JP7549214B2 - Light emitting device and method for manufacturing the same - Google Patents

Description

This disclosure relates to a light-emitting device and a method for manufacturing the same.

In recent years, LED modules using light-emitting diodes (LEDs) have been used for a variety of applications, and LED modules with high light-emitting properties have been proposed for these applications. For example, the light-emitting device disclosed in Patent Document 1 aims to improve the light extraction efficiency of the light-emitting device by using a highly reflective material for the substrate on which the light-emitting elements are arranged. There is a demand for further improvement in the light extraction efficiency of such light-emitting devices.

JP 2019-125683 A

The objective of this disclosure is to provide a light-emitting device with higher light extraction efficiency and a method for manufacturing the same.

A first aspect is a light emitting device as follows.
A light-emitting device comprising: a substrate; a first planar portion arranged on the substrate and having a first thickness, a second planar portion having a second thickness smaller than the first thickness, and a first convex portion having a third thickness larger than the first thickness; a reflective resin layer containing a first reflector and a first resin; and a light-emitting element arranged on the second planar portion of the reflective resin layer, wherein a portion of the side surface of the first convex portion is arranged in contact with a side surface of the light-emitting element.
The second aspect is a method for producing a light emitting device as follows.
A method for manufacturing a light emitting device, comprising the steps of: applying a reflective resin containing a reflective material and a first resin onto a substrate; arranging a light emitting element on the reflective resin applied to the substrate; and curing the reflective resin, wherein in the step of arranging the light emitting element, a part of the light emitting element is pressed into the reflective resin, and a first planar portion having a first thickness and on which the light emitting element is not arranged, a second planar portion on which the light emitting element is arranged and having a second thickness smaller than the first thickness, and a first convex portion in contact with a side surface of the light emitting element and having a third thickness larger than the first thickness are formed.

According to one embodiment of the present invention, it is possible to provide a light-emitting device with higher light extraction efficiency and a method for manufacturing the same.

1 is a schematic plan view of a light emitting device according to one embodiment of the present invention; This is a cross-sectional view of line 1B-1B' in Figure 1A. FIG. 1C is a schematic enlarged view of a portion X of FIG. FIG. 1D is a schematic enlarged view of a main part of FIG. 1C. 1B is a schematic cross-sectional view of a main part for explaining the path of light in the light emitting device of FIG. 1A. 4 is a schematic cross-sectional view of a light emitting device according to another embodiment of the present invention. 11 is a schematic cross-sectional view of a light-emitting device according to yet another embodiment of the present invention. 4 is a flowchart showing a method for manufacturing a light emitting device according to one embodiment of the present invention. 10 is a flowchart illustrating a method for manufacturing a light emitting device according to another embodiment of the present invention. 3A to 3C are schematic cross-sectional process diagrams illustrating a method for manufacturing a light emitting device according to one embodiment of the present invention. 3A to 3C are schematic cross-sectional process diagrams illustrating a method for manufacturing a light emitting device according to one embodiment of the present invention. 3A to 3C are schematic cross-sectional process diagrams illustrating a method for manufacturing a light emitting device according to one embodiment of the present invention. 3A to 3C are schematic cross-sectional process diagrams illustrating a method for manufacturing a light emitting device according to one embodiment of the present invention. 3A to 3C are schematic cross-sectional process diagrams illustrating a method for manufacturing a light emitting device according to one embodiment of the present invention. 5A to 5C are schematic cross-sectional views illustrating steps of a method for manufacturing a light emitting device according to another embodiment of the present invention. 5A to 5C are schematic cross-sectional views illustrating steps of a method for manufacturing a light emitting device according to another embodiment of the present invention. 5A to 5C are schematic cross-sectional views illustrating steps of a method for manufacturing a light emitting device according to another embodiment of the present invention. 5A to 5C are schematic cross-sectional views illustrating steps of a method for manufacturing a light emitting device according to another embodiment of the present invention. 5A to 5C are schematic cross-sectional views illustrating steps of a method for manufacturing a light emitting device according to another embodiment of the present invention. FIG. 11 is a schematic plan view showing a light emitting device according to still another embodiment of the present invention. This is a cross-sectional view of line 6B-6B' in Figure 6A. FIG. 11 is a schematic plan view showing a light emitting device according to still another embodiment of the present invention. FIG. 11 is a schematic plan view showing a light emitting device according to still another embodiment of the present invention. This is a cross-sectional view of line 8B-8B' in Figure 8A. 8B is a schematic cross-sectional process diagram for explaining a method for manufacturing the light emitting device of FIG. 8A. 8B is a schematic cross-sectional process diagram for explaining a method for manufacturing the light emitting device of FIG. 8A. 8B is a schematic cross-sectional process diagram for explaining a method for manufacturing the light emitting device of FIG. 8A.

The following describes the embodiments of the present invention with reference to the drawings. However, the embodiments shown below are merely examples for embodying the technical ideas of the present invention, and do not limit the present invention to the following. The sizes and positional relationships of the components shown in the drawings may be exaggerated for clarity. Furthermore, the same names and symbols generally indicate the same or similar components, and duplicate explanations will be omitted as appropriate. In this specification, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[Light-emitting device]
A light emitting device 10 of this embodiment includes a substrate 11, a reflective resin layer 12 disposed on the substrate 11, and a light emitting element 13 disposed on the reflective resin layer 12, as shown in FIGS. 1A and 1B.
The reflective resin layer 12 includes a first reflective material and a first resin. The reflective resin layer 12 also has a first planar portion 12A, a second planar portion 12B, and a first convex portion 12C, and the first planar portion 12A, the second planar portion 12B, and the first convex portion 12C are disposed on the substrate 11. The first planar portion 12A, the second planar portion 12B, and the first convex portion 12C each have a first thickness (indicated by "H1" in FIG. 1C), a second thickness (indicated by "H2" in FIG. 1C), and a third thickness (indicated by "H1+H3" in FIG. 1C). The second thickness H2 of the second planar portion 12B is smaller than the first thickness H1 of the first planar portion 12A. The first convex portion 12C protrudes from the upper end of the first planar portion 12A. The first convex portion 12C is disposed on the opposite side of the first flat portion 12A, i.e., on the side of the second flat portion 12B, with a part of its side surface in contact with the side surface of the light-emitting element 13. In the reflective resin layer 12, the part disposed directly under the light-emitting element 13 is the second flat portion 12B, the part connected to the second flat portion 12B and with a part of its side surface in contact with the side surface of the light-emitting element 13 is the first convex portion 12C, and the part in contact with the first convex portion 12C and extending to the outside of the first convex portion 12C (i.e., the periphery of the first convex portion 12C, the opposite side of the light-emitting element 13) is the first flat portion 12A. In this specification, the "thickness" of each member refers to the average value of the distance measured by setting the upper end and the lower end of each member in a direction perpendicular to the substrate.
The light emitting element 13 is disposed on the second flat portion 12 B of the reflective resin layer 12 .
With this configuration, light emitted from the side surface of the light-emitting element can be more easily guided upward by utilizing reflection by the first convex portion, thereby further improving the light emission and extraction efficiency of the light-emitting device.
The light emitting device may further have a frame 14 as shown in light emitting device 10A or 10C, 10B or 10D in Fig. 2A or 2B, Fig. 4E or Fig. 5E. In this case, the frame 14 may be disposed outside the reflective resin layer 12, that is, on the base 11, as shown in Fig. 2A or Fig. 5E, or may be disposed on the reflective resin layer 12, or may be disposed across from the base 11 to the reflective resin layer 12, as shown in Fig. 2B or Fig. 4E. The light emitting element 13 may be covered with a sealing member 15 disposed on the inside of the frame 14.

(Substrate 11)
The substrate 11 is a member on which the reflective resin layer 12 is disposed, and has a wiring layer.
Examples of materials for the substrate 11 include insulating materials such as resins and ceramics, and metal substrates having insulating materials formed on their surfaces. Among these, the substrate material is preferably a metal substrate containing at least one selected from the group consisting of aluminum and copper, from the viewpoints of processability and heat dissipation. The surface of these metal substrates may be covered with a film of a material with high reflectivity, such as silver, gold, or an alloy thereof.
The wiring layer may be formed of any metal capable of supplying current to the light-emitting element, such as copper, aluminum, gold, silver, platinum, titanium, tungsten, palladium, iron, nickel, or an alloy containing these metals. The wiring layer formed on the upper surface of the substrate 11 may have its top surface covered with a highly reflective material such as silver, gold, or an alloy thereof. When silver or an alloy thereof is used on the top surface of the wiring layer, there is a concern that the silver will turn into silver sulfide and turn black over time, reducing the initial brightness. However, as described above, by arranging the reflective resin layer 12 on the substrate 11, particularly on the wiring layer, the wiring layer can be protected from the external environment, and the wiring layer can be effectively prevented from turning black over time. As a result, not only the reflection of light emitted from the light-emitting element by the reflective resin layer 12, but also the prevention of changes over time makes it possible to ensure the quality of the light-emitting device with high light extraction efficiency for a long period of time. The wiring layer can be formed by electrolytic plating, electroless plating, vapor deposition, sputtering, or the like. For example, when Au bumps are used to mount a light emitting element on a substrate, the bonding strength between the light emitting element and the substrate can be improved by using Au on the outermost surface of the wiring layer.
The wiring layer is preferably formed as a pair of positive and negative patterns in various shapes and thicknesses on the substrate 11. The wiring layer may be disposed on at least one of the upper surface, the interior, and the lower surface of the substrate 11. Furthermore, the substrate 11 may have another wiring for connecting to a protection element in addition to the wiring layer disposed on the upper surface.

(Reflective resin layer 12)
The reflective resin layer 12 is a member disposed on the upper surface of the substrate 11. In particular, when a metal substrate is used as the substrate 11, the reflective resin layer 12 provides insulation and reflects light emitted from the light emitting element. This is a member that can prevent light from being absorbed by the substrate, efficiently reflect light, and improve the light extraction efficiency of the light emitting device.
The reflective resin layer 12 has a first flat portion 12A, a second flat portion 12B, and a first convex portion 12C. The second flat portion 12B is a portion where a light emitting element, which will be described later, is disposed. The area of the two flat portions is preferably the same as the area of the light emitting element. The thickness of the second flat portion 12B is smaller than the first thickness of the first flat portion 12A. This is because the reflective resin layer 12 After the material is placed on the top surface of the substrate 11, a part of the light emitting element 13 is pressed into the material, thereby forming a recess that follows the outline of the bottom surface and part of the side surface of the light emitting element 13, This is because the material of the reflective resin layer 12 is hardened while the recess is maintained. For example, when the first thickness H1 of the first flat portion 12A and the second thickness H2 of the second flat portion 12B are The difference may be 1 μm or more and 80 μm or less. The first thickness H1 of the first flat portion 12A is, for example, 10 μm or more and 100 μm or less, preferably 10 μm or more and 50 μm or less, and more preferably 10 μm or more and 30 μm or less. , 1 μm or more and 20 μm or less, preferably 1 μm or more and 15 μm or less, and more preferably 1 μm or more and 10 μm or less.

The first convex portion 12C protrudes from the upper end of the first planar portion 12A. The first convex portion 12C is arranged with a part of its side surface in contact with the side surface of the light-emitting element 13. Here, contact means that the reflective resin layer 12 constituting the first convex portion 12C is in direct contact with the side surface of the light-emitting element without another member being interposed. The thickness of the first convex portion 12C from the upper end of the first planar portion 12A (shown as "H3" in FIG. 1C) can be, for example, 0.3 times or less, preferably 0.2 times or less, and more preferably 0.1 times or less, the thickness of the light-emitting element. In other words, the difference between the third thickness and the first thickness of the first convex portion 12C can be 0.3 times or less, preferably 0.2 times or less, and more preferably 0.1 times or less, the thickness of the light-emitting element. By setting the thickness in this way, it is possible to suppress a decrease in luminous efficiency without inhibiting light emission from the side surface of the light-emitting element. Specifically, the third thickness (H1+H3) of the first convex portion 12C is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The maximum width of the first convex portion 12C from the side of the light-emitting element (shown as "W1" in FIG. 1C), that is, the distance to the first flat portion 12A on the substrate 11 side, is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The first convex portion 12C is preferably disposed so as to surround the light-emitting element. In this case, the first convex portion 12C may surround all or only a part of the periphery of the light-emitting element. As a result, as shown in FIG. 1E, the light L emitted from the light-emitting element to the substrate 11 side and emitted from the lower side of the light-emitting element can be effectively reflected upward, and the light extraction efficiency of the light-emitting device can be improved.

In a cross-sectional view taken in a direction perpendicular to the main surface of the substrate, the first convex portion 12C is preferably an arc-shaped portion that bulges outward and has an opposite side to the side surface of the light-emitting element. This shape of the first convex portion 12C can more efficiently reflect light from the adjacent light-emitting element to the outside of the light-emitting device when multiple light-emitting elements are arranged on the substrate than an inwardly recessed arc-shaped portion formed by a fluid resin creeping up against the side surface of the light-emitting element.
The first convex portion 12C is disposed such that the upper side surface thereof is spaced apart from the side surface of the light emitting element 13. The contact angle (angle α shown in FIG. 1D ) between the upper side surface of the first convex portion 12C and the side surface of the light emitting element is, for example, 90 degrees or more, preferably 105 degrees or more, more preferably 110 degrees or more, and even more preferably 120 degrees or more. In other words, the reflective resin layer 12 is in contact with the side surface of the light emitting element, but it is preferable that the reflective resin layer 12 is made of a material that is not easily wetted by the light emitting element 13.

Regardless of whether a single or multiple light-emitting elements are arranged on the substrate, the first flat portion 12A may be integrally arranged over a wide area on the upper surface of the substrate 11, particularly in the case where multiple light-emitting elements are arranged, around the multiple first convex portions 13C arranged in contact with each of the side surfaces of the multiple light-emitting elements 13, as shown in the light-emitting device 10 in Figures 1A and 1B. When the first flat portion 12A is integrally arranged over a wide area, the reflective resin layer 12 covers the upper surface of the substrate 11 over a wide area, so that the light emitted from the light-emitting element can be efficiently reflected to the light extraction surface side. In addition, for example, when a silver or silver alloy film is formed on the surface of the substrate, sulfurization of silver can be effectively prevented.
6A, 6B and 8A, 8B, the first flat portion 12A of the reflective resin layer 12 may be arranged separately for each light emitting element 13 around a plurality of first convex portions 13C arranged in contact with the side surfaces of the plurality of light emitting elements 13, as shown in the light emitting device 10E or 10G, or may be arranged with only a part spaced apart from the first convex portions 12C that are in contact with the side surfaces of adjacent light emitting elements 13, as shown in the light emitting device 10F in Fig. 7A. In this way, when a part or all of the first flat portion 12A is arranged with a space therebetween, when the light emitting element 13 is arranged on the reflective resin, it is possible to effectively prevent a defect such as the light emitting element flowing together with the resin on the reflective resin and coming into contact with an adjacent light emitting element before the reflective resin hardens.

Examples of the first reflecting material include titanium oxide, silicon oxide, zirconium oxide, potassium titanate, aluminum oxide, aluminum nitride, boron nitride, mullite, niobium oxide, barium sulfate, various rare earth oxides (e.g., yttrium oxide, gadolinium oxide), etc. Among these, titanium oxide is preferable from the viewpoint of improving reflectivity, and boron nitride is preferable from the viewpoint of thermal conductivity.
The first reflector preferably has a uniform particle diameter. This is because the light emitting element does not tilt, and when multiple light emitting elements are arranged, the heights of the multiple light emitting elements on the substrate can be made closer to a constant for each light emitting element. The first reflector can have a median diameter of, for example, 1 μm or less, preferably 0.5 μm or less, and more preferably 0.3 μm or less. In particular, it is preferable that the first reflector does not substantially contain particles with a median diameter larger than 2 μm. Here, "substantially not contained" means that the first reflector used contains 5% by weight or less, 3% by weight or less, 1% by weight or less, or 0.5% by weight or less. When large particles are not contained, even if the light emitting element is arranged on the reflective resin layer, the light emitting element does not tilt, and no unevenness is generated on the surface of the first flat portion, and the reflection efficiency can be improved by the smooth surface.

Examples of the first resin include thermosetting resins and thermoplastic resins. Specifically, modified epoxy resin compositions such as epoxy resin compositions, silicone resin compositions, and silicone-modified epoxy resins; modified silicone resin compositions such as epoxy-modified silicone resins; hybrid silicone resins; polyimide resin compositions, modified polyimide resin compositions; polyphthalamide (PPA); polycarbonate resins; polyphenylene sulfide (PPS); liquid crystal polymers (LCP); ABS resins; phenolic resins; acrylic resins; and PBT resins. Among these, resins or hybrid resins containing one or more of silicone resins, modified silicone resins, epoxy resins, modified epoxy resins, and acrylic resins are preferred, and in particular, thermosetting resins, that is, one or more selected from silicone resins and epoxy resins, are more preferred.
The reflective resin layer 12, particularly the first flat portion 12A or the second flat portion 12B, is preferably adjusted so that the light reflectance for light with a wavelength of 450 nm is, for example, 90% or more. For example, the first reflective material is adjusted to 5% to 80% by weight relative to the weight of the first resin, preferably 5% to 50% by weight, and more preferably 7% to 30% by weight.

(Light-emitting element 13)
The light-emitting element 13 is disposed on the substrate 11. Two or more light-emitting elements 13 may be disposed on the substrate 11 as shown in Figures 1A and 1B, or only one light-emitting element 13 may be disposed on the substrate 11 as shown in light-emitting devices 10A and 10C in Figures 2A, 2B, etc. It is preferable that the light-emitting element is directly bonded to the reflective resin layer without using any other adhesive.
The light-emitting element 13 is disposed inside the region surrounded by the first convex portion 12C. It is preferable to use a light-emitting diode as the light-emitting element 13. The light-emitting element can be selected from those with any wavelength. For example, blue and green light-emitting elements can be made of nitride semiconductors, ZnSe, or GaP. The light-emitting element has an emission peak wavelength within a wavelength range of, for example, 350 nm or more and 500 nm or less. In addition, GaAlAs, AlInGaP, etc. can be used as the red light-emitting element. Furthermore, semiconductor light-emitting elements made of other materials can also be used.
The light emitting element 13 is formed, for example, by laminating a nitride semiconductor layer on a light-transmitting support substrate, and the support substrate side is the main light extraction surface of the light emitting element 13. The support substrate may be removed, for example, by polishing, laser lift-off, etc. It is preferable that the light emitting element 13 has, for example, a pair of electrodes on the same side.
The light emitting element 13 is preferably disposed on the substrate 11 with the surface on which the electrodes are formed facing up and the surface opposite to the surface on which the electrodes are formed facing the substrate 11. In this case, the electrodes are electrically connected to a wiring layer on the substrate by wires.

(Frame body 14)
When only one light-emitting element is disposed on the substrate 11, the frame 14 is disposed so as to surround the light-emitting element 13 outside the first convex portion 12C as shown in Fig. 2A or 2B. In this case, the frame 14 may be disposed outside the first flat portion 12A, that is, on the substrate 11, or may be disposed on the first flat portion 12A, or may be disposed across the substrate 11 and the first flat portion 12A. When two or more light-emitting elements are disposed on the substrate 11, the frame 14 is preferably disposed so as to surround the entire light-emitting element 13 near the outer periphery of the substrate 11 and outside the first convex portion 12C as shown in Fig. 4D, 5D, 8A, or 8E.
The frame 14 is used to guide the light emitted from the light emitting elements upward. Therefore, the frame 14 is preferably formed of, for example, a material containing a second resin, particularly a material in which the second resin contains a second reflecting material. The second resin may be the same as the first resin described above. The second reflecting material may be the same as the first reflecting material described above. The first resin and the second resin may be made of the same material or different materials. The first reflecting material and the second reflecting material may be made of the same material or different materials.

The height, width, position, etc. of the frame 14 can be set as appropriate. For example, it is preferable that the frame 14 is arranged so that its upper surface is higher than the upper surface of the light-emitting element. Specifically, the height of the frame 14 can be 10 μm or more and 500 μm or less, and preferably 50 μm or more and 300 μm or less. By making the frame have such a height, when the light-emitting element 13 is covered with the sealing member 15 described later, even when the mounting form is face-up mounting and electrical connection is made using a wire, the loop top of the wire can be covered with the sealing member. The side of the frame 14, particularly the side facing the light-emitting element, may be arranged perpendicular to the substrate in a cross-sectional view perpendicular to the main surface of the substrate, or may be arranged in a straight or curved shape with a narrower width at the top.

(Sealing member 15)
2A, 2B or 4D, it is preferable that the sealing member 15 covers the reflective resin layer 12 and a part or all of the light emitting element 13, and it is more preferable that the sealing member 15 covers the entire light emitting element 13. The sealing member 15 may be disposed with any thickness as long as it covers the entire thickness direction and the upper surface of the light emitting element 13, and for example, it is preferable that the upper surface is disposed at a position equal to or lower than the height of the frame 14.
The sealing member 15 is preferably formed of a material containing a third resin, for example. Examples of the third resin include the same as the first resin described above. Among them, a light-transmitting resin that transmits 60% or more, 70% or more, 75% or more, or 80% or more of the light emitted from the light-emitting element 13 is preferable. In addition, the material containing the third resin may contain at least one of a phosphor or a light diffusing material capable of wavelength conversion of at least a part of the incident light.

The sealing member 15 may contain a phosphor. As the phosphor, one that can be excited by the light emitted from the light-emitting element is used. For example, phosphors that can be excited by a blue light-emitting element or an ultraviolet light-emitting element include yttrium aluminum garnet phosphors activated with cerium (YAG:Ce), lutetium aluminum garnet phosphors activated with cerium (LAG:Ce), silicate phosphors activated with europium ((Sr,Ba) ₂ SiO ₄ :Eu), β-sialon phosphors, nitride phosphors whose composition formulas are CaAlSiN ₃ :Eu or (Sr,Ca)AlSiN ₃ :Eu, fluoride phosphors activated with Mn, sulfide phosphors, and quantum dot phosphors. By combining these phosphors with a blue light-emitting element or an ultraviolet light-emitting element, a light-emitting device with a desired light emission color (for example, a white light-emitting device) can be manufactured.
Examples of light diffusing materials include titanium oxide, barium titanate, aluminum oxide, silicon oxide, zirconium oxide, aerosil, glass, glass fiber, wollastonite or other fillers, and aluminum nitride.
From the viewpoint of easily preventing the occurrence of voids, it is preferable that the material constituting the sealing member 15 contains a resin that has high fluidity and is cured by irradiation with heat or light. Examples of such materials include those that exhibit fluidity at a viscosity of 0.5 Pa·s to 30 Pa·s.

[Method of manufacturing the light-emitting device]
An example of a method for manufacturing the light emitting device of this embodiment will be described. The method for manufacturing the light emitting device of this embodiment includes the following steps, as shown in FIGS. 3A and 3B :
A step (S1) of applying a reflective resin onto a substrate;
The method includes a step (S2) of disposing a light-emitting element on the reflective resin, and a step (S4) of curing the reflective resin.
In this method, in the step (S2) of arranging the light-emitting element, a part of the light-emitting element is pressed into the reflective resin, so that after the reflective resin is cured, the reflective resin layer is formed with a first flat portion where the light-emitting element is not arranged, a second flat portion where the light-emitting element is arranged and has a thickness smaller than that of the first flat portion, and a first convex portion on the outer periphery of the light-emitting element.
By using such a manufacturing method, the above-mentioned light emitting device having good light extraction efficiency can be easily manufactured.
This method for manufacturing a light emitting device may include a step (S5) of forming a sealing member.
In addition, the manufacturing method of this light-emitting device may include a step (S3) of forming a frame around the light-emitting element after step S2, as shown in Figures 3A and 4A to 4E or Figures 8A to 8E, or may include a step (S3') of forming a frame on the substrate before step S1, as shown in Figures 3B and 5A to 5E.

(Step of applying reflective resin onto a substrate: S1)
As shown in Figures 3A and 4A, reflective resin 12a is applied onto substrate 11. As described above, reflective resin 12a includes a first reflective material and a first resin. Reflective resin 12a may be applied to the entire upper surface of substrate 11, or may cover the entire upper surface except for a partial region. In particular, it is preferable to apply reflective resin 12a so as to integrally cover the region where light emitting elements are arranged and the surrounding region.
The reflective resin 12a preferably contains an organic solvent together with the first reflective material and the first resin. The organic solvent may be any one that is commonly used in the field, and examples thereof include alcohols (isopropyl alcohol, 3-methoxybutanol, 3-methyl-3-methoxybutanol, etc.), ketones (cyclohexanone, etc.), esters (γ-butyrolactone, propylene glycol monomethyl ether acetate, ethyl lactate, etc.), ethers (diethyl ether, THF, propylene glycol monomethyl ether, etc.), hydrocarbons (cyclohexane, n-hexane, heptane, iso-octane, tridecane, etc.), aromatic hydrocarbons (xylene, toluene, etc.), etc. These may be used alone or in combination of two or more kinds. Among them, for example, those having a boiling point of 150°C to 300°C are preferable, and specifically, tridecane is more preferable. The solvent may be contained in an amount of, for example, 25 to 500% by weight of the total weight of the reflective resin, and in particular, when tridecane is used, it is preferable that the solvent be contained in an amount of 200 to 400% by weight of the total weight of the reflective resin.
The thickness of the reflective resin 12a is preferably adjusted so that the maximum thickness of the reflective resin layer after curing is 10 μm to 100 μm. The reflective resin is preferably applied to the substrate 11 with a uniform thickness. Examples of the application method include potting, various printing methods, spin coating, and other methods known in the art.

In this process, as shown in FIG. 8C, multiple pieces of reflective resin 12a may be arranged at a distance from each other in the areas corresponding to the mounting areas of the multiple light-emitting elements. The size of each piece of reflective resin 12a here may be, for example, 100% to 200% of the planar area of the light-emitting element, and preferably 110% to 180%.

(Step of arranging light emitting element on reflective resin: S2)
As shown in FIG. 3A and FIG. 4B, the light emitting element 13 is placed on the reflective resin 12a applied on the substrate 11. The light emitting element 13 is placed in a state where the reflective resin 12a is not yet cured. When the light emitting element 13 is placed on the reflective resin 12a, a part of the light emitting element 13 is pressed into the reflective resin. As a result, the surface 12aB (later to become the second flat portion) of the reflective resin 12a on which the light emitting element 13 is placed is pressed into the substrate 11 side, so that the thickness of the surface 12aB of the reflective resin 12a on which the light emitting element 13 is placed can be made smaller than the thickness of the surface 12aA (later to become the first flat portion) of the reflective resin 12a on which the light emitting element 13 is not placed. At this time, the light emitting element 13 is pressed against the reflective resin 12a, so that a part of the reflective resin 12a directly below the light emitting element 13 moves to the side of the light emitting element 13. As a result, a protuberance 12aC (later to become the first convex portion) of the reflective resin 12a can be formed on the outer periphery of the light emitting element 13. The bulge 12aC of the reflective resin 12a is in an outwardly bulging arc shape in a cross section perpendicular to the main surface of the substrate. For example, when a part of the light emitting element is pressed onto a layer of a resin with low viscosity, the resin creeps up to the side of the light emitting element and covers the side. In this case, the creeping resin is in an inwardly concave arc shape on the surface opposite to the side of the light emitting element in a cross section perpendicular to the main surface of the substrate. In contrast, the above-mentioned reflective resin 12a is in an outwardly bulging arc shape on the surface opposite to the side of the light emitting element 13 in a cross section perpendicular to the main surface of the substrate. In order to obtain such an outwardly bulging arc shape, it is preferable to adjust the composition of the reflective resin 12a, for example, as described above. Specifically, a transparent silicone resin having a viscosity of approximately 1 Pa·s to 5 Pa·s is mixed with a light-reflective first reflective material in the range of 5% to 200% by weight, and the viscosity of the material of the reflective resin 12a is adjusted to 1 Pa·s or more and 500 Pa·s or less, more preferably 10 Pa·s or more and 250 Pa·s or less.

Also, as shown in FIG. 8D, light emitting elements 13 may be arranged on a plurality of reflective resins 12a applied to the substrate 11. By arranging the reflective resins 12a in this manner, the light emitting elements 13 flow together with the resin, and contact with adjacent light emitting elements 13 can be effectively prevented. However, depending on the amount of each reflective resin 12a and/or the degree to which the light emitting elements 13 are pressed in, adjacent reflective resins 12a may be partially or entirely connected to each other.

(Step of forming a frame: S3)
Optionally, at an arbitrary stage, such as after arranging the light emitting element 13 on the reflective resin 12a or after applying the reflective resin 12a onto the substrate 11, a frame 14 is further formed on the substrate 11 around the light emitting element 13 as shown in Fig. 3A and Fig. 4C. The frame 14 may be formed directly on the substrate 11, or may be formed on the reflective resin 12a as shown in Fig. 4C.
As described above, the frame 14 can be formed using the second resin. The frame 14 can be formed by, for example, injection molding, potting molding, a resin printing method, a transfer molding method, compression molding, or the like.
The frame 14 may be formed by curing the second resin after curing the reflective resin 12a, but when the reflective resin 12a is applied onto a substrate, it is preferable to cure the second resin for forming the frame 14 together with curing the reflective resin 12a described below. This can simplify the manufacturing process.
In addition, after arranging multiple light-emitting elements 13 on the reflective resin 12a, a frame 14 may be formed around the multiple light-emitting elements 13 on the substrate 11 at any stage, such as before or after the reflective resin 12a has hardened, as shown in Figure 8E.

(Step of curing the reflective resin: S4)
3A and 4D, the reflective resin 12a is cured. In this case, when a second resin is disposed to form the frame 14, it is preferable to cure the second resin together with the reflective resin 12a.
The reflective resin 12a can be cured, for example, by heating at a temperature range of 50° C. to 200° C. for 5 to 300 minutes, more preferably at 80° C. to 180° C. for 10 to 120 minutes.
After the reflective resin 12a is cured in this manner, the solvent contained in the reflective resin 12a volatilizes completely and does not remain or does not substantially remain in the reflective resin layer 12. Here, substantially does not remain means that the solvent is 5% by weight or less, 3% by weight or less, 1% by weight or less, or 0.5% by weight or less of the material used. As a result, the reflective resin 12a shrinks due to curing, but the reflective resin layer 12 on which the light emitting element 13 is arranged becomes the second flat portion 12B, and the thickness can be made smaller than the thickness of the first flat portion 12A, which is the reflective resin layer 12 on which the light emitting element 13 is not arranged. In addition, the bulge of the reflective resin 12a formed by the movement of a part of the reflective resin 12a directly below the light emitting element 13 to the outside of the light emitting element 13 becomes the first convex portion 12C on the outer periphery of the light emitting element 13, and can be made into an arc shape that bulges outward in a cross-sectional view in a direction perpendicular to the main surface of the substrate. These reflective resin layers 12 can effectively reflect the light emitted from the lower side of the light emitting element upward, increasing the luminous flux and improving the light extraction efficiency. In addition, due to the first reflector in the reflective resin layer 12, heat can be more efficiently removed from the lower side of the light emitting element, reducing the thermal resistance. As a result, a large current can be passed through the light emitting device, which can contribute to improving the light extraction efficiency.
As described above, when multiple reflective resins 12a are applied onto a substrate while being spaced apart from each other, multiple first planar portions 12A can be formed, all of which are spaced apart from each other or only some of which are spaced apart and the other portions are connected, as shown in Figure 8E.

(Step S5 of forming sealing member)
3A and 4E , it is preferable to form a sealing member 15 so as to cover the light emitting element 13. In the case where the frame body 14 is formed, it is preferable to form the sealing member 15 inside the frame body 14 so as to cover the light emitting element 13.
The sealing member 15 can be formed by, for example, injection molding, potting molding, resin printing, transfer molding, compression molding, or the like.
This allows the manufacture of the light emitting device 10B as shown in FIG. 4E.
8A and 8B, a sealing member 15 may be formed inside the frame 14 so as to cover the light emitting element 13. In this manner, the light emitting device 10G can be manufactured.

In the above-described method for manufacturing a light-emitting device, a frame 14 may be formed on the substrate 11 (S3') as shown in Figs. 3B and 5A before step S1 of applying the reflective resin onto the substrate.
Thereafter, as shown in FIG. 3B and FIG. 5B, the reflective resin 12a is applied onto the substrate inside the frame 14 as described above (S1).
Next, as shown in Figures 3B and 5C, a light-emitting element is placed on the reflective resin 12a as described above (S2), and as shown in Figures 3B and 5D, the reflective resin 12a is hardened (S4) to form the reflective resin layer 12 as described above.
Subsequently, as shown in FIG. 3B and FIG. 5E, as described above, it is preferable to form a sealing member 15 so as to cover the light emitting element 13 (S5).
This allows the manufacture of a light emitting device 10D as shown in FIG. 5E.

By using this manufacturing method for a light-emitting device, as described above, it is possible to easily form a reflective resin layer 12 having a first planar portion 12A, a second planar portion 12B, and a first convex portion 12C. Therefore, the reflective resin layer 12 having such a unique shape can effectively reflect light emitted from below the side surface of the light-emitting element upward. This makes it possible to increase the luminous flux and improve the light extraction efficiency. In addition, heat can be dissipated more efficiently below the side surface of the light-emitting element, and thermal resistance can be reduced. As a result, a light-emitting device that can pass a large current and contribute to improving the light extraction efficiency can be manufactured by a simple method.

Furthermore, as shown in FIG. 3A, when the frame is formed after the reflective resin is applied to the substrate, the reflective resin layer can be reduced from creeping up onto the frame. Also, peeling of the reflective resin layer can be suppressed. On the other hand, as shown in FIG. 3B, when the frame is formed before the reflective resin is applied to the substrate, the application of the reflective resin to a predetermined location on the substrate can be efficiently positioned.

Example A light emitting device 10B shown in FIG. 4E was formed by the above-mentioned method for manufacturing a light emitting device.
This light emitting device 10B has a reflective resin layer 12 arranged on a substrate 11 made of an aluminum plate, and a plurality of light emitting elements 13 arranged on top of the reflective resin layer 12, and further includes a frame body 14 that surrounds the outside of the plurality of light emitting elements 13, and a sealing member 15 within the frame body 14 that covers the plurality of light emitting elements 13.
The reflective resin layer 12 contains a silicone resin as a first resin and titanium oxide having a median diameter of 0.2 μm as a first reflecting material at 30% by weight relative to the resin. The reflective resin layer 12 has a first planar portion 12A, a second planar portion 12B having a second thickness smaller than the first thickness of the first planar portion 12A, and a first convex portion 12C protruding from the first planar portion 12A. The first planar portion 12A and the second planar portion 12B have a light reflectance of 93% for light with a wavelength of 450 nm. The light emitting element 13 is disposed on the second planar portion 12B, and the first convex portion 12C is disposed so that a part of its side surface is in contact with the side surface of the light emitting element 13. In other words, the light emitting element 13 is disposed inside the first convex portion 12C.
In this light emitting device, the first thickness of the first flat portion 12A is 17 μm. The second thickness of the second flat portion 12B is 2 μm to 5 μm. The thickness of the first protrusion 12C from the upper end of the first flat portion 12A is 10 μm, that is, the third thickness (H1+H3) is 27 μm, the maximum width from the side surface of the light emitting element is 10 μm, and the contact angle between the upper side surface of the first protrusion 12C and the side surface of the light emitting element (the angle indicated by α in FIG. 1D ) is 120 degrees.
In contrast, as a comparative example, a light emitting device X was produced having a similar configuration except that the light emitting element was disposed on the substrate using a modified silicone resin without using a reflective resin layer.
When the brightness of the light emitting device 10B was compared with that of the light emitting device X, the brightness (total luminous flux) of the light emitting device 10B was 12.8% greater than that of the light emitting device X. It was found that the light emitting device 10B had a higher light extraction efficiency than that of the light emitting device X. Furthermore, when the thermal resistance of the light emitting device 10B was compared with that of the light emitting device X, the thermal resistance of the light emitting device 10B was 10% lower than that of the light emitting device X.

REFERENCE SIGNS LIST 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G Light emitting device 11 Substrate 12 Reflective resin layer 12A First flat portion 12B Second flat portion 12C First convex portion 12a Reflective resin 12aA, 12aB Surface of reflective resin 12a 12aC Protuberance of reflective resin 12a 13 Light emitting element 14 Frame 15 Sealing member

Claims (23)

A substrate;
a reflective resin layer disposed on the substrate, the reflective resin layer having a first planar portion having a first thickness, a second planar portion having a second thickness smaller than the first thickness, and a first convex portion having a third thickness larger than the first thickness, the reflective resin layer including a first reflective material and a first resin;
a light emitting element disposed on the second planar portion of the reflective resin layer,
The first protrusion is disposed so that a part of its side surface is in contact with a side surface of the light emitting element. The light-emitting device according to claim 1, wherein the first planar portion is disposed around the first convex portion and in contact with the first convex portion, and the first thickness is 10 μm or more and 100 μm or less. The light-emitting device according to claim 1 or 2, wherein the second thickness of the second planar portion is 1 μm or more and 20 μm or less. The light-emitting device according to any one of claims 1 to 3, wherein the area of the second planar portion is the same as the area of the light-emitting element. The light-emitting device according to any one of claims 1 to 4, wherein the substrate is a metal substrate containing at least one selected from aluminum, copper, and iron. The light-emitting device according to any one of claims 1 to 5, wherein the third thickness in the first convex portion is 30 μm or less. The light-emitting device according to any one of claims 1 to 6, wherein the third thickness of the first convex portion is 0.3 times or less the thickness of the light-emitting element. The light-emitting device according to any one of claims 1 to 7, wherein the first protrusion has a width of 25 μm or less. The light emitting device according to any one of claims 1 to 8, wherein the light emitting element has an emission peak wavelength within a wavelength range of 350 nm to 500 nm, and the first planar portion or the second planar portion has a light reflectance of 90% or more for light with a wavelength of 450 nm. The light-emitting device according to any one of claims 1 to 9, wherein the first protrusion is disposed to surround the light-emitting element. The light-emitting device according to any one of claims 1 to 10, wherein the first convex portion has an outwardly bulging arc shape in a cross-sectional view perpendicular to the main surface of the substrate. The light-emitting device according to any one of claims 1 to 11, wherein the contact angle between the side of the first convex portion and the side of the light-emitting element is 90 degrees or more. The light emitting device according to any one of claims 1 to 12, wherein the light emitting element is disposed inside the first convex portion, and a frame body is provided outside the first convex portion so as to surround the light emitting element and includes a second reflector and a second resin. The light-emitting device according to any one of claims 1 to 13, wherein the light-emitting element is directly bonded to the reflective resin layer. The light-emitting device according to any one of claims 1 to 14, wherein the first resin is at least one selected from a silicone resin and an epoxy resin. The light emitting device according to any one of claims 1 to 15, wherein the first reflector is at least one selected from the group consisting of titanium oxide, boron nitride, silicon oxide, and aluminum oxide. The light emitting device according to any one of claims 1 to 16, wherein the first reflector has a median diameter of 1 μm or less. a plurality of the light emitting elements disposed on the second plane portion;
18. The light-emitting device according to claim 1, wherein the first planar portion of the reflective resin layer is arranged integrally or partially or entirely spaced apart around a periphery of a plurality of first convex portions arranged in contact with each of the side surfaces of the plurality of light-emitting elements. A step of applying a reflective resin containing a reflective material and a first resin onto a substrate;
A step of disposing a light emitting element on the reflective resin applied to the substrate;
and curing the reflective resin.
A method for manufacturing a light emitting device, in a step of arranging the light emitting element, a part of the light emitting element is pressed into the reflective resin, and a first planar portion having a first thickness on which the light emitting element is not arranged, a second planar portion on which the light emitting element is arranged and having a second thickness smaller than the first thickness, and a first convex portion in contact with a side surface of the light emitting element and having a third thickness larger than the first thickness are formed. The method for manufacturing a light-emitting device according to claim 19, wherein in the step of arranging the light-emitting element, the first convex portion is formed so as to surround the light-emitting element. The method for manufacturing a light-emitting device according to claim 19 or 20, wherein in the step of arranging the light-emitting element, the first convex portion is formed to have an outwardly expanding arc shape in a cross-sectional view perpendicular to the main surface of the substrate. The method for manufacturing a light-emitting device according to any one of claims 19 to 21, wherein in the step of arranging the light-emitting elements, a plurality of the light-emitting elements are arranged on the reflective resin, and the first flat portion is integrally formed around a first protrusion that contacts each of the side surfaces of the plurality of light-emitting elements. In the step of applying the reflective resin onto the substrate, a plurality of reflective resins are arranged so as to be spaced apart from each other;
22. A method for manufacturing a light emitting device according to any one of claims 19 to 21, wherein in the step of arranging the light emitting elements, a plurality of the light emitting elements are respectively arranged on a plurality of the reflective resins spaced apart from each other, thereby forming a plurality of the first planar portions, some or all of which are spaced apart from each other.

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