Display device, method for manufacturing display device, connection film, and method for manufacturing connection film

Abstract

The invention provides a display device capable of obtaining excellent light transmission and visibility, a method for manufacturing the display device, a connecting film and a method for manufacturing the connecting film. A display device is provided with a plurality of light-emitting elements (30), a wiring substrate (20), and a cured film (40) that connects the plurality of light-emitting elements (30) and a connection film of the wiring substrate (20), the cured film (40) having a first surface (40a) having a root mean square height of 3.0 * 10-1 [mu] m or less, and the plurality of light-emitting elements (30) are mounted on the first surface (40a). As a result, light scattering can be suppressed, and excellent translucency and visibility can be obtained.

Description

Technical Field

[0001] The present technology relates to a display device and a method for manufacturing a display device in which light-emitting elements are connected and arranged through connecting films such as anisotropic conductive film (ACF) and adhesive film (NCF: Non Conductive Film). In particular, it relates to a display device and a method for manufacturing a display device in which LED elements such as Mini LED (Light Emitting Diode) and Micro LED are connected and arranged. This application claims priority based on Japanese patent application No. 2022-155321 filed in Japan on September 28, 2022, which is cited in this application by reference. Background Art

[0002] As the next generation of displays, the development of Mini LED and Micro LED displays has attracted attention. Mini LED and Micro LED displays are composed of tiny light-emitting elements arranged on a substrate, so the backlight required for liquid crystal displays can be omitted, the display can be made thinner, and further wide color gamut, high precision, and power saving can be achieved.

[0003] Patent Document 1 discloses a method for bonding LEDs using ACF. In the method described in Patent Document 1, ACF is bonded to the entire surface of the device mounting surface of the substrate, so excellent light transmittance and visibility may not be obtained.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Japanese Patent Application Publication No. 2017-157724. Summary of the invention

[0007] Problems to be solved by the invention

[0008] The present technology has been proposed in view of such existing actual conditions, and provides a display device and a method for manufacturing a display device, and a connecting film and a method for manufacturing a connecting film that can obtain excellent light transmittance and visibility.

[0009] Means of solving problems

[0010] The display device according to the present technology includes a plurality of light-emitting elements, a wiring substrate, and a cured film of a connection film connecting the plurality of light-emitting elements and the wiring substrate, wherein the cured film has a root mean square height of 3.0×10 -1 The plurality of light emitting elements are mounted on the first surface.

[0011] The manufacturing method of the display device according to the present technology comprises: arranging a circuit board having a root mean square height of 3.0×10 -1 The following is a step of arranging a connection film on the first surface, and a step of mounting a plurality of light emitting elements on the first surface and mounting the plurality of light emitting elements on a wiring substrate.

[0012] The connection film involved in the present technology has a root mean square height of 3.0×10 -1 The first surface below μm.

[0013] In the method for manufacturing the connection film according to the present technology, when the root mean square height is 3.0×10 -1 A connecting film is formed on a substrate film with a thickness of less than 10 μm, and the connecting film has a root mean square height of 3.0×10 -1 The first surface below μm.

[0014] Effects of the Invention

[0015] According to the present technology, light scattering can be suppressed, and excellent light transmittance and visibility can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] [ Figure 1 ] Figure 1 is a diagram for explaining an example of a method for manufacturing a connection film (conductive film, anisotropic conductive film) in this embodiment. Figure 1 (A) shows a preparation step of preparing a substrate film, Figure 1 (B) shows a step of forming a connection film (conductive film, anisotropic conductive film) on a base film, Figure 1 (C) shows a step of attaching a cover film to the connection film (conductive film, anisotropic conductive film).

[0017] [ Figure 2 ] Figure 2 is a cross-sectional view schematically showing an example of the display device in this embodiment.

[0018] [ Figure 3 ] Figure 3 is a diagram for explaining an example of a method for manufacturing a display device in this embodiment. Figure 3 (A) shows a step of arranging a connection film (conductive film, anisotropic conductive film) at a predetermined position on a wiring substrate. Figure 3 (B) shows a mounting step of mounting the light emitting element on the wiring substrate. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the present technology will be described in detail in the following order with reference to the drawings.

[0020] 1. Connecting membrane

[0021] 2. Method for manufacturing connecting film

[0022] 3. Display device

[0023] 4. Method for manufacturing display device

[0024] 5. Examples

[0025] <1. Connecting film>

[0026] The connection film (conductive film, anisotropic conductive film) according to this embodiment has a first surface having a root mean square height of a predetermined value or less. When a light emitting element is mounted using the connection film having such a first surface, a display device having excellent light transmittance and visibility can be obtained.

[0027] Here, the root mean square height (Sq: Root Mean Square Height (surface roughness: ISO 25178)) is a parameter obtained by extending the root mean square roughness (Rq: Root Mean Square deviation of the roughness profile, the root mean square deviation of the roughness profile (line roughness: JIS B 0601)) to the surface. As shown in formula (1), the root mean square roughness Rq is the root mean square of the roughness curve Z(x) under the reference length l, and as shown in formula (2), the root mean square height Sq is equivalent to the standard deviation of the distance from the average surface, which is equivalent to the standard deviation of the height. The root mean square height Sq can be measured using a three-dimensional non-contact surface roughness measuring instrument.

[0028] [Mathematical formula 1]

[0029]

[0030] The root mean square height of the first surface of the connecting film is preferably 3.0×10 -1 μm or less, more preferably 2.0×10 -1 μm or less, more preferably 1.0×10 -1 If the root mean square height increases, a large amount of light scattering occurs, making it difficult to obtain excellent light transmittance and visibility.

[0031] The haze of the connecting film is preferably less than 50%, more preferably less than 45%, and further preferably less than 40%. The haze can be measured using a haze meter (HAZEMETER) according to a method in accordance with JIS K7136.

[0032] The visible light transmittance of the connecting film is preferably 30% or more, more preferably 40% or more, and further preferably 45% or more. The transmittance in the visible light region (380 nm to 780 nm) can be measured using, for example, an ultraviolet-visible spectrophotometer.

[0033] The connecting film may include a base film having a root mean square height of a predetermined value or less on the first surface side. The root mean square height of the base film is preferably 3.0×10 -1 μm or less, more preferably 1.5×10 -1 μm or less, more preferably 0.05×10 -1 If the root mean square height of the base film becomes large, it is difficult to obtain a connecting film with a small root mean square height. In addition, from the perspective of operability, the connecting film may also be a film having a cover film provided on the second surface.

[0034] The storage modulus of the connection film at a temperature of 30°C measured in a tensile mode according to JIS K7244 after curing is preferably 100 MPa or more, and more preferably 2000 MPa or more. When the storage modulus at a temperature of 30°C is too low, there is a tendency that good conductivity cannot be obtained and the connection reliability is also reduced. The storage modulus at a temperature of 30°C can be measured according to JIS K7244 using a viscoelasticity tester (Vibron) in a tensile mode, for example, under measurement conditions of a frequency of 11 Hz and a heating rate of 3°C / min.

[0035] The adhesive for the connecting film is not particularly limited as long as it can be cured by energy such as heat or light, and can be appropriately selected from, for example, thermosetting adhesives, photocuring adhesives, and heat / light combined curing adhesives.

[0036] As a thermosetting adhesive, for example, a thermo-anionic polymerization resin composition comprising an epoxy compound and a thermo-anionic polymerization initiator, a thermo-cationic polymerization resin composition comprising an epoxy compound and a thermo-cationic polymerization initiator, a thermo-radical polymerization resin composition comprising a (meth)acrylate compound and a thermo-radical polymerization initiator, etc. can be listed. As a photocurable adhesive, for example, a photo-cationic polymerization resin composition comprising an epoxy compound and a photo-cationic polymerization initiator, a photo-radical polymerization resin composition comprising a (meth)acrylate compound and a photo-radical polymerization initiator, etc. can be listed. As a heat / light co-curing adhesive, a mixture of a thermosetting adhesive and a photocurable adhesive can be listed. It should be noted that the (meth)acrylate compound means any one of an acrylic monomer (oligomer) and a methacrylic monomer (oligomer).

[0037] (Thermal cationic polymerization resin composition)

[0038] Hereinafter, as a specific example of the thermosetting adhesive, a thermal cationic polymerization type resin composition including a film-forming resin, an epoxy compound, and a thermal cationic polymerization initiator will be described as an example.

[0039] As a film-forming resin, for example, a high molecular weight resin having an average molecular weight of 10,000 or more is equivalent to an average molecular weight of about 10,000 to 80,000 from the viewpoint of film-forming properties. As a film-forming resin, various resins such as polyvinyl acetal resin, phenoxy resin, butyral resin, polyester resin, polyurethane resin, polyester urethane resin, acrylic resin, polyimide resin, etc. can be listed, which can be used alone or in combination of two or more. Among them, from the viewpoints of film-forming state, connection reliability, etc., polyvinyl acetal resin is preferably used. Relative to 100 parts by mass of thermosetting adhesive, the content of the film-forming resin is preferably 20 to 70 parts by mass, more preferably 30 to 60 parts by mass or less, and further preferably 45 to 55 parts by mass.

[0040] The epoxy compound is not particularly limited as long as it has one or more epoxy groups in the molecule, and may be, for example, a bisphenol A epoxy resin, a bisphenol F epoxy resin, or a urethane-modified epoxy resin. Among them, hydrogenated bisphenol A glycidyl ether may be preferably used. As a specific example of hydrogenated bisphenol A glycidyl ether, for example, the product name "YX8000" manufactured by Mitsubishi Chemical Co., Ltd. may be cited. The content of the epoxy compound is preferably 30 to 60 parts by mass, more preferably 35 to 55 parts by mass or less, and further preferably 35 to 45 parts by mass relative to 100 parts by mass of the thermosetting adhesive.

[0041] As the thermal cationic polymerization initiator, a substance known as a thermal cationic polymerization initiator of epoxy compounds can be used, for example, a substance that generates an acid capable of causing a cationic polymerization type compound to undergo cationic polymerization by heat, and a known iodine initiator can be used. Salt, sulfonium salt, Salts, ferrocenes, etc. Among them, aromatic sulfonium salts that show good latency to temperature can be preferably used. As a specific example of the aromatic sulfonium salt-based polymerization initiator, for example, the product name "SI-60L" manufactured by Sanshin Chemical Industry Co., Ltd. can be cited. The content of the thermal cationic polymerization initiator is preferably 1 to 20 parts by mass, more preferably 5 to 15 parts by mass or less, and further preferably 8 to 12 parts by mass relative to 100 parts by mass of the thermosetting adhesive.

[0042] As other additives blended into the thermosetting adhesive, rubber components, inorganic fillers, silane coupling agents, diluent monomers, fillers, softeners, colorants, flame retardants, thixotropic agents, etc. may be blended as necessary.

[0043] The rubber component is not particularly limited as long as it is an elastomer with high cushioning properties (shock absorption), and specific examples thereof include acrylic rubber, silicone rubber, butadiene rubber, polyurethane resin (polyurethane elastomer), etc. As inorganic fillers, silicon dioxide, talc, titanium oxide, calcium carbonate, magnesium oxide, etc. can be used. Inorganic coatings can be used alone or in combination of two or more.

[0044] By using a thermosetting adhesive having such a structure, the curing reaction during laser forming of individual sheets can be suppressed, and rapid curing can be achieved by heat during thermocompression bonding.

[0045] (Connection film)

[0046] The connection film may be a conductive film further containing conductive particles. Examples of the conductive film include an isotropic conductive film and an anisotropic conductive film. Hereinafter, an anisotropic conductive film will be described as one embodiment of the conductive film.

[0047] As the conductive particles, the conductive particles used in the known anisotropic conductive film can be appropriately selected and used. For example, metal particles such as nickel (melting point 1455°C), copper (melting point 1085°C), silver (melting point 961.8°C), gold (melting point 1064°C), palladium (melting point 1555°C), tin (melting point 231.9°C), nickel boride (melting point 1230°C), ruthenium (melting point 2334°C), and flux as a tin alloy can be listed. In addition, metal-coated metal particles such as metals coated on the surface of metal particles such as nickel, copper, silver, gold, palladium, tin, nickel boride, and ruthenium can be listed. In addition, metal-coated resin particles such as metals coated on the surface of resin particles such as polymers containing at least one monomer selected from polyamide, polyphenylene melamine, styrene, and divinylbenzene as monomer units with metals such as nickel, copper, silver, gold, palladium, tin, nickel boride, and ruthenium can be listed. In addition, examples include metal-coated inorganic particles obtained by coating the surfaces of inorganic particles such as silicon dioxide, aluminum oxide, barium titanate, zirconium oxide, carbon black, silica glass, borosilicate glass, lead glass, soda-lime glass, and aluminosilicate glass with metals such as nickel, copper, silver, gold, palladium, tin, nickel boride, and ruthenium. In addition, the coating metal layer of the metal-coated resin particles and the metal-coated inorganic particles may be a single layer or a multilayer of different types of metals.

[0048] In addition, these conductive particles can also be subjected to an insulating coating treatment by, for example, coating with insulating particles such as a resin layer or resin particles, inorganic particles, etc. . Here, the particle size of the conductive particles does not include the portion subjected to the insulating coating treatment. The particle size of the conductive particles is appropriately changed according to the area of ​​the optical element to be installed, the electrode of the wiring substrate, the bump, etc., and is preferably 1 to 30 μm, more preferably 1 to 10 μm, and particularly preferably 1 to 3 μm. For example, in the case of installation of Micro LED components, since the area of ​​the electrode or bump is small, the particle size of the conductive particles is preferably 1 to 3 μm, more preferably 1 to 2.5 μm, and particularly preferably 1 to 2.2 μm. For the particle size, more than 200 particles can be measured by microscopic observation (optical microscope, metal microscope, electron microscope, etc.), and the average value can be taken.

[0049] In addition, in the case where the conductive particles are metal-coated resin particles or metal-coated inorganic particles coated with metal on the above-mentioned resin particles or inorganic particles, the coating thickness of the metal is preferably 0.005 μm or more, more preferably 0.01 μm or more, and preferably 10 μm or less, more preferably 1 μm or less, and further preferably 0.3 μm or less. In the case where the metal is coated with multiple layers, the coating thickness is the thickness of the entire metal coating. If the coating thickness of the metal is above the above lower limit and below the above upper limit, it is easy to obtain sufficient conductivity, and in addition, the conductive particles will not be too hardened, and it is easy to exert the characteristics of the above-mentioned resin particles or inorganic particles.

[0050] The coating thickness of the metal can be measured, for example, by observing the cross section of the conductive particles using a transmission electron microscope (TEM). For the above-mentioned coating thickness, it is preferred to calculate the average value of the coating thickness at any 5 locations as the coating thickness of one conductive particle, and it is more preferred to calculate the average value of the overall thickness of the coating portion as the coating thickness of one conductive particle. The above-mentioned coating thickness is preferably obtained by calculating the average value of the coating thickness of each conductive particle for any 10 conductive particles.

[0051] In addition, as the shape of the conductive particles, there can be listed shapes such as spherical, ellipsoidal, spike, and irregular shapes. Among them, spherical conductive particles are preferred because they are easy to control the particle size or particle size distribution. In addition, in order to improve connectivity, the conductive particles may have protrusions on the surface.

[0052] In the anisotropic conductive film, it is preferred that the conductive particles are arranged in a plane direction (regular arrangement when viewed from above). By arranging the conductive particles in a plane direction, the particle surface density becomes uniform, and the conductivity and insulation can be improved. The state in which the conductive particles are arranged in the plane direction can include, for example, a plane lattice pattern with an arrangement axis of more than one conductive particle arranged in a specified direction at a specified interval, and can also include a rhombus lattice (diamond lattice), a hexagonal lattice, a square lattice, a rectangular lattice, a parallelogram lattice, etc. In addition, the arrangement of the conductive particles in the plane direction can be random, or it can have a plurality of regions with different plane lattice patterns.

[0053] The particle surface density of the anisotropic conductive film can be appropriately designed according to the electrode size of the connection object. The lower limit of the particle surface density is not particularly limited as long as it does not hinder the performance, and can be 30 particles / mm 2 Above, 500 pieces / mm 2 Above, 20000 pieces / mm 2 Above, 40000 pieces / mm 2 Above, 50000 pieces / mm 2 The upper limit of the particle surface density can be 1500000 / mm 2 Below, 1,000,000 pieces / mm 2 Below, 500,000 pieces / mm 2 Below, 100,000 pieces / mm 2 As a result, even when the electrode size of the connection object is small, excellent conductivity and insulation can be obtained. Among them, the anisotropic conductive film preferably has an average particle size of conductive particles of 3.0 μm or less, and the conductive particles are 50,000 / mm 2 The particle surface density above is neatly arranged. The particle surface density of anisotropic conductive film is the density of the arranged part of the conductive particles when the film is formed during manufacturing. In the case of obtaining the particle number density from multiple monolithic sheets, the particle surface density can be obtained based on the area obtained by subtracting the intervals between monolithic sheets from the area including the monolithic sheets and the intervals and the number of particles.

[0054] The thickness of the anisotropic conductive film before connection is preferably greater than 1 μm and less than 10 μm, more preferably greater than 1 μm and less than 6 μm, and further preferably greater than 2 μm and less than 4 μm. Since the distance between the film and the surface on the electrode side of the Micro LED tends to become roughly the same, the thickness of the anisotropic conductive film before connection is preferably the average particle size of the conductive particles plus a thickness of preferably 1 to 4 μm, particularly preferably 1 to 2 μm. It can be measured using a known micrometer or digital thickness gauge. For the film thickness, for example, more than 10 points can be measured and the average can be obtained.

[0055] It should be noted that the connecting film is not limited to the above-mentioned anisotropic conductive film, but can also be a film formed by stacking a conductive particle layer containing conductive particles, an adhesive layer not containing conductive particles, an adhesive layer, etc., and the number of layers or stacking surface can be appropriately selected according to the object or purpose.

[0056] <2. Method for producing connecting film>

[0057] The method for manufacturing the connection film (conductive film, anisotropic conductive film) involved in this embodiment is a method for forming the connection film on a base film having a root mean square height of a predetermined value or less, thereby obtaining a connection film having a first surface on the base film side. Thus, the surface state of the base film can be reflected on the first surface of the connection film, and the first surface with a small root mean square height can be obtained.

[0058] Hereinafter, as one embodiment of a method for producing a connection film, a method for producing an anisotropic conductive film will be described.

[0059] Figure 1 is a diagram for explaining an example of a method for manufacturing an anisotropic conductive film according to this embodiment. Figure 1 (A) shows a preparation step of preparing a substrate film, Figure 1 (B) shows a step of forming an anisotropic conductive film on a substrate film. Figure 1 (C) shows a step of attaching a cover film to the anisotropic conductive film.

[0060] (Preparation process)

[0061] First, if Figure 1 As shown in (A), a base film 11 having a first surface 11a having a root mean square height of a predetermined value or less is prepared. The root mean square height of the base film 11 is preferably 3.0×10 -1 μm or less, more preferably 1.5×10 -1 μm or less, more preferably 0.05×10 -1 If the root mean square height of the base film 11 is large, it is difficult to obtain an anisotropic conductive film having a small root mean square height.

[0062] The substrate film 11 is not particularly limited as long as it can support the anisotropic conductive film 12 and can be peeled off from the anisotropic conductive film 12 at a desired time. As the material of the substrate film 11, for example, polyester such as polyethylene terephthalate (PET), polyolefin such as polypropylene (PP), plastic materials such as poly-4-methyl-1-pentene (PMP), polytetrafluoroethylene (PTFE), glass substrates such as quartz glass can be used. In addition, the substrate film 11 may have a peeling layer on the surface of the side bonded to the anisotropic conductive film 12, and the peeling layer may contain a peeling agent such as silicone resin or polyolefin resin.

[0063] The thickness of the substrate film 11 is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less, further preferably 60 μm or less, and further preferably 50 μm or less, from the viewpoint of being able to efficiently form a long-rolled film package. The lower limit of the thickness of the substrate film 11 is not particularly limited, but is preferably 8 μm or more from the viewpoint of operability when the connecting film is manufactured, slit, or wound onto a core.

[0064] (Formation process)

[0065] Then, if Figure 1 As shown in (B), an anisotropic conductive film 12 is formed on the first surface 11a of the substrate film 11. As a method for forming the anisotropic conductive film 12, for example, a method of applying a solution of a conductive adhesive on the substrate film 11 and drying it, or a method of forming an adhesive layer without conductive particles on the substrate film 11 and fixing the conductive particles in the resulting adhesive layer, etc. can be listed. The conductive particles can be arranged regularly or randomly when viewed from above. For the regular arrangement, a known method can be used as long as the effect of the invention is not impaired.

[0066] For example, the anisotropic conductive film 12 can be formed by applying an adhesive on the substrate film 11 and drying it to form a resin film, attaching the resin film to an arrangement sheet in which conductive particles are arranged in a predetermined arrangement at a predetermined particle density, and pressing the conductive particles into the resin film for transfer. Thus, the first surface of the anisotropic conductive film 12 can reflect the surface state of the first surface 11a of the substrate film 11, and a 3.0×10 -1 The following is the RMS height.

[0067] (Pasting process)

[0068] Then, if Figure 1 As shown in (C), a cover film 13 is attached to the second surface of the anisotropic conductive film 12 to produce a film laminate. The cover film 13 is not particularly limited as long as it can be peeled off from the second surface of the anisotropic conductive film 12 at a predetermined time. As the material of the cover film 13, the same material as the base film 11 can be used. In addition, the cover film 13 may also have a peeling layer on the surface of the side bonded to the anisotropic conductive film 12, similar to the base film 11. In addition, the thickness of the cover film 13 is not particularly limited, but is preferably smaller than that of the base film 11.

[0069] According to such a method for producing a connecting film, the surface state of the base film can be reflected on the first surface of the connecting film, and a 3.0×10 -1 The following is the RMS height.

[0070] [Modifications]

[0071] For example, in the case of Micro LED, the anisotropic conductive film can also be a single piece of a specified unit such as 1 pixel unit of a set of RGB. The shape of the single piece is not particularly limited and can be appropriately set according to the size of the electronic component to be connected. In the case of forming a single piece using a laser lift-off (LLO: Laser Lift Off) device, in order to suppress the occurrence of curling or defects, the shape of the single piece is preferably selected from at least one of a polygon composed of obtuse angles, a polygon with rounded corners, an ellipse, an oblong, and a circle.

[0072] The size (length × width) of the single piece can be appropriately set according to the size of the electronic component or electrode to be connected. The ratio of the area of ​​the single piece to the area of ​​the electronic component or electrode is preferably greater than 2, more preferably greater than 4, and further preferably greater than 5. Even in the case of a single piece, as long as the anisotropic conductive film is exposed from the outer shape of the Micro LED, the method of the present invention is considered necessary to suppress the influence of optical properties. In addition, the thickness of the single piece is the same as the thickness of the anisotropic conductive film, which is the average particle size of the conductive particles plus a thickness of preferably 1 to 4 μm, particularly preferably 1 to 2 μm, preferably greater than 1 μm and less than 10 μm, more preferably greater than 1 μm and less than 6 μm, and further preferably greater than 2 μm and less than 4 μm.

[0073] In addition, the distance between the monolithic sheets on the substrate film is preferably 3 μm or more, more preferably 5 μm or more, and more preferably 10 μm or more. In addition, the upper limit of the distance between the monolithic sheets is preferably 3000 μm or less, more preferably 1000 μm or less, and more preferably 500 μm or less. When the distance between the monolithic sheets is too small, it is difficult to transfer the monolithic sheets using LLO. When the distance between the monolithic sheets is large, it is preferred to paste the monolithic sheets. The distance between the monolithic sheets can be measured using a microscope (optical microscope, metal microscope, electron microscope, etc.).

[0074] The single piece can be formed by slitting or half-cutting, or by using a laser lift-off device. When the single piece is formed by using an LLO device, the base film only needs to be transparent to the laser, and preferably quartz glass having high transmittance in the full wavelength range.

[0075] When forming a single chip using an LLO device, a single chip of a specified shape composed of an anisotropic conductive film can be formed on the substrate film by irradiating the anisotropic conductive film provided on the substrate film with laser from the substrate film side and removing the irradiated portion of the anisotropic conductive film.

[0076] For example, by using a mask having a quadrilateral opening window, unnecessary portions of the anisotropic conductive film are removed from the base film, and a single piece of a predetermined shape can be formed from the remaining portion of the anisotropic conductive film. Also, for example, by using a mask having a light shielding portion of a predetermined shape formed in the opening window, unnecessary portions of the anisotropic conductive film around the single piece are removed from the base film, and a single piece of a predetermined shape can be formed from the remaining portion of the anisotropic conductive film.

[0077] In addition, when a single sheet is made using a laser stripping device, the reaction rate of the single sheet is 25% or less, preferably 20% or less, and more preferably 15% or less. In this way, excellent transferability can be obtained. It should be noted that the reaction rate of the curable resin film before laser irradiation or the single sheet obtained after laser irradiation can be measured, for example, by using FT-IR to obtain the reduction rate of the reactive group. For example, in the case of a curable resin film using the reaction of an epoxy compound, the sample can be irradiated with infrared rays and the IR spectrum can be measured to determine the methyl group (2930cm -1 Nearby) and epoxy (914cm -1 The peak height of the epoxy group (near the peak height of the methyl group) is calculated as the ratio of the peak height of the epoxy group to the peak height of the methyl group before and after the reaction (for example, before and after laser irradiation) as shown in the following formula.

[0078] Reaction rate (%) = {1-(a / b) / (A / B)}×100

[0079] In the above formula, A is the peak height of the epoxy group before the reaction, B is the peak height of the methyl group before the reaction, a is the peak height of the epoxy group after the reaction, and b is the peak height of the methyl group after the reaction. It should be noted that when other peaks overlap with the peak of the epoxy group, the peak height of the fully cured sample (reaction rate of 100%) can be set to 0%.

[0080] <3. Display device>

[0081] The display device according to this embodiment includes a plurality of light emitting elements, a wiring substrate, and a cured film of a connection film connecting the plurality of light emitting elements and the wiring substrate. The cured film has a root mean square height of 3.0×10 -1 The first surface below, a plurality of light emitting elements are mounted on the first surface. Here, for example, when the electrode of the light emitting element has a conical protrusion, an adhesive layer containing no conductive particles can be used as the connecting film. In addition, for example, when the electrode of the light emitting element has a flat bottom surface, an anisotropic conductive film can be used as the connecting film.

[0082] Figure 2 : is a cross-sectional view schematically showing an example of a display device according to this embodiment. Figure 2As shown in FIG. 1 , the display device includes a plurality of light emitting elements 30, a wiring substrate 20 on which the plurality of light emitting elements 30 are arranged, and a cured film 40 of an anisotropic conductive film connecting the plurality of light emitting elements 30 and the wiring substrate 20. Figure 2 In the embodiment, light is transmitted from the wiring substrate 20 side, but light is also transmitted from the cured film 40 side, which is visible. Figure 2 The direction of light can be reversed.

[0083] The wiring substrate 20 has a circuit pattern for the first conductive type and a circuit pattern for the second conductive type on the substrate, for example, the first electrode and the second electrode are respectively provided at positions corresponding to the first conductive type electrode on the p-side and the second conductive type electrode on the n-side, so that the light-emitting element 30 is arranged in sub-pixel (sub-pixel) units constituting one pixel. In addition, the wiring substrate 20 forms circuit patterns such as data lines and address lines of matrix wiring, which can turn on and off the light-emitting elements corresponding to each sub-pixel constituting one pixel. One pixel can be composed of three sub-pixels of R (red), G (green), and B (blue), or four sub-pixels of RGBW (white) and RGBY (yellow), or two sub-pixels of RG and GB.

[0084] In addition, when the display device is made into a transparent display, the wiring substrate 20 is preferably a light-transmitting substrate, and the base material is preferably glass, PET (polyethylene terephthalate), etc. The first electrode 22 and the second electrode 23 are preferably transparent conductive films such as ITO (Indium-Tin-Oxide), IZO (Indium-Zinc-Oxide), ZnO (Zinc-Oxide), and IGZO (Indium-Gallium-Zinc-Oxide).

[0085] The light emitting element 30 includes a body, a first conductive type electrode, and a second conductive type electrode, and has a horizontal structure in which the first conductive type electrode and the second conductive type electrode are arranged on the same side. The body includes a first conductive type cladding layer composed of, for example, n-GaN (e.g., composed of In x Al y Ga 1-x-y The active layer is composed of a N layer) and a second conductive type cladding layer composed of, for example, p-GaN, and has a so-called double heterostructure. The first conductive type electrode is formed on a part of the first conductive type cladding layer through a passivation layer, and the second conductive type electrode is formed on a part of the second conductive type cladding layer. If a voltage is applied between the first conductive type electrode and the second conductive type electrode, carriers are concentrated in the active layer and recombine, thereby generating light emission.

[0086] The cured film 40 is formed by curing the anisotropic conductive film 12. The cured film 40 may be formed, for example, on the entire surface of the display portion of the wiring substrate 20, or may be formed, for example, on a portion of the display portion such as a 1 pixel unit of a set of RGB by a single piece of a predetermined unit.

[0087] The root mean square height of the first surface of the cured film 40 on which the light emitting element 30 is mounted is preferably 3.0×10 -1 μm or less, more preferably 2.0×10 -1 μm or less, more preferably 1.0×10 -1 If the root mean square height increases, a large amount of light scattering occurs, making it difficult to obtain excellent light transmittance and visibility.

[0088] The haze of the cured film 40 is preferably less than 50%, more preferably less than 45%, and further preferably less than 40%. The haze can be measured using a haze meter according to a method in accordance with JIS K7136.

[0089] The visible light transmittance of the cured film 40 is preferably 30% or more, more preferably 40% or more, and further preferably 45% or more. The transmittance in the visible light region (380 nm to 780 nm) can be measured using, for example, an ultraviolet-visible spectrophotometer.

[0090] In the cured film 40, as in the above-mentioned anisotropic conductive film, it is preferred that the conductive particles are arranged neatly along the surface direction. In addition, the particle surface density of the cured film can be appropriately designed according to the electrode size of the light-emitting element 30. The lower limit of the particle surface density is not particularly limited as long as it does not hinder the performance, and can be 30 particles / mm 2 Above, 500 pieces / mm 2 Above, 20000 pieces / mm 2 Above, 40000 pieces / mm 2 Above, 50000 pieces / mm 2 The upper limit of the particle surface density can be 1500000 / mm 2 Below, 1,000,000 pieces / mm 2 Below, 500,000 pieces / mm 2 Below, 100,000 pieces / mm 2 As a result, even when the size of the electrodes of the light emitting element 30 is small, excellent conductivity and insulation properties can be obtained.

[0091] It should be noted that the particle surface density of the cured film 40 is the particle surface density of the conductive particles when the film is formed during manufacturing. This is the same whether the randomly configured part is measured or the arranged part is measured. In the case of obtaining the particle number density of a single piece of the cured film 40 formed in a specified unit, the particle surface density can be obtained based on the area obtained by removing the interval between the single pieces from the area including the single piece and the interval and the number of particles. For a single piece, it is sometimes inappropriate to express it with the number density, and sometimes it is appropriate to express it with the occupied area ratio of the particles in one single piece, or the particle size and the center distance between the particles and the number.

[0092] When the binder contains conductive particles, the thickness of the cured film 40 is preferably a thickness obtained by adding 1 to 4 μm, particularly preferably 1 to 2 μm, to the average particle size of the conductive particles. This can reduce the difference between the height Ha of the first surface of the cured film 40 between the light-emitting elements 30 and the height Hb of the bottom surface of the main body of the light-emitting element 30. The height Hb of the bottom surface of the main body of the light-emitting element 30 is the height excluding the electrode from the bottom surface, and when there is a height difference in the bottom surface, the average value of the bottom surface with the height difference can be taken.

[0093] The difference between the height Ha of the first surface of the cured film 40 between the light-emitting elements 30 and the height Hb of the bottom surface of the main body of the light-emitting element 30 is preferably 1 μm or less, more preferably 0.8 μm or less, and further preferably 0.6 μm or less. By reducing the difference between the height Ha of the first surface of the cured film 40 and the height Hb of the bottom surface of the main body of the light-emitting element 30, wrinkles can be suppressed on the first surface of the cured film 40, thereby suppressing light scattering.

[0094] According to such a display device, the first surface of the cured film 40 on which the light emitting element 30 is mounted is optically flat, so that light scattering can be suppressed, and excellent light transmittance and visibility that cannot be achieved by conventional connection such as pasting ACP, ACF, or NCF can be obtained.

[0095] [Connection structure]

[0096] In the above embodiment, a display device as a display in which the light emitting elements 30 are arranged is cited as an example, but the present technology can also be applied to a connection structure connecting a first electronic component and a second electronic component. That is, the connection structure includes a first electronic component, a second electronic component, and a cured film connecting the first electronic component and the second electronic component, and the cured film has a root mean square height of 3.0×10 -1 In the following first surface, a first electronic component is mounted on the first surface.

[0097] As the first electronic component and the second electronic component, for example, light-emitting elements, IC (Integrated Circuit), flexible substrates (FPC: Flexible Printed Circuits), LCD (Liquid Crystal Display) panels, organic EL (OLED) and other flat panel display (FPD) applications, touch panel applications, transparent substrates, printed wiring boards (PWB), etc. can be listed. The material of the printed wiring board is not particularly limited, for example, it can be epoxy glass such as FR-4 substrate, plastics such as thermoplastic resins, ceramics, etc. can also be used. In addition, the transparent substrate is not particularly limited as long as it is a substrate with high transparency, and glass substrates, plastic substrates, etc. can be listed. In addition, the second electronic component can be provided with, for example, a silicone rubber layer.

[0098] <4. Method for manufacturing display device>

[0099] The manufacturing method of the display device involved in this embodiment includes: a configuration step of configuring a connection film having a first surface with a root mean square height of less than a specified value at a specified position of a wiring substrate, and a mounting step of mounting a plurality of light-emitting elements on the first surface and mounting the plurality of light-emitting elements on the wiring substrate. Here, for example, in the case where the electrode of the light-emitting element has a conical protrusion, an adhesive layer containing no conductive particles can be used as the connection film. In addition, for example, in the case where the electrode of the light-emitting element has a flat bottom surface, an anisotropic conductive film can be used as the connection film.

[0100] Figure 3 is a diagram for explaining an example of a method for manufacturing a display device in this embodiment. Figure 3 (A) shows a step of arranging an anisotropic conductive film at a predetermined position on a wiring substrate. Figure 3 (B) shows a step of mounting the light emitting element on the wiring substrate. Here, the anisotropic conductive film 12, wiring substrate 20 and light emitting element 30 are the same as those described above for the connection film and display device, and thus are given the same reference numerals and their description is omitted.

[0101] (Configuration process)

[0102] like Figure 3 As shown in (A), in the placement step, the anisotropic conductive film 12 formed on the base film 11 is placed at a predetermined position on the wiring substrate 20. Specifically, Figure 1 In the film stack shown in (C), the covering film 13 is peeled off from the anisotropic conductive film 12, so that the second surface of the anisotropic conductive film 12 is in contact with the wiring substrate 20 and configured, and the base film 11 is peeled off from the anisotropic conductive film 12, and the first surface of the anisotropic conductive film 12 is used as the mounting surface.

[0103] The anisotropic conductive film 12 may be disposed on the entire surface of the display portion of the wiring substrate 20, or may be disposed on a portion of the display portion such as a 1 pixel unit of a set of RGB in a single piece of a predetermined unit.

[0104] There is no particular limitation on the method for arranging the anisotropic conductive film 12 on the wiring substrate 20. For example, when the anisotropic conductive film 12 is arranged on the entire surface of the display unit, a method of laminating the anisotropic conductive film 12 may be cited. In addition, when a single piece of the anisotropic conductive film 12 is arranged on a part of the display unit, a method of directly transferring the single piece from the base film 11 using an LLO device and arranging it on the wiring substrate 20 may be cited, and a method of transferring from a transfer material using a transfer material (imprint material) to which the single piece is previously attached and arranging it on the wiring substrate 20 may be cited.

[0105] (Installation process)

[0106] like Figure 3 As shown in (B), in the mounting process, the light emitting element 30 is mounted on the first surface of the anisotropic conductive film 12 arranged at a predetermined position of the wiring substrate 20. The method for arranging the light emitting element in the mounting process is not particularly limited. For example, a method of arranging the light emitting element on the wiring substrate using an LLO device, a method of arranging the light emitting element on the wiring substrate using a transfer material (imprint material) to which the light emitting element is previously attached from a transfer material, etc. can be cited.

[0107] As a method for connecting the light emitting element 30 to the wiring substrate 20, a connection method such as thermal compression bonding, optical compression bonding, and thermal and optical compression bonding used in known anisotropic conductive films can be appropriately selected. In addition, when the conductive particles are flux particles, the connection can be made by reflow soldering. As connection conditions, for example, the temperature is 150°C to 260°C, the pressure is 1MPa to 60MPa, and the time is 5 seconds to 300 seconds. By curing the anisotropic conductive film to form a cured film, the light emitting element 30 can be anisotropically connected to the wiring substrate 20.

[0108] [Method for producing a connection structure]

[0109] In addition, in the above-mentioned embodiment, a method for manufacturing a display device as a display is cited as an example, but the present technology is not limited to this, and can also be applied to a method for manufacturing a light-emitting device as a light source. In addition, it can also be applied to a method for manufacturing a connection structure that connects a first electronic component and a second electronic component. That is, the method for manufacturing a connection structure has: a configuration step of configuring a connection film having a first surface with a root mean square height of less than a specified value at a specified position of the first electronic component, and a mounting step of mounting a plurality of second electronic components on the first surface and mounting the plurality of second electronic components on the first electronic component. As the first electronic component and the second electronic component, those similar to the above-mentioned connection structure can be cited.

[0110] Example

[0111] <5. Example>

[0112] In this example, an anisotropic conductive film was produced, and Sq (root mean square height), haze, and visible light transmittance were evaluated. It should be noted that the present technology is not limited to these examples.

[0113] [Measurement of Sq (root mean square height)]

[0114] The Sq of the base film and the Sq of the surface on the base film side of the sample were measured using a three-dimensional non-contact surface roughness measuring instrument manufactured by Zygo Corporation.

[0115] [Measurement of haze]

[0116] The haze of the sample was measured using a haze meter (HM-150 manufactured by Murakami Color Research Laboratory) according to the method in accordance with JIS K7136. The haze was evaluated based on the haze (%) of both the plain glass side and the anisotropic conductive film side of the sample according to the following criteria. The haze evaluation is preferably B or higher.

[0117] A: Less than 40%

[0118] B: 40% or more and less than 50%

[0119] C: 50% or more

[0120] [Measurement of visible light transmittance]

[0121] The transmittance of the sample in the visible light region (380 nm to 780 nm) was measured using an ultraviolet-visible spectrophotometer (V-560 manufactured by JASCO Corporation). The visible light transmittance was evaluated based on the visible light transmittance (%) of the plain glass side and the anisotropic conductive film side of the sample according to the following standard. The evaluation of the visible light transmittance is preferably B or above.

[0122] A: More than 45%

[0123] B: 30% or more and less than 45%

[0124] C: Less than 30%

[0125] [Example 1]

[0126] (Fabrication of anisotropic conductive film)

[0127] An adhesive is prepared by mixing 50 wt % of a polyvinyl acetal resin (product name: KS-10, manufactured by Sekisui Chemical Co., Ltd.), 40 wt % of a high-purity hydrogenated epoxy resin (product name: YX8000, manufactured by Mitsubishi Chemical Co., Ltd.) and 10 wt % of a cationic polymerization initiator (product name: SI-60L, manufactured by Sanshin Chemical Co., Ltd.).

[0128] The adhesive was applied on the substrate film with a root mean square height (Sq) of 1.2×10 -3 , a 50μm thick PET (Poly Ethylene Terephthalate) film (product name: SP3040ASCR, manufactured by TOYOCLOTH Co., Ltd.) was placed on the film and dried to form a resin film. Then, conductive particles (average particle size 2.2μm, resin core metal coated particles, Ni plating 0.1μm thick, manufactured by Sekisui Chemical Co., Ltd.) were placed at a particle density of 58000 pcs / mm 2 The arrangement sheet arranged in a hexagonal lattice is attached to the resin film, and the conductive particles are transferred by pressing them into the resin film. Next, a 25 μm thick PET (polyethylene terephthalate) film (product name: RSP3030FA2S, manufactured by TOYO CLOTH Co., Ltd.) is attached to the transfer surface of the conductive particles as a cover film to produce an anisotropic conductive film with a thickness of 4 μm and in which the conductive particles are neatly arranged.

[0129] Then, for the anisotropic conductive film with a size of 30 mm × 40 mm and a thickness of 4 μm, the cover film was peeled off, and the transfer surface of the conductive particles was bonded to a plain glass with a size of 40 mm × 70 mm and a thickness of 0.4 mm, and then the base film was peeled off to prepare a sample having a first surface with an anisotropic conductive film on the surface. The bonding conditions were a temperature of 50° C., a vacuuming time of 10 seconds, a pressurizing time of 10 seconds, and a pressure of 0.1 MPa.

[0130] As shown in Table 1, the Sq of the sample of Example 1 is 6.0×10 -2 The haze was rated as A and the visible light transmittance was rated as A.

[0131] [Example 2]

[0132] In addition to using a root mean square height (Sq) of 1.1×10-1 A sample was prepared in the same manner as in Example 1 except that a PET film with a thickness of 50 μm and a thickness of 50 μm was used as a base film to prepare an anisotropic conductive film and the film was cured at a temperature of 200° C. for 10 minutes.

[0133] As shown in Table 1, the Sq of the sample of Example 2 is 8.0×10 -2 The haze was rated as A and the visible light transmittance was rated as A.

[0134] [Example 3]

[0135] In addition to using a root mean square height (Sq) of 1.1×10 -1 A sample was prepared in the same manner as in Example 1 except that a PET film having a thickness of 50 μm and a thickness of 50 μm was used as the base film.

[0136] As shown in Table 1, the Sq of the sample of Example 3 is 9.0×10 -2 The haze was evaluated as A and the visible light transmittance was evaluated as B.

[0137] [Example 4]

[0138] In addition to using a root mean square height (Sq) of 2.8×10 -1 A sample was prepared in the same manner as in Example 1 except that a PET film having a thickness of 50 μm and a thickness of 50 μm was used as the base film.

[0139] As shown in Table 1, the Sq of the sample of Example 4 is 2.6×10 -1 The haze was evaluated as B and the visible light transmittance was evaluated as B.

[0140] [Comparative Example 1]

[0141] In addition to using a root mean square height (Sq) of 5.0×10 -1 A sample was prepared in the same manner as in Example 1 except that a PET film having a thickness of 50 μm or more and a thickness of 50 μm was used as the base film.

[0142] As shown in Table 1, the Sq of the sample of Comparative Example 1 is 5.0×10 -1 The haze was evaluated as C and the visible light transmittance was evaluated as C.

[0143] [Comparative Example 2]

[0144] A sample was prepared in the same manner as in Example 1 except that a PET film having a root mean square height (Sq) of 7.0×10 −1 μm or more and a thickness of 50 μm was used as the base film.

[0145] As shown in Table 1, the Sq of the sample of Comparative Example 2 is 7.0×10 -1The haze was evaluated as C and the visible light transmittance was evaluated as C.

[0146] [Table 1]

[0147]

[0148] As shown in Table 1, in Comparative Examples 1 and 2, since the RMS height of the first surface of the anisotropic conductive film exceeds 3.0×10 -1 μm, it was not possible to obtain good haze evaluation and visible light transmittance evaluation.

[0149] On the other hand, in Examples 1 to 4, since the root mean square height of the first surface of the anisotropic conductive film is 3.0×10 -1 μm or less, good haze evaluation and visible light transmittance evaluation can be obtained, and it can be seen that the light transmittance and visibility of the display device can be improved. In addition, in Examples 1 to 3, since the root mean square height of the first surface of the anisotropic conductive film is 1.0×10 -1 μm or less, the haze can be lowered to less than 40%. In addition, a comparison between Example 2 and Example 3 shows that the visible light transmittance is improved by curing the anisotropic conductive film.

[0150] Explanation of symbols

[0151] 11 base film, 11a first surface, 12 connection film, 12a first surface, 13 cover film, 20 wiring substrate, 30 light emitting element, 40 cured film, 40a first surface.

Claims

1. A display device comprising a plurality of light emitting elements, a wiring substrate, and a cured film of a connection film connecting the plurality of light emitting elements and the wiring substrate, The cured film has a root mean square height of 3.0×10 -1 The first surface below μm, The plurality of light emitting elements are mounted on the first surface.

2. The display device according to claim 1, wherein: The haze of the cured film between the light-emitting elements is less than 50%, and the visible light transmittance of the cured film between the light-emitting elements is 30% or more.

3. The display device according to claim 1, wherein: The cured film includes conductive particles, and the thickness of the cured film is a thickness obtained by adding 1 to 2 μm to the average particle diameter of the conductive particles.

4. The display device according to claim 3, wherein: The average particle size of the conductive particles is 3.0 μm or less. The conductive particles are 50,000 / mm 2 The above particle surface densities are arranged neatly.

5. The display device according to claim 4, wherein: A difference between a height of the first surface of the cured film between the light emitting elements and a height of a bottom surface of the light emitting element body is 1 μm or less.

6. A method for manufacturing a display device, wherein: have: A circuit having a root mean square height of 3.0×10 -1 μm or less of the connecting film on the first surface, and A mounting step of mounting a plurality of light emitting elements on the first surface and mounting the plurality of light emitting elements on a wiring substrate.

7. Connect the membrane, which has an RMS height of 3.0×10 -1 The first surface below μm.

8. The connecting film according to claim 7, wherein: The haze is less than 50% and the visible light transmittance is more than 30%.

9. The connecting film according to claim 7, wherein: The conductive particles are provided, and the thickness is a thickness obtained by adding 1 to 2 μm to the average particle diameter of the conductive particles.

10. The connecting film according to claim 9, wherein The average particle size of the conductive particles is 3.0 μm or less. The conductive particles are 50,000 / mm 2 The above particle surface densities are arranged neatly.

11. The connecting film according to claim 7, wherein: The first surface side has a root mean square height of 3.0×10 -1 Substrate film below μm.

12. A method for producing a connecting film, wherein: The root mean square height is 3.0×10 -1 A connecting film is formed on a substrate film with a thickness of less than μm. The connecting film has a root mean square height of 3.0×10 -1 The first surface below μm.

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