TW201412923A - Electroconductive thin adhesive sheet - Google Patents

Abstract

The invention provides an electroconductive thin adhesive sheet which has good glueyness and electroconductibility, and excellent productbility even thin type. The thin adhesive sheet can implement thin type, and simultaneously has good glueyness and electroconductibility, and proper productbility. The total thickness of the thin adhesive sheet is smaller than 40μm. The thin adhesive sheet is characterized in that: the thin adhesive sheet comprises an electroconductive substrate and an electroconductive adhesive layer containing electroconductive particles, the diameter d50 of the electroconductive particles may be 4-12μm, the diameter d85 of the electroconductive particles may be 6-15μm, and the thickness of the adhesive layer may be 6-12μm.

Description

Conductive thin adhesive sheet

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

Because of its convenient operation, the conductive adhesive sheet is used for shielding the use of unnecessary leakage electromagnetic waves radiated from motors, electronic devices, etc., shielding the use of harmful space electromagnetic waves generated by other motors and electronic devices, and preventing In the case of the use of the grounding with static electricity, the conductive adhesive sheets used in these motors and electronic devices are also required to be thinned.

In the case of a thin conductive adhesive sheet, the following adhesive sheet is disclosed, which has a viscosity of a conductive adhesive containing a conductive filler dispersed in an adhesive substance on a conductive substrate. The adhesive layer (see Patent Documents 1 and 2). Although it is disclosed that these adhesive sheets have suitable electrical conductivity and splicability, when an ultra-thin type adhesive sheet which is required to be thinner in recent years is produced, electrical conductivity and jointability are required to be further improved. Further, when the adhesive sheet having the adhesive layer containing the conductive filler is extremely thin, it is easy to cause coating streaks in the adhesive layer, and it is difficult to obtain suitable productivity.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-263030

Patent Document 2: JP-A-2009-79127

The problem to be solved by the present invention is to provide a conductive thin adhesive sheet which has excellent bondability and conductivity even in a thin form and is excellent in productivity.

In the present invention, it has been found that the above-mentioned problem can be solved by the following thin conductive adhesive sheet which has a good bondability, electrical conductivity, and suitable productivity, and the conductive thin adhesive sheet is A thin adhesive sheet having a total thickness of 40 μm or less is characterized by comprising a conductive substrate and a conductive adhesive layer containing conductive particles, wherein the conductive particles have a particle diameter d50 of 4 to 12 μm and a d85 of 6 The thickness of the adhesive layer is 15 to 12 μm at 15 μm.

The conductive thin adhesive sheet of the present invention is useful as an electrical and electronic device because it is extremely thin and has good adhesion to an adherend and conductivity, and has suitable productivity. For shielding of electromagnetic waves, etc., for shielding of harmful space electromagnetic waves generated by other electrical and electronic equipment, and for preventing grounding with static electricity. In particular, it can be suitably used for a portable electronic device having a further thinning and having a strict limit on the volume inside the casing.

1‧‧‧Electrically conductive substrate

2‧‧‧ Conductive adhesive layer

Fig. 1 is a view showing an example of a configuration of a conductive thin adhesive sheet of the present invention.

Fig. 2 is a view showing an example of a configuration of a conductive thin adhesive sheet of the present invention.

The conductive adhesive sheet of the present invention is a thin adhesive sheet having a total thickness of 40 μm or less, which has a guide The electrically conductive substrate and the conductive adhesive layer containing the conductive particles have a particle diameter d50 of 4 to 12 μm, d85 of 6 to 15 μm, and a thickness of the adhesive layer of 6 to 12 μm.

Hereinafter, the conductive adhesive sheet of the present invention will be described in more detail based on the constituent elements. Further, the "Sheet" in the present invention means a form in which at least one layer of a conductive adhesive is provided on a conductive substrate or a release sheet, and includes, for example, a single sheet, a roll or a sheet. All of the product forms such as ribbons and tapes (tape-like).

(conductive particles)

The conductive particles used in the conductive adhesive sheet of the present invention have a particle diameter d50 of 4 to 12 μm and a particle diameter d85 of 6 to 15 μm. The d50 is preferably 4 to 10 μm, more preferably 5 to 9 μm, and the most preferred is 6 to 8 μm. Further, d85 is preferably 6.5 to 14 μm, more preferably 7 to 13 μm, and most preferably 8 to 11 μm. Moreover, the particle diameter d50 is a 50% cumulative value (median diameter) in the particle size distribution. The particle size d85 is an 85% cumulative value. These particle diameters are values measured by laser analysis and scattering. Examples of the measurement device include Microtrac MT3000II manufactured by Nikkiso Co., Ltd., and laser diffraction type particle size distribution analyzer SALD-3000 manufactured by Shimadzu Corporation.

The particle diameter d50 of the conductive particles should be 50 to 150% of the thickness of the adhesive layer, and d85 is 80 to 200%. By using the conductive particles in the above range, it is possible to have both conductivity, bondability, and productivity. The better d50 is 60~120%, and the best is 70~100%. The better d85 is 100~150%, and the better is 110~140%.

As the material of the conductive particles, metal powder particles such as gold, silver, copper, nickel, aluminum, or the like; conductive resins such as carbon or graphite; and surfaces of the resin or solid glass beads or hollow glass beads can be used. A material with a metal coating or the like. Among them, nickel powder particles, copper powder particles, and silver powder particles are preferred because of their excellent electrical conductivity, jointability, and productivity. More preferably, the nickel particles having a surface-shaped needle shape having a plurality of needle-like shapes on the surface of the particles produced by the carbonyl method, and smoothing the surface-like acicular particles to form spherical granules, Copper powder and silver powder produced by ultra-high pressure rotary water atomization. These conductive particles may be used by mixing two or more of d50 and d85 so as to fall within the above range. Especially because the particle size d50 is 10~12μm or more. The material obtained by mixing the particles and the particles of 5 to 7 μm is excellent in conductivity.

The shape of the conductive particles is preferably a spherical shape or a surface needle shape. Although the aspect ratio is not particularly limited, it is preferably 1 to 2, preferably 1 to 1.5, and most preferably 1 to 1.2. The aspect ratio can be measured by a scanning electron microscope.

The tap density of the conductive particles is not particularly limited, but is preferably 2 to 7 g/cm ³ because it is less likely to settle and aggregate during production. It is preferably 3 to 6 g/cm ³ , and the most preferred is 4 to 5 g/cm ³ .

The content of the conductive particles in the conductive adhesive layer is not particularly limited, but is preferably 10 to 65% by mass, preferably 20 to 50% by mass, more preferably 20 to 50% by mass in the conductive adhesive layer. The best is 22~41% by mass, and the best is 28~38% by mass. When the content of the conductive particles is within the above range, it is easy to have both conductivity, bondability, and productivity.

(adhesive composition)

The conductive adhesive layer used in the conductive adhesive sheet of the present invention is formed of a binder composition containing the above-mentioned conductive particles. As the adhesive composition for forming the conductive adhesive layer, an adhesive composition used in a usual adhesive sheet can be used. Examples of the adhesive composition include (meth)acrylic adhesives, urethane adhesives, synthetic rubber adhesives, natural rubber adhesives, and ketone adhesives. An agent or the like, but in view of weather resistance and heat resistance, it is preferred to use an acrylic copolymer having a (meth) acrylate alone or a copolymer containing a (meth) acrylate and another monomer as a base polymer. A (meth)acrylic adhesive composition in which an additive such as a tackifier resin or a crosslinking agent is mixed as needed.

In the acrylic copolymer, an acrylic copolymer having a (meth) acrylate monomer having 1 to 14 carbon atoms as a main monomer component can be preferably used as a (meth) group having 1 to 14 carbon atoms. Examples of the acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate. N-hexyl methacrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylate-2 -Ethylhexyl ester and other monomers, One type or two or more types are used. Among them, 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. Among them, n-butyl acrylate and 2-ethylhexyl acrylate can be preferably used, and they may be used singly 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, more preferably 90%, of the monomer component constituting the acrylic copolymer. 98.5 mass%.

Further, the acrylic copolymer used in the present invention is preferably a copolymer of a highly polar vinyl monomer, and examples of the highly polar vinyl monomer include a vinyl monomer having a carboxyl group and a hydroxyl group. One type or two or more types of the vinyl monomer, the vinyl monomer having a mercapto group, and the like can be used. Among them, since it is easy to adjust the bonding property of the adhesive to an appropriate range, it is preferred to use a carboxyl group-containing monomer.

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, or the like can be used. Among them, acrylic acid is preferably used as a copolymerization component.

When a vinyl monomer having a carboxyl group is used, the content thereof is preferably from 0.2 to 15% by mass, preferably from 0.4 to 10% by mass, more preferably from 0.5 to 6% by mass based on the monomer component constituting the acrylic copolymer. %. By including a vinyl monomer having a carboxyl group in this range, the bondability of the adhesive is easily adjusted to an appropriate range.

For the monomer having a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (A) A hydroxyl group-containing (meth) acrylate such as hexamethylene acrylate.

Further, examples of the monomer having a mercapto group include N-vinylpyrrolidone, N-vinylcaprolactam, propylene morpholine, acrylamide, N,N-dimethyl decylamine. Wait.

The other high-polarity vinyl monomer may, for example, be a sulfonic acid group-containing monomer such as vinyl acetate, ethylene oxide-modified succinic acid acrylate or 2-propenylamine-2-methylpropanesulfonic acid; A terminal alkoxy modified (meth) acrylate such as 2-methoxyethyl (meth)acrylate or 2-phenoxyethyl (meth)acrylate.

The content of the highly polar vinyl monomer is preferably from 0.2 to 15% by mass, preferably from 0.4 to 10% by mass, more preferably from 0.5 to 10% by mass, more preferably 0.5% by weight of the monomer component constituting the acrylic copolymer. ~6 mass%. By containing a highly polar vinyl monomer in this range, the bondability of the adhesive is easily adjusted to an appropriate range.

Although 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, it is preferred to carry out polymerization by solution polymerization from the viewpoint of production cost and productivity. The average molecular weight of the acrylic copolymer is preferably from 300,000 to 1.5 million, and more preferably from 500,000 to 1,200,000.

(gel fraction of the adhesive)

In the (meth)acrylic adhesive to be used in the conductive adhesive sheet of the present invention, in order to increase the cohesive force, it is preferred to form a three-dimensional crosslinked structure. The index of formation of a crosslinked structure is a gel fraction represented by an insoluble matter after being immersed in toluene which is a good solvent of a (meth)acrylic binder for 24 hours. In this case, it is preferably 25 to 60% by mass, preferably 30 to 40% by mass. When the gel fraction is less than 25% by mass, the cohesive ability in the shear direction is insufficient, and when it exceeds 60% by mass, the peeling resistance is lowered.

The gel fraction was calculated by the following formula.

Gel fraction (% by mass) = {(the mass of the adhesive after immersion in toluene) / (the mass of the adhesive before immersing in toluene)} × 100

*Adhesive quality = (mass of conductive adhesive sheet) - (mass of substrate) - (mass of conductive particles)

Examples of the formation of the crosslinked structure include known crosslinking agents and the like, such as an isocyanate crosslinking agent, an epoxy crosslinking agent, a chelate crosslinking agent, and an aziridine crosslinking agent. The type of the crosslinking agent is preferably selected based on the functional group of the monomer component. The amount of the crosslinking agent to be added is not particularly limited as long as the gel fraction can be adjusted to 25 to 60% by mass.

(additive)

Further, in order to improve the adhesion of the conductive adhesive sheet, a tackifying resin may be added. The tackifier resin to be added to the particle-dispersed conductive adhesive used in the present invention may, for example, be a rosin-based resin, a terpene-based resin, an aliphatic (C5-based) or an aromatic (C9-based). Petroleum resin; styrene resin, phenol resin, xylene resin, methacrylic resin, and the like. Among them, a rosin-based resin is preferable, and a polymerized rosin-based resin is particularly preferable. The amount of the tackifier resin to be added is preferably 10 to 50% by mass based on 100 parts by mass of the (meth)acrylic copolymer.

Various additives may be added to the adhesive used in the conductive adhesive sheet of the present invention as needed. The above additives may, for example, be plasticizers, softeners, metal deactivators, antioxidants, pigments, dyes, etc., and may be suitably used as needed.

(Particle dispersed conductive adhesive composition)

A method of dispersing the above-mentioned adhesive substance in the above-mentioned conductive particles includes a method of dispersing an adhesive substance, a solvent, conductive particles, and an additive with a dispersing mixer. Examples of commercially available dispersing mixers include a dissolver manufactured by Inoue Co., a butterfly mixer, a BDM 2-axis mixer, and a planetary mixer. Among them, a dissolver or a butterfly blender which is capable of applying a moderate degree of shearing of the adhesive during agitation is preferred.

The viscosity of the particle-dispersed conductive adhesive composition is not particularly limited, but is preferably 100 to 10000 mPa. s, preferably 500~8000mPa. s, the best is 1000~3000mPa. s. When the viscosity is low, it is easy to cause sedimentation of the conductive particles with the passage of time. On the other hand, if the viscosity is too high, coating streaks are liable to occur at the time of film coating. The method of adjusting the viscosity includes adjustment of the content and type of the solvent, and adjustment of the type and molecular weight of the adhesive substance. The adjustment of the content and type of the solvent is preferred because it is simple.

The solid content of the particle-dispersed conductive adhesive composition is not particularly limited, but is preferably 10 to 70%, preferably 30 to 55%, and most preferably 43 to 50%.

(thickness of conductive adhesive layer)

The thickness of the adhesive layer of the conductive adhesive sheet is 6 to 12 μm. It is preferably 7 to 11 μm, and particularly preferably 8 to 10 μm. When it is in the above range, coating streaks are less likely to occur, and it is preferable that the conductivity is excellent.

(conductive substrate)

The conductive substrate used in the conductive adhesive sheet of the present invention may, for example, be a metal foil substrate or a graphite substrate. Examples of the material of the metal foil include gold, silver, copper, aluminum, nickel, iron, tin, or an alloy thereof. Among them, aluminum foil and copper foil are preferable in terms of workability and cost. The roughened electrolytic copper foil is more excellent in electrical conductivity. Examples of the commercially available electrolytic copper foil include CF-T9FZ-HS-9 (9 μm) and CF-T9FZ-HS-9 (9 μm) manufactured by Fukuda Metal Foil Powder Co., Ltd. Examples of the commercially available rolled copper foil include TCU-H-8-RT (8 μm) manufactured by Nippon Foil Co., Ltd., and TPC (6 μm) manufactured by JX Nippon Mining & Metal Co., Ltd.

The thickness of the conductive substrate is preferably 1 to 24 μm, preferably 3 to 16 μm, and most preferably 6 to 12 μm. When it is in the above range, it is preferable because it can be made thinner and has excellent workability.

(release liner)

In the conductive adhesive sheet of the present invention, a release liner may be laminated on the adhesive layer. The release liner is not particularly limited, and conventionally known materials such as kraft paper, glassine paper, wood-free paper, and the like; polyethylene, polypropylene (OPP, CPP), polyparaphenylene can be used. a resin film such as ethylene glycol formate; a laminated paper obtained by laminating the paper and the resin film; and a single side of a material obtained by subjecting the paper to a filling treatment using clay or polyethylene glycol or On both sides, a material obtained by a release treatment such as a lanthanoid resin is applied.

(Construction of conductive adhesive sheets)

The conductive adhesive sheet of the present invention is a conductive adhesive sheet having a conductive adhesive layer formed of a binder composition containing the conductive particles and a conductive substrate, and has a total thickness of 40 μm or less. Adhesive sheet. The conductive adhesive sheet of the present invention is required to be thinner in a portable electronic device or the like, and has an extremely thin structure having a total thickness of 40 μm or less, and the conductive adhesive layer is used as an adhesive layer. Good bonding, electrical conductivity and productivity can be achieved.

The total thickness of the conductive adhesive sheet is 40 μm or less, preferably 35 μm or less, preferably 30 μm or less, and particularly preferably 20 μm or less. By ensuring the bonding property and the electrical conductivity within the above range, the thickness of the adhesive sheet can be reduced, which contributes to the reduction in thickness of the portable electronic device. Further, the total thickness of the conductive adhesive sheet means the thickness of the conductive adhesive sheet itself which does not contain the release liner.

An example of a suitable structure of the conductive adhesive sheet of the present invention is shown in Figs. 1 and 2 . FIG. 1 is a single-sided adhesive sheet in which a conductive adhesive layer 2 is laminated on a conductive substrate 1. In addition, FIG. 2 is a double-sided adhesive sheet in which the conductive adhesive layer 2 is laminated on both surfaces of the conductive substrate 1. Among these structures, a structure in which a release liner is provided on the surface of the adhesive layer 2 can be preferably used.

[Examples]

Although the embodiments are specifically described below, the present invention is not limited to the embodiments.

(Preparation of acrylic adhesive composition)

[Preparation of Acrylic Adhesive Composition 1]

In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 75.0 parts by mass of n-butyl acrylate, 19.0 parts by mass of 2-ethylhexyl acrylate, 3.9 parts of vinyl acetate, 2.0 parts of acrylic acid, and acrylic acid were used. 0.1 parts by mass of 2-hydroxyethyl ester and 0.1 parts by mass of 2,2'-azobisisobutyronitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and after nitrogen substitution, polymerization was carried out at 80 ° C. An acrylic copolymer having a mass average molecular weight of 600,000 was obtained in an hour. 100 parts by mass of the solid component of the acrylic copolymer solution, mixed polymerized rosin pentaerythritol ester (manufactured by Arakawa Chemical Co., Ltd., Pencel D-135, softening point 135 ° C) 10 parts by mass, disproportionated rosin glyceride (Arakawa Chemical ( 10 parts by mass of Super Ester A-100, softened at 100 ° C), and the solid content of the resin was adjusted to 45% by mass with ethyl acetate to prepare an acrylic adhesive composition 1.

[Preparation of Acrylic Adhesive Composition 2]

96.0 parts by mass of n-butyl acrylate, 0.1 parts by mass of 2-hydroxyethyl acrylate, 3.9 parts by mass of acrylic acid, and 2 as a polymerization initiator in a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel. 0.1 parts by mass of 2'-azobisisobutyronitrile was dissolved in 100 parts by mass of ethyl acetate, and after nitrogen substitution, the mixture was polymerized at 80 ° C for 12 hours to obtain an acrylic copolymer having a mass average molecular weight of 600,000. 100 parts by mass of the solid component of the acrylic copolymer solution, mixed polymerized rosin pentaerythritol ester (manufactured by Arakawa Chemical Co., Ltd., Pencel D-135, softening point 135 ° C) 10 parts by mass, disproportionated rosin glyceride (Arakawa Chemical ( 10 parts by mass of Super Ester A-100, softening point 100 ° C), and the resin solid content concentration was adjusted to 45% by mass with ethyl acetate to prepare an acrylic adhesive composition 2.

(Production of particle-dispersed conductive adhesive composition)

[Production of Particle Dispersion Conductive Adhesive Composition A]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 22.5 parts by mass of nickel powder) smoothed by Inco Limited company NI123, and 2 parts by mass of a crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass) The solid content concentration was adjusted to 47% by mass with ethyl acetate, and the mixture was mixed for 10 minutes with a dispersing mixer to prepare a particle-dispersed conductive adhesive A.

[Production of Particle Dispersion Conductive Adhesive Composition B]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 13.5 parts by mass of nickel powder after smoothing of NI123 manufactured by Inco Limited, and 2 parts by mass of crosslinker Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass) The solid content concentration was adjusted to 47% by mass with ethyl acetate, and mixed with a dispersing mixer for 10 minutes to prepare a particle-dispersed conductive adhesive B.

[Production of Particle Dispersion Conductive Adhesive Composition C]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 31.5 parts by mass of nickel powder after smoothing of NI123 manufactured by Inco Limited, and 2 parts by mass of crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass) The solid content concentration was adjusted to 47% by mass with ethyl acetate, and the mixture was mixed for 10 minutes with a dispersing mixer to prepare a particle-dispersed conductive adhesive C.

[Preparation of Particle Dispersion Conductive Adhesive Composition D]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 22.5 parts by mass of nickel powder after smoothing of NI123 manufactured by Inco Limited, and 2 parts by mass of crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass) The concentration of the solid component was adjusted to 55 mass%, and the mixture was mixed for 10 minutes with a dispersing mixer to prepare a particle-dispersed conductive adhesive D.

[Preparation of Particle Dispersion Conductive Adhesive Composition E]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 22.5 parts by mass of nickel powder after smoothing of NI123 manufactured by Inco Limited, and 2 parts by mass of crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass) The solid content concentration was adjusted to 40% by mass with ethyl acetate, and mixed with a dispersing mixer for 10 minutes to prepare a particle-dispersed conductive adhesive E.

[Preparation of Particle Dispersion Conductive Adhesive Composition F]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), copper powder CU-HWQ 5 μm (d50: 4.3 μm, d85: 7.0 μm, tap density: Fukuda Metal Foil Powder Co., Ltd.) was mixed: 4.8 g/cm ³ , ultra-high pressure rotary water atomization ultrafine powder) 22.5 parts by mass, crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content 40% by mass) 2 parts by mass, using acetic acid The ester was adjusted to a solid concentration of 47% by mass, and mixed with a dispersing mixer for 10 minutes to prepare a particle-dispersed conductive adhesive F.

[Production of Particle Dispersion Conductive Adhesive Composition G]

To 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), copper powder CU-HWQ 10 μm (d50: 10.0 μm, d85: 13.0 μm, tap density: Fukuda Metal Foil Powder Co., Ltd.) was mixed: 4.7 g/cm ³ , ultra-high pressure rotary water atomization ultrafine powder) 22.5 parts by mass, crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content 40% by mass) 2 parts by mass, using acetic acid The ester was adjusted to a solid concentration of 47% by mass, and mixed with a dispersing mixer for 10 minutes to prepare a particle-dispersed conductive adhesive G.

[Preparation of Particle Dispersion Conductive Adhesive Composition H]

For 100 parts by mass of the acrylic adhesive composition 1 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 21.4 parts by mass of nickel powder after smoothing of NI123 manufactured by Inco Limited, 1.1 parts by mass of nickel powder NI123 (d50: 10.7 μm, d85: 25.0 μm) manufactured by Inco Limited, and Crosslinker Burnock NC40 2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass), adjusted to a solid concentration of 47% by mass with ethyl acetate, and mixed by a dispersing mixer for 10 minutes to obtain particle-dispersed conductivity Adhesive agent H. Further, the mixed metal powder of 21.4 parts by mass of nickel powder NI123J manufactured by Fukuda Metal Foil Co., Ltd. and 1.1 parts by mass of nickel powder NI123 manufactured by Inco Limited Co., Ltd. had a d50 of 7.0 μm and a d85 of 11.0 μm.

[Production of Particle Dispersion Conductive Adhesive Composition J]

For 100 parts by mass of the acrylic adhesive composition 2 (solid content: 45 parts by mass), nickel powder NI123J (d50: 6.3 μm, d85: 10.0 μm, tap density: 4.3 g) was mixed with Fukuda Metal Foil Powder Co., Ltd. /cm ³ , 22.5 parts by mass of nickel powder) smoothed by N1123 manufactured by Inco Limited, and 2 parts by mass of crosslinking agent Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd., solid content: 40% by mass) The solid content concentration was adjusted to 47% by mass with ethyl acetate, and mixed with a dispersing mixer for 10 minutes to prepare a particle-dispersed conductive adhesive J.

[Preparation of Particle Dispersion Conductive Adhesive Composition K]

100 parts by mass of the above acrylic adhesive composition 1 (solid component 45 mass (Part 2), 22.5 parts by mass of nickel powder NI123 (d50: 10.7, d85: 25.0 μm) manufactured by Inco Limited, 25 parts by mass of ethyl acetate, and Crosslinker Burnock NC40 (isocyanate crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd.) 2 parts by mass, the solid content concentration was adjusted to 47% by mass with ethyl acetate, and mixed with a dispersing mixer for 10 minutes to prepare a particle-dispersed conductive adhesive K.

[Preparation of Particle Dispersion Conductive Adhesive Composition L]

22.5 mass of copper powder CU-HWQ 1.5 μm (d50:1.7, d85: 3.0 μm) made of Fukuda Metal Foil Powder Co., Ltd. was mixed with 100 parts by mass of the above-mentioned acrylic adhesive composition 1 (solid content: 45 parts by mass). 2 parts by mass of ethyl acetate, 25 parts by mass of a cross-linking agent, Burnock NC40 (isocyanate-based crosslinking agent manufactured by Dainippon Ink Chemical Co., Ltd.), and the solid content concentration was adjusted to 47% by mass with ethyl acetate, and mixed with a dispersing mixer. The particle-dispersed conductive adhesive L was prepared in minutes.

(Example 1)

[Manufacture of conductive adhesive sheets]

The particle-dispersed conductive adhesive composition A was coated on a release film "PET38×1A3" manufactured by Nippa Co., Ltd. with a comma coater so that the thickness of the adhesive layer after drying became 10 μm. The mixture was dried in a drier at 80 ° C for 2 minutes, and then bonded to both sides of an electrolytic copper foil (CF-T9FZ-SV, manufactured by Fukuda Metal Foil Co., Ltd.) having a thickness of 9 μm at 40 ° C. The conductive adhesive sheet of Example 1 was prepared by curing for 48 hours.

(Example 2)

The conductive adhesive sheet of Example 2 was produced in the same manner as in Example 1 except that the thickness of the adhesive layer after drying was changed from 10 μm to 8 μm.

(Example 3)

The conductive adhesive sheet of Example 3 was produced in the same manner as in Example 1 except that the thickness of the adhesive layer after drying was changed from 10 μm to 12 μm.

(Example 4)

The conductive adhesive sheet of Example 4 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition B.

(Example 5)

The conductive adhesive sheet of Example 5 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition C.

(Example 6)

The particle-dispersed conductive adhesive composition A was coated on a peeling film "PET38×1A3” manufactured by Nippa Co., Ltd. at 80% by a coat wheel coater so that the thickness of the adhesive layer after drying became 10 μm. After drying in a desiccator at ° C for 2 minutes, it was bonded to a single side (roughened surface side) of an electrolytic copper foil (CF-T9FZ-SV, manufactured by Fukuda Metal Foil Powder Co., Ltd.) having a thickness of 9 μm. The conductive adhesive sheet of Example 6 was prepared by curing at 40 ° C for 48 hours.

(Example 7)

The conductive adhesive sheet of Example 7 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition D.

(Example 8)

The conductive adhesive sheet of Example 8 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition E.

(Example 9)

The conductive adhesive sheet of Example 9 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition F.

(Embodiment 10)

The conductive adhesive sheet of Example 10 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition G.

(Example 11)

The conductive adhesive sheet of Example 11 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition H.

(Embodiment 12)

From the use of the particle-dispersed conductive adhesive composition A to the use of the particle-dispersed conductive adhesive composition J, an electrolytic copper foil (CF-T9FZ-SV, manufactured by Fukuda Metal Foil Powder Co., Ltd.) having a thickness of 9 μm was used. The conductive adhesive sheet of Example 12 was produced in the same manner as in Example 1 except that a rolled copper foil (TCU-H-8-RT, manufactured by Nippon Foil Co., Ltd.) having a thickness of 8 μm was used.

(Comparative Example 1)

The conductive adhesive sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition K.

(Comparative Example 2)

A conductive adhesive sheet of Comparative Example 2 was produced in the same manner as in Example 1 except that the particle-dispersed conductive adhesive composition A was used instead of the particle-dispersed conductive adhesive composition L.

(Comparative Example 3)

A conductive adhesive sheet of Comparative Example 3 was produced in the same manner as in Comparative Example 1, except that the thickness of the adhesive layer after drying was changed from 10 μm to 30 μm.

(Comparative Example 4)

In the same manner as in Example 1, except that the thickness of the adhesive layer after drying was changed from 10 μm to 5 μm, the conductive adhesive sheet of Comparative Example 4 was attempted, but the coating streaks were severe and the sample was not prepared.

(Comparative Example 5)

A conductive adhesive sheet of Comparative Example 5 was produced in the same manner as in Example 1 except that the thickness of the adhesive layer after drying was changed from 10 μm to 14 μm.

(Evaluation)

With respect to the conductive adhesive sheets produced in Examples 1 to 12 and Comparative Examples 1 to 3, the thickness, conductivity, bonding strength, and productivity of the adhesive sheets were evaluated.

[thickness (bonding sheet)]

The thickness of the adhesive sheet was measured by a thickness gauge "TH-102" manufactured by Tester Sangyo Co., Ltd.

In the case of a double-sided adhesive sheet, the thickness of the adhesive sheet of 40 μm or less is regarded as acceptable. In the case of one side, 30 μm or less is regarded as acceptable.

[thickness (adhesive layer)]

A sample of a 25 μm PET (S25 manufactured by Unijco Co., Ltd.) was placed on the adhesive layer formed on the release film formed in the same manner as in the above Examples and Comparative Examples, and a thickness gauge was used by Tester Sangyo Co., Ltd. TH-102" measures the thickness of the sample, and subtracts the thickness of the release film and the liner PET to obtain the thickness of the adhesive layer.

[joining force]

A stainless steel plate (hereinafter referred to as a stainless steel plate) which has been subjected to hairline polishing treatment with a water-resistant abrasive paper of No. 360 under the condition of a pressback of 2.0 kg of the roll in a condition of 23 ° C and 60% RH. A 20 mm conductive adhesive sheet sample was placed at room temperature for 1 hour, and then subjected to a tensile tester (Tensilon RTA-100, manufactured by A&D Co., Ltd.) at a normal temperature at a tensile speed of 300 mm/min. The 180 degree peeling joint force was measured. Further, in the double-sided adhesive sheet, PET 25 μm (S25 manufactured by Uniji Co., Ltd.) was placed on the opposite side of the measurement surface and then measured.

[resistance]

One side of a 30 mm long to 30 mm wide adhesive sheet was attached to a brass electrode having a length of 25 mm and a width of 25 mm. A copper foil (thickness 35 μm) of 30 mm × 80 mm was attached to the other side of the test piece. A load with a surface pressure of 20 N was applied from the upper surface of the brass electrode, and a current of 10 μA was measured by a milliohm meter (NF circuit design) at 23 ° C and 50% RH at a brass electrode and a copper foil connection terminal. The resistance value at the time.

The case of 500 mΩ or less is regarded as pass.

[Productivity (coating streaks)]

The particle-dispersed conductive adhesive composition was applied at a speed of 20 m/min by a hook coater to evaluate streaks on the coated surface of the adhesive. Moreover, the temperature was 23 °C.

◎: No streaks on the coated surface of the adhesive were confirmed at all.

○: Although some streaks on the coated surface of the adhesive were confirmed, there was no practical problem (the difference in bonding force was less than 10%).

X: A lot of streaks were formed on the adhesive-coated surface, and a practical problem occurred (the difference in bonding force was 10% or more).

××: The coated surfaces of the adhesive were all streaked and could not be produced.

[productive (settling)]

The particle-dispersed conductive adhesive composition was allowed to stand in a glass bottle, and the sedimentation of the conductive particles was evaluated. The temperature was 23 °C.

◎: The sedimentation of the conductive particles did not occur even after standing for 2 hours.

○: The sedimentation of the conductive particles did not occur even after standing for 1 hour.

×: Settling occurs in less than 1 hour

[particle size]

Iridium using a laser diffraction type particle size distribution analyzer SALD-3000 manufactured by Shimadzu Corporation The alcohol was used as a dispersion medium to measure the particle diameter of the conductive particles.

[viscosity]

The viscosity of the particle-dispersed conductive adhesive composition was measured by a B-type viscometer manufactured by Toki Sangyo Co., Ltd. The measurement conditions were measured under the conditions of using a No. 3 rotor and 12 RPM.

【table 3】

As is clear from the above table, the adhesive sheets of Examples 1 to 12 of the present invention have excellent bonding properties and electrical conductivity even when they are thin, and are less likely to cause coating streaks and sedimentation, and are excellent in productivity. On the other hand, the adhesive sheets of Comparative Examples 1 to 5 did not have these conductivity and productivity.

1‧‧‧Electrically conductive substrate

2‧‧‧ Conductive adhesive layer

Claims (5)

A conductive thin adhesive sheet having a total thickness of 40 μm or less, comprising a conductive substrate and a conductive adhesive layer containing conductive particles, wherein the conductive particles have a particle diameter d50 of 4 to 12 μm, and D85 is 6~15μm, and the thickness of the adhesive layer is 6~12μm. The conductive thin adhesive sheet according to claim 1, wherein the content of the conductive particles in the conductive adhesive layer is 10 to 65% by mass. The conductive thin adhesive sheet according to claim 1 or 2, wherein the conductive particle has a particle diameter d50 of 50 to 150% of the thickness of the adhesive layer, and d85 is a thickness of the adhesive layer. 80~200%. The conductive thin adhesive sheet according to claim 1 or 2, wherein the conductive substrate is a metal foil. The conductive thin adhesive sheet according to claim 1 or 2, wherein the conductive adhesive layer is an adhesive layer composed of an acrylic adhesive composition containing an acrylic copolymer.