Light-emitting device

Abstract

This light-emitting device comprises: a plurality of light sources arranged along a first direction; a light guide layer having a light-receiving part that receives light emitted from the light sources; and a lens member disposed between the light sources and the light guide layer. The shape of the lens member in a cross section orthogonal to the first direction is substantially uniform over the entirety thereof in the first direction. The lens member has a first light entry surface that introduces light from the light sources into the lens member and that has a shape that protrudes toward the light sources. The first light entry surface includes a first inclined surface and a second inclined surface that are inclined at an angle of 55-70° with respect to the optical axis of the light sources. A ratio L2 / L1 of the length L2 of the lens member along a second direction, which is orthogonal to both the optical axis of the light sources and the first direction, to the length L1 of each of the light sources along the second direction is 2 or less.

Description

Light-emitting device

[0001] The present invention relates to a light-emitting device.

[0002] In recent years, the use of next-generation semiconductor lighting (Solid State Lighting: SSL) represented by LED lighting has progressed. A configuration including a light source such as an LED and a light guide plate is widely used in lighting devices (which can also be referred to as "light-emitting devices"). The applicant of the present application proposes, in Patent Documents 1 and 2, a sheet-shaped lighting device having a light distribution structure utilizing total reflection by an interface of an air cavity (internal space).

[0003] International Publication No. 2019 / 182091, International Publication No. 2019 / 146628

[0004] A lighting device that illuminates reflective liquid crystal display devices, electronic paper displays (EPD), printed matters and the like from the front is called a front light.

[0005] When an object to be illuminated such as the above-described reflective liquid crystal display device is illuminated by a front light, depending on the design of the light extraction structure of the front light, there may be a relatively large amount of components in a direction greatly inclined with respect to the front direction (that is, components having a large polar angle) in the reflected light from the object to be illuminated. Such components are unnecessary when observing from the front direction, and also become stray light when observing from an oblique direction, causing a decrease in contrast ratio.

[0006] Therefore, when using a front light, it is preferable to reduce stray light. However, since front lights are required to be compact, the structure for reducing stray light is also required not to impair the compactness of the front light itself.

[0007] An object of an embodiment of the present invention is to provide a light-emitting device that can reduce stray light while maintaining the compactness of the device, and is suitably used as a front light.

[0008] The present specification discloses the light-emitting device described in the following items.

[0009] [Item 1] A light-emitting device comprising: a plurality of light sources arranged along a first direction; a light guide layer having a light-receiving portion for receiving light emitted from the plurality of light sources; and a lens member disposed between the plurality of light sources and the light guide layer, wherein the shape of the cross section of the lens member perpendicular to the first direction is substantially the same throughout the entire first direction; the lens member has a first light-receiving surface that introduces light from the plurality of light sources into the lens member and has a shape that is convex toward the plurality of light sources; the first light-receiving surface includes a first inclined surface and a second inclined surface that are inclined at an angle of 55° or more and 70° or less with respect to the optical axis of the plurality of light sources; and the ratio L2 / L1 of the length of the lens member along the second direction to the length L1 of each light source along the second direction perpendicular to both the optical axis of the plurality of light sources and the first direction is 2 or less.

[0010] [Item 2] The light-emitting device according to Item 1, wherein the first inclined surface and the second inclined surface are inclined at an angle of 60° or more and 65° or less with respect to the optical axis of the plurality of light sources.

[0011] [Item 3] The light-emitting device according to item 1 or 2, wherein the lens member further comprises a second light-emitting surface and a third light-emitting surface arranged to sandwich the first light-emitting surface, each of which is substantially parallel to the optical axis of the plurality of light sources.

[0012] [Item 4] The light-emitting device according to Item 3, wherein the lens member comprises a lens body portion having the first light-receiving surface, and a first flange portion and a second flange portion extending from both ends of the lens body portion in the second direction toward the plurality of light sources, the first flange portion having the second light-receiving surface and the second flange portion having the third light-receiving surface.

[0013] [Item 5] The light-emitting device according to any one of items 1 to 4, wherein the first light-receiving surface is located between the first inclined surface and the second inclined surface and further includes an orthogonal surface substantially perpendicular to the optical axes of the plurality of light sources.

[0014] [Item 6] The light-emitting device according to any one of items 1 to 5, wherein the light-emitting device has an emitting surface from which light is emitted, the light guide layer has a first main surface on the side of the emitting surface and a second main surface on the opposite side of the emitting surface, and the light-emitting device further comprises a direction-changing layer disposed on the side of the first main surface or the second main surface of the light guide layer, which directs a portion of the light propagating through the light guide layer toward the emitting surface.

[0015] [Item 7] The light-emitting device according to Item 6, wherein the direction conversion layer has a plurality of internal spaces that form an interface that totally reflects a portion of the light propagating through the light guide layer and directs it toward the emission surface.

[0016] [Item 8] The light-emitting device according to any one of items 1 to 7, wherein the thickness of the light guide layer is 5 mm or less.

[0017] According to embodiments of the present invention, it is possible to provide a light-emitting device that can reduce stray light while maintaining the compactness of the device, and which is suitable for use as a front light.

[0018] This is a schematic cross-sectional view of a light-emitting device 100A_L according to an embodiment of the present invention. This is a schematic plan view of the light-emitting device 100A_L. This is a schematic plan view of the light-emitting device 100A_L. This is a schematic cross-sectional view of the internal space IS of the direction conversion layer 30 of the light-emitting device 100A_L. This is a schematic plan view of the internal space IS. This is a schematic cross-sectional view of the lens member 20 and light source LS of the light-emitting device 100A_L. This is a schematic cross-sectional view of the lens member 20 and light source LS. This is a schematic cross-sectional view of the light-emitting device 100A_L. This is a schematic plan view of the light-emitting device 100A_L. This is a schematic cross-sectional view of the internal space IS of the direction conversion layer 30 of the light-emitting device 100A_L. This is a schematic plan view of the internal space IS. This figure shows how the object to be illuminated 1 is illuminated by a front light 900A_L equipped with a light source 900LS and a light guide plate 900A. This is a graph showing the angular distribution of the component contributing to stray light from the light incident from the light source 900LS to the light guide plate 900A. This figure is for explaining angle α. This figure shows the light distribution of Comparative Example 1. This figure shows the light distribution of Example 1. This figure shows the light distribution of Example 2. This figure shows the light distribution of Example 3. This figure shows the light distribution of Example 4. This figure shows the light distribution of Comparative Example 2. This is a graph showing the light distribution of Example 3 and the reference example. This figure is for explaining the conditions of the optical simulation. This is a graph showing the luminance distribution of reflected light LRb along the Y direction (light guidance direction in the light guide member 100A), calculated by optical simulation for Examples 1 to 4 and Comparative Examples 1 to 3. This figure is for explaining the configuration of Comparative Example 3. This is a graph showing the light distribution of reflected light LRb, calculated by optical simulation for Examples 1 to 4 and Comparative Example 3. Angle θ Ｐ This diagram is intended to explain the following. It is a graph showing the luminance at the center (at a distance of 800 mm) of the luminance distribution shown in Figure 15, and the peak luminance (stray light peak) in the ranges of 40° to 60° and -40° to -60° of the light distribution shown in Figure 17.

[0019] The light-emitting device according to an embodiment of the present invention will be described below with reference to the drawings. However, the light-emitting device according to an embodiment of the present invention is not limited to those exemplified in the following description.

[0020] The light-emitting device (illumination device) 100A_L in this embodiment will be described with reference to Figures 1 and 2. The light-emitting device (illumination device) 100A_L is a front light that illuminates an object to be illuminated (not shown), such as a reflective liquid crystal display device, EPD, or printed material, from the front. Figure 1 is a schematic cross-sectional view of the light-emitting device 100A_L, and Figure 2 is a schematic plan view of the light-emitting device 100A_L.

[0021] As shown in Figures 1 and 2, the light-emitting device 100A_L comprises a plurality of light sources LS, a light-guiding member (optical laminate) 100A including a light-guiding layer 10, and a lens member 20.

[0022] Multiple light sources LS are arranged along a predetermined direction D1 (in the illustrated example, this is a direction parallel to the X direction, and will hereafter be referred to as the "first direction"). Each light source LS is, for example, an LED device.

[0023] The light guide member 100A is in the form of a sheet. Here, "sheet-like" includes plate-like and film-like forms, and does not specify the rigidity (flexibility) or thickness of the sheet. The sheet-like light guide member can be used in various forms, such as roll-like.

[0024] The light guide member 100A receives light emitted from multiple light sources LS, propagates the light in the Y direction, and emits light in the -Z direction. Of course, the direction of light propagation has variation (distribution) from the Y direction, and the direction of light emission also has variation (distribution) from the -Z direction. The light emitted in the -Z direction becomes illumination light LRa for illuminating objects to be illuminated (not shown), such as reflective liquid crystal display devices, EPDs, and printed materials. One of the two main surfaces 100a and 100b of the light guide member 100A, 100a, is the "first emission surface" that emits illumination light LRa. The other of the two main surfaces 100a and 100b, 100b, is the "second emission surface" from which reflected light LRb from the object to be illuminated is emitted in the Z direction. In this specification, the first emission surface 100a is also simply referred to as the "emission surface".

[0025] The light guide member 100A comprises a light guide layer 10 and a direction changing layer 30.

[0026] The light guide layer 10 has a light-receiving portion that receives light emitted from multiple light sources LS, a first main surface 10a located on the side of the light-emitting surface 100a of the light guide member 100A, and a second main surface 10b located on the opposite side of the light-emitting surface 100a of the light guide member 100A. In the illustrated example, the light-receiving portion of the light guide layer 10 is the side surface (light-receiving side surface) 10c of the light guide layer 10 on the light source LS side. Also, in the illustrated example, the light guide layer 10 is located on the outermost surface on the second light-emitting surface 100b side of the light guide member 100A, so the second main surface 10b of the light guide layer 10 is the second light-emitting surface 100b of the light guide member 100A.

[0027] The direction conversion layer 30 is located on the first main surface 10a side of the light guide layer 10. The direction conversion layer 30 has the function of directing a portion of the light propagating through the light guide layer 10 toward the emission surface 100a side.

[0028] The direction conversion layer 30 has a plurality of internal spaces (optical cavities) IS. The plurality of internal spaces IS form an interface that totally reflects a portion of the light propagating through the light guide layer 10 and directs it toward the exit surface 100a. Each internal space IS has a first inclined surface ISa that directs a portion of the light propagating within the light guide layer 10 toward the exit surface 100a by total internal reflection (TIR), and a second inclined surface ISb on the opposite side of the first inclined surface ISa.

[0029] The direction changing layer 30 is composed of a shaping film 40 and an adhesive layer 50A. The main surface 40a of the shaping film 40 on the light guide layer 10 side has a plurality of recesses 41. The adhesive layer 50A is located between the shaping film 40 and the light guide layer 10. The light guide layer 10 and the shaping film 40 are bonded together by the adhesive layer 50A.

[0030] In the illustrated example, the adhesive layer 50B and the substrate layer 60 are arranged in this order on the exit surface 100a side of the direction conversion layer 30, and the shaping film 40 and the substrate layer 60 are bonded together by the adhesive layer 50B. The light guide layer 10 and the substrate layer 60 may be transparent substrates or films.

[0031] The visible light transmittance and haze value of the light guide member 100A can be controlled by adjusting the cross-sectional shape, size, arrangement density, and distribution of the internal space IS. The visible light transmittance of the light guide member 100A is, for example, 60% or more, preferably 80% or more. The haze value of the light guide member 100A is, for example, less than 30%, preferably less than 10%. Here, visible light is defined as light with a wavelength of 380 nm to 780 nm. The visible light transmittance and haze value can be measured, for example, using a haze meter (manufactured by Murakami Color Technology Laboratory: product name HM-150). From the viewpoint of viewing an object (display) through the light-emitting device 100A_L (light guide member 100A), it is preferable that the visible light transmittance of the light guide member 100A is 60% or more, and that the haze value of the light guide member 100A is less than 30%.

[0032] When the light guide member 100A is viewed from the normal direction of the emission surface 100a, the ratio of the area of ​​the multiple internal spaces IS (occupancy rate) is preferably 1% to 80%, and more preferably 1% to 50%. From the viewpoint of obtaining a low haze value, the occupancy rate of the internal spaces IS is preferably 30% or less, and more preferably 10% or less.

[0033] The shape and arrangement of the internal space IS will be explained with reference to Figures 3, 4, and 5. Figure 3 is a schematic plan view of the light-emitting device 100A_L. Figure 4 is a schematic cross-sectional view of the internal space IS, and Figure 5 is a schematic plan view of the internal space IS.

[0034] As shown in Figure 3, the multiple internal spaces IS can be discretely arranged, for example, in the light-guiding direction (Y direction) of the light-guiding layer 10 and in directions intersecting the light-guiding direction. The discrete arrangement may or may not have periodicity (regularity) in at least one direction. However, from the viewpoint of mass production, it is preferable that the multiple internal spaces IS are uniformly arranged. For example, in the example shown in Figure 3, multiple internal spaces IS having substantially the same shape and a curved surface convex in the same direction are discretely and periodically arranged in the light-guiding direction (Y direction) of the light-guiding plate 10 and in a direction perpendicular to the light-guiding direction (X direction). In this case, the pitch Px of the internal spaces IS in the X direction is preferably, for example, 10 μm or more and 500 μm or less, and the pitch Py of the internal spaces IS in the Y direction is preferably, for example, 10 μm or more and 500 μm or less. In the example shown in Figure 3, further internal spaces IS are provided that are offset by half a pitch in each of the Y and X directions.

[0035] As shown in Figure 3, when viewed from a plane from the direction normal to the emission surface 100a of the light guide member 100A, the first inclined surface ISa forms a curved surface that is convex toward the light source LS. When an LED device is used as the light source LS, the light emitted from each LED device spreads in the Y direction, so having a curved surface that is convex toward the light source LS allows the first inclined surface ISa to act uniformly on the light. The first inclined surface ISa may also be parallel to the X direction. Furthermore, instead of a discrete internal space IS, there may be an internal space such as a groove (e.g., a triangular prism) extending in the X direction.

[0036] As shown in Figure 4, the cross-sectional shape of the internal space IS (the shape of the cross section perpendicular to the X direction and parallel to the Y and Z directions in Figure 1) is, for example, a triangle with its apex angle on the first main surface side of the light guide member 100A (the -Z direction in Figure 1). The inclination angle θa of the first inclined surface ISa on the light source LS side is, for example, 10° to 70°. The inclination angle θb of the second inclined surface ISb is, for example, 50° to 100°. Note that the cross-sectional shape of the internal space IS is not limited to the triangle exemplified here, but may also be a trapezoid or the like.

[0037] As shown in Figure 5, the two-dimensional size of the internal space IS is defined by the length L and width W of the internal space IS. The length L of the internal space IS is preferably, for example, 10 μm or more and 500 μm or less. The width W of the internal space IS is preferably, for example, 1 μm or more and 100 μm or less. The length L of the internal space IS is, for example, twice or more the width W of the internal space IS. Furthermore, the height H of the internal space IS (see Figure 4) is preferably, for example, 1 μm or more and 100 μm or less from the viewpoint of light extraction efficiency.

[0038] As shown in Figures 1 and 2, the lens member 20 is positioned between the multiple light sources LS and the light guide layer 10. The cross-sectional shape of the lens member 20 perpendicular to the first direction D1 (the cross-sectional shape shown in Figure 1) is substantially the same throughout the entire first direction D1.

[0039] Now, with reference to Figure 6, the structure of the lens member 20 will be explained. Figure 6 is a schematic cross-sectional view showing the lens member 20 and the light source LS.

[0040] The lens member 20 has a lens body portion 21 and a first flange portion 22 and a second flange portion 23. The lens member 20 is formed from, for example, a resin material. Suitable resin materials include, for example, silicone, PMMA (polymethyl methacrylate), PC (polycarbonate), and PU (polyurethane). The refractive index of the lens member 20 is, for example, 1.40 or more and 1.62 or less.

[0041] The lens body 21 has a first light-receiving surface 20a that introduces light from multiple light sources LS into the lens member 20, and a light-emitting surface 20d through which the light introduced into the lens member 20 is emitted toward the light guide layer 10. The first light-receiving surface 20a has a shape that is convex toward the multiple light sources LS.

[0042] The first light incident surface 20a includes a first inclined surface s1, a second inclined surface s2, and an orthogonal surface s3. The first inclined surface s1 and the second inclined surface s2 are inclined at an angle θ of 55° or more and 70° or less with respect to the optical axis A1 of the plurality of light sources LS. Hereinafter, the angle θ is also referred to as "inclination angle". The orthogonal surface s3 is located between the first inclined surface s1 and the second inclined surface s2, and is substantially orthogonal to the optical axis A1 of the light source LS. Each of the first inclined surface s1, the second inclined surface s2 and the orthogonal surface s3 is substantially flat, but may include a curved surface (rounded portion) at an end thereof for manufacturing reasons.

[0043] Here, a direction D2 orthogonal to both the optical axis A1 of the light source LS and the first direction D1 (a direction parallel to the Z direction in the illustrated example) is referred to as a "second direction". The first flange portion 22 and the second flange portion 23 extend from both end portions of the lens body portion 21 in the second direction D2 toward the light source LS side. The first flange portion 22 has a second light incident surface 20b, and the second flange portion 23 has a third light incident surface 20c.

[0044] The second light incident surface 20b and the third light incident surface 20c are arranged so as to sandwich the first light incident surface 20a. Each of the second light incident surface 20b and the third light incident surface 20c is substantially parallel to the optical axis A1 of the light source LS.

[0045] In the light emitting device 100A_L, a ratio L2 / L1 of a length L2 of the lens member 20 along the second direction D2 to a length L1 of each light source LS along the second direction D2 is set within a predetermined range. Specifically, this ratio L2 / L1 is 2 or less.

[0046] Although FIG. 6 shows a configuration in which the first light incident surface 20a includes the orthogonal surface s3, as shown in FIG. 7, the first light incident surface 20a may not include the orthogonal surface s3. As shown in FIG. 6 and FIG. 7, it can be said that the first light incident surface 20a, the second light incident surface 20b, and the third light incident surface 20c are substantially M-shaped as a whole in a cross section orthogonal to the first direction D1 of the lens member 20 (that is, parallel to the second direction D2).

[0047] As described above, in the light-emitting device 100A_L according to the embodiment of the present invention, the shape of the cross-section of the lens member 20 perpendicular to the first direction D1 is substantially the same throughout the entire first direction D1. Therefore, the lens member 20 of the light-emitting device 100A_L can be easily manufactured, for example, by extrusion molding, and is highly mass-producible. Furthermore, since the first light-receiving surface 20a of the lens member 20 includes a first inclined surface s1 and a second inclined surface s2 that are inclined at an angle θ of 55° to 70° with respect to the optical axis A1 of the light source LS, stray light can be reduced while sufficiently maintaining light utilization efficiency, as will be described later in the verification results, thereby improving the contrast ratio. Moreover, since the ratio L2 / L1 of the length of the lens member 20 along the second direction D2 to the length L1 of each light source LS along the second direction D2 is 2 or less (i.e., the size of the lens member 20 along the second direction D2 does not exceed twice the size of the light source LS), it is easy to maintain the compactness of the light-emitting device 100A_L as a front light.

[0048] From the standpoint of compactness, the ratio L2 / L1 of the length of the lens member 20 to the length L1 of each light source LS is preferably 2 or less, and more preferably 1.7 or less, 1.5 or less, or 1.2 or less.

[0049] The inclination angle θ of the first inclined surface s1 and the second inclined surface s2 is preferably 60° or more from the viewpoint of maintaining sufficient light utilization efficiency, and preferably 65° or less from the viewpoint of reducing stray light.

[0050] Furthermore, the lens member 20 does not necessarily have to have a first flange portion 22 and a second flange portion 23 (i.e., it does not necessarily have to have a second light-receiving surface 20b and a third light-receiving surface 20c). As illustrated in Figure 6, if the lens member 20 has a first flange portion 22 and a second flange portion 23 (i.e., a second light-receiving surface 20b and a third light-receiving surface 20c), it is possible to suppress the direct contact of light emitted from the light source LS at a relatively large angle with respect to the optical axis A1 by interfacial Fresnel reflection with respect to a component outside the lens member 20 (e.g., a frame), thereby further improving the light utilization efficiency. Moreover, this is also advantageous in terms of positioning and fixing the lens member 20.

[0051] Furthermore, as already explained, the first light-receiving surface 20a of the lens member 20 may or may not include the orthogonal surface s3, but if the first light-receiving surface 20a includes the orthogonal surface s3, the manufacturing of the lens member 20 by extrusion molding becomes even easier.

[0052] Furthermore, as already explained, the embodiments of the present invention make it easy to maintain the compactness of the light-emitting device 100A_L as a front light. For this reason, the embodiments of the present invention are particularly useful in configurations where the light guide layer 10 is relatively thin (for example, the thickness of the light guide layer 10 is 5 mm or less). From the viewpoint of compactness, the thickness of the light guide layer 10 is preferably, for example, 5 mm or less, and more preferably 3 mm or less, 2 mm or less, 1 mm or less, or 0.5 mm or less.

[0053] Although Figure 1 shows an example where the direction changing layer 30 is located on the first main surface 10a side of the light guide layer 10, the direction changing layer 30 may also be located on the second main surface 10b side of the light guide layer 10, as shown in Figure 8. The direction changing layer 30 consists of a shaping film 40 having a main surface 40a with a plurality of recesses 41, and an adhesive layer 50A located on the main surface 40a side of the shaping film 40. A base layer 60 is located on the side of the adhesive layer 50A opposite to the shaping film 40, and the shaping film 40 and the base layer 60 are bonded together by the adhesive layer 50A. In addition, the light guide layer 10 and the shaping film 40 are bonded together by an adhesive layer 50B located on the second main surface 10b side of the light guide layer 10. In the example shown in Figure 8, the light guide layer 10 is located on the outermost surface of the light guide member 100A on the side of the emission surface 100a, so the first main surface 10a of the light guide layer 10 is the emission surface 100a of the light guide member 100A.

[0054] The light extraction structure of the light guide member 100A is not limited to the example provided herein and may be of various types. While Figure 1 and others illustrate a configuration in which light enters the light guide member 100A from one side (referred to as the "one-sided light entry configuration" in this specification), a configuration in which light enters the light guide member 100A from both sides (referred to as the "both-sided light entry configuration" in this specification) may also be adopted, as shown in Figure 9A. In the example shown in Figure 9A, in addition to a plurality of light sources LS (first light sources LS1) that emit light toward one end face 10c of the light guide layer 10, a plurality of light sources LS (second light sources LS2) that emit light toward the other end face 10d of the light guide layer 10 are provided, and a lens member 20 is also arranged between the latter light sources LS (second light sources LS2) and the light guide layer 10.

[0055] Figures 9B, 9C, and 9D show examples of the shape of the internal space IS when a configuration with light entering from both sides is adopted. In the example shown in Figure 9B, etc., when viewed from the normal direction to the emission surface 100a of the light guide member 100A, the first inclined surface ISa forms a curved surface that is convex toward the first light source LS1 side, and the second inclined surface ISb forms a curved surface that is convex toward the second light source LS2 side. The inclination angle θa of the first inclined surface ISa and the inclination angle θb of the second inclined surface ISb may be the same, for example.

[0056] Furthermore, the lens member 20 may be separate from the light guide layer 10, or it may be formed integrally with the light guide layer 10.

[0057] [Verification Results of Stray Light Reduction Effect] The lens member 20 of the light-emitting device 100A_L can control the light distribution of light emitted from the lens member 20 by adjusting the inclination angle θ of the first inclined surface s1 and the second inclined surface s2. The following describes the results of verification that stray light can be reduced by setting the inclination angle θ of the first inclined surface s1 and the second inclined surface s2 within a predetermined range.

[0058] Figure 10 shows how the object to be illuminated 1 is illuminated by a front light 900A_L, which is equipped with a light source 900LS and a light guide plate 900A. Of the reflected light from the object to be illuminated 1, the components in directions where the polar angle with respect to the front direction (0° direction) is 40° or more (range R1 in Figure 10) and in directions where it is -40° or more (range R2 in the figure) become stray light.

[0059] The inventors of this application first calculated the angular distribution of the component contributing to stray light from the light source 900LS incident on the light guide plate 900A using an optical model calculation. The calculation results are shown in Figure 11. The angle α shown in Figure 11 is the inclination angle with respect to the Y direction, as shown in Figure 12.

[0060] Figure 11 shows that the components incident on the light guide plate 900A at angles α between 20° and 42° and -20° and -42° mainly contribute to stray light. Therefore, it is thought that stray light can be reduced by reducing these components.

[0061] The light distribution of light emitted from the lens member 20 was verified by varying the inclination angle θ of the first inclined surface s1 and the second inclined surface s2 of the lens member 20. The refractive index of the lens member 20 was set to 1.58, and the light distributions of Examples 1, 2, 3, and 4 and Comparative Examples 1 and 2 were obtained by optical simulation. Lighttools from Synopsys was used as the simulation software. As shown in Table 1, the inclination angles θ for Examples 1, 2, 3, and 4 were 70°, 65°, 60°, and 55°, respectively, and the inclination angles θ for Comparative Examples 1 and 2 were 75° and 50°, respectively. The first light-receiving surface 20a was configured not to have an orthogonal surface s3 (as shown in Figure 7).

[0062]

[0063] Figures 13A, 13B, 13C, 13D, 13E, and 13F show the light distribution for Comparative Example 1, Example 1, Example 2, Example 3, Example 4, and Comparative Example 2, respectively (the luminous intensity in the figures is a relative value with 1 as the maximum).

[0064] Figures 13A to 13F show that the light distribution of the light emitted from the lens member 20 can be controlled by changing the tilt angle θ. Furthermore, a comparison of Figure 13A with Figures 13B to 13E shows that in Examples 1 to 4, there are fewer components of angles greater than 20° and greater than -20° compared to Comparative Example 1.

[0065] Figure 13G is a graph showing the light distribution of Example 3. Figure 13G also shows the light distribution of a reference example in which the lens member 20 is not placed. From Figure 13G, it can be seen that the placement of the lens member 20 significantly reduces the components that contribute to stray light (components with angles α between 20° and 42° and between -20° and -42°).

[0066] For Examples 1 to 4, the luminance distribution of reflected light LRb emitted from the second emission surface 100b of the light guide member 100A along the Y direction (light guide direction in the light guide member 100A) was calculated by optical simulation. Lighttools from Synopsys was used as the simulation software. For the simulation, it was assumed that the light-emitting device 100A_L, which has a configuration of light entering from both sides as shown in Figure 14, was illuminating the poster 1A, which was the object to be illuminated. Frames 70 with a U-shaped cross-section are arranged at both ends of the light guide member 100A, and the light source LS and lens member 20 are surrounded by the frames 70. The reflectance of the frames 70 was set to 40%. The length L3 along the longitudinal direction (light guide direction) of the light guide member 100A was set to 1600 mm. The length L, width W, and height H of the internal space IS were set to 103 μm, 17 μm, and 10 μm, respectively. The inclination angle θa of the first inclined surface ISa and the inclination angle θb of the second inclined surface ISb of the internal space IS were both set to 49°. The internal space IS was assumed to be filled with air (i.e., with a refractive index of approximately 1), and the refractive index of the light guide member 100A other than the internal space IS was set to 1.5.

[0067] The obtained luminance distribution is shown in Figure 15. Figure 15 is a graph in which the distance from one end in the longitudinal direction (light guidance direction) of the light guide member 100A is plotted on the horizontal axis and luminance is plotted on the vertical axis, showing the luminance distribution in the A-A' cross section in Figure 14. Figure 15 also shows the luminance distributions of Comparative Examples 1 and 2, which were calculated in the same manner as in Examples 1 to 4. Figure 15 also shows the luminance distribution of Comparative Example 3. As shown in Figure 16, Comparative Example 3 has a configuration in which, instead of providing a lens member 20 to reduce stray light, a black tape 910 with a width of 10 mm is attached to the end of the light guide plate 900A in the longitudinal direction (light guidance direction).

[0068] Furthermore, for Examples 1 to 4, the light distribution of reflected light LRb emitted from the second emission surface 100b of the light guide member 100A was calculated. The obtained light distribution is shown in Figure 17. Figure 17 shows the angle θ. Ｐ This graph has angle θ on the horizontal axis and brightness on the vertical axis. ＰAs shown in Figure 18, this is the polar angle in the light guide direction (longitudinal direction of the light guide member 100A) with respect to the normal direction of the second emission surface 100b. Figure 17 also shows the light distribution for Comparative Example 3.

[0069] Table 2 and Figure 19 are tables and graphs showing the luminance at the center (at a distance of 800 mm) of the luminance distribution shown in Figure 15, and the peak luminance (hereinafter also referred to as "stray light peak") in the ranges of 40° to 60° and -40° to -60° of the light distribution shown in Figure 17.

[0070]

[0071] Figures 15, 17, 19, and Table 2 show that in the range of tilt angle θ from 55° to 70° (Examples 1 to 4), as the tilt angle θ decreases, the stray light peak tends to decrease, and the central brightness tends to decrease as well. Furthermore, a comparison between Example 4 (tilt angle θ = 55°) and Comparative Example 2 (tilt angle θ = 50°) shows that when the tilt angle θ is less than 55°, the decrease in central brightness saturates, but the stray light peak begins to rise (i.e., stray light begins to increase). For this reason, it is preferable that the tilt angle θ is 55° or greater. Also, a comparison between Example 1 (tilt angle θ = 70°) and Comparative Example 1 (tilt angle θ = 75°) shows that when the tilt angle θ exceeds 70°, the central brightness begins to decrease. For this reason, it is preferable that the tilt angle θ is 70° or less.

[0072] Thus, it was confirmed that by having an inclination angle θ of the first inclined surface s1 and the second inclined surface s2 of the lens member 20 between 55° and 70°, stray light can be reduced while maintaining sufficient light utilization efficiency.

[0073] Furthermore, a comparison of the central brightness of Examples 1-3 with that of Example 4 shows that, from the viewpoint of maintaining sufficient light utilization efficiency, a tilt angle θ of 60° or more is more preferable. Additionally, a comparison of the stray light peak of Example 1 with that of Examples 2-4 shows that, from the viewpoint of reducing stray light, a tilt angle θ of 65° or less is more preferable.

[0074] [Examples of preferred configurations of the light guide layer, substrate layer, shaping film, and adhesive layer] The light guide layer 10 may be formed from a known material with high transmittance to visible light. The light guide layer 10 may be formed from, for example, an acrylic resin such as polymethyl methacrylate (PMMA), a polycarbonate (PC) resin, a cycloolefin resin, or glass (e.g., quartz glass, alkali-free glass, borosilicate glass). The refractive index nGP of the light guide layer 10 is, for example, 1.40 or more and 1.80 or less. Unless otherwise specified, the refractive index refers to the refractive index measured with an ellipsometer at a wavelength of 550 nm. The thickness of the light guide layer 10 may be set appropriately depending on the application. The thickness of the light guide layer 10 is, for example, 0.05 mm or more and 50 mm or less.

[0075] The thickness of the base layer 60 is, for example, 1 μm to 1000 μm, preferably 10 μm to 100 μm, and more preferably 20 μm to 80 μm. The refractive index of the base layer 60 is preferably 1.40 to 1.70, and more preferably 1.43 to 1.65.

[0076] The shaping film 40 for forming the internal space IS can be manufactured, for example, by the method described in Japanese Patent Publication No. 2013-524288. Specifically, for example, the shaping film 40 can be manufactured by coating the surface of a polymethyl methacrylate (PMMA) film with lacquer (for example, FineCure RM-64 manufactured by Sanyo Chemical Industries, Ltd.), embossing an optical pattern onto the film surface containing the lacquer, and then curing the lacquer.

[0077] The thickness of the adhesive layers 50A and 50B is, independently of each other, for example, 0.1 μm to 100 μm, preferably 0.3 μm to 100 μm, and more preferably 0.5 μm to 50 μm. The refractive index of the adhesive layers 50A and 50B is, independently of each other, preferably 1.42 to 1.60, and more preferably 1.47 to 1.58. Furthermore, the refractive index of the adhesive layers 50A and 50B is preferably close to the refractive index of the light guide layer 10, substrate layer 60, or shaping film 40 with which it is in contact, and the absolute value of the difference in refractive index is preferably 0.2 or less.

[0078] In this specification, the term "adhesive" is used to include pressure-sensitive adhesives (also called tacks). Specific examples of adhesives include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, epoxy-based adhesives, cellulose-based adhesives, and polyester-based adhesives. These adhesives may be used individually or in combination of two or more types.

[0079] Preferably, the adhesive layer 50A can be bonded without filling the recesses 41 of the shaping film 40. Suitable adhesives for forming the adhesive layer 50A include those described in the present applicant's International Publication No. 2021 / 167090, International Publication No. 2021 / 167091, or International Publication No. 2022 / 176658. All disclosures of these applications are incorporated herein by reference. In particular, the polyester-based adhesive described in International Publication No. 2022 / 176658 is preferred.

[0080] [Anti-reflective layer, anti-glare layer, and hard coat layer] The light-emitting device according to the embodiment of the present invention is not limited to the example described above and can be modified in various ways. For example, an anti-reflective layer, an anti-glare layer, and / or a hard coat layer (for example, with a pencil hardness of H or higher) may be provided instead of the base layer 60 of the light-emitting device 100A_L. Of course, the anti-reflective layer, anti-glare layer, and / or hard coat layer may also be provided on the base layer 60. Furthermore, the anti-reflective layer, anti-glare layer, and / or hard coat layer may be provided on the side of the light guide layer 10 opposite to the base layer 60. The anti-reflective layer, anti-glare layer, and hard coat layer can be formed using known materials and by known methods. Also, the base layer 60 and the adhesive layer 50B may simply be omitted.

[0081] According to embodiments of the present invention, it is possible to provide a light-emitting device that can reduce stray light while maintaining the compactness of the device, and which is suitable for use as a front light. The light-emitting device according to embodiments of the present invention is suitable for use in illuminating various objects to be illuminated from the front, such as reflective liquid crystal displays, EPDs, and printed materials.

[0082] 10: Light guide layer, 20: Lens member, 20a: First light-receiving surface, 20b: Second light-receiving surface, 20c: Third light-receiving surface, 20d: Light-emitting surface, 21: Lens body, 22: First flange, 23: Second flange, 30: Directional conversion layer, 40: Shaping film, 41: Recess, 50A, 50B: Adhesive layer, 60: Substrate layer, 100A: Light guide member, 100a: Light-emitting surface (first light-emitting surface), 100b: Second light-emitting surface, 100A_L: Light-emitting device, IS: Internal space, ISa: First inclined surface of the internal space, ISb: Second inclined surface of the internal space, LS: Light source, A1: Optical axis of the light source, LRa: Illumination light, LRB: Reflected light, s1: First inclined surface of the first light-receiving surface, s2: Second inclined surface of the first light-receiving surface, s3: Orthogonal surface of the first light-receiving surface

Claims

1. A light-emitting device comprising: a plurality of light sources arranged along a first direction; a light guide layer having a light-receiving portion for receiving light emitted from the plurality of light sources; and a lens member disposed between the plurality of light sources and the light guide layer, wherein the shape of the cross section of the lens member perpendicular to the first direction is substantially the same throughout the entire first direction; the lens member has a first light-receiving surface that introduces light from the plurality of light sources into the lens member and has a shape that is convex toward the plurality of light sources; the first light-receiving surface includes a first inclined surface and a second inclined surface that are inclined at an angle of 55° or more and 70° or less with respect to the optical axis of the plurality of light sources; and the ratio L2 / L1 of the length of the lens member along the second direction to the length L1 of each light source along the second direction perpendicular to both the optical axis of the plurality of light sources and the first direction is 2 or less.

2. The light-emitting device according to claim 1, wherein the first inclined surface and the second inclined surface are inclined at an angle of 60° or more and 65° or less with respect to the optical axis of the plurality of light sources.

3. The light-emitting device according to claim 1 or 2, wherein the lens member further comprises a second light-emitting surface and a third light-emitting surface arranged to sandwich the first light-emitting surface, the second light-emitting surface and the third light-emitting surface being substantially parallel to the optical axis of the plurality of light sources.

4. The light-emitting device according to claim 3, wherein the lens member comprises a lens body portion having the first light-receiving surface, and a first flange portion and a second flange portion extending from both ends of the lens body portion in the second direction toward the plurality of light sources, the first flange portion having the second light-receiving surface and the second flange portion having the third light-receiving surface.

5. The light-emitting device according to claim 1 or 2, wherein the first light-receiving surface further includes an orthogonal surface located between the first inclined surface and the second inclined surface, and substantially perpendicular to the optical axes of the plurality of light sources.

6. The light-emitting device according to claim 1 or 2, wherein the light-emitting device has an emitting surface for emitting light, the light guide layer has a first main surface on the side of the emitting surface and a second main surface on the opposite side of the emitting surface, and the light-emitting device further comprises a direction-changing layer disposed on the side of the first main surface or the second main surface of the light guide layer for directing a portion of the light propagating through the light guide layer toward the emitting surface.

7. The light-emitting device according to claim 6, wherein the direction-changing layer has a plurality of internal spaces that form an interface that totally reflects a portion of the light propagating through the light guide layer and directs it toward the emission surface.

8. The light-emitting device according to claim 1 or 2, wherein the thickness of the light guide layer is 5 mm or less.

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