JP2023003825A - Surface light source device and display device - Google Patents

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

The present disclosure relates to surface light source devices and display devices.

A surface light source device is known as a device that emits light in a planar manner. As disclosed in Patent Document 1, a surface light source device can be used as a backlight for a liquid crystal display device. Patent Literature 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, brightness unevenness occurs due to the arrangement of the light sources. This non-uniformity in brightness becomes more conspicuous when the thickness of the surface light source device is reduced.

JP2014-199831A

In the prior art, it has not been possible to sufficiently achieve a uniform in-plane distribution of brightness while reducing the thickness of the surface light source device. The present invention has been made in consideration of such points. SUMMARY OF THE INVENTION It is an object of the present invention to sufficiently homogenize the in-plane distribution of brightness while reducing the thickness of a surface light source device.

A surface light source device according to an embodiment of the present disclosure includes
a wavelength selective reflection 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 reflection 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 in the wavelength selective reflection layer is smaller than the reflectance of the primary light in the wavelength selective reflection layer.

In the surface light source device according to one embodiment of the present disclosure, the reflectance of the secondary light in the wavelength selective reflection layer may be 50% or less.

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

In the surface light source device according to one embodiment of the present disclosure,
A region having a certain area of the wavelength selective reflection layer and a region between the wavelength selective reflection layer and the light source substrate overlapping in a direction in which the wavelength selective reflection layer and the light source substrate face each other is defined as a reference volume region,
The volume of the wavelength converting agent included in one reference volume region is included in another reference volume region located between the one reference volume region and the one light source closest to the one reference volume region. It may be larger than the volume of said wavelength converting agent contained.

In the surface light source device according to one embodiment of the present disclosure, the volume of the wavelength conversion agent contained in any one reference volume region is any one located between the one reference volume region and the one light source. It may be equal to or larger than the volume of the wavelength conversion agent contained in another reference volume region.

In the surface light source device according to one 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 ratio of the area where the conversion agent-containing portion is arranged, and the content ratio of the wavelength conversion agent contained in the conversion agent-containing portion depend on the distance from the light source. may vary.

In the 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.

The converting agent-containing portion is provided on at least one of the wavelength selective reflective layer and the reflective layer.

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

In the surface light source device according to an embodiment of the present disclosure, the thickness of the conversion agent-containing portion, the ratio of the area where the conversion agent-containing portion is arranged, and the content of the wavelength conversion agent contained in the conversion agent-containing portion One or more of the percentages may vary with distance from the light source.

In the surface light source device according to one 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 part or all of an intermediate layer that maintains a constant distance between the wavelength selective reflection layer and the light source substrate.

In the surface light source device according to one embodiment of the present disclosure, the intermediate layer includes a first portion containing the wavelength conversion agent, and a content ratio of the wavelength conversion agent lower than that of the first portion, or the wavelength and a second portion that does not contain a converting agent.

In the surface light source device according to one embodiment of the present disclosure, the intermediate layer may contain a light diffusing component.

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

In the surface light source device according to one 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.

In the surface light source device according to one embodiment of the present disclosure, the intermediate layer may contact a portion of the light source from which the primary light is emitted.

In the surface light source device according to one embodiment of the present disclosure, the light source may emit light with a wavelength of less than 380 nm.

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

A surface light source device according to an embodiment of the present disclosure includes
an optical sheet having a light-entering side surface facing the wavelength-selective reflecting layer and a light-emitting side surface as an uneven surface facing the light-entering side surface;
The wavelength selective reflection layer may be positioned between the optical sheet and the light source substrate.

A display device according to an embodiment of the present disclosure includes:
any of the surface light source devices according to an embodiment of the present disclosure;
A display panel overlaid on the surface light source device.

SUMMARY OF THE INVENTION An object of the present invention is to reduce the thickness of a surface light source device while making the in-plane distribution of brightness sufficiently uniform.

FIG. 1 is a diagram for explaining an embodiment, and is a perspective view showing a display device and a surface light source device. 2 is a longitudinal sectional view of the surface light source device of FIG. 1. FIG. FIG. 3 is a plan view showing a light source substrate that can be included in the surface light source device of FIG. 2, showing an example of arrangement of a plurality of light sources. 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, showing an example of the configuration of the light source substrate. 5 is an enlarged cross-sectional view showing a conversion agent-containing portion that can be included in the surface light source device of FIG. 2. FIG. 6A is a cross-sectional view corresponding to FIG. 2, and is a view for explaining another example of the converting agent-containing portion. FIG. FIG. 6B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the converting agent-containing portion. 7A is a cross-sectional view corresponding to FIG. 2, illustrating still another example of the conversion agent-containing portion. FIG. FIG. 7B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the conversion agent-containing portion. FIG. 8 is a plan view illustrating still another example of the converting agent-containing portion. 9 is a cross-sectional view corresponding to FIG. 2, showing the surface light source device having the conversion agent-containing portion of FIG. 8. FIG. 10A is a cross-sectional view corresponding to FIG. 2, illustrating still another example of the converting agent-containing portion. FIG. FIG. 10B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the converting agent-containing portion. FIG. 11A is a cross-sectional view corresponding to FIG. 2, illustrating still another example of the conversion agent-containing portion. FIG. 11B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the conversion agent-containing portion. 12A is a cross-sectional view corresponding to FIG. 2, illustrating still another example of the converting agent-containing portion. FIG. FIG. 12B is a cross-sectional view corresponding to FIG. 2, and is a view for explaining still another example of the converting agent-containing portion. 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 explaining the wavelength dependence of reflectance and transmittance. 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. 2. FIG. 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. 2. FIG. 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. 2. FIG. 15B is a perspective view showing a unit optical element of the optical sheet of FIG. 15A. FIG. 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. 2. FIG. 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. 2. FIG. FIG. 16 is a longitudinal sectional view showing the surface light source device, and is a diagram for explaining the operation of the surface light source device. FIG. 17 is a vertical cross-sectional view showing the optical sheet and explaining the action of the optical sheet. FIG. 18 is a partially enlarged sectional view showing a surface light source device.

An embodiment of the present disclosure will be described below with reference to the drawings. In the drawings attached to this specification, for the convenience of illustration and ease of understanding, the scale and the ratio of vertical and horizontal dimensions are changed and exaggerated from those of the real thing. In addition, configurations and the like shown in some drawings may be omitted in other drawings.

In this specification, terms that specify shapes and geometric conditions and their degrees, such as "parallel", "perpendicular", "identical", length and angle values, etc., are limited to strict meanings. It is interpreted to include the extent to which similar functions can be expected without being

In this specification, terms such as "sheet", "film" and "plate" are not distinguished from each other based solely on a difference in designation. For example, an "optical sheet" cannot be distinguished from a member called an optical film or an optical plate only by the difference in name.

Further, 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. Point. In addition, the "sheet surface (film surface, plate surface)" refers to the sheet-like member (film-like) that is the target when the target sheet-like (film-like, plate-like) member is viewed as a whole and from a broad perspective. member, plate-shaped member).

In order to clarify the directional relationships among the drawings, some drawings show the first direction D1, the second direction D2 and the third direction D3 as common directions by the arrows with the same reference numerals. The tip side of the arrow is one side in each direction. An arrow pointing inward in the drawing along a direction perpendicular to the drawing is indicated by a circle with an x in it, as shown in FIG. 2, for example. An arrow pointing forward from the plane of the drawing along a direction perpendicular to the plane of the drawing is indicated by a dot in a circle, as shown in FIG. 3, for example.

1 to 18 are diagrams for explaining an embodiment. Among them, FIG. 1 is a perspective view schematically showing a display device 10 as an application example of the surface light source device 20. As shown in FIG. The display device 10 may display, for example, a moving image, a still image, character information, or an image composed of a combination thereof. The display device 10 may be used indoors or outdoors for various purposes such as displaying advertisements, presentations, television images, and various types of information. The display device 10 may be used, for example, as an in-vehicle liquid crystal display device. The display device 10 shown in FIG. 1 includes a surface light source device 20 having a light emitting surface 20a and a display panel 15 facing the light emitting surface 20a.

FIG. 2 is a longitudinal sectional view showing the surface light source device 20. As shown in FIG. 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 board 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 the third direction D3. The wavelength conversion agent 38 is positioned 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 the first direction D1 and the second direction D2. The first direction D1, the second direction D2 and the third direction D3 are orthogonal to each other. The surface light source device 20 and the display panel 15 are stacked in the third direction D3.

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 overlaid on the wavelength selective reflection layer 40 in the third direction D3. In the illustrated example, a reflective polarizer 60 forms the light emitting surface 20a.

The surface light source device 20 described in the present embodiment is devised to make the in-plane distribution of brightness sufficiently uniform while reducing the thickness of the surface light source device 20 . More specifically, it is devised to eliminate uneven 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 made uniform. . It should be noted 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. ".

Hereinafter, the display device 10 and the surface light source device 20 according to one embodiment will be described with reference to the illustrated specific examples.

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

In the illustrated example, the third direction D3 is 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 reflection layer 40, and the normal direction of the optical sheet 50. parallel to the normal direction and the normal direction of the reflective polarizer 60 . The third direction D3 is also called a front direction.

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 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.

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 decomposes 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. A liquid crystal cell has a pair of support plates and a liquid crystal disposed 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. Application of an electric field changes the orientation of the liquid crystal. As an example, a polarization component in a specific direction rotates its polarization direction by 90° when passing through a liquid crystal cell to which no electric field is applied. A polarization component in a specific direction maintains its polarization direction when passing through a liquid crystal cell to which an electric field is applied. Thereby, transmission and light blocking of a pair of polarizing plates arranged on both sides of the liquid crystal cell can be controlled depending on whether or not an electric field is applied to the liquid crystal cell.

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 a light source 23 and an optical member 30 stacked on the light source substrate 22 in the third direction D3. The light source 23 of the light source substrate 22 is provided within a region overlapping 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.

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

The light source 23 has a light emitting element that emits light. A light-emitting diode denoted as LED may be used as the light-emitting element. The dimensions of the light emitting diode are not particularly limited. From the viewpoint of making the image of the light source 23 inconspicuous, a small light-emitting diode such as a mini-LED or micro-LED may be used. Specifically, the lengths WL1 and WL2 of the sides 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. .

The emission wavelength of the light source 23 can be appropriately selected according to the application of the surface light source device 20 . Light emitted by the light source 23 is absorbed by the wavelength conversion agent 38 as primary light. Therefore, the emission wavelength of light source 23 can be appropriately selected according to the optical properties of wavelength conversion agent 38 . In the illustrated example, 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 rays. 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.

As an example, the light source 23 may be composed only of light emitting elements. 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.

Light distribution characteristics of the light source 23 are not particularly limited. Lambertian light distribution can typically be employed as the light distribution characteristic of the light source 23 . On the other hand, in the light emission luminous intensity distribution of the light source 23 whose optical axis is along the third direction D3, the peak luminous intensity may be obtained in a direction other than the third direction D3. For example, the bad wing light distribution disclosed in Patent Document 1 (JP6299811B) may be used as the light distribution characteristic of the light source 23 .

Like 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 according to the application of the surface light source device 20, the area of the light emitting surface 20a, and the like. From the viewpoint of eliminating uneven 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 arranged regularly on a plane perpendicular to the third direction D3. As an example of the 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 can be arranged at a constant pitch in each of three directions that are mutually inclined by 60°. In the square array, the light sources 23 can be arranged at a constant pitch in each of two directions orthogonal to each other.

In the example shown in FIG. 3, the plurality of light sources 23 are arranged at a constant pitch in each of a first direction D1 and a second direction D2 that are orthogonal to each other. In the illustrated example, 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 placement pitch PL1 and the placement pitch PL2 may be different. In the illustrated example, 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.

Next, the support substrate 25 that constitutes the light source substrate 22 together with the plurality of light sources 23 will be described. The support substrate 25 supports the plurality of light sources 23 from the side opposite to the optical member 30 in the third direction D3. The support substrate 25 is sheet-like. Support substrate 25 contains circuitry for powering light source 23 . The support substrate 25 has a light reflectivity that reflects light toward the optical member 30 .

The support substrate 25 shown in FIG. 4 has a sheet-like substrate body 26 , and a reflective layer 27 and wiring 29 provided on the substrate body 26 . The substrate body 26 extends in a direction perpendicular to the third direction D3. The substrate body 26 may have insulating properties. Substrate body 26 may be a spreadable resin film, such as 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. If the substrate body 26 and the reflective layer 27 are insulative, the wiring 29 may be positioned between the substrate body 26 and the reflective layer 27 as shown in FIG.

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 with respect to light of a specific wavelength emitted by the light source 23 or light used for light emission by the surface light source device 20 . The reflectivity of the reflective layer 27 may be specular reflection, also called specular reflection, diffuse reflection, or anisotropic diffuse reflection. By forming the reflective layer 27 with a white reflective layer containing white particles such as silicon dioxide, the reflective layer 27 can be imparted with diffuse reflectivity. From the viewpoint of uniforming the in-plane illuminance distribution of the light emitting surface 20a in combination with other configurations of the surface light source device 20, it is preferable to set the glossiness of the reflecting surface of the reflecting layer 27 to 70 or more. The term "glossiness" as used herein is a value measured in accordance with JISZ8741 with an incident angle of 20° using a gloss meter (VG7000) manufactured by Nippon Denshoku Industries. The reflective layer 27 may be a metal layer laminated on the substrate body 26, or may be a reflective diffractive optical element.

The wavelength converting agent 38 absorbs the primary light LA and emits secondary light LB having a wavelength different from the wavelength of the primary light LA. The light source 23 emits at least primary light LA. The reflectance of the primary light LA in the wavelength selective reflection layer 40 to be described later is higher than the reflectance of the secondary light LB in the wavelength selective reflection layer 40 . A quantum dot or a phosphor may be used as the wavelength conversion agent 38 .

Quantum dots are nanometer-sized particles of semiconductors. Quantum dots may be composed of one semiconductor compound. Quantum dots may be composed of two or more semiconductor compounds. A quantum dot may have, for example, a core-shell structure having a core made of a semiconductor compound and a shell made of a semiconductor compound different from the core.

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

When core-shell quantum dots are used, a material having a higher bandgap than the semiconductor compound forming the core may be used as the semiconductor forming the shell. In this case, the excitons are confined in the core, and the luminous efficiency of the quantum dots can be improved. As core-shell structures (core/shell) having such a bandgap magnitude relationship, 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, and the like.

The size of the quantum dots is adjusted in consideration of the desired wavelength of the secondary light LB. Quantum dots have a larger energy bandgap as the particle size decreases. As the crystal size decreases, the quantum dot emission shifts to the blue side, ie, to the higher energy side. By changing the size of the quantum dots, the wavelength of the secondary light LB can be adjusted. The average particle size of the quantum dots may be 20 nm or less, 0.5 nm or more and 20 nm or less, or 1 nm or more and 10 nm or less. The shape, dispersion state, etc. of the quantum dots are specified by a transmission electron microscope (TEM). The crystal structure and particle size of quantum dots are specified by X-ray crystal diffraction (XRD).

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 light emitted from the surface light source device 20 can be adjusted. In the example shown in FIG. 5, wavelength converting agents 38 include first wavelength converting agent 38A, second wavelength converting agent 38B, and third wavelength converting agent 38C. The first wavelength converting agent 38A, the second wavelength converting agent 38B, and the third wavelength converting agent 38C have different sizes. The first wavelength converting agent 38A, the second wavelength converting agent 38B, and the third wavelength converting agent 38C emit light of different wavelengths.

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 converting agent 38A, the second wavelength converting agent 38B, and the third wavelength converting agent 38C.

The wavelength conversion agent 38 may be installed in the surface light source device 20 while being contained in the conversion agent containing portion 35 . The converting agent-containing portion 35 shown in FIG. 5 has a wavelength converting agent 38 and a base material portion 36 holding the wavelength converting agent 38 . The conversion agent containing portion 35 can stably hold the wavelength conversion agent 38 at a predetermined position of the surface light source device 20 . By surrounding the wavelength conversion agent 38 with the base material portion 36, deterioration of the wavelength conversion agent 38 can be prevented. A resin may be used as the base material portion 36 . Examples of the resin forming the base material portion 36 include a thermoplastic resin, a cured product of a thermosetting resin composition, and a cured product of an ionizing radiation-curable resin composition. Conversion agent-containing portion 35 may have various configurations.

As an example, the conversion agent-containing portion 35 shown in FIG. 2 is positioned between the support substrate 25 and the wavelength selective reflection layer 40 in the third direction D3. The converting agent-containing portion 35 shown in FIG. 2 is sheet-shaped. The converting 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 reflective layer 40 and the support substrate 25 . The converting agent-containing portion 35 shown in FIG. 2 can be produced, for example, by applying a fluid resin composition containing the wavelength converting agent 38 to form a coating film, and drying the coating film.

The conversion agent-containing portion 35 shown in FIGS. 6A and 6B is positioned between the support substrate 25 and the wavelength selective reflection layer 40 in the third direction D3. The converting agent-containing portion 35 shown in FIGS. 6A and 6B is sheet-like. The converting agent containing portion 35 shown in FIGS. 6A and 6B extends in both the first direction D1 and the second direction D2. In the example shown in FIG. 6A, the conversion agent containing portion 35 is in contact with the wavelength selective reflective layer 40 . The converting agent-containing portion 35 shown in FIG. 6A may be bonded to the wavelength selective reflecting layer 40 . In the example shown in FIG. 6B, conversion agent-containing portion 35 is in contact with reflective layer 27 of support substrate 25 . The conversion agent containing portion 35 shown in FIG. 6B may be bonded to the reflective 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 FIGS. 6A and 6B, the conversion agent-containing portion 35 can be fabricated on the wavelength-selective reflective layer 40 or on the reflective layer 27, for example by printing.

In the example shown in FIGS. 7A and 7B, the surface light source device 20 has the intermediate layer 32 in contact with both the wavelength selective reflection layer 40 and the support substrate 25 in the third direction D3. The intermediate layer 32 may be bonded to both or one of the wavelength selective reflection layer 40 and the support substrate 25 . According to this example, the relative positions of the supporting substrate 25 and the wavelength selective reflecting layer 40 can be stably aligned, and the supporting substrate 25 and the wavelength selective reflecting layer 40 can be maintained at appropriate relative positions.

In the example shown in FIG. 7A, the intermediate layer 32 is a single layer composed of 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, a first portion 33A is arranged 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. In the example shown in FIG. 7B, second portion 33B may not contain wavelength converting agent 38 . The second portion 33B that does not contain the wavelength conversion agent 38 may be configured as a transparent resin layer. The second portion 33B may contain a light diffusing component. Examples of light diffusing components include metal compounds, gas-containing porous substances, resin beads surrounding metal compounds, white fine particles, and simple air bubbles.

As used herein, "transparent" means that the visible light transmittance is 50% or more, preferably 80% or more. Visible light transmittance is measured using a spectrophotometer (manufactured by Shimadzu Corporation "UV-3100PC", JIS K 0115 compliant product) at a wavelength of 380 nm or more and 780 nm or less at an incident angle of 0 ° for every 1 nm. It is specified as the average value of the total light transmittance at each wavelength when

In the example shown in FIG. 7B, the second portion 33B may contain the wavelength converting agent 38 in a different percentage content than the first portion 33A. The second portion 33B may contain a different size wavelength converting agent 38 than the first portion 33A. The first portion 33A may be arranged adjacent to the wavelength selective reflection layer 40 . The first portion 33A may be provided adjacent to the reflective layer 27 .

As described later in detail, in the present embodiment, in combination with the wavelength selective reflection layer 40, the illuminance of the light emitting surface 20a increases in the vicinity of the region where a large amount of the wavelength conversion agent 38 exists. The illuminance of the light emitting surface 20a is low in the vicinity of the region where only a small amount of the wavelength conversion agent 38 exists and the region where the wavelength conversion agent 38 does not exist. 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 directly above the light source 23 is high, and the illuminance of the light emitting surface 20a is low between the two adjacent light sources 23. Considering such a tendency, the arrangement of the wavelength conversion agent 38 may be adjusted in order to homogenize the illuminance distribution of the light emitting surface 20a. An example in which the distribution of the wavelength conversion agent 38 is provided will be described with reference to specific examples shown in FIGS. 8 to 11B.

FIG. 8 shows part of the support substrate 25 and the optical member 30 . The portion shown in FIG. 8 is the portion closest to one light source 23 . Within this portion, the volume of wavelength converting agent 38 contained in one region may be greater than the volume of wavelength converting agent 38 contained in another region that is closer to one light source 23 than that 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 wavelength converting agent 38 contained in one reference volume region 35V is determined by another reference located between the one reference volume region 35V and the one light source 23 closest to the one reference volume region 35V. It may be larger than the volume of wavelength converting agent 38 contained in volume region 35V.

Furthermore, within the portion shown in FIG. 8, the volume of wavelength converting agent 38 contained in the reference volume region 35V may increase with distance from one light source 23 . The volume of the wavelength conversion agent 38 contained in any one reference volume region 35V is included in any other reference volume region 35V located between the one reference volume region 35V and one light source 23. It may be equal to or larger than the volume of the wavelength conversion agent 38 .

When the surface light source device 20 contains multiple types of wavelength conversion agents 38, each type of wavelength conversion agent 38 preferably satisfies the above conditions. In the example shown in FIG. 5 with first through third wavelength converting agents 38A-38C included, each of the first through third wavelength converting agents 38A through 38C may be distributed as described above.

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

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

The volume of the third wavelength conversion agent 38C contained in one reference volume region 35V is the volume of another one located between the one reference volume region 35V and the one light source 23 closest to the one reference volume region 35V. It may be larger than the volume of the third wavelength conversion agent 38C contained in one reference volume region 35V. The volume of the third wavelength conversion agent 38C contained in any one reference volume region 35V is added to any other reference volume region 35V located between the one reference volume region 35V and one light source 23. It may be equal to or greater than the volume of the third wavelength conversion agent 38C contained.

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 FIGS. The change in the amount of wavelength converting agent 38 according to the distance from light source 23 may change continuously, as in the example shown in FIG. 10B, which will be described in detail below.

A constant area area 35A used to identify the reference volume area 35V may be assumed to be a 5 mm square, and the area of the area 35A may be 25 mm ² . When the emission wavelengths of the wavelength conversion agents 38 are uniform, the particle diameters of the wavelength conversion agents 38 are also generally uniform. In this case, the comparison of the volumes of the wavelength converting agents 38 contained in the reference volume region 35V may be confirmed by comparing the quantity of the wavelength converting agents 38 contained in the reference volume region 35V. The quantity of wavelength conversion agent 38 can be measured with a transmission electron microscope.

The change in the volume of the wavelength conversion agent 38 included in the reference volume region 35V depends on the thickness of the conversion agent-containing portion 35, the ratio of the area where the conversion agent-containing portion 35 is arranged, and the wavelength conversion agent included in the conversion agent-containing portion 35. It can be adjusted by the content ratio of the agent 38 or the like.

The ratio of the area on which the converting agent-containing portion 35 is arranged means the ratio of the area on which the converting agent-containing portion 35 is provided in a region having a certain area of the surface on which the converting agent-containing portion 35 is provided. means. That is, it is the ratio of the area (mm ² ) where the converting agent-containing portion 35 is provided to the constant area (mm ² ). Here, the fixed area (mm ² ) area is assumed to be a 5 mm square, and the fixed area may be 25 mm ² .

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

In the examples shown in FIGS. 8 and 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. In the example shown in FIGS. The intermediate layer 32 is divided into a plurality of parts according to the distance from the nearest light source 23 along the direction orthogonal to the third direction D3. The intermediate layer 32 includes a first portion 33A, a second portion 33B, and a third portion 33C. The first portion 33A is the farthest from the light source 23. As shown in FIG. The third portion 33C is closest to the light source 23. The third portion 33C surrounds the light source 23 when viewed from the third direction D3 shown in FIG. The second portion 33B surrounds the third portion 33C when viewed from the third direction D3 shown in FIG. The second portion 33B is located between the first portion 33A and the third portion 33C in the direction perpendicular to the third direction D3.

In the examples shown in FIGS. 8 and 9, the content (%) of the wavelength conversion agent 38 in the first portion 33A is higher than the content (%) of the wavelength conversion agent 38 in the second portion 33B. . The content ratio (%) of the wavelength conversion agent 38 in the second portion 33B is higher than the content ratio (%) of the wavelength conversion agent 38 in the third portion 33C. In this example, the first portion 33A and the second portion 33B are configured by the conversion agent-containing portion 35. As shown in FIG. The third portion 33C may be composed of the converting agent-containing portion 35, or may be composed of a transparent resin that does not contain the wavelength converting agent 38. As shown in FIG. The third portion 33C may contain a light diffusing component. Examples of light diffusing components include metal compounds, gas-containing porous substances, resin beads surrounding metal compounds, white fine particles, and simple air bubbles.

In the example shown in FIGS. 10A and 10B, the ratio (%) of the area where the conversion agent-containing portion 35 is arranged changes according to the distance from the light source 23. FIG. In the example shown in FIGS. 10A and 10B, the content ratio of the wavelength conversion agent 38 in the conversion agent-containing portion 35 is constant. In each example shown in FIGS. 10A and 10B, the thickness of the converting 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 40 a of the wavelength selective reflection layer 40 . The ratio of the area of the constant area of the light entrance side surface 40a where the conversion agent-containing portion 35 is provided increases as the distance from the nearest light source 23 increases. In the example shown in FIG. 10B, conversion agent-containing portion 35 is provided on reflective layer 27 of support substrate 25 . The proportion of the area of the reflective layer 27 having the constant area where the conversion agent-containing portion 35 is provided increases with increasing distance from the light source 23 . In the example shown in FIGS. 10A and 10B, the conversion agent-containing portion 35 may be dot-shaped. Dot-shaped converting agent-containing portions 35 may be formed on the wavelength selective reflective layer 40 or the reflective layer 27 by printing. The change in the ratio (%) of the area where the conversion agent-containing portion 35 is arranged may be continuous or stepwise.

In the example shown in FIGS. 11A and 11B, the thickness T (mm) of the converting agent-containing portion 35 in the third direction D3 changes according to the distance from the light source 23 . In the example shown in FIGS. 11A and 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 incident side surface 40a of the wavelength selective reflection layer 40. In the example shown in FIG. In this example, the conversion agent-containing portion 35 is provided in the area of the light incident side surface 40a excluding the area immediately above the light source 23 and the surrounding area. In the example shown in FIG. 11B, conversion agent containing portion 35 is provided on reflective layer 27 . In this example, conversion agent-containing portions 35 are provided in areas of reflective layer 27 excluding areas surrounding light source 23 . In the example shown in FIGS. 11A and 11B, the thickness T (mm) of the converting agent-containing portion 35 in the third direction D3 increases with increasing distance from the nearest light source 23 . The change in the thickness T (mm) of the converting agent-containing portion 35 in the third direction D3 may be continuous as in the illustrated example, or may be stepwise.

In the example shown in FIGS. 10A-11B, an intermediate layer 32 may be provided in contact with the support substrate 25 and the wavelength selective reflective layer 40 . 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 variation, the intermediate layer 32 may include a first portion 33A and a second portion 33B, the first portion 33A being constituted by the converting agent-containing portion 35 shown in FIGS. 10A-11B. . The second portion 33B may contain the wavelength converting agent 38 at a lower content rate than the first portion 33A, or may not contain the wavelength converting agent 38 . In these examples, as in the example shown in FIGS. 10A-11B, the volume of wavelength converting agent 38 in reference volume region 35V increases with distance from nearest light source 23. FIG.

The optical member 30 shown in FIG. 2 includes a wavelength selective reflection layer 40, an optical sheet 50, and a reflective polarizing plate 60 in order from the support substrate 25 side in the third direction D3. The wavelength selective reflection layer 40, the optical sheet 50, and the reflective polarizing plate 60 may be bonded to each other, may be simply in contact and not bonded, or may be separated from each other. may be

The wavelength selective reflection layer 40 is a reflection layer having wavelength selectivity. The reflectance of the wavelength selective reflection layer 40 changes according to the wavelength of incident light. The transmittance (%) of the wavelength selective reflection layer 40 changes according to the wavelength of incident light. The wavelength selective reflection layer 40 in this embodiment is used together with the wavelength conversion agent 38 described above. The wavelength converting agent 38 absorbs the primary light LA from the light source 23 and emits secondary light LB of different wavelength. The reflectance of the secondary light LB in the wavelength selective reflection layer 40 is smaller than the reflectance of the primary light LA in the wavelength selective reflection layer 40 . The transmittance of the secondary light LB in the wavelength selective reflection layer 40 is higher than the transmittance of the primary light LA in the wavelength selective reflection layer 40 .

The reflectance and transmittance of the wavelength selective reflection layer 40 are values measured using a spectrophotometer ("UV-3100PC" manufactured by Shimadzu Corporation, JIS K 0115 compliant product).

FIG. 13 is a graph showing an example of reflection characteristics and transmission characteristics of the wavelength selective reflection layer 40 depending on 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 visible light reflectance of the wavelength selective reflection layer 40 may be smaller than the invisible light reflectance of the wavelength selective reflection layer 40 .

The reflection characteristics and transmission characteristics shown in the graph of FIG. 13 are characteristics for light that travels in the normal direction of the wavelength selective reflection layer 40 and enters the wavelength selective reflection layer 40 . Further, in this specification, if there is no description of the incident direction of the incident light, the reflectance and the transmittance of the wavelength selective reflection layer 40 advances in the normal direction of the wavelength selective reflection layer 40 and enters the wavelength selective reflection layer 40. It means the characteristic for the light to be applied.

The reflectance of the wavelength selective reflection layer 40 for light with a wavelength of less than 360 nm, or the reflectance of the wavelength selective reflection layer 40 for light with a wavelength of 300 nm or more and less than 360 nm may be 30% or more, or 50% or more. , 80% or more, or 90% or more. The reflectance of the wavelength selective reflection layer 40 for light with a wavelength of less than 340 nm, or the reflectance of the wavelength selective reflection layer 40 for light with a wavelength of 300 nm or more and less than 340 nm may be 50% or more, or 80% or more. , 90% or more, or 95% or more. The reflectance of the wavelength selective reflection layer 40 with respect to the center wavelength light 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. may be

The reflectance of the wavelength selective reflection layer 40 for light with 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 reflection layer 40 for light with 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 reflection layer 40 with respect to the central wavelength of the secondary light LB emitted from the wavelength conversion agent 38 may be 50% or less, 20% or less, or 10% or less, It may be 5% or less.

When multiple types of wavelength conversion agents 38 are provided in the surface light source device 20, the reflectance of the wavelength selective reflection layer 40 with respect to the central wavelength of the secondary light LB emitted from each type of wavelength conversion agent 38 is , 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 with respect to the central wavelength of the first secondary light LB1 emitted from the first wavelength conversion agent 38A may be 50% or less. % or less, 10% or less, or 5% or less. The reflectance of the wavelength selective reflection layer 40 with respect to the center wavelength light of the second secondary light LB2 emitted from the second wavelength conversion agent 38B may be 50% or less, 20% or less, or 10% or less. , or 5% or less. The reflectance of the wavelength selective reflection layer 40 with respect to the center wavelength light of the third secondary light LB3 emitted from the third wavelength conversion agent 38C may be 50% or less, 20% or less, or 10% or less. , or 5% or less.

The transmittance of the wavelength selective reflection layer 40 for light with a wavelength of less than 360 nm, or the transmittance of the wavelength selective reflection layer 40 for light with a wavelength of 300 nm or more and less than 360 nm may be less than 70% or less than 50%. , may be less than 20%, or less than 10%. The transmittance of the wavelength selective reflection layer 40 for light with a wavelength of less than 340 nm, or the transmittance of the wavelength selective reflection layer 40 for light with a wavelength of 300 nm or more and less than 340 nm may be less than 50% or less than 20%. , may be less than 10%, or less than 5%. The transmittance of the wavelength selective reflection layer 40 to the light of the 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%. may be

The transmittance of the wavelength selective reflection layer 40 for light with a wavelength of 380 nm or more and 780 nm or less may be greater than 30%, may be 50% or more, may be 80% or more, or may be 90% or more. The transmittance of the wavelength selective reflection layer 40 for light with a wavelength of 420 nm or more and 700 nm or less may be 50% or more, 80% or more, 90% or more, or 95% or more. The transmittance of the wavelength selective reflection layer 40 to the center wavelength light of the secondary light LB emitted from the wavelength conversion agent 38 may be greater than 50%, may be greater than 80%, or may be greater than 90%. It may be large and may be greater than 95%.

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

The wavelength selective reflection layer 40 is not particularly limited as long as it has wavelength dependence of reflectance and transmittance. As a specific example, the wavelength selective reflection layer 40 may be a dielectric multilayer film with a high degree of freedom in designing reflection and transmission characteristics.

As the dielectric multilayer film forming the wavelength selective reflection layer 40, an inorganic compound multilayer film in which inorganic layers having different refractive indices are alternately laminated may be used. As another example, a resin multilayer film in which resin layers having different refractive indices are alternately laminated may be used as the wavelength selective reflection layer 40 .

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

A dielectric multilayer film as a resin multilayer film includes, for example, many layers of thermoplastic resin or thermosetting resin. The resin layer contains various additives such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducers, heat stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, and refractive index adjusters. A dopant or the like for the above may be added.

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

The number of laminated layers of the high refractive index resin layer and the low refractive index resin layer 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 layer and the low refractive index resin layer can be alternately laminated with 30 layers or more, and each layer may be laminated with 200 layers or more. Also, the total number of laminated layers of the high refractive index resin layers and the low refractive index resin layers can be, for example, 600 layers or more. If the number of laminated layers is too small, sufficient reflectance may not be obtained. Moreover, a desired reflectance can be easily obtained by setting the number of laminations within the above range.

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 forming the dielectric multilayer film may have the surface layers on both sides. The thickness of the surface layer may be 5 μm or more.

Examples of a method for producing a multilayer resin film that constitutes a dielectric multilayer film include a coextrusion method and the like. Specifically, the method for producing a laminated film described in JP-A-2008-200861 can be referred to.

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

In the example shown in FIGS. 14A and 14B, the optical sheet 50 has a light entrance side 50a and a light exit side 50b. Among them, the light incident side surface 50a is a flat surface. The light exit side surface 50b is an uneven surface 51. As shown in FIG. The body portion 52 faces the wavelength selective reflection layer 40 . The body portion 52 may contact the wavelength selective reflection layer 40 . The body portion 52 may be bonded to the wavelength selective reflection layer 40 . The optical sheet 50 includes a sheet-like 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 including elements called unit shaped elements, unit prisms, and unit lenses. The unit optical element 55 is provided on the body portion 52 . The uneven surface 51 is formed by a plurality of unit optical elements 55 .

The optical sheet 50 shown in FIG. 14A has a plurality of convex portions 53 provided on the surface of the body portion 52 facing the reflective polarizing plate 60 . In the example shown in FIG. 14A, a plurality of protrusions 53 are provided adjacent to each other without gaps. The optical sheet 50 shown in FIG. 14B has a plurality of concave portions 54 provided on the surface of the body portion 52 facing the reflective polarizing plate 60 . In the example shown in FIG. 14B, a plurality of recesses 54 are provided adjacent to each other without any gaps.

As shown in FIGS. 14A and 14B, the unit optical element 55 has an element surface 56 inclined with respect to the third direction D3. A unit optical element 55 is defined by this element surface 56 . The uneven surface 51 of the optical sheet 50 is formed by the element surfaces 56 of the unit optical elements 55 .

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

A plurality of unit optical elements 55 included in the optical sheet 50 may be arranged two-dimensionally. 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 . In other words, 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 rotationally symmetrical about the third direction D3. For example, each unit optical element 55 may be configured with 3-fold, 4-fold, or 6-fold symmetry about the third direction D3.

15A and 15B show specific examples of unit optical elements 55 in the optical sheet 50. FIG. In the example shown in FIGS. 15A and 15B, the multiple unit optical elements 55 are arranged in a square arrangement. The plurality of unit optical elements 55 are arranged at a constant pitch in the first direction D1. The plurality of 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 FIGS. 15A and 15B, a plurality of unit optical elements 55 are laid out 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 may be 0.1 mm or more and 0.5 mm or less. In the example shown in FIGS. 15A and 15B, the unit optical element 55 is configured as a quadrangular pyramid-shaped protrusion 53 or recess 54 having a square bottom surface. 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.

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

As shown in FIG. 15D, the plurality of unit optical elements 55 included in the optical sheet 50 may be arranged one-dimensionally. That is, a plurality of unit optical elements 55 may be arranged in the arrangement direction, and each unit optical element 55 may linearly extend 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 orthogonal to the arrangement direction. The unit optical elements 55 may be arranged in the first direction D1. The unit optical element 55 may extend linearly in the 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 in both the first direction D1 and the second direction D2. The arrangement direction of the unit optical elements 55 may be a direction inclined by 45° with respect to the first direction D1 and the second direction D2.

The plurality of unit optical elements 55 may be arranged irregularly or may be arranged regularly. By regularly arranging the plurality of unit optical elements 55, the design of the optical sheet 50 can be facilitated. Also, by regularly arranging the plurality of unit optical elements 55, it becomes easy to spread the unit optical elements 55 without gaps.

The reflective polarizing plate 60 is overlapped with the optical sheet 50 in the third direction D3. The optical sheet 50 is positioned between the reflective polarizing plate 60 and the wavelength selective reflecting layer 40 in the third direction D3. The reflective polarizing plate 60 transmits one linearly polarized light component and reflects the other linearly polarized light component. According to the reflective polarizing plate 60, it is possible to selectively transmit the linearly polarized light component that can be transmitted through the polarizing plate located on the surface light source device 20 side of the display panel 15. FIG. The light reflected by the reflective polarizing plate 60 can re-enter the reflective polarizing plate 60 with its polarization state changed by subsequent reflection or the like. As the reflective polarizing plate 60, "DBEF" (registered trademark) available from US 3M Company may be used. As the reflective polarizing plate 60, a high brightness polarizing sheet "WRPS" available from Shinwa Intertek Co., Ltd. in Korea, a wire grid polarizer, or the like may be used.

Next, the operation of generating planar light with the planar light source device 20 having the above configuration will be described mainly with reference to FIGS. 16 and 17. FIG.

As shown in FIG. 16, a light source 23 emits primary light LA. The primary light LA is, for example, ultraviolet rays. The wavelength of this primary light LA is less than 380 nm. Primary light LA emitted by the light source 23 travels toward the conversion agent-containing portion 35 containing the wavelength conversion agent 38 . A portion of the primary light LA enters the wavelength converting agent 38 and is absorbed, as shown in FIG. The wavelength conversion agent 38 that has absorbed the primary light LA emits secondary light LB. The secondary light LB is emitted from the wavelength converting agent 38 as diffused light regardless of the incident path of the primary light LA to the wavelength converting agent 38 . The remaining primary light LA that has entered the converting agent-containing portion 35 does not collide with the wavelength converting agent 38 and passes through the converting agent-containing portion 35 .

The primary light LA and the 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 in the wavelength selective reflection layer 40 is smaller than the reflectance of the primary light LA in the wavelength selective reflection layer 40 . For example, the reflectance of the secondary light LB in the wavelength selective reflection layer 40 is 50% or less. The reflectance of the primary light LA in 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 pass through the wavelength selective reflection layer 40 . As a result, only the secondary light LB emitted from the wavelength converting agent 38 exits in the area immediately above the light source 23 . As a result, it is possible to prevent the area immediately above the light source 23 from becoming too bright.

The surface light source device 20 shown in FIG. 16 is the same as the surface light source device 20 shown in FIG. In this example, by reducing the content ratio (%) of the wavelength conversion agent 38 in the conversion agent-containing portion 35, the illuminance in the area immediately above the light source 23 can be reduced.

As shown in FIG. 16, the light L161 and the light L162 as the primary light LA reflected by the wavelength selective reflection layer 40 are reflected by the reflection layer 27 and the wavelength selective reflection layer 40 until they are wavelength-converted by the wavelength conversion agent 38. be done. These light L161 and light L162 travel in a first direction D1 and a second direction D2 orthogonal to the third direction D3. The light L161 and the light L162 move away from the light source 23 and are absorbed by the wavelength converting agent 38 with a certain probability when passing through the converting agent containing portion 35 . These light L161 and light L162 are transmitted through the wavelength selective reflection layer 40 in a region distant from the light source 23 . As a result, it is possible to prevent the area away from the light source 23 from becoming too dark.

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 ratio (%) of the wavelength conversion agent 38 in the conversion agent-containing portion 35, the primary light LA moves in the first direction D1 and the second direction D2 orthogonal to the third direction D3. is promoted. Therefore, by reducing the content ratio (%) of the wavelength converting agent 38 in the converting agent containing portion 35, the area remote from the light source 23 can be brightened.

As described above, the cooperation of the wavelength conversion agent 38 and the wavelength selective reflection layer 40 effectively eliminates uneven brightness according to the distance from the light source 23, and the illuminance at the light exit side surface 40b of the wavelength selective reflection layer 40 is The distribution is well homogenized.

From the viewpoint of illuminance uniformity, the wavelength conversion agent 38 may be arranged in consideration of the arrangement of the light source 23 as shown in FIGS. 8 to 12A. Specifically, the volume of the wavelength conversion agent 38 contained in one reference volume region 35V is positioned between the one reference volume region 35V and the one light source 23 closest to the one reference volume region 35V. It may be larger than the volume of the wavelength conversion agent 38 contained in another reference volume region 35V. Furthermore, the volume of the wavelength conversion agent 38 contained in any one reference volume region 35V is transferred to any other reference volume region 35V located between one reference volume region 35V and one light source 23. It may be equal to or larger than the volume of the wavelength conversion agent 38 contained.

According to these specific examples, it is possible to suppress the conversion of the primary light LA into the secondary light LB by the wavelength conversion agent 38 in the area immediately above the light source 23 . Therefore, it is possible to more effectively prevent the area immediately above the light source 23 from becoming too bright. On the other hand, in areas away from the light source 23 in the first direction D1 or the second direction D2, 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 areas away from the light source 23 from becoming too dark. As a result, the surface light source device 20 can be sufficiently thinned, and the in-plane distribution of brightness can be made sufficiently uniform.

Also, in the area between the 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, the light emitted by one light source 23 can be prevented from moving to the vicinity of other light sources 23 . That is, the number of reflections of the primary light LA can be reduced. As a result, the reflection loss can be suppressed and the utilization efficiency of the light source 23 can be improved.

By the way, local dimming is known as a control method for controlling lighting and extinguishing 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 portion of the image is turned off and the light source 23 facing the bright portion of the image is turned on. Image contrast can be improved by using local dimming. Especially in a liquid crystal display device in which oblique light leaks from the display panel 15, local lighting is considered to be effective control. By setting the distribution of the arrangement of the wavelength conversion agent 38 as shown in FIGS. 8 to 12A, in the area between the two adjacent light sources 23, the wavelength conversion agent 38 converts the primary light LA to the secondary light LB. conversion of This can prevent the primary light LA emitted from one light source 23 from reaching the vicinity of the other light sources 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 another adjacent light source 23 . This makes it possible to effectively utilize local dimming.

As shown in FIG. 17, light transmitted through the wavelength selective reflection layer 40 travels toward the optical sheet 50 . As shown in FIG. 17 , the light exit side surface 50 b of the optical sheet 50 facing the wavelength selective reflection layer 40 is an uneven surface 51 . Lights L171 and L172 emitted from the wavelength selective reflection layer 40 travel in directions greatly inclined with respect to the third direction D3. These lights L171 and L172 are emitted from the optical sheet 50 after passing through the element surface 56 inclined in the direction opposite to the traveling direction of the third direction D3. The light beams L171 and L172 are refracted at the element surface 56 to bend the direction of travel. At this time, the traveling directions of the lights L171 and L172 are bent so that the angle with respect to the third direction D3 becomes small. That is, the angles formed by the traveling directions of the lights L171 and L172 with respect to the third direction D3 decrease due to the refraction of the lights L171 and L172 on the element surface 56 . That is, the optical sheet 50 exhibits the function of condensing the emitted light from the surface light source device 20 in the third direction D3.

The light emitted from the optical sheet 50 enters the reflective polarizing plate 60 . The reflective polarizing plate 60 transmits linearly polarized light components that can enter the display panel 15 and reflects linearly polarized light components that cannot enter the display panel 15 . The reflected light repeats reflection and the like, and can re-enter the reflective polarizing plate 60 as a linearly polarized component that can enter the display panel 15 . Such a polarization splitting function of the reflective polarizing plate 60 can significantly improve the utilization efficiency of the light source 23 .

As described above, the light emitting surface 20a emits light to illuminate the display panel 15, for example.

As noted above, light source 23 may emit light at wavelengths 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 reflection layer 40 with a non-uniform in-plane distribution of the light amount, the light-emitting surface 20a of the surface light source device 20 does not have color unevenness that can be perceived by an observer. can be suppressed. In this specific example, a layer containing an ultraviolet absorber may be provided between the wavelength selective reflection layer 40 and the display surface 15a in the third direction D3. For example, the optical sheet 50 and the reflective polarizing plate 60 may contain a layer containing an ultraviolet absorber.

By the way, the wavelength selective reflection layer 40 made of, for example, a dielectric multilayer film has a wavelength λ = λ/cos θ. That is, the optical action of the wavelength selective reflection layer 40 on light with a wavelength λx (nm) traveling in a direction inclined by θ (°) with respect to the third direction D3 is the light with a wavelength λ=λ/cos θ traveling in the third direction D3. can be the same as the optical action of the wavelength selective reflection layer 40 for Therefore, the same optical action as that for the primary light LA traveling in the third direction D3 can be exerted on the secondary light LB traveling obliquely.

From this point, in the specific example described above, the shortest wavelength (nm) of the secondary light LB obtained by conversion by the wavelength conversion agent 38 is 1.31 (=1/cos 40°) of the wavelength λ1 (nm) of the primary light. ) may be doubled or more. The shortest wavelength (nm) of the secondary light LB is the shortest wavelength of the emitted light emitted by the wavelength conversion agent 38 when the surface light source device 20 includes a plurality of types of wavelength conversion agents 38 . means the center wavelength of the emitted light. In the example shown in FIG. 5, the central wavelength (nm) of the first secondary light LB1 emitted from the first wavelength converting agent 38A is the shortest wavelength of the secondary light LB obtained by conversion by the wavelength converting agent 38. (nm).

According to this example, the secondary light LB traveling in the direction forming an angle of less than 40° with respect to the third direction D3 in the wavelength selective reflection layer 40 is reflected by the wavelength selective reflection layer 40 to the same extent as the primary light LA. can be suppressed. The reflectance in the wavelength selective reflection layer 40 of the secondary light LB traveling in a direction forming an angle of less than 40° with respect to the third direction D3 in the wavelength selective reflection layer 40 is calculated as can be reduced from the reflectance of Therefore, the transmittance of the wavelength selective reflection layer 40 for the secondary light LB can be sufficiently improved. As a result, unnecessary reflection can be avoided and the utilization efficiency of the light source 23 can be improved.

The wavelength selective reflection layer 40 can be produced using a resin having a refractive index of 1.4 or more and 1.6 or less. The total reflection critical angle at the interface between the wavelength selective reflection layer 40 and the air layer is 38.7° or more and 45.6° or less. That is, light traveling through 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 by 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 by the wavelength conversion agent 38 is 1.31 (=1/cos 40°) times or more the wavelength λ1 of the primary light LA, different Color unevenness can be suppressed in the surface light source device 20 in which the secondary light LB of a plurality of wavelengths is transmitted through the wavelength selective reflection layer 40 .

In the embodiment described above, the surface light source device 20 includes the wavelength selective reflection layer 40, the light source substrate 22, the wavelength conversion agent 38 positioned between the wavelength selective reflection layer 40 and the light source substrate 22, have The light source substrate 22 includes a light source 23 facing the wavelength selective reflection 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 secondary light having a wavelength different from the wavelength of the primary light LA. The reflectance of the secondary light LB in the wavelength selective reflection layer 40 is smaller than the reflectance of the primary light LA in the wavelength selective reflection layer 40 .

In this embodiment, the reflectance at the wavelength selective reflective layer 40 depends on the wavelength of light. Therefore, the primary light LA emitted from the light source 23 can be repeatedly reflected by the wavelength selective reflection layer 40 and the reflection 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 . As a result, it is possible to prevent the illuminance in the area immediately above the light source 23 from becoming too high. Higher illuminance can be obtained in areas away from the light source 23 . As a result, the distribution of brightness caused by the light source 23 is eliminated, and the in-plane distribution of illuminance can be effectively uniformed. Also, the primary light LA emitted from the light source 23 is suppressed from transmitting through the wavelength selective reflection layer 40 until it is converted into the secondary light LB by the wavelength conversion agent 38 . Therefore, even if the distance from the light source substrate 22 to the wavelength selective reflection layer 40 is shortened, the primary light LA can be sufficiently diffused between the wavelength selective reflection 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.

Incidentally, in the 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 increased in order to ensure the chance of collision between the primary light and the wavelength conversion agent. . However, in this 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 converting agent 38 . Therefore, even if the thickness of the conversion agent containing portion 35 containing the wavelength conversion agent 38 is reduced, the primary light LA can be sufficiently converted into the secondary light LB by the wavelength conversion agent 38 . By thinning the converting agent-containing portion 35 containing the wavelength converting agent 38, the surface light source device 20 can be further thinned. Moreover, 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.

In the specific example of one 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 . One or more of the thickness (mm) of the conversion agent-containing portion 35, the ratio (%) of the area where the conversion agent-containing portion 35 is arranged, and the content ratio (%) of the wavelength conversion agent 38 contained in the conversion agent-containing portion 35 changes according to the distance from the light source 23 . In such an example, the converting agent-containing portion 35 can be produced by a simple method such as printing or shaping. According to this converting agent-containing portion 35, the distribution of the wavelength converting agent 38 can be adjusted with a high degree of freedom. As a result, the surface light source device 20 can be sufficiently thinned, and the in-plane distribution of brightness can be made sufficiently uniform.

In the specific example of one 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 . The conversion agent-containing portion 35 constitutes 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 Japanese Patent No. 6299811, light is usually diffused by refraction or total reflection at a refractive index interface in order to achieve uniform brightness. On the other hand, in this embodiment, the wavelength conversion agent 38 of the wavelength selective reflection layer 40 diffuses the light emitted from the light source 23 . Therefore, the intermediate layer 32 can be arranged between the wavelength selective reflection layer 40 and the light source substrate 22 because it is not necessary to use an interface with a large refractive index difference. 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 part or all of the intermediate layer 32. are doing. The intermediate layer 32 allows the wavelength selective reflective layer 40 to be properly aligned with respect to the light source 23 . Also, the wavelength conversion agent 38 can be positioned at an appropriate position with respect to the light source 23 . As a result, the uniformity of the in-plane distribution of brightness can be stably ensured.

In the specific example of one embodiment described above, the intermediate layer 32 includes a first portion 33A containing the wavelength converting agent 38 and a content ratio (%) of the wavelength converting agent 38 lower than that of the first portion 33A. and a second portion 33B that does not contain 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 shaping. The distribution of the wavelength conversion agent 38 can be adjusted with a high degree of freedom by the intermediate layer 32 including the first portion 33A and the second portion 33B. As a result, the surface light source device 20 can be sufficiently thinned, and the in-plane distribution of brightness can be made sufficiently uniform.

In the specific example of one embodiment described above, the intermediate layer 32 is bonded to at least one of the wavelength selective reflection layer 40 and the light source substrate 22 . According to this embodiment, the intermediate layer 32 allows the wavelength-selective reflective layer 40 to be maintained in an appropriate position with respect to the light source 23 . Also, the wavelength conversion agent 38 can be maintained at an appropriate position with respect to the light source 23 . As a result, the in-plane distribution of brightness can be stably uniformed during use of the surface light source device 20 .

In the specific example of the embodiment described above, the optical sheet 50 has a light entrance side surface 50a facing the wavelength selective reflection layer 40 and a light exit side surface 50b facing the light entrance side surface 50a. is. The wavelength selective reflection layer 40 is positioned 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, lights L171 and L172 traveling from the wavelength selective reflection layer 40 to the optical sheet 50 travel in directions forming a large angle with respect to the third direction D3. The optical sheet 50 can bend the traveling directions of the lights L171 and L172 by refraction. That is, the optical sheet 50 can adjust the traveling directions of the lights L171 and L172 emitted from the wavelength selective reflection layer 40 so as to significantly reduce the angles formed by the traveling directions of the lights L171 and L172 with respect to the third direction D3. . Thereby, the front direction luminance of the surface light source device 20 can be effectively improved.

Although one embodiment has been described with reference to specific examples, the above specific examples do not limit one embodiment. The embodiment described above can be implemented in various other specific examples, and various omissions, replacements, changes, additions, etc. can be made without departing from the scope of the invention.

An example of modification will be described below with reference to the drawings. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding portions in the above-described specific example are used for portions that can be configured in the same manner as in the above-described specific example, and redundant description is omitted. omitted.

As an example, intermediate layer 32 may include a light diffusing component 39, as shown in FIG. 12B. Examples of the light diffusing component 39 include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles. By including the light diffusion component 39, the in-plane distribution of brightness can be made more uniform. Additionally, the distribution of the wavelength converting agent 38 can be made sufficiently inconspicuous. In the example shown in FIG. 12B, second portion 33B includes light diffusing component 39. In the example shown in FIG. The second portion 33B contains the wavelength converting agent 38 at a content rate (%) lower than that of the first portion 33A, or does not contain the wavelength converting agent 38 . Second portion 33B is at least partially located between first portion 33A and wavelength selective reflective 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 diffusion component 39. FIG.

As shown in FIG. 18, the intermediate layer 32 may be in contact with the portion of the light source 23 where the primary light LA is emitted. That is, intermediate layer 32 may be in contact with emission surface 23S of light source 23 . According to this example, the emitting surface 23 S of the light source 23 is in optical contact with the intermediate layer 32 . As shown in FIG. 18, the edges of the emission surface 23S are generally curved. Total reflection of the light L182 generated by the light source 23 can occur at this curved portion. By covering this curved portion with the intermediate layer 32, the refractive index difference is reduced and total reflection is suppressed. Thereby, the utilization efficiency of the light source 23 can be improved. In the first place, the usable light L181 is light traveling in an oblique direction and can contribute to uniform brightness. In addition, the intermediate layer 32 can protect the emission surface 23S of the light source 23 .

The optical member 30 may further include a second optical sheet stacked 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 on the optical sheet 50 and the arrangement direction of the unit optical elements 55 on the second optical sheet may be non-parallel or orthogonal.

D1: first direction, D2: second direction, D3: third direction, LA: primary light, LB: secondary light, LB1: first secondary light, LB2: second secondary light, LB3: third secondary light Next 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 35: Converting agent-containing part 35A: Area 35V: Reference volume area , 36: base material part, 38: wavelength conversion agent, 38A: first wavelength conversion agent, 38B: second wavelength conversion agent, 38C: third wavelength conversion agent, 39: light diffusion component, 40: wavelength selective reflection layer, 40a: light incident side surface 40b: light exit side surface 50: optical sheet 50a: light entrance side surface 50b: light exit side surface 51: uneven surface 52: body portion 53: convex portion 54: concave portion 55: unit optics element, 56: element surface, 60: reflective polarizing plate

Claims (13)

a wavelength selective reflection 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 reflection 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 surface light source device, wherein the reflectance of the secondary light in the wavelength selective reflection layer is smaller than the reflectance of the primary light in the wavelength selective reflection layer. If a region having a certain area of the wavelength selective reflection layer overlaps with the wavelength selective reflection layer and the light source substrate in the direction in which the wavelength selective reflection layer and the light source substrate face each other and is defined as a reference volume region, ,
The volume of the wavelength converting agent included in one reference volume region is included in another reference volume region located between the one reference volume region and the one light source closest to the one reference volume region. 2. The surface light source device according to claim 1, wherein the volume of said wavelength converting agent is larger than the volume of said wavelength converting agent. The volume of the wavelength conversion agent included in any one reference volume region is the wavelength conversion agent included in any other reference volume region located between the one reference volume region and the one light source. 3. The surface light source device according to claim 2, which is equal to or greater than the volume of the agent. A conversion agent-containing portion containing the wavelength conversion agent is 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 ratio of the area where the conversion agent-containing portion is arranged, and the content ratio of the wavelength conversion agent contained in the conversion agent-containing portion depend on the distance from the light source. 4. The surface light source device according to any one of claims 1 to 3, wherein A conversion agent-containing portion containing the wavelength conversion agent is provided between the wavelength selective reflection layer and the light source substrate,
The surface light source device according to any one of claims 1 to 4, wherein the conversion agent-containing portion constitutes part or all of an intermediate layer that maintains a constant distance between the wavelength selective reflection layer and the light source substrate. . The intermediate layer includes a first portion containing the wavelength converting agent and a second portion containing the wavelength converting agent at a lower content rate than the first portion or not containing the wavelength converting agent, The surface light source device according to claim 5. 7. The surface light source device according to claim 5, wherein said intermediate layer contains a light diffusing component. the second portion includes a light diffusing component;
7. The surface light source device of claim 6, wherein said second portion is at least partially located between said first portion and said wavelength selective reflective layer. 9. The surface light source device according to claim 5, wherein said intermediate layer is bonded to at least one of said wavelength selective reflection layer and said light source substrate. 10. The surface light source device according to claim 5, wherein said intermediate layer is in contact with a portion of said light source where said primary light is emitted. The surface light source device according to any one of claims 1 to 10, wherein the light source emits light with a wavelength of less than 380 nm. 12. The surface light source device according to claim 1, wherein the shortest wavelength of said secondary light is 1.31 times or more the wavelength of said primary light. The surface light source device according to any one of claims 1 to 12;
A display device comprising: a display panel stacked on the surface light source device.

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