Light guide body and lighting device

Abstract

The present invention reduces luminance unevenness. Provided is a light guide body in which light from a first light source is incident, and which is provided with a cavity in the inside thereof. The light guide body comprises a first end surface, and an emission surface that is continuous with the first end surface and intersects the first end surface. The light guide body reflects, by means of the cavity, a portion of light that is guided through the inside of the light guide body, and emits the light reflected by the cavity from the emission surface. In one cross-section intersecting each of the first end surface and the emission surface, the cavity includes, on at least a side at which the first end surface is located, a first arc-shaped curve that is convex toward the side at which the first end surface is located.

Description

Light guide and lighting device

[0001] The present invention relates to a light guide and a lighting device.

[0002] For example, Patent Document 1 discloses a lighting device having a first prism pattern and a second prism pattern that intersect at a right angle between a light source and a light guide plate, and Patent Document 2 discloses a lighting device having a moth-eye pattern and protrusions on the light incident surface of a light guide plate that receives light from a light source.

[0003] Patent No. 4691543 Patent No. 6068747

[0004] An object of the present invention is to reduce brightness unevenness.

[0005] A light guide according to one aspect of the present invention is a light guide into which light from a first light source is incident and which has a cavity provided therein, and which includes a first end face and an exit face that is continuous with and intersects the first end face, wherein the light guide reflects a portion of the light guided inside the light guide by the cavity and emits the light reflected by the cavity from the exit face, and the cavity, in a cross section that intersects with both the first end face and the exit face, includes a first arc-shaped curve that is convex toward the side where the first end face is located, at least on the side where the first end face is located.

[0006] According to the present invention, it is possible to reduce brightness unevenness.

[0007] 1 is a schematic plan view showing a first example of an illumination device including a laminate with a light guide layer according to the first embodiment. FIG. 1 is a schematic cross-sectional view taken along line II-II in FIG. 1. FIG. 2 is a schematic cross-sectional view showing a first example of a cavity included in the laminate with a light guide layer according to the first embodiment. FIG. 3 is a schematic plan view showing a first example of a cavity included in the laminate with a light guide layer according to the first embodiment. FIG. 4 is a schematic perspective view showing a second example of a cavity included in the laminate with a light guide layer according to the first embodiment. FIG. 5 is a schematic cross-sectional view showing a cavity according to a comparative example. FIG. 6 is a diagram showing first differential lines of first inclined surfaces of cavities according to the first example, second example, and comparative example. FIG. 7 is a diagram showing a two-dimensional luminance distribution of emitted light from a laminate with a light guide layer including a cavity according to the first example. FIG. 8 is a diagram showing a two-dimensional luminance distribution of emitted light from a laminate with a light guide layer including a cavity according to the comparative example. FIG. 9 is a diagram showing the luminance distribution in the Y direction of emitted light from the laminate with a light guide layer including a cavity according to each of the first example and the comparative example. 14 is a diagram showing the relationship between the emission angle in the Y direction and the luminous intensity of light emitted from a laminate with a light guide layer including a cavity according to each of the first example, the second example, and the comparative example. FIG. 15 is a schematic cross-sectional view showing a modified example of an illumination device including a laminate with a light guide layer according to the first embodiment. FIG. 16 is a schematic plan view showing an illumination device including a laminate with a light guide layer according to the second embodiment. FIG. 17 is a schematic cross-sectional view taken along line XIV-XIV in FIG. 13. FIG. 18 is a schematic cross-sectional view of a cavity included in a laminate with a light guide layer according to the second embodiment. FIG. 19 is a schematic plan view showing a cavity included in a laminate with a light guide layer according to the second embodiment. FIG. 19 is a diagram showing a first differential line of a first inclined surface of a cavity included in a laminate with a light guide layer according to the second embodiment. FIG. 19 is a diagram showing the luminance distribution in the Y direction of light emitted from a laminate with a light guide layer according to the second embodiment. FIG. 19 is a diagram showing the relationship between the emission angle in the Y direction and the luminous intensity of light emitted from a laminate with a light guide layer according to the second embodiment. FIG. 19 is a schematic cross-sectional view showing a modified example of an illumination device including a laminate with a light guide layer according to the second embodiment.

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same components are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0009] The following embodiments are intended to exemplify light guides and lighting devices embodying the technical concepts of the present invention, and are not intended to limit the present invention to the following embodiments. The dimensions, materials, shapes, relative positions, and other details of the components described below are intended for illustrative purposes only, and are not intended to limit the scope of the present invention unless otherwise specified. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0010] In the drawings shown below, directions are expressed using a Cartesian coordinate system having an X-axis, a Y-axis, and a Z-axis. The X-axis, the Y-axis, and the Z-axis are approximately perpendicular to one another. The direction in which the arrow representing the X-axis points is referred to as the +X direction or +X side, and the direction opposite to the +X direction is referred to as the -X direction or -X side. The direction in which the arrow representing the Y-axis points is referred to as the +Y direction or +Y side, and the direction opposite to the +Y direction is referred to as the -Y direction or -Y side. The direction in which the arrow representing the Z-axis points is referred to as the +Z direction or +Z side, and the direction opposite to the +Z direction is referred to as the -Z direction or -Z side.

[0011] The X direction along the X axis indicates a direction along the normal to the first end face of the light guide according to the embodiment. The Z direction along the Z axis indicates a direction along the normal to the emission surface of the light guide according to the embodiment. The Y direction along the Y axis indicates a direction intersecting the normal to the first end face and the normal to the emission surface of the light guide according to the embodiment. In this specification, "planar view" refers to viewing an object from the +Z direction. The +Z direction is referred to as "up" and the -Z direction is referred to as "down." However, the above directional expressions merely indicate relative positional relationships for the purpose of explanation and do not limit the directions in the embodiment.

[0012] In this specification and claims, "substantially parallel" means that the absolute value of the angular deviation from the parallel state is between 0 and 10 degrees. Furthermore, "substantially perpendicular" means that the absolute value of the angular deviation from the perpendicular state is between 0 and 10 degrees. "Arranged" does not necessarily mean direct contact, but also includes indirect arrangement, for example, via another member. Furthermore, in this specification, "thickness" refers to the length of the object in the Z direction. Furthermore, in this specification, cross-sectional views may be shown as end views showing only the cross section.

[0013] [First embodiment] <Overall configuration of lighting device according to first embodiment> The overall configuration of a lighting device including a laminate with a light guide layer according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic plan view showing an example of a lighting device 100 including a laminate with a light guide layer according to the first embodiment. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. In the example shown in Figure 2, part of light Lr1 emitted from a first light source LS1 is indicated by a dashed arrow.

[0014] The lighting device 100 includes a laminate 80 with a light guide layer and a first light source LS1. The laminate 80 with a light guide layer is a light guide having an internal cavity into which light from the first light source LS1 is incident. The laminate 80 with a light guide layer includes a first end surface 81 and an exit surface 82 that is continuous with and intersects with the first end surface 81.

[0015] 2 includes a light guide layer 10, a laminate 70, and a first adhesive layer 52. The first adhesive layer 52 is disposed between the light guide layer 10 and the laminate 70, and serves to bond the light guide layer 10 and the laminate 70 together. The laminate 70 includes a substrate 30 and a direction changing layer 60. The direction changing layer 60 includes a shaped film 62 and a second adhesive layer 54. The second adhesive layer 54 is disposed between the shaped film 62 and the substrate 30, and serves to bond the shaped film 62 and the substrate 30 together. The substrate 30 is disposed opposite a main surface 621 of the shaped film 62. The light guide layer 10 is disposed opposite the shaped film 62. The shaped film 62 is a film manufactured without cutting the material. 1 and 2 , a laminate 80 with a light guide layer will be described as an example of a light guide according to the embodiment, but the light guide according to the embodiment does not necessarily have to be a laminate with a light guide layer as long as the light guide has a cavity 64 inside. The light guide according to the embodiment may be composed of only a laminate having a cavity 64 inside, or may not be a laminate.

[0016] As shown in FIG. 2 , multiple cavities 64 are provided inside the direction-changing layer 60. Each of the multiple cavities 64 has a first inclined surface ISa and a second inclined surface ISb arranged on the opposite side of the first inclined surface ISa in the Y direction. For example, air is present inside the cavities 64. A plurality of recesses 622 are provided on the main surface 621 of the shaped film 62. The open portions of each of the multiple recesses 622 are blocked by the substrate 30 arranged on the main surface 621 via the second adhesive layer 54, thereby forming the cavities 64. The cavities 64 may also be referred to as internal spaces or air cavities.

[0017] The lighting device 100 is used, for example, with the light guide layer-equipped laminate 80 disposed on an adherend such as glass, a window, a wall, a floor, or a ceiling. The lighting device 100 causes light Lr1 emitted from the first light source LS1 to enter the inside of the light guide layer-equipped laminate 80 through the first end surface 81. The light guide layer-equipped laminate 80 reflects a portion of the light Lr1, which enters through the first end surface 81 and is guided inside the light guide layer-equipped laminate 80, by the cavity 64, and emits the light Lr1 reflected by the cavity 64 from the emission surface 82. The lighting device 100 can illuminate an indoor space in which the light guide layer-equipped laminate 80 is disposed, with the light Lr1 emitted from almost the entire emission surface 82 of the light guide layer-equipped laminate 80.

[0018] In a lighting device having a laminate with a light guide layer provided therein, when the laminate with a light guide layer is viewed in plan, brightness unevenness including a band-shaped dark area extending in the longitudinal direction of the end face may occur near the end face of the laminate with a light guide layer, where light is incident from the light source. The longitudinal direction of the end face of the laminate with a light guide layer corresponds to the X direction in the examples shown in FIGS. 1 and 2 . Brightness unevenness including a band-shaped dark area is thought to occur because there is an area inside the laminate with a light guide layer near the end face where light incident on the laminate with a light guide layer does not reach, or because the high directivity of light reflected by the cavity results in an area inside the laminate with a light guide layer where the light does not pass through. Brightness unevenness including a band-shaped dark area reduces the quality of the lighting device.

[0019] In this embodiment, as shown in FIG. 2 , in a cross section intersecting the first end face 81 and the light exiting surface 82, the cavity 64 includes a first arc-shaped curve AR1 that is convex toward the side where the first end face 81 is located, at least on the side where the first end face 81 is located. The cross section intersecting the first end face 81 and the light exiting surface 82 is, for example, a cross section parallel to the YZ plane shown in FIG. 2 . The first arc-shaped curve AR1 is an arc-shaped curve that constitutes a cross section of the first inclined surface ISa, which is a curved surface. The cavity 64 reflects the light Lr1 guided inside the light-guiding layer-equipped laminate 80 by the first inclined surface ISa that includes the first arc-shaped curve AR1, and causes the reflected light Lr1 to exit from the light exiting surface 82. The cavity 64 reflects the light Lr1 off the first inclined surface ISa including the first arc-shaped curve AR1, thereby making it possible to lower the directivity of the light Lr1 reflected by the cavity 64 compared to when the light Lr1 is reflected by a flat surface. By lowering the directivity of the light Lr1 reflected by the cavity 64, in this embodiment, it is possible to reduce the area inside the light-guiding layer-equipped laminate 80 through which the light Lr1 reflected by the cavity 64 does not pass. As a result, in this embodiment, it is possible to reduce band-like dark areas and reduce brightness unevenness. Furthermore, in this embodiment, by reducing brightness unevenness, it is possible to improve the quality of the lighting device 100.

[0020] The first arc-shaped curve AR1 shown in Fig. 2 is a parabola. By making the first arc-shaped curve AR1 a parabola, it is possible to reduce brightness unevenness such as band-like dark areas and reduce optical axis deviation of the light Lr1 emitted from the exit surface 82 with respect to the normal to the exit surface 82. Note that the optical axis deviation of the light Lr1 with respect to the normal to the exit surface 82 refers to the inclination of the optical axis of the light Lr1 with respect to the normal to the exit surface 82. The greater the inclination of the optical axis of the light Lr1 with respect to the normal to the exit surface 82, the greater the optical axis deviation of the light Lr1 with respect to the normal to the exit surface 82.

[0021] In the lighting device 100, the cavity 64 reflects a portion of the light Lr1 guided inside the laminate 80 with a light guide layer toward the emission surface 82. The light Lr1 reflected by the cavity 64 passes through the emission surface 82 and is emitted from the laminate 80 with a light guide layer. As a result, this embodiment can provide a surface-illumination type lighting device 100 that can emit light Lr1 incident from the first end surface 81 of the laminate 80 with a light guide layer from almost the entire emission surface 82. Furthermore, by including the laminate 80 with a light guide layer, the lighting device 100 can reduce brightness unevenness.

[0022] 1 and 2 illustrate a configuration in which the light Lr1 emitted from the first light source LS1 directly enters the first end surface 81, but this is not limiting. For example, the light Lr1 emitted from the first light source LS1 may indirectly enter the first end surface 81 via a light diffusing member disposed between the first light source LS1 and the first end surface 81. Note that "directly entering the first end surface 81" means that the light Lr1 enters the first end surface 81 without an intervening member. "indirectly entering the first end surface 81" means that the light Lr1 enters the first end surface 81 via an intervening member.

[0023] 2 , the surface of the light guide according to the first embodiment onto which light from the first light source LS1 is incident is not limited to the first end surface 81 of the laminate 80 with a light guide layer. For example, the surface of the light guide according to the first embodiment onto which light from the first light source LS1 is incident may be the exit surface 82 of the laminate 80 with a light guide layer, or may be the top surface 84, which is the surface opposite to the exit surface 82. For example, the surface onto which light is incident may be the vicinity of the first end surface 81 of the exit surface 82 (within 200 mm, 150 mm, or 100 mm from the end surface) so that the light source becomes a side-edge type lighting device. Furthermore, for example, the surface onto which light is incident may be the vicinity of the first end surface 81 of the top surface 84 (within 200 mm, 150 mm, or 100 mm from the end surface).

[0024] <Details of the Configuration of the Illumination Device 100> The following describes the details of the configuration of the illumination device 100. The illumination device 100 has a light distribution control structure having a plurality of cavities 64. The first inclined surface ISa in each of the plurality of cavities 64 directs a portion of the light Lr1 guided within the laminate 80 with a light-guiding layer toward the exit surface 82 by total internal reflection (TIR). Note that when the light Lr1 passes through an interface, it may be refracted according to the refractive index of the material that constitutes the interface.

[0025] The laminate 80 with a light guide layer is configured, by the light distribution control structure, to emit light Lr1 having a desired light distribution from the exit surface 82. The light distribution can be controlled by adjusting, for example, the cross-sectional shape, planar shape, size, arrangement density, distribution, etc. of the cavities 64.

[0026] The laminate 80 with a light guide layer has 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. Since the laminate 80 with a light guide layer has a high visible light transmittance and a low haze value, objects (displays) can be seen through the laminate 80 with a light guide layer. Visible light is light with a wavelength of 380 nm or more and 780 nm or less. The visible light transmittance and haze value can be measured using a haze meter (manufactured by Murakami Color Research Laboratory: product name HM-150) or the like.

[0027] The ratio of the area of ​​the plurality of cavities 64 to the area of ​​the light guide layer 10 (occupancy rate) is preferably 1% or more and 80% or less when the light guide layer 10 is viewed from the normal direction of the light exit surface 82. The upper limit of the occupation rate is more preferably 50% or less, and even more preferably 45% or less, and in order to obtain at least one of high transmittance and low haze value, it is preferably 30% or less, more preferably 10% or less, and even more preferably 5% or less.

[0028] For example, when the cavity occupancy rate is 50%, a haze value of 30% can be obtained. The cavity occupancy rate may be uniform, or may increase as the distance from the first light source LS1 increases so that brightness does not decrease even when the distance from the first light source LS1 increases. For mass production using a roll-to-roll method or a roll-to-sheet method, it is preferable that the cavity occupancy rate be uniform.

[0029] In the laminate 80 with a light guide layer, the light guide layer 10 and the shaped film 62 are bonded together by a first adhesive layer 52. The substrate 30 and the shaped film 62 are bonded together by a second adhesive layer 54 that constitutes the shaped film 62 and the direction changing layer 60. The light guide layer 10 and the substrate 30 may be transparent substrates or films.

[0030] 1, the cavities 64 are discretely arranged in the X and Y directions of the light guide layer 10. However, the discrete arrangement of the cavities 64 may be appropriately set depending on the shape of the light guide layer 10, the desired light distribution, etc.

[0031] 1, a plurality of cavities 64 having substantially the same shape and curved surfaces convex in the same direction are discretely and periodically arranged over the entire region in the X and Y directions. 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. 1, the laminate 80 with a light guide layer further includes cavities 64 that are shifted by half the pitch Px in the X direction and by half the pitch Py in the Y direction.

[0032] The first light source LS1 is, for example, an LED (Light Emitting Diode) device. A plurality of LED devices are arranged in a line in the X direction. There are no particular limitations on the number and arrangement of the LEDs. Note that the first light source LS1 is not limited to an LED device and may be a halogen lamp or the like.

[0033] The shaped film 62 can be produced according to the method described in JP-A-2013-524288. Specifically, the surface of a polymethyl methacrylate (PMMA) film is coated with lacquer (Finecure RM-64 manufactured by Sanyo Chemical Industries, Ltd.), an optical pattern is embossed on the film surface containing the lacquer, and then the lacquer is cured to produce the desired shaped film 62. The total thickness of the shaped film 62 is, for example, 130 μm.

[0034] The light guide layer 10 is formed of a known material with high transmittance to visible light. The light guide layer 10 is formed, for example, of an acrylic resin such as polymethyl methacrylate (PMMA), a polycarbonate (PC) resin, a cycloolefin resin, or glass (quartz glass, alkali-free glass, borosilicate glass, etc.). The refractive index nGP of the light guide layer 10 is, for example, 1.40 or more and 1.80 or less. Unless otherwise specified, the refractive index refers to the refractive index measured with an ellipsometer at a wavelength of 550 nm. The thickness of the light guide layer 10 can be appropriately set 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.

[0035] The thickness of the substrate 30 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 substrate 30 is independently preferably 1.40 to 1.70, and more preferably 1.43 to 1.65.

[0036] The thicknesses of the first adhesive layer 52 and the second adhesive layer 54 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 first adhesive layer 52 and the second adhesive layer 54 are each independently preferably from 1.42 to 1.60, and more preferably from 1.47 to 1.58. The refractive indexes of the first adhesive layer 52 and the second adhesive layer 54 are preferably close to the refractive index of the light guide 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.

[0037] The second adhesive layer 54 can preferably be bonded without filling the recesses 622 of the shaped film 62. Suitable adhesives for forming the second adhesive layer 54 include those described in International Application PCT / JP2021 / 006452, International Application PCT / JP2021 / 006453, or Japanese Patent Application No. 2021-025496 filed by the present applicant. The entire disclosures of these applications are incorporated herein by reference. In particular, the polyester-based adhesive described in Japanese Patent Application No. 2021-025496 is preferred.

[0038] (First Example of Cavity 64 in First Embodiment) The configuration of a first example of the cavity 64 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a schematic cross-sectional view showing a first example of the cavity 64 included in the laminate 80 with a light guide layer according to the first embodiment. Fig. 4 is a schematic plan view showing the first example of the cavity 64 included in the laminate 80 with a light guide layer according to the first embodiment.

[0039] The rise angle θa of the first arc-shaped curve AR1 on the side where the first end surface 81 is located is preferably 85° or less. In the example shown in Fig. 3, the rise angle θa of the first arc-shaped curve AR1 on the side where the first end surface 81 is located is 63°. When the rise angle θa of the first arc-shaped curve AR1 is 85° or less, the light-guiding layer-included laminate 80 can increase the directivity of the light Lr1 emitted from the exit surface 82 within a range where brightness unevenness such as band-like dark portions can be reduced, as will be described later with reference to Figs. 10 and 11 .

[0040] The inclination angle θb of the second inclined surface ISb is, for example, 50° or more and 100° or less. Here, if the inclination angle θb is smaller than 50°, stray light may be generated in an unintended direction. On the other hand, if the inclination angle θb exceeds 100°, it may become difficult to process the shaping film 62. By setting the rise angle θa and the inclination angle θb to 50° or more and 100° or less, the light extraction efficiency can be increased and the shaping film 62 can be easily processed.

[0041] 4 is a curved surface that is convex toward the first end surface 81 in a plan view. Here, light emitted from each of the multiple LED devices that make up the first light source LS1 has a spread in the Y direction. Therefore, the first inclined surface ISa acts uniformly on the light when the first inclined surface ISa has a curved surface that is convex toward the first light source LS1. Note that if a coupling optical system is provided between the first light source LS1 and the first end surface 81 of the laminate 80 with a light guide layer to allow highly parallel light (light that has a small spread in the Y direction) to be incident, the first inclined surface ISa may be parallel to the X direction.

[0042] In the first embodiment, the length L of the cavity 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 preferably, for example, at least twice the width W. The height H is preferably 1 μm or more and 100 μm or less. In the first example shown in FIGS. 3 and 4, the height H is 10 μm, the width W is 10 μm, and the length L is 20 μm.

[0043] (Second Example of Cavity 64 in First Embodiment) FIG. 5 is a schematic perspective view showing a second example of the cavity 64 included in the laminate 80 with a light guide layer according to the first embodiment. As shown in FIG. 5, the cavity 64 according to the second example has a cylindrical shape. In the second example shown in FIG. 5, the height H is 10 μm, the width W is 10 μm, and the length L is 10 μm. The radius of curvature of the cylindrical shape is 10 μm, the same as the height H. The rise angle θa and the inclination angle θb are both 90°. In other words, the cylindrical shape including the first inclined surface ISa is a semi-cylindrical shape. The first arc-shaped curve AR1 is a sectorial arc with a central angle of 90°.

[0044] (Comparative Example of Cavity) FIG. 6 is a schematic cross-sectional view showing a cavity 64X according to a comparative example. The cross section shown in FIG. 6 corresponds to a cross section of the cavity 64X intersecting with each of the first end surface 81 and the emission surface 82 of the laminate 80 with a light guide layer according to the first embodiment. In the comparative example shown in FIG. 6, the height H is 10 μm and the width W is 10 μm. The rise angle θa is 49°. The first inclined surface ISaX of the cavity 64X is flat. The cross section of the first inclined surface ISaX corresponding to a cross section intersecting with each of the first end surface 81 and the emission surface 82 includes a straight line ARX.

[0045] <First Differential Lines of the First Sloped Surface of the Cavity According to the First Example, the Second Example, and the Comparative Example> Next, the first differential lines of the first sloping surface of the cavity according to the first example, the second example, and the comparative example will be described with reference to Fig. 7. Fig. 7 is a diagram showing the first differential lines of the first sloping surface of the cavity according to the first example, the second example, and the comparative example. In Fig. 7, the horizontal axis indicates the position in the Y direction, and the vertical axis indicates the first differential value of the first sloping surface of the cavity. Note that the "position in the Y direction" on the horizontal axis is normalized with the width W of the cavity in the Y direction set to 1.

[0046] The solid linear differential line 71 is a line obtained by first differentiating the first arc-shaped curve AR1 of the cavity 64 according to the first example. The dashed linear differential line 72 is a line obtained by first differentiating the first arc-shaped curve AR1 of the cavity 64 according to the second example. The dashed linear differential line 73 is a line obtained by first differentiating the straight line ARX of the cavity 64X according to the comparative example.

[0047] The first arc-shaped curve AR1 of the cavity 64 according to the first example is convex toward the side where the first end face 81 is located and also convex toward the side where the light exit surface 82 is located, so the first differential line 71 has a negative slope. Furthermore, the first arc-shaped curve AR1 of the cavity 64 according to the first example is a parabola, so the first differential line 71 is a straight line.

[0048] The first arc-shaped curve AR1 of the cavity 64 according to the second example is convex toward the side where the first end face 81 is located and also convex toward the side where the light exit surface 82 is located, so the first differential line 72 has a negative slope. Furthermore, the first arc-shaped curve AR1 of the cavity 64 according to the second example is a sector arc with a central angle of 90°, so the first differential line 72 is a curve.

[0049] The first derivative line of the straight line ARX of the cavity 64X according to the comparative example is a straight line with no slope.

[0050] <Evaluation of Laminates with Light Guide Layer Having Cavity According to First Example, Second Example, and Comparative Example> Next, evaluation results of the light emitted from the laminate 80 with a light guide layer having the cavity 64 according to the first example, the laminate 80 with a light guide layer having the cavity 64 according to the second example, and the laminate 80 with a light guide layer having the cavity 64X according to the comparative example will be described. In the evaluation of the emitted light, the brightness unevenness and the relationship between the emission angle and luminous intensity of the emitted light were calculated by simulation and evaluated.

[0051] (Brightness Unevenness of Emitted Light) Evaluation results of brightness unevenness of emitted light will be described with reference to Fig. 8 to Fig. 10. Fig. 8 is a diagram showing a two-dimensional brightness distribution of emitted light from a laminate with a light guide layer including a cavity according to the first example. Fig. 9 is a diagram showing a two-dimensional brightness distribution of emitted light from a laminate with a light guide layer including a cavity according to a comparative example. Fig. 10 is a diagram showing the brightness distribution in the Y direction of emitted light from the laminate with a light guide layer including a cavity according to each of the first example and the comparative example.

[0052] Fig. 8 shows, in a plan view, a two-dimensional luminance distribution of light emitted from the exit surface 82 of a laminate 80 with a light guide layer, which includes a cavity 64 according to the first example. Fig. 9 shows, in a plan view, a two-dimensional luminance distribution of light emitted from the exit surface 82X of a laminate 80X with a light guide layer, which includes a cavity 64X according to a comparative example. In the examples shown in Figs. 8 and 9 , the luminance of light emitted from the exit surface of the laminate with a light guide layer is represented by the color of pixels constituting an image representing the two-dimensional luminance distribution. A darker pixel color represents a lower luminance, and a whiter pixel color represents a higher luminance.

[0053] In the laminate 80 with a light guide layer including the cavity 64 according to the first example shown in Fig. 8, the difference in luminance of the emitted light among the regions on the emission surface was smaller than in the laminate 80X with a light guide layer including the cavity 64X according to the comparative example shown in Fig. 9. In the comparative example shown in Fig. 9, the difference in luminance of the emitted light among the regions on the emission surface was large, resulting in greater luminance unevenness including dark areas S.

[0054] 10 , the horizontal axis represents the position of the laminate with a light guide layer in the Y direction. The position 0 mm represents the position where the first end surface 81 is disposed. Also, the larger the value of the position in the Y direction, the farther away from the first end surface 81 it is.

[0055] Graph 101, indicated by a solid line in Figure 10, shows the simulation results of the luminance distribution in the cross-sectional region P shown in Figure 8 of the emitted light from the laminate 80 with a light guide layer that includes the cavity 64 according to the first example. The maximum luminance value Q11 is the highest luminance value near the first end face 81. The low luminance value Q12 is the luminance value at a position near the first end face 81 where the luminance is minimal. The smaller the luminance ratio obtained by dividing the low luminance value Q12 by the maximum luminance value Q11, the greater the luminance unevenness, including band-like dark areas, etc. In evaluating the luminance unevenness, this luminance ratio was used as one of the evaluation indexes.

[0056] Graph 102, indicated by a dashed line in Fig. 10, shows the results of a simulation of the luminance distribution of light emitted from a laminate with a light guide layer including a cavity 64X according to a comparative example in the cross-sectional region PX shown in Fig. 9. The maximum luminance value QX1 is the highest luminance value near the first end face 81X. The low luminance value QX2 is the luminance value at a position where the luminance is minimal near the end face corresponding to the first end face 81X.

[0057] The difference between the highest luminance value Q11 and the lowest luminance value Q12 was much smaller than the difference between the highest luminance value QX1 and the lowest luminance value QX2. The luminance ratio between the highest luminance value Q11 and the lowest luminance value Q12 in Example 1 was approximately 90% in percentage. On the other hand, the luminance ratio between the highest luminance value QX1 and the lowest luminance value QX2 in the comparative example was 1% or less in percentage.

[0058] From the above, it was found that brightness unevenness can be reduced compared to the laminate 80 with a light-guiding layer having the cavity 64 of the first example, the laminate 80 with a light-guiding layer having the cavity 64 of the second example, and the laminate 80X with a light-guiding layer having the cavity 64X of the comparative example.

[0059] The laminate 80 with a light-guiding layer including the cavity 64 according to the first and second examples can reduce brightness unevenness compared to the laminate 80X with a light-guiding layer including the cavity 64X according to the comparative example. Therefore, from the viewpoint of reducing brightness unevenness, it is found that it is preferable that the first differential line 71 (see FIG. 7 ) of the first arc-shaped curve AR1 has a negative slope.

[0060] The light guide layer-equipped laminate 80 including the cavity 64 according to the first and second examples can reduce brightness unevenness compared to the light guide layer-equipped laminate 80X including the cavity 64X according to the comparative example. Therefore, it was found that, from the viewpoint of reducing brightness unevenness, the slope of the first differential line 71 of the first arc-shaped curve AR1 is preferably not less than −10 and less than 0. The lower limit is, for example, not less than −8, not less than −6, not less than −5, or not less than −4.

[0061] In addition, since the laminate 80 with a light-guiding layer having the cavity 64 according to the first and second examples can reduce brightness unevenness compared to the laminate 80X with a light-guiding layer having the cavity 64X according to the comparative example, it was found that from the viewpoint of reducing brightness unevenness, it is preferable that the first differential line 71 of the first arc-shaped curve AR1 is a straight line.

[0062] (Relationship between Emission Angle and Luminous Intensity of Emitted Light) Fig. 11 is a diagram showing an example of the relationship between the emission angle in the Y direction and the luminous intensity of light emitted from the laminates with a light guide layer including cavities according to each of Example 1, Example 2, and Comparative Example. In Fig. 11, the horizontal axis represents the emission angle of the emitted light in the Y direction relative to the normal to the emission surface of the laminate with a light guide layer. The vertical axis represents normalized luminous intensity according to the emission angle.

[0063] Graph 111, indicated by a solid line, shows an example of the relationship between the emission angle and luminous intensity in the light-guiding layer-included laminate 80 including the cavity 64 according to Example 1. Graph 112, indicated by a dashed line, shows an example of the relationship between the emission angle and luminous intensity in the light-guiding layer-included laminate 80 including the cavity 64 according to Example 2. Graph 113, indicated by a dashed line, shows the relationship between the emission angle and luminous intensity in the light-guiding layer-included laminate 80X including the cavity 64X according to the comparative example.

[0064] In the laminate 80 with a light guide layer including the cavity 64 according to the first example, the emission angle PA1 at which the luminous intensity reached a peak was 1.98°, and the half-value angle HA1 was 77.1°. In the laminate 80 with a light guide layer including the cavity 64 according to the second example, the emission angle PA2 at which the luminous intensity reached a peak was 37.6°, and the half-value angle HA2 was 101°. In the laminate 80X with a light guide layer including the cavity 64X according to the comparative example, the emission angle PAX at which the luminous intensity reached a peak was −3.96°, and the half-value angle HAX was 27.7°.

[0065] From the above, it was found that the laminate 80 with a light guide layer including the cavity 64 according to the first and second examples had a larger half-value angle in the Y direction than the laminate 80X with a light guide layer including the cavity 64X according to the comparative example, and was therefore able to emit light over a wider angle. Furthermore, it was found that the laminate 80 with a light guide layer including the cavity 64 according to the first and second examples was able to emit light over a wider angle, thereby reducing directivity and brightness unevenness.

[0066] In the laminate 80 with a light guide layer including the cavity 64 according to the first example, the output angle PA1 at which the luminous intensity reaches a peak is smaller in the Y direction than in the laminate 80 with a light guide layer including the cavity 64 according to the second example. This shows that the laminate 80 with a light guide layer including the cavity 64 according to the first example can reduce the optical axis deviation with respect to the normal to the output surface 82.

[0067] From the viewpoint of reducing brightness unevenness and reducing the optical axis deviation relative to the normal to the exit surface 82, it was found that the exit angle in the Y direction at which the luminous intensity of light Lr1 emitted from the exit surface 82 reaches its peak is preferably ±50° or less, and even more preferably ±30° or less.

[0068] 12 is a schematic cross-sectional view showing a modification of the lighting device 100 including the light-guiding layer-equipped laminate 80 according to the first embodiment. Fig. 12 shows a cross section corresponding to the line II-II in Fig. 1.

[0069] In the modification shown in Fig. 12, the light guide layer 10 is disposed opposite the substrate 30. Light incident from the first light source LS1 into the laminate 80 with a light guide layer is emitted from an exit surface 82 located on the opposite side from the light guide layer 10. The modification shown in Fig. 12 differs mainly from the lighting device 100 shown in Fig. 2 in these respects.

[0070] 12 also provides the same effects as those of the first embodiment. The light exit surface from which light exits the light guide layer-equipped laminate 80 may be at least one of the upper surface (the surface on the +Z side) and the lower surface (the surface on the −Z side) of the light guide layer-equipped laminate 80.

[0071] Second Embodiment Next, a description will be given of an illumination device including a laminate with a light guide layer according to a second embodiment. Note that the same names and symbols as those in the already described embodiments indicate the same or similar members or configurations, and detailed descriptions thereof will be omitted as appropriate.

[0072] Fig. 13 is a schematic plan view showing an illumination device 100 including a laminate with a light guide layer according to the second embodiment. Fig. 14 is a schematic cross-sectional view taken along line XIV-XIV in Fig. 13. Fig. 15 is a schematic cross-sectional view showing an example of a cavity 64 included in a laminate with a light guide layer 80 according to the second embodiment.

[0073] In this embodiment, the light guiding layer-equipped laminate 80a includes a second end surface 83 that is provided on the opposite side to the first end surface 81 and that directly receives light Lr2 from a second light source LS2 different from the first light source LS1. The cavity 64 differs from the first embodiment mainly in that, in a cross section that intersects with the first end surface 81 and the light exit surface 82, the cavity 64 further includes a second arc-shaped curve AR2 that is convex toward the side where the second end surface 83 is located. The lighting device 100 also includes a second light source LS2.

[0074] For example, in a configuration in which the cavity 64 includes the first arc-shaped curve AR1 only on the side where the first end face 81 is located in the above-mentioned cross section, the relationship between the emission angle and luminous intensity of the light reflected by the first inclined surface ISa may not necessarily be symmetrical with the relationship between the emission angle and luminous intensity of the light reflected by the second inclined surface ISb. If the relationship between the emission angle and luminous intensity of the light reflected by the first inclined surface ISa is not necessarily symmetrical with the relationship between the emission angle and luminous intensity of the light reflected by the second inclined surface ISb, a bias may occur in the illumination area by the light emitted from the emission surface 82, and the quality of the illumination device may be reduced.

[0075] In the present embodiment, the cavity 64 further includes, in a cross section intersecting the first end face 81 and the exit face 82, a second arc-shaped curve AR2 that is convex toward the side where the second end face 83 is located. This allows the shape of the second inclined face ISb to be closer to that of the first inclined face ISa, and the relationship between the emission angle and the luminous intensity of the light reflected by the first inclined face ISa can be made symmetrical with respect to the relationship between the emission angle and the luminous intensity of the light reflected by the second inclined face ISb. By making the relationship between the emission angle and the luminous intensity of the light reflected by the first inclined face ISa symmetrical with respect to the relationship between the emission angle and the luminous intensity of the light reflected by the second inclined face ISb, in the present embodiment, it is possible to reduce bias in the illumination area due to the light emitted from the exit face 82 and improve the quality of the lighting device 100.

[0076] The second arc-shaped curve AR2 is an arc-shaped curve that constitutes one cross section of the curved second inclined surface ISb. The cavity 64 reflects the light Lr2, which is emitted from the second light source LS2, enters the inside of the laminate 80 with a light guide layer through the second end surface 83, and is then guided inside the laminate 80 with a light guide layer, off the second inclined surface ISb including the second arc-shaped curve AR2, and emits the reflected light Lr2 from the emission surface 82. By reflecting the light Lr2 off the second inclined surface ISb including the second arc-shaped curve AR2, the cavity 64 can reduce the directivity of the light Lr2 reflected by the cavity 64 compared to when the light Lr2 is reflected by a flat surface. This reduces the area inside the laminate 80 with a light guide layer through which the light Lr2 reflected by the cavity 64 does not pass, thereby reducing band-like dark areas and brightness unevenness near the second end surface 83.

[0077] The second light source LS2 can be an LED device, similar to the first light source LS1. However, the second light source LS2 is not limited to an LED device and may be a halogen lamp or the like. Furthermore, the first light source LS1 and the second light source LS2 may be the same or different.

[0078] (Cavity 64 in Second Embodiment) Fig. 15 is a schematic cross-sectional view showing an example of a cavity 64 included in the laminate 80 with a light guide layer according to the second embodiment. Fig. 16 is a schematic plan view showing an example of a cavity 64 included in the laminate 80 with a light guide layer according to the second embodiment.

[0079] The rise angle θa of the first arcuate curve AR1 on the side where the first end face 81 is located is preferably 85° or less. The rise angle θb2 of the second arcuate curve AR2 on the side where the second end face 83 is located is preferably 85° or less. In the example shown in FIG. 15 , the first inclined surface ISa and the second inclined surface ISb have a substantially symmetrical shape about the central axis 64C of the cavity 64, which is parallel to the Z axis. The rise angle θa of the first arcuate curve AR1 is 73°. The rise angle θb2 of the second arcuate curve AR2 is also 73°. However, the first inclined surface ISa and the second inclined surface ISb do not necessarily have to be substantially symmetrical about the central axis 64C. The rise angles θa and θb2 are not limited to 73° and can be changed as appropriate.

[0080] Since the rise angle θb2 of the second arc-shaped curve AR2 on the side where the second end face 83 is located is 885° or less, as will be described later with reference to Figures 18 and 19, in the laminate 80 with a light-guiding layer, the directionality of the light Lr2 emitted from the exit surface 82 can be increased to a range where brightness unevenness such as band-like dark areas can be reduced.

[0081] 15 is a curved surface that is convex toward the second end surface 83 in a plan view. Here, light emitted from each of the multiple LED devices that make up the second light source LS2 has a spread in the Y direction. Therefore, the second inclined surface ISb acts on the light more uniformly when the second inclined surface ISb has a curved surface that is convex toward the second light source LS2. Note that if a coupling optical system is provided between the second light source LS2 and the second end surface 83 of the laminate 80 with a light guide layer to allow highly parallel light (light that has a small spread in the Y direction) to be incident, the second inclined surface ISb may be parallel to the X direction.

[0082] 16 , in this embodiment, the shape of the cavity 64 when the exit surface 82 is viewed in a plan view is elliptical. The ellipse EL that constitutes the cavity 64 when the exit surface 82 is viewed in a plan view has a minor axis EL1 that is oriented along the normal to the first end face 81 and a major axis EL2 that is orthogonal to the normal to the first end face 81. The value obtained by dividing the length of the major axis EL2 by the length of the minor axis EL1 is 1.65 or greater. The length of the major axis EL2 corresponds to the length of the cavity 64 in the Y direction. The length of the minor axis EL1 corresponds to the length of the cavity 64 in the X direction.

[0083] In this embodiment, by setting the value obtained by dividing the length of the major axis EL2 by the length of the minor axis EL1 to 1.65 or more, it is possible to reduce shape distortion during processing using an FTS (Fast Tool Servo) processing device, thereby enabling precise processing with small shape errors. The upper limit of the value obtained by dividing the length of the major axis EL2 by the length of the minor axis EL1 is preferably 20 or less, even more preferably 10 or less, and even more preferably 5 or less.

[0084] <First-order differential curves of one cross section of the cavity 64 in the second embodiment> Next, with reference to Fig. 17 , a first-order differential curve of one cross section of the cavity 64 included in the laminate 80 with a light guide layer according to the second embodiment will be described. Fig. 17 is a diagram showing an example of a first-order differential curve of one cross section of the cavity 64 included in the laminate 80 with a light guide layer according to the second embodiment. In Fig. 17 , the horizontal axis represents the position in the Y direction, and the vertical axis represents the first-order differential value of one cross section of the cavity 64. Note that the "position in the Y direction" on the horizontal axis is normalized with the width W of the cavity 64 in the Y direction set to 1.

[0085] In the light guide layer-equipped laminate 80 according to the second embodiment, the first inclined surface ISa and the second inclined surface ISb have shapes that are substantially symmetrical about the central axis 64C. The first inclined surface ISa and the second inclined surface ISb also have substantially symmetrical shapes about the central axis 64C. The first inclined surface ISa and the second inclined surface ISb have substantially the same effect. Therefore, in FIG. 17 , the first inclined surface ISa will be described as a representative example of the first inclined surface ISa.

[0086] The solid first-order differential line 71 is a line obtained by first differentiating the first arc-shaped curve AR1 of the cavity 64 according to the first example included in the light-guiding layer-equipped laminate 80 according to the first embodiment. The first-order differential line 71 is the same as that shown in FIG. 7 and is shown for comparison.

[0087] A dotted first-order differential line 171 is a line obtained by first differentiating the first arc-shaped curve AR1 of the cavity 64 included in the laminate 80 with a light-guiding layer according to this embodiment. The rise angle of the cavity 64 in the first embodiment is 63°, whereas the rise angle of the cavity 64 in this embodiment is 73°. Therefore, the slope of the first-order differential line 171 is steeper than that of the first-order differential line 71.

[0088] The first arc-shaped curve AR1 of the cavity 64 included in the laminate 80 with a light guide layer according to this embodiment is convex toward the side where the first end face 81 is located and also convex toward the side where the light exit surface 82 is located, so the first differential line 171 has a negative slope. Furthermore, the first arc-shaped curve AR1 of the cavity 64 included in the laminate 80 with a light guide layer according to this embodiment is a parabola, so the first differential line 171 is a straight line.

[0089] Evaluation of the laminate 80 with a light guide layer according to the second embodiment Next, the evaluation results of the light emitted from the laminate 80 with a light guide layer including the cavity 64 according to the second embodiment will be described. In the evaluation of the emitted light, the brightness unevenness and the relationship between the emission angle and luminous intensity of the emitted light were calculated by simulation and evaluated.

[0090] (Brightness Unevenness of Emitted Light) Evaluation results of brightness unevenness of emitted light will be described with reference to Fig. 18. Fig. 18 is a diagram showing an example of brightness distribution in the Y direction of light emitted from the light-guiding layer-equipped laminate 80 according to the second embodiment.

[0091] The way to interpret Figure 18 is the same as the way to interpret Figure 10 described above. Graph 101, indicated by a solid line in Figure 18, shows the simulation results of the luminance distribution in the cross-sectional region P of Figure 8 for light emitted from the light-guiding layer-equipped laminate 80 according to the first embodiment, which includes the cavity 64 according to the first example. Graph 101 is the same as graph 101 shown in Figure 10 described above. The difference between the maximum luminance and the lowest luminance in graph 181 is approximately the same as the difference between the maximum luminance and the lowest luminance in graph 101, and therefore the luminance ratio is also approximately the same. This shows that the light-guiding layer-equipped laminate 80 according to this embodiment can reduce luminance unevenness, similar to the light-guiding layer-equipped laminate 80 according to the first embodiment, which includes the cavity 64 according to the first example.

[0092] (Relationship Between Emission Angle and Luminous Intensity of Emitted Light) Fig. 19 is a diagram showing an example of the relationship between the emission angle in the Y direction and the luminous intensity of light emitted from the laminate with a light guide layer 80 according to this embodiment. In Fig. 19, the horizontal axis represents the emission angle of the emitted light in the Y direction relative to the normal to the emission surface 82 of the laminate with a light guide layer 80. The vertical axis represents normalized luminous intensity according to the emission angle.

[0093] Graph 191, indicated by a dotted line, shows the relationship between the output angle and luminous intensity in the laminate 80 with a light guide layer according to this embodiment. In FIG. 19 , the output angle PA3 at which the luminous intensity peaks is ±9°, and the half-value angle HA3 is 89.0°. Graph 191 in FIG. 19 reveals that the luminous intensity according to the output angle is approximately symmetrical around the output angle of 0°, as compared with graph 111 shown in FIG. 11 . By making the relationship between the output angle and luminous intensity of light reflected by the first inclined surface ISa closer to symmetry with the relationship between the output angle and luminous intensity of light reflected by the second inclined surface ISb, it is possible to reduce bias in the illumination area due to the light emitted from the output surface 82, thereby improving the quality of the lighting device 100.

[0094] Furthermore, the half-value angle of graph 191 is wider at 89.0° compared to the half-value angle of 77.1° in graph 111 shown in Fig. 11. This shows that the light-guiding layer-equipped laminate 80 according to this embodiment can emit light over a wider angle than the light-guiding layer-equipped laminate 80 according to the first embodiment. Furthermore, since the light-guiding layer-equipped laminate 80 according to this embodiment can emit light over a wider angle, it is possible to reduce directivity and brightness unevenness.

[0095] In the laminate 80 with a light guide layer according to this embodiment, the emission angle at which the luminous intensity reaches its peak in the Y direction is close to 0°, and therefore it has been found that the optical axis deviation of the light emitted from the laminate 80 with a light guide layer according to this embodiment with respect to the normal to the emission surface 82 can be reduced.

[0096] 13 and 14 illustrate a configuration in which the light Lr1 emitted from the first light source LS1 is directly incident on the first end surface 81 and the light Lr1 emitted from the second light source LS2 is directly incident on the second end surface 83, but the present invention is not limited to this. For example, the light Lr1 emitted from the first light source LS1 may be indirectly incident on the first end surface 81 via a light diffusing member disposed between the first light source LS1 and the first end surface 81. The light Lr2 emitted from the second light source LS2 may be indirectly incident on the second end surface 83 via a light diffusing member disposed between the second light source LS2 and the second end surface 83.

[0097] 12, the orientation of the cavity 64 can be reversed in the second embodiment as well. Fig. 20 is a schematic cross-sectional view showing a modification of the lighting device 100 including the light guide layer-equipped laminate 80 according to the second embodiment. Fig. 20 shows a cross section of the light guide layer-equipped laminate 80 taken along line II-II in Fig. 1.

[0098] In the modified example shown in Fig. 20 , the light guide layer 10 is disposed opposite the substrate 30. Light incident on the laminated body 80 with a light guide layer from the first light source LS1 is emitted from the emission surface 82 located on the opposite side from the light guide layer 10. Light incident on the laminated body 80 with a light guide layer from the second light source LS2 is emitted from the emission surface 82 located on the opposite side from the light guide layer 10. The modified example shown in Fig. 20 differs mainly from the lighting device 100 shown in Fig. 2 in these respects. In other words, the modified example shown in Fig. 20 differs from the lighting device 100 shown in Fig. 2 in that the orientation of the cavity 64 is reversed.

[0099] 20 also provides the same effects as those of the first embodiment. The light exit surface from which light exits the light guide layer-equipped laminate 80 may be at least one of the top surface (the surface on the +Z side) and the bottom surface (the surface on the −Z side) of the light guide layer-equipped laminate 80.

[0100] 14 , the surface of the light guide according to the second embodiment onto which light from the second light source LS2 is incident is not limited to the second end surface 83 of the laminate with a light guide layer 80. For example, the surface of the light guide according to the second embodiment onto which light from the second light source LS2 is incident may be the exit surface 82 of the laminate with a light guide layer 80, or may be the top surface 84, which is the surface opposite to the exit surface 82.

[0101] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0102] The laminate 80 with a light guide layer may have a low refractive index layer disposed on one side of the laminate 80 with a light guide layer and having a refractive index lower than that of the light guide layer 10 or the shaping film 62. The laminate 80 with a light guide layer may also have a low refractive index layer between the shaping film 62 and the substrate 30. The low refractive index layer preferably has a refractive index of 1.30 or less. The laminate 80 with a light guide layer may also have a hard coat layer or an anti-reflection layer.

[0103] The adherend on which the laminate 80 with a light guide layer is placed is not limited to glass, but may also be an electronic substrate such as a liquid crystal cell, or a non-light-transmitting member such as a ceiling, wall, or floor. The shaping film 62 is not limited to extracting light to the side opposite to the side on which the adherend is located, but may extract light to the side on which the adherend is located. In this case, if the adherend has high light transmittance, the extracted light may pass through the adherend, and if the adherend has low light transmittance, the adherend may reflect the light.

[0104] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the illustrated figures. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0105] The lighting device according to the embodiment can reduce brightness unevenness, and by being placed on building components such as glass, windows, walls, floors, and ceilings, it can illuminate the interior or exterior space of a building with reduced brightness unevenness.

[0106] Furthermore, the lighting device according to the embodiment can be used as a partition to suitably partition a room or conceal a desired space. Furthermore, by disposing the shape-imparting film, laminate, and laminate with a light guide layer provided in the lighting device according to the embodiment on a glass substrate of a display device such as a liquid crystal panel or an organic EL (Electro Luminescence) display panel, it is possible to brighten backlight illumination in the display device. In addition, the lighting device according to the embodiment can provide new uses other than those described above.

[0107] The present invention provides, for example, the following aspects. <1> A light guide into which light from a first light source is incident and which has an internal cavity, the light guide including a first end face and an exit face that is continuous with the first end face and intersects with the first end face, wherein the light guide reflects a portion of the light guided inside the light guide by the cavity and causes the light reflected by the cavity to exit from the exit face, and the cavity includes, in a cross section that intersects with the first end face and the exit face, a first arc-shaped curve that is convex toward at least the side where the first end face is located. <2> The light guide according to <1>, wherein the first arc-shaped curve is a parabola. <3> The light guide according to <1> or <2>, wherein a rise angle of the first arc-shaped curve on the side where the first end face is located is 85° or less. <4> The light guide according to any one of <1> to <3>, wherein a second derivative of the first arc-shaped curve is negative. <5> The light guide according to <4>, wherein a first derivative of the first arc-shaped curve is a straight line. <6> The light guide according to <5>, wherein a slope of a first derivative of the first arc-shaped curve is equal to or greater than -10 and less than 0. <7> The light guide according to any one of <1> to <6>, wherein an exit angle at which the luminous intensity of the light emitted from the exit surface reaches a peak is ±50° or less in a direction intersecting a normal to the first end face and a normal to the exit surface. <8> The light guide according to any one of <1> to <7>, wherein an exit angle at which the luminous intensity of the light emitted from the exit surface reaches a peak is ±30° or less in a direction intersecting a normal to the first end face and a normal to the exit surface. <9> The light guide according to any one of <1> to <8>, wherein the light guide includes a second end face into which light from a second light source is incident and which is provided on the opposite side of the light guide to the first end face, and the cavity further includes, in a cross section intersecting the first end face and the light exit face, a second arc-shaped curve that is convex toward the side where the second end face is located, on the side where the second end face is located.<10> The light guide according to any one of <1> to <9>, wherein the shape of the cavity when the light exit surface is viewed in a plane is elliptical, the ellipse constituting the cavity when the light exit surface is viewed in a plane has a minor axis in a direction along a normal to the first end face and a major axis in a direction perpendicular to the normal to the first end face, and a value obtained by dividing the length of the major axis by the length of the minor axis is 1.65 or more. <11> An illumination device comprising the light guide according to any one of <1> to <8> and the first light source. <12> An illumination device comprising the light guide according to <9>, the first light source, and the second light source.

[0108] This application claims priority based on Japanese Patent Application No. 2024-055661 filed with the Japan Patent Office on March 29, 2024, and includes the entire contents of this Japanese patent application.

[0109] 10 Light guide layer 30 Base material 52 First adhesive layer 54 Second adhesive layer 60 Direction conversion layer 62 Shaped film 621 Main surface 622 Recess 64 Cavity 64C Central axis 70 Laminate 71, 72, 73, 171 First differential line 80 Laminate with light guide layer 81 First end surface 82 Emission surface 83 Second end surface 84 Upper surface 100 Lighting device 101, 102, 111, 112, 113, 181, 191 Graph AR1 First arc-shaped curve AR2 Second arc-shaped curve EL Ellipse EL1 Minor axis EL2 Major axis H Height HA1, HA2, HA3 Half-value angle ISa First inclined surface ISb Second inclined surface L Length Lr1, Lr2 Light LS1 First light source LS2 Second light source P Cross-sectional area PA1, PA2, PA3 Emission angle Px, Py Pitch Q11 Maximum luminance value Q12 Lowest luminance value S Dark area Tz Distance W Width θa, θb2 Rise angle θb Inclination angle

Claims

1. A light guide into which light from a first light source is incident and which has an internal cavity, the light guide including a first end face and an exit face that is continuous with and intersects with the first end face, the light guide reflects a portion of the light guided inside the light guide by the cavity and causes the light reflected by the cavity to exit from the exit face, and the cavity, in a cross section that intersects with both the first end face and the exit face, includes a first arc-shaped curve that is convex toward the side where the first end face is located, at least on the side where the first end face is located.

2. The light guide of claim 1, wherein said first arcuate curve is a parabola.

3. The light guide according to claim 1, wherein the rising angle of the first arcuate curve on the side where the first end face is located is 85° or less.

4. The light guide of claim 1, wherein the second derivative of said first arcuate curve is negative.

5. The light guide of claim 4, wherein a first derivative of said first arcuate curve is a straight line.

6. The light guide according to claim 5, wherein the gradient of a first differential line of said first arc-shaped curve is equal to or greater than -10 and less than 0.

7. A light guide as described in claim 1, wherein the angle at which the luminous intensity of light emitted from the exit surface reaches its peak is ±50° or less in a direction intersecting the normal to the first end face and the normal to the exit surface.

8. A light guide as described in claim 1, wherein, within an imaginary plane intersecting the first end face and the exit surface, the exit angle at which the luminous intensity of the light emitted from the exit surface reaches its peak is ±30° or less.

9. The light guide according to claim 1, wherein the light guide receives light from a second light source and includes a second end face provided on the side of the light guide opposite to the first end face, and the cavity, in a cross section intersecting the first end face and the light exit surface, further includes a second arc-shaped curve convex on the side where the second end face is located, on the side where the second end face is located.

10. A light guide as described in claim 1, wherein the shape of the cavity when the light exit surface is viewed in a plane is elliptical, the ellipse constituting the cavity when the light exit surface is viewed in a plane has a minor axis along the normal to the first end face and a major axis perpendicular to the normal to the first end face, and the value obtained by dividing the length of the major axis by the length of the minor axis is 1.65 or more.

11. A lighting device comprising: a light guide according to any one of claims 1 to 8; and the first light source.

12. A lighting device comprising: the light guide according to claim 9; the first light source; and the second light source.

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