Method for manufacturing electromagnetic wave shielding member

Abstract

To provide a method for manufacturing an electromagnetic wave shielding member which is sufficiently reduced in weight.SOLUTION: A method for manufacturing an electromagnetic wave shielding member includes: a slurry formation step of mixing at least one kind of resin selected from the group consisting of a solid resin and a semi-solid resin, a conductive fiber and water, and preparing a slurry; a papermaking step of papermaking the slurry, and forming a sheet-like object; and a thermal press step of thermally pressing the sheet-like object, and forming it into an electromagnetic wave shielding member.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for producing 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 a method for manufacturing an electromagnetic wave shielding member that is sufficiently lightweight. [Means for solving the problem]

[0010] The method for producing an electromagnetic wave shielding member of the present invention is characterized by comprising a slurry formation step of mixing at least one resin selected from the group consisting of solid resins and semi-solid resins, conductive fibers, and water to prepare a slurry, a papermaking step of papermaking the slurry to form a sheet-like product, and a heat pressing step of heat-pressing the sheet-like product to form an electromagnetic wave shielding member.

[0011] In the method for producing an electromagnetic wave shielding member of the present invention, a slurry containing conductive fibers is paper-formed into a sheet-like material. 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 method for producing an electromagnetic wave shielding member of the present invention can produce an electromagnetic wave shielding member having a void therein. If there is a gap inside the electromagnetic wave shielding member, the electromagnetic wave shielding member can be made lighter.

[0012] In the method for producing an electromagnetic wave shielding member of the present invention, the weight ratio between the resin and the conductive fibers 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.

[0013] In the method for producing an electromagnetic wave shielding member of the present invention, the bulk density of the sheet-like material is 0.1 to 1.5 g / cm 3 It is preferable that: The bulk density of the sheet-like material within the above range means that voids are suitably formed between the conductive fibers. Therefore, voids are preferably formed in the electromagnetic wave shielding member obtained by hot pressing such a sheet-like material. Therefore, the electromagnetic wave shielding member produced can be suitably lightened in weight.

[0014] In the method for producing an electromagnetic wave shielding member of the present invention, the resin preferably contains at least one type of resin selected from the group consisting of thermosetting resins and thermoplastic resins. If these resins are used, the electromagnetic wave shielding member can be easily molded.

[0015] In the method for producing an electromagnetic wave shielding member of the present invention, the resin preferably comprises at least one resin selected from the group consisting of 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, liquid crystal polymer resin, phenolic resin, epoxy resin, polyurethane resin, melamine resin and unsaturated polyester resin. These resins are suitable as resins for electromagnetic wave shielding members.

[0016] In the method for producing an electromagnetic wave shielding member of the present invention, the resin is preferably made of resin fibers. When the resin is in the form of resin fibers, the resin fibers and the conductive fibers are both produced in the papermaking process. In the sheet-like material thus formed, voids are easily formed between the resin fibers, between the resin fibers and the conductive fibers, and between the conductive fibers. The electromagnetic wave shielding member obtained by hot pressing such a sheet-like material also has favorable voids. Therefore, the electromagnetic wave shielding member can be suitably reduced in weight.

[0017] In the method for producing an electromagnetic wave shielding member of the present invention, the resin fibers preferably have an average fiber diameter of 1 to 30 μm. In the method for producing an electromagnetic wave shielding member of the present invention, the resin fibers preferably have an average fiber length of 1 to 100 mm. If the average fiber diameter and average fiber diameter of the resin fibers are smaller than the above ranges, it becomes difficult for the fibers to be entangled with each other, and it becomes difficult to form a sheet-like product by papermaking. If the average fiber diameter and average fiber diameter of the resin fibers are larger than the above range, the water dispersibility deteriorates, making it difficult to form a sheet-like material by papermaking.

[0018] In the method for producing an electromagnetic wave shielding member of the present invention, the conductive fibers preferably have an average fiber diameter of 1 to 20 μm. If the average fiber diameter of the conductive fibers is less than 1 μm, the conductive fibers are likely to break during the production of the electromagnetic shielding member, and the electrical conductivity of the electromagnetic shielding member produced is likely to decrease, which in turn makes the electromagnetic shielding property of the electromagnetic shielding member produced more likely to decrease. If the average fiber diameter of the conductive fibers exceeds 20 μm, the flexibility decreases, making the sheet-like product difficult to handle.

[0019] In the method for producing an 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 μm, 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 μm, 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.

[0020] In the method for producing an electromagnetic wave shielding member of the present invention, the conductive fibers preferably 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 electrical conductivity of the electromagnetic wave shielding member produced can be ensured.

[0021] In the method for producing an 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 produced, thereby improving the electromagnetic wave shielding properties of the electromagnetic wave shielding member produced.

[0022] In the method for producing an electromagnetic wave shielding member of the present invention, the pressure of the heat press is preferably 1 to 10 MPa, and the temperature of the heat press is preferably 200 to 350°C. By carrying out the hot pressing under such conditions, it is possible to preferably form voids inside the electromagnetic wave shielding member to be manufactured, and it is possible to reduce the weight of the electromagnetic wave shielding member to be manufactured. Effect of the Invention

[0023] According to the present invention, a method for manufacturing an electromagnetic wave shielding member that is sufficiently lightweight can be provided. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an example of a slurry formation step in the method for producing an electromagnetic wave shielding member of the present invention. [Diagram 2]FIG. 2 is a diagram showing a schematic diagram of an example of a papermaking step in the method for producing an electromagnetic wave shielding member of the present invention. [Diagram 3] FIG. 3 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 4] FIG. 4 is a diagram showing an example of the heat pressing step in the method for producing an electromagnetic wave shielding member of the present invention. [Diagram 5] FIG. 5 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 6] FIG. 6 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

[0025] The method for producing an electromagnetic wave shielding member of the present invention will be described in detail below. However, the present invention is not limited to the following configurations, and can be modified as appropriate within the scope 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.

[0026] Next, the method for producing an electromagnetic wave shielding member of the present invention is characterized by including a slurry formation step of mixing at least one resin selected from the group consisting of solid resins and semi-solid resins, conductive fibers, and water to prepare a slurry, a papermaking step of papermaking the slurry to form a sheet-like product, and a heat pressing step of heat-pressing the sheet-like product to form an electromagnetic wave shielding member.

[0027] In the method for producing an electromagnetic wave shielding member of the present invention, a slurry containing conductive fibers is paper-formed into a sheet-like material. 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 method for producing an electromagnetic wave shielding member of the present invention can produce an electromagnetic wave shielding member having a void therein. If there is a gap inside the electromagnetic wave shielding member, the electromagnetic wave shielding member can be made lighter.

[0028] The method for producing an electromagnetic wave shielding member of the present invention includes (1) a slurry formation step, (2) a papermaking step, and (3) a hot pressing step, and may include any other steps as long as the effects of the present invention are achieved.

[0029] Each step will be described below with reference to the drawings.

[0030] (1) Slurry formation process FIG. 1 is a diagram showing a schematic diagram of an example of a slurry formation step in the method for producing an electromagnetic wave shielding member of the present invention. As shown in FIG. 1, 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.

[0031] If the slurry 10a contains the conductive fibers 12, the conductive fibers 12 come into contact with each other in the electromagnetic shielding member produced, and are also electrically connected to each other. Therefore, the electromagnetic shielding member produced is conductive as a whole. As a result, the electromagnetic waves reaching the electromagnetic shielding member to be manufactured are reflected and absorbed, that is, the electromagnetic shielding member to be manufactured exhibits an electromagnetic shielding effect.

[0032] The average fiber length of the conductive fibers 12 is preferably 1 to 100 mm, and more preferably 1 to 10 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.

[0033] The average fiber diameter of the conductive fibers 12 is preferably 1 to 20 μm, and more preferably 3 to 10 μm. If the average fiber diameter of the conductive fibers is less than 1 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 results in a decrease in the electromagnetic shielding property of the electromagnetic shielding member. If the average fiber diameter of the conductive fibers exceeds 20 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.

[0034] 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.

[0035] The conductive fibers 12 preferably include at least one selected from the group consisting of carbon fibers, metal fibers, and fibers coated with 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.

[0036] When the slurry 10a contains the resin fibers 11a, the resin fibers 11a and the conductive fibers 12 are both produced in a papermaking process described below. 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 produced can be suitably lightened in weight.

[0037] The average fiber diameter of the resin fibers 11a is preferably 1 to 30 μm, and more preferably 5 to 20 μm. The average fiber length of the resin fibers 11a is preferably 1 to 100 mm, and more preferably 1 to 10 μm. If the average fiber diameter and average fiber diameter of the resin fibers are smaller than the above ranges, it becomes difficult for the fibers to be entangled with each other, and it becomes difficult to form a sheet-like product by papermaking. If the average fiber diameter and average fiber diameter of the resin fibers are larger than the above range, the water dispersibility deteriorates, making it difficult to form a sheet-like material by papermaking.

[0038] 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. Even if at least one type of resin selected from the group consisting of non-fibrous solid resins and semi-solid resins is used instead of resin fibers, it is possible to provide voids in the electromagnetic wave shielding member produced, and the electromagnetic wave shielding member produced can be suitably lightweight.

[0039] In this specification, the term "solid resin and semi-solid resin" refers to a resin having a fixed shape.

[0040] The resin (including the resin fibers 11a) is preferably at least one type of resin selected from the group consisting of thermosetting resins and thermoplastic resins. When the resin is a thermoplastic resin, the resin is first softened and then hardened in a heat pressing step described below, thereby producing an electromagnetic wave shielding member. When the resin is a thermosetting resin, the conductive fibers 12 are pressed into the resin, and then the resin is hardened by heat to produce the electromagnetic wave shielding member.

[0041] 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.

[0042] Examples of the thermosetting resin include phenol resin, epoxy resin, polyurethane resin, melamine resin, and unsaturated polyester resin.

[0043] In the slurry 10a, the weight ratio of the resin (including the resin fibers 11a) to the conductive fibers 12 ([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 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.

[0044] 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 99.3 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.

[0045] In the slurry formation step, an amorphous resin having high fluidity may be mixed into the slurry 10a.

[0046] In the slurry formation step, conductive particles may be mixed into the slurry 10a. When the slurry 10a contains conductive particles, the conductive particles come into contact with each other and with the conductive fibers in the electromagnetic shielding member produced, improving the conductivity of the conductive resin portion, which in turn improves the conductivity of the electromagnetic shielding member and the electromagnetic shielding properties of the electromagnetic shielding member.

[0047] The conductive particles may be made of any material as long as it is conductive. For example, the conductive particles may be carbon particles, metal particles, and metal-coated particles, of which carbon particles are preferred. When the conductive particles are carbon particles, the electromagnetic wave shielding member produced can be made lighter in weight.

[0048] 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.

[0049] (2) Papermaking process FIG. 2 is a diagram showing a schematic diagram of an example of a papermaking step in the method for producing an electromagnetic wave shielding member of the present invention. FIG. 3 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.

[0050] As shown in FIG. 2, in the papermaking process, the slurry 10a is put into a papermaking machine 51 and dehydrated to produce a sheet-like material 10b.

[0051] As shown in FIG. 3, 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.

[0052] 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 wave shielding member obtained by hot pressing such a sheet-like material 10b also has suitable voids. Therefore, the electromagnetic wave shielding member produced can be suitably lightened in weight.

[0053] In the papermaking step, the sheet-like material 10b is preferably produced to have a thickness of 1 to 10 mm, and more preferably 2 to 7 mm.

[0054] (3) Heat pressing process FIG. 4 is a diagram showing an example of the heat pressing step in the method for producing an electromagnetic wave shielding member of the present invention. FIG. 5 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.

[0055] Next, as shown in FIG. 4, the sheet-like material 10b is placed in a press machine 52 and subjected to heat pressing. As a result, as shown in FIG. 5, a conductive resin part 10 containing conductive fibers 12 and resin 11 is formed, and the electromagnetic wave shielding member 1 is manufactured.

[0056] When the resin fibers 11a are made of a thermoplastic resin, the resin fibers 11a are first softened by heat and then hardened to form the conductive resin part 10 including the conductive fibers 12 and the resin 11. In this way, the electromagnetic wave shielding member 1 is manufactured. Furthermore, 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 to form a conductive resin part 10 including the conductive fibers 12 and the resin 11. In this way, the electromagnetic wave shielding member 1 is manufactured.

[0057] As shown in FIG. 5, 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 void portions 20.

[0058] The conditions for the hot pressing are not particularly limited and may be appropriately determined depending on the material used. For example, it is preferable to perform the hot pressing under the following conditions. The temperature of the heat press is preferably from 200 to 350°C, and more preferably from 280 to 320°C. The pressure of the heat press is preferably 1 to 10 MPa, and more preferably 1 to 5 MPa. The heat pressing time is preferably from 1 to 30 minutes, and more preferably from 5 to 20 minutes.

[0059] By carrying out the hot pressing under such conditions, it is possible to preferably form voids inside the electromagnetic wave shielding member to be manufactured, and it is possible to reduce the weight of the electromagnetic wave shielding member to be manufactured.

[0060] As shown in FIG. 5, the electromagnetic wave shielding member 1 is in a sheet shape and has a thickness direction T. 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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)

[0065] 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.

[0066] The thickness of the electromagnetic wave shielding member 1 is not particularly limited, but is preferably 1 to 10 mm, and more preferably 2 to 7 mm.

[0067] Since the electromagnetic wave shielding material 1 is produced by papermaking, the conductive fibers 12 are oriented in a direction P perpendicular to the thickness direction T of the electromagnetic wave 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.

[0068] 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.

[0069] As shown in FIG. 5, 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.

[0070] In the above-mentioned heat pressing step, the sheet-like material 10b is heat pressed as is to produce the sheet-like electromagnetic shielding member 1. However, in the method for producing an electromagnetic wave shielding member of the present invention, the sheet-like material 10b may be molded into a desired shape and then hot-pressed. For example, the sheet-like material 10b may be molded into a shape that constitutes the housing and then hot-pressed. The electromagnetic wave shielding member thus manufactured is shaped to form a housing.

[0071] By placing electronic components inside an electromagnetic wave shielding material shaped to form a housing, 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. The specific shape and dimensions of the electromagnetic wave shielding member that constitutes the housing are preferably set appropriately depending on the shape of the electronic components to be arranged and the arrangement position of the electromagnetic wave shielding member.

[0072] 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.

[0073] This specification describes the following:

[0074] The present disclosure (1) is a method for producing an electromagnetic wave shielding member, comprising: a slurry formation step of mixing at least one resin selected from the group consisting of solid resins and semi-solid resins, conductive fibers, and water to prepare a slurry; a papermaking step of papermaking the slurry to form a sheet-like material; and a heat pressing step of heat-pressing the sheet-like material to produce an electromagnetic wave shielding member.

[0075] The present disclosure (2) is the method for producing the electromagnetic wave shielding member according to the present disclosure (1), in which the weight ratio of the resin to the conductive fibers is [resin]:[conductive fibers]=95:5 to 30:70.

[0076] The present disclosure (3) provides a method for manufacturing a sheet-like material having a bulk density of 0.1 to 1.5 g / cm 3 This is a method for producing the electromagnetic wave shielding member according to the present disclosure (1) or (2).

[0077] The present disclosure (4) is a method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (3), wherein the resin contains at least one resin selected from the group consisting of thermosetting resins and thermoplastic resins.

[0078] The present disclosure (5) is a method for producing an electromagnetic wave shielding member according to the present disclosure (4), wherein the thermoplastic resin contains at least one resin selected from the group consisting of 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.

[0079] The present disclosure (6) is a method for producing an electromagnetic wave shielding member according to the present disclosure (4), wherein the thermosetting resin contains at least one resin selected from the group consisting of a phenolic resin, an epoxy resin, a polyurethane resin, a melamine resin, and an unsaturated polyester resin.

[0080] The present disclosure (7) is a method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (6), in which the resin is made of resin fibers.

[0081] The present disclosure (8) is the method for producing an electromagnetic wave shielding member according to the present disclosure (7), wherein the resin fibers have an average fiber diameter of 1 to 30 μm.

[0082] The present disclosure (9) is the method for producing an electromagnetic wave shielding member according to the present disclosure (7) or (8), wherein the resin fibers have an average fiber length of 1 to 100 mm.

[0083] The present disclosure (10) is the method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (9), wherein the conductive fibers have an average fiber diameter of 1 to 20 μm.

[0084] The present disclosure (11) is a method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (10), wherein the conductive fibers have an average fiber length of 1 to 100 mm.

[0085] The present disclosure (12) is a method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (11), wherein the conductive fibers have at least one shape selected from the group consisting of a straight shape and a crimped shape.

[0086] The present disclosure (13) is a method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (12), wherein the conductive fiber includes at least one selected from the group consisting of carbon fiber, metal fiber, and metal-coated fiber.

[0087] The present disclosure (14) is the method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (13), wherein the heat press is performed at a pressure of 1 to 10 MPa.

[0088] The present disclosure (15) is the method for producing an electromagnetic wave shielding member according to any one of the present disclosures (1) to (14), wherein the heat press is performed at a temperature of 200 to 350°C. EXAMPLES

[0089] EXAMPLES Hereinafter, examples that more specifically disclose the present invention will be described, however, the present invention is not limited to these examples.

[0090] 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.

[0091] (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.

[0092] (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.

[0093] Thereafter, the mixture was left to stand until it reached room temperature, and the polyphenylene sulfide resin was cured.

[0094] Through the above steps, an electromagnetic wave shielding member according to Example 1 having a thickness of 3.6 mm was manufactured.

[0095] 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. 6 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. 6, 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.

[0096] 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.

[0097] The electrical resistivity of the electromagnetic shielding member according to Example 1 was 2.79 Ω·m.

[0098] (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.

[0099] 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.

[0100] 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]

[0101] 1 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

Claims

1. A slurry forming step of mixing at least one resin selected from the group consisting of solid resins and semi-solid resins, conductive fibers, and water to prepare a slurry; a papermaking step of forming a sheet-like material from the slurry; and a heat pressing step of heat pressing the sheet-like material to form an electromagnetic wave shielding member.

2. 2. The method for producing an electromagnetic wave shielding member according to claim 1, wherein a weight ratio of the resin to the conductive fibers is [resin]:[conductive fibers]=95:5 to 30:

70.

3. The bulk density of the sheet-like material is 0.1 to 1.5 g / cm ３ The method for producing the electromagnetic wave shielding member according to claim 1 or 2,

4. The method for producing an electromagnetic wave shielding member according to claim 1 or 2, wherein the resin comprises at least one resin selected from the group consisting of a thermosetting resin and a thermoplastic resin.

5. 5. The method for producing an electromagnetic wave shielding member according to claim 4, wherein the thermoplastic resin comprises at least one resin selected from the group consisting of 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.

6. 5. The method for producing an electromagnetic wave shielding member according to claim 4, wherein the thermosetting resin comprises at least one resin selected from the group consisting of a phenolic resin, an epoxy resin, a polyurethane resin, a melamine resin, and an unsaturated polyester resin.

7. The method for producing an electromagnetic wave shielding member according to claim 1 or 2, wherein the resin is made of resin fibers.

8. The method for producing an electromagnetic wave shielding member according to claim 7, wherein the resin fibers have an average fiber diameter of 1 to 30 μm.

9. The method for producing an electromagnetic wave shielding member according to claim 7, wherein the resin fibers have an average fiber length of 1 to 100 mm.

10. 3. The method for producing an electromagnetic wave shielding member according to claim 1, wherein the conductive fibers have an average fiber diameter of 1 to 20 μm.

11. 3. The method for producing an electromagnetic wave shielding member according to claim 1, wherein the conductive fibers have an average fiber length of 1 to 100 mm.

12. The method for producing an electromagnetic wave shielding member according to claim 1 or 2, wherein the conductive fibers have at least one shape selected from the group consisting of a straight shape and a crimped shape.

13. The method for producing an electromagnetic wave shielding member according to claim 1 or 2, 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.

14. 3. The method for producing an electromagnetic wave shielding member according to claim 1, wherein the pressure of the heat press is 1 to 10 MPa.

15. The method for producing an electromagnetic wave shielding member according to claim 1 or 2, wherein the heat press temperature is 200 to 350°C.

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