JP2014001297A - Conductive adhesive tape - Google Patents

Abstract

The present invention provides a conductive pressure-sensitive adhesive tape having excellent conductivity and excellent followability to an adherend and dimensional stability.
A conductive adhesive tape having a pressure-sensitive adhesive layer containing conductive particles and a conductive base material, wherein the conductive base material is a foam base having a 50% compression load of 40 kPa / cm ² or more. A conductive pressure-sensitive adhesive tape comprising a material, wherein the pressure-sensitive adhesive layer has a thickness of 15 to 70 μm, and the content of conductive particles in the pressure-sensitive adhesive layer is 10 to 45 mass%. The electroconductive adhesive tape whose said adhesive layer is an adhesive layer which consists of an acrylic adhesive composition containing an acrylic copolymer.
[Selection figure] None

Description

  The present invention relates to a conductive pressure-sensitive adhesive tape using a conductive foam base material and a pressure-sensitive adhesive layer containing conductive particles.

  Conductive adhesive tape is used for shielding unwanted electromagnetic waves radiated from electronic devices, shielding harmful spatial electromagnetic waves generated by other electronic devices, and grounding for antistatic charging because of its ease of handling. It has been.

  In recent years, with the downsizing and thinning of electronic devices such as portable electronic terminals, there has been a demand for a reduction in the number of components inside the electronic devices, and the conductive adhesive tape also has functions such as component fixing and cushioning materials. It is demanded.

As a conductive resin foam member having both functions of a conductive material and a buffer seal material, for example, a volume resistivity is 10 ¹⁰ Ω · cm or less and a repulsive load at 50% compression is 5 N / cm ² or less. A resin foam member having an adhesive layer is disclosed in a resin foam (see Patent Document 1). The resin foam member has both flexibility and conductivity, and can fill a minute clearance between high-density electronic components, and can follow a step at a step portion even when compressed, and is low. It is disclosed to have a volume resistivity.

  However, in recent years, there has been a demand for further reduction in thickness of portable electronic devices. Furthermore, the screen size of information displays in portable electronic devices such as smartphones, tablet computers, notebook computers, and game machines has been increased. Therefore, the conductive adhesive tape has further improved followability to the adherend when it is thinned, and dimensional stability when used as a part processed into a narrow shape. There is a need for improvement.

JP2010-229398

  The problem to be solved by the present invention is to provide a conductive pressure-sensitive adhesive tape having good conductivity and excellent followability to an adherend and dimensional stability.

In the present invention, a conductive pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing conductive particles and a conductive base material, wherein the conductive base material is a foam having a 50% compression load of 40 kPa / cm ² or more. A conductive adhesive tape comprising a base material, the pressure-sensitive adhesive layer has a thickness of 15 to 70 μm, and the content of conductive particles in the pressure-sensitive adhesive layer is 10 to 45% by mass, and has good conductivity. However, they found that excellent followability to the adherend and dimensional stability could be realized, and solved the above problems.

  The conductive pressure-sensitive adhesive tape of the present invention has excellent conductivity by using a conductive foam base material having a high compressive strength and a conductive pressure-sensitive adhesive layer in which the content and thickness of the conductive particles are adjusted. In addition to having the ability to follow the adherend, suitable dimensional stability can be realized. For this reason, the conductive pressure-sensitive adhesive tape of the present invention can be suitably applied to electronic devices such as portable electronic terminals whose thickness has been reduced and volume restrictions in the housing are severe. Furthermore, the conductive pressure-sensitive adhesive tape of the present invention can also be waterproof due to suitable followability.

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

[Conductive substrate]
As the conductive substrate used in the electroconductive pressure-sensitive adhesive tape of the present invention, 50% compressive load is 40 kPa / cm ² or more, preferably 40~120kPa / cm ^2, more preferably foam 40~100kPa / cm ² Use a substrate. By using a conductive base material having a 50% compressive load within the above range, it is possible to realize followability to the adherend and suitable dimensional stability. In particular, by making it within this range, it is easy to suppress the elongation of the pressure-sensitive adhesive tape when used to cut into a narrow shape, especially cut with a narrow width of 5 mm or less, and the processed cut surface even when cutting Can be easily cut into a straight line, and good dimensional stability can be secured.

The conductive substrate only needs to have conductivity in the area direction and the volume direction, and the conductivity is preferably 10 ⁸ Ω or less as measured by the measurement method described later. More preferably, it is 10 ⁶ Ω or less. By using the foam base material having conductivity in the above range, sufficient conductivity of the conductive adhesive tape can be obtained, and static electricity applied from the human body to the electronic device can be grounded.

  As the conductive substrate used in the present invention, a conductive substrate obtained by foaming a resin containing a conductive material can be preferably used. Examples of conductive materials include metal powder particles such as gold, silver, copper, nickel, and aluminum, conductive resins such as carbon and graphite, resins, solid glass beads, and materials having a metal coating on the surface of hollow glass beads. Can be used. The shape of the conductive material is not particularly limited, and spherical or acicular particles can be used. Among these, it is easy to handle and inexpensive carbon particles can be preferably used.

  As the resin used for the conductive substrate, for example, known resins such as polyethylene, polypropylene, polyurethane, and ethylene vinyl acetate can be used singly or by blending two or more kinds of resins. In particular, a polyethylene resin and a polyurethane resin are preferable. Examples of the commercially available conductive base material include Bola LVA manufactured by Sekisui Chemical Co., Ltd., FOLEC-EC manufactured by INOAC.

  The thickness of the conductive substrate is preferably 3 mm or less, more preferably 0.1 mm to 2 mm, and more preferably 0.1 mm to 1 mm. When the thickness of the conductive substrate is in the above range, it is particularly suitable for application to electronic devices such as portable electronic terminals where volume reduction in the housing is severe and volume restrictions in the housing are severe. In addition, it becomes easy to ensure suitable followability and dimensional stability.

  The cell structure of the conductive base material is preferably a closed cell structure because it is possible to effectively prevent water from being cut from the cut surface of the foam base material. The expansion ratio of the conductive substrate is preferably 3 to 15 times. More preferably, it is 5 to 10 times. By setting the expansion ratio of the conductive substrate within the above range, it is possible to achieve both conformability to the adherend and dimensional stability when used as a part processed into a narrow shape.

(Adhesive layer)
The pressure-sensitive adhesive layer used for the conductive pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive layer containing conductive particles, and the content of the conductive filler in the pressure-sensitive adhesive layer is 10 to 45% by mass, preferably 15 to 40%. It is a mass% adhesive layer. By making the addition amount of electroconductive particle into the said range, favorable followable | trackability to a to-be-adhered body and electroconductivity can be made compatible.

  When the thickness of the pressure-sensitive adhesive layer is 15 to 70 μm, preferably 20 to 50 μm, it is possible to achieve both good followability to the adherend and conductivity even when the thickness is reduced.

  The pressure-sensitive adhesive layer used for the conductive pressure-sensitive adhesive tape of the present invention is formed from a pressure-sensitive adhesive composition containing conductive particles. As an adhesive composition, the adhesive composition used for a normal adhesive tape can be used. Examples of the pressure-sensitive adhesive composition include 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, but (meth) acrylate alone or (meth) An acrylic pressure-sensitive adhesive composition containing, as a base polymer, an acrylic copolymer composed of a copolymer of acrylate and another monomer can be preferably used from the viewpoint of suitable followability and adhesiveness.

  As the acrylic copolymer used for the acrylic pressure-sensitive adhesive composition, an acrylic copolymer having a main monomer component of a (meth) acrylate monomer having 1 to 14 carbon atoms can be preferably used, and the acrylic copolymer having 1 to 14 carbon atoms can be used. Examples of (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and n-hexyl (meth) acrylate. , N-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. 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 average molecular weight of the acrylic copolymer is preferably 300,000 to 1,500,000, more preferably 500,000 to 1,200,000.

(Crosslinking agent)
In the pressure-sensitive adhesive composition used in the present invention, it is preferable to use a crosslinking agent in order to improve the cohesive strength and adhesive strength. As a crosslinking agent, well-known crosslinking agents, such as an isocyanate type crosslinking agent, an epoxy type crosslinking agent, a chelate type crosslinking agent, an aziridine type crosslinking agent, can be used, for example. The type of the crosslinking agent is preferably selected according to the functional group of the monomer component described above. As an addition amount of a crosslinking agent, it is preferable to adjust in the quantity from which the gel fraction of the obtained adhesive layer becomes 25-60 mass%, More preferably, it is 30-40 mass%.

The gel fraction is calculated by the following formula.
Gel fraction (% by mass) = {(Adhesive layer mass after immersion in toluene) / (Adhesive layer mass before immersion in toluene)} × 100
[Adhesive layer mass = (Mass of conductive adhesive tape) − (Mass of substrate) − (Mass of conductive particles)]

(Tackifying resin)
Furthermore, a tackifying resin may be added to improve the adhesive strength of the conductive adhesive tape. Tackifying resins to be added to the particle-dispersed conductive adhesive used in the present invention include rosin resins, terpene resins, aliphatic (C5) and aromatic (C9) petroleum resins, and styrene resins. Examples thereof include phenolic resins, 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% with respect to 100 mass parts of (meth) acrylic-type copolymers.

(Additive)
Various additives may be added to the pressure-sensitive adhesive used in the conductive pressure-sensitive adhesive tape 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.

(Conductive particles)
Well-known electroconductive particle can be used for the electroconductive particle used for the adhesive layer of the electroconductive adhesive tape of this invention. The conductive particles are made of metal powder particles such as gold, silver, copper, nickel, and aluminum, conductive resins such as carbon and graphite, resins, solid glass beads, those having a metal coating on the surface of hollow glass beads, etc. Can be used. In particular, nickel powder produced by the carbonyl method and copper powder produced by the electrolytic method can be suitably used.

  The conductive particles preferably have a 50% average volume particle diameter of 10 to 200 μm, more preferably 10 to 100 μm, still more preferably 15 to 50 μm, and more preferably 15 to 40 μm. Is preferred. When the 50% average volume particle diameter is in the above range, it is possible to achieve both good dispersibility in the pressure-sensitive adhesive, good coatability during production, and good conductivity and adhesiveness. The volume particle diameter of the conductive particles is a value measured with a laser diffraction particle size distribution analyzer SALD-3000 manufactured by Shimadzu Corporation using isopropanol as a dispersion medium.

The apparent density of the conductive particles is 1.5 g / cm ³ or less because the conductive particles are less likely to settle after the conductive particles are added to the pressure-sensitive adhesive, and it is easy to maintain a uniform dispersed state for several hours. Is preferred. More preferably, it is 1.0 g / cm ³ or less. The apparent density of the conductive particles is a value measured according to JISZ2504-2000 “Measuring Method of Apparent Density of Metal Powder”.

  Surface treatment may be performed for the purpose of improving the dispersibility of the conductive particles in the resin. Examples of surface treatment agents that improve dispersibility include titanate coupling agents and aluminate coupling agents.

  As the conductive particles used in the present invention, as the commercially available conductive particles, nickel powders # 255 and # 287 manufactured by the carbonyl method of Incori Ltd. were manufactured by an electrolytic method manufactured by Fukuda Metal Foil Powder Co., Ltd. Preferred examples include copper powder FCC-115 and CE-25.

(Method for producing conductive adhesive)
As a manufacturing method of the conductive adhesive composition of the present invention, after manufacturing an acrylic copolymer by the above-described manufacturing method, conductive particles, additives, and organic solvents such as toluene and ethyl acetate are used for viscosity adjustment. The method of disperse | distributing with a dispersion stirrer is mentioned. 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 a viscosity of an electroconductive adhesive composition, Preferably it is 5000-5000 mPa * s, Most preferably, it is 1000-3000 mPa * s. If the viscosity is low, the conductive particles tend to settle out over time. On the other hand, if the viscosity is too high, coating streaks are likely to occur during coating.

(Conductive adhesive tape)
The conductive pressure-sensitive adhesive tape of the present invention uses the above-mentioned pressure-sensitive adhesive layer containing conductive particles and a conductive base material, thereby having excellent conductivity and excellent followability to an adherend. And dimensional stability can be realized.

  The conductive pressure-sensitive adhesive tape of the present invention may be a single-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer only on one side of the conductive substrate, or a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the substrate. Moreover, in these structures, the structure by which the peeling liner was provided in the surface of the adhesive layer can be used preferably.

(Peeling sheet)
In the conductive adhesive tape of the present invention, a release sheet can be laminated on the adhesive layer. The release sheet 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.

(Manufacturing method of adhesive tape)
The adhesive tape is produced by applying the adhesive composition to the release sheet at a certain thickness with a roll coater or die coater, etc., drying the diluted solvent with a dryer, and after drying, on one side of the conductive foam substrate A single-sided adhesive tape can be manufactured by pasting. Furthermore, a double-sided pressure-sensitive adhesive tape can be produced by applying a pressure-sensitive adhesive composition to a release liner and bonding the dried composition to the other side of the substrate.

  The total thickness of the conductive adhesive tape of the present invention is preferably 3 mm or less, and preferably 1 mm to 0.1 mm. The conductive pressure-sensitive adhesive tape of the present invention can realize suitable conductivity, followability and dimensional stability even in the above-mentioned thin configuration that can suitably cope with the demand for thinning of portable electronic devices and the like. It can be suitably applied to component fixing applications and buffer material applications that require electromagnetic shielding and antistatic functions.

  The width of the conductive pressure-sensitive adhesive tape of the present invention may be appropriately adjusted depending on the mode of use, but is preferably 5 mm or less, more preferably 2 mm or less, still more preferably 0.5 to 1.5 mm, and particularly preferably 0. 5 to 1.2 mm. The conductive pressure-sensitive adhesive tape of the present invention can be suitably applied to thin and small portable electronic devices because it can suitably realize excellent conductivity, followability and dimensional stability even in such an extremely narrow usage mode. it can.

  Since the adhesive tape of the present invention has such excellent characteristics, an electronic notebook, mobile phone, PHS, digital camera, music player, TV, notebook computer, smartphone, tablet computer, game machine, electronic book, etc. It can be suitably used for electromagnetic wave shielding use, antistatic use, etc. of portable electronic devices.

  The following examples are specifically described, but the present invention is not limited to these examples.

Example 1
[Adjustment of acrylic pressure-sensitive adhesive composition]
In a reaction vessel equipped with a condenser, a stirrer, a thermometer, and a dropping funnel, 96.0 parts by mass of n-butyl acrylate, 0.1 part by mass of 2-hydroxyethyl acrylate, 3.9 parts by mass of acrylic acid and a polymerization initiator 0.12 parts by mass of 2,2′-azobisisobutylnitrile was dissolved in 100 parts by mass of ethyl acetate, and after nitrogen substitution, polymerization was carried out at 80 ° C. for 12 hours. For 100 parts by mass of the solid content of this adhesive solution, 10 parts by mass of polymerized rosin pentaerythritol ester (Arakawa Chemical Co., Ltd., Pencel D-135, softening point 135 ° C.), disproportionated rosin glycerin ester (Arakawa Chemical ( Co., Ltd., Superester A-100, softening point 100 ° C.) 10 parts by mass were mixed, and the resin solid content concentration was adjusted to 45% by mass with ethyl acetate to prepare an acrylic pressure-sensitive adhesive composition.

[Preparation of conductive adhesive composition]
With respect to 100 parts by mass of the acrylic pressure-sensitive adhesive composition (solid content: 45 parts by mass), # 255 (nickel powder manufactured by Incori Ltd., 50% average volume particle diameter: 21.5 μm, apparent density as conductive particles) 0.6 g / cm ³ ) 9.0 parts by mass, 10 parts by mass of ethyl acetate, 0.85 parts by mass of resin cross-linking agent Coronate L (an isocyanate-based cross-linking agent manufactured by Nippon Polyurethane Industry Co., Ltd.) are added, and a dispersion stirrer And mixed for 10 minutes to prepare a conductive adhesive.

[Creation of adhesive tape]
The pressure-sensitive adhesive composition was coated on a release paper having a thickness of 130 μm so that the thickness of the pressure-sensitive adhesive layer after drying was 30 μm, dried in an oven at 80 ° C. for 2 minutes, and then having a thickness of 450 μm. After bonding to both sides of conductive foam base material LVA70045 (conductive polyethylene foam manufactured by Sekisui Chemical Co., Ltd., 50% compression load 45 kPa / cm ² , expansion ratio 7 times, independent foam structure), at 40 ° C. After curing for 48 hours, an adhesive tape was prepared.

(Example 2)
The conductive adhesive # 255 was used in the same manner as in Example 1 except that the amount of the conductive particle # 255 was changed to 18.0 parts by mass with respect to 100 parts by mass of the acrylic adhesive composition (solid content 45 parts by mass). Created a tape.

(Example 3)
The conductive adhesive # 255 was used in the same manner as in Example 1 except that the amount of the conductive particle # 255 was changed to 27.0 parts by mass with respect to 100 parts by mass of the acrylic adhesive composition (solid content 45 parts by mass). Created a tape.

Example 4
The conductive foam substrate was changed to a conductive foam FOLEC-EC with a thickness of 500 μm (polyurethane foam made by Inoac Corporation, 50% compression load 80 kPa / cm ² , expansion ratio 9 times, independent foam structure). A conductive adhesive tape was prepared in the same manner as in Example 2 except that.

(Example 5)
A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 2 except that the thickness of the pressure-sensitive adhesive layer after drying was changed to 20 μm.

(Example 6)
A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer after drying described in Example 1 was changed to 50 μm.

(Example 7)
With respect to 100 parts by mass (45 parts by mass of solid content) of the acrylic pressure-sensitive adhesive composition described in Example 1, copper powder of FCC-115A (Fukuda Metal Foil Powder Co., Ltd.), 50% average volume particle diameter: 22. A conductive adhesive tape was prepared in the same manner as in Example 2, except that 3 μm and the apparent density: 0.9 g / cm ³ ) were changed to 18.0 parts by mass.

(Comparative Example 1)
A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 2, except that the thickness of the pressure-sensitive adhesive layer after drying described in Example 1 was changed to 10 μm.

(Comparative Example 2)
A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 2 except that the thickness of the pressure-sensitive adhesive layer after drying described in Example 1 was changed to 100 μm.

(Comparative Example 3)
The conductive adhesive # 255 was used in the same manner as in Example 2 except that the amount of the conductive particle # 255 was changed to 4.5 parts by mass with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive composition (solid content 45 parts by mass). Created a tape.

(Comparative Example 4)
A conductive pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the amount of the conductive particles # 255 was changed to 45.0 parts by weight with respect to 100 parts by weight of the acrylic pressure-sensitive adhesive composition.

(Comparative Example 5)
Instead of the conductive particles # 255, # 123 (Nickel powder manufactured by Incori Ltd., 50% average particle size: 10.8 μm, apparent density: 2.4 g / cm ³ ) was used as the conductive particle. A conductive pressure-sensitive adhesive tape was produced in the same manner as in Example 2 except that 18.0 parts by mass was used with respect to 100 parts by mass of the composition.

(Comparative Example 6)
Conductive foam base material, conductive foam Softlon Z LD-32CN with a thickness of 900 μm (Sekisui Chemical Co., Ltd. polyethylene foam, 50% compression load 17 kPa / cm ² , expansion ratio 30 times, independent foam structure) A conductive adhesive tape was prepared in the same manner as in Example 2 except that the change was made to.

  About the adhesive tape obtained by the said Example and comparative example, the adhesive force, electroconductivity, followable | trackability, and dimensional stability were evaluated by the method shown below.

[Adhesive strength]
A PET film (S-25, manufactured by Unitika Co., Ltd.) having a thickness of 25 μm is bonded to one surface of a stainless steel plate (hereinafter referred to as a stainless steel plate) that has been subjected to hairline polishing treatment with No. 360 water-resistant abrasive paper, and cut to a width of 20 mm. The pressure-sensitive adhesive tape was affixed and reciprocated with a 2.0 kg roller in an environment of 23 ° C. and 50% RH, left at room temperature for 1 hour, and then pulled by a tensile tester (Tensilon RTG-1210, manufactured by A & D). The 180 ° peel adhesive strength was measured at a normal temperature and a tensile speed of 300 mm / min.

[Conductivity (resistance value)]
One surface of a 30 mm wide × 30 mm wide adhesive tape is attached to a 25 mm × 25 mm brass electrode. A copper foil (thickness: 35 μm) of 30 mm × 80 mm is attached to the other surface of the test piece. A terminal is connected to the brass electrode and copper foil while applying a load of 20N from the brass electrode, and a resistance value measuring machine (Lorestar GP, manufactured by Mitsubishi Chemical Corporation) in an environment of 23 ° C and 50% RH. The resistance value was measured at. The case of 10 ⁵ Ω or less was regarded as acceptable.
The resistance value of the conductive foam substrate used in the above examples and comparative examples was also measured by the same method.

[Followability]
1) By the method described in the dimensional stability test, the double-sided pressure-sensitive adhesive tape was processed into a frame shape having an outer diameter of 64 mm × 43 mm and a width of 2 mm. Samples rated “x” in the dimensional stability test were not subjected to the followability test.
2) Using the double-sided pressure-sensitive adhesive tape obtained above, a frame-shaped sample having an outer diameter of 64 mm × 43 mm and a width of 2 mm was prepared and attached to an acrylic plate having a thickness of 2 mm and an outer diameter of 65 mm × 45 mm (FIG. 1).
3) Next, a single-sided adhesive tape 2 for forming a polyethylene terephthalate substrate having a thickness of 30 μm, a width of 5 mm, and a length of 45 mm is provided in the center of another acrylic sheet having a thickness of 2 mm and an outer shape of 65 mm × 45 mm. The sheets are attached in parallel in the vertical direction at 1 cm intervals to create an acrylic plate with a step (FIG. 8).
4) After placing an acrylic plate with a double-sided adhesive tape on the adhesive tape portion of the stepped acrylic plate at 23 ° C., pressurize once with a 2 kg roller from the end (FIG. 9).
5) Visually evaluate the follow-up state of the double-sided pressure-sensitive adhesive tape in the vicinity of the step from the stepped acrylic plate side.
○: The double-sided adhesive tape is in close contact with the stepped acrylic plate.
X: Double-sided adhesive tape does not adhere to the stepped acrylic plate.

[Dimensional stability]
Using a sheet cutter (Color CAMM PRO PC-600, manufactured by Roland), it was evaluated whether the double-sided pressure-sensitive adhesive tape obtained above could be processed into a frame shape having an outer diameter of 64 mm × 43 mm and a width of 2 mm.
○: The double-sided adhesive tape can be processed into a predetermined shape.
X: The double-sided pressure-sensitive adhesive tape cannot be pulled into a predetermined shape. Alternatively, the processed tape is non-uniform in the width and thickness direction.

  As the said Example, the electroconductive adhesive tape of this invention had suitable electroconductivity, followable | trackability, and dimensional stability. On the other hand, the pressure-sensitive adhesive tape of the comparative example cannot have suitable conductivity, followability and dimensional stability.

Claims (3)

A conductive pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing conductive particles and a conductive base material,
The conductive substrate is a foam substrate having a 50% compression load of 40 kPa / cm ² or more,
The pressure-sensitive adhesive layer has a thickness of 15 to 70 μm,
Content of electroconductive particle in the said adhesive layer is 10-45 mass%, The electroconductive adhesive tape characterized by the above-mentioned. The conductive pressure-sensitive adhesive tape according to claim 1, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer. The conductive adhesive tape according to claim 1, wherein the conductive particles are at least one selected from nickel and copper.