JP2021183698A - Conductive adhesive sheet and portable electronic device - Google Patents

Abstract

To provide a conductive, thin, adhesive sheet which has good adhesiveness, conductivity and temporal stability of conductivity even though it is thin and has excellent productivity.SOLUTION: There is provided a conductive adhesive sheet having a total thickness of 50 μm or less which includes a conductive substrate and two conductive adhesive agent layers provided on both sides of the conductive substrate. Each of the conductive adhesive agent layers contains 0.01 to 10 mass% of at least one kind of conductive particles. The conductive particles have a particle size d50 of 12 μm-30 μm. Each of the conductive adhesive agent layers has a thickness of 1 to 12 μm.SELECTED DRAWING: None

Description

The present invention relates to a conductive pressure-sensitive adhesive sheet having a conductive base material and a conductive pressure-sensitive adhesive layer containing conductive particles, and a portable electronic device provided with the conductive pressure-sensitive adhesive sheet.

Due to its ease of handling, the conductive adhesive sheet is used for shielding unnecessary leaked electromagnetic waves radiated from electrical and electronic equipment, for shielding harmful spatial electromagnetic waves generated by electrical and electronic equipment, and for grounding to prevent static electricity. It is used for such purposes. In recent years, with the miniaturization and thinning of the electric / electronic devices, the conductive adhesive sheets used for them are also required to be thinned.

The thin conductive pressure-sensitive adhesive sheet having suitable conductivity and adhesiveness has a pressure-sensitive adhesive layer made of a conductive pressure-sensitive adhesive in which a conductive filler is dispersed in a pressure-sensitive adhesive on a conductive base material. Adhesive sheets are known (see Patent Documents 1 and 2).

However, with the recent further miniaturization and thinning of electric and electronic devices, the conductive adhesive sheet is also required to be further thinned. Further, there is also a problem that the adhesiveness of the conductive pressure-sensitive adhesive sheet decreases with time, and the conductivity decreases. However, a thin conductive pressure-sensitive adhesive sheet having excellent conductivity, stability over time, and adhesiveness has not yet been found.

Japanese Unexamined Patent Publication No. 2004-263030 Japanese Unexamined Patent Publication No. 2009-79127

The problem to be solved by the present invention is to provide a conductive pressure-sensitive adhesive sheet which has good adhesiveness and conductivity even if it is thin and whose conductivity does not easily decrease with time, and a portable electronic device provided with the conductive pressure-sensitive adhesive sheet. There is something in it.

The present inventors can solve the above problems by combining the total thickness of the pressure-sensitive adhesive sheet, the content of the conductive particles in the conductive pressure-sensitive adhesive layer, and the thickness of the conductive pressure-sensitive adhesive layer within a specific range. I found it.

That is, the present invention is a conductive pressure-sensitive adhesive sheet having a conductive base material and two conductive pressure-sensitive adhesive layers provided on both sides of the conductive base material and having a total thickness of 50 μm or less. Each layer of the conductive pressure-sensitive adhesive layer contains 0.01% by mass to 10% by mass of at least one kind of conductive particles, and the particle size d50 of the conductive particles is 12 μm to 30 μm, and the conductive pressure-sensitive adhesive layer. It relates to a conductive pressure-sensitive adhesive sheet having a thickness of 1 μm to 12 μm, respectively. Furthermore, the present invention relates to a portable electronic device provided with the conductive pressure-sensitive adhesive sheet.

Although the conductive pressure-sensitive adhesive sheet of the present invention is extremely thin, it has good adhesion to an adherend and conductivity, so that it has conductivity with time and stability, and is used in electrical and electronic devices and the like. It is useful for shielding electromagnetic waves used for shielding, shielding of harmful spatial electromagnetic waves generated by electrical and electronic equipment, and grounding and fixing to prevent static electricity. In particular, it can be suitably applied to portable electronic equipment applications in which the thickness is increasing and the volume limitation in the housing is strict.

It is a suitable example of the conductive pressure-sensitive adhesive sheet of the present invention. It is a suitable example of the conductive pressure-sensitive adhesive sheet of the present invention. It is a figure of the electron micrograph of the beaded conductive particles preferably used for the conductive pressure-sensitive adhesive sheet of this invention.

The conductive pressure-sensitive adhesive sheet of the present invention is a conductive pressure-sensitive adhesive sheet having a conductive base material and one layer or two or more types of conductive pressure-sensitive adhesive layers and having a total thickness of 50 μm or less. Each layer contains at least one kind of conductive particles in an amount of 0.01% by mass to 10% by mass, and the thickness of each layer of the conductive pressure-sensitive adhesive layer is 1 μm to 12 μm, respectively. ..

Hereinafter, the conductive pressure-sensitive adhesive sheet of the present invention will be described in more detail based on its constituent elements. The "sheet" in the present invention means a form in which a thin pressure-sensitive adhesive layer formed by using at least one layer of the conductive pressure-sensitive adhesive is provided on a conductive base material or a release sheet, for example. Includes all product forms such as leaf-shaped, roll-shaped, thin plate-shaped, and strip-shaped (tape-shaped).

(Conductive adhesive layer)
The conductive pressure-sensitive adhesive sheet of the present invention has one layer or two or more conductive pressure-sensitive adhesive layers. The conductive pressure-sensitive adhesive layer contains specific conductive particles and a pressure-sensitive adhesive component. The thickness of each layer of the conductive pressure-sensitive adhesive layer is 1 μm to 12 μm, preferably 2.5 μm to 10 μm, and preferably 4 μm to 8 μm. Even if the conductive pressure-sensitive adhesive layer is thin as described above, it is possible to achieve both excellent conductivity and excellent adhesiveness.

Even if the conductive thin pressure-sensitive adhesive sheet of the present invention is extremely thin as described above, it is possible to achieve both excellent conductivity, excellent adhesiveness, and temporal stability of conductivity.
The conductive pressure-sensitive adhesive layer can be formed by using a pressure-sensitive adhesive composition containing the conductive particles and a pressure-sensitive adhesive component.

(Conductive particles)
The conductive pressure-sensitive adhesive layer contains at least one kind of conductive particles. As the conductive particles, those having a particle size d50 in the range of 10 μm to 30 μm are used. As a result, it is possible to obtain a conductive thin pressure-sensitive adhesive sheet that has both excellent conductivity, adhesiveness, and conductivity with time.

The particle size d50 of the conductive particles is preferably 12 μm to 30 μm, and more preferably 10 μm to 26 μm.
The particle size d50 refers to a 50% cumulative value in the particle size distribution, and is a value measured by a laser analysis / scattering method. Examples of the measuring device include a Microtrack MT3000II manufactured by Nikkiso Co., Ltd., a laser diffraction type particle size distribution measuring device SALD-3000 manufactured by Shimadzu Co., Ltd., and the like.
Examples of the method for adjusting the particle size to the particle size d50 in the above range include a method of pulverizing conductive particles with a jet mill and a sieving method using a sieve or the like.

The particle diameter d50 of the conductive particles is preferably 100% to 500%, preferably 150% to 470%, and more preferably 150% to 470% with respect to the thickness of the conductive pressure-sensitive adhesive layer contained in the particles. Is more preferably 200% to 450% in order to achieve both even better conductivity, adhesiveness, and stability over time of conductivity.

The conductive particles include metal powder particles such as gold, silver, copper, nickel, and aluminum, conductive resin particles such as carbon and graphite, and a metal coating on the surface of the resin particles, solid glass beads, and hollow glass beads. Particles and the like can be used. Among them, it is more preferable to use nickel powder particles, copper powder particles, or silver powder particles as the conductive particles in order to achieve both even better conductivity and adhesiveness, and the particles are produced by the carbonyl method. Manufactured by surface needle-shaped nickel particles having a large number of needle-shaped particles on the surface, smoothed (treated (crushed)) spherical particles, or ultra-high pressure swirling water atomizing method. It is particularly preferable to use copper powder, silver powder, or the like.

Examples of the shape of the conductive particles include a spherical shape, a spike shape, a flake shape, and a bead shape in which a bond or the like is formed between a large number of conductive particles as shown in FIG. It is preferable from the viewpoint of achieving both excellent conductivity, adhesiveness, and stability over time.

The conductive particles are contained in an amount of 0.01% by mass to 10% by mass, but more preferably 0.1% by mass to 8% by mass, based on the total mass of the conductive pressure-sensitive adhesive layer contained in the particles. It is preferable that the content is preferably 0.5% by mass to 5% by mass in order to obtain a conductive thin pressure-sensitive adhesive sheet having further excellent conductivity, adhesiveness, and conductivity with time.

(Adhesive component)
As the pressure-sensitive adhesive composition used for forming the conductive pressure-sensitive adhesive layer, one containing the pressure-sensitive adhesive component together with the conductive particles can be used.

Examples of the pressure-sensitive adhesive composition include (meth) acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesive compositions, synthetic rubber-based pressure-sensitive adhesive compositions, natural rubber-based pressure-sensitive adhesive compositions, silicone-based pressure-sensitive adhesive compositions, and the like. An acrylic pressure-sensitive adhesive containing conductive particles, using a krill-based polymer as a base polymer, and containing the conductive fine particles and, if necessary, an additive such as a tackifier resin or a cross-linking agent. It is preferable to use the composition in order to form 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 having 1 to 14 carbon atoms can be preferably used. ..

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

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

The content of the (meth) acrylate having an alkyl group having 1 to 14 carbon atoms with respect to the total amount of the monomer component used for producing the acrylic polymer is in the range of 80% by mass to 98.5% by mass. It is preferably in the range of 90% by mass to 98.5% by mass, and more preferably.

As the monomer component that can be used for producing the acrylic polymer, it is preferable to use a highly polar vinyl monomer, if necessary, in addition to the above-mentioned ones.

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, or the like can be used alone or in combination of two or more. Among them, 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 a suitable 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 amber acid acrylate and the like can be used, and among them, acrylic. It is preferable to use acid.

When a vinyl monomer having a carboxyl group is used, the content thereof is preferably 0.2% by mass to 15% by mass with respect to the total amount of the monomer components used in the production of the acrylic polymer. , 0.4% by mass to 10% by mass, more preferably 0.5% by mass to 6% by mass, because it is easy to adjust the adhesiveness of the pressure-sensitive adhesive to a suitable range.

As the vinyl monomer having a hydroxyl group, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and the like are used. can do.

As the vinyl monomer having an amide group, for example, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide and the like can be used.

Other highly polar vinyl monomers include, for example, vinyl acetate, ethylene oxide-modified amber acid acrylate, sulfonic acid group-containing monomer such as 2-acrylamide-2-methylpropane sulfonic acid, 2-methoxyethyl (meth) acrylate, and 2 -Terminal alkoxy-modified (meth) acrylates such as phenoxyethyl (meth) acrylates can be used.

The content of the highly polar vinyl monomer is preferably 0.2% by mass to 15% by mass, preferably 0.4% by mass, based on the total amount of the monomer components used in the production of the acrylic polymer. It is more preferably 10% by mass, and more preferably 0.5% by mass to 6% by mass because it is easy to adjust the adhesiveness of the pressure-sensitive adhesive to a suitable range.

The acrylic polymer can be produced by polymerizing the above-mentioned monomer component by a known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method. Above all, it is preferable to adopt the solution polymerization method in order to improve the production cost and productivity.

As the acrylic polymer obtained by the above method, it is preferable to use a polymer having a weight average molecular weight in the range of 300,000 to 1.5 million, and a polymer having a weight average molecular weight in the range of 500,000 to 1.2 million is used. It is more preferable to do so.

As the pressure-sensitive adhesive composition that can be used for forming the conductive pressure-sensitive adhesive layer, those containing various additives can be used, if necessary.

As the additive, for example, an additive containing a tackifier resin can be used in order to further improve the adhesive strength of the conductive pressure-sensitive adhesive layer.

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

The tackifier resin is preferably used in the range of 10 parts by mass to 50 parts by mass with respect to 100 parts by mass of the acrylic polymer.

As the additive, in addition to the above-mentioned additives, dispersants, anti-sedimentants, plasticizers, softeners, metal deactivating agents, antioxidants, pigments, dyes and the like can be used, if necessary.

The dispersant and the anti-sedimentant are preferably used to prevent the conductive particles contained in the pressure-sensitive adhesive composition from settling over time.

As the sedimentation inhibitor, for example, a fatty acid amide resin, a urethane resin, or the like is preferably used.

The sedimentation inhibitor is preferably used in the range of 0.5% by mass to 10% by mass, more preferably in the range of 1% by mass to 6% by mass, based on the solid content of the pressure-sensitive adhesive component. It is more preferable to use it in the range of 1.5% by mass to 3% by mass.

As the pressure-sensitive adhesive composition that can be used for forming the conductive pressure-sensitive adhesive layer, a pressure-sensitive adhesive composition containing a cross-linking agent can be used, if necessary.

As the cross-linking agent, for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, a chelate-based cross-linking agent, an aziridine-based cross-linking agent, or the like can be used.

It is preferable that the type and amount of the cross-linking agent are appropriately selected according to the type of functional group and the amount of functional group of the adhesive component such as the acrylic polymer.

The cross-linking agent can 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 preferably forms a three-dimensional crosslinked structure in order to exhibit even more excellent cohesive force. Examples of the index for forming the crosslinked structure include a gel fraction representing an insoluble component when the conductive pressure-sensitive adhesive layer is immersed in toluene, which is a good solvent for a (meth) acrylic pressure-sensitive adhesive, for 24 hours. The gel content of the conductive pressure-sensitive adhesive layer is preferably 10% by mass to 40% by mass, and 15% by mass to 30% by mass further improves the cohesive force in the shear direction and resists peeling. It is more preferable because it can improve the properties.

The gel fraction is calculated by the following formula.
Gel fraction (% by mass) = {(mass of conductive pressure-sensitive adhesive layer after immersion in toluene) / (mass of conductive pressure-sensitive adhesive layer before immersion in toluene)} x 100
Mass of conductive pressure-sensitive adhesive layer = (mass of conductive thin pressure-sensitive adhesive sheet)-(mass of conductive base material)

The pressure-sensitive adhesive composition that can be used for forming the conductive pressure-sensitive adhesive layer can be produced, for example, by mixing the composition containing the acrylic polymer with the conductive particles.

Examples of the mixing method include a method of mixing and dispersing a composition containing the acrylic polymer or the like, conductive particles, and if necessary, an additive or the like using, for example, a dispersion stirrer or the like. .. Examples of the dispersion stirrer include a dissolver manufactured by Inoue Seisakusho, a butterfly mixer, a BDM twin-screw mixer, and a planetary mixer, and a dissolver or a butterfly mixer that easily uniformly disperses conductive particles such as metal powder without thickening is used. Is preferable.

As the pressure-sensitive adhesive composition that can be used 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 preferably in the range of 200 mPa · s to 4000 mPa · s. It is more preferable to use a material having a viscosity, and it is more preferable to use a material having a viscosity in the range of 200 Pa · s to 1000 mPa · s to prevent the conductive particles from settling over time and to prevent the pressure-sensitive adhesive composition. It is preferable to prevent the occurrence of coating streaks when coating.

Examples of the method for adjusting the viscosity of the pressure-sensitive adhesive composition within the above range include a method for adjusting the type and amount of the solvent, the type of the pressure-sensitive substance such as an acrylic polymer, the molecular weight thereof, and the like, and the type of the solvent. And the method of adjusting the amount used is preferable.

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, and more preferably in the range of 10% by mass to 30% by mass. It is more preferably in the range of 10% by mass to 20% by mass.

(Conductive base material)
Examples of the conductive base material used for manufacturing the conductive thin pressure-sensitive adhesive sheet of the present invention include a metal base material and a graphite base material.

As the metal base material, for example, a base material made of gold, silver, copper, aluminum, nickel, iron, tin or an alloy thereof can be used, and a base material made of aluminum or copper can be used. It is preferable because the conductive base material has excellent processability and is relatively low in cost.
As the base material made of copper, for example, a base material made of electrolytic copper, a base material made of rolled copper, or the like can be used.

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

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

The conductive substrate preferably has a thickness of 1 μm to 30 μm, more preferably 3 μm to 25 μm, and a metal foil or the like having a thickness of 5 μm to 20 μm is thin and thin. It is more preferable to obtain a conductive thin pressure-sensitive adhesive sheet having excellent processability.

(Peeling 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 for example, papers such as kraft paper, glassin paper, and high-quality paper, resin films such as polyethylene, polypropylene (OPP, CPP), and polyethylene terephthalate, and the papers and the resin film are laminated. Conventionally known such as laminated paper, one in which the surface of the paper is sealed with clay, polyvinyl alcohol, etc., and one in which one or both sides of the sealed paper are peeled with a silicon-based resin or the like. Can be used.

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

Further, in the conductive thin pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive composition containing the conductive particles is previously applied to the surface of the release liner and dried to form a conductive pressure-sensitive adhesive layer. Next, the conductive pressure-sensitive adhesive layer can also be produced by a method of transferring to one side or both sides of the conductive base material (so-called transfer method).

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

As a method of applying the conductive pressure-sensitive adhesive composition to the release liner or the conductive substrate, for example, a method of applying with a comma coater, a method of applying with a gravure coater, or a lip coater is used. And the method of painting. Among them, as the coating method, it is preferable to adopt a method of coating with a gravure coater or a method of coating with a lip coater, and it is preferable to adopt a method of coating with a microgravure coater. The thickness of the conductive pressure-sensitive adhesive layer can be formed with high accuracy, and as a result, it is more preferable to achieve both more excellent conductivity and adhesiveness.

1 and 2 show examples of suitable configurations of the conductive thin pressure-sensitive adhesive sheet of the present invention. FIG. 1 is a single-sided pressure-sensitive adhesive sheet in which a conductive pressure-sensitive adhesive layer 2 is laminated on a conductive base material 1. Further, FIG. 2 is a double-sided pressure-sensitive adhesive sheet in which the conductive pressure-sensitive adhesive layer 2 is laminated on both sides of the conductive base material 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.

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

(Preparation of Acrylic Adhesive Composition 1)
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 in a reaction vessel equipped with a cooling tube, a stirrer, a thermometer and a dropping funnel. After dissolving 0.1 part by mass of mass, 0.1 part by mass of 2-hydroxyethyl acrylate, and 0.1 part by mass of 2,2'-azobisisobutylnitrile as a polymerization initiator in 100 parts by mass of ethyl acetate and substituting with nitrogen, By polymerizing at 80 ° C. for 12 hours, an ethyl acetate solution of an acrylic polymer having a weight average molecular weight of 600,000 was obtained.

Pencel D-135 (manufactured by Arakawa Chemical Industry Co., Ltd., polymerized rosin pentaerythritol ester, softening point 135 ° C.), 10 parts by mass, super ester A-100 with respect to 100 parts by mass of the solid content of the ethyl acetate solution of the acrylic polymer. (Manufactured by Arakawa Chemical Industry Co., Ltd., disproportionate rosing lyserine ester, softening point 100 ° C.) By blending 10 parts by mass and adjusting the solid content concentration of the acrylic polymer to 40% by mass using ethyl acetate. An acrylic pressure-sensitive adhesive composition 1 was obtained.

[Preparation of Conductive Adhesive Composition]
(Preparation of Conductive Adhesive Composition A)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 0.4 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. as beaded conductive particles, and Vernock NC40 (DIC) as a cross-linking agent. A conductive pressure-sensitive adhesive composition A by mixing 2 parts by mass of an isocyanate-based cross-linking agent manufactured by Co., Ltd. with a solid content of 40% by mass) and 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer. Was prepared.

(Preparation of Conductive Adhesive Composition B)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 2.0 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. as beaded conductive particles, and Vernock NC40 (DIC) as a cross-linking agent. A conductive pressure-sensitive adhesive composition B by mixing 2 parts by mass of an isocyanate-based cross-linking agent manufactured by Co., Ltd. with a solid content of 40% by mass) and 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer. Was prepared.

(Preparation of Conductive Adhesive Composition C)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 0.4 parts by mass of nickel powder NI255T-280 (d50: 15.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. as bead-shaped conductive particles, and Vernock NC40 as a cross-linking agent. (Isocyanate-based cross-linking agent manufactured by DIC Co., Ltd., solid content 40% by mass) 2 parts by mass and 70 parts by mass of ethyl acetate as a diluting solvent are mixed for 10 minutes using a dispersion stirrer to form a conductive pressure-sensitive adhesive. Object C was prepared.

(Preparation of Conductive Adhesive Composition D)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 0.4 parts by mass of nickel powder NI255T-350 (d50: 13.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. as beaded conductive particles, and Vernock NC40 as a cross-linking agent. (Isocyanate-based cross-linking agent manufactured by DIC Co., Ltd., solid content 40% by mass) 2 parts by mass and 70 parts by mass of ethyl acetate as a diluting solvent are mixed for 10 minutes using a dispersion stirrer to form a conductive pressure-sensitive adhesive. Object D was prepared.

(Preparation of Conductive Adhesive Composition E)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 4.0 parts by mass of nickel powder NI123 (d50: 12.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. as spherical conductive particles, and Vernock NC40 (DIC stock) as a cross-linking agent. Conductive pressure-sensitive adhesive composition E by mixing 2 parts by mass of an isocyanate-based cross-linking agent manufactured by the company with a solid content of 40% by mass) and 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer. Was prepared.

(Preparation of Conductive Adhesive Composition F)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 6.0 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., and Vernock NC40 (isocyanate-based manufactured by DIC Co., Ltd.) as a cross-linking agent. A conductive pressure-sensitive adhesive composition E was prepared by mixing 2 parts by mass of a cross-linking agent and a solid content of 40% by mass with 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer.

(Preparation of Conductive Adhesive Composition G)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 6.0 parts by mass of nickel powder NI123 (d50: 12.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. as spherical conductive particles, and Vernock NC40 (DIC stock) as a cross-linking agent. The conductive pressure-sensitive adhesive composition G is obtained by mixing 2 parts by mass of an isocyanate-based cross-linking agent manufactured by the company with a solid content of 40% by mass) and 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer. Prepared.

(Preparation of Conductive Adhesive Composition H)
100 parts by mass of the acrylic pressure-sensitive adhesive composition, 0.02 parts by mass of nickel powder NI255T (d50: 26.0 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., and Vernock NC40 (isocyanate-based manufactured by DIC Co., Ltd.) as a cross-linking agent. A conductive pressure-sensitive adhesive composition H was prepared by mixing 2 parts by mass of a cross-linking agent and a solid content of 40% by mass with 70 parts by mass of ethyl acetate as a diluting solvent for 10 minutes using a dispersion stirrer.

(Example 1)
[Manufacturing of conductive thin adhesive sheet]
The conductive pressure-sensitive adhesive composition A is coated on a release film "PET 38 x 1 A3" manufactured by Nippa Corporation using a comma coater so that the thickness of the conductive pressure-sensitive adhesive layer after drying is 6 μm. After drying in a dryer at 80 ° C. for 2 minutes, the electrolytic copper foil (CF-T9FZ-HS-12, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) having a thickness of 15 μm was bonded to both sides and then 40 ° C. A conductive thin adhesive sheet was obtained by curing for 48 hours.

(Example 2)
A conductive thin pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition B was used instead of the conductive pressure-sensitive adhesive composition A.

(Example 3)
A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the conductive pressure-sensitive adhesive composition C was used instead of the conductive pressure-sensitive adhesive composition A.

(Example 4)
A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the conductive pressure-sensitive adhesive composition D was used instead of the conductive pressure-sensitive adhesive composition A.

(Example 5)
A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the thickness of the conductive pressure-sensitive adhesive layer after drying was set to 10 μm.

(Example 6)
A conductive thin pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition E was used instead of the conductive pressure-sensitive adhesive composition A.

(Example 7)
The electrolytic copper foil to be bonded is replaced with CF-T9FZ-HS-12 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. to CF-T8G-DK-18 (thickness 18 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. A conductive thin pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that it was changed to only one side.

(Comparative Example 1)
A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the conductive pressure-sensitive adhesive composition F was used instead of the conductive pressure-sensitive adhesive composition A.

(Comparative Example 2)
The electrolytic copper foil to be bonded is CF-T8G-DK-35 (thickness 35 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. instead of CF-T9FZ-HS-12 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the thickness of the pressure-sensitive adhesive layer was set to 10 μm.

(Comparative Example 3)
A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the conductive pressure-sensitive adhesive composition G was used instead of the conductive pressure-sensitive adhesive composition A.

(Comparative Example 4)
The conductive thinning method is the same as in Example 1 except that the conductive pressure-sensitive adhesive composition E is used instead of the conductive pressure-sensitive adhesive composition A and the thickness of the conductive pressure-sensitive adhesive layer after drying is 15 μm. I got an adhesive sheet.

(Comparative Example 5)
The same method as in Example 1 except that the conductive pressure-sensitive adhesive composition H is used instead of the conductive pressure-sensitive adhesive composition A and the copper foil to be bonded is TPC (thickness 6 μm) manufactured by JX Nippon Mining & Metals Co., Ltd. A conductive thin adhesive sheet was obtained.

(Comparative Example 6)
A conductive thin pressure-sensitive adhesive sheet was obtained by the same method as in Example 1 except that the thickness of the conductive pressure-sensitive adhesive layer after drying was set to 0.5 μm.

(evaluation)
The total thickness, conductivity, and adhesive strength of the conductive pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were evaluated.

[Total thickness of conductive adhesive sheet]
The total thickness of the conductive pressure-sensitive adhesive sheet was measured using a thickness gauge "TH-102" (manufactured by Tester Sangyo Co., Ltd.).

[Thickness of adhesive layer]
A part of the conductive pressure-sensitive adhesive layer formed on the surface of the release liner used when producing the conductive pressure-sensitive adhesive sheet in the above Examples and Comparative Examples was extracted, and one side thereof was S25 (manufactured by Unitika Ltd.). , Polyethylene terephthalate film, thickness 25 μm) to prepare a sample lined.

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

[Evaluation method of conductivity (measurement of resistance value)]
A brass electrode having a length of 10 mm and a width of 10 mm was attached to a surface made of one of the conductive pressure-sensitive adhesive layers of a conductive pressure-sensitive adhesive sheet having a width of 10 mm and a width of 10 mm.

A copper foil (thickness 35 μm) having a length of 7.5 mm and a width of 7.5 mm was attached to the other surface of the conductive pressure-sensitive adhesive sheet.

In an environment of 23 ° C and 50% RH, the terminals are connected to the brass electrode and the copper foil under a load of 20 N from the upper surface of the brass electrode, and a milliohm meter (NF Circuit Design Co., Ltd.) A current of 10 μA was passed using (manufactured by Brock), and the resistance value was measured. When the resistance value was 40 mΩ or less, it was evaluated as having excellent conductivity. Moreover, after 30 days passed, the resistance value was measured again. When the resistance value was 120 mΩ or less, it was evaluated that the conductivity was excellent in stability over time.

(Evaluation method of adhesiveness)
A 20 mm wide conductive adhesive sheet is placed on the surface of a stainless steel plate (hereinafter referred to as "stainless steel plate") that has been hairline-polished using No. 360 water-resistant abrasive paper, and a 2.0 kg roller in an environment of 23 ° C. and 60% RH. It was affixed by pressurizing one round trip.

After leaving the patch at room temperature for 1 hour, a tensile tester (Tencilon RTA-100, manufactured by A & D Co., Ltd.) was used to measure the peeling adhesive force at 180 degrees at a tensile speed of 300 mm / min at room temperature. When a double-sided adhesive sheet is used as the conductive adhesive sheet, the conductive adhesive layer on the opposite side of the surface attached to the stainless steel plate is lined with S25 (manufactured by Unitika Ltd., polyethylene terephthalate film, thickness 25 μm). bottom.
(Evaluation criteria for adhesive strength)
⊚: 7N / 20mm or more ○: 5N / 20mm or more, less than 7N / 20mm ×: less than 4N / 20mm

1 Conductive base material 2 Conductive adhesive layer

Claims (6)

A conductive pressure-sensitive adhesive sheet having a conductive base material and two conductive pressure-sensitive adhesive layers provided on both sides of the conductive base material and having a total thickness of 50 μm or less, and each layer of the conductive pressure-sensitive adhesive layer. At least one kind of conductive particles is contained therein in an amount of 0.01% by mass to 10% by mass, the particle size d50 of the conductive particles is 12 μm to 30 μm, and the thickness of each layer of the conductive pressure-sensitive adhesive layer is high. Conductive pressure-sensitive adhesive sheets each of 1 μm to 12 μm. The conductive pressure-sensitive adhesive sheet according to claim 1, wherein the conductive particles have a beaded shape. The conductive pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the particle size d50 of the conductive particles is 100% to 500% with respect to the thickness of the pressure-sensitive adhesive layer contained in the particles. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the conductive base material is a metal base material. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the conductive pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed by using an acrylic pressure-sensitive adhesive composition containing an acrylic polymer. A portable electronic device comprising the conductive adhesive sheet according to any one of claims 1 to 5.

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