Electromagnetic wave shielding film

Abstract

Provided is an electromagnetic wave shielding film covering electronic components and wiring mounted inside an electronic device, the electromagnetic wave shielding film being capable of sufficiently exhibiting characteristics as an electromagnetic wave shielding material while suppressing the thickness of a carbon nanotube nonwoven fabric, and being easy to handle. The electromagnetic wave shielding film is an electromagnetic wave shielding film comprising a carbon nanotube nonwoven fabric having a resistivity of 0.00005 to 0.05 Omega * cm and a thickness of 1 to 500 [mu] m, and a resin, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer, the release film comprising a laminated film in which two or more layers of the carbon nanotube nonwoven fabric are laminated and which has a total thickness of 5-1500 [mu] m, a pressure-sensitive adhesive layer laminated on one outermost surface of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer.

Description

Technical Field

[0001] This invention relates to an electromagnetic wave shielding film that covers electronic components, wiring, etc., installed inside electronic devices and shields them from electromagnetic waves. Background Technology

[0002] In recent years, research has focused on the practical application of high-speed communications such as 5G and 6G, utilizing electromagnetic waves in the millimeter-wave and terahertz frequency bands. As the number of wireless devices using electromagnetic waves in communication increases, the amount of electromagnetic waves present in space continues to rise. Therefore, electronic devices may malfunction due to interference from surrounding electromagnetic waves, or leak information due to their own generated electromagnetic waves. Furthermore, the accurate transmission and reception of various electromagnetic waves, from low to high frequencies, is crucial for advancing autonomous driving technologies such as automobiles.

[0003] To avoid obstacles caused by electromagnetic waves, electromagnetic wave shielding has become a crucial technical issue. Against this backdrop, there is a growing demand for electromagnetic wave shielding materials with excellent shielding performance in the microwave, millimeter-wave, and terahertz frequency bands. With the increasing utilization of electromagnetic waves, the demand for new functionalities in electromagnetic wave shielding materials, such as thin-film, lightweight, and large-area applications, is also rising.

[0004] Besides metallic materials, numerous electromagnetic wave shielding technologies have been proposed that utilize carbon black, graphene, carbon nanotubes, and conductive polymers as electromagnetic wave shielding materials. Among these, carbon nanotubes, made from carbon, have attracted attention as a promising electromagnetic wave shielding material.

[0005] As electromagnetic wave shielding materials using carbon nanotubes, there are paste materials in which carbon nanotubes are dispersed in resin (Patent Document 1) and water-based coatings dispersed in aqueous solution (Patent Document 2), etc. However, they are all difficult to process, and the carbon nanotubes used are also fine fibrous with a large specific surface area, which cannot be dispersed in large quantities. Therefore, their conductivity is not sufficient and is not at a level that can be tolerated for practical use.

[0006] In addition, a method has been disclosed for adding protonating agents such as hydrated hydrogen ions and hydrochloric acid to carbon nanotube sheets, and then adding iron, cobalt, and other ferromagnetic materials to improve conductivity (Patent Document 3). However, compared with metal foils such as aluminum and copper, the conductivity is low and the reflection loss is also small. Therefore, to obtain shielding performance equivalent to that of metals, the sheet thickness needs to be increased, which increases the attenuation loss and becomes a problem when installing in miniaturized equipment.

[0007] Recently, carbon nanotube condensed sheets have attracted attention as electromagnetic wave shielding materials. However, compared with metal foils such as aluminum and copper, these condensed sheets have low conductivity and cannot fully utilize their properties.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2009-144000

[0011] Patent Document 2: Japanese Patent Application Publication No. 2012-174833

[0012] Patent Document 3: Japanese Patent Application Publication No. 2015-187077 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] The present invention was made in view of the above-mentioned actual situation, and provides an electromagnetic wave shielding film for covering electronic components and wiring installed inside electronic devices, which suppresses the thickness of carbon nanotube nonwoven fabric, can fully exert its properties as an electromagnetic wave shielding material, is easy to handle, and is suitable for use as an electromagnetic wave shielding film.

[0015] Methods for solving problems

[0016] In order to achieve the above objectives, the inventors conducted in-depth research and discovered that the following electromagnetic wave shielding film achieves the above objectives, thus completing this invention.

[0017] Therefore, the present invention provides the following electromagnetic wave shielding film.

[0018] 1. An electromagnetic wave shielding film comprising a carbon nanotube nonwoven fabric with a resistivity of 0.00005 to 0.05 Ω·cm and a thickness of 1 to 500 μm, and a resin, comprising a laminated film having two or more layers of the carbon nanotube nonwoven fabric stacked together with a total thickness of 5 to 1500 μm, a pressure-sensitive adhesive layer stacked on one of the outermost surfaces of the laminated film, and a release film stacked on the adhesive surface of the pressure-sensitive adhesive layer.

[0019] 2. The electromagnetic wave shielding film according to claim 1, wherein the laminated film is a resin laminated film formed by laminating carbon nanotube nonwoven fabric and resin film.

[0020] 3. The electromagnetic wave shielding film according to claim 2, wherein the resin film is a thermoplastic resin film, and the softening point of the thermoplastic resin is below 400°C.

[0021] 4. The electromagnetic wave shielding film according to claim 3, wherein the thermoplastic resin constituting the thermoplastic resin film comprises one or more selected from polyethylene, polypropylene, fluoropolymer, polyethylene terephthalate, polyethylene naphthalate and polyimide.

[0022] 5. The electromagnetic wave shielding film according to claim 2, wherein the resin film is a thermosetting resin film, and the thermosetting resin is selected from one or more of epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenolic resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate ester resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin and acrylic resin.

[0023] 6. The electromagnetic wave shielding film according to claim 1, wherein the laminated film is an impregnated laminated film formed by laminating two or more layers of impregnated films in which resin is impregnated in carbon nanotube nonwoven fabric.

[0024] 7. The electromagnetic wave shielding film according to claim 1, wherein the laminated film is an impregnation film in which resin is impregnated in carbon nanotube nonwoven fabric, and a nonwoven fabric impregnation laminated film formed by laminating the carbon nanotube nonwoven fabric in the impregnation film.

[0025] 8. The electromagnetic wave shielding film according to claim 6 or 7, wherein the resin comprises one or more thermoplastic resins selected from polyethylene, polypropylene, fluoropolymer, polyethylene terephthalate, polyethylene naphthalate and polyimide.

[0026] 9. The electromagnetic wave shielding film according to claim 6 or 7, wherein the resin comprises one or more thermosetting resins selected from epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenolic resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate ester resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin and acrylic resin.

[0027] 10. The electromagnetic wave shielding film according to any one of 1 to 9, wherein the carbon nanotubes constituting the carbon nanotube nonwoven fabric are single-layer carbon nanotubes, multi-layer carbon nanotubes, or mixtures thereof.

[0028] The effects of the invention

[0029] The electromagnetic wave shielding film of the present invention, which has two or more layers of thin carbon nanotube nonwoven fabric, exhibits the same electromagnetic wave shielding performance as the case where only one layer of thick carbon nanotube nonwoven fabric is used. As an electromagnetic wave shielding material utilizing carbon nanotubes, its characteristics can be fully utilized. Attached Figure Description

[0030] Figure 1A A longitudinal cross-sectional view is shown to schematically illustrate an example of a first electromagnetic wave shielding film formed by laminating carbon nanotube nonwoven fabric and a resin film.

[0031] Figure 1B A longitudinal cross-sectional view is shown schematically as an example of a second electromagnetic wave shielding film as an impregnated laminated film.

[0032] Figure 1C A longitudinal cross-sectional view is shown to schematically illustrate an example of a third electromagnetic wave shielding film formed by laminating an impregnated membrane with a carbon nanotube nonwoven fabric.

[0033] Figure 2 A perspective view illustrating an example of a first electromagnetic wave shielding film being rolled up like glass cloth.

[0034] Figure 3 A perspective view illustrating an example of cutting a rolled electromagnetic wave shielding film into strips.

[0035] Figure 4A A longitudinal cross-sectional view is shown schematically, illustrating an example of peeling and attaching a release film from the first electromagnetic wave shielding film to the surface of an electronic component.

[0036] Figure 4B A longitudinal cross-sectional view is shown schematically, illustrating an example of peeling and attaching a release film from the second electromagnetic wave shielding film to the surface of an electronic component.

[0037] Figure 4C A longitudinal cross-sectional view is shown schematically, illustrating an example of peeling and attaching a release film from the third electromagnetic wave shielding film to the surface of an electronic component.

[0038] Figure 5 A perspective view illustrating an example of wrapping the surface of a copper wiring with an electromagnetic wave shielding film cut into strips.

[0039] Figure 6 This is a longitudinal cross-sectional view illustrating an example of an entire circuit board being covered with an electromagnetic wave shielding film. A portion of the cross-section is not depicted with diagonal lines.

[0040] Figure 7 This is a schematic diagram of the measurement system for electromagnetic wave shielding characteristics in the embodiment. Detailed Implementation

[0041] The present invention will now be described in detail.

[0042] The electromagnetic wave shielding film of the present invention comprises a carbon nanotube nonwoven fabric with a resistivity of 0.00005 to 0.05 Ω·cm and a thickness of 1 to 500 μm, and a resin. It comprises a laminated film consisting of two or more layers of the aforementioned carbon nanotube nonwoven fabric with a total thickness of 5 to 1500 μm, a pressure-sensitive adhesive layer laminated on one of the outermost surfaces of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer. As described above, there is no particular limitation as long as two or more layers of the aforementioned specific carbon nanotube nonwoven fabric are laminated. The number of layers containing the carbon nanotube nonwoven fabric can be two or more. Specifically, the following three embodiments can be listed as examples.

[0043] (1) The laminated film is a resin laminated film formed by laminating carbon nanotube nonwoven fabric and resin film.

[0044] (2) The laminated film is an impregnated laminated film formed by laminating two or more layers of impregnated film in which resin is impregnated in carbon nanotube nonwoven fabric.

[0045] (3) The laminated film is an impregnation film in which resin is impregnated in carbon nanotube nonwoven fabric and a nonwoven fabric impregnation laminated film formed by laminating the carbon nanotube nonwoven fabric in the impregnation film.

[0046] The electromagnetic wave shielding film, specifically in the laminated film selected from (1) resin laminated film, (2) impregnated laminated film and (3) nonwoven impregnated laminated film, has a pressure-sensitive adhesive layer laminated on one of its outermost surfaces and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer.

[0047] Hereinafter, the electromagnetic wave shielding film having the above-mentioned (1) resin laminated film is also referred to as the first electromagnetic wave shielding film, the electromagnetic wave shielding film having (2) impregnated laminated film is also referred to as the second electromagnetic wave shielding film, and the electromagnetic wave shielding film having (3) non-woven impregnated laminated film is also referred to as the third electromagnetic wave shielding film.

[0048] (1) An electromagnetic wave shielding film, which is an electromagnetic wave shielding film having a resistivity of 0.00005 to 0.05 Ω·cm and a thickness of 1 to 500 μm of carbon nanotube nonwoven fabric and resin, comprising two or more layers having the carbon nanotube nonwoven fabric, the laminated film being a resin laminated film formed by laminating carbon nanotube nonwoven fabric and resin film, and the resin laminated film having a total thickness of 5 to 1500 μm, a pressure-sensitive adhesive layer laminated on one of the outermost surfaces of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer.

[0049] (2) An electromagnetic wave shielding film, which is an electromagnetic wave shielding film having a resistivity of 0.00005 to 0.05 Ω·cm and a thickness of 1 to 500 μm of carbon nanotube nonwoven fabric and resin, comprising two or more layers of the carbon nanotube nonwoven fabric, the laminated film being an impregnation film consisting of two or more layers of resin impregnated in the carbon nanotube nonwoven fabric, an impregnation laminated film with a total thickness of 5 to 1500 μm, a pressure-sensitive adhesive layer laminated on one of the outermost surfaces of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer.

[0050] (3) An electromagnetic wave shielding film, which is an electromagnetic wave shielding film having a resistivity of 0.00005 to 0.05 Ω·cm and a thickness of 1 to 500 μm of carbon nanotube nonwoven fabric and resin, comprising two or more layers having the carbon nanotube nonwoven fabric, the laminated film being an impregnation film in which resin is impregnated with the carbon nanotube nonwoven fabric, and a nonwoven fabric impregnation laminated film in which the carbon nanotube nonwoven fabric is laminated with the impregnation film and has a total thickness of 5 to 1500 μm, a pressure-sensitive adhesive layer laminated on one of the outermost surfaces of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer.

[0051] In this invention, the laminated film requires two or more layers of the aforementioned carbon nanotube nonwoven fabric. As a whole, the laminated film only needs to have two or more layers of the specific carbon nanotube nonwoven fabric; there is no particular limitation as long as it has two or more layers, preferably two or three layers, more preferably two layers. As long as two or more layers of carbon nanotube nonwoven fabric are laminated, the carbon nanotube nonwoven fabric, resin film, and resin laminated film of the first electromagnetic wave shielding film can be selected from one or two or more layers, the impregnated film of the second electromagnetic wave shielding film can be selected from two or more layers, and the impregnated film, carbon nanotube nonwoven fabric, and nonwoven fabric impregnated laminated film of the third electromagnetic wave shielding film can each be selected from one or more layers.

[0052] <Carbon nanotube nonwoven fabric>

[0053] The carbon nanotube nonwoven fabric used in this invention has a thickness of 1–500 μm, preferably 1–300 μm. The carbon nanotube nonwoven fabric is formed by entanglement of multiple carbon nanotubes. The carbon nanotubes constituting the carbon nanotube nonwoven fabric are preferably single-layer carbon nanotubes, multi-layer carbon nanotubes, or mixtures thereof. Their diameter and length are not particularly limited; generally, the diameter is less than 50 nm and the length is less than 2 mm. The carbon nanotube nonwoven fabric used in this invention is preferably formed by entanglement of carbon nanotubes with a length of 10–500 μm.

[0054] Carbon nanotubes can be manufactured by reacting a carbon source such as methane with a catalyst such as ferrocene in the gas phase at a temperature of 1000–1500 °C. To improve the electrical conductivity of such nonwoven fabrics, nonwoven fabrics with high conductivity and a resistivity of 0.000005–0.05 Ω·cm, preferably 0.0001–0.01 Ω·cm, and more preferably 0.0005–0.003 Ω·cm are used. It should be noted that the resistivity is measured according to "JIS K7194:1994 Resistivity Test Method Based on Conductive Plastics Four-Probe Method".

[0055] 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 can be used. For example, by treating the carbon nanotube nonwoven fabric with a polysilazane compound or the like, a silica layer can be formed on the fiber surface of the carbon nanotube nonwoven fabric.

[0056] In the electromagnetic wave shielding film of the present invention, for example, in order to improve the wettability with thermosetting resins such as epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenolic resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate ester resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin and acrylic resin, 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.

[0057] Furthermore, by surface-treating the carbon nanotube nonwoven fabric with a coupling agent, the carbon nanotube nonwoven fabric and resin are tightly bonded, thereby improving the durability of the electromagnetic wave shielding sheet. Examples of coupling agents include silane coupling agents, alkoxide compounds of titanium, aluminum, etc. Silane coupling agents are preferred, and examples of preferred silane coupling agents include organosilicon compounds represented by the following formula (1).

[0058] Y-Si-X3(1)

[0059] (In the formula, Y is an organic group with reactive functional groups, and X is a hydrolyzable group.)

[0060] Examples of Y include amino, epoxy, hydroxyl, carboxyl, vinyl, methacryloyl, and mercapto groups; examples of X include alkoxy groups. Specifically, organosilicon compounds represented by formula (1) above can include, for example, γ-epoxypropoxypropyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, γ-aminobenzyltriethoxysilane, and γ-aminophenyltriethoxysilane. Alternatively, silane compounds such as polysilazane may also be used.

[0061] In the electromagnetic wave shielding film of the present invention, inorganic materials can be added to the carbon nanotube nonwoven fabric. Examples of inorganic materials include conductive inorganic materials and insulating inorganic materials. By filling the gaps in the fiber entanglement of the carbon nanotube nonwoven fabric with conductive inorganic materials, such as inorganic particles, inorganic fibers, or metal particles, the electrical conductivity can be further improved, and the electromagnetic wave shielding performance in the frequency range from millimeter waves to terahertz can be enhanced. Examples of conductive inorganic materials include inorganic particles such as carbon black, carbon nanotubes, graphene, and graphite; examples of inorganic fibers include short carbon fibers; and examples of metal particles include particles containing metals such as copper, iron, silver, and gold. Furthermore, conductive inorganic materials can be made from resin particles with a surface coating of these metals.

[0062] As an insulating inorganic material with high thermal conductivity, carbon nanotube nonwoven fabrics can have their thermal conductivity further improved by using inorganic particles and fibers, achieving a thermal conductivity of, for example, 50–80 W / mK. Examples of insulating inorganic particles include silicon dioxide, zinc oxide, aluminum oxide, boron nitride, and aluminum nitride. Examples of inorganic fibers include alumina short fibers, quartz fibers, and glass fibers.

[0063] There are no particular limitations on the shape of inorganic materials, but from the perspectives of heat dissipation and electrical conductivity, an average particle size of 0.5–30 μm is preferred. It should be noted that the average particle size of the inorganic material is the cumulative average diameter D in the volume average particle size distribution obtained by laser diffraction. 50 (Median diameter)

[0064] Regarding inorganic materials, they can be directly dispersed and immobilized on carbon nanotube nonwoven fabrics. Inorganic materials can be dispersed onto carbon nanotube nonwoven fabrics using any method, such as inserting the inorganic material into the carbon nanotube nonwoven fabric using a pressing device or laminator; dispersing the inorganic material in any solvent, spraying the dispersion onto the carbon nanotube nonwoven fabric, and then drying and removing the solvent; or combinations of these methods.

[0065] Any solvent can be used as the solvent for the dispersion, but highly volatile solvents are preferred, such as water, alcohols like ethanol and isopropanol, acetone, toluene, hydrocarbon solvents, and organosilicon solvents. The concentration of the dispersion is preferably 0.1 to 100 parts by mass relative to 100 parts by mass of the inorganic material. When the inorganic material is dispersed and immobilized on a carbon nanotube nonwoven fabric, the amount immobilized is preferably 0.01 to 1000 parts by mass relative to 100 parts by mass of the carbon nanotube nonwoven fabric. Furthermore, metal foils such as copper and aluminum can also be laminated onto the carbon nanotube nonwoven fabric.

[0066] <Resin film and protective layer of electromagnetic wave shielding film>

[0067] The electromagnetic wave shielding film of the present invention comprises a carbon nanotube nonwoven fabric with a resistivity of 0.00005 to 0.05 Ω·cm and a thickness of 1 to 500 μm, and a resin. It includes a laminated film consisting of two or more layers of the aforementioned carbon nanotube nonwoven fabric with a total thickness of 5 to 1500 μm, a pressure-sensitive adhesive layer laminated on one of the outermost surfaces of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer. Furthermore, the laminated film constituting the electromagnetic wave shielding film may have a protective layer disposed on the outermost surface opposite to the pressure-sensitive adhesive layer. The protective layer will be described later.

[0068] <Resin film of the first electromagnetic wave shielding film>

[0069] The first electromagnetic wave shielding film is an electromagnetic wave shielding film having a resistivity of 0.00005 to 0.05 Ω·cm, a thickness of 1 to 500 μm, a carbon nanotube nonwoven fabric, and a resin. It has two or more layers of the carbon nanotube nonwoven fabric stacked together, the stacked film being a resin stacked film formed by stacking carbon nanotube nonwoven fabric and a resin film, and a total thickness of 5 to 1500 μm. A pressure-sensitive adhesive layer is stacked on one of the outermost surfaces of the stacked film, and a release film is stacked on the adhesive surface of the pressure-sensitive adhesive layer.

[0070] Examples of resin films and protective layers include thermoplastic resin films and thermosetting resin films.

[0071] (Thermoplastic resin film)

[0072] Regarding thermoplastic resin films, from the perspective of film forming and electromagnetic wave shielding film processing, the softening point of the thermoplastic resin constituting the film is preferably below 400°C, more preferably below 300°C. There is no particular limitation on the lower limit of the softening point; for example, it can be set to 70°C or higher. The softening point of the thermoplastic resin can be determined using the method described in JIS K7196-1991 "Test Method for Softening Temperature of Thermoplastic Films and Sheets by Thermomechanical Analysis".

[0073] Examples of thermoplastic resins constituting thermoplastic resin films include polyethylene, polypropylene, fluoropolymers, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyphenylene ether, polyetheretherketone, polyetherketone, and polyethersulfone. These can be used individually or in combination of two or more. From the perspective of processability as an electromagnetic wave shielding film, polyethylene, polypropylene, fluoropolymers, polyethylene terephthalate, polyethylene naphthalate, and polyimide are preferred, and polyethylene, polypropylene, polyethylene terephthalate, and polyethylene naphthalate are more preferred. Furthermore, when heat resistance is required, polyimide films are preferred, and when chemical resistance and solvent resistance are further required, fluoropolymer films are preferred. It should be noted that known additives and other components may be added to the thermoplastic resin without impairing the effects of the present invention.

[0074] The thickness of the thermoplastic resin film is preferably 5 to 200 μm, more preferably 10 to 100 μm.

[0075] <Thermosetting Resin Film for First Electromagnetic Wave Shielding>

[0076] In the first electromagnetic wave shielding film, the thermosetting resin constituting the resin film can include epoxy resin, allylated epoxy resin, allylated polyphenylene ether resin, phenolic resin, polyimide resin, polyamide resin, bismaleimide resin, maleimide resin, cyanate ester resin, cyclopentadiene-styrene copolymer resin, polyester resin, silicone resin, and acrylic resin. These can be used individually or in combination. Among these, silicone resin and bismaleimide resin are preferred in terms of heat resistance and flexibility.

[0077] As for the silicone resin used in thermosetting silicone films, there are no particular limitations as long as it is a thermosetting silicone resin composition. Preferably, it includes addition-curing silicone resin compositions containing alkenyl groups, organohydrosiloxanes, and hydrosilylation catalysts, or condensation-curing silicone resin compositions containing alkoxysilyl and / or hydroxysilyl groups and condensation catalysts. From the viewpoint of various physical properties such as workability, shelf life, transparency, and electrical properties, addition-curing silicone resin compositions are preferred. As an addition-curing silicone resin composition, it is preferable to include (A) an alkenyl-containing organosiloxane with a resin structure, (B) an organohydrosiloxane with a resin structure, and (C) a platinum group metal catalyst.

[0078] As the bismaleimide resin used in the thermosetting resin film, a bismaleimide resin composition comprising a bismaleimide resin having a dimer acid backbone in its molecule and a reaction initiator is preferred. Other components, such as known additives, may be added to the thermosetting resin without impairing the effects of the present invention.

[0079] Regarding thermosetting resin films, it is possible to use thermosetting resin films that are pre-processed into film-like forms with a thickness preferably of 5 to 200 μm, more preferably 10 to 100 μm.

[0080] <Resin for impregnated films used in the second and third electromagnetic wave shielding films>

[0081] In the second and third electromagnetic wave shielding films, thermoplastic resins or thermosetting resins can be listed as resins used for impregnation of the impregnation film.

[0082] (Thermoplastic resin)

[0083] In the second and third electromagnetic wave shielding films, when the thermoplastic resin used for impregnation is impregnated with carbon nanotube nonwoven fabric, it can be dissolved in a solvent, or in the case of fluororesins, it can be used as a slurry-like resin dispersed in a dispersing solvent such as water, and then made into a liquid form. After impregnating the carbon nanotube nonwoven fabric with such a liquid thermoplastic resin, the solvent or dispersing solvent can be heated and dried to remove the solvent, thereby producing an impregnated film.

[0084] In the second and third electromagnetic wave shielding films, examples of thermoplastic resins used as the impregnating film include polyethylene, polypropylene, fluoropolymers, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyphenylene ether, polyetheretherketone, polyetherketone, and polyethersulfone. These can be used individually or in combination. Preferably, polyethylene, polypropylene, fluoropolymers, polyethylene terephthalate, polyethylene naphthalate, and polyimide are included. Other components, such as known additives, can be added to the thermoplastic resin without impairing the effects of the present invention.

[0085] (Thermosetting resin)

[0086] In the second and third electromagnetic wave shielding films, examples of thermosetting resins used for the impregnating films include epoxy resins, allylated epoxy resins, allylated polyphenylene ether resins, phenolic resins, polyimide resins, polyamide resins, bismaleimide resins, maleimide resins, cyanate ester resins, cyclopentadiene-styrene copolymer resins, polyester resins, silicone resins, and acrylic resins. These can be used individually or in combination of two or more. Epoxy resins and bismaleimide resins are preferred.

[0087] As epoxy resins, epoxy resins having two or more glycidyl groups in one molecule are preferably examples. Examples of epoxy resins used in this 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; phenolic varnish-type epoxy resins such as those having a biphenyl backbone, naphthalene backbone, dicyclopentadiene backbone, phenolic varnish-type epoxy resin, and cresol varnish-type epoxy resin; and multifunctional epoxy resins. These epoxy resins can be used alone or in combination of two or more.

[0088] As a curing agent for epoxy resin, any curing agent having phenolic hydroxyl or amino groups containing active hydrogen that forms a cross-linking structure with the epoxy resin can be used. As a curing agent containing phenolic hydroxyl groups, any phenolic resin with any structure can be used, as long as it is a phenolic resin containing phenolic hydroxyl groups. As a curing agent containing amino groups, an aromatic amine curing agent that can obtain epoxy resin cured products with high heat resistance and high elastic modulus is preferred.

[0089] As bismaleimide resins, those with a dimer acid backbone in the molecule are preferred due to their excellent heat resistance, low elasticity, toughness, and adhesion. Representative bismaleimide resins include SLK-6895 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.) and SLK-3000 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), as well as the SLK-2000 series (manufactured by Shin-Etsu Chemical Industry Co., Ltd.).

[0090] The amount of bismaleimide resin impregnated in the carbon nanotube nonwoven fabric is preferably 10 to 1000 parts by weight relative to 100 parts by weight of the nonwoven fabric.

[0091] When using bismaleimide resin as a thermosetting resin, it is preferable to use a reaction initiator of the bismaleimide resin as a curing catalyst. There are no particular limitations on the reaction initiator of the bismaleimide resin, as long as it promotes the crosslinking reaction. Examples include imidazoles, organophosphorus compounds, tertiary amines, quaternary ammonium salts, boron trifluoride amine complexes, organophosphorus compounds, organophosphorus salts, and organophosphorus salts; organic peroxides such as diallyl peroxide, dialkyl peroxide, peroxide carbonate, and hydroperoxide; and free radical polymerization initiators such as azoisobutyronitrile.

[0092] Among these, organic peroxides are preferred. Examples of organic peroxides include dicumyl peroxide, tert-butyl peroxybenzoate, tert-amyl peroxybenzoate, benzoyl peroxide, dilauryl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,1-di(tert-butylperoxy)cyclohexane, di-tert-butyl peroxide, and benzoyl peroxide.

[0093] The reaction initiator is preferably formulated at 0.05 to 10 parts by weight relative to 100 parts by weight of bismaleimide resin, and more preferably at 0.1 to 5 parts by weight.

[0094] A single reaction initiator can be used alone, or two or more can be used in combination.

[0095] In the second and third electromagnetic wave shielding films, other components, such as known additives, may be added to the thermosetting resin impregnated in the film, without impairing the effects of the present invention.

[0096] The resin impregnation content of the carbon nanotube nonwoven fabric is preferably 100 to 1000 parts by weight relative to 100 parts by weight of the nonwoven fabric, and more preferably 200 to 400 parts by weight.

[0097] <Additives in the resin of electromagnetic wave shielding film>

[0098] In the electromagnetic wave shielding film, other components such as known additives may be used without impairing the effects of the present invention. Examples of such 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 wave shielding film, or the thermoplastic resin and the thermosetting resin of the second electromagnetic wave shielding film. In particular, it is preferable to add them to the raw material of the thermosetting resin film, namely the thermosetting resin composition.

[0099] Regarding coupling agents, they can be used to improve the wetting and bonding strength between carbon nanotube nonwoven fabric and resin. Specific examples of coupling agents include those described as added to carbon nanotube nonwoven fabric; please refer to the description therein.

[0100] When this coupling agent is added, its usage amount is preferably 0.5 to 20 parts by weight relative to 100 parts by weight of the thermoplastic or thermosetting resin. The addition to the thermoplastic resin can be achieved, for example, by preparing a thermoplastic resin dissolved in a solvent and then adding the coupling agent thereto.

[0101] As inorganic materials, conductive inorganic materials and insulating inorganic materials can be listed. Conductive inorganic materials can further improve electrical conductivity and simultaneously enhance electromagnetic wave shielding performance in the frequency range from millimeter waves to terahertz. Insulating inorganic materials can further improve the thermal conductivity of carbon nanotube nonwoven fabrics. Specific examples of conductive and insulating inorganic materials include those described as materials added to carbon nanotube nonwoven fabrics, as described therein.

[0102] Regarding the inorganic material, a thermoplastic resin film or a thermosetting resin film can be laminated in the first electromagnetic wave shielding film, and the inorganic material can be dispersed in the thermoplastic resin or thermosetting resin to obtain a substance impregnated with carbon nanotube nonwoven fabric in the second electromagnetic wave shielding film. When inorganic material is added, the amount added is preferably 5 to 60 parts by weight, more preferably 10 to 50 parts by weight, relative to 100 parts by weight of these thermoplastic resins or thermosetting resins.

[0103] In this invention, the total thickness of the laminated film is 5–1500 μm, preferably 5–1000 μm, more preferably 10–500 μm, even more preferably 60–90 μm, and particularly preferably 34–90 μm. If the total thickness of the laminated film is within this range, it can fully exert its properties as an electromagnetic wave shielding material using carbon nanotubes. It should be noted that the total thickness of the laminated film includes the portion excluding the pressure-sensitive adhesive layer and the release film; if a protective layer is present, the protective layer is also included in the total thickness of the laminated film.

[0104] <Laminated film of the first electromagnetic wave shielding film>

[0105] In the first electromagnetic wave shielding film, the laminated film is a resin laminated film formed by laminating carbon nanotube nonwoven fabric and a resin film. The total thickness of the laminated film (resin laminated film) is 5 to 1500 μm, preferably 10 to 500 μm, and more preferably 34 to 90 μm. If the total thickness of the laminated film is within this range, it can fully exert its properties as an electromagnetic wave shielding material using carbon nanotubes. Furthermore, by having a configuration in which a release film is adhered to the laminated film through a pressure-sensitive adhesive layer, processing is also easy.

[0106] It should be noted that the total thickness of the laminated film is the thickness when the laminated film is completed. In the case of heating and pressurizing the thermoplastic resin film on the carbon nanotube nonwoven fabric, the subsequent total thickness is the total thickness after curing when the resin film is a thermosetting resin film and is cured after lamination.

[0107] <Laminated film of the second electromagnetic wave shielding film>

[0108] In the second and third electromagnetic wave shielding films, the impregnated film is a film obtained by impregnating a thermoplastic resin or a thermosetting resin into a carbon nanotube nonwoven fabric. The total thickness of the impregnated film is preferably 2.5 to 500 μm, more preferably 5 to 250 μm, and even more preferably 30 to 100 μm.

[0109] In the second electromagnetic wave shielding film, the laminated film is an impregnated laminated film formed by laminating two or more layers of impregnated films in which resin is impregnated in carbon nanotube nonwoven fabric. The total thickness of the laminated film (impregnated laminated film) is 5 to 1500 μm, preferably 5 to 1000 μm, more preferably 10 to 500 μm, and more preferably 60 to 90 μm. If the total thickness of the impregnated laminated film is within this range, it can fully exert its properties as an electromagnetic wave shielding material using carbon nanotubes.

[0110] <Laminated film of the third electromagnetic wave shielding film>

[0111] In the third electromagnetic wave shielding film, the laminated film is an impregnated film in which resin is impregnated with carbon nanotube nonwoven fabric, or a laminated impregnated film consisting of two or more layers, or a nonwoven fabric impregnated laminated film formed by laminating the carbon nanotube nonwoven fabric in the impregnated film or the laminated impregnated film. The total thickness of the laminated film (nonwoven fabric impregnated laminated film) is 5 to 1500 μm, preferably 10 to 500 μm, and more preferably 20 to 90 μm. If the total thickness is within this range, it can fully exert its properties as an electromagnetic wave shielding material using carbon nanotubes.

[0112] It should be noted that the total thickness of the laminated impregnated film or nonwoven impregnated laminated film is the thickness of the laminated impregnated film or nonwoven impregnated laminated film when it is completed. When a thermoplastic resin solution is impregnated into a carbon nanotube nonwoven fabric, the thickness is based on the thickness of the impregnated film after heat drying to remove the solvent. In the case where a thermosetting resin is impregnated into a carbon nanotube nonwoven fabric and then cured, the thickness is based on the cured thickness.

[0113] The electromagnetic wave shielding film has a pressure-sensitive adhesive layer laminated on one of the outermost surfaces of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer. The outermost surface can be any outermost surface that is feasible in each embodiment. In the second electromagnetic wave shielding film, it is one surface of the impregnated laminated film, and in the third electromagnetic wave shielding film, it is one surface of the nonwoven impregnated laminated film.

[0114] <Pressure-sensitive adhesive layer>

[0115] In the electromagnetic wave shielding film of the present invention, a pressure-sensitive adhesive is used to adhere and fix the electromagnetic wave shielding film to the surface of electronic components and the surface of circuit boards. Any material that can be used as a pressure-sensitive adhesive can be used, and acrylic resin pressure-sensitive adhesives or silicone resin pressure-sensitive adhesives that can produce products with broad adhesive strength are preferred.

[0116] As examples of silicone resin pressure-sensitive adhesives, KR100, KR130, KR3701, and KR3704 (all manufactured by Shin-Etsu Chemical Co., Ltd.) are representative examples.

[0117] This pressure-sensitive adhesive is diluted with a solvent such as toluene, and a catalyst is added. It is then coated onto one side of an electromagnetic wave shielding film. To remove the solvent, it is treated at 100–150°C for several minutes to allow it to heat-cur, thus forming a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer can be adjusted by varying the solvent dilution. Furthermore, regarding adhesion, it can be easily adjusted by mixing lightly adhesive and heavily adhesive pressure-sensitive adhesives. If bonding to a heatable component, a thermosetting adhesive or pressure-sensitive adhesive can be used. The thickness of the pressure-sensitive adhesive layer is preferably 5–100 μm, more preferably 10–70 μm.

[0118] <Mold Release Film>

[0119] In electromagnetic wave shielding films, polypropylene, PET, polyethylene films, fluoropolymer films, etc., can be used as release films. When the pressure-sensitive adhesive layer coated on the electromagnetic wave shielding film is difficult to peel off from the release film, a product treated with a release agent on the release film can be used.

[0120] Regarding the thickness of the release film, 10–50 μm is preferred for ease of use. Alternatively, a film treated with pear skin surface can also be used as the release film.

[0121] <Manufacturing Method of Electromagnetic Wave Shielding Film>

[0122] The first electromagnetic wave shielding film can be manufactured, for example, by laminating a resin film with a carbon nanotube nonwoven fabric and heating it to reduce its viscosity, or by a melt calendering method where a resin varnish is film-formed using a coating device and then transferred onto the carbon nanotube nonwoven fabric using a press or laminator. As described above, thermoplastic resin films and thermosetting resin films can be used as the resin film, and uncured, semi-cured, or fully cured thermosetting resin films can be used as the thermosetting resin film.

[0123] Melt calendering is advantageous in many ways, such as eliminating the need for solvent removal and providing a relatively good working environment. As a melt calendering method, it can be manufactured by widening a carbon nanotube nonwoven fabric to the necessary width using rods, clamping a film-formed thermoplastic or thermosetting resin between the top and bottom with release paper, peeling off the release paper relative to the direction of travel of the carbon nanotube nonwoven fabric, and feeding it to several pairs of heated metal rollers positioned at approximately the same height. These rollers are then clamped, thereby heating and pressurizing the thermoplastic or thermosetting resin onto the carbon nanotube nonwoven fabric. In melt calendering, the clamping pressure is linear; therefore, increasing the number of clamping rollers is preferable to achieve sufficient heating and pressurization. Alternatively, heating metal rollers can be omitted, and a forming press such as a heated multi-stage press can be used for pressure forming.

[0124] In the transfer printing method, a resin varnish is coated on a substrate film, the solvent is dried to obtain a resin film, and then carbon nanotube nonwoven fabric is laminated with the resin film. A laminator and a press are used to transfer the resin film onto the carbon nanotube nonwoven fabric.

[0125] The substrate film can be any type of film, and the resin film is easy to peel off. Preferred materials include PET film, PE film, PP film, Teflon (registered trademark) film, and AFLEX film.

[0126] Regarding the aforementioned substrate film, various surface treatments such as corona treatment, plasma treatment, or silicone treatment can be applied as needed. Any solvent can be used for the resin varnish, but highly volatile solvents are preferred, such as ethanol, alcohols like IPA, acetone, toluene, xylene, anisole, hydrocarbon solvents, and silicone solvents.

[0127] Regarding the concentration of the resin varnish, it is preferably 0.1 to 200 parts by weight relative to 100 parts by weight of the resin.

[0128] As a method for applying resin varnish to a substrate film, any method can be used, but spin coaters and rod coaters are preferred as they are easy to use. As a temperature for drying the resin film on the substrate film, a temperature at which the thermosetting resin does not react is preferred, and 30 to 120°C is more preferably preferred.

[0129] In addition, when the carbon nanotube nonwoven fabric and the resin film are laminated and pressed together using a laminator and a press, and the resin film is transferred onto the carbon nanotube nonwoven fabric, pressure and heat can be applied as needed.

[0130] After laminating a resin film onto a carbon nanotube nonwoven fabric using the above method, the semi-cured thermosetting resin film is cured by heating and pressurizing as needed to manufacture an electromagnetic wave shielding film. By selecting the chemical structures of the thermoplastic and thermosetting resins in the resin film and the curing method of the thermosetting resin, it is possible to produce laminated films that are as hard and tough as soft and shape-conforming.

[0131] The impregnated membrane constituting the second and third electromagnetic wave shielding membranes can be manufactured, for example, by a wet process in which a thermoplastic or thermosetting resin is dissolved in a solvent or dispersed in a dispersion solvent, reduced in viscosity, and impregnated in a carbon nanotube nonwoven fabric.

[0132] In the wet process, a thermoplastic or thermosetting resin is impregnated with carbon nanotube nonwoven fabric, and then the volatile solvent or dispersing solvent is removed to produce a resin film impregnated with the thermoplastic resin. Alternatively, an impregnated film impregnated with an uncured thermosetting resin can also be produced. If solvent remains in the impregnated film, it can cause adverse effects during molding and deteriorate the working environment. Therefore, the amount of solvent remaining in the impregnated film is preferably 1% by mass or less, and more preferably 0.5% by mass or less. The method for removing the solvent also depends on the boiling point of the solvent used, but it can be easily achieved by heat treatment at 80–150°C for about 10 minutes to 1 hour.

[0133] Laminated impregnated films can be manufactured by laminating two or more impregnated films and then heating and pressurizing them. Alternatively, laminated films of thermoplastic resins or laminated films of thermosetting resins can be manufactured by laminating impregnated films or laminated impregnated films with carbon nanotube nonwoven fabrics and then heating and pressurizing them.

[0134] Then, a pressure-sensitive adhesive layer is laminated on the outermost surface of the laminated film, specifically, for example, the outermost surface of the resin laminated film in the first electromagnetic wave shielding film, the outermost surface of the impregnated laminated film in the second electromagnetic wave shielding film, or the outermost surface of the nonwoven impregnated laminated film in the third electromagnetic wave shielding film. A release film is then laminated on the adhesive surface of the pressure-sensitive adhesive layer to obtain the electromagnetic wave shielding film of the present invention. The outermost surface is not particularly limited in any embodiment, as long as it is a desirable layer.

[0135] The total thickness of the electromagnetic wave shielding film is preferably 10–1600 μm, more preferably 10–1500 μm, and even more preferably 15–500 μm.

[0136] By using this forming method, it is possible to supply large-area electromagnetic wave shielding films of the required thickness in sheet or roll form, wound onto paper tubes, etc.

[0137] The electromagnetic wave shielding film of the present invention, processed in this way, is lightweight and has excellent electromagnetic wave shielding, processability, and ease of use. Therefore, it is suitable as a surface coating for electronic circuit boards containing a large number of electronic components, a storage container for automotive batteries that generate electromagnetic waves, a motor component, a sealing material for DC / DC converters, and other components requiring electromagnetic wave shielding.

[0138] Furthermore, it can also be used as a component or storage container for communication equipment that uses high frequencies above millimeter waves and requires electromagnetic shielding and heat resistance.

[0139] Figure 1AA longitudinal cross-sectional view is shown schematically as an example of the first electromagnetic wave shielding film. The electromagnetic wave shielding film 1a is an electromagnetic wave shielding film with a six-layer structure, comprising a four-layer laminated film consisting of a carbon nanotube nonwoven fabric 2, a resin film 3, and a protective layer 4, a pressure-sensitive adhesive layer 5 laminated on the surface of the carbon nanotube nonwoven fabric of the laminated film, and a release film 6 laminated on the adhesive surface of the pressure-sensitive adhesive layer 5.

[0140] The electromagnetic wave shielding film 1a is manufactured using the above-described molding method to produce a large-area electromagnetic wave shielding film of a specified thickness, such as... Figure 2 As shown, after the electromagnetic wave shielding film 8 is made into a roll like glass cloth, it is as follows: Figure 3 The electromagnetic wave shielding film, which is rolled into a roll, is cut into strips, and can be used as electromagnetic wave shielding film 9 cut into strips.

[0141] Regarding the first electromagnetic wave shielding film 1a with a 6-layer structure, for example, by peeling off the release film 6, as... Figure 4A As shown, the electronic components 11 are attached to the surface of the printed wiring board 10, thereby enabling the shielding of electromagnetic waves.

[0142] Similarly, Figure 1B The electromagnetic wave shielding film shown has a four-layer structure: a second electromagnetic wave shielding film 1b, an impregnation film 7 in which resin is impregnated with carbon nanotube nonwoven fabric, a pressure-sensitive adhesive layer 5 stacked on one side of the impregnation film 7, and a release film 6 stacked on the adhesive side of the pressure-sensitive adhesive layer 5. This electromagnetic wave shielding film is constructed, for example, by peeling off the release film 6. Figure 4B As shown, an impregnated film 7 is attached to the surface of the electronic component 11 disposed on the printed wiring board 10, thereby enabling electromagnetic wave shielding. Figure 1C A longitudinal cross-sectional view is shown to schematically illustrate an example of a third electromagnetic wave shielding film in which an impregnated membrane is laminated with a carbon nanotube nonwoven fabric.

[0143] In addition, such as Figure 5 As shown, electromagnetic waves can be shielded by wrapping the surface of the copper wiring 12 with an electromagnetic wave shielding film 9 cut into strips. Figure 6 As shown, regarding the first electromagnetic wave shielding film 1a with a 6-layer structure, for example, by peeling off the release film 6, as... Figure 6 As shown, the entire circuit board 13, including the surface of the electronic components 11 disposed on the printed wiring board 10, is coated with a protective layer, thereby enabling electromagnetic wave shielding. The second electromagnetic wave shielding films 1b and 1c are similarly coated. It should be noted that the portions with the same parallel diagonal lines in Figure 4 are portions consisting of a single layer. Figure 6 A section of the cross-section was not drawn with diagonal lines.

[0144] Example

[0145] The following examples illustrate the invention in more detail, but the 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 ​​of the present invention were determined using the methods described below.

[0146] Material

[0147] (1) Carbon nanotube nonwoven fabric

[0148] [Non-woven fabric 1]

[0149] A dispersion was prepared by stirring 100 parts by weight of water, 0.4 parts by weight of monolayer carbon nanotubes (EC1.5-P, manufactured by Meijo Nano Carbon Co., Ltd.), and 0.4 parts by weight of sodium deoxycholate (manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.) using a mixer (IFM-800DGM, manufactured by Iwatani Sangyo). The dispersion was then coated onto a release-treated PET film (E7006, manufactured by Toyobo Co., Ltd.) using a 1.5 mm gap doctor blade. After drying at 100°C for 1 hour, the film was peeled off from the PET film to obtain a nonwoven fabric. This monolayer carbon nanotube nonwoven fabric containing the ionic surfactant has a thickness of 10 μm and a resistivity of 0.00075 (Ω·cm).

[0150] [Non-woven fabric 2]

[0151] MIRALON T01 (manufactured by Huntsman)

[0152] Thickness 20 μm, resistivity 0.0015 (Ω·cm)

[0153] [Non-woven fabric 3]

[0154] CNTM30 (manufactured by Tortech)

[0155] Thickness 85μm, resistivity 0.0015 (Ω·cm)

[0156] (2) Thermoplastic resins and thermosetting resins

[0157] [Thermosetting Resin 1]

[0158] 10μm thick addition-curing silicone resin uncured film (LPS-AF500D, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0159] [Thermosetting Resin 2]

[0160] The bismaleimide resin represented by the following formula (2) (SLK-3000, manufactured by Shin-Etsu Chemical Industry Co., Ltd., number average molecular weight 5200)

[0161]

Chemistry 1

[0162]

[0163] (In the formula, n ≒ 5 (average value).)

[0164] [Thermoplastic resin film 1]

[0165] 25μm thick polyethylene terephthalate film (E5100, manufactured by Toyobo Co., Ltd.)

[0166] [Thermoplastic resin film 2]

[0167] 50μm thick polyethylene terephthalate film (E5100, manufactured by Toyobo Co., Ltd.)

[0168] (3) Pressure-sensitive adhesive 1

[0169] Silicone pressure-sensitive adhesive (trade name: KR3704, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0170] (4) Release film 1

[0171] Fluoropolymer membrane (50μm thickness) (trade names: AFLEX, manufactured by AGC Corporation)

[0172] [Determination Method]

[0173] (1) Resistivity

[0174] For resistivity measurement, the surface resistivity of carbon nanotube nonwoven fabric was determined according to "JIS K7194:1994 Resistivity Test Method for Conductive Plastics Using the Four-Probe Method". Specifically, a LORESTA-GX MCP-T700 (low-resistivity resistivity meter, manufactured by Nitto Seiko Analytech) was used. The resistivity was calculated using the measured values. The resistivity was calculated using the following formula.

[0175] Resistivity (Ω·cm) = Surface resistivity (Ω / cm) 2 ) × Thickness (cm)

[0176] (2) Electromagnetic wave shielding characteristics

[0177] As an electromagnetic wave shielding characteristic, electromagnetic wave shielding films cut into 12cm squares were used, and the transmission attenuation at 28GHz and 77GHz was measured using an electromagnetic wave shielding measurement device manufactured by KEYCOM. A schematic diagram of the measurement system is shown below. Figure 7Between two antennas on the y-axis connected to a vector network analyzer, the sample's electromagnetic wave shielding film is positioned orthogonally to the y-axis. Electromagnetic waves vibrating in the z-axis direction are irradiated, and the electromagnetic wave transmission attenuation (dB) through the sample is measured and recorded. An Anritsu MS46122B vector network analyzer was used for measurements at 28 GHz, and an Anritsu MS46522B was used for measurements at 77 GHz.

[0178] [Example 1: (1)]

[0179] A thermosetting resin film 1 and a nonwoven fabric 1 are alternately laminated, hot-pressed at 80°C, and then cured in a dryer at 150°C for 4 hours to produce a laminated film (resin laminated film) with a total thickness of 32 μm consisting of 4 layers. Pressure-sensitive adhesive 1 is applied to the nonwoven fabric 1 side of this 4-layer film, with the cured pressure-sensitive adhesive layer having a thickness of 10 μm, and then cured at 100°C for 1 hour. A release film 1 is then laminated onto the pressure-sensitive adhesive layer to produce an electromagnetic wave shielding film consisting of 6 layers. The transmission attenuation is measured using the above-described method to assess the shielding characteristics of the produced electromagnetic wave shielding film. The results are shown in Table 1. Furthermore, the release film is peeled off and applied to an electronic circuit board housing semiconductor elements, thereby enabling the fabrication of a circuit board with a shielding film covering the unevenness of the circuit surface. Figure 4A The shielding film can be easily peeled off from the circuit board covered by the shielding film.

[0180] [Example 2: (1)]

[0181] Nonwoven fabric 1 is laminated on both sides of a thermoplastic resin film 1 and hot-pressed at 240°C to produce a three-layer laminated film (resin laminated film). Then, as a protective layer, a thermosetting resin 1 film is laminated on one side of this three-layer resin laminated film, hot-pressed at 80°C, and cured in a dryer at 150°C for 4 hours to produce a four-layer resin laminated film with a total thickness of 51 μm. Pressure-sensitive adhesive 1 is applied to the nonwoven fabric 1 side of this four-layer film, with the cured pressure-sensitive adhesive layer having a thickness of 10 μm, and cured at 150°C for 1 hour. Finally, a release film 1 is laminated to produce a six-layer electromagnetic wave shielding film.

[0182] [Example 3: (1)]

[0183] Except that it is made into thermoplastic resin film 2, the electromagnetic wave shielding film is made in the same manner as in Example 2. It should be noted that the total thickness of the laminated film (resin laminated film) is 76 μm.

[0184] [Example 4: (2)]

[0185] A toluene solution comprising 100 parts by mass of thermosetting resin 2, 1 part by mass of curing catalyst (dicumyl peroxide (PERCUMYL D, manufactured by Nippon Oil Co., Ltd.), and 200 parts by mass of toluene was prepared. Nonwoven fabric 2 was impregnated with the toluene solution and heated at 100°C for 10 minutes to remove the toluene, thereby producing a semi-cured impregnated film with a thickness of 35 μm. Two sheets of this impregnated film were stacked and cured under pressure at 180°C and 0.5 MPa for 1 hour to produce an impregnated laminated film with a total thickness of 76 μm. Pressure-sensitive adhesive 1 was applied to one side of the laminated film (impregnated laminated film) with a cured pressure-sensitive adhesive layer thickness of 10 μm and then cured by heating. A release film 1 was then stacked to produce an electromagnetic wave shielding film consisting of four layers.

[0186] [Example 5: (1)]

[0187] Except for changing the carbon nanotube nonwoven fabric from nonwoven fabric 1 to nonwoven fabric 2, the electromagnetic wave shielding film was fabricated in the same manner as in Example 2. It should be noted that the total thickness of the laminated film is 71 μm.

[0188] [Example 6: (3)]

[0189] A toluene solution comprising 100 parts by mass of thermosetting resin 2, 1 part by mass of curing catalyst (dicumyl peroxide (PERCUMYL D, manufactured by Nippon Oil Co., Ltd.), and 200 parts by mass of toluene was prepared. Nonwoven fabric 2 was impregnated with the toluene solution and heated at 100°C for 10 minutes to remove the toluene, thereby producing a semi-cured impregnated film with a thickness of 40 μm. This impregnated film was laminated with nonwoven fabric 1 and cured under pressure at 180°C and 0.5 MPa for 1 hour to produce a laminated film (nonwoven impregnated laminated film) with a total thickness of 48 μm. Pressure-sensitive adhesive 1 was applied to the surface of the nonwoven fabric 1 of the laminated film (nonwoven impregnated laminated film) such that the thickness of the cured pressure-sensitive adhesive layer was 10 μm, and then cured by heating. The release film 1 was then laminated to produce an electromagnetic wave shielding film consisting of 4 layers.

[0190] [Comparative Example 1]

[0191] A thermosetting resin film 1, serving as a protective layer, is laminated onto a nonwoven fabric 1. After hot pressing at 80°C, it is cured in a dryer at 150°C for 4 hours to produce a laminated film with a total thickness of 16 μm consisting of two layers. Pressure-sensitive adhesive 1 is applied to the surface of the nonwoven fabric 1 of the two-layer film with a cured pressure-sensitive adhesive layer thickness of 10 μm. After curing at 150°C for 1 hour, a release film 1 is laminated to produce an electromagnetic wave shielding film consisting of four layers. To assess the shielding characteristics of the produced electromagnetic wave shielding film, the transmittance attenuation was measured using the aforementioned method after peeling off the release film. The results are shown in Table 1. Furthermore, by peeling off the release film and coating it onto an electronic circuit board containing semiconductor elements, a circuit board with a shielding film coating that follows the surface contours of the circuit can be produced. The shielding film can be easily peeled off from the shielding film-coated circuit board.

[0192] [Comparative Example 2]

[0193] Except for replacing the carbon nanotube nonwoven fabric with nonwoven fabric 2, an electromagnetic wave shielding film was fabricated in the same manner as in Comparative Example 1. It should be noted that the total thickness of the laminated film is 34 μm.

[0194] [Comparative Example 3]

[0195] Except for replacing the carbon nanotube nonwoven fabric with nonwoven fabric 3, an electromagnetic wave shielding film was fabricated in the same manner as in Comparative Example 1. It should be noted that the total thickness of the laminated film is 91 μm.

[0196] Table 1

[0197]

[0198] Table 2

[0199]

[0200] In the table: laminated films include laminated films, laminated impregnated films, and laminated nonwoven impregnated films.

[0201] As can be seen from the comparison between Example 1 and Comparative Example 2, and between Examples 2 to 6 and Comparative Example 3, the electromagnetic wave shielding film made by stacking two or more layers of carbon nanotube nonwoven fabric with thin film thickness exhibits the same electromagnetic wave shielding performance as the case of using only one layer of carbon nanotube nonwoven fabric with thick film thickness, thereby making the total thickness of the electromagnetic wave shielding film thinner.

[0202] Industrial availability

[0203] According to the present invention, electromagnetic wave shielding of electronic components and wiring installed inside electronic devices is easy, making them electronic devices that correspond to high-speed communications such as 5G and 6G. Therefore, their industrial value and industrial applicability are very high.

[0204] Explanation of reference numerals in the attached figures

[0205] 1a The first electromagnetic wave shielding film with 6 layers

[0206] 1b The second electromagnetic wave shielding film with 4 layers

[0207] 2. Carbon nanotube nonwoven fabric

[0208] 3. Resin film

[0209] 4. Protective layer

[0210] 5 Pressure-sensitive adhesive layer

[0211] 6. Release film

[0212] 7 impregnated membrane

[0213] 8. Electromagnetic wave shielding film wound into a roll

[0214] 9. Electromagnetic wave shielding film cut into strips

[0215] 10 Printed Wiring Board

[0216] 11 Electronic components

[0217] 12 Copper wiring

[0218] 13 Circuit board

[0219] 14. Test the sample

[0220] 15 antennas

[0221] 16 Incident Wave

[0222] 17 Through the waves

Claims

1. An electromagnetic wave shielding film, which is an electromagnetic wave shielding film having a carbon nanotube nonwoven fabric with an electrical resistivity of 0.00005 to 0.05 Ω-cm and a thickness of 1 to 500 μm, and a resin, having a laminated film in which two or more of the carbon nanotube nonwoven fabric are laminated and the total thickness is 5 to 1500 μm, a pressure-sensitive adhesive layer laminated on one outermost surface of the laminated film, and a release film laminated on the adhesive surface of the pressure-sensitive adhesive layer.

2. The electromagnetic wave shielding film according to claim 1, wherein The laminated film is a resin laminated film in which a carbon nanotube nonwoven fabric and a resin film are laminated.

3. The electromagnetic wave shielding film according to claim 2, wherein The resin film is a thermoplastic resin film, and the thermoplastic resin has a softening point of 400°C or lower.

4. The electromagnetic wave shielding film according to claim 3, wherein The thermoplastic resin constituting the thermoplastic resin film contains one or more selected from the group consisting of polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, and polyimide.

5. The electromagnetic wave shielding film according to claim 2, wherein The resin film is a thermosetting resin film, and the thermosetting resin is one or more selected from the group consisting of 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.

6. The electromagnetic wave shielding film according to claim 1, wherein The laminated film is an impregnated laminated film in which two or more of an impregnated film in which a resin is impregnated in a carbon nanotube nonwoven fabric are laminated.

7. The electromagnetic wave shielding film according to claim 1, wherein The laminated film is an impregnated laminated film in which an impregnated film in which a resin is impregnated in a carbon nanotube nonwoven fabric and the carbon nanotube nonwoven fabric are laminated.

8. The electromagnetic wave shielding film according to claim 6 or 7, wherein The resin contains a thermoplastic resin selected from the group consisting of polyethylene, polypropylene, fluororesin, polyethylene terephthalate, polyethylene naphthalate, and polyimide.

9. The electromagnetic wave shielding film according to claim 6 or 7, wherein The resin contains a thermosetting resin selected from the group consisting of 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.

10. The electromagnetic wave shielding film according to claim 1, 2, 6 or 7, wherein, The carbon nanotubes constituting the carbon nanotube nonwoven fabric are single-layer carbon nanotubes, multi-layer carbon nanotubes, or a mixture thereof.

Images