JP7755481B2 - Adhesive composition, anisotropic conductive film, connection structure, and method for manufacturing the connection structure - Google Patents

Description

The present invention relates to an adhesive composition, an anisotropic conductive film, a connection structure, and a method for manufacturing a connection structure.

Adhesive compositions such as anisotropic conductive paste (ACP) and film-like materials (anisotropic conductive films) such as anisotropic conductive film (ACF) are widely used as means for bonding electronic components to circuit boards and other components. For example, anisotropic conductive films are used to bond and electrically connect various terminals together, including when connecting the terminals of a flexible printed circuit (FPC) to the terminals of the glass substrate of an LCD panel (so-called FOG), and when connecting a driver IC to a glass substrate (so-called COG).

When connecting anisotropic conductive films in FOG, COG, etc., low-temperature, short-time compression bonding is required to minimize damage to the substrate. This is achieved by using a radically polymerizable compound and a radical polymerization initiator as adhesive components (see, for example, Patent Document 1).

JP 2015-185399 A

In recent years, as LCD panels have become more precise, the spacing between connected wiring has become narrower, and the required connection area has become smaller. To meet this demand, it is necessary to increase the amount of conductive particles blended into anisotropic conductive films.
On the other hand, if a coupling agent is added to an anisotropic conductive film to improve adhesion when bonding different materials such as FOG and COG, the adhesion between the conductive particles also improves, which can lead to problems such as short circuits becoming more likely to occur due to aggregation of the conductive particles.

The objective of the present invention is to provide an adhesive composition that can be used for joining substrates that require high adhesive strength due to differences in substrates, such as FOG and COG mounting, and that has excellent conductive particle dispersibility and connection reliability.

After extensive research into the above-mentioned problems, the inventors discovered that the above-mentioned problems could be solved by using an adhesive composition having the following composition, leading to the completion of the present invention.

That is, the present invention includes the following.
[1] A binder composition containing a polymerizable component and a film-forming component;
a polymerization initiator;
Conductive particles having a particle diameter of 1 μm or more and 10 μm or less;
an insulating filler having a particle size of 5% or less of the conductive particles;
a silane coupling agent;
and the amount of the insulating filler blended is 85% by mass or more and 200% by mass or less of the conductive particles.
[2] The adhesive composition according to claim 1, wherein the insulating filler is spherical.
[3] An anisotropic conductive film comprising the adhesive composition according to claim 1 or 2.
[4] A connection structure in which a first electronic component and a second electronic component are connected by the anisotropic conductive film according to claim 3.
[5] A method for manufacturing a connection structure, comprising a step of pressure-bonding a first electronic component and a second electronic component with the anisotropic conductive film described in claim 3 interposed therebetween.

The present invention provides an adhesive composition that can be used for bonding that requires high adhesive strength, such as FOG and COG mounting, and that has excellent conductive particle dispersibility and connection reliability.

The present invention will be described in detail below based on preferred embodiments. The present invention is not limited to the following description, and each component can be modified as appropriate without departing from the spirit of the present invention.

[Adhesive composition]
The adhesive composition of the present invention comprises a binder composition containing a polymerizable component and a film-forming component, a polymerization initiator, conductive particles having a particle diameter of 1 μm or more and 10 μm or less, an insulating filler having a particle diameter of 5% or less of the conductive particles, and a coupling agent, wherein the amount of the insulating filler mixed is 85% by mass or more and 200% by mass or less of the conductive particles.
Each component will be described in detail below.

<Binder Composition>
The adhesive composition of the present invention comprises a binder composition that includes a polymerizable component and a film-forming component.

(Polymerizable component)
The polymerizable component used in the adhesive composition of the present invention may be, for example, a thermal radical polymerization type, a thermal cationic polymerization type, or a thermal anionic polymerization type. A thermal radical polymerization type polymerizable component is preferred, as it allows pressure bonding at low temperature in a short time.

An example of a thermal radical polymerization type polymerizable component is (meth)acrylate. As the (meth)acrylate, monofunctional (meth)acrylate, difunctional (meth)acrylate, or trifunctional or higher functional (meth)acrylate can be used. Note that, in this specification, (meth)acrylate is used to encompass both acrylic acid esters (acrylates) and methacrylic acid esters (methacrylates).

Examples of monofunctional (meth)acrylates include polyalkylene glycol ester monomers and alkyl (meth)acrylates having a linear or branched alkyl group. Examples of polyalkylene glycol ester monomers include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polybutylene glycol mono(meth)acrylate.

Examples of bifunctional (meth)acrylates include tricyclodecane dimethanol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A EO-modified di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 2-hydroxy-3-acryloxypropyl (meth)acrylate, propoxylated bisphenol A di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, Examples include tetraethylene glycol di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, alkoxylated cyclohexanedimethanol di(meth)acrylate, ethoxylated (4) bisphenol A di(meth)acrylate, ethoxylated (10) bisphenol A di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, dioxane glycol di(meth)acrylate, and EO-modified isocyanuric acid di(meth)acrylate.

Examples of trifunctional or higher (meth)acrylates include EO-modified isocyanuric acid tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate, EO-modified pentaerythritol tri(meth)acrylate, ε-caprolactone-modified tris(acryloxyethyl)(meth)acrylate, ethoxylated (20) trimethylolpropane tri(meth)acrylate, propoxylated (3) trimethylolpropane tri(meth)acrylate, and propoxylated (6) trimethylolpropane tri(meth)acrylate. Examples of polymerizable components include pantaerythritol tri(meth)acrylate, ethoxylated (9) trimethylolpropane tri(meth)acrylate, propoxylated (3) glyceryl tri(meth)acrylate, ethoxylated (4) pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, EO-modified dipentaerythritol penta(meth)acrylate, and urethane (meth)acrylates having three to nine functionalities. The polymerizable components may be used alone or in combination of two or more.

In the adhesive composition of the present invention, the content of the polymerizable component is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 18% by mass or more, and even more preferably 20% by mass or more, based on 100% by mass of the non-volatile components in the adhesive composition. The upper limit of the content is not particularly limited, but is preferably 60% by mass or less, more preferably 55% by mass or less or 50% by mass or less.

(Components for film formation)
The film-forming component is not particularly limited as long as it has film-forming ability. The film-forming component may be appropriately selected depending on the purpose, and examples thereof include phenoxy resin, epoxy resin, polyvinyl acetal resin, unsaturated polyester resin, saturated polyester resin, urethane resin, butadiene resin, polyimide resin, polyamide resin, and polyolefin resin. The film-forming component may be used alone or in combination of two or more.
Among these, phenoxy resins can be preferably used from the viewpoints of film-forming properties, processability, and connection reliability.

From the viewpoint of film-forming properties, the polystyrene-equivalent weight-average molecular weight (Mw) of the film-forming component is preferably 10,000 or more, more preferably 15,000 or more, and even more preferably 20,000 or more. The upper limit of the Mw is not particularly limited, but is preferably 80,000 or less, more preferably 70,000 or less, and may be 60,000 or less. It may be selected appropriately depending on the other ingredients and intended use. It is preferable for the film-forming component to contain a phenoxy resin with a Mw of 50,000 or less, as this significantly prevents the occurrence of lifting at the connection points of the connection structure even after reliability testing in a high-temperature, high-humidity environment. The polystyrene-equivalent Mw of the film-forming component can be measured by gel permeation chromatography (GPC) and calculated using a calibration curve for standard polystyrene.

The content of the film-forming components in the adhesive composition is not particularly limited and may be determined appropriately depending on the purpose. However, when the non-volatile components in the adhesive composition are taken as 100% by mass, it is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. There is no particular upper limit to the content, but it is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

<Polymerization initiator>
The adhesive composition of the present invention contains a polymerization initiator. The polymerization initiator is selected according to the polymerizable component used. If the polymerizable component is a thermal radical polymerization type, a radical polymerization initiator is used. If the polymerizable component is a thermal cationic polymerization type, a cationic polymerization initiator is used. If the polymerizable component is a thermal anionic polymerization type, an anionic polymerization initiator is used.

An organic peroxide can be used as the radical polymerization initiator. The one-minute half-life temperature of the organic peroxide is preferably 130°C or lower, more preferably 80°C or higher and 120°C or lower. The one-minute half-life temperature is below the compression temperature; if the temperature is too high, it becomes difficult to achieve a high reaction rate. Furthermore, if the one-minute half-life temperature is too low, storage stability at room temperature decreases.

Examples of organic peroxides used as radical polymerization initiators include dilauroyl peroxide (1-minute half-life temperature: 116°C), benzoyl peroxide (1-minute half-life temperature: 130°C), di(4-methylbenzoyl) peroxide (1-minute half-life temperature: 128°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (1-minute half-life temperature: 124°C), di(3,5,5-trimethylhexanoyl) peroxide (1-minute half-life temperature: 113°C), t-butyl peroxypivalate (1-minute half-life temperature: 110°C), and t-hexyl peroxypivalate (1-minute half-life temperature: 1 09°C), t-butyl peroxyneoheptanoate (1-minute half-life temperature: 105°C), t-butyl peroxyneodecanoate (1-minute half-life temperature: 101°C), di(2-ethylhexyl)peroxydicarbonate (1-minute half-life temperature: 91°C), di(4-t-butylcyclohexyl)peroxydicarbonate (1-minute half-life temperature: 92°C), 1,1,3,3-tetramethylbutyl peroxyneodecanoate (1-minute half-life temperature: 85°C), di-sec-butyl peroxydicarbonate (1-minute half-life temperature: 85°C), cumyl peroxyneodecanoate (1-minute half-life temperature: 85°C), etc. Polymerization initiators may be used alone or in combination of two or more.

The amount of polymerization initiator blended is preferably 1 to 30 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of polymerizable components. If the amount of polymerization initiator is too low, reactivity will decrease, and if it is too high, product life will tend to be shortened.

<Conductive particles>
The adhesive composition of the present invention contains conductive particles. By including the conductive particles, the adhesive composition and a film-like product thereof can be used as a conductive paste and a conductive film, or an anisotropic conductive paste and an anisotropic conductive film.

The conductive particles may be any known conductive particles used in anisotropic conductive films. Examples of conductive particles include particles of metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, and gold; particles of alloys of these metals; and coated particles of metal oxides, carbon, graphite, glass, ceramics, and resins. When using metal-coated resin particles, examples of the resin particle material include epoxy resin, phenolic resin, acrylic resin, acrylonitrile-styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, and styrene resin. Furthermore, to prevent the risk of short circuits between terminals, the conductive particles may be further insulated, such as by coating the surface with an insulating thin film or by attaching insulating particles to the surface, as long as this does not impair the electrical conductivity after connection. These conductive particles may be used alone or in combination of two or more types.

The average particle diameter of the conductive particles is 1 μm or more and 10 μm or less, preferably 2 μm or more and 7 μm or less. The average particle diameter of the conductive particles can be determined, for example, by observing the particles using a scanning electron microscope (SEM), measuring the particle diameters of multiple conductive particles (n≧10), and calculating the average value. Alternatively, the average particle diameter can be measured (N=1000 or more) using an image particle size analyzer (e.g., FPIA-3000 (Malvern Instruments)).

The content of conductive particles in the adhesive composition is not particularly limited and may be determined appropriately depending on the purpose, but is preferably 1% by mass or more, and more preferably 2% by mass or more. From the perspective of achieving the desired anisotropic conductivity, the upper limit of the conductive particle content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

<Silane coupling agent>
The adhesive composition of the present invention contains a silane coupling agent. By including the silane coupling agent, the interfacial adhesion with inorganic materials can be improved. Examples of silane coupling agents include those having a vinyl group, an acrylic group, a methacrylic group, an epoxy group, a mercapto group, an amino group, an isocyanate group, a ureido group, or an imidazole group. The silane coupling agents may be used alone or in combination of two or more.

In the adhesive composition of the present invention, the content of the silane coupling agent is preferably 0.1% by mass or more and 5% by mass or less, when the total non-volatile components in the adhesive composition is taken as 100% by mass.

<Insulating filler>
The adhesive composition of the present invention contains an insulating filler having a particle size of 5% or less of the conductive particles. By containing an insulating filler with a predetermined particle size, aggregation of the conductive particles can be suppressed, preventing the occurrence of short circuits. If the particle size of the insulating filler is 5% or less of the conductive particles, aggregation of the conductive particles can be suppressed, but it is preferably 4% or less. There is no particular lower limit on the particle size of the insulating filler, but from the viewpoints of handleability, ease of production, etc., it is 0.1% or more, preferably 0.5% or more.

Examples of insulating fillers include inorganic oxides such as silica, titanium oxide, aluminum oxide, calcium oxide, and magnesium oxide; inorganic hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide; inorganic carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate, and barium carbonate; inorganic sulfates such as calcium sulfate and barium sulfate; inorganic silicates such as calcium silicate; and inorganic nitrides such as aluminum nitride, boron nitride, and silicon nitride. In addition, insulating fillers are not limited to inorganic materials; organic fillers can also be used. Examples of organic fillers include butadiene-based rubber particles, acrylic-based rubber particles, silicone-based rubber particles, and melamine-based particles.

The amount of insulating filler in the adhesive composition is 85% by mass or more and 200% by mass or less of the amount of conductive particles. By making the amount of insulating filler 85% by mass or more of the amount of conductive particles, it is possible to effectively prevent the conductive particles from aggregating. Furthermore, by making the amount of insulating filler 200% by mass or less of the amount of conductive particles, it is possible to prevent an increase in resistance value. The amount of insulating filler is preferably 90% by mass or more and 150% by mass or less.

The insulating filler is preferably spherical. A spherical shape improves the effect of inhibiting the aggregation of conductive particles. In this specification, "spherical" means that the ratio (aspect ratio) of the long axis (maximum length) to the short axis (shortest length) of the insulating filler is 1.5 or less. An insulating filler with a long axis to short axis ratio of 1.5 or less can achieve the effect of inhibiting the aggregation of conductive particles.

The adhesive composition of the present invention may further contain other components as needed. Such components include, for example, surface modifiers, flame retardants, colorants, and other known additives used in the production of adhesive compositions.

The adhesive composition of the present invention has high adhesive strength and can suppress the aggregation of conductive particles. Therefore, the adhesive composition of the present invention can prevent the occurrence of short circuits, even when used for bonding different substrates that require high adhesive strength, such as FOG mounting, which mounts an FPC to a glass substrate, or COG mounting, which mounts an IC to a glass substrate. Furthermore, the adhesive composition of the present invention can be easily produced by mixing and stirring the constituent components using a solvent.

[Anisotropic Conductive Film]
The adhesive composition of the present invention has good film-forming properties and can be suitably formed into an anisotropic conductive film. The present invention also includes an anisotropic conductive film made from the adhesive composition of the present invention.

The anisotropic conductive film of the present invention may consist of a single layer or multiple layers. When consisting of multiple layers, the anisotropic conductive film may include a first adhesive layer made of the adhesive composition of the present invention and a second adhesive layer made of the adhesive composition of the present invention provided on the first adhesive layer. Furthermore, a layer different from the adhesive layer of the present invention may be provided on the adhesive layer of the present invention. This layer may be sandwiched between the adhesive layers of the present invention on both sides. The layer different from the adhesive layer of the present invention may be a resin layer that is not an adhesive layer (does not contribute to adhesion). It is preferable that the layer different from the adhesive layer of the present invention is insulating.

Anisotropic conductive films can be produced, for example, by mixing the adhesive composition of the present invention with an organic solvent, if necessary, and then applying it to a release substrate and drying it to form an adhesive layer. The adhesive composition can be applied using a coating device such as a bar coater. Known coating methods for anisotropic conductive films, such as the doctor blade method, can also be used. When producing an anisotropic conductive film consisting of multiple layers, the above coating and drying steps can be repeated multiple times. Alternatively, the layers can be produced individually and then laminated using a method such as lamination.

The release substrate is not particularly limited as long as it is a film-like material that can support the anisotropic conductive film and can be peeled off from the anisotropic conductive film at the desired timing. Examples of materials that can be used for the release substrate include polyesters such as polyethylene terephthalate (PET), polyolefins such as polypropylene (PP), and plastic materials such as poly-4-methylpentene-1 (PMP) and polytetrafluoroethylene (PTFE). The release substrate may also be a substrate having a release layer on the surface that will be bonded to the anisotropic conductive film, and the release layer may contain a release agent such as a silicone resin or polyolefin resin.

The thickness of the release substrate is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less, even more preferably 60 μm or less, and even more preferably 50 μm or less. The lower limit of the thickness of the release substrate is not particularly limited, but from the viewpoint of ease of handling during slitting and production of the anisotropic conductive film, it is preferably 8 μm or more.

The thickness of the anisotropic conductive film of the present invention is not particularly limited and may be determined appropriately depending on the purpose, but is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The upper limit of the thickness of the adhesive layer is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less, even more preferably 60 μm or less, even more preferably 50 μm or less, and particularly preferably 40 μm or less. When multiple layers are laminated, this refers to the total thickness.

The anisotropic conductive film may be slit to a specified width. During slitting, a cover film may be provided on the exposed surface to prevent contamination of the adhesive layer by cutting debris, etc. In this case, the thickness may be selected appropriately depending on the purpose. The cover film may be a known film used when slitting anisotropic conductive film. In addition to being used in the manufacturing process for slitting, the cover film may be provided separately from the release substrate as a product used for connection purposes to prevent contamination during use. In this case, the cover film preferably has releasability and is preferably the same thickness as or thinner than the release substrate.

The anisotropic conductive film of the present invention has high adhesive strength and can suppress the aggregation of conductive particles. Therefore, the anisotropic conductive film of the present invention can prevent the occurrence of short circuits and other problems even when used in bonding that requires high adhesive strength due to the difference in substrates, such as FOG mounting, which mounts an FPC on a glass substrate, or COG mounting, which mounts an IC on a glass substrate.

[Connection structure]
The adhesive composition or anisotropic conductive film of the present invention can be used to produce a connection structure in which electronic components are bonded to each other. The present invention encompasses a connection structure in which a first electronic component and a second electronic component are connected by the adhesive composition or anisotropic conductive film of the present invention.

The first electronic component may be, for example, a general PWB, and examples thereof include rigid substrates, glass substrates, ceramic substrates, plastic substrates, and FPCs. The second electronic component may be, for example, an FPC, an IC chip, or a semiconductor element other than an IC chip. There are no particular restrictions on the electronic component, and there are no particular restrictions on the use of the connection structure. For example, it may be used in a portable information terminal or for electrical mounting in an automobile. In the present invention, a variety of connection structures may be manufactured, including, for example, FOBs, FOGs, FOPs, FOFs, COGs, and COPs.

[Method of manufacturing connection structure]
The method for producing the connection structure of the present invention is not particularly limited, as long as it is possible to produce a connection structure in which a first electronic component and a second electronic component are connected by the adhesive composition or anisotropic conductive film of the present invention. An example of a method for producing the connection structure of the present invention is shown below.

In one embodiment, the method for manufacturing a connection structure of the present invention includes a step of pressure-bonding a first electronic component and a second electronic component with the adhesive composition or anisotropic conductive film of the present invention interposed therebetween.

First, a first electronic component is placed on a stage, and the adhesive composition or anisotropic conductive film of the present invention is applied thereon. Next, a second electronic component is placed on the stage. After the adhesive composition or anisotropic conductive film of the present invention is applied to the first electronic component placed on the stage, the first electronic component and the second electronic component are aligned so that their electrodes face each other, and pre-bonding is performed from the second electronic component side using a crimping tool. The temperature, pressure, and time during pre-bonding may be determined appropriately depending on the specific design, and may be, for example, 60-80°C, 0.5-2 MPa, and 0.5-2 seconds. Pre-bonding of this type prior to the main bonding described below is advantageous because it allows for more precise alignment and connection between electronic components (the conductive portions of each component). Pre-bonding is expected to reduce misalignment during main bonding, which involves applying higher pressure.

After the temporary bonding, a crimping tool is used to perform the final bonding from the second electronic component side. The temperature, pressure, and time during the final bonding may be any known conditions used when bonding electronic components using anisotropic conductive film, and may be determined appropriately depending on the specific design. For example, even when bonding at a low temperature (e.g., 160°C or less) and for a short time (e.g., 10 seconds or less), it is possible to achieve good bonding between the first electronic component and the second electronic component.

Regarding whether temporary or permanent bonding is performed, a cushioning material (e.g., a cushioning sheet) may be provided between the second electronic component and the crimping tool. The type of cushioning material, including whether or not to use it, may be adjusted and determined appropriately depending on the combination of electronic components.

The adhesive composition or anisotropic conductive film of the present invention contains a silane coupling agent, and therefore exhibits high adhesive strength even when bonding different substrates such as FOG and COG. Furthermore, when pressure-bonded at low temperature for a short time, for example, at 150°C, 3 MPa, and for 10 seconds, a connection structure between an FPC and a glass substrate manufactured using the adhesive composition or anisotropic conductive film of the present invention can exhibit a high adhesive strength of 10 N/cm or more in a 90-degree peel test.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the examples shown below. In the following explanation, "parts" and "%" used to express amounts mean "parts by mass" and "% by mass," respectively, unless otherwise specified.

[Example 1]
- Preparation of adhesive composition -
40 parts by mass of phenoxy resin (trade name: YP-50, manufactured by Nippon Steel Chemical & Materials Co., Ltd., film-forming component), 25 parts by mass of urethane acrylate (trade name: UN-5500, manufactured by Negami Chemical Industrial Co., Ltd., polymerizable component), 25 parts by mass of EO-modified isocyanuric acid di- and triacrylate (trade name: M-315, manufactured by Toagosei Co., Ltd., polymerizable component), 2 parts by mass of dilauroyl peroxide (trade name: Perloyl L, manufactured by NOF Corporation, polymerization initiator), 2 parts by mass of benzoyl peroxide (trade name: Niper BW, manufactured by NOF Corporation), An adhesive composition was prepared by adding PMA (propylene glycol monomethyl ether) as a solvent to 1.0 part by mass of imidazole silane (trade name: IM-1000, manufactured by ENEOS Corporation, polymerization initiator), 3 parts by mass of conductive particles (Micropearl AU, manufactured by Sekisui Chemical Co., Ltd., Au—Ni plated resin particles, average particle size 4 μm), and 3 parts by mass of insulating filler (A) (trade name: YA050C, manufactured by Admatechs Corporation, average particle size 50 nm, spherical silica), and mixing them uniformly.

- Fabrication of anisotropic conductive film -
A PET film (50 μm thick, 250 mm square) was prepared as a release substrate. The adhesive composition was uniformly applied to this release substrate so that the thickness of the anisotropic conductive film (adhesive layer) after drying would be 25 μm. The resulting film was then dried in an oven at 80°C to form an adhesive layer on the release substrate.

[Example 2]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the amount of silane coupling agent was 1.5 parts by mass and the insulating filler (A) was changed to insulating filler (B) (product name: YA100C, manufactured by Admatechs Co., Ltd., average particle size 100 nm, spherical silica).

[Example 3]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the amount of silane coupling agent was 1.5 parts by mass and the insulating filler (A) was changed to insulating filler (C) (product name: MX100W, manufactured by Nippon Shokubai Co., Ltd., average particle size 150 nm, spherical silica).

[Comparative Example 1]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the insulating filler (A) and the silane coupling agent were not blended.

[Comparative Example 2]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that no silane coupling agent was added and the amount of insulating filler (A) added was changed to 1 part by mass.

[Comparative Example 3]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that no silane coupling agent was added and the amount of insulating filler (A) added was changed to 10 parts by mass.

[Comparative Example 4]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the amount of silane coupling agent was 1.5 parts by mass and the insulating filler (A) was changed to insulating filler (E) (trade name: R820, manufactured by Ishihara Sangyo Kaisha, Ltd., titanium oxide, irregular shape).

[Comparative Example 5]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the amount of silane coupling agent was changed to 1.5 parts by mass and the insulating filler (A) was changed to insulating filler (D) (trade name: X-52-7030, manufactured by Shin-Etsu Silicones Co., Ltd., average particle size 800 nm, spherical silica).

[Comparative Example 6]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the insulating filler (A) was not blended.

[Comparative Example 7]
An adhesive composition was prepared and an anisotropic conductive film was produced in the same manner as in Example 1, except that the silane coupling agent was not added and the amount of conductive particles added was changed to 6 parts by mass.

The testing and evaluation methods are explained below.

<Conductive Particle Aggregation and Aggregate Number>
The anisotropic conductive films prepared in the examples and comparative examples were visually observed on one A4 sheet at 200x magnification using an optical microscope to check for the presence or absence of aggregates (15 μm or more). Furthermore, for films where aggregates were confirmed, the number of aggregates was counted. The number of aggregates was converted into an A4 size area.

- Fabrication of connection structure -
The exposed surface of the adhesive layer was attached to an ITO glass substrate and temporarily fixed by pressure bonding at 45 ° C, 1 MPa, and 2 seconds. The release substrate was then peeled off, and a flexible printed circuit board (polyimide layer 25 μm, copper foil 18 μm, Au plating, L/S = 200 μm/200 μm) was connected and bonded to the adhesive layer. The FPC and glass substrate were thermocompression bonded via the adhesive layer, and all of the opposing conductive portions of the FPC and glass substrate were bonded with the cured product of the adhesive layer to obtain a connected connection structure. The thermocompression bonding conditions were 150 ° C, 3 MPa, and 10 seconds.

<Evaluation of Conduction Resistance>
The electrical resistance of the resulting connection structure was measured, and a resistance of 0.5Ω or less was indicated as ◯, and a resistance of more than 0.5Ω was indicated as Δ.

<Evaluation of adhesive strength>
The adhesive strength of the resulting connection structure was measured by a 90-degree peel test. Specifically, the FPC and the cured product were cut to a length of 1.0 cm, and the 1.0 cm FPC was gripped with a gripper and peeled vertically at room temperature (25°C) at a rate of 50 mm/min until the FPC peeled off from the glass substrate, and the load (N/cm) was measured. A Tensilon testing machine (STA-1150, manufactured by Orientec Co., Ltd.) was used for the measurement.

The evaluation results for the Examples and Comparative Examples are shown in Table 1.

Comparative Examples 1 and 6 confirmed that the addition of a coupling agent improved adhesive strength, but also increased the number of agglomerated conductive particles.

The adhesive compositions of Examples 1 to 3, which contain insulating filler with a particle size 5% or less of the conductive particles in a proportion of 85% to 200% by mass relative to the amount of conductive particles, were confirmed to be able to suppress the aggregation of conductive particles. Suppressing the aggregation of conductive particles can prevent the occurrence of short circuits and other problems. Furthermore, in Examples 1 to 3, no increase in resistance was observed even with the addition of insulating filler. Furthermore, in Example 1, high adhesive strength was confirmed even under low-temperature, short-time compression conditions. Furthermore, in Comparative Example 4, which contains non-spherical insulating filler, the insulating filler was contained in a proportion of 85% to 200% by mass relative to the amount of conductive particles, but no effect of suppressing the aggregation of conductive particles was observed.

Claims (5)

a binder composition containing a polymerizable component and a film-forming component;
a polymerization initiator;
Conductive particles having a particle diameter of 1 μm or more and 10 μm or less;
an insulating filler having a particle size of 5% or less of the conductive particles;
a silane coupling agent;
and no photocuring initiator, the blending amount of the insulating filler is 85% by mass or more and 200% by mass or less of the conductive particles , the polymerization initiator is an organic peroxide, and the one-minute half-life temperature of the organic peroxide is 80°C or more and 130°C or less . The adhesive composition of claim 1, wherein the insulating filler is spherical. An anisotropic conductive film made from the adhesive composition of claim 1 or 2. A connection structure in which a first electronic component and a second electronic component are connected by the anisotropic conductive film described in claim 3. A method for manufacturing a connection structure, comprising a step of crimping a first electronic component and a second electronic component together with the anisotropic conductive film described in claim 3 interposed therebetween.