KR102306299B1 - Conductive adhesive composition and conductive adhesive tape - Google Patents

Abstract

It contains an acrylic copolymer (A) and conductive particles (B), and the type 00 durometer hardness specified in ASTM D 2240 is 15 or more at 85 ° C. Even when tensioned by the repulsive force of the adherend under a high temperature environment, peeling, sagging , A conductive pressure-sensitive adhesive composition in which a decrease in conductivity is less likely to occur; and a conductive adhesive tape having a pressure-sensitive adhesive layer formed on one side or both surfaces of a conductive base material by the conductive pressure-sensitive adhesive composition.

Description

Conductive adhesive composition and conductive adhesive tape

The present invention relates to a conductive pressure-sensitive adhesive composition in which peeling, sagging, and a decrease in conductivity do not easily occur even when pulled by a repulsive force of an adherend in a high-temperature environment, and a conductive adhesive tape using the same. More specifically, it is related with the electrically conductive adhesive tape useful for the use of the electromagnetic wave shield in the inside of an electronic device, or the use (earth), for example.

In an electronic device, malfunction of a component or material destruction may generate|occur|produce by the adverse effect of static electricity or electromagnetic wave. For the purpose of preventing such adverse effects, there is a method in which an electrically conductive adhesive tape is used for parts inside the device. It is known that the electroconductive adhesive tape which added electroconductive particle to the adhesive layer using metal foil as a base material specifically, is useful for the use of an electromagnetic wave shield and grounding. In such a conductive adhesive tape, conductivity and adhesiveness are important performances, and various proposals for improving the performance have been made.

In Patent Document 1, a conductive adhesive tape having a specific thickness of an adhesive layer containing 14 to 45 parts by weight of a spherical and/or spike-shaped conductive filler having an aspect ratio of 1.0 to 1.5. is disclosed. And, unlike the adhesive tapes using the filamentous conductive filler or flaky conductive filler of each comparative example, this adhesive tape is excellent in adhesiveness and conductivity even when the pressure-sensitive adhesive layer is thinned, and has step absorbency. is considered

In Patent Document 2, an electroconductive thin pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a thickness of 6 to 12 μm is disclosed in Patent Document 2, which contains conductive particles having a particle diameter of d50 of 4 to 12 μm and a d85 of 6 to 15 μm. has been And even if this adhesive sheet is thin, it is excellent in adhesiveness and electroconductivity, and it is also considered that it is excellent also in productivity.

Patent Document 3 discloses a conductive adhesive tape in which the thickness t (μm) of the pressure-sensitive adhesive layer and the particle size d50 (μm) of the conductive particles have a relationship of t<d50, and the adhesive force of the pressure-sensitive adhesive layer is 4N/20mm or more. And it is thought that this adhesive tape has stable electroconductivity also in use over a long period of time or use under severe environmental conditions, and maintains adhesive force in consideration of workability.

Patent Document 4 discloses an electroconductive adhesive tape having a ratio t/d50 of the thickness t (µm) of the pressure-sensitive adhesive layer and the particle size d50 (µm) of the electroconductive particles of 0.2 or more and 4.0 or less. And it is considered that this adhesive tape has stable electroconductivity also in use over a long period of time and use under severe environmental conditions.

However, in recent years, there is a tendency for electronic devices to be further reduced in size and thickness. For example, information devices such as mobile phones, smart phones, and wearable terminals are becoming thinner and smaller. Therefore, each component which comprises them also becomes small, and the affixing area of an adhesive tape also becomes narrower. In addition, in electronic devices that have been miniaturized and thinned, for example, flexible printed circuits (FPCs), which are one of the components, are bent and arranged in a very narrow space, and the bending angle becomes an acute angle. many.

If the affixing area is small and the bending angle of the FPC is acute, the adhesive tape cannot withstand the repulsive force of the FPC and peels off or sagging (a state in which the adhesive layer is elongated and partially generated a shape like a number of threads) is generated. have. In addition, when the pressure-sensitive adhesive layer is softened by heat generated inside the electronic device (eg, heat generated by a battery), the possibility of peeling or sagging of the pressure-sensitive adhesive tape is higher. Moreover, even if peeling or sagging does not occur, only when the pressure-sensitive adhesive layer is slightly elongated, the contact points between the conductive particles decrease, the electrical resistance value becomes unstable, and there is a fear that the conductivity may decrease.

On the other hand, when a load is permanently applied to the conductive adhesive tape inside the device by a member such as a gasket, such a problem is unlikely to occur. In addition, when the pressure-sensitive adhesive layer is compressed, the contact between the conductive particles is increased to show a stable electric resistance value. However, in a device further downsized and thinned, the size of each part is small and it is difficult to install a member such as a gasket, and it is difficult to apply a load when there are irregularities on the surface. In addition, if the parts are thin, there is a risk of damage if a strong load is applied.

In Patent Documents 1 to 4, the problem resulting from the repulsive force of the adherend when heat is generated inside the device is not studied at all. For example, in Patent Document 1, in Examples, spike-like or spherical conductive particles are used, and in Comparative Examples, electrical resistance values of adhesive tapes using filamentous or flake-like conductive particles are measured in a state ( Paragraph [0067] of Patent Document 1). In patent document 2, the electrical resistance value of an adhesive sheet is measured while applying a load of 20 N of surface pressures at 23 degreeC (paragraph [0078] of patent document 2). In Patent Documents 3 and 4, the electrical resistance value of the sample is measured under the conditions after accelerating 85 ° C. x 85% RH or after repeating the temperature rise and fall in the range of -40 ° C. to 85 ° C., but this sample is adhesive Since it is obtained by pressing the laminate having the structure of the evaluation substrate/EVA film/glass plate to which the tape is adhered at a pressure of 0.1 MPa, and then thermosetting the EVA, the adhesive tape on the evaluation substrate is applied to the glass plate. It can be said that it is fixed in a compressed state (paragraph [0117] of patent document 3, paragraph [0107] of patent document 4).

That is, in Patent Documents 1 to 4, when the conductive adhesive tape is adhered in a narrow area to the inside of a miniaturized/thinned electronic device and heat is generated inside the device, peeling or sagging due to the repulsive force of the adherend such as FPC. The subject that this occurs, or the subject that the pressure-sensitive adhesive layer is slightly elongated due to the repulsive force of an adherend such as FPC and the electric resistance value becomes unstable is not studied at all. And in the conventional general conductive adhesive tape, it is difficult to solve such a subject.

Patent Document 1: Japanese Patent Laid-Open No. 2009-79127 Patent Document 2: Japanese Patent Laid-Open No. 2013-245234 Patent Document 3: Japanese Patent Laid-Open No. 2015-10109 Patent Document 4: Japanese Patent Laid-Open No. 2015-10110

An object of the present invention is to provide a conductive pressure-sensitive adhesive composition in which peeling, sagging, and a decrease in conductivity do not easily occur even when pulled by the repulsive force of an adherend in a high-temperature environment, and an adhesive tape using the same.

This invention contains an acryl-type copolymer (A) and electroconductive particle (B), It is an electroconductive adhesive composition whose Type 00 durometer hardness prescribed|regulated by ASTM D2240 is 15 or more in 85 degreeC.

Moreover, this invention is an electroconductive adhesive tape which has the adhesive layer formed with the said electroconductive adhesive composition on the single side|surface or both surfaces of an electroconductive base material.

ADVANTAGE OF THE INVENTION According to this invention, even if it is tension|tensile|stretched by the repulsive force of a to-be-adhered object in a high-temperature environment, peeling, sagging, and a fall of electroconductivity do not generate|occur|produce easily can provide the electrically conductive adhesive composition. This electroconductive adhesive composition is very useful as a material for forming the adhesive layer of an electroconductive adhesive tape. A conductive adhesive tape having such an adhesive layer is, for example, adhered in a small area inside a miniaturized/thin layered electronic device, heat is generated inside the device, and is stretched by the repulsive force of the adherend. , peeling, sagging, and deterioration of conductivity are unlikely to occur. Moreover, since it becomes unnecessary to compress an adhesive tape by members, such as a gasket, it is very useful also in order to implement|achieve new size reduction and thinning of an electronic device.

[Fig. 1] It is an electron micrograph of the filamentous nickel powder used in the Example.
[FIG. 2] It is an electron micrograph of the spike-like nickel powder used in the Example.
It is a schematic perspective view for demonstrating the measuring method of the repulsion-resistant electric resistance value in an Example.
It is a schematic sectional drawing for demonstrating the measuring method of the repulsion-proof electrical resistance value in an Example.

form for carrying out the invention

<Conductive pressure-sensitive adhesive composition>

The conductive adhesive composition of the present invention has a type 00 durometer hardness defined by ASTM D2240 of 15 or more at 85°C, preferably 20 to 90, and more preferably 25 to 70. This durometer hardness is a value measured immediately after storing a 6 mm-thick sample in the dryer at 85 degreeC for 1 hour, and specifically, as described in the Example mentioned later.

Since the conductive adhesive composition of the present invention has a high durometer hardness at high temperature (85° C.) compared with a conventional conductive adhesive composition, peeling and sagging are unlikely to occur even when tensioned by the repulsive force of an object to be adhered in a high-temperature environment. . In addition, like the conventional conductive adhesive tape, the adhesive layer is slightly elongated, the contact points between the conductive particles are reduced, the electrical resistance value becomes unstable, and the problem that the conductivity is remarkably lowered is also difficult to occur.

Generally, it cannot be said that the durometer hardness in room temperature and the durometer hardness in high temperature (85 degreeC) are necessarily proportional. This is because, specifically, the phenomenon that hardness decreases by heating varies depending on the type of material. Therefore, in order to improve the durometer hardness at high temperature (85 ° C), the type and blending amount of each component constituting the material are appropriately adjusted, not simply based on the durometer hardness at room temperature. , it becomes important to actually measure at a high temperature (85°C). The durometer hardness at a high temperature (85°C) of the conductive adhesive composition of the present invention is, for example, a component of the polymer chain of the acrylic copolymer (A). It can be adjusted by appropriately setting various conditions such as the type and ratio of the acrylic copolymer (A), the glass transition point (Tg) and molecular weight, the shape and blending amount of the conductive particles (B), and the type and blending amount of the crosslinking agent (C). can Moreover, you may adjust according to the kind and compounding quantity of an additive. More specifically, for example, as a component of the polymer chain of the acrylic copolymer (A), a relatively large amount of a component having a high glass transition point (Tg) is used, or the molecular weight of the acrylic copolymer (A) is increased, or , When the amount of the conductive particles (B) or the crosslinking agent (C) is relatively increased, or the addition amount of the component that is easily softened by heat is relatively decreased, the durometer hardness at high temperature (85°C) tends to increase. However, these methods are merely examples, and the present invention is not limited to the conductive pressure-sensitive adhesive composition obtained by adjusting the durometer hardness by these methods.

The electroconductive adhesive composition of this invention contains an acrylic copolymer (A) and electroconductive particle (B). The acrylic copolymer (A) is preferably contained as a base polymer in the composition. For example, when a silicone pressure sensitive adhesive is heated, a low molecular weight component may ooze out and workability|operativity, such as soldering, may be impaired, and a rubber type pressure sensitive adhesive deteriorates easily when heated. On the other hand, the acrylic pressure-sensitive adhesive is unlikely to cause such a problem. Electroconductive particle (B) is a component for providing electroconductivity to an adhesive composition.

The type of the acrylic copolymer (A) used in the present invention is not particularly limited, but (meth)acrylic acid alkyl ester (A1) having an alkyl group having 1 to 3 carbon atoms, (A1) having an alkyl group having 4 to 12 carbon atoms ( An acrylic copolymer comprising alkyl meth)acrylate (A2), a carboxyl group-containing monomer (A3), a hydroxyl group-containing monomer (A4), and vinyl acetate (A5) as constituents of a polymer chain is preferable. The durometer hardness in high temperature (85 degreeC) of the electroconductive adhesive composition of this invention can be adjusted by changing the specific kind and ratio of each of these components (A1) - (A4) suitably.

As a specific example of (meth)acrylic-acid alkylester (A1), methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate are mentioned. Especially, methyl (meth)acrylate is preferable. The content of the (meth)acrylic acid alkylester (A1) is preferably 20% by mass or less, more preferably 16% by mass or less, and particularly preferably 20% by mass or less, among 100% by mass of the constituents (monomer units) of the acrylic copolymer (A). Usually, it is 2-15 mass %.

As a specific example of (meth)acrylic acid alkylester (A2), butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate Acrylate, isononyl (meth)acrylate, and lauryl (meth)acrylate are mentioned. Especially, butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferable. Content of (meth)acrylic acid alkylester (A2) is in 100 mass % of structural components (monomer unit) of acrylic copolymer (A), Preferably it is 50-97 mass %, More preferably, it is 65-90 mass %. am.

Specific examples of the carboxyl group-containing monomer (A3) include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-carboxy-1-butene, 2-carboxy-1-pentene, and 2-carboxy-1. -Hexene and 2-carboxy-1-heptene are mentioned. Especially, acrylic acid and methacrylic acid are preferable, and acrylic acid is more preferable. The content of the carboxyl group-containing monomer (A3) is preferably 3% by mass or more, more preferably 3.5 to 15% by mass, particularly preferably in 100% by mass of the constituent (monomer unit) of the acrylic copolymer (A). is 7 to 12 mass %.

Specific examples of the hydroxyl group-containing monomer (A4) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer (A4) is preferably 0.01 to 2 mass%, more preferably 0.05 to 0.5 mass%, in 100 mass% of the constituents (monomer units) of the acrylic copolymer (A).

Content of vinyl acetate (A5) is in 100 mass % of structural components (monomer unit) of acrylic copolymer (A), Preferably it is 5 mass % or less, More preferably, it is 1-4 mass %.

The polymerization method for obtaining the acrylic copolymer (A) is not particularly limited, but radical solution polymerization is preferred from the viewpoint of easy polymer design. Moreover, you may prepare first the acrylic syrup which consists of an acrylic copolymer (A) and its monomer, and mix|blend a crosslinking agent (B) and an additional photoinitiator to this acrylic syrup, and it may superpose|polymerize.

In manufacture of an acrylic copolymer (A), you may copolymerize monomers other than component (A1) - (A5) in the range which does not impair the effect of this invention.

The weight average molecular weight of the acrylic copolymer (A) is preferably 450,000 or more, more preferably 500,000 to 1.8 million, particularly preferably 550,000 to 1.5 million. This weight average molecular weight is a value measured by GPC method. By changing the weight average molecular weight of an acrylic copolymer (A) suitably, the durometer hardness in high temperature (85 degreeC) of the electroconductive adhesive composition of this invention can be adjusted.

The theoretical Tg of the acrylic copolymer (A) is preferably -55°C or less, more preferably -75°C to -57°C. This theory Tg is a value calculated by the formula of FOX. By changing Tg of an acrylic copolymer (A) suitably, the durometer hardness in high temperature (85 degreeC) of the electroconductive adhesive composition of this invention can be adjusted.

In this invention, although an acrylic copolymer (A) is used at least as a resin component, within the range which does not impair the effect of this invention, you may use together other types of additive resin components. Specific examples include tackifying resins such as rosin tackifiers, terpene resins, petroleum resins, terpene phenol resins, and styrene resins.

The electroconductive particle (B) in particular used for this invention is not restrict|limited, Well-known electroconductive particle which can be used for an electroconductive adhesive composition can be used. Specific examples include metal particles, carbon particles, and graphite particles composed of metals such as nickel, copper, chromium, gold and silver, or alloys or modified products thereof. Moreover, the electroconductive resin particle which coat|covered the metal on the resin surface can also be used. You may use together 2 or more types of electroconductive particle. Especially, a metal particle is preferable, a nickel particle and a copper particle are more preferable, and a nickel particle is the most preferable.

The shape in particular of electroconductive particle (B) is not restrict|limited, Electroconductive particle of well-known shapes, such as a filament form, a spike form, a flake form, and a spherical shape, can be used. Especially, since the contact point of electroconductive particle increases easily and an electrical resistance value is stabilized, a filamentous shape, a spike shape, and a flake shape are preferable, and a filamentous shape and a spike shape are more preferable. The size in particular of electroconductive particle (B) is not restrict|limited, What is necessary is just to use the thing of a well-known size.

To [ the compounding quantity of electroconductive particle (B) / 100 mass parts of acrylic copolymer (A)), Preferably it is 2 mass parts or more, More preferably, it is 3-100 mass parts, Especially preferably, it is 5-75 mass parts. By changing the compounding quantity of electroconductive particle (B) suitably, the durometer hardness in high temperature (85 degreeC) of the electroconductive adhesive composition of this invention can be adjusted.

It is preferable that the electroconductive adhesive composition of this invention contains a crosslinking agent (C) further. The crosslinking agent (C) is a compound blended in order to react with the acrylic copolymer (A) to form a crosslinked structure. In particular, a compound capable of reacting with a carboxyl group and/or a hydroxyl group of the acrylic copolymer (A) is preferable, and an isocyanate-based crosslinking agent is more preferable. Specific examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and modified prepolymers thereof. These may use 2 or more types together.

The blending amount of the crosslinking agent (C) is preferably 0.02 to 2 parts by mass or more, more preferably 0.03 to 1 part by mass, particularly preferably 0.3 to 0.9 parts by mass with respect to 100 parts by mass of the acrylic copolymer (A). . By changing the compounding quantity of a crosslinking agent (C) suitably, the durometer hardness in high temperature (85 degreeC) of the electroconductive adhesive composition of this invention can be adjusted.

The conductive adhesive composition of this invention may contain additives, such as a silane coupling agent, antioxidant, and a rust preventive agent, as needed.

As a silane coupling agent, especially the silane coupling agent containing a glycidyl group is preferable. Specific examples include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethane. oxysilane, tris(trimethoxysilylpropyl)isocyanurate, etc. are mentioned. These may use two or more types together. To [ the compounding quantity of a silane coupling agent / 100 mass parts of acrylic copolymer (A) ], Preferably it is 0.01-0.5 mass part, More preferably, it is 0.02-0.5 mass part, Especially preferably, it is 0.03-0.3 mass part.

As the antioxidant, a hindered phenol-based antioxidant is particularly preferable. To [ the compounding quantity of antioxidant / 100 mass parts of acrylic copolymer (A) ], Preferably it is 0.01-1 mass part, More preferably, it is 0.02-0.5 mass part.

As a rust preventive agent, an imidazole type compound, a triazole type compound, a tetrazole type compound, and a thiadiazole type compound can be used, for example. Especially, a triazole type compound is preferable. Specific examples of the triazole-based compound include benzotriazole, 1-aminobenzotriazole, and 5-aminobenzotriazole. In particular, benzotriazole is preferable. Preferably the compounding quantity of a rust preventive agent (F) is 0.1-10 mass parts with respect to 100 mass parts of acrylic copolymer (A), More preferably, it is 0.3-5 mass parts, Especially preferably, it is 0.5-3 mass parts.

The conductive adhesive composition of this invention may contain other additives other than the silane coupling agent demonstrated above, antioxidant, and a rust preventive agent as needed. Specifically, for example, a tackifier, a plasticizer, a softener, a metal deactivator, and a pigment can be added for which it is known that it can be added to this type of electroconductive adhesive composition. And the durometer hardness in high temperature (85 degreeC) of the electroconductive adhesive composition of this invention can be adjusted by changing the kind and addition amount of various additives suitably.

<Conductive adhesive tape>

The electroconductive adhesive tape of this invention has the adhesive layer formed with the electroconductive adhesive composition of this invention on the single side|surface or both surfaces of an electroconductive base material. The electroconductivity of this base material also contributes to the effect of suppressing electrostatic charging and the effect of shielding electromagnetic waves. As the conductive substrate, a metal substrate (especially metal foil), a conductive nonwoven fabric substrate, or a conductive fabric substrate are preferable. Specific examples of the metal constituting the conductive substrate include copper, aluminum, nickel, stainless steel, iron, chromium, and titanium. Among them, copper and aluminum are preferable, and copper is most preferable. The thickness of the conductive substrate is preferably 3 to 50 µm, more preferably 5 to 35 µm, and particularly preferably 6 to 20 µm.

The thickness of an adhesive layer becomes like this. Preferably it is 2-100 micrometers, More preferably, it is 3-50 micrometers, Especially preferably, it is 5-30 micrometers, Most preferably, it is 7-20 micrometers. An adhesive layer may be formed only on the single side|surface of an electroconductive base material, and it is good also as a double-sided adhesive tape by forming in both surfaces.

An adhesive layer can be formed by crosslinking-reacting the electroconductive adhesive composition of this invention. For example, a conductive adhesive composition may be applied on a conductive substrate and cross-linked by heating to form a pressure-sensitive adhesive layer on the conductive substrate. Moreover, an electrically conductive adhesive composition is apply|coated on a release paper or another film, it is crosslinked by heating, an adhesive layer is formed, and this adhesive layer can also be bonded together on the single side|surface or both surfaces of an electroconductive base material. Coating apparatuses, such as a roll coater, a die coater, and a lip coater, can be used for application|coating of an electroconductive adhesive composition, for example. When heating after application|coating, the solvent in an electroconductive adhesive composition can also be removed together with the crosslinking reaction by heating.

The electroconductive adhesive composition of this invention is very useful as a material for forming the adhesive layer of the electroconductive adhesive tape which has an electroconductive base material and an adhesive layer as demonstrated above. However, the use of the conductive pressure-sensitive adhesive composition of the present invention is not limited thereto. For example, the conductive pressure-sensitive adhesive composition of the present invention may be molded on a sheet and used as a baseless type pressure-sensitive adhesive sheet, or may be dissolved in a solvent and applied as a liquid pressure-sensitive adhesive or adhesive.

Example

Hereinafter, the present invention will be described in more detail by way of Examples and Comparative Examples. In the following description, "part" means parts by mass, and "%" means % by mass.

<Production Examples 1 to 5 (Preparation of acrylic copolymer (A))>

In a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas introduction tube, the components (A1) to (A5) in the amounts (%) shown in Table 1, ethyl acetate, n-dodecanthiol and peroxide as a chain transfer agent 0.1 part of lauryl peroxide was charged as a system radical polymerization initiator. Nitrogen gas was enclosed in the reactor, and polymerization was carried out at 68°C for 3 hours and then at 78°C for 3 hours under a nitrogen gas stream while stirring. Then, it cooled to room temperature, and ethyl acetate was added. Thereby, the acrylic copolymer (A) of the theoretical Tg, weight average molecular weight (Mw), and a density|concentration shown in Table 1 was obtained.

The weight average molecular weight (Mw) of an acrylic copolymer (A) is the value which measured the molecular weight of the standard polystyrene conversion of an acrylic copolymer by the GPC method on the following measuring apparatus and conditions.

・Apparatus: LC-2000 series (manufactured by Nippon Bunko Co., Ltd.)

·Column: Shodex　KF-806MХ2ea, Shodex　KF-802Х1ea

·Eluent: tetrahydrofuran (THF)

・Flow rate: 1.0 mL/min

・Column temperature: 40℃

・Injection amount: 100 μL

・Detector: Refractometer (RI)

-Measurement sample: An acrylic polymer was dissolved in THF, a solution having an acrylic polymer concentration of 0.5% by mass was prepared, and dust was removed by filtration with a filter.

The theoretical Tg is a value computed by the formula of FOX.

The abbreviation in Table 1 shows the following compounds.

"MA": methyl acrylate

"2-EHA": 2-ethylhexyl acrylate

"BA": n-butyl acrylate

"AA": acrylic acid

"4-HBA": 4-hydroxybutyl acrylate

"HEMA": 2-hydroxyethyl methacrylate

"2-EHA": 2-hydroxyethyl acrylate

"Vac": Vinyl acetate

<Example 1>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 1, the electroconductive particle (B1) and the crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared.

This electroconductive adhesive composition was apply|coated so that the thickness of the adhesive layer after drying might be set to 16 micrometers on the silicone-treated release liner. Subsequently, the solvent was removed and dried at 110 degreeC, and it was made to crosslinking-react, and the adhesive layer was formed. This pressure-sensitive adhesive layer was bonded to the glossy surface side of 18 µm-thick electrodeposited copper foil (manufactured by Fukude Kinzoku Hakubun Kogyo Co., Ltd., trade name: CF-T9FZ-STD-18). And it was made to cure at 40 degreeC for 3 days, and the electroconductive adhesive tape was obtained.

<Example 2>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 2, the electroconductive particle (B1) and the crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape (however, the thickness of an adhesive layer is 15 micrometers).

<Example 3>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 3, the electroconductive particle (B1) and the crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape.

<Example 4>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 4, the electroconductive particle (B1) and the crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape (however, the thickness of an adhesive layer is 17 micrometers).

<Example 5>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 5, the electroconductive particle (B1) and the crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape (however, the thickness of an adhesive layer is 17 micrometers).

<Example 6>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 1, the electroconductive particle (B2) and a crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape.

<Example 7>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 1, the electroconductive particle (B3) and a crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape (however, the thickness of an adhesive layer is 17 micrometers).

<Comparative Example 1>

With respect to 100 parts of solid content of the acrylic copolymer (A) obtained in manufacture example 5, the electroconductive particle (B1) and the crosslinking agent (C) were added and mixed in the quantity (part) shown in Table 2, and the electroconductive adhesive composition was prepared. And it carried out similarly to Example 1, and obtained the electroconductive adhesive tape (however, the thickness of an adhesive layer is 17 micrometers).

The durometer hardness of each electroconductive adhesive composition of the above Examples 1-7 and the comparative example 1 was measured with the following method. A result is shown in Table 2.

(Durometer hardness of the conductive adhesive composition)

The conductive adhesive composition was apply|coated on the silicone-treated release liner so that the thickness after drying might be set to 50 micrometers. Subsequently, the solvent was removed and dried at 110°C, and cross-linking reaction was carried out at the same time to form a pressure-sensitive adhesive layer and cured at 40°C for 3 days. After curing, this was laminated until the thickness became 6 mm, and it was set as the measurement sample. This 6mm-thick sample was stored in an environment of 23°C, and the Type 00 durometer hardness (23°C) specified in ASTM D 2240 was measured. In addition, the sample was stored in a dryer at 85° C. for 1 hour, and the type 00 durometer hardness (85° C.) specified in ASTM D 2240 was measured.

The symbol in Table 2 shows the following electroconductive particle or compound.

"B1": filamentary nickel powder (manufactured by NOVAMET, trade name nickel powder 525LD, Fig. 1 is an electron micrograph of this filamentary nickel powder B1.)

"B2": spike-like nickel powder (manufactured by VALE, trade name nickel powder TYPE123, Fig. 2 is an electron micrograph of this spike-like nickel powder B2.)

"B3": flaky nickel powder (product made by NOVAMET, brand name HCA-1)

"C1": isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name Colonate (registered trademark) L-45E (solid content concentration: 45%)))

<Evaluation test>

The following method evaluated the electrical resistance value of the electroconductive adhesive tape obtained by the Example and the comparative example. A result is shown in Table 3.

(Repulsion resistance electric resistance value)

As shown in Fig. 3(A), the conductive adhesive tape 1 cut to a width of 20 mm and a length of 60 mm is placed on the resin plate 2 having a size of 40 mm × 40 mm with the pressure-sensitive adhesive layer 1b side facing up. fixed A double-sided tape (not shown) was used for this fixing. Next, as shown in FIG.3(B), the protrusion part (20mm) of the electroconductive adhesive tape 1 was folded back upward. In this folding-back part, the electroconductive base material 1a (copper foil) becomes the top. Next, as shown in FIG.3(C), the insulating tape 3 of 10 mm width was affixed on the upper half of the electroconductive adhesive tape 1. As shown in FIG. Next, as shown in FIG.3(D), it fixed under the resin board 2 so that the tape-shaped laminated body 4 of width 10mm and length 80mm might be protruded 20 mm at a time. This tape-shaped laminated body 4 was obtained by pasting up 50-micrometer-thick aluminum foil and a 125-micrometer-thick polyimide film with a 50-micrometer-thick double-sided tape. Double-sided tape (not shown) was used for this fixation, and it fixed so that the aluminum foil 4a side might become up. Next, as shown in Fig. 3(E), one side of the tape-like laminate 4 is folded back to the upper side, and the end of the aluminum foil 4a of the tape-like laminate 4 is attached to the conductive adhesive tape ( It was affixed to the adhesive layer 1b of 1) (a bonding area = 5 mm x 10 mm), and it crimped|bonded with a 2 kg roller. And the aluminum foil 4a of the tape-shaped laminated body 4 and the electroconductive base material 1a (copper foil) of the electroconductive adhesive tape 1 were connected to the tester terminal 5, respectively.

In the test body produced as mentioned above, as shown in FIG. 4, the edge part of the aluminum foil 4a of the tape-like laminated body 4, and the adhesive layer 1b of the electroconductive adhesive tape 1 are affixed. And the bending angle of the tape-like laminated body 4 is severe, and it is in the state which the force which stretches the adhesive layer 1b upward by the repulsive force was applied.

Immediately after the end of the aluminum foil 4a and the pressure-sensitive adhesive layer 1b are adhered (immediately after compression with a 2 kg roller), the voltage is adjusted so that a current of 0.1 A flows, R (resistance value) = V (voltage) / From the formula of I (current), the electrical resistance value (mΩ) of the pressure-sensitive adhesive layer 1b immediately after sticking was calculated. Thereafter, an acceleration test was performed at 85° C. for 24 hours, and the electrical resistance value (mΩ) was calculated in the same manner. However, at the time point 24 hours after the acceleration test, compression with a 2 kg roller was not performed.

As is clear from the results shown in Table 3, the conductive adhesive tapes of Examples 1 to 7 were 85° C. in a state in which a force to stretch the pressure-sensitive adhesive layer 1b in the thickness direction was applied by the repulsive force of the tape-like laminate 4 . Even when the accelerated test was conducted for 24 hours, the increase in the electrical resistance value was small. That is, in the conductive adhesive tapes of Examples 1 to 7, peeling or sagging did not occur even when exposed for a long time (24 hours) under high temperature (85° C.) in a narrow adhesion area (5 mm × 10 mm), and the decrease in conductivity was also small. all.

On the other hand, in the conductive adhesive tape of Comparative Example 1, since the adhesive layer was formed of a conductive adhesive composition having a low durometer hardness at 85 ° C., sagging occurs in the adhesive layer after the acceleration test, and the increase in electrical resistance value increases. , the conductivity decreased significantly.

Industrial Applicability

The electroconductive adhesive composition of this invention is very useful as a material for forming the adhesive layer of an electroconductive adhesive tape. The electroconductive adhesive tape which has such an adhesive layer is useful for the use of the electromagnetic wave shield for preventing the bad influence of the static electricity in the inside of an electronic device, or an electromagnetic wave, for example. Moreover, it is suitable for the use which is requested|required that peeling, sagging, and a fall of electroconductivity do not generate|occur|produce easily even if it is tension|tensile|stretched by the internal repulsive force. Specifically, for example, among various portable electronic devices such as mobile phones, smart phones, wearable terminals, tablets, car navigation systems, cameras, audio-visual devices, game devices, and information devices, it is suitable for the absence of miniaturized and thin-filmed electronic devices. can be used

1 Conductive adhesive tape
1a conductive substrate
1b adhesive layer
2 resin plate
3 Insulation tape
4 Tape-like laminate
4a aluminum foil
5 tester terminals

Claims (7)

A conductive pressure-sensitive adhesive composition containing an acrylic copolymer (A), conductive particles (B), and a crosslinking agent (C), and having a Type 00 durometer hardness defined in ASTM D 2240 of 15 or more at 85°C,
Acrylic copolymer (A) has (meth)acrylic acid alkyl ester (A1) which has a C1-C3 alkyl group, (meth)acrylic acid alkylester (A2) which has a C4-C12 alkyl group, carboxyl group A monomer containing (A3) and a monomer containing a hydroxyl group (A4) are included as constituents of a polymer chain,
The weight average molecular weight of the acrylic copolymer (A) is 750,000 or more,
In 100 mass % of the constituents (monomer unit) of the acrylic copolymer (A), 2 to 20 mass % of (meth)acrylic acid alkylester (A1) having an alkyl group having 1 to 3 carbon atoms, 4 to 12 carbon atoms 50-97 mass % of (meth)acrylic acid alkylester (A2) having an alkyl group of
0.02-1 mass part of crosslinking agent (C) is contained with respect to 100 mass parts of acrylic copolymer (A), The electrically conductive adhesive composition characterized by the above-mentioned. The method according to claim 1,
The electroconductive adhesive composition whose shape of electroconductive particle (B) is filamentous form, spike form, or flake form. The method according to claim 1,
The conductive adhesive composition in which the acrylic copolymer (A) contains 3 mass % or more of a carboxyl group containing monomer as a structural component of a polymer chain. The method according to claim 1,
The electroconductive adhesive composition whose theoretical Tg of an acrylic copolymer (A) is -55 degreeC or less. The conductive adhesive tape which has the adhesive layer formed by the conductive adhesive composition of Claim 1 on the single side|surface or both surfaces of an electroconductive base material. 6. The method of claim 5,
A conductive adhesive tape used for electromagnetic shielding or grounding in electronic devices. delete

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