JP2021091802A - Conductive adhesive sheet - Google Patents

Abstract

To provide a conductive adhesive sheet having high adhesive force and having excellent conductivity both at an initial stage and over time.SOLUTION: A conductive adhesive sheet 10 having an adhesive layer 2 is provided. The adhesive layer 2 contains a first conductive filler 3, a second conductive filler 4, and an adhesive. The first conductive filler 3 has a scaly shape. The shapes of the first conductive filler 3 and the second conductive filler 4 are different from each other. The content of the first conductive filler 3 is 55 pts.mass or less based on 100 pts.mass of the solid content of the adhesive.SELECTED DRAWING: Figure 1

Description

The present invention relates to a conductive pressure-sensitive adhesive sheet.

Due to its ease of handling, the conductive adhesive sheet is used to shield unnecessary leaked electromagnetic waves radiated from electrical or electronic devices, to shield harmful spatial electromagnetic waves generated from other electrical or electronic devices, and to prevent static electricity from being grounded. It is used for various purposes, and with the recent miniaturization and thinning of electric or electronic devices, the conductive adhesive sheets used for these are also required to be thinned and miniaturized.

As the conductive pressure-sensitive adhesive sheet, for example, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of a conductive pressure-sensitive adhesive in which a metal filler is dispersed in a pressure-sensitive substance is proposed on a conductive base material (for example, a patent). Reference 1).
Further, the conductivity having an adhesive layer containing a large-diameter conductive particle composed of a particle group having a particle size range of 15 μm or more and 50 μm or less and a small-diameter conductive particle composed of a particle group having a particle size range of 1 μm or more and 12 μm or less. Adhesive tapes have been proposed (see, for example, Patent Document 2).

JP-A-2018-53102 Japanese Patent No. 6106148

However, since the pressure-sensitive adhesive sheet described in Patent Document 1 has a metal filler added as conductive particles, it tends to peel off with time, and there is a problem that the conductivity decreases with time due to a decrease in contacts. ..
Further, since the conductive adhesive tape described in Patent Document 2 uses only two types of spherical conductive fillers, it is necessary to increase the amount of the conductive filler to be blended in order to realize a low resistance value. As a result, there is a problem that the adhesive strength is lowered.
An object of the present invention is to provide a conductive pressure-sensitive adhesive sheet having excellent conductivity both in the initial stage and over time while maintaining high adhesive strength.

The means for solving the above-mentioned problems are as follows.
<1> A conductive pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer.
The pressure-sensitive adhesive layer contains a first conductive filler, a second conductive filler, and a pressure-sensitive adhesive.
The shape of the first conductive filler is scaly,
The shapes of the first conductive filler and the second conductive filler are different.
The conductive pressure-sensitive adhesive sheet is characterized in that the content of the first conductive filler is 55 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive.
<2> The conductive pressure-sensitive adhesive sheet according to <1>, wherein the first conductive filler is at least one of scaly metal particles, graphite, and scaly particles metal-coated on a scaly base material. ..
<3> The conductive pressure-sensitive adhesive sheet according to any one of <1> to <2>, wherein the second conductive filler is spherical or filamentous metal particles.
<4> The mass ratio (A / B) of the content A of the first conductive filler in the pressure-sensitive adhesive layer and the content B of the second conductive filler in the pressure-sensitive adhesive layer is 1 /. The conductive pressure-sensitive adhesive sheet according to any one of <1> to <3>, which is 1 or more and 1/5 or less.
<5> The content of the first conductive filler is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. The conductive pressure-sensitive adhesive sheet according to the above.
<6> The content of the second conductive filler is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. The conductive pressure-sensitive adhesive sheet according to the above.
<7> The conductive pressure-sensitive adhesive sheet according to any one of <1> to <6>, wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive containing a (meth) acrylic polymer.
<8> The conductive pressure-sensitive adhesive sheet according to any one of <1> to <7>, which has a conductive base material.
<9> After a copper foil is attached to one surface of the conductive adhesive sheet, it is cut into a size of 15 mm width × 100 mm width, and two tin-plated plates are attached to the other adhesive layer of the conductive adhesive sheet. Change in resistance value obtained from the initial resistance value measured and the resistance value measured after the test piece was left at 23 ° C. for 168 hours for a test piece prepared by pasting the test piece so as to have a size of 15 mm × 15 mm. The conductive pressure-sensitive adhesive sheet according to any one of <1> to <8>, wherein the rate [(resistance value after standing for 168 hours / initial resistance value) × 100] is 250% or less.
<10> The conductive adhesive sheet according to any one of <1> to <9>, which is used for at least one of electromagnetic wave shielding and grounding inside and outside an electric or electronic device.

According to the present invention, it is possible to provide a conductive pressure-sensitive adhesive sheet having excellent conductivity both in the initial stage and over time while maintaining high adhesive strength.

FIG. 1 is a schematic cross-sectional view showing an example of the conductive pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the conductive pressure-sensitive adhesive sheet of the present invention. FIG. 3 is a schematic cross-sectional view showing another example of the conductive pressure-sensitive adhesive sheet of the present invention.

(Conductive adhesive sheet)
The conductive pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer contains a first conductive filler, a second conductive filler, and a pressure-sensitive adhesive.
The conductive pressure-sensitive adhesive sheet preferably has a conductive base material and a release liner in addition to the pressure-sensitive adhesive layer, and has other layers such as an intermediate layer and an undercoat layer as long as the object of the present invention is not impaired. You may be doing it.

As a result of diligent studies on means for suppressing an increase in the electric resistance value over time when metal particles are added to the pressure-sensitive adhesive layer, the present inventor has made a scaly first conductive filler in the pressure-sensitive adhesive layer. By using the first conductive filler and the second conductive filler having different shapes in combination, two types of conductive fillers having different shapes work synergistically on the surface of the pressure-sensitive adhesive layer. Since the amount of conductive filler that comes out is small, it is possible to suppress the decrease in contact points over time due to the large number of two types of conductive fillers coming into contact with each other inside the pressure-sensitive adhesive layer without impairing the high adhesive strength. It has been found that a conductive pressure-sensitive adhesive sheet having excellent conductivity can be obtained in any of these cases, and the present invention has been made.

The "sheet" in the conductive pressure-sensitive adhesive sheet of the present invention means a form consisting of only a pressure-sensitive adhesive layer, a form having at least one pressure-sensitive adhesive layer on a conductive base material or a release liner, for example, every leaf. , Roll-shaped, thin plate-shaped, or strip-shaped (tape-shaped), etc.
The "conductive adhesive sheet" may be referred to as a "conductive adhesive tape" or a "conductive adhesive film", but the following will be unified with the "conductive adhesive sheet". The surface of the pressure-sensitive adhesive layer in the conductive pressure-sensitive adhesive sheet may be referred to as an "adhesive surface".

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 an adhesive surface.

The double-sided adhesive type conductive pressure-sensitive adhesive sheet may be a so-called base material-less conductive double-sided pressure-sensitive adhesive sheet that does not have a conductive base material such as a metal foil, or has the conductive base material. It may be a so-called conductive double-sided pressure-sensitive adhesive sheet with a base material.

Examples of the base material-less conductive double-sided pressure-sensitive adhesive sheet include a conductive pressure-sensitive adhesive sheet 10 composed of only the pressure-sensitive adhesive layer 2, as shown in FIG.
Examples of the conductive double-sided pressure-sensitive adhesive sheet with a base material include a conductive pressure-sensitive adhesive sheet 10 in which pressure-sensitive adhesive layers 2 are formed on both sides of the conductive base material 1, as shown in FIG.

Further, as the single-sided adhesive type conductive adhesive sheet, for example, as shown in FIG. 3, a conductive adhesive sheet 10 in which an adhesive layer 2 is formed on one side of a conductive base material 1 such as a metal foil can be mentioned. Be done. In FIGS. 1 to 3, the first conductive filler 3 and the second conductive filler 4 contained in the pressure-sensitive adhesive layer 2 are schematically shown. Although not shown, it is preferable to have a release liner on the surface of the pressure-sensitive adhesive layer 2 in FIGS. 1 to 3.

<Adhesive layer>
The pressure-sensitive adhesive layer is a layer having conductivity (electrical conductivity) while providing an adhesive surface of a conductive pressure-sensitive adhesive sheet. When the adhesive surface of the pressure-sensitive adhesive layer is attached to the adherend, electrical conduction between the adherend such as a conductor and the pressure-sensitive adhesive layer is ensured.
The pressure-sensitive adhesive layer contains a first conductive filler, a second conductive filler, and a pressure-sensitive adhesive, and further contains other components as necessary.

<< Adhesive >>
Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer include (meth) acrylic pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive, polyester-based pressure-sensitive adhesive, synthetic rubber-based pressure-sensitive adhesive, natural rubber-based pressure-sensitive adhesive, silicone-based pressure-sensitive adhesive, and the like. Can be mentioned. Among these, a (meth) acrylic pressure-sensitive adhesive is preferable from the viewpoint of high adhesive strength.

-(Meta) acrylic adhesive-
The (meth) acrylic pressure-sensitive adhesive contains a (meth) acrylic polymer, preferably contains a tackifier resin and a cross-linking agent, and further contains other components as necessary.

-(Meta) acrylic polymer-
As the (meth) acrylic polymer, an acrylic copolymer containing a (meth) acrylate monomer having 1 to 14 carbon atoms as a main monomer component is preferably mentioned.
Examples of the (meth) acrylate having 1 to 14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and n. Examples thereof include −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 alone or in combination of two or more. Among these, (meth) acrylates having an alkyl group having 4 to 12 carbon atoms are preferable, and (meth) acrylates having a linear or branched structure having 4 to 9 carbon atoms are more preferable, and conductivity having high adhesive strength. From the viewpoint of obtaining an adhesive sheet, n-butyl acrylate and 2-ethylhexyl acrylate are more preferable.

The content of the (meth) acrylate having 1 to 14 carbon atoms in the (meth) acrylic polymer is preferably 70% by mass or more and 95% by mass or less in the monomer component constituting the (meth) acrylic polymer. More preferably, it is 80% by mass or more and 95% by mass or less.

As the monomer that can be used for producing the acrylic polymer, a highly polar vinyl monomer can be used, if necessary, in addition to the above-mentioned ones.
Examples of the highly polar vinyl monomer include a (meth) acrylic monomer having a hydroxyl group, a (meth) acrylic monomer having a carboxyl group, and a (meth) acrylic monomer having an amide group. .. These may be used alone or in combination of two or more.

Examples of the vinyl monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. Meta) Acrylate monomer and the like can be mentioned.

Examples of the vinyl monomer having a carboxyl group include (meth) acrylic monomer such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, and ethylene oxide-modified amber acid acrylate. Quantum and the like can be mentioned. Among these, it is preferable to use acrylic acid.

Examples of vinyl having an amide group include (meth) acrylic monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, and N, N-dimethylacrylamide.

As the highly polar vinyl monomer, in addition to the above-mentioned ones, sulfonic acid group-containing monomers such as vinyl acetate, ethylene oxide-modified amber acid acrylate, and 2-acrylamide-2-methylpropanosulphonic acid may be used. Can be done.

The highly polar vinyl monomer is preferably used in the range of 1.5% by mass or more and 20% by mass or less with respect to the total amount of the monomers used in the production of the acrylic polymer, and is 1.5% by mass. It is more preferable to use it in the range of 10% by mass or more, and it is preferable to use it in the range of 2% by mass or more and 8% by mass or less to obtain a pressure-sensitive adhesive layer that is well-balanced in terms of cohesive force, holding power, and adhesiveness. It is more preferable because it can be formed.

Among the highly polar vinyl monomers, the vinyl monomer having a hydroxyl group is preferably used when a material containing an isocyanate-based cross-linking agent is used as the pressure-sensitive adhesive. Specifically, examples of the vinyl monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate.
The vinyl monomer having a hydroxyl group is preferably used in a range of 0.01% by mass or more and 1.0% by mass or less with respect to the total amount of the monomers used in the production of the acrylic polymer, and is 0. It is more preferable to use it in the range of 0.03% by mass or more and 0.3% by mass or less.

The acrylic polymer can be produced by polymerizing the monomer by a known polymerization method such as a solution polymerization method, a massive polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these, the solution weight It is preferably produced by a legal or massive polymerization method.
At the time of the polymerization, if necessary, a peroxide-based thermal polymerization initiator such as benzoyl peroxide or lauroyl peroxide, an azo thermal polymerization initiator such as azobisisobutylnitrile, an acetophenone-based photopolymerization initiator, etc. Benzoin ether-based photopolymerization initiators, benzylketal-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, and the like can be used.

The (meth) acrylic polymer obtained by the above method preferably has a weight average molecular weight (Mw) of 500,000 or more and 2,500,000 or less, and preferably 700,000 or more and 2,000,000 or less. More preferably, it is more preferably 900,000 or more and 1,800,000 or less.
The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method.

The measurement of the molecular weight by the GPC method is a standard polystyrene-equivalent value measured under the following measurement conditions using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation.
[Measurement condition]
-Sample concentration: 0.5% by mass (tetrahydrofuran solution)
-Sample injection volume: 100 μL
-Eluent: THF (tetrahydrofuran)
・ Flow velocity: 1.0 mL / min ・ Measurement temperature: 40 ° C
・ Main column: TSKgel GMHHR-H (20) 2 pieces ・ Guard column: TSKgel HXL-H
・ Detector: Differential refractometer ・ Standard polystyrene molecular weight: 10,000 to 20,000,000 (manufactured by Tosoh Corporation)

-Adhesive-imparting resin-
As the (meth) acrylic pressure-sensitive adhesive, it is preferable to use one containing a tack-imparting resin in order to improve the adhesion to the adherend and the surface adhesive strength.
Examples of the tackifier resin include a rosin-based tackifier resin, a polymerizable rosin-based tackifier resin, a polymerizable rosin ester-based tackifier resin, a rosinphenol-based tackifier resin, a stabilized rosin ester-based tackifier resin, and a non-uniformity. Use rosin ester-based tackifier resin, hydrogenated rosin ester-based tackifier resin, terpen-based tackifier resin, terpenphenol-based tackifier resin, petroleum resin-based tackifier resin, (meth) acrylate-based tackifier resin, etc. Can be done.

Among them, the tackifier resins include disproportionate rosin ester-based tackifier resins, polymerizable rosin ester-based tackifier resins, rosinphenol-based tackifier resins, hydrogenated rosin ester-based tackifier resins, and (meth) acrylate-based resins. It is preferable to use the resin and the terpenphenol-based resin alone or in combination of two or more.

As the tackifier resin, it is preferable to use a resin having a softening point of 30 ° C. or higher and 180 ° C. or lower, and a resin having a softening point of 70 ° C. or higher and 140 ° C. or lower is provided with high adhesive performance. More preferable for forming the pressure-sensitive adhesive layer. When using a (meth) acrylate-based tackifier resin, it is preferable to use a resin having a glass transition temperature of 30 ° C. or higher and 200 ° C. or lower, and 50 ° C. or higher and 160 ° C. or lower. Is more preferable.

The tackifier resin is preferably used in a range of 5 parts by mass or more and 65 parts by mass or less, and 8 parts by mass or more and 55 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic polymer. However, it is more preferable because it is easy to secure the adhesion with the adherend.

-Crosslinking agent-
As the (meth) acrylic pressure-sensitive adhesive, it is preferable to use one containing a cross-linking agent in order to further improve the cohesive force of the pressure-sensitive adhesive layer. As the cross-linking agent, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, a metal chelate-based cross-linking agent, an aziridine-based cross-linking agent, or the like can be used. Among them, as the cross-linking agent, a cross-linking agent of a type in which the cross-linking agent is mixed after the production of the acrylic polymer to proceed the cross-linking reaction is preferable, and an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent having high reactivity with the acrylic polymer are used. Is preferable.

Examples of the isocyanate-based cross-linking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. Among these, trifunctional polyisocyanate compounds are preferable. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, trimethylolpropane adducts thereof, and triphenylmethane isocyanate.

As an index of the degree of cross-linking, the value of the gel fraction for measuring the insoluble content after immersing the pressure-sensitive adhesive layer in toluene for 24 hours is used. The gel content of the pressure-sensitive adhesive layer 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, and preferably 35% by mass or more and 60% by mass or less. More preferably, it is 40% by mass or more and 55% by mass or less.

The gel fraction refers to a value measured by the following method. An adhesive is applied onto the release liner so that the thickness after drying is 50 μm, dried at 100 ° C. for 3 minutes, aged at 40 ° C. for 2 days, cut into 50 mm squares, and used as a sample. .. Next, the mass (G1) of the sample before immersion in toluene is measured in advance, and the toluene-insoluble component of the sample after being immersed in a toluene solution at 23 ° C. for 24 hours is separated by filtering with a 300 mesh wire net. Then, the mass (G2) of the residue after drying at 110 ° C. for 1 hour is measured, and the gel fraction is determined according to the following formula. The mass (G3) of the first and second conductive fillers in the sample is calculated from the mass (G1) of the sample and the composition of the pressure-sensitive adhesive.
Gel fraction (mass%) = (G2-G3) / (G1-G3) x 100

<First conductive filler>
The first conductive filler is scaly, and examples thereof include scaly metal particles, graphite, and scaly particles in which a scaly base material is metal-coated.

The scaly particles may also be referred to as flaky particles, flat particles, flake-like particles, and the like.
In the present invention, the scaly particles mean particles having a substantially flat surface and having a thickness substantially uniform in the direction perpendicular to the substantially flat surface. Further, the scaly particles mean particles having a shape in which the thickness is very thin and the length of a substantially flat surface is very long. The length of the substantially flat surface is the diameter of a circle having the same projected area as the projected area of the scaly particles.
The shape of the substantially flat surface is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a rectangle, a square, a substantially circular shape, a substantially elliptical shape, a substantially triangular shape, a substantially quadrangle, a substantially pentagon, or a substantially hexagon. , A polygon such as a substantially heptagon or a substantially octagon, and a random indefinite shape. Among these, a substantially circular shape or a substantially elliptical shape is preferable.

Examples of the scaly metal particles include scaly metal particles made of metals such as nickel, iron, chromium, cobalt, aluminum, antimony, molybdenum, copper, silver, platinum and gold, and alloys such as solder and stainless steel. ..

Examples of graphite include natural graphite, quiche graphite, artificial graphite and the like. The artificial graphite may be anisotropic graphite, isotropic graphite, or a mixture thereof, but from the viewpoint of mechanical strength, it may be isotropic graphite. preferable. In addition, graphite may be crystalline or amorphous, or a mixture thereof. The graphite may be a carbon fiber reinforced carbon composite material (C / C composite) in which graphite is reinforced with carbon fibers.

Examples of the scaly base material in the scaly particles in which the scaly base material is metal-coated with metal include glass, silica, alumina, mica, and zirconia.
The content of the base material in the scaly particles metal-coated on the scaly base material is preferably 50% by mass or more, more preferably 65% by mass or more, and further preferably 80% by mass or more.
Examples of the method of coating the scaly base material with metal include metal plating. Examples of the metal used for metal plating include silver, gold, platinum, palladium, nickel, copper and aluminum. The content of metal plating in the scaly particles metal-coated on the scaly base material is preferably 10% by mass or more and 50% by mass or less, and more preferably 15% by mass or more and 30% by mass or less.

In the scaly first conductive filler, when the surface having the largest area is used as the main surface, the average thickness with respect to the main surface is preferably 0.5 μm or more and 6.0 μm or less, and 1.0 μm or more and 4.0 μm. The following is more preferable.
The average particle size of the main surface of the scaly first conductive filler is not particularly limited and may be appropriately selected depending on the intended purpose. For example, 10 μm or more and 200 μm or less is preferable, and 20 μm or more and 100 μm or less is more preferable. ..
The average particle size indicates a 50% cumulative volume particle size in a volume-based particle size distribution, and is a value measured by a laser diffraction / scattering method. For example, Microtrack MT300II manufactured by Nikkiso Co., Ltd., laser diffraction type particle size distribution measuring instrument SALD-3000 manufactured by Shimadzu Co., Ltd., and the like can be mentioned.
The ratio of the average particle size of the main surface to the average thickness of the main surface of the first conductive filler is preferably 10 or more and 100 or less, and more preferably 20 or more and 80 or less.
By satisfying the above range of the average thickness to the main surface, the average particle size, and the ratio of the average particle size of the main surface to the average thickness of the main surface, the conductivity in the thickness direction (Z-axis direction) of the adhesive sheet can be obtained. In addition, a conductive pressure-sensitive adhesive sheet having excellent conductivity in the plane direction (XY direction) can be obtained.

The content of the first conductive filler is 55 parts by mass or less, preferably 5 parts by mass or more and 50 parts by mass or less, and 10 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. Is more preferable, and 15 parts by mass or more and 40 parts by mass or less is further preferable. By setting the content of the first conductive filler in the above numerical range, it is possible to achieve both high adhesive strength and excellent conductivity at the initial stage and with time.

<Second conductive filler>
The second conductive filler has a shape different from that of the scaly first conductive filler and is not particularly limited as long as it has conductivity, and can be appropriately selected depending on the intended purpose. Examples thereof include metals such as nickel, iron, chromium, cobalt, aluminum, antimony, molybdenum, copper, silver, platinum and gold, and alloys such as solder and stainless steel. These may be used alone or in combination of two or more.
Among these, nickel, copper and silver are preferable, and nickel powder produced by the carbonyl method is more preferable.
Examples of the nickel powder produced by the carbonyl method include Ni123 (spherical) manufactured by Vale and Ni255 (filament) manufactured by Vale.

The shape of the metal particles is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include spherical shape, filament shape (bead shape), flake shape (thin section shape), and spike shape (barley shape). Be done. Among these, a spherical shape or a filament shape is preferable from the viewpoint of ensuring the adhesive strength and the ease of forming the conductive path by the metal particles in the pressure-sensitive adhesive layer.

The particle size of the metal particles is not particularly limited and may be appropriately selected depending on the intended purpose, but the particle size d40 is preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 20 μm or less.
The particle size d70 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 size d40 refers to a 40% cumulative volume particle size in the volume particle size distribution, and the particle size d70 refers to a 70% cumulative volume particle size in the volume particle size distribution, which is a value measured by a laser analysis / scattering method. Examples of the measuring device include a Microtrack MT3000II manufactured by Nikkiso Co., Ltd. and a laser diffraction type particle size distribution measuring device SALD-3000 manufactured by Shimadzu Co., Ltd.

Examples of the method for adjusting the particle diameters d40 and d70 in the numerical range include a method of pulverizing metal particles with a jet mill and a method of sieving with a sieve or the like.

The content of the second conductive filler is preferably 5 parts by mass or more and 50 parts by mass or less, more preferably 10 parts by mass or more and 45 parts by mass or less, and 15 parts by mass with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. More than 40 parts by mass or less is more preferable. By setting the content of the second conductive filler in the above range, it is possible to achieve both high adhesive strength and excellent conductivity at the initial stage and with time.

In the present invention, the mass ratio (A / B) of the content A of the first conductive filler in the pressure-sensitive adhesive layer and the content B of the second conductive filler in the pressure-sensitive adhesive layer is. , 1/1 or more and 1/5 or less are preferable, 1/1 or more and 1/3 or less are more preferable, and 1/1 or more and 1/2 or less are further preferable.
By setting the mass ratio (A / B) in the above range, it is possible to achieve both high adhesive strength and excellent conductivity at the initial stage and with time.

As a method of dispersing the first and second conductive fillers in the pressure-sensitive adhesive layer, for example, a (meth) acrylic polymer, first and second conductive fillers, a solvent, an additive and the like are dispersed in a dispersion stirrer. There is a method of dispersion. Examples of the commercially available dispersion stirrer include a dissolver manufactured by Inoue Seisakusho Co., Ltd., a butterfly mixer, a BDM twin-screw mixer, and a planetary mixer. Among these, a dissolver and a butterfly mixer that can apply a medium share with less thickening of the pressure-sensitive adhesive during stirring are preferable.

<Other ingredients>
Other components in the pressure-sensitive adhesive layer include, for example, cross-linking agents, anti-aging agents, UV absorbers, fillers, anti-polymerization agents, surface modifiers, anti-static agents, defoamers, viscosity modifiers, light-resistant stabilizers, etc. Additives such as weather stabilizers, heat stabilizers, antioxidants, leveling agents, organic pigments, inorganic pigments, pigment dispersants, plasticizers, softeners, flame retardants, metal defoamers, silica beads, organic beads; Examples thereof include inorganic fillers such as silicon, aluminum oxide, titanium oxide, zirconia, and antimony pentoxide.

The conductive adhesive tape of the present invention can be produced, for example, by applying the adhesive on a release liner or a conductive base material using a roll coater, a die coater, or the like, and drying the adhesive. Further, it can be produced by a transfer method in which a pressure-sensitive adhesive layer formed on a release liner and a conductive base material are bonded together.
In the double-sided adhesive tape, the pressure-sensitive adhesive is previously applied to the surface of the release liner using a roll coater or the like and dried to form a pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive layer is applied to both sides of the conductive substrate. It can be manufactured by a transfer method of bonding.

When the pressure-sensitive adhesive layer formed on the release liner and the conductive base material are bonded together, thermal laminating is preferable from the viewpoint of imparting excellent adhesion between the conductive base material and the pressure-sensitive adhesive layer. The temperature of the thermal laminate is preferably 60 ° C. or higher and 150 ° C. or lower, more preferably 70 ° C. or higher and 130 ° C. or lower, and further preferably 80 ° C. or higher and 110 ° C. or lower in order to suppress adhesion and shrinkage of the conductive base material.

-Peeling liner-
The release liner is not particularly limited and may be appropriately selected depending on the intended purpose. For example, papers such as kraft paper, glassin paper and high-quality paper, and resins such as polyethylene, polypropylene (OPP, CPP) and polyethylene terephthalate. Examples include films, laminated papers obtained by laminating the papers and resin films, and papers that have been sealed with clay or polyvinyl alcohol, and one or both sides of which have been peeled off with a silicone-based resin or the like. Be done.

− Conductive substrate −
Examples of the conductive base material that can be used for the conductive pressure-sensitive adhesive sheet of the present invention include a metal foil base material and a conductive base material obtained by plating a wet polyester-based non-woven fabric base material.
Examples of the material of the metal foil include gold, silver, copper, aluminum, nickel, iron, tin, and alloys thereof. Among these, a conductive base material containing copper is preferable, and copper foil is more preferable from the viewpoint of conductivity, processability, and cost.

It is preferable that the copper foil is subjected to a rust preventive treatment. Examples of the type of rust preventive treatment include organic rust preventive and inorganic rust preventive, and among them, inorganic rust preventive by chromate treatment is most preferable. Examples of commercially available electrolytic copper foils include CF-T9FZ-HS-12 (12 μm: chromate treatment) and CF-T9FZ-HS-9 (9 μm: chromate treatment) manufactured by Fukuda Metal Leaf Powder Industry Co., Ltd. Commercially available rolled copper foils include TCU-H-8-RT (8 μm: organic rust preventive treatment) manufactured by Nippon Foil Corporation, BAY-64T-DT (35 μm: chromate treatment) manufactured by JX Nippon Mining & Metals Co., Ltd., etc. Can be mentioned.

As the conductive base material in which the wet polyester-based non-woven fabric base material is plated, electroless metal plating is used as the plating. Examples of the metal to be plated include copper, nickel, silver, platinum, aluminum and the like. Among these, copper or nickel is preferable from the viewpoint of conductivity and cost.

The thickness of the conductive base material is preferably 1 μm or more and 40 μm or less, more preferably 3 μm or more and 35 μm or less, and further preferably 6 μm or more and 25 μm or less. Within the above numerical range, the thickness can be reduced and the workability is excellent, which is preferable.

The conductive pressure-sensitive adhesive sheet of the present invention may be a so-called base material-less conductive pressure-sensitive adhesive sheet that does not have a conductive base material, or a so-called base-attached conductive pressure-sensitive adhesive sheet that has a conductive base material. It may be.

The base material-less conductive pressure-sensitive adhesive sheet is composed of only the pressure-sensitive adhesive layer, and the average thickness of the pressure-sensitive adhesive layer is the total thickness of the conductive pressure-sensitive adhesive sheet. The base material-less conductive pressure-sensitive adhesive sheet is formed on the release liner and is covered with the release liner until use.
The average thickness of the base-less conductive pressure-sensitive adhesive sheet (average thickness of the pressure-sensitive adhesive layer) is preferably 30 μm or less, more preferably 5 μm or more and 25 μm or less, and further preferably 10 μm or more and 20 μm or less. When it is within the above numerical range, it is possible to achieve both excellent adhesiveness and conductivity and thinness.

The total thickness of the conductive pressure-sensitive adhesive sheet with a base material is preferably 100 μm or less, more preferably 65 μm or less, and even more preferably 50 μm or less. Within the above range, the conductive adhesive sheet can be made thinner while ensuring adhesiveness and conductivity, and can contribute to making the portable electronic device thinner. The total thickness of the conductive pressure-sensitive adhesive sheet is the thickness of the conductive pressure-sensitive adhesive sheet itself that does not include the release liner.

In the conductive adhesive sheet of the present invention, the conductive adhesive sheet is crimped to a stainless steel plate (SUS plate) in a temperature of 23 ° C. and a humidity of 50% RH using a 2 kg roller in one round trip. The 180-degree peeling adhesive force at 300 mm / min after crimping and allowing to stand for 1 hour is preferably 5 N / 25 mm or more.
Within the above range, peeling can be easily suppressed, and the conductive adhesive sheet can be peeled off in a poorly bonded product in the manufacturing process.

The conductive pressure-sensitive adhesive sheet of the present invention has a copper foil attached to one surface of the conductive pressure-sensitive adhesive sheet, cut into a size of 15 mm width × 100 mm width, and two sheets are applied to the other pressure-sensitive adhesive layer of the conductive pressure-sensitive adhesive sheet. From the initial resistance value measured and the resistance value measured after leaving the test piece at 23 ° C. for 168 hours for the test pieces prepared by attaching the tin-plated plates of No. 1 to each of the attachment areas so as to have an attachment area of 15 mm × 15 mm. The obtained rate of change of the resistance value [(resistance value after standing for 168 hours / initial resistance value) × 100] is preferably 250% or less, more preferably 200% or less, still more preferably 150% or less.
When the rate of change of the resistance value is 250% or less, excellent conductivity at the initial stage and with time can be realized.

<Use>
Since the conductive pressure-sensitive adhesive sheet of the present invention can achieve both high adhesive strength and excellent conductivity in the initial stage and with time, for example, for shielding electromagnetic waves used in electric or electronic equipment, and other electric and electronic devices. It is useful for shielding harmful spatial electromagnetic waves generated by equipment and for fixing the ground to prevent static electricity. Among these, it can be suitably applied to portable electronic device applications in which the thickness is getting thinner and the volume limitation in the housing is strict, and it is particularly suitable to be used by being attached to a built-in component of a small electronic terminal.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.

(Synthesis Example 1 of Acrylic Copolymer)
<Acrylic copolymer (1)>
In a reaction vessel equipped with a stirrer, a reflux cooler, a thermometer, a dropping funnel, and a nitrogen gas inlet, 92 parts by mass of n-butyl acrylate, 6 parts by mass of acrylic acid, and 2 parts by mass of 2-hydroxyethyl acrylate were added. , 0.2 parts by mass of 2,2'-azobisisobutylnitrile as a polymerization initiator is dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, it is polymerized at 80 ° C. for 8 hours to obtain an acrylic acid having a weight average molecular weight of 700,000. The polymer (1) was obtained.

The weight average molecular weight is the weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC), and was measured by the following method.
The molecular weight can be measured by the GPC method using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation under the following GPC measurement conditions based on polystyrene conversion values.
[Measurement condition]
-Sample concentration: 0.5% by mass (tetrahydrofuran solution)
-Sample injection volume: 100 μL
-Eluent: tetrahydrofuran (THF)
・ Flow velocity: 1.0 mL / min ・ Column temperature (measurement temperature): 40 ° C
・ Main column: 2 TSKgel GMHHR-H (20) ・ Guard column: “TSKgel HXL-H” manufactured by Tosoh Corporation
・ Detector: Differential refractometer ・ Standard polystyrene molecular weight: 10,000 to 20,000,000 (manufactured by Tosoh Corporation)

(Adhesive Preparation Example 1)
-Preparation of adhesive A-
With respect to 100 parts by mass of the acrylic copolymer (1), 5 parts by mass of a polymerizable rosin ester-based tackifier resin (D-125, manufactured by Arakawa Chemical Industry Co., Ltd.) and a petroleum-based tackifier resin (FTR6125, Mitsui Kagaku) (Manufactured by Co., Ltd.) 15 parts by mass was mixed and stirred, and then ethyl acetate was added to obtain a pressure-sensitive adhesive A having a solid content of 40% by mass.

(Example 1)
<Manufacturing of Conductive Adhesive Composition A>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 30 parts by mass of the second conductive filler (nickel, Ni255, manufactured by Vale, filamentous, particle size d40 = 17.2 nm, particle size d70 = 35.4 nm), 30 parts by mass, 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition A.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition A is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 1.

(Example 2)
<Manufacturing of Conductive Adhesive Composition B>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 20 parts by mass (average particle diameter 25 μm on the main surface), 40 parts by mass of the second conductive filler (nickel, Ni255, manufactured by Vale, filament, particle diameter d40 = 17.2 nm, particle diameter d70 = 35.4 nm), 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition B.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition B is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 2.

(Example 3)
<Manufacturing of Conductive Adhesive Composition C>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, Main surface average particle diameter 25 μm) 10 parts by mass, second conductive filler (nickel, Ni255, Vale, filament, particle diameter d40 = 17.2 nm, particle diameter d70 = 35.4 nm) 50 parts by mass, 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition C.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition C is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 3.

(Example 4)
<Manufacturing of Conductive Adhesive Composition D>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 45 parts by mass (average particle diameter 25 μm) on the main surface, 45 parts by mass of the second conductive filler (nickel, Ni255, manufactured by Vale, filament, particle diameter d40 = 17.2 nm, particle diameter d70 = 35.4 nm), 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition D.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition D is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 4.

(Example 5)
<Manufacturing of Conductive Adhesive Composition E>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 15 parts by mass (average particle diameter 25 μm on the main surface), 15 parts by mass of the second conductive filler (nickel, Ni255, manufactured by Vale, filament, particle diameter d40 = 17.2 nm, particle diameter d70 = 35.4 nm), 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition E.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition E is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 5.

(Example 6)
<Manufacturing of Conductive Adhesive Composition F>
First conductive filler (nickel flake powder, HCA-1, manufactured by Vale, scaly, average thickness of main surface 2 μm, average particles of main surface with respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A. Diameter 12.5 μm) 30 parts by mass, second conductive filler (nickel, Ni255, manufactured by Vale, filament, particle size d40 = 17.2 nm, particle size d70 = 35.4 nm) 30 parts by mass, Barnock D- 40 (manufactured by DIC Co., Ltd., trimethylol propane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was adjusted to 40% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition F.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition F is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 6.

(Example 7)
<Manufacturing of Conductive Adhesive Composition G>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 30 parts by mass of the second conductive filler (nickel, Ni123, manufactured by Vale, filamentous, particle size d40 = 8.2 nm, particle size d70 = 16.6 nm), 30 parts by mass, 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition G.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition G is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 7.

(Example 8)
<Manufacturing of Conductive Adhesive Composition H>
First conductive filler (nickel flake powder, HCA-1, manufactured by Vale, scaly, average thickness of main surface 2 μm, average particles of main surface with respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A. Diameter 12.5 μm) 30 parts by mass, second conductive filler (nickel, Ni123, manufactured by Vale, filament, particle size d40 = 8.2 nm, particle size d70 = 16.6 nm) 30 parts by mass, Barnock D- 40 (manufactured by DIC Co., Ltd., trimethylol propane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was adjusted to 40% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition H.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition H is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 8.

(Example 9)
<Manufacturing of Conductive Adhesive Composition I>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, Main surface average particle diameter 25 μm) 10 parts by mass, second conductive filler (nickel, Ni255, Vale, filament, particle diameter d40 = 17.2 nm, particle diameter d70 = 35.4 nm) 10 parts by mass, 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition I.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition I is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Example 9.

(Comparative Example 1)
<Manufacturing of Conductive Adhesive Composition J>
Second conductive filler (nickel, Ni255, manufactured by Vale, filament, particle size d40 = 17.2 nm, particle size d70 = 35.4 nm) 30 with respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A. 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was added to ethyl acetate. Was adjusted to 40% by mass and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition J.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition J is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive pressure-sensitive adhesive sheet of Comparative Example 1.

(Comparative Example 2)
<Manufacturing of Conductive Adhesive Composition K>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 30 parts by mass of Barnock D-40 (manufactured by DIC Co., Ltd., trimethylol propan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass), 2 parts by mass. The mixture was blended, the solid content concentration was adjusted to 40% by mass with ethyl acetate, and the mixture was mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition K.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition K is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Comparative Example 2.

(Comparative Example 3)
<Manufacturing of Conductive Adhesive Composition L>
With respect to 100 parts by mass (solid content) of the pressure-sensitive adhesive A, a first conductive filler (conductive particles obtained by plating glass flake powder with 20% by mass of silver, scaly, average thickness of main surface 2 μm, 60 parts by mass (average particle diameter 25 μm) on the main surface, 60 parts by mass of the second conductive filler (nickel, Ni255, manufactured by Vale, filament, particle diameter d40 = 17.2 nm, particle diameter d70 = 35.4 nm), 2 parts by mass of Vernock D-40 (manufactured by DIC Co., Ltd., trimethylolpropan adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was blended, and the solid content concentration was 40% by mass with ethyl acetate. The mass was adjusted to% and mixed with a dispersion stirrer to prepare a conductive pressure-sensitive adhesive composition L.

<Manufacturing of conductive adhesive sheet>
The obtained conductive pressure-sensitive adhesive composition L is coated on a conductive base material (electrolytic copper foil, average thickness 12 μm) with a comma coater so that the average thickness after drying is 25 μm, and dried at 80 ° C. After drying in a vessel for 2 minutes, it was cured at 40 ° C. for 48 hours to prepare a conductive adhesive sheet of Comparative Example 3.

Next, various characteristics of the obtained conductive pressure-sensitive adhesive sheets of Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated as follows. The results are shown in Tables 1 to 3.

<Measurement of average thickness of conductive adhesive sheet>
The average thickness of each conductive pressure-sensitive adhesive sheet is an average value obtained by measuring the thickness of the conductive pressure-sensitive adhesive sheet at five locations at 100 mm intervals in the length direction using a dial feeler gauge G type manufactured by Ozaki Seisakusho Co., Ltd.

<Evaluation method of adhesive strength>
The adhesive strength of the conductive pressure-sensitive adhesive sheet was determined by the following procedure according to the test method of 180-degree peeling adhesive strength of JIS-Z0237 (2000).
The conductive pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 25 mm in width.
Next, the pressure-sensitive adhesive layer on one side of the conductive pressure-sensitive adhesive sheet was lined with a polyester film having a thickness of 25 μm.
Next, under the conditions of an environmental temperature of 23 ° C. and a humidity of 50% RH, the backed conductive adhesive sheet is attached to a stainless steel plate (SUS plate), and the upper surface thereof is reciprocated once with a 2 kg roller to crimp them. After that, the test piece was left at the above temperature for 1 hour and used as a test piece.
The test piece is peeled off at a speed of 300 mm / min under the same temperature and humidity conditions as above using a Tencilon universal tensile tester (RTA100 manufactured by Orientec Co., Ltd.) to obtain 180 degree peeling adhesive strength. It was measured. When the adhesive strength was 5 N / 25 mm or more, it was evaluated as having excellent adhesiveness.

<Evaluation method of conductivity>
A copper foil (thickness 12 μm) was attached to one surface of the conductive pressure-sensitive adhesive sheet. The conductive adhesive sheet was cut into a size of 15 mm width × 100 mm width. The other adhesive layer of the cut conductive adhesive sheet was attached to two tin-plated plates so that the attachment area was 15 mm × 15 mm, respectively, to prepare a test piece. In an environment of 23 ° C and 50% RH, connect the terminal at a position about 100 mm away from the position where the conductive adhesive sheet is attached on the tin-plated surface, and use a resistivity meter (Loresta-GP MCP-T600, manufactured by Mitsubishi Chemical Corporation). A current of 10 μA was passed and the initial resistance value was measured.
The prepared test piece was left at 23 ° C. for 168 hours, and then the resistance value was measured in the same manner as described above. When the resistance value after 168 hours is 100 mΩ or less and the rate of change of the resistance value (resistance value after being left for 168 hours / initial resistance value) × 100 is 250% or less, it is evaluated as having excellent conductivity. did.

1 Conductive base material 2 Adhesive layer 3 First conductive filler 4 Second conductive filler 10 Conductive adhesive sheet

Claims (10)

A conductive pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer.
The pressure-sensitive adhesive layer contains a first conductive filler, a second conductive filler, and a pressure-sensitive adhesive.
The shape of the first conductive filler is scaly,
The shapes of the first conductive filler and the second conductive filler are different.
A conductive pressure-sensitive adhesive sheet, wherein the content of the first conductive filler is 55 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. The conductive pressure-sensitive adhesive sheet according to claim 1, wherein the first conductive filler is at least one of scaly metal particles, graphite, and scaly particles metal-coated on a scaly base material. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 2, wherein the second conductive filler is spherical or filamentous metal particles. The mass ratio (A / B) of the content A of the first conductive filler in the pressure-sensitive adhesive layer and the content B of the second conductive filler in the pressure-sensitive adhesive layer is 1/1 or more 1 The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which is / 5 or less. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the content of the first conductive filler is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. .. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the content of the second conductive filler is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive. .. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive containing a (meth) acrylic polymer. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 7, which has a conductive base material. After a copper foil is attached to one surface of the conductive adhesive sheet, it is cut into a size of 15 mm width × 100 mm width, and two tin-plated plates are attached to the other adhesive layer of the conductive adhesive sheet, each having an area of 15 mm ×. The rate of change of the resistance value [( The conductive adhesive sheet according to any one of claims 1 to 8, wherein the resistance value after being left for 168 hours / initial resistance value) × 100] is 250% or less. The conductive adhesive sheet according to any one of claims 1 to 9, which is used for at least one of electromagnetic wave shielding and grounding inside and outside an electric or electronic device.

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