JP2005191384A - Electromagnetic wave shielding material and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electromagnetic wave shielding materials which are excellent in dispersibility and electronic shielding performance in adding and dispersing a conductive filler such as a carbon nano-tube to resin serving as a base. <P>SOLUTION: Conductive nano-size fiber-shaped carbon materials whose diameters are 1 to 200nm and whose length is 1μm to 20μm are added to polymeric composition which is liquefied prior to polymerization or liquefied after being dissolved in organic solvent at the rate of 0.5 to 20 pts.wt. to 100 pts.wt., and mixed in the state of solution, and polymerized and solidified so that electromagnetic wave shielding materials can be configured. Furthermore, a conductive metallic thin film is laminated as necessary. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electromagnetic wave shielding material, and more particularly to an electromagnetic wave shielding material having an excellent electromagnetic wave shielding effect.

  In today's society, advanced information technology has progressed, and the need for efficient high-speed transmission of information technology has been advertised, and the processing form of information technology has shifted from the conventional analog method to the digital method. The transmission format is becoming established. In the information transmission processing adopting the digital method, the frequency of electronic circuits and the like for the purpose of further increasing the density of information is increasing.

  In general, in the digital circuit, the occurrence of electromagnetic interference noise is observed depending on the clock frequency adopted. However, since the signal voltage adopted by the digital circuit is low, it is easy to be sensitive to electromagnetic noise from the external environment. For this reason, there is a possibility that an electronic device having a digital circuit, an information-related device, and the like are easily caused by a failure such as a device malfunction due to electromagnetic noise.

  Therefore, electronic devices and information-related devices that incorporate digital circuits are required to cope with both not to generate electromagnetic interference noise from the inside of the circuit and not to be affected by electromagnetic noise from the external environment. As a main technique for shielding electromagnetic wave noise, for example, a method of adopting a conductive resin as an electromagnetic wave shielding material for a material constituting a housing containing an electronic device, an information-related device or the like, or an insulating resin molded body There has been proposed a method of employing an electromagnetic wave shielding material that has been subjected to a treatment such as metal plating, metal vapor deposition, or conductive coating.

Examples of the conductive resin used as the electromagnetic shielding material include conductive nano-sized fibrous carbon materials such as carbon nanotubes having a diameter of 1 to 100 nm and a length of 50 μm or less with respect to 100 parts by mass of the resin. An electromagnetic wave absorbing material that expresses high electromagnetic wave absorbing ability in a wide frequency range of 1 to 20 GHz by blending at a mass part ratio and is excellent in flexibility, workability, and workability is disclosed. However, specifically, in Example 2, 100 parts by mass of ethylene-propylene-terpolymer rubber was blended with 6 parts by mass of single-walled carbon nanotubes having an average diameter of 1.5 nm and an average length of 500 nm, An electromagnetic wave absorbing material is prepared by kneading using two roll meals, and the electromagnetic wave absorbing material is pressed to form a sheet of 0.6 mm thickness and 150 mm square. Although bonding the molded electromagnetic wave absorbing material and the aluminum foil is disclosed an absorption peak of -27dB near a frequency of about 3.8GHz was seen.
JP 2003-158395 A (Summary and Examples)

  However, the conductive resin described above employs a method of kneading the resin in a molten state as a means for blending the resin with carbon nanotube particles that are conductive fillers. As a result, the dispersion of the particles becomes non-uniform, When it is thin, there is a problem that sufficient electromagnetic wave absorptivity (shielding property) cannot be exhibited.

  That is, an object of the present invention is to provide an electromagnetic wave shielding material having excellent dispersibility and excellent electron shielding properties when a conductive filler such as carbon nanotube is added to and dispersed in a base resin. .

  The present invention has been achieved as a result of intensive studies in order to solve the above-described problems. That is, the first gist of the present invention is that the liquid is dissolved in an organic solvent or liquid before polymerization. 0.5 to 20 parts by mass of a conductive nano-sized fibrous carbon material having a diameter of 1 to 200 nm and a length of 1 to 20 μm is added to 100 parts by mass of the polymerizable composition, mixed in a solution state, polymerized, and solidified. It relates to the electromagnetic wave shielding material obtained.

  The second gist of the present invention is that conductive nano-sized fibrous carbon having a diameter of 1 to 200 nm and a length of 1 to 20 μm with respect to 100 parts by mass of the polymerizable composition dissolved in a liquid or organic solvent. The present invention relates to a method for producing an electromagnetic wave shielding material, wherein 0.5 to 20 parts by mass of a material is added and mixed, and then polymerized and solidified.

  The electromagnetic wave shielding material according to the present invention is obtained by adding a conductive nano-sized fibrous carbon material to a polymerization product, and the conductive nano-sized fibrous carbon material is polymerizable before the polymerization product is polymerized. Since it is added and mixed in the liquid phase of the composition, it has excellent dispersibility in the polymerization product, and as a result, has excellent electromagnetic shielding properties for the amount of conductive nano-sized fibrous carbon material added. In addition, the entire electromagnetic wave shielding material can be made extremely thin.

First, the electromagnetic wave shielding material according to the first aspect of the present invention is manufactured by the manufacturing method according to the second aspect of the present invention. Hereinafter, a method for producing the electromagnetic wave shielding material according to the first aspect of the present invention by the production method according to the second aspect of the present invention will be described.

  The electromagnetic wave shielding material of the present invention is prepared by adding a conductive nanosize fibrous carbon material to a polymerizable composition mainly composed of an oligomer or polymer that can be dissolved in a liquid or solvent before polymerization, The polymerizable composition is polymerized.

  The polymerizable composition is mainly composed of a polymerizable oligomer or polymer that is soluble in a polar organic solvent, and a flexible material is desired as the electromagnetic wave shielding material that is a polymerization product thereof. The component is preferably a rubber oligomer or polymer, more preferably a liquid rubber component or a liquid resin component. Examples of the components constituting such a polymerizable composition include liquid acrylonitrile butadiene rubber, liquid styrene butadiene rubber, liquid polybutadiene, liquid polyisoprene, Main component resins composed of reactive oligomers or polymers such as polychloroprene, and epoxy resins such as bisphenol A diglycidyl ether type epoxy resins, bisphenol F diglycidyl ether type epoxy resins and phenol novolac type epoxy resins which are curing agent components In particular, a combination of a polymerizable liquid acrylonitrile butadiene rubber (CTBN) having both ends substituted with carboxyl groups and a bisphenol A diglycidyl ether type epoxy resin is preferred. Used properly.

  The polymerizable liquid acrylonitrile butadiene rubber in which both ends are substituted with carboxyl groups is generally given by the chemical formula (1).

化学式（１）
上記式（１）において、ｘは５〜６の整数であり、ｙは１〜２の整数であり、ｚは１０〜１２の整数である。

Chemical formula (1)
In said formula (1), x is an integer of 5-6, y is an integer of 1-2, z is an integer of 10-12.

  As an example of the liquid acrylonitrile butadiene rubber in which both ends are substituted with carboxyl groups, for example, as a compound of Hycar CTBN (trade name) series manufactured by BF Goodrich, the viscosity is 55,000 to 625,000 mPa · s (27 ° C), molecular weight of 3,000 to 4,000, and acrylonitrile content of 10 to 27% are commercially available.

  The bisphenol A-based diglycidyl ether type epoxy resin is a compound having an epoxy ring at both ends. Examples of the bisphenol A-based diglycidyl ether type epoxy resin include DER-331 (Dow Chemical Japan Co., Ltd.). Product) available on the market. The viscosity is 11,000 to 15,000 cPs (25 ° C.), and is given by, for example, the following chemical formula 2.

化学式（２）

ここにｎは０〜２の整数である。

Chemical formula (2)

N is an integer of 0-2 here.

  When a liquid acrylonitrile butadiene rubber in which both ends are substituted with carboxyl groups and a bisphenol A diglycidyl ether type epoxy resin are used as a constituent of the polymerizable composition, both ends are substituted with carboxyl groups. The mixing ratio of the liquid acrylonitrile butadiene rubber and the bisphenol A diglycidyl ether type epoxy resin is usually 100: 10 to 100: 50, preferably 100: 30 (mass ratio).

  The above polymerizable composition has a high viscosity as it is, and exhibits a water tank-like shape and is inferior in operability such as stirring. It is practical to use as Examples of such an organic solvent include polar organic solvents such as acetone, ethyl methyl ketone, dichloromethane, and chloroform.

  The conductive nano-sized fibrous carbon material is a so-called nano-sized fibrous carbon material and has conductivity. As such a conductive nano-sized fibrous carbon material, a fibrous material having a diameter of 1 to 200 nm and a length of 1 μm to 20 μm is preferable, and examples thereof include carbon nanotubes and vapor-grown carbon fibers. Or it can mix | blend suitably and can be used.

  The above-mentioned carbon nanotubes are also called graphite fibril nanotubes, usually exhibiting a single-layer structure in which carbon hexagonal mesh faces are closed in a cylindrical shape, and a multilayer structure in which these single-layer structures are arranged concentrically. Or those in which a single layer structure and a multilayer structure coexist. These carbon nanotubes are produced by, for example, a gas phase decomposition reaction using a carbon-containing gas, an arc discharge method using a carbon rod carbon fiber, or a laser vapor deposition method. The above-mentioned carbon nanotubes usually have a fiber diameter of 1 nm to 50 nm, a fiber length of 1 μm to 50 μm, and a ratio of fiber length to fiber diameter, so-called aspect ratio is 20 to 1000, but is limited to these dimensions. It is not a thing. As the carbon nanotube, various known carbon nanotubes can be used. For example, Multiwall carbon nanotube (trade name, manufactured by Aldrich) or carbon nanotube MWCNT95 (trade name, manufactured by Irjin) is available on the market.

  In addition, the vapor-grown carbon fiber is usually formed as a first-stage formed fiber by catalytic action of a transition metal such as iron or nickel, and then a pyrolytic carbon layer is formed around the elementary fiber. It is a fibrous material having an annual ring-shaped cross section grown concentrically around a hollow fiber axis by vapor phase growth, and usually has a fiber diameter of 80 to 200 nm and a fiber length of 10 to 20 μm. The ratio of diameters, the so-called aspect ratio, is usually 50 to 200, but is not limited thereto. As such a vapor growth carbon fiber, a publicly known one can be used. For example, VGCF (trade name, manufactured by Showa Denko KK) is available on the market.

  The electromagnetic wave shielding material of the present invention is obtained by adjusting the concentration and / or viscosity by dissolving and diluting an organic solvent in the liquid polymerizable composition as required, and then adjusting the concentration and / or viscosity. If necessary, a tertiary amine catalyst is further added as a reaction catalyst, and then the polymerizable composition is polymerized and solidified. The solid content concentration and / or viscosity need not be particularly limited, but it is usually practical that the solid content concentration is 20 to 30% by mass and the viscosity is 5 to 30 (unit mPa · s). is there.

    The addition ratio of such conductive nano-sized fibrous carbon material can be appropriately selected depending on the desired electromagnetic wave shielding performance, but is usually from about 0.1 to 100 parts by mass of the liquid polymerizable composition excluding the solvent. 5 to 20 parts by mass, preferably 5 to 15 parts by mass. When the conductive nano-sized fibrous carbon material is added to the above polymerizable composition, each component is separately dissolved or dispersed in a polar organic solvent for dilution before addition, and then mixed. It is preferable to do this. And after mixing all the components, it is preferable to stir and disperse again and disperse | distribute uniformly.

  The tertiary amine catalyst is not particularly limited. For example, N, N-dimethylmethanamine, N, N-diethylethanamine, N, N-dipropylpropanamine, N, N-dibutylbutane An amine, N, N-diphenylbenzeneamine, or the like can be used. And although the addition amount in particular is not restrict | limited, Usually, it is 1-5 mass parts with respect to 100 mass parts of said polymeric composition solid content, Preferably it is 1-2 mass parts.

  The reaction solution containing the polymerizable composition, the conductive nano-sized fibrous carbon material, the tertiary amine catalyst added as necessary, and the diluting solvent can be solidified by a polymerization reaction to produce an electromagnetic wave shielding material. . The heat treatment conditions at the time of the polymerization are appropriately adjusted depending on the composition of the reaction solution of the polymerizable composition. For example, when a tertiary amine catalyst is not used, the temperature is usually 150 to 180 ° C. and 30 to 40. When a tertiary amine catalyst is used for 15 hours, it is normally 15 to 20 hours at 150 to 180 ° C. If sufficient reaction time is required without using a tertiary amine catalyst, electromagnetic waves can be used even when flexible and thin. An electromagnetic wave shielding material having excellent shielding properties can be obtained.

  The polymerization reaction mechanism of the polymerizable composition when the above amine catalyst is used is considered as follows. First, the carboxyl group of the liquid acrylonitrile butadiene rubber in which both ends as the main agent are substituted with carboxyl groups reacts with the tertiary amine catalyst to produce a carboxyl salt. The produced carboxyl salt quickly reacts with the bisphenol A diglycidyl ether type epoxy resin, the tertiary amine catalyst is eliminated, and the polymer chain extension reaction proceeds. These reactions are repeated to form a polymer chain. Tertiary amine catalyst reacts with carboxyl salt, then reacts with so-called pendant type hydroxyl group formed by reaction of carboxyl group and epoxy ring, and subsequently induces cross-linking reaction with bisphenol A diglycidyl ether type epoxy resin. Then, a product which is a polymer compound having a three-dimensional structure is formed.

  In addition, the electromagnetic wave shielding material of the present invention may be obtained by, for example, pouring the polymerizable composition into a predetermined mold, casting it in a mold, or applying it on the surface of another article. After forming into a predetermined shape, the solvent can be removed and a polymerization reaction can be performed under predetermined conditions.

  When casting in said mold, it is preferable to apply a release agent to the inner surface of the mold. As such a mold release agent, a solution of PFA, PEEK or PTFE can be mentioned. Among them, PFA is more preferable in terms of wear resistance and durability. Further, the method for applying the polymerizable composition is not particularly limited. For example, a roll coating method, a spin coating method, a spray coating method, a dipping coating method, and a manual operation using a brush or the like. It is possible to apply by a known application method such as a method of applying by the method of

  The electromagnetic wave shielding material of the present invention obtained as described above can be used as it is. However, in the case of a sheet-like material (electromagnetic wave shielding sheet), one side, both sides thereof, or two sheets are further provided. Metal foil can be laminated or sandwiched between the layers to form a composite sheet.

  As said metal foil, aluminum foil, copper foil, nickel foil, gold foil, silver foil, platinum foil etc. are mentioned, for example, Aluminum foil or copper foil is used suitably practically. The thickness of such a metal foil is generally appropriately selected according to the desired degree of electromagnetic wave shielding and the adhesion to the surface of the article during use, as the thicker the film, the better the shielding, and the thinner. Is normally 10 to 80 μm, preferably 20 to 40 μm. When the thickness exceeds 80 μm, flexibility and sealing properties are insufficient, and when the thickness is less than 10 μm, handling of the metal foil is difficult and the combined effect is not remarkable.

  When selecting the metal component of the above metal foil, the case having electrical conductivity in which information-related equipment, substrates, etc. are stored is often made of aluminum die cast due to its durability, weight reduction, weather resistance, etc. In many cases, it is more desirable that the metal foil is an aluminum foil of the same metal. This is because different metals come into contact with each other and the difference in oxidation-reduction potential inherent to each metal easily induces a potential difference at the contact interface. This is because erosion is likely to occur, and as a result, it is difficult to prevent electromagnetic interference from the external environment.

  When laminating or sandwiching these metal foils on the electromagnetic wave shielding sheet, it is practical to use a metal foil in which an adhesive layer is previously provided on one or both surfaces of the metal foil. . At this time, as the adhesive, a conductive adhesive is preferably used in order to maintain the conductivity between the layers of the electromagnetic wave shielding sheet and to sufficiently exhibit the electromagnetic wave shielding effect. For example, the metal foil base double-sided tape aluminum foil 20μ (trade name, manufactured by Teraoka Seisakusho Co., Ltd.) coated with an acrylic conductive adhesive, or the metal foil base double-sided tape copper is provided with such an adhesive layer. Foil 35μ (trade name, manufactured by Teraoka Seisakusho Co., Ltd.) is available on the market.

  The electromagnetic wave shielding composite sheet obtained as described above has, for example, an electromagnetic wave shielding effect of 20 dB even at a thickness of 0.35 mm, and a metal thin film layer such as an aluminum foil having a thickness of 20 μm laminated on one side is 38 dB. As described above, those laminated on both surfaces can have a shielding effect of 80 dB. Thus, an electromagnetic wave shielding composite sheet having a thin and excellent electromagnetic wave shielding effect can be provided.

  Examples The present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

In the present invention, the shielding performance as an electromagnetic shielding material or a composite sheet is measured at a measurement frequency of 500 MHz at room temperature using a vector network analyzer which is an electromagnetic shielding effect measuring device of a coaxial tube method measuring method according to ASTM D4935. The material parameter S21 which is a forward transmission characteristic was measured by scanning at 10 GHz, and the value at 4 GHz was read. The electromagnetic wave shielding effect SE is expressed by the ratio of the electromagnetic wave incident on the electromagnetic wave shielding material and the transmitted electromagnetic wave, and is given by the following formula (3).
SE = 10 × log (P _t / P _i ) (3)
Here, P _i is incident power, and P _t is transmitted power.

[Example 1]
Hycar CTBN (trade name, manufactured by BF Goodrich) 25 g, DER-331 (trade name, manufactured by Dow Chemical Japan Co., Ltd.) 7.5 g, and N, N-dibutylbutanamine 0.45 g as a curing catalyst The solution was added to 10 g of toluene, which is a polar solvent, and sufficiently stirred by stirring for 10 minutes using a magnetic stirrer. Separately, 4.50 g of carbon nanotube, Multiwall carbon nanotube (trade name, manufactured by Aldrich) was added to 100 parts by mass of toluene, which is an organic polar solvent, and sufficiently stirred and dispersed. Then, the above two solutions and dispersion are mixed, and the mixture is stirred at a temperature of 75 to 85 ° C. using a magnetic stirrer with a high-precision heating function, and further stirred for about 3 hours to polymerize the carbon nanotubes uniformly. Sex composition was obtained.

  A recess having an inner dimension of 150 mm × 150 mm and a depth of 2 mm is excavated on the smooth upper surface of an aluminum structural member having an outer dimension of 200 mm × 200 mm and a height of 20 mm, and perfluoroalkoxyalkane (PFA) is formed on the inner surface forming the recess. An aluminum casting form with an extremely uniform coating and releasable inner surface was produced. The above polymerizable composition solution, that is, 27.0 g of the polymerizable composition solution having a polar organic solvent toluene concentration of 68.8% by mass was cast into the recess of the apparatus.

  The aluminum mold frame in which the polymerizable composition solution was cast was allowed to stand for 12 hours in an explosion-proof electric drying furnace whose temperature was adjusted to 80 ° C. to volatilize the polar organic solvent component. Thereafter, the polymerizable composition was allowed to stand for 15 hours in an explosion-proof electric drying furnace whose temperature was adjusted to 150 ° C. to polymerize the polymerizable composition to obtain a black electromagnetic wave shielding sheet having a thickness of 0.35 mm and a smooth surface. After the curing polymerization reaction, the formed electromagnetic wave shielding sheet could be easily peeled off from the aluminum mold by the release layer formed by the PFA coating.

  About said electromagnetic wave shielding sheet | seat, as the layer structure shown in FIG. 1, the metal foil base material double-sided tape aluminum foil 20micromicrometer (metal foil) which has an acrylic conductive adhesive layer on both surfaces on the single side | surface of the said electromagnetic wave shielding sheet Of Teraoka Seisakusho Co., Ltd.). And embossed PET38x1-A3 (product name made by Nipper Co., Ltd.) is joined on the adhesive layer surface opposite to the metal foil base double-sided tape aluminum foil 20μ, and the metal foil base material of the electromagnetic wave shielding sheet described above. PET 50 (A) PL thin 11L (trade name, manufactured by Lintec Co., Ltd.) was bonded to the non-bonded surface of the double-sided tape-like aluminum foil 20 μm with an adhesive layer to obtain an electromagnetic wave shielding composite sheet in which metal foils were laminated. The above-mentioned PET 50 (A) PL thin 11L manufactured by Lintec Corporation is a colorless and transparent film having an adhesive layer on one side. About the electromagnetic wave shielding composite sheet laminated with the above metal foil, the electromagnetic wave shielding performance was measured by the above-described measurement method, and the results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Example 2]
In the same manner as in Example 1, a black electromagnetic wave shielding sheet having a thickness of 0.35 mm in which carbon nanotubes were uniformly dispersed and a smooth surface was obtained. The two electromagnetic wave shielding sheets obtained in this way were bonded to each other with a carbon-based conductive adhesive (KE3491 manufactured by Shin-Etsu Chemical Co., Ltd.), and colorless and transparent Lintec Co., Ltd. PET50 (on both sides of the bonded body) A) PL thin 11L was laminated and covered to obtain an electromagnetic wave shielding composite sheet in which two sheets as a final structure were laminated. The laminated electromagnetic wave shielding composite sheet was measured for electromagnetic wave shielding performance by the above-described measurement method, and further, the volume resistivity was measured using an MCP T-410 type (4 probe method) device manufactured by Mitsubishi Chemical. The results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Example 3]
In Example 1, in place of 4.50 g of carbon nanotube, Multiwall carbon nanotube (trade name, manufactured by Aldrich), except that 4.50 g of vapor-grown carbon fiber VGCF (trade name) manufactured by Showa Denko KK was used. In exactly the same manner as in Example 1, a 0.35 mm thick, black-surfaced electromagnetic wave shielding sheet in which vapor-grown carbon fibers were uniformly dispersed was obtained, and the layers shown in FIG. An electromagnetic wave shielding composite sheet in which the metal foil base double-sided tape aluminum foil 20 μ was laminated as described above was obtained. About the electromagnetic wave shielding composite sheet laminated with the above metal foil, the electromagnetic wave shielding performance was measured by the above measuring method, and the results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Example 4]
In the same manner as in Example 3, a black electromagnetic wave shielding sheet having a thickness of 0.35 mm in which vapor-grown carbon fibers were uniformly dispersed and a smooth surface was obtained. Two sheets of the electromagnetic wave shielding material obtained in this way are bonded to each other with a carbon-based conductive adhesive (KE3491 manufactured by Shin-Etsu Chemical Co., Ltd.), and are further made of colorless and transparent Lintec Co., Ltd. on both sides of the bonded body. PET 50 (A) PL thin 11L was laminated and covered to obtain an electromagnetic wave shielding composite sheet in which two sheets as the final structure were laminated. For this electromagnetic wave shielding composite sheet, the electromagnetic wave shielding performance is measured by the above-described measurement method, and further, the volume resistivity is measured using an MCP T-410 type (4 probe method) device manufactured by Mitsubishi Chemical, The results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Example 5]
In the same manner as in Example 1, a black electromagnetic wave shielding sheet having a thickness of 0.35 mm in which carbon nanotubes were uniformly dispersed and a smooth surface was obtained. Between the two electromagnetic wave shielding sheets thus obtained, the metal foil base double-sided tape aluminum foil 20 μ (trade name, manufactured by Teraoka Seisakusho Co., Ltd.) coated with an acrylic conductive adhesive on both sides is sandwiched. Further, as in the layer configuration shown in FIG. 3, the PET 50 (A) PL thin 11L (trade name, manufactured by Lintec Corporation) is bonded to both outer surfaces of the laminate by an adhesive layer. As a final configuration, an electromagnetic wave shielding composite sheet having a metal foil sandwiched between two sheets was obtained. The electromagnetic wave shielding performance of the electromagnetic wave shielding composite sheet was measured by the above-described measurement method, and the results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Example 6]
In the same manner as in Example 3, a black electromagnetic wave shielding sheet having a thickness of 0.35 mm, a smooth surface, and a black surface was obtained in which the above-mentioned vapor grown carbon fiber VGCF was uniformly dispersed. The metal foil base double-sided tape aluminum foil 20μ is laminated on both surfaces of the electromagnetic wave shielding sheet, and the two metal foil base double-sided tape aluminum foil 20μ is not covered as in the layer structure shown in FIG. The embossed PET 38 × 1-A3 was laminated and coated on the bonding surface side, and an electromagnetic wave shielding composite sheet having metal foil laminated on both sides as a final configuration was obtained. The electromagnetic wave shielding performance of the electromagnetic wave shielding composite sheet was measured by the above-described measurement method, and the results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Comparative Example 1]
Example 1 is the same as Example 1 except that 4.50 g of Ketjen Black EC (trade name, manufactured by Lion Corporation) was used instead of 4.50 g of carbon nanotube, Multiwall carbon nanotube (trade name, manufactured by Aldrich). Exactly in the same manner, a black electromagnetic wave shielding sheet having a thickness of 0.35 mm in which Ketjen Black EC is uniformly dispersed and a smooth surface is obtained. Further, as in Example 1, the layer structure shown in FIG. An electromagnetic wave shielding composite sheet in which metal foils were laminated was obtained. About the electromagnetic wave shielding composite sheet laminated with the above metal foil, the electromagnetic wave shielding performance was measured by the above measuring method, and the results are shown in Table 1 together with main raw material compositions. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Comparative Example 2]
In Example 3, a double laminated electromagnetic wave shielding composite sheet as a final structure was obtained in the same manner as in Example 3 except that 4.55 g of Ketjen Black EC was used instead of the vapor grown carbon fiber. It was. The electromagnetic wave shielding performance and volume specific resistivity of this electromagnetic wave shielding composite sheet were measured by the above-described measurement method using an MCP T-410 type (4 probe method) apparatus manufactured by Mitsubishi Chemical, and the results were used as main raw material compositions. The results are shown in Table 1. Further, a measurement chart of electromagnetic wave shielding performance is shown in FIG.

[Comparative Example 3]
100 g of Zetpol 4310 (HNBR rubber, AN = 18% by mass), 1 g of NOCLACK CD (anti-aging agent), 0.5 g part of NOCRACK MB (anti-aging agent), 2.5 g of TAIC (crosslinking aid) and the cross-linking agent perhexa 25B ( What was used in Example 3 while knead | mixing on the conditions of front roll 15rpm and rear roll 12rpm using the 2 roll type 6 inch test roll (made by Irie Iron Works) which heated 3g of organic peroxide) to 170 degreeC. Add 15 parts by mass of the same vapor-grown carbon fiber VGCF as in step 1, and knead for 30 minutes after completion of addition to obtain a carbon particle-containing rubber that is uniform in appearance. Use 100 ton press (manufactured by Toho Machinery) for this rubber. to bumping twice, and 20 minutes pressing at 170 ° C. · press pressure 150 kgf / cm ^2, thickness 0.5 mm, 100 mm × 1 Appearance was obtained excellent sheet by molding the two large sheets 0 mm. The volume resistivity of this sheet was measured using an MCP T-410 type (4-probe method) apparatus manufactured by Mitsubishi Chemical, but was not within the measurement range, and was estimated to be 10 ⁷ Ω · cm or more. The results are shown in Table 1 together with main raw material compositions.

[Summary of results by Examples and Comparative Examples]
As is clear from the results shown in Table 1, when carbon nanotubes, vapor-grown carbon fibers, and ketjen black EC are compared as conductive fine particles to be added, the volume-specificity of those using carbon nanotubes and vapor-grown carbon fibers The resistivity is overwhelmingly superior to that using Ketjen Black EC, but among those using carbon nanotubes and vapor-grown carbon fibers with excellent conductivity, the resin component is a polymer. When the metal foil is used in combination with the target electromagnetic wave shielding material obtained by adding conductive fine particles in the solution state before becoming a resin and copolymerizing the resin component in that state. In both cases, the electromagnetic wave shielding effect is superior to those of conventional addition methods by kneading in a molten state in a known resin. .

  The electromagnetic shielding material of the present invention is excellent in the dispersibility of the added conductive filler, and thus provides excellent electromagnetic shielding even with a thin sheet, thus preventing electromagnetic interference from the external environment. Protects and prevents malfunctions caused by electromagnetic waves in the high frequency band (GHz band) especially in fields such as electrical and electronic equipment, home appliances, advanced medical electronic equipment, precision electronic equipment, and automotive electronic equipment The industrial effect is great.

Layer structure explanatory drawing of the electromagnetic wave shielding composite sheet of Example 1, Example 3, and Comparative Example 1 Layer structure explanatory drawing of the electromagnetic wave shielding composite sheet of Example 6 Layer structure explanatory drawing of the electromagnetic wave shielding composite sheet of Example 5 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Example 1 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Example 2 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Example 3 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Example 4 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Example 5 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Example 6 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding composite sheet of Comparative Example 1 Electromagnetic wave shielding effect measurement chart of electromagnetic wave shielding sheet of Comparative Example 2

Explanation of symbols

1: Electromagnetic wave shielding sheet 2: Aluminum foil layer 3: Conductive adhesive layer applied to aluminum foil as above 4: PET film layer 5: Adhesive layer applied as above film 6: Embossed PET film layer

Claims (18)

Before polymerization, 0.5 to 20 mass of conductive nano-sized fibrous carbon material having a diameter of 1 to 200 nm and a length of 1 to 20 μm with respect to 100 parts by mass of a polymerizable composition that is dissolved in a liquid or an organic solvent. An electromagnetic wave shielding material obtained by adding a part, mixing in a solution state, polymerizing and solidifying.
2. The electromagnetic wave shielding material according to claim 1, wherein the conductive nano-sized fibrous carbon material is a carbon nanotube.
2. The electromagnetic wave shielding material according to claim 1, wherein the conductive nano-sized fibrous carbon material is a vapor-grown carbon fiber.
The said polymerizable composition has as a main component the liquid acrylonitrile butadiene copolymer by which the both terminal was substituted by the carboxyl group, and an epoxy-type resin, It is any one of Claim 1 to 3 characterized by the above-mentioned. Electromagnetic wave shielding material as described in any one of these.
The electromagnetic wave shielding material according to claim 4, wherein the epoxy resin is a bisphenol A diglycidyl ether type epoxy resin.
6. The electromagnetic wave shielding material according to claim 1, wherein the mixed solution is polymerized and solidified after being formed into a desired shape.
The electromagnetic wave shielding composite sheet according to claim 6, wherein the electromagnetic wave shielding material is in a sheet form and is formed by laminating a metal foil on at least one surface thereof.
The electromagnetic wave shielding according to claim 6, comprising a plurality of sheet-like electromagnetic wave shielding material layers, and a metal foil sandwiched between at least one interface between adjacent sheet-like electromagnetic wave shielding material layers. Composite sheet.
9. The electromagnetic wave shielding composite sheet according to claim 7, wherein each of the electromagnetic wave shielding materials has a thickness of 1 mm or less, and each metal foil has a thickness of 5 μm to 50 μm.
The electromagnetic shielding composite sheet according to any one of claims 7 to 9, wherein the metal foil is at least one selected from the group consisting of an aluminum foil, a copper foil, and a nickel foil.
0.5 to 20 parts by mass of a conductive nano-sized fibrous carbon material having a diameter of 1 to 200 nm and a length of 1 to 20 μm is added to 100 parts by mass of a polymerizable composition dissolved in a liquid or an organic solvent. A method for producing an electromagnetic wave shielding material, which comprises mixing and then polymerizing and solidifying.
The method for producing an electromagnetic wave shielding material according to claim 11, wherein the polymerizable composition comprises a liquid acrylonitrile butadiene rubber having both ends substituted with carboxyl groups and a bisphenol A diglycidyl ether type epoxy resin.
The method for producing an electromagnetic wave shielding material according to claim 11 or 12, wherein 1 to 5 parts by mass of a tertiary amine catalyst as a polymerization catalyst is used in combination with 100 parts by mass of the polymerizable composition.
The tertiary amine catalyst is at least one of NN-dimethylmethanamine, NN-diethylethanamine, NN-dipropylpropanamine, NN-dibutylbutanamine, NN-diphenylbenzeneamine. The manufacturing method of the electromagnetic wave shielding material of Claim 13.
15. The method for producing an electromagnetic wave shielding material according to claim 13, wherein the polymerization reaction is solidified by heating at 150 to 180 ° C. for 15 to 20 hours.
The method for producing an electromagnetic wave shielding material according to claim 11 or 12, wherein when a tertiary amine catalyst is not used as the polymerization catalyst, heating is performed at 150 to 180 ° C for 30 to 40 hours.
The method for producing an electromagnetic wave shielding material according to any one of claims 11 to 16, wherein the mixed solution is formed into a desired shape and then polymerized and solidified.
The electromagnetic wave according to claim 17, wherein the method of forming the desired shape is to first remove the solvent after casting the polymerizable composition solution into a mold having an inner surface that is releasable. Manufacturing method of shielding material.

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