a flat plate-like member, but its surface may have an uneven surface. The light diffusion plate 14 is preferably disposed substantially parallel to the substrate 11.

[0051] When the pitch between the tops 13a of the partitioning member 13 is P [mm], the light diffuser 14 is preferably disposed so that the distance OD between the light source 12 and the light diffuser 14 is, for example, 0.3P [mm] or less, and more preferably 0.25P [mm] or less. Here, the distance OD refers to the distance from the outermost surface of the substrate 11, i.e., from the outermost surface of the substrate 11 if the substrate 11 has a coating layer, wiring layer, or the like, to the underside of the light diffuser 14, as shown in Fig. 6. From another perspective, the distance H between the light diffuser 14 and the upper surface of the second bottom 13c of the partitioning member 13 shown in Fig. 6 is preferably 1.5 mm to 5 mm, and more preferably 2 mm to 3 mm.

[0052] The light diffusion plate 14 can be made of a material that has little light absorption for visible light, such as polycarbonate resin, polystyrene resin, acrylic resin, or polyethylene resin. In order to diffuse the incident light, the light diffusion plate 14 may have an uneven surface, or a material with a different refractive index may be dispersed in the light diffusion plate 14. The unevenness can have a size of, for example, 0.01 mm to 0.1 mm. The material with a different refractive index can be selected from, for example, polycarbonate resin, acrylic resin, etc.

[0053] The thickness and degree of light diffusion of the light diffusion plate 14 can be set appropriately, and commercially available materials such as light diffusion sheets, diffuser films, etc. For example, the thickness of the light diffusion plate 14 can be 1 mm to 2 mm at its thickest part.

[0054] In the surface light source 10, the substrate 11 has an irregular shape. Therefore, when as many light sources 12 as possible are arranged on the substrate 11 while maintaining a matrix arrangement in the first and second directions, an area where no light sources 12 are arranged will be formed on the outer edge of the substrate 11. If no countermeasures are taken, the periphery of the surface light source 10 (e.g., the area between the outermost periphery of the partitioning member 13 and the outer edge of the light diffuser plate 14) will be dark, which may result in brightness unevenness around the periphery of the surface light source. In FIG. 1 , for example, the dark area is noticeable in the area surrounded by the two-dot chain line F. In other words, if no countermeasures are taken, brightness unevenness will occur in part of the periphery of the surface light source 10. Therefore, in the surface light source 10, brightness unevenness is suppressed by making part of the periphery of the light diffuser plate 14 thinner than the center. If necessary, the entire periphery of the light diffuser plate 14 may be thinner than the center. The shape of the light diffuser plate 14 will be described in detail below.

[0055] The light diffuser 14 includes a thick plate portion 14a and a thin plate portion 14b that is thinner than the thick plate portion 14a. The thick plate portion 14a and the thin plate portion 14b are adjacent to each other and integrally formed. For convenience, in FIG. 5, the thick plate portion 14a is shown in white, and the thin plate portion 14b is shown with a dotted pattern. The light diffuser 14 may be composed of a single sheet or two or more layers. When the light diffuser 14 is composed of two layers, for example, a second layer narrower than the first layer may be provided on top of the first layer on the substrate side. In this case, the area where the second layer is located on the first layer may be the thick plate portion 14a, and the area where the second layer is not located on the first layer may be the thin plate portion 14b.

[0056] The boundary 14c between the thick plate portion 14a and the thin plate portion 14b is located, for example, opposite the outermost wall portion 13b of the partitioning member 13. This reduces the frequency of light diffusion and increases the amount of light that passes through the thin plate portion 14b on the outer edge side of the outermost wall portion 13b of the partitioning member 13. As a result, it is possible to suppress the occurrence of uneven brightness at the periphery of the surface light source 10. The boundary 14c may be located opposite the outermost apex 13a of the partitioning member 13.

[0057] When a wall portion 13b is located directly below or near the boundary between the thick plate portion 14a and the thin plate portion 14b of the light diffuser plate 14 (FIG. 3), part of the light incident on the thin plate portion 14b of the light diffuser plate 14 from the light source 12 is diffused by the thick plate portion 14a of the light diffuser plate 14 and then enters the thin plate portion 14b. The light incident on the thin plate portion 14b is diffused less frequently because the film thickness of the thin plate portion 14b is thin. This improves the light extraction at the thin plate portion 14b.

[0058] The thickness of the thin plate portion 14b is preferably 0.5 times or less the thickness of the thick plate portion 14a, which increases the amount of light extracted from the thin plate portion 14b region and prevents uneven brightness at the periphery of the surface light source 10.

[0059] The lower surface 14n (the surface on the light source 12 side) of the thick plate portion 14a and the lower surface 14t (the surface on the light source 12 side) of the thin plate portion 14b are on the same plane, and the upper surface 14m (the surface opposite the light source 12) of the thick plate portion 14a and the upper surface 14s (the surface opposite the light source 12) of the thin plate portion 14b are at different height positions.

[0060] That is, the height from the upper surface 11m of the substrate 11 to the lower surface 14t of the thin plate portion 14b is the same as the height from the upper surface 11m of the substrate 11 to the lower surface 14n of the thick plate portion 14a. On the other hand, the height from the upper surface 11m of the substrate 11 to the upper surface 14s of the thin plate portion 14b is lower than the height from the upper surface 11m of the substrate 11 to the upper surface 14m of the thick plate portion 14a.

[0061] The thin plate portion 14b is provided on at least a part of the periphery of the light diffuser plate 14 in a plan view. As shown in FIG. 5 , in the present embodiment, as an example, the thin plate portion 14b is provided on the entire periphery of the light diffuser plate 14 (the part indicated by the dot pattern). By providing the thin plate portion 14b on the entire periphery of the light diffuser plate 14, it is possible to increase the brightness of the entire periphery of the thin plate portion 14b and reduce brightness unevenness. However, the present invention is not limited to this, and the thin plate portion 14b may be provided on only a part of the periphery of the light diffuser plate 14.

[0062] In the surface light source 10, the width of the thin plate portion 14b in the X direction increases as the distance from the optical axis of the light source 12 located at the end in the X direction to the outer edge of the light diffuser plate 14 in the X direction increases. For example, as shown in Fig. 7, for one light source 121 and another light source 122 located at the end in the X direction among the multiple light sources 12, the distance L1 from the optical axis OA1 of the one light source 121 to the outer edge of the light diffuser plate 14 in the X direction is longer than the distance L2 from the optical axis OA2 of the other light source 122 to the outer edge of the light diffuser plate 14 in the X direction. In this case, as shown in Fig. 8, with respect to the width of the thin plate portion 14b in the X direction in the plan view, the width W1 in the X direction from the optical axis OA1 of the one light source 121 toward the outer edge of the light diffuser plate 14 is wider than the width W2 in the X direction from the optical axis OA2 of the other light source 122 toward the outer edge of the light diffuser plate 14.

[0063] Furthermore, in plan view, the width of the thin plate portion 14b in the Y direction increases as the distance from the optical axis of the light source 12 located at the end in the Y direction to the outer edge of the light diffuser plate in the Y direction increases. For example, as shown in Fig. 7, for one light source 123 and another light source 124 located at the ends in the Y direction among the multiple light sources 12, a distance L3 from the optical axis OA3 of the one light source 123 to the outer edge of the light diffuser plate 14 in the Y direction is longer than a distance L4 from the optical axis OA4 of the other light source 124 to the outer edge of the light diffuser plate 14 in the Y direction. In this case, as shown in Fig. 8, with respect to the width of the thin plate portion 14b in the Y direction in plan view, a width W3 in the Y direction from the optical axis OA3 of the one light source 123 toward the outer edge of the light diffuser plate 14 is wider than a width W4 in the Y direction from the optical axis OA4 of the other light source 124 toward the outer edge of the light diffuser plate 14.

[0064] 9 and 10 are diagrams showing the results of a simulation related to a light diffusion plate. Fig. 9 shows the simulation results for the surface light source 10, and Fig. 10 shows the simulation results (comparison example) for a surface light source 10X equipped with a light diffusion plate 14X of a constant plate thickness instead of the light diffusion plate 14 of the surface light source 10. In Figs. 9 and 10, many thin lines represent light rays.

[0065] Comparing the areas surrounded by dashed lines in FIGS. 9 and 10, it can be seen that the surface light source 10 provided with the thin plate portion 14b has more areas with high light density than the surface light source 10X without the thin plate portion, demonstrating good light extraction at the periphery of the light diffuser plate 14. In other words, it can be seen that uneven brightness on the light-emitting surface at the periphery of the light diffuser plate 14 can be suppressed. This is because providing the thin plate portion 14b on the light diffuser plate 14 reduces the frequency of light diffusion in the thin plate portion 14b, thereby increasing the amount of light transmitted through the thin plate portion 14b. Furthermore, light emitted from the side surface of the thick plate portion 14a exposed to the thin plate portion 14b and light reflected by the side surface of the thick plate portion 14a through the thin plate portion 14b are directed toward the upper surface of the light diffuser plate, thereby increasing the light density on the upper surface of the light diffuser plate.

[0066] Simulations were performed on the light diffusion plate 14, with the thickness of the thick plate portion 14a set to 1.2 mm and the thickness of the thin plate portion 14b changed to 0.4 mm, 0.2 mm, and 0.1 mm, and the luminance of light transmitted through the thin plate portion 14b in the area of ​​the thin plate portion 14b was calculated. As shown in Table 1, when the thin plate portion 14b was 0.4 mm, the luminance increased by 1.1 times compared to when the thin plate portion 14b was 1.2 mm (i.e., when the thin plate portion 14b was the same thickness as the thick plate portion 14a). Similarly, when the thin plate portion 14b was 0.2 mm, the luminance increased by 1.12 times. Furthermore, when the thin plate portion 14b was 0.1 mm, the luminance increased by 1.17 times.

[0067] [Table 1]

[0068] Furthermore, when comparing the light leaking out from the side surfaces of the light diffusion plate, it can be seen that the surface light source 10 provided with the thin plate portion 14b has less leakage than the surface light source 10X without the thin plate portion. That is, with the surface light source 10, light that conventionally leaked out to the sides can be directed toward the upper surface side of the light diffusion plate 14, and coupled with the reduced frequency of light diffusion in the thin plate portion 14b, the density of light rays on the upper surface side of the thin plate portion 14b can be increased.

[0069] Furthermore, in the surface light source 10, by providing the light diffusion plate 14 with the thin plate portion 14b, the amount of light leaking out from the side surface of the light diffusion plate 14 can be reduced.

[0070] In the surface light source 10, a wavelength conversion sheet that converts light from the light source 12 to light of a different wavelength may be disposed above the light diffuser plate 14. When a wavelength conversion sheet is disposed above the light diffuser plate 14, if light leaks out from the side surfaces of the light diffuser plate, the edge of the surface light source appears to have the emission color (e.g., blue) of the light emitting element 12a. However, in the surface light source 10, by providing the thin plate portion 14b on the light diffuser plate 14, the amount of light leaking out from the side surfaces of the light diffuser plate 14 can be reduced, thereby preventing the edge of the surface light source 10 from appearing to have the emission color of the light emitting element 12a. In other words, when a wavelength conversion sheet is disposed above the light diffuser plate 14, the phenomenon of light of a wavelength different from the wavelength converted by the wavelength conversion sheet leaking out from the side surfaces of the light diffuser plate 14 can be prevented.

[0071] Thus, in the surface light source 10, because the substrate 11 has an irregular shape, if as many light sources 12 as possible are arranged on the substrate 11 while maintaining a matrix arrangement in the first and second directions, an area where no light sources 12 are arranged will be created on the outer edge of the substrate 11. Furthermore, if no countermeasures are taken, for example, the area between the outermost periphery of the partitioning member 13 and the outer edge of the light diffuser plate 14 will be a dark area. In other words, if no countermeasures are taken, brightness unevenness will occur in part of the periphery of the surface light source 10. However, by providing the thin plate portion 14b on the periphery of the light diffuser plate 14, light extraction can be prioritized over light diffusion in the thin plate portion 14b, reducing the frequency of light diffusion and increasing the amount of light transmitted through the thin plate portion 14b. As a result, brightness unevenness at the periphery of the surface light source 10 can be suppressed.

[0072] However, since the thin plate portion 14b only needs to be provided in an area where brightness unevenness may occur, it is not necessary to provide the thin plate portion 14b over the entire peripheral area of ​​the light diffusion plate 14, and the thin plate portion 14b may be provided only in a partial area of ​​the peripheral area of ​​the light diffusion plate 14.

[0073] For the same reason, it is not necessary that the width of the thin plate portion 14b be wider in both the X direction and the Y direction as the distance from the optical axis of the light source 12 located at the end to the outer edge of the light diffuser plate 14 increases. In other words, it is sufficient that the width of the thin plate portion 14b be wider in at least one of the X direction and the Y direction as the distance from the optical axis of the light source 12 located at the end to the outer edge of the light diffuser plate 14 increases.

[0074] The surface light source 10 may include at least one selected from the group consisting of a wavelength conversion sheet, a prism sheet, and a polarizing sheet, above the light diffusion plate 14, which converts light from the light source 12 into light of a different wavelength. Specifically, as shown in Fig. 11, optical members such as a wavelength conversion sheet 72, a prism sheet (a first prism sheet 73 and a second prism sheet 74), and a polarizing sheet 75 may be arranged above the light diffusion plate 14 at a predetermined distance or directly or indirectly on the upper surface of the light diffusion plate 14, and a liquid crystal panel may be further arranged thereon to form a surface-emitting light-emitting device used as a light source for a direct-type backlight. The order of stacking these optical members may be set as desired.

[0075] (wavelength conversion sheet 72) The wavelength conversion sheet 72 may be disposed on either the upper or lower surface of the light diffusion plate 14. However, as shown in FIG. 11 , it is preferable to dispose it on the upper surface of the light diffusion plate 14. The wavelength conversion sheet 72 absorbs a portion of the light emitted from the light source 12 and emits light with a wavelength different from that of the light emitted from the light source 12. For example, the wavelength conversion sheet 72 can absorb a portion of the blue light from the light source 12 and emit yellow, green, and / or red light, thereby realizing a planar light source 10 that emits white light. Because the wavelength conversion sheet 72 is spaced apart from the light-emitting element 12a of the light source 12, phosphors with poor resistance to heat or light intensity that are difficult to use near the light-emitting element 12a can be used. This improves the performance of the planar light source 10 as a backlight. The wavelength conversion sheet 72 has a sheet or layer shape and contains the above-mentioned phosphors. The wavelength conversion sheet is sometimes referred to as a wavelength conversion layer.

[0076] (First prism sheet 73 and second prism sheet 74) The first prism sheet 73 and the second prism sheet 74 have a shape in which a plurality of prisms extending in a predetermined direction are arranged on their surfaces. For example, when the plane of the sheet is viewed two-dimensionally with the X direction and the Y direction perpendicular to the X direction, the first prism sheet 73 may have a plurality of prisms extending in the Y direction, and the second prism sheet 74 may have a plurality of prisms extending in the X direction. The first prism sheet 73 and the second prism sheet 74 can refract light incident from various directions toward the display panel facing the surface light source 10. This allows light emitted from the light-emitting surface of the surface light source 10 to be emitted mainly in a direction perpendicular to the upper surface, thereby increasing the brightness when the surface light source 10 is viewed from the front.

[0077] (Polarizing sheet 75) The polarizing sheet 75 selectively transmits light polarized in a direction that matches the polarization direction of a polarizing plate disposed on the backlight side of a display panel, such as a liquid crystal display panel, and reflects light polarized in a direction perpendicular to the polarization direction toward the first prism sheet 73 and the second prism sheet 74. A portion of the polarized light returning from the polarizing sheet 75 is reflected again by the first prism sheet 73, the second prism sheet 74, the wavelength conversion sheet 72, and the light diffuser 14. At this time, the polarization direction of the light changes and the light is converted into polarized light having the polarization direction of, for example, the polarizing plate of the liquid crystal display panel. The light then re-enters the polarizing sheet 75 and is emitted to the display panel. This aligns the polarization direction of the light emitted from the surface light source 10, enabling light polarized in a direction effective for improving the brightness of the display panel to be emitted with high efficiency. The polarizing sheet 75, the first prism sheet 73, the second prism sheet 74, and the like can be commercially available optical components for backlights.

[0078] In the surface light source 10, instead of providing the wavelength conversion sheet 72, the sealing member 12b may contain a wavelength conversion material such as a phosphor that absorbs light from the light emitting element 12a and emits light of a wavelength different from the output light from the light emitting element 12a. This makes it possible to realize a surface light source 10 that absorbs part of the blue light from the light source 12 in the sealing member 12b, emits yellow light, green light, and / or red light, and emits white light.

[0079] In addition to the wavelength converting material, the sealing member 12b may contain a diffusing agent for diffusing light from the light emitting element 12a, a coloring agent corresponding to the light emission color of the light emitting element 12a, etc. Diffusing agents, coloring agents, etc. that are known in the art can be used. Furthermore, the sealing member 12b may not contain a wavelength converting material such as a phosphor, and the light emitting element 12a may be, for example, a nitride-based semiconductor covered with a wavelength converting material such as a phosphor, i.e., the light emitting element 12a itself may emit white light.

[0080] <Modification 1 of the First Embodiment> In Modification 1 of the first embodiment, an example is shown in which the cross-sectional shape of the thin plate portion of the light diffusion plate is different from that of Embodiment 1. Note that in Modification 1 of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0081] 12 to 14 are schematic partially enlarged cross-sectional views illustrating the light diffusion plate in the surface light source according to Modification 1 of Embodiment 1. Fig. 15 is a schematic plan view illustrating the light diffusion plate in Fig. 14.

[0082] 12, the height from the upper surface 11m of the substrate 11 to the lower surface 24t of the thin plate portion 24b is the same as the height from the upper surface 11m of the substrate 11 to the lower surface 24n of the thick plate portion 24a. The thickness of the thin plate portion 24b gradually decreases from the boundary 24c with the thick plate portion 24a toward the outer edge of the light diffuser plate 24.

[0083] In this way, the boundary between the thick and thin plate portions does not need to be stepped as shown in Fig. 3, but may have a shape with a smoothly changing thickness as shown in Fig. 12. In this case, too, in the thin plate portion 24b, light extraction is prioritized over light diffusion, reducing the frequency of light diffusion and increasing the amount of light that passes through the thin plate portion 24b. As a result, it is possible to suppress uneven brightness around the edges of the surface light source.

[0084] 12, the thin plate portion 24b may have a shape in which the thickness gradually decreases from the boundary with the thick plate portion toward the outer edge of the light diffuser plate, rather than the entire thin plate portion 24b gradually decreasing in thickness as it approaches the outer edge of the light diffuser plate. For example, as in the light diffuser plate 34 shown in FIG. 13, the thin plate portion 34b may have a gradually decreasing thickness portion 34b1 in which the thickness gradually decreases from the boundary 34c with the thick plate portion 34a toward the outer edge of the light diffuser plate 34, and may further have a constant thickness portion 34b2 closer to the outer edge of the light diffuser plate 34 than the gradually decreasing thickness portion 34b1. The thickness of the constant thickness portion 34b2 may be the same as the thinnest portion of the gradually decreasing thickness portion 34b1, for example.

[0085] 14 and 15, the thin plate portion 44b may include a first thin plate portion 44b1 on the thick plate portion 44a side and a second thin plate portion 44b2 located closer to the outer edge of the light diffuser plate 44 than the first thin plate portion 44b1 and thinner than the first thin plate portion 44b1. By varying the thickness of the thin plate portion 44b in two stages, the brightness of the edge of the planar light source can be increased. That is, since dark areas are more noticeable at locations farther from the light source 12, the thickness of the light diffuser plate 14 can be made thinner as the distance from the light source 12 increases, thereby suppressing brightness unevenness at the periphery of the planar light source. The thickness of the thin plate portion 44b may vary in more than two stages. The cross-sectional shape of the thin plate portion 44b may also be a shape that appropriately combines the shapes illustrated in FIGS. 12 to 14.

[0086] For example, in a plan view, the second thin plate portion 44b2 is disposed closer to the outer edge of the light diffusion plate 44 than the region where the through holes 13d of the partitioning member 13 are disposed. The second thin plate portion 44b2 may be disposed in a section C where no light source 12 is disposed. A boundary 44c between the first thin plate portion 44b1 and the second thin plate portion 44b2 may be located at a position overlapping with the top portion 13a of the partitioning member 13 in a plan view.

[0087] It is not necessary to provide the first thin plate portion 44b1 and the second thin plate portion 44b2 over the entire periphery of the light diffusion plate 44, and only the first thin plate portion 44b1 may be provided in an area where brightness unevenness is unlikely to occur. For example, in region R in Fig. 15 where the light sources 12 are linearly arranged, brightness unevenness is unlikely to occur, so only the first thin plate portion 44b1 may be provided. Alternatively, if brightness unevenness is almost unlikely to occur in region R where the light sources 12 are linearly arranged in Fig. 15, the thin plate portion 44b need not be provided in region R.

[0088] <Modification 2 of the First Embodiment> In the second modification of the first embodiment, an example is shown in which the partitioning member has partitions of different sizes on the periphery. Note that in the second modification of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0089] FIG. 16 is a schematic partially enlarged plan view of a partitioning member according to Modification 2 of the first embodiment. FIG. 17 is a cross-sectional view taken along line BB in FIG. 16. In the partitioning member 23 shown in FIGS. 16 and 17, the top portion 23a and the wall portion 23b constituting the outermost partition C are disposed near the outer edge of the substrate 11. That is, in at least a part of the outermost partition C, the area of ​​the region surrounded by the wall portion 23b is larger in plan view than that of the partition C on the inner side. Note that, in the examples shown in FIGS. 16 and 17, the area of ​​the region surrounded by the wall portion 23b of the outermost partition C is enlarged in the X direction, but it may also be enlarged in the Y direction. Alternatively, the area of ​​the region surrounded by the wall portion 23b of the outermost partition C may include a mixture of a portion where the area is enlarged in the X direction and a portion where the area is enlarged in the Y direction.

[0090] 2 and 3, the area of ​​the second bottom 23c exposed in the compartments C is uniform in all compartments C in plan view, but this is not limiting. As in the examples of FIGS. 16 and 17, at least one of the regions surrounded by the wall portion 23b located at the outermost periphery of the partitioning member 23 may have a larger area in plan view than the region surrounded by the wall portion 23b located more inward than the outermost periphery.

[0091] In the structure of the partitioning member 23 shown in FIGS. 16 and 17 , the wall portions 23b constituting the outermost compartment C are located near the outer edge of the substrate 11, thereby improving light extraction to the light-emitting surface side. That is, in the structure of the partitioning member 23 shown in FIGS. 16 and 17 , the wall portions 23b are also located on the periphery of the substrate 11, so that more light can be sent to the thin plate portions 14b of the light diffuser plate 14. As a result, the occurrence of uneven brightness at the periphery of the surface light source 10 can be further suppressed. However, the wall portions 23b do not have to be provided on at least a portion of the outermost periphery of the partitioning member 23. Although the wall portions 23b of the partitioning member are not located at the boundary between the thick plate portions 14a and the thin plate portions 14b of the light diffuser plate 14 in FIGS. 16 and 17 , the wall portions 23b can also be provided at this position.

[0092] <Modification 3 of the First Embodiment> Modification 3 of the first embodiment shows modifications of members other than the light diffusion plate and the partition member. Note that in Modification 3 of the first embodiment, descriptions of the same components as those in the already described embodiments may be omitted.

[0093] Fig. 18A is a schematic enlarged partial cross-sectional view of the vicinity of the outer edge of the surface light source. As shown in Fig. 18A, the surface light source may have a frame 26 that surrounds the substrate 11 and the light diffusion plate 14. The frame 26 has an irregular shape, for example, a shape similar to that of the substrate 11, and has a first bottom 26a that is slightly larger than the substrate 11 in plan view.

[0094] The peripheral edge of the first bottom portion 26a is exposed in a ring shape outside the substrate 11, and a side wall 26b is provided on the exposed portion so as to surround the substrate 11. A lid 27 that surrounds the outer edges of the substrate 11 and the light diffuser plate 14 may be provided on the side of the side wall 26b opposite the first bottom portion 26a. The lid 27 is disposed in a position that does not obstruct the light emitted from each light source 12. The frame 26 and the lid 27 are formed from various materials, such as resin containing a reflective material, metal, ceramics, etc.

[0095] 18B , a wavelength conversion member 28 containing a phosphor can be disposed in a region between the substrate 11 and the light diffusion plate 14 on the inner surface of the side wall 26b. This allows a portion of the light from the light source 12 to be wavelength-converted by the wavelength conversion member 28 disposed on the inner surface of the side wall 26b, and the wavelength-converted light is extracted, thereby preventing the end of the surface light source 10 from appearing to have the emission color of the light-emitting element. When the wavelength conversion member 28 is disposed on the inner surface of the side wall 26b, the wall portion 13b of the partitioning member 13 may or may not be disposed between the light source 12 and the side wall 26b in a cross-sectional view of the surface light source. The wavelength conversion member 28 may be disposed over the entire inner surface of the side wall 26b, or may be disposed in a region of the inner surface of the side wall 26b below the lower surface of the light diffusion plate 14. When the wavelength conversion member 28 is disposed in a region below the lower surface of the light diffusion plate 14, the thin plate portion 14b of the light diffusion plate 14 may or may not cover the upper side of the wavelength conversion member 28. A material that emits yellow light (e.g., YAG) can be used as the wavelength conversion member 28. There may be one or more wavelength conversion members 28 disposed on the inner surface of the side wall 26b.

[0096] In this way, by providing the frame 26 and the lid 27 to the surface light source, it is possible to protect the substrate 11 and the light diffusion plate 14 from external impacts, etc. The light diffusion plate 14, the substrate 11, and the frame 26 may have similar irregular shapes.

[0097] FIG. 19 is a planar schematic diagram illustrating the outer shape of a substrate in a surface light source according to Modification 3 of the first embodiment, and only the substrate, light source, and partition member are shown. The shape of the light diffusion plate may be the same as that in FIG. 5, for example. The substrate 21 of the surface light source 20 shown in FIG. 19 has an irregular shape, and compared to the substrate 11 shown in FIG. 1, the area where the light source 12 is not disposed has been cut off. In other words, the outermost shape of the substrate 21 corresponds to the outermost shape of the partition member 13. In the example of FIG. 19, the substrate 21 is located in a position overlapping with the partition member 13 in a planar view (below the partition member 13).

[0098] In this way, the substrate 21 used in the planar light source may have a shape in which the area where the light source 12 is not disposed is cut off. In this case, by using the light diffuser plate 14 having the same shape as in Fig. 5, it is possible to reduce the frequency of light diffusion at the periphery of the light diffuser plate 14 and increase the amount of light that passes through the light diffuser plate 14. As a result, it is possible to suppress the occurrence of uneven brightness at the periphery of the planar light source.

[0099] The cross-sectional shape of the surface light source 10 may be a linear shape parallel to the XY plane as shown in Fig. 11 etc., or may be a shape curved relative to the XY plane. For example, it may be a curved shape in which the exit surface side is recessed in the X direction.

[0100] Second Embodiment In the second embodiment, an example of a liquid crystal display device using the surface light source according to the first embodiment as a backlight source will be described. Note that in the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0101] Fig. 20 is a structural diagram illustrating a liquid crystal display device according to the second embodiment. As shown in Fig. 20, the liquid crystal display device 1000 includes, from the top down, a liquid crystal panel 120, an optical sheet 110, and the surface light source 10 according to the first embodiment. In the surface light source 10, reference numeral 70 denotes an optical member such as a light diffusion plate or a wavelength conversion sheet. Here, the optical sheet 110 may include a DBEF (reflective polarizing sheet), a BEF (brightness enhancing sheet), a color filter, etc. in addition to or by replacing some of the optical members.

[0102] The liquid crystal display device 1000 is a so-called direct type liquid crystal display device in which a surface light source 10 is stacked below a liquid crystal panel 120. The liquid crystal display device 1000 irradiates the liquid crystal panel 120 with light emitted from the surface light source 10. In addition to the above-mentioned components, the liquid crystal display device 1000 may further include components such as a color filter.

[0103] Generally, in a direct-type liquid crystal display device, the liquid crystal panel and the surface light source are located close to each other, so there is a risk that color unevenness and brightness unevenness of the surface light source may affect the color unevenness and brightness unevenness of the liquid crystal display device. Therefore, a surface light source with less color unevenness and brightness unevenness is desired as the surface light source for a direct-type liquid crystal display device. By using the surface light source 10 in the liquid crystal display device 1000, it is possible to reduce the thickness of the surface light source 10 to 5 mm or less, 3 mm or less, 1 mm or less, etc., while suppressing brightness unevenness that occurs at the periphery and reducing overall brightness unevenness and color unevenness.

[0104] Note that the present invention is not limited to a case where one surface light source 10 is used as the backlight of one liquid crystal display device 1000, and a plurality of surface light sources 10 may be arranged and used as the backlight of one liquid crystal display device 1000. For example, by fabricating a plurality of small surface light sources 10 and inspecting each of them, the yield can be improved compared to fabricating one large surface light source 10 with a large number of mounted light sources 12.

[0105] In this way, the surface light source 10 is suitable for use as a backlight for the liquid crystal display device 1000, since uniform light is emitted from the optical member 70.

[0106] However, the surface light source 10 is not limited thereto, and can also be suitably used as a backlight for televisions, tablets, smartphones, smartwatches, head-up displays, digital signage, bulletin boards, etc. The surface light source 10 can also be used as a light source for lighting, and can be used for emergency lighting, line lighting, various types of illumination, in-vehicle installations, etc. Note that one or more of the modifications shown in Modifications 1 to 3 of the first embodiment may be applied to the surface light source 10 as appropriate.

[0107] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0108] For example, in the above embodiment, the lower surface (the surface facing the light source) of the thick plate portion of the light diffuser plate and the lower surface (the surface facing the light source) of the thin plate portion of the light diffuser plate are on the same plane. However, the upper surface (the surface opposite the light source) of the thick plate portion of the light diffuser plate and the upper surface (the surface opposite the light source) of the thin plate portion of the light diffuser plate may also be on the same plane. That is, the lower surface of the light diffuser plate may be thinned to provide a thin plate portion. For example, the light diffuser plate 14 shown in FIG. 6, the light diffuser plate 24 shown in FIG. 12, the light diffuser plate 34 shown in FIG. 13, and the light diffuser plate 44 shown in FIG. 14 may have a shape inverted upside down. In these cases, it is not expected that the amount of light directed from the side surface of the thick plate portion toward the upper surface of the light diffuser plate will increase. However, the frequency of light diffusion in the thin plate portion will decrease, increasing the amount of light transmitted through the thin plate portion, thereby achieving a certain effect of suppressing uneven brightness on the light-emitting surface at the periphery of the light diffuser plate.

[0109] Alternatively, the light diffuser may contain scattering particles such as titanium oxide particles or phosphor particles, and the concentration of the scattering particles contained in the thin plate portion may be made lower than the concentration of the scattering particles contained in the thick plate portion. This further reduces the frequency of light diffusion in the thin plate portion and further increases the amount of light transmitted through the thin plate portion, thereby improving the effect of suppressing uneven brightness on the light-emitting surface around the periphery of the light diffuser. Alternatively, a similar effect can be achieved by forming a scattering particle layer containing scattering particles on the upper and / or lower surface of the light diffuser, and making the concentration of scattering particles in the scattering particle layer formed in the thin plate portion lower than the concentration of scattering particles in the scattering particle layer formed in the thick plate portion. [Explanation of symbols]

[0110] 10, 20 Planar light source 11, 21 board 11m, 14m, 14s top 12 light source 12a Light-emitting element 12b Sealing member 12c light reflective film 12d Underfill 13, 23 Compartment members 13a, 23a top 13b, 23b wall section 13c, 23c 2nd bottom 13d through hole 14, 24, 34, 44 Light diffuser 14a, 24a, 34a, 44a thick plate section 14b, 24b, 34b, 44b Thin plate part 14c, 24c, 34c, 44c boundaries 14n, 14t, 24n, 24t bottom side 15 Covering material 18A, 18B conductor wiring 19 Joint materials 26 Frame 26a 1st bottom 26b side wall 27 Lid 28 Wavelength conversion material 34b1 Plate thickness tapering part 34b2 Constant thickness part 44b1 1st thin plate part 44b2 2nd thin plate part 70 Optical Components 72 Wavelength conversion sheet 73 First prism sheet 74 Second prism sheet 75 Polarizing Sheet 110 Optical Sheet 120 LCD panel 1000 lcd display device

Claims

1. a mounting board; a plurality of light sources arranged two-dimensionally on the mounting substrate in a plan view; a frame having a first bottom and side walls surrounding the mounting substrate; a wavelength converting member disposed on the side wall; a light diffusion plate disposed above the plurality of light sources and the wavelength conversion member, A surface light source in which the distance between the wavelength conversion member and the light source arranged on the outermost side of the plurality of light sources is greater than the distance between two adjacent light sources of the plurality of light sources.

2. The surface light source according to claim 1 , wherein the sidewall is perpendicular to the upper surface of the mounting substrate.

3. The surface light source according to claim 1 , wherein the light diffusion plate includes a portion between the outermost light source and the side wall, the portion having a thickness thinner than other regions.

Images