Electromagnetic wave shielding member

Abstract

To provide an electromagnetic wave shielding member which is sufficiently reduced in weight.SOLUTION: An electromagnetic wave shielding member includes a conductive resin part containing a resin and a conductive fiber, and a plurality of air gaps, wherein at least a part of the plurality of air gaps communicate with each other.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave shielding member. [Background technology]

[0002] Conventionally, in order to protect electronic components for in-vehicle use from electromagnetic waves, housings having electromagnetic wave shielding properties have been used as housings for electronic components. Metal housings made of metal materials such as aluminum are often used as such housings.

[0003] Metals such as aluminum have high electrical conductivity, and a housing made of such a metal has high electromagnetic wave shielding properties. On the other hand, metals are heavy, and making a housing out of such a metal increases the weight of the vehicle body.

[0004] Incidentally, in recent years, efforts have been made to reduce the weight of automobile bodies in order to improve fuel efficiency. As a method for reducing the weight, various members made of metallic materials have been replaced with members made of lightweight materials such as resin.

[0005] For example, if a housing made of metal is replaced with a housing made of conductive resin, which is a lighter material, the weight of the vehicle body can be reduced.

[0006] As such a conductive resin, Patent Document 1 discloses an electromagnetic wave absorbing sheet in which carbon fibers are dispersed in rubber so that the carbon fibers are not exposed on the rubber surface. Furthermore, Patent Document 1 discloses that a foaming agent is used when the radio wave absorbing sheet is manufactured, and air bubbles are provided in the radio wave absorbing sheet, thereby reducing the weight of the sheet. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-135189 A Summary of the Invention [Problem to be solved by the invention]

[0008] Although the electromagnetic wave absorbing sheet described in Patent Document 1 can achieve a certain degree of weight reduction, there is a problem in that the electromagnetic wave absorbing sheet cannot be sufficiently lightened in weight even if the pores are made larger and more numerous.

[0009] The present invention is an invention for solving the above problems, and an object of the present invention is to provide an electromagnetic wave shielding member that is sufficiently lightweight. [Means for solving the problem]

[0010] The electromagnetic wave shielding member of the present invention is characterized in that it comprises a conductive resin part containing resin and conductive fibers, and a plurality of voids, at least some of which are interconnected.

[0011] The electromagnetic wave shielding member of the present invention has electrical conductivity as a whole because the conductive resin portion contains conductive fibers. Therefore, electromagnetic waves that reach the electromagnetic wave shielding member of the present invention are reflected and absorbed by the conductive resin portion. In other words, the electromagnetic wave shielding member of the present invention can shield electromagnetic waves.

[0012] In the electromagnetic shielding member of the present invention, at least some of the gaps are interconnected, which increases the proportion of gaps in the electromagnetic shielding member and reduces the weight of the electromagnetic shielding member.

[0013] The electromagnetic wave shielding member of the present invention has a density of 0.1 to 1.5 g / cm 3 It is preferable that: Density: 0.1g / cm 3 If it is less than this, the strength of the electromagnetic wave shielding member is likely to decrease. Density: 1.5g / cm 3 If it exceeds this value, the weight of the entire electromagnetic wave shielding member is likely to increase.

[0014] In the electromagnetic wave shielding member of the present invention, the porosity of the electromagnetic wave shielding member is preferably 20 to 90 vol %. If the void ratio is within the above range, the electromagnetic wave shielding member can be sufficiently light-weighted. If the void ratio is less than 20 vol %, the proportion of the conductive resin portion will be high, making it difficult to reduce the weight of the electromagnetic wave shielding member. If the porosity exceeds 90 vol%, the strength is likely to decrease.

[0015] In the electromagnetic wave shielding member of the present invention, the electromagnetic wave shielding member is preferably in a sheet shape or a shape constituting a housing. Such an electromagnetic wave shielding member can be easily used as a housing for electronic components.

[0016] In the electromagnetic wave shielding member of the present invention, the conductive fibers are preferably oriented in a direction perpendicular to the thickness of the member. When the conductive fibers are oriented in a direction perpendicular to the thickness, a plurality of conductive fibers are likely to be in continuous contact with each other in the direction of the orientation of the conductive fibers. This makes it easier to ensure the conductivity of the conductive resin portion in the direction perpendicular to the thickness direction. As a result, the electromagnetic wave shielding properties of the electromagnetic wave shielding member are likely to be improved.

[0017] In the electromagnetic wave shielding member of the present invention, in a cross section parallel to the thickness direction of the electromagnetic wave shielding member, the void has a shape having a major axis and a minor axis, and it is preferable that the major axis of the void is oriented in a direction perpendicular to the thickness direction. An electromagnetic wave shielding member in which the conductive fibers are oriented in a direction perpendicular to the thickness direction can be produced by papermaking the conductive fibers. When the conductive fibers are made into a paper sheet, voids tend to form around the conductive fibers. The voids thus formed have a shape having a major axis and a minor axis, and the major axis tends to be oriented in the orientation direction of the conductive fibers (that is, the direction perpendicular to the thickness direction). Therefore, it can be said that an electromagnetic shielding material in which the major axes of the voids are oriented in a direction perpendicular to the thickness direction is an electromagnetic shielding material produced by papermaking conductive fibers.

[0018] In a cross section of the electromagnetic wave shielding member of the present invention, the conductive resin portion preferably forms a mesh-like structure. When the conductive resin portion is in a mesh shape, the proportion of voids can be increased while maintaining electrical conductivity.

[0019] In the electromagnetic wave shielding member of the present invention, the conductive fibers may be exposed in the gap, and at least a part of the wall surface of the gap may be formed from the resin. Even in this embodiment, the electromagnetic wave shielding member has sufficient electromagnetic wave shielding properties.

[0020] In the electromagnetic wave shielding member of the present invention, the conductive fibers preferably have an average fiber length of 1 to 100 mm. If the average fiber length of the conductive fibers is less than 1 mm, the number of contact points between the conductive fibers per conductive fiber is likely to be small, which tends to reduce the electrical conductivity of the electromagnetic shielding member, and as a result, the electromagnetic shielding properties of the electromagnetic shielding member are likely to be reduced. If the average fiber length of the conductive fibers exceeds 100 mm, the conductive fibers are likely to break during the production of the electromagnetic shielding member, and the electrical conductivity of the produced electromagnetic shielding member is likely to decrease, which in turn makes the electromagnetic shielding property of the electromagnetic shielding member more likely to decrease.

[0021] In the electromagnetic wave shielding member of the present invention, the conductive fibers may have at least one shape selected from the group consisting of a straight shape and a crimped shape. Regardless of the shape of the conductive fibers, the conductivity of the electromagnetic wave shielding member can be ensured.

[0022] In the electromagnetic wave shielding member of the present invention, the conductive fibers preferably include at least one type selected from the group consisting of carbon fibers, metal fibers, and fibers coated with a metal. These conductive fibers have sufficient conductivity and therefore can improve the conductivity of the electromagnetic wave shielding member, thereby improving the electromagnetic wave shielding properties of the electromagnetic wave shielding member.

[0023] In the electromagnetic wave shielding member of the present invention, the resin preferably includes at least one selected from the group consisting of thermoplastic resins and thermosetting resins. If these resins are used, the electromagnetic wave shielding member can be easily molded.

[0024] In the electromagnetic wave shielding member of the present invention, the weight ratio of the resin to the conductive fibers in the conductive resin portion is preferably [resin]:[conductive fibers]=95:5 to 30:70. When the weight ratio of the resin to the conductive fibers is within the above range, the electromagnetic wave shielding member can be made lighter while still achieving both strength and conductivity.

[0025] In the electromagnetic wave shielding member of the present invention, it is preferable that the conductive resin portion further contains conductive particles, and it is preferable that the conductive fibers and the conductive particles are in contact with each other. When the conductive resin portion contains conductive particles, the conductive particles come into contact with each other and with the conductive fibers, improving the conductivity of the conductive resin portion, thereby improving the conductivity of the electromagnetic wave shielding member and the electromagnetic wave shielding properties of the electromagnetic wave shielding member. Effect of the Invention

[0026] According to the present invention, it is possible to provide an electromagnetic wave shielding member that is sufficiently lightweight. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a perspective view showing an example of an electromagnetic wave shielding member according to a first embodiment of the present invention. [Figure 2A] FIG. 2A is a cross-sectional view of the electromagnetic shielding member shown in FIG. 1 taken along line AA. [Figure 2B]FIG. 2B is an enlarged view of the dashed line portion shown in FIG. 2A. [Diagram 3] FIG. 3 is a diagram showing an example of a slurry forming step in the method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a papermaking step in the method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention. [Diagram 5] FIG. 5 is a cross-sectional view that illustrates an example of a cross section of a sheet-like material obtained by a papermaking process in a direction perpendicular to the thickness direction. [Figure 6] FIG. 6 is a diagram showing an example of a heat pressing step in the method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view that shows a schematic example of a cross section of an electromagnetic wave shielding member obtained by a heat pressing process, taken along a direction perpendicular to the thickness direction. [Figure 8] FIG. 8 is a cross-sectional view showing an example of an electromagnetic wave shielding member according to a second embodiment of the present invention. [Figure 9] FIG. 9 is a photograph of a parallel cross section in the thickness direction of the electromagnetic shielding member according to Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The electromagnetic wave shielding member of the present invention will be specifically described below. However, the present invention is not limited to the following configuration, and can be appropriately modified and applied within the scope that does not change the gist of the present invention. Note that the present invention also includes a combination of two or more of the individual preferred configurations of the present invention described below.

[0029] (First embodiment) An electromagnetic wave shielding member according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an example of an electromagnetic wave shielding member according to a first embodiment of the present invention. FIG. 2A is a cross-sectional view of the electromagnetic shielding member shown in FIG. 1 taken along line AA. FIG. 2B is an enlarged view of the dashed line portion shown in FIG. 2A.

[0030] The electromagnetic wave shielding member 1 shown in FIG. 1 is in a sheet shape and has a thickness direction (the direction indicated by the symbol "T" in FIG. 1).

[0031] As shown in FIGS. 2A and 2B, the electromagnetic wave shielding member 1 includes a conductive resin portion 10 including a resin 11 and conductive fibers 12, and a plurality of void portions 20. Moreover, at least some of the plurality of gaps 20 are in communication with each other.

[0032] In the electromagnetic wave shielding member 1, the conductive resin portion 10 contains the conductive fibers 12, and therefore the electromagnetic wave shielding member 1 as a whole is conductive. That is, the conductive fibers 12 come into contact with each other and are electrically connected to each other, so that the conductive resin portion 10 becomes conductive. Furthermore, since the conductive resin portion 10 has conductivity, the electromagnetic waves that reach the electromagnetic wave shielding member 1 are reflected and absorbed by the conductive resin portion 10. That is, the electromagnetic wave shielding member 1 can shield electromagnetic waves.

[0033] In the electromagnetic shielding member 1, at least some of the gaps 20 are in communication with each other. This allows the proportion of the gaps 20 in the electromagnetic shielding member 1 to be increased, and the electromagnetic shielding member 1 to be made lighter.

[0034] The porosity of the electromagnetic wave shielding member 1 (that is, the proportion of the voids 20 in the conductive resin portion 10) is preferably 20 to 90 vol %, and more preferably 25 to 55 vol %. If the void ratio is within the above range, the electromagnetic shielding member 1 can be made sufficiently lightweight. If the void ratio is less than 20 vol %, the proportion of the conductive resin portion will be high, making it difficult to reduce the weight of the electromagnetic wave shielding member. If the porosity exceeds 90 vol%, the strength is likely to decrease.

[0035] In this specification, the "porosity of the electromagnetic wave shielding material" can be calculated from the volume and weight of the electromagnetic wave shielding material and the density of the conductive resin portion. The volume of the electromagnetic wave shielding member can be measured with a tape measure. The weight of the electromagnetic wave shielding member can be measured by a weighing scale and is equal to the weight of the conductive resin portion contained in the electromagnetic wave shielding member. The density of the conductive resin portion is calculated by the following method. The conductive resin part is cut out from any part filled with the electromagnetic wave shielding material into 25 cubes with a side length of 20 mm. Next, the weight of each cube is measured and the density of each cube is calculated. The average value of the densities is defined as the density of the conductive resin portion. The porosity of the electromagnetic wave shielding material can be calculated by the following formula (1). Porosity of electromagnetic wave shielding material (%) = 100 - (density of conductive resin part -1 × Weight of conductive resin part × Volume of electromagnetic wave shielding material -1 ×100) (1)

[0036] The electromagnetic wave shielding member 1 has a density of 0.1 to 1.5 g / cm 3 and preferably 0.1 to 1.2 g / cm 3 It is more preferable that: Density: 0.1g / cm 3 If it is less than this, the strength of the electromagnetic wave shielding member is likely to decrease. Density: 1.5g / cm 3 If it exceeds this value, the weight of the entire electromagnetic wave shielding member is likely to increase.

[0037] In the electromagnetic wave shielding member 1 , the conductive fibers 12 may be exposed in the gaps 20 , and at least a part of the wall surface of the gaps 20 may be formed from the resin 11 . Even in this embodiment, the electromagnetic wave shielding member 1 has sufficient electromagnetic wave shielding properties.

[0038] In the electromagnetic wave shielding member 1, the conductive resin portion 10 preferably forms a mesh-like structure in the cross section of the electromagnetic wave shielding member 1. When the conductive resin portion 10 has a mesh shape, the proportion of the void portions 20 can be increased while maintaining the conductivity.

[0039] The thickness of the electromagnetic wave shielding member 1 is not particularly limited, but is preferably 1.0 to 10.0 mm, and more preferably 2.0 to 7.0 mm.

[0040] As shown in FIGS. 2A and 2B, in the electromagnetic shielding material 1, the conductive fibers 12 are oriented in a direction P perpendicular to the thickness direction T of the electromagnetic shielding material 1. When the conductive fibers 12 are oriented in a direction P perpendicular to the thickness direction T, a plurality of conductive fibers 12 are easily in contact with each other so as to be continuous in the orientation direction of the conductive fibers 12. Therefore, the conductivity of the conductive resin portion 10 in the direction P perpendicular to the thickness direction T can be easily ensured. As a result, the electromagnetic wave shielding properties of the electromagnetic wave shielding member 1 tend to improve.

[0041] In this specification, "the conductive fibers are oriented in a direction perpendicular to the thickness direction of the electromagnetic shielding material" means that in any 3 mm x 3 mm field of view on a cross section perpendicular to the thickness direction of the electromagnetic shielding material, the proportion of conductive fibers that form an angle of 60° to 120° with the thickness direction of the electromagnetic shielding material is 90 to 100% of all conductive fibers observed in the field of view.

[0042] In the electromagnetic wave shielding member of the present invention, the conductive fibers do not need to be oriented in a fixed direction.

[0043] In the electromagnetic wave shielding member 1, the conductive fibers 12 preferably have an average fiber length of 1.0 to 100 mm, and more preferably 1.0 to 10.0 mm. If the average fiber length of the conductive fibers is less than 1.0 mm, the number of contact points between the conductive fibers per conductive fiber is likely to be small, which tends to reduce the electrical conductivity of the electromagnetic shielding member, and as a result, the electromagnetic shielding properties of the electromagnetic shielding member are likely to be reduced. If the average fiber length of the conductive fibers exceeds 100 mm, the conductive fibers are likely to break during the production of the electromagnetic shielding member, and the electrical conductivity of the produced electromagnetic shielding member is likely to decrease, which in turn makes the electromagnetic shielding property of the electromagnetic shielding member more likely to decrease.

[0044] In the electromagnetic wave shielding member 1, the conductive fibers 12 preferably have an average fiber diameter of 1.0 to 20.0 μm, and more preferably 3.0 to 10.0 μm. If the average fiber diameter of the conductive fibers is less than 1.0 μm, the strength of the conductive fibers is low, so that the conductive fibers are likely to break during the production of the electromagnetic shielding member, and the electrical conductivity of the produced electromagnetic shielding member is likely to decrease, which in turn makes the electromagnetic shielding property of the electromagnetic shielding member likely to decrease. If the average fiber diameter of the conductive fibers exceeds 20.0 μm, the flexibility of the conductive fibers decreases, making it difficult to form the electromagnetic wave shielding member into a desired shape. Furthermore, during the production of the electromagnetic wave shielding member, stress is likely to be generated, and the conductive fibers are likely to break.

[0045] In the electromagnetic wave shielding member 1, the conductive fibers 12 may have at least one shape selected from the group consisting of a straight shape and a crimped shape. Regardless of the shape of the conductive fibers 12, the conductivity of the electromagnetic wave shielding member 1 can be ensured.

[0046] In the electromagnetic wave shielding member 1, the conductive fibers 12 preferably include at least one type selected from the group consisting of carbon fibers, metal fibers, and fibers coated with a metal, and are more preferably carbon fibers. These conductive fibers 12 have sufficient conductivity, and therefore can improve the conductivity of the electromagnetic wave shielding member 1, thereby improving the electromagnetic wave shielding properties of the electromagnetic wave shielding member 1. In particular, if the conductive fibers 12 are carbon fibers, the electromagnetic shielding member 1 can be made lighter in weight.

[0047] In the electromagnetic wave shielding member 1, the resin 11 preferably contains at least one type selected from the group consisting of thermoplastic resins and thermosetting resins. If these resins are used, the electromagnetic wave shielding member can be easily molded.

[0048] Examples of thermoplastic resins include polyphenylene sulfide resin, polyethylene resin, polypropylene resin, polystyrene resin, acrylonitrile butadiene styrene resin, polyamide resin, polyacetal resin, polycarbonate resin, polytetrafluoroethylene resin, polyethersulfone resin, polyetheretherketone resin, polyimide resin, and liquid crystal polymer resin.

[0049] Examples of the thermosetting resin include phenol resin, epoxy resin, polyurethane resin, melamine resin, and unsaturated polyester resin.

[0050] In the electromagnetic wave shielding member 1, the weight ratio of the resin 11 to the conductive fibers 12 in the conductive resin portion 10, [resin]:[conductive fibers], is preferably 95:5 to 30:70, and more preferably 90:10 to 40:60. When the weight ratio of the resin 11 to the conductive fibers 12 is within the above range, the electromagnetic wave shielding member 1 can be made lighter while still maintaining both its strength and conductivity.

[0051] 2A and 2B, in the electromagnetic wave shielding member 1, the conductive resin portion 10 further contains conductive particles 13. Furthermore, the conductive fibers 12 and the conductive particles 13 are in contact with each other.

[0052] When the conductive resin part 10 contains the conductive particles 13, the conductive particles 13 come into contact with each other and with the conductive fibers 12, thereby improving the conductivity of the conductive resin part 10. As a result, the conductivity of the electromagnetic wave shielding member 1 is improved, and the electromagnetic wave shielding properties of the electromagnetic wave shielding member 1 are improved.

[0053] The conductive particles 13 may be made of any material as long as it has conductivity. For example, the conductive particles 13 may be carbon particles, metal particles, or particles coated with a metal. Of these, carbon particles are preferred. If the conductive particles 13 are carbon particles, the electromagnetic shielding member 1 can be made lighter in weight.

[0054] The average particle size of the conductive particles 13 is preferably 1 to 200 μm, and more preferably 1 to 30 μm. When the average particle diameter of the conductive particles 13 is within the above range, the conductive particles 13 and the conductive particles 13 and the conductive fibers 12 tend to come into suitable contact with each other.

[0055] The weight ratio of the conductive particles 13 in the conductive resin portion 10 is preferably 1 to 50% by weight, and more preferably 10 to 40% by weight. If the weight ratio of the conductive particles is less than 10% by weight, the amount of conductive particles is small, making it difficult for the conductive particles to come into contact with each other and with the conductive fibers, and making it difficult to achieve the effect of improving the conductivity of the conductive resin part. If the weight ratio of the conductive particles exceeds 40% by weight, it becomes difficult to reduce the weight of the electromagnetic wave shielding member.

[0056] In the electromagnetic wave shielding member of the present invention, the conductive resin portion does not necessarily need to contain conductive particles.

[0057] The electrical resistivity of the electromagnetic wave shielding member 1 is preferably 0.1 to 20 Ω·m.

[0058] The use of the electromagnetic wave shielding member 1 is not particularly limited, but it is preferably used as an electromagnetic wave shielding member for protecting electronic parts mounted on vehicles from electromagnetic waves.

[0059] Next, an example of a method for producing the electromagnetic wave shielding member according to the first embodiment of the present invention will be described. The electromagnetic wave shielding member according to the first embodiment of the present invention can be produced, for example, by a papermaking method for producing conductive fibers. When the conductive fibers are made into a paper sheet, voids tend to form between the conductive fibers, and these voids remain in the electromagnetic wave shielding member that is manufactured through a heat pressing process. Therefore, the above papermaking method makes it possible to produce an electromagnetic wave shielding member having voids therein. If there is a gap inside the electromagnetic wave shielding member, the electromagnetic wave shielding member can be made lighter.

[0060] Such a papermaking method includes a method including (1) a slurry formation step, (2) a papermaking step, and (3) a heat pressing step. Each step will be described below with reference to the drawings.

[0061] (1) Slurry formation process FIG. 3 is a diagram showing an example of a slurry forming step in the method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention. As shown in FIG. 3, in the slurry formation step, at least one type of resin fiber 11a selected from the group consisting of solid resins and semi-solid resins, conductive fiber 12, and water 14 are mixed to prepare a slurry 10a.

[0062] By using the resin fibers 11a, the resin fibers 11a and the conductive fibers 12 are both produced in a papermaking process, which will be described later. In the sheet-like material thus formed, voids are likely to be formed between the resin fibers 11a, between the resin fibers 11a and the conductive fibers 12, and between the conductive fibers 12. Voids are also preferably formed in the electromagnetic wave shielding member obtained by heat pressing such a sheet-like material. Therefore, the electromagnetic wave shielding member can be suitably reduced in weight.

[0063] In the slurry formation step, instead of the resin fibers 11a, at least one type of resin selected from the group consisting of non-fibrous solid resins and semi-solid resins may be used.

[0064] In this specification, the term "solid resin and semi-solid resin" refers to a resin having a fixed shape.

[0065] In the slurry formation step, an amorphous resin having high fluidity may be mixed into the slurry 10a.

[0066] In the slurry formation step, conductive particles may be mixed into the slurry 10a.

[0067] In the slurry formation step, other materials such as a dispersing agent and an organic binder may be mixed into the slurry 10a. The addition of a dispersant can prevent the conductive fibers from agglomerating. The addition of an organic binder makes it easier to form a sheet-like material in the papermaking process described below.

[0068] The weight percentage of water in the slurry 10a is not particularly limited, but is preferably 99.00 to 99.99% by weight, and more preferably 99.30 to 99.99% by weight. When the weight ratio of water is within the above range, a sheet-like material can be suitably formed in the papermaking step described below.

[0069] The preferred types, shapes, and other properties of the resin and conductive fibers used in the slurry formation step are as described above, and therefore will not be described here.

[0070] (2) Papermaking process FIG. 4 is a diagram showing an example of a papermaking step in the method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view that illustrates an example of a cross section of a sheet-like material obtained by a papermaking process in a direction perpendicular to the thickness direction.

[0071] As shown in FIG. 4, in the papermaking process, the slurry 10a is put into a papermaking machine 51 and dehydrated to produce a sheet-like material 10b.

[0072] As shown in FIG. 5, when the sheet-like material 10b is produced by papermaking, the resin fibers 11a and the conductive fibers 12 tend to be oriented in a direction P perpendicular to the thickness direction T of the sheet-like material 10b. Additionally, voids 20a are formed around the resin fibers 11a and the conductive fibers 12.

[0073] In the papermaking process, the bulk density of the sheet-like material 10b is 0.1 to 1.5 g / cm 3 It is preferable to make the paper so that the density is 0.1 to 1.2 g / cm 3 It is more preferable to perform papermaking so that the above-mentioned condition is satisfied. The bulk density of the sheet-like material 10b being within the above range means that gaps are suitably formed between the conductive fibers 12. Therefore, the electromagnetic shielding member 1 obtained by hot pressing such a sheet-like material 10b also has favorable voids formed therein. Therefore, the electromagnetic wave shielding member 1 can be suitably made lighter in weight.

[0074] (3) Heat pressing process FIG. 6 is a diagram showing an example of a heat pressing step in the method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view that shows a schematic example of a cross section of an electromagnetic wave shielding member obtained by a heat pressing process, taken along a direction perpendicular to the thickness direction.

[0075] Next, as shown in FIG. 6, the sheet-like material 10b is placed in a press machine 52 and subjected to heat pressing. When the resin fibers 11a are made of a thermoplastic resin, the resin fibers 11a are first softened by heat and then hardened, thereby producing the electromagnetic wave shielding member 1. When the resin fibers 11a are made of a thermosetting resin, the conductive fibers 12 are pressed into the resin fibers 11a, and then the resin fibers 11a are hardened by heat, thereby producing the electromagnetic wave shielding member 1.

[0076] The heat pressing process hardens the resin, and the voids 20a formed around the resin fibers 11a and the conductive fibers 12 of the sheet-like material 10b are fixed, forming the void portions 20.

[0077] The conditions for the heat press are not particularly limited, and are preferably determined appropriately depending on the material to be used. For example, the temperature of the heat press is preferably 200 to 350°C, and more preferably 280 to 320°C. For example, the pressure of the heat press is preferably 1 to 10 MPa, and more preferably 1 to 5 MPa.

[0078] As shown in FIG. 7 , in the electromagnetic shielding member 1 manufactured in this manner, in a cross section parallel to the thickness direction T of the electromagnetic shielding member 1, the void portion 20 has a shape having a major axis A1 and a minor axis A2, and the major axis A1 of the void portion 20 is oriented in a direction P perpendicular to the thickness direction T. As described above, when the conductive fibers 12 are made into a paper, the voids 20a tend to be generated around the conductive fibers 12. The voids 20a thus formed have a shape having a major axis A1 and a minor axis A2, and the major axis A1 tends to be oriented in the orientation direction of the conductive fibers 12 (that is, the direction P perpendicular to the thickness direction T). Therefore, it can be said that the electromagnetic shielding material 1 in which the major axes A1 of the voids 20 are oriented in the direction P perpendicular to the thickness direction T is produced by papermaking the conductive fibers 12.

[0079] The method for producing the electromagnetic wave shielding member according to the first embodiment of the present invention described above is a papermaking method. However, the manufacturing method of the electromagnetic wave shielding member of the present invention is not particularly limited as long as the electromagnetic wave shielding member includes a conductive resin part containing resin and conductive fibers, and a plurality of void parts, and at least a portion of the plurality of void parts are connected.

[0080] Second embodiment Next, an electromagnetic wave shielding member according to a second embodiment of the present invention will be described.

[0081] FIG. 8 is a cross-sectional view showing an example of an electromagnetic wave shielding member according to a second embodiment of the present invention. The electromagnetic wave shielding member 101 shown in FIG. 8 has a shape constituting a housing 101a. Except for its shape, the electromagnetic shielding member 101 has the same preferable configuration as the electromagnetic shielding member 1 according to the first embodiment of the present invention in terms of materials and the like.

[0082] By arranging electronic components (not shown) inside the electromagnetic wave shielding member 101, it is possible to block electromagnetic waves from the outside, and also to prevent electromagnetic waves generated by the electronic components from leaking to the outside.

[0083] It is preferable that the shape of the electromagnetic wave shielding member 101 is appropriately set according to the shape of the electronic components to be arranged and the arrangement position of the electromagnetic wave shielding member 101 .

[0084] The electromagnetic wave shielding member 101 can be produced in the above-described method for producing an electromagnetic wave shielding member according to the first embodiment of the present invention by producing a sheet-like material through a papermaking process, processing the sheet such as by folding the sheet into a predetermined shape, and then performing heat pressing.

[0085] The present specification discloses the following:

[0086] The present disclosure (1) is an electromagnetic wave shielding member including a conductive resin part containing resin and conductive fibers, and a plurality of void parts, wherein at least a portion of the plurality of void parts are interconnected.

[0087] The present disclosure (2) is a densitometer having a density of 0.1 to 1.5 g / cm 3 This is the electromagnetic wave shielding member according to the present disclosure (1).

[0088] The present disclosure (3) is the electromagnetic wave shielding member according to the present disclosure (1) or (2), wherein the electromagnetic wave shielding member has a porosity of 20 to 90 vol %.

[0089] The present disclosure (4) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (3), wherein the electromagnetic wave shielding member is in a sheet shape or a shape constituting a housing.

[0090] The present disclosure (5) is the electromagnetic wave shielding member according to the present disclosure (4), in which the conductive fibers are oriented in a direction perpendicular to the thickness direction of the electromagnetic wave shielding member.

[0091] The present disclosure (6) is an electromagnetic wave shielding member according to the present disclosure (5), in which, in a cross section parallel to the thickness direction of the electromagnetic wave shielding member, the void has a shape having a major axis and a minor axis, and the major axis of the void is oriented in a direction perpendicular to the thickness direction.

[0092] The present disclosure (7) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (6), in which the conductive resin portion forms a mesh-like structure in a cross section of the electromagnetic wave shielding member.

[0093] The present disclosure (8) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (7), in which the conductive fibers are exposed in the voids.

[0094] The present disclosure (9) is the electromagnetic shielding member according to any one of the present disclosures (1) to (8), in which at least a part of the wall surface of the gap is formed from the resin.

[0095] The present disclosure (10) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (9), wherein the conductive fibers have an average fiber length of 1 to 100 mm.

[0096] The present disclosure (11) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (10), wherein the conductive fibers have at least one shape selected from the group consisting of a straight shape and a crimped shape.

[0097] The present disclosure (12) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (11), wherein the conductive fiber includes at least one selected from the group consisting of carbon fiber, metal fiber, and metal-coated fiber.

[0098] The present disclosure (13) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (12), in which the resin includes at least one selected from the group consisting of a thermoplastic resin and a thermosetting resin.

[0099] The present disclosure (14) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (13), wherein the weight ratio of the resin to the conductive fibers in the conductive resin part is [resin]:[conductive fibers]=95:5 to 30:70.

[0100] The present disclosure (15) is the electromagnetic wave shielding member according to any one of the present disclosures (1) to (14), in which the conductive resin portion further contains conductive particles.

[0101] The present disclosure (16) is the electromagnetic wave shielding member according to the present disclosure (15), in which the conductive fibers and the conductive particles are in contact with each other. EXAMPLES

[0102] EXAMPLES Hereinafter, examples that more specifically disclose the present invention will be described, however, the present invention is not limited to these examples.

[0103] Example 1 (1) Slurry formation process A dispersant (product name: Meikasurf BH-25, manufacturer: Meisei Chemical Industry Co., Ltd.), carbon fiber (average fiber length: 3 mm, average fiber diameter: 7 μm) as conductive fiber, and polyphenylene sulfide resin fiber (thermoplastic resin with a softening point of approximately 260°C, average fiber length: 3 mm, average fiber diameter: 14.5 μm) as resin were added to water and mixed to prepare a slurry. The weight ratio of the carbon fibers to the polyphenylene sulfide resin fibers was carbon fibers:polyphenylene sulfide resin fibers=20:80.

[0104] (2) Papermaking process Next, the prepared slurry was placed in a papermaking machine and dehydrated to a bulk density of 0.66 g / cm 3 A sheet-like product was produced.

[0105] (3) Heat pressing process Next, the obtained sheet-like material was placed in a press machine and subjected to heat pressing under conditions of 2 MPa, 300° C., and 10 minutes. The polyphenylene sulfide resin fibers were softened by this heat pressing.

[0106] Thereafter, the mixture was left to stand until it reached room temperature, and the polyphenylene sulfide resin was cured.

[0107] Through the above steps, an electromagnetic wave shielding member according to Example 1 having a thickness of 3.6 mm was manufactured.

[0108] The electromagnetic shielding member according to Example 1 was cut parallel to the thickness direction, and a photograph of the cross section was taken. The photograph is shown in FIG. FIG. 9 is a photograph of a parallel cross section in the thickness direction of the electromagnetic shielding member according to Example 1. As shown in FIG. 9, in Example 1, it was confirmed that the conductive resin part 10 was composed of a resin 11 and conductive fibers 12, and that the conductive fibers 12 were oriented perpendicular to the thickness direction T. Furthermore, in Example 1, it was confirmed that the electromagnetic shielding member 1 contained a plurality of gaps 20, and the plurality of gaps 20 were in communication with each other.

[0109] The porosity of the electromagnetic shielding member of Example 1 was 53.1%. The density was 0.66 g / cm 3 It was. Therefore, it was found that the electromagnetic shielding member according to Example 1 was sufficiently lightweight.

[0110] The electrical resistivity of the electromagnetic shielding member according to Example 1 was 2.79 Ω·m.

[0111] (Measurement of electromagnetic shielding effect) The electromagnetic wave shielding effect of the electromagnetic wave shielding member according to Example 1 was measured by the KEC method. When measuring the electromagnetic wave shielding effect, the electromagnetic wave shielding member according to Example 1 was cut into a size of 150 mm length×150 mm width to prepare a measurement sample. As a result, the shielding effect against electromagnetic waves with frequencies from 100 kHz to 1 GHz was 40 dB or more. Therefore, it was found that the electromagnetic wave shielding member according to Example 1 exhibited a sufficient electromagnetic wave shielding effect.

[0112] Example 2 Porosity 30.8%, density 0.98g / cm 3 An electromagnetic wave shielding portion according to Example 2 was manufactured in the same manner as in Example 1, except that the thickness was 2.5 mm. When the electromagnetic wave shielding effect of Example 2 was measured, the shielding effect against electromagnetic waves having frequencies of 100 kHz to 1 GHz was 40 dB or more.

[0113] Comparative Example 1 Using an injection molding machine (Japan Steel Works, J220ADS-300H), a composition was prepared by kneading PPS pellets and carbon fibers (average fiber length: 3 mm, average fiber diameter: 7 μm) in a weight ratio of 70:30, and injection molding was performed into a flat plate. In this way, an electromagnetic wave shielding portion according to Comparative Example 1 having a thickness of 3.75 mm was manufactured. The density of the electromagnetic wave shielding portion according to Comparative Example 1 is 1.49 g / cm 3 and the porosity was 0%. That is, the electromagnetic wave shielding portion according to Comparative Example 1 had no voids. The electrical resistivity of the electromagnetic shielding member of Comparative Example 1 was 21.9 Ω·m. When the electromagnetic wave shielding effect of the comparative example 1 was measured, the shielding effect against electromagnetic waves of 100 kHz to 1 GHz was 40 dB or less, which was not sufficient. [Explanation of symbols]

[0114] 1, 101 Electromagnetic wave shielding material 10 Conductive resin part 10a Slurry 10b Sheet-like object 11 Resin 11a Resin fiber 12 Conductive fibers 13 Conductive particles 14 water 20 Cavity 20a void 51 Paper making machine 52 Press Machine 101a Case

Claims

1. A conductive resin portion including a resin and a conductive fiber; An electromagnetic wave shielding member including a plurality of gaps, The electromagnetic wave shielding member according to claim 1, wherein at least some of the plurality of voids are in communication with each other.

2. Density: 0.1 to 1.5 g / cm ３ 2. The electromagnetic wave shielding member according to claim 1,

3. 3. The electromagnetic wave shielding material according to claim 1, wherein the porosity of the electromagnetic wave shielding material is 20 to 90 vol %.

4. 3. The electromagnetic wave shielding member according to claim 1, wherein the electromagnetic wave shielding member is in a sheet shape or a shape constituting a housing.

5. The electromagnetic wave shielding member according to claim 4 , wherein the conductive fibers are oriented in a direction perpendicular to a thickness direction of the electromagnetic wave shielding member.

6. 6. The electromagnetic wave shielding member according to claim 5, wherein in a cross section parallel to a thickness direction of the electromagnetic wave shielding member, the void has a shape having a major axis and a minor axis, and the major axis of the void is oriented in a direction perpendicular to the thickness direction.

7. 3. The electromagnetic wave shielding member according to claim 1, wherein the conductive resin portion forms a mesh-like structure in a cross section of the electromagnetic wave shielding member.

8. 3. The electromagnetic shielding member according to claim 1, wherein the conductive fibers are exposed in the gaps.

9. The electromagnetic shielding member according to claim 1 , wherein at least a part of the wall surface of the gap is formed from the resin.

10. 3. The electromagnetic wave shielding material according to claim 1, wherein the conductive fibers have an average fiber length of 1 to 100 mm.

11. 3. The electromagnetic shielding member according to claim 1, wherein the conductive fibers have at least one shape selected from the group consisting of a straight shape and a crimped shape.

12. 3. The electromagnetic shielding member according to claim 1, wherein the conductive fibers include at least one type selected from the group consisting of carbon fibers, metal fibers, and fibers coated with a metal.

13. 3. The electromagnetic shielding member according to claim 1, wherein the resin comprises at least one selected from the group consisting of a thermoplastic resin and a thermosetting resin.

14. 3. The electromagnetic shielding member according to claim 1, wherein a weight ratio of the resin to the conductive fibers in the conductive resin portion is [resin]:[conductive fibers]=95:5 to 30:

70.

15. The electromagnetic wave shielding member according to claim 1 , wherein the conductive resin portion further contains conductive particles.

16. The electromagnetic wave shielding member according to claim 15 , wherein the conductive fibers and the conductive particles are in contact with each other.

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