Light guide film and lighting device

Abstract

Provided is a light guide film capable of improving the injection efficiency of light from a light source. The light guide film comprises: a film which includes a first principal surface, a second principal surface disposed on the opposite side to the first principal surface, and an end surface intersecting each of the first principal surface and the second principal surface, and which guides light that has been emitted from a light source including a light-emitting surface and that has been injected into the inside of the film; and a light injection member which injects light from the light source into the inside of the film and which includes an upper surface, a lower surface disposed on the opposite side to the upper surface, and a light incidence surface intersecting the upper surface, wherein the lower surface is disposed on the first principal surface so as to face the first principal surface. The thickness of the film is 1500 μm or less. The light source is disposed so that the light-emitting surface faces at least the light incidence surface. An angle α formed by the upper surface of the light injection member disposed on the first principal surface of the film and the normal to the second principal surface satisfies 60° ≤ α ≤ 120°.

Description

Light guide film and lighting device

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

[0002] A method has been proposed for realizing lighting and displays with high design value or entertainment value by arranging light-guiding films on glass, windows, walls, floors, ceilings, and the like.

[0003] For example, Patent Document 1 discloses a light-guiding film having a light-guiding layer having a light-receiving side surface that receives light emitted from a light source, and a light distribution control structure for light propagating within the light-guiding layer.

[0004] International Publication No. 2022 / 025067

[0005] However, in the light-guiding film of Patent Document 1, light from the light source is incident on the light-guiding layer only from the end surface of the light-guiding layer, so if the thickness of the light-guiding film is thin, the efficiency of light incidence on the light-guiding film may be low.

[0006] An object of the present invention is to provide a light guiding film that can improve the incidence efficiency of light from a light source.

[0007] A light-guiding film according to one aspect of the present invention includes a film including a first main surface, a second main surface disposed opposite the first main surface, and end surfaces intersecting the first main surface and the second main surface, the film guiding light emitted from a light source including a light-emitting surface and entering an interior thereof; and a light entrance member including a top surface, a bottom surface disposed opposite the top surface, and a light entrance surface intersecting the top surface, the bottom surface being disposed on the first main surface so as to face the first main surface, the light entrance member allowing light from the light source to enter the interior of the film; wherein the thickness of the film is 1500 μm or less; the light source is disposed so that the light-emitting surface faces at least the light entrance surface; and an angle α between the top surface of the light entrance member disposed on the first main surface of the film and a normal to the second main surface satisfies 60 degrees≦α≦120 degrees.

[0008] According to the present invention, it is possible to provide a light guiding film that can improve the incidence efficiency of light from a light source.

[0009] 11 is a schematic plan view of a lighting device including a light guiding film according to an embodiment. It is a schematic cross-sectional view along line II-II in FIG. 1 . It is a schematic plan view of a light extraction layer included in the light guiding film according to an embodiment. It is a schematic cross-sectional view along line IV-IV in FIG. 3 . It is a schematic cross-sectional view of a light extraction portion provided in the light extraction layer. It is a schematic cross-sectional view of a lighting device showing an example of light guiding using a light guiding film according to Comparative Example 1. It is a schematic cross-sectional view of a lighting device showing an example of light guiding using a light guiding film according to Comparative Example 2. It is a schematic cross-sectional view of a lighting device showing an example of light guiding using a light guiding film according to an embodiment. It is a schematic cross-sectional view of a lighting device including a light guiding film according to a first modified example. It is a schematic cross-sectional view of a lighting device including a light guiding film according to a second modified example. It is a schematic plan view of a lighting device including a light guiding film according to a third modified example. It is a schematic cross-sectional view along line XII-XII in FIG. 11 , showing an example of light guiding using a light guiding film according to the third modified example. It is a diagram showing an apparatus for evaluating the efficiency of light incidence into a light guiding film. It is a diagram showing a housing included in the apparatus for evaluating the efficiency of light incidence into a light guiding film. 10A and 10B are diagrams illustrating a method for evaluating the luminance value of light extracted from a light guiding film, a schematic cross-sectional view of an illumination device including a light guiding film according to Example 4, and a schematic cross-sectional view of an illumination device including a light guiding film according to Example 6.

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same components are given the same reference numerals, and duplicated descriptions will be omitted as appropriate.

[0011] The following embodiments are intended to exemplify light guiding films and lighting devices embodying the technical concepts of the present invention, and are not intended to limit the present invention to the following embodiments. The dimensions, materials, shapes, relative positions, etc. of the components described below are intended for illustrative purposes only, unless otherwise specified, and are not intended to limit the scope of the present invention. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0012] In the drawings shown below, directions are expressed using a Cartesian coordinate system having an X-axis, a Y-axis, and a Z-axis. The X-axis, the Y-axis, and the Z-axis are approximately perpendicular to one another. The direction in which the arrow representing the X-axis points is referred to as the +X direction or +X side, and the direction opposite to the +X direction is referred to as the -X direction or -X side. The direction in which the arrow representing the Y-axis points is referred to as the +Y direction or +Y side, and the direction opposite to the +Y direction is referred to as the -Y direction or -Y side. The direction in which the arrow representing the Z-axis points is referred to as the +Z direction or +Z side, and the direction opposite to the +Z direction is referred to as the -Z direction or -Z side.

[0013] The Z direction along the Z axis indicates the direction along the normal to the second main surface of the light guiding film according to the embodiment. In this specification, "planar view" refers to viewing an object from the Z direction. The +Z direction is referred to as "up" and the -Z direction is referred to as "down." However, these directional expressions merely represent relative positional relationships for the purpose of explanation and do not limit the directions of the embodiment. In this specification, "thickness" refers to the length of an object in the Z direction.

[0014] [Embodiments] <Configuration Example of a Lighting Device Including a Light Guiding Film According to an Embodiment> The configuration of a lighting device including a light guiding film according to an embodiment will be described with reference to Figures 1 to 5. Figure 1 is a schematic top view showing an example of a lighting device 100 including a light guiding film 10 according to an embodiment. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. Figure 3 is a schematic plan view of a light extraction layer 150 included in the light guiding film 10. Figure 4 is a schematic cross-sectional view taken along line IV-IV in Figure 3. Figure 5 is a schematic cross-sectional view of a light extraction portion 151 provided in the light extraction layer 150.

[0015] 1 and 2 , the lighting device 100 includes a light source 50 including a light-emitting surface 51, and a light-guiding film 10. The light-guiding film 10 guides light that is emitted from the light-emitting surface 51 of the light source 50 and enters the light-guiding film 10.

[0016] 1 and 2 , light guiding film 10 comprises film 1, which includes a first major surface 11, a second major surface 12 disposed opposite first major surface 11, and end surfaces 13 intersecting first major surface 11 and second major surface 12, and which guides light incident therein. Light guiding film 10 also comprises light incident member 2, which includes a top surface 21, a bottom surface 22 disposed opposite top surface 21, and a light incident surface 23 intersecting top surface 21, and which is disposed on first major surface 11 so that bottom surface 22 faces first major surface 11, and which allows light from light source 50 including light emitting surface 51 to enter film 1. From another perspective, light guiding film 10 is a film with a light incident member.

[0017] In this embodiment, the thickness of the film 1 is 1500 μm or less. The angle α between the upper surface 21 of the light incident member 2 disposed on the first main surface 11 of the film 1 and the normal N1 to the second main surface 12 satisfies 60 degrees≦α≦120 degrees. In the example shown in FIG. 2 , the light source 50 is disposed so that the light emitting surface 51 faces both the end surface 13 of the film 1 and the light incident surface 23 of the light incident member 2.

[0018] Illumination device 100 guides light incident from light source 50 using light guiding film 10 and emits the light in the +Z direction from almost the entire first major surface 11. Illumination device 100 is used, for example, with light guiding film 10 disposed on an adherend such as glass, a window, a wall, a floor, or a ceiling. Illumination device 100 can illuminate an indoor space or the like with the light emitted from first major surface 11.

[0019] For example, when the light-emitting surface of the light source is arranged opposite the edge of the film so that light emitted from the light source enters the interior of the film through the edge of the film, if the film is thin, a large portion of the light-emitting surface of the light source does not face the edge of the film. In the portion of the light-emitting surface that does not face the edge of the film, the light emitted from the light-emitting surface does not enter the interior of the film through the edge of the film. This may result in a low efficiency of light incidence into the film.

[0020] Light guide film 10 has light incident member 2 disposed on first main surface 11 of film 1, and is disposed so that light emitting surface 51 faces at least light incident surface 23. In this configuration, even if there is a portion of light emitting surface 51 that does not face end surface 13 of film 1, that portion faces light incident surface 23. As a result, even if there is a portion of light emitting surface 51 that does not face end surface 13 of film 1, light from light source 50 can be incident into film 1 through light incident surface 23.

[0021] 6 and 7, if the angle between the upper surface of the light incident member disposed on the first main surface of the film and the normal to the second main surface of the film is large, the light passing through the inside of the light incident member and incident on the upper surface may not be totally reflected by the upper surface and may pass through the upper surface and leak out of the light incident member, which may reduce the incidence efficiency of light entering the inside of the film via the light incident member.

[0022] 8 , in light guiding film 10, the angle α between upper surface 21 of light incident member 2 disposed on first main surface 11 of film 1 and normal N1 to second main surface 12 satisfies 60 degrees≦α≦120 degrees, so that light that passes through the inside of light incident member 2 and is incident on upper surface 21 can be totally reflected by upper surface 21. This reduces the light that leaks to the outside of light incident member 2 through upper surface 21, and improves the incidence efficiency of light that enters film 1 via light incident member 2.

[0023] The angle α can be adjusted as appropriate to allow light from the light source 50 to easily enter the film 1. For example, the lower limit of the angle α may be 70 degrees or more, more preferably 80 degrees or more, and the upper limit of the angle α may be 110 degrees or less, more preferably 100 degrees or less, and even more preferably 90 degrees or less.

[0024] In the light guiding film 10, the upper surface 21 of the light incident member 2 may be flat. Having the upper surface 21 be flat facilitates the manufacture of the light incident member 2, and therefore the manufacture of the light guiding film 10. However, the upper surface 21 is not limited to being flat, and may include at least a portion of a curved surface other than a flat surface as long as the angle α satisfies 60 degrees≦α≦120 degrees.

[0025] 1 and 2 , the light source 50 includes a plurality of LEDs (Light Emitting Diodes) arranged side by side in a direction in which the light incident surface 23 of the light incident member 2 extends (e.g., the X direction). The light source 50 is arranged so that a light emitting surface 51 faces at least the light incident surface 23. The plurality of LEDs are mounted on the +Y side surface of the wiring substrate 60. The light emitting surface 51 of the light source 50 is formed by the light emitting surface of each of the plurality of LEDs. The light source 50 can emit light from each of the light emitting surfaces of the plurality of LEDs arranged side by side in the X direction in accordance with a driving current or driving voltage supplied via the wiring substrate 60.

[0026] 1 and 2, the light incident member 2 is a rectangular parallelepiped with its longitudinal direction being the direction in which the light incident surface 23 extends (for example, the X direction). The light incident member 2 can be made of a resin material or glass material that has a transmittance of 60% or more for the light emitted from the light source 50. Examples of resin materials that can be used include acrylic resin, polycarbonate resin, cycloolefin polymer resin, and epoxy resin.

[0027] 1 and 2 , the length Fx represents the length of the film 1 in the direction in which the light incident surface 23 of the light incident member 2 extends (e.g., the X direction). The length Fy represents the length of the film 1 in the direction along the normal N2 of the light emitting surface 51 (e.g., the Y direction). The direction along the normal N2 of the light emitting surface 51 is a direction that intersects both the direction in which the light incident surface 23 of the light incident member 2 extends and the direction along the normal N1 of the second main surface 12. The length Bx represents the length of the light incident member 2 in the direction in which the light incident surface 23 of the light incident member 2 extends.

[0028] 2 , the length H represents the length of the light incident surface 23 in the direction along the normal N1 of the second main surface 12 (e.g., the Z direction). From another perspective, the length H is the distance between the upper surface 21 and the lower surface 22. The length W represents the length of the light emitting surface 51 of the light source 50 in the direction along the normal N1 of the second main surface 12. The length L represents the length of the light incident member 2 in the direction along the normal N2 of the light emitting surface 51 (e.g., the Y direction).

[0029] 2, the film 1 includes a first transparent layer 110, a first adhesive layer 120, a second transparent layer 130, a second adhesive layer 140, and a light extraction layer 150. The first transparent layer 110, the first adhesive layer 120, the second transparent layer 130, the second adhesive layer 140, and the light extraction layer 150 are laminated in this order from top to bottom.

[0030] (First Transmitting Layer 110 and Second Transmitting Layer 130) The first transmitting layer 110 and the second transmitting layer 130 can be made of a film having flat surfaces. The material used for the first transmitting layer 110 and the second transmitting layer 130 preferably has a low light absorption coefficient. For example, the material used for the first transmitting layer 110 and the second transmitting layer 130 can be an acrylic film such as PMMA (Poly Methyl Methylacrylate), a cycloolefin film such as COP (Cyclo Olefin Polymer), a polyethylene film such as PET (Polyethylene Terephthalate), a polycarbonate film, or the like. The material used for the first transmitting layer 110 and the material used for the second transmitting layer 130 can be the same or different.

[0031] From the viewpoint of increasing the incidence efficiency of light from the light source 50, the thickness of each of the first transmission layer 110 and the second transmission layer 130 is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 60 μm or more or 100 μm or more. On the other hand, from the viewpoint of providing flexibility, the thickness of each of the light guide layers of the first transmission layer 110 and the second transmission layer 130 is preferably 800 μm or less, more preferably 600 μm or less, even more preferably 500 μm or less or less than 500 μm, and particularly preferably 400 μm or less, 300 μm or less, or 200 μm or less. The refractive index of the first transmission layer 110 and the second transmission layer 130 is preferably 1.45 or more and 1.60 or less, for example.

[0032] (First adhesive layer 120 and second adhesive layer 140) The first adhesive layer 120 is disposed between the first transparent layer 110 and the second transparent layer 130, and bonds the first transparent layer 110 to the second transparent layer 130. The second adhesive layer 140 is disposed between the second transparent layer 130 and the light extraction layer 150, and bonds the second transparent layer 130 to the light extraction layer 150. The first adhesive layer 120 and the second adhesive layer 140 can transmit light incident from the light source 50.

[0033] At least one of an acrylic or polyester pressure-sensitive adhesive and an adhesive can be used for each of the first adhesive layer 120 and the second adhesive layer 140. The material used for the first adhesive layer 120 and the material used for the second adhesive layer 140 may be the same as or different from each other. The refractive index of each of the first adhesive layer 120 and the second adhesive layer 140 is preferably similar to the refractive index of each of the first transparent layer 110 and the second transparent layer 130, and is preferably, for example, 1.45 or more and 1.60 or less.

[0034] The ratio of the thickness of each of the first adhesive layer 120 and the second adhesive layer 140 to the total thickness of the film 1 can be 10% or more, preferably 15% or more, or 20% or more. There is no particular upper limit to this ratio, but it is, for example, 50% or less, or 40% or less. By using such a first adhesive layer 120 and second adhesive layer 140, the film 1 can have suitable flexibility.

[0035] (Light Extraction Layer 150) The light extraction layer 150 includes a light extraction portion 151 therein. The light extraction portion 151 may be a plurality of internal spaces provided in the light extraction layer 150. Each of the plurality of internal spaces forms an interface that directs light toward the +Z side by total internal reflection. The internal space is sometimes referred to as a cavity. The internal space has a triangular cross-sectional shape with an apex angle on the +Z side, i.e., a cross-sectional shape perpendicular to the X direction and parallel to the YZ plane, and directs light L propagating through the film 1 toward the +Y side toward the +Z side. The light directed toward the +Z side by the internal space is emitted from the film 1. In other words, the light guide film 10 can extract light from the first major surface 11 of the film 1 toward the +Z side by the light extraction portion 151 provided in the light extraction layer 150. "Extracting light" can also be referred to as "taking out light." The cross-sectional shape of the internal space is not limited to a triangle, and may be a trapezoid or the like as long as it has an interface that directs light propagating in the +Y direction to the +Z side. By changing the cross-sectional shape of the internal space, for example, the direction of the apex angle of the triangle, the outgoing direction of the light can be changed.

[0036] The light guiding film 10 extracts light guided by the film 1 using the light extraction portions 151 and can control the distribution of the extracted light, so that the visible light transmittance can be 60% or more and the haze value can be less than 10%. Furthermore, by adjusting the shape and arrangement of the multiple internal spaces in the light extraction portions 151, the light distribution, output efficiency, and luminance distribution of the light emitted from the film 1 can be controlled. The light extraction portions 151 are typically voids (air cavities) filled with air. However, the air cavities may be filled with a material having a refractive index lower than that of the light extraction layer 150 instead of air.

[0037] The light extraction layer 150 has a plurality of internal spaces, which are light extraction portions 151, arranged regularly or randomly along the second major surface 12, i.e., a plane substantially parallel to the XY plane. The size of each internal space can be selected as appropriate as long as it can be installed inside the light extraction layer 150. For the light extraction layer 150 containing the light extraction portions 151 therein, it is possible to use the light guide layers disclosed in, for example, WO 2019 / 182091, WO 2011 / 124765, WO 2019 / 087118, and WO 2011 / 127187. The disclosures of these publications are incorporated herein by reference in their entirety.

[0038] The light extraction layer 150 is produced, for example, by laminating a first film having no pattern and a second film having a desired fine pattern thereon, or by bonding them together with an adhesive (including a pressure-sensitive adhesive).

[0039] The micropatterns in the second film can be formed by laser patterning, direct laser imaging, laser drilling, masked or maskless laser or electron beam irradiation, etc. Individual properties can also be imparted by printing, inkjet printing, screen printing, etc., to change the material or refractive index value. Micro- or nano-dispensing, dosing, direct "writing", discrete laser sintering, micro-EDM (Electrical Discharge Machining), or micromachining, micro-molding, imprinting, embossing, and the like can also be used.

[0040] From the viewpoint of obtaining a good visible light transmittance and haze value of the light guiding film 10, the ratio (occupancy rate) of the area of ​​the multiple internal spaces that are the light extraction portions 151 to the area of ​​the light extraction layer 150 in a planar view is preferably 30% or less. The occupation rate of the internal spaces may be uniform, or may increase with increasing distance from the light source 50 so that brightness does not decrease even with increasing distance. The occupation rate of the internal spaces is preferably uniform. From the viewpoint of obtaining good brightness, the occupation rate of the internal spaces is preferably 1% or more. The occupation rate of the internal spaces is preferably 1% or more and 30% or less, with the upper limit being more preferably 25% or less. To obtain a high visible light transmittance, the occupation rate is preferably 10% or less, and more preferably 5% or less.

[0041] The above-described features of the light extraction portion 151 are not limited to the multiple internal spaces formed in the light extraction layer 150 exemplified here, but are common to various light distribution control structures. As a light distribution control structure formed by multiple internal spaces, for example, the light distribution structure described in International Publication No. 2019 / 087118 can be used.

[0042] The light extraction portion 151 is not limited to a plurality of internal spaces, but may be a plurality of prisms arranged in the light extraction layer 150. The light extraction layer 150 may be a prism sheet containing a plurality of prisms therein. A plurality of convex portions (prism portions) may be formed directly on the surface of the light extraction layer 150. The refractive index of the light extraction layer 150 is preferably approximately equal to the refractive index of the second adhesive layer 140, and the difference (absolute value) between the refractive indices is preferably 0.15 or less, and more preferably 0.1 or less.

[0043] A light distribution control structure in which the light extraction portions 151 are multiple internal spaces has higher light utilization efficiency than a light distribution control structure such as a prism sheet. Furthermore, the light distribution can be controlled by adjusting the cross-sectional shape (e.g., the angles θa and θb of the inclined surfaces in FIG. 5 ), size, arrangement density, distribution, etc. of the internal spaces. Meanwhile, the visible light transmittance and haze value of the light guiding film 10 can be controlled by adjusting the cross-sectional shape, size, arrangement density, and distribution of the multiple internal spaces of the light extraction portions 151. The visible light transmittance of the light guiding film 10 is 60% or more, preferably 65% ​​or more, 70% or more, 75% or more, or 80% or more. The haze value of the light guiding film 10 is less than 10%, and preferably less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, or less than 3%. The haze value can be measured using a haze meter.

[0044] The size and density of the internal spaces affect the haze value. Regarding the size of the internal spaces (length M, width r: see Figures 3 to 5), for example, the length M is preferably 10.0 μm or more and 500.0 μm or less, and the width r is preferably 1.0 μm or more and 100.0 μm or less. From the perspective of the light extraction efficiency of the light extraction layer 150, the height q is preferably 1.0 μm or more and 100.0 μm or less. The multiple internal spaces are preferably distributed discretely and uniformly, and are preferably arranged periodically, for example, as shown in Figure 3. In Figure 3, the pitch Px is preferably 10.0 μm or more and 500.0 μm or less, and the pitch Py is preferably 10 μm or more and 500 μm or less. The spacing E in Figure 3 is the spacing between the multiple internal spaces in the X direction. The spacing D in Figure 3 is the spacing between the multiple internal spaces in the Y direction.

[0045] The configuration of each layer in the film 1 can be changed as appropriate. The film 1 may be configured with only the light extraction layer 150, which is the minimum number of layers. Furthermore, when the film 1 includes multiple layers, it does not necessarily need to include an adhesive layer for bonding the layers together, and the layers may be directly bonded together.

[0046] <Function of Light Guiding Film 10> The function of light guiding film 10 will be described with reference to FIGS. 6 to 8. FIG. 6 is a schematic cross-sectional view of lighting device 100X, illustrating an example of light guiding by light guiding film 10X according to Comparative Example 1. FIG. 7 is a schematic cross-sectional view of lighting device 100Y, illustrating an example of light guiding by light guiding film 10Y according to Comparative Example 2. FIG. 8 is a schematic cross-sectional view of lighting device 100, illustrating an example of light guiding by light guiding film 10 according to an embodiment. FIGS. 6 to 8 show a cross section corresponding to line II-II in FIG. 1. For ease of understanding, in Comparative Examples 1 and 2, the same reference numerals as those shown in FIG. 2 may be used for convenience to designate components that are substantially the same as those in light guiding film 10 and lighting device 100 according to the embodiment.

[0047] In Comparative Example 1 shown in Figure 6, light guiding film 10X differs from light guiding film 10 in that it includes a light entrance member 2X whose upper surface 21X is a curved surface. The curved surface is, for example, a free-form surface. The curved upper surface 21X has a surface whose inclination varies depending on the position, and includes a region where the angle α between the upper surface 21X and normal N1 is less than 60 degrees. Light LX1 and light LX2 represent light emitted from light-emitting surface 51 of light source 50 and guided inside light entrance member 2X and film 1, respectively.

[0048] The light LX1 emitted from the light-emitting surface 51 passes through the light incident surface 23 and enters the interior of the light incident member 2X. The light LX1 that enters the interior of the light incident member 2X passes through the interior of the light incident member 2X and reaches the upper surface 21X. The angle of incidence of the light LX1 on the upper surface 21X is greater than the critical angle. Therefore, the light LX1 that enters the upper surface 21X is totally reflected by the upper surface 21X. The light LX1 that is totally reflected by the upper surface 21X enters the interior of the film 1 through the lower surface 22X of the light incident member 2X and the first main surface 11 of the film 1. The light LX1 that enters the interior of the film 1 is guided to the +Y side inside the film 1 while repeatedly being totally reflected by each of the first main surface 11 and the second main surface 12 of the film 1.

[0049] On the other hand, light LX2 emitted from the light-emitting surface 51 enters the interior of the light incident member 2X through the light incident surface 23. The light LX2 entering the interior of the light incident member 2X enters the interior of the film 1 through the lower surface 22X of the light incident member 2X and the first major surface 11 of the film 1. The light LX2 entering the interior of the film 1 is totally reflected by the second major surface 12 of the film 1, then enters the interior of the light incident member 2X through the first major surface 11 of the film 1 and the lower surface 22X of the light incident member 2X, passes through the interior of the light incident member 2X, and reaches the upper surface 21X. The angle of incidence of the light LX2 on the upper surface 21X is smaller than the critical angle. Therefore, the light LX2 entering the upper surface 21X is not totally reflected by the upper surface 21X and leaks out of the light incident member 2X through the upper surface 21X. The light LX2 leaking out of the light incident member 2X does not enter the interior of the film 1. This causes light loss in the light guiding film 10X. As described above, in the light guiding film 10X, the upper surface 21X is a curved surface including an area where the angle α is smaller than 60 degrees. As a result, some of the light passing through the inside of the light incident member 2X may not be totally reflected by the upper surface 21X and may leak out of the light incident member 2X through the upper surface 21X. As a result, the efficiency of light incidence into the film 1 decreases.

[0050] 7 , light guiding film 10Y differs from light guiding film 10 in that it includes a triangular prism-shaped light entrance member 2Y in which light entrance surface 23 and top surface 21Y are each inclined with respect to normal line N1 to second main surface 12. Top surface 21Y is a substantially flat surface whose angle α with normal line N1 is less than 60 degrees. Light LY1 and light LY2 represent light emitted from light-emitting surface 51 of light source 50 and guided through light entrance member 2Y and film 1, respectively.

[0051] Light LY1 emitted from the light-emitting surface 51 passes through the light incident surface 23 and enters the interior of the light incident member 2Y. The light LY1 that enters the interior of the light incident member 2Y passes through the interior of the light incident member 2Y and reaches the upper surface 21Y. The angle of incidence of the light LY1 on the upper surface 21Y is greater than the critical angle. Therefore, the light LY1 that enters the upper surface 21Y is totally reflected by the upper surface 21Y. The light LY1 that is totally reflected by the upper surface 21Y enters the interior of the film 1 through the lower surface 22Y of the light incident member 2Y and the first main surface 11 of the film 1. The light LY1 that enters the interior of the film 1 is guided to the +Y side inside the film 1 while repeatedly being totally reflected by each of the first main surface 11 and the second main surface 12 of the film 1.

[0052] On the other hand, light LY2 emitted from the light-emitting surface 51 enters the light incident member 2 through the light incident surface 23. The light LY2 entering the light incident member 2 passes through the lower surface 22Y of the light incident member 2Y and the first major surface 11 of the film 1 and then enters the film 1. The light LY2 entering the film 1 is totally reflected by the second major surface 12 of the film 1, then passes through the first major surface 11 of the film 1 and the lower surface 22Y of the light incident member 2Y and enters the light incident member 2Y, passes through the light incident member 2Y, and reaches the upper surface 21Y. The angle of incidence of light LY2 on the upper surface 21Y is smaller than the critical angle. Therefore, the light LY2 entering the upper surface 21Y is not totally reflected by the upper surface 21Y and leaks out of the light incident member 2Y through the upper surface 21Y. The light LY2 leaking out of the light incident member 2Y does not enter the film 1. This causes light loss in the light guiding film 10Y. Thus, in the light guiding film 10Y, the upper surface 21Y is a substantially flat surface with an angle α smaller than 60 degrees. As a result, some of the light passing through the inside of the light incident member 2Y may not be totally reflected by the upper surface 21Y and may pass through the upper surface 21Y and be emitted to the outside of the light incident member 2Y. As a result, the efficiency of light incidence into the film 1 decreases.

[0053] 8, the upper surface 21 is a substantially flat surface with an angle α satisfying the relationship 60°≦α≦120°. Light L1 and light L2 represent light emitted from the light-emitting surface 51 of the light source 50 and guided through the light incident member 2 and the film 1, respectively.

[0054] Light L1 emitted from the light-emitting surface 51 passes through the light incident surface 23 and enters the interior of the light incident member 2. Light L1 that enters the interior of the light incident member 2 passes through the interior of the light incident member 2 and reaches the upper surface 21. The angle of incidence of light L1 on the upper surface 21 is greater than the critical angle. Therefore, light L1 that enters the upper surface 21 is totally reflected by the upper surface 21. Light L1 that has been totally reflected by the upper surface 21 enters the interior of the film 1 through the lower surface 22 of the light incident member 2 and the first main surface 11 of the film 1. Light L1 that has entered the interior of the film 1 is guided to the +Y side inside the film 1 while repeatedly being totally reflected by each of the first main surface 11 and the second main surface 12 of the film 1.

[0055] On the other hand, light L2 emitted from the light-emitting surface 51 is incident on the light incident surface 23 and enters the interior of the light incident member 2. The light L2 incident on the light incident member 2 passes through the lower surface 22 of the light incident member 2 and the first main surface 11 of the film 1 and enters the interior of the film 1. The light L2 incident on the interior of the film 1 is totally reflected on the second main surface 12 of the film 1, then passes through the first main surface 11 of the film 1 and the lower surface 22 of the light incident member 2 and enters the interior of the light incident member 2, and reaches the upper surface 21 through the interior of the light incident member 2. The angle of incidence of light L2 on the upper surface 21 is greater than the critical angle. Therefore, the light L2 incident on the upper surface 21 is totally reflected on the upper surface 21 and enters the interior of the film 1 through the lower surface 22 of the light incident member 2 and the first main surface 11 of the film 1. The light L2 incident on the interior of the film 1 is guided to the +Y side inside the film 1 while repeatedly being totally reflected on each of the first main surface 11 and the second main surface 12 of the film 1.

[0056] Thus, in light guiding film 10, upper surface 21 has angle α that satisfies 60 degrees≦α≦120 degrees. As a result, compared to Comparative Examples 1 and 2, light that is not totally reflected at upper surface 21 of light incident member 2 and leaks out of light incident member 2 is reduced, and light guiding film 10 can improve the efficiency of light incidence into film 1.

[0057] [Modifications] Modifications of the light guiding film according to the embodiment will be described below. Note that the same names and symbols as those in the already described embodiments indicate the same or similar members or components, and detailed descriptions will be omitted as appropriate. This also applies to the examples described below.

[0058] <First Modification> A light guiding film according to a first modification will be described with reference to Fig. 9. Fig. 9 is a schematic cross-sectional view showing a lighting device 100a including a light guiding film 10 according to the first modification.

[0059] This modified example differs from the above-described embodiment in that a reflecting member 3 is disposed on an opposing surface 24 located on the opposite side of the light incident surface 23 of the light incident member 2. In the example shown in Fig. 9, the reflecting member 3 reflects light L3 that is emitted from the light emitting surface 51 of the light source 50 and incident on the opposing surface 24.

[0060] For example, if the opposing surface 24 is translucent to light from the light source 50, light L3 emitted from the light-emitting surface 51 that is incident on the opposing surface 24 may pass through the opposing surface 24 and leak out from the light incident member 2 to the outside, thereby reducing the efficiency of light incidence on the film 1.

[0061] In the light guiding film 10, the reflecting member 3 is disposed on the facing surface 24, so that the light L3 incident on the facing surface 24 is reflected by the reflecting member 3. This prevents the light L3 from leaking out from the light incident member 2, and allows the light L3 to enter the film 1 while being reflected by the light emitting surface 51, the second main surface 12, the top surface 21, or the like. As a result, the light guiding film 10 can improve the efficiency with which light is incident on the film 1.

[0062] <Second Modification> A light guiding film according to a second modification will be described with reference to Fig. 10. Fig. 10 is a schematic cross-sectional view showing a lighting device 100b including a light guiding film 10 according to the second modification.

[0063] This modification differs from the above-described embodiment in that the light incident surface 23 is inclined so as to move away from the light source 50 as it moves away from the first main surface 11 .

[0064] Due to the configuration of light guiding film 10, light incident on light incident member 2 from light source 50 can more easily enter film 1 compared to, for example, a case where upper surface 21 is approximately parallel to second main surface 12 and light incident surface 23 and light emitting surface 51 are each approximately perpendicular to second main surface 12. This allows light guiding film 10 to increase the efficiency with which light enters film 1.

[0065] Furthermore, the upper surface 21 of the light incident member 2 may be inclined so as to approach the second main surface 12 the farther away from the light source 50, the light incident surface 23 may be perpendicular to the upper surface 21 of the light incident member 2, and the light source 50 may be disposed so that the light emitting surface 51 is parallel to the light incident surface 23. This configuration also makes it easier for light incident on the light incident member 2 from the light source 50 to enter the film 1, thereby increasing the efficiency of light incidence on the film 1 in the light guiding film 10.

[0066] <Third Modification> An illumination device including a light guiding film according to a third modification will be described with reference to Figures 11 and 12. Figure 11 is a schematic plan view showing an illumination device 100c including a light guiding film 10 according to the third modification. Figure 12 is a schematic cross-sectional view taken along line XII-XII in Figure 11, showing an illumination device 100c illustrating an example of light guiding by the light guiding film 10.

[0067] In this modified example, the light incident member 2 includes a convex portion 25 that protrudes downward from the lower surface 22 of the light incident member 2 and is disposed between the light source 50 and the end surface 13 of the film 1. In the example shown in Fig. 12, the convex portion 25 is disposed between the light emitting surface 51 of the light source 50 and the end surface 13 of the film 1. A portion of the light from the light source 50 passes through the convex portion 25 and enters the interior of the film 1. These points differ from the above-described embodiment.

[0068] 12 , the convex portion 25 includes a convex portion lower surface 251 and a convex portion exit surface 252. The length of the convex portion 25 in the X direction is equal to the length of the light incident member 2 in the X direction. The length of the convex portion 25 in the Z direction, i.e., the thickness, is approximately equal to the length of the film 1 in the Z direction, i.e., the thickness. Furthermore, the length T represents the length of the convex portion 25 in the direction along the normal N2 of the light emitting surface 51 (Y direction). As described with reference to FIG. 2 , the length L represents the length of the light incident member 2 in the direction along the normal N2 of the light emitting surface 51.

[0069] 12 , when the convex portion 25 is disposed between the light-emitting surface 51 and the end surface 13, the convex portion lower surface 251 is located in approximately the same plane as the second main surface 12. The surface of the convex portion 25 facing the light-emitting surface 51, i.e., the surface on the −Y side of the convex portion 25, constitutes part of the light incident surface 23. The convex portion exit surface 252 is the surface of the convex portion 25 located on the opposite side to the surface facing the light-emitting surface 51. The convex portion exit surface 252 is disposed so as to face the end surface 13 of the film 1.

[0070] 12 , almost all of the light emitted from the light source 50 passes through the light incident surface 23 and enters the inside of the light incident member 2. Of the light emitted from the light source 50, the light that passes through the light incident surface 23 and enters the inside of the convex portion 25 passes through the inside of the convex portion 25, and then passes through the convex portion exit surface 252 and the end surface 13 and enters the inside of the film 1.

[0071] For example, light L4 emitted from the light-emitting surface 51 passes through the light incident surface 23 and enters the interior of the light incident member 2. The light L4 that enters the interior of the light incident member 2 passes through the interior of the light incident member 2 and reaches the upper surface 21. The angle of incidence of light L4 on the upper surface 21 is greater than the critical angle. Therefore, the light L4 that enters the upper surface 21 is totally reflected by the upper surface 21. The light L4 that is totally reflected by the upper surface 21 enters the interior of the film 1 through the lower surface 22 of the light incident member 2 and the first main surface 11 of the film 1. The light L4 that enters the interior of the film 1 is guided to the +Y side inside the film 1 while repeatedly being totally reflected by each of the first main surface 11 and the second main surface 12 of the film 1.

[0072] On the other hand, light L5 emitted from the light-emitting surface 51 passes through the light incident surface 23 and enters the interior of the light incident member 2. The light L5 that entered the interior of the light incident member 2 passes through the interior of the light incident member 2 and reaches the convex lower surface 251. The incident angle of light L5 on the convex lower surface 251 is greater than the critical angle. Therefore, the light L5 that entered the convex lower surface 251 is totally reflected by the convex lower surface 251. The light L5 that was totally reflected by the convex lower surface 251 passes through the interior of the light incident member 2 and reaches the upper surface 21. The incident angle of light L5 on the upper surface 21 is greater than the critical angle. Therefore, the light L5 that entered the upper surface 21 is totally reflected by the upper surface 21. The light L5 that was totally reflected by the upper surface 21 passes through the lower surface 22 of the light incident member 2 and the first main surface 11 of the film 1 and enters the interior of the film 1. The light L5 incident on the interior of the film 1 is guided inside the film 1 to the +Y side while repeatedly being totally reflected by each of the first main surface 11 and the second main surface 12 of the film 1.

[0073] As described above, in light guiding film 10 according to the third modification, light incident member 2 includes convex portions 25, and almost all of the light emitted from light source 50 is incident on film 1 via light incident member 2. This reduces the effect of light scattering due to roughness of the cut surface of the film edge that occurs during film processing, and increases the efficiency with which light is incident on film 1, compared to when a portion of the light emitted from light source 50 is incident on film 1 from edge surface 13.

[0074] Examples and Comparative Examples Examples and comparative examples will be described below, but the present invention is not limited to these examples in any way.

[0075] <Evaluation Method> (Common Specifications of the Light Guiding Films Evaluated) Specifications of the light guiding films common to the examples and comparative examples evaluated will be described with reference to the above-mentioned Figures 1 and 2 . The length Fy of film 1 was 250.0 mm, the length Fx of film 1 was 100.0 mm, and the length Bx of light entrance member 2 was 100.0 mm. The thickness of the film was 1500.0 μm or less. Furthermore, 24 LEDs (product number FB-120-N-K) manufactured by FKK Corporation were used as light source 50 for illuminating light into the light guiding film, arranged in the X direction.

[0076] (Method for evaluating incidence efficiency) First, a method for evaluating the incidence efficiency of light into a light guiding film will be described with reference to Fig. 13 and Fig. 14 . Fig. 13 is a diagram showing an example of an apparatus E for evaluating the incidence efficiency of light into a light guiding film. Fig. 14 is a diagram showing an example of a housing Mp in the apparatus E for evaluating the incidence efficiency of light into a light guiding film. Note that Figs. 13 and 14 illustrate an example of evaluating a light guiding film 10, but the incidence efficiency evaluation apparatus E can also evaluate light guiding films according to examples and comparative examples.

[0077] As the incident efficiency evaluation device E, an LED total luminous flux measurement system (HM-9165 manufactured by Otsuka Electronics Co., Ltd.) was used.

[0078] 13 and 14 , the incident efficiency evaluation device E includes a housing Mp, a driver Dr, an integrating hemisphere Ih, and a light measuring device Sr. The housing Mp has a mounting base M1 and a storage section M2. The housing Mp mounts the driver Dr and the lighting device 100 including the light guiding film 10 on the mounting base M1, and stores the driver Dr, the light source 50, the wiring board 60, the light incident member 2, and a portion of the film 1 inside the storage section M2. The driver Dr moves the lighting device 100 in the Y direction to adjust the position of the lighting device 100 in the Y direction. The integrating hemisphere Ih collects light emitted from the lighting device 100 placed on the mounting base M1 and spatially integrates it to make it uniform. The light measuring device Sr measures the amount of light emitted from the lighting device 100, which has been spatially integrated and homogenized by the integrating hemisphere Ih, and outputs the measurement results to an external device such as a PC (Personal Computer).

[0079] In Fig. 13, length Ey represents the length of incident efficiency evaluation device E in the Y direction. In Fig. 14, length My1 represents the length of mounting table M1 in the Y direction. Length My2 represents the length of storage section M2 in the Y direction. Thickness Mh1 represents the length from the bottom surface of mounting table M1 to the top surface of storage section M2. Thickness Mh2 represents the length from the top surface of film 1 of light guiding film 10 mounted on mounting table M1 to the top surface of storage section M2.

[0080] In the evaluation of the incidence efficiency of light into the light guiding film using the incidence efficiency evaluation device E, the length Ey was 1650.0 mm, the length My1 was 350.0 mm, the length My2 was 70.0 mm, the thickness Mh1 was 35.0 mm, and the thickness Mh2 was 34.5 mm. The evaluation was performed with 200 mm of the length Fy of the film 1 exposed from the storage portion M2 of the housing Mp.

[0081] As a specific procedure for evaluating the incidence efficiency of light into a light-guiding film using the incidence efficiency evaluation device E, first, the light-guiding film was placed on the mounting table M1 so that the first main surface 11 of the film 1 faced the +Z direction, and the amount of light emitted from the first main surface 11 was measured. Next, the light-guiding film was turned upside down, i.e., placed on the mounting table M1 so that the second main surface 12 of the film 1 faced the +Z direction, and the amount of light emitted from the second main surface 12 was measured. Here, to avoid overlapping measurements of the amount of light emitted from the +Y side end face of the film 1, i.e., the end face opposite to end face 13, during the measurements of the first main surface 11 and the second main surface 12, the +Y side end face of the film 1 was covered with black tape when measuring the amount of light emitted from the second main surface 12. The incidence efficiency of light into a light-guiding film was calculated using the following formula. <Incident efficiency> = <Amount of light emitted from film 1> / <Amount of light emitted from light source 50> Note that <Amount of light emitted from film 1> is the sum of the amounts of light emitted from each of the first main surface 11 of film 1, the second main surface 12 of film 1, and the end face on the +Y side of film 1.

[0082] (Method for Evaluating Brightness Value) Fig. 15 is a diagram showing an example of a method for evaluating the brightness value of light extracted from a light guiding film. While Fig. 15 illustrates an example in which light guiding film 10 is evaluated, the brightness value evaluation method can also be used to evaluate light guiding films according to the examples and comparative examples.

[0083] 15 , the luminance value of light extracted from the light guiding film was evaluated by measuring the luminance value of light emitted from film 1 using a two-dimensional optical radiometer Lm placed approximately 500 mm above the top surface of film 1 in light guiding film 10. The two-dimensional optical radiometer Lm used was an SR-5000-HS manufactured by TOPCON Corporation.

[0084] <Specifications and Evaluation Results of Examples and Comparative Examples> Table 1 shows the specifications and evaluation results of Examples 1 to 11 and Comparative Examples 1 and 2. Table 2 also shows the evaluation indexes for determining the brightness values ​​in Table 1.

[0085]

[0086]

[0087] (Specifications of Examples 1 to 3 and Example 5) Examples 1 to 3 and Example 5 in Table 1 are light-guiding films 10 according to the first modified example shown in Figure 9, with the length H of the light incident surface 23, the length W of the light-emitting surface 51 of the light source 50, and the length L of the light incident member 2 being different.

[0088] Specifications of Example 4 Example 4 in Table 1 corresponds to light guiding film 10 shown in FIG. 16. FIG. 16 is a schematic cross-sectional view showing an example of an illumination device including light guiding film 10 according to Example 4. In Example 4 shown in FIG. 16, length W of light emitting surface 51 is 2.0 mm, while length H of film 1 is 0.5 mm, meaning length H is shorter than length W. In Example 4, light L6 emitted from a region of light emitting surface 51 that does not face light incident surface 23 is not incident on light incident member 2 and is not incident on film 1.

[0089] Specifications of Example 6 Example 6 in Table 1 corresponds to light guiding film 10 shown in FIG. 17 . FIG. 17 is a schematic cross-sectional view showing an example of an illumination device including light guiding film 10 according to Example 6. In Example 6 shown in FIG. 17 , length W of light-emitting surface 51 is 2.0 mm, while length H of film 1 is 5.0 mm, meaning length H is longer than length W. In Example 6, some of the light that is emitted from light-emitting surface 51, passes through light incident surface 23, enters light incident member 2, and is then totally reflected by upper surface 21 leaks out of light incident member 2 from opposing surface 24, resulting in light not being incident on film 1. Light L7 shown in FIG. 17 represents such light that is emitted from opposing surface 24 and not incident on film 1.

[0090] (Specifications of Example 7) Example 7 in Table 1 corresponds to the light guiding film 10 according to the embodiment shown in FIGS.

[0091] (Specifications of Examples 8 to 10) Examples 8 to 10 in Table 1 are combinations of the light-guiding film 10 according to the first modified example and the light-guiding film 10 according to the third modified example, with the length H of the light incident surface 23, the length W of the light-emitting surface 51 of the light source 50, and the length L of the light incident member 2 being different.

[0092] (Specifications of Example 11) Example 11 in Table 1 corresponds to light guiding film 10 according to the third modified example shown in FIGS.

[0093] (Specifications of Comparative Example 1) Comparative Example 1 in Table 1 corresponds to light guiding film 10X according to Comparative Example 1 shown in FIG.

[0094] (Specifications of Comparative Example 2) Comparative Example 2 in Table 1 corresponds to light guiding film 10Y according to Comparative Example 2 shown in FIG.

[0095] (Evaluation Results of Each Example and Comparative Example) As shown in Table 1, in Examples 1 to 10, the incidence efficiency was 15% or more and the luminance value was judged to be C or more. In Comparative Examples 1 and 2, the incidence efficiency was 10% and the luminance value was judged to be D. From these results, it was found that when the thickness of film 1 is 1500.0 μm or less and the angle α satisfies 60 degrees≦α≦120 degrees, the incidence efficiency of light from the light source into light guiding film 10 is increased. It was also found that the luminance value of the light emitted from light guiding film 10 is increased, and from another perspective, the light emitted from light guiding film 10 is brighter. Furthermore, it was found that in Examples 8 and 9, the incidence efficiency was 30% or more and the luminance value was judged to be A, which is the most favorable result.

[0096] Furthermore, in light guiding film 10, it is preferable that 0.1 mm≦H / W≦3.0 mm be satisfied, where H is the length of light incident surface 23 in the direction along normal line N1 to second major surface 12 and W is the length of light emitting surface 51 of light source 50 in the direction along normal line N1 to second major surface 12. By satisfying this condition, light guiding film 10 can improve the efficiency of light incidence into film 1.

[0097] Furthermore, in light guiding film 10, it is preferable that 8.0 mm≦L≦100.0 mm be satisfied, where L is the length of light incident member 2 in the direction along normal N2 to light emitting surface 51. By satisfying this condition, light guiding film 10 can improve the efficiency of light incidence into film 1.

[0098] [Other Suitable Modifications] The light guiding film 10 according to the embodiment may have a low refractive index layer disposed on one side of the light guiding film 10, the low refractive index layer having a refractive index lower than that of the first transmission layer 110 and the second transmission layer 130. The low refractive index layer preferably has a refractive index of 1.30 or less. From the viewpoint of reducing the presence of the light guiding film 10 when it is placed on an adherend, the total thickness from the surface of the light guiding film 10 on the side opposite to the side on which the low refractive index layer is disposed to the surface of the light guiding film 10 on the side on which the low refractive index layer is disposed is preferably 1500.0 μm or less.

[0099] The substrate on which light guiding film 10 is disposed is not limited to glass, but may also be an electronic substrate such as a liquid crystal cell, or a non-light-transmitting member such as a ceiling, wall, or floor. Light extraction layer 150 is not limited to extracting light to the side opposite the adherend, but may also extract light to the side on which the adherend is located. In this case, if the adherend has high light transmittance, the extracted light may pass through the adherend, or if the adherend has low light transmittance, the adherend may reflect the light.

[0100] A substrate film may be further disposed on the first major surface 11. This substrate film may be a hard coat layer or an anti-reflection layer. Furthermore, a low refractive index layer may be disposed between the light extraction layer 150 and the substrate film.

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

[0102] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the illustrated figures. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0103] The light guiding film according to the embodiment can increase the incidence efficiency of light from a light source. Therefore, by combining it with a light source and placing it on architectural components such as glass, windows, walls, floors, and ceilings, it can brightly illuminate the interior or exterior space of a building. Furthermore, by placing it on a partition, it can suitably divide an interior space or conceal a desired space. Furthermore, by placing it on the glass substrate of a display device such as a liquid crystal panel or an organic electroluminescence (EL) display panel, it can brighten the backlight illumination of the display device. Furthermore, the light guiding film 10 can also be used as a flexible lighting film without being placed on an adherend. Furthermore, the light guiding film according to the embodiment can provide new uses other than those described above.

[0104] A surface lighting device can also be configured by a light-guiding film according to the embodiment and a light source arranged so that light is incident on the light incident surface of the light-guiding film directly or via a light incident member.

[0105] The present invention can be embodied, for example, as follows: <1> A light guiding film comprising: a film including a first main surface, a second main surface disposed opposite the first main surface, and end surfaces intersecting the first main surface and the second main surface, the film guiding light entering the film; and a light entrance member including an upper surface, a lower surface disposed opposite the upper surface, and a light entrance surface intersecting the upper surface, the light entrance member being disposed on the first main surface so that the lower surface faces the first main surface, the light entrance member allowing light emitted from a light source including a light emitting surface to enter the film, wherein the thickness of the film is 1500 μm or less, and an angle α between the upper surface of the light entrance member disposed on the first main surface of the film and a normal to the second main surface satisfies 60 degrees≦α≦120 degrees. <2> The light guiding film according to <1>, wherein the upper surface of the light entrance member is flat. <3> The light guiding film according to <1> or <2>, wherein a reflective member is arranged on an opposing surface of the light incident member that is located opposite to the light incident surface. <4> The light guiding film according to any one of <1> to <3>, wherein the light incident surface is inclined so as to move away from the light source with increasing distance from the first main surface. <5> The light guiding film according to any one of <1> to <4>, wherein the light incident member includes a convex portion that protrudes downward from the lower surface and is arranged between the light source and the end surface of the film, and a portion of light from the light source is incident into the film through the convex portion. <6> The light guiding film according to any one of <1> to <5>, wherein, where H is the length of the light incident surface in a direction along a normal to the second main surface and W is the length of the light emitting surface in a direction along the normal to the second main surface, 0.1 mm≦H / W≦3.0 mm is satisfied. <7> The light guiding film according to any one of <1> to <6>, wherein 8.0 mm≦L≦100.0 mm is satisfied, where L is the length of the light incident member in a direction along a normal to the light emitting surface. <8> An illumination device comprising: a light source including a light emitting surface; and the light guiding film according to any one of <1> to <7>.

[0106] This application claims priority based on Japanese Patent Application No. 2023-183754 filed with the Japan Patent Office on October 26, 2023, and includes the entire contents of this Japanese patent application.

[0107] REFERENCE SIGNS LIST 1 Film 11 First main surface 12 Second main surface 13 End surface 2 Light incident member 21 Upper surface 22 Lower surface 23 Light incident surface 24 Opposing surface 25 Convex portion 251 Convex portion lower surface 252 Convex portion emission surface 3 Reflecting member 10 Light guide film 50 Light source 51 Light emitting surface 60 Wiring board 100 Lighting device 110 First transmission layer 120 First adhesive layer 130 Second transmission layer 140 Second adhesive layer 150 Light extraction layer 151 Light extraction portion Bx, Fx, Fy, L, H, M, T, W Length N1 Normal to second main surface N2 Normal to light emitting surface Px, Py Pitch D, E Spacing q Height r Width Mp Housing M1 Mounting base M2 Storage section Mh1, Mh2 Thickness My1, My2 Length α Angle θa, θb Angle

Claims

1. A light guiding film comprising: a film including a first main surface, a second main surface arranged on the opposite side of the first main surface, and end surfaces intersecting each of the first main surface and the second main surface, and guiding light entering the film; and a light entrance member including an upper surface, a lower surface arranged on the opposite side of the upper surface, and a light entrance surface intersecting the upper surface, the lower surface being arranged on the first main surface so as to face the first main surface, and allowing light emitted from a light source including a light emitting surface to enter the film, wherein the thickness of the film is 1500 μm or less, and an angle α between the upper surface of the light entrance member arranged on the first main surface of the film and a normal to the second main surface satisfies 60 degrees≦α≦120 degrees.

2. The light guiding film of claim 1, wherein the upper surface of the light input member is flat.

3. The light guiding film according to claim 1, further comprising a reflecting member disposed on an opposing surface of the light incident member opposite the light incident surface.

4. The light guiding film of claim 1, wherein the light incident surface is inclined so as to move away from the light source with increasing distance from the first main surface.

5. The light-guiding film according to claim 1, wherein the light incident member includes a convex portion that protrudes downward from the lower surface and is disposed between the light source and the end surface of the film, and a portion of the light from the light source is incident on the inside of the film through the convex portion.

6. The light-guiding film of claim 1, wherein 0.1 mm≦H / W≦3.0 mm is satisfied, where H is the length of the light incident surface in the direction along the normal to the second principal surface, and W is the length of the light emitting surface in the direction along the normal to the second principal surface.

7. The light guiding film according to claim 1, wherein the length of the light incident member in the direction along the normal to the light emitting surface is L, and the length satisfies 8.0 mm≦L≦100.0 mm.

8. A lighting device comprising: a light source including a light emitting surface; and a light guiding film according to any one of claims 1 to 7.

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