TW201800531A - Conductive adhesive composition and conductive adhesive tape - Google Patents

Abstract

Disclosed are: a conductive adhesive composition comprising an acrylic copolymer (A) and conductive particles (B), wherein the conductive adhesive composition has a type OO durometer hardness according to ASTM D 2240 of 15 or more at 85 DEG C, and peeling, stringing and degradation of conductivity hardly occur even if the conductive adhesive composition is pulled by the repulsive force of an adherend in a high temperature environment; and a conductive adhesive tape having an adhesive layer formed by the conductive adhesive composition.

Description

Conductive adhesive composition and conductive adhesive tape

The present invention relates to a conductive adhesive composition which is less likely to cause peeling, drawing, and conductivity degradation even when stretched by a repulsive force of a laminate in a high-temperature environment, and a conductive adhesive tape using the conductive adhesive. More specifically, it relates to a conductive adhesive tape which is useful, for example, in the application of electromagnetic wave shielding or grounding inside an electronic device.

In an electronic device, there is a case where a component malfunctions or a material is broken due to an adverse effect of static electricity or electromagnetic waves. There is a method of using a conductive adhesive tape for parts inside the machine for the purpose of preventing such adverse effects. Specifically, it is known that a conductive adhesive tape in which a metal foil is used as a substrate and conductive particles are added to an adhesive layer is useful for electromagnetic wave shielding or grounding. In such a conductive adhesive tape, conductivity and adhesion are important properties, and various proposals have been made to improve the performance.

Patent Document 1 discloses a conductive adhesive tape having a specific thickness of an adhesive layer containing 14 to 45 parts by weight of a spherical and/or sharp conductive filler having an aspect ratio of 1.0 to 1.5. Further, unlike the adhesive tapes of the comparative examples in which a long-line conductive filler or a sheet-like conductive filler is used, the adhesive tape is excellent in adhesion and conductivity when the adhesive layer is formed into a thin film. Further, it has step absorption.

Patent Document 2 discloses a conductive thin adhesive sheet comprising conductive particles having a particle diameter d50 of 4 to 12 μm and d85 of 6 to 15 μm, and an adhesive layer having a thickness of 6 to 12 μm. Further, the adhesive sheet is excellent in adhesiveness and electrical conductivity even when it is thin, and is excellent in productivity.

Patent Document 3 discloses a conductive adhesive tape in which the thickness t (μm) of the adhesive layer and the particle diameter d50 (μm) of the conductive particles have a relationship of t < d50, and the adhesive force of the adhesive layer is 4N. /20mm or more. Moreover, the adhesive tape has a stable electrical conductivity when used over a long period of time or under severe environmental conditions, thereby maintaining the adhesiveness in consideration of workability.

Patent Document 4 discloses a conductive adhesive tape having a ratio t/d50 of a thickness t (μm) of the adhesive layer to a particle diameter d50 (μm) of the conductive particles of 0.2 or more and 4.0 or less. Moreover, the adhesive tape is also stable in electrical conductivity when used over long periods of time or under harsh environmental conditions.

However, in recent years, electronic devices have been in a tendency to be further miniaturized and thinned. For example, information machines such as mobile phones, smart phones, and wearable terminals are becoming thinner and smaller. As a result, the parts constituting the information machines are also reduced, and the attachment area of the adhesive tape is also narrowed. Further, in an electronic device that is miniaturized or thinned, there are many cases in which, for example, a flexible printed circuit (FPC) which is one of the components is bent and arranged in a very narrow space, and the bending angle is changed. Sharp angle.

If the attachment area is narrow and the bending angle of the FPC is an acute angle, the adhesive tape cannot be subjected to the rebound force of the FPC and peeled off, or the drawing is performed (the adhesive layer is pulled to partially produce a plurality of filament-like shapes) After that. Further, if the adhesive layer is softened by heat generated inside the electronic device (for example, heat generation of the battery), the possibility of peeling or drawing of the adhesive tape becomes higher. Further, for example, even if peeling or pulling does not occur In the wire, the contact layer of the conductive particles is reduced only because the adhesive layer is slightly pulled, the resistance value becomes unstable, and the conductivity is lowered.

On the other hand, if a load is applied to the conductive adhesive tape inside the machine by a member such as a spacer, it becomes difficult to cause such a problem. Further, when the adhesive layer is compressed, the conductive particles are increased in contact with each other to exhibit a stable resistance value. However, in a machine that is further miniaturized or thinned, it is difficult to provide a member such as a spacer for a small size of each component, and it is difficult to apply a load when the surface has irregularities. Moreover, in the case where the part is thin, if a strong load is applied, there is a possibility of breakage.

In Patent Documents 1 to 4, no research has been conducted on the problem caused by the repulsive force of the composite when heat is generated inside the machine. For example, Patent Document 1 uses sharp-pointed or spherical conductive particles in the examples, and in the comparative example, the resistance value of the adhesive tape using long-line or sheet-like conductive particles is measured in a normal state (Patent Document 1) Paragraph [0067]). In Patent Document 2, the resistance value of the pressure-sensitive adhesive sheet was measured at 23 ° C while applying a surface pressure of 20 N (Patent Document 2 [0078]). In Patent Documents 3 and 4, the resistance value of the sample is measured after the temperature is raised by 85 ° C × 85% RH or after the temperature is raised and lowered in the range of -40 ° C to 85 ° C, but the sample is 0.1 MPa. The pressure is applied to a laminate having an evaluation substrate/EV vinyl oxide (EVA) film/glass plate to which an adhesive tape is bonded, and the EVA is thermally cured to obtain a substrate. The upper adhesive tape is fixed to the glass plate in a compressed state (paragraph [0117] of Patent Document 3, paragraph [0107] of Patent Document 4).

In other words, in Patent Documents 1 to 4, no research has been conducted on the following aspects: the conductive property is bonded to a narrower area in an electronic device that is miniaturized or thinned. When the adhesive tape is applied to the inside of the machine, the FPC or the like is peeled off or drawn by the rebound force of the adhesive composition; or the adhesive layer is slightly pulled due to the rebound force of the FPC or the like, and the resistance value is changed. It is unstable. Moreover, conventional conductive adhesive tapes are difficult to solve such problems.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open Publication No. 2009-79127

Patent Document 2: Japanese Patent Laid-Open Publication 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 adhesive composition which is less likely to cause peeling, drawing, and electrical conductivity to be stretched by a repulsive force of a laminate in a high-temperature environment, and an adhesive tape using the same.

The present invention relates to a conductive adhesive composition comprising an acrylic copolymer (A) and conductive particles (B), which is specified in ASTM (American Society for Testing and Materials) D 2240. The hardness of the durometer is 15 or more at 85 °C.

Further, the present invention relates to a conductive adhesive tape having an adhesive layer formed of the conductive adhesive composition on one surface or both surfaces of a conductive substrate.

According to the present invention, it is possible to provide a conductive adhesive composition which is less likely to be peeled, drawn, and lowered in electrical conductivity even when stretched by a repulsive force of a laminate in a high-temperature environment. The conductive adhesive composition is very useful as a material for forming an adhesive layer of a conductive adhesive tape. The conductive adhesive tape having such an adhesive layer is bonded to a small-sized, thin-layered electronic device, for example, in a narrow area, generates heat inside the machine, and is stretched by the rebound force of the adhesive composition. In the case of the case, peeling, drawing, and conductivity are also less likely to occur. Further, since it is not necessary to compress the adhesive tape by a member such as a spacer, it is also very useful for further miniaturization and thinning of the electronic device.

1‧‧‧ Conductive adhesive tape

1a‧‧‧ Conductive substrate

1b‧‧‧Adhesive layer

2‧‧‧resin board

3‧‧‧Insulation tape

4‧‧‧Striped layered body

4a‧‧‧Aluminum foil

5‧‧‧Measurement machine terminals

Fig. 1 is an electron micrograph of a long-line nickel powder used in the examples.

Figure 2 is an electron micrograph of a sharp nickel powder used in the examples.

3(A) to (E) are schematic perspective views for explaining a method of measuring the rebound resistance resistance value of the embodiment.

Fig. 4 is a schematic cross-sectional view for explaining a method of measuring the rebound resistance resistance value of the embodiment.

<Conductive Adhesive Composition>

The conductive adhesive composition of the present invention is a composition having a hardness of OO type hardness as defined in ASTM D 2240 of 15 or more at 85 ° C, preferably 20 to 90, more preferably 25 to 70. Specifically, the hardness of the durometer is as follows: a sample having a thickness of 6 mm is dried in a dryer at 85 ° C as described in the examples below. Stored for 1 hour, and immediately after measurement.

The conductive adhesive composition of the present invention has a hardness tester at a high temperature (85 ° C) higher than that of the conventional conductive adhesive composition, and therefore stretches even in a high temperature environment due to the repulsive force of the bonded object. Peeling and drawing are difficult to occur. Further, it is also difficult to cause a problem that the adhesive layer is slightly pulled as in the conventional conductive adhesive tape, and the contact points of the conductive particles are reduced, the resistance value becomes unstable, and the electrical conductivity is remarkably lowered.

Generally, the durometer hardness at room temperature and the durometer hardness at high temperature (85 ° C) are not necessarily limited to a proportional relationship. The reason for this is that, in particular, the phenomenon in which the hardness is lowered by heating varies depending on the type of the material. Therefore, in order to improve the hardness of the durometer at a high temperature (85 ° C), it is important to appropriately adjust the kind or amount of each component of the constituent material and actually measure at a high temperature (85 ° C), instead of simply at room temperature. The hardness of the hardness meter below is standard. For example, the type or ratio of the constituent components of the polymer chain of the acrylic copolymer (A), the glass transition point (Tg) of the acrylic copolymer (A), the molecular weight, and the conductive particles (B) can be appropriately set. The hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention is adjusted under various conditions such as the shape, the blending amount, the kind of the crosslinking agent (C), and the blending amount. Further, it may be adjusted depending on the type of the additive or the amount of the additive. More specifically, for example, a constituent component in which the glass transition point (Tg) becomes high is used as a constituent component of the polymer chain of the acrylic copolymer (A), and the molecular weight of the acrylic copolymer (A) is changed. When the amount of the conductive particles (B) or the crosslinking agent (C) is relatively high, or the amount of the component which is easily softened by heat is relatively small, the hardness of the hardness is changed at a high temperature (85 ° C). High tendency. However, these methods are always exemplified, and the present invention is not limited to the conductive adhesive composition obtained by adjusting the hardness of the durometer by the methods.

The conductive adhesive composition of the present invention contains an acrylic copolymer (A) and conductive particles (B). The acrylic copolymer (A) preferably contains a base polymer as a composition. For example, when the polyoxygen-based adhesive is heated, the low-molecular-weight component bleeds out and the workability such as welding is inhibited, and the rubber-based adhesive is easily deteriorated when heated. On the other hand, acrylic adhesives are difficult to cause such problems. The conductive particles (B) are components for imparting conductivity to the adhesive composition.

The type of the acrylic copolymer (A) to be used in the present invention is not particularly limited, and is preferably an alkyl (meth)acrylate (A1) having an alkyl group having 1 to 3 carbon atoms and having a carbon atom. The alkyl (meth)acrylate (A2) having 4 to 12 alkyl groups, the carboxyl group-containing monomer (A3), the hydroxyl group-containing monomer (A4), and vinyl acetate (A5) are contained as a polymer. An acrylic copolymer of constituent components of the chain. The hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention can be adjusted by appropriately changing the specific type or ratio of the components (A1) to (A4).

Specific examples of the alkyl (meth)acrylate (A1) include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. Among them, methyl (meth)acrylate is preferred. The content of the alkyl (meth)acrylate (A1) is preferably 20% by mass or less, more preferably 16% by mass or less, based on 100% by mass of the constituent component (monomer unit) of the acrylic copolymer (A). Particularly good is 2 to 15% by mass.

Specific examples of the alkyl (meth)acrylate (A2) include butyl (meth)acrylate, isobutyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Octyl acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate. Among them, preferred is butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. The content of the alkyl (meth)acrylate (A2) is preferably from 50 to 97% by mass, more preferably 100% by mass of the constituent component (monomer unit) of the acrylic copolymer (A). It is 65 to 90% by mass.

Specific examples of the carboxyl group-containing monomer (A3) include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and 2-carboxy-1-butene. 2-carboxy-1-pentene, 2-carboxy-1-hexene, 2-carboxy-1-heptene. Among them, acrylic acid, methacrylic acid, and more preferably acrylic acid are 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 100% by mass of the constituent component (monomer unit) of the acrylic copolymer (A). It is 7 to 12% by 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) in 100% by mass of the constituent component (monomer unit) of the acrylic copolymer (A) is preferably 0.01 to 2% by mass, more preferably 0.05 to 0.5% by mass.

The content of the vinyl acetate (A5) in the component (monomer unit) of the acrylic copolymer (A) is preferably 5% by mass or less, more preferably 1 to 4% by mass.

The polymerization method for obtaining the acrylic copolymer (A) is not particularly limited, but in terms of the ease of designing the polymer, radical polymerization is preferred. Further, first, an acrylic syrup containing an acrylic copolymer (A) and a monomer thereof may be prepared, and a crosslinking agent (B) and an additional photopolymerization initiator may be added to the acrylic syrup to be polymerized.

When the acrylic copolymer (A) is produced, monomers other than the components (A1) to (A5) may be copolymerized in a range that does not impair the effects of the present invention.

The weight average molecular weight of the acrylic copolymer (A) is preferably 450,000 or more, more preferably 500,000 to 1.8,000,000, and particularly preferably 550,000 to 1,500,000. The weight average The molecular weight is a value measured by a gel permeation chromatography (GPC, Gel Permeation Chromatography) method. The hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention can be adjusted by appropriately changing the weight average molecular weight of the acrylic copolymer (A).

The theoretical Tg of the acrylic copolymer (A) is preferably -55 ° C or lower, more preferably -75 ° C to -57 ° C. The theoretical Tg is a value calculated by the formula of FOX (Fox). The hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention can be adjusted by appropriately changing the Tg of the acrylic copolymer (A).

In the present invention, at least the acrylic copolymer (A) is used as the resin component, but other types of added resin components may be used in combination within the range not impairing the effects of the present invention. Specific examples thereof include an adhesive-imparting resin such as a rosin-based adhesion-imparting agent, a terpene resin, a petroleum-based resin, a terpene-phenol-based resin, and a styrene-based resin.

The conductive particles (B) to be used in the present invention are not particularly limited, and known conductive particles known to be used for the conductive adhesive composition can be used. Specific examples include metal particles, carbon particles, and graphite particles containing a metal such as nickel, copper, chromium, gold, or silver, an alloy or a modified product thereof. Further, conductive resin particles obtained by coating a metal surface with a resin may be used. Two or more kinds of conductive particles may also be used in combination. Among them, metal particles are preferred, and nickel particles and copper particles are more preferred, and nickel particles are most preferred.

The shape of the conductive particles (B) is not particularly limited, and conductive particles of a known shape such as a filament shape, a spike shape, a flake shape, or a spherical shape can be used. In particular, the conductive particles are likely to have a large number of contacts and a stable electric resistance value, and are preferably long-line, sharp, or flake-shaped, and more preferably long-line or sharp. The size of the conductive particles (B) is not particularly limited, and any known size may be used.

The amount of the conductive particles (B) is relative to the acrylic copolymer (A) 100 parts by mass, preferably 2 parts by mass or more, more preferably 3 to 100 parts by mass, particularly preferably 5 to 75 parts by mass. The hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention can be adjusted by appropriately changing the blending amount of the conductive particles (B).

The conductive adhesive composition of the present invention preferably further contains a crosslinking agent (C). The crosslinking agent (C) is a compound which is prepared by reacting with the acrylic copolymer (A) to form a crosslinked structure. In particular, a compound which can react with a carboxyl group and/or a hydroxyl group of the acrylic copolymer (A) is preferred, and an isocyanate crosslinking agent is more preferred. Specific examples of the isocyanate crosslinking agent include toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the modified prepolymer. These may also be used in combination of two or more types.

The amount of the crosslinking agent (C) is preferably 0.02 to 2 parts by mass, more preferably 0.03 to 1 part by mass, even more preferably 0.3 to 0.9 part by mass, per 100 parts by mass of the acrylic copolymer (A). . The hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention can be adjusted by appropriately changing the amount of the crosslinking agent (C).

The conductive adhesive composition of the present invention may further contain an additive such as a decane coupling agent, an antioxidant, or a rust preventive agent as needed.

As the decane coupling agent, a decane coupling agent containing a glycidyl group is particularly preferred. Specific examples thereof include 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane, 3-glycidoxypropyltrimethoxydecane, and 3-glycidoxypropylmethyl. Diethoxy decane, 3-glycidoxypropyltriethoxy decane, tris-(trimethoxydecylpropyl)isocyanurate, and the like. These may also be used in combination of two or more types. The blending amount of the decane coupling agent is preferably 0.01 to 0.5 parts by mass, more preferably 0.02 to 0.5 parts by mass, even more preferably 0.03 to 0.3 parts by mass, per 100 parts by mass of the acrylic copolymer (A).

As an antioxidant, a hindered phenol-based antioxidant is particularly preferred. The amount of the antioxidant is preferably 0.01 to 1 part by mass, more preferably 0.02 to 0.5 part by mass, per 100 parts by mass of the acrylic copolymer (A).

As the rust inhibitor, for example, an imidazole compound, a triazole compound, a tetrazole compound, or a thiadiazole compound can be used. Among them, a triazole compound is preferred. Specific examples of the triazole-based compound include benzotriazole, 1-aminobenzotriazole, and 5-aminobenzotriazole. In particular, benzotriazole is preferred. The amount of the rust inhibitor (F) is 100 parts by mass of the acrylic copolymer (A), preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, particularly preferably 0.5 to 3 parts by mass.

The conductive adhesive composition of the present invention may optionally contain other additives than the above-described decane coupling agent, antioxidant, and rust inhibitor. Specifically, for example, an adhesion-imparting agent, a plasticizer, a softener, a metal deactivator, and a pigment which are known to be added to the conductive adhesive composition of this type can be added. Further, the hardness of the durometer at a high temperature (85 ° C) of the conductive adhesive composition of the present invention can be adjusted by appropriately changing the kind or amount of various additives.

<Electrically conductive adhesive tape>

The conductive adhesive tape of the present invention has an adhesive layer formed of the conductive adhesive composition of the present invention on one or both sides of the conductive substrate. The conductivity of the substrate also contributes to suppressing the effect of electrostatic charging or shielding electromagnetic waves. The conductive substrate is preferably a metal substrate (particularly a metal foil), a conductive nonwoven substrate or a conductive cloth substrate. 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 preferred, and copper is preferred. The thickness of the conductive substrate is preferably from 3 to 50 μm, more preferably from 5 to 35 μm, particularly preferably from 6 to 20 μm.

The thickness of the adhesive layer is preferably 2 to 100 μm, more preferably 3 to 50 μm, particularly preferably 5 to 30 μm, and most preferably 7 to 20 μm. The adhesive layer may be formed only on one side of the conductive substrate, or may be formed on both sides to form a double-sided adhesive tape.

The adhesive layer can be formed by subjecting the conductive adhesive composition of the present invention to a crosslinking reaction. For example, the conductive adhesive composition can be applied onto a conductive substrate, and a crosslinking reaction can be carried out by heating to form an adhesive layer on the conductive substrate. Further, the conductive adhesive composition may be applied onto a release paper or another film, and a crosslinking reaction may be carried out by heating to form an adhesive layer, and the adhesive layer may be attached to one side of the conductive substrate. Or two sides. When the conductive adhesive composition is applied, for example, a coating device such as a roll coater, a die coater, or a lip coater can be used. In the case of heating after coating, a crosslinking reaction by heating is carried out, and the solvent in the conductive adhesive composition can also be removed.

The conductive adhesive composition of the present invention is very useful as a material for forming an adhesive layer of a conductive adhesive tape having a conductive substrate and an adhesive layer as described above. However, the use of the conductive adhesive composition of the present invention is not limited thereto. For example, the conductive adhesive composition of the present invention can be formed into a sheet form and used as a non-base type adhesive sheet, and can be dissolved in a solvent. It is applied as a liquid adhesive or an adhesive.

Example

Hereinafter, the present invention will be described in further detail by way of examples and comparative examples. In the following description, "parts" means parts by mass, and "%" means mass%.

<Production Examples 1 to 5 (Preparation of Acrylic Copolymer (A))>

Reaction device with mixer, thermometer, reflux cooler and nitrogen inlet tube The components (A1) to (A5) in an amount (%) shown in Table 1, ethyl acetate, n-dodecyl mercaptan as a chain transfer agent, and a peroxide radical polymerization initiator were added. Oxidized Laurel 0.1 part. The reaction apparatus was purged with nitrogen gas and stirred at 68 ° C for 3 hours under a nitrogen gas stream, and then polymerized at 78 ° C for 3 hours. Next, ethyl acetate was added until it cooled to room temperature. Thereby, the theoretical copolymer Tg, the weight average molecular weight (Mw) and the concentration of the acrylic copolymer (A) shown in Table 1 were obtained.

The weight average molecular weight (Mw) of the acrylic copolymer (A) is a value measured by a GPC method using a standard polystyrene-equivalent molecular weight of the acrylic copolymer by the following measuring apparatus and conditions.

‧Device: LC-2000 Series (manufactured by JASCO Corporation)

‧Tube: Shodex KF-806M×2, Shodex KF-802×1

‧ Eluent: Tetrahydrofuran (THF)

‧ Flow rate: 1.0mL / min

‧column temperature: 40 ° C

‧Injection amount: 100μL

‧Detector: Refractometer (RI)

‧ Measurement sample: A solution obtained by dissolving an acrylic polymer in THF to a concentration of 0.5% by mass of an acrylic polymer, and removing the dirt by filtration using a filter.

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

[Table 1] Table 1 (Production Examples 1 to 5 of Component (A))

The ellipsis in Table 1 indicates the following compounds.

"MA": Methyl acrylate

"2-EHA": 2-ethylhexyl acrylate

"BA": n-butyl acrylate

"AA": Acrylic

"4-HBA": 4-hydroxybutyl acrylate

"HEMA": 2-hydroxyethyl methacrylate

"2-EHA": 2-hydroxyethyl acrylate

"Vac": vinyl acetate

<Example 1>

The conductive particles (B1) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 1 to prepare a mixture. Conductive adhesive composition.

The conductive adhesive composition was applied to a polyfluorene-treated release liner so that the thickness of the dried adhesive layer became 16 μm. Next, the solvent was removed, dried at 110 ° C, and subjected to a crosslinking reaction to form an adhesive layer. This adhesive layer was bonded to the glossy side of an 18 μm thick electrolytic copper foil (manufactured by Fukuda Metal Foil Powder Co., Ltd., trade name: CF-T9FZ-STD-18). Next, curing at 40 ° C 3 A conductive adhesive tape is obtained in the day.

<Example 2>

The conductive particles (B1) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 2, and mixed. Conductive adhesive composition. Next, a conductive adhesive tape (wherein the thickness of the adhesive layer was 15 μm) was obtained in the same manner as in Example 1.

<Example 3>

The conductive particles (B1) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 3, and mixed to prepare a conductive layer. Adhesive composition. Next, a conductive adhesive tape was obtained in the same manner as in Example 1.

<Example 4>

The conductive particles (B1) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 4, and mixed. Conductive adhesive composition. Next, a conductive adhesive tape (wherein the thickness of the adhesive layer was 17 μm) was obtained in the same manner as in Example 1.

<Example 5>

The conductive particles (B1) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 5, and mixed. Conductive adhesive composition. Next, conductivity was obtained in the same manner as in Example 1. Adhesive tape (wherein the thickness of the adhesive layer is 17 μm).

<Example 6>

The conductive particles (B2) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 1 to prepare a mixture. Conductive adhesive composition. Next, a conductive adhesive tape was obtained in the same manner as in Example 1.

<Example 7>

The conductive particles (B3) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 1 to prepare a mixture. Conductive adhesive composition. Next, a conductive adhesive tape (wherein the thickness of the adhesive layer was 17 μm) was obtained in the same manner as in Example 1.

<Comparative Example 1>

The conductive particles (B1) and the crosslinking agent (C) in an amount (parts) shown in Table 2 were added to 100 parts of the solid content of the acrylic copolymer (A) obtained in Production Example 5, and mixed. Conductive adhesive composition. Next, a conductive adhesive tape (wherein the thickness of the adhesive layer was 17 μm) was obtained in the same manner as in Example 1.

The durometer hardness of each of the conductive adhesive compositions of Examples 1 to 7 and Comparative Example 1 was measured by the following method. The results are shown in Table 2.

(hardness hardness of conductive adhesive composition)

The conductive adhesive composition is coated in such a manner that the thickness after drying becomes 50 μm. To the polysilicon-treated release liner. Next, the solvent was removed, dried at 110 ° C, and subjected to a crosslinking reaction to form an adhesive layer, which was cured at 40 ° C for 3 days. After the curing, the adhesive was laminated to a thickness of 6 mm to prepare a measurement sample. The sample having a thickness of 6 mm was stored in an environment of 23 ° C, and the hardness of the OO type durometer (23 ° C) specified in ASTM D 2240 was measured. Further, the sample was stored in a dryer at 85 ° C for 1 hour, and the hardness of the OO type durometer (85 ° C) specified in ASTM D 2240 was measured.

The ellipses in Table 2 indicate the following conductive particles or compounds.

"B1": Long-line nickel powder (manufactured by NOVAMET Co., Ltd., trade name Nickel Powder 525LD, Fig. 1 is an electron microscope photograph of the long-line nickel powder B1.)

"B2": Sharp nickel powder (manufactured by VALE, trade name Nickel Powder TYPE123, Fig. 2 is an electron micrograph of the sharp nickel powder B2.)

"B3": flaky nickel powder (manufactured by NOVAMET, trade name HCA-1)

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

<evaluation test>

The electric resistance values of the conductive adhesive tapes obtained in the examples and the comparative examples were evaluated by the following methods. The results are shown in Table 3.

(resistance to rebound resistance)

As shown in Fig. 3(A), the conductive adhesive tape 1 cut into a width of 20 mm and a length of 60 mm was fixed to the resin plate 2 of 40 mm × 40 mm square with the adhesive layer 1b side as the upper side. A double-sided tape (not shown) is used for this fixing. Next, as shown in Fig. 3(B), the protruding portion (20 mm) of the conductive adhesive tape 1 was folded upward. The folded portion is made of a conductive substrate 1a (copper foil). Next, as shown in Fig. 3(C), an insulating tape 3 having a width of 10 mm is attached to the upper half of the conductive adhesive tape 1. Next, as shown in Fig. 3(D), the belt-shaped laminated body 4 having a width of 10 mm and a length of 80 mm was fixed to the lower side of the resin sheet 2 so as to protrude by 20 mm. The strip-shaped laminated body 4 was obtained by laminating an aluminum foil having a thickness of 50 μm and a polyimide film having a thickness of 125 μm by a double-sided tape having a thickness of 50 μm. A double-sided tape (not shown) is used for this fixation, and the aluminum foil 4a side is fixed so that it may become the upper side. Next, as shown in Fig. 3(E), one side of the strip-shaped laminated body 4 is folded upward, and the end portion of the aluminum foil 4a of the strip-shaped laminated body 4 is attached to the adhesive layer 1b of the conductive adhesive tape 1 Attached area = 5 mm × 10 mm), and crimped with a 2 kg roller. Next, the aluminum foil 4a of the tape-like laminated body 4 and the conductive base material 1a (copper foil) of the conductive adhesive tape 1 are respectively connected to the measuring machine terminal 5.

As shown in FIG. 4, in the test body produced in this manner, the end portion of the aluminum foil 4a of the strip-shaped laminated body 4 was attached to the adhesive layer 1b of the conductive adhesive tape 1. Further, since the bending angle of the belt-shaped laminated body 4 is large, it is applied upward due to its rebounding force. The state of the force pulling the adhesive layer 1b.

Immediately after bonding the end of the aluminum foil 4a and the adhesive layer 1b (just after crimping with a 2 kg roller), the voltage is immediately adjusted by flowing a current of 0.1 A, according to R (resistance value) = V (voltage ) / I (current) formula calculates the resistance value (mΩ) of the adhesive layer 1b immediately after bonding. Thereafter, a 24 hour promotion test was carried out at 85 ° C, and the resistance value (mΩ) was calculated by the same method. However, at the time of 24 hours after the promotion test, the pressure bonding using a 2 kg roller was not performed.

According to the results shown in Table 3, the conductive adhesive tapes of Examples 1 to 7 were in a state in which the force of pulling the adhesive layer 1b in the thickness direction by the repulsive force of the tape-like laminated body 4 was applied at 85 ° C. The 24 hour boost test was carried out, and the increase in the resistance value was also small. That is, the conductive adhesive tapes of Examples 1 to 7 did not peel, draw, and conduct even when exposed to a high temperature (85 ° C) for a long time (24 hours) with a narrow bonding area (5 mm × 10 mm). The decline in sex is also small.

On the other hand, the conductive adhesive tape-based adhesive layer of Comparative Example 1 was formed of a conductive adhesive composition having a lower hardness at 85 ° C, so that drawing was performed in the adhesive layer after the test was promoted, and resistance was observed. The value rises and the conductivity is large decline.

(industrial availability)

The conductive adhesive composition of the present invention is very useful as a material for forming an adhesive layer of a conductive adhesive tape. The conductive adhesive tape having such an adhesive layer is useful, for example, in the application of electromagnetic wave shielding or grounding for preventing the adverse effects of static electricity or electromagnetic waves inside the electronic device. Further, it is preferable to use it even if it is stretched by the internal repulsive force, and it is difficult to cause peeling, drawing, and electrical conductivity. Specifically, for example, it can be used very preferably in miniaturization of various portable electronic devices such as mobile phones, smart phones, wearable terminals, tablets, car navigation, cameras, audio-visual machines, game machines, and information devices. A component of a thinned electronic machine.

1‧‧‧ Conductive adhesive tape

1a‧‧‧ Conductive substrate

1b‧‧‧Adhesive layer

2‧‧‧resin board

3‧‧‧Insulation tape

4‧‧‧Striped layered body

4a‧‧‧Aluminum foil

5‧‧‧Measurement machine terminals

Claims (7)

A conductive adhesive composition comprising an acrylic copolymer (A) and conductive particles (B), wherein the hardness of the OO type hardness tester specified in ASTM D 2240 is 15 or more at 85 °C. The conductive adhesive composition according to claim 1, wherein the conductive particles (B) have a shape of a filament, a spike or a sheet. The conductive adhesive composition of claim 1, wherein the acrylic copolymer (A) has a weight average molecular weight of 450,000 or more. The conductive adhesive composition according to claim 1, wherein the acrylic copolymer (A) contains 3% by mass or more of a carboxyl group-containing monomer as a constituent component of the polymer chain. The conductive adhesive composition of claim 1, wherein the theoretical Tg of the acrylic copolymer (A) is -55 ° C or lower. A conductive adhesive tape having an adhesive layer formed of the conductive adhesive composition of claim 1 on one side or both sides of a conductive substrate. The conductive adhesive tape of claim 6, which is used for electromagnetic wave shielding or grounding inside an electronic device.