Light-emitting device

Abstract

To provide a device that emits light with uniform brightness even though it has a configuration in which semiconductor light emitting elements are arranged at intervals.SOLUTION: A band-shaped opening is provided in a housing, and a diffuser plate is placed in the opening. A transparent film on which multiple semiconductor light-emitting elements are arranged at intervals is adhered to the inside of the diffuser plate. The inner wall of the housing has a structure that reflects while scattering light. A light-shielding layer that covers a predetermined area centered on the semiconductor light-emitting element is placed between the transparent film and the diffuser plate, and the light-shielding layer blocks a portion of the light from the semiconductor light-emitting element. This makes it possible to keep the difference in brightness between the light emitted from the diffuser plate in the area where the light-shielding layer is placed and the light emitted from the diffuser plate in the area where the light-shielding layer is not placed below a predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a linear or large area light emitting device. [Background technology]

[0002] There are known lighting devices that emit light from a surface by arranging multiple semiconductor light-emitting elements side by side. In such lighting devices, the brightness of the semiconductor light-emitting elements is high, while the brightness of the areas between the semiconductor light-emitting elements is low. Therefore, it is difficult to achieve uniform light emission, and the positions of the multiple semiconductor light-emitting elements become bright, granular bright spots.

[0003] Patent Document 1 proposes a lighting device that alleviates the problem of bright, granular spots occurring at the locations of multiple semiconductor light-emitting elements. In this lighting device, semiconductor light-emitting elements are bonded to the backside of a transparent substrate, on the surface of which a phosphor layer is formed, using a transparent adhesive layer. Light emitted from the bonded surface of the semiconductor light-emitting element is scattered by the phosphor layer and then emitted. Furthermore, light emitted from the opposite surface of the semiconductor light-emitting element is reflected by a reflective member, incident on the transparent substrate and the phosphor layer, and then scattered by the phosphor layer before being emitted. Patent Document 1 also discloses a structure in which the interface between the phosphor layer and the transparent substrate is roughened to further scatter the light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-66691 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 scatters light using a phosphor layer or the like, which can reduce the possibility of the semiconductor light-emitting element becoming a bright, granular spot, but it is difficult to make the brightness at the position where the semiconductor light-emitting element is located the same as the brightness of the area between the semiconductor light-emitting elements.

[0006] An object of the present invention is to provide a device that emits light with a uniform brightness even though it has a configuration in which semiconductor light emitting elements are arranged at intervals. [Means for solving the problem]

[0007] In order to achieve the above object, the light emitting device of the present invention comprises a housing with an opening, a diffuser plate disposed in the opening, a transparent film fixed to the surface of the diffuser plate facing the interior space of the housing, and a plurality of semiconductor light emitting elements mounted on the surface of the transparent film facing the interior space. The semiconductor light emitting elements are bare chips in which a plurality of semiconductor layers and electrodes are laminated. The semiconductor light emitting elements are arranged side by side at a predetermined interval and emit light from at least the surface facing the transparent film and the surface facing the interior space of the housing. The diffuser plate transmits light emitted by the semiconductor light emitting elements while scattering it. The inner wall of the housing has a structure in which at least the area facing the semiconductor light emitting elements reflects light while scattering it. A light-shielding layer is disposed between the transparent film and the diffuser plate, covering a predetermined area centered on the semiconductor light emitting elements, and the light-shielding layer transmits a portion of the light from the semiconductor light emitting elements and blocks the remainder. [Effects of the Invention]

[0008] According to the present invention, a light emitting device is provided that emits light with a uniform brightness even though it has a configuration in which semiconductor light emitting elements are arranged at intervals. [Brief explanation of the drawings]

[0009] [Figure 1] 1A is a top view of a light emitting device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA. [Figure 2] FIG. BB cross-sectional view of the light emitting device according to the embodiment. [Figure 3] Enlarged view of Figure 2. [Figure 4] FIG. 2 is an enlarged view of the AA cross section of the light emitting device according to the embodiment. [Figure 5] Enlarged view of Figure 4. [Figure 6] FIG. 4 is a bottom view of the diffusion plate of the light emitting device according to the embodiment. [Figure 7] FIG. 8 is a cross-sectional view taken along the line BB of a light emitting device according to a first modified example of the embodiment. [Figure 8] Enlarged view of Figure 7. [Figure 9] 2 is a cross section taken along line AA of a light emitting device according to a first modified example of the embodiment. [Figure 10] 10(a) to 10(d) are diagrams showing an outline of a light emitting device according to a second modification of the embodiment. [Figure 11] 10(a), (b), and (c) are a top view, a cross-sectional view taken along CC and a cross-sectional view taken along DD of a light-emitting device according to a fourth modification of the embodiment. [Figure 12] Enlarged view of Figure 11(b). [Figure 13] Enlarged view of Figure 11(c). [Figure 14] FIG. 10 is an explanatory diagram showing an example of wiring in a light emitting device according to a fourth modified example of the embodiment. [Figure 15] 10(a), (b), and (c) are a top view, an E-E cross-sectional view, and an F-F cross-sectional view of a light-emitting device according to a fifth modified example of the embodiment. [Figure 16] 13 is an FF cross-sectional view of a light emitting device according to a fifth modified example of the embodiment, in which the direction of curvature is different. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] A light emitting device according to one embodiment of the present invention will be described below.

[0011] 1(a) and 1(b) are a top view and an AA cross-sectional view of the light emitting device 1 of this embodiment. Figures 2 and 3 are a BB cross-sectional view of the light emitting device 1 and an enlarged view thereof. Figure 4 is an enlarged view of the AA cross-sectional view, and Figure 5 is a further enlarged view of the AA cross-sectional view. Figure 6 is a bottom view of the diffuser plate.

[0012] 1(a), the light emitting device 1 of this embodiment is configured to include a housing 10 having a strip-shaped opening 11, a diffusion plate 12 arranged in the opening 11, a transparent film 14 (see FIG. 2), an adhesive layer 15, a plurality of semiconductor light emitting elements 16, a protective layer 17, and a light-shielding layer 18. The size of the strip-shaped opening 11 can be designed to any desired size, but an example is a width of approximately 6 mm and a length of approximately 20 cm.

[0013] For ease of explanation, as shown in FIG. 2, the opening 11 side of the housing 10 (the side where the diffusion plate 12 is arranged) is referred to as the upper side, and the bottom side facing the opening 11 of the housing 10 is referred to as the lower side, but this does not limit the orientation of the light emitting device 1 when in use.

[0014] 2 and 3, the transparent film 14 is fixed to the underside of the diffusion plate 12 (the surface facing the internal space 13 of the housing 10) by a transparent adhesive layer 15. The transparent film 14 is made of resin, in this case, flexible, transparent polyimide. The semiconductor light emitting elements 16 are mounted on the underside of the transparent film 14 (the surface facing the internal space 13) at predetermined intervals (for example, 10 mm intervals) along the longitudinal direction of the strip-shaped opening 11.

[0015] 6 is mounted by being directly fixed to the underside (the surface on the inner space 13 side) of the transparent film 14. As an example, the wiring 20 is made of copper foil with a gold-plated layer on the surface thereof, and is placed on the underside of the transparent film 14 before the transparent film 14 hardens, and is then directly fixed to the transparent film 14 as the transparent film 14 hardens.

[0016] The semiconductor light emitting element 16 is a flip-chip bare chip LED having a pair of element electrodes 19 mounted on the upper surface of a plurality of stacked semiconductor layers, and emits light of a predetermined wavelength (e.g., red light) from the top, bottom, and side surfaces. The pair of element electrodes 19 are adhered to wiring 20 on the lower surface of the transparent film 14 by a conductive adhesive layer 21 such as an adhesive containing conductive particles. In this way, the semiconductor light emitting element 16 is flip-chip mounted to the wiring 20 on the lower surface of the transparent film 14.

[0017] That is, the semiconductor light emitting element 16 is mounted with the element electrodes 19 facing upward, and the amount of light emitted upward from the semiconductor light emitting element 16 is limited by the element electrodes 19. As a result, the amount of light emitted downward from the semiconductor light emitting element 16 is greater than the amount of light emitted upward, and therefore, in this embodiment, the lower surface of the semiconductor light emitting element 16 becomes the main light emitting surface.

[0018] A transparent protective layer 17 for protecting the semiconductor light emitting element 16 is disposed on the underside of the transparent film 14 in a dome shape for each semiconductor light emitting element 16 so as to cover the semiconductor light emitting element 16. In this example, the protective layer 17 is made of resin, for example, silicone resin. However, the protective layer 17 is not limited to being made of resin, and may be made of a transparent inorganic material such as glass.

[0019] The inner wall of the housing 10 has a structure in which at least the region (bottom region) facing the semiconductor light emitting element 16 reflects light while scattering it. The inner wall of the housing 10 preferably has a higher degree of scattered reflection. For example, the housing 10 may have a structure in which the inner wall facing the internal space 13 is provided with a layer of light-scattering particles (titanium oxide, etc.).

[0020] Alternatively, the entire housing 10 may be made of a resin (e.g., acrylic) containing light-scattering particles. For example, the thickness of the bottom and side surfaces of the housing 10 may be approximately 15 mm. When the housing 10 is made of a resin containing light-scattering particles, some light is diffusely reflected by the inner wall of the housing 10, while some light is diffusely reflected as it enters the inner wall. Therefore, multiple scattered reflection points exist along the thickness of the inner wall, complicating the direction of scattered reflection. This increases the optical path length of the primary light emitted from the primary light-emitting surface (bottom surface) of the semiconductor light-emitting element 16, from which it is diffusely reflected to the diffuser plate 12, allowing for more repeated diffuse reflections, thereby improving the luminance uniformity of the primary light.

[0021] Furthermore, the diffusely reflected primary emitted light is incident on the transparent film 14 from various angles and reaches the diffuser plate 12, so that the shadow of the wiring 20 is less likely to appear on the light emitted from the diffuser plate 12, thereby improving the uniformity of the brightness of the light emitted from the diffuser plate 12.

[0022] A light-shielding layer 25 made of a light-shielding paint or the like is disposed on the outer peripheral surface of the housing 10 to prevent light from leaking out.

[0023] The diffusion plate 12 has the property of transmitting light while scattering it. The diffusion plate 12 is formed, for example, from a resin (e.g., acrylic) containing light-scattering particles, and is 1 mm thick, 6 mm wide (the same as the opening 11), and approximately 20 cm long. As the light-scattering particles, known particles with light-scattering properties, such as TiO2 particles, can be used.

[0024] Therefore, light emitted from the top surface of semiconductor light emitting element 16 passes through transparent film 14 and transparent adhesive layer 15, is scattered by diffuser plate 12, and is emitted upward. On the other hand, light emitted from the bottom and side surfaces of semiconductor light emitting element 16 is diffused and reflected by the inner wall of housing 10, reaches transparent film 14, passes through transparent adhesive layer 15, is scattered by diffuser plate 12, and is emitted upward.

[0025] In this embodiment, a light-shielding layer 18 that covers a predetermined area centered on the semiconductor light-emitting element 16 is disposed between the transparent film 14 and the diffusion plate 12. As an example, the element size of the semiconductor light-emitting element 16 is 100 to 200 μm, whereas the size of the light-shielding layer 18 is a circle with a diameter of 1800 μm and a thickness of about 100 μm, centered on the semiconductor light-emitting element 16. As an example, the light-shielding layer 18 is made of a silicone resin in which carbon black is dispersed at a predetermined ratio.

[0026] The light-shielding layer 18 transmits a portion of the light from the upper surface of the semiconductor light-emitting element 16 and blocks the remainder. The transmittance of the light-shielding layer 18 is set so that the difference between the luminance of the light emitted upward from the diffusion plate 12 covering the area where the light-shielding layer 18 is disposed and the luminance of the light emitted from the diffusion plate 12 covering the area where the light-shielding layer 18 is not disposed is equal to or less than a predetermined value (for example, equal to or less than 1%). Specifically, the transmittance is controlled by designing the concentration of carbon black.

[0027] As a result, the light-shielding layer 18 makes the brightness of the light emitted upward from the diffusion plate 12 directly above the semiconductor light-emitting elements 16 arranged at a fixed interval equal to the brightness of the light emitted upward from the diffusion plate 12 in the region between the semiconductor light-emitting elements 16.

[0028] In addition, it is preferable that the size of the light-shielding layer 18 is formed larger than that of the protective layer 17 in order to prevent the light emitted from the semiconductor light-emitting element 16 from being reflected at the interface between the protective layer 17 and the internal space 13 of the housing 10 from being emitted from the diffusion plate 12 and increasing in brightness.

[0029] As described above, the light emitting device 1 of this embodiment has a structure in which multiple semiconductor light emitting elements 16 are arranged at intervals along the longitudinal direction of the opening 11, and yet can emit light of uniform brightness from the entire diffuser plate 12 arranged in the strip-shaped opening 11.

[0030] Furthermore, as described above, the light is diffusely reflected by the inner wall of the housing 10 and the area near the inner wall, so the light emitting device 1 can be made thinner than a device that does not utilize the diffuse reflection of the housing.

[0031] 3 and 5, the light-shielding layer 18 is thickest in the center and gradually becomes thinner toward the periphery, thereby smoothing the change in transmittance between the center and the region where the light-shielding layer 18 is not disposed. However, if the scattering characteristics of the diffuser 12 are sufficiently large, the scattering characteristics of the diffuser 12 prevent the change in transmittance between the periphery of the light-shielding layer 18 and the region where the light-shielding layer 18 is not disposed from affecting the brightness of the diffuser 12. Therefore, the thickness of the light-shielding layer 18 can be made uniform between the center and the periphery.

[0032] As described above, the semiconductor light-emitting element 16 is structured so that the amount of light emitted from its lower surface, which is its main light-emitting surface, is greater than the amount of light emitted from its upper surface. As a result, the amount of light that needs to be blocked by the light-shielding layer 18 to achieve uniform light emission from the diffuser plate 12 is less than when the upper surface of the semiconductor light-emitting element 16 is the main light-emitting surface, and the light emitted from the semiconductor light-emitting element 16 can be emitted to the outside from the diffuser plate 12 with high efficiency.

[0033] <<Variation 1>> A light emitting device according to a first modification of the above embodiment will be described with reference to FIGS. 7, 8 and 9. FIG.

[0034] In the embodiment, the protective layer 17 was shaped to cover each of the semiconductor light emitting elements 16, but in the light emitting device of Modification 1, as shown in Figures 7 to 9, a plurality of semiconductor light emitting elements 16 arranged side by side are covered by one protective layer 117 whose length in the longitudinal direction of the opening 11 is longer than the length (i.e., width) in the lateral direction of the opening 11. The surface of the protective layer 117 is curved in the lateral direction of the opening 11 (see the AA cross section in Figure 9).

[0035] A portion of the light emitted downward from semiconductor light emitting element 16 passes through protective layer 117 and is emitted downward, and is diffused by the inner wall of housing 10 and travels upward. As shown in Fig. 7 , a portion of the remaining light is reflected at the interface between protective layer 117 and the air in housing 10, and is guided within protective layer 117 in the longitudinal direction of opening 11 while passing through the interface between protective layer 117 and transparent film 14 toward transparent film 14, and is diffused by diffuser plate 12 and emitted upward. In addition, a portion of the guided light is also emitted downward from the interface between protective layer 117 and the air in housing 10.

[0036] In this way, in the light emitting device of Modification 1, a light component that is guided within protective layer 117 is generated, and therefore the uniformity of the light emitted from diffusion plate 12 in the longitudinal direction of opening 11 is improved.

[0037] Furthermore, in the light emitting device of Modification 1, the transparent film 14 in the region between adjacent semiconductor light emitting elements 16 is also covered with the protective layer 117, which has the advantage of improving the durability of the wiring 20 arranged on the transparent film 14.

[0038] <<Variation 2>> A light emitting device according to a second modification of the above embodiment will be described with reference to FIG.

[0039] In the embodiment, the strip-shaped opening 11 is linear, but it can be curved or bent as shown in Figures 10(a) to 10(d). In this case, the diffusion plate 12, the transparent film 14, and the wiring 20 are also curved or bent to correspond to the shape of the opening 11.

[0040] As a result, the light emitting device of the second modification is able to emit light uniformly even at the curved and bent portions of the diffusion plate 12.

[0041] Furthermore, by forming the outer shape of the housing 10 into the desired product shape and providing openings 11 at desired positions, the steering wheel of an automobile can be made into a light-emitting device that emits light in a strip-like pattern at a desired position, as shown in Figures 10(a) to 10(c). Also, as shown in Figure 10(d), a part of the interior of a vehicle can be made into a light-emitting device.

[0042] <<Variation 3>> A light emitting device according to a third modification of the above embodiment will now be described.

[0043] The light emitting device of this embodiment is not limited to a light emitting device for a vehicle, but can be used in various products for display or decoration. For example, it can be suitably used in amusement devices, etc. The light emitting device of this embodiment is also suitable as an illumination device that emits light uniformly.

[0044] <<Variation 4>> The light emitting device according to the fourth modification of the embodiment will be described with reference to FIGS.

[0045] 11(a), (b), and (c) are a top view, a cross-sectional view taken along CC and a cross-sectional view taken along DD of the light-emitting device of Modification 4. Fig. 12 and Fig. 13 are enlarged views of the cross-sectional views. Fig. 4 is a diagram showing an example of a wiring circuit.

[0046] The light-emitting device of the embodiment has a structure in which semiconductor light-emitting elements 16 are arranged in a row at intervals along the longitudinal direction of a narrow opening 11, for example, approximately 6 mm wide and 20 cm long, but in variant example 4, opening 11 is a large rectangle (for example, a 21 cm square) with approximately equal length and width.

[0047] A diffuser plate 12 is disposed in the opening 11, and semiconductor light-emitting elements 16 are arranged two-dimensionally at predetermined intervals on the surface of the diffuser plate 12 facing the internal space 13. For example, 35 wires 20 and strip-shaped transparent films 14, each having semiconductor light-emitting elements 16 arranged in a row as shown in FIG. 6 of the embodiment, are arranged in parallel at predetermined intervals on the lower surface of the diffuser plate 12 and fixed with an adhesive layer 15. This allows the semiconductor light-emitting elements 16 to be arranged two-dimensionally on the lower surface of the diffuser plate 12.

[0048] In this case, as shown in FIG. 14, the ends of a plurality of parallelly arranged wirings can be commonly connected to form wirings in which one end is connected to a power supply line and the other end is connected to a ground line.

[0049] In the light emitting device of the fourth modification, the structure other than that described above is the same as that of the embodiment, and therefore the description thereof will be omitted.

[0050] The light emitting device of the fourth modification has a configuration in which semiconductor light emitting elements 16 are arranged at predetermined intervals, but can emit light with uniform brightness from the entire large-area diffusion plate 12.

[0051] The shape of the wiring 20 is not limited to a straight line, and may be any wiring circuit as long as it can supply current to the semiconductor light emitting element 16 .

[0052] <<Variation 5>> The light emitting device according to the fifth modification of the embodiment will be described with reference to FIGS.

[0053] 15(a), (b), and (c) are a top view, an E-E cross-sectional view, and an F-F cross-sectional view of the light emitting device of the fifth modification.

[0054] The light emitting device of the fifth modification is a large rectangular shape like the light emitting device of the fourth modification, but differs from the fourth modification in that the diffusion plate 12 and the housing 10 are curved.

[0055] 15(a), (b), and (c), the upper surface of the diffusion plate 12 is curved in one direction (X direction) so as to have a concave shape. The transparent film 14 provided with the wiring 20 is flexible, and therefore can be attached to the curved diffusion plate 12. This allows the entire upper surface of the curved diffusion plate 12 to emit light uniformly.

[0056] The direction of the curvature may be such that the upper surface of the diffusion plate 12 has a convex shape as shown in FIG.

[0057] When the diffusion plate 12 is curved and a plurality of linear wirings 20 are arranged in parallel as in the present modification 5, the stress applied to the wirings 20 can be reduced by arranging the direction of the linear wirings 20 so that it coincides with the non-curved direction (Y direction in FIG. 15 ). However, the direction of the wirings 20 is not limited to this direction, and any desired wiring shape can be used.

[0058] <<Variation 6>> In the above-described embodiment and modifications 1 to 5, the protective layer 17 covering the semiconductor light emitting element 16 is transparent. However, the protective layer 17 may be formed of a transparent material containing light-scattering particles. Known particles having light-scattering properties, such as TiO2 particles, may be used as the light-scattering particles. The transparent material may be a resin, such as a silicone resin, or an inorganic material, such as glass.

[0059] As a result, the light guided within the protective layer 17 is scattered by the light-scattering particles, and the angle of incidence of light incident on the interface between the protective layer 17 and the transparent film 14 becomes more diverse than when the protective layer 17 is transparent. Similarly, the angle of incidence of light incident on the interface between the protective layer 17 and the air in the internal space 13 also becomes more diverse. Therefore, compared to when the protective layer 17 is transparent, the extraction efficiency of light guided within the protective layer 17 can be improved. In addition, the uniformity of the light emitted from the protective layer 17 is improved.

[0060] In addition, since the light passing through the protective layer 17 is also scattered by the light-scattering particles, the uniformity of the light emitted downward from the semiconductor light-emitting element 16 and passing through the protective layer 17, and the light reflected by the inner wall of the housing and going upward and passing through the protective layer 17, is improved.

[0061] For these reasons, when the protective layer 17 is formed from a resin containing light-scattering particles, the uniformity of the light emitted from the diffusion plate 12 can be further improved. [Explanation of symbols]

[0062] 1. Light-emitting device 11 Aperture 12 Diffuser 13 Interior Space 14 Transparent film 15 Adhesive layer 16 Semiconductor light emitting device 17 Protective layer 18 Light blocking layer 20 Wiring 25 Light blocking layer 117 Protective layer

Claims

1. a housing having an opening, a diffusion plate disposed in the opening, a transparent film fixed to a surface of the diffusion plate facing the internal space of the housing, and a plurality of semiconductor light-emitting elements mounted on a surface of the transparent film facing the internal space, The semiconductor light emitting elements are arranged side by side at intervals, and emit light from at least a surface on the transparent film side and a surface on the housing's internal space side; the diffusion plate transmits and scatters the light emitted by the semiconductor light emitting element, an inner wall of the housing having a diffuse reflection surface at least in a region facing the semiconductor light emitting element; The light emitting device is characterized in that the amount of light emitted from the surface of the housing facing the internal space of the semiconductor light emitting element is greater than the amount of light emitted from the surface facing the transparent film.

2. 2. The light emitting device according to claim 1, wherein an electrode of said semiconductor light emitting element is provided on said transparent film side.

3. 3. A light-emitting device according to claim 1, wherein a light-shielding layer is arranged in the direction from the semiconductor light-emitting element to the diffusion plate, for blocking at least a portion of the light emitted from the surface of the semiconductor light-emitting element facing the transparent film.

4. 4. The light-emitting device according to claim 3, wherein the transmittance of the light-shielding layer is set so that the difference between the brightness of the light emitted from the diffusion plate covering the area where the light-shielding layer is disposed and the brightness of the light emitted from the diffusion plate covering the area where the light-shielding layer is not disposed is equal to or less than a predetermined value.

5. 4. The light emitting device according to claim 3, wherein a transparent protective layer covering the semiconductor light emitting element is disposed on the surface of the transparent film facing the internal space.

6. 6. The light emitting device according to claim 5, wherein the area where the light blocking layer is in contact with the transparent film is larger than the area where the protective layer is in contact with the transparent film.

7. 6. The light emitting device according to claim 5, wherein the protective layer covers the entirety of the plurality of semiconductor light emitting elements.

8. 2. The light emitting device according to claim 1, wherein the diffusion plate of the opening is curved.

9. 2. The light emitting device according to claim 1, wherein the opening is strip-shaped, and the semiconductor light emitting elements are arranged in a line along the longitudinal direction of the strip-shaped opening.

10. 6. The light emitting device according to claim 5, wherein the protective layer is made of a transparent material in which a light diffusing material is dispersed.

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