A laminate, a coating member having the same, and a method for manufacturing the laminate

Abstract

Objective: To provide a laminate having a carbon nanotube layer stably stacked thereon, a coating member having the same, and a method for manufacturing the laminate. Solution: A laminate having an insulating layer (20) mainly comprising a resin composition, a cellulose fiber layer (30) mainly comprising microfibrous cellulose with a fiber width of 1000 nm or less laminated on the insulating layer (20), and a carbon nanotube layer (40) mainly comprising carbon nanotubes laminated on the cellulose fiber layer (30).

Description

Technology Field

[0001] The present invention relates to a laminate having a layer of carbon nanotubes, a coating member, and a method for manufacturing the laminate. Background Technology

[0002] Conventionally, to reduce noise such as electromagnetic waves, a laminate is known in which a metal thin film, such as copper or aluminum, or a metal thin film containing ferrite-based metal powder, is laminated onto a flexible insulating layer such as polyethylene resin. However, laminates using metal thin films have a thickness of 100 μm or more, which limits their applications and has led to the problem of being discarded. Therefore, recently, a laminate (noise suppression sheet) with a thin thickness has been developed by laminating a carbon nanotube layer as a conductive material onto an insulating layer (see, for example, Patent Documents 1 and 2). Prior art literature

[0003] Japanese Published Patent No. 2017-123303 Japanese Published Patent No. 2018-195854 The problem to be solved

[0004] In order to improve the noise suppression performance of the laminate, it is preferable to laminate a layer consisting of carbon nanotubes alone, as in Patent Document 1, onto a flexible insulating layer such as polyethylene resin, rather than making the carbon nanotube layer a layer mixed with carbon nanotubes and resin, as in Patent Document 2. However, since the surface of the carbon nanotube contains an abundance of negatively charged pi electrons, when the carbon nanotube is laminated onto a resin that also has a negatively charged surface, electrical repulsion occurs, or the carbon nanotubes aggregate when drying, and the adhesion between the carbon nanotube and the insulating layer is reduced, resulting in holes (concave parts) or ridges (shapes), and there was a problem in that a stable laminate could not be obtained.

[0005] The present invention aims to provide a laminate having a carbon nanotube layer stably stacked thereon, a coating member having the same, and a method for manufacturing the laminate. means of solving the problem

[0006] The laminate according to the present invention has an insulating layer mainly comprising a resin composition, a cellulose fiber layer mainly comprising microfibrous cellulose with a fiber width of 1000 nm or less laminated on the insulating layer, and a carbon nanotube layer mainly comprising carbon nanotubes laminated on the cellulose fiber layer.

[0007] In the above laminate, the thickness of the carbon nanotube layer is 20 μm or less, and the thickness of the entire laminate is 120 μm or less.

[0008] In the above laminate, the carbon nanotube layer can be configured such that it is formed using water-dispersible carbon nanotubes.

[0009] In the above laminate, a cellulose fiber layer mainly comprising microfibrous cellulose can be further laminated on the carbon nanotube layer, and a carbon nanotube layer mainly comprising carbon nanotubes can be further laminated on the cellulose fiber layer.

[0010] In the above laminate, an insulating layer mainly comprising a resin composition is laminated on the carbon nanotube layer, a cellulose fiber layer mainly comprising microfibrous cellulose is further laminated on the insulating layer, and a carbon nanotube layer mainly comprising carbon nanotubes is further laminated on the cellulose fiber layer.

[0011] In the above laminate, when the insulating layer is laminated on the carbon nanotube layer, the insulating layer can be configured to be formed in a laminated pattern in which the insulating layer is not laminated on a part of the carbon nanotube layer.

[0012] In the above laminate, the microfibrous cellulose can be configured to be a cellulose nanofiber with a fiber width of 100 nm or less.

[0013] In the above laminate, the film thickness in the two layers of the cellulose fiber layer and the carbon nanotube layer can be configured to be 1 to 10 μm.

[0014] The above laminate can be configured to be a laminate for absorbing and reflecting electromagnetic waves in the vicinity.

[0015] The above laminate can be configured to be a laminate for absorbing electromagnetic waves from the far-field.

[0016] The coating member according to the present invention is a coating member having the laminate.

[0017] A method for manufacturing a laminate according to the present invention involves applying an insulating layer mainly comprising a resin composition, applying a cellulose fiber layer mainly comprising microfibrous cellulose with a fiber width of 1000 nm or less on the insulating layer, and applying a carbon nanotube layer mainly comprising carbon nanotubes on the cellulose fiber layer. Effects of the invention

[0018] According to the present invention, a laminate having a carbon nanotube layer stably stacked thereon, a coating member having the same, and a method for manufacturing the laminate can be provided. Brief explanation of the drawing

[0019] [Fig. 1] This is a schematic diagram showing a cross-section of a laminate according to the first embodiment. [Fig. 2] This is a graph showing the electromagnetic wave absorption and electromagnetic wave reflection characteristics of a conventional laminate for electromagnetic waves of 5 GHz or less in the vicinity. [Fig. 3] This is a graph showing the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics of a laminate according to the first embodiment for electromagnetic waves of 5 GHz or less in the vicinity. [Fig. 4] This is a graph showing the electromagnetic wave absorption characteristics of a conventional laminate and a laminate according to the first embodiment for electromagnetic waves of 5 to 20 GHz in the vicinity. [Fig. 5] This is a schematic diagram showing a cross-section of a laminate according to the second embodiment. [Fig. 6] This is a graph showing the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics of the laminate according to the second embodiment for electromagnetic waves of 5 GHz or less in the vicinity. [Fig. 7] This is a graph showing the electromagnetic wave absorption characteristics of a conventional laminate and a laminate according to a second embodiment for electromagnetic waves of 5 to 20 GHz in the vicinity. [Fig. 8] (A) is a graph showing the relative permittivity of a laminate according to the second embodiment for electromagnetic waves of 18 to 30 GHz in the far-field system, and (B) is a graph showing the relative permittivity of a laminate according to the second embodiment for electromagnetic waves of 40 to 65 GHz or higher in the far-field system. [Fig. 9] This is a schematic diagram showing a cross-section of a coating member according to the third embodiment. [Fig. 10] This is a schematic diagram showing a cross-section of a laminate according to another embodiment. [Fig. 11] This is a schematic diagram showing a cross-section of a laminate according to another embodiment. [Fig. 12] This is a schematic diagram showing a cross-section of a laminate according to another embodiment. Specific details for implementing the invention

[0020] A laminate and a coating member according to the present invention will be described based on the drawings. The laminate according to the present invention is a film-type member that reflects and / or absorbs electromagnetic waves, and has an insulating layer and a conductive layer, and has a structure in which the conductive layer is laminated on the upper side of the insulating layer. Furthermore, as an embodiment of the laminate and coating member according to the present invention, a laminate and a coating member capable of effectively suppressing noise by reflecting and / or absorbing electromagnetic waves of the near field and also absorbing electromagnetic waves of plane waves will be described as an example. In addition, in the following, the insulating layer side (lower side of the drawing) with respect to the conductive layer will be referred to as "lower" or "lower side," and the conductive layer side (upper side of the drawing) with respect to the insulating layer will be referred to as "upper" or "upper side." In addition, in the present invention, "laminated on top of" includes cases where it is laminated directly on a certain layer, and also includes cases where it is not laminated directly on a certain layer but is laminated on the upper side of a certain layer.

[0021] 《First Embodiment》

[0022] FIG. 1 is a schematic diagram showing a cross-section of a laminate (1) according to a first embodiment. As shown in FIG. 1, the laminate (1) according to the first embodiment has, in order, a resin insulating layer (10), an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40). Specifically, in the laminate (1), an insulating coat layer (20) is laminated on the resin insulating layer (10), a cellulose fiber layer (30) is laminated on the insulating coat layer (20), and a carbon nanotube layer (40) is laminated on the cellulose fiber layer (30). In addition, in the laminate (1) according to the first embodiment, the resin insulating layer (10), the insulating coat layer (20), and the cellulose fiber layer (30) constitute an insulating layer, and the carbon nanotube layer (40) constitutes a conductive layer.

[0023] <Resin insulation layer (10)>

[0024] As for the resin insulating layer (10), it may be made of an insulating material and may include polyimide (PI); polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate; polyolefin resins such as polyethylene (PE) and polypropylene (PP); various acrylic resins such as polyethylene naphthalate (PEN), nylon, polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polyethersulfone (PES), polyvinyl alcohol (PVA), polycarbonate (PC), and polyarylate (PAR); urethane resins, fluorinated resins, styrene resins, epoxy resins, vinyl resins, etc. Additionally, a resin sheet may be used as the resin insulating layer (10), and in this case, a PI sheet or a polyester sheet is preferred, and in particular, the use of a PI sheet or a PET sheet is preferred. And, the resin insulating layer (10) is a layer mainly comprising the resin composition, specifically, comprising 50% or more, more preferably 80% or more of the resin composition.

[0025] The resin insulating layer (10) may have a single-layer structure, or a multi-layer structure of two or three or more layers. The shape (external form) of the resin insulating layer (10) is preferably a sheet type (thin flat type), such as a long-rod type, film type, tape type, or plate type. The thickness of the resin insulating layer (10) can be appropriately set according to the use of the laminate (1), but in this embodiment, in order to make the film thickness of the laminate (1) thin, the thickness of the resin insulating layer (10) is preferably 1 to 100 μm, and may be 1 to 20 μm.

[0026] <Insulating coating layer (20)>

[0027] As shown in FIG. 1, the insulating coat layer (20) is laminated on the resin insulating layer (10). The insulating coat layer (20) is a layer for increasing adhesion between the resin insulating layer (10) and the cellulose fiber layer (30) described later, and, for example, can be a layer mainly containing a water-based ester or urethane resin. In addition, the insulating coat layer (20) according to the present embodiment supports the carbon nanotube layer (40) applied on the insulating coat layer (20) and has the function of ensuring a certain film thickness containing a certain amount of carbon nanotubes in the carbon nanotube layer (40). Furthermore, the insulating coat layer (20) is not an essential component of the laminate (1) and may be omitted, but it is preferable to form it when it is necessary to ensure a certain film thickness in the carbon nanotube layer (40).

[0028] <Cellulose fiber layer (30)>

[0029] As shown in FIG. 1, the cellulose fiber layer (30) is laminated on the insulating coat layer (20) and mainly comprises fibrous cellulose having a fiber width (average diameter of the fiber) of 1000 nm or less. As such fibrous cellulose, cellulose nanofibers having a fiber width of 100 nm or less are preferred. The thickness of the cellulose fiber layer (30) can be appropriately set according to the use of the laminate (1), but in this embodiment, in order to thin the film thickness of the laminate (1), the thickness of the two layers combined of the insulating coat layer (20) and the cellulose fiber layer (30) is 1 to 5 μm. Furthermore, the cellulose fiber layer (30) is a layer mainly comprising fibrous cellulose having a fiber width of 1000 nm or less, and specifically, is a layer comprising 50% or more, more preferably 80% or more of the said fibrous cellulose.

[0030] Pulp fibers used as raw materials for fibrous cellulose include, for example, chemical pulps such as bamboo pulp, bleached kraft pulp (LBKP) and unbleached kraft pulp (LUKP) of hardwoods (LKP), bleached kraft pulp (NBKP) of softwoods (NKP) and unbleached kraft pulp (NUKP) of softwoods (NKP); and mechanical pulps such as stone gland pulp (SGP), pressurized stone gland pulp (PGW), refiner gland pulp (RGP), chemi-gland pulp (CGP), thermo-gland pulp (TGP), gland pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and bleached thermomechanical pulp (BTMP). Examples include waste paper pulp produced from recycled paper, recycled kraft envelopes, recycled magazines, recycled newspapers, recycled flyers, recycled office paper, recycled corrugated cardboard, recycled white paper, recycled Kent paper, recycled imitation paper, recycled paper bills, and recycled newsprint; and deinked pulp (DIP) obtained by deinking waste paper pulp. These may be used individually or in combination as long as they do not impair the effects of the present invention. Fiber-like cellulose is obtained by defibrating these pulp fibers through mechanical processing such as the beater method, DDR method, grinder method, aqueous counter-collision method, homogenizer, ball mill, roll mill, cutter mill, etc., or by chemical processing such as oxygen treatment or acid treatment (e.g., TEMPO oxidation treatment).

[0031] Additionally, the cellulose fiber layer (30) may optionally contain other papermaking agents as long as it does not impair the effects of the present invention. Examples of other papermaking agents include pigments, dyes, fillers, sizing agents, wear resistance enhancers, water-resistant agents, surfactants, waxes, rust inhibitors, conductive agents, and paper dust removal inhibitors. These may be used individually or in combination as long as they do not impair the effects of the present invention.

[0032] <Carbon nanotube layer (40)>

[0033] As shown in FIG. 1, the carbon nanotube layer (40) is laminated on the cellulose fiber layer (30). The carbon nanotube layer (40) is a layer mainly containing carbon nanotubes. The thickness of the carbon nanotube layer (40) can be appropriately set according to the use of the laminate (1), but when the film thickness of the laminate (1) is made thin, it is preferable to make the thickness of the carbon nanotube layer (40) 0.1 to 7 μm. Furthermore, the carbon nanotube layer (40) is a layer mainly containing carbon nanotubes, specifically, a layer containing 50% or more, more preferably 80% or more of carbon nanotubes.

[0034] In this way, in the laminate (1) according to the present embodiment, when the thickness of the laminate (1) is reduced, the thickness of the layer combining the insulating coat layer (20), the cellulose fiber layer (30), and the carbon nanotube layer (40) (when the insulating coat layer (20) is omitted, the layer combining the cellulose fiber layer (30) and the carbon nanotube layer (40)) becomes 1 to 10 μm. In this way, by reducing the thickness of the layer combining the insulating coat layer (20), the cellulose fiber layer (30), and the carbon nanotube layer (40) (when the insulating coat layer (20) is omitted, the layer combining the cellulose fiber layer (30) and the carbon nanotube layer (40)), the total film thickness of the laminate (1) can be reduced to 30 μm or less, and a laminate (1) with a thinner thickness compared to the conventional one can be provided.

[0035] In addition, carbon nanotubes are not particularly limited and can be manufactured by various methods such as arc discharge, laser evaporation, or chemical vapor deposition (CVD). Also, the structure of the carbon nanotubes is not particularly limited, but in order to secure high conductivity, it is preferable to have a structure having triple bonds between carbons, such as an acetylene backbone. In addition, the carbon nanotubes may be single-layer (e.g., 1 to 3 layers, typically 1 or 2 layers) or multi-layer (e.g., 4 to 200 layers, typically 4 to 60 layers), but it is preferable to compose the carbon nanotube layer (40) mainly with multi-layer carbon nanotubes. In addition, the carbon nanotubes may be composed of single-layer carbon nanotubes and multi-layer carbon nanotubes in any ratio (the mass ratio of single-layer carbon nanotubes to multi-layer carbon nanotubes is, for example, 100:0 to 50:50, preferably 100:0 to 80:20). Alternatively, carbon nanotubes can be vapor-grown carbon fibers (VGCF).

[0036] In addition, the length or diameter of the carbon nanotube is not particularly limited, but the carbon nanotube layer (40) according to the present embodiment can be configured as follows. For example, the length of the carbon nanotube can be 100 μm or less, and preferably 20 to 30 μm. In addition, the diameter of the carbon nanotube can be 50 nm or less, and preferably 20 nm or less.

[0037] The weight of the carbon nanotube layer (40) per unit area (1 square centimeter) of the laminate (1) (i.e., weight per unit area converted to solid content) is not particularly limited, but can be 0.1 μg or more, preferably 0.5 μg or more. By doing so, good conductivity can be imparted to the surface of the laminate (1). Also, the upper limit of the weight of the carbon nanotube layer (40) is not particularly limited, but if the weight per unit area of ​​the carbon nanotube layer (40) is too high, the carbon nanotube layer (40) may easily peel off from the cellulose fiber layer (30). From the perspective of preventing peeling, it is appropriate to make the weight of the carbon nanotube layer (40) per unit area (1 square centimeter) of the resin insulating layer (10) 30 μg or less, preferably 15 μg or less, more preferably 3.5 μg or less.

[0038] Method for manufacturing a laminate

[0039] An overview of the manufacturing method of the laminate (1) according to the present embodiment is described. The laminate (1) of the present embodiment can be manufactured, for example, by the following processes (1) and (2).

[0040] (1) A sheet-type resin insulating layer (10) is prepared, an insulating coat layer (20) is applied over the resin insulating layer (10) and dried, and then a cellulose fiber layer (30) is applied. The application of the insulating coat layer (20) and the cellulose fiber layer (30) can be performed by methods such as gravure printing, flexographic printing, silkscreen printing, and offset printing.

[0041] (2) After drying the cellulose fiber layer (30), a carbon tube layer forming slurry containing carbon nanotubes is applied to the cellulose fiber layer (30) and further dried to form a carbon nanotube layer (40) on the cellulose fiber layer (30). The application of the carbon nanotube layer (40) can also be performed by methods such as gravure printing, flexographic printing, silkscreen printing, and offset printing.

[0042] In addition, the thickness of the carbon nanotube layer (40) can be adjusted by continuously applying a slurry for forming the carbon nanotube layer in the printing method. Likewise, the thickness of the insulating coat layer (20) and the cellulose fiber layer (30) can also be adjusted by continuously applying them.

[0043] The carbon nanotube layer (40) is formed by applying a slurry for forming a carbon nanotube layer containing carbon nanotubes and a liquid medium onto a cellulose fiber layer (30) and evaporating the liquid solvent by heating. The slurry for forming a carbon nanotube layer according to this embodiment is a water-dispersible slurry in which carbon nanotubes are dispersed in water, which is a liquid solvent. Therefore, the carbon nanotube layer (40) formed by drying the slurry for forming a carbon nanotube layer can be made to contain almost no organic solvent residue or resin binder after the water evaporates.

[0044] In addition, the slurry for forming the carbon nanotube layer preferably has a liquid solvent (water) content of 95 mass% or more (in other words, a non-solvent component content of less than 5 mass%), and a liquid medium having a ratio of 97% or more is more preferable. In addition, as the liquid solvent, a mixture of alcohol and water may be used in addition to water. Furthermore, the slurry for forming the carbon nanotube layer may include various additives other than those mentioned above, within a scope that does not deviate from the purpose of the present invention. Preferred examples of additives include surfactants, defoaming agents, antioxidants, dispersants, viscosity modifiers, etc.

[0045] The heating temperature when drying the slurry for forming the carbon nanotube layer can be appropriately set by taking into account the composition of the liquid medium (especially the boiling point of the solvent), etc. Typically, it is preferable to set the drying temperature to approximately 40°C to 250°C (for example, approximately 60°C to 150°C). After drying, if necessary, heat treatment or cleaning treatment may be performed to remove additives contained in the carbon nanotube layer (40).

[0046] (Example 1)

[0047] Here, based on FIGS. 2 and 3, the measurement results of the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics of a conventional laminate and a laminate (1) according to the first embodiment regarding electromagnetic waves of 5 GHz or less in the vicinity are described. FIG. 2 is a graph showing the electromagnetic wave absorption characteristics (upper side of FIG. 2) and electromagnetic wave reflection characteristics (lower side of FIG. 2) of a conventional laminate regarding electromagnetic waves of 5 GHz or less in the vicinity, where the vertical axis represents the electromagnetic wave absorption rate (dB) and electromagnetic wave reflection rate (dB), and the horizontal axis represents the frequency (GHz). In addition, in FIG. 2, (A) is the measurement result measured without blocking in the laminate, (B) is the measurement result measured using a conventional laminate (commercial product 1), (C) is the measurement result measured using a conventional laminate (commercial product 2), and (D) is the measurement result measured using a conventional laminate (commercial product 3). In addition, in the examples shown in FIGS. 2 and 3, electromagnetic wave absorption performance and electromagnetic wave reflection characteristics were measured using a measuring device with a measurement frequency of up to 5 GHz by the microstrip line method (in accordance with IEC62333-2).

[0048] As shown in Figure 2, regarding electromagnetic waves of 5 GHz or lower in the vicinity, the electromagnetic wave absorption rate in conventional laminates (B) to (D) varied significantly with frequency. In addition, in conventional laminates (B) to (D), the electromagnetic wave reflectance was also non-uniform with frequency, and since reflection increased at specific wavelengths, there was concern that adverse effects would occur on the shielding target, such as modules.

[0049] In this regard, the measurement results of the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics of the laminate (1) according to the first embodiment for electromagnetic waves of 5 GHz or less in the vicinity are shown in FIG. 3. In FIG. 3, (E) shows the measurement results measured using the laminate (1) according to the present embodiment, in which the film thickness of the resin insulating layer (10) is 12.0 μm, and (F) shows the measurement results measured using the laminate (1) in which the film thickness of the resin insulating layer (10) is 4.5 μm. In addition, in FIG. 3, for reference, the above (B) to (D), which show the measurement results in a conventional laminate, are shown as thinner lines than (E) and (F).

[0050] As shown in FIG. 3, regarding electromagnetic waves of 5 GHz or less in the vicinity, it was found that in the laminates (1) (E) and (F) according to the first embodiment, while the film thickness is thin, a high electromagnetic wave absorption rate can be obtained in the frequency band up to 5 GHz compared to conventional laminates (B) to (D). In addition, in the laminates (1) (E) and (F) according to the first embodiment, the electromagnetic wave absorption rate curves gently with frequency, but compared to conventional laminates (B) to (D), the variation is gentle. Thus, regarding electromagnetic waves of 5 GHz or less in the vicinity, it was found that in the laminates (1) (E) and (F) according to the first embodiment, compared to conventional laminates (B) to (D), the electromagnetic wave absorption rate is high, and the variation in the electromagnetic wave absorption rate with respect to frequency is gentle and stable. In addition, regarding electromagnetic waves of 5 GHz or less in the vicinity, in the laminates (1) (E) and (F) according to the first embodiment, as shown in the lower part of FIG. 3, the electromagnetic wave reflectance also fluctuates gently and is stable compared to conventional laminates (B) to (D).

[0051] Next, based on FIG. 4, the measurement results of the electromagnetic wave absorption characteristics of a conventional laminate and a laminate (1) according to the first embodiment with respect to electromagnetic waves of 5 to 20 GHz in the vicinity are described. FIG. 4 is a graph showing the electromagnetic wave absorption characteristics of a conventional laminate and a laminate (1) according to the first embodiment with respect to electromagnetic waves of 5 to 20 GHz in the vicinity. In FIG. 4, the laminate of (B) above was used as the conventional laminate, and the laminate of (F) above was used as the laminate (1) according to the first embodiment. In addition, in the example shown in FIG. 4, the electromagnetic wave absorption performance and electromagnetic wave reflection characteristics were measured using a measuring device with a measurement frequency of 5 to 20 GHz by the microstrip line method (in accordance with IEC62333-2).

[0052] As shown in FIG. 4, it was found that the laminate (1) (F) according to the first embodiment can obtain a high electromagnetic wave absorption rate compared to conventional laminates (B) to (D), even for electromagnetic waves of 5 to 20 GHz or lower in the vicinity, just like the electromagnetic waves of 5 GHz or lower in the vicinity shown in FIG. 3. Additionally, although not shown, it was found that the laminate (1) according to the first embodiment can obtain a high electromagnetic wave absorption rate compared to the conventional one even for electromagnetic waves of 30 GHz or higher. Furthermore, as shown in FIG. 4, in the conventional laminate, there was a problem that the electromagnetic wave absorption characteristics were non-uniform depending on the frequency of the electromagnetic waves, but in the laminate (1) according to the present embodiment, it was found that the non-uniformity of the electromagnetic wave absorption characteristics depending on the frequency of the electromagnetic waves can be suppressed and the frequency dependence of the electromagnetic wave absorption becomes smaller.

[0053] As described above, the laminate (1) according to the first embodiment has a resin insulating layer (10), an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40). By laminating the insulating coat layer (20) on the resin insulating layer (10), laminating the cellulose fiber layer (30) on the insulating coat layer (20), and laminating the carbon nanotube layer (40) on the cellulose fiber layer (30), the film thickness of the laminate (1) can be thin while providing a laminate with excellent stability. That is, in the past, in order to block electromagnetic waves, a metal thin film such as copper or aluminum or a metal thin film including ferrite-based metal powder was laminated onto the insulating layer. As a result, the thickness became thick to about 100 μm, and there were problems such as low surface resistivity and excessively strong reflection of electromagnetic waves, which resulted in low absorption of electromagnetic waves, making it heavy and limiting its applications. In addition, in order to solve such problems, even when a configuration having a carbon nanotube layer is used, there was a problem in that the adhesion between the carbon nanotube layer and the insulating layer made of resin, etc. is low, so a stable laminate cannot be obtained. Regarding these problems, in the laminate (1) according to the first embodiment, the carbon nanotube layer (40) is not directly laminated on the resin insulating layer (10), but a cellulose fiber layer (30) is laminated on the resin insulating layer (10) (and insulating coat layer (20)), and the carbon nanotube layer (40) is laminated thereon. Since the adhesion between the resin insulating layer (10) (and insulating coat layer (20)) and the cellulose fiber layer (30), and the adhesion between the cellulose fiber layer (30) and the carbon nanotube layer (40) are each high, by making such a structure, a laminate (1) in which the carbon nanotube layer (40) is stably laminated can be provided. In this way, in the first embodiment, by having a carbon nanotube layer (40), the film thickness of the entire laminate (1) is thin, at 30 μm or less, and also, even with the carbon nanotube layer (40), a laminate (1) in which the carbon nanotube layer (40) is stably laminated can be provided.

[0054] In addition, as shown in FIGS. 2 and 3, in the laminate (1) according to the first embodiment, the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics for electromagnetic waves in the vicinity can be improved compared to the conventional method while keeping the film thickness thin. Specifically, since the surface resistivity of the carbon nanotube layer (40) of the laminate (1) is 50 to 1000 Ω / □, the electromagnetic wave absorption characteristics can be stably secured compared to the conventional method. As a result, the ability to absorb electromagnetic waves in the vicinity can be increased, and the noise suppression effect can be enhanced. Furthermore, in this embodiment, an insulating coat layer (20) is present below the carbon nanotube layer (40), thereby further enhancing the noise suppression effect. That is, in the laminate (1) according to the first embodiment, a noise suppression effect can be achieved by absorbing electromagnetic waves from the vicinity by the carbon nanotube layer (40). However, if the film thickness of the carbon nanotube layer (40) is thin, the carbon nanotube layer (40) may not be able to absorb some of the electromagnetic waves, and some of the electromagnetic waves may pass through. However, by forming an insulating coat layer (20) below the carbon nanotube layer (40), a boundary surface with a large difference in surface resistivity is formed between the carbon nanotube layer (40) and the insulating coat layer (20). Electromagnetic waves passing through the carbon nanotube layer (40) are reflected at the boundary surface, and the reflected electromagnetic waves can be reflected and absorbed by the carbon nanotube layer (40). By doing so, a higher noise suppression effect can be achieved in the laminate (1) according to the present embodiment. In addition, the laminate (1) according to the present embodiment is advantageous in that, compared to the conventional one, the frequency dependence of electromagnetic wave absorption is small, and the electromagnetic wave absorption characteristics are scattered according to frequency.

[0055] In addition, the laminate (1) according to the first embodiment has electromagnetic wave absorption performance up to 30 GHz, which is the entry point of millimeter waves, as a noise suppression range (electromagnetic wave absorption range). This can cover all frequency bands used in 5G (5th generation mobile communication system), such as the 3.5 GHz band, the 4.6-5 GHz band, and the 28 GHz band, and by applying the laminate (1) according to this embodiment to a noise suppression sheet for a 5G-compatible communication device, it is expected to serve as a noise suppression member for a 5G-compatible communication device.

[0056] 《Second Embodiment》

[0057] Next, a laminate (1a) according to the second embodiment will be described. FIG. 5 is a schematic diagram showing a cross-section of a laminate (1a) according to the second embodiment. As shown in FIG. 5, the laminate (1a) according to the second embodiment has the same structure as the laminate (1) according to the first embodiment, except that an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40) are further laminated on top of a carbon nanotube layer (40).

[0058] As shown in FIG. 5, in the laminate (1a) according to the second embodiment, a second insulating coat layer (20) is further laminated on top of the first layer of carbon nanotube layers (40), a second layer of cellulose fiber layers (30) is further laminated on top of the second layer of insulating coat layers (20), and a second layer of carbon nanotube layers (40) is further laminated on top of the second layer of cellulose fiber layers (30). In this way, in the laminate (1a) according to the second embodiment, by laminating multiple carbon nanotube layers (40), the thickness of the carbon nanotube layers (40) throughout the laminate (1a) is increased, and thereby, noise can be further reduced.

[0059] Also, since the moldability of the carbon nanotube layer (40) may be reduced when multiple carbon nanotube layers (40) are stacked, the laminate (1a) according to the second embodiment has a structure in which an insulating coat layer (20) and a cellulose fiber layer (30) are stacked on top of the carbon nanotube layer (40), and a carbon nanotube layer (40) is stacked thereon. In addition, when the insulating coat layer (20) is stacked on top of the carbon nanotube layer (40), the insulating coat layer (20) is stacked after the carbon nanotube layer (40) is dried. Also, since an alcohol solvent is used for the insulating coat layer slurry, the case in which the insulating coat layer (20) is directly stacked on top of the carbon nanotube layer (40) is different from the case in which the carbon nanotube layer (40) is stacked on top of the insulating coat layer (20), and can be stacked stably.

[0060] In addition, in the example shown in FIG. 5, a configuration in which two layers of carbon nanotube layers (40) are stacked is illustrated, but this configuration is not limited to this configuration, and a configuration in which three or four or more layers of carbon nanotube layers (40) are stacked can be used.

[0061] (Example 2)

[0062] Next, the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics of the laminate (1a) according to the second embodiment with respect to electromagnetic waves of 5 GHz or less in the vicinity are described. FIG. 6 is a graph showing the electromagnetic wave absorption characteristics and electromagnetic wave reflection characteristics of the laminate (1a) according to the second embodiment with respect to electromagnetic waves of 5 GHz or less in the vicinity. In FIG. 6, (G) represents the measurement result measured using a laminate (1a) with two layers of resin insulating layers (10) of 12 μm thickness stacked thereon, (H) represents the measurement result measured using a laminate (1a) with two layers of resin insulating layers (10) of 4.5 μm thickness stacked thereon, and (I) represents the measurement result measured using a laminate (1a) with three layers of resin insulating layers (10) of 4.5 μm thickness stacked thereon. Also, in FIG. 6, as in FIG. 3, the above (B) to (D), representing a conventional shielding film for the vicinity, are shown as thinner lines than (G) to (I). In addition, in the example shown in FIG. 6, electromagnetic wave absorption performance and electromagnetic wave reflection characteristics were measured using a measuring device with a measurement frequency up to 5 GHz by the microstrip line method (in accordance with IEC62333-2).

[0063] As shown in FIG. 6, regarding electromagnetic waves of 5 GHz or less in the vicinity, in the laminates (1a) (G) to (I) according to the second embodiment, the film thickness was thin, and the electromagnetic wave absorption rate was increased in most frequency bands compared to the conventional laminates (B) to (D). In addition, in the laminates (1a) (G) to (I) according to the second embodiment, since they have two layers of carbon nanotube layers (40), the electromagnetic wave absorption rate was increased even compared to the laminates (1) (E) and (F) according to the first embodiment.

[0064] In addition, in the laminates (1a) (G) to (I) according to the second embodiment, the electromagnetic wave absorption rate curves gently according to frequency, just like in the laminates (1) (G) to (I) according to the first embodiment, but compared to the conventional laminates (B) to (D), the variation in the electromagnetic wave absorption rate is gentle and stable overall.

[0065] Additionally, regarding electromagnetic waves of 5 GHz or lower in the vicinity, in the laminates (1a) (G) to (I) according to the second embodiment, as shown in FIG. 6, the electromagnetic wave absorption rate in a specific frequency band could be made particularly high. For example, in the laminate (1a) (G) in which two layers of a resin insulating layer (10) of 12 μm are stacked, the electromagnetic wave absorption rate in a frequency band around 5.0 to 5.5 GHz could be made particularly high, and in the laminate (1a) (I) in which three layers of a resin insulating layer (10) of 4.5 μm are stacked, the electromagnetic wave absorption rate in a frequency band around 5.3 to 5.8 GHz could be made particularly high. In this way, it was found that by changing the layer thickness or number of layers of each layer of the resin insulating layer (10), insulating coat layer (20), cellulose fiber layer (30), and carbon nanotube layer (40), the electromagnetic wave absorption characteristics of the laminate (1a) can be adjusted for electromagnetic waves of 5 GHz or less in the vicinity.

[0066] In addition, regarding electromagnetic waves of 5 GHz or less in the vicinity, in the laminates (1a) (G) to (I) according to the second embodiment, just like the laminates (1) (E) and (F) according to the first embodiment, the electromagnetic wave reflectance also becomes more gradual and stabilized overall compared to the conventional laminates (B) to (D).

[0067] Next, based on FIG. 7, the measurement results of the electromagnetic wave absorption characteristics of a conventional laminate and a laminate (1a) according to the second embodiment for electromagnetic waves in the near-field range of 5 to 20 GHz will be explained. FIG. 7 is a graph showing the electromagnetic wave absorption characteristics of a conventional laminate and a laminate (1a) according to the second embodiment for electromagnetic waves in the near-field range of 5 to 20 GHz. In FIG. 7, the laminate of (B) above was used as the conventional laminate, and the laminate of (H) above was used as the laminate (1a) according to the second embodiment. In addition, in the example shown in FIG. 7, the electromagnetic wave absorption performance and electromagnetic wave reflection characteristics were measured using a measuring device with a measurement frequency of 5 to 20 GHz by the microstrip line method (in accordance with IEC62333-2).

[0068] As shown in FIG. 7, it was found that the laminate (H) according to the second embodiment (1a) can obtain a high electromagnetic wave absorption rate compared to conventional laminates (B) to (D), even for electromagnetic waves of 5 to 20 GHz or lower in the vicinity, just like the electromagnetic waves of 5 GHz or lower in the vicinity shown in FIG. 6. Additionally, although not shown, it was found that the laminate (1a) according to the second embodiment can obtain a high electromagnetic wave absorption rate compared to the conventional one even for electromagnetic waves of 30 GHz or higher. Furthermore, as shown in FIG. 7, in the conventional laminate, there was a problem that the electromagnetic wave absorption characteristics were non-uniform depending on the frequency of the electromagnetic waves, but in the laminate (1a) according to the second embodiment, it was found that the non-uniformity of the electromagnetic wave absorption characteristics depending on the frequency of the electromagnetic waves can be suppressed and the frequency dependence of the electromagnetic wave absorption becomes smaller.

[0069] Next, based on FIG. 8, the measurement results of the dielectric constant characteristics of the conventional laminate and the laminate (1a) of the second embodiment for electromagnetic waves of 18 to 30 GHz in the far-field system will be explained. FIG. 8 (A) is a graph showing the dielectric constant of the laminate (1a) of the second embodiment for electromagnetic waves of 18 to 30 GHz in the far-field system, and FIG. 8 (B) is a graph showing the dielectric constant of the laminate (1a) of the first embodiment for electromagnetic waves of 40 to 65 GHz or higher in the far-field system. In the example shown in FIG. 8 (A), the dielectric constant of the laminate (1a) was calculated by measuring S11 (attenuation of reflected waves for the laminate) and S21 (attenuation of transmitted waves for the laminate) using a network analyzer by the waveguide method. In addition, in the example shown in (B) of Fig. 8, the permittivity was measured using a network analyzer in the same way by the free-space method.

[0070] As shown in FIG. 8 (A) and FIG. 8 (B), in the laminate (1a) according to the second embodiment, regarding electromagnetic waves of 18 to 30 GHz in the far-field, there is a large difference between the real and imaginary parts of the relative permittivity, so it is easy for electricity to flow and also easy to convert into thermal energy, that is, it is a property of absorbing electromagnetic waves in the far-field. And, when the laminate (1a) has the property of easy for electricity to flow, the surface resistivity tends to decrease and the reflection of electromagnetic waves tends to become stronger, but by adjusting the film thickness of the resin insulating layer (10), insulating coat layer (20), or carbon nanotube layer (40), the surface resistivity of the laminate (1a) can be adjusted, and as a result, it is thought that the absorption and reflection characteristics of electromagnetic waves in the far-field can be appropriately adjusted.

[0071] As described above, the laminate (1a) according to the second embodiment has the function of absorbing and reflecting electromagnetic waves in the near field and the function of absorbing electromagnetic waves in the far field, and can be provided for use in suppressing noise in the near field (e.g., suppressing noise generated from a smartphone battery, etc.) in addition to the function of suppressing noise in the far field (e.g., the function of absorbing electromagnetic lasers emitted from a vehicle device at a location spaced apart from the vehicle device, etc.). Furthermore, since the function of absorbing electromagnetic waves in the far field is attributed to the carbon nanotube layer (40), it is thought that the laminate (1) according to the first embodiment also has the function of absorbing electromagnetic waves in the far field. However, in the laminate (1a) according to the second embodiment, by further laminating an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40) on top of the carbon nanotube layer (40), the thickness of the carbon nanotube layer (40) throughout the laminate (1a) can be increased, and thereby, compared to the laminate (1) according to the first embodiment, the electromagnetic wave absorption characteristics and noise suppression effects for electromagnetic waves in the far and near fields can be exhibited more highly. That is, the carbon nanotube layer (40) can absorb electromagnetic waves in the near and far fields, but because the thickness of the carbon nanotube layer (40) is thin, some electromagnetic waves may pass through the carbon nanotube layer (40). However, in the laminate (1a) according to the second embodiment, a second insulating coat layer (20) is interposed between the first layer carbon nanotube layer (40) and the second layer carbon nanotube layer (40), and also, the first layer insulating coat layer (20) exists below the first layer carbon nanotube layer (40).Accordingly, in the laminate (1a) according to the second embodiment, due to the large difference in surface resistivity between the carbon nanotube layer (40) and the insulating coat layer (20), multiple interfaces that reflect electromagnetic waves are formed, and electromagnetic waves passing through the carbon nanotube layer (40) are reflected multiple times at the multiple interfaces, and the reflected electromagnetic waves are absorbed at each carbon nanotube layer (40), so compared to the laminate (1) according to the first embodiment, the electromagnetic wave absorption characteristics are high and the noise suppression effect is high.

[0072] In addition, by having a structure in which an insulating coat layer (20) and a cellulose fiber layer (30) are laminated on top of a first layer of carbon nanotube layer (40), and a second layer of carbon nanotube layer (40) is laminated thereon, the deterioration of the moldability of the laminate (1a) can be suppressed. Furthermore, in the laminate (1a) according to the second embodiment, compared to the laminate (1) according to the first embodiment, it has additional insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40), so the film thickness of the entire laminate (1a) becomes thicker, but the thickness of the three layers of insulating coat layer (20), cellulose fiber layer (30), and carbon nanotube layer (40) is about 1 to 12 μm, so a laminate (1a) with a sufficiently thin thickness compared to the conventional one can be provided. In addition, in the laminate (1a) according to the second embodiment, by varying the stacking shape of each layer, electromagnetic wave absorption characteristics at a specific frequency can be adjusted, as in the laminate (1a) of (G) shown in FIG. 6.

[0073] In addition, in the laminate (1a) according to the second embodiment, when multiple carbon nanotube layers (40) are laminated, the shielding performance in a specific frequency band may be adjusted by changing the film thickness of the carbon nanotube layers (40) layer by layer, or by changing the film thickness of the insulating coat layer (20) laminated between the carbon nanotube layers (40). Furthermore, when an insulating coat layer (20) is laminated on the carbon nanotube layer (40), the insulating coat layer (20) may not necessarily be formed on a specific part of the carbon nanotube layer (40), but may be configured to form the insulating coat layer (20) in a specific pattern such that the part where the carbon nanotube layer (40) is connected in the lamination direction (for example, the first layer of carbon nanotube layer (40) and the second layer of carbon nanotube layer (40) are connected) and the part where the insulating coat layer (20) is coated on the carbon nanotube layer (40). In this case, a highly conductive portion connected to the carbon nanotube layer (40) and a portion that absorbs electromagnetic waves with high efficiency, where the insulating coat layer (20) is coated on the carbon nanotube layer (40), can be formed at once, and it is possible to secure higher electromagnetic wave absorption performance through a synergistic effect. Also, since the cellulose fiber layer (30) is extremely thin and in a very small amount, even if the cellulose fiber layer (30) is formed normally, in the laminate (1a) after manufacturing, the carbon nanotube layer (40) can be connected in the portion where the insulating coat layer (20) is not laminated on the carbon nanotube layer (40). In addition, by utilizing the high thermal conductivity of the carbon nanotube layer (40) (carbon nanotube), the laminate (1a) according to this embodiment can be used as a thermal diffusion sheet. In this case, the heat diffusion effect may be adjusted by appropriately forming a layer that covers the entire surface of the carbon nanotube layer (40) with an insulating coat layer (20) and a layer that forms a pattern of the aforementioned insulating coat layer (20).

[0074] 《Third Embodiment》

[0075] Next, a coating member (2) according to the third embodiment will be described. FIG. 9 is a schematic diagram showing a cross-section of a coating member (2) according to the third embodiment. As shown in FIG. 9, the coating member (2) according to the third embodiment has the same structure as the laminate (1) according to the first embodiment, except that it has an adhesive layer (50) and a release film (60) below the resin insulating layer (10).

[0076] The adhesive layer (50) is an adhesive layer for adhering to other members, and known materials such as acrylic resin, silicone resin, polyester resin, polyvinyl acetate resin, polyvinyl ether resin, or urethane resin may be used. Additionally, the release film (60) is a film that can be peeled off more easily than the adhesive layer (50), and by peeling the release film (60) from the adhesive layer (50), the laminate (1) (a laminate (1) composed of the resin insulating layer (10), insulating coat layer (20), cellulose fiber layer (30), and carbon nanotube layer (40) of the third embodiment) can be adhered to an object.

[0077] As described above, the coating member (2) according to the third embodiment is a member for attaching a laminate (1) composed of a resin insulating layer (10), an insulating coat layer (20), and a cellulose fiber layer (30) to an object, and it is possible to easily impart shielding performance to the object through the laminate (1).

[0078] Although preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the description of the embodiments. Various modifications and improvements can be made to the embodiments, and forms incorporating such modifications or improvements are also included within the technical scope of the present invention.

[0079] For example, in the first to third embodiments described above, a resin insulating layer may be further installed on the carbon nanotube layer (40) on the outermost surface of the laminate (1, 1a) shown in FIG. 1 and 5 and the coating member (2) shown in FIG. 9, so as not to compromise electromagnetic wave absorption performance, thereby preventing the detachment of carbon fibers of the carbon nanotubes.

[0080] In addition, in the laminate (1a) according to the second embodiment described above, a configuration in which an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40) are further laminated on top of the first layer of carbon nanotube layer (40) is exemplified, but this configuration is not limited to this configuration, and depending on the desired degree of noise reduction, a configuration in which multiple insulating coat layers (20), cellulose fiber layers (30), and carbon nanotube layers (40) are laminated (for example, a configuration in which multiple layers are laminated, such as three layers, four layers, etc.) may be used. Also, as shown in FIGS. 10 and 11, a configuration in which multiple layers of the laminate (1) according to the first embodiment are overlapped through an adhesive layer (50) may be used. For example, in the laminate (1b) shown in FIG. 10, a second layer of carbon nanotubes (40) is laminated over a first layer of carbon nanotubes (40) through an adhesive layer (50), and then a cellulose fiber layer (30), an insulating coat layer (20), and a resin insulating layer (10) are laminated in order thereon. In addition, in the laminate (1c) shown in FIG. 11, a resin insulating layer (10) is further laminated over a first layer of carbon nanotubes (40) through an adhesive layer (50), and then an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40) are laminated in order thereon. By configuring in this way, in addition to increasing the noise suppression effect, noise suppression characteristics in a specific frequency band can also be adjusted. Also, although not illustrated, the laminate (1a) according to the second embodiment may be configured to be superimposed multiple times through an adhesive layer (50).

[0081] Additionally, as an example of lamination to improve electromagnetic wave absorption performance, as shown in (A) of FIG. 12, an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40) can be laminated in order on one side of a resin insulating layer (10), similar to the laminate (1) according to the first embodiment, and an insulating coat layer (20), a cellulose fiber layer (30), and a carbon nanotube layer (40) can also be laminated in order on the opposite side of the resin insulating layer (10) to form a laminate (1d). Additionally, as shown in (B) of FIG. 12, two laminates (1d) shown in (A) of FIG. 12 can be laminated with an adhesive layer (50) in between to form a laminate (1e). Furthermore, three or more laminates (1d) can be laminated by the adhesive layer (50). Explanation of the symbols

[0082] 1, 1a~d : Laminate 10: Resin insulation layer 20: Insulation coat layer 30: Cellulose fiber layer 40 : Carbon nanotube layer 2 : Coating member 50: Adhesive layer 60: Release film

Claims

Claim 1 A laminate comprising: an insulating layer comprising a resin composition; a cellulose fiber layer comprising microfibrous cellulose having a fiber width of 1000 nm or less, laminated on the insulating layer; and a carbon nanotube layer comprising carbon nanotubes, laminated on the cellulose fiber layer; wherein the thickness of the film of the carbon nanotube layer is 20 μm or less and the thickness of the film of the entire laminate is 120 μm or less. Claim 2 A laminate according to claim 1, wherein the cellulose fiber layer is a layer that is not separated from the insulating layer, and a detached layer separated from the insulating layer is laminated on the side opposite to the side of the insulating layer where the cellulose fiber layer is laminated. Claim 3 In claim 1, the carbon nanotube layer is a laminate formed using water-dispersible carbon nanotubes. Claim 4 A laminate according to claim 1, wherein a cellulose fiber layer containing microfibrous cellulose is further laminated on the carbon nanotube layer, and a carbon nanotube layer containing carbon nanotubes is further laminated on the cellulose fiber layer. Claim 5 A laminate according to claim 1, wherein an insulating layer comprising a resin composition is laminated on the carbon nanotube layer, a cellulose fiber layer comprising microfibrous cellulose is further laminated on the insulating layer, and a carbon nanotube layer comprising carbon nanotubes is further laminated on the cellulose fiber layer. Claim 6 In claim 5, when the insulating layer is laminated on the carbon nanotube layer, the insulating layer is formed in a laminated pattern in which the insulating layer is not laminated on a part of the carbon nanotube layer. Claim 7 In claim 1, the microfibrous cellulose is a laminate in which the fiber width is 100 nm or less, and the cellulose nanofiber is a cellulose nanofiber. Claim 8 A laminate according to claim 1, wherein the film thickness in the two layers of the cellulose fiber layer and the carbon nanotube layer is 1 to 10 μm. Claim 9 A laminate for absorbing and reflecting electromagnetic waves in the vicinity, as described in paragraph 1. Claim 10 A laminate for absorbing electromagnetic waves from the far side in claim 1. Claim 11 A coating member having a laminate as described in any one of claims 1 to 10. Claim 12 A method for manufacturing a laminate comprising: a step of forming an insulating layer by applying a coating material for an insulating layer comprising a resin composition; a step of forming a cellulose fiber layer by applying a cellulose fiber coating material comprising microfibrous cellulose having a fiber width of 1000 nm or less onto the insulating layer; and a step of forming a carbon nanotube layer by applying a carbon nanotube coating material comprising carbon nanotubes onto the cellulose fiber layer, wherein the thickness of the film of the carbon nanotube layer is 20 μm or less and the thickness of the film of the entire laminate is 120 μm or less.

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