Light guide member for lighting device and lighting device

Abstract

A light guide member (100A) for a lighting device having an emission surface comprises: a light guide layer (10) having a light receiving portion that receives light emitted from a light source (LS), a first main surface on the emission surface side and a second main surface on the side opposite to the first main surface; a light distribution control structure having a plurality of internal spaces (64), each of the plurality of internal spaces (64) having a first inclined surface (ISa) that directs part of light propagating within the light guide layer (10) to the emission surface by using total internal reflection, and a second inclined surface (ISb) on the side opposite that of the first inclined surface (ISa), and the first inclined surface (ISa) forming a curved surface that is convex toward the light source (LS) when viewed from the direction normal to the first main surface of the light guide layer (10); and an antireflection layer (40A) and / or an antiglare layer disposed on the first major surface side of the light guide layer (10).

Description

Light guide member for lighting device and lighting device

[0001] The present invention relates to a light-guiding member for a lighting device and a lighting device, and more particularly to a sheet-like light-guiding member for a lighting device and a lighting device, each of which includes a light source and a light-guiding layer. Here, the term "sheet-like" refers to a plate-like or film-like member, regardless of the rigidity (flexibility) and thickness of the sheet. The sheet-like lighting device can be used in various forms, such as a roll.

[0002] Sheet-shaped lighting devices including a light source and a light guide layer are used, for example, as backlights or frontlights of liquid crystal display devices. Furthermore, in recent years, the use of next-generation solid-state lighting (SSL), typified by LED lighting, has been increasing. For example, by combining architectural components with lighting devices, lighting with rich design and entertainment value, known as "archittainment lighting," has been proposed.

[0003] For example, Patent Document 1 discloses a window with dual-purpose lighting and single-sided illumination, which has a light source at the end of a plate-shaped transparent substrate, and functions as a lighting device that emits light emitted from the light source and guided through the transparent substrate from one side of the transparent substrate during illumination such as at night, and functions as a transparent window during non-illumination such as during the day. Furthermore, Patent Documents 2 to 5 disclose sheet-like lighting devices having a light distribution structure that utilizes total reflection at the interface of an air cavity (internal space). The disclosures of Patent Documents 2 to 5 are incorporated herein by reference in their entirety.

[0004] International Publication No. WO 2019 / 102959, International Publication No. WO 2019 / 182091, International Publication No. WO 2019 / 146628, International Publication No. WO 2011 / 124765, International Publication No. WO 2019 / 087118

[0005] From the viewpoints of practicality and design, the present invention aims to provide a light-guiding member for a lighting device, which has two principal surfaces facing in opposite directions, and emits light from one of the principal surfaces, and which appears transparent when viewed from the other principal surface side, and a lighting device.

[0006] According to an embodiment of the present invention, the following solutions are provided:

[0007] [Item 1] A light-guiding member for a lighting device having an emission surface, comprising: a light-receiving section that receives light emitted from a light source; a light-guiding layer that has a first main surface on the emission surface side and a second main surface opposite the first main surface; a light distribution control structure having a plurality of internal spaces, each of the plurality of internal spaces having a first inclined surface that directs a portion of light propagating within the light-guiding layer toward the emission surface by total internal reflection and a second inclined surface opposite the first inclined surface, wherein the first inclined surface forms a curved surface that is convex toward the light source side when viewed from a normal direction to the first main surface of the light-guiding layer; and an anti-reflection layer and / or an anti-glare layer that is arranged on the first main surface side of the light-guiding layer.

[0008] [Item 2] The light-guiding member for a lighting device according to Item 1, wherein the plurality of internal spaces are discretely arranged in a light-guiding direction of the light-guiding layer and in a direction intersecting the light-guiding direction.

[0009] [Item 3] The light-guiding member for an illumination device according to Item 1 or 2, further comprising: the antireflection layer disposed on the first main surface side of the light-guiding layer; and the antireflection layer having a single dielectric layer having a refractive index lower than a refractive index of the light-guiding layer, or a multilayer stack including a plurality of dielectric layers having refractive indices different from one another.

[0010] [Item 4] The light-guiding member for an illumination device according to Item 1 or 2, further comprising: the antireflection layer disposed on the first main surface side of the light-guiding layer; and the antireflection layer having a moth-eye structure or formed of a material having voids.

[0011] [Item 5] The light-guiding member for an illumination device according to any one of Items 1 to 4, further comprising the anti-glare layer disposed on the first main surface side of the light-guiding layer, wherein the anti-glare layer has an arithmetic mean roughness Ra of 0.8 μm or more and 1000 μm or less on a surface opposite to the light-guiding layer and a maximum height Rz of 5.0 μm or more and 1000 μm or less.

[0012] [Item 6] The light-guiding member for an illumination device according to any one of Items 1 to 5, wherein an inclination angle θa of the first inclined surface is 10° or more and 70° or less, and an inclination angle θb of the second inclined surface is 50° or more and 100° or less.

[0013] [Item 7] The light-guiding member for a lighting device according to any one of Items 1 to 6, wherein the light distribution control structure is formed on a direction changing layer provided on the first main surface side or the second main surface side of the light-guiding layer.

[0014] [Item 8] The light-guiding member for an illumination device according to any one of Items 1 to 7, wherein a ratio of an area of ​​the plurality of internal spaces to an area of ​​the light-guiding layer when viewed from the normal direction to the first main surface of the light-guiding layer is 80% or less.

[0015] [Item 9] The light-guiding member for an illumination device according to any one of Items 1 to 8, further comprising a low-refractive index layer on the second main surface side of the light-guiding layer, the low-refractive index layer having a refractive index lower than that of the light-guiding layer.

[0016] [Item 10] The light-guiding member for an illumination device according to any one of Items 1 to 9, wherein a maximum contrast ratio of luminance in a square region having a side length of 17.3 mm and located at an arbitrary location in a region where light leaks from a back surface located on the second main surface side of the light-guiding member for an illumination device is 1.1 or less.

[0017] [Item 11] The light-guiding member for a lighting device according to any one of Items 1 to 10, which has a visible light transmittance of 60% or more and a haze value of less than 30%.

[0018] [Item 12] An illumination device comprising: the light-guiding member for an illumination device according to any one of items 1 to 11; and a light source that emits light toward the light-receiving portion.

[0019] [Item 13] The lighting device according to item 12, wherein the light source includes a plurality of LED devices arranged along the light receiving portion of the light guide layer.

[0020] According to an embodiment of the present invention, there are provided a light-guiding member for a lighting device and a lighting device, which have two principal surfaces facing opposite directions, one of which emits light and which appears transparent when viewed from the other principal surface side. The light-guiding member for a lighting device and the lighting device according to some embodiments have a visible light transmittance of 60% or more and a haze value of less than 30%.

[0021] 1 is a schematic cross-sectional view of a lighting device 100A_L according to an embodiment of the present invention. FIG. 2 is a schematic plan view of the lighting device 100A_L. FIG. 3 is a schematic cross-sectional view of an internal space 64 that the lighting device 100A_L may have. FIG. 4 is a schematic plan view of the internal space 64. FIG. 5 is a schematic plan view showing variations of the internal space 64. FIG. 6 is a schematic cross-sectional view of a lighting device 100B_L according to another embodiment of the present invention. FIG. 7 is a schematic cross-sectional view of a lighting device 100C_L according to yet another embodiment of the present invention. FIG. 8 is a graph showing (a) the luminance distribution in a rectangular region located at the center of the back surface of the lighting device of Example 1, and (b) the relationship between the position on the horizontal line passing through the center of the rectangular region and the luminance. FIG. 9 is a graph showing (a) the luminance distribution in a rectangular region located at the center of the back surface of the lighting device of Example 2, and (b) the relationship between the position on the horizontal line passing through the center of the rectangular region and the luminance. FIG. 10 is a graph showing (a) the luminance distribution in a rectangular region located at the center of the back surface of the lighting device of Example 3, and (b) the relationship between the position on the horizontal line passing through the center of the rectangular region and the luminance. 1 is a graph showing (a) the luminance distribution in a rectangular region located at the center of the back surface of an illumination device according to Example 4, and (b) the relationship between luminance and the position on a horizontal line passing through the center of the rectangular region, of an illumination device according to Comparative Example 1. FIG. 1 is a graph showing (a) the luminance distribution in a rectangular region located at the center of the back surface of an illumination device according to Comparative Example 1, and (b) the relationship between luminance and the position on a horizontal line passing through the center of the rectangular region, of an illumination device according to a reference example. FIG. 2 is a schematic cross-sectional view of an illumination device 100A1_L according to another embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an illumination device 100A2_L according to yet another embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of an illumination device 900_L for a reference example.

[0022] DETAILED DESCRIPTION OF THE INVENTION Light-guiding members for lighting devices and lighting devices according to embodiments of the present invention will be described below with reference to the drawings. The light-guiding members for lighting devices and lighting devices according to the embodiments of the present invention are not limited to those exemplified below.

[0023] 1 shows a schematic cross-sectional view of a lighting device 100A_L according to an embodiment of the present invention. The lighting device 100A_L is a sheet-like lighting device having an emission surface (bottom in FIG. 1) that emits light LR and a back surface (top in FIG. 1) opposite the emission surface. The light LR is emitted in the −Z direction in FIG. 1.

[0024] The lighting device 100A_L includes a light source LS and a light-guiding member 100A that receives light emitted from the light source LS, propagates the light in the Y direction, and emits the light in the −Z direction. The light-guiding member 100A includes a light-receiving portion (e.g., a light-receiving side surface of the light-guiding layer 10 facing the light source LS) that receives the light emitted from the light source LS, a light-guiding layer 10 having a first main surface on the light-emitting side and a second main surface opposite the first main surface, a light distribution control structure having a plurality of internal spaces 64, and an anti-reflection layer 40A disposed on the first main surface side of the light-guiding layer 10 via an adhesive layer 52 and a base layer 32. In manufacturing the light-guiding member 100A, the base layer 32 on which the anti-reflection layer 40 is formed is disposed on the first main surface side of the light-guiding layer 10 via the adhesive layer 52. The light-emitting surface of the lighting device 100A_L is the surface of the anti-reflection layer 40A opposite the light-guiding layer 10.

[0025] Each of the multiple internal spaces 64 has a first inclined surface ISa that directs a portion of light propagating within the light-guiding layer 10 toward the light-emitting surface by total internal reflection (TIR), and a second inclined surface ISb opposite the first inclined surface ISa. The anti-reflection layer 40A includes a single dielectric layer having a refractive index lower than that of the light-guiding layer 10, or a multilayer stack of multiple dielectric layers having different refractive indices. The anti-reflection layer 40A prevents light directed toward the light-emitting surface from being Fresnel-reflected at the interface between the substrate layer 32 and the anti-reflection layer 40A and being directed toward the back surface. The anti-reflection layer 40A suppresses the Fresnel reflectance to 3% or less. The light LR emitted from the light source LS propagates within the light-guiding layer 10, is totally internally reflected by the first inclined surface ISa of the internal space 64, and passes through the light-guiding layer 10, the substrate layer 32, and the anti-reflection layer 40A. Of course, when the light LR passes through the interface, it may be refracted according to the refractive index of the material that constitutes the interface.

[0026] In the light-guiding member 100A, the light distribution control structure having a plurality of internal spaces 64 is formed in a direction changing layer 60 disposed on the second main surface side of the light-guiding layer 10 via an adhesive layer 54. The direction changing layer 60 having a plurality of internal spaces 64 is composed of a shaped film 62 having recesses 64 (denoted by the same reference numerals as the internal spaces 64) on its surface, and an adhesive layer 56. The plurality of internal spaces 64 may be formed within the light-guiding layer 10. A direction changing layer may also be formed on the first main surface side of the light-guiding layer 10.

[0027] The light distribution control structure is configured so that 80% or more of the light propagating within the light guide layer 10 is directed toward the exit surface. The proportion of the light propagating within the light guide layer 10 that is directed toward the exit surface can be controlled, for example, by adjusting the cross-sectional shape, planar shape, size, arrangement density, and distribution of the internal space 64. The cross-sectional shape of the internal space 64 is triangular as exemplified here, but is not limited to this and may be trapezoidal, etc.

[0028] When the light guide layer 10 is viewed from the normal direction of the main surface, the multiple internal spaces 64, which form the light distribution control structure, preferably occupy a ratio (occupancy rate) of the area of ​​the multiple internal spaces 64 to the area of ​​the light guide layer 10. The upper limit is preferably 50% or less, and even more preferably 45% or less. To achieve high transmittance and / or a low haze value, the ratio is preferably 30% or less, more preferably 10% or less, and even more preferably 5% or less. For example, a haze value of 30% can be achieved when the internal space occupancy rate is 50%. The occupancy rate of the internal spaces 64 may be uniform, or may increase with increasing distance from the light source LS so that brightness does not decrease even with increasing distance. For mass production using a roll-to-roll method or a roll-to-sheet method, a uniform occupancy rate of the internal spaces 64 is preferred.

[0029] In the light-guiding member 100A, the base layer 32 is bonded to the first main surface of the light-guiding layer 10 by an adhesive layer 52, and the shaped film 62 is bonded to the second main surface of the light-guiding layer 10 by an adhesive layer 54. Furthermore, in the light-guiding member 100A, the base layer 34 and the shaped film 62 are bonded together by an adhesive layer 56, which together with the shaped film 62 constitute the direction-changing layer 60. The light-guiding layer 10 and the base layers 32, 34 may be transparent substrates or films. In the light-guiding member 100A, the refractive indices of the base layer 32, adhesive layer 52, light-guiding layer 10, adhesive layer 54, and shaped film 62 are designed to be approximately equal to one another, thereby suppressing Fresnel reflection of light directed toward the light-emitting surface at the interfaces between these components. Preferred configurations of the light-guiding layer 10, base layers 32, 34, anti-reflection layer 40A, shaped film 62, and adhesive layers 52, 54, 56 will be described later.

[0030] The lighting device 100A_L may be characterized, for example, by a visible light transmittance of 60% or more and a haze value of less than 30%. The visible light transmittance is preferably 70% or more, and more preferably 80% or more. The haze value is preferably less than 10%, and more preferably 5% or less. The light-guiding member 100A according to the embodiment of the present invention has a high visible light transmittance and a low haze value, so that an object (display) can be seen through the light-guiding member 100A. Here, visible light is defined as light having a wavelength of 380 nm or more and 780 nm or less. The visible light transmittance and haze value can be measured, for example, using a haze meter (manufactured by Murakami Color Research Laboratory: product name HM-150).

[0031] Next, an example of the planar shape and arrangement of the internal space 64 will be described with reference to Fig. 2. Fig. 2 shows a schematic plan view of the lighting device 100A_L.

[0032] 2, the multiple internal spaces 64 are discretely arranged, for example, in the light guide direction (Y direction) of the light guide layer 10 and in the direction perpendicular to the light guide direction (X direction). The size (length L, width W: see FIGS. 3A and 3B) of the internal spaces 64 is, for example, preferably 10 μm or more and 500 μm or less for the length L and 1 μm or more and 100 μm or less for the width W. Furthermore, from the viewpoint of light extraction efficiency, the height H (see FIG. 3A) is preferably 1 μm or more and 100 μm or less.

[0033] Here, an example has been shown in which the multiple internal spaces 64 are discretely arranged in the light guide direction (Y direction) of the light guide layer 10 and in the direction perpendicular to the light guide direction (X direction). However, this is not limiting, and the multiple internal spaces 64 may be discretely arranged in the light guide direction (Y direction) of the light guide layer 10 and in a direction intersecting the light guide direction. The discrete arrangement of the internal spaces 64 may be appropriately set depending on the shape of the light guide layer 10, the desired light distribution, and the like. Note that, although light propagates in various directions within the light guide layer 10, the Y direction is referred to as the light guide direction, and light having a Y-direction component (non-zero) is said to be propagating in the Y direction. The same applies to other directions. In other words, light propagating in the -Y direction includes all light having a -Y-direction component (non-zero).

[0034] The multiple internal spaces 64 are, for example, discretely arranged in the light guide direction and in a direction intersecting the light guide direction. The discrete arrangement may or may not have periodicity (regularity) in at least one direction. However, from the viewpoint of mass productivity, it is preferable that the multiple internal spaces 64 are uniformly arranged. For example, in the example shown in FIG. 2, multiple internal spaces 64 having substantially the same shape and convex curved surfaces in the same direction are discretely and periodically arranged throughout the entire region of the light guide layer 10 in the light guide direction (Y direction) and the direction perpendicular to the light guide direction (X direction). In this case, the pitch Px is preferably, for example, 10 μm or more and 500 μm or less, and the pitch Py is preferably, for example, 10 μm or more and 500 μm or less. In the example shown in FIG. 2, the multiple internal spaces 64 are arranged with a half-pitch offset in each of the Y direction and the X direction. In Examples 1 to 4 described below, Px is 200 μm and Py is 100 μm.

[0035] 2 , when viewed from the normal direction to the first main surface of the light guide layer 10, the first inclined surface ISa forms a curved surface that is convex toward the light source LS. The light source LS is, for example, an LED device, and a plurality of LED devices are arranged in the X direction along the light receiving portion of the light guide layer 10. Because the light emitted from each of the plurality of LED devices has a spread in the Y direction, the first inclined surface ISa acts on the light more uniformly when the first inclined surface ISa has a curved surface that is convex toward the light source LS.

[0036] Depending on the application, the light guide layer 10 may have two light receiving sections located on opposite sides of each other, with a light source LS disposed in one light receiving section and another light source disposed in the other light receiving section. The light distribution control structure may have an internal space 64 including a convex curved surface on the light source LS side, but may not have an internal space including a convex curved surface on the other light source side. Alternatively, the light distribution control structure may have an internal space 64 including a convex curved surface on the light source LS side, and may have another internal space including a convex curved surface on the other light source side. The two types of internal spaces including convex curved surfaces facing opposite directions may be mixed and arranged within the light distribution control structure, or may be arranged separately.

[0037] Next, the shape of the internal space 64 will be described with reference to Figures 3A, 3B, and 3C. Figure 3A shows a schematic cross-sectional view of the internal space 64, Figure 3B shows a schematic plan view of the internal space 64, and Figure 3C shows schematic plan views showing variations of the internal space 64.

[0038] As shown in FIG. 3A , the cross-sectional shape of the internal space 64 is, for example, triangular. When the inclination angle θa of the first inclined surface ISa and the inclination angle θb of the second inclined surface ISb are within the following ranges, 80% or more of the light propagating within the light guide layer 10 can be directed toward the output surface. The inclination angle θa of the first inclined surface ISa on the light source LS side is, for example, 10° or more and 70° or less. If the inclination angle θa is less than 10°, the light extraction efficiency may decrease, and if it exceeds 70°, processing may become difficult. Furthermore, the inclination angle θb of the second inclined surface ISb is, for example, 50° or more and 100° or less. If the inclination angle θb is less than 50°, stray light may be generated in undesired directions, and if it exceeds 100°, the amount of light in undesired directions may increase. Furthermore, in order to increase the amount of light LR emitted from the exit surface and decrease the amount of light emitted toward the viewer, the inclination angle θa of the first inclined surface ISa is preferably, for example, 20° to 50°, and the inclination angle θb of the second inclined surface ISb is preferably, for example, 70° to 90°. In Examples 1 to 4 described below, the inclination angle θa of the first inclined surface ISa is 30°, and the inclination angle θb of the second inclined surface ISb is 70°.

[0039] As shown in Figures 3B and 3C, the length L of the internal space 64 is preferably 10 µm or more and 500 µm or less, and the width W is preferably 1 µm or more and 100 µm or less. The length L is, for example, at least twice the width W. The height H (see Figure 3A) is preferably 1 µm or more and 100 µm or less. When forming a shaped film having a recess having the planar shape shown in Figure 3B, a recess having the planar shape shown in Figure 3C may be formed depending on the processing accuracy of the mold. Even in such a case, the planar shape of the internal space can be characterized by the length L and width W. In Examples 1 to 4 described below, the length L of the internal space 64 is 80 µm, the width W is 20 µm, and the height H is 10 µm.

[0040] Next, the function of the antireflection layer 40A in the lighting device 100A_L will be described. The antireflection layer 40A does more than simply allow the light LR to efficiently exit from the exit surface. Before describing the function of the antireflection layer 40A, a problem that occurs when the light-guiding member 100A does not have the antireflection layer 40A will be described with reference to FIG. 8 .

[0041] FIG. 8 shows a schematic cross-sectional view of a lighting device 900_L for reference. The lighting device 900_L shown in FIG. 8 differs from the lighting device 100A_L shown in FIG. 1 in that the light-guiding member 900 does not include the adhesive layer 52, the base layer 32, or the anti-reflection layer 40A. As shown in FIG. 8 , of the light emitted from the light source LS, propagated through the light-guiding layer 10, and directed toward the light output surface by the light distribution control structure, most of the light LR1 passes through the first principal surface. On the other hand, 3% to 5% of the light LR2 directed toward the light output surface is Fresnel-reflected by the first principal surface. The Fresnel-reflected light LR2 enters the internal space 64 from the first inclined surface ISa, passes through the internal space 64, and is emitted in the Z direction from the back surface of the lighting device 900_L. The first inclined surface ISa, which has a convex curved surface, functions as a lens, forming an image of the light LR2 that has passed through the first inclined surface ISa. As a result, when the lighting device 900_L is viewed from the rear side, a pattern, i.e., a ghost, occurs due to the multiple internal spaces 64. The occurrence of the ghost reduces the design quality of the lighting device 900_L when viewed from the rear side.

[0042] In contrast, in the lighting device 100A_L according to the embodiment of the present invention, the anti-reflection layer 40A can suppress Fresnel reflection of light directed toward the light exit surface. As a result, the occurrence of ghost images is suppressed when the lighting device 100A_L is viewed from the back side, and the lighting device 100A_L appears transparent. The anti-reflection layer 40A not only efficiently emits light LR from the light exit surface to improve the light extraction efficiency, but also suppresses the occurrence of ghost images when the lighting device 100A_L is viewed from the back side, thereby improving the design of the lighting device 100A_L.

[0043] The occurrence of ghosts can be suppressed without the antireflection layer 40A. Next, with reference to FIG. 4, a light-guiding member for a lighting device and a lighting device according to another embodiment of the present invention will be described. FIG. 4 shows a schematic cross-sectional view of a lighting device 100B_L according to another embodiment of the present invention. As shown in FIG. 4, the lighting device 100B_L differs from the lighting device 100A_L shown in FIG. 1 in that the light-guiding member 100B has an anti-glare layer 40B instead of the antireflection layer 40A. Here, the differences from the lighting device 100A_L shown in FIG. 1 will be mainly described.

[0044] The anti-glare layer 40B is disposed on the first principal surface side of the light guide layer 10, and has irregular asperities on a surface 40BS opposite to the light guide layer 10. The light exit surface of the lighting device 100B_L is the surface 40BS of the anti-glare layer 40B. The refractive indices of the anti-glare layer 40B and the base layer 32 are designed to be approximately equal to each other, which makes it possible to suppress Fresnel reflection of light directed toward the light exit surface side at the interface between the anti-glare layer 40B and the base layer 32.

[0045] The anti-glare layer 40B diffuses light directed toward the light exit surface that is reflected by the surface 40BS in various directions, thereby suppressing the occurrence of ghosting when the illumination device 100B_L is viewed from the rear. However, excessive diffusion of light reflected by the surface 40BS can cause the illumination device 100B_L to appear cloudy when viewed from the rear, thereby reducing the design of the illumination device 100B_L. When the arithmetic mean roughness Ra of the surface 40BS of the anti-glare layer 40B is 0.8 μm or more and 1000 μm or less and the maximum height Rz is 5.0 μm or more and 1000 μm or less, the occurrence of ghosting when the illumination device 100B_L is viewed from the rear can be suppressed and the illumination device 100B_L can be suppressed from appearing cloudy. The arithmetic mean roughness Ra and the maximum height Rz can be measured, for example, using a laser microscope VK-X1000 manufactured by KEYENCE at a magnification of 5 times in a laser confocal mode.

[0046] Like the lighting device 100A_L shown in FIG. 1, the lighting device 100B_L shown in FIG. 4 can be characterized by, for example, a visible light transmittance of 60% or more and a haze value of less than 30%.

[0047] The occurrence of ghosting may be suppressed by both the anti-reflection layer 40A and the anti-glare layer 40B. Next, with reference to FIG. 5 , a light-guiding member for a lighting device and a lighting device according to yet another embodiment of the present invention will be described. FIG. 5 shows a schematic cross-sectional view of a lighting device 100C_L according to yet another embodiment of the present invention. As shown in FIG. 5 , the lighting device 100C_L differs from the lighting device 100B_L shown in FIG. 4 in that the light-guiding member 100C further includes an anti-reflection layer 40A. The light exit surface of the lighting device 100C_L is the surface of the anti-reflection layer 40A opposite the light-guiding layer 10. Here, the differences from the lighting device 100B_L shown in FIG. 4 will be mainly described.

[0048] By disposing the anti-reflection layer 40A on the anti-glare layer 40B, Fresnel reflection of light directed toward the light exit surface at the interface between the anti-glare layer 40B and the anti-reflection layer 40A can be suppressed. Any reflected light that still occurs can be diffused in various directions by the surface 40BS. Compared to the lighting device 100B_L shown in FIG. 4 , the lighting device 100C_L shown in FIG. 5 not only more efficiently emits light LR from the light exit surface to improve light extraction efficiency, but also further suppresses the occurrence of ghosting when viewing the lighting device 100C_L from the back side, thereby further improving the design of the lighting device 100C_L.

[0049] The lighting device 100C_L shown in FIG. 5 may have the characteristics of, for example, a visible light transmittance of 60% or more and a haze value of less than 30%, similar to the lighting device 100A_L shown in FIG. 1 and the lighting device 100B_L shown in FIG. 4 .

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, the refractive indexes of the components shown below are those measured with an ellipsometer at a wavelength of 550 nm.

[0051] Example 1 The lighting device of Example 1 has substantially the same structure as lighting device 100A_L shown in Figure 1. The light source of Example 1 includes 18 LED devices (Nichia Chemical, model number NS2W266G-HG) arranged at 6 mm intervals (the center-to-center distance between adjacent LEDs) along the light receiving section. The luminous flux of light emitted from each LED was 16.3 lm (20 mA), and the light distribution angle was 120° (the angle at which the brightness intensity is 1 / 2).

[0052] The light-guiding member of Example 1 has a laminated structure consisting of an anti-reflection layer / substrate layer / acrylic adhesive layer / acrylic plate / acrylic adhesive layer / textured film / polyester adhesive layer / PET (polyethylene terephthalate) film. The textured film was made of PBT. The light-guiding member had a width of 120 mm and a length of 170 mm. The refractive index and thickness of each component other than the substrate layer and anti-reflection layer included in the light-guiding member of Example 1 are shown in Table 1.

[0053]

[0054] In the laminate of Example 1 consisting of the substrate layer and the antireflection layer, the substrate layer is a TAC (triacetyl cellulose) film, and the antireflection layer has a laminate structure consisting of a hard coat layer, a high refractive index layer, and a low refractive index layer, in that order from the side closest to the TAC film. The hard coat layer is formed of acrylic, the high refractive index layer is formed of ZrO, and the low refractive index layer is formed of hollow silica. The refractive index and thickness of each component included in the laminate of Example 1 consisting of the substrate layer and the antireflection layer are shown in Table 2.

[0055]

[0056] The light guide member of the first embodiment can be manufactured by a known technique.

[0057] Example 2 The lighting device of Example 2 has substantially the same structure as the lighting device 100A_L shown in FIG. 1 . The lighting device of Example 2 has the same configuration as the lighting device of Example 1, except for the laminate consisting of the substrate layer and the anti-reflection layer. Of the laminate consisting of the substrate layer and the anti-reflection layer of Example 2, the substrate layer is a TAC film, and the anti-reflection layer has a laminate structure consisting of, in order from the side closest to the TAC film, a hard coat layer / a low refractive index layer. The hard coat layer is formed of acrylic, and the low refractive index layer is formed of hollow silica. The refractive index and thickness of each component included in the laminate consisting of the substrate layer and the anti-reflection layer of Example 2 are shown in Table 3.

[0058]

[0059] The light guide member of Example 2 can be manufactured by a known method.

[0060] Example 3 The lighting device of Example 3 has substantially the same structure as the lighting device 100B_L shown in FIG. 4 . The lighting device of Example 3 has the same configuration as the lighting device of Example 1, except for the laminate consisting of the base material layer and the anti-glare layer. In the laminate consisting of the base material layer and the anti-glare layer of Example 3, the base material layer is a TAC film, and the anti-glare layer is a textured layer formed of PMMA particles. The arithmetic mean roughness Ra of the surface of the textured layer was 1.2 μm, and the maximum height Rz was 6.0 μm or less. The refractive index and thickness of each component included in the laminate consisting of the base material layer and the anti-glare layer of Example 3 are shown in Table 4.

[0061]

[0062] The light guide member of Example 3 can be manufactured by a known method.

[0063] Example 4 The lighting device of Example 4 has substantially the same structure as the lighting device 100C_L shown in FIG. 5 . The lighting device of Example 4 has the same configuration as the lighting device of Example 1, except for the laminate consisting of the substrate layer, anti-glare layer, and anti-reflection layer. In the laminate consisting of the substrate layer, anti-glare layer, and anti-reflection layer of Example 4, the substrate layer is an acrylic film, the anti-glare layer is a roughened layer, and the anti-reflection layer is a low refractive index layer. The roughened layer is formed of PMMA particles, and the low refractive index layer is formed of hollow silica. The arithmetic mean roughness Ra of the surface of the roughened layer was 0.1 μm, and the maximum height Rz was 0.6 μm or less. Table 5 shows the refractive index and thickness of each component included in the laminate consisting of the substrate layer, anti-glare layer, and anti-reflection layer of Example 4.

[0064]

[0065] The light guide member of Example 4 can be manufactured by a known method.

[0066] <Comparative Example 1> The lighting device of Comparative Example 1 differs from the lighting device of Example 1 in that it has a PET film as a base layer and does not have an anti-reflection layer. The refractive index of the PET film was 1.65 and the thickness was 75 μm. In the lighting device of Comparative Example 1 which does not have an anti-reflection layer, Fresnel reflection of light directed toward the exit surface side is not suppressed.

[0067] <Reference Example> The lighting device of the reference example has substantially the same structure as the lighting device 900_L shown in Fig. 8. The lighting device of the reference example has a configuration in which the antireflection layer, the base layer, and the acrylic adhesive layer arranged on the first main surface side of the acrylic plate are removed from the lighting device of Example 1.

[0068] Next, the measurement results of the luminance distribution on the back surface of the illumination devices of Examples 1 to 4, the Comparative Example, and the Reference Example, and the presence or absence of ghosting, will be described with reference to Figures 6A to 6F. Figures 6A to 6F respectively show (a) the luminance distribution in a rectangular region (120 mm in the width direction, 48.5 mm in the length direction) located in the center of the back surface of the illumination devices of Examples 1 to 4, the Comparative Example, and the Reference Example, and (b) a graph showing the relationship between the position on a horizontal line (parallel to the width direction) passing through the center of the rectangular region and the luminance.

[0069] As shown in (a) of Figures 6A to 6D, no ghosting occurred when viewing the illumination devices of Examples 1 to 4 from the back. As shown in (b) of Figures 6A to 6D, the luminance changed gradually with respect to position, ignoring small vibrations.

[0070] In contrast, as shown in (a) of Figures 6E and 6F, when the illumination devices of Comparative Example 1 and Reference Example were viewed from behind, ghost images were generated. As shown in (b) of Figures 6A to 6D, the brightness fluctuated significantly with respect to position.

[0071] The maximum contrast ratio of luminance at a specific portion on the back surface of the lighting devices of Examples 1 to 4, Comparative Example 1, and Reference Example and the presence or absence of ghosting are shown in Table 6. The luminance at a specific portion on the back surface is the luminance at a portion symmetrical about the center, 17.3 mm long, on a horizontal line passing through the center of the above-mentioned rectangular region (see the region surrounded by the thick line in (b) of Figures 6A to 6F).

[0072]

[0073] In the lighting devices of Examples 1 to 4 in which no ghosting occurred, the maximum contrast ratio of luminance at a specific portion on the rear surface was 1.1 or less.

[0074] Furthermore, the inventors investigated the maximum contrast ratio of brightness in a square area (17.3 mm) located at any location within the area where light leaks from the back surface of the lighting device. The "light leakage area" refers to an area on the back surface where the brightness is 70% or more of the maximum brightness. The maximum contrast ratio of brightness in the square area located at any location within the area where light leaks from the back surface of the lighting devices in Examples 1 to 4, where no ghosting occurs, was 1.1 or less.

[0075] From the above, it has been found that by arranging an anti-reflection layer and / or an anti-glare layer on the first main surface side of the light guide layer, it is possible to suppress the occurrence of ghosts when the lighting device is viewed from the back.

[0076] Next, the arithmetic mean roughness Ra and maximum height Rz of the exit surface, haze value, luminous reflectance Y (wavelength 550 nm), and presence or absence of ghosting in the lighting devices of Examples 1 to 4 and Comparative Example 1 are shown in Table 7. Even in the lighting devices of Examples 1 and 2 and the lighting device of Comparative Example 1, which do not have an anti-glare layer, some degree of unevenness was formed on the exit surface during the manufacturing process.

[0077]

[0078] The haze values ​​of the lighting devices of Examples 1 to 4 were 4.0% or less, and the lighting devices were hardly cloudy. Furthermore, the luminous reflectance Y of the lighting devices of Examples 1 to 4 was 2.0% or less, and the lighting devices had high transparency.

[0079] The lighting device according to the embodiment of the present invention is not limited to the above example, and can be modified in various ways. Figures 7A, 7B, and 7C show examples of lighting devices having a light distribution control structure similar to that of lighting device 100A_L shown in Figure 1.

[0080] 7A differs from the lighting device 100A_L shown in FIG. 1 in that a hard coat layer 70 is disposed on the base layer 34 via an adhesive layer 58. The pencil hardness of the hard coat layer 70 may be, for example, H or higher. The hard coat layer 70 can improve the scratch resistance of the surface of the lighting device 100A1_L.

[0081] The lighting device 100A2_L shown in FIG. 7B differs from the lighting device 100A_L shown in FIG. 1 in that a low-refractive index layer 20 is disposed instead of the substrate layer 34. In the lighting device 100A_L shown in FIG. 1, light emitted from the light source LS, passing through the shaped film 62 without passing through the internal space 64, and traveling toward the substrate layer 34 is totally internally reflected at the interface between the substrate layer 34 and air and directed toward the light exit surface. If the upper surface of the substrate layer 34 is contaminated, total internal reflection may not occur in the contaminated area. This can result in problems such as light leakage from the contaminated area and / or changes in the distribution of light propagating within the light-guiding member. In contrast, in the lighting device 100A2_L shown in FIG. 7B, the interface between the shaped film 62 and the low-refractive index layer 20 is an interface that can totally internally reflect light propagating within the shaped film 62. The "interface between the shaping film 62 and the low refractive index layer 20" refers to the interface between the shaping film 62 and the adhesive layer 56, the interface between the low refractive index layer 20 and the adhesive layer 56, and / or the region between both interfaces. Light propagating within the shaping film 62 is not affected by the state of the interface between the low refractive index layer 20 and air. Therefore, the low refractive index layer 20 can improve the antifouling properties of the surface of the lighting device 100A2_L.

[0082] 7C differs from the lighting device 100A2_L shown in Fig. 7B in that a hard coat layer 70 is disposed on the low refractive index layer 20 via an adhesive layer 58. The hard coat layer 70 and the low refractive index layer 20 can improve the scratch resistance and stain resistance of the surface of the lighting device 100A2_L, respectively.

[0083] The hard coat layer 70 and the low refractive index layer 20 can be formed by known methods using known materials, and can also be applied to the lighting device 100B_L according to the other embodiment of the present invention and the lighting device 100C_L according to the still other embodiment of the present invention.

[0084] A preferred example of each component of the lighting device according to the embodiment of the present invention will be described.

[0085] The shaped film for forming the internal space can be manufactured, for example, as follows. A textured film was manufactured according to the method described in JP-A 2013-524288. Specifically, the surface of a polymethyl methacrylate (PMMA) film was coated with lacquer (Finecure RM-64 manufactured by Sanyo Chemical Industries, Ltd.), an optical pattern was embossed on the film surface containing the lacquer, and then the lacquer was cured to produce the desired textured film. The total thickness of the textured film was 130 μm, and the haze was 0.8%.

[0086] The light guide layer 10 is made of a known material with high transmittance for visible light. The light guide layer 10 is made of, for example, an acrylic resin such as polymethyl methacrylate (PMMA), a polycarbonate (PC) resin, a cycloolefin resin, or glass (for example, quartz glass, alkali-free glass, or borosilicate glass). The refractive index n of the light guide layer 10 is ＧＰ is, for example, 1.40 or more and 1.80 or less. The thickness of the light guide layer 10 can be set appropriately depending on the application. The thickness of the light guide layer 10 is, for example, 0.05 mm or more and 50 mm or less.

[0087] The thickness of the base layers 32, 34 is, for example, 1 μm to 1000 μm, preferably 10 μm to 100 μm, and more preferably 20 μm to 80 μm. The refractive index of the base layers 32, 34 is independently preferably 1.40 to 1.70, and more preferably 1.43 to 1.65.

[0088] The thicknesses of the adhesive layers 52, 54, 56, and 58 are each independently, for example, from 0.1 μm to 100 μm, preferably from 0.3 μm to 100 μm, and more preferably from 0.5 μm to 50 μm. The refractive indexes of the adhesive layers 52, 54, 56, and 58 are each independently preferably from 1.42 to 1.60, and more preferably from 1.47 to 1.58. The refractive indexes of the adhesive layers 52, 54, 56, and 58 are preferably close to the refractive index of the light-guiding layer 10 or the shaping film 62 to which they are in contact, and the absolute value of the difference in refractive index is preferably 0.2 or less.

[0089] The adhesive layer 56 can preferably be bonded without filling the recesses 64 on the surface of the shaped film 62. Suitable adhesives for forming the adhesive layer 56 include those described in International Publication Nos. 2021 / 167090, 2021 / 167091, or International Application PCT / JP2022 / 004554 by the present applicant. The entire disclosures of these applications are incorporated herein by reference. In particular, polyester-based adhesives described in International Application PCT / JP2022 / 004554 are preferred.

[0090] The anti-reflection layer 40A may be a single low refractive index layer, but is preferably an alternate laminate of high refractive index layers and low refractive index layers. The high refractive index layer has a refractive index of, for example, 1.9 or more, preferably 2.0 or more. Examples of high refractive index materials include titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, indium tin oxide (ITO), antimony-doped tin oxide (ATO), etc. Among these, titanium oxide or niobium oxide is preferred. The low refractive index layer has a refractive index of, for example, 1.6 or less, preferably 1.5 or less. Examples of low refractive index materials include silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, lanthanum fluoride, etc. Among these, silicon oxide is preferred. In particular, niobium oxide (Nb ２ O ５ ) thin film as a low refractive index layer, and silicon oxide (SiO ２ In addition to the low refractive index layer and the high refractive index layer, a medium refractive index layer having a refractive index of about 1.6 to 1.9 may be provided.

[0091] The thickness of each of the high-refractive-index layer and the low-refractive-index layer is about 5 nm to 200 nm, preferably about 15 nm to 150 nm, and may be designed to reduce the reflectance of visible light depending on the refractive index, layer structure, etc.

[0092] The anti-reflection layer 40A is preferably laminated on the hard coat layer via a primer layer. Materials constituting the primer layer include, for example, metals such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, tungsten, aluminum, zirconium, and palladium; alloys of these metals; and oxides, fluorides, sulfides, or nitrides of these metals. Among these, oxides are preferred as the material for the primer layer, with silicon oxide being particularly preferred. The primer layer is preferably an inorganic oxide layer having a lower oxygen content than the stoichiometric composition. Among inorganic oxides with a non-stoichiometric composition, those with the composition formula SiO ｘ Silicon oxide represented by the formula (0.5≦x<2) is preferred. The thickness of the primer layer is, for example, about 1 nm or more and 20 nm or less, and preferably 3 nm or more and 15 nm or less.

[0093] The method for forming the thin film constituting the anti-reflection layer 40A is not particularly limited, and either a wet coating method or a dry coating method may be used. Dry coating methods such as vacuum deposition, CVD, sputtering, and electron beam vapor deposition are preferred because they can form thin films with a uniform thickness. Among these, sputtering is preferred because it has excellent uniformity in film thickness and is easy to form a dense film. For example, the anti-reflection layer described in JP 2020-52221 A can be suitably used. The entire disclosure of JP 2020-52221 A is incorporated herein by reference.

[0094] The antireflection layer 40A does not necessarily have to have a single low refractive index layer or an alternating laminate of high refractive index layers and low refractive index layers. The antireflection layer 40A may have a so-called moth-eye structure. Alternatively, the antireflection layer 40A may be formed of a material having voids, similar to the low refractive index layer 20 described below.

[0095] The refractive index n of the low refractive index layer 20 Ｌ１are each independently, for example, preferably 1.30 or less, more preferably 1.20 or less, and even more preferably 1.15 or less. The low refractive index layer 20 is preferably solid, and the refractive index is, for example, 1.05 or more. The difference between the refractive index of the light guide layer 10 and the refractive index of the low refractive index layer 20 is preferably 0.20 or more, more preferably 0.23 or more, and even more preferably 0.25 or more. The low refractive index layer 20 having a refractive index of 1.30 or less can be formed using, for example, a porous material. The thickness of the low refractive index layer 20 is each independently, for example, 0.3 μm or more and 5 μm or less.

[0096] When the low refractive index layer is a porous material having voids therein, the porosity is preferably 35 vol% or more, more preferably 38 vol% or more, and particularly preferably 40 vol% or more. Within this range, a low refractive index layer with a particularly low refractive index can be formed. The upper limit of the porosity of the low refractive index layer is, for example, 90 vol% or less, preferably 75 vol% or less. Within this range, a low refractive index layer with excellent strength can be formed. The porosity is a value calculated from the refractive index measured with an ellipsometer using the Lorentz-Lorenz formula.

[0097] The low-refractive index layer may be, for example, a voided low-refractive index layer as disclosed in Patent Document 3. The entire disclosure of Patent Document 3 is incorporated herein by reference. Specifically, the voided low-refractive index layer includes silica particles, microporous silica particles, approximately spherical particles such as hollow silica nanoparticles, fibrous particles such as cellulose nanofibers, alumina nanofibers, and silica nanofibers, and flat particles such as nanoclay composed of bentonite. In one embodiment, the voided low-refractive index layer is a porous body formed by direct chemical bonding of particles (e.g., microporous particles). Furthermore, at least some of the particles constituting the voided low-refractive index layer may be bonded to each other via a small amount (e.g., less than the mass of the particles) of a single binder component. The porosity and refractive index of the low-refractive index layer can be adjusted by the particle size, particle size distribution, etc. of the particles constituting the low-refractive index layer.

[0098] Methods for obtaining a low refractive index layer having voids include, for example, methods described in JP 2010-189212 A, JP 2008-040171 A, JP 2006-011175 A, WO 2004 / 113966 A, and references thereto. The disclosures of JP 2010-189212 A, JP 2008-040171 A, JP 2006-011175 A, and WO 2004 / 113966 A are incorporated herein by reference in their entirety.

[0099] A porous silica body can be suitably used as the low refractive index layer having voids. The porous silica body can be produced by, for example, the following methods. Examples include a method of hydrolyzing and polycondensing a silicon compound; hydrolyzable silanes and / or silsesquioxane, and at least one of their partial hydrolyzates and dehydration condensates; a method using porous particles and / or hollow microparticles; a method of producing an aerogel layer by utilizing the springback phenomenon; and a method using a pulverized gel in which a gel-like silicon compound obtained by a sol-gel method is pulverized and the resulting pulverized microporous particles are chemically bonded together with a catalyst or the like. However, the low refractive index layer is not limited to a porous silica body, and the production method is not limited to the exemplified methods, and any production method may be used. However, the porous layer is not limited to a porous silica body, and the production method is not limited to the exemplified methods, and any production method may be used. The silsesquioxane may be (RSiO １．５ , R is a hydrocarbon group) as a basic structural unit, and ２ Although it is strictly different from silica, which has silsesquioxane as a basic structural unit, it has something in common with silica in that it has a network structure cross-linked by siloxane bonds. Therefore, in this specification, porous materials containing silsesquioxane as a basic structural unit are also referred to as porous silica materials or silica-based porous materials.

[0100] The porous silica material can be composed of microporous particles of a gel-like silicon compound bonded to one another. Examples of the microporous particles of the gel-like silicon compound include pulverized gel-like silicon compounds. The porous silica material can be formed, for example, by applying a coating liquid containing pulverized gel-like silicon compounds to a substrate. The pulverized gel-like silicon compounds can be chemically bonded (e.g., siloxane bonded) by, for example, the action of a catalyst, light irradiation, heating, etc.

[0101] Hardness H of hard coat layer 70 Ｈ１ The hardness H of the hard coat layer 70 is preferably H or more, more preferably 2H or more, and even more preferably 4H or more, in terms of pencil hardness. Ｈ１ Although there is no particular upper limit to the pencil hardness, it is preferably 6H or less, more preferably 5H or less. The pencil hardness is measured by a method conforming to the "Pencil Hardness Test" of JIS K 5400. The thickness of each hard coat layer 70 is independently preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less, and even more preferably 3 μm or more and 15 μm or less. When the thickness of the hard coat layer 70 is within this range, it has good scratch resistance.

[0102] The hard coat layer 70 can be made of any suitable material as long as it satisfies the above-mentioned characteristics. The hard coat layer 70 is, for example, a cured layer of a thermosetting resin or an ionizing radiation (e.g., visible light, ultraviolet) curable resin. Examples of such curable resins include acrylates such as urethane (meth)acrylate, polyester (meth)acrylate, and epoxy (meth)acrylate, silicon resins such as polysiloxane, unsaturated polyester, and epoxy resin. The hard coat layer 70 can be formed, for example, by applying a material containing a solvent and a curable compound to the surface of the target substrate and curing it. Details of hard coat layers suitable for use as the hard coat layer 70 are described, for example, in Japanese Patent Application Laid-Open No. 2011-237789. The entire disclosure of Japanese Patent Application Laid-Open No. 2011-237789 is incorporated herein by reference.

[0103] The light-guiding member for a lighting device and the lighting device according to the embodiment of the present invention can emit light from one of two main surfaces facing in opposite directions and appear transparent when viewed from the other main surface side, and can provide new uses that combine practicality and design.

[0104] 10: light-guiding layer, 20: low-refractive-index layer, 32, 34: substrate layer, 40A: anti-reflection layer, 40B: anti-glare layer, 52, 54, 56, 58: adhesive layer, 60: direction-changing layer, 62: shaping film, 64: internal space, recess, 70: hard coat layer, 100A, 100B, 100C, 900: light-guiding member for lighting device, 100A_L, 100B_L, 100C_L, 900_L: lighting device, ISa: first inclined surface, ISb: second inclined surface, LR, LR1, LR2: light, LS: light source

Claims

1. A light guide member for a lighting device having an exit surface, comprising: a light receiving portion that receives light emitted from a light source, a light guide layer having a first main surface on the exit surface side and a second main surface opposite to the first main surface; a light distribution control structure having a plurality of internal spaces, each of the plurality of internal spaces having a first inclined surface that directs a part of the light propagating in the light guide layer toward the exit surface side by total internal reflection, and a second inclined surface opposite to the first inclined surface, and when viewed from the normal direction of the first main surface of the light guide layer, the first inclined surface forms a convex curved surface on the light source side; a light distribution control structure; an antireflection layer and / or an antiglare layer disposed on the first main surface side of the light guide layer; A light guide member for a lighting device having the above.

2. The light guide member for a lighting device according to claim 1, wherein the plurality of internal spaces are discretely arranged in the light guide direction of the light guide layer and in a direction intersecting the light guide direction.

3. Having the antireflection layer disposed on the first main surface side of the light guide layer, The light guide member for a lighting device according to claim 1 or 2, wherein the antireflection layer has a single dielectric layer having a refractive index lower than that of the light guide layer, or a multilayer laminate composed of a plurality of dielectric layers having different refractive indices.

4. Having the antireflection layer disposed on the first main surface side of the light guide layer, The light guide member for a lighting device according to claim 1 or 2, wherein the antireflection layer has a moth-eye structure or is formed of a material having voids.

5. Having the antiglare layer disposed on the first main surface side of the light guide layer, The light guide member for a lighting device according to claim 1 or 2, wherein the arithmetic mean roughness Ra of the surface of the antiglare layer opposite to the light guide layer is 0.8 μm or more and 1000 μm or less, and the maximum height Rz is 5.0 μm or more and 1000 μm or less.

6. The inclination angle θa of the first inclined surface is 10° or more and 70° or less, The light guide member for a lighting device according to claim 1 or 2, wherein the inclination angle θb of the second inclined surface is 50° or more and 100° or less.

7. The light guide member for a lighting device according to claim 1 or 2, wherein the light distribution control structure is formed in a direction conversion layer provided on the first main surface side or the second main surface side of the light guide layer.

8. The light guide member for a lighting device according to claim 1 or 2, wherein the ratio of the area of the plurality of internal spaces to the area of the light guide layer when viewed from the normal direction to the first main surface of the light guide layer is 80% or less.

9. The light guide member for a lighting device according to claim 1 or 2, having a low refractive index layer having a refractive index lower than that of the light guide layer on the second main surface side of the light guide layer.

10. The light guide member for a lighting device according to claim 1 or 2, wherein the maximum contrast ratio of the luminance in a square region having a side length of 17.3 mm, which is located at an arbitrary position among the regions where light leaks from the back surface located on the second main surface side of the light guide member for a lighting device, is 1.1 or less.

11. The light guide member for a lighting device according to claim 1 or 2, having a visible light transmittance of 60% or more and a haze value of less than 30%.

12. The light guide member for a lighting device according to claim 1 or 2, a light source that emits light toward the light receiving portion, A lighting device comprising:

13. The lighting device according to claim 12, wherein the light source includes a plurality of LED devices arranged along the light receiving portion of the light guide layer.