Filler array film

Abstract

To improve the transparency of a connection structure of a first article and a second article, which is obtained by connecting a micro first article such as a μ LED electrode and a second article such as a transparent display substrate using a filler array film.SOLUTION: In a filler array film 1A in which a filler 2 is arranged in an insulating adhesive layer 10, the high-density areas 4 of the filler are spaced apart and regularly arranged, with a plurality of unevenly distributed areas 3 of the filler 2 in each high-density area 4. The average visible light transmittance of the filler array film is 40% or more.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a filler array film in which fillers are arranged in a resin layer, a method of connecting a minute first article to a second article such as a substrate using the filler array film, and a connection structure obtained by the method. Here, examples of the minute first article include minute light-emitting elements such as mini LEDs and μLEDs.

Background Art

[0002] A μLED display formed by arranging μLEDs, which are minute light-emitting elements, on a substrate can thin the display by omitting the backlight required for a liquid crystal display, and is expected to be a display capable of achieving a wide color gamut, high definition, and power saving. Further, it is also expected for use as a transparent display. The same applies when used as a light source. Since it can be made lighter and thinner than conventional ones, performance improvements such as portability are expected. In view of the so-called "telework" that has been active in recent years, various demands for displays are increasing, and it is expected to meet these demands.

[0003] As a method for manufacturing a display in which μLEDs are arranged, Patent Document 1 describes picking up red, blue, and green μLED arrays formed on a carrier substrate with a transfer head, arranging them on a transfer destination substrate such as a display substrate, and joining the μLED array and the transfer destination substrate by welding a solder layer. Then, a contact line is formed thereon with ITO or the like.

[0004] Further, Patent Document 2 describes a method of arranging μLEDs formed on a wafer on a substrate, connecting them to the substrate using an anisotropic conductive film in which conductive particles are dispersed in an adhesive component using a hydrogenated epoxy compound or the like, and then lifting off the wafer. According to the method using the anisotropic conductive film described in Patent Document 2, a display using μLEDs can be easily obtained.

[0005] Patent Document 3 describes a two-stage connection method for connecting an IC chip and an FPC using an anisotropic conductive film having a conductive particle arrangement layer with a conductive particle area occupancy rate of 35% or less in a plan view. This method uses a pulse heater type bonder to improve the efficiency of capturing conductive particles, and involves a first stage where the IC chip and FPC are pressed into the insulating resin layer of the anisotropic conductive film to temporarily fix the electrodes closer to the conductive particle arrangement layer, and a second stage where permanent bonding is performed. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2015-500562 [Patent Document 2] Japanese Patent Publication No. 2017-157724 [Patent Document 3] Japanese Patent Publication No. 2019-216097 [Overview of the project] [Problems that the invention aims to solve]

[0007] As the size of μLEDs decreases to achieve higher resolution displays, and consequently the size of the LED electrodes also decreases, it becomes difficult to reliably capture conductive particles on the electrodes of individual μLEDs when using an anisotropic conductive film in which conductive particles are simply mixed into an insulating material.

[0008] In response to this, one possible approach is to use conductive particles with smaller particle sizes to increase the number density of conductive particles in the anisotropic conductive film.

[0009] However, arranging small conductive particles at a high number density across the entire surface of an anisotropic conductive film increases the risk of short circuits and also raises concerns about negative impacts on the design, such as reduced light transmission. Therefore, connecting μLEDs to a transparent display substrate using such anisotropic conductive film is likely to result in a decrease in yield and will not allow for the creation of a transparent display with high design flexibility.

[0010] Therefore, the object of the present invention is to provide a filler array film that enables the creation of a transparent connecting structure between a first article, such as a microLED, and a second article, such as a transparent display substrate, by using a filler array film to connect the first article and the second article, and to provide a connecting structure between a first article and a second article obtained using such a filler array film. [Means for solving the problem]

[0011] The inventors of the present invention conceived that when connecting a connection point of a minute first article, such as an electrode of a μLED, to a connection point of a second article, such as an electrode of a transparent display substrate, using a filler array film in which fillers such as conductive particles are arranged in an insulating resin layer, if the fillers in the filler array film form high-density regions that are regularly arranged in accordance with the arrangement of the first article, and within these high-density regions the fillers form unevenly distributed regions corresponding to the connection points of the first article, then unnecessary fillers that do not participate in the connection can be reduced as much as possible, and the resin flow during connection passes between the high-density regions of the fillers and is less likely to affect the high-density regions, so the fillers are reliably trapped between the connection points of the first article and the connection points of the second article, preventing short circuits where adjacent connection points in the film plane direction are unnecessarily connected by fillers, and when the first article is a light-emitting element such as a μLED, the concentration of fillers in the high-density regions allows light from the light-emitting element to pass through areas other than the high-density regions with high transmittance, thereby improving the luminous efficiency of the light-emitting device on which the light-emitting element is mounted. Based on these ideas, the inventors completed the present invention.

[0012] In other words, the present invention is a filler array film in which a filler is arranged in an insulating adhesive layer, The high-density regions of the filler are arranged regularly with gaps between them. Multiple areas of uneven filler distribution are formed within each high-density region. The present invention provides a filler array film having an average visible light transmittance of 40% or more.

[0013] Furthermore, the present invention relates to a connection method in which, with a plurality of first articles arranged on a second article, the connection portions of individual first articles and the connection portions of second articles are connected by heating or pressurizing them via a filler arrangement film in which fillers are arranged in an insulating resin layer. As a filler array film, The insulating adhesive layer has a regular arrangement of high-density filler regions at intervals. Multiple areas of uneven filler distribution are formed within each high-density region. This invention provides a connection method that uses a filler array film in which the average visible light transmittance of the filler array film is 40% or more.

[0014] Furthermore, the present invention relates to a connection structure in which, when a plurality of first articles are arranged on a second article, the connection portions of individual first articles and the connection portions of second articles are connected via fillers, The filler forms high-density regions corresponding to the arrangement of the first article. The present invention provides a connection structure in which the filler is unevenly distributed within a high-density region, corresponding to the connection portion of the first article. [Effects of the Invention]

[0015] When using the filler array film of the present invention, if a connection point of a minute first article, such as an electrode of a μLED, is connected to a connection point of a second article, such as an electrode of a transparent display substrate, by heating or pressurizing the filler array film, one or more fillers are reliably captured between the connection points of the first article and the second article, and the risk of fillers connecting between adjacent connection points in the film plane direction, i.e., between connection points of the first article or between connection points of the second article, is low. Therefore, the risk of short circuits when connecting electronic components such as μLEDs to a substrate can be reduced.

[0016] Furthermore, when the first item is a light-emitting element such as a μLED, the high-density regions of the filler are arranged in accordance with the arrangement of the light-emitting elements, so the emission of light from the light-emitting elements is less likely to be obstructed by the filler. Therefore, the luminous efficiency of the light-emitting device on which the light-emitting elements are mounted is improved.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is an arrangement diagram of fillers in the filler array film 1A of an embodiment. [Figure 2] FIG. 2 is a correspondence diagram between the arrangement of fillers in the filler array film 1A of an embodiment and the connection part of an article connected by the filler array film 1A. [Figure 3] FIG. 3 is a cross-sectional view of the filler array film 1A of an embodiment. [Figure 4] FIG. 4 is an arrangement diagram of fillers in the filler array film 1B of an embodiment.

Modes for Carrying Out the Invention

[0021] Here, the visible light transmittance of the filler array film is the average transmittance of visible light (wavelength 400-700 nm) measured using a visible light transmittance measuring device. The visible light transmittance is measured after the film has been cured. This average transmittance can be measured, for example, by measuring the transmittance over an area of ​​10 mm x 10 mm.

[0022] In this way, visible light transmittance can be measured within a 10 x 10 mm area. By measuring at 5, preferably 10 or more, random locations within the 10 x 10 mm area, the visible light transmittance can be calculated from the average.

[0023] Alternatively, the visible light transmittance can be measured by setting the measurement area so that the number density of conductive particles in that area is within approximately ±10% of the average number density. In this way, when μLEDs are arranged on one side of the substrate, it becomes easier to check whether the conductive particles necessary for connection are unevenly distributed, and it becomes easier to determine the suitability of the film used for connection. It can also be used to determine whether the film to be attached to the substrate contains unnecessary conductive particles, thus contributing to the productivity of the connection structure. Furthermore, it contributes to improved convenience by reducing constraints on the design of the connection structure. The 10 x 10 mm area can be an area (connection area) where multiple μLEDs are arranged, not just on one side, but even when considering cases where the film is cut to a size equivalent to or larger than this size and used, calculating the visible light transmittance as described above is considered to contribute to productivity and other improvements.

[0024] As shown in Figure 2, each μLED 20 connected using the filler array film 1A of this embodiment has two electrodes 21 and is regularly arranged in a grid pattern on the wafer 22.

[0025] Regarding the external shape and size of the μLED20, for example, if the external shape is rectangular, its longest side is 200 μm or less, or less than 150 μm, or less than 50 μm, or less than 20 μm. More specifically, examples of rectangles include 10 μm × 20 μm, 7 μm × 14 μm, and 5 μm × 5 μm. Note that the external shape of the μLED is not limited to a rectangle; for example, it may also be rhombus-shaped.

[0026] Furthermore, the external shape and size of the electrode 21 are not particularly limited, but when the μLED is small, a rectangle with a long side of 5 μm to 50 μm and a short side of 3 μm to 40 μm can be used, and the spacing Ls between electrodes 21 in a single μLED 20 can be appropriately selected depending on the method of use. The lower limit is preferably 3 μm or more, more preferably 5 μm or more, for the convenience of the mounting process. There is no particular limit to the upper limit. In the case of elements that are larger than μLEDs or mini-LEDs and used alone, it may be 3000 μm or less. In the case of display applications, it may be 1000 μm or less, 500 μm or less, 150 μm or less, or 20 μm or less.

[0027] In the filler array film 1A, high-density regions 4 of filler 2 are formed corresponding to the outer shape of the μLED (first item) 20, and are regularly arranged with spacing corresponding to the arrangement of the μLEDs. Within each high-density region 4, the filler 2 is unevenly distributed to positions corresponding to the individual electrodes (connections) 21 of the μLED (first item) 20, thereby forming unevenly distributed regions 3. The unevenly distributed regions 3 and high-density regions 4 can be recognized as the outer shape of the aggregate of filler 2.

[0028] Here, the position of the eccentric region 3 corresponding to the electrode 21 of the μLED 20 means that when a plurality of μLEDs in a predetermined arrangement state and a filler arrangement film are aligned, the electrode 21 of each μLED 20 and the eccentric region 3 overlap in a plan view, and the space between the electrodes 21 of each μLED 20 and the space between the eccentric regions 3 overlap. Preferably, the electrode 21 is located within the eccentric region 3, or one or more of the conductive particles 2 constituting the eccentric region 3 overlap with the electrode 21.

[0029] Furthermore, the arrangement of the high-density regions 4 in correspondence with the arrangement of the μLEDs 20 means that, due to the alignment described above, each μLED 20 and the high-density region 4 overlap in a plan view, and the space between each μLED overlaps with the space between the high-density regions 4. Preferably, for each μLED 20, the total area of ​​the conductive particles 2 that make up the high-density region 4 and are outside the outer shape of the μLED 20 is within 50% of the outer shape of the μLED 20. More preferably, all the conductive particles 2 that make up the high-density region 4 are located within the outer shape of each μLED 20.

[0030] The area of ​​the high-density region 4, that is, the area of ​​the contour shape of the high-density region that circumsects the outer conductive particles 2 among the conductive particles 2 constituting the high-density region 4, can be, for example, a rectangle with sides of 10 μm to 1000 μm, but it is desirable that it can satisfy the following ratio with respect to the outer shape of the corresponding μLED 20. That is, if the lower limit of the ratio of the area of ​​the contour shape of the high-density region 4 to the planar area of ​​the outer shape of the μLED 20 is reduced, the conductive particles 2 will be more likely to fit within the outer shape of the μLED 20. This ratio is preferably 0.1 times or more, more preferably 0.2 times or more, and even more preferably 0.5 times or more, in order to make it easier for the electrodes to capture the conductive particles. On the other hand, if the upper limit is increased, concerns about insufficient conductive particles being captured by the electrodes can be avoided, but there is a risk of impairing transparency and aesthetics, so it is preferably 1.5 times or less, more preferably 1.3 times or less, and even more preferably 1.2 times or less.

[0031] Furthermore, the statement that the high-density region 4 is arranged in accordance with the arrangement of μLEDs means that the arrangement direction and arrangement pitch of the high-density region 4 are equal to the arrangement direction and arrangement pitch of the μLEDs.

[0032] As described above, the uneven distribution regions 3 of the conductive particles in the filler array film 1A correspond to the electrodes 21 of the μLED 20, and the high-density regions 4 correspond to the outer shape of the μLED 20. Therefore, if we define L1 as the nearest neighbor distance between high-density regions 4 (i.e., the distance between a conductive particle constituting a certain high-density region and the conductive particle constituting the high-density region closest to that high-density region), L2 as the nearest neighbor distance between uneven distribution regions 3 within each high-density region (i.e., the distance between a conductive particle constituting a certain uneven distribution region within each high-density region 4 and the conductive particle constituting the uneven distribution region closest to that uneven distribution region), and L3 as the nearest neighbor distance between conductive particles 2 within an uneven distribution region, L1>L2>L3 This is preferable.

[0033] When multiple μLEDs 20 arranged on a wafer 22 are connected to a substrate by heating and pressurizing them via a filler array film 1A, L1 and L2 are appropriately determined according to the external shape, array pitch, and inter-electrode distance of the μLEDs, in order to minimize the influence of the resin flow of the insulating resin layer 10 of the filler array film 1A on the arrangement of conductive particles 2 within the high-density region 4.

[0034] Furthermore, since a deviation of approximately ±10% is permitted in the alignment between the unevenly distributed region 3 of the filler array film 1A, the electrode 21 of the μLED 20, and the electrode of the substrate, the area of ​​the unevenly distributed region 3, that is, the area of ​​the contour shape of the conductive particles 2 constituting the unevenly distributed region 3 that circumscribes the filler on the outer periphery, may be 0.5 to 1.8 times the planar area of ​​the corresponding electrode 21 of the μLED 20, and preferably 1.0 to 1.2 times. Within this range, there is an appropriate number of conductive particles, so both capture and short circuits can be achieved, and a good capture state is easily obtained and confirmed.

[0035] In the present invention, a single high-density region 4 can have a number of unevenly distributed regions 3 corresponding to the number of connection parts of a single first article, and in particular, it can have three or fewer such regions, and in this embodiment, two unevenly distributed regions 3 are present.

[0036] Regarding the relationship between the nearest neighbor distance L3 between conductive particles within the unevenly distributed region 3 and the average particle diameter D of the conductive particles 2, the lower limit of the ratio L3 / D is preferably 0.3 or more, more preferably 0.5 or more, and the upper limit is preferably 4 or less, more preferably 3 or less.

[0037] The arrangement of conductive particles 2 in the unevenly distributed region 3 may be random or regular. However, from the viewpoint of improving the capture ability of conductive particles at each electrode 21, a planar lattice pattern having one or more alignment axes in which conductive particles are arranged at a predetermined pitch in a predetermined direction is preferred. Examples include rhombic lattices, hexagonal lattices, square lattices, rectangular lattices, and parallelepiped lattices. Furthermore, there may be regions with different planar lattice patterns.

[0038] (Number density of fillers) The density of the fillers in the uneven distribution region 3 of the filler array film 1A is designed according to the object to which the filler array film 1A is connected. When the filler array film is an anisotropic conductive film, it is desirable to minimize irregular arrangement or aggregation of conductive particles in order to stably connect minute components using the anisotropic conductive film and to avoid the risk of short circuits. In particular, when the particle size of the conductive particles is less than 3 μm, it is desirable to minimize irregular arrangement or aggregation of conductive particles in the uneven distribution region 3.

[0039] The number density of fillers in the uneven distribution region 3 is designed according to the object to which the filler array film 1A is connected. For example, 50,000 pieces / mm 2 The above is preferable, with a yield of 500,000 pieces / mm 2 The above is more preferable. On the other hand, the number density of fillers between the high-density regions 4 is 1000 pieces / mm 2 The following is preferable, and more preferably substantially zero. Therefore, even if the number density of fillers is high in the unevenly distributed region 3, the visible light transmittance between high-density regions 4 can be approximately 40% or more, and the visible light transmittance of the entire filler array film can be 40% or more, preferably 50% or more.

[0040] Furthermore, when the filler array film 1A is used to connect a first item such as a μLED to a second item such as a transparent display substrate, the high-density region 4 becomes a region sandwiched between the first and second items. Therefore, in order to improve the light transmittance after the connection of the first and second items, the number density between unevenly distributed regions 3 within the high-density region 4 does not necessarily have to be zero. For example, as shown in the filler array film 1B in Figure 4, filler 2 may be present between two unevenly distributed regions 3 within the high-density region 4. In order to reduce unnecessary fillers that are not involved in the connection, the number of fillers between unevenly distributed regions 3 within a single high-density region 4 is preferably 50% or less, and more preferably 20% or less, of the number of fillers in the unevenly distributed region 3.

[0041] The filler area occupancy rate in the filler distribution region 3 can be determined in a way that maintains the degree of freedom in the layout of the objects connected by the filler array film, and may be 5% or more, preferably 8% or more, and more preferably 8% to 85%.

[0042] In this embodiment, filler area occupancy refers to the conductive particle area occupancy, and is the number density of conductive particles (particles / mm²) in a plan view of the unevenly distributed region 3 of the filler array film. 2 ) × Average planar area of ​​one conductive particle (mm²) 2 It can be calculated as ( / piece) × 100.

[0043] The number density of conductive particles can be determined by observation using a metallurgical microscope, or by measuring the observed image using image analysis software (for example, WinROOF (Mitani Corporation) or A-Image-kun (registered trademark) (Asahi Kasei Engineering Corporation)). The number of particles observed on the filler array film is measured. If the filler array film is made into extremely small pieces, the number density should be measured using the value measured before the film was made into pieces.

[0044] (Filler) In this embodiment, the particle size of the conductive particles 2 used as filler is not particularly limited, but the lower limit of the particle size is preferably 1 μm or more. The upper limit of the particle size is preferably 50 μm or less, and more preferably 20 μm or less, from the viewpoint of the trapping efficiency of the conductive particles in the connecting structure. Depending on the size of the electrode, the particle size of the conductive particles may be required to be less than 3 μm, preferably less than 2.5 μm, and more preferably less than 2 μm. If the particle size is less than 1 μm, it may be treated as an aggregate of 1 μm or larger.

[0045] The average particle size can be the value measured using an image-type particle size analyzer (for example, the FPIA-3000 manufactured by Malvern). In this case, the number of particles should be 1000 or more, preferably 2000 or more.

[0046] Furthermore, the type of conductive particles can be appropriately selected from among the conductive particles used in known anisotropic conductive films. For example, conductive particles include metal particles such as nickel, cobalt, silver, copper, gold, and palladium; alloy particles such as solder; metal-coated resin particles; and metal-coated resin particles with insulating fine particles attached to the surface. Two or more types can also be used in combination. Among these, metal-coated resin particles are preferred because, after connection, the resin particles repel each other, making it easier to maintain contact with the terminals and resulting in stable conductivity. In addition, the surface of the conductive particles may be subjected to an insulating treatment using known techniques that does not impair the conductivity characteristics.

[0047] In the filler array film of the present invention, the fillers are appropriately selected from inorganic fillers (metal particles, metal oxide particles, metal nitride particles, etc.), organic fillers (resin particles, rubber particles, etc.), and fillers containing a mixture of organic and inorganic materials (for example, particles with a resin core and a metal-plated surface (metal-coated resin particles), conductive particles with insulating fine particles attached to their surface, conductive particles with an insulating treatment applied to their surface, etc.) according to the performance required for the application, such as hardness and optical performance.

[0048] For example, when a filler array film is used as a conductive film or an anisotropic conductive film, conductive particles are included as fillers. Depending on the application of the filler array film, fillers other than conductive particles may also be used.

[0049] When filler array films are used for adjusting the color development of micro-optical elements such as μLEDs, or as black matrices in color displays, known dyes, pigments, light-scattering particles, etc., may be used as fillers. When the filler array film is used as an optical film or a matte film, silica fillers, titanium oxide fillers, styrene fillers, acrylic fillers, melamine fillers, and various titanates can be used. For capacitor films, titanium oxide, magnesium titanate, zinc titanate, bismuth titanate, lanthanum oxide, calcium titanate, strontium titanate, barium titanate, barium zirconate titanate, lead zirconate titanate, and mixtures thereof can be used. For adhesive films, polymer-based rubber particles, silicone rubber particles, etc., may be included.

[0050] (Cross-sectional structure of filler array film) Figure 3 is a cross-sectional view AA of the filler array film 1A shown in Figure 1. In the uneven distribution region 3 of the filler array film 1 in this embodiment, conductive particles 2 are arranged in the insulating resin layer 10.

[0051] The insulating resin layer 10 may consist of a single insulating resin layer or a laminate of multiple resin layers. Preferably, the ends of the conductive particles 2 are positioned approximately on one face of the layer. Approximate alignment means, for example, including an error of about ±10% of the particle diameter. When the insulating resin layer is a laminate of multiple resin layers, for example, as shown in Figure 3, it can consist of a high-viscosity binder resin layer 11 that holds the conductive particles 2 and an adhesive layer 12 with lower viscosity than the high-viscosity binder resin layer 11. The resins constituting this high-viscosity binder resin layer 11 and adhesive layer 12 can be, for example, the same as the binder and adhesive layers constituting the insulating resin layer described in Patent Document 3. Different fillers may be placed on different layers during lamination.

[0052] However, in order to improve the transparency of the insulating resin layer after the filler array film 1A has been used to connect the first article and the second article, it is preferable to add as little inorganic filler as possible to the insulating resin layer 10 (high viscosity binder resin layer 11, adhesive layer 12). Furthermore, when epoxy resin is used for the insulating resin layer 10, it is preferable to use epoxy resin that does not have conjugated double bonds.

[0053] Furthermore, rubber components may be added to the insulating resin layer 10 as needed. Rubber components may also be added to prevent warping and distortion of the connecting structure. The rubber component is not particularly limited as long as it is an elastomer with high cushioning (shock absorption) properties. Specific examples include acrylic rubber, silicone rubber, butadiene rubber, and polyurethane resin (polyurethane elastomer).

[0054] The thickness of the insulating resin layer 10 is set such that, when the μLED and the substrate are connected by heating and pressurizing them via the filler array film 1, unnecessary resin flow occurs in the insulating resin layer, and resin overflow and blocking occurs when the filler array film 1 is wound into a coil. The lower limit of the layer thickness is 0.6 times or more, preferably 0.9 times or more, and more preferably 1 time or more, the average particle diameter of the conductive particles 2, and the upper limit is 3 times or less, preferably 2 times or less, and more preferably 1.5 times or less. If the thickness of the insulating resin layer 10 is less than 0.6 times the average particle diameter of the conductive particles 2, the conductive particles 2 will be exposed from the insulating resin layer 10, making it difficult to temporarily attach the filler array film to the μLED or substrate when connecting the μLED and the substrate using the filler array film 1. On the other hand, if it exceeds 3 times, excessive resin flow occurs when connecting the μLED and the substrate, the conductive particles 2 are carried away by the resin flow, and the ability of the electrodes to capture the conductive particles decreases.

[0055] Furthermore, for manufacturing reasons that take into account the arrangement of particles, the thickness of the insulating resin layer 10 is preferably 2 μm or more at the lower limit, and more preferably 3 μm or more. As for the upper limit, since excessively large layer thickness can easily cause misalignment during connection, it is preferably 32 μm or less, more preferably 20 μm or less, and even more preferably 8 μm or less.

[0056] Furthermore, in the present invention, the μLED itself is small, and the size of the μLED and the size of the conductive particles are closer than in conventional designs. There is a concern that the μLED may be prone to misalignment, but it is preferable that the connection structure avoids this misalignment. For these reasons, the thickness of the insulating resin layer 10 is required to fall within the above range.

[0057] (Method for manufacturing filler array film) The filler array film 1A can be manufactured in the same manner as known anisotropic conductive films, except that the conductive particles are arranged in a specific configuration as described above. For example, similar to the method for manufacturing an anisotropic conductive film described in Patent Document 3, first, a mold is prepared in which recesses corresponding to the arrangement pattern of conductive particles are formed, conductive particles 2 are filled into the mold, a high-viscosity binder resin layer 11 formed on a release film is bonded on top of the conductive particles 2, the conductive particles 2 are pressed into the high-viscosity binder resin layer 11 and transferred, and an adhesive layer 12 is laminated onto the transferred surface.

[0058] (Connection method using filler array film) A method for connecting the electrodes of multiple μLEDs 20 to the electrodes of a substrate when multiple μLEDs 20 are regularly arranged on a wafer 22 using a filler array film 1A involves first aligning and attaching the filler array film 1A to the electrodes of the substrate, then aligning and attaching the filler array film 1A to the μLEDs 20 arranged on the wafer 22, and finally heating and pressing to connect the electrodes of the μLEDs 20 to the electrodes of the substrate. In this case, the connection may be made by heating and pressing in a two-stage method as described in Patent Document 3. Alternatively, if the conductive particles are solder particles or the like, the connection may be made by reflow soldering.

[0059] During this heating and pressurizing process, the insulating resin layer of the filler array film 1 flows and fills the gap between the opposing surfaces of the μLED 20 and the substrate, and hardens to bond the μLED 20 and the substrate. At this time, the fluidity of the resin is high between high-density regions 4 where conductive particles are not present, and within the high-density regions 4, the fluidity of the resin is lower than between the high-density regions 4 themselves. Therefore, the conductive particles 2 in the unevenly distributed regions 3, which are positioned within the high-density regions 4 corresponding to the electrodes of the μLEDs, are less affected by the resin flow between the high-density regions 4, and the electrodes 21 of each μLED 20 can reliably capture the conductive particles 2.

[0060] Furthermore, within the high-density region 4, the unevenly distributed regions 3 are arranged with a distance L2 between them corresponding to the arrangement of the electrodes 21, thus suppressing the occurrence of short circuits between electrodes 21 within a single μLED.

[0061] In addition, in the filler array film 1, conductive particles 2 are substantially absent between high-density regions 4. Therefore, after connecting a μLED to the substrate, the light emitted by the μLED 20 is not blocked by the conductive particles 2 in between. Consequently, the luminous efficiency of the light-emitting device on which the μLED is mounted is improved compared to using a filler array film in which conductive particles are uniformly present across the entire film surface.

[0062] The filler array film may also be in the shape of individual pieces. The size of the individual pieces can be designed to suit the object, but for example, one side can be 5 μm or more and 150 m or less. This is expected to allow for applications such as adjusting color and light, which will be described later. That is, the first and second articles may be connected with the individual pieces of film, or the individual pieces of film may be placed only on the electrodes. Piece formation can be done by making cuts using mechanical methods, chemical methods, lasers, etc. The cuts do not need to be deep enough to reach the substrate, and half-cuts are acceptable.

[0063] The temporary attachment of the filler array film, film transfer, and mounting of the μLEDs onto the substrate can be carried out using known methods such as stamping materials or laser-based methods (laser lift-off method), or methods that apply thereto (for example, methods described in Japanese Patent Publication No. 9-124020, Japanese Patent Publication No. 2011-76808, Japanese Patent No. 6636017, Japanese Patent No. 6187665, etc.), and are not particularly limited as long as they can achieve the effects of the invention.

[0064] (Connection structure) In the example, the connection structure between the μLED 20 and the substrate, connected using the filler array film 1A in the manner described above, has fillers 2 within the eccentric region 3 that constitute the connection point between the electrode 21 of the μLED 20 and the electrode of the substrate. Although the example uses a μLED as an example, the connection structure in the present invention may be a mini-LED.

[0065] As described above, the resin flow during connection does not significantly affect the arrangement of conductive particles 2 within the high-density region 4. Therefore, similar to before connection, high-density regions formed by the aggregation of multiple unevenly distributed regions exist after connection, corresponding to the mounting positions of the μLEDs, and these high-density regions are arranged in accordance with the arrangement of the μLEDs.

[0066] Therefore, the visible light transmittance in the connection structure in the portion where the μLED and substrate are not connected to the filler array film is higher than the average visible light transmittance of the filler array film, which is 40%, and preferably 50% or more. Thus, the luminous efficiency of this connection structure is significantly improved compared to when a filler array film is used in which conductive particles are uniformly distributed across the entire film at the same number density as the conductive particle 2 in the unevenly distributed region 3 of this connection structure. Furthermore, the capture efficiency of conductive particles at each electrode is also high, and the rate of short circuits is reduced.

[0067] The connection method using the filler array film of the present invention and the connection structure obtained thereby have been described above based on the case in which the first item is a μLED, the second item is a substrate on which a wiring circuit for the μLED is formed, and the filler of the filler array film is conductive particles. However, the present invention is not limited thereto.

[0068] For example, the first item may be a light-scattering film, a black matrix layer, etc., the second item may be a transparent substrate (a substrate on which μLEDs are mounted), etc., and the filler may be silica or black-colored particles, etc., to adjust the color of the connecting structure between the first and second items. [Examples]

[0069] The present invention will be described in detail below based on examples. Examples 1-4, Comparative Examples 1-4 (Fabrication of anisotropic conductive films) A resin was mixed according to the resin composition shown in Table 1, applied to a release film, and dried (60°C, 3 minutes) to obtain an adhesive film.

[0070] [Table 1]

[0071] On the other hand, a mold having recesses for filling conductive particles (average particle diameter 2.2 μm or 3.2 μm, 0.2 μm Ni-plated resin particles, Sekisui Chemical Co., Ltd.) was prepared in the same manner as described in Japanese Patent Publication No. 6187665, with the conductive particles arranged in the configuration shown in Table 2. The conductive particles were then filled into the recesses, the adhesive film shown in Table 1 was placed over it, and the conductive particles were pressed into the adhesive film to produce an anisotropic conductive film.

[0072] [Table 2]

[0073] (Evaluation of anisotropic conductive films) The particle trapping ability, conductivity resistance, insulation, and visible light transmittance of the anisotropic conductive films of Examples 1-4 and Comparative Examples 1-4 were evaluated as follows. The results are shown in Table 2.

[0074] (i) Particle trapping ability The anisotropic conductive films of Examples 1-4 and Comparative Examples 1-4 were attached to ITO / NdMo patterned glass, and an evaluation IC chip modeled after a μLED was heat-pressed onto it (reached temperature 150°C, pressurized 30 MPa, 10 seconds) to obtain a mounted assembly. This evaluation IC chip has an electrode layout in which two 10 μm × 10 μm bumps (with a 7 μm space between bumps) are arranged at a 30 μm pitch on approximately one surface of a 1.5 cm × 1.5 cm area.

[0075] By observing 100 bumps in this implementation, the number of conductive particles trapped in each bump was measured. The lowest number among these 100 bumps was used for evaluation according to the following criteria.

[0076] A: 5 or more B: 3~4 pieces C: 1~2 pieces D:0 pieces

[0077] (ii) Conductivity The conductivity resistance of 100 of the above-mentioned mountings was measured and evaluated according to the following criteria. A: Less than 30Ω B: 30Ω or more and less than 100Ω C: 100Ω or more and less than 300Ω D: 300Ω or more

[0078] (iii) Insulation The conductivity resistance was measured for the 100 bump spaces of the above-mentioned implementation, and 10 7 A value of Ω or less was determined to be a short. The number of shorts was evaluated according to the following criteria.

[0079] A: No short B: Short 1 piece C: 2 short pieces D: 3 or more shorts

[0080] (iv)Visible light transmittance The visible light transmittance (400-700 nm) of the anisotropic conductive films of Examples 1-4 and Comparative Examples 1-4 was measured, and the average transmittance (measurement area 10 mm x 10 mm) was evaluated according to the following criteria. A UV-2450 (Shimadzu Corporation / JIS Z 8729) was used for transmittance measurement. In this case, the samples for visible light transmittance measurement were those with the anisotropic conductive film attached to a substrate, left at 200°C for 1 minute to allow curing. Visible light transmittance allows us to see how the excess resin in the connection structure affects the result. It also allows us to determine whether the conductive particle arrangement is suitable for the connection area and to confirm whether sufficient transparency is ensured when used in the connection structure.

[0081] A: 50% or more B: 35% or more C: 20% or more D: Less than 20%

[0082] Table 2 shows that when an anisotropic conductive film is used in the example in which conductive particles are unevenly distributed on the bumps of a μ-chip or μ-LED, excellent evaluations of B or higher are obtained for particle capture ability, conductivity resistance, insulation, and visible light transmittance.

[0083] In contrast, Comparative Example 1, in which conductive particles are uniformly distributed throughout the film at the same number density as the unevenly distributed region of Example 1, exhibits inferior visible light transmittance. Furthermore, Comparative Example 2, with a lower overall number density of the film, receives a B rating for visible light transmittance, but exhibits inferior particle capture and conductivity resistance. In Comparative Example 4, the overall number density of the film is equal to the number density of conductive particles in the unevenly distributed region of Example 1, but the insulation and visible light transmittance are significantly inferior due to the random arrangement of the conductive particles. In Comparative Example 3, where the overall number density of the film is even lower than in Comparative Example 4, the particle capture and conductivity resistance are significantly inferior due to the random arrangement of the conductive particles. [Explanation of Symbols]

[0084] 1A, 1B Filler Arrangement Film 2. Filler, conductive particles 3 Uneven distribution area 4 High density area 10 Insulating resin layer 11. High-viscosity binder resin layer 12 Adhesive layer 20 1st article, μLED 21 electrodes 22 wafers L1: Distance between nearby regions of high density L2 nearest neighbor distance between eccentric regions L3 Neighboring distance between fillers in the eccentric region Ls μLED electrode distance

Claims

1. A filler array film in which fillers are arranged in an insulating adhesive layer, The high-density regions of the filler are arranged regularly with gaps between them. Multiple areas of uneven filler distribution are formed within each high-density region. The average visible light transmittance of the filler array film is 40% or more. A filler array film in which the high-density region of the filler is a region formed in accordance with the outer shape of the first article connected by the filler array film, and the unevenly distributed region of the filler is a region that is unevenly distributed at positions corresponding to the individual connection parts of the first article.

2. The filler arrangement film according to Claim 1, which satisfies the inequality L1 > L2 > L3, where L1 is the nearest neighbor distance between high-density regions, L2 is the nearest neighbor distance between unevenly distributed regions within a high-density region, and L3 is the nearest neighbor distance between fillers within an unevenly distributed region.

3. The filler array film according to claim 1 or 2, wherein the high-density region is a rectangle with sides of 10 μm to 1000 μm.

4. The number density of fillers in the unevenly distributed filler region within the high-density region is 50,000 pieces / mm². ２ The filler array film according to any one of claims 1 to 3.

5. The number density of fillers in the unevenly distributed filler region within the high-density region is 500,000 / mm². ２ The filler array film according to claim 4, as described above.

6. The number density of fillers between high-density regions is 1000 particles / mm². ２ A filler array film according to any one of claims 1 to 5 below.

7. A filler array film according to any one of claims 1 to 6, wherein the number of fillers between unevenly distributed regions within a high-density region is 50% or less of the number of fillers in the unevenly distributed region.

8. A filler array film according to any one of claims 1 to 7, wherein the area occupancy rate of the filler in the filler-unevenly distributed region is 5% or more.

9. A filler-arranged film according to any one of claims 1 to 8, wherein the fillers in the unevenly distributed regions are arranged in a square grid, a rectangular grid, or a hexagonal grid.

10. A filler array film according to any one of claims 1 to 9, wherein the visible light transmittance between high-density regions is 50% or more.

11. A filler array film in which a filler is disposed in an insulating adhesive layer, The high-density regions of the filler are arranged regularly with gaps between them. Multiple areas of uneven filler distribution are formed within each high-density region. The average visible light transmittance of the filler array film is 40% or more. The high-density region of the filler is a region formed in accordance with the outer shape of the first article connected by the filler array film, and the unevenly distributed region of the filler is a region that is unevenly distributed at positions corresponding to the individual connection parts of the first article. Let L1 be the nearest neighbor distance between high-density regions, L2 be the nearest neighbor distance between unevenly distributed regions within a high-density region, and L3 be the nearest neighbor distance between fillers within an unevenly distributed region. If the inequality L1 > L2 > L3 is satisfied, The high-density region is a rectangle with sides of 10 μm to 1000 μm. The number density of fillers in the unevenly distributed filler region within the high-density region is 50,000 / mm² or more. The number density of fillers between high-density regions is 1000 particles / mm² or less. The number of fillers between unevenly distributed regions within a high-density region is 50% or less of the number of fillers in the unevenly distributed region. A filler array film in which the filler area occupancy rate in the filler-unevenly distributed region is 5% or more.

12. A connection method in which, with multiple first articles arranged on a second article, the connection portions of individual first articles and the connection portions of the second articles are connected by heating or pressurizing them via a filler arrangement film in which fillers are arranged in an insulating resin layer, A connection method using a filler array film, wherein the filler array film has high-density regions of filler arranged regularly at intervals in an insulating adhesive layer, multiple unevenly distributed regions of filler are formed in each high-density region, the average visible light transmittance of the filler array film is 40% or more, the high-density regions of filler are regions formed corresponding to the outer shape of the first article, and the unevenly distributed regions of filler are regions that are unevenly distributed at positions corresponding to individual connection parts of the first article.

13. The connection method according to claim 12, wherein the area of ​​the contour shape of each high-density region is 0.1 times or more and 1.5 times or less the planar area of ​​the first article.

14. The connection method according to claim 12, wherein the area of ​​each individual unevenly distributed region is 0.5 times or more and 1.8 times or less the planar area of ​​the connection portion of the first article.

15. The connection method according to any one of claims 12 to 14, wherein the thickness of the insulating resin layer is three times or less the average particle diameter of the filler.

16. The connection method according to any one of claims 12 to 15, wherein the first article is a μLED and the second article is a transparent display substrate.

17. A connection structure in which multiple first articles are arranged regularly on a second article, and the connection parts of each first article are connected to the connection parts of the second article via fillers, The filler forms a high-density region corresponding to the outer shape of the first article. The high-density regions are arranged regularly on the second article, corresponding to the regular arrangement of the first article. A connection structure in which the filler is unevenly distributed within the high-density region, forming a distribution region where the filler is unevenly distributed at positions corresponding to individual connection parts of the first article.

18. The connecting structure according to claim 17, wherein the visible light transmittance of the portion in which the first article and the second article are not connected is 50% or more.

19. The connection structure according to claim 17 or 18, wherein the first article is a μLED and the second article is a transparent display substrate.

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