Electromagnetic wave absorbing material

Abstract

To provide an electromagnetic wave absorbing material that has excellent curved surface followability and maintains electromagnetic wave absorbing properties after a heat resistance test.SOLUTION: An electromagnetic wave absorbing material 10 includes an electromagnetic wave absorption layer 20, a spacer layer 30, and a reflective layer 40, and the electromagnetic wave absorbing layer 20, the spacer layer 30, and the reflective layer 40 are laminated in this order, and the relative permittivity of the spacer layer 30 is 5 or more, and the melting point of the spacer layer 30 is 150°C or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave absorbing member. [Background technology]

[0002] There is known a sheet-like electromagnetic wave absorbing member that selectively absorbs electromagnetic waves of a predetermined frequency. The electromagnetic wave absorbing member, for example, comprises a first frequency selective shielding layer and a second frequency selective shielding layer. In such an electromagnetic wave absorbing member, each layer absorbs electromagnetic waves of a predetermined frequency by the fine line patterns of FSS (Frequency Selective Surface) elements formed on the first frequency selective shielding layer and the second frequency selective shielding layer, and as a whole, the electromagnetic wave absorbing member selectively shields electromagnetic waves of two different frequencies.

[0003] Depending on the application, the electromagnetic wave absorbing member is required to adhere closely to the curved surface when attached to the curved surface.

[0004] Patent Document 1 describes an electromagnetic wave absorbing member in which the product of the Young's modulus and the thickness of the magnetic layer is 0.1 to 1000 MPa mm, and the relative dielectric constant of the magnetic layer is 1 to 10, making it easy to attach to uneven surfaces. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-4003 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the electromagnetic wave absorbing member described in Patent Document 1 has excellent curved surface conformability, it has a problem in that it is poor at maintaining electromagnetic wave absorbing properties after a heat resistance test.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide an electromagnetic wave absorbing member that is excellent in curved surface conformability and in maintaining electromagnetic wave absorbing properties after a heat resistance test. [Means for solving the problem]

[0008] The present invention provides the following electromagnetic wave absorbing member. [1] An electromagnetic wave absorbing layer, a spacer layer, and a reflective layer; the electromagnetic wave absorbing layer, the spacer layer, and the reflective layer are laminated in this order; The spacer layer has a relative dielectric constant of 5 or more, The spacer layer has a melting point of 150° C. or higher. [2] The electromagnetic wave absorbing member according to [1], wherein the spacer layer has a thickness of 200 μm or more and 450 μm or less. [3] The electromagnetic wave absorbing member according to [1], wherein the spacer layer has a Young's modulus of 50 MPa or more. [4] Bending stiffness: 300 N·mm 2 The electromagnetic wave absorbing member according to [1], Effect of the Invention

[0009] According to the present invention, it is possible to provide an electromagnetic wave absorbing member that is excellent in curved surface conformability and in maintaining electromagnetic wave absorbing properties after a heat resistance test. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a surface along the thickness direction of an electromagnetic wave absorbing member according to an embodiment of the present invention; [Diagram 2] 1 is a top view showing an example of an electromagnetic wave absorbing layer constituting an electromagnetic wave absorbing member according to an embodiment of the present invention. [Diagram 3] 1 is a schematic diagram showing a method for measuring the bending rigidity of an electromagnetic wave absorbing member according to one embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The electromagnetic wave absorbing member of the present invention will be specifically described to allow a better understanding of the gist of the invention, and unless otherwise specified, is not intended to limit the present invention.

[0012] In this specification, the term "electromagnetic wave absorbing pattern" refers to an object that is a collection of geometrically shaped units and selectively absorbs electromagnetic waves of a certain frequency. The "electromagnetic wave absorbing pattern" can be said to have the same function as an antenna. In this specification, the term "electromagnetic waves in the millimeter wave region" refers to electromagnetic waves with a wavelength of 1 mm to 10 mm. The term "electromagnetic waves in the millimeter wave region" can also be said to be electromagnetic waves with a frequency of 30 GHz to 300 GHz. In this specification, the use of "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower limit and upper limit.

[0013] [Electromagnetic wave absorbing material] FIG. 1 is a cross-sectional view of a surface along the thickness direction of an electromagnetic wave absorbing member according to one embodiment of the present invention. 1, the electromagnetic wave absorbing member 10 of this embodiment includes an electromagnetic wave absorbing layer 20, a spacer layer 30, and a reflective layer 40. The electromagnetic wave absorbing layer 20, the spacer layer 30, and the reflective layer 40 are laminated in this order.

[0014] The reflective layer 40 is disposed on the other surface (rear surface) 20b side of the electromagnetic wave absorbing layer 20. The spacer layer 30 is disposed between the electromagnetic wave absorbing layer 20 and the reflective layer 40. That is, the electromagnetic wave absorbing layer 20 and the reflective layer 40 are laminated with the spacer layer 30 interposed therebetween.

[0015] The electromagnetic wave absorbing layer 20 may be a single layer, or may include a substrate 21 and an electromagnetic wave absorbing pattern 22 formed on the substrate 21 as shown in FIG. When the electromagnetic wave absorbing layer 20 is a single layer, the electromagnetic wave absorbing layer 20 is made of the same material as the electromagnetic wave absorbing pattern 22 described later.

[0016] In the electromagnetic wave absorbing member 10 of this embodiment, the spacer layer 30 has a relative dielectric constant of 5 or more, preferably 7 or more, more preferably 8 or more, and particularly preferably 9 or more. If the relative dielectric constant of the spacer layer 30 is less than the lower limit, the thickness of the spacer layer 30 becomes large. If the relative dielectric constant of the spacer layer 30 is 5 or more, the thickness of the spacer layer 30 can be reduced. This allows the electromagnetic wave absorbing member 10 to have excellent curved surface conformability. The upper limit of the dielectric constant of the spacer layer 30 may be 30 or less, 25 or less, 20 or less, or 15 or less, in order to prevent the Young's modulus of the spacer layer 30 from becoming too high.

[0017] The relative dielectric constant of the spacer layer 30 can be measured by the method described in the examples below.

[0018] In the electromagnetic wave absorbing member 10 of this embodiment, the melting point of the spacer layer 30, i.e., the melting point of the material constituting the spacer layer 30, is 150°C or higher, preferably 160°C or higher, and more preferably 170°C or higher. If the melting point of the spacer layer 30 is below the lower limit, the relative dielectric constant changes after a heat resistance test, resulting in a decrease in performance. From the viewpoint of preventing the Young's modulus of the spacer layer 30 from becoming too high, the upper limit of the melting point of the spacer layer 30 may be 400°C or lower, 300°C or lower, 240°C or lower, or 190°C or lower.

[0019] The melting point of the spacer layer 30 can be measured by the method described in the examples below.

[0020] In the electromagnetic wave absorbing member 10 of this embodiment, the thickness of the spacer layer 30 is preferably 200 μm or more and 450 μm or less, more preferably 250 μm or more and 400 μm or less, and particularly preferably 300 μm or more and 340 μm or less. When the thickness of the spacer layer 30 is equal to or more than the lower limit, it is easy to obtain a spacer layer 30 having a high relative dielectric constant. When the thickness of the spacer layer 30 is equal to or less than the upper limit, bending rigidity is low and curved surface conformability is improved.

[0021] When the wavelength shortening effect of the spacer layer 30 is taken into consideration, the thickness of the spacer layer 30 is appropriately changed according to the wavelength of the electromagnetic wave to be absorbed and the relative dielectric constant of the spacer layer 30 . When the wavelength shortening effect of the spacer layer 30 is taken into consideration, the thickness of the spacer layer 30 preferably satisfies the following formula (1). (Thickness of spacer layer 30)=(λ)×(1 / 4) / (ε) 1 / 2 ...Equation (1) In the above formula (1), λ is the wavelength of the incident electromagnetic wave, and ε is the relative dielectric constant of the spacer layer 30. The thickness of the spacer layer 30 may be appropriately adjusted for absorption characteristics. For example, it can be changed within a range of 0.1 to 3.0 times the thickness of the spacer layer 30 obtained by formula (1).

[0022] When the relationship between the thickness of the spacer layer 30 and the wavelength λ satisfies the above formula (1), the electromagnetic wave absorbing member 10 has a so-called λ / 4 structure, which further increases the maximum absorption amount of the electromagnetic wave by the electromagnetic wave absorbing member 10. The thickness of the spacer layer 30 can be appropriately set within the range of 200 μm to 450 μm inclusive according to the wavelength λ of the electromagnetic wave to be absorbed. The spacer layer 30 may be made of a material having a high dielectric constant. If the spacer layer 30 is a layer having a high dielectric constant, the thickness of the spacer layer 30 can be made relatively thin. When the dielectric constant of the spacer layer 30 is taken into consideration, the spacer layer 30 preferably contains at least one selected from the group consisting of barium titanate, titanium oxide, and strontium titanate.

[0023] The thickness of the spacer layer 30 can be measured by a constant pressure thickness gauge manufactured by Teclock Corporation.

[0024] The Young's modulus of the spacer layer 30 is preferably 1000 MPa or less, more preferably 600 MPa or less, and even more preferably 400 MPa or less. When the Young's modulus of the spacer layer 30 is equal to or less than the upper limit, the curved surface conformability is improved. From the viewpoint of shape retention, the lower limit of the Young's modulus of the spacer layer 30 may be 50 MPa or more, 100 MPa or more, or 200 MPa or more.

[0025] The Young's modulus of the spacer layer 30 can be measured in accordance with JIS K7127:1999 "Plastics-Test methods for tensile properties-Part 3: Test conditions for films and sheets".

[0026] The electromagnetic wave absorbing member 10 of this embodiment has a bending rigidity of 240 N mm 2 It is preferable that the load is less than 180 N mm 2 It is preferable that it is less than 100 N mm 2 When the bending rigidity of the electromagnetic wave absorbing member 10 is equal to or less than the upper limit, the ability to conform to a curved surface is improved. From the viewpoint of shape retention, the lower limit of the bending rigidity of the electromagnetic wave absorbing member 10 is 10 N mm 2 It may be more than 30N mm 2 It may be more than 60N·mm 2 It may be more than that.

[0027] The bending rigidity of the electromagnetic wave absorbing member 10 can be measured by the method described in the examples below.

[0028] Moreover, the total thickness of the electromagnetic wave absorbing member 10 of this embodiment (the total thickness from the outermost surface of the electromagnetic wave absorbing layer, i.e., the surface of the electromagnetic wave absorbing pattern 22 (one surface (surface) 20a of the electromagnetic wave absorbing layer 20) to the surface (other surface) 40b on the installation surface side of the reflective layer 40) is preferably 350 μm to 800 μm, more preferably 400 μm to 600 μm, and particularly preferably 450 μm to 520 μm, from the viewpoint of achieving both curved surface conformability and electromagnetic wave absorption properties.

[0029] "Electromagnetic wave absorbing layer" The electromagnetic wave absorbing layer 20 is made of a frequency selective surface (FSS). A frequency selective surface is a surface that can block only electromagnetic waves of a specific frequency by forming a continuous structure of a shape smaller than the wavelength using a conductive material or the like.

[0030] Fig. 2 is a top view showing an example of an electromagnetic wave absorbing layer in this embodiment. As shown in Fig. 2, the electromagnetic wave absorbing layer 20 is an electromagnetic wave absorbing film having a flat substrate 21 and an electromagnetic wave absorbing pattern 22 formed on one surface 21a of the substrate 21. The electromagnetic wave absorbing pattern 22 is composed of a first electromagnetic wave absorbing pattern 51, a second electromagnetic wave absorbing pattern 52, and a third electromagnetic wave absorbing pattern 53.

[0031] The Young's modulus of the electromagnetic wave absorbing layer 20 is preferably 10 GPa or less, more preferably 7 GPa or less, and even more preferably 5 GPa or less. When the Young's modulus of the electromagnetic wave absorbing layer 20 is equal to or less than the upper limit, the bending rigidity is reduced and the curved surface conformability is improved. From the viewpoint of shape retention, the lower limit of the Young's modulus of the electromagnetic wave absorbing layer 20 may be 0.5 GPa or more, 1 GPa or more, or 3 GPa or more.

[0032] The Young's modulus of the electromagnetic wave absorbing layer 20 can be measured in accordance with JIS K7127:1999 "Plastics-Test methods for tensile properties-Part 3: Test conditions for films and sheets".

[0033] (First electromagnetic wave absorption pattern) 2, the first electromagnetic wave absorbing pattern 51 is composed of a plurality of first units u1. Each of the first units u1 is a geometrical figure. In other words, the first electromagnetic wave absorbing pattern 51 can be said to be an assembly of first units u1 which are geometric figures. Each of the first units u1 functions as an antenna. The first electromagnetic wave absorbing pattern 51 may be, for example, a fine line pattern of an FSS element.

[0034] In the first electromagnetic wave absorbing pattern 51, a plurality of first arrays R1 are formed, in which a plurality of first units u1 are arranged along the direction indicated by the double-headed arrow P in Fig. 2. It can also be said that the first electromagnetic wave absorbing pattern 51 has a plurality of first arrays R1. The first electromagnetic wave absorbing pattern 51 can be configured by forming a plurality of first arrays R1 on the substrate 21 at predetermined intervals along the direction indicated by the double-headed arrow P. The intervals between the multiple first arrays R1 are not particularly limited, and the intervals between the multiple first arrays R1 may be regular or irregular.

[0035] As shown in Fig. 2, the first unit u1 has a cross shape that is symmetrical in the vertical and horizontal directions. Specifically, the first unit u1 has one cross portion S1 and four end portions T1. The cross portion S1 is composed of a straight line portion parallel to the x-axis direction in Fig. 2 and a straight line portion parallel to the y-axis direction. Straight line end portions T1 contact both ends of the straight line portion parallel to the x-axis direction and both ends of the straight line portion parallel to the y-axis direction so as to be perpendicular to each straight line portion.

[0036] By adjusting the length of the first unit u1 in the x-axis direction and the length of each of the four ends T1 in the x-axis direction, the electromagnetic wave absorption characteristics of the first unit u1 functioning as one antenna can be adjusted. Similarly, the electromagnetic wave absorption characteristics can be adjusted in the y-axis direction.

[0037] However, the shape of the first unit is not limited to a cross shape. The shape of the first unit is not particularly limited as long as the frequency value at which the amount of electromagnetic wave absorbed by the first electromagnetic wave absorbing pattern 51 shows a maximum value is A [GHz]. For example, examples of the shape of the figure that is the first unit include a circle, an annular shape, a straight line, a square, a polygon, an H-shape, a Y-shape, a V-shape, and the like.

[0038] In the electromagnetic wave absorbing layer 20, the shapes of the multiple first units u1 are the same. However, the shapes of the multiple first units u1 do not have to be the same figures. In another example of the present invention, the shapes of the multiple first units may be the same or different as long as the absorption characteristics can be adjusted to a target frequency.

[0039] The first electromagnetic wave absorbing pattern 51 selectively absorbs an electromagnetic wave having a frequency of A [GHz]. The frequency value A [GHz] is the frequency value at which the amount of electromagnetic wave absorbed by the first electromagnetic wave absorbing pattern 51 exhibits a maximum value in the range of 20 GHz to 110 GHz. The frequency value A [GHz] at which the amount of electromagnetic wave absorbed by the first electromagnetic wave absorbing pattern 51 exhibits a maximum value can be specified by, for example, the following method X.

[0040] Method X: Electromagnetic waves are irradiated onto a standard film described below while changing the frequency within the range of 20 GHz to 110 GHz, and the frequency of the electromagnetic waves at which the amount of electromagnetic waves absorbed by the standard film is maximum is defined as A [GHz].

[0041] The standard film has a flat standard substrate and a standard pattern formed on the standard substrate. Details of the standard substrate can be the same as those of the substrate 21. Therefore, details of the standard substrate will be described in detail in the description of the substrate 21 below.

[0042] The standard pattern consists of only a number of standard units whose shapes are identical to each other. In the case of a standard film, it can be said that a standard pattern consisting of only one type of shape whose shapes are identical is formed on a standard substrate. The standard pattern can be formed by a fine line pattern of a normal FSS element. Usually, the standard pattern is the same electromagnetic wave absorbing pattern as the first electromagnetic wave absorbing pattern 51 (same shape as unit u1).

[0043] In a standard film, multiple standard units are arranged on a standard substrate so that the distance between the ends of the figure is 1 mm. For example, if the figure of the standard unit is a cross, the intersection of the cross is the center of the figure, and the ends of the figure are the parts that are farthest from the center along each of the directions of the two straight lines that make up the cross.

[0044] The material of the standard unit constituting the standard pattern is not particularly limited as long as it is such that when the standard film is irradiated with electromagnetic waves varying within the range of 20 GHz to 110 GHz, the amount of electromagnetic waves absorbed by the standard film can reach a maximum value. The material details of the standard unit may be the same as those of the first unit.

[0045] The amount of electromagnetic radiation absorbed by a standard film can be calculated using the following formula (1). Absorption = input signal – reflection characteristic (S11) – transmission characteristic (S21) (1) The input signal is a measure of the intensity of the electromagnetic wave at the source when the electromagnetic wave is irradiated onto a standard film. The reflection characteristic (S11) is an index of the intensity of the electromagnetic wave reflected by the standard film when the standard film is irradiated with electromagnetic waves from an irradiation source. The reflection characteristic (S11) can be measured by the free space method using, for example, a vector network analyzer. The transmission characteristic (S21) is an index of the intensity of the electromagnetic wave that passes through the standard film when the standard film is irradiated with electromagnetic waves from an irradiation source. The transmission characteristic (S21) can be measured, for example, by the free space method using a vector network analyzer.

[0046] The frequency A [GHz] can be determined, for example, by the following method. First, a standard film is irradiated with electromagnetic waves while changing the frequency within a range of 20 GHz to 110 GHz, and the amount of electromagnetic waves absorbed by the standard film is calculated by the above formula (1). Next, an absorption spectrum is created by plotting the changed frequency on the horizontal axis and the absorption calculated by the above formula (1) on the vertical axis. Usually, in this absorption spectrum, there is one frequency value on the horizontal axis at which the absorption is maximum. Therefore, a single peak is formed on the plot where the absorption of the electromagnetic wave is at a local maximum. In this way, the frequency of the electromagnetic wave at which the absorption of the electromagnetic wave is at its maximum can be determined as A [GHz].

[0047] In method X, when the value of frequency A can be predicted in advance, the frequency of the electromagnetic wave irradiated to the standard film may be changed within a range narrower than 20 GHz to 110 GHz. For example, the frequency of the electromagnetic wave irradiated to the standard film may be changed within a range of 50 GHz to 110 GHz.

[0048] The first electromagnetic wave absorbing pattern 51 absorbs electromagnetic waves having a frequency of A [GHz] specified by the above-mentioned method X. In the electromagnetic wave absorbing layer 20 of this embodiment, the frequency value A is preferably 20 GHz to 110 GHz, more preferably 60 GHz to 100 GHz, further preferably 65 GHz to 95 GHz, and particularly preferably 70 GHz to 90 GHz. When the frequency value A is within the above numerical range, the electromagnetic wave absorbing layer 20 can absorb electromagnetic waves in the millimeter wave region, and can be easily applied to automobile parts, road peripheral members, building exterior wall related materials, windows, communication devices, radio telescopes, etc.

[0049] The material of the first unit u1 is not particularly limited as long as the absorption characteristics can be adjusted to a desired frequency. Examples of the material of the first unit include thin metal wires, conductive thin films, and conductive paste deposits. Examples of the metal material include copper, aluminum, tungsten, iron, molybdenum, nickel, titanium, silver, gold, and alloys containing two or more of these metals (for example, steels such as stainless steel and carbon steel, brass, phosphor bronze, zirconium-copper alloy, beryllium copper, iron-nickel, nichrome, nickel-titanium, Kanthal, Hastelloy, rhenium-tungsten, etc.). Examples of materials for the conductive thin film include metal particles, carbon nanoparticles, and carbon fibers.

[0050] The distance between the ends of the figure that is the first unit u1 is not particularly limited as long as the absorption characteristics can be adjusted to a desired frequency. For example, the intervals between the ends of the figures that are the first units u1 may all be the same or may be different from each other. However, it is preferable that the intervals between the ends of the figures that are the first units u1 are the same from the viewpoint of making it easier to design an electromagnetic-wave-absorbing film that is less susceptible to the effects of the surrounding environment and improving the precision of the frequency band of the electromagnetic waves that are absorbed during manufacturing.

[0051] (Second electromagnetic wave absorption pattern) As shown in FIG. 2, the second electromagnetic wave absorbing pattern 52 is composed of a plurality of second units u2. The second electromagnetic wave absorbing pattern 52 is formed in the same manner as the first electromagnetic wave absorbing pattern 51 .

[0052] The second electromagnetic wave absorbing pattern 52 selectively absorbs electromagnetic waves having a frequency of B [GHz] that satisfies the following formula (2). The frequency value B [GHz] is the frequency value when the amount of electromagnetic waves absorbed by the second electromagnetic wave absorbing pattern 52 shows a maximum value. The frequency value B [GHz] satisfies the following formula (2). 1.037×A≦B≦1.30×A...Equation (2)

[0053] As shown in the above formula (2), the second electromagnetic wave absorbing pattern 52 absorbs electromagnetic waves having a frequency of 1.037×A [GHz] to 1.30×A [GHz]. It is preferable that the second electromagnetic wave absorbing pattern 52 absorbs electromagnetic waves having a frequency of 1.17×A [GHz] to 1.30×A [GHz]. Since the second electromagnetic wave absorbing pattern 52 absorbs electromagnetic waves with frequencies of 1.037×A [GHz] or more, in a frequency band higher than A [GHz], the peak of the amount of electromagnetic waves absorbed by the second electromagnetic wave absorbing pattern 52 and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorbing pattern 51 sufficiently overlap each other. As a result, the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorbing film is expanded to a frequency band higher than A [GHz], compared with a film having only the first electromagnetic wave absorbing pattern 51. Since the second electromagnetic wave absorbing pattern 52 absorbs electromagnetic waves with frequencies of 1.30×A [GHz] or less, in a frequency band higher than A [GHz], the difference in frequency between the peak of the amount of electromagnetic waves absorbed by the second electromagnetic wave absorbing pattern 52 and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorbing pattern 51 becomes small. As a result, a single peak is formed at which the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorbing film is maximized. As described above, since the second electromagnetic wave absorbing pattern 52 absorbs electromagnetic waves with frequencies of 1.037×A [GHz] to 1.30×A [GHz], the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorbing film is extended to the higher frequency band.

[0054] The material of the second unit constituting the second electromagnetic wave absorbing pattern 52 is not particularly limited as long as it can absorb electromagnetic waves of B [GHz], and is not particularly limited as long as the absorption characteristics can be adjusted to the desired frequency. The material of the second unit is the same as that described for the material of the first unit u1.

[0055] (Third electromagnetic wave absorption pattern) As shown in FIG. 2, the third electromagnetic wave absorbing pattern 53 is composed of a plurality of third units u3. The third electromagnetic wave absorbing pattern 53 is formed in the same manner as the first electromagnetic wave absorbing pattern 51 .

[0056] The third electromagnetic wave absorbing pattern 53 selectively absorbs an electromagnetic wave having a frequency C [GHz] that satisfies the following formula (3). The frequency value C [GHz] is the frequency value when the amount of electromagnetic wave absorbed by the third electromagnetic wave absorbing pattern 53 shows a maximum value. The frequency value C [GHz] satisfies the following formula (3). 0.60×A≦C≦0.963×A...Equation (3)

[0057] As shown in the above formula (3), the third electromagnetic wave absorbing pattern 53 absorbs electromagnetic waves having a frequency of 0.60×A [GHz] to 0.963×A [GHz]. It is preferable that the third electromagnetic wave absorbing pattern 53 absorbs electromagnetic waves having a frequency of 0.60×A [GHz] to 0.83×A [GHz]. Since the third electromagnetic wave absorbing pattern 53 absorbs electromagnetic waves with frequencies of 0.60×A [GHz] or more, in a frequency band lower than A [GHz], the frequency difference between the peak of the amount of electromagnetic waves absorbed by the third electromagnetic wave absorbing pattern 53 and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorbing pattern 51 becomes small. As a result, a single peak is formed at which the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorbing layer 20 is maximized. Since the third electromagnetic wave absorbing pattern 53 absorbs electromagnetic waves with frequencies of 0.963×A [GHz] or less, in a frequency band lower than A [GHz], the peak of the amount of electromagnetic waves absorbed by the third electromagnetic wave absorbing pattern 53 sufficiently overlaps with the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorbing pattern 51. As a result, the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorbing film is expanded to a frequency band lower than A [GHz], compared to a film having the first electromagnetic wave absorbing pattern 51 alone. As described above, since the third electromagnetic wave absorbing pattern 53 absorbs electromagnetic waves with frequencies of 0.60×A [GHz] to 0.963×A [GHz], the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorbing layer 20 is extended to the lower frequency band.

[0058] The material of the third unit u3 constituting the third electromagnetic wave absorbing pattern 53 is not particularly limited as long as it can absorb electromagnetic waves of C [GHz], and is not particularly limited as long as the absorption characteristics can be adjusted to the desired frequency. The material of the third unit u3 is the same as that described for the material of the first unit u1.

[0059] In the electromagnetic wave absorbing layer 20 shown in FIG. 2, the first array R1, the second array R2, and the third array R3 are arranged adjacent to each other along the direction indicated by the double-headed arrow P. In this manner, the first array R1, the second array R2, and the third array R3 are arranged adjacent to each other on the substrate 21, so that the frequency band of the electromagnetic wave selectively absorbed by the second electromagnetic wave absorbing pattern 52 and the frequency band of the electromagnetic wave selectively absorbed by the third electromagnetic wave absorbing pattern 53 overlap with each other, based on the frequency value A [GHz] of the peak position of the electromagnetic wave selectively absorbed by the first electromagnetic wave absorbing pattern 51. As a result, the absorption range of the electromagnetic wave absorbed by the entire electromagnetic wave absorbing layer 20 is easily expanded to both the high frequency side and the low frequency side, based on the frequency value A [GHz] of the peak position.

[0060] The distance d1 between the first unit u1 and the second unit u2, the distance d2 between the second unit u2 and the third unit u3, and the distance d3 between the third unit u3 and the first unit u1, each shown in FIG. 2, may be the same as or different from each other. The distance d1 may be, for example, 0.2 mm to 4 mm, 0.3 mm to 2 mm, or 0.5 mm to 1 mm. The distance d2 may be, for example, 0.2 mm to 4 mm, 0.3 mm to 2 mm, or 0.5 mm to 1 mm. The distance d3 may be, for example, 0.2 mm to 4 mm, 0.3 mm to 2 mm, or 0.5 mm to 1 mm. When the intervals d1, d2, and d3 are each within the above-mentioned numerical ranges, the absorption range of the electromagnetic waves absorbed by the entire electromagnetic wave absorbing layer 20 tends to be further expanded with the frequency value A [GHz] at the peak position as the reference.

[0061] In the electromagnetic wave absorbing layer 20, the first unit u1, the second unit u2, and the third unit u3 have the same shapes. However, the shapes of the first unit u1, the second unit u2, and the third unit u3 do not have to be the same figures. That is, in another example of the present invention, the shapes of the first unit u1, the second unit u2, and the third unit u3 may be the same or different from each other.

[0062] The base material 21 is not particularly limited as long as it has a flat plate shape and can form the first electromagnetic wave absorbing pattern 51, the second electromagnetic wave absorbing pattern 52, and the third electromagnetic wave absorbing pattern 53 on one surface 21a. The base material 21 may have a single-layer structure or a multi-layer structure.

[0063] The thickness of the substrate 21 may be, for example, 5 μm to 500 μm, 15 μm to 200 μm, or 25 μm to 100 μm. The thickness of the first electromagnetic wave absorbing pattern 51, the thickness of the second electromagnetic wave absorbing pattern 52, and the thickness of the third electromagnetic wave absorbing pattern 53 are not particularly limited. These thicknesses can be changed arbitrarily according to the desired characteristics. Furthermore, these three thicknesses may be the same or different from each other, and are preferably the same in consideration of productivity. From the viewpoint of achieving both electromagnetic wave absorption properties and curved surface conformability, the thicknesses of the first electromagnetic wave absorbing pattern 51, the second electromagnetic wave absorbing pattern 52, and the third electromagnetic wave absorbing pattern 53 are preferably 0.1 μm to 300 μm, more preferably 1 μm to 150 μm, and particularly preferably 10 μm to 80 μm.

[0064] The material of the substrate 21 can be appropriately selected depending on the application of the electromagnetic wave absorbing member 10 . For example, the base material 21 may be made of a transparent material in order to provide transparency to the electromagnetic wave absorbing member 10. Alternatively, the base material 21 may be made of a flexible material in order to provide conformability to the curved surface of the electromagnetic wave absorbing member 10. The surface of the base material 21 may be smoothed in order to improve the transparency and three-dimensional formability of the electromagnetic wave absorbing member 10.

[0065] For example, the base material 21 can be made of a resin. The resin may be a thermoplastic resin or a thermosetting resin. However, when the three-dimensional formability of the electromagnetic wave absorbing member 10 is taken into consideration, the base material 21 preferably contains a thermoplastic resin. Examples of thermoplastic resins include polyolefin resins, polyester resins, polyester-polyether resins, polyacrylic resins, polystyrene resins, polyimide resins, polyimideamide resins, polyamide resins, polyurethane resins, polycarbonate resins, polyarylate resins, melamine resins, epoxy resins, urethane resins, silicone resins, and fluororesins. Specific examples of polyolefin resins include polypropylene, polyethylene, etc. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.

[0066] The substrate 21 may contain optional components within the scope of not impairing the effects of the present invention. Examples of the optional components include inorganic fillers, colorants, curing agents, antioxidants, light stabilizers, flame retardants, conductive agents, antistatic agents, plasticizers, etc.

[0067] In consideration of further improving the electromagnetic wave absorbing performance of the electromagnetic wave absorbing member 10, the thickness, dielectric constant, electrical conductivity, and magnetic permeability of the substrate 21 can be appropriately set. When the electrical characteristics of the electromagnetic waves to be absorbed are taken into consideration, the substrate 21 may be a layer having a high dielectric constant. When the substrate 21 is a layer having a high dielectric constant, the thickness of the electromagnetic wave absorbing member 10 can be made relatively thin.

[0068] The electromagnetic wave absorbing layer 20 can be produced, for example, by the following method. First, a base material 21 is prepared. Next, a first electromagnetic wave absorbing pattern 51, a second electromagnetic wave absorbing pattern 52, and a third electromagnetic wave absorbing pattern 53 are formed on one surface 21a of the base material 21. When each electromagnetic wave absorbing pattern is formed, it is formed so that the frequency value at which the amount of electromagnetic waves absorbed by each electromagnetic wave absorbing pattern shows a maximum value is a predetermined value [GHz]. The order in which the electromagnetic wave absorbing patterns are formed is not particularly limited, and the electromagnetic wave absorbing patterns may be formed in the same process or in separate processes.

[0069] The method for forming each electromagnetic wave absorbing pattern is not particularly limited as long as it can form a predetermined frequency. Examples of the method for forming each electromagnetic wave absorbing pattern include the following methods. A printing method in which each electromagnetic wave absorbing pattern is printed on one surface 21a of the base material 21 using a conductive paste. A developing method for developing each electromagnetic wave absorbing pattern on one surface 21a of the base material 21. A method in which a thin metal film is provided on one surface 21a of the base material 21 by sputtering, vacuum deposition, or lamination of metal foil, and a pattern of the thin metal film is formed on one surface 21a of the base material 21 by photolithography. A method in which a metal wire is disposed on one surface 21a of a substrate 21.

[0070] "Spacer layer" The spacer layer 30 is provided on the other surface 21 b of the base material 21 of the electromagnetic wave absorbing layer 20 . The spacer layer 30 has two surfaces 30a and 30b. The surface 30a of the spacer layer 30 faces the other surface 21b of the substrate 21. A reflective layer 40 is provided on the other surface 30b of the spacer layer 30. The spacer layer 30 may be a single layer structure or a multi-layer structure.

[0071] The material of the spacer layer 30 can be appropriately selected depending on the application. For example, when used for the exterior of an automobile, it is preferable to select a material that has the ability to conform to curved surfaces and has excellent heat resistance. Examples of the flexible material include a plastic film, a nonwoven fabric, a rubber sheet, etc. Among these, a plastic film is preferred from the viewpoint of ease of kneading with the filler. As a specific example of the resin constituting the plastic film, for example, one having a high melting point selected from the thermoplastic resins explained for the substrate 21 above can be used.

[0072] The spacer layer 30 may contain a filler. There are no particular limitations on the filler as long as it has a high dielectric constant, and examples of the filler include barium titanate, strontium titanate, calcium titanate, and titanium oxide.

[0073] The filler content in the spacer layer 30 is preferably 20% by volume or more and 60% by volume or less, more preferably 25% by volume or more and 50% by volume or less, and particularly preferably 30% by volume or more and 45% by volume or less. If the filler content exceeds the upper limit, the spacer layer 30 may become brittle and may be difficult to manufacture. If the filler content is less than the lower limit, the spacer layer 30 may need to be too thick to obtain the required electromagnetic wave absorption properties, and curved surface conformability may not be obtained.

[0074] It is preferable that an adhesive layer is provided on the two surfaces 30a, 30b of the spacer layer 30. This makes it possible to easily attach the electromagnetic wave absorbing layer 20 and the reflective layer 40 to each of the two surfaces 30a, 30b. Details and preferred aspects of the adhesive layer may be the same as those described below for the adhesive layer in the reflective layer.

[0075] "Reflective layer" The reflective layer 40 has two surfaces 40a and 40b. The surface 40a of the reflective layer 40 faces the other surface 30b of the spacer layer 30. The reflective layer 40 is not particularly limited in shape as long as it can reflect the electromagnetic waves that arrive at the surface of the electromagnetic wave absorbing member 10 and transmit through the electromagnetic wave absorbing member 10. A part of the electromagnetic waves that arrive at the electromagnetic wave absorbing member 10 is reflected by or absorbed by the electromagnetic wave absorbing layer 20. On the other hand, the electromagnetic waves that are neither reflected nor absorbed by the electromagnetic wave absorbing layer 20 transmit through the electromagnetic wave absorbing layer 20. The electromagnetic waves that transmit through the electromagnetic wave absorbing layer 20 are reflected by the reflective layer 40 towards the electromagnetic wave absorbing layer 20. For example, if the reflective layer 40 has conductivity in the surface direction of either of the two faces 40a, 40b, it can reflect the electromagnetic waves transmitted through the electromagnetic wave absorbing layer 20. Specifically, a resin film such as polyethylene terephthalate to which a metal foil such as aluminum foil or copper foil, or a metal plate such as a copper plate is attached may be used as the reflective layer 40. Instead of the metal foil or metal plate, a transparent conductive film such as ITO, or a mesh sheet formed of metal wires may be used. Among these, a metal plate is preferable in terms of high conductivity.

[0076] Considering the reflection characteristics of the reflective layer 40, a metal wire, a conductive thread, a twisted thread containing a metal wire and a conductive thread, or a conductive thin film may be provided on the other surface 40b of the reflective layer 40. The conductive thin film can be provided on the surface 40b by, for example, a printing method such as screen printing, gravure printing, or an inkjet method; a sputtering method or vacuum deposition; or photolithography.

[0077] The Young's modulus of the reflective layer 40 is preferably 6 GPa or less, more preferably 5.5 GPa or less, and even more preferably 5 GPa or less. When the Young's modulus of the reflective layer 40 is equal to or less than the upper limit, the curved surface conformability is improved. The lower limit of the Young's modulus of the reflective layer 40 may be 0.5 GPaPa or more, 1 GPa or more, or 3 GPa or more.

[0078] The Young's modulus of the reflective layer 40 can be measured in accordance with JIS K7127:1999 "Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets".

[0079] When the spacer layer 30 is formed on an object having electrical conductivity, such as a metal, the object having electrical conductivity, such as a metal, serves as the reflective layer 40, and therefore the reflective layer 40 can be omitted.

[0080] For the purpose of applying the electromagnetic wave absorbing member 10 to the surfaces of various articles, an adhesive layer may be provided on the other surface 40b of the reflective layer 40. When an adhesive layer is provided on the other surface 40b of the reflective layer 40, a release film may be provided on the surface of the adhesive layer opposite to the side in contact with the surface 40b. The release film is removed when the electromagnetic wave absorbing member 10 is used. Covering the adhesive surface with the release film improves handling during distribution.

[0081] Examples of adhesives constituting the adhesive layer include heat-seal type adhesives that adhere by heat, adhesives that develop stickiness when moistened, pressure-sensitive adhesives (adhesives) that adhere by pressure, etc. Among these, adhesives (pressure-sensitive adhesives) are preferred from the viewpoint of simplicity. Specific examples of the adhesive include acrylic adhesives, urethane adhesives, rubber adhesives, polyester adhesives, silicone adhesives, polyvinyl ether adhesives, etc. Among these, at least one selected from the group consisting of acrylic adhesives, urethane adhesives, and rubber adhesives is preferred, and acrylic adhesives are more preferred.

[0082] The electromagnetic wave absorbing member 10 of this embodiment may also include a protective layer formed on one surface (front surface) 20a of the electromagnetic wave absorbing layer 20. The protective layer is not particularly limited as long as it can protect the electromagnetic wave absorbing layer 20 .

[0083] According to the electromagnetic wave absorbing member 10 of this embodiment, the spacer layer 30 has a relative dielectric constant of 5 or more and a melting point of 150° C. or more, and therefore has excellent curved surface conformability and excellent maintenance of electromagnetic wave absorbency after a heat resistance test. If a resin with a low melting point is used as the resin constituting the spacer layer, the thickness of the spacer layer and the distribution of the filler contained in the spacer layer will change due to the heat resistance test, and the electromagnetic wave absorbency will decrease.

[0084] The electromagnetic wave absorbing member 10 of this embodiment has excellent shape retention because the Young's modulus of the spacer layer 30 is 50 MPa or more. Here, excellent shape retention means that the film thickness does not change even when subjected to thermal or physical action, and the electromagnetic wave absorbing properties do not change. EXAMPLES

[0085] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0086] [Example 1] "Production of electromagnetic wave absorbing materials" An electromagnetic wave absorbing member was produced as follows. Copper was vapor-deposited onto a substrate made of a PET film (product name: PET50A4160, manufactured by Toyobo Co., Ltd.) having a thickness of 50 μm to form a copper thin film. Thereafter, the copper thin film was patterned into an electromagnetic wave absorbing pattern by photolithography to form an electromagnetic wave absorbing pattern as shown in Fig. 2, thereby obtaining an electromagnetic wave absorbing layer having an electromagnetic wave absorbing pattern. The thickness of the electromagnetic wave absorbing pattern was set to 20 µm. Next, a polyester-polyether copolymer (product name: P-55B, manufactured by Toyobo Co., Ltd.) as a resin and barium titanate (product name: BT-UP2, manufactured by Nippon Kagaku Co., Ltd.) as a filler were kneaded at 200°C and 40 rpm for 5 minutes using a Labo Plastomill (model name: 4C150, manufactured by Toyo Seiki Seisakusho Co., Ltd.) to prepare a mixed material with a barium titanate content of 40 volume %. The above mixed material was pressed at 200° C. for 3 minutes using a hydraulic hot press (model name: SA-302, manufactured by Tester Sangyo Co., Ltd.) to obtain a spacer layer having a thickness of 300 μm. As a material for the adhesive layer, an acrylic copolymer with a weight average molecular weight of 800,000 consisting of 70% by mass of 2-ethylhexyl acrylate, 29% by mass of n-butyl acrylate, 0.5% by mass of acrylic acid, and 0.5% by mass of 2-hydroxyethyl acrylate was prepared. An acrylic adhesive solution was prepared by adding 1 part by mass (solid content equivalent) of an isocyanate-based crosslinking agent and 8 parts by mass of an ultraviolet absorber (product name: Tinuvin 477, manufactured by BASF Japan Ltd.) to 100 parts by mass (solid content equivalent) of the acrylic copolymer, and diluting the mixture with ethyl acetate. Next, the above acrylic adhesive solution was applied onto a release film, dried at 90° C. for 1 minute, and then cured at room temperature for 1 week to obtain an adhesive layer having a thickness of 20 μm. Next, the above-mentioned adhesive layer was laminated on one surface of the spacer layer. Next, a 50 μm thick Metalme TS manufactured by Toray Advanced Film Co., Ltd. was prepared as a reflective layer, and both sides of the film were laminated so as to be covered with an adhesive layer. That is, a laminate of release film / adhesive layer / reflective layer / adhesive layer / release film was obtained. Next, the release film on the electromagnetic wave absorbing layer side laminated to the reflective layer was peeled off, and the exposed adhesive layer was laminated on the surface of the spacer layer opposite to the surface on the electromagnetic wave absorbing layer side. Next, the release film on the electromagnetic wave absorbing layer side of the spacer layer was peeled off, and the exposed adhesive layer was laminated to the side opposite the side of the electromagnetic wave absorbing layer on which the electromagnetic wave absorbing pattern was formed, to obtain an electromagnetic wave absorbing member with an adhesive layer.

[0087] [Example 2] An electromagnetic wave absorbing member with an adhesive layer of Example 2 was obtained in the same manner as Example 1, except that the content of barium titanate in the mixed material for producing the spacer layer was 35 volume % and the thickness of the spacer layer was 350 μm.

[0088] [Example 3] An electromagnetic wave absorbing member with an adhesive layer of Example 3 was obtained in the same manner as in Example 1, except that polyester (manufactured by Bell Polyester Products) was used as the resin and the thickness of the spacer layer was 360 μm.

[0089] [Example 4] The electromagnetic wave absorbing member with an adhesive layer of Example 4 was obtained in the same manner as in Example 1, except that the content of barium titanate in the mixed material for producing the spacer layer was 25 volume % and the thickness of the spacer layer was 425 μm.

[0090] [Comparative Example 1] An electromagnetic wave absorbing member with an adhesive layer of Comparative Example 1 was obtained in the same manner as in Example 1, except that the resin constituting the mixed material for producing the spacer layer was ethylene-vinyl acetate copolymer resin (EVA, manufactured by Dow Mitsui Polychemicals), the barium titanate content in the mixed material was 45 volume %, and the thickness of the spacer layer was 300 μm.

[0091] [Comparative Example 2] An electromagnetic wave absorbing member with an adhesive layer of Comparative Example 2 was obtained in the same manner as in Example 1, except that the resin constituting the mixed material for producing the spacer layer was low-density polyethylene (LDPE, manufactured by Japan Polystyrene Co., Ltd.), the barium titanate content in the mixed material was 20 volume %, and the thickness of the spacer layer was 470 μm.

[0092] [evaluation] The following evaluations were carried out on the electromagnetic wave absorbing members of Examples 1 to 4 and Comparative Examples 1 and 2. The results are shown in Table 1.

[0093] "Evaluation of relative dielectric constant" The relative dielectric constants of the spacer layers obtained in the examples and comparative examples were measured using a dielectric constant measuring device (40 GHz TE mode) manufactured by AET Corporation and a network analyzer (model name: MS46122B) manufactured by Anritsu Corporation.

[0094] "Measurement of Young's modulus (tensile elastic modulus)" The electromagnetic wave absorbing layer, the spacer layer and the reflective layer were cut into test pieces measuring 15 mm long x 150 mm wide, and the tensile modulus E was measured in accordance with JIS K7127:1999 "Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets". Specifically, the above test pieces were subjected to a tensile test at a speed of 200 mm / min using a tensile tester (product name: Autograph AG-IS 500N, manufactured by Shimadzu Corporation) with the chuck distance set to 100 mm, to measure the tensile modulus (MPa) of the electromagnetic wave absorbing layer, the spacer layer and the reflective layer.

[0095] "Melt point measurement" The melting point of the spacer layer was measured using a DSC (model: Q2000) manufactured by TA Instruments Co., Ltd. The measurement conditions were set as follows: Temperature rise condition: 20℃ / min Measurement temperature range: -50℃~250℃

[0096] "Heat resistance evaluation" A heat resistance test of the spacer layer was conducted using a high-temperature, constant-temperature chamber (model: PHH-102) manufactured by Espec Corporation. The temperature of the high-temperature, constant-temperature chamber was set to 120°C, and the spacer layer was placed in the high-temperature, constant-temperature chamber for 240 hours. The relative dielectric constant of the spacer layer was measured after it was removed from the high-temperature, constant-temperature chamber, and the change before and after the test was evaluated.

[0097] "Evaluation of curved surface conformity" The electromagnetic wave absorbing material was attached to curved surfaces of different diameters, and the curved surface conformability of the electromagnetic wave absorbing material was evaluated. The minimum diameter (mm) of the curved surface on which the electromagnetic wave absorbing material can be attached without causing appearance defects such as wrinkles or loose edges was evaluated.

[0098] "Evaluation of bending rigidity" The bending rigidity of the electromagnetic wave absorbing member was calculated using FIG. 3 and the following formula (11). The position of the centroid of the electromagnetic wave absorbing material in Figure 3 is y cand the width of the electromagnetic wave absorbing member was W. Furthermore, the thicknesses of the electromagnetic wave absorbing layer, the spacer layer and the reflective layer were t1, t2 and t3, respectively, and the heights to the centers of the respective layers were y1, y2 and y3. The areas (A1, A2, A3) of the electromagnetic wave absorbing layer, the spacer layer and the reflective layer, as well as the overall area A, y1, y2, y3 were calculated from the following formulas (11) to (17). A1 = W × t1 (11) A2 = W × t2 (12) A3 = W × t3 (13) A = A1 + A2 + A3 (14) y1=t1 / 2 (15) y2=t1+t2 / 2 (16) y3=t1+t2+t3 / 2 (17) Using the values ​​obtained from equations (11) to (17), the centroid y of the electromagnetic wave absorbing material is calculated. c was calculated using the following formula (18). y c =(A1y1+A2y2+A3y3) / A (18) Here, the second moments of area I1, I2, I3 and I c1 , I c2 , I c3 was calculated from the following formulas (20) to (25). I1 = (W × t1 3 ) / 12 (20) I2 = (W × t2 3 ) / 12 (21) I3 = (W × t3 3 ) / 12 (22) I c1 =I1+A1×(y c -y1) 2 (twenty three) I c2 =I2+A2×(y c -y2) 2 (twenty four) I c3 =I3+A3×(y c -y3) 2 (twenty five) The second moment of area I of the electromagnetic wave absorbing member was calculated from the following formula (26), and the bending rigidity of the electromagnetic wave absorbing member was found from the following formula (27). I=I c1 +I c2 +I c3 (26) Bending stiffness (N mm 2 )=E(N / mm 2 )×I(mm 4 ) (27)

[0099] "Evaluation of return loss" A heat resistance test of the electromagnetic wave absorbing material was conducted using a high-temperature, constant-temperature chamber (model name: PHH-102) manufactured by Espec Corporation. The temperature of the high-temperature, constant-temperature chamber was set to 120°C, and the electromagnetic wave absorbing material was placed in the high-temperature, constant-temperature chamber for 240 hours. The return loss of the electromagnetic wave absorbing material after it was removed from the high-temperature, constant-temperature chamber was measured, and the change before and after the test was evaluated. The return loss was measured by the free space method.

[0100] [Table 1]

[0101] The results shown in Table 1 demonstrate that the electromagnetic wave absorbing members of Examples 1 to 4 are excellent in terms of curved surface conformability and in terms of maintaining electromagnetic wave absorbing properties after a heat resistance test. On the other hand, it was found that the electromagnetic wave absorbing member of Comparative Example 1 was poor in maintaining the electromagnetic wave absorbing properties after the heat test. It was found that the electromagnetic wave absorbing member of Comparative Example 2 was inferior in curved surface conformability and in maintaining electromagnetic wave absorbing properties after the heat resistance test. [Industrial Applicability]

[0102] The electromagnetic wave absorbing member of the present invention can be suitably used as an electromagnetic wave absorbing member for transportation equipment such as automobiles. [Explanation of symbols]

[0103] 10 Electromagnetic wave absorbing materials 20 Electromagnetic wave absorbing layer 21 Base material 22 Electromagnetic wave absorption pattern 30 Spacer layer 40 reflective layer 51 First electromagnetic wave absorption pattern 52 Second electromagnetic wave absorption pattern 53 The third electromagnetic wave absorption pattern

Claims

1. The electromagnetic wave absorbing layer, the spacer layer, and the reflective layer are included. the electromagnetic wave absorbing layer, the spacer layer, and the reflective layer are laminated in this order; The spacer layer has a relative dielectric constant of 5 or more, The spacer layer has a melting point of 170° C. or higher and 190° C. or lower.

2. 2. The electromagnetic wave absorbing member according to claim 1, wherein the spacer layer has a thickness of 200 μm or more and 450 μm or less.

3. 2. The electromagnetic wave absorbing member according to claim 1, wherein the spacer layer has a Young's modulus of 50 MPa or more.

4. Bending stiffness: 300N・mm ２ 2. The electromagnetic wave absorbing member according to claim 1, wherein:

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