Light guide member for lighting device, and lighting device

Abstract

Provided is a light guide member for a lighting device, having a first emission surface and a second emission surface. Said light guide member includes: a light receiving section that receives light emitted from a light source; a light guide layer (10) having a first main surface on a first emission-surface side, and a second main surface on a second emission-surface side; and a light distribution control structure having a plurality of interior spaces (64). Each of the plurality of interior spaces (64) has a first sloping surface (ISa) that directs, by total internal reflection, a portion of the light that propagates inside the light guide layer (10) toward the first emission surface. The plurality of interior spaces (64) are discretely arranged in the light-guiding direction of the light guide layer (10) and in a direction intersecting the light-guiding direction. The first emission surface emits an illumination beam for illuminating a target object (70), and the second emission surface emits a reflected beam that is produced by the target object (70) being illuminated with the illumination beam and that passes through 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] There is a need to illuminate paintings displayed in dark rooms in museums without compromising their aesthetic appeal. Spotlights are commonly used to illuminate objects such as paintings. However, spotlights have the drawback of compromising the aesthetic appeal of the object and the spotlight. Furthermore, if a viewer is positioned between the object and the spotlight, their shadow will be cast onto the object.

[0006] Therefore, an object of the present invention is to provide a transparent lighting device that can be placed in front of an object and emits light to illuminate the object, and a light-guiding member for a lighting device that is suitable for use in such a lighting device.

[0007] According to embodiments of the present invention, there is provided the following solutions: [Item 1] A light-guiding member for a lighting device having a first exit surface and a second exit surface opposite to the first exit surface, comprising: a light-receiving unit that receives light emitted from a light source, a light-guiding layer having a first main surface on the first exit surface side and a second main surface on the second exit surface side, and 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 first exit surface by total internal reflection, and a second inclined surface opposite to the first inclined surface, the plurality of internal spaces being discretely arranged in a light-guiding direction of the light-guiding layer and a direction intersecting the light-guiding direction, the first exit surface emitting irradiation light for irradiating an object, and the second exit surface emitting reflected light that is generated by irradiating the object with the irradiation light and that passes through the light-guiding layer. [Item 2] The light-guiding member for a lighting device according to item 1, wherein an inclination angle θa of the first inclined surface is 20° or more and 50° or less, and an inclination angle θb of the second inclined surface is 70° or more and 90° or less. [Item 3] The light-guiding member for a lighting device according to item 1 or 2, 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. [Item 4] The light-guiding member for a lighting device according to any one of items 1 to 3, 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. [Item 5] The light-guiding member for a lighting device according to any one of items 1 to 4, wherein when viewed from the normal direction to the first main surface of the light-guiding layer, the first inclined surface forms a curved surface that is convex toward the light source. [Item 6] The light-guiding member for an illumination device according to any one of Items 1 to 5, wherein the illumination light emitted from the first light exit surface has a first light distribution, and a light ray with the highest intensity in the first light distribution is defined as a first principal ray, and a polar angle θ1 of the first principal ray from a normal to the first light exit surface is equal to or greater than 0° and equal to or less than 40°.[Item 7] The light-guiding member for a lighting device according to any one of items 1 to 6, wherein the second exit surface emits light that propagates through the light-guiding layer and does not pass through the object, the light having a second light distribution, and wherein a second principal ray is a light ray with the highest intensity in the second light distribution, and a polar angle θ2 of the second principal ray from a normal to the second exit surface is 40° or more and 85° or less. [Item 8] The light-guiding member for a lighting device according to any one of items 1 to 7, comprising a first antireflection layer disposed on the first principal surface side of the light-guiding layer. [Item 9] The light-guiding member for a lighting device according to any one of items 1 to 8, comprising a second antireflection layer disposed on the second principal surface side of the light-guiding layer. [Item 10] The light-guiding member for a lighting device according to item 9, comprising a low-refractive index layer between the light-guiding layer and the second antireflection layer, the low-refractive index layer having a refractive index lower than that of the light-guiding layer. [Item 11] A light-guiding member for a lighting device according to any one of items 1 to 10, having a visible light transmittance of 60% or more and a haze value of less than 30%. [Item 12] A lighting device comprising: the light-guiding member for a lighting device according to any one of items 1 to 11; and a light source that emits light toward the light-receiving unit.

[0008] According to an embodiment of the present invention, for example, the design quality of the appearance including the object and the lighting device is not reduced, and the shadow of the observer is not projected onto the object regardless of the observer's position.

[0009] 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 photograph of an object seen through the lighting device of Example 1. FIG. 8 is a photograph of an object seen through the lighting device of Example 2. FIG. 9 is a photograph of an object seen through a lighting device of a comparative example. FIG. 10 is a schematic cross-sectional view of another lighting device 100A1_L according to an embodiment of the present invention. FIG. 11 is a schematic cross-sectional view of yet another lighting device 100A2_L according to an embodiment of the present invention.

[0010] 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.

[0011] FIG. 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 two light-emitting surfaces facing in opposite directions. The lighting device 100A_L can be placed in front of an object 70. The lighting device 100A_L and the object 70 may be placed with a gap between them or may be placed so that they come into contact with each other. The distance between the lighting device 100A_L and the object 70 may be, for example, 0 cm or more and 100 cm or less, more preferably 50 cm or less, and even more preferably 10 cm or less. The object 70 may be, for example, a painting, a poster, an advertisement, a reflective display, or electronic paper.

[0012] The illumination device 100A_L has a first exit surface (bottom in FIG. 1 ) that emits illumination light LRa for illuminating the object 70, and a second exit surface (top in FIG. 1 ) that emits reflected light LRb, which is generated by illuminating the object 70 with the illumination light LRa and passes through the illumination device 100A_L. Light LRc, which is different from the reflected light LRb, is also emitted from the second exit surface; this light LRc will be described later. The illumination light LRa is emitted in the −Z direction in FIG. 1 , and the reflected light LRb is emitted in the Z direction. The reflected light LRb enters the eyes of an observer positioned on the second exit surface side, allowing the observer to view the object 70. Unlike a configuration in which a spotlight is used to illuminate the object 70, the observer's shadow is not cast on the object 70, regardless of the observer's position. In a configuration using a spotlight, a location where the spotlight can be installed near the object 70 is required, which limits the location where the object 70 can be placed. In contrast, the lighting device 100A_L can be placed in front of the object 70, which increases the degree of freedom in the location where the object 70 can be placed.

[0013] 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 section that receives the light emitted from the light source LS, a light-guiding layer 10 having a first main surface on the first emission side and a second main surface on the second emission side, and a light distribution control structure having a plurality of internal spaces 64. The light-receiving section may be, for example, the light-receiving side surface of the light-guiding layer 10 on the light source LS side. The light-guiding member 100A further includes a first anti-reflection layer 40A disposed on the first main surface side of the light-guiding layer 10 via an adhesive layer 52 and a first base layer 30A, and a second anti-reflection layer 40B disposed on the second main surface side of the light-guiding layer 10 via an adhesive layer 56 and a second base layer 30B. In manufacturing the light-guiding member 100A, the first base layer 30A having the first antireflection layer 40A formed thereon is disposed on the first main surface side of the light-guiding layer 10 via an adhesive layer 52. Similarly, the second base layer 30B having the second antireflection layer 40B formed thereon is disposed on the second main surface side of the light-guiding layer 10 via an adhesive layer 56. The first emission surface of the lighting device 100A_L is the surface of the first antireflection layer 40A opposite to the light-guiding layer 10, and the second emission surface is the surface of the second antireflection layer 40B opposite to the light-guiding layer 10.

[0014] Each of the multiple internal spaces 64 has a first inclined surface ISa that directs a portion of the light propagating within the light-guiding layer 10 toward the first exit surface by total internal reflection (TIR), and a second inclined surface ISb opposite the first inclined surface ISa.

[0015] 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 arranged 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 numeral as the internal spaces 64) on its surface, and an adhesive layer 56. Note that the internal spaces 64 are not limited to this example, and may be formed in a direction-changing layer arranged on the first main surface side of the light-guiding layer 10, for example. Alternatively, a plurality of internal spaces 64 may be formed within the light-guiding layer 10.

[0016] 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 first exit surface. The illumination light emitted from the first exit surface has a first light distribution. The second exit surface emits, in addition to reflected light LRb, leaked light LRc that propagates within the light guide layer 10 and does not pass through the object 70. The leaked light LRc has a second light distribution. The light ray with the greatest intensity in the first light distribution is defined as the first principal ray, and the light ray with the greatest intensity in the second light distribution is defined as the second principal ray. For example, the polar angle θ1 of the first principal ray from the normal to the first exit surface is smaller than the polar angle θ2 of the second principal ray from the normal to the second exit surface. For example, the polar angle θ1 is equal to or greater than 0° and less than 40°. The lower limit is preferably 5° or greater, and more preferably 10° or greater. If the reflectance of the object 70 is low or if the object 70 diffuses the irradiated light like paper, the polar angle θ1 may approach 0°. On the other hand, if the reflectance of the object 70 is high, a polar angle θ1 of 0° may cause the observer to perceive the reflected light as dazzling, potentially reducing the visibility of the object 70. Even in this case, the visibility of the object 70 can be improved by reducing the amount of light emitted from the light source LS to reduce the glare of the reflected light. The polar angle θ2 is greater than or equal to 40° and less than 85°.

[0017] By illuminating the object 70 with the highly directional irradiation light LRa, an observer whose eyes receive the reflected light LRb can clearly view the object 70. As a result, the visibility of the object 70 can be improved. Although the leaked light LRc is also emitted from the second exit surface, because the polar angle θ2 of the second orientation distribution is within the above-mentioned angle range, the leaked light LRc does not enter the observer's eyes, and the visibility of the object 70 is not reduced.

[0018] The proportion of light that is directed toward the first light exit surface side among the light propagating within the light guide layer 10, as well as the first and second light distributions, 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 or the like.

[0019] 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.

[0020] The first antireflection layer 40A may be 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 first antireflection layer 40A suppresses Fresnel reflection of light directed toward the first light-emitting surface at the interface between the first substrate layer 30A and the first antireflection layer 40A. The first antireflection layer 40A suppresses Fresnel reflectance to 3% or less. The illumination light LRa emitted from the first light-emitting surface is emitted from the light source LS, propagates through the light-guiding layer 10, is totally reflected by the first inclined surface ISa of the internal space 64, and passes through the light-guiding layer 10, the first substrate layer 30A, and the first antireflection layer 40A. Of course, the illumination light LRa may be refracted as it passes through the interface depending on the refractive index of the material constituting the interface.

[0021] The second antireflection layer 40B has a configuration similar to that of the first antireflection layer 40A. The second antireflection layer 40B suppresses Fresnel reflection of the reflected light LRb at the interface between the second base layer 30B and the second antireflection layer 40B. The second antireflection layer 40B suppresses the Fresnel reflectance to 3% or less. The reflected light LRb emitted from the second exit surface is light that passes through the light-guiding member 100A. Of course, when the reflected light LRb passes through the interface, it may be refracted according to the refractive index of the material that constitutes the interface.

[0022] In the light-guiding member 100A, a first base layer 30A is bonded to a first main surface of the light-guiding layer 10 by an adhesive layer 52, and a shaped film 62 is bonded to a second main surface of the light-guiding layer 10 by an adhesive layer 54. In the light-guiding member 100A, a second base layer 30B and the shaped film 62 are further bonded to each other by an adhesive layer 56, which together with the shaped film 62 constitutes a direction-changing layer 60. The light-guiding layer 10 and the base layers 30A and 30B may be transparent substrates or films. In the light-guiding member 100A, the light-guiding layer 10, the base layers 30A and 30B, the adhesive layers 52, 54, and 56, and the shaped film 62 are designed to have substantially equal refractive indices. As a result, Fresnel reflection of light directed toward the first emission surface and reflected light LRb at the interfaces between these components can be suppressed. Preferred configurations of the light guide layer 10, the base layers 30A and 30B, the anti-reflection layers 40A and 40B, the shape-transfer film 62, and the adhesive layers 52, 54, and 56 will be described later.

[0023] The lighting device 100A_L is transparent and 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, allowing objects (displays) to 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).

[0024] Since the lighting device 100A_L is transparent, the design of the appearance including the object 70 and the lighting device 100A_L is not impaired.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] The multiple internal spaces 64 are discretely arranged, for example, in the light guide direction and in a direction intersecting the light guide direction. The discrete arrangement of the multiple internal spaces 64 helps reduce the occupied area ratio of the internal spaces 64 to achieve high transmittance and / or a low haze value. 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 and 2 described below, Px is 200 μm and Py is 100 μm.

[0029] 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.

[0030] 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.

[0031] As shown in FIG. 3A , the cross-sectional shape of the internal space 64 is, for example, triangular. The inclination angle θa of the first inclined surface ISa on the light source side (light incident side) is, for example, 10° or more and 70° or less. If the inclination angle θa is less than 10°, the light utilization efficiency may be low, and if it exceeds 70°, processing may be difficult. Furthermore, the inclination angle θb of the second inclined surface ISb on the opposite side of the first inclined surface ISa is, for example, 50° or more and 100° or less. If the inclination angle θb is less than 50°, the amount of light in undesired directions may increase, and if it exceeds 100°, the amount of light in undesired directions may also increase. Furthermore, in order to increase the amount of irradiation light LRa emitted from the first exit surface and reduce the amount of leakage light LRc emitted from the second exit surface, 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 and 2 described below, the inclination angle θa of the first inclined surface ISa is 40°, and the inclination angle θb of the second inclined surface ISb is 70°.

[0032] As shown in Figures 3B and 3C, in the planar shape of the internal space 64 when viewed from the normal direction to the first main surface of the light guide layer 10, 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. Note that 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 and 2 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.

[0033] Next, a light-guiding member for a lighting device and a lighting device according to another embodiment of the present invention will be described with reference to Fig. 4. 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 it includes a low refractive index layer 20. Here, the differences from the lighting device 100A_L shown in Fig. 1 will be mainly described.

[0034] The light-guiding member 100B has a low-refractive-index layer 20 and a third base layer 30C between the light-guiding layer 10 and the second anti-reflection layer 40B, more specifically, between the shaping film 62 and the second base layer 30B. In manufacturing the light-guiding member 100B, the third base layer 30C on which the low-refractive-index layer 20 is formed is disposed on the second main surface side of the light-guiding layer 10. The low-refractive-index layer 20 has a refractive index lower than the refractive index of the light-guiding layer 10 and the shaping film 62. In the light-guiding member 100B, the shaping film 62 and the third base layer 30C are bonded together by an adhesive layer 56, and the low-refractive-index layer 20 and the second base layer 30B are bonded together by an adhesive layer 58.

[0035] 1 , which does not have a low refractive index layer 20, light emitted from a light source LS and incident on the interface between the second antireflection layer 40B and air at an angle equal to or greater than the critical angle is totally reflected and directed toward the shape-imparting film 62. If the upper surface of the second antireflection layer 40B is dirty, total reflection may not occur in the dirty areas. This can cause problems such as light leakage from the dirty areas and / or changes in the distribution of light propagating within the light-guiding member.

[0036] In contrast, in the lighting device 100B_L shown in FIG. 4 , the interface between the third base material layer 30C and the low-refractive index layer 20 is an interface that can totally reflect light that propagates through the shaped film 62 and is incident on the interface. Such light is not affected by the state of the interface between the second anti-reflection layer 40B and air. Therefore, the low-refractive index layer 20 can improve the antifouling properties of the second exit surface of the lighting device 100B_L.

[0037] The first irradiation light LRa1 and the first reflected light LRb1 shown in Fig. 4 are the same as the irradiation light LRa and the reflected light LRb shown in Fig. 1. The second irradiation light LRa2 shown in Fig. 4 is light that is emitted from the light source, is totally reflected at the interface between the third base layer 30C and the low-refractive-index layer 20, is totally reflected at the first inclined surface ISa of the internal space 64, and passes through the light-guiding layer 10, the first base layer 30A, and the first anti-reflection layer 40A. The second reflected light LRb2 shown in Fig. 4 is reflected light generated by irradiating the object 70 with the second irradiation light LRa2, and passes through the lighting device 100B_L.

[0038] In the lighting device 100A_L shown in Fig. 1 , the light emitted from the light source and totally reflected at the interface between the second antireflection layer 40B and the air can also be directed toward the first light exit surface by the light distribution control structure. In the lighting device 100B_L shown in Fig. 4 , the light emitted from the light source and totally reflected at the interface between the third base layer 30C and the low refractive index layer 20 can be more efficiently directed toward the first light exit surface. Therefore, in the lighting device 100B_L shown in Fig. 4 , the amount of reflected light emitted from the second light exit surface can be increased compared to the lighting device 100B_L shown in Fig. 1 .

[0039] 4 is transparent like the lighting device 100A_L shown in Fig. 1, and may have characteristics such as a visible light transmittance of 60% or more and a haze value of less than 30%. Because the lighting device 100B_L is transparent, the design of the appearance including the object 70 and the lighting device 100B_L is not impaired.

[0040] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Note that the refractive indexes of the components shown below are those measured with an ellipsometer at a wavelength of 550 nm, unless otherwise specified.

[0041] 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).

[0042] The light-guiding member of Example 1 has a laminated structure consisting of a first anti-reflection layer, a first substrate layer, an acrylic adhesive layer, an acrylic plate, an acrylic adhesive layer, a textured film, a polyester adhesive layer, a second substrate layer, and a second anti-reflection layer. The textured film was formed of PMMA. 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 first and second substrate layers and the first and second anti-reflection layers included in the light-guiding member of Example 1 are shown in Table 1.

[0043]

[0044] The laminate on the first main surface side of Example 1, consisting of the first substrate layer and the first antireflection layer, and the laminate on the second main surface side, consisting of the second substrate layer and the second antireflection layer, have the same configuration. Of each laminate, the substrate layer is a TAC film, and the antireflection layer has a laminate structure consisting of a hard coat layer / low refractive index layer, in that order from the side closest to the TAC film. 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 antireflection layer of Example 1 are shown in Table 2.

[0045]

[0046] The light guide member of Example 1 can be manufactured by a known method.

[0047] Example 2 The lighting device of Example 2 has substantially the same structure as the lighting device 100B_L shown in FIG. 4. The lighting device of Example 2 has the same configuration as the lighting device of Example 1, except that it has a third substrate layer, a low refractive index layer, and an acrylic adhesive layer between the polyester adhesive layer and the second substrate layer of Example 1, in that order from the side closest to the polyester adhesive layer. The third substrate layer is an acrylic film, and the low refractive index layer is made of a porous silica material. The refractive indices and thicknesses of the third substrate layer, low refractive index layer, and acrylic adhesive layer of Example 2 are shown in Table 3.

[0048]

[0049] The light guide member of Example 2 can be manufactured by a known method.

[0050] Comparative Example 1 In the lighting device of Comparative Example 1, a microlens sheet with prisms formed on one surface and a flat surface was used instead of the acrylic plate / acrylic adhesive layer / textured film of Example 1. The microlens sheet functions as both a light guide layer and a light extraction function. Furthermore, the surface of the microlens sheet on which the object is placed is flat, and the opposite surface is machined to form multiple prisms (concave portions) in a two-dimensional pattern. The multiple prisms on the microlens sheet were arranged at a pitch of 300 μm, with each prism having a height of 8 μm and a diameter of 30 μm. Other than the microlens sheet, the lighting device of Comparative Example 1 had the same configuration as the lighting device of Example 1. The refractive index of the microlens sheet was 1.51 and the thickness was 500 μm.

[0051] Next, with reference to FIGS. 5A to 5C , the visibility of an object viewed through the lighting devices of Examples 1 and 2 and Comparative Example 1 will be described. The object was a piece of paper on which "Under the Great Wave off Kanagawa," one of Katsushika Hokusai's "Thirty-six Views of Mount Fuji," was printed. The lighting devices of Examples 1 and 2 and Comparative Example 1 were placed on the object. FIGS. 5A to 5C are photographs of the object viewed through the lighting devices of Examples 1 and 2 and Comparative Example 1, respectively. As shown in FIG. 5A , the lighting device of Example 1 obtained a sufficient amount of light from the second light-emitting surface, making the object fully visible. As shown in FIG. 5B , the lighting device of Example 2 obtained a greater amount of light from the second light-emitting surface than the lighting device of Example 1, making the entire object more clearly visible. In contrast, as shown in FIG. 5C , the lighting device of Comparative Example 1 did not obtain a sufficient amount of light from the second light-emitting surface, making the object only partially visible.

[0052] Furthermore, the inventors compared the angular dependence of the intensity of light emitted from the second exit surface between the lighting device of Example 1 and the lighting device of the comparative example. In the lighting device of Example 1, the angular dependence of the intensity of the emitted light showed a clear single peak with a maximum intensity at an angle of 3° and a full width at half maximum of approximately 15°. This single peak was caused by reflected light LRb that passed through the object 70 as shown in FIG. 1. In the lighting device of Example 1, there was almost no leakage light LRc that did not pass through the object 70 as shown in FIG. 1. It was found that in the lighting device of Example 1, most of the light propagating through the light-guiding layer was emitted from the first exit surface as highly directional irradiation light.

[0053] In contrast, in the lighting device of Comparative Example 1, the angular dependence of the intensity of the emitted light showed a relatively low peak where the intensity was maximized at an angle of around 10°, and a relatively high peak where the intensity was maximized in an angle range of 60° or more. The relatively low peak was caused by reflected light that passed through the object, and the relatively high peak was caused by leaked light that did not pass through the object. The maximum value of the relatively low peak in the lighting device of Comparative Example 1 was about 1 / 5 of the maximum value of the clear single peak in the lighting device of Example 1. It was found that in the lighting device of Comparative Example 1, much of the light propagating through the light-guiding layer was emitted as leaked light.

[0054] As described above, the lighting device according to the embodiment of the present invention can improve the visibility of an object compared to conventional lighting devices.

[0055] 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 6A and 6B show examples of lighting devices having a light distribution control structure similar to that of the lighting device 100A_L shown in Figure 1.

[0056] The lighting device 100A1_L shown in FIG. 6A differs from the lighting device 100A_L shown in FIG. 1 in that it includes a hard coat layer 80 instead of the second antireflection layer 40B. The hard coat layer 80 may have a pencil hardness of, for example, H or higher. The hard coat layer 80 can improve the scratch resistance of the second light-emitting surface of the lighting device 100A1_L. The second light-emitting surface is the surface of the hard coat layer 80 opposite the light-guiding layer 10. The second light-emitting surface is located opposite the first light-emitting surface facing the object 70, and may be subject to contact by a viewer or collision with an object. Even in such cases, scratches on the second light-emitting surface of the lighting device 100A1_L can be suppressed.

[0057] The lighting device 100A2_L shown in FIG. 6B differs from the lighting device 100A_L shown in FIG. 1 in that it includes a low-refractive index layer 22 and a fourth base layer 30D between the light-guiding layer 10 and the first base layer 30A. In the lighting device 100A2_L shown in FIG. 6B, the light-guiding layer 10 and the fourth base layer 30D are bonded together by an adhesive layer 52, and the low-refractive index layer 22 and the first base layer 30A are bonded together by an adhesive layer 58. The low-refractive index layer 22 can improve the antifouling properties of the first light exit surface of the lighting device 100A2_L. Note that the second anti-reflection layer 40B shown in FIG. 6B may be replaced with a hard coat layer 80.

[0058] The hard coat layer 80 shown in FIG. 6A and the low refractive index layer 22 shown in FIG. 6B can also be applied to the lighting device 100B_L according to another embodiment of the present invention.

[0059] A preferred example of each component of the lighting device according to the embodiment of the present invention will be described.

[0060] 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%.

[0061] 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.

[0062] The thickness of the base layers 30A, 30B, 30C, and 30D is, for example, 1 μm or more and 1000 μm or less, preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 80 μm or less. The refractive index of each of the base layers 30A, 30B, 30C, and 30D is preferably 1.40 or more and 1.70 or less, and more preferably 1.43 or more and 1.65 or less.

[0063] 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.

[0064] 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, and Japanese Patent Application No. 2021-025496 filed 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.

[0065] The antireflection layers 40A and 40B may be a single low refractive index layer, but are preferably an alternating 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.

[0066] 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 determined based on the refractive index, layer structure, etc., to reduce the reflectance of visible light.

[0067] The anti-reflection layers 40A and 40B are preferably laminated on the hard coat layer via a primer layer. Examples of materials constituting the primer layer include 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.

[0068] The method for forming the thin films constituting the antireflection layers 40A and 40B 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 film thickness uniformity and is easy to form a dense film. For example, the antireflection layer described in JP 2020-52221 A can be suitably used. The entire disclosure of JP 2020-52221 A is incorporated herein by reference.

[0069] The antireflection layers 40A and 40B do not necessarily have to have a single low refractive index layer or an alternating laminate of high and low refractive index layers. The antireflection layers 40A and 40B may have a so-called moth-eye structure. Alternatively, the antireflection layers 40A and 40B may be formed of a material having voids, similar to the low refractive index layers 20 and 22 described below.

[0070] The refractive index n of the low refractive index layers 20 and 22 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 layers 20, 22 are preferably solid, and the refractive index thereof 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 layers 20, 22 is preferably 0.20 or more, more preferably 0.23 or more, and even more preferably 0.25 or more. The low refractive index layers 20, 22 having a refractive index of 1.30 or less may be formed using, for example, a porous material. The thickness of the low refractive index layers 20, 22 is each independently, for example, 0.3 μm or more and 5 μm or less.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] Hardness H of hard coat layer 80 Ｈ１ The hardness H of the hard coat layer 80 is preferably H or more, more preferably 2H or more, and even more preferably 4H or more, in terms of pencil hardness. Ｈ１Although 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 the hard coat layer 80 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 80 is within this range, it has good scratch resistance.

[0077] The hard coat layer 80 can be made of any suitable material as long as it satisfies the above-mentioned characteristics. The hard coat layer 80 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 80 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 80 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.

[0078] The light-guiding member for a lighting device and the lighting device according to the embodiment of the present invention can be used to illuminate, for example, paintings exhibited in dark rooms in art museums, posters and advertisements on the street at night, reflective displays and electronic paper. The light-guiding member for a lighting device and the lighting device according to the embodiment of the present invention can provide new uses that combine practicality and design.

[0079] 10: light-guiding layer, 20, 22: low-refractive-index layer, 30A, 30B: substrate layer, 40A, 40B: anti-reflection layer, 52, 54, 56, 58: adhesive layer, 60: direction-changing layer, 62: shaping film, 64: internal space, recess, 70: object, 80: hard coat layer, 100A, 100B: light-guiding member for lighting device, 100A_L, 100A1_L, 100A2_L, 100B_L: lighting device, ISa: first inclined surface, ISb: second inclined surface, LRa, LRa1, LRa2: irradiated light, LRb, LRb1, LRb2: reflected light, LRc: leaked light, LS: light source

Claims

1. A light guide member for a lighting device having a first light emitting surface and a second light emitting surface on the side opposite to the first light emitting surface, a light receiving portion that receives light emitted from a light source, a light guide layer having a first main surface on the first light emitting surface side and a second main surface on the second light emitting surface side, a light distribution control structure having a plurality of internal spaces and having, each of the plurality of internal spaces has a first inclined surface that directs a part of the light propagating in the light guide layer toward the first light emitting surface side by total internal reflection, and a second inclined surface on the side opposite to the first inclined surface, and 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, the first light emitting surface emits irradiation light for irradiating an object, the second light emitting surface emits reflected light generated by irradiating the object with the irradiation light and passing through the light guide layer, a light guide member for a lighting device.

2. The inclination angle θa of the first inclined surface is 20° or more and 50° or less, The inclination angle θb of the second inclined surface is 70° or more and 90° or less, the light guide member for a lighting device according to claim 1.

3. 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, the light guide member for a lighting device according to claim 1 or 2.

4. 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, the light guide member for a lighting device according to claim 1 or 2.

5. When viewed from the normal direction to the first main surface of the light guide layer, the first inclined surface forms a curved surface convex toward the light source side, the light guide member for a lighting device according to claim 1 or 2.

6. The irradiation light emitted from the first emission surface has a first light distribution, When the light ray with the highest intensity in the first light distribution is defined as the first principal ray, The polar angle θ1 from the normal to the first emission surface of the first principal ray is 0° or more and 40° or less. The light guide member for a lighting device according to claim 1 or 2.

7. The second emission surface emits light that propagates within the light guide layer and does not pass through the object and has a second light distribution, When the light ray with the highest intensity in the second light distribution is defined as the second principal ray, The polar angle θ2 from the normal to the second emission surface of the second principal ray is 40° or more and 85° or less. The light guide member for a lighting device according to claim 1 or 2.

8. The light guide member for a lighting device according to claim 1 or 2, having a first antireflection layer disposed on the first major surface side of the light guide layer.

9. The light guide member for a lighting device according to claim 1 or 2, having a second antireflection layer disposed on the second major surface side of the light guide layer.

10. The light guide member for a lighting device according to claim 9, having a low refractive index layer having a refractive index lower than that of the light guide layer between the light guide layer and the second antireflection layer.

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 and a lighting device comprising the same.