WO2023100959A1 - Optical member, surface light source device, display device, and wavelength conversion sheet - Google Patents

Abstract

This optical member comprises: a selective transmission sheet including a selective transmission part; and a wavelength conversion sheet superposed on the selective transmission sheet. The transmittance of the selective transmission part with respect to light having a specific wavelength and entering the selective transmission part at a certain incident angle of more than 0° is greater than the transmittance of the selective transmission part with respect to light having the specific wavelength but entering the selective transmission part at an incident angle of 0°. The wavelength conversion sheet includes a first surface and a second surface opposite to the first surface. At least one of the first and second surfaces includes a protrusion-recess surface. The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light. The secondary light has a wavelength different from that of the primary light.

Description

Optical member, surface light source device, display device and wavelength conversion sheet

The present invention relates to optical members, surface light source devices, display devices and wavelength conversion sheets.

As disclosed in Patent Document 1 (JP2013-519232A), a surface light source device having a monochromatic light source is known. The surface light source device of Patent Document 1 includes a fluorescent layer containing a wavelength conversion agent. When light from a light source impinges on the wavelength converting agent, the wavelength converting agent absorbs the light from the light source and emits light of a different wavelength. By including a sufficient amount of wavelength converting agent in the fluorescent layer, the emission color can be adjusted.

The present disclosure aims to reduce the amount of wavelength conversion agent.

An embodiment of the present disclosure relates to the following [1] to [62].

[1] a selective transmission sheet including a selective transmission portion;
and a wavelength conversion sheet superimposed on the selective transmission sheet,
The transmittance of the selective transmission section for the light of the specific wavelength incident on the selective transmission section at an incident angle greater than 0° is the transmittance of the light of the specific wavelength incident on the selective transmission section at an incident angle of 0°. is greater than the transmittance of the selective transmission portion of
The wavelength conversion sheet includes a first surface and a second surface facing the first surface,
at least one of the first surface and the second surface includes an uneven surface;
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
The optical member, wherein the secondary light has a wavelength different from that of the primary light.

[2] the first surface is positioned between the selectively permeable sheet and the second surface;
The optical member according to [1], wherein the second surface includes the uneven surface.

[3] The optical member of [2], wherein the selective transmission sheet is joined to the wavelength conversion sheet.

[4] further comprising a light diffusion sheet joined to the selective transmission sheet,
The optical member of [2] or [3], wherein the selective transmission sheet is positioned between the light diffusion sheet and the wavelength conversion sheet.

[5] The wavelength conversion sheet includes a wavelength conversion section containing the wavelength conversion agent, a first barrier layer and a second barrier layer superimposed on the wavelength conversion section, and the uneven surface superposed on the second barrier layer an optical element portion including
the wavelength conversion part is located between the first barrier layer and the second barrier layer,
The optical member according to any one of [2] to [4], wherein the second barrier layer is positioned between the wavelength conversion section and the optical element section.

[6] The first surface is positioned between the selectively permeable sheet and the second surface,
The optical member according to [1], wherein the first surface includes the uneven surface.

[7] The optical member according to [6], wherein the selective transmission portion has a transmittance of 5% or less with respect to the light of the specific wavelength incident on the selective transmission portion at an incident angle of 0°.

[8] The optical member according to [6] or [7], wherein the transmittance of the selective transmission portion with respect to the light of the specific wavelength emitted from the selective transmission sheet at an emission angle of 0° is 5% or less.

[9] The transmittance of the selective transmission portion for the light of the specific wavelength emitted from the selective transmission sheet at an emission angle of 0° or more and 35° or less in absolute value is the maximum value of the transmittance of the selective transmission portion. The optical member according to any one of [6] to [8], which is half or less.

[10] The inclination angle θp (°) of the element surface that constitutes the uneven surface and the refractive index np of the portion that constitutes the element surface of the wavelength conversion sheet satisfy the following formula,
sin ⁻¹ (1/np)≦90−θp
The optical system according to any one of [6] to [9], wherein the tilt angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane. Element.

[11] Inclination angle θp (°) of the element surface forming the uneven surface, refractive index np of the portion forming the element surface of the wavelength conversion sheet, and angle θx (°) with respect to the incident direction to the wavelength conversion sheet satisfies
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the light incident on the selective transmission portion from the selective transmission sheet at an incident angle at which the transmittance of the light of the specific wavelength in the selective transmission portion is 1/2 of the maximum value. The optical member according to any one of [6] to [10], wherein the angle between the emission direction and the lamination direction.

[12] Inclination angle θp (°) of the element surface forming the uneven surface, refractive index np of the portion forming the element surface of the wavelength conversion sheet, and angle θx (°) with respect to the incident direction to the wavelength conversion sheet satisfies
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak from the selective transmission sheet of the light incident on the selective transmission section at an incident angle at which the transmittance of the light of the specific wavelength at the selective transmission section is 1/10 of the maximum value. The optical member according to any one of [6] to [11], wherein the angle between the emitting direction and the stacking direction.

[13] The wavelength conversion agent includes a first conversion agent that absorbs the primary light and emits first secondary light, and a second conversion agent that absorbs the primary light and emits second secondary light. , including
the wavelength of the second secondary light is longer than the wavelength of the first secondary light;
the wavelength of the first secondary light is longer than the wavelength of the primary light;
The optical member according to any one of [1] to [12], wherein the conversion efficiency of the second conversion agent in the wavelength conversion sheet is higher than the conversion efficiency of the first conversion agent in the wavelength conversion sheet.

[14] The wavelength conversion sheet includes: a wavelength conversion section containing the wavelength conversion agent; a first barrier layer and a second barrier layer superimposed on the wavelength conversion section; an optical element portion including
the wavelength conversion part is located between the first barrier layer and the second barrier layer,
The optical member according to any one of [6] to [13], wherein the first barrier layer is positioned between the wavelength conversion section and the optical element section.

[15] a light diffusion sheet;
and a wavelength conversion sheet superimposed on the light diffusion sheet,
The wavelength conversion sheet includes a first surface and a second surface facing the first surface,
The first surface is located between the light diffusion sheet and the second surface,
the second surface includes an uneven surface;
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
The optical member, wherein the secondary light has a wavelength different from that of the primary light.

[16] The optical member according to any one of [1] to [15], wherein the transmission internal haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light is 45% or less.

[17] The optical member according to any one of [1] to [16], wherein the transmission internal haze of the wavelength conversion sheet is 50% or less.

[18] a selective transmission sheet including a selective transmission portion;
and a wavelength conversion sheet superimposed on the selective transmission sheet,
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The wavelength conversion sheet includes an uneven surface,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein the transmission internal haze of the wavelength conversion sheet for light having a wavelength different from that of the primary light is 45% or less.

[19] The optical member according to [18], wherein the transmission internal haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light is 18% or less.

[20] a selective transmission sheet including a selective transmission part;
and a wavelength conversion sheet superimposed on the selective transmission sheet,
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The wavelength conversion sheet includes an uneven surface,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein the transmission internal haze of the wavelength conversion sheet is 50% or less.

[21] The optical member according to [20], wherein the transmission internal haze of the wavelength conversion sheet is 20% or less.

[22] The difference between the transmission internal haze of the wavelength conversion sheet for light of a wavelength different from the primary light and the transmission internal haze of the wavelength conversion sheet is 5% or less of [16] to [21]. any optical member;

[23] The wavelength conversion sheet includes a first surface and a second surface opposite to the first surface,
the first surface is positioned between the selectively permeable sheet and the second surface;
The optical member according to any one of [18] to [22], wherein the first surface includes the uneven surface.

[24] The transmittance of the selective transmission portion for light of a specific wavelength incident on the selective transmission portion at an incident angle greater than 0° is the specific wavelength incident on the selective transmission portion at an incident angle of 0°. is greater than the transmittance of the selective transmission portion for light of [23].

[25] The inclination angle θp (°) of the element surface that constitutes the uneven surface and the refractive index np of the portion that constitutes the element surface of the wavelength conversion sheet satisfy the following formula,
sin ⁻¹ (1/np)≦90−θp
The optical member according to [23] or [24], wherein the inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane.

[26] Inclination angle θp (°) of the element surface forming the uneven surface, refractive index np of the portion forming the element surface of the wavelength conversion sheet, and angle θx (°) with respect to the incident direction to the wavelength conversion sheet satisfies
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the light incident on the selective transmission portion from the selective transmission sheet at an incident angle at which the transmittance of the light of the specific wavelength in the selective transmission portion is 1/2 of the maximum value. The optical member according to any one of [23] to [25], wherein the angle between the emitting direction and the stacking direction.

[27] Inclination angle θp (°) of the element surface forming the uneven surface, refractive index np of the portion forming the element surface of the wavelength conversion sheet, and angle θx (°) with respect to the incident direction to the wavelength conversion sheet satisfies
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak from the selective transmission sheet of the light incident on the selective transmission section at an incident angle at which the transmittance of the light of the specific wavelength at the selective transmission section is 1/10 of the maximum value. The optical member according to any one of [23] to [26], wherein the angle between the emitting direction and the stacking direction.

[28] The wavelength conversion sheet includes a first surface and a second surface opposite to the first surface,
the first surface is positioned between the selectively permeable sheet and the second surface;
The optical member according to any one of [18] to [22], wherein the second surface includes the uneven surface.

[29] The transmittance of the selective transmission section for light of a specific wavelength incident on the selective transmission section at an incident angle of 0° is the transmittance of the specific wavelength incident on the selective transmission section at an incident angle greater than 0°. The optical member according to [28], wherein the transmittance of the selective transmission portion for light is greater than that of the selective transmission portion.

[30] The wavelength conversion sheet includes an optical element portion including the uneven surface,
The optical element section includes a plurality of unit optical elements,
The optical member according to any one of [1] to [29], wherein each unit optical element includes an element surface forming the uneven surface.

[31] The wavelength conversion sheet includes: a wavelength conversion section containing the wavelength conversion agent; a first barrier layer and a second barrier layer superimposed on the wavelength conversion section; an optical element portion including
the wavelength conversion part is located between the first barrier layer and the second barrier layer,
The optical member according to any one of [18] to [30], wherein one of the first barrier layer and the second barrier layer is positioned between the wavelength converting section and the optical element section.

[32] a selective transmission sheet including a selective transmission portion;
an optical sheet having an uneven surface;
a wavelength conversion sheet positioned between the selective transmission sheet and the optical sheet;
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The uneven surface faces the wavelength conversion sheet,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein a transmission haze of the wavelength conversion sheet for light having a wavelength different from that of the primary light is 45% or less.

[33] The optical member according to [32], wherein the transmission haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light is 18% or less.

[34] a selective transmission sheet including a selective transmission portion;
an optical sheet having an uneven surface;
a wavelength conversion sheet positioned between the selective transmission sheet and the optical sheet;
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The uneven surface faces the wavelength conversion sheet,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein the wavelength conversion sheet has a transmission haze of 50% or less.

[35] The optical member of [34], wherein the transmission haze of the wavelength conversion sheet is 20% or less.

[36] Any one of [32] to [35], wherein the difference between the transmission haze of the wavelength conversion sheet and the transmission haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light is 5% or less. optical member.

[37] The transmittance of the selective transmission section for light of a specific wavelength incident on the selective transmission section at an incident angle greater than 0° is the specific wavelength incident on the selective transmission section at an incident angle of 0°. The optical member according to any one of [32] to [36], wherein the transmittance of the selective transmission portion with respect to the light of

[38] The optical sheet includes a plurality of unit optical elements,
The optical member according to any one of [32] to [37], wherein each unit optical element includes an element surface forming the uneven surface.

[39] The wavelength conversion sheet includes a wavelength conversion section containing the wavelength conversion agent, and a first barrier layer and a second barrier layer superimposed on the wavelength conversion section,
The optical member according to any one of [32] to [38], wherein the wavelength converting portion is positioned between the first barrier layer and the second barrier layer.

[40] The inclination angle θp (°) of the element planes forming the uneven surface and the refractive index np of the portion forming the element planes of the optical sheet satisfy the following formula,
sin ⁻¹ (1/np)≦90−θp
[32] to [39], wherein the inclination angle θp (°) is an angle between the element plane and a plane orthogonal to the lamination direction of the selective transmission sheet, the wavelength conversion sheet, and the optical sheet. any optical member;

[41] The inclination angle θp (°) of the element planes forming the concave-convex surface, the refractive index np of the portions forming the element planes of the optical sheet, and the angle θx (°) with respect to the incident direction to the optical sheet are satisfies the following equation,
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is the angle between the plane perpendicular to the lamination direction of the selective transmission sheet, the wavelength conversion sheet and the optical sheet and the element plane,
The angle θx (°) is the peak of the light incident on the selective transmission portion from the selective transmission sheet at an incident angle at which the transmittance of the light of the specific wavelength in the selective transmission portion is 1/2 of the maximum value. The optical member according to any one of [32] to [40], wherein the angle between the emitting direction and the stacking direction.

[42] The inclination angle θp (°) of the element planes forming the concave-convex surface, the refractive index np of the portions forming the element planes of the optical sheet, and the angle θx (°) with respect to the incident direction to the optical sheet are satisfies the following equation,
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is the angle between the plane perpendicular to the lamination direction of the selective transmission sheet, the wavelength conversion sheet and the optical sheet and the element plane,
The angle θx (°) is the peak from the selective transmission sheet of the light incident on the selective transmission section at an incident angle at which the transmittance of the light of the specific wavelength at the selective transmission section is 1/10 of the maximum value. The optical member according to any one of [32] to [41], wherein the angle between the emitting direction and the stacking direction.

[43] The wavelength conversion agent includes a first conversion agent that absorbs the primary light and emits first secondary light, and a second conversion agent that absorbs the primary light and emits second secondary light. , including
the wavelength of the second secondary light is longer than the wavelength of the first secondary light;
The optical member according to any one of [1] to [42], wherein the first secondary light has a longer wavelength than the primary light.

[44] an optical member according to any one of [1] to [43];
and a light source facing the optical member.

[45] an optical member according to any one of [1] to [43];
A surface light source device comprising a light source substrate having a reflective layer facing the optical member and a light source for emitting light incident on the optical member.

[46] an optical member according to any one of [6] to [31];
a light source facing the optical member,
The inclination angle θp (°) of the element surface forming the uneven surface, the refractive index np of the portion forming the element surface of the wavelength conversion sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula of
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the luminance angular distribution on the surface of the selective transmission sheet facing the wavelength conversion sheet obtained in a state where the constituent elements closer to the wavelength conversion sheet than the selective transmission sheet are removed. A surface light source device, which is an angle between a direction in which half the luminance is obtained and the lamination direction.

[47] an optical member according to any one of [6] to [31];
a light source facing the optical member,
The inclination angle θp (°) of the element surface forming the uneven surface, the refractive index np of the portion forming the element surface of the wavelength conversion sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula of
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the luminance angular distribution on the surface of the selective transmission sheet facing the wavelength conversion sheet obtained in a state where the constituent elements closer to the wavelength conversion sheet than the selective transmission sheet are removed. A surface light source device, which is an angle between a direction in which luminance of 1/10 of luminance is obtained and the lamination direction.

[48] an optical member according to any one of [32] to [42];
a light source facing the optical member,
The inclination angle θp (°) of the element planes forming the uneven surface, the refractive index np of the portions forming the element planes of the optical sheet, and the angle θx (°) with respect to the direction of incidence on the optical sheet are obtained by the following equations: The filling,
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is the angle between the plane perpendicular to the lamination direction of the selective transmission sheet, the wavelength conversion sheet and the optical sheet and the element plane,
The angle θx (°) is the peak of the luminance angular distribution on the surface of the selective transmission sheet facing the wavelength conversion sheet obtained in a state where the constituent elements closer to the wavelength conversion sheet than the selective transmission sheet are removed. A surface light source device, which is an angle between a direction in which half the luminance is obtained and the lamination direction.

[49] an optical member according to any one of [32] to [42];
a light source facing the optical member,
The angle of inclination θp (°) of the element surface that constitutes the uneven surface, the refractive index np of the portion that constitutes the element surface of the optical sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula,
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is the angle between the plane perpendicular to the lamination direction of the selective transmission sheet, the wavelength conversion sheet and the optical sheet and the element plane,
The angle θx (°) is the peak of the luminance angular distribution on the surface of the selective transmission sheet facing the wavelength conversion sheet obtained in a state where the constituent elements closer to the wavelength conversion sheet than the selective transmission sheet are removed. A surface light source device, which is an angle between a direction in which luminance of 1/10 of luminance is obtained and the lamination direction.

[50] further comprising a reflective polarizing plate superimposed on the optical member;
The surface light source device according to any one of [44] to [49], wherein the optical member is positioned between the light source and the reflective polarizing plate.

[51] further comprising a light control sheet superimposed on the optical member,
The surface light source device according to any one of [44] to [49], wherein the optical member is positioned between the light source and the light control sheet.

[52] The surface light source device according to any one of [44] to [51], wherein the portion of the optical member closest to the light source substrate and the light source substrate are bonded.

[53] A surface light source device according to any one of [44] to [52];
A display device comprising: a display panel stacked on the surface light source device.

[54] a first surface;
a second surface facing the first surface;
a wavelength converting agent positioned between the first surface and the second surface;
An optical element portion that constitutes at least one of the first surface and the second surface is provided,
The optical element section includes a plurality of unit optical elements,
at least one of the first surface and the second surface includes an uneven surface configured by a plurality of unit optical elements;
The wavelength conversion agent absorbs primary light of a specific wavelength and emits secondary light,
The wavelength conversion sheet, wherein the secondary light has a wavelength different from the specific wavelength.

[55] The first surface is located between the light source emitting light of the specific wavelength and the second surface,
The wavelength conversion sheet of [54], wherein the second surface includes the uneven surface.

[56] The first surface is located between the light source emitting light of the specific wavelength and the second surface,
The wavelength conversion sheet of [54], wherein the first surface includes the uneven surface.

[57] a selective transmission sheet including a selective transmission portion in which the transmittance of light of a specific wavelength incident at an incident angle greater than 0° is greater than the transmittance of light of the specific wavelength incident at an incident angle of 0°; , the wavelength conversion sheet according to any one of [54] to [56], which is used repeatedly.

[58] The wavelength conversion sheet according to any one of [54] to [57], wherein the transmission internal haze for light with a wavelength different from that of the primary light is 45% or less.

[59] The wavelength conversion sheet according to any one of [54] to [58], which has a transmission internal haze of 50% or less.

[60] a first surface;
a second surface facing the first surface;
a wavelength converting agent positioned between the first surface and the second surface;
The wavelength conversion agent absorbs primary light of a specific wavelength and emits secondary light,
the secondary light has a wavelength different from the specific wavelength;
A wavelength conversion sheet, wherein a transmission haze of light having a wavelength different from that of the primary light is 45% or less.

[61] a first surface;
a second surface facing the first surface;
a wavelength converting agent positioned between the first surface and the second surface;
The wavelength conversion agent absorbs primary light of a specific wavelength and emits secondary light,
the secondary light has a wavelength different from the specific wavelength;
A wavelength conversion sheet having a transmission haze of 50% or less.

[62] a selective transmission sheet including a selective transmission portion in which the transmittance of light of a specific wavelength incident at an incident angle greater than 0° is greater than the transmittance of light of the specific wavelength incident at an incident angle of 0°; , the wavelength conversion sheet of [60] or [61], which is used repeatedly.

According to the present disclosure, the amount of wavelength conversion agent can be reduced.

FIG. 1 is a diagram for explaining an embodiment, and is a perspective view showing a display device and a surface light source device. FIG. 2 is a vertical cross-sectional view of the first aspect of the surface light source device shown in FIG. 1, showing an optical member and a light source substrate that can be included in the first aspect of the surface light source device. FIG. 3 is a plan view showing the light source substrate shown in FIG. 2, showing an example of arrangement of a plurality of light sources. FIG. 4 is a cross-sectional view showing the light source substrate shown in FIG. 2, showing an example of the configuration of the light source substrate. 5 is a cross-sectional view showing an example of the configuration of the optical member shown in FIG. 2. FIG. FIG. 6 is a perspective view showing a light diffusion sheet that can be included in the surface light source device shown in FIG. 5, showing an example of unit diffusion elements of the light diffusion sheet. FIG. 7 is a graph showing an example of optical characteristics of a selective transmission portion that can be included in the optical member shown in FIG. 8A is a cross-sectional view showing an example of a wavelength conversion sheet that can be included in the optical member shown in FIG. 2. FIG. 8B is a cross-sectional view showing another example of a wavelength conversion sheet that can be included in the optical member shown in FIG. 2. FIG. FIG. 9 is a vertical cross-sectional view showing an example of a wavelength conversion section that can be included in the wavelength conversion sheet shown in FIGS. 8A and 8B. FIG. 10A is a plan view showing an example of an optical element portion that can be included in the wavelength conversion sheet shown in FIGS. 8A and 8B, showing the arrangement of unit optical elements that can be included in the optical element portion. FIG. 10B is a perspective view showing a specific example of the unit optical element shown in FIG. 10A. FIG. 10C is a diagram corresponding to FIG. 10A and showing another example of arrangement of unit optical elements. 11A is a plan view showing another example of an optical element portion that can be included in the wavelength conversion sheet shown in FIGS. 8A and 8B, showing the arrangement of unit optical elements that can be included in the optical element portion; FIG. there is FIG. 11B is a perspective view showing one specific example of the unit optical element shown in FIG. 11A. 12 is a perspective view showing an example of a light control sheet that can be included in the surface light source device shown in FIG. 2. FIG. 13A and 13B are explanatory diagrams of the action of a wavelength conversion sheet that can be included in the optical member shown in FIG. FIG. 14 is a view corresponding to FIG. 5 and a longitudinal sectional view showing another example of the optical member. FIG. 15 is a diagram showing the in-plane distribution of radiant intensity on the light emitting surface of the surface light source device according to Example A1. FIG. 16 is a diagram showing the in-plane distribution of radiant intensity on the light emitting surface of the surface light source device according to Comparative Example A1. FIG. 17 is a longitudinal sectional view of the surface light source device shown in FIG. 1, showing another example of optical members and light source substrates that can be included in the surface light source device. 18 is a longitudinal sectional view showing a specific example of a selective transmission sheet that can be included in the optical member shown in FIG. 17. FIG. FIG. 19 is a graph showing a first specific example and a second specific example of optical characteristics of a selective transmission portion that can be included in the selective transmission sheet shown in FIG. 20 is a cross-sectional view showing an example of a wavelength conversion sheet that can be included in the optical member shown in FIG. 17. FIG. 21 is a cross-sectional view showing another example of a wavelength conversion sheet that can be included in the optical member shown in FIG. 17. FIG. FIG. 22 is a vertical cross-sectional view showing an example of a wavelength conversion section that can be included in the wavelength conversion sheet shown in FIGS. 20 and 21. FIG. FIG. 23A is a plan view showing an example of an optical element portion that can be included in the wavelength conversion sheet shown in FIGS. 20 and 21, showing the arrangement of unit optical elements that can be included in the optical element portion. FIG. 23B is a perspective view showing one specific example of the unit optical element shown in FIG. 23A. FIG. 23C is a diagram corresponding to FIG. 23A and showing another example of arrangement of unit optical elements. 24A and 24B are explanatory views of the action of a wavelength conversion sheet that can be included in the optical member shown in FIG. 17. FIG. 25 is a graph showing an example of the angular distribution of brightness on the second surface of the selective transmission sheet that can be included in the optical member shown in FIG. 17. FIG. FIG. 26 is a graph corresponding to FIG. 19 and showing another specific example of the optical characteristics of the selective transmission portion. FIG. 27 is a cross-sectional view corresponding to FIG. 24 and showing a modification of the wavelength conversion sheet that can be included in the optical member. FIG. 28 is a longitudinal sectional view of the surface light source device shown in FIG. 1, showing still another example of optical members and light source substrates that can be included in the surface light source device. 29 is a longitudinal sectional view showing one specific example of a wavelength conversion sheet that can be included in the optical member shown in FIG. 28. FIG. 30 is a cross-sectional view showing an example of an optical sheet that can be included in the optical member shown in FIG. 28. FIG. 31 is a cross-sectional view showing another example of an optical sheet that can be included in the optical member shown in FIG. 28. FIG. 32A is a plan view showing an example of arrangement of unit optical elements that can be included in the optical sheet shown in FIGS. 30 and 31. FIG. FIG. 32B is a perspective view showing one specific example of the unit optical element shown in FIG. 32A. FIG. 32C is a diagram corresponding to FIG. 32A and showing another example of arrangement of unit optical elements. 33A and 33B are cross-sectional views illustrating the action of an optical sheet that can be included in the optical member shown in FIG.

An embodiment of the present disclosure will be described below with reference to the drawings. In addition, 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 appropriately changed and exaggerated from those of the real thing. Configurations and the like shown in some drawings may be omitted in other drawings. In addition, although a plurality of aspects of one embodiment will be described, in the following description and drawings, the same reference numerals are used for portions that can be configured in the same manner among the plurality of aspects, and overlapping descriptions will be omitted.

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 only on the difference in designation. For example, a "wavelength conversion sheet" cannot be distinguished from a member called a wavelength conversion film or a wavelength conversion plate only by the difference in name. A "selectively permeable sheet" cannot be distinguished from a member called a selectively permeable film or a selectively permeable plate only by the difference in name. An "optical sheet" cannot be distinguished from a member called an optical film or an optical plate only by the difference in name.

In this specification, the normal direction of the 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. "Sheet surface (film surface, plate surface)" refers to a sheet-like member (film-like 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 commonly labeled arrows. The tip side of the arrow is the first side in each direction. The side opposite to the tip of the arrow is the second side in each direction. For example, as shown in FIG. 2, a symbol with an X in a circle indicates an arrow pointing into the drawing along a direction perpendicular to the drawing. For example, as shown in FIG. 3, the dot-in-a-circle symbol indicates an arrow pointing forward from the plane of the drawing along a direction perpendicular to the plane of the drawing.

The attached drawings are diagrams for explaining one embodiment. FIG. 1 is a perspective view schematically showing a surface light source device 20 and a display device 10 as an application example of an optical member 30 according to this embodiment. 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.

<First aspect>
2 to 16 are diagrams for explaining the first aspect of the present embodiment. FIG. 2 is a longitudinal sectional view showing one specific example of the surface light source device 20 in the first mode. As shown in FIG. 2, the surface light source device 20 may include, as main components, a light source 23 and an optical laminate 21 that adjusts the optical path of the light emitted from the light source 23 . The optical laminate 21 may include an optical member 30 that adjusts the optical path. The optical layered body 21 and the optical member 30 may face the light source 23 . The optical member 30 may be a sheet-like member. The optical member 30 may face the light source 23 in its normal direction. The optical layered body 21 and the optical member 30 may be diffusion members that diffuse the light emitted from the light source 23 . The optical layered body 21 and the optical member 30 can effectively suppress in-plane variations in illuminance caused by the arrangement of the light sources 23 . Due to the diffusion in the optical layered body 21 and the optical member 30, the illuminance at each position on the light emitting side surface 30b of the optical layered body 21 and the optical member 30, or an imaginary light parallel to the light emitting side surface 30b located near the light emitting side surface 30b. The illuminance at each position on the light receiving surface of can be effectively uniformed.

The display device 10, the surface light source device 20, the optical layered body 21, and the optical member 30 in the first aspect will be described below with reference to the illustrated specific examples.

As shown in FIG. 1, the display panel 15 overlaps the surface light source device 20 in the third direction D3. The display panel 15 is arranged facing the light emitting surface 20 a of the surface light source device 20 . The display panel 15 includes a display surface 15a on which an image is displayed as a surface facing the first side, ie, the side opposite to the surface light source device 20 in the third direction D3. In the illustrated example, the display panel 15 is flat. The display panel 15 extends in a first direction D1 and a second direction D2 orthogonal to the third direction D3. The display panel 15 has a rectangular shape when viewed from the third direction D3. The first direction D1 and the second direction D2 are orthogonal to each other. The first direction D1 and the second direction D2 are orthogonal to the third direction D3.

The display panel 15 is configured as, for example, a transmissive liquid crystal display panel. A part of the light incident from the surface light source device 20 is transmitted through the display panel 15 as a liquid crystal display panel, whereby an image is displayed on the display surface 15a. 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.

The surface light source device 20 includes a light emitting surface 20a that planarly emits light. The surface light source device 20 is configured as a direct type backlight. Surface light source device 20 includes light source 23 and optical member 30 . A light source 23 is provided in a region overlapping with the optical member 30 in projection in the third direction D3.

A surface light source device 20 shown in FIG. 2 includes a light source substrate 22 including a light source 23 and an optical laminated body 21 . The illustrated optical laminate 21 includes an optical member 30 , a first light control sheet 81 , a second light control sheet 82 and a reflective polarizing plate 85 . The light source substrate 22, the optical member 30, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 are stacked in this order in the third direction D3. The light source substrate 22, the optical member 30, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 are sheet-shaped. The light source substrate 22, the optical member 30, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 extend in the first direction D1 and the second direction D2.

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 from the light source 23 is absorbed by a wavelength conversion agent 67, which will be described later, as primary light LA. Therefore, the emission wavelength of light source 23 can be appropriately selected according to the optical properties of wavelength conversion agent 67 . In the illustrated example, the light source 23 emits blue light. The wavelength of the light emitted from the light source 23 may be 430 nm or more and 500 nm or less.

The light distribution characteristics of the light source 23 are not particularly limited. The light distribution characteristic of the light source 23 may be Lambertian light distribution. 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. The light source 23 may have a bad wing light distribution, for example disclosed in JP6299811B. 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.

The light source board 22 may include a plurality of light sources 23 like the illustrated surface light source device 20 . 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 suppressing 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 employed. 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 the first direction D1 and the second direction D2 that are orthogonal to each other. In the illustrated example, the arrangement pitch PL1 of the light sources 23 in the first direction D1 and the arrangement pitch PL2 of the light sources 23 in the second direction D2 are the same. 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 second side in the third direction D3. The support substrate 25 is sheet-like. Support substrate 25 may include circuitry for powering light source 23 . The support substrate 25 may have light reflectivity to reflect light toward the optical member 30 .

The support substrate 25 shown in FIG. 4 includes 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 the first direction D1 and the second direction D2. The substrate body 26 may have insulating properties. The substrate body 26 may be a resin film, such as a polyethylene terephthalate film. The wiring 29 is electrically connected to the light source 23 . The wiring 29 is electrically connected to a terminal (not shown) of the light source 23 via solder or the like. 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 main body 26 from the optical member 30 side. 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 reflection on the reflective layer 27 may be specular reflection, also called specular reflection, diffuse reflection, or anisotropic diffuse reflection. The reflective layer 27 having diffuse reflectivity may include a white reflective layer containing white particles such as titanium oxide and silicon dioxide. The reflective layer 27 may be a metal layer laminated on the substrate body 26, or may be a reflective diffractive optical element.

The optical member 30 includes a selective transmission sheet 40 and a wavelength conversion sheet 60 in this order. The selective transmission sheet 40 and the wavelength conversion sheet 60 are stacked in the third direction D3. That is, the third direction D3 is the lamination direction of the selective transmission sheet 40 and the wavelength conversion sheet 60 . The selective transmission sheet 40 is positioned closer to the second side in the third direction D3 than the wavelength conversion sheet 60 is. The wavelength conversion sheet 60 is positioned closer to the first side in the third direction D3 than the selective transmission sheet 40 is. The selective transmission sheet 40 and the wavelength conversion sheet 60 may be bonded together. The selective transmission sheet 40 and the wavelength conversion sheet 60 may simply be in contact and may not be joined together. The selectively transmitting sheet 40 and the wavelength converting sheet 60 may be separated from each other.

Constituent elements other than the optical member 30, such as the display panel 15, the light source substrate 22, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85, will be described in the first aspect later. It can also be used in other aspects to do. Also, regarding the selective transmission sheet 40 of the optical member 30 and the light diffusion sheet 50 described later, the configuration described in the first mode can also be used in other modes described later.

In the illustrated example, both the selective transmission sheet 40 and the wavelength conversion sheet 60 extend in the first direction D1 and the second direction D2. In the illustrated example, the wavelength conversion sheet 60 constitutes the light output side surface 30b of the optical member 30. As shown in FIG. The light exit side surface 30b faces the first side that is the viewer side in the third direction D3. The illustrated optical member 30 further has a light diffusion sheet 50 . The light diffusing sheet 50 is located on the second side, which is the light source side opposite to the viewer side in the third direction D3, relative to the selectively transmitting sheet 40 . The light diffusion sheet 50 constitutes the light entrance side surface 30 a of the optical member 30 . The light incident side surface 30a faces the second side in the third direction D3. The illustrated light diffusion sheet 50 is bonded to the selective transmission sheet 40 . The light diffusion sheet 50 does not have to be bonded to the selective transmission sheet 40 . The light diffusion sheet 50 may be provided separately from the optical member 30 .

The light diffusion sheet 50 changes the traveling direction of light emitted from the light source 23 . The light diffusion sheet 50 has a light diffusion function of diffusing light. The light diffusion sheet 50 may contain a resin binder and a light diffusion component dispersed in the resin binder. Examples of the light diffusing component include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles. The light diffusion sheet 50 may contain a diffractive optical element. The light diffusion sheet 50 may be a layer including a matte surface. The light diffusion sheet 50 may include microlenses and linear array lenses. In this embodiment, the light diffusion sheet 50 may be omitted from the optical member 30 .

The light diffusion sheet 50 includes a first surface 50a and a second surface 50b. The first surface 50a faces the second side in the third direction D3. The first surface 50a constitutes the light incident side surface 30a. The second surface 50b faces the first side in the third direction D3. The light diffusion sheet 50 is bonded to the selective transmission sheet 40 on the second surface 50b. The light diffusion sheet 50 may be directly bonded to the selective transmission sheet 40 . The light diffusion sheet 50 may be bonded to the selective transmission sheet 40 via a bonding layer such as an adhesive layer or adhesive layer.

In the examples shown in FIGS. 5 and 6, the first surface 50a of the light diffusion sheet 50 is an uneven surface 51. In the example shown in FIGS. The light diffusion sheet 50 includes a sheet-like body portion 52 and a plurality of unit diffusion elements 55 each formed as a convex portion 53 or a concave portion. The unit diffusion element 55 is an element that changes the traveling direction of light by refraction, reflection, or the like. The unit diffusion element 55 is a concept including elements called unit shape element, unit prism, unit lens, and unit optical element. A unit diffusion element 55 is provided on the body portion 52 . The unit diffusion element 55 faces the light source substrate 22 . The uneven surface 51 is configured by a plurality of unit diffusion elements 55 .

The light diffusion sheet 50 shown in FIG. 5 includes a plurality of convex portions 53 provided on the body portion 52 . In the examples shown in FIGS. 5 and 6, the plurality of protrusions 53 are arranged two-dimensionally. That is, the convex portions 53 are arranged in two or more non-parallel directions. A plurality of convex portions 53 may be provided adjacent to each other without a gap. The light diffusion sheet 50 may include a plurality of recesses provided in the body portion 52 . The plurality of recesses may be arranged two-dimensionally. A plurality of recesses may be provided adjacent to each other without a gap. The unit diffusion element 55 shown in FIGS. 5 and 6 includes an element surface 56 inclined with respect to the third direction D3. Element faces 56 define unit diffusion elements 55 . The uneven surface 51 of the light diffusion sheet 50 is composed of the element surfaces 56 of the unit diffusion elements 55 .

The optical properties of the light diffusion sheet 50 are affected by the tilt angles of the element surfaces 56 of the unit diffusion elements 55 . Therefore, the configuration of the unit diffusion element 55 can be appropriately adjusted based on the optical characteristics required for the surface light source device 20 and the optical member 30. FIG. For example, the inclination angles of a plurality of element surfaces 56 included in one unit diffusion element 55 may be different from each other or may be the same. The light diffusion sheet 50 may include unit diffusion elements 55 different in at least one of shape and orientation, or may include only unit diffusion elements 55 that are the same as each other.

The plurality of unit diffusion elements 55 included in the light diffusion sheet 50 are preferably arranged two-dimensionally. According to this example, the element surfaces 56 of the unit diffusion elements 55 included in the light diffusion sheet 50 face various directions. As a result, the light diffusion sheet 50 can guide light in various directions by the two-dimensionally arranged unit diffusion 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 effectively uniformed. Each unit diffusion element 55 may be configured rotationally symmetrical about an axis parallel to the third direction D3. For example, each unit diffusion element 55 may be configured with 3-fold, 4-fold, or 6-fold symmetry about an axis parallel to the third direction D3. The plurality of unit diffusion elements 55 may be arranged irregularly or may be arranged regularly.

FIG. 6 shows a specific example of the unit diffusion elements 55 in the light diffusion sheet 50. FIG. In the example shown in FIG. 6, the arrangement of the plurality of unit diffusion elements 55 is a square arrangement. A plurality of unit diffusion elements 55 are arranged at a constant pitch in the first direction D1. A plurality of unit diffusion elements 55 are arranged at a constant pitch in the second direction D2. The unit diffusion elements 55 may be arranged in directions inclined in the first direction D1 and the second direction D2. For example, the plurality of unit diffusion elements 55 may be arranged at a constant pitch in two directions that are inclined ±45° with respect to the first direction D1. The arrangement pitches of the unit diffusion elements 55 in the two directions may be the same or different. The arrangement pitch of the unit diffusion elements 55 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. As shown in FIG. 6, the unit diffusion element 55 may be configured as a quadrangular pyramid-shaped protrusion 53 or recess having a square bottom surface. The height or depth of each unit diffusion 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 diffusion elements 55 shown in FIGS. 5 and 6 can be made by embossing or resin molding.

The selectively permeable sheet 40 includes a selectively permeable portion 45 . The transmission characteristics and reflection characteristics of the selective transmission portion 45 have incident angle dependency. The reflectance and transmittance of the selective transmission portion 45 change depending on the incident angle. The incident angle means the angle (°) formed by the traveling direction of incident light with respect to the normal direction of a member such as a sheet on which light is incident. The emission angle means the angle (°) formed by the direction of travel of emitted light with respect to the normal direction of a member such as a sheet from which the light is emitted.

The selectively permeable sheet 40 includes a first surface 40a and a second surface 40b. The first surface 40a faces the second side in the third direction D3. The second surface 40b faces the first side in the third direction D3. The illustrated selective transmission sheet 40 is composed of only the selective transmission portion 45 . The selective transmission portion 45 includes a first surface 45a and a second surface 45b. The first surface 45a faces the second side in the third direction D3. The second surface 45b faces the first side in the third direction D3. The first surface 45 a of the selectively transmitting portion 45 constitutes the first surface 40 a of the selectively transmitting sheet 40 . The second surface 45 b of the selectively transmitting portion 45 constitutes the second surface 40 b of the selectively transmitting sheet 40 . The first surface 40a and the second surface 40b are parallel flat surfaces.

Unlike the illustrated example, the selectively permeable sheet 40 may include a protective film that protects the selectively permeable portion 45 . In this example, the protective film may constitute the first surface 40a and the second surface 40b.

The transmittance of the selective transmission portion 45 for light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° is the transmittance of the light of a specific wavelength incident on the selective transmission portion 45 at an incident angle greater than 0°. It is smaller than the transmittance of the selective transmission portion 45 . That is, the transmittance of the selectively transmitting portion 45 for the vertically incident specific wavelength light is lower than the transmittance of the selectively transmitting portion 45 for the specific wavelength light incident on the selectively transmitting portion 45 from at least one oblique direction. . The reflectance of the selective transmission portion 45 for light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° is It is larger than the reflectance of the selective transmission portion 45 . That is, the reflectance of the selectively transmitting portion 45 for the vertically incident specific wavelength light is higher than the reflectance of the selectively transmitting portion 45 for the specific wavelength light incident on the selectively transmitting portion 45 from at least one oblique direction. The selective transmission portion 45 can also be described as a selective reflection sheet or a light reflection sheet.

The selective transmission section 45 may have various transmission characteristics and reflection characteristics.

The transmittance of the selective transmission portion 45 for light of a specific wavelength incident at an incident angle of 0° may be less than 5%, less than 3%, or less than 1%. The reflectance of the selective transmission portion 45 for light of a specific wavelength incident at an incident angle of 0° may be 95% or higher, 97% or higher, or 99% or higher.

The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 30° or less in absolute value may be half or less of the maximum transmittance of the selective transmission portion 45. , the maximum transmittance of the selective transmission portion 45 may be 1/5 or less, or the maximum transmittance of the selective transmission portion 45 may be 1/10 or less. The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 45° or less in absolute value may be half or less of the maximum transmittance of the selective transmission portion 45. , the maximum transmittance of the selective transmission portion 45 may be 1/5 or less, or the maximum transmittance of the selective transmission portion 45 may be 1/10 or less. The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 55° or less in absolute value may be half or less of the maximum transmittance of the selective transmission portion 45. , the maximum transmittance of the selective transmission portion 45 may be 1/5 or less, or the maximum transmittance of the selective transmission portion 45 may be 1/10 or less.

The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 35° or less in absolute value may be less than 10%, less than 5%, or less than 1%. It's okay. The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 40° or less in absolute value may be less than 10%, less than 5%, or less than 1%. It's okay. The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 45° or less in absolute value may be less than 15%, less than 10%, or less than 5%. It's okay. The transmittance of the selective transmission portion 45 with respect to light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° or more and 50° or less in absolute value may be less than 15%, less than 10%, or less than 5%. It's okay.

The absolute value of the incident angle at which the maximum transmittance of the selective transmission portion 45 is obtained may be 50° or more, 55° or more, or 60° or more. The absolute value of the incident angle at which the maximum transmittance of the selective transmission portion 45 is obtained may be 80° or less, 75° or less, or 70° or less.

FIG. 7 is a graph showing an example of optical characteristics of the selective transmission portion 45. FIG. As shown in FIG. 7, the transmittance at the selective transmission portion 45 of light having a specific wavelength whose absolute value is 0° or more and 30° or less may be less than 15%, less than 8%, or 3%. may be less than The transmittance at the selective transmission portion 45 of light of a specific wavelength whose absolute value is 0° or more and 50° or less may be less than 15%, less than 10%, or less than 5%.

The reflectance at the selective transmission portion 45 of light having a specific wavelength whose absolute value is 0° or more and 30° or less may be 85% or more, 92% or more, or 97% or more. The reflectance at the selective transmission portion 45 of light having a specific wavelength whose absolute value is 0° or more and 50° or less may be 85% or more, 90% or more, or 95% or more.

As shown in FIG. 7, the transmittance at the selective transmission portion 45 of light of a specific wavelength incident at an incident angle of 60° or more and 70° or less in absolute value may be 50%. As the absolute value of the incident angle increases within the range of 0° to 65°, the transmittance of the light of the specific wavelength at the selective transmission portion 45 may increase.

The reflectance at the selective transmission portion 45 of light of a specific wavelength incident at an incident angle of 60° or more and 70° or less in absolute value may be 50%. As the absolute value of the incident angle increases in the range of 0° to 65°, the reflectance of the light of the specific wavelength at the selective transmission portion 45 may decrease.

The optical characteristics of the selective transmission portion 45 described here are that the first surface 45a and the second surface 45b of the selective transmission portion 45 are parallel, and the first surface 45a and the second surface 45b are adjacent to the air layer. is assumed.

The light of the specific wavelength can be appropriately set according to the application of the surface light source device 20 and the optical member 30. The light emitted from the light source 23 may be light of a specific wavelength. Visible light may be light of a specific wavelength. "Visible light" means light with a wavelength of 380 nm or more and 780 nm or less.

The reflectance of the selective transmission portion 45 is a value measured using a variable angle photometer (goniophotometer) GP-200 manufactured by Murakami Color Research Laboratory. The transmittance of the selective transmission portion 45 is the total light transmittance measured according to JIS K7361-1:1997. The transmittance of the selective transmission portion 45 is a value measured using a goniophotometer GP-200 manufactured by Murakami Color Research Laboratory.

The selective transmission section 45 is not particularly limited as long as it has incident angle dependency of reflectance and incident angle dependency of transmittance. The selective transmission section 45 may include a dielectric multilayer film, a reflective volume hologram, a cholesteric liquid crystal structure layer, a retroreflective film, or a reflective diffractive optical element. A dielectric multilayer film is excellent in that the degree of freedom in designing reflection characteristics and transmission characteristics is relatively high. The transmission characteristics shown in FIGS. 6A and 6B are an example of the transmission characteristics of a dielectric multilayer film. The selective transmission section 45 may include a reflective structure that is structurally imparted with incident angle dependency of reflectance and incident angle dependency of transmittance. Reflective structures are superior in that they are less wavelength dependent.

The dielectric multilayer film forming the selective transmission portion 45 may include alternately laminated low refractive index layers and high refractive index layers having different refractive indexes. The low refractive index layer and the high refractive index layer may be inorganic compound layers or resin layers. A multilayer film constituting a dielectric multilayer film may have a protective layer on one side or both sides. The material of the protective layer may be polyethylene terephthalate or polyethylene naphthalate. The thickness of the protective layer may be 5 μm or more. A coextrusion method or the like may be adopted as a method for manufacturing the dielectric multilayer film. Specifically, the method for producing a laminated film described in JP2008-200861A may be employed. A commercially available laminated film may be used as the dielectric multilayer film. Examples of commercially available dielectric multilayer films include Picassus (registered trademark) manufactured by Toray Industries, Inc. and ESR manufactured by 3M.

As shown in FIGS. 8A and 8B, the wavelength conversion sheet 60 includes a first surface 60a and a second surface 60b. The first surface 60a faces the second side in the third direction D3. The second surface 60b faces the first side in the third direction D3. In this embodiment, at least one of the first surface 60a and the second surface 60b includes an uneven surface 61. As shown in FIG. In the first aspect, the second surface 60b includes an uneven surface 61. As shown in FIG. The wavelength conversion sheet 60 contains a wavelength conversion agent 67 . The wavelength converting agent 67 absorbs primary light and emits secondary light with a different wavelength than the primary light.

The illustrated second surface 60b is an uneven surface 61 over the entire surface. The illustrated wavelength conversion sheet 60 is bonded to the selective transmission sheet 40 via the first surface 60a. The wavelength conversion sheet 60 may be directly bonded to the second surface 50b of the light diffusion sheet 50. FIG. As shown in FIG. 9, the light diffusion sheet 50 may be bonded to the second surface 50b of the selective transmission sheet 40 via a bonding layer 35 such as an adhesive layer or adhesive layer.

In the example shown in FIGS. 8A and 8B, the wavelength conversion sheet 60 includes a first barrier layer 63, a wavelength conversion section 65, a second barrier layer 64 and an optical element section . The first barrier layer 63, the wavelength conversion section 65, the second barrier layer 64 and the optical element section 70 are stacked in this order in the third direction D3. The first barrier layer 63, the wavelength conversion section 65, the second barrier layer 64, and the optical element section 70 are arranged in this order from the first side toward the second side in the third direction D3. The first barrier layer 63, the wavelength conversion section 65, the second barrier layer 64 and the optical element section 70 are sheet-like. The first barrier layer 63, the wavelength conversion section 65, the second barrier layer 64 and the optical element section 70 extend in the first direction D1 and the second direction D2.

In the example shown in FIGS. 8A and 8B, the wavelength converting portion 65 includes a first surface 65a and a second surface 65b. The first surface 65a faces the second side in the third direction D3. The second surface 65b faces the first side in the third direction D3. The wavelength converting portion 65 is bonded to the first barrier layer 63 on the first surface 65a. The wavelength converting portion 65 is bonded to the second barrier layer 64 on the second surface 65b.

The wavelength converting portion 65 may include a base material portion 66 that holds the wavelength converting agent 67 . Resin may be used as the base material portion 66 . Examples of the resin forming the base material portion 66 include a thermoplastic resin, a cured product of a thermosetting resin composition, and a cured product of an ionizing radiation-curable resin composition.

The wavelength conversion agent 67 absorbs primary light LA of a certain wavelength and emits secondary light LB having a wavelength different from the wavelength of the primary light LA. A quantum dot or a phosphor may be used as the wavelength conversion agent 67 . The wavelength of the primary light LA may be the wavelength of light emitted from the light source 23 . That is, the light emitted from the light source 23 may contain primary light LA of a certain wavelength.

Quantum dots are nanometer-sized semiconductor particles. 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 wavelength conversion part 65 may contain a plurality of quantum dots with different emission wavelengths as the wavelength conversion agent 67 . 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 Figure 9, the wavelength converting agent 67 includes a first converting agent 67A and a second converting agent 67B. The first conversion agent 67A and the second conversion agent 67B have different sizes. The first conversion agent 67A and the second conversion agent 67B emit light of different wavelengths.

As a specific example, the light source 23 may emit blue light having a wavelength of 430 nm or more and 500 nm or less. The first conversion agent 67A 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 as the first secondary light LB1. The second conversion agent 67B 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 as the second secondary light LB2. According to this example, the surface light source device 20 emits light of various colors by additive color mixing of the first secondary light LB1, the second secondary light LB2, and the primary light LA that has not been wavelength-converted by the wavelength conversion section 65. can be released. By adjusting the contents of the first conversion agent 67A and the second conversion agent 67B, the surface light source device 20 can emit white light.

The wavelength conversion section 65 may contain a light scattering component that scatters transmitted light. The light scattering component may be dispersed within the matrix portion 66 . Examples of light-scattering components include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles.

The first barrier layer 63 is bonded to the first surface 65a of the wavelength conversion section 65. The first barrier layer 63 constitutes the first surface 60a. The second barrier layer 64 is bonded to the second surface 65b of the wavelength conversion section 65. As shown in FIG. The first barrier layer 63 and the second barrier layer 64 have the function of protecting the wavelength conversion agent 67 from oxygen and moisture.

The first barrier layer 63 and the second barrier layer 64 may have oxygen barrier properties. In this example, the oxygen permeability of the first barrier layer 63 and the second barrier layer 64 is 1.0×10 ⁻¹ cc/m ² /day/atm or less under conditions of 23° C. and 90% relative humidity. It may well be 1.0×10 ⁻² cc/m ² /day/atm or less. The oxygen permeability can be measured using an oxygen gas permeability meter (OX-TRAN 2/21 manufactured by MOCON).

The first barrier layer 63 and the second barrier layer 64 may have water vapor barrier properties. In this example, the water vapor permeability of the first barrier layer 63 and the second barrier layer 64 may be 1.0×10 ⁻¹ g/m ² /day or less under conditions of 40° C. and 90% relative humidity, It may be 1.0×10 ⁻² g/m ² /day or less. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (DELTAPERM (manufactured by Technolox)).

The first barrier layer 63 and the second barrier layer 64 are formed by using a material capable of exhibiting barrier properties, using a physical vapor deposition (PVD) method such as a sputtering method or an ion plating method, or a chemical vapor deposition (CVD) method. or a coating method such as roll coating or spin coating. As materials, inorganic oxides, metals, sol-gel materials, and the like may be used. As inorganic oxides, silicon oxide (SiO _x ), aluminum oxide (Al _n O _m ), titanium oxide (TiO ₂ ), yttrium oxide, boron oxide (B ₂ O ₃ ), calcium oxide (CaO), silicon carbide oxynitride ( _{SiOxNyCz )} and the like _are exemplified. Examples of metals include Ti, Al, Mg, Zr, and the like. Examples of sol-gel materials include siloxane-based sol-gel materials.

The optical element section 70 includes a first surface 70a and a second surface 70b. The first surface 70a faces the second side in the third direction D3. The second surface 70b faces the first side in the third direction D3. The optical element portion 70 is bonded to the second barrier layer 64 on the first surface 70a. The second surface 70b constitutes the second surface 60b. The second surface 70 b constitutes the light exit side surface 30 b of the optical member 30 . The second surface 70 b includes an uneven surface 61 .

In the example shown in FIGS. 8A and 8B, the optical element portion 70 includes a plurality of unit optical elements 75 each formed as a convex portion 73 or a concave portion 74 . The unit optical element 75 is an element that changes the traveling direction of light by refraction, reflection, or the like. The unit optical element 75 is a concept including elements called unit shaped elements, unit prisms, and unit lenses. The unit optical element 75 constitutes the first surface 60a. A concave-convex surface 61 is formed by the unit optical element 75 .

The optical element portion 70 shown in FIG. 8A includes a sheet-like body portion 72 and a plurality of convex portions 73 provided on the body portion 72 . In the example shown in FIG. 8A, a plurality of protrusions 73 may be provided adjacent to each other without gaps. The optical element portion 70 shown in FIG. 8B includes a body portion 72 having a plurality of recesses 74 therein. In the example shown in FIG. 8B, multiple recesses 74 may be provided adjacent to each other without gaps.

As shown in FIGS. 8A and 8B, the unit optical element 75 has an element surface 76 inclined with respect to the third direction D3. A unit optical element 75 is defined by this element surface 76 . The uneven surface 61 of the wavelength conversion sheet 60 is composed of the element surfaces 76 of the unit optical elements 75 .

The optical characteristics of the uneven surface 61 are affected by the inclination angles of the element surfaces 76 of the unit optical elements 75 . Therefore, the cross-sectional shape of the unit optical element 75 can be appropriately adjusted based on the optical properties required for the surface light source device 20 and the optical member 30 . The inclination angles of a plurality of element surfaces 56 included in one unit optical element 75 may be different from each other or may be the same. The optical element section 70 may include unit optical elements 75 that differ in at least one of shape and orientation, or may include only unit optical elements 75 that are the same as each other.

The element faces 76 may be somewhat curved, unlike the examples shown in FIGS. 8A and 8B. The unit optical element 75 may have the outer shape of a portion of a sphere such as a hemisphere, or the outer shape of a portion of a spheroid.

The plurality of unit diffusion elements 55 may be arranged two-dimensionally. According to this example, the element surfaces 76 of the unit optical elements 75 included in the optical element portion 70 face various directions. As a result, the optical element section 70 can guide light in various directions by the two-dimensionally arranged unit optical elements 75 . In other words, light can be guided in a plurality of non-parallel directions, and the in-plane distribution of illuminance can be effectively uniformed. Each unit optical element 75 may be configured rotationally symmetrical about an axis parallel to the third direction D3. For example, each unit optical element 75 may be configured with 3-fold, 4-fold, or 6-fold symmetry about an axis parallel to the third direction D3.

The plurality of unit optical elements 75 may be arranged irregularly or may be arranged regularly. By regularly arranging the unit optical elements 75, the design of the optical element section 70 can be facilitated. By regularly arranging the plurality of unit optical elements 75, it becomes easy to spread the unit optical elements 75 without gaps.

When the dimensions of the unit optical elements 75 are large when observed from the third direction D3, unevenness in brightness due to the shape of the unit optical elements 75 is more likely to be visually recognized. From the viewpoint of preventing such a problem, the maximum length of the unit optical element 75 in the direction perpendicular to the stacking direction D3 may be 1.5 mm or less, 1 mm or less, or 0.5 mm or less. The arrangement pitch of the unit optical elements 75 may be 0.01 mm or more and 1.5 mm or less. Furthermore, from the viewpoint of effectively homogenizing the in-plane distribution of illuminance on the light emitting side surface 30b of the optical member 30 when applied to the surface light source device 20, the arrangement pitch of the unit optical elements 75 is 0.05 mm or more and 1 mm. It may be less than or equal to 0.1 mm or more and 0.5 mm or less. The height or depth of the unit optical element 75 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.

10A and 10B show a specific example of the unit optical element 75 included in the optical element section 70. FIG. In the example shown in FIGS. 10A and 10B, the multiple unit optical elements 75 are arranged in a square arrangement. The plurality of unit optical elements 75 are arranged at a constant pitch in the first direction D1. The plurality of unit optical elements 75 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. 10A and 10B, the plurality of unit optical elements 75 may be 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 unit optical elements 75 may be arranged in directions inclined in the first direction D1 and the second direction D2. For example, in the example shown in FIG. 10C, the plurality of unit optical elements 75 are arranged at a constant pitch in two directions that are inclined ±45° with respect to the first direction D1. The arrangement of FIG. 10C can be applied to the unit optical element 75 shown in FIG. 10B. According to this example, the element surface 76 faces in two directions that are inclined by ±45° with respect to the first direction D1, and the light can be spread in these two directions.

11A and 11B show another specific example of the unit optical element 75 included in the optical element section 70. FIG. In the example of the optical element portion 70 shown in FIGS. 11A and 11B, unit optical elements 75 having the same bottom surface shape are arranged in four directions. As a result, the plurality of unit optical elements 75 having the same bottom shape and orientation are arranged at a constant pitch in each of the first direction D1 and the second direction D2. The arrangement pitches in the two directions may be the same or different. In the illustrated example, the arrangement pitches in each of the two directions are the same. The unit optical element 75 has a triangular pyramid shape with an isosceles right triangle bottom surface.

The optical element portion 70 shown in FIGS. 8A to 11B can be produced by embossing or resin molding. The optical element portion 70 including the unit optical elements 75 may be bonded to the second barrier layer 64 via a bonding layer containing adhesive or adhesive. An optical element portion 70 including unit optical elements 75 may be fabricated on the second barrier layer 64 .

The optical element section 70 may include a diffractive optical element.

As described above, the surface light source device 20 includes the first light control sheet 81 , the second light control sheet 82 and the reflective polarizing plate 85 that are superimposed on the optical member 30 .

The first light control sheet 81 and the second light control sheet 82 exert optical actions such as reflection, refraction, and diffraction on incident light. The first light control sheet 81 and the second light control sheet 82 may have functions suitable for the uses of the optical member 30 and the surface light source device 20 .

12 shows one specific example of the first light control sheet 81 and the second light control sheet 82. FIG. The first light control sheet 81 and the second light control sheet 82 shown in FIG. 12 are prism sheets including a plurality of linearly extending unit prisms 84 . The light control sheets 81 and 82 may function as light condensing sheets that restrict the traveling direction of incident light to a narrow angular range. The prism sheet includes a sheet-like body portion 83 and a plurality of unit prisms 84 provided on the body portion 83 . The unit prisms 84 may extend linearly in a direction orthogonal to the arrangement direction of the plurality of unit prisms 84 . That is, the first light control sheet 81 and the second light control sheet 82 are prism sheets in which the unit prisms 84 are linearly arranged.

The linearly arranged unit prisms 84 shown in FIG. 12 mainly adjust the luminance angular distribution within the plane parallel to both the arrangement direction of the unit prisms 84 and the third direction D3. Therefore, the first light control sheet 81 and the second light control sheet 82 may be incorporated into the optical member 30 such that the arrangement directions of the unit prisms 84 are non-parallel. For example, the arrangement direction of the unit prisms 84 of the first light control sheet 81 may be orthogonal to the arrangement direction of the unit prisms 84 of the second light control sheet 82 . The prism sheet shown in FIG. 12 may be "BEF" (registered trademark) available from 3M Company, USA. The prism sheet shown in FIG. 12 bends the traveling direction of transmitted light so that the angle between the traveling direction of transmitted light and the third direction D3 is small. The prism sheet shown in FIG. 12 functions as a condensing sheet.

The reflective polarizing plate 85 transmits one linearly polarized component and reflects the other linearly polarized component. According to the reflective polarizing plate 85 , it is possible to selectively transmit the linearly polarized light component that can be transmitted through the polarizing plate positioned on the surface light source device 20 side of the display panel 15 . The light reflected by the reflective polarizing plate 85 can re-enter the reflective polarizing plate 85 with its polarization state changed by subsequent reflection or the like. Thereby, the utilization efficiency of the light emitted from the light source 23 can be improved. The reflective polarizer 85 may be "DBEF" (registered trademark) available from 3M USA. The reflective polarizing plate 85 may be a high brightness polarizing sheet "WRPS" available from Shinwa Intertek, Korea, a wire grid polarizer, or the like.

Next, the operation of generating planar light with the planar light source device 20 having the above configuration will be described.

As shown in FIG. 2, the light source 23 emits primary light LA. The primary light LA is, for example, blue light. The wavelength of the blue primary light LA may be 430 nm or more and 500 nm or less. A light L21 emitted from the light source 23 travels toward the optical member 30 . As shown in FIG. 5 , the primary light LA from the light source 23 is incident on the light diffusion sheet 50 of the optical member 30 . The light diffusion sheet 50 has a light diffusion function. In the illustrated example, the first surface 50a of the light diffusion sheet 50 forming the light incident side surface 30a of the optical member 30 is an uneven surface 51. As shown in FIG. As shown in FIG. 5 , the light L51 changes its traveling direction when entering the light diffusion sheet 50 .

The primary light LA from the light source 23 passes through the light diffusion sheet 50 and enters the selective transmission portion 45 of the selective transmission sheet 40 . The transmittance of the selective transmission portion 45 depends on the incident angle. The transmittance of the selectively transmitting portion 45 for the primary light LA incident at an incident angle greater than 0° is greater than the transmittance of the selectively transmitting portion 45 for the primary light LA incident at an incident angle of 0°. With the optical characteristics shown in FIG. 7, the transmittance of the selective transmission portion 45 for light incident on the selective transmission portion 45 at an incident angle of 0° is 1% or less. Further, the transmittance of the selective transmission portion 45 with respect to light incident on the selective transmission portion 45 at an incident angle of 0° or more and 40° or less in terms of absolute value is half or less of the maximum transmittance of the selective transmission portion 45. there is Furthermore, the transmittance of the selective transmission portion 45 increases as the incident angle increases within a wide range of absolute values from 0° to 65°. The transmittance is 5% or less when the absolute value of the incident angle is in the range of 0° or more and 30° or less. That is, light inclined with respect to the third direction D3 can be transmitted through the selective transmission portion 45 with a higher transmittance than light traveling in the third direction D3.

A region facing the light source 23 in the third direction D3 and a surrounding region near the region are defined as an immediately overhead region. A large amount of light from the light source 23 is directly incident on this directly overhead region. However, the angle of incidence of light on the directly overhead region is small. Therefore, the light L21 emitted from the light source 23 and traveling to the selective transmission sheet 40 is reflected with a high reflectance in the directly overhead region. In the directly overhead region, light passes through the selective transmission sheet 40 with low transmittance. As a result, it is possible to prevent the light emitting surface 20a from becoming too bright in the directly overhead region.

A large amount of light L52 reflected by the selective transmission portion 45 is transmitted through the light diffusion sheet 50 and directed toward the light source substrate 22, as shown in FIG. This light L52 is diffused by the light diffusion sheet 50 . This allows the lights L22 and L52 to travel in directions greatly inclined with respect to the third direction D3. As shown in FIG. 2 , the light L22 is reflected by the reflective layer 27 of the light source substrate 22 . Due to this reflection, the light L23 reflected by the reflective layer 27 travels toward the optical member 30 in the third direction D3. As shown in FIG. 2, the light L23 re-enters the optical member 30 at a position away from the light source 23 in the first direction D1 or the second direction D2 perpendicular to the third direction D3.

The light diffusion sheet 50 can change the traveling direction of the light L23 re-entering the optical member 30 to a direction greatly inclined with respect to the third direction D3. The light L24 diffused by the light diffusion sheet 50 can be transmitted through the selective transmission sheet 40 with high transmittance in a spaced region away from the light source 23 in the direction orthogonal to the third direction D3. This can prevent the light emitting surface 20a from becoming too dark in the spaced region.

By combining the diffusion function of the light diffusion sheet 50 and the selective transmission function of the selective transmission portions 45 according to the incident angle as described above, in-plane variations in brightness depending on the arrangement of the light sources 23 can be suppressed. Thereby, the illuminance at each position on the second surface 40b of the selective transmission sheet 40 can be effectively uniformed.

As shown in FIG. 8A, the wavelength conversion sheet 60 includes a first barrier layer 63, a wavelength conversion section 65, a second barrier layer 64, and an optical element section 70 from the second side in the third direction D3. The light emitted from the selective transmission sheet 40 passes through the first barrier layer 63 of the wavelength conversion sheet 60 and travels toward the wavelength conversion section 65 .

As shown in FIG. 9, the wavelength converting portion 65 contains a wavelength converting agent 67. A portion of the light traveling through the wavelength converting portion 65 collides with the wavelength converting agent 67 . The wavelength conversion agent 67 absorbs the primary light LA emitted from the light source 23 and emits secondary light LB with a different wavelength. In the illustrated example, the wavelength converting portion 65 includes a first converting agent 67A and a second converting agent 67B. The first conversion agent 67A absorbs a portion L91 of the blue primary light LA and emits green first secondary light LB1. The second conversion agent 67B absorbs a portion L92 of the blue primary light LA and emits a red second secondary light LB2.

Most of the light L24 (see FIG. 2) traveling through the wavelength conversion sheet 60 travels in a direction greatly inclined with respect to the third direction D3 due to the transmission characteristics of the selective transmission portion 45. Therefore, even if the thickness of the wavelength conversion section 65 is reduced, the optical path length of the light L24 in the wavelength conversion section 65 is increased. Therefore, it becomes easier for the light to enter the wavelength conversion agent 67 in the wavelength conversion sheet 60 . Since the wavelength conversion agent 67 can be used efficiently, the content of the wavelength conversion agent 67 in the selective transmission portion 45 can be reduced.

As shown in FIG. 9, a portion L93 of the primary light LA does not enter the wavelength conversion agent 67 and reaches the second surface 60b.

As shown in FIG. 8A, the light L81 that has passed through the wavelength conversion section 65 passes through the second barrier layer 64 and travels to the optical element section 70. As shown in FIG. The optical element section 70 includes a plurality of unit optical elements 75 . The optical element portion 70 has an uneven surface 61 on the second surface 60 b of the wavelength conversion sheet 60 . The uneven surface 61 is composed of the element surfaces 76 of the unit optical elements 75 . The second surface 60b constitutes the light output side surface 30b. The light L<b>81 is refracted by the uneven surface 61 and emitted from the optical member 30 .

As shown in FIG. 8A, in the illustrated example, the traveling direction angle formed by the traveling direction with respect to the third direction D3 can be reduced due to the refraction at the element surface 76 that constitutes the light exit side surface 30b. That is, the element surface 76 of the optical element portion 70 exerts a condensing function on the emitted light. The light-collecting function of the optical element section 70 can reduce the burden of correcting the optical path of the light transmitted through the optical member 30 . Therefore, the utilization efficiency of the light transmitted through the optical member 30 can be improved. In addition, the number and thickness of members incorporated in the surface light source device 20 can be reduced, and the surface light source device 20 can be thinned.

As described above, the light L25 (see FIG. 2) such as the primary light LA, the first secondary light LB1 and the second secondary light LB2 can be emitted from the optical member 30 to the first side in the third direction D3. . The light L25 emitted from the optical member 30 passes through the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85, and is emitted from the light emitting surface 20a of the surface light source device 20. FIG. Thus, the light emitting surface 20a of the surface light source device 20 emits light.

By the way, as shown in FIGS. 2 and 13, the lights L26, L131, and L132 incident on the second surface 60b of the wavelength conversion sheet 60 can be reflected by the second surface 60b. Lights L26, L131, and L132 reflected by the second surface 60b travel to the second side in the third direction D3. By being reflected by any interface, for example, the surface of the reflective layer 27, these lights can turn around in the traveling direction in the third direction D3 and enter the light output side surface 30b again. These lights travel in the first direction D1 and the second direction D2 perpendicular to the third direction D3 until they reach the light exit side surface 30b again. Therefore, by utilizing the reflection on the light exit side surface 30b, it is possible to more effectively suppress in-plane variations in brightness due to the arrangement of the light source 23. FIG. That is, the wavelength conversion sheet 60 can reinforce or complement the optical characteristics of the selective transmission portion 45 having the incident angle dependence, and can further sufficiently uniform the in-plane distribution of the illuminance.

In FIG. 13, the thickness of the wavelength conversion sheet 60 is shown to be thin in order to facilitate understanding of the optical action regarding the optical path within the wavelength conversion sheet 60 . Also, in FIG. 13, illustration of the wavelength conversion agent 67 is omitted. Actually, a wavelength conversion agent 67 is provided between the first surface 60a and the second surface 60b of the wavelength conversion sheet 60. As shown in FIG. By utilizing the reflection on the second surface 60 b of the wavelength conversion sheet 60 , the wavelength conversion agent 67 is positioned within the circulating optical path of the light emitted from the light source 23 . In particular, the wavelength conversion agent 67 is dispersed inside the wavelength conversion sheet 60 that turns back the traveling direction in the third direction D3 in the circulating optical path. Therefore, in the wavelength conversion sheet 60 containing the wavelength conversion agent 67, the light travels in a direction inclined with respect to the third direction D3. The optical path length in the wavelength conversion sheet 60 becomes very long. As a result, the utilization efficiency of the wavelength conversion agent 67 can be significantly improved, and the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be greatly reduced. For example, the thickness of the wavelength converting portion 65 can be reduced, and the thicknesses of the optical member 30 and the surface light source device 20 in the third direction D3 can be reduced. The density of the wavelength conversion agent 67 in the wavelength conversion section 65 can be reduced.

In the illustrated wavelength converting portion 65 , the wavelength converting agent 67 is dispersed within the base material portion 66 . The refractive index of the base material portion 66 may be smaller than the refractive index of the optical element portion 70 . The refractive index of the base material portion 66 may be smaller than the refractive index of the selective transmission portion 45 . According to such setting of the refractive index, the light travels in a direction greatly inclined with respect to the third direction D3 within the wavelength conversion section 65 . This makes it possible to ensure a longer optical path length in the wavelength conversion section 65 . Therefore, the content of the wavelength conversion agent 67 in the wavelength conversion section 65 can be reduced. The thickness of the wavelength converting portion 65 can be made thin.

In the wavelength conversion sheet 60, a barrier layer may not be provided on the side end face of the wavelength conversion portion 65 in some cases. According to this example, the deterioration of the wavelength conversion agent 67 located near the side end surface progresses, and the color of the peripheral portion of the wavelength conversion portion 65 may change. According to the present embodiment, the content of the wavelength converting agent 67 in the wavelength converting portion 65 can be reduced as described above. Therefore, the area ratio of the wavelength conversion agent 67 per unit area in the projection in the third direction D3 can be reduced. Accordingly, even when no barrier layer is provided on the side end surface of the wavelength conversion section 65, color change in the peripheral portion can be suppressed.

Here, the transmittance of the selective transmission portion 45, which is a dielectric multilayer film, increases with respect to light with a longer wavelength than the specific wavelength. More specifically, the incident angle at which the transmittance starts to increase is small for light with a long wavelength. The selective transmission of the selective transmission portion 45, which depends on the angle of incidence, becomes weaker with respect to light with a wavelength greater than the specific wavelength. Therefore, the selective transmission portion 45 cannot effectively exhibit the selective transmission property depending on the incident angle with respect to the secondary light LB having a wavelength longer than the specific wavelength. In other words, the selective transmission section 45 cannot reflect the secondary light LB similarly to the primary light LA.

Therefore, from the viewpoint of sufficiently uniforming the in-plane distribution of the illuminance, after the primary light LA is sufficiently circulated between the optical member 30 and the light source substrate 22 to uniform the in-plane distribution of the illuminance, the primary light It is preferable to convert LA into secondary light LB. That is, from the viewpoint of suppressing in-plane variations in brightness, it is preferable to reduce the content of the wavelength conversion agent 67 in the selective transmission portion 45 that is in the circulating optical path.

Further, the primary light LA may be selectively reflected on the light exit side surface 30b. The reflectance of the primary light LA on the light exit side surface 30b may be greater than the reflectance of the secondary light LB on the light exit side surface 30b. As shown in FIG. 9 , the traveling direction of the secondary light LB emitted from the wavelength converting agent 67 does not depend on the traveling direction of the primary light LA before being absorbed by the wavelength converting agent 67 . As shown in FIG. 9, the secondary light LB is emitted from the wavelength conversion agent 67 over a wide angular range. The angular distribution of luminance caused by the secondary light LB is uniformed to some extent on the second surface 65b of the wavelength converting section 65. As shown in FIG. That is, the traveling direction angle of the secondary light LB is dispersed within a wide angle range. On the other hand, the traveling direction angle of the primary light LA depends on the transmission characteristics of the selective transmission portion 45 and falls within a relatively narrow angle range. The angle of incidence (°) shown in FIG. 7 is the angle of incidence from an air layer with a refractive index of one. Here, it is assumed that the refractive index of transparent resin generally used for optical members is 1.4 or more and 1.7 or less. It is assumed that the selective transmission portion 45 intensively transmits light with an incident angle of 45° to 70° from the air layer. In this reference assumption, the traveling direction angle (°) of the light passing through the selective transmission portion 45 and traveling through the resin, that is, the angle (°) between the traveling direction and the third direction D3 is about 25° to 40°. becomes. The inclination angle θp (°) of the element surface 76 forming the light output side surface 30b may be adjusted so that the primary light LA with this limited traveling direction angle is reflected by the light output side surface 30b.

The inclination angle θp is the angle (°) between the element plane 76 and the plane orthogonal to the third direction D3. It is also envisioned that the element face 76 is not flat. The inclination angle θp of the element surface 76 is specified at the center position of the element surface 76 in the third direction D3. In the illustrated example in which the optical element portion 70 constitutes the second surface 60b, the element surface 76 as the convex portion 73 has a base end portion connected to the main body portion 72 of the element surface 76 and a second surface extending from the main body portion 72. The inclination angle θp is specified at the position that is the center in the third direction D3 from the tip that is the most distant in the three directions D3. In the illustrated example in which the optical element portion 70 constitutes the second surface 60b, the element surface 76 as the concave portion 74 is the base end portion of the element surface 76 that is closest to the selective transmission sheet 40 in the third direction D3. The inclination angle θp is specified at the center position in the stacking direction D3 between the (deepest portion) and the tip portion (bank portion) farthest away from the selectively permeable sheet 40 in the stacking direction D3.

FIG. 13 shows an optical path in which the traveling direction in the third direction D3 is turned back by reflection on the element surface 76. FIG. Both the light L131 and the light L132 are incident on the first element surface 76A that is inclined to the same side as the traveling direction with respect to the third direction D3. The lights L131 and L132 are reflected by the first element surface 76A. The inclination angle θp may be set so that the reflection on the first element surface 76A is total reflection. Assuming the reference conditions described above, the inclination angle θp may be 5° or more, 10° or more, or 15° or more.

Further, the inclination angle θp may be set so that the traveling direction of the light is turned back in the third direction D3 by the reflected light from the first element surface 76A and directed toward the second side. Assuming the reference conditions described above, the inclination angle θp may be 35° or less, 30° or less, or 25° or less.

The lights L131 and L132 are then incident on the second element surface 76B facing the first element surface 76A. The light L131 is further reflected by the second element surface 76B. Due to the reflection on the second element surface 76B, the traveling direction of the light L131 is turned back in the third direction D3 to face the second side. Preferably, this reflection is total internal reflection. The tilt angle θp may be set so that the reflection on the second element surface 76B is total reflection. Assuming the reference conditions described above, the inclination angle θp may be 38° or less, 35° or less, or 32° or less.

The light L132 is refracted by the second element surface 76B and emitted from the unit optical element 75. After that, the light L132 enters another adjacent unit optical element 75 via the third element surface 76C. Next, the light L132 is reflected by the fourth element surface 76D of another unit optical element 75. As shown in FIG. Due to the reflection on the fourth element surface 76D, the traveling direction of the light L132 is turned back in the third direction D3 to face the second side.

As for the traveling direction of the light L132, due to refraction on the second element surface 76B when emitted from the first unit optical element 75, the traveling direction of the light may be turned back in the third direction D3 toward the second side. . The inclination angle θp may be set so that the traveling direction of the light is turned back in the third direction D3 by refraction on the second element surface 76B and directed toward the second side. Assuming the reference conditions described above, the inclination angle θp may be 38° or less, 35° or less, or 32° or less. As another condition, although it continues to travel to the first side in the third direction D3 after being refracted on the second element surface 76B, like the light L132, the refraction on the second element surface 76B causes the traveling direction angle The inclination angle θp may be set such that . In other words, although the light continues to travel toward the first side in the third direction D3 even after being refracted on the second element surface 76B, the traveling direction of the light changes with respect to the third direction D3 due to the refraction on the second element surface 76B. The tilt angle θp may be set so that the tilt angle θp is greater. Assuming the reference conditions described above, the inclination angle θp may be 55° or less, 50° or less, or 45° or less.

By setting the inclination angle θp of the element surface 76 as described above, the primary light LA whose traveling direction angle is adjusted by the selective transmission section 45 is selectively emitted from the light exit side surface 30b formed by the element surface 76. can be reflected Thereby, the illuminance distribution can be more effectively uniformed.

Note that in the illustrated example, the wavelength conversion sheet 60 is joined to the selective transmission sheet 40 . According to this example, the utilization efficiency of the light emitted from the light source 23 can be improved. FIG. 9 shows the optical path of light L94 assuming that a gap is provided between the wavelength conversion sheet 60 and the selective transmission sheet 40. FIG. In FIG. 9, light L94 and light L91 are emitted from the selective transmission sheet 40 in the same direction. Light L94 incident on the wavelength conversion sheet 60 through the gap is reflected by the first surface 60a of the wavelength conversion sheet 60 . Depending on the transmission characteristics of the selective transmission portion 45, the lights L91 and L94 travel in directions greatly inclined with respect to the third direction D3. Therefore, the light L94 is reflected at the first surface 60a of the wavelength conversion sheet 60 with a high reflectance. Such light L94 becomes stray light and reduces light utilization efficiency. On the other hand, by bonding the selective transmission sheet 40 and the wavelength conversion sheet 60 via, for example, the bonding layer 35, the incident angle to the first surface 60a of the wavelength conversion sheet 60 can be reduced. As a result, the reflection on the first surface 60a can be suppressed, and the light utilization efficiency can be improved.

In the embodiment described above, the optical member 30 includes the selective transmission sheet 40 including the selective transmission portion 45, the first surface 60a on the side of the selective transmission sheet 40, and the second surface facing the first surface 60a. and a wavelength conversion sheet 60 including 60b. The transmittance of the selective transmission portion 45 for light of a specific wavelength incident on the selective transmission portion 45 at an incident angle greater than 0° is is greater than the transmittance of the selective transmission portion 45 of . At least one of the first surface 60 a and the second surface 60 b includes an uneven surface 61 . In the first aspect of the present embodiment, second surface 60b includes uneven surface 61 . The wavelength conversion sheet 60 includes a wavelength conversion agent 67 that absorbs primary light LA and emits secondary light LB. The secondary light LB has a wavelength different from that of the primary light LA.

According to the optical member 30 according to the first aspect of the present embodiment, the primary light LA from the light source 23 can be reflected by the second surface 60b of the wavelength conversion sheet 60. That is, the second surface 60b can reflect light directed toward the first side, which is the viewer side, in the third direction D3. Therefore, a circulating optical path in which the primary light LA circulates can be formed between the second surface 60b of the wavelength conversion sheet 60 and the light source substrate 22 and the like. According to the present embodiment, the wavelength conversion agent 67 is included in the wavelength conversion sheet 60 that folds back in the third direction D3. The primary light LA travels in a direction inclined with respect to the third direction D3 within the wavelength conversion sheet 60 depending on the transmission characteristics of the selective transmission portion 45 . Therefore, the content of the wavelength conversion agent 67 in the wavelength conversion sheet 60 can be greatly reduced. Rather, by reducing the content of the wavelength conversion agent 67 that emits the secondary light LB in various directions, the circulation of the primary light LA using reflection on the second surface 60b can be promoted. That is, the circulation of the primary light LA can significantly reduce the content of the wavelength conversion agent 67 while suppressing the in-plane variation in brightness caused by the arrangement of the light sources 23 and suppressing the in-plane variation in illuminance. It is also possible to reduce the thickness of the optical member 30 and the optical laminate 21 and to reduce the thickness of the surface light source device 20 .

Although the first aspect of the present embodiment has been described with reference to specific examples, the above-described specific examples do not limit the first aspect of the present embodiment. The first aspect of the present 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.

For example, a spacer may be arranged between the light source substrate 22 and the optical member 30 in the surface light source device 20 described above. A transparent resin layer may be provided between the light source substrate 22 and the optical member 30, and the resin layer may function as a spacer. The resin layer may be made of a thermoplastic resin. The resin layer may contain a light diffusion component. Examples of the light diffusing component include metal compounds, gas-containing porous substances, resin beads surrounding metal compounds, white fine particles, mere air bubbles, and crystalline interfaces.

For example, in the specific example described above, one or more of the first light control sheet 81 , the second light control sheet 82 and the reflective polarizing plate 85 may be omitted from the optical laminate 21 of the surface light source device 20 . Also, the light diffusion sheet 50 may be omitted from the optical member 30 .

Alternatively, the selective transmission sheet 40 may be omitted from the optical member 30 as another form. In this modified example, the optical member 30 may include the light diffusion sheet 50 and the wavelength conversion sheet 60 . The light diffusion sheet 50 and the wavelength conversion sheet 60 may be bonded together as shown in FIG. In the example shown in FIG. 14, the light diffusion sheet 50 includes a main body portion 52 and a plurality of unit diffusion elements 55. As shown in FIG. The light diffusion sheet 50 can exhibit a light diffusion function by the uneven surface 51 formed by the element surfaces 56 of the unit diffusion elements 55 . The body portion 52 may contain a light diffusing component. Examples of the light diffusing component include metal compounds, gas-containing porous substances, resin beads surrounding metal compounds, white fine particles, mere air bubbles, and crystalline interfaces. In the optical member 30 shown in FIG. 14 as well, due to the light diffusion function of the light diffusion sheet 50, the traveling direction of the light incident on the wavelength conversion sheet 60 can be greatly inclined with respect to the third direction D3. Therefore, while reducing the amount of the wavelength conversion agent 67 contained in the wavelength conversion sheet 60, the in-plane variation in brightness can be effectively suppressed.

Here, the above-described first aspect of the present embodiment will be described in more detail using an example, but the above-described first aspect of the present embodiment is not limited to this example.

The surface light source devices of Example A1 and Comparative Example A1 were manufactured as follows.

<Example A1>
The surface light source device of Example A1 had the configuration shown in FIG. The surface light source device included a light source substrate including a light source, an optical member, a first light control sheet, a second light control sheet, and a reflective polarizing plate. The support substrate had a white reflective layer containing titanium oxide. Diffuse reflection with a reflectance of 95% was used for reflection on the reflective layer of the support substrate. The light sources were arranged in a square array on the support substrate as shown in FIG. The arrangement pitch of the light sources in the first direction was 6 mm. The arrangement pitch of the light sources in the second direction perpendicular to the first direction was 6 mm. As each light source, a light-emitting diode that emits blue light with a central wavelength of 450 nm was used. The planar shape of this light-emitting diode was a rectangular shape of 0.2 mm×0.4 mm. The light-emitting diode was arranged on the support substrate such that the sides of the light-emitting diode were along the first direction and the second direction. The distance along the third direction D3 from the surface of the light source facing the optical member to the light incident side surface of the optical member was set to 0.5 mm.

In the surface light source device of Example A1, as shown in FIG. 5, the optical member included a light diffusion sheet, a selective transmission sheet and a wavelength conversion sheet in this order from the second side in the third direction D3. The selectively permeable sheet contained a selectively permeable portion. A light diffusion sheet and a wavelength conversion sheet were bonded to the selective transmission portion. A dielectric multilayer film obtained from Toray Industries, Inc. was used for the selective transmission portion. The selective transmission portion had transmission characteristics shown in FIG. 7 for light of 450 nm. The wavelength conversion sheet contained a first barrier layer, a wavelength conversion section, a second barrier layer and an optical element section, as shown in FIG. 8A. The light diffusing sheet and the optical element portion were molded by supplying an ultraviolet curable resin composition before curing between the mold and the body portion and curing the composition between the mold and the body portion.

The optical element portion includes a body portion and unit optical elements as convex portions arranged on the body portion. The optical element portion included unit optical elements having configurations such as shapes and arrangements described with reference to FIGS. 11A and 11B. As shown in FIG. 11A, unit optical elements of the same shape were arranged on the surface of the main body with no space between them, while changing the orientation of the bottom surface in four types. Each unit optical element had a triangular pyramid shape and included three element faces. The bottom surface of the unit optical element was in the shape of an isosceles right triangle. The element faces of the unit optical element included equilateral element faces extending from equilateral sides of the isosceles right triangle forming the base and base element faces extending from the base of the isosceles right triangle forming the base. . The base is the side facing the vertex forming a right angle with the base. The length of each of the two equilateral sides of the isosceles right triangle forming the bottom was set to 0.1 mm. The inclination angle θp of each equilateral element surface was 45°. The inclination angle θp of the base element surface was 45°.

The light diffusing sheet included a sheet-like main body joined to the selective transmission sheet, and unit diffusion elements as recesses arranged on the main body. The light diffusion sheet included unit diffusion elements having configurations such as shapes and arrangements described with reference to FIGS. 11A and 11B. As shown in FIG. 11A, unit diffusion elements of the same shape were arranged on the surface of the main body with no space between them, with the orientation of the bottom surface changed in four types. Each unit diffuser element had a triangular pyramidal shape and included three element faces. The base of the unit diffuser element was an isosceles right triangle shape. The element faces of the unit diffusion elements included equilateral element faces extending from the equilateral sides of the isosceles right triangle forming the base and base element faces extending from the base of the isosceles right triangle forming the base. . The length of each of the two equilateral sides of the isosceles right triangle forming the bottom was set to 0.1 mm. The inclination angle θp of each equilateral element surface was 45°. The inclination angle θp of the base element surface was 45°. As a result, the concave-convex surface formed by the element surfaces of the unit diffusion elements was configured identically to the concave-convex surface formed by the element surfaces of the unit optical elements, except that the concave-convex surfaces were reversed.

QF-6000 available from Showa Denko Materials was used as the wavelength converter. As the first light control sheet and the second light control sheet, two sheets of brightness enhancement film BEF (registered trademark) available from 3M Company were used. As for the first light control sheet, the longitudinal direction of the prisms extended in the second direction. As for the second light control sheet, the longitudinal direction of the prisms extended in the first direction. As a reflective polarizer, a brightness enhancement film DBEF (registered trademark) available from 3M Company was used.

In the surface light source device of Example A1, the distance along the third direction from the surface of the light source facing the optical member to the light incident side surface of the optical member facing the light source was 0.5 mm.

<Comparative Example A1>
In the surface light source device of Comparative Example A1, instead of the wavelength conversion sheet of Example A1, a laminate including the first barrier layer, the wavelength conversion section and the second barrier layer was joined to the selective transmission section of the selective transmission sheet. That is, in the surface light source device of Comparative Example A1, the optical element portion was omitted from the optical member of Example A1. Further, in the surface light source device of Comparative Example A1, the content of the wavelength converting agent contained in the wavelength converting portion was 1.5 times the content of the wavelength converting agent of Example A1. The surface light source device of Comparative Example A1 was otherwise the same as the surface light source device of Example A1.

<Evaluation>
Regarding the surface light source devices of Example A1 and Comparative Example A1, the distribution of radiant intensity on the light emitting surface of the surface light source device was measured while the light source was emitting light. The measurement range of the radiant intensity was a circular evaluation area with a radius of 6 mm centered on one light source. The evaluation area was set so that the light source was positioned at the center of the evaluation area when observed from the third direction. 15 and 16 show in-plane distributions of radiant intensity on the light emitting surfaces of the surface light source devices of Example A1 and Comparative Example A1, respectively. 15 and 16 show the magnitude of the radiant intensity at each position within the evaluation area by the color density at that position. Colors are darker at positions where the radiation intensity is low. In FIGS. 15 and 16, the black area indicates the outside of the evaluation area. In FIGS. 15 and 16, circles centered on the light source are indicated by white lines. The white-lined circle is superimposed on the radiant intensity distribution for the purpose of indicating the position of the center of the light source.

With respect to the surface light source device of Comparative Example A1 shown in FIG. 16, the radiant intensity distribution was uneven according to the arrangement of the light sources, and the positions of the light sources could be grasped. The in-plane distribution of radiant intensity of the surface light source device of Example A1 was sufficiently uniform with respect to the in-plane distribution of radiant intensity of the surface light source device of Comparative Example A1. In Example A1 shown in FIG. 15, the brightness distribution was uniform, making it difficult to find the position of the light source.

<Second aspect>
17 to 25 are diagrams for explaining the second aspect of the present embodiment. Among FIGS. 1 to 16, some drawings such as FIG. 1, FIG. 3, and FIG. 4 are diagrams for explaining the second aspect. FIG. 17 is a longitudinal sectional view showing one specific example of the surface light source device 20 in the second mode. The surface light source device 20 shown in FIG. 17 can be applied to the display device 10 of FIG. The second mode differs from the above-described first mode in the optical element portion 70 included in the wavelength conversion sheet 60 of the optical member 30 . The second aspect can be configured in the same manner as the above-described first aspect except for the optical element portion 70 included in the wavelength conversion sheet 60 . That is, the surface light source device 20 in the second aspect may include the light source substrate 22 described above as the first aspect. The optical laminate 21 in the second aspect may include the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 described in the first aspect. The optical member 30 in the second aspect may include the selective transmission sheet 40 and the light diffusion sheet 50 described as the first aspect.

As shown in FIG. 17, the surface light source device 20 may include a light source 23 and an optical laminate 21 that adjusts the optical path of the light emitted from the light source 23 as main components. The optical laminate 21 may include optical members 30 . The optical layered body 21 and the optical member 30 may face the light source 23 . The optical layered body 21 and the optical member 30 may be sheet-like members. The optical layered body 21 and the optical member 30 may face the light source 23 in their normal direction. The optical layered body 21 and the optical member 30 may be diffusion members that diffuse the light emitted from the light source 23 . The optical layered body 21 and the optical member 30 can effectively suppress in-plane variations in illuminance caused by the arrangement of the light sources 23 . Due to the diffusion in the optical layered body 21 and the optical member 30, the illuminance at each position on the light emitting side surface 30b of the optical layered body 21 and the optical member 30, or an imaginary light parallel to the light emitting side surface 30b located near the light emitting side surface 30b. The illuminance at each position on the light receiving surface of can be effectively uniformed.

The display device 10, the surface light source device 20, and the optical laminated body 21 in the second aspect will be described below with reference to the illustrated specific examples. The display panel 15 of the display device 10 may be configured in the same manner as the above-described display panel 15 described as the first mode. The light source substrate 22 of the surface light source device 20 may be configured in the same manner as the above-described light source substrate 22 described as the first mode. The optical laminate 21 may include the optical member 30 , the first light control sheet 81 , the second light control sheet 82 and the reflective polarizing plate 85 in order from the light source substrate 22 . Of these, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 are the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85, respectively, described as the first mode. It may have the same configuration as the polarizing plate 85 .

The optical member 30 includes a selective transmission sheet 40 and a wavelength conversion sheet 60 in order from the light source substrate 22 . The selective transmission sheet 40 and the wavelength conversion sheet 60 are stacked in the third direction D3. That is, the third direction D3 is the lamination direction of the selective transmission sheet 40 and the wavelength conversion sheet 60 . The selective transmission sheet 40 is positioned closer to the second side in the third direction D3 than the wavelength conversion sheet 60 is. The wavelength conversion sheet 60 is positioned closer to the first side in the third direction D3 than the selective transmission sheet 40 is. In the illustrated example, the selective transmission sheet 40 and the wavelength conversion sheet 60 are both sheet-like members extending in the first direction D1 and the second direction D2. In the illustrated example, the selective transmission sheet 40 constitutes the light incident side surface 30 a of the optical member 30 . In the illustrated example, the wavelength conversion sheet 60 constitutes the light output side surface 30b of the optical member 30. As shown in FIG. The selective transmission sheet 40 and the wavelength conversion sheet 60 may be bonded to each other, may be simply in contact and not bonded, or may be separated from each other. Note that the optical member 30 may include the light diffusion sheet 50 as in the first aspect. The first surface 50a of the light diffusion sheet 50 may constitute the light incident side surface 30a.

The selectively permeable sheet 40 includes a selectively permeable portion 45 . The selective transmission sheet 40 and the selective transmission section 45 may be the same as the selective transmission sheet 40 and the selective transmission section 45 described in the first mode. The reflectance and transmittance of the selective transmission portion 45 change depending on the incident angle. In the example shown in FIG. 18 , the selective transmission sheet 40 is composed of only the selective transmission portion 45 . The illustrated selective transmission portion 45 is sheet-shaped.

The illustrated selectively permeable sheet 40 includes a first surface 40a and a second surface 40b. The first surface 40a faces the second side that is the light source side in the third direction D3, and the second surface 40b faces the first side that is the viewer side in the third direction D3. The selective transmission portion 45 includes a first surface 45a and a second surface 45b. The first surface 45a faces the second side in the third direction D3. The second surface 45b faces the first side in the third direction D3. The first surface 45 a of the selectively transmitting portion 45 constitutes the first surface 40 a of the selectively transmitting sheet 40 . The second surface 45 b of the selectively transmitting portion 45 constitutes the second surface 40 b of the selectively transmitting sheet 40 . The first surface 40a and the second surface 40b are parallel flat surfaces.

The transmission characteristics and reflection characteristics of the selective transmission portion 45 have incident angle dependency. The transmission characteristics and reflection characteristics of the selective transmission portion 45 may be the same as the transmission characteristics and reflection characteristics described above as the first mode.

FIG. 19 shows a first specific example and a second specific example of the transmission characteristics of the selective transmission portion 45. FIG. The incident angle (°) on the horizontal axis in the graph of FIG. 19 indicates the incident angle when the selective transmission portion 45 forms an interface with the air layer. In the first specific example and the second specific example shown in FIG. 19, the transmittance of the selective transmission portion 45 takes the maximum value in the range where the absolute value of the incident angle is 65° or more and 70° or less. The transmittance of the selective transmission portion 45 increases as the incident angle increases from 0° to the maximum incident angle. The maximum transmittance of the selective transmission portion 45 is 40% or more and 50% or less. The optical characteristics of the selective transmission portion 45 described here are that the first surface 45a and the second surface 45b of the selective transmission portion 45 are parallel, and the first surface 45a and the second surface 45b are adjacent to the air layer. is assumed.

The first and second specific examples of transmission characteristics shown in FIG. 19 are also applicable to the selective transmission portion 45 of the first mode. The first specific example and second specific example of the transmission characteristics shown in FIG. 19 are also applicable to the selective transmission portion 45 of the third and fourth modes described later.

As shown in FIGS. 20 and 21, the wavelength conversion sheet 60 includes a first surface 60a and a second surface 60b. The first surface 60a faces the second side that is the light source side in the third direction D3. The second surface 60b faces the first side that is the viewer side in the third direction D3. In this embodiment, at least one of the first surface 60a and the second surface 60b includes an uneven surface 61. As shown in FIG. In the second aspect, the first surface 60 a includes an uneven surface 61 . The illustrated first surface 60a is an uneven surface 61 over the entire surface. The second surface 60b includes a flat surface. The illustrated second surface 60b is entirely flat. The second surface 60b may be a surface perpendicular to the third direction D3.

20 and 21, the wavelength conversion sheet 60 includes an optical element section 70, a first barrier layer 63, a wavelength conversion section 65 and a second barrier layer 64 in order from the selective transmission sheet 40. I'm in. The optical element portion 70, the first barrier layer 63, the wavelength converting portion 65 and the second barrier layer 64 are stacked in this order in the third direction D3. The optical element portion 70, the first barrier layer 63, the wavelength conversion portion 65, and the second barrier layer 64 are arranged in this order from the first side toward the second side in the third direction D3. The optical element portion 70, the first barrier layer 63, the wavelength conversion portion 65 and the second barrier layer 64 are sheet-like. The optical element portion 70, the first barrier layer 63, the wavelength converting portion 65 and the second barrier layer 64 extend in the first direction D1 and the second direction D2.

The optical element portion 70, the first barrier layer 63, the wavelength conversion portion 65 and the second barrier layer 64, which constitute the wavelength conversion sheet 60, can be configured in the same manner as the corresponding portions described above as the first. The wavelength conversion sheet 60 in the second aspect may differ from the wavelength conversion sheet 60 in the first aspect only in the arrangement of the optical element portions 70 . The wavelength conversion sheet 60 in the second aspect may be configured in the same manner as the wavelength conversion sheet 60 in the first aspect except for the arrangement of the optical element portion 70 . In the example shown in FIGS. 20 and 21, the first surface 70a of the optical element portion 70 constitutes the first surface 60a. In the example shown in FIGS. 20 and 21, the second barrier layer 64 forms the second surface 60b and the light output side surface 30b.

The wavelength conversion part 65 may contain a plurality of quantum dots with different emission wavelengths as the wavelength conversion agent 67 . 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 Figure 22, the wavelength converting agent 67 includes a first converting agent 67A and a second converting agent 67B. The first conversion agent 67A and the second conversion agent 67B have different sizes. The first conversion agent 67A and the second conversion agent 67B emit light of different wavelengths.

As shown in FIG. 22 , the wavelength converting portion 65 may include a base material portion 66 and a wavelength converting agent 67 . The wavelength conversion agent 67 includes a first conversion agent 67A that absorbs the primary light LA and emits first secondary light LB1, and a second conversion agent 67B that absorbs the primary light LA and emits second secondary light LB2. and may include In this example, the wavelength of the second secondary light LB2 is longer than the wavelength of the first secondary light LB1. The wavelength of the first secondary light LB1 is longer than the wavelength of the primary light LA. The conversion efficiency of the second conversion agent 67B in the wavelength conversion section 65 may be higher than the conversion efficiency of the first conversion agent 67A. This point may be the same for the first aspect, the third aspect described later, and the fourth aspect described later.

The conversion efficiency of the wavelength conversion agent is the amount of light (W) of the primary light LA incident on the first surfaces 60a and 65a of the wavelength conversion sheet 60 or the wavelength conversion portion 65 with respect to the second surface of the wavelength conversion sheet 60 or the wavelength conversion portion 65. It is evaluated by the ratio (%) of the light quantity (W) of the target secondary light LB emitted from 60b and 65b. This evaluation is performed with the first surfaces 60a, 65a and the second surfaces 60b, 65b of the wavelength conversion sheet 60 or the wavelength conversion portion 65 as flat surfaces perpendicular to the third direction D3. It can be said that the higher the ratio of the secondary light LB, the higher the conversion efficiency. In measuring the conversion efficiency, the incident angle of the primary light LA to the first surfaces 60a and 65a of the wavelength conversion sheet 60 or the wavelength conversion portion 65 is 0°. The first secondary light LB1 and the second secondary light LB2 emitted from the second surfaces 60b and 65b of the wavelength conversion sheet 60 or the wavelength conversion portion 65 are collected in an integrating sphere, and the light amount (W) of the first secondary light LB1 is and the light quantity (W) of the second secondary light LB. This allows the conversion efficiency to be specified.

The optical element portion 70 includes a second surface 70b facing the first side, which is the viewer side in the third direction D3. The optical element portion 70 is bonded to the first barrier layer 63 on the second surface 70b. The optical element portion 70 includes a first surface 70a facing a first side that is the light source side in the third direction D3. The first surface 70 a of the optical element portion 70 constitutes the first surface 60 a of the wavelength conversion sheet 60 . The first surface 70 a includes an uneven surface 61 . The optical element portion 70 may differ from the optical element portion 70 of the first aspect only in the arrangement within the wavelength conversion sheet 60 . The optical element portion 70 may be configured in the same manner as the optical element portion 70 of the first mode except for the arrangement within the wavelength conversion sheet 60 .

In the example shown in FIGS. 20 and 21, the optical element portion 70 includes a plurality of unit optical elements 75 each formed as a convex portion 73 or a concave portion 74 . The unit optical element 75 is an element that changes the traveling direction of light by refraction, reflection, or the like. The unit optical element 75 directly faces the selective transmission sheet 40 . A concave-convex surface 61 is formed by the unit optical element 75 .

The optical element portion 70 shown in FIG. 20 includes a sheet-like body portion 72 and a plurality of convex portions 73 provided on the body portion 72 . In the example shown in FIG. 20, the plurality of protrusions 73 may be provided adjacent to each other without gaps. The optical element portion 70 shown in FIG. 21 includes a body portion 72 provided with a plurality of recesses 74 on the surface facing the selective transmission sheet 40 in the third direction D3. In the example shown in FIG. 21, the plurality of recesses 74 may be provided adjacent to each other without gaps.

As shown in FIGS. 20 and 21, the unit optical element 75 has an element surface 76 inclined with respect to the third direction D3. A unit optical element 75 is defined by this element surface 76 . The uneven surface 61 of the wavelength conversion sheet 60 is composed of the element surfaces 76 of the unit optical elements 75 .

The optical characteristics of the uneven surface 61 are affected by the inclination angles of the element surfaces 76 of the unit optical elements 75 . Therefore, the cross-sectional shape of the unit optical element 75 can be appropriately adjusted based on the optical properties required for the surface light source device 20 and the optical member 30 . The inclination angles of a plurality of element surfaces 76 included in one unit optical element 75 may be different from each other or may be the same. The optical element section 70 may include unit optical elements 75 that differ in at least one of shape and orientation, or may include only unit optical elements 75 that are the same as each other.

Unlike the examples shown in FIGS. 20 and 21, the element faces 76 may be somewhat curved. The unit optical element 75 may have the outer shape of a portion of a sphere such as a hemisphere, or the outer shape of a portion of a spheroid.

The plurality of unit diffusion elements 55 may be arranged two-dimensionally. According to this example, light can be guided in a plurality of non-parallel directions, and the in-plane distribution of illuminance can be effectively uniformed. Each unit optical element 75 may be configured rotationally symmetrical about an axis parallel to the third direction D3. For example, each unit optical element 75 may be configured with 3-fold, 4-fold, or 6-fold symmetry about an axis parallel to the third direction D3.

The plurality of unit optical elements 75 may be arranged irregularly or may be arranged regularly. By regularly arranging the unit optical elements 75, the design of the optical element section 70 can be facilitated. By regularly arranging the plurality of unit optical elements 75, it becomes easy to spread the unit optical elements 75 without gaps. The dimensions, arrangement pitch, etc. of the unit optical elements 75 may be the same as in the first mode.

23A and 23B show specific examples of unit optical elements 75 included in the optical element section 70. FIG. In the example shown in FIGS. 23A and 23B, the multiple unit optical elements 75 are arranged in a square arrangement. The plurality of unit optical elements 75 are arranged at a constant pitch in the first direction D1. The plurality of unit optical elements 75 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. 23A and 23B, the plurality of unit optical elements 75 may be 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 unit optical elements 75 may be arranged in directions inclined in the first direction D1 and the second direction D2. For example, in the example shown in FIG. 23C, the plurality of unit optical elements 75 are arranged at a constant pitch in two directions that are inclined ±45° with respect to the first direction D1. The arrangement of FIG. 23C can be applied to the unit optical element 75 shown in FIG. 23B. According to this example, the element surface 76 faces in two directions that are inclined by ±45° with respect to the first direction D1, and the light can be spread in these two directions.

The optical element section 70 and the unit optical elements 75 may have the configurations described with reference to FIGS. 11A and 11B as the first mode.

The optical element portion 70 shown in FIGS. 20 to 23C can be produced by embossing or resin molding. The optical element portion 70 including the unit optical elements 75 may be bonded to the first barrier layer 63 via a bonding layer containing adhesive or adhesive. An optical element portion 70 including unit optical elements 75 may be fabricated on the first barrier layer 63 .

The optical element section 70 may include a diffractive optical element.

Next, the operation of generating planar light with the planar light source device 20 having the above configuration will be described.

As shown in FIG. 17, the light source 23 emits primary light LA. The primary light LA is, for example, blue light. The wavelength of the blue primary light LA may be 430 nm or more and 500 nm or less. A light L21 emitted from the light source 23 travels toward the optical member 30 . As shown in FIG. 18 , primary light LA from light source 23 is incident on selective transmission sheet 40 of optical member 30 . As shown in FIG. 18 , the selective transmission sheet 40 includes a selective transmission portion 45 .

The primary light LA from the light source 23 enters the selective transmission section 45 . The transmittance of the selective transmission portion 45 depends on the incident angle. The transmittance of the selectively transmitting portion 45 for the primary light LA incident at an incident angle greater than 0° is greater than the transmittance of the selectively transmitting portion 45 for the primary light LA incident at an incident angle of 0°. With the optical characteristics shown in FIG. 19, the transmittance of the selective transmission portion 45 for light incident on the selective transmission portion 45 at an incident angle of 0° is 5% or less. In addition, the transmittance of the selective transmission portion 45 for light emitted from the selective transmission sheet 40 at an emission angle of 0° or more and 35° or less in absolute value is half or less of the maximum value of the transmittance of the selective transmission portion 45. there is Furthermore, the transmittance of the selective transmission portion 45 increases as the output angle increases within a wide range of absolute values from 0° to 65°. The transmittance is 10% or less when the absolute value of the output angle is in the range of 0° or more and 50° or less. That is, light inclined with respect to the third direction D3 can be transmitted through the selective transmission portion 45 with a higher transmittance than light traveling in the third direction D3. The output angle means the angle (°) formed by the traveling direction of the output light with respect to the normal direction of the member such as a sheet from which the light is output.

A region facing the light source 23 in the third direction D3 and a surrounding region near the region are defined as an immediately overhead region. A large amount of light is incident on this directly overhead region. However, the angle of incidence of light on the directly overhead region is small. Therefore, the light L171 emitted from the light source 23 and traveling to the selective transmission sheet 40 is reflected with high reflectance in the directly overhead region. In the directly overhead region, light passes through the selective transmission sheet 40 with low transmittance. As a result, it is possible to prevent the light emitting surface 20a from becoming too bright in the directly overhead region.

A large amount of light L172 reflected by the selective transmission portion 45 is directed toward the light source substrate 22. As shown in FIG. 17, the light L172 is reflected by the reflective layer 27 of the light source substrate 22. As shown in FIG. Due to this reflection, the light L173 reflected by the reflective layer 27 travels toward the optical member 30 in the third direction D3. The reflection on the reflective layer 27 may be diffuse reflection. Due to diffuse reflection, the angle formed by the traveling direction of the reflected light L173 with respect to the third direction D3 increases. As shown in FIG. 17, the light L173 re-enters the optical member 30 at a position away from the light source 23 in the first direction D1 or the second direction D2 orthogonal to the third direction D3.

The light L173 can re-enter the selectively transmissive sheet 40 in a spaced region away from the light source 23 in the direction orthogonal to the third direction D3. When the reflected light L173 travels in a direction greatly inclined with respect to the third direction D3, the light L173 can be transmitted through the selective transmission sheet 40 . This can prevent the light emitting surface 20a from becoming too dark in the spaced region.

With the selective transmission function of the selective transmission portion 45 as described above, in-plane variations in brightness according to the arrangement of the light sources 23 can be suppressed. Thereby, the illuminance at each position on the second surface 40b of the selective transmission sheet 40 can be effectively uniformed.

As shown in FIG. 20, the light L201 emitted from the selective transmission sheet 40 travels toward the wavelength conversion sheet 60. As shown in FIG. The wavelength conversion sheet 60 includes an optical element section 70, a first barrier layer 63, a wavelength conversion section 65, and a second barrier layer 64 from the second side, which is the light source side in the third direction D3. The optical element portion 70 has an uneven surface 61 on the first surface 60 a of the wavelength conversion sheet 60 . As shown in FIG. 20 , the light L201 changes its traveling direction when entering the optical element section 70 . The light L201 passes through the first barrier layer 63 and travels toward the wavelength conversion section 65 .

As shown in FIG. 22, the wavelength converting portion 65 contains a wavelength converting agent 67. As shown in FIG. A portion of the light L221 traveling through the wavelength converting portion 65 collides with the wavelength converting agent 67. As shown in FIG. The wavelength conversion agent 67 absorbs the primary light LA emitted from the light source 23 and emits secondary light LB with a different wavelength. In the illustrated example, the wavelength converting portion 65 includes a first converting agent 67A and a second converting agent 67B. The first conversion agent 67A absorbs a portion L221 of the blue primary light LA and emits green first secondary light LB1. The second conversion agent 67B absorbs a portion L222 of the blue primary light LA and emits a red second secondary light LB2.

Most of the light L174 (see FIG. 17) traveling through the wavelength conversion sheet 60 travels in a direction greatly inclined with respect to the third direction D3 due to the transmission characteristics of the selective transmission portion 45 . Therefore, even if the thickness of the wavelength conversion section 65 is reduced, the optical path length of the light L174 in the wavelength conversion section 65 is increased. Therefore, it becomes easier for the light to enter the wavelength conversion agent 67 in the wavelength conversion sheet 60 . Since the wavelength conversion agent 67 can be used efficiently in this manner, the content of the wavelength conversion agent 67 in the selective transmission portion 45 can be reduced.

The traveling direction of the secondary light LB emitted from the wavelength converting agent 67 does not depend on the traveling direction of the primary light LA before being absorbed by the wavelength converting agent 67 . As shown in FIG. 22, the secondary light LB is emitted from the wavelength conversion agent 67 over a wide range of angles. The angular distribution of luminance caused by the secondary light LB is uniformed to some extent on the second surface 60b of the wavelength conversion sheet 60 . Most of the secondary light LB emitted from the wavelength conversion agent 67 passes through the flat second surface 60 b and exits from the wavelength conversion sheet 60 .

As shown in FIG. 22, part L223 of the primary light LA does not enter the wavelength conversion agent 67, but enters the second surface 60b. A portion of such light L223 also passes through the flat second surface 60b and exits from the wavelength conversion sheet 60. As shown in FIG.

As described above, the light L175 (see FIG. 17) such as the primary light LA, the first secondary light LB1, and the second secondary light LB2 is emitted from the light exit side surface 30b of the optical member 30 in the first direction in the third direction D3. emit to the side. The light L175 passes through the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 and exits from the light exit side surface of the optical laminate 21. FIG. Thus, the light emitting surface 20a constituted by the optical layered body 21 emits light.

By the way, as shown in FIGS. 17 and 24, the lights L176 and L241 incident on the second surface 60b of the wavelength conversion sheet 60 can be reflected by the second surface 60b. Lights L176 and L241 reflected by the second surface 60b travel to the second side in the third direction D3. Such light can turn around in the traveling direction in the third direction D3 by being reflected by any interface, for example, the surface of the reflective layer 27, and can enter the wavelength conversion sheet 60 again. Most of such light, when incident on the second surface 60b, travels in a direction greatly inclined with respect to the third direction D3 due to the optical characteristics of the selective transmission portion 45. As shown in FIG. Therefore, the lights L176 and L241 are reflected by the second surface 60b with a relatively high reflectance. Lights L176 and L241 reflected by the wavelength conversion sheet 60 travel in a first direction D1 or a second direction D2 perpendicular to the third direction D3 and leave the light source 23 . Therefore, by utilizing the reflection on the second surface 60b, it is possible to effectively suppress in-plane variations in brightness due to the arrangement of the light source 23. FIG. That is, the wavelength conversion sheet 60 can reinforce or supplement the optical characteristics of the selective transmission portion 45 having the incident angle dependence, and sufficiently uniform the in-plane distribution of the illuminance.

In FIG. 24, the thickness of the wavelength conversion sheet 60 is shown to be thin in order to facilitate understanding of the optical action regarding the optical path within the wavelength conversion sheet 60. FIG. Also, in FIG. 24, illustration of the wavelength conversion agent 67 is omitted. Actually, a wavelength conversion agent 67 is provided between the first surface 60a and the second surface 60b of the wavelength conversion sheet 60. As shown in FIG. By utilizing the reflection on the second surface 60 b of the wavelength conversion sheet 60 , the wavelength conversion agent 67 is positioned within the circulating optical path of the light emitted from the light source 23 . In particular, the wavelength conversion agent 67 is dispersed inside the wavelength conversion sheet 60 that turns back the traveling direction in the third direction D3 in the circulating optical path. Therefore, in the wavelength conversion sheet 60 containing the wavelength conversion agent 67, the light travels in a direction inclined with respect to the third direction D3. The optical path length in the wavelength conversion sheet 60 becomes very long. As a result, the utilization efficiency of the wavelength conversion agent 67 can be significantly improved, and the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be greatly reduced. For example, the thickness of the wavelength converting portion 65 can be reduced, and the thicknesses of the optical member 30, the optical laminate 21, and the surface light source device 20 in the third direction D3 can be reduced. The density of the wavelength conversion agent 67 in the wavelength conversion section 65 can be reduced.

In the wavelength conversion sheet 60, a barrier layer may not be provided on the side end face of the wavelength conversion portion 65 in some cases. According to this example, the deterioration of the wavelength conversion agent 67 located near the side end surface progresses, and the color of the peripheral portion of the wavelength conversion portion 65 may change. According to the present embodiment, the content of the wavelength converting agent 67 in the wavelength converting portion 65 can be reduced as described above. Therefore, the area ratio of the wavelength conversion agent 67 per unit area in the projection in the third direction D3 can be reduced. Accordingly, even when no barrier layer is provided on the side end surface of the wavelength conversion section 65, color change in the peripheral portion can be suppressed.

Here, the transmittance of the selective transmission portion 45, which is a dielectric multilayer film, changes with different wavelengths. The transmittance of the selective transmission portion 45, which is a dielectric multilayer film, tends to increase with respect to light with a longer wavelength than the specific wavelength. In other words, the selective transmission of the selective transmission portion 45, which depends on the angle of incidence, becomes weaker with respect to light with a wavelength greater than the specific wavelength. Therefore, the selective transmission portion 45 cannot effectively exhibit the selective transmission property depending on the incident angle with respect to the secondary light LB having a wavelength longer than the specific wavelength. In other words, the selective transmission section 45 cannot reflect the secondary light LB similarly to the primary light LA.

Therefore, from the viewpoint of sufficiently uniforming the in-plane distribution of the illuminance, after the primary light LA is sufficiently circulated between the optical member 30 and the light source substrate 22 to uniform the in-plane distribution of the illuminance, the primary light It is preferable to convert LA into secondary light LB. That is, from the viewpoint of suppressing in-plane variations in brightness, it is preferable to reduce the content of the wavelength conversion agent 67 in the selective transmission portion 45 that is in the circulating optical path.

In the illustrated example, the first surface 60a of the wavelength conversion sheet 60 is configured by the optical element section 70. As shown in FIG. The optical element section 70 includes a plurality of unit optical elements 75 . A unit optical element 75 as a convex portion 73 or a concave portion 74 includes a plurality of element surfaces 76 . A plurality of element surfaces 76 constitute the first surface 60a. According to this example, as shown in FIG. 24, the light L241 incident on the wavelength conversion sheet 60 is directed in the element surface 76 forming the uneven surface 61 in the direction opposite to the traveling direction with respect to the third direction D3. Incident on the inclined element surface 76 is facilitated. In this case, the light L<b>241 maintains a traveling direction greatly inclined to the third direction D<b>3 even after being incident on the unit optical element 75 . As a result, the incident angle θy on the flat second surface 60b of the wavelength conversion sheet 60 increases, and the reflectance on the second surface 60b increases. By promoting reflection on the second surface 60b, in-plane variations in brightness can be effectively uniformed.

From the viewpoint of sufficiently uniforming the in-plane distribution of illuminance, the reflection on the second surface 60b of the wavelength conversion sheet 60 may be total reflection. Specifically, the formula (A), which is the total reflection condition using the incident angle θy (°) to the second surface 60b, may hold.
np×Sinθy≧1 Formula (A)
“np” in the formula (A) is the refractive index of the portion forming the element surface 76 of the wavelength conversion sheet 60 . Therefore, “np” may be the refractive index of the portion that constitutes the unit optical element 75 . Strictly speaking, "np" should be the refractive index of the portion forming the second surface 60b. As shown in FIGS. 20 and 21, the second surface 70b of the optical element portion 70, the first surface 65a and the second surface 65b of the wavelength conversion portion 65, and the second surface 60b of the wavelength conversion sheet 60 are normally They are parallel to each other and substantially orthogonal to the third direction D3. Therefore, “np” in formula (A) may be the refractive index that constitutes the element surface 76 of the wavelength conversion sheet 60 .

The inclination angle θp of the element surface 76 may be determined as follows so as not to hinder the light traveling toward the second surface 60b at the incident angle that satisfies the formula (A).
sin ⁻¹ (1/np)≦90−θp (X)
θp (°) in the formula (X) is the angle (°) between the plane perpendicular to the third direction D3 and the element plane 76 . When the formula (X) is satisfied, light traveling in a direction inclined at an angle equal to or greater than the critical angle (°) for total reflection with respect to the third direction D3 is incident on the second surface 60b without being incident on the element surface 76. can promote With such a setting, light circulation between the wavelength conversion sheet 60 and the light source substrate 22 is promoted, and the in-plane distribution of illuminance can be effectively uniformed.

As shown in FIG. 24, regarding the optical path of the light L241 incident on the element surface 76 of the unit optical element 75, the following formula holds.
θ1=θx-θp Expression (B)
Sinθ1=np×Sinθ2 Formula (C)
θy=θp+θ2 Formula (D)
θx (°) in the formula (B) is the angle (°) between the traveling direction of the light L241 toward the wavelength conversion sheet 60 and the third direction D3. θp (°) in equation (B) is the angle (°) between the plane perpendicular to the third direction D3 and the element plane 76 on which the light L241 is incident. θ1 (°) in equation (C) is the incident angle (°) of the light L241 with respect to the element surface 76 on which the light L241 is incident. θ2 (°) in equation (C) is the refraction angle (°) of the light L241 at the element surface 76 through which the light L241 passes. That is, θ2 (°) is the angle between the normal direction to the element surface 76 and the traveling direction of light after refraction at the element surface 76 .

By rewriting formula (A) using formulas (B) to (D), the following conditional formula (E) is obtained.
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp Expression (E)
When the formula (E) is satisfied, light traveling in a direction slanted by θx (°) with respect to the third direction D3 passes through the element surface 76 and enters the wavelength conversion sheet 60, and then passes through the second surface 60b. reflect. The refractive index np of the portion forming the element surface 76 and the inclination angle θp (°) of the element surface 76 are set so that the formula (E) is established for at least part of the light incident on the wavelength conversion sheet 60. may With such a setting, light circulation between the wavelength conversion sheet 60 and the light source substrate 22 is promoted, and the in-plane distribution of illuminance can be effectively uniformed.

Here, the light traveling angle θx (°) used in the formula (E) is applied to the selective transmission portion 45 at an incident angle at which the transmittance of light of a specific wavelength in the selective transmission portion 45 is 1/2 of the maximum value. The first specific angle θx1 (°) may be the angle (°) between the peak emission direction of the incident light from the selective transmission sheet 40 and the third direction D3. The incident angle at which the transmittance is 1/2 of the maximum value is set to be smaller than the incident angle at which the transmittance is at the maximum value. In an actual surface light source device, most of the traveling directions of light emitted from the selective transmission sheet 40 and directed to the wavelength conversion sheet 60 are inclined by the first specific angle θx1 with respect to the third direction D3. Therefore, when the following formula (F) using the first specific angle θx1 is satisfied, much light traveling from the selective transmission sheet 40 to the wavelength conversion sheet 60 is totally reflected by the wavelength conversion sheet 60 . As a result, when the formula (F) is satisfied, the light circulation between the wavelength conversion sheet 60 and the light source substrate 22 can be promoted, and the in-plane distribution of illuminance can be effectively uniformed.
sin ^-1 (1/np)≤sin ^-1 (sin(θx1-θp)/np)+θp ・・・Formula (F)

In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. Therefore, the inclination angle θp of the element surface 76 is preferably 16° or more.

As another example, the light traveling angle θx (°) used in the formula (E) is set to the incident angle at which the transmittance of the light of the specific wavelength in the selective transmission portion 45 is 1/10 of the maximum value. The second specific angle θx2 (°) may be the angle (°) between the peak emission direction of the light incident on 45 from the selective transmission sheet 40 and the third direction D3. The incident angle at which the transmittance is 1/10 of the maximum value is smaller than the incident angle at which the transmittance is at the maximum value. The light traveling at the second specific angle θx2 is light with a very small incident angle among the incident lights on the wavelength conversion sheet 60 . If this light with a small incident angle satisfies the conditions for total reflection on the second surface 60 b , most of the light incident on the wavelength conversion sheet 60 can satisfy the conditions for total reflection on the wavelength conversion sheet 60 . Therefore, when the following formula (G) using the second specific angle θx2 is satisfied, light circulation between the wavelength conversion sheet 60 and the light source substrate 22 can be further promoted, and the in-plane distribution of illuminance can be greatly improved. can be substantially homogenized.
sin ^-1 (1/np)≤sin ^-1 (sin(θx2-θp)/np)+θp Formula (G)

In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. Therefore, the inclination angle θp of the element surface 76 is preferably 30° or more.

As still another example, the light traveling angle θx (°) used in the formula (E) is a third specific angle θx3 may be According to this example, of the light incident on the wavelength conversion sheet 60 in the surface light source device 20 actually used, the light with a relatively small incident angle satisfies the total reflection condition on the second surface 60b. Therefore, when the following formula (H) using the third specific angle θx3 is satisfied, light circulation between the wavelength conversion sheet 60 and the light source substrate 22 can be promoted, and the in-plane distribution of illuminance can be effectively uniformed. can be
sin ^-1 (1/np)≤sin ^-1 (sin(θx3-θp)/np)+θp Expression (H)
The third specific angle θx3 is specified from the luminance angular distribution on the second surface 40 b of the selective transmission sheet 40 . With this luminance angular distribution, light is emitted from the light source 23 in a state in which the surface light source device 20 is removed from the constituent elements on the first side, which is closer to the observer in the third direction D3 than the selective transmission sheet 40, and the second surface 40b Distribution of luminance in each direction measured above. An example of this luminance angular distribution is shown in FIG. The half-value angle in the luminance angle distribution is the minimum value of the magnitude (absolute value) of the angle between the third direction D3 and the direction in which half the peak luminance is obtained in the luminance angle distribution.

It should be noted that the expressions (F), (G) and (H) need not be satisfied by the inclination angle θp over the entire area of the element surface 76, and if this condition is satisfied over 50% or more of the element surface 76, Advantageously, the in-plane distribution of illuminance can be made uniform. Preferably, the inclination angle θp in the area of 70% or more of the element surface 76, more preferably the inclination angle θp in the area of 80% or more of the element surface 76, is expressed by the formulas (F), (G), and (H). It is filled.

The conditions for total reflection described above are the conditions for the light L241 shown in FIG. This light L241 passes through one element surface 76 and travels through the wavelength conversion sheet 60 . This light L241 enters the second surface 60b without entering the other element surface 76. As shown in FIG. On the other hand, it is also assumed that the light L242 that has passed through one element surface 76 is incident on another element surface 76 that faces the one element surface 76 . This light L242 can be totally reflected by another element surface 76 and enter the second surface 60b at a small incident angle. The reflectance of this light L242 on the second surface 60b is reduced.

From the viewpoint of suppressing the generation of such light L242 and promoting reflection on the second surface 60b, the angle between the traveling direction of the light traveling in the unit optical element 75 and the third direction D3 is It may be less than or equal to the angle between 76 and the third direction D3. Specifically, the following formula (I) may be satisfied. Formula (J), which is obtained by rewriting formula (I) in consideration of formulas (B) to (D) described above, may be satisfied. The angles and refractive indices used in formulas (I) and (J) are as described above.
θp+θ2≦90−θp Formula (I)
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp Expression (J)
Here, the light traveling angle θx (°) used in the formula (J) may be the above-described first specific angle θx1 (°).

Here, the light traveling angle θx (°) used in the formula (J) may be the above-described second specific angle θx2 (°). When the following formula (L) using the second specific angle θx2 is satisfied, at least part of the light incident on the unit optical element 75 from the one element surface 76 is directed to another element facing the one element surface 76 It can be incident on the second surface 60 b without being incident on the surface 76 . Therefore, when formula (L) is satisfied, light circulation can be expected between the wavelength conversion sheet 60 and the light source substrate 22, and in-plane variations in illuminance can be suppressed.
sin ^-1 (sin(θx2-θp)/np)+θp≦90-θp ・・・Formula (L)

In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. Therefore, the inclination angle θp of the element surface 76 is preferably 45° or less.

As another example, the light traveling angle θx (°) used in formula (J) is the direction in which the brightness of 1/10 of the peak brightness in the brightness angular distribution on the second surface 40b of the selective transmission sheet 40 is obtained. , and the third direction D3 may be a fourth specific angle θx4, which is the angle (°) between them. According to this example, in the surface light source device 20 actually used, at least part of the light incident on the unit optical element 75 from one element surface 76 is projected onto another element surface 76 facing the one element surface 76 . can be incident on the second surface 60b without being incident on the second surface 60b. Therefore, when the following formula (M) using the third specific angle θx4 is satisfied, light circulation can be expected between the wavelength conversion sheet 60 and the light source substrate 22, and in-plane variations in illuminance can be suppressed.
sin ^-1 (sin(θx4-θp)/np)+θp≦90-θp Expression (M)
The fourth specific angle θx4 is specified from the luminance angular distribution on the second surface 40 b of the selective transmission sheet 40 . With this luminance angular distribution, light is emitted from the light source 23 in a state in which the surface light source device 20 is removed from the constituent elements on the first side, which is closer to the observer in the third direction D3 than the selective transmission sheet 40, and the second surface 40b Distribution of luminance in each direction measured above. An example of this luminance angular distribution is shown in FIG. The angle between the direction in which the luminance of 1/10 of the peak luminance in the luminance angular distribution is obtained and the third direction D3 is the direction in which the luminance of 1/10 of the peak luminance in the luminance angular distribution is obtained and the third direction. It is the minimum value of the magnitudes (absolute values) of the angles with D3.

It should be noted that the expressions (K), (L) and (M) need not be satisfied by the inclination angle θp over the entire area of the element surface 76, and if this condition is satisfied over 50% or more of the element surface 76, Advantageously, the in-plane distribution of illuminance can be made uniform. Preferably, the inclination angle θp in the area of 70% or more of the element surface 76, more preferably the inclination angle θp in the area of 80% or more of the element surface 76, the formulas (K), (L) and (M) are: It is filled.

The specific angle θx is preferably 35° or more in order to satisfy both the above formulas (E) and (J). By setting the specific angle θx to 35° or more, the inclination angle θp has an appropriate range within the range of the refractive index np of the portion forming the element surface 76 from 1.50 to 1.60. From this point, the angle formed by the traveling direction of the light traveling from the selective transmission sheet 40 to the wavelength conversion sheet 60 with respect to the third direction D3 may be 35° or more, 40° or more, or 45° or more. Further, the transmittance of the selective transmission portion 45 with respect to the light of the specific wavelength emitted from the selective transmission sheet 40 at the emission angle of 0° or more and 35° or less in terms of absolute value is half or less of the maximum value of the transmittance of the selective transmission portion 45. , or 1/10 or less of the maximum transmittance of the selective transmission portion 45 .

In the embodiment described above, the optical member 30 includes the selective transmission sheet 40 including the selective transmission portion 45, the first surface 40a on the side of the selective transmission sheet 40, and the second surface 40b facing the first surface 40a. and a wavelength conversion sheet 60 containing. The transmittance of the selective transmission portion 45 for light of a specific wavelength incident on the selective transmission portion 45 at an incident angle greater than 0° is the light of the selective transmission portion 45 incident on the selective transmission portion 45 at an incident angle of 0°. is greater than the transmittance of the selective transmission portion 45 for . At least one of the first surface 60 a and the second surface 60 b includes an uneven surface 61 . In the second aspect of the present embodiment, the first surface 60a of the wavelength conversion sheet 60 includes an uneven surface.

According to the optical member 30 according to the second aspect of the present embodiment, the primary light LA from the light source 23 can be reflected by the second surface 60b of the wavelength conversion sheet 60. That is, the second surface 60b of the wavelength conversion sheet 60 can reflect light directed toward the first side, which is the viewer side, in the third direction D3. That is, a circulation optical path in which the primary light LA circulates can be formed between the second surface 60b of the wavelength conversion sheet 60 and the light source substrate 22 and the like. According to the present embodiment, the wavelength conversion agent 67 is included in the wavelength conversion sheet 60 that folds back in the third direction D3. The primary light LA travels in the wavelength conversion sheet 60 in a direction inclined with respect to the third direction D3. Therefore, the content of the wavelength conversion agent 67 in the wavelength conversion sheet 60 can be greatly reduced. Rather, by reducing the content of the wavelength conversion agent 67 that emits the secondary light LB in various directions, the circulation of the primary light LA using reflection on the second surface 60b can be promoted. That is, the circulation of the primary light LA can significantly reduce the content of the wavelength conversion agent 67 while suppressing the in-plane variation in brightness caused by the arrangement of the light sources 23 and suppressing the in-plane variation in illuminance. It is also possible to reduce the thickness of the optical member 30 and the optical laminate 21 and to reduce the thickness of the surface light source device 20 .

Here, the results of the simulation conducted by the inventors will be explained. The simulation was a ray tracing simulation using LightTools manufactured by Synopsys.

The simulation target was the surface light source device shown in FIGS. 3, 4, 17 to 20, 22, 23A and 23B. That is, the surface light source device included a light source substrate and an optical laminate. The optical laminate included an optical member, a first light control sheet, a second light control sheet and a reflective polarizing plate. The optical member included a selective transmission sheet and a wavelength conversion sheet. The first surface of the wavelength conversion sheet had an uneven surface. On the light source substrate, blue micro light-emitting diodes were arranged at a pitch of 6 mm in both the first direction and the second direction. The distance along the third direction D3 from the surface of the light source facing the optical member 30 to the light incident side surface of the optical member was set to 0.5 mm. The selectively permeable sheet contained only the selectively permeable portion. The first surface and the second surface of the selective transmission portion were parallel to each other. The first surface and the second surface were orthogonal to the third direction D3. The wavelength conversion sheet contained an optical element portion, a first barrier layer, a wavelength conversion portion and a second barrier layer. The first light control sheet and the second light control sheet were "BEF" (registered trademark) available from US 3M Company. The reflective polarizing plate was “DBEF” (registered trademark) available from 3M Company, USA.

The inclination angles θp of the element surfaces included in the optical element portion described above were changed as shown in Tables 1 and 2. For each tilt angle θp to be simulated, the content of the wavelength conversion agent was changed to investigate the content of the wavelength conversion agent that can make the emission color white and uniform the in-plane distribution of illuminance. For any simulation target, the wavelength conversion agent consists of a first conversion agent that absorbs blue light from the light source and emits green light, and a second conversion agent that absorbs blue light from the light source and emits red light. and included. The conversion efficiency by the 1st conversion agent and the conversion efficiency by the 2nd conversion agent were set to 11:20. By making the conversion efficiency of the second conversion agent 67B in the wavelength conversion section 65 greater than the conversion efficiency of the first conversion agent 67A, the color balance could be improved.

The simulation results are shown in Tables 1 and 2. Table 1 shows the results of a simulation using the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. Table 2 shows the results of a simulation using the selective transmission portion 45 having the transmission characteristics of the second specific example shown in FIG. The column of "conversion efficiency" in Tables 1 and 2 shows the conversion efficiency that can suppress the in-plane variation of the illuminance most for each simulation target in terms of relative ratio. In the column of "Comprehensive evaluation" in Tables 1 and 2, evaluation is made based on low optimum conversion efficiency and uniformity of in-plane distribution of illuminance. Samples marked with "X" in the "Comprehensive Evaluation" column are the samples with the lowest evaluation. Samples marked with "○" in the "Comprehensive evaluation" column are samples with good evaluation. In the "Comprehensive evaluation", samples with high evaluation were marked with more "○".

As shown in Tables 1 and 2, the in-plane distribution of illuminance can be made uniform while the conversion efficiency is reduced when the tilt angle θp of the unit optical elements included in the optical element section is in the range of 10° or more and 50° or less. In the range where the tilt angle θp of the unit optical elements included in the optical element portion is 30° or more and 45° or less, the in-plane distribution of illuminance can be made more uniform while the conversion efficiency is further reduced.

Although the second aspect of the present embodiment has been described with reference to specific examples, the above-described specific examples do not limit the second aspect of the present embodiment. The second aspect of the present 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.

In the illustrated example, the first surface 60a of the wavelength conversion sheet 60 includes an uneven surface. In addition to the first surface 60a of the wavelength conversion sheet 60 including an uneven surface, the second surface 60b of the wavelength conversion sheet 60 may include an uneven surface. Since at least one of the first surface 60a and the second surface 60b includes an uneven surface, it is possible to cause total reflection on the second surface 60b.

<Third aspect>
1 to 27 are also diagrams for explaining the third aspect of the present embodiment. In the third aspect, the light scattering properties of the wavelength conversion sheet 60 are adjusted. In the third aspect, the transmission haze of the wavelength conversion sheet 60 is adjusted. The third mode can be configured in the same manner as the first mode except for the transmission haze of the wavelength conversion sheet 60 . The third mode can be configured in the same manner as the second mode except for the transmission haze of the wavelength conversion sheet 60 .

For example, as shown in FIG. 17, a surface light source device 20 in the third aspect may include, as main components, a light source 23 and an optical laminate 21 that adjusts the optical path of light emitted from the light source 23. . The optical laminate 21 may include optical members 30 . The optical layered body 21 and the optical member 30 may face the light source 23 . The optical layered body 21 and the optical member 30 may be sheet-like members. The optical layered body 21 and the optical member 30 may face the light source 23 in their normal direction. The optical layered body 21 and the optical member 30 may be diffusion members that diffuse the light emitted from the light source 23 . The optical layered body 21 and the optical member 30 can effectively suppress in-plane variations in illuminance caused by the arrangement of the light sources 23 . Due to the diffusion in the optical layered body 21 and the optical member 30, the illuminance at each position on the light emitting side surface 30b of the optical member 30, or the illuminance on a virtual light receiving surface parallel to the light emitting side surface 30b located near the light emitting side surface 30b. The illumination intensity at each position can be effectively homogenized.

The display device 10, the surface light source device 20, and the optical member 30 in the third embodiment will be described below mainly with reference to the specific examples shown in FIGS. 17 to 25. FIG. The display panel 15 of the display device 10 may be configured in the same manner as the above-described display panel 15 described as the first mode. The light source substrate 22 of the surface light source device 20 may be configured in the same manner as the above-described light source substrate 22 described as the first mode. The optical laminate 21 may include the optical member 30 , the first light control sheet 81 , the second light control sheet 82 and the reflective polarizing plate 85 in order from the light source substrate 22 . Of these, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 are the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85, respectively, described as the first mode. It may have the same configuration as the polarizing plate 85 .

The optical member 30 includes a selective transmission sheet 40 and a wavelength conversion sheet 60 in this order. The selective transmission sheet 40 and the wavelength conversion sheet 60 are stacked in the third direction D3. Both the selective transmission sheet 40 and the wavelength conversion sheet 60 may be sheet-like members extending in the first direction D1 and the second direction D2. In the illustrated example, the selective transmission sheet 40 constitutes the light incident side surface 30 a of the optical member 30 . In the illustrated example, the wavelength conversion sheet 60 constitutes the light output side surface 30b of the optical member 30. As shown in FIG. The selective transmission sheet 40 and the wavelength conversion sheet 60 may be bonded to each other, may be simply in contact and not bonded, or may be separated from each other. Note that the optical member 30 may include the light diffusion sheet 50 as in the first aspect. The first surface 50a of the light diffusion sheet 50 may constitute the light incident side surface 30a.

The selectively permeable sheet 40 includes a selectively permeable portion 45 . The reflectance and transmittance of the selective transmission portion 45 change depending on the incident angle. The selective transmission portion 45 has its transmission characteristics adjusted so that the transmittance changes according to the incident angle. The selective transmission portion 45 has its reflection characteristics adjusted so that the reflectance changes according to the incident angle. The selective transmission sheet 40 and the selective transmission section 45 may be configured in the same manner as the above-described selective transmission sheet 40 and selective transmission section 45 described as the first mode, respectively. The selective transmission sheet 40 and the selective transmission section 45 may be configured in the same manner as the above-described selective transmission sheet 40 and selective transmission section 45 described as the second mode.

The transmission characteristics and reflection characteristics of the selective transmission portion 45 have incident angle dependency. The transmittance of the selective transmission portion 45 and the reflectance of the selective transmission portion 45 change according to the incident angle. The transmission characteristics and reflection characteristics of the selective transmission portion 45 may have wavelength dependence. The transmittance of the selective transmission portion 45 and the reflectance of the selective transmission portion 45 may change according to the wavelength.

The selective transmission section 45 is not particularly limited as long as it has incident angle dependency of reflectance and incident angle dependency of transmittance, as described above. The selective transmission section 45 may include a dielectric multilayer film, a reflective volume hologram, a cholesteric liquid crystal structure layer, a retroreflective film, or a reflective diffractive optical element. A dielectric multilayer film, a reflective volume hologram, a cholesteric liquid crystal structure layer, and a reflective diffractive optical element have wavelength dependence.

In the third aspect, the transmission haze of the wavelength conversion sheet 60 is low. The wavelength conversion sheet 60 may be configured in the same manner as the above-described wavelength conversion sheet 60 described as the first mode, as long as the transmission haze is set within the range described below. The wavelength conversion sheet 60 may be configured in the same manner as the above-described wavelength conversion sheet 60 described as the second mode, as long as the transmission haze is set within the range described below.

As shown in FIGS. 20 and 21, the wavelength conversion sheet 60 includes a first surface 60a and a second surface 60b. The first surface 60a faces the second side that is the light source side in the third direction D3. The second surface 60b faces the first side that is the viewer side in the third direction D3. The wavelength conversion sheet 60 includes an uneven surface 61 on at least one of the first surface 60a and the second surface 60b. Hereinafter, the wavelength conversion sheet 60 will be described with reference to the illustrated example in which the first surface 60 a includes the uneven surface 61 . The illustrated first surface 60a is an uneven surface 61 over the entire surface. The second surface 60b includes a flat surface. The illustrated second surface 60b is entirely flat. The second surface 60b may be a surface perpendicular to the third direction D3.

The wavelength conversion sheet 60 contains a wavelength conversion agent 67 . The wavelength converting agent 67 absorbs primary light and emits secondary light with a different wavelength than the primary light.

20 and 21, the wavelength conversion sheet 60 includes an optical element section 70, a first barrier layer 63, a wavelength conversion section 65 and a second barrier layer 64 in order from the light source substrate 22. may contain. The optical element portion 70, the first barrier layer 63, the wavelength converting portion 65 and the second barrier layer 64 are stacked in this order in the third direction D3. The optical element portion 70, the first barrier layer 63, the wavelength conversion portion 65 and the second barrier layer 64 may be sheet-like. The optical element section 70, the first barrier layer 63, the wavelength converting section 65 and the second barrier layer 64 may extend in the first direction D1 and the second direction D2.

The optical element section 70 may be the same as the optical element section 70 described above as the first aspect. The optical element portion 70 may be the same as the optical element portion 70 described above as the second aspect. The first barrier layer 63 may be the same as the first barrier layer 63 described above as the first aspect. The first barrier layer 63 may be the same as the first barrier layer 63 described above as the second aspect. The wavelength conversion section 65 may be the same as the wavelength conversion section 65 described above as the first mode. The wavelength conversion section 65 may be the same as the wavelength conversion section 65 described above as the second mode. The second barrier layer 64 may be the same as the second barrier layer 64 described above as the first aspect. The second barrier layer 64 may be the same as the second barrier layer 64 described above as the second embodiment.

The wavelength conversion section 65 may contain a light scattering component that scatters transmitted light. The light scattering component may be dispersed within the matrix portion 66 . Examples of light-scattering components include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles. The transmission haze of the wavelength conversion sheet 60 can be adjusted by the type and content of the light scattering component.

Next, the operation of generating planar light with the planar light source device 20 according to the third aspect will be described. An example in which the first surface 60a of the wavelength conversion sheet 60 includes an uneven surface 61, that is, the surface light source device 20 shown in FIGS. 17 to 25 will be described below.

As described in the second aspect, the selective transmission function of the selective transmission portion 45 can suppress in-plane variations in brightness according to the arrangement of the light sources 23 . Thereby, the illuminance at each position on the second surface 40b of the selective transmission sheet 40 can be effectively uniformed.

As shown in FIGS. 17 and 20, the lights L174 and L201 transmitted through the selective transmission sheet 40 travel toward the wavelength conversion sheet 60. As shown in FIGS. As shown in FIG. 20, the light L201 changes its traveling direction to some extent due to refraction at the element surface 76 when entering the optical element section 70 . The light L201 passes through the first barrier layer 63 and travels toward the wavelength conversion section 65 .

Most of the light L174 (see FIG. 17) transmitted through the selective transmission sheet 40 travels in a direction greatly inclined with respect to the third direction D3 due to the transmission characteristics of the selective transmission portion 45. In the illustrated example, the traveling direction of this light L174 is further inclined with respect to the third direction D3 due to refraction at the second surface 40b of the selective transmission sheet 40. FIG. Furthermore, the first surface 60 a of the wavelength conversion sheet 60 , which is the incident surface, is an uneven surface 61 . As in the example shown in FIG. 20, the light L201 incident on the wavelength conversion sheet 60 is likely to enter the element surface 76 inclined in the direction opposite to the traveling direction of the light L201 with respect to the third direction D3. When the light L201 is incident on the element surface 76, the traveling direction of the light L201 is unlikely to change significantly. As a result, as shown in FIG. 20, the light L201 traveling through the wavelength conversion sheet 60 tends to travel in a direction greatly inclined with respect to the third direction D3. Along with this, the optical path length of the light L174 in the wavelength conversion section 65 becomes longer. Therefore, it becomes easier for the light to enter the wavelength conversion agent 67 in the wavelength conversion sheet 60 . As a result, since the wavelength conversion agent 67 can be used efficiently, the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be reduced.

The traveling direction of the secondary light LB emitted from the wavelength converting agent 67 does not depend on the traveling direction of the primary light LA before being absorbed by the wavelength converting agent 67 . As shown in FIG. 22, the secondary light LB is emitted from the wavelength conversion agent 67 over a wide range of angles. The angular distribution of luminance caused by the secondary light LB is uniformed to some extent on the second surface 60b of the wavelength conversion sheet 60 . Most of the secondary light LB emitted from the wavelength conversion agent 67 can pass through the flat second surface 60 b and exit from the wavelength conversion sheet 60 .

As shown in FIG. 22, part L223 of the primary light LA does not enter the wavelength conversion agent 67, but enters the second surface 60b. A part of such light L223 can also pass through the flat second surface 60b and be emitted from the wavelength conversion sheet 60. FIG.

As described above, the light L175 (see FIG. 17) such as the primary light LA, the first secondary light LB1 and the second secondary light LB2 is emitted from the wavelength conversion sheet 60 to the first side in the third direction D3. do. The light L175 passes through the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 and exits from the light exit side surface 30b of the optical member 30. FIG. In this manner, the light emitting side surface 30b of the optical member 30 emits light.

By the way, as shown in FIGS. 17 and 24, the lights L176 and L241 incident on the second surface 60b of the wavelength conversion sheet 60 can be reflected by the second surface 60b. Lights L176 and L241 reflected by the second surface 60b travel to the second side in the third direction D3. Such light can turn around in the traveling direction in the third direction D3 by being reflected by any interface, for example, the surface of the reflective layer 27, and can enter the wavelength conversion sheet 60 again.

Lights L176 and L241 reflected by the second surface 60b of the wavelength conversion sheet 60 travel in the first direction D1 and the second direction D2 orthogonal to the third direction D3. That is, the lights L176 and L241 leave the light source 23 in a direction orthogonal to the third direction D3. Therefore, by utilizing the reflection on the second surface 60b, it is possible to effectively suppress in-plane variations in brightness due to the arrangement of the light source 23. FIG. That is, the wavelength conversion sheet 60 can reinforce or supplement the optical characteristics of the selective transmission portion 45 having the incident angle dependence, and sufficiently uniform the in-plane distribution of the illuminance.

In addition, the primary light LA can be selectively reflected on the second surface 60b with a very high reflectance. In the illustrated example, the first surface 60 a of the wavelength conversion sheet 60 includes an uneven surface 61 formed by the optical element portion 70 . The optical element section 70 includes a plurality of unit optical elements 75 . A unit optical element 75 as a convex portion 73 or a concave portion 74 includes a plurality of element surfaces 76 . The plurality of element surfaces 76 constitute the uneven surface 61 of the first surface 60a. According to this example, as shown in FIG. 24, the light L241 as the primary light LA incident on the wavelength conversion sheet 60 travels in the third direction D3 among the element surfaces 76 forming the uneven surface 61. It becomes easier for the light to be incident on the element surface 76 inclined in the opposite direction. The direction of travel of this light L241 is not greatly bent by refraction on the uneven surface 61 when incident on the wavelength conversion sheet 60 . That is, the primary light LA can maintain a traveling direction that is very greatly inclined with respect to the third direction D3 within the wavelength conversion sheet 60 . As a result, the incident angle θy on the flat second surface 60b of the wavelength conversion sheet 60 increases. Accordingly, the primary light LA that has not been wavelength-converted by the wavelength conversion agent 67 is reflected at the second surface 60b with high reflectance. Furthermore, the primary light LA can be totally reflected by the second surface 60b due to the large incident angle.

On the other hand, the direction in which the secondary light LB is emitted from the wavelength conversion agent 67 does not depend on the direction of incidence on the wavelength conversion agent 67 . Therefore, the secondary light LB is diffused light and cannot be reflected at a high reflectance on the second surface 60b.

As described above, the second surface 60b selectively reflects the primary light LA with a high reflectance due to the combination of the transmission characteristics of the selective transmission portion 45 that affects the emission direction of the primary light LA and the uneven surface 61. do. A wavelength conversion agent 67 is positioned in the circulating optical path between the wavelength conversion sheet 60 of the primary light LA and the light source substrate 22 .

In order to strengthen the function of maintaining the traveling direction of the primary light LA by the uneven surface 61, the element surface 76 orthogonal to the direction in which the peak luminance of the primary light LA is obtained is formed on the second surface 40b of the selective transmission sheet 40. may be used. By determining the inclination angle of the concave-convex surface 61 in consideration of the transmission characteristics of the selective transmission portion 45 that affects the emission direction of the primary light LA, the second surface 60b can selectively emit the primary light LA at a high angle. Reflectance can be reflected.

By utilizing the reflection on the second surface 60 b of the wavelength conversion sheet 60 , the wavelength conversion agent 67 is positioned within the circulating optical path of the light emitted from the light source 23 . In particular, the wavelength conversion agent 67 is dispersed inside the wavelength conversion sheet 60 that turns back the traveling direction in the third direction D3 in the circulating optical path. Therefore, the optical path length of the primary light LA in the wavelength conversion sheet 60 containing the wavelength conversion agent 67 becomes very long.

Thus, the primary light LA is selectively reflected by the second surface 60b. Thereby, the in-plane distribution of the illuminance caused by the primary light LA can be made sufficiently uniform. A wavelength conversion agent 67 is provided in the circulating optical path of the primary light LA between the second surface 60b and the light source substrate 22 in the third direction D3. As a result, the in-plane distribution of illuminance can be made sufficiently uniform, and color unevenness within the light emitting surface 20a can be suppressed. Since the primary light LA is selectively reflected by the second surface 60b and circulated, the utilization efficiency of the wavelength conversion agent 67 can be significantly improved, and the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be greatly reduced. can be reduced to For example, the thickness of the wavelength converting portion 65 can be reduced, and the thicknesses of the optical member 30, the optical laminate 21, and the surface light source device 20 in the third direction D3 can be reduced. The density of the wavelength conversion agent 67 in the wavelength conversion section 65 can be reduced.

In the wavelength conversion sheet 60, a barrier layer may not be provided on the side end face of the wavelength conversion portion 65 in some cases. According to this example, the deterioration of the wavelength conversion agent 67 located near the side end surface progresses, and the color of the peripheral portion of the wavelength conversion portion 65 may change. According to the present embodiment, the content of the wavelength converting agent 67 in the wavelength converting portion 65 can be reduced as described above. Therefore, the area ratio of the wavelength conversion agent 67 per unit area in the projection in the third direction D3 can be reduced. Accordingly, even when no barrier layer is provided on the side end surface of the wavelength conversion section 65, color change in the peripheral portion can be suppressed.

Also, the transmittance of the selective transmission portion 45, which is a dielectric multilayer film, has wavelength dependence. That is, the transmittance of the selective transmission portion 45, which is a dielectric multilayer film, changes with different wavelengths. The transmittance of the selective transmission portion 45, which is a dielectric multilayer film, tends to increase with respect to light with a longer wavelength than the specific wavelength. In other words, the selective transmission of the selective transmission portion 45, which depends on the angle of incidence, becomes weaker with respect to light with a wavelength greater than the specific wavelength. Therefore, the selective transmission portion 45 cannot effectively exhibit the selective transmission property depending on the incident angle with respect to the secondary light LB having a wavelength longer than the specific wavelength. In other words, the selective transmission section 45 cannot reflect the secondary light LB similarly to the primary light LA.

Therefore, from the viewpoint of sufficiently uniforming the in-plane distribution of the illuminance, after the primary light LA is sufficiently circulated between the optical member 30 and the light source substrate 22 to uniform the in-plane distribution of the illuminance, the primary light It is preferable to convert LA into secondary light LB. That is, it is preferable to reduce the content of the wavelength conversion agent 67 in the selective transmission portion 45 in the circulating optical path also from the viewpoint of suppressing in-plane variations in brightness. In addition, by uniformizing the in-plane distribution of illuminance caused by the primary light LA and reducing the density of the wavelength conversion agent 67, color unevenness can be effectively suppressed.

However, the function of homogenizing the in-plane distribution of illuminance and the function of suppressing color unevenness by using a wavelength conversion sheet including an uneven surface in combination with a selective transmission sheet having incident angle dependence are the same as those of the conventional wavelength conversion unit (wavelength conversion unit). sheet) was not sufficiently demonstrated. When a conventional wavelength conversion part is used, even if the wavelength conversion sheet is provided with an uneven surface, the usage amount of the wavelength conversion agent cannot be reduced. Moreover, even if the color of the light-emitting surface can be made white by using a large amount of the wavelength conversion agent, the color unevenness of the light-emitting surface cannot be sufficiently eliminated in some cases.

When the inventors of the present invention investigated the cause of this problem, they found that the scattering agent used in the conventional wavelength conversion part had an effect. A conventional wavelength converting portion contains a large amount of scattering agent along with the wavelength converting agent. In the conventional wavelength conversion section, the optical path length within the wavelength conversion section is ensured by containing a scattering agent. By using a scattering agent, the amount of wavelength conversion agent used can be reduced to about half. In the conventional wavelength conversion section, a scattering agent is used to reduce the amount of the wavelength conversion agent used, thereby coping with the color change caused by the wavelength conversion agent. In this conventional wavelength conversion section, the primary light LA traveling through the wavelength conversion sheet is diffused. That is, the distribution of the traveling direction of the primary light LA according to the transmission characteristics of the selective transmission portion is eliminated by the scattering agent, and the primary light LA cannot be selectively reflected on the second surface of the wavelength conversion sheet. For this reason, it was considered that when a conventional wavelength conversion portion is used, even if the wavelength conversion sheet is provided with an uneven surface corresponding to the transmission characteristics of the selective transmission portion, the in-plane distribution of illuminance cannot be sufficiently uniformized.

As a result of confirmation by the present inventors, by setting an upper limit to the transmission internal haze (%) of the wavelength conversion sheet 60 for light of a wavelength different from that of the primary light LA, the amount of the wavelength conversion agent 67 used can be greatly reduced. , the in-plane distribution of illuminance could be made sufficiently uniform, and color unevenness could be sufficiently suppressed. Specifically, by setting the transmission internal haze to 45% or less, the amount of the wavelength conversion agent 67 used can be significantly reduced, the in-plane distribution of illuminance can be made sufficiently uniform, and color unevenness can be effectively reduced. was suppressed to From the viewpoint of reducing the usage amount of the wavelength conversion agent 67 while uniforming the in-plane distribution of illuminance and color, the transmission internal haze may be 18% or less, 12% or less, or 7% or less. Furthermore, it may be 5% or less.

The transmission internal haze (%) of the wavelength conversion sheet 60 for light with a wavelength different from that of the primary light LA may be 1% or more. Even if this transmission internal haze is reduced to less than 1%, it is difficult to further reduce the usage amount of the wavelength conversion agent 67 . Therefore, from the viewpoint of color unevenness and illuminance uniformity, the transmission internal haze may be set to 1% or more.

The transmission internal haze (%) of the wavelength conversion sheet 60 is a value measured in accordance with JIS K7136:2000 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. That is, the transmission internal haze (%) is the ratio (%) of the diffuse transmittance to the total light transmittance.

"Internal haze" means haze caused by scattering inside the wavelength conversion sheet 60 . “Internal haze” means haze caused by scattering other than scattering on the first surface 60 a and the second surface 60 b of the wavelength conversion sheet 60 . For the measurement of the "internal haze", it is possible to use a sample in which the uneven surface 61 of the wavelength conversion sheet 60 is filled with a material having the same refractive index as the material forming the uneven surface 61 to form a flat surface. Alternatively, for the measurement of the "internal haze", it is possible to use a sample obtained by removing the portion (the unit optical elements 75 in the above example) forming the uneven surface 61 of the wavelength conversion sheet 60 to form a flat surface. One of the samples with the uneven surface 61 buried and the sample with the uneven surface 61 removed is selected in consideration of the structure of the wavelength conversion sheet 60 and the like, and the internal haze can be measured with higher accuracy. Let the measured value about a sample be a value of an internal haze.

"Light with a wavelength different from that of the primary light LA" means light other than light having a wavelength that can excite the wavelength conversion agent 67 contained in the wavelength conversion sheet 60 to be measured. That is, "light having a wavelength different from that of the primary light LA" means light having no wavelength capable of exciting the wavelength conversion agent 67 contained in the wavelength conversion sheet 60 to be measured. The haze value of the sample is measured by irradiating the sample to be measured with the measurement light emitted from the light source of the haze meter, which passes through a band-pass filter that regulates the transmission of primary light. A band-pass filter with a primary light transmittance of 5% or less is used. The band-pass filter used for measurement may shield not only the light within the wavelength range that can excite the wavelength conversion agent 67, but also the light within the wavelength range.

The primary light LA is absorbed by the wavelength conversion agent 67 . At this time, the wavelength conversion agent 67 emits the secondary light LB in a direction irrelevant to the direction of incidence of the primary light LA. By eliminating the optical path conversion function of the wavelength conversion agent 67, the degree of the scattering function caused by the scattering agent of the wavelength conversion sheet 60 can be evaluated more accurately. That is, by limiting the wavelength of the light used for measurement, the degree of diffusion of the primary light LA just before it enters the uneven surface 61 can be evaluated with high accuracy. Therefore, "light having a wavelength different from that of the primary light LA" is used for measurement of the transmitted internal haze.

As described above, according to this embodiment, the usage amount of the wavelength conversion agent 67 can be reduced. In the wavelength conversion sheet 60 in which the content of the wavelength conversion agent 67 is sufficiently reduced, the optical path conversion function of the wavelength conversion agent 67 exerted on transmitted light is weakened. As a result, the transmission internal haze (%) of the wavelength conversion sheet 60 in which the content of the wavelength conversion agent 67 is reduced is measured without limiting the wavelength of the measurement light, using only light with a wavelength different from that of the primary light LA. It is a small value similar to the transmission internal haze (%) measured by Further, even when measured using the total light emitted from the light source incorporated in the above haze meter, the transmission internal haze (%) of the wavelength conversion sheet 60, in which the content of the wavelength conversion agent 67 can be reduced, is is a value that is significantly different from the transmission internal haze (%) of the wavelength conversion sheet. From this point of view, the transmission internal haze (%) when all the light from the light source of the above-mentioned haze meter is used for measurement is also sufficiently uniform in-plane distribution of illuminance, while reducing the amount of wavelength conversion agent 67 used. It serves as an index to distinguish the obtained wavelength conversion sheet 60 from the conventional wavelength conversion sheet.

That is, the transmission inside of the wavelength conversion sheet 60 measured in accordance with JIS K7136: 2000 without limiting the measurement light from the built-in light source using the above-mentioned haze meter HM-150 manufactured by Murakami Color Research Laboratory By setting the upper limit of the haze (%), the usage amount of the wavelength conversion agent 67 can be greatly reduced, and the in-plane distribution of illuminance can be made sufficiently uniform. Specifically, by setting the transmission internal haze to 50% or less, the amount of the wavelength conversion agent 67 used can be greatly reduced, the in-plane distribution of illuminance can be made sufficiently uniform, and color unevenness can be effectively reduced. was suppressed to From the viewpoint of reducing the usage amount of the wavelength conversion agent 67 while uniforming the in-plane distribution of illuminance and color, the transmission internal haze may be 20% or less, 15% or less, or 10% or less. Furthermore, it may be 5% or less.

Transmissive internal haze (%) of the wavelength conversion sheet 60 measured in accordance with JIS K7136: 2000 without limiting the measurement light from the built-in light source using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. may be 1% or more. Even if this transmission internal haze is reduced to less than 1%, it is difficult to further reduce the usage amount of the wavelength conversion agent 67 . Therefore, from the viewpoint of color unevenness and illuminance uniformity, the transmission internal haze may be set to 1% or more.

The difference between the transmission internal haze (%) of the wavelength conversion sheet 60 for light with a wavelength different from that of the primary light LA and the normal transmission internal haze (%) measured without limiting the measurement light from the built-in light source of the haze meter may be 5% or less, or 3% or less. The difference between the transmission internal haze (%) of the wavelength conversion sheet 60 for light with a wavelength different from that of the primary light LA and the normal transmission internal haze (%) measured without limiting the measurement light from the built-in light source of the haze meter may be 0% or more. According to such an example, the wavelength conversion agent 67 can be sufficiently reduced.

By the way, from the viewpoint of sufficiently uniforming the in-plane distribution of illuminance, the reflection on the second surface 60b of the wavelength conversion sheet 60 may be total reflection. Specifically, the formula (A) described in the second aspect may hold. In addition, the inclination angle θp of the element surface 76 may satisfy the expression (X) described in the second aspect so as not to hinder the light traveling toward the second surface 60b at the incident angle that satisfies the expression (A). .

In the third aspect, as shown in FIG. 24, regarding the optical path of the light L241 incident on the element surface 76 of the unit optical element 75, the formula (E) described in the second aspect may hold. When the formula (E) is satisfied, light traveling in a direction slanted by θx (°) with respect to the third direction D3 passes through the element surface 76 and enters the wavelength conversion sheet 60, and then passes through the second surface 60b. reflect. The refractive index np of the portion forming the element surface 76 and the inclination angle θp (°) of the element surface 76 are set so as to satisfy the formula (E) for at least part of the light incident on the wavelength conversion sheet 60. may With such a setting, light circulation between the wavelength conversion sheet 60 and the light source substrate 22 is promoted, and the in-plane distribution of illuminance can be effectively uniformed.

In the third mode, the light traveling angle θx (°) in formula (E) is set in the same manner as in the second mode, and one or more of the above formulas (F), (G) and (H) are satisfied. good too.

For example, the light traveling angle θx (°) used in formula (E) is an incident angle at which the transmittance of light of a specific wavelength in the selective transmission portion 45 is 1/2 of the maximum value, and enters the selective transmission portion 45. The first specific angle θx1 (°), which is the angle (°) between the peak emission direction of the light from the selectively transmissive sheet 40 and the third direction D3, may also be used. That is, the above formula (F) may be satisfied. In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. Therefore, the inclination angle θp of the element surface 76 is preferably 16° or more.

As another example, the light traveling angle θx (°) used in equation (E) is an incident angle at which the transmittance of light of a specific wavelength in the selective transmission portion 45 is 1/10 of the maximum value. It may be the second specific angle θx2 (°), which is the angle (°) between the peak emission direction of the light incident on 45 from the selective transmission sheet 40 and the third direction D3. That is, the above formula (G) may be satisfied. In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. Therefore, the inclination angle θp of the element surface 76 is preferably 30° or more.

As still another example, the light traveling angle θx (°) used in the formula (E) is a third specific angle θx3 It's okay. That is, the above formula (H) may be satisfied.

It should be noted that the expressions (F), (G) and (H) need not be satisfied by the inclination angle θp over the entire area of the element surface 76, and if this condition is satisfied over 50% or more of the element surface 76, Advantageously, the in-plane distribution of illuminance can be made uniform. For the inclination angle θp preferably in the area of 70% or more of the element surface 76, more preferably in the area of 80% or more of the element surface 76, formulas (F), (G) and (H) are obtained. It is filled.

The conditions for total reflection described above are the conditions for the light L241 shown in FIG. This light L241 passes through one element surface 76 and travels through the wavelength conversion sheet 60 . This light L241 enters the second surface 60b without entering the other element surface 76. As shown in FIG. On the other hand, it is also assumed that the light L242 that has passed through one element surface 76 is incident on another element surface 76 that faces the one element surface 76 . This light L242 can be totally reflected by another element surface 76 and enter the second surface 60b at a small incident angle. The reflectance of this light L242 on the second surface 60b is reduced.

From the viewpoint of suppressing the generation of such light L242 and promoting reflection on the second surface 60b, the element surface 76 is arranged so that the formulas (I) and (J) described in the second aspect are established. The refractive index np of the constituent portion and the inclination angle θp (°) of the element surface 76 may be set. Here, the light traveling angle θx (°) used in the formula (J) may be the above-described first specific angle θx1 (°).

Also, the light traveling angle θx (°) used in the formula (J) may be the second specific angle θx2 (°) described above. That is, the above formula (L) may be satisfied. As another example, the light traveling angle θx (°) used in formula (J) is the direction in which 1/10 of the peak luminance in the luminance angular distribution on the second surface 40b of the selective transmission sheet 40 is obtained. , and the third direction D3 may be a third specific angle θx4, which is the angle (°) between . That is, the above formula (M) may be satisfied. Equations (L) and (M) do not have to be satisfied by the inclination angle θp over the entire area of the element surface 76. If this condition is satisfied over 50% or more of the area of the element surface 76, the in-plane illuminance is predominantly Uniform distribution. Preferably, the inclination angle θp in the area of 70% or more of the element surface 76, more preferably the inclination angle θp in the area of 80% or more of the element surface 76, the expressions (L) and (M) are satisfied.

In the third aspect of the present embodiment described above, the optical member 30 includes the selective transmission sheet 40 including the selective transmission portion 45 and the wavelength conversion sheet 60 overlaid on the selective transmission sheet 40 . The selective transmission portion 45 has a transmission characteristic in which the transmittance changes according to the incident angle. The wavelength conversion sheet 60 includes an uneven surface 61 . The wavelength conversion sheet 60 includes a wavelength conversion agent 67 that absorbs primary light LA and emits secondary light LB. The secondary light LB has a wavelength different from that of the primary light LA. The transmission internal haze of the wavelength conversion sheet 60 for light having a wavelength different from that of the primary light LA may be 45% or less, and the transmission internal haze of the wavelength conversion sheet 60 may be 50% or less.

In the third aspect of the present embodiment described above, the wavelength conversion sheet 60 includes a first surface 60a, a second surface 60b facing the first surface 60a, and a surface between the first surface 60a and the second surface 60b. and a wavelength converting agent 67 located at . An optical element portion 70 that forms at least one of the first surface 60a and the second surface 60b is provided. The optical element section 70 includes a plurality of unit optical elements 75 . At least one of the first surface 60 a and the second surface 60 b includes an uneven surface 61 composed of a plurality of unit optical elements 75 . The wavelength conversion agent 67 absorbs the primary light LA of a specific wavelength and emits the secondary light LB. The secondary light LB has a wavelength different from the specific wavelength. The transmission internal haze of the wavelength conversion sheet 60 for light having a wavelength different from that of the primary light LA may be 45% or less. The transmission internal haze of the wavelength conversion sheet 60 may be 50% or less.

According to the third aspect of the present embodiment, the primary light LA mainly travels in the direction within a narrow angular range corresponding to the transmission characteristics of the selective transmission portion 45 within the wavelength conversion sheet 60 . On the other hand, the secondary light LB emitted from the wavelength conversion agent 67 in the wavelength conversion sheet 60 travels in a direction irrelevant to the traveling direction of the primary light LA. By setting the transmission internal haze of the wavelength conversion sheet 60 to 45% or less for light of a wavelength different from that of the primary light LA, or by setting the transmission internal haze of the wavelength conversion sheet 60 to 50% or less, the wavelength conversion sheet 60 The direction of travel of the primary light LA within can be maintained within a narrow angular range that can be distinguished from the directions of travel of many secondary lights LB. Therefore, by adjusting the configuration of the concave-convex surface 61 according to the transmission characteristics of the selective transmission portion 45, the wavelength conversion sheet 60 can selectively reflect the primary light LA with a high reflectance. That is, the primary light LA that has not been wavelength-converted in the wavelength conversion sheet 60 circulates between the wavelength conversion sheet 60 and the light source substrate 22 . Thereby, the in-plane distribution of the illuminance can be made sufficiently uniform. Further, since the wavelength conversion agent 67 is positioned in the circulating optical path of the primary light LA, the wavelength conversion agent 67 can be used efficiently. Therefore, the usage amount of the wavelength conversion agent 67 can be reduced. By reducing the content of the wavelength conversion agent 67 in the wavelength conversion sheet 60, the in-plane distribution of illuminance caused by the primary light LA can be made sufficiently uniform, and accordingly color unevenness can be effectively suppressed. Also, by reducing the amount of the wavelength conversion agent 67 used, the thickness of the wavelength conversion sheet 60 and the thickness of the optical member 30 can be reduced.

Although the third aspect of the present embodiment has been described with reference to specific examples, the above-described specific examples do not limit the third aspect of the present embodiment. The third aspect of the present 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.

The transmission characteristics of the selective transmission portion 45 of the selective transmission sheet 40 can be changed in various ways. As an example, the selective transmission portion 45 may have the transmission characteristics shown in FIG. Even with the transmission characteristics shown in FIG. 26, the transmittance changes according to the incident angle. Specifically, the transmittance of the selective transmission portion 45 for light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° is a specific wavelength incident on the selective transmission portion 45 at an incident angle greater than 0°. It may be higher than the transmittance of the selective transmission portion 45 for light of the wavelength. That is, the transmittance of the selectively transmitting portion 45 for the vertically incident specific wavelength light is higher than the transmittance of the selectively transmitting portion 45 for the specific wavelength light incident on the selectively transmitting portion 45 from at least one oblique direction. may The reflectance of the selective transmission portion 45 for light of a specific wavelength incident on the selective transmission portion 45 at an incident angle of 0° is It may be smaller than the reflectance of the selective transmission portion 45 . In other words, the reflectance of the selectively transmitting portion 45 for the vertically incident specific wavelength light is lower than the reflectance of the selectively transmitting portion 45 for the specific wavelength light incident on the selectively transmitting portion 45 from at least one oblique direction. good too. The transmittance of the selective transmission portion 45 may decrease as the incident angle increases. The transmittance of the selective transmission portion 45 may be maximum when the incident angle is 0°. The transmittance of the selective transmission portion 45 may be 15% or less, 10% or less, or 5% or less at an incident angle of 20° or more.

In the illustrated example, the first surface 60a of the wavelength conversion sheet 60 includes an uneven surface. Instead of the first surface 60a of the wavelength conversion sheet 60 including the uneven surface, the second surface 60b of the wavelength conversion sheet 60 may include the uneven surface as shown in FIG. In addition to the first surface 60 a of the wavelength conversion sheet 60 including the uneven surface, the second surface 60 b of the wavelength conversion sheet 60 may include the uneven surface 61 . In the example shown in FIG. 27, the optical element portion 70 includes unit optical elements 75 as convex portions 73 on the second surface 60b. The optical element portion 70 may include a unit optical element 75 as the recess 74 on the second surface 60b.

The wavelength conversion sheet 60 shown in FIG. 27 functions as a retroreflection sheet, and intensively reflects light L271 traveling in a direction that is not greatly inclined in the third direction D3. This wavelength conversion sheet 60 may be combined with a selective transmission sheet 40 that mainly transmits light traveling in a narrow angular range around the third direction D3. The wavelength conversion sheet 60 shown in FIG. 27 is suitable, for example, in combination with the selective transmission sheet 40 having transmission characteristics shown in FIG. According to this combination, the primary light LA that has not been wavelength-converted by the wavelength conversion portion 65 of the wavelength conversion sheet 60 is reflected, especially totally reflected, by the concave-convex surface 61 and turns back in the traveling direction in the third direction. On the other hand, the secondary light LB wavelength-converted by the wavelength conversion portion 65 of the wavelength conversion sheet 60 is easily emitted from the wavelength conversion sheet 60 via the uneven surface 61 .

In addition, in FIG. 27, the thickness of the wavelength conversion sheet 60 is shown to be thin in order to facilitate understanding of the optical action regarding the optical path in the wavelength conversion sheet 60 . Also, in FIG. 27, illustration of the wavelength conversion agent 67 and the wavelength conversion section 65 is omitted. Actually, a wavelength conversion agent 67 is provided between the first surface 60a and the second surface 60b of the wavelength conversion sheet 60. As shown in FIG. A wavelength conversion sheet 60 shown in FIG. 27 may include a first barrier layer 63 and a second barrier layer 64 .

As another example, both the first surface 60 a and the second surface 60 b of the wavelength conversion sheet 60 may include the uneven surface 61 . In this example, the first surface 60 a and the second surface 60 b may partially include the uneven surface 61 . The arrangement of the uneven surface 61 may correspond to the arrangement of the light source 23 .

The above-described third aspect of the present embodiment will be described in more detail below using examples, but the above-described third aspect of the present embodiment is not limited to the following examples.

<Surface light source device>
Samples 1 to 18 of surface light source devices were produced. The surface light source devices of Samples 1-18 had the configurations shown in FIGS. 3, 4, 17-20, 22, 23A and 23B. That is, the surface light source device included a light source substrate and an optical laminate. In Samples 1-18, the optical laminate included an optical member, a first light control sheet, a second light control sheet and a reflective polarizing plate. The optical member included a selective transmission sheet and a wavelength conversion sheet. The light source substrate, selective transmission sheet, first light control sheet, second light control sheet and reflective polarizing plate were common among samples 1 to 18.

(Light source board)
On the light source substrate, blue micro light-emitting diodes were arranged at a pitch of 6 mm in both the first direction and the second direction. As each light source, a light-emitting diode that emits blue light with a central wavelength of 450 nm was used. The planar shape of this light-emitting diode was a rectangular shape of 0.2 mm×0.4 mm. The light-emitting diode was arranged on the support substrate such that the sides of the light-emitting diode were along the first direction and the second direction. The distance along the third direction D3 from the surface of each light source facing the optical member to the light incident side surface of the optical member was set to 0.5 mm. The reflective layer of the light source substrate was a white polyethylene terephthalate plate containing titanium oxide. The reflective layer had a reflectance of 95% and was diffusely reflective.

(selectively transparent sheet)
The selectively permeable sheet contained only the selectively permeable portion. The selective transmission part was a dielectric multilayer film having the transmission characteristics of the first specific example shown in FIG. In the surface light source devices of Samples 1 to 18, the first surface of the selective transmission sheet was a flat surface configured by the selective transmission portion. In the surface light source devices of Samples 1 to 18, the second surface of the selective transmission sheet was a flat surface configured by the selective transmission portion. The first and second surfaces of the selectively permeable sheet were parallel to each other and perpendicular to the third direction.

(wavelength conversion sheet)
For the surface light source devices of Samples 1 to 18, wavelength conversion sheets were produced as follows.

The wavelength conversion sheets of samples 1 to 9 included an optical element portion, a first barrier layer, a wavelength conversion portion and a second barrier layer. Wavelength converting sheet samples 10-18 included a first barrier layer, a wavelength converting portion and a second barrier layer. Wavelength conversion sheet samples 10 to 18 did not contain an optical element portion. In the wavelength conversion sheet samples 10 to 18, the first surface of the wavelength conversion sheet was a flat surface constituted by the first barrier layer. In the wavelength conversion sheet samples 1 to 9, the first surface of the wavelength conversion sheet was an uneven surface formed by the optical element portion. In the wavelength conversion sheet samples 1 to 18, the second surface of the wavelength conversion sheet was a flat surface constituted by the second barrier layer. Between samples 1-18, the first barrier layer and the second barrier layer were constructed identically. The optical elements of samples 1 to 9 were constructed identically. As shown in FIG. 10B, the optical element portions of samples 1 to 9 included unit optical elements in the shape of a regular quadrangular pyramid. As shown in FIG. 10A, the plurality of unit optical elements were arranged without gaps at a pitch of 0.1 mm in the first direction and the second direction. The inclination angle θp of the element surface included in the optical element portion was set to 40°.

The wavelength conversion portion of samples 1 to 7 and 9 of the wavelength conversion sheet contained a base material, and a wavelength conversion agent and a scattering agent dispersed in the base material. The wavelength converting portion of Sample 8 included a base material and a wavelength converting agent dispersed in the base material. The wavelength converting portion of Sample 8 did not contain a scattering agent. The wavelength conversion portions of Samples 1 to 9 differed from each other in the content of the scattering agent and the content of the wavelength conversion agent, and otherwise had the same configuration. The wavelength converting agents included a first converting agent that absorbs blue light from the light source and emits green light, and a second converting agent that absorbs blue light from the light source and emits red light.

In the surface light source devices of Samples 1 to 8, the content of the wavelength conversion agent was determined by ray tracing simulation using LightTools manufactured by Synopsys. For the surface light source devices of Samples 1 to 8, the content of the wavelength conversion agent was determined in a simulation for the surface light source device of each sample so that the light emitting surface could emit white light. The content of the wavelength converting agent in the wavelength converting portions of Samples 10 to 17 was the same as the content of the wavelength converting agent in the wavelength converting portions of Samples 1 to 8, respectively. The wavelength converting agent content of samples 9 and 18 was five times the wavelength converting agent content of the sample with the lowest wavelength converting agent content. The amount of the wavelength converting agent contained in the wavelength converting portion of Samples 1 to 18 is shown in the column of "content ratio" in Table 3 as a relative ratio.

Samples 10 to 18 had the same configuration as samples 1 to 9, respectively, except that the optical element portion was not provided. That is, sample 10 differed from sample 1 in that no optical element portion was provided, and had the same configuration as sample 1 in other respects. Sample 11 differed from Sample 2 in that no optical element section was provided, and had the same configuration as Sample 2 in other respects. Sample 12 differed from Sample 3 in that no optical element portion was provided, and had the same configuration as Sample 3 in other respects. Sample 13 was different from Sample 4 in that no optical element portion was provided, and had the same configuration as Sample 4 in other respects. Sample 14 was different from Sample 5 in that no optical element portion was provided, and had the same configuration as Sample 5 in other respects. Sample 15 differed from Sample 6 in that no optical element portion was provided, and had the same configuration as Sample 6 in other respects. Sample 16 was different from Sample 7 in that no optical element portion was provided, and had the same configuration as Sample 7 in other respects. Sample 17 differed from Sample 8 in that no optical element portion was provided, and had the same configuration as Sample 8 in other respects. Sample 18 was different from Sample 9 in that no optical element portion was provided, and had the same configuration as Sample 9 in other respects.

(First light control sheet, second light control sheet, reflective polarizing plate)
The first light control sheet and the second light control sheet were "BEF" (registered trademark) available from US 3M Company. The first light control sheet was arranged so that the longitudinal direction of the prisms was parallel to the first direction. The second light control sheet was arranged so that the longitudinal direction of the prisms was parallel to the second direction. The reflective polarizing plate was “DBEF” (registered trademark) available from 3M Company, USA.

<Evaluation 1>
The light-emitting surfaces of the surface light source devices of Samples 1 to 18 were caused to emit light, and the presence or absence of uneven brightness and uneven color was confirmed. The results are shown in the "Evaluation 1" column of Table 3. In the surface light source devices of the samples marked with "O", the in-plane distribution of brightness and color was made uniform. Samples with more uniform in-plane distribution of brightness and color are marked with more "O". At least one of brightness unevenness and color unevenness occurred in the sample surface light source devices marked with "x". Samples marked with one or more "o" were determined to be non-defective, and samples marked with "x" were determined to be defective.

<Evaluation 2>
The color of the light-emitting surfaces of the surface light source devices of Samples 1 to 18 was checked while the light-emitting surfaces were illuminated. The results are shown in the "Evaluation 2" column of Table 3. Table 3 also shows the presence or absence of the optical element portion, that is, the presence or absence of the concave-convex surface formed by the optical element portion.

<Evaluation 3>
The transmission internal haze of the wavelength conversion sheets of samples 1 to 18 was measured. The haze was measured in accordance with JIS K7136:2000 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. The column of "Haze 1" in Table 3 shows the measurement results of the transmission internal haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light. In the measurement of "Haze 1", the light from the light source of the haze meter was passed through the bandpass filter and entered the sample. In the "Haze 1" measurement, substantially no light with a wavelength of 500 nm or less was incident on the sample. The transmission internal haze of each sample was measured by setting all the light from the light source of the haze meter to be incident on the sample, and the measurement results are shown in the column of "Haze 2" in Table 3.

When a sample with a haze 1 value of 45% or less was used, the result of evaluation 1 was "○○" or higher. When a sample with a haze 2 value of 50% or less was used, the result of evaluation 1 was "○○" or higher.

A sample with an uneven surface due to the optical element portion could change the color of the light-emitting surface more than a sample without an optical element portion containing the same amount of wavelength conversion agent. From this point, it was thought that the uneven surface of the optical element part promotes the circulation of primary light, improves the utilization efficiency of the wavelength conversion agent, and reduces the usage amount of the wavelength conversion agent. In addition, by reducing the transmission internal haze of the wavelength conversion sheet, unevenness in brightness and unevenness in color can be made inconspicuous using a smaller amount of the wavelength conversion agent. From this point, it was thought that the circulation of primary light would be promoted by reducing the transmission internal haze, the efficiency of utilization of the wavelength conversion agent could be improved, and the usage amount of the wavelength conversion agent could be reduced.

<Fourth Aspect>
28 to 33 are diagrams for explaining the fourth aspect of the present embodiment. Some drawings such as FIG. 1, FIG. 3, and FIG. 4 among FIGS. 1 to 27 are diagrams for explaining the fourth aspect. FIG. 28 is a longitudinal sectional view showing one specific example of the surface light source device 20 in the fourth aspect. The surface light source device 20 shown in FIG. 28 can be applied to the display device 10 of FIG. The fourth mode differs from the third mode in that the optical member 30 includes an optical sheet S70 in addition to the selective transmission sheet 40 and the wavelength conversion sheet 60. FIG. The fourth aspect may be configured identically to the third aspect except for the optical sheet S70.

FIG. 28 is a longitudinal sectional view showing one specific example of the surface light source device 20 in the fourth aspect. As shown in FIG. 28, the surface light source device 20 in the fourth aspect may include, as main components, a light source 23 and an optical laminate 21 that adjusts the optical path of the light emitted from the light source 23. The optical laminate 21 may include optical members 30 . The optical layered body 21 and the optical member 30 may face the light source 23 . The optical layered body 21 and the optical member 30 may be sheet-like members. The optical layered body 21 and the optical member 30 may face the light source 23 in their normal direction. The optical layered body 21 and the optical member 30 may be diffusion members that diffuse the light emitted from the light source 23 . The optical layered body 21 and the optical member 30 can effectively suppress in-plane variations in illuminance caused by the arrangement of the light sources 23 . Due to the diffusion in the optical layered body 21 and the optical member 30, the illuminance at each position on the light emitting side surface 30b of the optical member 30, or the illuminance on a virtual light receiving surface parallel to the light emitting side surface 30b located near the light emitting side surface 30b. The illumination intensity at each position can be effectively homogenized.

The display device 10, the surface light source device 20, and the optical member 30 in the fourth aspect will be described below mainly with reference to specific examples shown in FIGS. The display panel 15 of the display device 10 may be configured in the same manner as the above-described display panel 15 described as the first mode. The light source substrate 22 of the surface light source device 20 may be configured in the same manner as the above-described light source substrate 22 described as the first mode. The optical laminate 21 may include the optical member 30 , the first light control sheet 81 , the second light control sheet 82 and the reflective polarizing plate 85 in order from the light source substrate 22 . Of these, the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85 are the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85, respectively, described as the first mode. It may have the same configuration as the polarizing plate 85 .

The optical member 30 includes a selective transmission sheet 40, a wavelength conversion sheet 60 and an optical sheet S70 in this order. The selective transmission sheet 40, the wavelength conversion sheet 60 and the optical sheet S70 are stacked in the third direction D3. That is, the third direction D3 is the lamination direction of the selective transmission sheet 40, the wavelength conversion sheet 60, and the optical sheet S70. In the third direction D3, the wavelength conversion sheet 60 is positioned between the selective transmission sheet 40 and the optical sheet S70. The selective transmission sheet 40 is positioned between the wavelength conversion sheet 60 and the light source substrate 22 in the third direction D3. The optical sheet S70 is positioned between the wavelength conversion sheet 60 and the display panel 15 in the third direction D3. In the illustrated example, the selective transmission sheet 40, the wavelength conversion sheet 60 and the optical sheet S70 are sheet-shaped members extending in the first direction D1 and the second direction D2. In the illustrated example, the selective transmission sheet 40 forms the light entrance side surface 30a of the optical member 30. As shown in FIG. In the illustrated example, the optical sheet S70 constitutes the light exit side surface 30b of the optical member 30. As shown in FIG. The selective transmission sheet 40 and the wavelength conversion sheet 60 may be bonded to each other, may be simply in contact and not bonded, or may be separated from each other. The wavelength conversion sheet 60 and the optical sheet S70 may be bonded to each other, may be simply in contact and not bonded, or may be separated from each other. Note that the optical member 30 may include the light diffusion sheet 50 as in the first aspect. The first surface 50a of the light diffusion sheet 50 may constitute the light incident side surface 30a.

The selectively permeable sheet 40 includes a selectively permeable portion 45 . The reflectance and transmittance of the selective transmission portion 45 change depending on the incident angle. The selective transmission portion 45 has its transmission characteristics adjusted so that the transmittance changes according to the incident angle. The selective transmission portion 45 has its reflection characteristics adjusted so that the reflectance changes according to the incident angle. The selective transmission sheet 40 and the selective transmission section 45 may be configured in the same manner as the above-described selective transmission sheet 40 and selective transmission section 45 described as the first mode, respectively. The selective transmission sheet 40 and the selective transmission section 45 may be configured in the same manner as the above-described selective transmission sheet 40 and selective transmission section 45 described as the second mode. The selective transmission sheet 40 and the selective transmission section 45 may be configured in the same manner as the above-described selective transmission sheet 40 and selective transmission section 45 described as the third mode.

The transmission characteristics and reflection characteristics of the selective transmission portion 45 have incident angle dependency. The transmittance of the selective transmission portion 45 and the reflectance of the selective transmission portion 45 change according to the incident angle. The transmission characteristics and reflection characteristics of the selective transmission portion 45 may have wavelength dependence. The transmittance of the selective transmission portion 45 and the reflectance of the selective transmission portion 45 may change according to the wavelength.

As shown in FIG. 29, the wavelength conversion sheet 60 contains a wavelength conversion agent 67. The wavelength converting agent 67 absorbs primary light and emits secondary light with a different wavelength than the primary light.

The wavelength conversion sheet 60 includes a first surface 60a and a second surface 60b. The first surface 60a faces the second side that is the light source side in the third direction D3. The second surface 60b faces the first side that is the viewer side in the third direction D3. In the illustrated example, the first surface 60a and the second surface 60b are parallel flat surfaces. In the illustrated example, the first surface 60a and the second surface 60b are orthogonal to the third direction D3.

In the fourth aspect, both the first surface 60a and the second surface 60b may be flat surfaces. In the fourth aspect, neither the first surface 60 a nor the second surface 60 b may include the uneven surface 61 . As will be described later, the optical sheet S70 includes an uneven surface 71 that can function similarly to the uneven surface 61 . 4th aspect WHEREIN: The wavelength conversion sheet 60 does not need to contain the optical element part 70. FIG. An optical sheet S70, which will be described later, may be configured in the same manner as the optical element portion 70. FIG.

In the example shown in FIG. 29, the wavelength conversion sheet 60 includes a first barrier layer 63, a wavelength conversion section 65 and a second barrier layer 64 in this order. The first barrier layer 63, the wavelength converting section 65 and the second barrier layer 64 are stacked in this order in the third direction D3. The first barrier layer 63, the wavelength conversion section 65, and the second barrier layer 64 are arranged in this order from the second side to the first side in the third direction D3. The 1st barrier layer 63, the wavelength conversion part 65, and the 2nd barrier layer 64 are sheet-shaped. The first barrier layer 63, the wavelength conversion section 65 and the second barrier layer 64 extend in the first direction D1 and the second direction D2.

The first barrier layer 63 may be the same as the first barrier layer 63 described above as the first mode. The first barrier layer 63 may be the same as the first barrier layer 63 described above as the second aspect. The first barrier layer 63 may be the same as the first barrier layer 63 described above as the third aspect. The wavelength conversion section 65 may be the same as the wavelength conversion section 65 described above as the first mode. The wavelength conversion section 65 may be the same as the wavelength conversion section 65 described above as the second mode. The wavelength conversion section 65 may be the same as the wavelength conversion section 65 described above as the third mode. The second barrier layer 64 may be the same as the second barrier layer 64 described above as the first aspect. The second barrier layer 64 may be the same as the second barrier layer 64 described above as the second embodiment. The second barrier layer 64 may be the same as the second barrier layer 64 described above as the third aspect.

The wavelength conversion section 65 may contain a light scattering component that scatters transmitted light. The light scattering component may be dispersed within the matrix portion 66 . Examples of light-scattering components include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles. The transmission haze of the wavelength conversion sheet 60 can be adjusted by the type and content of the light scattering component.

The optical sheet S70, as shown in FIGS. 30 and 31, includes a first surface 70a and a second surface 70b. The first surface 70a faces the second side that is the light source side in the third direction D3. The second surface 70b faces the first side that is the viewer side in the third direction D3. The optical sheet S<b>70 includes an uneven surface 71 . The first surface 70 a includes an uneven surface 71 . The uneven surface 71 faces the wavelength conversion sheet 60 . The second surface 70b may include a flat surface. The illustrated second surface 70b is entirely flat. The second surface 70b may be a surface perpendicular to the third direction D3. In the illustrated example, the optical sheet S70 is positioned between the wavelength conversion sheet 60 and the first light control sheet 81 described later in the third direction D3.

The optical sheet S70 may be configured in the same manner as the optical element section 70 in the third aspect. That is, the optical sheet S<b>70 may include the body portion 72 and the plurality of unit optical elements 75 similarly to the optical element portion 70 . The body portion 72 of the optical sheet S70 may be configured in the same manner as the body portion 72 of the optical element portion 70 in the third aspect. The unit optical elements 75 of the optical sheet S70 may be configured in the same manner as the unit optical elements 75 of the optical element section 70 in the third aspect.

In the example shown in FIGS. 30 and 31, the optical sheet S70 includes a plurality of unit optical elements 75 each formed as a convex portion 73 or a concave portion 74. The unit optical element 75 is an element that changes the traveling direction of light by refraction, reflection, or the like. The unit optical element 75 is a concept including elements called unit shaped elements, unit prisms, and unit lenses. The unit optical element 75 directly faces the wavelength conversion sheet 60 . An uneven surface (prism surface) 71 is formed by the unit optical element 75 .

The optical sheet S70 shown in FIG. 30 includes a sheet-like main body portion 72 and a plurality of convex portions 73 provided on the main body portion 72 . In the example shown in FIG. 30, a plurality of convex portions 73 may be provided adjacent to each other without gaps. The optical sheet S70 shown in FIG. 31 includes a body portion 72 provided with a plurality of concave portions 74 on the surface facing the wavelength conversion sheet 60 in the third direction D3. In the example shown in FIG. 31, the plurality of recesses 74 may be provided adjacent to each other without any gaps.

As shown in FIGS. 30 and 31, the unit optical element 75 has an element surface 76 inclined with respect to the third direction D3. A unit optical element 75 is defined by this element surface 76 . The concave-convex surface (prism surface) 71 of the optical sheet S70 is composed of element surfaces (element prism surfaces) 76 of unit optical elements (unit prisms) 75 .

The optical characteristics of the uneven surface 71 are affected by the inclination angles of the element surfaces 76 of the unit optical elements 75 . Therefore, the cross-sectional shape of the unit optical element 75 can be appropriately adjusted based on the optical properties required for the surface light source device 20 and the optical member 30 . The inclination angles of a plurality of element surfaces 76 included in one unit optical element 75 may be different from each other or may be the same. The optical sheet S70 may include unit optical elements 75 that differ in at least one of shape and orientation, or may include only unit optical elements 75 that are the same as each other. The optical sheet S<b>70 may include both the unit optical elements 75 as the convex portions 73 and the unit optical elements 75 as the concave portions 74 .

Unlike the examples shown in FIGS. 30 and 31, the element surfaces (element prism surfaces) 76 may be somewhat curved. The unit optical element 75 may have the outer shape of a portion of a sphere such as a hemisphere, or the outer shape of a portion of a spheroid.

A plurality of unit diffusion elements 75 may be arranged two-dimensionally. According to this example, the element surfaces 76 of the unit optical elements 75 included in the optical sheet S70 face various directions. As a result, the optical sheet S70 can guide light in various directions by the two-dimensionally arranged unit optical elements 75 . In other words, light can be guided in a plurality of non-parallel directions, and the in-plane distribution of illuminance can be effectively uniformed. Each unit optical element 75 may be configured rotationally symmetrical about an axis parallel to the third direction D3. For example, each unit optical element 75 may be configured with 3-fold, 4-fold, or 6-fold symmetry about an axis parallel to the third direction D3.

The plurality of unit optical elements 75 may be arranged irregularly or may be arranged regularly. By regularly arranging the plurality of unit optical elements 75, the design of the optical sheet S70 can be facilitated. By regularly arranging the plurality of unit optical elements 75, it becomes easy to spread the unit optical elements 75 without gaps. The dimensions and arrangement pitch of the unit optical elements 75 may be the same as those in other embodiments.

32A and 32B show specific examples of the unit optical elements 75 included in the optical sheet S70. In the example shown in FIGS. 32A and 32B, the multiple unit optical elements 75 are arranged in a square arrangement. The plurality of unit optical elements 75 are arranged at a constant pitch in the first direction D1. The plurality of unit optical elements 75 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. 32A and 32B, the plurality of unit optical elements 75 may be 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 unit optical elements 75 may be arranged in directions inclined in the first direction D1 and the second direction D2. For example, in the example shown in FIG. 32C, the plurality of unit optical elements 75 are arranged at a constant pitch in two directions inclined by ±45° with respect to the first direction D1. The arrangement of FIG. 32C can be applied to the unit optical element 75 shown in FIG. 32B. According to this example, the element surface 76 faces in two directions that are inclined by ±45° with respect to the first direction D1, and the light can be spread in these two directions.

The optical sheet S70 shown in FIGS. 30 to 32C can be produced by embossing or resin molding. The optical sheet S70 including the unit optical elements 75 may be bonded to the wavelength conversion sheet 60 and the first light control sheet 81 via a bonding layer containing an adhesive or an adhesive.

Next, the operation of generating planar light with the planar light source device 20 according to the fourth aspect will be described.

As described in the second aspect, the selective transmission function of the selective transmission portion 45 can suppress in-plane variations in brightness according to the arrangement of the light sources 23 . Thereby, the illuminance at each position on the second surface 40b of the selective transmission sheet 40 can be effectively uniformed.

As shown in FIG. 28, the light L284 transmitted through the selective transmission sheet 40 travels toward the wavelength conversion sheet 60. As shown in FIG. As shown in FIG. 29, the wavelength conversion sheet 60 includes a first barrier layer 63, a wavelength conversion section 65, and a second barrier layer 64 from the second side which is the light source side in the third direction D3.

As shown in FIG. 29, the wavelength converting portion 65 contains a wavelength converting agent 67. As shown in FIG. Lights L 291 and L 292 traveling through the wavelength converting portion 65 can collide with the wavelength converting agent 67 . The wavelength conversion agent 67 absorbs the primary light LA emitted from the light source 23 and emits secondary light LB with a different wavelength. In the illustrated example, the wavelength converting portion 65 includes a first converting agent 67A and a second converting agent 67B. The first conversion agent 67A absorbs a portion L291 of the blue primary light LA and emits green first secondary light LB1. The second conversion agent 67B absorbs a portion L292 of the blue primary light LA and emits a red second secondary light LB2.

Most of the light L284 (see FIG. 28) transmitted through the selective transmission sheet 40 travels in a direction greatly inclined with respect to the third direction D3 due to the transmission characteristics of the selective transmission portion 45. Therefore, as shown in FIG. 29, the lights L291, L292, and L293 traveling through the wavelength conversion sheet 60 tend to travel in directions greatly inclined with respect to the third direction D3. Along with this, the optical path length of the light L284 in the wavelength conversion section 65 becomes longer. Therefore, it becomes easier for the light to enter the wavelength conversion agent 67 in the wavelength conversion sheet 60 . As a result, since the wavelength conversion agent 67 can be used efficiently, the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be reduced.

The traveling direction of the secondary light LB emitted from the wavelength converting agent 67 does not depend on the traveling directions of the primary lights LA, L291, L292 before being absorbed by the wavelength converting agent 67. As shown in FIG. 29, the secondary light LB is emitted from the wavelength conversion agent 67 over a wide angular range. The angular distribution of luminance caused by the secondary light LB is uniformed to some extent on the second surface 60b of the wavelength conversion sheet 60 . Most of the secondary light LB emitted from the wavelength conversion agent 67 passes through the flat second surface 60 b and exits from the wavelength conversion sheet 60 .

As shown in FIG. 29, part L293 of the primary light LA does not enter the wavelength conversion agent 67, but enters the second surface 60b. A part of such light L293 can also pass through the flat second surface 60b and be emitted from the wavelength conversion sheet 60. FIG.

As described above, the light L285 (see FIG. 28) such as the primary light LA, the first secondary light LB1 and the second secondary light LB2 is emitted from the wavelength conversion sheet 60 to the first side in the third direction D3. do.

As shown in FIGS. 28 and 30, the lights L285 and L301 transmitted through the wavelength conversion sheet 60 travel toward the optical sheet S70. As shown in FIGS. 30 and 31, the optical sheet S70 includes unit optical elements 75 on the second side, which is the light source side in the third direction D3. The unit optical element 75 provides an uneven surface 71 to the first surface 70a of the optical sheet S70. As shown in FIG. 30, the light L301 changes its traveling direction somewhat due to refraction at the element surface 76 when entering the optical sheet S70. The light L285 can then exit the optical sheet S70 via the flat second surface 70b.

The light L286 emitted from the optical sheet S70 passes through the first light control sheet 81, the second light control sheet 82, and the reflective polarizing plate 85, and is emitted from the light emitting side surface 30b of the optical member 30. In this manner, the light emitting side surface 30b of the optical member 30 emits light.

By the way, as shown in FIGS. 28 and 33, the lights L285 and L331 incident on the second surface 70b of the optical sheet S70 can be reflected by the second surface 70b. Lights L287 and L331 reflected by the second surface 70b travel to the second side in the third direction D3. Such light can turn around in the traveling direction in the third direction D3 by being reflected by any interface, for example, the surface of the reflective layer 27, and can enter the wavelength conversion sheet 60 again.

Lights L287 and L331 reflected by the second surface 70b of the optical sheet S70 travel in the first direction D1 and the second direction D2 orthogonal to the third direction D3. That is, the lights L287 and L331 leave the light source 23 in a direction orthogonal to the third direction D3. Therefore, by utilizing the reflection on the second surface 70b, it is possible to effectively suppress in-plane variations in brightness due to the arrangement of the light source 23. FIG. That is, the optical sheet S70 can reinforce or complement the optical characteristics of the selective transmission portions 45 having the incident angle dependence, and sufficiently uniform the in-plane distribution of the illuminance.

Further, as described below, the primary light LA can be selectively reflected at a very high reflectance on the second surface 70b. The primary light LA (see FIG. 28) of the light L285 transmitted through the wavelength conversion sheet 60 maintains its traveling direction in a direction greatly inclined with respect to the third direction D3, similarly to when it is emitted from the selective transmission sheet 40. can. In the illustrated example, the traveling directions of the lights LA and L285 are further inclined with respect to the third direction D3 due to refraction on the second surface 60b of the wavelength conversion sheet 60. FIG. On the other hand, the first surface 70a of the optical sheet S70 includes an uneven surface 71. As shown in FIG. The optical sheet S70 includes a plurality of unit optical elements 75. As shown in FIG. A unit optical element 75 as a convex portion 73 or a concave portion 74 includes a plurality of element surfaces 76 . The plurality of element surfaces 76 constitute the uneven surface 71 of the first surface 70a.

On the other hand, as shown in FIG. 332, the light L331 as the primary light LA incident on the optical sheet S70 travels in the element surface 76 forming the uneven surface 71 in the direction opposite to the traveling direction with respect to the third direction D3. Incident on the inclined element surface 76 is facilitated. The traveling direction of this light L331 is not greatly bent by refraction on the uneven surface 71 when incident on the optical sheet S70. That is, the primary light LA can maintain a traveling direction that is very greatly inclined with respect to the third direction D3 within the optical sheet S70. As a result, the incident angle θy on the flat second surface 70b of the optical sheet S70 increases. Accordingly, the primary light LA that has not been wavelength-converted by the wavelength conversion agent 67 is reflected at the second surface 70b with high reflectance. Furthermore, since the incident angle θy increases, the primary light LA can be totally reflected by the second surface 70b. In FIG. 33, the thickness of the optical sheet S70 is shown to be thin in order to facilitate understanding of the optical action regarding the optical path in the optical sheet S70. Further, in FIG. 33, the wavelength conversion sheet 60 is omitted assuming that the wavelength conversion sheet 60 does not change the optical path.

On the other hand, the direction in which the secondary light LB is emitted from the wavelength conversion agent 67 does not depend on the direction of incidence on the wavelength conversion agent 67 . Therefore, the secondary light LB is diffused light and cannot be reflected at a high reflectance on the second surface 70b.

As described above, by combining the transmission characteristics of the selective transmission sheet 40 that affects the emission direction of the primary light LA and the concave-convex surface 71 of the optical sheet S70, the second surface 70b of the optical sheet S70 has a primary light It selectively reflects LA with high reflectance. A wavelength conversion sheet 60 containing a wavelength conversion agent 67 is positioned in the circulating optical path between the optical sheet S70 of the primary light LA and the light source substrate 22 . Therefore, the utilization efficiency of the wavelength conversion agent 67 can be improved, and the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be reduced.

In order to strengthen the function of maintaining the traveling direction of the primary light LA by the uneven surface 71, the element surface 76 orthogonal to the direction in which the peak luminance of the primary light LA is obtained is formed on the second surface 40b of the selective transmission sheet 40. may be used. An element surface 76 orthogonal to the direction in which the peak luminance of the primary light LA is obtained on the second surface 60b of the wavelength conversion sheet 60 may be used. By determining the inclination angle of the concave-convex surface 71 in consideration of the transmission characteristics of the selective transmission portions 45 that affect the incident direction of the primary light LA to the optical sheet S70, the second surface 70b of the optical sheet S70 can LA can be selectively reflected with high reflectance.

As described above, the primary light LA is selectively reflected by the second surface 70b. Thereby, the in-plane distribution of the illuminance caused by the primary light LA can be made sufficiently uniform. A wavelength conversion sheet 60 containing a wavelength conversion agent 67 is provided in the circulating optical path of the primary light LA between the optical sheet S70 and the light source substrate 22 in the third direction D3. As a result, the in-plane distribution of illuminance can be made sufficiently uniform, and color unevenness within the light emitting surface 20a can be suppressed. Further, since the primary light LA is selectively reflected by the second surface 70b of the optical sheet S70 and circulated, the utilization efficiency of the wavelength conversion agent 67 can be significantly improved, and the wavelength conversion agent 67 to the wavelength conversion portion 65 The content can be greatly reduced. For example, the thickness of the wavelength converting portion 65 can be reduced, and the thicknesses of the optical member 30, the optical laminate 21, and the surface light source device 20 in the third direction D3 can be reduced. The density of the wavelength conversion agent 67 in the wavelength conversion section 65 can be reduced.

In the wavelength conversion sheet 60, a barrier layer may not be provided on the side end face of the wavelength conversion portion 65 in some cases. According to this example, the deterioration of the wavelength conversion agent 67 located near the side end surface progresses, and the color of the peripheral portion of the wavelength conversion portion 65 may change. According to the present embodiment, the content of the wavelength converting agent 67 in the wavelength converting portion 65 can be reduced as described above. Therefore, the area ratio of the wavelength conversion agent 67 per unit area in the projection in the third direction D3 can be reduced. Accordingly, even when no barrier layer is provided on the side end surface of the wavelength conversion section 65, color change in the peripheral portion can be suppressed.

Also, the transmittance of the selective transmission portion 45, which is a dielectric multilayer film, has wavelength dependence. That is, the transmittance of the selective transmission portion 45, which is a dielectric multilayer film, changes with different wavelengths. The transmittance of the selective transmission portion 45, which is a dielectric multilayer film, tends to increase with respect to light with a longer wavelength than the specific wavelength. In other words, the selective transmission of the selective transmission portion 45, which depends on the angle of incidence, becomes weaker with respect to light with a wavelength greater than the specific wavelength. Therefore, the selective transmission portion 45 cannot effectively exhibit the selective transmission property depending on the incident angle with respect to the secondary light LB having a wavelength longer than the specific wavelength. In other words, the selective transmission section 45 cannot reflect the secondary light LB similarly to the primary light LA.

Therefore, from the viewpoint of sufficiently uniforming the in-plane distribution of the illuminance, after the primary light LA is sufficiently circulated between the optical member 30 and the light source substrate 22 to uniform the in-plane distribution of the illuminance, the primary light It is preferable to convert LA into secondary light LB. That is, it is preferable to reduce the content of the wavelength conversion agent 67 in the selective transmission portion 45 in the circulating optical path also from the viewpoint of suppressing in-plane variations in brightness. In addition, by uniformizing the in-plane distribution of illuminance caused by the primary light LA and reducing the density of the wavelength conversion agent 67, color unevenness can be effectively suppressed.

However, the function of homogenizing the in-plane distribution of illuminance and the function of suppressing color unevenness by using an optical sheet including an uneven surface in combination with a selective transmission sheet having incident angle dependence are the same as those of the conventional wavelength conversion unit (wavelength conversion sheet ) was not sufficiently demonstrated. In the case of using a conventional wavelength converting portion, even if the optical sheet is provided with an uneven surface, the usage amount of the wavelength converting agent cannot be reduced. Even if the color of the light-emitting surface can be made white by using a large amount of the wavelength conversion agent, the color unevenness of the light-emitting surface cannot be sufficiently eliminated in some cases.

When the inventors of the present invention investigated the cause of this problem, they found that the scattering agent used in the conventional wavelength conversion part had an effect. A conventional wavelength converting portion contains a large amount of scattering agent along with the wavelength converting agent. In the conventional wavelength conversion section, the optical path length within the wavelength conversion section is ensured by containing a scattering agent. By using a scattering agent, the amount of wavelength conversion agent used can be reduced to about half. In the conventional wavelength conversion section, a scattering agent is used to reduce the amount of the wavelength conversion agent used, thereby coping with the color change caused by the wavelength conversion agent. In this conventional wavelength conversion section, the primary light LA that passes through the selective transmission section and travels through the wavelength conversion sheet is diffused. That is, the distribution of the traveling direction of the primary light LA according to the transmission characteristics of the selective transmission section is eliminated by the scattering agent of the wavelength conversion section. Therefore, the primary light LA diffusely transmitted through the wavelength conversion sheet 60 cannot be selectively reflected on the second surface of the optical sheet after entering the optical sheet. For this reason, it was considered that when a conventional wavelength conversion portion is used, the in-plane distribution of illuminance cannot be made sufficiently uniform even if the optical sheet is provided with an uneven surface corresponding to the transmission characteristics of the selective transmission portion.

As a result of confirmation by the present inventors, by setting an upper limit to the transmission haze (%) of the wavelength conversion sheet 60 for light of a wavelength different from that of the primary light LA, the amount of the wavelength conversion agent 67 used can be greatly reduced while The in-plane distribution of illuminance could be made sufficiently uniform, and color unevenness could be sufficiently suppressed. Specifically, by setting the transmission haze to 45% or less, the in-plane distribution of illuminance can be made sufficiently uniform while the usage amount of the wavelength conversion agent 67 is significantly reduced, and color unevenness can be effectively reduced. I was able to suppress it. From the viewpoint of reducing the usage amount of the wavelength conversion agent 67 while uniforming the in-plane distribution of illuminance and color, the transmission haze may be 18% or less, 12% or less, 7% or less, and further. It may be 5% or less.

The transmission haze (%) of the wavelength conversion sheet 60 for light with a wavelength different from that of the primary light LA may be 1% or more. Even if this transmission haze is reduced to less than 1%, it is difficult to further reduce the usage amount of the wavelength conversion agent 67 . Therefore, from the viewpoint of color unevenness and illuminance uniformity, the transmission haze may be set to 1% or more.

The transmission haze (%) of the wavelength conversion sheet 60 is a value measured in accordance with JIS K7136:2000 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. That is, the transmission haze (%) is the ratio (%) of the diffuse transmittance to the total light transmittance. The “light having a wavelength different from that of the primary light LA” is as described in the third aspect, and is other than light having a wavelength capable of exciting the wavelength conversion agent 67 contained in the wavelength conversion sheet 60 to be measured. means the light of

The primary light LA is absorbed by the wavelength conversion agent 67 . At this time, the wavelength conversion agent 67 emits the secondary light LB in a direction irrelevant to the direction of incidence of the primary light LA. By eliminating the optical path conversion function of the wavelength conversion agent 67, the degree of the scattering function caused by the scattering agent of the wavelength conversion sheet 60 can be evaluated more accurately. That is, by limiting the wavelength of the light used for measurement, the degree of diffusion of the primary light LA just before it enters the uneven surface 71 can be evaluated with high accuracy. Therefore, "light having a wavelength different from that of the primary light LA" is used for measuring the transmission haze.

As described above, according to this embodiment, the usage amount of the wavelength conversion agent 67 can be reduced. As described in the third aspect, the transmission haze (%) when all the light from the light source of the above-mentioned haze meter is used for measurement can also The wavelength conversion sheet 60 capable of reducing the amount is distinguished from the conventional wavelength conversion sheet, and serves as an indicator. The transmission haze (% ), the usage amount of the wavelength conversion agent 67 can be greatly reduced, and the in-plane distribution of illuminance can be made sufficiently uniform. Specifically, by setting the transmission haze to 50% or less, the amount of the wavelength conversion agent 67 used can be greatly reduced, the in-plane distribution of illuminance can be sufficiently uniformed, and color unevenness can be effectively reduced. I was able to suppress it. From the viewpoint of reducing the usage amount of the wavelength conversion agent 67 while uniforming the in-plane distribution of illuminance and color, the transmission haze may be set to 20% or less, 15% or less, or 10% or less, and further. It may be 5% or less.

The transmission haze (%) of the wavelength conversion sheet 60 measured according to JIS K7136:2000 without limiting the measurement light from the built-in light source using a haze meter HM-150 manufactured by Murakami Color Research Laboratory is , 1% or more. Even if this transmission haze is reduced to less than 1%, it is difficult to further reduce the usage amount of the wavelength conversion agent 67 . Therefore, from the viewpoint of color unevenness and illuminance uniformity, the transmission haze may be set to 1% or more.

The difference between the transmission haze (%) of the wavelength conversion sheet 60 for light with a wavelength different from that of the primary light LA and the normal transmission haze (%) measured without limiting the measurement light from the built-in light source of the haze meter, It may be 5% or less, or 3% or less. The difference between the transmission haze (%) of the wavelength conversion sheet 60 for light with a wavelength different from that of the primary light LA and the normal transmission haze (%) measured without limiting the measurement light from the built-in light source of the haze meter is 0. % or more. According to such an example, the wavelength conversion agent 67 can be sufficiently reduced.

By the way, from the viewpoint of sufficiently uniforming the in-plane distribution of illuminance, the reflection on the second surface 70b of the optical sheet S70 may be total reflection. Specifically, the formula (XA), which is the total reflection condition using the incident angle θy (°) to the second surface 70b, may hold.
np×Sin θy≧1 Formula (XA)
"np" in the formula (XA) is the refractive index of the portion forming the element surface 76 of the optical sheet S70. Therefore, “np” may be the refractive index of the portion that constitutes the unit optical element 75 .

The inclination angle θp of the element surface 76 may be determined as follows so as not to hinder the light traveling toward the second surface 70b at the incident angle that satisfies the formula (XA).
sin ⁻¹ (1/np)≦90−θp (XX)
θp (°) in the formula (XX) is the angle (°) between the element plane 76 and the plane perpendicular to the third direction D3. When the formula (XX) is satisfied, light traveling in a direction inclined at an angle equal to or greater than the critical angle (°) for total reflection with respect to the third direction D3 is incident on the second surface 70b without being incident on the element surface 76. can promote With such a setting, the light circulation between the optical sheet S70 and the light source substrate 22 is promoted, and the in-plane distribution of illuminance can be effectively uniformed.

As shown in FIG. 33, regarding the optical path of the light L331 incident on the element surface 76 of the unit optical element 75, the following formula holds.
θ1=θx−θp Expression (XB)
Sin θ1=np×Sin θ2 Expression (XC)
θy=θp+θ2 Formula (XD)
θx (°) in the formula (XB) is the angle (°) between the traveling direction of the light L331 toward the optical sheet S70 and the third direction D3. θp (°) in equation (XB) is the angle (°) between the plane orthogonal to the third direction D3 and the element plane 76 on which the light L331 is incident. θ1 (°) in the formula (XC) is the incident angle (°) of the light L331 with respect to the element surface 76 on which the light L331 is incident. θ2 (°) in the formula (XC) is the refraction angle (°) of the light L331 at the element surface 76 through which the light L331 passes. That is, θ2 (°) is the angle between the normal direction to the element surface 76 and the traveling direction of light after refraction at the element surface 76 .

Rewriting formula (XA) using formulas (XB) to (XD) gives the following conditional formula (XE).
sin ^-1 (1/np)≤sin ^-1 (sin(θx-θp)/np)+θp Expression (XE)
When the formula (XE) is satisfied, light traveling in a direction inclined by θx (°) with respect to the third direction D3 passes through the element surface 76 and enters the optical sheet S70, and then is totally reflected by the second surface 70b. do. The refractive index np of the portion forming the element surface 76 and the inclination angle θp (°) of the element surface 76 are set so that the formula (XE) is established for at least part of the light incident on the optical sheet S70. good too. With such a setting, the light circulation between the optical sheet S70 and the light source substrate 22 is promoted, and the in-plane distribution of illuminance can be effectively uniformed.

Here, the light traveling angle θx (°) used in the formula (XE) is applied to the selective transmission portion 45 at an incident angle at which the transmittance of light of a specific wavelength in the selective transmission portion 45 is 1/2 of the maximum value. The first specific angle θx1 (°) may be the angle (°) between the peak emission direction of the incident light from the selective transmission sheet 40 and the third direction D3. The incident angle at which the transmittance is 1/2 of the maximum value is set to be smaller than the incident angle at which the transmittance is at the maximum value. In an actual surface light source device, many of the traveling directions of light emitted from the selective transmission sheet 40, transmitted through the wavelength conversion sheet 60 while maintaining the traveling direction, and directed toward the optical sheet S70 are different from the third direction D3. The direction is inclined by an angle equal to or greater than the first specific angle θx1. Therefore, when the following formula (XF) using the first specific angle θx1 is satisfied, most of the light directed toward the optical sheet S70 is totally reflected by the optical sheet S70. As a result, when the formula (XF) is satisfied, light circulation between the optical sheet S70 and the light source substrate 22 can be promoted, and the in-plane distribution of illuminance can be effectively uniformed.
sin ^-1 (1/np)≤sin ^-1 (sin(θx1-θp)/np)+θp Formula (XF)

In combination with the selective transmission portion 45 having the transmission characteristic of the first specific example shown in FIG. For example, the inclination angle θp of the element surface 76 is preferably 16° or more.

As another example, the light traveling angle θx (°) used in the formula (XE) is set to the incident angle at which the transmittance of light of a specific wavelength in the selective transmission portion 45 is 1/10 of the maximum value. The second specific angle θx2 (°) may be the angle (°) between the peak emission direction of the light incident on 45 from the selective transmission sheet 40 and the third direction D3. The incident angle at which the transmittance is 1/10 of the maximum value is smaller than the incident angle at which the transmittance is at the maximum value. The light traveling at the second specific angle θx2 is light with a very small incident angle among the incident lights that enter the optical sheet S70 after passing through the wavelength conversion sheet 60 while maintaining the traveling direction. If this light with a small incident angle satisfies the total reflection condition on the second surface 70b, most of the light incident on the optical sheet S70 can satisfy the total reflection condition on the optical sheet S70. Therefore, when the following formula (XG) using the second specific angle θx2 is satisfied, the light circulation between the optical sheet S70 and the light source substrate 22 can be further promoted, and the in-plane distribution of illuminance can be very effectively controlled. can be homogenized to
sin ^-1 (1/np)≤sin ^-1 (sin(θx2-θp)/np)+θp Expression (XG)

In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. For example, the inclination angle θp of the element surface 76 is preferably 30° or more.

As still another example, the light traveling angle θx (°) used in the formula (XE) is a third specific angle θx3 may be According to this example, of the light incident on the optical sheet S70 in the surface light source device 20 actually used, the light with a relatively small incident angle satisfies the total reflection condition on the second surface 70b. Therefore, when the following formula (XH) using the third specific angle θx3 is satisfied, light circulation between the optical sheet S70 and the light source substrate 22 can be promoted, and the in-plane distribution of illuminance can be effectively uniformed. can.
sin ^-1 (1/np)≤sin ^-1 (sin(θx3-θp)/np)+θp Expression (XH)
The third specific angle θx3 is specified from the luminance angular distribution on the second surface 40 b of the selective transmission sheet 40 . With this luminance angular distribution, light is emitted from the light source 23 in a state in which the surface light source device 20 is removed from the constituent elements on the first side, which is closer to the observer in the third direction D3 than the selective transmission sheet 40, and the second surface 40b Distribution of luminance in each direction measured above. An example of this angular distribution of brightness is shown in FIG. 25 described above. The half-value angle in the luminance angle distribution is the minimum value of the magnitude (absolute value) of the angle between the third direction D3 and the direction in which half the peak luminance is obtained in the luminance angle distribution.

It should be noted that the formulas (XF), (XG) and (XH) need not be satisfied by the inclination angle θp over the entire area of the element surface 76, and if this condition is satisfied over 50% or more of the element surface 76, Advantageously, the in-plane distribution of illuminance can be made uniform. Preferably, the inclination angle θp in the area of 70% or more of the element surface 76, more preferably the inclination angle θp in the area of 80% or more of the element surface 76 is expressed by formulas (XF), (XG) and (XH). It is filled.

The conditions for total reflection described above are the conditions for the light L331 shown in FIG. This light L331 passes through one element surface 76 and travels through the optical sheet S70. This light L331 enters the second surface 70b without entering the other element surface 76. As shown in FIG. On the other hand, it is also assumed that the light L332 that has passed through one element surface 76 is incident on another element surface 76 that faces the one element surface 76 . This light L332 can be totally reflected by another element surface 76 and enter the second surface 70b at a small incident angle. The reflectance of this light L332 on the second surface 70b is reduced.

From the viewpoint of suppressing the generation of such light L332 and promoting reflection on the second surface 70b, the angle between the traveling direction of the light traveling in the unit optical element 75 and the third direction D3 is It may be less than or equal to the angle between 76 and the third direction D3. Specifically, the following formula (XI) may be satisfied. Equation (XJ), which is obtained by rewriting equation (XI) in consideration of equations (XB) to (XD) described above, may be satisfied. The angles and refractive indices used in formulas (XI) and (XJ) are as described above.
θp+θ2≦90−θp Formula (XI)
sin ^-1 (sin(θx-θp)/np)+θp≤90-θp Expression (XJ)
Here, the light traveling angle θx (°) used in the formula (XJ) may be the above-described first specific angle θx1 (°).

Here, the light traveling angle θx (°) used in the formula (XJ) may be the above-described second specific angle θx2 (°). When the following formula (XL) using the second specific angle θx2 is satisfied, at least part of the light incident on the unit optical element 75 from the one element surface 76 is directed to another element facing the one element surface 76. It can be incident on the second surface 70 b without being incident on the surface 76 . Therefore, when the formula (XL) is satisfied, light circulation can be expected between the optical sheet S70 and the light source substrate 22, and in-plane variations in illuminance can be suppressed.
sin ^-1 (sin(θx2-θp)/np)+θp≦90-θp ・・・Formula (XL)

In combination with the selective transmission portion 45 having the transmission characteristics of the first specific example shown in FIG. For example, the inclination angle θp of the element surface 76 is preferably 45° or less.

As another example, the light traveling angle θx (°) used in the formula (XJ) is the direction in which the brightness of 1/10 of the peak brightness in the brightness angular distribution on the second surface 40b of the selective transmission sheet 40 is obtained. , and the third direction D3 may be a fourth specific angle θx4, which is the angle (°) between them. According to this example, in the surface light source device 20 actually used, at least part of the light incident on the unit optical element 75 from one element surface 76 is projected onto another element surface 76 facing the one element surface 76 . can be incident on the second surface 70b without being incident on the second surface 70b. Therefore, when the following formula (XM) using the third specific angle θx4 is satisfied, light circulation can be expected between the optical sheet S70 and the light source substrate 22, and in-plane variations in illuminance can be suppressed.
sin ^-1 (sin(θx4-θp)/np)+θp≦90-θp Expression (XM)
The fourth specific angle θx4 is specified from the luminance angular distribution on the second surface 40 b of the selective transmission sheet 40 . With this luminance angular distribution, light is emitted from the light source 23 in a state in which the surface light source device 20 is removed from the constituent elements on the first side, which is closer to the observer in the third direction D3 than the selective transmission sheet 40, and the second surface 40b Distribution of luminance in each direction measured above. An example of this luminance angular distribution is shown in FIG. 25 described above. The angle between the direction in which the luminance of 1/10 of the peak luminance in the luminance angular distribution is obtained and the third direction D3 is the direction in which the luminance of 1/10 of the peak luminance in the luminance angular distribution is obtained and the third direction. It is the minimum value of the magnitudes (absolute values) of the angles with D3.

It should be noted that the expressions (XL) and (XM) do not need to be satisfied by the inclination angle θp over the entire area of the element surface 76, and if this condition is satisfied over 50% or more of the element surface 76, the illuminance will be superior. In-plane distribution can be made uniform. Preferably, the inclination angle θp in the area of 70% or more of the element surface 76, more preferably the inclination angle θp in the area of 80% or more of the element surface 76, the expressions (XL) and (XM) are satisfied.

The specific angle θx is preferably 35° or more in order to satisfy both the above formulas (XE) and (XJ). By setting the specific angle θx to 35° or more, the inclination angle θp has an appropriate range within the range of the refractive index np of the portion forming the element surface 76 from 1.50 to 1.60. From this point, the angle formed by the traveling direction of the light traveling from the selective transmission sheet 40 to the wavelength conversion sheet 60 with respect to the third direction D3 may be 35° or more, 40° or more, or 45° or more. Further, the transmittance of the selective transmission portion 45 with respect to the light of the specific wavelength emitted from the selective transmission sheet 40 at the emission angle of 0° or more and 35° or less in terms of absolute value is half or less of the maximum value of the transmittance of the selective transmission portion 45. , or 1/10 or less of the maximum transmittance of the selective transmission portion 45 .

In the fourth aspect of the present embodiment described above, the optical member 30 includes the selective transmission sheet 40 including the selective transmission portion 45, the optical sheet S70 having the uneven surface 71, and the selective transmission sheet 40 and the optical sheet S70. and a wavelength conversion sheet 60 positioned therebetween. The selective transmission portion 45 has a transmission characteristic in which the transmittance changes according to the incident angle. The uneven surface 71 faces the wavelength conversion sheet 60 . The wavelength conversion sheet 60 includes a wavelength conversion agent 67 that absorbs primary light LA and emits secondary light LB. The secondary light LB has a wavelength different from that of the primary light LA. The transmission haze of the wavelength conversion sheet 60 for light having a wavelength different from that of the primary light LA may be 45% or less, and the transmission haze of the wavelength conversion sheet 60 may be 50% or less.

In the fourth aspect of the present embodiment described above, the wavelength conversion sheet 60 includes a first surface 60a, a second surface 60b facing the first surface 60a, and a surface between the first surface 60a and the second surface 60b. and a wavelength converting agent 67 located at . The wavelength conversion agent 67 absorbs the primary light LA of a specific wavelength and emits the secondary light LB. The secondary light LB has a wavelength different from the specific wavelength. The transmission haze of the wavelength conversion sheet 60 for light having a wavelength different from that of the primary light LA may be 45% or less, and the transmission haze of the wavelength conversion sheet 60 may be 45% or less.

According to the fourth aspect of the present embodiment, the primary light LA transmitted through the selective transmission sheet 40 is transmitted through the wavelength conversion sheet 60 without being excessively diffused, and enters the optical sheet S70. Therefore, the primary light LA mainly travels in directions within a narrow angular range according to the transmission characteristics of the selective transmission portions 45 within the optical sheet S70. On the other hand, the secondary light LB emitted from the wavelength conversion agent 67 in the wavelength conversion sheet 60 travels in a direction irrelevant to the traveling direction of the primary light LA. By setting the transmission haze of the wavelength conversion sheet 60 to 45% or less for light of a wavelength different from that of the primary light LA, or by setting the transmission haze of the wavelength conversion sheet 60 to 50% or less, The direction of travel of primary light LA can be maintained within a narrow angular range that can be distinguished from the direction of travel of many secondary beams LB. Therefore, by adjusting the configuration of the concave-convex surface 71 according to the transmission characteristics of the selective transmission portion 45, the optical sheet S70 can selectively reflect the primary light LA with a high reflectance. That is, the primary light LA that has not been wavelength-converted in the wavelength conversion sheet 60 circulates between the optical sheet S70 and the light source substrate 22 . Thereby, the in-plane distribution of the illuminance can be made sufficiently uniform. Further, since the wavelength conversion sheet 60 containing the wavelength conversion agent 67 is positioned in the circulating optical path of the primary light LA, the wavelength conversion agent 67 can be used efficiently. Therefore, the usage amount of the wavelength conversion agent 67 can be reduced. In other words, the content of the wavelength conversion agent 67 in the wavelength conversion portion 65 can be reduced. By reducing the content of the wavelength conversion agent 67 in the wavelength conversion sheet 60, the in-plane distribution of illuminance caused by the primary light LA can be made sufficiently uniform, and accordingly color unevenness can be effectively suppressed. Also, by reducing the amount of the wavelength conversion agent 67 used, the thickness of the wavelength conversion sheet 60 and the thickness of the optical member 30 can be reduced.

Although the fourth aspect of the present embodiment has been described with reference to specific examples, the above-described specific examples do not limit the fourth aspect of the present embodiment. The fourth aspect of the present 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.

The above-described fourth aspect of the present embodiment will be described in more detail below using examples, but the above-described fourth aspect of the present embodiment is not limited to the following examples.

<Surface light source device>
Surface light source device samples X1 to X9 including a light source substrate and an optical member were produced. The surface light source devices of samples X1 to X9 had the configurations shown in FIGS. 3, 4, 18, 19, 28, 29, 30, 32A and 32B. That is, the surface light source devices of samples X1 to X9 included a light source substrate and an optical laminate. The optical laminate included an optical member, a first light control sheet, a second light control sheet and a reflective polarizing plate. The optical members included a selective transmission sheet, a wavelength conversion sheet, and an optical sheet.

The light source substrate had a common configuration among the surface light source devices of samples X1 to X9. The selective transmission sheet, the optical sheet, the first light control sheet, the second light control sheet, and the reflective polarizing plate had common configurations among the surface light source devices of samples X1 to X9.

(Light source board)
On the light source substrate, blue micro light-emitting diodes were arranged at a pitch of 6 mm in both the first direction and the second direction. As each light source, a light-emitting diode that emits blue light with a central wavelength of 450 nm was used. The planar shape of this light-emitting diode was a rectangular shape of 0.2 mm×0.4 mm. The light-emitting diode was arranged on the support substrate such that the sides of the light-emitting diode were along the first direction and the second direction. The distance along the third direction D3 from the surface of each light source facing the optical member to the light incident side surface of the optical member was set to 0.5 mm. The reflective layer of the light source substrate was a white polyethylene terephthalate plate containing titanium oxide. The reflective layer had a reflectance of 95% and was diffusely reflective.

(selectively transparent sheet)
The selectively permeable sheet contained only the selectively permeable portion. The selective transmission part was a dielectric multilayer film having the transmission characteristics of the first specific example shown in FIG. In the surface light source devices of Samples X1 to X9, the first surface of the selective transmission sheet was a flat surface configured by the selective transmission portion. In the surface light source devices of Samples X1 to X9, the second surface of the selective transmission sheet was a flat surface configured by the selective transmission portion. The first and second surfaces of the selectively permeable sheet were parallel to each other and perpendicular to the third direction.

(wavelength conversion sheet)
For the surface light source devices of Samples X1 to X9, wavelength conversion sheets were produced as follows.

The wavelength conversion sheets of samples X1 to X9 included a first barrier layer, a wavelength conversion section and a second barrier layer. The first barrier layer and the second barrier layer had a common configuration among the surface light source devices of Samples X1 to X9. In the surface light source devices of Samples X1 to X9, the first surface of the wavelength conversion sheet was a flat surface composed of the first barrier layer. In the surface light source devices of Samples X1 to X9, the second surface of the wavelength conversion sheet was a flat surface composed of the second barrier layer. The first and second surfaces of the wavelength conversion sheet were parallel to each other and perpendicular to the third direction.

In the surface light source device of sample X8, the wavelength conversion part contained a base material and a wavelength conversion agent dispersed in the base material. In the surface light source device of Sample X8, the wavelength converting portion did not contain a scattering agent. In other sample surface light source devices, the wavelength converting portion included a base material, and a wavelength converting agent and a scattering agent dispersed in the base material. The wavelength conversion portions of samples X1 to X9 differed from each other in the content of the scattering agent and the content of the wavelength conversion agent, and otherwise had the same configuration. The wavelength converting agents included a first converting agent that absorbs blue light from the light source and emits green light, and a second converting agent that absorbs blue light from the light source and emits red light.

In the surface light source devices of samples X1 to X8, the content of the wavelength conversion agent was determined by ray tracing simulation using LightTools manufactured by Synopsys. For the surface light source devices of samples X1 to X8, the content of the wavelength conversion agent was determined in a simulation for the surface light source device of each sample so that the light emitting surface could emit white light. The content of the wavelength converting agent in sample X9 was five times the content of the wavelength converting agent in the sample with the lowest content of the wavelength converting agent. The amount of the wavelength converting agent contained in the wavelength converting portion of Samples X1 to X9 is shown in the column of "content ratio" in Table 4 as a relative ratio.

(optical sheet)
The optical sheets of the surface light source devices of Samples X1 to X9 had a common configuration. As shown in FIG. 32B, the optical sheets of samples X1 to X9 included unit optical elements in the shape of regular quadrangular pyramids. The first surface of the optical sheet was an uneven surface formed by the element surfaces of the unit optical elements. The second surface of the optical sheet was a flat surface perpendicular to the third direction. As shown in FIG. 32A, the plurality of unit optical elements were arranged without gaps at a pitch of 0.1 mm in the first direction and the second direction. The inclination angle θp of the element planes included in the optical sheet was set to 40°.

(First light control sheet, second light control sheet, reflective polarizing plate)
The first light control sheet and the second light control sheet were "BEF" (registered trademark) available from US 3M Company. The first light control sheet was arranged so that the longitudinal direction of the prisms was parallel to the first direction. The second light control sheet was arranged so that the longitudinal direction of the prisms was parallel to the second direction. The reflective polarizing plate was “DBEF” (registered trademark) available from 3M Company, USA.

<Evaluation 1>
For samples X1 to X9, the light emitting surface of the surface light source device was caused to emit light, and the presence or absence of unevenness in brightness and color was confirmed. The results are shown in the column of "Evaluation 1" in Table 4. In the surface light source devices of the samples marked with "O", the in-plane distribution of brightness and color was made uniform. Samples with more uniform in-plane distribution of brightness and color are marked with more "O". At least one of brightness unevenness and color unevenness occurred in the sample surface light source devices marked with "x".

<Evaluation 2>
The colors of the light emitting surfaces of the surface light source devices of the samples X1 to X9 were checked while emitting light. The results are shown in the "Evaluation 2" column of Table 4.

<Evaluation 3>
Transmission haze was measured for samples X1 to X9. The haze was measured in accordance with JIS K7136:2000 using a haze meter HM-150 manufactured by Murakami Color Research Laboratory. The measurement results of the transmission haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light are shown in the "Haze 1" column of Table 4. In the measurement of "Haze 1", the light from the light source of the haze meter was passed through the bandpass filter and entered the sample. In the "Haze 1" measurement, substantially no light with a wavelength of 500 nm or less was incident on the sample. Each sample was measured so that all the light from the light source of the haze meter was incident on the sample.

When a sample with a haze 1 value of 45% or less was used, the result of evaluation 1 was "○" or higher. When a sample with a haze 2 value of 50% or less was used, the result of evaluation 1 was "Good" or higher.

A sample containing an optical sheet with an uneven surface could change the color of the light-emitting surface more than a sample without an optical sheet containing the same amount of wavelength conversion agent. From this point, it was thought that the uneven surface of the optical sheet promotes the circulation of primary light, improves the utilization efficiency of the wavelength conversion agent, and reduces the usage amount of the wavelength conversion agent. In addition, by reducing the transmission haze of the wavelength conversion sheet, unevenness in brightness and unevenness in color can be made inconspicuous using a smaller amount of the wavelength conversion agent. From this point, it was thought that by reducing the transmission haze of the wavelength conversion sheet, the circulation of the primary light is promoted, the utilization efficiency of the wavelength conversion agent can be improved, and the usage amount of the wavelength conversion agent can be reduced.

Although the present embodiment has been described with reference to specific examples, the above-described specific examples do not limit the present embodiment. The present 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.

For example, although the wavelength conversion sheet 60 includes the wavelength conversion section 65, the first barrier layer 63, and the second barrier layer 64, the present invention is not limited to this example. In this embodiment, one or more of the first barrier layer 63 and the second barrier layer 64 may be omitted. In an example in which the first barrier layer 63 and the second barrier layer 64 are omitted, the wavelength conversion agent 67 may contain a coating layer with barrier properties.

A spacer may be arranged between the light source substrate 22 and the optical member 30 in the surface light source device 20 of the present embodiment. A transparent resin layer may be provided between the light source substrate 22 and the optical member 30, and the resin layer may function as a spacer. The resin layer may be made of a thermoplastic resin. The resin layer may contain a light diffusion component. Examples of the light diffusing component include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles.

The spacer may be joined to the light source substrate 22 or may be seamlessly formed integrally with the light source substrate 22 . The spacer may be bonded to the optical member 30 (the selective transmission sheet 40 in the illustrated example), or may be integrally formed seamlessly with the optical member 30 (the selective transmission sheet 40 in the illustrated example). good. The spacer may be bonded to both the light source substrate 22 and the optical member 30 (the selective transmission sheet 40 in the illustrated example), or may be bonded to the light source substrate 22 and the optical member 30 (the selective transmission sheet 40 in the illustrated example). Both may be integrally formed seamlessly. A functional layer functioning as a spacer may be bonded to at least one of the light source substrate 22 and the optical member 30 .

By providing spacers and functional layers, the relative positions of the light source substrate 22 and the optical member 30 can be maintained, and warping of the light source substrate 22 and the warping of the optical member 30 can be suppressed. By bonding a spacer or a functional layer to at least one of the light source substrate 22 and the optical member 30, warping of the light source substrate 22 and warping of the optical member 30 can be suppressed more effectively.

In the present embodiment, one or more of the first light control sheet 81, the second light control sheet 82 and the reflective polarizing plate 85 may be omitted from the optical laminate 21.

In this embodiment, the optical member 30 or the optical laminate 21 may further include other components. For example, the optical member or optical laminate 21 may further include a light diffusion sheet that diffuses light. The light diffusion sheet may include a base material and a light diffusion component dispersed in the base material. Examples of the light diffusing component include metal compounds, gas-containing porous substances, resin beads around which metal compounds are retained, white fine particles, and simple air bubbles. The light diffusion sheet may have unevenness on its surface. The light diffusion sheet may be positioned between the wavelength conversion sheet 60 and the first light control sheet 81 in the third direction D3. The wavelength conversion sheet 60 may be positioned between the light diffusion sheet and the selective transmission sheet 40 in the third direction D3.

10: display device, 15: display panel, 15a: display surface, 20: surface light source device, 20a: light emitting surface, 21: optical laminate, 22: light source substrate, 23: light source, 25: support substrate, 26: substrate body , 27: reflective layer, 29: wiring, 30: optical member, 30a: light input side surface, 30b: light output side surface, 35: bonding layer, 40: selective transmission sheet, 40a: first surface, 40b: second surface 40b, 45: selective transmission part, 45a: first surface, 45b: second surface, 46: dielectric multilayer film, 50: light diffusion sheet, 50a: first surface, 50b: second surface, 51: uneven surface, 52: Body part 53: Convex part 55: Unit diffusion element 56: Element surface 60: Wavelength conversion sheet 60a: First surface 60b: Second surface 61: Concavo-convex surface 63: First barrier layer 64 : second barrier layer 65: wavelength conversion part 65a: first surface 65b: second surface 66: base material part 67: wavelength conversion agent 67A: first conversion agent 67B: second conversion agent 70: optical element portion, 70S: optical sheet, 70a: first surface, 70b: second surface, 71: uneven surface, 72: body portion, 73: convex portion, 74: concave portion, 75: unit optical element, 76: Element surface 76A: First element surface 76B: Second element surface 81: First light control sheet 82: Second light control sheet 83: Main body 84: Unit prism 85: Reflective polarizing plate D1: first direction, D2: second direction, D3: third direction, LA: primary light, LB: secondary light, LB1: first secondary light, LB2: second secondary light

Claims (50)

a selectively transmitting sheet including a selectively transmitting portion;
and a wavelength conversion sheet superimposed on the selective transmission sheet,
The transmittance of the selective transmission section for the light of the specific wavelength incident on the selective transmission section at an incident angle greater than 0° is the transmittance of the light of the specific wavelength incident on the selective transmission section at an incident angle of 0°. is greater than the transmittance of the selective transmission portion of
The wavelength conversion sheet includes a first surface and a second surface facing the first surface,
at least one of the first surface and the second surface includes an uneven surface;
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
The optical member, wherein the secondary light has a wavelength different from that of the primary light. the first surface is positioned between the selectively permeable sheet and the second surface;
2. The optical member according to claim 1, wherein said second surface includes said uneven surface. The optical member according to claim 2, wherein the selective transmission sheet is joined to the wavelength conversion sheet. further comprising a light diffusion sheet joined to the selective transmission sheet,
3. The optical member according to claim 2, wherein the selective transmission sheet is positioned between the light diffusion sheet and the wavelength conversion sheet. The wavelength conversion sheet includes a wavelength conversion portion containing the wavelength conversion agent, a first barrier layer and a second barrier layer superimposed on the wavelength conversion portion, and an optical disc layer superimposed on the second barrier layer and including the uneven surface. including an element part and
the wavelength conversion part is located between the first barrier layer and the second barrier layer,
3. The optical member according to claim 2, wherein said second barrier layer is positioned between said wavelength conversion section and said optical element section. the first surface is positioned between the selectively permeable sheet and the second surface;
2. The optical member according to claim 1, wherein said first surface includes said uneven surface. 7. The optical member according to claim 6, wherein the transmittance of the selective transmission portion with respect to the light of the specific wavelength incident on the selective transmission portion at an incident angle of 0° is 5% or less. The transmittance of the selective transmission portion with respect to the light of the specific wavelength emitted from the selective transmission sheet at an emission angle of 0° or more and 35° or less in absolute value is half or less of the maximum value of the transmittance of the selective transmission portion. 7. The optical member according to claim 6, wherein The inclination angle θp (°) of the element surface that constitutes the uneven surface and the refractive index np of the portion that constitutes the element surface of the wavelength conversion sheet satisfy the following formula,
sin ⁻¹ (1/np)≦90−θp
7. The optical member according to claim 6, wherein said inclination angle θp (°) is an angle between said element plane and a plane perpendicular to the stacking direction of said selective transmission sheet and said wavelength conversion sheet. The inclination angle θp (°) of the element surface forming the uneven surface, the refractive index np of the portion forming the element surface of the wavelength conversion sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula of
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the light incident on the selective transmission portion from the selective transmission sheet at an incident angle at which the transmittance of the light of the specific wavelength in the selective transmission portion is 1/2 of the maximum value. 7. The optical member according to claim 6, which is an angle between the emitting direction and the stacking direction. The inclination angle θp (°) of the element surface forming the uneven surface, the refractive index np of the portion forming the element surface of the wavelength conversion sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula of
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak from the selective transmission sheet of the light incident on the selective transmission section at an incident angle at which the transmittance of the light of the specific wavelength at the selective transmission section is 1/10 of the maximum value. 7. The optical member according to claim 6, which is an angle between the emitting direction and the stacking direction. The wavelength conversion sheet includes a wavelength conversion section containing the wavelength conversion agent, a first barrier layer and a second barrier layer superimposed on the wavelength conversion section, and an optical disc including the uneven surface superimposed on the first barrier layer. including an element part and
the wavelength conversion part is located between the first barrier layer and the second barrier layer,
The optical member according to any one of claims 6 to 11, wherein the first barrier layer is positioned between the wavelength converting section and the optical element section. a light diffusion sheet;
and a wavelength conversion sheet superimposed on the light diffusion sheet,
The wavelength conversion sheet includes a first surface and a second surface facing the first surface,
The first surface is located between the light diffusion sheet and the second surface,
the second surface includes an uneven surface;
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
The optical member, wherein the secondary light has a wavelength different from that of the primary light. 2. The optical member according to claim 1, wherein the transmission internal haze of the wavelength conversion sheet for light of a wavelength different from that of the primary light is 45% or less. The optical member according to claim 1, wherein the transmission internal haze of the wavelength conversion sheet is 50% or less. a selectively transmitting sheet including a selectively transmitting portion;
and a wavelength conversion sheet superimposed on the selective transmission sheet,
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The wavelength conversion sheet includes an uneven surface,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein the transmission internal haze of the wavelength conversion sheet for light having a wavelength different from that of the primary light is 45% or less. 17. The optical member according to claim 16, wherein the transmission internal haze of the wavelength conversion sheet for light with a wavelength different from that of the primary light is 18% or less. a selectively transmitting sheet including a selectively transmitting portion;
and a wavelength conversion sheet superimposed on the selective transmission sheet,
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The wavelength conversion sheet includes an uneven surface,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein the transmission internal haze of the wavelength conversion sheet is 50% or less. The optical member according to claim 18, wherein the transmission internal haze of the wavelength conversion sheet is 20% or less. The difference between the transmission internal haze of the wavelength conversion sheet for light of a wavelength different from that of the primary light and the transmission internal haze of the wavelength conversion sheet is 5% or less, according to any one of claims 14 to 19. The optical member described. The wavelength conversion sheet includes a first surface and a second surface opposite to the first surface,
the first surface is positioned between the selectively permeable sheet and the second surface;
The optical member according to any one of claims 14 to 19, wherein the first surface includes the uneven surface. The transmittance of the selective transmission section for the light of the specific wavelength incident on the selective transmission section at an incident angle greater than 0° is the transmittance of the light of the specific wavelength incident on the selective transmission section at an incident angle of 0°. 22. The optical member according to claim 21, wherein the transmittance of the selective transmission portion of is greater than that of the selective transmission portion of . The wavelength conversion sheet includes a first surface and a second surface opposite to the first surface,
the first surface is positioned between the selectively permeable sheet and the second surface;
The optical member according to any one of claims 14 to 19, wherein the second surface includes the uneven surface. The transmittance of the selective transmission section with respect to light of a specific wavelength incident on the selective transmission section at an incident angle of 0° is defined as: 24. The optical member according to claim 23, wherein the transmittance is higher than the transmittance of the selective transmission portion. The wavelength conversion sheet includes an optical element portion including the uneven surface,
The optical element section includes a plurality of unit optical elements,
19. The optical member according to any one of claims 1, 13, 16, and 18, wherein each unit optical element includes an element surface that constitutes the uneven surface. The wavelength conversion sheet includes a wavelength conversion section containing the wavelength conversion agent, a first barrier layer and a second barrier layer superimposed on the wavelength conversion section, and an optical disc including the uneven surface superimposed on the first barrier layer. including an element part and
the wavelength conversion part is located between the first barrier layer and the second barrier layer,
The optical member according to any one of claims 16 to 19, wherein one of said first barrier layer and said second barrier layer is positioned between said wavelength converting section and said optical element section. a selectively transmitting sheet including a selectively transmitting portion;
an optical sheet having an uneven surface;
a wavelength conversion sheet positioned between the selective transmission sheet and the optical sheet;
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The uneven surface faces the wavelength conversion sheet,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein a transmission haze of the wavelength conversion sheet for light having a wavelength different from that of the primary light is 45% or less. 28. The optical member according to claim 27, wherein the transmission haze of the wavelength conversion sheet for light having a wavelength different from that of the primary light is 18% or less. a selectively transmitting sheet including a selectively transmitting portion;
an optical sheet having an uneven surface;
a wavelength conversion sheet positioned between the selective transmission sheet and the optical sheet;
The selective transmission part has a transmission characteristic in which the transmittance changes according to the incident angle,
The uneven surface faces the wavelength conversion sheet,
The wavelength conversion sheet contains a wavelength conversion agent that absorbs primary light and emits secondary light,
the secondary light has a wavelength different from the wavelength of the primary light;
The optical member, wherein the wavelength conversion sheet has a transmission haze of 50% or less. The optical member according to claim 29, wherein the transmission haze of the wavelength conversion sheet is 20% or less. The difference between the transmission haze of the wavelength conversion sheet and the transmission haze of the wavelength conversion sheet for light having a wavelength different from that of the primary light is 5% or less, according to any one of claims 27 to 30. optical components. The transmittance of the selective transmission section for the light of the specific wavelength incident on the selective transmission section at an incident angle greater than 0° is the transmittance of the light of the specific wavelength incident on the selective transmission section at an incident angle of 0°. 31. The optical member according to any one of claims 27 to 30, wherein the transmittance of the selective transmission portion of . The optical sheet includes a plurality of unit optical elements,
31. The optical member according to any one of claims 27 to 30, wherein each unit optical element includes an element surface forming said uneven surface. The wavelength conversion sheet includes a wavelength conversion section containing the wavelength conversion agent, and a first barrier layer and a second barrier layer superimposed on the wavelength conversion section,
31. The optical member according to any one of claims 27 to 30, wherein said wavelength converting portion is located between said first barrier layer and said second barrier layer. The wavelength conversion agent includes a first conversion agent that absorbs the primary light and emits first secondary light, and a second conversion agent that absorbs the primary light and emits second secondary light. ,
the wavelength of the second secondary light is longer than the wavelength of the first secondary light;
30. The optical member according to any one of claims 1, 13, 16, 18, 27, and 29, wherein the wavelength of the first secondary light is longer than the wavelength of the primary light. an optical member according to any one of claims 1, 13, 16, 18, 27, and 29;
and a light source facing the optical member. an optical member according to any one of claims 1, 13, 16, 18, 27, and 29;
A surface light source device comprising a light source substrate having a reflective layer facing the optical member and a light source for emitting light incident on the optical member. an optical member according to any one of claims 6 to 11, 16, and 18;
a light source facing the optical member,
The inclination angle θp (°) of the element surface forming the uneven surface, the refractive index np of the portion forming the element surface of the wavelength conversion sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula of
sin ^-1 (1/np) ≤ sin ^-1 (sin(θx-θp)/np)+θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the luminance angular distribution on the surface of the selective transmission sheet facing the wavelength conversion sheet obtained in a state where the constituent elements closer to the wavelength conversion sheet than the selective transmission sheet are removed. A surface light source device, which is an angle between a direction in which half the luminance is obtained and the lamination direction. an optical member according to any one of claims 6 to 11, 16, and 18;
a light source facing the optical member,
The inclination angle θp (°) of the element surface forming the uneven surface, the refractive index np of the portion forming the element surface of the wavelength conversion sheet, and the angle θx (°) with respect to the incident direction to the wavelength conversion sheet are as follows. satisfies the formula of
sin ^-1 (sin(θx-θp)/np)+θp≦90-θp
The inclination angle θp (°) is an angle between a plane orthogonal to the lamination direction of the selective transmission sheet and the wavelength conversion sheet and the element plane,
The angle θx (°) is the peak of the luminance angular distribution on the surface of the selective transmission sheet facing the wavelength conversion sheet obtained in a state where the constituent elements closer to the wavelength conversion sheet than the selective transmission sheet are removed. A surface light source device, which is an angle between a direction in which luminance of 1/10 of luminance is obtained and the lamination direction. Further comprising a reflective polarizing plate superimposed on the optical member,
37. The surface light source device of claim 36, wherein the optical member is positioned between the light source and the reflective polarizing plate. further comprising a light control sheet superimposed on the optical member,
37. The surface light source device according to claim 36, wherein said optical member is positioned between said light source and said light control sheet. a surface light source device according to claim 36;
A display device comprising: a display panel stacked on the surface light source device. a first surface;
a second surface facing the first surface;
a wavelength converting agent positioned between the first surface and the second surface;
An optical element portion that constitutes at least one of the first surface and the second surface is provided,
The optical element section includes a plurality of unit optical elements,
at least one of the first surface and the second surface includes an uneven surface configured by a plurality of unit optical elements;
The wavelength conversion agent absorbs primary light of a specific wavelength and emits secondary light,
The wavelength conversion sheet, wherein the secondary light has a wavelength different from the specific wavelength. the first surface is located between the light source emitting light of the specific wavelength and the second surface;
44. The wavelength conversion sheet according to claim 43, wherein said second surface includes said uneven surface. the first surface is located between the light source emitting light of the specific wavelength and the second surface;
44. The wavelength conversion sheet according to claim 43, wherein said first surface includes said uneven surface. a selective transmission sheet including a selective transmission portion in which the transmittance of light of a specific wavelength incident at an incident angle greater than 0° is greater than the transmittance of light of the specific wavelength incident at an incident angle of 0°; 44. The wavelength conversion sheet according to claim 43, which is used. The wavelength conversion sheet according to any one of claims 43 to 46, wherein the transmission internal haze for light with a wavelength different from that of the primary light is 45% or less. The wavelength conversion sheet according to any one of claims 43 to 46, which has a transmission internal haze of 50% or less. a first surface;
a second surface facing the first surface;
a wavelength converting agent positioned between the first surface and the second surface;
The wavelength conversion agent absorbs primary light of a specific wavelength and emits secondary light,
the secondary light has a wavelength different from the specific wavelength;
A wavelength conversion sheet, wherein a transmission haze of light having a wavelength different from that of the primary light is 45% or less. a first surface;
a second surface facing the first surface;
a wavelength converting agent positioned between the first surface and the second surface;
The wavelength conversion agent absorbs primary light of a specific wavelength and emits secondary light,
the secondary light has a wavelength different from the specific wavelength;
A wavelength conversion sheet having a transmission haze of 50% or less.

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