Light emitting device

Abstract

To provide a light-emitting device which has less reduction in total luminous flux due to narrowing of an angle and is easily manufactured.SOLUTION: A light-emitting portion that is disposed on the substrate, includes a light-emitting layer, and emits light from the light-emitting layer as emitted light from an upper surface located on a side opposite to the substrate; An optical function portion including a pedestal portion disposed above a light emission surface of the light-emitting portion and spaced apart from an upper surface of the light-emitting portion, the pedestal portion including a plate-shaped portion extending to cover the light emission surface of the light-emitting portion in a top view, and a plurality of projections formed on the upper surface of the pedestal portion; A low refractive index portion made of a low refractive index substance having a refractive index lower than that of the optical function portion, wherein each of the plurality of convex portions is a pyramid or a truncated pyramid whose bottom surface is disposed on the upper surface of the pedestal portion.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a light emitting device including a light emitting element and a method for manufacturing the same. [Background technology]

[0002] BACKGROUND ART Light emitting devices that use light emitting elements such as light emitting diodes (LEDs) as light sources have been known.

[0003] For example, Patent Document 1 discloses a light emitting device having a semiconductor light emitting element, a wavelength conversion element and a transparent element stacked on the semiconductor light emitting element, and the transparent element is provided with multiple hemispherical protrusions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2019 / 0326490 Summary of the Invention [Problem to be solved by the invention]

[0005] In a light-emitting device such as that described in Patent Document 1, the protrusion that serves as the light-emitting surface is hemispherical, so when the angle of incidence of light on the curved surface exceeds the angle of total reflection, the light is repeatedly totally reflected at the spherical surface and returns to the light-emitting surface. This light returns to the wavelength conversion member and the light-emitting element, causing light absorption by the reflective mirror of the element, resulting in a problem of reduced luminous flux.

[0006] Furthermore, because hemispherical optical lenses have a circular cross section, they have flat areas even when closely packed. The light beam emitted from the flat areas exhibits a Lambertian (wide-angle) light distribution, which causes a problem of deteriorating the narrow-angle performance of the emitted light.

[0007] Furthermore, when fabricating a mold for forming hemispherical close-packed or nearly close-packed array lenses, the thickness of the portions corresponding to the close contact between the lenses becomes too thin, making fabrication difficult.

[0008] The present invention has been made in view of the above problems, and has as its object to provide a light emitting device that is easy to manufacture and in which the reduction in total luminous flux due to narrowing of the angle is small. [Means for solving the problem]

[0009] The light emitting device of the present invention comprises a substrate, a light emitting section arranged on the substrate, including a light emitting layer, and emitting light from the light emitting layer as emitted light from an upper surface located opposite the substrate, an optical function section made of a translucent material, a base section arranged above the light emitting surface of the light emitting section and spaced apart from the upper surface of the light emitting section, and including a plate-shaped section extending to cover the light emitting surface of the light emitting section in a top view, and a plurality of convex sections formed on the upper surface of the base section, a light reflecting section arranged to cover the side of the light emitting section, and a low refractive index section filling a gap between the upper surface of the light emitting section and the lower surface of the plate-shaped section and made of a low refractive index material having a refractive index lower than that of the optical function section, wherein each of the plurality of convex sections is a pyramid or a truncated pyramid whose bottom surface is arranged on the upper surface of the base section. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a top view of a light emitting device according to Example 1 of the present invention. [Figure 2] 1 is a cross-sectional view of a light emitting device according to Example 1 of the present invention. [Figure 3] 1 is a perspective view showing the shape of a pyramid in a structural portion of a light guide of a light emitting device according to Example 1 of the present invention. [Figure 4] FIG. 3 is a diagram showing the optical path of emitted light in a light emitting device of a first comparative example. [Figure 5] 2 is a diagram showing the optical path of emitted light in the light emitting device according to the first embodiment of the present invention. FIG. [Figure 6]10 is a graph showing the relationship between the angle between the side surface and the bottom surface of the structure and the ±θ luminous flux Lambertian distribution ratio. [Figure 7] FIG. 10 is a top view of a light emitting device of a second comparative example. [Figure 8] FIG. 10 is a cross-sectional view of a light emitting device of a second comparative example. [Figure 9] 10 is a graph showing the relationship between the radius of the hemispherical lens and the ±θ luminous flux Lambertian distribution ratio in the second comparative example. [Figure 10A] FIG. 10 is a diagram showing the shape of a mold for a lens array when fabricating a light emitting device of a second comparative example. [Figure 10B] 10A and 10B are diagrams showing the shape of a mold for a lens array when fabricating a light emitting device according to an embodiment of the present invention. [Figure 11] FIG. 4 is a cross-sectional view of a light emitting device according to Example 2 of the present invention. [Figure 12A] 10 is a cross-sectional view of a light emitting device in which the light shading of the light exit surface is small. [Figure 12B] FIG. 10 is a cross-sectional view of a light emitting device when the light exit surface is not shielded. [Figure 12C] FIG. 10 is a cross-sectional view of a light emitting device in which the light shading of the light exit surface is large. [Figure 13] 10 is a graph showing the relationship between the size ratio of the light exit surface of the light emitting part and the lower surface of the light guide body and the ±30° luminous flux Lambertian distribution ratio. [Figure 14] 10 is a flowchart showing a method for manufacturing a light emitting device according to Example 2 of the present invention. [Figure 15A] FIG. 10 is a cross-sectional view of a light emitting device according to Modification 1 of the present invention. [Figure 15B] 10 is a graph showing the relationship between the height of a square pyramid and a truncated square pyramid and the ±30° luminous flux Lambertian distribution ratio. [Figure 16A] FIG. 10 is a top view of a light emitting device according to Modification 2 of the present invention. [Figure 16B] FIG. 10 is a cross-sectional view of a light emitting device according to Modification 2 of the present invention. [Figure 17A] FIG. 10 is a top view of a light emitting device according to a third modified example of the present invention. [Figure 17B] FIG. 10 is a cross-sectional view of a light emitting device according to Modification 3 of the present invention. [Figure 18] 10 is a graph showing the relationship between the array size of the structure and the ±θ luminous flux ratio. [Figure 19A] 10 is a cross-sectional view of a light emitting device in which the thickness of a low refractive index portion is small. FIG. [Figure 19B] FIG. 10 is a cross-sectional view of a light emitting device in which the thickness of a low refractive index portion is large. [Figure 20] 10 is a graph showing the relationship between the thickness of the AirGap and the ±30° luminous flux Lambertian distribution ratio. [Figure 21A] FIG. 10 is a cross-sectional view of a light emitting device in which the thickness of the base is small. [Figure 21B] FIG. 10 is a cross-sectional view of a light emitting device in which the thickness of the base portion is large. [Figure 22] 10 is a graph showing the relationship between the thickness of the base and the ±30° luminous flux Lambertian distribution ratio. [Figure 23A] FIG. 10 is a top view of a light emitting device according to a fourth modified example of the present invention. [Figure 23B] FIG. 10 is a cross-sectional view of a light emitting device according to a fourth modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail. In the following description of each embodiment and in the accompanying drawings, the same reference numerals are used to designate substantially the same or equivalent parts. [Example]

[0012] 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 AA.

[0013] (Light-emitting device) The light emitting device 100 includes a substrate 10, a light emitting section 20 including a semiconductor light emitting element 21 arranged on the substrate 10 and a wavelength converting member 22 arranged on the semiconductor light emitting element 21, a light guide 30 arranged above the light emitting section 20, and a light reflecting section 40 covering the side surface of the light emitting section 20. The upper surface of the light emitting section 20 and the lower surface of the light guide 30 are spaced apart, and a low refractive index section 50 having a refractive index lower than that of the light guide 30 is formed between them.

[0014] (substrate) The substrate 10 is an insulating substrate made of ceramic such as aluminum nitride (AlN) and has a rectangular upper surface. The substrate 10 has a pair of wiring electrodes (not shown) made of metal on its upper surface that can supply power to the semiconductor light emitting element 21 from outside the substrate 10. For example, the wiring electrodes are formed so as to be electrically connected to the lower surface of the substrate 10 via a through electrode or the like. The substrate 10 may also be made of an insulating material other than ceramic, such as a resin material.

[0015] (light-emitting element) The semiconductor light emitting element 21 is a light emitting diode (LED) having a rectangular upper surface and a gallium nitride (GaN)-based semiconductor structure layer including a light emitting layer that emits blue light. When mounted on the substrate 10, the semiconductor light emitting element 21 is, for example, a flip-chip LED element that includes a semiconductor structure layer formed on the lower surface of a light-transmitting growth substrate and a pair of element electrodes (not shown) provided on the semiconductor structure layer, and is configured to emit light from the upper surface of the growth substrate. The upper surface of the semiconductor light emitting element 21 serves as a light emitting surface that emits light.

[0016] The pair of element electrodes of the semiconductor light emitting element 21 are electrically connected to a pair of wiring electrodes formed on the substrate 10. That is, the semiconductor light emitting element 21 is mounted on the substrate 10 in a flip-chip manner, and is configured so that power can be supplied from the outside via the wiring electrodes formed on the substrate 10, making it possible to conduct electricity.

[0017] A light-reflecting layer may be formed on the lower surface of the semiconductor structure layer of the semiconductor light-emitting element 21, particularly between the semiconductor structure layer and the pair of element electrodes. This light-reflecting layer reflects light emitted downward on the side opposite the growth substrate and directs it toward the upper surface, which is the light-emitting surface of the semiconductor light-emitting element 21, thereby improving the light extraction efficiency from the upper surface, which is the light-emitting surface, of the growth substrate.

[0018] In this embodiment, the semiconductor light emitting element 21 has a chip size of, for example, a square with a side length D1 of approximately 1.0 mm on each side of the top surface. The top surface of the growth substrate of the semiconductor light emitting element 21 also has a square shape of approximately 1.0 mm on each side. That is, the light emitting surface of the semiconductor light emitting element 21 has a square shape of approximately 1.0 mm on each side.

[0019] The semiconductor light emitting element 21 is not limited to the above structure, shape, and dimensions. For example, the top surface shape of the semiconductor light emitting element may be a rectangle or a rhombus having long and short sides.

[0020] (wavelength conversion material) The wavelength conversion member 22 is disposed on the semiconductor light emitting element 21 via a light-transmitting adhesive (not shown) applied to the upper surface of the semiconductor light emitting element 21 .

[0021] 2, the wavelength conversion member 22 is formed so that its bottom surface covers the light emission surface of the semiconductor light emitting element 21, i.e., the upper surface of the semiconductor light emitting element 21. Therefore, the bottom surface of the wavelength conversion member 22 serves as a light incident surface through which light emitted from the semiconductor light emitting element 21 enters.

[0022] Furthermore, light incident from the light incident surface, which is the bottom surface of wavelength conversion member 22, is guided from the bottom surface to top surface 22S and exits from the top surface. Of the light incident from the light incident surface, which is the bottom surface of wavelength conversion member 22, light traveling toward the side surface of wavelength conversion member 22 is reflected by light reflecting section 40, which will be described later, toward the wavelength conversion member 22 and exits from top surface 22S of wavelength conversion member 22. In other words, top surface 22S of wavelength conversion member 22 serves as the light exit surface of light emitting section 20.

[0023] Wavelength conversion member 22 is a ceramic material made of alumina (Al2O3) containing yttrium aluminum garnet (YAG:Ce) phosphor particles using cerium (Ce) as an activator. Wavelength conversion member 22 converts a portion of the blue light from semiconductor light emitting element 21 that enters through the bottom surface, which is the light incident surface, into yellow light, and emits white light from top surface 22S, which is the light exit surface.

[0024] In this embodiment, the bottom surface of the wavelength conversion member 22 is formed to have a shape that is approximately the same as the top surface of the semiconductor light emitting element 21. That is, when the semiconductor light emitting element 21 is a chip having an upper surface shape of a square with a side length D1 of approximately 1.0 mm as exemplified above, the bottom surface of the wavelength conversion member 22 also has a square shape with a side length of the same length as the side length D1 of the semiconductor light emitting element 21 as exemplified above.

[0025] Regarding the shape, the size is approximately the same, with an allowable error of about 0.1 mm on each side, and the range of 0.9 mm to 1.1 mm on each side is sufficient, and the size may also be 0.8 mm to 1.2 mm on each side depending on the element shape, etc.

[0026] Furthermore, the bottom surface of the wavelength conversion member 22 is formed into a shape corresponding to the light-emitting region on the upper surface of the semiconductor light-emitting element 21, depending on the form of the semiconductor light-emitting element 21. In this embodiment, the upper surface of the semiconductor light-emitting element 21 forms the light-emitting surface of the semiconductor light-emitting element 21, and the upper surface of the semiconductor light-emitting element 21 is the light-emitting region, but depending on the configuration of the semiconductor light-emitting element 21, there are cases where the entire upper surface of the semiconductor light-emitting element 21 is not the light-emitting region.

[0027] For example, in the case where the light emitting region and the electrode pad for wire bonding are formed separately for the semiconductor light emitting element 21 having an electrode to which power is supplied by wire bonding, the wavelength conversion member 22 is formed in a shape that covers only the light emitting region and does not cover the electrode pad for wire bonding. In other words, the shape of the bottom surface of the wavelength conversion member 22 is substantially the same as the shape of the light emitting region on the upper surface of the semiconductor light emitting element 21.

[0028] The wavelength conversion member 22 may be designed to be slightly larger than the upper surface of the semiconductor light emitting element 21. In this case, it is preferable that the translucent adhesive between the semiconductor light emitting element 21 and the wavelength conversion member 22 covers the semiconductor light emitting element 21 from the upper surface to the side surface, and has a fillet shape that widens upward on the side surface of the semiconductor light emitting element 21. In this case, the light reflecting portion 40 covers the fillet-shaped adhesive side surface, and the light reflecting portion 40 covers the side surface of the semiconductor light emitting element via the fillet-shaped adhesive side surface.

[0029] With this configuration, light emitted from the side surface of the semiconductor light-emitting element 21 can be reflected upward at the interface between the adhesive and the light reflecting portion 40, and the light emitted from the side surface of the semiconductor light-emitting element 21 can be efficiently guided to and incident on the wavelength conversion member 22.

[0030] (light guide) The light guide 30 is an optically functional part disposed above the upper surface 22S of the wavelength conversion member 22, and is made up of a member integrally formed with a flat base 31 and a plurality of structural parts 32 formed on the upper surface of the base 31. The light guide 30 is made of, for example, a silicone resin having a refractive index n=1.41.

[0031] Light emitted from the upper surface 22S of the wavelength conversion member 22 enters the lower surface of the base 31 via the low-refractive-index portion 50 provided at the bottom of the light guide 30, propagates through the light guide 30, and is emitted to the outside of the light-emitting device 1 from the surface of the structural portion 32. That is, the lower surface of the base 31 of the light guide 30 functions as the light incident surface of the light guide 30, and each surface of the structural portion 32 functions as the light exit surface of the light guide 30. Note that, for convenience of explanation, the boundaries between the base and each of the multiple structural portions are indicated by dashed lines in FIG. 2, but this does not necessarily mean that there is a physical boundary surface between the base 31 and the structural portion 32. The base 31 and the structural portion 32 may be made of the same material and integrated, or the base 31 and the structural portion 32 may be made of different materials and have a boundary surface.

[0032] The base 31 is a flat plate-shaped portion arranged to cover the upper surface 22S of the wavelength conversion member 22, and is adhered (bonded) to the upper surface 22S of the wavelength conversion member 22 via a bonding adhesive 60. The bonding adhesive 60 is provided along the outer edge of the upper surface 22S of the wavelength conversion member 22. This creates a predetermined distance between the upper surface 22S of the wavelength conversion member 22 and the bottom surface of the base 31. In other words, the bonding adhesive 60 functions like a spacer that protrudes vertically from the upper surface of the wavelength conversion member 22 and abuts against the lower surface of the light guide 30.

[0033] For example, the bonding adhesive 60 has a thickness of 1 μm or more, which is thick enough to form a gap for the low refractive index portion 50 described below. In this embodiment, the pedestal portion 31 has a thickness T1 of approximately 50 μm.

[0034] The light emitting surface, which is the upper surface of the light emitting unit 20, is located directly below the base 31. In this embodiment, the outer edge of the lower surface of the base 31 is located outside the outer edge of the upper surface 22S of the wavelength converting member 22 in top view.

[0035] The upper and lower surfaces of the pedestal 31 have a square shape with a side length D2. Here, the length D2 is larger than the side length D1 of the upper surface 22S of the wavelength conversion member 22. In other words, when viewed from above, the pedestal 31 has a square shape that is larger by a width Wa (=D2-D1) than the upper surface 22S of the wavelength conversion member 22, which also has a square shape.

[0036] Here, it is preferable that upper surface 22S of wavelength conversion member 22, which is the light emission surface of light-emitting section 20, is smaller than the bottom surface of pedestal 31, which is the lower surface of light guide 30, and has a size that is at least 90% of that size. That is, it is preferable that the relationship between length D1 of one side of upper surface 22S of wavelength conversion member 22 and length D2 of one side of the lower surface of the pedestal satisfy the following relational expression (Equation 1). (Number 1) 0.9×D2 <D1<D2 The structural portion 32 is a convex portion made of a pyramidal lens that has a bottom surface on the upper surface of the base portion 31 and is arranged so that its apex protrudes upward. A plurality of the structural portions 32 are arranged on the upper surface of the base portion 31.

[0037] 3 is a diagram showing a square pyramid PM, which is an example of a pyramid constituting the structural unit 32 of this embodiment. The square pyramid PM of this embodiment has a square bottom located on the upper surface of the base 31, and four side surfaces formed of identical isosceles triangles. The angle φ between the side surfaces and the bottom surface is in the range of 0°<φ<90°.

[0038] The apex angle of the quadrangular pyramid that constitutes the structural portion 32 is preferably formed to be 40° to 160°, and more preferably 60° to 120°.

[0039] In this embodiment, a total of 25 structural elements 32 are arranged in a matrix of 5 rows and 5 columns along the X and Y directions in Fig. 1 on the upper surface of the base 31 of the light guide 30. The structural elements 32 have a quadrangular pyramid shape and are arranged so that each side of their square-shaped base faces extends along the X and Y directions, respectively. The structural elements 32 are arranged so that their bottom faces are adjacent to each other (i.e., so that they are spread out over the upper surface of the base 31), and there are no flat areas between the structural elements.

[0040] The arrangement area of ​​the structural unit 32 is located in the center of the upper surface of the base 31, and has a square shape with a side length D3. Here, the length D3 is smaller than the side length D2 of the upper surface of the base 31. In other words, a flat area with a width Wb (=D2-D3) is formed on the outer edge of the upper surface of the base 31 so as to surround the area where the structural unit 32 is arranged.

[0041] Here, it is preferable that the width Wb satisfy the following relational expression (Equation 2). (Number 2) 0≦Wb<10μm (Light reflecting part) The light reflecting portion 40 is made of a white resin such as a silicone resin containing light-scattering particles such as titanium oxide (TiO2) particles, and has light reflectivity. The light reflecting portion 40 is provided so as to cover the side surfaces of the semiconductor light-emitting element 21 and the wavelength converting member 22, and to expose the upper surface 22S of the wavelength converting member 22.

[0042] The light reflecting portion 40 reflects or scatters light that reaches the side surfaces from the inside of the semiconductor light emitting element 21 and the wavelength converting member 22 so that the light returns inward, thereby preventing light from leaking out from the side surfaces of the semiconductor light emitting element 21 and the wavelength converting member 22, and improving the light extraction efficiency of the light emitting device 100.

[0043] (low refractive index part) The low refractive index portion 50 is provided in the gap formed between the upper surface 22S of the wavelength conversion member 22 and the lower surface of the base portion 31 of the light guide 30, and is an area where a low refractive index substance with a refractive index smaller than that of the material constituting the light guide 30 is present.

[0044] In this embodiment, the low refractive index portion 50 is formed by filling the space formed between the lower surface of the light guide 30 and the upper surface 22S of the wavelength conversion member 22 with air (refractive index n=1.0). In other words, the low refractive index portion 50 in this embodiment is formed by a so-called AirGap.

[0045] Light emitted from the upper surface 22S of the wavelength conversion member 22 passes through the low refractive index portion 50 and enters the light guide 30, which has a refractive index higher than that of the low refractive index portion 50. At this time, the light emitted from the upper surface 22S of the wavelength conversion member 22 is narrowed in the optical axis direction, which is perpendicular to the upper surface 22S of the wavelength conversion member 22, at the interface between the low refractive index portion 50 and the light guide 30, and then enters the base 31 of the light guide 30. Therefore, by providing the low refractive index portion 50 between the upper surface 22S of the wavelength conversion member 22 and the lower surface of the base 31 of the light guide 30, it is possible to increase the narrow-angle component of the light emitted from the light emitting device 1.

[0046] In this description, the narrow-angle component of light emitted from the light emitting device 1 refers to the component of light emitted within a range of 30° with respect to the optical axis direction perpendicular to the upper surface 22S of the wavelength converting member 22.

[0047] (Narrowing the angle of emitted light) Next, the operation of narrowing the angle of emitted light from the light emitting device 100 of this embodiment will be described with reference to FIGS.

[0048] 4 is a diagram showing the optical path of emitted light from a light emitting device 100A of a first comparative example, which has a light guide 30 that, unlike the light emitting device 100 of this embodiment, is not provided with a structure such as the structural portion 32 of this embodiment, but is provided with only a portion corresponding to the base portion 31 of this embodiment. Note that hatching of the light guide 30 is omitted here to clearly show the optical path of the emitted light.

[0049] The light emitted from the light emission point on the upper surface 22S of the wavelength conversion member 22 exhibits a Lambertian distribution and is incident on the lower surface of the light guide 30 via the low refractive index portion 50. The direction of all light rays incident on the light guide 30 falls within a total reflection angle determined by the refractive index of the low refractive index portion 50 and the light guide 30 with respect to the vertical direction.

[0050] In the light emitting device 100A of the first comparative example, the light guide 30 is not provided with a structure such as the structural portion 32, and therefore the light emitted from the upper surface of the light guide 30 returns to a Lambertian distribution. That is, the light emitted from the light guide 30 is emitted at a wide angle.

[0051] Fig. 5 is a diagram showing the optical path of emitted light in the light emitting device 100 of this embodiment using an enlarged cross-sectional view in which the wavelength conversion member 22 and the light guide 30 in the cross section of Fig. 2 are partially enlarged. As in Fig. 4, the hatching of the light guide 30 (base portion 31 and structural portion 32) is omitted here to clearly show the optical path of the emitted light.

[0052] Light emitted from the light emission point on the upper surface 22S of the wavelength conversion member 22 is incident on the lower surface of the base 31 of the light guide 30 via the low refractive index portion 50. The directions of all light rays incident on the light guide 30 from the lower surface of the base 31 are within a total reflection angle determined by the refractive index of the low refractive index portion 50 and the light guide 30 with respect to the vertical direction.

[0053] In the light emitting device 100 of this embodiment, a structure 32 having a quadrangular pyramid shape is provided on a base 31. If the apex angle of the quadrangular pyramid is α and the incident angle of light incident on the light guide 30 from the low refractive index section 50 is θ (θ<45°), the incident angle β of the light on the slope of the quadrangular pyramid is expressed by the following relational expression (Equation 3). (Number 3) β=90°-(θ+α / 2) Here, for example, if α = 90°, then β = 45° - θ ≦ 45°, and the emitted light is tilted vertically, narrowing the angle. In addition, since there is less light returning to the light exit surface due to total reflection, it is possible to prevent a reduction in the total luminous flux due to the narrowing angle.

[0054] FIG. 6 is a graph showing the relationship between the angle between the side and base of a square pyramid (hereinafter referred to as the side-to-base angle) and the ±θ luminous flux Lambertian distribution ratio. Here, the ±θ luminous flux Lambertian distribution ratio is a parameter that indicates the degree of narrow-angle characteristics of a light source, and is a value obtained by taking the optical axis direction of the light source as 0° and calculating the ratio of the luminous flux existing within the range from 0° to directions tilted ±θ° from the optical axis direction to the total luminous flux, relative to that in the case of Lambertian distribution. In other words, assuming a cone shape with the light source as its apex and the optical axis direction as its central axis, and the apex angle of the cone as 2θ, this parameter indicates the ratio of the luminous flux existing within the cone to the total luminous flux, and the ratio becomes higher as the narrow-angle characteristics become stronger. Note that, in the case of a general Lambertian light source, the ratio of the luminous flux within ±θ to the total luminous flux is expressed as sin 2 (θ). For example, the luminous flux ratio within ±30° is calculated as sin 2 (30°)=25%, the luminous flux ratio within ±45° is sin 2 (45°)=50%, the luminous flux within ±60° is sin 2(60°) = 75%. By multiplying this ±θ luminous flux ratio by the total luminous flux, the luminous flux contained within ±θ° for that light source can be calculated. If the proportion of luminous flux contained within ±θ° is higher than that of this Lambertian light source, it can be understood that narrow-angle characteristics are exhibited. Therefore, in FIG. 6, the ±θ luminous flux Lambertian distribution ratio = luminous flux ratio within ±θ of the narrow-angle light source according to the present invention ÷ luminous flux ratio within ±θ of the Lambertian light source (i.e., sin 2 (θ)). The vertical axis is defined in the same way in Figures 9, 13, 15B, 18, 20, and 22, which will be described later.

[0055] As shown in FIG. 6, when the angle between the side and bottom surfaces is between 15° and 75°, the light emitted within ±30° has narrower angle characteristics than the Lambertian distribution.

[0056] The ±40° luminous flux ratio has the best narrow-angle performance when the side-to-base angle is in the range of 40° to 55°. The ±60° luminous flux ratio has the ability to collect more than 90% of the luminous flux over a wide range of side-to-base angles of 45° or less, and can collect more than 95% of the total luminous flux when the side-to-base angle is 30° or less. Additionally, within the entire range of the side-to-base angle, the reduction in total luminous flux remains within a range of 5% or less.

[0057] On the other hand, when the light emitted from the light guide 30 exhibits a Lambertian light distribution as in the first comparative example, the luminous flux emitted within ±30°, for example, is about 25% of the total luminous flux as described above. Therefore, the structure 32 of this embodiment can achieve narrow-angle characteristics better than those of a Lambertian light distribution.

[0058] Fig. 7 is a top view showing the configuration of a light emitting device 200, as a second comparative example, in which a hemispherical structure 32X is provided on a light guide 30. Fig. 8 is a cross-sectional view taken along line XX of the light emitting device 200 shown in Fig. 7.

[0059] The light guide 30X is composed of a flat base 31 and a plurality of structural portions 32X formed on the top surface of the base 31.

[0060] The structural portions 32X are hemispherical lenses formed so as to protrude upward on the upper surface of the base portion 31. The structural portions 32X are arranged on the upper surface of the base portion 31 so as to be symmetrical with respect to the center point of the upper surface of the base portion 31, as shown in FIG.

[0061] Here, a total of 25 structural portions 32X are arranged in a matrix of 5 rows and 5 columns along the X and Y directions in Fig. 7. Each of the structural portions 32X has a hemispherical shape with a radius R1.

[0062] In the light emitting device 200 of the second comparative example, the light exit surface of the structure 32X is hemispherical, so when the angle of incidence of light on the curved surface exceeds the angle of total reflection, the light is repeatedly totally reflected at the curved surface and returns to the light exit surface. These rays of light return to the wavelength conversion member 22 and the semiconductor light emitting element 21, causing light absorption by the reflective mirror (not shown) of the element, resulting in a reduction in luminous flux.

[0063] Furthermore, a hemispherical optical lens has a circular cross section, and even in the case of closest packing, the structure 32X has a flat area as shown by "FA" in Fig. 7. Light rays emitted from the flat area exhibit a Lambertian distribution, which deteriorates the narrow-angle performance of the emitted light.

[0064] 9 is a graph showing the narrow angle characteristics of a hemispherical lens and the change in total light flux, where an example is shown in which the spacing between the centers of the hemispheres of the structure 32X is 100 μm.

[0065] When the radius of the hemispherical lens is 100 μm, i.e., the lens spacing is 0, the narrow-angle performance is good, but the change in luminous flux is large, with a reduction of more than 8%. On the other hand, as the lens spacing increases, the narrow-angle performance deteriorates.

[0066] Furthermore, in the light emitting device 200 of the second comparative example, it is more difficult to fabricate the structural portion 32X than in the light emitting device 100 of this example.

[0067] 10A is a cross-sectional view of a mold TM1 used to fabricate a hemispherical lens array. The mold TM1 has a narrow, pointed apex VP1, which corresponds to the position between adjacent hemispherical lenses, making it difficult to fabricate. As mentioned above, narrowing the lens spacing is preferable to improve narrow-angle performance, but because the apex VP1 is difficult to fabricate, it is impossible to reduce the lens spacing to zero.

[0068] 10B is a cross-sectional view of a mold TM2 used to fabricate the pyramidal array that constitutes the structural portion 32 of this example. In the mold TM2, the apex VP2, which is the portion corresponding to the position between adjacent quadrangular pyramids, is gentler than the apex VP1 of the mold TM1, making it easier to shape.

[0069] As described above, according to the light emitting device 100 of this embodiment, it is possible to provide a light emitting device in which the reduction in total luminous flux due to narrowing of the angle is small and which is easy to manufacture. [Example]

[0070] Next, a description will be given of a second embodiment of the present invention. Fig. 11 is a cross-sectional view showing the configuration of a light emitting device 100A of the second embodiment.

[0071] (Light blocking part) The light emitting device 100A of this embodiment has a light-shielding portion 70 provided along the outer edge of the upper surface 22S of the wavelength converting member 22 between the upper surface 22S of the wavelength converting member 22 and the bottom surface of the base portion 31 of the light guide 30. The light-shielding portion 70 is made of, for example, a metal reflective film such as aluminum or a dielectric multilayer film.

[0072] In the above-described first embodiment, the flat plate of the base 31 of the light guide 30 is large, and the arrangement area of ​​the structural part 32 on the base 31 is larger than the upper surface 22S of the wavelength conversion member 22. In contrast, in the light emitting device 100A of this embodiment, a light-shielding part is provided on the periphery of the upper surface 22S of the wavelength conversion member 22, thereby realizing that the upper surface 22S of the wavelength conversion member 22 is smaller in size than the lower surface of the base 31 and the arrangement area of ​​the structural part 32.

[0073] 11, a part (outer edge part) of the upper surface 22S of the wavelength conversion member 22 is shielded by the light-shielding portion 70, and therefore the arrangement area of ​​the pyramids constituting the structure 32 becomes relatively larger than the light emission surface of the light-emitting portion 20. As a result, as in the case of Example 1, the arrangement area of ​​the pyramids covers the entire light emission surface above the light emission surface, and therefore the narrow angle performance of the emitted light can be further improved.

[0074] Fig. 12A is a cross-sectional view showing the configuration of a light-emitting device in which the horizontal width of the light-shielding portion 70 is small and the degree of light blocking is relatively low. Fig. 12B is a cross-sectional view showing the configuration of a light-emitting device in which the light-shielding portion 70 is not provided and the arrangement area of ​​the structural portion 32 on the upper surface of the base portion 31 has approximately the same size as the light emission surface of the light-emitting portion 20. Fig. 12C is a cross-sectional view showing the configuration of a light-emitting device in which the horizontal width of the light-shielding portion 70 is large and the degree of light blocking is relatively high.

[0075] 13 is a graph showing the relationship between the size ratio of the light exit surface of the light-emitting unit 20 to the arrangement area of ​​the structural unit 32 and the ±30° luminous flux Lambertian luminous distribution ratio. When the size ratio is 1.0, that is, when the light exit surface of the light-emitting unit 20 and the arrangement area of ​​the structural unit 32 on the upper surface of the base 31 are the same size, the ±30° luminous flux Lambertian luminous distribution ratio is approximately 1.24. The luminous distribution ratio peaks when the size ratio is around 0.95, and when the size ratio is below 0.85, the value of the luminous distribution ratio drops more than when the size ratio is 1.0.

[0076] Therefore, it is preferable that the light-shielding portion 70 is formed so that the size of the arrangement area of ​​the structural portion 32 on the base portion 31 is slightly larger than the size of the light exit surface of the light-emitting portion 20, for example, approximately 85 to 98%.

[0077] (Manufacturing method) Next, a method for manufacturing the light emitting device 100A of this embodiment will be described with reference to the manufacturing flow shown in FIG.

[0078] First, a multilayer mirror or a metal mirror is formed on the upper surface of the wavelength conversion member 22 and patterned (STEP 101).

[0079] Next, a similar multilayer mirror or metal mirror is formed on a transparent substrate and patterned (STEP 102).

[0080] The wavelength conversion member 22 patterned in STEP 101 and the light-transmitting member (transparent substrate) patterned in STEP 102 are patterned together, and then bonded together using a transparent adhesive or eutectic solder material (STEP 103). This allows the pedestal 31 and the wavelength conversion member 22 to be bonded together while maintaining a gap between them as a low refractive index portion.

[0081] A pyramid (frustum) is imprinted on the upper surface of the light-transmitting member (the side opposite to the side to which the wavelength conversion member 22 is bonded) (STEP 104).

[0082] Dicing is performed along the pattern to separate the light guide 30 and the wavelength conversion member 22 into individual pieces (STEP 105). Then, the individual pieces of the light guide 30 and the wavelength conversion member 22 bonded together are placed on the upper surface of the semiconductor light emitting element 21 via a transparent adhesive or the like, and the wavelength conversion member 22 and the side surfaces of the semiconductor light emitting element 21 are covered with the light reflecting portion 40.

[0083] In this way, the light emitting device 100A of this example can be fabricated.

[0084] (Variation 1) In the above-described Examples 1 and 2, the structure 32 is described as a quadrangular pyramid. However, the structure 32 may have a truncated pyramid shape with an upper surface at the apex, rather than a pure pyramid with a pointed apex.

[0085] FIG. 15A is a cross-sectional view showing a light emitting device 100B of Modification 1 that includes a structural portion 32B having a truncated quadrangular pyramid shape.

[0086] 15B is a graph showing the relationship between the height of the square pyramid and the truncated square pyramid and the ±30° Lambertian luminous flux distribution ratio. Here, the height of the truncated square pyramid is shown as a percentage, with the height when the side surface of the truncated square pyramid is extended upward to form a square pyramid being 100%.

[0087] As can be seen from the graph, when the height of the truncated square pyramid is 75% of the height of the square pyramid, the narrow angle is almost the same as that of a square pyramid. In other words, even if the apex angle is not as pronounced as in a square pyramid during manufacturing, there is little impact on the narrow angle performance.

[0088] Furthermore, it is easier to manufacture a truncated pyramid than a pyramid in imprint technology, etc. Therefore, the light emitting device 100B of Modification 1 is even easier to manufacture than the light emitting device 100 of the above embodiment.

[0089] (Variation 2) In the above-described first and second embodiments, the structures 32 are arranged in a matrix of 5 rows and 5 columns on the upper surface of the base 31 of the light guide 30. However, the number and arrangement of the structures 32 are not limited to this.

[0090] Fig. 16A is a top view of a light emitting device 100C according to Modification 2 of the present invention, and Fig. 16B is a cross-sectional view of the light emitting device 100C taken along line CC shown in Fig. 16A.

[0091] In Modification 2, four structural elements 32C are arranged in a matrix of two rows and two columns along the X and Y directions in Fig. 16A on the upper surface of base 31C of light guide 30C. Like the structural elements 32 of each of the above embodiments, structural elements 32C of Modification 2 have a quadrangular pyramid shape and are arranged so that each side of the square-shaped base is oriented along the X and Y directions, respectively. Furthermore, structural elements 32C are arranged on the upper surface of base 31C without any gaps between them, and there are no flat portions between the structural elements.

[0092] (Variation 3) Fig. 17A is a top view of a light emitting device 100D according to Modification 2 of the present invention, and Fig. 17B is a cross-sectional view of the light emitting device 100D taken along line DD shown in Fig. 17A.

[0093] In Modification 3, a total of 100 structural elements 32D are arranged in a matrix of 10 rows and 10 columns along the X and Y directions in Fig. 17A on the upper surface of base 31D of light guide 30D. Like structural elements 32 of each of the above embodiments and structural element 32C of Modification 2, structural elements 32D of Modification 3 have a quadrangular pyramid shape and are arranged so that each side of their square bottom faces are oriented along the X and Y directions, respectively. Furthermore, structural elements 32D are arranged on the upper surface of base 31D without any gaps between them, and there are no flat portions between the structural elements.

[0094] 18 is a graph showing the relationship between the array size (the number of rows and columns of the square pyramidal structure array) and the ±30° luminous flux Lambertian distribution ratio. As can be seen from the graph, even if the array size changes, there is no significant difference in the ±30° luminous flux Lambertian distribution ratio, i.e., narrow-angle performance.

[0095] However, the larger the surface structure of the structure portion, the more pronounced the surface luminance distribution becomes, which is likely to adversely affect the light distribution of the lamp when the light-emitting device is used in a lamp. Therefore, it is preferable to form a large number of small narrow-angle structures as in Variation 3, rather than a small number of large narrow-angle structures as in Variation 2. For example, by utilizing imprint technology, it is possible to create a narrow-angle structure with small surface irregularities as in Variation 3.

[0096] (Thickness of low refractive index part) 19A is a cross-sectional view of a light emitting device in which the thickness of the low refractive index section 50 is small, i.e., the width of the light emitting section 20 in the direction perpendicular to the light emitting surface is narrow. Fig. 19B is a cross-sectional view of a light emitting device in which the thickness of the low refractive index section 50 is large, i.e., the width of the light emitting section 20 in the direction perpendicular to the light emitting surface is wide.

[0097] 20 is a graph showing the relationship between the thickness and the ±30° Lambertian luminous flux distribution ratio when the low refractive index section 50 is made of an AirGap. As can be seen from the graph, the thicker the AirGap, the worse the narrow angle performance.

[0098] Therefore, it is preferable that the vertical width of the low refractive index portion 50 is as small as possible (that is, the thickness is as thin as possible).

[0099] (Base thickness) Fig. 21A is a cross-sectional view of a light emitting device in which the thickness of base 31 is small, and Fig. 21B is a cross-sectional view of a light emitting device in which the thickness of base 31 is large.

[0100] 22 is a graph showing the relationship between the thickness of the base 31 and the ±30° Lambertian luminous flux distribution ratio. As can be seen from the graph, the thicker the base 31, the worse the narrow angle performance.

[0101] Therefore, it is preferable that the width in the vertical direction of the base portion 31 is as small as possible (that is, the thickness is as thin as possible).

[0102] (Variation 4) In the above-described second embodiment, in order to improve the narrow angle performance, the light-shielding portion 70 is provided along the outer edge of the upper surface 22S of the wavelength conversion member 22. However, the position where the light-shielding portion 70 is formed is not limited thereto, and the light-shielding portion 70 may be formed along the outer edge of the bottom surface of each of the quadrangular pyramids that form the structural portion 32.

[0103] Fig. 23A is a cross-sectional view showing a light emitting device 100E having such a configuration according to Modification 4. Fig. 23B is a cross-sectional view taken along line EE of light emitting device 100E shown in Fig. 23A.

[0104] In the light emitting device 100E of the fourth modification, a light-shielding portion 70 is provided along the outer edge of the base of each quadrangular pyramid, in other words, along the boundary between adjacent quadrangular pyramids, below the base 31 of the light guide 30. With this configuration, compared to the second embodiment, the size of the light exit surface of the light emitting portion 20 can be made even smaller than the size of the arrangement area of ​​the structural portion 32 on the base 31.

[0105] The size of the portion of the underside of base 31 where light-shielding portion 70 is not provided and light emitted from light-emitting portion 20 passes through (hereinafter referred to as the transmissive portion) can be determined according to the required narrow-angle performance. Taking into consideration changes in luminous flux, the area of ​​the transmissive portion is preferably 25% or more of the lower portion of base 31. For example, if the transmissive portion has a quadrangular shape (e.g., a square) similar to the base of the quadrangular pyramid, the length of one side of the transmissive portion is preferably 50% or more of the length of one side of the base of the quadrangular pyramid.

[0106] The present invention is not limited to the above-described embodiments and modifications. For example, in the above-described embodiments, the structural unit 32 is described as a quadrangular pyramid, but the shape of the structural unit 32 is not limited to this and may be a triangular pyramid, a hexagonal pyramid, or another pyramid. That is, the structural unit 32 may be a pyramid having a bottom surface that can be packed without gaps in the arrangement area on the upper surface of the base 31. Similarly, in Modification 1, the structural unit 32B is described as a truncated quadrangular pyramid, but the structural unit 32B may be a truncated triangular pyramid, a hexagonal pyramid, or another pyramid having a bottom surface that can be packed without gaps in the arrangement area on the upper surface of the base 31.

[0107] Furthermore, the structural portion 32 (32B) does not necessarily have to be composed of only a pyramid or a truncated pyramid, but may be composed of a combination with another three-dimensional shape. That is, it is sufficient that the portion arranged on the upper surface of the base has the shape of a pyramid or a truncated pyramid, and for example, another three-dimensional shape may be provided on top of the truncated pyramid to integrally form a structural portion (convex portion).

[0108] In the above embodiment, the pedestal 31 has a flat plate-like shape, and the bonding adhesive 60 functions as a spacer, thereby forming a gap between the pedestal 31 and the upper surface 22S of the wavelength conversion member 22. However, the pedestal 31 does not necessarily have to be composed of only a flat plate-like portion, and may have, for example, a shape with legs attached to the flat plate-like portion. With this configuration, the legs function as a spacer, thereby making it possible to form a gap between the pedestal 31 and the upper surface 22S of the wavelength conversion member 22.

[0109] Although the present invention has been described using a flip-chip LED element as an example of a semiconductor light-emitting element, the present invention is not limited to this. For example, the semiconductor light-emitting element may be a thin-film element in which a semiconductor structure layer is bonded to a conductive substrate or a thermally conductive substrate (e.g., a silicon (Si) substrate). [Explanation of symbols]

[0110] 100 Light-emitting device 10 Substrate 20 Light-emitting part 21 Semiconductor light emitting element 22 Wavelength conversion material 30 Light guide 31 Base 32 Structural section 40 Light reflecting part 50 Low refractive index section 60 Bonding Adhesives

Claims

1. A substrate; a light-emitting section disposed on the substrate, including a light-emitting layer, and emitting light from the light-emitting layer as emitted light from an upper surface located on the opposite side to the substrate; an optical function unit including a base portion made of a light-transmitting member, the base portion being arranged above the light exit surface of the light-emitting unit at a distance from the upper surface of the light-emitting unit, the base portion including a plate-like portion extending to cover the light exit surface of the light-emitting unit in a top view, and a plurality of convex portions formed on the upper surface of the base portion; a light reflecting portion provided to cover a side surface of the light emitting portion; a low refractive index portion that fills a gap between an upper surface of the light emitting portion and a lower surface of the plate-shaped portion and is made of a low refractive index material having a refractive index lower than that of the optical function portion; and The light emitting device is characterized in that each of the plurality of protrusions is a pyramid or a truncated pyramid whose bottom surface is disposed on the upper surface of the base portion.

2. The light-emitting device according to claim 1, characterized in that the arrangement area of ​​the plurality of convex portions on the base portion has an area larger than the light-emitting surface of the light-emitting portion, and is arranged above the light-emitting surface so as to cover the entire light-emitting surface.

3. 2. The light emitting device according to claim 1, wherein the low refractive index portion is made of a gas that fills the void.

4. The light emitting device according to claim 1 , further comprising a light shielding portion provided in the gap so as to cover an outer edge of the light emitting surface.

5. The light emitting device according to claim 1 , further comprising a light shielding portion provided on the underside of the base portion so as to cover the outer edges of each of the plurality of protrusions when viewed from above.

6. 2. The light emitting device according to claim 1, wherein each of the plurality of protrusions is formed as a triangular pyramid, a quadrangular pyramid, or a hexagonal pyramid.

7. 2. The light emitting device according to claim 1, wherein each of the plurality of protrusions is a truncated triangular pyramid, a truncated square pyramid, or a truncated hexagonal pyramid.

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