JP2019001931A - Conductive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that the present invention has a small adhesive area and has good adhesiveness, conductivity and reworkability even when bonded to an uneven portion, and the conductivity does not easily decrease with time. The purpose is to provide a conductive pressure-sensitive adhesive sheet. According to the present invention, a conductive pressure-sensitive adhesive sheet having a conductive base material and a conductive pressure-sensitive adhesive layer has a tensile strength when the conductive pressure-sensitive adhesive layer is deformed by 10% at 23 ° C. , 3.0 to 6.0 N / cm2, the present invention relates to a conductive pressure-sensitive adhesive sheet. [Selection diagram] None

Description

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

  Conductive adhesive sheet is easy to handle, shields unnecessary electromagnetic waves radiated from electricity and electronic equipment, shields harmful electromagnetic waves from other electrical and electronic equipment, and grounds for antistatic charge With the recent miniaturization and thinning of electrical and electronic equipment, conductive adhesive sheets used for these are also required to be thin.

  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 material is disclosed on a conductive substrate (Patent Documents 1 to 3). 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 pressure-sensitive adhesive sheet has been reduced with the reduction in the space of the electronic substrate, so that there has been a problem that peeling tends to occur with time and the conductivity is lowered.
In addition, when the adhesive sheet is bonded to the concavo-convex portion of the electronic substrate, there is a problem that peeling occurs with time and conductivity is lowered.

JP 2004-263030 A JP 2009-79127 A

  The problem to be solved by the present invention is a conductive adhesive having a small adhesion area and having good adhesion, conductivity, reworkability even when pasted on an uneven portion, and the conductivity is not easily lowered over time. To provide a sheet.

In this invention, it is a conductive adhesive sheet which has a conductive base material and a conductive adhesive layer, Comprising: Tensile strength when deform | transforming 10% of the said conductive adhesive layer under 23 degreeC is 3.0. the electroconductive pressure-sensitive adhesive sheet, which is a ~6.0N / cm ^2, the above-mentioned problems are eliminated.

  The conductive thin pressure-sensitive adhesive sheet of the present invention has good adhesion and conductivity to an adherend while being thin, so that it is used for shielding electromagnetic waves used in electric and electronic devices, and other electric and electronic devices. It is useful for shielding harmful electromagnetic waves that are generated more and for fixing static electricity to prevent static charge. In particular, the present invention can be suitably applied to portable electronic device applications that are becoming thinner and have severe volume restrictions within the housing. In particular, it is suitable for use by attaching to a built-in component of a small electronic terminal.

It is the schematic which shows the structural example of the electroconductive adhesive sheet of this invention. It is the schematic which shows the structural example of the electroconductive adhesive sheet of this invention. It is a microscope picture of an example of the bead-like electroconductive particle used suitably for the electroconductive adhesive sheet of this invention. It is a schematic diagram showing the electroconductivity evaluation of the electroconductive adhesive sheet of this invention.

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

  Below, the electroconductive adhesive sheet of this invention is demonstrated in more detail based on the component. The “sheet” in the present invention means a form in which at least one thin layer of conductive adhesive is provided on a conductive substrate or a release sheet. For example, each sheet, a roll, or a thin plate All product forms such as strips and strips (tapes) are included.

(Conductive adhesive layer)
The tensile strength when the conductive pressure-sensitive adhesive layer used in the conductive pressure-sensitive adhesive sheet of the present invention is deformed by 10% at 23 ° C. is 3.0 to 6.0 N / cm ² , but 3.5 to 5 0.5 N / cm ² is preferable, and 4.0 to 5.0 N / cm ² is more preferable. The increase in resistance value over time is due to the contact of the conductive filler on the conductive member with the metal filler added to the conductive adhesive layer due to the peeling at the interface between the conductive adhesive layer of the conductive adhesive sheet and the bonded conductive member. Disappears and rises. The peeling phenomenon occurs when the conductive pressure-sensitive adhesive layer extends. Therefore, when the tensile strength of the conductive pressure-sensitive adhesive layer is in the above range, the conductive pressure-sensitive adhesive layer is difficult to stretch, and therefore, peeling over time can be suppressed, and an increase in resistance value over time can be easily suppressed.

The tensile strength when the conductive pressure-sensitive adhesive layer is deformed by 10% at 23 ° C. is a conductive adhesive having a thickness of 0.4 mm, a width of 10 mm and a length of 20 mm 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 22 mm length [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 in the above range, both good adhesion and thinness can be achieved.

(Adhesive composition)
The conductive pressure-sensitive adhesive layer used for 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 forming the conductive pressure-sensitive adhesive layer, a pressure-sensitive adhesive composition used for a normal pressure-sensitive adhesive sheet 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, and silicone-based pressure-sensitive adhesives. A (meth) acrylic copolymer containing a copolymer of (meth) acrylate and other monomers as a base polymer, and additives such as tackifiers and crosslinking agents blended as necessary. The pressure-sensitive adhesive composition can be preferably used from the viewpoint of weather resistance and heat resistance.

  As an acrylic copolymer, the acrylic copolymer which has a C1-C14 (meth) acrylate monomer as a main monomer component can be used preferably, As a C1-C14 (meth) acrylate, 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, Monomers such as isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like, and one or more of these are used. Among these, (meth) acrylates having 4 to 12 carbon atoms in the alkyl group are preferable, and (meth) acrylates having a linear or branched structure having 4 to 9 carbon atoms are 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 in the monomer component constituting the acrylic copolymer, and is 90 to 98. More preferably, it is 5 mass%.

  The acrylic copolymer used in the present invention is also preferably copolymerized with a highly polar vinyl monomer. Examples of the highly polar vinyl monomer include a vinyl monomer having a carboxyl group, a vinyl monomer having a hydroxyl group, and a vinyl having an amide group. A monomer etc. are mentioned, These 1 type (s) or 2 or more types are used. Among these, a carboxyl group-containing monomer can be preferably used because it easily adjusts 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 succinic acid acrylate, etc. can be used. It is preferable to use it as a polymerization component.

  When using the vinyl monomer which has a carboxyl group, it is preferable that the content is 0.2-15 mass% in the monomer component which comprises an acryl-type copolymer, 0.4-10 mass% It is more preferable that it is 0.5-6 mass%. By containing in the said range, it is easy to adjust the adhesiveness of an 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, 6-hydroxyhexyl (meth) acrylate and the like ( A (meth) acrylate can be used.

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

  Other highly polar vinyl monomers include vinyl acetate, ethylene oxide modified succinic acid acrylate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropane sulfonic acid, 2-methoxyethyl (meth) acrylate, 2-phenoxyethyl ( And terminal alkoxy-modified (meth) acrylates such as (meth) acrylate.

  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 component constituting the acrylic copolymer. More preferably, it is 0.5-6 mass%. By containing in the said range, it is easy to adjust the adhesiveness of an adhesive to a suitable range.

  The acrylic copolymer can be obtained by copolymerization by a known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method. However, from the viewpoint of production cost and productivity, solution polymerization is possible. It is preferable to be polymerized by. The weight average molecular weight Mw of the acrylic copolymer is preferably 3.5 million to 2,000,000, more preferably 600,000 to 1,800,000, and even more preferably 700,000 to 1,600,000. When the weight average molecular weight Mw is within the above range, initial adhesiveness to metal and cohesive force necessary for peeling can be imparted to the conductive pressure-sensitive adhesive layer.

In the present invention, the weight average molecular weight Mw of the acrylic copolymer can be measured by gel permeation chromatography (GPC). More specifically, as a GPC measurement device, “SC8020” manufactured by Tosoh Corporation can be used to measure and obtain the following GPC measurement conditions based on polystyrene conversion values.
(GPC measurement conditions)
Sample concentration: 0.5% by weight (tetrahydrofuran solution)
Sample injection volume: 100 μL
・ Eluent: Tetrahydrofuran (THF)
・ Flow rate: 1.0 mL / min
Column temperature (measurement temperature): 40 ° C
Column: “TSKgel GMHHR-H” manufactured by Tosoh Corporation
・ Detector: Differential refraction

(Additive)
Furthermore, 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 obtained by copolymerizing a nitrogen atom-containing vinyl monomer. By copolymerizing a nitrogen atom-containing vinyl monomer, an interaction with the acrylic copolymer can be formed, and an excellent cohesive force can be imparted to the conductive pressure-sensitive adhesive layer.

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

  Of these, amino group-containing monomers and amide group-containing monomers are preferred. Of these, amino group-containing monomers are particularly preferred. By using the nitrogen-containing vinyl monomer, it is possible to form an interaction with the (meth) acrylic copolymer and to give the conductive pressure-sensitive adhesive layer the tensile strength necessary to suppress peeling over time.

  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 weight, based on the total amount of the copolymer. By setting the content of the nitrogen atom-containing vinyl monomer in this range, the conductive adhesive layer can be imparted with the tensile strength necessary to form an interaction with the acrylic copolymer and to suppress peeling over time. .

  The copolymer preferably has a weight average molecular weight Mw of 5,000 to 100,000, more preferably 5,000 to 80,000, and still more preferably 5,000 to 50,000. When the weight average molecular weight Mw is within the above range, the conductive adhesive layer can be provided with a tensile strength necessary to suppress peeling over time.

  Furthermore, in order to improve the adhesive strength of the conductive adhesive sheet, a tackifier resin may be added. Tackifying resins to be added to the conductive adhesive used in the present invention are rosin resins, terpene resins, aliphatic (C5) and aromatic (C9) petroleum resins, styrene resin phenolic resins, Examples include xylene resins and methacrylic resins. Among these, a rosin resin is preferable, and a polymerized rosin resin is particularly preferable. As addition amount of tackifying resin, it is preferable to add 10-50 mass parts with respect to 100 mass parts (solid content) of a (meth) acrylic-type copolymer.

  Various additives may be added to the pressure-sensitive adhesive used in the conductive pressure-sensitive adhesive sheet of the present invention, if necessary. As said additive, a plasticizer, a softener, a metal deactivator, antioxidant, a pigment, dye, etc. are mentioned, for example, It uses suitably as needed.

(Triazole compound)
The pressure-sensitive adhesive used for the conductive pressure-sensitive adhesive sheet of the present invention contains a triazole compound. Examples of the triazole compound include benzotriazole, tolyltriazole and its potassium salt, 3- (N-salicyloyl) amino-1,2,4 triazole, 2- (2′-hydroxy-5methylphenyl) benzotriazole and the like. Of these, benzotriazole is preferable because it has a high effect of preventing solubility and adhesive strength from decreasing.

  Although it does not specifically limit as content of a triazole type compound, 0.05-3.0 mass parts is preferable with respect to 100 mass parts (solid content) of an acrylic adhesive composition. Among these, 0.1 to 1.5 parts by mass is preferable, and 0.3 to 1.0 part by mass is most preferable. By setting it as the said content, it becomes easy to obtain especially suitable holding power, and it becomes easy to suppress especially the adhesive force fall after a high temperature, high humidity environment test.

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

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

(Conductive particles)
The conductive particles used in the conductive adhesive sheet of the present invention are made of metal powder particles such as gold, silver, copper, nickel, and aluminum, conductive resins such as carbon and graphite, resin, solid glass beads, and hollow glass. Those having a metal coating on the surface of the beads can be used. Among these, 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-like shapes on the surface of the particles produced by the carbonyl method, those obtained by smoothing the surface needle-shaped particles into spherical particles, Examples thereof include copper powder and silver powder produced by a high-pressure swirling water atomization 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 shape, or a bead shape in which bonds or the like are formed between a large number of conductive particles as shown in FIG.

  Although it does not specifically limit as a particle diameter of electroconductive particle, It is preferable that particle diameter d50 is 5-30 micrometers, It is preferable that it is 10-25 micrometers, It is more preferable that it is 12-20 micrometers, Most preferably, it is 13-18 micrometers. Moreover, it is preferable that particle diameter d90 is 25-60 micrometers, it is preferable that it is 27-55 micrometers, it is more preferable that it is 30-50 micrometers, and it is most preferable that it is 31-50 micrometers. In addition, when mixing 2 or more types of electroconductive particle, it is preferable that the particle diameters d50 and d90 after mixing are the said ranges.

The particle diameter d50 indicates a 50% cumulative value in the particle size distribution, the particle diameter d90 indicates a 90% cumulative value in the particle size distribution, and is a value measured by a laser analysis / scattering method. Examples of the measuring device include Nikkiso Microtrack MT3000II, Shimadzu Laser Diffraction Particle Size Analyzer SALD-3000, and the like.
Examples of the method of adjusting the particle diameter d50 within the above range include a method of pulverizing conductive particles with a jet mill and a sieving method using a sieve.

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

  Although it does not specifically limit as content of the electroconductive particle in an electroconductive adhesive layer, 10-100 mass parts is preferable with respect to 100 mass parts (solid content) of an acrylic adhesive composition, More preferably, it is 20-80 mass parts, More preferably, it is 30-70 mass parts, and 40-60 mass parts is the most preferable. By making content of electroconductive particle into the said range, it becomes easy to make electroconductivity, adhesiveness, and productivity compatible.

  Examples of the method for dispersing the conductive particles in the acrylic pressure-sensitive adhesive composition include a method of 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 biaxial mixer, and a planetary mixer. Among them, a dissolver or a butterfly mixer that can apply a medium share with little thickening of the pressure-sensitive adhesive during stirring is preferable.

  Although it does not specifically limit as solid content of an acrylic adhesive composition, 10 to 70% is preferable, More preferably, it is 30 to 55%, Most preferably, it is 43 to 50%.

(Conductive substrate)
Examples of the conductive substrate used in the conductive adhesive sheet of the present invention include a conductive substrate obtained by plating a metal foil substrate or a wet polyester nonwoven fabric substrate. 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 a copper foil is more preferable in terms of conductivity, workability, and cost.

  Further, the copper foil is preferably subjected to a rust prevention treatment. Examples of the rust prevention treatment include organic rust prevention and inorganic rust prevention. Among them, inorganic rust prevention 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 Co., Ltd. Examples of commercially available rolled copper foils include TCU-H-8-RT (8 μm: organic rust prevention treatment) manufactured by Nippon Foil Co., Ltd., BAY-64T-DT (35 μm: chromate treatment) manufactured by JX Nippon Mining & Metals. It is done.

  As the electroconductive substrate obtained by plating the wet polyester nonwoven fabric substrate, electroless metal plating is used as the plating. Examples of the metal to be plated include copper, nickel, silver, platinum, and aluminum. Among them, copper or nickel is preferable from the viewpoint of conductivity and cost.

  As thickness of a conductive base material, 1-40 micrometers is preferable, More preferably, it is 3-35 micrometers, Most preferably, it is 6-25 micrometers. If it is the said range, since thickness reduction is possible and it is excellent in workability, it is preferable.

(Release 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, paper such as kraft paper, glassine 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 paper, papers that have been subjected to sealing treatment with clay, polyvinyl alcohol, etc., and one side or both sides that have been subjected to a release treatment such as silicon-based resin can be used.

(Conductive adhesive sheet)
The electroconductive adhesive sheet of this invention is an electroconductive adhesive sheet which has the said electroconductive adhesive layer and an electroconductive base material.

  The conductive pressure-sensitive adhesive sheet of the present invention is bonded to SUS in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH using a 2 kg roller with one reciprocation, and left at rest for 1 hour. The 180 ° peel adhesive strength in min is preferably 5 to 15 N / 20 mm for SUS. When it is within the above range, it is easy to suppress peeling, and the conductive adhesive sheet can be peeled off in a poorly bonded product in the manufacturing process.

  The total thickness of the conductive 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. By being in the said range, thickness reduction of an adhesive sheet can be achieved, ensuring adhesiveness and electroconductivity, and it can contribute to thickness reduction of a portable electronic device. The total thickness of the conductive adhesive sheet is the thickness of the conductive adhesive sheet itself that does not include a release liner.

  The conductive adhesive sheet of the present invention can be prepared by a generally used method. Specifically, it can be produced by a method of applying on a release liner, drying or curing, forming a conductive pressure-sensitive adhesive layer, and bonding to a conductive substrate.

  When laminating the conductive adhesive layer formed on the release liner and the conductive substrate, heat lamination gives excellent adhesion between the conductive substrate and the conductive adhesive layer. It is preferable from the viewpoint. The temperature of the heat laminate is preferably 60 ° C. to 150 ° C., more preferably 70 ° C. to 130 ° C., and further preferably 80 ° C. to 110 ° C. in terms of suppressing adhesion and shrinkage of the conductive substrate.

  The example of the suitable structure of the electroconductive adhesive sheet of this invention is shown in FIG.1 and FIG.2. FIG. 1 is a single-sided pressure-sensitive adhesive sheet in which a conductive pressure-sensitive adhesive layer 2 is laminated on a conductive substrate 1. FIG. 2 shows a double-sided pressure-sensitive adhesive sheet in which a conductive pressure-sensitive adhesive layer 2 is laminated on both surfaces of a conductive substrate 1. In these configurations, a configuration in which a release liner is provided on the surface of the pressure-sensitive adhesive layer 2 can be preferably used.

  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 copolymer In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 91.5 parts by mass of n-butyl acrylate, 0.5 parts by mass of 2-hydroxyethyl acrylate, 8.0 parts by weight of acrylic acid and 0.2 parts of 2,2′-azobisisobutylnitrile as a polymerization initiator are dissolved in 100 parts by weight of ethyl acetate, and after substitution with nitrogen, polymerization is carried out at 80 ° C. for 8 hours to obtain a weight average. 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 acrylic acid copolymer (1) except that 95.5 parts by mass of n-butyl acrylate and 4.0 parts by mass of acrylic acid are used. Got.

<Acrylic copolymer (3)>
An acrylic copolymer (3) having a weight average molecular weight of 1,500,000 was obtained in the same manner as the acrylic acid copolymer (1) except that 0.1 part of 2,2′-azobisisobutylnitrile was used.

<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 0.5 part of 2,2′-azobisisobutylnitrile was used.

<Acrylic copolymer (5)>
Preparation of acrylic copolymer In a reaction vessel equipped with a stirrer, cold flow cooler, thermometer, dropping funnel and nitrogen gas inlet, 95.0 parts by weight of methyl methacrylate, 5.0 parts by weight of dimethylaminoethyl methacrylate and a polymerization initiator As follows, 1.0 part by mass of 2,2′-azobisisobutylnitrile is dissolved in 100 parts by mass of ethyl acetate, substituted with nitrogen, polymerized at 80 ° C. for 8 hours, and a methacrylic copolymer having a weight average molecular weight of 20,000 (5 )

<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 0.6 part of 2,2′-azobisisobutylnitrile was used.

<Adhesive (A)>
20 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 (A) having a resin solid content of 25%.

<Adhesive (B)>
10 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 (B) having a resin solid content of 25%.

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

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

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

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

<Adhesive (G)>
The acrylic copolymer (1) was diluted with 100 parts by mass 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 an 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. with respect to 100 parts by mass of the pressure-sensitive adhesive (A) (solid content: 25 parts by mass) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive 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. with respect to 100 parts by mass of the pressure-sensitive adhesive (A) (solid content: 25 parts by mass) E-2XM (Epoxy cross-linking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.63 parts by mass and benzotriazole 0.23 parts by mass are mixed, and the solid content concentration is adjusted to 25% by mass with ethyl acetate. And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive adhesive (2A).

[Preparation of conductive adhesive composition (3A)]
Nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., 5.7 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive (A) (solid content 25 parts by mass), E-2XM (Epoxy cross-linking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.63 parts by mass and benzotriazole 0.23 parts by mass are mixed, and the solid content concentration is adjusted to 25% by mass with ethyl acetate. And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive adhesive (3A).

[Preparation of conductive adhesive composition (4A)]
Nickel powder NI525 (d50: 14.3 μm, d90: 40.5 μm) manufactured by Nikko Rica Co., Ltd., 11.3 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive (A) (solid content: 25 parts by mass), crosslinking agent E- 2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.63 part by mass and benzotriazole 0.23 part by mass were mixed, and the solid content concentration was adjusted to 25% by mass with ethyl acetate and dispersed. A conductive adhesive (4A) was prepared by mixing for 10 minutes with a stirrer.

[Preparation of conductive adhesive composition (1B)]
Nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., 11.3 parts by mass with respect to 100 parts by mass (solid content: 25 parts by mass) of the pressure-sensitive adhesive (B) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive 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. with respect to 100 parts by mass of the pressure-sensitive adhesive (C) (solid content 25 parts by mass) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive adhesive (1C).

[Preparation of conductive adhesive composition (1D)]
Nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., 11.3 parts by mass with respect to 100 parts by mass of the pressure-sensitive adhesive (D) (solid content 25 parts by mass), crosslinking Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive adhesive (1D).

[Preparation of conductive adhesive composition (1E)]
Nickel powder NI255T (d50: 16.2 μm, d90: 51.2 μm) manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., 11.3 parts by mass with respect to 100 parts by mass (solid content: 25 parts by mass) of the pressure-sensitive adhesive (E) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive 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. with respect to 100 parts by mass (solid content 25 parts by mass) of the pressure-sensitive adhesive (F) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive 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. with respect to 100 parts by mass (solid content: 25 parts by mass) of the pressure-sensitive adhesive (G) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive 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 Co., Ltd. with respect to 100 parts by mass (solid content: 25 parts by mass) of the pressure-sensitive adhesive (H) Agent E-2XM (epoxy crosslinking agent manufactured by Soken Chemical Co., Ltd., solid content 2% by mass) 0.16 part by mass, benzotriazole 0.23 part by mass, the solid content concentration is adjusted to 25% by mass with ethyl acetate And it mixed for 10 minutes with the dispersion stirrer, and produced the electroconductive adhesive (1H).

(Creation of plated nonwoven fabric)
[Plating nonwoven fabric A]
Miki Special Paper-made wet polyester nonwoven fabric “Type A” (basis weight 10 g / m ² , thickness 15 μm, polyester fiber diameter 5 μm (average diameter)), aqueous solution containing stannous chloride 10 g / L and hydrochloric acid 20 mL / L 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, an aqueous solution containing copper sulfate 10 g / L, formaldehyde 7 mL / L, sodium hydroxide 8 g / L, ethylenediaminetetraacetic acid 4 sodium (EDTA-4Na) 30 g / L, and a stabilizer (0.25 mL / L) at 40 ° C. For 20 minutes and then washed with water. Then, it plated so that the amount of copper plating might be 6 g / m < ² > using the electrolytic copper plating liquid (Okuno Pharmaceutical Co., Ltd. make, Top Lucina SF). Furthermore, the nickel plating amount is 4 g / L in an electric nickel plating solution containing nickel sulfate 240 g / L, nickel chloride 45 g / L, boric acid 30 g / L, saccharin 2 g / L, 1,4-butynediol 0.2 g / L. Plating nonwoven fabric A was prepared by plating to m ² , washing with water, and further drying.

Example 1
[Creation of conductive adhesive sheet]
The conductive pressure-sensitive adhesive composition (1A) was coated on a release film “PET38 × 1 A3” manufactured by Nippers with a comma coater so that the thickness of the pressure-sensitive adhesive layer after drying was 18 μm, and a dryer at 80 ° C. After being dried for 2 minutes, it was heat-laminated at 80 ° C. on one surface of an electrolytic copper foil (CF-T9FZ-HS-12, manufactured by Fukuda Metal Foil Co., Ltd.) having a thickness of 12 μm treated with inorganic rust (chromate). After that, curing was carried out at 40 ° C. for 48 hours to prepare the conductive adhesive sheet of Example 1.

(Example 2)
A conductive pressure-sensitive adhesive sheet of Example 2 was prepared in the same manner as 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)
A 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)
A 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)
A 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
A conductive pressure-sensitive adhesive sheet of Example 9 was prepared in the same manner as in Example 1 except that the plated nonwoven 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 following evaluation was performed about the conductive adhesive sheet created in Examples 1-9 and Comparative Examples 1-3, and the obtained result was shown to the following table.

[Conductivity evaluation]
As shown in FIG. 4, the adhesive surface of a copper foil with a pressure-sensitive adhesive layer that has been subjected to tin plating of 50 mm width × 50 mm width is bonded to two surfaces of a glass panel having a level difference of 1 mm, and a conductive evaluation jig having a level difference of 1 mm is obtained. Created. The adhesive surface of the adhesive sheet cut to a width of 5 mm × 13 mm was bonded to the two surfaces of the jig created above with a width of 5 mm × 5 mm, and then pressed with a load of 100 g / cm ² for 3 seconds. After being allowed to stand 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 resistance resistivity meter (Loresta-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 conductive adhesive sheet sample with a width of 25 mm is attached to a stainless steel plate (hereinafter referred to as a stainless steel plate) subjected to hairline polishing treatment with No. 360 water-resistant polishing paper, and a 2.0 kg roller 1 reciprocating pressure is applied in an environment of 23 ° C. and 50% RH. After leaving at room temperature for 1 hour, 180 ° peel adhesion was measured at room temperature at a tensile rate of 300 mm / min with a tensile tester (Tensilon RTA-100, manufactured by A & D).

[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 adhesive residue.
X: There is an adhesive residue of 10% or more.

DESCRIPTION OF SYMBOLS 1 Conductive base material 2 Conductive adhesive layer 3 Glass panel 4 Adhesive layer 5 Copper foil 6 Tin plating 7 Conductive adhesive sheet

Claims (10)

A conductive pressure-sensitive adhesive sheet having a conductive base material and a conductive pressure-sensitive adhesive layer, and having a tensile strength of 3.0 to 6.0 N when the conductive pressure-sensitive adhesive layer is deformed by 10% at 23 ° C. A conductive pressure-sensitive adhesive sheet characterized by being / cm ² . The conductive adhesive sheet according to claim 1, wherein the conductive particles are beaded. The content of conductive particles in the conductive adhesive layer is 10 to 100 parts by mass with respect to 100 parts by mass (solid content) of the (meth) acrylic adhesive composition. Conductive adhesive sheet. The conductive pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein a particle diameter d50 of the conductive particles is 5 to 30 µm. The conductive adhesive sheet according to claim 1, wherein the conductive adhesive layer has a thickness of 30 μm or less. The conductive adhesive sheet according to claim 1, wherein the conductive substrate is a conductive substrate containing copper. The conductive adhesive sheet according to any one of claims 1 to 6, wherein the conductive substrate is a copper foil substrate subjected to an inorganic rust prevention treatment. The conductive substrate is a conductive substrate obtained by plating a wet polyester nonwoven fabric substrate, and the plating includes electroless metal plating. The conductive adhesive sheet according to item. The conductive adhesive sheet according to any one of claims 1 to 8, wherein the sticking area is 10 mm x 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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