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

Abstract

The purpose of the present invention is to provide an adhesive composition which is capable of forming an anisotropic conductive film that is capable of suppressing the connection resistance between electrodes to a low level.　The present invention provides an adhesive composition wherein the difference between the curing start temperature and the curing end temperature is 20°C or less.

Description

Adhesive composition, connection structure, and method for manufacturing connection structure

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

[0002] In the fields of devices such as semiconductors, liquid crystal displays, smartphones, personal computers, earphones, smartwatches, and wearable devices, anisotropically conductive films are used for fixing electronic components, connecting circuits, and the like. Anisotropically conductive films are formed, for example, by dispersing conductive particles in an adhesive film. For example, Patent Document 1 discloses an anisotropically conductive film formed by dispersing conductive particles in an insulating adhesive composition containing a (meth)acrylate-based monomer composition, a radical polymerization initiator, and a film-forming resin, in which the (meth)acrylate-based monomer composition contains a (meth)acrylate-based monomer having a cyclic ester residue or a cyclic amide residue.

[0003] By sandwiching an anisotropically conductive film between opposing electronic components and thermocompression bonding, the adhesive component in the anisotropically conductive film melts and flows, trapping conductive particles between the opposing electrodes and electrically connecting the opposing electrodes. At this time, the melted and flowed adhesive component fills and hardens between adjacent conductive particles, adjacent electrodes in the same electronic component, and the like, allowing the electronic components to be bonded and fixed together while maintaining insulation between adjacent electrodes in the same electronic component.

[0004] JP 2010-242101 A

[0005] In recent years, micro-OLED-equipped devices used for AR / VR applications have become more functional, smaller, and thinner. In such devices, components with low heat resistance, such as micro-OLEDs, are located near the mounting portion using an anisotropic conductive film, so it is undesirable to perform thermocompression bonding at high temperatures during mounting. Therefore, it is necessary to use an anisotropic conductive film that can be cured at low temperatures (e.g., 130°C or less).

[0006] However, when a low-temperature curable anisotropic conductive film is used, the problem of adhesive residues between the electrodes and the conductive particles becomes particularly apparent. Specifically, when thermocompression bonding is performed at low temperatures during mounting, the adhesive components in the anisotropic conductive film may not flow sufficiently before curing proceeds, resulting in adhesive residues between the electrodes and the conductive particles, which may increase the connection resistance between the electrodes.

[0007] Therefore, an object of one aspect of the present invention is to provide an adhesive composition that can form an anisotropic conductive film that can keep the connection resistance between electrodes low.

[0008] The curing end temperature of the adhesive composition is appropriately selected so that curing of the adhesive composition is completed according to the thermocompression bonding temperature. Therefore, when thermocompression bonding is performed at low temperatures, the curing end temperature is lower than when thermocompression bonding is performed at high temperatures, and accordingly, the curing initiation temperature of the adhesive composition is also typically lower. On the other hand, in order to properly connect electronic components to each other, the adhesive components must flow during thermocompression bonding. However, as the curing initiation temperature of the adhesive composition decreases, the temperature range in which the adhesive components can flow (temperature range below the curing initiation temperature) narrows. As a result, the time during which the adhesive components can flow is shortened, and the problem of insufficient flow becomes apparent during thermocompression bonding at low temperatures. As a result of extensive research, the inventors have found that by reducing the difference between the curing initiation temperature and the curing end temperature of the adhesive composition, the temperature range in which the adhesive components can flow before curing of the adhesive composition (temperature range below the curing initiation temperature) becomes relatively wider, thereby ensuring a longer time during which the adhesive components can flow. As a result, adhesive component residue is less likely to occur between the electrodes and the conductive particles, and connection resistance between the electrodes can be reduced.

[0009] In some aspects, the present invention provides the following items [1] to [8]. [1] An adhesive composition in which the difference between the curing initiation temperature and the curing completion temperature is 20°C or less. [2] The adhesive composition according to [1], in which the curing completion temperature is 130°C or less. [3] The adhesive composition according to [1] or [2], in which the curing initiation temperature is 85°C or more. [4] The adhesive composition according to any one of [1] to [3], which contains a (meth)acrylate. [5] The adhesive composition according to any one of [1] to [4], which contains conductive particles. [6] A connection structure comprising: a first electronic component having a first electrode; a second electronic component having a second electrode; and a connection part disposed between the first electronic component and the second electronic component and electrically connecting the first electrode and the second electrode to each other, wherein the connection part comprises a cured product of the adhesive composition according to any one of [1] to [5]. [7] A method for producing a connection structure, comprising the steps of: placing the adhesive composition according to any one of [1] to [5] between a first electronic component having a first electrode and a second electronic component having a second electrode; and thermocompression bonding the first electronic component and the second electronic component via the adhesive composition to electrically connect the first electrode and the second electrode to each other. [8] The method according to [7], in which thermocompression bonding is performed at 130°C or less.

[0010] According to one aspect of the present invention, it is possible to provide an adhesive composition that can form an anisotropic conductive film that can keep the connection resistance between electrodes low.

[0011] Fig. 2 is a schematic cross-sectional view showing one embodiment of an adhesive film; Fig. 3 is a schematic cross-sectional view showing another embodiment of an adhesive film; Fig. 4 is a schematic cross-sectional view showing one embodiment of a connection structure; Fig. 5 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a connection structure.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[0013] <Adhesive Composition> In the adhesive composition according to one embodiment, the curing initiation temperature (T ｏｎ ) and curing end temperature (T ｏｆｆ The adhesive composition is a thermosetting adhesive composition that hardens when heated. ｏｎ and Tｏｆｆ The curing start temperature and curing end temperature are determined by DSC measurement of the adhesive composition under the conditions of a temperature rise rate of 10°C / min and a measurement temperature range of 40°C to 250°C. ｏｎ is the temperature at the intersection of the tangent to the inflection point between the rising edge of the DSC curve and the peak top, which corresponds to the curing reaction of the adhesive composition in the obtained DSC curve, and the extrapolation of the baseline of the DSC curve. ｏｆｆ is the temperature at the intersection of the tangent to the inflection point between the peak top and the falling edge of the DSC curve and the extrapolation of the baseline of the DSC curve.

[0014] T of adhesive composition ｏｎ and T ｏｆｆ The difference between (T ｏｆｆ -T ｏｎ ) may be 18°C ​​or less, 16°C or less, 15°C or less, or 14°C or less. ｏｆｆ -T ｏｎ is above 0°C, and may be 1°C or higher, or 5°C or higher.

[0015] Curing start temperature (T ｏｎ ) may be 80°C or higher, 85°C or higher, or 87°C or higher, from the viewpoint of promoting flow of the adhesive composition before curing. ｏｎ may be 120°C or less, 110°C or less, 105°C or less, 103°C or less, or 101°C or less.

[0016] Curing end temperature (T ｏｆｆ ) may be 130°C or less, 120°C or less, or 110°C or less from the viewpoint of improving the reaction rate of the curing reaction of the adhesive composition at low temperatures (hereinafter also simply referred to as "reaction rate"). ｏｆｆ may be 100°C or higher, or 105°C or higher.

[0017] The adhesive composition may include a (meth)acrylate. Examples of (meth)acrylates include (poly)urethane (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, dimethyloltricyclodecane diacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, 2-hydroxy-1,3-diacryloxypropane, 2,2-bis[4-(acryloxymethoxy)phenyl]propane, 2,2-bis[4-(acryloxypolyethoxy)phenyl]propane, dicyclopentenyl acrylate, tricyclodecanyl acrylate, bis(acryloxyethyl)isocyanurate, ε-caprolactone-modified tris(acryloxyethyl)isocyanurate, tris(acryloxyethyl)isocyanurate, and ethylene oxide-modified phosphate di(meth)acrylate.

[0018] The content of (meth)acrylate may be 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more, and may be 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less, based on the total mass of the solid content contained in the adhesive composition (in cases where the adhesive composition contains conductive particles described below, this refers to the solid content contained in the adhesive composition other than the conductive particles; hereinafter also referred to as "adhesive components").

[0019] The adhesive composition may contain only (meth)acrylate as the polymerizable substance, or may contain other polymerizable substances other than (meth)acrylate. The polymerizable substance is a substance having a functional group that polymerizes by radicals. Examples of other polymerizable substances include maleimide compounds.

[0020] The content of polymerizable substances other than (meth)acrylates may be 10% by mass or less, 5% by mass or less, or 1% by mass or less, based on the total mass of the adhesive components.

[0021] The adhesive composition may contain a curing agent (thermal radical polymerization initiator). A curing agent is a compound that decomposes upon heating to generate free radicals.

[0022] Examples of the curing agent include peroxides and azo compounds. Examples of the peroxides include diacyl peroxides such as dioctanoyl peroxide, dilauroyl peroxide, distearoyl peroxide, and dibenzoyl peroxide; peroxydicarbonates such as bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, and di-2-ethylhexyl peroxydicarbonate; t-butyl peroxypivalate, t-hexyl peroxypivalate, and the like. peroxymethyl butyl ether, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t peroxy esters such as 1,1-bis(t-butylperoxylaurate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butyl peroxybenzoate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, and t-butyl peroxyacetate; peroxy ketals such as 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-2-methylcyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, and 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane; dialkyl peroxides such as dicumyl peroxide, t-butylcumyl peroxide, and di-t-butyl peroxide; and hydroperoxides such as p-menthane hydroperoxide.

[0023] Examples of azo compounds include 2,2'-azobis(2,4-dimethylvaleronitrile) and 2,2'-azobisisobutyronitrile.

[0024] As the curing agent, one of the above peroxides and azo compounds may be used alone, or two or more may be used in combination. By selecting the type of curing agent (when two or more curing agents are used in combination, the combination of two or more curing agents), the T of the adhesive composition can be controlled. ｏｎ It is possible to adjust the viscosity. The adhesive composition preferably contains at least one of a diacyl peroxide and a peroxyester as a curing agent. The one-minute half-life temperature of the diacyl peroxide and the peroxyester may each independently be 90 to 175°C. Furthermore, the molecular weight of the diacyl peroxide and the peroxyester may each independently be 180 to 1,000.

[0025] The content of the curing agent may be 0.05% by mass or more, 0.1% by mass or more, 1% by mass or more, or 2% by mass or more, and may be 20% by mass or less, 10% by mass or less, or 8% by mass or less, based on the total mass of the adhesive components.

[0026] The adhesive composition may contain a cure modifier. The cure modifier is a compound that quickly reacts with initiating radicals generated by decomposition of the curing agent, and with propagating radicals generated when the initiating radicals attack the radical polymerizable compound, and generates radicals again when heated to 60°C or higher, thereby promoting the polymerization of the radical polymerizable compound. By adding such a cure modifier or adjusting the content of such a cure modifier, T ｏｆｆ and T ｏｎ can be adjusted respectively, so that T ｏｆｆ -T ｏｎ can be adjusted to fall within the above range. Furthermore, the flowability of the adhesive composition can be adjusted by adding a cure modifier or adjusting the content of the cure modifier.

[0027] The curing regulator may be, for example, an amine compound having a divalent organic group represented by the following general formula (A). In general formula (A), X １ , X ２ , X ３ and X ４ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Here, the alkyl group includes not only linear alkyl groups but also branched and cyclic alkyl groups.

[0028] The amine compound having a divalent organic group represented by general formula (A) may be an amine compound represented by the following general formula (1). In general formula (1), R １ and R ２ each independently represents a hydrogen atom, a hydroxyl group, or a monovalent organic group; X １ , X ２ , X ３ and X ４ each independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

[0029] The organic group refers to a substituent containing carbon. The structure of this substituent is not particularly limited. ２ Examples of monovalent organic groups that can be used as R include alkyl groups having 1 to 10 carbon atoms, aryl groups, alkoxy groups having 2 to 20 carbon atoms, ether groups, and ester groups. Examples of alkyl groups having 1 to 10 carbon atoms include methyl groups. Examples of alkoxy groups having 2 to 20 carbon atoms include octoxy groups. The ester groups can be formed by the reaction of R ２ is a hydroxyl group, with a monocarboxylic acid such as methacrylic acid or 2-methylhexanoic acid, a dicarboxylic acid such as sebacic acid, or a tetracarboxylic acid.

[0030] R in the above general formula (1) １ may be a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 10 carbon atoms, an aryl group, an alkoxy group having 2 to 20 carbon atoms, or a monovalent organic group represented by the following general formula (2): An example of an alkyl group having 1 to 10 carbon atoms is a methyl group. An example of an alkoxy group having 2 to 20 carbon atoms is an octoxy group.

[0031] In general formula (2), R３ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ４ represents an ester group having 1 to 5 carbon atoms, a benzyl ester group, a carboxyl group, or an aryl group; R ５ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a phenoxy group, an aryl group, a carbonyloxy group having 1 to 20 carbon atoms, a phenylcarbonyloxy group, or a vinyl group, and n represents an integer of 1 to 20. However, the phenoxy group, the aryl group, and the phenylcarbonyloxy group may be substituted with an alkyl group having 1 to 5 carbon atoms. The amine compound may be used alone or in combination of two or more types.

[0032] The cure regulator preferably has one or more aminoxyl structures in the molecule, and since such cure regulators exist as stable radicals even in air, they have the advantage of improving the storage stability of the adhesive composition.

[0033] Specific examples of the compound having an aminoxyl structure include 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2-dimethyl-6-phenylpiperidine-1-oxyl, 2,2,6-trimethyl-6-phenylpiperidine-1-oxyl, 2,6-diphenylpiperidine-1-oxyl, 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-carboxy- C-2,2,6,6-tetramethylpiperidine-1-oxyl, 3-carboxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-(2-chloroacetamido)-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxylbenzoate, 4-(2-iodoacetamido)-2,2,6,6-tetramethylpiperidine ethylpiperidine-1-oxyl, 4-isothiocyanato-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-isocyanato-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2-dimethyl-6-cyclohexylpiperidine-1-oxyl, 2,6-dicyclohexylpiperidine-1-oxyl Examples of the compound having an aminoxyl structure include 2,2-dimethyl-6-cyclopentylpiperidine-1-oxyl, 2,6-dicyclopentylpiperidine-1-oxyl, 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,5-diphenylpyrrolidine-1-oxyl, 2,2-dimethyl-5-phenylpyrrolidine-1-oxyl, and 2,2,5-trimethyl-5-phenylpyrrolidine-1-oxyl. The compound having an aminoxyl structure may be used alone or in combination of two or more.

[0034] The content of the cure adjuster may be 0.001% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.07% by mass or more, based on the total mass of the adhesive components, and may be 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 1% by mass or less.

[0035] The adhesive composition may contain a thermoplastic resin. Examples of the thermoplastic resin include polyamide resin, phenoxy resin, (meth)acrylic resin, polyimide resin, polyester resin, polyurethane resin, polyester urethane resin, and polyvinyl butyral resin. These thermoplastic resins may be used alone or in combination of two or more.

[0036] The content of the thermoplastic resin may be 20% by mass or more and 50% by mass or less based on the total mass of the adhesive components.

[0037] The adhesive composition may further contain other components such as an adhesion promoter, a coupling agent (e.g., a silane coupling agent), an ion trapping agent, a visualization agent, a dispersant, a photoradical polymerization initiator, a filler, etc. The content of the other components may be, for example, 1% by mass or more and 20% by mass or less, based on the total mass of the adhesive components.

[0038] The adhesive composition may contain conductive particles. The conductive particles may have a non-conductive core and a conductive layer provided on the core. It is preferable that substantially the entire surface of the core is covered with the conductive layer, but a portion of the core surface may be exposed without being covered with the conductive layer, as long as the function of electrically connecting electronic components is maintained.

[0039] The core is formed of a non-conductive material such as glass, ceramic, or resin, and is preferably formed of resin. Examples of resins include acrylic resin, styrene resin, silicone resin, polybutadiene resin, and copolymers of the monomers that make up these resins. The core may be a particle containing a polymer containing at least one monomer selected from styrene and divinylbenzene as a monomer unit. The polymer may further contain (meth)acrylate as a monomer unit. The diameter of the core may be, on average, for example, 1 μm or more, or 2 μm or more, and may be 40 μm or less, 30 μm or less, or 20 μm or less.

[0040] The conductive layer is formed of, for example, Ni, Cu, Ag, Ru, or Pd, or an alloy containing these metal elements. The alloy may be, for example, an alloy containing Ni (Ni alloy). Examples of Ni alloys include Ni-B, Ni-P, and Ni-W-B. The thickness of the conductive layer may be, for example, 50 nm or more and 300 nm or less. The thickness of the conductive layer can be measured using an electron microscope.

[0041] The conductive layer may consist of one, two, or three or more conductive layers. When the conductive layer consists of two conductive layers, the conductive particle may have a first conductive layer provided on the outermost surface of the conductive particle and a second conductive layer provided between the first conductive layer and the core. The first conductive layer is formed of, for example, Au or Pd. The second conductive layer is formed of, for example, Ni. The thickness of the first conductive layer may be, for example, 2 nm or more and 200 nm or less. The thickness of the second conductive layer may be, for example, 50 nm or more and 300 nm or less.

[0042] The conductive particles may be substantially spherical. A plurality of protrusions may be formed on the surface of the conductive particles. The plurality of protrusions may be formed of a single conductive layer or two conductive layers.

[0043] The average particle size of the conductive particles may be, for example, 1 μm or more and 40 μm or less. The average particle size of the conductive particles is determined by measuring the particle sizes of 10 conductive particles by SEM observation and calculating the average value of the obtained 10 data.

[0044] The content of the conductive particles may be 5% by mass or more, or 10% by mass or more, and may be 30% by mass or less, or 25% by mass or less, based on the total mass of the solid content in the adhesive composition.

[0045] The content of the conductive particles may be 0.1% by volume or more, 50% by volume or less, or 40% by volume or less, based on the total volume of the solid content in the adhesive composition.

[0046] The adhesive composition may be in the form of a paste or a film. Fig. 1 is a schematic cross-sectional view showing one embodiment of a film-like adhesive composition (adhesive film). As shown in Fig. 1, in one embodiment, the adhesive film 1 is composed of a single layer made of an adhesive component (insulating adhesive) 2 and conductive particles 3 dispersed in the adhesive component 2.

[0047] In another embodiment, the adhesive film may have two or more regions. The adhesive film may include a first region containing a first adhesive component and a second region adjacent to the first region containing a second adhesive component. Each of the first region and the second region may be a layer.

[0048] For example, as shown in FIG. 2 , the adhesive film 1 may have a two-layer structure including a layer 1A containing conductive particles 3A (a first adhesive layer consisting of adhesive component 2A and conductive particles 3A dispersed in adhesive component 2A) and a layer 1B not containing conductive particles (a second adhesive layer consisting of adhesive component 2B). In this case, the first adhesive layer 1A may contain the above-mentioned polymerizable substance, curing agent, cure adjuster, thermoplastic resin, conductive particles, and other components as needed. The second adhesive layer 1B may contain the above-mentioned polymerizable substance, curing agent, cure adjuster, thermoplastic resin, and other components as needed. The types of components contained in the second adhesive layer 1B may be the same as or different from those in the first adhesive layer 1A.

[0049] The contents of the polymerizable substance, curing agent, cure adjuster, thermoplastic resin, and other components in the first adhesive layer and the second adhesive layer may each independently be the same as the contents of each component in the adhesive composition described above. In this case, "based on the total mass of the adhesive components" should be read as "based on the total mass of the adhesive components contained in the first adhesive layer" or "based on the total mass of the adhesive components contained in the second adhesive layer."

[0050] When the adhesive composition is in the form of a film, the T ｏｎ and T ｏｆｆ is determined by DSC measurement of the entire adhesive film. When the adhesive film has two or more regions, T is determined by DSC measurement of the entire adhesive film having two or more regions. ｏｎ and T ｏｆｆ For example, T of the adhesive film 1 shown in FIG. ｏｎ and T ｏｆｆ When determining the thickness, a laminate of the first adhesive layer 1A and the second adhesive layer 1B is used as the measurement object, and DSC measurement is carried out by the method described above.

[0051] The thickness of the adhesive film 1 may be, for example, 5 μm or more, or 10 μm or more, and may be 50 μm or less, 30 μm or less, or 20 μm or less.

[0052] The adhesive composition (adhesive film 1) may be a conductive adhesive composition (conductive adhesive film) or an anisotropically conductive adhesive composition (anisotropically conductive adhesive film). The adhesive composition can be suitably used for producing a connection structure.

[0053] <Connection structure> A connection structure according to one embodiment includes a first electronic component having a first electrode, a second electronic component having a second electrode, and a connection portion disposed between the first electronic component and the second electronic component and electrically connecting the first electrode and the second electrode to each other, wherein the connection portion includes a cured product of the adhesive composition described above.

[0054] 3 is a schematic cross-sectional view showing one embodiment of a connection structure 10. As shown in FIG. 3, the connection structure 10 includes a first electronic member 4 and a second electronic member 5 facing each other, and a connection portion 6 connecting the first electronic member 4 and the second electronic member 5 between the first electronic member 4 and the second electronic member 5.

[0055] The first electronic component 4 includes a first substrate 41 and a first electrode 42 formed on a main surface 41 a of the first substrate 41. The second electronic component 5 includes a second substrate 51 and a second electrode 52 formed on a main surface 51 a of the second substrate 51.

[0056] There are no particular limitations on the first electronic member 4 and the second electronic member 5 as long as they are members having electrodes formed thereon that require electrical connection. Examples of members having electrodes formed thereon include active elements such as diodes such as micro OLEDs, semiconductor chips, transistors, and thyristors; passive elements such as capacitors, resistors, and coils; and substrates having electrodes such as printed circuit boards.

[0057] The first substrate 41 and the second substrate 51 may be a silicon substrate, a glass substrate, a flexible substrate, etc. The flexible substrate may contain at least one thermoplastic resin selected from the group consisting of polyimide (PI), polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene naphthalate (PEN), for example.

[0058] Examples of electrode materials for forming the first electrode 42 and the second electrode 52 include metals such as Ag, Ni, Al, Au, Cu, Ti, and Mo, metal oxides such as ITO and IZO, and conductors such as silver nanowires and carbon nanotubes. The first electrode 42 and the second electrode 52 may be made of the same material or different materials.

[0059] The first electronic member 4 and the second electronic member 5 may each be provided with one first electrode 42 or one second electrode 52, but preferably a large number of electrodes are provided at predetermined intervals.

[0060] The connection portion 6 contains an insulating material 7, which is a cured product of the adhesive composition, and conductive particles 3. The conductive particles 3 may be disposed not only between the opposing first electrode 42 and second electrode 52, but also between the main surface 41 a of the first substrate 41 and the main surface 51 a of the second substrate 51. In the connection structure 10, the first electrode 42 and the second electrode 52 are electrically connected via the conductive particles 3. That is, the conductive particles 3 are in contact with both the first electrode 42 and the second electrode 52.

[0061] In the connection structure 10, as described above, the opposing first electrode 42 and second electrode 52 are electrically connected via the conductive particles 3. This sufficiently reduces the connection resistance between the first electrode 42 and the second electrode 52. This allows the current to flow smoothly between the first electrode 42 and the second electrode 52, allowing the first electronic member 4 and the second electronic member 5 to fully exhibit their functions.

[0062] <Method for manufacturing connection structure> The connection structure can be manufactured by a method comprising the steps of: placing the adhesive composition between a first electronic component having a first electrode and a second electronic component having a second electrode; and thermocompression bonding the first electronic component and the second electronic component via the adhesive composition to electrically connect the first electrode and the second electrode to each other.

[0063] 4 is a schematic cross-sectional view showing one embodiment of a method for manufacturing a connection structure. As shown in FIG. 4( a), first, an adhesive film 1 (a film-like adhesive composition) is placed on a main surface 41 a of a first electronic component 4. When the adhesive film 1 is laminated on a substrate (not shown), the adhesive film 1 side of the substrate is placed on the first electronic component 4 so that it faces the first electronic component 4. When the adhesive film 1 has a first adhesive layer 1A and a second adhesive layer 1B as shown in FIG. 2, it is preferable to place the first adhesive layer 1A side in contact with the main surface 41 a of the first electronic component 4, from the viewpoint of increasing the number of conductive particles captured between the opposing electrodes.

[0064] After the adhesive film 1 is placed on the main surface 41 a of the first electronic member 4, the laminate of the adhesive film 1 and the first electronic member 4 may be pressed in the stacking direction to temporarily connect the adhesive film 1 to the first electronic member 4. At this time, heating may be performed together with the pressing.

[0065] 4(b), the second electronic component 5 is further placed on the adhesive film 1 placed on the first electronic component 4 so that the second electrode 52 faces the first electronic component 4 (i.e., the first electrode 42 and the second electrode 52 are placed opposite each other, and the adhesive film 1 is placed between the first electronic component 4 and the second electronic component 5). If the adhesive film 1 is laminated on a substrate (not shown), the substrate is peeled off and then the second electronic component 5 is placed on the adhesive film 1.

[0066] The first electronic member 4 and the second electronic member 5 are then thermocompression bonded together via the adhesive film 1. The thermocompression bonding is performed, for example, by applying heat and pressure in the direction of arrow A in FIG. 4(b). The application of heat and pressure in the direction of arrow A hardens the adhesive film 1, and the first electrode 42 and the second electrode 52 are electrically connected to each other. As a result, a connection structure 10 as shown in FIG. 3 is obtained.

[0067] The thermocompression bonding may be performed, for example, at 5 MPa or more and 20 MPa or less per total connection area.ｏｎ The thermocompression bonding may be performed at a temperature of, for example, 100° C. or higher, and at a temperature of 170° C. or lower, 150° C. or lower, or 130° C. or lower. The pressure application time and heating time during thermocompression bonding may be, for example, 10 seconds or longer and 60 seconds or shorter.

[0068] In the connection structure 10 obtained as described above, it is possible to bring the conductive particles 3 into contact with both the opposing first electrode 42 and second electrode 52, and the connection resistance between the first electrode 42 and the second electrode 52 can be sufficiently reduced.

[0069] By applying pressure to the adhesive film 1 while heating it, the adhesive component 2 can be cured to form the insulating material 7 while the distance between the first electrode 42 and the second electrode 52 is kept sufficiently small. This allows the first electronic member 4 and the second electronic member 5 to be firmly connected via the connecting portion 6.

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0071] <Synthesis of polyurethane acrylate (UA1)> 2,500 parts by mass (2.50 mol) of poly(1,6-hexanediol carbonate) (trade name: Duranol T5652, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight 1,000) and 666 parts by mass (3.00 mol) of isophorone diisocyanate (manufactured by Sigma-Aldrich Co.) were uniformly added dropwise over 3 hours to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser with a calcium chloride drying tube, and a nitrogen gas inlet tube. Next, nitrogen gas was sufficiently introduced into the reaction vessel, and the reaction vessel was heated to 70 to 75°C to allow the mixture to react. Next, 0.53 parts by mass (4.3 mmol) of hydroquinone monomethyl ether (Sigma-Aldrich) and 5.53 parts by mass (8.8 mmol) of dibutyltin dilaurate (Sigma-Aldrich) were added to the reaction vessel, followed by the addition of 238 parts by mass (2.05 mol) of 2-hydroxyethyl acrylate (Sigma-Aldrich), and the mixture was allowed to react for 6 hours at 70°C in an air atmosphere. This yielded polyurethane acrylate (UA1). The weight-average molecular weight of polyurethane acrylate (UA1) was 15,000. The weight-average molecular weight was measured by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene under the following conditions. (Measurement conditions) Apparatus: GPC-8020 manufactured by Tosoh Corporation Detector: RI-8020 manufactured by Tosoh Corporation Column: Gelpack GLA160S+GLA150S manufactured by Hitachi Chemical Co., Ltd. Sample concentration: 120 mg / 3 mL Solvent: tetrahydrofuran Injection volume: 60 μL Pressure: 2.94×10 ６ Pa (30kgf / cm ２ ) Flow rate: 1.00mL / min

[0072] Comparative Example 1 (Preparation of First Adhesive Composition) A first adhesive composition was prepared using 17 parts by mass of dimethyloltricyclodecane diacrylate (product name: DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.) as a polymerizable substance, 30 parts by mass of the polyurethane acrylate (UA1) prepared as described above, and 1.5 parts by mass of ethylene oxide-modified phosphate dimethacrylate (product name: PM-21, manufactured by Nippon Kayaku Co., Ltd.) as a curing agent, 2.5 parts by mass of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (product name: Perhexa 25O, manufactured by NOF Corporation) as a thermoplastic resin, and A first adhesive composition was obtained by mixing 45 parts by mass of a urethane resin (product name: UR-8200, manufactured by Toyobo Co., Ltd.), 2.8 parts by mass of 3-glycidoxypropyltrimethoxysilane (product name: SH-6040, manufactured by Dow Corning Toray Co., Ltd.) as a silane coupling agent, 2.5 parts by mass of Aerosil (product name: R-202, manufactured by Nippon Aerosil Co., Ltd.) as a filler, and 26 parts by mass of conductive particles (average particle size: 3 μm) having a non-conductive core and a conductive layer provided on the core, and having a plurality of protrusions formed on the surface.

[0073] (Preparation of Second Adhesive Composition) A second adhesive composition was prepared using 30 parts by mass of dimethyloltricyclodecane diacrylate (product name: DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.) as a polymerizable substance, 27.5 parts by mass of the polyurethane acrylate (UA1) prepared as described above, and 2.5 parts by mass of ethylene oxide-modified phosphate dimethacrylate (product name: PM-21, manufactured by Nippon Kayaku Co., Ltd.), 5.0 parts by mass of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (product name: Perhexa 25O, manufactured by NOF Corporation) as a curing agent, and 1.0 parts by mass of a thermosetting resin. A second adhesive composition was obtained by mixing 27.5 parts by mass of polyester urethane resin (product name: UR-4800, manufactured by Toyobo Co., Ltd.) as a plastic resin, 15 parts by mass of phenoxy resin (product name: YP-70, manufactured by Nippon Steel Chemical & Material Co., Ltd.), 5 parts by mass of 3-glycidoxypropyltrimethoxysilane (product name: SH-6040, manufactured by Dow Corning Toray Co., Ltd.) as a silane coupling agent, and 8 parts by mass of Aerosil (product name: R-202, manufactured by Nippon Aerosil Co., Ltd.) as a filler.

[0074] The first adhesive composition was applied to a substrate (a 50 μm-thick PET film) using an applicator to prepare a first adhesive layer. A second adhesive layer was prepared using the second adhesive composition in the same manner as the first adhesive layer. The first adhesive layer and the second adhesive layer were then bonded together using a laminator to prepare an adhesive film (thickness: 14 μm).

[0075] Example 1 An adhesive film was prepared in the same manner as in Comparative Example 1, except that in the second adhesive composition, the amount of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane used as the curing agent was changed to 4.8 parts by mass, and 0.5 parts by mass of dilauroyl peroxide (product name: Perloyl L, manufactured by NOF Corporation) used as the curing agent and 0.1 parts by mass of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (manufactured by Tokyo Chemical Industry Co., Ltd.) used as the cure adjuster were further added. The content of conductive particles based on the total volume of the adhesive film was 1% by volume.

[0076] Example 2 An adhesive film was produced in the same manner as in Example 1, except that in the second adhesive composition, the blending amount of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane as a curing agent was changed to 4.5 parts by mass and the blending amount of dilauroyl peroxide was changed to 1.0 part by mass. The content of conductive particles based on the total volume of the adhesive film was 1% by volume.

[0077] Example 3 An adhesive film was produced in the same manner as in Example 1, except that in the second adhesive composition, the blending amount of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane as a curing agent was changed to 4.0 parts by mass and the blending amount of dilauroyl peroxide was changed to 2.0 parts by mass. The content of conductive particles based on the total volume of the adhesive film was 1% by volume.

[0078] Example 4 An adhesive film was produced in the same manner as in Example 1, except that in the second adhesive composition, the amount of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane used as a curing agent was changed to 3.5 parts by mass and the amount of dilauroyl peroxide was changed to 3.0 parts by mass. The content of conductive particles based on the total volume of the adhesive film was 1% by volume.

[0079] Example 5 An adhesive film was produced in the same manner as in Example 1, except that in the second adhesive composition, the blending amount of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane as a curing agent was changed to 3.0 parts by mass and the blending amount of dilauroyl peroxide was changed to 4.0 parts by mass. The content of conductive particles based on the total volume of the adhesive film was 1% by volume.

[0080] Example 6 An adhesive film was produced in the same manner as in Example 1, except that in the second adhesive composition, the blending amount of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane as a curing agent was changed to 2.5 parts by mass and the blending amount of dilauroyl peroxide was changed to 5.0 parts by mass. The content of conductive particles based on the total volume of the adhesive film was 1% by volume.

[0081] (Curing initiation temperature and curing completion temperature of adhesive film) DSC measurement was carried out on each of the adhesive films (5 mg each) of Comparative Example 1 and Examples 1 to 6 under a nitrogen gas flow using a differential scanning calorimeter (DSC) (product name: DSC7, manufactured by Perkin Elmer) under the conditions of a temperature rise rate of 10°C / min and a measurement temperature range of 40°C to 250°C. The curing initiation temperature (T ｏｎ ) and curing end temperature (T ｏｆｆ The difference between the curing start temperature and the curing end temperature (T ｏｆｆ -T ｏｎ The results are shown in Table 1.

[0082] (Preparation of Electronic Components) The following electronic components were prepared. Glass Component: A glass component was prepared, including a glass substrate and Ti / Al / Ti wiring formed on the glass substrate. The thickness of this glass substrate was 0.7 mm, and the wiring on the glass component had a line width of 300 μm and an electrode height of 750 nm. Flexible Circuit Board (FPC): An FPC was prepared, including a resin film substrate based on polyethylene terephthalate (PET) and wiring provided on the resin film substrate. The wiring of this FPC had electrodes consisting of a Cu layer with a pitch of 70 μm (space 35 μm, electrode width 35 μm, thickness 18 μm), a 0.5 μm thick Ni layer, and a 2.5 μm thick Au layer formed in that order on the Cu layer.

[0083] (Preparation of Connection Structure) The adhesive film of Comparative Example 1 was placed on a glass member, and an FPC was placed on the adhesive film to prepare a laminate of the glass member, adhesive film, and FPC. At this time, the main surface of the glass substrate (the surface on which wiring was formed) and the main surface of the resin film substrate (the surface on which wiring was formed) were arranged to face each other. The first adhesive layer of the adhesive film was also arranged to contact the glass member. A silicone rubber cushioning material was placed on the FPC side of the prepared laminate, and heating and pressurization were performed on the cushioning material using a thermocompression bonding device (heating method: pulse heat type, manufactured by Ohashi Manufacturing Co., Ltd.) to prepare the connection structure of Comparative Example 1, which included a glass member, a cured adhesive film, and an FPC. The heating temperature was 120°C, the pressurizing pressure was 14 MPa, and the heating and pressurizing times were 30 seconds. Here, the heating temperature refers to the set temperature of the thermocompression bonding device, and the pressurizing pressure refers to the pressure relative to the total connection area. Furthermore, the connection structures of Examples 1 to 6 were prepared using the adhesive films of Examples 1 to 6 in the same manner as described above.

[0084] (Connection Resistance Between Electrodes) For each of the connection structures of Comparative Example 1 and Examples 1 to 6, the connection resistance between the electrodes (between the electrodes of the glass member and the electrodes of the FPC) during low-temperature connection was measured using a digital multimeter by the four-terminal method. The results are shown in Table 1.

[0085] (Reaction Rate) The connection structures of Comparative Example 1 and Examples 1 to 6 prepared by the above-described method were disassembled, and the cured adhesive film was scraped off to prepare 5 mg of evaluation samples for Comparative Example 1 and Examples 1 to 6. Next, the evaluation samples of Comparative Example 1 and Examples 1 to 6 were each measured using a differential scanning calorimetry (DSC) device (product name: DSC7, manufactured by Perkin Elmer) under a nitrogen gas flow at a measurement temperature range of 30°C to 250°C and a heating rate of 10°C / min, and the calorific value (J / g) of each evaluation sample was calculated. 5 mg of each adhesive film of Comparative Example 1 and Examples 1 to 6 was weighed out and used as a control sample for each Comparative Example and Example. Each control sample was subjected to DSC measurement in the same manner as above, and the calorific value of the control sample was calculated. The reaction rate for each Comparative Example and Example was calculated using the following formula. The results are shown in Table 1. Reaction rate (%) = {1 - (calorific value of evaluation sample / calorific value of control sample)} x 100

[0086]

[0087] 1...adhesive film, 1A...first adhesive layer, 1B...second adhesive layer, 2, 2A, 2B...adhesive component, 3, 3A...conductive particles, 4...first electronic component, 5...second electronic component, 6...connection portion, 7...insulating material, 10...connection structure, 41...first substrate, 42...first electrode, 51...second substrate, 52...second electrode.

Claims

1. An adhesive composition in which the difference between the curing start temperature and the curing end temperature is 20°C or less.

2. The adhesive composition according to claim 1, wherein the curing end temperature is 130°C or lower.

3. The adhesive composition according to claim 1 or 2, wherein the curing initiation temperature is 85°C or higher.

4. The adhesive composition according to claim 1 or 2, which comprises a (meth)acrylate.

5. The adhesive composition according to claim 1 or 2, which contains conductive particles.

6. A connection structure comprising: a first electronic component having a first electrode; a second electronic component having a second electrode; and a connection portion disposed between the first electronic component and the second electronic component and electrically connecting the first electrode and the second electrode to each other, wherein the connection portion comprises a cured product of the adhesive composition according to claim 5.

7. A method for manufacturing a connection structure, comprising the steps of: placing the adhesive composition according to claim 5 between a first electronic component having a first electrode and a second electronic component having a second electrode; and thermocompression bonding the first electronic component and the second electronic component via the adhesive composition to electrically connect the first electrode and the second electrode to each other.

8. The method according to claim 7, wherein the thermocompression is carried out at 130° C. or lower.