WO2017110096A1 - 電磁波吸収材料及び電磁波吸収体 - Google Patents
電磁波吸収材料及び電磁波吸収体 Download PDFInfo
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Definitions
- the present invention relates to an electromagnetic wave absorbing material and an electromagnetic wave absorber, and more particularly to an electromagnetic wave absorbing material and an electromagnetic wave absorber containing an insulating material and a conductive material.
- a noise suppressor containing a conductive material and an insulating material has been proposed, which does not attenuate electromagnetic waves in the low frequency region, but can attenuate electromagnetic waves in a relatively high frequency region (for example, see Patent Document 1).
- an electromagnetic wave absorbing material containing a conductive material and an insulating material and capable of absorbing electromagnetic waves in a frequency region of 1 GHz or higher has been proposed (for example, see Patent Document 2).
- an object of the present invention is to provide an electromagnetic wave absorbing material that can absorb an electromagnetic wave in a high frequency region and an electromagnetic wave absorber including an electromagnetic wave absorbing layer made of the electromagnetic wave absorbing material.
- the present inventors have intensively studied in order to achieve the above object. And the present inventors mix
- the present invention aims to solve the above-mentioned problems advantageously, and the electromagnetic wave absorbing material of the present invention includes a fibrous carbon nanostructure and an insulating material, and contains the insulating material.
- the amount C of the fibrous carbon nanostructure when the amount is 100 parts by mass is 5 parts by mass or more and 15 parts by mass or less, or the fibrous carbon nanostructure is obtained from an adsorption isotherm.
- the content C is 0.3 parts by mass or more and 0.8 parts by mass or less, and absorbs electromagnetic waves in a frequency region exceeding 20 GHz. It is characterized by doing.
- the insulating material is an insulating polymer
- the insulating polymer includes (a) a thermoplastic resin and / or a thermosetting resin, and (b) a rubber and / or an elastomer. It is preferable that it is either.
- the electromagnetic wave absorbing material contains the insulating polymer (a) or (b)
- the electromagnetic wave absorbing material can further improve the ability to absorb electromagnetic waves in a high frequency region exceeding 20 GHz, and the electromagnetic wave absorbing material can be used in general. Can increase the sex.
- the fibrous carbon nanostructure when the content C of the fibrous carbon nanostructure is 5 parts by mass or more and 15 parts by mass or less, the fibrous carbon nanostructure is a multi-walled carbon nanotube. Is preferred. In the production of the electromagnetic wave absorbing material, the production efficiency of the electromagnetic wave absorbing material can be increased by using multi-walled carbon nanotubes.
- the present invention aims to advantageously solve the above problems, and the electromagnetic wave absorber of the present invention is characterized by comprising an electromagnetic wave absorbing layer formed using the above-mentioned electromagnetic wave absorbing material.
- the electromagnetic wave absorber can sufficiently enhance the ability to absorb electromagnetic waves in a high frequency region exceeding 20 GHz. Can do.
- the present invention aims to advantageously solve the above-mentioned problems, and the electromagnetic wave absorber of the present invention includes a plurality of electromagnetic wave absorption layers including a fibrous carbon nanostructure and an insulating material.
- the fibrous carbon nanostructures and / or insulating materials contained in each layer of the electromagnetic wave absorbing layer are the same or different types, and a plurality of the electromagnetic wave absorbing layers are arranged from the side far from the electromagnetic wave incident side. 1 electromagnetic wave absorbing layer, second electromagnetic wave absorbing layer,..., N-th electromagnetic wave absorbing layer, and the fibrous carbon nano-particles when the content of the insulating material in each layer of the plurality of electromagnetic wave absorbing layers is 100 parts by mass.
- the content of the structure is A1 part by mass, A2 part by mass,... An part by mass, respectively, the following conditions (1-1) or (1-2) and (2) or (3) Is established, 5 ⁇ A1 ⁇ 15 (1-1)
- the fibrous carbon nanostructure is a fibrous carbon nanostructure in which the t-plot obtained from the adsorption isotherm shows a convex shape, 0.3 ⁇ A1 ⁇ 0.8 (1) -2)
- n is 2, A1> A2 (2)
- n is a natural number of 3 or more, A1> A2 ⁇ ... ⁇ An (3)
- the content of the fibrous carbon nanostructure in the first electromagnetic wave absorber layer is the largest. According to such a configuration, the electromagnetic wave absorbing ability of the electromagnetic wave absorber can be further improved.
- the insulating material is an insulating polymer
- the insulating polymer includes (a) a thermoplastic resin and / or a thermosetting resin, and (b) a rubber and / or an elastomer. It is preferable that it is either. If the electromagnetic wave absorber contains the insulating polymer (a) or (b) above, the ability of the electromagnetic wave absorber to absorb electromagnetic waves in the high frequency region above 20 GHz is further improved, and the general purpose of the electromagnetic wave absorbing material Can increase the sex.
- the fibrous carbon nanostructure is a multi-walled carbon nanotube when the condition (1-1) is satisfied.
- the production efficiency of the electromagnetic wave absorber can be increased.
- the electromagnetic wave absorber according to the present invention preferably further comprises an insulating layer on the outermost surface on the incident side of the electromagnetic wave.
- Such an electromagnetic wave absorber is more excellent in the ability to absorb electromagnetic waves in a high frequency region such as more than 20 GHz and has excellent durability.
- the electromagnetic wave absorber according to the present invention preferably has a total thickness of 1 ⁇ m or more and 500 ⁇ m or less. By setting the total thickness of the electromagnetic wave absorber within the above range, the electromagnetic wave absorbing ability in a high frequency region can be sufficiently secured, and the self-supporting property when formed into a film shape can be sufficiently secured.
- an electromagnetic wave absorbing material and an electromagnetic wave absorber that can absorb an electromagnetic wave in a high frequency region exceeding 20 GHz.
- 3 is a graph showing an example of a typical t-plot.
- the electromagnetic wave absorbing material of the present invention contains a fibrous carbon nanostructure and an insulating material, and is not particularly limited. Can be used on the body. And the electromagnetic wave absorption material and electromagnetic wave absorber of this invention are excellent in the electromagnetic wave absorptivity in a high frequency area
- the electromagnetic wave absorbing material of the present invention contains a fibrous carbon nanostructure and an insulating material. Furthermore, in the electromagnetic wave absorbing material, the content C of the fibrous carbon nanostructure when the content of the insulating material is 100 parts by mass is 5 parts by mass or more and 15 parts by mass or less, or the fibrous carbon nanostructure. When the structure is a fibrous carbon nanostructure having a convex shape in the t-plot obtained from the adsorption isotherm, the content C is 0.3 parts by mass or more and 0.8 parts by mass or less. Need. And according to the electromagnetic wave absorption material of this invention, the electromagnetic wave of a high frequency area
- the following points are known for electromagnetic wave absorption of a composite material containing a fibrous carbon nanostructure and an insulating material.
- an electromagnetic wave is irradiated to a composite material containing a fibrous carbon nanostructure and an insulating material, the electromagnetic wave is repeatedly reflected between the fibrous carbon nanostructures in the composite material to attenuate the electromagnetic wave.
- the fibrous carbon nanostructure reflects electromagnetic waves, the fibrous carbon nanostructure absorbs the electromagnetic waves and converts them into heat.
- the energy of electromagnetic waves increases as the frequency increases, it seems that the higher the content of the fibrous carbon nanostructure, the more effective the electromagnetic wave absorbing ability in the high frequency region.
- the present inventors investigated electromagnetic wave absorption ability in a high frequency region by variously adjusting the blending amount of the fibrous carbon nanostructure with respect to 100 parts by mass of the insulating material. As a result, the present inventors have surprisingly found that the electromagnetic wave absorbing ability in such a high frequency region can be remarkably improved within the blending amount range in which the above-described content can be realized.
- the compounding quantity of each material at the time of manufacturing an electromagnetic wave absorption material is equal to content of each material contained in the manufactured electromagnetic wave absorption material.
- the fibrous carbon nanostructure used in the electromagnetic wave absorbing material of the present invention is not particularly limited, and any fibrous carbon nanostructure can be used.
- the fibrous carbon nanostructure is not particularly limited, and may be made of only carbon nanotubes (hereinafter sometimes referred to as “CNT”). Mixtures with fibrous carbon nanostructures may be used. More specifically, as the fibrous carbon nanostructure that can be used for the electromagnetic wave absorbing material of the present invention, a fibrous carbon nanostructure in which the t-plot obtained from the adsorption isotherm shows a convex shape, Other fibrous carbon nanostructures can be mentioned.
- the “fibrous carbon nanostructure” usually refers to a fibrous carbon material having an outer diameter (fiber diameter) of less than 1 ⁇ m.
- fiber or “fibrous” generally refers to a structure having an aspect ratio of 5 or more.
- aspect ratio the diameter and length of 100 fibrous carbon nanostructures selected at random using a transmission electron microscope were measured, and the average value of the ratio of the diameter to the length (length / diameter). Can be obtained by calculating.
- the fibrous carbon nanostructure in which the t-plot has an upwardly convex shape is not particularly limited as long as the t-plot obtained from the adsorption isotherm exhibits an upwardly convex shape.
- CNT, Vapor grown carbon fiber or the like can be used. These may be used individually by 1 type and may use 2 or more types together. If fibrous carbon nanostructures with a convex t-plot are used, the fibrous carbon nanostructures are less likely to agglomerate with each other, and the amount of addition required to achieve the desired performance is reduced. can do. Thereby, an electromagnetic wave absorbing material excellent in electromagnetic wave absorbing ability and conductivity in a high frequency region exceeding 20 GHz and excellent in durability can be obtained.
- the fibrous carbon nanostructure including CNTs is preferable as the fibrous carbon nanostructure having an upwardly convex t-plot.
- the CNT to be contained in the fibrous carbon nanostructure having an upwardly convex t-plot CNT that has not been subjected to opening treatment is preferable.
- t-plot shows an upwardly convex shape
- adsorption is a phenomenon in which gas molecules are removed from the gas phase to the solid surface, and is classified into physical adsorption and chemical adsorption based on the cause.
- physical adsorption is used in the nitrogen gas adsorption method used for obtaining the t-plot. Normally, if the adsorption temperature is constant, the number of nitrogen gas molecules adsorbed on the fibrous carbon nanostructure increases as the pressure increases.
- the plot of the relative pressure (ratio of adsorption equilibrium pressure P and saturated vapor pressure P0) on the horizontal axis and the amount of nitrogen gas adsorption on the vertical axis is called the “isothermal line”. Nitrogen gas adsorption while increasing the pressure The case where the amount is measured is referred to as an “adsorption isotherm”, and the case where the amount of nitrogen gas adsorption is measured while reducing the pressure is referred to as a “desorption isotherm”.
- the t-plot is obtained by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm measured by the nitrogen gas adsorption method.
- the average thickness t of the nitrogen gas adsorption layer is plotted against the relative pressure P / P0, and the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure is obtained from the known standard isotherm and the above conversion is performed.
- t-plot method by de Boer et al.
- FIG. 1 a typical t-plot of a sample having pores on the surface is shown in FIG.
- the growth of the nitrogen gas adsorption layer is classified into the following processes (1) to (3).
- the following steps (1) to (3) change the slope of the t-plot as shown in FIG. (1)
- Monomolecular adsorption layer formation process of nitrogen molecules on the entire surface
- Multimolecular adsorption layer formation and capillary condensation filling process in the pores accompanying it (3) Apparent filling of the pores with nitrogen Formation process of multimolecular adsorption layer on non-porous surface
- the t-plot of the fibrous carbon nanostructure used in the present invention is located on a straight line passing through the origin in the region where the average thickness t of the nitrogen gas adsorption layer is small as shown in FIG.
- the plot is shifted downward from the straight line and shows an upwardly convex shape.
- the shape of the t-plot is such that the ratio of the internal specific surface area to the total specific surface area of the fibrous carbon nanostructure is large, and a large number of openings are formed in the carbon nanostructure constituting the fibrous carbon nanostructure. As a result, the fibrous carbon nanostructure hardly aggregates.
- the bending point of the t-plot of the fibrous carbon nanostructure is preferably in a range satisfying 0.2 ⁇ t (nm) ⁇ 1.5, and 0.45 ⁇ t (nm) ⁇ 1.5. More preferably, it is in a range satisfying 0.55 ⁇ t (nm) ⁇ 1.0.
- the fibrous carbon nanostructures are more difficult to aggregate, and an electromagnetic wave absorption layer that can form an electromagnetic wave absorption layer that is more excellent in the absorption characteristics of electromagnetic waves in a high frequency region can be formed.
- a material is obtained.
- the “position of the bending point” is an intersection of the approximate line A in the process (1) described above and the approximate line B in the process (3) described above.
- the fibrous carbon nanostructure preferably has a ratio (S2 / S1) of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot of 0.05 or more and 0.30 or less.
- S2 / S1 is 0.05 or more and 0.30 or less, the fibrous carbon nanostructures are more difficult to aggregate, and an electromagnetic wave that can form an electromagnetic wave absorption layer that is more excellent in the absorption characteristics of electromagnetic waves in a high frequency region. An absorbent material is obtained.
- the total specific surface area S1 and the internal specific surface area S2 of the fibrous carbon nanostructure are not particularly limited, but individually, S1 is preferably 400 m 2 / g or more and 2500 m 2 / g or less, and 800 m 2.
- the total specific surface area S1 and the internal specific surface area S2 of the fibrous carbon nanostructure can be obtained from the t-plot. Specifically, referring to the t-plot shown in FIG. 1, first, the total specific surface area S1 is determined from the slope of the approximate line in the process (1), and the external specific surface area S3 is determined from the slope of the approximate line in the process (3). Can be obtained respectively. Then, the internal specific surface area S2 can be calculated by subtracting the external specific surface area S3 from the total specific surface area S1.
- the measurement of the adsorption isotherm of the fibrous carbon nanostructure, the creation of the t-plot, and the calculation of the total specific surface area S1 and the internal specific surface area S2 based on the analysis of the t-plot are, for example, commercially available measuring devices.
- "BELSORP (registered trademark) -mini” manufactured by Nippon Bell Co., Ltd.).
- the CNT in the fibrous carbon nanostructure is a single-walled carbon nanotube. And / or may include multi-walled carbon nanotubes.
- the CNT contained in the fibrous carbon nanostructure whose t-plot has a convex shape is preferably a single-walled carbon nanotube, more preferably a single-walled carbon nanotube. preferable. If single-walled carbon nanotubes are used as the fibrous carbon nanostructures whose t-plot has an upwardly convex shape, it is possible to improve the thin film properties and the ability to absorb electromagnetic waves in a high frequency range with a good balance.
- the fibrous carbon nanostructure having a t-plot having an upwardly convex shape the ratio (3 ⁇ /) of the value (3 ⁇ ) obtained by multiplying the standard deviation ( ⁇ ) of the diameter by 3 with respect to the average diameter (Av). It is preferable to use a fibrous carbon nanostructure having an Av) of more than 0.20 and less than 0.60, more preferably a fibrous carbon nanostructure having a 3 ⁇ / Av of more than 0.25, and a 3 ⁇ / Av of 3 ⁇ / Av. It is more preferable to use a fibrous carbon nanostructure exceeding 0.40.
- an electromagnetic wave absorbing material capable of forming an electromagnetic wave absorbing layer that is more excellent in electromagnetic wave absorbing ability in a high frequency region can be obtained.
- “Average diameter (Av) of fibrous carbon nanostructure” and “standard deviation of diameter of fibrous carbon nanostructure ( ⁇ : sample standard deviation)” are randomized using a transmission electron microscope, respectively. It can be determined by measuring the diameter (outer diameter) of 100 fibrous carbon nanostructures selected. The average diameter (Av) and standard deviation ( ⁇ ) of the fibrous carbon nanostructure may be adjusted by changing the production method and production conditions of the fibrous carbon nanostructure, or may be obtained by different production methods. You may adjust by combining multiple types of the obtained fibrous carbon nanostructure.
- the diameter measured as described above is plotted on the horizontal axis and the frequency is plotted on the vertical axis, and approximated by Gaussian. In this case, a normal distribution is usually used.
- the fibrous carbon nanostructure As a fibrous carbon nanostructure having an upwardly convex t-plot, the fibrous carbon nanostructure has a peak of Radial Breathing Mode (RBM) when evaluated using Raman spectroscopy. It is preferable to have. Note that there is no RBM in the Raman spectrum of a fibrous carbon nanostructure composed of only three or more multi-walled carbon nanotubes.
- RBM Radial Breathing Mode
- the fibrous carbon nanostructure in which the t-plot has an upwardly convex shape has a ratio of the G band peak intensity to the D band peak intensity in the Raman spectrum (G / D ratio). Is preferably 1 or more and 20 or less.
- G / D ratio is 1 or more and 20 or less, it is possible to form an electromagnetic wave absorbing layer that is excellent in dispersibility of the fibrous carbon nanostructure in the electromagnetic wave absorbing material and that is further excellent in electromagnetic wave absorption characteristics in a high frequency region. An electromagnetic wave absorbing material is obtained.
- the average length of the structure at the time of synthesis is preferably 100 ⁇ m or more.
- the average length of the structure at the time of synthesis is 5000 ⁇ m or less. Is preferred.
- the aspect ratio (length / diameter) of the fibrous carbon nanostructure having an upwardly convex t-plot preferably exceeds 10.
- the BET specific surface area of the fibrous carbon nanostructure having an upwardly convex t-plot is preferably 400 m 2 / g or more, more preferably 600 m 2 / g or more, and 800 m 2. / G or more is more preferable, 2500 m 2 / g or less is preferable, and 1200 m 2 / g or less is more preferable. If the BET specific surface area of the fibrous carbon nanostructure whose t-plot has an upwardly convex shape is 400 m 2 / g or more, the electromagnetic wave absorbing ability in the high frequency region of the electromagnetic wave absorbing material can be sufficiently secured.
- the BET specific surface area of the fibrous carbon nanostructure having a t-plot having an upwardly convex shape is 2500 m 2 / g or less, an electromagnetic wave absorbing material having excellent film formability can be produced.
- the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.
- the fibrous carbon nanostructure having a t-plot having an upwardly convex shape is formed on a base material having a catalyst layer for carbon nanotube growth on the surface according to the super growth method described later.
- the mass density of the fibrous carbon nanostructure as the aggregate is 0.002 g / cm 3 or more and 0.2 g / cm 3 or less. It is preferable that If the mass density is 0.2 g / cm 3 or less, the connection between the fibrous carbon nanostructures becomes weak. Therefore, the fibrous carbon nanostructures are uniformly dispersed, and the electromagnetic wave absorption in the high frequency region of the electromagnetic wave absorbing material Performance can be further enhanced. Further, if the mass density is 0.002 g / cm 3 or more, the integrity of the fibrous carbon nanostructure can be improved, and the handling can be facilitated because it can be prevented from being broken.
- the fibrous carbon nanostructure whose t-plot has an upwardly convex shape has a plurality of micropores.
- the fibrous carbon nanostructure whose t-plot has an upwardly convex shape preferably has micropores whose pore diameter is smaller than 2 nm, and the abundance thereof is the micropore volume determined by the following method. , Preferably 0.40 mL / g or more, more preferably 0.43 mL / g or more, still more preferably 0.45 mL / g or more, and the upper limit is usually about 0.65 mL / g.
- the fibrous carbon nanostructure having a t-plot having an upwardly convex shape has the above-described micropores, so that the fibrous carbon nanostructure is more difficult to aggregate.
- the micropore volume can be adjusted, for example, by appropriately changing the preparation method and preparation conditions of the fibrous carbon nanostructure.
- Vp (V / 22414) ⁇ (M / ⁇ ).
- P is a measurement pressure at the time of adsorption equilibrium
- P0 is a saturated vapor pressure of liquid nitrogen at the time of measurement
- M is an adsorbate (nitrogen) molecular weight of 28.010
- ⁇ is an adsorbate (nitrogen).
- the micropore volume can be determined using, for example, “BELSORP (registered trademark) -mini” (manufactured by Nippon Bell Co., Ltd.).
- a fibrous carbon nanostructure having a t-plot with a convex shape is formed by, for example, supplying a raw material compound and a carrier gas onto a base material having a catalyst layer for producing carbon nanotubes on the surface, and thereby forming a chemical vapor.
- CVD method phase growth method
- oxidizing agent catalyst activation material
- the catalyst layer can be formed efficiently on the surface of the base material by a wet process.
- the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.
- the fibrous carbon nanostructure manufactured by the super growth method may be comprised only from SGCNT, and may be comprised from SGCNT and the non-cylindrical carbon nanostructure which has electroconductivity.
- the fibrous carbon nanostructure has a single-layer or multi-layer flat cylindrical carbon nanostructure (hereinafter referred to as “graphene nanotape”) having a tape-like portion whose inner walls are close to or bonded to each other over the entire length. (GNT) ”) may be included.
- “graphene nanotape” having a tape-like portion whose inner walls are close to or bonded to each other over the entire length. (GNT) ") may be included.
- “having the tape-like portion over the entire length” means “continuous over 60% or more, preferably 80% or more, more preferably 100% of the length in the longitudinal direction (full length)”. Or intermittently has a tape-like portion ”.
- GNT is presumed to be a substance in which a tape-like part in which inner walls are close to each other or bonded is formed over the entire length from the synthesis, and a carbon six-membered ring network is formed in a flat cylindrical shape.
- the And the shape of GNT is a flat cylindrical shape, and the presence of a tape-like part in which the inner walls are close to each other or bonded in GNT is, for example, that GNT and fullerene (C60) are sealed in a quartz tube.
- TEM transmission electron microscope
- the shape of GNT is a shape which has a tape-shaped part in the center part of the width direction, and the shape of the cross section orthogonal to the extending direction (axial direction) is the cross-sectional length in the vicinity of both ends in the cross-sectional longitudinal direction. It is more preferable that the maximum dimension in the direction orthogonal to the direction is larger than the maximum dimension in the direction orthogonal to the longitudinal direction of the cross section in the vicinity of the central portion in the longitudinal direction of the cross section. preferable.
- “near the central portion in the longitudinal direction of the cross section” means the longitudinal width of the cross section from the longitudinal center line of the cross section (a straight line passing through the longitudinal center of the cross section and perpendicular to the longitudinal direction line).
- the “near the end in the longitudinal direction of the cross section” means the area outside the longitudinal direction of “near the center in the longitudinal direction of the cross section”.
- the fibrous carbon nanostructure containing GNT as a non-cylindrical carbon nanostructure has a catalyst layer on the surface when synthesizing CNTs by a super-growth method using a substrate having the catalyst layer on the surface. It can be obtained by forming a substrate (hereinafter sometimes referred to as “catalyst substrate”) by a predetermined method. Specifically, the fibrous carbon nanostructure containing GNT is obtained by applying a coating liquid A containing an aluminum compound onto a substrate, drying the applied coating liquid A, and then forming an aluminum thin film (catalyst) on the substrate.
- the coating liquid B containing the iron compound is applied onto the aluminum thin film, and the applied coating liquid B is dried at a temperature of 50 ° C. or less to form the iron thin film (catalyst layer) on the aluminum thin film.
- the fibrous carbon nanostructure whose t-plot has a convex shape is a metal impurity contained in the fibrous carbon nanostructure from the viewpoint of reducing impurities in the electromagnetic wave absorbing material and producing a long-life product.
- the concentration of is preferably less than 5000 ppm, and more preferably less than 1000 ppm.
- the concentration of metal impurities is, for example, a transmission electron microscope (TEM), a scanning electron microscope (SEM), an energy dispersive X-ray analysis (EDAX), a gas phase decomposition apparatus, and an ICP mass spectrometry (VPD, ICP / MS).
- the metal impurities include metal catalysts used for producing fibrous carbon nanostructures.
- metals belonging to alkali metals, alkaline earth metals, Groups 3 to 13 and lanthanoid groups belong to each other.
- metal elements such as elements, Si, Sb, As, Pb, Sn, and Bi, and metal compounds containing these. More specifically, Al, Sb, As, Ba, Be, Bi, B, Cd, Ca, Cr, Co, Cu, Ga, Ge, Fe, Pb, Li, Mg, Mn, Mo, Ni, K, Examples thereof include metal elements such as Na, Sr, Sn, Ti, W, V, Zn, and Zr, and metal compounds containing these.
- the fibrous carbon nanostructure having a t-plot having an upwardly convex shape is further improved in terms of dispersibility of the fibrous carbon nanostructure in the electromagnetic wave absorbing material and can form a uniform electromagnetic wave absorbing layer. It is preferable that particulate impurities having a diameter of more than 500 nm are substantially not contained, more preferably particulate impurities having a particle diameter of more than 300 nm are substantially not contained, and particulate impurities having a particle diameter of more than 100 nm are contained. More preferably, it is substantially not contained, and it is particularly preferred that substantially no particulate impurities having a particle size of more than 45 nm are contained. In the present specification, the concentration of particulate impurities can be measured by applying a fibrous carbon nanostructure dispersion liquid on a substrate and using the product name “surfscan” manufactured by KLA Tencor Corporation.
- fibrous carbon nanostructures As other fibrous carbon nanostructures other than fibrous carbon nanostructures that can be used as fibrous carbon nanostructures used in electromagnetic wave absorbing materials and whose t-plot obtained from the adsorption isotherm shows a convex shape. Includes a fibrous carbon nanostructure in which the t-plot obtained from the adsorption isotherm does not show an upwardly convex shape. More specifically, fibrous carbon nanostructures in which the t-plot obtained from the adsorption isotherm has a downwardly convex shape can be mentioned. Preferably, the other fibrous carbon nanostructures include multi-walled CNTs.
- the multilayer CNT is not particularly limited, and a CNT having a plurality of layers can be used. Preferably, a multilayer CNT having 3 to 15 layers is more preferable.
- “multilayer” refers to a state in which at least two or more single-layer tubes are nested. If multi-walled CNTs are used, there is an advantage that the productivity of the electromagnetic wave absorbing material is excellent because the dispersibility in a solvent is higher than when single-walled CNTs are used.
- the BET specific surface area of the multilayer CNT is preferably 150 m 2 / g or more, more preferably 200 m 2 / g or more, and preferably 550 m 2 / g or less, and less than 400 m 2 / g. It is more preferable that If the BET specific surface area of multilayer CNT is 150 m ⁇ 2 > / g or more, the electromagnetic wave absorption capability in the high frequency area
- the multi-walled CNT is not particularly limited, and can be produced by, for example, a laser ablation method, an arc heat radiation CVD (Chemical Vapor Deposition) method, a plasma CVD method, a gas phase method, a combustion method, or the like.
- multilayer CNTs manufactured by any method can be used.
- examples of commercially available multilayer CNTs include, for example, “Baytubes C150P” and “Baytubes C70P” manufactured by Bayer Material Science, “Nanocyl 7000” manufactured by Nanocyl, and Kumho Petrochemical. (Kumho Petrochemical) “K-nanos-100P”, Cnano “Flotube 9000”, Jeo (JEIO) “JC142” and the like.
- the average diameter (Av) of the fibrous carbon nanostructure used for the electromagnetic wave absorbing material of the present invention is preferably 0.5 nm or more, more preferably 1 nm or more, and 15 nm or less. Preferably, it is 10 nm or less.
- the average diameter (Av) of the fibrous carbon nanostructure is 0.5 nm or more, the electromagnetic wave absorbing ability in the high frequency region of the electromagnetic wave absorbing material can be further enhanced.
- the average diameter (Av) of the fibrous carbon nanostructure is 15 nm or less, the flexibility of the electromagnetic wave absorbing material can be improved.
- the content C of the fibrous carbon nanostructure when the content of the insulating material is 100 parts by mass is 5 parts by mass or more and 15 parts by mass or less, or the fibrous carbon
- the content C is 0.3 parts by mass or more and 0.8 parts by mass or less. is there. This is because by setting the content of the insulating material within the above range, the electromagnetic wave absorbing ability in the high frequency region can be sufficiently enhanced.
- the content of the fibrous carbon nanostructure is 100% of the content of the insulating material.
- the content of the fibrous carbon nanostructure is 6 masses when the content of the insulating material is 100 parts by mass. Part or more, preferably 7 parts by weight or more, more preferably 13 parts by weight or less, and even more preferably 10 parts by weight or less.
- an insulating polymer is preferably used as the insulating material.
- Such insulating polymer is (A) a thermoplastic resin and / or a thermosetting resin, (B) rubber and / or elastomer, It can be either.
- the insulating material and the insulating polymer preferably have a volume resistivity of 10 11 ⁇ ⁇ cm or more measured according to JIS K 6911.
- the insulating polymer contains either (a) or (b) as a main component.
- “main component” means that 50% by mass or more, preferably more than 50% by mass, and more preferably 100% by mass with respect to 100% by mass of the insulating polymer. .
- the ability of the electromagnetic wave absorbing material to absorb electromagnetic waves in a high frequency region exceeding 20 GHz can be further improved. Furthermore, when the insulating polymer (a) is used, the electromagnetic wave absorbing material can be provided with excellent strength and durability. Moreover, when the said insulating polymer (b) is used as an insulating material, the softness
- thermoplastic resin and the thermosetting resin contained in the insulating polymer are not particularly limited, and known thermoplastic resins and thermosetting resins having insulating properties can be used.
- thermoplastic resins and thermosetting resins include cellulose resins, cellulose acetates, cellulose nitrates, cellulose acetate butyrate, casein plastics, soy protein plastics, phenol resins, urea resins, melamine resins, benzoguanamine resins.
- the rubber and elastomer contained in the insulating polymer are not particularly limited, and rubber and elastomer having known insulating properties can be used.
- rubbers and elastomers include natural rubber (NR), epoxidized natural rubber (ENR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), ethylene propylene rubber (EPR, EPDM), butyl rubber (IIR), chlorobutyl rubber (CIIR), acrylic rubber (ACM), silicone rubber (Q), fluorine rubber (FKM), butadiene rubber (BR), epoxidized butadiene rubber (EBR), epichlorohydrin rubber (CO) , CEO), urethane rubber (U), polysulfide rubber (T), acrylonitrile butadiene rubber, ethylene vinyl acetate rubber, vinyl pyridine rubber, polyisoprene rubber, and other rubbers and elastomers.
- the insulating filler is not particularly limited, and a known inorganic filler or organic filler, and an insulating filler can be used. Examples of such an insulating filler include silica, talc, clay, titanium oxide and the like. These may be used alone or in combination of two or more.
- the electromagnetic wave absorbing material according to the present invention may contain a known additive depending on the application.
- Known additives include, for example, antioxidants, heat stabilizers, light stabilizers, UV absorbers, crosslinking agents, pigments, colorants, foaming agents, antistatic agents, flame retardants, lubricants, softeners, and tackifiers.
- Agents, plasticizers, mold release agents, deodorants, fragrances and the like can be used individually by 1 type or in combination of multiple types.
- the electromagnetic wave absorbing material absorbs electromagnetic waves in a frequency region exceeding 20 GHz.
- the electromagnetic wave absorbing material preferably has a reflection attenuation amount of an electromagnetic wave having a frequency of 60 GHz of 7 dB or more, and more preferably 10 dB or more.
- the electromagnetic wave absorbing material preferably has a reflection attenuation amount of electromagnetic waves having a frequency of 76 GHz of 6 dB or more, more preferably 9 dB or more, and further preferably 10 dB or more.
- the electromagnetic wave absorbing material always has a reflection attenuation amount in a frequency range of more than 60 GHz and less than 76 GHz, which is always larger than the smaller one of the reflection attenuation amounts at the frequencies of 60 GHz and 76 GHz. This is because if the return loss in the high frequency regions such as the frequencies of 60 GHz and 76 GHz is within the above range, the electromagnetic wave shielding performance in the high frequency region is remarkably excellent.
- “reflection loss” can be measured by the method described in Examples.
- the electromagnetic wave absorbing material of the present invention is rich in flexibility when (b) rubber and / or elastomer which is an insulating polymer is used as the insulating material.
- the tensile fracture strain value (%) measured by a tensile test based on JIS K 6251 is preferably 100% or more, more preferably 150% or more, and more preferably 200% or more. Further preferred.
- “value of tensile breaking strain (%)” is the length of the original specimen when the specimen is broken (cut) in a tensile test based on JIS K 6251. It is a value expressed by dividing by 100 percent. If the value of tensile breaking strain is equal to or greater than the above lower limit value, the electromagnetic wave absorbing material has sufficient flexibility, and can exhibit sufficient durability when formed into a thin film, for example.
- the electromagnetic wave absorber of the present invention includes at least one electromagnetic wave absorbing layer including a fibrous carbon nanostructure and an insulating material. Furthermore, the electromagnetic wave absorber of the present invention includes at least one electromagnetic wave absorbing layer formed using the electromagnetic wave absorbing material of the present invention. An electromagnetic wave absorber provided with an electromagnetic wave absorbing layer formed using the electromagnetic wave absorbing material of the present invention is excellent in electromagnetic wave absorbing ability in a high frequency region.
- the term “electromagnetic wave absorber” refers to a structure including an electromagnetic wave absorbing layer obtained by molding a material containing an insulating resin and a fibrous carbon nanostructure into a layer (film) shape.
- electromagnetic wave absorbing material is an electromagnetic wave absorbing material in a state existing as a material before being formed as an electromagnetic wave absorbing layer, or in a broad sense, a shape / It is also used as a term including a molded body formed into a structure.
- the electromagnetic wave absorber according to the present invention may be a single layer type electromagnetic wave absorber having a single electromagnetic wave absorption layer, or may be a multilayer type electromagnetic wave absorber having a plurality of electromagnetic wave absorption layers.
- the electromagnetic wave absorber according to the present invention when the electromagnetic wave absorber according to the present invention is a multilayer electromagnetic wave absorber, the electromagnetic wave absorber according to the present invention includes a plurality of electromagnetic wave absorption layers including fibrous carbon nanostructures and an insulating material. And the fibrous carbon nanostructure and / or insulating material contained in each layer may be the same or different types.
- the plurality of electromagnetic wave absorbing layers are defined as a first electromagnetic wave absorbing layer, a second electromagnetic wave absorbing layer,..., An nth electromagnetic wave absorbing layer from the side far from the electromagnetic wave incident side, and insulation in each layer of the plurality of electromagnetic wave absorbing layers.
- the content of the fibrous carbon nanostructure is 100 parts by mass when the material content is A1 parts by mass, A2 parts by mass,. ) Or (1-2) and (2) or (3), and among all the layers constituting the electromagnetic wave absorber, the content of the fibrous carbon nanostructure in the first electromagnetic wave absorption layer is Most often.
- n 2 to 5 is preferable.
- the fibrous carbon nanostructure that increases from the side closer to the electromagnetic wave incident side toward the far side (from the electromagnetic wave incident side toward the inner side in the traveling direction of the electromagnetic wave)
- the fibrous carbon nanostructure that increases from the side closer to the electromagnetic wave incident side toward the far side (from the electromagnetic wave incident side toward the inner side in the traveling direction of the electromagnetic wave)
- the content A1 in the first layer varies depending on the type of fibrous carbon nanostructure included in the first electromagnetic wave absorbing layer.
- the fibrous carbon nanostructure is a fibrous carbon nanostructure having a t-plot having an upwardly convex shape
- the content of the fibrous carbon nanostructure depends on the insulating material in the first electromagnetic wave absorbing layer.
- the content is 100 parts by mass, it is preferably 0.4 parts by mass or more, preferably 0.8 parts by mass or less, and more preferably 0.6 parts by mass or less.
- the fibrous carbon nanostructure is a multilayer CNT
- the content of the fibrous carbon nanostructure is 5 parts by mass or more when the content of the insulating material in the first electromagnetic wave absorbing layer is 100 parts by mass. It is preferably 6 parts by mass or more, more preferably 8 parts by mass or more, preferably 13 parts by mass or less, and more preferably 10 parts by mass or less.
- the contents A2 to An in the second layer to the nth layer are not necessarily equal to or higher than the same lower limit value as that of the first electromagnetic wave absorbing layer, and may be an amount less than the lower limit value.
- the content A2 to An is 0.05 or more. Is preferably 0.1 or more, more preferably 0.2 or more, and preferably 0.6 or less.
- the content A2 to An is preferably 0.1 or more, more preferably 0.5 or more, and 1.0 or more. More preferably, it is preferably 3.0 or less.
- the contents A1 to An of the adjacent electromagnetic wave absorption layers are the ratios (A i , A i + 1 ) of the contents of the fibrous carbon nanostructures in two adjacent electromagnetic wave absorption layers, respectively ( A i + 1 / A i ) is preferably as follows:
- the ratio (A i + 1 / A i ) is 1/10 or more and 4/5 or less. Is preferable, and it is more preferably 1/5 or more and 1/2 or less.
- the ratio (A i + 1 / A i ) is preferably 1/7 or more and 1/2 or less.
- the electromagnetic wave absorbing layers are preferably adjacent to each other. This is because the electromagnetic wave absorbing ability in the high frequency region can be further improved.
- the fibrous carbon nanostructures contained in the plurality of electromagnetic wave absorbing layers are preferably the same. This is because the production efficiency of the electromagnetic wave absorber can be increased by adopting such a configuration.
- the insulating materials contained in the plurality of electromagnetic wave absorbing layers may be the same or different, but are preferably the same. This is because, with such a configuration, the electromagnetic wave absorbing ability of the electromagnetic wave absorber can be further improved and the durability can be enhanced.
- the electromagnetic wave absorber of the present invention preferably includes an insulating layer on the outermost surface on the electromagnetic wave incident side.
- the insulating layer may be an insulating layer whose volume resistivity measured according to JIS K 6911 is 10 11 ⁇ ⁇ cm or more.
- the insulating layer includes an insulating material, and the insulating material is not particularly limited, and an insulating material that can be blended with the electromagnetic wave absorbing material can be used.
- the insulating material contained in the electromagnetic wave absorbing layer and the insulating material contained in the insulating layer may be the same or different.
- the insulating layer may contain known additives as described above for the electromagnetic wave absorbing material, if necessary.
- the insulating layer examples include a polyethylene terephthalate film and a polyimide film.
- Such an electromagnetic wave absorber is further excellent in the ability to absorb an electromagnetic wave in a high frequency range of more than 20 GHz, and is excellent in durability when the electromagnetic wave absorber is thin.
- the versatility of an electromagnetic wave absorber can also be improved by arrange
- the thickness of the electromagnetic wave absorption layer of the single layer type electromagnetic wave absorber is preferably 500 ⁇ m or less, more preferably 100 ⁇ m or less, and 80 ⁇ m. Is particularly preferably 40 ⁇ m or less, more preferably 1 ⁇ m or more, and even more preferably 10 ⁇ m or more. If the thickness of the film-shaped electromagnetic wave absorber is 500 ⁇ m or less, the electromagnetic wave absorbing ability in the high frequency region can be further sufficiently enhanced. Since it can be used for applications, it is highly versatile. In addition, the thickness of the film-like electromagnetic wave absorbing material can be arbitrarily controlled in a molding step or the like in a manufacturing method described later. Further, the thickness of the film-like electromagnetic wave absorbing material can be measured by the method described in Examples described later.
- the total thickness of the electromagnetic wave absorber of the present invention is preferably 500 ⁇ m or less, more preferably 200 ⁇ m or less, and 120 ⁇ m or less. Is more preferable. Further, the total thickness of the electromagnetic wave absorber of the present invention may be 100 ⁇ m or less. Furthermore, the total thickness of the electromagnetic wave absorber of the present invention is preferably 1 ⁇ m or more, and more preferably 10 ⁇ m or more.
- the total thickness of the plurality of electromagnetic wave absorption layers is preferably within the same numerical range as in the case of the single layer type. .
- the electromagnetic wave absorbing material and the electromagnetic wave absorber of the present invention include a step of dispersing a fibrous carbon nanostructure and an insulating material in a solvent to obtain a slurry composition for an electromagnetic wave absorbing material (a slurry composition preparing step for an electromagnetic wave absorbing material), And it can manufacture through the process (molding process) of obtaining an electromagnetic wave absorption material or an electromagnetic wave absorber from the obtained slurry composition for electromagnetic wave absorption materials.
- slurry composition preparation process for electromagnetic wave absorbing material In the electromagnetic wave absorbing material slurry composition preparation step (hereinafter, also simply referred to as “slurry composition preparation step”), the fibrous carbon nanostructure and the insulating material as described above are dispersed in a solvent, whereby the electromagnetic wave absorption material is obtained.
- a slurry composition (hereinafter also simply referred to as “slurry composition”) is prepared.
- the solvent is not particularly limited, for example, water; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol Alcohols such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, dioxane and tetrahydrofuran; N, N-dimethylformamide and N-methyl Amide polar organic solvents such as pyrrolidone; aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, paradichlorobenzene; and the like can be used. These may be used alone or in
- the additive arbitrarily added to the slurry composition is not particularly limited, and examples thereof include additives generally used for preparing a dispersion such as a dispersant.
- the dispersant used in the slurry composition preparation step is not particularly limited as long as it can disperse the fibrous carbon nanostructure and can be dissolved in the solvent described above. it can.
- examples of the surfactant include sodium dodecylsulfonate, sodium deoxycholate, sodium cholate, sodium dodecylbenzenesulfonate, and the like. These dispersants can be used alone or in combination of two or more.
- the dispersion method in the slurry composition preparation step is not particularly limited, but is a nanomizer, an optimizer, an ultrasonic disperser, a ball mill, a sand grinder, a dyno mill, a spike mill, a DCP mill, a basket mill, a paint conditioner, A general dispersion method using a high-speed stirring device, a high-pressure homogenizer, or the like can be employed.
- a slurry composition preparation process it is preferable to implement the process (fibrous carbon nanostructure dispersion liquid preparation process) of preparing a fibrous carbon nanostructure dispersion liquid beforehand before mixing with an insulating material in a slurry composition preparation process. Furthermore, in the preparation step of the fibrous carbon nanostructure dispersion liquid, the preliminary dispersion liquid obtained by adding the fibrous carbon nanostructure to the solvent and dispersing by a general dispersion method is described in detail below. It is preferable to prepare a dispersion of a fibrous carbon nanostructure by subjecting it to a dispersion treatment for obtaining a cavitation effect or a dispersion treatment for obtaining a crushing effect.
- the dispersion treatment that provides a cavitation effect is a dispersion method that uses a shock wave that is generated when a vacuum bubble generated in water bursts when high energy is applied to a liquid.
- the fibrous carbon nanostructure can be favorably dispersed.
- the dispersion treatment for obtaining a cavitation effect at a temperature of 50 ° C. or less from the viewpoint of suppressing a change in concentration due to volatilization of the solvent.
- Specific examples of the dispersion treatment that provides a cavitation effect include dispersion treatment using ultrasonic waves, dispersion treatment using a jet mill, and dispersion treatment using high shear stirring. Only one of these distributed processes may be performed, or a plurality of distributed processes may be combined. More specifically, for example, an ultrasonic homogenizer, a jet mill, and a high shear stirring device are preferably used. These devices may be conventionally known devices.
- the coarse dispersion may be irradiated with ultrasonic waves using an ultrasonic homogenizer.
- the irradiation time may be appropriately set depending on the amount of fibrous carbon nanostructures. Moreover, what is necessary is just to set the frequency
- the number of treatments is preferably 2 or more, more preferably 5 or more, preferably 100 or less, and more preferably 50 or less.
- the pressure is preferably 20 MPa to 250 MPa, and the temperature is preferably 15 ° C. to 50 ° C.
- a jet mill When a jet mill is used, it is preferable to add a surfactant as a dispersant to the solvent. This is because the jet mill apparatus can be operated stably while suppressing the viscosity of the treatment liquid.
- a high-pressure wet jet mill is suitable as the jet mill dispersion device.
- “Nanomaker (registered trademark)” manufactured by Advanced Nano Technology
- “Nanomizer” manufactured by Nanomizer
- Nanonovaita Manufactured by Yoshida Kikai Kogyo Co., Ltd.
- “Nanojet Pal (registered trademark)” manufactured by Jokosha
- stirring and shearing may be applied to the coarse dispersion with a high shear stirring device.
- the operation time time during which the machine is rotating
- the peripheral speed is preferably 20 m / s or more and 50 m / s or less
- the temperature is preferably 15 ° C. or more and 50 ° C. or less.
- blend polysaccharide as a dispersing agent. Since an aqueous solution of polysaccharide has a high viscosity and is easily subjected to shear stress, dispersion is further promoted.
- Examples of the high shear stirrer include a stirrer represented by “Ebara Milder” (manufactured by Ebara Seisakusho), “Cabitron” (manufactured by Eurotech), “DRS2000” (manufactured by IKA), etc .; (Trademark) CLM-0.8S “(made by M Technique Co., Ltd.), a stirrer represented by" TK Homomixer "(made by Tokushu Kika Kogyo Co., Ltd.); Examples thereof include a stirrer represented by Tokushu Kika Kogyo Co., Ltd.).
- the dispersion treatment for obtaining the above-described cavitation effect it is more preferable to perform the dispersion treatment for obtaining the above-described cavitation effect at a temperature of 50 ° C. or lower. This is because a change in concentration due to the volatilization of the solvent is suppressed.
- Dispersion treatment that provides a crushing effect can uniformly disperse fibrous carbon nanostructures, as well as fibrous carbon nanostructures caused by shock waves when bubbles disappear, compared to the dispersion treatment that provides the cavitation effect described above. This is advantageous in that it can suppress damage.
- a shearing force is applied to the coarse dispersion to pulverize and disperse the fibrous carbon nanostructures, and the coarse dispersion is loaded with a back pressure.
- the back pressure applied to the coarse dispersion may be reduced to atmospheric pressure all at once, but is preferably reduced in multiple stages.
- a dispersion system having a disperser having the following structure may be used.
- the disperser has a disperser orifice having an inner diameter d1, a dispersion space having an inner diameter d2, and a terminal portion having an inner diameter d3 from the inflow side to the outflow side of the coarse dispersion liquid (where d2>d3> d1)).
- the inflowing high-pressure for example, 10 to 400 MPa, preferably 50 to 250 MPa
- coarse dispersion passes through the disperser orifice, and becomes a high flow rate fluid with decreasing pressure.
- the high-velocity coarse dispersion liquid flowing into the dispersion space flows at high speed in the dispersion space and receives a shearing force at that time.
- the flow rate of the coarse dispersion decreases, and the fibrous carbon nanostructure is well dispersed.
- a fluid having a pressure (back pressure) lower than the pressure of the inflowing coarse dispersion liquid flows out from the terminal portion as the dispersion liquid of the fibrous carbon nanostructure.
- the back pressure of the coarse dispersion can be applied to the coarse dispersion by applying a load to the flow of the coarse dispersion.
- a rough pressure can be obtained by disposing a multistage step-down device downstream of the disperser.
- a desired back pressure can be applied to the dispersion. Then, by reducing the back pressure of the coarse dispersion in multiple stages using a multistage pressure reducer, bubbles are generated in the dispersion when the dispersion of the fibrous carbon nanostructure is finally released to atmospheric pressure. Can be suppressed.
- the disperser may include a heat exchanger for cooling the coarse dispersion and a cooling liquid supply mechanism. This is because the generation of bubbles in the coarse dispersion can be further suppressed by cooling the coarse dispersion that has been heated to a high temperature by applying a shearing force with the disperser. In addition, it can suppress that a bubble generate
- the occurrence of cavitation can be suppressed, so damage to the fibrous carbon nanostructure caused by cavitation that is sometimes a concern, especially when the bubbles disappear. Damage to the fibrous carbon nanostructure due to the shock wave can be suppressed.
- a dispersion treatment apparatus having a thin tube flow path is used, and the coarse dispersion liquid is pumped to the thin tube flow path to apply shear force to the coarse dispersion liquid.
- Dispersion treatment in which the fibrous carbon nanostructure is dispersed is preferable. If the fibrous carbon nanostructure is dispersed by pumping the coarse dispersion liquid into the capillary channel and applying shear force to the coarse dispersion liquid, the occurrence of damage to the fibrous carbon nanostructure is suppressed and the fibrous carbon nanostructure is suppressed.
- the carbon nanostructure can be well dispersed.
- distribution process from which a crushing effect is acquired can be implemented by controlling a dispersion
- the known additive according to the use of the electromagnetic wave absorbing material as described above can be optionally blended with the slurry composition obtained as described above.
- the mixing time is preferably 10 minutes to 24 hours.
- the insulating material dispersion is prepared in advance by adding the above-described insulating material to the above-described solvent and performing a dispersion treatment prior to mixing with the fibrous carbon nanostructure. It is preferable.
- the distributed processing method a general distributed method as described above can be adopted.
- a latex of a resin may be used instead of the dispersion obtained by adding an insulating material to a solvent.
- the resin latex include (1) a method of obtaining a latex by emulsifying a solution of a resin dissolved in an organic solvent in water optionally in the presence of a surfactant, and removing the organic solvent as necessary (2 )
- the monomer constituting the resin can be obtained by emulsion polymerization or suspension polymerization to directly obtain a latex.
- an insulating filler can be mix
- the resin may be uncrosslinked or crosslinked.
- the organic solvent used for the preparation of the latex is not particularly limited as long as it can be mixed with the fibrous carbon nanostructure dispersion liquid obtained as described above. Can be used.
- the solid content concentration of the latex is not particularly limited, but is preferably 20% by mass or more, more preferably 60% by mass or more, and more preferably 80% by mass or less from the viewpoint of uniform dispersibility of the latex.
- the molding method in the molding step can be appropriately selected according to the use, the type of insulating material used, and the like.
- examples of the forming method include a film forming method by coating and the like, and a forming method into a desired shape.
- the electromagnetic wave absorbing material and the electromagnetic wave absorber obtained as described below contain fibrous carbon nanostructures in a state of being dispersed substantially uniformly in a matrix made of an insulating material.
- the electromagnetic wave absorbing material and the electromagnetic wave absorber may optionally be subjected to a crosslinking treatment.
- a film-like (layer-like) electromagnetic wave absorbing material can be formed (formed) from the slurry composition described above by any known film-forming method.
- An electromagnetic wave absorbing layer can be formed by forming an electromagnetic wave absorbing material into a layer.
- the electromagnetic wave absorbing layer can also be obtained by depositing a material containing a fibrous carbon nanostructure and an insulating resin. Specifically, for example, by applying the slurry composition onto a known film-forming substrate that can form the above-described insulating layer, such as a polyethylene terephthalate (PET) film or a polyimide film, and then drying the composition. The solvent is removed from the slurry composition.
- PET polyethylene terephthalate
- the application is not particularly limited, and can be performed by a known method such as a brush coating method or a casting method. Moreover, drying can be performed by a known method, for example, it can perform by vacuum-drying or leaving still in a draft.
- a single-layer electromagnetic wave absorber can be manufactured through such a film forming method.
- the multilayer electromagnetic wave absorber mentioned above can be manufactured as follows.
- a plurality of types of slurry compositions prepared at a desired blending amount for forming a multilayer are applied by a known method onto a known film-forming substrate.
- a multilayer electromagnetic wave absorber can be formed. More specifically, for example, on a PET film constituting an insulating layer, first, one slurry composition is applied and dried to form one electromagnetic wave absorbing layer, and then another slurry is formed on the electromagnetic wave absorbing layer.
- the composition can be applied and dried to form another electromagnetic wave absorption layer, and a multilayer electromagnetic wave absorber comprising two electromagnetic wave absorption layers and an insulating layer as the outermost layer can be produced.
- the application and drying method is not particularly limited, and a general method as described above can be adopted.
- an electromagnetic wave absorbing material that has been solidified through a known coagulation method or drying method can be formed into a desired shape.
- the slurry composition can be coagulated by a method of adding an electromagnetic wave absorbing material to a water-soluble organic solvent, a method of adding an acid to the electromagnetic wave absorbing material, a method of adding a salt to the electromagnetic wave absorbing material, or the like.
- the water-soluble organic solvent it is preferable to select a solvent that does not dissolve the insulating material in the slurry composition and dissolves the dispersant. Examples of such an organic solvent include methanol, ethanol, 2-propanol, ethylene glycol, and the like.
- Examples of the acid include acids generally used for latex coagulation, such as acetic acid, formic acid, phosphoric acid, and hydrochloric acid.
- examples of the salt include known salts generally used for latex coagulation, such as sodium chloride, aluminum sulfate, and potassium chloride.
- the electromagnetic wave absorbing material obtained by solidification and drying can be molded by a molding machine according to a desired molded product shape, for example, a punch molding machine, an extruder, an injection molding machine, a compressor, a roll machine, or the like. .
- the BET specific surface area of the fibrous carbon nanostructures used in Examples and Comparative Examples was measured as follows. After fully drying a dedicated cell for a fully automatic specific surface area measuring device ("Macsorb (registered trademark) HM model-1210" manufactured by Mountec Co., Ltd.) by heat treatment at 110 ° C for 5 hours or more, fibrous carbon nanostructure 20mg was weighed and placed in a cell. Thereafter, the cell was provided at a predetermined position of the measuring apparatus, and the BET specific surface area was measured by automatic operation.
- Macsorb registered trademark
- HM model-1210 manufactured by Mountec Co., Ltd.
- the measurement principle of this apparatus follows the method of measuring the specific surface area by measuring the adsorption / desorption isotherm of liquid nitrogen at 77 K and measuring the specific surface area from this adsorption / desorption isotherm curve by the BET (Brunauer-Emmett-Teller) method.
- ⁇ T-plot> The t-plots of the fibrous carbon nanostructures used in Examples and Comparative Examples were measured as follows. A t-plot was prepared by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm obtained by measuring the BET specific surface area. The t-plot measurement principle follows the t-plot method by de Boer et al.
- thermoplastic resin and / or thermosetting resin as insulating material and electromagnetic wave absorbing material using them>
- the tensile rupture strength and the tensile rupture strain of the strip sample pieces for the insulating material tensile test and the strip sample pieces for the electromagnetic wave absorbing material tensile test prepared in Examples and Comparative Examples were measured as follows.
- Rate of change (%) ⁇ (value of strip sample piece for electromagnetic wave absorbing material tensile test / value of strip sample piece for tensile test of insulating material) ⁇ 100 ⁇ ⁇ 100 And durability was evaluated according to the following evaluation criteria.
- the obtained test specimen was subjected to a tensile test according to JIS K 6251 using a tensile tester (manufactured by Shimadzu Corporation, “Autograph AGS-X”) at a tensile speed of 500 ⁇ 50 mm / min.
- the tensile fracture strain value (%) which is a value expressed by 100 minutes by dividing the length of the specimen when the specimen is broken (cut) by the length of the original specimen, is expressed in accordance with the following criteria. evaluated. The greater the tensile breaking strain value, the greater the flexibility.
- Example 2-1 to Comparative Example 2-4 A: The value of tensile breaking strain is 150% or more B: The value of tensile breaking strain is less than 150% (Example 3-1 to Comparative Example 3-4) A: The value of tensile breaking strain is 200% or more B: The value of tensile breaking strain is 100% or more and less than 200% C: The value of tensile breaking strain is less than 100%
- ⁇ Thickness of electromagnetic wave absorbing layer> Using a micrometer (manufactured by Mitutoyo Co., Ltd., 293 series, “MDH-25”), the thickness of 10 points was measured for the electromagnetic wave absorbers produced in Examples and Comparative Examples. The thickness of the electromagnetic wave absorbing layer was determined by subtracting the thickness of 38 ⁇ m of the PET film (constituting the insulating layer) used as the material.
- the electromagnetic wave absorption performance of the electromagnetic wave absorber was evaluated by measuring the return loss (dB) of the electromagnetic wave.
- the electromagnetic wave absorbers manufactured in Examples and Comparative Examples as test specimens, they were attached so that the electromagnetic wave absorber layer side having a higher fibrous carbon nanostructure concentration would face the conductive metal plate. That is, when the conductive metal plate was attached to the measurement system, the electromagnetic wave absorber was installed so that the electromagnetic wave was incident on the insulating layer side of the electromagnetic wave absorber.
- the S (Scattering) parameter (S11) at one port was measured by the free space method.
- the electromagnetic wave shielding performance of the electromagnetic wave absorber was evaluated by measuring the transmission attenuation amount (dB) of the electromagnetic wave.
- the transmission attenuation amount of the electromagnetic wave absorber manufactured in Examples and Comparative Examples is the same as the above-described measurement of the return loss except that the electromagnetic wave absorber is not attached to the conductive metal plate and is installed in the measurement system by the free space method.
- the S21 parameter was measured, and the transmission attenuation (dB) was calculated according to the following equation (2). The larger the transmission attenuation, the better the electromagnetic shielding performance.
- the electromagnetic wave shielding performance is a shielding performance by reflecting and absorbing electromagnetic waves, and is different from the electromagnetic wave absorbing performance representing the property of removing the electromagnetic waves by absorbing the electromagnetic waves and converting them into thermal energy.
- Transmission attenuation (dB) 20 log
- Example 1-1 Carbon nanotubes (SGCNT) obtained by the super-growth method described in Japanese Patent No. 4,621,896 were used as fibrous carbon nanostructures having a t-plot having a convex shape. Specifically, SGCNT was synthesized under the following conditions.
- Carbon compound ethylene; supply rate 50 sccm Atmosphere (gas) (Pa): Helium, hydrogen mixed gas; supply rate 1000 sccm Pressure 1 atmospheric pressure water vapor addition amount (ppm): 300 ppm Reaction temperature (° C): 750 ° C Reaction time (min): 10 minutes Metal catalyst (abundance): Iron thin film; thickness 1 nm Substrate: Silicon wafer
- the obtained SGCNT had a BET specific surface area of 880 m 2 / g, and the t-plot had an upwardly convex shape.
- a radial breathing mode (RBM) spectrum was observed in a low wavenumber region of 100 to 300 cm ⁇ 1 characteristic of single-walled carbon nanotubes.
- SGCNT was added to the chloroform solvent so that the concentration was 0.2%, and the mixture was stirred with a magnetic stirrer for 24 hours to perform preliminary dispersion of SGCNT.
- a multi-stage pressure-reducing high-pressure homogenizer Mr.
- PC polycarbonate
- an insulating polymer dispersion Using an insulating polymer dispersion, coating and drying were repeated on a polyimide film to produce a strip sample piece for an insulating polymer tensile test, and a tensile test was performed. Next, as a solid content ratio, the fibrous carbon nanostructure dispersion liquid and the insulating polymer dispersion liquid are mixed so that SGCNT is 0.3 parts with respect to 100 parts of PC which is an insulating material, and an electromagnetic wave absorbing material is obtained. A slurry composition was prepared. On the polyimide film, application and drying of the slurry composition were repeated to produce strip sample pieces for the electromagnetic wave absorbing material tensile test, and the tensile test was performed. Next, an electromagnetic wave absorber was produced.
- the organic solvent is sufficiently volatilized by natural drying at 25 ° C. for 1 week or more in a thermostatic environment equipped with a local exhaust device. Then, a thin film layer of an electromagnetic wave absorbing material was formed on the polyimide film, and an electromagnetic wave absorber including a polyimide film as an insulating layer (surface layer) and SGCNT and PC as an electromagnetic wave absorbing layer was produced. Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Further, when the transmission attenuation amount of the electromagnetic wave absorber was measured by the above-described method, it was 5 dB at 60 GHz and 5 dB at 76 GHz.
- Example 1-2 SGCNT synthesized in Example 1-1 was used, SGCNT was added to a cyclohexane solvent so that the concentration became 0.2%, and the mixture was stirred with a magnetic stirrer for 24 hours to perform preliminary dispersion of SGCNT. Next, a multi-stage pressure-reducing high-pressure homogenizer (Mr.
- a polycycloolefin resin (manufactured by Nippon Zeon Co., Ltd., “ZEONOR 1020R”) was added to a cyclohexane solvent so as to have a concentration of 2%, and sufficiently stirred to prepare an insulating polymer dispersion. Using an insulating polymer dispersion, coating and drying were repeated on a polyimide film to produce a strip sample piece for an insulating polymer tensile test, and a tensile test was performed.
- PCO polycycloolefin resin
- a fibrous carbon nanostructure dispersion liquid and an insulating polymer dispersion liquid are mixed so that SGCNT is 0.5 part with respect to 100 parts of PCO, and a slurry composition as an electromagnetic wave absorbing material was made.
- a slurry composition as an electromagnetic wave absorbing material was made.
- application and drying of the slurry composition were repeated to produce strip sample pieces for the electromagnetic wave absorbing material tensile test, and the tensile test was performed.
- an electromagnetic wave absorber was produced. After applying the slurry composition to a support film (polyimide film with a thickness of 25 ⁇ m) as an insulating layer, the organic solvent is sufficiently volatilized by natural drying at 25 ° C.
- Example 1-3 A metal mold for a molded product having a thickness of 200 ⁇ m, a width of 100 mm, and a length of 200 mm is provided on a polyimide film, and epoxy curing is performed on 100 parts of an epoxy resin (manufactured by Mitsubishi Chemical, “jER828”). Filled with an epoxy mixture containing 33 parts of an agent (Mitsubishi Chemical, “jER Cure LV11”), left to stand at 25 ° C. for 24 hours, and then thermally cured at 80 ° C. for 24 hours, thickness 200 ⁇ m, width 100 mm An epoxy resin sheet having a length of 200 mm was formed.
- an epoxy resin manufactured by Mitsubishi Chemical, “jER828”. Filled with an epoxy mixture containing 33 parts of an agent (Mitsubishi Chemical, “jER Cure LV11”), left to stand at 25 ° C. for 24 hours, and then thermally cured at 80 ° C. for 24 hours, thickness 200 ⁇ m, width 100 mm
- the sheet was cut into a strip shape having a width of 10 mm and a length of 200 mm, a strip sample piece for an insulating polymer tensile test was prepared, and a tensile test was performed.
- SGCNT synthesized in Example 1-1 0.8 part of SGCNT was added to 100 parts of the liquid epoxy resin, and a thin film swirl type dispersion apparatus ("Primix 50-50" manufactured by Primix Co., Ltd.) was added. )), And a dispersion mixing treatment at 20 ° C. and a shear rate of 50 m / s for 5 minutes was performed to prepare a CNT-dispersed epoxy resin solution.
- a metal mold for a molded product having a thickness of 200 ⁇ m, a width of 100 mm, and a length of 200 mm is provided on a polyimide film, and the slurry composition is filled in the mold and left to stand at 25 ° C. for 24 hours. Heat cured at 24 ° C.
- a thin film layer of an electromagnetic wave absorbing material was formed, and an electromagnetic wave absorber including a polyimide film as an insulating layer (surface layer) and SGCNT and an epoxy resin as an electromagnetic wave absorbing layer was produced.
- Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber.
- the transmission attenuation amount was measured by the above-mentioned method about the electromagnetic wave absorber, it was 10 dB at 60 GHz and 9 dB at 76 GHz.
- Example 1-4 A metal mold for a molded product having a thickness of 200 ⁇ m, a width of 100 mm, and a length of 200 mm is provided on a polyimide film, and PTFE resin (manufactured by Daikin Industries, Ltd., “Polyflon PTFE-M12”) is filled in the mold. Then, after pre-compression molding at 25 ° C. and 70 MPa in a compression molding machine, the polyimide film was removed and baked in an electric furnace in a nitrogen atmosphere at 360 ° C. for 30 minutes, thickness 200 ⁇ m, width 100 mm, length A 200 mm PTFE resin sheet was formed.
- PTFE resin manufactured by Daikin Industries, Ltd., “Polyflon PTFE-M12
- the sheet was cut into a strip shape having a width of 10 mm and a length of 200 mm, a strip sample piece for an insulating polymer tensile test was prepared, and a tensile test was performed.
- SGCNT synthesized in Example 1-1 was used, SGCNT was added to a cyclohexane solvent so that the concentration became 0.2%, and the mixture was stirred with a magnetic stirrer for 24 hours to perform preliminary dispersion of SGCNT.
- a high-pressure dispersion processing unit having a 200 ⁇ m diameter narrow tube flow path unit and filled into a multi-stage pressure-reducing high-pressure homogenizer (“BERYU SYSTEM PRO” manufactured by Mie Co., Ltd.) having a multi-stage pressure control device (multi-stage pressure reducer).
- BERYU SYSTEM PRO manufactured by Mie Co., Ltd.
- multi-stage pressure control device multi-stage pressure reducer
- the fibrous material is used so that SGCNT is 0.5 part with respect to 100 parts of PTFE resin.
- the carbon nanostructure dispersion liquid and the PTFE resin suspension were mixed, filled in a thin film swirl type dispersion apparatus, and subjected to a dispersion mixing process at 20 ° C. and a shear rate of 50 m / s for 5 minutes. Then, the obtained solution was filled in a conical dryer, and the solvent was sufficiently evaporated while rotating and stirring at a temperature of 80 ° C.
- an electromagnetic wave absorbing material mixed solid powder of SGCNT and PTFE resin.
- a metal mold for a molded product having a thickness of 200 ⁇ m, a width of 100 mm, and a length of 200 mm is provided on a polyimide film, and an electromagnetic wave absorbing material is filled in the mold, and at 25 ° C. and 70 MPa in a compression molding machine. After pre-compression molding, the polyimide film is removed, and fired at 360 ° C. for 30 minutes in an electric furnace in a nitrogen atmosphere to form a sheet having a thickness of 200 ⁇ m, a width of 100 mm, and a length of 200 mm.
- a strip of 10 mm and a length of 200 mm was cut out to produce a strip sample piece for an electromagnetic wave absorbing material tensile test, and a tensile test was performed.
- an electromagnetic wave absorber was produced.
- An electromagnetic wave absorbing material is placed on a support film (a polyimide film having a thickness of 25 ⁇ m), preliminarily compression molded at 25 ° C. and 70 MPa by a compression molding machine, the polyimide film is removed, and 360 ° C. in an electric furnace in a nitrogen atmosphere. And baked in 30 minutes to produce an electromagnetic wave absorber.
- Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Further, the transmission attenuation of the obtained electromagnetic wave absorber was 8 dB at 60 GHz and 7 dB at 76 GHz.
- Example 1-5 In the same manner as in Example 1-1, the fibrous carbon nanostructure dispersion liquid and the insulating polymer dispersion liquid were mixed so that the solid content ratio was 0.1 part of SGCNT with respect to 100 parts of PC.
- a composition 1-2 was prepared, and the fibrous carbon nanostructure dispersion liquid and the insulating polymer dispersion liquid were mixed so that the SGCNT was 0.3 parts with respect to 100 parts of PC as a solid content ratio.
- Product 1-1 was produced. Next, after applying the slurry composition 1-2 to a support film (polyimide film having a thickness of 25 ⁇ m) as an insulating layer, it was naturally dried at 25 ° C. for 1 week or more in a constant temperature environment equipped with a local exhaust device.
- a support film polyimide film having a thickness of 25 ⁇ m
- the organic solvent was sufficiently volatilized to form a second electromagnetic wave absorbing layer containing 0.1 part of SGCNT on the polyimide film, and the thickness of the second electromagnetic wave absorbing layer was measured. Furthermore, after the slurry composition 1-1 is applied to the surface of the second electromagnetic wave absorbing layer, the organic solvent is sufficiently volatilized by natural drying at 25 ° C. for 1 week or more in a constant temperature environment equipped with a local exhaust device. Thereby, the 1st electromagnetic wave absorption layer was formed and the multilayer electromagnetic wave absorber which consists of a surface layer (insulating layer), a 2nd electromagnetic wave absorption layer, and a 1st electromagnetic wave absorption layer was produced. Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber.
- the thickness of the first electromagnetic wave absorption layer was calculated by subtracting the thickness of the insulating layer and the second electromagnetic wave absorption layer from the total thickness. Moreover, the transmission attenuation amount of the obtained electromagnetic wave absorber was 6 dB at 60 GHz and 6 dB at 76 GHz.
- the strip sample pieces for the insulating polymer tensile test and the strip sample pieces for the electromagnetic wave absorbing material tensile test were prepared in the same manner as in Example 1-1.
- Example 1-1 As the solid content ratio, except that the fibrous carbon nanostructure dispersion liquid and the insulating polymer dispersion liquid were mixed so that SGCNT was 0.1 part with respect to 100 parts of PC, and a layer having a thickness of 60 ⁇ m was formed.
- An electromagnetic wave absorbing material and an electromagnetic wave absorber were produced in the same manner as in Example 1-1.
- a strip sample piece for the insulating polymer tensile test was produced in the same manner as in Example 1-1.
- a strip sample piece for the electromagnetic wave absorbing material tensile test was prepared by repeatedly applying and drying a mixed solution of 0.1 part of SGCNT on a polyimide film with respect to 100 parts of the PC obtained above. Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber.
- the transmission attenuation amount of the obtained electromagnetic wave absorber was 1 dB at 60 GHz and 1 dB at 76 GHz.
- a multi-walled carbon nanotube (manufactured by Nanocyl, “Nanocyl (registered trademark) NC 7000”) is used instead of SGCNT, and the MWCNT is 0.3 with respect to 100 parts of PC as a solid content ratio.
- the fibrous carbon nanostructure dispersion liquid and the insulating polymer dispersion liquid were mixed to form a layer having a thickness of 60 ⁇ m, the electromagnetic wave absorbing material and An electromagnetic wave absorber was produced.
- a strip sample piece for the insulating polymer tensile test was produced in the same manner as in Example 1-1.
- a strip sample piece for the electromagnetic wave absorbing material tensile test was prepared by repeatedly applying and drying a mixed solution of 0.3 part of MWCNT on a polyimide film with respect to 100 parts of PC obtained above.
- Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Further, the transmission attenuation of the obtained electromagnetic wave absorber was 3 dB at 60 GHz and 2 dB at 76 GHz.
- PC polycarbonate
- PCO polycycloolefin resin
- PTFE polytetrafluoroethylene resin
- Example 2-1 SGCNT synthesized in the same manner as in Example 1-1 was used, added to a methyl ethyl ketone solvent so as to have a concentration of 0.2%, and stirred with a magnetic stirrer for 24 hours to perform preliminary dispersion of SGCNT.
- the same dispersion treatment as in Example 1-1 was performed to obtain a fibrous carbon nanostructure dispersion liquid.
- an uncrosslinked fluororubber made by DuPont, “Viton GBL200S” as an insulating polymer is added to a methyl ethyl ketone solvent so that the concentration becomes 2%, and the insulating polymer solution is sufficiently stirred. Produced.
- fibrous carbon nanostructure dispersion liquid and insulating polymer solution were mixed so that SGCNT was 0.3 part with respect to 100 parts of fluororubber to prepare a slurry composition.
- an electromagnetic wave absorber was produced.
- the insulating layer (surface layer) is a PET film, an electromagnetic wave in the same manner as in Example 1-1 except that a PET film (Lumirror S10 type, Toray Co., Ltd., thickness 38 ⁇ m) is used as the supporting film as the insulating layer.
- An electromagnetic wave absorber having an absorption layer made of an electromagnetic wave absorbing material was produced. Table 1 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Further, when the transmission attenuation amount of the electromagnetic wave absorber was measured by the above-described method, it was 5 dB at 60 GHz and 5 dB at 76 GHz.
- Example 2 Using an uncrosslinked hydrogenated nitrile rubber (HNBR) (manufactured by Nippon Zeon Co., Ltd., “ZP2001”) as the insulating polymer, the solid content ratio is such that SGCNT is 0.5 part with respect to 100 parts of HNBR.
- An electromagnetic wave absorbing material was prepared in the same manner as in Example 2-1, except that a slurry composition was prepared by mixing the carbon nanostructure dispersion liquid and the insulating polymer solution, and the thickness of the electromagnetic wave absorbing layer was 34 ⁇ m. And the electromagnetic wave absorber was produced. Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Moreover, the transmission attenuation amount of the obtained electromagnetic wave absorber was 7 dB at 60 GHz and 7 dB at 76 GHz.
- HNBR uncrosslinked hydrogenated nitrile rubber
- Non-crosslinked nitrile rubber (NBR) ("DN3350", manufactured by Nippon Zeon Co., Ltd.) is used as the insulating polymer, and the fibrous carbon is such that the SGCNT is 0.8 parts with respect to 100 parts of NBR as the solid content ratio.
- a slurry composition was prepared by mixing the nanostructure dispersion liquid and the insulating polymer solution, and the electromagnetic wave absorbing material and the electromagnetic wave were obtained in the same manner as in Example 2-1, except that the thickness of the electromagnetic wave absorbing layer was 29 ⁇ m.
- An absorber was prepared. Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Moreover, the transmission attenuation amount of the obtained electromagnetic wave absorber was 10 dB at 60 GHz and 9 dB at 76 GHz.
- Example 2-4 An uncrosslinked acrylic rubber ("AR12" manufactured by Nippon Zeon Co., Ltd.) is used as the insulating polymer, and the fibrous carbon nanostructure has a solid content ratio of 8 parts SGCNT per 100 parts acrylic rubber.
- An electromagnetic wave absorbing material and an electromagnetic wave absorber were prepared in the same manner as in Example 2-1, except that a slurry composition was prepared by mixing the dispersion and the insulating polymer solution, and the thickness of the electromagnetic wave absorbing layer was 80 ⁇ m. Produced. Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Further, the transmission attenuation of the obtained electromagnetic wave absorber was 8 dB at 60 GHz and 7 dB at 76 GHz.
- Example 2-5 In the same manner as in Example 2-1, the fibrous carbon nanostructure dispersion liquid and the insulating polymer solution were mixed so that the solid content ratio was 0.1 part of SGCNT with respect to 100 parts of fluororubber, A slurry composition 2-2 was prepared, and the fibrous carbon nanostructure dispersion liquid and the insulating polymer solution were mixed so that the SGCNT was 0.3 part with respect to 100 parts of fluororubber as a solid content ratio. A slurry composition 2-1 was prepared.
- the organic solvent is sufficiently volatilized by natural drying at 25 ° C. for 1 week or longer to form a second electromagnetic wave absorbing layer (intermediate layer) containing 0.1 part of SGCNT on the PET film, and the thickness of the second electromagnetic wave absorbing layer is set. It was measured. Furthermore, after applying the slurry composition 2-1 to the surface of the second electromagnetic wave absorbing layer, the organic solvent is sufficiently volatilized by natural drying at 25 ° C.
- the 1st electromagnetic wave absorption layer was formed and the multilayer electromagnetic wave absorber which consists of a surface layer (insulating layer), a 2nd electromagnetic wave absorption layer, and a 1st electromagnetic wave absorption layer was produced.
- Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber.
- the thickness of the first electromagnetic wave absorption layer was calculated by subtracting the thickness of the insulating layer and the second electromagnetic wave absorption layer from the total thickness.
- the transmission attenuation amount of the obtained electromagnetic wave absorber was 6 dB at 60 GHz and 6 dB at 76 GHz.
- Example 2-1 As a solid content ratio, the fibrous carbon nanostructure dispersion liquid and the insulating polymer solution were mixed so that SGCNT was 0.1 part with respect to 100 parts of fluororubber, and a layer having a thickness of 60 ⁇ m was formed. In the same manner as in Example 2-1, an electromagnetic wave absorbing material and an electromagnetic wave absorber were produced. Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Moreover, the transmission attenuation amount of the obtained electromagnetic wave absorber was 1 dB at 60 GHz and 1 dB at 76 GHz.
- a slurry composition 2-3 was prepared by mixing the fibrous carbon nanostructure dispersion liquid and the insulating polymer solution so that SGCNT was 0.1 part with respect to 100 parts of fluororubber as a solid content ratio.
- An electromagnetic wave absorbing material and an electromagnetic wave absorber were produced in the same manner as in Comparative Example 1, except that the slurry composition 2-3 was repeatedly applied and dried on the PET film to form a 500 ⁇ m thick layer.
- Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber.
- the transmission attenuation of the obtained electromagnetic wave absorber was 2 dB at 60 GHz and 2 dB at 76 GHz.
- Example 2-3 As the solid content ratio, except that the fibrous carbon nanostructure dispersion liquid and the insulating polymer solution were mixed so that SGCNT was 5 parts with respect to 100 parts of fluororubber to form a layer having a thickness of 55 ⁇ m.
- An electromagnetic wave absorbing material and an electromagnetic wave absorber were produced in the same manner as Example 2-1.
- Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber.
- the transmission attenuation amount of the obtained electromagnetic wave absorber was 23 dB at 60 GHz and 21 dB at 76 GHz.
- Multi-walled carbon nanotube (manufactured by Nanocyl, “Nanocyl (registered trademark) NC 7000”) is used instead of SGCNT.
- the electromagnetic wave absorbing material in the same manner as in Example 2-1, except that the fibrous carbon nanostructure dispersion liquid and the insulating polymer solution were mixed to form a layer having a thickness of 60 ⁇ m so as to be 3 parts. And the electromagnetic wave absorber was produced. Table 2 shows the results of each evaluation using the obtained electromagnetic wave absorbing material and electromagnetic wave absorber. Moreover, the transmission attenuation of the obtained electromagnetic wave absorber was 2 dB at 60 GHz and 2 dB at 76 GHz.
- HNBR hydrogenated nitrile rubber
- NBR nitrile rubber
- Example 3-1 Manufacture of electromagnetic wave absorbing material> [Preparation of slurry composition for electromagnetic wave absorbing material] ⁇ CNT dispersion preparation process ⁇ For methyl ethyl ketone as an organic solvent, a multi-walled carbon nanotube (Nanocyl, “NC7000”, number average diameter: 9.5 nm, number average length: 1.5 ⁇ m, as a fibrous carbon nanostructure as a conductive material, Purity: 90%, metal oxide: 10%, BET specific surface area: 250-300 m 2 / g, t-plot is convex downward) was added to a concentration of 0.2%, and 24 times with a magnetic stirrer. The mixture was stirred for a time to obtain a CNT preliminary dispersion.
- a multi-walled carbon nanotube Nanocyl, “NC7000”, number average diameter: 9.5 nm, number average length: 1.5 ⁇ m, as a fibrous carbon nanostructure as a conductive material, Purity: 90%, metal oxide: 10%, B
- a multi-stage step-down high-pressure homogenizer manufactured by Mieken Co., Ltd., product name “BERYU”
- BERYU product name “BERYU”
- a pressure of 120 MPa was intermittently and instantaneously applied to the preliminary dispersion, and the dispersion was fed into the capillary channel to obtain a CNT dispersion.
- ⁇ Manufacture of electromagnetic wave absorber> Applying the slurry composition to a PET film (Toray Co., Ltd., “Lumirror S10”, thickness 38 ⁇ m), which is a film forming substrate as an insulating layer, in a constant temperature environment draft equipped with a local exhaust device, The organic solvent was sufficiently volatilized by natural drying at 25 ° C. for 1 week or longer.
- an electromagnetic wave absorbing layer containing fluororubber as an insulating material and CNT as a fibrous carbon nanostructure is directly compared to an insulating layer containing PET as an insulating material. It is an applied single-layer type electromagnetic wave absorber.
- the thickness of the electromagnetic wave absorption layer and the return loss of the electromagnetic wave absorber were measured according to the above-described method. The results are shown in Table 3. Furthermore, when the transmission attenuation amount of the electromagnetic wave absorber was measured by the above method, it was 7 dB at 60 GHz and 7 dB at 76 GHz.
- Example 3-2 As an insulating material for the electromagnetic wave absorbing layer, uncrosslinked hydrogenated acrylonitrile butadiene rubber (HNBR, manufactured by Nippon Zeon Co., Ltd., “Zetpol 2001”) is used instead of fluorine rubber, and the insulating material is HNBR and a fibrous carbon nanostructure.
- HNBR uncrosslinked hydrogenated acrylonitrile butadiene rubber
- Zetpol 2001 uncrosslinked hydrogenated acrylonitrile butadiene rubber
- the insulating material is HNBR and a fibrous carbon nanostructure.
- a slurry composition was prepared and an electromagnetic wave absorbing material was formed in the same manner as in Example 3-1, except that the blending amount ratio with a certain CNT was changed as shown in Table 3.
- the obtained electromagnetic wave absorbing material was measured for tensile fracture strain and evaluated for flexibility. The results are shown in Table 3.
- the obtained electromagnetic wave absorber was obtained in the same manner as in Example 3-1, except that the layer thickness of the electromagnetic wave absorbing layer was changed as shown in Table 3. Various measurements were carried out.
- the obtained electromagnetic wave absorber had a transmission attenuation of 16 dB at 60 GHz and 15 dB at 76 GHz. Other measurement results are shown in Table 3.
- Example 3-3 Non-crosslinked acrylonitrile butadiene rubber (NBR, manufactured by Nippon Zeon Co., Ltd., “Nipol N3350”) is used as an insulating material for the electromagnetic wave absorption layer, and NBR which is an insulating material and CNT which is a fibrous carbon nanostructure.
- a slurry composition was prepared and an electromagnetic wave absorbing material was formed in the same manner as in Example 3-1, except that the blending amount ratio was changed as shown in Table 3.
- the obtained electromagnetic wave absorbing material was measured for tensile fracture strain and evaluated for flexibility. The results are shown in Table 3.
- the obtained electromagnetic wave absorber was obtained in the same manner as in Example 3-1, except that the layer thickness of the electromagnetic wave absorbing layer was changed as shown in Table 3.
- the transmission attenuation of the obtained electromagnetic wave absorber was 18 dB at 60 GHz and 18 dB at 76 GHz. Other measurement results are shown in Table 3.
- Example 3-4 As an insulating material for the electromagnetic wave absorbing layer, uncrosslinked acrylic rubber (manufactured by Zeon Corporation, “Nipol AR12”) is used instead of fluoro rubber, and the insulating material acrylic rubber and the fibrous carbon nanostructure CNT are A slurry composition was prepared and an electromagnetic wave absorbing material was formed in the same manner as in Example 3-1, except that the blending ratio was changed as shown in Table 3. The obtained electromagnetic wave absorbing material was measured for tensile fracture strain and evaluated for flexibility. The results are shown in Table 3.
- the obtained electromagnetic wave absorber was obtained in the same manner as in Example 3-1, except that the layer thickness of the electromagnetic wave absorbing layer was changed as shown in Table 3.
- the transmission attenuation of the obtained electromagnetic wave absorber was 11 dB at 60 GHz and 10 dB at 76 GHz. Other measurement results are shown in Table 3.
- Example 3-5 Manufacture of electromagnetic wave absorbing material> A multilayer electromagnetic wave absorber was produced as the electromagnetic wave absorber.
- the slurry composition prepared in the same manner as in Example 3-1 is referred to as a first slurry composition.
- the second slurry was prepared in the same manner as in Example 3-1, except that the blending ratio of the fluororubber as the insulating material and the CNT as the fibrous carbon nanostructure was changed to 100 parts: 1 part.
- a composition was prepared.
- an electromagnetic wave absorbing layer (hereinafter also referred to as “first electromagnetic wave absorbing layer”) was formed on the second electromagnetic wave absorbing layer using the first slurry composition.
- the thickness of the electromagnetic wave absorption layer was measured in substantially the same manner as the measurement method described above for the obtained electromagnetic wave absorber in which the insulating layer, the second electromagnetic wave absorption layer, and the first electromagnetic wave absorption layer are adjacent to each other.
- the thickness of the first electromagnetic wave absorbing layer was determined by subtracting the thickness of the insulating layer and the second electromagnetic wave absorbing layer from the total thickness of the measured electromagnetic wave absorber.
- the reflection attenuation and transmission attenuation of the obtained electromagnetic wave absorber were measured in the same manner as in Example 3-1.
- the amount of transmission attenuation of the obtained electromagnetic wave absorber was 14 dB at 60 GHz and 13 dB at 76 GHz.
- the measurement results of the return loss are shown in Table 3.
- Example 3-1 A slurry composition was prepared in the same manner as in Example 3-1, except that the blending ratio of the fluororubber as the insulating material and the multi-walled carbon nanotube as the fibrous carbon nanostructure was changed as shown in Table 3.
- An electromagnetic wave absorbing material was formed.
- the obtained electromagnetic wave absorbing material was measured for tensile fracture strain and evaluated for flexibility. The results are shown in Table 3.
- the obtained electromagnetic wave absorber was obtained in the same manner as in Example 3-1, except that the layer thickness of the electromagnetic wave absorbing layer was changed as shown in Table 3.
- Various measurements were carried out.
- the transmission attenuation of the obtained electromagnetic wave absorber was 3 dB at 60 GHz and 2 dB at 76 GHz in Comparative Example 3-1, and 21 dB at 60 GHz and 0 dB at 76 GHz in Comparative Example 3-2. Other measurement results are shown in Table 3.
- the obtained electromagnetic wave absorber was obtained in the same manner as in Example 3-1, except that the layer thickness of the electromagnetic wave absorbing layer was changed as shown in Table 3.
- the transmission attenuation of the electromagnetic wave absorber was 1 dB at 60 GHz and 1 dB at 76 GHz. Other measurement results are shown in Table 3.
- Example 3 Example 3 except that carbon black (manufactured by Can carb, “Thermax N990”, average particle diameter 280 nm, t-plot is unknown) was used as the conductive material instead of the fibrous carbon nanostructure of the electromagnetic wave absorbing layer.
- a slurry composition was prepared to form an electromagnetic wave absorbing material.
- the obtained electromagnetic wave absorbing material was measured for tensile fracture strain and evaluated for flexibility. The results are shown in Table 3.
- the obtained electromagnetic wave absorber was obtained in the same manner as in Example 3-1, except that the layer thickness of the electromagnetic wave absorbing layer was changed as shown in Table 3.
- Various measurements were carried out.
- the transmission attenuation of the electromagnetic wave absorber was 0.3 dB at 60 GHz and 0.1 dB at 76 GHz. Other measurement results are shown in Table 3.
- HNBR hydrogenated nitrile rubber
- NBR nitrile rubber
- MWCNT multi-walled carbon nanotube
- CFMP milled carbon fiber
- PET polyethylene terephthalate
- the content of the fibrous carbon nanostructure having a predetermined attribute is predetermined when the fibrous carbon nanostructure and the insulating material are included and the blending amount of the insulating material is 100 parts. It can be seen that the electromagnetic wave absorber of each example within the range exhibits a return loss of 10 dB or more at each measured frequency, and has a sufficiently high electromagnetic wave absorption capability in a high frequency region exceeding 20 GHz. On the other hand, in the comparative example in which the content or attribute of the fibrous carbon nanostructure does not satisfy the predetermined condition, it can be seen that the electromagnetic wave absorbing ability in a high frequency region exceeding 20 GHz is insufficient.
- an electromagnetic wave absorbing material and an electromagnetic wave absorber capable of absorbing electromagnetic waves in a high frequency region exceeding 20 GHz can be obtained.
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Abstract
Description
5≦A1≦15 ・・・(1-1)
前記繊維状炭素ナノ構造体が吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合に、0.3≦A1≦0.8 ・・・(1-2)
nが2の場合、A1>A2 ・・・(2)
nが3以上の自然数の場合、A1>A2≧・・・≧An ・・・(3)
さらに、電磁波吸収体を構成する全ての層のうち、第1電磁波吸収層における繊維状炭素ナノ構造体の含有量が最も多いことを特徴とする。
かかる構成によれば、電磁波吸収体の電磁波吸収能を一層向上させることができる。
本発明の電磁波吸収材料は、繊維状炭素ナノ構造体及び絶縁材料を含有し、特に限定されることなく、次世代無線LAN、自動車レーダブレーキ、光伝送装置、及びマイクロ波通信機器などの電磁波吸収体に用いることができる。そして、本発明の電磁波吸収材料及び電磁波吸収体は、20GHz超の高周波数領域における電磁波吸収能に優れる。
ここで、本発明の電磁波吸収材料は、繊維状炭素ナノ構造体及び絶縁材料を含有する。さらに、かかる電磁波吸収材料は、絶縁材料の含有量を100質量部としたときの繊維状炭素ナノ構造体の含有量Cが5質量部以上15質量部以下であるか、又は、繊維状炭素ナノ構造体が吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合に、含有量Cが0.3質量部以上0.8質量部以下であることを必要とする。そして、本発明の電磁波吸収材料によれば、通常、20GHz超の高周波数領域の電磁波を吸収することができる。
ここで、電磁波のエネルギーは周波数が高いほど大きくなるため、高周波数領域における電磁波吸収能を高めるには、繊維状炭素ナノ構造体の含有量が多いほど有効であるようにも思われる。
しかし、本発明者らは、絶縁材料100質量部に対する繊維状炭素ナノ構造体の配合量を種々調節して高周波数領域での電磁波吸収能を調査した。その結果、本発明者らは、驚くべきことに、上記した含有量を実現可能な配合量範囲で、かかる高周波数領域での電磁波吸収能を顕著に向上しうることを新たに見出した。
なお、本明細書において、電磁波吸収材料を製造する際の各材料の配合量は、製造された電磁波吸収材料に含まれる各材料の含有量に等しい。
本発明の電磁波吸収材料に使用する繊維状炭素ナノ構造体としては、特に限定されることなく、あらゆる繊維状炭素ナノ構造体を用いることができる。そして、繊維状炭素ナノ構造体としては、特に限定されることなく、カーボンナノチューブ(以下、「CNT」と称することがある。)のみからなるものを用いてもよいし、CNTと、CNT以外の繊維状炭素ナノ構造体との混合物を用いてもよい。
より具体的には、本発明の電磁波吸収材料に使用しうる繊維状炭素ナノ構造体としては、吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体や、その他の繊維状炭素ナノ構造体が挙げられる。
なお、本明細書において、「繊維状炭素ナノ構造体」は、通常、外径(繊維径)が1μm未満の繊維状の炭素材料を指す。さらに、本明細書において「繊維」又は「繊維状」とは、通常、アスペクト比が5以上である構造体を指す。なお、アスペクト比は、透過型電子顕微鏡を用いて無作為に選択した繊維状炭素ナノ構造体100本の直径及び長さを測定し、直径と長さとの比(長さ/直径)の平均値を算出することにより求めることができる。
t-プロットが上に凸な形状を示す繊維状炭素ナノ構造体としては、吸着等温線から得られるt-プロットが上に凸な形状を示す限りにおいて特に限定されることなく、例えば、CNT、気相成長炭素繊維などを用いることができる。これらは、1種単独で使用してもよいし、2種以上を併用してもよい。t-プロットが上に凸な形状を示す繊維状炭素ナノ構造体を使用すれば、繊維状炭素ナノ構造体同士が凝集しにくくなり、また所望の性能を発揮させるために必要な添加量を低減することができる。これにより、20GHz超の高周波数領域での電磁波吸収能や導電性に優れ、且つ耐久性に優れる電磁波吸収材料が得られる。
ここで、一般に、吸着とは、ガス分子が気相から固体表面に取り去られる現象であり、その原因から、物理吸着と化学吸着に分類される。そして、t-プロットの取得に用いられる窒素ガス吸着法では、物理吸着を利用する。なお、通常、吸着温度が一定であれば、繊維状炭素ナノ構造体に吸着する窒素ガス分子の数は、圧力が大きいほど多くなる。また、横軸に相対圧(吸着平衡状態の圧力Pと飽和蒸気圧P0の比)、縦軸に窒素ガス吸着量をプロットしたものを「等温線」といい、圧力を増加させながら窒素ガス吸着量を測定した場合を「吸着等温線」、圧力を減少させながら窒素ガス吸着量を測定した場合を「脱着等温線」という。
そして、t-プロットは、窒素ガス吸着法により測定された吸着等温線において、相対圧を窒素ガス吸着層の平均厚みt(nm)に変換することにより得られる。即ち、窒素ガス吸着層の平均厚みtを相対圧P/P0に対してプロットした、既知の標準等温線から、相対圧に対応する窒素ガス吸着層の平均厚みtを求めて上記変換を行うことにより、繊維状炭素ナノ構造体のt-プロットが得られる(de Boerらによるt-プロット法)。
(1)全表面への窒素分子の単分子吸着層形成過程
(2)多分子吸着層形成とそれに伴う細孔内での毛管凝縮充填過程
(3)細孔が窒素によって満たされた見かけ上の非多孔性表面への多分子吸着層形成過程
ここで、「屈曲点の位置」とは、前述した(1)の過程の近似直線Aと、前述した(3)の過程の近似直線Bとの交点である。
また、繊維状炭素ナノ構造体の全比表面積S1及び内部比表面積S2は、特に限定されないが、個別には、S1は、400m2/g以上2500m2/g以下であることが好ましく、800m2/g以上1200m2/g以下であることがさらに好ましい。一方、S2は、30m2/g以上540m2/g以下であることが好ましい。
ここで、繊維状炭素ナノ構造体の全比表面積S1及び内部比表面積S2は、そのt-プロットから求めることができる。具体的には、図1に示すt-プロットにより説明すると、まず、(1)の過程の近似直線の傾きから全比表面積S1を、(3)の過程の近似直線の傾きから外部比表面積S3を、それぞれ求めることができる。そして、全比表面積S1から外部比表面積S3を差し引くことにより、内部比表面積S2を算出することができる。
なお、「繊維状炭素ナノ構造体の平均直径(Av)」及び「繊維状炭素ナノ構造体の直径の標準偏差(σ:標本標準偏差)」は、それぞれ、透過型電子顕微鏡を用いて無作為に選択した繊維状炭素ナノ構造体100本の直径(外径)を測定して求めることができる。そして、繊維状炭素ナノ構造体の平均直径(Av)及び標準偏差(σ)は、繊維状炭素ナノ構造体の製造方法や製造条件を変更することにより調整してもよいし、異なる製法で得られた繊維状炭素ナノ構造体を複数種類組み合わせることにより調整してもよい。
そして、t-プロットが上に凸な形状を示す繊維状炭素ナノ構造体のアスペクト比(長さ/直径)は、10を超えることが好ましい。
なお、本明細書において、「BET比表面積」とは、BET法を用いて測定した窒素吸着比表面積を指す。
ここで、「マイクロ孔容積(Vp)」は、繊維状炭素ナノ構造体の液体窒素温度(77K)での窒素吸脱着等温線を測定し、相対圧P/P0=0.19における窒素吸着量をVとして、式(I):Vp=(V/22414)×(M/ρ)より、算出することができる。なお、Pは吸着平衡時の測定圧力、P0は測定時の液体窒素の飽和蒸気圧であり、式(I)中、Mは吸着質(窒素)の分子量28.010、ρは吸着質(窒素)の77Kにおける密度0.808g/cm3である。マイクロ孔容積は、例えば、「BELSORP(登録商標)-mini」(日本ベル(株)製)を使用して求めることができる。
なお、本明細書において「テープ状部分を全長に亘って有する」とは、「長手方向の長さ(全長)の60%以上、好ましくは80%以上、より好ましくは100%に亘って連続的に又は断続的にテープ状部分を有する」ことを指す。
ここで、GNTの断面形状において、「断面長手方向の中央部近傍」とは、断面の長手中心線(断面の長手方向中心を通り、長手方向線に直交する直線)から、断面の長手方向幅の30%以内の領域をいい、「断面長手方向の端部近傍」とは、「断面長手方向の中央部近傍」の長手方向外側の領域をいう。
本明細書において、金属不純物の濃度は、例えば、透過型電子顕微鏡(TEM)、走査型電子顕微鏡(SEM)、エネルギー分散型X線分析(EDAX)、気相分解装置及びICP質量分析(VPD、ICP/MS)などにより測定することができる。
ここで、金属不純物とは、繊維状炭素ナノ構造体を製造する際に用いた金属触媒などが挙げられ、例えば、アルカリ金属、アルカリ土類金属、第3~13族、ランタノイド族の各属する金属元素、Si、Sb、As、Pb、Sn、Biなどの金属元素、及びこれらを含む金属化合物などが挙げられる。より具体的には、Al、Sb、As、Ba、Be、Bi、B、Cd、Ca、Cr、Co、Cu、Ga、Ge、Fe、Pb、Li、Mg、Mn、Mo、Ni、K、Na、Sr、Sn、Ti、W、V、Zn、Zrなどの金属元素及びこれらを含む金属化合物が挙げられる。
なお、本明細書において、粒子状不純物の濃度は、基板上に繊維状炭素ナノ構造体分散液を塗布し、表面を商品名「surfscan」KLA Tencor Corporation製などを用いて測定することができる。
電磁波吸収材料に使用する繊維状炭素ナノ構造体として用いうる、吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体以外のその他の繊維状炭素ナノ構造体としては、吸着等温線から得られるt-プロットが上に凸な形状を示さない繊維状炭素ナノ構造体が挙げられる。より具体的には、吸着等温線から得られるt-プロットが下に凸な形状を示す繊維状炭素ナノ構造体が挙げられる。また、好ましくは、上記その他の繊維状炭素ナノ構造体としては、多層CNTが挙げられる。
具体的には、市販の多層CNTとしては、例えば、バイエルマテリアルサイエンス(Bayer Material Science)社製の「Baytubes C150P」及び「Baytubes C70P」、ナノシル(Nanocyl)社製の「Nanocyl 7000」、クムホ石油化学(Kumho Petrochemical)社製の「K-nanos-100P」、シーナノ(CNano)社製の「Flotube 9000」、ジェイオ(JEIO)社の「JC142」などを挙げることができる。
さらに、本発明の電磁波吸収材料に使用する繊維状炭素ナノ構造体の平均直径(Av)は、0.5nm以上であることが好ましく、1nm以上であることが更に好ましく、15nm以下であることが好ましく、10nm以下であることが更に好ましい。繊維状炭素ナノ構造体の平均直径(Av)が0.5nm以上であれば、電磁波吸収材料の高周波数領域における電磁波吸収能を更に高めることができる。また、繊維状炭素ナノ構造体の平均直径(Av)が15nm以下であれば、電磁波吸収材料の柔軟性を向上させることができる。
本発明の電磁波吸収材料は、絶縁材料の含有量を100質量部としたときの前記繊維状炭素ナノ構造体の含有量Cが5質量部以上15質量部以下であるか、又は、繊維状炭素ナノ構造体が吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合に、前記含有量Cが0.3質量部以上0.8質量部以下である。絶縁材料の含有量を上記範囲内とすることで、高周波数領域での電磁波吸収能を十分に高めることができるからである。
繊維状炭素ナノ構造体が、上記その他の繊維状炭素ナノ構造体である場合には、繊維状炭素ナノ構造体の含有量は、絶縁材料の含有量を100質量部としたときに、6質量部以上であることが好ましく、7質量部以上であることがより好ましく、13質量部以下であることが好ましく、10質量部以下であることがより好ましい。
絶縁材料としては、絶縁性高分子を用いることが好ましい。かかる絶縁性高分子は、
(a)熱可塑性樹脂及び/又は熱硬化性樹脂、
(b)ゴム及び/又はエラストマー、
の何れかでありうる。なお、本明細書において、絶縁材料及び絶縁性高分子は、JIS K 6911に準拠して測定される体積抵抗率が1011Ω・cm以上であることが好ましい。また、絶縁性高分子は、上記(a)又は(b)の何れかを主成分とする。なお、本明細書において、「主成分とする」とは、絶縁性高分子100質量%に対して、50質量%以上、好ましくは50質量%超、より好ましくは100質量%を占めることをいう。
絶縁材料として、上記絶縁性高分子(a)又は(b)を用いた場合には、電磁波吸収材料の20GHz超の高周波数領域の電磁波に対する吸収能を一層向上させることができる。さらに、上記絶縁性高分子(a)を用いた場合には、電磁波吸収材料に優れた強度及び耐久性をもたらすことができる。また、絶縁材料として、上記絶縁性高分子(b)を用いた場合には、電磁波吸収材料に優れた柔軟性をもたらすことができる。よって、電磁波吸収材料の用途に応じて、電磁波吸収材料の柔軟性や強度を調節することができるため、電磁波吸収材料の汎用性を高めることができる。
絶縁性高分子に含まれる熱可塑性樹脂、熱硬化性樹脂としては、特に限定されることなく、既知の絶縁性を有する熱可塑性樹脂、熱硬化性樹脂を用いることができる。そのような熱可塑性樹脂、熱硬化性樹脂としては、例えば、セルロース系樹脂、セルロースアセテート、セルロースニトレート、セルロースアセテートブチレート、カゼインプラスチック、大豆タンパクプラスチック、フェノール樹脂、ユリア樹脂、メラミン樹脂、ベンゾグアナミン樹脂、エポキシ樹脂、ジアリルフタレート樹脂、不飽和ポリエステル樹脂、ビスフェノールA型エポキシ樹脂、ノボラック型エポキシ樹脂、多官能基エポキシ樹脂、脂環状エポキシ樹脂、アルキド樹脂、ウレタン樹脂、塩化ビニル樹脂、ポリエチレン、ポリプロピレン、ポリスチレン、ナイロン、ビニロン、アクリル繊維、レーヨン、ポリ酢酸ビニル、ビニルエーテル樹脂、ABS樹脂、AS樹脂、アクリル樹脂、メタクリル樹脂、ポリアセタール、ポリイミド、ポリカーボネート、変性ポリフェニレンエーテル(PPE)、ポリエチレンテレフタレート、ポリブチレンテレフタレート、ポリアリレート、ポリスルホン、ポリフェニレンスルフィド、ポリエーテルエーテルケトン、ポリテトラフルオロエチレンなどのフッ素樹脂、ポリアミド、ポリイミド、ポリシクロオレフィンなどを用いることができる。これらは1種類のみを単独で用いてもよいし、2種類以上を混合して用いてもよい。
絶縁性高分子に含まれるゴム、エラストマーとしては、特に限定されることなく、既知の絶縁性を有するゴム、エラストマーを用いることができる。そのようなゴム、エラストマーとしては、例えば、天然ゴム(NR)、エポキシ化天然ゴム(ENR)、スチレン-ブタジエゴム(SBR)、ニトリルゴム(NBR)、クロロプレンゴム(CR)、エチレンプロピレンゴム(EPR,EPDM)、ブチルゴム(IIR)、クロロブチルゴム(CIIR)、アクリルゴム(ACM)、シリコーンゴム(Q)、フッ素ゴム(FKM)、ブタジエンゴム(BR)、エポキシ化ブタジエンゴム(EBR)、エピクロルヒドリンゴム(CO,CEO)、ウレタンゴム(U)、ポリスルフィドゴム(T)、アクリロニトリルブタジエンゴム、エチレン酢酸ビニルゴム、ビニルピリジンゴム、ポリイソプレンゴムなどのエラストマー類;オレフィン系(TPO)、ポリ塩化ビニル系(TPVC)、ポリエステル系(TPEE)、ポリウレタン系(TPU)、ポリアミド系(TPEA)、スチレン系(SBS)などの熱可塑性エラストマー;及びこれらの混合物を用いることができる。これらは1種類のみを単独で用いてもよいし、2種類以上を混合して用いてもよい。
さらに、絶縁材料に対して、任意の絶縁性充填剤を配合しても良い。かかる絶縁性充填材としては、特に限定されることなく、既知の無機充填剤や有機充填剤であって、絶縁性を有する充填剤を用いることができる。そのような絶縁性充填剤としては、例えば、シリカ、タルク、クレー、酸化チタンなどが挙げられる。これらは1種類のみを単独で用いてもよいし、2種類以上を混合して用いてもよい。
本発明による電磁波吸収材料は、用途に応じて既知の添加剤を含有していても良い。既知の添加剤としては、例えば、酸化防止剤、熱安定剤、光安定剤、紫外線吸収剤、架橋剤、顔料、着色剤、発泡剤、帯電防止剤、難燃剤、滑剤、軟化剤、粘着付与剤、可塑剤、離型剤、防臭剤、香料などが挙げられる。これらは、一種単独で、或いは複数種を組み合わせて用いることができる。
[電磁波の反射減衰量]
さらに、電磁波吸収材料は、20GHz超の周波数領域の電磁波を吸収する。特に、電磁波吸収材料は、周波数60GHzの電磁波の反射減衰量が7dB以上であることが好ましく、10dB以上であることがより好ましい。さらに、電磁波吸収材料は、周波数76GHzの電磁波の反射減衰量が6dB以上であることが好ましく、9dB以上であることがより好ましく、10dB以上であることが更に好ましい。更にまた、電磁波吸収材料は60GHz超76GHz未満の周波数範囲における反射減衰量が、周波数60GHz及び76GHzの際の各反射減衰量のうち、小さい方の値よりも常に大きいことが好ましい。周波数60GHz及び76GHzといった高周波数領域における反射減衰量が上記範囲内であれば、高周波数領域における電磁波遮断性能に顕著に優れるからである。
なお、本明細書において「反射減衰量」は実施例に記載の方法により測定することができる。
本発明の電磁波吸収材料は、絶縁材料として、絶縁性高分子である(b)ゴム及び/又はエラストマーを用いた場合には柔軟性に富む。この場合、JIS K 6251に準拠した引張試験により測定された引張破断ひずみの値(%)が100%以上であることが好ましく、150%以上であることがより好ましく、200%以上であることが更に好ましい。なお、本明細書において、「引張破断ひずみの値(%)」は、JIS K 6251に準拠した引張試験において試験体が破断(切断)した際の試験体の長さを元の試験体の長さで除して100分率で表現した値である。引張破断ひずみの値が上記下限値以上であれば、電磁波吸収材料が十分な柔軟性を有し、例えば、薄膜状に成形した場合に、十分な耐久性を呈することができる。
本発明の電磁波吸収体は、繊維状炭素ナノ構造体及び絶縁材料を含む電磁波吸収層を少なくとも一層備える。さらに、本発明の電磁波吸収体は、本発明の電磁波吸収材料を用いて形成された電磁波吸収層を少なくとも一層備える。本発明の電磁波吸収材料を用いて形成した電磁波吸収層を備える電磁波吸収体は、高周波数領域での電磁波吸収能に優れる。
また、本明細書では、「電磁波吸収体」とは、絶縁性樹脂及び繊維状炭素ナノ構造体を含む材料を層(膜)状に成形して得た電磁波吸収層を備える構造物を指す用語として用いる。これに対して、上述した「電磁波吸収材料」は、電磁波吸収層として成形される前の段階において材料として存在している状態の電磁波吸収材料や、広義には、電磁波吸収層を備えない形状/構造に成形された成形体をも含む用語として用いる。
本発明による電磁波吸収体は、単一の電磁波吸収層を備える単層型電磁波吸収体であっても良いし、電磁波吸収層を複数層備える多層型電磁波吸収体であっても良い。
特に、本発明による電磁波吸収体が多層型電磁波吸収体である場合には、本発明による電磁波吸収体は、繊維状炭素ナノ構造体と、絶縁材料とを含む電磁波吸収層を複数備える。そして、各層に含有される繊維状炭素ナノ構造体及び/又は絶縁材料は、同一又は相異なる種類でありうる。さらに、複数の電磁波吸収層を、電磁波の入射側に遠い側から、第1電磁波吸収層、第2電磁波吸収層・・・、第n電磁波吸収層とし、複数の電磁波吸収層の各層における、絶縁材料の含有量を100質量部としたときの繊維状炭素ナノ構造体の含有量を、それぞれ、A1質量部,A2質量部,・・・An質量部とした場合に、下記条件(1-1)又は(1-2)、及び(2)又は(3)が成立し、さらに、電磁波吸収体を構成する全ての層のうち、第1電磁波吸収層における繊維状炭素ナノ構造体の含有量が最も多い。ここで、電磁波吸収体の生産性の観点から、n=2~5であることが好ましい。
5≦A1≦15 ・・・(1-1)
前記繊維状炭素ナノ構造体が吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合に、0.3≦A1≦0.8 ・・・(1-2)
nが2の場合、A1>A2 ・・・(2)
nが3以上の自然数の場合、A1>A2≧・・・≧An ・・・(3)
繊維状炭素ナノ構造体がt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合には、繊維状炭素ナノ構造体の含有量は、第1電磁波吸収層における絶縁材料の含有量を100質量部としたときに、0.4質量部以上であることが好ましく、また、0.8質量部以下であることが好ましく、0.6質量部以下であることがより好ましい。
繊維状炭素ナノ構造体が多層CNTである場合には、繊維状炭素ナノ構造体の含有量は、第1電磁波吸収層における絶縁材料の含有量を100質量部としたときに、5質量部以上であることが好ましく、6質量部以上であることがより好ましく、8質量部以上であることがより好ましく、13質量部以下であることが好ましく、10質量部以下であることがより好ましい。
特に、隣接する各電磁波吸収層の含有量A1~Anは、隣接するある2つの電磁波吸収層の繊維状炭素ナノ構造体の含有量をそれぞれAi、Ai+1とした場合に、それらの比率(Ai+1/Ai)が以下の通りであることが好ましい。繊維状炭素ナノ構造体がt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合には、比率(Ai+1/Ai)が1/10以上4/5以下であることが好ましく、1/5以上1/2以下であることがより好ましい。また、繊維状炭素ナノ構造体が多層CNTである場合には、比率(Ai+1/Ai)が1/7以上1/2以下であることが好ましい。
さらにまた、上記複数の電磁波吸収層に含有される繊維状炭素ナノ構造体は、同一であることが好ましい。このような構成とすることにより、電磁波吸収体の製造効率を高めることができるからである。
ちなみに、上記複数の電磁波吸収層に含有される絶縁材料は同一であっても相異なっていても良いが、同一であることが好ましい。このような構成とすることにより、電磁波吸収体の電磁波吸収能を一層向上させることができるとともに、耐久性も高めることができるからである。
本発明の電磁波吸収体は、電磁波入射側の最表面に絶縁層を備えることが好ましい。絶縁層は、JIS K 6911に準拠して測定される体積抵抗率が1011Ω・cm以上である絶縁性の層であれば良い。絶縁層は、絶縁材料を含んでなり、かかる絶縁材料としては、特に限定されることなく、電磁波吸収材料に配合可能な絶縁材料を用いることができる。電磁波吸収層に含有される絶縁材料と、絶縁層に含有される絶縁材料とは、同一であっても相異なっていても良い。なお、絶縁層は、必要に応じて、上記電磁波吸収材料について上述したような既知の添加剤を含有しうる。絶縁層としては、例えば、ポリエチレンテレフタレートフィルム、ポリイミドフィルム等が挙げられる。
このような電磁波吸収体は、20GHz超といった高周波数領域の電磁波の吸収能に一層優れ、且つ電磁波吸収体が薄い場合の耐久性に優れる。また、絶縁層を電磁波吸収体の最表面に配設することで、電磁波吸収体の汎用性を高めることもできる。
―単層型電磁波吸収体の厚さ―
本発明による電磁波吸収体が単層型である場合には、かかる単層型電磁波吸収体の電磁波吸収層の厚さは、500μm以下であることが好ましく、100μm以下であることがより好ましく、80μm以下であることが特に好ましく、40μm以下であることがさらに特に好ましく、1μm以上であることが好ましく、10μm以上であることがより好ましい。膜状の電磁波吸収体の厚さが500μm以下であれば、高周波数領域における電磁波吸収能を一層十分に高めることができ、さらに、上記範囲の厚さの膜状の電磁波吸収体は、種々の用途に用いることができるため、汎用性が高い。
なお、膜状の電磁波吸収材料の厚さは、後述する製造方法における成形工程等において任意に制御することができる。また、膜状の電磁波吸収材料の厚さは、後述の実施例に記載の方法で測定することができる。
また、本発明による電磁波吸収体が多層型電磁波吸収体である場合であっても、複数の電磁波吸収層の合計厚さが、上記単層型の場合と同様の数値範囲内となることが好ましい。
本発明の電磁波吸収材料及び電磁波吸収体は、繊維状炭素ナノ構造体と絶縁材料とを溶媒に分散させて電磁波吸収材料用スラリー組成物を得る工程(電磁波吸収材料用スラリー組成物調製工程)と、得られた電磁波吸収材料用スラリー組成物から電磁波吸収材料又は電磁波吸収体を得る工程(成形工程)とを経て製造することができる。
電磁波吸収材料用スラリー組成物調製工程(以下、単に「スラリー組成物調製工程」ともいう)では、上述したような繊維状炭素ナノ構造体及び絶縁材料を溶媒中に分散させることで、電磁波吸収材料用スラリー組成物(以下、単に「スラリー組成物」ともいう)を調製する。
スラリー組成物調製工程では、溶媒として、特に限定されることなく、例えば、水;メタノール、エタノール、n-プロパノール、イソプロパノール、n-ブタノール、イソブタノール、t-ブタノール、ペンタノール、ヘキサノール、ヘプタノール、オクタノール、ノナノール、デカノールなどのアルコール類;アセトン、メチルエチルケトン、シクロヘキサノンなどのケトン類;酢酸エチル、酢酸ブチルなどのエステル類;ジエチルエーテル、ジオキサン、テトラヒドロフランなどのエーテル類;N,N-ジメチルホルムアミド、N-メチルピロリドンなどのアミド系極性有機溶媒;トルエン、キシレン、クロロベンゼン、オルトジクロロベンゼン、パラジクロロベンゼンなどの芳香族炭化水素類;などを用いることができる。これらは1種類のみを単独で用いてもよいし、2種類以上を混合して用いてもよい。
更に、スラリー組成物に任意に配合される添加剤としては、特に限定されることなく、分散剤などの分散液の調製に一般に使用される添加剤が挙げられる。そして、スラリー組成物調製工程にて用いる分散剤としては繊維状炭素ナノ構造体を分散可能であり、前述した溶媒に溶解可能であれば、特に限定されることなく、界面活性剤を用いることができる。
これらの分散剤は、1種または2種以上を混合して用いることができる。
好ましくは、スラリー組成物調製工程における分散方法としては、特に限定されることなく、ナノマイザー、アルティマイザー、超音波分散機、ボールミル、サンドグラインダー、ダイノミル、スパイクミル、DCPミル、バスケットミル、ペイントコンディショナー、高速攪拌装置、高圧ホモジナイザーなどを用いた一般的な分散方法を採用することができる。
なお、スラリー組成物調製工程では、絶縁材料との混合に先立って繊維状炭素ナノ構造体分散液を予め調製する工程(繊維状炭素ナノ構造体分散液調製工程)を実施することが好ましい。さらに、繊維状炭素ナノ構造体分散液調製工程では、繊維状炭素ナノ構造体を溶媒に対して添加し、一般的な分散方法にて分散して得た予備分散液を、以下に詳細に説明するキャビテーション効果が得られる分散処理または解砕効果が得られる分散処理に供して繊維状炭素ナノ構造体分散液を調製することが好ましい。
キャビテーション効果が得られる分散処理は、液体に高エネルギーを付与した際、水に生じた真空の気泡が破裂することにより生じる衝撃波を利用した分散方法である。この分散方法を用いることにより、繊維状炭素ナノ構造体を良好に分散させることができる。
また、ジェットミルを用いる場合も、処理回数は、繊維状炭素ナノ構造体の量等により適宜設定すればよい。例えば、処理回数としては2回以上が好ましく、5回以上がより好ましく、100回以下が好ましく、50回以下がより好ましい。また、圧力は20MPa~250MPaが好ましく、温度は15℃~50℃が好ましい。ジェットミルを用いる場合には分散剤として界面活性剤を溶媒にさらに加えるのが好ましい。処理液の粘度を抑えて安定してジェットミル装置が運転可能であるからである。ジェットミル分散装置としては高圧湿式ジェットミルが好適であり、具体的には、「ナノメーカー(登録商標)」(アドバンスト・ナノ・テクノロジィ社製)、「ナノマイザー」(ナノマイザー社製)、「ナノヴェイタ」(吉田機械興業社製)、「ナノジェットパル(登録商標)」(常光社製)等が挙げられる。
解砕効果が得られる分散処理は、繊維状炭素ナノ構造体を均一に分散できることは勿論、上記したキャビテーション効果が得られる分散処理に比べ、気泡が消滅する際の衝撃波による繊維状炭素ナノ構造体の損傷を抑制することができる点で有利である。
なお、粗分散液に背圧を負荷する場合、粗分散液に負荷した背圧は、大気圧まで一気に降圧させてもよいが、多段階で降圧することが好ましい。
すなわち、分散器は、粗分散液の流入側から流出側に向かって、内径がd1の分散器オリフィスと、内径がd2の分散空間と、内径がd3の終端部と(但し、d2>d3>d1である。)、を順次備える。
そして、この分散器では、流入する高圧(例えば10~400MPa、好ましくは50~250MPa)の粗分散液が、分散器オリフィスを通過することで、圧力の低下を伴いつつ、高流速の流体となって分散空間に流入する。その後、分散空間に流入した高流速の粗分散液は、分散空間内を高速で流動し、その際にせん断力を受ける。その結果、粗分散液の流速が低下すると共に、繊維状炭素ナノ構造体が良好に分散する。そして、終端部から、流入した粗分散液の圧力よりも低い圧力(背圧)の流体が、繊維状炭素ナノ構造体の分散液として流出することになる。
そして、粗分散液の背圧を多段降圧器により多段階で降圧することで、最終的に繊維状炭素ナノ構造体の分散液を大気圧に開放した際に、分散液中に気泡が発生するのを抑制できる。
なお、熱交換器等の配設に替えて、粗分散液を予め冷却しておくことでも、繊維状炭素ナノ構造体を含む溶媒中で気泡が発生することを抑制できる。
また、スラリー組成物調製工程では、繊維状炭素ナノ構造体との混合に先立って、上述した溶媒に対して、上述した絶縁材料を添加し、分散処理することで絶縁材料分散液を予め調製することが好ましい。分散処理方法としては、上述したような一般的な分散方法を採用することができる。
成形工程における成形方法は、用途や使用した絶縁材料の種類等に応じて適宜選択することができる。例えば、成形方法としては、塗布等による成膜方法や、所望形状への成形方法が挙げられる。
なお、以下のようにして得られる電磁波吸収材料及び電磁波吸収体は、繊維状炭素ナノ構造体が、絶縁材料からなるマトリックス中に略均一に分散させた状態で含有している。なお、電磁波吸収材料及び電磁波吸収体には、任意に架橋処理を施してもよい。
成形工程では、既知のあらゆる成膜方法により、上述したスラリー組成物から膜状(層状)の電磁波吸収材料を成膜(形成)することができる。電磁波吸収材料を成膜して層状にすることにより、電磁波吸収層とすることができる。また、電磁波吸収層は、繊維状炭素ナノ構造体及び絶縁性樹脂を含む材料を成膜することによっても、得ることができる。
具体的には、例えば、スラリー組成物を、たとえば、ポリエチレンテレフタレート(PET)フィルムや、ポリイミドフィルムなど、上述した絶縁層を構成しうる既知の成膜基材上に塗布した後、乾燥させることにより、スラリー組成物から溶媒を除去する。なお、塗布は、特に限定されることなく、ハケ塗り法やキャスト法などの既知の方法にて行うことができる。また、乾燥は、既知の方法にて行うことができ、例えば、真空乾燥や、ドラフト内に静置することにより行うことができる。
単層型電磁波吸収体は、このような成膜方法を経て製造することができる。
また、上述した多層型電磁波吸収体は、以下のようにして製造することができる。
例えば、上述した電磁波吸収材料用スラリー組成物調製工程において、多層を形成するための所望の配合量で調製した複数種のスラリー組成物を、既知の成膜基材上に既知の方法にて塗布することで、多層型電磁波吸収体を形成することができる。より詳細には、例えば、絶縁層を構成するPETフィルム上に、まず、一のスラリー組成物を塗布及び乾燥して、一の電磁波吸収層を形成した後に、かかる電磁波吸収層上に他のスラリー組成物を塗布及び乾燥して、他の電磁波吸収層を形成して、2層の電磁波吸収層と、最表層に絶縁層とを備える多層型電磁波吸収体を製造することができる。このとき、塗布及び乾燥方法は、特に限定されることなく、上述したような一般的な方法を採用することができる。
あるいは、公知の凝固方法や、乾燥方法を経て固形状とした電磁波吸収材料を、所望形状に成形することもできる。例えば、凝固方法としては、電磁波吸収材料を水溶性の有機溶媒に加える方法、酸を電磁波吸収材料に加える方法、塩を電磁波吸収材料に加える方法等によりスラリー組成物を凝固させることができる。ここで、水溶性の有機溶媒としては、スラリー組成物中の絶縁材料が溶解せず、かつ、分散剤が溶解する溶媒を選択することが好ましい。このような有機溶媒としては、例えば、メタノール、エタノール、2-プロパノール、エチレングリコール等が挙げられる。また、酸としては、酢酸、蟻酸、リン酸、塩酸等の、ラテックスの凝固に一般的に用いられる酸が挙げられる。さらに、塩としては、塩化ナトリウム、硫酸アルミニウム、塩化カリウム等の、ラテックスの凝固に一般的に用いられる公知の塩が挙げられる。
そして、凝固や乾燥により得られた電磁波吸収材料は、所望の成形品形状に応じた成形機、例えば、打ち抜き成形機、押出機、射出成形機、圧縮機、ロール機等により成形することができる。
実施例および比較例において、BET比表面積、t-プロット、引張破断強度、引張破断ひずみ、電磁波吸収材料の柔軟性、電磁波吸収体を構成する電磁波吸収層の厚さ、電磁波吸収体の反射減衰量(dB)、電磁波吸収体の透過減衰量(dB)は、それぞれ以下の方法を使用して測定または評価した。
実施例、比較例で使用した繊維状炭素ナノ構造体のBET比表面積は、以下のように測定した。
全自動比表面積測定装置(株式会社マウンテック製、「Macsorb(登録商標)HM model-1210」)専用のセルを、110℃、5hr以上の熱処理で十分乾燥させた後、繊維状炭素ナノ構造体20mgを秤量し、セル内に入れた。その後、セルを測定装置の所定の位置に備え付け、自動操作によりBET比表面積を測定した。なお、この装置の測定原理は、液体窒素の77Kでの吸脱着等温線を測定し、この吸脱着等温曲線から、BET(Brunauer-Emmett-Teller)法にて比表面積を測定する方法に従う。
実施例、比較例で使用した繊維状炭素ナノ構造体のt-プロットは、以下のように測定した。
上記BET比表面積の測定で得られた、吸着等温線において、相対圧を窒素ガス吸着層の平均厚みt(nm)に変換することにより、t-プロットを作成した。なお、t-プロットの測定原理は、de Boerらによるt-プロット法に従う。
実施例、比較例で作製した絶縁材料引張試験用の短冊サンプル片及び電磁波吸収材料引張試験用の短冊サンプル片の引張破断強度及び引張破断ひずみは、以下のように測定した。
JIS K 7127に従い、厚み25μmのポリイミドフィルム(東レデュポン株式会社製、「カプトン100Hタイプ」)上に厚さ200μm、幅10mm、長さ200mmのサンプル片を有する短冊状シートを形成した後、ポリイミドフィルムを取り除いたサンプル片を、引張試験機(株式会社島津製作所製、「オートグラフAGS-X」)用いて、25℃、引張速度5.0mm/minの条件にて測定した。
また、引張破断強度の変化率(%)及び、引張破断ひずみの変化率(%)は、以下の式より算出した。
変化率(%)={(電磁波吸収材料引張試験用の短冊サンプル片の値/絶縁材料引張試験用の短冊サンプル片の値)×100}-100
そして、以下の評価基準により、耐久性を評価した。
A:引張破断強度及び引張破断ひずみの値の変化率が-20%以上であった
B:引張破断強度又は引張破断ひずみの値の変化率が-20%より低かった
各実施例、各比較例にて製造したスラリー組成物の一部を攪拌機付きの容器にとりだし、撹拌しながら自然乾燥により有機溶媒を揮発させ固形分を取り出した後、60℃、24時間以上真空乾燥をし、電磁波吸収材料を得た。得られた電磁波吸収材料を、JIS K 6251に従ってJIS 3号ダンベル形状に成形して試験体を得た。得られた試験体について、引張試験機(株式会社島津製作所製、「オートグラフAGS-X」)を用いて、引張速度を500±50mm/分としてJIS K 6251に従って引張試験を実施した。試験体が破断(切断)した際の試験体の長さを元の試験体の長さで除して100分率で表現した値である引張破断ひずみの値(%)を、以下の基準に従って評価した。引張破断ひずみの値が大きいほど、柔軟性に富む。
(実施例2-1~比較例2-4)
A:引張破断ひずみの値が150%以上
B:引張破断ひずみの値が150%未満
(実施例3-1~比較例3-4)
A:引張破断ひずみの値が200%以上
B:引張破断ひずみの値が100%以上200%未満
C:引張破断ひずみの値が100%未満
マイクロメータ((株)ミツトヨ製、293シリーズ、「MDH-25」)を用いて、実施例、比較例にて製造した電磁波吸収体について10点の厚さを測定し、その平均値から、基材として用いたPETフィルム(絶縁層を構成する)の厚さ38μmを差し引き、電磁波吸収層の厚さとした。
電磁波吸収体の電磁波吸収性能は、電磁波の反射減衰量(dB)を測定することにより評価した。
実施例、比較例で製造した電磁波吸収体を試験体として、導電金属板に対して、繊維状炭素ナノ構造体濃度がより高い電磁波吸収体層側が直面するように、添付した。すなわち、測定システムに導電金属板を取り付けた際に、電磁波吸収体の絶縁層側に電磁波が入射するように、電磁波吸収体を設置した。
測定システム(KEYCOM社製、「DPS10」)を用いて、フリースペース(自由空間)法にてワンポートでのS(Scattering)パラメータ(S11)を測定した。周波数60~90GHzについて測定を実施した。ここで、上記測定システムには、ベクトルネットワークアナライザ(アンリツ社製、「ME7838A」)と、アンテナ(部品番号「RH15S10」、及び「RH10S10」)とを採用した。表1~3に、60GHz及び76GHzの電磁波を照射した際のSパラメータ(S11)より、下記式(1)に従って反射減衰量(dB)を算出した結果(絶対値)を示す。反射減衰量が大きいほど、電磁波吸収性能に優れる。
反射減衰量(dB)=20log|S11|・・・(1)
電磁波吸収体の電磁波シールド性能は、電磁波の透過減衰量(dB)を測定することにより評価した。
実施例、比較例で製造した電磁波吸収体の透過減衰量は、電磁波吸収体を導電金属板に添付せず、フリースペース法による測定システムに設置した以外は、上述した反射減衰量の測定と同様の試験条件において、S21パラメータを測定して、下記式(2)に従って透過減衰量(dB)を算出した。透過減衰量が大きいほど、電磁波シールド性能に優れる。
なお、電磁波シールド性能は、電磁波を反射及び吸収することによる遮蔽性能であり、電磁波を吸収して熱エネルギーに変換することによって電磁波を除去する性質を表す電磁波吸収性能とは異なる。
透過減衰量(dB)=20log|S21|・・・(2)
t-プロットが上に凸な形状を示す繊維状炭素ナノ構造体として、特許第4,621,896号公報に記載のスーパーグロース法で得たカーボンナノチューブ(SGCNT)を用いた。具体的には次の条件において、SGCNTを合成した。
炭素化合物:エチレン;供給速度50sccm
雰囲気(ガス)(Pa):ヘリウム、水素混合ガス;供給速度1000sccm
圧力1大気圧
水蒸気添加量(ppm):300ppm
反応温度(℃):750℃
反応時間(分):10分
金属触媒(存在量):鉄薄膜;厚さ1nm
基板:シリコンウェハー
得られたSGCNTは、BET比表面積880m2/gであり、t-プロットは上に凸の形状であった。また、ラマン分光光度計での測定において、単層カーボンナノチューブに特長的な100~300cm-1の低波数領域にラジアルブリージングモード(RBM)のスペクトルが観察された。
合成したSGCNTを使用し、クロロホルム溶媒中に濃度が0.2%になるようにSGCNTを添加し、マグネチックスターラーで24時間撹拌し、SGCNTの予備分散を実施した。
次いで、直径200μmの細管流路部を有する高圧分散処理部(ジェットミル)に連結して多段圧力制御装置(多段降圧器)を有する多段降圧型高圧ホモジナイザー(株式会社美粒製、「BERYU SYSTEM PRO」)に充填し、断続的かつ瞬間的に120MPaの圧力を粗分散液に負荷し、細管流路に送り込み分散処理を行い、繊維状炭素ナノ構造体分散液を得た。
別途、クロロホルム溶媒中に、ポリカーボネート(PC)(出光興産株式会社製、「タフロンA1900」)の濃度が2%になるように添加し、充分撹拌し絶縁性高分子分散液を作製した。絶縁性高分子分散液を用い、ポリイミドフィルム上に塗布・乾燥を繰り返し、絶縁性高分子引張試験用の短冊サンプル片を作製し引張試験を実施した。
次に、固形分比率として、絶縁材料であるPC100部に対しSGCNTが0.3部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、電磁波吸収材料としてのスラリー組成物を作製した。ポリイミドフィルム上に、スラリー組成物の塗布・乾燥を繰り返し、電磁波吸収材料引張試験用の短冊サンプル片を作製し引張試験を実施した。
次いで、電磁波吸収体の作製を行った。絶縁層としての支持フィルム(厚み25μmのポリイミドフィルム)に、スラリー組成物を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然乾燥により有機溶剤を充分揮発させ、ポリイミドフィルム上に電磁波吸収材料の薄膜層を形成させ、絶縁層(表面層)にポリイミドフィルム、電磁波吸収層にSGCNTとPCとを含む電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、電磁波吸収体について上述の方法により透過減衰量を測定したところ、60GHzで5dB、76GHzで5dBであった。
実施例1-1で合成したSGCNTを使用し、シクロヘキサン溶媒中に濃度が0.2%になるようにSGCNTを添加し、マグネチックスターラーで24時間撹拌し、SGCNTの予備分散を実施した。
次いで、直径200μmの細管流路部を有する高圧分散処理部(ジェットミル)に連結して多段圧力制御装置(多段降圧器)を有する多段降圧型高圧ホモジナイザー(株式会社美粒製、「BERYU SYSTEM PRO」)に充填し、断続的かつ瞬間的に120MPaの圧力を粗分散液に負荷し、細管流路に送り込み分散処理を行い、繊維状炭素ナノ構造体分散液を得た。
別途、シクロヘキサン溶媒中に、ポリシクロオレフィン樹脂(PCO)(日本ゼオン株式会社製、「ゼオノア1020R」)の濃度が2%になるように添加し、充分撹拌し絶縁性高分子分散液を作製した。絶縁性高分子分散液を用い、ポリイミドフィルム上に塗布・乾燥を繰り返し、絶縁性高分子引張試験用の短冊サンプル片を作製し引張試験を実施した。
次に、固形分比率として、PCO100部に対しSGCNTが0.5部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、電磁波吸収材料としてのスラリー組成物を作製した。ポリイミドフィルム上に、スラリー組成物の塗布・乾燥を繰り返し、電磁波吸収材料引張試験用の短冊サンプル片を作製し引張試験を実施した。
次いで、電磁波吸収体の作製を行った。絶縁層としての支持フィルム(厚み25μmのポリイミドフィルム)に、スラリー組成物を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然乾燥により有機溶剤を充分揮発させ、ポリイミドフィルム上に電磁波吸収材料の薄膜層を形成させ、絶縁層(表面層)にポリイミドフィルム、電磁波吸収層にSGCNTとPCとを含む電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、電磁波吸収体について上述の方法により透過減衰量を測定したところ、60GHzで7dB、76GHzで7dBであった。
ポリイミドフィルム上に、厚さ200μm、幅100mm、長さ200mmの成形物用の金属製金型を備え、金型内に、エポキシ樹脂(三菱化学製、「jER828」)100部に対し、エポキシ硬化剤(三菱化学製、「jERキュアLV11」)33部を配合したエポキシ混合液を充填し、25℃、24時間静置したのち、80℃、24時間で熱硬化させ、厚さ200μm、幅100mm、長さ200mmのエポキシ樹脂シートを形成した。そのシートを、幅10mm、長さ200mmの短冊状に切り出し、絶縁性高分子引張試験用の短冊サンプル片を作製し引張試験を実施した。
実施例1-1で合成したSGCNTを使用し、液状の上記エポキシ樹脂100部に対し、SGCNTを0.8部添加し、薄膜旋回型分散装置(プライミクス株式会社製、「フィルミクス50-50型」)に充填し、20℃、せん断速度50m/s、5分間の分散混合処理を実施し、CNT分散エポキシ樹脂溶液を作製した。さらに、CNT分散エポキシ樹脂溶液100部に、上記エポキシ硬化剤33部を配合し、スラリー組成物を作製した。ポリイミドフィルム上に、厚さ200μm、幅100mm、長さ200mmの成形物用の金属製金型を備え、金型内に、スラリー組成物を充填し、25℃、24時間静置したのち、80℃、24時間で熱硬化させ、厚さ200μm、幅100mm、長さ200mmのシートを形成し、幅10mm、長さ200mmの短冊状に切り出し、電磁波吸収材料引張試験用の短冊サンプル片を作製し引張試験を実施した。
次いで、電磁波吸収体の作製を行った。絶縁層としての支持フィルム(厚み25μmのポリイミドフィルム)に、スラリー組成物を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然硬化により、ポリイミドフィルム上に電磁波吸収材料の薄膜層を形成させ、絶縁層(表面層)にポリイミドフィルム、電磁波吸収層にSGCNTとエポキシ樹脂とを含む電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、電磁波吸収体について上述の方法により透過減衰量を測定したところ、60GHzで10dB、76GHzで9dBであった。
ポリイミドフィルム上に、厚さ200μm、幅100mm、長さ200mmの成形物用の金属製金型を備え、金型内に、PTFE樹脂(ダイキン工業株式会社製、「ポリフロンPTFE-M12」)を充填し、圧縮成型機にて、25℃、70MPaで予備圧縮成型したのちポリイミドフィルムを取り除き、窒素雰囲気にした電気炉内で、360℃、30分で焼成し、厚さ200μm、幅100mm、長さ200mmのPTFE樹脂シートを形成した。そのシートを、幅10mm、長さ200mmの短冊状に切り出し、絶縁性高分子引張試験用の短冊サンプル片を作製し引張試験を実施した。
実施例1-1で合成したSGCNTを使用し、シクロヘキサン溶媒中に濃度が0.2%になるようにSGCNTを添加し、マグネチックスターラーで24時間撹拌し、SGCNTの予備分散を実施した。
次いで、直径200μmの細管流路部を有する高圧分散処理部に連結して多段圧力制御装置(多段降圧器)を有する多段降圧型高圧ホモジナイザー(株式会社美粒製、「BERYU SYSTEM PRO」)に充填し、断続的かつ瞬間的に120MPaの圧力を粗分散液に負荷し、細管流路に送り込み分散処理を行い、繊維状炭素ナノ構造体分散液を得た。
別途、シクロヘキサン溶媒中に、PTFE樹脂の濃度が5%になるように添加してPTFE樹脂懸濁液を調製した後、PTFE樹脂100部に対しSGCNTが0.5部になるように、繊維状炭素ナノ構造体分散液とPTFE樹脂懸濁液を混合し、薄膜旋回型分散装置に充填し、20℃、せん断速度50m/s、5分間の分散混合処理を実施した。そして、得られた溶液を、コニカルドライヤーに充填し、80℃の温度で回転撹拌しながら充分に溶媒を揮発させ、電磁波吸収材料(SGCNTとPTFE樹脂との混合固体粉)を作製した。ポリイミドフィルム上に、厚さ200μm、幅100mm、長さ200mmの成形物用の金属製金型を備え、金型内に、電磁波吸収材料を充填し、圧縮成型機にて、25℃、70MPaで予備圧縮成型したのちポリイミドフィルムを取り除き、窒素雰囲気にした電気炉内で、360℃、30分で焼成し、厚さ200μm、幅100mm、長さ200mmのシートを形成し、得られたシートを幅10mm、長さ200mmの短冊状に切り出し、電磁波吸収材料引張試験用の短冊サンプル片を作製し引張試験を実施した。
次いで、電磁波吸収体の作製を行った。支持フィルム(厚み25μmのポリイミドフィルム)上に、電磁波吸収材料をのせ、圧縮成型機にて、25℃、70MPaで予備圧縮成型したのちポリイミドフィルムを取り除き、窒素雰囲気にした電気炉内で、360℃、30分で焼成し、電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで8dB、76GHzで7dBであった。
実施例1-1と同様にして、固形分比率として、PC100部に対しSGCNTが0.1部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、スラリー組成物1-2を作製し、固形分比率として、PC100部に対しSGCNTが0.3部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、スラリー組成物1-1を作製した。
次いで、絶縁層としての支持フィルム(厚み25μmのポリイミドフィルム)に、スラリー組成物1-2を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然乾燥により有機溶剤を充分揮発させ、ポリイミドフィルム上にSGCNTを0.1部含有した第2電磁波吸収層を形成させ、第2電磁波吸収層の厚さを測定した。
さらに、上記第2電磁波吸収層表面に、スラリー組成物1-1を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然乾燥により有機溶剤を充分揮発させることにより、第1電磁波吸収層を形成し、表面層(絶縁層)、第2電磁波吸収層、第1電磁波吸収層からなる多層の電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。なお、第1電磁波吸収層の厚さは、全厚さから、絶縁層及び第2電磁波吸収層の厚さを引いて算出した。また、得られた電磁波吸収体の透過減衰量は、60GHzで6dB、76GHzで6dBであった。
なお、絶縁性高分子引張試験用の短冊サンプル片及び電磁波吸収材料引張試験用の短冊サンプル片は実施例1-1と同様にして作製した。
固形分比率として、PC100部に対しSGCNTが0.1部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、厚さ60μmの層を形成した以外は、実施例1-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
なお、絶縁性高分子引張試験用の短冊サンプル片は、実施例1-1と同様にして作製した。また、電磁波吸収材料引張試験用の短冊サンプル片は、上記で得られたPC100部に対しSGCNTが0.1部の混合液をポリイミドフィルム上に塗布・乾燥を繰り返して作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで1dB、76GHzで1dBであった。
固形分比率として、PC100部に対しSGCNTが5部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、厚さ80μmの層を形成した以外は、実施例1-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
なお、絶縁性高分子引張試験用の短冊サンプル片は、実施例1-1と同様にして作製した。また、電磁波吸収材料引張試験用の短冊サンプル片は、上記で得られたPC100部に対しSGCNTが5部の混合液をポリイミドフィルム上に塗布・乾燥を繰り返して作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで22dB、76GHzで22dBであった。
固形分比率として、PCO100部に対しSGCNTが5部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、厚さ60μmの層を形成した以外は、実施例1-2と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
なお、絶縁性高分子引張試験用の短冊サンプル片は、実施例1-2と同様にして作製した。また、電磁波吸収材料引張試験用の短冊サンプル片は、上記で得られたPCO100部に対しSGCNTが5部の混合液をポリイミドフィルム上に塗布・乾燥を繰り返して作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで23dB、76GHzで21dBであった。
繊維状炭素ナノ構造体として、SGCNTの代わりに多層カーボンナノチューブ(MWCNT)(Nanocyl社製、「Nanocyl(登録商標)NC 7000」)を用い、固形分比率として、PC100部に対しMWCNTが0.3部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子分散液を混合し、厚さ60μmの層を形成した以外は、実施例1-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
なお、絶縁性高分子引張試験用の短冊サンプル片は、実施例1-1と同様にして作製した。また、電磁波吸収材料引張試験用の短冊サンプル片は、上記で得られたPC100部に対しMWCNTが0.3部の混合液をポリイミドフィルム上に塗布・乾燥を繰り返して作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで3dB、76GHzで2dBであった。
「PC」はポリカーボネートを、
「PCO」はポリシクロオレフィン樹脂を、
「PTFE」はポリテトラフルオロエチレン樹脂を、
それぞれ示す。
実施例1-1と同様にして合成したSGCNTを使用し、メチルエチルケトン溶媒中に濃度が0.2%になるように添加し、マグネチックスターラーで24時間撹拌し、SGCNTの予備分散を実施した。
次いで、実施例1-1と同様の分散処理を行い、繊維状炭素ナノ構造体分散液を得た。
別途、メチルエチルケトン溶媒中に、絶縁性高分子としての未架橋のフッ素ゴム(デュポン社製、「Viton GBL200S」)を、濃度が2%になるように添加し、充分撹拌し絶縁性高分子溶液を作製した。
固形分比率として、フッ素ゴム100部に対してSGCNTが0.3部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合し、スラリー組成物を作製した。
次いで、電磁波吸収体の作製を行った。絶縁層としての支持フィルムに、PETフィルム(東レ株式会社製、ルミラーS10タイプ、厚み38μm)を用いた以外は、実施例1-1と同様にして、絶縁層(表面層)がPETフィルム、電磁波吸収層が電磁波吸収材料から構成される電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表1に示す。また、電磁波吸収体について上述の方法により透過減衰量を測定したところ、60GHzで5dB、76GHzで5dBであった。
絶縁性高分子として未架橋の水素化ニトリルゴム(HNBR)(日本ゼオン株式会社製、「ZP2001」)を用い、固形分比率として、HNBR100部に対しSGCNTが0.5部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合してスラリー組成物を作製し、電磁波吸収層の厚さを34μmとした以外は、実施例2-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで7dB、76GHzで7dBであった。
絶縁性高分子として未架橋のニトリルゴム(NBR)(日本ゼオン株式会社製、「DN3350」)を用い、固形分比率として、NBR100部に対しSGCNTが0.8部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合してスラリー組成物を作製し、電磁波吸収層の厚さを29μmとした以外は、実施例2-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで10dB、76GHzで9dBであった。
絶縁性高分子として未架橋のアクリルゴム(日本ゼオン株式会社製、「AR12」)を用い、固形分比率として、アクリルゴム100部に対しSGCNTが8部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合してスラリー組成物を作製し、電磁波吸収層の厚さを80μmとした以外は、実施例2-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで8dB、76GHzで7dBであった。
実施例2-1と同様にして、固形分比率として、フッ素ゴム100部に対しSGCNTが0.1部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合し、スラリー組成物2-2を作製し、固形分比率として、フッ素ゴム100部に対しSGCNTが0.3部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合し、スラリー組成物2-1を作製した。
次いで、絶縁層としての支持フィルム(東レ株式会社製、ルミラーS10タイプ、厚み38μmのPETフィルム)に、スラリー組成物2-2を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然乾燥により有機溶剤を充分揮発させ、PETフィルム上にSGCNTが0.1部含有した第2電磁波吸収層(中間層)を形成させ、第2電磁波吸収層の厚さを測定した。
さらに、上記第2電磁波吸収層表面に、スラリー組成物2-1を塗布したのち、局所排気装置を備えた恒温環境のドラフト内で、25℃、1週間以上自然乾燥により有機溶剤を充分揮発させることにより、第1電磁波吸収層を形成し、表面層(絶縁層)、第2電磁波吸収層、第1電磁波吸収層からなる多層の電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。なお、第1電磁波吸収層の厚さは、全厚さから、絶縁層及び第2電磁波吸収層の厚さを引いて算出した。また、得られた電磁波吸収体の透過減衰量は、60GHzで6dB、76GHzで6dBであった。
固形分比率として、フッ素ゴム100部に対しSGCNTが0.1部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合し、厚さ60μmの層を形成した以外は、実施例2-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで1dB、76GHzで1dBであった。
固形分比率として、フッ素ゴム100部に対しSGCNTが0.1部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合してスラリー組成物2-3を作製し、PETフィルム上に、スラリー組成物2-3の塗布・乾燥を繰り返して、厚さ500μmの層を形成した以外は、比較例1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで2dB、76GHzで2dBであった。
固形分比率として、フッ素ゴム100部に対しSGCNTが5部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合し、厚さ55μmの層を形成した以外は、実施例2-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで23dB、76GHzで21dBであった。
繊維状炭素ナノ構造体として、SGCNTの代わりに多層カーボンナノチューブ(MWCNT)(Nanocyl社製、「Nanocyl(登録商標)NC 7000」)を用い、固形分比率として、フッ素ゴム100部に対しMWCNTが0.3部になるように、繊維状炭素ナノ構造体分散液と絶縁性高分子溶液を混合し、厚さ60μmの層を形成した以外は、実施例2-1と同様にして、電磁波吸収材料及び電磁波吸収体を作製した。
得られた電磁波吸収材料及び電磁波吸収体を用いた各評価の結果を、表2に示す。また、得られた電磁波吸収体の透過減衰量は、60GHzで2dB、76GHzで2dBであった。
なお、表2中、
「HNBR」は水素化ニトリルゴムを、
「NBR」はニトリルゴムを、
それぞれ示す。
<電磁波吸収材料の製造>
[電磁波吸収材料用スラリー組成物の調製]
―CNT分散液調製工程―
有機溶媒としてのメチルエチルケトンに対して、導電材料である繊維状炭素ナノ構造体としての多層カーボンナノチューブ(Nanocyl社製、「NC7000」、個数平均直径:9.5nm、個数平均長さ:1.5μm、純度:90%、金属酸化物:10%、BET比表面積:250~300m2/g、t-プロットは下に凸)を濃度が0.2%となるように添加し、マグネチックスターラーで24時間撹拌し、CNTの予備分散液を得た。
次いで、直径200μmの細管流路部を有する高圧分散処理部(ジェットミル)に連結して多段圧力制御装置(多段降圧器)を有する多段降圧型高圧ホモジナイザー(株式会社美粒製、製品名「BERYU SYSTEM PRO」)に充填し、断続的かつ瞬間的に120MPaの圧力を上記予備分散液に印加し、細管流路に送り込み分散処理を行い、CNT分散液を得た。
―混合工程―
上記CNT分散液とは別途に、有機溶媒としてのメチルエチルケトンに対して、絶縁材料としてのフッ素ゴム(デュポン社製、「Viton GBL200S」)を濃度が2%になるように添加し、撹拌してフッ素ゴムを溶解させて絶縁材料溶液を得た。
そして、かかる絶縁材料溶液と、上述のCNT分散液とを、絶縁材料であるフッ素ゴムと繊維状炭素ナノ構造体であるCNTとの配合量比率が100部:6部となるように混合し、電磁波吸収材料用スラリー組成物を調製した。
絶縁層としての成膜基材であるPETフィルム(東レ株式会社製、「ルミラー S10」、厚さ38μm)に対してスラリー組成物を塗布し、局所排気装置を備えた恒温環境のドラフト内で、25℃で、1週間以上自然乾燥して有機溶媒を充分揮発させた。得られた電磁波吸収体は、絶縁材料としてPETを含有してなる絶縁層に対して、絶縁材料としてのフッ素ゴムと、繊維状炭素ナノ構造体としてのCNTとを含有する電磁波吸収層が、直接適用された単層型の電磁波吸収体である。かかる電磁波吸収体について、上述の方法に従って、電磁波吸収層の厚さ及び電磁波吸収体の反射減衰量を測定した。結果を表3に示す。さらに、電磁波吸収体について上述の方法により透過減衰量を測定したところ、60GHzで7dB、76GHzで7dBであった。
電磁波吸収層の絶縁材料としてフッ素ゴムに代えて未架橋の水素化アクリロニトリルブタジエンゴム(HNBR、日本ゼオン株式会社製、「Zetpol 2001」)を用い、絶縁材料であるHNBRと繊維状炭素ナノ構造体であるCNTとの配合量比率を表3に示す通りに変更した以外は実施例3-1と同様にして、スラリー組成物を調製し、電磁波吸収材料を形成した。得られた電磁波吸収材料について、引張破断ひずみの測定及び柔軟性の評価を行った。結果を表3に示す。
そして、かかるスラリー組成物を用いて電磁波吸収体を製造するにあたり、電磁波吸収層の層厚を表3に示すように変更した以外は実施例3-1と同様にして、得られた電磁波吸収体について各種測定を実施した。得られた電磁波吸収体の透過減衰量は、60GHzで16dB、76GHzで15dBであった。その他の測定結果は、表3に示す。
電磁波吸収層の絶縁材料としてフッ素ゴムに代えて未架橋のアクリロニトリルブタジエンゴム(NBR、日本ゼオン株式会社製、「Nipol N3350」)を用い、絶縁材料であるNBRと繊維状炭素ナノ構造体であるCNTとの配合量比率を表3に示す通りに変更した以外は実施例3-1と同様にして、スラリー組成物を調製し、電磁波吸収材料を形成した。得られた電磁波吸収材料について、引張破断ひずみの測定及び柔軟性の評価を行った。結果を表3に示す。
そして、かかるスラリー組成物を用いて電磁波吸収体を製造するにあたり、電磁波吸収層の層厚を表3に示すように変更した以外は実施例3-1と同様にして、得られた電磁波吸収体について各種測定を実施した。得られた電磁波吸収体の透過減衰量は、60GHzで18dB、76GHzで18dBであった。その他の測定結果は、表3に示す。
電磁波吸収層の絶縁材料としてフッ素ゴムに代えて未架橋のアクリルゴム(日本ゼオン株式会社製、「Nipol AR12」)を用い、絶縁材料であるアクリルゴムと繊維状炭素ナノ構造体であるCNTとの配合量比率を表3に示す通りに変更した以外は実施例3-1と同様にして、スラリー組成物を調製し、電磁波吸収材料を形成した。得られた電磁波吸収材料について、引張破断ひずみの測定及び柔軟性の評価を行った。結果を表3に示す。
そして、かかるスラリー組成物を用いて電磁波吸収体を製造するにあたり、電磁波吸収層の層厚を表3に示すように変更した以外は実施例3-1と同様にして、得られた電磁波吸収体について各種測定を実施した。得られた電磁波吸収体の透過減衰量は、60GHzで11dB、76GHzで10dBであった。その他の測定結果は、表3に示す。
<電磁波吸収材料の製造>
電磁波吸収体として、多層型電磁波吸収体を製造した。ここで、多層系の各層を構成する電磁波吸収層の形成に用いるスラリー組成物を区別するために、実施例3-1と同様にして調製したスラリー組成物を第1のスラリー組成物と称することとする。そして、絶縁材料であるフッ素ゴムと繊維状炭素ナノ構造体であるCNTとの配合量比率が100部:1部となるように変更した以外は実施例3-1と同様にして第2のスラリー組成物を調製した。
そして、かかる第1及び第2のスラリー組成物を用いて電磁波吸収体を製造するにあたり、まず、絶縁層としての成膜基材であるPETフィルム(東レ株式会社製、「ルミラー S10」、厚さ38μm)に対して、上記第2のスラリー組成物を塗布し、局所排気装置を備えた恒温環境のドラフト内で、25℃で、1週間以上自然乾燥して有機溶媒を充分揮発させた。第2のスラリー組成物を用いて形成された電磁波吸収層(以下、「第2の電磁波吸収層」ともいう)の厚さを、上述の測定方法に従って測定した。結果を表3に示す。
そして、同様にして、第2の電磁波吸収層上に、上記第1のスラリー組成物を用いて電磁波吸収層(以下、「第1の電磁波吸収層」ともいう)を形成した。得られた絶縁層、第2の電磁波吸収層、及び第1の電磁波吸収層が相互に隣接してなる電磁波吸収体について上述した測定方法とほぼ同様にして電磁波吸収層の厚さを測定したが、測定した電磁波吸収体の全厚みから、絶縁層及び第2の電磁波吸収層の厚さを差し引いて、第1の電磁波吸収層の厚さとした。
また、得られた電磁波吸収体の反射減衰量及び透過減衰量を実施例3-1と同様にして測定した。得られた電磁波吸収体の透過減衰量は、60GHzで14dB、76GHzで13dBであった。反射減衰量の測定結果は、表3に示す。
絶縁材料であるフッ素ゴムと繊維状炭素ナノ構造体である多層カーボンナノチューブとの配合量比率を表3に示す通りに変更した以外は実施例3-1と同様にして、スラリー組成物を調製し、電磁波吸収材料を形成した。得られた電磁波吸収材料について、引張破断ひずみの測定及び柔軟性の評価を行った。結果を表3に示す。
そして、かかるスラリー組成物を用いて電磁波吸収体を製造するにあたり、電磁波吸収層の層厚を表3に示すように変更した以外は実施例3-1と同様にして、得られた電磁波吸収体について各種測定を実施した。得られた電磁波吸収体の透過減衰量は、比較例3-1では60GHzで3dB、76GHzで2dBであり、比較例3-2では、60GHzで21dB、76GHzで0dBであった。その他の測定結果は、表3に示す。
電磁波吸収層の繊維状炭素ナノ構造体に代えて、導電材料としてミルドカーボンファイバー(日本ポリマー産業株式会社製、「CFMP-30X」、平均繊維長:40μm、平均繊維径:7μm、t-プロットは不明)を用いた以外は実施例3-1と同様にして、スラリー組成物を調製し、電磁波吸収材料を形成した。得られた電磁波吸収材料について、引張破断ひずみの測定及び柔軟性の評価を行った。結果を表3に示す。
そして、かかるスラリー組成物を用いて電磁波吸収体を製造するにあたり、電磁波吸収層の層厚を表3に示すように変更した以外は実施例3-1と同様にして、得られた電磁波吸収体について各種測定を実施した。電磁波吸収体の透過減衰量は、60GHzで1dB、76GHzで1dBであった。その他の測定結果は、表3に示す。
電磁波吸収層の繊維状炭素ナノ構造体に代えて、導電材料としてカーボンブラック(Can carb社製、「サーマックスN990」、平均粒子径280nm、t-プロットは不明)を用いた以外は実施例3-1と同様にして、スラリー組成物を調製し、電磁波吸収材料を形成した。得られた電磁波吸収材料について、引張破断ひずみの測定及び柔軟性の評価を行った。結果を表3に示す。
そして、かかるスラリー組成物を用いて電磁波吸収体を製造するにあたり、電磁波吸収層の層厚を表3に示すように変更した以外は実施例3-1と同様にして、得られた電磁波吸収体について各種測定を実施した。電磁波吸収体の透過減衰量は、60GHzで0.3dB、76GHzで0.1dBであった。その他の測定結果は、表3に示す。
「HNBR」は水素化ニトリルゴムを、
「NBR」はニトリルゴムを、
「MWCNT」は多層カーボンナノチューブを、
「CFMP」はミルドカーボンファイバーを、
「PET」はポリエチレンテレフタレートをそれぞれ示す。
Claims (9)
- 繊維状炭素ナノ構造体と、絶縁材料と、を含み、
前記絶縁材料の含有量を100質量部としたときの前記繊維状炭素ナノ構造体の含有量Cが5質量部以上15質量部以下であるか、又は、
前記繊維状炭素ナノ構造体が吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合に、前記含有量Cが0.3質量部以上0.8質量部以下であり、
20GHz超の周波数領域の電磁波を吸収する電磁波吸収材料。 - 前記絶縁材料が絶縁性高分子であり、該絶縁性高分子は、
(a)熱可塑性樹脂及び/又は熱硬化性樹脂、
(b)ゴム及び/又はエラストマー、
の何れかである、請求項1に記載の電磁波吸収材料。 - 前記繊維状炭素ナノ構造体の含有量Cが5質量部以上15質量部以下である場合に、前記繊維状炭素ナノ構造体が多層カーボンナノチューブである、請求項1又は2に記載の電磁波吸収材料。
- 請求項1~3の何れかに記載の電磁波吸収材料を用いて形成した電磁波吸収層を備える電磁波吸収体。
- 繊維状炭素ナノ構造体と、絶縁材料とを含む電磁波吸収層を複数備え、
複数の前記電磁波吸収層の各層に含有される繊維状炭素ナノ構造体及び/又は絶縁材料は、同一又は相異なる種類であり、
複数の前記電磁波吸収層を、電磁波の入射側に遠い側から、第1電磁波吸収層、第2電磁波吸収層・・・、第n電磁波吸収層とし、
複数の前記電磁波吸収層の各層における、前記絶縁材料の含有量を100質量部としたときの前記繊維状炭素ナノ構造体の含有量を、それぞれ、A1質量部,A2質量部,・・・An質量部とした場合に、
下記条件(1-1)又は(1-2)、及び(2)又は(3)が成立し、
5≦A1≦15 ・・・(1-1)
前記繊維状炭素ナノ構造体が吸着等温線から得られるt-プロットが上に凸な形状を示す繊維状炭素ナノ構造体である場合に、0.3≦A1≦0.8 ・・・(1-2)
nが2の場合、A1>A2 ・・・(2)
nが3以上の自然数の場合、A1>A2≧・・・≧An ・・・(3)
さらに、電磁波吸収体を構成する全ての層のうち、第1電磁波吸収層における繊維状炭素ナノ構造体の含有量が最も多い、電磁波吸収体。 - 前記絶縁材料が絶縁性高分子であり、該絶縁性高分子は、
(a)熱可塑性樹脂及び/又は熱硬化性樹脂、
(b)ゴム及び/又はエラストマー、
の何れかである請求項5に記載の電磁波吸収体。 - 前記条件(1-1)が成立する場合に、前記繊維状炭素ナノ構造体が、多層カーボンナノチューブである、請求項5又は6に記載の電磁波吸収体。
- 前記電磁波の入射側の最表面に、絶縁層を更に備える、請求項4~7の何れかに記載の電磁波吸収体。
- 総厚みが1μm以上500μm以下である、請求項4~8の何れかに記載の電磁波吸収体。
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Publication number | Priority date | Publication date | Assignee | Title |
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JP2019036585A (ja) * | 2017-08-10 | 2019-03-07 | 東洋インキScホールディングス株式会社 | 真空成形用電磁波シールド積層体、およびこれを用いた電磁波シールド成形体 |
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WO2020244994A1 (en) | 2019-06-05 | 2020-12-10 | Basf Se | Electromagnetic wave transmission reducing material |
JP2021534265A (ja) * | 2018-06-27 | 2021-12-09 | カール・フロイデンベルク・カー・ゲー | 電磁放射線遮蔽用組成物 |
US20220071068A1 (en) * | 2019-01-28 | 2022-03-03 | Zeon Corporation | Electromagnetic wave absorbing sheet |
WO2022112524A1 (en) | 2020-11-30 | 2022-06-02 | Basf Se | Electromagnetic waves absorbing material |
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Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008126690A1 (ja) * | 2007-03-29 | 2008-10-23 | Kabushiki Kaisha Asahi Rubber | 電磁波シールドシート及びrfidプレート |
JP2009155593A (ja) * | 2007-12-28 | 2009-07-16 | Mitsubishi Rayon Co Ltd | カーボンナノチューブ含有組成物および硬化物 |
JP2015105213A (ja) * | 2013-11-29 | 2015-06-08 | 日本ゼオン株式会社 | カーボンナノチューブ及びその分散液、並びに自立膜及び複合材料 |
WO2015093600A1 (ja) * | 2013-12-20 | 2015-06-25 | 株式会社クラレ | 電磁波吸収体およびその製造方法 |
Family Cites Families (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003158395A (ja) | 2001-11-22 | 2003-05-30 | Kansai Research Institute | 電磁波吸収材料 |
WO2003054087A2 (en) * | 2001-12-19 | 2003-07-03 | E.I. Du Pont De Nemours And Company | Polyamide resin compositions with electromagnetic interference shielding properties and articles formed therefrom |
JP2004356352A (ja) * | 2003-05-28 | 2004-12-16 | Kyocera Corp | 高周波回路用パッケージ |
EP3181518A1 (en) | 2004-07-27 | 2017-06-21 | National Institute of Advanced Industrial Science and Technology | Aligned single-walled carbon nanotube bulk structure, production process and use |
CN1791322A (zh) * | 2005-10-18 | 2006-06-21 | 南开大学 | 一种兼具电磁屏蔽及雷达吸波功能的复合材料及制备方法 |
TW200800606A (en) * | 2006-06-29 | 2008-01-01 | Shiu Li Technology Co Ltd | Multi-layered composite capable of conducting heat and absorbing electromagnetic wave and manufacturing method thereof |
JP5424606B2 (ja) | 2008-10-01 | 2014-02-26 | 日本バルカー工業株式会社 | ノイズ抑制体とその製造方法 |
CA2758570A1 (en) * | 2009-04-24 | 2010-12-16 | Applied Nanostructured Solutions, Llc | Cnt-based signature control material |
CN101805491B (zh) * | 2009-09-22 | 2012-07-25 | 漳州市奈特新型建材有限责任公司 | 一种具有电磁波遮蔽效果的复合材料及其制备方法 |
FR2975219B1 (fr) | 2011-05-11 | 2014-10-31 | Arkema France | Procede de fabrication d'un materiau absorbant les radiations d'ondes electromagnetiques, comprenant des nanoparticules de carbone, et materiau obtenu par le procede. |
JP2013021260A (ja) * | 2011-07-14 | 2013-01-31 | Sony Corp | 電磁波吸収材及びその製造方法、フレキシブルプリント配線板、並びに、電子機器 |
JP6481612B2 (ja) * | 2013-06-13 | 2019-03-13 | 住友ベークライト株式会社 | 電磁波シールド用フィルム、および電子部品搭載基板 |
CN105658573A (zh) * | 2013-10-31 | 2016-06-08 | 日本瑞翁株式会社 | 碳纳米管 |
-
2016
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- 2016-12-22 KR KR1020187016960A patent/KR102575899B1/ko active IP Right Grant
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Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2008126690A1 (ja) * | 2007-03-29 | 2008-10-23 | Kabushiki Kaisha Asahi Rubber | 電磁波シールドシート及びrfidプレート |
JP2009155593A (ja) * | 2007-12-28 | 2009-07-16 | Mitsubishi Rayon Co Ltd | カーボンナノチューブ含有組成物および硬化物 |
JP2015105213A (ja) * | 2013-11-29 | 2015-06-08 | 日本ゼオン株式会社 | カーボンナノチューブ及びその分散液、並びに自立膜及び複合材料 |
WO2015093600A1 (ja) * | 2013-12-20 | 2015-06-25 | 株式会社クラレ | 電磁波吸収体およびその製造方法 |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2019036585A (ja) * | 2017-08-10 | 2019-03-07 | 東洋インキScホールディングス株式会社 | 真空成形用電磁波シールド積層体、およびこれを用いた電磁波シールド成形体 |
JP2021534265A (ja) * | 2018-06-27 | 2021-12-09 | カール・フロイデンベルク・カー・ゲー | 電磁放射線遮蔽用組成物 |
US20220071068A1 (en) * | 2019-01-28 | 2022-03-03 | Zeon Corporation | Electromagnetic wave absorbing sheet |
WO2020244995A1 (en) | 2019-06-05 | 2020-12-10 | Basf Se | Electromagnetic waves absorbing material |
WO2020244994A1 (en) | 2019-06-05 | 2020-12-10 | Basf Se | Electromagnetic wave transmission reducing material |
WO2022112524A1 (en) | 2020-11-30 | 2022-06-02 | Basf Se | Electromagnetic waves absorbing material |
CN114684802A (zh) * | 2022-03-25 | 2022-07-01 | 华东理工大学 | 一种磁性铁-钴-镍合金/碳系列复合吸波材料及其制备方法和应用 |
CN114684802B (zh) * | 2022-03-25 | 2023-08-11 | 华东理工大学 | 一种磁性铁-钴-镍合金/碳系列复合吸波材料及其制备方法和应用 |
Also Published As
Publication number | Publication date |
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CN108370654B (zh) | 2020-02-07 |
CN108370654A (zh) | 2018-08-03 |
KR102575899B1 (ko) | 2023-09-06 |
TWI726963B (zh) | 2021-05-11 |
JPWO2017110096A1 (ja) | 2018-10-11 |
EP3397039A1 (en) | 2018-10-31 |
KR20180098547A (ko) | 2018-09-04 |
JP6950533B2 (ja) | 2021-10-13 |
US20180370197A1 (en) | 2018-12-27 |
TW201801601A (zh) | 2018-01-01 |
EP3397039A4 (en) | 2019-09-11 |
US11235560B2 (en) | 2022-02-01 |
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