Light-emitting device

Abstract

To provide a light-emitting device capable of improving the extraction efficiency of emitted light.SOLUTION: A light-emitting device includes a light-emitting element including a semiconductor structure layer having a light-emitting layer, a phosphor layer formed on the light-emitting element and including a phosphor that is excited by light emitted from the light-emitting layer and emits fluorescence, a light-transmitting layer formed on the phosphor layer and having a transparent layer with a side surface that slopes outwardly as it faces upward, and a wire grid portion formed on the light-transmitting layer and including a light-transmitting substrate and a wire grid made of a plurality of linear metal bodies each arranged in a periodic row on the upper surface of the light-transmitting substrate.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a light-emitting device including a light-emitting element. [Background technology]

[0002] Light-emitting devices having a polarizing layer that transmits specific light have been disclosed. For example, Patent Document 1 discloses a light-emitting device including a light-emitting element (LED die), a phosphor layer formed on one main surface of the light-emitting element, a light polarizing layer made of a wire grid formed on the phosphor layer, and a light-reflecting layer formed on the other main surface of the light-emitting element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2011-501460 Summary of the Invention [Problem to be solved by the invention]

[0004] In the light emitting device described in Patent Document 1, of the light that reaches the light polarization layer, the polarized component having a vibration direction perpendicular to the longitudinal direction of the wire grid is transmitted through the light polarization layer, while the polarized component parallel to the longitudinal direction is reflected by the light polarization layer. Furthermore, even if the polarized component has a vibration direction perpendicular to the longitudinal direction of the wire grid, the component that enters the light polarization layer from the phosphor layer at an angle exceeding the critical angle is totally reflected.

[0005] In the light-emitting device described in Patent Document 1, for example, the component reflected by the light polarizing layer as described above may be reflected by the light reflecting layer and enter the light polarizing layer again. However, even when light is reflected by the light polarizing layer, a portion of the light is absorbed by the light polarizing layer, and therefore, the more light is reflected between the light polarizing layer and the light reflecting layer, the more the light extraction efficiency of the light-emitting device as a whole may decrease.

[0006] The present invention has been made in view of the above-mentioned points, and has an object to provide a light emitting device that can improve the extraction efficiency of emitted light. [Means for solving the problem]

[0007] The light emitting device according to the present invention is characterized by comprising: a light emitting element including a semiconductor structure layer having a light emitting layer; a phosphor layer formed on the light emitting element and including a phosphor that is excited by light emitted from the light emitting layer and emits fluorescence; a light-transmitting layer formed on the phosphor layer and having a transparent layer with a side surface that slopes outwardly as it faces upward; and a wire grid portion formed on the light-transmitting layer and including a light-transmitting substrate and a wire grid made of a plurality of linear metal bodies that are each periodically arranged in rows on the upper surface of the light-transmitting substrate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a top view of the light emitting device according to the first embodiment. [Figure 2] 1 is a cross-sectional view of a light emitting device according to a first embodiment. [Figure 3] FIG. 2 is a diagram schematically illustrating the refractive index distribution of a light-transmitting layer. [Figure 4] FIG. 2 is a cross-sectional view showing a simulation model for verifying the light emitting device according to the first embodiment. [Figure 5] 10 is a graph showing the ratio of luminous flux to the angle formed between the top surface and the side surface of a light-transmitting layer in a simulation model. [Figure 6] 10 is a graph showing the ratio of luminous flux to the angle formed between the top surface and the side surface of a light-transmitting layer in a simulation model. [Figure 7] 10 is a graph showing the ratio of luminous flux to the angle formed between the top surface and the side surface of a light-transmitting layer in a simulation model. [Figure 8] FIG. 10 is a cross-sectional view showing a modified example of the simulation model. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals. [Example]

[0010] [Outline of Light-Emitting Device 100] The configuration of a light emitting device 100 according to Example 1 will be described with reference to Figures 1 and 2. Figure 1 is a top view of the light emitting device 100 according to Example 1. Figure 2 is a cross-sectional view of the light emitting device 100 shown in Figure 1 taken along line 2-2.

[0011] The light emitting device 100 includes a substrate structure 11, a light emitting element 12, a phosphor layer 13, a light-transmitting layer 14, a wire grid portion 15, and a covering member 16. In Fig. 2, the vertical direction in the drawing corresponds to the height direction of the light emitting device 100, and the horizontal direction in the drawing corresponds to the width direction of the light emitting device 100. In Fig. 2, a central axis CL passing through the center of the upper surface when the light emitting device 100 is viewed from above is indicated by a two-dot chain line.

[0012] [Substrate structure 11] First, a description will be given of the configuration of substrate structure 11. Substrate structure 11 has flat plate portion 21 having a rectangular top surface shape, and frame body portion 22 having a frame shape formed along the outer edge of the top surface of flat plate portion 21.

[0013] That is, the substrate structure 11 is a concave structure configured so that the upper surface of the flat plate portion 21 is exposed by the frame portion 22. The substrate structure 11 is made of a material having electrical insulation properties and light reflectivity, such as aluminum oxide (Al2O3).

[0014] [Light-emitting element 12] Next, a description will be given of the configuration of the light emitting element 12. The light emitting element 12 is a light emitting diode (LED) having a rectangular top surface provided on the top surface of the flat plate portion 21. The light emitting element 12 is configured to include a semiconductor structure layer 24 and a transparent substrate 25.

[0015] The semiconductor structure layer 24 is a semiconductor laminate consisting of an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer (none of which are shown), each of which is made primarily of gallium nitride (GaN). When the light-emitting device 100 is driven, blue light having a peak wavelength of approximately 450 nm is emitted from the light-emitting layer of the semiconductor structure layer 24.

[0016] The transparent substrate 25 is a flat substrate provided on the semiconductor structure layer 24. The transparent substrate 25 is made of a material such as sapphire (Al2O3) that is translucent to the blue light emitted from the light emitting layer of the semiconductor structure layer 24. The transparent substrate 25 also serves as a growth substrate for growing semiconductor crystals that will become the semiconductor structure layer 24 described above.

[0017] In the light emitting device 100, the light emitting element 12 has an n-electrode and a p-electrode (not shown) connected to the n-type semiconductor layer and the p-type semiconductor layer of the semiconductor structure layer 24, which are electrically connected to wiring pads (not shown) formed on the upper surface of the flat plate portion 21. That is, in the light emitting device 100, the light emitting element 12 is flip-chip mounted on the flat plate portion 21.

[0018] [Phosphor layer 13] Next, we will explain the phosphor layer 13. The phosphor layer 13 is a plate-like body with a rectangular upper surface that is provided on the upper surface of the transparent substrate 25 of the light-emitting element 12. The phosphor layer 13 has the same size as the light-emitting element 12 in a plan view when the phosphor layer 13 is viewed from above.

[0019] Phosphor layer 13 is made of a phosphor that emits fluorescence when excited by blue light as excitation light emitted from light emitting element 12. The fluorescence emitted from the phosphor when excited by blue light has a broad green to orange wavelength range spanning 480 to 700 nm, and has a yellow peak wavelength at 520 to 570 nm.

[0020] The phosphor layer 13 is, for example, a ceramic phosphor plate made of an alumina (Al2O3) or silicon dioxide (SiO2) medium containing yttrium aluminum garnet (YAG:Ce) phosphor particles activated with cerium (Ce).

[0021] The phosphor layer 13 is not limited to a phosphor plate containing YAG:Ce phosphor particles. For example, it may be a phosphor plate in which YAG, the base material of the phosphor particles, is used as a medium. In this case, the phosphor layer 13 may be a polycrystalline or single crystalline material. For example, the phosphor layer 13 may be formed by dispersing phosphor particles such as YAG:Ce in a translucent resin such as silicone resin.

[0022] When excitation light (blue light) emitted from light-emitting element 12 is incident on phosphor layer 13, part of the light passes through phosphor layer 13 as is, and part of the light excites the phosphors, causing the excited phosphors to emit fluorescence. Therefore, the excitation light that passed through phosphor layer 13 without contributing to the generation of fluorescence and the fluorescence emitted from the phosphors are emitted from the upper surface of phosphor layer 13.

[0023] [Transparent layer 14] Next, the light-transmitting layer 14 will be described. The light-transmitting layer 14 is provided on the upper surface of the phosphor layer 13, and is a light-transmitting body having a shape similar to an upside-down truncated quadrangular pyramid. In other words, the light-transmitting layer 14 has side surfaces 14S that slope outward from the upper surface of the phosphor layer 13 upward. In the light-emitting device 100, the light-transmitting layer 14 is a GRIN (Gradient Index) lens whose refractive index changes continuously inside.

[0024] Here, the refractive index distribution of the light-transmitting layer 14 will be described with reference to Fig. 3. Fig. 3 is a graph schematically showing only the light-transmitting layer 14 extracted from Fig. 2 and the refractive index distribution of the light-transmitting layer 14 in the width direction.

[0025] 3, the horizontal axis represents the distance from the central axis CL passing through the light-transmitting layer 14, i.e., the distance from a point on the central axis CL in the width direction of the light-transmitting layer 14, and the vertical axis represents the refractive index within the light-transmitting layer 14. In the following description, the light-transmitting layer 14 will be described as having a shape of an inverted square truncated pyramid.

[0026] In the light-emitting device 100, the refractive index of the light-transmitting layer 14 is highest at the portion where the central axis CL passes, as shown in Fig. 3, and decreases from the central axis CL toward the side surface 14S, i.e., the farther away from the central axis CL. Therefore, the refractive index of the light-transmitting layer 14 is lowest at the outer edge of the upper surface. Note that the refractive index of the light-transmitting layer 14 in the vertical direction in the figure, i.e., from the upper surface to the lower surface of the light-transmitting layer 14, is constant.

[0027] Here, if the maximum refractive index of the light-transmitting layer 14 is defined as maximum refractive index n1, the minimum refractive index is defined as minimum refractive index n2, and the refractive index at a position r away from the center of the light-transmitting layer 14 in the width direction is defined as n(r), the refractive index n(r) is expressed by the following Equation 1 using the maximum refractive index n1, where √A is a gradient coefficient.

[0028]

number

[0029] In this case, if the length of one side of the upper surface of the light-transmitting layer 14 is length D, the minimum refractive index n2 is given by the following formula 2, because the longest distance from the central axis CL is half the length of the diagonal of the square (√2D / 2). Furthermore, the length D is given by the following formula 3, which is derived from formula 2.

[0030]

number

[0031]

number

[0032] Furthermore, if the lens pitch of the light-transmitting layer 14 is the pitch P and the thickness of the light-transmitting layer 14 is the thickness T, the relationship between the pitch P and the thickness T is expressed by the following Formula 4. Therefore, the gradient coefficient √A is expressed by Formula 5, which is derived from Formula 4.

[0033]

number

[0034]

number

[0035] In the light emitting device 100 of this embodiment, the maximum refractive index n1 of the light transmitting layer 14 is greater than the refractive index of the phosphor layer 13, and the minimum refractive index n2 of the light transmitting layer 14 is smaller than the refractive index of the phosphor layer.

[0036] The light-transmitting layer 14 is made of glass that is translucent to the blue light emitted from the light-emitting element 12 and the yellow fluorescence emitted from the phosphor layer 13. The light-transmitting layer 14 is manufactured, for example, by forming a radial refractive index distribution in a cylindrical rod made of glass by ion exchange treatment, and then processing the rod after the refractive index distribution formation into a quadrangular pyramid shape.

[0037] [Wire grid section 15] 2, the configuration of the wire grid section 15 will be described. The wire grid section 15 includes a light-transmitting substrate 27 and a wire grid .

[0038] The light-transmitting substrate 27 is a flat substrate with a rectangular upper surface that is provided on the upper surface of the light-transmitting layer 14. When viewed from above, the light-transmitting substrate 27 has the same size as the upper surface of the light-transmitting layer 14. The light-transmitting substrate 27 is made of a material such as glass that is transparent to the above-mentioned blue light and yellow fluorescence.

[0039] In the light emitting device 100 of this embodiment, the refractive index of the light-transmitting substrate 27 is smaller than the maximum refractive index n1 and equal to or larger than the minimum refractive index n2 of the light-transmitting layer 14. The refractive index of the light-transmitting substrate 27 is also smaller than the refractive index of the phosphor layer 13.

[0040] Wire grid 28 is configured by forming a row of a plurality of linear metal bodies on the upper surface of light-transmitting substrate 27. As shown in Fig. 1, wire grid 28 has each metal body extending from one to the other of two opposing sides of the upper surface of light-transmitting substrate 27. Wire grid 28 is made of, for example, aluminum (Al).

[0041] In the wire grid 28, each of the metal bodies is arranged on the upper surface of the light-transmitting substrate 27 at a period P shorter than the wavelength of the blue light and the yellow fluorescent light. w The period P w For example, the width W of each metal body is 150 nm. w is 60 nm, and the height H w is 165 nm.

[0042] In the wire grid 28, the period P w By setting as above, of the blue light and yellow fluorescence, TM polarized light, which is a component having an electric field vector perpendicular to the longitudinal direction of the wire grid 28, is transmitted through the wire grid 28, and TE polarized light, which is a component having an electric field vector parallel to the longitudinal direction, is reflected by the wire grid 28. In other words, the wire grid section 15 functions as a polarizing layer that transmits only light vibrating in a specific direction and reflects light vibrating in other directions.

[0043] The wire grid 28 can be formed, for example, by forming a metal film made of Al on the entire upper surface of the light-transmitting substrate 27 by ion beam deposition, forming a resist mask on the upper surface of the area that will become the wire grid 28, and then removing the metal film in the unmasked areas by dry etching.

[0044] [Covering material 16] Next, we will explain the configuration of the covering member 16. The covering member 16 is a resin member that continuously covers the side surfaces of the light emitting element 12, the side surfaces of the phosphor layer 13, and the side surfaces of the light-transmitting substrate 27 of the wire grid portion 15.

[0045] The covering member 16 is configured to include, for example, a translucent silicone resin as a matrix material and white titanium dioxide (TiO2) particles as light-scattering particles dispersed in the matrix material.

[0046] The covering member 16 has the above-described configuration and reflects light in the visible light range that is incident on the covering member 16. Therefore, the covering member 16 reflects blue light emitted from the light-emitting element 12 and yellow light emitted from the phosphor layer 13.

[0047] [Improved light extraction efficiency] Here, an improvement in the extraction efficiency of light emitted from the light emitting device 100 will be described with reference to FIG.

[0048] As described above, in the wire grid section 15, of the light incident on the wire grid section 15, TM polarized light, which is a component having an electric field vector perpendicular to the longitudinal direction of the wire grid 28, passes through the wire grid 28, and TE polarized light, which is a component having an electric field vector parallel to the longitudinal direction, is reflected by the wire grid 28.

[0049] At this time, for example, fluorescent components of the fluorescent light emitted from the fluorescent material layer 13 that are incident on the wire grid section 15 at an angle exceeding the critical angle are totally reflected by the wire grid section 15 even if they are TM polarized light.

[0050] The TM polarized light reflected by the wire grid portion 15 is reflected by, for example, the upper surface of the phosphor layer 13 or the upper surface of the flat plate portion 21, and the incident angle when it enters the wire grid portion 15 again changes.

[0051] For example, if the incident angle of TM polarized light reflected by the upper surface of the phosphor layer 13 to the wire grid section 15 is equal to or less than the critical angle, the light passes through the wire grid section 15; otherwise, the light is repeatedly reflected between the wire grid section 15 and the phosphor layer 13 until the incident angle becomes equal to or less than the critical angle.

[0052] Once the fluorescence emitted from the phosphor layer 13 enters the wire grid section 15, a portion of the fluorescence is absorbed by the wire grid section 15. Therefore, even if TM polarized light is repeatedly reflected between the wire grid section 15 and the phosphor layer 13 and then passes through the wire grid section 15, the resulting luminous flux will be smaller than the TM polarized light flux that passes through the wire grid section 15 without being reflected even once.

[0053] Therefore, for example, if the TM-polarized fluorescence incident on the wire grid section 15 contains many components exceeding the critical angle, the overall luminous flux obtained will be small even if the light is repeatedly reflected and then transmitted through the wire grid section 15. In other words, there is a risk that the extraction efficiency of light extracted from the light emitting device 100 will decrease.

[0054] In the light-emitting device 100 of this embodiment, as described above, the refractive index of the light-transmitting layer 14 decreases from the central axis CL toward the side surface 14S. Therefore, for example, fluorescence emitted from the phosphor layer 13 and incident on the center of the lower surface of the light-transmitting layer 14 is refracted in a curved direction from the central axis CL of the light-transmitting layer 14 toward the side surface 14S toward the upper surface of the light-transmitting layer 14, as shown by the dashed arrow in Fig. 2 .

[0055] Therefore, in the light emitting device 100, the fluorescent component emitted at a larger angle relative to the central axis CL, i.e., the fluorescent component that may have a larger incident angle when entering the wire grid section 15, is refracted so as to bend more within the light-transmitting layer 14.

[0056] Therefore, in the light emitting device 100 of this embodiment, even TM polarized light that exceeds the critical angle when emitted from the phosphor layer 13 is likely to become equal to or smaller than the critical angle by being refracted within the light-transmitting layer 14. That is, according to the light emitting device 100 of this embodiment, the provision of the light-transmitting layer 14 makes it possible to reduce the amount of fluorescent components reflected by the wire grid portion 15.

[0057] Therefore, according to the light-emitting device 100 of this embodiment, it is possible to increase the amount of fluorescent components emitted from the phosphor layer 13 and transmitted through the wire grid portion 15, thereby improving the extraction efficiency of the emitted light compared to, for example, a light-emitting device having a light-transmitting layer 14 that does not have the refractive index distribution described above.

[0058] Furthermore, in the light emitting device 100 of this embodiment, as described above, the side surface 14S is inclined outward toward the upper side of the light-transmitting layer 14. Because the side surface 14S is inclined outward in this manner, the light emitting device 100 can obtain a higher light extraction efficiency than a light emitting device in which the side surface 14S is perpendicular to the upper surface of the phosphor layer 13.

[0059] Specifically, in the light-emitting device 100 of this embodiment, by tilting the side surface 14S outward, the distance from the center of the light-transmitting layer 14 to the side surface 14S is longer than when, for example, the side surface 14S is perpendicular to the upper surface of the phosphor layer 13. Therefore, in the light-emitting device 100 of this embodiment, for example, light traveling laterally from the center of the light-transmitting layer 14 is more likely to travel upward due to the refractive index distribution before reaching the side surface 14S, as shown in Fig. 2. In other words, in the light-emitting device 100, the refractive index distribution of the light-transmitting layer 14 makes it difficult for light to be reflected by the side surface 14S.

[0060] Here, the light reflected by the side surface 14S travels within the light-transmitting layer 14 from the side with a smaller refractive index distribution to the side with a larger refractive index distribution, which causes a decrease in the light extraction efficiency of the light-emitting device 100, so it is desirable to suppress the reflection of light by the side surface 14S as much as possible.

[0061] In the light-emitting device 100 of this embodiment, the side surface 14S is inclined outward, which makes it easier for light traveling from the center of the light-transmitting layer 14 to enter the light-transmitting substrate 27 before reaching the side surface 14S. As a result, a higher light extraction efficiency can be obtained compared to, for example, a case where the side surface 14S is perpendicular to the top surface of the phosphor layer 13.

[0062] Furthermore, even if the fluorescence emitted from the phosphor layer 13 and traveling through the light-transmitting layer 14 reaches the side surface 14S, the fluorescence is likely to be reflected upward by the side surface 14S, and therefore, for example, a fluorescence component with an angle less than the critical angle can be converted into a fluorescence component with an angle equal to or less than the critical angle. Therefore, according to the light-emitting device 100 of this embodiment, it is possible to increase the fluorescence component traveling toward the wire-grid portion 15.

[0063] Therefore, according to the light-emitting device 100 of this embodiment, the side surface 14S is inclined outward toward the upper part of the light-transmitting layer 14, thereby improving the extraction efficiency of the emitted light compared to, for example, a light-emitting device in which the side surface 14S is perpendicular to the upper surface of the phosphor layer 13.

[0064] In the light-emitting device 100 of this embodiment, the side surfaces 14S of the light-transmitting layer 14 are inclined outward toward the upper side, and the refractive index inside the layer is continuously varied. However, the light-transmitting layer 14 may have only one of these features. That is, the light-transmitting layer 14 may have only the side surfaces 14S inclined outward, or may have the refractive index distribution described above inside the layer.

[0065] In the light-emitting device 100 of this embodiment, the light-transmitting layer 14 has been described as having the shape of an upside-down truncated square pyramid, but the shape is not limited to this. For example, if the top surface shape of the light-emitting element 12 is circular, the light-transmitting layer 14 may have the shape of an upside-down truncated cone to match the shape of the light-emitting element 12.

[0066] In the light-emitting device 100 of this embodiment, the refractive index and refractive index distribution of the light-transmitting layer 14, the phosphor layer 13, and the light-transmitting substrate 27 can be measured using an appropriate method, such as a minimum deviation method or spectroscopic ellipsometry. The magnitude relationship of the refractive indexes of the light-transmitting layer 14, the phosphor layer 13, and the light-transmitting substrate 27 can be evaluated based on the refractive index at a specific wavelength included in the wavelength band of light emitted from the upper surface of the phosphor layer 13.

[0067] In the light emitting device 100 of this embodiment, a cover film may be formed on the wire grid 28 to protect the surface thereof. For example, a cover film made of zirconium oxide (ZrO2) or silicon oxide (SiO2) may be formed on the upper surface of the light-transmitting substrate 27 or the surface of the wire grid 28 by atomic layer deposition (ALD), sputtering, CVD, or the like.

[0068] [verification] 4 to 7, the following describes the verification performed on a model simulating the light emitting device 100 of this embodiment and a model of a comparative example, and the verification results. In this verification, the luminous flux of each model and the preferable range of the angle between the upper surface and the side surface of the light-transmitting layer were verified. In this verification, the lighting design analysis software Light Tools (manufactured by Synopsys, Inc.) was used. In this verification, the refractive index shown below is the value at a wavelength of 550 nm.

[0069] 4 is a cross-sectional view of a simulation model 110 used in this verification. In this verification, model 110 is composed of a phosphor layer 31, a light-transmitting layer 32 disposed on the phosphor layer 31, and a polarizing layer 33 disposed on the light-transmitting layer 32.

[0070] In model 110, phosphor layer 31 has a square upper surface shape, with a side length D1 of 1000 μm. Phosphor layer 31 also has a thickness T1 of 100 μm and a refractive index of 1.58. It is assumed that fluorescence with a wavelength of 550 nm is scattered uniformly from the upper surface of phosphor layer 31 in a Lambertian scattering manner.

[0071] In model 110, the light-transmitting layer 32 has the shape of an upside-down truncated quadrangular pyramid, similar to the light-transmitting layer 14. In model 110, the light-transmitting layer 32 has three thicknesses T2: 300 μm, 500 μm, and 1000 μm. The angle between the top surface and the side surface of the light-transmitting layer 32 is defined as angle θ.

[0072] In the model 110 used in this verification, the refractive index of the light-transmitting layer 32 is highest in a cylindrical first region A1 that includes the central axis CL, and the refractive index decreases over a predetermined width from the first region A1 outward. Therefore, as shown by the dashed dotted line in Fig. 4, the light-transmitting layer 32 has a plurality of annular regions with a predetermined width (e.g., 0.1 mm) formed around the first region A1, each having a circular top surface. Note that the number of annular regions in Fig. 4 is merely a schematic representation, and in reality, more annular regions are formed than are shown.

[0073] In the model 110 used in this verification, the refractive index within each annular region is set to be the same. In other words, in the model 110, the refractive index of the light-transmitting layer 32 is the same from the top surface to the bottom surface of the light-transmitting layer 32. In the following description, the annular region located at the outermost periphery of the light-transmitting layer 32 and having the smallest refractive index will be referred to as the second region A2.

[0074] In the light-transmitting layer 32 of the model 110, the refractive index n1 in the first region A1 is set to be larger than the refractive index of the phosphor layer 31, and the refractive index n2 in the second region A2 is set to be smaller than the refractive index of the phosphor layer 31. For example, in the light-transmitting layer 32, the refractive index n1 in the first region A1 is set to be 1.6 to 1.8, and the refractive index n2 in the second region A2 is set to be 1.3 to 1.5.

[0075] In model 110, polarizing layer 33 is a light-transmitting plate that transmits the TM-polarized component of the fluorescence that reaches polarizing layer 33 via light-transmitting layer 32. Polarizing layer 33 also reflects 90% of the TM-polarized component of the fluorescence that exceeds the critical angle and the TE-polarized component, and absorbs 10%. Polarizing layer 33 has a refractive index of 1.51 and a thickness T3 of 700 μm.

[0076] Here, two comparative models used as comparative examples in this verification will be described. The first comparative model is a model that does not have the light-transmitting layer 32 of model 110. Specifically, the first comparative model is a model that consists only of a phosphor layer 31 and a polarizing layer 33 that have the same size.

[0077] The second comparative model has the same configuration as model 110, but differs from model 110 in that the light-transmitting layer 32 has a uniform refractive index. Specifically, in the second comparative model, the refractive index of the light-transmitting layer 32 as a whole is the refractive index n2 described above.

[0078] Fig. 5 is a graph showing the change in the luminous flux emitted from the upper surface of the polarizing layer 33 when the angle θ of the light-transmitting layer 32 of the above-mentioned model 110 is changed. In Fig. 5, the horizontal axis represents the angle θ, and the vertical axis represents the ratio of the luminous flux of model 110 to the luminous flux of the first comparative model.

[0079] 5, it can be seen that the luminous flux ratio decreases as the angle θ increases, that is, as the side surface of the light-transmitting layer 32 becomes more perpendicular to the top surface. In particular, when the thickness T2 of the light-transmitting layer 32 is 1000 μm, it can be seen that the luminous flux ratio falls below 1.0 when the angle θ exceeds 60°.

[0080] From Figure 5, it was confirmed that for the light-transmitting layer 32 of model 110, when the angle θ was set to 10° or more and 60° or less, the maximum refractive index n1 was set to 1.6 or more and 1.8 or less, the minimum refractive index n2 was set to 1.3 or more and 1.5 or less, the pitch was set to 0.01 or more and 0.03 or less, and the light-transmitting layer thickness Z was set to 0.3 mm or more and 0.5 mm or less, a higher luminous flux was generally obtained than in the first comparison model.

[0081] Fig. 6 is a graph showing the change in the luminous flux emitted from the upper surface of the polarizing layer 33 when the angle θ of the light-transmitting layer 32 of the second comparative model is changed. In Fig. 6, the horizontal axis represents the angle θ, and the vertical axis represents the ratio of the luminous flux of the second comparative model to the luminous flux of the first comparative model.

[0082] 6, it can be seen that the luminous flux ratio decreases as the angle θ increases, that is, as the side surface of the light-transmitting layer 32 becomes more perpendicular to the top surface. In particular, when the thickness T2 of the light-transmitting layer 32 is 1000 μm, it can be seen that the luminous flux ratio falls below 1.0 when the angle θ exceeds 50°.

[0083] 6, the second comparative model also achieved a higher luminous flux than the first comparative model when the angle θ was between 10° and 60°, the refractive index n2 was between 1.3 and 1.5, and the light-transmitting layer thickness Z was between 0.3 mm and 0.5 mm. In other words, it was confirmed that even if a refractive index distribution is not formed in the light-transmitting layer 32, a higher luminous flux than the first comparative model can be achieved when the refractive index of the light-transmitting layer 32 having sloped side surfaces is smaller than the refractive index of the phosphor layer and smaller than the refractive index of the light-transmitting substrate.

[0084] Fig. 7 is a graph showing the change in the luminous flux emitted from the upper surface of the polarizing layer 33 when the angle θ of the light-transmitting layer 32 of the above-mentioned model 110 is changed. In Fig. 7, the horizontal axis represents the angle θ, and the vertical axis represents the ratio of the luminous flux of model 110 to the luminous flux of the second comparative model.

[0085] 7, the luminous flux ratio increases as the angle θ increases, that is, as the side surface of the light-transmitting layer 32 becomes more perpendicular to the top surface. In particular, when the thickness T2 of the light-transmitting layer 32 is 1000 μm, the luminous flux ratio becomes greater than 1.0 when the angle θ exceeds 40°.

[0086] 5 and 7, when the light-transmitting layer 32 has a refractive index distribution, the angle θ between the upper surface and the side surface of the light-transmitting layer 32 is preferably 60° or less, and is particularly preferably in the range of 40° to 60°. Also, when the light-transmitting layer 32 does not have a refractive index distribution, the angle θ is preferably 50° or less, as shown in FIGS. 6 and 7.

[0087] Note that the model 110 used in this verification has a cylindrical first region A1 including the central axis CL of the light-transmitting layer 32 and a plurality of regions with different refractive indexes of a predetermined width around the first region A1, with the refractive index decreasing toward the periphery, but the refractive index distribution of the light-transmitting layer 32 is not limited to this. For example, the light-transmitting layer 32 may be configured at least with the above-described first region A1 and another region that is formed to surround the first region A1 and has a refractive index lower than that of the first region A1.

[0088] Specifically, the light-transmitting layer 32 may be divided into two regions: a cylindrical first region A1 that includes the central axis CL and has the highest refractive index, and a second region A2 that is a peripheral region of the first region A1 and has the lowest refractive index, as shown in a modified model 120 of Fig. 8. Furthermore, the light-transmitting layer 32 may have regions with different widths, as in the light-transmitting layer 32 of the model 120 of Fig. 8.

[0089] In the model 110 used in this verification, the refractive index was the same in each of the multiple regions with different refractive indices in the light-transmitting layer 32, but a refractive index distribution may be formed in each region. That is, a refractive index distribution may be provided in the first region A1 or the second region A2, and for example, the refractive index may decrease from the center of the first region A1 toward the outer edge of the first region A1. [Explanation of symbols]

[0090] 100 Light-emitting device 110 model 11 Substrate structure 12 Light-emitting element 13, 31 Phosphor layer 14, 32 Translucent layer 15 Wire grid section 16 Covering material 21 Flat plate part 22 Frame body part 24 Semiconductor structural layer 25 Transparent substrate 27 Transparent substrate 28 Wire Grid 33 Polarizing layer

Claims

1. a light emitting device including a semiconductor structure layer having a light emitting layer; a phosphor layer formed on the light emitting element and including a phosphor that emits fluorescence when excited by light emitted from the light emitting layer; a transparent layer formed on the phosphor layer and having an upwardly inclined side surface; a wire grid section formed on the light-transmitting layer, the wire grid section including a light-transmitting substrate and a wire grid made of a plurality of linear metal bodies periodically arranged in rows on an upper surface of the light-transmitting substrate; A light emitting device comprising:

2. 2. The light emitting device according to claim 1, wherein the refractive index of the transparent layer decreases toward the side surface of the transparent layer.

3. 3. The light emitting device according to claim 2, wherein the refractive index of the light transmitting layer decreases from a central axis passing through the center of the light transmitting layer toward the side surface in a top view of the light transmitting layer.

4. 4. The light-emitting device according to claim 2, wherein the light-transmitting layer has a first region formed from the top surface to the bottom surface inside the light-transmitting layer and having the highest refractive index within the light-transmitting layer, and a second region formed from the top surface to the bottom surface of the light-transmitting layer, including the outermost side surface of the light-transmitting layer, surrounding the first region, and having the lowest refractive index within the light-transmitting layer.

5. 5. The light emitting device according to claim 4, wherein the refractive index of the first region of the light-transmitting layer is greater than the refractive index of the phosphor layer and the refractive index of the light-transmitting substrate of the wire grid portion.

6. 6. The light emitting device according to claim 5, wherein the refractive index of the second region of the light-transmitting layer is smaller than the refractive index of the phosphor layer and the refractive index of the light-transmitting substrate of the wire grid portion.

7. The light emitting device according to claim 3 , wherein the light-transmitting layer is a GRIN lens.

8. 4. The light emitting device according to claim 1, further comprising a light-reflective covering member continuously covering each side surface of the light emitting element, the phosphor layer, the light-transmitting layer and the light-transmitting substrate.

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