JP2005277145A - Adhesive sheet for shielding electromagnetic wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive sheet for shielding an electromagnetic wave which is excellent in shield characteristics of the electromagnetic wave and in adhesiveness. <P>SOLUTION: The adhesive sheet for shielding the electromagnetic wave comprises a conductive base material including conductive metal layers on both sides of a resin film, and an adhesive layer which is laminated at least on one surface of the conductive metal layers, wherein the adhesive layer is composed of a conductive adhesive agent including an adhesive material and a nickel powder produced by a carbonyl method, the conductive adhesive agent includes the nickel powder of 50 to 100 mass parts to the adhesive material of 100 mass parts, and the nickel powder includes (1) a particle (A) in which a volume particle diameter of 50% is 50% to 80% of a thickness of the adhesive layer, (2) a particle (B) in which the volume particle diameter of 50% is less 50% of the thickness of the adhesive layer, and (3) a mass ratio (A):(B) of the particle (A) and the particle (B) is 40:60 to 80:20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electromagnetic wave shielding pressure-sensitive adhesive sheet using a conductive pressure-sensitive adhesive. Specifically, it is used for shielding unnecessary electromagnetic waves radiated from digital devices and cables of electric and electronic devices, shielding harmful spatial electromagnetic waves generated from other electric and electronic devices, and grounding for preventing static electricity. It is related with the adhesive sheet for electromagnetic wave shields excellent in the electroconductivity and electromagnetic wave shield characteristic which are made.

  Conductive adhesive sheets are used for grounding to prevent static electricity as well as for grounding to prevent static electricity, as well as for digital devices for electrical and electronic equipment, for shielding unwanted electromagnetic waves radiated from cables, and from other electrical and electronic equipment. It is used for shielding harmful electromagnetic waves. In digital devices such as mobile phones that aim for miniaturization and weight reduction, there is a demand for a conductive adhesive sheet having excellent electromagnetic shielding characteristics.

  As the conductive adhesive sheet, a particle-dispersed conductive adhesive in which conductive particles such as metal particles are dispersed in an adhesive resin, and a conductive base material provided with a conductive layer on a metal foil or resin film, A combined conductive adhesive sheet is known. As the conductive particles, powder made of copper, silver, nickel, aluminum, carbon, or the like is used. As the adhesive resin, acrylic resin, rubber, silicon resin, or the like is used.

  To obtain conductivity in the sheet thickness direction in a conductive adhesive sheet using a particle-dispersed conductive adhesive, the conductive particles are exposed from the surface of the adhesive layer and are in contact with the conductive substrate. Is known to be necessary (see, for example, Patent Document 1 and Patent Document 2). In these prior arts, it is described that a conductive pressure-sensitive adhesive sheet having excellent conductivity and adhesiveness can be obtained when the particle diameter of the conductive particles is equal to, or equal to or greater than twice the thickness of the pressure-sensitive adhesive. . However, there is a trade-off relationship between conductivity and adhesiveness, and the adhesiveness tends to decrease when conductive particles are exposed on the surface of the pressure-sensitive adhesive layer. Therefore, the conductive pressure-sensitive adhesive sheet disclosed in the prior art is The adhesiveness was inferior even though the conductivity was excellent.

  In particular, since the conductive particles have a particle size distribution, if a large amount of conductive particles having a particle size equal to or greater than the thickness of the pressure-sensitive adhesive is added, the conductive particles having an excessively large particle size that adversely affects the adhesiveness. Since the ratio also increases, the decrease in adhesive strength becomes significant. In order to prevent this, Patent Document 2 describes that the conductive particles are screened and the conductive particles having a specific particle size range are selected, but using such a process increases the number of manufacturing steps. In addition, conductive particles that are out of the intended particle size range are discarded, which is disadvantageous in terms of manufacturing cost.

  In addition, regarding the electromagnetic wave shielding effect in the conductive adhesive sheet disclosed in the prior art, this has not been studied, and even if the electromagnetic wave shielding characteristics are actually measured, the electromagnetic wave shielding adhesive sheet It was not a practical level.

  An example in which a polyalkyl silicone pressure-sensitive adhesive is used as the pressure-sensitive adhesive of the conductive pressure-sensitive adhesive sheet and nickel powder is used as the conductive particles has also been reported (see, for example, Patent Document 3). However, even in this technique, a conductive pressure-sensitive adhesive sheet having both excellent conductivity and adhesiveness is not disclosed. Furthermore, the electromagnetic shielding effect was not practical.

  By the way, it is known that the electromagnetic wave shielding characteristics of the conductive adhesive sheet depend on the material and thickness of the conductive base material, which is a shield material, and the conductivity of the adhesive (see Non-Patent Document 1). Generally, the thicker the conductive substrate, the higher the electromagnetic wave shielding effect. However, when the conductive adhesive sheet is used as an electromagnetic wave shielding adhesive sheet, there is a limit to the thickness of the conductive substrate that can be used due to the problem of the stiffness of the conductive substrate and the weight of the tape. For example, a thickness of 10 to 80 μm is usually used for a copper foil and a thickness of 20 to 100 μm is used for an aluminum foil. Moreover, when using an electroconductive adhesive sheet as an electromagnetic wave shielding material, in order to fully draw out the shielding effect of an electroconductive base material, it is necessary to electrically connect with the metal housing which is a to-be-adhered body. Therefore, high conductivity is required for the pressure-sensitive adhesive that joins the conductive substrate and the metal casing.

  Non-Patent Document 1 describes that a conductive pressure-sensitive adhesive sheet that imparts conductivity when an embossed metal foil penetrates through the pressure-sensitive adhesive layer instead of conductive particles has excellent electromagnetic shielding properties. Has been.

  However, since the pressure-sensitive adhesive layer is elastically restored after the conductive sheet is attached, there is a problem that the conductivity and electromagnetic wave shielding characteristics deteriorate with time. If the adhesive layer is designed so that it is difficult to recover elastically, the cohesive force will also be insufficient. It was necessary to fix.

  On the other hand, when the total thickness is the same as a characteristic of the electromagnetic wave shielding characteristics, if the conductive base material layer, which is a shielding material, is multilayered, the electromagnetic wave having a frequency of 1 MHz or more is shielded from the single layer due to the effect of multiple reflection. It is described that the effect is high (see Non-Patent Document 2). However, the non-patent document 1 and the non-patent document 2 do not disclose an electromagnetic wave shielding pressure-sensitive adhesive sheet having good electromagnetic wave shielding characteristics and excellent adhesiveness.

Japanese Patent Publication No.46-15240 Japanese Patent Laid-Open No. 5-222346 JP 2001-146578 A (Example 3) Industrial Materials, vol. 3 52-58 (1994, March issue) Industrial Materials, vol. 3 22-30 (1994, March issue)

  An object of the present invention is to provide an electromagnetic wave shielding pressure-sensitive adhesive sheet that is excellent in electromagnetic wave shielding properties and has excellent adhesiveness in order to solve the above-described drawbacks of the prior art.

  As a result of intensive studies, the present inventors have used a particle-dispersed conductive adhesive using two or more types of conductive particles having a specific particle size, and a conductive substrate having a specific structure. The present inventors have found that an electromagnetic wave shielding pressure-sensitive adhesive sheet excellent in adhesiveness and electromagnetic wave shielding characteristics can be obtained, and have completed the present invention.

That is, the present invention relates to an electromagnetic wave shielding pressure-sensitive adhesive sheet comprising a conductive base material provided with a conductive metal layer on both surfaces of a resin film, and a pressure-sensitive adhesive layer laminated on at least one surface of the conductive metal layer. The adhesive layer is made of an adhesive material and a conductive adhesive containing nickel powder produced by a carbonyl method, and the conductive adhesive contains 50 nickel powders per 100 parts by mass of the adhesive material. ~ 100 parts by mass, the nickel powder,
(1) particles (A) having a 50% volume particle diameter of 50% to 80% of the thickness of the adhesive layer;
(2) containing particles (B) having a 50% volume particle diameter of less than 50% of the thickness of the adhesive layer, and (3) mass ratio of particles (A) to particles (B) (A): (B ) 40: 60-80: 20
The present invention provides a pressure-sensitive adhesive sheet for electromagnetic wave shielding.

  Furthermore, this invention provides the electronic device characterized by sticking said adhesive sheet for electromagnetic wave shields.

  Since the particles (A) used in the present invention have a 50% volume particle diameter of 50% to 80% of the thickness of the adhesive layer, the particles (A) are exposed more than necessary from the surface of the adhesive layer, There are very few particles having an excessively large particle size that significantly deteriorates the adhesiveness of the pressure-sensitive adhesive sheet for electromagnetic wave shielding of the present invention. On the other hand, since an appropriate amount of particles (B) having a 50% volume particle diameter of less than 50% of the thickness of the adhesive layer is contained, a conduction path through the particles (B) is formed inside the adhesive layer. Since it is added to the conduction path formed by (A), the pressure-sensitive adhesive sheet for electromagnetic wave shielding of the present invention is excellent in conductivity, and thus becomes a pressure-sensitive adhesive sheet excellent in electromagnetic wave shielding characteristics.

  As mentioned above, according to this invention, the adhesive sheet for electromagnetic wave shields which is very excellent in adhesiveness and electromagnetic wave shield characteristics can be obtained. The electromagnetic wave shielding adhesive sheet of the present invention is used for shielding unwanted electromagnetic waves radiated from digital devices, cables, etc. of electric and electronic devices, shielding harmful spatial electromagnetic waves generated from other electric and electronic devices, and electrostatic charging. This is useful for grounding prevention.

  Below, the adhesive sheet for electromagnetic wave shielding 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 the conductive adhesive is provided on the conductive metal layer of the conductive substrate. For example, each sheet, a roll, or a thin plate All product forms such as strips and strips (tapes) are included.

(Configuration of electromagnetic wave shielding adhesive sheet)
An embodiment of the pressure-sensitive adhesive sheet for electromagnetic wave shielding of the present invention will be described with reference to the drawings.

  The basic structure of the pressure-sensitive adhesive sheet for electromagnetic wave shielding of the present invention is shown in FIG. In FIG. 1, a conductive base material 9 is formed by laminating a conductive metal layer 2 on both sides of a resin film 1, and an adhesive layer 3 made of a conductive adhesive is further formed on one conductive metal layer 2. It is an example of embodiment of the adhesive sheet for electromagnetic wave shielding laminated | stacked. In FIG. 2, a conductive base material 10 is formed by laminating a conductive metal layer composed of a conductive treatment layer 2a and a plating layer 2b formed thereon on both sides of a resin film 1, and further, It is an example of embodiment of the adhesive sheet for electromagnetic wave shield which laminated | stacked the adhesion layer 3 which consists of a conductive adhesive on a conductive metal layer.

  FIG. 3 shows a conductive substrate 11 by laminating a conductive metal layer composed of a conductive treatment layer 2a and a plating layer 2b formed thereon on both sides of a resin film 1 having a conductive through hole 4. 1 is an example of an embodiment of an adhesive sheet for electromagnetic wave shielding, in which an adhesive layer 3 made of a conductive adhesive is laminated on one conductive metal layer 2. The conductive through hole 4 is formed on both sides of the resin film by introducing a conductive material for forming the conductive treatment layer 2a and a metal for forming the plating layer 2b into a through hole formed in the resin film described later. Thus, a conductive passage for electrically connecting the conductive metal layers is formed.

  The electromagnetic wave shielding pressure-sensitive adhesive sheet having the structure of FIGS. 1 to 3 is preferably produced in a roll-shaped (rolled) embodiment. In that case, it is preferable that the surface of the conductive metal layer 2 or the plating layer 2a on which the adhesive layer 3 is not laminated is subjected to a release treatment with a silicon-type resin or the like. Moreover, it can also be set as the form which laminated | stacked the peeling sheet 5 on the electroconductive adhesive layer 3 like FIGS. In such a form, in addition to the embodiment of each leaf, it is not necessary to perform a release treatment on the surface of the conductive metal layer 2 or the plating layer 2a of the electromagnetic wave shielding pressure-sensitive adhesive sheet. It is preferable when electrical connection is required on the surface of the adhesive sheet.

  7-9 showed the form which laminated | stacked the adhesion layer 3 which consists of an electroconductive adhesive on both surfaces of the electroconductive base materials 9-11, and laminated | stacked the peeling sheet 5 on the one electroconductive adhesive layer 3. FIG. Is. 10-12 showed the form which laminated | stacked the adhesion layer 3 which consists of an electroconductive adhesive on both surfaces of the electroconductive base materials 9-11, and laminated | stacked the peeling sheet 5 on both the electroconductive adhesive layers 3. FIG. Is. The electromagnetic wave shielding pressure-sensitive adhesive sheet of the present invention can also have a form in which one or more conductive pressure-sensitive adhesive layers are laminated as described above.

(Resin film)
Examples of the material of the resin film used for the conductive substrate include conventionally known materials such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene, polypropylene, polyamide, polyimide, polyvinyl chloride, and polystyrene. It is not limited. Further, the presence or absence of the stretching treatment of the resin film and the degree of crystallization are not particularly limited, but it is preferable to use a biaxially stretched film when mechanical strength and dimensional stability are generally required, When high heat resistance is required, polyamide, polyimide, polyethylene naphthalate and the like are preferable. Moreover, when adhesiveness with an electroconductive process layer is requested | required, it is preferable to use an unstretched film and a film with a low crystallinity degree.

  The resin film having a thickness of 2 to 100 μm that has been conventionally used can be used, but preferably 2 to 50 μm, more preferably 2 to 20 μm. When the thickness is less than 2 μm, the productivity of the conductive base material is lowered.

  Furthermore, the thickness of the resin film in the case of providing a through hole is preferably 2 to 40 μm, more preferably 4 to 25 μm, and further preferably 4 to 16 μm. If it exceeds 40 μm, the through-holes must be enlarged in order to obtain conductivity, and the electromagnetic shielding characteristics are deteriorated.

The size of the through hole is not particularly defined, but is preferably 200 μm ² or less, more preferably 0.2 to ²⁰ μm ^{2 in} view of electromagnetic wave shielding characteristics. When the size of the through hole is less than 0.2 μm ² , it is not preferable because the conductivity of the through hole is difficult to ensure depending on the thickness of the resin film. The number of the through holes is not particularly limited if the good conductivity can be secured, the total area of the through-holes in the 10000 ² is 100～3000Myuemu ^2, preferably 500~2000μm ^2. The total area of the through-holes depends on the size of the through-holes, but if it exceeds 3000 μm ² , it is not preferable because the resin film strength is lowered and the electromagnetic shielding properties of the conductive substrate are lowered. Although the shape of the through hole is not particularly defined, a circular shape or an oval shape is preferable in terms of the strength of the conductive base material and the ease of forming the through hole. Formation of the through hole in the resin film can be performed by means such as pressing a mold provided with a needle like a heated sword mountain against the resin film, but is not particularly limited.

(Conductive substrate)
As the conductive base material used for the electromagnetic wave shielding pressure-sensitive adhesive sheet of the present invention, one having a conductive metal layer on both sides of the resin film is used. The thickness of the conductive metal layer is preferably 1 μm or more on one side, and preferably 4 μm or more. If the thickness is less than 1 μm, electromagnetic wave shielding characteristics cannot be expected. Further, the upper limit of the thickness is not particularly limited, but there is a problem that the stiffness of the conductive substrate is too strong, so copper is preferably 40 μm or less, nickel is 25 μm or less, iron foil is 25 μm or less, and aluminum is preferably 80 μm or less. .

As a method of providing a conductive metal layer on both sides of a resin film, a method of laminating a metal foil such as copper foil, aluminum foil, nickel foil, or iron foil, or a plating layer after providing a conductive treatment layer on the surface of the resin film The method of forming is mentioned. When providing electroconductivity in the thickness direction of an electroconductive base material, the method of forming a plating layer after providing a conductive treatment layer in the resin film which has a through-hole is preferable.

The conductive treatment layer is provided for forming a plating layer on the resin film. Conductive treatment layer
It can be formed of a conductive coating film formed of a conductive paint, a metal thin film formed of metal deposition or sputtering, or the like. The conductive coating film can be formed by blending a conductive material composed of one or more of silver, copper, aluminum, nickel and conductive carbon into the resin. Preferred are copper, nickel, and conductive carbon. The metal thin film can be formed by vapor deposition or sputtering of one or more metals selected from silver, copper, nickel, aluminum, and tin. Preferred are copper and nickel. The conductive treatment layer may be formed by using a metal thin film and a conductive coating film as needed. The resistance value of the conductive treatment layer of the present invention is preferably 1.3 Ω / cm or less because of ease of plating treatment.

  The resistance value in the surface direction of the plating layer is preferably 40 mΩ / cm or less, more preferably 10 μΩ / cm or less. The metal of the plating layer is preferably copper or nickel. The thickness of the plating layer is preferably 1 μm or more and preferably 4 μm or more on one side. If the thickness is less than 1 μm, the effect of electromagnetic wave shielding characteristics cannot be expected. Further, the upper limit of the thickness is not particularly limited, but there are problems such as a decrease in productivity of the plating treatment and excessive strength of the conductive base material. Therefore, it is preferable that copper is 25 μm or less and nickel is 20 μm or less.

(Adhesive composition)
As an adhesive substance used for the electromagnetic wave shielding adhesive sheet of the present invention, known acrylic, rubber-based, and silicon-based adhesives can be used, among which (meth) acrylic adhesives are used. It is preferable. In particular, as a (meth) acrylic pressure-sensitive adhesive, a (meth) acrylic copolymer containing an acrylate ester having an alkyl group having 2 to 14 carbon atoms as a monomer component is suitable for weather resistance and heat resistance. To preferred. Examples of such monomers include acrylic copolymers such as n-butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and isononyl acrylate, and methacrylic copolymers such as 2-ethylhexyl methacrylate. .

Furthermore, as a monomer component, (meth) acrylic acid ester having a polar group such as a hydroxyl group, a carboxyl group, or an amino group in the side chain and other vinyl monomers are added in a range of 0.01 to 15% by mass. Is preferred. Preferably, it is preferable in terms of adjustment of the gel fraction to appropriately define a monomer component having a functional group that reacts with it to form a crosslinking point in accordance with a crosslinking agent described later. In the case of an isocyanate-based crosslinking agent, it is preferable to add a monomer component having a hydroxyl group in the side chain in the range of 0.01 to 2.0% by mass. In the case of an epoxy-based crosslinking agent or a chelate-based crosslinking agent, it is preferable to add a monomer component containing a carboxyl group in the range of 0.1 to 12% by mass.
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.

(Gel fraction of adhesive)
The (meth) acrylic pressure-sensitive adhesive used for the electromagnetic wave shielding pressure-sensitive adhesive sheet of the present invention preferably forms a three-dimensional cross-linked structure in order to improve cohesion. 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 25-60 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 60% 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 electromagnetic wave shielding adhesive sheet)-(Substrate mass)-(Mass of conductive particles)

  Examples of the formation of the crosslinked structure include known crosslinking agents such as isocyanate crosslinking agents, epoxy crosslinking agents, chelate crosslinking agents, and aziridine crosslinking agents. The type of the crosslinking agent is preferably selected according to the functional group of the monomer component described above. The addition amount of the crosslinking agent is not particularly defined as long as the gel fraction can be adjusted to 25 to 60% by mass.

(Additive)
Furthermore, in order to improve the adhesive strength of the electromagnetic wave shielding adhesive sheet, a tackifier resin may be added. Tackifying resins to be added to the particle-dispersed conductive adhesive used in the present invention are rosin resins, terpene resins, aliphatic (C5) and aromatic (C9) petroleum resins, and styrene resins. Examples thereof include phenolic resins, xylene resins, and methacrylic resins. 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.

  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)
The conductive particles used for the electromagnetic wave shielding pressure-sensitive adhesive sheet of the present invention are nickel powder produced by a carbonyl method, particles (A) having a 50% volume particle diameter of 50% to 80% of the pressure-sensitive adhesive layer thickness, and the pressure-sensitive adhesive layer. Particles (B) having a thickness of less than 50% are used in combination. Thus, by blending a specific nickel powder having a specific 50% volume particle diameter to adjust the particle size distribution of the conductive particles (for example, a particle size distribution having two or more peaks), High conductivity equivalent to that of conductive particles having a conventional single distribution can be realized, and sufficient adhesiveness that cannot be obtained by the conventional technology can be obtained. When the 50% volume particle diameter of the particles (A) exceeds 80% of the thickness of the pressure-sensitive adhesive layer, the adhesiveness is lowered.

The apparent density of the particles (A) having a 50% volume particle diameter of 50% to 80% of the thickness of the adhesive layer is 1.5 g / cm ³ or less, preferably 1.0 g / cm ³ or less, more preferably 0.4. ~ 0.8 g / cm ³ . If it exceeds 1.5 g / cm ³ , the mass per particle is large and the sedimentation rate of the conductive particles is high when dispersed in the adhesive solution. It becomes difficult to obtain a solution. Moreover, since it is not bulky, since it is necessary to add electroconductive particle excessively, it is not preferable.

  The particle size distribution of the particles (A) having a 50% volume particle diameter of 50% to 80% of the thickness of the adhesive layer is preferably a ratio of 95% volume particle diameter to 5% volume particle diameter (95% volume particle diameter / The numerical value of (5% volume particle diameter) is 10 to 30, more preferably 15 to 25. If it is less than 10, the conductivity decreases. On the other hand, if it exceeds 30, the adhesiveness is lowered. Examples of such nickel powder include, but are not limited to, nickel powders # 210, # 255, and # 287 manufactured by Inco Corporation.

On the other hand, the apparent density of the particles diameter of 50% volume particle is less than 50% of the thickness of the adhesive layer (B) is 3.0 g / cm ³ or less, preferably 1.6~2.6g / cm ^3. If it exceeds 3.0 g / cm ³ , the mass per particle is large and the sedimentation rate of the conductive particles increases when dispersed in the adhesive solution. It becomes difficult to obtain a working solution.

  The particle size distribution of the particles (B) having a 50% volume particle diameter of less than 50% of the thickness of the adhesive layer is preferably a ratio of 95% volume particle diameter to 5% volume particle diameter (95% volume particle diameter / 5% The numerical value of (volume particle diameter) is 15 or less, more preferably 5-12. If it exceeds 15, the effect of the addition is reduced, which is not preferable.

  Examples of such nickel powder include, but are not limited to, nickel powders # 123 and # 110 manufactured by Inco Corporation.

The nickel powder produced by the carbonyl method is a method for producing nickel powder from nickel carbonyl by the following reaction.
Ni (CO) ₄ → Ni + 4CO
Nickel powders have various shapes, but have a dendritic (dendritic) surface, a sea urchin shape (FIG. 12), or a filament shape (FIG. 13). Those are preferred. Examples of the shape shown in FIG. 12 include Inco Corporation nickel powder # 123, and examples of the shape shown in FIG. 13 include # 255 and # 287.

(Apparent density)
The apparent density of the conductive particles was measured according to JISZ2504-2000 “Measuring Method of Apparent Density of Metal Powder”.

(Volume particle size)
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.

(Amount of conductive particles added)
The addition amount of the conductive particles is preferably 50 to 100 parts by mass and more preferably 60 to 85 parts by mass with respect to 100 parts by mass of the adhesive substance. In the case of less than 50 parts by mass, the conductivity is lowered. When it exceeds 100 parts by mass, the adhesiveness is lowered. Moreover, particle | grains (A) and particle | grains (B) are used in the range from which mass ratio (A) :( B) will be 40: 60-80: 20. More preferably, it is 50: 50-70: 30. When the particle (A) is less than 40% by mass, the conductivity is lowered. When it exceeds 80 mass%, adhesiveness falls. It becomes possible to make high electroconductivity and adhesiveness compatible by mix | blending in such a ratio. Further, there are effects such as the correspondence to the set width of the pressure-sensitive adhesive layer of the electromagnetic wave shielding pressure-sensitive adhesive sheet and the influence on physical properties due to the fluctuation of the coating thickness.

(Thickness of conductive adhesive layer)
The thickness of the pressure-sensitive adhesive layer of the electromagnetic wave shielding pressure-sensitive adhesive sheet is appropriately set according to the 50% volume particle diameter of the conductive particles, but is preferably 10 to 100 μm, more preferably 15 to 75 μm. Especially, it is especially preferable that it is 20-40 micrometers. If it is the said range, since it is excellent in the initial stage adhesiveness to a rough surface, and it is excellent also in electroconductivity and electromagnetic wave shielding characteristics, it is preferable.

(Peeling sheet)
In the pressure-sensitive adhesive sheet for electromagnetic wave shielding of the present invention, a release sheet can be laminated on the pressure-sensitive adhesive layer. The release sheet is not particularly limited. For example, paper such as kraft paper, glassine paper, high-quality paper, and non-woven fabric, resin films such as polyethylene, polypropylene (OPP, CPP), and polyethylene terephthalate, and the paper and resin films are laminated. Conventionally known ones such as laminated papers, papers that have been sealed with clay, polyvinyl alcohol, etc., and one or both sides have been subjected to a release treatment such as silicon resin, long-chain alkyl treatment, fluorine treatment, etc. Can be used. The release treatment of the release sheet used for the double-sided pressure-sensitive adhesive sheet of the present invention is preferably a silicon resin.

  The pressure-sensitive adhesive layer coating solution (pressure-sensitive adhesive solution) used for the double-sided pressure-sensitive adhesive sheet of the present invention is prepared by dissolving the above pressure-sensitive adhesive and, if necessary, other additives in an organic solvent. The organic solvent is not particularly limited as long as it dissolves the above-described blending components and does not react with the functional group of the crosslinking agent, but is well-known and commonly used, such as ethyl acetate, toluene, xylene, n-hexane, acetone, methyl ethyl ketone. These organic solvents can be used alone or in combination. Preferred are ethyl acetate, n-hexane, acetone, and methyl ethyl ketone.

  The pressure-sensitive adhesive layer can be formed by forming a pressure-sensitive adhesive solution on a release sheet with a roll coater or die coater, and then transferring it to the support. If there is a support, apply it directly on the support. A conventionally known method such as a method for performing the method can be appropriately used.

  Examples will be specifically described below, but the present invention is not limited to these examples.

[Preparation of Conductive Substrate A]
A PET film having a thickness of 12 [mu] m, 200 per 10,000 ² round holes of diameter ^{2μm (3.1μm 2) (628μm 2} ) drilled after, copper-based so that each 1.0μm in thickness after drying on both sides The conductive paint was applied and dried. Further, copper was electroplated on both sides until the thickness became 9 μm, and a conductive substrate A consisting of 5 layers of “copper 9 μm / conductive treatment 1 μm / PET 12 μm / conductive treatment 1 μm / copper 9 μm” was produced.

[Preparation of conductive substrate B]
A PET film having a thickness of 4 [mu] m, 2,500 per 10,000 ² round holes of diameter ^{1μm (0.78μm 2) (1,950μm 2} ) After opening, so that each 1.0μm in thickness after drying to the double-sided copper The system conductive paint was applied and dried. Further, copper was electroplated on both sides until the thickness became 2 μm, and a conductive base material B consisting of 5 layers of “copper 3 μm / conductive treatment 1 μm / PET 4 μm / conductive treatment 1 μm / copper 3 μm” was produced.

[Preparation of Conductive Substrate C]
A PET film having a thickness of 25 [mu] m, 300 per 10,000 ² round holes of diameter ^{2μm (3.1μm 2) (942μm 2} ) drilled after, copper-based so that each 1.0μm in thickness after drying on both sides The conductive paint was applied and dried. Further, copper was electroplated on both surfaces until the thickness became 5 μm, and a conductive substrate A consisting of five layers of “copper 5 μm / conductive treatment 1 μm / PET 25 μm / conductive treatment 1 μm / copper 5 μm” was produced.

[Preparation of conductive substrate D]
A conductive substrate D was produced in the same manner as the conductive substrate A except that no holes were formed.

[Preparation of conductive substrate E]
Electrolytic plating was performed on both surfaces of a nickel foil having a thickness of 10 μm until the thickness became 15 μm, and a conductive substrate E composed of three layers of “copper 15 μm / nickel 10 μm / copper 15 μm” was produced.

[Preparation 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 particle-dispersed conductive adhesive composition]
With respect to 100 parts by mass (45 parts by mass of solid content) of the acrylic pressure-sensitive adhesive composition, # 287 (nickel powder manufactured by Incori Ltd., 50% average particle size: 19.7 μm, apparent density: 0.8 g / cm ³ ) 20.0 parts by mass, # 123 (nickel powder manufactured by Incori Ltd., 50% average particle size: 10.8 μm, apparent density: 2.4 g / cm ³ ) 10.0 parts by mass, ethyl acetate 10 parts by mass Then, 1.3 parts by mass of a cross-linking agent Coronate L (an isocyanate-based cross-linking agent manufactured by Nippon Polyurethane Industry) was added in a resin solid content ratio, and mixed for 10 minutes with a dispersion stirrer to prepare a particle-dispersed conductive adhesive.

(Example 1)
[Preparation of electromagnetic wave shielding adhesive sheet]
The particle-dispersed conductive pressure-sensitive adhesive is coated on a release paper having a thickness of 130 μm so that the thickness of the pressure-sensitive adhesive layer after drying is 33 μm, and is dried in an oven at 80 ° C. for 2 minutes. After being bonded to the conductive base material A, it was cured at 40 ° C. for 48 hours to produce an electromagnetic wave shielding pressure-sensitive adhesive sheet (50% average particle size of # 287 was 60.0% of the pressure-sensitive adhesive layer thickness, # 123 is 32.7%). The gel fraction was 41%.

(Example 2)
For electromagnetic wave shielding as in Example 1, except that # 287 is changed to 20.0 parts by mass and # 123 is changed to 20.0 parts by mass with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive composition described in Example 1. An adhesive sheet was prepared.

(Example 3)
An electromagnetic wave shielding adhesive sheet was prepared in the same manner as in Example 1 except that # 287 was changed to 36 parts by mass and # 123 was changed to 9 parts by mass with respect to 100 parts by mass of the acrylic adhesive composition described in Example 1. did.

Example 4
An electromagnetic wave shielding pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that # 287 was changed to 16 parts by mass and # 123 was changed to 22 parts by mass with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive composition described in Example 1. did.

(Example 5)
An electromagnetic wave shielding adhesive sheet was prepared in the same manner as in Example 1 except that the conductive substrate B was used.

(Example 6)
An electromagnetic wave shielding adhesive sheet was prepared in the same manner as in Example 1 except that the conductive substrate C was used.

(Example 7)
An electromagnetic wave shielding adhesive sheet was prepared in the same manner as in Example 1 except that the conductive substrate D was used.

(Comparative Example 1)
An adhesive sheet for electromagnetic wave shielding was obtained in the same manner as in Example 1 except that a rolled copper foil having a thickness of 35 μm (BAC-13-T, manufactured by Japan Energy Co., Ltd.) was used as the conductive substrate.

(Comparative Example 2)
An electromagnetic wave shielding adhesive sheet was obtained in the same manner as in Example 1 except that the conductive substrate E was used.

(Comparative Example 3)
The pressure-sensitive adhesive sheet for electromagnetic wave shielding as in Example 1 except that # 287 is changed to 40.0 parts by mass and # 123 is not used with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive composition described in Example 1. Got.

(Comparative Example 4)
Adhesive for electromagnetic wave shielding in the same manner as in Example 1 except that # 287 was not used and # 123 was changed to 40.0 parts by mass with respect to 100 parts by mass of the acrylic adhesive composition described in Example 1. A sheet was obtained.

(Comparative Example 5)
The pressure-sensitive adhesive sheet for electromagnetic wave shielding in the same manner as in Example 1 except that # 287 is changed to 20.0 parts by mass and # 123 is not used with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive composition described in Example 1. Got.

(Comparative Example 6)
An electromagnetic wave shielding adhesive sheet was obtained in the same manner as in Example 1 except that the thickness of the conductive adhesive in Example 1 was changed to 50 μm. (The 50% average particle size of # 287 is 39.4% of the pressure-sensitive adhesive layer thickness, and # 123 is 21.6%)

(Comparative Example 7)
An electromagnetic wave shielding adhesive sheet was obtained in the same manner as in Example 1 except that the thickness of the conductive adhesive in Example 1 was changed to 20 μm. (The 50% average particle size of # 287 is 98.5% of the thickness of the pressure-sensitive adhesive layer, and # 123 is 54.0%)

(Comparative Example 8)
An electromagnetic wave shielding adhesive sheet was obtained in the same manner as in Example 1 except that # 287 in Example 1 was changed to 9 parts by mass and # 123 was changed to 27 parts by mass.

(Comparative Example 9)
An electromagnetic wave shielding adhesive sheet was obtained in the same manner as in Example 1 except that the conductive particles were not blended.

(Comparative Example 10)
The electromagnetic shielding characteristics of the embossed type conductive adhesive sheet (conductive adhesive sheet manufactured by Sumitomo 3M Limited, # 1245) were evaluated. As a result, the electromagnetic wave shielding property after application for 10 minutes showed a high electromagnetic wave shielding property of 61 dB, but when remeasured after 1 hour after application, the electromagnetic wave shielding property was 40 dB.

(Evaluation)
About the adhesive sheet for electromagnetic wave shield produced in Examples 1-7 and Comparative Examples 1-9, adhesive force, resistance value, and electromagnetic wave shielding characteristic were measured, and it was shown in Table 1, Table 2, and Table 3.

A 20 mm width electromagnetic wave shielding adhesive sheet sample is applied to a stainless steel plate (hereinafter referred to as a stainless steel plate) that has been subjected to hairline polishing treatment with water-resistant abrasive paper having an adhesive strength of 360, and a 2.0 kg roller 1 reciprocating pressure in an environment of 23 ° C. and 60% RH. Affixed and allowed to stand 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).

A test piece having a resistance value of 25 mm width × 80 mm length was affixed to a copper plate with a reciprocating pressure of 2.0 kg roller at room temperature so that the application area was 6.25 cm ² , and 1 in an environment of 23 ° C. and 60% RH. After standing for a period of time, connect the terminal to the end of the test piece and the end of the copper plate (the part that is not bonded) in the same environment, and measure the resistance when a current of 10 μA is applied using a milliohm meter (NF circuit design). did.

A rectangular hole having a length of 2 cm and a width of 0.5 cm is formed in the center of an aluminum plate having an electromagnetic shielding characteristic of 20 cm square and a thickness of 0.4 mm (FIG. 10). A test specimen for measurement was prepared by pasting the sample with a 2.0 kg roller 1 reciprocating pressure so as to close the hole with the electromagnetic wave shielding adhesive sheet of each of Examples and Comparative Examples cut to 4 cm in length and 2 cm in width (see FIG. 11). After leaving for 1 hour in an environment of 23 ° C. and 60% RH, attach the adhesive surface of the electromagnetic wave shielding adhesive sheet to the transmitting antenna side on the magnetic field mode measurement jig of the electromagnetic wave shielding characteristic measuring device (Spectrum Analyzer MS2661C, manufactured by Anritsu Corporation). Set the aluminum plate so that the rectangular hole is perpendicular to the transmitting antenna. The attenuation (dB) when radiating radio waves with a frequency of 1 GHz was measured. The value obtained by subtracting the attenuation amount of only the jig was defined as the electromagnetic wave shielding characteristic.

＊ テープの厚さ方向には、導電性なし

* No electrical conductivity in the tape thickness direction

Moreover, in order to investigate the electroconductivity with respect to metals other than copper, when the resistance value at the time of sticking the electroconductive adhesive tape of Example 1 to a stainless steel plate (SUS304) was evaluated, it was 300m (ohm) /6.25cm < ² >, It was confirmed that the electromagnetic wave shielding pressure-sensitive adhesive sheet of the invention can also provide good conduction to stainless steel.

  Electronic devices suitable for shielding electromagnetic waves using the electromagnetic wave shielding adhesive sheet of the present invention include, as specific examples, a mobile phone, a portable personal computer, a portable information terminal device (PDA), and a digital still camera. And electronic devices mounted on automobiles.

It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. It is a schematic sectional drawing which shows an example of the structure of the adhesive sheet for electromagnetic wave shields. Jig for measuring electromagnetic shielding characteristics Test piece for measuring electromagnetic shielding properties It is a photograph of a sea urchin-like nickel powder. It is a photograph of filamentous nickel powder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resin film 2 Conductive metal layer 2a Conductive treatment layer 2b Plating layer 3 Adhesive layer 4 made of conductive adhesive 4 Conductive through hole 5 Release sheet 6 0.4 mm thick aluminum plate 7 2 cm long x 0.5 cm wide Rectangular hole 8 4 cm long × 2 cm wide electromagnetic shielding adhesive sheet 9 Conductive substrate 10 Conductive substrate 11 Conductive substrate

Claims (12)

An electromagnetic wave shielding pressure-sensitive adhesive sheet comprising a conductive substrate provided with a conductive metal layer on both surfaces of a resin film, and an adhesive layer laminated on at least one surface of the conductive metal layer, The adhesive layer is composed of an adhesive substance and a conductive adhesive containing nickel powder produced by the carbonyl method, and the conductive adhesive contains 50 to 100 parts by mass of the nickel powder with respect to 100 parts by mass of the adhesive substance. And the nickel powder is
(1) particles (A) having a 50% volume particle diameter of 50% to 80% of the thickness of the adhesive layer;
(2) containing particles (B) having a 50% volume particle diameter of less than 50% of the thickness of the adhesive layer, and (3) mass ratio of particles (A) to particles (B) (A): (B ) 40: 60-80: 20
An adhesive sheet for electromagnetic wave shielding, characterized in that The conductive metal layer is a layer composed of a conductive treatment layer having a resistance value of 1.3 Ω / cm or less formed on the surface of the resin film, and a plating layer formed on the conductive treatment layer. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to claim 1, wherein the thickness of the plating layer is 1.0 µm or more and the resistance value in the surface direction is 40 mΩ / cm or less. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to claim 2, wherein the conductive treatment layer is a conductive coating film formed from a conductive paint. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to claim 3, wherein the conductive paint contains a conductive material composed of one or more of silver, copper, aluminum, nickel, and conductive carbon. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to claim 2, wherein the conductive treatment layer is a metal thin film formed by vapor deposition or sputtering of a metal. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to claim 5, wherein the metal thin film is at least one metal selected from silver, copper, aluminum, nickel and tin. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to any one of claims 2, 3, 4, 5 and 6, wherein the plating layer is a layer containing copper or nickel as a main component. The resin film is a film in which conductive through holes are formed in the thickness direction, and the resistance value in the thickness direction of the resin film is 10 mΩ / 6.25 cm ² or less. The adhesive sheet for electromagnetic wave shielding in any one of 4, 5, 6 or 7. The ratio of 95% volume particle diameter to 5% volume particle diameter of the particles (A) (95% volume particle diameter / 5% volume particle diameter) is 10 to 30, and the 95% volume particle diameter of the particles (B). And the ratio of the 5% volume particle diameter (95% volume particle diameter / 5% volume particle diameter) is 15 or less, according to any one of claims 1, 2, 3, 4, 5, 6, 7, or 8. Adhesive sheet for electromagnetic wave shielding. The apparent density of the particles (A) is 1.5 g / cm ³ or less, and the apparent density of the particles (B) is 3.0 g / cm ³ or less. The adhesive sheet for electromagnetic wave shields in any one of 7, 8, or 9. The pressure-sensitive adhesive sheet for electromagnetic wave shielding according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, wherein the adhesive substance contains a (meth) acrylic pressure-sensitive adhesive. An electronic apparatus comprising the electromagnetic wave shielding adhesive sheet according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11.

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