Semiconductor light-emitting device

Abstract

The present invention comprises a substrate, a frame body that is formed so as to stand erect on the substrate and defines an accommodation space in the interior thereof, a light-emitting element that is placed inside the accommodation space, a phosphor plate which is provided on the light-emitting element and of which the upper surface is a light-emitting surface, a sealing resin in which the light-emitting element is embedded and which is formed within the accommodation space at such a depth as to cover at least part of the side surface of the phosphor plate, and a light-blocking mask that is provided on the frame body and has an opening entirely included inside the outer edge of the light-emitting surface in top view, the sealing resin being a light-reflective resin, the reverse surface of the light-blocking mask being light-reflective, and the phosphor plate and the light-blocking mask being provided such that the light-emitting surface of the phosphor plate and the reverse surface of the light-blocking mask sandwich an air layer at a fixed interval.

Description

Semiconductor light-emitting device

[0001] The present invention relates to a semiconductor light-emitting device, and more particularly to a semiconductor light-emitting device provided with a light-shielding mask.

[0002] In recent years, development of road projection lamps that project figures and pictograms onto the road surface has been progressing for driver assistance and autonomous driving. Road projection lamps are required to have performance such as the ability to project clear images, little color unevenness, and high brightness.

[0003] Patent Document 1 discloses a method for manufacturing a light emitting device configured to control the light distribution pattern by blocking part of the emitted light with a light blocking member. The light emitting device described in Patent Document 1 is formed so that the upper surface of the phosphor layer and the upper surface of the light blocking member are on the same plane.

[0004] Patent Document 2 discloses a semiconductor light-emitting device in which the thickness of a phosphor-containing layer formed on the surface of a semiconductor layer becomes thinner from the center toward the outer edge, and non-emitting portions that do not emit light are provided at the corners of the light-emitting surface of the semiconductor layer.

[0005] JP 2011-165965 A JP 2010-92897 A

[0006] In semiconductor light-emitting devices such as road projection lamps, a sharp projected image is required, and in order to project a clear image, it is necessary to block light from all around the light-emitting surface, etc. However, in conventional technologies, even if a clear projected image can be achieved, there are problems such as a decrease in light-emitting efficiency.

[0007] The present invention has been made in consideration of the above points, and aims to provide a semiconductor light-emitting device equipped with a light-shielding mask that blocks part of the light emitted from a phosphor, which can project a clear image and has high brightness and luminous flux with little color unevenness.

[0008] The semiconductor light emitting device of the present invention comprises: a substrate; a frame formed upright on the substrate and defining an internal storage space; a light emitting element placed inside the storage space; a phosphor plate provided on the light emitting element and having an upper surface as a light emitting surface; a sealing resin that embeds the light emitting element and is formed within the storage space to a depth that covers at least a portion of the side surface of the phosphor plate; and a light-shielding mask provided on the frame and having an opening that, when viewed from above, is entirely contained within the inside outer edge of the light emitting surface, wherein the sealing resin is a light-reflective resin, the back surface of the light-shielding mask is light-reflective, and the phosphor plate and the light-shielding mask are provided with a fixed gap between the light emitting surface of the phosphor plate and the back surface of the light-shielding mask with an air layer between them.

[0009] 1 is a perspective view schematically showing a semiconductor light emitting device according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view schematically showing a cross section of the semiconductor light emitting device taken along line A-A in FIG. 1; FIG. 3 is a cross-sectional view schematically showing a cross section of the semiconductor light emitting device before a sealing resin and a light-shielding mask are provided; FIG. 4 is a top view showing the internal structure of the semiconductor light emitting device; FIG. 5 is a cross-sectional view schematically showing a portion (upper portion) of the cross section of the semiconductor light emitting device taken along line A-A in FIG. 1; FIG. 6 is a diagram schematically showing the optical path of light emitted from a phosphor plate; FIG. 7 is a diagram showing the luminous flux maintenance (%) versus the distance DM between the light-emitting surface of the phosphor plate and the rear surface of the light-shielding mask; FIG. 8 is a diagram showing the luminance of the light-emitting surface versus the distance DM between the light-emitting surface of the phosphor plate and the rear surface of the light-shielding mask; FIG. 9 is a diagram showing the luminous flux maintenance (%) versus the aperture ratio (%) of the aperture of the light-shielding mask; and FIG. 10 is a diagram showing the luminance of the light-emitting surface 25S versus the aperture ratio (%). It is a diagram comparing the luminous flux of the semiconductor light emitting device and the maximum luminance and average luminance of the luminance distribution of the light-emitting surface for each of cases (i) to (iv). 12A is a plan view showing a light-shielding mask used in the semiconductor light-emitting device of Modification 1. FIG. 12B is a view of the semiconductor light-emitting device of Modification 1 when the light-shielding mask is removed, as viewed from the top. FIG. 12C is a plan view showing a light-shielding mask used in the semiconductor light-emitting device of Modification 2. FIG. 12D is a view of the semiconductor light-emitting device of Modification 2 when the light-shielding mask is removed, as viewed from the top. FIG. 12E is a cross-sectional view schematically showing a cross section of the semiconductor light-emitting device of Modification 2 taken along line B-B shown in FIG.

[0010] In the following, preferred embodiments of the present invention will be described, but these may be modified and combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

[0011] [First Embodiment] Fig. 1 is a perspective view schematically showing a semiconductor light emitting device 10 according to a first embodiment of the present invention. Fig. 2A is a cross-sectional view schematically showing the cross section of the semiconductor light emitting device 10 taken along line A-A shown in Fig. 1. Fig. 2B is a cross-sectional view schematically showing the cross section of the semiconductor light emitting device 10 before the sealing resin 31 and the light-shielding mask 33 are provided.

[0012] The semiconductor light-emitting device 10 according to this embodiment is a road projection lamp that is mounted on a vehicle and projects letters and marks onto the road surface. The semiconductor light-emitting device 10 is disposed, for example, on the left and right sides of the front of the vehicle. It can also be applied to street lights and floodlights, and can be used for displaying on specific objects, such as road markings and projection mapping.

[0013] In this specification, a vehicle is described as an automobile, but the present invention is not limited to this. That is, in this specification, a vehicle refers to a vehicle such as a motorcycle, an airplane, a ship, and manned or unmanned transportation or moving means.

[0014] As shown in FIG. 2A , the semiconductor light-emitting device 10 includes a lead 11, which is a substrate, and a frame 12 that is connected to the lead 11 and extends upright from the lead 11. The lead 11 is made of a pair of lead pieces, a p-side lead (anode lead) and an n-side lead (cathode lead), which are spaced apart. The lead 11 is made of a metal (e.g., iron or copper alloy). The spaced apart portion is made of the same material as the frame 12 so as to be insulated. In the present invention, an LED element 23 is mounted on the upper surface of the n-side lead 11. The surface of the lead 11 may be plated with a metal film (e.g., Ag or Au). By using the substrate 11 as a lead frame, heat generated by the semiconductor light-emitting element can be efficiently dissipated.

[0015] Furthermore, the frame 12 is formed from a light-blocking resin, but is not limited to this. It can also be formed from a light-reflective resin. The frame 12 is assembled and fixed to the substrate 11. The substrate 11 and the frame 12 define an accommodation space 12K, which is a space that surrounds and accommodates a light source made up of a semiconductor light-emitting element and a phosphor.

[0016] A light-emitting diode element (hereinafter referred to as an LED element) 23, which is a semiconductor light-emitting element, is mounted on the lead 11. Specifically, the LED element 23 has a rectangular shape, and a first element electrode 23A (e.g., an n-electrode) provided on the back surface of the LED element 23 is joined and electrically connected to the lead 11 (cathode lead) by a bonding material 21A.

[0017] A rectangular phosphor (hereinafter referred to as a phosphor plate) 25 is adhered to the upper surface (light emitting surface) of the LED element 23 with an adhesive 24. The adhesive 24 is made of a material that is transparent to the light emitted from the LED element 23. The adhesive 24 may be, for example, an adhesive made of silicone resin, but is not limited to this.

[0018] The LED elements 23 are, for example, blue LEDs, and the phosphor plate 25 contains, for example, a yellow or orange phosphor, and white or amber light is emitted from the light emission surface 25S (upper surface) of the phosphor plate 25. The LED elements 23 and the phosphor plate 25 can be appropriately selected depending on the desired wavelength of emitted light.

[0019] 2B, a second element electrode 23B (e.g., a p-electrode) is provided on the end of the top surface of the LED element 23. The second element electrode 23B is connected to the lead 11 (anode lead) by a bonding wire BW.

[0020] One end of a Zener diode 27, which is a protection element for the LED element 23, is joined and electrically connected to the lead 11 (cathode lead). The other end of the Zener diode 27 is connected to the lead 11 (anode lead) by a bonding wire BW.

[0021] 2A , sealing resin 31 is provided in housing space 12K of frame 12 so as to cover the periphery of LED element 23 and phosphor plate 25. More specifically, sealing resin 31 is formed to a depth that embeds the entire LED element 23 and covers at least a portion of the side surface of phosphor plate 25.

[0022] The sealing resin 31 is made of a light-reflective material, and may be, for example, a silicone resin containing a reflective filler such as titanium oxide, but is not limited to this.

[0023] It is preferable that the sealing resin 31 be formed so as to bury the bonding wires BW and the Zener diode 27 entirely.

[0024] A light-shielding mask 33 is provided on the frame 12 and is adhered to the frame 12 with an adhesive 15. The adhesive 15 may be, for example, a silicone resin adhesive. As shown in FIG. 1 , an opening 33A (mask opening) having, for example, a direction indicating figure (arrow shape) is provided on the frame 12. The light-shielding mask 33 is formed spatially separated from the phosphor plate 25.

[0025] 3 is a top view showing the internal structure of semiconductor light-emitting device 10. Specifically, it shows the interior of semiconductor light-emitting device 10 as viewed from a direction perpendicular to light-emitting surface 25S of phosphor plate 25 (top side) with light-shielding mask 33 removed. The arrangement of openings 33A of light-shielding mask 33 is shown by dashed lines, and line A-A shown in FIG. 1 is also shown.

[0026] In a top view, opening 33A of light-shielding mask 33 is arranged so that the entire opening 33A is encompassed inside the outer edge of light exit surface 25S (upper surface) of phosphor plate 25. In other words, opening 33A of light-shielding mask 33 and phosphor plate 25 are arranged in a positional relationship such that the outer edge of opening 33A is spaced apart from the outer edge of light exit surface 25S of phosphor plate 25 in a direction parallel to light-shielding mask 33.

[0027] 4 is a cross-sectional view schematically showing a part of the cross section (the upper part excluding the leads 11) of the semiconductor light-emitting device 10 taken along the line A-A shown in FIG. 1. The positional relationship between the light-shielding mask 33 and the phosphor plate 25 is shown in more detail.

[0028] Light exit surface 25S of phosphor plate 25 is a flat surface, and back surface 33B of light-shielding mask 33, i.e., the surface facing light exit surface 25S, is also configured as a flat surface. In addition, back surface 33B of light-shielding mask 33 is a light-reflective surface, and back surface 33B of light-shielding mask 33 is provided parallel to light exit surface 25S of phosphor plate 25.

[0029] The light-shielding mask 33 is made of, for example, stainless steel, but is not limited to this, and a material with higher light reflectivity, such as aluminum (Al), can be used. The back surface 33B of the light-shielding mask 33 may be subjected to a light-reflective surface treatment, or may be coated or adhered with a light-reflective film, such as a metal film. In this case, the base material of the light-shielding mask 33 may be glass, ceramic, resin, or the like.

[0030] The light-shielding mask 33 is provided so that a certain distance DM is maintained between the light-emitting surface 25S of the phosphor plate 25 and the rear surface 33B of the light-shielding mask 33, with an air layer sandwiched therebetween.

[0031] The sealing resin 31 is formed from the side surface of the phosphor plate 25 to the inner wall surface of the frame 12. The surface 31S of the sealing resin 31 is a curved surface that is convex downward, that is, a curved surface that is convex toward the lead 11 (the bottom surface of the frame 12).

[0032] In this embodiment, the light exit surface 25S of the phosphor plate 25 has a size of 1 mm x 1 mm, and the light-shielding mask 33 has a thickness of 0.1 mm. However, the sizes of the phosphor plate 25 and the light-shielding mask 33 are not limited to these.

[0033] 5 is a schematic diagram showing the optical path of light emitted from phosphor plate 25. Light L1 emitted from phosphor plate 25 is multiple-reflected between rear surface 33B of light-shielding mask 33 and surface 31S of sealing resin 31, and the multiple-reflected light returns to phosphor plate 25, and then is re-emitted from opening 33A of light-shielding mask 33 (re-emitted light L2).

[0034] That is, the returning light that returns to the phosphor plate 25 is scattered and propagated within the phosphor plate 25. Inside the phosphor plate 25, the returning light re-excites the phosphor plate 25, causing it to emit fluorescent light, increasing the brightness of the light exit surface 25S. Here, it is preferable that the position of the surface 31S of the sealing resin 31 that contacts the frame 12 is higher than the position that contacts the phosphor plate 25. This increases the light extraction efficiency. That is, the proportion of re-emitted light L2 increases.

[0035] 6 is a diagram showing the luminous flux maintenance (%) of semiconductor light-emitting device 10 versus distance DM between light-emitting surface 25S of phosphor plate 25 and back surface 33B of light-shielding mask 33. Note that the luminous flux maintenance (%) is shown assuming that the luminous flux from the entire light-emitting surface 25S of phosphor plate 25 is 100% when light-shielding mask 33 is not present, i.e., when the luminous flux from the entire light-emitting surface 25S of phosphor plate 25 is 100%.

[0036] 7 is a diagram showing the luminance of light exit surface 25S relative to distance DM between light exit surface 25S of phosphor plate 25 and rear surface 33B of light-shielding mask 33. Note that the luminance is shown assuming that the luminance when light-shielding mask 33 is not present, i.e., the luminance from the entire surface of light exit surface 25S of phosphor plate 25, is 1.

[0037] As shown in Figures 6 and 7, it can be seen that the luminous flux and brightness of the semiconductor light-emitting device 10 are improved when there is a gap (DM>0) compared to when the back surface 33B of the light-shielding mask 33 is in contact with the light-emitting surface 25S (DM=0).

[0038] The distance DM between the light exit surface 25S and the rear surface 33B of the light-shielding mask 33 is preferably within a range of 15 to 350 μm, and more preferably within a range of 15 to 100 μm.

[0039] In this embodiment, the phosphor plate 25 has a rectangular parallelepiped shape with the light exit surface 25S measuring approximately 1 mm x 1 mm, but the suitable range of the above-mentioned distance DM does not depend greatly on the size of the phosphor plate 25.

[0040] Fig. 8 is a graph showing the luminous flux maintenance factor (%) versus the aperture ratio (%) of the opening 33A of the light-shielding mask 33. Fig. 9 is a graph showing the luminance of the light-emitting surface 25S versus the aperture ratio (%). Here, aperture ratio is expressed as [area of ​​the opening 33A of the light-shielding mask 33] / [area of ​​the light-emitting surface 25S of the phosphor plate 25]. When the light-shielding mask 33 is not present, the aperture ratio and luminance are 100%. The graph also shows the results for the cases where the light-shielding mask 33 is made of stainless steel (SUS) and aluminum.

[0041] 8 and 9, it can be seen that when the aperture ratio is reduced, the luminous flux decreases but the brightness increases. Furthermore, the aperture ratio and brightness are higher when the light-shielding mask 33 is made of aluminum than when it is made of stainless steel (SUS).

[0042] That is, the higher the reflectivity of the light-shielding mask 33, the higher the luminous flux and luminance. Therefore, it was confirmed that the luminous flux and luminance are enhanced by multiple reflections between the rear surface 33B of the light-shielding mask 33 and the front surface 31S of the sealing resin 31, and by fluorescent emission due to light returning to the phosphor plate 25.

[0043] 10 shows the maximum luminance and average luminance of the luminance distribution of the light flux and light exit surface 25S of the semiconductor light-emitting device 10 in the following cases: (i) when there is no light-shielding mask 33, (ii) when the light-shielding mask 33 is made of stainless steel (SUS), (iii) when the light-shielding mask 33 is made of aluminum (Al), and (iv) when the light-shielding mask 33 is made of aluminum and both surfaces of the light-shielding mask 33 are blackened by black anodizing. In each of the cases (ii) to (iv), the LED elements 23 were caused to emit light with the same optical output as in the case (i) when there is no light-shielding mask 33.

[0044] The luminance varied depending on the light-shielding mask 33, with the order being (iii) Al > (ii) SUS > (iv) Al (black treatment). In other words, it is believed that the reflectance of the light-shielding mask 33 contributed to the luminance of the semiconductor light-emitting device 10. Furthermore, regardless of whether or not the mask was black treatment, no glare occurred. The luminous flux and luminance of the semiconductor light-emitting device 10 are determined by the light directly emitted from the light-emitting surface 25S and the re-emitted light L2. Therefore, with the configurations (ii) to (iii), it is possible to provide a semiconductor light-emitting device that can emit light with a clear shape corresponding to the desired mask shape, and has high luminance and luminous flux with little color unevenness.

[0045] 11A is a plan view showing a light-shielding mask 33 used in a semiconductor light-emitting device 50 according to a first modification of the first embodiment. The light-shielding mask 33 is provided with an opening 33A (mask opening) consisting of three opening pieces 33A1, 33A2, and 33A3. The three opening pieces 33A1, 33A2, and 33A3 as a whole correspond to one figure.

[0046] 11B is a diagram of semiconductor light-emitting device 50 of Modification 1 viewed from the top (top view) when light-shielding mask 33 is removed. In the top view, opening 33A is arranged so that three opening pieces 33A1, 33A2, and 33A3 of opening 33A are entirely contained within the inner periphery of light-emitting surface 25S of one phosphor plate 25.

[0047] Semiconductor light emitting device 50 is similar to semiconductor light emitting device 10 of the first embodiment in that light-shielding mask 33 is provided so that there is a constant distance DM between light-emitting surface 25S of phosphor plate 25 and back surface 33B of light-shielding mask 33. According to Modification 1, since one phosphor plate 25 is placed on the upper surfaces of multiple semiconductor light emitting elements, the yield and positional accuracy of phosphor plate 25 can be improved compared to when phosphor plate 25 is formed independently for each of the multiple semiconductor light emitting elements, and the desired clear image can be provided.

[0048] 12A is a plan view showing a light-shielding mask 68 used in a semiconductor light-emitting device 60 according to a second modification of the first embodiment. The light-shielding mask 68 is provided with an opening 73 consisting of a plurality (n) of opening pieces. More specifically, the light-shielding mask 68 is provided with three (n=3) opening pieces, i.e., openings 73 (mask openings) consisting of a first opening piece 73A, a second opening piece 73B, and a third opening piece 73C.

[0049] 12B is a diagram of semiconductor light-emitting device 60 of Modification 2 viewed from the top when light-shielding mask 68 is removed. Semiconductor light-emitting device 60 is provided with rectangular phosphor plates 65, 66, and 67 corresponding to first opening piece 73A, second opening piece 73B, and third opening piece 73C, respectively.

[0050] In the semiconductor light-emitting device 60, the first opening piece 73A, the second opening piece 73B and the third opening piece 73C are arranged so as to be encompassed within the inner periphery of each of the light emission surfaces 65S, 66S and 67S of the phosphor plates 65, 66 and 67, respectively, when viewed from above.

[0051] Fig. 12C is a cross-sectional view schematically showing a cross section of semiconductor light-emitting device 60 taken along line B-B in Fig. 12A. Semiconductor light-emitting device 60 has LED elements 63A, 63B, and 63C, and phosphor plates 65, 66, and 67 are adhered to LED elements 63A, 63B, and 63C, respectively, with a transparent adhesive.

[0052] The LED elements 63A, 63B, and 63C are connected to leads 11A, 11B, and 11C, respectively, which are electrically isolated from one another. The LED elements 63A, 63B, and 63C, the protective elements, and their respective wiring and bonding wires are not shown in the figure. Therefore, the LED elements 63A, 63B, and 63C are configured to be able to be driven to emit light independently.

[0053] As shown in FIG. 12C, the light-shielding mask 68 is provided so that there is a constant distance DM between the light-emitting surfaces 65S, 66S, 67S of the phosphor plates 65, 66, 67 and the rear surface 68B of the light-shielding mask 68.

[0054] The luminous flux and brightness are enhanced by multiple reflections between the rear surface 68B of the light-shielding mask 68 and the surface 31S of the sealing resin 31, and by fluorescent emission due to light returning to the phosphor plates 65, 66, and 67. The presence of the sealing resin 31 between the phosphor plates 65, 66, and 67 increases the proportion of re-emitted light L2. This results in high brightness and luminous flux. Furthermore, it is preferable that the sealing resin 31 between the phosphor plates 65, 66, and 67 has a curved surface that is convex toward the substrate (leads). This results in even higher brightness and luminous flux.

[0055] In addition, in Modification 2, a case has been described in which three aperture pieces and the same number (i.e., three) of phosphor plates corresponding to the three aperture pieces are provided, but the number of aperture pieces and the number of phosphor plates may be different (m ≠ n). That is, a plurality (n pieces, n ≧ 2) of aperture pieces and a plurality (m pieces, n ≧ m ≧ 2) of phosphor plates corresponding to the plurality of aperture pieces may be provided. For example, two or more aperture pieces that expose the light exit surface of one phosphor plate may be provided.

[0056] Furthermore, when a plurality of phosphor plates are provided, the number of LED elements does not necessarily have to be the same as the number of phosphor plates. For example, a plurality of phosphor plates may be provided on one LED element.

[0057] For example, when a plurality of phosphor plates are provided, by making the plurality of phosphor plates different from one another in phosphor color, it is possible to provide a semiconductor light emitting device such as a projection lamp that can emit light of a different emission color for each aperture piece. Also, although the case where the plurality of aperture pieces have the same shape has been exemplified, the plurality of aperture pieces may have different shapes from one another.

[0058] According to Modification 2, since the brightness of the phosphor plate in each opening piece is high, it is possible to project a clear image with reduced bleeding, color unevenness, and crosstalk, and it is possible to provide a semiconductor light emitting device that has high brightness and luminous flux with little color unevenness. As described in detail above, according to the present disclosure, it is possible to provide a semiconductor light emitting device that can project a clear image with little color unevenness and has high brightness and luminous flux.

[0059] 10, 50, 60: Semiconductor light emitting device 11: Substrate (lead) 12: Frame 12K: Storage space 23, 63A, 63B, 63C: LED element 23A: First element electrode 23B: Second element electrode 25, 65, 66, 67: Phosphor plate 25S, 65S, 66S, 67S: Light emission surface 31: Sealing resin 31S: Surface of sealing resin 33, 68: Light-shielding mask 33A, 73: Opening 33A1, 33A2, 33A3: Opening piece 73A, 73B, 73C: First to third opening pieces DM: Mask spacing L1: Emitted light L2: Re-emitted light

Claims

1. A semiconductor light emitting device comprising: a substrate; a frame formed on the substrate and defining an internal storage space; a light emitting element placed inside the storage space; a phosphor plate provided on the light emitting element and having an upper surface as a light emitting surface; a sealing resin that embeds the light emitting element and is formed within the storage space to a depth that covers at least a portion of a side surface of the phosphor plate; and a light-shielding mask provided on the frame and having an opening that is entirely contained within the inside of the outer edge of the light emitting surface in a top view, wherein the sealing resin is a light-reflective resin, the back surface of the light-shielding mask is light-reflective, and the phosphor plate and the light-shielding mask are provided with a fixed gap between the light emitting surface of the phosphor plate and the back surface of the light-shielding mask with an air layer between them.

2. The semiconductor light emitting device according to claim 1, wherein the constant distance between the light emitting surface of the phosphor plate and the rear surface of the light-shielding mask is within a range of 15 to 350 μm.

3. The semiconductor light emitting device according to claim 1, wherein the constant distance between the light emitting surface of the phosphor plate and the rear surface of the light-shielding mask is within a range of 15 to 100 μm.

4. The semiconductor light emitting device according to claim 1, wherein said sealing resin has a curved surface that is convex toward said substrate.

5. A semiconductor light emitting device according to claim 1, comprising: a plurality of said light emitting elements; and a plurality of said phosphor plates, each of said light emitting elements being provided on said light emitting elements; said opening of said light-shielding mask having a plurality of aperture pieces, each of said plurality of aperture pieces being provided corresponding to one of said light emitting surfaces of said plurality of said phosphor plates.

6. The semiconductor light emitting device according to claim 5, wherein said plurality of light emitting elements are electrically isolated from one another and wired so as to be independently drivable.

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