JP6996121B2 - Conductive adhesive sheet - Google Patents

Description

The present invention relates to a conductive pressure-sensitive adhesive sheet having a conductive base material and a pressure-sensitive adhesive layer containing conductive particles.

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

As the conductive pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of a conductive pressure-sensitive adhesive in which a conductive filler is dispersed in a pressure-sensitive adhesive is disclosed on a conductive base material (Patent Documents 1 to 1). 2). It is disclosed that these pressure-sensitive adhesive sheets have suitable conductivity and adhesiveness.

However, in recent small electronic terminals and the like, the adhesive area of the adhesive sheet has become smaller due to the smaller space of the electronic substrate, so that there is a problem that peeling easily occurs over time and the conductivity is lowered.
Further, when the adhesive sheet is attached to the uneven portion of the electronic substrate, there is a problem that the adhesive sheet is peeled off with time and the conductivity is lowered.

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

The problem to be solved by the present invention is that the adhesive area is small, and even when the adhesive is bonded to the uneven portion, the conductive adhesive has good adhesiveness, conductivity, and reworkability, and the conductivity does not easily decrease with time. To provide a sheet.

In the present invention, the conductive pressure-sensitive adhesive sheet has a conductive base material and a conductive pressure-sensitive adhesive layer, and the tensile strength of the conductive pressure-sensitive adhesive layer when deformed by 10% at 23 ° C. is 3.0. The above-mentioned problem was solved by the conductive pressure-sensitive adhesive sheet characterized by being ~ 6.0 N / cm ² .

Since the conductive thin adhesive sheet of the present invention is thin and has good adhesiveness and conductivity to an adherend, it is used for shielding electromagnetic waves used in electric and electronic devices, and other electric and electronic devices. It is useful for shielding more harmful spatial electromagnetic waves and for fixing the ground to prevent static electricity. In particular, it can be suitably applied to portable electronic device applications in which the volume is becoming thinner and the volume limitation in the housing is strict. In particular, it is suitable for use by attaching to a built-in component of a small electronic terminal.

It is a schematic diagram which shows the structural example of the conductive pressure-sensitive adhesive sheet of this invention. It is a schematic diagram which shows the structural example of the conductive pressure-sensitive adhesive sheet of this invention. It is a micrograph of an example of the beaded conductive particles preferably used for the conductive pressure-sensitive adhesive sheet of the present invention. It is a schematic diagram which shows the conductivity evaluation of the conductive pressure-sensitive adhesive sheet of this invention.

The conductive pressure-sensitive adhesive sheet of the present invention is characterized by having a tensile strength of 3.0 to 6.0 N / cm ² when the conductive pressure-sensitive adhesive layer is deformed by 10% at 23 ° C. It is a sheet.

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

(Conductive adhesive layer)
The tensile strength of the conductive pressure-sensitive adhesive layer used for the conductive pressure-sensitive adhesive sheet of the present invention when deformed by 10% at 23 ° C. is 3.0 to 6.0 N / cm ² , but 3.5 to 5 It is preferably .5 N / cm ² and more preferably 4.0 to 5.0 N / cm ² . The increase in resistance value over time is due to the contact of the metal filler added into the conductive pressure-sensitive adhesive layer with the conductive member due to peeling at the interface between the conductive pressure-sensitive adhesive layer of the conductive pressure-sensitive adhesive sheet and the bonded conductive member. Disappears and rises. The peeling phenomenon occurs when the conductive pressure-sensitive adhesive layer is stretched. Therefore, when the tensile strength of the conductive pressure-sensitive adhesive layer is within the above range, the conductive pressure-sensitive adhesive layer is difficult to stretch, so that it is possible to suppress peeling over time and it is easy to suppress an increase in resistance value over time.

The tensile strength of the conductive pressure-sensitive adhesive layer when deformed by 10% at 23 ° C. was 0.4 mm in thickness, 10 mm in width and 20 mm in length using a tensile test at 23 ° C. The agent layer was pulled in the length direction at a speed of 300 mm / min, the strength when the length became 22 mm was measured, and the tensile strength was calculated by the following formula.
Tensile strength at 10% deformation [N / cm ² ] = strength at length 22 mm [N] / cross-sectional area 0.04 [cm ² ]

The thickness of the conductive pressure-sensitive adhesive layer is preferably 30 μm or less, more preferably 5 to 25 μm, and particularly preferably 10 to 20 μm. When it is within the above range, both good adhesiveness and thinness can be achieved.

(Adhesive composition)
The conductive pressure-sensitive adhesive layer used in the conductive pressure-sensitive adhesive sheet of the present invention is formed from a pressure-sensitive adhesive composition containing conductive particles. As the pressure-sensitive adhesive composition for forming the conductive pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition used for ordinary pressure-sensitive adhesive sheets can be used. Examples of the pressure-sensitive adhesive composition include (meth) acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, natural rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, and the like. An acrylic copolymer composed of a copolymer of (meth) acrylate and another monomer is used as a base polymer, and an additive such as a tackifier resin or a cross-linking agent is added to the base polymer as needed. The pressure-sensitive adhesive composition can be preferably used from the viewpoint of weather resistance and heat resistance.

As the acrylic copolymer, an acrylic copolymer containing a (meth) acrylate monomer having 1 to 14 carbon atoms as a main monomer component can be preferably used, and as the (meth) acrylate having 1 to 14 carbon atoms, for example, Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, Examples thereof include monomers such as isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate, and one or more of these may be used. Of these, a (meth) acrylate having an alkyl group having 4 to 12 carbon atoms is preferable, and a (meth) acrylate having a linear or branched structure having 4 to 9 carbon atoms is more preferable. Of these, n-butyl acrylate and 2-ethylhexyl acrylate can be preferably used, and these may be used alone or in combination.

The content of the (meth) acrylate having 1 to 14 carbon atoms in the acrylic copolymer is preferably 80 to 98.5% by mass, preferably 90 to 98.5% by mass, based on the monomer components constituting the acrylic copolymer. It is more preferably 5.5% by mass.

Further, the acrylic copolymer used in the present invention is preferably copolymerized with a highly polar vinyl monomer, and the highly polar vinyl monomer includes a vinyl monomer having a carboxyl group, a vinyl monomer having a hydroxyl group, and a vinyl having an amide group. Monomers and the like can be mentioned, and one or more of these may be used. Among them, the carboxyl group-containing monomer can be preferably used because it is easy to adjust the adhesiveness of the pressure-sensitive adhesive to a suitable range.

As the vinyl monomer having a carboxyl group, 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 acrylic acid is used together. It is preferable to use it as a polymerization component.

When a vinyl monomer having a carboxyl group is used, the content thereof is preferably 0.2 to 15% by mass, preferably 0.4 to 10% by mass in the monomer components constituting the acrylic copolymer. Is more preferable, and 0.5 to 6% by mass is further preferable. By containing it in the above range, it is easy to adjust the adhesiveness of the pressure-sensitive adhesive to a suitable range.

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

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

Other highly polar vinyl monomers include vinyl acetate, ethylene oxide-modified amber acid acrylate, sulfonic acid group-containing monomers such as 2-acrylamide-2-methylpropanesulfonic acid, 2-methoxyethyl (meth) acrylate, and 2-phenoxyethyl (2-methoxyethyl (meth) acrylate). Examples thereof include terminal alkoxy-modified (meth) acrylates such as meta) acrylates.

The total content of the highly polar vinyl monomer is preferably 0.2 to 15% by mass, more preferably 0.4 to 10% by mass in the monomer components constituting the acrylic copolymer. , 0.5 to 6% by mass, more preferably. By containing it in the above range, it is easy to adjust the adhesiveness of the pressure-sensitive adhesive to a suitable range.

The acrylic copolymer can be obtained by copolymerizing by a known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method, but from the viewpoint of production cost and productivity, solution polymerization can be obtained. It is preferably polymerized by. The weight average molecular weight Mw of the acrylic copolymer is preferably 3.5 million to 2 million, more preferably 600,000 to 1.8 million, and even more preferably 700,000 to 1.6 million. When the weight average molecular weight Mw is within the above range, the conductive pressure-sensitive adhesive layer can be provided with the initial adhesiveness to the metal and the cohesive force required for peeling.

In the present invention, the weight average molecular weight Mw of the acrylic copolymer can be measured by gel permeation chromatography (GPC). More specifically, it can be obtained by measuring with the following GPC measuring conditions by the polystyrene conversion value using "SC8020" manufactured by Tosoh Corporation as a GPC measuring device.
(GPC measurement conditions)
-Sample concentration: 0.5% by weight (tetrahydrofuran solution)
-Sample injection amount: 100 μL
-Eluent: Tetrahydrofuran (THF)
・ Flow velocity: 1.0 mL / min
-Column temperature (measurement temperature): 40 ° C
-Column: "TSKgel GMHR-H" manufactured by Tosoh Corporation
・ Detector: Differential refractometer

(Additive)
Further, in order to adjust the tensile strength of the conductive pressure-sensitive adhesive layer of the present invention to a suitable range, it is preferable to contain a polymer in which a nitrogen atom-containing vinyl monomer is copolymerized. By copolymerizing the nitrogen atom-containing vinyl monomer, it is possible to form an interaction with the acrylic copolymer and impart an excellent cohesive force to the conductive pressure-sensitive adhesive layer.

The nitrogen atom-containing vinyl monomer has no problem as long as it contains a nitrogen atom and can be copolymerized with the above-mentioned (meth) acrylate monomer having 1 to 8 carbon atoms. For example, an amino group-containing monomer and an amide group-containing monomer , Nitrogen-based heterocyclic ring-containing monomer, cyano group-containing monomer, imide group-containing monomer and the like. Examples of these monomers include (meth) amino group-containing monomers such as (meth) aminomethyl acrylate, (meth) aminoethyl acrylate, (meth) aminopropyl acrylate, and (meth) aminoisopropyl acrylate. Examples thereof include aminoalkyl acrylate and (meth) acrylate (N-substituted) aminoalkyl. Examples of the (meth) acrylic acid (N-substituted) aminoalkyl include (meth) acrylic acid N-alkylaminoalkyl such as (meth) acrylic acid N- (t-butyl) aminoethyl; (meth) acrylic acid. Examples thereof include N, N-dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminoethyl and N, N-dimethylaminopropyl (meth) acrylates.

Among them, amino group-containing monomers and amide group-containing monomers are preferable. Of these, amino group-containing monomers are particularly preferable. By using the nitrogen-containing vinyl monomer, it is possible to impart the tensile strength required for forming an interaction with the (meth) acrylic copolymer and suppressing peeling over time to the conductive pressure-sensitive adhesive layer.

The content of the nitrogen atom-containing vinyl monomer in the copolymer is preferably 1 to 30% by weight, more preferably 1 to 20% by mass, based on the total amount of the copolymer. By setting the content of the nitrogen atom-containing vinyl monomer in the above range, it is possible to impart the tensile strength required for forming an interaction with the acrylic copolymer and suppressing peeling over time to the conductive pressure-sensitive adhesive layer. ..

The weight average molecular weight Mw of the copolymer is preferably 5,000 to 100,000, more preferably 5,000 to 80,000, and even more preferably 5,000 to 50,000. When the weight average molecular weight Mw is within the above range, the conductive pressure-sensitive adhesive layer can be imparted with the tensile strength required for suppressing peeling over time.

Further, in order to improve the adhesive strength of the conductive adhesive sheet, an adhesive resin may be added. The tackifier resin added to the conductive pressure-sensitive adhesive used in the present invention includes rosin-based resin, terpene-based resin, petroleum resin such as aliphatic (C5 series) and aromatic (C9 series), styrene resin phenol-based resin, and the like. Examples thereof include xylene-based resins and methacrylic-based resins. Among them, a rosin-based resin is preferable, and a polymerized rosin-based resin is particularly preferable. The amount of the tackifier resin added is preferably 10 to 50 parts by mass with respect to 100 parts by mass (solid content) of the (meth) acrylic copolymer.

Various additives may be added to the pressure-sensitive adhesive used for the conductive pressure-sensitive adhesive sheet of the present invention, if necessary. Examples of the additive include plasticizers, softeners, metal deactivators, antioxidants, pigments, dyes and the like, and are appropriately used as necessary.

(Triazole compound)
The pressure-sensitive adhesive used in the conductive pressure-sensitive adhesive sheet of the present invention contains a triazole-based compound. Examples of the triazole compound include benzotriazole, tolyltriazole and a potassium salt thereof, 3- (N-salicyloyl) amino-1,2,4triazole, 2- (2'-hydroxy-5methylphenyl) benzotriazole and the like. Among them, benzotriazole is preferable because it has a high solubility and an effect of preventing a decrease in adhesive strength.

The content of the triazole-based compound is not particularly limited, but is preferably 0.05 to 3.0 parts by mass with respect to 100 parts by mass (solid content) of the acrylic pressure-sensitive adhesive composition. Among them, 0.1 to 1.5 parts by mass is preferable, and 0.3 to 1.0 parts by mass is most preferable. By setting the content to this level, it becomes easy to obtain a particularly suitable holding force, and it becomes particularly easy to suppress a decrease in the adhesive force after the high temperature and high humidity environment test.

(Gel fraction of adhesive)
The (meth) acrylic pressure-sensitive adhesive used in the conductive pressure-sensitive adhesive sheet of the present invention preferably forms a three-dimensional crosslinked structure in order to improve the cohesive force. As an index for forming the crosslinked structure, the gel fraction represented by the insoluble matter after being immersed in toluene, which is a good solvent for the (meth) acrylic pressure-sensitive adhesive, for 24 hours is used. In that case, it is preferably 25 to 80% by mass, more preferably 30 to 40% by mass. If the gel fraction is less than 25% by mass, the cohesive force in the shear direction is insufficient, and if it exceeds 80% by mass, the peeling resistance is lowered.

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

(Conductive particles)
The material of the conductive particles used in the conductive pressure-sensitive adhesive sheet of the present invention is metal powder particles such as gold, silver, copper, nickel and aluminum, conductive resins such as carbon and graphite, resins and solid glass beads, and hollow glass. Those having a metal coating on the surface of the beads can be used. Among them, nickel powder particles, copper powder particles and silver powder particles are preferable because they are excellent in conductivity, adhesiveness and productivity. More preferred are surface needle-shaped nickel particles having a large number of needle-shaped particles on the surface of the particles produced by the carbonyl method, smoothed surface needle-shaped particles to form spherical particles, and super. Examples include copper powder and silver powder produced by the high-pressure swirling water atomizing method. Two or more kinds of these conductive particles may be mixed and used.

Examples of the shape of the conductive particles include a spherical shape, a surface needle-like 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. 3 and connected to each other. Among them, the bead shape is preferable.

The particle diameter of the conductive particles is not particularly limited, but the particle diameter d50 is preferably 5 to 30 μm, preferably 10 to 25 μm, and more preferably 12 to 20 μm. Most preferably, it is 13 to 18 μm. Further, the particle diameter d90 is preferably 25 to 60 μm, preferably 27 to 55 μm, more preferably 30 to 50 μm, and most preferably 31 to 50 μm. When two or more kinds of conductive particles are mixed, it is preferable that the mixed particle diameters d50 and d90 are in the above range.

The particle size d50 refers to a 50% cumulative value in the particle size distribution, and the particle size d90 refers to a 90% cumulative value in the 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., 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 diameter to the particle diameter 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.

It is preferable that the particle diameter d50 of the conductive particles is 50 to 150% of the thickness of the pressure-sensitive adhesive layer, and d90 is 100 to 300%. By using conductive particles in the above range, it is easy to achieve both conductivity, adhesiveness, and productivity. d50 is more preferably 60 to 120%, most preferably 70 to 100%. d90 is more preferably 120 to 250%, more preferably 150 to 200%.

The content of the conductive particles in the conductive pressure-sensitive adhesive layer is not particularly limited, but is preferably 10 to 100 parts by mass with respect to 100 parts by mass (solid content) of the acrylic pressure-sensitive adhesive composition. It is more preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and most preferably 40 to 60 parts by mass. By setting the content of the conductive particles in the above range, it becomes easy to achieve both conductivity, adhesiveness, and productivity.

Examples of the method for dispersing the conductive particles in the acrylic pressure-sensitive adhesive composition include a method for dispersing a (meth) acrylic copolymer, a solvent, conductive particles, additives and the like with a dispersion stirrer. Examples of the commercially available dispersion stirrer include a dissolver manufactured by Inoue Seisakusho, a butterfly mixer, a BDM 2-axis mixer, and a planetary mixer. Among them, a dissolver and a butterfly mixer that can apply a medium share with less thickening of the adhesive during stirring are preferable.

The solid content of the acrylic pressure-sensitive adhesive composition is not particularly limited, but is preferably 10 to 70%, more preferably 30 to 55%, and most preferably 43 to 50%.

(Conductive base material)
Examples of the conductive base material 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 them, a conductive base material containing copper is preferable, and copper foil is more preferable in terms of conductivity, processability, and cost.

Further, it is preferable to apply a rust preventive treatment to the copper foil. 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 Foil Powder Industry Co., Ltd. Examples of commercially available rolled copper foil include TCU-H-8-RT (8 μm: organic rust preventive treatment) manufactured by Nippon Foil Corporation and BAY-64T-DT (35 μm: chromate treatment) manufactured by JX Nippon Mining & Metals Co., Ltd. Be done.

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

The thickness of the conductive substrate is preferably 1 to 40 μm, more preferably 3 to 35 μm, and most preferably 6 to 25 μm. Within the above range, it is preferable because it can be made thinner and has excellent workability.

(Peeling liner)
In the conductive pressure-sensitive adhesive sheet of the present invention, a release liner can be laminated on the pressure-sensitive adhesive layer. The release liner is not particularly limited, 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 laminates obtained by laminating the papers and resin films. Conventionally known papers, such as those obtained by sealing the papers with clay or polyvinyl alcohol and having a peeling treatment of a silicon-based resin or the like on one or both sides of the paper, can be used.

(Conductive adhesive sheet)
The conductive pressure-sensitive adhesive sheet of the present invention is a conductive pressure-sensitive adhesive sheet having the above-mentioned conductive pressure-sensitive adhesive layer and a conductive base material.

In an environment where the temperature of the conductive adhesive sheet of the present invention is 23 ° C. and the relative humidity is 50% RH, the conductive adhesive sheet is crimped against SUS in one reciprocating crimping frequency using a 2 kg roller, and then allowed to stand for 1 hour at 300 mm /. The 180 ° peeling adhesive force in min is preferably 5 to 15 N / 20 mm with respect to SUS, respectively. 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 total thickness of the conductive pressure-sensitive adhesive sheet of the present invention is preferably 85 μm or less, more preferably 65 μm or less, and particularly preferably 50 μm or less. Within the above range, the adhesive sheet can be made thinner while ensuring adhesiveness and conductivity, which 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.

The conductive pressure-sensitive adhesive sheet of the present invention can be prepared by a commonly used method. Specifically, it can be manufactured by a method of applying it on a release liner, drying or curing it to form a conductive pressure-sensitive adhesive layer, and then attaching it to a conductive substrate.

When laminating the conductive pressure-sensitive adhesive layer formed on the release liner and the conductive base material, thermal laminating imparts excellent adhesion between the conductive base material and the conductive pressure-sensitive adhesive layer. Preferred from the viewpoint. The temperature of the thermal laminating is preferably 60 ° C. to 150 ° C., more preferably 70 ° C. to 130 ° C., and even more preferably 80 ° C. to 110 ° C. in order to suppress adhesion and shrinkage of the conductive substrate.

1 and 2 show examples of suitable configurations of the conductive 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 copolymer]
<Acrylic copolymer (1)>
Preparation of acrylic polymer In a reaction vessel equipped with a stirrer, a cold current cooler, a thermometer, a dropping funnel and a nitrogen gas inlet, 91.5 parts by mass of n-butyl acrylate, 0.5 part by mass of 2-hydroxyethyl acrylate, 8.0 parts by mass of acrylic acid and 0.2 parts of 2,2'-azobisisobutylnitrile as a polymerization initiator are dissolved in 100 parts by mass of ethyl acetate, polymerized at 80 ° C. for 8 hours after substitution with nitrogen, and weight averaged. An acrylic copolymer (1) having a molecular weight of 800,000 was obtained.

<Acrylic copolymer (2)>
Acrylic copolymer (2) having a weight average molecular weight of 800,000 in the same manner as the acrylic acid copolymer (1) except that n-butyl acrylate is 95.5 parts by mass and acrylic acid is 4.0 parts by mass. Got

<Acrylic copolymer (3)>
An acrylic copolymer (3) having a weight average molecular weight of 1.5 million was obtained in the same manner as the acrylic acid copolymer (1) except that the amount was 2,2'-azobisisobutylnitrile (0.1 part).

<Acrylic copolymer (4)>
An acrylic copolymer (3) having a weight average molecular weight of 300,000 was obtained in the same manner as the acrylic acid copolymer (1) except that the amount was 2,2'-azobisisobutylnitrile (0.5 part).

<Acrylic copolymer (5)>
Preparation of Acrylic Copolymer In a reaction vessel equipped with a stirrer, a cold current cooler, a thermometer, a dropping funnel and a nitrogen gas inlet, 95.0 parts by mass of methyl methacrylate, 5.0 parts by mass of dimethylaminoethyl methacrylate and a polymerization initiator. As a result, 1.0 part by mass of 2,2'-azobisisobutylnitrile was dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, the polymer was polymerized at 80 ° C. for 8 hours to obtain a methacrylic copolymer having a weight average molecular weight of 20,000 (5). ) Was obtained.

<Acrylic copolymer (6)>
An acrylic copolymer (6) having a weight average molecular weight of 60,000 was obtained in the same manner as the acrylic acid copolymer (5) except that the amount was 2,2'-azobisisobutylnitrile (0.6 part).

<Adhesive (A)>
To 100 parts by mass of the acrylic copolymer (1), 20 parts by mass of the acrylic copolymer (5) was added and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (A) having a resin solid content of 25%.

<Adhesive (B)>
To 100 parts by mass of the acrylic copolymer (1), 10 parts by mass of the acrylic copolymer (5) was added and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (B) having a resin solid content of 25%.

<Adhesive (C)>
To 100 parts by mass of the acrylic copolymer (2), 20 parts by mass of the acrylic copolymer (5) was added and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (C) having a resin solid content of 25%.

<Adhesive (D)>
To 100 parts by mass of the acrylic copolymer (3), 20 parts by mass of the acrylic copolymer (5) was added and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (D) having a resin solid content of 25%.

<Adhesive (E)>
To 100 parts by mass of the acrylic copolymer (1), 20 parts by mass of the acrylic copolymer (6) was added and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (E) having a resin solid content of 25%.

<Adhesive (F)>
To 100 parts by mass of the acrylic copolymer (4), 20 parts by mass of the acrylic copolymer (5) was added and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (F) having a resin solid content of 25%.

<Adhesive (G)>
100 parts by mass of the acrylic copolymer (1) was diluted with ethyl acetate to obtain a pressure-sensitive adhesive (G) having a resin solid content of 25%.

<Adhesive (H)>
60 parts by mass of the acrylic copolymer (5) was added to 100 parts by mass of the acrylic copolymer (1) and diluted with ethyl acetate to obtain a pressure-sensitive adhesive (H) having a resin solid content of 25%.

(Preparation of Conductive Adhesive Composition)
[Preparation of Conductive Adhesive Composition (1A)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (A). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1A).

[Preparation of Conductive Adhesive Composition (2A)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (A). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) was blended with 0.63 part by mass and benzotriazole 0.23 part by mass, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (2A).

[Preparation of Conductive Adhesive Composition (3A)]
With respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (A), 5.7 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd. was crosslinked. Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) was blended with 0.63 part by mass and benzotriazole 0.23 part by mass, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (3A).

[Preparation of Conductive Adhesive Composition (4A)]
11.3 parts by mass of nickel powder NI525 (d50: 14.3 μm, d90: 40.5 μm) manufactured by Nikko Rika Co., Ltd. with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (A), cross-linking agent E-. 2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.63 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate and dispersed. The mixture was mixed with a stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (4A).

[Preparation of Conductive Adhesive Composition (1B)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (B). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1B).

[Preparation of Conductive Adhesive Composition (1C)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (C). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1C).

[Preparation of Conductive Adhesive Composition (1D)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (D). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1D).

[Preparation of Conductive Adhesive Composition (1E)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (E). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1E).

[Preparation of Conductive Adhesive Composition (1F)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (F). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1F).

[Preparation of Conductive Adhesive Composition (1G)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (G). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1G).

[Preparation of Conductive Adhesive Composition (1H)]
11.3 parts by mass of nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., bridged with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (H). Agent E-2XM (epoxy-based cross-linking agent manufactured by Soken Kagaku Co., Ltd., solid content 2% by mass) 0.16 part by mass and benzotriazole 0.23 part by mass were blended, and the solid content concentration was adjusted to 25% by mass with ethyl acetate. Then, the mixture was mixed with a dispersion stirrer for 10 minutes to prepare a conductive pressure-sensitive adhesive (1H).

(Creation of plated non-woven fabric)
[Plated non-woven fabric A]
An aqueous solution containing Miki Tokushu Paper's wet polyester non-woven fabric "Type A" (basis weight 10 g / m ² , thickness 15 μm, polyester fiber diameter 5 μm (average diameter)), stannous chloride 10 g / L, and hydrochloric acid 20 mL / L. Was immersed in water for about 5 minutes at room temperature, and then washed with water. Next, it was immersed in an aqueous solution containing 1 g / L of palladium chloride and 20 mL / L of hydrochloric acid at room temperature for about 10 minutes, and then washed with water. Next, 40 ° C. in an aqueous solution containing 10 g / L of copper sulfate, 7 mL / L of formaldehyde, 8 g / L of sodium hydroxide, 30 g / L of ethylenediaminetetraacetic acid 4 sodium (EDTA-4Na), and a stabilizer (0.25 mL / L). Soaked in water for 20 minutes and then washed with water. Then, using an electrolytic copper plating solution (manufactured by Okuno Pharmaceutical Co., Ltd., Top Lucina SF), the copper was plated to a plating amount of 6 g / m ² . Further, the nickel plating amount is 4 g / L in an electric nickel plating solution containing 240 g / L of nickel sulfate, 45 g / L of nickel chloride, 30 g / L of boric acid, 2 g / L of saccharin, and 0.2 g / L of 1,4-butindiol. It was plated to ^m2 , washed with water, and further dried to prepare a plated non-woven fabric A.

(Example 1)
[Creation of conductive adhesive sheet]
The conductive pressure-sensitive adhesive composition (1A) is coated on a release film "PET 38 x 1 A3" manufactured by Nipper Co., Ltd. with a comma coater so that the thickness of the pressure-sensitive adhesive layer after drying is 18 μm, and a dryer at 80 ° C. After drying in the medium for 2 minutes, it was heat-laminated at 80 ° C. on one side of a 12 μm thick inorganic rust-preventive (chromate) treated electrolytic copper foil (CF-T9FZ-HS-12, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.). Then, it was cured at 40 degreeC for 48 hours to prepare the conductive pressure-sensitive adhesive sheet of Example 1.

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

(Example 3)
A conductive pressure-sensitive adhesive sheet of Example 3 was prepared in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition (3A) was used instead of the conductive pressure-sensitive adhesive composition (1A).

(Example 4)
The conductive pressure-sensitive adhesive sheet of Example 4 was prepared in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition (4A) was used instead of the conductive pressure-sensitive adhesive composition (1A).

(Example 5)
A conductive pressure-sensitive adhesive sheet of Example 5 was prepared in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition (1B) was used instead of the conductive pressure-sensitive adhesive composition (1A).

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

(Example 7)
The conductive pressure-sensitive adhesive sheet of Example 7 was prepared in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition (1D) was used instead of the conductive pressure-sensitive adhesive composition (1A).

(Example 8)
The conductive pressure-sensitive adhesive sheet of Example 8 was prepared in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition (1E) was used instead of the conductive pressure-sensitive adhesive composition (1A).

(Example 9)
The conductive pressure-sensitive adhesive sheet of Example 9 was prepared in the same manner as in Example 1 except that the plated non-woven fabric A was used instead of the electrolytic copper foil treated with inorganic rust prevention (chromate).

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

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

(Comparative Example 3)
A conductive pressure-sensitive adhesive sheet of Comparative Example 3 was prepared in the same manner as in Example 1 except that the conductive pressure-sensitive adhesive composition (1H) was used instead of the conductive pressure-sensitive adhesive composition (1A).

(evaluation)
The conductive pressure-sensitive adhesive sheets prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were evaluated as follows, and the obtained results are shown in the table below.

[Evaluation of conductivity]
As shown in FIG. 4, the adhesive surfaces of the tin-plated copper foil having a 50 mm width × 50 mm width and having an adhesive layer are bonded to two surfaces of a glass panel having a step of 1 mm, and a conductivity evaluation jig having a step of 1 mm is attached. Created. The adhesive surface of the adhesive sheet cut into a width of 5 mm × 13 mm was bonded to the two surfaces of the jig prepared above with a width of 5 mm × 5 mm, and then pressurized with a load of 100 g / cm for ³ seconds. After leaving it for 300 hours in an environment of 23 ° C. and 50% RH, the resistance value when a current of 10 μA was passed was measured with a low resistivity resistivity meter (Lorester-GP manufactured by Mitsubishi Chemical Analytech Co., Ltd.).
⊚: less than 300 mΩ ○: 300 mΩ to less than 500 mΩ ×: 500 mΩ or more

[Adhesive strength]
A 25 mm wide conductive adhesive sheet sample was pressure-bonded to a stainless steel plate (hereinafter referred to as "stainless steel plate") that had been hairline-polished with No. 360 water-resistant abrasive paper under a 2.0 kg roller reciprocating pressure at 23 ° C and 50% RH. After leaving it at room temperature for 1 hour, the peeling adhesive strength was measured at a tensile tester (Tencilon RTA-100, manufactured by A & D Co., Ltd.) at a tensile speed of 300 mm / min at 180 degrees.

[Reworkability]
When the adhesive strength was measured, the adhesive residue on the stainless steel plate due to poor adhesion of the plating and poor adhesion of the adhesive was evaluated.
◯: No glue residue.
X: There is adhesive residue of 10% or more.

1 Conductive base material 2 Conductive adhesive layer 3 Glass panel 4 Adhesive layer 5 Copper foil 6 Tin-plated 7 Conductive adhesive sheet

Claims (10)

A conductive pressure-sensitive adhesive sheet having a conductive base material and a conductive pressure-sensitive adhesive layer.
The conductive pressure-sensitive adhesive layer contains a (meth) acrylic pressure-sensitive adhesive composition.
The (meth) acrylic pressure-sensitive adhesive composition is a (meth) acrylic copolymer having a weight average molecular weight of 600,000 to 1.8 million, and a (meth) acrylic copolymer having a weight average molecular weight of 5,000 to 100,000. , Triazole-based compounds, and cross-linking agents,
The (meth) acrylic copolymer having a weight average molecular weight of 600,000 to 1.8 million is a copolymer obtained by copolymerizing a (meth) acrylate monomer having 1 to 14 carbon atoms and a highly polar vinyl monomer.
The highly polar vinyl monomer contains a vinyl monomer having a carboxyl group and a vinyl monomer having a hydroxyl group.
The content of the (meth) acrylate monomer having 1 to 14 carbon atoms in the (meth) acrylic copolymer having a weight average molecular weight of 600,000 to 1.8 million is 80% by mass to 98.5% by mass.
The content of the highly polar vinyl monomer in the (meth) acrylic copolymer having a weight average molecular weight of 600,000 to 1.8 million is 0.2% by mass to 15% by mass.
The (meth) acrylic copolymer having a weight average molecular weight of 5,000 to 100,000 is a copolymer obtained by copolymerizing a (meth) acrylate monomer having 1 to 8 carbon atoms and a nitrogen atom-containing vinyl monomer. can be,
The content of the nitrogen atom-containing vinyl monomer in the (meth) acrylic copolymer having a weight average molecular weight of 5,000 to 100,000 is 1% by mass to 30% by mass.
The mass of the triazole-based compound is 0.05 parts by mass to 3.0 parts by mass with respect to 100 parts by mass (solid content) of the (meth) acrylic pressure-sensitive adhesive composition.
A conductive pressure-sensitive adhesive sheet having a tensile strength of 3.0 to 6.0 N / cm ² when the conductive pressure-sensitive adhesive layer is deformed by 10% at 23 ° C. The conductive pressure-sensitive adhesive sheet according to claim 1, wherein the conductive pressure-sensitive adhesive layer contains beaded conductive particles. Claim 1 or 2 in which the content of the conductive particles in the conductive pressure-sensitive adhesive layer is 10 to 100 parts by mass with respect to 100 parts by mass (solid content) of the (meth) acrylic pressure-sensitive adhesive composition. The conductive adhesive sheet described in. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the conductive particles have a particle diameter d50 of 5 to 30 μm. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the conductive pressure-sensitive adhesive layer has a thickness of 30 μm or less. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the conductive base material is a conductive base material containing copper. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the conductive base material is a copper foil base material that has been subjected to an inorganic rust preventive treatment. One of claims 1 to 6 , wherein the conductive base material is a conductive base material obtained by plating a wet polyester-based non-woven base material, and the plating includes electroless metal plating. The conductive pressure-sensitive adhesive sheet described in the section. The conductive adhesive sheet according to any one of claims 1 to 8, wherein the sticking area is 10 mm × 10 mm or less. The conductive adhesive sheet according to any one of claims 1 to 9, which is used by being attached to a built-in component of a small electronic terminal.

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