Light-emitting device

Abstract

A light emitting device with high contrast and a method for manufacturing the same are provided. [Solution] The light emitting device 1 includes a substrate 10, a plurality of light emitting elements 12 mounted on the substrate 10 and arranged in a matrix, a phosphor layer 14 provided on the plurality of light emitting elements 12, and a plurality of wire pads 15 provided on both sides of the area on the top surface of the substrate 10 where the plurality of light emitting elements 12 are mounted. The phosphor layer 14 has a plurality of phosphor particles 16 and a glass layer 17 that covers the surfaces of the phosphor particles 16. The phosphor particles 16 are bonded to each other via the glass layer 17. An air layer 18 is formed between the phosphor particles 16.

Description

Technical Field

[0001] The embodiments relate to a position light-emitting device.

Background Art

[0002] In recent years, in automotive headlamps, a light distribution variable headlamp (ADB: Adaptive Driving Beam) that irradiates light only on a selected area has been developed. By applying ADB to high beams, for example, light can be projected only on areas other than the areas where oncoming vehicles and preceding vehicles exist, without projecting light on those areas. As a result, the driver's field of view of the host vehicle can be ensured without disturbing the driving of other vehicles.

[0003] In a light-emitting device used for ADB, for example, a plurality of light-emitting diodes (LEDs) are mounted on a substrate, and the light emitted from each LED is irradiated only in a specific direction by the optical system of the headlamp. Then, by selecting the LEDs to be lit, only the selected area is illuminated.

[0004] In ADB, it is desired to surely project light on the area to be projected and surely stop projecting light on the area where light should not be projected. For this reason, for the light-emitting device used for ADB, it is desirable that the contrast between the lit LEDs and the unlit LEDs is high when viewed from the optical system.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The embodiment is made in view of the above problems, and provides a light-emitting device with high contrast between a lighting area and a non-lighting area. placement It aims to provide.

Means for Solving the Problems

[0007] The light-emitting device according to the embodiment includes a substrate, a plurality of light-emitting elements mounted on the substrate, and a phosphor layer provided on the plurality of light-emitting elements. The phosphor layer has a plurality of phosphor particles and a glass layer covering the surface of the phosphor particles. The phosphor particles are bonded to each other via the glass layer. An air layer is formed between the phosphor particles.

[0008] The manufacturing method of the light-emitting device according to the embodiment includes a step of spraying a slurry material containing polysilazane and a plurality of phosphor particles on a substrate on which a plurality of light-emitting elements are mounted, and heating the substrate on which the slurry material is sprayed to convert the polysilazane into silica, covering the phosphor particles with a glass layer containing the silica, and forming an air layer between the phosphor particles.

Effects of the Invention

[0009] According to the embodiment, a light-emitting device with high contrast between a lighting area and a non-lighting area can be realized. placement It can be realized.

Brief Description of the Drawings

[0010]

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Best Mode for Carrying Out the Invention

[0011] <First Embodiment> First, the first embodiment will be described. FIG. 1 is a plan view showing a light-emitting device according to this embodiment. FIG. 2 is a cross-sectional view showing a light-emitting device according to this embodiment. FIG. 3 is a partially enlarged cross-sectional view showing region A of FIG. 2.

[0012] As shown in FIG. 1, in the light-emitting device 1 according to this embodiment, a substrate 10 is provided. The substrate 10 is a wiring substrate on which wiring (not shown) is provided on an insulating board, and the insulating board is formed of, for example, ceramics having high heat resistance and thermal conductivity, such as aluminum nitride such as AlN.

[0013] As shown in FIGS. 1 and 2, on the upper surface of the substrate 10, a plurality of, for example, 96 light-emitting elements 12 are mounted via bumps 11. The light-emitting element 12 is an LED chip and emits, for example, blue light. The 96 light-emitting elements 12 are arranged in a matrix of, for example, 4 rows and 24 columns. On both sides of the region where the light-emitting elements 12 are mounted on the upper surface of the substrate 10, wire pads 15 for supplying power to each light-emitting element 12 are provided. For example, when 96 light-emitting elements 12 are provided, 52 wire pads 15 are provided on each side, for a total of 104. Wires are bonded to each wire pad 15 and connected to an external power source. Thereby, each light-emitting element 12 can be individually controlled.

[0014] A light-shielding layer 13 is provided between the light-emitting elements 12. The light-shielding layer 13 covers at least a part, for example, the whole of the side surface of the light-emitting element 12. The light-shielding layer 13 is a layer that blocks the propagation of light between the light-emitting elements 12, and may be a light-reflecting layer that reflects light or a light-absorbing layer that absorbs light. When the light-shielding layer 13 is a light-reflecting layer, it can be formed of, for example, a white resin. When the light-shielding layer 13 is a light-reflecting layer, while maintaining a high contrast, the light extraction efficiency is improved, and the luminance and luminous flux are improved. On the other hand, when the light-shielding layer 13 is a light-absorbing layer, it can be formed of, for example, a black resin. The black resin can be formed, for example, by incorporating carbon particles made of carbon powder or metal particles made of aluminum (Al) or the like into a silicone resin. When the light-shielding layer 13 is a light-absorbing layer, the contrast is further improved. The light-shielding layer 13 may be formed of a resin or ceramic of a color other than white and black. In FIG. 1, the light-shielding layer 13 is not shown. A phosphor layer 14 is provided on the light-emitting element 12 and the light-shielding layer 13. The phosphor layer 14 is continuously formed on all of the light-emitting elements 12 and the light-shielding layer 13.

[0015] As shown in FIG. 3, in the phosphor layer 14, a plurality of phosphor particles 16 are provided. The phosphor particles 16 absorb blue light and emit yellow light, for example. Further, a glass layer 17 is provided in the phosphor layer 14. The glass layer 17 is made of silica (SiO2) and covers the surface of the phosphor particles 16. The glass layer 17 binds the phosphor particles 16 to each other, the light-emitting element 12 and the phosphor particles 16, and the light-shielding layer 13 and the phosphor particles 16, and holds the phosphor particles 16 in the phosphor layer 14. Further, the glass layer 17 protects the phosphor particles 16 from moisture in the air and the like. An air layer 18 is formed between the phosphor particles 16, between the light-emitting element 12 and the phosphor particles 16, and between the light-shielding layer 13 and the phosphor particles 16.

[0016] Hereinafter, an example of the dimensions of each part will be shown. The shape of the light-emitting element 12 is flat, for example, 1 mm (millimeter) in length, 1 mm in width, and 150 μm (micrometer) in height. The thickness of the phosphor layer 14 is, for example, 40 μm. The diameter of the phosphor particles 16 is, for example, 2 to 23 μm, and for example, 5 to 15 μm. The thickness of the glass layer 17 is, for example, 1 μm.

[0017] Next, the operation of the light-emitting device according to this embodiment will be described. FIG. 4 is a cross-sectional view showing the operation of the light-emitting device according to this embodiment. As shown in FIG. 4, when power is supplied to the light-emitting element 12 via the substrate 10, the light-emitting element 12 emits blue light. When this blue light is absorbed by the phosphor particles 16 in the phosphor layer 14, the phosphor particles 16 emit yellow light. As a result, white light is emitted from the entire phosphor layer 14. Each light-emitting element 12 can be independently controlled. FIG. 4 shows the case where the light-emitting element 12 at the left end of the figure is lit and the other light-emitting elements 12 are turned off. The broken line L with arrows shown in FIG. 4 indicates an example of the light path.

[0018] As shown by the broken line L, when the blue light emitted from the light-emitting element 12 and the yellow light emitted from the phosphor particles 16 are about to enter the glass layer 17 from the air layer 18 within the phosphor layer 14, the probability that these lights are reflected at the interface between the air layer 18 and the glass layer 17 is high. Therefore, the lateral propagation of light within the phosphor layer 14, that is, the propagation in the arrangement direction of the light-emitting elements 12 is inhibited. As a result, most of the blue light emitted from a certain light-emitting element 12 and most of the yellow light radiated from the phosphor particles 16 by this blue light are emitted from the region corresponding to the directly above region of this light-emitting element 12 in the phosphor layer 14. Therefore, when the light-emitting device 1 is viewed from the outside, the contrast between the lit region and the unlit region is high.

[0019] Next, the manufacturing method of the light-emitting device according to this embodiment will be described. FIGS. 5A to 5D, FIG. 6, FIGS. 7A to 7C are diagrams showing the manufacturing method of the light-emitting device according to this embodiment.

[0020] First, as shown in FIG. 5A, phosphor particles 16 are prepared. Next, as shown in FIG. 5B, a large number of phosphor particles 16, polysilazane, and an organic solvent are mixed to prepare a slurry material 50. The structural formula of the polysilazane is as shown in FIG. 5C. As the organic solvent, for example, heptane or dibutyl ether is used. Note that the organic solvent may not be included. The slurry material 50 does not contain a resin material.

[0021] On the other hand, as shown in FIG. 5D, a plurality of light-emitting elements 12 are mounted on a substrate 10 via bumps 11. Next, a light-shielding layer 13 made of, for example, a white resin or a black resin is formed between and around the light-emitting elements 12. Thereby, a base 51 is manufactured.

[0022] Next, as shown in FIG. 6, for example, the slurry material 50 is sprayed and applied onto the base 51 heated to a temperature of 60 degrees. At this time, the slurry material 50 is sprayed while being stirred by a stirring means 53 in a container 52. Thereby, in the slurry material 50, the dispersed state of the phosphor particles 16 can be uniformly maintained. The organic solvent contained in the slurry material 50 starts to evaporate immediately after being sprayed onto the base 51.

[0023] Next, as shown in FIG. 7A, the base 51 onto which the slurry material 50 has been sprayed is heated to a temperature of 180 degrees in, for example, the air. Thereby, the slurry material 50 is fired, the organic solvent contained in the slurry material 50 further evaporates, and the polysilazane reacts with moisture in the air.

[0024] Thereby, as shown in FIG. 7B, the polysilazane is converted to silica on the surface of the phosphor particles 16 to form a glass layer 17. The structural formula of the silica is as shown in FIG. 7C. The phosphor particles 16 are bonded to each other via the glass layer 17. Also, at this stage, the organic solvent is substantially completely removed, and an air layer 18 is formed between the phosphor particles 16. As a result, a phosphor layer 14 is formed. In this way, the light-emitting device 1 according to the present embodiment is manufactured.

[0025] Next, a usage example of the light-emitting device according to this embodiment will be described. FIG. 8 is a cross-sectional view showing a high-beam unit equipped with the light-emitting device according to this embodiment. FIG. 9 is a diagram showing the operation of a headlamp equipped with the light-emitting device according to this embodiment.

[0026] As shown in FIG. 8, the light-emitting device 1 is mounted on the high-beam unit 70. In the high-beam unit 70, a heat sink 71 is provided, and the substrate 10 (see FIG. 2) of the light-emitting device 1 is joined to the heat sink 71. Further, an optical system 72 is provided on the light-emitting surface side of the light-emitting device 1. In the optical system 72, one or more convex lenses 74 and one or more concave lenses 75 are provided in a housing 73. The optical system 72 emits the light incident from each light-emitting element 12 of the light-emitting device 1 in mutually different directions. The high-beam unit 70 may be provided with a control circuit for individually controlling the light-emitting elements 12. The high-beam unit 70 constitutes a headlamp of an automobile together with a low-beam unit, a small lamp unit, and the like.

[0027] FIG. 9 is a diagram schematically showing the view seen from the driver of an automobile. As shown in FIG. 9, among the headlamps equipped with the light-emitting device 1 according to this embodiment, the low-beam unit is not an ADB (adaptive driving beam headlamp), and the low-beam unit projects light over the entire low-beam region RL.

[0028] On the other hand, the high-beam unit 70 is an ADB. In the high-beam unit 70, by individually turning on or off the light-emitting elements 12, the high-beam region RH can be divided into the same number of regions as the light-emitting elements 12, and selective light projection can be performed on an arbitrary region. For example, when 96 light-emitting elements 12 are arranged in a 4-row and 24-column matrix in the light-emitting device 1, the high-beam region RH can be divided into a total of 96 regions of 4 rows in the vertical direction and 24 columns in the horizontal direction, and it is possible to select whether to project light on each region.

[0029] For example, in the example shown in FIG. 9, in the high beam region RH, light is projected onto regions other than the rear glass of the preceding vehicle 81, and light is projected onto regions other than the front glass of the oncoming vehicle 82. By reducing the light intensity when projecting onto the sign 83, the reflected glare can be reduced. By irradiating the body parts of the pedestrians 84 and 85 with strong light without projecting light onto their heads, the presence of the pedestrians 84 and 85 can be emphasized. As a result, the visibility for the driver of the host vehicle is improved without dazzling the driver of the preceding vehicle 81, the driver of the oncoming vehicle 82, the pedestrians 84 and 85. Furthermore, the distance ahead on the road can be illuminated. Note that the preceding vehicle 81, the oncoming vehicle 82, the sign 83, the pedestrians 84 and 85 are automatically recognized by sensors.

[0030] Next, the effects of the present embodiment will be described. In the present embodiment, in the process shown in FIG. 5B, a slurry material 50 containing phosphor particles 16 and polysilazane and not containing a resin material is produced. In the process shown in FIG. 6, the slurry material 50 is sprayed onto the substrate 51. In the process shown in FIG. 7A, the slurry material 50 is fired. As a result, the polysilazane contained in the slurry material 50 is converted into silica, and as shown in FIG. 3, the phosphor particles 16 are bonded to each other by the glass layer 17, and an air layer 18 is formed between the phosphor particles 16. As a result, as shown in FIG. 4, since light is reflected at the interface between the air layer 18 and the glass layer 17, the lateral propagation of light within the phosphor layer 14 can be suppressed. Thereby, the contrast between the lit region and the unlit region in the light-emitting device 1 can be improved.

[0031] As a result, for example, as shown in FIGS. 8 and 9, when the light-emitting device 1 is used as a light source for ADB, the difference in light intensity between the region where light is to be projected and the region where light is not to be projected can be increased. As a result, it can contribute to the safe driving of the vehicle.

[0032] Further, by spraying the slurry material 50 without containing a resin material, it can be applied thinly and uniformly over the entire upper surface of the substrate 51. Thereby, a phosphor layer 14 with a thin and uniform thickness can be formed. By forming the phosphor layer 14 thinly, the lateral propagation of light within the phosphor layer 14 can be more effectively suppressed, and the contrast can be further improved. In addition, color unevenness of the light emitting surface due to thickness variation of the phosphor layer can be reduced, and a more uniform irradiation surface can be obtained.

[0033] Furthermore, in the present embodiment, since the phosphor layer 14 is in contact with the light emitting element 12, heat is easily dissipated from the phosphor layer 14 through the light emitting element 12. Thereby, for the phosphor particles 16 and the light shielding layer 13, deterioration of temperature characteristics and resin deterioration due to high temperature can be suppressed.

[0034] Moreover, in the present embodiment, the phosphor layer 14 does not contain a resin material and is formed of an inorganic material. Therefore, the light emitting device 1 according to the present embodiment has high reliability. In particular, it has high reliability when driven in a high temperature environment.

[0035] <Second Embodiment> Next, the second embodiment will be described. FIG. 10 is a cross-sectional view showing a light emitting device according to the present embodiment. FIG. 11 is a partially enlarged cross-sectional view showing region B of FIG. 10.

[0036] As shown in FIGS. 10 and 11, the light emitting device 2 according to the present embodiment is different from the light emitting device 1 (see FIGS. 1 to 3) according to the aforementioned first embodiment in that a light shielding layer 21 is provided and a filler 22 is contained in the phosphor layer 14.

[0037] The light-shielding layer 21 is disposed between the light-emitting elements 12 and penetrates vertically through the upper portion of the light-shielding layer 13 and the entire phosphor layer 14. Similar to the light-shielding layer 13, the light-shielding layer 21 may be, for example, a light-reflecting layer made of a white resin or a light-absorbing layer made of a black resin. For example, by forming the light-shielding layer 13 with a white resin and the light-shielding layer 21 with a black resin, high luminance and high contrast can be achieved simultaneously for the entire light-emitting device 2. The filler 22 is, for example, ceramic particles made of silicon oxides such as SiO2, titanium oxides such as TiO2, or aluminum oxides such as Al2O3, or metal particles made of aluminum (Al) or the like.

[0038] The light-emitting device 2 according to this embodiment can be manufactured by spraying a slurry material 50 mixed with the filler 22 in the process shown in FIG. 5B onto a substrate 51 in the process shown in FIG. 6, forming a groove by half-dicing between the light-emitting elements 12 after firing the phosphor layer 14, and embedding the light-shielding layer 21 in this groove.

[0039] In this embodiment, the phosphor layer 14 is segmented by the light-shielding layer 21 for each light-emitting element 12, and excessive phosphor particles 16 are removed from between the light-emitting elements 12, so that the contrast can be further improved.

[0040] Also, since the filler 22 is contained in the phosphor layer 14, the surface of the phosphor layer 14 can be modified. Further, since the filler 22 is contained in the phosphor layer 14, the viscosity of the slurry material 50 increases, making it easier to handle the slurry material 50. Furthermore, the dispersion of the phosphor particles 16 can be made more uniform, reducing coating unevenness. The configurations, manufacturing methods, operations, and effects other than those described above in this embodiment are the same as those of the aforementioned first embodiment.

[0041] <Third Embodiment> Next, the third embodiment will be described. FIG. 12 is a partially enlarged cross-sectional view showing the light-emitting device according to this embodiment.

[0042] As shown in FIG. 12, in the light-emitting device 3 according to the present embodiment, a resin layer 31 is provided in the lowermost layer portion of the phosphor layer 14. The resin layer 31 is made of, for example, a silicone resin, is in contact with the light-emitting element 12 and the light-shielding layer 13, and its thickness is less than the diameter of the phosphor particles 16, for example, 1 to 10 μm. The lower part of the lowermost phosphor particles 16 in the phosphor layer 14 is embedded in the resin layer 31.

[0043] When manufacturing the light-emitting device 3 according to the present embodiment, after the step of producing the substrate 51 shown in FIG. 5D and before the step of spraying the slurry material 50 shown in FIG. 6, as a pretreatment for spray coating, a resin material, for example, a silicone resin, is thinly applied. This application is performed, for example, by a spin coating method or a spray method. Thereby, the resin layer 31 is formed on the upper surface of the substrate 51.

[0044] As a result, in the step shown in FIG. 6, when the slurry material 50 is sprayed, among the phosphor particles 16 contained in the slurry material 50, the lower parts of some of the phosphor particles 16 are buried in the resin layer 31. Thereby, the phosphor particles 16 can be stably arranged on the upper surface of the substrate 51, and the arrangement of the phosphor particles 16 is made uniform. As a result, variations in the adhesion thickness of the phosphor particles 16 can be reduced, and color unevenness of light emission can be suppressed.

[0045] Since the resin layer 31 is thinner than the phosphor layer 14, the action of transmitting light in the lateral direction is small, and the influence on the contrast is small. However, depending on the design of the headlamp, there may be cases where it is better to propagate light somewhat in the lateral direction within the light-emitting element 3. In this case, the resin layer 31 is formed thicker. The configurations, manufacturing methods, operations, and effects other than those described above in the present embodiment are the same as those of the first embodiment described above.

[0046] As a pretreatment for spray coating the slurry material 50, polysilazane may be applied on the substrate 51. Thereby, instead of the resin layer 31, a thin glass layer is formed. Also by this, the same effects as in the present embodiment can be obtained.

[0047] In each of the above embodiments, an example of applying the light-emitting device to ADB has been shown, but the application range of the light-emitting device is not limited to this. For example, it may be applied to a spotlight or projection mapping. In this case, the emission color may be made different for each light-emitting element.

[0048] Each of the above-described embodiments is an example embodying the present invention, and the present invention is not limited to these embodiments. For example, in each of the above-described embodiments, those in which some components or steps are added, deleted, or changed are also included in the present invention. Also, each of the above-described embodiments can be implemented in combination with each other.

[0049] <Test Example> Next, test examples will be described. This test example is an example in which the light-emitting devices according to the first and second embodiments described above are observed with a microscope. FIG. 13A is an optical micrograph of the light-emitting device according to the first embodiment, FIG. 13B is its SEM micrograph, and FIG. 13C is an SEM micrograph showing region C of FIGS. 13A and 13B. FIG. 14A is an optical micrograph of the light-emitting device according to the second embodiment, FIG. 14B is its SEM micrograph, and FIG. 14C is an SEM micrograph showing region D of FIGS. 14A and 14B.

[0050] In this test example, according to the method described in the first embodiment, a sample S1 corresponding to the light-emitting device 1 according to the first embodiment and a sample S2 corresponding to the light-emitting device 2 according to the second embodiment were produced. Then, these samples were embedded in a resin for cross-section hardening, cut and polished to obtain samples for cross-section observation. And these samples were observed with an optical microscope and an SEM.

[0051] In sample S1, the light-shielding layer 13 was formed of a white silicone resin, the phosphor layer 14 was formed of a glass material and phosphor particles 16, and the thickness of the phosphor layer 14 was set to 50 μm. The phosphor particles 16 were formed of YAG, and the average particle diameter of the phosphor particles 16 was set to 16 μm. As shown in FIGS. 13A to 13C, in sample S1, an air layer 18 was observed in the phosphor layer 14. Note that the air layer 18 appears black in the SEM photograph.

[0052] In sample S2, the light-shielding layer 13 was formed of a white silicone resin, the phosphor layer 14 was formed of a glass material, phosphor particles 16, and nanofillers, and the thickness of the phosphor layer 14 was set to 30 μm. The mass ratio of (glass material:phosphor particles:nanofillers) in the phosphor layer 14 was set to (100:50:1). The phosphor particles 16 were formed of YAG, the average particle diameter of the phosphor particles 16 was set to 10 μm, and the nanofillers were formed of silica. As shown in FIGS. 14A to 14C, in sample S2, the nanofillers could not be observed, but the air layer 18 was observed.

Industrial Applicability

[0053] The present invention can be used, for example, as a light source for lighting devices such as headlamps and spotlights, and as a light source for display devices such as projection mapping.

Description of Reference Numerals

[0054] 1, 2, 3: Light-emitting device 10: Substrate 11: Bump 12: Light-emitting element 13: Light-shielding layer 14: Phosphor layer 15: Wire pad 16: Phosphor particles 17: Glass layer 18: Air layer 21: Light-shielding layer 22: Filler 31: Resin layer 50: Slurry material 51: Substrate 52: Container 53: Stirring means 70: High beam unit 71: Heat sink 72: Optical system 73: Housing 74: Convex lens 75: Concave lens 81: Leading vehicle 82: Oncoming vehicle 83: Sign 84, 85: Pedestrian RH: High beam area RL: Low beam area S1, S2: Sample

Claims

1. A substrate, a plurality of light-emitting elements mounted on the substrate and arranged in a matrix, a phosphor layer provided on the plurality of light-emitting elements, a plurality of wire pads provided on both sides of a region on the upper surface of the substrate where the plurality of light-emitting elements are mounted, a light-shielding layer disposed between the plurality of light-emitting elements and between the substrate and the light-emitting elements, covering at least a part of the side surface of the light-emitting elements, comprising: the phosphor layer is also disposed on the light-shielding layer, in a top view, a region where the light-shielding layer and the phosphor layer are in contact is in a lattice shape surrounding each of the plurality of light-emitting elements, the phosphor layer, a plurality of phosphor particles, a glass layer covering the surface of the phosphor particles, having: the phosphor particles are bonded to each other via the glass layer, an air layer is formed between the phosphor particles, the plurality of light-emitting elements are light-emitting devices that can be independently controlled.

2. The light-emitting device according to claim 1, wherein the phosphor layer further has a filler.

3. In a top view, the substrate is rectangular, The light-emitting device according to claim 1 or 2, wherein the wire pads are arranged in a row along a pair of long sides of the substrate, respectively.

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