KR102530373B1 - Conductive adhesive sheet - Google Patents

Abstract

[Problem] An object to be solved by the present invention is to provide a thin conductive adhesive sheet having good adhesiveness, conductivity and conductivity stability over time even when thin, and excellent in productivity.
[Solution] The present invention is a conductive adhesive sheet having a total thickness of 50 µm or less, comprising a conductive substrate and one or two or more conductive adhesive layers, wherein at least one type of conductive particle is 0.01% by mass in each layer of the conductive adhesive layer. to 10% by mass, and the thickness of each layer of the conductive pressure-sensitive adhesive layer is 1 μm to 12 μm, respectively.

Description

Conductive adhesive sheet {CONDUCTIVE ADHESIVE SHEET}

The present invention relates to a conductive adhesive sheet having a conductive substrate and a conductive adhesive layer containing conductive particles.

Because of its ease of handling, the conductive adhesive sheet is used for shielding electromagnetic waves that do not need to be copied from electrical and electronic devices, shielding harmful spatial electromagnetic waves generated from electrical and electronic devices, and grounding to prevent static electricity. It is becoming. In recent years, along with miniaturization and thinning of the electrical/electronic devices, thinning of the conductive adhesive sheet used for these devices is also required.

As a thin conductive adhesive sheet having appropriate conductivity and adhesiveness, a pressure-sensitive adhesive sheet having an adhesive layer made of a conductive adhesive in which a conductive filler is dispersed in an adhesive substance is known on a conductive substrate (see Patent Documents 1 and 2). .

However, with the further miniaturization and thinning of electrical/electronic devices in recent years, further thinning has been demanded for the conductive adhesive sheet as well. In addition, there was also a problem that the adhesiveness of the conductive adhesive sheet decreased with time and the conductivity decreased. However, a thin conductive adhesive sheet having excellent conductivity, stability over time and adhesiveness has not yet been found.

Japanese Patent Publication No. 2004-263030 Japanese Patent Laid-Open No. 2009-79127

An object to be solved by the present invention is to provide a conductive adhesive sheet having good adhesiveness and conductivity even when thin, and whose conductivity is difficult to decrease with time.

The inventors of the present invention found that the above problems could be solved by combining the total thickness of the pressure sensitive adhesive sheet, the content of conductive particles in the conductive pressure sensitive adhesive layer, and the thickness of the conductive pressure sensitive adhesive layer within a specific range.

That is, the present invention is a conductive adhesive sheet having a total thickness of 50 µm or less, comprising a conductive substrate and one or two or more conductive adhesive layers, wherein at least one type of conductive particle is present in an amount of 0.01% to 10% in each layer of the conductive adhesive layer. It relates to a conductive pressure-sensitive adhesive sheet containing mass%, and the thickness of each layer of the conductive pressure-sensitive adhesive layer is 1 μm to 12 μm, respectively.

Since the conductive adhesive sheet of the present invention has excellent adhesion to adherends and conductivity while being ultra-thin, it has stability over time in conductivity and is used for shielding electromagnetic waves used in electrical/electronic devices, etc., and prevents harmful effects generated from electrical/electronic devices. It is useful for shielding electromagnetic waves in space and ground fixing to prevent electrostatic charge. In particular, it can be suitably applied to applications in portable electronic devices where thinning is progressing and there are severe restrictions on the volume within the housing.

1 is a suitable example of the conductive adhesive sheet of the present invention.
2 is a suitable example of the conductive adhesive sheet of the present invention.
Fig. 3 is an electron micrograph of bead-shaped conductive particles suitably used in the conductive adhesive sheet of the present invention.

The conductive adhesive sheet of the present invention is a conductive adhesive sheet having a total thickness of 50 µm or less, comprising a conductive substrate and one or two or more conductive adhesive layers, wherein at least one type of conductive particle is 0.01% by mass in each layer of the conductive adhesive layer. -10% by mass, and the thickness of each layer of the conductive adhesive layer is 1 μm to 12 μm, respectively.

Below, the conductive adhesive sheet of the present invention will be described in more detail based on its components. In addition, the "sheet" in the present invention means a form in which a thin pressure-sensitive adhesive layer formed using at least one layer of conductive pressure-sensitive adhesive is provided on a conductive substrate or on a release sheet, for example, a sheet or roll type. , or in the form of products such as thin plates, strips (tape), etc.

(Conductive pressure-sensitive adhesive layer)

The conductive adhesive sheet of the present invention has one layer or two or more conductive adhesive layers. The conductive adhesive layer contains specific conductive particles and an adhesive component. The thickness of each layer of the conductive pressure-sensitive adhesive layer is 1 μm to 12 μm, respectively, preferably 2.5 μm to 10 μm, and preferably 4 μm to 8 μm. The conductive pressure-sensitive adhesive layer, even if it is thin, can achieve both excellent conductivity and excellent adhesiveness.

The conductive thin pressure-sensitive adhesive sheet of the present invention, even if it is very thin as described above, can achieve both excellent conductivity, excellent adhesiveness, and stability over time of conductivity.

The conductive adhesive layer can be formed by using an adhesive composition containing the conductive particles and an adhesive component.

(conductive particles)

The said conductive adhesive layer contains at least 1 sort(s) of electroconductive particle. As for the said electroconductive particle, the thing whose particle diameter d50 is in the range of 10 micrometer - 30 micrometer is used. As a result, it is possible to obtain a conductive thin pressure-sensitive adhesive sheet having excellent conductivity, adhesiveness, and stability over time of conductivity.

The particle diameter d50 of the conductive particles is preferably in the range of 12 μm to 30 μm, and more preferably in the range of 10 μm to 26 μm.

In addition, the said particle diameter d50 points out the 50% cumulative value in a particle size distribution, and is a value measured by the laser analysis/scattering method. Examples of the measuring device include Microtrac MT3000II manufactured by Nikkiso Co., Ltd. and SALD-3000 Laser Diffraction Particle Size Distribution Analyzer manufactured by Shimadzu Corporation.

As a method of adjusting the particle diameter d50 within the above range, for example, a method of pulverizing conductive particles with a jet mill or a sieving method using a sieve or the like can be cited.

The particle diameter d50 of the conductive particles is preferably 100% to 500%, preferably 150% to 470%, and more preferably 200% to 450% of the thickness of the conductive pressure-sensitive adhesive layer containing the particles. , it is more preferable to achieve both superior conductivity and stability over time of adhesiveness and conductivity.

Examples of the conductive particles include metal powder particles such as gold, silver, copper, nickel, and aluminum; conductive resin particles such as carbon and graphite; particles and the like can be used. Among them, as the conductive particles, it is more preferable to use nickel powder particles, copper powder particles, or silver powder particles to achieve both excellent conductivity and adhesiveness, and a number of needle-like particles on the surface of the particles produced by the carbonyl method It is particularly preferable to use surface needle-shaped nickel particles having a surface needle-shaped particle, smoothing treatment (pulverization treatment) of the surface needle-shaped particle to obtain spherical particles, or copper powder or silver powder produced by an ultra-high pressure whirling water atomization method. .

Examples of the shape of the conductive particles include a spherical shape, a spike shape, a flake shape, and a bead shape in which bonds are formed between a plurality of conductive particles shown in FIG. It is preferable from the viewpoint of coexistence of adhesiveness and stability over time of conductivity.

The said conductive particle contains 0.01 mass % - 10 mass % with respect to the total mass of the conductive adhesive layer which the particle contains, but it is more preferable to contain 0.1 mass % - 8 mass %, and 0.5 mass % - 5 mass % What is contained is particularly preferable for obtaining a conductive thin pressure-sensitive adhesive sheet having further excellent conductivity and adhesiveness, and stability over time of conductivity.

(adhesive component)

As an adhesive composition used for formation of the said electroconductive adhesive layer, what contains an adhesive component together with the said electroconductive particle can be used.

Examples of the pressure-sensitive adhesive composition include (meth)acrylic pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive composition, synthetic rubber-based pressure-sensitive adhesive composition, natural rubber-based pressure-sensitive adhesive composition, silicone pressure-sensitive adhesive composition, etc. It is preferable to use an acrylic pressure-sensitive adhesive composition made of a polymer and containing the above conductive fine particles and, if necessary, additives such as a tackifying resin and a crosslinking agent for forming a conductive pressure-sensitive adhesive layer having excellent weather resistance and heat resistance.

As the acrylic polymer, for example, an acrylic polymer obtained by polymerizing a monomer component containing a (meth)acrylate monomer having an alkyl group of 1 to 14 carbon atoms can be suitably used.

Examples of the (meth)acrylate having an alkyl group of 1 to 14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. Acrylate, t-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate ) acrylate, 2-ethylhexyl (meth)acrylate, etc. can be used alone or in combination of two or more.

Especially, as the (meth)acrylate having an alkyl group having 1 to 14 carbon atoms, it is preferable to use (meth)acrylate having an alkyl group having 4 to 12 carbon atoms, and having 4 to 9 carbon atoms. It is more preferable to use a (meth)acrylate having a phosphorus linear or branched alkyl group, and it is more preferable to use n-butyl acrylate or 2-ethylhexyl acrylate alone or in combination.

The content of the (meth)acrylate having an alkyl group having 1 to 14 carbon atoms relative to the total amount of the monomer components used in the production of the acrylic polymer is preferably in the range of 80% by mass to 98.5% by mass, It is more preferable that it is the range of 90 mass % - 98.5 mass %.

It is preferable to use a high polarity vinyl monomer as needed other than the above as a monomer component usable for manufacture of the said acrylic polymer.

As the highly polar vinyl monomer, a vinyl monomer having a carboxyl group, a vinyl monomer having a hydroxyl group, a vinyl monomer having an amide group, etc. may be used alone or in combination of two or more. Especially, it is preferable to use a vinyl monomer having a carboxyl group as the highly polar vinyl monomer because it is easy to adjust the adhesiveness of the conductive pressure-sensitive adhesive layer to an appropriate range.

As the vinyl monomer having a carboxyl group, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, etc. can be used, and among them, acrylic acid is used. It is desirable to do

When using a vinyl monomer having a carboxyl group, the content is preferably 0.2% by mass to 15% by mass, and more preferably 0.4% by mass to 10% by mass with respect to the total amount of monomer components used for production of the acrylic polymer. It is preferable, and since it is easy to adjust the adhesiveness of an adhesive to an appropriate range, it is more preferable that it is 0.5 mass % - 6 mass %.

As a vinyl monomer which has a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylates and the like can be used.

Examples of the vinyl monomer having an amide group include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N,N-dimethylacrylamide.

Examples of other highly polar vinyl monomers include sulfonic acid group-containing monomers such as vinyl acetate, ethylene oxide-modified succinic acid acrylate, 2-acrylamide-2-methylpropanesulfonic acid, and 2-methoxyethyl (meth)acrylate. , terminal alkoxy-modified (meth)acrylates such as 2-phenoxyethyl (meth)acrylate, and the like can be used.

The content of the highly polar vinyl monomer is preferably 0.2% by mass to 15% by mass, more preferably 0.4% by mass to 10% by mass, and 0.5% by mass relative to the total amount of the monomer components used for production of the acrylic polymer. It is more preferable that it is % - 6 mass % because it is easy to adjust the adhesiveness of an adhesive to an appropriate range.

The acrylic polymer can be produced by polymerizing the above monomer components by a known method such as solution polymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. Especially, it is preferable to employ|adopt the said solution polymerization method in order to improve the production cost and productivity.

It is preferable to use what has a weight average molecular weight in the range of 300,000 - 1,500,000 as an acrylic polymer obtained by the said method, and it is more preferable to use what has a weight average molecular weight in the range of 500,000 - 1,200,000.

As an adhesive composition usable for formation of the said conductive adhesive layer, what contains various additives can be used as needed.

As said additive, in order to further improve the adhesive force of a conductive adhesive layer, for example, what contains tackifying resin can be used.

As the tackifying resin, rosin-based resins, terpene-based resins, petroleum resins such as aliphatic (C5-based) or aromatic (C9-based) resins, styrene-based resins, phenolic resins, xylene-based resins, methacrylic resins, etc. can be used. It is preferable to use a rosin-based resin, and it is more preferable to use a polymerized rosin-based resin.

It is preferable to use the said tackifying resin in the range of 10 mass parts - 50 mass parts with respect to 100 mass parts of said acrylic polymers.

As the additive, in addition to the above, a dispersant, an antisettling agent, a plasticizer, a softener, a metal deactivator, an antioxidant, a pigment, a dye, and the like can be used as necessary.

It is preferable to use the said dispersing agent and an antisettling agent to prevent sedimentation of the electroconductive particle contained in the said adhesive composition with time.

As the anti-settling agent, it is preferable to use, for example, a fatty acid amide resin, a urethane resin, or the like.

It is preferable to use the said antisettling agent in the range of 0.5 mass % - 10 mass % with respect to the solid content of the adhesive component, it is more preferable to use it in the range of 1 mass % - 6 mass %, and it is 1.5 mass % - 3 mass % It is more preferable to use it in the range of %.

As an adhesive composition usable for formation of the said conductive adhesive layer, what contains a crosslinking agent can be used as needed.

Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and an aziridine crosslinking agent.

It is preferable to appropriately select the type and amount of the crosslinking agent according to the type and amount of functional groups of the adhesive component such as the acrylic polymer.

The crosslinking agent may be appropriately adjusted and used so that the gel fraction of the conductive pressure-sensitive adhesive layer is in the range of 25% by mass to 60% by mass.

(Gel fraction of conductive adhesive layer)

The conductive pressure-sensitive adhesive layer expresses even more excellent cohesive force, but it is preferable to form a three-dimensional cross-linked structure. As an indicator of the formation of a cross-linked structure, the gel fraction representing the insoluble content when the conductive pressure-sensitive adhesive layer is immersed in, for example, toluene, which is a good solvent for (meth)acrylic pressure-sensitive adhesive, for 24 hours is exemplified. The gel fraction of the conductive pressure-sensitive adhesive layer is preferably 10% by mass to 40% by mass, and 15% by mass to 30% by mass can further improve the cohesive force in the shear direction and improve peeling resistance. more preferable because

The gel fraction is calculated with the following formula.

Gel fraction (mass %) = {(mass of conductive adhesive layer after being immersed in toluene)/(mass of conductive adhesive layer before being immersed in toluene)} × 100

Mass of conductive adhesive layer = (mass of conductive thin adhesive sheet) - (mass of conductive substrate)

The adhesive composition usable for formation of the said conductive adhesive layer can be manufactured by mixing the composition containing the said acrylic polymer, and the said electroconductive particle, for example.

As said mixing method, the method of mixing and disperse|distributing the composition containing the said acrylic polymer etc., electroconductive particle, and an additive etc. as needed, for example using a dispersion stirrer etc. is mentioned, for example. Examples of the dispersion stirrer include a dissolver manufactured by Inoue Seisakusho, a butterfly mixer, a BDM twin-screw mixer, and a planetary mixer. It is desirable to do

As the pressure-sensitive adhesive composition usable for forming the conductive pressure-sensitive adhesive layer, it is preferable to use a pressure-sensitive adhesive composition having a viscosity in the range of 100 mPa s to 8000 mPa s, and to use a pressure-sensitive adhesive composition having a viscosity in the range of 200 mPa s to 4000 mPa s. It is more preferable, and it is preferable to use one having a viscosity in the range of 200 mPa·s to 1000 mPa·s to prevent sedimentation of conductive particles over time and to prevent coating streaks from occurring when coating the pressure-sensitive adhesive composition. do.

As a method of adjusting the viscosity of the pressure-sensitive adhesive composition to the above range, a method of adjusting the type or amount of solvent, the type or molecular weight of an adhesive substance such as an acrylic polymer, etc. method is preferred.

The non-volatile content of the pressure-sensitive adhesive composition is not particularly limited, but is preferably in the range of 10% by mass to 35% by mass, more preferably in the range of 10% by mass to 30% by mass, and 10% by mass to 20% by mass. It is more preferably in the range of %.

(conductive substrate)

Examples of the conductive substrate used for producing the conductive thin adhesive sheet of the present invention include metal substrates and graphite substrates.

As the metal substrate, for example, a substrate made of gold, silver, copper, aluminum, nickel, iron, tin, alloys thereof, etc. can be used, and it is preferable to use a substrate made of aluminum or copper to improve the workability of the conductive substrate. It is excellent and relatively low cost, so it is preferable.

As the substrate made of the above-mentioned copper, a substrate made of electrolytic copper, a substrate made of rolled copper, and the like can be used, for example.

As the base material made of electrolytic copper, CF-T9FZ-HS-12 (thickness 12 μm), CF-T8G-DK-18 (thickness 18 μm), CF-T8G-DK-35 (thickness 35 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. ) can be used.

As the rolled copper foil, TCU-H-8-RT (thickness: 8 μm) manufactured by Nippon Mining Co., Ltd. or TPC (thickness: 6 μm) manufactured by JX Nikko Nippon Metal Co., Ltd. can be used.

As the conductive substrate, a thickness of 1 μm to 30 μm is preferable, a thickness of 3 μm to 25 μm is more preferable, and a thin metal foil or the like having a thickness of 5 μm to 20 μm is used to obtain a thin conductive thin adhesive sheet having excellent processability. more preferable

(release liner)

A release liner may be laminated on the surface of the conductive pressure-sensitive adhesive layer constituting the conductive thin pressure-sensitive adhesive sheet of the present invention, if necessary.

The release liner is not particularly limited, and examples thereof include paper such as graft paper, glassine paper, and quality paper, resin films such as polyethylene, polypropylene (OPP, CPP), and polyethylene terephthalate, and the above paper and resin films. Laminated laminated paper, one in which the surface of the above-mentioned papers is filled with clay or polyvinyl alcohol, etc., or one in which one or both sides of the above-mentioned paper are peeled with a silicone-based resin or the like can be used. there is.

The conductive thin pressure-sensitive adhesive sheet of the present invention can be produced, for example, by coating the pressure-sensitive adhesive composition containing conductive particles on one or both surfaces of the conductive substrate and drying it (so-called direct coating method).

Further, in the conductive thin pressure sensitive adhesive sheet of the present invention, a conductive pressure sensitive adhesive layer is formed by applying the pressure sensitive adhesive composition containing the conductive particles to the surface of a release liner in advance and drying the pressure sensitive adhesive composition, and then, the conductive pressure sensitive adhesive layer is formed as described above. It can also be manufactured by a method of transferring to one side or both sides of a conductive substrate (so-called transfer method).

It is preferable to cure the conductive thin pressure-sensitive adhesive sheet produced by any of the methods described above for 48 hours or more in the range of 20°C to 50°C to advance the crosslinking reaction of the conductive pressure-sensitive adhesive layer.

As a method of coating the conductive adhesive composition on the release liner or the conductive substrate, for example, a method of coating using a comma coater, a method of coating using a gravure coater, a method of coating using a lip coater, etc. can be heard Among them, as the above coating method, it is preferable to employ a method of coating using a gravure coater or a method of coating using a lip coater, and adopting a method of coating with a micro gravure coater is a conductive adhesive layer The thickness of can be formed with high precision, and as a result, it is more preferable to achieve both more excellent conductivity and adhesiveness.

Examples of suitable configurations of the conductive thin adhesive sheet of the present invention are shown in FIGS. 1 and 2 . 1 is a single-sided PSA sheet in which a conductive adhesive layer 2 is laminated on a conductive substrate 1. 2 is a double-sided pressure-sensitive adhesive sheet in which conductive adhesive layers 2 are laminated on both surfaces of a conductive substrate 1 . In these configurations, a configuration in which a release liner is provided on the surface of the pressure-sensitive adhesive layer 2 can be preferably used.

[Example]

Examples are specifically described below, but the present invention is not limited to these examples.

(Preparation of acrylic pressure-sensitive adhesive composition 1)

In a reaction vessel equipped with a cooling tube, a stirrer, a thermometer and a 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, and 2-hydroxyethyl After dissolving 0.1 parts by mass of acrylate and 0.1 part by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator in 100 parts by mass of ethyl acetate, replacing with nitrogen, polymerizing at 80° C. for 12 hours, weight average molecular weight An ethyl acetate solution of 600,000 acrylic polymer was obtained.

10 parts by mass of pen cell D-135 (manufactured by Arakawa Chemical Industry Co., Ltd., polymerized rosin pentaerythritol ester, softening point 135 ° C.) based on 100 parts by mass of the solid content of the ethyl acetate solution of the acrylic polymer, Super Ester A-100 (Arakawa Chemical Industry Co., Ltd. product disproportionated rosin glycerin ester, softening point 100 degreeC) 10 mass parts were mix|blended, and the acrylic adhesive composition 1 was obtained by adjusting the solid content concentration of an acrylic polymer to 40 mass % using ethyl acetate.

[Preparation of the conductive adhesive composition]

(Preparation of conductive adhesive composition A)

100 parts by mass of the acrylic adhesive composition 1, 0.4 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. as bead-shaped conductive particles, and Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Corporation, solid content 40) as a crosslinking agent The conductive adhesive composition A was prepared by mixing 2 mass %) and 70 mass parts of ethyl acetate as a dilution solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition B)

100 parts by mass of the acrylic adhesive composition 1, 2.0 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. as bead-shaped conductive particles, and Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Corporation, solid content 40) as a crosslinking agent The conductive adhesive composition B was prepared by mixing 2 parts by mass) and 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition C)

100 parts by mass of the acrylic pressure-sensitive adhesive composition 1, 0.4 parts by mass of nickel powder NI255T-280 (d50: 15.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. as bead-shaped conductive particles, and Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Co., Ltd., as a crosslinking agent, Conductive adhesive composition C was prepared by mixing 2 mass parts of 40 mass % of solid content), and 70 mass parts of ethyl acetate as a dilution solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition D)

100 parts by mass of the acrylic pressure-sensitive adhesive composition 1, 0.4 parts by mass of nickel powder NI255T-350 (d50: 13.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. as bead-shaped conductive particles, and Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Co., Ltd., as a crosslinking agent, Conductive adhesive composition D was prepared by mixing 2 mass parts of 40 mass % of solid content), and 70 mass parts of ethyl acetate as a dilution solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition E)

100 parts by mass of the acrylic pressure-sensitive adhesive composition 1, 4.0 parts by mass of nickel powder NI123 (d50: 12.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. as spherical conductive particles, and Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Corporation, solid content 40 mass parts) as a crosslinking agent The conductive adhesive composition E was prepared by mixing %) 2 mass parts with 70 mass parts of ethyl acetate as a dilution solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition F)

100 parts by mass of the acrylic pressure-sensitive adhesive composition 1, 6.0 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd., and 2 parts by mass of Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Corporation, 40% by mass solid content) as a crosslinking agent The conductive adhesive composition E was prepared by mixing 70 parts by mass of ethyl acetate as a dilution solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition G)

100 parts by mass of the acrylic adhesive composition 1, 6.0 parts by mass of nickel powder NI123 (d50: 12.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. as spherical conductive particles, and Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Corporation, solid content 40 mass parts) as a crosslinking agent The conductive adhesive composition G was prepared by mixing %) 2 mass parts and 70 mass parts of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer.

(Preparation of conductive adhesive composition H)

100 parts by mass of the acrylic adhesive composition 1, 0.02 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd., and 2 parts by mass of Burnock NC40 (isocyanate-based crosslinking agent manufactured by DIC Corporation, 40% by mass solid content) as a crosslinking agent The conductive adhesive composition H was prepared by mixing 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer.

(Example 1)

[Production of conductive thin adhesive sheet]

After coating the conductive adhesive composition A on the release film “PET38×1 A3” manufactured by Nippa Co., Ltd. using a comma coater so that the thickness of the conductive adhesive layer after drying is 6 μm, and drying for 2 minutes in a dryer at 80 ° C. After bonding on both sides of an electrolytic copper foil (CF-T9FZ-HS-12 manufactured by Fukuda Metal Foil Co., Ltd.) having a thickness of 15 μm, curing at 40° C. for 48 hours to obtain a conductive thin adhesive sheet.

(Example 2)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except that conductive adhesive composition B was used instead of conductive adhesive composition A.

(Example 3)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except for using the conductive adhesive composition C instead of the conductive adhesive composition A.

(Example 4)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except for using the conductive adhesive composition D instead of the conductive adhesive composition A.

(Example 5)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except that the thickness of the conductive adhesive layer after drying was 10 µm.

(Example 6)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except that conductive adhesive composition E was used instead of conductive adhesive composition A.

(Example 7)

The bonded electrolytic copper foil was replaced by CF-T9FZ-HS-12 manufactured by Fukuda Metal Foil Industry Co., Ltd. and replaced with CF-T8G-DK-18 (thickness 18 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd., and the bonded surface was changed to only one side. A conductive thin adhesive sheet was obtained in the same manner as in Example 1 except for the above.

(Comparative Example 1)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except that conductive adhesive composition F was used instead of conductive adhesive composition A.

(Comparative Example 2)

The bonded electrolytic copper foil was replaced by CF-T9FZ-HS-12 manufactured by Fukuda Metal Foil Industrial Co., Ltd. and CF-T8G-DK-35 (thickness 35 μm) manufactured by Fukuda Metal Foil Industrial Co., Ltd. was used, and the thickness of the conductive adhesive layer after drying was A conductive thin adhesive sheet was obtained in the same manner as in Example 1 except that the thickness was 10 µm.

(Comparative Example 3)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except that conductive adhesive composition G was used instead of conductive adhesive composition A.

(Comparative Example 4)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1 except that the conductive adhesive composition E was used instead of the conductive adhesive composition A and the thickness of the conductive adhesive layer after drying was 15 µm.

(Comparative Example 5)

Conductive thin adhesive sheet in the same manner as in Example 1, except that the conductive adhesive composition H was used instead of the conductive adhesive composition A, and the bonded copper foil was TPC (thickness: 6 μm) manufactured by JX Nikko International Metals Co., Ltd. got

(Comparative Example 6)

A conductive thin adhesive sheet was obtained in the same manner as in Example 1, except that the thickness of the conductive adhesive layer after drying was 0.5 µm.

(evaluation)

The total thickness, conductivity, and adhesive strength of the conductive adhesive sheets obtained in Examples and Comparative Examples were evaluated.

[Total thickness of conductive adhesive sheet]

The total thickness of the conductive adhesive sheet was measured using a thickness meter "TH-102" (manufactured by Tester Sangyo Co., Ltd.).

[Thickness of the adhesive layer]

A part of the conductive adhesive layer formed on the surface of the release liner used when producing the conductive adhesive sheet in the above Examples and Comparative Examples was extracted, and one side thereof was S25 (polyethylene terephthalate film, thickness 25 μm, manufactured by Unitika Co., Ltd.) A padded sample was prepared.

The release liner was peeled off from the sample, and its thickness was measured using a thickness meter "TH-102" (manufactured by Tester Sangyo Co., Ltd.), and the value obtained by subtracting the thickness of S25 was used as the thickness of the conductive adhesive layer.

[Evaluation method of conductivity (measurement of resistance value)]

A brass electrode measuring 10 mm in length x 10 mm in width was attached to one side of the conductive adhesive layer of the conductive adhesive sheet having a width of 10 mm x 10 mm.

A 7.5 mm long x 7.5 mm wide copper foil (thickness: 35 µm) was pasted on the other side of the conductive adhesive sheet.

Under an environment of 23 ° C. and 50% RH, in a state where a load of 20 N of surface pressure is applied from the top surface of the brass electrode, terminals are connected to the brass electrode and the copper foil, and a milliohm meter (NF Circuit Design Block Co., Ltd. ) was used to flow a current of 10 μA, and the resistance value was measured. A case where the resistance value was 40 mΩ or less was evaluated as having excellent conductivity. Moreover, after lapse of 30 days, the resistance value was measured again. The case where the resistance value was 120 mΩ or less was evaluated as being excellent in stability over time of the conductivity.

(Evaluation method of adhesiveness)

A 20 mm wide conductive adhesive sheet is pressed 1 reciprocally with a 2.0 kg roller on the surface of a stainless steel plate (hereinafter referred to as "stainless steel plate") subjected to hairline polishing using No. 360 water-resistant abrasive paper in an environment of 23°C and 60% RH. attached

After the attachment was left at room temperature for 1 hour, the 180-degree peel adhesive strength was measured at room temperature at a tensile speed of 300 mm/min using a tensile tester (Tensiron RTA-100, manufactured by A&D). In the case of using a double-sided pressure-sensitive adhesive sheet as the conductive pressure-sensitive adhesive sheet, the conductive pressure-sensitive adhesive layer on the opposite side of the surface pasted on the stainless steel plate was covered with S25 (polyethylene terephthalate film, thickness 25 μm, manufactured by Unitica Co., Ltd.).

(Evaluation criteria for adhesion)

◎：7N/20mm or more

○: 5 N/20 mm or more, less than 7 N/20 mm

×: Less than 4N/20mm

[Table 1]

[Table 2]

1 Conductive substrate
2 conductive adhesive layer

Claims (6)

A conductive adhesive sheet having a total thickness of 50 μm or less, comprising a conductive substrate and one or two or more conductive adhesive layers, wherein at least one type of conductive particle is contained in an amount of 0.01% to 10% by mass, The thickness of each layer of the conductive pressure-sensitive adhesive layer is 1 μm to 12 μm, respectively,
The conductive adhesive sheet in which the shape of the conductive particles is a bead shape. The method of claim 1,
The conductive adhesive sheet, wherein the particle diameter d50 of the conductive particles is 12 μm to 30 μm. According to claim 1 or claim 2,
The conductive adhesive sheet in which the particle diameter d50 of the conductive particles is 100% to 500% of the thickness of the PSA layer containing the particles. According to claim 1 or claim 2,
The conductive adhesive sheet in which the conductive substrate is a metal substrate. According to claim 1 or claim 2,
The conductive pressure-sensitive adhesive sheet wherein the conductive pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed using an acrylic pressure-sensitive adhesive composition containing an acrylic polymer. delete

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