Light guide and lighting device

Abstract

To improve the diffusion of light incident on the light guide. [Solution] The light guide is a light guide into which light from a light source is incident, and includes an end face and an exit surface that is continuous with the end face and intersects the end face, 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 surface, the cavity has a convex shape in a first cross section that intersects the end face and the exit surface, and includes a flat portion at the top of the convex shape.

Description

Technical Field

[0006] , , , , , , , ,

[0005]

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

Background Art

[0002] For example, Patent Document 1 discloses a lighting device provided with a first prism pattern and a second prism pattern that intersect each other at right angles between a light source and a light guide plate. Further, Patent Document 2 discloses a lighting device having a moth-eye pattern and protrusions on an incident surface of a light guide plate for incident light from a light source.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to improve the diffusibility of light incident on a light guide.

Means for Solving the Problems

[0005] A light guide according to one aspect of the present invention is a light guide provided with a cavity inside and into which light from a light source is incident, and includes an end face and an emission face that is continuous with the end face and intersects the end face. The light guide reflects a part of the light guided inside the light guide by the cavity, emits the light reflected by the cavity from the emission face, the cavity has a convex shape in a first cross section intersecting each of the end face and the emission face, and includes a flat portion at the top of the convex shape.

Effects of the Invention

[0006] According to the present invention, the diffusivity of light incident on the light guide can be improved. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic plan view showing a lighting device equipped with a light guide according to an embodiment. [Figure 2] This is a schematic cross-sectional view of the line II-II in Figure 1. [Figure 3] This is a schematic cross-sectional view showing the shape of the first cross-section of the cavity in the light guide body according to the embodiment. [Figure 4] This is a schematic perspective view showing the cavity of the light guide according to the embodiment. [Figure 5] This figure shows the shape of the cavity in the second cross-section of the light guide body according to the embodiment. [Figure 6] This is a schematic perspective view showing the manufacturing process of a mold for producing a recess in the cavity of a light guide according to an embodiment. [Figure 7] This figure shows the relationship between the viewing angle and the normalized brightness of the light extracted from the exit surface for each cavity shape. [Figure 8] This figure shows the relationship between the viewing angle and the normalized brightness of the light extracted from the opposite side of the emission surface, for each cavity shape. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same reference numerals are used for the same components, and redundant explanations are omitted as appropriate.

[0009] The embodiments shown below illustrate light guides and lighting devices that embody the technical concept of the present invention, and the present invention is not limited to the embodiments shown below. The size and positional relationships of the components shown in the drawings may be exaggerated for clarity of explanation.

[0010] In the diagrams shown below, a Cartesian coordinate system with X, Y, and Z axes is used to represent direction. The X, Y, and Z axes are approximately orthogonal to each other. The direction in which the arrow representing the X axis points is denoted as the +X side, and the opposite direction is denoted as the -X side. The direction in which the arrow representing the Y axis points is denoted as the +Y side, and the opposite direction is denoted as the -Y side. The direction in which the arrow representing the Z axis points is denoted as the +Z side, and the opposite direction is denoted as the -Z side.

[0011] The Z-direction along the Z-axis corresponds to the direction along the normal to the emission surface of the light guide according to the embodiment. The Y-direction along the Y-axis corresponds to the direction along the normal to the end face of the light guide according to the embodiment. In this specification, "plan view" means viewing the 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 represent relative positional relationships for explanatory purposes and do not limit the directions of the embodiments.

[0012] In this specification and in the claims, "parallel" means that the angular deviation from the parallel state is ±10 degrees or less. "Orthogonal" means that the angular deviation from the orthogonal state is ±10 degrees or less. "To be positioned" is not limited to direct contact, but also includes indirect positions, such as those arranged via other members. Furthermore, in this specification, "thickness" or "height" refers to the length in the Z direction.

[0013] <Configuration of a lighting device equipped with a light guide according to an embodiment> Referring to Figures 1 and 2, the configuration of the lighting device equipped with a light guide according to the embodiment will be described. Figure 1 is a schematic plan view showing the lighting device 100 equipped with a light guide 80 according to the embodiment. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. In the example shown in Figure 2, a portion of the light Lt emitted from the light source LS is indicated by a dashed-dotted arrow.

[0014] The lighting device 100 includes a light guide 80 and a light source LS. The light guide 80 has a cavity 64 inside and is a light guide into which light Lt from the light source LS is incident. The light guide 80 includes an end face 81 and an exit face 82 that is continuous with and intersects the end face 81.

[0015] In the example shown in FIG. 2, the light guide 80 is a laminated body with a light guide layer, including a light guide layer 10, a laminated body 70, and a first adhesive layer 52. The first adhesive layer 52 is disposed between the light guide layer 10 and the laminated body 70 and is a layer that adheres the light guide layer 10 and the laminated body 70. The laminated body 70 includes a base material 30 and a direction conversion layer 60. The direction conversion layer 60 includes a shaped film 62 and a second adhesive layer 54.

[0016] The second adhesive layer 54 is disposed between the shaped film 62 and the base material 30 and is a layer that adheres the shaped film 62 and the base material 30. The base material 30 is disposed opposite to the first main surface 621 of the shaped film 62 via the second adhesive layer 54. The light guide layer 10 is disposed opposite to the second main surface 622 of the shaped film 62 via the second adhesive layer 54. The shaped film 62 is a film manufactured without shaving the material. In the examples shown in FIGS. 1 and 2, a light guide 80, which is a laminated body with a light guide layer as an example of the light guide according to the embodiment, will be described. However, if there is a cavity 64 inside the light guide, the light guide according to the embodiment does not necessarily have to be a laminated body with a light guide layer. The light guide according to the embodiment may be composed only of a laminated body having a cavity 64 inside, or may not be a laminated body.

[0017] As shown in FIG. 2, a plurality of cavities 64 are provided inside the direction conversion layer 60. Each of the plurality of cavities 64 has a first inclined surface ISa and a second inclined surface ISb disposed on the opposite side of the first inclined surface ISa in the Y direction. For example, air exists inside the cavity 64. A plurality of recesses are provided on the first main surface 621 of the shaped film 62. The cavities 64 are formed by closing the open portions of each of the plurality of recesses with a base material 30 disposed on the first main surface 621 via the second adhesive layer 54. The cavity 64 can also be referred to as an internal space.

[0018] The lighting device 100 is used, for example, in a state where the light guide 80 is disposed on an adherent such as glass, a window, a wall, a floor, or a ceiling. The lighting device 100 causes the light Lt emitted from the light source LS to enter the inside of the light guide 80 through the end face 81. In the light guide 80, the light Lt enters from the end face 81. The light guide 80 reflects part of the light Lt guided inside the light guide 80 by the cavity 64, and causes the light Lt reflected by the cavity 64 to exit from the exit surface 82. From another perspective, the light guide 80 can extract the light Lt reflected by the cavity 64 from the exit surface 82. The lighting device 100 can illuminate an indoor space or the like where the light guide 80 is disposed with the light Lt emitted from substantially the entire exit surface 82 of the light guide 80. Note that the reflection by the cavity 64 includes at least one of regular reflection and diffuse reflection.

[0019] The lighting 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 part of the light Lt guided inside the light guide 80 toward the exit surface 82 side by total internal reflection (TIR). Note that the light Lt can be refracted according to the refractive index of the substance constituting the interface when passing through the interface.

[0020] The light guide 80 is configured to emit the light Lt having a desired light distribution from the exit surface 82 by the light distribution control structure. The light distribution can be controlled, for example, by adjusting the cross-sectional shape, planar shape, size, arrangement density, distribution, etc. of the cavity 64.

[0021] The light guide 80 has a visible light transmittance of 60% or more and a haze value of less than 30%. Preferably, the visible light transmittance is 70% or more, and more preferably 80% or more. Preferably, the haze value is less than 10%, and more preferably 5% or less. Because the light guide 80 has a high visible light transmittance and a low haze value, objects or displays can be seen through the light guide 80. Visible light is light with a wavelength of 380 nm to 780 nm. The visible light transmittance and haze value can be measured using a haze meter (manufactured by Murakami Color Technology Laboratory: product name HM-150), etc.

[0022] The ratio of the area of ​​the multiple cavities 64 to the area of ​​the light guide layer 10, i.e., the occupied area ratio, is preferably 1% to 80% when the light guide layer 10 is viewed from the direction normal to the emission surface 82. The upper limit of the above occupied area ratio is more preferably 50% or less, and even more preferably 45% or less. In order to obtain at least one of high transmittance and low haze value, it is preferably 30% or less, even more preferably 10% or less, and even more preferably 5% or less.

[0023] For example, when the cavity occupancy rate is 50%, a haze value of 30% can be obtained. The cavity occupancy rate of 64 may be uniform, and the occupancy rate may increase with increasing distance so that the brightness does not decrease even when the distance from the light source LS increases. For mass production using the roll-to-roll method or the roll-to-sheet method, it is preferable that the cavity occupancy rate of 64 be uniform.

[0024] In the light guide 80, the light guide layer 10 and the shaping film 62 are bonded together by a first adhesive layer 52. Furthermore, the shaping film 62 and the substrate 30 are bonded together by a second adhesive layer 54 that constitutes the direction-changing layer 60. The light guide layer 10 and the substrate 30 may be transparent substrates or films.

[0025] In the example shown in Figure 1, the multiple cavities 64 are spaced apart in the X and Y directions of the light guide layer 10. However, the spacing of the cavities 64 may be appropriately set according to the shape of the light guide layer 10 or the desired light distribution.

[0026] In the example shown in Figure 1, a plurality of cavities 64 having substantially the same shape and a curved surface convex in the same direction are arranged throughout the entire region, periodically separated in the X and Y directions. 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 Figure 1, the light guide 80 further has cavities 64 arranged with a shift of 1 / 2 of the pitch Px in the X direction and 1 / 2 of the pitch Py in the Y direction.

[0027] The light source LS is, for example, an LED (Light Emitting Diode) device. Multiple LED devices are arranged in a line in the X direction. There are no particular restrictions on the number or arrangement of LEDs. Note that the light source LS is not limited to LED devices, but may also be a halogen lamp or the like.

[0028] The shaping film 62 can be manufactured according to the method described in Japanese Patent Publication No. 2013-524288. Specifically, the desired shaping film 62 can be manufactured by coating the surface of a polymethyl methacrylate (PMMA) film with lacquer (FineCure RM-64, manufactured by Sanyo Chemical Industries, Ltd.), embossing an optical pattern onto the film surface containing the lacquer, and then curing the lacquer. The total thickness of the shaping film 62 is, for example, 130 μm.

[0029] The light guide layer 10 is formed from a known material with high transmittance to visible light. For example, the light guide layer 10 may be made from 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 to 1.80. 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. For example, the thickness of the light guide layer 10 is 0.05 mm to 50 mm.

[0030] The thickness of the substrate 30 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 the substrate 30 is preferably 1.40 or more and 1.70 or less, and more preferably 1.43 or more and 1.65 or less, independently of each other.

[0031] The thickness of the first adhesive layer 52 and the second adhesive layer 54 is, independently of each other, for example, 0.1 μm to 100 μm, preferably 0.3 μm to 100 μm, and more preferably 0.5 μm to 50 μm. The refractive index of the first adhesive layer 52 and the second adhesive layer 54 is, independently of each other, preferably 1.42 to 1.60, and more preferably 1.47 to 1.58. Furthermore, the refractive index of the first adhesive layer 52 and the second adhesive layer 54 is preferably close to the refractive index of the light guide layer 10 or shaping film 62 in contact with them, and the absolute value of the difference in refractive index is preferably 0.2 or less.

[0032] Preferably, the second adhesive layer 54 can be bonded to the shaping film 62 without filling in any recesses. Suitable adhesives for forming the second adhesive layer 54 include those described in the present applicant's international applications PCT / JP2021 / 006452, PCT / JP2021 / 006453, or Japanese Patent Application No. 2021-025496. All 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.

[0033] <Configuration of Cavity 64> Referring to Figures 3 and 4, the configuration of the cavity 64 provided in the light guide 80 will be described in detail. Figure 3 is a schematic cross-sectional view showing the shape of the cavity 64 in its first cross-section. Figure 4 is a schematic perspective view showing the cavity 64.

[0034] In this embodiment, as shown in Figure 3, the cavity 64 has a convex shape in a first cross-section that intersects with the end face 81 and the ejection face 82 shown in Figure 2, and includes a flat portion 640 at the top of the convex shape.

[0035] In the examples shown in Figures 3 and 4, the first cross-section is a cross-section parallel to the YZ plane. In the example shown in Figure 3, the cavity 64 has an arc-shaped convex form in the first cross-section that is convex on the side where the ejection surface 82 is located, for example, on the +Z side, and includes a flat portion 640 parallel to the ejection surface 82. The convex form has a mirror-symmetric shape with respect to the central axis 64C of the cavity 64 that extends in the direction normal to the ejection surface 82. However, the convex form of the cavity 64 may be any shape as long as it is convex on the +Z side and includes a flat portion 640 at its apex. For example, the convex form in the first cross-section of the cavity 64 may be a substantially trapezoidal shape with the flat portion 640 as the upper base and the opposite side of the flat portion 640 as the lower base, or it may be a substantially circular arc shape with a flat apex. Furthermore, the convex form may have a non-mirror-symmetric shape with respect to the central axis 64C of the cavity 64. Furthermore, the flat portion 640 does not necessarily have to be parallel to the ejection surface 82.

[0036] In the cavity 64, the first inclination angle θa of the first inclined surface ISa is, for example, 10° or more and 70° or less. If the first inclination angle θa is less than 10°, the controllability of light distribution may be insufficient, and the light extraction efficiency from the light guide 80 may be insufficient. On the other hand, if the first inclination angle θa exceeds 70°, for example, processing the shaping film 62 may become difficult. The second inclination angle θb of the second inclined surface ISb is, for example, 50° or more and 100° or less. If the second inclination angle θb is less than 50°, stray light may be generated in an unintended direction. If the second inclination angle θb exceeds 100°, for example, processing the shaping film 62 that constitutes the light extraction layer 11 may become difficult. The length L of the cavity 64 in the X direction is preferably 10 μm or more and 500 μm or less. The width W of the cavity 64 in the Y direction is preferably 1 μm or more and 100 μm or less. The length L is, for example, twice or more the width W. The height H corresponding to the length of the cavity 64 in the Z direction is preferably 1 μm or more and 100 μm or less.

[0037] In this embodiment, in a first cross-section parallel to the YZ plane, the flat width Wt in the direction along the exit surface 82 of the flat portion 640 is preferably 5 μm or less, and more preferably 3 μm or less.

[0038] Furthermore, in this embodiment, the cavity 64 may have a free curve shape in a second cross-section parallel to the end face 81. The second cross-section is a cross-section parallel to the XZ plane in Figures 3 and 4. However, the cavity 64 is not limited to a free curve shape in the second cross-section, and may have an arc shape, a circular arc shape, or a cosine shape following a cosine function.

[0039] Here, Figure 5 shows the shape of the cavity 64 in a second cross-section. In Figure 5, Graph 50 shows an example of a cosine shape of the cavity 64 in the second cross-section that follows the cosine function. Graph 51 shows an example of an arc shape of the cavity 64 in the second cross-section.

[0040] <Effects of the light guide 80> Next, the effects of the light guide 80 will be explained. First, before explaining the effects of the light guide 80, the manufacturing method of the shaping film that constitutes the cavity in the light guide 80 and other light guides will be explained.

[0041] In the method for manufacturing a shaped film, for example, a mold is manufactured and used that has mold recesses that are approximately the same shape as the recesses that constitute the cavity. Here, Figure 6 is a schematic perspective view showing the manufacturing process of a mold for manufacturing the recesses of the cavity of a light guide. As shown in Figure 6, the mold recesses 64a are formed by cutting the base material of the mold 300 with a cutting tool 200, which moves at least in the X direction. Using a mold 300 in which multiple such mold recesses 64a are formed, an intermediate transfer body having multiple convex portions, which are the inverse shape of the mold recesses 64a, is manufactured. By transferring the inverse shape of the convex portions to the shaped film using this intermediate transfer body, recesses that constitute the cavity are formed in the shaped film.

[0042] In the above-described method for manufacturing the shaped film, the inverted shape of the tool bit 200 is indirectly transferred to the recess of the cavity in the Y direction. The thinness of the tip of the tool bit 200 in the Y direction is determined by the width of the cavity in the Y direction. Therefore, if the width of the cavity corresponding to the Y direction, for example the width W of cavity 64 in Figure 3, becomes narrower, the tip of the tool bit 200 becomes thinner and may become prone to chipping. If the tip of the tool bit 200 chips, the mold 300 cannot be manufactured. As a result, it becomes impossible to manufacture the shaped film that constitutes the cavity using the mold 300.

[0043] On the other hand, if the width of the cavity corresponding to the Y direction, for example the width W of cavity 64 in Figure 3, is wide, the light diffusion due to the cavity may decrease. When the light diffusion due to the cavity decreases, brightness unevenness occurs in the light extracted from the light guide, and it becomes difficult to obtain the desired light distribution.

[0044] In this embodiment, as shown in Figures 3 and 4, the cavity 64 has a convex shape in a first cross-section parallel to the YZ plane, and includes a flat portion 640 at the top of the convex shape. This convex shape is an inverse shape of the tip portion of the cutting tool 200, corresponding to the shape of the tip portion of the cutting tool 200. By including a flat portion 640 at the top of the convex shape of the cavity 64, it is possible to avoid the tip portion of the cutting tool 200 becoming extremely thin. This makes it possible to narrow the width W of the cavity 64 in Figure 3 while avoiding the tip portion of the cutting tool 200 becoming prone to chipping. As a result, in this embodiment, the diffusion of light Lt incident on the light guide 80 can be improved. By improving the diffusion of light Lt incident on the light guide 80, the brightness unevenness of the light Lt extracted from the light guide 80 is reduced, and it becomes easier to obtain a desired light distribution. The lighting device 100 having the light guide 80 can illuminate with light Lt with reduced brightness unevenness, or light Lt with a desired light distribution. Furthermore, from the viewpoint of suitably reducing the brightness unevenness of the light Lt extracted from the light guide 80, or from the viewpoint of suitably obtaining a desired light distribution, in the first cross section parallel to the YZ plane, the convex shape is preferably convex on the side where the emission surface 82 is located, and in the first cross section, the flat portion 640 is more preferably parallel to the emission surface 82.

[0045] Figure 7 shows the relationship between the viewing angle and the normalized brightness of the light extracted from the exit surface 82 side for each shape of the cavity 64. Figure 8 shows the relationship between the viewing angle and the normalized brightness of the light extracted from the side opposite the exit surface 82 for each shape of the cavity 64.

[0046] In Figures 7 and 8, Graph 71, shown by a solid line, shows the relationship between the viewing angle and normalized luminance of light Lt extracted from a light guide 80 having a cavity 64 containing a flat portion 640 with a flat width Wt of 3 μm. Graph 72, shown by a dashed line, shows the relationship between the viewing angle and normalized luminance of light Lt extracted from a light guide 80 having a cavity 64 containing a flat portion 640 with a flat width Wt of 5 μm. The first tilt angle θa and the second tilt angle θb of the cavity 64 in Graphs 71 and 72 are both 73 degrees.

[0047] In Figures 7 and 8, graph 73, shown by the dashed line, shows the relationship between the viewing angle and normalized luminance of light Lt extracted from a light guide 80 having a cavity 64 that does not include the flat portion 640. In graph 73, the first tilt angle θa and the second tilt angle θb of the cavity 64 are both 63 degrees. Graph 74, shown by the double dashed line, shows the relationship between the viewing angle and normalized luminance of light Lt extracted from a light guide 80 having a cavity 64 that does not include the flat portion 640. In graph 74, the first tilt angle θa and the second tilt angle θb of the cavity 64 are both 73 degrees. Note that all graphs shown in Figures 7 and 8 are experimental results.

[0048] As shown in Figure 7, the change in normalized brightness of the light Lt extracted from the output surface 82 side of the light guide 80 with respect to the viewing angle was smaller in Graphs 71 and 72 compared to Graphs 73 and 74. In particular, in the range of viewing angles of ±40 degrees or less, the change in normalized brightness with respect to the viewing angle in Graphs 71 and 72 was smaller compared to Graphs 73 and 74. In other words, it was found that in a light guide 80 in which the cavity 64 includes a flat portion 640, the change in normalized brightness of the light Lt extracted from the output surface 82 side with respect to the viewing angle is smaller compared to a light guide in which the cavity 64 does not include a flat portion 640. Therefore, in a light guide 80 in which the cavity 64 includes a flat portion 640, it is possible to extract light Lt with reduced brightness unevenness.

[0049] The change in normalized brightness of the light Lt extracted from the output surface 82 of the light guide 80 with respect to the viewing angle was smaller in Graph 71 than in Graph 72. In particular, in the range of viewing angles of ±40 degrees or less, the change in normalized brightness with respect to the viewing angle in Graphs 71 and 72 was smaller compared to Graphs 73 and 74. In other words, it was found that in the light guide 80 including a flat section 640 with a flat width Wt of 3 μm, the change in normalized brightness of the light Lt extracted from the output surface 82 with respect to the viewing angle was smaller compared to the light guide 80 including a flat section 640 with a flat width Wt of 5 μm. Therefore, in the light guide 80 having a cavity 64 including a flat section 640 with a flat width Wt of 3 μm, it is possible to extract light Lt with reduced brightness unevenness compared to the light guide 80 having a cavity 64 including a flat section 640 with a flat width Wt of 5 μm.

[0050] On the other hand, the relationship between the normalized luminance and viewing angle of the light Lt extracted from the side opposite to the output surface 82 shown in Figure 8 did not show as much difference between graphs 71, 72, 73, and 74 as it did in Figure 7. In other words, the relationship between the normalized luminance and viewing angle of the light Lt extracted from the side opposite to the output surface 82 does not differ significantly depending on the shape of the cavity 64. Furthermore, in the viewing angle range of ±40 degrees or less, the normalized luminance of the light Lt was almost zero in all of graphs 71, 72, 73, and 74. In other words, regardless of the shape of the cavity 64, it was found that almost no light Lt is extracted from the side opposite to the output surface 82 in the viewing angle range of ±40 degrees or less.

[0051] In this embodiment, the cavity 64 can have a free curve shape in a second cross-section parallel to the end face 81. By having a free curve shape, the free curve shape in the second cross-section of the cavity 64 can be determined according to the intended use of the light guide 80, thereby optimizing the diffusion and light distribution of the light Lt.

[0052] In this embodiment, the cavity 64 may have an arc shape in the second cross-section. Having an arc shape in the cavity 64 allows for optimization of the light diffusion and light distribution of the light guide 80 according to its intended use. Furthermore, having an arc shape in the cavity 64 makes it easier to design and manufacture compared to the case where the cavity 64 has a free curve shape.

[0053] In this embodiment, the cavity 64 may have an arc shape or a cosine shape that follows a cosine function. Having an arc shape or a cosine shape makes it easier to design and manufacture the cavity 64 compared to having a free curve shape or an arc shape.

[0054] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all illustrative to specifically illustrate the technology of the present invention, and the present invention is not limited to these illustrative figures. Furthermore, the connection relationships between the components are illustrative to specifically illustrate the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0055] The light guide and lighting device according to this embodiment can improve the diffusion of light incident on the light guide, and by being placed on building components such as glass, windows, walls, floors, and ceilings, they can illuminate the interior or exterior space of a building with reduced brightness unevenness.

[0056] Furthermore, the light guide and lighting device according to the embodiment can be used as a partition to suitably partition a room or to conceal a desired space. In addition, by placing the light guide and 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, the backlight illumination of the display device can be made brighter. Moreover, the light guide and lighting device according to the embodiment can provide new applications other than those mentioned above.

[0057] Examples of the present invention are as follows: <1> A light guide having a cavity inside into which light from a light source is incident, comprising an end face and an exit face continuous with and intersecting the 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 has a convex shape in a first cross section intersecting the end face and the exit face, and includes a flat portion at the top of the convex shape. <2> In the first cross-section, the convex shape is convex on the side where the ejection surface is located. <1> This is the light guide described in [reference]. <3> In the first cross-section, the flat portion is parallel to the ejection surface, <1> or the above <2> This is the light guide described in [reference]. <4> The cavity has a free curve shape in a second cross-section parallel to the end face, <1> from the above <3> It is a light guide described in any one of the following. <5> The cavity, in a second cross-section parallel to the end face, includes an arc shape, <1> from the above <3> It is a light guide described in any one of the following. <6> The cavity has, in a second cross-section parallel to the end face, an arc shape or a cosine shape following a cosine function, <1> from the above <3> It is a light guide described in any one of the following. <7> In the first cross-section, the width of the flat portion in the direction along the exit surface is 5 μm or less. <1> from the above <6> It is a light guide described in any one of the following. <8> In the first cross-section, the width of the flat portion in the direction along the exit surface is 3 μm or less. <1> from the above <6> It is a light guide described in any one of the following. <9> The aforementioned <1> from the above <8> A lighting device having a light guide described in any one of the above, and the light source. [Explanation of Symbols]

[0058] 10 Light guide layer 30 Base material Graphs 50 and 51 52 First adhesive layer 54 Second adhesive layer 60 Directional Conversion Layer 62 Shaping film 621 First Main Surface 622 Second Main Surface 64 Cavity 64a Mold recess 64C center axis 70-layer structure 71, 72, 73, 74 Graphs 80 Light guide 81 End face 82 Ejection surface 100 Lighting devices 200 bytes 300 molds 640 Flat area H Height ISa First Incline ISb 2nd slope Lt light LS light source Px, Py pitch W width Wt flat width θa 1st inclination angle θb 2nd inclination angle

Claims

1. A light guide body having a cavity inside into which light from a light source enters, It includes an end face and an exit surface that is continuous with the end face and intersects the end face, The light guide reflects a portion of the light guided through its interior by the cavity, and causes the light reflected by the cavity to be emitted from the emission surface. The light guide has a convex shape in a first cross-section that intersects the end face and the exit face, and includes a flat portion at the top of the convex shape.

2. The light guide according to claim 1, wherein in the first cross-section, the convex shape is convex on the side where the emission surface is located.

3. The light guide according to claim 1, wherein in the first cross-section, the flat portion is parallel to the emission surface.

4. The light guide according to claim 1, wherein the cavity has a free curve shape in a second cross-section parallel to the end face.

5. The light guide according to claim 1, wherein the cavity includes an arc shape in a second cross-section parallel to the end face.

6. The light guide according to claim 1, wherein the cavity has an arc shape or a cosine shape following a cosine function in a second cross-section parallel to the end face.

7. The light guide according to claim 1, wherein in the first cross-section, the width of the flat portion in the direction along the emission surface is 5 μm or less.

8. The light guide according to claim 1, wherein in the first cross-section, the width of the flat portion in the direction along the emission surface is 3 μm or less.

9. A light guide according to any one of claims 1 to 8, A lighting device having the aforementioned light source.

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