Adhesive composition, adhesive film, connection structure, and method for producing connection structure

Abstract

To provide an adhesive composition having a high adhesive strength and a long storage life.SOLUTION: An adhesive composition contains a binder composition containing a cationic polymerizable component and a film-forming component, a cationic polymerization initiator that is a quaternary ammonium salt-based heat acid generator, and a silane coupling agent having two or more mercapto groups in one molecule, with its main chain being an organic chain, where the content of the silane coupling agent is 0.3 mass% or more and 3 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition, an adhesive film, a connection structure, and a method for producing a connection structure. [Background technology]

[0002] Adhesive compositions and film-like materials (adhesive films) such as anisotropic conductive paste (ACP) and anisotropic conductive film (ACF) are widely used as means for bonding electronic components to circuit boards, etc. For example, anisotropic conductive films are used to bond and electrically connect various terminals together, including connecting terminals of a flexible printed circuit board (FPC) to terminals of a glass substrate of an FPD panel (so-called FOG).

[0003] In order to achieve low-temperature, rapid curing properties for such adhesive compositions, it has been proposed to use, as the polymerizable compound, an alicyclic epoxy compound that has higher cationic polymerization reactivity than general-purpose glycidyl ether compounds, and to use, as a polymerization initiator that is not inhibited by oxygen and that exhibits dark reactivity, a sulfonium salt-based thermal acid generator that generates protons when heated (Patent Documents 1 to 3).

[0004] Furthermore, with regard to adhesive compositions, the storage and transportation period from production to actual use is becoming longer due to factors such as the globalization of commercial transactions. Adhesive compositions that use a combination of an alicyclic epoxy compound and a sulfonium salt-based thermal acid generator exhibit excellent adhesive properties when used immediately after production, but since it is difficult to control the product life due to storage conditions, a technology has been proposed in which a quaternary ammonium salt-based thermal acid generator is used as a cationic polymerization initiator (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-176112 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-308596 [Patent Document 3] International Publication No. 2012 / 018123 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-152354 Summary of the Invention [Problem to be solved by the invention]

[0006] The use of a quaternary ammonium salt-based thermal acid generator as shown in Patent Document 4 can suppress changes in the adhesive composition over time and improve its storage life. However, when joining different substrates such as an FPC and a glass substrate, the adhesive strength is insufficient, causing the adhesive composition to float between or on the wiring, which can make it difficult to ensure connection reliability.

[0007] An object of the present invention is to provide an adhesive composition that can be used for bonding substrates that require high adhesive strength, such as FOG mounting, in which an FPC is mounted on a glass substrate, and that also has excellent storage life. [Means for solving the problem]

[0008] As a result of extensive research into the above problems, the present inventors have found that the above problems can be solved by an adhesive composition having the following composition, and have thus completed the present invention.

[0009] That is, the present invention includes the following. [1] A binder composition containing a cationically polymerizable component and a film-forming component; a cationic polymerization initiator that is a quaternary ammonium salt-based thermal acid generator; and a silane coupling agent having two or more mercapto groups in one molecule and an organic main chain, wherein the content of the silane coupling agent is 0.3% by mass or more and 3% by mass or less. [2] The adhesive composition according to claim 1, wherein the cationically polymerizable component is a bifunctional alicyclic epoxy compound. [3] The adhesive composition according to claim 1 or 2, wherein the molecular weight of the silane coupling agent is 500 or more. [4] The adhesive composition according to any one of claims 1 to 3, wherein the silane coupling agent has one or more alkoxysilyl groups and two or more mercapto groups in one molecule. [5] The adhesive composition according to claim 4, wherein the ratio of the number of mercapto groups to the number of alkoxysilyl groups in the silane coupling agent is 2 or more. [6] An adhesive film comprising the adhesive composition according to any one of claims 1 to 5 and conductive particles. [7] A connection structure in which a first electronic component and a second electronic component are connected by the adhesive film described in claim 6. [8] A method for manufacturing a connection structure, comprising a step of crimping a first electronic component and a second electronic component together with the adhesive film described in claim 6 interposed therebetween. [Effects of the Invention]

[0010] According to the present invention, an adhesive composition can be provided which can be used for bonding that requires high adhesive strength, such as FOG mounting, in which an FPC is mounted on a glass substrate, and which can maintain high adhesiveness even after storage at room temperature or in a refrigerated environment. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, the term "alicyclic epoxy compound" refers to an epoxy compound having an alicyclic ring in the molecule. In the alicyclic epoxy compound, the oxirane ring may be formed by two carbon atoms and one oxygen atom constituting the alicyclic ring, or may be formed as a glycidyl group separate from the alicyclic ring.

[0012] The present invention will be described in detail below with reference to preferred embodiments thereof. The present invention is not limited to the following description, and each component can be appropriately modified within the scope of the present invention.

[0013] [Adhesive composition] The adhesive composition of the present invention comprises a binder composition containing a cationically polymerizable component and a film-forming component, a cationic polymerization initiator that is a quaternary ammonium salt-based thermal acid generator, and a silane coupling agent that has two or more mercapto groups in one molecule and whose main chain is an organic chain, and is characterized in that the content of the silane coupling agent is 0.3% by mass or more and 3% by mass or less. Each component will be described in detail below.

[0014] <Binder composition> The adhesive composition of the present invention comprises a binder composition that contains a cationically polymerizable component and a film-forming component.

[0015] (cationically polymerizable component) The cationically polymerizable component used in the adhesive composition of the present invention is a compound having a functional group that polymerizes in the presence of a cationic species, and examples thereof include epoxy compounds, vinyl ether compounds, cyclic ether compounds, etc. Among these, epoxy compounds having two or more epoxy groups per molecule are preferred, and alicyclic epoxy compounds having high reactivity can be suitably used.

[0016] Examples of alicyclic epoxy compounds include difunctional alicyclic epoxy compounds having two epoxy groups per molecule, trifunctional alicyclic epoxy compounds having three epoxy groups per molecule, tetrafunctional alicyclic epoxy compounds having four epoxy groups per molecule, and pentafunctional alicyclic epoxy compounds having five epoxy groups per molecule. The alicyclic epoxy compound can be appropriately selected from cycloalkene oxide epoxy compounds and diglycidyl ether compounds of alicyclic alcohols.

[0017] The cycloalkene oxide type epoxy compound is a compound having an epoxycycloalkyl group. The number of carbon atoms in the epoxycycloalkyl group is preferably 3 to 10. In a preferred embodiment, the number of carbon atoms in the epoxycycloalkyl group is more preferably 4 to 10, even more preferably 6 to 10, still more preferably 6 to 8, and particularly preferably 6.

[0018] The cycloalkene oxide type epoxy compound can be produced, for example, by directly epoxidizing a compound having two or more cycloalkene skeletons, or by polymerizing a monofunctional or more cycloalkene oxide type epoxy compound having a polymerizable functional group (e.g., a (meth)acrylic group, an allyl group, a silanol group, etc.) to form a bifunctional or more cycloalkene oxide type epoxy compound.

[0019] In the cycloalkene oxide type epoxy compound, the structure other than the epoxycycloalkyl group is not particularly limited, and any structure may be used as long as it does not inhibit reactivity. From the viewpoint of realizing an adhesive composition exhibiting excellent adhesive properties, it is suitable to have a structure such that the epoxy equivalent is preferably 500 or less, more preferably 400 or less, even more preferably 350 or less, even more preferably 300 or less, particularly preferably 250 or less, and especially preferably 200 or less. The lower limit of the epoxy equivalent of the cycloalkene oxide type epoxy compound is not particularly limited, but is preferably 70 or more, more preferably 80 or more, even more preferably 90 or more, and even more preferably 95 or more.

[0020] Specific examples of the difunctional cycloalkene oxide type epoxy compound include 3,4-epoxycyclohexenylmethyl-3',4'-epoxycyclohexenecarboxylate, diepoxybicyclohexyl, and the like.

[0021] A diglycidyl ether compound of an alicyclic alcohol is a compound having an alicyclic ring and two or more glycidyl groups in one molecule. The alicyclic ring may have any structure as long as it does not inhibit reactivity, and may be a single ring or a condensed ring, and one or more alicyclic rings may be contained in one molecule. From the viewpoint of realizing an adhesive composition that exhibits excellent adhesive properties, it is preferable that the compound has a structure in which the epoxy equivalent falls within the same range as described above for the cycloalkene oxide type epoxy compound.

[0022] Diglycidyl ether compounds of alicyclic alcohols can be produced, for example, by hydrogenating the aromatic ring of an aromatic alcohol diglycidyl ether (e.g., a bisphenol-type diglycidyl ether such as bisphenol A diglycidyl ether) to form an alicyclic ring, or by glycidyl etherifying an aliphatic alcohol (e.g., a hydrogenated bisphenol such as hydrogenated bisphenol A). Specific examples of diglycidyl ether compounds of alicyclic alcohols include hexahydrobisphenol A diglycidyl ether.

[0023] The cationically polymerizable component may be used alone or in combination of two or more.

[0024] In the adhesive composition of the present invention, the content of the cationically 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 nonvolatile 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.

[0025] (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 (weight average molecular weight of 10,000 or more), 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.

[0026] 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 Mw is not particularly limited, but it may be preferably 80,000 or less, more preferably 70,000 or less, or even 60,000 or less. It may be appropriately selected depending on the other ingredients and the intended use. It is preferable for the film-forming component to contain a phenoxy resin with a Mw of 50,000 or less, since this can significantly prevent the occurrence of lifting at the connection points of the connection structure even after reliability testing under high-temperature, high-humidity environments. The polystyrene-equivalent Mw of the film-forming component can be measured by gel permeation chromatography (GPC) and calculated using a calibration curve of standard polystyrene.

[0027] The content of the film-forming component in the adhesive composition is not particularly limited and may be determined appropriately depending on the purpose, but 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, even more preferably 30% by mass or more, and even more preferably 40% by mass or more. The upper limit of the content is not particularly limited, but is preferably 70% by mass or less, more preferably 60% by mass or less.

[0028] <Cationic polymerization initiator> The adhesive composition of the present invention contains a quaternary ammonium salt-based thermal acid generator as a cationic polymerization initiator. The adhesive composition of the present invention, which uses a quaternary ammonium salt-based thermal acid generator as a cationic polymerization initiator, can suppress deterioration in adhesiveness even when stored for a certain period of time under room temperature or refrigerated conditions.

[0029] As the quaternary ammonium salt-based thermal acid generator, a salt of a quaternary ammonium cation and an acid anion or a borate anion can be suitably used. The quaternary ammonium cations include those of the formula: NR a R b R c R d+ In the formula, R a , R b , R c and R d is a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms or an aryl group having 6 to 12 carbon atoms, each of which may have a hydroxyl group, a halogen atom, an alkoxy group, an amino group, an ester group or the like.

[0030] The acid anion may be either an inorganic acid anion or an organic acid anion, and examples thereof include a hexafluoroantimonate anion, a hexafluorophosphate anion, a trifluoromethanesulfonate anion, a perfluorobutanesulfonate anion, a dinonylnaphthalenesulfonate anion, a dinonylnaphthalenesulfonate anion, a p-toluenesulfonate anion, and a dodecylbenzenesulfonate anion.

[0031] Examples of the borate anion include alkylborate anions and arylborate anions. The borate anion may have a halogen atom. Among them, arylborate anions having a fluorine atom (F-; fluoro group) are preferred, and tetrakis(pentafluorophenyl)borate anions are particularly preferred.

[0032] The quaternary ammonium salt-based thermal acid generators may be used singly or in combination of two or more.

[0033] Specific examples of quaternary ammonium salt-based thermal acid generators include CXC-1612, CXC-1733, CXC-1738, TAG-2678, CXC-1614, TAG-2689, TAG-2690, TAG-2700, CXC-1802-60, and CXC-1821 manufactured by King Industries, Inc. These are available from Kusumoto Chemicals Co., Ltd.

[0034] The content of the quaternary ammonium salt-based thermal acid generator in the adhesive composition is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and even more preferably 7% by mass or more, based on 100% by mass of the total non-volatile components of the cationically polymerizable components. The upper limit of the content is not particularly limited, but is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0035] <Silane coupling agent> The adhesive composition of the present invention contains a silane coupling agent having two or more mercapto groups in one molecule and an organic main chain.

[0036] The silane coupling agent used in the adhesive composition of the present invention is not particularly limited as long as it has two or more mercapto groups, one or more alkoxysilyl groups, and an organic chain having a mercapto group and an alkoxysilyl group as a side chain or terminal group in one molecule. A silane coupling agent having two or more mercapto groups can improve adhesion to the metal wiring of an FPC, thereby improving adhesive strength. The alkoxysilyl group of the silane coupling agent is preferably a trialkoxysilyl group, more preferably a trimethoxysilyl group.

[0037] A preferred embodiment of the silane coupling agent is a compound represented by the following formula (1).

[0038] [ka] In the above formula (1), R is selected from a hydroxyl group, a mercapto group, or an alkoxysilyl group represented by the following formula (2), and n is an integer of 1 to 100, provided that at least one R is an alkoxysilyl group represented by the following formula (2), and at least two R are mercapto groups. [ka] In the above formula (2), R' is an alkyl group having 1 to 6 carbon atoms, X is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m is an integer of 1 to 3.

[0039] Furthermore, a preferred embodiment of the silane coupling agent is a compound represented by the following formula (3). [ka] In the above formula (3), R is selected from a hydroxyl group, a mercapto group, or an alkoxysilyl group represented by the following formula (4), a is an integer of 4 or more and 10 or less, and b, c, and d are integers of 0 or more and 10 or less, provided that at least one of R is an alkoxysilyl group represented by the following formula (4), and at least two of R are mercapto groups. [ka] In the above formula (4), R' is an alkyl group having 1 to 6 carbon atoms, X is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m is an integer of 1 to 3.

[0040] In the silane coupling agent used in the adhesive composition of the present invention, the ratio of the number of mercapto groups to the number of alkoxysilyl groups is preferably 2 or more, more preferably 3 or more. Furthermore, the ratio of the number of mercapto groups to the number of alkoxysilyl groups is preferably 10 or less, more preferably 7 or less. Having a ratio of the number of mercapto groups to the number of alkoxysilyl groups of 2 or more provides excellent compatibility with the binder composition, which is an organic component, and improves adhesion by bonding with the binder composition or the insulating resin of the FPC. On the other hand, having a ratio of the number of mercapto groups to the number of alkoxysilyl groups of 10 or less can improve adhesive strength to inorganic components such as glass substrates.

[0041] The silane coupling agent used in the adhesive composition of the present invention has an organic main chain, and therefore has excellent compatibility and adhesion with the binder composition. Specific examples of the silane coupling agent used in the adhesive composition of the present invention include X-12-1154 and X-12-1156 manufactured by Shin-Etsu Chemical Co., Ltd.

[0042] The silane coupling agent used in the adhesive composition of the present invention preferably has a polystyrene-equivalent weight average molecular weight of 500 to 3000. If the polystyrene-equivalent weight average molecular weight is less than 500, production may be difficult, and if the polystyrene-equivalent weight average molecular weight is greater than 3000, workability during production may be impaired.

[0043] In the adhesive composition of the present invention, the content of the silane coupling agent is 0.3% by mass or more and 3% by mass or less, when the total non-volatile components in the adhesive composition is 100% by mass. If the content of the silane coupling agent is less than 0.3% by mass or more than 3% by mass, the adhesive strength may decrease, and peeling may occur between the adhesive composition and the substrate.

[0044] <Conductive particles> The adhesive composition of the present invention may contain conductive particles. By containing 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.

[0045] 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, resins, and the like. When using metal-coated resin particles, in which resin particles are coated with a metal, examples of the resin particle material include epoxy resin, phenolic resin, acrylic resin, acrylonitrile-styrene (AS) resin, benzoguanamine resin, divinylbenzene-based resin, and styrene-based resin. Furthermore, the conductive particles may be further insulated, such as by coating the surface of an insulating thin film or by attaching insulating particles to the surface, to avoid the risk of short circuits between terminals, 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.

[0046] The average particle diameter of the conductive particles is not particularly limited and may be determined appropriately depending on the purpose, but is preferably 40 μm or less, more preferably 30 μm or less, even more preferably 25 μm or less, and even more preferably 20 μm or less. The lower limit of the average particle diameter is not particularly limited, but is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. The average particle diameter of the conductive particles can be determined, for example, by observing with a scanning electron microscope (SEM), measuring the particle diameters of multiple conductive particles (n≧10), and calculating the average value. Alternatively, it may be a measurement (N=1000 or more) measured using an image particle size distribution analyzer (e.g., FPIA-3000 (Malvern Instruments)).

[0047] When conductive particles are used, the content of the 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, more preferably 2% by mass or more, and even more preferably 3% by mass or more. From the viewpoint of obtaining the desired anisotropic conductivity, the upper limit of the content is preferably 30% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and even more preferably 20% by mass or less.

[0048] The adhesive composition of the present invention may further contain other components as needed, such as known additives used in the production of adhesive compositions, such as fillers that do not inhibit conductivity, such as organic fillers (e.g., butadiene-based rubber particles, acrylic-based rubber particles, and silicone-based rubber particles), insulating inorganic fillers (e.g., silica fillers), surface modifiers, flame retardants, coupling agents, and colorants.

[0049] The adhesive composition of the present invention has high adhesive strength and can suppress deterioration of adhesiveness even when stored for a certain period of time under room temperature or refrigerated conditions. Therefore, the adhesive composition of the present invention can be suitably used for bonding different substrates that require high adhesive strength, such as FOG mounting, in which an FPC is mounted on a glass substrate. Furthermore, when the adhesive composition contains conductive particles, it can be used as a conductive paste or an anisotropic conductive paste.

[0050] [Adhesive film] The adhesive composition of the present invention has good film-forming properties and can be suitably formed into a film-like product (adhesive film). The present invention also includes an adhesive film made from the adhesive composition of the present invention.

[0051] The adhesive film of the present invention may consist of a single layer or multiple layers. When the adhesive film consists of multiple layers, it includes at least 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. At least one of the first adhesive layer and the second adhesive layer preferably contains conductive particles. Furthermore, the adhesive layer of the present invention may be provided with a layer different from that of the present invention. This layer may be sandwiched between the front and rear adhesive layers of the present invention. In this case, the conductive particles may be contained in at least one of the adhesive layers of the present invention, or in a different layer. This different layer may be a layer made of an adhesive composition different from that of the present invention, or may be a resin layer that is not an adhesive layer (does not contribute to adhesion). It is preferable that the layer different from that of the present invention is insulating.

[0052] The adhesive film 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 adhesive film coating methods, such as a doctor blade method, can be used. When producing an adhesive 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 laminate or the like.

[0053] The release substrate is not particularly limited as long as it is a film-like material that can support the adhesive film and can be peeled off from the adhesive 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 adhesive film, and the release layer may contain a release agent such as a silicone resin or a polyolefin resin.

[0054] 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 is preferably 8 μm or more from the viewpoint of ease of handling during production and slitting of the adhesive film.

[0055] The thickness of the adhesive 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, the total thickness is used.

[0056] The adhesive film may be slit to a desired width. During slitting, a cover film may be provided on the exposed surface to prevent contamination of the adhesive layer by cutting chips or the like. In this case, the thickness may be selected appropriately depending on the purpose. The cover film may be a known film used when slitting the adhesive 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 is preferably releasable and preferably has the same or thinner thickness as the release substrate.

[0057] The adhesive film of the present invention has high adhesive strength and can suppress deterioration of adhesiveness even when stored for a certain period of time under room temperature or refrigerated conditions. Therefore, the adhesive composition of the present invention can be suitably used for bonding different substrates that require high adhesive strength, such as FOG mounting, in which an FPC is mounted on a glass substrate. Furthermore, when conductive particles are contained, it can be used as a conductive paste or an anisotropic conductive paste.

[0058] [Connection structure] The adhesive composition or adhesive 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 adhesive film of the present invention.

[0059] 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. Examples of the second electronic component include FPCs, IC chips, and semiconductor elements other than IC chips. 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 personal digital assistant (PDA) or for in-vehicle electrical mounting. In the present invention, for example, a variety of connection structures can be manufactured, including FOBs, FOGs, FOPs, FOFs, COGs, and COPs. The present invention is particularly suitable for FOGs and FOPs.

[0060] [Method of manufacturing the 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 adhesive film of the present invention. An example of a method for producing the connection structure of the present invention is shown below.

[0061] In one embodiment, the method for producing 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 adhesive film of the present invention interposed therebetween.

[0062] First, a first electronic component is placed on a stage, and the adhesive composition or adhesive film of the present invention is applied thereon. Then, a second electronic component is placed on the stage. After the adhesive composition or adhesive 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. Pre-bonding is then performed from the second electronic component side using a crimping tool. The temperature, pressure, and time during pre-bonding can be determined appropriately depending on the specific design, and may be, for example, 60 to 80°C, 0.5 to 2 MPa, and 0.5 to 2 seconds. Pre-bonding is preferably performed prior to the full-bonding described below, because it allows for more accurate alignment and connection between the electronic components (the conductive portions of each component). Pre-bonding is expected to reduce misalignment during full-bonding, which requires higher pressure.

[0063] After the temporary pressure bonding, a final pressure bonding is performed from the second electronic component side using a pressure bonding tool. The temperature, pressure, and time during the final pressure bonding may be any known conditions used when bonding electronic components using an adhesive film, and may be appropriately determined depending on the specific design. For example, even if the pressure bonding is performed at a low temperature (e.g., 200°C or less, 180°C or less, or 160°C or less) and for a short time (e.g., 10 seconds or less, 8 seconds or less, or 6 seconds or less), the first electronic component and the second electronic component can be well bonded.

[0064] Regardless of whether temporary or permanent bonding is performed, a buffer material (e.g., a buffer sheet) may be provided between the second electronic component and the crimping tool. The buffer material, including whether or not to use it, may be adjusted and determined appropriately depending on the combination of electronic components.

[0065] The adhesive composition or adhesive film of the present invention can suppress a decrease in adhesiveness even when stored for a certain period of time under room temperature or refrigerated conditions. For example, when bonded under bonding conditions of 160°C, 3 MPa, and 5 seconds, a connection structure between an FPC and a glass substrate produced using the adhesive composition or adhesive film of the present invention can exhibit an adhesive strength of 10 N / cm or more in a 90-degree peel test, regardless of whether the adhesive composition (adhesive film) used was immediately after production or an adhesive composition (adhesive film) stored for a certain period of time under room temperature or refrigerated conditions. [Example]

[0066] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples shown below. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0067] [Example 1] -Preparation of adhesive composition- 26.4 parts of bisphenol F type epoxy resin (trade name: Epicoat 4007P, manufactured by Mitsubishi Chemical Corporation, Mw = 20,000 to 30,000), 26.4 parts of phenoxy resin (trade name: FX293, manufactured by Nippon Steel Chemical & Material Co., Ltd., Mw = 40,000 to 50,000), 18.9 parts of bifunctional alicyclic epoxy compound (trade name: Celloxide 2021P, manufactured by Daicel Corporation, a compound represented by the following formula (5)), 7.6 parts of bisphenol A type epoxy resin (trade name: YL980, manufactured by Mitsubishi Chemical Corporation, Mw = 300 to 2,200), 0.8 parts of silane coupling agent (trade name: X-12-1154, manufactured by Shin-Etsu Chemical Co., Ltd.), quaternary ammonium salt-based thermal acid generator (trade name: CXC-1821, manufactured by King Chemical Co., Ltd.) An adhesive composition was obtained by uniformly mixing 2.3 parts of PEG-400 (manufactured by Sekisui Chemical Co., Ltd.) with 5.0 parts of conductive particles (trade name: Micropearl, manufactured by Sekisui Chemical Co., Ltd., Ni resin particles having an average particle size of 4 μm) and 12.6 parts of butadiene rubber (trade name: RKB-5515B, manufactured by Resinous Kasei Co., Ltd.) with PMA as a solvent to a total solids content of 43.4%.

[0068] [ka]

[0069] -Preparation of adhesive film- A PET film (50 μm thick) was prepared as a release substrate. The adhesive composition was uniformly applied to this release substrate so that the thickness of the adhesive film (adhesive layer) after drying would be 18 μm. The composition was then dried in an oven at 70°C for 5 minutes to form an adhesive layer on the release substrate. A cover film was then laminated at 45°C onto the exposed surface of the adhesive layer.

[0070] [Examples 2 and 3, Comparative Examples 1 and 2] Adhesive compositions were prepared and adhesive films were produced in the same manner as in Example 1, except that the blending amounts of the silane coupling agent and the like were changed as shown in Table 1.

[0071] [Comparative Examples 3 to 6] The silane coupling agent was changed to one having one epoxy group per molecule (trade name: A187, manufactured by Dow Corning Toray Co., Ltd.), one having two or more epoxy groups per molecule (trade name: X-12-981S, manufactured by Shin-Etsu Chemical Co., Ltd.), one having two or more isocyanate groups per molecule (trade name: X-12-1159L, manufactured by Shin-Etsu Chemical Co., Ltd.), or one having two or more amino groups per molecule (trade name: X-12-972F, manufactured by Shin-Etsu Chemical Co., Ltd.), and the amounts of each component were changed as shown in Table 1. Except for this, adhesive compositions were prepared and adhesive films were produced in the same manner as in Example 1.

[0072] [Example 4, Comparative Examples 7 to 10] An adhesive composition was prepared and an adhesive film was produced in the same manner as in Example 1, except that a tetrafunctional thiol compound (trade name: Karenz MT PE1, manufactured by Showa Denko K.K.) was added and the type of silane coupling agent and the amount of each component were changed as shown in Table 1.

[0073] The test and evaluation methods are explained below.

[0074] <Crimped state> - Fabrication of connection structure - The adhesive films prepared in the Examples and Comparative Examples were slit to a width of 1.0 mm, and the cover film was then peeled off. Next, the adhesive film was attached to the edge of an AlMoIZO glass substrate (0.7 mm thick) so that the exposed surface of the adhesive layer was bonded to the glass substrate, and uniform pressure was applied on a hot plate at 45°C. The release substrate was then peeled off, and the gold wiring portion of a flexible printed circuit board (FPC; 50 μm thick) was connected and bonded so that the exposed surface of the adhesive layer was completely covered. 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 by the cured adhesive layer, resulting in a connected structure. The thermocompression bonding conditions were 160°C, 3 MPa, and 5 seconds.

[0075] The resulting connection structure was observed with a differential interference microscope immediately after bonding and after being placed in a pressure cooker (110°C, 85% RH) for 32 hours to observe the metal thin film on the AlMoIZO glass substrate. The results were evaluated on a three-point scale: strong bonding (good), weak bonding (lower bonding), and insufficient bonding (no visible irregularities).

[0076] <Adhesive layer lifting> - Fabrication of connection structure - The adhesive films prepared in the Examples and Comparative Examples were slit to a width of 1.0 mm, and the cover film was then peeled off. Next, the adhesive film was attached to the edge of a SiN glass substrate or an ITO glass substrate (each 0.7 mm thick) so that the exposed surface of the adhesive layer was bonded to the glass substrate, and a uniform force was applied on a hot plate at 45°C. The release substrate was then peeled off, and the gold wiring portion of a flexible printed circuit board (FPC; 50 μm thick) was connected and bonded so that the exposed surface of the adhesive layer was completely covered. 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, resulting in a connected structure. Thermocompression bonding conditions were 160°C, 3 MPa, and 5 seconds.

[0077] The resulting connection structure was visually inspected for any lifting of the adhesive layer immediately after bonding and after being placed in a pressure cooker (110°C, 85% RH) for 32 hours. The evaluation was based on three levels: no lifting (◯), slight lifting (△), and lifting (×).

[0078] <Evaluation of conduction resistance> The connection structure between the ITO glass substrate and FPC, which had been evaluated for adhesive layer lifting, was measured for electrical resistance immediately after bonding and after being kept in a pressure cooker (110°C, 85% RH) for 32 hours.

[0079] <Evaluation of adhesive strength> The connection structures whose crimping state was evaluated were subjected to a 90-degree peel test to measure adhesive strength. 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 pulled vertically at room temperature (25°C) at a speed 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 adhesive strength of connection structures stored at 55°C for 12 hours was also evaluated in the same manner.

[0080] Table 1 shows the components and evaluation results of the examples and comparative examples.

[0081] [Table 1]

[0082] The results in Table 1 confirm that when a silane coupling agent containing two or more mercapto groups per molecule is used, a high adhesive strength of 10 N / cm is achieved even when joining different substrates, such as glass and FPC.

[0083] Furthermore, according to Comparative Examples 3 to 6, when a silane coupling agent whose main chain is an organic chain and has two or more reactive groups other than mercapto groups, such as epoxy groups, isocyanate groups, and amino groups, per molecule is used, it was confirmed that the adhesive strength is insufficient, problems with pressure bonding and lifting occur, and the conductive resistance also increases.

[0084] Furthermore, adhesive compositions containing a tetrafunctional thiol compound to confirm the effect of mercapto groups (Comparative Examples 7 to 10, Example 4) showed no significant differences in adhesive strength or compression state compared to adhesive compositions containing no tetrafunctional thiol compound (Comparative Examples 3 to 6, Example 2), confirming that silane coupling agents containing two or more mercapto groups per molecule are useful for improving adhesive strength.

Claims

1. a binder composition containing a cationic polymerizable component and a film-forming component made of a resin having a weight average molecular weight of 10,000 or more and 80,000 or less; a cationic polymerization initiator which is a quaternary ammonium salt-based thermal acid generator; and a silane coupling agent having two or more mercapto groups in one molecule and an organic main chain, wherein the content of the silane coupling agent is 0.3% by mass or more and 3% by mass or less.

2. The adhesive composition of claim 1 , wherein the cationically polymerizable component comprises a difunctional cycloaliphatic epoxy compound.

3. 3. The adhesive composition according to claim 1, wherein the silane coupling agent has a molecular weight of 500 or more.

4. 4. The adhesive composition according to claim 1, wherein the silane coupling agent has one or more alkoxysilyl groups and two or more mercapto groups in one molecule.

5. The adhesive composition according to claim 4 , wherein the silane coupling agent has a ratio of the number of mercapto groups to the number of alkoxysilyl groups of 2 or more.

6. An adhesive film comprising the adhesive composition according to any one of claims 1 to 5 and conductive particles.

7. A connection structure in which a first electronic component and a second electronic component are connected by the adhesive film according to claim 6.

8. A method for producing a connection structure, comprising a step of pressure-bonding a first electronic component and a second electronic component with the adhesive film according to claim 6 interposed therebetween.

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