Conductive microsphere containing spacer layer, ultra-dispersed anisotropic conductive film and preparation method of ultra-dispersed anisotropic conductive film

Abstract

The invention relates to the technical field of materials, and discloses a conductive microsphere containing a spacer layer, an ultra-dispersed anisotropic conductive film and a preparation method. The conductive microsphere sequentially comprises a core conductive layer, an insulating layer and a spacing layer or sequentially comprises a core conductive layer and a spacing layer from inside to outside. The spacing layer of the conductive microspheres is one or a combination of acrylate resin and a curing agent thereof, epoxy resin and a curing agent thereof, and polyurethane resin and a curing agent thereof. The ultra-dispersed anisotropic conductive film is composed of a conductive film layer containing conductive microspheres and a non-conductive film layer not containing conductive microspheres. In the dispersing and coating process of subsequent preparation of the ACF, due to the existence of the spacing layer, the conductive layer parts of the conductive microspheres cannot be collided together, so that the conductive part of each conductive microsphere in the prepared ACF is uniformly dispersed, the agglomeration problem of the traditional conductive microspheres is fundamentally solved, and the risk of short circuit is further reduced.

Description

Technical Field

[0001] The invention relates to the technical field of materials, in particular to a conductive microsphere containing a spacer layer, a super-dispersed anisotropic conductive film and a preparation method thereof. Background Art

[0002] Anisotropic Conductive Film (ACF) is mainly used for bonding the upper and lower interfaces and circuit conduction in the display industry. As the precision of display screens becomes higher and higher, the upper and lower pixels per unit area are getting higher and higher, the pitch of the lines on each interface of the display screen is getting smaller and smaller, and the gaps between the lines are also getting smaller and smaller. In order to meet this fine pitch requirement and avoid the accumulation of conductive microspheres in the gaps between the lines, thereby causing short circuits, super-dispersed anisotropic conductive film products have appeared in the industry. This product mainly solves the problem of uniform dispersion and agglomeration of conductive microspheres in ACF film, and realizes a uniform spacing between the conductive microspheres.

[0003] The existing ACF film is mainly composed of conductive microspheres and resin adhesives. The selection of conductive microspheres has an important impact on the performance of the product. Conductive particles are divided into carbon particles such as carbon black and graphite, metal particles and polymer particles with metal layers on the surface, multi-layered conductive microspheres, etc.

[0004] Chinese patent CN 204689937 U discloses the use of nickel-containing conductive microspheres. By applying a magnetic field, more than 70% of the conductive microspheres can be separated from other adjacent conductive microspheres. The conductive microspheres can be platinum-based precious metals such as gold and silver, or the surface of the nickel can be coated with precious metals such as gold. Furthermore, the above-mentioned metals and other conductive substances can also be used to coat non-conductive glass, ceramics, plastics, etc. The material obtained, in this case, a nickel layer can also be provided to form a multi-layer structure. Although the conductive microspheres have a two-layer or multi-layer structure, the agglomerated parts have been removed by screening to ensure that the particles are distinct. When preparing the ACF film, it is also necessary to add a resin adhesive binder. Through magnetic field control and coating process, there is still no way to ensure that each conductive microsphere can be evenly dispersed, and there is a certain probability of agglomeration.

[0005] Chinese patent CN 115772369 A discloses a conductive ball with a three-layer core-shell structure, with a thermoplastic resin material in the center to provide elasticity and avoid damage to the substrate during later use; a conductive layer in the middle; and a thermosetting resin material as an insulating layer to avoid short circuits caused by collisions of the conductive balls during use, and to form hydrogen bonds with graphene oxide to improve dispersibility; and after curing, due to its irreversibility, the shape recovery rate is low and the conductivity is good. Although the conductive microspheres can avoid agglomeration to a certain extent, they cannot completely eliminate the agglomeration phenomenon. Even if the conductive microspheres have been sieved to remove the agglomerated parts, the particles are clearly separated. However, when preparing the conductive layer of the ACF film, a composite material of graphene oxide and polymer needs to be added. Due to electrostatic adsorption and other reasons, there is still no way to ensure that each conductive microsphere can be evenly dispersed, and there is a certain probability of agglomeration. In addition, the ACF film prepared by it includes a three-layer structure, the process is complicated, and the problem of conductive microsphere aggregation cannot be completely solved.

[0006] Therefore, there is an urgent need to develop a conductive microsphere containing a spacer layer, a super-dispersed anisotropic conductive film and a preparation method to fundamentally eliminate the problem of conductive microsphere aggregation and further reduce the risk of short circuit. Summary of the invention

[0007] In view of the above-mentioned problems, the purpose of the present invention is to provide a conductive microsphere containing a spacer layer, a super-dispersed anisotropic conductive film and a preparation method. The present invention designs a conductive microsphere with a special structure, which includes a conductive layer, an insulating layer and a spacer layer from the inside to the outside, or includes a core conductive layer and a spacer layer from the inside to the outside. The spacer layer is a resin and its curing agent. In the subsequent dispersion and coating process of preparing the ACF film, due to the presence of the spacer layer, the conductive layer part of the conductive microsphere cannot touch each other, thus completely solving the problem of agglomeration of a certain proportion of conductive microspheres in the super-dispersed ACF film.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: A conductive microsphere containing a spacer layer comprises, from the inside out, a core conductive layer, an insulating layer and a spacer layer, or comprises, from the inside out, a core conductive layer and a spacer layer; the spacer layer is one or a combination of an acrylate resin and a curing agent thereof, an epoxy resin and a curing agent thereof, and a polyurethane resin and a curing agent thereof.

[0009] Preferably, the core conductive layer is a metal ball, or a polymer microsphere or a silicon dioxide microsphere with a metal layer coated on the surface.

[0010] Preferably, the metal used for the metal ball or the metal layer is selected from conductive metals such as nickel alloy, gold, tin alloy, silver, and copper alloy.

[0011] Preferably, the insulating layer is formed by polymer particles or silicon dioxide particles wrapped around the core conductive layer.

[0012] Preferably, the diameter of the core conductive layer is d. The average thickness 11 of the insulating layer is between 10 and 500 nanometers. The thickness 12 of the spacer layer is between 0.25 and 2d.

[0013] In some embodiments, the diameter of the core conductive layer d = 3.0 ± 0.1 um; the average thickness of the insulating layer 11 = 0.3 um; the thickness of the spacer layer 12 = 2.0 ± 0.2 um. Or the diameter of the core conductive layer d = 3.0 ± 0.1 um; the average thickness of the insulating layer 11 = 0.3 um; the thickness of the spacer layer 12 = 1.0 ± 0.2 um.

[0014] Preferably, the conductive microspheres are prepared by the following steps: (1) Preparation of the core conductive layer: preparing metal balls by metal granulation, or coating the surface of polymer microspheres or silica microspheres with a metal layer; (2) Coating the core conductive layer with an insulating layer: The surface of the core conductive layer is treated with a silane coupling agent to adsorb a layer of hydrophobic insulating spheres to form an insulating layer, wherein the diameter of the insulating spheres is 10-500 nanometers; (3) Coating the spacer layer: The core conductive layer of the coating insulating layer is dispersed in water containing a hydrophilic polymerizable monomer, and a hydrophobic initiator is added. The initiator is enriched on the surface of the conductive microspheres. Under heating or UV light, the initiator is polymerized on the surface of the conductive microspheres to form a spacer layer; The amount of the hydrophilic polymerizable monomer added is 20-300% of the total mass of the conductive microspheres coated with the insulating layer, and the amount of the initiator added is 0.01-25% of the total mass of the monomers; when the spacer layer is wrapped, the hydrophilic polymerizable monomer is partially polymerized under the action of the initiator, and the degree of polymerization is 10-80%.

[0015] Alternatively, the conductive microspheres are prepared by the following steps: (1) Preparation of the core conductive layer: preparing metal balls by metal granulation, or coating the surface of polymer microspheres or silica microspheres with a metal layer; (2) Coating the spacer layer: The metal ball or the conductive microsphere coated with the conductive layer is treated with a silane coupling agent and then dispersed in water containing a hydrophilic polymerizable monomer. A hydrophobic initiator is added. The initiator is enriched on the surface of the conductive microsphere. Under heating or UV light, the initiator is polymerized on the surface of the conductive microsphere to form a spacer layer. The amount of the hydrophilic polymerizable monomer added is 20-300% of the total mass of the metal ball or the conductive microsphere coated with the conductive layer, and the amount of the initiator added is 0.01-25% of the total mass of the monomer; when the spacer layer is wrapped, the hydrophilic polymerizable monomer is partially polymerized under the action of the initiator, and the degree of polymerization is 10-80%.

[0016] Preferably, the hydrophilic polymerizable monomer is one or a combination of (meth)acrylic acid, carboxyl (meth)acrylate, amino (meth)acrylate, hydroxyl (meth)acrylate, sulfonic (meth)acrylate, hydrophilic acrylate-modified epoxy resin, polyoxyethylene epoxy resin, polyoxypropylene epoxy resin, polyethylene glycol epoxy resin, and hydrophilic acrylate-modified polyurethane; the hydrophobic initiator is one or a combination of organic peroxide initiator, azo initiator, hydrophobic amine, and photopolymerization initiator.

[0017] Preferably, the photopolymerization free radical system initiator is one or a combination of benzoin ether, acylphosphine oxide, benzophenone and thioxanthone.

[0018] Preferably, the prepared conductive microspheres are sieved to remove non-single-coated conductive microspheres, thereby ensuring that the prepared conductive microspheres are single-coated.

[0019] Another object of the present invention is to disclose a super-dispersed anisotropic conductive film, which is composed of a conductive film layer and a non-conductive film layer, and the conductive film layer contains the above-mentioned conductive microspheres.

[0020] Another object of the present invention is to disclose a method for preparing a superdispersed anisotropic conductive film, comprising the following steps: (1) mixing the above-mentioned conductive microspheres with a solvent, coating the mixture on a substrate, and forming a spacer layer into a continuous phase by heating, UV irradiation or light pressing to obtain a conductive film layer; (2) forming a film by coating one or a combination of epoxy resin and its curing agent, acrylate resin and its curing agent, polyurethane resin and its curing agent to obtain a non-conductive film layer; (3) Compounding the conductive film layer with the non-conductive film layer to form a double-layer ultra-dispersed anisotropic conductive film.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention designs a conductive microsphere with a special structure, which includes a conductive layer, an insulating layer and a spacer layer from the inside to the outside, or includes a core conductive layer and a spacer layer from the inside to the outside. The spacer layer is a resin and a curing agent. In the subsequent dispersion and coating process of preparing the ACF film, the conductive layer parts of the conductive microspheres cannot touch each other because of the presence of the spacer layer, thus completely solving the problem of agglomeration of a certain proportion of conductive microspheres in the ultra-dispersed ACF film.

[0022] The present invention controls the thickness of the conductive microsphere spacer layer, controls the dispersion distance between the conductive microsphere core conductive layer parts, and controls the number of the conductive microsphere core conductive layer in the ACF unit area.

[0023] The super-dispersed anisotropic conductive film prepared by the present invention separates each conductive microsphere by a conductive microsphere spacing layer, so that the conductive part of each conductive microsphere in the prepared super-dispersed anisotropic conductive film is evenly dispersed, fundamentally solving the agglomeration problem of traditional conductive microspheres, thereby further reducing the risk of short circuit.

[0024] The ultra-dispersed anisotropic conductive film of the present invention is prepared by a double-layer structure of a conductive film layer and a non-conductive film layer. The conductive film layer is formed by coating a mixture of conductive microspheres and a solvent, and the non-conductive film layer is formed by coating a resin and its curing agent. It has a simple structure and is easy to operate, and completely solves the problem of aggregation of conductive microspheres. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of a conductive microsphere containing a spacer layer according to the present invention; Figure 2 is a metallographic microscope schematic diagram of the superdispersed anisotropic conductive film in Example 1 of the present invention; Figure 3 is a metallographic microscope schematic diagram of the superdispersed anisotropic conductive film in Example 2 of the present invention; Figure 4 is a metallographic microscope schematic diagram of the superdispersed anisotropic conductive film in Example 3 of the present invention; Figure 5 is a metallographic microscope schematic diagram of the anisotropic conductive film in Comparative Example 1 of the present invention; Figure 6 It is a metallographic microscope schematic diagram of the anisotropic conductive film in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. The reagents and instruments used in the embodiments are all conventional products that can be obtained commercially unless otherwise specified. The experimental methods used in the embodiments are all conventional experimental methods or technical means in the art unless otherwise specified.

[0027] like Figure 1As shown, an embodiment of the present invention provides a conductive microsphere containing a spacer layer, which includes a core conductive layer 1, an insulating layer 2 and a spacer layer 3 from the inside to the outside. Alternatively, the conductive microsphere includes a core conductive layer 1 and a spacer layer 3 from the inside to the outside, that is, does not contain an insulating layer 2. The spacer layer 3 is one or a combination of an acrylate resin and a curing agent thereof, an epoxy resin and a curing agent thereof, and a polyurethane resin and a curing agent thereof.

[0028] The core conductive layer is a metal ball or a microsphere with a metal layer coated on the surface. In some embodiments, the core conductive layer is a polymer microsphere or a silicon dioxide microsphere with a metal layer coated on the surface. The metal used in the metal ball or metal layer is selected from a conductive metal such as nickel alloy, gold, tin alloy, silver, copper alloy, etc.

[0029] The insulating layer is formed by polymer particles or silicon dioxide particles wrapped around the core conductive layer.

[0030] The spacer layer is one or a combination of epoxy resin and its curing agent, acrylate resin and its curing agent, polyurethane resin and its curing agent.

[0031] The diameter of the core conductive layer is d. The average thickness of the insulating layer l1 is 10-500 nanometers. The thickness of the spacer layer l2 is between 0.25-2d. In some embodiments, the diameter of the core conductive layer d=3.0±0.1um; the average thickness of the insulating layer l1=0.3um; the thickness of the spacer layer l2=2.0±0.2um. Or the diameter of the core conductive layer d=3.0±0.1um; the average thickness of the insulating layer l1=0.3um; the thickness of the spacer layer l2=1.0±0.2um.

[0032] In some embodiments, the conductive microspheres are prepared by the following steps: (1) Preparation of the core conductive layer: preparing metal balls by metal granulation, or coating the surface of polymer microspheres or silica microspheres with a metal layer; (2) Coating the core conductive layer with an insulating layer: The surface of the core conductive layer is treated with a silane coupling agent to adsorb a layer of hydrophobic insulating spheres to form an insulating layer, wherein the diameter of the insulating spheres is 10-500 nanometers; (3) Coating the spacer layer: The core conductive layer of the coating insulating layer is dispersed in water containing a hydrophilic polymerizable monomer, and a hydrophobic initiator is added. The initiator is enriched on the surface of the conductive microspheres. Under heating or UV light, the initiator is polymerized on the surface of the conductive microspheres to form a spacer layer; The amount of the hydrophilic polymerizable monomer added is 20-300% of the total mass of the conductive microspheres coated with the insulating layer, and the amount of the initiator added is 0.01-25% of the total mass of the monomers; when the spacer layer is wrapped, the hydrophilic polymerizable monomer is partially polymerized under the action of the initiator, and the degree of polymerization is 10-80%.

[0033] Alternatively, the conductive microspheres are prepared by the following steps: (1) Preparation of the core conductive layer: preparing metal balls by metal granulation, or coating the surface of polymer microspheres or silica microspheres with a metal layer; (2) Coating the spacer layer: The metal ball or the conductive microsphere coated with the conductive layer is treated with a silane coupling agent and then dispersed in water containing a hydrophilic polymerizable monomer. A hydrophobic initiator is added. The initiator is enriched on the surface of the conductive microsphere. Under heating or UV light, the initiator is polymerized on the surface of the conductive microsphere to form a spacer layer. The amount of the hydrophilic polymerizable monomer added is 20-300% of the total mass of the metal ball or the conductive microsphere coated with the conductive layer, and the amount of the initiator added is 0.01-25% of the total mass of the monomer; when the spacer layer is wrapped, the hydrophilic polymerizable monomer is partially polymerized under the action of the initiator, and the degree of polymerization is 10-80%.

[0034] During the preparation process, FTIR can be used to measure the 1680 cm-1 before and after the reaction. -1 Double bond and 910cm -1 The degree of polymerization was determined by the change in the peak area of ​​the epoxy group at the bottom of the column, and the termination time of the reaction was determined accordingly.

[0035] The hydrophilic polymerizable monomer is one or a combination of (meth)acrylic acid, carboxyl (meth)acrylate, amino (meth)acrylate, hydroxyl (meth)acrylate, sulfonic (meth)acrylate, hydrophilic acrylate-modified epoxy resin, polyoxyethylene epoxy resin, polyoxypropylene epoxy resin, polyethylene glycol epoxy resin, and hydrophilic acrylate-modified polyurethane; the hydrophobic initiator is one or a combination of organic peroxide initiator, azo initiator, hydrophobic amine, and photopolymerization initiator.

[0036] Preferably, the photopolymerization initiator is one or a combination of benzoin ether, acylphosphine oxide, benzophenone and thioxanthone.

[0037] Preferably, the prepared conductive microspheres are sieved to remove non-single-coated conductive microspheres, thereby ensuring that the prepared conductive microspheres are single-coated.

[0038] An embodiment of the present invention provides a super-dispersed anisotropic conductive film, which is composed of a conductive film layer and a non-conductive film layer, and the conductive film layer contains the conductive microspheres.

[0039] The method for preparing the super-dispersed anisotropic conductive film comprises the following steps: (1) mixing the above-mentioned conductive microspheres with a solvent, coating the mixture on a substrate, and forming a spacer layer into a continuous phase by heating, UV irradiation or light pressing to obtain a conductive film layer; (2) forming a film by coating one or a combination of epoxy resin and its curing agent, acrylate resin and its curing agent, polyurethane resin and its curing agent to obtain a non-conductive film layer; (3) Compounding the conductive film layer with the non-conductive film layer to form a double-layer ultra-dispersed anisotropic conductive film.

[0040] The present invention is further described below by way of Examples 1-3 and Comparative Examples 1-2.

[0041] Example 1 Conductive microspheres include a core conductive layer, an insulating layer and a spacer layer from the inside out. The preparation method is as follows: (1) A nickel metal layer is plated on the surface of the silica microspheres by chemical plating to obtain a core conductive layer with a diameter of d = 3.0 ± 0.1 um.

[0042] (2) After being treated with a silane coupling agent, a layer of hydrophobic insulating spheres (silicon dioxide particles) is adsorbed on the surface of the core conductive layer to form an insulating layer with an average thickness of l1 = 0.3 um.

[0043] (3) 25 g of conductive microspheres coated with an insulating layer were dispersed in 200 g of an aqueous solution containing 20 g of carboxyl acrylate epoxy resin, 20 g of polyethylene glycol epoxy resin, 20 g of polyoxyethylene epoxy resin, 10 g of polyethylene glycol diacrylate, 1.5 g of initiator benzoyl peroxide, and 10 g of epoxy curing agent D2000, wherein benzoyl peroxide and D2000 were enriched on the surface of the conductive microspheres. The reaction was carried out at 60°C for 3 min to achieve a polymerization degree of 80%. A spacer layer was formed on the surface of the conductive microspheres by polymerization, and the thickness of the spacer layer was l2 = 2.0 ± 0.2 um. (4) Screening the prepared conductive microspheres to remove non-single-particle coated conductive microspheres.

[0044] The super-dispersed anisotropic conductive film is composed of a conductive film layer containing the above conductive microspheres and a non-conductive film layer not containing the above conductive microspheres. The preparation method is as follows: (1) Conductive film layer: Disperse 50g of conductive microspheres in 50g of ethanol and apply it on the PET substrate. Control the coating thickness so that the coating thickness does not exceed 2 times the total diameter of the conductive microspheres. Bake to evaporate the ethanol, and heat and lightly press (50°C) with a hot pressing roller to form a continuous phase conductive film layer.

[0045] The polymerization degree of the spacer layer of the conductive microspheres is 80%, and the thermosetting resin has not yet been completely formed. The hot pressing temperature during the preparation of the conductive film layer did not reach the temperature required for continued polymerization, and the unpolymerized part of the spacer layer of the conductive microspheres softened under hot pressing to form a continuous phase.

[0046] (2) Non-conductive film layer: Disperse 25 g of bisphenol A epoxy resin 128E, 10 g of phenolic epoxy resin 301, 25 g of phenolic resin YP-50, and 20 g of epoxy curing agent HX-3088 evenly in 100 g of toluene, apply the mixture on a PET substrate, and bake to volatilize the toluene to obtain a non-conductive film layer.

[0047] (3) The conductive film layer and the non-conductive film layer are heat-pressed and laminated (80°C) by a laminating machine to obtain a double-layer ultra-dispersed anisotropic conductive film. During the lamination, the hot pressing temperature reaches the temperature required for continued polymerization, and the unpolymerized part of the spacer layer of the conductive microspheres continues to polymerize.

[0048] Figure 2 This is a photo of the super-dispersed anisotropic conductive film prepared by the above method under a metallographic microscope. It can be seen that the conductive part of each conductive microsphere is evenly dispersed and separated without agglomeration.

[0049] Example 2 Conductive microspheres include a core conductive layer, an insulating layer and a spacer layer from the inside out. The preparation method is as follows: (1) A nickel metal layer is plated on the surface of the silica microspheres by chemical plating to obtain a core conductive layer with a diameter of d = 3.0 ± 0.1 um.

[0050] (2) After being treated with a silane coupling agent, a layer of hydrophobic insulating spheres (silicon dioxide particles) is adsorbed on the surface of the core conductive layer to form an insulating layer with an average thickness of l1 = 0.3 um.

[0051] (3) 25 g of conductive microspheres coated with an insulating layer were uniformly dispersed in 100 g of an aqueous solution containing 10 g of carboxyl acrylate epoxy resin, 10 g of polyethylene glycol epoxy resin, 10 g of polyoxyethylene epoxy resin, 5 g of polyethylene glycol diacrylate, 0.75 g of initiator benzoyl peroxide, and 5 g of epoxy curing agent D2000, wherein benzoyl peroxide and D2000 were enriched on the surface of the conductive microspheres. The mixture was reacted at 60 °C for 3 min to achieve a polymerization degree of 80%. A spacer layer was formed on the surface of the conductive microspheres with a thickness of l2 = 1.0 ± 0.2 um.

[0052] (4) Screening the prepared conductive microspheres to remove non-single-particle coated conductive microspheres.

[0053] The super-dispersed anisotropic conductive film is composed of a conductive film layer containing the above conductive microspheres and a non-conductive film layer not containing the above conductive microspheres. The preparation method is as follows: (1) Conductive film layer: Disperse 50g of conductive microspheres in 75g of ethanol and apply it on a PET substrate. Control the coating thickness so that the coating thickness does not exceed 2 times the total diameter of the conductive microspheres. Bake to evaporate the ethanol, and heat and lightly press (50°C) with a hot pressing roller to form a continuous phase conductive film layer.

[0054] The polymerization degree of the spacer layer of the conductive microspheres is 80%, and the thermosetting resin has not yet been completely formed. The hot pressing temperature during the preparation of the conductive film layer did not reach the temperature required for continued polymerization, and the unpolymerized part of the spacer layer of the conductive microspheres softened under hot pressing to form a continuous phase.

[0055] (2) Non-conductive film layer: Disperse 25 g of bisphenol A epoxy resin 128E, 10 g of phenolic epoxy resin 301, 25 g of phenolic resin YP-50, and 20 g of epoxy curing agent HX-3088 evenly in 100 g of toluene, apply the mixture on a PET substrate, and bake to volatilize the toluene to obtain a non-conductive film layer.

[0056] (3) The conductive film layer and the non-conductive film layer are heat-pressed and laminated (80°C) by a laminating machine to obtain a double-layer ultra-dispersed anisotropic conductive film. During the lamination, the hot pressing temperature reaches the temperature required for continued polymerization, and the unpolymerized part of the spacer layer of the conductive microspheres continues to polymerize.

[0057] Figure 3 This is a photo of the super-dispersed anisotropic conductive film prepared by the above method under a metallographic microscope. It can be seen that the conductive part of each conductive microsphere is evenly dispersed and separated without agglomeration.

[0058] Comparative Example 1 and Example 2, Figure 2 and Figure 3 : The core conductive layer and insulating layer of the conductive microspheres are the same size. By controlling the thickness of the spacer layer, the dispersion distance between the core conductive layer parts of the conductive microspheres can be controlled, and the number of the core conductive layers of the conductive microspheres in the unit area of ​​the ACF can also be controlled.

[0059] Example 3 The conductive microspheres include a core conductive layer and a spacer layer from the inside to the outside. The preparation method is as follows: (1) A nickel metal layer is plated on the surface of the silica microspheres by chemical plating to obtain a core conductive layer with a diameter of d = 3.0 ± 0.1 um.

[0060] (2) 25 g of conductive microspheres coated with a conductive layer were treated with a silane coupling agent and then dispersed in 200 g of an aqueous solution containing 20 g of a carboxyl acrylate epoxy resin, 20 g of a polyethylene glycol epoxy resin, 20 g of a polyoxyethylene epoxy resin, 10 g of a polyethylene glycol diacrylate, 1.5 g of an initiator benzoyl peroxide, and 10 g of an epoxy curing agent D2000, wherein benzoyl peroxide and D2000 were enriched on the surface of the conductive microspheres. The reaction was carried out at 60°C for 3 min to achieve a polymerization degree of 80%. A spacer layer was formed on the surface of the conductive microspheres by polymerization, and the thickness of the spacer layer was l2 = 2.0 ± 0.2 um.

[0061] (3) Screening the prepared conductive microspheres to remove non-single-particle coated conductive microspheres.

[0062] The super-dispersed anisotropic conductive film is composed of a conductive film layer containing the above conductive microspheres and a non-conductive film layer not containing the above conductive microspheres. The preparation method is as follows: (1) Conductive film layer: Disperse 50g of conductive microspheres in 75g of ethanol and apply it on a PET substrate. Control the coating thickness so that the coating thickness does not exceed 2 times the total diameter of the conductive microspheres. Bake to evaporate the ethanol, and heat and lightly press (50°C) with a hot pressing roller to form a continuous phase conductive film layer.

[0063] The degree of polymerization of the spacer layer of the conductive microspheres is 80%, and the thermosetting resin has not yet been completely formed. The hot pressing temperature during the preparation of the conductive film layer did not reach the temperature required for continued polymerization. The unpolymerized reaction part in the spacer layer of the conductive microspheres softened under hot pressing to form a continuous phase. (2) Non-conductive film layer: 25g of bisphenol A epoxy resin 128E, 10g of phenolic epoxy resin 301, 25g of phenolic resin YP-50, and 20g of epoxy curing agent HX-3088 were evenly dispersed in 100g of toluene, coated on the PET substrate, and baked to volatilize the toluene to obtain a non-conductive film layer.

[0064] (3) The conductive film layer and the non-conductive film layer are heat-pressed and laminated (80°C) by a laminating machine to obtain a double-layer ultra-dispersed anisotropic conductive film. During the lamination, the hot pressing temperature reaches the temperature required for continued polymerization, and the unpolymerized part of the spacer layer of the conductive microspheres continues to polymerize.

[0065] Figure 4 This is a photo of the super-dispersed anisotropic conductive film prepared by the above method under a metallographic microscope. It can be seen that the conductive part of each conductive microsphere is evenly dispersed and separated without agglomeration.

[0066] Comparative Example 1 Conductive microspheres: The conductive microspheres used have no spacer layer, but only a double-layer structure of a conductive layer and an insulating layer. The preparation method is as follows: (1) A nickel metal layer is plated on the surface of the silica microspheres by chemical plating to obtain a core conductive layer with a diameter of d = 3.0 ± 0.1 um.

[0067] (2) After being treated with a silane coupling agent, a layer of hydrophobic insulating spheres (silicon dioxide particles) is adsorbed on the surface of the core conductive layer to form an insulating layer with an average thickness of l1 = 0.3 um.

[0068] The preparation method of the anisotropic conductive film is as follows: (1) Conductive film layer: 20g of carboxyl acrylate epoxy resin, 20g of polyethylene glycol epoxy resin, 20g of polyoxyethylene epoxy resin, 10g of polyethylene glycol diacrylate, 1.5g of initiator benzoyl peroxide, and 10g of epoxy curing agent D2000 were dispersed in 100g of toluene, and reacted at 60°C for 3min to make the polymerization degree reach 80% to obtain a resin solution. 25g of conductive microspheres coated with an insulating layer were evenly dispersed in the above solution to obtain a coating solution. The above coating solution was coated on a PET substrate, the coating thickness was controlled, and it was baked (50°C) to volatilize the toluene to prepare a conductive film layer.

[0069] (2) Non-conductive film layer: Disperse 25 g of bisphenol A epoxy resin 128E, 10 g of phenolic epoxy resin 301, 25 g of phenolic resin YP-50, and 20 g of epoxy curing agent HX-3088 evenly in 100 g of toluene, apply the mixture on a PET substrate, and bake to volatilize the toluene to obtain a non-conductive film layer.

[0070] (3) The conductive film layer and the non-conductive film layer are hot-pressed and laminated (80°C) using a laminating machine to produce a double-layer ACF.

[0071] Figure 5 This is a photo of the anisotropic conductive film prepared by the above method under a metallographic microscope.

[0072] Comparative Example 2 (Ultra-dispersed ACF was prepared with reference to the technology of CN204689937U) Conductive microspheres: The conductive microspheres used have no spacer layer, but only a double-layer structure of a conductive layer and an insulating layer. The preparation method is as follows: (1) A nickel metal layer is plated on the surface of the silica microspheres by chemical plating to obtain a core conductive layer with a diameter of d = 3.0 ± 0.1 um.

[0073] (2) After being treated with a silane coupling agent, a layer of hydrophobic insulating spheres (silicon dioxide particles) is adsorbed on the surface of the core conductive layer to form an insulating layer with an average thickness of l1 = 0.3 um.

[0074] The preparation method of the anisotropic conductive film is as follows: (1) Conductive film layer: 20g of carboxyl acrylate epoxy resin, 20g of polyethylene glycol epoxy resin, 20g of polyoxyethylene epoxy resin, 10g of polyethylene glycol diacrylate, 1.5g of benzoyl peroxide as initiator, and 10g of epoxy curing agent D2000 were dispersed in 100g of toluene, and reacted at 60°C for 3min to achieve a polymerization degree of 80% to obtain a resin solution. 25g of conductive microspheres coated with an insulating layer were evenly dispersed in the above solution to obtain a coating solution. The above coating solution was coated on a PET substrate, the coating thickness was controlled, and the toluene was volatilized by baking (50°C) and a magnetic field was applied at the same time to obtain a conductive film layer.

[0075] (2) Non-conductive film layer: Disperse 25 g of bisphenol A epoxy resin 128E, 10 g of phenolic epoxy resin 301, 25 g of phenolic resin YP-50, and 20 g of epoxy curing agent HX-3088 evenly in 100 g of toluene, apply the mixture on a PET substrate, and bake to volatilize the toluene to obtain a non-conductive film layer.

[0076] (3) The conductive film layer and the non-conductive film layer are hot-pressed and laminated (80°C) using a laminating machine to produce a double-layer ACF.

[0077] Figure 6 is a photo of the ACF prepared by the above method under a metallographic microscope.

[0078] It can be seen that in comparative example 1-2, when the conductive microspheres have no spacer layer, even if the conductive microspheres have been sieved to remove the agglomerated parts to ensure that each particle is distinct, there is still no way to ensure that each conductive microsphere can be evenly dispersed during the magnetic field control and coating process, and there is a certain probability of agglomeration.

[0079] Compared with Comparative Example 1-2, in Example 1-3, the conductive layer of the conductive microspheres is separated by the spacer layer when preparing the conductive microspheres, and the non-single dispersed conductive microspheres are removed by subsequent screening. In the subsequent dispersion and coating process, due to the presence of the spacer layer, the conductive layer of the conductive microspheres cannot touch each other, thus completely solving the problem of agglomeration of a certain proportion of conductive microspheres in the ultra-dispersed ACF.

[0080] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A conductive microsphere containing a spacer layer, characterized in that: The core conductive layer, the insulating layer and the spacer layer are sequentially included from the inside to the outside, or the core conductive layer and the spacer layer are sequentially included from the inside to the outside; the spacer layer is one or a combination of acrylate resin and its curing agent, epoxy resin and its curing agent, polyurethane resin and its curing agent; By controlling the thickness of the spacer layer, the distance between the core conductive layer parts of the conductive microspheres is controlled, and the number of the core conductive layer of the conductive microspheres in the unit area of ​​the ACF is controlled.

2. The conductive microsphere containing a spacer layer according to claim 1, characterized in that: The core conductive layer is a metal ball, or a polymer microsphere or a silicon dioxide microsphere with a metal layer coated on the surface.

3. The conductive microsphere containing a spacer layer according to claim 2, characterized in that: The metal used for the metal ball or metal layer is selected from nickel alloy, gold, tin alloy, silver and copper alloy.

4. The conductive microsphere containing a spacer layer according to claim 1, characterized in that: The insulating layer is formed by polymer particles or silicon dioxide particles wrapped around the core conductive layer.

5. The conductive microsphere containing a spacer layer according to claim 1, characterized in that: The diameter of the core conductive layer is d; the average thickness 11 of the insulating layer is between 10 and 500 nanometers; and the thickness 12 of the spacer layer is between 0.25 and 2d.

6. The conductive microsphere containing a spacer layer according to claim 5, characterized in that: The diameter of the core conductive layer is d=3.0±0.1um; the average thickness of the insulating layer is 11=0.3um; the thickness of the spacer layer is 12=2.0±0.2um; or the diameter of the core conductive layer is d=3.0±0.1um; the average thickness of the insulating layer is 11=0.3um; the thickness of the spacer layer is 12=1.0±0.2um.

7. The conductive microsphere containing a spacer layer according to claim 1, characterized in that: The conductive microspheres are prepared by the following steps: (1) Preparation of the core conductive layer: preparing metal balls by metal granulation, or coating the surface of polymer microspheres or silica microspheres with a metal layer; (2) Coating the core conductive layer with an insulating layer: The surface of the core conductive layer is treated with a silane coupling agent to adsorb a layer of hydrophobic insulating spheres to form an insulating layer, wherein the diameter of the insulating spheres is 10-500 nanometers; (3) Coating the spacer layer: The core conductive layer of the coating insulating layer is dispersed in water containing a hydrophilic polymerizable monomer, and a hydrophobic initiator is added. The initiator is enriched on the surface of the conductive microspheres. Under heating or UV light, the initiator is polymerized on the surface of the conductive microspheres to form a spacer layer; The amount of the hydrophilic polymerizable monomer added is 20-300% of the total mass of the conductive microspheres coated with the insulating layer, and the amount of the initiator added is 0.01-25% of the total mass of the monomers; when the spacer layer is wrapped, the hydrophilic polymerizable monomer is partially polymerized under the action of the initiator, and the degree of polymerization is 10-80%; Alternatively, the conductive microspheres are prepared by the following steps: (1) Preparation of the core conductive layer: preparing metal balls by metal granulation, or coating the surface of polymer microspheres or silica microspheres with a metal layer; (2) Coating the spacer layer: The metal ball or the conductive microsphere coated with the conductive layer is treated with a silane coupling agent and then dispersed in water containing a hydrophilic polymerizable monomer. A hydrophobic initiator is added. The initiator is enriched on the surface of the conductive microsphere. Under heating or UV light, the initiator is polymerized on the surface of the conductive microsphere to form a spacer layer. The amount of the hydrophilic polymerizable monomer added is 20-300% of the total mass of the metal ball or the conductive microsphere coated with the conductive layer, and the amount of the initiator added is 0.01-25% of the total mass of the monomer; when the spacer layer is wrapped, the hydrophilic polymerizable monomer is partially polymerized under the action of the initiator, and the degree of polymerization is 10-80%; The hydrophilic polymerizable monomer is one or a combination of (meth)acrylic acid, carboxyl (meth)acrylate, amino (meth)acrylate, hydroxyl (meth)acrylate, sulfonic (meth)acrylate, hydrophilic acrylate-modified epoxy resin, polyoxyethylene epoxy resin, polyoxypropylene epoxy resin, polyethylene glycol epoxy resin, and hydrophilic acrylate-modified polyurethane; the hydrophobic initiator is one or a combination of organic peroxide initiator, azo initiator, hydrophobic amine, and photopolymerization initiator.

8. The conductive microsphere containing a spacer layer according to claim 7, characterized in that: The prepared conductive microspheres are sieved to remove non-single coated conductive microspheres.

9. A superdispersed anisotropic conductive film, characterized in that: The super-dispersed anisotropic conductive film is composed of a conductive film layer and a non-conductive film layer, and the conductive film layer contains the conductive microspheres according to any one of claims 1 to 8.

10. A method for preparing a superdispersed anisotropic conductive film according to claim 9, characterized in that: The following steps are involved: (1) Mixing the conductive microspheres according to any one of claims 1 to 8 with a solvent, coating the mixture on a substrate, and forming a spacer layer into a continuous phase by heating, UV irradiation or light pressing to obtain a conductive film layer; (2) forming a film by coating one or a combination of epoxy resin and its curing agent, acrylate resin and its curing agent, polyurethane resin and its curing agent to obtain a non-conductive film layer; (3) Compounding the conductive film layer with the non-conductive film layer to form a double-layer ultra-dispersed anisotropic conductive film.

Images