Electromagnetic wave shielding film

Abstract

To provide an electromagnetic wave shield film that covers an electronic component and a wire, mounted to an internal part of an electron device that can sufficiently exert a characteristic as an electromagnetic wave shield member by a carbon nano tube, and can be easily handled.SOLUTION: In a first electromagnetic wave shield film 1a having a five-layer structure, a resin film 3 where a specific resistance is 0.005 Ω*cm or less; a thickness is 500 μm or less; a direction where a tension strength becomes the maximum is a vertical direction; and a tension strength ratio of the vertical direction / a lateral direction where a direction vertical to the vertical direction is the lateral direction is 0.5 to 2.0 is laminated onto front and back surfaces of a carbon nanotube nonwoven fabric 2, and the first electromagnetic wave shield film has a lamination film having a total thickness of 10 to 1000 μm or an impregnation film in which a resin is impregnated into the carbon nanotube nonwoven fabric, and which has a total thickness of 10 to 1000 μm, an adhesive agent layer 4 laminated onto one surface of the lamination film or the impregnation film, and a separation type film 5 laminated onto an adhesive surface of the adhesive agent layer.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] This invention relates to an electromagnetic shielding film that covers electronic components and wiring mounted inside electronic devices to shield against electromagnetic waves. [Background technology]

[0002] In recent years, high-speed communications such as 5G and 6G, which utilize electromagnetic waves in the millimeter wave and terahertz bands, are being considered for future practical application. The number of wireless devices that use electromagnetic waves for communication is increasing, and the ever-increasing amount of electromagnetic waves poses risks such as electronic devices malfunctioning due to interference from surrounding electromagnetic waves, and information leakage due to electromagnetic waves emitted by the devices themselves. Furthermore, in order to promote the rapidly advancing autonomous driving of automobiles and other vehicles, the transmission and reception of electromagnetic waves must be carried out correctly in various electromagnetic environments, from low-frequency electromagnetic waves to millimeter-wave radar.

[0003] To avoid interference from such electromagnetic waves, electromagnetic shielding measures have become a crucial technological challenge. Against this backdrop, there is a demand for electromagnetic shielding materials with excellent shielding performance in the microwave, millimeter-wave, and terahertz wave bands. With the increasing sophistication of electromagnetic wave utilization, there is also a growing need for new functionalities in electromagnetic shielding materials, such as thinner films, lighter weights, and larger surface areas.

[0004] Numerous electromagnetic shielding technologies have been proposed using materials other than metals, such as carbon black, graphene, carbon nanotubes, conductive polymers, and dielectric oxides. Among these, carbon nanotubes, made from carbon, are attracting attention as a promising electromagnetic shielding material.

[0005] Electromagnetic wave shielding materials using carbon nanotubes include paste materials in which carbon nanotubes are dispersed in resin (Patent Document 1) and aqueous paints in which carbon nanotubes are dispersed in aqueous solution (Patent Document 2). However, both are difficult to handle and their shielding performance is insufficient to be practical. The carbon nanotubes used are also in the form of fine fibers, so they have a large specific surface area and cannot be dispersed in large quantities in the resin, resulting in insufficient electrical conductivity. Furthermore, there is an electromagnetic wave shielding material that uses a carbon nanotube sheet formed by charged spinning (Patent Document 3), but it has problems such as low strength and difficulty in handling.

[0006] An electromagnetic shielding material (Patent Document 4) has been disclosed in which a protonating agent such as hydronium ions or hydrochloric acid is added to a carbon nanotube sheet, and ferromagnetic materials such as iron or cobalt are added to improve conductivity. However, the protonating agent is a strongly acidic compound, which poses a problem in terms of handling. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2009-144000 [Patent Document 2] Japanese Patent Publication No. 2012-174833 [Patent Document 3] Japanese Patent Publication No. 2008-218859 [Patent Document 4] Patent No. 6182176 [Overview of the project] [Problems that the invention aims to solve]

[0008] Carbon nanotubes, made from carbon, are attracting attention as electromagnetic shielding materials. However, because carbon nanotubes are in the form of fine fibers, they have a large specific surface area and cannot be dispersed in large quantities in resins. As a result, electromagnetic shielding materials using carbon nanotubes have not been able to fully utilize their properties.

[0009] The objective of the present invention is to provide an electromagnetic shielding film that can fully exhibit its properties as an electromagnetic shielding material using carbon nanotubes, is easy to handle, and covers electronic components and wiring mounted inside electronic devices. [Means for solving the problem]

[0010] In light of these circumstances, the inventors conducted diligent research and, as a result, discovered that the following electromagnetic shielding film achieves the above objective, thus completing the present invention. In other words, the present invention is the following electromagnetic wave shielding film. [1] A laminated film having a total thickness of 10 to 1000 μm, formed by laminating a resin film onto the front and back surfaces of a carbon nanotube nonwoven fabric having a resistivity of 0.005 Ω·cm or less, a thickness of 500 μm or less, and a tensile strength ratio in the longitudinal / transverse direction (with the direction perpendicular to the longitudinal direction being the transverse direction) of 0.5 to 2.0, and An adhesive layer laminated on one side of the laminated film, An electromagnetic wave shielding film having a release film laminated on the adhesive surface of the adhesive layer. [2] An impregnated film is made by impregnating a carbon nanotube nonwoven fabric with a resin, having a resistivity of 0.005 Ω·cm or less, a thickness of 500 μm or less, a tensile strength ratio in the longitudinal / transverse direction (where the direction with maximum tensile strength is defined as the longitudinal direction and the direction perpendicular to the longitudinal direction is defined as the transverse direction) of 0.5 to 2.0, with a total thickness of 10 to 1000 μm. An adhesive layer laminated on one side of the impregnated film, An electromagnetic wave shielding film having a release film laminated on the adhesive surface of the adhesive layer. [3] The electromagnetic wave shielding film according to [1] or [2], wherein the carbon nanotubes in the carbon nanotube nonwoven fabric are single-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture thereof. [4] The electromagnetic wave shielding film according to [1], wherein the resin film is a thermoplastic resin film and the softening point of the thermoplastic resin in the film is 400°C or lower. [5] The electromagnetic wave shielding film described in [4], wherein the thermoplastic resin film comprises one or more thermoplastic resins selected from polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, and polyimide. [6] The electromagnetic wave shielding film according to [1], wherein the resin film is a thermosetting resin film, and the thermosetting resin in the film comprises one or more selected from epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenolic resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin, and acrylic resin. [7] The electromagnetic wave shielding film according to [2], wherein the impregnation resin is a thermoplastic resin, and the thermoplastic resin comprises one or more selected from polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, and polyimide. [8] The electromagnetic wave shielding film according to [2], wherein the impregnation resin is a thermosetting resin, and the thermosetting resin comprises one or more selected from epoxy resins, allylated epoxy resins, allylated polyphenylene ether resins, phenolic resins, polyimide resins, polyamide resins, bismaleimide resins, maleimide resins, cyanate resins, cyclopentadiene-styrene copolymer resins, polyester resins, silicone resins, and acrylic resins.

[0011] The electromagnetic wave shielding film of the present invention utilizes carbon nanotubes to fully leverage their properties as an electromagnetic wave shielding material by using a laminated film in which a resin film is laminated on both the front and back surfaces of a carbon nanotube nonwoven fabric, or an impregnated film in which a thermosetting resin is impregnated. Furthermore, by attaching a release film to these laminated or impregnated films via an adhesive layer, handling is made easy. In other words, an electromagnetic wave shielding film with excellent electromagnetic wave shielding properties and ease of handling is provided. [Effects of the Invention]

[0012] The electromagnetic shielding film of the present invention can fully exhibit its properties as an electromagnetic shielding material using carbon nanotubes, and is also easy to handle. [Brief explanation of the drawing]

[0013] [Figure 1A] This is a schematic longitudinal cross-sectional view showing an example of a first electromagnetic wave shielding film with a five-layer structure. [Figure 1B] This is a schematic longitudinal cross-sectional view showing an example of a second electromagnetic shielding film with a three-layer structure. [Figure 2] This is a schematic perspective view showing an example of a five-layer electromagnetic shielding film wound into a roll, similar to glass cloth. [Figure 3] This is a schematic perspective view showing an example of a roll of electromagnetic shielding film cut into tape-like strips. [Figure 4A] This is a schematic longitudinal cross-sectional view showing an example where the release film is peeled off from the first electromagnetic wave shielding film, which has a five-layer structure, and attached to the surface of an electronic component. [Figure 4B] This is a schematic longitudinal cross-sectional view showing an example where the release film has been peeled off from the second electromagnetic wave shielding film, which has a three-layer structure, and attached to the surface of an electronic component. [Figure 5] This is a schematic perspective view showing an example where the surface of copper wiring is wrapped with an electromagnetic shielding film cut into strips. [Figure 6]This is a schematic longitudinal cross-sectional view showing an example where the entire circuit board is covered with an electromagnetic shielding film. [Figure 7] This is a schematic diagram of the measurement system for electromagnetic wave shielding characteristics in the example. [Figure 8] This is a schematic diagram of the measurement system for electromagnetic wave shielding characteristics in the low-frequency range. [Figure 9A] This chart shows the results of measuring the electromagnetic shielding characteristics of copper foil in the 100-6000MHz range. [Figure 9B] This chart shows the results of measuring the electromagnetic shielding characteristics of the adhesive electromagnetic shielding film used in Example 7 in the 100-6000MHz range. [Figure 10] This chart shows the results of measuring the transmission attenuation at 60-90 GHz for the adhesive electromagnetic shielding film used in Example 7. [Figure 11] This photograph shows an example of a prototype electromagnetic wave shielding film of the present invention, including its appearance with the adhesive layer. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below. The electromagnetic wave shielding film of the present invention uses a carbon nanotube nonwoven fabric having a resistivity of 0.005 Ω·cm or less, a thickness of 500 μm or less, and a tensile strength ratio in the longitudinal / transverse direction (where the direction with maximum tensile strength is the longitudinal direction and the direction perpendicular to the longitudinal direction is the transverse direction) of 0.5 to 2.0, and comprises (A) a laminated film having a total thickness of 10 to 1000 μm by laminating a resin film on the front and back surfaces of the carbon nanotube nonwoven fabric, or (B) an impregnated film having a total thickness of 10 to 1000 μm by impregnating the carbon nanotube nonwoven fabric with resin. The electromagnetic wave shielding film comprises an adhesive layer laminated on one side of the laminated film or impregnated film, and a release film laminated on the adhesive surface of the adhesive layer. Hereinafter, the electromagnetic shielding film having (A) a laminated film will also be referred to as the first electromagnetic shielding film, and the electromagnetic shielding film having (B) an impregnated film will also be referred to as the second electromagnetic shielding film.

[0015] <Carbon nanotube nonwoven fabric> The carbon nanotube nonwoven fabric used in this invention has a thickness of 500 μm or less, preferably 5 to 300 μm. The carbon nanotube nonwoven fabric is made up of multiple carbon nanotubes intertwined with each other. The carbon nanotubes constituting the carbon nanotube nonwoven fabric are single-walled carbon nanotubes, multi-walled carbon nanotubes, or mixtures thereof. Their diameter and length are not particularly limited, but generally they have a diameter of 50 nm or less and a length of 2 mm or less. The carbon nanotube nonwoven fabric used in this invention preferably consists of carbon nanotubes with a length of 10 to 500 μm intertwined with each other. Carbon nanotubes can be produced by reacting a carbon source such as methane with a catalyst such as ferrocene in the gas phase at a temperature of 1000°C to 1500°C. To improve the electrical conductivity of such nonwoven fabrics, a highly conductive nonwoven fabric with a resistivity of 0.005 Ω·cm or less, preferably 0.003 Ω·cm or less, is used. Carbon nanotube nonwoven fabrics can be manufactured by methods such as directly stretching carbon nanotubes or by compressing them. Alternatively, carbon nanotubes can be suspended in water or an organic solvent, and a sheet can be made using methods such as filtration or papermaking, which is then dried to produce a nonwoven fabric.

[0016] Depending on the manufacturing method, carbon nanotube nonwoven fabrics may exhibit anisotropy in density. This can result in anisotropy in the electric field attenuation rate and a decrease in the electric field attenuation rate. Therefore, carbon nanotube nonwoven fabrics without anisotropy should be selected and used. Whether or not the nonwoven fabric is uniformly entangled in the longitudinal and transverse directions can be easily determined by measuring the tensile strength of the nonwoven fabric in various directions, defining the direction with the maximum tensile strength as the longitudinal direction, and the direction perpendicular to the longitudinal direction as the transverse direction, and then calculating the ratio of the longitudinal to transverse tensile strengths. Carbon nanotube nonwoven fabrics have a longitudinal / transverse tensile strength ratio of 0.5 to 2.0, preferably 0.6 to 1.85. Within this range, an appropriate electromagnetic shielding effect can be obtained against high-frequency vibration directions.

[0017] Commercially available nonwoven fabrics of carbon nanotubes possessing the above-mentioned properties include nonwoven fabrics with a thickness of 20 to 80 μm, such as MIRALON (manufactured by Huntsman, 20 μm thick, resistivity 3.5E-03 (Ω·cm), tensile strength ratio 1.30).

[0018] Furthermore, nonwoven fabrics can be manufactured by dispersing single-layer or multi-layer carbon nanotube powder in a solvent, such as water, or an organic solvent such as alcohol or N-methyl-2-pyrrolidone (NMP), coating it onto a support film using a coater, and drying it. Nonwoven fabrics can also be manufactured by filtering the mixture using filter paper and drying the CNTs on the filter paper. The amount of carbon nanotubes added per 100 parts by mass of solvent is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 2 parts by mass, and even more preferably 0.05 to 0.5 parts by mass. When the amount added is within this range, the viscosity of the dispersion is appropriate and cost-effective in the above manufacturing method. Furthermore, ionic surfactants can be used to improve the dispersibility and conductivity of carbon nanotubes. Examples of ionic surfactants include sodium deoxycholate, sodium cholate, sodium dodecylsulfonate, sodium dodecylbenzenesulfonate, sodium dodecyldiphenyloxidesulfonate, and cetyltrimethylammonium bromide. These may be used individually or in combination of two or more. Among these, sodium deoxycholate is particularly preferred. The amount of ionic surfactant added per 1 part by mass of carbon nanotubes is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 1 to 10 parts by mass. When the amount added is within this range, the dispersion of carbon nanotubes is sufficient, the adhesion and bonding to thermoplastic resins and thermosetting resins are sufficient, and there is no bleeding to the film surface. Nonwoven fabrics prepared from a dispersion containing an ionic surfactant may have the ionic surfactant removed by immersion in water or an organic solvent. Preferred organic solvents include alcohols such as methanol, ethanol, and IPA, as well as NMP.

[0019] In the electromagnetic wave shielding film of the present invention, a carbon nanotube nonwoven fabric having a silica layer on the surface of the carbon nanotube fibers may be used. For example, a silica layer can be formed on the fiber surface of the carbon nanotube nonwoven fabric by treating the carbon nanotube nonwoven fabric with a polysilazane compound or the like.

[0020] In the electromagnetic wave shielding film of the present invention, the fiber surface of the carbon nanotube nonwoven fabric can also be surface-treated with a sizing agent, i.e., a diluted solution of a thermosetting resin, in order to improve wettability with thermosetting resins such as epoxy resin, polyimide resin, and bismaleimide resin. Furthermore, by surface-treating the carbon nanotube nonwoven fabric with a coupling agent, the carbon nanotube nonwoven fabric and the resin adhere closely together, improving the durability of the electromagnetic wave shielding sheet. Examples of coupling agents include silane coupling agents and alkoxide compounds such as titanium and aluminum. Among these, silane coupling agents are preferred, and a preferred silane coupling agent is, for example, a compound represented by the general formula Y-Si-X3. Here, Y is an organic group having a functional group such as an amino group, epoxy group, hydroxyl group, carboxyl group, vinyl group, methacrylic group, or mercapto group, and X is a hydrolyzable functional group such as an alkoxy group. Examples of compounds represented by the general formula Y-Si-X3 include γ-glycidoxypropyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminobenzyltriethoxysilane, and γ-aminophenyltriethoxysilane. Furthermore, silane compounds such as polysilazanes can also be used.

[0021] In the electromagnetic shielding film of the present invention, inorganic materials may be added to the carbon nanotube nonwoven fabric. Examples of inorganic materials include conductive inorganic materials and insulating inorganic materials. By filling the gaps between the intertwined fibers of carbon nanotube nonwoven fabric with conductive inorganic materials, such as inorganic particles, inorganic fibers, or metal particles, the electrical conductivity can be further enhanced, and the electromagnetic wave shielding performance in the millimeter-wave to terahertz frequency range can be improved. Examples of conductive inorganic materials include carbon black, carbon nanotubes, graphene, and graphite as inorganic particles, carbon short fibers as inorganic fibers, and particles made of metals such as copper, iron, silver, and gold as metal particles. Alternatively, resin particles coated with these metals may also be used as conductive inorganic materials. By using inorganic particles or inorganic fibers as highly thermally conductive insulating inorganic materials, the thermal conductivity of carbon nanotube nonwoven fabric can be further enhanced, for example, to 50-80 W / mK. Examples of inorganic particles among insulating inorganic materials include silica, zinc oxide, alumina, boron nitride, and aluminum nitride. Examples of inorganic fibers include alumina short fibers, quartz fibers, and glass fibers.

[0022] The shape of the inorganic material is not particularly limited, but an average particle size of 0.5 μm to 30 μm is preferred in terms of heat dissipation and electrical conductivity. The average particle size of the inorganic material is the D50 value measured by laser diffraction.

[0023] Inorganic materials can be directly sprayed onto carbon nanotube nonwoven fabrics for immobilization. Inorganic materials can be sprayed onto carbon nanotube nonwoven fabrics by any method, such as packing the inorganic material into the carbon nanotube nonwoven fabric using a press or laminator, dispersing the inorganic material in any solvent and spraying the dispersion onto the carbon nanotube nonwoven fabric, followed by drying and removing the solvent, or a combination of these methods. Any solvent can be used as the solvent for the dispersion, but highly volatile solvents are preferred, such as water, alcohols such as ethanol and isopropyl alcohol, acetone, toluene, hydrocarbon solvents, and silicone solvents. The concentration of the dispersion is preferably 0.1 to 100 parts by mass per 100 parts by mass of inorganic material. When inorganic materials are dispersed onto a carbon nanotube nonwoven fabric for immobilization, the amount of immobilization is preferably 0.01 to 100 parts by mass per 100 parts by mass of the carbon nanotube nonwoven fabric.

[0024] Furthermore, metal foils such as copper and aluminum can be laminated onto the carbon nanotube nonwoven fabric.

[0025] <Resin film of the first electromagnetic wave shielding film> In the first electromagnetic wave shielding film, the resin film in the laminated film is a thermoplastic resin film or a thermosetting resin film. (Thermoplastic resin film) Of these, the thermoplastic resin film is preferably one in which the softening point of the thermoplastic resin in the film is 400°C or lower, from the viewpoint of film molding and electromagnetic wave shielding film processing. The lower limit of the softening point is not particularly limited, but for example, it is 70°C or higher. The softening point of thermoplastic resins can be measured according to JIS K7196-1991, "Test method for softening temperature of thermoplastic plastic films and sheets by thermomechanical analysis." Examples of thermoplastic resins used in the film include polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyphenylene ether, polyether ether ketone, polyether ketone, and polyether sulfone. These may be used individually or in combination of two or more. Among these, polyethylene, polypropylene, polyethylene terephthalate, and polyethylene naphthalate are preferred from the viewpoint of processability as an electromagnetic wave shielding film. Furthermore, polyimide film is preferred when heat resistance is required, and fluororesin film is preferred when chemical resistance and solvent resistance are also required. Other components, such as known additives, may be added to the thermoplastic resin, as long as they do not impair the effects of the present invention. The thermoplastic resin film used is one in which the thermoplastic resin has been pre-processed into a film with a thickness preferably of 5 to 200 μm, more preferably of 10 to 100 μm.

[0026] (Thermosetting resin film) In the first electromagnetic wave shielding film, examples of the thermosetting resin in the laminated film include epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenol resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin, and acrylic resin. These may be used alone or in combination of two or more. Among them, silicone resin and bismaleimide resin are preferable from the viewpoints of heat resistance and flexibility.

[0027] The silicone resin used for the thermosetting resin film is not particularly limited as long as it is a thermosetting silicone resin composition, but an addition-curing type silicone resin composition containing an alkenyl group-containing organopolysiloxane, an organohydrogenpolysiloxane, and a hydrosilylation catalyst, and a condensation-curing type silicone resin composition containing an alkoxysilyl group and / or a hydroxysilyl group-containing organopolysiloxane and a condensation catalyst. It is preferable to use one or more resins selected from the above. From the viewpoints of workability, storage stability, transparency, electrical properties and other physical properties, the addition-curing type silicone resin composition is particularly preferable. As the addition-curing type silicone resin composition, the following addition-curing type silicone resin composition containing (A) an alkenyl group-containing organopolysiloxane, (B) an organohydrogenpolysiloxane having a resin structure, and (C) a platinum group metal-based catalyst is preferable.

[0028] (A) The alkenyl group-containing organopolysiloxane is an organopolysiloxane containing a resin structure. The organopolysiloxane having a resin structure (i.e., a three-dimensional network structure) is composed of R 1 , b , (4-a-b) / 2 , a , 4 , 3 , 2 , 3 SiO 1.5 units, R 2 2SiO units, and R 3 a R 4 b SiO (4-a-b) / 2 units (where R 1 , R 2 , and R 3R represents a methyl group, ethyl group, propyl group, cyclohexyl group, or phenyl group. 4 represents a vinyl group or an allyl group, where a is 0, 1, or 2, b is 1 or 2, and a+b is 2 or 3. ), the R 2 This is an organopolysiloxane with a resin structure that partially contains a structure in which at least a portion of 2SiO units are continuously repeated, with the number of repetitions being 5 to 300, preferably 10 to 300, more preferably 15 to 200, and even more preferably 20 to 100.

[0029] Note that the above R 2 A structure in which at least a portion of 2SiO units are repeated continuously, with a number of repeats ranging from 5 to 300, refers to a linear diorganopolysiloxane chain structure represented by the following general formula. [ka] (Here, m represents an integer between 5 and 300.)

[0030] R present in the organopolysiloxane of component (A) 2 It is preferable that at least a portion of the total 2SiO units, preferably 50 mol% or more (50-100 mol%), and particularly 80 mol% or more (80-100 mol%), form a chain structure represented by the above general formula within the molecule.

[0031] In the molecule of component (A) above, R 2 The 2SiO units act to extend the polymer molecules into a linear chain, R 1 SiO 1.5 The unit involves branching or forming a three-dimensional network of polymer molecules. 3 a R 4 b SiO (4-a-b) / 2 R in units 4 (Vinyl group or allyl group) is the R that component (B) described later possesses 3 c H d SiO (4-c-d) / 2It plays a role in curing addition-curing silicone resin compositions by undergoing a hydrosilylation addition reaction with hydrogen atoms (i.e., SiH groups) bonded to the silicon atoms of the unit.

[0032] The molar ratio of the three essential siloxane units constituting component (A), i.e., R 1 SiO 1.5 Unit: R 2 2SiO units:R 3 a R 4 b SiO (4-a-b) / 2 A molar ratio of 90-24:75-9:50-1, and particularly 70-28:70-20:10-2 (with a total of 100), is preferable in terms of the properties of the resulting cured product.

[0033] R 3 a R 4 b SiO (4-a-b) / 2 The unit is R 3 R 4 SiO units, R 3 2R 4 SiO 0.5 Unit, R 4 2SiO units, and R 3 R 4 2SiO 0.5 This indicates that it is either one type of siloxane unit selected from the units, or a combination of two or more types of siloxane units. 3 a R 4 b SiO (4-a-b) / 2 Preferably, the organopolysiloxane contains a total of 0.001 mol / 100g or more of vinyl groups and allyl groups, more preferably 0.025 mol / 100g or more, and even more preferably 0.03 to 0.3 mol / 100g.

[0034] Furthermore, if the weight-average molecular weight of component (A) measured by gel permeation chromatography (GPC) is in the range of 3,000 to 1,000,000, and particularly 10,000 to 100,000, the polymer is solid or semi-solid, which is preferable in terms of workability, curability, etc.

[0035] Such organopolysiloxanes with a resin structure can be synthesized by combining the compounds that serve as raw materials for each unit in the resulting polymer such that the three types of siloxane units described above are in a desired molar ratio, and then performing co-hydrolysis condensation, for example, in the presence of an acid.

[0036] Furthermore, of the organopolysiloxane of component (A) mentioned above, 90 mol% or more (90-100 mol%), particularly 95 mol% or more (95-100 mol%) of the siloxane units constituting component (A) is R 1 SiO 1.5 Unit, R 2 2SiO units, and R 3 a R 4 b SiO (4-a-b) / 2 The unit consists of three types of siloxane units, and 0 to 10 mol%, particularly 0 to 5 mol%, may be other siloxane units. Specifically, when producing the organopolysiloxane of component (A) by co-hydrolysis and condensation of the above raw material compounds, R 1 SiO 1.5 Unit, R 2 2SiO units and / or R 3 a R 4 b SiO (4-a-b) / 2 In addition to the units, siloxane units having a silanol group may be produced as a by-product. The organopolysiloxane of component (A) may contain such silanol group-containing siloxane units in an amount of 10 mol% or less (0-10 mol%), preferably 5 mol% or less (0-5 mol%), relative to the total siloxane units. Examples of the above silanol group-containing siloxane units include R 1 (HO)SiO units, R 1 (HO)2SiO 0.5 Unit, R2 2(HO)SiO 0.5 unit, R 3 a R 4 b (HO)SiO (3-a-b) / 2 unit, R 3 a R 4 b (HO)2SiO (2-a-b) / 2 unit (where R 1 ~R 4 , a and b are as described above.) can be mentioned.

[0037] Component (B) in the addition-curable silicone resin composition is an organohydrogenpolysiloxane having a resin structure (i.e., a three-dimensional network structure), R 1 SiO 1.5 unit, R 2 2SiO unit, and R 3 c H d SiO (4-c-d) / 2 unit (where R 1 , R 2 , R 3 are as described above, c is 0, 1 or 2, d is 1 or 2, and c + d is 2 or 3.), at least a part of the R 2 2SiO units are continuously repeated, and the number of repetitions is 5 to 300, preferably 10 to 300, more preferably 15 to 200, still more preferably 20 to 100, and it is an organohydrogenpolysiloxane having a resin structure that partially contains a linear siloxane structure.

[0038] Note that at least a part of the R 2 2SiO units are continuously repeated, and the structure with the number of repetitions being 5 to 300 is, as described above for component (A), at least a part of the R 2 2SiO units present in component (B), preferably 50 mol% or more (50 to 100 mol%), particularly 80 mol% or more (80 to 100 mol%), form a linear diorganopolysiloxane chain structure represented by the general formula (1) in the molecule of component (B).

[0039] (B) Even within the molecule of component R 2 The 2SiO units act to extend the polymer molecules into a linear chain, R 1 SiO 1.5 The unit involves branching or forming a three-dimensional network of polymer molecules. 3 c H d SiO (4-c-d) / 2 The hydrogen atoms bonded to the silicon within the unit play a role in curing the addition-curing type silicone resin composition by undergoing a hydrosilylation addition reaction with the alkenyl group of component (A).

[0040] (B) The molar ratio of the three essential siloxane units that make up component R 1 SiO 1.5 Unit: R 2 2SiO units:R 3 c H d SiO (4-c-d) / 2 A molar ratio of 90-24:75-9:50-1, and particularly 70-28:70-20:10-2 (with a total of 100), is preferable in terms of the properties of the resulting cured product.

[0041] Furthermore, the polystyrene-equivalent weight-average molecular weight of component (B) calculated by GPC is preferably in the range of 3,000 to 1,000,000, and particularly preferably in the range of 10,000 to 100,000, from the standpoint of workability and the properties of the cured product.

[0042] Such resin-structured organohydrogen polysiloxanes can be synthesized by combining the compounds that serve as raw materials for each unit in the resulting polymer in a desired molar ratio of the three types of siloxane units, and then performing co-hydrolysis.

[0043] Furthermore, the organohydrogen polysiloxane in component (B) contains 90 mol% or more (90-100 mol%), particularly 95 mol% or more (95-100 mol%) of the siloxane units that make up component (B), R 1 SiO 1.5 Unit, R 2 2SiO units, and R 3c H d SiO (4-c-d) / 2 The unit consists of three types of siloxane units, and 0 to 10 mol%, particularly 0 to 5 mol%, may be other siloxane units. Specifically, when producing the organopolysiloxane of component (B) by co-hydrolysis and condensation of the above raw material compounds, R 1 SiO 1.5 Unit, R 2 2SiO units, and R 3 c H d SiO (4-c-d) / 2 In addition to the units, siloxane units having a silanol group may be produced as a by-product. The organopolysiloxane of component (B) may contain such silanol group-containing siloxane units in an amount of 10 mol% or less (0-10 mol%), preferably 5 mol% or less (0-5 mol%), relative to the total siloxane units. Examples of the above silanol group-containing siloxane units include R 1 (HO)SiO units, R 1 (HO)2SiO 0.5 Unit, R 2 2(HO)SiO 0.5 Unit, R 3 c H d (HO)SiO (3-c-d) / 2 Unit, R 3 c H d (HO)2SiO (2-c-d) / 2 Unit (here, R 1 ~R 3 , c and d are as described above.)

[0044] The amount of organohydrogenpolysiloxane in component (B) is preferably such that the molar ratio of hydrogen atoms (SiH groups) bonded to silicon atoms in component (B) to the total amount of vinyl groups and allyl groups in component (A) is 0.1 to 4.0, particularly preferably 0.5 to 3.0, and even more preferably 0.8 to 2.0. If the ratio is 0.1 or higher, the curing reaction will proceed and a silicone cured product can be obtained, and if the ratio is 4.0 or lower, a large amount of unreacted SiH groups will not remain in the cured product, and there is no risk of the physical properties of the cured product changing over time.

[0045] In addition-curing silicone resin compositions, (C) platinum group metal catalysts are added to promote the addition-curing reaction and include platinum-based, palladium-based, and rhodium-based catalysts. From a cost perspective, examples include platinum-based catalysts such as platinum, platinum black, and chloroplatinic acid, such as H2PtCl6·mH2O, K2PtCl6, KHPtCl6·mH2O, K2PtCl4, K2PtCl4·mH2O, PtO2·mH2O (where m is a positive integer), and complexes of these with hydrocarbons such as olefins, alcohols, or vinyl group-containing organopolysiloxanes. These catalysts can be used individually or in combination of two or more.

[0046] The amount of component (C) is sufficient for hardening and is typically used in a range of 0.1 to 500 ppm, particularly preferably 0.5 to 100 ppm, as a platinum group metal in terms of mass relative to the total amount of components (A) and (B).

[0047] In addition to the components (A), (B), and (C) described above, various additives known on their own may be added to the addition-curing silicone resin composition as needed. Examples of additives include inorganic fillers and adhesive aids. Inorganic fillers may be added for purposes such as reducing the coefficient of thermal expansion. Examples of inorganic fillers include reinforcing inorganic fillers such as fumed silica, fumed titanium dioxide, and fumed alumina, and non-reinforcing inorganic fillers such as fused silica, alumina, calcium carbonate, calcium silicate, titanium dioxide, ferric oxide, and zinc oxide. These inorganic fillers can be blended as appropriate in a total amount of 100 parts by mass or less (0 to 100 parts by mass) per 100 parts by mass of the total amount of components (A) and (B). Addition-curing silicone resin compositions may contain adhesive additives as needed to impart adhesion. Examples of adhesive additives include linear or cyclic organosiloxane oligomers containing 4 to 50, preferably 4 to 20, silicon atoms, each molecule containing at least two, preferably two or three, functional groups selected from a hydrogen atom bonded to a silicon atom (SiH group), an alkenyl group bonded to a silicon atom (e.g., Si-CH=CH2 group), an alkoxysilyl group (e.g., trimethoxysilyl group), and an epoxy group (e.g., glycidoxypropyl group, 3,4-epoxycyclohexylethyl group); organooxysilyl-modified isocyanurate compounds represented by the following general formula (2) and / or their hydrolysis condensates (organosiloxane-modified isocyanurate compounds).

[0048] For specific examples of bismaleimide resins used in thermosetting resin films, please refer to the examples described in the (Thermosetting Resins) section below. Other components, such as known additives, may be added to the thermosetting resin, as long as they do not impair the effects of the present invention. The thermosetting resin film used is one in which the thermosetting resin has been pre-processed into a film with a thickness preferably of 5 to 200 μm, more preferably of 10 to 100 μm.

[0049] <Resin for the second electromagnetic shielding film> In the second electromagnetic shielding film, the impregnation resin in the impregnation film is a thermoplastic resin or a thermosetting resin. (thermoplastic resin) In the second electromagnetic wave shielding film, the thermoplastic resin can be used in liquid form when impregnating the carbon nanotube nonwoven fabric, either dissolved in a solvent or, in the case of fluororesins, dispersed in a dispersion solvent such as water. After impregnating the carbon nanotube nonwoven fabric with the liquid thermoplastic resin in this way, the solvent or dispersion solvent can be removed by heating and drying to obtain an impregnated film. In the second electromagnetic wave shielding film, examples of thermoplastic resins in the impregnated film include polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyphenylene ether, polyether ether ketone, polyether ketone, and polyether sulfone. These may be used individually or in combination of two or more. Other components, such as known additives, may be added to the thermoplastic resin, as long as they do not impair the effects of the present invention.

[0050] (thermosetting resin) In the second electromagnetic wave shielding film, examples of thermosetting resins in the impregnation film include epoxy resins, allylated epoxy resins, allylated polyphenylene ether resins, phenolic resins, polyimide resins, polyamide resins, bismaleimide resins, maleimide resins, cyanate resins, cyclopentadiene-styrene copolymer resins, polyester resins, silicone resins, and acrylic resins. These may be used individually or in combination of two or more types. Among these, epoxy resins and bismaleimide resins shown below are preferred.

[0051] Preferably, the epoxy resin is one having two or more glycidyl groups in one molecule. Examples of epoxy resins used in the present invention include bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol AD-type epoxy resin, and bisphenol S-type epoxy resin; novolac-type epoxy resins such as epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, epoxy resins having a dicyclopentadiene skeleton, phenol novolac-type epoxy resin, and cresol novolac-type epoxy resin; and polyfunctional epoxy resins. These epoxy resins may be used individually or in combination of two or more types.

[0052] Any curing agent for epoxy resins that has a phenolic hydroxyl group or an amino group with active hydrogen and forms a crosslinked structure with the epoxy resin can be used. For curing agents with phenolic hydroxyl groups, any phenolic resin having a phenolic hydroxyl group can be used. For curing agents with amino groups, aromatic amine curing agents that yield epoxy resin cured products with high heat resistance and high modulus are preferred.

[0053] As bismaleimide resins, those represented by the following general formulas (1) and (2) are preferred due to their excellent heat resistance, low elasticity, toughness, and adhesive properties. [ka] (In formula (1), A represents a hydrocarbon group derived from the dimer acid skeleton.) [ka] (In formula (2), B is an independent tetravalent organic group having a cyclic structure, and X is an independent divalent hydrocarbon group having 6 to 200 carbon atoms, at least one of which is a hydrocarbon group derived from a dimer acid skeleton. n is between 1 and 100.)

[0054] Dimer acid is a liquid dibasic acid mainly composed of a 36-carbon dicarboxylic acid, produced by the dimerization of 18-carbon unsaturated fatty acids derived from natural materials such as vegetable oils. Dimer acid does not have a single skeleton but possesses multiple structures and several isomers exist. Representative dimer acids are classified as linear, monocyclic, aromatic cyclic, and polycyclic. In this specification, the dimer acid skeleton refers to a group derived from a dimer amine having a structure in which the carboxyl group of a dimer acid is replaced with a primary aminomethyl group, and the hydrocarbon group derived from the dimer acid skeleton is given as its average structure -C 36 H 70 It is sometimes written as -.

[0055] A typical bismaleimide resin of formula (1) is the bismaleimide resin shown in formula (3) below (SLK-6895; trade name, manufactured by Shin-Etsu Chemical Co., Ltd.). [ka] (C 36 H 72 (This refers to hydrocarbon groups derived from the dimer acid skeleton.) In formula (2), B independently represents a tetravalent organic group having a cyclic structure, and is preferably one of the tetravalent organic groups shown in the following structural formulas.

[0056] [ka] (The bonds in the above structural formula that are not bonded to substituents are bonded to the carbonyl carbon that forms the cyclic imide structure in formula (2).)

[0057] Furthermore, in formula (2), X is independently a divalent hydrocarbon group having 6 to 200 carbon atoms, preferably 8 to 100, and more preferably 10 to 50 carbon atoms. In particular, it is preferable that the branched divalent hydrocarbon group is one in which one or more hydrogen atoms are substituted with an alkyl or alkenyl group having 6 to 200 carbon atoms, preferably 8 to 100, and more preferably 10 to 50 carbon atoms. The branched divalent hydrocarbon group may be either a saturated aliphatic hydrocarbon group or an unsaturated hydrocarbon group, and may have an alicyclic structure or an aromatic ring structure in the middle of the molecular chain. At least one of X in formula (2) is a hydrocarbon group derived from a dimer acid skeleton.

[0058] In formula (2), n is between 1 and 100, preferably between 1 and 60, and more preferably between 1 and 50. If n is too large, solubility and fluidity may decrease, potentially resulting in poor moldability such as impregnation.

[0059] A typical bismaleimide resin of formula (2) is the following resin of formula (4) (SLK-3000; trade name, manufactured by Shin-Etsu Chemical Co., Ltd.). [ka]

[0060] The bismaleimide resins of formulas (1) and (2) may be used individually or in combination of two or more.

[0061] Representative bismaleimide resins include the SLK-6895 (manufactured by Shin-Etsu Chemical Co., Ltd.) and SLK-3000 (manufactured by Shin-Etsu Chemical Co., Ltd.) mentioned above, as well as the SLK-2000 series (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0062] The amount of bismaleimide resin impregnating the carbon nanotube nonwoven fabric is preferably 10 to 1000 parts by mass per 100 parts by mass of the nonwoven fabric.

[0063] When using bismaleimide resin as a thermosetting resin, it is preferable to use a reaction initiator for bismaleimide resin in combination as a curing catalyst. The reaction initiator for bismaleimide resin is not particularly limited as long as it promotes the crosslinking reaction, but examples include ionic catalysts such as imidazoles, organophosphorus compounds, tertiary amines, quaternary ammonium salts, boron trifluoride amine complexes, organophosphines, and organophosphonium salts; organic peroxides such as diallyl peroxide, dialkyl peroxide, peroxide carbonate, and hydroperoxide; and radical polymerization initiators such as azoisobutyronitrile. Among these, organic peroxides are preferred, and examples of organic peroxides include dicumyl peroxide, t-butyl peroxybenzoate, t-amyl peroxybenzoate, dibenzoyl peroxide, diuraloyl peroxide, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, 1,1-di(t-butyl peroxy)cyclohexane, di-t-butyl peroxide, and dibenzoyl peroxide. The reaction initiator is preferably added in an amount of 0.05 to 10 parts by mass, and more preferably in an amount of 0.1 to 5 parts by mass, per 100 parts by mass of bismaleimide resin. The reaction initiator may be used alone or in combination of two or more types.

[0064] The bismaleimide resins represented by general formulas (1) and (2) may be used in combination with other thermosetting resins. By using bismaleimide resin alone or in combination with other thermosetting resins as the thermosetting resin impregnating the carbon nanotube nonwoven fabric, greater toughness can be imparted. Furthermore, the bismaleimide resins represented by general formulas (1) and (2) may be mixed with the thermoplastic resins described above before use.

[0065] In the second electromagnetic wave shielding film, other components, such as known additives, may be added to the thermosetting resin in the impregnated film, as long as they do not impair the effects of the present invention.

[0066] <Additives to the resin in the first and second electromagnetic shielding films> Other components, such as known additives, may be used in the first and second electromagnetic shielding films, as long as they do not impair the effects of the present invention. Examples of other components include coupling agents and inorganic materials. The coupling agent and inorganic material may be added to either the thermoplastic resin film and the thermosetting resin film of the first electromagnetic shielding film, or to either the thermoplastic resin or the thermosetting resin of the second electromagnetic shielding film. Addition to the thermosetting resin composition, which is the raw material for the thermosetting resin film, is particularly preferred.

[0067] Coupling agents can be used to improve the wettability and adhesive strength between the carbon nanotube nonwoven fabric and the resin. Specific examples of coupling agents, such as those added to the carbon nanotube nonwoven fabric, are mentioned above and should be referred to. When adding such a coupling agent, the appropriate amount to use is in the range of 0.5 to 20 parts by mass per 100 parts by mass of thermoplastic resin or thermosetting resin. Addition to thermoplastic resin can be carried out, for example, by preparing a thermoplastic resin dissolved in a solvent and then adding the coupling agent to it.

[0068] Examples of inorganic materials include conductive inorganic materials and insulating inorganic materials. Conductive inorganic materials can further enhance electrical conductivity and improve electromagnetic wave shielding performance in the millimeter wave to terahertz frequency band. Insulating inorganic materials can further enhance the thermal conductivity of carbon nanotube nonwoven fabrics. Specific examples of conductive and insulating inorganic materials include those added to carbon nanotube nonwoven fabrics, as described above; please refer to those descriptions. In the first electromagnetic shielding film, the inorganic material may be laminated as a thermoplastic resin film or a thermosetting resin film, and in the second electromagnetic shielding film, the inorganic material may be dispersed in a thermoplastic resin or thermosetting resin and impregnated into a carbon nanotube nonwoven fabric. When an inorganic material is added, the amount added is preferably 5 to 60 parts by mass, and more preferably 10 to 50 parts by mass, per 100 parts by mass of the thermoplastic resin or thermosetting resin.

[0069] <Laminated film of the first electromagnetic wave shielding film> In the first electromagnetic wave shielding film, the laminated film is made by laminating a resin film on the front and back surfaces of a carbon nanotube nonwoven fabric. The total thickness of the laminated film is 10 to 1000 μm, preferably 20 to 500 μm. Within this range, the properties of the carbon nanotube as an electromagnetic shielding material can be fully utilized. Furthermore, by attaching a release film to the laminated film via an adhesive layer, handling is also made easier. The total thickness of the laminated film is the thickness when the laminated film is completed. If the thermoplastic resin film is laminated onto the carbon nanotube nonwoven fabric by heating and pressurizing, the total thickness is the thickness after that point. If the resin film is a thermosetting resin film that hardens after lamination, the total thickness is the thickness after hardening.

[0070] <Impregnated film for the second electromagnetic wave shielding film> In the second electromagnetic wave shielding film, the impregnated film is made by impregnating a carbon nanotube nonwoven fabric with an impregnation resin, i.e., a thermoplastic resin or a thermosetting resin. The total thickness of the impregnated film is 10 to 1000 μm, preferably 20 to 500 μm. Within this range, the properties of the carbon nanotube as an electromagnetic shielding material can be fully utilized. Furthermore, by attaching a release film to the impregnated film via an adhesive layer, handling is also made easier. The total thickness of the impregnated film is the thickness when the impregnated film is completed, which is the total thickness of the impregnated film after the thermoplastic resin solution has been impregnated into the carbon nanotube nonwoven fabric and then heated and dried to remove the solvent, or, in the case where a thermosetting resin is impregnated into the carbon nanotube nonwoven fabric and then cured, it is the total thickness after curing.

[0071] <Adhesive layer> In the first and second electromagnetic shielding films, an adhesive is used to attach and fix the electromagnetic shielding film to the surface of electronic components or circuit boards. Any available adhesive can be used, but acrylic resin or silicone resin is preferred because a wide range of adhesive strengths are available. Representative examples of silicone resins include KR100, KR130, KR3701, and KR3704, all manufactured by Shin-Etsu Chemical Co., Ltd. This type of adhesive is diluted with a solvent such as toluene, a catalyst is added, and then it is applied to one side of an electromagnetic shielding film. The adhesive layer is then formed by heat curing at a temperature of 100°C to 150°C for several minutes to remove the solvent. The thickness of the adhesive layer can be adjusted by changing the dilution of the solvent. Furthermore, the adhesive strength can be easily adjusted by mixing a light-tack adhesive with a heavy-tack adhesive. For bonding to heatable materials, thermosetting adhesives or bonding agents may also be used. The thickness of the adhesive layer is preferably 10 to 100 μm, more preferably 20 to 70 μm.

[0072] <Release film> In the first and second electromagnetic shielding films, polypropylene, PET, polyethylene film, fluororesin film, etc., can be used as the release film. If the adhesive layer applied to the electromagnetic shielding film is difficult to peel off from the release film, a release film treated with a release agent can be used. For ease of use, the thickness of the release film is preferably 10 to 50 μm. Alternatively, a film with a textured finish can be used as the release film.

[0073] <Method for manufacturing electromagnetic wave shielding film> The first electromagnetic shielding film can be manufactured, for example, by a melt-rolling method in which a resin film is laminated on the front and back surfaces of a carbon nanotube nonwoven fabric and heated to reduce its viscosity before being laminated onto the carbon nanotube nonwoven fabric, or by a transfer method in which a resin varnish is formed into a film using a coater, etc., and then transferred to the carbon nanotube nonwoven fabric using a press or laminator. As the resin film, a thermoplastic resin film or a thermosetting resin film can be used, and as the thermosetting resin film, an uncured, semi-cured, or fully cured thermosetting resin film can be used.

[0074] The melt rolling method has several advantages, including the fact that it does not require the removal of solvents and the working environment is relatively good. In the melt rolling method, carbon nanotube nonwoven fabric is widened to the required width using a bar or similar device, a film-formed thermoplastic resin or thermosetting resin is sandwiched between release paper from above and below, and then the release paper is peeled off and the nonwoven fabric is fed to several pairs of heated metal rolls installed at approximately the same height as the direction of travel of the carbon nanotube nonwoven fabric. By nipping these rolls, the thermoplastic resin or thermosetting resin is heated and pressurized onto the carbon nanotube nonwoven fabric. In the melt rolling method, since the nip pressure is linear pressure, it is better to increase the number of nip rolls to ensure sufficient heating and pressurization. Alternatively, the product may be pressure-molded using a molding press such as a multi-stage press that can be heated without using heated metal rolls.

[0075] In the transfer method, a resin varnish is coated onto a base film, the solvent is dried to obtain a resin film, and then both sides of a carbon nanotube nonwoven fabric are sandwiched between the resin films and pressed together using a laminator or press to transfer the resin film onto the carbon nanotube nonwoven fabric. Any film can be used as the base film, but resin films tend to peel off easily. PET film, PE film, PP film, Teflon® film, Aflex film, etc. are preferred. The above-mentioned base film can be subjected to various surface treatments, such as corona treatment, plasma treatment, or silicone treatment, as needed. Any solvent can be used as the solvent for resin varnish, but highly volatile solvents are preferred. Examples include alcohols such as ethanol and IPA, acetone, toluene, xylene, anisole, hydrocarbon solvents, and silicone solvents. The concentration of the resin varnish is preferably 0.1 to 200 parts by mass per 100 parts by mass of resin. Any method can be used to coat the base film with resin varnish, but the use of a spin coater or bar coater is preferred because it is easy to do so. The temperature at which the resin film on the base film is dried is preferably a temperature at which the thermosetting resin does not react, and is preferably 30°C to 120°C. Furthermore, when sandwiching both sides of the carbon nanotube nonwoven fabric between resin films and pressing them together using a laminator or press, and transferring the resin film to the carbon nanotube nonwoven fabric, pressure or heat can be applied as needed.

[0076] After laminating the resin film onto the carbon nanotube nonwoven fabric using the method described above, if a thermosetting resin film is used, the semi-cured thermosetting resin film is cured by heating and pressurizing as needed to produce an electromagnetic wave shielding film. By selecting the chemical structure of thermoplastic and thermosetting resins in resin films, and the curing method for thermosetting resins, it is possible to produce laminated films ranging from hard and tough to flexible and shape-conforming.

[0077] The second electromagnetic shielding film can be manufactured, for example, by a wet process in which a thermoplastic resin or thermosetting resin is dissolved in a solvent, or dispersed in a dispersion solvent to reduce its viscosity, and then impregnated into a carbon nanotube nonwoven fabric. In the wet method, a resin film impregnated with thermoplastic resin or thermosetting resin is produced by impregnating a carbon nanotube nonwoven fabric with a thermoplastic resin or thermosetting resin, and then removing a volatile solvent or dispersion solvent. This process yields a resin film impregnated with thermoplastic resin or a prepreg impregnated with uncured thermosetting resin. If solvent remains in the prepreg, it can negatively affect the molding process and worsen the working environment, among other problems. Therefore, the amount of solvent remaining in the prepreg should be 1% by mass or less, preferably 0.5% by mass or less. Depending on the boiling point of the solvent used, solvent removal can be easily achieved by heat treatment at 80°C to 150°C for 10 minutes to 1 hour. A thermoplastic resin-impregnated film is produced by impregnating a carbon nanotube nonwoven fabric with a thermoplastic resin using the method described above. Alternatively, a thermosetting resin-impregnated film is produced by impregnating a carbon nanotube nonwoven fabric with a thermosetting resin using the method described above, and then curing the semi-cured thermosetting resin by heating and pressurizing it.

[0078] Subsequently, an adhesive layer is laminated to one side of the three-layer laminated film in the first electromagnetic wave shielding film, or the impregnated film in the second electromagnetic wave shielding film, and a release film is laminated to the adhesive surface of the adhesive layer to obtain the electromagnetic wave shielding film of the present invention.

[0079] By processing using this molding method, large-area electromagnetic shielding films of a predetermined thickness can be supplied in sheet or roll form, wound onto paper tubes or the like.

[0080] The electromagnetic shielding film of the present invention, processed in this manner, is lightweight and offers excellent electromagnetic shielding properties, processability, and ease of use. Therefore, it is suitable for applications requiring electromagnetic shielding, such as surface coatings for electronic circuit boards with numerous electronic components, housings for automobile batteries and other electromagnetic wave-generating devices, motor components, and DC / DC converter encapsulants. Furthermore, it can be used as a component or container for communication equipment that uses high frequencies above millimeter waves and requires electromagnetic shielding and heat resistance.

[0081] Figure 1A is a schematic longitudinal cross-sectional view showing an example of the first electromagnetic wave shielding film. This electromagnetic wave shielding film 1a is a five-layer electromagnetic wave shielding film having a three-layer laminated film in which resin films 3 are laminated on the front and back surfaces of a carbon nanotube nonwoven fabric 2, an adhesive layer 4 laminated on one side of the laminated film, and a release film 5 laminated on the adhesive surface of the adhesive layer 4.

[0082] This electromagnetic wave shielding film 1a can be manufactured by processing it using the molding method described above to produce an electromagnetic wave shielding film of a predetermined thickness and large area. As shown in Figure 2, it can be wound into a roll like glass cloth to form an electromagnetic wave shielding film 6. Then, as shown in Figure 3, the rolled electromagnetic wave shielding film 6 can be cut into tape shapes and used as an electromagnetic wave shielding film 7 cut into tape shapes.

[0083] The first electromagnetic wave shielding film 1a, which has a five-layer structure, can shield electromagnetic waves by, for example, peeling off the release film 5 and attaching it to the surface of an electronic component 8 provided on a printed circuit board 9, as shown in Figure 4A. Similarly, the second electromagnetic wave shielding film 1b, shown in Figure 1B, which has a three-layer structure, namely an impregnated film 10 made by impregnating a carbon nanotube nonwoven fabric with resin, an adhesive layer 4 laminated on one side of the impregnated film 10, and a release film 5 laminated on the adhesive side of the adhesive layer 4, can shield electromagnetic waves by, for example, peeling off the release film 5 and attaching the impregnated film 10 to the surface of an electronic component 8 provided on a printed circuit board 9, as shown in Figure 4B.

[0084] Furthermore, as shown in Figure 5, electromagnetic waves can be shielded by wrapping the surface of the copper wiring 11 with an electromagnetic wave shielding film 7 cut into a tape shape. As shown in Figure 6, the first electromagnetic wave shielding film 1a, which has a five-layer structure, can shield electromagnetic waves by, for example, peeling off the release film 5 and attaching it to cover the entire circuit board 12, including the surface of the electronic components 8 provided on the printed wiring board 9, as shown in Figure 6. The second electromagnetic wave shielding film 1b works in the same way. [Examples]

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are shown below. Furthermore, the physical properties and characteristic values ​​in the present invention were measured by the following methods.

[0086] material (1) Carbon nanotube nonwoven fabric Nonwoven fabric 1 MIRALON T01 (manufactured by Huntsman) Thickness 20 μm, resistivity 3.5E-03 (Ω·cm), tensile strength ratio 1.30 Nonwoven fabric 2 A dispersion was prepared by mixing 100 parts by mass of water and 0.05 parts by mass of single-walled carbon nanotubes (EC1.5-P, manufactured by Meijo Nanocarbon Co., Ltd.) in a mixer (IFM-800D, manufactured by Iwatani Corporation). After filtering the dispersion, the water was removed by drying at 80°C for 4 hours to obtain a single-walled carbon nanotube nonwoven fabric. This single-walled carbon nanotube nonwoven fabric had a thickness of 40 μm, a resistivity of 1.05E-03 (Ω·cm), and a tensile strength ratio of 1.08. Nonwoven fabric 3 A dispersion was prepared by mixing 100 parts by mass of water and 0.05 parts by mass of multi-walled carbon nanotubes (EC2.0-P, manufactured by Meijo Nanocarbon Co., Ltd.) in a mixer (IFM-800D, manufactured by Iwatani Corporation). After filtering the dispersion, a nonwoven fabric was prepared by drying it at 80°C for 4 hours. The prepared nonwoven fabric was impregnated for 30 seconds in a 5% by mass polysilazane solution (X-45-870, manufactured by Shin-Etsu Chemical Co., Ltd.) diluted with dibutyl ether, then removed and cured at 150°C for 2 hours. After curing, the mass of the CNT nonwoven fabric increased by 44.3% by mass, and surface analysis revealed that a silica layer had formed on the surface of the carbon nanotube fibers. This polysilazane-treated multi-walled carbon nanotube nonwoven fabric had a thickness of 42 μm, a resistivity of 1.60E-03 (Ω·cm), and a tensile strength ratio of 1.08. Nonwoven fabric 4 A dispersion was prepared by mixing 100 parts by mass of water, 0.4 parts by mass of single-walled carbon nanotubes (EC1.5-P, manufactured by Meijo Nanocarbon Co., Ltd.), and 0.4 parts by mass of the ionic surfactant sodium deoxycholate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in a mixer (Iwateni Corporation, IFM-800D). The dispersion was coated onto a release-treated PET film (E7006, manufactured by Toyobo Ester Co., Ltd.) using a doctor blade with a clearance of 1.5 mm, dried at 100°C for 1 hour, and peeled off the PET film to obtain a nonwoven fabric. This ionic surfactant-containing single-walled carbon nanotube nonwoven fabric had a thickness of 20 μm, a resistivity of 7.50E-04 (Ω·cm), and a tensile strength ratio of 1.02. Nonwoven fabric 5 (Nonwoven fabric for comparative example) A dispersion was prepared by mixing 100 parts by mass of water and 0.10 parts by mass of multi-walled carbon nanotubes (EC2.0-P, manufactured by Meijo Nanocarbon Co., Ltd.) in a mixer (IFM-800D, manufactured by Iwatani Corporation). After filtering the dispersion, the material was dried at 80°C for 4 hours while being pulled uniaxially in the planar direction to obtain a multi-walled carbon nanotube nonwoven fabric. This multi-walled carbon nanotube nonwoven fabric had a thickness of 182 μm, a resistivity of 5.50E-03 (Ω·cm), and a tensile strength ratio of 2.32.

[0087] (2)Thermoplastic resin, thermosetting resin Thermoplastic resin film 1 30μm thick polypropylene film (Silfan, manufactured by Gunze Corporation) Thermoplastic resin film 2 Thermoplastic fluoropolymer film with a thickness of 35 μm (Fluon PFA, manufactured by AGC Corporation) Thermosetting resin 1 The bismaleimide resin represented by formula (4) above (SLK-3000, manufactured by Shin-Etsu Chemical Co., Ltd., number average molecular weight 5200) Thermosetting resin film 2 Uncured silicone resin film with a thickness of 40 μm (PLF-100D, manufactured by Shin-Etsu Chemical Co., Ltd.) (3) Adhesive 1 KR100 (manufactured by Shin-Etsu Chemical Co., Ltd.) (4) Release film 1 Release-treated PET film (thickness 40μm) (manufactured by Shin-Etsu Film Co., Ltd.)

[0088] Measurement method (1) Tensile strength ratio The tensile strength of the nonwoven fabric was measured by cutting a 10 mm x 100 mm test piece from the fabric and measuring it using a Shimadzu Autograph (AGS-500NS). The average of five measurements was taken as the tensile strength. The tensile strength was measured in various directions of the nonwoven fabric, and the direction with the maximum tensile strength was defined as the longitudinal direction, and the direction perpendicular to the longitudinal direction was defined as the transverse direction. The tensile strength ratio in the longitudinal / transverse direction was then obtained. (2) Specific resistance The surface resistivity of carbon nanotube nonwoven fabrics was measured using a Loresta-GX MCP-T700 (low-resistivity resistivity meter, manufactured by Nitto Seiko Analytech Co., Ltd.), a Hiresta-UX MCP-HT800 (high-resistivity resistivity meter, manufactured by Nitto Seiko Analytech Co., Ltd.), and an EC-80P (eddy current resistance meter, manufactured by NAPSON Corporation). The resistivity was calculated using these measurements. The resistivity was calculated using the following formula. Specific resistance (Ω cm) = surface resistivity (Ω / □) x thickness (cm) (3) Electromagnetic shielding characteristics As an electromagnetic shielding characteristic, an electromagnetic shielding film cut to a 12 cm square was used, and the electric field attenuation rate in two orthogonal directions, vertical and horizontal, at 70 GHz was measured using an electromagnetic shielding measurement device manufactured by Keycom. A schematic diagram of the measurement system is shown in Figure 7. The nonwoven fabric sample was placed between two antennas on the y-axis connected to a vector network analyzer (MS46522B, manufactured by Anritsu Corporation) so that its surface was perpendicular to the y-axis. By irradiating the sample with electromagnetic waves having electric field oscillations in the z-axis direction, the electromagnetic waves transmitted through the sample were measured, and the transmission attenuation amount (dB) was recorded. In addition, by tilting the angle of the sample by 90 degrees around the y-axis, the transmission attenuation amount (dB) in both the vertical and horizontal directions was measured, and the electric field attenuation rate was determined. Furthermore, the electromagnetic shielding characteristics in the low-frequency range of 100 MHz to 6000 MHz were measured using the method shown in Figure 8. An organic substrate (in Figure 8, reference numeral 18 indicates a microstrip line commonly used as a transmission line in printed circuit board wiring) on ​​which various electronic components were mounted was wrapped in the measurement sample 13. An alternating magnetic field 19 was applied to the measurement sample 13 from a probe 17 placed on top of the sample at a distance from it, and the electromagnetic shielding characteristics in the 100 MHz to 6000 MHz range were measured. Furthermore, as an electromagnetic shielding characteristic in the high-frequency range, the transmission attenuation (dB) in the 60GHz to 90GHz range was measured using the method shown in Figure 7.

[0089] Example 1 A thermoplastic resin film 1 was laminated on top of a nonwoven fabric 1, and a laminated film with a total thickness of 75 μm was prepared by heat pressing at 150°C to create a three-layer structure. Adhesive 1 was applied to one side of this three-layer film to a thickness of 20 μm and heated and cured at 150°C for 1 hour. Then, a release film 1 was laminated to create a five-layer electromagnetic wave shielding film. As a measure of the shielding characteristics of the prepared electromagnetic wave shielding film, the electric field attenuation rate was measured using the measurement method described above after peeling off the release film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating an electronic circuit board on which semiconductor elements are mounted, a shielded film-coated circuit board that conforms to the irregularities of the circuit surface was prepared (Figure 4A). The shielding film could be easily peeled off the shielded film-coated circuit board.

[0090] Example 2 A thermoplastic resin film 2 was laminated on top of a nonwoven fabric 2, and a laminated film with a total thickness of 108 μm was fabricated by heat pressing at 325°C. One side of this three-layer film was treated with Ar plasma for 30 seconds, adhesive 1 was applied to a thickness of 30 μm, and heated and cured at 150°C for 1 hour. Then, a release film 1 was laminated to create a five-layer electromagnetic shielding film. As a measure of the shielding characteristics of the fabricated electromagnetic shielding film, the electric field attenuation rate was measured using the measurement method described above after peeling off the release film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating an electronic circuit board on which semiconductor elements are mounted, a shielded film-coated circuit board that conforms to the irregularities of the circuit surface was fabricated. The shielding film could be easily peeled off the shielded film-coated circuit board.

[0091] Example 3 A toluene solution was prepared consisting of 100 parts by mass of thermosetting resin 1, 1 part by mass of curing catalyst (dicumyl peroxide (Perkmyl D, manufactured by NOF Corporation)), and 200 parts by mass of toluene. After impregnating nonwoven fabric 1 with this toluene solution, the toluene was dried off by heating at 100°C for 10 minutes to produce a nonwoven fabric impregnated with semi-cured bismaleimide resin. This nonwoven fabric was pressure-cured at 180°C and 0.5 MPa for 1 hour to produce an impregnated film with a total thickness of 24 μm. Adhesive 1 was applied to one side of the resin-impregnated nonwoven fabric sheet to a thickness of 30 μm and heat-cured, and then a release film 1 was laminated to produce a three-layer electromagnetic wave shielding film. Furthermore, by peeling off the release film and coating an electronic circuit board on which semiconductor elements are mounted, a shielding film-coated circuit board that follows the irregularities of the circuit surface could be produced. The shielding film could be easily peeled off the shielding film-coated circuit board.

[0092] Example 4 An electromagnetic wave shielding film consisting of three layers was prepared in the same manner as in Example 3, except that the carbon nanotube nonwoven fabric was replaced with nonwoven fabric 3. The total thickness of the impregnated film was 46 μm. The electric field attenuation rate was measured using this film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating an electronic circuit board on which semiconductor elements are mounted, a shielding film-coated circuit board that conforms to the irregularities of the circuit surface was fabricated. The shielding film could be easily peeled off the shielding film-coated circuit board.

[0093] Example 5 A thermosetting resin film 2 was laminated above and below a nonwoven fabric 1 to create a laminated film with a total thickness of 94 μm. Then, an electromagnetic wave shielding film consisting of five layers was fabricated using the same method as in Example 2. However, the pressure molding temperature was set to 150°C. As a measure of the shielding characteristics of the fabricated electromagnetic wave shielding film, the electric field attenuation rate was measured using the measurement method described above after peeling off the release film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating an electronic circuit board with semiconductor elements mounted on it, a shielded film-coated circuit board that conformed to the surface irregularities of the circuit was fabricated. The shielded film could be easily peeled off the shielded film-coated circuit board.

[0094] Example 6 An electromagnetic wave shielding film was fabricated in the same manner as in Example 5, except that the carbon nanotube nonwoven fabric was replaced with nonwoven fabric 4. The total thickness of the laminated film was 98 μm. The electric field attenuation rate was measured using this film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating an electronic circuit board on which semiconductor elements are mounted, a shielding film-coated circuit board that conforms to the irregularities of the circuit surface was fabricated. The shielding film could be easily peeled off the shielding film-coated circuit board.

[0095] Example 7 The electromagnetic shielding film with an adhesive layer on one side, fabricated in Example 3, was used to encase the entire organic substrate on which various electronic components were mounted. The electromagnetic shielding characteristics in the 100 MHz to 6000 MHz range were then compared with those of a 36 μm copper foil using the method shown in Figure 8. The results are shown in Figures 9(A) and (B).

[0096] Example 8 The 55 μm thick adhesive electromagnetic shielding film used in Example 7 was prepared as a 50 mm square sheet, and the transmission attenuation in the high-frequency range of 60 GHz to 90 GHz was measured according to the method shown in Figure 7. The results are shown in Figure 10.

[0097] Example 9 The electromagnetic shielding film with an adhesive layer on one side, fabricated in Example 3, was used to encase the entire organic substrate on which various electronic components were mounted, and its electromagnetic shielding characteristics from 100 Hz to 1 MHz were evaluated. Numerous electromagnetic noises of approximately 10 dB were generated in the measured frequency band, but the electromagnetic waves could be shielded by using the film of this embodiment.

[0098] Comparative Example 1 An electromagnetic wave shielding film was prepared in the same manner as in Example 5, except that the carbon nanotube nonwoven fabric was replaced with nonwoven fabric 5. The total thickness of the laminated film was 260 μm. The electric field attenuation rate was measured using this film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating an electronic circuit board on which semiconductor elements are mounted, a shielding film-coated circuit board that conforms to the irregularities of the circuit surface was fabricated. The shielding film could be easily peeled off the shielding film-coated circuit board.

[0099] [Table 1]

[0100] The electromagnetic shielding films of Examples 1 to 6, which used carbon nanotube nonwoven fabric with a low tensile strength ratio in the longitudinal / transverse direction, exhibited a high electric field attenuation rate. Furthermore, the adhesive electromagnetic wave shielding film of the present invention was able to shield all electromagnetic waves from the low frequency range of 100 Hz to the high frequency range of 90 GHz. Figure 11 shows the appearance of a prototype of an adhesive-layer electromagnetic shielding film. [Industrial applicability]

[0101] According to the present invention, electromagnetic shielding for electronic components and wiring mounted inside electronic devices is easily achieved, and the resulting electronic devices are compatible with high-speed communications such as 5G and 6G, thus possessing very high industrial value and potential for industrial application. [Explanation of symbols]

[0102] 1a First electromagnetic shielding film with a 5-layer structure 1b A second electromagnetic shielding film with a three-layer structure. 2. Carbon nanotube nonwoven fabric 3. Resin film 4. Adhesive layer 5. Release film 6. Electromagnetic shielding film rolled into a roll. 7. Electromagnetic shielding film cut into strips. 8 Electronic Components 9 Printed circuit board 10 Resin-impregnated nonwoven fabric (impregnated film) 11 Copper Wiring 12 Circuit boards 13. Samples to be measured 14 Antennas 15 Incident wave 16 Transmitted wave 17 probe 18 microstrip lines 19 AC magnetic field

Claims

1. A laminated film having a total thickness of 10 to 1000 μm, formed by laminating a resin film onto the front and back surfaces of a carbon nanotube nonwoven fabric having a resistivity of 0.005 Ω·cm or less, a thickness of 500 μm or less, and a tensile strength ratio in the longitudinal / transverse direction (with the direction perpendicular to the longitudinal direction being the transverse direction) of 0.5 to 2.0, and An adhesive layer laminated on one side of the laminated film, An electromagnetic wave shielding film having a release film laminated on the adhesive surface of the adhesive layer.

2. An impregnated film made by impregnating a carbon nanotube nonwoven fabric with a resin, having a resistivity of 0.005 Ω·cm or less, a thickness of 500 μm or less, a tensile strength ratio in the longitudinal / transverse direction (where the direction of maximum tensile strength is defined as the longitudinal direction and the direction perpendicular to the longitudinal direction as the transverse direction) of 0.5 to 2.0, with a total thickness of 10 to 1000 μm, An adhesive layer laminated on one side of the impregnated film, An electromagnetic wave shielding film having a release film laminated on the adhesive surface of the adhesive layer.

3. The electromagnetic wave shielding film according to claim 1 or 2, wherein the carbon nanotubes in the carbon nanotube nonwoven fabric are single-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture thereof.

4. The electromagnetic wave shielding film according to claim 1, wherein the resin film is a thermoplastic resin film, and the softening point of the thermoplastic resin in the film is 400°C or lower.

5. The electromagnetic wave shielding film according to claim 4, wherein the thermoplastic resin film comprises one or more thermoplastic resins selected from polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, and polyimide.

6. The electromagnetic wave shielding film according to claim 1, wherein the resin film is a thermosetting resin film, and the thermosetting resin in the film comprises one or more selected from epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenolic resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin, and acrylic resin.

7. The electromagnetic wave shielding film according to claim 2, wherein the impregnation resin is a thermoplastic resin, and the thermoplastic resin comprises one or more selected from polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, and polyimide.

8. The electromagnetic wave shielding film according to claim 2, wherein the impregnation resin is a thermosetting resin, and the thermosetting resin comprises one or more selected from epoxy resins, allylated epoxy resins, allylated polyphenylene ether resins, phenolic resins, polyimide resins, polyamide resins, bismaleimide resins, maleimide resins, cyanate resins, cyclopentadiene-styrene copolymer resins, polyester resins, silicone resins, and acrylic resins.

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