JP2023151156A - Electromagnetic wave absorbing material, and aiming partition - Google Patents

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

The present invention relates to an electromagnetic wave absorbing member and an aiming partition including the same.

BACKGROUND ART A sheet-shaped electromagnetic wave absorbing member that selectively absorbs electromagnetic waves of a predetermined frequency is known. The electromagnetic wave absorbing member includes, for example, 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 due to the thin line pattern of the FSS (Frequency Selective Surface) element formed in the first frequency selective shielding layer and the second frequency selective shielding layer. , selectively shields electromagnetic waves of two different frequencies as a whole.

Since electromagnetic wave absorbing members have a large area depending on their use, they are required to be rolled up and made smaller when being stored or transported. To this end, electromagnetic wave absorbing members are required to have a bendable structure.

Patent Document 1 describes an electromagnetic wave absorbing member including a plurality of electromagnetic wave absorbers that are arranged at predetermined intervals and capable of absorbing electromagnetic waves for the purpose of bending.

Patent No. 6869704

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 existing in the gap. Therefore, in Patent Document 1, reflection is suppressed by providing a gap reflecting section in the gap and directing the electromagnetic waves toward the electromagnetic wave absorbing member. Therefore, it is necessary to increase the thickness of the electromagnetic wave absorbing member, and the thickness is approximately 10 mm to 15 mm. As a result, the weight of the electromagnetic wave absorbing member increases, and although winding is possible, it becomes difficult to wind it up into a small size.

The present invention has been made in view of the above circumstances, and provides an electromagnetic wave absorbing member that can be wound into a smaller size and can suppress unnecessary reflection of electromagnetic waves, and an aiming partition equipped with the same. With the goal.

The present invention provides the following electromagnetic wave absorbing member and an aiming partition including the same.
[1] Includes an electromagnetic wave absorption 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,
A plurality of slits substantially parallel to the thickness direction of the electromagnetic wave absorption layer and the spacer layer are formed from the outermost surface of the electromagnetic wave absorption layer, and the electromagnetic wave absorption layer and the spacer layer are formed through the plurality of slits. The stack is divided into multiple regions,
An electromagnetic wave absorbing member, wherein the width of the plurality of slits is less than 10 mm.
[2] The electromagnetic wave absorbing member according to [1], wherein the distance between the plurality of slits is 1 cm or more and 30 cm or less when viewed in plan of the electromagnetic wave absorbing member.
[3] The electromagnetic wave absorbing member according to [1], wherein the spacer layer is made of a foam.
[4] The electromagnetic wave absorbing member according to [1], wherein the reflective layer is made of a conductor.
[5] A support member, a support plate supported by the support member, and a front plate disposed on at least one surface 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].

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.

1 is a cross-sectional view along the thickness, schematically showing an electromagnetic wave absorbing member according to an embodiment of the present invention. FIG. 2 is a top view showing an example of an electromagnetic wave absorbing layer that constitutes an electromagnetic wave absorbing member according to an embodiment of the present invention. It is a top view showing an example of the 1st electromagnetic wave absorption pattern of the electromagnetic wave absorption layer which constitutes the electromagnetic wave absorption member concerning one embodiment of the present invention. It is a top view showing an example of the 2nd electromagnetic wave absorption pattern of the electromagnetic wave absorption layer which constitutes the electromagnetic wave absorption member concerning one embodiment of the present invention. It is a top view showing an example of the 3rd electromagnetic wave absorption pattern of the electromagnetic wave absorption layer which constitutes the electromagnetic wave absorption member concerning one embodiment of the present invention. 3 is a sectional view taken along line VIII-VIII in FIG. 2. FIG. 1 is a cross-sectional view along the thickness, schematically showing an electromagnetic wave absorbing member according to an embodiment of the present invention. FIG. 1 is a side view schematically showing an aiming partition according to an embodiment of the present invention. FIG. 1 is a side view schematically showing an aiming partition according to an embodiment of the present invention. FIG. 3 is a diagram showing the results of evaluating the amount of return loss of the aiming partition in Example 1, Comparative Example 1, and Comparative Example 2.

The electromagnetic wave absorbing member of the present invention and the aiming partition provided with the same are specifically explained in order to better understand the purpose of the present invention, and unless otherwise specified, the present invention is not limited to the present invention.

As used herein, the term "electromagnetic wave absorption pattern" refers to an object that is a collection of geometric units and selectively absorbs electromagnetic waves of a certain frequency. It can be said that the "electromagnetic wave absorption pattern" has a function similar to that of a so-called antenna.
In this specification, "electromagnetic waves in the millimeter wave region" means electromagnetic waves with a wavelength of 1 mm to 10 mm. "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, "~" indicating a numerical range means that the numerical values described before and after it are included as lower and upper limits.

[Electromagnetic wave absorbing member]
FIG. 1 schematically shows an electromagnetic wave absorbing member according to an embodiment of the present invention, and is a sectional view taken along the thickness.
As shown in FIG. 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. Further, the electromagnetic wave absorbing layer 20, the spacer layer 30, and the reflective layer 40 are laminated in this order.

The reflective layer 40 is arranged on the other surface (back surface) 20b side of the electromagnetic wave absorption layer 20. The spacer layer 30 is arranged 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 in between.

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

In the electromagnetic wave absorbing member 10 of this embodiment, a plurality of A slit 50 is formed. Further, the laminate 60 made up of the electromagnetic wave absorbing layer 20 and the spacer layer 30 is divided into a plurality of regions (region 60A, region 60B, and region 60C in FIG. 1) via the plurality of slits 50. The slit 50 may be parallel to the thickness direction of the electromagnetic wave absorption 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. Good too.

In the electromagnetic wave absorbing member 10 of this embodiment, the width of the plurality of slits 50, that is, the width W0 of the slit 50 on the outermost surface of the electromagnetic wave absorbing layer 20 (one surface 21a of the base material 21) in FIG. 1 is less than 10 mm. Yes, preferably 5 mm or less, 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 deteriorate.

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 to each other at the ends of the plurality of slits 50 on the reflective layer 40 side. That is, it is preferable that the reflective layer 40 is not exposed at the ends of the plurality of slits 50 on the reflective layer 40 side. Thereby, the obtained electromagnetic wave absorbing member 10 can be made to have excellent durability against repeated winding.

In the electromagnetic wave absorbing member 10 of this embodiment, 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 even more preferably 3 cm or more and 10 cm or less, in a plan view of the electromagnetic wave absorbing member 10. . If the distance d0 is less than the lower limit, the frequency of dividing the laminate 60 by the slits 50 increases, and the absorption characteristics of the electromagnetic wave absorbing layer 20 may deteriorate. When the distance d0 exceeds the upper limit value, the winding performance of the electromagnetic wave absorbing member 10 decreases, and the storage size of the electromagnetic wave absorbing member 10 increases. The distance d0 is the distance between the center line c passing through the slit 50 in parallel to the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30.

The slit 50 is formed by making a cut in the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30 using a cutter or the like. When the electromagnetic wave absorbing member 10 is unfolded into a flat state (unrolled), the physical gap (the gap caused by the slit 50) in the electromagnetic wave absorbing member 10 is minimal, so that electromagnetic waves are not emitted from the reflective layer 40. Reflections are also minimized. Therefore, the electromagnetic wave absorbing member 10 of this embodiment has the best electromagnetic wave absorbing property when it is rolled up and used in a flat state. Therefore, as in Patent Document 1, there is no need to provide a gap reflecting section in the gap, and there is no need to consider oblique reflection thereof, so the thickness can be reduced. Therefore, the winding performance of the electromagnetic wave absorbing member 10 can be improved.

The electromagnetic wave absorbing member 10 of this embodiment preferably has a bending rigidity of 1.0×10 ⁻⁴ Pa·mm ⁴ or more and 2250 Pa·mm ⁴ or less, and preferably 1.7×10 ⁻³ Pa·mm ⁴ or more and 1040 Pa·mm ⁴ The following are more preferable, and 6.7×10 ⁻³ Pa·mm ⁴ or more and 390 Pa·mm ⁴ or less are even more preferable.

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

"Electromagnetic wave absorption layer"
The electromagnetic wave absorption 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 with a shape smaller than the wavelength using a conductive member or the like.

FIG. 2 is a top view showing an example of the electromagnetic wave absorption layer in this embodiment. As shown in FIG. 2, the electromagnetic wave absorbing layer 20 is an electromagnetic wave absorbing film having a flat base material 21 and an electromagnetic wave absorbing pattern 22 formed on one surface 21a of the base material 21. The electromagnetic wave absorption pattern 22 includes a first electromagnetic wave absorption pattern 71, a second electromagnetic wave absorption pattern 72, and a third electromagnetic wave absorption pattern 73.

(First electromagnetic wave absorption pattern)
FIG. 3A is a top view showing the first electromagnetic wave absorption pattern 71. FIG.
As shown in FIG. 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.
That is, it can be said that the first electromagnetic wave absorption pattern 71 is a collection of first units u1 that are geometric figures.
Each of the first units u1 functions as one antenna. The first electromagnetic wave absorption pattern 71 may be, for example, a thin line pattern of an FSS element.

In the first electromagnetic wave absorption pattern 71, 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. 3(a). It can also be said that the first electromagnetic wave absorption pattern 71 has a plurality of first arrays R1. The first electromagnetic wave absorption pattern 71 can be constructed by forming a plurality of first arrays R1 on the base material 21 at predetermined intervals along the direction indicated by the double-headed arrow P.
The interval between the plurality of first arrays R1 is not particularly limited. The intervals between the first arrays R1 may be regular or irregular.

FIG. 3(b) is a top view showing the first unit u1.
FIG. 3(b) is a top view showing the first unit u1 forming the first electromagnetic wave absorption pattern 71. FIG.
As shown in FIG. 3(b), the shape of the first unit u1 is a cross shape that is vertically and horizontally symmetrical. 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 and a straight line portion parallel to the y-axis direction in FIG. 3(b). Each straight end portion T1 is in contact with each of 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 orthogonal to each straight line portion.

By adjusting the length L1 of the first unit u1 in the x-axis direction and the length W1 of each of the four ends T1 in the x-axis direction, the electromagnetic waves generated by the first unit u1 functioning as one antenna can be adjusted. Absorption properties can be adjusted. Similarly, the electromagnetic wave absorption characteristics can be adjusted in the y-axis direction as well.

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 has a maximum value is A [GHz].
For example, the shape of the figure that is the first unit includes a circular shape, an annular shape, a linear shape, a square shape, a polygonal shape, an H-shape, a Y-shape, a V-shape, and the like.

In the electromagnetic wave absorption layer 20, the shapes of the plurality of first units u1 are the same. However, the shapes of the plurality of first units u1 do not have to be the same figure. In other examples of the present invention, the shapes of the plurality of first units may be the same or different as long as the absorption characteristics can be adjusted to a target frequency.

The first electromagnetic wave absorption pattern 71 selectively absorbs electromagnetic waves having a frequency of A [GHz]. The frequency value A [GHz] is the frequency value when 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 waves absorbed by the first electromagnetic wave absorption pattern 71 has a maximum value can be specified by, for example, method X and method Y below.

method shall be.
Method Y: From an electromagnetic wave absorbing film having a base material and a plurality of electromagnetic wave absorbing patterns formed on the base material, the electromagnetic wave absorbing pattern is removed from the base material so that only a single electromagnetic wave absorbing pattern remains. Next, a film having only a single electromagnetic wave absorption pattern is irradiated with electromagnetic waves while changing the frequency within the range of 20 GHz to 110 GHz, and the frequency of the electromagnetic waves when the amount of electromagnetic wave absorption of the film reaches the maximum value is determined as A. [GHz].

The standard film has a flat standard base material and a standard pattern formed on the standard base material.
The details of the standard base material can be the same as those of the base material 21. Therefore, details of the standard base material will be explained in detail in the description of the base material 21 described later.

The standard pattern consists only of a plurality of standard units having the same shape. In the standard film, it can be said that a standard pattern consisting of only one type of figure having the same shape is formed on the standard base material. 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 absorption pattern as the first electromagnetic wave absorption pattern 71.
In the standard pattern, the shapes of the plurality of standard units are not particularly limited as long as they are the same figures. Examples of the shape of the figure which is a standard unit include a circular shape, an annular shape, a linear shape, a square shape, a polygonal shape, a cross shape, an H shape, a Y shape, a V shape, and the like. Usually, the shape of the standard unit is the same as the first unit u1.

In the standard film, a plurality of standard units are arranged on a standard base material such that the distance between the edges of the figures is 1 mm. For example, if the standard unit figure is a cross, the intersection of the crosses is the center of the figure, and the edge of the figure is the farthest distance from the center along each of the two straight line parts that make up the cross. This is the part where

The material of the standard units constituting the standard pattern must be in a manner that allows the amount of electromagnetic waves absorbed by the standard film to take the maximum value when the standard film is irradiated with electromagnetic waves while changing the frequency within the range of 20 GHz to 110 GHz. However, there are no particular limitations.
The details of the material of the standard unit can be the same as those of the first unit.

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 the standard film is irradiated with electromagnetic waves.
The reflection characteristic (S11) is an index of the intensity of electromagnetic waves reflected by the standard film when the standard film is irradiated with electromagnetic waves from the irradiation source. The reflection characteristics (S11) can be measured, for example, by a free space method using a vector network analyzer.
The transmission characteristic (S21) is an index of the intensity of electromagnetic waves that pass through the standard film when the standard film is irradiated with electromagnetic waves from the irradiation source. The transmission characteristics (S21) can be measured, for example, by a free space method using a vector network analyzer.

For example, the frequency A [GHz] can be specified by the following method.
First, a standard film is irradiated with electromagnetic waves while changing 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 equation (1).
Next, an absorption spectrum diagram is created in which the changed frequency is plotted on the horizontal axis and the absorption amount calculated by the above formula (1) is plotted on the vertical axis. Usually, in this absorption spectrum diagram, there is one frequency value on the horizontal axis where the amount of absorption is the maximum value. Therefore, a single peak is formed in the plot where the amount of electromagnetic wave absorption reaches its maximum value. In this way, the frequency of electromagnetic waves when the amount of absorption of electromagnetic waves takes the maximum value can be set to A [GHz].

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

The first electromagnetic wave absorption pattern 71 absorbs electromagnetic waves whose frequency is A [GHz] specified by method X described above.
In the electromagnetic wave absorbing layer 20 in 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 absorption layer 20 can absorb electromagnetic waves in the millimeter wave region, and is applicable to automobile parts, road peripheral materials, building external wall related materials, windows, communication equipment, radio telescopes, etc. It becomes easier and easier to do.

In method Y, similarly to method X, the amount of electromagnetic waves absorbed by the film can be measured. That is, the film is irradiated with electromagnetic waves while changing the frequency within the range of 20 to 110 [GHz], and the amount of electromagnetic waves absorbed by the film is calculated using the above equation (1).
Next, an absorption spectrum diagram is created in which the frequency is plotted on the horizontal axis and the absorption amount calculated by the above formula (1) is plotted on the vertical axis. Usually, in this absorption spectrum diagram, there is one frequency value on the horizontal axis where the amount of absorption is the maximum value. Therefore, a single peak is formed in the plot where the amount of electromagnetic wave absorption reaches its maximum value. In this way, the frequency of electromagnetic waves when the amount of absorption of electromagnetic waves takes the maximum value can be set to A [GHz].

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 the material of the first unit include a thin metal wire, a conductive thin film, and a fixed conductive paste.
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, steel such as carbon steel, brass, phosphor bronze, zirconium copper alloy, beryllium copper, iron nickel, nichrome, nickel titanium, kanthal, hastelloy, rhenium tungsten, etc.).
Examples of the material for the conductive thin film include metal particles, carbon nanoparticles, and carbon fibers.

The interval between the ends of the figure, which is the first unit u1, is not particularly limited as long as the absorption characteristics can be adjusted to the desired frequency.
For example, the distances between the ends of the figures that are the first unit u1 may be the same or different. However, since it becomes easier to design an electromagnetic wave absorption film that is less affected by the surrounding environment, and the accuracy of the frequency band of the electromagnetic waves to be absorbed improves during manufacturing, the distance between the edges of the figure, which is the first unit u1, is , are preferably identical to each other.

(Second electromagnetic wave absorption pattern)
FIG. 4A is a top view showing the second electromagnetic wave absorption pattern 72. FIG.
As shown in FIG. 4(a), the second electromagnetic wave absorption pattern 72 is composed of a plurality of 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 an aggregate of second units u2 that are geometric figures.
Each of the second units u2 functions as one antenna. The second electromagnetic wave absorption pattern 72 may be, for example, a thin line pattern of an FSS element.

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 FIG. 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 array R2 on the base material 21 at predetermined intervals along the direction indicated by the double-headed arrow P.
The interval between the plurality of second arrays R2 is not particularly limited. The intervals between the second arrays R2 may be regular or irregular.

FIG. 4(b) is a top view showing the second unit u2.
As shown in FIG. 4(b), the shape of the second unit u2 is a cross shape that is vertically and horizontally symmetrical. Specifically, the second unit u2 has one cross portion S2 and four end portions T2. The cross portion S2 is composed of a straight line portion parallel to the x-axis direction and a straight line portion parallel to the y-axis direction in FIG. 4(b). Each straight end T2 is in contact with each of 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 orthogonal to each straight line portion.

In the electromagnetic wave absorption layer 20, the length L2 of the second unit u2 in the x-axis direction is shorter than the length L1 of the first unit u1 in the x-axis direction. In addition, the length W2 of each of the four ends T2 in the x-axis direction or the y-axis direction is shorter than the length W1 of each of the four ends T1 of the first unit u1.
By adjusting the length L2 of the second unit u2 in the x-axis direction and the length W2 of each of the four ends T2 in the x-axis direction, the electromagnetic waves generated by the second unit u2 functioning as one antenna can be adjusted. Absorption properties can be adjusted. Similarly, the electromagnetic wave absorption characteristics can be adjusted in the y-axis direction as well.

In the electromagnetic wave absorption layer 20, the shapes of the plurality of second units u2 are the same. However, the shapes of the plurality of second units u2 do not have to be the same figure. In other examples of the present invention, the shapes of the plurality of second units may be the same or different as long as the absorption characteristics can be adjusted to the desired frequency.

The second electromagnetic wave absorption pattern 72 selectively absorbs electromagnetic waves whose frequency is 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 absorption pattern 72 shows a maximum value. The frequency value B [GHz] satisfies the following formula (2).
1.037×A≦B≦1.30×A...Formula (2)

As shown in the above equation (2), the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves having a frequency of 1.037×A [GHz] to 1.30×A [GHz]. The second electromagnetic wave absorption pattern 72 preferably absorbs electromagnetic waves having a frequency of 1.17×A [GHz] to 1.30×A [GHz].
Since the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with a frequency of 1.037×A [GHz] or more, the amount of electromagnetic waves absorbed by the second electromagnetic wave absorption pattern 72 in a frequency band higher than A [GHz] is The peak and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorption pattern 71 sufficiently overlap. 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 absorption film is expanded to a frequency band higher than A [GHz].
Since the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with a frequency of 1.30×A [GHz] or less, the amount of electromagnetic waves absorbed by the second electromagnetic wave absorption pattern 72 in a frequency band higher than A [GHz] is The difference in frequency between the peak and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorption pattern 71 becomes smaller. As a result, a single peak is formed in which the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorbing film becomes a maximum value.
From the above, since the second electromagnetic wave absorption pattern 72 absorbs electromagnetic waves with a frequency of 1.037×A [GHz] to 1.30×A [GHz], the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorption film is is extended to the higher frequency band.

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 desired frequency. For example, the shape of the figure that is the second unit includes a circular shape, an annular shape, a linear shape, a rectangular shape, a polygonal shape, an H-shape, a Y-shape, a V-shape, and the like.

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 desired frequency. Not done.
The material of the second unit is the same as that described for the material of the first unit u1.

The interval between the ends of the figure, which is the second unit u2, is not particularly limited as long as the absorption characteristics can be adjusted to the desired frequency.
For example, the intervals between the ends of the figures that are the second unit u2 may be the same or different. However, since it becomes easier to design an electromagnetic wave absorption film that is less affected by the surrounding environment, and the accuracy of the frequency band of the electromagnetic waves to be absorbed improves during manufacturing, the distance between the edges of the figure, which is the second unit u2, is , are preferably identical to each other.

(Third electromagnetic wave absorption pattern)
FIG. 5A is a top view showing the third electromagnetic wave absorption pattern 73. FIG.
As shown in FIG. 5(a), the third electromagnetic wave absorption pattern 73 is composed of a plurality of third units u3. Each of the third units u3 is a geometric figure. That is, it can be said that the third electromagnetic wave absorption pattern 73 is an aggregate of third units u3 that are geometric figures.
Each of the third units u3 functions as one antenna. The third electromagnetic wave absorption pattern 73 may be, for example, a thin line pattern of an FSS element.

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 FIG. 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 array R3 on the base material 21 at predetermined intervals along the direction indicated by the double-headed arrow P.
The spacing between the plurality of third arrays R3 is not particularly limited. The intervals between the third arrays R3 may be regular or irregular.

FIG. 5(b) is a top view showing the third unit u3.
As shown in FIG. 5(b), the shape of the third unit u3 is a cross shape that is vertically and horizontally symmetrical. Specifically, the third unit u3 has one cross portion S3 and four end portions T3. The cross portion S3 is composed of a straight line portion parallel to the x-axis direction and a straight line portion parallel to the y-axis direction in FIG. 5(b). Each straight end T3 is in contact with each of 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 orthogonal to each straight line portion.

In the electromagnetic wave absorption layer 20, the length L3 of the third unit u3 in the x-axis direction is longer than the length L1 of the first unit u1 in the x-axis direction. In addition, the length W3 of each of the four ends T3 in the x-axis direction or the y-axis direction is longer than the length W1 of each of the four ends T1 of the first unit u1.
By adjusting the length L3 of the third unit u3 in the x-axis direction and the length W3 of each of the four ends T3 in the x-axis direction, the electromagnetic waves generated by the third unit u3 functioning as one antenna can be adjusted. Absorption properties can be adjusted. Similarly, the electromagnetic wave absorption characteristics can be adjusted in the y-axis direction as well.

In the electromagnetic wave absorption layer 20, the shapes of the plurality of third units u3 are the same. However, the shapes of the plurality of third units u3 do not have to be the same figure. In other examples of the present invention, the shapes of the plurality of third units may be the same or different as long as the absorption characteristics can be adjusted to a target frequency.

The third electromagnetic wave absorption pattern 73 selectively absorbs electromagnetic waves whose frequency is C [GHz] that satisfies the following formula (3). The frequency value C [GHz] is the frequency value when the amount of electromagnetic waves absorbed by the third electromagnetic wave absorption pattern 73 shows a maximum value. The frequency value C [GHz] satisfies the following formula (3).
0.60×A≦C≦0.963×A...Formula (3)

As shown in the above equation (3), the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves having a frequency of 0.60×A [GHz] to 0.963×A [GHz]. The third electromagnetic wave absorption pattern 73 preferably absorbs electromagnetic waves having a frequency of 0.60×A [GHz] to 0.83×A [GHz].
Since the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with a frequency of 0.60×A [GHz] or more, the amount of electromagnetic waves absorbed by the third electromagnetic wave absorption pattern 73 in the frequency band lower than A [GHz] is The difference in frequency between the peak and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorption pattern 71 becomes smaller. As a result, a single peak is formed in which the amount of electromagnetic waves absorbed by the entire electromagnetic wave absorbing layer 20 becomes a maximum value.
Since the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with a frequency of 0.963×A [GHz] or less, the amount of electromagnetic waves absorbed by the third electromagnetic wave absorption pattern 73 in the frequency band lower than A [GHz] is The peak and the peak of the amount of electromagnetic waves absorbed by the first electromagnetic wave absorption pattern 71 sufficiently overlap. 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 only the first electromagnetic wave absorbing pattern 71.
From the above, since the third electromagnetic wave absorption pattern 73 absorbs electromagnetic waves with a frequency of 0.60×A [GHz] to 0.963×A [GHz], the electromagnetic wave absorbed by the entire electromagnetic wave absorption layer 20 is The amount is extended to the lower frequency band.

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 a desired frequency. For example, the shape of the figure that is the third unit includes a circular shape, an annular shape, a linear shape, a rectangular shape, a polygonal shape, an H-shape, a Y-shape, a V-shape, and the like.

The material of the third unit u3 constituting the third electromagnetic wave absorption pattern 73 is not particularly limited as long as it is capable of absorbing C [GHz] electromagnetic waves. Not limited.
The material of the third unit u3 is the same as that described for the material of the first unit u1.

The distance between the ends of the figure, which is the third unit u3, is not particularly limited as long as the absorption characteristics can be adjusted to the desired frequency.
For example, the distances between the ends of the figures that are the third unit u3 may be the same or different. However, since it becomes easier to design an electromagnetic wave absorbing film that is less affected by the surrounding environment, and the accuracy of the frequency band of the electromagnetic waves to be absorbed improves during manufacturing, the distance between the edges of the figure, which is the third unit u3, is , are preferably identical to each other.

In the electromagnetic wave absorbing layer 20 shown in FIG. 2, a first array R1, a second array R2, and a third array R3 are arranged along the direction indicated by a double arrow P so as to be adjacent to each other. In this way, since the first array R1, the second array R2, and the third array R3 are arranged on the base material 21 so as to be adjacent to each other, the first electromagnetic wave absorption pattern 71 selectively absorbs The frequency band of electromagnetic waves selectively absorbed by the second electromagnetic wave absorption pattern 72 and the electromagnetic waves selectively absorbed by the third electromagnetic wave absorption pattern 73 based on the frequency value A [GHz] of the peak position of the electromagnetic waves Both frequency bands overlap. As a result, the absorption range of electromagnetic waves absorbed by the entire electromagnetic wave absorption layer 20 is likely to be expanded to both the high frequency side and the low frequency side with respect to the frequency value A [GHz] at the peak position.

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 between the third unit u3 and the first unit u1 shown in FIG. The distance d3 may be the same or different.
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 distance d1, distance d2, and distance d3 are each within the above numerical range, the absorption range of electromagnetic waves absorbed by the entire electromagnetic wave absorption layer 20 is likely to be further expanded with respect to the frequency value A [GHz] at the peak position. Become.

In the electromagnetic wave absorption layer 20, the shapes of the first unit u1, the second unit u2, and the third unit u3 are the same. However, the shapes of the first unit u1, the second unit u2, and the third unit u3 do not have to be the same figure. 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 the same or different.

The electromagnetic wave absorption layer 20 may have a plurality of second electromagnetic wave absorption patterns 72. For example, in addition to the second electromagnetic wave absorption pattern 72, the electromagnetic wave absorption layer 20 may further include an electromagnetic wave absorption pattern 72a and an electromagnetic wave absorption pattern 72b described below.
Electromagnetic wave absorption pattern 72a: An electromagnetic wave absorption pattern in which the value of the frequency at which the absorbed amount of electromagnetic waves shows a maximum value is D [GHz] that satisfies the following formula (4).
Electromagnetic wave absorption pattern 72b: An electromagnetic wave absorption pattern in which the frequency value at which the absorbed amount of electromagnetic waves shows a maximum value is E [GHz] that satisfies 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 method X or method Y.

When the electromagnetic wave absorption layer 20 further includes an electromagnetic wave absorption pattern 72a and an electromagnetic wave absorption pattern 72b in addition to the second electromagnetic wave absorption pattern 72, the amount of electromagnetic wave absorbed by the second electromagnetic wave absorption pattern 72 has a maximum value. The value of the frequency indicating this is preferably 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 absorption layer 20 toward the higher frequency side is even more remarkable, and the effects of the present invention can be obtained even more noticeably.

The electromagnetic wave absorption layer 20 may have a plurality of third electromagnetic wave absorption patterns. For example, in addition to the third electromagnetic wave absorption pattern 73, the electromagnetic wave absorption layer 20 may further include an electromagnetic wave absorption pattern 73a and an electromagnetic wave absorption pattern 73b described below.
Electromagnetic wave absorption pattern 73a: An electromagnetic wave absorption pattern in which the frequency value at which the amount of absorbed electromagnetic waves shows a maximum value is F [GHz] that satisfies the following formula (6).
Electromagnetic wave absorption pattern 73b: An electromagnetic wave absorption pattern in which the frequency value at which the amount of absorbed electromagnetic waves shows a maximum value is G [GHz] that satisfies 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 formulas (6) and (7), A is the frequency [GHz] specified by method X or method Y described above.

When the electromagnetic wave absorption layer 20 further includes an electromagnetic wave absorption pattern 73a and an electromagnetic wave absorption pattern 73b in addition to the third electromagnetic wave absorption pattern 73, the amount of electromagnetic wave absorbed by the third electromagnetic wave absorption pattern 73 reaches a maximum value. The value of the frequency shown is preferably 0.60×A [GHz] to 0.83×A [GHz]. In this case, the effect of extending the frequency band of electromagnetic waves that can be absorbed by the entire electromagnetic wave absorbing layer 20 to the lower frequency side is even more remarkable, and the effects of the present invention can be obtained even more noticeably.

FIG. 6 is a cross-sectional view taken along line VIII-VIII of the electromagnetic wave absorbing layer 20 in FIG.
The base material 21 has two surfaces 21a and 21b facing each other. 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. As shown in FIG. 6, a plurality of first units u1, a plurality of second units u2, and a plurality of third units u3 are provided on one surface 21a of the base material 21, respectively.

The base material 21 is not particularly limited as long as it is flat and has a form in which the first electromagnetic wave absorption pattern 71, the second electromagnetic wave absorption pattern 72, and the third electromagnetic wave absorption pattern 73 can be formed on one surface 21a. Not done. The base material 21 may have a single layer structure or a multilayer structure.

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 absorption pattern 71, the thickness H2 of the second electromagnetic wave absorption pattern 72, and the thickness H3 of the third electromagnetic wave absorption pattern 73 are not particularly limited. Thickness H1, thickness H2, and thickness H3 can be arbitrarily changed according to desired characteristics. Further, the thickness H1, the thickness H2, and the thickness H3 may be the same or different.
The thickness H1, the thickness H2, and the thickness H3 may be, for example, 1 μm to 100 μm, 5 μm to 50 μm, or 10 μm to 30 μm. The thicker each of the thickness H1, the thickness H2, and the thickness H3, the better the electromagnetic wave absorbability, but the higher the manufacturing cost. Taking this point into consideration, each of the thicknesses H1, H2, and H3 may be set.

The material of the base material 21 can be appropriately selected depending on the use of the electromagnetic wave absorbing member 10.
For example, in order to provide the electromagnetic wave absorbing member 10 with transparency, the base material 21 may be made of a transparent material. In addition, the base material 21 may be made of a flexible material for the purpose of providing followability to the curved surface of the electromagnetic wave absorbing member 10. For the purpose of improving the transparency and three-dimensional formability of the electromagnetic wave absorbing member 10, the surface of the base material 21 may be made smooth.

For example, the base material 21 can be made of resin. The resin may be a thermoplastic resin or a thermosetting resin. However, when considering the three-dimensional formability of the electromagnetic wave absorbing member 10, it is preferable that the base material 21 contains a thermoplastic resin.
Examples of thermoplastic resins include polyolefin resins, polyester resins, polyacrylic resins, polystyrene resins, polyimide resins, polyimide amide resins, polyamide resins, polyurethane resins, polycarbonate resins, polyarylate resins, melamine resins, epoxy resins, urethane resins, Examples include silicone resin and fluororesin.
Specific examples of polyolefin resins include polypropylene, polyethylene, and the like. Specific examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and the like.

The base material 21 may contain optional components within a range that does not impair the effects of the present invention. Examples of optional components include inorganic fillers, colorants, curing agents, anti-aging agents, light stabilizers, flame retardants, conductive agents, antistatic agents, and plasticizers.

Considering further improvement of the electromagnetic wave absorption performance of the electromagnetic wave absorbing member 10, the thickness, dielectric constant, electrical conductivity, and magnetic permeability of the base material 21 can be set as appropriate.
When considering the electrical characteristics of electromagnetic waves to be absorbed, the base material 21 may be a layer with a high dielectric constant. When 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 thin.

The electromagnetic wave absorption layer 20 can be produced, for example, by the method described below.
First, the 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, the first electromagnetic wave absorption pattern 71 is formed so that the value of the frequency at which the absorption amount of the electromagnetic wave absorbed by the first electromagnetic wave absorption pattern 71 is a maximum value is A [GHz]. do.
When forming the second electromagnetic wave absorption pattern 72, it is formed so that the frequency value at which the amount of electromagnetic wave absorbed by the second electromagnetic wave absorption pattern 72 has a maximum value is B [GHz].
When forming the third electromagnetic wave absorption pattern 73, it is formed so that the frequency value at which the amount of electromagnetic wave absorbed by the third electromagnetic wave absorption pattern 73 has 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 may be formed in separate processes.

The method of 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 methods.
A printing method in which each electromagnetic wave absorption pattern is printed on one surface 21a of a base material 21 using a conductive paste.
A developing method in which each electromagnetic wave absorption pattern is developed on one surface 21a of the base material 21.
A method in which a metal thin 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 metal thin film is formed on the one surface 21a of the base material 21 by photolithography.
A method of arranging a metal wire on one surface 21a of a base material 21.

In the printing method, each electromagnetic wave absorption pattern is printed on one surface 21a of the base material 21 to form each unit u1, u2, u3 which is a figure. The printing method is not particularly limited. Examples include methods such as screen printing, gravure printing, and inkjet printing.
Examples of the conductive paste used for printing include a paste-like composition containing at least one member selected from the group consisting of metal particles, carbon nanoparticles, and carbon fibers and a binder resin component. Examples of the metal particles include particles of metals such as copper, silver, nickel, and aluminum.
Examples of the binder resin component include thermoplastic resins such as polyester resins, (meth)acrylic resins, polystyrene resins, and polyamide resins; thermosetting resins such as epoxy resins, amino resins, and polyimide resins. However, the metal particles and the binder resin component are not limited to these examples.
The conductive paste may further contain a black pigment such as carbon black. When the conductive paste further contains a black pigment, the metallic luster of the metal powder constituting the printed electromagnetic wave absorption pattern can be suppressed, and the reflection of external light can be suppressed.

In the developing method, an electromagnetic wave absorption pattern is developed on one surface 21a of the base material 21 to form each unit u1, u2, u3 which is a figure.
There are two types of development methods: a negative development method in which the developed material appears in the exposed areas that are not covered by an exposure mask, and a positive development method in which the developed material appears in the unexposed areas that are covered by the exposure mask. There is. That is, in the negative developing method, each unit u1, u2, u3 is formed as a developed object in a shape opposite to the exposure mask. On the other hand, in the positive developing method, each unit u1, u2, u3 is formed as a developed object in the same shape as the exposure mask. Silver is usually used as the metal for the developed product.

An example of a method for forming an electromagnetic wave absorption pattern using photolithography includes the following method.
First, a resist is applied to one surface 21a of the base material 21, heat treated, and then the solvent is removed from the resist. Next, a desired pattern is exposed to light on the resist, and the resist pattern is developed to form a layer consisting of the resist pattern. Next, a vapor deposited film is formed over the entire surface of the layer made of the base material and the resist pattern, and a resist stripping agent is used to simultaneously remove the layer made of the resist pattern and the vapor deposited film placed thereon. Thereby, an electromagnetic wave absorption pattern can be formed on the surface of the base material.
As another example, a metal thin film is provided on one surface 21a of the base material 21, a resist is applied to a part of the surface of the metal thin film, and heat treatment is performed. Next, the portions of the metal thin film to which the resist is not applied are removed by etching. Thereafter, 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 constituting each electromagnetic wave absorption pattern.

Specific examples of the metal constituting the metal wire include the same metals as those described above as the materials for the units u1, u2, and u3. In addition, the metal wire may be plated with tin, zinc, silver, nickel, chromium, nickel-chromium alloy, solder, etc., and may have its surface coated with a carbon material, polymer, etc. Examples of the carbon material that coats 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.

"Spacer layer"
The spacer layer 30 is provided on the other surface 21b of the base material 21 that the electromagnetic wave absorption layer 20 has.
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. A reflective layer 40 is provided on the other surface 30b of the spacer layer 30.
The spacer layer 30 may have a single layer structure or a multilayer structure.

The material of the spacer layer 30 can be selected as appropriate depending on the purpose of the partition. For example, the spacer layer 30 may be made of a transparent material for the purpose of providing transparency to the partition. Alternatively, the spacer layer 30 may be made of a flexible material for the purpose of providing followability to the curved surface of the partition.
Examples of flexible materials include plastic films, rubber, paper, cloth, nonwoven fabrics, foams, rubber sheets, and the like. Among these, foam is preferred from the viewpoint of making the electromagnetic wave absorbing member 10 lightweight.
As a specific example of the resin constituting the plastic film, the same thermoplastic resin as described for the base material 21 above can be used, for example.
As the foam, for example, a foamed sheet formed into a sheet shape by foaming the resin constituting the plastic film can be used. Specific examples of foam sheets include polyethylene foam, polypropylene foam, polyurethane foam, and the like.

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 dielectric constant of the spacer layer 30.
When considering the wavelength shortening effect of the spacer layer 30, the thickness of the spacer layer 30 in the z-axis direction preferably satisfies the following formula (8).
(Thickness of spacer layer 30 in z-axis direction) = (λ) x (1/4)/(ε) ^1/2 ...Equation (8)
In the above formula (8), λ is the wavelength of the incoming electromagnetic wave, and ε is the relative dielectric constant 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 in the z-axis direction of the spacer layer 30 obtained by equation (8).

When the relationship between the thickness of the spacer layer 30 in the z-axis direction and the wavelength λ satisfies the above formula (8), the electromagnetic wave absorbing member 10 has 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 depending on the wavelength λ of the electromagnetic wave to be absorbed. The thickness of the spacer layer 30 may be, for example, 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. When the spacer layer 30 is a layer with a high dielectric constant, the thickness of the spacer layer 30 can be made relatively thin.
When considering the dielectric constant of the spacer layer 30, it is preferable that the spacer layer 30 contains at least one member selected from the group consisting of barium titanate, titanium oxide, and strontium titanate.

By increasing the dielectric constant of the spacer layer 30, the thickness of the spacer layer 30 can be reduced. Thereby, the electromagnetic wave absorbing member 10 can be made lightweight.

The two surfaces 30a, 30b of the spacer layer 30 are preferably adhesive. Thereby, the electromagnetic wave absorbing layer 20 and the reflective layer 40 can be bonded to each of the two surfaces 30a and 30b. For example, by employing a multilayer structure in which the two surfaces 30a, 30b are adhesive layers containing an adhesive, the two surfaces 30a, 30b can be made adhesive.
The details and preferred embodiments of the adhesive layer can be the same as those described for the adhesive layer in the base material 21.

"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 can reflect electromagnetic waves that have come onto the surface of the electromagnetic wave absorbing member 10 and passed through the electromagnetic wave absorbing member 10 . A part of the electromagnetic waves that come to the electromagnetic wave absorbing member 10 is 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 absorption layer 20 are transmitted through the electromagnetic wave absorption layer 20. The electromagnetic waves that have passed through the electromagnetic wave absorbing layer 20 are reflected by the reflective layer 40 toward the electromagnetic wave absorbing layer 20 .
For example, if the reflective layer 40 is conductive in the plane direction of the two surfaces 40a and 40b, the electromagnetic waves transmitted through the electromagnetic wave absorbing layer 20 can be reflected. Specifically, the reflective layer 40 may be formed by bonding a metal foil such as copper foil or a metal plate such as a copper plate to a resin film such as polyethylene terephthalate. Instead of the metal foil or metal plate, a mesh sheet formed of a conductive film such as ITO, a metal wire, etc. may be used. Among these, metal plates are preferred from the viewpoint of high conductivity.

In consideration of 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 the surface 40b by, for example, a printing method such as screen printing, gravure printing, or an inkjet method; sputtering or vacuum deposition; or photolithography.

When the spacer layer 30 is formed of a conductive object such as a metal, the reflective layer 40 can be omitted because the conductive object such as a metal plays the role of the reflective layer 40.

The other surface 40b of the reflective layer 40 may be adhesive for the purpose of applying the electromagnetic wave absorbing member 10 to the surfaces of various articles. When the other surface 40b of the reflective layer 40 is 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. The release film covers the adhesive surface, making it easier to handle 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.

Examples of the adhesive include a heat-seal type adhesive that adheres by heat; an adhesive that exhibits stickiness by wetting; a pressure-sensitive adhesive (adhesive) that adheres by pressure; and the like. Among these, pressure-sensitive 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, and the like. 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.

Further, the electromagnetic wave absorbing member 10 of this embodiment may include a protective layer formed on one surface (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.

The thickness of the protective layer is preferably 1 μm to 500 μm, more preferably 3 μm to 100 μm, even more preferably 5 μm to 50 μm. When the thickness of the protective layer is equal to or greater than the above lower limit, the unevenness of the electromagnetic wave absorbing layer 20 can be sufficiently followed and protected. When the thickness of the protective layer is equal to or less than the above upper limit, the composition constituting the protective layer is suppressed from seeping out from the side surfaces, and flexibility can be imparted to the partition.

[Method for manufacturing electromagnetic wave absorbing member]
The electromagnetic wave absorbing member 10 can be manufactured, for example, by the following method.
A composition is prepared that includes a modified polyolefin resin and a polyphenylene ether resin having reactive groups.
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 contain various additives in addition to the modified polyolefin resin and the polyphenylene ether resin having a reactive group, if necessary. Examples of additives include silane coupling agents and curing agents.
The curing agent is not particularly limited as long as it starts a curing reaction. Since it has excellent stability over time and productivity, a curing agent that initiates a curing reaction by heating is preferably used. It is preferable that the composition contains a curing agent because the curing reaction proceeds more efficiently. Examples of the curing agent that initiates the curing reaction by heating include thermal cationic polymerization initiators and other heat-reactive curing agents.
As the silane coupling agent, a known silane coupling agent 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; esters such as ethyl acetate and butyl acetate. Ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; Aliphatic hydrocarbon solvents such as n-pentane, n-hexane, and n-heptane; Alicyclic carbonization such as cyclopentane, cyclohexane, and methylcyclohexane Examples include hydrogen-based solvents; and the like.

The above-mentioned composition is applied onto the release-treated surface of the release film, and the resulting coating film is dried to form an adhesive layer. The method of applying the composition is not particularly limited. Examples of the coating method include methods using printing methods such as screen printing, gravure printing, and inkjet printing. The release-treated surface of another release film is bonded onto this adhesive layer to obtain an adhesive sheet.
Next, one side of the release film of the adhesive sheet is peeled off, and the exposed one side of the adhesive sheet is attached to the other side 20b of the electromagnetic wave absorbing layer 20.

Next, the other side of the release film of the adhesive sheet is peeled off, and a material that will become the spacer layer 30 is attached to the other exposed surface of the adhesive sheet.
Next, as in the case of the spacer layer 30, 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.
The electromagnetic wave absorbing member 10 is obtained by the above method.

According to the electromagnetic wave absorbing member 10 of the present embodiment, a plurality of slits 50 are formed from the outermost surface of the electromagnetic wave absorbing layer 20 and are substantially parallel to the thickness direction of the electromagnetic wave absorbing layer 20 and the spacer layer 30. Since the laminate 60 consisting of the electromagnetic wave absorbing layer 20 and the spacer layer 30 is divided into a plurality of regions, and the width W0 of the plurality of slits 50 is less than 10 mm, as shown in FIG. It has flexibility and can be rolled up into a smaller size. Further, according to the electromagnetic wave absorbing member 10 of the present embodiment, at least a portion of the adjacent spacer layers 30 are connected to each other at the ends of the plurality of slits 50 on the reflective layer 40 side, so that at the reflective layer 40, Unnecessary reflection of electromagnetic waves can be suppressed.

Further, the electromagnetic wave absorbing member 10 of this embodiment is not limited in size, but one of its features is that it can be easily made into a large area, and even if it is large, it can be rolled up and stored compactly. From that point of view, the size of the side (horizontal) substantially parallel to the slit extending direction is preferably 0.1 m or more and 10 m or less, more preferably 0.5 m or more and 5 m or less, and 0.8 m or more. It is particularly preferable that the length is 1.8 m or less. Further, the size of the side perpendicular to the slit extending direction (vertical: the side to be wound) is preferably 0.1 m or more and 10 m or less, more preferably 0.5 m to 5 m, and 1. It is particularly preferable that the length is 5 m or more and 3.0 m or less.

[Aiming partition]
FIG. 8 is a side view schematically showing an aiming partition according to an embodiment of the present invention.
As shown in FIG. 8, the aiming partition 100 of this embodiment includes 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 embodiment described above.

The aiming partition 100 of this embodiment includes, for example, a pair of support members 110 that are spaced apart from each other at a predetermined interval. Further, the pair of support members 110 are arranged so that the longitudinal direction thereof runs along the vertical direction. The pair of support members 110 may be arranged so that the longitudinal direction thereof is substantially vertical, and may have a length that can support the front plate 130.

As shown in FIG. 8, the aiming partition 100 preferably has a crosspiece 140 between the 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 crosspiece 140. Thereby, the front plate 130 can be supported more stably by the support member 110.
Further, the front plate 130 is bonded onto the support plate 120 via an adhesive layer 150.

The support plate 120 has a rectangular shape in plan view. The support plate 120 is fixed to the pair of support members 110. In FIG. 8, the support plate 120 is arranged from one support member 110A to the other support member 110B. Note that the support plate 120 may be fixed to the pair of support members 110 and may be arranged so that its short side is along the vertical direction or a substantially vertical direction, and the position where the support plate 120 is coupled to the pair of support members 110 is determined. Not particularly limited.

The size (area) of the support plate 120 when viewed in plan is adjusted as appropriate depending on the projected area when the automobile to be aimed using the aiming partition 100 is viewed from the front. The size of the support plate 120 in plan view is preferably, for example, 2 m long x 2.5 m wide, and the above-mentioned size may be obtained by lining up a plurality of small aiming partitions. When arranging multiple small aiming partitions, keeping the gaps between the partitions small will suppress leakage of radio waves. Note that in this specification, length refers to the vertical direction of the page, and horizontal refers to the horizontal direction of the page.

"Supporting member"
The length of the support member 110 is adjusted as appropriate depending on the size (area) of the front plate 130 when viewed from above.
Examples of the material constituting the support member 110 include resin, nonmetallic materials such as wood, and metal. In order to further improve the effect of adjusting the aiming work environment by the aiming partition 100, it is preferable that the support member 110 is made of a non-metallic material that hardly reflects electromagnetic waves.

As means for fixing the support plate 120 to the support member 110, adhesives, adhesives, screws, bolts and nuts, etc. are used. The material of the means for fixing the support plate 120 is preferably a non-metallic material that hardly reflects electromagnetic waves, such as resin or wood. Note that conductive materials such as metals reflect electromagnetic waves and are therefore not suitable as means for fixing the support plate 120.

The support plate 120 provided with the front plate 130 may be removable from the support member 110. In order to make the support plate 120 removable from the support member 110, the support member 110 is provided with a frame material having a shape that follows the outer shape of the support plate 120, and the support plate 120 is inserted into the frame material. The support plate 120 may be fitted to 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 and fixed to the support member 110 with the hook. In this way, the aiming partition 100 can be disassembled into the support member 110 and the front plate 130, making it easy to transport and eliminating the need for a large storage space.

"Support plate"
It is preferable that the support plate 120 has flexibility. When the support plate 120 has flexibility, a resin sheet, paper, textile, or the like is used as the support plate 120. The resin constituting the resin sheet is not particularly limited, but includes, for example, the resin constituting the base material 21 described above. Since the support plate 120 has flexibility, the support plate 120 provided with the front plate 130 can be wound up into a roll. In this way, the aiming partition 100 is easy to transport and does not require a large storage space.

"Ban"
The crosspiece 140 is provided, for example, along the lateral direction of the support plate 120, as shown in FIG.
Examples of the material constituting the crosspiece 140 include nonmetallic materials that do not substantially reflect electromagnetic waves, such as resin and wood, and metals. In order to further improve the effect of preparing the aiming work environment by the aiming partition 100, it is preferable that the crosspiece 140 is made of a non-metallic material that hardly reflects electromagnetic waves.

"Adhesive layer"
Examples of the adhesive forming the adhesive layer 150 include strong acrylic adhesives, which are appropriately selected depending on the material of the attachment surface.

The aiming partition 100 of this embodiment is lightweight and includes a support member 110, a support plate 120 supported by the support member 110, and a front plate 130 disposed on at least one surface 120a of the support plate 120. It is easy to transport and does not require a large storage space. Therefore, according to the aiming partition 100 of this embodiment, it is possible to easily prepare a working environment for aiming an automobile.

Although FIG. 8 shows an example in which the electromagnetic wave absorbing layer 20, the spacer layer 30, the reflective layer 40, the adhesive layer 150, and the support plate 120 are laminated in this order, the aiming partition of the present invention is not limited to this. In the aiming partition of the present invention, when a conductive material is used as the support plate 200, as shown in FIG. may be stacked in this order.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1]
Assuming a radar for an advanced driving support system, a copper thin film was formed by vapor depositing copper on a base material made of PET film (product name: PET50A4160, manufactured by Toyobo Co., Ltd.).
Thereafter, the copper thin film was patterned into an electromagnetic wave absorption pattern by photolithography to obtain an electromagnetic wave absorption layer.
On the back side of the obtained electromagnetic wave absorption layer, a foamed urethane sheet (product name: PORON HH-48, manufactured by INOAC Corporation) with a thickness of 2 mm was placed as a spacer layer, and an aluminum vapor-deposited PET film (flexural rigidity: 8.33 Pa) was placed as a reflective layer.・mm ⁴ ) were laminated in this order to produce an electromagnetic wave absorbing member.
On the obtained electromagnetic wave absorbing member, from the outermost surface of the electromagnetic wave absorbing layer, approximately parallel to the thickness direction of the electromagnetic wave absorbing layer and the spacer layer, cut with a cutter blade the slit width (0.1 mm) shown in Table 1 at 10 cm intervals. to form multiple slits. As a result, an electromagnetic wave absorbing member having slits and having a size of 1.5 m in width and 2.0 m in length was obtained.
The electromagnetic wave absorbing member was attached onto a support plate made of PET film (trade name: PET50A4160, manufactured by Toyobo Co., Ltd.) via an adhesive.
Furthermore, the electromagnetic wave absorbing member affixed on the support plate was attached to a pair of support members arranged apart from each other at a predetermined interval to obtain an aiming partition.

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

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

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

[Comparative example 1]
An aiming partition of Comparative Example 1 was obtained in the same manner as in Example 1, except that the electromagnetic wave absorbing member was cut with a slit width (10 mm) shown in Table 1.

[Comparative example 2]
An aiming partition of 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.

[evaluation]
"Return loss"
Using the free space method, the S21 values of the aiming partitions of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were obtained using a network analyzer, and the return loss of each aiming partition was evaluated. The results are shown in Table 1 and FIG. Note that FIG. 10 shows the return loss amounts of Example 1, Comparative Example 1, and Comparative Example 2.

"Rewindability"
The electromagnetic wave absorbing members of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were wound up by hand, and it was visually confirmed whether the materials could be wound up without wrinkles. "○" indicates that there are no wrinkles or folds in the electromagnetic wave absorbing material when it is unfolded after being rolled up and used as an aiming partition again. The case where there was a problem was evaluated as "x". The results are shown in Table 1.

From the results shown in Table 1 and FIG. 10, it was found that the aiming partitions of Examples 1 to 4 had excellent return loss, and that the electromagnetic wave absorbing member of Example 1 had excellent winding properties.
On the other hand, it was found that the aiming partition of Comparative Example 1 had poor return loss, and the electromagnetic wave absorbing member of Comparative Example 1 had excellent winding properties.
It was also found that the aiming partition of Comparative Example 2 had excellent return loss, and the electromagnetic wave absorbing member of Comparative Example 2 had poor winding properties.

The electromagnetic wave absorbing member of the present invention can be suitably used for aiming partitions used for aiming of automobiles.

10 Electromagnetic wave absorption member 20 Electromagnetic wave absorption layer 21 Base material 22 Electromagnetic wave absorption pattern 30 Spacer layer 40 Reflection layer 50 Slit 60 Laminated body 71 First electromagnetic wave absorption pattern 72 Second electromagnetic wave absorption pattern 73 Third electromagnetic wave absorption pattern 100 For aiming Partition 110 Support member 120 Support plate 130 Front plate 140 Crosspiece 150 Adhesive layer

Claims (5)

It has an electromagnetic wave absorption 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,
A plurality of slits substantially parallel to the thickness direction of the electromagnetic wave absorption layer and the spacer layer are formed from the outermost surface of the electromagnetic wave absorption layer, and the electromagnetic wave absorption layer and the spacer layer are formed through the plurality of slits. The stack is divided into multiple regions,
An electromagnetic wave absorbing member, wherein the width of the plurality of slits is less than 10 mm. The electromagnetic wave absorbing member according to claim 1, wherein, in a plan view of the electromagnetic wave absorbing member, an interval between the plurality of slits is 1 cm or more and 30 cm or less. The electromagnetic wave absorbing member according to claim 1, wherein the spacer layer is made of a foam. The electromagnetic wave absorbing member according to claim 1, wherein the reflective layer is made of a conductor. comprising a support member, a support plate supported by the support member, and a front plate disposed on at least one surface of the support plate,
A partition for aiming, wherein the front plate is the electromagnetic wave absorbing member according to any one of claims 1 to 4.

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