Repairing method of light-emitting device and light-emitting device

Abstract

To provide a light-emitting device to which a plurality of μLEDs are mounted, capable of preferably lighting each repaired μLED after the μLED which had a lighting failure is repaired.SOLUTION: In repairing a light-emitting device 10 to which a plurality of μLEDs are mounted via a first conductive film 4 in which a first conductive particle 3 is held by a first insulation resin layer 2, each μLED of a repair object is specified from the μLEDs mounted, and is removed from a translucent substrate 5 by a laser lift off method;a μLED 1y for repairing is installed to a part of the translucent substrate in which the μLED is removed after a conductive film 40 for repair, to which a second conductive particle 30 is stored by a second insulation resin layer 20 is individually installed; and the μLED for repair is thermally crimped, and is mounted to the translucent substrate. The second conductive particle of the second conductive film for repair having a particle diameter larger than that of the first conductive particle of the first conductive film or being hardly crushed than the first conductive particle of the first conductive film is used.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for repairing a light emitting device in which μLEDs (Light Emitting Diodes) are mounted as light emitting elements, and the light emitting device. Specifically, the present invention relates to a method for repairing a μLED having a defective light emitting state among a plurality of mounted μLEDs to a good μLED, and a light emitting device having the repaired μLED. [Background technology]

[0002] In recent years, light-emitting devices such as full-color displays in which a huge number of μLEDs are mounted on a panel substrate have been attracting attention (see FIG. 7). Such a light-emitting device 10 has a structure in which a large number of μLEDs 100 are mounted on a light-transmitting substrate 104 by thermocompression bonding via an (anisotropic) conductive film 103 in which conductive particles 102 are held on a thermosetting insulating resin layer 101. In this structure, in order to ensure electrical continuity between the μLEDs 100 and the light-transmitting substrate 104, the conductive particles 102 are mounted by thermocompression bonding between the electrodes 100a of the μLEDs 100 and the electrodes (not shown) of the light-transmitting substrate 104 so as to be crushed.

[0003] Incidentally, in such a light emitting device 10, when some of the μLEDs are not lit, the unlit μLEDs are repaired (Patent Documents 1, 2, etc.). Specifically, as shown in Fig. 8, first, the unlit μLEDs 100 are selectively removed from the transparent substrate 104 together with the conductive film by irradiating the laser L from the transparent substrate 104 side by the laser lift-off method, and then, as shown in Fig. 9, a repair conductive film 103a having the same configuration as the conductive film 103 and a repair μLED 100R having the same configuration as the μLED 100 are placed in the part of the transparent substrate 104 from which the unlit μLEDs were removed by stamping or laser lift-off, etc., and the repair μLED 100R is pressed into the transparent substrate 104 by a heat tool 105 having a surface area much larger than that of the repair μLED 100R, as shown in Fig. 10. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-140934 A [Patent Document 2] JP 2021-144970 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the μLED 100R is pressed in as shown in Fig. 10, the insulating resin layer 101 constituting the conductive film 103 between the μLED 100 around the repair μLED 100R and the transparent substrate 104 has already hardened at that point, so it is difficult to deform by pressing with the heat tool 105. Therefore, when the repair μLED 100R can only be pressed in to the same height as the μLED 100 around it and the heat tool 105 is pulled up, a springback phenomenon occurs as shown in Fig. 11, and the conductive particles 102a between the electrode 100Ra of the repair μLED 100R and the electrode (not shown) of the transparent substrate 104 are not crushed, the conductive resistance increases, and in some cases the repair μLED 100R does not light up, which causes the need to repair again.

[0006] The present invention seeks to solve the problems of the conventional art, and aims to repair a μLED that is not properly lit in an illumination device in which multiple μLEDs are mounted by thermocompression on a translucent substrate via a conductive film in which conductive particles are held in an insulating resin layer, so that the repaired μLED will light up properly when repairing a μLED that is not properly lit. [Means for solving the problem]

[0007] The inventors hypothesized that the above-mentioned conventional problems were caused by the use of the same conductive film as the initial conductive film used when initially installing the μLEDs on the transparent substrate as the repair conductive film used when installing the repair μLEDs on the transparent substrate, and studied the conductive particles constituting the initial conductive film and the repair conductive film. As a result, as described below, it was found that the above-mentioned problems of the present invention can be solved if the conductive particles of the repair conductive film have a larger particle size than the conductive particles of the initial conductive film, or if the conductive particles of the repair conductive film are more difficult to crush than the conductive particles of the initial conductive film, and the present invention was completed.

[0008] That is, the present invention is a method for repairing a light-emitting device in which a plurality of μLEDs are mounted on a light-transmitting substrate by thermocompression bonding via a first conductive film in which first conductive particles are held in a first insulating resin layer, the method comprising the following steps (A) to (F): (Process A) A process to identify the μLED to be repaired from among multiple μLEDs implemented: (Process B) The process of removing the μLED to be repaired from the transparent substrate by laser lift-off: (Process C) a step of disposing a repair conductive film, in which second conductive particles are held in a second insulating resin layer, in an individual piece on a portion of the light-transmitting substrate from which the μLED has been removed; (Process D) A step of installing a repair μLED on a repair conductive film installed on a light-transmitting substrate; (Process E) A step of mounting the repair μLED on a light-transmitting substrate by thermocompression bonding; and (Process F) A process to check the operation of light-emitting devices equipped with repair μLEDs having This is a repair method in which the second conductive particles of the second conductive film for repair have a larger particle size than the first conductive particles of the first conductive film, or the second conductive particles of the second conductive film for repair are more difficult to crush than the first conductive particles of the first conductive film.

[0009] The present invention also provides a light-emitting device in which a plurality of μLEDs are mounted on a light-transmitting substrate, For the majority of the μLEDs, the first conductive particles are mounted on the light-transmitting substrate by compression (e.g., thermocompression) via a first conductive film in which the first conductive particles are held in a first insulating resin layer, and for the remaining small number of μLEDs, the second conductive particles are mounted on the light-transmitting substrate by compression (e.g., thermocompression) via a repair second conductive film in which the second conductive particles are held in a second insulating resin layer, To provide a light emitting device in which the second conductive particles of a repair second conductive film have a larger particle size than the first conductive particles of the first conductive film, or the second conductive particles of the repair second conductive film are less crushed than the first conductive particles of the first conductive film. Effect of the Invention

[0010] The method for repairing a light-emitting device of the present invention is characterized in that (a) the second conductive particles of the second conductive film for repair have a larger particle size than the first conductive particles of the first conductive film, or (b) the second conductive particles of the second conductive film for repair are less likely to be crushed than the first conductive particles of the first conductive film (in other words, the compressive elastic modulus is 20% higher). This makes it possible to achieve stable conduction between the opposing electrodes to be connected. Therefore, according to the method for repairing a light-emitting device of the present invention, in a light-emitting device in which a plurality of μLEDs are mounted on a transparent substrate by compression bonding (for example, thermocompression bonding) via a conductive film in which conductive particles are held in an insulating resin layer, when a μLED that is not properly lit is repaired, the repaired μLED can be made to light up properly, making it unnecessary to perform repair again. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is an explanatory diagram showing a state in which some μLEDs of a light-emitting device are not lit before the repair method of the present invention is applied. [Diagram 2] FIG. 2 is a process explanatory diagram of the repair method of the present invention. [Diagram 3] FIG. 3 is a process explanatory diagram of the repair method of the present invention. [Figure 4] FIG. 4 is a process explanatory diagram of the repair method of the present invention. [Diagram 5] FIG. 5 is a process explanatory diagram of the repair method of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view of a light emitting device after the repair method of the present invention has been applied. [Figure 7] FIG. 7 is an explanatory diagram showing a state in which some μLEDs of a conventional light-emitting device are not lit. [Figure 8] FIG. 8 is a process diagram illustrating a conventional method for repairing a light emitting device. [Figure 9] FIG. 9 is a process diagram illustrating a conventional method for repairing a light emitting device. [Figure 10] FIG. 10 is a process diagram illustrating a conventional method for repairing a light emitting device. [Figure 11] FIG. 11 is an explanatory diagram showing a state in which some μLEDs of a light-emitting device are not lit after a conventional method for repairing a light-emitting device is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] <Method of repairing a light-emitting device> The present invention is a method for repairing a light emitting device, and a light emitting device to which the repair method is applied typically has a structure shown in Fig. 1. That is, the repair method for a light emitting device 10 in which a plurality of μLEDs 1 are mounted by thermocompression bonding on a light transmissive substrate 5 via a first conductive film 4 in which first conductive particles 3 are held on a first insulating resin layer 2, comprises the following steps (A) to (F). Below, each step will be described, followed by a description of the characteristics of the conductive particles that characterize the present invention, and then a description of each component applicable to the repair method.

[0014] (Process A) Step A is a step of identifying a μLED to be repaired from among the multiple μLEDs mounted. Indicators for identifying the μLED to be repaired include whether it is lit, whether the amount of light emitted is insufficient, whether there is an appearance abnormality in color, shape, or size, and whether there is an alignment error. Usually, the one that is not lit is the one to be repaired. In the case of FIG. 1, the unlit μLED in the center is identified as the one to be repaired. As shown in FIG. 1, the light emitting device 10 before repair has a structure in which multiple μLEDs 1 are mounted on a transparent substrate 5 by thermocompression bonding via a first conductive film 4 in which a first conductive particle 3 is held by a thermoset first insulating resin layer 2. In such a light emitting device 10, a crushed conductive particle 2 is arranged between an electrode 1a of the μLED 1 and an electrode (not shown) of the transparent substrate 5.

[0015] (Process B) Step B is a step of removing the μLED to be repaired (for example, an unlit μLED) from the transparent substrate by the laser lift-off method. Specifically, as shown in FIG. 2, the unlit μLED 1x to be removed is irradiated with a laser L from the side of the transparent substrate 5 of the light-emitting device 10, and the unlit μLED 1x can be selectively transferred to a separately prepared adhesive film together with the first conductive film 4 directly below it (in other words, the first conductive film 4 located between the unlit μLED 1x and the transparent substrate 5) and removed. As a laser lift-off device for carrying out the laser lift-off method, a commercially available laser lift-off device (for example, the product name "Invisi LUM-XTR", manufactured by Shin-Etsu Chemical Co., Ltd.) can be used. In addition, the laser lift-off conditions can be appropriately selected in consideration of the shape, constituent material, and structure of the μLED and light-emitting device to be repaired, the recommended conditions of the laser lift-off device to be used, and the like. In addition, the first conductive film 4 may be anisotropically conductive.

[0016] (Process C) Step C is a step of disposing a repair conductive film in a piece form, in which the second conductive particles are held in the second insulating resin layer, on the portion of the translucent substrate from which the μLEDs have been removed. Specifically, as shown in FIG. 3, a repair second conductive film 40 in which the second conductive particles 30 are held in the second insulating resin layer 20 is disposed in a piece form on the exposed surface of the translucent substrate 5 of the light-emitting device 10 from which the μLEDs have been removed. As a method for disposing the repair second conductive film 40 in a piece form, a known method such as a stamp method, a screen printing method, or an inkjet method can be adopted, but it is preferable to dispose it by a laser lift-off method. For example, the second conductive film 40 for repair, in which the second insulating resin layer 20 holds the second conductive particles 30, is formed on the entire surface of the adhesive layer of the transparent substrate, and a laser is applied from the transparent substrate side by the laser lift-off method to remove unnecessary second conductive film 40 for repair, so that the second conductive film 40 for repair remains in pieces, thereby obtaining a conductive film transfer sheet having a large number of individual pieces of the second conductive film 40 for repair, and the second conductive film 40 for repair of the conductive film transfer sheet is aligned with the exposed surface of the light-transmitting substrate 5, and the second conductive film 40 for repair of the conductive film transfer sheet is transferred to the exposed surface of the light-transmitting substrate 5 by applying a laser from the transparent substrate side. The second conductive film 40 for repair may be anisotropically conductive.

[0017] (Process D) Step D is a step of installing the repair μLED on the repair conductive film installed on the light-transmitting substrate. Specifically, as shown in FIG. 4, the repair μLED 1y is installed on the exposed second repair conductive film 40 of the light-emitting device 10 from which the μLED has been removed, from its electrode 1ya side. A known method can be adopted as a method for installing the repair μLED 1y on the second repair conductive film 40. For example, a laser can be irradiated onto the repair μLED 1y from the back side of the μLED wafer substrate by the laser lift-off method, and the repair μLED 1y can be directly transferred to the second repair conductive film 40. Alternatively, the repair μLED can be transferred to an adhesive transfer sheet in advance, and then transferred from the transfer sheet to the second repair conductive film 40.

[0018] (Process E) Step E is a step of mounting the repair μLED on the light-transmitting substrate by thermocompression bonding. Specifically, as shown in Fig. 5, the repair μLED 1y is pressed into the light-transmitting substrate 5 while being heated from above with a heat tool H, and the second conductive particles 30 of the second repair conductive film 40 are crushed while the thermosetting second insulating resin layer 20 is thermally cured to mount the repair μLED 1y. This makes it possible to obtain the light-emitting device 10 having the structure shown in Fig. 6.

[0019] (Process F) Process F is a process for checking the operation of the light emitting device in which the repair μLED is mounted. Specifically, the light emitting device is operated and it is confirmed that the repair μLED 1y is lit. This completes the repair of the light emitting device.

[0020] <Characteristics of the Conductive Particles Characterizing the Method for Repairing a Light-Emitting Device of the Present Invention> The method for repairing a light emitting device of the present invention is characterized in that (a) the second conductive particles of the second repair conductive film have a larger particle size than the first conductive particles of the first conductive film, or (b) the second conductive particles of the second repair conductive film are less likely to be crushed than the first conductive particles of the first conductive film (in other words, have a 20% higher compressive elastic modulus). Of course, (a) and (b) may be satisfied simultaneously.

[0021] In the former case (a), when a repair conductive film and a repair μLED are placed on a translucent substrate in order to mount the repair μLED, the height of the repair μLED from the surface of the translucent substrate becomes higher than the height of the surrounding μLEDs that have already been mounted.As a result, when the repair μLED is mounted by thermocompression using a heat tool, pressure can be sufficiently concentrated on the second conductive particles, and stable conductivity can be achieved between the opposing electrodes to be connected.

[0022] The average particle size D1 of the first conductive particles in the first conductive film is preferably 1 μm or more, more preferably 1.5 μm or more, preferably 5 μm or less, and more preferably 3 μm or less, from the viewpoint of particle capture efficiency and application to the size of μLED. The average particle size D2 of the second conductive particles is preferably 1.1 times or more, more preferably 1.3 times or more, preferably 2 times or less, and more preferably 1.7 times or less of the average particle size D1 of the first conductive particles, in order to apply it to the size of μLED and ensure repairability. The average particle size of the conductive particles can be measured by a known method, for example, by an imaging particle size distribution analyzer (FPIA-3000, manufactured by Malvern Panalytical).

[0023] In the latter case (b), when the repair μLED is mounted by thermocompression using a heat tool, the oxide film on the surface of the opposing electrodes to be connected can be broken through with little pressure, and stable conductivity can be achieved between the opposing electrodes to be connected.

[0024] The crushability of the conductive particles can be evaluated by the compression modulus. This is because the higher the compression modulus of the conductive particles, the more difficult the conductive particles are to crush. Also, the evaluation is performed at 20% compression (20% K value) because the conduction by the compressed conductive particles becomes stable when compressed by 20%. The 20% compression modulus E1 (20% K value) of the first conductive particles is preferably 2000 MPa or more, more preferably 3000 MPa or more, preferably 6000 MPa or less, more preferably 5000 MPa or less in order to apply it to μLEDs. Moreover, the 20% compression modulus E2 (20% K value) of the second conductive particles is preferably 1.1 times or more, more preferably 1.3 times or more, preferably 2.5 times or less, more preferably 2 times or less, and preferably 4000 MPa or more and 10000 MPa or less, in order to apply it to the size of μLEDs and ensure repairability. The 20% compressive elastic modulus can be calculated by measuring the compression deformation of the conductive particles when a compressive load is applied to the conductive particles using a micro-compression testing machine (e.g., Fischerscope H-100 manufactured by Fisher Instruments), using the following formula where F is the load value (N) when the conductive particles are compressed by 20%, S is the compression displacement (mm) when the conductive particles are compressed by 20%, and R is the average radius (mm) of the conductive particles.

[0025]

number

[0026] As described above, according to the method for repairing a light-emitting device of the present invention, in a light-emitting device in which multiple μLEDs are mounted by thermocompression on a translucent substrate via a conductive film in which conductive particles are held in an insulating resin layer, by repairing a μLED that is not properly lit, the repaired μLED can be made to light up properly, making it unnecessary to repair it again.

[0027] <Description of an example of a component applied to the repair method of the present invention> (Light emitting device 10) The light-emitting device 10 to which the repair method of the present invention is applied uses μLEDs as light-emitting elements, and examples thereof include image display devices such as full-color displays and lighting devices. Instead of μLEDs, the method can be applied to other minute light-emitting elements such as mini-LEDs or minute components (electronic components). One example of the size is one with a maximum length of one side of 200 μm or less. In some cases, the size can be as large as 10 to 30 μm square, making manual work extremely difficult.

[0028] (μLED1) The μLED can be a known one, preferably a flip-chip type with a maximum length of 3 μm or more and 100 μm or less when viewed in a plane, and an electrode arranged on one side. The electrode can be appropriately applied to known μLEDs, for example, a transparent electrode such as indium ITO can be preferably applied. The thickness of the electrode is preferably 0.1 μm or more, more preferably 1 μm or more, preferably 5 μm or less, more preferably 3 μm or less.

[0029] (First conductive film 4) The first conductive film 4 has first conductive particles 3 held in the first insulating resin layer 2, and can be used as a conductive film or anisotropic conductive film. The first conductive film 4 may be applied in a solid form over the entire surface of the light-transmitting substrate 5, or may be applied in individual pieces by a stamp method, an inkjet method, a laser lift-off method, or the like.

[0030] (First conductive particle 3) The first conductive particles 3 constituting the first conductive film 4 can be appropriately selected from those used in known conductive films or anisotropic conductive films. Examples include metal particles such as nickel, copper, silver, gold, palladium, and solder, and metal-coated resin particles in which the surface of resin particles such as polyamide and polybenzoguanamine is coated with a metal such as nickel or gold. This allows electrical continuity even when the μLED does not have a connection site such as a solder bump.

[0031] Regarding the first conductive particles 3, the average particle size has already been described, but the lower limit of the particle surface density is preferably 500 particles / mm 2 The upper limit is preferably 200,000 pieces / mm 2 Less than or equal to 150,000 pieces / mm 2 Less than 120,000 pieces / mm 2 It can be as follows:

[0032] The first conductive particles 3 may be arranged randomly in the field of view of the film surface, but are preferably arranged independently. In this case, it is preferable that 95% or more of the conductive particles are independent based on the number of particles. Furthermore, it is preferable that the conductive particles are not only arranged independently, but also arranged regularly. In particular, it is preferable that the particle arrangement in each direction perpendicular to each other in the field of view of the film surface is periodically repeated. For example, lattice arrangements such as hexagonal lattice, rectangular lattice, oblique lattice, square lattice, and other rectangular lattices can be mentioned. In addition, the conductive particles may be arranged in a row of linearly arranged particles at a predetermined interval in parallel with each other at a predetermined interval. In this way, by regularly arranging the conductive particles in the field of view of the film surface, the conductive particle surface density can be made uniform, and the transfer rate of μLED by irradiation with laser light can be further improved.

[0033] (First insulating resin layer 2) The first insulating resin layer 2 holds the first conductive particles 3 and is formed from a thermosetting resin composition that is thermally cured when thermocompression bonding is performed with a heat tool H in order to reliably hold the conductive particles. From the viewpoint of conductive particle capture ability, the layer thickness before thermocompression bonding is preferably 3 μm or more, more preferably 4 μm or more, and preferably 10 μm or less, and more preferably 7 μm or less.

[0034] The first insulating resin layer 2 preferably exhibits excellent cushioning properties (shock absorption properties) for stable attachment to the light-transmitting substrate 5. This can suppress the occurrence of defects such as displacement, deformation, breakage, and loss of the μLEDs, and improve the transfer rate of the μLEDs by laser irradiation. Such cushioning properties can be evaluated by durometer A hardness and / or storage modulus, as described below.

[0035] The durometer A hardness of the first insulating resin layer 2 is preferably 20 or more and 40 or less, more preferably 20 or more and 35 or less, and particularly preferably 20 or more and 30 or less. If the durometer A hardness is too high, the first insulating resin layer is too hard, and defects such as deformation and breakage of the μLED tend to occur easily, and if the durometer A hardness is too low, the first insulating resin layer 2 is too soft, and defects such as displacement of the μLED tend to occur easily. The durometer A hardness of the first insulating resin layer 2 can be measured in accordance with JIS K6253 using durometer A as rubber hardness (Japanese Industrial Standard JIS-A hardness).

[0036] The storage modulus of the first insulating resin layer 2 is preferably 60 MPa or less, more preferably 30 MPa or less, and particularly preferably 10 MPa or less. If the storage modulus is too high, the impact of the μLEDs ejected at high speed by laser irradiation cannot be absorbed, and the transfer rate of the μLEDs tends to decrease. The storage modulus can be determined by a dynamic viscoelasticity test using an indentation tester (temperature 30°C, frequency 200 Hz, using a flat punch with a diameter of 100 μm, target indentation depth 1 μm, frequency sweeping in the range of 1 to 200 Hz).

[0037] The storage modulus (30°C) of the thermosetting resin layer formed by thermal curing of the first insulating resin layer 2 measured in a tensile mode in accordance with JIS K7244 is preferably 100 MPa or more, more preferably 2000 MPa or more. If the storage modulus at a temperature of 30°C is too low, good electrical conductivity cannot be obtained and connection reliability tends to decrease. The storage modulus at a temperature of 30°C can be measured in a tensile mode using a viscoelasticity tester (Leovibron, A&D Co., Ltd.) in accordance with JIS K7244 under measurement conditions of, for example, a frequency of 11 Hz and a temperature rise rate of 3°C / min.

[0038] The thermosetting resin composition for forming the first insulating resin layer 2 preferably contains a rubber component, a film-forming resin, a thermosetting resin, a thermosetting agent, and an inorganic filler. If necessary, other known additives may be contained within the scope not impairing the effects of the invention.

[0039] *Rubber component The rubber component contained in the thermosetting resin composition is a component for imparting cushioning (shock absorption) to the first insulating resin layer, and is not particularly limited as long as it is an elastomer with good cushioning properties. Specific examples include, for example, acrylic rubber, silicone rubber, butadiene rubber, and polyurethane resin (polyurethane-based elastomer). Among these, it is preferable to use one or more selected from acrylic rubber and silicone rubber. The content of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, relative to 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler.

[0040] *Film forming resin Examples of the film-forming resin include various resins such as phenoxy resin, polyester resin, polyurethane resin, polyester urethane resin, acrylic resin, polyimide resin, butyral resin, etc., preferably having a weight average molecular weight of about 10,000 to 80,000 from the viewpoint of film-forming properties, and these may be used alone or in combination of two or more. Among these, it is preferable to use phenoxy resin from the viewpoint of film formation state, connection reliability, etc. The content of the film-forming resin is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, particularly preferably 35 parts by mass or more, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, relative to 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler.

[0041] *Thermosetting resin Examples of the thermosetting resin include epoxy compounds and (meth)acrylate compounds, and epoxy compounds are particularly preferred. These compounds may be monomers, oligomers, or polymers. The content of the thermosetting resin is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, particularly preferably 25 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less, relative to 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler.

[0042] The epoxy compound that can be used as the thermosetting resin is not particularly limited as long as it is an epoxy compound having one or more epoxy groups in the molecule, and may be, for example, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a urethane-modified epoxy resin. Among these, a high-purity bisphenol A type epoxy resin can be preferably used. A specific example of a high-purity bisphenol A type epoxy resin is the product name "YL980" manufactured by Mitsubishi Chemical Corporation. When an epoxy compound is used as the thermosetting resin, the content of the epoxy compound is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 45 parts by mass or less, relative to 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler.

[0043] *Heat curing agent The thermosetting agent is selected according to the thermosetting resin. For example, when the thermosetting resin is an epoxy compound, a thermal anionic polymerization initiator or a thermal cationic polymerization initiator can be preferably selected, and a thermal cationic polymerization initiator that can suppress the curing reaction by laser light and rapidly cure by heat can be more preferably selected. The content of the thermosetting agent can be determined according to the type of the thermosetting agent and the type of the thermosetting resin. The content of the thermosetting agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, particularly preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and particularly preferably 6 parts by mass or less, based on 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler.

[0044] In addition, the thermal cationic polymerization initiator preferably applicable to the epoxy compound is one that generates an acid capable of cationic polymerization of a cationic polymerization type compound by heat, and known iodonium salts, sulfonium salts, phosphonium salts, ferrocenes, etc. can be used. Among these, aromatic sulfonium salts that show good latency against temperature can be preferably used. A specific example of an aromatic sulfonium salt-based polymerization initiator is San-Aid SI-60L manufactured by Sanshin Chemical Industry Co., Ltd. The content of such a thermal cationic polymerization initiator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, particularly preferably 3 parts by mass or more, more preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less, relative to 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler.

[0045] *Inorganic filler The inorganic filler in the thermosetting resin composition is used for the purpose of adjusting the durometer A hardness, storage modulus at a frequency of 200 Hz, and storage modulus after curing of the first insulating resin layer 2, and may be silica, talc, titanium oxide, calcium carbonate, magnesium oxide, silane coupling agent, filler, softener, colorant, flame retardant, thixotropic agent, etc. The inorganic filler may be used alone or in combination of two or more kinds.

[0046] The content of the inorganic filler is preferably 1 part by mass or more, more preferably 5 parts by mass or more, particularly preferably 8 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, particularly preferably 12 parts by mass or less, based on 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler. In particular, when the content of the rubber component is 2 parts by mass or more and 10 parts by mass or less, based on 100 parts by mass of the total of the rubber component, the film-forming resin, the thermosetting resin, the thermosetting agent, and the inorganic filler, by setting the content of the inorganic filler to 8 parts by mass or more and 12 parts by mass or less, it is possible to easily achieve the desired durometer A hardness, storage modulus at a frequency of 200 Hz, and storage modulus after curing.

[0047] (Individual piece of second conductive film 40 for repair) The individualized second conductive film 40 for repair is a conductive film provided on an exposed portion of the light-transmitting substrate 5 from which the μLED to be repaired has been removed, and has second conductive particles 30 held in the second insulating resin layer 20. As a method for dividing the second conductive film 40 for repair, a known method can be adopted, such as a screen printing method, an inkjet method, or a laser lift-off method, but the laser lift-off method can be preferably adopted.

[0048] The second insulating resin layer 20 and the second conductive particles 30 constituting the second repair conductive film 40 can be configured similarly to the first insulating resin layer 2 and the first conductive particles 3, except for the average particle size and crush resistance of the conductive particles described in paragraphs 0020 to 0026. They may be configured differently to be adjusted according to the purpose.

[0049] (Repair μLED 1y and its electrode 1ya) The repair μLED 1y and its electrode 1ya can have the same configuration as the μLED 1 and its electrode 1a already described.

[0050] (Transparent substrate 5) As the light-transmitting substrate 5, a light-transmitting substrate of a known light-emitting device using μLED can be used, for example, a glass substrate, a quartz substrate, a methacrylate substrate, a polycarbonate substrate, etc. The thickness and degree of light-transmitting property of the light-transmitting substrate 5 may be any thickness and degree of light-transmitting property that allow the laser lift-off method to be applied.

[0051] <Light emitting device> The light emitting device 10 having the repaired μLED obtained by carrying out the above-described method for repairing the light emitting device is also a part of the present invention. That is, as shown in FIG. 6, the light emitting device 10 in which a plurality of μLEDs 1 are mounted on a transparent substrate 5 has a structure in which the majority of the μLEDs 1 are mounted on the transparent substrate 5 by thermocompression via a first conductive film 4 in which the first conductive particles 3 are held on a first insulating resin layer 2, and the remaining few μLEDs 1y (repaired μLEDs) are mounted on the transparent substrate 5 by thermocompression via a second conductive film 40 for repair in which the second conductive particles 30 are held on a second insulating resin layer 20. In the embodiment of FIG. 6, the first conductive film 4 and the second conductive film 40 for repair are in a thermally cured state.

[0052] In this light-emitting device 10, the second conductive particles 30 of the second conductive film 40 for repair have a larger particle size than the first conductive particles 3 of the first conductive film 4, or the second conductive particles 30 of the second conductive film 40 for repair are crushed more than the first conductive particles 3 of the first conductive film 4. The average particle size and crushing manner of the conductive particles are as described in the repair method of the light-emitting device of the present invention. In addition, when the second conductive particles have a larger particle size than the first conductive particles, the height from the surface of the light-transmitting substrate to the surface of the repaired μLED is higher than the height of the surrounding unrepaired μLED. The light-emitting device of the present invention having such a structure can realize stable conduction between the opposing electrodes to be connected, and can eliminate or greatly reduce the need to repair the repaired μLED. EXAMPLES

[0053] The present invention will be specifically described below with reference to examples and comparative examples.

[0054] Reference example: Relationship between the degree of crushing of conductive particles and whether the LED lights up or not (Creating conductive films) A thermosetting insulating resin composition was prepared by uniformly mixing 50 parts by mass of a phenoxy resin (PKHH, Tomoe Engineering Co., Ltd.), 40 parts by mass of a liquid epoxy resin (YL980, Mitsubishi Chemical Corporation), 5 parts by mass of fumed silica (RY200, Nippon Aerosil Co., Ltd.), and 5 parts by mass of a cationic polymerization initiator (San-Aid SI-60L, Sanshin Chemical Industry Co., Ltd.).

[0055] The obtained insulating resin composition was applied to a transparent glass substrate having a thickness of 0.7 mm, and dried at 60° C. for 3 minutes to form a thermosetting insulating resin layer having a thickness of 4 μm. Conductive particles 1 to 7 (Micropearl Series AU, Sekisui Chemical Co., Ltd.) having the average particle diameter and 20% compressive elastic modulus (20% K value) shown in Table 1 were added to this insulating resin layer by the conductive particle regular arrangement treatment described in paragraphs 0111-0112 and FIG. 1A of Japanese Patent No. 6187665, to form a layer having a particle density of 58,000 particles / mm. 2 A conductive film was created on the transparent substrate by arranging the ITO electrodes in a regular hexagonal lattice pattern as follows: On the surface of the transparent substrate facing the conductive film, a transparent ITO electrode pattern with a thickness of 200 nm was formed corresponding to the electrodes of the μLED to be mounted.

[0056] (Creating a light-emitting device) The μLEDs (number of electrodes: 2, electrode dimensions: length 15 μm × width 12 μm, electrode height: 2 μm) with electrodes formed on one side of the conductive film were placed at a density of 2518 pieces / cm. 2 The μLEDs of the μLED wafer, arranged with a vertical pitch of 216 μm and a horizontal pitch of 192 μm, were placed side by side with the μLEDs facing each other, and the μLEDs were transferred using the laser lift-off method under the following conditions, and a light-emitting device was created by thermocompression bonding (main bonding) using a heat tool (160°C, 60 MPa constant, 30 seconds). This enabled the comparison of the crushing rate of conductive particles 1 to 7 before and after bonding in increments of approximately 5%, and the relationship between the crushing rate and whether the particles light up or not was examined.

[0057] Laser lift-off equipment used: Shin-Etsu Engineering LUM-XTR Laser: Excimer laser with 248 nm wavelength Laser light pulse energy: 600J Fluence: 150J / cm 2 Pulse width (irradiation time): 30000 picoseconds Pulse frequency: 0.01kHz Number of irradiation pulses: 1 pulse for each μLED

[0058] Table 1 shows the results of checking the on / off operation of the obtained light-emitting device. From the results in Table 1, it was found that it is difficult to light up the μLED unless the conductive particles break through the surface oxide film of the transparent electrode of the light-transmitting substrate and a certain contact area with the opposing electrode is secured. For example, conductive particle 2 has a 20% higher K value and is harder than conductive particle 1, but the size of the conductive particles is too small, so the contact area with the electrode is not sufficient, and it is believed that the superiority of conductive particle 2 could not be confirmed. Therefore, it is clear that when repairing the μLED of a light-emitting device, it is necessary to consider the size of the conductive particles and the amount of crushing of the conductive particles after repair.

[0059] [Table 1]

[0060] Examples 1-6 and Comparative Examples 1-5 A light-emitting device was produced in the same manner as in the reference example. However, the conductive particles in the present pressure-bonding conductive film had the average conductive particle diameter (particle diameter [μm]) and 20% K value [MPa] shown in Table 2, and the insulating resin layer thickness (resin thickness [μm]) of the conductive film was set to the thickness shown in Table 2. In addition, the particle diameter (particle crush [μm]) in the thickness direction (crushing direction) of the conductive particles after thermocompression bonding, and the distance from the light-transmitting substrate surface to the μLED surface after thermocompression bonding (μLED outermost surface height [μm]) were set as shown in Table 2.

[0061] Next, for the unlit μLEDs of the light-emitting device, the μLEDs were peeled off together with the heat-cured conductive film directly below them using a laser lift-off method under the following conditions.

[0062] Laser lift-off equipment used: Shin-Etsu Engineering LUM-XTR Laser: Excimer laser with 248 nm wavelength Laser light pulse energy: 600J Fluence: 150J / cm 2 Pulse width (irradiation time): 30000 picoseconds Pulse frequency: 0.01kHz Number of irradiation pulses: 1 pulse for each μLED

[0063] Next, the repair conductive film shown in Table 2 was transferred to the exposed portion of the transparent substrate from which the unlit μLED and the thermally cured conductive film directly below were removed, according to the above-mentioned laser lift-off method, and then the same μLED for repair as the μLED used in the main pressure bonding was transferred and further thermocompressed. However, as the conductive particles of the repair conductive film, those with the average particle diameter (particle diameter [μm]) and 20% K value [MPa] shown in Table 2 were used, and the insulating resin layer thickness of the conductive film (resin thickness [μm]) was set to the thickness shown in Table 2. In addition, the particle diameter (particle crush [μm]) of the conductive particles in the thickness direction (crush direction) after thermocompression bonding during repair, and the distance from the surface of the transparent substrate to the μLED light-emitting surface after thermocompression bonding (μLED outermost surface height [μm]) were set as shown in Table 2. The operation confirmation results of the light-emitting device that was repaired are shown in Table 2.

[0064] In addition, Examples 1-2 and Comparative Examples 1-3 are examples that focus on the importance of the size of the conductive particles, Examples 3-4 and Comparative Examples 4-5 are examples that focus on the importance of the resistance of the conductive particles to crushing, and Examples 5-6 are examples that focus on the importance of both the size of the conductive particles and the resistance of the conductive particles to crushing.

[0065] [Table 2]

[0066] The results of Example 1-2 in Table 2 show that the repair was successful when the size of the conductive particles in the conductive film for repair was larger than that of the conductive film used for the final pressure bonding. In contrast, the results of Comparative Example 1-3 show that the repair was unsuccessful when the size of the conductive particles in the conductive film for repair was the same as or smaller than that of the conductive particles in the conductive film used for the final pressure bonding.

[0067] Moreover, from the results of Example 3-4 in Table 2, it can be seen that the repair was successful when the conductive particles of the conductive film for repair were less prone to crushing (harder) than the conductive particles of the conductive film used for the final pressure bonding. In contrast, from the results of Comparative Example 4-5, it can be seen that the repair was unsuccessful when the conductive particles of the conductive film for repair were the same in resistance to crushing (hardness) as or softer than the conductive particles of the conductive film used for the final pressure bonding.

[0068] The results of Examples 5-6 in Table 2 show that the size and resistance to crushing (hardness) of the conductive particles in the conductive film for repair were larger and more resistance to crushing (harder) than the conductive particles in the conductive film used for the actual pressure bonding, and the repair was successful. [Explanation of symbols]

[0069] 10 Light emitting device 1μLED 1a μLED electrode 1x Unlit μLED to be removed 1y Repair μLED 1ya Repair μLED1y electrode 2. First insulating resin layer 3. First conductive particle 4. First conductive film 5 Translucent substrate 20 Second insulating resin layer 30 Second conductive particle 40 Second conductive film for repair 100μLED 100a μLED100 electrode 101 Insulating resin layer 102 Conductive particles 102a: Conductive particles between the electrode of the light-transmitting substrate 104 and the electrode 100Ra of the repair μLED 100R 103 Conductive Film 103a Conductive film for repair 104 Translucent substrate 100R Repair μLED 100Ra Repair electrode for μLED100R H, 105 Heat Tools L Laser

Claims

1. A method for repairing a light-emitting device in which multiple μLEDs are mounted on a translucent substrate by thermocompression bonding via a first conductive film in which first conductive particles are held in a first insulating resin layer, comprising the following steps (A) to (F): (Process A) The process of identifying the μLED to be repaired from among the multiple μLEDs that are installed: (Process B) The process of removing the μLED to be repaired from the translucent substrate: (Process C) A step of placing individual pieces of a repair conductive film, in which second conductive particles are held in a second insulating resin layer, onto the portion of the translucent substrate from which the μLED has been removed; (Process D) The process of installing a repair μLED on a repair conductive film placed on a light-transmitting substrate. Length; (Process E) The process of thermocompressing and mounting a repair μLED onto a translucent substrate; and (Process F) The process of verifying the operation of a light-emitting device equipped with a repair μLED. It has, A repair method in which the second conductive particles of the repair second conductive film have a larger particle size than the first conductive particles of the first conductive film, or the second conductive particles of the repair second conductive film are less susceptible to crushing than the first conductive particles of the first conductive film.

2. The repair method according to claim 1, wherein the average particle size D1 of the first conductive particles is 1 μm or more and 5 μm or less, and the average particle size D2 of the second conductive particles is 1.1 times or more and 2 times or less than D1.

3. The repair method according to claim 1, wherein the 20% compressive modulus E1 (20% K value) of the first conductive particle is 2000 MPa or more and 6000 MPa or less, and the 20% compressive modulus E2 (20% K value) of the second conductive particle is 1.1 times or more and 2.5 times or less of E1.

4. The repair method according to claim 1, wherein the first conductive film and the second conductive film for repair each have anisotropic conductivity.

5. The repair method according to claim 1, wherein in step A, a μLED that does not light up when the light-emitting device is operated is identified as a μLED to be repaired.

6. The repair method according to claim 1, wherein in step B, the μLED to be repaired is removed together with the first conductive film directly beneath it.

7. The repair method according to claim 1, wherein in step C, the conductive film for repair is installed in piece form by the laser lift-off method.

8. The repair method according to claim 1, wherein in step D, a repair μLED is installed by the laser lift-off method.

9. A light-emitting device in which multiple μLEDs are mounted on a translucent substrate, For the majority of μLEDs, the first conductive particles are mounted to a translucent substrate by thermocompression bonding via a first conductive film in which the first conductive particles are held in a first insulating resin layer, while for the remaining few μLEDs, the second conductive particles are mounted to a translucent substrate by thermocompression bonding via a second conductive film for repairs in which the second conductive particles are held in a second insulating resin layer. A light-emitting device in which the second conductive particles of the repair second conductive film have a larger particle size than the first conductive particles of the first conductive film, or in which the second conductive particles of the repair second conductive film are less crushed than the first conductive particles of the first conductive film.

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