JP2016207996A - Conductive coating foam sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive coating foam sheet capable of repeating compression recovery and maintaining sufficient conductivity even after repeating compression recovery.SOLUTION: A conductive coating foam sheet 1 includes: a foam sheet 2, having a plurality of independent foams 2A; and a conductive coat 3, coating a surface of the foam sheet 2. The foam sheet coated with the conductive coat has a foam sheet 2 and a conductive coat 3. A thickness of the foam sheet 2 is less than or equal to 1 mm. An average aspect ratio of the independent foams 2A is greater than or equal to 1.2 and less than or equal to 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive coated foam sheet comprising a foam sheet having a plurality of bubbles and a conductive film covering the surface of the foam sheet.

  In electronic devices such as mobile phones, electromagnetic shielding materials are used for gaskets, cushioning materials, packings, and the like. In electronic devices, a grounding conductive material is used in a gap between the housing and the substrate.

  The electromagnetic wave shielding material and the grounding conductive material are required to have impact resistance. Therefore, a foam coated with a conductive film may be used as an electromagnetic shielding material or a conductive material for grounding.

  For example, Patent Document 1 below discloses a conductor having a deformed profile in which a conductive envelope is wound around and adhered to the surface of a string-like sponge body. Patent Document 1 describes that the string-like sponge body is obtained by slicing or slitting an elastic foam block such as polyurethane sponge.

  Moreover, the following patent document 2 discloses an electromagnetic shielding material sheet in which a conductive film is bonded to one surface of a core material. In Patent Document 2, the core material is an acrylic foam formed of a self-adhesive acrylic foam resin material, and the sheet can be placed on a substrate or a housing and pressed. It is described. Patent Document 2 describes that the electromagnetic shielding material sheet has a thickness of 1 mm or less.

JP 9-312492 A JP 2014-111262 A

  As in Patent Document 1, the method of slicing or slitting the elastic foam block has a problem that it is difficult to obtain a thin foam sheet. For this reason, generally the thickness of an elastic foam tends to become thick.

  In particular, the conductive coated foam sheet used in electronic devices such as miniaturized and thin portable electronic terminals can repeat compression recovery even when the thickness is small, and is sufficient even after repeated compression recovery. It is preferable that conductivity can be maintained.

  However, in Patent Documents 1 and 2, polyurethane sponge or acrylic foam is used as the foam, and the bubbles in the foam are not closed cells but open cells. For this reason, when the foam is thinned, there is a problem that the conductivity decreases after repeated compression recovery.

  An object of the present invention is to provide a conductive coated foam sheet that can repeat compression recovery and maintain sufficient conductivity even after repeated compression recovery.

  According to a wide aspect of the present invention, a foamed sheet having a plurality of closed cells and a conductive film covering the surface of the foamed sheet, the foamed sheet coated with the conductive film, the foamed sheet and the above There is provided a conductive coated foamed sheet having a conductive film, wherein the foamed sheet has a thickness of 1 mm or less, and an average aspect ratio of the closed cells is 1.2 or more and 5 or less.

  In a specific aspect of the electrically conductive coated foam sheet according to the present invention, a direction obtained by averaging the length directions of the closed cells is parallel to a direction perpendicular to the thickness direction of the foam sheet, or The direction is inclined at 30 ° or less with respect to the direction orthogonal to the thickness direction.

  In a specific aspect of the electrically conductive coated foam sheet according to the present invention, the foam sheet is obtained by extrusion molding, and the average diameter of the closed cells in the flow direction at the time of extrusion molding of the foam sheet is determined in the thickness direction of the foam sheet. The ratio of the closed cell to the average diameter is 1.2 or more and 5 or less.

  The conductive coated foam sheet according to the present invention preferably includes a first conductive pressure-sensitive adhesive layer disposed on one surface of the foamed sheet coated with the conductive film. The conductive coated foam sheet according to the present invention is preferably a conductive support layer disposed on the surface of the first conductive pressure-sensitive adhesive layer opposite to the conductive coating side, and the conductive support. A second conductive pressure-sensitive adhesive layer disposed on the surface of the layer opposite to the first conductive pressure-sensitive adhesive layer side.

  In a specific aspect of the conductive coated foam sheet according to the present invention, the conductive coated foam sheet includes a conductive layer or an insulating layer disposed on one surface of the foamed sheet coated with the conductive film.

  In a specific aspect of the conductive coated foamed sheet according to the present invention, the conductive coated foamed sheet includes two foamed sheets coated with the conductive film, and is between two foamed sheets coated with the conductive film. A conductive layer or an insulating layer.

  In a specific aspect of the conductive coated foam sheet according to the present invention, the conductive layer or the insulating layer is an insulating layer.

  On the specific situation with the electrically conductive coating foam sheet which concerns on this invention, the said conductive film has coat | covered the at least 1 side surface of the said foam sheet, and the conductive film which coat | covers the side surface of the said foam sheet has a slit.

  The conductive coating foam sheet according to the present invention is suitably used for a grounding conductive material or an electromagnetic shielding material.

  The conductive coating foam sheet according to the present invention includes a foam sheet having a plurality of closed cells and a conductive coating covering the surface of the foam sheet. The foam sheet covered with the conductive film has the foam sheet and the conductive film. Further, in the conductive coated foam sheet according to the present invention, the thickness of the foam sheet is 1 mm or less, and the average aspect ratio of the closed cells is 1.2 or more and 5 or less, so compression recovery can be repeated, In addition, sufficient conductivity can be maintained even after repeated compression recovery.

Fig.1 (a) is a typical perspective view of the electrically conductive covering foam sheet which concerns on the 1st Embodiment of this invention, FIG.1 (b) is a model in alignment with the AA 'line of Fig.1 (a). FIG. Fig.2 (a) is a typical perspective view of the electrically conductive covering foam sheet which concerns on the 2nd Embodiment of this invention, FIG.2 (b) is a model in alignment with the AA 'line of Fig.2 (a). FIG. Fig.3 (a) is a typical perspective view of the electrically conductive covering foam sheet which concerns on the 3rd Embodiment of this invention, FIG.3 (b) is a model in alignment with the AA 'line of Fig.3 (a). FIG.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  Fig.1 (a) is a typical perspective view of the electrically conductive covering foam sheet which concerns on the 1st Embodiment of this invention. FIG. 1B is a schematic cross-sectional view taken along the line A-A ′ of FIG. In FIG. 1 and FIGS. 2 and 3 to be described later, the thickness, size, and shape of each layer and bubble are appropriately changed from the actual size and shape for convenience of illustration.

  The conductive coated foam sheet 1 shown in FIGS. 1A and 1B includes a foam sheet 2, a conductive film 3, a first conductive pressure-sensitive adhesive layer 4, a conductive support layer 5, and a second conductive pressure-sensitive adhesive. Layer 6 is provided.

  The foam sheet 2 has a length direction and a width direction. The foam sheet 2 has a rectangular shape. The thickness of the foam sheet 2 is 1 mm or less.

  The foam sheet 2 has a plurality of closed cells 2A. The closed cells 2 </ b> A are formed inside the foam sheet 2. The foam sheet 2 is a closed cell foam. The average aspect ratio of the closed cells 2A in the foam sheet 2 is 1.2 or more and 5 or less.

  The conductive film 3 covers the surface of the foam sheet 2. The conductive coating 3 covers the periphery of the foam sheet 2. The conductive coating 3 covers the outer periphery of the foam sheet 2. The conductive coating 3 covers the first surface 2a (lower surface), the second surface 2b (upper surface), and the side surfaces 2c on both sides in the width direction of the foam sheet 2. Therefore, the conductive coating 3 is wound around the outer periphery of the foam sheet 2. The conductive coating 3 also covers the side surfaces 2 c on both sides in the length direction of the foamed sheet 2. The foamed sheet 2 and the conductive coating 3 form a conductive coated foamed sheet body. The conductive coated foam sheet body is a foam sheet coated with a conductive film.

  The conductive coating 3 is provided in the conductive coated foamed sheet 1 so that the first surface 2a and the second surface 2b of the foamed sheet 2 can be electrically connected. The conductive coating 3 may cover the entire surface of the foamed sheet 2, may cover only part of the surface of the foamed sheet 2, or covers only at least one side surface 2 c of the foamed sheet 2. May be. Moreover, in order to improve electroconductivity more, the conductive film 3 may be provided in the two side surfaces 2c of the foam sheet 2, and may be provided in the three side surfaces 2c and the four side surfaces 2c. For example, the side surfaces 2 c on both sides in the length direction of the foamed sheet 2 may not be covered with the conductive coating 3.

  The conductive coating 3 covering the side surfaces 2c on both sides in the width direction of the foam sheet 2 has a first slit 3A and a second slit 3B on the outer surface. The first slit 3 </ b> A and the second slit 3 </ b> B extend in the thickness direction of the foam sheet 2. In addition, the slit may be provided only on one side surface in the width direction of the foamed sheet covered with the conductive coating 3, or may be provided on two side surfaces. Moreover, the slit may be provided in the conductive film which coat | covers the side surface of the both sides of the length direction of a foam sheet. The slit is preferably provided, but may not be provided. Moreover, although not shown in figure, the foam sheet 2 has a 1st slit and a 2nd slit. The first slit in the foamed sheet 2 is continuous with the first slit 3 </ b> A in the conductive film 3, and the second slit in the foamed sheet 2 is continuous with the second slit 3 </ b> B in the conductive film 3. The conductive coated foam sheet 1 has a slit including a cut part that cuts the conductive film 3 and a cut part that forms a cut in the foam sheet 2. The said cutting part is an opening part of a conductive film. The cut portion is a concave portion of the foam sheet. The slit in the conductive coating foam sheet 1 reaches the foam sheet 2. When the slits in the conductive coated foam sheet are formed to reach not only the metal film but also the foam sheet, the conductive film compared to the case where the slit in the conductive coated foam sheet is formed only in the metal film. It is possible to more effectively suppress the growth of cracks occurring in the film. The foam sheet preferably has a slit. The foam sheet preferably has a slit on the side surface. The foam sheet preferably has a slit on its side surface that extends in the thickness direction of the foam sheet. The foam sheet preferably has a slit forming a cut in the foam sheet, and preferably has a cut portion formed by the slit.

  The first conductive pressure-sensitive adhesive layer 4 is disposed on the first surface 2a (one surface) side of the foamed sheet 2 and laminated. The first conductive pressure-sensitive adhesive layer 4 has conductivity. The first conductive pressure-sensitive adhesive layer 4 is formed of a conductive pressure-sensitive adhesive.

  The conductive support layer 5 is disposed and laminated on the surface of the first conductive pressure-sensitive adhesive layer 4 on the side opposite to the conductive coating 3 side. The conductive support layer 5 has conductivity. The conductive support layer 5 can be plastically deformed.

  The 2nd electroconductive adhesive layer 6 is arrange | positioned on the surface on the opposite side to the 1st electroconductive adhesive layer 4 side of the electroconductive support body layer 5, and is laminated | stacked. The second conductive pressure-sensitive adhesive layer 6 has conductivity. The second conductive pressure-sensitive adhesive layer 6 is formed of a conductive pressure-sensitive adhesive.

  Fig.2 (a) is a typical perspective view of the electrically conductive covering foam sheet which concerns on the 2nd Embodiment of this invention. FIG. 2B is a schematic cross-sectional view taken along the line A-A ′ of FIG.

  A conductive-coated foam sheet 11 shown in FIG. 2 includes one conductive-coated foam sheet main body formed by the foam sheet 2 and the conductive film 3 shown in FIG. That is, the conductive coating foam sheet 11 includes one foam sheet coated with a conductive film. The conductive coating foam sheet 11 further includes a conductive layer or an insulating layer 12 disposed on one surface of the foam sheet covered with the conductive film. The conductive coated foam sheet 11 has a laminated structure of a foam sheet / conductive layer or insulating layer 12 covered with a conductive film.

  Fig.3 (a) is a typical perspective view of the electrically conductive covering foam sheet which concerns on the 3rd Embodiment of this invention. FIG. 3B is a schematic cross-sectional view taken along the line A-A ′ of FIG.

  The conductive coating foam sheet 21 shown in FIG. 3 includes two conductive coating foam sheet bodies formed by the foam sheet 2 and the conductive coating 3 shown in FIG. That is, the conductive coated foam sheet 21 includes two foam sheets coated with a conductive film. The conductive coating foam sheet 21 further includes a conductive layer or an insulating layer 22 between the two foam sheets coated with the conductive film. The conductive coated foam sheet 21 has a laminated structure of a foam sheet covered with a conductive film / conductive layer or an insulating layer 22 / a foam sheet covered with a conductive film. In this way, by using a foam sheet coated with a plurality of conductive films, cushioning properties are improved, and for example, the load applied to one foam sheet coated with the conductive film during compression is reduced. Cracks are less likely to occur.

  The conductive coated foam sheet may have three or more foam sheets coated with a conductive film, and may have two or more conductive layers or insulating layers. For example, a conductive coated foam sheet is a laminated structure of a foam sheet coated with a conductive film / conductive layer or an insulating layer / foam sheet coated with a conductive film / conductive layer or a foam sheet coated with an insulating layer / conductive film. You may have.

  The conductive layer or insulating layer is preferably an insulating layer. In the conductive coated foam sheet in which the insulating layer is disposed between the two foam sheets coated with the conductive film, direct current or alternating current can be selectively passed or selectively blocked. Moreover, it functions similarly to a capacitor, and can reduce high frequency components of noise included in direct current or alternating current.

  In addition, although it is preferable that the electrically conductive coating foam sheet is equipped with the 1st electroconductive adhesive layer, the electroconductive support body layer, and the 2nd electroconductive adhesive layer, it does not need to be equipped with these. Moreover, the conductive coating foam sheet may have only the 1st electroconductive adhesive layer. Also, a conductive adhesive layer may be disposed on the second surface (the other surface) side opposite to the first surface (the one surface) side of the conductive coating foam sheet. A support layer may be disposed. It is preferable that the foamed sheet (conductive coated foamed sheet main body) covered with the conductive film is used for an application in which the foamed sheet is fixed to the fixing target member with the conductive adhesive tape. This application is different from the application in which the foam sheet coated with the conductive film (conductive coated foam sheet body) is fixed to the fixing target member only by the metal material, and is used for fixing to the fixing target member by soldering. Different. It is preferable that the said conductive adhesive tape contains a conductive adhesive (1st conductive adhesive layer). More preferably, the conductive pressure-sensitive adhesive tape includes a first conductive pressure-sensitive adhesive layer, a conductive support layer, and a second conductive pressure-sensitive adhesive layer. In the fixing in the conductive adhesive tape, the compression recovery can be repeated, and sufficient conductivity can be effectively maintained even after the compression recovery is repeated.

  Since conduction | electrical_connection reliability and electromagnetic wave shielding property can be improved, the electrically conductive coating foam sheet which concerns on this invention is used suitably for the electrically conductive material for grounding, or an electromagnetic wave shielding material. The conductive coating foam sheet according to the present invention is preferably used for a conductive material for grounding, and is preferably used for an electromagnetic shielding material. The electrically conductive coated foam sheet according to the present invention is suitably used for electronic equipment.

  Hereinafter, other details of the conductive coating foam sheet according to the present invention will be described.

(Foam sheet)
The foam sheet is a closed cell foam having a plurality of closed cells. The closed cell foam is a foam formed of a single cell or a composite of a plurality of cells having about 2 to 3 cells. For example, when the closed-cell foam is submerged in water under specific conditions, the water absorption is 5% or less (MIL-R6130C).

  The thickness of the foam sheet is 1 mm or less. The thickness of the foamed sheet is preferably 0.5 mm or less, and more preferably 0.25 mm or less because it can cope with thinning of electronic parts and the like. From the viewpoint of further improving impact resistance, conduction reliability and electromagnetic wave shielding properties, the thickness of the foamed sheet is preferably 0.05 mm or more, more preferably 0.1 mm or more.

  The average aspect ratio of closed cells in the foam sheet is 1.2 or more and 5 or less. The closed cells preferably have a flat shape. From the viewpoint of further improving impact resistance, conduction reliability and electromagnetic wave shielding properties, the average aspect ratio of closed cells is preferably 1.3 or more, and preferably 3 or less.

  The aspect ratio is major axis / minor axis. The average aspect ratio is an average of the aspect ratios of a plurality of closed cells.

  The direction in which the length direction of the closed cells is averaged is parallel to the direction orthogonal to the thickness direction of the foam sheet, or is inclined at 30 ° or less with respect to the direction orthogonal to the thickness direction of the foam sheet. Preferably there is. When the direction in which the length direction of the closed cells is averaged is inclined with respect to the direction orthogonal to the thickness direction of the foamed sheet, the inclination angle is more preferably 15 ° or less.

  Corresponding to the reduction in thickness, from the viewpoint of further improving impact resistance, conduction reliability and electromagnetic wave shielding properties, the average diameter of closed cells in the flow direction at the time of extrusion molding of the expanded sheet is reduced. The ratio to the average diameter is preferably 1.2 or more, more preferably 1.3 or more, preferably 5 or less, more preferably 3 or less.

  Corresponding to the reduction in thickness, from the viewpoint of further improving impact resistance, conduction reliability and electromagnetic shielding properties, the ratio of the average diameter of closed cells in the width direction of the foam sheet to the average diameter of bubbles in the thickness direction of the foam sheet is , Preferably 1.2 or more, more preferably 1.3 or more, preferably 5 or less, more preferably 3 or less.

  As the method for producing the foam sheet, for example, the above-mentioned closed cell foam can be used, and an appropriate method capable of obtaining a foam sheet in which the bubbles have a flat shape can be adopted. The said foam sheet can be manufactured with a manufacturing method provided with the following processes (1)-(3), for example.

  Step (1): A step of melting and kneading a composition containing a resin, a pyrolytic foaming agent, and other optional components added as necessary to form a sheet-shaped foam composition

  Step (2): A step of foaming the sheet-shaped foam composition by heating to a temperature higher than the decomposition temperature of the pyrolytic foaming agent.

  Step (3): Step of stretching the sheet-shaped foam composition so that the bubbles inside the resulting foamed sheet have a flat shape.

  Hereinafter, steps (1) to (3) will be specifically described.

Step (1):
In said process (1), additives, such as resin and a thermal decomposition type foaming agent, and other arbitrary components are supplied to extruders, such as a single screw extruder or a twin screw extruder, etc., and a thermal decomposition type foaming agent is supplied. It is melted and kneaded at a temperature lower than the decomposition temperature, and extruded by extrusion or the like to obtain a sheet-shaped foam composition.

<Resin>
The resin is not particularly limited, and examples thereof include polyolefins such as polyethylene and polypropylene; polystyrenes and polyurethanes. The said resin may be used independently and may use 2 or more types together.

<Pyrolytic foaming agent>
The pyrolyzable foaming agent is preferably a pyrolyzable foaming agent having a decomposition temperature higher than the melting temperature of the resin, for example. For example, it is preferable to use a chemical foaming agent having a decomposition temperature of 160 to 270 ° C. The chemical foaming agent may be an organic foaming agent or an inorganic foaming agent. The said thermal decomposition type foaming agent may be used independently and may use 2 or more types together.

  Examples of the organic foaming agent include azo compounds such as azodicarbonamide, metal salts of azodicarboxylic acid (such as barium azodicarboxylate), and azobisisobutyronitrile; nitroso compounds such as N, N′-dinitrosopentamethylenetetramine Hydrazine derivatives such as hydrazodicarbonamide, 4,4′-oxybis (benzenesulfonylhydrazide), toluenesulfonylhydrazide; semicarbazide compounds such as toluenesulfonyl semicarbazide, and the like.

  Examples of the inorganic foaming agent include ammonium acid, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, and anhydrous monosodium citrate.

  An azo compound or a nitroso compound is preferable from the viewpoint of forming fine bubbles and improving the economical efficiency and safety, and azodicarbonamide, azobisisobutyronitrile, or N, N′-dinitrosopentamethylenetetramine. Is more preferable, and azodicarbonamide is still more preferable.

  The pyrolytic foaming agent can be used in an appropriate amount so as to form the closed cells.

<Other additives>
You may use additives other than the said thermal decomposition type foaming agent. Examples of additives other than the thermal decomposition type foaming agent include a decomposition temperature adjusting agent, an antioxidant, a cell nucleating agent, a colorant, a flame retardant, an antistatic agent, and a filler.

  The decomposition temperature adjusting agent is blended in order to lower the decomposition temperature of the pyrolytic foaming agent, increase the decomposition rate, or adjust the decomposition rate. Examples of the decomposition temperature adjusting agent include zinc oxide, zinc stearate, urea and the like. The said decomposition temperature regulator may be used independently and may use 2 or more types together.

  The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants such as 2,6-di-t-butyl-p-cresol. The said antioxidant may be used independently and may use 2 or more types together.

Step (2):
In said process (2), a sheet-shaped foam composition is heated and foamed more than the decomposition temperature of a thermal decomposition type foaming agent. Usually, a process (2) is implemented after the said process (1).

  The temperature for heating and foaming can be appropriately adjusted depending on the decomposition temperature of the pyrolytic foaming agent. The temperature for heating and foaming is appropriately selected according to the types of the resin and the pyrolytic foaming agent.

  The method of foaming the foam composition is not particularly limited, and examples thereof include a method of heating with hot air, a method of heating with infrared rays, a method using a salt bath, and a method using an oil bath. These methods may be used in combination.

Step (3):
In the above step (3), for example, the sheet-shaped foam composition is stretched so that the bubbles inside the resulting foamed sheet have a flat shape. Preferably, it extends | stretches in the flow direction at the time of extrusion molding. The stretching may be performed after foaming the sheet-shaped foam composition, or may be performed while foaming the sheet-shaped foam composition. Stretching can be performed with a known apparatus such as a uniaxial stretching machine and a biaxial stretching machine.

  When extending | stretching after foaming a sheet-like foam composition, it is preferable to extend | stretch continuously, maintaining the molten state at the time of foaming, without cooling a foam composition. However, after cooling the foam composition, it may be stretched again by heating to a molten or softened state.

  Moreover, when extending | stretching a sheet-like foam composition, the draw ratio in the flow direction at the time of extrusion molding is suitably selected so that said closed cell may be formed. As the draw ratio increases, it becomes even easier to make the closed cells of the foamed sheet have the above flat shape. When the stretch ratio is low, the sheet-shaped foam composition is prevented from breaking during stretching, or the foaming gas escapes from the foam composition being foamed, and the foam ratio is reduced. Flexibility and tensile strength are improved, and the quality of the foamed sheet becomes even more uniform.

(Conductive coating)
A conductive film that is a metal film can be formed by metal-coating the surface of the foamed sheet by a technique such as metal deposition, sputtering, plating, or coating of a metal paste such as silver paste. The conductive film is not limited to the metal film formed by the above-described method, but a coated body in which the surface of a cloth-like material such as a woven fabric, a knitted fabric, or a nonwoven fabric is coated with a metal, a metal net, or a synthetic resin. A coated body in which the surface of the net is coated with metal or a coated body in which the surface of the synthetic resin film is coated with metal may be used.

  From the viewpoint of improving the denseness of the conductive film, making it harder to cause cracks in the conductive film, and further improving the conductive reliability, the conductive film may be formed by a metal vapor deposition method, a sputtering method, or a plating method. Preferably, it is formed by sputtering or plating, and more preferably formed by plating.

  Examples of the metal that is the material of the conductive coating include titanium, copper, nickel, tin, silver, and gold, and alloys containing these metals. These metals may be used independently and may use 2 or more types together. From the viewpoint of increasing the denseness of the conductive film, making it harder to cause cracks in the conductive film, and further improving the conductive reliability, the material of the conductive film is preferably an alloy containing nickel and copper.

  The conductive film preferably has a slit. The conductive coating covering the side surface of the foam sheet preferably has a slit. The conductive coating covering the side surface of the foam sheet preferably has a slit extending in the thickness direction of the foam sheet. The conductive coating covering the side surface of the foam sheet preferably has a slit on the outer surface extending in the thickness direction of the foam sheet. The conductive film preferably has a slit that cuts the conductive film, and preferably has a cut portion formed by the slit. When the slit is provided, the growth of cracks generated in the conductive film can be effectively suppressed. The cracks are caused by accumulation of metal fatigue based on stress generated by repeatedly applying expansion / contraction motion such as a spring by compression recovery of the conductive coated foam sheet and the foam sheet to the metal. Moreover, even if the crack extended in the length direction of a foam sheet arises in a conductive film, the expansion of a crack can be prevented in a slit part. For this reason, conduction reliability and electromagnetic wave shielding properties are effectively enhanced. When the slits in the conductive coated foam sheet are formed to reach not only the metal film but also the foam sheet, the conductive film compared to the case where the slit in the conductive coated foam sheet is formed only in the metal film. It is possible to more effectively suppress the growth of cracks occurring in the film. Note that the slit may not be provided. Further, the number of the slits is not limited.

  The thickness of the conductive film is preferably 0.001 μm or more, more preferably 0.01 μm or more, preferably 10 μm or less, more preferably 1 μm or less. When the thickness of the conductive film is equal to or more than the above lower limit, the handleability of the conductive film is further enhanced, and cracks are less likely to occur in the conductive film. When the thickness of the conductive coating is less than or equal to the above upper limit, the conductive coating foam sheet becomes even thinner.

(Conductive pressure-sensitive adhesive layer (first conductive pressure-sensitive adhesive layer and second conductive pressure-sensitive adhesive layer))
The conductive adhesive layer is formed of a conductive adhesive. Although it does not specifically limit as said electroconductive adhesive, The adhesive (adhesive containing an electroconductive filler) which mix | blended the electroconductive filler can be used suitably.

  The conductive filler is not particularly limited, and examples thereof include metal powders such as gold powder, silver powder, copper powder, aluminum powder, and iron powder, and carbon materials such as graphite and carbon black. These may be used alone or in combination of two or more.

  Examples of the pressure sensitive adhesive include rubber pressure sensitive adhesive, acrylic pressure sensitive adhesive, silicone pressure sensitive adhesive, and polyurethane pressure sensitive adhesive. These may be used alone or in combination of two or more.

  It does not specifically limit as a form of the said adhesive, For example, the form of a hot-melt-type adhesive, a solvent-type adhesive, and an emulsion-type adhesive is mentioned.

  The thickness of the conductive adhesive layer (each thickness of the first conductive adhesive layer and the second conductive adhesive layer) is not particularly limited. The thickness of the conductive adhesive layer is preferably 0.5 μm or more, more preferably 1 μm or more, preferably 50 μm or less, more preferably 25 μm or less. When the thickness of the conductive pressure-sensitive adhesive layer is not less than the above lower limit, the thickness of the conductive pressure-sensitive adhesive layer becomes even more uniform. When the thickness of the conductive pressure-sensitive adhesive layer is not more than the above upper limit, the conductive coated foam sheet is further thinned.

(Conductive support layer)
The conductive support layer is preferably formed of a conductive material that can be plastically deformed. As the conductive material capable of plastic deformation, for example, metal foil such as copper foil and aluminum foil can be used. In the case where the conductive support layer is provided, when the conductive coating foam sheet is disposed on the uneven base, the conductive support layer is plastically deformed into a shape along the unevenness of the base. Since the unevenness of the plastically deformed conductive support layer is absorbed by the cushioning property of the foamed sheet, the upper surface of the conductive coated foamed sheet can be flattened. Therefore, the conductive coating foam sheet can be disposed without adding excessive stress to the conductive support layer. Thereby, even if there are irregularities in the base, it is possible to prevent a reduction in the contact area between the conductive coating foam sheet and the adherend to be electrically connected, and the conductivity and durability are further effectively improved.

(Conductive layer and insulating layer)
Examples of the material for the conductive layer include materials having the same conductivity as the material for the conductive film. The conductive layer may be a pressure-sensitive adhesive layer containing a conductive filler.

  Resin is mentioned as a material of the said insulating layer. The resin is not particularly limited. For example, polyolefin, polyethersulfone, polysulfone, polycarbonate, cycloolefin polymer, cycloolefin copolymer, polyarylate, polyamide, polyimide, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene Naphthalate, triacetyl cellulose, cellulose nanofiber, etc. are mentioned. These may be used alone or in combination.

  The thickness of the conductive layer or insulating layer is preferably 0.5 μm or more, more preferably 1 μm or more, preferably 50 μm or less, more preferably 25 μm or less. When the thickness of the conductive layer or the insulating layer is not less than the above lower limit, the thickness of the conductive layer or the insulating layer becomes even more uniform. When the thickness of the conductive layer or the insulating layer is not more than the above upper limit, the conductive coated foam sheet is further thinned.

  Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is not limited to the following examples.

Example 1
Production of foam sheet:
A foamed sheet having a plurality of closed cells and a thickness of 0.08 mm was obtained by extrusion foaming a polyethylene resin. In the obtained foamed sheet, the average aspect ratio of closed cells is 1.5, and the direction in which the length direction of closed cells is averaged is 30 ° or less (specifically with respect to the direction perpendicular to the thickness direction of the foamed sheet). The average diameter of the closed cells in the flow direction (the length direction of the foamed sheet) during the extrusion molding of the foamed sheet is relative to the average diameter of the closed cells in the thickness direction of the foamed sheet. The ratio was 1.5, and the ratio of the average diameter of closed cells in the width direction of the foamed sheet to the average diameter of closed cells in the thickness direction of the foamed sheet was 1.05. The obtained foamed sheet was cut into a size of 100 mm in length and 5 mm in width.

Production of foam sheet with conductive coating:
A metal-deposited resin film (a film having a nickel underlayer of 0.02 μm and a copper surface layer of 0.6 μm deposited on the surface of a PET film having a thickness of 16 μm) is applied to the entire surface of the obtained foam sheet. A conductive film having a conductive film thickness of 0.62 μm was formed, and a foam sheet having a conductive film was obtained.

Production of conductive coated foam sheet:
A copper foil having a thickness of 48 μm was prepared as a conductive support layer. A conductive filler was blended with the acrylic pressure-sensitive adhesive to obtain a conductive pressure-sensitive adhesive. Using the obtained conductive adhesive, a first conductive adhesive layer having a thickness of 18 μm is formed on the first surface of the copper foil, and a thickness of 18 μm is formed on the second surface of the copper foil. 2 electroconductive adhesive layers were formed and the electroconductive support body layer with an electroconductive adhesive layer was obtained. A conductive support layer with a conductive pressure-sensitive adhesive layer was laminated on the first surface of the obtained foamed sheet having a conductive film to obtain a conductive coated foamed sheet. In Example 1, the entire thickness of the conductive coating foam sheet was 0.3 mm.

(Example 2)
Using a slit device in the conductive coating, slits extending in the thickness direction (vertical direction) at equal intervals in the conductive coating on both sides in the width direction of the foamed sheet having the conductive coating are used to lengthen the foam sheet having the conductive coating. Example 1 except that a piece having a length of 5 mm and a width of 5 mm is obtained by cutting at an interval of 5 mm in the vertical direction, and two slits on one side are formed so as to divide the side surface into three symmetrically on both sides of the cut piece. In the same manner as above, a conductive coated foam sheet was obtained. In addition, the slit had the cut part which cut | disconnects a conductive film, and the notch part which has formed the cut in a foam sheet.

Example 3
In the production of a foam sheet having a conductive film, the conductive film was formed by a sputtering method, silver was used as a material for the conductive film, and the total thickness of the obtained conductive coated foam sheet was 0.2 mm. Thus, the foamed sheet which has a conductive film was obtained like Example 1 except having changed the thickness of the double-sided adhesive tape and the thickness of the foamed sheet. A conductive-coated foamed sheet was obtained in the same manner as in Example 1 except that the foamed sheet having the obtained conductive film was used.

Example 4
Using a slit device in the conductive coating, slits extending in the thickness direction (vertical direction) at equal intervals in the conductive coating on both sides in the width direction of the foamed sheet having the conductive coating are used to lengthen the foam sheet having the conductive coating. Example 3 except that a piece having a length of 5 mm and a width of 5 mm is obtained by cutting at an interval of 5 mm in the length direction, and two slits on one side are formed so as to divide the side surface into three symmetrically on both sides of the cut piece. In the same manner as above, a conductive coated foam sheet was obtained. In addition, the slit had the cut part which cut | disconnects a conductive film, and the notch part which has formed the cut in a foam sheet.

(Example 5)
In the production of the foamed sheet having a conductive film, a foamed sheet having a conductive film was obtained in the same manner as in Example 1 except that the conductive film was formed by plating. A conductive-coated foamed sheet was obtained in the same manner as in Example 1 except that the foamed sheet having the obtained conductive film was used.

(Example 6)
Using a slit device in the conductive coating, slits extending in the thickness direction (vertical direction) at equal intervals in the conductive coating on both sides in the width direction of the foamed sheet having the conductive coating are used to lengthen the foam sheet having the conductive coating. Example 5 except that it was cut at 5 mm intervals in the length direction to form a cut piece having a length of 5 mm and a width of 5 mm, and two slits on one side were formed on both sides of the cut piece so as to divide the side face into three symmetrically. In the same manner as above, a conductive coated foam sheet was obtained. In addition, the slit had the cut part which cut | disconnects a conductive film, and the notch part which has formed the cut in a foam sheet.

(Comparative example)
Conductive coated foaming in the same manner as in Example 1 except that a foamed sheet (Roron Suinoac Co., Ltd., Polon SR-S-70P) having open cells that are not closed cells and having a thickness of 0.15 mm was used. A sheet was obtained. Also in the comparative example, the entire thickness of the conductive coating foam sheet was 0.3 mm.

(Evaluation)
(1) Evaluation of cracks The following tests were performed on the five conductive coated foamed sheets obtained in Examples 1 and 2 to observe whether cracks occurred. In addition, the case where a crack occurred in all of the five conductive coating foam sheets evaluated was judged as a reproducible result, and it was concluded that “a crack occurred”. In addition, evaluation of the crack repeated compression and recovery | restoration repeatedly in the thickness direction using the dynamic fatigue testing machine, repeating the pressurization and pressure-removal in the thickness direction of the electrically conductive coating foam sheet obtained in Example 1,2. After repeatedly compressing and recovering 1 million times, it was evaluated whether or not a crack was formed in the conductive film.

  As a result, in Examples 1 and 2, there were both a conductive coated foam sheet with cracks and a conductive coated foam sheet with no cracks. With respect to the conductive coated foam sheet in which cracks occurred, in Example 2, the cracks stopped at the slit portion, and the length of the cracks was shorter than in Example 1.

(2) Evaluation of electrical conductivity (electrical resistance) and impact resistance (repulsive force) The upper and lower surfaces (on the surface) of the conductive coated foam sheets of Example 1 and Comparative Example cut out to a size of 5 mm in length and 5 mm in width If there is a conductive adhesive layer, contact the copper electrode with the surface of the conductive adhesive layer), sandwich the upper and lower surfaces of the conductive coated foam sheet with the copper electrode, and apply a load from the upper copper electrode. The distance between the upper and lower electrodes was adjusted by compressing the conductive coated foam sheet. By changing the load applied to the upper electrode, the distance between the upper and lower electrodes was changed as shown in Tables 1 to 4, and the electrical resistivity and the load required to adjust the predetermined distance were measured. Thereby, continuity (electrical resistance) and impact resistance (repulsive force) were evaluated.

  The results of Example 1 are shown in Table 1 below, the results of Comparative Examples are shown in Table 2 below, the evaluation results of Example 3 are shown in Table 3, and the evaluation results of Example 5 are shown in Table 4. In Tables 1 to 4, σ is a standard deviation (number of samples: 5) of repulsive force or electrical resistance.

  In Example 1, when the distance between the upper and lower electrodes was 240 to 160 μm, the electric resistance was sufficiently small, and when Example 1 and the comparative example were compared at the same distance, the impact resistance (repulsive force) was good. In Examples 3 and 5, the electrical resistance was sufficiently small when the distance between the upper and lower electrodes was 240 to 160 μm.

  The lower copper electrode is replaced with a copper electrode with a concavo-convex pattern formed on the surface, and the conductive coating foam sheet of Example 1 and Comparative Example is used, and the gap between the upper and lower electrodes is set to 60 μm. When the sheet was compressed, in the conductive coated foamed sheet of the comparative example, deformation that appears to be the influence of the uneven pattern formed on the lower electrode was observed on the surface of the upper copper electrode after the test. On the other hand, in the conductive coated foam sheet of Example 1, no deformation was observed on the upper electrode surface after the test.

  Further, regarding the obtained conductive coated foam sheet, Example 5 is compared with Examples 1 and 3, Example 3 is compared with Example 1, Example 6 is compared with Examples 2 and 4, Example 4 was confirmed to be superior in corrosion resistance in the corrosion resistance test under acidic conditions as compared with Example 2.

  In addition, with respect to the obtained conductive coated foam sheet, Example 2 compared to Example 1, Example 4 compared to Example 3, Example 6 compared to Example 5, and the conductive film was cracked by slits. It was confirmed that is difficult to occur. Further, it was confirmed that even in Examples 4 and 6, the corrosion resistance was excellent even if there was a slit, and in Example 6, the corrosion resistance was considerably excellent even if there was a slit.

  Moreover, the specific Example which formed the slit which has the cut part which cut | disconnects a conductive film, and the cut part which has formed the cut in a foam sheet was shown. Evaluations were also made for a cut portion for cutting the conductive film and a case where a slit was formed only in the conductive film without forming a cut in the foam sheet. As a result, when the slits in the conductive coated foam sheet are formed so as to reach not only the metal film but also the foam sheet, compared to the case where the slit in the conductive coated foam sheet is formed only in the metal film. It was confirmed that the growth of cracks generated in the conductive film can be more effectively suppressed.

DESCRIPTION OF SYMBOLS 1 ... Conductive coating foam sheet 2 ... Foam sheet 2A ... Closed cell 2a ... 1st surface 2b ... 2nd surface 2c ... Side surface 3 ... Conductive film 3A ... 1st slit 3B ... 2nd slit 3a ... 1st Surface 3b ... Second surface 4 ... First conductive adhesive layer 5 ... Conductive support layer 6 ... Second conductive adhesive layer 11 ... Conductive coated foam sheet 12 ... Conductive layer or insulating layer 21 ... Conductive Covering foam sheet 22 ... conductive layer or insulating layer

Claims (11)

A foam sheet having a plurality of closed cells;
A conductive film covering the surface of the foam sheet,
A foam sheet coated with a conductive film has the foam sheet and the conductive film,
The foam sheet has a thickness of 1 mm or less,
The electrically conductive coated foamed sheet, wherein the average aspect ratio of the closed cells is 1.2 or more and 5 or less.   The direction in which the length direction of the closed cells is averaged is parallel to the direction orthogonal to the thickness direction of the foam sheet, or inclined at 30 ° or less with respect to the direction orthogonal to the thickness direction of the foam sheet. The electrically conductive coated foamed sheet according to claim 1, wherein the electrically conductive coated foamed sheet is in the same direction.   The conductive coated foam sheet according to claim 1, further comprising a first conductive pressure-sensitive adhesive layer disposed on one surface of the foamed sheet coated with the conductive film. A conductive support layer disposed on the surface of the first conductive pressure-sensitive adhesive layer opposite to the conductive film side;
The conductive coated foam sheet according to claim 3, further comprising a second conductive pressure-sensitive adhesive layer disposed on a surface opposite to the first conductive pressure-sensitive adhesive layer side of the conductive support layer. .   The conductive coating foam sheet of any one of Claims 1-4 provided with the conductive layer or insulating layer arrange | positioned at one surface of the foamed sheet coat | covered with the said conductive film. Two foam sheets coated with the conductive film,
The conductive coated foam sheet according to claim 5, further comprising a conductive layer or an insulating layer between the two foam sheets coated with the conductive film.   The conductive coating foam sheet according to claim 5 or 6, wherein the conductive layer or the insulating layer is an insulating layer. The conductive coating covers at least one side of the foam sheet;
The conductive coating foam sheet of any one of Claims 1-7 in which the conductive film which coat | covers the side surface of the said foam sheet has a slit.   The conductive coating foam sheet according to any one of claims 1 to 8, which is used for a conductive material for grounding or an electromagnetic shielding material.   The conductive coating foam sheet according to claim 9, which is used for a conductive material for grounding.   The conductive coating foam sheet according to claim 9, which is used for an electromagnetic shielding material.

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