Surface light source device and display device

Abstract

To make an in-surface distribution of lightness sufficiently uniform while making a surface light source device thin.SOLUTION: A surface light source device has a wavelength-selective reflection layer 40, a light source substrate 22 including a light source 23 facing the wavelength-selective reflection layer and a support substrate 25 supporting the light source, and a wavelength conversion agent located between the wavelength-selective reflection layer 40 and the light source device 22. The light source substrate 22 includes a reflection layer opposed to the wavelength-selective reflection layer 40. The wavelength conversion agent absorbs primary light from the light source 23 and emits secondary light having a wavelength different from the wavelength of the primary light. The reflection factor of the wavelength-selective reflection layer 40 to the secondary light is smaller than the reflection factor of the wavelength-selective reflection layer 40 to the primary light.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] A surface light source device is known as a device that emits light in a planar manner. As disclosed in Patent Document 1, the surface light source device can be used as a backlight for a liquid crystal display device. Patent Document 1 discloses a direct-type surface light source device in which a light source faces an optical member. In the direct-type surface light source device, unevenness in brightness occurs due to the arrangement of the light source. This unevenness in brightness becomes more noticeable when the surface light source device is made thinner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP2014-199831A Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, it has not been possible to sufficiently uniform the in-plane distribution of brightness while reducing the thickness of the surface light source device. The present invention has been made in consideration of this point. The object of the present invention is to sufficiently uniform the in-plane distribution of brightness while reducing the thickness of the surface light source device. [Means for solving the problem]

[0005] A surface light source device according to an embodiment of the present disclosure includes: A wavelength selective reflective layer; a light source substrate including a light source facing the wavelength selective reflection layer and a support substrate supporting the light source; a wavelength conversion agent located between the wavelength selective reflective layer and the light source substrate, the light source substrate includes a reflective layer facing the wavelength-selective reflective layer; The wavelength conversion agent absorbs primary light from the light source and emits secondary light having a wavelength different from that of the primary light; The reflectance of the secondary light at the wavelength-selective reflective layer is smaller than the reflectance of the primary light at the wavelength-selective reflective layer.

[0006] In the surface light source device according to the embodiment of the present disclosure, the wavelength selective reflection layer may have a reflectance of the secondary light of 50% or less.

[0007] In the surface light source device according to the embodiment of the present disclosure, the wavelength selective reflection layer may have a reflectance of 90% or more for the primary light.

[0008] In a surface light source device according to an embodiment of the present disclosure, A region between the wavelength selective reflecting layer and the light source substrate, which overlaps an area having a certain area of ​​the wavelength selective reflecting layer and the wavelength selective reflecting layer in a direction in which the wavelength selective reflecting layer and the light source substrate face each other, is defined as a reference volume region, The volume of the wavelength conversion agent contained in one reference volume region may be larger than the volume of the wavelength conversion agent contained in another reference volume region located between the one reference volume region and a light source closest to the one reference volume region.

[0009] In a surface light source device according to one embodiment of the present disclosure, the volume of the wavelength conversion agent contained in any one of the reference volume regions may be greater than or equal to the volume of the wavelength conversion agent contained in any other reference volume region located between the one of the reference volume regions and the one of the light sources.

[0010] In a surface light source device according to an embodiment of the present disclosure, A conversion agent-containing portion containing the wavelength conversion agent may be provided between the wavelength selective reflection layer and the light source substrate, One or more of the thickness of the conversion agent-containing portion, the proportion of the area in which the conversion agent-containing portion is arranged, and the content of the wavelength conversion agent contained in the conversion agent-containing portion may vary depending on the distance from the light source.

[0011] In the surface light source device according to the embodiment of the present disclosure, a conversion agent-containing portion containing the wavelength conversion agent may be provided between the wavelength selective reflection layer and the light source substrate.

[0012] The conversion agent-containing portion is provided on at least one of the wavelength-selective reflection layer and the reflection layer.

[0013] In the surface light source device according to the embodiment of the present disclosure, the conversion agent-containing portion may be provided apart from both the wavelength-selective reflection layer and the reflection layer.

[0014] In a surface light source device according to one embodiment of the present disclosure, one or more of the thickness of the conversion agent-containing portion, the proportion of the area in which the conversion agent-containing portion is arranged, and the content proportion of the wavelength conversion agent contained in the conversion agent-containing portion may vary depending on the distance from the light source.

[0015] In a surface light source device according to an embodiment of the present disclosure, a conversion agent-containing portion containing the wavelength conversion agent is provided between the wavelength selective reflection layer and the light source substrate, The conversion agent-containing portion may constitute a part or the whole of an intermediate layer that maintains a constant distance between the wavelength selective reflection layer and the light source substrate.

[0016] In a surface light source device according to one embodiment of the present disclosure, the intermediate layer may include a first portion containing the wavelength conversion agent and a second portion containing the wavelength conversion agent at a content rate lower than that of the first portion or not containing the wavelength conversion agent.

[0017] In the surface light source device according to the embodiment of the present disclosure, the intermediate layer may include a light diffusing component.

[0018] In a surface light source device according to an embodiment of the present disclosure, the second portion comprises a light diffusing component; The second portion may be located at least partially between the first portion and the wavelength-selective reflective layer.

[0019] In the surface light source device according to the embodiment of the present disclosure, the intermediate layer may be bonded to at least one of the wavelength selective reflection layer and the light source substrate.

[0020] In the surface light source device according to the embodiment of the present disclosure, the intermediate layer may be in contact with a portion of the light source from which the primary light is emitted.

[0021] In the surface light source device according to the embodiment of the present disclosure, the light source may emit light having a wavelength of less than 380 nm.

[0022] In the surface light source device according to the embodiment of the present disclosure, the shortest wavelength of the secondary light may be 1.31 times or more as long as the wavelength of the primary light.

[0023] A surface light source device according to an embodiment of the present disclosure includes: The optical sheet may further include an optical sheet having a light-entering side surface facing the wavelength-selective reflecting layer and a light-exiting side surface as an uneven surface facing the light-entering side surface, The wavelength-selective reflective layer may be located between the optical sheet and the light source substrate.

[0024] A display device according to an embodiment of the present disclosure includes: Any one of the surface light source devices according to an embodiment of the present disclosure; The surface light source device includes a display panel overlapped with the surface light source device. Effect of the Invention

[0025] An object of the present invention is to achieve a thin surface light source device while achieving a sufficiently uniform in-plane distribution of brightness. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram for explaining an embodiment of the present invention, and is a perspective view showing a display device and a surface light source device. [Diagram 2] FIG. 2 is a vertical sectional view of the surface light source device of FIG. [Diagram 3]FIG. 3 is a plan view showing a light source substrate that can be included in the surface light source device of FIG. 2, and shows an example of an arrangement of a plurality of light sources. [Figure 4] FIG. 4 is a cross-sectional view showing a light source substrate that can be included in the surface light source device of FIG. 2, and shows an example of the configuration of the light source substrate. [Diagram 5] 5 is an enlarged cross-sectional view showing a converter-containing portion that can be included in the surface light source device of FIG. [Figure 6A] FIG. 6A is a cross-sectional view corresponding to FIG. 2, and is a view for explaining another example of the conversion-agent-containing portion. [Figure 6B] FIG. 6B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the conversion-agent-containing portion. [Figure 7A] FIG. 7A is a cross-sectional view corresponding to FIG. 2, and is a view illustrating still another example of the conversion-agent-containing portion. [Figure 7B] FIG. 7B is a cross-sectional view corresponding to FIG. 2, and is a view illustrating still another example of the conversion-agent-containing portion. [Figure 8] FIG. 8 is a plan view illustrating still another example of the conversion-agent-containing portion. [Figure 9] FIG. 9 is a cross-sectional view corresponding to FIG. 2, showing a surface light source device having the conversion agent-containing portion of FIG. [Figure 10A] FIG. 10A is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the conversion-agent-containing portion. [Figure 10B] FIG. 10B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the conversion-agent-containing portion. [Figure 11A] FIG. 11A is a cross-sectional view corresponding to FIG. 2, and is a view illustrating still another example of the conversion-agent-containing portion. [Figure 11B] FIG. 11B is a cross-sectional view corresponding to FIG. 2, and is a view illustrating still another example of the conversion-agent-containing portion. [Figure 12A] FIG. 12A is a cross-sectional view corresponding to FIG. 2, and is a view illustrating still another example of the conversion-agent-containing portion. [Figure 12B] FIG. 12B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the conversion-agent-containing portion. [Figure 13] FIG. 13 is a graph showing an example of optical characteristics of a wavelength-selective reflection layer that can be included in the surface light source device of FIG. 2, and is a graph illustrating the wavelength dependency of reflectance and transmittance. [Figure 14A] 14A is a cross-sectional view showing an example of an optical sheet that can be included in the surface light source device of FIG. [Figure 14B] 14B is a cross-sectional view showing another example of an optical sheet that can be included in the surface light source device of FIG. [Figure 15A] 15A is a plan view showing an example of a specific configuration of an optical sheet that can be included in the surface light source device of FIG. [Figure 15B] FIG. 15B is a perspective view showing a unit optical element of the optical sheet of FIG. 15A. [Figure 15C] 15C is a plan view showing another example of a specific configuration of an optical sheet that can be included in the surface light source device of FIG. [Figure 15D] 15D is a perspective view showing still another example of a specific configuration of an optical sheet that can be included in the surface light source device of FIG. [Figure 16] FIG. 16 is a vertical cross-sectional view showing the surface light source device, illustrating the operation of the surface light source device. [Figure 17] FIG. 17 is a vertical cross-sectional view showing an optical sheet, illustrating the function of the optical sheet. [Figure 18] FIG. 18 is a partially enlarged cross-sectional view showing the surface light source device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios are appropriately changed and exaggerated from those of the actual objects for the convenience of illustration and understanding. In addition, configurations shown in some drawings may be omitted in other drawings.

[0028] In this specification, terms that specify shapes or geometric conditions and their degrees, such as "parallel," "orthogonal," and "same," as well as values ​​of lengths and angles, are not limited to their strict meanings, but are interpreted to include a range within which similar functions can be expected.

[0029] In this specification, terms such as "sheet," "film," and "plate" are not distinguished from one another solely on the basis of differences in name. For example, an "optical sheet" cannot be distinguished from a member called an optical film or an optical plate solely on the basis of differences in name.

[0030] In this specification, the normal direction of a sheet-like (sheet-like, plate-like) member refers to the normal direction to the sheet surface of the target sheet-like (film-like, plate-like) member. Also, the "sheet surface (film surface, plate surface)" refers to the surface that coincides with the planar direction of the target sheet-like (film-like, plate-like) member when the target sheet-like (film-like, plate-like) member is viewed overall and globally.

[0031] In order to clarify the relationship between directions between the drawings, some drawings show the first direction D1, the second direction D2, and the third direction D3 as common directions by arrows with common symbols. The tip of the arrow is one side of each direction. An arrow pointing into the paper in a direction perpendicular to the paper surface of the drawing is shown by a symbol with a cross in a circle, as shown in Figure 2, for example. An arrow pointing out from the paper in a direction perpendicular to the paper surface of the drawing is shown by a symbol with a dot in a circle, as shown in Figure 3, for example.

[0032] 1 to 18 are diagrams for explaining an embodiment. FIG. 1 is a perspective view that shows a display device 10 as an application example of a surface light source device 20. The display device 10 may display, for example, a moving image, a still image, text information, or an image composed of a combination of these. The display device 10 may be used for various purposes, such as advertisements, presentations, television images, and display of various information, indoors or outdoors. The display device 10 may be used, for example, as a liquid crystal display device for vehicle mounting. The display device 10 shown in FIG. 1 has a surface light source device 20 having a light-emitting surface 20a, and a display panel 15 facing the light-emitting surface 20a.

[0033] FIG. 2 is a vertical cross-sectional view showing the surface light source device 20. The surface light source device 20 has a light source substrate 22, an optical member 30, and a wavelength conversion agent 38 as main components. The light source substrate 22 includes a light source 23. The optical member 30 includes a wavelength selective reflection layer 40. The light source substrate 22 and the optical member 30 face each other in a third direction D3. The wavelength conversion agent 38 is located between the light source substrate 22 and the wavelength selective reflection layer 40 in the third direction D3. The light source substrate 22, the optical member 30, and the wavelength selective reflection layer 40 are sheet-shaped. The light source substrate 22, the optical member 30, and the wavelength selective reflection layer 40 extend in a first direction D1 and a second direction D2. The first direction D1, the second direction D2, and the third direction D3 are perpendicular to each other. The surface light source device 20 and the display panel 15 are stacked in the third direction D3.

[0034] In the illustrated example, the optical member 30 includes a plurality of sheet-like members. The illustrated optical member 30 has an optical sheet 50 and a reflective polarizing plate 60 superimposed on the wavelength-selective reflecting layer 40 in the third direction D3. In the illustrated example, the reflective polarizing plate 60 forms the light-emitting surface 20a.

[0035] The surface light source device 20 described in this embodiment is designed to sufficiently uniform the in-plane distribution of brightness while making the surface light source device 20 thinner. More specifically, the surface light source device 20 is designed to eliminate unevenness in brightness caused by the presence of the light source 23. As a result, the illuminance at each position on the light-emitting surface 20a of the surface light source device 20, or the illuminance at each position on a virtual light-receiving surface parallel to the light-emitting surface 20a located near the light-emitting surface 20a, is uniformed. Note that the "illuminance of the light-emitting surface 20a" used in the following description means "illuminance on the light-emitting surface 20a" or "illuminance on a virtual light-receiving surface parallel to the light-emitting surface 20a located near the light-emitting surface 20a".

[0036] Hereinafter, a display device 10 and a surface light source device 20 according to an embodiment will be described with reference to a specific example shown in the drawings.

[0037] First, the display panel 15 of the display device 10 will be described. The display panel 15 has a display surface 15a on which an image is displayed. The display surface 15a faces the opposite side to the surface light source device 20 in the third direction D3, that is, toward the viewer. In the illustrated example, the display panel 15 has a rectangular shape when observed from the third direction D3.

[0038] In the illustrated example, the third direction D3 is parallel to the normal direction of the display surface 15a, the normal direction of the light-emitting surface 20a, the normal direction of the light source substrate 22, the normal direction of the wavelength-selective reflecting layer 40, the normal direction of the optical sheet 50, and the normal direction of the reflective polarizing plate 60. The third direction D3 is also referred to as the front direction.

[0039] The display panel 15 is configured as, for example, a transmissive liquid crystal display panel. The display panel 15 forms an image on the display surface 15a by adjusting the transmittance of the display panel 15 for each pixel. The display panel 15 includes a liquid crystal layer having a liquid crystal material. The light transmittance of the display panel 15 changes according to the strength of the electric field applied to the liquid crystal layer.

[0040] As an example of such a display panel 15, a liquid crystal display panel having a pair of polarizing plates and a liquid crystal cell (liquid crystal layer) arranged between the pair of polarizing plates may be used. The polarizing plate separates incident light into two orthogonal polarized components, transmits the polarized component in one direction, and absorbs the polarized component in the other direction orthogonal to the one direction. The liquid crystal cell has a pair of support plates and liquid crystal arranged between the pair of support plates. The liquid crystal cell is designed so that an electric field can be applied to each region forming one pixel. The orientation of the liquid crystal changes when an electric field is applied. As an example, a polarized component in a specific direction rotates its polarization direction by 90° when passing through a liquid crystal cell to which an electric field is not applied. The polarized component in a specific direction maintains its polarization direction when passing through a liquid crystal cell to which an electric field is applied. This allows the transmission and light blocking of a pair of polarizing plates arranged on both sides of the liquid crystal cell to be controlled depending on whether or not an electric field is applied to the liquid crystal cell.

[0041] Next, the surface light source device 20 will be described. The surface light source device 20 has a light-emitting surface 20a that emits planar light. The surface light source device 20 includes a light source substrate 22 having light sources 23, and an optical member 30 that is overlapped with the light source substrate 22 in the third direction D3. The light sources 23 of the light source substrate 22 are provided in an area that overlaps with the light-emitting surface 20a when projected in the third direction D3. The surface light source device 20 is configured as a so-called direct-type backlight.

[0042] The light source substrate 22 includes a light source 23 and a support substrate 25. In the illustrated example, the light source substrate 22 has a rectangular shape when viewed from the third direction D3.

[0043] The light source 23 has a light-emitting element that emits light. As the light-emitting element, a light-emitting diode, denoted as LED, may be used. The size of the light-emitting diode is not particularly limited. From the viewpoint of making the image of the light source 23 less noticeable, a small light-emitting diode, for example, a mini LED or a micro LED, may be used. Specifically, the length WL1, WL2 of one side of the light source 23 having a rectangular shape when observed from the third direction D3 shown in FIG. 3 may be 0.5 mm or less, or 0.2 mm or less.

[0044] The emission wavelength of the light source 23 may be appropriately selected depending on the application of the surface light source device 20. The light emitted by the light source 23 is absorbed by the wavelength conversion agent 38 as primary light. Therefore, the emission wavelength of the light source 23 may be appropriately selected depending on the optical characteristics of the wavelength conversion agent 38. In the illustrated example, the light source 23 may emit invisible light. Invisible light is light other than visible light. Visible light is light having a wavelength of 380 nm or more and 780 nm or less. The light source 23 may emit ultraviolet light. The wavelength of the light from the light source 23 may be less than 380 nm, 360 nm or less, 350 nm or less, or 340 nm or less.

[0045] As one example, the light source 23 may be composed of only a light emitting element. As another example, the light source 23 may include, in addition to the light emitting element, optical elements such as a cover and a lens that adjust the light distribution from the light emitting element.

[0046] The light distribution characteristic of the light source 23 is not particularly limited. Typically, a Lambertian light distribution can be adopted as the light distribution characteristic of the light source 23. On the other hand, in the emission luminous intensity distribution of the light source 23 whose optical axis is aligned with the third direction D3, a peak luminous intensity may be obtained in a direction other than the third direction D3. For example, the bud wing light distribution disclosed in Patent Document 1 (JP6299811B) may be used as the light distribution characteristic of the light source 23.

[0047] As in the illustrated surface light source device 20, the light source substrate 22 may include a plurality of light sources 23. The number of light sources 23 is appropriately selected depending on the application of the surface light source device 20, the area of ​​the light-emitting surface 20a, and the like. In order to eliminate unevenness in brightness caused by the arrangement of the light sources 23, the plurality of light sources 23 included in the surface light source device 20 may be regularly arranged on a surface perpendicular to the third direction D3. As an example of a regular arrangement of the light sources 23, a honeycomb arrangement or a square arrangement may be adopted. In the honeycomb arrangement, the light sources 23 may be arranged at a constant pitch in each of three directions inclined at 60° to each other. In the square arrangement, the light sources 23 may be arranged at a constant pitch in each of two directions perpendicular to each other.

[0048] In the example shown in Fig. 3, the light sources 23 are arranged at a constant pitch in each of a first direction D1 and a second direction D2 perpendicular to each other. In the example shown in the figure, the arrangement pitch PL1 in the first direction D1 and the arrangement pitch PL2 of the light sources 23 in the second direction D2 are the same. In the example shown in Fig. 2, the arrangement pitch PL1 and the arrangement pitch PL2 may be different. In the example shown in the figure, the first direction D1 and the second direction D2 are parallel to the side edges of the rectangular surface light source device 20 and the optical member 30, respectively. The arrangement pitch PL1 and the arrangement pitch PL2 may each be 0.2 mm or more and 10 mm or less.

[0049] Next, the support substrate 25 constituting the light source substrate 22 together with the multiple light sources 23 will be described. The support substrate 25 supports the multiple light sources 23 from the side opposite to the optical member 30 in the third direction D3. The support substrate 25 is sheet-shaped. The support substrate 25 includes a circuit that supplies power to the light sources 23. The support substrate 25 has light reflectivity that reflects light toward the optical member 30.

[0050] The support substrate 25 shown in FIG. 4 has a sheet-shaped substrate body 26, and a reflective layer 27 and wiring 29 provided on the substrate body 26. The substrate body 26 spreads in a direction perpendicular to the third direction D3. The substrate body 26 may have insulating properties. The substrate body 26 may be a spreading resin film, for example, a polyethylene terephthalate film. The wiring 29 is electrically connected to the light source 23. The wiring 29 is electrically connected to a terminal (not shown) of the light source 23 via solder or the like. When the substrate body 26 and the reflective layer 27 have insulating properties, the wiring 29 may be located between the substrate body 26 and the reflective layer 27 as shown in FIG. 4.

[0051] The reflective layer 27 is laminated on the substrate body 26 from the wavelength selective reflective layer 40 side in the third direction D3. The reflective layer 27 covers the area on the substrate body 26 where the light source 23 is not arranged. The reflective layer 27 is reflective to light of a specific wavelength emitted by the light source 23 or to light used for emission in the surface light source device 20. The reflectivity of the reflective layer 27 may be regular reflection, also called specular reflection, diffuse reflection, or anisotropic diffuse reflection. The reflective layer 27 can be imparted with diffuse reflectivity by forming the reflective layer 27 from a white reflective layer containing white particles such as silicon dioxide. From the viewpoint of uniforming the in-plane distribution of the illuminance of the light emitting surface 20a in combination with other configurations of the surface light source device 20, it is preferable that the gloss of the reflective surface of the reflective layer 27 is 70 or more. The gloss here is a value measured using a gloss meter (VG7000) manufactured by Nippon Denshoku Kogyo Co., Ltd. at an incident angle of 20° in accordance with JISZ8741. The reflective layer 27 may be a metal layer laminated on the substrate body 26, or may be a reflective diffractive optical element.

[0052] The wavelength conversion agent 38 absorbs the primary light LA ​​and emits secondary light LB having a wavelength different from that of the primary light LA. The light source 23 emits at least the primary light LA. The reflectance of the primary light LA ​​at a wavelength selective reflection layer 40 described later is higher than the reflectance of the secondary light LB at the wavelength selective reflection layer 40. Quantum dots or phosphors may be used as the wavelength conversion agent 38.

[0053] A quantum dot is a nanometer-sized semiconductor particle. A quantum dot may be composed of one type of semiconductor compound. A quantum dot may be composed of two or more types of semiconductor compounds. A quantum dot may have a core-shell structure having, for example, a core made of a semiconductor compound and a shell made of a semiconductor compound different from the core.

[0054] Examples of the material of the core of the quantum dot include II-VI group semiconductor compounds such as MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe and HgTe. Examples of the material of the core of the quantum dot include III-V group semiconductor compounds such as AlN, AlP, AlAs, AlSb, GaAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, TiP, TiAs and TiSb. Examples of the material of the core of the quantum dot include semiconductor compounds such as IV group semiconductors such as Si, Ge and Pb, or semiconductor crystals containing semiconductors.

[0055] When using core-shell quantum dots, a material having a higher band gap than the semiconductor compound forming the core may be used as the semiconductor constituting the shell. In this case, excitons are confined in the core, and the luminous efficiency of the quantum dots can be improved. Examples of core-shell structures (core / shell) having such a band gap relationship include CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, InGaP / ZnSSe, etc.

[0056] The size of the quantum dots is adjusted in consideration of the desired wavelength of the secondary light LB. As the particle diameter of the quantum dots becomes smaller, the energy band gap becomes larger. As the crystal size becomes smaller, the emission of the quantum dots shifts to the blue side, that is, to the high energy side. The wavelength of the secondary light LB can be adjusted by changing the size of the quantum dots. The average particle diameter of the quantum dots may be 20 nm or less, 0.5 nm or more to 20 nm or less, or 1 nm or more to 10 nm or less. The shape, dispersion state, etc. of the quantum dots are identified by a transmission electron microscope (TEM). The crystal structure and particle diameter of the quantum dots are identified by X-ray crystal diffraction (XRD).

[0057] The surface light source device 20 may include a plurality of quantum dots with different emission wavelengths as the wavelength conversion agent 38. By adjusting the content of each quantum dot, the color of the light emitted from the surface light source device 20 can be adjusted. In the example shown in FIG. 5, the wavelength conversion agent 38 includes a first wavelength conversion agent 38A, a second wavelength conversion agent 38B, and a third wavelength conversion agent 38C. The first wavelength conversion agent 38A, the second wavelength conversion agent 38B, and the third wavelength conversion agent 38C have sizes different from each other. The first wavelength conversion agent 38A, the second wavelength conversion agent 38B, and the third wavelength conversion agent 38C emit light of different wavelengths from each other.

[0058] The first wavelength conversion agent 38A may absorb the primary light LA ​​from the light source 23 and emit blue light having a wavelength of 430 nm or more and 500 nm or less. The second wavelength conversion agent 38B may absorb the primary light LA ​​from the light source 23 and emit green light having a wavelength of 500 nm or more and 600 nm or less. The third wavelength conversion agent 38C may absorb the primary light LA ​​from the light source 23 and emit red light having a wavelength of 600 nm or more and 750 nm or less. According to this example, the surface light source device 20 can emit white light by adjusting the contents of the first wavelength conversion agent 38A, the second wavelength conversion agent 38B, and the third wavelength conversion agent 38C.

[0059] The wavelength conversion agent 38 may be installed in the surface light source device 20 in a state where it is contained in the conversion agent-containing portion 35. The conversion agent-containing portion 35 shown in FIG. 5 has the wavelength conversion agent 38 and a base material portion 36 that holds the wavelength conversion agent 38. The conversion agent-containing portion 35 allows the wavelength conversion agent 38 to be stably held at a predetermined position in the surface light source device 20. The wavelength conversion agent 38 is surrounded by the base material portion 36, so that deterioration of the wavelength conversion agent 38 can be prevented. A resin may be used as the base material portion 36. Examples of resins that constitute the base material portion 36 include thermoplastic resins, cured products of thermosetting resin compositions, and cured products of ionizing radiation curable resin compositions. The conversion agent-containing portion 35 may have various configurations.

[0060] As an example, the conversion agent-containing portion 35 shown in FIG. 2 is located between the support substrate 25 and the wavelength selective reflection layer 40 in the third direction D3. The conversion agent-containing portion 35 shown in FIG. 2 is sheet-shaped. The conversion agent-containing portion 35 shown in FIG. 2 extends in both the first direction D1 and the second direction D2. In the example shown in FIG. 2, the conversion agent-containing portion 35 is separated from the wavelength selective reflection layer 40 and the support substrate 25. The conversion agent-containing portion 35 shown in FIG. 2 can be produced, for example, by applying a resin composition having flowability including a wavelength conversion agent 38 to form a coating film and drying the coating film.

[0061] The conversion agent-containing portion 35 shown in FIG. 6A and FIG. 6B is located between the support substrate 25 and the wavelength selective reflection layer 40 in the third direction D3. The conversion agent-containing portion 35 shown in FIG. 6A and FIG. 6B is sheet-shaped. The conversion agent-containing portion 35 shown in FIG. 6A and FIG. 6B spreads in both the first direction D1 and the second direction D2. In the example shown in FIG. 6A, the conversion agent-containing portion 35 contacts the wavelength selective reflection layer 40. The conversion agent-containing portion 35 shown in FIG. 6A may be bonded to the wavelength selective reflection layer 40. In the example shown in FIG. 6B, the conversion agent-containing portion 35 contacts the reflection layer 27 of the support substrate 25. The conversion agent-containing portion 35 shown in FIG. 6B may be bonded to the reflection layer 27. By bonding the wavelength selective reflection layer 40 to another member, the arrangement of the wavelength selective reflection layer 40 is stabilized. In the example shown in Figures 6A and 6B, the conversion agent-containing portion 35 can be fabricated on the wavelength-selective reflecting layer 40 or on the reflecting layer 27, for example by printing.

[0062] 7A and 7B, the surface light source device 20 has an intermediate layer 32 in contact with both the wavelength selective reflecting layer 40 and the third direction D3 of the support substrate 25. The intermediate layer 32 may be bonded to both or either of the wavelength selective reflecting layer 40 and the support substrate 25. According to this example, the relative positions of the support substrate 25 and the wavelength selective reflecting layer 40 can be stably aligned, and further, the support substrate 25 and the wavelength selective reflecting layer 40 can be maintained in an appropriate relative position.

[0063] In the example shown in FIG. 7A, the intermediate layer 32 is a single layer constituted by the conversion agent-containing portion 35. On the other hand, in the example shown in FIG. 7B, the intermediate layer 32 has a first portion 33A and a second portion 33B. The first portion 33A and the second portion 33B are overlapped in the third direction D3. In the example shown in FIG. 7B, the first portion 33A is disposed between two second portions 33B in the third direction D3. In the example shown in FIG. 7B, the first portion 33A is constituted by the conversion agent-containing portion 35. In the example shown in FIG. 7B, the second portion 33B may not contain the wavelength conversion agent 38. The second portion 33B that does not contain the wavelength conversion agent 38 may be constituted as a transparent resin layer. The second portion 33B may contain a light diffusing component. Examples of the light diffusing component include a metal compound, a porous substance containing a gas, resin beads that hold a metal compound around it, white fine particles, and even simple air bubbles.

[0064] As used herein, "transparent" means that the visible light transmittance is 50% or more, and preferably 80% or more. The visible light transmittance is specified as the average value of the total light transmittance at each wavelength when measured at an incident angle of 0° at every 1 nm in the measurement wavelength range of 380 nm to 780 nm using a spectrophotometer (Shimadzu Corporation's "UV-3100PC", compliant with JIS K 0115).

[0065] 7B, the second portion 33B may contain the wavelength conversion agent 38 at a content ratio different from that of the first portion 33A. The second portion 33B may contain the wavelength conversion agent 38 having a size different from that of the first portion 33A. The first portion 33A may be disposed adjacent to the wavelength-selective reflecting layer 40. The first portion 33A may be provided adjacent to the reflective layer 27.

[0066] As will be described in detail later, in this embodiment, the illuminance of the light-emitting surface 20a is high in the vicinity of the area where a large amount of the wavelength conversion agent 38 is present in combination with the wavelength-selective reflection layer 40. The illuminance of the light-emitting surface 20a is low in the vicinity of the area where only a small amount of the wavelength conversion agent 38 is present or where no wavelength conversion agent 38 is present. On the other hand, as a general tendency of the direct-type surface light source device 20, the illuminance of the light-emitting surface 20a is high directly above the light source 23 and low above the middle between two adjacent light sources 23. In consideration of such a tendency, the arrangement of the wavelength conversion agent 38 may be adjusted to make the illuminance distribution of the light-emitting surface 20a uniform. An example in which the wavelength conversion agent 38 is arranged with a distribution will be described with reference to specific examples shown in Figs. 8 to 11B.

[0067] FIG. 8 shows a portion of the support substrate 25 and the optical member 30. The portion shown in FIG. 8 is the portion closest to a certain light source 23. In this portion, the volume of the wavelength conversion agent 38 contained in a certain region may be larger than the volume of the wavelength conversion agent 38 contained in another region closer to the certain light source 23 than the certain region. A region overlapping the region 35A having a certain area of ​​the wavelength selective reflection layer 40 in the third direction D3 is defined as a reference volume region 35V. The volume of the wavelength conversion agent 38 contained in one reference volume region 35V may be larger than the volume of the wavelength conversion agent 38 contained in another reference volume region 35V located between the one reference volume region 35V and one light source 23 closest to the one reference volume region 35V.

[0068] 8, the volume of the wavelength conversion agent 38 included in the reference volume region 35V may increase with increasing distance from one light source 23. The volume of the wavelength conversion agent 38 included in any one reference volume region 35V may be equal to or greater than the volume of the wavelength conversion agent 38 included in any other reference volume region 35V located between the one reference volume region 35V and one light source 23.

[0069] When the surface light source device 20 contains multiple types of wavelength conversion agents 38, it is preferable that each type of wavelength conversion agent 38 satisfies the above condition. In the example shown in Fig. 5 in which first to third wavelength conversion agents 38A to 38C are included, each of the first to third wavelength conversion agents 38A to 38C may be distributed as described above.

[0070] That is, the volume of the first wavelength conversion agent 38A contained in one reference volume region 35V may be larger than the volume of the first wavelength conversion agent 38A contained in another reference volume region 35V located between the one reference volume region 35V and one light source 23 closest to the one reference volume region 35V. The volume of the first wavelength conversion agent 38A contained in any one reference volume region 35V may be equal to or larger than the volume of the first wavelength conversion agent 38A contained in any other reference volume region 35V located between the one reference volume region 35V and one light source 23.

[0071] The volume of the second wavelength conversion agent 38B contained in one reference volume region 35V may be larger than the volume of the second wavelength conversion agent 38B contained in another reference volume region 35V located between the one reference volume region 35V and one light source 23 closest to the one reference volume region 35V. The volume of the second wavelength conversion agent 38B contained in any one reference volume region 35V may be equal to or larger than the volume of the second wavelength conversion agent 38B contained in any other reference volume region 35V located between the one reference volume region 35V and one light source 23.

[0072] The volume of the third wavelength conversion agent 38C included in one reference volume region 35V may be larger than the volume of the third wavelength conversion agent 38C included in another reference volume region 35V located between the one reference volume region 35V and one light source 23 closest to the one reference volume region 35V. The volume of the third wavelength conversion agent 38C included in any one reference volume region 35V may be equal to or larger than the volume of the third wavelength conversion agent 38C included in any other reference volume region 35V located between the one reference volume region 35V and one light source 23.

[0073] The change in the volume of the wavelength conversion agent 38 contained in the reference volume region 35V according to the distance from the light source 23 may change stepwise, as in the examples shown in Figures 8 and 9. The change in the amount of the wavelength conversion agent 38 according to the distance from the light source 23 may change continuously, as in the example shown in Figure 10B, which will be described in detail later.

[0074] The area 35A of a certain area used to specify the reference volume region 35V is assumed to be a square of 5 mm on each side, and the area of ​​the area 35A is set to 25 mm 2 When the emission wavelengths of the wavelength conversion agents 38 are uniform, the particle sizes of the wavelength conversion agents 38 are also approximately uniform. In this case, the comparison of the volumes of the wavelength conversion agents 38 contained in the reference volume region 35V may be confirmed by comparing the quantities of the wavelength conversion agents 38 contained in the reference volume region 35V. The quantity of the wavelength conversion agents 38 can be measured using a transmission electron microscope.

[0075] The change in the volume of the wavelength conversion agent 38 contained in the reference volume region 35V can be adjusted by the thickness of the conversion agent-containing portion 35, the proportion of the area in which the conversion agent-containing portion 35 is arranged, and the content of the wavelength conversion agent 38 contained in the conversion agent-containing portion 35, etc.

[0076] The ratio of the area where the conversion agent-containing portion 35 is arranged means the ratio of the area where the conversion agent-containing portion 35 is provided to a region having a certain area of ​​the surface where the conversion agent-containing portion 35 is provided. 2 ) relative to the area (mm 2 ) where the ratio is a constant area (mm 2 ) is assumed to be a square with a side length of 5 mm, and the area is set to 25 mm 2 It is also possible to use the following.

[0077] The content ratio is a constant volume (mm 3 The volume (mm 3) is a percentage (%). The volume of the wavelength conversion agent 38 contained in the conversion agent-containing portion 35 is obtained by multiplying the volume of one wavelength conversion agent 38 by the quantity measured using a transmission electron microscope. The volume of one wavelength conversion agent 38 is determined using the particle size measured by the above-mentioned method, assuming that the wavelength conversion agent 38 has a spherical shape.

[0078] In the example shown in FIG. 8 and FIG. 9, the surface light source device 20 has an intermediate layer 32 in contact with the support substrate 25 and the wavelength selective reflection layer 40. The intermediate layer 32 is divided into a plurality of parts according to the distance from the nearest light source 23 along the direction perpendicular to the third direction D3. The intermediate layer 32 includes a first part 33A, a second part 33B, and a third part 33C. The first part 33A is the furthest from the light source 23. The third part 33C is the closest to the light source 23. When observed from the third direction D3 shown in FIG. 8, the third part 33C surrounds the light source 23. When observed from the third direction D3 shown in FIG. 8, the second part 33B surrounds the third part 33C. The second part 33B is located between the first part 33A and the third part 33C in the direction perpendicular to the third direction D3.

[0079] In the example shown in FIG. 8 and FIG. 9, the content (%) of the wavelength conversion agent 38 in the first portion 33A is greater than the content (%) of the wavelength conversion agent 38 in the second portion 33B. The content (%) of the wavelength conversion agent 38 in the second portion 33B is greater than the content (%) of the wavelength conversion agent 38 in the third portion 33C. In this example, the first portion 33A and the second portion 33B are composed of the conversion agent-containing portion 35. The third portion 33C may be composed of the conversion agent-containing portion 35 or may be composed of a transparent resin that does not contain the wavelength conversion agent 38. The third portion 33C may contain a light diffusing component. Examples of the light diffusing component include a metal compound, a porous substance containing a gas, resin beads that hold a metal compound around it, white fine particles, and even simple air bubbles.

[0080] In the examples shown in FIG. 10A and FIG. 10B, the ratio (%) of the area where the conversion agent-containing portion 35 is arranged varies depending on the distance from the light source 23. In the examples shown in FIG. 10A and FIG. 10B, the content ratio of the wavelength conversion agent 38 in the conversion agent-containing portion 35 is constant. In each example shown in FIG. 10A and FIG. 10B, the thickness of the conversion agent-containing portion 35 in the third direction D3 is constant. In the example shown in FIG. 10A, the conversion agent-containing portion 35 is provided on the surface of the wavelength selective reflection layer 40 facing the support substrate 25. That is, it is provided on the light incident side surface 40a of the wavelength selective reflection layer 40. The ratio of the area where the conversion agent-containing portion 35 is provided in a region having a constant area of ​​the light incident side surface 40a increases as it moves away from the nearest light source 23. In the example shown in FIG. 10B, the conversion agent-containing portion 35 is provided on the reflective layer 27 of the support substrate 25. The ratio of the area where the conversion agent-containing portions 35 are provided in a region having a certain area of ​​the reflective layer 27 increases with increasing distance from the light source 23. In the example shown in Fig. 10A and Fig. 10B, the conversion agent-containing portions 35 may be in the form of dots. The dot-shaped conversion agent-containing portions 35 may be formed on the wavelength-selective reflection layer 40 or the reflective layer 27 by printing. The change in the ratio (%) of the area where the conversion agent-containing portions 35 are provided may be continuous or stepwise.

[0081] In the example shown in FIG. 11A and FIG. 11B, the thickness T (mm) of the conversion agent-containing portion 35 in the third direction D3 changes depending on the distance from the light source 23. In the example shown in FIG. 11A and FIG. 11B, the content ratio of the wavelength conversion agent 38 in the conversion agent-containing portion 35 is constant. In the example shown in FIG. 11A, the conversion agent-containing portion 35 is provided on the light-entering side surface 40a of the wavelength-selective reflection layer 40. In this example, the conversion agent-containing portion 35 is provided in an area of ​​the light-entering side surface 40a excluding an area directly above the light source 23 and an area surrounding the light source 23. In the example shown in FIG. 11B, the conversion agent-containing portion 35 is provided on the reflection layer 27. In this example, the conversion agent-containing portion 35 is provided in an area of ​​the reflection layer 27 excluding an area surrounding the light source 23. In the example shown in FIG. 11A and FIG. 11B, the thickness T (mm) of the conversion agent-containing portion 35 in the third direction D3 increases with increasing distance from the nearest light source 23. The change in thickness T (mm) of the conversion-agent-containing portion 35 in the third direction D3 may be continuous as in the illustrated example, or may be stepwise.

[0082] In the examples shown in Figs. 10A to 11B, an intermediate layer 32 in contact with the support substrate 25 and the wavelength selective reflection layer 40 may be provided. Fig. 12A shows an example in which an intermediate layer 32 is provided in the surface light source device 20 of Fig. 11A. Fig. 12B shows an example in which an intermediate layer 32 is provided in the surface light source device 20 of Fig. 11B. In such a modified example, the intermediate layer 32 may include a first portion 33A and a second portion 33B, and the first portion 33A may be constituted by the conversion agent-containing portion 35 shown in Figs. 10A to 11B. The second portion 33B may contain the wavelength conversion agent 38 at a content rate lower than that of the first portion 33A, or may not contain the wavelength conversion agent 38. In these examples, as in the examples shown in Figs. 10A to 11B, the volume of the wavelength conversion agent 38 in the reference volume region 35V increases with increasing distance from the nearest light source 23.

[0083] 2 includes, in this order from the support substrate 25 side in the third direction D3, a wavelength-selective reflecting layer 40, an optical sheet 50, and a reflective polarizing plate 60. The wavelength-selective reflecting layer 40, the optical sheet 50, and the reflective polarizing plate 60 may be bonded to each other, may simply be in contact with each other and not bonded, or may be spaced apart from each other.

[0084] The wavelength-selective reflecting layer 40 is a reflecting layer having wavelength selectivity. The reflectance of the wavelength-selective reflecting layer 40 changes depending on the wavelength of the incident light. The transmittance (%) of the wavelength-selective reflecting layer 40 changes depending on the wavelength of the incident light. The wavelength-selective reflecting layer 40 in this embodiment is used together with the above-mentioned wavelength conversion agent 38. The wavelength conversion agent 38 absorbs the primary light LA ​​from the light source 23 and emits secondary light LB of a different wavelength. The reflectance of the secondary light LB at the wavelength-selective reflecting layer 40 is smaller than the reflectance of the primary light LA ​​at the wavelength-selective reflecting layer 40. The transmittance of the secondary light LB at the wavelength-selective reflecting layer 40 is larger than the transmittance of the primary light LA ​​at the wavelength-selective reflecting layer 40.

[0085] The reflectance and transmittance of the wavelength selective reflection layer 40 are values ​​measured using a spectrophotometer (Shimadzu Corporation's "UV-3100PC", compliant with JIS K 0115).

[0086] Fig. 13 is a graph showing an example of the reflection and transmission characteristics of the wavelength-selective reflecting layer 40 according to the wavelength. In the graph shown in Fig. 13, the vertical axis indicates reflectance (%) and transmittance (%). In the graph shown in Fig. 13, the horizontal axis indicates the wavelength (nm) of incident light. In the example shown in Fig. 13, the reflectance of visible light in the wavelength-selective reflecting layer 40 may be smaller than the reflectance of invisible light in the wavelength-selective reflecting layer 40.

[0087] 13 are characteristics for light that travels in the normal direction of the wavelength selective reflecting layer 40 and is incident on the wavelength selective reflecting layer 40. Furthermore, in the present specification, unless there is any explanation of the incident direction of the incident light, the reflectance and transmittance of the wavelength selective reflecting layer 40 refer to the characteristics for light that travels in the normal direction of the wavelength selective reflecting layer 40 and is incident on the wavelength selective reflecting layer 40.

[0088] The reflectance of the wavelength selective reflecting layer 40 to light with a wavelength of less than 360 nm, or the reflectance of the wavelength selective reflecting layer 40 to light with a wavelength of 300 nm or more and less than 360 nm, may be 30% or more, 50% or more, 80% or more, or 90% or more. The reflectance of the wavelength selective reflecting layer 40 to light with a wavelength of less than 340 nm, or the reflectance of the wavelength selective reflecting layer 40 to light with a wavelength of 300 nm or more and less than 340 nm, may be 50% or more, 80% or more, 90% or more, or 95% or more. The reflectance of the wavelength selective reflecting layer 40 to light with a central wavelength of the primary light LA ​​emitted by the light source 23 may be 90% or more, 93% or more, 95% or more, or 98% or more.

[0089] The reflectance of the wavelength selective reflecting layer 40 for light having a wavelength of 380 nm or more and 780 nm or less may be less than 70%, less than 50%, less than 20%, or less than 10%. The reflectance of the wavelength selective reflecting layer 40 for light having a wavelength of 420 nm or more and 700 nm or less may be less than 50%, less than 20%, less than 10%, or less than 5%. The reflectance of the wavelength selective reflecting layer 40 for light having a central wavelength of the secondary light LB emitted from the wavelength conversion agent 38 may be 50% or less, 20% or less, 10% or less, or 5% or less.

[0090] When a plurality of types of wavelength conversion agents 38 are provided in the surface light source device 20, the reflectance of the wavelength selective reflection layer 40 for the light of the central wavelength of the secondary light LB emitted from each type of wavelength conversion agent 38 may be 50% or less, 20% or less, 10% or less, or 5% or less. In the example shown in FIG. 5, the reflectance of the wavelength selective reflection layer 40 for the light of the central wavelength of the first secondary light LB1 emitted from the first wavelength conversion agent 38A may be 50% or less, 20% or less, 10% or less, or 5% or less. The reflectance of the wavelength selective reflection layer 40 for the light of the central wavelength of the second secondary light LB2 emitted from the second wavelength conversion agent 38B may be 50% or less, 20% or less, 10% or less, or 5% or less. The reflectance at the wavelength selective reflecting layer 40 for light of the central wavelength of the third secondary light LB3 emitted from the third wavelength conversion agent 38C may be 50% or less, 20% or less, 10% or less, or 5% or less.

[0091] The transmittance of the wavelength selective reflecting layer 40 for light with a wavelength of less than 360 nm, or the transmittance of the wavelength selective reflecting layer 40 for light with a wavelength of 300 nm or more and less than 360 nm, may be less than 70%, less than 50%, less than 20%, or less than 10%. The transmittance of the wavelength selective reflecting layer 40 for light with a wavelength of less than 340 nm, or the transmittance of the wavelength selective reflecting layer 40 for light with a wavelength of 300 nm or more and less than 340 nm, may be less than 50%, less than 20%, less than 10%, or less than 5%. The transmittance of the wavelength selective reflecting layer 40 for light with a central wavelength of the primary light LA ​​emitted by the light source 23 may be less than 10%, less than 8%, less than 5%, or less than 2%.

[0092] The transmittance of the wavelength selective reflecting layer 40 for light having a wavelength of 380 nm or more and 780 nm or less may be greater than 30%, greater than 50%, greater than 80%, or greater than 90%. The transmittance of the wavelength selective reflecting layer 40 for light having a wavelength of 420 nm or more and 700 nm or less may be greater than 50%, greater than 80%, greater than 90%, or greater than 95%. The transmittance of the wavelength selective reflecting layer 40 for light having a central wavelength of the secondary light LB emitted from the wavelength conversion agent 38 may be greater than 50%, greater than 80%, greater than 90%, or greater than 95%.

[0093] When a plurality of types of wavelength conversion agents 38 are provided in the surface light source device 20, the transmittance of the wavelength selective reflection layer 40 for the light of the central wavelength of the secondary light LB emitted from each type of wavelength conversion agent 38 may be greater than 50%, greater than 80%, greater than 90%, or greater than 95%. In the example shown in FIG. 5, the transmittance of the wavelength selective reflection layer 40 for the light of the central wavelength of the first secondary light LB1 emitted from the first wavelength conversion agent 38A may be greater than 50%, greater than 80%, greater than 90%, or greater than 95%. The transmittance of the wavelength selective reflection layer 40 for the light of the central wavelength of the second secondary light LB2 emitted from the second wavelength conversion agent 38B may be greater than 50%, greater than 80%, greater than 90%, or greater than 95%. The transmittance in the wavelength selective reflecting layer 40 for light of the central wavelength of the third secondary light LB3 emitted from the third wavelength conversion agent 38C may be greater than 50%, greater than 80%, greater than 90%, or greater than 95%.

[0094] The wavelength-selective reflective layer 40 is not particularly limited as long as it has wavelength dependency of reflectance and transmittance. As a specific example, a dielectric multilayer film having high design freedom of reflection characteristics and transmission characteristics may be used as the wavelength-selective reflective layer 40.

[0095] A multilayer film of an inorganic compound in which inorganic layers having different refractive indexes are alternately laminated may be used as the dielectric multilayer film constituting the wavelength-selective reflecting layer 40. As another example, a resin multilayer film in which resin layers having different refractive indexes are alternately laminated may be used as the wavelength-selective reflecting layer 40.

[0096] The dielectric multilayer film as the multilayer film of inorganic compounds is obtained by alternately laminating high refractive index inorganic layers and low refractive index inorganic layers by, for example, a CVD method, a sputtering method, a vacuum deposition method, or a wet coating method. The thickness of the multilayer film of inorganic compounds may be 0.5 μm or more and 10 μm or less. The refractive index of the inorganic compound contained in the high refractive index inorganic layer may be 1.7 or more and 2.5 or less. Examples of the inorganic compound contained in the high refractive index inorganic layer include those mainly composed of titanium oxide, zirconium oxide, tantalum pentoxide, niobium pentoxide, lanthanum oxide, yttrium oxide, zinc oxide, zinc sulfide, and indium oxide, and those containing small amounts of titanium oxide, tin oxide, cerium oxide, and the like. The refractive index of the inorganic compound contained in the low refractive index inorganic layer may be 1.2 or more and 1.6 or less. Examples of the inorganic compound contained in the low refractive index inorganic layer include silica, alumina, lanthanum fluoride, magnesium fluoride, and sodium aluminum hexafluoride.

[0097] The dielectric multilayer film as a resin multilayer film contains many layers of, for example, thermoplastic resin or thermosetting resin. The resin layers may contain various additives, such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducing agents, heat stabilizers, lubricants, infrared absorbing agents, ultraviolet absorbing agents, and doping agents for adjusting the refractive index.

[0098] Among the resin layers having different refractive indices, the difference in the in-plane average refractive index between the high refractive index resin layer and the low refractive index resin layer may be 0.03 or more, 0.05 or more, or 0.1 or more.

[0099] The number of high-refractive index resin layers and low-refractive index resin layers stacked is adjusted according to the reflection characteristics and transmission characteristics required for the wavelength-selective reflection layer 40. For example, the high-refractive index resin layers and low-refractive index resin layers can be stacked alternately in 30 layers or more, or 200 layers or more. The total number of high-refractive index resin layers and low-refractive index resin layers stacked can be, for example, 600 layers or more. If the number of layers is too small, sufficient reflectance may not be obtained. Also, by having the number of layers in the above range, the desired reflectance can be easily obtained.

[0100] The resin multilayer film constituting the dielectric multilayer film may have a surface layer containing polyethylene terephthalate or polyethylene naphthalate with a thickness of 3 μm or more on at least one side. The resin multilayer film constituting the dielectric multilayer film may have the above surface layer on both sides. The thickness of the surface layer may be 5 μm or more.

[0101] Examples of methods for producing the resin multilayer film constituting the dielectric multilayer film include co-extrusion, etc. Specifically, reference can be made to the method for producing a laminated film described in JP-A-2008-200861.

[0102] The optical sheet 50 is laminated on the wavelength selective reflecting layer 40 from the side opposite to the light source 23 in the third direction D3. The optical sheet 50 is installed in order to achieve various functions. The optical sheet 50 shown in Figs. 14A and 14B adjusts the optical path of light transmitted through the wavelength selective reflecting layer 40. The illustrated optical sheet 50 can adjust the luminance angular distribution on the light emitting surface 20a of the surface light source device 20.

[0103] In the example shown in FIG. 14A and FIG. 14B, the optical sheet 50 has a light-entering side surface 50a and a light-exiting side surface 50b. Of these, the light-entering side surface 50a is a flat surface. The light-exiting side surface 50b is an uneven surface 51. The main body portion 52 faces the wavelength-selective reflecting layer 40. The main body portion 52 may be in contact with the wavelength-selective reflecting layer 40. The main body portion 52 may be bonded to the wavelength-selective reflecting layer 40. The optical sheet 50 includes a sheet-like main body portion 52 and a plurality of unit optical elements 55 each formed as a convex portion 53 or a concave portion 54. The unit optical element 55 is an element that changes the traveling direction of light by refraction, reflection, or the like. The unit optical element 55 is a concept that includes elements called unit shaped elements, unit prisms, and unit lenses. The unit optical elements 55 are provided on the main body portion 52. The uneven surface 51 is formed by the plurality of unit optical elements 55.

[0104] The optical sheet 50 shown in Fig. 14A has a plurality of convex portions 53 provided on the surface of the main body 52 that faces the reflective polarizing plate 60. In the example shown in Fig. 14A, the plurality of convex portions 53 are provided adjacent to each other with no gaps. The optical sheet 50 shown in Fig. 14B has a plurality of concave portions 54 provided on the surface of the main body 52 that faces the reflective polarizing plate 60. In the example shown in Fig. 14B, the plurality of concave portions 54 are provided adjacent to each other with no gaps.

[0105] 14A and 14B, the unit optical elements 55 have element surfaces 56 inclined with respect to the third direction D3. The unit optical elements 55 are defined by the element surfaces 56. The concave-convex surface 51 of the optical sheet 50 is formed by the element surfaces 56 of the unit optical elements 55.

[0106] The optical characteristics of the optical sheet 50 are affected by the inclination angle of the element surface 56 of the unit optical element 55. Therefore, the cross-sectional shape of the unit optical element 55 can be appropriately adjusted based on the optical characteristics required for the surface light source device 20 and the optical member 30. For example, the inclination angles of the element surfaces 56 included in one unit optical element 55 may be different from each other or may be the same. The optical sheet 50 may include unit optical elements 55 that are different in at least one of the shape and the orientation, or may include only unit optical elements 55 that are the same as each other. Unlike the examples of FIG. 14A and FIG. 14B, the light-entering side surface 50a of the optical sheet 50 may be an uneven surface 51 formed by the element surfaces 56 of the unit optical elements 55. In this example, the light-emitting side surface 50b of the optical sheet 50 may be a flat surface or may be an uneven surface 51.

[0107] The unit optical elements 55 included in the optical sheet 50 may be two-dimensionally arranged. According to this example, the element surfaces 56 of the unit optical elements 55 included in the optical sheet 50 face various directions. As a result, the optical sheet 50 can guide light in various directions by the two-dimensionally arranged unit optical elements 55. That is, the light can be guided in a plurality of non-parallel directions, and the in-plane distribution of illuminance can be made uniform. Each unit optical element 55 may be configured to be rotationally symmetric about the third direction D3. For example, each unit optical element 55 may be configured to be three-fold, four-fold, or six-fold symmetric about the third direction D3.

[0108] 15A and 15B show specific examples of unit optical elements 55 in the optical sheet 50. In the example shown in FIG. 15A and FIG. 15B, the arrangement of the unit optical elements 55 is a square arrangement. The unit optical elements 55 are arranged at a constant pitch in the first direction D1. The unit optical elements 55 are also arranged at a constant pitch in the second direction D2. The arrangement pitch in the first direction D1 and the arrangement pitch in the second direction D2 may be the same or different. In the example shown in FIG. 15A and FIG. 15B, the unit optical elements 55 are arranged closely together without gaps. In the illustrated example, the arrangement pitch in the first direction D1 and the arrangement pitch in the second direction D2 are the same. The arrangement pitch in the first direction D1 and the arrangement pitch in the second direction D2 may be 0.05 mm or more and 1 mm or less, or 0.1 mm or more and 0.5 mm or less. 15A and 15B, unit optical elements 55 are configured as quadrangular pyramid-shaped convex portions 53 or concave portions 54 having a square base. The height or depth of each unit optical element 55 in the third direction D3 may be 0.025 mm or more and 0.5 mm or less, or may be 0.05 mm or more and 0.25 mm or less.

[0109] The unit optical elements 55 may be arranged in directions inclined to the first direction D1 and the second direction D2. For example, in the example shown in Fig. 15C, a plurality of unit optical elements 55 are arranged at a constant pitch in two directions inclined at ±45° with respect to the first direction D1. The arrangement of Fig. 15C can be applied to the unit optical elements 55 shown in Fig. 15B. According to this example, the element surface 56 faces two directions inclined at ±45° with respect to the first direction D1, and light can be spread in these two directions.

[0110] As shown in FIG. 15D, the unit optical elements 55 included in the optical sheet 50 may be arranged one-dimensionally. That is, the unit optical elements 55 may be arranged in the arrangement direction, and each unit optical element 55 may extend linearly in a direction non-parallel to the arrangement direction. In the example shown in FIG. 15D, each unit optical element 55 extends linearly in a direction perpendicular to the arrangement direction. The unit optical elements 55 may be arranged in a first direction D1. The unit optical elements 55 may extend linearly in a second direction D2. The arrangement direction of the unit optical elements 55 may be the second direction D2. The arrangement direction of the unit optical elements 55 may be a direction inclined to both the first direction D1 and the second direction D2. The arrangement direction of the unit optical elements 55 may be a direction inclined at 45° with respect to the first direction D1 and the second direction D2.

[0111] The plurality of unit optical elements 55 may be arranged irregularly or regularly. By arranging the plurality of unit optical elements 55 regularly, the design of the optical sheet 50 can be facilitated. Furthermore, by arranging the plurality of unit optical elements 55 regularly, it becomes easy to arrange the unit optical elements 55 closely together without any gaps.

[0112] The reflective polarizing plate 60 is overlapped with the optical sheet 50 in the third direction D3. The optical sheet 50 is located between the reflective polarizing plate 60 and the wavelength selective reflection layer 40 in the third direction D3. The reflective polarizing plate 60 transmits one linearly polarized component and reflects the other linearly polarized component. The reflective polarizing plate 60 can selectively transmit the linearly polarized component of light that can pass through the polarizing plate located on the surface light source device 20 side of the display panel 15. The light reflected by the reflective polarizing plate 60 can change its polarization state by subsequent reflection or the like and enter the reflective polarizing plate 60 again. The reflective polarizing plate 60 may be "DBEF" (registered trademark) available from 3M, USA. The reflective polarizing plate 60 may be a high brightness polarizing sheet "WRPS" available from Shinwa Intertek, Korea, a wire grid polarizer, or the like.

[0113] Next, the operation of the surface light source device 20 having the above-mentioned configuration when generating surface light will be described mainly with reference to FIGS.

[0114] As shown in FIG. 16, the light source 23 emits primary light LA. The primary light LA ​​is, for example, ultraviolet light. The wavelength of this primary light LA ​​is less than 380 nm. The primary light LA ​​emitted by the light source 23 travels toward the conversion agent-containing portion 35 containing the wavelength conversion agent 38. As shown in FIG. 5, a portion of the primary light LA ​​is incident on the wavelength conversion agent 38 and absorbed. The wavelength conversion agent 38 that absorbs the primary light LA ​​emits secondary light LB. The secondary light LB is emitted from the wavelength conversion agent 38 as diffuse light, regardless of the incident path of the primary light LA ​​to the wavelength conversion agent 38. The remaining primary light LA ​​that is incident on the conversion agent-containing portion 35 does not collide with the wavelength conversion agent 38 and passes through the conversion agent-containing portion 35.

[0115] The primary light LA ​​and secondary light LB that have passed through the conversion agent-containing portion 35 enter the wavelength-selective reflection layer 40. The wavelength-selective reflection layer 40 has optical characteristics shown in FIG. 13, for example. That is, the reflectance of the secondary light LB at the wavelength-selective reflection layer 40 is smaller than the reflectance of the primary light LA ​​at the wavelength-selective reflection layer 40. For example, the reflectance of the secondary light LB at the wavelength-selective reflection layer 40 is 50% or less. The reflectance of the primary light LA ​​at the wavelength-selective reflection layer 40 is 90% or more. Therefore, most of the primary light LA ​​can be reflected by the wavelength-selective reflection layer 40. Most of the secondary light LB can be transmitted through the wavelength-selective reflection layer 40. As a result, only the secondary light LB emitted from the wavelength conversion agent 38 is emitted in the area directly above the light source 23. This makes it possible to prevent the area directly above the light source 23 from becoming too bright.

[0116] The surface light source device 20 shown in Fig. 16 is the same as the surface light source device 20 shown in Fig. 2, and has a sheet-shaped conversion agent-containing portion 35. In this example, by reducing the content (%) of wavelength conversion agent 38 in the conversion agent-containing portion 35, the illuminance in the area directly above the light source 23 can be reduced.

[0117] As shown in FIG. 16, the light L161 and the light L162 as the primary light LA ​​reflected by the wavelength selective reflecting layer 40 are reflected by the reflecting layer 27 and the wavelength selective reflecting layer 40 until they are wavelength converted by the wavelength conversion agent 38. These lights L161 and L162 proceed in the first direction D1 and the second direction D2 perpendicular to the third direction D3. The lights L161 and L162 move away from the light source 23, and are absorbed by the wavelength conversion agent 38 with a certain probability when passing through the conversion agent-containing portion 35. These lights L161 and L162 pass through the wavelength selective reflecting layer 40 in an area away from the light source 23. This makes it possible to prevent the area away from the light source 23 from becoming too dark.

[0118] The surface light source device 20 shown in Fig. 16 has a sheet-shaped conversion agent-containing portion 35. In this example, by reducing the content (%) of the wavelength conversion agent 38 in the conversion agent-containing portion 35, the movement of the primary light LA ​​in the first direction D1 and the second direction D2 perpendicular to the third direction D3 is promoted. Therefore, by reducing the content (%) of the wavelength conversion agent 38 in the conversion agent-containing portion 35, an area far from the light source 23 can be brightened.

[0119] As described above, the wavelength conversion agent 38 and the wavelength-selective reflecting layer 40 work together to effectively eliminate uneven brightness depending on the distance from the light source 23, and the illuminance distribution on the light-emitting side surface 40b of the wavelength-selective reflecting layer 40 is sufficiently uniform.

[0120] From the viewpoint of uniforming the illuminance, the wavelength conversion agent 38 may be arranged in consideration of the arrangement of the light source 23, as shown in Fig. 8 to Fig. 12A. Specifically, the volume of the wavelength conversion agent 38 included in one reference volume region 35V may be made larger than the volume of the wavelength conversion agent 38 included in another reference volume region 35V located between the reference volume region 35V and one light source 23 closest to the reference volume region 35V. Furthermore, the volume of the wavelength conversion agent 38 included in any one reference volume region 35V may be made larger than the volume of the wavelength conversion agent 38 included in any other reference volume region 35V located between the reference volume region 35V and one light source 23.

[0121] According to these specific examples, in the area directly above the light source 23, the primary light LA ​​can be suppressed from being converted into secondary light LB by the wavelength conversion agent 38. Therefore, it is possible to more effectively prevent the area directly above the light source 23 from becoming too bright. On the other hand, in the area away from the light source 23 in the first direction D1 or the second direction D2, it is possible to promote the conversion of the primary light LA ​​into secondary light LB by the wavelength conversion agent 38. Therefore, it is possible to prevent the area away from the light source 23 from becoming too dark. This allows the surface light source device 20 to be sufficiently thin while sufficiently uniforming the in-plane distribution of brightness.

[0122] Also, in the area between two adjacent light sources 23, the conversion of the primary light LA ​​into the secondary light LB by the wavelength conversion agent 38 can be promoted. Therefore, it is possible to prevent the light emitted from one light source 23 from moving to the vicinity of another light source 23. In other words, it is possible to reduce the number of reflections of the primary light LA. This makes it possible to suppress reflection losses and improve the utilization efficiency of the light sources 23.

[0123] Meanwhile, local dimming is known as a control method for controlling the turning on and off of the light source 23 of the surface light source device 20 in accordance with the image displayed by the display device 10. In local dimming, the light source 23 facing the dark part of the image is turned off, and the light source 23 facing the bright part of the image is turned on. By using local dimming, the contrast of the image can be improved. In particular, in a liquid crystal display device in which oblique light leaks from the display panel 15, local dimming is considered to be an effective control. By setting a distribution in the arrangement of the wavelength conversion agent 38 as shown in Figs. 8 to 12A, the conversion of the primary light LA ​​to the secondary light LB by the wavelength conversion agent 38 is promoted in the area between two adjacent light sources 23. This makes it possible to prevent the primary light LA ​​emitted from one light source 23 from reaching the vicinity of another light source 23. Therefore, the primary light LA ​​emitted from one light source 23 is easily converted into the secondary light LB while moving to the midpoint between the one light source 23 and the adjacent other light source 23. This makes it possible to effectively utilize local dimming.

[0124] As shown in FIG. 17, the light transmitted through the wavelength selective reflecting layer 40 travels toward the optical sheet 50. As shown in FIG. 17, the light output side surface 50b of the optical sheet 50 facing the wavelength selective reflecting layer 40 is an uneven surface 51. The light L171, L172 emitted from the wavelength selective reflecting layer 40 travels in a direction greatly inclined with respect to the third direction D3. These light L171, L172 pass through the element surface 56 inclined in the opposite direction to the traveling direction and the third direction D3 as a center, and are emitted from the optical sheet 50. The light L171, L172 is refracted at the element surface 56 and the traveling direction is bent. At this time, the traveling direction of the light L171, L172 is bent so that the angle with respect to the third direction D3 becomes smaller. In other words, the angle that the traveling direction of the light L171, L172 makes with respect to the third direction D3 is reduced by the refraction of the light L171, L172 at the element surface 56. That is, the optical sheet 50 exerts a function of concentrating the light emitted from the surface light source device 20 in the third direction D3.

[0125] The light exiting the optical sheet 50 is incident on the reflective polarizing plate 60. The reflective polarizing plate 60 transmits the linearly polarized component that can be incident on the display panel 15 and reflects the linearly polarized component that cannot be incident on the display panel 15. The reflected light may be reflected repeatedly, and may re-enter the reflective polarizing plate 60 as a linearly polarized component that can be incident on the display panel 15. Due to the polarization separation function of the reflective polarizing plate 60, the utilization efficiency of the light source 23 may be significantly improved.

[0126] In this manner, the light emitting surface 20a emits light to illuminate the display panel 15, for example.

[0127] As described above, the light source 23 may emit light with a wavelength of less than 380 nm. In this specific example, the primary light LA ​​emitted from the light source 23 is invisible light. Therefore, even if the primary light LA ​​passes through the wavelength-selective reflecting layer 40 with a non-uniform in-plane distribution of the amount of light, it is possible to suppress the occurrence of color unevenness perceived by the observer on the light-emitting surface 20a of the surface light source device 20. In this specific example, a layer containing an ultraviolet absorbing agent may be provided between the wavelength-selective reflecting layer 40 and the display surface 15a in the third direction D3. For example, the optical sheet 50 or the reflective polarizing plate 60 may include a layer containing an ultraviolet absorbing agent.

[0128] Incidentally, the wavelength selective reflection layer 40 made of, for example, a dielectric multilayer film can exert an optical effect on light of wavelength λx (nm) traveling in a direction inclined by θ (°) with respect to the third direction D3 similar to the optical effect on light of wavelength λ = λ / cosθ traveling in the third direction D3. That is, the optical effect of the wavelength selective reflection layer 40 on light of wavelength λx (nm) traveling in a direction inclined by θ (°) with respect to the third direction D3 can be similar to the optical effect of the wavelength selective reflection layer 40 on light of wavelength λ = λ / cosθ traveling in the third direction D3. Therefore, an optical effect similar to the optical effect on primary light LA ​​traveling in the third direction D3 can also be exerted on secondary light LB traveling in an oblique direction.

[0129] From this point of view, in the above-mentioned specific example, the shortest wavelength (nm) of the secondary light LB obtained by conversion in the wavelength conversion agent 38 may be 1.31 (=1 / cos40°) times or more the wavelength λ1 (nm) of the primary light. The shortest wavelength (nm) of the secondary light LB means the central wavelength of the light emitted by the type of wavelength conversion agent 38 that emits the shortest wavelength of light when multiple types of wavelength conversion agents 38 are contained in the surface light source device 20. In the example shown in FIG. 5, the central wavelength (nm) of the first secondary light LB1 emitted from the first wavelength conversion agent 38A is the shortest wavelength (nm) of the secondary light LB obtained by conversion in the wavelength conversion agent 38.

[0130] According to this example, it is possible to suppress the secondary light LB traveling in a direction that forms an angle of less than 40° with the third direction D3 in the wavelength selective reflecting layer 40 from being reflected by the wavelength selective reflecting layer 40 to the same extent as the primary light LA. The reflectance of the secondary light LB traveling in a direction that forms an angle of less than 40° with the third direction D3 in the wavelength selective reflecting layer 40 in the wavelength selective reflecting layer 40 can be reduced to be lower than the reflectance of the primary light LA ​​in the wavelength selective reflecting layer 40. Therefore, it is possible to sufficiently improve the transmittance of the secondary light LB of the wavelength selective reflecting layer 40. This makes it possible to avoid unnecessary reflection and improve the utilization efficiency of the light source 23.

[0131] The wavelength selective reflection layer 40 may be made of a resin having a refractive index of 1.4 or more and 1.6 or less. The critical angle of total reflection at the interface between such a wavelength selective reflection layer 40 and an air layer is 38.7° or more and 45.6° or less. That is, light traveling in the wavelength selective reflection layer 40 in a direction that forms an angle of more than 40° with respect to the third direction D3 is likely to be totally reflected at the light output side surface 40b of the wavelength selective reflection layer 40. Therefore, according to an example in which the shortest wavelength (nm) of the secondary light LB obtained by conversion with the wavelength conversion agent 38 is 1.31 (=1 / cos40°) times or more the wavelength λ1 of the primary light LA, color unevenness can be suppressed in the surface light source device 20 in which a plurality of secondary lights LB having different wavelengths pass through the wavelength selective reflection layer 40.

[0132] In the embodiment described above, the surface light source device 20 has a wavelength selective reflective layer 40, a light source substrate 22, and a wavelength conversion agent 38 located between the wavelength selective reflective layer 40 and the light source substrate 22. The light source substrate 22 includes a light source 23 facing the wavelength selective reflective layer 40 and a support substrate 25 supporting the light source 23. The support substrate 25 includes a reflective layer 27 facing the wavelength selective reflective layer 40. The wavelength conversion agent 38 absorbs the primary light LA ​​from the light source 23 and emits secondary light LB having a wavelength different from that of the primary light LA. The reflectance of the secondary light LB at the wavelength selective reflective layer 40 is smaller than the reflectance of the primary light LA ​​at the wavelength selective reflective layer 40.

[0133] In this embodiment, the reflectance of the wavelength-selective reflecting layer 40 depends on the wavelength of the light. Therefore, the primary light LA ​​emitted from the light source 23 can be repeatedly reflected by the wavelength-selective reflecting layer 40 and the reflecting layer 27 until it is absorbed by the wavelength conversion agent 38 and converted into secondary light LB of a different wavelength. That is, the primary light LA ​​emitted from the light source 23 can travel in the first direction D1 and the second direction D2 perpendicular to the third direction D3 until it collides with the wavelength conversion agent 38. This can prevent the illuminance in the area directly above the light source 23 from becoming too high. The illuminance in the area away from the light source 23 can be increased. As a result, the brightness distribution caused by the light source 23 is eliminated, and the in-plane distribution of the illuminance can be effectively uniformed. In addition, the primary light LA ​​emitted from the light source 23 is suppressed from passing through the wavelength-selective reflecting layer 40 until it is converted into secondary light LB by the wavelength conversion agent 38. Therefore, even if the distance from the light source substrate 22 to the wavelength-selective reflecting layer 40 is shortened, the primary light LA ​​can be sufficiently diffused between the wavelength-selective reflecting layer 40 and the light source substrate 22. As a result, the surface light source device 20 can be made sufficiently thin, while the in-plane distribution of brightness can be made sufficiently uniform.

[0134] In addition, in a conventional direct type surface light source device such as Patent Document 1 (JP2014-199831A), the thickness of the layer containing the wavelength conversion agent is made thick in order to ensure a collision opportunity between the primary light and the wavelength conversion agent. However, in the present embodiment, the primary light LA ​​can be repeatedly reflected by the wavelength selective reflection layer 40 and the reflection layer 27 until it collides with the wavelength conversion agent 38. Therefore, even if the thickness of the conversion agent-containing portion 35 containing the wavelength conversion agent 38 is made thin, the primary light LA ​​can be sufficiently converted into the secondary light LB by the wavelength conversion agent 38. By making the conversion agent-containing portion 35 containing the wavelength conversion agent 38 thinner, the surface light source device 20 can be made thinner. In addition, since the amount of the wavelength conversion agent 38 used can be reduced, the manufacturing cost of the surface light source device 20 can be reduced.

[0135] In the specific example of the embodiment described above, the conversion agent-containing portion 35 containing the wavelength conversion agent 38 is provided between the wavelength selective reflection layer 40 and the light source substrate 22. At least one of the thickness (mm) of the conversion agent-containing portion 35, the ratio (%) of the area in which the conversion agent-containing portion 35 is arranged, and the content (%) of the wavelength conversion agent 38 contained in the conversion agent-containing portion 35 varies depending on the distance from the light source 23. In such an example, the conversion agent-containing portion 35 can be produced by a simple method such as printing or molding. According to this conversion agent-containing portion 35, the distribution of the wavelength conversion agent 38 can be adjusted with a high degree of freedom. As a result, the surface light source device 20 can be made sufficiently thin while the in-plane distribution of brightness can be sufficiently uniformed.

[0136] In the specific example of the embodiment described above, a conversion agent-containing portion 35 containing a wavelength conversion agent 38 is provided between the wavelength selective reflection layer 40 and the light source substrate 22. The conversion agent-containing portion 35 constitutes a part or all of the intermediate layer 32 that maintains a constant distance between the wavelength selective reflection layer 40 and the light source substrate 22. For example, as disclosed in Patent No. 6299811, in order to achieve uniform brightness, light is usually diffused by refraction or total reflection at the refractive index interface. On the other hand, in this embodiment, the light emitted from the light source 23 is diffused by the wavelength conversion agent 38 of the wavelength selective reflection layer 40. Therefore, since an interface with a large refractive index difference does not need to be used, the intermediate layer 32 can be disposed between the wavelength selective reflection layer 40 and the light source substrate 22. Furthermore, the intermediate layer 32 may be filled between the wavelength selective reflection layer 40 and the light source substrate 22. In the specific example described above, the conversion agent-containing portion 35 containing the wavelength conversion agent 38 is provided between the wavelength selective reflection layer 40 and the light source substrate 22, and the conversion agent-containing portion 35 constitutes a part or all of the intermediate layer 32. The intermediate layer 32 allows the wavelength selective reflecting layer 40 to be aligned at an appropriate position with respect to the light source 23. Also, the wavelength conversion agent 38 can be aligned at an appropriate position with respect to the light source 23. As a result, uniformity of the in-plane distribution of brightness can be stably ensured.

[0137] In the specific example of the embodiment described above, the intermediate layer 32 includes a first portion 33A containing a wavelength conversion agent 38 and a second portion 33B containing the wavelength conversion agent 38 at a content rate (%) lower than that of the first portion 33A or not containing the wavelength conversion agent 38. In this specific example, the first portion 33A and the second portion 33B can be produced by a simple method such as printing or molding. The intermediate layer 32 including the first portion 33A and the second portion 33B allows the distribution of the wavelength conversion agent 38 to be adjusted with a high degree of freedom. This allows the surface light source device 20 to be sufficiently thin while the in-plane distribution of brightness to be sufficiently uniform.

[0138] In the specific example of the embodiment described above, the intermediate layer 32 is bonded to at least one of the wavelength selective reflecting layer 40 and the light source substrate 22. According to this specific example, the intermediate layer 32 can maintain the wavelength selective reflecting layer 40 in an appropriate position relative to the light source 23. Also, the wavelength conversion agent 38 can be maintained in an appropriate position relative to the light source 23. This allows the in-plane distribution of brightness to be stably and uniformly achieved while the surface light source device 20 is in use.

[0139] In the specific example of the embodiment described above, the optical sheet 50 has a light-entering side surface 50a facing the wavelength-selective reflecting layer 40 and a light-exiting side surface 50b facing the light-entering side surface 50a, and the light-exiting side surface 50b is an uneven surface 51. The wavelength-selective reflecting layer 40 is located between the optical sheet 50 and the light source substrate 22 in the third direction D3. As shown in FIG. 17, in this specific example, the light L171, L172 traveling from the wavelength-selective reflecting layer 40 to the optical sheet 50 travels in a direction that forms a large angle with the third direction D3. The optical sheet 50 can bend the traveling direction of the light L171, L172 by refraction. That is, the optical sheet 50 can adjust the traveling direction of the light L171, L172 so that the angle that the traveling direction of the light L171, L172 emitted from the wavelength-selective reflecting layer 40 forms with the third direction D3 is significantly reduced. This can effectively improve the front direction luminance of the surface light source device 20.

[0140] Although one embodiment has been described with reference to a specific example, the above-mentioned specific example does not limit the embodiment. The above-mentioned embodiment can be embodied in various other specific examples, and various omissions, substitutions, changes, additions, etc. can be made without departing from the spirit of the embodiment.

[0141] An example of the modification will be described below with reference to the drawings. In the following description and the drawings used in the following description, parts that can be configured similarly to the above-mentioned specific example are designated by the same reference numerals as those used for the corresponding parts in the above-mentioned specific example, and duplicated descriptions will be omitted.

[0142] As an example, as shown in FIG. 12B, the intermediate layer 32 may include a light diffusing component 39. Examples of the light diffusing component 39 include a metal compound, a porous substance containing gas, resin beads surrounding a metal compound, white fine particles, and even simple air bubbles. By including the light diffusing component 39, the in-plane distribution of brightness can be made more uniform. In addition, the distribution of the wavelength conversion agent 38 can be made sufficiently inconspicuous. In the example shown in FIG. 12B, the second portion 33B includes the light diffusing component 39. The second portion 33B includes the wavelength conversion agent 38 at a lower content rate (%) than the first portion 33A, or does not include the wavelength conversion agent 38. The second portion 33B is at least partially located between the first portion 33A and the wavelength selective reflection layer 40. According to the configuration shown in FIG. 12B, the distribution of the first portion 33A in which the wavelength conversion agent 38 is dispersed at a high concentration can be made more effectively inconspicuous by diffusion by the light diffusing component 39.

[0143] As shown in FIG. 18, the intermediate layer 32 may be in contact with a portion of the light source 23 from which the primary light LA ​​is emitted. That is, the intermediate layer 32 may be in contact with the emission surface 23S of the light source 23. According to this example, the emission surface 23S of the light source 23 is in optical contact with the intermediate layer 32. As shown in FIG. 18, the edge of the emission surface 23S is usually curved. At this curved portion, total reflection of the light L182 generated by the light source 23 may occur. By covering this curved portion with the intermediate layer 32, the refractive index difference is reduced, suppressing total reflection. This can improve the utilization efficiency of the light source 23. In the first place, the light L181 that can be used is light that travels in an oblique direction, which can contribute to uniform brightness. In addition, the intermediate layer 32 can protect the emission surface 23S of the light source 23.

[0144] The optical member 30 may further include a second optical sheet superimposed on the optical sheet 50 in the third direction D3. In this example, the optical sheet 50 and the second optical sheet may both be the optical sheets shown in Fig. 15D. The arrangement direction of the unit optical elements 55 in the optical sheet 50 and the arrangement direction of the unit optical elements 55 in the second optical sheet may be non-parallel or perpendicular to each other. [Explanation of symbols]

[0145] D1: 1st direction, D2: 2nd direction, D3: 3rd direction, LA: primary light, LB: secondary light, LB1: 1st secondary light, LB2: 2nd secondary light, LB3: 3rd secondary light, 10: Display device, 15: Display panel, 15a: Display surface, 20: Surface Light source device, 20a: light emitting surface, 22: light source substrate, 23: light source, 23S: emission surface, 25: support substrate, 26: substrate body, 27: reflective layer, 29: wiring, 30: optical member, 32: intermediate layer, 33A: first part, 33B: second part, 3 5: conversion agent-containing portion, 35A: area, 35V: reference volume region, 36: base material portion, 38: wavelength conversion agent, 38A: first wavelength conversion agent, 38B: second wavelength conversion agent, 38C: third wavelength conversion agent, 39: light diffusing component, 40: wavelength selective reflection layer, 40a: light incident side, 40b: light exiting side, 50: optical sheet, 50a: light incident side, 50b: light exiting side, 51: uneven surface, 52: main body portion, 53: convex portion, 54: concave portion, 55: unit optical element, 56: element surface, 60: reflective polarizing plate

Claims

1. A wavelength selective reflective layer; a light source substrate including a light source facing the wavelength selective reflection layer and a support substrate supporting the light source; a wavelength conversion agent located between the wavelength selective reflective layer and the light source substrate, the light source substrate includes a reflective layer facing the wavelength-selective reflective layer; The wavelength conversion agent absorbs primary light from the light source and emits secondary light having a wavelength different from that of the primary light; the reflectance of the secondary light at the wavelength-selective reflective layer is smaller than the reflectance of the primary light at the wavelength-selective reflective layer, If an area having a certain area of ​​the wavelength selective reflecting layer and an area between the wavelength selective reflecting layer and the light source substrate that overlaps in a direction in which the wavelength selective reflecting layer and the light source substrate face each other are defined as a reference volume area, A surface light source device, wherein the volume of the wavelength conversion agent contained in one reference volume region is larger than the volume of the wavelength conversion agent contained in another reference volume region located between the one reference volume region and a light source closest to the one reference volume region.

2. 2. The surface light source device of claim 1, wherein the volume of the wavelength conversion agent contained in any one of the reference volume regions is greater than or equal to the volume of the wavelength conversion agent contained in any other reference volume region located between the one of the reference volume regions and the one of the light sources.

3. a conversion agent-containing portion containing the wavelength conversion agent is provided between the wavelength selective reflection layer and the light source substrate, 3. The surface light source device of claim 1, wherein one or more of the thickness of the conversion agent-containing portion, the proportion of the area in which the conversion agent-containing portion is arranged, and the content ratio of the wavelength conversion agent contained in the conversion agent-containing portion change depending on the distance from the light source.

4. a conversion agent-containing portion containing the wavelength conversion agent is provided between the wavelength selective reflection layer and the light source substrate, 3 . The surface light source device according to claim 1 , wherein the conversion agent-containing portion constitutes a part or all of an intermediate layer that maintains a constant distance between the wavelength selective reflection layer and the light source substrate.

5. The surface light source device according to claim 4 , wherein the intermediate layer includes a first portion containing the wavelength conversion agent and a second portion containing the wavelength conversion agent at a content rate lower than that of the first portion or not containing the wavelength conversion agent.

6. The surface light source device according to claim 4 , wherein the intermediate layer contains a light diffusing component.

7. the second portion comprises a light diffusing component; The surface light source device according to claim 5 , wherein the second portion is at least partially located between the first portion and the wavelength-selective reflecting layer.

8. 8. The surface light source device according to claim 4, wherein the intermediate layer is bonded to at least one of the wavelength selective reflection layer and the light source substrate.

9. 9. The surface light source device according to claim 4, wherein the intermediate layer is in contact with a portion of the light source from which the primary light is emitted.

10. 10. The surface light source device according to claim 1, wherein the light source emits light having a wavelength of less than 380 nm.

11. 11. The surface light source device according to claim 1, wherein the shortest wavelength of the secondary light is 1.31 times or more as long as the wavelength of the primary light.

12. A surface light source device according to any one of claims 1 to 11, A display device comprising the surface light source device and a display panel overlapped therewith.

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