Illumination device and method for manufacturing the same

Abstract

To provide a lighting device in which controllable light can be increased.SOLUTION: A lighting device includes: a first light guide body 10 having prism surfaces on which a plurality of concave prisms 11 each having a concave shape; a second light guide body 20 having prism surfaces on which a plurality of convex prisms 21 each having a convex shape; and a light source 30 emitting light incident to at least one end surface of the first light guide body 10 and the second light guide body 20. The first light guide body 10 and the second light guide body 20 are arranged so that the plurality of concave prisms 11 and the plurality of convex prisms 21 are engaged via an air layer 2.SELECTED DRAWING: Figure 1C

Description

[Technical field]

[0001] The present invention relates to a lighting device and a manufacturing method thereof, and more particularly to a lighting device using a light guide and a manufacturing method thereof. [Background technology]

[0002] Conventionally, an edge-light type lighting device has been known as a lighting device using a light guide. The edge-light type lighting device includes a light guide plate, which is a light guide, and a light source disposed opposite an end surface of the light guide plate.

[0003] As an example of this type of illumination device, Patent Document 1 discloses a surface light source device that includes a plate-shaped light guide plate having a first main surface that is a prism surface on which a plurality of concave prisms are formed, and a light source arranged opposite to the end face of the light guide plate.

[0004] In such an illumination device, light emitted from the light source enters the light guide plate from an end face, is guided inside the light guide plate, is reflected by multiple prisms, and is emitted to the outside of the light guide plate from a second main surface facing away from the first main surface (prism surface). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-219609 Summary of the Invention [Problem to be solved by the invention]

[0006] In an illumination device using a light guide having a plurality of prisms formed on a first main surface, the light distribution of light emitted to the outside from the second main surface serving as a light extraction surface can be controlled by adjusting the shape and arrangement of the prisms, etc. For example, the light distribution angle of the light emitted from the light extraction surface can be controlled by adjusting the base angle of the prisms, etc.

[0007] However, in conventional lighting devices using such light guides, light leaks from the first main surface (prism surface) on which the prisms are formed. In other words, a part of the light emitted from the light source and incident on the light guide leaks out of the light guide from the prism surface as leaked light. For example, nearly half of the light incident on the light guide may become leaked light. Moreover, this leaked light is difficult to control.

[0008] Thus, conventional lighting devices using a light guide having a plurality of prisms have a problem in that the light emitted from the light guide contains a large amount of light that is difficult to control.

[0009] The present invention has been made to solve such problems, and has an object to provide an illumination device and a manufacturing method thereof that can increase the amount of light that can be controlled, even when a light guide having a plurality of prisms formed therein is used. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, one aspect of the lighting device of the present invention comprises a first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, and a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, wherein the first light guide and the second light guide are arranged such that the plurality of concave prisms and the plurality of convex prisms are fitted together via an air layer.

[0011] Furthermore, one aspect of a manufacturing method for an illumination device according to the present invention is a manufacturing method for an illumination device including a first light guide having a prism surface on which a plurality of first prisms, each of which is concave, are formed, and a second light guide having a prism surface on which a plurality of second prisms, each of which is convex, are formed, wherein the first light guide and the second light guide are manufactured using a stamper made from the same master. Effect of the Invention

[0012] It is possible to obtain an illumination device that uses a light guide in which a plurality of prisms are formed, and yet can control a large amount of light. [Brief description of the drawings]

[0013] [Figure 1A] FIG. 1A is a perspective view of a lighting device according to an embodiment. [Figure 1B] FIG. 1B is a cross-sectional view of the illumination device according to the embodiment taken along line IB-IB in FIG. 1A. [Figure 1C] FIG. 1C is a cross-sectional view of the lighting device according to the embodiment taken along line IC-IC in FIG. 1A. [Figure 2A] FIG. 2A is a perspective view of a portion of each of a first light guiding body and a second light guiding body in a lighting device according to an embodiment, as viewed from below. [Figure 2B] FIG. 2B is a perspective side view of a portion of each of the first light guiding body and the second light guiding body in the lighting device according to the embodiment. [Diagram 3] FIG. 3 is a diagram for explaining a method for producing the first light guide and the second light guide. [Figure 4A] FIG. 4A is a diagram showing the configuration of a lighting device of a comparative example and an image of light distribution. [Figure 4B] FIG. 4B is a diagram for explaining the optical action of the illumination device of the comparative example. [Figure 4C] FIG. 4C is a diagram showing the light distribution of the lighting device of the comparative example. [Figure 5A] FIG. 5A is a diagram showing a configuration of an illumination device according to an embodiment and an image of light distribution. [Figure 5B] FIG. 5B is a diagram for explaining the optical action of the illumination device according to the embodiment. [Figure 5C] FIG. 5C is a diagram illustrating a light distribution of the lighting device according to the embodiment. [Figure 6] FIG. 6 is a diagram showing the relationship between the base angles of the concave prism and the convex prism and the luminous flux of the front light, the luminous flux of the back light, the fixture efficiency, and the light distribution in the lighting device according to the embodiment. [Figure 7] FIG. 7 is a diagram showing the relationship between the thickness of the second light guide and the luminous flux of the front light, the luminous flux of the back light, the device efficiency, and the light distribution in the lighting device according to the embodiment. [Figure 8] FIG. 8 is a diagram showing the relationship between the thickness of the air layer between the concave prism and the convex prism, the luminous flux of the front light, the luminous flux of the back light, the fixture efficiency, and the light distribution in the lighting device according to the embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing a configuration of an illumination device according to the first modification. [Figure 10] FIG. 10 is a cross-sectional view showing a configuration of an illumination device according to the second modification. [Figure 11] FIG. 11 is a cross-sectional view showing a configuration of an illumination device according to the third modification. [Figure 12] FIG. 12 is a diagram showing the luminous flux of the front light, the luminous flux of the back light, the device efficiency, and the light distribution in each of the illumination devices according to the embodiment, the modification 1, the modification 2, and the modification 3. In FIG. [Figure 13] FIG. 13 is a cross-sectional view showing a configuration of an illumination device according to the fourth modification. [Figure 14A] FIG. 14A is a perspective view of an illumination device according to Modification 5. FIG. [Figure 14B] FIG. 14B is a cross-sectional view of the illumination device according to Modification 5 taken along line XIVB-XIVB in FIG. 14A. [Figure 14C] 14C is a cross-sectional view of the illumination device according to Modification 5 taken along line XIVC-XIVC in FIG. 14A. [Figure 15] FIG. 15 is a diagram showing a state in which the gap between the first light guide and the second light guide is larger in the center in the lighting device according to the embodiment. [Figure 16] FIG. 16 is a diagram for explaining an illumination device according to the sixth modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, arrangement and connection forms of the components, steps (processes), etc. shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, among the components in the following embodiments, components that are not described in the independent claims will be described as optional components.

[0015] Each figure is a schematic diagram and is not necessarily illustrated precisely. In each figure, the same reference numerals are used for substantially the same configurations, and duplicated explanations may be omitted or simplified. In each figure, the X-axis, Y-axis, and Z-axis represent the three axes of a three-dimensional Cartesian coordinate system. The X-axis and Y-axis are mutually orthogonal, and are both orthogonal to the Z-axis.

[0016] (Embodiment) First, the configuration of the lighting device 1 according to the embodiment will be described with reference to Figs. 1A, 1B, 1C, 2A, and 2B. Fig. 1A is a perspective view of the lighting device 1 according to the embodiment. Fig. 1B is a cross-sectional view of the lighting device 1 taken along line IB-IB in Fig. 1A. Fig. 1C is a cross-sectional view of the lighting device 1 taken along line IC-IC in Fig. 1A. Figs. 2A and 2B are perspective views showing a part of each of the first light guide 10 and the second light guide 20 in the lighting device 1. In Figs. 2A and 2B, the first light guide 10 and the second light guide 20 are shown farther apart than they actually are so that the shape of the concave prism 11 of the first light guide 10 and the shape of the convex prism 21 of the second light guide 20 can be easily seen.

[0017] As shown in FIGS. 1A to 1C, the lighting device 1 includes a first light guide 10, a second light guide 20, a light source 30, and a holding member 40.

[0018] The first light guide 10 and the second light guide 20 are optical members having a function of guiding light. In the present embodiment, the first light guide 10 and the second light guide 20 are plate-like light guide plates. Specifically, the first light guide 10 and the second light guide 20 are flat light guide plates having a rectangular shape in a plan view. As an example, the thickness of each of the first light guide 10 and the second light guide 20 is about several mm to several cm, but is not limited thereto. The thickness of the first light guide 10 and the thickness of the second light guide 20 may be the same or different.

[0019] The first light guide 10 and the second light guide 20 are light-transmitting members having translucency at least in the visible light region. The transmittance of the first light guide 10 and the second light guide 20 is preferably high, and is preferably at least 50% or more. Specifically, the first light guide 10 and the second light guide 20 are preferably transparent to visible light. The transparent first light guide 10 and the transparent second light guide 20 have a high transmittance that allows the other side to be seen through. In this case, the transmittance of each of the transparent first light guide 10 and the transparent second light guide 20 to visible light is 70% or more, preferably 80% or more, and more preferably 90% or more. The first light guide 10 and the second light guide 20 may be translucent not only in the visible light region but also in the near-infrared region. That is, the first light guide 10 and the second light guide 20 may be translucent in the visible light region and the near-infrared region.

[0020] The first light guide 10 and the second light guide 20 are made of a material having translucency. The first light guide 10 and the second light guide 20 are transparent substrates transparent to visible light, such as a transparent resin substrate made of a transparent resin material or a glass substrate made of a transparent glass material. As the transparent resin substrate, an acrylic substrate made of an acrylic resin or a polycarbonate substrate made of a polycarbonate resin can be used. The transparent resin substrate may be a rigid substrate that does not have flexibility, or a flexible substrate that has flexibility. In this embodiment, a rigid and transparent acrylic substrate is used as the first light guide 10 and the second light guide 20.

[0021] The first light guide 10 has a first main surface 10a, a second main surface 10b facing away from the first main surface 10a, a first end surface 10c, and a second end surface 10d facing away from the first end surface 10c.

[0022] The first main surface 10a and the second main surface 10b are surfaces that are visible when the flat-plate-like first light guide 10 is viewed from above. The first main surface 10a and the second main surface 10b face each other in the thickness direction of the flat-plate-like first light guide 10. In this embodiment, the first main surface 10a and the second main surface 10b are each flat and substantially parallel to each other. Since the first light guide 10 has a substantially rectangular shape in a planar view, the first main surface 10a and the second main surface 10b also have a substantially rectangular shape.

[0023] 1C, a plurality of concave prisms 11, each having a concave shape, are formed on the first main surface 10a. In other words, the first main surface 10a is a concave prism surface on which the plurality of concave prisms 11 are formed. In this manner, the first light guide 10 is a concave prism light guide plate having the plurality of concave prisms 11.

[0024] In the present embodiment, the multiple concave prisms 11 have a function of reflecting light guided inside the first light guide 10. Therefore, the concave prisms 11 have a reflection surface (light control surface) that reflects a part of the light guided inside the first light guide 10 toward the second main surface 10b.

[0025] Each of the concave prisms 11 has an axisymmetric concave shape. As an example, each of the concave prisms 11 has an axisymmetric cone shape or hemispherical shape. That is, in this case, each of the concave prisms 11 is a concave portion in a shape in which a part of the plane of the first main surface 10a is hollowed out in a cone shape or hemispherical shape. As shown in FIG. 2A and FIG. 2B, in this embodiment, each of the concave prisms 11 has an axisymmetric cone shape. Therefore, as shown in FIG. 1C, when cut by a plane parallel to the thickness direction of the first light guide 10, the cross-sectional shape of each of the concave prisms 11 is an isosceles triangle. The inner surface of the cone-shaped concave prism 11 is a reflection surface (light control surface) that reflects a part of the light guided inside the first light guide 10 toward the second main surface 10b.

[0026] The plurality of concave prisms 11 thus configured are two-dimensionally arranged on the first main surface 10a. Specifically, when viewed from the direction perpendicular to the first main surface 10a, the concave prisms 11 are arranged along a first direction (X-axis direction in this embodiment) from one of the first end surface 10c and the second end surface 10d to the other, and along a second direction (Y-axis direction in this embodiment) substantially perpendicular to the first direction. The concave prisms 11 may be formed over the entire first main surface 10a, or may be formed partially.

[0027] The second main surface 10b is a light exit surface (light output surface) through which light incident on the first light guide 10 is output to the outside of the first light guide 10. Therefore, the second main surface 10b serves as a light emitting surface that emits light in a pseudo manner by outputting light guided through the first light guide 10 to the outside. In other words, the second main surface 10b is a light extraction surface for extracting light guided through the first light guide 10, and serves as the front surface of the lighting device 1. In this embodiment, the second main surface 10b is a flat surface on which no prisms are formed.

[0028] Each of the first end face 10c and the second end face 10d is one of the multiple side faces of the first light guide 10. In this embodiment, since the first light guide 10 is a flat light guide plate having a rectangular shape in a plan view, each of the first end face 10c and the second end face 10d is one of the four side faces and has a long rectangular shape. The first end face 10c and the second end face 10d face each other in a direction perpendicular to the thickness direction of the first light guide 10. That is, the second end face 10d is located on the opposite side to the first end face 10c. As an example, each of the first end face 10c and the second end face 10d is a flat surface and is approximately parallel to each other. Note that the first end face 10c and the second end face 10d are not limited to flat surfaces, and may be curved surfaces that are curved concavely or convexly. Also, the first end face 10c and the second end face 10d may be inclined surfaces.

[0029] In the present embodiment, the first end face 10c is a light incident surface (light entrance surface) into which light emitted from the light source 30 is incident. Specifically, the first end face 10c faces the light source 30. In other words, the first end face 10c is the surface on the light source 30 side, and the second end face 10d is the surface on the opposite side to the light source 30 side.

[0030] Next, a description will be given of the second light guide 20. The second light guide 20 has a third main surface 20a, a fourth main surface 20b facing away from the third main surface 20a, a third end surface 20c, and a fourth end surface 20d facing away from the third end surface 20c.

[0031] The third main surface 20a and the fourth main surface 20b are surfaces that are visible when the flat second light guide 20 is viewed from above. The third main surface 20a and the fourth main surface 20b face each other in the thickness direction of the flat second light guide 20. In this embodiment, the third main surface 20a and the fourth main surface 20b are each flat and substantially parallel to each other. Since the second light guide 20 has a substantially rectangular shape in a plan view, the third main surface 20a and the fourth main surface 20b also have a substantially rectangular shape.

[0032] 1C, the third main surface 20a of the second light guide 20 is the surface on the first light guide 10 side. That is, the third main surface 20a of the second light guide 20 faces the first main surface 10a of the first light guide 10. On the other hand, the fourth main surface 20b of the second light guide 20 is the surface on the opposite side to the first light guide 10 side. In the present embodiment, the second light guide 20 is a light guide plate having the same size as the first light guide 10 as a whole, so that the third main surface 20a and the fourth main surface 20b of the second light guide 20 and the first main surface 10a and the second main surface 10b of the first light guide 10 each have the same size and shape, but are not limited thereto. In other words, the third major surface 20a and the fourth major surface 20b of the second light guide 20 and the first major surface 10a and the second major surface 10b of the first light guide 10 may have different shapes or sizes.

[0033] A plurality of convex prisms 21, each having a convex shape, are formed on the third main surface 20a of the second light guide 20. That is, the third main surface 20a is a convex prism surface on which the plurality of convex prisms 21 are formed. In this manner, the second light guide 20 is a convex prism light guide plate having the plurality of convex prisms 21. The fourth main surface 20b of the second light guide 20 is the back surface (rear surface) of the lighting device 1. In this embodiment, the fourth main surface 20b is a flat surface on which no prisms are formed.

[0034] Each of the plurality of convex prisms 21 has an axially symmetric convex shape. As an example, each of the plurality of convex prisms 21 has an axially symmetric cone shape or a hemispherical shape. That is, in this case, each of the convex prisms 21 is a convex portion protruding from the third main surface 20a in a cone shape or a hemispherical shape. As shown in FIG. 2A and FIG. 2B, in this embodiment, each of the plurality of convex prisms 21 has an axially symmetric cone shape. Therefore, as shown in FIG. 1C, when cut along a plane parallel to the thickness direction of the second light guide 20, the cross-sectional shape of each of the convex prisms 21 is an isosceles triangle.

[0035] The plurality of convex prisms 21 thus configured are two-dimensionally arranged on the third main surface 20a. Specifically, when viewed from a direction perpendicular to the main surface of the third main surface 20a, the plurality of convex prisms 21 are arranged along a first direction (X-axis direction in this embodiment) from one of the third end surface 20c and the fourth end surface 20d to the other, and along a second direction (Y-axis direction in this embodiment) substantially perpendicular to the first direction.

[0036] The multiple convex prisms 21 of the second light guide 20 correspond one-to-one to the multiple concave prisms 11 of the first light guide 10. Therefore, the multiple convex prisms 21 of the second light guide 20 and the multiple concave prisms 11 of the first light guide 10 are the same in number and are formed at the same positions.

[0037] Moreover, when each convex prism 21 of the second light guide 20 and each concave prism 11 of the first light guide 10 are fitted together, the convex prism 21 and the concave prism 11 are structured to fit together. In this embodiment, the convex prism 21 and the concave prism 11 are completely fitted together. Therefore, the first light guide 10 and the second light guide 20 have surface shapes in which the convex and concave shapes are substantially completely reversed, and the shape and size of each concave prism 11 of the first light guide 10 and the shape and size of each convex prism 21 of the second light guide 20 are the same.

[0038] Therefore, the base angle θ (first prism angle) of each concave prism 11 of the first light guide 10 is the same as the base angle θ (second prism angle) of each convex prism 21 of the second light guide 20. For example, the base angle θ of each of the concave prism 11 and the convex prism 21 is 10° or more and 70° or less, preferably 20° or more and 65° or less, but is not limited thereto. When the concave prism 11 and the convex prism 21 are axially symmetrical conical shapes, the base angle θ is the base angle of an isosceles triangle whose cross section is shaped like that of the concave prism 11 and the convex prism 21. As an example, the base angle θ of each of the concave prism 11 and the convex prism 21 is 55°. It is preferable that the base angle θ of the concave prism 11 and the base angle θ of the convex prism 21 are the same, but they may be different.

[0039] Each of the third end face 20c and the fourth end face 20d is one of the multiple side faces of the second light guide 20. The third end face 20c is an end face on the same side as the first end face 10c of the first light guide 10, and the fourth end face 20d is an end face on the same side as the second end face 10d of the first light guide 10. In this embodiment, the second light guide 20 is a flat light guide plate having a rectangular shape in a plan view, similar to the first light guide 10, so each of the third end face 20c and the fourth end face 20d is one of the four side faces and has a long rectangular shape. The third end face 20c and the fourth end face 20d face each other in a direction perpendicular to the thickness direction of the second light guide 20. That is, the fourth end face 20d is located on the opposite side to the third end face 20c. As an example, the third end face 20c and the fourth end face 20d are flat surfaces and are approximately parallel to each other. The third end face 20c and the fourth end face 20d are not limited to flat surfaces, and may be curved surfaces that are concavely or convexly curved. The third end face 20c and the fourth end face 20d may be inclined surfaces.

[0040] The first light guide 10 and the second light guide 20 can be manufactured by the method shown in Fig. 3. Fig. 3 is a diagram for explaining the method of manufacturing the first light guide 10 and the second light guide 20.

[0041] Specifically, as shown in FIG. 3(a), first, a master substrate 100 that serves as a master for producing the first light guide 10 and the second light guide 20 is prepared.

[0042] 3(b), a father stamper 101 is produced as a first stamper based on the master substrate 100. The concave-convex shape of the father stamper 101 is an inverted shape of the concave-convex shape of the master substrate 100.

[0043] 3(c), a mother stamper 102 is produced as a second stamper based on the father stamper 101. The concave-convex shape of the mother stamper 102 is an inverted shape of the concave-convex shape of the father stamper 101. At this time, it is preferable to produce multiple mother stampers 102 from one father stamper 101.

[0044] 3(d), a son stamper 103 is produced as a third stamper based on the mother stamper 102. The concave-convex shape of the son stamper 103 is an inverted shape of the concave-convex shape of the mother stamper 102. At this time, it is preferable to produce multiple son stampers 103 from one mother stamper 102.

[0045] The first light guide 10 can be produced by a transfer method using a sun stamper 103. For example, the first light guide 10 can be produced by injection molding using a mold incorporating the sun stamper 103. At this time, by using a plurality of sun stampers 103, a plurality of first light guides 10 can be produced simultaneously.

[0046] The second light guide 20 can be produced by a transfer method using a mother stamper 102. For example, the second light guide 20 can be produced by injection molding using a mold incorporating the mother stamper 102. At this time, by using a plurality of mother stampers 102, a plurality of second light guides 20 can be produced simultaneously.

[0047] In this way, the first light guide 10 and the second light guide 20 are manufactured using stampers made from the same master. In other words, the first light guide 10 and the second light guide 20 can be manufactured simply by replacing the stampers. In this embodiment, the first light guide 10 and the second light guide 20 are manufactured by injection molding using a mold incorporating a stamper made from the same master. In the first light guide 10 and the second light guide 20 manufactured in this way, the concave prism 11 and the convex prism 21 are completely fitted together.

[0048] The lighting device 1 uses the first light guide 10 and the second light guide 20 thus manufactured. Specifically, as shown in FIG. 1A and FIG. 1C, the first light guide 10 and the second light guide 20 are arranged so as to overlap each other. In this case, as shown in FIG. 1C, the first light guide 10 and the second light guide 20 are arranged so that the multiple concave prisms 11 of the first light guide 10 and the multiple convex prisms 21 of the second light guide 20 are fitted together with an air layer 2 being a minute gap. That is, the first light guide 10 and the second light guide 20 are stacked such that the first main surface 10a, which is the concave prism surface of the first light guide 10, faces the third main surface 20a, which is the convex prism surface of the second light guide 20, and the multiple concave prisms 11 and the multiple convex prisms 21 are not in contact with each other. In this manner, the air layer 2 is interposed between the multiple concave prisms 11 of the first light guide 10 and the multiple convex prisms 21 of the second light guide 20. The first light guide 10 and the second light guide 20 stacked with the air layer 2 interposed therebetween can also be regarded as one light guide member in the lighting device 1.

[0049] The thickness (air gap) of the air layer 2 between the first light guide 10 and the second light guide 20 is, for example, less than half the depth of each of the plurality of concave prisms 11 or less than half the height of each of the plurality of convex prisms 21, but is not limited thereto. The upper limit of the thickness of the air layer 2 is not particularly limited, but as an example, the thickness of the air layer 2 is 1 mm or less. The lower limit of the thickness of the air layer 2 is not particularly limited, but as an example, the thickness of the air layer 2 is 1 μm or more. In this embodiment, the thickness of the air layer 2 is 0.01 mm (10 μm). The thickness of the air layer 2 is almost constant over the entire area of ​​the first main surface 10a and the third main surface 20a.

[0050] Light emitted from the light source 30 is incident on the first light guide 10 and the second light guide 20 in the overlapped state. The light source 30 emits light to be incident on at least one end surface of the first light guide 10 and the second light guide 20. As shown in FIG. 1A and FIG. 1C, in this embodiment, the light emitted from the light source 30 is incident only on the first light guide 10 of the first light guide 10 and the second light guide 20. That is, the light source 30 is arranged so that the light emitted from the light source 30 is incident only on the first end surface 10c of the first light guide 10. Therefore, in the lighting device 1, the first light guide 10 is a main light guide plate, and the second light guide 20 is a sub-light guide plate.

[0051] Specifically, the light source 30 is disposed on the side of the first end face 10c of the first light guide 10. For example, the light source 30 is disposed opposite to the first end face 10c of the first light guide 10, and the light emission surface of the light source 30 faces the first end face 10c of the first light guide 10. That is, the lighting device 1 is an edge-light type lighting device. The optical axis of the light source 30 is in a direction from the first end face 10c to the second end face 10d of the first light guide 10. Specifically, the optical axis of the light source 30 is perpendicular to the first end face 10c of the first light guide 10 and parallel to the first main surface 10a of the first light guide 10.

[0052] The light source 30 is an LED module including a light emitting diode (LED). In the present embodiment, the light source 30 emits white light. Therefore, the white light emitted from the light source 30 is incident on the first end surface 10c, which is the light incident surface of the first light guide 10.

[0053] The light source 30 has a light emitting element 31 and a mounting substrate 32 on which the light emitting element 31 is mounted. One or more light emitting elements 31 are mounted on the mounting substrate 32. In this embodiment, a plurality of light emitting elements 31 are mounted on the mounting substrate 32. The mounting substrate 32 is an elongated substrate, for example, a wiring substrate on which metal wiring is formed in a predetermined pattern. As the base substrate of the mounting substrate 32, a resin substrate, a ceramic substrate, a metal substrate coated with an insulating film, or the like can be used.

[0054] The light emitting element 31 is an LED light source composed of an LED. Specifically, the light emitting element 31 is a white LED light source that emits white light. The light emitting element 31 is, for example, an individually packaged surface mount device (SMD) type LED element, and includes a white resin or ceramic container (package) having a recess, one or more LED chips that are primarily mounted on the bottom of the recess of the container, and a sealing member that fills the recess of the container and seals the LED chip. The sealing member is composed of a light-transmitting resin material such as silicone resin. The sealing member may be a phosphor-containing resin that contains a wavelength conversion material such as a phosphor.

[0055] The LED chip is an example of a semiconductor light-emitting element that emits light using a specific DC power, and is a bare chip that emits monochromatic visible light. The LED chip is, for example, a blue LED chip that emits blue light when powered. In this case, in order to obtain white light, the sealing material contains a yellow phosphor such as YAG (yttrium aluminum garnet) that fluoresces using the blue light from the blue LED chip as excitation light.

[0056] Thus, the light emitting element 31 in this embodiment is a white LED element composed of a blue LED chip and a yellow phosphor. Specifically, the yellow phosphor absorbs a part of the blue light emitted by the blue LED chip, is excited, and emits yellow light, and this yellow light is mixed with the blue light not absorbed by the yellow phosphor to become white light. Note that the sealing member is not limited to the yellow phosphor, and may also contain a red phosphor and a green phosphor.

[0057] The multiple light-emitting elements 31 are arranged in a line on the mounting substrate 32 along the longitudinal direction of the mounting substrate 32. The multiple light-emitting elements 31 arranged in a line function as a line light source that emits light in a line. In this embodiment, the multiple light-emitting elements 31 are mounted in a row at approximately equal intervals along the longitudinal direction of the mounting substrate 32. Each light-emitting element 31 is arranged on the mounting substrate 32 such that its main light-emitting surface faces the first end surface 10c (light incident surface) of the first light guide 10.

[0058] The light source 30 may be a COB (Chip On Board) type LED module instead of an SMD type LED module. When the light source 30 is a COB type LED module, a light emitting element, which is an LED chip, is directly mounted on the mounting substrate 32. In this case, for example, blue LED chips are used as the light emitting elements, and a plurality of these blue LED chips are mounted in a row on the mounting substrate 32, and the blue LED chips are individually or collectively sealed with a sealing member made of silicone resin containing a yellow phosphor.

[0059] In addition, separately from light source 30 or as part of light source 30, if necessary, an optical component such as a light distribution variable mechanism such as a lens that changes the light distribution of light emitted from light source 30, a filter that controls the wavelength of light emitted from light source 30, or a diffuser plate that scatters and transmits light emitted from light source 30 may be provided.

[0060] The light source 30 is driven by power supplied from a power supply unit (not shown). The power supply unit has, for example, a power supply (power supply circuit) made up of a circuit board on which a plurality of circuit components are mounted, and a housing for accommodating the power supply. The power supply converts the power received by the power supply unit into a predetermined power and supplies the power to the light source 30. This drives the light source 30 to emit light. The power supply unit may be included in the lighting device 1, or may be disposed separately from the lighting device 1. In other words, the lighting device 1 may be of a type with a built-in power supply, or may be of a type that receives power from an external power supply.

[0061] The light source 30 may be disposed in a housing (not shown). The housing is, for example, a bottomed cylindrical box-shaped storage member having an opening, and is made of, for example, a metal material or a resin material. The light source 30 is disposed at the bottom of the housing. In this case, the mounting board 32 of the light source 30 is placed on the bottom surface of the housing. The opening of the housing may be closed by the first end surface 10c of the first light guide 10, but is not limited to this. The light source 30 and the housing may be integrally configured as a light source unit.

[0062] 1A and 1B, the first light guide 10 and the second light guide 20 are held by a holding member 40. The holding member 40 is a holder that holds the first light guide 10 and the second light guide 20. Specifically, the holding member 40 holds both ends of the first light guide 10 and the second light guide 20 in a state in which the first light guide 10 and the second light guide 20 are overlapped with an air layer 2 interposed therebetween.

[0063] In the present embodiment, the holding member 40 is configured by a pair of a first holding tool 41 and a second holding tool 42. Each of the first holding tool 41 and the second holding tool 42 is a frame having a U-shaped cross section.

[0064] 1B, the first holder 41 and the second holder 42 sandwich the outer circumferential ends of the first light guide 10 and the second light guide 20 in a state where the first light guide 10 and the second light guide 20 are stacked on top of each other. Specifically, the first holder 41 covers one side surface in the Y-axis direction of the first light guide 10 and one side surface in the Y-axis direction of the second light guide 20, and sandwiches the outer circumferential end of the second main surface 10b of the first light guide 10 and the outer circumferential end of the fourth main surface 20b of the second light guide 20. The second holder 42 covers the other side surface in the Y-axis direction of the first light guide 10 and the other side surface in the Y-axis direction of the second light guide 20, and sandwiches the outer circumferential end of the second main surface 10b of the first light guide 10 and the outer circumferential end of the fourth main surface 20b of the second light guide 20.

[0065] Next, the optical characteristics of the illumination device 1 according to the present embodiment will be described in comparison with the optical characteristics of an illumination device 1X of a comparative example.

[0066] First, the optical characteristics of the illumination device 1X of the comparative example will be described with reference to Fig. 4A to Fig. 4C. Fig. 4A is a diagram showing the configuration and light distribution image of the illumination device 1X of the comparative example. Fig. 4B is a diagram for explaining the optical action of the illumination device 1X. Fig. 4C is a diagram showing the light distribution of the illumination device 1X.

[0067] 4A, the lighting device 1 of the comparative example is configured such that the second light guide 20 is not provided in the lighting device 1 of the above-described embodiment. That is, the lighting device 1 of the comparative example is configured such that, of the first light guide 10 and the second light guide 20 in the lighting device 1 of the above-described embodiment, only the first light guide 10 is provided.

[0068] 4A, in the illumination device 1X of the comparative example, light emitted from the light source 30 enters the first light guide 10 from the first end face 10c of the first light guide 10. The incident light L1 from the light source 30 that enters the first light guide 10 is guided within the first light guide 10 from the first end face 10c toward the second end face 10d while repeatedly being totally reflected by the first main surface 10a and the second main surface 10b.

[0069] 4B, a part of the incident light L1 guided through the first light guide 10 that reaches the concave prism 11 is totally reflected at the interface between the concave prism 11 and the air layer to become reflected light L1a. The reflected light L1a is guided toward the second main surface 10b and is emitted from the second main surface 10b to the outside of the first light guide 10.

[0070] In the illumination device 1X of the comparative example configured as described above, the shape and arrangement of the concave prism 11 can be adjusted to control the reflected light L1a reflected by the concave prism 11, and the light distribution angle of the light emitted to the outside from the second main surface 10b, which is the light extraction surface, can be controlled. That is, the reflected light L1a reflected by the concave prism 11 can be controlled as a control light. For example, the base angle (prism angle) of the concave prism 11 can be adjusted to adjust the direction of the reflected light L1a reflected by the concave prism 11. As a result, the direction of the control light emitted to the outside from the second main surface 10b can be adjusted, as shown by the dashed ellipse in FIG. 4A.

[0071] 4B, in the lighting device 1X of Comparative Example 1, another part of the incident light L1 that reaches the concave prism 11 is not totally reflected at the interface between the concave prism 11 and the air layer, but becomes transmitted light L1b that passes through the concave prism 11. This transmitted light L1b leaks out from the first main surface 10a of the first light guide 10 as leakage light.

[0072] Specifically, as shown by the light distribution indicated by the dashed line in Fig. 4C, almost no light leakage is observed in the YZ cross section of the first light guide 10, but light leakage occurs in the XZ cross section as shown by the light distribution indicated by the solid line in Fig. 4C. That is, light leakage is likely to occur in the traveling direction of the light emitted from the light source 30 (the X-axis direction in Fig. 4A). Moreover, this light leakage is difficult to control.

[0073] In this way, in the illumination device 1X of the comparative example in which only the first light guide 10 is used, the light emitted from the first light guide 10 contains a large amount of light that is difficult to control.

[0074] Next, the optical characteristics of the lighting device 1 according to the present embodiment will be described with reference to Figs. 5A to 5C. Fig. 5A is a diagram showing the configuration and light distribution image of the lighting device 1 according to the embodiment. Fig. 5B is a diagram for explaining the optical action of the lighting device 1. Fig. 5C is a diagram showing the light distribution of the lighting device 1.

[0075] 5A, in the lighting device 1 according to the present embodiment, light emitted from the light source 30 enters the first light guide 10 from the first end face 10c of the first light guide 10. As in the lighting device 1 of the comparative example, the incident light L1 from the light source 30 that enters the first light guide 10 is guided within the first light guide 10 from the first end face 10c to the second end face 10d while repeatedly being totally reflected at the first main surface 10a and the second main surface 10b.

[0076] 5B, a portion of the incident light L1 guided through the first light guide 10 that reaches the concave prism 11 is totally reflected at the interface between the concave prism 11 and the air layer 2 to become reflected light L1a, as in the illumination device 1 of the comparative example. The reflected light L1a is guided toward the second main surface 10b and is emitted from the second main surface 10b to the outside of the first light guide 10.

[0077] Moreover, another portion of the incident light L1 that reaches the concave prism 11 is not totally reflected at the interface between the concave prism 11 and the air layer, as in the illumination device 1 of the comparative example, but becomes transmitted light L1b that transmits through the concave prism 11. At this time, unlike the illumination device 1 of the comparative example, the illumination device 1 of this embodiment is provided with a second light guide 20 having a convex prism 21 that fits into the concave prism 11, so that the transmitted light L1b that has transmitted through the concave prism 11 of the first light guide 10 enters the inside of the second light guide 20 from the convex prism 21.

[0078] In this case, the convex prism 21 is shaped to fit into the concave prism 11, and the surfaces of the convex prism 21 and the concave prism 11 are parallel to each other, so that the transmitted light L1b that passes through the concave prism 11 passes straight through the convex prism 21 with almost no refraction at the surface of the convex prism 21 and enters the inside of the second light guide 20.

[0079] The transmitted light L1b incident on the second light guide 20 is guided within the second light guide 20 from the third end face 20c to the fourth end face 20d while repeatedly being totally reflected by the third main surface 20a and the fourth main surface 20b of the second light guide 20. A part of the transmitted light L1b that reaches the fourth main surface 20b of the second light guide 20 is emitted to the outside from the fourth main surface 20b, while the other part of the transmitted light L1b that reaches the fourth main surface 20b of the second light guide 20 is totally reflected by the fourth main surface 20b of the second light guide 20 and travels toward the third main surface 20a on which the convex prism 21 is formed.

[0080] The transmitted light L1b that is reflected by the fourth main surface 20b and reaches the convex prism 21 passes through the convex prism 21 and re-enters the first light guide 10 from the concave prism 11. At this time, as described above, the convex prism 21 has a shape that fits into the concave prism 11, and the surface of the convex prism 21 and the surface of the concave prism 11 are parallel, so that the transmitted light L1b that enters the concave prism 11 from the convex prism 21 travels straight and enters the inside of the first light guide 10 with almost no refraction at the surface of the concave prism 11.

[0081] The transmitted light L1b re-entering the first light guiding body 10 from the second light guiding body 20 via the convex prism 21 and the concave prism 11 is guided within the first light guiding body 10. In this manner, the transmitted light L1b passing through the concave prism 11 of the first light guiding body 10 and entering the second light guiding body 20 becomes light that is guided again through the first light guiding body 10. Note that, according to the results of simulations performed by the present inventors, it was found that a high proportion of the transmitted light L1b entering the second light guiding body 20 from the first light guiding body 10 returns to the first light guiding body 10.

[0082] Then, the transmitted light L1b re-entering the first light guide 10 from the second light guide 20 is guided again inside the first light guide 10 from the first end face 10c toward the second end face 10d, and is emitted to the outside from the second main surface 10b (light extraction surface) of the first light guide 10. Specifically, the light incident on the first light guide 10 from the light source 30 can be extracted from the second main surface 10b of the first light guide 10 as planar illumination light. For example, a portion of the transmitted light L1b that enters the first light guide 10 from the convex prism 21 through the concave prism 11 passes straight through the inside of the first light guide 10 and exits from the second main surface 10b to the outside of the first light guide 10 without being totally reflected at the second main surface 10b, or exits from the second main surface 10b to the outside of the first light guide 10 while repeatedly being totally reflected between the second main surface 10b and the first main surface 10a.

[0083] In this way, according to the lighting device 1 of the present embodiment, the transmitted light L1b, which would become leakage light in the lighting device 1X of the comparative example, is made incident on the second light guide 20 from the convex prism 21, so that the transmitted light L1b can be returned to the first light guide 10 and emitted from the second main surface 10b of the first light guide 10, which is the front surface of the lighting device 1. In other words, in the lighting device 1 of the present embodiment, light that would become leakage light can be converted into control light and used as illumination light.

[0084] Specifically, as shown in the light distribution in the XZ cross section indicated by the solid line in FIG. 4C above, a lot of leakage light occurred in the illumination device 1X of the comparative example, whereas as shown in the light distribution in the XZ cross section indicated by the solid line in FIG. 5C, it can be seen that almost no leakage light occurs in the illumination device 1 of the present embodiment.

[0085] As described above, according to the lighting device 1 of the present embodiment, by using the second light guide 20 in addition to the first light guide 10, it is possible to increase the amount of light that can be controlled (control light).

[0086] Moreover, as shown in FIG. 5C, it was found that the backlight (rear surface light) emitted from the fourth main surface 20b (back surface) of the second light guide 20 to the outside is emitted in a direction perpendicular to the fourth main surface 20b, not in an oblique direction with respect to the fourth main surface 20b. That is, although the fourth main surface 20b of the second light guide 20 is the back surface of the lighting device 1, the backlight emitted from the fourth main surface 20b of the second light guide 20 can be extracted in a direction perpendicular to the fourth main surface 20b (direction facing the fourth main surface 20b) like the front light emitted from the second main surface 10b of the first light guide 10. As a result, in the lighting device 1 according to this embodiment, although the first light guide 10 and the second light guide 20 are overlapped, the transparency can be maintained. In addition, in the lighting device 1 according to this embodiment, the backlight can also be used as control light. In this case, not only the second main surface 10b of the first light guide 10 but also the second main surface 40b of the second light guide 20 serves as a pseudo light emitting surface. That is, the fourth main surface 20b of the second light guide 20 also serves as a light extraction surface.

[0087] Furthermore, in the illumination device 1 of the present embodiment, the ratio of the luminous flux of light (front light) emitted from the front side to the luminous flux of light (back light) emitted from the back side can be changed compared to the illumination device 1X of the comparative example. Specifically, in the illumination device 1X of the comparative example, the ratio of the luminous flux of light (front light) emitted to the outside from the second main surface 10b of the first light guide 10 to the luminous flux of light (back light) emitted to the outside from the first main surface 10a of the first light guide 10 was 1.2:1. On the other hand, in the illumination device 1 according to the present embodiment, the ratio of the luminous flux of light (front light) emitted to the outside from the second main surface 10b of the first light guide 10 to the luminous flux of light (back light) emitted to the outside from the fourth main surface 20b of the second light guide 20 was 2.5:1. In this way, in the illumination device 1 of the present embodiment, the luminous flux of the front light relative to the back light can be increased, and the proportion of light that can be extracted from the front can be increased. This makes it possible to realize light distribution characteristics that have been difficult to achieve until now.

[0088] Here, the effect of the base angle θ (prism angle) of the concave prism 11 of the first light guide 10 and the convex prism 21 of the second light guide 20 on the front light and rear light was examined by simulation, and the results of the examination will be described with reference to Fig. 6. Fig. 6 is a diagram showing the relationship between the base angle θ of the concave prism 11 and the convex prism 21 and the luminous flux of the front light, the luminous flux of the rear light, the device efficiency, and the light distribution in the lighting device 1 according to the embodiment. The device efficiency refers to the light extraction efficiency of the lighting device.

[0089] In this simulation, the shapes of the concave prisms 11 and convex prisms 21 formed in the central 60 mm square rectangular region of a 100 mm square rectangular light guide plate (100 mm long x 100 mm wide) were axisymmetric conical (φ250 μm), the numbers of the concave prisms 11 and convex prisms 21 were set so that the coverage, which is the area occupied by the prisms in the 60 mm square rectangular region, was 30%, the first light guide 10 and the second light guide 20 were acrylic plates with a thickness of 2 mm, and the thickness of the air layer 2 between the concave prisms 11 and the convex prisms 21 was 0.01 mm. Furthermore, a reflecting member was arranged on each end face of the first light guide 10 and the second light guide 20 (excluding the light entrance face where the light source 30 is arranged) to reflect the light emitted from the end face back into the light guide.

[0090] The luminous flux of the front light and the rear light, the fixture efficiency, and the light distribution were obtained when the base angle θ of the concave prism 11 and the convex prism 21 was changed to 20°, 30°, 32.5°, 35°, 40°, 45°, 50°, 55°, 60°, and 65°. The controlled light ratio was calculated as controlled light ratio = front light / rear light. The results are shown in Figure 6.

[0091] As shown in Fig. 6, it can be seen that the smaller the base angle θ, the lower the fixture efficiency (light extraction efficiency). Conversely, the larger the base angle θ, the higher the fixture efficiency.

[0092] It is also found that when the base angle θ of the concave prism 11 and the convex prism 21 is between 20° and 40°, the luminous flux of the rear light becomes smaller than the luminous flux of the front light, and the controlled light ratio becomes higher. In this case, it is found that the controlled light ratio becomes maximum (locally maximum) at around 32.5°.

[0093] Also, as shown in the light distribution in Fig. 6, when the base angle θ exceeds 40°, the light distribution angle of the rear light increases, and the emission direction of the rear light becomes the front direction of the rear surface. In this way, by setting the base angle θ of the concave prism 11 and the convex prism 21 to at least 45° to 60°, the light distribution angle of the front light and the rear light can be increased and directed toward the front direction. It was also found that by setting the base angle θ to about 50° to 60°, the front light and the rear light are distributed in two directions.

[0094] Next, the effect of the thickness of the second light guide 20 (convex light guide plate) on the front light and back light was examined by simulation, and the examination results will be described with reference to Fig. 7. Fig. 7 is a diagram showing the relationship between the thickness of the second light guide 20 and the luminous flux of the front light, the luminous flux of the back light, the fixture efficiency, and the light distribution in the lighting device 1 according to the embodiment.

[0095] In this simulation, the shapes of the concave prism 11 and the convex prism 21 were axially symmetric conical shapes (φ250 μm), the first light guide 10 was an acrylic plate with a thickness of 2 mm, the thickness of the air layer 2 between the concave prism 11 and the convex prism 21 was 0.01 mm, and the base angle θ of the concave prism 11 and the convex prism 21 was 50°.

[0096] The thickness of the second light guide 20 made of an acrylic plate was changed to 2 mm, 1.5 mm, 1.0 mm, and 0.7 mm, and the luminous flux of the front light, the luminous flux of the rear light, the fixture efficiency, and the light distribution were obtained. The results are shown in FIG.

[0097] As shown in Fig. 7, it can be seen that the thinner the second light guide 20 is, the higher the device efficiency (light extraction efficiency) is. It can also be seen that the thickness of the second light guide 20 has almost no effect on the light distribution. Therefore, it is preferable that the thickness of the second light guide 20 is smaller than the thickness of the first light guide 10. This can increase the light extraction efficiency of the lighting device 1.

[0098] Next, the influence of the thickness of the air layer 2 between the concave prism 11 and the convex prism 21 (the gap between the first light guide 10 and the second light guide 20) on the front light and the rear light was examined by simulation, and the results of the examination will be described with reference to Fig. 8. Fig. 8 is a diagram showing the relationship between the thickness of the air layer 2 between the concave prism 11 and the convex prism 21 and the luminous flux of the front light, the luminous flux of the rear light, the fixture efficiency, and the light distribution in the lighting device 1 according to the embodiment.

[0099] In this simulation, the shapes of the concave prism 11 and the convex prism 21 were axially symmetric conical shapes (φ250 μm), the first light guide 10 and the second light guide 20 were acrylic plates with a thickness of 2 mm, and the base angle θ of the concave prism 11 and the convex prism 21 was 50°.

[0100] The luminous flux of the front light, the luminous flux of the rear light, the fixture efficiency, and the light distribution were obtained when the thickness of the air layer 2 was changed to 0.01 mm, 0.05 mm, and 0.10 mm (i.e., when the gap between the first light guide 10 and the second light guide 20 was changed). The results are shown in Fig. 8.

[0101] 8, it is preferable to bring the concave prism 11 and the convex prism 21 close to each other so that the thickness of the air layer 2 is about 0.05 mm or less. In other words, when the thickness of the air layer 2 is 0.05 mm, the thickness of the air layer 2 is half or less of the depth of the concave prism 11, or the thickness of the air layer 2 is half or less of the height of the convex prism 21. Therefore, it is preferable that the thickness of the air layer 2 is half or less of the depth of the concave prism 11 or half or less of the height of the convex prism 21.

[0102] As described above, the lighting device 1 of this embodiment comprises a first light guide 10 having a concave prism surface on which a plurality of concave prisms 11 are formed, a second light guide 20 having a convex prism surface on which a plurality of convex prisms 21 are formed, and a light source 30 that emits light to be incident on at least one end surface of the first light guide 10 and the second light guide 20, and the first light guide 10 and the second light guide 20 are arranged so that the plurality of concave prisms 11 and the plurality of convex prisms 21 are fitted together via an air layer 2.

[0103] This makes it possible to convert leak light into control light, and increase the amount of control light that can be controlled by the first light guide 10 and the second light guide 20. Therefore, it is possible to realize a lighting device with high light extraction efficiency.

[0104] In this case, the plurality of concave prisms 11 and the plurality of convex prisms 21 may preferably have an axially symmetric conical or hemispherical shape.

[0105] This configuration makes it difficult for uncontrollable light (uncontrolled light) to occur, so that the amount of control light can be further increased.

[0106] In the lighting device 1 according to the present embodiment, the light source 30 is disposed so that the light emitted from the light source 30 is incident on the first end surface 10c of the first light guide 10.

[0107] With this configuration, the light extraction efficiency can be increased as compared to a case in which the light emitted from the light source 30 is incident on the third end surface 20c of the second light guide 20.

[0108] (Modification) Although the lighting device according to the present invention has been described based on the embodiment, the present invention is not limited to the above embodiment.

[0109] For example, in the above embodiment, only two light guide plates, the first light guide 10 and the second light guide 20, are used, but the present invention is not limited to this. Specifically, in addition to the first light guide 10 and the second light guide 20, a third light guide may be further used.

[0110] In this case, as in the lighting device 1A according to the first modification shown in FIG. 9, in addition to the first light guide 10 and the second light guide 20A, a third light guide 50 may be arranged opposite the second light guide 20A.

[0111] The third light guide 50 has a fifth main surface 50a, a sixth main surface 50b facing away from the fifth main surface 50a, a fifth end surface 50c, and a sixth end surface 50d facing away from the fifth end surface 50c. The fifth main surface 50a of the third light guide 50 is a surface on the second light guide 20A side, and is a concave prism surface on which a plurality of concave prisms 51, each of which has a concave shape, are formed. Specifically, the third light guide 50 has the same structure as the first light guide 10. Therefore, the third light guide 50 and the first light guide 10 can use the same light guide plate.

[0112] In this modification, in the second light guide 20A, if the multiple convex prisms 21 formed on the third main surface 20a are defined as first convex prisms, then the multiple convex prisms 22 are formed as second convex prisms, each having a convex shape, on the fourth main surface 20b which is the surface on the third light guide 50 side. In other words, the second light guide 20A is a double-sided convex prism light guide plate in which convex prisms are formed on both sides.

[0113] In the illumination device 1A of this modification, similarly to the above embodiment, the first light guide 10 and the second light guide 20A are arranged such that the multiple concave prisms 11 of the first light guide 10 and the multiple convex prisms 21 (first convex prisms) of the second light guide 20A are fitted together via the air layer 2. In the illumination device 1A of this modification, the second light guide 20A and the third light guide 50 are further arranged such that the multiple convex prisms 22 (second convex prisms) of the second light guide 20A and the multiple concave prisms 51 of the third light guide 50 are fitted together via the air layer 2. Specifically, the first light guide 10, the second light guide 20A, and the third light guide 50 are stacked together via the air layer 2. In other words, the second light guide 20A, which has convex prisms 21 and 22 formed on both sides, is sandwiched between a first light guide 10, which has a concave prism 11 formed on one side, and a third light guide 50, which has a concave prism 51 formed on one side.

[0114] Furthermore, the illumination device 1A in this modification uses two light sources 30. Specifically, one of the two light sources 30 is arranged so that light emitted from the light source 30 enters the first end surface 10c of the first light guide 10, as in the above embodiment. On the other hand, the other of the two light sources 30 is arranged so that light emitted from the light source 30 enters the fifth end surface 50c of the third light guide 50. More specifically, one of the two light sources 30 is arranged facing the first end surface 10c of the first light guide 10, and the other of the two light sources 30 is arranged facing the fifth end surface 50c of the third light guide 50. That is, the two light sources 30 are arranged on the side of the light guide plate (the first light guide 10 and the third light guide 50) in which the concave prism is formed.

[0115] In this manner, the lighting device 1A in this modification further includes a third light guide 50 facing the second light guide 20A, in comparison with the lighting device 1 according to the above embodiment. In this case, the convex prism 22 of the second light guide 20A and the concave prism 51 of the third light guide 50 are fitted together through the air layer 2, similar to the concave prism 11 of the first light guide 10 and the convex prism 21 of the second light guide 20A. This allows light leaking from the fourth main surface 20b of the second light guide 20A to be guided to the third light guide 50 and re-entered into the second light guide 20A, based on the same principle as the optical action of the concave prism 11 of the first light guide 10 and the convex prism 21 of the second light guide 20 in the above embodiment. Therefore, the lighting device 1A in this modification can improve the light extraction efficiency more than the lighting device 1 according to the above embodiment.

[0116] Next, a description will be given of Modification 2. When a third third light guide is used, the third light guide 50 may be disposed opposite the second light guide 20 as in the illumination device 1A according to Modification 1 shown in Fig. 9, but the third light guide 60 may be disposed opposite the first light guide 10B as in the illumination device 1B according to Modification 2 shown in Fig. 10.

[0117] The third light guide 60 in this modification has a fifth main surface 60a, a sixth main surface 60b facing away from the fifth main surface 60a, a fifth end surface 60c, and a sixth end surface 60d facing away from the fifth end surface 60c. The fifth main surface 60a of the third light guide 60 is a surface on the first light guide 10B side, and is a convex prism surface on which a plurality of convex prisms 61, each having a convex shape, are formed. Specifically, the third light guide 60 has the same structure as the second light guide 20. Therefore, the third light guide 60 and the second light guide 20 can use the same light guide plate.

[0118] In this modification, in the first light guide 10B, if the multiple concave prisms 11 formed on the first main surface 10a are defined as first concave prisms, then the multiple second concave prisms, each having a concave shape, are formed as concave prisms 12 on the second main surface 10b, which is the surface on the third light guide 60 side. In other words, the first light guide 10B is a double-sided concave prism light guide plate in which concave prisms are formed on both sides.

[0119] In the illumination device 1B of this modification, similarly to the above embodiment, the first light guide 10B and the second light guide 20 are arranged such that the multiple concave prisms 11 (first concave prisms) of the first light guide 10B and the multiple convex prisms 21 of the second light guide 20 are fitted together with the air layer 2 therebetween. In the illumination device 1B of this modification, the first light guide 10B and the third light guide 60 are further arranged such that the multiple concave prisms 11 (second concave prisms) of the first light guide 10B and the multiple convex prisms 61 of the third light guide 60 are fitted together with the air layer 2 therebetween. Specifically, the first light guide 10B, the second light guide 20, and the third light guide 50 are stacked together with the air layer 2 therebetween. That is, the first light guide 10B having concave prisms 11 and 12 formed on both sides is sandwiched between the second light guide 20 having a convex prism 21 formed on one side, and the third light guide 60 having a convex prism 61 formed on one side. In this modification, the light source 30 is disposed to the side of only the light guide plate (first light guide 10B) on which the concave prism is formed.

[0120] In this manner, the lighting device 1B in this modification further includes a third light guide 60 facing the first light guide 10B, in comparison with the lighting device 1 according to the above embodiment. In this case, the concave prism 12 of the first light guide 10B and the convex prism 61 of the third light guide 60 are fitted together with the air layer 2 therebetween, as in the concave prism 11 of the first light guide 10B and the convex prism 21 of the second light guide 20. This makes it possible to increase the amount of light that can be extracted from the first main surface 10a of the first light guide 10B. Therefore, the lighting device 1B in this modification can improve the light extraction efficiency more than the lighting device 1 according to the above embodiment.

[0121] Next, a third modification will be described. In the illumination device 1 according to the above embodiment, the light emitted from the light source 30 is incident on the first light guide 10, but the present invention is not limited to this. For example, as in an illumination device 1C according to a third modification shown in FIG. 11, the light emitted from the light source 30 may be incident on the second light guide 20. That is, as shown in FIG. 11, the light source 30 may be arranged so that the light emitted from the light source 30 is incident on the third end surface 20c of the second light guide 20. Specifically, in this modification, the light source 30 is arranged on the side of the third end surface 20c of the second light guide 20. For example, the light source 30 is arranged opposite to the third end surface 20c of the second light guide 20, and the light emission surface of the light source 30 faces the third end surface 20c of the second light guide 20.

[0122] The configuration of the lighting device 1C according to this modification can provide the same effect as the lighting device 1 according to the above embodiment. However, the lighting device 1C according to this modification has a lower light extraction efficiency than the lighting device 1 according to the above embodiment, which is configured so that the light emitted from the light source 30 is incident on the first end surface 10c of the first light guide 10. For this reason, in the lighting device 1C according to this modification, it is preferable to make the thickness of the first light guide 10 smaller than the thickness of the second light guide 20. This can improve the light extraction efficiency.

[0123] Here, a simulation was performed to compare the luminous flux of front light, the luminous flux of back light, the fixture efficiency, and the light distribution for the lighting device 1 in the above embodiment, the lighting device 1A of Variation 1 shown in Fig. 9, the lighting device 1B of Variation 2 shown in Fig. 10, and the lighting device 1C of Variation 3 shown in Fig. 11, and the results will be described with reference to Fig. 12. Fig. 12 is a diagram showing the luminous flux of front light, the luminous flux of back light, the fixture efficiency, and the light distribution for each of the lighting devices of the embodiment, Variation 1, Variation 2, and Variation 3.

[0124] In this simulation, the first light guide 10 and the second light guide 20 were made of acrylic plates with a thickness of 2 mm, the shapes of the concave prism 11 and the convex prism 21 were axially symmetric conical shapes, the base angle θ of the concave prism 11 and the convex prism 21 was set to 55°, and the thickness of the air layer 2 between the concave prism 11 and the convex prism 21 was set to 0.01 mm.

[0125] 12, it was found that by using the third light guides 50 and 60 in addition to the first light guide 10 and the second light guide 20, the light distribution becomes symmetrical between the front and back and the light extraction efficiency is higher than when only the first light guide 10 and the second light guide 20 are used. It was also found that the light extraction efficiency is higher when the light emitted from the light source 30 is made to enter a light guide having a concave prism formed therein.

[0126] Next, an illumination device 1D according to Modification 4 will be described with reference to Fig. 13. Fig. 13 is a cross-sectional view showing the configuration of an illumination device 1D according to Modification 4. Fig. 13 is a cross-sectional view corresponding to Fig. 1C.

[0127] 13, an illumination device 1D according to this modification further includes a reflecting member 70 in addition to the components of the illumination device 1 according to the above embodiment. Other than that, the illumination device 1D is the same as the illumination device 1 according to the above embodiment.

[0128] The reflective member 70 has a function of reflecting light. The reflective member 70 may have a specular surface or a white surface. In this modification, the reflective member 70 has a specular surface. As an example, the reflective member 70 is a reflective sheet on which a specular metal film is formed. The reflective member 70 is not limited to a metal material, and may be made of a resin material such as a white resin, or may be made of a metal material and a resin material.

[0129] The reflecting member 70 is disposed opposite the second main surface 10b of the first light guide 10 or the fourth main surface 20b of the second light guide 20. With this configuration, light can be extracted from only one of the second main surface 10b of the first light guide 10 and the fourth main surface 20b of the second light guide 20. In this modification, since the second main surface 10b of the first light guide 10 is the light extraction surface (front surface), the reflecting member 70 is disposed opposite the fourth main surface 20b (rear surface) of the second light guide 20. Specifically, the reflecting member 70 is disposed so that the reflecting surface of the reflecting member 70 is in contact with the fourth main surface 20b of the second light guide 20. With this, the light leaking from the fourth main surface 20b of the second light guide 20 can be reflected by the reflecting member 70 and returned to the second light guide 20, so that the light can be emitted to the outside only from the second main surface 10b of the first light guide 10.

[0130] Next, an illumination device 1E according to Modification 5 will be described with reference to Figs. 14A to 14C. Fig. 14A is a perspective view of illumination device 1E according to Modification 5. Fig. 14B is a cross-sectional view of illumination device 1E taken along line XIVB-XIVB in Fig. 14A. Fig. 14C is a cross-sectional view of illumination device 1E taken along line XIVC-XIVC in Fig. 14A.

[0131] 14A to 14C, an illumination device 1E according to this modification further comprises a first reflecting member 81, a second reflecting member 82, and a third reflecting member 83 in addition to the components of the illumination device 1 according to the above embodiment. All other components are the same as the illumination device 1 according to the above embodiment.

[0132] The first reflecting member 81, the second reflecting member 82, and the third reflecting member 83 have a function of reflecting light. The first reflecting member 81, the second reflecting member 82, and the third reflecting member 83 may have a specular surface or may have a white surface. In this modification, the first reflecting member 81, the second reflecting member 82, and the third reflecting member 83 have a specular surface. As an example, the first reflecting member 81, the second reflecting member 82, and the third reflecting member 83 are reflective sheets on which a metal film having a specular surface is formed. Note that the first reflecting member 81, the second reflecting member 82, and the third reflecting member 83 are not limited to a metal material, and may be made of a resin material such as a white resin, or may be made of a metal material and a resin material.

[0133] The first reflecting member 81 is disposed opposite to the second end face 10d of the first light guide 10. Specifically, the first reflecting member 81 is disposed such that the reflecting surface of the first reflecting member 81 is in contact with the second end face 10d.

[0134] In this manner, by positioning the first reflecting member 81, light that is about to leak out from the second end face 10d of the first light guide 10 can be reflected by the first reflecting member 81 and returned to the first light guide 10, thereby increasing the amount of light that is emitted to the outside from the second main surface 10b, which is the light extraction surface.

[0135] The second reflecting member 82 is disposed opposite to the fourth end face 20d of the second light guide 20. Specifically, the second reflecting member 82 is disposed such that the reflecting surface of the second reflecting member 82 is in contact with the fourth end face 20d.

[0136] Moreover, the third reflecting member 83 is disposed opposite to the third end face 20c of the second light guide 20. Specifically, the third reflecting member 83 is disposed such that the reflecting surface of the third reflecting member 83 is in contact with the third end face 20c.

[0137] By arranging the second reflecting member 82 and the third reflecting member 83 in this manner, light leaking out from the third end face 20c and the fourth end face 20d of the second light guide 20 can be reflected by the second reflecting member 82 and the third reflecting member 83 and returned to the second light guide 20, thereby increasing the amount of light that re-enters the first light guide 10 from the second light guide 20. As a result, the amount of light that exits to the outside from the second main surface 10b, which is the light extraction surface of the first light guide 10, can be increased, thereby improving the light extraction efficiency.

[0138] Next, a fifth modified example will be described. In the lighting device 1 according to the above embodiment, the outer circumferential ends of the first light guide 10 and the second light guide 20 are sandwiched by the holding member 40. Specifically, the holding member 40 applies a load to both ends of the first light guide 10 and the second light guide 20 in a direction (the X direction in this embodiment) perpendicular to the direction in which the light incident on the first light guide 10 or the second light guide 20 is guided.

[0139] For this reason, in the lighting device 1 according to the above embodiment, it may be difficult to apply force to the central portions of the first light guide 10 and the second light guide 20. In this case, as shown in Fig. 15, the gap (air layer 2) between the first light guide 10 and the second light guide 20 is larger at the central portion than at the outer circumferential end portion. For example, as shown in Fig. 15, the first light guide 10 and the second light guide 20 are curved so as to be convex outward.

[0140] In this way, when the gap between the first light guide 10 and the second light guide 20 becomes larger at the center, the interval (air layer 2) between the concave prism 11 and the convex prism 21 becomes larger at the center of the first light guide 10 and the second light guide 20. In other words, the fit between the concave prism 11 and the convex prism 21 becomes loose at the center. As a result, the optical action of the first light guide 10 and the second light guide 20 becomes non-uniform within the plane, and there is a risk that the desired light distribution characteristics cannot be obtained.

[0141] 16(a), in this modification, before a load is applied by the holding member 40, the first light guide 10 is warped so as to be convex toward the second light guide 20, and the second light guide 20 is warped so as to be convex toward the first light guide 10. In other words, the first light guide 10 and the second light guide 20 are warped in advance so as to be convex in the directions facing each other.

[0142] For example, when the first light guide 10 and the second light guide 20 are resin-molded, the molding conditions can be adjusted to make the first light guide 10 and the second light guide 20 warped in advance. Alternatively, the first light guide 10 and the second light guide 20 can be warped by applying stress to parts of the flat first light guide 10 and the second light guide 20 that are not warped and then performing an annealing treatment.

[0143] In this way, by using the first light guide 10 and the second light guide 20 in a warped state before applying a load with the holding member 40, when the outer circumferential ends of the first light guide 10 and the second light guide 20 are sandwiched by the holding member 40 and a load is applied to both ends of the first light guide 10 and the second light guide 20 from the X-axis direction as shown in (b) of Fig. 16, the gap (air layer 2) between the first light guide 10 and the second light guide 20 can be made uniform over the entire in-plane area. That is, the interval between the concave prism 11 and the convex prism 21 can be made uniform over the entire first main surface 10a of the first light guide 10 and the third main surface 20a of the second light guide 20. This makes it possible to keep the gap between the first light guide 10 and the second light guide 20 constant over time. That is, even if the outer peripheral ends of the first light guide 10 and the second light guide 20 are sandwiched by the holding member 40, the fitting state between all the concave prisms 11 and all the convex prisms 21 can be made the same, and this state can be maintained for a long period of time. Therefore, the optical action of the first light guide 10 and the second light guide 20 can be maintained constant over the entire surface for a long period of time, thereby realizing a highly reliable lighting device.

[0144] In the above embodiment, only the concave prism 11 is formed on the first main surface 10a (concave prism surface) of the first light guide 10, and only the convex prism 22 is formed on the third main surface 20a (convex prism surface) of the second light guide 20, but this is not limited thereto. For example, at least one additional convex prism having a convex shape may be formed on the first main surface 10a (concave prism surface) of the first light guide 10 on which the multiple concave prisms 11 are formed, and at least one additional concave prism having a concave shape may be formed on the third main surface (convex prism surface) of the second light guide 20 on which the multiple convex prisms 22 are formed. In this case, the additional convex prism formed on the first light guide 10 and the additional concave prism formed on the second light guide 20 are fitted together via an air layer, similar to the concave prism 11 and the convex prism 21. The additional convex prism may have the same shape and size as the convex prism 21, or may have a different shape and size from the convex prism 21. Furthermore, the additional concave prism may have the same shape and size as the concave prism 11, or may have a different shape and size from the concave prism 11. The number of sets of the additional convex prism and the additional concave prism may be one or more, but it is preferable that the number is less than the number of sets of the concave prism 11 and the convex prism 21. Furthermore, the additional convex prism and the additional concave prism can also be applied to modified examples.

[0145] In the above embodiment, the first light guide 10 and the second light guide 20 are manufactured by injection molding using a mold incorporating a stamper made from the same master, but the present invention is not limited to this. For example, the first light guide 10 and the second light guide 20 may be manufactured by roll transfer using a stamper made from the same master, or may be manufactured by other methods. The first light guide 10 and the second light guide 20 may be manufactured without using a stamper made from the same master. However, by manufacturing the first light guide 10 and the second light guide 20 using a stamper made from the same master, the gap between the concave prism 11 and the convex prism 21 can be precisely constant over the entire area, so that the control light can be controlled more precisely.

[0146] Other modified examples will be described below.

[0147] In the above embodiment, the light source 30 is configured to emit white light by using a blue LED chip and a yellow phosphor, but is not limited to this. For example, instead of using a yellow phosphor, a phosphor-containing resin containing red and green phosphors may be used in combination with a blue LED chip to emit white light.

[0148] In the above embodiment, the light emitting element 31 of the light source 30 uses a blue LED chip that emits blue light, but the present invention is not limited to this. For example, the light emitting element 31 may use an LED chip that emits a color other than blue. For example, the light emitting element 31 may use an LED chip that emits ultraviolet light. In this case, the phosphor particles may be a combination of phosphors that emit the three primary colors (red, green, and blue). Furthermore, although phosphors are used as wavelength conversion materials, wavelength conversion materials other than phosphors may be used. For example, materials containing a substance that absorbs light of a certain wavelength and emits light of a different wavelength from the absorbed light, such as semiconductors, metal complexes, organic dyes, and pigments, may be used as wavelength conversion materials.

[0149] In the above embodiment, the light source 30 is an LED module using an LED, but is not limited to this. For example, the light source 30 may be a solid-state light-emitting element other than an LED, such as a semiconductor laser or an organic EL (Electro Luminescence), or may be a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL).

[0150] In addition, the present invention also includes forms obtained by applying various modifications to the above-described embodiments that a person skilled in the art may think of, and forms realized by arbitrarily combining the components and functions of the above-described embodiments without departing from the spirit of the present invention. [Explanation of symbols]

[0151] 1, 1A, 1B, 1C, 1D, 1E lighting equipment 2. Air layer 10, 10B 1st light guide 10a First main surface 10b Second main surface 11, 12, 51 Concave prism 20, 20A Second light guide 20a Third main surface 20b 4th principal surface 21, 22, 61 Convex prism 30 light source 40 Retaining member 50, 60 Third light guide 70 Reflective material 100 Master board (master board)

Claims

1. a first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, is formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, The first light guide and the second light guide are made of the same material, The plurality of concave prisms and the plurality of convex prisms are axially symmetrical conical or hemispherical. Lighting equipment.

2. the plurality of concave prisms and the plurality of convex prisms are axially symmetric conical in shape, a base angle of each of the plurality of concave prisms and a base angle of each of the plurality of convex prisms are greater than or equal to 45° and less than or equal to 60°; 10. The lighting device of claim 1.

3. the plurality of concave prisms and the plurality of convex prisms are axially symmetric conical in shape, a base angle of each of the plurality of concave prisms and a base angle of each of the plurality of convex prisms are equal to or greater than 20° and equal to or less than 40°; 10. The lighting device of claim 1.

4. The light source is disposed so that light emitted from the light source is incident on an end surface of the first light guide. The lighting device according to any one of claims 1 to 3.

5. A first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, are formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, The first light guide and the second light guide are made of the same material, the light source is disposed such that light emitted from the light source is incident on an end surface of the first light guide, the first light guide and the second light guide are plate-shaped light guide plates, The thickness of the second light guide is smaller than the thickness of the first light guide. Lighting equipment.

6. The light source is disposed so that light emitted from the light source is incident on an end surface of the second light guide. The lighting device according to any one of claims 1 to 3.

7. A first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, are formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, The first light guide and the second light guide are made of the same material, the light source is disposed such that light emitted from the light source is incident on an end surface of the second light guide, the first light guide and the second light guide are plate-shaped light guide plates, The thickness of the first light guide is smaller than the thickness of the second light guide. Lighting equipment.

8. A first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, are formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, The first light guide and the second light guide are made of the same material, the first light guide has a first main surface which is a prism surface on which the plurality of concave prisms are formed, and a second main surface facing away from the first main surface, the second light guide has a third main surface which is a prism surface on which the plurality of convex prisms are formed, and a fourth main surface facing away from the third main surface, Further, a reflecting member having a specular surface is provided opposite the second main surface or the fourth main surface. Lighting equipment.

9. a first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, is formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, a thickness of the air layer is equal to or less than half the depth of each of the plurality of concave prisms or equal to or less than half the height of each of the plurality of convex prisms; Lighting equipment.

10. a first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, is formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, a holding member for holding the first light guide and the second light guide, the holding member applies a load to both ends of the first light guide and the second light guide in a direction perpendicular to a direction in which light incident on the first light guide or the second light guide is guided, Before a load is applied by the holding member, the first light guide is warped so as to be convex toward the second light guide, and the second light guide is warped so as to be convex toward the first light guide. Lighting equipment.

11. a first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, is formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, At least one additional convex prism having a convex shape is formed on the prism surface on which the plurality of concave prisms are formed in the first light guide, At least one additional concave prism having a concave shape is formed on the prism surface on which the plurality of convex prisms are formed in the second light guide, the additional convex prism and the additional concave prism are fitted together via an air gap; Lighting equipment.

12. A first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, are formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a third light guiding body having a prism surface on which a plurality of concave prisms, each of which has a concave shape, are formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, The first light guide and the second light guide are made of the same material, the second light guide has a third main surface which is a prism surface on which the plurality of convex prisms are formed, and a fourth main surface facing away from the third main surface, the plurality of convex prisms formed on the third main surface are defined as first convex prisms, a plurality of second convex prisms, each having a convex shape, are formed on the fourth main surface of the second light guide, The second light guide and the third light guide are arranged such that the second convex prisms and the third light guide are fitted to each other with an air layer between them. Lighting equipment.

13. A first light guide having a prism surface on which a plurality of concave prisms, each of which has a concave shape, are formed; a second light guide having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a third light guiding body having a prism surface on which a plurality of convex prisms, each of which has a convex shape, is formed; a light source that emits light to be incident on at least one end surface of the first light guide and the second light guide, the first light guide and the second light guide are arranged such that the concave prisms and the convex prisms are fitted together with an air layer therebetween, The first light guide and the second light guide are made of the same material, the first light guide has a first main surface which is a prism surface on which the plurality of concave prisms are formed, and a second main surface facing away from the first main surface, the plurality of concave prisms formed on the first main surface are called first concave prisms; a plurality of second concave prisms, each having a concave shape, are formed on the second main surface of the first light guide; the first light guide and the third light guide are arranged such that the second concave prisms and the third light guide are fitted to each other via an air layer; Lighting equipment.

14. A method for manufacturing an illumination device including a first light guiding body having a prism surface on which a plurality of first prisms, each of which has a concave shape, are formed, and a second light guiding body having a prism surface on which a plurality of second prisms, each of which has a convex shape, are formed, comprising: The first light guide and the second light guide are manufactured using a stamper manufactured from the same master. A method for manufacturing a lighting device.

15. The first light guide and the second light guide are manufactured by injection molding using a mold incorporating the stamper or by roll transfer using the stamper. A method for manufacturing an illumination device according to claim 14.

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