Electromagnetic wave absorbing material, aiming partition

Abstract

To provide an electromagnetic wave absorbing member that can be rolled up into a smaller size and can suppress unnecessary reflection of electromagnetic waves, and an aiming partition including the same.SOLUTION: An electromagnetic wave absorbing member 10 includes an electromagnetic wave absorbing layer 20, a spacer layer 30, and a reflective layer 40 that are laminated in this order, and a plurality of slits 50 are formed from the outermost surface of the electromagnetic wave absorbing layer 20, substantially parallel to the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30, and a laminate 60 consisting of the electromagnetic wave absorbing layer 20 and the spacer layer 30 is divided into a plurality of regions through a plurality of slits 50, and the widths w of the plurality of slits 50 are less than 10 mm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic wave absorbing member and an aiming partition equipped therewith. [Background technology]

[0002] A sheet-like electromagnetic wave absorbing member that selectively absorbs electromagnetic waves of a predetermined frequency is known. The electromagnetic wave absorbing member comprises, for example, a first frequency-selective shielding layer and a second frequency-selective shielding layer. In such an electromagnetic wave absorbing member, 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 cause each layer to absorb electromagnetic waves of a predetermined frequency, thereby selectively shielding electromagnetic waves of two different frequencies as a whole.

[0003] Electromagnetic wave absorbing materials can be large in area depending on the application, so they need to be able to be rolled up and made smaller for storage and transport. Therefore, electromagnetic wave absorbing materials need to have a flexible structure.

[0004] Patent Document 1 describes an electromagnetic wave absorbing member comprising a plurality of electromagnetic wave absorbers arranged at predetermined intervals for the purpose of bending, and capable of absorbing electromagnetic waves. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6869704 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the electromagnetic wave absorbing member described in Patent Document 1, electromagnetic waves are unnecessarily reflected due to the influence of the electromagnetic wave reflecting member present in the gap. Therefore, in Patent Document 1, a gap reflecting section is provided in the gap to direct the electromagnetic waves toward the electromagnetic wave absorbing member, thereby suppressing reflection. As a result, the thickness of the electromagnetic wave absorbing member needs to be increased, reaching approximately 10 mm to 15 mm. Consequently, the weight of the electromagnetic wave absorbing member increases, and although it can be rolled up, it becomes difficult to roll it up into a small size.

[0007] The present invention has been made in view of the above circumstances, and aims to provide an electromagnetic wave absorbing member that can be rolled up to a smaller size and suppress the unnecessary reflection of electromagnetic waves, and an aiming partition equipped therewith. [Means for solving the problem]

[0008] The present invention provides the following electromagnetic wave absorbing member and aiming partition equipped therewith. [1] Having 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 stacked in this order. Multiple slits are formed from the outermost surface of the electromagnetic wave absorbing layer, substantially parallel to the thickness direction of the electromagnetic wave absorbing layer and the spacer layer, and the laminate consisting of the electromagnetic wave absorbing layer and the spacer layer is divided into multiple regions through these multiple slits. An electromagnetic wave absorbing member in which the width of the plurality of slits is less than 10 mm. [2] The electromagnetic wave absorbing member according to [1], wherein, in a plan view of the electromagnetic wave absorbing member, the interval between the plurality of slits is 1 cm or more and 30 cm or less. [3] The electromagnetic wave absorbing member according to [1], wherein the spacer layer is made of foam. [4] The electromagnetic wave absorbing member according to [1], wherein the reflective layer is made of a conductor. [5] comprising a support member, a support plate supported by the support member, and a front plate disposed on at least one side of the support plate, The aiming partition, wherein the front plate is the electromagnetic wave absorbing member according to any one of [1] to [4].

Effects of the Invention

[0009] According to the present invention, it is possible to provide an electromagnetic wave absorbing member that can be rolled up into a smaller size and can suppress unnecessary reflection of electromagnetic waves, and an aiming partition including the same.

Brief Description of Drawings

[0010] [Figure 1] FIG. 1 is a cross-sectional view taken along a plane along the thickness, schematically showing an electromagnetic wave absorbing member according to an embodiment of the present invention. [Figure 2] FIG. 2 is a top view showing an example of an electromagnetic wave absorbing layer constituting the electromagnetic wave absorbing member according to an embodiment of the present invention. [Figure 3] FIG. 3 is a top view showing an example of a first electromagnetic wave absorption pattern of an electromagnetic wave absorbing layer constituting the electromagnetic wave absorbing member according to an embodiment of the present invention. [Figure 4] FIG. 4 is a top view showing an example of a second electromagnetic wave absorption pattern of an electromagnetic wave absorbing layer constituting the electromagnetic wave absorbing member according to an embodiment of the present invention. [Figure 5] FIG. 5 is a top view showing an example of a third electromagnetic wave absorption pattern of an electromagnetic wave absorbing layer constituting the electromagnetic wave absorbing member according to an embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view taken along line VIII-VIII in FIG. 2. [Figure 7] FIG. 7 is a cross-sectional view taken along a plane along the thickness, schematically showing an electromagnetic wave absorbing member according to an embodiment of the present invention. [Figure 8] FIG. 8 is a side view schematically showing an aiming partition according to an embodiment of the present invention. [Figure 9] FIG. 9 is a side view schematically showing an aiming partition according to an embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing results of evaluating return loss of the aiming partition in Example 1, Comparative Example 1, and Comparative Example 2. MODE FOR CARRYING OUT THE INVENTION

[0011] The following is a specific description of the electromagnetic wave absorbing member of the present invention and an aiming partition including the same to facilitate better understanding of the gist of the invention, and the present invention is not limited thereto unless otherwise specified.

[0012] As used herein, the term "electromagnetic wave absorbing pattern" refers to an aggregate of units each being a geometric figure, and means an object that selectively absorbs electromagnetic waves of a specific frequency. It can also be said that the "electromagnetic wave absorbing pattern" has a function similar to that of a so-called antenna. As used herein, the term "electromagnetic wave in the millimeter wave region" means an electromagnetic wave having a wavelength of 1 mm to 10 mm. It can also be said that "electromagnetic wave in the millimeter wave region" is an electromagnetic wave having a frequency of 30 GHz to 300 GHz. In the present specification, the symbol "~" indicating a numerical range means that the numerical values described before and after the symbol are included as the lower limit and the upper limit, respectively.

[0013] ELECTROMAGNETIC WAVE ABSORBING MEMBER FIG. 1 is a cross-sectional view along a thickness direction, schematically showing an electromagnetic wave absorbing member according to an embodiment of the present invention. As shown in FIG. 1, the electromagnetic wave absorbing member 10 of the present embodiment includes an electromagnetic wave absorbing layer 20, a spacer layer 30, and a reflective layer 40. Further, 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 (back 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, and may include a base material 21 and an electromagnetic wave absorbing pattern 22 formed on the base material 21 as shown in FIG. 1. When the electromagnetic wave absorbing layer 20 is a single layer, the electromagnetic wave absorbing layer 20 is formed of the same material as that of the electromagnetic wave absorbing pattern 22 described later.

[0016] In the electromagnetic wave absorbing member 10 of this embodiment, a plurality of slits 50 are formed in the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30 from the outermost surface of the electromagnetic wave absorbing layer 20 (in Figure 1, one side (top surface) 21a of the base material 21). Furthermore, the laminate 60 consisting of the electromagnetic wave absorbing layer 20 and the spacer layer 30 is divided into a plurality of regions (in Figure 1, region 60A, region 60B, region 60C) via the plurality of slits 50. The slits 50 may be parallel to the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30, or the slit width may be narrowed toward the side edge of the reflective layer 40 in the spacer layer 30.

[0017] In the electromagnetic wave absorbing member 10 of this embodiment, the width of the multiple slits 50, that is, the width W0 of the slits 50 on the outermost surface of the electromagnetic wave absorbing layer 20 (one surface 21a of the base material 21) in Figure 1, is less than 10 mm, preferably 5 mm or less, and more preferably 2 mm or less. If the width W0 exceeds the upper limit, the absorption characteristics of the electromagnetic wave absorbing layer 20 will decrease.

[0018] In the electromagnetic wave absorbing member 10 of this embodiment, it is preferable that at least a portion of adjacent spacer layers 30 are connected at the reflective layer 40 side end of the multiple slits 50. That is, it is preferable that the reflective layer 40 is not exposed at the reflective layer 40 side end of the multiple slits 50. This makes the resulting electromagnetic wave absorbing member 10 more resistant to repeated winding.

[0019] In the electromagnetic wave absorbing member 10 of the present embodiment, in a plan view of the electromagnetic wave absorbing member 10, the interval d0 between the plurality of slits 50 is preferably 1 cm or more and 30 cm or less, more preferably 2 cm or more and 20 cm or less, and still more preferably 3 cm or more and 10 cm or less. If the interval d0 is less than the lower limit described above, the frequency of dividing the laminate 60 by the slits 50 increases, which may reduce the absorption characteristics of the electromagnetic wave absorbing layer 20. If the interval d0 exceeds the upper limit described above, the windability of the electromagnetic wave absorbing member 10 decreases, and the storage size of the electromagnetic wave absorbing member 10 increases. Note that the interval d0 is the distance between center lines c that pass through the slits 50 parallel to the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30.

[0020] The slits 50 are formed by making cuts in the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30 with a cutter or the like. In a state where the electromagnetic wave absorbing member 10 is deployed in a planar shape (in an unrolled state), physical gaps (gaps caused by the slits 50) in the electromagnetic wave absorbing member 10 are minimized, so reflection of electromagnetic waves from the reflective layer 40 is also minimized. Therefore, the electromagnetic wave absorbing member 10 of the present embodiment exhibits the most excellent electromagnetic wave absorbing performance when the rolled member is unrolled and used in a planar shape. For this reason, unlike Patent Document 1 mentioned above, there is no need to provide a gap reflection portion in the gap, and there is also no need to consider oblique reflection therefrom, so the thickness can be reduced. Accordingly, the windability of the electromagnetic wave absorbing member 10 can be improved.

[0021] The electromagnetic wave absorbing member 10 of the present embodiment has a flexural rigidity of 1.0×10 -4 Pa·mm 4 or more and 2250 Pa·mm 4 or less, preferably 1.7×10 -3 Pa·mm 4 or more and 1040 Pa·mm 4 or less, more preferably 6.7×10 -3 Pa·mm 4 or more and 390 Pa·mm 4 or less, and even more preferably.

[0022] The bending stiffness of the electromagnetic wave absorbing member 10 is determined by the product of the Young's modulus and the second moment of area of ​​the reflective layer 40. In this specification, the second moment of area is calculated using a rectangular model with a unit width of 20 cm.

[0023] "Electromagnetic wave absorption layer" The electromagnetic wave absorbing layer 20 consists 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 with a shape smaller than the wavelength using a conductive material or the like.

[0024] Figure 2 is a top view showing an example of an electromagnetic wave absorbing layer in this embodiment. As shown in Figure 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 consists of a first electromagnetic wave absorbing pattern 71, a second electromagnetic wave absorbing pattern 72, and a third electromagnetic wave absorbing pattern 73.

[0025] (First electromagnetic wave absorption pattern) Figure 3(a) is a top view showing the first electromagnetic wave absorption pattern 71. As shown in Figure 3(a), the first electromagnetic wave absorption pattern 71 is composed of a plurality of first units u1. Each of the first units u1 is a geometric figure. In other words, the first electromagnetic wave absorption pattern 71 can be described as a collection of the first unit u1, which is a geometric figure. Each of the first units u1 functions as a single antenna. The first electromagnetic wave absorption pattern 71 may be, for example, a fine-line pattern of FSS elements.

[0026] In the first electromagnetic wave absorption pattern 71, multiple first arrays R1 are formed, in which multiple first units u1 are arranged along the direction indicated by the double-headed arrow P in Figure 3(a). It can also be said that the first electromagnetic wave absorption pattern 71 has multiple first arrays R1. The first electromagnetic wave absorption pattern 71 can be constructed by forming multiple first arrays R1 on the substrate 21 at predetermined intervals along the direction indicated by the double-headed arrow P. There are no particular restrictions on the spacing between multiple first sequences R1. The spacing between first sequences R1 may be regular or irregular.

[0027] Figure 3(b) is a top view showing the first unit u1. Figure 3(b) is a top view showing the first unit u1 that constitutes the first electromagnetic wave absorption pattern 71. As shown in Figure 3(b), the shape of the first unit u1 is a cross shape that is symmetrical both vertically and horizontally. Specifically, the first unit u1 has one cross section S1 and four ends T1. The cross section S1 is composed of a straight section parallel to the x-axis direction and a straight section parallel to the y-axis direction in Figure 3(b). Each of the straight ends T1 is attached to both ends of the straight section parallel to the x-axis direction and to both ends of the straight section parallel to the y-axis direction, perpendicular to each straight section.

[0028] By adjusting the x-axis length L1 of the first unit u1 and the x-axis lengths W1 of each of the four ends T1, the electromagnetic wave absorption characteristics of the first unit u1, which functions as a single antenna, can be adjusted. The electromagnetic wave absorption characteristics can be adjusted in the y-axis direction in a similar manner.

[0029] 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 waves absorbed by the first electromagnetic wave absorption pattern 71 shows a maximum value is A [GHz]. For example, the shapes of the first unit, a geometric figure, can include circles, rings, straight lines, squares, polygons, H-shapes, Y-shapes, V-shapes, and so on.

[0030] In the electromagnetic wave absorbing layer 20, the shapes of the multiple first units u1 are identical to each other. However, the shapes of the multiple first units u1 do not have to be identical. In other examples of the present invention, the shapes of the multiple first units may be identical or different to each other, as long as the absorption characteristics can be adjusted to the target frequency.

[0031] The first electromagnetic wave absorption pattern 71 selectively absorbs electromagnetic waves with 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 absorption pattern 71 shows a maximum value in the range of 20 GHz to 110 GHz. The frequency value A [GHz] at which the amount of electromagnetic wave absorption by the first electromagnetic wave absorption pattern 71 reaches its maximum can be determined, for example, by the following methods X and Y.

[0032] Method X: An electromagnetic wave is irradiated onto a standard film described later while varying the frequency within the range of 20 GHz to 110 GHz. The frequency of the electromagnetic wave at which the amount of electromagnetic wave absorbed by the standard film reaches its maximum value is defined as A [GHz]. Method Y: From a substrate and an electromagnetic wave absorbing film having multiple electromagnetic wave absorbing patterns formed on the substrate, the electromagnetic wave absorbing patterns are removed from the substrate so that only a single electromagnetic wave absorbing pattern remains. Next, the film having only the single electromagnetic wave absorbing pattern is irradiated with electromagnetic waves while varying the frequency within the range of 20 GHz to 110 GHz, and the frequency of the electromagnetic wave at which the amount of electromagnetic wave absorption by the film reaches its maximum is defined as A [GHz].

[0033] A standard film comprises a standard substrate which is in the shape of a flat plate and a standard pattern formed on the standard substrate. The details of the standard substrate can be the same as those of substrate 21. Therefore, the details of the standard substrate will be explained in detail in the description of substrate 21 below.

[0034] A standard pattern consists only of multiple standard units, each having the same shape. In the case of a standard film, it can be said that a standard pattern consisting of only one type of shape is formed on the standard substrate. A standard pattern can be formed by a fine-line pattern of a typical FSS element. Typically, the standard pattern is the same electromagnetic wave absorption pattern as the first electromagnetic wave absorption pattern 71. In a standard pattern, the shapes of multiple standard units are not particularly limited as long as they are identical figures. Examples of standard unit shapes include circles, rings, lines, squares, polygons, crosses, H-shapes, Y-shapes, and V-shapes. Typically, the shape of a standard unit is identical to the first unit u1.

[0035] In a standard film, multiple standard units are arranged on a standard substrate such that the distance between the edges of the shapes is 1 mm. For example, if the shape of a standard unit is a cross shape, the intersection of the cross is the center of the shape, and the edges of the shape are the parts furthest from the center along the direction of each of the two straight lines that make up the cross.

[0036] The material of the standard unit constituting the standard pattern is not particularly limited, as long as it is such that the amount of electromagnetic waves absorbed by the standard film can be maximized when the standard film is irradiated with electromagnetic waves while varying the GHz range from 20 GHz to 110 GHz. The details of the material for the standard unit can be the same as those for the first unit.

[0037] The amount of electromagnetic waves absorbed by the standard film can be calculated using the following formula (1). Absorption amount = Input signal - Reflection characteristics (S11) - Transmission characteristics (S21) ... (1) The input signal is an indicator of the intensity of electromagnetic waves at the irradiation source when electromagnetic waves are irradiated onto a standard film. The reflection characteristic (S11) is an indicator of the intensity of electromagnetic waves reflected by a standard film when electromagnetic waves are irradiated onto the standard film from an irradiation source. The reflection characteristic (S11) can be measured, for example, by the free-space method using a vector network analyzer. Transmission characteristics (S21) are an indicator of the intensity of electromagnetic waves transmitted through a standard film when electromagnetic waves are irradiated onto the standard film from an irradiation source. Transmission characteristics (S21) can be measured, for example, using the free-space method with a vector network analyzer.

[0038] The frequency A [GHz] can be determined, for example, by the following method. First, electromagnetic waves are irradiated onto a standard film while varying the frequency within the range of 20 GHz to 110 GHz, and the amount of electromagnetic waves absorbed by the standard film is calculated using the above formula (1). Next, an absorption spectrum diagram is created by plotting the changed frequencies on the horizontal axis and the absorption amount calculated by equation (1) on the vertical axis. Typically, in this absorption spectrum diagram, there is one value on the horizontal axis corresponding to the frequency at which the absorption amount is maximum. Therefore, a single peak is formed in the plot where the absorption amount of the electromagnetic wave is at its maximum. Thus, the frequency of the electromagnetic wave at which the absorption amount of the electromagnetic wave is maximum can be denoted as A [GHz].

[0039] In method X, if the value of frequency A can be predicted in advance, the frequency of the electromagnetic wave irradiated onto the standard film may be varied within a range narrower than 20 GHz to 110 GHz. For example, the frequency of the electromagnetic wave irradiated onto the standard film may be varied within the range of 50 GHz to 110 GHz.

[0040] The first electromagnetic wave absorption pattern 71 absorbs electromagnetic waves whose frequency is A [GHz] as determined by the method X described above. 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, even more 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, making it easier to apply to automobile parts, roadside components, building exterior wall materials, windows, communication equipment, radio telescopes, etc.

[0041] In method Y, similar to method X, the amount of electromagnetic wave absorption by the film can be measured. Specifically, electromagnetic waves are irradiated onto the film while varying the frequency within the range of 20 to 110 [GHz], and the amount of electromagnetic wave absorbed by the film is calculated using the above formula (1). Next, an absorption spectrum diagram is created by plotting frequency on the horizontal axis and the amount of absorption calculated by equation (1) on the vertical axis. Typically, in this absorption spectrum diagram, there is one value on the horizontal axis corresponding to the frequency at which the absorption amount is maximum. Therefore, a single peak is formed in the plot where the absorption amount of the electromagnetic wave is at its maximum value. In this way, the frequency of the electromagnetic wave at which the absorption amount of the electromagnetic wave is maximum can be defined as A [GHz].

[0042] The material of the first unit u1 is not particularly limited, as long as its absorption characteristics can be adjusted to the desired frequency. Examples of materials for the first unit include fine metal wires, conductive thin films, and conductive paste fixatives. Examples of metal materials include copper, aluminum, tungsten, iron, molybdenum, nickel, titanium, silver, gold, or alloys containing two or more of these metals (for example, stainless steel, carbon steel, brass, phosphor bronze, zirconium copper alloy, beryllium copper, iron nickel, nichrome, nickel titanium, Kanthal, Hastelloy, rhenium tungsten, etc.). Examples of materials for conductive thin films include metal particles, carbon nanoparticles, and carbon fibers.

[0043] The distance between the ends of the first unit u1 is not particularly limited, as long as the absorption characteristics can be adjusted to the desired frequency. For example, the spacing between the ends of the first unit u1 figure may all be the same or they may be different. However, it is preferable that the spacing between the ends of the first unit u1 figure be the same, as this makes it easier to design an electromagnetic wave absorbing film that is less affected by the surrounding environment and improves the accuracy of the frequency band of absorbed electromagnetic waves during manufacturing.

[0044] (Second electromagnetic wave absorption pattern) Figure 4(a) is a top view showing the second electromagnetic wave absorption pattern 72. As shown in Figure 4(a), the second electromagnetic wave absorption pattern 72 is composed of multiple second units u2. Each of the second units u2 is a geometric figure. In other words, the second electromagnetic wave absorption pattern 72 can be said to be a collection of second units u2, which are geometric figures. Each of the second units u2 functions as a single antenna. The second electromagnetic wave absorption pattern 72 may be, for example, a fine-line pattern of FSS elements.

[0045] In the second electromagnetic wave absorption pattern 72, a second array R2 is formed in which a plurality of second units u2 are arranged along the direction indicated by the double-headed arrow P in Figure 4(a). It can also be said that the second electromagnetic wave absorption pattern 72 has a plurality of second arrays R2. The second electromagnetic wave absorption pattern 72 can be constructed by forming the second arrays R2 on the substrate 21 at predetermined intervals along the direction indicated by the double-headed arrow P. There are no particular restrictions on the spacing between multiple second sequences R2. The spacing between the second sequences R2 may be regular or irregular.

[0046] Figure 4(b) is a top view showing the second unit u2. As shown in Figure 4(b), the shape of the second unit u2 is a cross shape that is symmetrical both vertically and horizontally. Specifically, the second unit u2 has one cross section S2 and four ends T2. The cross section S2 is composed of a straight section parallel to the x-axis direction and a straight section parallel to the y-axis direction in Figure 4(b). Each of the straight ends T2 is in contact with both ends of the straight section parallel to the x-axis direction and both ends of the straight section parallel to the y-axis direction, perpendicular to each respective straight section.

[0047] In the electromagnetic wave absorbing layer 20, the x-axis length L2 of the second unit u2 is shorter than the x-axis length L1 of the first unit u1. In addition, the x-axis or y-axis length W2 of each of the four end portions T2 is shorter than the W1 of each of the four end portions T1 of the first unit u1. By adjusting the x-axis length L2 of the second unit u2 and the x-axis lengths W2 of each of the four ends T2, the electromagnetic wave absorption characteristics of the second unit u2, which functions as a single antenna, can be adjusted. The electromagnetic wave absorption characteristics can be adjusted in the y-axis direction in a similar manner.

[0048] In the electromagnetic wave absorbing layer 20, the shapes of the multiple second units u2 are identical to each other. However, the shapes of the multiple second units u2 do not have to be identical. In other examples of the present invention, the shapes of the multiple second units may be identical or different to each other, as long as the absorption characteristics can be adjusted to the target frequency.

[0049] The second electromagnetic wave absorption pattern 72 selectively absorbs electromagnetic waves with a frequency of B [GHz] that satisfies the following equation (2). The frequency value B [GHz] is the frequency value at which the amount of electromagnetic wave absorbed by the second electromagnetic wave absorption pattern 72 reaches its maximum value. The frequency value B [GHz] satisfies the following equation (2). 1.037×A≦B≦1.30×A...Equation (2)

[0050] As shown in equation (2) above, the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with frequencies from 1.037 × A [GHz] to 1.30 × A [GHz]. Preferably, the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with frequencies from 1.17 × A [GHz] to 1.30 × A [GHz]. Since the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with frequencies of 1.037 × A [GHz] or higher, the peak of electromagnetic wave absorption by the second electromagnetic wave absorption pattern 72 and the peak of electromagnetic wave absorption by the first electromagnetic wave absorption pattern 71 overlap sufficiently in the frequency band higher than A [GHz]. As a result, compared to a film having only the first electromagnetic wave absorption pattern 71, the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorbing film is extended to the frequency band higher than A [GHz]. Since the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with frequencies below 1.30 × A [GHz], the frequency difference between the peak of electromagnetic wave absorption by the second electromagnetic wave absorption pattern 72 and the peak of electromagnetic wave absorption by the first electromagnetic wave absorption pattern 71 becomes smaller in the frequency band above A [GHz]. As a result, a single peak is formed where the amount of electromagnetic wave absorbed by the entire electromagnetic wave absorption film reaches its maximum value. Therefore, since the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with frequencies from 1.037 × A [GHz] to 1.30 × A [GHz], the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorption film is extended to the higher frequency band.

[0051] However, the shape of the second unit is not limited to a cross shape. The shape of the second unit is not particularly limited as long as the absorption characteristics can be adjusted to the target frequency. For example, the shape of the figure that is the second unit can be a circle, ring, straight line, square, polygon, H-shape, Y-shape, V-shape, etc.

[0052] The material of the second unit constituting the second electromagnetic wave absorption pattern 72 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 target frequency. The material of the second unit is the same as that described for the material of the first unit, u1.

[0053] The distance between the ends of the second unit u2 is not particularly limited, as long as the absorption characteristics can be adjusted to the desired frequency. For example, the spacing between the ends of the second unit u2 figure may all be the same or they may be different. However, it is preferable that the spacing between the ends of the second unit u2 figure be the same, as this makes it easier to design an electromagnetic wave absorbing film that is less affected by the surrounding environment and improves the accuracy of the frequency band of absorbed electromagnetic waves during manufacturing.

[0054] (Third electromagnetic wave absorption pattern) Figure 5(a) is a top view showing the third electromagnetic wave absorption pattern 73. As shown in Figure 5(a), the third electromagnetic wave absorption pattern 73 is composed of multiple third units u3. Each of the third units u3 is a geometric figure. In other words, the third electromagnetic wave absorption pattern 73 can be said to be a collection of third units u3, which are geometric figures. Each of the third units u3 functions as a single antenna. The third electromagnetic wave absorption pattern 73 may be, for example, a fine-line pattern of FSS elements.

[0055] In the third electromagnetic wave absorption pattern 73, a third array R3 is formed in which a plurality of third units u3 are arranged along the direction indicated by the double-headed arrow P in Figure 5(a). It can also be said that the third electromagnetic wave absorption pattern 73 has a plurality of third arrays R3. The third electromagnetic wave absorption pattern 73 can be constructed by forming the third arrays R3 on the substrate 21 at predetermined intervals along the direction indicated by the double-headed arrow P. There are no particular restrictions on the spacing between multiple third sequences R3. The spacing between third sequences R3 may be regular or irregular.

[0056] Figure 5(b) is a top view showing the third unit u3. As shown in Figure 5(b), the shape of the third unit u3 is a cross shape that is symmetrical both vertically and horizontally. Specifically, the third unit u3 has one cross section S3 and four ends T3. The cross section S3 is composed of a straight section parallel to the x-axis direction and a straight section parallel to the y-axis direction in Figure 5(b). Each of the straight ends T3 is in contact with both ends of the straight section parallel to the x-axis direction and both ends of the straight section parallel to the y-axis direction, perpendicular to each straight section.

[0057] In the electromagnetic wave absorbing layer 20, the x-axis length L3 of the third unit u3 is longer than the x-axis length L1 of the first unit u1. In addition, the x-axis or y-axis length W3 of each of the four end portions T3 is longer than the W1 of each of the four end portions T1 of the first unit u1. By adjusting the x-axis length L3 of the third unit u3 and the x-axis lengths W3 of each of the four ends T3, the electromagnetic wave absorption characteristics of the third unit u3, which functions as a single antenna, can be adjusted. The electromagnetic wave absorption characteristics can be adjusted in the y-axis direction in a similar manner.

[0058] In the electromagnetic wave absorbing layer 20, the shapes of the multiple third units u3 are identical to each other. However, the shapes of the multiple third units u3 do not have to be identical. In other examples of the present invention, the shapes of the multiple third units may be identical or different, as long as the absorption characteristics can be adjusted to the desired frequency.

[0059] The third electromagnetic wave absorption pattern 73 selectively absorbs electromagnetic waves with a frequency C [GHz] that satisfies the following equation (3). The frequency value C [GHz] is the frequency value at which the amount of electromagnetic wave absorption by the third electromagnetic wave absorption pattern 73 reaches its maximum value. The frequency value C [GHz] satisfies the following equation (3). 0.60×A≦C≦0.963×A...Equation (3)

[0060] As shown in equation (3) above, the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with frequencies from 0.60 × A [GHz] to 0.963 × A [GHz]. Preferably, the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with frequencies from 0.60 × A [GHz] to 0.83 × A [GHz]. Since the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with frequencies of 0.60 × A [GHz] or higher, the frequency difference between the peak of electromagnetic wave absorption by the third electromagnetic wave absorption pattern 73 and the peak of electromagnetic wave absorption by the first electromagnetic wave absorption pattern 71 becomes smaller in the frequency band lower than A [GHz]. As a result, a single peak is formed where the amount of electromagnetic wave absorbed by the entire electromagnetic wave absorption layer 20 reaches its maximum value. Since the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with frequencies of 0.963 × A [GHz] or less, the peak of electromagnetic wave absorption by the third electromagnetic wave absorption pattern 73 and the peak of electromagnetic wave absorption by the first electromagnetic wave absorption pattern 71 overlap sufficiently in the frequency band lower than A [GHz]. As a result, the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorption film is extended to the frequency band lower than A [GHz] compared to a film having the first electromagnetic wave absorption pattern 71 alone. Therefore, since the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with frequencies from 0.60 × A [GHz] to 0.963 × A [GHz], the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorption layer 20 is extended to the lower frequency band.

[0061] However, the shape of the third unit u3 is not limited to a cross shape. The shape of the third unit u3 is not particularly limited as long as the absorption characteristics can be adjusted to the target frequency. For example, the shape of the figure of the third unit can be a circle, ring, straight line, square, polygon, H-shape, Y-shape, V-shape, etc.

[0062] The material of the third unit u3 constituting the third electromagnetic wave absorption pattern 73 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 target frequency. The material of the third unit u3 is the same as that described for the material of the first unit u1.

[0063] The spacing between the ends of the third unit u3 is not particularly limited, as long as the absorption characteristics can be adjusted to the desired frequency. For example, the spacing between the edges of the third unit u3 figure may all be the same or they may be different. However, it is preferable that the spacing between the edges of the third unit u3 figure be the same, as this makes it easier to design an electromagnetic wave absorbing film that is less affected by the surrounding environment and improves the accuracy of the frequency band of absorbed electromagnetic waves during manufacturing.

[0064] In the electromagnetic wave absorbing layer 20 shown in Figure 2, the first array R1, the second array R2, and the third array R3 are arranged along the direction indicated by the double arrow P so that they are adjacent to each other. In this way, because the first array R1, the second array R2, and the third array R3 are arranged adjacent to each other on the substrate 21, the frequency bands of electromagnetic waves selectively absorbed by the second electromagnetic wave absorbing pattern 72 and the frequency bands of electromagnetic waves selectively absorbed by the third electromagnetic wave absorbing pattern 73 overlap, with respect to the frequency value A [GHz] of the peak position of the electromagnetic waves selectively absorbed by the first electromagnetic wave absorbing pattern 71. As a result, the electromagnetic wave absorption range absorbed by the entire electromagnetic wave absorbing layer 20 is easily extended to both the high-frequency and low-frequency sides, with respect to the frequency value A [GHz] of the peak position.

[0065] The intervals d1 between the first unit u1 and the second unit u2, d2 between the second unit u2 and the third unit u3, and d3 between the third unit u3 and the first unit u1, as shown in Figure 2, may be the same or different from each other. The interval d1 can be, for example, 0.2mm to 4mm, 0.3mm to 2mm, or 0.5mm to 1mm. The interval d2 can be, for example, 0.2mm to 4mm, 0.3mm to 2mm, or 0.5mm to 1mm. The spacing d3 can be, for example, 0.2mm to 4mm, 0.3mm to 2mm, or 0.5mm to 1mm. If intervals d1, d2, and d3 are each within the aforementioned numerical range, the absorption range of electromagnetic waves absorbed by the entire electromagnetic wave absorption layer 20 is more likely to be further extended with respect to the peak frequency value A [GHz].

[0066] In the electromagnetic wave absorbing layer 20, the shapes of the first unit u1, the second unit u2, and the third unit u3 are identical. However, the shapes of the first unit u1, the second unit u2, and the third unit u3 do not have to be identical. That is, in other examples of the present invention, the shapes of the first unit u1, the second unit u2, and the third unit u3 may be identical or different.

[0067] The electromagnetic wave absorbing layer 20 may have a plurality of second electromagnetic wave absorbing patterns 72. For example, in addition to the second electromagnetic wave absorbing pattern 72, the electromagnetic wave absorbing layer 20 may further include the following electromagnetic wave absorbing pattern 72a and electromagnetic wave absorbing pattern 72b. Electromagnetic wave absorbing pattern 72a: an electromagnetic wave absorbing pattern in which the frequency value at which the absorption amount of absorbed electromagnetic waves reaches a maximum value is D [GHz] satisfying the following formula (4). Electromagnetic wave absorbing pattern 72b: an electromagnetic wave absorbing pattern in which the frequency value at which the absorption amount of absorbed electromagnetic waves reaches a maximum value is E [GHz] satisfying the following formula (5). 1.037×A≦D<1.09×A···Formula (4) 1.09×A≦E<1.17×A···Formula (5) In the above formula (4) and the above formula (5), A is the frequency [GHz] specified by the above-mentioned method X or method Y.

[0068] When the electromagnetic wave absorbing layer 20 further includes the electromagnetic wave absorbing pattern 72a and the electromagnetic wave absorbing pattern 72b in addition to the second electromagnetic wave absorbing pattern 72, the frequency value at which the absorption amount of electromagnetic waves absorbed by the second electromagnetic wave absorbing pattern 72 reaches a maximum value is preferably from 1.17×A [GHz] to 1.30×A [GHz]. In this case, the effect of expanding the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorbing layer 20 toward the high frequency side is more remarkable, and the effect of the present invention can be obtained more remarkably.

[0069] The electromagnetic wave absorbing layer 20 may have a plurality of third electromagnetic wave absorbing patterns. For example, in addition to the third electromagnetic wave absorbing pattern 73, the electromagnetic wave absorbing layer 20 may further include the following electromagnetic wave absorbing pattern 73a and electromagnetic wave absorbing pattern 73b. Electromagnetic wave absorbing pattern 73a: an electromagnetic wave absorbing pattern in which the frequency value at which the absorption amount of absorbed electromagnetic waves reaches a maximum value is F [GHz] satisfying the following formula (6). Electromagnetic wave absorbing pattern 73b: an electromagnetic wave absorbing pattern in which the frequency value at which the absorption amount of absorbed electromagnetic waves reaches a maximum value is G [GHz] satisfying the following formula (7). 0.91×A<F≦0.963×A···Formula (6) 0.83×A<G≦0.91×A ··· Formula (7) In the following formula (6) and the following formula (7), A is the frequency [GHz] specified by the above-mentioned method X or method Y.

[0070] When the electromagnetic wave absorbing layer 20 further has an electromagnetic wave absorbing pattern 73a and an electromagnetic wave absorbing pattern 73b in addition to the third electromagnetic wave absorbing pattern 73, the frequency value at which the absorption amount of electromagnetic waves absorbed by the third electromagnetic wave absorbing pattern 73 reaches a maximum value is preferably 0.60×A [GHz] to 0.83×A [GHz]. In this case, the effect of expanding the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorbing layer 20 toward the low frequency side is more remarkable, and the effect of the present invention can be obtained more remarkably.

[0071] Figure 6 is a sectional view taken along line VIII-VIII of the electromagnetic wave absorbing layer 20 in Figure 2. The base material 21 has two mutually opposing surfaces 21a and 21b. A first electromagnetic wave absorbing pattern 71, a second electromagnetic wave absorbing pattern 72, and a third electromagnetic wave absorbing pattern 73 are formed on one surface 21a of the base material 21. As shown in Figure 6, a plurality of first units u1, a plurality of second units u2, and a plurality of third units u3 are respectively provided on one surface 21a of the base material 21.

[0072] The base material 21 is not particularly limited as long as it is flat and can be formed with the first electromagnetic wave absorbing pattern 71, the second electromagnetic wave absorbing pattern 72, and the third electromagnetic wave absorbing pattern 73 on the one surface 21a. The base material 21 may have a single-layer structure or a multi-layer structure.

[0073] The thickness K of the base material 21 may be, for example, 5 μm to 500 μm, 15 μm to 200 μm, or 25 μm to 100 μm. The thickness H1 of the first electromagnetic wave absorbing pattern 71, the thickness H2 of the second electromagnetic wave absorbing pattern 72, and the thickness H3 of the third electromagnetic wave absorbing pattern 73 are not particularly limited. The thickness H1, the thickness H2, and the thickness H3 can be arbitrarily changed according to desired properties. Further, the thickness H1, the thickness H2, and the thickness H3 may be the same as or different from each other. Thicknesses H1, H2, and H3 can be, for example, 1 μm to 100 μm, 5 μm to 50 μm, or 10 μm to 30 μm. The thicker each of thicknesses H1, H2, and H3, the better the electromagnetic wave absorption, but the higher the manufacturing cost. This point may be taken into consideration when setting the thicknesses H1, H2, and H3.

[0074] The material of the base material 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 to ensure the transparency of the electromagnetic wave absorbing member 10. Alternatively, the base material 21 may be made of a flexible material to ensure the conformability of the electromagnetic wave absorbing member 10 to curved surfaces. The surface of the base material 21 may be made smooth to improve the transparency and three-dimensional moldability of the electromagnetic wave absorbing member 10.

[0075] For example, the base material 21 can be made of resin. The resin may be either a thermoplastic resin or a thermosetting resin. However, when considering the three-dimensional moldability of the electromagnetic wave absorbing member 10, it is preferable that the base material 21 includes a thermoplastic resin. Examples of thermoplastic resins include polyolefin resins, polyester resins, polyacrylic resins, polystyrene resins, polyimide resins, polyimidoamide 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 and polyethylene. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0076] The base material 21 may contain optional components as long as they do not impair the effects of the present invention. Examples of optional components include inorganic fillers, colorants, curing agents, antioxidants, light stabilizers, flame retardants, conductive agents, antistatic agents, plasticizers, and the like.

[0077] The thickness, dielectric constant, electrical conductivity, and magnetic permeability of the base material 21 can be appropriately set to allow for further improvement of the electromagnetic wave absorption performance of the electromagnetic wave absorbing member 10. When considering the electrical characteristics of the electromagnetic waves to be absorbed, the base material 21 may be a layer with a high dielectric constant. If the base material 21 is a layer with a high dielectric constant, the thickness of the electromagnetic wave absorbing member 10 can be made relatively thinner.

[0078] The electromagnetic wave absorbing layer 20 can be fabricated, for example, by the following method. First, a base material 21 is prepared. Next, a first electromagnetic wave absorption pattern 71, a second electromagnetic wave absorption pattern 72, and a third electromagnetic wave absorption pattern 73 are formed on one surface 21a of the base material 21. Here, when forming the first electromagnetic wave absorption pattern 71, it is formed such that the frequency value at which the amount of electromagnetic waves absorbed by the first electromagnetic wave absorption pattern 71 shows a maximum value is A [GHz]. When forming the second electromagnetic wave absorption pattern 72, it is formed such that the frequency value at which the amount of electromagnetic waves absorbed by the second electromagnetic wave absorption pattern 72 shows a maximum value is B [GHz]. When forming the third electromagnetic wave absorption pattern 73, it is formed such that the frequency value at which the amount of electromagnetic waves absorbed by the third electromagnetic wave absorption pattern 73 shows a maximum value is C [GHz]. The order in which the first electromagnetic wave absorption pattern 71, the second electromagnetic wave absorption pattern 72, and the third electromagnetic wave absorption pattern 73 are formed is not particularly limited. The first electromagnetic wave absorption pattern 71, the second electromagnetic wave absorption pattern 72, and the third electromagnetic wave absorption pattern 73 may be formed in the same process, or they may be formed in separate processes.

[0079] The method for forming each electromagnetic wave absorption pattern is not particularly limited, as long as it can form a predetermined frequency. Examples of methods for forming each electromagnetic wave absorption pattern include the following: A printing method for printing each electromagnetic wave absorption pattern onto one surface 21a of a substrate 21 using a conductive paste. A developing method for developing each electromagnetic wave absorption pattern on one surface 21a of a substrate 21. A method for forming a metal thin film on one surface 21a of a substrate 21 by sputtering, vacuum deposition, or lamination of metal foils, and then forming a pattern of the metal thin film on one surface 21a of the substrate 21 by photolithography. A method for arranging a metal wire on one surface 21a of a base material 21.

[0080] In the printing method, each electromagnetic wave absorption pattern is printed on one surface 21a of the substrate 21 to form the geometric units u1, u2, and u3. The printing method is not particularly limited. Examples include screen printing, gravure printing, and inkjet printing. Examples of conductive pastes used in printing include paste-like compositions comprising at least one selected from the group consisting of metal particles, carbon nanoparticles, and carbon fibers, and a binder resin component. Examples of metal particles include copper, silver, nickel, and aluminum. Examples of binder resin components include thermoplastic resins such as polyester resin, (meth)acrylic resin, polystyrene resin, and polyamide resin; and thermosetting resins such as epoxy resin, amino resin, and polyimide resin. However, the metal particles and binder resin components are not limited to these examples. The conductive paste may further contain a black pigment such as carbon black. The inclusion of a black pigment in the conductive paste can suppress the metallic luster of the metal powder constituting the printed electromagnetic wave absorption pattern, thereby reducing the reflection of ambient light.

[0081] In the development method, an electromagnetic wave absorption pattern is developed on one surface 21a of the substrate 21 to form the geometric units u1, u2, and u3. There are two types of development methods: negative-type development, where the developed material appears in the exposed areas without being covered by an exposure mask, and positive-type development, where the developed material appears in the unexposed areas covered by an exposure mask. In other words, in negative-type development, each unit u1, u2, and u3 is formed as the developed material in the opposite shape to the exposure mask. On the other hand, in positive-type development, each unit u1, u2, and u3 is formed as the developed material in the same shape as the exposure mask. Silver is usually used as the metal for the developed material.

[0082] One example of a method for forming electromagnetic wave absorption patterns using photolithography is the following method. First, a resist is applied to one side 21a of the substrate 21, heat-treated, and then the solvent is removed from the resist. Next, a desired pattern is exposed to the resist, and the resist pattern is developed to form a layer consisting of the resist pattern. Then, a vapor-deposited film is formed over the entire surface on the substrate and the layer consisting of the resist pattern, and both the layer consisting of the resist pattern and the vapor-deposited film on top of it are removed simultaneously using a resist stripping agent. This allows an electromagnetic wave absorption pattern to be formed on the surface of the substrate. As another example, a thin metal film is provided on one surface 21a of the substrate 21, a resist is applied to a portion of the surface of the thin metal film, and then heat-treated. Next, the thin metal film in the areas where the resist is not applied is removed by etching. After that, the resist is removed as necessary to form an electromagnetic wave absorption pattern. A metal plating layer, not shown, may be further provided on the surface of each unit u1, u2, u3 that constitutes each electromagnetic wave absorption pattern.

[0083] Specific examples of metals constituting the metal wire include the same metals as those mentioned above as the material for each unit u1, u2, and u3. In addition, the metal wire may be plated with tin, zinc, silver, nickel, chromium, nickel-chromium alloy, solder, etc., and its surface may be coated with carbon materials, polymers, etc. Examples of carbon materials used to coat the surface of the metal wire include carbon black, activated carbon, hard carbon, soft carbon, mesoporous carbon, amorphous carbon such as carbon fiber; graphite; fullerene; graphene; and carbon nanotubes.

[0084] "Spacer layer" The spacer layer 30 is provided on the other surface 21b of the substrate 21 of the electromagnetic wave absorbing layer 20. The spacer layer 30 has two surfaces 30a and 30b. One surface 30a of the spacer layer 30 is in contact with the other surface 21b of the base material 21. The other surface 30b of the spacer layer 30 is provided with a reflective layer 40. The spacer layer 30 may have a single-layer structure or a multi-layer structure.

[0085] The material of the spacer layer 30 can be appropriately selected depending on the application of the partition. For example, the spacer layer 30 may be made of a transparent material to provide transparency to the partition. Alternatively, the spacer layer 30 may be made of a flexible material to provide conformability to curved surfaces of the partition. Flexible materials include plastic films, rubber, paper, cloth, nonwoven fabrics, foams, and rubber sheets. Among these, foams are preferred because they make the electromagnetic wave absorbing member 10 lightweight. As a specific example of the resin constituting the plastic film, for example, the same type of thermoplastic resin as described above for the base material 21 can be used. As the foam, for example, a foamed sheet can be used, which is made by foaming the resin that constitutes the plastic film and forming it into a sheet. Specific examples of foamed sheets include polyethylene foam, polypropylene foam, polyurethane foam, and the like.

[0086] When considering the wavelength shortening effect of the spacer layer 30, the thickness of the spacer layer 30 is appropriately changed according to the wavelength of the electromagnetic wave to be absorbed and the relative permittivity of the spacer layer 30. When considering the wavelength shortening effect of the spacer layer 30, it is preferable that the thickness of the spacer layer 30 in the z-axis direction satisfies the following equation (8). (Thickness of spacer layer 30 in the z-axis direction) = (λ) × (1 / 4) / (ε) 1 / 2 ...Equation (8) In equation (8) above, λ is the wavelength of the incoming electromagnetic wave, and ε is the relative permittivity of the spacer layer 30. The thickness of the spacer layer 30 in the z-axis direction may be adjusted as appropriate 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 in the z-axis direction obtained in equation (8).

[0087] When the relationship between the thickness of the spacer layer 30 in the z-axis direction and the wavelength λ satisfies equation (8) above, the electromagnetic wave absorbing member 10 becomes a so-called λ / 4 structure. This further increases the maximum value of the amount of electromagnetic waves absorbed by the electromagnetic wave absorbing member 10. The thickness of the spacer layer 30 can be appropriately set according to the wavelength λ of the electromagnetic wave to be absorbed. For example, the thickness of the spacer layer 30 may be 25 μm to 5000 μm, 50 μm to 4500 μm, or 100 μm to 4000 μm. The spacer layer 30 may be made of a material with a high dielectric constant. If the spacer layer 30 is a layer with a high dielectric constant, the thickness of the spacer layer 30 can be made relatively thinner. When considering the dielectric constant of the spacer layer 30, it is preferable that the spacer layer 30 contains at least one selected from the group consisting of barium titanate, titanium oxide, and strontium titanate.

[0088] By increasing the dielectric constant of the spacer layer 30, the thickness of the spacer layer 30 can be reduced. This makes the electromagnetic wave absorbing member 10 lighter.

[0089] It is preferable that the two surfaces 30a and 30b of the spacer layer 30 are adhesive. This allows the electromagnetic wave absorption layer 20 and the reflection layer 40 to be bonded to each of the two surfaces 30a and 30b. For example, the two surfaces 30a and 30b can be made adhesive by employing a multilayer structure in which the two surfaces 30a and 30b are adhesive layers containing an adhesive. Details and preferred embodiments of the adhesive layer can be the same as those described for the adhesive layer on the substrate 21.

[0090] "Reflective layer" The reflective layer 40 has two surfaces 40a and 40b. One surface 40a of the reflective layer 40 is in contact with the other surface 30b of the spacer layer 30. The reflective layer 40 is not particularly limited as long as it is capable of reflecting electromagnetic waves that fly onto the surface of the electromagnetic wave absorbing member 10 and pass through the electromagnetic wave absorbing member 10. Of the electromagnetic waves that fly onto the electromagnetic wave absorbing member 10, some are reflected by the electromagnetic wave absorbing layer 20 or absorbed by the electromagnetic wave absorbing layer 20. On the other hand, electromagnetic waves that are neither reflected nor absorbed by the electromagnetic wave absorbing layer 20 pass through the electromagnetic wave absorbing layer 20. Electromagnetic waves that pass through the electromagnetic wave absorbing layer 20 are reflected back to the electromagnetic wave absorbing layer 20 by the reflective layer 40. For example, if the reflective layer 40 is conductive in the planar direction of the two surfaces 40a and 40b, it can reflect electromagnetic waves that have passed through the electromagnetic wave absorption layer 20. Specifically, the reflective layer 40 may be made by laminating a metal foil such as copper foil or a metal plate such as copper plate onto a resin film such as polyethylene terephthalate. Instead of metal foil or metal plate, a mesh sheet made of a surface conductive film such as ITO or metal wire may be used. Among these, metal plates are preferred in terms of their high conductivity.

[0091] Considering the reflective properties of the reflective layer 40, a metal wire, a conductive thread, a twisted yarn 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 surface 40b by printing methods such as screen printing, gravure printing, or inkjet printing; sputtering or vacuum deposition; or photolithography.

[0092] When the spacer layer 30 is formed on an object that has conductivity, such as a metal, the object that has conductivity, such as a metal, acts as the reflective layer 40, and therefore the reflective layer 40 can be omitted.

[0093] For the purpose of applying the electromagnetic wave absorbing member 10 to the surface of various articles, the other surface 40b of the reflective layer 40 may be made adhesive. If the other surface 40b of the reflective layer 40 is made adhesive, a release film may be provided to cover the surface 40b. The release film is removed when the electromagnetic wave absorbing member 10 is used. Covering the adhesive surface with a release film improves handling during distribution. For example, by adopting a multilayer structure in which the other surface 40b of the reflective layer 40 is an adhesive layer containing an adhesive, the other surface 40b of the reflective layer 40 can be made adhesive.

[0094] Examples of adhesives include heat-seal adhesives that bond using heat, adhesives that become adhesive when wet, and pressure-sensitive adhesives (adhesives) that bond using pressure. Among these, adhesives (pressure-sensitive adhesives) are preferred from the viewpoint of simplicity. Specific examples of adhesives include acrylic adhesives, urethane adhesives, rubber adhesives, polyester adhesives, silicone adhesives, and polyvinyl ether adhesives. Among these, at least one selected from the group consisting of acrylic adhesives, urethane adhesives, and rubber adhesives is preferred, with acrylic adhesives being more preferred.

[0095] Furthermore, the electromagnetic wave absorbing member 10 of this embodiment may include a protective layer formed on one side (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 absorption layer 20.

[0096] The thickness of the protective layer is preferably 1 μm to 500 μm, more preferably 3 μm to 100 μm, and even more preferably 5 μm to 50 μm. If the thickness of the protective layer is greater than or equal to the lower limit, it can adequately follow and protect the irregularities of the electromagnetic wave absorbing layer 20. If the thickness of the protective layer is less than or equal to the upper limit, seepage from the sides of the composition constituting the protective layer is suppressed, and flexibility can be given to the partition.

[0097] [Manufacturing method for electromagnetic wave absorbing material] The electromagnetic wave absorbing member 10 can be manufactured, for example, by the following method. A composition is prepared containing a modified polyolefin resin and a polyphenylene ether resin having a reactive group. The composition is obtained by adding a modified polyolefin resin and a polyphenylene ether resin having a reactive group to a solvent, stirring and mixing them, and dissolving the resin in the solvent. The composition may optionally contain various additives in addition to the modified polyolefin resin and the polyphenylene ether resin having reactive groups. Examples of additives include silane coupling agents and curing agents. The curing agent is not particularly limited as long as it initiates the curing reaction. Because of its excellent stability over time and productivity, a curing agent that initiates the curing reaction by heating is preferred. The inclusion of a curing agent in the above composition is preferable because it allows the curing reaction to proceed more efficiently. Examples of curing agents that initiate the curing reaction by heating include thermal cationic polymerization initiators and other heat-reactive curing agents. As the silane coupling agent, known silane coupling agents can be used. Among these, organosilicon compounds having at least one alkoxysilyl group in the molecule are preferred. The solvent is not particularly limited as long as it can dissolve the modified polyolefin resin and the polyphenylene ether resin having a reactive group, but examples include aromatic hydrocarbon solvents such as benzene and toluene; ester solvents such as ethyl acetate and butyl acetate; isoketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone n; aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-heptane; and alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane and methylcyclohexane.

[0098] The above composition is applied to the release surface of a release film, and the resulting coating is dried to form an adhesive layer. The method of applying the composition is not particularly limited. Examples of application methods include printing methods such as screen printing, gravure printing, and inkjet printing. An adhesive sheet is obtained by laminating the release surface of another release film onto this adhesive layer. Next, one side of the release film of the adhesive sheet is peeled off, and the exposed side of the adhesive sheet is attached to the other side 20b of the electromagnetic wave absorbing layer 20.

[0099] Next, the other side of the release film on the adhesive sheet is peeled off, and the material that will become the spacer layer 30 is attached to the other side of the exposed adhesive sheet. Next, the material that will become the reflective layer 40 is attached to the other surface 30b of the spacer layer 30 via the adhesive sheet, in the same manner as with the spacer layer 30. By the above method, an electromagnetic wave absorbing member 10 is obtained.

[0100] According to the electromagnetic wave absorbing member 10 of this embodiment, a plurality of slits 50 are formed from the outermost surface of the electromagnetic wave absorbing layer 20, substantially parallel to the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30. The laminate 60 consisting of the electromagnetic wave absorbing layer 20 and the spacer layer 30 is divided into a plurality of regions via the plurality of slits 50. Since the width W0 of the plurality of slits 50 is less than 10 mm, as shown in Figure 7, the electromagnetic wave absorbing member 10 is flexible and can be wound into a smaller size. Furthermore, according to the electromagnetic wave absorbing member 10 of this embodiment, at least a portion of adjacent spacer layers 30 are connected at the ends of the plurality of slits 50 on the reflection layer 40 side, so that the reflection layer 40 does not unnecessarily reflect electromagnetic waves.

[0101] Furthermore, the electromagnetic wave absorbing member 10 of this embodiment is not limited in size, but can be easily made to have a large area, and even if it is large, it can be wound up and stored compactly, which is one of its features. From this viewpoint, the size of the side (horizontal) substantially parallel to the slit extension direction is preferably 0.1m or more and 10m or less, more preferably 0.5m or more and 5m or less, and particularly preferably 0.8m or more and 1.8m or less. Also, the size of the side (vertical: the side that is wound up) perpendicular to the slit extension direction is preferably 0.1m or more and 10m or less, more preferably 0.5m to 5m, and particularly preferably 1.5m or more and 3.0m or less.

[0102] [Partition for aiming] Figure 8 is a schematic side view showing an aiming partition according to one embodiment of the present invention. As shown in Figure 8, the aiming partition 100 of this embodiment comprises a support member 110, a support plate 120, and a front plate 130. The front plate 130 is the electromagnetic wave absorbing member 10 of the above-described embodiment.

[0103] The aiming partition 100 of this embodiment includes, for example, a pair of support members 110 arranged at a predetermined interval and spaced apart from each other. The pair of support members 110 are arranged so that their longitudinal direction is aligned with the vertical direction. The pair of support members 110 may also be arranged so that their longitudinal direction is substantially aligned with the vertical direction, as long as they are long enough to support the front panel 130.

[0104] As shown in Figure 8, it is preferable that the aiming partition 100 has a crossbar 140 between a pair of support members 110. Furthermore, it is preferable that the support plate 120 is fixed to the pair of support members 110 and the crossbar 140. This allows the front plate 130 to be supported more stably by the support members 110. Furthermore, the front panel 130 is joined to the support panel 120 via an adhesive layer 150.

[0105] The support plate 120 is rectangular in shape when viewed from above. The support plate 120 is fixed to a pair of support members 110. In Figure 8, the support plate 120 is positioned from one support member 110A to the other support member 110B. The support plate 120 only needs to be positioned so that its shorter side is aligned with the vertical or approximately vertical direction while fixed to the pair of support members 110, and the position where it connects to the pair of support members 110 is not particularly limited.

[0106] The size (area) of the support plate 120 when viewed from above is appropriately adjusted according to the projected area when viewing the vehicle being aimed using the aiming partition 100 from the front. The size of the support plate 120 when viewed from above is preferably, for example, 2m in height and 2.5m in width, but multiple small aiming partitions can be arranged to achieve the aforementioned size. When multiple small aiming partitions are arranged, reducing the gaps between the partitions will suppress radio wave leakage. In this specification, height refers to the vertical direction of the paper, and width refers to the horizontal direction of the paper.

[0107] "Support member" The length of the support member 110 is adjusted as appropriate according to the size (area) of the front panel 130 when viewed from above. Examples of materials that make up the support member 110 include non-metallic materials such as resin and wood, and metal. In order to further improve the effect of preparing the working environment for aiming by the aiming partition 100, it is preferable that the support member 110 be made of a non-metallic material that hardly reflects electromagnetic waves.

[0108] The means used to fix the support plate 120 to the support member 110 include adhesives, screws, bolts and nuts, etc. The material of the means for fixing the support plate 120 is preferably a non-metallic material that does not reflect electromagnetic waves, such as resin or wood. Conductive materials such as metals are not suitable for fixing the support plate 120 because they reflect electromagnetic waves.

[0109] The support plate 120, which has the front panel 130, may be removable from the support member 110. In order to make the support plate 120 removable from the support member 110, a frame material shaped to conform to the outer shape of the support plate 120 may be provided on the support member 110, and the support plate 120 may be inserted into the frame material or fitted into the frame material. Alternatively, a hook or the like may be provided on the outer edge of the support plate 120, and the support plate 120 may be hooked onto the support member 110 and fixed in place. In this way, the aiming partition 100 can be disassembled into the support member 110 and the front panel 130, making it easy to transport and eliminating the need for a large storage space.

[0110] "Support plate" The support plate 120 is preferably flexible. If the support plate 120 is flexible, it can be made of a resin sheet, paper, fabric, etc. The resin that makes up the resin sheet is not particularly limited, but for example, the resin that makes up the base material 21 can be used. Because the support plate 120 is flexible, the support plate 120 with the front plate 130 can be rolled up. In this way, the aiming partition 100 is easy to transport and does not require a large storage space.

[0111] "Sandbar" As shown in Figure 8, the crossbar 140 is provided, for example, along the lateral direction of the support plate 120. Examples of materials that make up the crossbar 140 include non-metallic materials that hardly reflect electromagnetic waves, such as resin and wood, and metals. In order to further improve the effect of preparing the working environment for aiming with the aiming partition 100, it is preferable that the crossbar 140 be made of a non-metallic material that hardly reflects electromagnetic waves.

[0112] "Adhesive layer" Examples of adhesives used to form the adhesive layer 150 include acrylic-based strong adhesives, but they are selected appropriately depending on the material of the surface to which they are applied.

[0113] The aiming partition 100 of this embodiment comprises a support member 110, a support plate 120 supported by the support member 110, and a front plate 130 positioned on at least one surface 120a of the support plate 120. Therefore, it is lightweight, easy to transport, and does not require a large storage space. Accordingly, the aiming partition 100 of this embodiment makes it easy to create a suitable working environment for automobile aiming.

[0114] In Figure 8, an example is shown where the electromagnetic wave absorbing layer 20, spacer layer 30, reflective layer 40, adhesive layer 150, and support plate 120 are stacked in this order, but the aiming partition of the present invention is not limited to this. In the aiming partition of the present invention, if a conductive material is used as the support plate 200, the electromagnetic wave absorbing layer 20, spacer layer 30, adhesive layer 150, and support plate 200 may be stacked in this order, as shown in Figure 9. [Examples]

[0115] 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.

[0116] [Example 1] Assuming a radar for advanced driver-assistance systems, a copper thin film was formed by depositing copper onto a substrate made of PET film (product name: PET50A4160, manufactured by Toyobo Co., Ltd.). Subsequently, the copper thin film was patterned into an electromagnetic wave absorption pattern using photolithography to obtain an electromagnetic wave absorption layer. On the back surface of the resulting electromagnetic wave absorbing layer, a 2mm thick foamed urethane sheet (product name: PORON HH-48, manufactured by Inoac Corporation) was used as a spacer layer, and an aluminum-deposited PET film (bending rigidity: 8.33 Pa·mm) was used as a reflective layer. 4 ) and were stacked in this order to create an electromagnetic wave absorbing member. On the obtained electromagnetic wave absorbing member, cuts were made with a cutter blade at 10 cm intervals, with a slit width (0.1 mm) as shown in Table 1, approximately parallel to the thickness direction of the electromagnetic wave absorbing layer and the spacer layer, starting from the outermost surface of the electromagnetic wave absorbing layer, thereby forming multiple slits. As a result, an electromagnetic wave absorbing member with slits formed thereon, measuring 1.5 m in width and 2.0 m in height, was obtained. The electromagnetic wave absorbing member was attached to a support plate made of PET film (product name: PET50A4160, manufactured by Toyobo Co., Ltd.) via an adhesive. Furthermore, an aiming partition was obtained by attaching electromagnetic wave absorbing members, which were attached to a support plate, to a pair of support members that were spaced apart from each other at a predetermined interval.

[0117] [Example 2] An aiming partition for Example 2 was obtained in the same manner as in Example 1, except that a slit with a width of 2 mm as shown in Table 1 was made in the electromagnetic wave absorbing member.

[0118] [Example 3] An aiming partition for Example 3 was obtained in the same manner as in Example 1, except that a slit with the width shown in Table 1 (4 mm) was cut into the electromagnetic wave absorbing member.

[0119] [Example 4] An aiming partition for Example 4 was obtained in the same manner as in Example 1, except that a slit with the width shown in Table 1 (7 mm) was cut into the electromagnetic wave absorbing member.

[0120] [Comparative Example 1] A targeting partition for Comparative Example 1 was obtained in the same manner as in Example 1, except that a slit with a width of 10 mm as shown in Table 1 was made in the electromagnetic wave absorbing member.

[0121] [Comparative Example 2] A targeting partition for Comparative Example 2 was obtained in the same manner as in Example 1, except that no cuts were made in the electromagnetic wave absorbing member.

[0122] [evaluation] "Reflection loss" Using the free-space method, the S21 values ​​of the aiming partitions for Examples 1-4, Comparative Example 1, and Comparative Example 2 were acquired with a network analyzer, and the return loss of each aiming partition was evaluated. The results are shown in Table 1 and Figure 10. Figure 10 shows the return loss of Example 1, Comparative Example 1, and Comparative Example 2.

[0123] "Retractability" The electromagnetic wave absorbing members of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were rolled up by hand, and it was visually confirmed whether they could be rolled up without wrinkles or creases. After rolling them up, they were unrolled and used again as aiming partitions. If no wrinkles or creases were found in the electromagnetic wave absorbing member when unrolled, it was evaluated as "○" (○). If wrinkles or creases were found in the electromagnetic wave absorbing member when unrolled, it was evaluated as "×" (×). The results are shown in Table 1.

[0124] [Table 1]

[0125] From the results shown in Table 1 and Figure 10, it was found that the aiming partitions of Examples 1 to 4 exhibited excellent reflection attenuation, and the electromagnetic wave absorbing member of Example 1 exhibited excellent winding properties. On the other hand, the aiming partition of Comparative Example 1 was found to have inferior reflection attenuation, while the electromagnetic wave absorbing member of Comparative Example 1 was found to have excellent winding properties. Furthermore, it was found that the aiming partition in Comparative Example 2 had excellent reflection attenuation, while the electromagnetic wave absorbing member in Comparative Example 2 had poor winding properties. [Industrial applicability]

[0126] The electromagnetic wave absorbing member of the present invention can be suitably used in aiming partitions used for automobile aiming. [Explanation of Symbols]

[0127] 10 Electromagnetic wave absorbing member 20 Electromagnetic wave absorption layer 21 Base material 22 Electromagnetic wave absorption patterns 30 Spacer layer 40 reflective layer 50 slits 60-layer structure 71. First electromagnetic wave absorption pattern 72. Second electromagnetic wave absorption pattern 73. Third electromagnetic wave absorption pattern 100 Aiming Partition 110 Support member 120 Support plate 130 Front plate 140 slats 150 Adhesive layer

Claims

1. It has 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 stacked in this order. Multiple slits are formed from the outermost surface of the electromagnetic wave absorbing layer, substantially parallel to the thickness direction of the electromagnetic wave absorbing layer and the spacer layer, and the laminate consisting of the electromagnetic wave absorbing layer and the spacer layer is divided into multiple regions through these multiple slits. At the reflective layer-side ends of the multiple slits, at least a portion of adjacent spacer layers are connected. An electromagnetic wave absorbing member in which the width of the plurality of slits is less than 10 mm.

2. The electromagnetic wave absorbing member according to claim 1, wherein, in a plan view of the electromagnetic wave absorbing member, the spacing between the plurality of slits is 1 cm or more and 30 cm or less.

3. The electromagnetic wave absorbing member according to claim 1, wherein the spacer layer is made of foam.

4. The electromagnetic wave absorbing member according to claim 1, wherein the reflective layer is made of a conductor.

5. It comprises a support member, a support plate supported by the support member, and a front plate disposed on at least one side of the support plate, The front panel is an electromagnetic wave absorbing member according to any one of claims 1 to 4, an aiming partition.

Images