Planar light source and liquid crystal display device

Abstract

The present application provides a planar light source, comprising: a mounting substrate of a special shape; a plurality of light sources arranged in two dimensions in a first direction on the mounting substrate and a second direction perpendicular to the first direction when viewed from above; and a light diffusion plate provided above the plurality of light sources, the light diffusion plate comprising a thick plate portion and a thin plate portion thinner than the thick plate portion, the thin plate portion being provided in at least a portion of the light diffusion plate located outward of each light source arranged at an outermost circumference when viewed from above, a distance from an optical axis of one light source to an outer edge of the light diffusion plate in the first direction being longer than a distance from an optical axis of another light source to the outer edge of the light diffusion plate in the first direction, and a width of the thin plate portion in the first direction when viewed from above being wider than a width of the thin plate portion in the first direction from the optical axis of the one light source toward the outer edge of the light diffusion plate than a width of the thin plate portion in the first direction from the optical axis of the another light source toward the outer edge of the light diffusion plate.

Description

TECHNICAL FIELD

[0001] The present application relates to a planar light source and a liquid crystal display device. BACKGROUND

[0002] A planar light source using a light emitting element such as a light emitting diode is widely used as a backlight of a liquid crystal display device, a light source for a display, and the like.

[0003] As one example of such a planar light source, a configuration including two-dimensionally arranged light emitting elements and a light diffusion plate disposed above each light emitting element can be given. In this planar light source, the light diffusion plate includes diffusion particles for diffusing light from a light emitting portion of the light emitting element, and a convex portion protruding toward the light emitting element side in a gentle curved surface shape is integrally formed in at least a region of a surface on the light emitting element side corresponding to the light emitting portion of the light emitting element.

[0004] <Related Art Documents>

[0005] <Patent Documents>

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-221779 SUMMARY

[0007] <Problems to be Solved by the Invention>

[0008] An object of the present application is to suppress unevenness in brightness occurring at a peripheral edge in a planar light source having a shape in plan view that is a special shape.

[0009] <Means for Solving the Problems>

[0010] A planar light source of one embodiment of the present application includes a mounting substrate having a special shape in plan view; a plurality of light sources two-dimensionally arranged in a first direction over the mounting substrate and a second direction perpendicular to the first direction; and a light diffusion plate provided above the plurality of light sources, the light diffusion plate including a thick plate portion and a thin plate portion thinner than the thick plate portion, the thin plate portion being provided in at least a part of the light diffusion plate on an outer side than each of the light sources disposed on an outermost periphery in plan view, a distance from an optical axis of one of the light sources to an outer edge of the light diffusion plate in the first direction is longer than a distance from an optical axis of another of the light sources to the outer edge of the light diffusion plate in the first direction, and a width of the thin plate portion in the first direction in plan view is wider than a width of the thin plate portion in the first direction from the optical axis of the one of the light sources toward the outer edge of the light diffusion plate than a width of the thin plate portion in the first direction from the optical axis of the another of the light sources toward the outer edge of the light diffusion plate.

[0011] <Effects of the Invention>

[0012] According to one embodiment of the present application, in a planar light source having a shape in plan view that is a deformed shape, unevenness in luminance that occurs at the periphery can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic plan view illustrating a planar light source of the first embodiment.

[0014] Figure 2 is a schematic enlarged plan view of the E portion of Figure 1

[0015] Figure 3 is a sectional view along the A-A line of Figure 2

[0016] Figure 4 is a schematic plan view illustrating the arrangement of each light source in the planar light source of the first embodiment.

[0017] Figure 5 is a schematic plan view illustrating a light diffusion plate in the planar light source of the first embodiment.

[0018] Figure 6 is an enlarged sectional view of the vicinity of the light source of Figure 3

[0019] Figure 7 is a schematic plan view illustrating the width of the thin plate portion (one).

[0020] Figure 8 is a schematic plan view illustrating the width of the thin plate portion (two).

[0021] Figure 9 is a graph showing the results of simulation relating to the light diffusion plate (one).

[0022] Figure 10 is a graph showing the results of simulation relating to the light diffusion plate (two).

[0023] Figure 11 is a schematic sectional view illustrating the arrangement of optical components.

[0024] Figure 12 is a schematic enlarged sectional view of a light diffusion plate in the planar light source of the first embodiment of the modification 1 (one).

[0025] Figure 13 is a schematic enlarged sectional view of a light diffusion plate in the planar light source of the first embodiment of the modification 1 (two).

[0026] Figure 14 ​​​is a schematic partial enlarged cross-sectional view (3) of the light-diffusing plate in the planar light source of Modification 1 of the first embodiment.

[0027] Figure 15 is a plan view of the light-diffusing plate of Modification 1 of the first embodiment. Figure 14

[0028] Figure 16 is a schematic partial enlarged plan view of the partition member of Modification 2 of the first embodiment.

[0029] Figure 17 is a cross-sectional view along the B-B line of Modification 2 of the first embodiment. Figure 16

[0030] Figure 18A is a schematic partial enlarged cross-sectional view (1) of the vicinity of the outer edge of the planar light source.

[0031] Figure 18B is a schematic partial enlarged cross-sectional view (2) of the vicinity of the outer edge of the planar light source.

[0032] Figure 19 is a plan view schematically illustrating the outer shape of the substrate in the planar light source of Modification 3 of the first embodiment.

[0033] Figure 20 is a configuration view of the liquid crystal display device of the second embodiment.

[0034] Explanation of Reference Numerals

[0035] 10, 20 Planar light source

[0036] 11, 21 Substrate

[0037] 11m, 14m, 14s Upper surface

[0038] 12 Light source

[0039] 12a Light-emitting element

[0040] 12b Sealing member

[0041] 12c Light-reflecting film

[0042] 12d Underfill material

[0043] 13, 23 Partition member

[0044] 13a, 23a Top portion

[0045] 13b, 23b Wall portion

[0046] 13c, 23c, 26a Bottom portion

[0047] 13d Through hole​​

[0048] 14, 24, 34, 44 light diffusion plate

[0049] 14a, 24a, 34a, 44a thick plate portion

[0050] 14b, 24b, 34b, 44b thin plate portion

[0051] 14c, 24c, 34c, 44c boundary

[0052] 14n, 14t, 24n, 24t lower surface

[0053] 15 cover member

[0054] 18A, 18B conductor wiring

[0055] 19 joining member

[0056] 26 frame

[0057] 26b side wall

[0058] 27 cover

[0059] 28 wavelength conversion member

[0060] 34b1 plate thickness gradually decreasing portion

[0061] 34b2 plate thickness constant portion

[0062] 44b1 first thin plate portion

[0063] 44b2 second thin plate portion

[0064] 70 optical member

[0065] 72 wavelength conversion sheet

[0066] 73 first prism sheet

[0067] 74 second prism sheet

[0068] 75 polarizing sheet

[0069] 110 optical sheet

[0070] 120 liquid crystal panel

[0071] 1000 liquid crystal display device DETAILED DESCRIPTION

[0072] The following describes modes for carrying out the present application with reference to the drawings. Note that in the following description, terms indicating specific directions, positions, and the like (for example, "upper," "lower," and other terms including these terms) are used as necessary. However, the use of these terms is to make the understanding of the present application with reference to the drawings easy, and the technical scope of the present application is not limited by the meanings of these terms. Also, portions shown by the same reference numerals in multiple drawings represent the same or equivalent portions or components.

[0073] Also, the embodiments shown below exemplify planar light sources for embodying the technical idea of the present application, and do not limit the present application to the embodiments below. Also, the dimensions, materials, shapes, relative arrangement, and the like of the constituent components described below are not intended to limit the scope of the present application to only these, but are intended to exemplify. Also, the contents described in one embodiment can be applied to other embodiments, modified examples. Also, the size, positional relationship, and the like of the components shown in the drawings are sometimes exaggerated for the sake of explicit description.

[0074] <First Embodiment>

[0075] (planar light source 10)

[0076] Figure 1 is a schematic plan view of the planar light source of the first embodiment exemplified. Figure 2 is a schematic partial enlarged plan view of the E portion of Figure 1 Figure 3 is a cross-sectional view along the A-A line of Figure 2 Figure 4 is a schematic plan view exemplifying the arrangement of each light source in the planar light source of the first embodiment, which is a view of Figure 1 with the partition member and the light diffusion plate removed. Figure 5 is a schematic plan view exemplifying the light diffusion plate in the planar light source of the first embodiment. Figure 6 is a partial enlarged cross-sectional view of the vicinity of the light source of Figure 3

[0077] As shown in Figures 1-6 , the planar light source 10 is a surface-emitting light emitting device having a substrate 11, a light source 12, a partition member 13, and a light diffusion plate 14. However, the partition member 13 is not an essential constituent element of the planar light source 10, and is provided as necessary. In the case where the partition member 13 is not provided, for example, a support body for supporting the light diffusion plate 14 can be provided.

[0078] Note that in the following description, plan view means viewing an object from the normal direction of the upper surface 11m of the substrate 11, and planar shape means the shape of an object viewed from the normal direction of the upper surface 11m of the substrate 11.​​​

[0079] On the substrate 11 that is a mounting substrate, a plurality of light sources 12 each of which includes a light emitting diode are arranged. Note that the number of the light sources 12 arranged on the substrate 11 is not limited, and any number of the light sources 12 can be arranged on the substrate 11.

[0080] The partition member 13 is arranged on the same side of the substrate 11 as the light sources 12. The partition member 13 includes a top portion 13a arranged in a grid shape in plan view, and a wall portion 13b that surrounds each of the light sources 12 in plan view, and has a plurality of regions that surround the light sources 12. The wall portion 13b of the partition member 13 extends from the top portion 13a toward the substrate 11 side, for example, and in a cross-sectional view, the width of the region surrounded by the opposing wall portions 13b becomes narrower toward the substrate 11 side.

[0081] The range (i.e., the region and the space) surrounded by the wall portion 13b is defined as one partition C, and the partition member 13 includes a plurality of the partitions C. In the present embodiment, one light source 12 is arranged in one partition C. However, two or more light sources 12 can be arranged in one partition C. In this case, for example, three light sources 12 of red, green, and blue can be arranged in one partition C. Alternatively, two light sources 12 of white and warm color can be arranged in one partition C.

[0082] The light diffusion plate 14 is an optical member that is placed on the top portion 13a of the partition member 13 and arranged above the light sources 12. The surface light source 10 can improve the uniformity of light by having the light diffusion plate 14. The light diffusion plate 14 of the present embodiment has a portion with a thin plate thickness at the periphery in order to suppress the unevenness of brightness generated at the periphery of the surface light source 10.

[0083] Note that the outermost contour portion of each member in plan view is referred to as an outer edge, and the region having a width including the outer edge is referred to as a peripheral edge. In particular, in the light diffusion plate 14, the peripheral edge of the light diffusion plate 14 is set to the region that is located outward of each of the light sources 12 arranged at the outermost periphery in plan view. The peripheral edge does not necessarily indicate a ring-shaped region.

[0084] Hereinafter, each element constituting the surface light source 10 will be described in detail.

[0085] (Substrate 11)

[0086] The substrate 11 is a member for placing a plurality of light sources 12, and is a shaped other than a rectangle. Here, the shaped other than a rectangle refers to a shape in which a part of a complete rectangular shape is deformed or the entire rectangular shape is deformed, for example, in order to correspond to a specific product shape.

[0087] As Figure 6As shown, conductor wiring 18A and 18B for supplying electric power to the light source 12 such as the light emitting element 12a are formed on the upper surface 11m of the substrate 11. The regions of the conductor wiring 18A and 18B that are not electrically connected are covered by the covering member 15.

[0088] As the material of the substrate 11, at least the pair of conductor wiring 18A and conductor wiring 18B can be insulated and separated, and for example, ceramics, resins, composite materials, and the like can be cited. As the ceramics, for example, alumina, mullite, forsterite, glass ceramic, nitrides (for example, AlN), carbides (for example, SiC), LTCC, and the like can be cited. As the resins, for example, phenol resin, epoxy resin, polyimide resin, BT resin, polyphthalamide (PPA), polyethylene terephthalate (PET), and the like can be cited. As the composite material, for example, a composite material in which inorganic fillers such as glass fiber, SiO2, TiO2, Al2O3, and the like are mixed in the above-described resins, a glass fiber reinforced resin (glass epoxy resin), a metal substrate in which an insulating layer is formed on a metal member, and the like can be cited.

[0089] The thickness of the substrate 11 can be appropriately selected. The substrate 11 can be either of a flexible substrate or a rigid substrate that can be manufactured by a roll to roll method. The rigid substrate can be a thin rigid substrate that can be bent. The conductor wiring 18A and conductor wiring 18B are only required to be conductive members, and the material thereof is not particularly limited, and a material generally used for a wiring layer of a circuit substrate or the like can be used. A plating film, a light reflecting film, or the like can be formed on the surface of the conductor wiring 18A and conductor wiring 18B.

[0090] It is preferable that the covering member 15 be formed of an insulating material. As the material of the covering member 15, the same materials as those exemplified as the material of the substrate 11 can be cited. By using a material containing a white filler or the like in the above-described resins as the covering member 15, the light emitted from the light source 12 is reflected, and the light extraction efficiency of the planar light source 10 can be improved.

[0091] (light source 12)

[0092] The plurality of light sources 12 are arranged in two dimensions in a first direction above the substrate 11 in plan view, and a second direction perpendicular to the first direction. The first direction and the second direction are, for example, the X direction and the Y direction of Figure 1 the like.

[0093] The light source 12 is a light emitting member, and includes, for example, a light emitting element itself that emits light by itself, a light emitting member after a light emitting element is sealed with a light-transmissive resin or the like, and a surface mounting type light emitting device (also referred to as an LED) after a light emitting element is packaged. For example, as the light source 12, a surface mounting type light emitting device such as a white LED, a blue LED, a green LED, a red LED, a yellow LED, a UV LED, a phosphor converted LED, and the like can be cited. Figure 6As shown, a light source in which the light-emitting element 12a is covered by a sealing member 12b can be an example. The light source 12 can be a light source using one light-emitting element 12a, or it can use multiple light-emitting elements as a single light source 12. Alternatively, the light source 12 can be composed of a resin having a light-reflective material surrounding the sides of the light-emitting element, and a light-transmitting member covering the upper surface of the light-emitting element and the upper surface of the resin containing the light-reflective material. It can also be composed of a light-transmitting member covering the upper surface of the light-emitting element, and a resin having a light-reflective material surrounding the sides of the light-emitting element and the sides of the light-transmitting member. The light-transmitting member here can include a phosphor. A light-transmitting bonding member for bonding the light-emitting element and the light-transmitting member can be provided between the light-emitting element and the light-transmitting member.

[0094] The light source 12 can have any light distribution characteristics, but a wide light distribution is preferred in order to provide illumination with minimal brightness unevenness in each partition C surrounded by the wall 13b of the partition member 13. In particular, it is preferable that each of the light sources 12 has a batwing-like shape. Light distribution characteristics. This suppresses the amount of light emitted from the light source 12 in the upward direction, expands the light distribution of each light source 12, and by illuminating the wall portion 13b and the bottom portion 13c with the expanded light, it is possible to suppress the brightness unevenness in each partition C surrounded by the wall portion 13b.

[0095] Here, the light distribution characteristics of a bat wing refer to the luminous intensity distribution, with the optical axis L as 0°, exhibiting a stronger luminous intensity than 0° at angles where the absolute value of the light distribution angle is greater than 0°. It should be noted that, as... Figure 6 As shown, the optical axis OA is defined as a line that passes through the center of the light source 12 and intersects perpendicularly with the upper surface 11a of the substrate 11.

[0096] In particular, as a light source 12 with bat wing light distribution characteristics, for example, such as Figure 6 As shown, a light source using a light-emitting element 12a with a light-reflecting film 12c on its upper surface can be cited as an example. By providing a light-reflecting film 12c on the upper surface of the light-emitting element 12a, the upward light from the light-emitting element 12a is reflected by the light-reflecting film 12c, thereby suppressing the amount of light directly above the light-emitting element 12a, and batwing light distribution characteristics can be obtained. Since the light-reflecting film 12c can be formed directly on the light-emitting element 12a, it is not necessary to combine a special lens for batwing light distribution, and the thickness of the light source 12 can be made thinner.

[0097] The light-reflecting film 12c can be any of the following: a metal film such as silver or copper, a film containing a white filler in resin, or a combination thereof. Furthermore, as a dielectric multilayer film (DBR film), the light-reflecting film 12c can exhibit reflectivity angle dependence relative to the incident angle with respect to the emission wavelength of the light-emitting element 12a. Specifically, it is preferable to set the reflectivity of the light-reflecting film 12c so that oblique incidence is lower than perpendicular incidence. This slows down the change in brightness on the surface of the light-emitting element 12a, suppressing extreme darkening conditions such as the surface of the light-emitting element 12a becoming a dark spot.

[0098] As a light source 12, for example, a light source with a height of 100 μm to 500 μm for the light-emitting element 12a directly mounted on the substrate 11 can be cited. A light source with a thickness of 0.1 μm to 3.0 μm for the light-reflecting film 12c can be cited. Even including the sealing member 12b, the thickness of the light source 12 can be set to about 0.5 mm to 2.0 mm.

[0099] Preferably, multiple light sources 12 are wired on the substrate 11 in a manner that allows them to be driven independently of each other and allows dimming control (e.g., local dimming or high dynamic range) of each light source 12.

[0100] (Light-emitting element 12a)

[0101] As the light-emitting element 12a, a known light-emitting element can be used. For example, a light-emitting diode (LED) is preferably used as the light-emitting element 12a. The light-emitting element 12a can be a light-emitting element of any wavelength. For example, as a blue or green light-emitting element, a light-emitting element using nitride semiconductors such as GaN, InGaN, AlGaN, and AlInGaN can be used. Furthermore, as a red light-emitting element, GaAlAs, AlInGaP, etc., can be used. Moreover, semiconductor light-emitting elements made of materials other than these can also be used. The composition, color, size, and number of light-emitting elements used can be appropriately selected according to the purpose.

[0102] like Figure 6 As shown, the light-emitting element 12a can be exemplified by a flip-chip mounted across the bonding member 19, with a pair of positive and negative conductor wires 18A and 18B provided on the upper surface 11a of the substrate 11. However, the light-emitting element 12a is not limited to flip-chip mounting and can also be mounted face up.

[0103] The bonding component 19 is a component used to fix the light-emitting element 12a to the substrate or conductor wiring, and can be an insulating resin or a conductive component, etc. Figure 6In the case of flip-chip mounting shown, a member having electrical conductivity is used. Specifically, 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, a Sn-containing alloy, a Sn-Cu-containing alloy, a Sn-Cu-Ag-containing alloy, an Au-Ge-containing alloy, an Au-Si-containing alloy, an Al-containing alloy, a Cu-In-containing alloy, a mixture of a metal and a flux, and the like.

[0104] (sealing member 12b)

[0105] The sealing member 12b covers the light emitting element 12a for the purpose of protecting the light emitting element 12a from the external environment and optically controlling (e.g., obtaining a batwing light distribution characteristic) light output from the light emitting element 12a, and the like. The sealing member 12b is formed of a light-transmissive material. As the material of the sealing member 12b, a light-transmissive resin such as an epoxy resin, a silicone resin, or a mixed resin thereof, glass, or the like can be used. Among these, a silicone resin is preferably used in consideration of light resistance and ease of molding. In the sealing member 12b, a diffusing agent for diffusing light from the light emitting element 12a, a coloring agent corresponding to the light emitting color of the light emitting element 12a, or the like can be contained. The diffusing agent, coloring agent, and the like can use agents known in the art.

[0106] The sealing member 12b can be in direct contact with the substrate 11. The sealing member 12b is adjusted to a viscosity that enables printing, coater coating, or the like, and can be hardened by heat treatment, light irradiation. As the shape of the sealing member 12b, for example, a substantially hemispherical shape, a convex shape that is long in cross section in the direction perpendicular to the upper surface 11a of the substrate 11, a convex shape that is flat in cross section, a circular shape or an elliptical shape in plan view, or the like can be given. Here, the convex shape that is long in cross section means a shape in which the maximum length in the direction perpendicular to the upper surface 11a of the substrate 11 is longer than the maximum length in the direction parallel to the upper surface 11a of the substrate 11 in cross section. Also, the convex shape that is flat in cross section means a shape in which the maximum length in the direction parallel to the upper surface 11a of the substrate 11 is longer than the maximum length in the direction perpendicular to the upper surface 11a of the substrate 11 in cross section. The sealing member 12b can be disposed as an underfill 12d between the lower surface of the light emitting element 12a and the upper surface 11a of the substrate 11.

[0107] (separating member 13)

[0108] The wall portion 13b of the partition member 13 can be configured as a grid in top view. In top view, the boundary of adjacent partitions C can be regarded as the top 13a. Preferably, the partition member 13 has a bottom portion 13c within the partition C that is connected to the lower end of the wall portion 13b. In other words, the partition member 13 preferably forms the partition C by the bottom portion 13c and the wall portion 13b. The bottom portion 13c can extend to the periphery of the substrate 11 in top view. In this case, the bottom portion 13c can be located on the outer edge of the substrate 11, closer to the outermost wall portion 13b. The periphery of the partition member 13 can have a portion that coincides with the periphery of the substrate 11. Preferably, the partition member 13 is a reflective component.

[0109] The partition member 13, for example, within partition C, has a through hole 13d at approximately the center of its bottom 13c for accommodating the light source 12. Figure 6 As shown, the light source 12 is preferably disposed within the through hole 13d. The shape and size of the through hole 13d are such that the light source 12 is fully exposed, and it is preferably set such that the outer edge of the through hole 13d is only located near the light source 12. Thus, when the separating member 13 is reflective, the light from the light source 12 is also reflected at the bottom 13c, which can improve the light extraction efficiency.

[0110] The top 13a is the highest point of the wall portion 13b. The top 13a can be a plane, but it is preferable that the area around the top 13a is angular. That is, it is preferable that the longitudinal section of the wall portion 13b constituting the top 13a forms an acute triangle, and more preferably an acute isosceles triangle.

[0111] Preferably, the acute angle of the acute triangle or acute isosceles triangle is set, that is, the angle of the top 13a side of the wall 13b. Figure 2 The angle α in the figure is, for example, 60° to 90°. By setting it to such a range, the space and area occupied by the partition member 13 can be reduced, and the height of the partition member 13 can be reduced, thereby enabling the miniaturization and thinning of the light-emitting device 10.

[0112] The spacing P between the top 13a of the separating members 13 can be appropriately adjusted according to the size of the light source used, the size and performance of the intended light-emitting device, etc. Examples of spacing P include 1mm to 50mm, preferably 5mm to 20mm, and more preferably 6mm to 15mm. Preferably, the wall portion 13b surrounding the light source 12 is formed on the separating C side by a surface that slopes upward from the bottom 13c and near the upper surface 11a of the substrate 11.

[0113] Further, the height of the partition member 13, i.e., the length from the lower surface of the bottom 13c to the top 13a of the partition member 13 is preferably 8 mm or less, and is preferably about 1 mm to 4 mm in the case of setting a thinner light emitting device. Further, the distance from the lower surface of the bottom 13c to the light diffusion plate 14 is preferably about 8 mm or less, and is preferably about 2 mm to 4 mm in the case of setting a thinner light emitting device. Thus, the backlight unit including the optical member such as the light diffusion plate 14 can be set to be extremely thin. The thickness of the partition member 13 can be, for example, 100 μm to 300 μm.

[0114] The shape of the partition C formed by the partition member 13 surrounding the light source 12, i.e., the shape of the region partitioned by the wall portion 13b is a quadrangle in plan view, but is not limited thereto, and can be, for example, a circle, an ellipse, or the like. However, in order to efficiently arrange a plurality of light sources 12, a polygon such as a triangle, a quadrangle, a hexagon, or the like is preferable. Thus, depending on the area of the light emitting surface of the light emitting device 10, the light emitting region can be easily partitioned into an arbitrary number of regions by the wall portion 13b, and thus the light emitting regions can be arranged at a high density.

[0115] The number of the partitions C partitioned by the wall portion 13b can be arbitrarily set, and the shape of the wall portion 13b and the arrangement, the number of the partitions C, and the like can be changed depending on the desired size of the light emitting device. Depending on the number and the position of the light source 12 arranged on the substrate 11, the partition member 13 can be set to have a shape in which, for example, three partitions C are adjacent to each other and the ends of the three tops are concentrated at one point in plan view, Figure 6 four partitions C are adjacent to each other and the four tops are concentrated, a shape in which six partitions C are adjacent to each other and the six tops are concentrated at one point, and the like. In the case where the four partitions C are adjacent to each other and the four tops are concentrated, the shape of the partitions C in plan view is a quadrangle.

[0116] The partition member 13 is preferably arranged on the substrate 11, and the lower surface of the bottom 13c of the partition member 13 is preferably fixed to the upper surface 11a of the substrate 11. In particular, in order to prevent the emitted light from the light source 12 from entering between the substrate 11 and the partition member 13, the periphery of the through hole 13d is preferably fixed using an adhesive member having light reflectivity. More preferably, the adhesive member having light reflectivity is annularly arranged along the outer edge of the through hole 13d. The adhesive member can be a double-sided tape, a hot-melt type adhesive sheet, a thermosetting resin or a thermoplastic resin, or the like. These adhesive members preferably have a high flame retardancy. However, the partition member 13 can be fixed to the substrate 11 using a fastening screw.

[0117] As described above, the partition member 13 preferably has light reflectivity. Thereby, light emitted from the light source 12 can be efficiently reflected by the wall portion 13b and the bottom portion 13c. In particular, in the case where the wall portion 13b has an inclination as described above, light emitted from the light source 12 is irradiated to the wall portion 13b, and the light can be reflected in the upward direction. Thereby, the contrast can be further improved even in the case where the adjacent partition C is not lit. In addition, the reflection of light in the upward direction can be efficiently performed.

[0118] The partition member 13 can be formed using a resin containing a reflective material composed of metal oxide particles such as titanium oxide, aluminum oxide, silicon oxide, or the like, or can be formed using a resin not containing a reflective material, and then a reflective material can be provided on the surface. Alternatively, a resin including fine bubbles can be used. In this case, light is reflected at the interface of the bubbles. In addition, as the resin used in the partition member 13, an acrylic resin, a polycarbonate resin, a cyclic polyolefin resin, a thermoplastic resin such as polyethylene terephthalate (PET) or polyester, or a thermosetting resin such as an epoxy resin or silicone, or the like can be cited. It is preferable that the reflectance of the partition member 13 with respect to the emitted light from the light source 12 be set to 70% or more.

[0119] The partition member 13 can be formed by a molding method using a metal mold, a molding method by light molding, or the like. As the molding method using a metal mold, a molding method such as injection molding, extrusion molding, compression molding, vacuum molding, air pressure molding, punch molding, or the like can be applied. For example, by performing vacuum molding using a reflective sheet formed of PET or the like, a partition member 13 in which the bottom portion 13c and the wall portion 13b are formed integrally can be formed.

[0120] (Light diffusion plate 14)

[0121] The light diffusion plate 14 is a member of a special shape for diffusing and transmitting incident light, and one can be disposed above a plurality of light sources 12. The light diffusion plate 14 is preferably a flat plate-shaped member, but a concave-convex can be disposed on the surface thereof. The light diffusion plate 14 is preferably disposed substantially in parallel to the substrate 11.

[0122] In the case where the gap between the top portions 13a of the partition members 13 is set to P (mm), the light diffusion plate 14 is preferably disposed so that the distance OD from the light source 12 is, for example, 0.3P (mm) or less, and more preferably so that the distance OD from the light source 12 is 0.25P (mm) or less. Here, as shown in FIG. 6, the distance OD means the distance from the top surface of the substrate 11, that is, the distance from the top surface of the substrate 11 having a cover layer, a wiring layer, or the like on the surface thereof to the lower surface of the light diffusion plate 14. From another viewpoint, with respect to the light diffusion plate 14, it is preferable that, for example, Figure 6 the distance OD from the light source 12 be 0.3P (mm) or less, and more preferably 0.25P (mm) or less.Figure 1 The distance H from the upper surface of the bottom portion 13c of the partition member 13 is 1.5 mm to 5 mm, and more preferably 2 mm to 3 mm.

[0123] The light diffusion plate 14 can be made of a material that has a small light absorption with respect to visible light, such as polycarbonate resin, polystyrene resin, acrylic resin, polyethylene resin, or the like. In order to diffuse the incident light, the light diffusion plate 14 can be provided with a concave-convex on its surface, or a material having a different refractive index can be dispersed in the light diffusion plate 14. The concave-convex can be set to a size of, for example, 0.01 mm to 0.1 mm. As the material having a different refractive index, polycarbonate resin, acrylic resin, or the like can be used.

[0124] The thickness of the light diffusion plate 14 and the degree of light diffusion can be appropriately set, and a commercially available component can be used as a light diffusion sheet, a diffuse film, or the like. For example, the thickness of the light diffusion plate 14 can be set to 1 mm to 2 mm at the thickest portion.

[0125] In the planar light source 10, since the substrate 11 has a shaped form, in a case where the light sources 12 are arranged in a matrix in the first direction and the second direction while being laid on the substrate 11 as much as possible, an area in which the light sources 12 are not arranged is generated on the outer edge side of the substrate 11. Also, if no countermeasure is taken, the periphery of the planar light source 10 (for example, an area between the outermost periphery of the partition member 13 and the outer edge of the light diffusion plate 14) becomes a dark portion, and sometimes brightness unevenness is generated in the periphery of the planar light source. In the Figure 5 In the planar light source 10, since the substrate 11 has a shaped form, in a case where the light sources 12 are arranged in a matrix in the first direction and the second direction while being laid on the substrate 11 as much as possible, an area in which the light sources 12 are not arranged is generated on the outer edge side of the substrate 11. Also, if no countermeasure is taken, the periphery of the planar light source 10 (for example, an area between the outermost periphery of the partition member 13 and the outer edge of the light diffusion plate 14) becomes a dark portion, and sometimes brightness unevenness is generated in the periphery of the planar light source. In the

[0126] The light diffusion plate 14 includes a thick plate portion 14a and a thin plate portion 14b that is thinner than the thick plate portion 14a, and the thick plate portion 14a and the thin plate portion 14b are arranged adjacent to each other and are formed integrally. Note that in the Figure 3 In the planar light source 10, since the substrate 11 has a shaped form, in a case where the light sources 12 are arranged in a matrix in the first direction and the second direction while being laid on the substrate 11 as much as possible, an area in which the light sources 12 are not arranged is generated on the outer edge side of the substrate 11. Also, if no countermeasure is taken, the periphery of the planar light source 10 (for example, an area between the outermost periphery of the partition member 13 and the outer edge of the light diffusion plate 14) becomes a dark portion, and sometimes brightness unevenness is generated in the periphery of the planar light source. In the

[0127] The boundary 14c between the thick plate portion 14a and the thin plate portion 14b is located, for example, opposite to the outermost periphery of the wall portion 13b of the separating member 13. Therefore, on the outer edge side of the wall portion 13b of the separating member 13, the frequency of light diffusion can be reduced, thereby increasing the light transmitted through the thin plate portion 14b. As a result, the generation of brightness unevenness at the periphery of the planar light source 10 can be suppressed. The boundary 14c may also be located opposite to the top 13a of the outermost periphery of the separating member 13.

[0128] The wall portion 13b is located directly below the boundary between the thick plate portion 14a and the thin plate portion 14b of the light diffusion plate 14. Figure 5 In the case of light incident from the light source 12 into the thin plate portion 14b of the light diffusion plate 14, a portion of the light diffused in the thick plate portion 14a of the light diffusion plate 14 enters the thin plate portion 14b. Since the film thickness of the thin plate portion 14b is relatively thin, the diffusion frequency of the light entering the thin plate portion 14b decreases. Therefore, light extraction from the thin plate portion 14b is improved.

[0129] Preferably, the thickness of the thin plate portion 14b is 0.5 times or less than the thickness of the thick plate portion 14a. As a result, the light extracted from the region of the thin plate portion 14b increases, thereby suppressing the generation of brightness unevenness at the periphery of the planar light source 10.

[0130] The lower surface 14n (the surface on the side of the light source 12) of the thick plate portion 14a and the lower surface 14t (the surface on the side of the light source 12) of the thin plate portion 14b are located on the same plane. The upper surface 14m (the surface on the side opposite to the light source 12) of the thick plate portion 14a and the upper surface 14s (the surface on the side opposite to the light source 12) of the thin plate portion 14b are at different positions in the height direction.

[0131] 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.

[0132] When viewed from above, the thin plate portion 14b is located at least a portion of the periphery of the light diffusion plate 14. For example... Figure 7 As shown, in this embodiment, as an example, a thin plate portion 14b is provided over the entire periphery of the light diffuser 14 (the portion shown by the dot pattern). By providing the thin plate portion 14b over the entire periphery of the light diffuser 14, the brightness of the entire periphery of the thin plate portion 14b can be increased, thereby reducing brightness unevenness. However, it is not limited to this; the thin plate portion 14b may also be provided only over a portion of the periphery of the light diffuser 14.

[0133] In the planar light source 10, in plan view, the further the portion from the optical axis of the light source 12 at the end in the X direction to the outer edge of the light-diffusing plate 14 in the X direction, the wider the width of the thin plate portion 14b in the X direction. For example, as shown in FIG. 6, in one light source 121 at the end in the X direction among the plurality of light sources 12 and the other light source 122, the distance Ll from the optical axis OAl of the one light source 121 to the outer edge of the light-diffusing 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-diffusing plate 14 in the X direction. In this case, as shown in FIG. 6, in plan view, the width Wl of the thin plate portion 14b in the X direction from the optical axis OAl of the one light source 121 toward the outer edge of the light-diffusing plate 14 is wider than the width W2 of the thin plate portion 14b in the X direction from the optical axis OA2 of the other light source 122 toward the outer edge of the light-diffusing plate 14. Figure 8 Figure 7

[0134] Further, in plan view, the further the portion from the optical axis of the light source 12 at the end in the Y direction to the outer edge of the light-diffusing plate in the Y direction, the wider the width of the thin plate portion 14b in the Y direction. For example, as shown in FIG. 7, in one light source 123 at the end in the Y direction among the plurality of light sources 12 and the other light source 124, the distance L3 from the optical axis OA3 of the one light source 123 to the outer edge of the light-diffusing plate 14 in the Y direction is longer than the distance L4 from the optical axis OA4 of the other light source 124 to the outer edge of the light-diffusing plate 14 in the Y direction. In this case, as shown in FIG. 7, in plan view, the width W3 of the thin plate portion 14b in the Y direction from the optical axis OA3 of the one light source 123 toward the outer edge of the light-diffusing plate 14 is wider than the width W4 of the thin plate portion 14b in the Y direction from the optical axis OA4 of the other light source 124 toward the outer edge of the light-diffusing plate 14. Figure 8 Figure 9

[0135] Figure 10 and Figure 9 are graphs showing simulation results related to the light-diffusing plate. Figure 10 is a simulation result of the planar light source 10, Figure 9 is a simulation result of the planar light source 10X in which a light-diffusing plate 14X having a constant plate thickness is mounted instead of the light-diffusing plate 14 of the planar light source 10 (comparative example). In Figure 10 and Figure 9 In FIGS. 8 to 11, many thin lines represent light rays.

[0136] If Figure 10 and Figure 11 ​​​​It is confirmed that the planar light source 10 provided with the thin plate portion 14b has more portions where the light density is higher than the planar light source 10X not provided with the thin plate portion, and the light extraction is good in the periphery of the light diffusion plate 14. That is, it is confirmed that the luminance unevenness of the light emitting surface in the periphery of the light diffusion plate 14 can be suppressed. This is because, by providing the thin plate portion 14b in the light diffusion plate 14, the frequency of light diffusion in the thin plate portion 14b is reduced, and thus the light transmitted through the thin plate portion 14b is increased. In addition, the light emitted from the side surface of the thick plate portion 14a exposed on the thin plate portion 14b side and the light reflected on the side surface of the thick plate portion 14a by being transmitted through the thin plate portion 14b are directed toward the upper surface side of the light diffusion plate, and thus the light density on the upper surface side of the light diffusion plate is increased.

[0137] With respect to the light diffusion plate 14, the thickness of the thick plate portion 14a was set to 1.2 mm, and the thickness of the thin plate portion 14b was changed to each of 0.4 mm, 0.2 mm, and 0.1 mm, and a simulation was performed, and the luminance of the light transmitted through the thin plate portion 14b in the region of the thin plate portion 14b was calculated. As shown in Table 1, in the case where the thin plate portion 14b was 0.4 mm, the result of an increase of 1.1 times was obtained, as compared with the case where the thin plate portion 14b was 1.2 mm (i.e., the thickness of the thin plate portion 14b was the same as that of the thick plate portion 14a). Similarly, in the case where the thin plate portion 14b was 0.2 mm, the result of an increase of 1.12 times was obtained. In addition, in the case where the thin plate portion 14b was 0.1 mm, the result of an increase of 1.17 times was obtained.

[0138] (Table 1)

[0139]

[0140] In addition, if the light leaked out from the side surface of the light diffusion plate is compared, it is confirmed that the planar light source 10 provided with the thin plate portion 14b has less light leakage than the planar light source 10X not provided with the thin plate portion. That is, in the planar light source 10, both the light previously leaked in the lateral direction is directed toward the upper surface side of the light diffusion plate 14, and the frequency of light diffusion in the thin plate portion 14b is reduced, and thus the light density on the upper surface side of the plate portion 14b can be increased.

[0141] In addition, by providing the thin plate portion 14b in the light diffusion plate 14 in the planar light source 10, the amount of light leaked out from the side surface of the light diffusion plate 14 can be reduced.

[0142] In the planar light source 10, above the light-diffusing plate 14, there is sometimes provided a wavelength conversion sheet for converting light from the light source 12 into light of a different wavelength. In the case where a wavelength conversion sheet is provided above the light-diffusing plate 14, if light leaks out from the side surface of the light-diffusing plate, the end portion of the planar light source appears to be the light-emitting color (e.g., blue) of the light-emitting element 12a. However, since in the planar light source 10 the amount of light that leaks out from the side surface of the light-diffusing plate 14 can be reduced by providing the thin plate portion 14b in the light-diffusing plate 14, the phenomenon of the end portion of the planar light source 10 appearing to be the light-emitting color of the light-emitting element 12a can be suppressed. That is, in the case where a wavelength conversion sheet is provided above the light-diffusing plate 14, the phenomenon of light of a wavelength different from the wavelength converted by the wavelength conversion sheet leaking out from the side surface of the light-diffusing plate 14 can be suppressed.

[0143] Thus, in the planar light source 10, since the substrate 11 is of a special shape, in the case where the light sources 12 are laid out on the substrate 11 while maintaining the matrix arrangement in the first direction and the second direction as much as possible, a region in which no light source 12 is provided is generated on the outer edge side of the substrate 11. Also, if no countermeasure is taken, the region between the outermost periphery of the partition member 13 and the outer edge of the light-diffusing plate 14, for example, becomes a dark portion. That is, if no countermeasure is taken, unevenness in brightness is generated in a part of the periphery of the planar light source 10. However, by providing the thin plate portion 14b in the periphery of the light-diffusing plate 14, light extraction is given priority over light diffusion in the thin plate portion 14b, so that the frequency of light diffusion can be reduced and the light that passes through the thin plate portion 14b can be increased. As a result, the generation of unevenness in brightness in the periphery of the planar light source 10 can be suppressed.

[0144] However, since the thin plate portion 14b is provided in a portion in which unevenness in brightness is feared, the thin plate portion 14b does not necessarily have to be provided in the entire region of the periphery of the light-diffusing plate 14, and the thin plate portion 14b can be provided only in a part of the region of the periphery of the light-diffusing plate 14.

[0145] In addition, based on the same reason, in both the X direction and the Y direction, the farther the distance from the optical axis of the light source 12 located at the end portion to the outer edge of the light-diffusing plate 14, the wider the width of the thin plate portion 14b does not need to be. That is, in at least one of the X direction and the Y direction, the farther the distance from the optical axis of the light source 12 located at the end portion to the outer edge of the light-diffusing plate 14, the wider the width of the thin plate portion 14b can be.

[0146] Note that the planar light source 10 can have at least one selected from the group consisting of a wavelength conversion sheet that converts light from the light source 12 into light of a different wavelength, a prism sheet, and a polarizing sheet, above the light-diffusing plate 14. Specifically, as shown in FIG. 9, the planar light source 10 can have a wavelength conversion sheet 14a, a prism sheet 14b, and a polarizing sheet 14c provided in this order from the bottom. Figure 11As shown, the wavelength conversion sheet 72, the prism sheet (the first prism sheet 73 and the second prism sheet 74), the polarizing sheet 75, and the like optical members can be arranged above the light diffusion plate 14 at a prescribed distance or directly or indirectly on the upper surface of the light diffusion plate 14, and further, a liquid crystal panel can be arranged thereon, and the light emitting device can be used as a surface light emitting type light emitting device for a direct type backlight light source. The stacking order of these optical members can be arbitrarily set.

[0147] (wavelength conversion sheet 72)

[0148] The wavelength conversion sheet 72 can be arranged on either of the upper surface or the lower surface of the light diffusion plate 14, as shown in Figures 12-14 The wavelength conversion sheet 72 absorbs a part of the light emitted from the light source 12, and emits light of a wavelength different from that of the light emitted from the light source 12. For example, a light emitting device 10 that absorbs a part of the blue light from the light source 12 and emits yellow light, green light, and / or red light by the wavelength conversion sheet 72, and emits white light can be realized. Since the wavelength conversion sheet 72 is apart from the light emitting element 12a of the light source 12, a phosphor or the like that is difficult to use in the vicinity of the light emitting element 12a and has poor resistance to heat or light intensity can be used. Thus, the performance of the light emitting device 10 as a backlight can be improved. The wavelength conversion sheet 72 has a sheet shape or a layer shape, and includes the above-described phosphor or the like. Note that the wavelength conversion sheet is sometimes referred to as a wavelength conversion layer.

[0149] (first prism sheet 73 and second prism sheet 74)

[0150] The first prism sheet 73 and the second prism sheet 74 have a shape in which a plurality of prisms are arranged in a prescribed direction on the surface thereof. For example, when the plane of the prism sheet is observed in two dimensions in the x direction and the y direction that is at right angles to the x direction, the first prism sheet 73 can have a plurality of prisms extending in the y direction, and the second prism sheet 74 can 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 each direction toward the direction of the display panel opposite to the light emitting device 10. Thus, light emitted from the light emitting surface of the light emitting device 10 can be mainly emitted in the direction perpendicular to the upper surface, and the luminance from the case where the light emitting device 10 is observed from the front can be improved.

[0151] (polarizing sheet 75)

[0152] The polarizing plate 75 can selectively transmit light having a polarization direction that is aligned with the polarization direction of a polarizing plate disposed on the back light side of a display panel such as a liquid crystal display panel, and reflect polarized light having 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 returned from the polarizing plate 75 is reflected again by the first prism sheet 73, the second prism sheet 74, the wavelength conversion sheet 72, and the light diffusion plate 14. At this time, the polarization direction is changed, for example, to a polarization direction having the polarization direction of the polarizing plate of the liquid crystal display panel, and the light is incident again on the polarizing plate 75 and is emitted toward the display panel. Thus, the polarization direction of the light emitted from the light emitting device 10 is unified, and light having a polarization direction effective for increasing the brightness of the display panel can be efficiently emitted. The polarizing plate 75, the first prism sheet 73, the second prism sheet 74, and the like can be used as optical members for back light, and commercially available optical members can be used.

[0153] Note that in the planar light source 10, a wavelength conversion material such as a phosphor that absorbs light from the light emitting element 12a and emits light having a different wavelength from the output light from the light emitting element 12a can be contained in the sealing member 12b instead of the wavelength conversion sheet 72. Thus, a light emitting device 10 that emits white light by, for example, absorbing a portion of blue light from the light source 12 in the sealing member 12b and emitting yellow light, green light, and / or red light can be implemented.

[0154] The sealing member 12b can contain a diffusing agent for diffusing light from the light emitting element 12a, a coloring agent corresponding to the emission color of the light emitting element 12a, and the like in addition to the wavelength conversion material. The diffusing agent, the coloring agent, and the like can be agents known in the art. Furthermore, a light emitting element 12a in which a nitride-based semiconductor is covered with a wavelength conversion material such as a phosphor, i.e., an element in which the light emitting element 12a itself emits white light, can be used instead of the wavelength conversion material in the sealing member 12b.

[0155] <Modification Example 1 of First Embodiment>

[0156] In the modification example 1 of the first embodiment, an example in which the cross-sectional shape of the thin plate portion of the light diffusion plate is different from that of the first embodiment is shown. Note that in the modification example 1 of the first embodiment, the description of the same components as those of the already described embodiment is sometimes omitted.

[0157] Figure 15 is a schematic partially enlarged cross-sectional view of the light diffusion plate in the planar light source of the modification example 1 of the first embodiment. Figure 14 is a schematic plan view of the light diffusion plate of Figure 12 .

[0158] In Figure 3In the light diffusion plate 24 shown, 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. Furthermore, the thickness of the thin plate portion 24b gradually decreases as it approaches the outer edge of the light diffusion plate 24 from the boundary 24c with the thick plate portion 24a.

[0159] Thus, the boundary between the thick plate section and the thin plate section does not need to be as shown. Figure 12 As shown, it is stepped, and can be like... Figure 12 The shape shown is characterized by a smooth change in thickness. In this case, light extraction is prioritized over light diffusion in the thin plate portion 24b, thereby reducing the frequency of light diffusion and increasing the amount of light transmitted through the thin plate portion 24b. As a result, the generation of brightness unevenness at the periphery of the planar light source can be suppressed.

[0160] Alternatively, it can be different. Figure 13 The shape of the thin plate portion 24b shown in the light diffusion plate 24 is such that it gradually thins out as a whole, but rather the thin plate portion has a shape in which the thickness gradually decreases from the boundary with the thick plate portion towards the outer edge of the light diffusion plate. For example, as Figure 14 As shown in the light diffusion plate 34, the thin plate portion 34b may have a thickness-reducing portion 34b1 that gradually thins as it approaches the outer edge of the light diffusion plate 34 from the boundary 34c with the thick plate portion 34a. Furthermore, a thickness-constant portion 34b2 may be present on the side of the light diffusion plate 34 closer to the outer edge than the thickness-reducing portion 34b1. The thickness of the thickness of the thickness-constant portion 34b2 is, for example, the same as the thinnest portion of the thickness-reducing portion 34b1.

[0161] In addition, such as Figure 15 as well as Figures 12-14 As shown in the light diffuser 44, the thin plate portion 44b may include a first thin plate portion 44b1 on the side of the thick plate portion 44a, and a second thin plate portion 44b2 located on the outer edge side of the light diffuser 44 that is thinner than the first thin plate portion 44b1. In this way, by changing the thickness of the thin plate portion 44b in two stages, the brightness at the edge of the planar light source can be improved. That is, since the dark areas become more pronounced further away from the light source 12, by making the thickness of the light diffuser 14 thinner further away from the light source 12, the generation of brightness unevenness at the periphery of the planar light source can be suppressed. The change in the thickness of the thin plate portion 44b can also be in two or more stages. Furthermore, the cross-sectional shape of the thin plate portion 44b can be set to... Figure 15 The shapes shown in the diagram are appropriately combined.

[0162] The second thin plate portion 44b2 is disposed, for example, on the outer edge side of the light-diffusing plate 44 with respect to the region in which the through-hole 13d of the partition member 13 is disposed, in plan view. The second thin plate portion 44b2 can also be disposed in the partition C in which the light source 12 is not disposed. The boundary 44c between the first thin plate portion 44b1 and the second thin plate portion 44b2 can also be located at a position overlapping the top portion 13a of the partition member 13 in plan view.

[0163] Note that it is not necessarily required to provide the first thin plate portion 44b1 and the second thin plate portion 44b2 in all regions of the periphery of the light-diffusing plate 44. It is also possible to provide only the first thin plate portion 44b1 in a region in which it is difficult to generate unevenness in luminance. For example, in the region R in which the light source 12 is disposed in a linear shape in the first embodiment, it is difficult to generate unevenness in luminance, and thus it is possible to provide only the first thin plate portion 44b1 in the region R. Figure 15 Figure 16 In the region R in which the light source 12 is disposed in a linear shape in the first embodiment, it is difficult to generate unevenness in luminance, and thus it is possible to provide only the first thin plate portion 44b1 in the region R. Alternatively, in a case where unevenness in luminance is not substantially generated in the region R in which the light source 12 is disposed in a linear shape in the first embodiment, it is also possible to not provide the thin plate portion 44b in the region R.

[0164] <Modification Example 2 of the First Embodiment>

[0165] In the modification example 2 of the first embodiment, an example in which the partition member has partitions of different sizes in the periphery is shown. Note that in the modification example 2 of the first embodiment, the description of the same constituent parts as those of the already-described embodiments is sometimes omitted.

[0166] Figure 17 is a schematic partial enlarged plan view of the partition member of the modification example 2 of the first embodiment. Figure 16 is a cross-sectional view along the B-B line of Figure 16 . In the partition member 23 shown in Figure 17 and Figure 16 , 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 than that of the inner partition C in plan view. Note that in the example of Figure 17 and Figure 2 , although the area of the region surrounded by the wall portion 23b of the outermost partition C is enlarged in the X direction, it can also be enlarged in the Y direction. Alternatively, it can be a mixed state in which a part of the area of the region surrounded by the wall portion 23b of the outermost partition C is enlarged in the X direction and a part thereof is enlarged in the Y direction.

[0167] In this way, in the example of Figure 3 and Figure 16 , although the area of the bottom portion 23c exposed in the partition C is equal in all of the partitions C in plan view, it is not limited thereto. For example, in the example of Figure 17 ​and Figure 16 As shown in the example of FIG. 17, in plan view, at least one of the regions surrounded by the wall portions 23b located at the outermost periphery of the partition member 23 is larger in area than the regions surrounded by the wall portions 23b located at the inner periphery than the outermost periphery.

[0168] In Figure 17 and Figure 16 the configuration of the partition member 23 shown in FIG. 18, the wall portion 23b of the partition C constituting the outermost periphery is located near the outer edge of the substrate 11, thereby improving light extraction toward the exit surface side. That is, in Figure 17 and Figure 16 the configuration of the partition member 23 shown in FIG. 18, since the wall portion 23b is also located at the periphery of the substrate 11, more light can be delivered to the thin plate portion 14b of the light-diffusing plate 14. As a result, generation of luminance unevenness at the periphery of the planar light source 10 can be further suppressed. However, the wall portion 23b can not be provided at least at a portion of the outermost periphery of the partition member 23. Note that in Figure 17 and Figure 18A , although the wall portion 23b of the partition member is not disposed at the position of the boundary between the thick plate portion 14a and the thin plate portion 14b of the light-diffusing plate 14, the wall portion 23b can be provided at this position.

[0169] <Modification Example 3 of First Embodiment>

[0170] In the modification example 3 of the first embodiment, a modification example of a component other than the light-diffusing plate and the partition member is shown. Note that in the modification example 3 of the first embodiment, the explanation of the same constituent parts as those of the already explained embodiments is sometimes omitted.

[0171] Figure 18A is a schematic partial enlarged cross-sectional view of the vicinity of the outer edge of the planar light source. As shown in Figure 18B , the planar light source can have a frame 26 that surrounds the substrate 11 and the light-diffusing plate 14. The frame 26 is a special-shaped form, which is, for example, similar to the shape of the substrate 11 and has a bottom portion 26a that is one circle larger than the substrate 11 in plan view.

[0172] The periphery of the bottom portion 26a is exposed from the outside of the substrate 11 in a ring shape, and a side wall 26b is provided at the exposed portion in a manner of surrounding the substrate 11. The lid 27 can be provided at the side opposite to the bottom portion 26a of the side wall 26b in a manner of surrounding the outer edge of the substrate 11 and the light-diffusing plate 14. The lid 27 is disposed at a position that does not obstruct the emitted light from each light source 12. The frame 26 and the lid 27 are formed of various materials such as resin including a reflective material, metal, ceramic, and the like.

[0173] Note that, as shown in Figure 19As shown, the wavelength conversion member 28 including a phosphor can be arranged in the area between the substrate 11 and the light diffusion plate 14 in the inner side surface of the side wall 26b. Thereby, a part of the light from the light source 12 is wavelength-converted by the wavelength conversion member 28 arranged in the inner side surface of the side wall 26b to take out light of a wavelength conversion thickness, and thus it is possible to suppress the phenomenon that the end portion of the planar light source 10 appears to be the light emission color of the light emission element. In the case where the wavelength conversion member 28 is arranged in the inner side surface of the side wall 26b, in the cross section of the planar light source, the wall portion 13b of the partition member 13 can be arranged between the light source 12 and the side wall 26b, or can not be arranged. The wavelength conversion member 28 can be arranged in the entire inner side surface of the side wall 26b, or can be arranged in the area on the lower side than the lower surface of the light diffusion plate 14 in the inner side surface of the side wall 26b. In the case where the wavelength conversion member 28 is arranged in the area on the lower side than the lower surface of the light diffusion plate 14, the thin plate portion 14b of the light diffusion plate 14 can or can not cover the upper portion of the wavelength conversion member 28. As the wavelength conversion member 28, a material (for example, YAG) that emits yellow light can be used. The wavelength conversion member 28 arranged in the inner side surface of the side wall 26b can be a single one, or can be a plurality of members.

[0174] Thus, by providing the frame 26 and the cover 27 in the planar light source, it is possible to protect the substrate 11 and the light diffusion plate 14 from impacts and the like from the outside. Note that the light diffusion plate 14, the substrate 11, and the frame 26 can be similarly shaped irregular shapes.

[0175] Figure 5 is a schematic plan view that explains the outer shape of the substrate in the planar light source of the third modification of the first embodiment, and only the substrate, the light source, and the partition member are illustrated. The shape of the light diffusion plate can be, for example, the same as Figure 19 . Figure 1 The substrate 21 of the planar light source 20 shown is an irregular shape, and is a shape in which the area where the light source 12 is not arranged is cut out, as compared with Figure 19 the substrate 11 shown. That is, the outermost shape of the substrate 21 is a shape that corresponds to the outermost shape of the partition member 13. In the example of Figure 5 , the substrate 21 is located at a position that overlaps the partition member 13 in plan view (the lower side of the partition member 13).

[0176] Thus, the substrate 21 used in the planar light source can be a shape in which the area where the light source 12 is not arranged is cut out. In this case, by using a light diffusion plate 14 that is the same shape as Figure 11 , it is also possible to reduce the frequency of light diffusion at the periphery of the light diffusion plate 14, and thus increase the light that transmits through the light diffusion plate 14. As a result, it is possible to suppress the generation of luminance unevenness at the periphery of the planar light source.

[0177] The cross-sectional shape of the planar light source 10 can be, for example, as shown inFigure 20 The straight line shape parallel to the XY plane as shown in FIG. 1A, for example, can be a curved shape with respect to the XY plane. For example, in the X direction, it can be a curved shape in which the exit surface side is concave.

[0178] <Second Embodiment>

[0179] In the second embodiment, an example of a liquid crystal display device using the planar light source of the first embodiment as a backlight is shown. Note that in the second embodiment, the description of the same components as those of the already described embodiments is sometimes omitted.

[0180] Figure 20 is a configuration view of the liquid crystal display device of the second embodiment. As shown in Figure 6 the liquid crystal display device 1000 includes, in order from the upper side, a liquid crystal panel 120, an optical sheet 110, and the planar light source 10 of the first embodiment. Note that in the planar light source 10, the reference numeral 70 shows optical members such as a light diffusion plate, a wavelength conversion sheet, and the like. Here, the optical sheet 110 can include a DBEF (reflective polarizing sheet), a BEF (brightness rising sheet), a color filter, and the like in addition to or instead of the optical members.

[0181] The liquid crystal display device 1000 is a so-called direct type liquid crystal display device in which the planar light source 10 is stacked below the liquid crystal panel 120. The liquid crystal display device 1000 radiates light radiated from the planar light source 10 toward the liquid crystal panel 120. Note that in addition to the above-described configuration members, members such as a color filter can be included.

[0182] Generally, in a direct type liquid crystal display device, since the distance between the liquid crystal panel and the planar light source is short, there is a concern that color unevenness and brightness unevenness of the planar light source affect color unevenness and brightness unevenness of the liquid crystal display device. Therefore, as a planar light source for a direct type liquid crystal display device, a planar light source with less color unevenness and brightness unevenness is desired. By using the planar light source 10 in the liquid crystal display device 1000, it is possible to make the thickness of the planar light source 10 thinner, for example, 5 mm or less, 3 mm or less, 1 mm or less, and the like, while suppressing brightness unevenness at the periphery and making the overall color unevenness and brightness unevenness less.

[0183] Note that it is not limited to the case where one planar light source 10 is used as a backlight for one liquid crystal display device 1000, and a plurality of planar light sources 10 can be arranged to be used as a backlight for one liquid crystal display device 1000. For example, compared to the case where one larger planar light source 10 is made by making a plurality of smaller planar light sources 10 and individually inspecting and the like, the number of light sources 12 to be mounted can be increased, and thus the yield can be improved.

[0184] Thus, since the planar light source 10 emits uniform light from the optical member 70, it is suitable for use as a backlight for the liquid crystal display device 1000.

[0185] However, the planar light source 10 can also be suitably used as a backlight for a television, a tablet, a smartphone, a smartwatch, a head-mounted display, a digital signage, a bulletin board, and the like. In addition, the planar light source 10 can also be used as a light source for illumination, and can also be used as an emergency light, line illumination, or various colored lights, installation for vehicle use, and the like. Note that one or more of the modifications shown in Modification Examples 1 to 3 of the first embodiment can be appropriately implemented in the planar light source 10.

[0186] The above-described preferred embodiments and the like have been described in detail, but are not limited to the above-described embodiments and the like, and various modifications and substitutions can be made to the above-described embodiments and the like without departing from the scope of the claims.

[0187] For example, in the above-described embodiments, the lower surface (light source side surface) of the thick plate portion of the light diffusion plate and the lower surface (light source side surface) of the thin plate portion are located on the same plane, but the upper surface (surface on the side opposite to the light source) of the thick plate portion of the light diffusion plate and the upper surface (surface on the side opposite to the light source) of the thin plate portion can be located on the same plane. That is, the thin plate portion can be provided on the lower surface side of the light diffusion plate. For example, the light diffusion plate 14 shown in FIG. 1, the light diffusion plate 24 shown in FIG. 2, the light diffusion plate 34 shown in FIG. 3, and the light diffusion plate 44 shown in FIG. 4 can be inverted upside down. In these cases, although an increase in light from the side surface of the thick plate portion toward the upper surface side of the light diffusion plate cannot be expected, an increase in light that transmits through the thin plate portion due to a lower frequency of light diffusion in the thin plate portion can be obtained, and thus a certain effect of suppressing unevenness in brightness of the light emitting surface in the periphery of the light diffusion plate can be obtained. Figure 12 the light diffusion plate 14 shown in FIG. 1, Figure 13 the light diffusion plate 24 shown in FIG. 2, Figure 14 the light diffusion plate 34 shown in FIG. 3, ​ the light diffusion plate 44 shown in FIG. 4 can be inverted upside down. In these cases, although an increase in light from the side surface of the thick plate portion toward the upper surface side of the light diffusion plate cannot be expected, an increase in light that transmits through the thin plate portion due to a lower frequency of light diffusion in the thin plate portion can be obtained, and thus a certain effect of suppressing unevenness in brightness of the light emitting surface in the periphery of the light diffusion plate can be obtained.

[0188] In addition, scattering particles such as titanium oxide particles and phosphor particles can be contained in the light diffusion plate, and the concentration of the scattering particles contained in the thin plate portion can be lower than the concentration of the scattering particles contained in the thick plate portion. Thus, the frequency of light diffusion in the thin plate portion can be further reduced, and the light that transmits through the thin plate portion can be further increased, and thus the effect of suppressing unevenness in brightness of the light emitting surface in the periphery of the light diffusion plate can be improved. Alternatively, by forming a scattering particle layer containing scattering particles on the upper surface and / or the lower surface of the light diffusion plate, and making the concentration of the scattering particles in the scattering particle layer formed in the thin plate portion lower than the concentration of the scattering particles in the scattering particle layer formed in the thick plate portion, the same effect can be obtained.

Claims

1. A planar light source comprising: a mounting substrate of anisotropic shape; a plurality of light sources arranged in two dimensions in a first direction on the mounting substrate and a second direction perpendicular to the first direction; and a light diffusion plate provided above the plurality of light sources, wherein the light diffusion plate includes a thick plate portion and a thin plate portion thinner than the thick plate portion, a boundary between the thick plate portion and the thin plate portion, the thin plate portion is provided in at least a portion of the light diffusion plate on an outer side than each of the light sources arranged on an outermost periphery when viewed in plan, in a case where a distance from an optical axis of one light source to an outer edge of the light diffusion plate in the first direction is longer than a distance from an optical axis of another light source to the outer edge of the light diffusion plate in the first direction, the one light source and the another light source being among the plurality of light sources, a width of the thin plate portion in the first direction when viewed in plan is wider than a width of the thin plate portion in the first direction from the optical axis of the one light source toward the outer edge of the light diffusion plate than a width of the thin plate portion in the first direction from the optical axis of the another light source toward the outer edge of the light diffusion plate.

2. The planar light source according to claim 1, wherein, in a case where a distance from an optical axis of one light source to an outer edge of the light diffusion plate in the second direction is longer than a distance from an optical axis of another light source to the outer edge of the light diffusion plate in the second direction, the one light source and the another light source being among the plurality of light sources, a width of the thin plate portion in the second direction when viewed in plan is wider than a width of the thin plate portion in the second direction from the optical axis of the one light source toward the outer edge of the light diffusion plate than a width of the thin plate portion in the second direction from the optical axis of the another light source toward the outer edge of the light diffusion plate.

3. The planar light source according to claim 1 or 2, wherein, a height from an upper surface of the mounting substrate to a surface of the thin plate portion on a light source side is the same as a height from the upper surface of the mounting substrate to a surface of the thick plate portion on the light source side, and a height from the upper surface of the mounting substrate to a surface of the thin plate portion on a side opposite to the light source is lower than a height from the upper surface of the mounting substrate to a surface of the thick plate portion on the side opposite to the light source.

4. The planar light source according to claim 1 or 2, wherein, a height from an upper surface of the mounting substrate to a surface of the thin plate portion on a light source side is the same as a height from the upper surface of the mounting substrate to a surface of the thick plate portion on the light source side, and the thin plate portion has a portion in which a thickness gradually decreases as approaching an outer edge of the light diffusion plate from the boundary with the thick plate portion.

5. The planar light source according to claim 1 or 2, wherein, the thin plate portion is provided in all regions of a peripheral edge of the light diffusion plate.

6. The planar light source according to claim 1 or 2, further comprising a partition member including a wall portion surrounding each of the light sources when viewed in plan, and having a plurality of regions surrounded by the wall portion.

7. The planar light source according to claim 6, wherein, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The boundary between the thin plate portion and the thick plate portion is located at a position opposite to the wall portion of the outermost periphery of the partition member.

8. The planar light source according to claim 6, wherein The partition member has a bottom portion connected to a lower end of the wall portion, The bottom portion has a through hole for arranging the light source.

9. The planar light source according to claim 8, wherein The bottom portion extends to the periphery of the mounting substrate when viewed from above.

10. The planar light source according to claim 1 or 2, wherein The thin plate portion includes a first thin plate portion on the thick plate portion side, and a second thin plate portion located on the outer edge side of the light diffusion plate than the first thin plate portion and having a smaller plate thickness than the first thin plate portion.

11. The planar light source according to claim 6, wherein In at least a portion of the outermost periphery of the partition member, the wall portion is not provided.

12. The planar light source according to claim 1 or 2, wherein Further comprising a frame that surrounds the mounting substrate and the light diffusion plate.

13. The planar light source according to claim 12, wherein The frame is a special shape, and is a similar shape to the mounting substrate.

14. The planar light source according to claim 12, wherein The light diffusion plate is a special shape.

15. The planar light source according to claim 12, wherein The light diffusion plate, the mounting substrate, and the frame are special shapes that are similar shapes.

16. The planar light source according to claim 6, wherein When viewed from above, the area of at least one of the regions of the partition member located at the outermost periphery is larger than the area of the region located on the inner periphery side than the outermost periphery.

17. The planar light source according to claim 1 or 2, wherein Further comprising a wavelength conversion layer for converting light from the light source into light of a different wavelength above the light diffusion plate.

18. A liquid crystal display device that uses the planar light source according to any one of claims 1 to 17 as a backlight.

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