Surface light source device and display device

Abstract

The invention relates to a surface light source device and a display device. The surface light source device (20) has a light diffusion section (50) and a light reflection section (70) in this order. The light diffusion section (50) has light transmissivity and light diffusivity. The reflectance of light of a specific wavelength incident at an angle of incidence of 0 DEG in the light reflecting portion (70) is 80% or more. The reflectance of at least a portion of the light of the specific wavelength incident at an angle of incidence having an absolute value greater than 45 DEG in the light reflecting portion (70) is less than 50%.

Description

[0001] This application is a divisional application. The Chinese national application number of the original application is 202180012824.9, the application date is March 31, 2021, and the name of the invention is “Diffusing component, surface light source device and display device”. Technical Field

[0002] The present invention relates to a diffusion component, a method for manufacturing the diffusion component, a surface light source device, a display device and a dielectric multilayer film. Background Art

[0003] Patent document 1 (JP6299811B) discloses a surface light source device that emits light in a planar shape. The surface light source device can be used as a backlight source for a liquid crystal display device. The surface light source device of Patent document 1 is a direct-down type, and the light source is directly opposite to the diffusion component. In a direct-down type surface light source device, uneven brightness will occur due to the configuration of the light source. If the surface light source device becomes thinner, the uneven brightness becomes significant. Summary of the invention

[0004] In the prior art, it is not possible to achieve a thinner surface light source device and at the same time make the in-plane distribution of brightness sufficiently uniform. An object of the present invention is to achieve a thinner surface light source device and at the same time make the in-plane distribution of brightness sufficiently uniform.

[0005] The first diffusion member of the present invention comprises a light diffusion part and a light reflection part in this order.

[0006] The light diffusion part has light transmittance and light diffusion properties.

[0007] In the light reflecting portion, the reflectivity of light of a specific wavelength incident at an incident angle of 0° is 80% or more, and the reflectivity of at least a portion of the light of the specific wavelength incident at an incident angle having an absolute value greater than 45° is less than 50%.

[0008] The second diffusion member of the present invention includes a light diffusion portion and a light reflection portion in this order.

[0009] The light diffusion part has light transmittance and light diffusion properties.

[0010] In the light reflecting portion, the transmittance of light of a specific wavelength incident at an incident angle of 0° is lower than the transmittance of light of the specific wavelength incident at an incident angle greater than 0°.

[0011] In the first and second diffusion members of the present invention, the light diffusion portion may be formed as a concave-convex surface constituting the surface of the light reflection portion.

[0012] In the first and second diffusion members of the present invention, the light diffusion portion may have a concavo-convex surface facing a side opposite to the light reflection portion and may be joined to the light reflection portion.

[0013] In the first and second diffusion members of the present invention, the light diffusion portion may include an optical sheet having a concavoconvex surface having light diffusion property on the light reflecting portion side in a lamination direction of the light diffusion portion and the light reflecting portion.

[0014] In the first and second diffusion members of the present invention, the light diffusion portion may include an optical sheet having a light diffusing concavoconvex surface on a side opposite to the light reflecting portion side in a lamination direction of the light diffusion portion and the light reflecting portion.

[0015] In the first and second diffusion members of the present invention, the light diffusion portion may include an optical sheet having a concave-convex surface having light diffusion properties on both sides in a lamination direction of the light diffusion portion and the light reflection portion.

[0016] In the first and second diffusion members of the present invention, the light diffusion section may include two or more optical sheets having light diffusion properties.

[0017] In the first and second diffusion components of the present invention, the light diffusion part may include a microlens having two or more unit optical elements. The unit optical element may include an element surface, and the element surface has a normal direction inclined at an angle greater than 45° relative to the stacking direction of the light diffusion part and the light reflection part. The unit optical element may include an element surface, and the element surface has a normal direction inclined at an angle less than 45° relative to the stacking direction of the light diffusion part and the light reflection part.

[0018] The first and second diffusion members of the present invention may be provided with markings indicating directions in which the light diffusion portions should be arranged.

[0019] The first and second diffusion members of the present invention may further include an optical element portion provided on the side of the light reflecting portion opposite to the light diffusing portion and having a concavoconvex surface on the side opposite to the light reflecting portion.

[0020] The third diffusion member of the present invention comprises a light diffusion portion, a light reflection portion and an optical element portion in this order.

[0021] The light diffusion part has light transmittance and light diffusion properties.

[0022] In the light reflecting portion, the transmittance of light of a specific wavelength incident at an incident angle of 0° is lower than the transmittance of light of the specific wavelength incident at an incident angle greater than 0°.

[0023] The optical element portion has a concavoconvex surface on a side opposite to the light reflecting portion.

[0024] In the first to third diffusion members of the present invention, the concavo-convex surface may include an element surface having a normal direction inclined at an angle of 25° or less with respect to a lamination direction of the light reflecting portion and the optical element portion.

[0025] In the first to third diffusion members of the present invention, the optical element portion may be bonded to the light reflecting portion.

[0026] In the first to third diffusion members of the present invention, the optical element portion may include a microlens having two or more unit optical elements.

[0027] In the first to third diffusion members of the present invention,

[0028] The optical element portion may include a microlens having two or more unit optical elements.

[0029] The unit optical element may be a convex portion protruding toward a side opposite to the light reflecting portion.

[0030] In the first to third diffusion members of the present invention,

[0031] The optical element portion may include a microlens having two or more unit optical elements.

[0032] The unit optical element may include an element surface having a normal direction inclined at an angle of 25° or less with respect to a stacking direction of the light reflecting portion and the optical element portion.

[0033] The above-mentioned element surface may form the above-mentioned concavo-convex surface.

[0034] In the first to third diffusion members of the present invention,

[0035] The optical element portion may include a microlens having two or more unit optical elements.

[0036] The unit optical element includes a curved element surface, and the element surface may form the concavoconvex surface.

[0037] In the first to third diffusion members of the present invention,

[0038] The optical element portion may include a microlens having two or more unit optical elements.

[0039] The unit optical element may have a size of a square smaller than 1.5 mm square when viewed from a stacking direction of the optical element portion and the light reflecting portion.

[0040] In the first to third diffusion members of the present invention,

[0041] The optical element portion may include a microlens having two or more unit optical elements.

[0042] The unit optical element may include an element surface formed into a rough surface, and the element surface may form the concavoconvex surface.

[0043] In the first to third diffusion members of the present invention,

[0044] The optical element portion may include two or more unit optical elements arranged in one direction.

[0045] Each unit optical element may extend linearly along another direction that is not parallel to the one direction.

[0046] In the first to third diffusion members of the present invention,

[0047] The optical element portion may include two or more unit optical elements arranged in one direction.

[0048] Each unit optical element may extend linearly along another direction that is not parallel to the above-mentioned one direction.

[0049] The unit optical element may be a convex portion protruding toward a side opposite to the light reflecting portion.

[0050] In the first to third diffusion members of the present invention,

[0051] The optical element portion may include two or more unit optical elements arranged in one direction.

[0052] Each unit optical element may extend linearly along another direction that is not parallel to the above-mentioned one direction.

[0053] The unit optical element may include an element surface having a normal direction inclined at an angle of 25° or less with respect to a stacking direction in which the light reflecting portion and the optical element portion are stacked.

[0054] In the first to third diffusion members of the present invention,

[0055] The optical element portion may include two or more unit optical elements arranged in one direction.

[0056] Each unit optical element may extend linearly along another direction that is not parallel to the above-mentioned one direction.

[0057] The unit optical element includes a curved element surface, and the element surface may form the concavoconvex surface.

[0058] In the first to third diffusion members of the present invention,

[0059] The optical element portion may include two or more unit optical elements arranged in one direction.

[0060] Each unit optical element may extend linearly along another direction that is not parallel to the above-mentioned one direction.

[0061] The unit optical element may include an element surface formed into a rough surface, and the element surface may form the concavoconvex surface.

[0062] The surface light source device of the present invention comprises:

[0063] Any one of the first to third diffusion members of the present invention; and

[0064] The light source emits the light incident on the diffusion component.

[0065] In the surface light source device of the present invention, the light emitted from the light source may be P-polarized light.

[0066] In the surface light source device of the present invention,

[0067] The light source includes two or more light sources arranged regularly.

[0068] At least one of the light diffusion section and the optical element section may include a microlens having two or more unit optical elements arranged in a direction not parallel to an arrangement direction of the two or more light sources.

[0069] In the surface light source device of the present invention,

[0070] The light source includes two or more light sources arranged regularly.

[0071] At least one of the light diffusion unit and the optical element unit includes a microlens having two or more unit optical elements.

[0072] The unit optical element may include an element surface having a normal direction that is not parallel to an arrangement direction of the two or more light sources when viewed from a stacking direction in which the light diffusion portion and the light reflection portion are stacked.

[0073] The surface light source device of the present invention further comprises a supporting substrate, the supporting substrate supporting the light source from a side opposite to the diffusion member.

[0074] The diffusion member may further include a thermoplastic resin layer provided on the support substrate side of the light diffusion portion.

[0075] The surface light source device of the present invention further comprises a supporting substrate, the supporting substrate supporting the light source from a side opposite to the diffusion member.

[0076] The diffusion member may further include a thermoplastic resin layer provided on the support substrate side of the light diffusion portion.

[0077] A display device of the present invention includes any one of the above-mentioned surface light source devices of the present invention.

[0078] The first dielectric multilayer film of the present invention is a dielectric multilayer film used in combination with at least one of a diffractive optical element and a microlens, wherein:

[0079] The reflectivity of light of a specific wavelength incident at an incident angle of 0° is 80% or more, and the reflectivity of at least a portion of the light of the specific wavelength incident at an incident angle having an absolute value greater than 45° is less than 50%.

[0080] The second dielectric multilayer film of the present invention is a dielectric multilayer film used in combination with at least one of a diffractive optical element and a microlens, wherein:

[0081] The transmittance of light of a specific wavelength incident at an incident angle of 0° is lower than the transmittance of light of the specific wavelength incident at a certain incident angle greater than 0°.

[0082] The first method for manufacturing a diffusion member of the present invention comprises the following steps:

[0083] a step of irradiating the resin composition between the mold and the light reflecting portion with ionizing radiation to cure the resin composition; and

[0084] A step of peeling the mold from the light diffusing portion which is composed of a cured product of the resin composition and is laminated on the light reflecting portion.

[0085] The manufacturing method of the second diffusion member of the present invention comprises the following steps:

[0086] a step of irradiating the resin composition between the mold and the dielectric multilayer film with ionizing radiation to cure the resin composition; and

[0087] A step of peeling the mold from the microlens or diffractive optical element formed of the cured product of the resin composition and laminated with the dielectric multilayer film.

[0088] The manufacturing method of the third diffusion component of the present invention comprises the following steps:

[0089] The step of curing the resin composition applied on one surface of the dielectric multilayer film to form a light diffusion portion having a concavoconvex surface on the dielectric multilayer film; and

[0090] A step of curing the resin composition applied on the other surface of the dielectric multilayer film to form an optical element portion having a concavoconvex surface on the dielectric multilayer film.

[0091] According to the present invention, it is possible to achieve a reduction in the thickness of a surface light source device and to make the in-plane distribution of brightness sufficiently uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Figure 1 It is a diagram for explaining a first specific example of one embodiment, and is a perspective view showing a display device and a surface light source device.

[0093] Figure 2 yes Figure 1 A longitudinal cross-sectional view of a surface light source device.

[0094] Figure 3 It is shown Figure 2 A top view of multiple light sources of a surface light source device.

[0095] Figure 4 It is used to illustrate Figure 2 The surface light source device may include a diffusion component, and the light diffusion portion thereof is a graph showing the diffusion characteristics brought about by the light diffusion portion, and illustrates the angular distribution of the radiation intensity.

[0096] Figure 5 It is shown Figure 2 The perspective view of the light diffusion portion of the diffusion member that may be included in the surface light source device is a view for explaining the light diffusion characteristics of the diffractive optical element constituting the light diffusion portion.

[0097] Figure 6 It is used to illustrate Figure 5 A graph of the light diffusion characteristics of a diffractive optical element, showing the angular distribution of the radiation intensity.

[0098] Figure 7 It is shown Figure 2 A longitudinal cross-sectional view of an example of a microlens that may be included in the surface light source device.

[0099] Figure 8 It is shown Figure 2 A longitudinal cross-sectional view of another example of a microlens that may be included in the surface light source device.

[0100] Fig. 9 It is shown Figure 2 A longitudinal cross-sectional view of another example of a microlens that may be included in the surface light source device.

[0101] Fig.10 It is shown Figure 2 A longitudinal cross-sectional view of another example of a microlens that may be included in the surface light source device.

[0102] Fig.11A It is shown Figure 2 A top view of an example of a specific structure of a microlens that may be included in the surface light source device.

[0103] Fig. 11B It is shown Fig.11A A stereogram of a unit optical element of a microlens.

[0104] Fig. 12A It is shown Figure 2 A top view of another example of a specific structure of a microlens that may be included in the surface light source device.

[0105] Fig. 12B It is shown Fig. 12A A stereogram of a unit optical element of a microlens.

[0106] Fig.13A It is shown Figure 2 A top view of an example of a specific structure of a microlens that may be included in the surface light source device.

[0107] Fig. 13B It is shown Fig.13A A stereogram of a unit optical element of a microlens.

[0108] Fig.14A It is shown Figure 2 A top view of an example of a specific structure of a microlens that may be included in the surface light source device.

[0109] Fig. 14B It is shown Fig.14A A stereogram of a unit optical element of a microlens.

[0110] Fig.15 It is shown Figure 2 The graph is a graph showing an example of optical characteristics of a light reflecting portion of a diffusion member that may be included in the surface light source device, and is a graph for explaining the reflection angle dependence of the reflectance and the transmittance.

[0111] Fig.16 It is shown Figure 2 A graph showing another example of optical characteristics of a light reflecting portion of a diffusion member that may be included in a surface light source device.

[0112] Fig.17 It is shown Figure 2 A graph showing still another example of the optical characteristics of the light reflecting portion that may be included in the surface light source device.

[0113] Fig.18 Yes Fig.17 A graph in which a portion of a graph is enlarged.

[0114] Fig.19 It is a longitudinal sectional view showing the surface light source device, and is a diagram for explaining the functions of the diffusion member and the surface light source device.

[0115] Fig. 20 is with Figure 2 The corresponding longitudinal cross-sectional view of the surface light source device is a view for explaining the functions of the diffusion member and the surface light source device.

[0116] Fig.21 is with Figure 2 The corresponding longitudinal cross-sectional view of the surface light source device is a view for explaining the functions of the diffusion member and the surface light source device.

[0117] Fig. 22 is with Figure 2 The corresponding longitudinal cross-sectional view of the surface light source device is a view for explaining the functions of the diffusion member and the surface light source device.

[0118] Fig.23A This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 1.

[0119] Fig. 23B This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 2.

[0120] Fig.23C This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 3.

[0121] Fig.23D This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 4.

[0122] Fig.23E This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 5.

[0123] Fig.23F This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 6.

[0124] Figure 23G This is a simulation result for calculating the in-plane distribution of the illuminance of the surface light source device of Sample 7.

[0125] Fig.24 is a diagram for illustrating a second specific example of an embodiment, showing Figure 2 A longitudinal cross-sectional view of an example of a diffusion component that may be included in the surface light source device.

[0126] Fig.25A It is shown Fig.24 A longitudinal cross-sectional view of an example of a microlens that may be included in the optical element portion of the diffusion component.

[0127] Fig.25B It is shown Fig.24 A longitudinal cross-sectional view of another example of a microlens that may be included in the optical element portion of the diffusion component.

[0128] Fig.26 It is shown Fig.24 A stereoscopic view of another example of the optical element portion of the diffusion component.

[0129] Fig. 27 is with Fig.25A The corresponding longitudinal cross-sectional view of the optical element portion is a view for explaining the function of the optical element portion.

[0130] Fig.28 is with Figure 2 The corresponding longitudinal cross-sectional view of the surface light source device is a diagram for explaining an example in which the diffusion member includes a thermoplastic resin layer.

[0131] Fig.29 is with Figure 2 The corresponding longitudinal cross-sectional view of the surface light source device is a diagram for explaining an example in which the diffusion member includes a thermoplastic resin layer.

[0132] It is a diagram for explaining an example in which a surface light source device includes a void-forming layer.

[0133] Fig.30 Yes Description Figure 2 or Fig.24 A side view of an example of a method for manufacturing a light diffusion portion and an optical element portion that a diffusion component may include.

[0134] Fig.31 Yes Description Figure 2 or Fig.24 FIG. 1 is a diagram showing an example of a layer structure of a light diffusing portion that a diffusing component may include.

[0135] Fig.32 Yes Description Figure 2 or Fig.24 FIG. 1 is a diagram showing another example of a method for manufacturing a light diffusion portion and an optical element portion that a diffusion component may include.

[0136] Fig.33 Yes Description Figure 2 or Fig.24 FIG. 1 is a diagram showing an example of a layer structure of a light diffusing portion that a diffusing component may include.

[0137] Fig.34 1 is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Example 1.

[0138] Fig.35 This is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Example 2.

[0139] Fig.36 1 is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Example 3.

[0140] Fig.37 1 is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Example 4.

[0141] Fig.38This is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Example 5.

[0142] Fig.39 This is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Example 6.

[0143] Fig.40 3 is a diagram showing the in-plane distribution of radiation intensity on the light emitting surface of the surface light source device of Comparative Example 1. DETAILED DESCRIPTION

[0144] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. It should be noted that in the drawings attached to the specification of this case, for the sake of convenience of illustration and understanding, the scale and aspect ratio may be appropriately changed and exaggerated compared with the actual situation. In addition, the structure shown in some drawings may be omitted in other drawings.

[0145] In this specification, the terms "sheet", "film", and "plate" are not distinguished from each other only by different names. For example, "sheet" is a concept that also includes components that can be called "film" and "plate", and is not distinguished only by different names.

[0146] In addition, in this specification, the normal direction of a sheet (film, plate) component refers to the normal direction of the target sheet (film, plate) component relative to the sheet surface. In addition, the "sheet surface (film surface, plate surface)" refers to the surface that is consistent with the plane direction of the target sheet (film, plate) component when the target sheet (film, plate) component is observed as a whole and globally.

[0147] In addition, the terms such as "parallel", "perpendicular", "same" and the like or the values ​​of lengths and angles used in this specification to define shapes, geometric conditions and their degrees are not limited to the strict meanings but are interpreted to include a range to which the same function can be expected.

[0148] It should be noted that, in order to clarify the directional relationship between the drawings, in some drawings, the first direction D1, the second direction D2 and the stacking direction D3 are indicated by arrows as common directions between the drawings. The front end side of the arrow is one side of each direction D1, D2, and D3. Figure 2 As shown in FIG. 1 , an arrow pointing inward in a direction perpendicular to the paper plane of the accompanying drawings is represented by a symbol with an X in a circle. Figure 3 As shown, an arrow pointing from the paper surface toward the front in a direction perpendicular to the paper surface of the accompanying drawing is represented by a symbol with a dot in a circle.

[0149] Figures 1 to 40 is a diagram for explaining one embodiment. Figure 11 is a perspective view schematically showing a display device 10 as an application example of a surface light source device 20 and a diffusion component 40. The display device 10 displays an image such as an animation, a still image, text information, or a combination thereof. The display device 10 can be used as a liquid crystal display device for vehicle use, for example. In addition, the display device 10 can also be used for various purposes such as advertising, display, television images, and display of various information indoors or outdoors. Figure 1 The display device 10 shown includes: a surface light source device 20 having a light emitting surface 20 a ; and a display panel 15 arranged to face the light emitting surface 20 a .

[0150] Figure 2 FIG. 2 is a longitudinal sectional view showing a surface light source device 20 as a first specific example. Figure 2 As shown, the surface light source device 20 includes, as main components, a light source 22 and a diffusion component 40 for adjusting the optical path of light emitted from the light source 22. The diffusion component 40 is arranged directly opposite to the light source 22. That is, the diffusion component 40 is a sheet-like component that faces the light source 22 in its normal direction. The diffusion component 40 can effectively eliminate the uneven brightness caused by the presence of the light source 22 by diffusing the light emitted from the light source 22. As a result, the illumination at each position on the light emitting side surface 40b of the diffusion component 40, or the illumination at each position on the imaginary light receiving surface parallel to the light emitting side surface 40b and located near the light emitting side surface 40b, can be made uniform. In particular, the diffusion component 40 described in the present embodiment has been studied so that the in-plane distribution of the brightness can be sufficiently uniform while achieving the thinness of the surface light source device 20.

[0151] The “illuminance of the light-emitting side surface 40 b ” used in the following description refers to the “illuminance on the light-emitting side surface 40 b ” or the above-mentioned “illuminance on the light-receiving surface”.

[0152] Hereinafter, the display device 10 , the surface light source device 20 , and the diffusion member 40 in one embodiment will be described with reference to a first specific example shown in the drawings.

[0153] First, the display panel 15 of the display device 10 is described. Figure 1 As shown, the display panel 15 is stacked with the surface light source device 20 in the stacking direction D3. The display panel 15 is arranged to face the light emitting surface 20a of the surface light source device 20. The display panel 15 has a display surface 15a for displaying an image as a surface facing the opposite side of the surface light source device 20 in the stacking direction D3. In the example shown in the figure, the display panel 15 is formed in a rectangular shape when viewed from the stacking direction D3, that is, when viewed from the front direction.

[0154] The display panel 15 is configured as a transmissive liquid crystal display panel, for example. A portion of the light incident from the surface light source device 20 is transmitted through the display panel 15 as a liquid crystal display panel, so that an image is displayed on the display surface 15a. The display panel 15 includes a liquid crystal layer having a liquid crystal material. The light transmittance of the display panel 15 changes according to the intensity of the electric field applied to the liquid crystal layer.

[0155] As an example of the display panel 15, a liquid crystal display panel having a pair of polarizers and a liquid crystal unit (liquid crystal layer) disposed between the pair of polarizers can be used. The polarizer has a polarizing element. The polarizing element decomposes the incident light into two perpendicular polarization components. The polarization component in one direction passes through the polarizing element. The polarization component in another direction perpendicular to one direction is absorbed by the polarizing element. The liquid crystal unit has a pair of supporting plates and a liquid crystal disposed between the pair of supporting plates. The liquid crystal unit is configured to be able to apply an electric field to each area forming a pixel. As an example, the orientation of the liquid crystal of the liquid crystal unit to which the electric field is applied changes. As an example, the polarization component in a specific direction emitted from the surface light source device 20 and passing through the polarizer on the surface light source device 20 side of the liquid crystal unit rotates its polarization direction by 90° when passing through the liquid crystal unit to which the electric field is not applied. The polarization component in a specific direction maintains its polarization direction when passing through the liquid crystal unit to which the electric field is applied. By whether or not an electric field is applied to the liquid crystal unit, it is possible to control whether the polarization component in a specific direction that has passed through a polarizer is further passed through another polarizer or absorbed and cut off in another polarizer.

[0156] Next, the surface light source device 20 is described. The surface light source device 20 has a light emitting surface 20a that emits planar light. The surface light source device 20 is configured as a direct-down type backlight. In the projection to the stacking direction D3, a light source 22 is provided in an area overlapping with the light emitting surface 20a. In the illustrated example, the normal direction of the display panel 15, the normal direction of the display surface 15a, the normal direction of the light emitting surface 20a, the normal direction of the diffusion component 40, the normal directions of the later-described light diffusion portion 50, the light reflection portion 70 and the optical element portion 110 included in the diffusion component 40, and the normal direction of the later-described supporting substrate 25 that supports the light source 22 are parallel to each other. In the illustrated example, these normal directions coincide with the stacking direction D3, and are also referred to as the front direction.

[0157] The light source 22 has a light emitting element that emits light. As the light emitting element, a light emitting diode can be exemplified. A light emitting diode is also referred to as an LED. The size of the light emitting diode used as the light source 22 is not particularly limited. From the perspective of making the image of the light source 22 inconspicuous, a small light emitting diode such as a mini LED or a micro LED can be used. Specifically, Figure 3The lengths WL1 and WL2 of one side of the quadrilateral light source 22 when viewed in the stacking direction D3 shown may be preferably 0.5 mm or less, and more preferably 0.2 mm or less.

[0158] The light emission wavelength of the light source 22 can be appropriately selected according to the purpose of the surface light source device 20. For example, the surface light source device 20 can have a light emitting element that emits blue light and a light emitting element that emits yellow light to generate white light. In addition, the surface light source device 20 can have a light emitting element that emits blue light, a light emitting element that emits green light, and a light emitting element that emits red light to generate white light. In addition, when a plurality of light emitting elements are provided, one light source 22 can include a plurality of light emitting elements that are arranged close to each other, or can include only a single light emitting element. That is, a plurality of light sources 22 with different light emission wavelengths can be used.

[0159] As a specific example shown in the figure, the light source 22 may include a light emitting diode emitting blue light with a wavelength of 450 nm as a light emitting element. According to this example, a light emitting diode with a large output can be used as the light source 22. On the other hand, by using an element capable of changing the wavelength such as a phosphor, white light can also be emitted.

[0160] As one example, the light source 22 may be composed only of a light emitting element. As another example, the light source 22 may include an optical element such as a cover or lens for adjusting the light distribution from the light emitting element, or a phosphor that absorbs light from the light emitting element and emits light of a different wavelength.

[0161] The light distribution characteristics of the light source 22 are not particularly limited. The light distribution characteristics of the light source 22 may be Lambertian light distribution. If it is Lambertian light distribution, in the luminous intensity distribution from the light source 22 toward the stacking direction D3, the highest peak intensity is obtained in the stacking direction D3 as the optical axis, and an intensity half of the peak intensity is obtained in the direction inclined 60° from the optical axis. As another example, the peak intensity may also be obtained in a direction other than the stacking direction D3. For example, the batwing light distribution disclosed in Patent Document 1 (JP6299811B) may be used as the light distribution characteristics of the light source 22.

[0162] The surface light source device 20 may have a plurality of light sources 22 or a single light source 22. The number of light sources 22 is appropriately selected according to the purpose of the surface light source device 20, the area of ​​the light-emitting surface 20a, etc. From the perspective of eliminating the uneven brightness caused by the configuration of the light sources 22, the plurality of light sources 22 included in the surface light source device 20 are preferably regularly arranged on a plane perpendicular to the stacking direction D3. For example, a plurality of light sources 22 may be arranged in the following arrangement: a honeycomb arrangement arranged at a certain interval in three directions inclined at 60° to each other; a square arrangement arranged at a certain interval in two directions perpendicular to each other.

[0163] exist Figure 3 In the example shown, a plurality of light sources 22 are arranged at a certain interval in the first direction D1 and the second direction D2 which are perpendicular to each other. In the example shown in the figure, the arrangement pitch PL1 in the first direction D1 and the light distribution pitch PL2 of the light source 22 in the second direction D2 are the same. However, not limited to the example shown in the figure, the arrangement pitch PL1 and the arrangement pitch PL2 may also be different. In the example shown in the figure, the first direction D1 and the second direction D2 are parallel to the side edges of the surface light source device 20 and the diffusion component 40 which form a rectangular shape, respectively. The arrangement pitch PL1 and the arrangement pitch PL2 of the light source 22 may be greater than 0.2 mm and less than 10 mm, respectively.

[0164] In addition, the light source 22 may emit only P-polarized light when incident on the diffusion component 40. P-polarized light refers to light that vibrates on a plane including the traveling direction of the light when incident on the diffusion component 40 and the normal direction of the light incident side surface 40a of the diffusion component 40. By making the light source 22 emit only P-polarized light, when the dielectric multilayer film described later is used for the light reflecting portion 70, the transmittance of light incident at a large incident angle can be fully improved, and the desired optical characteristics can be given to the diffusion component 40. As a result, the in-plane distribution of the illumination of the light emitting side surface 40b of the diffusion component 40 can be effectively made uniform.

[0165] Incidentally, the illustrated surface light source device 20 has a supporting substrate 25 that supports the light source 22 in addition to the light source 22 and the diffusion component 40. The supporting substrate 25 supports a plurality of light sources 22 from the side opposite to the diffusion component 40 in the stacking direction D3. The supporting substrate 25 includes a circuit that supplies power to the light source 22. The supporting substrate 25 is a sheet-like component. The supporting substrate 25 has a light reflectivity that reflects light and directs it toward the diffusion component 40. The light reflectivity of the supporting substrate 25 is not particularly limited as long as it can be exerted on the light emitted from the light source 22 or the light used for emitting light in the surface light source device 20. The light used for emitting light in the surface light source device 20 may include light emitted from the light source 22 and converted in wavelength, etc.

[0166] As a specific structure, such as Figure 2As shown, it has: a sheet-like substrate body 26; a reflective layer 27 stacked on the substrate body 26 from the side of the diffusion component 40 in the stacking direction D3; and a wiring 28 electrically connected to the light source 22. The substrate body 26 extends in a direction perpendicular to the stacking direction D3, and the substrate body 26 has insulation. The reflective layer 27 has reflectivity to the light emitted from the light source 22 or the light used for emitting light in the surface light source device 20. The reflectivity in the reflective layer 27 can be regular reflection called specular reflection, diffuse reflection, and further anisotropic diffuse reflection. The substrate body 26 can be a resin film containing diffusion particles, such as a white polyethylene terephthalate film. The reflective layer 27 can be a metal layer stacked on the substrate body 26, or a reflective diffractive optical element. The wiring 28 is electrically connected to the terminal (not shown) of the light source 22 via solder or the like. When the substrate body 26 and the reflective layer 27 have insulation, the wiring 28 is preferably located between the substrate body 26 and the reflective layer 27.

[0167] It should be noted that if Figure 2 As shown by the double-dotted line in FIG. 1 , the light source 22 may be covered with a packaging material 23. The packaging material 23 is provided corresponding to each light source 22. Figure 2 and Figure 3 In the example shown, the sealing material 23 is arranged two-dimensionally like the light source 22. In the example shown in the figure, the surface and side surfaces of the light source 22 facing the diffusion member 40 are covered with the sealing material 23. The sealing material 23 is fixed to the support substrate 25. The portion where the light source 22 is electrically connected to the wiring 28 may also be covered with the sealing material 23. As a material constituting the sealing material 23, a thermosetting resin such as a silicone resin or an epoxy resin, or a thermoplastic resin such as an olefin resin can be used.

[0168] It should be noted that in Figure 2 In the example shown, the diffusion member 40 is disposed on the sealing material 23. That is, the diffusion member 40 is supported by the sealing material 23 and is separated from the light source 22 and the support substrate 25 in the stacking direction D3. The sealing material 23 can be bonded to the diffusion member 40 by bonding, adhering, welding, etc. It should be noted that Figure 2 The distance DX shown is the distance between the light source 22 and the diffusion member 40 along the stacking direction D3. In other words, the distance DX is the distance between the surface of the light source 22 facing the diffusion member 40 and the light incident side surface 40a of the diffusion member 40 along the stacking direction D3.

[0169] Next, the diffusion member 40 will be described. The diffusion member 40 includes a light diffusion portion 50 and a light reflection portion 70 in this order. The light diffusion portion 50 is located on the light entrance side of the light to be diffused by the diffusion member 40 with reference to the light reflection portion 70. The light reflection portion 70 is located on the light exit side of the light to be diffused by the diffusion member 40 with reference to the light diffusion portion 50. Figure 2 In the example shown, the diffusion component 40 is in sheet form. The diffusion component 40 extends along the first direction D1 and the second direction D2 perpendicular to the stacking direction D3. The light diffusion portion 50 forms the light incident side surface 40a of the diffusion component 40. The light reflection portion 70 forms the light exit side surface 40b of the diffusion component 40. It should be noted that the light diffusion portion 50 and the light reflection portion 70 may be joined to each other, may only be in contact without being joined, and may also be spaced apart from each other.

[0170] First, the light diffusion part 50 is described. The light diffusion part 50 has light transmittance and light diffusion properties for light emitted from the light source 22 or light used for emitting light in the surface light source device 20. The light diffusion part 50 has light transmittance and light diffusion properties for visible light. The light diffusion part 50 may include an optical sheet 55 that is merely overlapped with other components or joined to other components by bonding or adhesion, may be an optical sheet 55, may be a part of an optical sheet 55, a component, a structure, etc., and may also be a surface of an optical sheet, a component, a structure, etc.

[0171] As the light transmittance of the light diffusion part 50, for example, the total light transmittance of the light diffusion part 50 is preferably 50% or more, more preferably 70% or more, and further preferably 90% or more. By making the total light transmittance of the light diffusion part 50 within the above range, the utilization efficiency of the light from the light source 22 is improved. In addition, when the light diffusion part 50 is used for the surface light source device 20, the in-plane distribution of the illumination on the light emitting side surface 40b of the diffusion component 40 can be effectively made uniform. Therefore, the light diffusion part 50 is made of a material that has high transmittance to the light emitted from the light source 22 or the light used for emitting light in the surface light source device 20. It should be noted that the total light transmittance is a value measured by the method according to JIS K7361-1:1997 with the incident angle set to 0 degrees. The total light transmittance is a value measured using an ultraviolet visible near-infrared spectrophotometer V-7200 manufactured by JASCO Corporation.

[0172] The light diffusion brought by the light diffusion part 50 can be isotropic diffusion or anisotropic diffusion. The light diffusion part 50 can diffuse light in a direction within a specific angle range. The specific angle range can be one or multiple and spaced from each other. In addition, the diffusion generated by the light diffusion part 50 is not limited to diffusing the transmitted light, but can also diffuse the reflected light.

[0173] As the light diffusion property of the light diffusion part 50, the diffusion angle α of the light incident on the light diffusion part 50 is preferably 10° or more, more preferably 15° or more, and further preferably 20° or more. In addition, the diffusion angle of the light incident on the light diffusion part 50 is preferably 85° or less, more preferably 60° or less, and further preferably 50° or less. By making the diffusion angle of the light diffusion part 50 within this range, when the diffusion component 40 is used in the surface light source device 20, the in-plane distribution of the illumination on the light output side surface 40b of the diffusion component 40 can be effectively made uniform.

[0174] The diffusion angle α refers to the full width at half maximum (FWHM) in the angular distribution of radiation intensity (watt / steradian) obtained when light is incident on the light-entering side surface of the light diffusion portion 50 at an incident angle of 0°. Figure 4 : is a graph showing the angular distribution of the radiation intensity on the light emitting side surface of the light diffusing portion 50 when a parallel light beam is incident on the incident side surface of the light diffusing portion 50 at an incident angle of 0°. Figure 4 The vertical axis of the curve is the value of the radiation intensity, and the horizontal axis is the emission angle. The full width at half maximum in the angular distribution of the radiation intensity corresponding to the diffusion angle α is the maximum transmitted light intensity I obtained in the angular distribution of the radiation intensity. max The width (°) of the emission angle range where the radiation intensity is half.

[0175] The angular distribution of radiation intensity can be measured using a goniophotometer or a goniospectrocolorimeter. The diffusion angle α can be measured using, for example, a goniophotometer GP-200 manufactured by Murakami Color Research Laboratory.

[0176] The incident angle is the angle (°) formed by the direction of incident light relative to the normal direction of the sheet or other component on which the light enters. The exit angle is the angle (°) formed by the direction of incident light relative to the normal direction of the sheet or other component on which the light exits.

[0177] also, Figure 5 It is right Figure 4 Differently, a perspective view is provided to explain other preferred light diffusion characteristics of the light diffusion portion 50. Figure 5 In the embodiment, the light ray L51 is incident on the light diffusion part 50 at an incident angle of 0°. That is, the light ray L51 is vertically incident on the light diffusion part 50. The light ray L51 is diffused by optical effects such as refraction, reflection, and diffraction in the light diffusion part 50. Figure 5In the light diffusion section 50 shown, the light L51 mainly travels on the following optical path: from the vertex of a cone whose vertex is located on the light diffusion section 50 and whose bottom surface is arranged parallel to the light diffusion section 50 toward each position on the circumference of the bottom surface. In this example, when the light is incident on the light diffusion section 50 at an incident angle of 0°, the radiation intensity on the side of the light diffusion section 50 facing the light reflection section 70 has a peak at an exit angle other than 0°. More preferably, when the light is incident on the light diffusion section 50 at an incident angle of 0°, the radiation intensity on the side of the light diffusion section 50 facing the light reflection section 70 has a peak at an exit angle other than 0° in the angle distribution within any plane including the exit direction with an exit angle of 0°. The absolute value of the exit angle with the peak of the radiation intensity can preferably be 30° to 60°, more preferably 30° to 50°, and further preferably 30° to 45°. In addition, the absolute value of the exit angle of more than 90% of the light incident on the light diffusion portion 50 at an incident angle of 0° may be 30° to 60°. The absolute value of the exit angle of more than 95% of the light incident on the light diffusion portion 50 at an incident angle of 0° may be 30° to 60°. The absolute value of the exit angle of more than 98% of the light incident on the light diffusion portion 50 at an incident angle of 0° may be 30° to 60°.

[0178] By giving the light diffusion portion 50 a reference Figure 5 The light diffusion property described above can prevent the illuminance in the area directly above the light source 22 from becoming too high, and can increase the illuminance in the area spaced apart from the light source 22 in the direction perpendicular to the stacking direction D3. As a result, the in-plane distribution of the illuminance can be effectively made uniform. In particular, from the perspective of uniform in-plane distribution of the illuminance, the reflectivity of the light reflecting portion 70 incident on the light reflecting portion 70 described later at an incident angle of an absolute value of 0° or more and below a peak angle is preferably 80% or more. More preferably, it is 85% or more, and further preferably, it is 90% or more. Here, the peak angle refers to the absolute value of the angle of incidence having a peak value of the radiation intensity.

[0179] Figure 6 The solid line represents the incident light when the incident angle is 0°. Figure 5 FIG. 5 is a graph showing the angular distribution of the radiation intensity on the light emitting side surface of the light diffusion portion 50 .

[0180] The light diffusion unit 50 is not particularly limited, and various structures having light transmittance and light diffusion properties may be adopted. The light diffusion unit 50 may include at least one of a transmissive diffractive optical element 60 and a microlens 65 .

[0181] The diffractive optical element 60 is an element that performs diffraction on incident light. The diffractive optical element 60 may be a holographic element. A diffractive optical element having diffraction characteristics for achieving desired light diffusion can be designed relatively easily. For example, the diffractive optical element 60 may have Figure 6 Diffuse properties shown.

[0182] The microlens 65 has a plurality of unit optical elements 66. Figure 7 to Figure 10 As shown in FIG. 1 , the unit optical element 66 is an element that changes the direction of light by refraction or reflection. The unit optical element 66 is a concept that includes elements called unit shape elements, unit prisms, and unit lenses. The unit optical element 66 is configured as a convex portion 68 or a concave portion 69. Figure 7 to Figure 10 In the example shown, the light diffusion section 50 includes a main body 58, and a unit optical element 66 as a convex portion 68 is formed on the main body 58. However, as described later, the light diffusion section 50 may include a main body 58 and a unit optical element 66 as a concave portion 69 provided on the main body 58. The main body 58 is sheet-shaped. The main body 58 extends along the first direction D1 and the second direction D2 perpendicular to the stacking direction D3. Figure 2 In the illustrated example, the main body portion 58 is joined to the light reflecting portion 70 .

[0183] like Figure 7 to Figure 10 As shown, the unit optical element 66 has an element surface 67 inclined with respect to the stacking direction D3. The unit optical element 66 is drawn by the element surface 67. The microlens 65 has a concavoconvex surface 52 formed by the element surface 67 of the unit optical element 66. The microlens 65 can bend the traveling direction of the incident light by the concavoconvex surface 52.

[0184] The concavo-convex surface 52 may face any direction in the stacking direction D3. Figure 7 and Figure 8 In the embodiment, the concavo-convex surface 52 faces the side of the light source 22 in the stacking direction D3. Fig. 9 and Fig.10 In the embodiment, the concavoconvex surface 52 faces the side of the light reflecting portion 70 in the stacking direction D3. The concavoconvex surface 52 can bend the traveling directions of the light L71, L81, L91, and L101 incident from the light source 22 side, and can bend the traveling directions of the light L72, L82, L92, and L102 incident from the light reflecting portion 70 side. In particular, as Figure 7 to Figure 10 As shown in FIG. 1 , the microlens 65 can bend the traveling direction of light incident from a direction with a small inclination angle relative to the stacking direction D3, and increase the inclination angle relative to the stacking direction D3 compared to the incident direction. That is, the inclination angle of the traveling direction of the outgoing light from the light diffusion portion 50 relative to the stacking direction D3 can be made larger than the inclination angle of the traveling direction of the incident light to the light diffusion portion 50 relative to the stacking direction D3.

[0185] exist Figure 7 and Fig. 9 In the example shown, the light L71, L72, L91, and L92 are refracted on the element surface 67, so that the traveling direction of the light changes. Figure 8 and Fig.10 In the example shown, the light L82 and L101 are reflected on the element surface 67, preferably totally reflected, so that the traveling direction of the light changes. Figure 7 and Fig. 9 The change in the direction of travel in the refraction shown, Figure 8 and Fig.10 The change in the traveling direction in the reflection shown is likely to become larger. The greater the inclination of the normal direction ND of the element surface 67 relative to the stacking direction D3, in other words, the more the element surface 67 stands up from the stacking direction D3, the easier it is for light to be reflected on the element surface 67. More specifically, when the normal direction ND of the element surface 67 forms an inclination angle θa greater than 45° relative to the stacking direction D3, light that is not greatly inclined relative to the stacking direction D3 is reflected on the element surface 67, resulting in a tendency for the traveling direction of the light to be greatly inclined relative to the stacking direction D3.

[0186] From this perspective, Figure 8 and Fig.10 As shown, the unit optical element 66 may include an element surface 67, and the element surface 67 has a normal direction ND inclined at an inclination angle θa greater than 45° relative to the stacking direction D3. The element surface 67 stands along the stacking direction D3, so it is easy to cause reflection, preferably total reflection. That is, according to the unit optical element 66 including the element surface 67, the optical path of the light passing through the microlens 65 can be greatly bent by reflection, preferably by total reflection. By greatly adjusting the traveling direction of the light, the in-plane distribution of the illumination can be more effectively made uniform.

[0187] The diffusion characteristics of the microlens 65 are affected by the inclination angle θa of the element surface 67 of the unit optical element 66. Therefore, the cross-sectional shape of the microlens 65 can be appropriately adjusted based on the optical characteristics required for the surface light source device 20 and the diffusion component 40. For example, the inclination angles θa of the multiple element surfaces 67 included in a unit optical element 66 can be different from each other or the same. The multiple unit optical elements 66 included in the microlens 65 can be different from each other in structure such as shape, orientation, and size. The multiple unit optical elements 66 included in the microlens 65 can have the same structure as each other.

[0188] It should be noted that, from the perspective of making the illumination uniform by combining with the reflection characteristics of the light reflecting portion 70, it is preferable to increase the inclination angle θa or reduce the inclination angle θa according to the arrangement of the unit optical elements 66 and the optical characteristics of other parts. For example, as in the second specific example described later, when used in combination with the optical element portion 110, the inclination angle θa is preferably 25° or less, more preferably 20° or less, and further preferably 15° or less.

[0189] In addition, if Figure 7 to Figure 10 As shown by the double-dotted line in the figure, the element surface 67 may be slightly curved. The unit optical element 66 may have a partial shape of a sphere such as a hemisphere, or may have a partial shape of a rotating ellipsoid. When the unit optical element 66 includes a curved element surface 67, the optical path of the light passing through the microlens 65 is bent in various directions by reflection and refraction. Thus, the in-plane distribution of the illumination can be made more uniform more effectively. In addition, the change in the angular distribution of the radiation intensity can be effectively smoothed.

[0190] For reasons similar to those for the curved element surface 67, the unit optical element 66 may include an element surface 67 formed as a rough surface. The element surface 67 as a rough surface scatters light in various directions. Thus, the in-plane distribution of illumination can be more effectively made uniform. In addition, the change in the angular distribution of radiation intensity can be effectively smoothed.

[0191] The plurality of unit optical elements 66 included in the microlens 65 are arranged in two dimensions. Therefore, the element surface 67 of the unit optical element 66 included in the microlens 65 faces various directions. As a result, the microlens 65 can guide light to various directions using the two-dimensionally arranged unit optical elements 66. The plurality of unit optical elements 66 can be arranged irregularly or regularly. By arranging the plurality of unit optical elements 66 regularly, the design of the microlens 65 becomes easy, and it is easy to fill the unit optical elements 66 without gaps.

[0192] Here, refer to Figures 11A to 14B A description will be given of a plurality of specific examples of the microlens 65. In particular, the microlens 65 shown in these figures is an object of simulation described later.

[0193] First, in Fig.11A and Fig. 11B In the example shown, the arrangement of the plurality of unit optical elements 66 is a square arrangement. The plurality of unit optical elements 66 are arranged at a certain pitch in the first direction D1. The plurality of unit optical elements 66 are also arranged at a certain 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 the figure, the arrangement pitch in the first direction D1 and the arrangement pitch in the second direction D2 are the same as each other, which is 0.1 mm. Fig. 11B As shown in FIG. 1 , each unit optical element 66 has a shape in which the bottom of a cone is cut off from four sides. Fig.11A The cones are arranged at a shorter arrangement pitch than the cone bottoms shown by the dotted lines, and the overlapping portions of the cones adjacent to each other in the first direction D1 and the second direction D2 are cut off, thereby producing microlenses 65. Fig.11A and Fig. 11B In the example shown, a plurality of unit optical elements 66 are laid out without gaps. As an example, the height of each unit optical element 66 in the stacking direction D3 is 0.09 mm. The illustrated unit optical element 66 has an element surface 67 corresponding to the side surface of a cone. When viewed from the stacking direction D3, each unit optical element 66 can diffuse light radially.

[0194] Then, in Fig. 12A and Fig. 12B In the example shown, the arrangement of the plurality of unit optical elements 66 is a square arrangement. The plurality of unit optical elements 66 are arranged at a certain pitch in two directions inclined at ±45° relative to the first direction D1. The arrangement pitch in each direction may be the same or different. In the example shown in the figure, the arrangement pitch of the unit optical elements 66 in the two directions is the same as each other, which is 0.1 mm. Fig. 12A and Fig. 12B As shown, the unit optical element 66 has a quadrangular pyramid shape with a square bottom surface. As an example, the height of each unit optical element 66 in the stacking direction D3 is 0.07 mm.

[0195] exist Fig.13A and Fig. 13B In the example shown, the microlens 65 has two types of unit optical elements 66. The various types of unit optical elements 66 are arranged at a certain interval in the second direction D2 and in two directions inclined at ±60° relative to the second direction. That is, the two types of unit optical elements 66 are arranged at a certain interval in three directions inclined at 60° to each other. The arrangement of the unit optical elements 66 shown in the figure is also called a honeycomb arrangement. The arrangement pitches in each direction may be the same or different. In the example shown in the figure, the arrangement pitches of the unit optical elements 66 in the three directions are the same as each other. The shape of the bottom surfaces of the two unit optical elements 66 is the same. The shape of the bottom surface is an equilateral triangle. The orientations of the bottom surfaces of the two unit optical elements 66 are different. If one unit optical element 66 is rotated 60°, the orientation of the bottom surface of one unit optical element 66 is consistent with the orientation of the bottom surface of the other unit optical element 66. Fig.13A and Fig. 13BIn the example shown, the unit optical element 66 has a triangular pyramid shape whose bottom surface is an equilateral triangle. In the example shown in the figure, as an example, the height of the bottom surface of the unit optical element 66 is 0.1 mm. In addition, as an example, the height of the unit optical element 66 is 0.08 mm. Each unit optical element 66 can be a regular triangular pyramid shape.

[0196] Then, in Fig.14A and Fig. 14B In the example shown, unit optical elements 66 having the same shape on the bottom surface are arranged in four directions. As a result, a plurality of unit optical elements 66 having the same shape and orientation on the bottom surface are arranged at a certain interval in the first direction D1 and the second direction D2, respectively. The arrangement intervals in the two directions may be the same or different. In the example shown in the figure, the arrangement intervals in the two directions are the same. The unit optical element 66 has a triangular pyramid shape having a right isosceles triangle shape on the bottom surface. In the example shown in the figure, as an example, the equilateral length of the right isosceles triangle constituting the bottom surface is 0.1 mm. As an example, the height of the unit optical element 66 is 0.01 mm.

[0197] exist Figures 11A to 14B In the four specific examples shown, the perpendicular line from the vertex of the cone constituting the unit optical element 66 to the bottom surface can pass through the center of gravity of the bottom surface. Figures 11A to 14B In the four specific examples shown, the unit optical element 66 protrudes toward the light source 22 in the stacking direction D3. That is, the unit optical element 66 is a convex portion 68 protruding from the main body 58. However, as described above, the unit optical element 66 may be a concave portion 69 formed in the main body 58.

[0198] Incidentally, if the size of the unit optical element 66 when viewed from the stacking direction D3 is large, uneven brightness is observed due to the shape of the unit optical element 66. In order to prevent this inconvenience, the maximum length of the unit optical element 66 in the direction perpendicular to the stacking direction D3 is preferably 1.5 mm or less, more preferably 1 mm or less, and further preferably 0.5 mm or less.

[0199] In addition, if the size of the unit optical element 66 when viewed from the stacking direction D3 is large, it is necessary to position the unit optical element 66 relative to the light source 22. Specifically, in a direction perpendicular to the stacking direction D3, such as the first direction D1 or the second direction D2, it is necessary to determine the relative positions of the light source 22 and the unit optical element 66. This positioning operation is complicated and becomes a burden on manufacturing. From the perspective of eliminating the need for such positioning, when viewed from the stacking direction D3, in two mutually perpendicular directions, it is preferred that a unit optical element 66 has a size that is smaller than three times the size of the light source 22. As described above, from Figure 3The length WL1 and WL2 of one side of the quadrilateral light source 22 when observed in the stacking direction D3 shown is preferably less than 0.5 mm, more preferably less than 0.2 mm. From this aspect, when observed from the stacking direction D3, the unit optical element 66 preferably has a size smaller than a 1.5 mm square square, and more preferably has a size smaller than a 0.6 mm square square. Here, one size is smaller than another size means that one outer contour is located on or inside the other outer contour in at least any direction. It is further preferred that, when observed from the stacking direction D3, the size of the unit optical element 66 along any direction can be less than three times the size of the light source 22 along that direction. The outgoing light from the diffuser 40 using these unit optical elements 66 does not depend on the relative position of the diffuser 40 and the light source 22 along the directions D1 and D2 perpendicular to the stacking direction D3, and has certain light distribution characteristics. That is, the surface light source device 20 can be assembled without positioning the diffusion member 40 and the light source 22 in the directions D1 and D2 perpendicular to the stacking direction D3. That is, the diffusion member 40 can be arranged on the light source 22 without alignment.

[0200] The arrangement pitch of the unit optical element 66 having such a size can be 0.01 mm to 1.5 mm. From the perspective of effectively making the in-plane distribution of the illumination on the light-emitting side surface 40 b of the diffuser 40 uniform when used in the surface light source device 20, the arrangement pitch of the unit optical element 66 is preferably 0.05 mm to 1 mm, and more preferably 0.1 mm to 0.5 mm.

[0201] In addition, if Figure 7 to Figure 10 As can be seen and confirmed in the simulation described later, especially in the results of sample 3, the microlens 65 diffuses light along the normal direction ND of the element surface 67 when viewed from the stacking direction D3. In other words, the microlens 65 guides light along the normal direction ND of the element surface 67 viewed from the stacking direction D3. Figure 2 It can be seen that the arrangement interval of the plurality of light sources 22 becomes shorter along the arrangement direction of the light sources 22, but becomes longer in a direction not parallel to the arrangement direction of the light sources 22. Therefore, from the perspective of making the in-plane distribution of the illumination uniform, it is preferred that the unit optical element 66 includes an element surface 67 having a normal direction ND that is not parallel to the arrangement direction of the plurality of light sources 22 when viewed from the stacking direction D3. More preferably, the unit optical element 66 includes an element surface 67 having a normal direction ND that is inclined at an angle of not less than 35° and not more than 55° relative to the arrangement direction of the plurality of light sources 22 when viewed from the stacking direction D3. According to this configuration, light can be effectively diffused in a direction not parallel to the arrangement direction of the plurality of light sources 22 by reflection or refraction in the unit optical element 66. As a result, the in-plane distribution of the illumination can be more effectively made uniform.

[0202] For example, in Fig. 12A and Fig. 12B In the example shown, the unit optical element 66 has four element surfaces 67. When viewed from the stacking direction D3, the normal directions ND of the four element surfaces 67 are all inclined by 45° with respect to the first direction D1 and the second direction D2, which are the arrangement directions of the light sources 22. Figure 3 As shown, when the light sources 22 are arranged in a square, the positions CP (refer to Figure 3 ) tends to become the darkest. The four light sources 22 include: two light sources 22A adjacent to each other in one arrangement direction D1; and two other light sources 22B adjacent to the two light sources 22A from one side in another arrangement direction D2. Fig. 12A and Fig. 12B In the example shown, light is effectively guided toward the position CP which tends to be darkest, and the in-plane distribution of illuminance can be effectively made uniform.

[0203] As described above, by pre-adjusting the size of the unit optical element 66 and the size of the light source 22, it is possible to eliminate the need to position the light source 22 and the microlens 65 in a direction perpendicular to the stacking direction D3. On the other hand, as described above, it is effective to position the normal direction ND of the element surface 67 included in the unit optical element 66 so as not to be parallel to the arrangement direction of the light source 22. From this perspective, the marker 42 (see Figure 1 ), the mark 42 indicates the direction in which the diffusion component 40 should be arranged. The mark 42 functions as a so-called alignment mark. The mark 42 provided on the diffusion component 40 can indicate the direction of the normal direction ND of the element surface 67. Alternatively, the mark 42 can indicate the preferred direction in which the diffusion component 40 should be arranged relative to the light source 22 or the supporting substrate 25. Alternatively, as Figure 1 As shown, the mark 42 can indicate the arrangement direction of the light sources 22 that is preferred for the diffusion component 40. In addition, a mark related to the arrangement direction of the light sources 22 can also be provided on the support substrate 25, and based on the mark of the support substrate 25 and the mark 42 of the diffusion component 40, the diffusion component 40 is positioned in an appropriate direction relative to the arrangement of the light sources 22.

[0204] In addition, the light diffusion section 50 may include a microlens 65 having a plurality of unit optical elements 66 arranged in a direction not parallel to the arrangement direction of the plurality of light sources 22. That is, the arrangement direction of the plurality of unit optical elements 66 may be not parallel to the arrangement direction of the plurality of light sources 22. According to this configuration, it is possible to effectively make the ripples caused by the overlap of the arrangement of the unit optical elements 66 and the arrangement of the light sources 22 inconspicuous.

[0205] In the above, the diffractive optical element 60 and the microlens 65 that can be used for the light diffusion section 50 are described. However, the diffractive optical element 60 and the microlens 65 are merely examples, and other elements having both light transmittance and light diffusion properties may be used as the light diffusion section 50. In particular, the elements having the specific characteristics of light transmittance and light diffusion properties described above may be appropriately used as the light diffusion section 50. As another example of the light diffusion section 50, an optical sheet having a light transmittance base material and light diffusion particles dispersed in the base material may be used as the light diffusion section 50.

[0206] Next, the light reflecting portion 70 will be described. The light reflecting portion 70 is located on the side of the light diffusing portion 50 opposite to the light source 22 in the stacking direction D3. The light reflecting portion 70 has light reflectivity for reflecting visible light. The reflectance and transmittance of the light reflecting portion 70 vary depending on the incident angle.

[0207] The transmittance of the light of a specific wavelength incident at an incident angle of 0° in the light reflecting portion 70 is lower than the transmittance of the light of a specific wavelength incident at a certain incident angle greater than 0° in the light reflecting portion 70. That is, the transmittance of the light of a specific wavelength incident at a vertical angle in the light reflecting portion 70 is lower than the transmittance of the light of a specific wavelength incident from at least a certain oblique direction in the light reflecting portion 70. The reflectance of the light of a specific wavelength incident at an incident angle of 0° in the light reflecting portion 70 is higher than the reflectance of the light of a specific wavelength incident at a certain incident angle greater than 0° in the light reflecting portion 70. That is, the reflectance of the light of a specific wavelength incident at a vertical angle in the light reflecting portion 70 is higher than the reflectance of the light of a specific wavelength incident from at least a certain oblique direction in the light reflecting portion 70. The light reflecting portion 70 may also be referred to as a selective light reflecting portion, a light transmitting portion, or a selective light transmitting portion.

[0208] As an example, the light reflecting portion 70 reflects light of a specific wavelength incident at an incident angle of 0° at a reflectivity of 80% or more. The light reflecting portion 70 transmits light of a specific wavelength incident at an incident angle of 0° at a transmittance of less than 20%. In addition, the light reflecting portion 70 reflects at least a portion of light of a specific wavelength incident at an incident angle having an absolute value greater than 45° at a reflectivity of less than 50%. The light reflecting portion 70 transmits at least a portion of light of a specific wavelength incident at an incident angle having an absolute value greater than 45° at a transmittance of more than 50%. The light reflecting portion 70 has an incident angle dependence of reflectivity. In addition, the light reflecting portion 70 has an incident angle dependence of transmittance.

[0209] Fig.15 Graph showing an example of reflection characteristics and transmission characteristics according to the incident angle of the light reflecting portion 70. Fig.15In the characteristics of the light reflecting portion 70 shown, as the absolute value of the incident angle to the light reflecting portion 70 becomes smaller, the reflectivity of the specific wavelength light in the light reflecting portion 70 becomes larger. The reflectivity of the specific wavelength light in the light reflecting portion 70 with an absolute value of the incident angle of 70° or more and less than 90° may be less than 70%, less than 60%, or less than 50% in the light reflecting portion 70. The reflectivity of the specific wavelength light in the light reflecting portion 70 with an absolute value of the incident angle of 60° or less may be more than 50% and less than 100%, more than 80% and less than 100%, or more than 90% and less than 100%. The reflectivity of the specific wavelength light in the light reflecting portion 70 with an incident angle of 0° may be more than 80% and less than 100%, more than 90% and less than 100%, or more than 95% and less than 100%.

[0210] exist Fig.15 In the characteristics of the light reflecting portion 70 shown, as the absolute value of the incident angle to the light reflecting portion 70 becomes smaller, the transmittance of the light of a specific wavelength in the light reflecting portion 70 becomes smaller. The transmittance of the light of a specific wavelength whose absolute value of the incident angle is greater than or equal to 70° and less than or equal to 90° in the light reflecting portion 70 may be greater than or equal to 30%, greater than or equal to 40%, or greater than or equal to 50%. The transmittance of the light of a specific wavelength whose absolute value of the incident angle is less than or equal to 60° in the light reflecting portion 70 may be greater than or equal to 0% and less than 50%, greater than or equal to 0% and less than 20%, or greater than or equal to 0% and less than 10%. The transmittance of the light of a specific wavelength whose incident angle is 0° in the light reflecting portion 70 may be greater than or equal to 0% and less than 20%, greater than or equal to 0% and less than 10%, or greater than or equal to 0% and less than 5%.

[0211] The light of a specific wavelength can be appropriately set according to the purpose of the surface light source device 20 or the diffusion component 40. Typically, the light emitted from the light source 22 or the light used for emitting light in the surface light source device 20 can be used as the light of a specific wavelength. The light of a specific wavelength can be made into visible light. "Visible light" refers to light with a wavelength of more than 380nm and less than 780nm. The reflectivity of the light reflecting portion is a value measured using a goniophotometer GP-200 manufactured by Murakami Color Research Institute. The transmittance of the light reflecting portion is the total light transmittance measured in accordance with JIS K7361-1:1997. The transmittance of the light reflecting portion is a value measured using a goniophotometer GP-200 manufactured by Murakami Color Research Institute.

[0212] Fig.16 is a graph showing another example of the optical characteristics of the light reflecting portion. Fig.16 The light reflecting portion having the optical characteristics shown in FIG. Fig.15 The light reflecting parts shown have different optical characteristics. Fig.16Graphs showing the reflection characteristics and transmission characteristics of the light reflecting portion with respect to light having a wavelength of 450 nm, which is blue light.

[0213] like Fig.16 As shown, the reflectivity of the light of a specific wavelength whose absolute value of the incident angle is between 0° and 30° can be 80% or more, 90% or more, or 95% or more at the light reflecting portion 70. The reflectivity of the light of a specific wavelength whose absolute value of the incident angle is between 0° and 45° can be 80% or more, 85% or more, or 90% or more at the light reflecting portion 70. According to this reflection characteristic, by combining with the light diffusion portion 50, it is possible to effectively prevent the illuminance in the area directly above the light source 22 from becoming too high, and it is possible to effectively make the in-plane distribution of the illuminance uniform.

[0214] like Fig.16 As shown, the transmittance of light of a specific wavelength whose absolute value of the incident angle is between 0° and 30° can be less than 20%, less than 10%, or less than 5% at the light reflecting portion 70. The transmittance of light of a specific wavelength whose absolute value of the incident angle is between 0° and 45° can be less than 20%, less than 15%, or less than 10% at the light reflecting portion 70. According to such transmission characteristics, by combining with the light diffusion portion 50, it is possible to effectively prevent the illuminance in the area directly above the light source 22 from becoming too high, and it is possible to effectively make the in-plane distribution of the illuminance uniform.

[0215] like Fig.16 As shown, the reflectivity of the light of a specific wavelength incident at a certain incident angle of 45° to 75° in absolute value at the light reflecting portion 70 can be 50%. The reflectivity of the light of a specific wavelength incident at a certain incident angle of 50° to 60° in absolute value at the light reflecting portion 70 can be 50%. As the absolute value of the incident angle increases in the range of 50° to 60°, the reflectivity of the light of a specific wavelength at the light reflecting portion can become smaller. In the area spaced apart from the light source 22 in the direction perpendicular to the stacking direction D3, the light traveling in the direction inclined relative to the stacking direction D3 becomes more. Therefore, according to these reflection characteristics, by combining with the diffusion characteristics of the light diffusing portion 50, the illumination in the area spaced apart from the light source 22 can be increased, and the in-plane distribution of the illumination can be effectively made uniform.

[0216] like Fig.16As shown, the transmittance of light of a specific wavelength incident at a certain incident angle of 45° to 75° in absolute value can be 50% in the light reflecting portion 70. The transmittance of light of a specific wavelength incident at a certain incident angle of 50° to 60° in absolute value can be 50% in the light reflecting portion 70. As the absolute value of the incident angle increases in the range of 50° to 60°, the transmittance of light of a specific wavelength in the light reflecting portion can become larger. In the area spaced apart from the light source 22 in the direction perpendicular to the stacking direction D3, the light traveling in the direction inclined relative to the stacking direction D3 becomes more. Therefore, according to these transmission characteristics, by combining with the diffusion characteristics of the light diffusion portion 50, the illumination in the area spaced apart from the light source 22 can be improved, and the in-plane distribution of the illumination can be effectively made uniform.

[0217] Fig.17 and Fig.18 FIG. 1 is a graph showing another example of the optical characteristics of the light reflecting portion. Fig.17 and Fig.18 The optical characteristics of the light reflecting portion shown are different from those having Fig.16 The optical characteristics of the light reflecting portion shown are also different from those having Fig.16 The optical characteristics of the light reflecting portion are shown. Fig.17 and Fig.18 : is a graph showing the transmission characteristics of the light reflecting portion with respect to light having a wavelength of 450 nm, which is blue light.

[0218] like Fig.17 and Fig.18 As shown, the transmittance of light of a specific wavelength whose absolute value of the incident angle is between 0° and 30° can be less than 15%, less than 8%, or less than 3% at the light reflecting portion 70. The transmittance of light of a specific wavelength whose absolute value of the incident angle is between 0° and 45° can be less than 50%, less than 40%, or less than 30% at the light reflecting portion 70. According to this transmission characteristic, by combining with the diffusion characteristic of the light diffusion portion 50, it is possible to effectively prevent the illuminance in the area directly above the light source 22 from becoming too high, and it is possible to effectively make the in-plane distribution of the illuminance uniform.

[0219] The reflectivity of the light of a specific wavelength whose absolute value of the incident angle is between 0° and 30° can be 85% or more, 92% or more, or 97% or more at the light reflecting portion 70. The reflectivity of the light of a specific wavelength whose absolute value of the incident angle is between 0° and 45° can be 50% or more, 60% or more, or 70% or more at the light reflecting portion 70. According to this reflection characteristic, by combining with the diffusion characteristic of the light diffusion portion 50, it is possible to effectively prevent the illuminance in the area directly above the light source 22 from becoming too high, and it is possible to effectively make the in-plane distribution of the illuminance uniform.

[0220] like Fig.17 and Fig.18 As shown, the transmittance of the light of a specific wavelength incident at a certain incident angle of 40° to 60° in absolute value in the light reflecting portion 70 can be 50%. The transmittance of the light of a specific wavelength incident at a certain incident angle of 45° to 55° in absolute value in the light reflecting portion 70 can be 50%. As the absolute value of the incident angle increases in the range of 30° to 60°, the transmittance of the light of a specific wavelength in the light reflecting portion can increase. As the absolute value of the incident angle increases in the range of 50° to 50°, the transmittance of the light of a specific wavelength in the light reflecting portion can increase. In the region spaced apart from the light source 22 in the direction perpendicular to the stacking direction D3, the light traveling in the direction inclined relative to the stacking direction D3 becomes more. Therefore, according to the reflection characteristics of the light reflecting portion 70 having these reflection characteristics, by combining with the diffusion characteristics of the light diffusing portion 50, the illumination in the region spaced apart from the light source 22 can be improved, and the in-plane distribution of the illumination can be effectively made uniform.

[0221] The reflectivity of the light of a specific wavelength incident at a certain incident angle of 40° to 60° in absolute value at the light reflecting portion 70 can be 50%. The reflectivity of the light of a specific wavelength incident at a certain incident angle of 45° to 55° in absolute value at the light reflecting portion 70 can be 50%. As the absolute value of the incident angle increases in the range of 30° to 60°, the reflectivity of the light of a specific wavelength at the light reflecting portion can become smaller. As the absolute value of the incident angle increases in the range of 50° to below, the reflectivity of the light of a specific wavelength at the light reflecting portion can become smaller. In the region spaced apart from the light source 22 in the direction perpendicular to the stacking direction D3, the light traveling in the direction inclined relative to the stacking direction D3 becomes more. Therefore, according to the reflection characteristics of the light reflecting portion 70 having these reflection characteristics, by combining with the diffusion characteristics of the light diffusing portion 50, the illumination in the region spaced apart from the light source 22 can be improved, and the in-plane distribution of the illumination can be effectively made uniform.

[0222] The light reflecting portion 70 overlaps with the light diffusing portion 50 in the stacking direction D3. When the light reflecting portion 70 and the light diffusing portion 50 are not joined by bonding or adhesion, for example, when the light reflecting portion 70 and the light diffusing portion 50 are simply overlapped, the light reflecting portion 70 may have a rough surface facing the light diffusing portion 50. That is, the light incident side surface of the light reflecting portion 70 may be a rough surface. By providing the light reflecting portion 70 with a rough surface, the light reflecting portion 70 and the light diffusing portion 50 can be prevented from sticking. In addition, by the light scattering property of the rough surface, the change in the angular distribution of the radiation intensity can be effectively smoothed.

[0223] As the light reflecting portion 70, there is no particular limitation as long as it has the incident angle dependence of the reflectivity and the incident angle dependence of the transmittance. As the light reflecting portion 70, a reflective volume hologram, a cholesteric liquid crystal structure layer, a retroreflective film, and a reflective diffraction optical element can be used. In particular, a dielectric multilayer film with a relatively high degree of freedom in designing the reflection characteristics and the transmission characteristics is suitable as the light reflecting portion 70. In addition, a reflective structure that is structurally endowed with the incident angle dependence of the reflectivity and the incident angle dependence of the transmittance due to its low wavelength dependence is also suitable as the light reflecting portion 70.

[0224] As the dielectric multilayer film constituting the light reflecting portion 70, an inorganic compound multilayer film in which inorganic layers having different refractive indices are alternately laminated can be used. As the dielectric multilayer film constituting the light reflecting portion 70, a resin multilayer film in which resin layers having different refractive indices are alternately laminated can be used.

[0225] In the resin layers with different refractive indices, the difference between the in-plane average refractive index of the high refractive index resin layer with a high refractive index and the low refractive index resin layer with a low refractive index is preferably 0.03 or more, more preferably 0.05 or more, and further preferably 0.1 or more. If the difference in the above-mentioned in-plane average refractive index is large, the desired reflectivity and transmittance can be easily achieved.

[0226] The difference between the in-plane average refractive index of the high refractive index resin layer and the refractive index in the thickness direction is preferably 0.03 or more. The difference between the in-plane average refractive index of the low refractive index resin layer and the refractive index in the thickness direction is preferably 0.03 or less. According to this example, even if the incident angle increases, it is difficult to reduce the reflectivity of the reflection peak.

[0227] The number of layers of high refractive index resin layer and low refractive index resin layer is adjusted according to the reflection characteristic or transmission characteristic required by light reflecting part 70. For example, high refractive index resin layer and low refractive index resin layer can be alternately laminated more than 30 layers, and can also be alternately laminated more than 200 layers. The total number of layers of high refractive index resin layer and low refractive index resin layer can be, for example, more than 600 layers. When the number of layers is too small, sometimes sufficient reflectivity cannot be obtained. In addition, by making the number of layers be within the above range, the desired reflectivity and transmittance can be easily obtained.

[0228] The multilayer film of the resin constituting the dielectric multilayer film may have a surface layer containing polyethylene terephthalate or polyethylene naphthalate with a thickness of 3 μm or more on one side or both sides. The thickness of the surface layer may be 5 μm or more. The surface layer can protect the surface of the multilayer film of the resin.

[0229] As a method for producing a multilayer film of resin constituting the dielectric multilayer film, a coextrusion method etc. can be adopted. Specifically, a method for producing a laminated film described in Japanese Patent Application Laid-Open No. 2008-200861 can be adopted.

[0230] As the multilayer film of the resin constituting the dielectric multilayer film, a commercially available laminated film can be used, and examples thereof include Picasus (registered trademark) manufactured by Toray Industries, Ltd. and ESR manufactured by 3M Company.

[0231] Next, the main reference Figure 19 to Figure 22 The effect of generating planar light in the planar light source device 20 using the diffusion member 40 having the above structure will be described. It should be noted that, Figure 19 to Figure 22 In the figure, the amount of light traveling in the direction of an arrow is represented by the thickness of the arrow.

[0232] like Fig.19 As shown, first, light LP1 is emitted from the light source 22. Figure 19 to Figure 22 In the example shown, the light source 22 emits light LP1 having a wavelength of 450 nm as blue light, and the light reflecting portion 70 has the above-mentioned reflection characteristics for the light emitted from the light source 22. When a general light source 22 is used, a large amount of light LP1 is emitted toward the stacking direction D3. The light LP1 is incident on the light diffusing portion 50 of the diffusing member 40. The light diffusing portion 50 has light transmittance and light diffusing properties. The light LP1 is transmitted through the light diffusing portion 50 and diffused.

[0233] It should be noted that the light diffusion portion 50 has Figure 5 and Figure 6 In the case of the diffusion characteristics shown, the light LP1 traveling along the stacking direction D3 mostly travels in a direction inclined with respect to the stacking direction D3.

[0234] Then, if Fig. 20 As shown, the light LP2 and LP3 diffused in the light diffusion part 50 are directed toward the light reflection part 70 of the light diffusion part 50. For example, the light reflection part 70 can reflect light incident at an incident angle of 0° with a reflectivity of more than 80%. On the other hand, the light reflection part 70 can reflect at least a portion of light incident at an incident angle with an absolute value greater than 45° with a reflectivity of 50%. That is, the light reflection part 70 transmits only the light LP3 that is very greatly inclined relative to the stacking direction D3, and reflects the other light LP2. In the area including the position directly facing the light source 22 and the surrounding area, that is, the area directly above the light source 22, there is a tendency for a large amount of light to travel in a direction that is not greatly inclined relative to the stacking direction D3. According to the reflection characteristics of the light reflection part 70, it is possible to suppress a large amount of light with a small incident angle from passing through the light reflection part 70.

[0235] In particular, when the light reflecting portion 70 reflects the light LP2 incident on the light reflecting portion 70 at a peak angle at which the radiation intensity of the light diffused by the light diffusing portion 50 peaks, the image of the light source 22 can be suppressed from becoming brighter directly above the light source 22, that is, from being perceived. Figure 6 In the case of the light diffusion unit 50 having the diffusion characteristics shown in FIG. 1 , a large amount of light travels in the direction of the emission angle of 20° to 50°. Fig.15 or Fig.16 The light reflecting portion 70 having the reflection characteristics shown reflects the light emitted from the light diffusing portion 50 in the direction of the emission angle of 20° to 50° with a reflectivity of 90% or more. That is, most of the light LP1 emitted from the light source 22 and traveling to the diffusing member 40 is reflected at least once by the light reflecting portion 70. Therefore, it is possible to extremely effectively suppress the area directly above the light source 22 from becoming brighter.

[0236] Then, if Fig.21 As shown, the light LP2 reflected by the light reflecting portion 70 diffusely transmits the light diffusing portion 50 again, and travels in a direction that is more inclined with respect to the stacking direction D3. That is, the light LP2 reflected by the light reflecting portion 70 diffusely transmits the light diffusing portion 50 twice, thereby traveling in a direction that is more inclined with respect to the stacking direction D3. As a result, the light LP4 diffusely transmitted by the light diffusing portion 50 twice travels in a direction perpendicular to the stacking direction D3. In the example shown in the figure, the light LP4 travels in a manner spaced apart from the light source 22 along the first direction D1. Thereafter, as shown in FIG. Fig.21 As shown, light LP4 twice diffusely transmitted through the light diffusion part 50 is reflected by the support substrate 25 supporting the light source 22. Then, light LP5 travels further away from the light source 22 in a direction perpendicular to the stacking direction D3 and travels toward the diffusion member 40 again in the stacking direction D3.

[0237] like Fig. 22 As shown, the light LP5 directed toward the diffusion member 40 is diffusely transmitted through the light diffusion section 50 and diffused. The light LP6 diffused in the light diffusion section 50 is then mostly directed toward the light reflection section 70. Among the light LP6, the light with a large incident angle to the light reflection section 70 is transmitted through the light reflection section 70. On the other hand, the light with a small incident angle to the light reflection section 70 is reflected by the light reflection section 70 again.

[0238] As described above, by combining the light diffuse transmittance of the light diffusion part 50 and the light reflectivity of the light reflection part 70, the light distribution characteristics of the light source 22 will not be greatly limited, and the light emitted from the light source 22 can be effectively expanded in a direction orthogonal to the stacking direction D3. As a result, the uneven brightness caused by the existence of the light source 22 can be effectively eliminated, that is, the image of the light source 22 can be effectively made inconspicuous. By the light diffusion of the diffusion component 40, the surface light source device 20 can also be greatly thinned. As a result, the thinning of the surface light source device 20 can be achieved, and at the same time, the illumination at each position on the surface of the light emitting side of the light reflection part 70 can be effectively made uniform, that is, the in-plane distribution of the illumination can be effectively made uniform.

[0239] Here, the results of simulations performed by the present inventors are described. The simulation targets are the surface light source devices of samples 1 to 7. The simulations were performed by ray tracing simulation using LightTools manufactured by Synopsys.

[0240] For samples 1 to 5, Figure 19 to Figure 22 The surface light source device 20 shown. The surface light source devices 20 of samples 1 to 5 include a light source 22, a support substrate 25 supporting the light source 22, and a diffusion member 40 arranged opposite to the light source 22 and the support substrate 25 in the stacking direction D3. The light source 22 is provided with a light emitting diode on the support substrate 25. The reflection at the surface of the support substrate 25 is diffuse reflection with a reflectivity of 95%.

[0241] In the surface light source devices 20 of samples 1 to 5, the diffusion member 40 has a light diffusion portion 50 and a light reflection portion 70 in order from the light source side. The surface light source devices 20 of samples 1 to 5 are common, and the light reflection portion 70 has Fig.15 In the surface light source device 20 of sample 1, the light diffusion portion 50 is a dielectric multilayer film having the reflection characteristics and the transmission characteristics shown. Figure 6 In the surface light source device 20 of sample 2, the light diffusion portion 50 is a diffractive optical element 60 having a diffusion characteristic as shown. Fig.11A and Fig. 11B The microlenses 65 have the shapes, sizes, and arrangements described above. In the surface light source device 20 of sample 3, the light diffusion portion 50 has the reference Fig. 12A and Fig. 12B The microlenses 65 have the shapes, sizes, and arrangements described above. In the surface light source device 20 of sample 4, the light diffusion section 50 has the reference Fig.13A and Fig. 13B The microlenses 65 have the shapes, sizes, and arrangements described above. In the surface light source device 20 of sample 5, the light diffusion section 50 has the reference Fig.14A and Fig. 14B The shape, size, arrangement and other structures of the microlenses 65 are described.

[0242] In the surface light source devices 20 of samples 1 to 5, the thickness of the diffusion member 40 along the stacking direction D3 is 200 μm. In addition, in the surface light source devices 20 of samples 1 to 5, the distance DX from the surface of the light source 22 facing the diffusion member 40 to the light incident side surface of the diffusion member 40 facing the light source 22 along the stacking direction D3 (refer to Figure 2 ) is 0.5mm.

[0243] Sample 6 is the same as Samples 1 to 5 except that the diffusion member 40 in Samples 1 to 5 is replaced with a light diffusion sheet "OPALUSB910" manufactured by Keiwa Co., Ltd. In the surface light source device of Sample 6, the distance from the surface of the light source facing the diffusion member to the light incident side surface of the light diffusion sheet facing the light source along the lamination direction is 0.5 mm. The thickness of the light diffusion sheet is 100 μm.

[0244] Sample 7 is the same as Samples 1 to 5 except that the diffusion member 40 in Samples 1 to 5 is not included. That is, the surface light source device of Sample 7 only includes the support substrate 25 and the light source 22 supported by the support substrate 25 .

[0245] For samples 1 to 5, the light receiving surface as a virtual surface extending in the first direction D1 and the second direction D2 was set at a position 1 mm away from the surface of the support substrate 25 facing the diffusion member 40, while the light source 22 was emitting light, and the illuminance at each position on the light receiving surface was simulated. The illuminance was calculated as an area on the light receiving surface having a length of 6 mm in the first direction D1 and a length of 6 mm in the second direction D2, centered on the light source 22. That is, in the projection to the stacking direction D3, the light source 22 was located at the center of the light receiving surface having an area of ​​6 mm×6 mm. Figures 23A to 23E Calculated in-plane distributions of illuminance on the light receiving surface of the surface light source devices 20 of samples 1 to 5 are shown in FIG.

[0246] Under the same conditions, the same light receiving surfaces as those of samples 1 to 5 were set for the surface light source devices of samples 6 and 7, and the in-plane distribution of the illuminance on the light receiving surfaces was calculated. Fig.23F and Figure 23G 2 and 3 show the in-plane distribution of the illuminance on the light receiving surface calculated for the surface light source devices of samples 6 and 7, respectively.

[0247] Figures 23A to 23G A graph showing the in-plane distribution of the illuminance on the light-receiving surface having an area of ​​6 mm×6 mm is shown, and a graph showing the illuminance at each position on a straight line along the first direction D1 passing through a position on the light-receiving surface in the third direction D3 facing the light source 22 is shown. In the graph showing the in-plane distribution, the illuminance at each position on the light-receiving surface is represented by color, and the illuminance at the position with a lighter color is higher. Figures 23A to 23GThe results shown show the relative illumination at each location within each sample and do not compare illumination between different samples.

[0248] According to the simulation results, in samples 1 to 5, although the gap between the light source 22 and the diffusion component 40 is 0.5 mm, which is extremely short compared to about 2.5 mm in patent document 1 (JP6299811B), the in-plane distribution of the illumination in the area separated by 3 mm from the light source in the first direction D1 and the second direction D2 can be well uniform. From this aspect, when the diffusion component 40 of this embodiment is used as the surface light source device 20, it is confirmed that the surface light source device 20 can be significantly thinned while making the in-plane distribution of the illumination sufficiently uniform. In addition, in the surface light source device 20 of samples 2 to 5 using the microlens 65, it is confirmed that the light can be effectively guided in the direction of the normal direction ND along the element surface 67 in the observation direction from the stacking direction D3.

[0249] In one embodiment described above, the diffusion component 40 has a light diffusion portion 50 and a light reflection portion 70 in sequence. When the diffusion component of this embodiment is used for a surface light source device, the light emitted from the light source 22 can be effectively expanded in a direction orthogonal to the stacking direction D3 by combining the light transmittance and light diffusion of the light diffusion portion 50 with the reflection characteristics of the light reflection portion 70. As a result, the thinning of the surface light source device can be achieved, and the uneven brightness caused by the presence of the light source 22 can be effectively eliminated, that is, the image of the light source 22 can be effectively made inconspicuous. As a result, the thinning of the surface light source device 20 can be achieved, and the illumination at each position on the light emitting side surface 40b as the light emitting side of the diffusion component 40 can be effectively made uniform, that is, the in-plane distribution of the illumination can be effectively made uniform.

[0250] In the first specific example of the above-mentioned embodiment, when the light is incident on the light diffusion part 50 at an incident angle of 0°, the radiation intensity of the light-emitting side surface of the light diffusion part 50 facing the light reflection part 70 has a radiation intensity peak at a peak angle other than the peak angle of 0°. In addition, the reflectivity of the light of a specific wavelength incident on the light reflection part 70 at an incident angle of an absolute value of 0° or more and below the peak angle is 50% or more, and more preferably 80% or more in the light reflection part 70. According to this example, most of the light incident on the light diffusion part 50 at an incident angle of 0° and diffused in the light diffusion part 50 is reflected by the light reflection part 70 without passing through the light reflection part 70. That is, most of the light emitted from the light source 22 is reflected more than once in the light reflection part 70 and is folded back in the direction of travel in the stacking direction D3. As a result, the light emitted from the light source 22 is promoted to travel in a direction orthogonal to the stacking direction D3. By promoting the reflection at the light reflecting portion 70 in this way, the in-plane distribution of the illumination can be made uniform, and the distance DX between the light source 22 and the diffusion member 40 along the stacking direction D3 can be shortened. That is, the thinning of the surface light source device 20 can be achieved, and the brightness unevenness caused by the existence of the light source 22 can be effectively eliminated, and the in-plane portion of the illumination can be effectively made uniform.

[0251] As a specific example of the above embodiment, the specific wavelength can be set to 450 nm. In this example, a light emitting diode that emits blue light with a large output can be used as the light source 22. Alternatively, white light can be emitted by using a fluorescent substance or the like.

[0252] The first specific example of one embodiment has been described above. Figure 24 to Figure 27 , a second specific example of an embodiment is described. The second specific example is different from the first specific example in that the diffusion component 40 has an optical element portion 110. The second specific example can adopt the same structure as the first specific example in the structure other than the optical element portion 110. In the following description, the optical element portion 110 is mainly described. In the following description of the second specific example and the drawings used in the following description, the same symbols as those used for the corresponding parts in the above-mentioned specific example are used for the parts that can be constructed in the same way as the first specific example, and repeated descriptions are omitted.

[0253] like Fig.24 As shown, the optical element portion 110 is located on the light emitting side of the diffusion member 40 where the light to be diffused is located with respect to the light reflecting portion 70. The optical element portion 110 forms the light emitting side surface 40b of the diffusion member 40.

[0254] As described above, the reflection characteristics and transmission characteristics of the light reflecting portion 70 are incident angle dependent. The light reflecting portion 70 reflects light at a low incident angle, and turns the traveling direction of the light back toward the stacking direction D3. The traveling direction of the light passing through the light reflecting portion 70 mainly becomes a direction within an angle range that is greatly inclined relative to the stacking direction D3 due to the reflection characteristics and transmission characteristics of the light reflecting portion 70. The optical element portion 110 enhances the reflection characteristics and transmission characteristics of the light reflecting portion 70. The optical element portion 110 reflects a portion of the incident light from the light reflecting portion 70. Through the cooperation of the light reflecting portion 70 and the optical element portion 110, the in-plane distribution of the illumination can be made more uniform.

[0255] As a specific composition, Fig.24 As shown, the optical element portion 110 has a concave-convex surface 112. The concave-convex surface 112 faces the side opposite to the light reflecting portion 70 in the stacking direction D3. In other words, the concave-convex surface 112 faces the light emitting side in the stacking direction D3. The light can change its traveling direction due to refraction or reflection on the concave-convex surface 112. The optical element portion 110 may include an optical sheet 115 that merely overlaps with other components or is joined to other components by bonding or adhesion, may be the optical sheet 115, may be a part of the optical sheet 115, components, structures, etc., and may also be a surface of the optical sheet 115, components, structures, etc. Fig.24 In the example shown, the optical element portion 110 is bonded to the light reflecting portion 70. Fig.24 In the illustrated example, the light diffusion portion 50 , the light reflection portion 70 , and the optical element portion 110 are bonded and can be handled as a single unit.

[0256] It should be noted that, in order to distinguish from the concavoconvex surface 52 of the light diffusion section 50, the concavoconvex surface of the light diffusion section 50 is sometimes referred to as the first concavoconvex surface 52, and the concavoconvex surface of the optical element section 110 is sometimes referred to as the second concavoconvex surface 112. The light reflection section 70 and the optical element section 110 include parts or elements with the same name in addition to the concavoconvex surfaces. With regard to these parts or elements, the parts and elements of the light diffusion section 50 are sometimes referred to as "first", and the parts and elements of the optical element section 110 are sometimes referred to as "second".

[0257] The optical element portion 110 is light-transmitting. As the light transmittance of the optical element portion 110, for example, the total light transmittance of the optical element portion 110 is preferably 50% or more, more preferably 70% or more, and further preferably 90% or more. By making the total light transmittance of the optical element portion 110 within the above range, the utilization efficiency of the light from the light source 22 can be improved. In addition, when the optical element portion 110 is used in the surface light source device 20, the in-plane distribution of the illumination on the light-emitting side surface 40b of the diffusion component 40 can be effectively made uniform. Therefore, the optical element portion 110 is made of a material that has high transmittance to the light emitted from the light source 22 or the light used for emitting light in the surface light source device 20. It should be noted that the total light transmittance is a value measured by a method based on JIS K7361-1:1997.

[0258] The optical element portion 110 is not particularly limited, and may have various structures having a concave-convex surface 112. Fig.25A and Fig.25B As shown in FIG. 1 , the optical element section 110 may include a microlens 125. In this example, the microlens 125 forms the concave-convex surface 112. The unit optical element 126 is a concept including elements called unit shape elements, unit prisms, and unit lenses. The unit optical element 126 may be as follows: Fig.25A The unit optical element 126 may also be configured as a convex portion 128. Fig.25B The configuration shown is a recess 129 .

[0259] exist Fig.25A and Fig.25B In the example shown, the optical element section 110 has a base 118. The base 118 is sheet-shaped. The base 118 extends in a first direction D1 and a second direction D2 perpendicular to the stacking direction D3. Fig.25A and Fig.25A In the example shown, the base 118 is joined to the light reflecting portion 70. Fig.25A In the example shown, the unit optical element 126 as the protrusion 128 is provided on the base 118. Fig.25B In the example shown, the unit optical element 126 as the recessed portion 129 is formed in the base portion 118 .

[0260] like Fig.25A and Fig.25B As shown, the unit optical element 126 has an element surface 127 inclined with respect to the stacking direction D3. The unit optical element 126 is drawn by the element surface 127. The microlens 125 has a concave-convex surface 112 formed by the element surface 127 of the unit optical element 126. The microlens 125 can bend the traveling direction of the incident light through the concave-convex surface 112.

[0261] The optical properties of the concave-convex surface 112 are affected by the inclination angle θb of the element surface 127 of the unit optical element 126. Therefore, the cross-sectional shape of the unit optical element 126 can be appropriately adjusted based on the optical properties required for the surface light source device 20 and the optical element portion 110. For example, the inclination angles θb of the multiple element surfaces 127 included in a unit optical element 126 can be different from each other or the same. The multiple unit optical elements 126 included in the microlens 125 can be different from each other in structure such as shape, orientation, and size. The multiple unit optical elements 126 included in the microlens 125 can have the same structure as each other.

[0262] As described above, the traveling direction of the light passing through the light reflecting portion 70 is mainly a direction within an angle range that is greatly inclined relative to the stacking direction D3 due to the reflection characteristics and transmission characteristics of the light reflecting portion 70. The optical element portion 110 enhances the reflection characteristics and transmission characteristics of the light reflecting portion 70. The optical element portion 110 reflects a portion of the incident light from the light reflecting portion 70. Through the cooperation of the light reflecting portion 70 and the optical element portion 110, the in-plane distribution of the illumination can be made more uniform. From the perspective of making the function of this optical element portion 110 more effective, the inclination angle θb of the normal direction NDA of the element surface 127 relative to the stacking direction D3 can be less than 25°, less than 20°, or less than 15°. The inclination angle θb can be greater than 0°. From the perspective of ensuring the above-mentioned function of the optical element portion 110, the inclination angle θb can be greater than 3°, greater than 5°, or greater than 8°.

[0263] It should be noted that it is also assumed that each element surface 127 is not flat. The inclination angle θb of the element surface 127 is specified at the center position of the element surface 127 in the stacking direction D3. With respect to the element surface 127 as the convex portion 128, the inclination angle θb is specified at the center position in the stacking direction D3 of the base end portion connected to the base 118 and the front end portion farthest from the base 118 in the stacking direction D3 in the element surface 127. With respect to the element surface 127 as the concave portion 129, the inclination angle θb is specified at the center position in the stacking direction D3 of the base end portion (deepest portion) closest to the light reflecting portion 70 in the stacking direction D3 and the front end portion farthest from the light reflecting portion 70 in the stacking direction D3 in the element surface 127.

[0264] In addition, if Fig.25A and Fig.25BAs shown by the double-dotted line, the element surface 127 may be slightly curved. The unit optical element 126 may have a partial shape of a sphere such as a hemisphere, or may have a partial shape of a rotating ellipsoid. When the unit optical element 126 includes a curved element surface 127, the optical path of the light passing through the microlens 65 is bent in various directions by reflection and refraction. Thus, the in-plane distribution of the illumination can be made more uniform more effectively. In addition, the change in the angular distribution of the radiation intensity can be effectively smoothed.

[0265] For the same reason as the curved element surface 127, the unit optical element 126 may include an element surface 127 formed as a rough surface. The element surface 127 as a rough surface scatters light in various directions. Thus, the in-plane distribution of illumination can be more effectively made uniform. In addition, the change in the angular distribution of radiation intensity can be effectively smoothed.

[0266] A plurality of unit optical elements 126 are arranged in two dimensions. That is, a plurality of unit optical elements 126 can be arranged in two or more directions that are not parallel to each other. Therefore, the element surface 127 of the unit optical element 126 faces various directions. As a result, it is possible to guide light to various directions using the two-dimensionally arranged unit optical elements 126. A plurality of unit optical elements 126 can be arranged irregularly or regularly. By arranging a plurality of unit optical elements 126 regularly, the design of the microlens 125 becomes easy, and it is easy to cover the unit optical elements 126 without gaps.

[0267] The arrangement and shape of the second unit optical element 126 of the optical element section 110 are as described in detail. Figures 11A to 14B As shown in FIG. 1 , the arrangement or shape of the first unit optical element 66 included in the light diffusion section 50 may be used. For example, as the structure of the unit optical element 126, the structure described above may be used. Figures 11A to 14B The structure shown. Figures 11A to 14B In the four specific examples shown, the perpendicular line from the vertex of the cone constituting the unit optical element 126 to the bottom surface can pass through the center of gravity of the bottom surface. Figures 11A to 14B In the four specific examples shown, the unit optical element 126 is a recess 129 formed in the base 118. Figures 11A to 14B In the four specific examples shown, the unit optical element 126 may be a convex portion 128 protruding from the base portion 118 on the side opposite to the light source 22 in the stacking direction D3.

[0268] If the size of the unit optical element 126 is large when viewed from the stacking direction D3, uneven brightness is observed due to the shape of the unit optical element 126. In order to prevent this problem, the maximum length of the unit optical element 126 in the direction perpendicular to the stacking direction D3 is preferably 1.5 mm or less, more preferably 1 mm or less, and further preferably 0.5 mm or less.

[0269] If the size of the unit optical element 126 when observed from the stacking direction D3 becomes larger, it is necessary to position the unit optical element 126 relative to the light source 22. This is the same as the need to position the unit optical element 66 of the light diffusion section 50 relative to the above-mentioned light source 22. Therefore, it is preferred that the unit optical element 126 of the optical element section 110 is constructed in the same manner as the unit optical element 66 of the light diffusion section 50. That is, when observed from the stacking direction D3, in two directions perpendicular to each other, it is preferred that one unit optical element 126 has a size that is smaller than three times the size of the light source 22. For example, when observed from the stacking direction D3, the unit optical element 126 preferably has a size that is smaller than a square of 1.5 mm square, and more preferably has a size that is smaller than a square of 0.6 mm square. It is further preferred that, when observed from the stacking direction D3, the size of the unit optical element 126 along any direction can be less than three times the size of the light source 22 along that direction.

[0270] The arrangement pitch of the unit optical element 126 having such a size can be 0.01 mm to 1.5 mm. From the perspective of effectively making the in-plane distribution of the illumination on the light-emitting side surface 40 b of the diffuser 40 uniform when used in the surface light source device 20, the arrangement pitch of the unit optical element 126 is preferably 0.05 mm to 1 mm, and more preferably 0.1 mm to 0.5 mm.

[0271] When observed from the stacking direction D3, the concave-convex surface 112 of the optical element portion 110 guides light to the normal direction NDA of the element surface 127. Therefore, from the perspective of making the in-plane distribution of illumination uniform, it is preferred that the concave-convex surface 112 includes an element surface 127, wherein the element surface 127 has a normal direction NDA that is not parallel to the arrangement direction of the plurality of light sources 22 when observed from the stacking direction D3. More preferably, the unit optical element 126 includes an element surface 127, wherein the element surface 127 has a normal direction ND that is inclined at an angle of not less than 35° and not more than 55° relative to the arrangement direction of the plurality of light sources 22 when observed from the stacking direction D3. According to this configuration, light can be guided to a direction that is not parallel to the arrangement direction of the plurality of light sources 22 through reflection and refraction in the unit optical element 126. Thus, the in-plane distribution of illumination can be made more effectively uniform. For example, according to Fig. 12A and Fig. 12B The arrangement of the unit optical elements 126 shown in FIG. Figure 3The combination of the light sources 22 arranged as shown can effectively make the in-plane distribution of the illumination uniform. The mark 42 can indicate the direction of the normal direction NDA of the element surface 127.

[0272] In addition, the optical element section 110 may include a plurality of unit optical elements 126 arranged in a direction that is not parallel to the arrangement direction of the plurality of light sources 22. That is, the arrangement direction of the plurality of unit optical elements 126 may be not parallel to the arrangement direction of the plurality of light sources 22. According to this configuration, the ripples caused by the overlap of the arrangement of the unit optical elements 126 and the arrangement of the light sources 22 can be effectively suppressed.

[0273] In addition, if Fig.26 As shown, the plurality of unit optical elements 126 may be arranged in one dimension. In this example, the plurality of unit optical elements may be arranged in one direction, and each unit optical element 126 extends linearly in another direction that is not parallel to the one direction. Fig.26 As shown, each unit optical element 126 can extend linearly along another direction perpendicular to one direction. Each unit optical element 126 can extend linearly along another direction. The arrangement direction of the unit optical elements 126 can be the first direction D1, the second direction D2, or a direction that is not parallel to both the first direction D1 and the second direction D2. For example, the arrangement direction of the unit optical elements 126 can be inclined by more than 25° and less than 65° relative to both the first direction D1 and the second direction D2, or can be inclined by more than 35° and less than 55° relative to both the first direction D1 and the second direction D2.

[0274] The cross-sectional shape of the linear unit optical element 126 at the cross section orthogonal to the length direction is not particularly limited, and may be a polygonal shape such as a triangle shape, a pentagonal shape, or a shape in which one or more corners of a polygonal shape are chamfered. The arrangement spacing of the linear unit optical element 126 can be set as above, specifically, it can be 0.01 mm or more and 1.5 mm or more, 0.05 mm or more and 1 mm or less, and more preferably 0.1 mm or more and 0.5 mm or less. Other structures of the linear unit optical element 126 can adopt the structure of the unit optical element 126 constituting the above-mentioned microlens 125. For example, the inclination angle θb of the element surface 127 of the linear unit optical element 126 can be 25° or less, 20° or less, or 15° or less. The inclination angle θb can be greater than 0°. The inclination angle θb can be 3° or more, 5° or more, or 8° or more. The element surface 127 of the linear unit optical element 126 can be a curved surface. The element surface 127 of the linear unit optical element 126 may be a rough surface. The unit optical element 126 may include an element surface 127 having a normal direction ND inclined at an angle of 35° to 55° with respect to the arrangement direction of the plurality of light sources 22 when viewed from the stacking direction D3.

[0275] Next, the operation of generating planar light in the planar light source device 20 using the diffusion member 40 having the above-described structure will be described. The light source 22 emits light LP1 having a wavelength of 450 nm as blue light. The light reflecting portion 70 has a function to reflect the light emitted from the light source 22. Fig.17 and Fig.18 Features shown.

[0276] The optical action up to the transmitted light reflecting portion 70 is similar to that described in the first specific example. Figure 19 to Figure 22 The optical effect is the same as described. That is, by combining the light diffuse transmittance of the light diffusion part 50 and the light reflectivity of the light reflecting part 70, the light distribution characteristics of the light source 22 will not be greatly limited, and the light emitted from the light source 22 can be effectively expanded along the directions D1 and D2 perpendicular to the stacking direction D3. As a result, the uneven brightness caused by the existence of the light source 22 can be effectively eliminated, that is, the image of the light source 22 can be effectively made inconspicuous. Through the light diffusion of this diffuse component 40, the surface light source device 20 can also be greatly thinned. As a result, the thinning of the surface light source device 20 can be achieved, and at the same time, the illumination at each position on the surface of the light emitting side of the light reflecting part 70 can be effectively made uniform, that is, the in-plane distribution of the illumination can be effectively made uniform.

[0277] Then, the light passing through the light reflecting portion 70 enters the optical element portion 110 of the diffusion member 40. Fig. 27As shown, the optical element portion 110 has a concavoconvex surface 112 on the light emitting side separated from the light source 22 in the stacking direction D3. A portion L271 of the incident light to the optical element portion 110 is reflected on the concavoconvex surface 112. The reflected light L271 at the concavoconvex surface 112 is folded back in the traveling direction in the stacking direction D3 toward the light source 22 side in the stacking direction D3. The reflected light L271 passes through the light reflecting portion 70 and diffusely transmits the light diffusing portion 50, and is reflected at the supporting substrate 25. The reflected light at the supporting substrate 25 can be incident on the diffusion component 40 again at a position separated from the light source 22 in the vertical direction of the stacking direction D3, similarly to the above-mentioned reflected light LP2. Therefore, by reflection in the optical element portion 110, the light emitted from the light source 22 can be effectively expanded in the direction perpendicular to the stacking direction D3. As a result, the brightness in the area separated from the light source 22 where the brightness is likely to become insufficient can be fully ensured. That is, the reflection characteristics of the light reflecting portion 70 can be enhanced by the reflection in the optical element portion 110 , and the uniformity of the in-plane distribution of the illuminance can be further promoted.

[0278] Another part L272 of the incident light to the optical element portion 110 passes through the concavo-convex surface 112 , and then the light L272 is emitted from the light emitting side surface 40 b of the diffusion member 40 formed by the concavo-convex surface 112 of the optical element portion 110 .

[0279] As described above, the uneven brightness caused by the existence of the light source 22 can be effectively eliminated, and the illumination on the light-emitting surface 20a can be effectively made uniform. In particular, by utilizing the optical element portion 110 to enhance the reflective characteristics of the light reflecting portion 70, the thinning of the surface light source device 20 can be achieved, and the light can be guided in a direction perpendicular to the stacking direction D3. As a result, the thinning of the surface light source device 20 can be achieved, and the illumination at each position on the light-emitting side surface 40b of the diffusion component 40 can be effectively made uniform, that is, the in-plane distribution of the illumination can be effectively made uniform.

[0280] Here, refer to Fig. 27 The optical function of the optical element unit 110 is described in more detail. Fig. 27 As shown, the optical element portion 110 of this embodiment has a concavoconvex surface 112 on the side opposite to the light reflecting portion 70. Fig. 27 As shown, the light L271 and L272 traveling in the optical element section 110 travels in a direction greatly inclined relative to the stacking direction D3 due to the optical characteristics of the light reflecting section 70. In the cross section of the optical element section 110 along the stacking direction D3, the concave-convex surface 112 includes: a same-side element surface 127A inclined toward the same side as the light traveling direction with the stacking direction D3 as a reference; and a reverse-side element surface 127B inclined toward the opposite side of the light traveling direction with the stacking direction D3 as a reference. Fig. 27As shown, the incident angle θx of the light L271 incident on the same-side element surface 127A is greater than the incident angle θy of the light L271 toward the flat surface perpendicular to the stacking direction D3. Therefore, the light L271 is easily reflected on the same-side element surface 127A. In this way, the optical element part 110 can reflect a part of the light that has passed through the light reflecting part 70 by having a concave-convex surface 112 on the side opposite to the light reflecting part 70 in the stacking direction D3, thereby enhancing the optical characteristics of the light reflecting part 70. As a result, the illumination at each position on the light-emitting side surface 40b of the diffusion component 40 can be effectively made uniform, that is, the in-plane distribution of the illumination can be effectively made uniform.

[0281] It should be noted that, from the perspective of promoting uniform in-plane distribution of illumination, the reflection of the concave-convex surface 112 is preferably total reflection. Considering the refractive index of transparent resin materials widely used in optical applications, total reflection is likely to occur when the incident angle of light L271 on the element surface 127 is as large as about 40°. Considering the reflection characteristics and transmission characteristics of the light reflecting portion 70, the inclination angle θb of the normal direction NDA of the element surface 127 relative to the stacking direction D3 is preferably 25° or less, more preferably 20° or less, and further preferably 15° or less. By adjusting the inclination angle θb of the element surface 127 to this range, the illumination at each position on the light-emitting side surface 40b of the diffusion component 40 can be made more uniform.

[0282] In addition, if the tilt angle θb increases, it is difficult for light to enter the same-side element surface 127A causing reflection. From this point of view, the tilt angle θb formed by the normal direction NDA of the element surface 127 relative to the stacking direction D3 is also preferably 25° or less, more preferably 20° or less, and further preferably 15° or less. By adjusting the tilt angle θb of the element surface 127 to this range, the illumination at each position on the light-emitting side surface 40b of the diffusion component 40 can be made more uniform.

[0283] exist Fig. 27 In the example shown, the unit optical element 126 is a convex portion 128. In the unit optical element 126 as the convex portion 128, most of the area of ​​the element surface 127 is located on the light reflecting portion 70 side in the stacking direction D3. Therefore, light traveling in the optical element portion 110 is easily incident not only on the above-mentioned reverse side element surface 127B, but also on the above-mentioned same side element surface 127A. Therefore, according to the optical element portion 110 having the unit optical element 126 as the convex portion 128, the reflection in the optical element portion 110 can be promoted, and the illumination at each position on the light exit side surface 40b of the diffusion component 40 can be made more uniform.

[0284] By setting the lower limit of the inclination angle θb, it is possible to make it difficult for light traveling in a direction that is greatly inclined relative to the stacking direction D3 among the light traveling in the optical element section 110 to be incident on the above-mentioned same-side element surface 127A. Therefore, by setting the lower limit of the inclination angle θb, the concave-convex surface 112 exerts a selective reflection characteristic, that is, selectively reflects the light traveling in a direction with a smaller inclination angle relative to the stacking direction D3 among the light traveling in the optical element section 110. Thus, through the reflection of the optical element section 110, the reflection characteristics and transmission characteristics of the light reflecting section 70 can be enhanced. That is, the light incident on the optical element section 110 travels in a direction that is greatly inclined relative to the stacking direction D3 due to the optical characteristics of the light reflecting section 70. In addition, the optical element section 110 selectively reflects the light traveling in a direction with a smaller inclination angle relative to the stacking direction D3 among the light traveling in the light reflecting section 70. On the contrary, the optical element section 110 selectively transmits light traveling in a direction with a larger inclination angle relative to the stacking direction D3 among the light traveling in the light reflecting section 70. Thus, the illumination at each position on the light exiting side surface 40b of the diffusion member 40 can be made more uniform. From this aspect, the inclination angle θb formed by the normal direction NDA of the element surface 127 relative to the stacking direction D3 is preferably 3° or more, more preferably 5° or more, and further preferably 8° or more.

[0285] In the combination with the optical element portion 110 including the second concave-convex surface 112 having the above-mentioned upper limit value of the inclination angle θb, the first concave-convex surface 52 of the light diffusion portion 50 may include the first element surface 67 having a normal direction ND inclined at an inclination angle θa of 25° or less relative to the stacking direction D3. The author of the present case has conducted repeated and in-depth experiments, and as a result, the inclination angle θa of the normal direction ND of the first element surface 67 relative to the stacking direction D3 is preferably 25° or less, more preferably 20° or less, and further preferably 15° or less. In addition, the inclination angle θa is preferably 3° or more, more preferably 5° or more, and further preferably 8° or more. According to the combination of the light diffusion portion 50 having such a first element surface 67 and the light diffusion portion 50 having the second element surface 127 having the above-mentioned inclination angle θb of 25° or less, the illumination at each position on the light exit side surface 40b of the diffusion component 40 can be made more uniform.

[0286] like Fig. 27As shown, the light L272 is refracted at the reverse element surface 127B when passing through the reverse element surface 127B. The emission angle θz of the light L272 is smaller than the emission angle θw of the light L272X when it is assumed to pass through a flat surface perpendicular to the stacking direction D3 and emit. That is, the concave-convex surface 112 of the optical element portion 110 exerts a focusing function on the emitted light. The focusing function of the optical element portion 110 can reduce the burden of correcting the optical path of the light passing through the diffuse component 40. As a result, the utilization efficiency of the light passing through the diffuse component 40 can be improved. In addition, the number of components assembled in the surface light source device 20 and the thickness of the components can be reduced, which can contribute to the thinning of the surface light source device 20.

[0287] In the second specific example of one embodiment described above, the diffusion member 40 has, in order: a light diffusion portion 50 having light transmittance and light diffusion; a light reflection portion 70 whose transmittance of light of a specific wavelength incident at an incident angle of 0° is lower than the transmittance of light of a specific wavelength incident at a certain incident angle greater than 0°; and an optical element portion 110 having a concave-convex surface 112 on the side opposite to the light reflection portion 70. When the diffusion member 40 of one embodiment is used for a surface light source device, the light emitted from the light source 22 can be effectively expanded in a direction perpendicular to the stacking direction D3 by combining the light transmittance and light diffusion of the light diffusion portion 50 with the reflection characteristics of the light reflection portion 70. In addition, the concave-convex surface 112 of the optical element portion 110 enhances the reflection characteristics of the light reflection portion 70, thereby effectively expanding the light in a direction perpendicular to the stacking direction D3. As a result, the surface light source device can be made thinner, and the brightness unevenness caused by the presence of the light source 22 can be effectively eliminated, that is, the image of the light source 22 can be effectively made inconspicuous. As a result, the surface light source device 20 can be made thinner, and at the same time, the illumination at each position on the light-emitting side surface 40b of the diffusion component 40 can be effectively made uniform, that is, the in-plane distribution of the illumination can be effectively made uniform.

[0288] Although one embodiment has been described above with reference to specific examples, these specific examples do not limit one embodiment. The above-mentioned one embodiment can be implemented by various other specific examples, and various omissions, substitutions, changes, additions, etc. can be made as long as they do not deviate from the scope of the gist.

[0289] In the following description and the drawings used in the following description, for parts that can be configured in the same manner as the above-mentioned specific example, the same symbols as those used for the corresponding parts in the above-mentioned specific example are used, and repeated descriptions are omitted.

[0290] like Figure 2As shown by the double dotted line, the surface light source device 20 can have other components in addition to the light source 22, the supporting substrate 25 and the diffusion component 40. As other components added to the surface light source device 20, a wavelength conversion plate 76, a light diffusion plate 77, a reflective polarizer 78, etc. can be exemplified. The wavelength conversion plate 76 has, for example, a phosphor, absorbs light from the light source 22, and emits light with a wavelength different from the wavelength of the absorbed light. For example, the light source 22 can emit blue light, and the wavelength conversion plate 76 converts part of the blue light into red light and green light. According to this example, the reflection characteristics of the light reflecting part 70 can be adjusted for light in a limited wavelength region. Therefore, the light reflecting part 70 can be given an ideal reflection characteristic corresponding to the diffuse transmission characteristics of the light diffusion part 50, and at the same time, as the surface light source device 20, white planar light can be generated. The light diffusion plate 77 can smoothly change the angular distribution of the radiation intensity on the light-emitting surface 20a of the surface light source device 20. The reflective polarizer 78 transmits only the linear polarization component light available in the display panel 15, and reflects the linear polarization component light not available in the display panel 15. The polarization component of the light reflected by the reflective polarizer can be changed into the polarization component available in the display panel 15 by reflection in the subsequent optical path.

[0291] In addition, if Fig.28 As shown in FIG. 1 , the diffusion member 40 may further include a thermoplastic resin layer 80, which is located on the side of the light diffusion portion 50 opposite to the light reflection portion 70 in the stacking direction D3. By providing the thermoplastic resin layer 80, the relative positions of the support substrate 25 supporting the light source 22 and the diffusion member 40 in the stacking direction D3 can be determined. The thermoplastic resin layer 80 functions as a spacer. In addition, the thermoplastic resin layer 80 may be bonded to at least one of the support substrate 25 and the diffusion member 40. In this case, the thermoplastic resin layer 80 may function as a sealing material that covers and protects the light source 22, and the relative positional relationship between the support substrate 25 and the diffusion member 40 in the stacking direction D3 may be effectively stabilized.

[0292] As the material of the thermoplastic resin layer 80, for example, a thermoplastic resin such as an olefin resin having light transmittance can be used to make it. In addition, the thermoplastic resin layer 80 can include a base material composed of a thermoplastic resin and diffusing particles dispersed in the base material. In this example, the diffusing component 40 also has light diffusivity in the thermoplastic resin layer 80. In addition, when the thermoplastic resin layer 80 has diffusivity and functions as the light diffusing part 50, the diffusing component 40 can include the thermoplastic resin layer 80, the light reflecting part 70 and the optical element part 110.

[0293] In addition, if Fig.29 As shown, the thermoplastic resin layer 80 may be provided with a recessed portion 80a on the side facing the support substrate 25. Fig.29In the example shown, the light L291 emitted from the light source 22 is refracted at the interface between the gap V between the thermoplastic resin layer 80 and the light source 22 and the thermoplastic resin layer 80. As a result, the light L281 from the light source 22 can be effectively diffused, and the in-plane distribution of the illumination can be effectively made more uniform. The light from the light source 22 can also be diffused more effectively by adjusting the shape of the recessed portion 80a.

[0294] The light diffusion part 50 of the diffusion member 40 may have a concave-convex surface 52 to exhibit light diffusion. Fig.30 As shown in FIG. 1 , the light diffusion section 50 can be produced by molding using an ionizing radiation curing resin. An example of a method for producing the light diffusion section 50 will be described below.

[0295] like Fig.30 As shown, the wound substrate 90 is fed out and conveyed to a position facing the mold 100 by the guide roller 101. Then, a resin composition 91 is supplied between the mold 100 and the substrate 90. The resin composition 91 contains an uncured ionizing radiation curable resin. Next, the resin composition 91 between the mold 100 and the substrate 90 is irradiated with ionizing radiation such as ultraviolet rays or electron beams by the exposure device 102 to cure the resin composition 91. Thereafter, the light diffusion portion 50 composed of the cured product of the resin composition 91 and laminated with the substrate 90 is peeled off from the mold 100 while being guided by the guide roller 101. As described above, Fig.30 As shown, an optical sheet 55 including a substrate 90 and a light diffusion section 50 formed on the substrate 90 is obtained. According to this manufacturing method, a diffractive optical element 60 or a microlens 65 having the above-mentioned concavoconvex surface 52 can be manufactured as the light diffusion section 50.

[0296] exist Fig.30 In the manufacturing method shown, the light diffusion part 50 is continuously manufactured by a roll-to-roll method. However, the present invention is not limited to this example, and the light diffusion part 50 in a single sheet form may be manufactured by molding.

[0297] It should be noted that the optical element section 110 of the diffusion member 40 has a second concavo-convex surface 112. The optical element section 110 having the second concavo-convex surface 112 can be manufactured in the same manner as the light diffusion section 50 having the first concavo-convex surface 52. Fig.30 By using the above-mentioned manufacturing method, an optical element unit 110 composed of a cured product of a resin composition 91 is formed on a substrate 90, thereby obtaining an optical sheet 115 having a substrate 90 and the optical element unit 110 formed on the substrate 90. According to this manufacturing method, as the optical element unit 110, a microlens 125 having a second concave-convex surface 112 formed by the element surface 127 of the above-mentioned unit optical element 126 can be manufactured.

[0298] Can be used Fig.30 The optical sheet 55 shown is used to make the diffusion member 40. The substrate 90 used in the optical sheet 55 is not particularly limited, and a wide range of sheet-like materials can be used. From the perspective of adhesion with the light diffusion unit 50, a resin film can be used as the substrate 90. As long as the substrate 90 is directly used as a part of the diffusion member 40, a material having light transmittance can be used for the substrate 90.

[0299] In addition, as the substrate 90, the light reflecting portion 70, for example, a dielectric multilayer film can be used. As the dielectric multilayer film, a multilayer film of a relatively flexible resin layer is preferred. In this case, Fig.31 As shown, the light diffusion part 50 included in the diffusion member 40 has a concave-convex surface 52 facing the side opposite to the light reflecting part 70 in the stacking direction D3 and is joined to the light reflecting part 70. In the diffusion member 40, the light diffusion part 50 and the light reflecting part 70 are joined, so the handling property of the diffusion member 40 is improved. Therefore, the diffusion member 40 can be easily assembled into the surface light source device 20. In addition, since the light diffusion part 50 and the light reflecting part 70 are joined, the surface light source device 20 can be stably installed.

[0300] Similarly, the light reflecting portion 70, such as a dielectric multilayer film, can be used as the substrate 90, and the optical element portion 110 can be manufactured on the substrate 90. In this case, Figure 25A to Figure 26 As shown, the optical element portion 110 included in the diffusion component 40 has a concave-convex surface 112 facing the side opposite to the light reflecting portion 70 in the stacking direction D3 and is bonded to the light reflecting portion 70. In the diffusion component 40, since the light reflecting portion 70 and the optical element portion 110 are bonded, the handling property of the diffusion component 40 is improved. Therefore, the diffusion component 40 can be easily assembled into the surface light source device 20. In addition, since the light reflecting portion 70 and the optical element portion 110 are bonded, the surface light source device 20 can be stably installed.

[0301] In addition, the light reflecting portion 70 can be used as the substrate 90. Fig.30 The manufacturing method described in the invention forms a light diffusion portion 50 on one side of the substrate 90, and then Fig.30 The manufacturing method described above forms the optical element section 110 on the other side of the substrate 90. Either the light diffusion section 50 or the optical element section 110 may be manufactured first. Fig.24As shown, a diffusion component 40 is obtained in which the light diffusion part 50, the light reflection part 70 and the optical element part 110 are stacked in the stacking direction D3 and bonded to each other. In the diffusion component 40, since the light diffusion part 50, the light reflection part 70 and the optical element part 110 are bonded, the handling property of the diffusion component 40 is improved. Therefore, the diffusion component 40 can be easily assembled into the surface light source device 20. In addition, since the light diffusion part 50, the light reflection part 70 and the optical element part 110 are bonded, the surface light source device 20 can be stably set.

[0302] like Fig.32 As shown, the light diffusion portion 50 can be manufactured by embossing. Fig.32 In the manufacturing method shown, first, a substrate 90 including a thermoplastic resin layer as at least a molding surface is placed on a support table 106. Next, a heated mold 105 is pressed against the substrate 90 to transfer the concavoconvexity of the mold 105 to the substrate 90. Thereafter, the mold 105 is spaced apart from the molded substrate 90, thereby obtaining an optical sheet 55 as a light diffusion portion 50 composed of the substrate 90 to which the shape of the mold 105 is transferred. Similarly, by using embossing, an optical element portion 110 composed of the substrate 90 to which the shape of the mold 105 is transferred can be manufactured as an optical sheet 115.

[0303] It should be noted that through Fig.32 When the light diffusion unit 50 and the optical element unit 110 are produced by embossing as shown, a dielectric multilayer film having a thermoplastic resin layer as the outermost layer may be used as the substrate 90. Fig.33 As shown in FIG. 4 , the light diffusion part 50 included in the diffusion member 40 can be formed as a concave-convex surface 52 constituting the surface of the light reflection part 70. Figure 25A to Figure 26 As shown, the optical element portion 110 included in the diffusion member 40 can be formed into a concave-convex surface 112 constituting the surface of the light reflection portion 70. In addition, the light reflection portion 70 can be used as the substrate 90. Fig.32 The embossing process shown in the figure forms a light diffusion portion 50 on one side of the substrate 90, and then Fig.32The embossing process shown forms the optical element portion 110 on the other side of the substrate 90. Either the light diffusion portion 50 or the optical element portion 110 may be produced first. Thus, the light diffusion portion 50 is formed as one surface of the light reflection portion 70, and the optical element portion 110 is formed as the other surface of the light reflection portion 70. In the diffuser component 40 thus obtained, the outermost layer of the light reflection portion 70 is integrally formed with at least one of the light diffusion portion 50 and the optical element portion 110. According to such a diffuser component 40, the diffuser component 40 and the surface light source device 20 can be thinned. According to the diffuser component 40, the light reflection portion 70 can be integrally formed with at least one of the light diffusion portion 50 and the optical element portion 110 without a joint. Thus, the surface light source device 20 can be stably set.

[0304] In addition, refer to Fig.26 , shows an example in which the optical element section 110 includes linear unit optical elements 126 arranged in one direction. The light diffusion section 50 may also include linear unit optical elements 66 arranged in one direction. The multiple unit optical elements 66 arranged in one dimension in the light diffusion section 50 can be configured in the same manner as the multiple unit optical elements 126 arranged in one dimension in the above-mentioned optical element section 110. In addition, the arrangement direction of the multiple unit optical elements 66 included in the light diffusion section 50 and the arrangement direction of the multiple unit optical elements 126 included in the optical element section 110 may be parallel, non-parallel, inclined, or perpendicular.

[0305] Example

[0306] Hereinafter, the above-mentioned one embodiment will be described in more detail using examples, but the above-mentioned one embodiment is not limited to these examples.

[0307] The surface light source devices of Examples 1 to 6 and Comparative Example 1 were manufactured as follows.

[0308] <Example 1>

[0309] The surface light source device of Example 1 has Figure 2 The surface light source device of Example 1 has a wavelength conversion plate, a light diffusion plate, and a reflective polarizer in addition to a light source, a supporting substrate, and a diffusion component. The supporting substrate has a white reflective layer containing titanium oxide. The reflection of the reflective layer of the supporting substrate is diffuse reflection with a reflectivity of 95%. Figure 3As shown, the light sources are arranged on the supporting substrate in a square arrangement. The arrangement pitch of the light sources in the first direction is 6 mm. The arrangement pitch of the light sources in the second direction perpendicular to the first direction is 6 mm. As each light source, a light emitting diode emitting blue light with a central wavelength of 450 nm is used. The planar shape of the light emitting diode is a rectangular shape of 0.2 mm×0.4 mm. The light emitting diodes are arranged on the supporting substrate 25 in such a way that the sides of the light emitting diodes are along the first direction and the second direction.

[0310] In the surface light source device of Example 1, Figure 2 As shown in FIG. 1 , the diffusion component has a light diffusion part, a light reflection part, and an optical element part in the stacking direction D3 from the light source side. As the light reflection part, a dielectric multilayer film obtained from Toray Industries, Ltd. is used. The light reflection part has a 450 nm wavelength. Fig.17 and Fig.18 The optical element part is molded on one surface of the light reflecting part. Then, the light diffusion part is molded on the other surface of the light reflecting part. Fig.30 As described above, the optical element part and the light diffusion part are formed by supplying the UV curable resin composition before curing between the mold and the light reflection part and curing it between the mold and the light reflection part. As a result, a diffusion component is obtained in which the light diffusion part, the light reflection part and the optical element part are sequentially connected in the stacking direction. It should be noted that, unlike Fig.30 In the roll-to-roll manufacturing method shown, the diffusion member of Example 1 is manufactured in a single sheet.

[0311] The optical element portion of the diffusion component is located on the side of the light reflecting portion opposite to the light source. The optical element portion has a sheet-like base portion joined to the light reflecting portion, and a second unit optical element arranged on the base portion as a convex portion. The optical element portion has a second unit optical element having a reference Fig.14A and Fig. 14B The shape and arrangement of the structure. Fig.14AAs shown, the bottom surface orientation of the second unit optical element of the same shape is changed into four types, and is arranged on the surface of the base without gaps. Each second unit optical element has a triangular pyramid shape and has three second element surfaces. As a collection of the second element surfaces of the second unit optical elements, a second microlens is formed. The bottom surface of the second unit optical element is a right isosceles triangle shape. The element surface of the second unit optical element includes: an equilateral element surface extending from the equilateral side of the right isosceles triangle shape constituting the bottom surface; and a base element surface extending from the base of the right isosceles triangle shape constituting the bottom surface. The lengths of the two sides of the equilateral side forming the right isosceles triangle shape constituting the bottom surface are 0.1 mm respectively. The inclination angle θb formed by the normal direction NDA of each equilateral element surface relative to the stacking direction D3 is 16.5°. The inclination angle θb formed by the normal direction NDA of the base element surface relative to the stacking direction D3 is 16.5°.

[0312] The light diffusion part of the diffusion member is located on the light source side of the light reflection part. The light diffusion part has: a sheet-shaped main body part joined to the light reflection part; and a first unit optical element arranged on the main body part as a concave part. The light diffusion part has a first unit optical element having a reference Fig.14A and Fig. 14B The shape or arrangement of the structure. Fig.14A As shown, the bottom surface orientation of the first unit optical element of the same shape is changed into four types, and is arranged on the surface of the main body without gaps. Each first unit optical element has a triangular pyramid shape and has three first element surfaces. As a collection of the first element surfaces of the first unit optical elements, a first microlens is formed. The bottom surface of the first unit optical element is a right isosceles triangle shape. The element surface of the second unit optical element includes: an equilateral element surface extending from the equilateral side of the right isosceles triangle shape constituting the bottom surface; and a base element surface extending from the base of the right isosceles triangle shape constituting the bottom surface. The lengths of the two sides of the equilateral side forming the right isosceles triangle shape constituting the bottom surface are 0.1 mm respectively. The inclination angle θb formed by the normal direction ND of each equilateral element surface relative to the stacking direction D3 is 16.5°. The inclination angle θb formed by the normal direction ND of the base element surface relative to the stacking direction D3 is 16.5°. As a result, the first concavo-convex surface of the light diffusion portion and the second concavo-convex surface of the optical element portion have the same structure except that the concavo-convexity is reversed.

[0313] As the wavelength conversion sheet, QF-6000 available from Showa Denko Materials was used. As the light diffusion sheet, two sheets of brightness enhancement films BEF (registered trademark) available from 3M were used. For one brightness enhancement film BEF, the length direction of the prisms extended in the first direction. For the other brightness enhancement film BEF, the length direction of the prisms extended in the second direction. As the reflective polarizing plate, a brightness enhancement film DBEF (registered trademark) available from 3M was used.

[0314] In the surface light source device of Example 1, the thickness of the diffusion component along the stacking direction is 70 μm. In addition, in the surface light source device of Example 1, the distance DX along the stacking direction from the surface facing the light source and the diffusion component to the light incident side surface facing the light source of the diffusion component is (refer to Figure 2 ) is 0.5mm.

[0315] <Example 2>

[0316] The surface light source device of Example 2 is different from the surface light source device of Example 1 in the inclination angle θa of the first element surface, but has the same structure as that of Example 1. The inclination angle θa formed by the normal direction ND of each equilateral element surface included in the first element surface of the light diffusion part relative to the stacking direction D3 is 30°. The inclination angle θa formed by the normal direction ND of the bottom element surface included in the first element surface relative to the stacking direction D3 is 40°.

[0317] <Example 3>

[0318] The surface light source device of Example 3 is different from the surface light source device of Example 1 in the inclination angle θa of the first element surface, but has the same structure as that of Example 1. The inclination angle θa formed by the normal direction ND of each equilateral element surface included in the first element surface of the light diffusion part relative to the stacking direction D3 is 40°. The inclination angle θa formed by the normal direction ND of the bottom element surface included in the first element surface relative to the stacking direction D3 is 45°.

[0319] <Example 4>

[0320] The surface light source device of Example 4 is different from the surface light source device of Example 1 in the inclination angle θb of the second element surface, but has the same structure as that of Example 1. The inclination angle θb formed by the normal direction ND of each equilateral element surface included in the second element surface of the optical element part relative to the stacking direction D3 is 30°. The inclination angle θb formed by the normal direction NDA of the bottom element surface included in the second element surface relative to the stacking direction D3 is 40°.

[0321] <Example 5>

[0322] The surface light source device of Example 5 is different from the surface light source device of Example 1 in the inclination angle θb of the second element surface, but has the same structure as that of Example 1. The inclination angle θb formed by the normal direction ND of each equilateral element surface included in the second element surface of the optical element part relative to the stacking direction D3 is 40°. The inclination angle θb formed by the normal direction NDA of the bottom element surface included in the second element surface relative to the stacking direction D3 is 45°.

[0323] <Example 6>

[0324] The surface light source device of Example 6 is different from the surface light source device of Example 1 in the diffusion component, and has the same structure otherwise. The diffusion component of Example 6 is composed of a light diffusion part and a light reflection part. The diffusion component of Example 6 does not have an optical element part. The light reflection part of Example 6 is the same as the light reflection part of Example 1. In the surface light source device of Comparative Example 1, the thickness of the diffusion component along the stacking direction is 55μm.

[0325] <Example 7>

[0326] The surface light source device of Example 7 is different from the surface light source device of Example 1 in the inclination angle θb of the second element surface, but has the same structure as that of Example 1. The inclination angle θb formed by the normal direction ND of each equilateral element surface included in the first element surface of the light diffusion part relative to the stacking direction D3 is 5.5°. The inclination angle θb formed by the normal direction ND of the bottom element surface included in the first element surface relative to the stacking direction D3 is 5.5°.

[0327] <Comparative Example 1>

[0328] The surface light source device of Comparative Example 1 is the same as the surface light source device of Example 1 except that the diffusion component is replaced by the light diffusion plate HBS222 manufactured by Huihe Co., Ltd. The light diffusion plate is located on the light source side of the wavelength conversion plate. In the surface light source device of Comparative Example 3, the light source and the supporting substrate are opposite to the light diffusion plate in the stacking direction. In the surface light source device of Comparative Example 1, the distance along the stacking direction from the surface facing the light source and the light diffusion plate to the light incident side surface facing the light diffusion plate and the light source is 0.5 mm.

[0329] <Evaluation>

[0330] With respect to the surface light source devices of Examples 1 to 7 and Comparative Example 1, the distribution of the radiation intensity on the light-emitting surface of the surface light source devices was measured while the light sources were emitting light. The measurement range of the radiation intensity was a square evaluation area having a length of 18 mm in the first direction and a length of 18 mm in the second direction on the light-emitting surface of the surface light source device. The evaluation area was set so that one light source was located at the center of the evaluation area when observed from the third direction. With respect to the surface light source devices of Examples 1 to 6 and Comparative Example 1, the in-plane distribution of the radiation intensity on the light-emitting surface is shown in FIG. Figures 34 to 40 . Figures 34 to 40 It is a top view showing an evaluation area having an area of ​​18 mm×18 mm. Figures 34 to 40 The intensity of the radiation at each position in the evaluation area is indicated by the depth of the color at that position. A position with low radiation intensity is indicated by a darker color.

[0331] about Fig.40 The surface light source device of the comparative example 1 shown produces uneven distribution of radiation intensity corresponding to the arrangement of the light sources, and the position of the light source can be clearly identified. Compared with the in-plane distribution of the radiation intensity of the surface light source device of the comparative example 1, the in-plane distribution of the radiation intensity of the surface light source devices of Examples 1 to 7 can be made sufficiently uniform. Among them, especially with regard to Examples 1 and 7, the distribution of brightness is uniform, and it is difficult to know the position of the light source. The ratio of the minimum value of the radiation intensity in the evaluation area of ​​each surface light source device 20 to the maximum value of the radiation intensity (= minimum value of radiation intensity / maximum value of radiation intensity) is 97% in Example 1, 95% in Example 2, 94% in Example 3, 93% in Example 4, 92% in Example 5, 90% in Example 6, 96% in Example 7, and 50% in Comparative Example 1.

[0332] Explanation of symbols

[0333] 10: display device, 20: surface light source device, 22: light source, 40: diffusion component, 42: marking, 50: light diffusion part, 52: concave-convex surface, 53: diffusion main body, 53a: concave-convex surface, 54: reflection coating part, 58: main body, 65: microlens, 66: unit optical element, 67: element surface, 68: convex part, 69: concave part, 70: light reflecting part, 110: optical element part, 112: concave-convex surface, 115: optical sheet, 118: base, 125: microlens, 126: unit optical element, 127: element surface, 128: convex part, 129: concave part.

Claims

1. A surface light source device, which is a direct-down type surface light source device, comprising: two or more light sources arranged in two dimensions, which emit blue light of a specific wavelength; a diffusion component, which is directly opposite to the two or more light sources; a light diffusion sheet, which is stacked with the diffusion component; and a wavelength conversion sheet, which is located between the diffusion component and the light diffusion sheet, wherein: In the stacking direction of the diffusion member, the wavelength conversion sheet and the light diffusion sheet, the diffusion member is located between the light source and the light diffusion sheet, The diffusion member includes a light diffusion portion and a light reflection portion including a dielectric multilayer film. The light diffusion part has light transmittance and light diffusion properties, In the dielectric multilayer film, the transmittance of the light of the specific wavelength incident at an incident angle of 0° is lower than the transmittance of the light of the specific wavelength incident at an incident angle greater than 0°, The light reflecting portion is located between the light diffusing portion and the wavelength conversion sheet in the stacking direction. The wavelength conversion sheet absorbs light from the light source and emits light with a wavelength different from that of the absorbed light.

2. A surface light source device, which is a direct-down type surface light source device, comprising: two or more light sources arranged in two dimensions, which emit green light of a specific wavelength; a diffusion component, which is directly opposite to the two or more light sources; a light diffusion sheet, which is stacked with the diffusion component; and a wavelength conversion sheet, which is located between the diffusion component and the light diffusion sheet, wherein: In the stacking direction of the diffusion component, the wavelength conversion sheet and the light diffusion sheet, the diffusion component is located between the light source and the light diffusion sheet, The diffusion member includes a light diffusion portion and a light reflection portion including a dielectric multilayer film. The light diffusion part has light transmittance and light diffusion properties, In the dielectric multilayer film, the transmittance of the light of the specific wavelength incident at an incident angle of 0° is lower than the transmittance of the light of the specific wavelength incident at an incident angle greater than 0°, The light reflecting portion is located between the light diffusing portion and the wavelength conversion sheet in the stacking direction. The wavelength conversion sheet absorbs light from the light source and emits light with a wavelength different from that of the absorbed light.

3. A surface light source device, which is a direct-down type surface light source device, comprising: two or more light sources arranged in two dimensions, which emit red light of a specific wavelength; a diffusion component, which is directly opposite to the two or more light sources; a light diffusion sheet, which is stacked with the diffusion component; and a wavelength conversion sheet, which is located between the diffusion component and the light diffusion sheet, wherein: In the stacking direction of the diffusion member, the wavelength conversion sheet and the light diffusion sheet, the diffusion member is located between the light source and the light diffusion sheet, The diffusion member includes a light diffusion portion and a light reflection portion including a dielectric multilayer film. The light diffusion part has light transmittance and light diffusion properties, In the dielectric multilayer film, the transmittance of the light of the specific wavelength incident at an incident angle of 0° is lower than the transmittance of the light of the specific wavelength incident at an incident angle greater than 0°, The light reflecting portion is located between the light diffusing portion and the wavelength conversion sheet in the stacking direction. The wavelength conversion sheet absorbs light from the light source and emits light with a wavelength different from that of the absorbed light.

4. The surface light source device according to any one of claims 1 to 3, wherein: The light diffusion portion is formed as a concavoconvex surface constituting the surface of the light reflection portion.

5. The surface light source device according to any one of claims 1 to 3, wherein: The light diffusion portion has a concavo-convex surface facing a side opposite to the light reflection portion, and is joined to the light reflection portion.

6. The surface light source device according to any one of claims 1 to 3, wherein: The light diffusion unit includes a microlens having two or more unit optical elements. 7 . The surface light source device according to claim 6 , further comprising an indication indicating a direction in which the light diffusion portion should be arranged. 8 . The surface light source device according to claim 1 , further comprising an optical element portion provided on a side of the light reflecting portion opposite to the light diffusing portion and having a concave-convex surface on a side opposite to the light reflecting portion.

9. The surface light source device according to claim 8, wherein: The concavoconvex surface includes an element surface having a normal direction inclined at an angle of 25° or less with respect to a stacking direction in which the light reflecting portion and the optical element portion are stacked.

10. The surface light source device according to claim 8, wherein: The optical element portion is bonded to the light reflecting portion.

11. The surface light source device according to claim 8, wherein: The optical element unit includes a microlens having two or more unit optical elements. The unit optical element is a convex portion protruding toward a side opposite to the light reflecting portion.

12. The surface light source device according to claim 8, wherein: The optical element unit includes a microlens having two or more unit optical elements. The unit optical element includes an element surface having a normal direction inclined at an angle of 25° or less with respect to a stacking direction of the light reflecting portion and the optical element portion. The element surface forms the concavo-convex surface.

13. The surface light source device according to claim 8, wherein: The optical element section has two or more unit optical elements arranged in one direction, Each unit optical element extends linearly along another direction that is not parallel to the one direction.

14. The surface light source device according to claim 13, wherein: The unit optical element is a convex portion protruding toward a side opposite to the light reflecting portion.

15. The surface light source device according to claim 13, wherein: The unit optical element includes an element surface having a normal direction inclined at an angle of 25° or less with respect to a stacking direction of the light reflecting portion and the optical element portion. The element surface forms the concavo-convex surface.

16. The surface light source device according to any one of claims 1 to 3, wherein: The light source includes two or more light sources arranged regularly, The light diffusion section includes a microlens having two or more unit optical elements arranged in a direction not parallel to an arrangement direction of the two or more light sources.

17. The surface light source device according to any one of claims 1 to 3, wherein: The light source includes two or more light sources arranged regularly, The light diffusion part includes a microlens having two or more unit optical elements. The unit optical element includes an element surface having a normal direction that is not parallel to an arrangement direction of the two or more light sources when viewed from a stacking direction in which the light diffusion portion and the light reflection portion are stacked.

18. The surface light source device according to any one of claims 1 to 3, wherein: The diffusion member further includes an optical element portion, which is provided on a side of the light reflecting portion opposite to the light diffusion portion and has a concave-convex surface on a side opposite to the light reflecting portion. The light source includes two or more light sources arranged regularly, The optical element section includes a microlens having two or more unit optical elements arranged in a direction not parallel to an arrangement direction of the two or more light sources.

19. A display device comprising the surface light source device according to any one of claims 1 to 3.

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