conductive adhesive sheet

Abstract

To provide a conductive adhesive sheet which has excellent conductivity while keeping high adhesive strength.SOLUTION: A conductive adhesive sheet includes a copper foil, a nickel-plated layer on at least one surface of the copper foil, and a conductive adhesive layer on the nickel-plated layer. The conductive adhesive layer includes a conductive filler and an adhesive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a conductive adhesive sheet. [Background technology]

[0002] Due to their ease of handling, conductive adhesive sheets are used for shielding against unwanted leakage electromagnetic waves radiated from electrical or electronic equipment, shielding against harmful spatial electromagnetic waves generated from other electrical or electronic equipment, and for grounding to prevent static electricity buildup. With the recent miniaturization and thinning of electrical and electronic equipment, there is a growing demand for thinner and smaller conductive adhesive sheets used in these applications.

[0003] Conventional conductive adhesive sheets are known to be those in which a metal foil base material is chromium plated (sometimes referred to as "chromate") as a rust-preventive treatment. However, such conductive adhesive sheets have the problem of not being able to achieve sufficient conductivity.

[0004] As for the plating treatment of the metal foil, for example, to prevent rusting of the copper foil, 1 to 30 mg / m² of copper foil area is applied to the copper foil. 2 It has been proposed to perform nickel plating treatment to achieve the specified plating amount (see, for example, Patent Document 1). However, it has not been disclosed that excellent conductivity can be obtained by nickel plating the copper foil that serves as the base material for the conductive adhesive sheet. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-165037 [Overview of the project] [Problems that the invention aims to solve]

[0006] An object of the present invention is to provide a conductive adhesive sheet that retains high adhesiveness and has excellent conductivity.

Means for Solving the Problems

[0007] The means for solving the above problems are as follows. <1> A copper foil, A nickel plating layer on at least one surface of the copper foil, A conductive adhesive layer on the nickel plating layer, and having The conductive adhesive layer is a conductive adhesive sheet characterized by containing a conductive filler and an adhesive. <2> The conductive adhesive sheet according to <1>, wherein the average thickness of the nickel plating layer is 0.03 μm or more. <3> The conductive adhesive sheet according to any one of <1> to <2>, wherein the average thickness of the nickel plating layer is 0.05 μm or more. <4> The conductive adhesive sheet according to any one of <1> to <3>, wherein the conductive filler is nickel. <5> The conductive adhesive sheet according to any one of <1> to <4>, having the nickel plating layer on both surfaces of the copper foil. <6> The conductive adhesive sheet according to any one of <1> to <5>, having the conductive adhesive layer on both outermost surfaces of the conductive adhesive sheet.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a conductive adhesive sheet that retains high adhesiveness and has excellent conductivity.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the conductive adhesive sheet of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing another example of the conductive adhesive sheet of the present invention. [Figure 3]Figure 3 is a schematic cross-sectional view showing another example of the conductive adhesive sheet of the present invention. [Modes for carrying out the invention]

[0010] (Conductive adhesive sheet) The conductive adhesive sheet of the present invention comprises a copper foil, a nickel plating layer, and a conductive adhesive layer, and optionally includes other layers.

[0011] In the conductive adhesive sheet of the present invention, "sheet" includes all product forms, such as individual leaves, rolls, thin plates, or strips (tapes). While "conductive adhesive sheet" is sometimes referred to as "conductive adhesive tape" or "conductive adhesive film," the term "conductive adhesive sheet" will be used consistently in the following explanation. The surface of the conductive adhesive layer in a conductive adhesive sheet may be referred to as the "adhesive surface." Furthermore, if the conductive adhesive sheet has a release liner, the "outermost surface" of the conductive adhesive sheet refers to the outermost surface of the sheet excluding the release liner.

[0012] The conductive adhesive sheet of the present invention may be a double-sided adhesive type in which both sides of the sheet are adhesive surfaces, or a single-sided adhesive type in which only one side of the sheet is adhesive.

[0013] Examples of the single-sided adhesive conductive adhesive sheet include, as shown in Figure 1, a conductive adhesive sheet 10 comprising a copper foil 1, a nickel plating layer 3 on at least one surface of the copper foil 1, and a conductive adhesive layer 2 containing a conductive filler 4 and an adhesive 5 formed on the nickel plating layer 3. Furthermore, as the single-sided adhesive conductive adhesive sheet, it is preferable to form a nickel plating layer 3 on both sides of the copper foil 1, for example, as shown in Figure 2. By forming the nickel plating layer 3 on both sides of the copper foil 1, warping of the copper foil 1 can be prevented.

[0014] An example of the double-sided adhesive conductive adhesive sheet is the conductive adhesive sheet 10 shown in Figure 3, which has a copper foil 1 and a nickel plating layer 3 formed on both surfaces of the copper foil 1, with a conductive adhesive layer 2 formed on each of the nickel plating layers 3. In other words, the conductive adhesive sheet 10 shown in Figure 3 has a conductive adhesive layer 2 on both of its outermost surfaces.

[0015] <Copper foil> The copper foil is used as the base material for the conductive adhesive sheet. There are no particular restrictions on the copper foil mentioned above; it can be appropriately selected according to the purpose, and commercially available products can be used.

[0016] There are no particular restrictions on the average thickness of the copper foil, and it can be appropriately selected depending on the purpose, but it is preferably 1 μm to 40 μm, more preferably 3 μm to 35 μm, and even more preferably 6 μm to 25 μm. When the average thickness is 1 μm to 40 μm, it is possible to make it thinner and it has excellent processability. The average thickness of the copper foil can be measured by using a TH-102 (thickness gauge, manufactured by Tester Sangyo Co., Ltd.) to measure the thickness at five points at 100 mm intervals along the length, and then calculating the average value.

[0017] <Nickel plating layer> The nickel plating layer is a layer formed on at least one surface of the copper foil in the conductive adhesive sheet. The nickel plating layer can be formed on at least one surface of the copper foil by performing a plating treatment using a nickel plating bath containing nickel.

[0018] The nickel in the nickel plating layer is not particularly limited and can be appropriately selected depending on the purpose. Examples include elemental nickel, nickel-chromium, nickel-zinc, nickel-phosphorus, nickel-boron, and nickel-phosphorus-boron. Among these, elemental nickel and nickel-zinc are preferred.

[0019] The nickel content in the nickel plating layer is not particularly limited and can be appropriately selected according to the purpose. However, with respect to the total amount of the nickel plating layer, 50% by mass or more is preferable, and 70% by mass or more 100% by mass or less is more preferable, and 90% by mass or more and 100% by mass or less is even more preferable. The method for measuring the nickel content in the nickel plating layer is not particularly limited and can be appropriately selected according to the purpose. For example, it can be measured by a fluorescent X-ray measurement method, a microscopic cross-section measurement method, or the like.

[0020] The nickel content per unit area of the nickel plating layer is not particularly limited and can be appropriately selected according to the purpose. However, it is 40 mg / m 2 or more and 50,000 mg / m 2 or less is preferable, 250 mg / m 2 or more and 45,000 mg / m 2 or less is more preferable, 1,000 mg / m 2 or more and 44,250 mg / m 2 or less is even more preferable, 4,000 mg / m 2 or more and 44,250 mg / m 2 or less is particularly preferable. When the nickel content per unit area is 250 mg / m 2 or more, a conductive adhesive sheet having excellent conductivity can be obtained.

[0021] The average thickness of the nickel plating layer is not particularly limited and can be appropriately selected according to the purpose. However, 0.03 μm or more is preferable, 0.05 μm or more is more preferable, 0.05 μm or more and 5 μm or less is even more preferable, and 0.1 μm or more and 5 μm or less is particularly preferable. When the average thickness is 0.03 μm or more, a conductive adhesive sheet having excellent conductivity can be obtained. When the nickel plating layer is formed on both surfaces of the copper foil 1, the average thickness of the nickel plating layer formed on each surface is preferably the same in order to prevent warping (curl) of the copper foil. In the case where the nickel plating layer is formed on both surfaces of the copper foil 1, the average thickness of the nickel plating layer refers to the average thickness of the nickel plating layer formed on one of the surfaces. There are no particular restrictions on the method for measuring the average thickness of the nickel plating layer, and it can be appropriately selected depending on the purpose. For example, it can be measured using an X-ray fluorescence analyzer EA1400 (manufactured by Hitachi High-Tech Corporation) or an X-ray fluorescence thickness gauge FT230 (manufactured by Hitachi High-Tech Corporation). Specifically, it is the average value of thickness measurements taken at five locations at 100 mm intervals along the length using an X-ray fluorescence thickness gauge FT230.

[0022] There are no particular restrictions on the resistance value of the copper foil on which the nickel plating layer is formed, and it can be appropriately selected according to the purpose, but it is preferably 40 mΩ or less, and more preferably 10 mΩ or less. There are no particular restrictions on the method for measuring the resistance of the nickel plating layer, and it can be appropriately selected depending on the purpose. For example, it can be measured by the following method. Specifically, under conditions of 23°C and 50%RH, a brass electrode (10mm wide x 10mm wide) is subjected to a surface pressure of 20N. The brass electrode is then connected to a copper foil (10mm wide x 10mm wide) with a nickel-plated layer, and a current of 10μA is passed through it using a milliohmmeter (manufactured by NF Circuit Design Block Co., Ltd.) to measure the resistance.

[0023] There are no particular limitations on the method for forming the nickel plating layer, and it can be appropriately selected depending on the purpose. Examples include electroplating and electroless plating. Among these, electroplating is preferred.

[0024] There are no particular limitations on the electroplating process, and it can be appropriately selected depending on the purpose. For example, a nickel plating layer can be formed by immersing the entire copper foil or one side in a nickel plating bath and performing electroplating.

[0025] There are no particular restrictions on the nickel plating bath used in the electrolytic plating process, and it can be appropriately selected according to the purpose. For example, a nickel plating bath with the following composition can be used. [Composition of nickel plating bath] Nickel 45g / L ·Boric acid (H3BO3) 4g / L

[0026] There are no particular restrictions on the temperature of the electroplating process, and it can be appropriately selected depending on the purpose, but a temperature of 10°C to 30°C is preferred.

[0027] There are no particular restrictions on the pH of the nickel plating bath in the electrolytic plating process described above, and it can be appropriately selected depending on the purpose, but a pH of 3.0 to 5.0 is preferred.

[0028] There are no particular restrictions on the duration of the electroplating process, and it can be appropriately selected depending on the purpose, but it is preferably between 1 second and 300 seconds.

[0029] There are no particular restrictions on the current density in the electroplating process, and it can be appropriately selected according to the purpose, but 0.1 A / dm 3 More than 1.0A / dm 3 The following are preferable.

[0030] <Conductive adhesive layer> The conductive adhesive layer is a layer that provides an adhesive surface to the conductive adhesive sheet while also being conductive (electrically conductive). When the adhesive surface of the conductive adhesive layer is attached to an object such as a conductor, electrical conductivity is ensured between the object and the adhesive layer. The conductive adhesive layer contains a conductive filler and an adhesive, and further contains other components such as carbon particles as needed.

[0031] <<Conductive Filler>> The conductive filler is not particularly limited as long as it is a conductive particle such as metal powder, and can be appropriately selected according to the purpose. Examples include metals such as nickel, iron, chromium, cobalt, aluminum, antimony, molybdenum, copper, silver, platinum, and gold, as well as alloys such as solder and stainless steel. These may be used individually or in combination of two or more types. Among these, nickel and silver are preferred, with nickel being preferred because it provides excellent conductivity.

[0032] As the aforementioned nickel, nickel powder produced by the carbonyl process is preferred. There are no particular restrictions on the nickel powder produced by the carbonyl process described above, and it can be appropriately selected depending on the purpose. Examples include NI255T (filamentous form) from Fukuda Metal Foil & Powder Industry Co., Ltd., Ni123 (spherical form) from Vale, and Ni255 (filamentous form) from Vale.

[0033] There are no particular restrictions on the shape of the conductive filler, and it can be appropriately selected depending on the purpose. Examples include spherical, filamentous (bead-like), flake-like (thin flake-like), and spike-like (chestnut-burr-like) shapes. Among these, spherical or filamentous shapes are preferred from the viewpoint of ensuring adhesive strength and facilitating the formation of conductive paths by the conductive filler in the adhesive layer.

[0034] There are no particular restrictions on the particle size d40 of the conductive filler, and it can be appropriately selected depending on the purpose, but it is preferably 3 μm or more and 30 μm or less, and more preferably 10 μm or more and 20 μm or less. There are no particular restrictions on the particle size d50 of the conductive filler, and it can be appropriately selected according to the purpose, but it is preferably 3 μm or more and 35 μm or less, more preferably 10 μm or more and 30 μm or less, and even more preferably 12 μm or more and 28 μm or less. There are no particular restrictions on the particle size d70 of the conductive filler, and it can be appropriately selected depending on the purpose, but it is preferably 10 μm or more and 50 μm or less, and more preferably 20 μm or more and 40 μm or less. The particle diameter d40 refers to the 40% cumulative volume particle diameter in the volume particle size distribution, the particle diameter d50 refers to the 50% cumulative volume particle diameter in the volume particle size distribution, and the particle diameter d70 refers to the 70% cumulative volume particle diameter in the volume particle size distribution. These values ​​are measured by laser analysis and scattering. There are no particular restrictions on the measuring device, and it can be appropriately selected according to the purpose. Examples include the Microtrac MT3000II manufactured by Nikkiso Co., Ltd. and the SALD-3000 laser diffraction particle size distribution analyzer manufactured by Shimadzu Corporation. The particle size d50 of the conductive filler measured by the above measurement method is preferably 50% to 300% (0.5 to 3 times) of the average thickness of the conductive adhesive layer, more preferably 80% to 200% (0.8 to 2 times), and even more preferably 100% to 150% (1 to 1.5 times). This makes it easier to conduct electricity and provides better conductivity.

[0035] Methods for adjusting the particle sizes d40, d50, and d70 to fall within the aforementioned numerical ranges include, for example, grinding the conductive filler with a jet mill or using a sieving method.

[0036] The content of the conductive filler is preferably 145 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 0.1 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the solid content of the adhesive described later. When the content of the conductive filler is 145 parts by mass or less, it is possible to achieve both high adhesive strength and excellent conductivity both initially and over time.

[0037] <<Adhesive>> There are no particular restrictions on the adhesive, and it can be appropriately selected depending on the purpose. Examples include (meth)acrylic adhesives, urethane adhesives, polyester adhesives, synthetic rubber adhesives, natural rubber adhesives, silicone adhesives, and styrene adhesives. Among these, (meth)acrylic adhesives and styrene adhesives are preferred in terms of high adhesion, low cost, and high durability.

[0038] -(meth)acrylic adhesive- The (meth)acrylic adhesive is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that it contains a (meth)acrylic polymer, a tackifying resin and a crosslinking agent, and further, other components may be included as needed. "(meth)acrylic" is used to mean acrylic or methacrylic, and "(meth)acrylate" is used to mean acrylate or methacrylate.

[0039] -(meth)acrylic polymer- The (meth)acrylic polymer is not particularly limited and can be appropriately selected depending on the purpose, but acrylic copolymers having (meth)acrylate monomers with 1 to 14 carbon atoms as the main monomer component are preferred. The C1-C14 (meth)acrylate is not particularly limited and can be appropriately selected depending on the purpose. Examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. These may be used individually or in combination of two or more. Among these, (meth)acrylates with 4-C12 alkyl groups are preferred, (meth)acrylates having a linear or branched structure with 4-C9 atoms are more preferred, and n-butyl acrylate and 2-ethylhexyl acrylate are even more preferred because they provide a conductive adhesive sheet with high adhesive strength.

[0040] There are no particular restrictions on the content of carbon 1 to carbon 14 (meth)acrylate in the (meth)acrylic polymer, and it can be appropriately selected depending on the purpose. However, it is preferably 70% to 95% by mass of the monomer components constituting the (meth)acrylic polymer, and more preferably 80% to 95% by mass.

[0041] In addition to those mentioned above, highly polar vinyl monomers can be used as monomers for the production of the aforementioned acrylic polymer, as needed. The aforementioned highly polar vinyl monomer is not particularly limited and can be appropriately selected depending on the purpose. Examples include (meth)acrylic monomers having hydroxyl groups, (meth)acrylic monomers having carboxyl groups, and (meth)acrylic monomers having amide groups. These may be used individually or in combination of two or more.

[0042] The vinyl monomer having a hydroxyl group is not particularly limited and can be appropriately selected depending on the purpose. Examples include (meth)acrylic monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate.

[0043] The vinyl monomer having a carboxyl group is not particularly limited and can be appropriately selected depending on the purpose. Examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, and (meth)acrylic monomers such as ethylene oxide-modified succinic acid acrylate. Among these, acrylic acid is preferred.

[0044] The vinyl having the amide group is not particularly limited and can be appropriately selected depending on the purpose. Examples include (meth)acrylic monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N,N-dimethylacrylamide.

[0045] In addition to those mentioned above, other highly polar vinyl monomers that can be used include vinyl acetate, ethylene oxide-modified succinic acid acrylate, and sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid.

[0046] The high-polarity vinyl monomer is preferably 1.5% to 20% by mass, more preferably 1.5% to 10% by mass, and even more preferably 2% to 8% by mass, relative to the total amount of monomer used in the production of the acrylic polymer, as this allows for the formation of a conductive adhesive layer with a balanced cohesive force, holding power, and adhesiveness.

[0047] Among the highly polar vinyl monomers, the vinyl monomer having a hydroxyl group is preferably used when an isocyanate-based crosslinking agent is used as the adhesive. Specifically, there are no particular restrictions on the vinyl monomer having a hydroxyl group, and it can be appropriately selected depending on the purpose. Examples include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. The vinyl monomer having hydroxyl groups is preferably in an amount of 0.01% by mass or more and 1.0% by mass or less, and more preferably 0.03% by mass or more and 0.3% by mass or less, relative to the total amount of monomers used in the production of the acrylic polymer.

[0048] The acrylic polymer can be produced by polymerizing the monomer using known polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. Among these, production by solution polymerization or bulk polymerization is preferred. During the polymerization described above, peroxide-based thermal polymerization initiators such as benzoyl peroxide and lauroyl peroxide, azo thermal polymerization initiators such as azobisisobutylnitrile, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, benzyl ketal-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, etc., can be used as needed.

[0049] The weight-average molecular weight (Mw) of the (meth)acrylic polymer obtained by the above method is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 500,000 to 2,500,000, more preferably 700,000 to 2,000,000, and even more preferably 900,000 to 1,800,000. The aforementioned weight-average molecular weight is the weight-average molecular weight on a standard polystyrene basis, measured by gel permeation chromatography (GPC).

[0050] Molecular weight is measured using the GPC method and is a standard polystyrene equivalent value, measured under the following conditions using a GPC instrument (HLC-8329GPC) manufactured by Tosoh Corporation. [Measurement conditions] • Sample concentration: 0.5% by mass (tetrahydrofuran solution) • Sample injection volume: 100 μL • Eluent: THF (tetrahydrofuran) ·Flow rate: 1.0mL / min ·Measurement temperature: 40℃ • This column: TSKgel GMHHR-H (20) x 2 • Guard column: TSKgel HXL-H • Detector: Differential refractometer Standard polystyrene molecular weight: 10,000-20,000,000 (manufactured by Tosoh Corporation)

[0051] -Adhesive-forming resin- As the (meth)acrylic adhesive, it is preferable to use one that contains a tackifying resin in order to improve adhesion to the adherend and surface bonding strength. There are no particular restrictions on the tackifying resin, and it can be appropriately selected depending on the purpose. Examples include rosin-based tackifying resins, polymerizable rosin-based tackifying resins, polymerizable rosin ester-based tackifying resins, rosin-phenol-based tackifying resins, stabilized rosin ester-based tackifying resins, disproportionated rosin ester-based tackifying resins, hydrogenated rosin ester-based tackifying resins, terpene-based tackifying resins, terpene-phenol-based tackifying resins, petroleum resin-based tackifying resins, and (meth)acrylate-based tackifying resins. Among these, it is preferable to use disproportionate rosin ester tackifying resins, polymerizable rosin ester tackifying resins, rosin phenol tackifying resins, hydrogenated rosin ester tackifying resins, (meth)acrylate resins, and terpene phenol resins individually or in combination of two or more.

[0052] It is preferable to use a tackifying resin having a softening point of 30°C to 180°C, and more preferable to use one having a softening point of 70°C to 140°C for forming an adhesive layer with high adhesive performance. When using a (meth)acrylate-based tackifying resin, it is preferable to use one with a glass transition temperature of 30°C to 200°C, and more preferable to use one with a glass transition temperature of 50°C to 160°C.

[0053] There are no particular restrictions on the content of the tackifying resin, and it can be appropriately selected depending on the purpose, but it is preferably 5 parts by mass or more and 65 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer, and more preferably 8 parts by mass or more and 55 parts by mass or less, as this makes it easier to ensure adhesion with the adherend.

[0054] -Crosslinking agent- As for the (meth)acrylic adhesive, it is preferable to use one that contains a crosslinking agent in order to further improve the cohesive strength of the adhesive layer. There are no particular restrictions on the crosslinking agent, and it can be appropriately selected depending on the purpose. Examples include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents. Among these, crosslinking agents that are mixed after the production of the acrylic polymer to allow the crosslinking reaction to proceed are preferred, and isocyanate-based crosslinking agents and epoxy-based crosslinking agents, which have high reactivity with acrylic polymers, are preferred.

[0055] The isocyanate crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. Among these, trifunctional polyisocyanate compounds are preferred. The aforementioned trifunctional isocyanate compound is not particularly limited and can be appropriately selected depending on the purpose. Examples include tolylene diisocyanate or its trimethylolpropane adducts, triphenylmethane isocyanate, and the like.

[0056] As an indicator of the degree of crosslinking, the gel fraction value, which is the amount of insoluble material measured after immersing the adhesive layer in toluene for 24 hours, is used. There are no particular restrictions on the gel fraction of the adhesive layer, and it can be appropriately selected according to the purpose, but it is preferably 10% by mass or more and 70% by mass or less, more preferably 25% by mass or more and 65% by mass or less, even more preferably 35% by mass or more and 60% by mass or less, and particularly preferably 40% by mass or more and 55% by mass or less.

[0057] The gel fraction refers to the value measured by the following method. An adhesive composition is applied to a release sheet so that the thickness after drying is 50 μm, dried at 100°C for 3 minutes, and aged at 40°C for 2 days. This is then cut into 50 mm squares and used as the sample. Next, the mass of the sample before immersion in toluene (G1) is measured in advance. After immersion in toluene solution at 23°C for 24 hours, the toluene-insoluble portion of the sample is separated by filtration through a 300-mesh wire mesh, and the mass of the residue after drying at 110°C for 1 hour (G2) is measured. The gel fraction is then determined according to the following formula. The weight of conductive particles (metal particles) in the sample (G3) is calculated from the mass of the sample (G1) and the composition of the adhesive. Gel fraction (mass%)=(G2-G3) / (G1-G3)×100

[0058] <<Carbon particles>> The conductive adhesive layer may contain carbon particles. The conductive adhesive layer can exhibit opacity by containing carbon particles. There are no particular restrictions on the carbon particles, and they can be appropriately selected depending on the purpose. Examples include carbon black, glassy carbon, graphite, graphene, fullerene, carbon nanotubes, and carbon fibers. These can be used individually or in combination of two or more. There are no particular restrictions on the shape of the carbon particles, and they can be appropriately selected depending on the purpose. Examples include spherical, elliptical, columnar, cylindrical, and fibrous shapes.

[0059] There are no particular restrictions on the carbon black mentioned above, and it can be appropriately selected depending on the purpose. Examples include furnace black, channel black, acetylene black, thermal black, and lamp black.

[0060] There are no particular restrictions on the graphite, and it can be appropriately selected depending on the purpose. Examples include natural graphite, quiche graphite, and artificial graphite. The artificial graphite may be anisotropic graphite, isotropic graphite, or a mixture thereof, but isotropic graphite is preferred from the viewpoint of the mechanical strength of the carbon particles. The graphite may be crystalline or amorphous, or a mixture thereof. The graphite may also be a carbon fiber reinforced carbon composite (C / C composite) in which graphite is reinforced with carbon fibers.

[0061] There are no particular restrictions on the fullerene, and it can be appropriately selected depending on the purpose, for example, C 60 , C 70 , C 80 , C 84 , C 96 These are some examples.

[0062] The carbon nanotube is a cylindrical carbon polyhedron having a structure in which graphite sheets, whose main structure is a six-membered carbon ring, are closed in a cylindrical shape. The carbon nanotube can be a single-walled carbon nanotube having a structure in which one layer of graphite sheets is closed in a cylindrical shape, a double-walled carbon nanotube having a structure in which two layers of graphite sheets are closed in a cylindrical shape, or a multi-walled carbon nanotube having a multi-layer structure in which three or more layers of graphite sheets are closed in a concentric cylindrical shape, and any of these can be used.

[0063] There are no particular restrictions on the average particle size of the carbon particles, and they can be appropriately selected depending on the purpose, but it is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. When the average particle size of the carbon particles is 100 nm or less, it is possible to achieve both high adhesive strength and excellent conductivity both initially and over time. The average particle diameter of the carbon particles is the average particle diameter based on volume, and examples of measuring devices include the Microtrac MT3000II manufactured by Nikkiso Co., Ltd. and the SALD-3000 laser diffraction particle size distribution analyzer manufactured by Shimadzu Corporation.

[0064] There are no particular restrictions on the content of the carbon particles, and it can be appropriately selected depending on the purpose, but it is 75 parts by mass or less per 100 parts by mass of the solid content of the adhesive, preferably 3 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 30 parts by mass or less, and even more preferably 10 parts by mass or more and 20 parts by mass or less. When the content of the carbon particles is within the above range, it is possible to achieve both high adhesive strength and excellent conductivity both initially and over time.

[0065] One method for dispersing the conductive filler in the conductive adhesive layer is to disperse the adhesive, the conductive filler, the carbon particles, the solvent, the additives, etc., using a dispersion stirrer. Commercially available dispersion stirrers include dissolvers, butterfly mixers, BDM twin-shaft mixers, and planetary mixers manufactured by Inoue Seisakusho Co., Ltd. Among these, dissolvers and butterfly mixers that can apply a moderate share, resulting in minimal thickening of the adhesive during stirring, are preferred.

[0066] <Other ingredients> Other components in the conductive adhesive layer are not particularly limited and can be appropriately selected depending on the purpose. Examples include additives such as anti-aging agents, UV absorbers, fillers, polymerization inhibitors, surface modifiers, antistatic agents, defoamers, viscosity modifiers, light stabilizers, weather stabilizers, heat stabilizers, antioxidants, leveling agents, organic pigments, inorganic pigments, pigment dispersants, plasticizers, softeners, flame retardants, metal deactivators, silica beads, organic beads, etc., as well as inorganic fillers such as silicon dioxide, aluminum oxide, titanium dioxide, zirconia, and antimony pentoxide.

[0067] There are no particular restrictions on the average thickness of the conductive adhesive layer, and it can be appropriately selected depending on the purpose, but it is preferably 1 μm to 40 μm, more preferably 3 μm to 35 μm, and even more preferably 6 μm to 25 μm. The average thickness of the conductive adhesive layer can be measured by using a TH-102 (thickness gauge, manufactured by Tester Sangyo Co., Ltd.) to measure the thickness at five points at 100 mm intervals along the length and calculating the average value.

[0068] The conductive adhesive layer can be configured with a conductive nonwoven fabric layer (hereinafter referred to as the "conductive nonwoven fabric layer") within the conductive adhesive layer, resulting in a laminated structure of three or more layers in the order of conductive adhesive layer, conductive nonwoven fabric layer, and conductive adhesive layer. This improves the conductivity and electromagnetic shielding properties of the conductive adhesive tape.

[0069] The conductive nonwoven fabric layer is not particularly limited and can be appropriately selected depending on the purpose, but examples include a nonwoven fabric with a metal plating layer such as copper or nickel formed on it.

[0070] The average thickness of the conductive nonwoven fabric layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 3 μm to 50 μm, more preferably 5 μm to 30 μm, and particularly preferably 8 μm to 25 μm. This makes it possible to obtain a thin conductive adhesive sheet with excellent conductivity, electromagnetic shielding properties, and adhesiveness. There are no particular restrictions on the method for measuring the average thickness, and it can be appropriately selected depending on the purpose. For example, a method similar to the one used for measuring the average thickness of the copper foil can be used.

[0071] There are no particular limitations on the method for manufacturing the conductive adhesive sheet of the present invention, and a suitable method can be selected depending on the purpose. For example, it can be manufactured by applying a composition containing the adhesive and the conductive filler onto the copper foil using a roll coater or die coater, and then drying it. Alternatively, it can be manufactured by a transfer method in which a conductive adhesive layer formed on a release liner is bonded to the copper foil. When manufacturing the conductive adhesive sheet as a double-sided adhesive sheet, the conductive adhesive layer can be formed by first applying a composition containing the adhesive and the conductive filler to the surface of a release liner using a roll coater or the like, drying it, and then laminating the conductive adhesive layer to both sides of a copper foil using a transfer method.

[0072] When bonding the conductive adhesive layer formed on the release liner to the copper foil, thermal lamination is preferable from the viewpoint of providing excellent adhesion between the copper foil and the conductive adhesive layer. The temperature for the heat lamination is preferably 60°C to 150°C, more preferably 70°C to 130°C, and even more preferably 80°C to 110°C in terms of adhesion and suppressing shrinkage of the substrate.

[0073] -Release Liner- There are no particular restrictions on the release liner, and it can be appropriately selected according to the purpose. Examples include papers such as kraft paper, glassine paper, and fine paper; resin films such as polyethylene, polypropylene (OPP, CPP), and polyethylene terephthalate; laminated paper made by laminating the papers and resin films; and papers that have been treated with a sealant such as clay or polyvinyl alcohol, and then treated with a release agent such as a silicone resin on one or both sides.

[0074] There are no particular restrictions on the average total thickness of the conductive adhesive sheet, and it can be appropriately selected depending on the purpose, but it is preferably 100 μm or less, more preferably 65 μm or less, and even more preferably 50 μm or less. When the total thickness is 100 μm or less, it is possible to make the conductive adhesive sheet thinner while ensuring adhesion and conductivity, which contributes to the thinning of portable electronic devices. Note that the average total thickness of the conductive adhesive sheet is the thickness of the conductive adhesive sheet itself, excluding the release liner.

[0075] The conductive adhesive sheet of the present invention is preferably such that, when the conductive adhesive sheet is pressed onto a stainless steel plate (SUS plate) using a 2 kg roller in an environment of 23°C and 50% RH with one back-and-forth pressure, and after standing for 1 hour, the 180-degree peel adhesion strength at 300 mm / min is 8 N / 25 mm or more. Within the above range, peeling is easily suppressed, and the conductive adhesive sheet can be removed from defective products in the manufacturing process.

[0076] The conductive adhesive sheet of the present invention is prepared by attaching copper foil to one side of the conductive adhesive sheet, cutting it to a size of 15 mm width × 100 mm width, and attaching two tin-plated plates to the adhesive layer on the other side of the conductive adhesive sheet so that the attachment area is 15 mm × 15 mm for each test piece. Preferably, the rate of change of resistance [(resistance after 168 hours / initial resistance) × 100], calculated from the initial resistance value measured and the resistance value measured after leaving the test piece at 23°C for 168 hours, is 300% or less, more preferably 200% or less, and even more preferably 150% or less. If the rate of change of the resistance value is 300% or less, excellent conductivity can be achieved both initially and over time.

[0077] <Application> The conductive adhesive sheet of the present invention achieves both high adhesive strength and excellent conductivity both initially and over time, making it useful for applications such as shielding electromagnetic waves in electrical or electronic equipment, shielding harmful spatial electromagnetic waves generated by other electrical or electronic equipment, and grounding for static electricity prevention. Among these applications, it is particularly suitable for use in portable electronic devices where thinning is progressing and volume limitations within the housing are strict, and is especially suitable for use by attaching it to internal components of small electronic terminals. [Examples]

[0078] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0079] (Plating treatment of copper foil) -Example of copper foil A manufacturing process- The entire copper foil (average thickness 10 μm, untreated, surface roughness Rz=0.38 μm on the glossy side, surface roughness Rz=1.40 μm on the matte side) was immersed in a nickel plating bath of the following composition at 20°C, pH 3.5, and current density 0.2 A / dm². 3 Electroplating was performed under the following conditions, and a nickel plating layer (average thickness 0.5 μm, 4.425 g / m²) was applied to both sides of the copper foil (one side being a glossy surface and the other a matte surface). 2 A copper foil A (average thickness 11 μm) was obtained in which the following was formed. [Composition of nickel plating bath] Nickel 45g / L ·Boric acid (H3BO3) 4g / L The resistance of the obtained copper foil A was measured to be 4 mΩ. The surface roughness Rz of the nickel plating layer on the glossy side of copper foil A was 0.44 μm, and the surface roughness Rz of the nickel plating layer on the matte side was 1.40 μm. The average thickness of copper foil A and the plating layer, the resistance value of copper foil A, and the surface roughness of the nickel plating layer on the glossy side and the nickel plating layer on the matte side of copper foil A were measured using the following method.

[0080] <Measurement of the average thickness of copper foil A and the plating layer> The average thickness of the copper foil is the average value obtained by measuring the thickness at five points at 100 mm intervals along the length using a TH-102 (thickness gauge, manufactured by Tester Sangyo Co., Ltd.). The average thickness of the plating layer is the average of five thickness measurements taken at 100 mm intervals along the length using an X-ray fluorescence thickness gauge FT230.

[0081] <Measurement of the resistance of copper foil A> A brass electrode (10mm x 10mm) was attached to one side of copper foil A (10mm x 10mm). Under conditions of 23°C and 50% RH, a surface pressure of 20N was applied from the conductive adhesive sheet attachment point on the brass electrode. The brass electrode and copper foil A were connected, and a current of 10μA was passed through using a milliohmmeter (manufactured by NF Circuit Design Block Co., Ltd.), and the resistance value was measured.

[0082] <Method for measuring the surface roughness of glossy and matte surfaces of copper foil A> The surface roughness of the glossy and matte surfaces of copper foil A was measured in accordance with JIS B0601-2013.

[0083] -Example of copper foil B manufacturing- In the manufacturing example of copper foil A, the plating process was carried out in the same manner as in the manufacturing example of copper foil A, except that the plating process was performed so that the average thickness of the nickel plating layer was 0.05 μm. A nickel plating layer (average thickness 0.05 μm, 0.4425 g / m²) was applied to both sides of the copper foil (one side being a glossy surface and the other side being a matte surface). 2 A copper foil B (average thickness 10 μm) was obtained in which the following was formed. The resistance of copper foil B was measured in the same manner as that of copper foil A and was found to be 4 mΩ. The surface roughness Rz of the nickel plating layer on the glossy side of copper foil B was 0.41 μm, and the surface roughness Rz of the nickel plating layer on the matte side was 1.40 μm.

[0084] -Example of copper foil C manufacturing- One side of a copper foil (average thickness 10 μm, untreated) is immersed in the nickel plating bath at 20°C, pH 3.5, and current density 0.2 A / dm². 3 Electroplating was performed under the following conditions, and a nickel plating layer (average thickness 0.05 μm, 0.4425 g / m²) was applied to one side (glossy side) of the copper foil. 2 A copper foil was formed. Subsequently, one side of the other copper foil was immersed in a chromium plating bath of the following composition: 30°C, pH 2.3, current density 5A / dm². 3 Electroplating was performed under the following conditions, and a chromium plating layer (average thickness 0.005 μm, 0.036 g / m²) was applied to one side (matte side) of the copper foil. 2 A copper foil C (average thickness 10 μm) with the following structure was obtained. [Composition of chromium plating bath] Chromium: 5g / L The resistance of the obtained copper foil C was measured in the same manner as copper foil A and was found to be 4 mΩ. The surface roughness Rz of the nickel plating layer on the glossy side of copper foil C was 0.41 μm, and the surface roughness Rz of the chromium plating layer on the matte side was 1.40 μm.

[0085] -Example of copper foil D manufacturing- One side of a copper foil (average thickness 10 μm, untreated) is immersed in the nickel plating bath at 20°C, pH 3.5, and current density 0.2 A / dm². 3 Electroplating was performed under the following conditions, and a nickel plating layer (average thickness 0.03 μm, 0.2655 g / m²) was applied to one side (glossy side) of the copper foil. 2 A copper foil was formed. Then, the other side of the copper foil was immersed in the chromium plating bath at 30°C, pH 2.3, and current density 5A / dm². 3 Electroplating was performed under the following conditions, and a chromium plating layer (average thickness 0.005 μm, 0.036 g / m²) was applied to one side (matte side) of the copper foil. 2 A copper foil D (average thickness 10 μm) with the following structure was obtained. The resistance of the obtained copper foil D was measured in the same manner as copper foil A and was found to be 4 mΩ. The surface roughness Rz of the nickel plating layer on the glossy side of copper foil D was 0.41 μm, and the surface roughness Rz of the chromium plating layer on the matte side was 1.40 μm.

[0086] -Example of copper foil E manufacturing- The entire copper foil (average thickness 10 μm, untreated) is immersed in the chromium plating bath at 30°C, pH 2.3, and current density 5 A / dm². 3 Electroplating was performed under the following conditions, and a chromium plating layer (average thickness 0.005 μm, 0.036 g / m²) was applied to both sides of the copper foil (one side being a glossy surface and the other a matte surface). 2 A copper foil E (average thickness 10 μm) was obtained in which the following was formed. The resistance of the obtained copper foil E was measured in the same manner as that of copper foil A and was found to be 4 mΩ. The surface roughness Rz of the chromium plating layer on the glossy side of copper foil E was 0.41 μm, and the surface roughness Rz of the chromium plating layer on the matte side was 1.40 μm.

[0087] -Example of copper foil F manufacturing- The entire copper foil (average thickness 10 μm, untreated) is immersed in a benzotriazole treatment bath of the following composition, and after rust prevention treatment at 25°C and pH 0.7, it is dried, and a benzotriazole layer (average thickness 0.1 μm, 0.137 g / m²) is applied to both sides of the copper foil (one side being a glossy surface and the other a matte surface). 2 A copper foil F (average thickness 10 μm) was obtained in which the ) was formed. [Composition of Benzotriazole-treated Bath] Hydrochloric acid: 0.2 M / L • Ammonium chloride: 1.0 M / L • Benzotriazole: 0.2 M / L The resistance of the obtained copper foil F was measured in the same manner as that of copper foil A and was found to be 4 mΩ. The surface roughness Rz of the benzotriazole layer on the glossy side of copper foil F was 0.41 μm, and the surface roughness Rz of the benzotriazole layer on the matte side was 1.40 μm.

[0088] (Examples of conductive nonwoven fabric manufacturing) Wet-laid polyester nonwoven fabric (basis weight 5.5 g / m²) 2 A sample (with an average thickness of 14 μm and an average diameter of 4.5 μm of polyester fibers, manufactured by Nippon Paper Papilia Co., Ltd.) was immersed in an aqueous solution containing 10 g / L of stannous chloride and 20 ml / L of hydrochloric acid at room temperature for approximately 5 minutes, and then rinsed with water. Next, the samples were immersed in an aqueous solution containing 1 g / L palladium chloride and 20 ml / L hydrochloric acid at room temperature for approximately 10 minutes, and then rinsed with water. Next, a wet polyester nonwoven fabric was obtained by electroless plating treatment, which involved immersion in an electroless plating solution containing 10 g / L copper sulfate, 7 ml / L formaldehyde, 8 g / L sodium hydroxide, and 30 g / L ethylenediaminetetraacetate tetrasodium (EDTA-4Na) at 40°C for 20 minutes, followed by rinsing with water.

[0089] The aforementioned electroless plated wet polyester nonwoven fabric was immersed in an electrolytic copper plating solution (Okuno Pharmaceutical Co., Ltd., Toplutina SF), and the amount of copper plated was 6 g / m². 2 The fabric was subjected to electrolytic copper plating to obtain an electrolytic copper-plated wet polyester nonwoven fabric.

[0090] The aforementioned electrolytic copper-plated wet polyester nonwoven fabric is immersed in an electrolytic nickel plating solution containing 240 g / L nickel sulfate, 45 g / L nickel chloride, 30 g / L boric acid, 2 g / L saccharin, and 0.2 g / L 1,4-butynediol, resulting in a nickel plating amount of 4 g / m². 2 The material was electroplated with nickel to achieve the desired properties, then washed with water and dried. After that, it was compressed using a calender roll at 100°C to produce a conductive nonwoven fabric with an average thickness of 10 μm.

[0091] (Example of acrylic copolymer synthesis 1) <Ethyl acetate solution of acrylic copolymer> In a reaction vessel equipped with a stirrer, condenser, thermometer, and dropping funnel, 75.0 parts by mass of n-butyl acrylate, 19.0 parts by mass of 2-ethylhexyl acrylate, 3.9 parts by mass of vinyl acetate, 2.0 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and 0.1 parts by mass of 2,2'-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate. After purging with nitrogen, polymerization was carried out at 80°C for 12 hours to obtain an acrylic copolymer (1) with a weight-average molecular weight of 600,000. The weight-average molecular weight of the acrylic copolymer was measured by the following method.

[0092] <Weight-average molecular weight of acrylic copolymers> The molecular weight of acrylic copolymers is measured using the GPC method and is expressed as a standard polystyrene equivalent value, using a GPC instrument (HLC-8329GPC) manufactured by Tosoh Corporation under the following measurement conditions. [Measurement conditions] • Sample concentration: 0.5% by mass (tetrahydrofuran solution) • Sample injection volume: 100 μL • Eluent: THF (tetrahydrofuran) ·Flow rate: 1.0mL / min ·Measurement temperature: 40℃ • This column: TSKgel GMHHR-H (20) x 2 • Guard column: TSKgel HXL-H • Detector: Differential refractometer Standard polystyrene molecular weight: 10,000-20,000,000 (manufactured by Tosoh Corporation)

[0093] (Example 1 of preparation of conductive adhesive composition) - Preparation of adhesive - To 100 parts by mass (solids) of the acrylic copolymer (1), 10 parts by mass of polymerized rosin pentaerythritol ester (Pensel D-135, manufactured by Arakawa Chemical Industries, Ltd., softening point 135°C) and 10 parts by mass of disproportionated rosin glycerin ester (Super Ester A-100, manufactured by Arakawa Chemical Industries, Ltd.) were mixed and stirred, and then ethyl acetate was added to obtain an acrylic adhesive with a solids content of 40% by mass of the acrylic polymer.

[0094] -Preparation of conductive adhesive composition- Conductive adhesive composition A was prepared by mixing 1 part by mass of NI255T (nickel powder, manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., d50: 26.0 μm) as a conductive filler, 2 parts by mass of Barnock NC-40 (manufactured by DIC Corporation, solids content 40% by mass) as a crosslinking agent, and 70 parts by mass of ethyl acetate with 100 parts by mass of the aforementioned acrylic adhesive (solids content) in a dispersion stirrer for 10 minutes.

[0095] (Example 2 of preparation of conductive adhesive composition) Conductive adhesive composition B was prepared in the same manner as in the conductive adhesive composition preparation example 1, except that the content of NI255T as a conductive filler was changed from 1 part by mass to 5 parts by mass.

[0096] (Preparation example of conductive adhesive composition 3) - Preparation of adhesive - 100 parts by mass of styrene-isoprene block copolymer composition a (a mixture of styrene-isoprene block copolymer and styrene-isoprene triblock copolymer, 24% by mass of styrene-derived structural units represented by the following chemical formula (1), with 67% by mass of styrene-isoprene block copolymer relative to the total amount of composition a), 40 parts by mass of Quinton G115 (C5 / C9 petroleum resin, manufactured by Nippon Zeon Co., Ltd., softening point 115°C), and polymerized rosin ester resin A styrene-based adhesive with a solid content of 40% by mass was obtained by mixing 30 parts by mass of Pencel D-160 (manufactured by Arakawa Chemical Industries, Ltd., softening point 150°C to 165°C), 5 parts by mass of polybutene (Nisseki Polybutene HV-50, manufactured by JX Nippon Oil & Energy Corporation, pour point -12.5°C), and 1 part by mass of an antioxidant (tetrakis-[methylene-3-(3'5'-di-t-butyl-4-hydroxyphenyl)propionate]methane), dissolving the mixture in toluene as a solvent, and stirring. [ka]

[0097] -Preparation of conductive adhesive composition- Conductive adhesive composition C was prepared by mixing 100 parts by mass (solids) of the aforementioned styrene-based adhesive with 1 part by mass of NI255T (nickel powder, manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., d50: 26.0 μm) as a conductive filler, 2 parts by mass of Barnock NC-40 (manufactured by DIC Corporation, solids content 40% by mass) as a crosslinking agent, and 70 parts by mass of ethyl acetate in a dispersion stirrer for 10 minutes.

[0098] (Example 1) <Preparation of conductive adhesive sheets> The obtained conductive adhesive composition was coated onto release film A (PET38×1, A3, manufactured by Nippa Co., Ltd.) using a comma coater to achieve an average thickness of 10 μm after drying, and dried in an 80°C dryer for 2 minutes to form a conductive adhesive layer. Next, the formed conductive adhesive layer was bonded to both sides of a conductive nonwoven fabric (average thickness 10 μm) to obtain a conductive nonwoven fabric having conductive adhesive layers on both sides. The release film on one side of the conductive nonwoven fabric having conductive adhesive layers on both sides is peeled off, and the copper foil A (average thickness 11 μm, resistance value 4 mΩ, glossy side: nickel plating layer (average thickness 0.5 μm, 4.425 g / m²) is removed. 2 Matte surface: Nickel plating layer (average thickness 0.5 μm, 4.425 g / m²) 2 After bonding the glossy surface of the material to the conductive adhesive sheet of Example 1, the material was pressed using a laminator at a linear pressure of 100 N / cm at 40°C and cured at 40°C for 48 hours. The structure and composition of the prepared conductive adhesive sheet are shown in Table 1. In Table 1, conductive adhesive layer 1 refers to the conductive adhesive layer formed on the copper foil side relative to the conductive nonwoven fabric layer, and conductive adhesive layer 2 refers to the conductive adhesive layer formed on the opposite side of the copper foil relative to the conductive nonwoven fabric layer. The average thickness of the obtained conductive adhesive sheet, adhesive layer, and plating layer was measured as follows.

[0099] <Measurement of the average thickness of conductive adhesive sheets> The average thickness of each conductive adhesive sheet is the average of five thickness measurements taken at 100mm intervals along the length of the sheet (excluding the release film) using a TH-102 (thickness gauge, manufactured by Tester Sangyo Co., Ltd.).

[0100] <Measurement of the average thickness of the adhesive layer> A sample was prepared by extracting a portion of the conductive adhesive layer formed on the surface of the release film used to manufacture the conductive adhesive sheet, and backing one side of it with S25 (a polyethylene terephthalate film manufactured by Unitika Ltd., with an average thickness of 25 μm). The release film was peeled off the sample, and its average thickness was measured using a TH-102 (a thickness gauge manufactured by Tester Sangyo Co., Ltd.). The thickness of the conductive adhesive layer was determined by subtracting the thickness of S25 from this measurement.

[0101] (Example 2) In Example 1, the conductive adhesive sheet of Example 2 was prepared in the same manner as in Example 1, except that copper foil A was replaced with copper foil B.

[0102] (Example 3) In Example 1, the conductive adhesive sheet of Example 3 was prepared in the same manner as in Example 1, except that copper foil A was replaced with copper foil C.

[0103] (Example 4) In Example 4, a conductive adhesive sheet was prepared in the same manner as in Example 1, except that copper foil A was replaced with copper foil D.

[0104] (Example 5) In Example 1, the conductive adhesive composition A obtained was coated onto a release film (PET38×1, A3, manufactured by Nippa Co., Ltd.) using a comma coater so that the average thickness after drying was 10 μm, dried in an 80°C dryer for 2 minutes, the release film was peeled off, and the sheet was bonded to the glossy side of the copper foil A, and then cured at 40°C for 48 hours. Except for these steps, the conductive adhesive sheet of Example 5 was prepared in the same manner as in Example 1.

[0105] (Example 6) In Example 1, the conductive adhesive composition B obtained was coated onto a release film (PET38×1, A3, manufactured by Nippa Co., Ltd.) using a comma coater so that the average thickness after drying was 20 μm, dried in an 80°C dryer for 2 minutes, the release film was peeled off, and the sheet was bonded to the glossy surface of the copper foil A, and then cured at 40°C for 48 hours. Except for these steps, the conductive adhesive sheet of Example 6 was prepared in the same manner as in Example 1.

[0106] (Example 7) In Example 1, the conductive adhesive composition C obtained was coated onto a release film (PET38×1, A3, manufactured by Nippa Co., Ltd.) using a comma coater so that the average thickness after drying was 10 μm, dried in an 80°C dryer for 2 minutes, the release film was peeled off, and the sheet was bonded to the glossy surface of the copper foil A, and then cured at 40°C for 48 hours. Except for these steps, the conductive adhesive sheet of Example 7 was prepared in the same manner as in Example 1.

[0107] (Comparative Example 1) A conductive adhesive sheet for Comparative Example 1 was prepared in the same manner as in Example 5, except that copper foil A was replaced with copper foil E.

[0108] (Comparative Example 2) A conductive adhesive sheet for Comparative Example 2 was prepared in the same manner as in Example 5, except that copper foil A was replaced with copper foil F.

[0109] Next, the conductive adhesive sheets obtained from Examples 1-7 and Comparative Examples 1-2 were evaluated for various properties as follows. The results are shown in Tables 1 and 2. In the tables, "Average Thickness (μm)*" indicates the average thickness of the copper foil on which the plating layer or benzotriazole layer is formed (thickness including the plating layer, etc.).

[0110] <Method for evaluating adhesive strength> The conductive adhesive sheets obtained in the examples and comparative examples were cut to a width of 25 mm. Next, under ambient temperature of 23°C and humidity of 50%RH, the conductive adhesive sheet was attached to a stainless steel plate (SUS plate, a stainless steel plate that had been hairline polished using 360-grit waterproof abrasive paper), and the upper surface was pressed together by rolling a 2kg roller back and forth once. After that, the specimen was left at room temperature for 1 hour to be used as the test piece. The aforementioned test specimens were peeled off at a speed of 300 mm / min using a Tensilon universal tensile testing machine (Tensilon RTA-100, manufactured by A&D Co., Ltd.) under the same temperature and humidity conditions as above, and the 180-degree peel adhesion strength was measured. A adhesion strength of 8 N / 25 mm or higher was evaluated as having excellent adhesion.

[0111] <Method for evaluating conductivity> A brass electrode (10mm x 10mm) was attached to one of the conductive adhesive layers of a conductive adhesive sheet (10mm x 10mm). Under conditions of 23°C and 50% RH, a load of 20N was applied to the brass electrode from the conductive adhesive sheet attachment point. The brass electrode and the conductive adhesive sheet were connected, and a current of 10μA was passed through using a milliohmmeter (manufactured by NF Circuit Design Block Co., Ltd.). The resistance value was measured, and the conductivity was evaluated based on the evaluation criteria below. [Evaluation Criteria] ◎: Resistance value of 10mΩ or less ○: Resistance value greater than 10mΩ and less than or equal to 20mΩ ×: Resistance value exceeds 20mΩ

[0112] [Table 1]

[0113] [Table 2] [Explanation of symbols]

[0114] 1 copper foil 2 Conductive adhesive layer 3. Nickel plating layer 4. Conductive filler 5. Adhesive 10 Conductive adhesive sheet

Claims

1. Copper foil and A nickel plating layer is provided on at least one surface of the copper foil, The nickel plating layer has a conductive adhesive layer, The conductive adhesive sheet is characterized in that the conductive adhesive layer includes a conductive filler and an adhesive.

2. The conductive adhesive sheet according to claim 1, wherein the average thickness of the nickel plating layer is 0.03 μm or more.

3. The conductive adhesive sheet according to any one of claims 1 to 2, wherein the average thickness of the nickel plating layer is 0.05 μm or more.

4. The conductive adhesive sheet according to any one of claims 1 to 2, wherein the conductive filler is nickel.

5. The conductive adhesive sheet according to any one of claims 1 to 2, wherein the nickel plating layer is on both surfaces of the copper foil.

6. The conductive adhesive sheet according to any one of claims 1 to 2, wherein the conductive adhesive layer is located on the outermost surface of both of the conductive adhesive sheets.

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